JPH0725559B2 - Mold for optical element molding - Google Patents

Description

The present invention relates to a mold member used in an optical element molding apparatus,
In particular, the present invention relates to an optical element molding die member that has good mold releasability at high temperatures, can easily realize high precision, and has good durability. Such an optical element molding die member is suitably used, for example, as a die member for high precision molding that directly forms an optical surface.

[Problems to be Solved by Conventional Techniques and Inventions] Generally, optical elements such as lenses, prisms, mirrors, and filters have a functional surface, that is, light, after grinding a material such as glass into a desired outer shape. It is manufactured by polishing the transmitting and / or reflecting surface into an optical surface.

In the production of the optical element as described above, in order to obtain a desired surface precision (that is, precision such as surface shape and surface roughness) by grinding and polishing, a skilled worker needs a considerable amount of time to process the surface. It was necessary to do. Further, in the case of manufacturing an optical element having an aspherical functional surface, more sophisticated grinding and polishing techniques are required and the processing time must be extended.

Therefore, recently, in place of the traditional optical element manufacturing method as described above, press molding is performed by containing the optical element material in a molding die having a predetermined surface accuracy and applying pressure while heating. Immediately thereafter, a method for forming an overall shape including a functional surface is being performed. According to this, an optical element can be manufactured relatively easily and in a short time even when the functional surface is an aspherical surface. Such a press molding method is suitable for continuous production of optical elements.

The properties required for the mold member used in the above press molding are sufficient hardness, good heat resistance, good mirror-finishing workability, and the fact that fusion does not occur with the optical element material during molding. Can be given.

Therefore, conventionally, as such press-molding die members, many types such as metals, ceramics, and materials obtained by coating these with appropriate materials have been proposed.

For example, Japanese Unexamined Patent Publication No. 49-51112 discloses a die member using 13Cr martensitic steel.
Japanese Patent No. 613 discloses a mold member using silicon carbide (SiC) and a mold member using silicon nitride (Si ₃ N ₄ ),
Japanese Unexamined Patent Publication (Kokai) No. 60-246230 discloses a die member obtained by coating a cemented carbide with a noble metal, and Japanese Patent Publication No. 62-21.
Japanese Patent No. 733 discloses a mold member coated with titanium nitride.

However, the above 13Cr martensitic steel is apt to be oxidized, and there is a problem that Fe is diffused into the glass material during press forming at a high temperature and the glass is colored. In addition, the above SiC and Si ₃
N ₄ is generally said to be difficult to oxidize, but some oxidation occurs at high temperatures, and a SiO ₂ film is formed on the surface of the mold member, so fusion with glass tends to occur and hardness is too high. The workability is extremely poor. Further, since the material having the surface coated with a noble metal has a low hardness, it is easily scratched and deformed. Further, the material whose surface is coated with titanium nitride shows quite good characteristics, but when it is continuously used at a high temperature for a long period of time, there is a drawback that fusion with glass is likely to occur.

Therefore, in view of the above-mentioned conventional technique, the present invention provides a long-life optical element molding die member that can be easily manufactured with high precision, has little accuracy deterioration during press molding, and does not cause fusion bonding particularly at high temperature for a long time. The purpose is to do.

[Means for Solving the Problems] According to the present invention, in order to achieve the above objects, at least a molding surface is coated with tantalum carbide, and an optical element molding die member, and At least a molding surface is coated with tantalum carbide, and a tantalum layer is provided as a lower layer of the tantalum carbide coating layer, and an optical element molding die member is provided.

In the optical element molding die member of the present invention, the tantalum carbide preferably has a tantalum content of 20 to 80 atom%.

Further, according to the present invention, in order to achieve the above-mentioned object, at least the molding surface is coated with tantalum carbide, and the tantalum carbide coating layer has a composition changing in the thickness direction. An optical element molding die member is provided.

In this optical element molding die member of the present invention, the tantalum carbide coating layer preferably has a composition in which the tantalum content is gradually increased from the surface to the die base material side, and the tantalum carbide coating layer is formed with the die base material. Tantalum content at the interface 45
It is preferable that the tantalum carbide coating layer has a tantalum content on the surface of 20 to 80 atomic%.

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

FIG. 1 is a schematic sectional view showing a first embodiment of a mold member according to the present invention. In this figure, 130 indicates a mold base material, and 132
Indicates a tantalum carbide coating layer formed on the molding surface of the mold base material.

In the present invention, for example, cemented carbide or sintered SiC can be used as the mold base material 130. These base materials are formed into desired external shapes by processing such as cutting, grinding, and polishing, and especially the molding surface is finished to the desired surface accuracy.

To form the tantalum carbide layer 132 on the surface of the base material 130, for example, a physical vapor phase method (PVD method) such as an activated reactive vapor deposition method by Bunshah method or a reactive sputtering method, a plasma CVD method, or a photo CVD method. Or a chemical vapor deposition method (CVD method) such as a thermal CVD method is used.

