JPH0255511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a mold for an optical element used, for example, in producing lenses, prisms, and other optical elements by press molding.

(Prior Art) As a method for producing optical elements made of optical glass, such as lenses, for example, an optical element forming material (hereinafter sometimes simply referred to as optical material) softened in a heating furnace is pressed. A method of molding is widely known. In this method, an optical element is produced by press-molding an optical material that has been softened by heating to a temperature equal to or higher than its transition point using, for example, a mold consisting of an upper mold and a lower mold. Therefore, compared to a method in which optical materials are directly polished, the above-mentioned method is attracting attention as a manufacturing technology that has high reproducibility in the quality of individual products and is excellent in mass production.

Examples of mold materials constituting the optical element mold (hereinafter sometimes simply referred to as a mold) for use in the above-mentioned method include those disclosed in JP-A-52-45613 and JP-A-60-195026. The technology disclosed in JP-A-59-123631 uses a material mainly composed of tungsten carbide and cobalt, silicon nitride (SiN _x ), and various other cemented carbide alloys. ing. That is, when producing an optical element by the above-mentioned press molding using an optical material such as optical glass, which has a relatively high softening temperature, the mold is made of a cemented carbide whose hardness decreases little under high temperature conditions. . A base material made of such a material is directly polished using a machine tool such as a spherical surface generator (curve generator) to form an effective molding surface for manufacturing optical elements with a curvature according to the design. A mold is produced.

(Problems to be Solved by the Invention) However, in the conventional optical element mold manufacturing method described above, the effective molding surface of the mold is made by polishing a base material made of cemented carbide, which has poor workability. It will be done. Therefore, especially when it is necessary to form the above-mentioned effective molding surface as an aspherical surface, there is a problem in that it is very difficult to grind and polish an extremely hard base material.

On the other hand, optical materials such as plastics, which have a low softening temperature, use base materials that are relatively easy to work with, but such materials have a relatively high softening temperature, such as optical glass. There is a problem that a mold that can withstand pressure molding of optical materials cannot be obtained.

In view of the above-mentioned conventional problems, it is an object of the present invention to form a mold with high precision in accordance with the design of an optical element, even in a mold used for optical materials such as optical glass, which have a high softening temperature. It is an object of the present invention to provide a method for manufacturing a mold for an optical element that can be formed using the following methods.

(Means for Solving the Problem) In order to achieve this object, the mold for an optical element of the present invention provides a method for forming an optical element by press-molding an optical element forming material softened by heating. In manufacturing a mold for an optical element having an effective molding surface of The method is characterized by including a step of placing a core material above the first electroformed layer and then growing and forming a second electroformed layer on the surfaces of the first electroformed layer and the core material.

(Function) According to the structure of the method for manufacturing a mold for an optical element of the present invention, since the effective molding surface is formed as an electroformed layer, it becomes easy to form a curved surface according to the design of the optical element, and substantially Multiple molds having the same effective molding surface can be repeatedly produced.

(Example) Hereinafter, an example of the method for manufacturing a mold for an optical element of the present invention will be described with reference to the drawings. still,
The drawings referred to in the following description are shown only schematically to facilitate understanding of the invention.
The present invention is not limited to these illustrated examples. In addition, in the following description, in order to facilitate understanding of this invention, explanation will be given under numerical conditions, shape, material, arrangement relationship, or other specific conditions, but this invention is limited only to these specific conditions. Please understand that this is not something that will be done.

First, the production of the master mold used in the production method of this example will be explained.

The master mold used in the method of the present invention is capable of depositing a first electroformed layer that serves as an effective molding surface in press molding of an optical element. Therefore, as a requirement for the material constituting the master mold, it is possible to deposit metal by electroforming.

It has excellent workability in forming a curved surface corresponding to the effective molding surface of an optical element mold.

The following points can be mentioned.

Various materials such as nickel, oxygen-free copper, phosphor bronze, lead, aluminum, and others can be considered as materials that meet these requirements, but in this example, the case where the master mold is constructed using nickel will be explained. do.

Embodiments of the present invention will be described below with reference to FIGS. 1A to 1E.

FIGS. 1A to 1E are explanatory diagrams showing schematic cross-sections of a mold for an optical element that is in the middle of being manufactured, for each manufacturing process, in order to explain an embodiment of the present invention.

First, the mold material made of nickel was ground using an ultra-precision lathe, and then polished.
A master mold 12 having a curved surface 10 as shown in
get. This curved surface 10 is formed as a convex shape that is substantially the same as the shape of the desired optical element, and in this example, it is formed as an aspheric surface.

Next, the above-mentioned master mold 12 is immersed in the electrolytic layer, and the first electroformed layer 14 is formed by electrodeposition until a predetermined layer thickness is achieved by a conventionally well-known electroforming method (first
Figure B).

