JPH05294642A - Mold for molding optical glass element and production of optical glass element - Google Patents

Abstract

PURPOSE:To obtain high-precision optical glass elements by using a mold having formed a specific multi-layer film on the molding face of a processing parent material comprising a cermet having a specific composition, a sintered compact of WC, etc., heating glass lump and press molding. CONSTITUTION:A parent material composed of a super hard alloy consisting essentially of tungsten carbide, a cermet consisting essentially of titanium carbide or titanium nitride or a sintered material of tungsten carbide is prepared. The, the parent material is processed in high accuracy into a shape of a desired optical glass element to prepare a mold 11. The molding face of the mold 11 is provided with a multi-layer film 12 obtained by alternately laminating a nitride film and a carbide film or a boride film and a platinum-group alloy film. Then glass lump of target molding is placed between a pair of upper and lower molds 11, heated to >= the softening point of the glass lump and press molded to produce an optical glass element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass element manufacturing method for manufacturing an optical glass element having a highly precise shape, and a molding die required for the method.

[0002]

2. Description of the Related Art Good quality of image formation is required when a high precision optical glass element is manufactured by pressure molding. Therefore, as a mold material, it is chemically inert to glass even at high temperatures, and the molding surface of the glass is sufficiently hard to resist damage such as scratches. It is necessary that the surface has excellent thermal shock resistance so that plastic deformation or grain growth does not occur and repeated molding can be performed, and further that workability is excellent so that ultra-precision processing can be performed.
Conventionally known mold materials include SiC or Si
₃ N ₄ has been reported (see JP-A-52-45613).

Recently, a die in which a platinum group alloy thin film is coated on a cemented carbide base material has also been proposed (Japanese Patent Laid-Open No. 60-246230).

[0004]

However, when such SiC or Si ₃ N ₄ is used as a mold material, since these materials have extremely high hardness, they can be processed into a mold having a desired shape. It is very difficult to do this, and since all of these materials are highly reactive with glass at high temperatures, repeated press molding causes the glass to adhere to the mold, resulting in high-precision optics. There is a problem that the glass element cannot be molded.

Further, a die in which a platinum group alloy thin film is coated on a cemented carbide base material is excellent in workability, and a high-precision optical glass element can be formed by repeatedly press-forming a low melting point glass. However, when high-melting-point glass is press-molded, surface roughness occurs due to grain growth, making it impossible to form a highly accurate optical glass element.

In view of the problems of the conventional method for manufacturing an optical glass element having a high melting point, the present invention is chemically inert to glass even at a high temperature, and becomes a glass molding surface. The part is sufficiently hard, is not easily damaged by scratches, etc., and the molding surface does not undergo plastic deformation or grain growth due to molding at high temperature, and it has excellent thermal shock resistance so that it can be repeatedly molded. Thus, it is an object of the present invention to provide a mold for molding an optical glass element which is excellent in workability.

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, a cemented carbide containing tungsten carbide (WC) as a main component, titanium carbide (TiC) or titanium nitride (TiN), which is processed into a shape of an optical glass element with high precision. ), An optical glass in which a multilayer film in which a nitride film, a carbide film or a boride film and a platinum group alloy film are alternately laminated is formed on the molding surface of a base material made of a cermet or WC sintered body containing It is a mold for molding an element.

Further, the present invention is a cemented carbide containing WC as a main component, which is processed into a shape of an optical glass element with high precision, and TiC.
Alternatively, a multilayer film in which a nitride film, a carbide film or a boride film and a platinum group alloy film are alternately laminated is formed on a molding surface of a base material made of cermet or WC sintered body containing TiN as a main component. Between a pair of upper and lower molding dies, a glass lump to be molded is placed, heated to a temperature equal to or higher than the softening point of the glass, and then pressure-molded to manufacture an optical glass element, which is a method for manufacturing an optical glass element. ..

[0009]

In the present invention, a multilayer film in which a nitride, a carbide or a boride having excellent heat resistance and a platinum group alloy having poor reactivity with molten glass are alternately laminated is formed on the mold surface, It is possible to manufacture a mold having both advantages by improving reactivity with glass, which is a drawback of nitrides, carbides, or borides, and remarkably improving heat resistance, which is a drawback of platinum group alloys. Therefore, by using the mold of the present invention, BK-
7, it becomes possible to press-mold high melting point optical glass such as SK type and La type.

