JPS63222023A - Production of optical element - Google Patents

Abstract

PURPOSE:To readily produce an optical element such as lens or prism having concave and convex shape or non-spherical surface at a short time in good productivity, by arranging a raw material for optical element molding coated with carbon thin film into a mold for molding and molding the raw material under pressure. CONSTITUTION:Chemically stable carbon thin film 21 having excellent uniformness and strength and free from melting with a mold for molding is applied to faces 22a and 22b for molding functional face of a glass raw material for optical element molding formed to a prescribed shape by treatment such as grinding, polishing or melt solidification so as to have 1-100nm thickness by spattering, etc. Then the carbon thin film 21-coated raw material 22 is arranged in the mold for molding and heated and molded under pressure and then subjected to annealing treatment in order to burn and remove the carbon thin film to provide the desired optical element (e.g. convex lens) 32.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for manufacturing optical elements such as convex lenses, concave lenses, Fresnel lenses, aspheric lenses, prisms, and filters.

[Conventional technology]

Many optical elements such as lenses, prisms, and filters are
Conventionally, molding has been done mainly by polishing materials such as glass. However, such a molding method that mainly involves polishing requires a considerable amount of time and skill, and in particular, molding an aspherical lens by polishing requires even more advanced polishing technology. In addition, the processing time becomes even longer, making it extremely difficult to produce in large quantities in a short period of time.

Therefore, attention is being paid to a method of simply and efficiently molding optical elements such as lenses by simply inserting and arranging an optical element molding material into a pair of molds and pressurizing the material.

As a typical pressure molding method, a reheat press method can be mentioned as a method capable of molding a highly accurate optical element.

The reheat press method involves measuring out the required amount of a glass material, such as a glass material, that has been melted and solidified in advance, heating it to a predetermined temperature to soften it, and then putting it into a mold. This is a method of molding optical elements by applying pressure. In addition, in JP-A-47-11277, a glass material that has been melted and solidified in advance is put into a mold, the inside of the mold is heated, and when the glass material becomes moldable, it is pressurized. A method is disclosed in which a glass lens is molded by cooling the glass lens while it is held in a mold.

By applying such a pressure molding method, it is possible to mold optical elements more easily and in a shorter time than with conventional molding methods that mainly rely on polishing, and it is especially suitable for molding that is difficult to mold. It has become possible to easily mold optical elements with aspherical surfaces.

[Problems to be solved by the invention]

However, when an optical element is molded using a pressure molding method, it is possible to obtain a predetermined precision in the shape of the molded optical element, but the functional ik of the molded optical element is
It was easy to cause cracks and fusion, and it was not always possible to obtain a sufficient optical function.

This functional sac is because during the pressure molding process, the optical element molding material and the surface of the mold that pressure molds it come into close contact at high temperature for a relatively long period of time. The material and the surface of the mold are fused together, and when the optical element molded from the mold is modeled after molding, the minute fused portion of the material surface with the mold remains fused to the mold surface. This is caused by defects such as pinholes and minute dents that occur on the molding surface.

Since these defects occur on the pressure-molded surface of the optical element regardless of the type of mold material, they have become an unavoidable problem in the pressure-molding method.

The present invention was made in view of these problems, and its purpose is to prevent the fusion of the mold and the molded optical element, to have a predetermined shape and precision, and to create a cloudy pattern on the molded functional surface. An object of the present invention is to provide a method for manufacturing an optical element that can be easily and efficiently molded by simply pressurizing an optical element molding material with a molding die.

[Means for solving problems]

That is, in the pressure molding method for optical elements of the present invention, a material for molding an optical element in a moldable state, the surface of which is to be molded with a functional surface coated with a thin carbon film, is placed in a mold, and then the material is molded using a nuclear mold. The method is characterized in that it includes a step of pressurizing the optical element molding material to mold a functional surface of the optical element.

In the method of the present invention, at a desired stage before pressure-molding the optical element, a thin carbon film is coated on the surface of the optical element molding material on which the functional surface is previously molded.

Hereinafter, the method of the present invention will be explained in detail with reference to the drawings, taking as an example the molding of a convex lens made of glass.

FIG. 1 is an example of a pressure molding apparatus for optical elements that can be used in the method of the present invention.

1 is a Pelger main body, 2 is a lid, 3 is an upper mold having a surface for molding the first functional surface of the optical element, and 4 is a lower mold having a surface for molding the second functional surface of the optical element. A mold, 5 is a presser for holding and pressing the upper mold 3, 6 is a mold, 7 is a holder, 8 is a heater for heating the inside of the molding device, 9 is a pressurizer for pushing up and pressurizing the lower mold 4 Rod, 10 is an air cylinder for operating the pressure rod 9, 11 is an oil diversion pump, 12.13.14.16.18 is a valve, 1
5 is an inert gas inflow pipe, 17 is an inert gas exhaust pipe, 19 is a temperature sensor, and 20 is a water cooling pipe for cooling the inside of the apparatus.

