JPH02102136A - Mold for molding optical element and production thereof - Google Patents

Abstract

PURPOSE:To provide a totally durable mold for molding optical elements by forming the optical element-molding mold into a two-layered structure comprising a thin molding mold main body and a durable connector capable of disposing a butt surface only in a necessary thickness. CONSTITUTION:The mold 7 for molding the optical elements is integrally composed of a molding mold main body 5 prepared by press-molding glass with heating and a connector 6 having a butt surface 6a used on the molding of the optical elements and made of a heat-resistant metal (e.g., WC-Ni series cemented carbide) or ceramic having approximately the same linear expansion coefficient as the above-mentioned molding mold main body 5. For the production of the optical element-molding mold 7, the molding mold main body 5 is simultaneously integrally bonded to the connector 6 in the press-molding process (wherein a mold raw material 4 is inserted between a molding matrix 3 and the connector 6 and pressed with the connector 6 in a heated state; 3b is a molding surface) of the molding mold main body 5.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a mold for molding an optical element and a method for manufacturing the same.

[Conventional technology]

Generally, in order to obtain optical elements such as lenses, prisms, filters, etc., a method is used in which a molding element of the optical element is placed between a pair of molds for molding the optical element, and the molded element is hot press-molded.

Conventionally, in order to manufacture molds for molding optical elements used in such molding methods, especially molds for molding aspherical surfaces, a high-precision grinding or cutting process is performed using a high-precision, high-rigidity, ultra-precision CNC lathe. The method used was to ensure accuracy and then, if necessary, polish it for a short period of time to create a perfect mirror surface.

However, for example, a mold for molding an aspherical objective lens for optical pickup, etc. In order to manufacture a mold that requires shape accuracy of ItIm or less, the above conventional manufacturing method requires the following steps:
Due to wear of the cutting tool or the grindstone, it has been difficult to process a large number of molds continuously with high precision. Furthermore, the shape accuracy of the molding molds varied widely, resulting in variations in the performance of the optical elements finally obtained, and the yield was low. Furthermore, the time required for processing is extremely long, resulting in an extremely expensive product.

Therefore, in order to eliminate the above-mentioned drawbacks, the present applicant filed a patent application in 1983-
In No. 186816, a mold material made of glass,
We proposed a method for manufacturing a mold for molding an optical element, in which a mold for molding an optical element is obtained by transferring the molding mold onto the mold material by hot pressure molding with a molding mold.

Furthermore, the present applicant has proposed a mold for molding glass products made of glass or glass ceramics containing nitrogen and fluorine in Japanese Patent Application No. 134580/1983 as a mold for molding optical elements made of glass. Furthermore, the patent application 1986-1
No. 34581 proposed a mold for molding glass products, which is made of glass having a tapering temperature higher than the molding holding temperature, and whose molding surface is coated with a release film.

Furthermore, in the invention described in JP-A No. 62-226825, a pressed glass mold having a transition point temperature lower than the pressing temperature is used, and an anti-fusion layer is interposed between the glass body to be formed and the glass mold. A manufacturing method is disclosed.

[Problem to be solved by the invention]

A mold for molding an optical element requires an abutting surface of a certain length to suppress mutual eccentricity of the optical surfaces of the optical element to be molded.

However, all of the molds in the prior art are integrally molded from glass or glass ceramics.

For this reason, there are disadvantages in that chipping and abrasion are likely to occur, there are problems with the durability of the impact surface, and it is difficult to maintain eccentricity accuracy of the optical element for a long period of time.

Further, when a mold is provided with a face for molding, the thickness of the mold increases, and this is particularly noticeable in molds for camera lenses.

However, glass has a weakness in thermal shock resistance, which is unique to glass, and as the thickness of the mold increases, the molding process of the molding surface itself and the molding process of optical elements using it, especially During the cooling process, so-called cans are formed,
This had the disadvantage that the life of the mold made of glass was shortened.

Therefore, the present invention has been developed in view of the drawbacks in the prior art, and has an eccentricity prevention surgical part that is durable and has excellent thermal shock resistance, so that it has overall durability. The object of the present invention is to provide a mold for molding an optical element made of hot press molded glass and a method for manufacturing the same.

[Means to solve the problem]

As shown in the conceptual diagram of FIG. The mold body 5 is heated to a temperature at which it can be molded, and is press-molded using molding molds 2 and 3 to obtain a molding mold body 5.

The joined body 6 has an impact surface 6a for reducing eccentricity during molding of the optical element, and is made of a heat resistant metal or ceramic having a coefficient of linear expansion approximately equal to that of the mold body 5.

The optical center axis of the molding surface 5a of the mold body 5 and the center axis of the impact surface 6a of the joined body 6 are made to coincide with each other.

[For production]

According to the mold for molding an optical element and the manufacturing method thereof according to the present invention, the two-layer structure includes a thin mold body and a durable bonded body that can provide a required length of the impact surface. With this structure, the mold can be used for a long period of time.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of a mold for molding an optical element and a method for manufacturing the same according to the present invention will be described in detail below with reference to the drawings.

