JP3255690B2 - Optical element molding die and manufacturing method - Google Patents

Abstract

PURPOSE:To readily obtain the subject metallic mold capable of preventing a fin and a shrinkage from occurring in a formed product by working a forming surface after joining plural materials having different thermal conductivities and preventing a gap or a stepped part from occurring. CONSTITUTION:Plural materials 1 and 2 having different thermal conductivities are joined to form a metallic mold material 5 so as to provide a forming surface 4 where the materials 1 and 2 having the different thermal conductivities of the material 5 are continuous. Thereby, the objective metallic mold having one or more joining parts 3 and the forming surface 4 in which the materials 1 and 2 are continuous to form a continuous surface passing through the joining parts 3. As a result, a phenomenon called a shrinkage and a fin caused by an increased difference in temperature distribution in the interior of the glass are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding an optical element and a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, there has been known a manufacturing method in which a glass material is heated and softened to form an optical element under pressure. In the above manufacturing method, it is important to accurately transfer the mold shape to the glass. However, in the case of a molded article having a large difference in thickness, the difference in temperature distribution inside the glass increases, which is a phenomenon called so-called sink mark. There is a drawback that occurs.

[0005] Therefore, in order to solve the above-mentioned drawbacks, there has been proposed a method of forming a molding surface portion with materials having different thermal conductivities to make a difference in a cooling rate of glass. For example, in the invention described in Japanese Patent Application Laid-Open No. 1-148716, a glass optical element molding die which is concentrically divided by at least two or more mold members is disclosed.

[0004]

However, there is considerable difficulty in manufacturing a concentrically divided mold as disclosed in Japanese Patent Application Laid-Open No. 1-148716.

[0005] That is, even if there is a small gap or a step between the divided molds, the glass penetrates there and burrs are generated. Therefore, the inner and outer diameters of the parts concentrically combined must be formed within a tolerance of 1 to 2 μm in terms of the diameter, cylindricity, and the like so that the gaps and steps are reduced, and processing is extremely difficult. In particular, heat-resistant materials used as molds for molding glass optical elements are cemented carbides and various ceramics, and it is difficult at present to process these difficult-to-cut materials with the above-mentioned tolerances.

[0006] Even if it can be processed, it is difficult to combine it because the gap between the members is very small, and the workability is poor. When combining
If there is even a slight inclination, both members will be damaged.

Furthermore, it is actually impossible to produce a product having no gap at all, and the mold disclosed in the above-mentioned publication can be used for molding a product which does not hinder use even if burrs are generated. Or, it is limited to the case where post-processing after molding may increase the cost significantly.

Accordingly, the present invention has been developed in view of the above-mentioned problems in the prior art, and has an effect of preventing sink marks and being easy to manufacture by forming the mold surface with materials having different thermal conductivity. An object of the present invention is to provide an optical element molding die and a manufacturing method.

[0009]

According to the present invention, there is provided an optical element molding die made of two or more kinds of materials for heat-softening and press-molding a glass material. A joining surface mounted and joined to a second material having a different thermal conductivity from the first material; and a molding surface formed continuously on the first material and the second material across the joining surface. .

In a method of manufacturing a mold for molding an optical element comprising two or more kinds of materials for heat-softening and press-molding a glass material, a first material having a predetermined thermal conductivity is defined as the first material. Placing on the second material having a different thermal conductivity and joining, and connecting the first material and the second material continuously across the joining surface where the first material and the second material are joined. And processing the molding surface.

[0011]

According to the present invention, since two or more materials having different thermal conductivities are joined in advance, it is not necessary to tighten processing tolerances, and it is not necessary to combine them. Further, since the molding surface is processed after joining, no gap or step is generated.

[0012]

Embodiment 1 FIGS. 1 and 2 are sectional views showing the present embodiment. C-B as the first material of high purity (99% or more)
N powder 85wt%, TiN11wt%, TiC2w
The mixed powder composed of t% and the balance of Ni was placed on the WC-based cemented carbide 2 at a temperature of 150 ° C. and a pressure of 40000 kg / c.
and sintered at m ² was obtained as WC-based cemented carbide 2 as the second material integrally bonded article of the c-BN sintered body 1 as the first material (see FIG. 1).

Subsequently, a schematic shape of the flange portion 5 for fixing the molding surface 4 and the mold to the mount is formed on the integrally joined product by electric discharge machining. Further, each part is finished to a predetermined dimensional accuracy by grinding (see FIG. 2). Next, the molding surface 4 is polished to finish it to a desired roughness and shape.

In the optical element molding die manufactured by the above method, the center of the molding surface 4 is a cemented carbide (having a thermal conductivity of 0.17 ca).
1 / cm · sec · deg), and the outer periphery is formed of a c-BN sintered body (thermal conductivity: 0.09 cal / cm · sec · deg), which has the effect of preventing sink marks. Since there is no gap or step between the cemented carbide and the c-BN sintered body, no burrs are formed on the molded product.

According to this embodiment, since the bonding portion 3 is a diffusion bonding at the time of sintering, the bonding strength is extremely strong even when hot, and the bonding portion 3 is displaced even at a high temperature and a high load at the time of molding a glass optical element. There is no peeling.

[0016]

Embodiment 2 FIG. 3 is a sectional view showing the present embodiment. This embodiment is the same as or similar to FIG. 2 in the first embodiment.
Thereafter, a Cr plating having a thickness of 0.1 mm is applied to the molding surface 4 (see FIG. 3). Subsequently, the molding surface 4 was polished to obtain a desired roughness and shape.

