JPS61281029A - Mold for press molding optical glass element - Google Patents

Abstract

PURPOSE:A mold for press molding, providing easily an optical glass element having high accuracy, obtained by coating the press molding face with a thin film of a specific noble metal alloy. CONSTITUTION:The pressing faces 11a and 12a set on the top mold 11 and the bottom mold 12 are polished into mirrorlike faces with an ultrafine diamond whetstone, and the mirrorlike faces are covered with a thin film obtained by dispersing 0.01-10wt% one or more oxides such as ZrO2, TiO2, Ta2O5, etc., into a noble metal alloy containing >=5wt% Pt and the rest of one or more elements selected from Ir, Os, Pd, Rh and Ru by sputtering method. Then, the prepared molds 11 and 12 are set on the piston cylinders 15 and 16 of a press machine, the mass 17 such as optical glass of lead oxide type is pressed and the prepared molded glass is taken out from the outlet 19.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used in the production of optical glass elements by direct press molding of high precision optical glass elements that do not require a polishing process after press molding. The present invention relates to a mold for press molding an optical glass element.

(Prior Art) 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. When manufacturing this aspherical lens, it is difficult to process and mass-produce it using the polishing method, which is the conventional manufacturing method for optical lenses, so direct press molding is considered promising.For example, As described in Japanese Patent Publication No. 54-38126, a lump of optical glass is heated and pressure-molded on a mold with an aspherical shape that has been finished to a desired surface quality and high precision, or This is a method of manufacturing an optical lens by subjecting a lump to heat and pressure molding without requiring a subsequent polishing process.

(Problems to be Solved by the Invention) However, in the method for manufacturing an optical glass lens as described above, it is necessary that the optical glass lens obtained by press molding has excellent image forming performance. In the case of a spherical lens, a very high degree of area is required. Therefore, as a press-molding mold for optical glass elements, the chemical action on the optical glass at high temperatures is minimal, the pressing surface of the mold is not susceptible to damage such as scratches and abrasions, and the high precision achieved by press-forming. It must have properties such as not changing.

Various materials have been studied for this purpose, but conventional mold materials do not meet the above requirements, such as low reactivity with optical glass, oxidation resistance, and high strength at high temperatures. As a mold material with excellent reactivity and oxidation resistance for optical glass,
A mold coated with precious metals is on sale. Since the hardness of noble metals themselves is not high, efforts have been made to increase the hardness by coating noble metals on high hardness base materials such as cemented carbide or cermet. However, as the number of times the optical glass element is pressed increases, the highly precise pressing surface of the mold deforms, albeit very slightly, and the optical properties of the optical glass element change. It is necessary to prevent the highly precise press surface from deforming by increasing the hardness of the noble metal coating layer.

(Means for Solving the Problems) In order to solve the above problems, the present invention covers the press forming surface with a thin film containing 0.01 to 10% by weight of oxide dispersed in a noble metal alloy. It is characterized by:

(Function) As a result of research, the present inventors found that 0001-
It has been found that by dispersing 10% by weight of an oxide, the hardness of the noble metal coating layer becomes extremely high, and the scratch resistance and abrasion resistance of the press molding surface are improved. As mentioned above, noble metal itself is a soft material, and by coating a highly hard base material such as cemented carbide or cermet with noble metal, the apparent hardness increases. By uniformly dispersing 0.01 to 10% by weight of oxides in precious metals, the hardness of the precious metal coating thin film itself increases, making it possible to improve the scratch resistance and wear resistance of press molding molds. It is something. Here, a suitable oxide for the dispersion is zirconium oxide (
ZrOt), tantalum oxide ('rho, ), tantalum oxide (Ta20r), niobium oxide (Flb20f)
), lanthanum oxide (LatOi), vanadium oxide (vlol), hafnium oxide (HfOl), helium oxide (BeO) and yttrium oxide (YzO).
*). The amount of oxide dispersed in the noble metal is preferably 0.01 to 10% by weight, and the amount of oxide is 0.0% by weight.
If it is less than 1% by weight, the effect of hardening the noble metal thin film will be small, and if it is more than 10% by weight, the noble metal thin film and glass will tend to react, and the highly accurate press surface will change in quality.

(Example) An example of the present invention will be described in detail below based on the drawings.

Cylindrical WC-10T with a diameter of 30 am and a length of 50 am
Two rods of cemented carbide having a composition of iC-10TaC-8Co were prepared, and a press surface (11b) with a notch (11b) around the periphery and a concave shape with a radius of curvature of 4B-m was formed by electrical discharge machining (as shown in Fig. 1). A pair of molds for press molding is formed, consisting of an upper mold (11) having a concave press surface (12a) with a radius of curvature of 200 cm.

