JP2555810B2 - Mold for press-molding optical glass element and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press-molding die used in a process of manufacturing an optical glass element such as a lens or a prism by press-molding, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, in order to achieve simplification and weight reduction of optical equipment, attempts to make an aspherical optical glass lens have been actively made. By using this aspherical lens, the number of constituent lenses is reduced, and the objective is achieved by reducing the thickness of the lens. For the aspherical lens, the conventional polishing method in lens production is applied. However, there is a problem in that it is difficult to mass-produce by the conventional polishing method.

Therefore, in producing an aspherical lens, a glass gob is molded with high precision using a die on an aspherical surface that has been finished to a predetermined surface accuracy in advance, or the heated glass gob is press-molded, A method of manufacturing without a polishing step after molding is considered promising. Achieved this technique,
Also, in order to reduce the manufacturing cost by mass-producing the lens and industrially develop it, it has high chemical stability under high temperature, does not react with glass, and scratches the press surface. There is a need for a press-molding die that is difficult and has excellent wear resistance so that high-precision pressing can be repeated and that it has high thermal shock resistance.

Up to now, as a material for forming a press-molding die, a cemented carbide, a cermet, or silicon carbide, which has the characteristics that the hardness is high, the press-molding surface is not easily scratched, and the wear resistance is excellent, Something like silicon nitride was used.

[0005]

However, although cemented carbide and cermet are easy to finish the molding surface with high precision and are excellent in wear resistance, Co, Ni and Mo used for sintering are used.
Such an auxiliary material has a drawback that it easily reacts with glass. Further, although silicon carbide and silicon nitride have better wear resistance than cemented carbide and cermet, they are difficult to be processed with high precision because they are brittle substances, and the auxiliary material used for sintering is glass. It has a drawback that it easily reacts with.

Therefore, the present invention provides a press-molding die for an optical glass element, which is excellent in abrasion resistance, has high chemical stability, is hard to react with glass, has excellent thermal shock resistance, and is suitable for mass production of optical glass elements. It is intended to provide a manufacturing method.

[0007]

According to the present invention, according to the above object, a surface of a mold substrate modified by irradiation with an inert gas ion and / or a nitrogen ion is coated with a boron nitride-containing film to form a molding surface. The present invention provides a press-molding die for an optical glass element. Further, according to the present invention, according to the above object, a predetermined surface of a substrate is irradiated with inert gas ions and / or nitrogen ions to modify the surface, and then a boron element-containing substance is vacuum-deposited or sputtered on the surface. A method for manufacturing a press-molding die for an optical glass element, characterized in that a molding surface is formed by irradiating ions containing nitrogen ions at the same time, alternately or after the adhesion by the method. is there.

The base of the mold is stainless steel, high speed
Various metals such as tool steel or tungsten carbide (W
Various cemented carbides containing C) as the main component, or titanium carbide
(TiC), alumina (Al₂O₃), Titanium nitride (T
iN), chromium carbide (Cr₃C ₂) Etc.
Met and zirconia (ZrO₂), Silicon nitride (S
i₃N_Four), Silicon carbide (SiC), etc.
It can be obtained by finishing to a fixed shape and surface accuracy. In addition,
Any material other than the above materials can be used as the mold base material.
can do.

When a predetermined surface of the molding die substrate is irradiated with an inert gas ion and / or a nitrogen ion, the irradiation ion 1
The acceleration energy per piece is preferably 40 KeV or less. If it exceeds 40 KeV, damage to the forming mold due to irradiation ions becomes excessive, which may result in deterioration of hardness of the ion irradiation surface.

The ion dose is 1 × 10.
^A preferable example is ¹⁵ pieces / cm ² or more and 1 × 10 ¹⁷ pieces / cm ² or less. If it is less than 1 × 10 ¹⁵ pieces / cm ² , the effect of ion irradiation does not appear remarkably and 1 × 10 ¹⁷ pieces / cm ²
If it exceeds cm ² , damage to the mold due to irradiation ions may be excessive. Further, in the above method, as the boron element-containing substance used for vacuum deposition or sputtering,
A simple substance of boron, an oxide of elemental boron, a nitride, or the like is selected. Further, the vacuum vapor deposition source system is not particularly limited, and for example, a system using means such as electron beam (EB), laser or high frequency is appropriately selected.

