JPH09194221A - Die for forming glass optical element and forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die for forming optical elements with which forming in the atm. is possible and the durability thereof is greatly improved as a result of variously examining the material quality of the forming surface of the die for forming. SOLUTION: At the time of press forming the glass optical elements, the forming surface of the die for transferring to the optical function surfaces of the glass optical elements is composed of a surface layer 3 contg. 0.1 to 20atom.% Li in a noble metal 2 having good oxidation resistance or its alloy. The this surface layer 3 is formed to >=10nm thickness.

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 capable of manufacturing a highly accurate glass optical element such as an aspherical lens by press-molding a softened glass material, and a molding using the same. Regarding the method.

[0002]

2. Description of the Related Art In recent years, a lens used in an optical device or the like has been obtained by accommodating a softened glass material in a press-molding die having a predetermined surface accuracy and performing press-molding without a polishing step. A method of manufacturing a glass optical element such as is proposed. This method is described in, for example, Japanese Patent Publication No. 61-3.
No. 2263 gazette, however, this is one in which the glass is subjected to a grinding process into a predetermined shape and then heat-molded, so that the glass material is prepared in advance, so that the production cost is low. Takes.

On the other hand, JP-A-59-195541
Japanese Patent Publication No. 4-16414, Japanese Patent Publication No. 7-45
Japanese Patent No. 327 proposes a method of extracting a certain amount of molten glass and press-molding the glass.

Japanese Patent Laid-Open No. 59-195541 proposes a method of molding through a gas cushion with a molding die made of a porous member, but no gas layer is present at the pressure of the pressing stage. , The glass comes into contact with the mold surface and causes fusion. In molding in air, Si
Materials such as C are oxidized and deteriorated, and have no durability.

Japanese Patent Publication No. 4-16414 proposes a method of press-molding in a state where the surface temperature of the glass when it is received by the mold is below the softening temperature, but this is also the case in press-molding in the atmosphere. , The stainless steel mold is oxidized and deteriorated, and has no durability.

In order to solve the problem of the durability of such a mold in the atmosphere, Japanese Patent Publication No. 7-45327 discloses that
The first heat processing jig receives the molten glass, conveys these into a non-oxidizing atmosphere, transfers the glass to the second heat processing jig for precision molding, and then performs molding We are trying to prevent fusion of glass to the mold and to improve durability. However, this method requires two types of molds and
Since the atmosphere is controlled, the size of the device becomes large and the cost of the device also increases.

As described above, in the method of directly press-molding molten glass in the atmosphere, which is advantageous in terms of cost,
Releasability (fusion) of the mold material to high temperature glass and oxidation resistance (fog of the molded product due to deterioration of surface roughness) will be major problems in the future.

The present invention has been made based on the above circumstances, and as a result of various studies on the material of the molding surface of the molding die, it can be molded in the atmosphere and its durability is greatly improved. It is an object of the present invention to provide an improved optical element molding die.

[0009]

Therefore, in the present invention,
During press molding of the glass optical element, the molding surface of the mold to be transferred to the optical function surface of the glass optical element is a precious metal having good oxidation resistance or its alloy containing Li of 0.1 to 20a.
It is characterized in that it is composed of a surface layer containing TOM% (atomic ratio), and that the surface layer is formed to have a thickness of 10 nm or more.

In this case, the noble metal having good oxidation resistance is Pt, Ir, Os, Pd, Au, Rh or Ru.
It is characterized by being composed of any one of them or an alloy consisting of some of them. Further, as an embodiment of the present invention, the surface layer containing Li is preferably formed by an ion implantation method or an ion beam mixing method. Further, the present invention is characterized by a method of press-molding an optical element using the glass optical element molding die described above.

This makes it possible to improve the mold releasability and the oxidation resistance of the molding die with respect to glass. Regarding this oxidation resistance, in particular, the precious metal is a stable material for glass and the oxidation resistance is high. In addition, since Li is present in the surface layer, the mold releasability is improved. This principle has never been clarified,
Probably, the Li contained in the surface may function as a lubricant when pressed at a high temperature.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 schematically shows an embodiment of an optical element molding die according to the present invention. In FIG. 1, reference numeral 1 is a mold base material using cemented carbide,
2 is a film using a noble metal such as Pt, 3 is L in the Pt film
It is a surface layer containing i.

