JPS63151631A - Mold for forming optical element - Google Patents

Abstract

PURPOSE:To obtain a mold capable of carrying out specular abrasion without causing fusing with glass at high temperature and slightly being oxidized, by coating a molding face of a mold for forming an optical element made of glass with a coating film of tungsten carbide. CONSTITUTION:In a mold to be used in press molding of an optical element 4 made of glass, a thin film layer 2 of a coating film of tungsten carbide is formed on a molding face of a mold parent material 1 consisting of a carbide alloy to be brought into contact with the glass element 4. In order to mold the optical element 4 by using the mold, a glass material 3 laid between molds is press molded. As a method to form the thin film layer of a coating film of tungsten carbide on the mold parent material 1 is used CVD method or PVD method. A carbide alloy is preferably used as the mold parent material element. Other materials having a coefficient of thermal expansion close to that of the carbide alloy may be used. The mold has excellent releasability from glass and extremely low surface deterioration even with repeated use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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.

[Conventional technology] 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 manufactures lenses easily and inexpensively. Recently, it has come to be used for manufacturing not only lenses but also prisms and other optical elements made of glass.

Properties required of the mold material used for press molding of such glass optical elements include hardness, heat resistance, mold releasability, and mirror workability. Conventionally, many proposals have been made as this type of mold material, such as metals, ceramics, and materials coated with these materials.

To give some examples, JP-A-49-51112
13Cr martensitic steel is used in JP-A-52-456.
13 is SiC and Si3N4 or JP-A-60-246
No. 230 proposes a material in which a cemented carbide is coated with a noble metal.

However, 13(:r martensitic steel is easily oxidized,
Furthermore, it has the disadvantage that Fe diffuses into the glass at high temperatures and colors the glass. In addition, although Si[: -5s3Na is generally considered to be difficult to oxidize, oxidation still occurs at high temperatures, and a 5102 film is formed on the surface, causing fusion with glass. The disadvantage is that the mold itself has extremely poor workability. In addition, materials coated with precious metals are less prone to fusion, but are extremely soft and have the disadvantage of being easily scratched and easily deformed.

[Objective of the Invention] The object of the present invention is to provide an optical element molding mold 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 is suitable for molding optical elements made of glass. An object of the present invention is to provide a mold for molding an optical element that has a high hardness and is resistant to oxidation.

As a result of research with the above purpose in mind, the present inventor used a cemented carbide or a base material with a coefficient of thermal expansion similar to this, and the forming surface that contacts the glass material was made of tungsten carbide (W).
It has been discovered that the desired purpose can be achieved by using a mold provided with the coating described in C).

[Summary of the Invention] As described above, the present invention is characterized in that, in an optical element molding die used for press molding optical elements made of glass, the molding surface in contact with the glass material is made of tungsten carbide (WC). The reason is that it is coated with

Although it is preferable to use cemented carbide as the base material of the mold, the base material is not limited to cemented carbide, and other materials with similar coefficients of thermal expansion can be used.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

1 and 2 show one embodiment of a mold for molding an optical element according to the present invention. In the figures, 1 is a mold base material made of cemented carbide, and 2 is a glass material of the mold base material. A coating layer of tungsten carbide (WC) is shown formed on the molding surface in contact with the molding surface.

FIG. 1 shows the optical element before press molding, and FIG. 2 shows the optical element after molding. As shown in Figure 1,
By press-molding the glass material 3 placed between the molds, an optical element 4 such as a lens is formed as shown in FIG. As described above, the PVD method or the CVD method is used to form the tungsten carbide film on the base material 1 of the mold. FIG. 3 shows a method of forming a tungsten carbide film by a method generally called a sputtering method among such PVD methods.

In Fig. 3, 11 is the outer wall of the device, 12 is cooling water, 1
3 is an electrode, 14 is argon gas, 15 is a mold base material, 16 is a substrate holder, 17 is a hydrocarbon gas, 18 is a vacuum exhaust hole, and 19 is tungsten. When forming a film, a mold base material 15 that has been cleaned with an organic solvent is placed in the apparatus.

Before vapor deposition, argon gas 14 is introduced to clean the surface of the base material by argon ion bombardment. Next, hydrocarbon (acetylene) is applied to the tungsten target on the electrode 13.
A tungsten carbide film is generated on the surface of the base metal by introducing gas and applying a tungsten carbide coating. In this way, an optical element molding die having a tungsten carbide coating on the molding surface that contacts the glass material is obtained.

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 1 below shows the types of mold materials used in the experiment.

Table 1 Nos. 1 to 3 are comparative materials, and Nos. 14 to 5 are materials proposed for one pair of the present invention. Cemented carbide (WC) is used as the base material.
90! (+Co10%i) and sintered SiC were used.

