CN1305789C - Mould for forming optical elements and the optical elements - Google Patents

Abstract

The die is comprised of a die base material consisting of a sintered hard alloy or silicon carbide, a surface layer formed on the surface of the die base material and brought into contact with a glass material in press molding, and an intermediate layer formed between the die base material and the surface layer. The surface layer is formed from at least one element selected from among platinum, palladium, iridium, osmium, ruthenium, and rhenium or an alloy or compound containing these elements. The intermediate layer has a surface base material layer which consists of at least a substance selected from among tungsten, carbon, tungsten carbide, and silicon carbide, is in an amorphous state or in a crystalline state with a crystal grain diameter smaller than that of the substance constituting the die base material, and is brought into contact with the surface of the die base material.

Description

Molds and optical elements for forming optical elements

technical field

The present invention relates to an optical element molding die for producing optical elements such as lenses and prisms by press-molding glass raw materials, and the optical elements formed therefrom.

Background technique

In recent years, as a method of manufacturing optical elements from such a glass raw material, there is a press molding method using a molding die. With this manufacturing method, there is an advantage that the optical element can be manufactured simply and inexpensively because grinding processing is not required. In the past, various researches have been carried out on this kind of mold for forming optical elements for stamping, so that the forming surface that contacts the glass raw material during the forming process can maintain the surface roughness, so that it can be used for a long time. in the shaping of optical components.

That is, such a mold for molding an optical element has a mold base material, a noble metal layer, and an intermediate layer. The base material of the mold is made of superhard alloy and cermet which are sintered with chromium, titanium and other metal materials as bonding materials; the precious metal layer is in direct contact with the glass raw material in the process of manufacturing optical elements; the intermediate layer is formed between the base material of the mold and the precious metal Formed in the middle of the layer (for example, please refer to Japanese Patent Publication No. 62-28093).

The precious metal layer is formed of precious metal materials such as platinum and iridium, and is used to prevent fusion of glass raw materials. In addition, the intermediate layer is formed of one or more materials selected from the following various materials: titanium nitride, chromium carbide, titanium carbide, niobium carbide, tantalum carbide, silicon carbide, alumina, zirconium, titanium, chromium.

The purpose of forming the above-mentioned intermediate layer containing metal materials such as titanium and chromium is to prevent the metal components contained in the mold base material from being precipitated toward the forming surface. In addition, the purpose of forming this intermediate layer is to improve the bonding force between the mold base material and the noble metal layer, prevent the noble metal layer from peeling off, and suppress the increase in the roughness of the forming surface by relieving the thermal cycle stress during stamping forming.

However, in the aforementioned conventional optical element molding dies, the intermediate layer is formed of a compound containing metal materials such as titanium and chromium. In this way, during the repeated press forming, the metal material is deposited on the forming surface, that is, on the surface of the noble metal layer, and a problem such as fusing of the glass raw material occurs. In addition, a trace amount of oxygen penetrates into the interior of the intermediate layer from the noble metal layer, and the above-described trace amount of oxygen oxidizes the intermediate layer to reduce the bonding force.

In addition, due to the heat during stamping, the metal material precipitated on the forming surface will be oxidized, and uneven grain growth will occur on the forming surface of the noble metal layer, so the surface roughness of the forming surface will gradually decrease. growing problem. From the above facts, it can be seen that repeated press molding causes problems such as deterioration of the surface accuracy of the molded optical element and failure of demolding due to sticking of glass raw materials.

In addition, the inventors of the present invention found out the main cause of non-uniform crystal growth on the forming surface of the noble metal layer due to the heat during press forming, as a result of intensive studies.

That is, the present inventors found that the increase in the roughness of the molded surface that occurs during the molding of the optical element is related to the crystallization state of the film formed on the molded surface of the intermediate layer and the noble metal layer. In addition, it was found that noble metal materials such as platinum and iridium forming the surface layer are affected by the crystal orientation of each crystal grain of the intermediate layer formed directly below and the mold base material. It has also been found that when a metal material such as titanium or chromium is used for the intermediate layer, the respective crystal orientations of the crystal grains of the intermediate layer are affected by the crystal orientations of the individual crystal grains of the mold base material directly below.

Therefore, it can be seen from the above that when the intermediate layer is formed using crystal grains having a diameter larger than the crystal grain diameter of the material constituting the mold base material, and when the intermediate layer is formed of a noble metal material, the crystal orientation of each crystal of the noble metal layer , will be affected by the crystal orientation of each crystal grain of the intermediate layer itself, and the crystal orientation of each crystal grain of the mold base material separated by the intermediate layer. In addition, it is also found that in the process of stamping and forming, the grains of each mold base material are different in the speed and degree of grain growth and oxidation due to heating.

