JPH01301528A - Method for press forming optical glass element - Google Patents

Abstract

PURPOSE:To enable formation of an optical element with a high accuracy at a low cost, by hot-press forming an optical glass gob having macroscopic waves with a press forming mold. CONSTITUTION:An optical glass gob 3 having macroscopic undulation waves is hot-press formed with top and bottom press forming forces 1 and 2 to form an optical glass element (formed lens) 4. The surface of the optical glass gob is instantaneously heated in a moment the optical glass gob contacts the press forming molds and softened according to the above-mentioned method. However, since the interior of the optical glass gob is not instantaneously heated without softening even the interior of the glass due to bad heat conduction of the optical glass, deformation of the optical glass gob is slowly advanced in a state of disconnected macroscopic waves to press form the desired optical glass element without taking in air between the macroscopic waves.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a press-molding method for optical glass elements, in which high-precision optical glass elements such as lenses and prisms are hot-press-molded using a press mold. .

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 direct press molding is considered to be promising.

This direct press molding method involves heating and pressure molding a lump of optical glass on an aspherical mold that has been finished with the desired surface quality and surface precision, or molding a lump of optical glass that has been heated in advance. This is a method of manufacturing optical glass lenses by performing heating and pressure molding without requiring a subsequent polishing process. (For example, Japanese Patent Publication No. 54-38126) Problems to be Solved by the Invention Optical glass elements such as aspherical lenses and prisms are required to have extremely high surface precision, so they cannot be used in press molding. It is important to control the shape, weight, and especially surface condition of optical glass lumps, and optical glass lumps have become expensive, and as a result, press-molded optical glass elements have become expensive.

Polishing, heat processing, or etching treatment is performed to make the surface of the optical glass block free of defects (for example, to have a mirror-like surface roughness of 0.1 micron or less, preferably 0.01 micron or less). As a result, optical glass blocks have become expensive, and there has been a strong desire to develop a method that can produce high-precision optical glass elements at low cost.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a press-molding method for an optical glass element in which an optical glass lump having macroscopic undulations is hot-press-molded using a press mold. It is.

Effect When an optical glass gob with microscopic irregularities (e.g. submicron level) on its surface is press-molded using a high-temperature press mold, the moment the press mold comes into contact with the optical glass gob, The surface of the optical glass gob (approximately several microns) is instantaneously heated to soften the surface of the optical glass gob. Then, the microscopic irregularities existing on the surface of the optical glass gob connect and form closed pores, leaving a large number of closed pores on the surface of the optical glass gob.

On the other hand, when an optical glass gob with macroscopic undulations on its surface is press-molded using a high-temperature press-molding mold, the surface of the optical glass gob instantly appears when the press-molding mold comes into contact with the optical glass gob. The temperature rises instantaneously, and the surface of the optical glass lump softens. However, due to the poor thermal conductivity of optical glass, the temperature inside the optical glass gob is not instantaneously raised and the inside of the glass is not softened, so the deformation of the optical glass gob gradually progresses without the macroscopic waviness being connected. , the desired optical glass element is press-molded without air being trapped between the macroscopic undulations.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a glass press molding die and an optical glass gob used in the present invention. Cemented carbide (WC-5TiC-8Co) was used as the base material of the press molding die, and the upper die l
A concave molding surface 3 with a radius of curvature of 200 fins was formed on the lower die 2, and a concave molding surface 4 with a radius of curvature of 46 fins was formed on the lower mold 2, respectively. These molded surfaces 3 and 4 were lapped using ultrafine diamond powder, and the surfaces had a mirror surface with a maximum roughness (Rmax) of about 80 in about 1 hour. A thin film of platinum-iridium-osmium alloy (Pt-1r-Os) was coated on the mirror-finished molding surfaces 3 and 4 by sputtering. An upper mold 1 and a lower mold 2 for molding an optical glass element were produced by such a method.

