JPH0741325A - Optical element forming die - Google Patents

Abstract

PURPOSE:To prevent the fusion of glass to an optical element forming die, improve the durability and increase the die strength by implanting a specified amt. of nitrogen ion in the forming surface of the die made of AlN. CONSTITUTION:An assistant such as Y2 O3 is added to an AlN powder, water or alcohol is added and kneaded, and the kneaded material is formed into a desired shape, dried and sintered to produce an optical element forming die blank 1. Nitrogen ion is then implanted in the forming surface 2 of the blank 1 at >=1X10<6> ion/cm2 to prevent the fusion due to an aluminum compd. except AlN contained as impurities, hence the aluminum compd. is nitrided, and an AlN film is formed. Consequently, the fusion of glass to the die is prevented when an optical element is formed, and the hardness and bending strength of AlN are improved by the implanted nitrogen ion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die, and more particularly to a molding die used for obtaining an optical element by pressing heat-softened glass with a molding die.

[0002]

2. Description of the Related Art Conventionally, a molding die used for manufacturing an optical element by heating and softening glass is generally required to have heat resistance and releasability from glass. Therefore, heat-resistant ceramics and heat-resistant coating agents are used in the molding die. However, since the ceramic material is produced by sintering powder through an auxiliary agent,
The heating causes changes in the bonds between the particles and the particles grow. Further, the heat-resistant coating material has low adhesion to the base material, which causes a problem of thin profit.

Therefore, in order to solve the above problems, for example, in the invention described in Japanese Patent Laid-Open No. 3-83825, AlN using yttrium and / or thorium as an auxiliary agent.
It is disclosed that the particles are prevented from changing and the adhesiveness is improved by sintering or vapor-depositing. Further, the invention described in Japanese Patent Laid-Open No. 3-208821 discloses a method in which a halide of aluminum and a gas are reacted with each other in a microwave to perform vapor deposition.

[0004]

However, the above-mentioned respective prior arts have the following problems. That is, as in the invention described in JP-A-3-83825, when an auxiliary agent is added, a compound of the auxiliary agent and AlN is produced between particles during sintering. In addition, a film is formed as a compound with AlN by vapor deposition. Further, as in the invention described in JP-A-3-208821, when AlN is formed by the reaction with a gas, a compound with an impurity mixed in the gas is formed. Further, unreacted aluminum is directly formed as a film.

Since these compounds are liable to react at a high temperature, they are likely to react with each other when hot glass comes into contact therewith to cause fusion. Although the durability of 5,000 shots is described in the examples of the invention, when the high softening point glass or the molten glass is molded, the durability is low and the problem of fusion occurs.

Therefore, the present invention has been made in view of the above-mentioned problems, and even when molding a glass having a high softening point or a molten glass, fusion with the glass does not occur and a highly durable optical element molding is formed. The purpose is to provide a mold.

[0007]

The present invention provides an optical element molding die in which at least the molding surface is made of AlN, and nitrogen ions are added to the molding surface at 1 × 10 ⁶ ion / cm 2.
It is composed of ^two or more injections.

[0008]

In general, in the sintered body of AlN, the auxiliary agent is liquid-layer sintered at the AlN grain boundary. When the auxiliary agent is Y ₂ O ₃ , a compound of aluminum, yttria and oxygen is formed at the grain boundary. Further, in the case of vapor deposition, when an auxiliary agent is mixed in the target, a compound of aluminum and the auxiliary agent is generated. Furthermore, in the case of vapor deposition by gas reaction, compounds other than AlN are generated due to impurities contained in the introduced gas. These aluminum compounds other than AlN cause fusion with glass.

Therefore, nitrogen ions are implanted as a means for nitriding the aluminum compound and forming AlN. FIG. 1 is a graph showing an XRD pattern when nitrogen ions are implanted into a surface on which an AlN film is formed by a PVD method using an AlN substrate as a target. (A) in FIG.
Is before ion implantation, and (b) is nitrogen ion 2 × 10
^This is a pattern when ¹⁷ ion / cm ^{2 was} injected. From this figure, by implanting nitrogen ions, (00
2) It can be confirmed that the axis is growing. From this result, it was confirmed that the aluminum compound produced by vapor deposition forms AlN by implanting nitrogen ions.

