JPH0360435A - Production of optical glass element - Google Patents

Abstract

PURPOSE:To obtain an optical glass element which is free from surface blemish with high precision and good productivity at a low cost by thermally softening a specified glass gob with a heated working jig, thermally pressing and molding the obtained molding body of optical glass with a mold for pressing. CONSTITUTION:Molten glass 14 consisting of SiO2 and BaO, etc., is melted at about 1200 deg.C and dropped on a first heated working jig 24 bad in wettability to glass through a nozzle 12 in the atmosphere such as gaseous N2. Then a second heated working jig 16 described hereunder is stuck to this glass 14. Thereafter the jig 16 is inverted by an arm 25 and this glass 14 is placed on the jig 16. This jig 16 is good in wettability to glass and the optical surface is coated by noble metal such as Ta, Re. Then glass 14 is thermally deformed at about 780 deg.C for 20 minutes by the jig 16 and thereafter pressed at about 30kg/cm<2> at about 680 deg.C for about 2 minutes by a mold 20 for press-molding to obtain an optical glass element 22. Then the element 22 is slowly cooled at about 400 deg.C and taken out from a takeout 23. Thereafter it is manufactured and worked to produce the optical glass element wherein the surface roughness (RMS) of a press-molded surface has an optical specular surface of about 20Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to optical glass elements such as high-precision optical glass elements such as lenses and prisms, and optical glass molded bodies used as materials for reheat brace TC type optical glass elements. Regarding the manufacturing method.

2. Description of the Related Art In recent years, there has been a trend toward aspheric optical glass lenses, which can simultaneously simplify the lens structure of optical equipment and reduce the weight of the lens portion. In manufacturing this aspherical lens, processing and mass production are difficult using the polishing method, which is a conventional optical lens manufacturing method, and a molding method using a mold is considered to be promising.

The molding method using this mold involves placing aluminum hydroxide on a mold that has been finished to the desired surface quality and precision in advance.
In this method, a lump of optical glass is heat-molded in a state in which a mold release agent such as magnesium carbonate or carbon is coated or coated, or a lump of optical glass in a molten state is heat-molded. (For example, Special Publication No. 54-60312
Problems to be Solved by the Invention In the case of optical glass elements such as aspherical lenses and prisms, the surface is required to be free from defects or adhesion of mold release agents, and to have a surface roughness and surface precision. Optical glass elements and optical glass molded bodies used as raw materials for reheat press molding of optical glass elements have become very expensive.

In other words, it is necessary to perform polishing or etching treatment to make the surface of the optical glass molded body defect-free (for example, a mirror surface with a surface roughness of 0.005 microns or less in RMS), and the optical glass molded body is expensive. has become,
There has been a strong desire to develop a method that can produce high-precision optical glass moldings at low cost.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention produces a glass gob by receiving molten glass in a non-oxidizing atmosphere using a first heat processing jig that does not have an approximate shape to a desired optical glass element. a step of inverting and replacing the glass gob and the second thermal processing jig with the glass gob adhered to a second thermal processing jig having a shape similar to that of the desired optical glass element; A method for producing an optical glass element, which includes the steps of: producing an optical glass molded body using the surface tension of the glass gob that has been thermally softened with a heat processing jig; and heating and press-molding the optical glass molded body with a press molding die. This is what we provide.

Since the molten glass at high temperature is in an extremely active state chemically, it caused great damage to the thermal processing jig and reacted or fused with the optical glass. Although it is effective to use the thermal processing jig without heating it to prevent this, large wrinkle-like defects due to thermal contraction occur on the contact surface of the glass gob in contact with the thermal processing jig. On the other hand, the surface of the glass gob that was not in contact with the heat processing jig was a very smooth surface.

In order to remove wrinkle-like defects on the surface of the glass gob in contact with the thermal processing jig, the molten glass is applied to the first thermal processing jig, which does not have an approximate shape to the desired optical glass element, and then the desired optical glass element is applied to the smooth surface of the glass gob. A second thermal processing jig having an approximate shape is brought into contact with the optical glass element, and the glass gob is attached to the second thermal processing jig. inverting the second heat processing jig with the glass gob attached to the second heat processing jig to stably replace the glass gob from the first heat processing jig to the second heat processing jig; Using a heated second thermal processing jig, the glass gob with its wrinkled side facing up is subjected to large deformations due to the surface tension of the glass.

Further, by heating and press-molding this optical glass molded body using a press mold, an optical glass element with no defects on the surface can be manufactured.

The first heat processing jig that receives the molten glass directly is made of materials that have poor wettability with the molten glass and have excellent mold release properties, such as carbon, boron nitride, aluminum nitride, chromium nitride, and stainless steel. There is. In addition, the thin film that coats the second heat processing jig and the press molding die is a precious metal that reacts with or slightly adheres to the optical glass in a non-oxidizing atmosphere.