Here, the material constituting the first electroformed layer 14 described above will be explained.

As already explained, the mold produced by applying the present invention is used for press-molding optical materials such as glass in a softened state. Therefore, as a requirement for the material constituting the first electroformed layer 14 described above, it is necessary to maintain sufficient hardness (strength) at the transition temperature of the optical material according to the design of the optical element. The master mold 12 (curved surface 10) that satisfies these requirements and is described above
The following various alloys can be considered as examples of substances that can be deposited on the surface of the metal by electroforming.

First, the first electroformed layer 14 contains about 40% by weight or more of nickel as a main component, and the remaining less than about 60% by weight (hereinafter referred to as the balance) is made of chromium (Cr) and cobalt (Co). , molybdenum (Mo), niobium (Nb), iron (Fe), titanium (Ti), or aluminum (Al). At this time, it is preferable that the seven metals selected to account for the balance described above are contained within the composition range described below (however, the unit is expressed in weight % in the first electroformed layer).

0.5≦Cr≦30 0.5≦Co≦30 1.0≦Mo≦25 0.5≦Nb≦5.0 0.5≦Fe≦20 0.5≦Ti≦5.0 0.5≦Al≦6.0 As an example of such a composition, in this example, Ni is An electrodeposition solution containing about 70% by weight, about 20% by weight of Cr, and about 10% by weight of Co was placed in an electrolytic bath to form a first electroformed layer 14 as shown in FIG. 1B.

By growing this first electroformed layer 14 on the upper side of the master mold 12, the above-mentioned convex spherical surface 10
An effective molding surface 16 having a concave shape corresponding to this is formed.

Next, the master mold 12 in the state shown in FIG.
After being taken out from the electrolytic layer, a core material 18 for the purpose of reinforcement is placed on the upper side of the first electroforming tank 14 that has been formed. Here, like the first electroformed layer 14, the above-mentioned core material 18 was made of stainless steel in consideration of maintaining strength at high temperatures. In addition, in order to improve the adhesion between the core material 18 and the first electroformed layer 14, one surface of the core material 18 where these two components contact each other is ground and polished in advance, as described above. Curved surface 1
This was done as an approximate spherical shape with respect to 0.

Thereafter, with the core material 18 placed above the first electroformed layer 14 formed on the upper side of the master mold 12, electroforming was performed again using the above-mentioned electrodeposition liquid, and as shown in FIG. Forming a second electroformed layer 20 as shown in
A base material 22 is obtained.

In forming this second electroformed layer 20, the above-mentioned core material 18 is completely surrounded by the above-mentioned first electroformed layer 14 and the second electroformed layer 20 obtained in this step. It is best to do this until it is done. In other words, by forming the second electroformed layer 20 in this manner, the above-mentioned core material 18 is subjected to insert processing. Also,
When placing the core material 18 on the first electroformed layer 14 and forming the second electroformed layer 20, the first electroformed layer 14 and the core material 18 are crimped or by other means. , a base material 22 having sufficient adhesion can be obtained.

Next, after removing the above-mentioned base material 22 from the master mold 12, the base material 22 is processed to be attached to a press molding device, which will be described later.
A mold 24 for an optical element as an example of the present invention is obtained as shown in FIG.

In this example, when the mold 24 obtained through the above-mentioned process is used for actual press molding, the releasability between the mold 24 and the optical element after molding, or the oxidation resistance of the mold 24 In order to improve the quality, a thin film 26 was applied to the effective molding surface 16 of the mold 24 described above. This thin film 26 was deposited by a sputtering method using platinum Pt as a target, and a uniform thin film 26 with a thickness of about 2 (μm) was obtained (FIG. 1E).

The above-mentioned thin film will be explained below.

Conventionally, when molding optical elements by press molding, a technique is known in which a mold is used in a reducing gas atmosphere in order to prevent deterioration of the mold due to oxidation. The deterioration of the mold described above results in deformation of the effective molding surface 16 of the mold. Therefore, in this embodiment, a material with excellent oxidation resistance is coated on the effective molding surface 16 to extend the life of the mold 24 and improve the mold releasability when manufacturing optical elements. did.

Thin film constituent materials that achieve the above purpose include the aforementioned platinum (Pt), noble metals such as gold (Au), rhodium (Rh), titanium nitride (TiN), and alumina (Al ₂ O ₃ ). , silicon nitride (Si ₃ N ₄ )
Possible ceramic materials such as Moreover, as a technique for depositing this thin film, the thin film may be deposited by any suitable technique such as sputtering method, vapor deposition method, ion plating method, etc. depending on the respective physical properties.

