JP2003170480A - Method for molding lens by injection/compression molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for molding a lens by injection/compression molding, capable of suppressing the deformation of the molding at the time of releasing as much as possible. <P>SOLUTION: The method for molding the lens by injection compression molding comprises the step of moving a movable mold to a position in which a thickness of a cavity becomes thicker by a predetermined thickness than that of the molding in the state in which the mold is closed, the step of sealing molten resin in the mold after the molten resin is injected in the cavity, the step of compressing the molten resin, the step of cooling the molten resin, and the step of lowering the pressure applied to the molten resin in the cavity while maintaining the relative position between the fixed mold and the movable mold for a predetermined period substantially constant, and then opening the movable mold from the fixed mold. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens injection compression molding method for molding a lens by injection compression molding a thermoplastic resin. For example, the present invention relates to an injection compression molding method for a lens capable of suppressing deformation of a molded product as much as possible.

[0002]

2. Description of the Related Art Conventionally, an injection compression molding method has been known as a molding method for obtaining a spectacle lens from a thermoplastic resin. This injection compression molding method corrects the shrinkage of the molten resin, and in order to obtain a uniform and highly accurate shape accuracy, the molding die is clamped leaving a compression allowance in the eyeglass lens molding cavity, and then the eyeglasses This is a method of obtaining a spectacle lens by injecting a molten resin into a lens molding cavity and filling it, compressing the compression margin, and then cooling the molten resin. (For example, JP-A-9-277327 and JP-A-9-216.
Further, in the cooling step described above, the molten resin compressed in the mold clamped with a constant mold clamping force has a resin pressure in the mold that is reduced by the mold shrinkage caused by cooling. As the cooling progresses, the resin pressure inside the mold further decreases, and when the cooling is completed, the molded product is removed in the eject process.
It is released from the mold.

[0003]

By the way, in order to obtain a highly accurate lens, it is important to improve the transferability by which the uneven surface shape of the eyeglass lens molding cavity is accurately transferred to the lens. It is important to suppress shrinkage deformation, generation of internal strain, and deformation during mold release. Therefore, a cooling step is required to uniformly and sufficiently cool the molten resin filled in the eyeglass lens molding cavity. In the conventional injection compression molding method,
In the cooling step, the pressure applied to the resin is kept constant, and the resin is cooled for a predetermined time. After that, the mold is opened at once and the pressure applied to the resin is rapidly reduced. Therefore,
In this method, if the cooling time is not sufficient, the molded product is likely to be deformed at the time of mold release. Further, there is a problem that partial peeling may occur depending on how the mold is opened in the mold releasing step, and a mold releasing defect called separation is likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lens injection compression molding method which solves the above-mentioned conventional problems and can suppress deformation of a molded product at the time of mold release as much as possible.

[0005]

A lens injection compression molding method according to the present invention includes a fixed mold and a movable mold that moves forward and backward with respect to the fixed mold, and a pair of cavities for forming a lens uneven surface between the molds. A lens injection compression molding method for molding a lens made of a thermoplastic resin by using a molding die having a lens molding cavity including a forming member, wherein the molding die is closed and the mold is closed. A cavity volume setting step of moving the movable cavity forming member to a position where the thickness of the lens molding cavity becomes a predetermined thickness thicker than the thickness of the molded product, and the lens molding cavity set in the cavity volume setting step. Resin injection and encapsulation process of injecting the thermoplastic molten resin into the cavity and then confining the molten resin in the molding die, and the cavity shape of the movable die. A resin pressurizing step of advancing the member toward the fixed cavity forming member and compressing the molten resin injected into the lens molding cavity, and a predetermined time for presetting the molten resin after the resin pressing step is completed. A cooling step of cooling, and a predetermined period after the cooling step is finished,
An initial mold releasing operation for lowering the pressure applied to the molten resin in the lens molding cavity while maintaining the relative position of the movable mold cavity forming member and the fixed mold cavity forming member substantially constant, and thereafter And a mold releasing step of performing a main mold releasing operation of opening the movable mold with respect to the fixed mold.