[0010]

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

First, an embodiment of the method for manufacturing an optical glass element of the present invention will be described. First, a cermet mainly composed of TiN having a diameter of 20 mm and a thickness of 6 mm is processed into a pair of optical glass lens press-molding dies having upper and lower dies having concave press surfaces having a radius of curvature of 46 mm and 200 mm, respectively. did. The press surfaces of these molds were mirror-polished using ultrafine diamond abrasive grains. Next, a multilayer film was formed on the mirror-polished press surface by a sputtering method. In this multilayer film, TiN and Pt-Ir alloy were alternately laminated in an amount of 300 Å, and the total film thickness was about 1 μm.

FIG. 1 is a cross-sectional view of one side of the mold thus manufactured. On the surface of the base material 11 in which the cermet containing TiN as a main component is precisely processed into the inverted shape of the lens,
A multilayer film 12 is formed by alternately laminating 300 N each of TiN and Pt-Ir alloy.

Such upper and lower molds are set in the press molding machine shown in FIG. In FIG. 2, fixed block 2 for upper mold
Reference numeral 1 is a block for fixing the upper mold 23, in which the upper mold heater 22 is embedded. The lower die fixing block 27 is a block for fixing the lower die 25, and the lower die heater 26 is embedded therein. An upper mold thermocouple 28 is embedded in the upper mold 23, and a lower mold thermocouple 29 is embedded in the lower mold 25. A glass gob 24 to be processed is sandwiched between the upper mold 23 and the lower mold 25. In addition, 210 is a plunger, 211 is a positioning sensor, 212 is a stopper, and 213 is a cover.

Molding is performed using such a press molding machine. That is, SK processed into a spherical shape with a radius of 10 mm
-14 Place the glass gob 24 on the lower mold 25, place the upper mold 23 on it, raise the temperature to 700 ° C. as it is, and hold the pressure for 2 minutes by a pressing pressure of about 40 Kg / cm ^{2 in} a nitrogen atmosphere. Then, after that, it is cooled to 600 ° C. in that state, the molded optical glass element is taken out, and the press molding step of the optical glass element is completed.

By repeating the above steps, at the end of the 10,000th press, the upper and lower molds 23 and 25 are removed from the molding machine, and the state of the pressed surface is observed by an optical microscope, and at the same time, the surface roughness at that time is measured. (Rms value, Å) was measured to evaluate the mold accuracy of each. As a comparative experiment,
A conventionally used mold of a SiC sintered body and a mold in which a Pt-Ir alloy film is formed on a cemented carbide base material containing WC as a main component are produced, and the mold is subjected to press molding 10,000 times in the same manner. The accuracy was evaluated.

The results of the press test are shown in Table 1.

[0017]

[Table 1] Sample No. The conventional die made of the SiC sintered body of No. 2 was press-molded several times, and the glass adhered to the surface of both the upper and lower dies, and the glass could not be pressed any more.

Sample No. In the conventional die in which the Pt-Ir alloy film of the WC base material of No. 3 was formed, the surface roughness gradually increased as the number of times of press forming increased, and the upper die was 57.9 Å after 10,000 times of pressing. , The lower die became 68.1Å, which shows that the surface is considerably rougher than before pressing. When these surfaces are observed with a microscope, grain growth is recognized and it is found that the heat resistance is not good.

As described above, it has been impossible to repeatedly press-mold high-melting-point glass such as SK-14 glass with high precision using a mold used for press-molding conventional glass.

Compared with these molds, the sample No. The mold of the present invention of No. 1 did not change the surface condition at all even after repeatedly press-molding SK-14 glass, and no change in surface roughness was observed even after pressing 10,000 times. That is, TiN and Pt-Ir alloy are alternately laminated by 300 Å to suppress the reactivity with TiN, which is a drawback of TiN, and is a drawback of Pt-Ir alloy.
The heat resistance could be improved.

As described above, by using the mold of the present invention, it becomes possible to perform the press molding with high accuracy even with high melting point glass such as SK-14 glass.

