JPH02243522A - Mold for forming optical element - Google Patents

Abstract

PURPOSE:To obtain a mirror-polished mold resistant to surface deterioration and usable at a high temperature without causing welding of glass by forming a sintered diamond at a part where an optical element forming mold is brought into contact with glass. CONSTITUTION:A mixture of diamond particles having an average particle diameter of several - several tens mum and a 1-10vol.% of a sintering assistant such as Co or Ni having an average particle diameter of several hundreds mum is placed on a mold preform 1 made of a sintered material such as C or SiC and sintered by heating at 1,500-2,000 deg.C for about 1hr under a pressure of 5-8GPa. The formed sintered diamond 2 is mirror-polished to obtain a mold for forming an optical element having desired form. A spherical glass raw material 3 is placed on the lower mold 54 of the above mold, a lid 52 of a vacuum chamber 51 is closed, water is passed through a water-cooling pipe 70, an electric current is applied to a heater 58, the chamber 51 is evacuated to <=10<-2>Torr by opening a valve 62, the valve 62 is closed, an inert gas is introduced into the chamber 51 by opening a valve 66 and the upper mold 53 is lowered by operating a pneumatic cylinder 60 to effect the compression molding of the raw material 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a mold used for manufacturing optical elements made of glass, such as lenses and prisms, by press molding a glass material.

[Prior art] The technology of manufacturing lenses by press-molding glass materials without requiring a polishing process eliminates the complicated processes required in conventional lens manufacturing, and makes it possible to easily and inexpensively manufacture lenses. In recent years, it has come to be used not only in the production of lenses but also prisms and other optical elements made of glass.

The properties required of the mold material used for press molding of such glass optical elements are hardness.

One example is °1t, which is excellent in heat resistance, female moldability, mirror workability, etc. Conventionally, many proposals have been made for this type of mold material, such as metals, ceramics, and materials coated with these materials. To give some examples, 13C "martensitic steel" is disclosed in JP-A-49-51112;
4, Japanese Patent Application Laid-Open No. 60-246230 discloses a material in which cemented carbide is coated with precious metals, and Japanese Patent Application Laid-Open No. 61-1831
No. 34 also proposes a material coated with a diamond thin film or a diamond-like carbon film.

[Problems to be Solved by the Invention] However, 13Cr martensitic steel is easily oxidized and further has the disadvantage that Fe diffuses into the glass at high temperatures, causing the glass to become colored. In addition, although SiC and 513N4 are generally considered to be difficult to oxidize, oxidation still occurs at high temperatures, forming a 5iOz film on the surface, which causes fusion with the glass, and furthermore, due to its high hardness, processing of the mold itself is difficult. It has the disadvantage of being extremely bad. Materials coated with precious metals are less prone to fusion, but because they are extremely soft, they are easily scratched and easily deformed. In addition, since the surface of the material coated with a diamond thin film lacks smoothness, the resulting optical element lacks specularity.

Furthermore, the film called a diamond-like carbon film is not determined by the type; ■ it consists only of carbon water, but the type of bonding is an amorphous film consisting of sp, sp'', and sp'hybrids; (1) an amorphous film containing hydrogen atoms in addition to carbon atoms (hereinafter abbreviated as a-C:H film); (2) a film containing minute diamonds or a structure of both minute graphite and amorphous. Also, for each stage mentioned above, ■ is the ratio of sp, sp'', sp',
■ is the size of graphite, ■ is the ratio of hydrogen and carbon, ■
If the ratio of crystalline to amorphous is different, the properties of the film will differ. In particular, if there are many multiple bonds, or if the multiple bonds are delocalized (the posterior thread is long,
Films containing graphite microcrystals tend to reduce lead oxide, a component of glass, and lead precipitation occurs.
This method has disadvantages such as poor mold durability and reduced surface precision of the optical element.

Therefore, an object of the present invention is to provide a mold for molding an optical element suitable for molding a glass optical element. In particular, it does not cause fusion with glass at high temperatures, is capable of mirror polishing, and has an appropriate hardness. The present invention provides a mold for molding an optical element that is resistant to oxidation and does not cause lead precipitation.

[Means for Solving the Problems] According to the present invention, in an optical element forming mold used for press coating of an optical element made of glass, at least the part of the mold that comes into contact with the glass is made of diamond particles and a sintering aid. A mold for molding an optical element, which is a diamond sintered body, is provided.