Further, when the nitrogen ion-implanted mold and the conventional mold were molded and compared, it was found that the conventional mold material was 50.
Fusion of glass occurred at 00 shots, but fusion of glass did not occur even when 10,000 shots were formed in the mold into which nitrogen ions were injected.

[0011]

Embodiment 1 FIGS. 2 to 4 show the present embodiment, FIG. 2 is a side view of a mold blank, FIG. 3 is a schematic configuration diagram of an apparatus used for ion implantation, and FIG. 4 is an outline of an apparatus used for molding. It is a block diagram.

The production of the AlN sintered body will be described below.
In this example, Y ₂ O ₃ was used as an auxiliary agent. Y ₂ was added to AlN powder with an impurity oxygen content of 0.9% or less and an average particle size of 1.5 μm.
Add 4 wt% of O ₃ powder, add water or alcohol, and knead for 5 hours. After kneading, BN having the shape shown in FIG.
Cast into a material mold. Moisture is evaporated at about 200 ° C. and then sintered in a sintering furnace. The sintering atmosphere was a nitrogen atmosphere. The outer shape of the sintered mold blank 1 is finished by grinding. Further, the molding surface 2 is ground to a shape close to the shape of the molded lens, and after grinding, it is polished with diamond powder. Polished surface shape accuracy PV 0.2μm or less, surface roughness Rmax 0.08μm
Finish to the following.

Next, the ion implantation method will be described. Nitrogen ions were implanted into the mold blank 1 by the apparatus shown in FIG. The mold blank 1 was set on the holding table 3, and the inside of the apparatus was evacuated to 2 × 10 ⁻⁶ Torr. Subsequently, N ₂ gas is introduced from the apparatus gas introduction port 6 to ionize it in the ion generation unit 10 including the filament 7, the coil 8 and the extraction electrode 9, and the mass analysis unit including the magnet 11 and the slit 12 and the like. An accelerating portion 14 that passes through 13 and includes an accelerating tube 4 and an XY scanning electrode
Then, N ions were injected into the molding surface 2 of the mold blank 1 at an acceleration voltage of 650 keV and an injection amount of 1 × 10 ¹⁶ ions / cm ² . By this method, the molding surface 2 of the ion-implanted mold blank 1 was analyzed by XRD, and as a result, a peak of AlN was confirmed on the surface portion. However, peaks of other compounds were confirmed in the AlN material that was not ion-implanted.

Next, the molding method will be described. The glass is heated and melted in the melting crucible 15 to a glass viscosity of 10 ² poise. After melting, the plunger 17 is raised to discharge a fixed amount of the molten glass 16 from the nozzle. After discharging, the molten glass 16 is cut by the shearing shear 18, and the glass gob 19 is dropped on the transport tray 20. After dropping, the surface is heated by the heater 21 to remove the shear mark generated in the cutting step. After the shear mark is removed, the transfer tray 22 is transferred by the transfer arm 22 between the upper and lower molds 24 and 23, and the transfer arm 22 is rotated by 180 °, whereby the glass gob 1 is moved.
9 is dropped onto the lower mold 23. After the glass gob 19 is dropped, the transfer arm 22 is further retracted, and the lower die 23 is moved up to the upper die 24, so that the pressing pressure is 5 kg / cm ² , the pressing time is 5 seconds, and then the pressing pressure is 55 kg / cm ² , the pressing pressure is 55 kg / cm ² . Press molding was performed for 20 seconds. The upper mold 24 and the lower mold 23 are heated and held at a temperature corresponding to a glass viscosity of 10 ¹⁰ to 10 ¹³ poise.

When continuous molding was carried out with the molding die of this embodiment, 1500 high precision optical elements without fusion with glass were obtained.
It was possible to continue 0 shots. However, in the mold without ion implantation, fusion occurred after 5000 shots. Further, by implanting nitrogen ions into the AlN sintered body, the intensity of the implanted surface portion is 3 at the initial bending strength value.
Those was 5 kgf / mm ² is increased to 42kgf / mm ^2, it is also effective to improve the strength was confirmed.

