JPH03146427A - Method and mold for forming glass optical element and forming preform - Google Patents

Abstract

PURPOSE:To obtain sufficient transferability without being affected by the shape of a lens by gradually abutting the nonoptical functional surface of a preform against the forming surface of a forming mold corresponding to the former surface and then forming the lens. CONSTITUTION:The upper die 4 having a spherical forming surface 4a and the lower die 3 having an aspherical forming surface 3b are freely reciprocatingly inserted in the sleeve 9 of the forming mold 10. The preform 8 having a nonoptical functional surface 8 consisting of optical functional surfaces 8a and 8b, a shoulder carrying part 8c1 and a shoulder tapered part 8c2 and the nonoptical functional surface 8d consisting of a tapered part on the peripheral side surface is inserted between the upper die 3 and lower die 4. The preform 8 is then pressed by the upper and lower dies 3 and 4 to abut the shoulder 4c of the upper die 4 against the flat part 8c1 of the shoulder 8c of the preform 8, and then gradually abutted from the center of the tapered part 8c2 toward the outer periphery to transfer the shoulder 4c of the upper die 4 to the preform 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to molding of glass optical elements, and in particular,
The present invention relates to a method for molding a meniscus lens having a spherical cutout, a mold, and a molding preform.

[Conventional technology]

Conventionally, when molding a glass optical element, a glass preform (hereinafter simply referred to as PF) having a shape that approximates the shape of the desired final product is set in a preform mold, and the PF is molded under predetermined molding conditions. One method that has been adopted is to press-mold the material in a mold and transfer the molding surface of the mold to the PF.

However, it is known that it is difficult to obtain good transferability when molding a meniscus lens having a spherical cutout by the above method, and as a means to ensure the transferability, PF thickness Development of shape optimization and control of molding conditions such as mold temperature control is underway.

Figure 6 shows a meniscus lens 1 having a spherical cutout.
In this example, this meniscus lens l has lens optically functional surfaces 1a and lb and a non-optically functional surface 1e.

The lens optically functional surface 1a has an aspherical shape, and the non-optically functional surface 1e has a shoulder portion, and the non-optically functional surface 1a has an aspherical shape.
f is the outer peripheral side surface.

In the figure, 1c indicates the medium thickness, and 1d indicates the depth of the cutout.

Therefore, when molding the meniscus lens 1 shown in FIG. 6 by the molding method, a specific example of optimizing the PF thickness shape, which can be cited as a means of improving transferability, is to obtain the desired lens quality, that is, the optical Functional aspect 1a
In order to ensure the shape accuracy of , lb, and the depth d of the medium thickness IC1, the radius of curvature of the optical functional surfaces 2a and 2b of the PF2 shown in Fig. 7, the depth 2d of the medium thickness 2C1, etc. were examined. being done.

For example, when setting the radius of curvature of the optically functional surface 2a of PF2, as shown in FIG. During the molding process, care has been taken to ensure that the glass transfer progresses from the center of the lens to the outer periphery.

Further, in setting the ball cutout depth 2d, as shown in FIG. 9, the relationship with the ball cutout depth 4b of the upper die 4 is taken into consideration.

That is, the notch depth 2d of PF2 is the notch depth 4 of the upper mold 4.
If it is too large compared to b, as shown in FIG. 10, contact will start from the shoulder 2e of the upper mold 4 during molding, resulting in the transfer of the molding surface 4a to the optical functional surface 2a. Before completion, the outer peripheries of the optically functional surface 2a of the PF 2 and the molding surface 3a of the lower mold 3 come into contact with each other, creating a closed chamber gap 6 and causing a transfer failure between the outer periphery and the center.

On the other hand, if the depth 2d of the PF2 is too small compared to the depth 4b of the upper die 4, the shoulder 2e of the PF2 and the shoulder 4C of the upper die 4 will be separated from the PF2 as shown in FIG. In order to avoid sufficient contact with the shoulder portion 2e of the optical functional surface 2a,
This results in poor transfer.

On the other hand, in setting the molding conditions as a means of improving transferability, measures have been taken such as setting the lower mold temperature, which requires a large amount of deformation of the optical functional surface 2a, to be higher than the upper mold temperature.

[Problem to be solved by the invention]

However, the transferability improving means used in the conventional molding method when applied to molding a meniscus lens having a spherical cutout has the following drawbacks.

That is, for example, the optical functional surface 1a of the lens to be molded
If the aspherical shape is such that its outer periphery is suddenly displaced inward with respect to the approximate shape, the lower mold molding surface 3a and the outer periphery of the optically functional surface 2a of PF2 may come into close contact with each other at the start of molding. Therefore, it is difficult to deal with the above-mentioned concept of setting the radius of curvature of the optically functional surface 2a of the PF2 and the depth of the notch 2d, and the concept of setting the molding conditions, and it becomes difficult to obtain sufficient transferability. .

Furthermore, in order to ensure transferability, if the mold temperature and molding pressure are increased too much, the optical functional surfaces 1a and 1b of the molded lens will be placed between the glass and the mold on the molding surfaces 4a and 3b of the upper and lower molds 4.3. If fusion occurs or the lens shoulder 1e or outer peripheral side surface If
This will cause problems.

