JPS60264332A - 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 chromium carbide 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 mirrors polished (max. surface roughness; about 0.02mu) and coated with a noble metal layer (ablout 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 heat forming a lump of optical glass in a mold with an aspherical shape that has been pre-finished to the desired surface quality and precision, or After molding the soul-like object using a heat press, we painstakingly polished the culm.
This is a method of manufacturing optical lenses without using.

However, the method for manufacturing the optical glass lens described in -1- must be excellent to the extent that the image form of the It crystallinity of the obtained lens is not impaired after press molding. especially,
In the case of an aspherical lens, it is required that it can be molded with high surface accuracy. However, as an API, the chemical action on glass at high temperatures is minimal;
The glass pressing surface of the pear must have properties such as being resistant to damage such as scratches and having high fracture resistance against thermal shock.

For this purpose, tungsten carbide ('wc
) is said to be suitable, and various studies have been carried out on it.

1,',) Tungsten (W), which is the constituent element of tungsten carbide (WC) used as the base material 41, is said to be a strategic material because it is an extremely rare element in terms of resources. , which is inevitably very expensive. In fact, tungsten carbide (WC), which is the main component of cemented carbide, has poor oxidation properties at high temperatures, so when glass is press-formed for a long time, one strand of tungsten carbide (WC), which makes up the base material, is The alloy is oxidized and the surface accuracy decreases. Therefore, in order to prevent oxidation of tungsten carbide (WC), it is necessary to strictly maintain the atmosphere during press molding to be a non-oxidizing atmosphere. Therefore, when using a mold whose base material is a cemented carbide whose main component is tungsten carbide (WC), it is necessary to make the press atmosphere a non-oxidizing atmosphere (oxygen partial pressure of about 1 to 10X10-2 torr). , the press equipment must be kept sufficiently airtight. Furthermore, when glass is supplied or removed, the non-oxidizing atmosphere is broken and it is necessary to return to the non-oxidizing atmosphere, which increases the time required for one cycle during press molding. When a cemented carbide containing tungsten carbide (WC) as a main component is used as the base material as in -1r below, it is inevitable that the press equipment becomes complicated or larger. Another drawback is that the time required for press molding cannot be shortened.

OBJECTS OF THE INVENTION The first object of the present invention is to easily perform high-precision mold processing in which water is retained in a mold for direct press molding of glass lenses, and to use pears produced in this manner. Direct press molding of optical glass lenses with good image forming quality provides a mold for press molding optical glass elements that can be easily and inexpensively produced in large quantities.

Composition of the Invention The press-molding mold for an optical glass element of the present invention is a cermet base material mainly composed of chromium carbide (Cr3C2), and is coated with iridium (Ir), osmium (08), palladium (Pd), rhodium ( The present invention is characterized in that a noble metal alloy layer is formed consisting of platinum (PT) and at least one element selected from the group consisting of Rh) and ruthenium (Ru).

Here, chromium carbide (Cr 3C
The cermet whose main component is 2) is a cemented carbide whose main component is tungsten carbide (WC), which has been studied in various ways as a mold for press molding of glass lenses, even when performing general grinding processing. It has the feature of being able to perform mold processing with the same high precision as that of the conventional method, and also being able to easily process the maximum surface roughness (Rmax) of the mold surface to an accuracy of 0.02 μm or less.

Furthermore, the coefficient of thermal expansion of the cermet used as the base material is
In the case of zamenote whose main component is chromium carbide (Cr3c2), it is 10 to 11 x 10-6/°C, and iridium (Ir) and osmium (Os).