In this embodiment, the molding method in which the molten glass is dropped is described, but a molding method using a preform obtained by polishing the glass into an approximate shape has the same effect.
Although the ion implantation amount is set to 1 × 10 ¹⁶ ions / cm ² , the same effect can be obtained even if the ion implantation amount is reduced to 1 × 10 ⁶ ions / cm ² . However, if it is less than that, the Al compound becomes A
The effect decreases because it is not completely changed to 1N. Conversely, 1
Although a fusion effect with glass can be obtained even by injecting at a dose of × 10 ¹⁶ ions / cm ² or more, the surface roughness is lowered due to the reduction of spatter. Therefore, when the surface is rough, the molding surface is re-polished so that the injection layer is not lost. Thereby, the same effect can be obtained.

[0017]

Example 2 In this example, AlN is deposited on a SiC substrate by CVD.
This is an example of vapor deposition by the method and further implantation of nitrogen ions. The SiC base material is processed into the same shape as the mold blank 1 in the first embodiment. Here, the molding surface has a shape accuracy PV.
Finish to 0.5 μm or less and surface roughness Rmax of 0.3 μm or less. After processing the substrate, an AlN film was formed by the CVD method. Set the SiC substrate in the CVD device and set it to 3 × 10 ^-6
Evacuate to Torr. After evacuation, AlCl ₃ gas and NH ₃ gas are introduced at a ratio of 1: 1 until the pressure becomes 4 × 10 ⁻³ Torr. 1200 when gas is introduced
Heat to ~ 1300 ° C. Upon heating, the introduced gas reacts to generate AlN and HCl. AlN is formed and grown on the SiC substrate, and HCl gas is exhausted. The reaction was carried out for about 15 hours to form a film of about 20 μm. After forming the film, the molding surface is re-polished, and the shape accuracy PV is 0.2 μm or less,
Finished to a surface roughness Rmax of 0.08 μm or less.

Ion implantation was performed under the same conditions as in Example 1 above. The molding method was the same as in Example 1 above.

When continuous molding was carried out with the molding die of this embodiment, 1000 high-precision optical elements were obtained without fusion with glass.
It was possible to continue 0 shots. However, in the mold without ion implantation, fusion occurred after 4000 shots. Further, by implanting nitrogen ions into the AlN vapor deposition film, the hardness of the implanted surface portion was 1050 Hv, but was increased to 1300 Hv, and there was also an effect of improving the surface hardness.

In this embodiment, the CVD method is used as the vapor deposition method, but the PVD method using the AlN substrate as a target can also obtain the same effect. Further, the molding method is a molding method in which molten glass is dropped, but a molding method using a preform obtained by polishing glass into an approximate shape has the same effect. Further, the ion implantation amount is 1 × 10 ¹⁶ ion / c
Although m ² is set, the same effect can be obtained even if the pressure is reduced to 1 × 10 ⁶ ion / cm ² . But below that, Al
The effect is reduced because the compound does not completely change to AlN. On the contrary, even if 1 × 10 ¹⁶ ions / cm ² or more is injected, the effect of fusing with glass can be obtained, but the surface roughness is lowered due to the reduction of sputtering. Therefore, when the surface is rough, the molding surface is re-polished so that the injection layer is not lost. Thereby, the same effect can be obtained.

[0021]

As described above, according to the optical element molding die of the present invention, by implanting nitrogen ions into the optical element molding die whose molding surface is made of AlN,
It is possible to prevent fusion with glass, and durability is improved. Furthermore, since the hardness and the bending strength of AlN are improved by the ion implantation, the mold strength can be improved.

[Brief description of drawings]

FIG. 1 is a graph showing the present invention.

FIG. 2 is a side view showing the first embodiment.

FIG. 3 is a schematic configuration diagram showing a first embodiment.

FIG. 4 is a schematic configuration diagram showing a first embodiment.

[Explanation of symbols]

 1 type blank 2 molding surface

Claims (1)

[Claims] 1. An optical element molding die having at least a molding surface formed of AlN, wherein the molding surface is formed by implanting nitrogen ions at 1 × 10 ⁶ ion / cm ² or more. Mold for molding.