JPH08104529A - Method for forming optical element and device therefor - Google Patents

Abstract

PURPOSE: To facilitate installing and taking out of spacers, to simplify the correspondence to mold regeneration and to easily and uniformly adjust the thickness of formed goods by providing the peripheral parts in succession to the forming surfaces of metal molds for forming with plane parts parallel with the rear surfaces and installing the spacers in these plane parts. CONSTITUTION: This method comprises providing the peripheral parts of the upper mold and the lower mold with the plane parts facing each other on the outer sides of the forming surfaces of their central parts, respectively and installing the spacers therebetween to adjust the thickness of the formed goods. Spacer materials which satisfy a relation α1 >α2 are used as the spacer materials, when the coefft. of thermal expansion of the spacer material is defined as α1 and the coefft. of thermal expansion of the forming material as α2 . Preforms 13 are placed on the forming surfaces of the lower mold shown in Fig. and the annular spacers 4 are placed on the plane parts 16 of the lower mold 10. The molds are heated by heaters 12 while an inert gas is passed in quartz tubes 11. A cylinder 14 is lowered to form the preforms 13 while the preforms are crushed to bring the spacers 4 into contact with the plane part 16 of the upper mold 20 when 420 deg.C is attained.

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 and apparatus for forming an optical element by pressing an optical element material softened by heating to obtain an optical element by cooling. .

[0002]

2. Description of the Related Art In the conventional glass molding method, when molding a plurality of optical elements at the same time by using a plurality of molding dies, in order to make the thicknesses of all molded products equal, the dimensions of the molding dies must be adjusted. It is possible to make them all the same.
However, in this case, when a defect occurs in one of the plurality of molding dies and the dimensions are shortened by reprocessing, it is necessary to shorten all the dies having no problem to have the same dimensions. It takes a lot of work. Therefore, a spacer is usually installed between the mold and the mold base or between the flange of the mold and the one that holds the flange, and the spacer is installed for each pair of molding dies. For example, as shown in FIG. 4, the spacer 10S is placed between the lower mold 10 and the lower mold base 10B. However, in this case, it takes time to set and take out the spacer 10S. Moreover, since the total dimensions of the upper mold, the lower mold, and the spacers are aligned to be the same, the spacer dimensions must be increased if the mold dimensions are shortened by reworking the mold. Spacers cannot be used, new ones must be prepared, and an enormous number of spacers are required each time reproduction is repeated. Further, even if the spacer is taken out every time the wall thickness is adjusted, the die holder must be removed from the die base, which requires a lot of time.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, facilitates installation and removal of spacers, facilitates mold remanufacturing, and can easily and uniformly adjust the wall thickness of a molded product. An object of the present invention is to provide a method and apparatus for molding an optical element.

[0004]

SUMMARY OF THE INVENTION According to the present invention, it has been found that the above object can be achieved by providing a flat surface portion parallel to the back surface in the peripheral portion following the molding surface of a molding die and installing a spacer on this flat surface portion. It was completed based on.

That is, in the method of molding an optical element according to the present invention, when the optical element is molded by heating and pressing the optical element material between the upper mold and the lower mold, the peripheral parts of the upper mold and the lower mold are Each of them is characterized in that flat portions facing each other are provided outside the molding surface of the central portion, and a spacer is provided between the flat portions to adjust the wall thickness of the molded product. Further, the present invention is a device for molding an optical element by heating and pressing an optical element material using a molding die including an upper mold and a lower mold, wherein the peripheral parts of the upper mold and the lower mold are respectively formed. The present invention provides a molding device for an optical element, characterized in that flat parts facing each other are provided outside the molding surface of the central part, and a spacer is installed between the flat parts.

In the present invention, a molding die is used in which a flat portion of the molding die is provided on the outer peripheral portion of the center molding surface, a spacer is installed on the flat portion, and a pair of molds are formed. Since the molding is performed by contacting via the spacer, the thickness of the molded product can be easily controlled and adjusted by adjusting the size of the spacer.

Further, even if the height dimension of the mold is shortened by continuing the molding and regenerating only the molding surface excluding the flat portion of the mold, the spacer can be shortened. It can be used by Further, the spacer can be taken out each time the spacer is ground during the dimension adjustment, simply by lifting the upper die.

As the spacer material, it is preferable to use a material satisfying the relationship of α ₁ > α ₂ when the thermal expansion coefficient of the spacer material is α ₁ and the thermal expansion coefficient of the molding material is α ₂ . When α ₁ <α ₂ , the shrinkage amount when shrinking after molding becomes spacer <molding material, and the molded product shrinks while the space between the molds is held down by the spacer,
The molded product and the mold do not adhere to each other, and the surface of the molded product is destroyed.
Even if α ₁ = α ₂ , the surface of the molded product is broken because the molded product is not sufficiently subjected to the molding pressure. As a specific example, when the molding material is optical glass PSK50 made by Sumita Optical Glass, SUS3 is used as the spacer material.
04 steel can be used.