The thermal expansion coefficient of the noble metal layer consisting of platinum (pt) and at least one element selected from the group consisting of palladium (Pd), rhodium (Rh) and ruthenium (Ru) is 9 to 11 x 10-6/°C. Tungsten carbide (WC) has been proposed to be suitable as a press-molding mold for glass elements that can withstand the thermal shock and heat cycle of press-molding because the coefficients of thermal expansion of the two are well matched. ) The press molding mold for the optical glass element of the present invention uses an inexpensive cermet as a base material, compared to a mold in which an L'' metal layer is formed on -11 of a base material made of cemented carbide mainly composed of In addition, chromium carbide (Cr3C2), which is one of the seven components, has excellent surface oxidizing properties, so there is no need to set the atmosphere during press molding more strictly than before.
It is possible to simplify or downsize the press equipment, and it is also possible to significantly shorten the cycle time of press molding. In addition, because the thermal expansion coefficients of the cermet base material and the precious metal layer formed on it are well matched, it has strong adhesion that can withstand heat cycles caused by repeated molding. It has the following advantages.

In addition, in the precious metal layer formed on the cermet, the alloy composition is platinum (Pt) with a thickness of 60 to 99, 4 degrees,
ka8i11. ．． 4. Ir), O7 Ou4 (.) 1.
<Alloys consisting of at least one element selected from the group consisting of radium (Pd), rhodium (Rh), and ruthenium (Ru) are specified according to the straight gravity meter for each composition)
This is because the suitability as a press-molding January mold material for famous optical glass elements differs depending on the type of material. In other words, if the alloy composition (wt%) is within the scope of the claims of the present invention, it is possible to press-form an optical glass element well, but if the composition is less than the specified composition N (weight percentage), the strength of the noble metal layer or Due to its low hardness, after press molding, fine scratches occur on the mold surface and plastic deformation occurs, reducing the precision of the surface shape. This is because if the composition amount (% by weight) is exceeded, the press-molded glass will be colored and the noble metal layer will easily volatilize at high temperatures.

Example explanation J Examples of the present invention will be described below.

Example: Cylindrical Cr3C2- with a diameter of 30 mm and a length of 50 mm.
A cermet rod of 13Nii was prepared, and a mold 11 with a concave pressing surface 11' with a radius of curvature of 46 mm and a notch 11'' around the periphery as shown in FIG. 1 was formed by electrical discharge machining. A pair of molds for press molding was formed, consisting of a lower mold 12 having a concave pressing surface 12' with a diameter of 200 mm.

The press-molded surface of this mold was mirror-polished using ultra-fine diamond grains. As a result, it was possible to perform mirror finishing with an accuracy of maximum surface roughness of 0.02/Lm within one hour. Next, a binary alloy layer such as a platinum-rhodium (Pt-Rh) alloy layer and a platinum-rhodium-iridium (Pt-Rh) alloy layer with a thickness of 2 μm are deposited on this mirror surface by sputtering.
-Ir) ternary alloys such as alloy layers, rhodium-iridium-radium (Pt-Rh-Ii-Pd
) Quaternary alloys such as alloy layers, platinum-rhodium-iridium-radium-osmium (Pt-Rh-I
r-Pd-Os) alloy layer and platinum-rhodium-iridium-palladium-osmium-ruthenium (Pt-Rh-Ir-Pd-Os-Ru
) Alloys such as alloy layers were formed.

Molds 11 and 12 thus prepared were processed into a spherical shape with a radius of 20 mm using lead oxide optical glass consisting of 70% PB○, 27% SiO2, and the remainder as trace components. One piece of the lump was heated and pressed to form a lens with convex surfaces on both sides.

During glass press molding, the mold temperature was 600°C and the press pressure was maintained at 40 degrees for 2 minutes, then cooled together with the mold to 1300°C, and the molded glass was taken out from the molded glass outlet 19. Each molded glass and mold was evaluated. After repeating this pressing process 500 times,
The mold used was removed and the mold surface was observed after press molding was performed 600 times.

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

For comparison, a press machine, which has been proposed to be suitable as a press mold and has been subjected to various studies, was set in place of the mold of the present invention, and molded under the same press conditions as two series. The results are shown in Table 1.

As a result of press forming using a die in which a precious metal layer was formed on a cemented carbide whose main component is tungsten carbide (WC), the oxygen partial pressure in the press atmosphere was several torr, so the base material tungsten The carbide (WC) was oxidized and the surface roughness of the mold was reduced. That is, tungsten carbide (WC) after being press-formed 500 times.
) The surface roughness of the mold with a noble metal layer formed on the cemented carbide whose main component was "-" was reduced to 0.20 μm.

