JPH0791075B2 - Molds for glass optical elements - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a laser device, a camera,
The present invention relates to a mold for one-mold molding of various glass optical elements such as lenses and prisms used in microscopes, telescopes, optical fiber devices and the like.

[0002]

2. Description of the Related Art Conventionally, to manufacture a camera lens or the like,
In addition to the step of molding the glass material into a predetermined shape, many steps such as a base polishing step for ensuring the shape and accuracy of the molded article and a finish polishing step for finishing the surface of the polished article were required. Therefore, according to such a traditional manufacturing method, lenses and the like cannot be manufactured inexpensively and in large quantities,
Further, it has been difficult to obtain an aspherical shape.

Therefore, recently, one-mold molding of lenses and the like has been performed by a precision press mold. As a mold used for this, heat resistance, heat conductivity, It has been proposed to form a chemically vapor-deposited layer of silicon carbide having extremely excellent robustness and the like and polish the surface of the layer (hereinafter referred to as "conventional type"). It is to be noted that, although a mold in which the whole mold is made of a non-oxide ceramic material (SiC, Si ₃ N ₄ , WC, etc.) having low reactivity with the optical glass has been proposed, there is a problem in durability etc. It has a short life and cannot be manufactured inexpensively.

[0004]

By the way, in order to manufacture a high-quality optical element made of glass by one-mold molding, the surface of the vapor deposition layer, which is the molding surface, has an RMS roughness of 10Å or less (more preferably 5Å or less). It is necessary to polish it to a super smooth surface, and such surface polishing is generally performed by carefully polishing the surface of the vapor deposition layer with fine diamond abrasive grains.

However, in the conventional type, since the crystal plane of the vapor deposition layer is non-oriented or weakly oriented, it is extremely difficult to polish the surface of the vapor deposition layer to the above-mentioned ultra-smooth surface.

That is, when chemical vapor deposition of silicon carbide is performed under normal film forming conditions, the crystal plane of the vapor deposition layer tends to be non-oriented or weakly oriented to the (111) plane in the Miller index display. . In such a non-oriented or weakly oriented vapor-deposited layer, the polishing property due to the difference in crystal orientation is not uniform, and a step difference between crystals is generated, so that a highly smooth surface cannot be obtained. For example, the (111) plane has a very high atomic density and a very low chemical activity on the surface as compared with other azimuth planes. Will be cut faster and deeper, and more pits will be generated. Such pits cannot be eliminated no matter how carefully polishing is performed, and it is extremely difficult to obtain a super smooth surface as described above.

Further, if the crystal plane is non-oriented or weakly oriented, the thermal conductivity on the surface of the vapor-deposited layer is not uniform, and there is a possibility that a large thermal strain will occur on the shaping surface during shaping. Furthermore, when the molding surface is deteriorated by the reaction with glass during molding, the deterioration degree is not uniform. Therefore, the precision of the molded product is likely to vary, and quality control is extremely difficult.

In view of the above points, the present invention makes it possible to polish the surface of the vapor-deposited layer to an ultra-smooth surface, and to produce high-quality glass optical elements inexpensively in large quantities without causing precision variations. The object is to provide a mold that can be produced.

[0009]

The present invention provides a molding die for a glass optical element, which comprises a chemical vapor deposition layer of silicon carbide formed on the surface of a die portion of a die body, in order to achieve the above object. In particular, it is proposed that the crystal plane in the silicon carbide vapor deposition layer is strongly oriented to the (220) plane in the Miller index display. In this silicon carbide deposited layer, the X-ray diffraction intensity of the (220) plane is preferably 100 times or more (more preferably 500 times or more) that of any other crystal plane.

[0010]

Since the crystal plane of the vapor-deposited layer is strongly oriented to the (220) plane, the polishing property becomes uniform and polishing to an ultra-smooth surface is possible, unlike the case where the crystal plane is not oriented or weakly oriented. it can. Moreover, since the (220) plane has a lower atomic density and a lower chemical inertness than the (111) plane, when strongly oriented to the (111) plane or when the (111) plane is mixed. Compared with the case of non-orientation and weak orientation, the molding surface can be easily surface-polished with less polishing energy. Therefore, according to the molding die in which the molding surface has such an ultra-smooth surface, the glass optical element having a highly smooth surface can be favorably one-mold molded.

Further, since the crystal plane of the vapor deposition layer is strongly oriented in a specific azimuth plane, the thermal conductivity of the molding surface becomes uniform,
The thermal strain generated during molding is extremely small. Moreover, even when the molding surface is deteriorated due to the reaction with glass during molding, the deterioration becomes uniform. Therefore, the precision of the molded product hardly varies, and the quality control becomes extremely easy.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be specifically described below based on the embodiment shown in FIG.

In the molding die 1 of this embodiment, as shown in FIG. 1, a mold body 2 is molded into a predetermined shape (FIG. A), and a chemical vapor deposition layer 3 of silicon carbide is formed on the surface of a mold portion 2a of the mold body 2. Is formed (FIG. B), the vapor deposition layer 3 is surface-polished (FIG. C), and the release film 4 is formed on the polishing surface 3a (FIG. D).
It was obtained.

That is, as shown in FIG. 1 (A), the mold body 2 is a β-type silicon carbide sintered body obtained by a method such as pressureless sintering, hot press sintering, hot isostatic pressing or the like ( Bulk density of 3.0 or more) is ground into a predetermined shape. The shape of the mold portion 2a is adapted to the final shape obtained by coating the vapor deposition layer 3 and the release film 4.