According to such a lens injection compression molding method, first, in the cavity volume setting step, the molding die is closed, and in this closed state,
The movable cavity forming member is moved to a position where the thickness of the lens molding cavity becomes a predetermined thickness larger than the thickness of the molded product. Next, in the resin injection and encapsulation process, the molten resin is injected into the set lens molding cavity. When the molten resin is injected, the cavity for lens molding is set to be thicker than the thickness of the molded product, so that the resin can be smoothly injected and filled without causing an inappropriate resin resistance with the molding die. . The molten resin injected into the cavity is enclosed in the mold. That is, the molten resin is prevented from returning (backflowing) to the outside of the mold.

Next, in the resin pressing step, the movable mold cavity forming member is advanced toward the fixed mold cavity forming member. At this time, since the molten resin is filled and contained in the molding die including the lens molding cavity, the molten resin in the lens molding cavity is pressurized. The resin pressurizing step may be started after the injection and filling of the resin is completed, or immediately before the completion of the injection and filling of the resin. Next, in the cooling step, the molten resin is cooled after the completion of the resin pressing step for a predetermined time set in advance. Then, the molten resin in the lens molding cavity is
It is cooled in a compressed state and gradually solidifies and contracts as the cooling progresses.

Finally, in the mold releasing process, after the cooling process is completed, in the initial mold releasing operation, the relative positions of the movable mold cavity forming member and the fixed mold cavity forming member are maintained substantially constant for a predetermined period. In this state, the pressure applied to the molten resin in the lens molding cavity is reduced, and then the movable mold is opened with respect to the fixed mold. In other words, in the initial mold release process, even if the pressure applied to the resin in the lens molding cavity is reduced, the relative position between the movable mold cavity forming member and the fixed mold cavity forming member is maintained substantially constant. Therefore, the deformation of the molded product can be suppressed. That is, since the relative position between the movable mold cavity forming member and the fixed mold cavity forming member is maintained substantially constant despite reducing the pressure applied to the resin, the cooling process can be shortened. Also, the molded product is less likely to be deformed in the releasing step, and a highly accurate lens molded product can be obtained. Therefore, a highly accurate lens can be obtained, and at the same time, the molding cycle can be shortened.

In the above structure, in the cooling step, the relative position of the movable mold cavity forming member and the fixed mold cavity forming member is maintained substantially constant for a predetermined time set in advance, and the inside of the lens forming cavity is maintained. It is desirable that the pressure applied to the molten resin is gradually reduced at a rate slower than the pressure reduction rate in the mold release step. With this configuration, even in the cooling process, the pressure applied to the molten resin in the lens molding cavity is maintained while the relative position between the movable mold cavity forming member and the fixed mold cavity forming member is maintained substantially constant. Since the temperature is gradually lowered at a slow speed, the obtained molded product is cooled uniformly. As a result, the occurrence of sink marks and distortion can be reduced, and moreover,
The cooling time and thus the entire molding cycle can be shortened.

Further, in at least the initial mold releasing process among the mold releasing process and the cooling process, the change in the distance between the movable mold cavity forming member and the fixed mold cavity forming member is taken out as the thickness of the lens forming cavity during compression. It is desirable to reduce the pressure applied to the molten resin in the lens molding cavity while maintaining the difference within the difference from the thickness of the molded product. Here, the value of the difference between the thickness of the cavity for molding the lens at the time of compression and the thickness of the take-out molded product usually takes different values depending on the material characteristics of the lens and the lens power.

Further, a pair of space holding plates are connected to each other by a tie bar, and a movable die plate is movably provided along the tie bar, and the movable die is attached to one of the pair of space holding plates. While mounting the fixed molds respectively, a toggle link mechanism for advancing and retracting the movable mold with respect to the fixed mold is provided between the other of the pair of spacing plates and the movable die plate, and the toggle link mechanism is extended. The mold, the mold is closed, and the toggle link mechanism is moved to the extension limit position so that the tie bar has a desired elongation value in the state where the lens molding cavity is set to the minimum volume. , A mold clamping force adjusting step of adjusting a distance between the pair of spacing plates, and the resin pressing step includes It is desirable to operate the Rurinku mechanism to stretch operation limit position.

