JP3134583B2 - Press mold for optical glass element and method for producing 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 molding of an optical glass element, and more particularly to a mold for press-molding an optical glass element used for press-molding a high-precision optical glass element, and a method of manufacturing a mold therefor.

[0002]

2. Description of the Related Art In order to repeatedly mold a high-precision optical glass element by press molding, the mold material is stable even at high temperatures, has excellent oxidation resistance, is inert to glass, and has a shape when pressed. It is necessary to have a material having excellent mechanical strength so that the accuracy is not lost, but on the other hand, it must be excellent in workability and easy to perform precision processing.

[0003] As a mold material which satisfies the above-mentioned conditions necessary for the press molding mold of an optical glass element to some extent, a mixed material of titanium carbide (TiC) and a metal (JP-A-59-121126) or a super hard Noble metal thin film formed on an alloy base material (JP-A-62-96331)
Are being studied.

[0004]

However, no conventional mold material has been obtained which satisfies all of the above conditions. For example, when a mixed material of TiC and a metal is used as a mold, it is very hard and has excellent mechanical strength, but is inferior in workability and difficult to perform high-precision processing. Further, it has a drawback that it easily reacts with lead (Pb) or an alkali element which is a component of the optical glass element.

[0005] In a mold in which a noble metal thin film is formed on a cemented carbide base material, when the cemented carbide is machined using a diamond grindstone, the diamond grindstone is severely worn, and precise shape machining is difficult. Special processing equipment is required. Further, there is a problem that the processing time is long and the die cost is very high.

[0006] As described above, the conventional mold material has not yet satisfied all of the requirements for the mold material described above.

The present invention solves such a conventional problem,
An object of the present invention is to provide a press-molding die that can repeatedly press-mold an optical glass element having a shape that is difficult to machine.

[0008]

In order to achieve this object, the present invention provides a method for forming a base material comprising a cemented carbide containing WC as a main component, a cermet containing TiC or TiN as a main component, or a WC sintered body. Si or SiO ₂ as a processing layer
After forming a thin film and performing precision processing by a dry etching method, Pt, Pd, Ir,
At least one of Rh, Os, Ru, Re, W, and Ta
By providing a mold formed by forming a noble metal-based alloy thin film containing more than one type of metal, a press-forming mold for forming an optical glass element having a shape difficult to machine by machining is provided. .

[0009]

According to the present invention, by using a cemented carbide containing WC as a main component, a cermet containing TiC or TiN as a main component, or a WC sintered body as a mold base material, the mold base material has sufficient strength to withstand press forming. , Si or SiO for processing layer
By using the _two thin films and finely processing the thin films by dry etching, the processed layer can be processed into a shape that is difficult to machine.

Further, Pt, Pd, Ir,
At least one of Rh, Os, Ru, Re, W, and Ta
By using a noble metal-based alloy thin film containing more than one kind of metal, fusion with glass is prevented. Therefore, the mold of the present invention satisfies all the necessary conditions required as the mold material described above.

When glass is press-formed using the mold of the present invention thus produced, it becomes possible to mass-produce optical glass elements having a shape difficult to machine. In addition, since the number of times this mold can be repeatedly used is greatly increased as compared with the conventional one, it has made it possible to manufacture optical glass elements which could not be obtained by conventional press molding at low cost and in large quantities. is there.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a press-molding die for a diffraction grating, which is an embodiment of the press-molding die according to the present invention, together with a method of manufacturing the same.

First, as shown in FIG.
A flat surface serving as a pressed surface of a disk-shaped hard metal preform 11 mainly composed of WC and having a thickness of 5 mm and a thickness of 5 mm was polished to a mirror surface using ultrafine diamond abrasive grains.

Next, as shown in FIG. 2B, a 1 μm thick Si thin film 12 is coated on the mirror surface by sputtering, and then, as shown in FIG. A novolak-based photoresist 13 was applied with a uniform thickness, and prebaked.

Next, as shown in FIG. 1D, a line-and-space pattern photomask 14 having a line-to-space ratio of 1: 1 and a pitch of 100 μm is brought into close contact with the photoresist 13 and a mercury lamp is used. After the photoresist is exposed to light, development and post-baking are performed, as shown in FIG.
A photoresist mask was formed as shown in FIG. The mold in this state was placed on the cathode of the RF plasma dry etching apparatus.

Then, an RF plasma of a CF ₄ etching gas is generated, and ions such as CF ₃ ⁺ in the plasma are generated.
By colliding with the mold placed on the cathode, the portion of the Si thin film 12 where there was no photoresist mask was etched.
The remaining resist was removed by O ₂ plasma ashing, and a 100 μm thick Si thin film 12 was formed as shown in FIG.
Grooves with pitch irregularities were formed.

Next, as shown in FIG. 1G, a 3 μm thick Pt—Ir alloy thin film 15 is
m to form a diffraction grating press-molding die. A mold using an SiO ₂ thin film for the intermediate layer was produced in the same manner.

As described above, it was possible to easily manufacture a press-molding mold for a diffraction grating having a shape that is very difficult to manufacture by machining.

Next, a method of press-forming glass as a forming material by using the press-forming mold for the diffraction grating produced will be described.

FIG. 2 is a schematic view of the press molding machine used in this embodiment. In FIG. 2, 21 is an upper mold fixed block, 22 is an upper mold heater, 23 is an upper mold, 24 is a glass material, 25 is a lower mold, 26 is a lower mold heater, 2
7 is a fixed block for the lower mold, 28 is a thermocouple for the upper mold, 29 is a thermocouple for the lower mold, 210 is a plunger, 211 is a positioning sensor, 212 is a stopper, and 213 is a cover.

