JPS6097301A - Resin optical element and method for producing said element - Google Patents

Abstract

PURPOSE:To obtain a resin optical element such as a thick walled lens which consists of a joined body of plural layers consisting of the same material and has excellent surface accuracy by disposing a resin block in forming dies, casting the same material as the resin block into the dies and forming said element. CONSTITUTION:Dies 5 having the cavity thinner than the wall thickness of a lens to be manufactured are used. A molten transparent resin is injected and packed through a gate into the cavity and is cooled to form a resin block 1. Both walls of the dies 5 are then moved each slightly toward the right and left in parting directions to set the cavity of the dies 5 at the same size as the wall thickness of the lens to be manufactured. The molten resin of the same materials as the block 1 is injected through a gate 21 into the cavity so as to be packed in the space between the cavity and the block 1 then the resin is cooled, by which the intended lens is obtd. The sink mark owing to shrinkage during cooling is thus absorbed and therefore the lens having high surface accuracy is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a resin optical element such as a lens using resin, which is used, for example, as a photographic lens or finder lens of a camera, and a method for manufacturing the resin optical element. This invention relates to improvements in, in particular, thick-walled resin optical elements and their manufacturing methods.

[Prior art]

Optical elements such as lenses using optical glass require manufacturing processes such as polishing, so it is difficult to mass-produce them. On the other hand, resin optical elements such as plasti and cremmet have come to be widely used because they are mass-produced by injection molding or compression molding using molds.

In injection molding, thermoplastic and transparent resin, such as styrene or polycarbonate, is heated and melted, and light is injected into a lens-shaped mold through a gate with a small cross-sectional area. The molten plastic that enters the mold cavity fills the mold with air expelled, and after cooling, the molding is completed.

The lens taken out in this manner has sink marks due to shrinkage during cooling, and is molded into a shape different from that of the mold.

This phenomenon is particularly noticeable in thick lenses. For this reason, when injection molding thick lenses, the cooling process for the resin to solidify takes a long time, and to prevent sinks caused by molding shrinkage, it is continued by holding pressure for the time until the gate solidifies. The conventional method was to apply pressure. .

However, there is a limit to the excessive molding time, and even if the gate is solidified and the pressure is continued by holding pressure, the sink marks will not be reduced. For example, in the case of thick lenses, a considerable amount of resin is required to be replenished during solidification due to the large body contraction.
There is a problem in that the surface accuracy of the lens is difficult to achieve because sufficient compensation cannot be applied to the sink area. It is an object of the present invention to provide a resin 3E optical element with high precision and a method for manufacturing the resin optical element that allows the resin optical element with high precision to be obtained.

[Structure of the invention]

The above objective resin optical element having a good M degree can be achieved by a resin optical element made of a composite of a plurality of layers made of the same material.

The manufacturing method of this resin optical element is to place it in resin molding dust, and then inject the same material as the block in this state and mold it. This is achieved by the method of manufacturing the element.

That is, as a method of obtaining a high-precision thick lens by injection molding, the thickness cross section is divided into 2 or 3 parts 1 - 5 and molded in 2 steps. In addition to dividing and absorbing body contraction during cooling,
The problem of unbalanced pimples caused by body storage in the first process is also solved by making the meat approximately the same thickness in the 7132 process, making it possible to achieve high surface accuracy. The present invention provides a method for manufacturing a resin optical element such as a thick lens, and a resin optical element obtained by this method.

〔Example〕

Figure 1 shows an example of a convex lens, and Figure 1 (a) shows a lens block l that is primarily molded from a transparent plastic resin, using a mold smaller than the shape of the gate 11. The material is melted and then injected into the mold.

Figure 1(b) shows the above-mentioned primary molding process.The same material as the above-mentioned plastic resin is injected into a mold that allows for approximately equal thickness to be applied to both sides of Ri 1, and then cooled. then 2
This figure shows a convex lens according to the present invention having a high surface accuracy after forming the next molding 2.

FIG. 2 shows an embodiment of a concave lens, and FIG. 2(a) shows a lens block 3 and a gate 31 which are primarily molded from a transparent plastic resin. Second
Figure (b) shows a concave lens according to the present invention having a secondary molding 4 on both sides of a primary molding block 30, similar to a convex lens, and having a highly accurate surface area.