According to this structure, a toggle link mechanism is used as a mechanism for moving the movable die forward and backward with respect to the fixed die, and the toggle link mechanism is extended to close the molding die and A mold that adjusts the distance between the pair of spacing plates so that the extension amount of the tie bar reaches the desired value when the toggle link mechanism is operated to the extension limit position and the lens molding cavity is set to the minimum volume. Since the tightening force adjusting step is provided, the operation control in the resin pressing step can be simplified. In other words, when the toggle link mechanism is operated to the extension operation limit position and the lens molding cavity is set to the minimum volume, the pair of intervals is set so that the extension amount of the tie bar becomes a preset desired value (for example, ΔL). If the distance between the holding plates is adjusted, the toggle link mechanism only has to be operated to the extension operation limit position in the resin pressing step. The amount of expansion of the tie bar in the resin pressurizing process is the amount of expansion (ΔL) in the mold clamping force adjustment process and the amount of expansion of the tie bar (α) due to the mold volume not being completely closed due to the resin volume in the lens molding cavity. Therefore, if the elongation amount (ΔL) is set in consideration of the elongation amount (α) in the mold clamping force adjustment process, the toggle link mechanism will be set at the extension operation limit position in the resin pressurizing process. All you have to do is run it.

Further, if such a method is adopted, the operation control in the cooling process and the mold releasing process can be performed more easily. For example, in the cooling step, when the molten resin is cooled for a preset time, the molten resin in the lens molding cavity is cooled in a compressed state, and gradually solidifies as the cooling progresses, It will be contracted. The movable die plate is gradually advanced as the resin shrinks. When the movable die plate advances, the distance between the pair of distance holding plates decreases, that is, the tie bar elastically recovers, and the pressure acting on the molten resin in the lens molding cavity gradually decreases. To go.

In this way, as the molten resin in the lens molding cavity is gradually cooled and solidified and shrinks, the molten resin in the lens molding cavity is advanced through the movement of the movable die plate and elastic recovery of the tie bar. It is possible to gradually and gradually reduce the pressure acting on. Therefore, as a result of uniformly cooling the entire obtained molded product, it is possible to reduce the occurrence of sink marks and distortions, and further, it is possible to shorten the cooling time and eventually the entire molding cycle. Of course, as the molding die, a molding die is used in which the thickness of the lens molding cavity of the molding die is smaller than the thickness of the molded product in a state where the toggle link mechanism is operated to the extension operation limit position.

Further, in the mold clamping force adjusting step, it is desirable that the other space holding plate is adjusted so as to be close to and away from the one space holding plate. Usually, the injection compression device is equipped with a mold thickness adjusting device for adjusting the distance between the two spacing plates by moving the other spacing plate closer to and away from the one spacing plate.
By using the mold thickness adjusting device, the other spacing plate can be moved closer to or away from the one spacing plate.

In the resin injection and encapsulation step, after the molten resin is injected into the lens molding cavity, a blocking member is projected into a sprue which communicates with the lens molding cavity through a runner to melt the molten resin. It is desirable to block the nozzle passage that ejects. With such a method, since it is sufficient to simply project the blocking member into the nozzle passage, when the injection of the molten resin into the lens molding cavity is completed, the injected and filled molten resin is immediately confined inside. be able to. Therefore, even when the resin pressurizing step is started immediately before the completion of injection, the reverse flow of the resin can be reliably prevented.