Press surface (lla) (12a) of this mold (II) (12)
) is mirror-polished using ultra-fine diamond grains,
On this mirror surface, a thin film of 2 .mu.m thick is formed by sputtering using various oxides uniformly dispersed in various alloys such as platinum-rhodium (Pt--Rh) alloy shown in Table 1.

The molds (II) and (12) thus created were set in the piston cylinders (15) and (16) of the press machine shown in Fig. 2, and PbO was heated to 70% in a nitrogen atmosphere.
A spherical block (17) with a radius of 20■■ was pressed using lead oxide optical glass consisting of 27% by weight of 5IOz and the rest of trace components to create a lens with convex surfaces on both sides. . The mold temperature during press molding of optical glass is 50
The temperature was 0℃, the press pressure was 40''/-, and the above condition was changed to 2
After holding for a minute, the mold was cooled to 300° C. together with the mold, and the molded glass was taken out from the take-out port (I9). After repeating this press molding process 10,000 times, the mold used was removed and the Vickers hardness (Hv) and surface roughness of the mold after 10,000 presses were measured, and the surface condition of the optical glass lens after press molding was measured. The above results are shown in Table 1.

As is clear from Table 1, zirconium oxide (ZrO
As the amount of added oxides such as titanium oxide (TIO, ) increases, the Vickers hardness increases, reaching 100
Even after press molding was performed 00 times, the highly accurate surface shape and surface roughness of the mold surface remained almost unchanged. In addition, there were no minute scratches on the surface of the optical glass after press molding, and the optical properties were also very good.

On the other hand, when the amount of oxide added is less than 0.01% by weight, the noble metal alloy is not sufficiently hardened, and the surface roughness of the mold becomes approximately 0.1 μm. The optical properties of the optical glass lens were also degraded. If the amount of oxide added is more than 10% by weight, the oxide dispersed in the precious metal alloy will precipitate and react with the optical glass, leaving reaction traces on the mold surface and furthermore impairing the optical properties of the optical glass after press molding. was also decreasing.

In this example, the base material was Wc-10TIC-10Ta.
c-8C.

Although a cemented carbide having a composition of
TIN, CrzOi, AJ! Cermets such as 103 can also be used. In addition, Zr (
Ceramics such as h, At10s, etc. can also be used. Although a concave press molding die is used to explain the present invention, the shape of the die is not limited to the above shape, and it goes without saying that a convex shape or a planar shape may be used. Further, in this example, one type and two types of oxides were added, but the same effects as in this example were also obtained when three or more types of oxides were added.

Margin below (Effects of the Invention) As explained above, the press-molding mold for an optical glass element according to the present invention has a press-molding surface of the optical glass element in which 0.01 to 10% by weight of oxide is dispersed in the noble metal alloy. Compared to conventionally used press molding molds for optical glass elements, it is characterized by being coated with a thin film made of precious metal alloys by dispersing 20°01 to 10% by weight of oxides. The thin film hardens and wear resistance improves. As a result, even after press molding was performed 10,000 times, the surface roughness of the press molding surface of the mold hardly changed, and the optical properties of the obtained optical glass element were also very excellent.

Therefore, by using the press molding mold for an optical glass element of the present invention, it becomes possible to obtain an optical glass element with high precision very easily, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 shows a press-molding mold for an optical glass element in an example of the present invention, and FIG. 2 is a diagram showing a press machine used in the example. (11)... Upper mold, (+2)... Lower mold, (lla)
...Press surface of upper die, (12a)...Press surface of lower die, (17)...Raw material glass lump. Figure 1, π2 diagram

Claims (3)

[Claims] (1) A mold for press-molding an optical glass element, characterized in that the press-molding surface of the optical glass element is coated with a thin film containing 0.01 to 10% by weight of an oxide dispersed in a noble metal alloy. (2) The noble metal alloy contains 5% by weight or more of platinum (Pt), with the balance being iridium (Ir), osmium (Os),
Claim 1, characterized in that it is an alloy containing at least one element selected from palladium (Pd), rhodium (Rh), and ruthenium (Ru).
A press-molding mold for the optical glass element described in 1. (3) The oxides include zirconium oxide (ZrO_2), titanium oxide (TiO_3), tantalum oxide (Ta_2O_
5), niobium oxide (Nb_2O_5), lanthanum oxide (
La_2O_3), vanadium oxide (V_2O_5),
Hafnium oxide (HfO_2), beryllium oxide (Be
The mold for press-molding an optical glass element according to claims 1 and 2, characterized in that the mold contains at least one of yttrium oxide (Y_2O_3) and yttrium oxide (Y_2O_3).