JPH06144849A - Apparatus for forming optical element, its production and method for forming optical element - Google Patents

Abstract

PURPOSE:To provide a method for forming an optical element, almost free from occurrence of defective products by developing a forming apparatus of the optical element capable of inexpensively preventing fusion of a drum type inner surface and an optical element material and its production. CONSTITUTION:This apparatus for forming an optical element is characterized by providing a carbonaceous thin film 5 on the inner surface of a drum mold 4. An optical element 7 is placed among an upper mold 1 and a lower mold 2 and a drum mold 4 having a carbonaceous thin film 5 inside and the optical element material 7 is heated and softened and formed under pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding apparatus for molding an optical element by heating and softening an optical element material and press-molding it between a pair of molding dies and barrel dies, a method of manufacturing the device, and an optical element. Molding method.

[0002]

2. Description of the Related Art To manufacture an optical element,
Conventionally, an effective molding surface according to the design of the optical element is formed on the molding die, the optical element material is heated and softened, and pressed between a pair of molding die composed of an upper die and a lower die and a body die to form an effective molding surface. There is known a press molding method for molding into a predetermined shape according to the above.
Since the protective film for the purpose of oxidation resistance and wettability is provided on the effective molding surface of this molding die, fusion does not occur between the die and the optical element material during molding, but the inner surface of the barrel die In the case of a molding method in which the outer diameter of the optical element is regulated by, the inner surface of the barrel and the optical element material come into contact with each other under pressure at a high temperature, so fusion occurs and the molded optical element is removed. However, there is a problem that it becomes impossible or a chip occurs in the outer diameter portion. In order to avoid the above problems, the same protective film as that of the molding die may be provided on the inner surface of the barrel die, but as the protective film of the molding die, an expensive material such as a platinum film is conventionally used, so that the cost is reduced. As it gets higher,
It is difficult to provide this type of protective film on the elongated inner diameter of the barrel shape.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to prevent fusion between the inner surface of the barrel die and the optical element material at the time of molding at low cost, and to improve the yield, and an optical element molding apparatus. It is an object of the present invention to develop a manufacturing method and to provide a molding method capable of efficiently manufacturing a high quality optical element at low cost.

[0004]

SUMMARY OF THE INVENTION The present invention has found that a carbonaceous thin film can be easily and inexpensively formed on a slender inner diameter portion of a barrel shape and can prevent fusion of optical element materials. Based on this, the above-mentioned object is achieved. That is, the molding apparatus of the optical element of the present invention is a molding apparatus for molding the optical element by heating and softening the optical element material and press-molding between the pair of molding dies and the barrel die, at least the inner surface of the barrel die, It is characterized in that a carbonaceous thin film is provided in a portion that comes into contact with the optical element material during molding.

As described above, the apparatus for molding an optical element of the present invention is provided with a carbon thin film on at least a portion of the inner surface of the barrel die which comes into contact with the optical element material during molding. That is, the carbonaceous thin film may be provided only on a portion that comes into contact with the optical element material during molding, or may be provided on the periphery including the portion or on the entire inner surface of the barrel mold. The thickness of the carbon thin film is preferably 0.01 μm to 2.00 μm. If this film thickness is less than 0.01 μm, fusion to the barrel die cannot be avoided. On the other hand, when it exceeds 2.00 μm, the carbonaceous substance is likely to fall from the inner diameter of the barrel mold, foreign matter may be mixed into the molded product, and it takes time to adhere the foreign matter.

In the present invention, the carbonaceous thin film includes not only a thin film made of pure carbon but also a thin film made mainly of carbon. The method of forming such a carbonaceous thin film is not particularly limited, and various methods can be adopted, for example, carbon black, graphite,
Apply oil (various machine oils, cooking oil, etc.) and other organic substances with a dropper, a thin brush, etc. by any method by vaporizing by rubbing against charcoal, rubbing, etc., and heat this to soot A method of burning a material that generates soot by burning, such as candles, wood, etc., can be considered. The carbonaceous thin film thus formed gradually peels off as the molding is repeated, so that the thickness of the thin film is about 1000.
It is preferable to renew the carbonaceous thin film once per molding.