In the present invention, tantalum carbide means one having a structure of, for example, an interstitial carbide containing carbides such as TaC and Ta ₂ C, provided that tantalum element simple substance or carbon element simple substance may be mixed.

The tantalum carbide layer 132 can change the atomic ratio of carbon to tantalum in its composition in a considerable range, but as a practical range, for example, the tantalum content is
It is preferably about 20 to 80 atom%.

Although the thickness of the tantalum carbide layer 132 is appropriately set depending on the manufacturing conditions, it may be set to a thickness (for example, 0.1 to 10 μm, preferably about 1 μm) so that desired characteristics can be exhibited during use.

Since the tantalum carbide layer 132 has a remarkably low fusion property with glass particularly at high temperatures and has a good mold release property, it has been necessary to industrially perform high precision molding for fusion with the mold member. It can be applied well to molding using high melting point glass, which is said to be difficult, and further applied to the production of optical elements in which the primary molded glass or molten glass is housed in a mold device and press molded. There is an advantage that an optical element with good accuracy can be obtained even if it is repeatedly used.

FIG. 2 is a schematic sectional view showing a second embodiment of the mold member according to the present invention. In this figure, 130 indicates a mold base material, and 131
Indicates the tantalum layer formed on the molding surface of the mold base material, 13
2 indicates a tantalum carbide coating layer formed on the tantalum layer.

In the present invention, for example, cemented carbide or sintered SiC can be used as the mold base material 130. These base materials are formed into desired external shapes by processing such as cutting, grinding, and polishing, and especially the molding surface is finished to the desired surface accuracy.

A tantalum layer 131 and a tantalum carbide layer are formed on the surface of the base material 130.
To form 132 in this order, for example, evaporation and Bunsh
Physical vapor phase method (PVD method) such as activated reaction vapor deposition method, sputtering method and reactive sputtering method by ah method, or chemical vapor phase method (CVD method) such as plasma CVD method, optical CVD method and thermal CVD method To use.

Although the thickness of the tantalum layer 131 is appropriately set depending on the manufacturing conditions, it may be set to a thickness (for example, 0.01 to 5 μm, preferably about 0.2 μm) so that desired characteristics can be exhibited during use.

The tantalum layer 131 has a function of increasing the bonding force between the die base material 130 and the tantalum carbide layer 132 and preventing peeling of the coating layer during use. That is, when the tantalum carbide layer is formed directly on the mold base material 130 without forming the tantalum layer 131, a relatively large internal stress remains in the tantalum carbide layer. Although the residual internal stress can be reduced by appropriately setting the film forming conditions of the tantalum carbide layer, if the film forming conditions are changed, the internal structure of the film may be changed and desired surface accuracy may not be obtained. Therefore, it is not realistic to set the conditions for optimizing only the decrease of the internal stress. Therefore, the mold base material
By interposing the tantalum layer 131 between the tantalum carbide layer 132 and the tantalum carbide layer 132, the residual internal stress of the coating layer composed of the tantalum carbide layer 132 and the tantalum layer 131 is maintained while maintaining a good internal structure of the tantalum carbide layer 132. Can be reduced. Thus, in use, a mold member having good durability can be obtained in which the coating layer is not easily peeled off even if it is subjected to a heat history due to repeated press molding at a relatively high temperature.

In the present invention, tantalum carbide means one having a structure of, for example, an interstitial carbide containing carbides such as TaC and Ta ₂ C, provided that tantalum element simple substance or carbon element simple substance may be mixed.

The tantalum carbide layer 132 can change the atomic ratio of carbon to tantalum in its composition in a considerable range, but as a practical range, for example, the tantalum content is
It is preferably about 20 to 80 atom%.

Although the thickness of the tantalum carbide layer 132 is appropriately set depending on the manufacturing conditions, it may be set to a thickness (for example, 0.1 to 10 μm, preferably about 1 μm) so that desired characteristics can be exhibited during use.

Since the tantalum carbide layer 132 has a remarkably low fusion property with glass particularly at high temperatures and has a good mold release property, it has been necessary to industrially perform high precision molding for fusion with the mold member. It can be applied well to molding using high melting point glass, which is said to be difficult, and further applied to the production of optical elements in which the primary molded glass or molten glass is housed in a mold device and press molded. There is an advantage that an optical element with good accuracy can be obtained even if it is repeatedly used.

FIG. 3 is a schematic sectional view showing a third embodiment of the mold member according to the present invention. In this figure, 130 indicates a mold base material, and 13
2'denotes a tantalum carbide coating layer formed on the molding surface of the mold base material.

In the present invention, for example, cemented carbide or sintered SiC can be used as the mold base material 130. These base materials are formed into desired external shapes by processing such as cutting, grinding, and polishing, and especially the molding surface is finished to the desired surface accuracy.