It is preferable to use tungsten, tankle, rhenium, hafnium alone or an alloy thereof.

In the present invention, the non-oxidizing atmosphere in which the optical glass and these thin films do not react or fuse together is nitrogen, argon,
Inert gases such as helium, and these inert gases with hydrogen or -carbon oxide.

Carbon oxides of carbon dioxide, methane, ethane ethylene,
Hydrocarbons such as toluene, halogenated hydrocarbons such as trichloroethylene and trichlorotrifluoroethane, alcohols such as ethylene glycol and glycerin, F-
It is a mixture of fluorocarbons such as 113 and F-11 as appropriate.

These atmospheres are appropriately selected depending on conditions such as the composition of the optical glass, the composition of the thin film coated on the thermal processing jig, the temperature and time of thermal deformation, the temperature and time of press molding, and the shape of the optical glass molded body.

Example An embodiment of the present invention will be described below based on the drawings.

Example 1 FIG. 1 is a sectional view of a first thermal processing jig, a second thermal processing jig, and a press molding die used in the present invention. Carbon was used as the first heat processing jig and processed into a flat shape. Cemented carbide (WC-5TiC) is used as the base material of the second heat processing jig.
-8Co) with a concave optical surface 1 with a radius of curvature of 15
was formed. This optical surface 1 was further lapped using ultrafine diamond powder, and the surface roughness (RMS) was made into a mirror surface of about 30 in about 1 hour. A thin 1II2 layer of platinum-iridium-osmium alloy (Pt-1r-Os) was coated on the mirror-finished surface of the heat processing jig by sputtering. Similar to the second heat processing jig, the base material is cemented carbide (W).
A concave optical surface l with a radius of curvature of 20 is formed using C-5TiC-8Co), and a thin film 2 of platinum-iridium-osmium alloy (PL-1r-Os) is coated by sputtering. It was used as a mold for molding.

The molten glass 14 used was barium borosilicate glass consisting of 30% by weight of silica (Si02), 50% by weight of barium oxide (Bad), 15% by weight of boric acid (B208), and the remainder being trace components. After melting this glass at 1200'C, about 3 grams of molten glass 14 was mixed from a nozzle 12 maintained at 800°C at a rate of 20 liters/min of nitrogen gas and 2 liters/min of hydrogen gas. It was dropped into the first heat processing jig 24 held in the molding machine. The first heat processing jig 24 has a diameter of 200 mm in advance.
℃, and immediately after dropping, the second thermal processing jig 24 was brought into contact with the molten glass 14 to adhere the molten glass 14 to the second thermal processing jig 24.

The second thermal processing jig 24 with the molten glass 14 attached thereto is reversed by the arm 25, and the second thermal processing jig 16 is placed in the second thermal processing jig 16.
The molten glass 14 was replaced as shown in the figure. After being thermally deformed at 630° C. for 210 minutes using the second heat processing jig 16, it was press molded using a press mold 20. Press molding conditions are mold temperature 560'C, press pressure 30kg/c+i,
Breathing time was 2 minutes. Thereafter, it was slowly cooled to 300'C, and the optical glass element 22 was taken out from the takeout port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press molded part is an optical mirror surface of about 25, and no defects such as bubbles, scratches, or peeling marks are observed, and the surface accuracy is high. The optical performance was within two Newton rings and within one-fifth of a sweetfish, and its optical performance was extremely excellent.

Example 2 10 Using boron nitride as a heat processing jig,
It was processed into a convex shape with a radius of curvature of 45. A concave optical surface 1 with a radius of curvature of 45 fins was formed using austenitic steel (SUS316) as the base material of the second heat processing jig. This optical surface 1 was further lapped using ultrafine diamond powder to give a mirror surface with a surface roughness (RMS) of about 30 in about 1 hour. On the mirror surface of the heat processing jig,
Platinum-iridium-osmium alloy (P
A thin film 2 of L-1r-O3) was coated. Similar to the second heat processing jig, the base material is austenitic steel (SUS31).
6) to form a concave optical surface 1 with a radius of curvature of 150+nm.
A thin film 2 of rhodium-gold-tungsten alloy (Rh-Au-W) was coated by sputtering to form a press mold.

