JPH0353260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding optical elements such as convex lenses, concave lenses, Fresnel lenses, aspheric lenses, prisms, and filters. The present invention relates to a method of molding an optical element having a predetermined shape and precision simply by applying pressure.

Many optical elements such as lenses, prisms, and filters have conventionally been formed by a method mainly involving polishing of 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 a considerable amount of time and skill.
More advanced polishing techniques were required, and the processing time was also 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, which has been melted and solidified in advance as a material for molding optical elements, heating it to a predetermined temperature to soften it, and then putting it into a mold for processing. This is a method of molding optical elements by pressing. Also, 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, and the molded glass lens is placed inside the mold. A method of molding a glass lens by cooling the glass lens while it is being held is disclosed.

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 involve polishing, and it is possible to mold optical elements more easily in a shorter time than with conventional molding methods that mainly involve polishing. It has now become possible to easily mold optical elements with highly aspherical surfaces.

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 surface of the molded optical element tends to become cloudy, and the optical In terms of physical functions, it was not always possible to obtain sufficient functionality.

This clouding of the functional surface is caused by the fact that during the pressure molding process, the optical element molding material and the surface of the mold in which it is pressure molded come into close contact at high temperatures for a relatively long period of time. The material is fused to the surface of the mold, and when the molded optical element is released from the mold after molding, a minute fused portion of the surface of the material with the mold remains fused to the mold surface. This is caused by defects such as pinholes and minute dents that occur on the molded surface due to molding.

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 apply a thin film that does not cause the above-mentioned fusion with the mold onto the surface of the optical element molding material that will be molded by the mold. The coating prevents fusion between the mold and the molded optical element, and allows the optical element to have a predetermined shape and precision and no clouding on the molded functional surface. It is an object of the present invention to provide a new molding method that allows molding to be performed simply and with good productivity simply by applying pressure.

The above object can be achieved by the following method of the present invention.

That is, in the pressure molding method for optical elements of the present invention, a moldable optical element molding material whose surface on which the functional surface is to be molded is coated in advance with a thin film having a mold release function is placed in a mold. The present invention is characterized by comprising a step of pressurizing the material for molding an optical element using the mold 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, the surface of the optical element molding material on which the functional surface is to be molded is coated with a thin film having a mold release function in advance. .

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 bell gear main body, 2 is a lid, 3 is an upper mold having a surface for molding a first functional surface of an optical element;
4 is a lower mold having a surface for molding the second functional surface of the optical element, 5 is a presser foot for holding and pressing the upper mold 3, 6 is a body mold, 7 is a holder, and 8 is a heating device for heating the inside of the molding device. 9 is a pressure rod for pushing up and pressurizing the lower mold 4; 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, 15 is an inert gas inflow pipe, 17 is an inert gas exhaust pipe, 19 is a temperature sensor, 20
is a water cooling pipe for cooling the inside of the device.

In order to mold a convex lens according to the method of the present invention, first, as shown in FIG. A thin film 21 is coated on surfaces 22a and 22b of the (glass material) 22 on which the functional surfaces are to be molded.

The thin film coated in the method of the present invention mainly protects the functional surface of the optical element molding material during the molding process, and also protects the surface of the film from being exposed to the mold for a relatively long time 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 be fused from the mold. It is provided for the purpose of imparting good mold releasability.

Therefore, the thin film provided in the method of the present invention is uniform on the material for molding optical elements, has sufficient strength as a protective film, is chemically stable, and has good compatibility with the mold. It is formed from a material that can form a continuous coating that does not cause fusion as described above.

As a material for forming such a thin film, any material that can form a thin film that has the above-mentioned characteristics and that will not change in quality or be destroyed during pressure molding as described later can be used. Materials can also be used, such as calcium fluoride, magnesium fluoride, copper, silver, chromium, titanium, cerium, chromium oxide, alumina, germanium, ZnS
etc. can be mentioned.

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 and shape of the material 22, and vapor deposition such as vacuum evaporation, sputtering, plasma CVD, etc. is performed. A predetermined film thickness can be laminated on a predetermined surface of the material 22 by appropriately using various film forming methods such as a method, an impregnation method, or a coating method.

The thickness of the thin film is preferably about 1 nm to 100 nm.

Next, the material 22 provided with the thin film 21 in this manner is placed on the lower mold 4 by opening the lid 2 of the bell gear 1, and then placing the upper mold 3 and closing the lid 2. , and turn on the heater 8.

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 12 is opened to start evacuation, and when the pressure inside the bell gear 1 drops to about 10 ^-2 Torr or less, the valve 12 is closed, and the valve 16 is opened to supply N ₂ gas as an inert gas to the bell gear 1. to be introduced within.

The heater 8 is heated to a temperature at which the glass material 22 can be formed.
When the glass material 22 is heated by the upper mold 3 and the lower mold 4, the air cylinder 10 is operated to push up the lower mold 4 with a predetermined pressure via the pressure rod 9, and the glass material 22 is pressurized by the upper mold 3 and the lower mold 4 to form the glass material. do.

Finally, while controlling the heater 8, the inside of the bell gear 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 bell gear, and the lid 2 is opened. When the internal pressure has risen to a level where it can be used, 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.

