JPS59121126A - Mold for molding optical element - Google Patents

Abstract

PURPOSE:The titled mold capable of forming an optical element having improved surface precision by heating and pressurizing method, consisting of a mixture of titanium carbide and a metal. CONSTITUTION:A mixture of 100pts.wt. titanium carbide and about 20-35pts.wt. metal (e.g., molybdenum, nickel, or cobalt) is molded into a given shape, sintered, densified by hot press procession at constant pressure, and the surface of the mold is polished until the surface roughness reaches <=about 0.05mu, to give a mold for molding an optical glass element. Since the mold has a coefficient of linear expansion almost equal to that of optical glass, it will not cause fastening under heating, has improved hardness and durability, and improved mirror surface properties, so that a prepared optical element can be directly used without polishing it.

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 considerable time and skill. Furthermore, manufacturing an aspherical lens by polishing requires a more sophisticated polishing technique and requires a longer processing time. In contrast to a method of manufacturing an optical element using a continuous polishing process, there is a method of manufacturing an optical element by molding using heat and pressure. 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. it is,
It is not easy to mold an optical element with the surface precision necessary for an optical element. That is, conventionally, many molds made of graphite have been used, but when a graphite mold is used, it has not been possible to manufacture an optical element with good surface accuracy. The main object of the present invention is to provide a mold that can produce 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 formed from a mixture of titanium carbide and metal. That is, in the present invention, by using a mold made of titanium carbide and metal, an optical element having high surface accuracy can be manufactured by heating and pressing. As mentioned above, many molds made of graphite have traditionally been used as molds for making optical elements, but because graphite is porous, no matter how much it is polished, the surface precision is not sufficient for optical elements. However, in the present invention, by using a mold made of titanium carbide and metal, the surface roughness can be improved. It is possible to obtain a mold having an inner wall surface of 5/1 ooμ or less, and to produce an optical element having a surface precision that accurately corresponds to such surface roughness. Therefore, it is preferable that the surface roughness of the inner wall of the mold according to the present invention is normally set to ''/100μ or less, particularly 3/1ooμ or less, and molds with such high surface precision are made of titanium carbide and titanium carbide. It is preferable to manufacture a sintered metal body by applying high pressure to the surface to make the surface free of bores that would impede surface roughness, and then polishing it.Carbonization to form a mold The composition ratio of titanium and metal is set as appropriate, but in general, the proportion of metal is 15 to 40 parts per 100 parts (by weight) of titanium carbide.
parts, particularly in the range from 20 to 35 parts. Further, as such a metal, molybdenum is particularly preferred, and nickel, cobalt, etc. are also preferred.

However, a mixture of titanium carbide, nickel, and molybdenum has a linear expansion coefficient of 8.3X10', which is almost the same as 8.2X10' for optical glass (SrI2), and no burning occurs. In addition, it has the advantages that the glass does not easily stick to the mold (high quality), has high hardness (Hv1850), is excellent in durability, and can obtain the aforementioned high specularity. .

The optical element molded by heating and pressurizing with the 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 vary depending on the various glasses used and MgF * CaF
It is appropriately set depending on the two types of crystal materials such as t Ti0z and Zn8, but 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 from occurring due to 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 group mold will be described.

Example 1 A material was prepared by mixing 100 parts by weight of titanium carbide, 12 parts by weight of nickel, and 6 parts by weight of molybdenum, pressing the mixture into an outer diameter of 17 m and a thickness of 15 Wn, and then sintering the material using the hot isostatic pressing method (HIP).
5000 k using gas (Arjun) as the pressure medium.
It was densified by applying a high pressure of g/ca.

Next, use a curve generator (spherical surface generator) to grind the surface in the same way as creating the spherical surface of the lens, and reduce the surface roughness to 10.
I made it about tt. Furthermore, the surface was lapped using alumina abrasive grains with a grain size of 10μ to obtain a surface roughness of about 1μ, which was then polished using a diamond with a grain size of 0.5μ, and the roughness was measured using a stylus as shown in Figure 1 (a). Maximum roughness Rm measured by method
ax was set to 0.015μ or less.

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

In Figure 2, 1 is the main body of the vacuum chamber (Belscher), 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 rotary pump, 12, 13.14 is a nonolube, 15
is the nitrogen gas introduction pipe, 16 is the nozzle valve, 17 is the discharge nozzle, 18 is the valve, 19 is the temperature sensor, and 20 is the water cooling nozzle. Reference numeral 21 indicates a stand on which a vacuum chamber (Pelzya) is placed.