The surface of the mold portion 2a of the mold body 2 is shown in FIG.
As shown in (B), pure β-type silicon carbide is chemically vapor deposited in a non-oxidizing atmosphere to form a silicon carbide vapor deposition layer 3 having a thickness of 200 μm. This silicon carbide deposited layer 3
The crystal plane of the is controlled by the vapor deposition temperature and the vapor deposition rate (for example, the vapor deposition temperature 1300 to 1500 ° C., the vapor deposition rate 10 to several tens of μ).
m / h), as shown in FIGS. 3 and 4, the film is strongly oriented on the (220) plane in the Miller index display. In such an orientation, the X-ray diffraction intensity of the (220) plane should be 100 times or more (more preferably 500 times or more) that of any other crystal plane ((111) plane or the like). preferable. In this example, the X-ray diffraction intensity ratio of the (220) plane to other crystal planes is 500 or more in its peak intensity as shown in FIG. In FIG. 3, the surface texture of the vapor-deposited layer 3 is magnified 800 times by a Nomarski microscope, and the portion that looks like a protrusion is the (111) plane. Further, FIG. 4 is an X-ray diffraction diagram of the vapor deposition layer 3 (CuKα: 30 KV × 30 mA, full scale: 50 KCPS, slit: 1 ° -1 ° -0.1 mm,
Scan: 2 ° / min, chart: 20 mm / min, main peak intensity: 27 KCPS).

The surface of the silicon carbide deposited layer 3 is shown in FIG.
As shown in (C), the ultra-smooth surface 3a having an RMS roughness of 10 Å or less is surface-polished. That is, in this embodiment, the surface of the vapor deposition layer 3 is roughened by diamond abrasive grains, and then further precision-polished by the diamond abrasive grains so that the surface of the vapor deposition layer 3 has a surface roughness of RMS.
The ultra-smooth surface 3a is 5 Å or less and the shape accuracy is λ / 4 or less. In such surface polishing, as shown in FIG. 2, since the crystal plane of the silicon carbide vapor-deposited layer 3 is strongly oriented to the (220) plane, the polishing ability due to the crystal orientation as in the case of non-orientation is weak. Therefore, a high-level smooth surface 3a can be obtained. Moreover, the atomic density and the chemical inertness of the surface are lower than those of the (111) plane (220)
Since the surface is strongly oriented, the ultra-smooth surface 3a in which polishing scratches and pits are not generated can be extremely easily obtained with less polishing energy. Such polishing property becomes even better as the orientation becomes higher.

As shown in FIG. 1D, the molding surface 3a thus finished to have an ultra-smooth surface is coated with boron nitride by magnetron sputtering to form a release film having a thickness of 0.5 μm or less. 4 is formed.

According to the molding die 1 thus obtained, since the molding surface 3a is constituted by an ultra-smooth surface (surface roughness: RMS 5 Å or less, shape accuracy: λ / 4 or less), the surface is extremely smooth. A highly accurate optical element can be favorably one-molded. Moreover, since the crystal plane of the vapor deposition layer 3 forming the molding surface 3a is strongly oriented to the (220) plane as shown in FIG. 2, the thermal conductivity on the molding surface 3a becomes uniform and occurs during molding. Thermal strain is extremely small.
That is, by increasing the crystal orientation of the vapor deposition layer 3, it is possible to significantly improve the uniformity of thermal characteristics on the molding surface 3a, suppress the occurrence of thermal strain as much as possible, and improve the durability of the molding die 1. Can be significantly improved. Moreover, even when the molding surface 3a is deteriorated due to the reaction with the glass during molding, the deterioration becomes uniform. Therefore, the precision of the molded product hardly varies, and the quality control becomes extremely easy.

The present invention is not limited to the above-described embodiments, but can be appropriately improved and changed without departing from the basic principle of the present invention. For example, as the constituent material of the mold body 2, in addition to the β-type silicon carbide described above, α
Type silicon carbide, tungsten, tungsten carbide,
A heat resistant hard material such as syrincon nitride can be appropriately selected. Further, the release film 4 is provided as needed, and may not be necessary depending on the molding conditions of the optical element.

[0020]

As can be easily understood from the above description, according to the present invention, the crystal plane in the chemical vapor deposition layer of silicon carbide is strongly oriented to the (220) plane, resulting in a very smooth molding surface. Further, it is possible to easily obtain the above, and further to suppress the occurrence of thermal strain as much as possible by ensuring the uniformity of the thermal characteristics on the molding surface, and to greatly improve the durability of the molding die. Therefore, according to the molding die of the present invention, glass optical elements of various shapes such as an aspherical lens can be mass-produced with high quality at low cost without causing precision variations.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram showing an embodiment of a molding die according to the present invention.

FIG. 2 is a conceptual diagram showing a polishing mode of a silicon carbide vapor deposition layer.

FIG. 3 is a Nomarski micrograph showing a crystal structure of a silicon carbide vapor deposition layer at a magnification of 800 times.

FIG. 4 is an X-ray diffraction diagram of a silicon carbide vapor deposition layer.

[Explanation of symbols]

1 ... Mold, 2 ... Mold body, 2a ... Mold part, 3 ... Chemical vapor deposition layer of silicon carbide, 3a ... Polishing surface (molding surface), 4 ... Release film.

Claims (2)

[Claims] 1. A molding die for a glass optical element, comprising a chemical vapor deposition layer of silicon carbide formed on the surface of a die portion of a die body, wherein a crystal plane in the vapor deposition layer of silicon carbide is represented by a mirror index (220). A mold for glass optical elements, characterized in that the surface is strongly oriented. 2. (220) in the above-mentioned silicon carbide vapor deposition layer
The X-ray diffraction intensity of the plane is 1 for any other crystal plane.
The molding die for a glass optical element according to claim 1, wherein the molding die is at least 00 times.