JP2686122B2 - High-precision molding method for plastic lens and molding apparatus therefor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-precision molding method for a plastic lens and a molding apparatus therefor for obtaining a plastic lens having high-accuracy transferability.

[Conventional technology]

A technique disclosed in Japanese Patent Publication No. 59-53858 is known as a means for obtaining a plastic lens having a highly accurate transfer property. In order to prevent "sinking" of the thick-walled part that occurs during molding due to the increased wall-thickness of the center part of the prescription lens, this technique moves the mold after filling the cavity with molten resin. This is a molding method in which the core is pressed into the optical surface.

[Problems to be solved by the invention]

However, the above-mentioned conventional technique has the following problems because it is a technique of only pressing a molded product through a moving core of a mold by a fixed amount after filling a cavity with a molten resin.

That is, as is known, generally, the cooling rate of the molded product during molding is partially different, and the thick part of the molded product has a larger shrinkage rate than the thin part. Therefore, there occurs a situation in which the thin portion quickly solidifies during molding.

Therefore, in the technique of pressing the molded product by a fixed amount through the moving core of the mold as in the above-mentioned conventional technique, the thin-walled portion solidifies quickly during molding, and therefore the moving core as a whole does not Since the thin portion is solidified even when is pressed, the resin does not move, and as a result, the thick portion is not pressed, resulting in a "sink". or,
If the thin portion is forcibly pressed in the solidified state, stress is generated in the thin portion, and the surface shape is distorted. Further, since the above-mentioned conventional technique is a means for directly applying pressure to the optical surface of the molded product, there is a problem in that the surface shape is distorted and the surface accuracy is significantly deteriorated.

The present invention has been made in view of the above-mentioned problems of the prior art, has a highly accurate transferability, and a high-precision molding method of a plastic lens for producing a plastic lens without residual distortion, and It is an object of the present invention to provide the molding device.

[Means for solving the problem]

In view of the above problems, the molding method according to the present invention, in a cavity portion of a molding die in which a porous member that communicates with a compressed gas source is provided in at least a part of a die surface that is in contact with a non-optical surface of a molded article. After the molten resin is filled, and after the molten resin is completely filled in the cavity, the non-optical surface of the molded product is pressed by the gas flowing through the compressed gas source and the porous member during the cooling process and the cooling process. It is a thing.

Further, the molding apparatus according to the present invention, the porous member is disposed on at least a part of the mold surface in contact with the non-optical surface of the molded product,
The porous member is configured to communicate with a compressed gas source.

(Operation)

In the above molding method, since the optical surface of the molded product can be molded in a state of being in close contact with the transfer surface of the mold, a plastic lens having a highly accurate transfer property and no residual distortion can be molded.

Moreover, in the above-mentioned molding apparatus, injection molding having the above-mentioned action can be carried out.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a vertical sectional view of a high-precision molding apparatus 1 (injection molding die) 1 for plastic lenses used in the first embodiment of the present invention, and FIG. It is sectional drawing of the AA line arrow direction in a figure.

As shown in the figure, the high precision molding apparatus 1 includes a mold section 2, a gas compression apparatus 3 connected to the mold section 2, and an injection molding apparatus 4.
And the gas compression device 3 is an injection molding device 4
It is electrically connected to.

The mold part 2 is composed of a fixed side mold 5, a movable side mold 6 and the like. Both molds 5 and 6 are clamped with a constant pressure on a parting surface (mold clamping surface) 8 during molding. It is supposed to be done.

A plurality of fixed cores 9 are fitted and fixed to the fixed-side mold 5, and the molding surface side of each fixed core 9 faces the parting surface 8. A movable core 10 is inserted and fitted in the movable side mold 6 corresponding to each fixed core 9.
Is a direction orthogonal to the parting surface 8 (vertical direction)
It has a slidable structure. A cavity portion of the lens, which is a molded product, is provided between the opposing surfaces of the fixed core 9 and the movable core.
11 is formed, and this cavity portion 11
It is set so that the molten resin flows into and is filled from the injection molding device 4.

As shown in FIG. 2, the movable mold 6 is internally provided with a porous member 12 so as to be in contact with the outer peripheral portion of each cavity portion 11. The porous member 12 has a gas passage hole 13, Tube 14
It is connected to the gas compression device 3 via the. That is, the compressed gas sent from the gas compression device 3 is made to flow into the porous member 12, and the compressed gas that has flowed into the porous member 12 is set to flow out uniformly to the cavity 11. is there. Also, the parting surface 8 of the porous member 12
A coating process for preventing gas outflow is applied to the side surface so that the gas flowing into the porous member 12 does not flow out from the parting surface 8.

