JPH11157852A - Manufacture of mold for forming glass optical element and forming method of glass optical element, using the same mold manufactured therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacture of a metallic mold used for high temp. press forming of a glass optical element, which enables the working of a mold material into the objective mold having a precise shape without causing any cracks in the mold and also to provide the press forming method of a glass optical element, using the mold thus manufactured. SOLUTION: This manufacture of the metallic mold comprises: a stage for forming an electroless nickel-plated layer consisting of Ni and P as a layer to be subjected to cutting, on a base material selected from cemented carbides, cermets, ceramics and iron base alloys and subjecting this layer to ultraprecision cutting with a diamond cutting tool to perform finish working of an optical surface shape with desired accuracy; and another stage for performing heat treatment of the resulting forming surface of the mold after the finish working. This forming method of a glass optical element comprises: forming an intermediate layer consisting of a nitride or carbide ceramic material on the forming surface of the mold; further forming a release layer consisting of a DLC(diamond-like carbon) film on the upper surface of the intermediate layer; and forming the glass optical element at a 390 to 490 deg.C forming temp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold for press-molding a glass optical element and a method for press-molding a glass optical element.

[0002]

2. Description of the Related Art Conventionally, in the molding of plastic lenses, Ni and P capable of ultra-precision cutting have been used as molding dies.
An optical mirror surface is generally processed by cutting a layer of electroless nickel plating made of diamond with a diamond tool. In this case, since the molding temperature is 200 ° C. or less, the heat treatment was performed in the range of 200 to 250 ° C. before cutting.

[0003]

However, in the above conventional example, it is possible when the molding temperature is 200 ° C. or less, such as plastics, but heat treatment at a high temperature is necessary in press molding of glass. It is. However, when the heat treatment temperature is raised to 300 ° C. or higher, the crystallization of the electroless nickel plating proceeds, and if the heat treatment is performed before cutting,
In ultra-precision cutting with a diamond bite, the wear of the cutting tool progressed quickly and it was not possible to cut well. Also,
If the coefficient of thermal expansion of the base material is significantly different from that of electroless nickel plating, there is a problem that cracks occur due to the difference in the amount of heat shrinkage at the time of cooling after heating.

Accordingly, an object of the present invention is to provide a method of manufacturing a press molding die capable of processing a mold used for a glass optical element molded at a high temperature into a precise shape without causing cracks, and An object of the present invention is to provide a press molding method capable of obtaining a glass optical element having excellent surface shape accuracy and surface roughness even in continuous molding using the mold.

[0005]

The present invention provides: 1. A step of finishing the optical surface shape to a desired accuracy by ultra-precision cutting using a diamond bite on the electroless nickel plating layer made of Ni and P, and a step of performing a heat treatment after the processing. The thermal expansion coefficient of the base material is 10 × 10 ^{-6 to} 16 × 10
^-6 . 3. The heat treatment temperature is at least 10 degrees higher than the molding temperature. A method for producing a glass optical element molding die, wherein the heat treatment temperature is in the range of 400 to 500 ° C. Also, 1. Forming a molding die manufactured by a process of finishing the optical surface shape to the desired accuracy by ultra-precision cutting using a diamond bite on an electroless nickel plating layer composed of Ni and P, and a process of performing a heat treatment after the process. An intermediate layer made of nitride or carbide ceramics and the like, and a release layer made of a DLC film (diamond-like carbon film, diamond-like carbon film) are provided on the upper surface.
1. Form glass in the range of 0 ° C. to 490 ° C. The thermal expansion coefficient of the base material is 10 × 10 ^{-6 to} 16 × 10
^-6 . 3. The heat treatment temperature is at least 10 degrees higher than the molding temperature. A method for forming a glass optical element, wherein the heat treatment temperature is in the range of 400 to 500 ° C.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Mold Production] As shown in FIG.
Heat-treated with a thermal expansion coefficient of 13 × 10 ⁻⁶ mainly composed of iron, having a molding surface 41 processed within ± 10 μm from the design shape accuracy of the optical element molding surface (concave shape with a radius of curvature of 20 mm). An electroless nickel plating layer 4 made of Ni and P is formed on the molding surface of the iron-based alloy type base material 42 as a processing layer.
A total of 20 molds each having No. 3 having a plating thickness of 50 μm were prepared.

[0007] Of these, type 10 is a single-crystal precision diamond bit as it is, and is subjected to precision cutting within ± 0.1 µm from the design shape accuracy, and the other type 10 is 450 ° C / 1 hour.
After heat treatment in a non-oxidizing atmosphere, precision cutting similar to that described above was performed. At that time, the state of wear of the diamond bite and the surface state of the processed plating layer were observed. Table 1 shows the processing results.

[0008]

As can be seen from Table 1, in the processing of the electroless nickel plating layer without heat treatment, the surface roughness of the plated layer processed in both the first type and the tenth type is good, and abrasion of the diamond tool occurs. Did not. However, in the processing of the electrolytic nickel plating layer subjected to the heat treatment at 450 ° C. for one hour,
No die wear occurred on the mold, but the surface roughness was slightly coarser than that of the unheated mold. Furthermore, 1
In the 0-th type, bite wear occurred and the surface roughness was extremely deteriorated. It is considered that the cause was that Ni of the electroless nickel plating layer was crystallized by the heat treatment at 450 ° C. for one hour.
FIG. 3 shows the result of X-ray diffraction analysis of the state of crystallization of the electroless nickel plating layer with or without heat treatment. FIG. 3 shows that no crystallization of Ni was observed without heat treatment, but at 450 ° C. /
A sharp peak of Ni (200), that is, crystallization was observed after the heat treatment for 1 hour.