(First Embodiment) FIGS. 2 to 5 are cross-sectional views showing a first embodiment of the present invention.

FIG. 2a shows a press molding apparatus used in an embodiment of the present invention, in which a cylindrical heating ring 1 with a heater 1a installed therein has a joined body 6 on the top and a molding mold 3 on the bottom. It is fitted.

And this zygote 6. The molding mother die 3 has an axis that coincides with the axis of the ring 1.

The joined body 6 is provided so as to be movable in the axial direction so as to generate a pressing force by a pressurizing device (not shown), for example, a pressing plate connected to an air cylinder.

Further, the joined body 6 is formed of a WC-Ni cemented carbide having a linear expansion coefficient of 6.5XIO-' (at room temperature) which is approximately equal to the linear expansion coefficient of 6.0XIO-' (at room temperature) of the mold material La5FO16, which will be described later. Only the bonding surface 6a is subjected to oxidation treatment such as heat treatment in an oxidizing atmosphere.

As shown in FIGS. 3(a) and 3(b), the lower molding mother mold 3 has a molding mother mold main body 3a made of WC-Ni cemented carbide, and a molding surface 3b of the molding surface 3b which is formed of a desired optical element. The shape corresponds to the shape, in this example, it is formed into an aspherical shape. This molding surface 3b is processed using a method conventionally used to create an aspherical surface.
Ultra-precision grinding or cutting was performed using a C lathe to ensure high shape accuracy, followed by short polishing to create a perfect mirror surface.

The above-mentioned high shape accuracy means, for example, that the molding mold 3 for manufacturing the aspherical objective lens mold for the P2Q amplifier has a deviation from the designed shape of 0.1 μm or less and a surface roughness. This indicates approximately 0.07 μm or less.

In addition, a 0.1 μm CrN mold release coating 3 is applied to the molding surface 3b of the molding matrix body 3a by the ion-blating method.
c is formed.

On the other hand, since the molding material for the optical element to be finally obtained in this example is SF6, the molding material 4 of the optical element molding mold has a yield temperature higher than the yielding point temperature of about 480'C. It is made of La5F016 with a point temperature.

Here, the shape of the mold material 4 is preferably polished (pre-processed) into a spherical shape that approximates the desired aspherical surface.

In addition, the material used for the heating ring 1 is also suitable for the joined body 6 during heating.
In order to align the axes of the molding matrix 3 and the joined body 6,
It is made of a material whose coefficient of linear expansion is the same or slightly smaller than that of the material of the molding matrix 3.

Zygote 6. A mold material 4 for an optical element mold and a body mold 8 forming the outer periphery of the mold material 4 are fitted between the molding mother molds 3 .

This body mold 8 regulates the outer periphery of the mold material 4, and as shown in FIG.
It has a function of making b smaller than the operative part 6b of the zygote, and is made of SiC having a linear expansion coefficient smaller than that of the mold material 4 (4,0x10-6) so that it can be separated after molding.

In order to manufacture a mold for molding an optical element using a press molding apparatus having such a configuration, the heating temperature is set to 740'C, which is around the softening point of the mold material 4 made of La5F016, and the temperature of the bonded body 6 connected to the pressurizing apparatus is set to 740'C. 50k for mold material 4 due to action
A pressure of g/C- was applied and maintained for about 1 hour.

After such press molding, the mold material 4 is slowly cooled to about 200°C.
When the body 7 of the mold for molding an optical element was taken out in the state after molding, there was no fusion of the mold material 4 to the release coating 3c of the molding matrix 3, and the heat of the mold body 7 for molding A mold body 7 for molding an optical element in which the high shape accuracy of the molding mother mold 3 is directly transferred without any formation of holes due to impact (during cooling).
I was able to get The joined body 6 of the mold body 7 and the mold material 4 were integrally joined in a strongly fused state, and no deterioration in transfer accuracy due to internal stress was observed as described above.

The mold body 7 for molding an optical element has a molding surface 5 of the mold body 7 for molding.
A 0.1 μm NgFt release coating 5c is formed on the mold body 7 by vacuum evaporation, and the surface roughness of the molding surface 5a of the optical element molding mold body 7 is about 0.02 μm. The surface roughness was less than 1/2 of that of .

The mold 7 for molding an optical element obtained in this manner has both high shape accuracy and surface precision, and by this press molding, molds for molding of the same quality can be mass-produced without variation and at low cost. - Considering the long life of the product, if the mold life is N shots, if one molding mother mold 3 is manufactured, the actual mold life will be NXN, and mass production can be carried out sufficiently. For example, when N=1,000, 1 million shots are possible, and when N=10,000, 100 million shots are possible.

Next, as shown in FIG. 5, an optical element was press-molded using the optical element molding die 7 obtained in this example.

In FIG. 5, reference numeral 9 denotes a heating ring having a heater 9a therein, and a pair of molds 71 and 72 according to the present invention are fitted into this heating ring 9.

