JPH03295822A - Method of forming optical element - Google Patents

Abstract

PURPOSE:To produce an optical element having no cooling strain and to reduce the time for cooling by providing processes of precooling, rapid heating, compression heating and cooling. CONSTITUTION:A plastic forming material 1 is mounted on a hole 2 of a carrier 3 and carried from a path 20 to a cooling furnace 5 to be precooled. Since the furnace 5 is preliminarily supplied with cool air from a cooler 4 to certain temp., the material 1 is cooled as soon as it is put into the surface, and is enough cooled to the inside area. Then the material 1 is carried from the furnace 5 through a path 21 and rapidly inserted to the adjacent heating furnace 7 through a path 22, where only the surface of the material 1 is rapidly heated. Then the material 1 is carried from the furnace 7 through a path 23 and sent to between upper and lower dies 5a, 8b of the adjacent forming die machine, where the material is subjected to compression heating between the dies. Then the material 1 as molded is cooled by upper and lower temp. controller 9a, 9b and then released.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding an optical element formed by heat compression molding.

[Conventional technology]

A method of manufacturing an optical element having relatively large dimensions and a large thickness deviation is proposed in Japanese Patent Publication No. 139336 and Japanese Patent Publication No. 139337. The technical content of the above publication will be explained below.

In the former technique disclosed in Japanese Patent Publication No. 139336, a molding material is molded in a casting mold by bulk polymerization. In addition, the latter, namely, Tokuho 1393
The technique disclosed in Japanese Patent No. 37 discloses a manufacturing method in which a molded material is molded by injection molding and then cut into a predetermined shape using a lathe or an NC lathe.

The technology in each of the above-mentioned publications is that the molding material that has been formed or formed in each process is heated in advance to a temperature that minimizes the stress strain of the material in a compression molding mold having a predetermined shape. Store it. The internal temperature of the stored molding material is 10°C higher than the glass transition point of the molding material, and the temperature near the surface of the molding material is approximately equal to the compression molding mold temperature, so that the internal temperature of the molding material is increased. When the temperature is lower than the temperature near the surface, only the area near the surface of the molding material is melted into a fluid state. At this point, compression molding is performed and at the same time cooling of the mold is started, and after reaching a temperature at which the molded product can be taken out, the mold is opened and the molded optical element is taken out.

[Problem to be solved by the invention]

The above-mentioned Japanese Patent Publication No. 139336 and Japanese Patent Publication No. 1393
In the method for manufacturing an optical element disclosed in Publication No. 37, the temperature of the molding material is raised to at least 10° C. higher than the glass transition point of the molding material. Generally, when a molding material is cooled in a mold, cooling starts from the surface of the molding material. Therefore, even if the surface is sufficiently cooled, heat remains inside the thick portion. Therefore, a temperature distribution occurs in the molding material, causing a difference in the amount of shrinkage between the thin wall portion and the thick wall portion.This difference in shrinkage amount causes distortion in the optical element to be molded.

The present invention has been made in consideration of these problems.
It is an object of the present invention to provide a method for molding an optical element with high precision and less distortion by quickly improving distortion due to non-uniform cooling of a molding material by heat compression molding.

Means and operation for solving CFllB] The present invention includes a pre-cooling process in which a molding material that has been previously processed or molded into a predetermined shape is cooled in a cooling furnace, and a cooling process that instantly cools the molding material cooled in this cooling process. A rapid heating step in which the molding material heated in this rapid heating step is heated and compressed in a heating compression mold and cooled, and the molding material cooled in this heating compression and cooling step is heated. This is a method of molding an optical element, which includes a step of taking it out from a compression mold.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

In each embodiment, the same configuration and members are designated by the same reference numerals, and the explanation thereof will be given in the first embodiment and will be omitted in other embodiments.

(First Embodiment) Figures 1(a), (■), (C), and (b) show a first embodiment of an optical element according to the present invention, and explain the main parts of each molding process of the molding method. FIG. 3 is a sectional view taken from the front;

The box shape shown in FIG. 1(a) is a cooling furnace 5 for cooling the material to be formed. Conveyance paths 20.degree. 21 for conveying the material to be formed are formed on the left and right walls of the cooling furnace 5. Further, a cooling device 4 for cooling the inside of the cooling furnace 5 and cooling the material 1 to be formed is disposed above the cooling furnace 5 .

A hole 2 is bored at the tip of the transport path 20.21 for transporting the material to be formed 1, which is smaller in area (diameter) than the forming material 1 and larger in diameter than the molding dies 8a and 8b of the forming material 1. As shown in the figure, the belt-shaped conveyance member 3 is connected to the conveyance path 2 on the left side wall.
0 to the conveyance path 21 on the right side wall.

As shown in FIG. 1(B), a box-shaped box adjacent to the cooling furnace 5 is a heating furnace 7 that heats the material 1 to be formed.