To form the tantalum carbide layer 132 'on the surface of the base material 130, for example, a physical vapor phase method (PVD method) such as an activated reactive vapor deposition method by the Bunshah method or a reactive sputtering method, a plasma CVD method or an optical CVD method. Chemical vapor phase method (CVD method) such as a thermal CVD method or a thermal CVD method is used.

In the present invention, tantalum carbide means one having a structure of, for example, an interstitial carbide containing carbides such as TaC and Ta ₂ C, provided that tantalum element simple substance or carbon element simple substance may be mixed.

The composition (that is, the atomic ratio of tantalum to carbon) of the tantalum carbide layer 132 'changes in the thickness direction.

4 (a) to (i) are graphs showing examples of the distribution of the tantalum content rate in the thickness direction of the tantalum carbide layer 132 '. In the figure, the vertical axis represents the tantalum (Ta) content (atomic%), the horizontal axis represents the thickness based on the interface with the mold base material 130, and the thickness of the tantalum carbide layer 132 'is t. It is said that.

4 (a) to 4 (e), the Ta content changes linearly, and in FIGS. 4 (f) and 4 (g), the Ta content changes linearly. In (h), the Ta content changes linearly, and in FIG. 4 (i), the Ta content changes stepwise.

The tantalum carbide layer 132 ′ has an atomic ratio of Ta and C of about 1: 1 on the surface (that is, a surface that comes into contact with the optical element material during press molding) and a Ta content ratio at the interface with the base material 130 is comparable. It is preferable that the height is high. This is because it is advantageous that the content of Ta is as high as possible in order to increase the bonding strength with the die base material and prevent the peeling of the tantalum carbide layer during the press forming. From this point of view, the tantalum carbide layer 13
2 ′ is practically, for example, the Ta content on the surface is 20 to 8
The content of Ta at the interface with the base material is preferably 45 to 10%.
It is preferably 0 atom%.

The compositional distribution in the thickness direction of the tantalum carbide layer 132 'as described above can be obtained by appropriately setting the manufacturing conditions in the PVD method or the CVD method when forming the tantalum carbide layer.

The thickness of the tantalum carbide layer 132 'is appropriately set depending on the manufacturing conditions, but it may be set to a thickness (for example, 0.1 to 10 μm, preferably about 1 μm) so that desired characteristics can be exhibited during use.

Since the tantalum carbide layer 132 'has a remarkably low fusion property with glass at a high temperature and has a good releasability, high precision molding has been industrially carried out for fusion with a mold member. It can be applied well to molding using high melting point glass, which is said to be difficult, and is further applied to the manufacturing of optical elements in which primary molded glass or molten glass is housed in a mold device and press molded. There is an advantage that an optical element with good accuracy can be obtained even if it is repeatedly used.

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

Manufacture and molding example 1: Cemented carbide [WC (90%) + Co (10%)] and sintered SiC are used as a base material to form a mold base material, and a tantalum carbide layer is formed on the base metal molding surface. Then, the mold member according to the present invention shown in FIG. 1 was manufactured as follows. For comparison, a mold member in which the molding surface of the mold base material was not coated and a mold member in which a SiC layer or a TiN layer was formed on the molding surface were manufactured. Table 1 shows a list of manufactured die members. In Table 1, No. 1 and No. 2 are examples of the present invention, and No. 3 and No.
4, No. 5 and No. 6 are comparative examples.

The mold members were manufactured as follows.

First, the mold base material was cut, and then the molding surface corresponding to the functional surface (optical surface) of the molding optical element was processed to a desired surface accuracy. The molding surface of the die base material is a concave surface 1. First, it is ground to a desired curvature by grinding with a diamond grindstone, and then it is polished with a diamond powder with a particle size of 1 μm to obtain a surface shape accuracy of about 1 Newton ring and Rmax.
Finished to a surface roughness accuracy of about 0.02 μm.

Next, for N.o1 and No. 2, the tantalum carbide layer was formed on the molding surface of the mold base material by the activated reaction vapor deposition method using the Bunshah method.

The tantalum carbide layer was formed as follows.

The mold base material obtained as described above was washed with an organic solvent and set in a vacuum chamber. Next, the inside of the vacuum chamber is about 1 × 10 ⁻⁵ To
The pressure was reduced to rr or less, and at the same time, the die base material was heated to about 300 ° C. Then, a hydrocarbon gas (methane and acetylene) was introduced as a reaction gas at 3 × 10 ⁻⁴ to 8 × 10 ⁻⁴ Torr, and metal tantalum was evaporated by an electron gun while applying an ionization voltage of about 50V. As a result, the evaporated tantalum and carbon reacted to be deposited on the surface of the die base material to form a tantalum carbide layer. The tantalum content of the obtained tantalum carbide layer was 50 atomic%. The thickness of the tantalum carbide layer is about 1 μm.
Met.