The method of molding an optical element according to the present invention is characterized by molding the optical element using the above-mentioned molding apparatus according to the present invention. According to this method, since the optical element is not fused to the barrel die, it can be easily taken out without causing defects such as chipping. Some carbonaceous material may adhere to the outer diameter portion (edge portion) of the optical element molded by this method, which can be easily removed by ultrasonic cleaning or wiping.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to the drawings. FIG. 1 is a schematic explanatory view showing a state of a molding portion before press molding using an optical element molding apparatus according to an embodiment of the present invention. In FIG. 1, a protective film 3 is applied to the effective molding surfaces of the base materials of the upper mold 1 and the lower mold 2 for the purpose of improving oxidation resistance and wettability. The base material of the molding die is not particularly limited and various materials can be used, and examples thereof include those made of tungsten carbide, silicon carbide, silicon nitride, chromium oxide and the like. These base materials are ground to a desired aspherical surface by ultra-precision machining, and then the surface roughness is R using a diamond paste polishing material.
_The surface is polished so that _max = 0.02 µm or less.
The protective film 3 is made of a noble metal, a ceramic, or a mixture of a noble metal and a ceramic, using a sputtering method, an ion plating method, a chemical vapor deposition (CV) method.
It is formed by any method such as the D) method. Here, examples of the noble metal include platinum, rhodium, and gold, and examples of the ceramic include titanium nitride, titanium carbide, silicon nitride,
Examples thereof include silicon carbide and alumina.

A carbonaceous thin film 5 is formed on the inner surface of the barrel die 4. Reference numeral 6 is a thickness adjusting member for the molded product. The method of forming the carbon thin film 5 is as described above, and will be specifically described in the following examples. After the lower mold 2 and the barrel mold 4 are combined, the optical element material 7 is placed on the lower mold 2, the upper mold 1 is set, and the process of heating the optical element material is started.

Next, the state of the molding portion during press molding will be described with reference to FIG. The optical element material 7 placed between the upper mold 1 and the lower mold 2 as shown in FIG. 1 and the barrel mold 4 is heated and softened by the heater 8 as shown in FIG. The heating temperature is measured by the thermocouple 9. At high temperatures,
Atmospheric gas supply port 1 to prevent deterioration of mold members due to oxidation
An inert gas such as nitrogen gas can be supplied from zero. When the optical element material 7 is softened, the cylinder 11 is lowered and pressed with a desired pressure to be molded. After that, the molded product can be taken out with good releasability by slowly cooling and removing the pressure when the temperature of the molded portion becomes lower than the transition point of the optical element material.

Example 1 The upper mold 1 and the lower mold 2 shown in FIG. 1 were prepared by grinding the base material tungsten carbide WC into a desired aspherical shape by an ultra-precision lathe, and then using a diamond paste abrasive to surface the surfaces. Polishing is performed so that the roughness R _max = 0.02 μm or less. Next, a platinum film 3 having a film thickness of 1 μm was formed on the surface of the base material of the molding surface by sputtering for the purpose of resistance to oxidation and wettability to obtain a molding die. The body die 4 is manufactured by using the same material WC as the forming die base material. As shown in FIG. 3, the graphite rod 12 is pressed against the inner surface of the body die 4 to form the body die 4 as shown by an arrow. The carbonaceous thin film 5 having a film thickness of 0.1 μm was formed by rubbing by rotation and vertical movement of the graphite rod 12. Compressed air was blown onto the inner surface of the barrel mold to blow off excess graphite so that excess graphite did not enter the optical element material 7 as foreign matter.

At the time of setting, first, the lower mold 2 and the barrel mold 4 are combined, and spherical F2 glass (made by OHARA CORPORATION) is placed on the lower mold 2 as the optical element material 7, and the upper mold 1 is placed on the barrel mold 4. It was inserted inside and gently applied to the glass. In this state, it was heated to 500 ° C. by the heater 8. The temperature is
It was measured with a thermocouple 9. Nitrogen gas (N ₂ ) was flown from the atmosphere gas supply port 10 in order to prevent deterioration of the mold and the molded member due to oxidation at high temperature. When the temperature reached 500 ° C., the cylinder 11 was lowered, and F2 glass as an optical element material was press-molded at a pressure of about 100 kg / cm ² . The wall thickness was adjusted by the wall thickness adjusting member 6.