The press-molding mold for the diffraction grating produced by the above method is referred to as an upper mold 23, and the lower mold 25 has a diameter of 20 mm.
A flat surface of a 5 mm thick hard metal disc mainly composed of WC is polished to a mirror surface, and the surface of the base metal is sputtered onto the surface.
A flat type in which a Pt-Ir alloy thin film having a thickness of μm was formed as a protective layer was used. A radius of 10 mm is placed on the lower mold 25,
SF-based flat glass 24 processed into a disk shape with a thickness of 1 mm
And put the upper mold 23 on it,
And kept at a pressure of about 40 kg / cm ² for 2 minutes in a nitrogen atmosphere, and then cooled to 400 ° C. as it was, and the molded optical glass element was taken out and the optical glass was removed. The step of press forming the element is completed.

At the end of the 10000th press by repeating the above steps, the upper and lower dies 23 and 25 are removed from the press molding machine, the state of the press surface is observed with an optical microscope, and the surface roughness of the press surface at that time ( RMS values, Δ) were measured to evaluate the accuracy of each mold.

As a comparative experiment, since the conventional mold material cannot be directly processed into the high-precision diffraction grating shape shown in the present embodiment, the flat type and the cemented carbide base of the conventionally used SiC sintered body were used. A mold in which a Pt thin film was formed on a material was prepared, set in the press molding machine shown in FIG. 2, and the above-described press molding process was repeated 10,000 times to evaluate the same mold accuracy. These results are shown in (Table 1).

[0025]

[Table 1]

Sample No. In the mold made of the SiC sintered body of No. 3, the glass adhered to the surface of both the upper and lower molds by 50 times of press molding, and the glass could not be further pressed. That is, No. It can be seen that the optical element cannot be mass-produced with the mold No. 3.

The sample No. In the mold coated with a Pt sputtered film as in No. 4, no glass adhesion occurs, but after pressing 10,000 times, the surface roughness (RMS value)
It turned out to be very coarse at 264.3 °, and the surface became cloudy, indicating that it was not practical.

On the other hand, the sample No. 1 and No. 1 In the mold of Example 2 of Example 2, the surface condition was hardly changed even after being repeatedly pressed 10,000 times, and the surface roughness was hardly changed from that before pressing. That is, a glass flat plate is press-formed using the press-forming mold for the diffraction grating obtained by the method of the present invention, so that a large number of optical glass elements having a shape that is difficult to manufacture by machining such as a diffraction grating. Press molding is now possible.

As described above, the mold of the present invention satisfies all of the requirements for directly press-molding the above-described high-precision optical glass element, and has an optical shape such as a diffraction grating which could not be produced by molding. It has become possible to press-mold glass elements in large quantities.

Although a press mold for a diffraction grating is used in the embodiments to explain the present invention, a fine optical element (for example, a micro lens array, a micro Fresnel lens, etc.) other than the diffraction grating can be formed. Needless to say. In addition, WC is used as the base material for the press molding die.
Is used, but TiN or TN
Exactly the same results were obtained when a cermet or WC sintered body containing iC as a main component was used as a base material.

[0031]

As described above, the present invention uses a cemented carbide, a cermet, and a WC sintered body as a base material in producing a press mold for an optical glass element, and forms an intermediate layer on the base material. After forming a Si or SiO ₂ thin film and precisely processing the thin film into a desired shape by a dry etching method, Pt, Pd, Ir, Rh,
By forming a noble metal-based alloy thin film containing at least one kind of metal among Os, Ru, Re, W, and Ta, it can be manufactured by machining that satisfies all necessary conditions for a glass forming mold material. It provides a mold for press-forming optical glass elements with difficult-to-form shapes, and by repeatedly pressing optical glass using this mold, optical glass elements with shapes that could not be obtained by conventional press-forming are inexpensive. In addition, it has become possible to mass-produce.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a press mold for a diffraction grating according to one embodiment of the present invention.

FIG. 2 is a schematic diagram of a press machine for forming a diffraction grating using the mold for forming the diffraction grating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Cemented carbide base material 12 Si thin film 13 Photoresist 14 Photomask 15 Pt-Ir alloy thin film 21 Upper die fixing block 22 Upper die heater 23 Upper die 24 Glass material 25 Lower die 26 Lower die heater 27 Lower Mold fixed block 28 Upper mold thermocouple 29 Lower mold thermocouple 210 Plunger 211 Positioning sensor 212 Stopper 213 Cover

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hidenao Kataoka 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-6-1911863 (JP, A) JP-A-5-205 24865 (JP, A) JP-A-4-170331 (JP, A) JP-A-60-264333 (JP, A) JP-A-62-96331 (JP, A) JP-A-59-121126 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 11/00

Claims (2)

(57) [Claims] 1. A cemented carbide mainly containing tungsten carbide (WC), a cermet mainly containing titanium carbide (TiC) or titanium nitride (TiN), or a WC sintered body as a base material. A thin film of Si or SiO ₂ is provided as an intermediate layer on a base material, and platinum (Pt), palladium (Pd), iridium (I
r), a noble metal-based alloy thin film containing at least one metal selected from the group consisting of rhodium (Rh), osmium (Os), ruthenium (Ru), rhenium (Re), tungsten (W), and tantalum (Ta). A press molding die for an optical glass element, characterized in that: 2. A cemented carbide mainly containing tungsten carbide (WC) as a base material, a cermet mainly containing titanium carbide (TiC) or titanium nitride (TiN), or a WC sintered body. Or SiO ₂
A thin film is formed, and the thin film is precisely processed into a desired shape by a dry etching method.
A mold for press-molding an optical glass element, wherein the mold is formed by forming a noble metal-based alloy thin film containing at least one metal selected from the group consisting of t, Pd, Ir, Rh, Os, Ru, Re, W and Ta. Manufacturing method.