To form such a molding die, first, a cemented carbide as a base material is processed into a predetermined shape, and then a molding surface serving as a glass contact portion has a surface roughness of Rmax of 1
Mirror polishing to 0 nm or less. Then, a Pt film having a thickness of 2 μm is formed on the entire surface of the base material by sputtering, and Li is ion-implanted only on the molding surface.
The processing conditions in this case are, for example, an injection amount of 1 × 1.
0 ¹⁴ to 10 ¹⁸ ions / cm ² , accelerating voltage 0.5 to 1
Set to 50 keV. In addition, by changing the injection thickness and injection concentration, various samples were prepared, and by actual press molding,
Evaluate the results. In addition, in order to clarify the difference between the present invention and the prior art, for comparison, a sample without Li ion implantation is also prepared, and the result is evaluated by press molding.

FIG. 2 is a schematic view of a molding apparatus for molding using the molding die of FIG. 1, wherein reference numeral 4 is a glass melting furnace, 5 is a heater, 6 is glass in a molten state,
7 is a nozzle and 8 is a glass preform. Further, reference numerals 10 and 11 are a lower mold and an upper mold for molding having the configuration shown in FIG. The glass 6 presented here is a borosilicate glass having the composition shown in Table 1 below.

[0015]

[Table 1] [Example 1] Using this molding apparatus, in order to verify the results of press molding, an optical element is molded from a glass material by the following procedure. First, the nozzle outlet 7
The temperature of the glass preform 8a is adjusted by controlling the temperature of a.
1180 ℃ (equivalent to glass viscosity of 10 ^1.1 Pa · s)
The glass of 850 mm ³ is made into a droplet shape and taken out. The glass preform 8 taken out was cooled by a cooling gas 9 at 750 ° C.
⁽ Corresponding to ^4.8 Pa · s), and lower mold 10
Is set to These are carried to the right, and at this position, the glass preform 8 is lowered by the lowering of the upper mold 11.
Press molded. At this time, the lower mold 10 and the upper mold 11 are controlled at 580 ° C. (corresponding to a glass viscosity of 10 ^{10 3} Pa · s), and a pressure of 2 k is applied by a pressurizing means (not shown).
A Pa load is applied for 20 seconds. At the end of pressing, the glass was 590 ° C (glass viscosity: 10 ^9.8 Pa
・ Equivalent to s), and then raise the upper mold,
The molded lens (optical element) is taken out.

The lens thus obtained is
It had a good shape accuracy of 0.5 or less Newton. At this time, Table 2 shows the Li injection conditions of each mold and the molding results.

[0017]

[Table 2] As in Comparative Examples 2 and 6, the Li concentration is 20 atom.
%, The surface roughness of the mold became 30 nm or more in Rmax due to ion implantation, and the molded product transferred it, so that it became cloudy from the first shot. Further, as in Comparative Examples 3, 4, 5, and 7, the Li concentration is 0.1 atom.
If it is less than%, the releasability is poor, and fusion occurs at the first shot as in the case without the injection treatment.

Further, as in Comparative Examples 8, 9, and 10, when the implantation depth was as shallow as about 7 nm, the first shot was OK, but the fusion occurred at the second shot. After that, when the surface composition of the mold is analyzed, Li is almost eliminated,
From this, it can be inferred that the Li-containing layer was brought to the glass surface after molding.

On the other hand, the injection amount is about 0.1 to 20a.
The surface layer containing tom% does not concentrate near the outermost surface, and the distributed mold does not cause fusion and has good mold releasability, and despite molding in the atmosphere,
No oxidation of the mold surface was observed, and the surface roughness did not decrease even after 1000 shots.

As described above, by using the molding die having the Pt surface layer containing Li on the molding surface of the mold, it is possible to avoid oxidation and deterioration of the mold in molding the molten glass in the atmosphere. Moreover, fusion with glass can be prevented. [Second Embodiment] Similar to the first embodiment, a cemented carbide is used as a die base material, processed into a predetermined shape, mirror-polished, and then sputtered to form an Ir film as a noble metal thereon. Was formed to a thickness of 2 μm. Then, Li was ion-implanted at a treatment thickness of 100 nm and a treatment concentration of 2 atom%. The followings were prepared as comparative examples in order to evaluate the results of the present invention. However, all the molding surfaces of the base material were polished to have a surface roughness Rmax of 10 nm or less, and the Li injection conditions were all the same as above.

1. Cemented carbide and Li-injected into it 2. 2. Stainless steel and Li injected into it. Sintered SiC and Li injected therein [Example 2] The same glass as in Example 1 was molded using these molds, and the molding mold was evaluated. The molding conditions are the same as in Example 1. The molding results are shown in Table 3.

