JPH04219331A - Method for molding optical element - Google Patents

Abstract

PURPOSE:To carry out press molding without requiring much flow and improve durability of a mold by acting bending force on a glass element when a glass raw material heated and softened is molded under pressure. CONSTITUTION:A glass raw material 1 heated and softened is put between a fixed upper mold 2 and vertically movable lower mold 3. Then press molding of the glass raw material 1 is carried out by raising the lower mold 3. The peripheral part 1a outside optical function face in the glass raw material 1 is vertically pressed during press molding process or after press molding process.

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 method in which a glass material softened by heating is press-molded using a pair of dies.

0002

2. Description of the Related Art Conventionally, the following invention has been disclosed as a method for press-molding a glass material softened by heating using a pair of molds.

For example, in the invention described in JP-A-61-146723, when molding an aspherical lens,
A method of molding using a glass material having a shape similar to the shape of the aspherical lens has been proposed.

0004

[Problems to be Solved by the Invention] However, even when glass materials with similar shapes are used, it is difficult to obtain highly accurate transferability when attempting to mold a lens with a large amount of aspherical surface. In order to obtain high-precision transferability, the heating temperature of the glass material is raised even higher to reduce its viscosity.
Operations such as raising the mold temperature, increasing the pressing load, and providing a sufficient annealing time are required. This operation is significantly detrimental to the durability of the mold. Furthermore, there is a drawback that the cycle time increases due to the extension of the annealing time. Furthermore, a similar drawback occurs when a lens with a small radius of curvature requires an assembly surface.

Furthermore, even if the shape of the glass material is approximated to the shape of an aspherical lens, a gap is created between the glass material and the aspherical mold. The gap must be filled by the flow of the glass due to pressure, and this flow promotes a reaction at the interface between the mold and the glass, deteriorating the durability of the mold.

[0006] Therefore, the present invention was developed in view of the drawbacks of the prior art, and uses a glass material having an approximate shape to mold a lens with a large amount of aspherical surface or a lens with an assembly surface. The purpose of the present invention is to provide an optical element molding method that can efficiently perform high-precision molding.

[0007]

[Means for Solving the Problems] The present invention includes a step of heating a glass material, a step of conveying it between a pair of molds, and a step of pressing, and the glass material softened by heating is heated between a pair of molds. In an optical element molding method in which molding is performed by pressing, the outer periphery of the glass material outside the optically functional surface is pressed in the pressing direction of the mold during and/or after the pressing step.

FIG. 1 is a conceptual diagram of an optical element molding method according to the present invention.

Reference numeral 1 denotes a heated and softened glass material, and this glass material 1 is placed between a fixed upper mold 2 and a vertically movable lower mold 3. Then, the lower mold 3 is raised to perform press molding. During or after this pressing step, the outer peripheral portion 1a of the glass material 1 outside the optically functional surface is pressed upward to perform molding.

0010

[Operation] In the present invention, the outer peripheral portion of the glass material outside the optically functional surface is pressed during or after the step of pressing the glass material. By this pressing, it is possible to apply not only deformation due to glass flow but also deformation due to bending force to the optically functional surface.

That is, the gap created between the glass material and the aspherical mold can be interpolated not only by deformation due to the flow of the glass, but also by adding deformation due to bending force.

0012

Embodiments Hereinafter, embodiments of the optical element molding method according to the present invention will be described in detail with reference to the drawings.

[0013]

Embodiment 1 FIG. 2 is a partial longitudinal sectional view of an apparatus used in a first embodiment of the optical element molding method according to the present invention.

Reference numeral 11 denotes an aspherical upper mold which is fixedly held, and a lower mold 12 is held below the upper mold 11 and is disposed opposite to the upper mold 11 on the same axis line so as to be vertically movable. . A ring 13 is fitted on the outer peripheral surface of the lower mold 12, and a substantially cylindrical carrier 14 having a stepped portion 14a formed on the inner peripheral surface is placed on the upper part of the ring 13. The position of the conveyor 14 relative to the lower mold 12 is regulated by a ring 13.