To mold a convex lens according to the method of the present invention, first, as shown in FIG. 2, a material (glass The carbon thin film 21 is coated on the surfaces 22m and 22b of the raw material 22 on which the functional surfaces are to be formed.

The carbon thin film coated in the method of the present invention mainly protects the surface on which the functional side of the optical element molding material is molded during the molding process, and also protects the surface of the film from being relatively close to the mold at high temperatures. Even if they are in close contact for a long period of time, there will be no fusion in the minute parts of the contact surface with the mold, which was observed with the glass materials mentioned above, and the molded optical element will not come out of the mold. This is provided for the purpose of providing a good template.

Therefore, the carbon thin film provided in the method of the present invention is
Forms a continuous film on the optical element molding material that is uniform, has sufficient strength as a protective film, is chemically stable, and does not cause the aforementioned fusion with the mold. It is formed from a carbon material that can be used. The carbon thin film can be removed, for example, by burning it in an annealing process after molding.

In order to coat such a thin film 21 on a predetermined surface of the material 22, the material for forming the thin film as described above is selected according to the material, shape, etc. of the material 22, and vapor deposition such as vacuum evaporation, sputtering, plasma CVD, etc. is performed. A predetermined film thickness can be deposited on a predetermined surface of the material 22 by appropriately using various film forming methods such as a method, an impregnation method using a carbon powder dispersion, or a coating method.

The thickness of the carbon thin film is preferably about 1 nm to 1100 nm.

Next, the material 22 provided with the thin film 21 in this manner is placed on the lower mold 4 with the lid 2 of the Pelger 1 placed, the upper mold 3 is placed, the lid 2 is closed, and the water cooling pipe 20 Water is flowed through and the heater 8 is energized.

At this time, the inert gas valves 16 and 18 and the exhaust valve are closed. Note that the oil diversion pump 11 is always operated.

Next, the valve f12 is opened to start evacuation, and when the pressure inside the Pel jar 1 becomes approximately 1O-2 Torr or less, the valve 12 is closed, and the pallet f16 is opened to supply N2 gas as an inert gas into the Pel jar 1. to be introduced.

When the glass material 22 is heated by the heater 8 to a temperature at which it can be molded, the air cylinder 10 is activated to push up the lower mold 4 with a predetermined pressure via the pressure rod 9, and the glass material 22 is moved to the upper mold 3. Pressure is applied and molded using the lower die 4.

Finally, while controlling the heater 8, the inside of the Pell Jar 1 is gradually cooled, and when it has cooled to a predetermined temperature, the valve 16 is closed, the valve 13 is opened to introduce air into the Pell Jar, and the lid 2 is opened. When the internal pressure has risen to a level where it is possible to do so, the lid 2 is opened, the presser foot 5 is removed, and the molded convex lens 32 as shown in FIG. 3, which has already been provided with thin films on two functional surfaces, is taken out. Thereafter, the convex lens 32 is annealed to ensure its optical properties.
At this time, the carbon thin film 21 burns and disappears, so that a convex lens 32 as shown in FIG. 4 is obtained.

Further, for example, the carbon thin film 21 can also be peeled off by a method of finish polishing using a nonwoven fabric. Obtained convex lens 3
On the surface of the functional surface of No. 2, there are no microscopic defects such as pinholes or dents, which have been problems in the past, as described above, and therefore the functional surface is not sound. It has precision.

In addition, the operating conditions such as the pressure during molding in the above process, the cooling rate and time after pressure molding, and the temperature at which the molded optical element is taken out depend on the material of the optical element molding material used. , can be appropriately selected depending on the precision of the optical element to be molded.

In this example, a convex lens was molded by the method of the present invention, but the upper and lower molds 3 and 4 were replaced with upper and lower molds compatible with an optical element having the desired shape and precision. By this, optical elements such as concave lenses, Fresnel lenses, aspheric lenses, prisms, and filters can be molded.

According to the method for manufacturing an optical element of the present invention as described above, by providing a thin film in advance on the molded surface of the material for molding an optical element, the functional surface of the optical element is protected throughout the molding process,
In addition, it is possible to prevent fusion in minute parts due to high temperature adhesion between the molding surface of the material and the molding mold, which was observed in conventional pressure molding methods, and it is possible to prevent the molded optical fibers from forming from the mold. The patternability of the element has been improved.

Therefore, the functional surface of the optical element molded by the optical element manufacturing method of the present invention is free from minute defects such as pinholes and dents, has a predetermined shape and precision, and has a t9
It is possible to obtain an optical (10) element consisting of a functional surface free of .

