JPS62119128A - Forming of optical glass element - Google Patents

Abstract

PURPOSE:To improve the accuracy of pressing and to prolong the life of dies for press-forming an optical glass element by coating the pressing surfaces of the dies with thin films each contg. a prescribed percentage of a prescribed nitride dispersed in the alloy of a platinum group metal. CONSTITUTION:The pressing surfaces of press forming dies are coated with thin films each contg. 0.01-10wt% one or more kinds of nitrides dispersed in the alloy of a platinum group metal. The nitrides are selected among the nitrides of Ti, Cr, Ta, Nb, Si, B, Al, Hf, Zr and V. An optical glass element is precisely formed with the dies at elevated temp. and pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 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 production of optical glass elements such as lenses and prisms.

2. Description of the Related Art In recent years, there has been a trend toward aspheric optical glass lenses, which can simultaneously simplify the lens structure of optical equipment and reduce the weight of the lens portion. In manufacturing this aspherical lens, processing and mass production are difficult using the polishing method, which is a conventional optical lens manufacturing method, and direct press molding is considered to be promising.

This direct press molding method involves heating and press-molding a lump of optical glass on an aspherical mold that has been finished with the desired surface quality and surface precision in advance, or molding a lump of optical glass that has been heated in advance. This is a method of manufacturing optical glass lenses by performing heating and pressure molding without requiring a subsequent polishing process. (For example, Special Publication No. 54-3812
Problems to be Solved by Koyuki No. 6 Old Invention However, in manufacturing the above-mentioned optical glass lens, it is necessary that the optical glass lens obtained by press molding has excellent image forming performance, especially in the case of an aspherical lens. A very high degree of area is required. Therefore, as a mold for molding optical glass elements, the chemical effects on optical glass at high temperatures are minimal, the press surface of the mold is not easily damaged by scratches and abrasions, and the high surface precision does not change due to press molding. It is necessary to have the following characteristics.

Various materials are being considered for this purpose, but conventional mold materials do not fully satisfy the requirements such as low reactivity with optical glass, oxidation resistance, and high strength at high temperatures. Molds coated with platinum group alloys are seen as promising mold materials with excellent reactivity and oxidation resistance.

Platinum group elements are superior to other metal materials, ceramics, etc. in terms of low reactivity with optical glass and oxidation resistance, but the hardness of platinum group elements is in the low category. If platinum group elements are alloyed together, the hardness will be greater than in the case of platinum group elements alone.

However, if an optical glass with a softening point exceeding 700°C, such as barium borosilicate glass, is press-molded many times, even a mold coated with a platinum group alloy will change its surface condition, albeit slightly. do. That is, the highly accurate area degree and surface roughness of the platinum group alloy thin film, which is the press forming surface, changes. In order to press-form optical glass with a softening point of over 700°C with high precision, the press-molding mold must have properties such as high hardness, no reaction with the optical glass, and excellent oxidation resistance even at high temperatures. Must be prepared.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a method for precisely molding optical glass by heating and pressing, using titanium (Ti) and chromium (Cr) as platinum group alloys.

Tantalum (Ta), Niobium (Nb), Silicon (Si)
), boron (B), aluminum (/l).

At least one nitride with hafnium (Hf), zirconium (Zr), or vanadium (V) R0,01
The present invention provides a method for molding an optical glass element using a press molding die coated with a thin film containing 10% by weight of the present invention.

As a result of research, the inventors discovered that titanium (Ti) is added to platinum group alloys in a method for precisely molding optical glass by heating and pressing.
, chromium (Cr), tantalum (Ta), =op (Nb)
, silicon (Si).

Boron (B), aluminum (,1M), hafnium (
Hf), zirconium (Zr), or vanadium (V
) and at least one selected from nitrides of 0.
By using a press molding mold coated with a thin film weighed by 0.01 to 10%, the softening point is 700, such as borosilicate glass, barium borosilicate glass, and lanthanum glass.
It becomes possible to press-form optical glass at temperatures exceeding ℃.