The inventors of the present invention have found from the above two points that the crystal growth and oxidation speed of each base material grain and the degree of progress have different effects on each crystal of the noble metal layer. Since the crystal growth and oxidation speed of each crystal of the noble metal layer, Depending on the degree of progress, non-uniform crystal growth, etc. will occur, and the roughness of the molding surface will increase.

Contents of the invention

The present invention has been made in view of the above circumstances, and its object is to provide an optical element capable of producing an optical element with high surface precision by preventing the increase in the surface roughness of the molding surface when the optical element is repeatedly formed by press forming. Molds for forming optical components, and optical components formed with such molds.

To achieve the above objects, the present invention proposes the following various means.

The first aspect of the present invention is a mold for forming optical elements, which is a mold for forming optical elements for optical elements such as lenses and prisms by punching glass raw materials. It is characterized in that it has the following parts: A mold base material made of sintered superhard alloy or silicon carbide; a surface layer formed on the surface of the above mold base material and in contact with the above-mentioned glass raw material during the stamping process; and, a surface layer between the above mold base material and the surface layer intermediate layer formed between. The above-mentioned surface layer is formed of at least one element selected from the following elements: platinum, palladium, iridium, osmium, ruthenium, rhenium, or an alloy or compound containing these elements. The above-mentioned intermediate layer has a surface layer of a base material, which is in an amorphous state, or in a crystalline state formed of crystal grains having a diameter smaller than that of the grains constituting the above-mentioned mold base material, tungsten, carbon, tungsten carbide , silicon carbide at least one material. The base material surface layer is in contact with the surface of the mold base material.

According to the mold for molding an optical element of the present invention, the surface layer of the base material is formed in an amorphous state, or in a crystalline state formed of crystal grains having a diameter smaller than that of the crystal grains constituting the above-mentioned mold base material. In the process of stamping and forming, the different crystallographic orientations of each grain of the mold base material should not affect the surface layer.

This point is proposed based on the above-mentioned findings of the present inventors' studies, that is, when the intermediate layer is formed of crystal grains larger than the crystal grains of the material constituting the mold base material, When formed in the state, the crystallographic orientation of the surface layer and the intermediate layer will be affected by the crystallographic orientation of each crystal grain in the mold base material, so that when the mold for optical element molding is heated during the stamping process, it is found that it is different from the glass raw material The reason why the roughness of the forming surface of the contact surface layer increases.

Therefore, in the case of the constitution according to the present invention, even if the crystals in the mold base material grow and oxidize due to heating the mold for optical element molding, the crystal grains of the mold base material and the crystal grain boundaries will not be separated. The influence spreads to the surface layer, thereby preventing the increase in the roughness of the molding surface in contact with the glass raw material.

The mold for molding an optical element proposed in the second aspect of the present invention is the mold for molding an optical element described in the first aspect, and is further characterized in that the crystal grains in the above-mentioned crystalline state have a diameter between 2μm or less.

According to the mold for forming optical elements of this invention, the reason why the diameter of the crystal grains on the surface layer of the base material must be below 2 μm is because the crystal grains of the base material of the mold made of sintered superhard alloy or silicon carbide Particle diameter, at least greater than 2 μm.

The mold for molding an optical element proposed by the third aspect of the present invention is the mold for molding an optical element described in the first or second aspect, and is further characterized in that the above-mentioned intermediate layer also has a A metal layer between the surface layer of the base material and the surface layer is composed of at least one metal material selected from chromium, titanium, aluminum, and molybdenum.

According to the mold for forming an optical element of this invention, since a metal layer composed of at least one metal material of chromium, titanium, aluminum, and molybdenum is formed between the surface layer of the base material, sufficient bonding force can be obtained. , At the same time, it can also relieve the stress generated by the thermal cycle during stamping and forming. Therefore, even if press forming is repeated, peeling of the surface layer can be reliably prevented.

The mold for molding an optical element proposed in the fourth aspect of the present invention is the mold for molding an optical element described in the third aspect, further characterized in that the intermediate layer further has a Between the above-mentioned surface layer is a nitride layer composed of nitride containing at least one metal material among chromium, titanium, aluminum and molybdenum.