Diamond is chemically inert and stable without reacting with optical glass elements that contain large amounts of lead or alkali elements at the high temperatures where optical elements are molded. No precipitation or fusion with glass. In addition, since it has very high hardness, it does not cause scratches on the mold surface or plastic deformation during press molding. As described above, diamond has excellent properties as a material for molds for molding optical elements. However, due to the problems mentioned in Section 11, it is very difficult to put it into practical use.

The present inventor has discovered that a diamond sintered body obtained by sintering diamond particles with a suitable sintering aid has the advantages of diamond that it does not fuse with glass at high temperatures, is resistant to oxidation, and does not cause lead precipitation, and has an appropriate hardness. It has been found that this material is most suitable as a mold material for molding optical elements, as it has the advantage of being mirror-polished.

Next, the present invention will be specifically explained.

Various methods are known for producing diamond sintered bodies, including diamond particles having a uniform grain size of several micrometers to several tens of micrometers and several hundred Co particles.

Metal powder such as Ni or Fe with a content of 1 to 20v
After adjusting and mixing to a range of o1%, 5 to 8 GP
a. Obtained by sintering at a high temperature and pressure of 1500 to 2000°C for about 1 hour.

In addition, by sintering a WC sintered body containing several w% of Co and diamond powder at high temperature and high pressure, carbon
After forming a film of sintering aid to j by moving the sintering aid to the diamond powder layer to form a direct bond between the diamond particles, or by forming the sintering aid on the diamond particles in advance by vacuum evaporation, sputtering, etc., There are methods such as sintering in a high-temperature, high-pressure chamber. According to this method, the sintering aid is homogeneously distributed in the sintered body as very fine particles, and the amount added can be reduced compared to other methods. These methods form direct bonds between diamond particles. There is also a method of sintering at low pressure and high temperature using ceramics such as SiC as the main binder.

The diamond sintered body may be produced by any method, but it is better to use as little sintering aid as possible.

That is, although a diamond sintered body consisting only of diamond particles without using a sintering aid would be ideal, it is currently extremely difficult to obtain such a body. Therefore,
A sintering aid is added, but the amount added is lov
If it exceeds ol%, the influence of the physical properties of the auxiliary becomes strong and the mechanical strength represented by hardness decreases, and some auxiliaries may cause fusion with the glass or reduce lead oxide and inhibit the precipitation of Pb. This is not desirable as it may cause a problem. If the amount of the auxiliary agent added is less than 1 vol%, a usable sintered body cannot be obtained.

In addition to the above-mentioned transition metals, the sintering aids used include:
Any material that can obtain a diamond sintered body with sufficient mechanical strength may be used; 'Zr, IN, V,
Nb, Ta, Cr, Mo, V4, Ru,
Os.

Rh, lr, Ni, Pd, PL, C
u, ^g, ^u, Si.

Ge, Sn, Pb elements, their oxides and carbides.

It may be a nitride, a boron material, or a mixture or alloy thereof. Furthermore, there is no problem even if a trace amount of elements, compounds, or mixtures other than those mentioned above are mixed in the diamond sintered body within a range of several tens of thousand ppm or less.

Next, in order to use this sintered body as a mold for molding an optical element, the sintered body may be ground into a desired shape and then mirror-polished.

However, since there is a limit to the thickness of the diamond sintered body that can generally be obtained, a diamond sintered body forming base such as WC is processed in advance to form a mold shape for optical element molding, and then the diamond sintered body is processed. sintered and formed;
Thereafter, mirror polishing is performed to obtain a mold for molding an optical element having a desired shape.

As for the polishing method, - by using the diamond 131 MM polishing method known in Japan, a mirror surface ω is obtained.
[Can be polished.

[Examples] Specific examples of the present invention will be described below with reference to the drawings.

Embodiment FIGS. 1 and 2 show a mold for molding an optical element according to the present invention.
2 shows two embodiments.

FIG. 1 shows the optical element before press molding, and FIG. 2 shows the optical element after molding. 1 in Figure 1 is the mold base material,
2 is a diamond sintered body formed before molding in contact with the glass material of the mold base material.

:3 is glass wood, and 4 in FIG. 2 is an optical element. By press-molding a glass material 3 placed between molds as shown in FIG. 1, an optical element 4 such as a lens is molded as shown in FIG. 2.