Since nitride is a covalent compound, it is stable even at high temperatures and is a high-strength compound. By dispersing this nitride into the platinum group alloy, the grain boundaries of the platinum group alloy thin film are strengthened, resulting in high strength and high hardness even at high temperatures, allowing the highly accurate surface shape of the press forming surface to be maintained. Ru. Further, by dispersing nitrides in the platinum group alloy, the constituent particles of the platinum group alloy thin film are made finer and denser, and the surface roughness of the press-formed surface is further reduced.

In addition, in the present invention, the amount of nitride dispersed in the platinum group alloy is 0.
．． The reason why the range is specified as 0.01 to 10% by weight is that if it is less than 0.01% by weight, the above effect will be reduced, and if it is more than 10% by weight, the optical glass and the thin film will easily react or the optical glass will be lost. This is because it becomes easier to see through. Further, the present invention does not particularly specify the base material of the mold, but the base material may be any material that has excellent oxidation resistance, heat resistance, workability, and high temperature strength, such as martensitic stainless steel, Austenitic steel, tungsten alloy 9 cemented carbide, thermeft, molybdenum, glassy carbon, zirconia, silicon carbide, etc. can be used.

Example Examples are shown below.

(Example 1) FIG. 1 is a perspective view of an upper die 1 and a lower die 2 of a press molding die used in the present invention. Both upper and lower types 1 and 2,
Using a cylindrical material of austenite W4 (for example, 5U3310), the upper mold 1 has a concave molding surface 4 with a radius of curvature of 46fi and a plurality of ■-shaped notches 3 on its periphery, and the lower mold 2
A concave molding surface 5 with a radius of curvature of 200 fins was formed on each of the surfaces.

These forming surfaces 4 and 5 were ramped using ultrafine diamond powder, and the maximum surface roughness R was achieved in about 2 hours.
max) made it a mirror surface of 100 people. A film made by adding various metals to platinum group alloys with various compositions shown in Table 1 on the surfaces of molded surfaces 4 and 5, which have become mirror surfaces! A thin film of 800 people was formed by sputtering.

Nitrogen ions (N2'') were injected into this thin film at a rate of 10 ions/d at an accelerating voltage of 50 KV to change the added metal into nitride. By this method, the upper mold 1 for molding an optical glass element and A lower mold 2 was obtained.

FIG. 2 shows a partially broken surface of the above-mentioned glass press molding molds 1 and 2, with heaters 6 and 7 wound around the outer diameter surfaces, respectively, and attached to the upper and lower plungers 8 and 9 of the press. In the same figure, Siri h (S i02 ) 30
Barium borosilicate glass lump IO consisting of 50% by weight of barium oxide (BaO), 15% by weight of boric acid (82,03), and the balance being trace components.
is held by the raw material supply jig 11, heated to 780°C in the preheating furnace 12, and then heated to 730°C between glass press molding molds 1 and 2 at a press pressure of 40 kg/-. Press-molded.

The molded lens, which was cooled to a temperature of 400° C. together with the upper and lower molds, was taken out from the takeout port 13 after the upper plunger 8 was returned.

Through such a process, after performing glass press molding 100 times using a mold coated with various thin films shown in Table 1, the surface roughness of molding surfaces 4 and 5 of the mold (Rmax) and micro The results of observing the Vickers hardness (Hv) and the surface condition of the molded glass lens were
Shown in the table.

As is clear from Table 1, a molding die in which austenitic steel is coated with a thin film of nitride dispersed in a platinum group alloy has a roughened molding surface even after press-molding barium borosilicate glass 100 times. I hadn't woken up. In addition, the micro Vickers hardness of the mold is 800.
The front and back surfaces showed extremely high hardness, and no minute scratches were observed. The surface precision of the molded optical glass lens did not change, and its optical performance was extremely excellent.

In the case of a platinum group alloy thin film that does not contain nitrides, as is clear from the comparative example, the molding surface of the mold was extremely slightly rough, and the optical performance of the molded optical glass lens was slightly degraded. .