When the sputtering method is adopted, the sputtering method is not particularly limited, and the sputtering is performed by means such as ion beam, magnetron, or high frequency. In the above method, the deposition amount of the boron-containing substance during the film formation and the nitrogen ions are adjusted so that the atomic ratio of boron and nitrogen (B / N composition ratio) contained in the formed thin film is 20 or less. The irradiation dose of the contained ions is adjusted appropriately.

This is because the BN-containing thin film has a B / N composition ratio of 2
This is because if it exceeds 0, there is a risk that the boron particles react with the glass material during the molding of the optical glass element. The molding die of the present invention has a boron nitride (B
N) has high chemical stability and is hard to react with glass. Various types of boron nitride are conceivable. Among them, when the boron nitride has a cubic crystal structure (c-BN) or a wurtzite crystal structure (w-BN), these are Has high hardness, excellent wear resistance, and excellent impact resistance, so the optical glass molding die coated with it is safe even when press molding is repeated, and it is easy to mass produce lenses. As a result, it is preferable in that the lens manufacturing cost can be reduced.

Further, according to the mold of the present invention, the mold base can be made with high accuracy by using a cemented carbide, cermet or the like having excellent processing accuracy, and this can be utilized. A high optical glass element can be molded. According to the method of the present invention, the film containing boron nitride on the molding surface is formed by the deposition of the elemental boron-containing substance under vacuum or the deposition by sputtering, at the same time, alternately or after the deposition by irradiation with ions containing nitrogen ions. As a result, c-BN or w
-It is possible to form BN, and by forming these, the hardness and chemical stability of the film are increased, and further, the abrasion resistance of the film,
The reactivity with glass can be significantly improved.

Further, according to the method of the present invention, the BN-containing film is formed by irradiation with ions containing nitrogen ions, so that the above-mentioned c-B can be obtained without particularly heating the mold.
Since N and w-BN can be formed at a low temperature, thermal deformation of the forming die does not occur, and thus a die capable of high precision press forming can be manufactured. Furthermore, in the method of the present invention, the BN-containing film is formed by irradiation with ions containing nitrogen ions, so that the above-mentioned c-
BN and w-BN can be formed with good adhesion, and even when press molding is repeated by forming these films,
The film does not peel off, and as a result, a mold that can be mass-produced by press molding can be obtained.

Further, according to the method of the present invention, by irradiating the substrate surface of the press-molding die with inert gas ions and / or nitrogen ions, the irradiated ions are lattice points of crystals of the substance constituting the molding die substrate. Or replace an atom in
Lattice defects occur by invading between the lattice points and the irradiated portion is cured. As a result, the hardness of the mold base itself increases,
Provided is a mold having further improved wear resistance and markedly improved press molding productivity.

Further, in the method of the present invention, particularly when the surface of the mold base is pre-irradiated with nitrogen ions, the surface is nitrided, and then the affinity with the BN-containing film to be formed is improved, so that the BN-containing film is formed. The adhesiveness is remarkably improved, and as a result, it is possible to provide a molding die in which the productivity of press molding is remarkably improved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an example of a manufacturing apparatus for a press-molding die for an optical glass element according to the present invention, and FIG. 2 is a schematic cross-sectional view of the press-molding die thus obtained. In FIG. 1, 1 is a mold base, 2 is a holder for supporting the mold base, 3 is an evaporation source for evaporating a substance containing a boron element, 4 is an ion source for irradiating ions, and 5 is molding. A film thickness monitor for measuring the number of boron vapor-deposited on a predetermined surface of the mold base and its film thickness, and 6 is an ion current measuring device for measuring the number of ions irradiated on the mold base. . Note that these are housed in a vacuum container 100 whose pressure is reduced to a predetermined pressure by a vacuum pump 10.

In obtaining the press mold according to the present invention, first, the mold base 1 is supported by the holder 2, and then the inside of the vacuum container 100 is evacuated to a high vacuum of 1 × 10 ^-5 torr or less. Then, the molding surface of the molding die is irradiated with inert gas ions or / and nitrogen ions from the ion source 4. At this time, the acceleration energy per irradiated ion is 40
Keep it below KeV.

The ion dose is 1 × 10 ¹⁵ ions / c
m ² or more and 1 × 10 ¹⁷ pieces / cm ² or less. afterwards,
Using the evaporation source 3 on the press molding surface of the mold base 1,
A substance 30 containing elemental boron is vacuum deposited. Simultaneously with, or alternately with, the vacuum deposition of the substance containing the boron element, or after the vapor deposition, the ion source 4 irradiates the vapor deposition surface with the ions 40 containing nitrogen ions. Ion 40
The nitrogen ion or a mixture thereof with an inert gas ion is selected. The method of the ion source 4 is not particularly limited, and, for example, a Kauffman type, a bucket type or the like can be adopted.