According to the mold for forming optical elements of this invention, since the nitride layer formed of nitrides such as chromium nitride, titanium nitride, aluminum nitride, aluminum titanium nitride, molybdenum nitride, etc., has excellent resistance Therefore, even if the press forming is repeated, it is possible to prevent oxygen from intruding into the interior of the intermediate layer from the forming surface of the surface layer. In this way, oxygen does not reach the metal layer formed of chromium, titanium, etc., so that a decrease in bonding force due to oxidation of the metal layer can be prevented. Therefore, peeling of the surface layer can be prevented for a long time.

In addition, since the nitride layer is a very stable compound, metal materials such as titanium and chromium in the metal layer do not precipitate on the forming surface of the surface layer. Therefore, it is possible to prevent the roughness of the molding surface from being increased due to the oxidation of the precipitated metal material, and to prevent the glass feedstock from being fused to the molding surface during press molding.

The optical element molding mold proposed in the fifth aspect of the present invention is the optical element molding mold described in the fourth aspect, further characterized in that the nitride layer has a concentration of nitrogen element Gradually decreasing nitrogen concentration gradient layers towards the metal layer.

According to the mold for optical element molding of this invention, since the nitride layer made of nitrogen compound has no obvious boundary with the metal layer made of metal material not containing nitrogen, even if the temperature of press forming is raised, the nitrogen The compound layer will not be peeled off from the metal layer. Therefore, the surface layer is not exposed, and the roughness of the molding surface of the surface layer can be reliably prevented from increasing.

A sixth aspect of the present invention provides an optical element characterized in that it is formed by molding a glass raw material using the optical element molding die described in the first aspect of the present invention.

As described above, according to the first aspect of the present invention, tungsten, carbon, tungsten carbide 1. The surface layer of the base material composed of at least one material in silicon carbide, making it in contact with the base material of the mold, can prevent the roughness of the forming surface of the surface layer in contact with the glass raw material from increasing, so that it can be made into a surface with high precision. Optical element.

Furthermore, according to the second aspect of the present invention, since the grain diameter of the surface layer of the base material is 2 μm or less, it is possible to reliably prevent the surface layer from being affected by the different crystal orientations of the individual crystal grains of the mold base material.

In addition, according to the third aspect of the present invention, since there is a metal layer composed of at least one metal material among chromium, titanium, aluminum, and molybdenum between the surface layer of the base material, the During the process, it can reliably prevent the fusion of glass raw materials caused by the peeling of the surface layer, so that optical elements with high surface precision can be produced.

In addition, according to the fourth aspect of the present invention, since the nitride layer formed of titanium or chromium is formed between the metal layer and the surface layer, in addition to preventing the glass raw material from fusing to the forming surface during the press forming process, In addition, it is possible to prevent the reduction of bonding force due to the oxidation of the metal material forming the metal layer, so that an optical element with high surface precision can be manufactured over a long period of time.

In addition, according to the fifth aspect of the present invention, since the boundary between the nitride layer and the metal layer is not sharp, the roughness of the forming surface of the surface layer can be reliably prevented from increasing, thereby making it possible to achieve surface accuracy over a longer period of time. High optics.

Also, according to the sixth aspect of the present invention, since the surface precision of the optical element is high, an optical element with high optical precision can be obtained.

Description of drawings

Fig. 1 is the schematic diagram of the formation of the mold that the optical element molding of the first, second embodiment of the present invention is used;

2 is an enlarged cross-sectional view of the main part of FIG. 1 in the mold for forming an optical element according to the first embodiment of the present invention;

3 is an enlarged cross-sectional view of the main part of FIG. 1 in a mold for forming an optical element according to a second embodiment of the present invention;

Detailed ways

1, 2 show a first embodiment of the present invention. The mold for forming an optical element in this embodiment is a mold for producing a convex lens (optical element) by press molding. As shown in FIG. 1, the mold 1 for forming such an optical element has the following parts: a pair of mold base materials 2, 2; formed on the surface 2a of each mold base material 2, with The surface layer 3 of the molding surface 3 a which the glass raw material M contacts; and the intermediate layer 4 formed between the two mold base materials 2 and the surface layer 3 .

The mold base material 2 is made of sintered cemented carbide or silicon carbide, and its surface 2a is made into a concave shape matching the curvature radius of the convex lens.

As shown in FIG. 2 , the intermediate layer 4 is composed of a base material surface layer 5 , a metal layer 6 and a nitride layer 7 . The base material surface layer 5 is in contact with the surface 2 a of the mold base material 2 , and is composed of materials such as amorphous tungsten or tungsten carbide formed of crystal grains of 1 to 2 μm. The metal layer 6 is formed in contact with the surface 5a of the base material surface layer 5, and is made of metal materials such as chromium and titanium. The nitride layer 7 is formed in contact with the surface 6a of the metal layer 6, and is composed of a nitride containing elements such as chromium and titanium.