In preparation for manufacturing optical glass elements, flint-based glass (SrI2) was prepared with an outer diameter of 15.8 mm and a thickness of 2.
A disk-shaped threshold is layered on both sides (this is called a blank). Open the lid 2 of the vacuum chamber 1, place the blank 22 on the lower mold 4, set the upper mold 3, and then open the lid 2 of the vacuum chamber.
Close it, let water flow through the water cooling tube, and turn on the heater 8. At this time, the nitrogen gas valves 16 and 18 are closed and the exhaust system/? Valve 2°13.14 is also closed. The oil rotating Ponzo 11 is constantly rotating. The valve 12 is opened to begin evacuation, and when the temperature becomes less than 10'Torr, the valve 12 is closed and the valves 16 and 18 are opened to introduce nitrogen gas into the vacuum chamber. When the temperature reaches 650° C., the air cylinder 10 is activated and molding is performed at a pressure of 10 −. Continue to apply pressure until the temperature drops below the transition point, and during this time reduce the cooling rate to 10
'C71s control. After that, 20″C/III
Cooling is performed at the above rate, and when the temperature drops to below 200° C., valves 16 and 18 are closed, leak valve 13 is opened, and air is introduced into vacuum chamber 1. Then, the lid 2 is opened, the upper mold presser 5 is removed, and the molded product is taken out.

As described above, 7 lint optical glass (8F14
) (Softening point 5P = 586℃, transition point Tg = 485℃
) was used to mold a lens having the shape and dimensions shown in FIG. 3, resulting in a lens with approximately the same surface roughness as that shown in FIG. 1(a). FIG. 4 shows the molding conditions at this time, that is, a time-temperature relationship diagram.

Example 2 Titanium carbide, cobalt, and molybdenum were mixed in the same proportions as in Example 1, and after pressing to an outer diameter of 17 mm and thickness of 151 mm and 11 mm, the sintered material was heated to a gas ( The material was densified by applying a high pressure of 5000 V using argon (argon) as a pressure medium.

When this material was subjected to the same treatment as in Example 1 and a lens was molded, exactly the same results as in Example 1 could be obtained.

The same lenses as in the above examples were molded on the same equipment using conventional graphite molds.

In this case, the surface roughness of the mold is Rmax O, 3μ, as shown in Figure 1 (B), and the molded lens has a roughness of Rmax O, 3μ, as shown in Figure 1 (B).
As shown in c), only surface roughness of RmaxQ and gμ was obtained.

[Brief explanation of drawings]

Figure 1 (a) shows an example of the surface roughness of a mold according to the present invention, and Figures 1 (b) and (c) show the surface roughness of a similar mold made of conventional graphite and the surface of a molded lens. A diagram showing roughness, Figure 2 is a sectional view showing a lens molding device, Figure 3 is a diagram showing the shape and dimensions of an example of a lens to be molded, and Figure 4 is a time-temperature relationship diagram during molding. It is.・・・・・・−777゜Honda Kodaira 1 J--ノ temporary decoration 1: Figure 1 (a) Figure 1 (b) Vertical 1 scale 004 left Horizontal 1 scale 0.05 mRRm 0. Defense Figure 1 (c) Figure 2 2 Figure 3 Procedural Amendment Yo 1, Indication of the case Relationship to 1989 Patent Application No. 23/yλ2 Case Applicant 4, Agent Address Chiyoda-ku, Tokyo 2-6-2 Marunouchi Shigesu Building 330) Amendment The following matters in the specification of the application are to be amended. On page 4, line 2 of d-1, the word "mixing" is corrected to "sintering." 2. In the 5th line of page 4, the text ``f (high mold quality)'' is corrected to ``(mold release quality)''. 3. On the 2nd line of page 6, replace "vacuum chamber (Berge 1 = -) body" with "closed container"
I am corrected. 4. On page 6, line 11, ``vacuum chamber (Belge P-)'' is corrected to ``closed container.'' 5. On page 6, lines 16 and 18, and on page 7, lines 4-5, the words ``vacuum chamber'' are corrected to ``closed container.'' 6. In the second line at the bottom of page 6, correct the text ``Turn on the power switch 8.'' to ``Turn on the power to the switch 8.'' 7. On page 7, lines 3 and 4, [Palzu 16,184 is corrected to read "Palzu 16." 8, page 7, lines 10-11, it says ``Close paludu 16 and 18, open Tsukuba J-shizu 13, and put it in the vacuum chamber 1.''"Inside," he corrected.

Claims (1)

[Claims] A mold for molding an optical element, characterized in that it is formed from a mixed material of titanium carbide and metal.