The molten glass 14 is a lanthanum-based glass consisting of 8% by weight of zirconia (ZrO2), 30% by weight of lanthanum oxide (La2O3), 42% by weight of boric acid (B208), 10% by weight of calcium oxide (Cab), and the remainder being trace components. Using. 14 pieces of this glass
After melting at 00''C, approximately 3 grams of molten glass 14 was heated from the nozzle 12 maintained at 950°C with nitrogen gas at 20 liters/min and trichlorotrifluoroethane (C2C1
3F8) Gas was dropped into the first heat processing jig 24 held in the molding machine in a halogenated hydrocarbon atmosphere mixed at a ratio of 1 liter to 7 minutes. The first heat processing jig 24 has a diameter of 400 mm in advance.
°C, and immediately after dropping, the second thermal processing jig 24 is brought into contact with the molten glass 14.
The molten glass 14 was attached to the glass. The second thermal processing jig 24 to which the f9 molten glass 14 was attached was turned over by the arm 25, and the molten glass 14 was replaced with the second thermal processing jig 16 as shown in FIG. 780°C in the second heat processing jig 16
After being thermally deformed for 120 minutes, it was press-molded using a press molding die 20. Press molding conditions are mold temperature 680°C
, press pressure was 30 kg/c4, and press time was 2 minutes. Thereafter, it was slowly cooled to 400"C, and the optical glass element 22 was taken out from the takeout port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is approximately an optical mirror surface, and no defects such as bubbles, scratches, or peeling marks are observed, and the surface accuracy is high. The optical performance is within 2 Newton rings and 1/5 Newton ring, and its optical performance is extremely excellent.Example 3 Aluminum nitride was used as the first heat processing jig and processed into a convex shape with a radius of curvature of 200 mm. did. A concave optical surface 1 with a radius of curvature of 200 mm was formed using cermet (TtC-10Mo-9N+) as the base material of the second thermal processing jig.This optical surface 1 was further formed using ultrafine diamond powder. The surface roughness (RMS) was measured in about 1 hour.
) made a mirror surface of about 30 people.

A thin film 2 of platinum-tantalum-rhenium alloy (Pt, -Ta-Re) is deposited on the mirror-finished surface of the heat processing jig by sputtering.
coated. Similar to the second heat processing jig, a concave optical surface 1 with a radius of curvature of 500M is formed using cermet (TiC-10Mo-9Ni) as the base material, and a platinum-tantalum-rhenium alloy ( A thin film 2 of PL-Ta-Re) was coated to prepare a mold for press molding.

The molten glass 14 contains 65 weight percent of silica (Sin2), 9 weight percent of potassium oxide (K2O), 10 weight percent of boric acid (B20B), and sodium oxide (
A borosilicate glass containing 10% by weight of Na20) and the remainder consisting of trace components was used.

After melting this glass at 1,350°C, about 3 grams of molten glass 14 was poured into the nozzle 12 maintained at 920°C using argon gas at 20 liters/min and ethylene (C2H,
The mixture was dropped into the first heat processing jig 24 held in a molding machine in which a hydrocarbon atmosphere was mixed at a rate of 1 linter/min. The first thermal processing jig 24 is heated to 550'C in advance,
Immediately after dropping, the second thermal processing jig 24 was brought into contact with the molten glass 14 to adhere the molten glass 14 to the second thermal processing jig 24. The second thermal processing jig 24 with the molten glass 14 attached thereon was turned over by the arm 25, and the molten glass 14 was replaced with the second thermal processing jig 16 as shown in FIG. After being thermally deformed at 780° C. for 5 minutes using the second thermal processing jig 16, it was press-molded using a press molding die 20. Press molding conditions are mold temperature 680°C, press pressure 80kg/cj
, the press time was 1 minute. Thereafter, it was slowly cooled to 380''C, and the optical glass element 22 was taken out from the takeout port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is approximately 20% optical mirror surface, and no defects such as bubbles, scratches, or peeling marks are observed, and the surface accuracy is high. Its optical performance was extremely excellent, with the distance being within two Newton's rings and within one-fifth of Newton's ring.

Example 4 Martensitic stainless steel (SUS420) was used as a first heat processing jig and processed into a flat shape. Using silicon as the base material of the second heat processing jig, the radius of curvature is 55
A concave optical surface 1 of m was formed. This optical surface l is further lapped using ultra-fine diamond powder, approximately 1
The surface roughness (RMS) was approximately 20 times mirror-like. A thin layer of rhodium-gold-tungsten alloy (Rh-Au-W) is applied to the mirror-finished surface of the heat processing jig by sputtering.
T! ! 2 was coated. Similar to the second thermal processing jig, silicon is used as the base material to form a concave optical surface 1 with a radius of curvature of 100 mm, and a rhodium-gold-tungsten alloy (Rh-Au-W) is formed by sputtering. The mold was coated with the GL film 2 and used as a mold for press molding.

The molten glass 14 contains 52 weight percent of silica (Si02), 6 weight percent of potassium oxide (K2O), 35 weight percent of lead oxide (PbO), and sodium oxide (N
a20) A heavy flint glass consisting of 5% by weight and the remainder being trace components was used.

