JPS63288924A - Die member for molding optical element - Google Patents

Abstract

PURPOSE:To easily and repeatedly press-mold optical elements such as lenses having directly and accurately molded optical surfaces with superior workability without deteriorating the accuracy for a long period by using the title die members for molding an optical element obtd. by coating at least the molding surfaces of matrixes with boron carbonitride. CONSTITUTION:A matrix material having a coefft. of thermal expansion relatively close to that of boron carbonitride, e.g., a sintered hard alloy consisting of 90% WC and 10% Co or sintered SiC is cut, ground and polished to obtain a matrix 30 having a desired external shape and a molding surface finished to prescribed surface accuracy. A boron carbonitride layer 32 of a desired thickness is then formed on the molding surface by PVD or CVD to obtain a die member for molding an optical element. An optical element having a prescribed shape is press-molded by using upper and lower die members obtd. by the above-mentioned method.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a mold member used in an optical element molding device,
In particular, the present invention relates to a mold member for molding optical elements that can easily achieve high precision and has good durability. Such a mold member for molding an optical element is suitably used, for example, as a mold member for high-precision molding to directly form an optical surface.

[Prior Art and Problems Therewith] Generally, optical elements such as lenses, prisms, mirrors, and filters are manufactured by grinding a material such as glass into a desired shape, and then forming a functional surface, that is, a surface through which light can pass through and/or It is manufactured by polishing the reflective surface to create an optical surface.

However, in the production of optical elements such as those described above, in order to obtain the desired surface accuracy (i.e., accuracy of surface shape and surface roughness) through grinding and polishing, skilled workers spend a considerable amount of processing time. It was necessary to do it. Further, when manufacturing an optical element having an aspherical surface, more advanced grinding and polishing techniques are required, and the processing time is inevitably increased.

Therefore, in recent years, instead of the traditional optical element manufacturing method as described above, press molding has been developed in which the optical element material is housed in a mold with a predetermined surface accuracy and then heated and pressurized. Methods of immediately forming the overall shape, including the functional aspects, are becoming popular. According to this,
Even when the functional surface is an aspherical surface, the optical element can be manufactured relatively easily and in a short time. Such a press molding method is suitable for continuous production of optical elements.

The properties required of mold members used in press molding as described above include sufficient hardness, good heat resistance, good mirror workability, and no fusion with optical element materials during molding. can be given.

Therefore, many types of mold members for press molding have been proposed in the past, such as metals, ceramics, and materials coated with appropriate materials.

For example, in JP-A-49-51112, 13Cr
= A mold member using p-rutinsite steel is disclosed,
JP-A-52-45613 discloses silicon carbide (Si
C) fJ member using silicon nitride (Si3N+)
A mold member using
Publication No. 60 discloses a mold member using tungsten carbide (WC) based cemented carbide and a mold member using alumina (A1203) based ceramics.
Japanese Patent No. 6230 discloses a mold member in which a cemented carbide is coated with a noble metal.

However, the above-mentioned 13Cr martensitic steel is easily oxidized, and furthermore, during press molding at a high temperature, Fe diffuses into the glass material and the glass becomes colored. In addition, the above S
iC and 513N4 are generally not easily oxidized, but at high temperatures some oxidation occurs and 5i0 is formed on the surface of the mold member.
Since the film No. 2 is formed, it is easy to fuse with the glass, and furthermore, the hardness is too high, resulting in extremely poor workability. Furthermore, cemented carbide is used as a binder.
o is easily oxidized (there is a disadvantage that it is eroded by glass during use). Furthermore, since alumina ceramics are originally oxides, they have the disadvantage of causing fusion with glass. Furthermore, materials whose surfaces are coated with precious metals have low hardness and are therefore easily damaged and deformed.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide a mold member for molding an optical element that can be easily manufactured with high precision and has a long life with little deterioration in precision during press molding.

[Means for Solving the Problems] According to the present invention, in order to achieve the above objects, in a mold member for molding an optical element, at least the molding surface of the mold base material is coated with boron carbonitride. A mold member for molding an optical element is provided.

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

FIG. 1 is a schematic sectional view showing an embodiment of a mold member according to the present invention. In this figure, 30 indicates a mold base material, and 32 represents a boron carbonitride coating formed on the molding surface of the base material. Show layers.