Further, as a lens injection compression molding method of the present invention, a tie bar connecting a pair of spacing plates to each other, a movable die plate movably provided along the tie bars, and the pair of spacing plates. A mold having a lens forming cavity therein, which includes a pair of cavity forming members for forming a concave-convex surface for a lens, provided between the movable die and the movable die plate, and the other of the pair of spacing plates and the movable die. An advancing / retreating mechanism that is provided between the movable die plate and the plate to move the movable die plate back and forth with respect to one of the spacing plates, and the molding die is fixed to the one of the spacing holding plates to form the lens molding cavity therein. And a movable die fixed to the movable die plate. , A mold main body having a cavity forming member for forming the lens molding cavity therein, a mold mounting member fixed to the movable die plate and movably holding the mold main body toward the fixed mold, and this mold mounting An elastic member interposed between the member and the mold body,
The elastic member is configured to open and close the die mounting member and the die body at a fixed interval, and the movable die plate holds one of the gaps when the forming die is closed by the operation of the advancing / retreating mechanism. A lens injection compression molding method for molding a lens made of a thermoplastic resin by using a molding device having a structure in which a cavity for molding a lens is contracted when advancing toward a plate. A cavity volume setting step of closing the mold and moving the cavity forming member of the movable mold to a position where the thickness of the lens molding cavity becomes a predetermined thickness thicker than the thickness of the lens molded product in the mold closed state; After injecting the thermoplastic molten resin into the lens molding cavity set in the cavity volume setting step, the molten resin Resin injection encapsulation step of encapsulating in the molding die, and actuation of the advancing / retreating mechanism to form the cavity forming member of the movable die fixed to the movable die plate to the cavity forming of the fixed die fixed to one of the gap holding plates. In the lens molding cavity, the lens molding cavity is advanced toward the member and the relative position between the other spacing plate and the movable die plate is held constant at a position where the thickness of the lens molding cavity is equal to or less than the thickness of the lens molding product. A resin pressurizing step of compressing the molten resin injected into the resin, a cooling step of cooling the molten resin for a predetermined time after the resin pressing step is finished, and the other of the other held constant after the cooling step. By operating the advancing / retreating mechanism in a direction of reducing the distance between the distance holding plate and the movable die plate, the movable die is operated for a predetermined period in the initial release. An initial mold releasing operation of lowering the pressure applied to the molten resin in the lens molding cavity while maintaining the relative position of the cavity forming member and the cavity forming member of the fixed mold substantially constant, and thereafter, to the fixed mold. On the other hand, it may be configured to include a mold releasing step of performing a main mold releasing operation of opening the movable mold. Even in this case, the same effect as above can be expected.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. [Apparatus Configuration] In this embodiment, the injection compression molding method according to the present invention is applied to an injection compression molding apparatus for spectacle lenses (meniscus-shaped spectacle lenses: single focus, multifocal, progressive multifocal). The overall configuration of this embodiment is shown in FIG. The material of the spectacle lens molded here is PM
It is a thermoplastic resin such as MA (polymethylmethacrylate) or PC (polycarbonate). The injection compression molding apparatus of the present embodiment includes a mold clamping device 60 having a molding die 50.
An injection device 80 as an injection means for plasticizing and measuring the raw material resin and injecting it into the molding die 50, and a mold temperature adjusting device 5 for controlling the temperature of the molding die 50 to a preset temperature.
1 and 1.

The mold clamping device 60 comprises a fixed die plate 61 and a rear plate 62 as a pair of spacing plates.
And the fixed die plate 61 and the rear plate 62
A plurality of tie bars 63 connecting the two to each other, a movable die plate 64 movably provided along the tie bars 63, and a movable die plate 64 provided between the rear plate 62 and the movable die plate 64. A toggle link mechanism 65 as an advancing / retreating mechanism for advancing / retreating with respect to the plate 61 is configured. The molding die 50 is provided between the fixed die plate 61 and the movable die plate 64.
Is provided. The fixed die plate 61 is a mount 66.
It is fixed to. The rear plate 62 is fixed to a frame 66 via a mold thickness adjusting device 67. The mold thickness adjusting device 67 is a well-known device and can move the rear plate 62 closer to and away from the fixed die plate 61. Here, the mold thickness adjusting device 67 constitutes a space adjusting means for adjusting the distance between the fixed die plate 61 as a pair of space holding plates and the rear plate 62. Further, since the rear plate 62 connected to the tie bar 63 is slidable via the mold thickness adjusting device 67, the tie bar 6
It can handle the growth of 3. Further, the tie bar 63 is provided with an extension amount detection sensor 68 as tie bar extension amount detecting means for detecting the extension amount of the tie bar 63.