On the other hand, in the press molding mold for the optical glass element of the present invention, the oxygen partial pressure in the press atmosphere is several torr.
Despite the high price, even after press-molding lead oxide optical glass 600 times, it does not react with jl: 7'', and the noble metal layer formed on J-lyr does not peel off, and the mold surface has no peeling. As in the case of cemented carbide whose main component is fine scratches, the maximum surface roughness of the mold of the present invention is set to 0.02μ.
It can be seen that the time required to process the base material to m is 1 hour, and that the base material can be easily processed. Chromium carbide (Cr3C2) used in the present invention is cheaper than tungsten carbide (WC) and can reduce the manufacturing cost of press molding molds. Furthermore, even after pressing the glass 500 times, even though the pressing atmosphere was a nitrogen atmosphere with an oxygen partial pressure of several forts.
The mold surface was not oxidized, and the surface accuracy was 0.025, which was almost the same as before press molding. In this way, by using the press molding die of the present invention, there is no need to strictly control the press atmosphere compared to the case of a die using cemented carbide as the base material, and the press equipment can be simplified and downsized. I understand that.

In this example, the cermet used as the base material for the press molding mold for the optical glass element was a Cr3C2-13Ni composition, but other additives to the cermet used as the base material were Tic, TaC, Mo2C. .

A cermet containing WC, W, etc. can be used. Furthermore, although a concave press molding die was used to explain the present invention, the shape of the die surface is not limited to the shape of this example, and may be adapted to the shape of an optical glass element such as a prism. Needless to say, anything is fine.

Margin below 4 Table 1 Pressing results of lead oxide optical glass 23 The * mark in the upper right corner of Trial PI = l = i indicates a comparative example.

As is clear from the explanation, "Optics 5 of the present invention is a press-molding mold for optical glass elements characterized by forming a noble metal layer, and has been conventionally used for press-molding optical glass elements. Compared to cemented carbide whose main component is tungsten carbide (WC), which is said to be suitable for molds and has been studied in various ways, it is possible to obtain mold surfaces with the same degree of ease and precision. . In addition, since chromium carbide (Cr3C2), the main component of the base material, has high oxidation resistance, there is no need to maintain a highly non-oxidizing atmosphere during press forming, making it possible to simplify and downsize the press equipment. Furthermore, there is an advantage that the mold surface roughness after press molding is not reduced even though the press atmosphere is a nitrogen atmosphere containing several torr of enzyme.

Since the thermal expansion coefficients of the cermet used as the base material, the blue gold, and the ten-layer layer are very similar, the precious metal layer does not peel off even after repeated molding.

Therefore, by using the press-molding mold for an optical glass element of the present invention, it is possible to easily form a high-density glass element.

[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. 11...'' - mold, 12...lower mold, 11
'... Press surface of river mold, 12'... Press surface of lower die, 11''... Notch part, 13...
...'' - Mold heater, 14... Lower mold heater, 15...-1] Mold piston cylinder, 16... Lower mold piston cylinder , 17・
・°...Raw material glass body, 18...Raw glass supply jig, 19...Formed glass inlet/outlet,
20... Raw glass preheating furnace, 21...
...Oi. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) A mold for press-molding an optical glass element, characterized in that a noble metal layer is formed on the second side of a cermet base material whose main component is chromium carbide (Cr3C2). (2) The first layer of prize money is iridium (Ir), osmium (
Claim 1, characterized in that it is an alloy consisting of platinum (pt) and at least one element selected from the group consisting of palladium (Pd), rhodium (Rh), and ruthenium (Ru). A press-molding mold for the optical glass element described in 1. (3) The noble metal layer contains 60 to 99% by weight of platinum (Pt),
A patent characterized in that the remainder is an alloy consisting of at least one element selected from the group consisting of iridium (Ir), osmium (OB), nonoradium (Pd), rhodium (Rh), and ruthenium (Ru). A press-molding mold for an optical glass element according to claim 1 or 2.