According to the procedure described above, the predetermined surface of the molding die substrate 1 is first modified by irradiation with inert gas ions and / or nitrogen ions, and then the boron nitride (B
A thin film containing N) is formed, and the constituent atoms of the mold substrate and a mixed layer thereof are formed at the interface between the mold substrate 1 and the BN-containing thin film by collision and recoil of the vapor deposition substance and ions. A BN-containing thin film having excellent adhesion to the mold substrate is formed.

The acceleration energy of the ions irradiated on the vapor deposition material is preferably 40 KeV or less per ion. When it exceeds 40 KeV, damage to the mold due to irradiation ions becomes excessive, which is not preferable. In addition, the atomic number ratio (B / N composition ratio) of boron and nitrogen contained in the formed thin film is 20 or less,
The deposition amount of the boron-containing substance during film formation and the irradiation amount of ions containing nitrogen ions are appropriately adjusted.

The B / N composition ratio is adjusted by the film thickness monitor 5
And the ion current measuring device 6. Monitor 5
Is, for example, a crystal vibrating film thickness meter, and the measuring device 6 is a Faraday cup or the like provided with a secondary electron suppressing electrode. According to the above method, a BN (h-B) having a hexagonal system galaphite structure, which is soft and has high chemical stability, is contained in a BN-containing thin film.
In addition to N), BN (c-BN) having a cubic and zinc blende type structure which is hard and has high chemical stability and BN (w-BN) having a hexagonal wurtzite type structure are contained. Conventionally, c-BN
Since w and BN can be synthesized only under high temperature and high pressure, it was difficult to coat the molding surface of the mold as a thin film. However, according to this example, the vapor-deposited boron atoms are excited by the collision between the ions and the vapor-deposited boron atoms, and the thin film synthesis of c-BN or w-BN is possible under the non-thermal equilibrium process.

Since these BNs are stable even at high temperatures, and c-BN has high hardness and high abrasion resistance, the mold coated with the BN-containing thin film can react with the optical glass material even at high temperatures. It has no scratches and is not easily scratched. By cooling the holder 2 supporting the mold base 1 with water, it is possible to cool the mold base during the formation of the BN-containing thin film, thereby further preventing thermal deformation of the mold base during film formation. Is. Even if the mold base is cooled during film formation, the adhesion between the BN-containing thin film and the mold base and the content of c-BN or w-BN do not change.

As shown in FIG. 2, the optical glass element press-molding mold thus obtained has a molding surface formed of the boron nitride-containing thin film 1a, and the substrate surface 1b is formed before the BN film is formed. The implanted ions are distributed,
At the interface between 1a and 1b, a mixed layer composed of both constituent atoms is formed. A desired optical glass element can be mass-produced by sandwiching a heated glass block in these molds and pressing.

Next, examples of the present invention will be specifically described. Example 1 As shown in a cross section in FIG. 3, an upper die substrate 7 having a concave pressing surface 70 having a predetermined radius of curvature (46 mm) and a predetermined curvature using a cemented carbide made of tungsten carbide (WC). A lower die substrate 8 having a concave pressing surface 80 having a radius (200 mm) is prepared.

The press surfaces 70 and 80 of this die substrate were mirror-polished with diamond or c-BN abrasive grains (Rmax = 20Å in this embodiment). Next, the mold bases 7 and 8 are housed in the apparatus shown in FIG. 1, and the degree of vacuum is 2 × 10 ^−6.
The vacuum container 100 was evacuated to a high vacuum of not more than torr. After that, one nitrogen ion is applied to each press surface of the molded substrate.
Irradiation was performed at 1 × 10 ¹⁶ pieces / cm ² with an acceleration energy of 0 KeV.

Then, the vaporized substance 30 is deposited on the ion-irradiated surface.
As a raw material, a simple substance of boron having a purity of 99% was selected, and a boron thin film was formed on the pressing surfaces 70 and 80 by the EB evaporation source 3. Simultaneously with the vapor deposition of the boron thin film, nitrogen gas having a purity of 99.999% was introduced into the ion source 4 (at this time, the vacuum degree in the vacuum container was 6 × 10 ⁻⁵ torr).
r) and nitrogen ions 40 were applied to the boron film.