After that, the mixture was gradually cooled, and when the temperature of the molding part fell below the transition point of the optical element material (400 ° C.), the pressure was removed,
The cylinder 11 was raised, and the molded product was extracted from the upper mold and the barrel mold. Since the molded lens did not cause fusion on the molding surface and the contact surface with the barrel mold, it could be easily taken out only by reversing the molding block with the upper mold removed. Although some graphite was sometimes attached to the edge portion of the molded lens, this could be easily removed during ultrasonic cleaning. After forming the carbonaceous thin film, 500 lenses were continuously molded, but in the meantime, there was never a case where the lens could not be taken out or was forcibly taken out to cause a chip.

Example 2 As shown in FIG. 4, mechanical oil was dripped on the inner surface of the barrel die 4 using a dropper 13 and applied. The oil-coated barrel was left in a heating furnace at 1000 ° C. for 1 hour to decompose and soot the oil. As a result, the film thickness is about 0.3 on the inner surface of the barrel mold.
It was possible to form a carbon thin film of μm. Except for using this barrel mold, the same operation as in Example 1 was repeated to obtain 500
Although individual lenses were molded, during that time, it never happened that they could not be taken out or were forcibly taken out to cause chipping.

Example 3 As shown in FIG. 5, a flame of a candle 14 was brought close to the inner surface of the barrel so that a soot was deposited on the inner surface of the barrel to form a carbon thin film having a thickness of about 0.3 μm. We were able to. Except for using this barrel mold, 500 lenses were continuously molded by the same operation as in Example 1, but during that time, it was impossible to take out or forcibly take out a lens to cause a chip never occurred. It was

[0016]

According to the present invention, it is possible to obtain an optical element molding apparatus in which fusion between the inner surface of the barrel die and the optical element material is extremely easily and surely prevented during molding of the optical element. In this molding apparatus, the fusion preventing means can be provided without requiring an expensive material, and can be manufactured at low cost by a simple operation. Therefore, by using the molding apparatus of the present invention, it is possible to efficiently provide a high-quality optical element with extremely few defective products, without damaging the barrel mold.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a state of a molding portion before press molding using an optical element molding apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing a state of a molding section during press molding using the molding apparatus shown in FIG.

FIG. 3 is a schematic explanatory view showing one embodiment of a method for forming a carbonaceous thin film on the inner surface of a barrel mold.

FIG. 4 is a schematic explanatory view showing another embodiment of a method of forming a carbonaceous thin film on the inner surface of a barrel mold.

FIG. 5 is a schematic explanatory view showing another embodiment of a method of forming a carbonaceous thin film on the inner surface of a barrel mold.

[Explanation of symbols]

 1 Upper mold 2 Lower mold 3 Protective film 4 Body 5 Carbonaceous thin film 6 Thickness adjusting member 7 Optical element material 8 Heater 9 Thermocouple 12 Graphite rod 13 Dropper 14 Candle

Claims (7)

[Claims] 1. A molding apparatus for molding an optical element by heating and softening an optical element material and press-molding the optical element material between a pair of a molding die and a body die, wherein at least the inner surface of the body die is in contact with the optical element material at the time of molding. An apparatus for forming an optical element, characterized in that a carbonaceous thin film is provided in a portion to be formed. 2. The thickness of the carbonaceous thin film is from 0.01 μm to 2.
The apparatus for molding an optical element according to claim 1, which has a diameter of 00 μm. 3. A manufacturing apparatus for an optical element according to claim 1, wherein a carbon thin film is formed on at least a portion of the inner surface of the barrel die which is in contact with the optical element material during molding. Production method. 4. A carbonaceous thin film having a thickness of 0.01 μm to 2.
The method for manufacturing an optical element molding apparatus according to claim 3, wherein the optical element molding apparatus has a thickness of 00 μm. 5. The formation of a carbonaceous thin film is carried out by rubbing carbon black, graphite, charcoal or the like by rubbing or vapor deposition, or by applying oil or another organic substance and subjecting it to high temperature soot. The method for manufacturing an optical element molding apparatus according to claim 3, which is performed. 6. The method for manufacturing an optical element molding apparatus according to claim 5, wherein the carbonaceous thin film is formed by burning a material that generates soot by burning, such as candles and wood. 7. A method of molding an optical element, which comprises molding an optical element using the molding apparatus according to claim 1.