The surface layer 3 is made of a metal material such as platinum or iridium, and is formed in contact with the surface 7 a of the nitride 7 . This surface layer 3 is formed by PVD (Physical Vapor Growth) or CVD (Chemical Vapor Growth) such as RF spatter, ion beam spray, or vapor deposition.

In addition, the surface layer 5 of the base material can be formed by the following various methods: PVD and CVD methods such as radio frequency spraying, ion beam spraying, and vapor deposition, ion implantation of the material forming the surface layer 5 of the base material; Ions such as gas are accelerated electrically and then irradiated on the base material of the mold to form a film on the material forming the surface layer 5 of the base material; ion beam mixing method in which the film is formed while injecting ions. In addition, in order to effectively suppress the growth of crystals, it is best to form the surface of the base material in the process of controlling the temperature of the material of the surface layer 5 of the base material and the base material 2 below the crystal growth temperature of the material of the surface layer 5 of the base material. Layer 5. By means of these methods, it is possible to control the formation of the base material surface layer 5 in an amorphous state or in a crystalline state composed of crystal grains of 1 to 2 μm.

Nine types of molds for optical element molding were produced by variously changing the materials of the mold base material 2, the base material surface layer 5, the metal layer 6, the nitride layer 7, and the surface layer 3, and their forming methods. The specific composition of these molds is shown in Table 1.

Table 1 Forming mold Mold base material Surface layer of base metal metal layer nitride layer surface layer 1 Cemented carbide WC Cr CrN Pt-Ir 2 Cemented carbide WC Cr CrN Ir-Re 3 Cemented carbide WC Cr CrN Pt 4 Cemented carbide WC Ti CrN Pt-Ir 5 Cemented carbide WC Ti CrN Ir-Re 6 Cemented carbide WC Ti CrN Pt 7 SiC SiC Cr CrN Pt-Ir 8 SiC SiC Cr CrN Ir-Re 9 SiC SiC Cr CrN Pt Comparative example 1 SiC none Ti TiN Pt-Ir Comparative example 2 Cemented carbide none Cr none Pt-Ir Comparative example 3 Cemented carbide none none none Pt-Ir

The manufacturing methods of forming dies 1 to 3 in Table 1 are as follows.

First, a mold base material 2 composed of cemented carbide (WC) as the main component is made by sintering, and the mold base material 2 is formed on the surface 2a of the mold base material 2 by ion beam spraying. The base material surface layer 5 made. Next, a metal layer 6 made of chromium (Cr) is formed by ion beam spraying, and then a nitride made of chromium nitride (CrN) is formed by reactive spraying of chromium while flowing nitrogen gas. Layer 7. Finally, the surface layer 3 made of platinum-iridium alloy (Pt-Ir), or iridium-rhenium alloy (Ir-Re), or platinum (Pt) is formed by sputtering.

In addition, the manufacturing methods of forming dies 4 to 6 in Table 1 are as follows.

First, a mold base material 2 composed of cemented carbide (WC) as the main component is made by sintering, and the mold base material 2 is formed on the surface 2a of the mold base material 2 by ion beam spraying. The base material surface layer 5 made. Next, a metal layer 6 made of titanium (Ti) is formed by radio frequency spraying, and then a nitride layer made of titanium nitride (TiN) is formed by reactive spraying of chromium while flowing nitrogen gas. 7. Finally, the surface layer 3 made of platinum-iridium alloy (Pt-Ir), or iridium-rhenium alloy (Ir-Re), or platinum (Pt) is formed by sputtering.

In addition, the manufacturing methods of forming dies 7 to 9 in Table 1 are as follows.

First, a mold base material 2 with silicon carbide (SiC) as the main component is made by sintering, and a base material surface layer 5 made of silicon carbide (SiC) is formed on the surface 2a of the mold base material 2 by CVD. film forming. Then, the surface 5a of the base material surface layer 5 is ground to a mirror surface. Next, a metal layer 6 formed of chromium (Cr) is formed by radio frequency spraying, and then a nitride layer 7 composed of chromium nitride (CrN) is formed by reactive spraying of chromium while flowing nitrogen gas. . Finally, the surface layer 3 made of platinum-iridium alloy (Pt-Ir), or iridium-rhenium alloy (Ir-Re), or platinum (Pt) is formed by radio frequency spraying.