Finally, from the functional aspect of this convex lens 32, the thin film 21 is peeled off by finishing polishing with a nonwoven fabric or pickling, etc., and the convex lens 32 as shown in FIG.
Get 2. Note that the thin film 21 may be formed of metal, for example, and the functional surface may be used as a mirror surface.
If the material is used as a functional component as it is, this peeling operation is not necessary. On the functional surface of the convex lens 32 obtained, no microscopic defects such as pinholes or dents, which have been problems in the past, as described above, were observed, and therefore there was no clouding on the functional surface, and the convex lens 32 It has a predetermined shape and precision.

On the other hand, since the thin film 21 has good releasability from the mold, the molding surface of the mold is maintained in the state before the molding process, and can be used again in good condition.

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 by replacing the molding upper mold 3 and lower mold 4 with upper molds and lower molds corresponding to an optical element having the desired shape and precision. , concave lenses, Fresnel lenses, aspheric lenses, prisms, filters, and other optical elements can be molded.

According to the optical element molding method of the present invention as described above, by providing a thin film in advance on the molded surface of the optical element molding material, the functional surface of the optical element is protected throughout the molding process, and the conventional processing method is improved. It is possible to prevent fusion in minute parts due to high-temperature adhesion between the molded surface of the material and the molding mold, which was observed in pressure molding, and it is possible to release the molded optical element from the mold. sex has improved.

Therefore, the functional surface of the optical element molded by the optical element molding method of the present invention is free from minute defects such as pinholes and dents, has a predetermined shape and precision, and has no cloudiness. It is possible to obtain an optical element having a functional aspect that does not exist.

Further, by providing a thin film having a mold release function on the optical element molding material, it is possible to significantly improve productivity and improve the performance of the molded lens. That is, since the material is provided with a thin film having a mold release function, there is no need to perform any treatment to obtain a mold release effect, such as applying a mold release agent to the mold. Therefore, as in the case of applying a mold release agent to a mold, it is necessary to apply a mold release agent to the mold before each molding, and then perform the complicated work of removing the remaining mold release agent from the mold after molding. do not have. Moreover, by providing the material with a thin film having a mold release function, the working process can be simplified, and the process of cleaning the mold becomes unnecessary, so that the working time (molding time) can be shortened.

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

EXAMPLE First, as shown in FIG. 2, a thin film of magnesium fluoride ( nd=
20nm, where n = refractive index of magnesium fluoride,
d=film thickness).

Next, the material 22 with the thin film of magnesium fluoride provided on the surface to be formed is placed between the molybdenum upper mold 3 and lower mold 4 of the molding mold of the apparatus shown in FIG. water was run through the tank, and the heater 8 was energized.

At this time, the inert gas valves 16 and 18 and the exhaust valve 12 were closed, and the oil diversion pump 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 mm, a radius of curvature of 20 mm, and the surface accuracy and shape are Newton rings, power within 3 lines, irregularity within 1 line, center. Line average surface roughness (JIS
B0610-1970) Concave mirror finish within 0.02μ. The surface forming the functional surface of the lower mold 4 was mirror-finished to have an outer diameter of 17 mm, a radius of curvature of 55 mm, and a concave surface with the same surface precision as the upper mold 3.

Next, the valve 12 is opened to start evacuation, and when the pressure inside the bell gear 1 drops to about 10 ^-2 Torr or less, the valve 12 is closed, and the valve 16 is opened to supply N ₂ gas as an inert gas to the bell gear 1. to be introduced within.

When the glass material 22 is heated to a moldable temperature (580°C) by the heater 8, the air cylinder 10 is activated and the air is heated through the pressure rod 9.
The lower die 4 was pushed up with a pressure of 10 kg/cm ² 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 bell jar 1 is gradually cooled down for one hour, and when it has cooled to below 200°C, the valve 16 is closed, the valve 13 is opened to introduce air into the bell jar, and the lid 2 is closed.
When the internal pressure has risen to the point where it is possible to open the lens, open the lid 2, remove the presser foot 5, and take out the molded convex lens 32, which already has thin films on two functional surfaces, as shown in FIG. Ta.

Finally, the thin film 21 was removed from the convex lens 32 by final polishing using a nonwoven fabric.

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

When the surface of the functional surface of the convex lens obtained in this comparative example was observed using a scanning electron microscope with a magnification of 3750 times, fine pinholes and depressions were observed all over 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 product.

[Brief explanation of drawings]

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.
A schematic cross-sectional view of an example of a material for molding an optical element used in the method of the present invention. FIG. , FIG. 4 is a schematic cross-sectional view of an example of an optical element molded by the method of the present invention. 1: Belgear 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, 5: presser foot for holding and pressing the upper mold 3, 6: body mold, 7: holder, 8: heating inside of the molding device 9: Pressure rod for pushing up and pressurizing the lower die 4, 10: Air cylinder for operating the pressure rod 9, 11: Oil diversion pump, 12, 13, 14, 16, 18: Valve, 15: Inert gas inflow pipe, 17: Inert gas exhaust pipe, 19: Temperature sensor, 2
0: Water cooling pipe for cooling the inside of the device, 21: Thin film, 22: Material for molding optical elements, 22a, 22
b: Surface on which the functional surface is 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 in advance with a thin film having a mold release function is placed in a mold, and the mold is used to mold the optical element molding material. 1. A method for molding an optical element, comprising the steps of molding a functional surface of the optical element by applying pressure, and removing the thin film from the molded functional surface.