JPS61132523A - Process for producing molded glass - Google Patents

Abstract

PURPOSE:To obtain a molded glass article having high dimensionalaccuracy without necessitating the grinding and polishing works, by punching a fluid glass with a punching form. CONSTITUTION:The glass rod 1 extruded with a high-accuracy extrusion molding machine is heated with a heater 2 to attain a viscosity of 10<8>-10<12.5> poise, and supplied to a punching mold composed of the punches 3, 4 and the dies 5, 6 heated at a temperature corresponding to the glass viscosity of 10<8.5>-10<13> poise. The die 6 and the punch 4 are transferred with the cylinders 7, 8 to the position of the rod 1, and at the same time, the rod 1 is pressed with the die 5 by the aid of the cylinder 9. The punch 3 is forwarded with the cylinder 10, and the rod 1 is punched and cut with the punch 3 and the die 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a punching method for obtaining a glass molded body with high dimensional accuracy. In particular, it is characterized in that it can be used as a press lens or a preform thereof that does not require grinding or polishing after press molding.

[Prior Art] Recently, research has been actively conducted on methods of manufacturing press lenses that do not require grinding or polishing after press molding and have high shape accuracy and smooth surfaces. U.S. Patent No. 3.833.347, U.S. Patent No. 4,139,67
Examples of this can be seen in U.S. Patent No. 7, U.S. Patent No. 4,168.961, etc.
The molding method shown in this document uses a special mold material with an optical mirror surface, a non-oxidizing atmosphere, and a mold temperature of 7.65% (10 poise). (temperature corresponding to the viscosity of)), held at that temperature for 1 to 5 minutes, press with a load on the mold, and lower the mold temperature to a temperature lower than the glass transition temperature while maintaining the load. It is.

Although this method significantly lengthens the molding cycle time, recently a molding method has been disclosed which shortens the molding cycle time. JP-A-58-8134 uses a glass preform with a shape similar to the final product,
The glass preform and mold are heated to a temperature corresponding to a glass viscosity of about 10 poise or more and 1012 poise or less, then pressed under a load, and then
A molding method is disclosed in which the temperature is lowered to a temperature corresponding to a glass viscosity lower than 13 poise, after which the load is released and the glass formed article is removed from the mold. Also, special request
In No. 9-140548, a glass preform is inserted into a mold, and the viscosity of the glass preform is 108.5 to 10.
At a temperature equivalent to 10.5 poise, press with a push rod separate from the upper mold for several seconds to several tens of seconds, then move the push rod back to release the load, leaving the glass molded object wrapped in the mold. A method for manufacturing a press lens is disclosed, which is characterized by cooling the glass until the viscosity of the glass reaches 1011.5 poise or more.

[Problems to be Solved by the Invention] The above-mentioned Japanese Patent Application Laid-open No. 58-8134 and Japanese Patent Application No. 1983 proposed to shorten the molding cycle time as described above.
A common feature of the invention of No. 140548 is that pressing is performed with a relatively high viscosity, and when the viscosity is high, the amount of elongation and deformation of the glass becomes smaller, so a preform with a shape close to the final shape is used. This is the point where it is used. As a conventional technique for obtaining a preform having a shape close to the final shape, there is first a method of grinding and polishing into a spherical surface. Although this method is considered effective when press-molding an aspherical lens, it has little meaning when press-molding a spherical lens. Furthermore, even in the case of press forming into an aspherical surface, grinding and polishing methods that require a long cold working process are not necessarily preferred methods. A second option is a conventional press technique that creates an approximate shape. In other words, the molten glass is
It is dropped and cut at a viscosity of 0 to 103 poise, then received in a mold at a temperature lower than the glass transition point, and is then cut at a viscosity of 2 to 10 Jl/
This is a method of press molding at a pressure of Cl. However, this method causes small bubbles called shear marks, large sink marks, and generally large variations in capacity and dimensions, so it is not suitable as a preform for press lenses.

[Object of the Invention] An object of the present invention is to economically produce a preform or lens with high dimensional accuracy for a press lens without performing cold working. As a preform for press lenses,
The closer the shape is to the final product, the more advantageous it is, and the present invention shows that high-precision molding technology for glass sheets or rods is currently available.
Taking note of the fact that this technology has progressed considerably, this technology is characterized by hot punching and forming with high precision, similar to cold punching of metal.

[Means for Solving the Problems] In order to achieve the above object, the present invention is such that a glass molded body is obtained by punching fluid glass with a punching die.

Cold punching is widely used for metals, but glass is a material that is brittle and fractures, so it cannot be punched using cold punching dies. In the present invention, when the glass is raised above the glass transition temperature, viscous flow occurs,
This product was created by discovering that it can be punched and formed using a punching die. That is, the present invention is characterized by punching fluid glass with a punching die, and preferably converts glass having a viscosity of 10 to 1012.5 poise into a glass viscosity of io 8.5 to 1013 poise. A glass molded body with high dimensional accuracy is obtained by punching with a punching die at a corresponding temperature.

The mold temperature may be equal to the glass temperature or may be slightly lower. By punching a sheet or rod formed into a lens shape with high precision and without any deposits, it is effective as a preform for a press lens. If the viscosity is lower than this range, deformation and shrinkage after molding will be large, sufficient dimensional accuracy will not be achieved, and capacity fluctuations due to punching will be relatively large. Additionally, in general, fusion between the glass and the mold tends to occur. Even within the scope of the present invention, it is desirable to maintain the mold in a non-oxidizing atmosphere in order to prevent the mold from becoming rough due to oxidation and to extend the life of the mold.

If the viscosity exceeds 1013 poise, punching is impossible.

