JPS59123631A - Mold for molding optical element - Google Patents

Abstract

PURPOSE:To provide the titled mold for molding by heating under pressure an optical element such as lens, prism, filter, etc. that is high in surface accuracy, by making the mold up of a material containing as major constituents tungsten carbide and cobalt. CONSTITUTION:For example, 100pts.wt. tungsten carbide, 1-25pts.wt., in particular 3-10pts.wt., cobalt and, if required, nickel, etc. are mixed, sintered and pressed to produce the intended mold consisting of a material containing mainly tungsten carbide anc cobalt.

Description

[Detailed description of the invention] The present invention relates to a mold for molding an optical element.

Optical elements such as lenses, prisms, and filters are conventionally
Most are manufactured by polishing glass. However, polishing requires time and skill. In addition, manufacturing an aspherical lens by polishing requires a more sophisticated polishing technique and requires a longer processing time.

In contrast to such a method of manufacturing an optical element using a polishing process, there is a method of manufacturing an optical metal by molding by heating and pressing. According to this molding method, optical elements can be manufactured in a short time, and aspherical lenses can also be manufactured easily and in a short time in the same way as spherical lenses. There are still problems that need to be improved in the molding method. The problem is that it is not easy to mold an optical element with the surface precision necessary for an optical element. That is, in the past, molds made of graphite were often used, but when graphite molds were used, it was not possible to manufacture optical glass elements with good surface precision. . The main object of the present invention is to provide a mold that can manufacture an optical element with good surface accuracy by selecting a mold material.

The mold for molding an optical element according to the present invention is characterized in that it is made of a material whose main components are tungsten carbide and Conolite. That is, according to the present invention, an optical element having high surface precision can be manufactured by heating and pressing by using a mold made of a material whose main components are tungsten carbide and carbon dioxide. As mentioned above, molds made of graphite have traditionally been used in many cases for making optical elements, but since graphite is porous, no matter how much it is polished, it
Although it has not been possible to obtain a mold with an inner wall surface that is optically rough enough to produce an element with sufficient surface precision as an optical element, the present invention uses a mold whose main components are tungsten carbide and cobalt. By using this method, it is possible to obtain a mold having an inner wall surface with a surface roughness of 5/100 μm or less, and to produce an optical element having a surface precision that accurately corresponds to such surface roughness. Therefore, the surface roughness of the inner wall of the mold according to the present invention is usually 5/1
The thickness is preferably set to 00μ or less, particularly 3/100μ or less. In order to create a mold with such high surface precision, high pressure is applied to the surface of the sintered body of tungsten carbide and cobalt to form a bore (which would impede surface precision) on the surface.
Preferably, the material is made without any cavities and is further polished. The composition ratio of tungsten carbide and cobalt forming the mold is set appropriately, but in general, a range of 1 to 25 parts, particularly 3 to 10 parts of cobalt is suitable for 100 parts (by weight) of tungsten carbide. . Further, other components such as nickel may be added as appropriate.

In this way, by adding cobalt to tungsten carbide, it is possible to obtain a mold that is highly dense and does not change shape at high temperatures.However, materials whose main components are tungsten carbide and cobalt have a coefficient of linear expansion. 5
8.2 of flint optical glass (SrI2) at ×10
X10 It is very small and does not cause so-called burning, the glass does not stick to the mold (Mold Sumira), and its thermal conductivity is higher than that of ceramics (0.91m/-).It has a high hardness (Hv1500). ) have excellent durability;
It also has the advantage that the high specularity described above can be obtained.

An optical element molded by heat and pressure using a mold according to the present invention does not require post-polishing and can be used as an optical element as it is. In addition, the heating and pressing conditions in the molding process are different from the various glasses used and MgF2. CaF2P
Although it is appropriately set depending on the type of crystal material such as Tie□p ZnS, in the case of glass, the temperature of the glass during pressurization is equal to or higher than the glass transition point. It may be heated in advance before being placed in the mold, or it may be heated together with the mold after being placed in the mold.

However, in order to prevent oxidation caused by heating, this molding step is preferably carried out in a vacuum or in an inert atmosphere such as nitrogen gas or helium.

Hereinafter, an example of manufacturing an optical element using a mold according to the present invention and a comparative example of manufacturing an optical element using a conventional graphite mold will be described.

Example 1 Tungsten carbide (wc) pulverized to a particle size of 1 to 2μ
Mix part by weight of cobalt (co)s with part by weight of OO to obtain an outer diameter of 1
After pressing to a thickness of 15 mm and a thickness of 7 mm, the sintered material was densified by hot isostatic pressing (HIP) using a cis body (argon) as a pressure medium and applying a surface pressure of 5000 kp/-.

Next, use a curve generator (spherical surface generator) to grind the surface to a surface roughness of 10 μm using the same method used to create the spherical surface of the lens.
I made it to the extent. Furthermore, lapping was performed using alumina abrasive grains with a particle size of 10μ to give a surface roughness of about 1μ.
The Rmax was increased to 0.03μ or less as shown in FIG.

The lens molding apparatus and processing procedure will be explained with reference to FIG.