The value detected by the elongation detecting sensor 68 is displayed on a display (not shown) in the range of 0 to 1000 με in the apparatus of this embodiment, for example. The extension amount of the tie bar 63 can be obtained from the detection value (strain amount) of the extension amount detection sensor 68 displayed on this display. In other words, 1με = 1 microstrain = 0.0 per 1m
Since the extension amount is 01 mm, the extension amount of the tie bar 63 can be obtained based on the strain amount displayed on the display. Further, the mold clamping force [ton] can be obtained from the following formula. Mold clamping force [ton] = με (display strain amount) × simple coefficient The simple coefficient is obtained by the elastic coefficient of the tie bar, the diameter of the tie bar, and the number of tie bars.

The toggle link mechanism 65 is provided between the movable die plate 64 and the rear plate 62, and has a plurality of toggle links 71A and 71B whose middle portion is inwardly bendable.
A ball screw 72 supported in the center of the rear plate 62 in parallel with the tie bar 63 and rotated by a mold clamping motor (not shown), a cross head 73 screwed to the ball screw 72, and the cross head 73. Connection link 74 for connecting the bent portions of the toggle links 71A and 71B
It is composed of A and 74B. Therefore, when the crosshead 73 moves forward (moves to the right in FIG. 1), the toggle links 71A and 71B extend (the movable die plate 64 advances) via the connecting links 74A and 74B, and conversely, the crosshead 73 moves. When retracted (moved to the left in FIG. 1), the toggle links 71A, 71 are connected via the connecting links 74A, 74B.
B bends inward (movable die plate 64 retracts). Regarding the toggle link mechanism, there are various mechanisms such as a double link mechanism, which is structurally complicated,
In the description of the present embodiment, the principle aspect will be mainly described.

The injection device 80 comprises an injection cylinder unit 82 for plasticizing, kneading and measuring the raw material resin fed from the hopper 81. A screw (not shown) is housed inside the injection cylinder unit 82, and a long injection nozzle 85 that can be inserted into the molding die 50 is attached to the tip thereof. A band heater (not shown) is wound around the injection cylinder unit 82. The mold temperature adjusting device 51 is connected to each part (insert, insert guide member, etc.) of the mold 50 so as to be able to supply a temperature control fluid. That is, the temperature of the supplied temperature control fluid is controlled by the mold temperature adjusting device 51 so that the temperature of each part of the molding die 50 is set in advance according to the type of lens to be molded.

FIG. 2 is a sectional view of the molding die 50, and FIG.
3 is a sectional view taken along line III-III, and FIG. 4 is a sectional view taken along line IV-IV in FIG. As shown in FIG. 2, the molding die 50 includes a movable die 1 and a fixed die 2 which are divided into right and left on a parting line PL. Two spectacle lens molding cavities 3 and a runner 49 connected to each of the spectacle lens molding cavities 3 via a gate G and connecting these cavities 3 are formed between them. For the runner 49, the sprue 4 formed by the sprue bush 47
8 is formed at a right angle. Here, a mold constructing body 45 is formed including two eyeglass lens molding cavities 3, a runner 49 and a sprue 48. The runner 49 and the sprue 48 form a resin flow path inside the molding die 50.

