JPH0716942A - Mold for optical element - Google Patents

Abstract

PURPOSE:To easily release an optical element having good appearance quality from a mold by forming the surface of a part or the whole other than an optical function surface of the molding surface of the optical element from a porous material. CONSTITUTION:The surface of a part or the whole other than the optical function surface of the molding surface of the optical element is formed from a porous material. That is, a mold base material 1 is formed and the molding surface is processed into a desired shape up to a molding surface diameter 2. Next, a stepped part 6 is formed on the outer peripheral side of the diameter 3 of the optical function surface. Next, Cr2O3 is applied to molding processing 23 surfaces 5, 6 by an explosion flame spraying method in a void ratio of 10%. Thereafter, the molding processing surface 5 is ground along with a flame spraying film 7 and exposed to be subjected to grinding processing to be formed into a desired shape. The surface part where the flame spraying film 7 of the processing surface remains is masked and a Cr-N film 8 is applied to other surface by a PV method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die for pressing an optical element such as a lens, a prism or a filter.

[0002]

2. Description of the Related Art In recent years, optical elements such as lenses, prisms and filters have been molded by heating and softening an optical glass material and pressing it with a pair of optical element molding dies opposed to each other. However, this method requires a releasing force for releasing in the step of releasing the press-molded optical element from the mold. As a conventional method for suppressing this releasing force, Japanese Patent Application Laid-Open No. 62-240535 is disclosed. In this method, an optical element molding die is formed of a porous material, and gas is supplied to the interface between the die and the optical element through porous internal fine pores to release the optical element from the molding die.

[0003]

However, in the above-mentioned method, the molding surface of the molding die is also made of a porous material, and when the optical glass element is molded, a fine portion of the molding surface is transferred. Therefore, there is a problem that not only the surface accuracy of the optical element is lowered, but also the surface roughness is increased and the appearance quality as the optical element is deteriorated.

The present invention has been made in view of the above-mentioned conventional problems, and an optical element can be easily released from an optical element molding die after press molding, and an optical element having good appearance quality can be molded. An object of the present invention is to provide a mold for optical element molding that can be performed.

[0005]

In order to solve the above problems, the present invention provides that a part or all of the molding surface for molding an optical element other than the optically functional surface is formed of a porous material. Characterize.

[0006]

In the above structure, the surface other than the optical function surface of the molding surface has a surface made of a porous material.
After the press molding, when releasing the optical element from the mold, gas is supplied between the surface of the optical element and the molding surface of the optical element molding mold through a large number of holes existing inside the porous material. , This creates a thin void due to the gas. And
The release progresses while the voids spread like wedges in the molding surface.

Therefore, as compared with an optical element molding die in which there is no surface made of a porous material in the molding surface, the external force required for releasing the optical element, that is, the so-called releasing force, becomes smaller. Therefore, the occurrence of defects such as cracking of the optical element that occurs when a large releasing force is generated is eliminated. On the other hand, since the optical functional surface of the molding surface is not a porous material, sufficient specularity can be imparted, whereby an optical element with high surface accuracy, low surface roughness and good appearance quality can be molded.

[0008]