Here, a sintered body of WC and SiC was used as the mold 1 material.・W is sputtered onto diamond particles with an average particle diameter of 1 to 2 μm to form a film of 5 wt% (approximately 1 vol. Sintering was carried out at .50 Pa and 1500° C. for 30 minutes. When the obtained diamond sintered body was analyzed by X-ray diffraction, there were only peaks of diamond and WC, and no peak of W. In addition, when the hardness of this sintered body layer was measured, it was found to be 7000 kg/
It was mm'. When this diamond sintered body layer was mirror polished, what was its surface roughness? ,,, 0.02μm
Met.

Next, an example in which a glass lens was press-molded using the mold for molding an optical element according to the present invention will be described in detail. -Table I shows the size of the mold materials used in the experiment.

Table 1 Nos. 1 to 3 are comparative materials, and Nos. 4 to 5 are materials proposed in the present invention. Cemented carbide, sintered WC, and sintered SiC were used as base materials. FIG. 3 shows the lens molding apparatus used in the above example.

In Fig. 3, 51 is the main body of the vacuum chamber, 52 is its lid, 53 is an upper mold for molding optical elements, 54 is a lower mold, 55 is an L-shaped presser for holding the upper mold, and 56 is a mold for use. , 57 is a mold holder, 58 is a cover, 59 is a lifting rod that lifts up the upper mold, 60 is an air cylinder that operates the lifting rod,
61 is an oil rotary pump, 62, 63, 64 is a valve, 65
66 is a valve, 67 is a leak vibe, 68 is a valve, 69 is a temperature sensor, 70 is a water cooling pipe, and 71 is a stand that supports a vacuum chamber.

The process of manufacturing the lens will be described next.

A glass material made of flint optical glass (SnI2) adjusted to a predetermined thickness and made into a spherical shape is placed in the cavity of the mold, and this is placed in the apparatus.

After placing the mold containing the glass material in the apparatus, the lid 52 of the vacuum chamber 51 is closed, water is run through the water cooling pipe 70, and current is passed through the heater 58. At this time, the nitrogen gas valves 66 and 68 are closed. Exhaust system valves 62, 63, 64 are also closed. Note that the oil rotary pump 61 is constantly rotating.

The valve 62 is opened to begin exhaustion, and when the temperature reaches IO-"rorr or higher, the valve 62 is closed, and the valve 66 is opened to introduce nitrogen gas from the cylinder into the vacuum chamber. When the temperature reaches a predetermined temperature, the air cylinder 60 is activated. 10 kg/cm
'' for 5 minutes. After removing the pressure, cool at a cooling rate of 1 °C/min until below the dislocation point, and then cool at a rate of 0 °C/min or more. 2
When the temperature drops to 00° C. or lower, the valve 66 is closed and the leak valve 63 is opened to introduce air into the vacuum chamber 51. Then, the lid 52 is opened, the upper mold holder is removed, and the molded product is taken out.

As described above, the lens 4 shown in FIG. 2 was molded using the flint optical glass SF+4 (softening point 5p=586° C., dislocation point Tg=485° C.). FIG. 4 shows the molding conditions at this time, that is, a time-temperature relationship diagram.

Next, the surface roughness of the molded lens and the surface roughness of the mold before and after molding were measured. The results are shown in Table 2.

Next, melting 4'J was performed, and after molding No. 1.4.5 200 times using the same mold, the surface roughness was measured. The results are shown in Table 3.

Table 3 As is clear from the results in Table 29 and Table 3 above, the mold material according to the present invention has excellent mold releasability from glass, and the surface deterioration is extremely small compared to conventional mold materials even after repeated use.

Next, using molds No. I to 5, optical glass was press-molded using a molding apparatus n shown in FIG.

In Figure 5, +04 is the intake exchange chamber, and 10
6 is a molding chamber, 108 is a vapor deposition chamber, and 110 is a replacement chamber for taking out. II2゜114.116 is a gate valve! ! 8 is a rail, and +20 is a pallet that is conveyed on the rail in the direction of the arrow.

124°138.140,150 are cylinders, 1
26.152 is a valve. +28 is a heater arranged along the rail +18 in the molding chamber 106.