As shown in Table 1, molds 1 for molding optical elements of three comparative examples for comparison with the above-mentioned molding molds 1 to 9 were also produced. Among them, there are comparative example 1 in which base material surface layer 5 is omitted; comparative example 2 in which base material surface layer 5 and nitride layer 7 are omitted; and base material surface layer 5, metal layer 6 and Comparative example 3 of nitride layer 7. The manufacturing process of these three comparative examples 1 to 3 is the same as that of forming die 1 or 4 .

In addition, the composition of the nitride layer 7 in the forming dies 1 to 3 and the forming dies 7 to 9 is described as CrN in Table 1, but Cr or Cr ₂ N may actually be mixed with CrN. In addition, the composition of the nitride layer 7 in molding dies 4 to 6 and comparative example 1 is described as TiN in Table 1, but actually, Ti or Ti ₂ N may be mixed with TiN. In addition, the composition of the nitride layer 7 in the molding dies 4 to 6 and the comparative example 1 is not limited to TiN, for example, titanium aluminum nitride (TiAlN) may be used.

For the above 12 kinds of molds 1 for forming optical elements, the temperature of the mold 1 for forming optical elements was fixed at 580°C, and the experiment of the number of times of actual press forming was repeated using glass raw material M, until the surface layer 3 was formed. Until the molding surface 3a and the finished product of the convex lens fail. The experimental results are shown in Table 2.

Table 2 Forming mold Forming times unpleasant sight 1～9 More than 3000 times No Comparative example 1 about 140 times Blackening of formed parts due to increased mold surface roughness Comparative example 2 about 70 times Glass fusion and finished product damage due to chromium precipitation Comparative example 3 about 50 times The glass is welded due to film peeling, and the molded part is blackened due to the increased surface roughness of the mold

According to the results in Table 2, the examples of the present invention, that is, the molding dies 1 to 9, did not find defects in the molding surface 3a of the surface layer 3 and the molding even after more than 3000 press moldings. On the contrary, in Comparative Example 1, after molding was repeated about 140 times, defects such as blackening occurred on the surface of the molded article.

In Comparative Example 1, when the surface roughness on the molding surface 3 a of the surface layer 3 at this point was measured, no numerical increase in the roughness was found. However, when the crystal grains forming such a molding surface 3a are observed with an electron microscope, the same pattern as the crystal grains and grain boundaries of the mold base material 2 can be seen, and fine unevenness exists on a part of the surface of each crystal grain. , and obvious grain boundaries can be seen. This is because the crystal grains exposed on the surface 2a of the mold base material 2 have different crystallographic directions, and the crystal grain directions of the metal layer 6 and the surface layer 3 formed on this basis are subjected to the crystallization of the mold base material 2. Depending on the orientation, different films are formed on the unit grain. That is, it can be considered that the degrees of crystal growth and oxidation are different on the same unit crystal grains as the crystal grains of the mold base material 2 due to the difference in the heat received by the metal layer 6 and the surface layer 3 during forming. , so the roughness of the forming surface 3a increases.

In addition, when the surface of the molded product is carefully observed, the same pattern as that of the molding surface 3a of the surface layer 3 can be seen. Based on the above, it can be considered that slight changes in the surface shape of the molding surface 3a are copied to the surface of the molded article, and thus blackening occurs.

On the other hand, when the molding surface 3a of the surface layer 3 of the molding dies 1 to 9 is carefully observed, it is found that its crystal grains and grain boundary patterns are different from those of the die base material 2, so it can be seen that the metal layer 6, the nitride layer 7 and the surface layer 3 are not affected by the grain and crystallographic boundaries of the mold base material 2. This is considered to be because the diameter of the crystal grains of the base material surface layer 5 is 2 μm or less, which is smaller than the diameter of the crystal grains of the mold base material 2 .

Therefore, in the case of molding molds 1 to 9, by heating the mold 1 for molding optical elements, even if crystal growth and oxidation occur in the mold base material 2, due to the crystal grains and crystal boundaries of the mold base material 2 The influence of 2 is not transmitted to the surface layer 3, so that the roughness of the molding surface 3a in contact with the glass raw material can be prevented from increasing.

In addition, in Comparative Example 2, the glass raw material M was fused to the molding surface 3a of the surface layer 3 when the press molding was repeated about 70 times. Furthermore, when the press forming is continued repeatedly, the formed part is broken and cannot be further formed. When the molding surface 3a is observed in detail, it can be seen that the color changes in a part of the molding surface 3a. According to elemental analysis, this discoloration part is definitely chromium and chromium oxide, and chromium in the metal layer 6 is precipitated on the forming surface 3a, and a part of it is oxidized. Therefore, it is considered that the glass raw material M is fused to these chromium and chromium oxide during the press forming process.

