JPS60264333A - Mold for press molding of optical glass element - Google Patents

Abstract

PURPOSE:To provide the titled mold available at a low cost and capable of directly pressing an optical glass lens product having high image-forming quality in high accuracy, by applying a noble metal layer to a preform made of a specific thermet. CONSTITUTION:A cylindrical thermet rod composed mainly of titanium nitride is machined by electrical discharge machining to obtain a top force 11 having concave pressing face 11' furnished with notches 11'' and a bottom force 12 having concave pressing face 12'. The pressing faces are mirror polished (max. surface roughness; about 0.02mu) and coated with a noble metal layer (about 2mu thick) by sputtering, etc. The objective mold for the direct pressing of an optical element can be manufactured by this process. The above noble metal layer is made of an alloy of (A) about 60-99wt% Pt and (B) about 40-1wt% one or more metals selected from Ir, Os, Pd, Rh and Ru.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing optical glass elements, and in particular can be used when directly press-molding high-precision optical glass elements that do not require a polishing process after press-molding. The present invention relates to a press-molding mold for optical glass elements.

Conventional Structures and Their Problems In recent years, optical glass lenses have been trending toward aspheric surfaces that can simultaneously simplify the lens structure of optical equipment and reduce the weight of the lens portion. In manufacturing this aspherical lens, the optical polishing method, which is a conventional method for manufacturing optical lenses, has difficulty in processing and mass production, so direct press molding is viewed as promising.

This direct press molding method involves heating and molding a lump of optical glass on an aspherical mold that has been finished to the desired surface quality and precision, or heating a lump of glass that has been heated in advance. This is a method of manufacturing optical lenses by performing press molding without requiring any further polishing steps.

However, the method for manufacturing the optical glass lens described above is
After press molding, the image forming quality of the obtained lens must be excellent to the extent that it is not impaired. In particular, in the case of an aspherical lens, it is required that it can be molded with high surface accuracy.

Therefore, as a mold material, it must have minimal chemical effect on the glass at high temperatures, be resistant to damage such as scratches on the glass pressing surface of the mold, and have high fracture resistance against thermal shock. It must have the following characteristics.

For this purpose, tungsten carbide ('W
It is said that a type in which a cemented carbide base material whose main component is C) and a layer coated with a noble metal layer is suitable, and various studies have been conducted.

However, Tanges 1, which is used as the base material,
Tungsten (W), which is a constituent element of ten carbide (WC), is an extremely rare element in terms of resources, so it is called a strategic material, and it is inevitably very expensive. Because cemented carbide has a high microhardness, it is extremely difficult to process, and it takes approximately 1.
It also takes time. Furthermore, in molds that have a cemented carbide base material coated with a precious metal, there is a difference in the coefficient of thermal expansion between the two, so when the mold is rapidly heated and cooled, the coated precious metal may peel off.

OBJECTS OF THE INVENTION An object of the present invention is to easily perform the high-precision mold processing required for a mold for direct press molding of glass lenses, and to achieve good image forming quality by using the mold produced in this way. The present invention provides a press-molding mold for optical glass elements that allows direct press-molding of optical glass lenses to be mass-produced easily and inexpensively.

Structure of the Invention The press-molding mold for an optical glass element of the present invention has a cermet base material mainly composed of titanium nitride (T i N ), and a base material of iridium (Ir) and osmium (Os).
), palladium (Pd), rhodium (Rh), and ruthenium (Ru), and platinum (pH).

Here, titanium nitride (T i
Cermets whose main component is tungsten carbide (WC), which has been studied in various ways as press molding molds for glass lenses, can be used even in general grinding processes. It has the feature of being able to perform mold processing with extremely high precision, and also being able to easily finish the maximum surface roughness (Rmax) of the mold surface to an accuracy of 0.0211 m or less.

Furthermore, the coefficient of thermal expansion of the cermet used as the base material is
In the case of cermets whose main component is titanium nitride (T i N ), the temperature is 9 to 10 × 107 °C, and the temperature is 9 to 10 × 107 °C, and the temperature is 9 to 10 × 107 °C, and the temperature is
, at least one element selected from the group consisting of rhodium (Rh) and ruthenium (I(u)) and platinum (pt
) The coefficient of thermal expansion of the noble metal layer is 9 to 11×10−
6/℃. Since the thermal expansion coefficients of the above-mentioned cermet matrix and the noble metal layer formed on it are well matched, the glass is resistant to thermal shock during press molding and heat cycles during repeated molding. It can be said that it is a press molding mold that has strong adhesive strength that can be applied even to other types of materials.