(Left below) (Example 2) Cemented carbide (WC>) was processed into the same shape as in Example 1, and molded surfaces 4 and 5 were wrapped with ultrafine diamond powder, and the surface was polished in about 1 hour. Maximum roughness Rmax) is approximately 1
I made it a mirror surface of 00 people. Thin films having a thickness of approximately 800 mm were formed by adding various metals to platinum group alloys having various compositions shown in Table 2 by sputtering. 1 at an accelerating voltage of 50 KV to this thin film.
Nitrogen ions (N2+) were implanted at a rate of 0" ions/d to convert the added metal into nitride. In this manner, an upper mold 1 and a lower mold 2 for molding optical glass cords were obtained.

In the same manner as in Example 1, silica (S i02 ) 10
Weight percent, barium oxide (B a 0) 25 weight percent, boric acid (B203) 30 weight percent,
Lanthanum-based optical glass consisting of 20% by weight of lanthanum oxide (La203) and the remainder being trace components was heated to a preheating temperature of 750°C, a molding temperature of 710°C, and a press pressure of 40°C.
Press molding was carried out under the conditions of r/cat and press time of 2 minutes, and the molded lens was taken out at 400°C.

After performing glass press molding 100 times using molds coated with various thin films shown in Table 2, the surface roughness (RIlax) and micro Vickers hardness (Hv) of molding surfaces 4 and 5 of the mold were determined. Table 2 shows the observation results of the surface conditions of the molded glass lenses.

As is clear from Table 2, the molding die in which cemented carbide is coated with a thin film of platinum group alloy with nitride dispersed in it,
Even after the lanthanum-based optical glass was press-molded 100 times, the molded surface did not become rough. Furthermore, the molding mold had a very high hardness of approximately 800 microscopic Vickers hardness, and no fine scratches were generated on the molding surface. The molded optical glass lens had a highly accurate surface shape transferred from the mold, and had excellent optical performance.

On the other hand, when a platinum group alloy thin film containing no nitrides was coated, as is clear from the comparative example in Table 2, the molding surface of the mold was very slightly rough, and the molded optical The optical performance of the glass lens was also slightly degraded.

Note that the platinum group alloy composition is not limited to the alloy compositions used in Examples 1 and 2 of the present invention, and similar results were obtained with other alloy compositions.

In Examples 1 and 2, cases were shown where one to four types of nitrides were dispersed in a platinum group alloy, but the same effect was obtained when five or more types of nitrides were dispersed. In the example, a nitride was created by implanting nitrogen ions into a metal added to a platinum group alloy, but a mold similar to the present invention can also be created by spunting a platinum group alloy target and a nitride target. It is possible to do so.

(Left below) As described in detail, according to the present invention, the softening point of barium borosilicate optical glass, lanthanum-based optical glass, etc. is 700°C, compared to the conventional molding method for optical glass elements.
It is possible to press-form optical glass with extremely high precision.

With a long-life mold that can be press-molded 100 times, the number of mold replacements is greatly reduced, making it possible to mass-produce high-precision optical glass elements, and significantly improving productivity and reducing manufacturing costs. There is.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a glass press mold used in the present invention, and FIG. 2 is a partially broken section of the plunger portion of a press device to which the mold shown in FIG. 1 is attached. l...Top mold, 2...Bottom mold, 3...
...Notch, 4゜5...Molding surface, 6.7...
...heater, 8,9...plunger, 10.
... Optical glass lump, 11 ... Raw material supply jig, 12 ... Preheating furnace, 13 ... Takeout port. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1

Claims (2)

[Claims] (1) 0.0% of at least one type of nitride in platinum group alloy
A method for molding an optical glass element, which comprises precision molding an optical glass element by heating and pressurizing it using a press molding die coated with a thin film containing 1 to 10% by weight of the dispersed material. (2) Nitride is titanium (Ti), chromium (Cr), tantalum (Ta), niobium (Nb), silicon (Si),
Boron (B) Aluminum (Al), Hafnium (Hf)
), zirconium (Zr), or a nitride of vanadium (V).