[0022]

[Table 3] All of the materials to which Li was not injected were fused at the first shot. All of the Li-implanted materials have no fusion adhesion and have good releasability. However, cemented carbide has a first shot, stainless steel has a fifth shot, and SiC has a 20th shatter.
At the ot'th eye, the surface of the molded product began to fog, and the surface roughness of the lens molding die surface after the molding was measured and found to be Rmax of 30 nm or more.

On the other hand, the Ir film according to the present invention has L
With i injection, press molding is continuously performed for 1000 sh
Even when the process was carried out up to ot, no fusion or fogging occurred and good moldability was exhibited. When the surface roughness was measured after molding, Rmax was 10 nm or less, which was unchanged from before molding.

As a noble metal, in addition to Ir, O
A film made of s, Pd, Au, Rh, Ru, or some of these alloys and injecting Li into this film was also examined, but good results were obtained as in the case of the Ir film. was gotten.

As described above, by using a molding die in which Li is ion-implanted into a film of a noble metal having a good oxidation resistance such as Pt or Ir, good releasability and fogging are avoided. Improved durability and continuous 1000 shots
Even with the above, molding without fusion and fogging is possible. Further, the ion implantation method makes it possible to incorporate Li into the surface of the bulk material, which is impossible with the ion beam mixing method described later. [Third Embodiment] In this embodiment, a cemented carbide is used as a die base material, processed into a predetermined shape and polished, and then a Pt film is formed to a thickness of 2 μm by sputtering. In the process, while depositing Pt as it is, Li
To form a Li-containing surface layer. [Example 3] Table 4 shows the Li content and processing thickness of the molding die, including the results of the press molding.
Shown in

[0026]

[Table 4] As is clear from Table 4, the processed thickness of 6 nm is
At the first shot of the press molding, glass fusion occurred. Regarding the Li concentration, 20 atom
%, The surface roughness of the mold is Rma after press molding.
x was 30 nm or more, and due to the transfer, clouding occurred in the molded product. Further, when it is less than 0.1 atom%,
Glass fusion occurred at the first shot.

As described above, by forming a surface layer having a Li content of 0.1 to 20 atom% in the molding die of 10 nm or more, the releasability can be improved and fusion can be prevented. Also, with this ion beam mixing method,
When the Li-containing layer is formed, it becomes easy to control the concentration distribution, which cannot be controlled by the ion implantation method, and Li can be contained in the thin film.

[0028]

As described above, according to the present invention, when the glass optical element is press-molded, the molding surface of the mold to be transferred to the optically functional surface of the glass optical element is made of a noble metal having good oxidation resistance, or Li in the alloy is 0.1 to 20 atom
%, By including the surface layer containing it, and forming the surface layer to a thickness of 10 nm or more, the mold releasability and oxidation resistance can be improved, and press molding from molten glass in the atmosphere Thus, it is possible to prevent fusion of glass and generation of fog.

Further, according to the present invention, there is an advantage that a surface layer having excellent releasability and cloudiness durability can be easily formed on a molding die including a bulk material. When the treatment thickness and the treatment concentration of the surface layer are controlled, this can be easily carried out and the molding cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a schematic view of a molding die used in a first embodiment of the present invention.

FIG. 2 also shows a schematic view of the apparatus used in the above embodiment.

[Explanation of symbols]

 1 Base material 2 Pt film (noble metal) 3 Li-containing layer 4 Glass melting furnace 5 Heater 6 Glass in molten state 7 Nozzle 8 Glass preform 9 Cooling gas 10 Lower mold 11 Upper mold

Claims (5)

[Claims] 1. When press-molding a glass optical element,
The molding surface of the mold to be transferred to the optical function surface of the glass optical element,
A noble metal having good oxidation resistance, or an alloy thereof is composed of a surface layer containing 0.1 to 20 atom% of Li, and the surface layer is formed to have a thickness of 10 nm or more. Mold for glass optical element molding. 2. A noble metal having good oxidation resistance is Pt or I.
The glass optical element molding die according to claim 1, wherein the glass optical element molding die is made of any one of r, Os, Pd, Au, Rh, and Ru, or an alloy thereof. 3. The glass optical element molding die according to claim 1, wherein the surface layer containing Li is formed by an ion implantation method. 4. The glass optical element molding die according to claim 1, wherein the surface layer containing Li is formed by an ion beam mixing method. 5. A glass optical element molding method comprising press-molding an optical element using the glass optical element molding die according to claim 1.