FIG. 4 shows the lens molding apparatus used in the above example.

In the figure, 21 is the main body of the vacuum chamber, 22 is its lid, 23 is an upper mold for molding optical elements, 24 is a lower mold, 25 is an upper mold holder for holding down the upper mold, 26 is a body mold, 27 2 is a mold holder, 28 is a heater, 29 is a lifting rod for lifting up the lower mold, 30 is an air cylinder for operating the lifting rod, 3
1 is an oil rotary pump, 32, 33, 34 is a valve, 35 is an inert gas inflow pipe, 36 is a valve, 37 is a leak pipe, 38 is a valve, 39 is a temperature sensor, 40 is a water cooling pipe, 41 is a vacuum chamber Indicates the supporting platform.

The process of manufacturing the lens will be described below.

First, the base material of the mold is processed into a predetermined shape, and the lens molding surface is mirror polished. Next, SiC and WC films are formed by sputtering. The film thickness was 0.5 to 1.5 μm. Next, the flint type optical glass (SF14) is adjusted to a predetermined amount, and the spherical glass material is placed in the cavity of the mold, and this is installed in the apparatus.

After the mold containing the glass material is placed in the apparatus, the lid 22 of the vacuum chamber 21 is closed, water is allowed to flow through the water cooling pipe 40, and an electric current is passed through the heater 28. At this time, the nitrogen gas valves 36 and 38 are closed, and the exhaust system valves 32, 33, and 34 are also closed. Note that the oil rotary pump 31 is always rotating.

The valve 32 is opened to begin evacuation, and when the temperature becomes less than 10 -2 Torr, the valve 32 is closed, and the valve 36 is opened to introduce nitrogen gas from the cylinder into the vacuum chamber. When the temperature reaches a predetermined temperature, the air cylinder 30 is operated to pressurize it at a pressure of 10 kg/am2 for 5 minutes.

After removing the pressure, the cooling rate is 1°C/min until it becomes below the dislocation point, and then -2°t: / m
Cooling is performed at a rate of at least i.sub.in, and when the temperature drops to 200'l or less, the valve 36 is closed, the leak valve 33 is opened, and air is introduced into the vacuum chamber 21. Then, the lid 22 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 5F14 (softening point 5p-sae DEG C., dislocation point Tg 485 DEG C.). FIG. 5 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, fusion bonding was performed, and the surface roughness of No. 1.4.5 was measured after 100 moldings using the same mold. The results are shown in Table 3.

Table 3 [Effects of the Invention] As is clear from the results in Tables 2 and 3 above, the mold material according to the present invention has excellent mold releasability from glass, and its surface does not deteriorate compared to conventional mold materials even after repeated use. are extremely rare.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing one embodiment of the mold for molding an optical element according to the present invention, with FIG. 1 showing the state before press molding, and FIG. 2 showing the state after press molding. FIG. 3 is a schematic diagram of an apparatus used to form a tungsten carbide film on the molding surface of a mold base material, and FIG. 4 is a cross-sectional view showing a lens molding apparatus using the mold for molding optical elements according to the present invention. Figure, 5th
The figure is a time-temperature relationship diagram during lens molding. 1... Mold base material 2... Covering material 3... Glass material 4... Molded lens 11...
Outer wall of vapor deposition apparatus 12... Cooling water 13... Electrode
14... Argon gas 15... Mold base material 16... Substrate holder 17... Hydrocarbon gas 18... Exhaust hole 19... Tungsten
21... Vacuum chamber body 22... Lid
23... Upper mold 24... Lower mold 25.
・・Upper mold press 26・Tone mold z7・・
・Mold holder 28... Heater 29...
Lifting rod 30...Air cylinder 31...Oil rotary pump 32.33.34...Valve 35.
...Inflow pipe 36...Valve 37...
・Outflow pipe 38...Valve 39...
Temperature sensor 40...Water cooling pipe 41...Unit, U Fig. 4 Clear air time (minutes) Procedural amendment 1999 Relationship to the incident on January 1st, 2019 Application Person's address (residence) East °C::I - Ota-kucho, “, Ryo’21
- Name of No. 13, No. 12 (100) Canon 1, Zhu Shiki Company 4, Agent 8, Contents of the amendment - 4-14-7'; Maji - Amendment in the specification of the present application The following matters have been corrected: Note 1, in the first line of page 11, the words ``perform fusion'' will be corrected to ``do not cause fusion.''

Claims (1)

[Claims] A mold for press-molding an optical element made of glass, characterized in that the molding surface that comes into contact with the glass material is coated with a tungsten carbide (WC) coating.