Gas compression device 3 electrically connected to injection molding device 4
Is configured so that the compressed gas is caused to flow out in response to an injection completion signal from the injection molding device 4, and is further set to stop the gas flow out after a predetermined time has passed via a timer.

Next, a method of molding a plastic lens using the high precision molding apparatus 1 having the above-described configuration will be described.

First, molten resin is injected from the injection molding device 4 into each cavity.
Inject into 11 for injection molding. FIGS. 3a, 3b and 3c show the solidified state of the resin in the cavity 11 after injection molding. FIG. 3A shows a state at the time of completion of injection, in which the resin in the cavity portion 11 is in a liquid phase state 11a. FIG. 3b shows the state after a short time has elapsed after the completion of injection (during the holding process to the cooling step), and the surface layer of the resin exhibits a slightly solid state 11b. At the time of the state shown in Fig. 3b, a signal is given to the gas compression device 3,
Pressure is applied to the outer peripheral portion 15 of the lens, which is a molded body, through the tube 14, the gas passage hole 13, and the porous member 12. Then, the molded body is cooled in a state where gas pressure is applied to the lens outer peripheral portion 15. FIG. 3c shows a state in which the resin is all solid and contracts.

As described above, in the molding method of the present embodiment, the lens outer peripheral portion 15 that is a molded body is cooled in a state by applying pressure by gas, so that only the lens outer peripheral portion 15 has a `` sink '' as the resin shrinks. 16 (see FIG. 3c) can be generated. As a result, since the lens optical surface is cooled and solidified in a state of being in close contact with both cores 9 and 10, it is possible to mold the plastic lens 11c (see FIG. 3c) having highly accurate transferability. In addition, since it is a method of evenly applying pressure to the outer peripheral portion of the lens, which is a molded product, with a gas, the outer peripheral portion of the lens can be compressed according to the "sink" that accompanies the cooling of the lens, and extremely high precision optics without residual distortion A plastic lens having a surface can be molded.

In the above embodiment, the optical surfaces of both cores 9 and 10 are formed in a convex shape, and therefore the shape of the molded product is also a biconcave lens, but is not limited to this. ,
For example, a lens 2 having a meniscus shape as shown in FIGS.
Of course, it can be applied to the molding of the convex lens 21 as shown in FIG. In this case, in the lens shape shown in FIG. 4b, the area of the lens outer peripheral portion 20a is small, and even if the porous member 12 is arranged in this portion, it is difficult to obtain the effect of the compression by the gas, so that it is shown in the figure. Fixed core 9
It is preferable to dispose the porous member 12 on the non-optical surface portion 22 of the cavity so that an effective gas compression effect can be obtained.

Further, in this embodiment, nothing is formed on the outer peripheral portion of the molded lens, but it is shown in FIGS. 6a and 6b (a view taken along the line BB in FIG. 6a). So that the cavity part 11
At least 1 on the inner peripheral surface of the porous member 12 contacting the outer peripheral portion of the
It is also possible to form recesses 30 in a plurality of places and form a plastic lens 31 by applying a coating process for preventing gas outflow to the inner peripheral surface of each recess 30. According to such a molding method and the molding apparatus 1, even if a pressure is applied to the outer peripheral portion of the molded body by gas to cause a “sink” in the outer peripheral portion of the molded lens, the concave portion
The portion of the protrusion 32 (see FIG. 6c) on the outer peripheral portion of the lens formed on 30 does not cause a sink mark. Therefore, a plastic lens that can be positioned with extremely high precision with respect to the optical system
There is an advantage that 31 can be produced (see FIG. 6c). Other effects are the same as those of the first illustration.

(Second Embodiment) FIGS. 7A and 7B show a second embodiment of the present invention. Since the configuration other than the molding portion is the same as that in FIG. 1, its description is omitted.

As shown in the figure, in this embodiment, the cavity portion 11
The inner peripheral surfaces of the porous member 12 and the fixed-side and movable-side dies 5 and 6 are machined so that the outer peripheral portion 40 has a convex shape. The other configuration is the same as that of the first embodiment, and the description is omitted.