Further, the upper molding mold 71 is connected to a pressing device (not shown), and can be moved and pressed in the axial direction. Then, between the image forming molds 71 and 72, there is a S which has been pre-processed such as polishing into a spherical shape that approximates the desired aspherical surface.
A molding material 10 for an optical element made of F6 is provided.

With such a press molding device, the heating temperature can be adjusted to the molding material 1.
The temperature was set at 530°C, which is near the softening point of 0, and the molding material 10 was heated at approximately 3°C while applying pressure of 20kg/cd.
It was held for 0 minutes. After this press molding, the optical element was slowly cooled to about 200°C and taken out. This optical element is molded into a mold 7
The high shape accuracy and surface accuracy of 1.72 were transferred as they were and were good. Even when the molding molds 71 and 72 were used continuously, the southern part 6b did not wear out or break, and had sufficient durability.

In addition, in this example, the molding temperature of the molding mother mold 3 is as follows:
Although the softening point of the mold material 4 was set near, the present invention is not limited to such embodiments.If the yielding point of the mold material 4 is higher than that, molding can be performed at a molding pressure of several tens of kg/ci. Sufficient strength can be obtained as a mold. Moreover, the material of the molding matrix 3 is not limited to cemented carbide, but may be SiC.

5ixCa, single crystal W, Cr3C, alloy 9 quartz glass such as quartz ga alloy, etc.Furthermore, the shape of the molding matrix 3 is not limited to an aspherical surface, and may be spherical or flat.

The mold release coating 3C of the molding matrix 3 is made of TiN, CrCN, c-
BN, a-BN, AnN, SiC, WC.

TiB2. Ceramic films such as Tic, B, and C can also provide the same effect as in the embodiment.

Further, the material of the joined body 6 is not limited to cemented carbide, but may include SiC, Si3C, and the like.

The same effect as in the embodiment can be obtained if the material is a metal or ceramic having a coefficient of linear expansion approximately equal to that of the mold material, such as single crystal W, Cr, C, alloy, or heat-resistant stainless steel.

(Second example) FIG. 6 is a sectional view showing a second embodiment of the present invention.

The mold used for manufacturing the optical element shown in this example has a concave portion 6C on the joining surface 6a of the joined body 6 of the first example.
The other components are the same in that they are formed with a .

By forming the concave portion 6C on the joining surface 6a of the joined body 6 in the mold body 11, the mold material 4 is formed during molding.
flows into the recess 6c, and the mold material part 1 of the mold body 11
The joint between 1a and the joined body 6 is integrally molded.

In this embodiment, by providing the recess 6c, the contact area between the mold material portion 11a and the joined body 6 becomes larger, thereby achieving the effect of more firmly joining them.

Note that the above effect can be made more pronounced by making the side surfaces of the recess 6c have a reverse slope, or by making the cross section of the recess 6c L-shaped or upwardly shaped so that it is difficult to separate the mold material 11a and the joined body 6. be able to.

(Third example) FIG. 7 is a sectional view showing a third embodiment of the present invention.

The mold used for manufacturing the optical element shown in this embodiment has a mold material 4 corresponding to the shape of the release coating 3c of the molding matrix 3 on the bonding surface 6a of the bonded body 6 of the first embodiment. They differ in that they are formed by providing a convex joint 6d that has approximately the same thickness after molding, and the other configurations are the same, and the other configurations will be designated by the same number. The explanation will be omitted.

In this embodiment, by providing the joint portion 6d, the mold material portion 12a of the mold body 12 is molded to have approximately the same thickness and is transferred to the molding surface 12b.

By molding the mold material 12a of the mold body 12 to have the same thickness, the temperature distribution within the mold material 12a is made uniform, which improves the accuracy of transfer to the molding surface 12b, and
The effect of further reducing variations can be obtained.

〔Effect of the invention〕

As described above, according to the mold for molding an optical element and the method for manufacturing the same according to the present invention, a mold for molding an optical element that can be used for a long period of time by pressure molding can be obtained, thereby making it possible to produce high-precision molds such as aspherical shapes. optical elements can be mass-produced at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conceptual diagram of a mold for molding an optical element according to the present invention and a method for manufacturing the same, and FIGS.
2 is a sectional view showing a pressing device, FIG. 3 is a sectional view showing a molding matrix, FIG. 4 is a sectional view showing a mold, and FIG. 5 is a sectional view showing a pressing device. , FIG. 6 is a sectional view showing the second embodiment, and FIG. 7 is a sectional view showing the third embodiment. 1...Heating ring 2.3...Molding mold 4...
・Mold material 5...Mold body 6...Joint body 1...Heating II nog 2.3...Mold material 4...Mold material 5...Mold body 6...・Joint salary chart

Claims (2)

[Claims] (1) It has a mold body made of hot press-formed glass and an impact surface for molding optical elements, and is made of a heat-resistant metal or ceramic having a coefficient of linear expansion almost equal to that of the mold body. What is claimed is: 1. A mold for molding an optical element, characterized in that the joined body is integrally constructed. (2) Manufacturing a mold for molding an optical element, which is characterized in that the mold body and the assembly are integrally joined at the same time during the press molding process of the mold body. Method.