The mold used in the present invention may be made of any material as long as it has sufficient high-temperature strength and high-temperature hardness, does not fuse with glass having a high viscosity of 108 poise or more, and does not cause significant surface roughness. For example, tungsten carbide or tungsten carbide coated with a ceramic coating is effective. Also, if the clearance of the punching die is large, it will cause a gap, so the punching die and its assembly should be made with high precision and the clearance should be approximately 10μ.
It is necessary to keep it below m. The purpose of the present invention is to create a preform for obtaining a pressed lens with extremely high shape accuracy as described above, but if the mold is finished with an optical mirror surface, high surface precision is not required within the scope of the present invention. Optical lenses that are not made can be made. Also, at this time, after punching and forming, the glass is cooled together with the mold, and the glass viscosity is 1011°.
Surface accuracy can be improved by removing the material after it reaches 5 poise or more.

[Example 1] FIG. 1 shows a schematic cross-sectional view of a forming apparatus for carrying out the method of the present invention, and FIGS. 2 to 4 show partially enlarged views of the punching and forming operation.

The forming device ties the left and right fixing plates 11.18 to 19.
Cylinder 7 connected at 20 and provided on both rotation plates 17 and 18
．． Attach movable plates 21 and 22 to piston rod 9.

Left and right master molds 11.12 are provided on the movable plate 21.22 via rods 23.23. Orad 23.23 has support plate 2
4.25 is slidably supported, and the master die 11.12 is also slidably supported by a mold precision guide 15.15 provided between the support plates. Matrix 11.
12 has an in-mold heater 13.14 and dies 5.6 facing each other. In addition, a cylinder 10.8 is provided in the center of the support plate 24.25, the piston rods of which extend into the mother die, and punches 3.4 are provided which can be slid relative to the respective die.

In the example shown, heavy flint optical glass 5FII (glass transition temperature 435°C) is extruded into a rod shape with high precision using a known technique, and then a die made of tungsten carbide is used to extrude it into a rod shape with a diameter of 1611 m and a center wall thickness of 3.0 m. 5mm1
A case of manufacturing a preform having a biconvex lens shape is shown.

The glass rod 1 extruded by a high-precision extrusion molding machine is heated to a temperature of 109 poise (490°C) by a heater 2.
). A punching mold consisting of a punch 3.4 polished to an optical mirror surface and a die 5.6 was maintained at 490° C., which corresponds to the glass viscosity of 109 poise, and the die 6 and punch 4 were first formed using cylinders 7 and 8 as shown in FIG. I brought it to the rod position straight away, and re-dyed 5 to cylinder 9 for about 400k.
Hold rod 1 with pressure of O. After that, by advancing the punch 3 with the cylinder 10, the bunch 3 and die 6 are moved as shown in FIG. Punching and cutting was carried out at a pressure of 600 k<l. At this time, a back pressure of approximately 160 kQ is applied to the bunch 4 by the cylinder 8. Continuing with this operation, the bunch 4 stops at the shoulder 16 as shown in Fig.
Pressing was performed under the pressure of 1) to obtain a glass molded body in the shape of a biconvex lens. In addition, through this operation, N2 is released from the gap between the molds.
Gas was allowed to flow in to prevent the skin from becoming rough due to oxidation of the mold. The obtained glass molded body had an outer diameter accuracy of ±5 μm and a center wall thickness repeatability of ±20 μm, and had sufficient spherical shape accuracy and mirror surface texture to be used as a press lens preform. .

[Example 2] Using a technique similar to the rod forming method, 5F11 heavy flint optical glass was pulled down into a sheet in the same manner as in Example 1, and the viscosity of the sheet was reduced to 8.5 to 10 poise (507°C) using a heater 2. ), punching was carried out in the same manner as in Example 1 using a punching mold heated to 478°C, which corresponds to a glass viscosity of 1 o 9.5 poise, and by continuously pressing at a pressure of 400 ka/cm2, A preform for a press lens in the shape of a biconcave lens with a diameter of 10 m1R and a center wall thickness of 2 cm was obtained.

[Effects of the Invention] According to the present invention, a preform with high dimensional accuracy for obtaining a high-precision press lens that does not require grinding or polishing after press molding can be produced in a short time and economically without any cold working. can be manufactured according to Further, for lenses whose surface precision is not too critical, the ones manufactured by the present invention can be used as final products. Furthermore, in the case of a two-plane glass filter, etc., by punching out a sheet, an extremely precise outer diameter can be obtained, so there is no need for cold punching or rounding.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a glass punching and forming apparatus according to the present invention, and FIGS. 2 to 4 are enlarged sectional views showing the state during punching and forming. 1...Glass rod, 2...Heater, 3.4...
Punch, 5.6...Die, 7-10...Cylinder,
11.12... [F13, 14... type heater, 15
···guide.

Claims (1)

[Claims] 1. A method for obtaining a glass molded article, which comprises punching fluid glass with a punching die. 2 10^8~10^1^2^. Glass having a viscosity of ^5 poise is 10^8^. A method for obtaining a glass molded body according to claim 1, wherein the glass molded body is punched with a punching die at a temperature corresponding to a glass viscosity of ^5 to 10^1^3 poise to obtain a glass molded body with high dimensional accuracy. 3 10^8~10^1^2^. A sheet or rod-shaped glass having a viscosity of ^5 poise is heated to 10^8^. ＾５～
Claim 2: A lens with high dimensional accuracy or a glass molded body having a shape similar to a lens is produced by punching with a punching die whose surface in contact with glass at a temperature corresponding to a glass viscosity of 10^1^3 poise is mirror-finished. A method for obtaining the described glass molded body. 4 10^1^1^. A method for obtaining a glass molded article according to claim 3, characterized in that the glass molded article is taken out at a glass viscosity of ^5 poise or more.