Explaining the method of molding with the molding apparatus of this embodiment, first, the cavity 11 is filled with molten resin from an injection molding apparatus (not shown). Next, when the resin is in the state shown in FIG. 3B, the gas is pumped through the gas inlet hole 13. Then, the molded body is cooled in a state where this gas is pumped, and is solidified as shown in FIG.
Is molded.

According to the present embodiment, even if pressure is applied to the outer peripheral portion of the molded body during molding to cause a "shake" 41 in the outer peripheral portion of the lens, which is a molded product, as shown in FIG. The part does not have a concave shape. Therefore, the "shake" 41 on the outer peripheral portion of the lens 41 does not enter the optical effective diameter range of the lens 42, and a lens with high precision can be formed even when the lens effective diameter is as small as possible. There is an advantage that can be. The other effects are the same as those of the first embodiment, and the description thereof will be omitted.

(Third Embodiment) FIGS. 8A and 8B show a third embodiment of the present invention. The eighth
FIGS. A and b show the same plane section as FIG.

In this embodiment, as shown in the figure, a gate shut pin 50 is slidably arranged in each gate portion of the movable side mold 6 in a direction orthogonal to the inflow direction of the molten resin, and the gate shut pin 50 is provided. The actuator 51 is configured so that movement can be controlled in the longitudinal direction. Gate shut pin 50
Has a gate hole 52 penetrating therethrough.
When the molten resin is injected, the runner portion 53 and the cavity portion 11 are communicated with each other, and after the resin inflow is completed, the runner portion 53 and the cavity portion 11
Movement is controlled so as to block the communication path with 11. Further, the same porous member 54 as the porous member 12 disposed on the outer peripheral portion of each cavity portion 11 is fixedly provided at a portion of the tip end portion of the gate shut pin 50 on the cavity portion 11 side. Reference numeral 55 indicates a hole for guiding the pin sliding.

Explaining the method of molding with the molding apparatus 1 of the present embodiment, first, the molten resin is caused to flow into the cavity portion 11,
After the inflow is completed, the gate shut pin 50 is moved via the actuator 51 as shown in FIG. 8B, and the communication between the cavity portion 11 and the runner portion 53, which are in communication with each other, is cut off. At this time, the porous member 54 at the tip of the gate shut pin 50 is located exactly on the side surface of the cavity 11 as shown in FIG. 8B.

After that, through the same steps as in the first embodiment, compressed air is made to flow into the side surface of the cavity 11 from the gas compression device 3, and the side surface of the molded body is pressed according to the contraction of the resin in the cavity 1.

According to the present embodiment, in addition to the effects of the first embodiment, it is possible to uniformly press the entire circumference of the molded body and to mold a plastic lens having an extremely high-precision optical surface without distortion at the gate portion. There is.

〔The invention's effect〕

As described above, according to the invention of claim 1 of the present invention, the optical surface is brought into close contact with the transferability (molding surface) of the mold only by generating the “sinking” only on the non-optical surface of the molded product. Since it can be molded in the open state, it is possible to mold a plastic lens having extremely high precision transferability and no residual distortion.

Further, according to the invention of claim 2, it is possible to carry out the molding method having the above effects.

[Brief description of the drawings]

1 and 2 are a longitudinal sectional view of a first embodiment of the present invention and a sectional view taken along the line AA in FIG. 1, and FIGS. 3a, 3b and 3c are views after injection molding. Sectional views showing the solidified state of the resin in the cavity, FIGS. 4a, b, and 5 are sectional views showing other application examples of the lens shape, and FIGS. 6a, b, and c are the first embodiment. FIGS. 7a and 7b are vertical sectional views showing a second embodiment of the present invention, and FIGS. 8a and 8b are horizontal sectional views showing a third embodiment of the present invention. It is a figure. 3 ... Gas compression device (compressed gas source) 9, 10 ... Mold 11 ... Cavity 12 ... Porous member

Claims (2)

(57) [Claims] 1. A molten resin is filled in a cavity portion of a molding die in which a porous member communicating with a compressed gas source is provided on at least a part of a die surface which is in contact with a non-optical surface of a molded product. After the filling into the cavity portion is completed, the non-optical surface of the molded product is pressed by the gas flowing through the compressed gas source and the porous member during the cooling process to the high pressure of the plastic lens. Precision molding method. 2. A plastic lens characterized in that a porous member is disposed on at least a part of a mold surface in contact with a non-optical surface of a molded article, and the porous member is communicated with a compressed gas source. High precision molding equipment.