JPH0248497B2 - KOGAKUGARASUSOSHINOSEIKEIHOHO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for molding high-precision optical glass elements that does not require a polishing step after press molding in the manufacture of optical glass elements such as lenses and prisms. BACKGROUND OF THE INVENTION 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, processing and mass production are difficult using the polishing method, which is a conventional method for manufacturing optical lenses, and direct press molding is viewed as promising. This direct press molding method involves heating and pressure molding a lump of optical glass on an aspherical mold that has been finished to the desired surface quality and surface precision, or molding a lump of glass that has been heated in advance. This is a method of manufacturing optical lenses by performing heating and pressure molding without requiring a subsequent polishing process (for example, Japanese Patent Publication No. 38126/1983). Problems to be Solved by the Invention In manufacturing the above-mentioned optical glass lenses, it is necessary that the optical glass lenses obtained by press molding have excellent image forming performance, and especially in the case of aspherical lenses, the image forming performance is very high. Surface accuracy is required. Therefore, as a press molding mold for optical glass elements, it is necessary to use properties such as minimal chemical action on the optical glass at high temperatures and resistance to damage such as scratches and abrasions caused by sticking to the press molding surface of the mold. Must have. Various materials are being considered for this purpose, but conventional mold materials have poor reactivity with optical glass,
Does not fully satisfy requirements such as oxidation resistance, high strength at high temperatures, and surface smoothness. Molds coated with noble metals are considered promising as mold materials with excellent reactivity and oxidation resistance for optical glass. Precious metals themselves do not have high hardness, so cemented carbide,
Efforts have been made to increase hardness by coating a highly hard base material such as cermet, zirconia, alumina, or silicon carbide with a noble metal. However, as the number of times the optical glass element is pressed increases, the highly precise pressing surface of the mold, that is, the part coated with precious metal, deforms, albeit very slightly, and the optical properties of the optical glass element change. In order to improve the durability of the mold, it is necessary to increase the hardness of the press-molded surface of the optical glass element to prevent the highly accurate press-molded surface from deforming. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that the press forming surface contains 0.01 to 10% by weight of Va in the precious metal alloy.
The present invention provides a method for molding an optical glass element in which optical glass is precisely molded by heating and pressurizing it using a mold coated with a thin film containing a group element. Effect As a result of intensive research, the inventors found that by adding 0.01 to 10% by weight of Va group elements to noble metal alloys, the crystal grains and structure of noble metal alloys become finer, and the Va group elements are added to noble metal alloys. It has been found that the hardness of the thin film to which the compound is added becomes extremely high, and the scratch resistance and abrasion resistance of the press-molded surface are improved. As mentioned above, the noble metal alloy itself is a soft material, and when a noble metal alloy is coated on a highly hard base material such as cemented carbide, cermet, or ceramics, the apparent hardness increases. however,
In a thin film in which 0.01 to 10% by weight of a Va group element is added to a noble metal alloy, the hardness of the thin film itself increases, so the scratch resistance and wear resistance of the molding die are significantly improved. Suitable additive elements here include Va group elements, ie, vanadium (V), niobium (Nb), and tantalum (Ta). These elements refine the crystal grains and structure of precious metal alloys, strengthen precipitation, or reduce dislocations.
Significantly hardens the press molding surface. If the amount of the Va group element added is less than the scope of the claims of the present patent application,
Since the above effects cannot be obtained, the content is set to 0.01% by weight or more. Furthermore, if the amount of the Va group element added is large, the crystal grains and structure will become coarse and the specularity of the press-molded surface will deteriorate, so the amount should be 10% by weight or less. Examples Examples will be shown below. Cylindrical WC−10TiC− with a diameter of 30 mm and a length of 50 mm.
Prepare two cemented carbide rods with a composition of 10TaC−8Co,
An upper mold 11 with a concave radius of curvature of 46 mm and a lower mold 1 with a concave shape with a radius of curvature of 200 mm has a notch 11'' on the periphery as shown in Fig. 1 by electrical discharge machining.
It was processed into the shape of a pair of press molding surfaces consisting of 2. The press-molded surface of this mold was mirror-polished using ultrafine diamond abrasive grains. Next, apply a layer of 0.01 μm on this mirror surface using the sputtering method to a thickness of 2 μm as shown in Table 1.
Thin films of noble metal alloys containing ~10% by weight of various Group Va elements were formed. The molds 11 and 12 produced in this way are used in a piston cylinder 15 of a press machine shown in FIG.
and 16, PbO was set to 70 in a nitrogen atmosphere.
A spherical lump 17 with a radius of 15 mm was pressed with a lead oxide optical glass consisting of 27% by weight of SiO ₂ and the rest of trace components to produce a lens with convex surfaces on both sides. The mold temperature during press molding of optical glass was 500°C, and the press pressure was 40Kg/cm ² . After maintaining the above conditions for 2 minutes, the mold was cooled to 300°C, and the molded glass was removed from the molded glass outlet 19. I took it out. After repeating this press molding process 10,000 times, the mold used was removed and the Vickers hardness (Hv) of the mold after 10,000 presses was measured.
The surface roughness was measured, and the surface condition of the optical glass lens after press molding was observed. The results are shown in Table 1. As is clear from Table 1, vanadium (V),
As the amount of niobium (Nb) and tantalum (Ta) added increases, the Bitkers hardness (Hv) increases,
Even after press molding was performed 10,000 times, the highly accurate surface shape and surface roughness of the mold surface remained almost unchanged. Furthermore, there were no minute scratches on the optical glass surface after press molding, and the optical properties were also very excellent. On the other hand, when the amount of the Va group element added is less than 0.01% by weight, the mold surface is not sufficiently hardened and the surface roughness of the mold is approximately 0.1 μm, and the resulting optical glass lens The optical properties of the film were also deteriorated. When the amount of the Va group element added is more than 10% by weight, the Va group element is precipitated in the noble metal alloy, the surface roughness of the mold is roughened to about 0.4 μm, and the optical properties of the obtained optical glass lens are also deteriorated. It was declining. In this example, WC-10TiC-10TaC-
Cemented carbide with 8Co composition was used, but other materials such as TiC-based cermet, TiN-based cermet,
Needless to say, materials such as Cr ₃ C _two- base cermet, Al ₂ O _three -base cermet, zirconia, alumina, or glassy carbon may also be used. Further, the shape of the molding surfaces 4 and 5 is not limited to the shape of this embodiment, and it goes without saying that the shape of a prism, a filter, or the like may be used.