In Fig. 2, 1 is the main body of the vacuum chamber, 2 is its lid, 3 is an upper mold for molding optical elements, 4 is its lower mold,
5 is an upper mold presser for holding down the upper mold; 6 is a mold; 7 is a mold holder; 8 is a heater; 9 is a lifting rod for lifting up the lower mold; 10 is an air cylinder for operating the lifting rod; 1
1 is an oil pump, 12, 13, 14 is a valve, 15 is a nitrogen gas introduction pipe, 16 is a valve, 17 is an exhaust non-vector, 18 is a valve, 19 is a temperature sensor, 20 is a water cooling pipe, 21 is a vacuum tank (Pelger ) ◎ Before manufacturing the optical element, as a preparation, flint-based optical glass (SF14) with an outer diameter of 15.8 mm and a thickness of 2 mm is shown.
Cut into a disk shape and keep both sides young (this is called a blank). Open the lid 2 of the vacuum chamber 1, place the blank 22 on the soil of the lower mold 4, set the mold 3, and then close the lid 2 of the vacuum chamber, let water flow through the water cooling pipe 20, and turn on the heater 8.

At this time, the nitrogen gas valves 16 and 18 are closed and the exhaust system valves 12 and 13 are closed.

14 is also closed. Incidentally, the oil rotating pump 11 is constantly rotating.

The valve 12 is opened to begin evacuation, and when the pressure becomes below 10 Torr, the valve 12 is closed and the valves 16 and 18 are opened to introduce crab gas from the cylinder into the vacuum chamber.

When the temperature reaches 650° C., the air cylinder 10 is operated and molding is performed at a pressure of 1 Q kl/am2. Apply pressure until the temperature drops below the transition point, and during this time reduce the cooling rate to 10°C.
control the position. Thereafter, cooling is carried out at a rate of 20° C./min or higher, and when the temperature drops to 200° C. or lower, the valves 16 and 18 are closed, the leak valve 13 is opened, and air is introduced into the vacuum chamber 1. Then, the lid 2 is opened, the upper mold presser 5 is removed, and the molded product is taken out.

As above, flint optical glass (SF14)
(Softening point SP = 586°C, transition point Tg = 485°C) was used to mold a lens with the shape and dimensions shown in Figure 3. As a result, the mold with the surface roughness shown in Figure 1 (a) and We were able to obtain lenses with approximately the same surface roughness.

FIG. 4 shows the molding conditions at this time, that is, a time-temperature relationship diagram.

Example 2 The same procedure as in Example 1 was carried out using 100 parts by weight of tungsten carbide ground to a particle size of 1 to 2 μm in the same manner as in Example 1, and 5 parts by weight of cobalt and 5 parts by weight of nickel. A mold with a surface roughness Rmax of 0.03μ or less was made.

When a lens was molded using the same lens molding apparatus and processing procedure as in Example 1, the same results as in Example 1 were obtained.

Comparative Example A conventional graphite mold was polished and the same lens as in Example 1 above was molded using the same equipment.

In this case, the surface roughness of the mold is as shown in Figure 1 (b).
With Rmax O, 3 μ, the molded lens could only have a surface roughness of Rmax O, 2, as shown in Figure 1 (C).

[Brief explanation of the drawing]

1st M, a diagram showing an example of the surface roughness of the mold according to the present invention,
Figures 1 (B) and (C) are diagrams showing the surface roughness of a conventional graphite mold and the surface roughness of a molded lens, Figure 2 is a sectional view showing a lens molding device, and Figure 3 is a molding FIG. 4 is a time-temperature relationship diagram during molding. ■...Basic vacuum chamber price 2...Lid: 3...Upper mold 4...Lower mold...Upper mold presser 6...Body chamber 7 -Small mold router 8...Heater 9...With Raising rod 10...Air syringe 11...Oil rotation 1〈,,ra 12.13.14...Pal 15...
Nitrogen gas introduction pipe 16...Palzu 17・Discharge pipe 18...Palzu 15)...Warm Ift switch 2
0...Water-cooled bike or 21...units Figure 1 (A) Figure 1 (B) Figure 1 (C) Figure 2 Procedural amendment 1. Indication of fact No. 1 Showa 7 year patent application No. Z311 Otsu No. 3, relationship with the case of the person making the amendment Application Address (Residence) 3-chome Shimokuko, Il1-ku, University of Tokyo [130i
No. f2 Name (Name) (1,00) Canon Co., Ltd. 4
11 people Address: 2-6-2, Marunouchi, Chiyoda-ku, Tokyo 330-1, Building 330-1, 2-chome, Marunouchi, Chiyoda-ku, Tokyo Total: 1'-21'ft*r+Radeko Shisa Agitaba (-17 Revised Moon Elephant Supplement) The following matters have been amended in the specification of the original application. In Note 1, page 6, line 9, the statement "1 is the vacuum chamber (Pelger) body" is corrected to "1 is the airtight container."2. In the 3rd line from the bottom of No. 61, ``21 is a vacuum chamber (Pelger)'' is corrected by 4J to read ``F21 is a closed container.'' 3. Page 7, lines 3, 5, and 122. In line 188, "vacuum chamber" should be corrected to "airtight container." 4. On page 7, line 6, "turn on heater 8." should be replaced with "Turn on heater 8." 5, page 7, line 11 and lines 17-18, “Palzu 16,
18" should be corrected to read "valve 16". 6. In the 18th line of the 7th member, correct "Leak Pulp 13" to "Nori Shizu 13". 7. On page 9, line 12, [1... Vacuum chamber body] is corrected to "1... Airtight container."

Claims (1)

[Claims] A mold for molding an optical element, characterized in that it is formed from a material whose main components are tungsten carbide and cobalt.