JPH06340433A - Optical element molding method - Google Patents

Abstract

(57) [Summary] [Object] To provide a molding method of an optical element, which does not cause a defect such as a dent in a molded product and can obtain a good molded product without pressing. In a method of molding an optical element in which a preform 6 of an optical element material is softened by heating and is molded between a lower mold 4 and an upper mold 5, R of a concave preform surface molded by a convex mold (however, , R represents a radius of curvature), and R is the convex R> preform R, and R of the convex preform surface formed by the concave mold is concave R <preform R. This is a method of molding an optical element, characterized in that the assembling, the setting of the preform 6 and the setting of the upper mold 5 are performed in a vacuum chamber 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of molding an optical element, which comprises heating and softening an optical element material between a pair of molding dies composed of an upper die and a lower die.

[0002]

2. Description of the Related Art In the conventional glass molding method, if there is a space surrounded by the mold and the preform, the gas in the space leaks out even if the mold is pressed. Instead, a dent was formed in the molded product. Therefore, the preform surface facing the convex molding surface must be a convex surface or a flat surface or a concave surface having a radius R larger than the radius of curvature of the molding surface of the mold (hereinafter, referred to as R). It is necessary to have a convex surface having an R smaller than the mold R, which greatly limits the preform shape, and when considering the volume of the optical element, the optical element is designed especially in the case of a concave surface type having a small R. There were some things I couldn't do.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, does not cause defects such as dents in a molded product, and can obtain a good molded product without pressing, and a method for molding an optical element. The purpose is to provide.

[0004]

SUMMARY OF THE INVENTION The present inventors have found that R of a concave preform surface formed by a convex mold is R> preform R or R of a convex preform surface formed by a concave mold.
However, it has been found that even when the concave shape R <the preform R, if the molding member and the preform are set in a vacuum, it is possible to effectively prevent the occurrence of the depression in the molded product.
The present invention has been completed based on such findings.

That is, a method of molding an optical element according to the present invention is a method of molding an optical element in which a preform of an optical element material is softened by heating and molded between a pair of molding dies. R of the preform surface of
It is characterized in that convex R> preform R, and R of the convex preform surface formed by the concave is concave R <preform R, and the molding member and the preform are set in a vacuum.

In the method of the present invention, the R of the concave preform surface formed by the convex mold as described above is the convex R.
> Preform R, R on the convex preform surface formed by the concave mold is concave R <preform R,
A preform is produced and a closed space is created between the mold and the preform surface.

In order to carry out the method of the present invention, first, a preform as described above is placed on a lower die which is a combination of a barrel die and a lower die, and the upper die is placed on the preform. And preform set in vacuum. Generally, this vacuum is preferably set to a pressure of 1 × 10 ⁻¹ Torr or less.
At a pressure higher than 1 × 10 ^-1 Torr, the optical element material has a weak pulling force on the surface of the mold, and the mold shape is not accurately transferred. At that time, a slight pressure (pressure that does not damage the preform) is applied between the upper and lower molds so that the vacuum in the closed space formed by the mold surface and the preform surface does not leak, and it is tightened. Is preferred.

Next, a heating step of the preform is carried out. At this time, the clamping between the upper and lower molds is left as it is, and the molding member is heated at a pressure higher than the vacuum pressure at the time of setting the molding member and the preform. Is preferred. That is, it is preferable to heat the molding member block in which the preform is set under a pressure higher than the pressure in the closed space. When heated in this state, when the optical element material softens, the optical element material pulls on the surface of the molding die so as to eliminate the low pressure region, so molding is performed without pressing, and this is performed. A molded product can be obtained simply by taking out after cooling. This eliminates the need for a large pressing machine. Of course, press molding can also be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail based on embodiments with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a cross-sectional view of a molding member shown with a preform set. In this mold, the cemented carbide WC, which is the base material 1, is ground to a desired aspherical surface with an ultra-precision lathe, and then a surface roughness R is obtained by using a diamond paste abrasive.
It is manufactured by polishing so that _max = 0.02 μm or less, and forming a platinum film 2 having a thickness of 1 μm on the surface of this base material for the purpose of oxidation resistance and wettability. In this embodiment, an aspherical surface having an approximate R12.0 mm is used as the lower mold, and an R70 mm spherical surface is used as the upper mold. As the preform, the lower mold side has a convex shape R30 mm, and the upper mold side has a concave shape R.
A 30 mm lenticular preform was used. for that reason,
A closed space 11 was created between the upper mold and the preform 6, and a closed space 12 was created between the lower mold and the preform 6. The material of the preform is F2 glass manufactured by OHARA.

