JPS60264331A - Press molding mold for optical glass elements - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 process.

However, the manufacturing method for the double optical glass lens must be so good that the imaging quality of the resulting lens is not impaired after press molding. 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, a mold in which a noble metal layer is coated on a cemented carbide base material mainly composed of tungsten carbide WC is considered suitable, and various studies have been made.

However, the tongue i used as the base material:'
Care Car A()'WCO*□□Blue7ke, KenW is an extremely rare element in terms of resources, so it is called a strategic material, and it is inevitably very expensive. Tungsten carbide WC, which is the main component of cemented carbide, has poor oxidation resistance at high temperatures, so during long press forming of glass, the cemented carbide that makes up the base material is susceptible to oxidation. surface accuracy decreases. Therefore, in order to prevent oxidation of the tungsten carbide WC, it is necessary to strictly maintain the atmosphere during press molding in a non-oxidizing atmosphere. Therefore, when using a mold made of cemented carbide whose main component is tungsten carbide WC, the press atmosphere must be a non-oxidizing atmosphere (with an oxygen partial pressure of 1 to 10 x 1
(approximately 0-2 tov), and the press equipment must be kept sufficiently airtight. When supplying or removing glass, 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. As described above, when a cemented carbide containing tungsten carbide WC as a main component is used as a base material, it is unavoidable that the press equipment becomes complicated or larger. Another problem is that the time required for press molding cannot be shortened.

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 results by using the mold thus produced.
Direct press molding of optical glass lenses having high forming quality provides a mold for press molding optical glass elements that can be mass-produced easily and inexpensively.

Composition of the Invention The press-molding mold for an optical glass element of the present invention consists of a cermet base material mainly composed of alumina Al2O3, a group consisting of iridium Ir, osmium Os, palladium Pd, rhodium Rh, and ruthenium Ru: It is characterized by forming a noble metal alloy consisting of at least one element selected from the above and platinum pt.

Therefore, the cermet mainly composed of alumina A12O3 used as the base material can be used even when performing general grinding, since the cermet mainly composed of tungsten carbide WC, which has been variously studied as a mold for press molding of glass lenses. It has the feature of being able to perform mold processing with the same high precision as that of cemented carbide, and the maximum surface roughness Rmax of the mold surface can be reduced to Q.
, 0211m or less.

Furthermore, the thermal expansion coefficient of the cermet used as the base material is 8 in the case of a cermet whose main component is alumina Al2O3.
~9×10-6/C, and the thermal expansion coefficient of the noble metal layer consisting of platinum pt and at least one element selected from the group consisting of iridium Ir, osmium Os, palladium Pd, rhodium Rh, and ruthenium Ru is 9 ~11
×1o-6/°C. In this way, the thermal expansion coefficients of the above-mentioned cermet base material and the precious metal layer formed on it are well matched, making it resistant to thermal shock during press molding of glass and heat cycles during repeated molding. It can be said that it is a press molding mold that has strong adhesive strength that can withstand even harsh conditions.

Therefore, various studies have been made for the same purpose, and a base material made of cemented carbide mainly composed of tungsten carbide WC, which has been proposed to be suitable as a mold for press molding of optical glass elements, has been developed. The press molding mold for the optical glass element of the present invention uses a cheaper cermet as the base material, and the main component alumina Al2O3 has excellent oxidation resistance, so it is easier to press mold than the mold with a noble metal layer formed thereon. It is not necessary to control the atmosphere more strictly than before, the press apparatus can be simplified or downsized, and the press molding cycle time can be significantly shortened. 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 noble metal layer formed on the cermet, the alloy composition is such that platinum pt is 60-99% by weight, and the balance J' is 75% by weight.
:(!J,?*Ir, off 62..8.7,5.tsu4
The alloy is defined as an alloy consisting of at least one element selected from the group consisting of Pd, rhodium Rh, and ruthenium Ru because its suitability as a mold material for press molding of various optical glass elements differs depending on the composition amount (weight ratio). It's for a reason. That is, the alloy composition of the claims of the present invention (
If the composition is less than the specified composition (weight percentage), the strength or hardness of the noble metal layer is low, and fine particles may appear on the mold surface after press forming. The highly accurate surface shape deteriorates due to the occurrence of scratches and plastic deformation. Moreover, if the composition amount (weight %) is more than the specified I- value, 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 diameter 30mm, length 50mm cylindrical shape A12o3-
A pair of press molding molds is prepared by preparing a cermet rod having a composition of 26Cr, and a lower mold 12 having a press surface 12'' having a notch 11'' on the periphery as shown in FIG. 1 by electrical discharge machining. Processed into shape.

The press-molded surface of this mold was mirror-polished using ultrafine or diamond abrasive grains. As a result, it was possible to perform mirror finishing with an accuracy of maximum surface roughness of 0.02 μm within one hour. Next, a binary alloy layer such as a platinum-rhodium (pt-ph) alloy layer, a platinum-rhodium-iridium (Pt-Ph-I
r) Ternary alloys such as metal alloys, quaternary alloys such as platinum-rhodium-iridium-palladium (Pt-Rh-Ir-Pd) alloy layers, platinum-rhodium-iridium-palladium-osmium (Pt-Rh- Ir-Pd-Os)
Quinary alloys such as alloy layers and platinum-rhodium-iridium-palladium-osmium ruthenium A (Pt
-Rh-Ir-Pd-Os-Ru) alloys were formed.