After melting this glass to 1250″C″i′, 750″C″i′
Approximately 5 grams of molten glass 1 from nozzle 12 held at ℃
4, helium gas 20 liters/min, carbon dioxide gas 2
The mixture was dropped into the heat processing jig 24 held in the molding machine in a mixed atmosphere at a rate of 1/min. 10. Leave the thermal processing jig 24 unheated, and immediately after dropping the molten glass 14
A second thermal processing jig 124 was brought into contact with the molten glass 14 to adhere to the second thermal processing jig 24. molten glass 1
The second thermal processing jig 24 to which the glass particles 4 were attached was turned over by the arm 25, and the molten glass 14 was replaced with the second thermal processing jig 16 as shown in FIG. 61 with second heat processing jig 16
After heat deforming at 0°C for 15 minutes, press mold 2
Breath molding was performed at 0.

Press molding conditions are mold temperature 550°C, press pressure 80°C.
kg/cd, press time was 1 minute. then 3
It was slowly cooled to 80° C., and the optical glass element 22 was taken out from the take-out port 23.

In the optical glass element 22 manufactured by such a process, the surface roughness (RMS) of the press-molded surface is approximately 20% optical mirror surface, and no defects such as bubbles, scratches, or peeling marks are observed, and the surface accuracy is high. Its optical performance was extremely excellent, with the distance being within two Newton's rings and within one-fifth of Newton's ring.

The method for producing an optical glass element of the present invention includes a step of producing a glass gob by receiving molten glass in a first thermal processing jig that does not have an approximate shape to the desired optical glass element in a non-oxidizing atmosphere; a step of inverting and replacing the glass gob and the second thermal processing jig with the glass gob adhered to a second thermal processing jig having a shape similar to that of the glass element;
Manufacture of an optical glass element, including a step of producing an optical glass molded body using the surface tension of the glass gob that has been thermally softened in a second thermal processing jig, and a step of heating and press-molding the optical glass molded body with a press mold. This method is characterized by the fact that the conditions such as the molding atmosphere, the temperature of the optical glass, the composition of the thin film coated on the thermal processing jig, the temperature and time of thermal deformation, and the shape of the optical glass molded product are not specified. It is not limited to the examples.

As described in detail, the method for manufacturing an optical glass element of the present invention involves processing molten glass into a shape approximately similar to that of a desired optical glass element in order to remove wrinkle-like defects on the surface of the glass gob in contact with a thermal processing jig. After receiving the glass gob with the first heat processing jig, a second heat processing jig having an approximate shape to the desired optical glass element is brought into contact with the smooth surface of the glass gob, and the glass gob is placed in the second heat processing jig. Make it adhere. inverting the second heat processing jig with the glass gob attached to the second heat processing jig to stably replace the glass gob from the first heat processing jig to the second heat processing jig; The glass gob with the wrinkled side facing up is greatly deformed using the heated second thermal processing jig due to the surface tension of the glass, and this optical glass molded body is then heated and pressure molded using a press mold. , it is possible to manufacture an optical glass element with no defects on the surface.

That is, the present invention makes it possible to mass-produce high-precision optical glass elements, and has a significant effect on improving productivity and reducing manufacturing costs.

[Brief explanation of drawings]

FIG. 1(a) is an explanatory diagram of a first thermal processing jig for explaining the present invention, FIG. 1(b) is an explanatory diagram of a second thermal processing jig for explaining the present invention, FIG. 1(C) is a sectional view of a press mold, and FIG. 2 is a sectional view of an embodiment of the present invention showing an apparatus for manufacturing an optical glass element. 1...Optical surface, 2...Thin film, IO...
...Glass melting furnace, 11... Heater,
12... Nozzle, 13... Nozzle heater, 14... Molten glass, 15...
Heater, 16...Second thermal processing jig, 17
... Gas inlet, 18 ... Optical glass molded body, 19 ... Press cylinder, 20 ...
... Breath molding mold, 21 ... Conveyor, 2
2... Optical glass element, 23... Output port, 24... First thermal processing jig, 25...
····arm.

Claims (4)

[Claims] (1) In a non-oxidizing atmosphere, a step of producing a glass gob by receiving molten glass with a first thermal processing jig that does not have an approximate shape to the desired optical glass element; a step of inverting and replacing the glass gob and a second heat processing jig with the glass gob adhered to the heat processing jig; optical A method for producing an optical glass element, comprising the steps of producing a glass molded body and heating and press-molding the optical glass molded body in a press mold. (2) The method for manufacturing an optical glass element according to (1), wherein the first thermal processing jig has poor wettability with the molten glass. (3) Claim (1) wherein the second heat processing jig and the press molding die are processed into a desired shape and optical surface, and are coated with a chemically stable thin film that has good wettability with the molten glass. )
A method of manufacturing the optical glass element described above. (4) The method for manufacturing an optical glass element according to claim (3), wherein the thin film is made of a noble metal, tungsten, tantalum, rhenium, or hafnium, or an alloy thereof.