As for No. 6, the TiN layer was formed on the molding surface of the mold base material by the activated reactive vapor deposition method by the Bunshah method in the same manner as in No. 1 and No. 2. The thickness of the obtained TiN layer was about 1 μm.

For No. 5, the SiC layer was formed on the molding surface of the base material by the usual sputtering method. The thickness of the obtained SiC layer was about 1 μm.

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

FIG. 5 is a sectional view showing an apparatus used for press molding.

In FIG. 5, 4 is a substitution chamber for taking in, 6 is a forming chamber, 8 is a vapor deposition chamber, and 10 is a substitution chamber for taking out. 12, 14 and 16 are gate valves, 18 is a rail, and 20 is a pallet that can be conveyed on the rail in the direction of arrow A. 24, 38, 40, 50 are hydraulic cylinders, 26,
52 is a valve. A heater 28 is arranged along the rail 18 in the molding chamber 6.

Inside the molding chamber 6, a heating zone 6-1, a press zone 6-2, and a slow cooling zone 6-3 are sequentially arranged along the pallet conveying direction. In the press zone 6-2, the molding upper die member 30 is fixed to the lower end of the rod 34 of the hydraulic cylinder 38, and the molding lower die member 32 is fixed to the upper end of the rod 36 of the hydraulic cylinder 40. ing. The upper mold member 30 and the lower mold member 32 are the mold members according to the present invention shown in FIG. In the vapor deposition chamber 8, a container containing the vapor deposition material 46.
42 and a heater 44 for heating the container are arranged.

Flint optical glass (SF14, softening point Sp = 586 ° C., glass transition point Tg = 485 ° C.) was roughly processed into a predetermined shape and size to obtain a blank for molding.

Place glass blank on pallet 20 and take in replacement chamber 4
20-1 in the inside and push the pallet at that position in the direction A by the rod 24 of the hydraulic cylinder 24 to move the gate valve 12
It is conveyed to the position 20-2 in the molding chamber 6 over the space, and thereafter, a pallet is newly inserted into the replacement chamber 4 at predetermined timing in the same manner.
-2 → …… → Sequentially transported to the position of 20-8. In the meantime, in the heating zone 6-1, the glass blank is gradually heated by the heater 28 to reach the softening point or higher at the position 20-4, and then conveyed to the press zone 6-2, where the hydraulic cylinders 38, 40 are conveyed. 1 by operating the upper mold member 30 and the lower mold member 32.
Press at a pressure of 0 kg / cm ² for 5 minutes, then release the applied pressure and cool to below the glass transition point, then hydraulic cylinder 3
The upper mold member 30 and the lower mold member 40 were released from the glass molded product by operating 8, 40. At the time of the pressing, the pallet was used as a body member for molding. Then, in the slow cooling zone 6-3, the glass molded product was gradually cooled. The molding chamber 6 was filled with an inert gas.

The pallet that has reached the position 20-8 in the forming chamber 6 will pass through the gate valve 16 in the deposition chamber 8 in the next transfer.
Transported to position 20-9. Usually, vacuum deposition is performed here, but this deposition was not performed in this embodiment. Then, in the next transportation, the material was transported beyond the gate valve 16 to the position 20-10 in the take-out replacement chamber 10. Then, at the time of the next conveyance, the hydraulic cylinder 50 was operated and the glass molded article was taken out of the apparatus 2 by the rod 48.

The surface roughness of the molding surface of the mold members 30 and 32 before and after the above-described press molding, the surface roughness of the optical surface of the molded optical element, and the releasability between the molding optical element and the mold members 30 and 32. Is shown in Table 2.

Next, with respect to No. 1, No. 2, No. 3 and No. 6 in which fusion did not occur, press molding was continuously performed 10,000 times using the same mold member. Table 3 shows the surface roughness of the molding surface of the mold members 30 and 32 and the surface roughness of the optical surface of the molded optical element at this time.

As described above, in the examples of the present invention, good surface accuracy could be sufficiently maintained even when used for repeated press molding, and an optical element having good surface accuracy could be formed without causing fusion.

Further, the mold member of the present invention example having a tantalum carbide layer on the molding surface, compared to the mold member having a TiN layer in the same base material, there is almost no difference when the molding frequency is small, but the molding frequency is large. However, it was found that the decrease in releasability was extremely small.

The melting point of tantalum carbide, 3880 ° C, is higher than the melting point of titanium nitride, 2947 ° C, and the thermal stability is good, and even if metallic tantalum is present in the tantalum carbide, it is harder to oxidize than metallic Ti, so that it has wettability with glass. Low. Therefore, it can be inferred that the mold members of the examples of the present invention are less likely to cause fusion with glass during glass molding.