Therefore, various lateral sides have been conventionally made for the same purpose, and on a base material made of cemented carbide mainly composed of tungsten carbide (WC), which has been proposed to be suitable as a press molding mold for optical glass elements. The press-molding mold for the optical glass element of the present invention uses an inexpensive cermet as a base material, and the thermal expansion coefficients of the base material and the coated precious metal layer match better than the mold with a noble metal layer formed on the base material. Therefore, it can withstand heat cycles caused by repeated molding at high temperatures, and the time required for one cycle of press molding can be significantly shortened. and,
During processing, the cermet used in the present invention has excellent welding resistance, so the maximum surface roughness of the base material can be reduced to 0.02μ.
It takes about 60 minutes to process a size of less than m, which reduces the processing time compared to conventional mold processing.
It has the advantage that it has a good bitterness.

In addition, in the noble metal layer formed on the cermet, the alloy composition is platinum (pt) of 60 to 99% by weight, and the rest is iridium (Ir), osmium (Os), and palladium (
Pd), rhodium (Rh) and ruthenium (Ru)
The reason for specifying the alloy as an alloy consisting of at least one element selected from the group consisting of is that the suitability as a mold material for press molding of various optical glass elements differs depending on the respective composition amount (weight %). In other words, if the alloy composition (wt%) falls within the scope of the claims of the present invention, it is possible to press-form an optical glass element well, but if the specified composition amount (wt%)
In the following cases, since the strength or hardness of the noble metal layer is low, fine scratches or plastic deformation occur on the mold surface after press forming, resulting in a highly accurate surface shape. This is because if the composition amount (% by weight) is more than the specified amount, the press-molded glass will be colored and the noble metal layer will easily volatilize at high temperatures.

Description of examples Examples of the present invention will be described below.

Example: Cylindrical (7) TiN-30T with a diameter of 30 mm and a length of 60 H.
A cermet rod having a composition of iC-7Mo is prepared, and a notch 11" is formed around the periphery as shown in FIG. 1 by electric discharge machining.
Concave press surface 11' with a certain radius of curvature 46 (goods)
A pair of molds for press molding was formed, consisting of an upper mold 11 having a radius of curvature of 2° and a lower mold 12 having a concave pressing surface 12' with a radius of curvature of 2°.

The press-molded surface of this mold was mirror-polished using ultrafine diamond abrasive grains. As a result, it was possible to perform mirror finishing with an accuracy of maximum surface roughness of 0.021 zm within 60 minutes. Next, a binary alloy of platinum-rhodium (Pt-Rh), platinum-rhodium-iridium (Pt-R
h-I r ) alloy layer, platinum-rhodium-iridium-palladium (Pt-Rh-I r
-Pd) quaternary alloy such as alloy layer, platinum-rhodium-
Iridium-palladium-osmium (Pt-Rh-I
ternary alloys such as r-Pd-Os) alloy layers and platinum-rhodium-iridium-palladium-osmium-
A large alloy such as a ruthenium (pt-Rh-Ir-Pd-〇5-Ru) alloy layer is formed (-).

The molds 11 and 12 thus produced were set in the piston cylinders 16 and 16 of the press machine shown in FIG. 2, and in a nitrogen atmosphere, PbO was 70% and SiO
A block of lead oxide optical glass made of 27 pieces of lead oxide-based optical glass and the rest of trace components was heated and pressed into a spherical shape with a radius of 20 inches to form a lens with convex surfaces on both sides. The mold temperature during glass press molding was soo℃ and the press pressure was 40℃.
After holding at Kg/cd for 2 minutes, it was kept at 300℃.
The molded glass was cooled together with the mold until the temperature reached 10, and the molded glass was taken out from the molded glass outlet 19, and the molded glass and the mold were each evaluated. After repeating this pressing process 1000 times, the mold used was removed and the surface of the mold after 1000 press moldings was observed.

The above press experiment was repeated on a pair of molds with different total compositions as shown in Table 1.
The molded glass and mold after press molding were evaluated, and the results are shown in Table 1.