Conveyance paths 22 and 23 for conveying the material to be formed 1 are formed on the left and right side wall surfaces of the heating furnace 7, in the same way as the cooling furnace 5, respectively. Furthermore, a heating device 6 is disposed at an upper portion of the heating furnace 7 to rapidly heat the inside of the main body 7 and heat the material 1 to be formed that is being conveyed.

Further, as shown in FIG. 1(C), a pair of molds for heating compression molding and cooling are disposed adjacent to the heating furnace 7. That is, an upper mold 8a whose distal end surface is formed into a predetermined concave shape is attached at its base end to the fixing device 24 via an upper temperature controller. Further, at a position corresponding to the upper mold 8a, a lower mold 8b having a predetermined concave shape at its tip end is connected to the air cylinder 10 via a lower temperature controller 9b at its base end. However, the molding material 1 is molded by moving upward to match the tip end surface of the upper mold 8a.

FIG. 1(d) shows the state in which the molded material 1 molded in FIG. 1(C) is carried out from the molding die.

The molding method of this embodiment with the above configuration will be explained below.

First, a molded material 1 made of plastic that has been injection-molded to a shape close to the final shape is placed in the hole 2 of the conveying member 3, and the conveying path 2
0 into the cooling furnace 5 and pre-cooled.

Since the inside of the cooling furnace 5 is cooled to a constant temperature by sending air cooled in advance from the cooler 4, the molding material 1 starts cooling immediately after being inserted, and the inside of the molding material 1 is sufficiently cooled. In this case, for example, by setting the inside of the cooling furnace 5 to 0° C. or lower and setting the inside of the molding material 1 to 10° C. or lower, sufficient cooling can be achieved.

The precooled molding material 1 is carried out from the cooling furnace 5 through the conveyance path 21 by driving the conveyance member 3, and then quickly inserted into the conveyance path 22 of the adjacent heating furnace 7 and rapidly heated. That is, the temperature inside the heating furnace 7 is set by the heater 6 to a temperature much higher than the glass transition temperature of the molding material 1.

In this case, the forming material 1 is heated in the heating furnace 7 for rapid heating.
For example, in a rapid heating method in which only the surface of the substrate is rapidly heated, the heating temperature is set between 300 and 500° C., and the heating time is set between 10 and 30 seconds.

In the above-mentioned rapid heating state, the temperature inside the thick portion of the molding material 1 is sufficiently lower than the glass transition point temperature of the molding material 1.

The rapidly heated forming material 1 is transferred to the conveying path 23 of the heating furnace 7.
The mold is immediately transported by the transport member 3 between the upper mold 8a and the lower mold 8b of the adjacent mold apparatus.

The molding material 1 that has been conveyed is transferred to the molding material 1 of the conveying member 3.
It is inserted between the upper mold 8a and the lower mold 8b, and is set to stop at a position that matches the position of the hole 2 in which the mold is placed, and the position of the upper mold 8a and the lower mold 8b. There is.

Simultaneously with the stop of the conveying member 3, the air cylinder 10 is activated to raise the lower mold 8b and pass through the hole 2 of the conveying member 3 to form the lower surface of the molding material 1 and the upper molding surface of the lower mold 8b. The molding material 1 is placed on the molding surface of the lower mold 8b and lifted upward.

The lifted molding material l further rises to the upper mold 8
It will be in a state where it is sandwiched between the molding surface parts of a.

At this time, the upper mold 8a and the lower mold 8b are connected to the upper temperature controller 9a.
and the lower temperature regulator 9b, respectively, to maintain the temperature around the glass transition point of the molding material 1. The molding material 1 sandwiched between the upper mold 8a and the lower mold 8b is further pressurized by an air cylinder 10. Furthermore, since the temperature near the surface of the molding material 1 is much higher than the glass transition temperature, the shapes of the surfaces of the upper mold 8a and the lower mold 8b are transferred to the molding material 1. After the transfer, the molding material 1 is left as it is, and the upper mold 8a and the lower mold 8b are connected to each other for upper temperature control! It is cooled by S9a and lower temperature controller 9b, respectively. In this case, since the molding material 1 is cooled at a temperature lower than the glass transition temperature, the vicinity of the surface of the molding material 10 is quickly cooled. In this heating compression molding process, the temperature inside the thick portion of the molding material 1 is lower than the glass transition point temperature of the molding material 1. Therefore, during cooling, there is almost no temperature distribution inside the molding material 1.

The heated, molded and cooled molded lens 11 is separated from the upper mold 8a by lowering the lower mold 8b by operating the air cylinder 10, as shown in FIG. 1(A). Then, it is placed again on the upper surface of the hole 2 of the conveying member 3 and taken out to the outside, completing the entire molding process.

In addition, PMMA, PCPS, etc. are used as the material of the plastic lens used in the above-mentioned present example. Also,
In this embodiment, a material to be formed having a biconvex shape is used, but the present invention is not limited to this, and it goes without saying that a concave lens or a prism may be used, or even a glass material may be used.