In the above embodiment, Bunsha is used as the method for forming the tantalum carbide layer.
Although the activated reactive vapor deposition method based on the h method is used, the tantalum carbide layer can also be formed using another method, for example, a reactive sputtering method.

FIG. 6 is a schematic configuration diagram of a reactive sputtering apparatus for forming a tantalum carbide layer.

In FIG. 6, 140 is a vacuum chamber. An exhaust port 142 is connected to the vacuum chamber, and the exhaust port is connected to a decompression source (not shown). A heater 144 is arranged above the vacuum chamber 140, and 145 is its power source. A die base material support 146 is disposed below the heater 144, and the die base material 148 is supported on the support with the molding surface facing downward. 149 is a bias power source for applying a bias voltage to the die base material. A coil 150 for glow discharge generation is arranged below the die base material 148, 151 is a high frequency power source thereof, and 152 is a matching circuit. A cathode electrode 154 is arranged in the lower portion of the vacuum chamber 140, and a tantalum target 156 is arranged on the electrode. 157 is a power source for applying a voltage to the cathode electrode 154. 158 is a pipe for supplying argon gas toward the tantalum target 156, and 160 is the mold base material 1
Towards 48 toward hydrocarbon gas (methane and acetylene)
Is a pipe for supplying.

At the time of forming the tantalum carbide layer, the mold base material 148 finished to a predetermined accuracy is washed with an organic solvent and then the mold base material support 146.
Supported by. Next, the vacuum chamber 140 is evacuated to a predetermined degree of vacuum, an argon gas is introduced from a pipe 158, a high frequency voltage is applied to the coil 150 by a high frequency power source to generate glow discharge, and a mold power source is generated by a bias power source 149. Material 148
Negative voltage is applied to the mold base material 14
Perform 8 sputter cleaning. After that, a high-frequency or direct-current voltage is applied to the cathode electrode 154 by the power source 157 to generate a glow discharge of argon in the vicinity of the tantalum target 156, and the tantalum target is bombarded with argon ions, and at the same time, hydrocarbons are discharged from the pipe 160. A gas (methane and acetylene) is introduced, a high frequency voltage is applied to the coil 150 by the power supply 151 to form a hydrocarbon plasma, and a negative bias voltage is applied to the mold base material 148 by the bias power supply 149 to generate the above hydrocarbons. Reactive sputtering of tantalum can be performed by drawing the carbon ions in the plasma toward the mold base material 148. As a result, a tantalum carbide layer is formed on the surface of the mold base material 148.

The ratio of carbon to tantalum in the tantalum carbide layer can be set to a desired value by appropriately setting film forming conditions. The film forming conditions that greatly affect the ratio include the degree of vacuum in the vacuum chamber 140, the pressure of the argon gas and the pressure of the hydrocarbon gas, the voltage of the power supplies 145, 149, 151, 157, and the like.

According to the reactive sputtering method as described above, a hydrocarbon gas is supplied in the vicinity of the die base material to form a hydrocarbon gas plasma, so that a tantalum carbide layer having an arbitrary carbon / tantalum ratio can be easily formed. it can.

Using such a reactive sputtering method, a mold member in which a tantalum carbide layer having a carbon content of 50 atomic% and a tantalum content of 50 atomic% is formed on the forming surface of a cemented carbide base material similar to No. 1 above. (No.7) was obtained.

Using No. 7, press molding was continuously performed 12000 times in the same manner as described with reference to FIG. Then, with respect to No. 1 described above, press molding was further performed up to a total of 12000 times. Table 4 shows the surface roughness of the molding surface of the mold member and the surface roughness of the optical surface of the molded optical element at this time.

From Table 4, it can be seen that the No. 7 mold member is slightly better than the No. 1 mold member after 12000 presses.

Manufacture and forming example 2: Cemented carbide [WC (90%) + Co (10%)] and sintered SiC are used as a base material to form a die base material, and a tantalum layer and tantalum carbide are formed on the base material forming surface. The layers were formed in this order to produce the mold member according to the invention shown in FIG. 2 above as follows.
For comparison, a mold member not coated on the molding surface of the mold base material, a mold member having a SiC layer or a TiN layer formed on the molding surface, and a tantalum carbide layer directly formed on the molding surface were formed. The mold member (which corresponds to that of the first embodiment,
Here, a comparative example) was manufactured. Table 5 shows a list of manufactured die members. In Table 5, No. 8
And No. 9 is an embodiment of the present invention, No. 10, No. 11, No. 1
2, No. 13, No. 14 and No. 15 are comparative examples.

The mold members were manufactured as follows.

First, the mold base material was cut, and then the molding surface corresponding to the functional surface (optical surface) of the molding optical element was processed to a desired surface accuracy. The molding surface of the die base material is a concave surface. First, it is processed into a desired curvature by grinding with a diamond grindstone, and then it is polished with a diamond powder having a particle diameter of 1 μm.
Surface shape accuracy of one Newton ring and Rmax 0.02
The surface roughness accuracy was about μm.