In the present invention, it is preferable to use a material having a coefficient of thermal expansion relatively similar to that of boron carbonitride as the base material 30. As such a base material, for example, cemented carbide or sintered SiC can be used. . These base materials are given a desired external shape by cutting, grinding, polishing, etc., and in particular, the molding surface is finished to a desired surface precision.

In order to form the boron carbonitride layer 32 on the surface of the base material 30, for example, a physical vapor phase method (PVD method) or a chemical vapor phase method (CVN method) is used.9 The thickness of the boron carbonitride layer 32 is The thickness is determined as appropriate depending on the manufacturing conditions, but may be set to a thickness that provides sufficient durability in view of the desired characteristics during use.

The boron carbonitride layer also has strong oxidation resistance at high temperatures, so it has low fusion bonding with glass and good mold releasability, so an optical element with good precision can be obtained even if it is repeatedly used.

Hereinafter, examples of manufacturing a mold member according to the present invention and glass molding using the same will be shown. At the same time, for comparison, examples of manufacturing a conventional mold member and glass molding using the same will also be shown.

Manufacturing and molding example: A mold base material is made using cemented carbide [WC (90%) + Co (10%)] and sintered SiC as base material, and a boron carbonitride layer is formed on the molding surface of the base material. A mold member according to the present invention was manufactured as follows. In addition, for comparison, a mold member in which the molding surface of the mold base material is not coated and a mold member in which the molding surface is coated with S
A mold member on which an IC layer was formed was manufactured. A list of manufactured mold members is shown in Table 1. In Table 81, No. 1
and N082 are examples of the present invention, No, 3°No,
4 and No. 5 are comparative examples.

Table 1 First, the mold base material was cut, and then the molding surface corresponding to the functional surface (optical surface) of the molded optical element was processed to a desired surface precision. The molding surface of the mold base material is a concave surface, and it is first processed into the desired curvature by grinding with a diamond grindstone, and then polished using diamond powder with a particle size of IJLm to obtain the surface shape accuracy of one Newton ring kneading degree and Rma.
It was finished with a surface roughness accuracy of about 0.024°C.

Next, for No. 1 and No. 062, a boron carbonitride layer was formed on the forming surface of the base material by a method called activated reaction vapor deposition using the apparatus shown in FIG.

In FIG. 2, 40 is an airtight chamber of the vapor deposition apparatus. An exhaust port 42 is connected to the airtight chamber, and the exhaust port is connected to a decompression source (not shown). A heater 44 is arranged in the upper part of the airtight chamber 40, and a mold base material support 46 is arranged below the heater. A mold base material 48 is supported on the support body with the molding surface facing downward. A water-cooled hearth 50 is arranged in the lower part of the airtight chamber 40, and boron 52 is accommodated in the hearth. 54 and 58 are electron guns, and argon gas is introduced into the airtight chamber 40 through the electron gun 54, and nitrogen gas and methane gas are introduced into the airtight chamber 40 through the electron gun 56.

When forming the boron carbonitride layer, the mold base material 48 obtained as described above was washed with acetone, and the pressure inside the airtight chamber 40 was reduced to about 6 x 1 O-3 Torr while it was supported by the support 46. The surface of the mold base material 48 was bombarded with argon ions introduced from the electron gun 54 to perform cleaning for about 30 minutes. Then, the boron 52 on the water-cooled hearth 50 was heated and evaporated by a low voltage, high current (30 V, 40 A) electron beam. At the same time, nitrogen gas and methane gas are introduced into the airtight chamber 40.
A boron carbonitride layer was introduced into the mold base material 48 from an electron gun 56 to form a boron carbonitride layer on the surface of the mold base material 48. At this time, the temperature of the mold base material 48 is 5
It is 00℃.

The pressure of nitrogen gas and methane gas was 6XIO-4 Torr. The thickness of the obtained boron carbonitride layer was about IILm. For No. 5 above, a silicon carbide layer was similarly formed on the molding surface of the mold base material using the apparatus shown in FIG. did. At this time, nitrogen gas was not introduced and silicon was accommodated on the water-cooled hearth 50 instead of boron. The thickness of the silicon carbide layer was about 1 #Lm.