On the other hand, in molding dies 1 to 9 and comparative example 1, even when the molding surface 3a of the surface layer 3 was observed in detail, the above-mentioned discolored portion was not seen. This is because nitrides such as chromium nitride, titanium nitride, and aluminum titanium nitride have very stable properties as compounds and prevent the metal material forming the metal layer 6 from depositing on the forming surface 3 a of the surface layer 3 . Therefore, during the press forming process, it is possible to prevent the glass raw material M from being fused to the forming surface 3a.

In addition, since these nitrides have excellent heat resistance and oxidation resistance, oxygen intrusion into the metal layer 6 from the forming surface 3a of the surface layer 3 can be prevented even if press forming is repeated. Therefore, even if the press forming is repeated, the metal material forming the metal layer 6 can be prevented from being reduced in bonding force due to oxidation.

In addition, in Comparative Example 3, the glass raw material M was welded to the molding surface 3a of the surface layer 3 when the press molding was repeated about 50 times, and a part of the molded product developed a defect called blackening. When such a molding surface 3a is carefully observed, it can be confirmed that the surface layer 3 is peeled off from the mold base material 2 due to a decrease in bonding force. In addition, it was also found that the welding of the glass raw material M and the blackening of the molded product occurred at the peeled portion of the surface layer 3 . From this fact, it is considered that the molded product is blackened due to the fusion of the glass raw material M due to the exposure of the mold base material 2 and the increase in surface roughness due to the oxidation of the exposed mold base material 2 .

On the other hand, in molding dies 1 to 9 and Comparative Example 1, no peeling of the surface layer 3 was observed even when the molding surface 3 a of the surface layer 3 was observed in detail. This shows that the chromium and titanium forming the metal layer 6 have a strong bonding force, and the metal layer 6 prevents the peeling of the surface layer 3 .

As mentioned above, the mold 1 used for forming optical elements is made of amorphous or crystalline tungsten, carbon, tungsten carbide, and silicon carbide formed by grains with a particle size of 1 to 2 μm. The surface layer 5 of the base material made of any material is formed in contact with the base material 2 of the mold, so in the process of stamping and forming, the roughness of the forming surface 3a of the surface layer 3 in contact with the glass raw material M can be reliably prevented. The increase can form a convex lens with high surface precision.

In addition, since the metal layer 6 made of titanium or chromium is formed between the surface layer 5 of the base material, the nitride layer 7, and the surface layer 3, it is possible to reliably prevent damage to the surface layer during repeated press forming. 3, the peeled glass material M is welded to the molding surface 3a, thereby forming a convex lens with high surface precision.

Also, since the nitride layer 7 made of titanium and chromium is formed between the metal layer 6 and the surface layer 3, it is possible to prevent the peeling material M from being welded to the forming surface 3a during the press forming process, and , can also prevent the reduction of bonding force due to the oxidation of the metal material forming the metal layer 6, so that the convex lens with high surface precision can be formed for a long time.

In addition, since the surface precision of the convex lens molded by using such an optical element molding die 1 is high, a convex lens with high optical precision can be obtained.

Next, FIG. 3 shows a second embodiment of the present invention. The structure of this embodiment is basically the same as that of the optical element molding die 1 shown in FIGS. 1 and 2, except that the structure of the nitride layer 7 is different. Here, only the nitride layer 7 in FIG. 3 will be described, and the same reference numerals will be assigned to the same components as those in FIGS. 1 and 2, and descriptions thereof will be omitted.

That is, nitride layer 7 of the present embodiment has nitrogen concentration gradient layer 8 in which the nitrogen concentration gradually decreases toward metal layer 6 . Three types of molds 1 for forming optical elements having such a nitrogen concentration gradient layer 8 were produced. The specific constitution of these molds is shown in Table 3.

table 3 Forming mold Mold base material Surface layer of base metal metal layer Nitriding Concentration Gradient Layer nitride layer surface layer 10 Cemented carbide WC Cr have CrN Pt-Ir 11 Cemented carbide WC Cr have CrN Ir-Re 12 Cemented carbide WC Cr have CrN Pt comparative example Cemented carbide WC Cr none CrN Pt-Ir

The forming methods of the forming dies 10 to 12 in Table 3 are as follows.