The molds 11 and 12 produced in this way were heated with nitrogen 1fi, pbo carb r o %, S 102
A lump 17 made of lead oxide optical glass made of 27 pieces and the rest made of trace components into a spherical shape with a radius of 20 + n + n.
was heated and pressed to form a lens with convex surfaces on both sides.

The mold temperature during press molding of the glass was 600"C1. The press pressure was 401 (g/CIA). After holding for 2 minutes, the mold was cooled to -13oo'c, and the molded glass was taken out from the molded glass outlet 19. , each of the molded glass and mold was evaluated.Such a pressing process was
After repeating 0 times, the mold used was removed and the surface of the mold after 500 press moldings was observed.

The above press experiments were 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. It was shown to.

For comparison, the mold of the present invention was set in a tank press machine, which has been proposed to be suitable as a press molding mold and various studies have been conducted, and molded under the same pressing conditions as described above. The results are shown in Table 1.

As a result of press forming using a mold in which a noble metal layer was formed on a cemented carbide whose main component was tungsten carbide WC, the oxygen partial pressure in the press atmosphere was several tov.
The base material, tungsten carbide WC, was oxidized and the surface roughness of the mold was reduced.

That is, after press molding was performed 500 times, the surface roughness of the mold in which a noble metal layer was formed on a cemented carbide whose main component was tungsten carbide WC decreased by 0.20 μm.

On the other hand, the press-molding mold for the optical glass element of the present invention has yl,・ lj 72,
! "'.1"")-Jy"1"Jy"1"There is no peeling of the metal layer and no minute scratches on the mold surface. It has advantages such as almost no deterioration in surface accuracy. Mainly uses tungsten carbide WC. As in the case of the component cemented carbide, the time required to process the mold of the present invention to a maximum surface roughness of 0.02 μm is 1 hour, indicating that the base material can be easily processed. Alumina Al2 used in the present invention
O3 is cheaper than tungsten carbide WC, and can reduce the manufacturing cost of press molding molds. Furthermore, even though the press atmosphere is a nitrogen atmosphere with an oxygen partial pressure of several toV, the mold surface is not oxidized even after pressing the glass 500 times, and the surface accuracy is 0.025 before press forming. The surface accuracy was almost maintained. 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. Things change.

In this example, the cermet used as the base material of the press molding mold for the optical glass element had a composition of A1203-26Cr, but the cermet composition used as the base material is not limited to the above composition, and other materials may be used. As an additive, Mg
a, Cao, Fe 203.5IO2, MO1Fe
etc. 3 can be used.

Although a concave press molding mold was used to explain the present invention, the shape of the mold surface is not limited to the shape of this example, and can be adapted to the shape of an optical glass element such as a prism. It goes without saying that anything you do is fine.

Margin below 4 Table 1 Press molding results of lead oxide optical glass 23. 25, 26. Effects of the Invention As is clear from the above description, the press-molding mold for an optical glass element of the present invention is characterized in that a noble metal layer is formed on a cermet whose main component is alumina A12o3. This is a press molding mold for optical glass elements, and compared to cemented carbide whose main component is tungsten carbide WC, which has been considered suitable as a press molding mold for optical glass elements and has been studied in various ways. Also, a mold surface with high precision can be easily obtained even in general grinding and mirror finishing. In addition, since alumina Al2O'3, which is the main component of the base material, has high oxidation resistance, there is no need to maintain the atmosphere during press molding in a highly non-oxidizing atmosphere.
There are advantages in that the press apparatus can be simplified and miniaturized, and the mold surface roughness after press molding does not deteriorate even though the press atmosphere is a nitrogen atmosphere with an oxygen partial pressure of several toV.

Since the coefficient of thermal expansion matches very well with that of the cermet precious metal layer used as the base material, repeated 27, - failures will not occur.

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 effect is extremely large.

[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... Upper mold, 12... Lower mold, 11'
...Press surface of upper die, 12'...Press surface of lower die, 11''...Notch part, 13.
...Heating heater for the upper mold, 14... Heater for the lower mold, 15...... For the upper mold (stone cylinder, 16... Piston cylinder for the lower mold) , 17...
... Raw glass lumps, 18... Raw glass supply jig, 19... Molded glass outlet, 20
...Raw material glass preheating furnace, 21...Shell. 11゛ Name of agent Patent attorney Toshio Nakao et al. Figure 1

Claims (1)

[Claims] (1) A press molding mold for an optical glass element, characterized in that a noble metal layer is formed on a cermet base material whose main component is alumina Al2O3. (Bar The noble metal layer is made of isodium Ir, osmium Os. Barakam Pd, rhodium Rh and ruthenium Ru.
At least one element selected from the group consisting of platinum p
The mold for press-molding an optical glass element according to claim 1, wherein the mold is an alloy consisting of: t. ('4 The noble metal layer is composed of 60 to 99% by weight of platinum PT, the balance being iridium Ir, osmium O8, palladium P
3. The mold for press-molding an optical glass element according to claim 1 or 2, wherein the mold is an alloy consisting of at least one element selected from the group consisting of rhodium Rh and ruthenium Ru.