Next, regarding N.o8 and No. 9 above, the vapor deposition method and Bunsha
A tantalum layer and a tantalum carbide layer were formed in this order on the molding surface of the die base material by the activated reaction vapor deposition method by the h method.

The tantalum layer and the tantalum carbide layer were formed as follows.

The mold base material obtained as described above was washed with an organic solvent and set in a vacuum chamber. Next, the inside of the vacuum chamber is about 1 × 10 ⁻⁵ To
The pressure was reduced to rr or less, and at the same time, the die base material was heated to about 300 ° C. The metal tantalum was then evaporated with an electron gun. As a result, evaporated tantalum was deposited on the surface of the base material and a tantalum layer was formed. The thickness of the tantalum layer was about 0.2 μm. Subsequently, while evaporating the metal tantalum, a hydrocarbon gas (methane and acetylene) was added as a reaction gas at 3 × 10 ^−4.
˜8 × 10 ⁻⁴ Torr was introduced, and an ionization voltage of about 50 V was applied. As a result, the evaporated tantalum and carbon reacted to deposit on the tantalum layer to form a tantalum carbide layer. The tantalum content of the obtained tantalum carbide layer was 50 atomic%. The thickness of the tantalum carbide layer was about 1 μm.

For No. 13, No. 14 and No. 15 above, No. 8 and N above
As in the case of o.9, a TiN layer or a tantalum carbide layer was formed on the molding surface of the mold base material by the activated reaction vapor deposition method by the Bunshah method. The thickness of the obtained TiN layer or tantalum carbide layer was about 1 μm in each case.

For No. 12, the SiC layer was formed on the molding surface of the base material by the usual sputtering method. Obtained SiC
The layer thickness was about 1 μm.

Next, using the mold member manufactured as described above, press molding of optical glass was performed in the same manner as in Example 1 of the above manufacturing and molding.

Surface Roughness of Molding Surfaces of Mold Members 30, 32 Before and After Press Molding, Surface Roughness of Optical Surface of Molded Optical Element, and Releasability between Molding Optical Element and Mold Members 30, 32 Table 6 Shown in.

Next, No.8, No.9, No.10, No.13, No.1 without fusion
For No. 4 and No. 15, press molding was performed 10,000 times continuously using the same mold member. Table 7 shows the surface roughness of the molding surface of the mold members 30 and 32 and the surface roughness of the optical surface of the molded optical element at this time.

As described above, in the examples of the present invention, good surface accuracy could be sufficiently maintained even when used for repeated press molding, and an optical element having good surface accuracy could be formed without causing fusion.

The surface roughness was good in the above-mentioned 10,000 times of press molding.
No.14, No.14, No.15, No.14, No.14, and No.15 were tried by using the same mold member and press molding up to 20000 times continuously.
Although the coating layer peeled off by 15 times in all reaching 14000 times, no peeling of the coating layer occurred in any of No. 8 and No. 9 times up to 20000 times and both the mold member and the optical element had a surface. The roughness did not deteriorate so much.

In the above embodiment, the vapor deposition method and the activated reactive vapor deposition method by the Bunshah method are used as the method for forming the tantalum layer and the tantalum carbide layer, but the tantalum layer and the tantalum carbide layer are other methods such as the sputtering method and the reactive sputtering method. It can also be formed by using. This method can be performed using the apparatus shown in FIG.

When forming the tantalum layer and the tantalum carbide layer, the mold base material 148 finished to a predetermined accuracy is washed with an organic solvent and then supported by the mold base material support 146. Next, the vacuum chamber 140 is evacuated to a predetermined degree of vacuum, argon gas is introduced from a pipe 158, a high frequency voltage is applied to the coil 150 by a high frequency power source to generate glow discharge, and further a bias power source 149.
Thus, a negative voltage is applied to the mold base material 148 to perform sputter cleaning of the mold base material 148 with argon ions.
After that, a high-frequency or direct-current voltage is applied to the cathode electrode 154 by the power source 157 to generate a glow discharge of argon in the vicinity of the tantalum target 156, and the tantalum target is bombarded with argon ions to generate a bias power source 149.
Thus, a negative bias voltage can be applied to the mold base material 148 to perform tantalum sputtering. As a result, a tantalum layer is formed on the surface of the mold base material 148. Subsequently, a hydrocarbon gas (methane and acetylene) is further introduced from a pipe 160, a high frequency voltage is applied to the coil 150 by a power supply 151 to form a hydrocarbon plasma, and carbon ions in the plasma are generated in the mold base material 148. Reactive sputtering of tantalum can be performed by pulling it in the direction. Thereby, a tantalum carbide layer is formed on the tantalum layer.