First, a mold base material 2 made of cemented carbide with tungsten carbide (WC) as the main component is formed by sintering, and then tungsten carbide (WC) is formed on the surface 2a of the mold base material 2 by ion beam spraying. ) composed of base material surface layer 5. Next, a metal layer 6 made of chromium (Cr) is formed by ion beam spraying film forming method, and then, during the film forming process of chromium, the introduction amount of nitrogen gas is gradually increased, starting from 0 sccm and increasing to 8 sccm, forming a nitrogen concentration gradually The increasing nitrogen concentration slopes the layer 8 . Then, the rest of the nitride layer 7 made of chromium nitride (CrN) was formed by the reactive spraying method of spraying chromium while keeping the introduced amount of nitrogen gas at 8 sccm. Finally, the surface layer 3 made of platinum-iridium alloy (Pt-Ir), iridium-rhenium alloy (Ir-Re), or platinum (Pt) is formed by ion beam spraying.

Moreover, as a comparative example with these molding dies 10-12, the comparative example 4 which was comprised similarly to the molding die 1 mentioned in 1st Example was produced. These forming dies 10-12 and Comparative Example 4, except for the presence or absence of the nitrogen concentration gradient layer 8, the materials of the rest of the die base material 2, the base material surface layer 5, the metal layer 6, the nitride layer 7 and the surface layer 3 all the same.

For the molds 1 for molding the above four types of optical elements, the actual repeated press molding was carried out with glass raw material M, and the molding surface 3a of the surface layer 3 and the formed convex lens molded article were tested until a defect occurred. The experiment of forming times. The temperature of the mold 1 for forming an optical element during molding was 580° C. before 3000 times of press molding, and 600° C. during the subsequent press molding. The results of the experiment are shown in Table 4.

Table 4 Forming mold Forming times at 580°C unpleasant sight Forming times at 600°C unpleasant sight 10～12 3000 times none More than 2000 times none Comparative example 4 3000 times none About 1500 times Glass fusion due to film peeling

According to the results in Table 4, even if press forming was performed 3,000 times at 580° C., no defects occurred in the molding dies 10 to 12 and Comparative Example 4. However, press forming was further performed at 600° C., and as a result, no defect occurred even if press forming was performed more than 2,000 times in the molding dies 10 to 12 . On the contrary, in Comparative Example 4, fusion of the glass raw material M occurred after about 1500 times of press forming.

When the molded surface 3a of the surface layer 3 of Comparative Example 4 was observed in detail, it was found that part of the surface layer 3 and the nitride layer 7 were peeled off from the metal layer 6, and chromium in the metal layer 6 was exposed at the peeled part. It can be considered that the glass material M is welded to the chromium of the metal layer 6 .

As mentioned above, with the mold 1 for forming optical elements, since the nitrogen concentration gradient layer 8 is formed, there is no clear boundary between the metal layer 6 and the nitride layer 7, and even if the temperature of the press molding is raised, the nitrogen concentration is reduced. Since the compound layer 7 does not peel off from the metal layer 6, the roughness of the molding surface 3a of the surface layer 3 can be reliably prevented from increasing. Therefore, convex lenses with high surface precision can be formed over a longer period of time.

In addition, since the surface precision of the convex lens molded using such an optical element molding die 1 is high, a convex lens with high surface precision can be obtained.

In addition, in the above-mentioned embodiment, the crystal grain diameter of the base material surface layer 5 is 1-2 μm, but it is not limited to this range, at least, it can be smaller than the crystal grain diameter of the mold base material 2 . However, the crystal grain diameter of the surface layer 5 of the base material should preferably be small, particularly preferably less than 1 μm.

In addition, in the above-mentioned embodiment, the base material surface layer 5 is formed on the surface 2a of the mold base material 2, but it is not limited to this, as long as the amorphous state is formed on the basis of at least the metal layer 6 , or a crystalline state in which crystal grains having a grain diameter smaller than that of the mold base material 2 are formed. Therefore, for example, as long as ions such as argon are implanted from the surface 2a of the mold base material 2 after the mold base material 2 is formed, an amorphous state is formed near the surface 2a of the mold base material 2, or a crystal grain diameter of 1 is formed. It is sufficient to form the metal layer 6 on the surface 2a of the mold base material 2 in a crystalline state composed of crystal grains with a small grain diameter of -2 μm.