Inside the molding chamber 106, heating zones 106-1. They are a breath zone 106-2 and an annealing zone +06-3. Breath zone 106-2
An upper mold member 130 for molding is fixed to the lower end of the rod 134 of the cylinder 138, and a lower mold member 132 for molding is fixed to the L end of the rod 136 of the cylinder 140. These upper mold member +30 and lower mold member +32 are the mold members according to the present invention shown in FIG. 2 above. Inside the vapor deposition chamber 108, there is a container 142 containing a vapor deposition substance 146 and a heater 14 for heating the container.
4 is placed.

Flint optical glass (Sl”14, midpoint 5p=586
℃, glass transition point T g = 485° C.) and processed into a predetermined shape and size to obtain a blank for molding.

A glass blank is placed on the pallet 120, placed in the position 120-1 in the intake/displacement chamber +04, and the pallet at the position (n) is pushed in the Δ direction by the rod 122 of the cylinder 124, past the gate valve +12 and into the molding chamber 106. 12 of
The pallets are transported to the position 0-2, and the pallets are sequentially placed into the intake replacement chamber 104 at predetermined timing in the same manner as before.
This time, the pallet was placed in the molding room 106 +20-2→
...→l It was sequentially transported to the position 20-8. During this time, the heating zone! In 06-1, the glass blank is gradually heated by the heater 128 to a temperature above the softening point at a position of +20-4, and then transported to the breath zone 1062,
Here, by operating the cylinders 138 and 140, the 112 mold member 130 and the lower mold member 132 produce lOkg/cm.
Press for 5 minutes at a pressure of
0 was activated to release the upper mold member +30 and the upper mold member 132 from the glass molded product. During the pressing, the pallet was used as a molding cylindrical member. After that,
In the slow cooling zone 106-3, the glass molded product was gradually cooled. Note that the molding chamber +06 was filled with inert gas.

The pallet that reached the position 120-8 in the molding chamber 106 was next transported beyond the gate valve +14 to the position 17C in the deposition chamber 108 at +20-9. Normally, vacuum evaporation is performed here, but this evaporation was not performed in this example. Then, in the fifth conveyance, the +
It was transported to the 20-10 position. Then, during the next conveyance, the cylinder 150 was operated and the glass molded product was taken out of the molding apparatus 102 by the rod 148.

The mold member 130 after press forming 11 as described above
．． The surface roughness of the molding surface of 132 and the optical surface of the molded optical element, as well as the molded optical element and mold member 13
Table 4 shows the mold releasability with 0.132.

Next, press molding was continuously performed 10,000 times using the same mold member for Nos., 1, and 4.5 in which no fusion occurred. Table 5 shows the surface roughness of the molded surfaces of the empty members 130 and 132 and the optical surface of the molded optical element at this time.

Table 5 As shown above, in the examples of the present invention, good surface precision could be sufficiently maintained even when used in repeated press molding, and optical elements with good surface precision could be molded without any fusion occurring.

Example 2 A diamond sintered body was formed on a SiC sintered body as a base using diamond particles having an average particle size of 2 μm or more and several hundred Co fine powders.

At this time, the addition i1 of CO as a sintering aid was 5°10.
15 vol 1%, and this was sintered in the same manner as in Example 1 at 7.7 GPa and 2000° C. for 1 hour. After mirror polishing the surface of this diamond sintered body, its surface roughness and hardness were measured. The results are shown in Table 6.

Table 6 Next, using these molds, flint-based optical glass (SI='+4
) was pressed in the same manner as in Example 1.

The surface roughness of the molded lens and the surface roughness of the mold before and after molding were measured. The results are shown in Table 7.

As a result, when the Cog5 addition fjl exceeded lovol%, PbO was reduced and l'b was precipitated, and as a result, the surface roughness of the mold and lens after molding was large and mirror surfaces could not be obtained.

Next, after performing molding 200 times using the same mold for Nos. 6 and 7, the surface roughness was determined by 1#1. The results are shown in Table 8.

Table 8 Using SiCm viscous? , 7 GPa, and 2000° C. for 1 hour to form a diamond sintered body. next,
After mirror polishing this sintered body, its surface roughness and hardness were measured. The surface roughness was 0.03 μm in R,, and the hardness was 7000 kg/mff1" in terms of Vickers hardness. Using this mold, optical glass was molded in the same manner as in Example 2, and the results are shown in Table 9. We obtained the results shown below.