The ratio of carbon to tantalum in the tantalum carbide layer can be set to a desired value by appropriately setting film forming conditions. The film forming conditions that greatly affect the ratio include the degree of vacuum in the vacuum chamber 140, the pressure of the argon gas and the pressure of the hydrocarbon gas, the voltage of the power supplies 145, 149, 151, 157, and the like.

According to the reactive sputtering method as described above, a hydrocarbon gas is supplied in the vicinity of the die base material to form a hydrocarbon gas plasma, so that a tantalum carbide layer having an arbitrary carbon / tantalum ratio can be easily formed. it can.

Using such a reactive sputtering method, mold members (No. 16, No. 17) having a base material, a tantalum layer and a tantalum carbide layer similar to those of Nos. 8 and 9 were obtained. The tantalum content of the tantalum carbide layer obtained at this time was 50 atom%.
Met.

When No. 16 and No. 17 were subjected to continuous press molding for 20000 times in the same manner as described with reference to FIG. 5, no separation of the tantalum layer and the tantalum carbide layer occurred. The surface roughness of both the mold member and the optical element did not deteriorate so much.

Manufacture and molding example 3: A mold base material is made using cemented carbide [WC (90%) + Co (10%)] and sintered SiC as a base material, and the above is formed in the thickness direction on the forming surface of the base material. A tantalum carbide layer having the composition distribution shown in FIG. 4 (c) was formed to manufacture the mold member according to the present invention shown in FIG. 3 as described below. For comparison, the molding surface of the above-mentioned mold base material is not covered and the molding surface is covered with Si.
A mold member having a C layer or a TiN layer formed thereon, and further, a mold member having a tantalum carbide layer having a uniform composition in the thickness direction formed on the molding surface (which corresponds to that of Example 1 above, but here is a comparison. Manufactured by way of example). Table 8 shows a list of manufactured die members. In Table 8, No. 18 and No. 19
Is an embodiment of the present invention, No. 20, No. 21, No. 22, No. 23,
No. 24 and No. 25 are comparative examples.

The mold members were manufactured as follows.

First, the mold base material was cut, and then the molding surface corresponding to the functional surface (optical surface) of the molding optical element was processed to a desired surface accuracy. The molding surface of the die base material is a concave surface. First, it is processed into a desired curvature by grinding with a diamond grindstone, and then it is polished with a diamond powder having a particle diameter of 1 μm.
Surface shape accuracy of one Newton ring and Rmax 0.02
The surface roughness accuracy was about μm.

Next, with respect to No. 18 and No. 19, a tantalum carbide layer was formed on the molding surface of the mold base material by the activated reaction vapor deposition method by the Bunshah method.

The tantalum carbide layer was formed as follows.

The mold base material obtained as described above was washed with an organic solvent and set in a vacuum chamber. Next, the inside of the vacuum chamber is about 1 × 10 ⁻⁵ To
The pressure was reduced to rr or less, and at the same time, the die base material was heated to about 300 ° C. Then, a hydrocarbon gas (methane and acetylene) was introduced as a reaction gas, and metal tantalum was evaporated by an electron gun while applying an ionization voltage of about 50V. At this time, the hydrocarbon gas (methane and acetylene) was changed from 3 × 10 ^-4 to 8
It was gradually increased to × 10 ^-4 Torr, and at the same time, the evaporation amount of metal tantalum was gradually decreased by adjusting the electron gun. As a result, the evaporated tantalum and carbon reacted to be deposited on the surface of the die base material to form a tantalum carbide layer. The tantalum content distribution in the thickness direction of the obtained tantalum carbide layer was as shown in FIG. 4 (c). The thickness of the tantalum carbide layer was about 1 μm.

Regarding No. 24 and No. 25, except for maintaining the hydrocarbon gas introduction amount and the electron gun under constant conditions, the tantalum carbide layer was formed in the same manner as in No. 18 and No. 19, respectively. Formed. The tantalum content of the obtained tantalum carbide layer was 50 atomic%. The thickness of each tantalum carbide layer was about 1 μm.

For No. 23, a TiN layer was formed on the molding surface of the mold base material by the activated reactive vapor deposition method by the Bunshah method in the same manner as No. 24 and No. 25. The thickness of the obtained TiN layer was about 1 μm.

For No. 22, the SiC layer was formed on the molding surface of the base material by the usual sputtering method. Obtained SiC
The layer thickness was about 1 μm.

Next, using the mold member manufactured as described above, press molding of optical glass was performed in the same manner as in Example 1 of the above manufacturing and molding.

The surface roughness of the molding surface of the mold members 30 and 32 before and after the above-described press molding, the surface roughness of the optical surface of the molded optical element, and the releasability between the molding optical element and the mold members 30 and 32. Is shown in Table 9.

Next, No.18, No.19, No.20, No.23, N without fusion occurrence
For o.24 and No.25, continuous 10000 using the same mold member
Press molding was performed once. Table 10 shows the surface roughness of the molding surface of the mold members 30 and 32 and the surface roughness of the optical surface of the molded optical element at this time.