Next, optical glass was press-molded using the mold member manufactured as described above.

FIG. 3 is a sectional view showing the apparatus used for press molding.

In FIG. 3, 1 is a closed container, 2 is its lid, 3.4 is the mold member for molding an optical element (biconvex lens), 3 is an upper mold member, and 4 is a lid. This is the lower mold member. 5 is an upper mold presser, 6 is a mold adjusting member, and 7
is a mold holder, 8 is a heater, 9 is a lower mold push-up rod, and 10 is an air cylinder that drives the chain line. 11 is an oil rotary pump; 12, 13.
14 is a valve, 15 is a nitrogen gas introduction pipe, 16 is a valve, 17 is an exhaust pipe, 18
is a valve, 19 is a temperature sensor, 20 is a water cooling pipe, and 21 is a stand of the closed container 1.

Flint optical glass (SF 14, softening point 5p=5
A blank for molding was prepared in a spherical shape with a predetermined weight and a temperature of 86°C (glass transition point Tg=485°C).

The lid 2 of the closed container 1 was opened, the upper die member 3 and the upper die holder 5 were removed, the blank was placed on the lower die member 4, and the upper die member 3 and the upper die holder 5 were attached.

Furthermore, after closing M2, water was allowed to flow through the water cooling pipe 20, and the heater 8 was energized. At this time, the nitrogen gas valve 16,
After the valve 18 and the exhaust system valve 12, 13, and 14 are closed, the oil rotary pump 11 is operated, and the valve 1 is closed.
2 was opened, and the inside of the container 1 was evacuated. The degree of vacuum inside container 1 is 1
After the pressure reaches O-2 Torr, close the valve 12 and open the valve 16°18 to supply nitrogen gas from the cylinder to the closed container 1.
introduced inside. After reaching a predetermined temperature, the air cylinder 10 was operated and press molding was performed for 5 minutes at a pressure of 10 kg/cm2. Remove the pressure and cool at a rate of approximately 1°C/min until below the glass transition point, then cool to 20°C.
Cooling is performed at a rate of 1/min or more, and after the temperature has fallen below 200°C, valves 16 and 18 are closed, and leak valve 1 is closed.
Open the lid 2 to introduce air into the sealed container.
was opened, the upper mold member 3 and the upper mold holder 5 were removed, and the molded optical element was taken out.

4th rI! J is a diagram showing the temperature change of glass during press molding.

The surface roughness of the molding surface of the mold member 3.4 before and after press molding as described above, the surface roughness of the optical surface of the molded optical element, and the mold releasability between the molded optical element and the mold member 3.4. The details are shown in Table 2.

Table 2 Next, No. 001, No. 2, and No. 013 with no fusion occurrence.
Table 3 shows the surface roughness of the molding surface of mold member 3.4 and the surface roughness of the optical surface of the molded optical element after 100 consecutive press moldings using the same mold member. .

As shown in Table 3, in the examples of the present invention, even when used repeatedly in press molding, good surface precision could be maintained, and optical elements with good surface precision could be molded.

In the above embodiments, a flint-based optical glass is used as the optical glass to be molded, but other glasses such as crown-based glasses can also be molded with good precision.

[Effects of the Invention] According to the present invention as described above, by coating the molding surface of the mold base material with boron carbonitride, it is possible to provide a mold member for molding optical elements that has a long life and less accuracy deterioration during repeated press molding. be done. Further, the mold member of the present invention is easy to manufacture because a material with good workability can be selected as the base material.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a mold member according to the present invention. FIG. 2 shows an apparatus used for forming a boron carbonitride layer in the production of a mold member according to the invention. FIG. 3 is a sectional view of a press molding apparatus for optical elements. FIG. 4 is a diagram showing the temperature change of glass during press molding. 3.4: Mold member, 30: Mold base material, 32: Boron carbonitride layer, 48: Mold base material. Agent Patent Attorney Seki Taira Yamashita Figure 1 Figure 2 ↑ N2. C) (4

Claims (1)

[Claims] (1) A mold member for molding an optical element, characterized in that at least the molding surface of the mold base material is coated with boron carbonitride.