In addition, the combination of the mold base material 2 and the materials of other layers constituting the mold 1 for molding an optical element is not limited to the combination of the molding molds 1 to 12 . That is, as long as the mold base material 2 is a material selected from cemented carbide such as tungsten carbide, and a material mainly composed of silicon carbide, the base material surface layer 5 only needs to be selected from tungsten, carbon, tungsten carbide, and silicon carbide. More than one material of choice will do. That is, for example, the composition of the base material surface layer 5 in the molding dies 1 to 6 may be changed from tungsten carbide (WC) to tungsten (W). In addition, the composition of the base material surface layer 5 in the molding dies 7 to 9 may be changed from silicon carbide (SiC) to carbon (C). In the case of the above composition, the base material surface layer 5 may be formed by an ion implantation method other than the PVD method or the CVD method.

In addition, as long as the metal layer 6 is at least one selected from the following various metal materials: chromium, titanium, aluminum, molybdenum; the nitride layer 7 only needs to be a nitride containing at least one element selected from the following elements You can: chromium, titanium, aluminum, molybdenum. However, ideally, the metal material of the metal layer 6 and the metal material contained in the nitride in the nitride layer 7 are the same metal material.

Also, the surface layer 3 may be at least one material selected from platinum, palladium, iridium, osmium, ruthenium, and rhenium, or any one selected from alloys and compounds containing these elements. That is, the surface layer 3 may be, for example, formed of alloys such as platinum-palladium alloy (Pt-Pd), platinum-rhenium alloy (Pt-Re), iridium-ruthenium alloy (Ir-Ru), or only made of iridium (Ir-Ru). ), osmium (Os), iron (Ru), rhenium (Re) and other metal materials.

In addition, the intermediate layer 4 of the mold 1 for forming an optical element is composed of the surface layer 5 of the base material, the metal layer 6 and the nitride layer 7, but it is not limited to this structure, and may be formed of only the base material. The surface layer 5 and the metal layer 6 are formed. Even with such a configuration, the effect of preventing fusion of the glass raw material M due to peeling of the surface layer 3 during press molding can be reliably obtained.

In addition, the configuration of the intermediate layer 4 may further omit the metal layer 6 from the above configuration, that is, it may also be composed of only the surface layer 5 of the base material. Even with such a configuration, the effect of preventing the roughness of the molding surface 3a of the surface layer 3 from being increased due to contact with the glass material M during press molding can be reliably obtained.

In addition, the optical element forming mold 1 can be used for forming convex lenses, but not limited thereto, it can also be used for forming optical elements such as planar lenses, concave lenses, prisms, or elements having optical surfaces.

Above, the embodiments of the present invention have been described in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and the present invention includes all design changes within the scope not departing from the gist of the present invention.

Claims (6)

1. mould that is used for frit is carried out the optical element shaping usefulness of drawing is characterized in that it has following various piece:

The mold base material made from agglomerating superhard alloy or silicon carbide; On the surface of above-mentioned mold base material, form the upper layer that in the process of drawing, contacts with above-mentioned frit; And, the middle layer that between above-mentioned mold base material and upper layer, forms,

Above-mentioned upper layer is that at least a element of selecting from following column element forms: platinum, palladium, iridium, osmium, ruthenium, rhenium, or by the alloy that contains these elements, compound formation;

Above-mentioned middle layer has the mother metal upper layer, it is by non-grains attitude, or by the crystal grain diameter of the material grain formation crystalline state littler than the crystal grain diameter that constitutes above-mentioned mold base material, at least a material in tungsten, carbon, wolfram varbide, the silicon carbide constitutes;

Above-mentioned mother metal upper layer contacts with the surface of above-mentioned mold base material.

2. the mould of optical element shaping usefulness as claimed in claim 1 is characterized in that, the diameter of the crystal grain of above-mentioned crystalline state is below 2 μ m.

3. the mould of optical element shaping usefulness as claimed in claim 1 or 2 is characterized in that, above-mentioned middle layer also has between above-mentioned mother metal upper layer and above-mentioned upper layer, the metal level that is made of at least a metallic substance in chromium, titanium, aluminium, the molybdenum.

4. the mould of optical element shaping usefulness as claimed in claim 3 is characterized in that, above-mentioned middle layer also has between above-mentioned metal level and above-mentioned upper layer, the nitride layer that is made of the nitride that contains at least a element in chromium, titanium, aluminium, the molybdenum.

5. the mould of optical element shaping usefulness as claimed in claim 4 is characterized in that, above-mentioned nitride layer has the nitrogen concentration of element dipping bed that the concentration of nitrogen element reduces gradually towards above-mentioned metal level.

6. an optical element is characterized in that, the die forming of the optical element shaping usefulness that it is to use in the claim 1 to be put down in writing is made with frit.

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