As described above, in the examples of the present invention, good surface accuracy could be sufficiently maintained even when used for repeated press molding, and an optical element having good surface accuracy could be formed without causing fusion.

The surface roughness was good in the above-mentioned 10,000 times of press molding.
For No. 18, No. 24, No. 24, No. 24, No. 24, No. 25
In o.25, the coating layer peeled off by 14,000 times in both cases, but in No. 18 and No. 19, neither peeling of the coating layer occurred up to 20000 times and both the mold member and the optical element. The surface roughness did not deteriorate so much.

In the above embodiment, Bunsha is used as the method for forming the tantalum carbide layer.
Although the activated reactive vapor deposition method based on the h method is used, the tantalum carbide layer can also be formed using another method, for example, a reactive sputtering method. This method can be carried out by using the apparatus shown in FIG.

At that time, the ratio of carbon to tantalum in the tantalum carbide layer can be set to a desired value by appropriately setting the film forming conditions. The film forming conditions that greatly affect the ratio are:
There are the degree of vacuum in the vacuum chamber 140, the pressure of the argon gas and the pressure of the hydrocarbon gas, the voltage of the power supplies 145, 149, 151, 157, and the like. By performing film formation while appropriately changing these film formation conditions, it is possible to form a tantalum carbide layer whose composition distribution changes in the thickness direction.

According to the reactive sputtering method as described above, a hydrocarbon gas is supplied in the vicinity of the die base material to form a hydrocarbon plasma, so that a tantalum carbide layer having an arbitrary carbon / tantalum ratio distribution can be easily formed. it can.

Although the flint type optical glass is used as the optical glass to be formed in the above-mentioned examples, the mold member of the present invention can also form other crown type glasses with good accuracy in the same manner. .

In the above example, the tantalum carbide layer formed by the PVD method or the CVD method is used as it is, but the tantalum carbide layer may be formed relatively thick by the method, and then the surface may be mirror-polished before use. it can. Further, even when a defect is generated on the surface by a large number of presses, such polishing can regenerate a good surface.

[Effects of the Invention] According to the present invention as described above, since the molding surface is covered with the tantalum carbide layer, accuracy deterioration is less likely to occur during repeated press molding, and fusion bonding with glass is achieved even when used at high temperatures. Provided is a long-life optical element molding die member that does not cause

Furthermore, the Knoop hardness Hk of tantalum carbide is, for example, 2900, which is harder to be scratched because it has a higher hardness than TiN having a Knoop hardness of 2000. An optical element with good surface accuracy can be manufactured for a long period of time.

In addition, the mold member of the present invention can be manufactured easily because it can be selected as a mold base material having good workability.

Further, according to the present invention, by providing the tantalum layer as the lower layer of the tantalum carbide layer, the internal stress of the coating layer is small, and the bonding force between the coating layer and the die base material is large, and therefore the die base material with good durability is provided. Is obtained.

Furthermore, according to the present invention, by changing the composition of the tantalum carbide layer in the thickness direction so that the mold base material side has a high tantalum content, the internal stress of the coating layer is small and the coating layer and the mold base material are Therefore, a die base material having a high joining strength and having a good durability can be obtained.

[Brief description of drawings]

1 to 3 are schematic sectional views showing a mold member according to the present invention. FIGS. 4A to 4I are graphs showing the tantalum content distribution in the thickness direction of the tantalum carbide layer. FIG. 5 is a sectional view of an apparatus used for press-molding an optical element. FIG. 6 is a view showing an apparatus used for manufacturing the mold member according to the present invention. 30,32: Mold member, 130: Mold base material, 131: Tantalum layer, 132, 13
2 ': tantalum carbide layer, 148: type base material.

Claims (7)

[Claims] 1. A mold member for molding an optical element, characterized in that at least a molding surface is covered with tantalum carbide. 2. An optical element molding die member, wherein at least a molding surface is coated with tantalum carbide, and a tantalum layer is provided as a lower layer of the tantalum carbide coating layer. 3. The optical element molding die member according to claim 1, wherein the tantalum carbide has a tantalum content of 20 to 80 atom%. 4. An optical element molding die member, characterized in that at least the molding surface is coated with tantalum carbide, and the composition of the tantalum carbide coating layer changes in the thickness direction. 5. The optical element molding die member according to claim 4, wherein the tantalum carbide coating layer has a composition in which the tantalum content gradually increases from the surface to the die base material side. 6. The optical element molding die member according to claim 4, wherein the tantalum carbide coating layer has a tantalum content of 45 to 100 atom% at the interface with the die base material. 7. The optical element molding die member according to claim 4, wherein the tantalum carbide coating layer has a tantalum content of 20 to 80 atom% on the surface.