At this time, the acceleration energy of nitrogen ions is 10 KeV per ion, and the acceleration energy of nitrogen ions, irradiation dose, and boron are adjusted so that the B / N composition ratio of the final film formed is 1. The evaporation amount of was adjusted. The pressing surfaces 70 and 80 of the mold bases 7 and 8 covered by the above process have hardnesses of Vickers hardness (Hv).
Is 4500 (measured with a load of 10 g) and surface roughness R
max was 20Å.

Further, B coated on the press surfaces 70 and 80
The film thickness of the N-containing thin film was 2 μm. Using the press mold thus obtained, a glass block 9 having a radius of 20 mm and composed of 70% by weight of lead oxide (PbO), 27% by weight of silicon oxide (SiO ₂ ) and 3% by weight of a minor component was pressed in a nitrogen atmosphere.

The pressing conditions were a mold temperature of 500 ° C. and a pressing pressure of 40 kg / cm ² , and the same conditions were maintained for 2 minutes.
Then, after cooling to 300 ° C., the molded lens was taken out. This pressing step was repeated 1000 times, and the hardness (Hv) and the surface roughness of the pressing surface of the mold after use were measured, but they remained substantially as they were. Next, Examples 2 to 9 will be described. In these Examples, the conditions are the same as those in Example 1 except for the type of the molding die base material, the ion irradiation conditions, the film forming conditions, and the like.

Example 2 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹⁶ ions / cm ² , and then the nitrogen ion energy was 2 KeV. , A BN-containing thin film having a thickness of 2 μm while adjusting the energy of nitrogen ions, the ion irradiation amount, and the vapor deposition amount of boron so that the B / N composition ratio of the BN-containing film becomes 1.
m was formed into a film.

Example 3 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹⁶ ions / cm ² , and then the nitrogen ion energy was 10 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Example 4 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion at 1 × 10 ¹⁶ ions / cm ² , and then the nitrogen ion energy was 2 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Example 5 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹⁵ ions / cm ² , and then the nitrogen ion energy was 2 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Example 6 The same type substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹⁷ ions / cm ² , and then the nitrogen ion energy was 2 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Example 7 The same type of substrate as used in Example 1 was mixed with argon ions and nitrogen ions (mixing was carried out by using argon gas and nitrogen gas as an ion source at a vacuum degree in a vacuum container). Each ion was introduced at 2.5 × 10 ⁻⁵ torr) at 10 KeV per ion.
After irradiating 1 × 10 ¹⁷ pieces / cm ² with the acceleration energy of, the nitrogen ion energy, the ion irradiation amount, and the deposition amount of boron are adjusted so that the nitrogen ion energy is 2 KeV and the B / N composition ratio of the film is 3. While adjusting, a BN-containing thin film was formed to a film thickness of 2 μm.

Example 8 A film was formed under the same conditions as in Example 1 except that a mold base containing zirconia (ZrO ₂ ) as a main component was used. Example 9 Film formation was performed under the same conditions as in Example 1 except that a mold base made of cermet containing TiN as a main component containing 30 wt% TiC and 7 wt% Mo was used.

As to the hardness of the press surface of the mold coated by the method of Examples 2 to 9, the Vickers hardness (Hv) is 4500 in Examples 2 to 6, 8 and 9 and 5 in Example 7.
000 (measured with a 10 g load). The surface roughness was Rmax = 20Å in all cases. Next, a comparative example will be described.

Comparative Example 1 The same mold base as used in Example 1 (mold base containing WC as a main component) was used, and the same glass as in Example 1 was used without coating the pressed surface of the BN-containing thin film. I made a press. Comparative Example 2 Using the same mold base as used in Example 8 (mold base containing ZrO ₂ as a main component), the same glass press as in Example 1 was used without coating the pressing surface with a BN-containing thin film. went.

Comparative Example 3 The same glass substrate as in Example 1 was used, using the same type of substrate as that used in Example 9 (cermet containing TiN as a main component) without coating the BN-containing thin film on the pressing surface. I went. Comparative Example 4 The same mold base as used in Example 1 (mold base containing WC as a main component) was used, and the same B as in Example 1 was applied to the pressing surface.
The N-containing thin film was coated. However, at this time, irradiation with nitrogen ions was not performed before forming the BN film.

Comparative Example 5 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹³ ions / cm ² , and then the nitrogen ion energy was 10 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Comparative Example 6 The same type of substrate as used in Example 1 was irradiated with nitrogen ions at an acceleration energy of 10 KeV per ion of 1 × 10 ¹⁸ ions / cm ² , and then the nitrogen ion energy was 10 KeV. A BN-containing thin film having a thickness of 2 μm was formed while adjusting the nitrogen ion energy, the ion irradiation dose, and the vapor deposition amount of boron so that the B / N composition ratio of the film became 3.