For comparison, we fabricated a mold with a noble metal layer formed on the second side of a cemented carbide alloy whose main component is tungsten carbide (WC), which has been proposed to be suitable as a press mold and has undergone various studies. , instead of the mold of the present invention, was set in the press machine shown in FIG. 2 and molded under the same press conditions as described above, and the results are shown in Table 1.

The time required to process the cemented carbide whose main component is tungsten carbide (WC) was one hour, but the time required to process the cermet whose main component is titanium carbide (TiN) used in the present invention was It was within 6° minutes. Surface roughness of the mirror-finished surface of the seasonal wood used in the present invention Rma
x) was 0.02 μm or less, and a very beautiful finished surface was obtained.

In a mold in which a noble metal was formed on a cemented carbide whose main component was tungsten carbide (WC), the noble metal layer peeled off after approximately SOO times of press molding due to the large difference in thermal expansion coefficient between the two.

On the other hand, in the press molding mold for the optical glass element of the present invention, the thermal expansion coefficient of the cermet used as the base material is 9 to 9.
10×10-6/℃, and the thermal expansion coefficient of the noble metal layer is 9
˜11×10 −69° C., and their thermal expansion coefficients match very well. Therefore, no peeling of the noble metal layer occurred even after press molding was performed 1000 times.

Moreover, the glass element obtained by press molding had very excellent optical performance.

In this example, the cermet used as the base material for the press molding die for the optical glass element was TiN-30Ti (knee 7
Although the composition was Mo, the composition of the cermet as the base material is not limited to the above composition, and other additives include TaC, W'C, NbC, and TaN.

Cermets containing MoC, Cr3C2, Ni, Co, etc. can be used. In addition, to explain the present invention, 1.
' 16 K @ surface shape. 7.7. using a mold f,
5. It goes without saying that the shape of the mold surface is not limited to the shape of this embodiment, and may be adapted to the shape of an optical glass element such as a prism.

Margin below 13...-1 Table 1 Press molding results of lead oxide optical glass 14'.
・ JP-A-264333 (6) 22 23 Effects of the invention Jl ・ It is clear from the explanation below;
JP-A-HGO on top of cermet containing TiN)
-264333 (7) A cemented carbide whose main component is tungsten carbide (WC), which is said to be suitable as a mold for press molding of optical glass elements characterized by the formation of a noble metal layer, and has been studied in various ways. Compared to conventional methods, it is easier to process mold surfaces with high precision, and a finished surface with excellent specularity can be obtained. Because the thermal expansion coefficients of the cermet used for Sundashungetsu and the precious metal layer match well, it can withstand heat cycles caused by repeated molding at high temperatures, and can be used for heating, press molding, rapid cooling, and removal. It is possible to shorten the time required for cycles.

Therefore, by using the press-molding mold for an optical glass element of the present invention, it is possible to obtain an optical glass element with high precision very easily, and the effects thereof are extremely unique.

[Brief explanation of the drawing]

FIG. 1 is a view showing a press-molding mold for an optical glass element in an example of the present invention, and FIG. 2 is a view showing a press machine used in the same example. 26 be 11...upper mold, 12...lower mold, 11'.
...Press surface of upper die, 12'...Press surface of lower die, 1'...Notch part, 13...
... Heater for upper mold, 14 ... Heater for lower mold, 16 ... Piston cylinder for L-type, 16
...Piston cylinder for lower mold, 17...
- Raw glass lumps, 18... Raw glass supply jig, 19... Molded glass outlet, 20.
...Raw material glass preheating furnace, 21...Shell. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
figure

Claims (2)

[Claims] (1) A mold for press-molding an optical glass element, characterized in that a noble metal layer is formed on a cermet base material whose main component is titanium nitride (T i N ). (2) The noble metal layer is made of platinum (pt) and at least one element selected from the group consisting of iridium (Ir), osmium (Os), palladium (Pd), odium (Rh), and ruthenium (Ru). The press-molding mold for an optical glass element according to claim 1, wherein the mold is an alloy of: @), the noble metal layer contains 60 to 99% by weight of platinum (pt),
The remaining portion is an alloy consisting of at least one element selected from the group consisting of iridium (Ir), osmium (Os), palladium (Pd), rhodium (Rh) and ruthenium (Ru). A press-molding mold for an optical glass element according to item 1 or 2.