【table】

【table】

[Table] Effects of the Invention As is clear from the above description, the method for forming an optical glass element of the present invention is such that the press-molded surface of the optical glass element is formed by forming a precious metal alloy containing 0.01 to 10% by weight.
It is characterized by precisely molding optical glass by heating and pressurizing it using a mold coated with a thin film containing Va group elements, and is 0.01 to 10% by weight.
By adding at least one element selected from vanadium (V), niobium (Nb), and tantalum (Ta), the noble metal alloy thin film is hardened and wear resistance and scratch resistance are improved. As a result, even after press molding was performed 10,000 times, the shape accuracy and 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 the method for molding an optical glass element of the present invention, an optical glass element with very high precision can be easily manufactured, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a press-molding mold for an optical glass element in an embodiment of the present invention, and FIG. 2 is a partially cutaway front view showing a press machine used in the same embodiment. 11...Upper die, 12...Lower die, 11'...Press surface of upper die, 12'...Press surface of lower die, 11''...
...Cut portion, 13...Heating heater for upper mold, 14
... Heater for lower mold, 15 ... Piston cylinder for upper mold, 16 ... Piston cylinder for lower mold, 1
7... Raw glass lumps, 18... Raw glass supply jig, 19... Molded glass outlet, 20...
...Raw material glass preheating furnace, 21...Shell.

Claims (1)

[Claims] 1. Optical glass is heated and pressurized using a mold in which the press-molded surface of the optical glass element is coated with a thin film containing 0.01 to 10% by weight of a Va group element added to a noble metal alloy. A method for molding an optical glass element, which is characterized by precision molding. 2. The noble metal alloy contains at least 5% by weight of platinum (Pt), with the balance being at least selected from iridium (Ir), osmium (Os), palladium (Pd), rhodium (Rh), and ruthenium (Ru). 2. The method for forming an optical glass element according to claim 1, wherein the optical glass element is made of one element.