[0015] In the forming method using the apparatus having the above configuration, first, the glass material 15 is placed on the conveyor 14, and after heating it in a heating furnace (not shown) to around its softening point,
It is transported and placed on the ring 13 fitted around the outer periphery of the lower mold 12 (see FIG. 2). At this time, the glass material 15 is transferred to the conveyor 14.
The position is determined by a ring 13 fitted to the outer periphery of the lower die 12 via the ring 13 . Further, the bottom dead center of the conveyor 14 is determined by the ring 13, and in the positioning state, the glass material 15 and the lower die 12 have a gap and do not come into contact with each other.

In this state, the lower mold 12 and the ring 13 are raised together, and the glass material 15 placed on the conveyor 14 is
The upper surface of the mold is brought into contact with the molding surface of the upper mold 11 (see FIG. 3).

Furthermore, when the lower mold 12 and the ring 13 are raised together, the glass material 15 is bent upward by the stepped portion 14a of the carrier 14 (see FIG. 4).
Press molded (see Figure 5).

Further, during the press molding in the above process (see FIG. 5), when the upper mold 11 and the lower mold 12 reach the predetermined lens thickness position, only the ring 13 is raised and the conveying tool 14 is moved. lift. Then, an upward bending action occurs on the glass material 15 due to the stepped portion 14a of the carrier 14 (see FIG. 6).
reference).

Hereinafter, the molded aspherical lens 16 (see FIG. 7) according to this embodiment has an outer diameter of 16 mm, a medium thickness of 3.2 mm, and is biconvex and has an aspherical surface amount of 150 μm that is spaced apart toward the outer circumference with respect to the paraxial R. A molding example is shown.

The portion of the glass material 15 used for molding that corresponds to the molding surface of the upper die 11 is an aspherical spherical surface with a paraxial radius (shown by a broken line in FIG. 7). Therefore, there is a gap of approximately 150 μm between the upper mold 11 and the glass material 15 near the outer periphery.

Furthermore, the bottom dead center of the conveyor 14 is determined by simulation taking into account the aspherical amount, the paraxial radius, the spherical radius, the outer diameter of the lens, etc. The bottom dead center of the gap between the glass material 15 and the lower mold 12 was set to 0.5 mm.

[0022] When press molding is performed in this state, the conveyor 14
The upper mold 11 is attached to the glass material 15 which is supported on the outer periphery by
A bending action is exerted by the pressure. At this time, since the upper mold 11 near the outer periphery and the glass material 15 are separated by about 150 μm, pressure is applied to the upper mold 11 side of the glass material 15 from near the center. Further, the portion of the glass material 15 corresponding to the lower mold 12 is processed to have a spherical shape that is almost similar to the shape of the lower mold 12, and is formed so that the lower mold 12 and the glass material 15 are in even contact with each other without any gaps. ing. Here, due to the action of the bending force, the glass material 15 warps upward toward the upper mold 11, so that a gap actually occurs between the lower mold 12 and the glass material 15 when pressed.

[0023] When molded in this way, the glass material 15
On the aspherical side of the glass material 15, the aspherical region on the outer periphery is reliably transferred by the action of bending force, which reduces the heating energy for the glass material 15, reduces the pressing load, and It is possible to shorten the pressing time. Normally, the heating temperature of the glass material 15 is set according to the amount of asphericity, so the spherical side of the glass material 15 is pressed and fluidized more than necessary. However, by applying a bending force, the heating energy can be reduced, and the flow from the center can be pressed to a minimum.

[0024] When the amount of asphericity is large, the glass material 1
The heating temperature of step 5 was raised to lower the viscosity, the mold temperature was raised, or the pressing load was increased.
It was possible to perform the molding under the molding conditions for around 75 μm compared to the molding conditions for 50 μm.

According to this embodiment, even in the case of a lens with a large amount of aspherical surface, it is not necessary to ensure transferability by a large amount of flow, and the durability of the mold can be greatly improved.

[0026]

[Embodiment 2] This embodiment has the same structure as the first embodiment, and the explanation of the structure will be omitted.