In the case of a molding apparatus having a plurality of pairs of molds installed,
It is necessary to make contact with the spacer on the upper and lower mold flats of each pair, but if the height of the mold is different, even if the cylinder connected to the flat mold base is lowered (or raised), it is only the longest mold. Do not touch. Therefore, it is preferable to install a spring between the mold base and the mold for urging the mold in a direction in which the paired molds are always in contact with each other. As a result, the difference in height between the molds is absorbed by the expansion and contraction of the spring. The spring can be installed between one or both of the paired molds and the base.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the embodiments of the present invention with reference to the drawings. 1 is a cross-sectional view of a mold used in the present invention, FIG. 2 is a cross-sectional view showing a molding portion of an optical element molding apparatus according to an embodiment of the present invention immediately after completion of molding, and FIG. FIG. 6 is a cross-sectional view showing a molding part of the molding device shown in FIG.

As shown in FIG. 1, the upper mold 20 and the lower mold 10 for molding used in the present invention have a molding surface 1 at the center thereof.
7 and has annular flat portions 16 facing each other for installing spacers in the peripheral portion. The plane portion 16 is orthogonal to the mold axis. This upper mold 20 and lower mold 1
In No. 0, the thin film 2 for the purpose of heat resistance, oxidation resistance and wettability is formed on the surface of the base material 1 on the molding surface side. In order to manufacture such a die, first, the forming surface of the cemented carbide tungsten carbide WC which is the base material is ground by an ultra-precision lathe, and then the surface roughness R _max is obtained by using a diamond abrasive.
Polishing is performed to 0.02 μm or less, and various ceramics or a noble metal thin film such as gold, platinum or platinum group metal is formed on the surface by a method such as sputtering or ion plating. The flat surface portion 16 is provided continuously to the molding surface 17 and, as shown by the chain line in FIG.
7 may be formed to have a step. In this case, the thickness of the spacer is increased by the step difference.

The apparatus for molding an optical element shown in FIGS. 2 and 3 is one in which a plurality of pairs of dies are installed in the same molding apparatus, and the upper die 20 is attached to the flange of the upper die 20 by the upper die pressing base 8. Upper mold base 20B by holding down 20F part
Attached to. The upper mold base 20B is connected to the upper cylinder 14. On the other hand, the lower die 10 is supported on the lower die base 10B by the lower die presser base 9.
A spring 6 is installed between the back surface of 0 and the lower die base 10B, whereby the lower die 10 is biased upward. The protruding end is regulated at a position where the flange 10F abuts on the stepped portion of the lower die pressing table 9.

In the molding apparatus of the present invention, the spacer 4 is installed on the flat portion 16 in the peripheral portion of the upper mold 20 and the lower mold 10 to adjust the thickness of the optical element molded product 5. Therefore, when only the molding surface 17 of the upper die 20 is reprocessed and the height dimension becomes short, the spacer 4 can be easily taken out by lifting the upper die 20, and the spacer 4 is cut and By shortening the height dimension,
The size can be easily adjusted. Then, when the flat surface portion 16 of the upper die 20 and the spacer 4 come into contact with each other by the heating and pressing of the molding material, the lower die 10 lowers a little (spring 6).
Will shrink). This lowering amount (spring contraction amount) becomes larger for a set of molds having longer dimensions. This amount can absorb the difference in size between the molds. Even if the height of the mold is different, the space formed by the upper and lower molds and the spacer is not changed. That is, the thickness of the spacer 5 determines the thickness of the molded product 5. Since the mold clamping force is always applied by the spring, the molding is always properly performed.

A concrete example of molding the optical element by the illustrated molding apparatus of the present invention will be described. As shown in FIG. 3, after the preform 13 is placed on the molding surface of the lower die, the annular spacer 4 is placed on the flat surface portion 16 of the lower die 10. After that, the upper mold 20 was lowered by the cylinder 14 to the extent that it did not come into contact with the preform 13, and the quartz tube 11 was heated by the heater 12 while being purged with an inert gas. The temperature was measured by thermocouple 15.

When the temperature reaches 420 ° C., the cylinder 14 is lowered, and at that time, the molding surface 17 of the upper mold 20 first contacts the preform 13, and the preform 13 is crushed and molded, and finally the upper mold 20. The spacer 4 comes into contact with the flat portion 16 of 20. Molding pressure is usually 100 kg /
It should be around cm ² . At this time, the viscosity and molding pressure of the preform 13 and the lower spring 6 of the lower mold 10 are
The flat portion 16 of the is surely contacted with the spacer 4.

When the molding progresses and the spacer 4, the upper die 20, and the die flat portion 16 of the lower die 10 are brought into uniform contact with each other, the spring 6 contracts and the lower die 10 is lowered a little. At this time, even if the height is different for each mold, depending on the amount of expansion and contraction of the spring,
The size of the space formed by the upper and lower molds 20 and 10 and the spacer 4 is always kept constant. Therefore, after the molding is completed, the heater is stopped and cooled, and when the temperature reaches the glass transition temperature of the molding material or less, the pressure is released and the cylinder is raised. A plurality of can be manufactured at one time.