Since the optical element is molded using the above-mentioned molding method, almost no distortion occurs during cooling, and optical elements obtained by heat compression molding rarely experience optical distortion.
Furthermore, since only the vicinity of the surface of the molding material is heated, the molding time is short, which is advantageous.

(Second Embodiment) FIG. 2 is a sectional view from the front showing essential parts of a cooling furnace of a method for molding an optical element according to a second embodiment of the present invention.

In this embodiment, explanations of the same molding method and the same molding apparatus as those of the first embodiment described above will be omitted. Therefore, only the differences from the first embodiment will be explained.

As shown in FIG. 2, the difference in configuration from the first embodiment is that a cooling mold device is disposed within the cooling furnace 5. That is, the tip molding surfaces of the cylindrical upper cooling mold 12a and the lower cooling mold 12b are arranged to face each other, and the upper mold 12a
The proximal end of the cooler 13a is attached to the distal end of the cooler 13a.
The proximal end surfaces of a are attached to the upper wall surface of the cooling furnace 5, respectively.

Further, the base end of the lower mold 12b is attached to the tip surface of the cooler 13b, and the base end surface of the cooler 13b is attached to the tip surface of an air cylinder 14 that is movable in the vertical direction and is provided outside the cooling furnace 5. The molded lens 1 is connected to the upper mold 12a by the vertical movement of the air cylinder 14 to cool the lens 1 to be molded.

Further, in the left and right side walls of the cooling furnace 5, transport ports 25 and 26 of the transport member 3 for transporting the lens 1 to be molded are opened.

In this embodiment, the molding method of this embodiment having the above-mentioned configuration will be described below, the same molding steps as those of the first embodiment will be omitted, and only the differences will be explained.

It is placed in the tip hole 2 of the conveying member 3 and is connected to the conveying port 2 of the cooling furnace 5.
The molded material 1 conveyed from 5 is stopped between the upper cooling mold 12a and the lower cooling mold 12b, which are spaced apart from each other, at a position where the hole 2 and the molding surfaces of the upper and lower molds 12a and 12b coincide with each other. do. Simultaneously with the stoppage, the lower mold 12b rises due to the operation of the air cylinder 14, passes through the hole 2 of the conveying member 3, comes into contact with the lower surface of the placed material 1 to be formed, is lifted, and further rises to release the upper mold 12b. The upper surface of the material 1 to be molded comes into contact with the molding surface of the mold 12a, resulting in a light (sandwiched) state.

In the above state, the upper cooling mold 12a and the lower cooling mold 12b are kept at a constant temperature, for example, the cooling mold 12a, by the coolers 13a and 13b.

By setting temperature 12b at 0° C. or lower, preliminary cooling is quickly achieved.

The pre-cooled material 1 to be formed is separated from the upper cooling mold 12a by lowering the cooling lower mold 12b as well as by the lowering operation of the air cylinder 14. Furthermore, it is lowered and placed on the hole 2 of the conveying member 3 again, and the lower cooling mold 12
b further descends and stops at the original position.

On the other hand, the molded member 1 placed in the hole 2 of the conveying member 3 is conveyed from the conveying port 26 to the adjacent heating furnace 7, which is the next step, and is heated.

According to this embodiment using the above molding method, the time for the pre-cooling step can be shortened compared to the first embodiment.

〔Effect of the invention〕

According to the present invention using the above-mentioned molding method, by providing the pre-cooling process of the molding material, the rapid heating process, the heating compression molding process, and the cooling process, the molded optical element has a quality free from cooling distortion. You will get a superior product. In addition, the time required for the cooling process in hot compression molding can be shortened, resulting in an excellent effect in terms of cost.

[Brief explanation of drawings]

FIGS. 1(a), 1), (C), and (d) show the molding process of the first embodiment of the method for molding an optical element according to the present invention, and FIG. Figure 1(C) is a cross-sectional view from the front showing the main parts of the heating furnace in the forming process following Figure 1(a). A front view showing in cross section a part of the main part of the apparatus used in the heating compression molding process and the cooling process of the molding process following Figure 1 (C), Figure 1 (B) is shown in Figure 1 (C) FIG. 2 is a cross-sectional view from the front showing a part of the operating state of the apparatus; FIG. ■... Molding material 2... Hole 3... Conveying member 4.13a, 13b... Cooler 5... Cooling furnace 6... Heater 7... Heating furnace 8a, 12a. ...Upper mold 8b, 12b...Lower mold a...Upper temperature controller b...Lower temperature controller 0.14...Air cylindert...Plastic lens 24...Fixed Device

Claims (1)

[Claims] (1) A preliminary cooling process in which a molding material that has been processed or molded into a predetermined shape is cooled in a mold or a cooling furnace, and a rapid heating process in which the molding material cooled in this cooling process is instantaneously heated. , a step of heating and compressing the molding material heated in this rapid heating step in a heating compression mold and cooling it;
A method for molding an optical element, comprising the steps of taking out the molding material cooled in the heating compression and cooling steps from the heating compression mold.