Embodiment 1 FIGS. 1 to 3 show Embodiment 1 of the present invention, in which a mold base 1 is formed of a WC-Ni-Cr alloy, and a surface to be a molding surface is processed into a desired shape up to a molding surface diameter 2. To do. Next, a step is formed on the outer peripheral side with respect to the optical function surface diameter 3 and processed into a shape similar to a desired shape for molding. Here, in this embodiment, the molding surface diameter 2 is φ20 mm and the optical function surface diameter 3 is φ1.
The diameter of the stepped portion 6 is 8 mm and the diameter of the stepped portion 6 is 18.5 mm. The desired shape is a U surface with a curvature R = 32.5 mm, a height of the stepped portion is 0.15 mm, and a curvature R of the stepped portion 6 is 32.65 mm. All the molding surfaces 5 and 6 were mirror surfaces, and Rmax was 0.03 mm or less. Next, as shown in FIG. 2, Cr ₂ O ₃ was explosively sprayed onto the formed surfaces 5 and 6 by an explosive spraying method to obtain a porosity of 1 at a thickness of 0.20 mm.
The coating was performed under the condition of 0%. At this time, a thermal spray coating of Ni-Cr or Ni-Al is used as an intermediate layer with the mold base material.
Coated to a thickness of 00 μm. After that, the molding surface was ground together with the sprayed coating 7 to expose the molding surface 5. After that, polishing processing is performed, and the surface roughness of the molding processing surface 5 is Rmax.
= 0.028 μm to obtain a desired shape. At this time, the thermal spray coating coated on the molding surface 6 remains on the molding surface,
The surface roughness was Rmax = 0.18 μm. The surface portion of the processed surface where the thermal spray coating 7 remains is masked, and the Cr-N film 8 is formed on the other surface as shown in FIG.
A film having a thickness of 0.5 μm or less was formed by the VD method.

A glass material having a trade name of SK11 (manufactured by OHARA CORPORATION) was press-molded using the optical element molding die molded in this manner. Then, after molding, the releasing force at the time of releasing was measured. The mold release force was measured by the weight required to separate the mold from the optical element. The mold releasing force in the case where the porous material was not provided on the conventional molding surface was 15 to 30 kgf, whereas the mold releasing force of this example was hardly generated. Further, the appearance quality of the molded optical element is good, and the surface accuracy of the optical function surface is Rmax = 0.027 μm.
The optical performance was sufficiently satisfied. Therefore, the optical element molding die of the present embodiment can suppress the releasing force and ensure the appearance that sufficiently satisfies the optical performance.

[0010]

[Embodiment 2] FIG. 4 shows Embodiment 2 of the present invention, in which a mold base material 1 is molded from an AlN sintered body, and a porous carbon is molded into a ring shape on the outer peripheral portion of the mold base material 1. 10 is provided. The molding surface of this mold was mirror-polished while being combined with the outer peripheral mold 10. By this processing, the molding surface 11 made of the AlN sintered body including the optical function surface has a surface roughness R.
max = 0.032 μm. On the other hand, the molding surface 12 provided on the outer periphery and made of porous carbon has a surface roughness of Rma.
x was 0.15 μm. The outer peripheral die 10 is pressed against the die base material 1 by the die retainer 5 so as not to come off.

In this embodiment, the molding surface 11 of the mold base 1 has a diameter of 22 mm, and the molding surface 12 of the outer peripheral mold 10 has a maximum outer diameter of φ.
24.5 mm, the curvature of the molding surface is R = 28.5 mm
It is the U side of. The glass material of BK7 was press-molded using the optical element molding pattern thus molded. When the releasing force was measured in the same manner as in Example 1, the releasing force was not generated, the appearance quality of the optical element was good, and the surface roughness of the optical functional surface was Rmax = 0.033 μm. Was satisfied enough.

[0012]

INDUSTRIAL APPLICABILITY As described above, the optical element molding die of the present invention can press-mold an optical element having an appearance quality sufficiently satisfying the optical performance, and release it at the time of releasing after the press-molding. The mold force can be suppressed, and since the mold release force is small, troubles during mold release such as continuous molding can be eliminated.
Mass production can be performed efficiently.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a mold substrate in Example 1 of the present invention.

FIG. 2 is a cross-sectional view covering a porous material.

FIG. 3 is a sectional view of the first embodiment of the present invention.

FIG. 4 is a sectional view of a second embodiment of the present invention.

[Explanation of symbols]

 1 type base material 2 molding surface diameter 3 optical functional surface diameter 7 porous material

Claims (1)

[Claims] 1. A mold for molding an optical element, characterized in that a part or all of the surface of the molding surface for molding the optical element other than the optically functional surface is formed of a porous material.