Hereinafter, the single-sided aspherical lens 17 according to this embodiment has an outer diameter of φ14 mm, a medium thickness of 1.6 mm, and is biconcave and has an aspherical surface amount of 85 μm that escapes inward toward the outer circumference with respect to the paraxial R.
(See FIG. 8) shows an example of molding.

In this embodiment, the lower mold 12 is an aspherical mold, and the surface of the glass material 15 corresponding to the lower mold 12 side is an aspherical spherical surface with a paraxial R (shown by a broken line in FIG. 8). ing. The surface corresponding to the spherical side (the side of the upper die 11) is processed to approximate the surface of the upper die 11.

The glass material 15 is conveyed between the upper and lower molds 11 and 12 by a conveyor 14 and positioned by a ring 13 fitted around the outer periphery of the lower mold 12.
It is fixed at the bottom dead center determined by. In this state, the glass material 15 and the lower mold 12 do not come into contact with each other.

As the lower die 12 rises, the glass material 15, which is pressed by the upper die 11 and whose outer periphery is supported by the carrier 14, is deformed by the bending force. If pressing is performed with the paraxial radius unchanged as in the conventional method, the glass material 15 and the lower die 12 come into contact first at their outer peripheries, making it impossible for air to escape at the center, resulting in deterioration of transferability. However, in this embodiment, due to the deformation of the bending force, the radius of the outer periphery increases, so that the outer periphery does not come into contact first. Further, the shape is approximately approximate to an aspherical shape.

According to this embodiment, the bending force causes the glass material 15 to have a shape that is more similar to an aspherical shape than the paraxial radius before being pressed, making it possible to avoid forming due to a large amount of flow, and to improve mold durability. It can greatly contribute to improving sexual performance.

[0032]

Embodiment 3 FIG. 9 is a partial vertical sectional view of an apparatus used in Embodiment 3 of the optical element molding method according to the present invention.

[0033] In this example, the upper mold 1 in Example 1 is
The difference is that an impact surface 18 is formed on the outer peripheral surface of the lower part of the first embodiment, and the other configurations are the same, so the same components are given the same numbers and the explanation thereof will be omitted.

In this embodiment, an assembly surface is added to the lens 15, and the structure and operation are the same as those of the first embodiment, so a description thereof will be omitted.

According to this embodiment, it is possible to make the glass flow to the impact surface 18 of the upper mold 11, which was difficult in the conventional molding method, by reducing the viscosity of the glass by the action of bending force and Molding can be carried out without adversely affecting the durability of the mold, such as raising the temperature or increasing the pressing force.

[0036]

[Effects of the Invention] As explained above, according to the optical element molding method according to the present invention, a lens having a large amount of aspherical surface can be press-molded without requiring a large amount of flow, and mold durability can be improved. .

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an optical element molding method according to the present invention.

FIG. 2 is a partial vertical sectional view of the device used in Example 1.

FIG. 3 is a partial vertical cross-sectional view of the device used in Example 1.

FIG. 4 is a partial vertical sectional view of the device used in Example 1.

FIG. 5 is a partial vertical sectional view of the device used in Example 1.

FIG. 6 is a partial vertical cross-sectional view of the device used in Example 1.

7 is a side view of a lens molded in Example 1. FIG.

8 is a side view of a lens molded in Example 2. FIG.

9 is a partial longitudinal sectional view of the device used in Example 3. FIG.

[Explanation of symbols]

1 Glass material 2 Upper mold 3 Lower mold 11 Upper mold 12 Lower mold 13 Ring 14 Transport equipment 15 Glass material 16 Lens 17 Lens 18 Collision

Claims (1)

[Claims] Claim 1: An optical element that comprises the steps of heating a glass material, transporting it between a pair of molds, and pressing the glass material, and molding the glass material by pressing the softened glass material between the pair of molds. In the molding method, during the pressing step and/or
Alternatively, an optical element molding method characterized in that after the pressing step, the outer peripheral part of the glass material outside the optically functional surface is pressed in the pressing direction of the mold.