The mold body 4 of the movable mold 1 comprises an insert guide member 5 and mold plates 6 and 7. Mold body 8 of fixed mold 2
Consists of an insert guide member 9 and a template 10.
Inside each of the insert guide members 5 and 9, optical inserts 11 and 12 for forming a spectacle lens that form the cavity 3 are housed so as to be slidable in a direction perpendicular to the parting line PL. There is. Although not shown, the insert guide members 5, 9 and the inserts 11, 12 are provided with temperature control fluid circulation grooves for circulating the temperature control fluid supplied from the mold temperature control device 51. Mold body 8 of fixed mold 2
Is the mold attachment member 15 fixed to the fixed die plate 61.
It is fixed to. The mold body 4 of the movable mold 1 includes the first member 1
6A and the second member 16B are attached to the mold mounting member 16 as shown in FIG.
Are connected by bolts 17 shown in FIG.
A disc spring 17A, which is an elastic member and is inserted into the outer periphery of the bolt 17, is interposed between the and the die mounting member 16.
The mold mounting member 16 is fixed to the movable die plate 64.

A gap S is provided between the die body 4 and the die mounting member 16, and the die body 4 and the die mounting member 16 are guided by the guide pins 18 to form the gap S.
It can be opened and closed left and right only for minutes. That is,
After the mold is closed, the movable die plate 64 advances to press the mold mounting member 16 through the movable die plate 64, thereby closing the gap S.

The mold mounting member 16 is provided with a hydraulic cylinder 19. A piston rod 21 connected to a piston 20 of the hydraulic cylinder 19 penetrates through a back insert 22 fixed to one end surface of the hydraulic cylinder 19 and has a T-shaped clamp member 23 at its tip. The T-shaped clamp member 23 is disengageably engaged with a T-shaped groove 24 formed in the other end surface of the insert 11. This allows
The insert 11 is replaceable. Mold mounting member 1
5, a hydraulic cylinder 26 is provided. Piston rod 2 connected to piston 27 of hydraulic cylinder 26
8 has a T-shaped clamp member 29 at its tip, which penetrates through the mold attachment member 15. The T-shaped clamp member 29 is
The insert 12 is engaged with a T-shaped groove 30 formed on one end surface of the insert 12 so as to be disengageable. As a result, the insert 12 can be replaced.

A pressure receiving member 32 is provided at the other end of the hydraulic cylinder 19.
Is fixed. Hole 33 formed in die mounting member 16
By the eject rod 34 inserted from the pressure receiving member 3
When 2 is pressed, the hydraulic cylinder 19, the back insert 22 and the insert 11 are also pressed, and the cavity 3
The lens molded in 1 is projected when the movable mold 1 and the fixed mold 2 are divided. An eject pin 35 is disposed in the center of the movable die 1 and the die mounting member 16 so as to be movable back and forth in the left-right direction. At the other end of the eject pin 35, a pressure receiving member 36 that is displaceable in the left-right direction with a constant stroke is fixed. When the pressure receiving member 36 is pressed by the eject rod 38 inserted from the hole 37 formed in the die mounting member 16, the eject pin 35 is pushed out.

The spring force of the spring 40 wound around the outer circumference of the eject return pin 39 acts on the pressure receiving member 32 in the leftward direction in FIG. In addition, the pressure receiving member 36,
As shown in FIG. 4, the spring force of the spring 42 wound around the outer periphery of the eject return pin 41 acts leftward in FIG. 4, and the pressure receiving member 36 is positioned at a predetermined position. Therefore, the eject rods 34, 38
When is retracted, the pressure receiving members 32 and 36 are also retracted and returned to the old position.

As shown in FIG. 4, the nozzle shut mechanism 90 has a nozzle shut pin 91 as a blocking member. The nozzle shut pin 91 is fitted into the side wall of the sprue bush 47 so as to be able to advance and retract in a direction substantially perpendicular to the center line of the sprue bush 47, and the rear end thereof is connected to the connecting piece 92.
Is connected to the piston rod 94 of the hydraulic cylinder 93 via. The hydraulic cylinder 93 has a cylinder mounting plate 95.
It is fixed to the mold mounting member 15 via. When the injection nozzle 85 is pressed against the sprue bush 47,
Nozzle shut pin 91 slides to eject nozzle 85
The backflow of the resin is blocked by closing the opening at the tip of the resin (see, for example, Japanese Utility Model Publication No. 6-9826).