C-BN sintered body (Vickers hardness Hv = 4)
500) and cemented carbide (Vickers hardness Hv = 1400)
Since the hardness is greatly different from the above, the degree of wear during polishing is different and it is difficult to form a continuous surface. However, in this embodiment, the polishing is extremely easy due to the Cr plating on both members. I was able to.

[0018]

Embodiment 3 FIGS. 4 to 7 are sectional views showing this embodiment. 11 is W (thermal conductivity 0.38 ca) as the second material
1 / cm · sec · deg), and the cross section is formed in a convex shape (see FIG. 4). 12 is the first
Si ₃ N ₄ as material (thermal conductivity 0.07 cal / c
(m · sec · deg), and is processed into a size that can be placed on the base 11 (see FIG. 5). Base 11
The sintered body 12 and the sintered body 12 were overlapped with each other via an active metal shell mainly composed of Ni and Ti, and joined by a hot press method (see FIG. 6).

Subsequently, the joined body of the base 11 and the sintered body 12 was processed so that the upper molding surface 13 became convex (see FIG. 7). Furthermore, in order to improve the mold releasability with glass,
The thickness 5 is formed on the molding surface 13 by RF magnetron sputtering.
An AlN film of 000 ° was formed.

In the mold manufactured by the above method, the center of the mold corresponding to the thin portion of the molded product is formed of Si ₃ N _{4 having} poor heat conductivity, and has an effect of preventing sink marks.

According to this embodiment, an active metal mold is used. Although the bonding strength during hot welding is slightly inferior to that of each of the above embodiments, it is a very simple method and can be easily implemented. it can.

The present invention does not limit the material of the members to be joined to the material of the present embodiment, but can be selected from various materials as long as the materials have relatively close linear expansion coefficients and different thermal conductivity. It is. Further, instead of the active metal mold used in the present embodiment, a joining method using silver brazing may be used.

[0023]

Embodiment 4 FIGS. 8 and 9 are sectional views showing this embodiment. A powder 22 as a first material in which a powder of SiC and Si ₃ N ₄ is mixed at a ratio of 1: 1 is placed on a SiC sintered body 21 as a second material, and a Si ₃ N ₄ powder 2 is further placed thereon.
3 (see FIG. 8). In the relationship between the powder 22 and the powder 23, the powder 22 corresponds to the second material,
Corresponds to the first material. Then, this was changed to 10 MPa, 1
HIP processing is performed at 700 ° C. By this processing, SiC
(Thermal conductivity of 0.20 cal / cm · sec · deg) to Si ₃ N ₄ (thermal conductivity of 0.07 cal / cm · sec)
Deg) formed of graded material.

Subsequently, this is processed into a desired molding surface 24 shape. Further, Si is formed on the molding surface 24 by thermal CVD.
A C film 25 is formed to a thickness of 0.2 mm. This SiC film 2
5 is precisely ground and polished to a shape conforming to the molded product. Subsequently, a 6000 ° HfN film 26 was formed on the molding surface 24 by an ion beam sputtering method to improve the releasability (see FIG. 9).

According to this embodiment, the thermal conductivity of the mold gradually changes from the center of the mold corresponding to the thick part of the molded article toward the outer periphery of the mold corresponding to the thin part. The effect of equalizing the temperature to prevent sink marks is extremely large.

(Reference Example) FIGS. 10 and 11 are sectional views showing a reference example. In the reference example, the fourth embodiment differs from the fourth embodiment in that the members are overlapped in the vertical direction, but the members are overlapped in the horizontal direction, and the other components are the same. The description is omitted. In the reference example, a powder 22 of SiC and Si ₃ N ₄ and a Si ₃ N ₄ powder 23 are sequentially superposed on the outer peripheral surface of a cylindrical SiC sintered body 21 so as to be concentric (FIG. 10). reference). Next, the upper end is processed into a desired shape of the molding surface 24 (see FIG. 11). Hereinafter, the configuration is the same as that of the fourth embodiment, and the description of the configuration is omitted.

[0027]

[0028]

[0029]

As described above, according to the optical element molding die and the manufacturing method according to the present invention, it is possible to prevent the occurrence of burrs in the molded product and to prevent the occurrence of sink marks. The mold can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first embodiment.

FIG. 2 is a sectional view showing the first embodiment.

FIG. 3 is a sectional view showing a second embodiment.

FIG. 4 is a sectional view showing a third embodiment.

FIG. 5 is a sectional view showing a third embodiment.

FIG. 6 is a sectional view showing a third embodiment.

FIG. 7 is a sectional view showing a third embodiment.

FIG. 8 is a sectional view showing a fourth embodiment.

FIG. 9 is a sectional view showing a fourth embodiment.

FIG. 10 is a sectional view showing a reference example.

FIG. 11 is a sectional view showing a reference example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 c-BN sintered compact 2 WC-base cemented carbide 3 Joint 4 Molding surface 5 Flange

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C03B 11/00-11/16

Claims (2)

(57) [Claims] 1. An optical element molding die made of two or more types of materials for heat-softening and press-molding a glass material, wherein a first material having a predetermined thermal conductivity is replaced with a first material having a predetermined thermal conductivity. And a joining surface mounted on and joined to a different second material, and a molding surface formed continuously on the first material and the second material so as to cross the joining surface. Mold for molding optical elements. 2. A method of manufacturing a mold for molding an optical element comprising two or more types of materials for heat-softening and press-molding a glass material, wherein a first material having a predetermined thermal conductivity is defined as a first material. Placing on the second material having a different thermal conductivity and joining; and continuously joining the first material and the second material across the joining surface where the first material and the second material are joined. A method of processing a molding surface by using the method.