FIG. 2 is a process chart showing a method for setting a molding member and a preform according to the present invention. This setting step proceeds from the left in the direction of the arrow in the vacuum chamber 9 shown in FIG. The inside of the vacuum chamber 9 is 3 × by the vacuum pump 10.
The pressure was 10 ^-3 Torr. First, after assembling the body die 3 and the lower die 4, the preform 6 is set on the lower die 4 by the preform holding member 7, and then the upper die 5 is inserted into the body die 3 by the upper die holding member 8. Then, the preform 6 was lowered and set.

In this way, when the upper mold, the lower mold, the barrel mold and the preform are set, the vacuum (decompression) in the closed space formed between the molding surface of the molding die and the surface of the preform does not leak. It is preferable to apply a slight tightening pressure between the upper mold and the lower mold. In this example, a pressure of about 10 kgf / cm ² was applied between the upper mold and the lower mold. This work was also performed in the vacuum chamber 9.

FIG. 3 is a cross-sectional view of a molding member block 13 in which a preform is held in a molding member composed of an upper mold, a lower mold and a body mold while the upper and lower molds are clamped by a clamping member. The tightening member used is one in which columns are installed on the upper and lower pedestals 14, and the columns are divided by the interposition of springs 15 and pulled by the springs 15. The spring and the support pillar are rotatable, and the upper support pillar and the screw portion 16 provided on the upper base move the upper support pillar up and down to adjust the tightening force between the upper mold and the lower mold. A weight may be installed on the upper mold instead of the tightening member shown in FIG.

Next, the heating and cooling process (molding process) shown in FIG. 4 is performed. The molded member block 13 assembled as described above is taken out from the vacuum chamber 9, and the nitrogen gas inlet 17
Sent from the inside into the airtight chamber 18 into which nitrogen gas is introduced,
The heater 19 was heated to 570 ° C., which is higher than the deformation point of the preform material by 100 ° C. The molding member block may be pressed at the time of heating, but since the optical element material is pulled by the surface of the molding die so as to eliminate the low pressure region due to the pressure difference between the enclosed space in the block and its surroundings, the pressing is performed. Molding is performed as it is without doing. Then, it is sent to the cooling stage and cooled by the cooling mechanism 20 to a temperature not higher than the glass transition point.
Cooled to 0 ° C.

Then, it is taken out from the atmosphere-sealed chamber 18,
FIG. 5 is a cross-sectional view of the molding member after removing the tightening member.
Shown in. Due to the pressure difference between the closed space between the mold and the preform and the surroundings, the two were in close contact with each other and molded. As shown in FIG. 6, the molded lens 21 taken out was a clean aspherical lens in which the mold shape was precisely transferred and had no depression.

[0016]

EFFECTS OF THE INVENTION According to the method of the present invention, the R of the concave preform surface formed by the convex mold, which cannot be used conventionally, can be obtained.
Is a convex R> preform R, or R of the convex preform surface formed by a concave mold is a concave R <preform R, a mold shape is precisely transferred, It is possible to easily obtain a clean optical element having no dent defect. Further, since the pressing step can be omitted at the time of molding, a large-scale pressing machine becomes unnecessary and the facility cost is remarkably reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a molding member shown with a preform set in an example of the present invention.

FIG. 2 is a process drawing showing a method for setting a molding member and a preform in an example of the present invention.

FIG. 3 is a cross-sectional view of a molding member block according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a molding process in an example of the present invention.

FIG. 5 is a cross-sectional view of a molded member after molding in the example of the present invention.

FIG. 6 is a cross-sectional view of a lens formed according to an example of the present invention.

[Explanation of symbols]

 1 Base Material 2 Platinum Film 3 Body 4 Lower Mold 5 Upper Mold 6 Preform 7 Preform Hold Member 8 Upper Mold Hold Member 9 Vacuum Chamber 10 Vacuum Pump 11 Sealed Space 12 Sealed Space 13 Molding Member Block 15 Spring 16 Screw Part 18 Atmosphere closed chamber 19 Heater 20 Cooling mechanism 21 Molded lens

Claims (4)

[Claims] 1. In a method of molding an optical element, wherein a preform of an optical element material is softened by heating and molded between a pair of molding dies, R of a concave preform surface formed by a convex mold (provided that R is R Represents the radius of curvature), and R is the convex R> preform R, R of the convex preform surface formed by the concave mold is R <preform R, and the set of molding member and preform is in vacuum. A method for molding an optical element, characterized in that 2. The method for molding an optical element according to claim 1, wherein the vacuum is set to a pressure of 1 × 10 ⁻¹ Torr or less. 3. The method of molding an optical element according to claim 1, wherein the upper mold and the lower mold are clamped to maintain a vacuum in a closed space formed between the mold and the preform. 4. The optical element according to claim 1, 2 or 3, wherein the clamping between the upper and lower molds is left as it is, and the molding member is heated at a pressure higher than the vacuum pressure at the time of setting the molding member and the preform. Molding method.