Examples 1 to 9 and Comparative Examples 1 to 6 described above
For each of the above, the roughness (Rmax) of the molding surface after 1000 presses and the surface roughness of the molded glass lens were examined, and the results shown in Table 1 were obtained.

[0044]

[Table 1]

As described above, in Examples 1 to 9, by coating the hard BN-containing thin film, the surface roughness of the mold did not change even after press molding 1000 times, and the surface was not scratched. Therefore, the surface state of the glass after molding is good, the polishing step after press molding is unnecessary, and since there was no reaction with the glass during pressing, the glass after press molding has discoloration or cloudiness. I couldn't see it. Furthermore, this characteristic was the same even when the number of presses was 1500.

On the other hand, in Comparative Examples 1 to 3, since the surface of the mold was scratched, the glass surface after molding was also scratched, and the sintering aid and the like were deposited, so that the mold The surface roughness of the glass deteriorated, the surface accuracy of the glass after molding deteriorated, and discoloration was observed in some of the objects due to the sintering aid contained in the molding die material adhering to the lens. Further, in Comparative Examples 4 to 6, when the number of presses exceeded 1000, part of the BN film began to peel off.

Further, in the mold bases used in Examples 1 to 6, the pressing surface of the mold base using the SiC sintered body was Rm.
Compared with the time required for mirror-finishing to ax = 20Å (about 30 hours), the desired accuracy (Rmax = 20Å) could be achieved in an extremely short time (about 1.5 hours). Therefore, according to the present invention, even a material having a hardness that can be processed with high precision can be used as a base body of a molding die that can withstand press working 1000 times or more.

As described above, according to the embodiments of the present invention, it is possible to provide a press molding die for an optical glass element having the following advantages. 1. Since hard c-BN and w-BN are contained in the film, the hardness of the press surface is remarkably increased, and the wear resistance of the mold is increased. Therefore, even if the same molding base material is repeatedly used for press molding, the surface of the mold is not scratched.

Therefore, the precision of the glass surface after molding can be maintained, and the polishing step after press molding can be omitted. In addition, due to the extended life of the mold,
The number of times of mold replacement is significantly reduced, which makes it possible to improve press molding productivity and reduce costs. 2. Since the press surface of the mold is coated with the thin film containing hard BN, the hardness of the mold base (base material) itself does not need to be high, and therefore, the mold base can be easily processed with high precision. . 3. Since the press surface is covered with a hard BN-containing thin film that is chemically stable even at high temperatures, the reaction of glass with the sintering aids etc. contained in various molding dies that have been used conventionally Since the glass can be press-molded without being processed, the surface state of the glass after molding is extremely good.

[0050]

As described above, according to the present invention, an optical glass element which is excellent in abrasion resistance, has high chemical stability, hardly reacts with glass, has excellent thermal shock resistance, and is suitable for mass production of optical glass elements. It is possible to provide the press mold and the manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an example of a molding die manufacturing apparatus according to the present invention.

2 is a cross-sectional view of an example of a mold obtained by the apparatus shown in FIG.

FIG. 3 is a cross-sectional view of a mold base used in an example.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 molding base 2 base holder 3 vapor deposition source 30 boron element-containing substance 4 ion source 40 ions 5 film thickness monitor 6 ion current measuring device 7, 8 example substrate 70, 80 film forming surface of substrate 9 glass lump

Claims (3)

(57) [Claims] 1. A press molding of an optical glass element, characterized in that a surface of a mold substrate modified by irradiation with an inert gas ion and / or a nitrogen ion is coated with a boron nitride-containing film to form a molding surface. Type. 2. A predetermined surface of a substrate is irradiated with inert gas ions and / or nitrogen ions to modify the surface, and then a boron element-containing substance is deposited on the surface by a vacuum deposition method or a sputtering method. A method for manufacturing a press-molding die for an optical glass element, characterized in that the molding surface is formed by irradiating ions containing nitrogen ions at the same time, alternately or after the deposition. 3. The acceleration energy per ion when irradiating the inert gas ion and / or the nitrogen ion is 40 KeV or less, and the ion irradiation amount is 1 ×.
The method according to claim 2, wherein the number is 10 ¹⁵ pieces / cm ² or more and 1 × 10 ¹⁷ pieces / cm ² or less.