〔Example〕

Hereinafter, the method of the present invention will be explained in more detail using Examples.

Example 1 First, as shown in FIG. 2, a carbon thin film (film thickness 2
0 nm) was formed.

Next, the material 22 with the carbon thin film provided on the surface to be formed is placed in the first
It was placed between the upper mold 3 and the lower mold 4 made of molybdenum of the molding mold of the apparatus shown in the figure, water was flowed through the water cooling/heating 20, and the heater 8 was energized.

At this time, the inert gas pulps 16 and 18 and the exhaust pulp 12 were closed, and the oil diversion bong 7°11 was always operated.

The surface forming the functional surface of the optical element of the upper mold 3 has an outer diameter of 17 m, a radius of curvature of 20 IiI, and a Newton's ring in terms of surface precision and shape. Line average surface roughness JIS B0610-19
70) The concave surface was processed to within 0.02μ. The surface forming the functional surface of the lower mold 4 has an outer diameter of 17 m1 and a radius of curvature of 5.
The mold was mirror-finished to a concave shape with a size of 5 fl and a surface precision similar to that of the upper mold 3.

Next, the pulp 12 is opened to start evacuation, and when the pressure inside the Pel Jar 1 becomes approximately 10 Torr or less, the valve 12 is closed, and the valve 16 is opened to supply N2 gas as an inert gas into the Pel Jar 1. to be introduced.

When the glass material 22 is heated to a moldable temperature (600°C) by the heater 8, the air cylinder 1
0 was activated, the lower die 4 was pushed up with a pressure of 10 Kf/n'' via the pressure rod 9, and the material 22 was pressurized by the upper die 3 and the lower die 4 for 5 minutes.

Finally, while controlling the heater 8, the inside of the Pelger 1 is
The pulp 16 is gradually cooled over a period of time, and when it has cooled to below 200°C, the pulp 16 is closed, the nozzle 13 is opened to introduce air into the pellet jar, and when the internal pressure rises to the extent that the lid 2 can be opened, the pulp 16 is closed. The lid 2 was opened, the presser foot 5 was removed, and the molded convex lens 32 as shown in FIG. 3, which had already been provided with thin films on two functional surfaces, was taken out.

Finally, the carbon thin film 21 was removed by performing a predetermined annealing process.

When the surface of the functional surface of the obtained convex lens 32 was observed using a scanning electron microscope with a magnification of 3750 times, no minute defects such as pinholes or dents were observed on the functional surface, and therefore there was no cyst, and the convex lens 32 was a lens having a shape and precision corresponding to the shape and precision of a surface forming a functional surface of a predetermined mold.

Comparative Example 1 For comparison, a convex lens was pressure molded in the same manner as in the previous example except that no carbon thin film was provided.

Regarding the convex lens obtained in this comparative example, when the surface of the formed functional surface was observed using a scanning electron microscope with a magnification of 3750 times, it was found that there were fine pinholes and depressions on the surface of the functional surface. As a result, the functional aspect of the lens obtained in this comparative example was cloudy, and did not satisfy the precision and quality required as a product13).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing essential parts of an example of an optical element molding apparatus used in the method of the present invention, and FIG. 2 is a schematic diagram of an example of a material for molding optical elements used in the method of the present invention. cross section,
FIG. 3 is a schematic cross-sectional view of an example of an optical element having a carbon thin film on its functional surface formed by the method of the present invention, and FIG. 4 is a schematic cross-sectional view of an example of an optical element formed by the method of the present invention. FIG. 1: Perger body, 2: Lid, 3: Upper mold having a surface for molding the first functional surface of the optical element, 4: Lower mold having a surface for molding the second functional surface of the optical element. Mold, 5: Presser foot for holding and pressing the upper mold 3, 6: Mold,
7: Holder, 8: Heater for heating the inside of the molding device, 9: Pressure rod for pushing up and pressurizing the lower mold 4, 10: Air cylinder for operating the pressure rod 9, 11: Oil lamp Diversion pump, 12.13.14.16.18: Valve, 15: Inert gas inflow nozzle, 17: Inert gas exhaust pipe, 19: Temperature sensor, 20: Water cooling nozzle for cooling the inside of the device 4, 21: Carbon thin film, 22: Optical element molding material, 22a, 22b, surfaces on which bifunctional surfaces are molded, 32: Molded optical element.

Claims (1)

[Claims] (1) A moldable optical element molding material whose surface on which the functional surface is to be molded is coated with a carbon thin film in advance is placed in a molding mold, and the optical element molding material is pressurized by the mold. 1. A method of manufacturing an optical element, comprising the step of molding a functional surface of the optical element.