The optical glass lump 3 contains 50% by weight of silica (S i Ot ), 35% by weight of lead oxide (PbO),
The remainder is potassium oxide (KzO) and arsenic oxide (A S
After melting lead oxide-based optical glass consisting of trace components such as t Os ) and antimony oxide (SbzO+) at 1200°C, it was dripped at a nozzle temperature of 800°C and received by austenite a (SU 5316) heated to 450°C. Press molding was performed for 10 seconds to obtain a product having the shape shown in FIG. 1(A).

Then, as shown in FIG. 1(B), using the above-mentioned press molding molds 1 and 2 heated to 500°C, a press pressure of 4
Press molding was carried out under the conditions of 0 kg/aJ and press time of 1 minute. The molded lens 4 was cooled as it was, separated from the upper and lower molds at 430°C, immediately placed in an annealing furnace for slow cooling, and taken out at 300°C to obtain a molded lens 4 as shown in FIG. 1(C).

Through such a process, lead oxide based optical glass was press-molded, and the surface roughness of the optical glass gob 3 and the molded lens 4 was measured. As a result, the optical glass gob 3 had a number of lO as shown in Fig. Although there were micron undulations, the molded lens 4 press-molded by the method described above had a mirror surface with a surface roughness (Rmax) of approximately 90 as shown in Figures 2 (B) and (C), and was observed under an optical microscope. As a result of observation, no closed pores were found on the molded surface. Furthermore, the surface accuracy was within 2 Newton rings and within 1/5 of an American ring, and the optical performance was extremely excellent and the product yield was also very good.

Furthermore, the above-mentioned austenitic steel (S U 5316)
Optical glass lumps 3 with different surface roughness were prepared by varying the temperature and time of exposure, and the same press molding, cooling, measurement and evaluation as described above were performed, and the results are summarized in Table 1.

Table 1 Macroscopic waviness is an approximately sinusoidal wave, and if the distance between the peaks is the size of the waviness, and the difference between the peaks and valleys is the height of the waviness, then, for example, the outer diameter If the lens shape is about 2011, the macroscopic waviness is several tens of microns.
It is preferable that the height of the undulation is in the range from m to several aml, and the height of the undulation is one-tenth or less of the size of the undulation, and such macroscopic undulation has the above-mentioned effect.

Note that the press-molding method for an optical glass element of the present invention is characterized in that an optical glass element having macroscopic undulations is hot-press-molded using a press-molding mold to produce an optical glass element. The material of the press molding mold, the type of optical glass lump, the manufacturing method, the size of macroscopic waviness,
Other press molding conditions etc. are not limited to this example.

As described in detail, the method for press-molding an optical glass element of the present invention involves hot press-molding an optical glass lump having macroscopic undulations using a press-molding mold to produce an optical glass element. Therefore, when an optical glass gob with macroscopic undulations on its surface is press-molded using a high-temperature press-molding mold, the surface of the optical glass gob instantly changes as soon as the press-molding mold comes into contact with the optical glass gob. The temperature rises over time, softening the surface of the optical glass gob. However, due to the poor thermal conductivity of optical glass, the temperature inside the optical glass gob is not instantaneously raised and the inside of the glass is not softened, so the deformation of the optical glass gob gradually progresses without the macroscopic waviness being connected. , the desired optical glass element is press-molded without air being trapped between the macroscopic undulations. 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 the drawing]

Figure 1 is an explanatory schematic diagram showing that an optical glass element is produced by press-molding an optical glass gob with macroscopic undulations using a press-molding mold, and Figure 2 is an explanatory diagram of the optical glass gob and molded lens. It is an explanatory view showing a measurement result of surface roughness. l...Top mold, 2...Bottom mold, 3...
...Optical glass lump, 4...Molded lens. Name of agent: Patent attorney Toshio Nakao Haka 1 Meiten 1 unit

Claims (1)

[Claims] A press-molding method for optical glass elements in which an optical glass block with macroscopic undulations is hot-press-molded using a press mold.