In order to explain the present invention, a cermet containing TiN as a main component was used as the base material of the press-molding die in the examples, but tungsten carbide (WC) was the main component. Similar results were obtained even when a cermet or WC sintered body containing a cemented carbide, titanium carbide (TiC), or titanium nitride (TiN) as a main component was used as the base material.

The multilayer film is a film in which TiN and Pt-Ir alloy are alternately laminated in an amount of 300 Å.
Other heat-resistant nitride film, carbide film or boride film,
Similar results were obtained by using a multilayer film in which other platinum group alloy films having poor reactivity with glass were alternately laminated. Furthermore, examples of the nitride film include TiN, silicon nitride (Si ₃ N ₄ ), aluminum nitride (Al
N), tantalum nitride (TaN), zirconium nitride (ZrN), titanium aluminum nitride (TiAlN), or the like is possible. Further, examples of the carbonized film include TiC and silicon carbide (Si
C), tantalum carbide (TaC), zirconium carbide (ZrC) or chrome carbide (Cr ₂₎
C ₃ ) is possible. Further, as an example of the boride film, zirconium boride (ZrB ₂ ), niobium boride (NbB ₂ ) or tantalum boride (TaB ₂ ) can be used. As an example of the platinum group alloy film, an alloy film containing at least one of platinum (Pt), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os) can be used. is there.

[0024]

As is clear from the above description,
The present invention is processed into a shape of an optical glass element with high precision,
A nitride film, a carbide film or a boride film and a platinum group alloy film are alternately formed on the molding surface of a base material made of WC-based cemented carbide, TiC or TiN-based cermet or WC sintered body. By forming a multi-layer film laminated on the above, it is possible to provide a mold for press molding of an optical glass element which has good heat resistance and does not react with glass.

Therefore, by using the mold of the present invention, high melting point glass such as SK-14 can be repeatedly press-molded with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a press molding die according to an embodiment of the present invention.

FIG. 2 is a schematic view of a press molding machine incorporating a press molding die for an optical glass element of the present invention.

[Explanation of symbols]

11 Base material obtained by precisely processing a cermet mainly composed of TiN into an inverted shape of a lens 12 Multilayer film in which 300 Å of TiN and Pt-Ir alloy are alternately laminated 24 Glass material

Claims (6)

[Claims] 1. A cemented carbide containing tungsten carbide (WC) as a main component, titanium carbide (TiC) or titanium nitride (TiN) as a main component, which is processed into a shape of an optical glass element with high accuracy, or Molding of an optical glass element, characterized in that a multilayer film in which a nitride film, a carbide film or a boride film and a platinum group alloy film are alternately laminated is formed on a molding surface of a base material made of a WC sintered body. Mold for. 2. The nitride film comprises TiN, silicon nitride (Si ₃ N ₄ ) and aluminum nitride (Al
N), tantalum nitride (TaN), zirconium nitride (ZrN), or titanium aluminum nitride (TiAlN), The mold for molding an optical glass element according to claim 1. 3. The optical element according to claim 1, wherein the carbonized film is TiC, silicon carbide (SiC), tantalum carbide (TaC), zirconium carbide (ZrC) or chromium carbide (Cr ₂ C ₃ ). Mold for molding glass elements. 4. The boride film is zirconium boride (Z
The mold for molding an optical glass element according to claim 1, which is rB ₂ ), niobium boride (NbB ₂ ) or tantalum boride (TaB ₂ ). 5. The platinum group alloy film is platinum (Pt), rhodium (Rh), iridium (Ir), ruthenium (Ru).
Alternatively, it is an alloy film containing at least one kind of metal in osmium (Os), and the mold for molding an optical glass element according to claim 1. 6. A cemented carbide containing WC as a main component, which is processed into a shape of an optical glass element with high precision, TiC or TiN.
A pair of top and bottom formed by forming a multilayer film in which a nitride film, a carbide film or a boride film and a platinum group alloy film are alternately laminated on the molding surface of a base material made of cermet or WC sintered body containing A glass lump to be molded is placed between the molding dies, heated to a softening point of the glass or higher, and pressure-molded to manufacture an optical glass element. ..