Even with thick lenses, plano-convex or plano-concave, lenses with large curvatures that are flat or close to flat tend to have larger sink marks due to body contraction. Therefore, the secondary molding according to the present invention does not necessarily have to be provided on both surfaces of the lens. FIG. 3 shows an embodiment of the present invention in which secondary molding was performed only on the surface with large sink marks. Figure 3(a) shows the primary forming of a convex lens.
The secondary molding 2a is shown, and FIG. 3(b) shows the primary molding 3a and the secondary molding 4a using a concave lens.

Such a resin optical element according to the present invention is molded by the following two manufacturing methods. Let us now explain the convex lens shown in FIG. FIG. 4 shows the manufacturing method of the first embodiment, in which one mold is used to produce the first. This is a method in which a cavity is provided for the second step, and the process can be completed in two shots.

FIG. 4(a) shows the first step, in which gold m5 having the same radius of curvature as the lens being fitted on both sides is set. However, the cavity of the mold 5 is set so that it is thinner than the wall thickness of the lens to be molded, and the gate 11 is also injected with molten resin and then cooled to form a fire molding process as shown in Figure 1. to form.

Figure 4(b) shows the second process, in which the primary molding professional,
The mold 5 is left as it is, and both sides of the mold 5 are moved slightly in the left and right directions, and the cavity of the mold 5 is set to have the same thickness as the lens to be molded. Next, the same resin as the previous one is injected to fill the gap of approximately the same size between the cavity and the primary molded block 1, and then cooled and secondary molded. Lens 0 molded using this manufacturing method absorbs sink marks,
Having high surface accuracy and 1. Cru.

FIG. 5 shows the manufacturing method of the second embodiment, in which two molds 6 and 7 are used, and a primary molded block is moved from the first mold 7 to the second mold 8. Here, the second mold 7 is a cavity mold having the same shape as the lens to be manufactured, and
The Jl gold mold 6 is a mold with a cavity that is almost similar to the small mold 7, which is slightly smaller.

First, using the mold 6 shown in FIG. 5(a), gate 1 is
The molten resin is injected from step 1 and then cooled at step 1-.
A molded block 1 with an l-shaped hole as shown in the figure is molded.

Next, primary molding pro 4. Transfer the second
The lens is set in the mold 7 so that the distance between both sides of the lens is almost equal, and then the resin of the same size as the resin before the gate 41 is injected to fill the gap between the cavity and the primary molding block 1. After that, it is cooled and subjected to secondary molding. Lenses molded using such a manufacturing method absorb sink marks and have high surface accuracy.

The manufacturing method of the embodiment shown in Figures ε, 4, and 5 is an example in which secondary molding is performed on both side surfaces of the lens. Of course, it is possible to do this, but if this is the case, provide cavities for the first and second processes in one mold as shown in the example above. I! The construction method is suitable for 11-I. 1 [Effects of the Invention] Conventionally, glass lenses have been used as a) i! Although it is suitable for i-products, it had a fatal manufacturing defect of poor lens shape accuracy, but the present invention overcomes this and provides a lens with high surface accuracy and its manufacturing method. [I read Rugototo 1.

[Brief explanation of the drawing]

Fig. L1 shows a convex lens of the present invention, ETL Fig. 1 (a) shows a convex lens formed by primary molding, and Fig. 1 (b) shows a convex lens formed by primary molding. The second cause is the concave lens that caused the misfire, as shown in Figure 2 (
A) is a primary molded block, and 2nd (b) is a concave lens consisting of primary and secondary molding. Fig. 3 shows a convex lens (a) and a concave lens (b) showing another embodiment of the present invention. 4 and 5 are explanatory views for explaining the manufacturing method of the present invention, respectively. 1.3... Primary molded block 2.4... Secondary molded 5, 6.7... Gold Type 11,
2J, Ko11, 41...Gate Dai Nukato Kuwabara
Yoshisaki Fig. 1 (0) (b) Fig. 2 (θ) (1)) Fig. 3 (') (1)) Fig. 4 (0) (I))

Claims (2)

[Claims] (1) A resin optical element consisting of a composite of multiple layers made of the same material. (2) A method of manufacturing a resin optical element consisting of a bonded body of multiple layers made of the same material by placing a resin material in a mold and then injecting and molding the same material as the block in this state.