Next, the die cut without heat treatment and the die cut after heat treatment were placed at 450 ° C. for 1 hour.
Heat treatment was performed in a non-oxidizing atmosphere, and changes in surface shape and surface roughness and the presence or absence of film peeling were confirmed. As a result, neither the surface shape change (Table 4) nor the surface roughness change was observed in both types. Also, no film peeling was observed.

In preparation for forming a glass with the mold manufactured by the above two methods, 1 μm of TiN is formed on a glass forming surface of the mold, that is, a precision cut surface of the electroless nickel plating by a vacuum evaporation method. A 0.5 μm DLC film was formed thereon. Here, no deviation in the surface shape due to the formation of the two types of thin films was observed. FIG. 1 is a structural view of the glass molding die of the present invention manufactured by the above method, and FIG. 2 shows a manufacturing procedure. In FIG. 1, 11 is a DLC film,
12 is a TiN film, 13 is a precision-cut electroless nickel plating layer, and 14 is a mold base material.

Table 2 shows the two types of mold manufacturing methods described above.

[0013]

[Molding Test] Using each of the molds manufactured by the above two methods, a molding test was performed 100 times continuously with glass having a molding temperature of 400 ° C.
Film peeling and surface condition of the molded product were checked.

Here, FIG. 5 is a schematic diagram showing a molding state of the continuous molding. 51 and 52 are an upper die and a lower die having a radius of curvature of 20 mm. 53 is a spherical glass material adjusted to a desired volume. Reference numeral 54 denotes a press shaft to which the upper die is attached,
It can be pressed with a load of 0 kgf. Furthermore, a heater, a glass material, a molded product stocker, and a handling mechanism (not shown) are provided, and the glass material is manually supplied to the lower mold forming surface, heated, and heated at 400 ° C. for 5 minutes.
After pressing for 300 minutes, the mold is released at 300 ° C. and the molded product is discharged by hand. This step was repeated 100 times.

Table 3 shows the results of the molding test for 100 consecutive shots.

[0017]

As can be seen from Table 3, deterioration of the mold of the present invention and the comparative mold due to continuous molding, that is, a change in the shape of the molding surface, an increase in surface roughness, peeling of the plating film, cracks, etc. are recognized. I couldn't. However, as described above, the surface roughness of the comparative mold is 50 nm, and this roughness is directly transferred to a molded product, and the molded product has a 50 nm swirling state. 20n
The molded product was coarser than m and could not withstand practical use.

On the other hand, the molded product of the mold of the present invention had a surface roughness of 10 nm even at the 100th shot, and was sufficiently practical.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, a mold used for a glass optical element molded at a high temperature can be processed into a precise shape without causing cracks. The glass optical element excellent in surface shape accuracy and surface roughness was able to be formed even in continuous molding by the press molding method of the glass optical element used.

Preferably, the coefficient of thermal expansion is from 10 × 10 ^-6 to
Ni as a cutting layer on a base material selected from 16 × 10 ^-6 cemented carbide, cermet, ceramics and iron-based alloy
And an electroless nickel plating layer made of P, and finishing the optical surface shape to a desired accuracy by ultra-precision cutting using a diamond tool on the cutting layer, and then performing a heat treatment at a temperature higher than the molding temperature by 10 degrees or more. Further, using a mold for molding a glass optical element in which an intermediate layer made of nitride or carbide ceramics or the like is provided on the optical surface, that is, a molding surface, and a release layer made of a DLC film is provided on the upper surface thereof, the molding temperature is 3
When a glass optical element in the range of 90 to 490 ° C. was molded, an optical element that could withstand practical use even in continuous molding could be molded.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a glass molding die according to the present invention.

FIG. 2 shows a procedure for manufacturing a glass molding die according to the present invention.

FIG. 3 shows an X-ray diffraction analysis result of electroless nickel plating.

FIG. 4 is a configuration diagram of a glass forming mold provided with electroless nickel plating.

FIG. 5 is a schematic view of a continuous molding state.

Claims (8)

[Claims] 1. An electroless nickel plating layer made of Ni and P is provided as a cutting layer on a base material selected from the group consisting of cemented carbide, cermet, ceramics, and iron-based alloy. A method for manufacturing a glass optical element molding die, comprising: a step of finishing an optical surface shape to a desired accuracy by ultraprecision cutting using a diamond tool; and a step of performing a heat treatment after the processing. 2. The base material has a coefficient of thermal expansion of 10 × 10 ⁻⁶ or ^less .
The method for producing a glass optical element molding die according to claim 1, wherein the mold is 16 × 10 ⁻⁶ . 3. The method according to claim 1, wherein the heat treatment temperature is at least 10 degrees higher than the molding temperature. 4. The method for manufacturing a glass optical element molding die according to claim 1, wherein the heat treatment temperature is in a range of 400 to 500 ° C. 5. An electroless nickel plating layer made of Ni and P is provided as a cutting layer on a base material selected from the group consisting of a cemented carbide, a cermet, a ceramic and an iron-based alloy. An intermediate surface made of nitride or carbide ceramics is formed on the molding surface of the molding die manufactured by the process of finishing the optical surface shape to the desired accuracy by ultra-precision cutting using a diamond tool and the process of performing heat treatment after processing. A method for forming a glass optical element, comprising: forming a layer and a release layer made of a DLC film on an upper surface thereof; 6. The base material having a coefficient of thermal expansion of 10 × 10 ⁻⁶ or ^less .
6. The method for forming a glass optical element according to claim 5, wherein the ^ratio is 16 × 10 ⁻⁶ . 7. The method for molding a glass optical element according to claim 5, wherein the heat treatment temperature is higher than the molding temperature by 10 degrees or more. 8. The method for forming a glass optical element according to claim 5, wherein the heat treatment temperature is in a range of 400 to 500 ° C.