This can is caused by the difference in the linear expansion coefficient of the PF2 glass and the linear expansion coefficient of the upper mold 4 and the separate mold 5, which have smaller linear expansion coefficients, when the molded lens is cooled. When the molding pressure is too high and the lens and the shoulder 4C of the upper mold 4 or the molding surface 5a of the separate mold 5 come into excessive contact, glass shrinkage is restricted and occurs.

As mentioned above, molding a meniscus lens with a spherical cutout not only requires sufficient consideration of the PF and molding conditions, but also
Depending on the shape of the lens, it is difficult to obtain a product of desired quality.

Therefore, the present invention was developed in view of the problems in the conventional molding methods, and provides a method and molding method for a meniscus lens having a spherical cutout, which can obtain sufficient transferability regardless of the lens shape. The purpose is to provide molds and molding preforms.

[Means and effects for solving the problems] The method for molding a glass optical element of the present invention is a spherical cut-out method in which a preform is press-molded in a mold, and the molding surface of the mold is transferred to the preform. In the method for molding a meniscus lens having a non-optically functional surface of the preform,
The molding surface of the mold corresponding to this non-optical functional surface,
This method is characterized by molding in which the optically functional surfaces of the PF are brought into gradual contact with each other, so that molding progresses with the optically functional surfaces of the PF always in mid-contact with the molding surface of the mold, and the non-optically functional surfaces of the PF are The mold used to carry out the method of the present invention is such that the entire surface does not come into close contact with the molding surface of the mold at the same time. In a mold for a meniscus lens having a spherical cutout portion, which is molded by transferring the above to a preform, the molding surface corresponding to the non-optically functional surface of the preform is, with respect to the non-optically functional surface of the preform,
The molding preform is characterized by having a shape that gradually comes into contact with each other, and the molding preform is a spherical cut-out shape that is formed by press-molding the preform with a mold and transferring the molding surface of the mold to the preform. A preform for molding a meniscus lens having a shape such that a non-optically functional surface of the preform gradually comes into contact with a molding surface of the mold corresponding to the non-optically functional surface. It is characterized by having.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) Fig. 1 is an explanatory diagram showing the first embodiment of the present invention, Fig. 2 is a sectional view of a preform used in its implementation, and Fig. 3 is a sectional view of a meniscus lens after molding. be.

Therefore, the molding die 10 shown in the first figure has an upper and lower mold 4.3 and a separate mold 5 which are housed in the sleeve 9 so as to be movable forward and backward, and the molding surfaces 4a and 3a of the upper and lower molds 4.3 are eccentric between the surfaces. is guaranteed by the sleeve 9, the molding surface 4a of the upper mold 4 has a spherical shape, and the molding surface 3a of the lower mold 3 has an aspherical shape.

Furthermore, as shown in FIG. 2, the PF8 used in this example has optical functional surfaces 8a and 8b and non-optical functional surfaces 8c and 8d.
The non-optically functional surface 8C is composed of a shoulder assembly 8c+ and a shoulder taper aCt, and the non-optically functional surface 8d is composed of an outer peripheral side tapered part, and the angle formed by the shoulder taper part 8C8 is 2° from the outer periphery. The side tapered portion 8d is formed at an angle of 2° inward with respect to the central axis.

An example of the shape and dimensions of the PF8 is as follows.

Outer diameter (8g) φ15aa Ball notch diameter (8h) φ5m Ball notch depth (8f) 3111 Medium thickness (8e) 6-shoulder flat part (8cl) 1m Now, with the mold 10 consisting of the above TL power, PF8
A method of forming the meniscus lens 11 into a T-shape using the following will be described below.

First, as shown in FIG. 1, the PF 8 is set between the upper and lower molds 4.3 of the mold 10.

Thereafter, when the PF8 is press-molded using the upper and lower molds 4.3 under predetermined molding conditions, the shoulder 4c of the upper mold 4 and the shoulder 8 of the PF8 are formed.
c, first the flat part 9c contacts, and then the tapered part 8c8
are brought into contact gradually from the center toward the outer periphery.

On the other hand, regarding the molding surface 3a of the lower mold 3 and the optical functional surface 8a of the PF8, the chi? Since the outer circumferential portion of the shoulder portion 4c of the upper die 4 does not come into contact with the outer circumferential portion 8c of the upper die 4, no force is generated that would cause the outer circumferential portions of the optical functional surface 8a and the molding surface 3a of the lower die 3 to come into contact with each other. , molding progresses always in the middle contact state, and good transferability is ensured.

In addition, the shoulder 8C of the PF8 and the outer circumferential side 8d have a taper, so that the shoulder 8C of the PF8, the shoulder 4C of the upper mold 4, the outer circumferential side 8d of the PF8, and the molding surface 5a of the separate mold 5
The two do not come into close contact with each other over the entire surface, and the formation of cans due to restraint during glass shrinkage is prevented.

The shoulder portion 11a of the lens 11 after molding is mostly flat, although a slight tapered portion 11a2 may remain on the outer periphery due to the transfer of the shoulder portion 4C of the upper mold 4, as shown in FIG. Although a tapered portion r 1 bz may remain on the outer circumferential side surface 11b, most of it becomes a surface 11b parallel to the central axis due to the transfer of the molding surface 5a of the separate mold 5.

Therefore, the reference surface when assembling the lens 11 is the outer peripheral side surface 11b1 in the radial direction, and the shoulder flat portion 11a in the optical axis direction.
It is possible to use l as is.

(Second Embodiment) FIG. 4 is an explanatory diagram showing a second embodiment of the present invention, and FIG. 5 is a sectional view of a lens after molding.

Therefore, in the groove bottom of the mold lO used in this example, the upper mold 12 has a molding surface shoulder 12a that is connected to the shoulder 13 of the PF13.
2 in the direction in which the gap with a opens from the center toward the outer periphery.
The point formed by the tapered part with an angle of 1 is the 1st point.
This is different from the upper mold 4 of the embodiment, but other configurations are the same, and the same components are given the same numbers and their explanations will be omitted.

Furthermore, the shape of the PF13 used in this embodiment is the same as that of the first embodiment except for the shape of the shoulder portion 8C of the PF8, and the description of the shape and specific dimensions are as follows. Omitted.

The shoulder portion 13a of the PF 13 is formed by a flat portion, and the outer circumferential side surface 13b is formed by a tapered portion having an angle of 2@ inward with respect to the central axis, similar to the outer circumferential side surface 8d of the PF8.

Therefore, when molding the lens 14 using the PF 13 having the above shape with the mold 10 having these configurations, the PF 1 is placed between the upper and lower molds 12.3 as in the first embodiment.
After setting 3, press molding is performed under predetermined molding conditions. In the molding process, molding progresses in a mid-hit state, ensuring good transferability and easy operation. It also prevents the occurrence of

As shown in FIG. 5, the lens 14 molded in this example may have a slight flat portion 14a remaining on the outer periphery of the shoulder portion 12a due to the transfer of the shoulder portion 12a of the upper mold 12. However, most of the portion is formed as a tapered portion 14a+, and the outer circumferential side surface 14b is a surface parallel to the central axis as in the first embodiment.

From the above points, when using the molding method in this example, if an assembly reference surface in the optical axis direction is not required when assembling the lens 14, there is an advantage that a PF with a simpler shape that is cheaper than the first example can be molded. have

In the above description, in the example, a case was described in which the molding surface of the PF or the molding die was configured with a taper, but instead of this, the same could be achieved by providing an R shape with an appropriate curvature. Furthermore, in the first embodiment, a required configuration is given to the shape of the PF, and in the second embodiment, a case will be described in which the required configuration is given to both the PF and the mold. However, it is also possible to implement the method by providing only the configuration of the mold with a configuration that allows the molding surface to gradually come into contact with the non-optically functional surface of the preform (for example, a configuration in which the tapered portion or the rounded portion is provided). Of course it is possible.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, conventionally,
Even aspherical lenses, for which it has been difficult to obtain good transferability, can now be molded under reasonable temperature and pressure conditions, and the molded lens is not restrained by the mold during cooling shrinkage, causing cans. Furthermore, since smooth transfer proceeds under relatively low temperature and low pressure conditions, defects such as fusion between the glass and the mold can be reduced and the life of the mold can be extended.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a first embodiment of the present invention, Fig. 2 is a cross-sectional view of a preform used in its implementation, Fig. 3 is a cross-sectional view of a meniscus lens after molding, and Fig. 4 is an explanatory diagram of the present invention. the second of
FIG. 5 is a cross-sectional view of a lens after molding, and FIGS. 6 to 11 are explanatory views showing a conventional method of molding a meniscus lens having a spherical cutout. 11゜14... Meniscus lens with a spherical cutout 13... Preform 2, 8゜3... Lower die 4.12... Upper die 5... Body wall 9... Sleeve 10.・Molding mold

Claims (3)

[Claims] (1) A method for molding a meniscus lens having a spherical cutout, which is formed by press-molding a preform with a mold and transferring the molding surface of the mold to the preform, wherein the non-optically functional surface of the preform and A method for molding a glass optical element, characterized in that molding is carried out by gradually bringing the non-optically functional surface and the corresponding molding surface of the mold into contact with each other. (2) In a mold for a meniscus lens having a spherical cutout, which is formed by press-molding a preform with a mold and transferring the molding surface of the mold to the preform, on the non-optically functional surface of the preform. The corresponding molding surface is
A mold for a glass optical element, characterized in that it has a shape that gradually comes into contact with a non-optically functional surface of the preform. (3) In a preform for molding a meniscus lens having a spherical cutout, which is formed by press-molding the preform with a mold and transferring the molding surface of the mold to the preform, the preform has a non-optical function. A preform for molding a glass optical element, characterized in that a surface has a shape that gradually comes into contact with a molding surface of the mold, which corresponds to the non-optically functional surface.