Table 9 Example 3 Ni was formed into a film by sputtering on diamond particles having a skewered diameter of 2 μm. When the amount of Ni was determined by atomic absorption spectrometry, the content of Ni was 1% Ivo. This Ni film is also formed on the diamond particles. No precipitation of PB was observed during this molding.

Further, after molding was performed 200 times using this mold, the surface roughness was measured.9 The results are shown in Table 10.

Table 10 and the surface roughness of the mold before and after molding were measured. Table 1 shows the results! Shown below.

Table 11 Example 4 A mold base was formed by sputtering 50 μm of “d” on the surface of a WC-10% Co superalloy. It was sintered at 6.5 GPa and 1500°C for 50 minutes. After mirror polishing this sintered diamond, its surface roughness, hardness, and composition were measured. The surface roughness was 0.04 μm in Rsaw and Vickers hardness. 6500 kg/+a
m”, surface X-ray diffraction analysis revealed only diamond and TaC peaks.Next, using this mold, flint-based optical glass f (SF+4
) was molded in the same manner as in Example 1. Surface roughness of the molded lens Also, no precipitation of Ilb was observed in this molding.

Historically, after molding was performed 200 times using this mold, the surface roughness was measured. The results are summarized in Table 12. Table 12 [Effects of the Invention] The mold for molding optical elements of the present invention has excellent moldability with glass, is capable of mirror polishing, and is superior to conventional molds even after repeated use. In comparison, surface deterioration is extremely low.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing an embodiment of the mold for molding an optical element according to the present invention, and FIG. 1 is a press molding 1) 11
Figure 2 shows the state after press molding. 3 and 5 are cross-sectional views showing a lens molding apparatus using the mold for molding an optical element according to the present invention; FIG. 3 is a discontinuous molding type, and FIG. 5 is a continuous molding type. Fourth
FIG. 3 is a time-temperature relationship diagram during lens molding. 1... Type LJ material, 2... Diamond sintered body, 3
... Glass material, 4... Molded lens, 51.
... Vacuum chamber body, 52 ... Lid, 53 ..." Type 2,
54... To plastic, 55... 1-type press, 56...
mold, 57... mold holder, 58... heater, 5
9... with], bar, 60... air cylinder, 61
...oil rotary pump, 62°63.64...valve,
65...Inflow vibe, 66...Valve, 67...
Outflow vibrator, 68... Valve, 69... Temperature sensor, 70... Water-cooled vibe, 71... Unit. 102... Molding device, 104... Intake replacement chamber,
106... Molding room, 108... Steam stone room, +10...
・Removal replacement chamber, 112...gate valve, 114
...Gate valve, 116...Gate valve, +1
8...Rel, 120...Pallet, 122...Lot, 124...Cylinder, 126...Valve, 1
28...Heater, 130...Upper mold, 132...
・G type, +34...Rod, +36...Rod, 1
38...Cylinder, 140...Cylinder, 142.
... Container, +44 ... Heater, +46 ... Evaporation substance, +48 ... Rod, 150 ... Cylinder, 152
···valve. Agent: Patent Attorney Yama F. Minoru ・1-Figure Procedural Amendment Band 1999 1 1427 Director General of the Japan Patent Office Yoshi 1) Moon Takeshi 1, Indication of Case Patent Application No. 1983-307933 2.9! Name of the optical element mold 3, Relationship with the case of the person making the amendment Patent applicant name (+00) Canon Co., Ltd. 4, Agent 〒105 21!03 (431) +8316, Contents of the amendment (1) Details Page 29, lines 2-5 of the present invention...extremely few. "A diamond sintered body made by sintering diamond particles with a suitable sintering aid does not cause fusion with glass at high temperatures, does not precipitate lead or alkali elements contained in glass,
In addition, mirror finishing is possible while maintaining appropriate hardness. According to the present invention, by using a diamond sintered body as the molding surface of the mold, it was possible to obtain a mold for molding an optical element with excellent moldability and durability. 5. Subject of amendment

Claims (1)

[Claims] 1. In an optical element molding die used for press-molding an optical element made of glass, at least a portion of the die that comes into contact with the glass is made of a diamond sintered body made of diamond particles and a sintering aid. A mold for molding an optical element. 2. The content of sintering aid in the diamond sintered body is 1 to 1
The mold for molding an optical element according to claim 1, wherein the content is 0 vol%.