Hereinafter, with reference to the drawings, a process for manufacturing an optical element using a mold produced according to the present invention will be described.

FIGS. 2A to 2C are diagrams for explaining the manufacturing process of a convex lens having an aspherical surface using a mold according to an embodiment of the present invention. In these figures, the mold 24 and the thin film 26 described with reference to FIG. and 24b are shown with their respective reference numerals.
Both of these molds have been described with reference to FIGS. 1A-E. This was produced according to an embodiment of this invention.

To briefly explain the configuration of the press molding apparatus shown in FIG. The molds 24b are respectively attached to the hydraulic cylinders 28b. 30 indicates a thermocouple for measuring the temperature of the mold 24a or 24b;
0 is arranged in each of the above-mentioned hydraulic cylinders 28a and 28b. Further, 32 is a heater provided in the heating furnace, 34 is a molding section, and 36 is a gas inlet communicating with the molding section.

First, an optical glass 38 (SFS01, manufactured by Ohara Optical Glass Co., Ltd.; transition point: about 393° C.) is prepared as an example of an optical element forming material, and the optical glass 38 is polished into a spherical shape. During this polishing process, the volume was adjusted by converting the weight into volume.

After that, the optical glass 38 whose volume has been adjusted as described above is placed above the concave portion constituting the effective molding surface of the mold 24b, the molding portion 34 is isolated from the outside air, and the molds 24a and 24b are closed. Temperature of thermocouple 30
While measuring by
Heating is performed using the heater 32 until the temperature reaches 420°C. At this time, in order to reduce deterioration of the molds 24a and 24b, the gas inlet 36 is
Nitrogen gas was introduced into the molding section 34 through the molding section 34 to create a reducing atmosphere and heating was performed.

Subsequently, the molds 24a and 2 are heated as described above.
After the temperature of 4b reaches approximately 420° ^C , as can be seen from FIG. Optical glass 38 is press-molded.

Subsequently, the heater 32 is stopped and the optical glass 38 immediately after press molding and the molds 28a and 28b are allowed to cool. Thereafter, when it is confirmed by the thermocouple 30 that the temperature of the molds 24a and 24b is lower than the transition point of the optical material used (approximately 390°C or less), the molded product is removed from the press molding device. An optical element 40 as shown in FIG. 2C is obtained.

The optical element 40 thus obtained has an aspherical surface substantially the same as the curved surface 11 formed in the master mold 12 described above, and the mold produced by the method of the present invention has extremely high precision. It was confirmed that the finish was good.

Furthermore, when optical elements were repeatedly press-molded using the molds 24a and 24b, the optical elements could be manufactured with high reproducibility.

The embodiments of the present invention have been described above with reference to the manufacturing process of an optical element using the fabricated mold. However, the method for producing a mold for an optical element according to the present invention is not limited to the above-mentioned embodiments, and numerical conditions, shapes, materials, arrangement relationships, and other conditions are within the scope of the present invention. Obviously, any suitable design changes and modifications may be made therein.

(Effects of the Invention) As is clear from the above description, according to the method for manufacturing a mold for an optical element of the present invention, the effective molding surface of the mold is formed as an electroformed layer. Therefore, it is easy to form the effective molding surface of the mold by using a master mold made of a material with high workability that allows easy formation of curved surfaces according to the design of the optical element, and the effective molding surface is substantially the same. A plurality of molds can be repeatedly produced.

Therefore, even if the optical material has a high softening temperature, it is possible to form an effective molding surface with high precision according to the design of the optical element, and it is possible to easily and easily produce an excellent mold for an optical element. As a result, optical elements having excellent characteristics can be provided at low cost.

[Brief explanation of drawings]

1A to 1E are explanatory diagrams showing schematic cross-sections of each manufacturing process of a mold for an optical element in order to explain an embodiment of the present invention, and FIGS. FIG. 3 is a diagram illustrating an example of how a mold is used. 10...Curved surface (aspherical surface), 12...Master mold,
14... First electroformed layer, 16... Effective molding surface (aspherical surface), 18... Core material, 20... Second electroformed layer, 22
... Base material, 24, 24a, 24b ... Molding mold for optical element, 26 ... Thin film, 28a, 28b ... Hydraulic cylinder, 30 ... Thermocouple, 32 ... Heater,
34... Molding section, 36... Gas inlet, 38...
Optical glass, 40...optical element.

Claims (1)

[Scope of Claims] 1. In producing an optical element mold having an effective molding surface for forming an optical element by press molding an optical element forming material softened by heating, at least , a step of depositing a first electroformed layer on a curved surface corresponding to the effective forming surface; and a step of depositing a second electroformed layer after placing a core material on the upper side of the first electroformed layer. A method for producing a mold for an optical element, characterized in that: