JPH01316252A - Forming method for optical element - Google Patents

Abstract

PURPOSE:To improve transferability of a molded surface and form a desired optical element easily by pinching a material to be processed composed of optical thermoplastic resin by upper and lower punches, heat softening the material to be processed while reverse phase vibration is applied to the upper and lower punched respectively and respective molded surfaces are transferred to the material to be processed while the intervals of respective molded surfaces are narrowed. CONSTITUTION:A spherical material 25 to be molded which is composed of thermoplastic resin is fed and placed on a molding surface 17a of a lower punch 17 and the material 25 to be molded is pinched by upper and lower punches 16 and 17. Guide components 23 and 24 are controlled to be brought into contact with each other, and upper and lower vibration actuators 3 and 4 are actuated to vibrate the upper and lower punches 16 and 17. At that time, vibration phases of the upper and lower punches 16 and 17 are reverse, and the material 25 to be molded is heat softened by vibration. During said vibration, the material 25 to be molded is pressurized through the upper and lower punches 16 and 17 wherein the interval is made narrow by means of pressure P generated by the upper and lower molding actuators 14 and 15. The shapes of the molding surfaces 16a and 17a of the upper and lower punches 16 and 17 are transferred to the material 25 to be molded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for molding an optical element using vibration, and in particular to a method in which the molding surfaces of upper and lower punches are transferred to a workpiece made of a thermoplastic resin by vibration. The present invention relates to a method for molding an optical element.

[Conventional technology]

Methods for obtaining optical elements made of plastic include injection molding, casting, etc., direct cutting of a material blank with a cutting tool such as a diamond, and the molding process is shown in Figures 5a, b, and c. With the thermoplastic plastic flat plate 40 fixed with the upper and lower dies 41, 42 (Figure a), by vibrating the upper and lower punches 43, 44 while pressing the flat plate 40 (Figure b), heat due to self-heating is generated in the flat plate 40. There is a so-called vibration thermoforming method (Japanese Patent Application No. 62-224719), which is softened and punched into a desired finished surface shape 47 at each molding surface 45 and 46 (Figure C).

From these methods, processing is performed by selecting the most suitable method for the optical element to be processed.

[Problem to be solved by the invention]

However, the conventional technology has the following problems. The injection molding method requires a large amount of capital investment in molding molds and molding equipment, and the injection molding process requires good transfer of the lens surface shape when the molded product is cooled and hardened after injecting the molten resin. There was a problem in that it was difficult to control the pressure adjustment, etc. In addition, in the case of casting, the mold is cheaper, but since the resin is solidified and molded without applying pressure, there is a problem that the resin shrinks and the molded surface cannot be transferred well in thick parts. There is a limit to the surface accuracy, and increasing the surface accuracy requires a long machining process and processing time. Furthermore, in the prior art molding method for plano-convex lenses by vibration thermoforming, as shown in FIG. 5, the molding surface 45 of the upper punch 43 is concave, and the molding surface 46 of the lower punch 44 is flat. Therefore, since the molding proceeds with air remaining in the space 48 formed by the concave surface of the upper punch 43 and the flat plate (workpiece) 40, the concave surface is sufficiently transferred to the molded product. However, poor appearance occurred and the desired optical performance could not be obtained. This phenomenon also applies to biconvex lenses. In particular, as shown in Fig. 6, the upper punch 4
Since heat generated by vibration is propagated to the workpiece 40 as shown by the wavy line around the outer peripheral edge (land portion) 49 of the molding surface of No. 3, the entire molding surface of the workpiece is uniformly spread. It is difficult to heat the product to a high temperature, and it is also likely to cause poor appearance.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for molding an optical element that has good transferability on a molding surface and can be easily molded into a desired optical element.

[Means and effects for solving the problem] In the vibratory thermoforming method, the present invention provides an upper punch and a lower punch that vibrate in opposite phases and come into contact with the workpiece at the center of the forming surface in the early stage of forming. This eliminates the air-retaining space formed by the forming surfaces of the upper and lower punches and the workpiece, thereby improving the transferability and formability of the forming surface.

〔Example〕

Hereinafter, the present invention will be explained in detail based on examples.

(First Example) FIG. 1 is an explanatory cross-sectional view of a molding apparatus 1 for carrying out the method for molding a biconvex lens according to the present invention.

In the figure, a support base (fixed base) 2 of a molding device 1 is connected to an upper vibration frame 5.4 via opposing upper and lower vibration actuators 3.4. A lower vibration excitation frame 6 is equipped to freely excite. The upper vibration frame 5 has three sliding shafts 7 parallel to each other.
(two shafts are shown in the figure), and each sliding shaft portion 7 is slidably fitted into a guide hole portion 8 on the lower vibration excitation frame 6 side. Spring receiving portions 9 and 10 are formed at the base of the sliding shaft portion 7 and the entrance portion of the guide hole portion 8, respectively, and a compression coil spring 11 is interposed between the upper excitation frame 5. Lower vibration frame 6
are biased so that they are opposite to each other.

The upper and lower excitation frames 5.6 are equipped with upper-bottom actuator 1.
4. Lower forming actuators 15 are fixedly mounted at opposing positions, and a removable upper punch 16 is provided at the end of each actuator 14, 15 with forming surfaces 16a, 17a.
．． The lower punches 17 are attached respectively. Therefore, the upper and lower punches 16 and 17 are on the same axis and are configured to be freely movable and driven in the axial direction via the respective forming actuators 14 and 15. The upper and lower vibration actuators 3.4 and the upper and lower molding actuators 14.15 are connected to a hydraulic control device 22 via hydraulic control pipes 18, 19, 20.21, and the upper and lower punches 16.17 are hydraulically connected. Control device 2
2, the operation is controlled in opposite phases, that is, in the directions of approaching and departing from each other. The forming apparatus 1 also includes guide members 23.2 provided around the upper and lower punches 16.17 so as to slide and guide the upper and lower punches 16.17.
4 are arranged, and are controlled by a hydraulic control device 1e (22) to contact or separate via respective actuators (not shown) attached to the support base 2.

Next, a method of molding a lens using the lens molding apparatus 1 having the above configuration will be described. First, the guide member 23
．． 24, the upper and lower punches 16.17 are controlled to move in the opposite direction via the upper and lower forming actuators 14.15. Then, the molded product 1 of the lower punch 17
A spherical molded body (workpiece) 25 made of thermoplastic resin is supplied and placed on 7a. Next, the upper and lower punches 16.
17 is actuated via the upper and lower molding actuators 14 and 15 to clamp the object 25 to be molded.

Then, the guide members 23 and 24 are controlled so as to come into contact with each other (
Fig. 2 a state). Next, the upper and lower vibration actuators 3.4
is activated to vibrate the upper and lower punches 16°17 via the upper and lower forming actuators 14 and 15. During this vibration operation, the vibration phases of the upper and lower punches 16 and 17 are opposite to each other as shown by the arrows in FIG. and,
During this vibration, the upper and lower punches 16 and 17 are subjected to pressure P by the upper and lower molding actuators 14 and 15, narrowing the gap.
Pressure is applied to the object 25 through the pressurizer (the state shown in FIG. 2).

Through this vibration pressing step, the shapes of the forming surfaces 16a and 17a of the upper and lower punches 16 and 17 are transferred to the object to be formed 25, respectively.

As described above, according to the molding method of this embodiment, the molded object 25 having a spherical surface first contacts the center portions of the molding surfaces 16a and 17a of the upper and lower bonders 16 and 17 (so-called middle contact). During molding, air is not trapped between the molding surfaces 16a, 17a and the object to be molded 25, the molding surfaces 16a, 17a are transferred well, and a lens having a highly accurate surface shape can be molded.

In addition, in the above embodiment, the vibration actuator 3,
4 was kept constant, but when the object 25 to be formed is thermally softened and vibration pressure is applied by the upper and lower forming actuators 14 and 15, the frequency is gradually decreased from the point when the desired amount of deformation is reached, or By applying vibration pressure while vibrating intermittently and gradually reducing the deformed area due to thermal softening, extremely good transfer of the molding surfaces 16a and 17a to the molded object 25 can be achieved. In addition, the sliding shaft part 9° guide hole lO
Of course, the number can be changed as appropriate. In the above embodiment, the guide member 2 is provided around the upper and lower punches 16 and 17.
3.24, but if the object to be formed 25 does not fall from above the forming surface 17a of the lower punch 17, the guide member 23
There is no need for ゜24.

(Second Embodiment) FIGS. 3a and 3b are cross-sectional views showing the main parts of a molding apparatus of a second embodiment of the lens molding method according to the present invention, and FIG. 4 is a perspective view of the vicinity of the molding part of the upper and lower punches. It is.

In this example, the end faces (forming surfaces) of the upper and lower punches 26 and 27 are
Land portions 28 and 29 are provided in each of the land portions 28 and 29, and cutouts 30 and 31 are formed in a portion of each land portion. This cutout 30.31
is an escape space 32 in which excess resin that is compressed during vibration thermoforming of the workpiece 25 can be stored.

Since the other configurations are the same as those of the first embodiment, illustration and description thereof will be omitted. Incidentally, a plurality of notches 30.degree. 31 may be provided on the land portions 28 and 29, and the positions thereof may be changed or the shapes thereof may be changed (FIG. 4).

The molding process of this example is the same as that of the first example, but according to this example, the excess resin is stored in the notches 30 and 31, so the internal stress of the molded product is reduced.
Furthermore, it is possible to mold the lens 33 which is preferable in terms of optical performance. Furthermore, when compressing the workpiece 25 with the upper and lower punches 26, 27, each molding actuator 14, 15 can press until the land portions 28, 29 come into contact with each other, so that the thickness of each molded product obtained is It is also possible to eliminate variations in thickness. Furthermore, it becomes possible to classify the types of lenses based on the position and shape of the notches.

In addition, the above 1. In the second example, a spherical optical thermoplastic resin was used as the workpiece, but the invention is not limited to this.
When the molding surfaces of the upper and lower punches are surrounded by guide members, long rod-shaped objects such as rondo lenses can also be molded.

In this case, if the molding surface is a concave surface, the end surface of the rod-shaped workpiece may be a convex object having a radius of curvature smaller than the radius of curvature of the concave surface. Further, when the molding surface is a convex surface, the end surface of the rod-shaped workpiece may be a concave object having a radius of curvature larger than the radius of curvature of the convex surface, a flat surface, or an appropriate convex object.

(Effect of the invention) By using a so-called middle workpiece that initially comes into contact with the center of each forming surface of the upper and lower punches, there is a gap between each forming surface of the upper and lower punches and the workpiece. ,
Since no air is trapped during vibration thermoforming, the respective molding surfaces are transferred well, and an optical element with a good appearance can be obtained.

In addition, especially for mid-to-high optical elements, heating is performed from the center of the molding surface (the thick part of the molded object), so the entire workpiece can be heated uniformly, and it is possible to avoid defects in appearance. It is also possible to obtain molded products without

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram of a molding apparatus for implementing the lens molding method according to the present invention, FIGS. 2 a and b are process explanatory diagrams,
3a and 3b are cross-sectional explanatory views of essential parts of a molding apparatus according to a second embodiment of the molding method according to the present invention, FIG. 4 is a perspective view of the vicinity of the molding section, and FIGS. 5 and 6 are based on the prior art. It is such an explanatory diagram. 1...Forming device 2...Support stand 3...Upper vibration actuator 4...Lower vibration actuator 5...Upper vibration frame 6...Lower vibration frame 14...Lower molding Actuator 15... Lower forming actuator 16.26... Upper punch 17.27... Lower punch 16a, 17a... Forming surface 23.24... Guide member 30.31... Notch Patent application People Olympus Optical Industry Co., Ltd. Figure 2 (a) (b) Figure 5

Claims (1)

[Scope of Claim] In a method of molding an optical element while thermally softening a workpiece held between upper and lower punches by vibration, an optical element that contacts at the center of each molding surface of the upper punch and the lower punch. A workpiece made of thermoplastic resin is placed on the lower punch, the workpiece is held between the upper and lower punches, and the workpiece is heated while applying vibrations of opposite phase to the upper and lower punches. A method for molding an optical element, characterized by transferring each molding surface onto a workpiece while softening and narrowing the interval between the molding surfaces.