[Lens Molding Procedure] First, the inserts 11 and 12 are exchanged according to the type of lens to be molded. When the inserts 11 and 12 are replaced, the movable mold 1 including the mold mounting member 16 is retracted to separate the fixed mold 2 from the mold. In addition, the piston rod 21 of the hydraulic cylinder 19 is advanced and the piston rod 28 of the hydraulic cylinder 26 is advanced, so that the piston rod 2
T-shaped clamp member 2 attached to the tip of 1, 2
3, 29 are projected from the insert guide members 5, 9.

The inserts 11 and 12 newly mounted on the mold bodies 4 and 8 of the movable mold 1 and the fixed mold 2 are horizontally transferred while being held by a robot arm (not shown), and the T-shaped groove 24 of the inserts 11 and 12 is transferred. , 30 are engaged with the T-shaped clamp members 23, 29. After this, hydraulic cylinder 1
The piston rod 21 of the hydraulic cylinder 26 and the piston rod 21 of the hydraulic cylinder 26.
8 is retracted and the insert 12 is retracted. As a result, the inserts 11 and 12 have the insert guide members 5 and 5.
9 is fitted. Thus, in the case of the plus lens molding, the insert having the cavity 3 having the central wall thickness larger than that of the peripheral portion is formed, and in the case of the minus lens molding, the cavity 3 having the center wall thickness smaller than that of the peripheral portion is formed. Replace with each insert.

The molding of the spectacle lens having the meniscus shape is performed according to the procedure shown in the flow chart of FIG. In ST (step) 1, the resin pressurizing condition is set. This is because the cavity 3 has an appropriate pressure in advance.
It is for adjusting the mold clamping force according to the characteristics of the lens to be molded (lens shape, lens dioptric power, etc.) in order to add to the resin inside. For example, as shown in FIG. 6, an appropriate mold clamping force is set in advance corresponding to the lens power, and the resin pressing condition is set based on this. Of course, it is obvious that the resin pressurizing condition is changed according to the lens resin property, and the lens resin property must be considered in all molding conditions.

First, as shown in FIG. 7A, the molding die 50 is closed until the parting line PL is in close contact. That is, the cross head 73 of the toggle link mechanism 65
Is moved forward in a direction approaching the movable die plate 64, the toggle links 71A and 71B extend and the movable die plate 64 advances toward the fixed die plate 61,
The disc spring 17A interposed between the die main body 4 and the die mounting member 16 of the movable die 1 is closed with a gap S (S1) kept in a non-compressed state. Then, as shown in FIG. 7B, when the crosshead 73 is further advanced and moved to the origin (zero position), the toggle links 71A and 71B are fully extended. Then, the tie bar 63 is extended and a mold clamping force is generated. At this time (during mechanical END mold clamping), the cavity 3 is set to be smaller than the molded lens volume (wall thickness), as shown in FIG. That is, the cavity 3 is set to be smaller than the take-out molded product (wall thickness) at the time of mechanical end mold clamping.

The closer the crosshead position is to the movable die plate 64 when the disc spring 71A is closed without being compressed, the more the toggle links 71A and 71B are extended, and the amount of extension of the tie bar 63 is small. The power becomes weak. That is, the position of the crosshead when the mold is closed is determined by the distance between the fixed die plate 61 and the rear plate 62.
Set the mold clamping force by adjusting the position of. Here, as shown in FIGS. 7A and 7B, with respect to the distance L between the fixed die plate 61 and the rear plate 62 when the molding die 50 is closed along the parting line PL (state A). , Tie bar 6 during mechanical end mold clamping (state B)
The mold clamping force is set by controlling the elongation amount ΔL of 3.

In ST2, weighing is performed. Injection device 8
At 0, the raw material resin put into the hopper 81 is plasticized, and the plasticized molten resin is introduced into the injection cylinder unit 82 and weighed. Here, a required amount of molten resin is measured in a mold structure 45 having two lens molding cavities 3, a runner 49 and a sprue 48.