Example 1 Tungsten Carbide WC, which is the base material for the upper and lower molds
Was ground to a desired molding surface with an ultra-precision lathe, and then a diamond paste abrasive was used to surface roughness R _max =
It is polished to 0.02 μm or less, and a platinum film is formed on this surface by sputtering for the purpose of heat resistance, oxidation resistance and wettability to a thickness of 1 μm.
And lower mold 10. Plural sets of these upper and lower molds were set in the same molding apparatus as shown in FIGS. 2 and 3.

A preform 13 (PSK50 manufactured by Sumita Optical Glass Co., Ltd.) was placed on the molding surface 17 of the lower die 10, and a spacer 14 made of SUS304 was placed on the flat surface portion 16 of the lower die 10. After that, the upper mold 2 with the cylinder 14
0 is lowered until it does not come into contact with the preform 13,
Next, the quartz tube 11 was heated by the heater 12 while purging with nitrogen gas.

When the temperature reaches 420 ° C., the cylinder 14 is lowered, the molding surface 17 of the upper mold 20 first contacts the preform 13, and the preform is pressed while molding, and finally the flat surface of the upper mold 20. The part 16 is pressed until it contacts the spacer 4. Molding pressure is about 100 kg / cm ²
And After that, the material was slowly cooled, and when the temperature of the molding part reached 350 ° C., which was below the transition point of the optical element material, the pressure was removed, the cylinder was raised, and after cooling to a temperature at which it could be taken out, the molded product was taken out. It was The obtained molded product is
All were good products with uniform thickness.

[0020]

By using the molding method and apparatus of the present invention,
By providing a flat part on the outer peripheral part of the molding surface of the upper mold and the lower mold, and installing a spacer on the flat part, it is possible to easily adjust the wall thickness of the molded product, and a plurality of pairs of molding metal It is possible to easily obtain a molded product having a uniform thickness even in a molding device in which a mold is installed. When the height of the mold becomes shorter due to the mold regeneration, it can be dealt with by cutting the same spacer, and it is not necessary to prepare a huge number of spacers. In addition, at that time, the spacer can be installed and taken out easily only by raising the upper mold. Further, in a molding apparatus in which a plurality of pairs of molding dies are installed, a spring is installed in at least one of the upper mold and the lower mold to urge the mold in a direction in which the upper mold and the lower mold are close to each other, Even if the height dimension is different for each mold, the dimension difference can be absorbed by the expansion and contraction of the spring, and a molded product having a uniform and uniform thickness can always be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold used for an optical element molding apparatus of the present invention.

FIG. 2 is a cross-sectional view showing a molding portion of an optical element molding apparatus showing an embodiment of the present invention in a state immediately after completion of molding.

3 is a cross-sectional view showing a molding part of the molding apparatus shown in FIG. 1 in a state before molding.

FIG. 4 is a sectional view of a conventional optical element molding apparatus.

[Explanation of symbols]

 1 Base Material 2 Thin Film 4 Spacer 5 Molded Product 6 Spring 8 Upper Mold Holding Base 9 Lower Mold Holding Base 10 Lower Mold 10B Lower Mold Base 11 Quartz Tube 12 Heater 13 Preform 14 Upper Cylinder 15 Thermocouple 16 Flat Surface 17 Molding Surface 20 Upper mold 20B Upper mold base

Claims (7)

[Claims] 1. When molding an optical element by heating and pressing an optical element material between an upper die and a lower die, the peripheral parts of the upper die and the lower die are respectively outside the molding surface of the central portion thereof. 1. A method for molding an optical element, comprising: providing flat portions facing each other, and adjusting a wall thickness of a molded product by disposing a spacer between the flat portions. 2. The method for molding an optical element according to claim 1, wherein a spring for applying an approaching pressure between the upper mold and the lower mold is provided in at least one of the upper mold and the lower mold. 3. The spacer material according to claim ₁ , wherein a material satisfying the relationship of α ₁ > α ₂ is used, where α _{1 is} the coefficient of thermal expansion of the spacer material and α ₂ is the coefficient of thermal expansion of the molding material. Optical element molding method. 4. An apparatus for molding an optical element by heating and pressing an optical element material using a molding die including an upper die and a lower die, wherein the center of each of the peripheral portions of the upper die and the lower die is formed. An apparatus for molding an optical element, characterized in that flat parts facing each other are provided outside a molding surface of the parts, and spacers are provided between the flat parts. 5. A spring for urging the molds in at least one of the upper mold and the lower mold for urging the molds in such a manner that both molds that apply an approaching pressure between the molds are tightened with each other.
A molding device for the optical element described. 6. The material according to claim 4, wherein the spacer material is a material satisfying the relationship of α ₁ > α ₂ when the thermal expansion coefficient of the spacer material is α ₁ and the thermal expansion coefficient of the molding material is α ₂ . Optical element molding equipment. 7. The optical element molding apparatus according to claim 4, 5 or 6, wherein a plurality of pairs of molding dies including an upper mold and a lower mold are installed in one molding device.