At ST3, the parting line PL
To close the mold. As shown in FIG. 9, the toggle link mechanism 6
When the crosshead 73 of No. 5 is moved forward, the toggle link 7
1A and 71B extend and the movable die plate 64 advances toward the fixed die plate 61. Therefore, the disc spring 17 interposed between the die body 4 of the movable die 1 and the die mounting member 16 is provided.
The molding die 50 is closed at the parting line PL while maintaining the gap S while A is not compressed. In this state,
The gap S is set to the maximum opening amount (S1). Also,
As shown in FIG. 10, the cavity 3 is enlarged more than the thickness of the molded product plus the thickness.

In ST4, the cavity volume is set. As shown in FIG. 11, when the crosshead 73 is advanced to a preset position (cavity volume setting position), the toggle links 71A and 71B extend and the movable die plate 64 moves toward the fixed die plate 61,
It is moved to the cavity expansion position. The amount of cavity expansion is determined by setting the crosshead position. As a result, the gap S of the molding die 50 is reduced (gap S3), leaving the cavity expansion. At this time, as shown in FIG. 12, the volume (wall thickness) of the cavity 3 is larger than the lens volume (wall thickness) to be molded, that is, the wall thickness of the take-out molded product. Further, since the disc spring 17A is compressed, some mold clamping force is generated as its reaction force (therefore, the distance between the fixed die plate 61 and the rear plate 62 is L ').

In ST5, injection is performed. The molten resin measured in the measuring step is injected into the mold structure 45 through the passage of the injection nozzle 85. That is, the molten resin introduced into the injection cylinder unit 82 of the injection device 80 and measured is injected by the rotation of the screw. Then,
Molten resin is filled into the cavity 3 through the injection nozzle 85, the sprue 48 of the sprue bush 47, the runner 49, and the gate G. When the resin is filled in the cavity 3, the injection speed is controlled to be constant. Further, since the cavity 3 is greatly expanded, the molding die 50
Injection filling proceeds without generating an inappropriate resin resistance.

At ST6, the resin is sealed in the mold. Immediately before the completion of injection filling of the molten resin, the crosshead 73
Immediately starts, and the injection nozzle 85 is immediately closed by the nozzle shut mechanism 90 after completion of injection filling. That is, the nozzle shut pin 91 is replaced with the sprue 48.
It is made to project inward and the tip of the passage of the injection nozzle 85 is closed. Thereby, the molten resin is enclosed in the molding die 50.

In ST7, resin pressure is applied. ST6
When the crosshead 73 moves forward to the origin (zero position) and stops when the crosshead 73 starts moving forward, the toggle links 71A and 71B are fully extended, so the molten resin contained in the mold 50 is compressed and pressed. To be done.
At this time, as shown in FIG. 13, the cavity volume (wall thickness) of the molding die 50 when the molding die 50 is closed to the mechanical end is made smaller than the lens volume (wall thickness) to be molded. Even if the lens to be molded is filled with a required amount of molten resin and compressed, the gap S of the molding die 50 is set so as not to be completely closed to the mechanical END (end). Since the gap S between the mold body 4 and the mold mounting member 16 is not completely closed, that is, there is the gap S4, the insert 11 in contact with the mold mounting member 16 directly pushes the resin in the cavity 3. . As a result, the resin in the cavity 3 is compressed between the thickness of the take-out molded product and the thickness at the time of mechanical END mold clamping, as shown in FIG. Here, the amount of expansion of the tie bar 63, which indicates the pressure for compressing the resin in the cavity 3, is such that the amount of expansion of the tie bar 63 due to the mold clamping force (ΔL) and the capacity of the resin in the cavity 3 prevent the molding die 50 from closing completely. The total amount (ΔL + α) is the sum of the amount of expansion (α) of the tie bar 63 coming from. From this, in order to apply an appropriate pressure to the resin in the cavity 3, the resin capacity and the mold clamping force, which are related to each other, may be appropriately determined according to the lens characteristics.

In ST8, cooling is performed. This includes
The mold temperature adjusting device 5 is arranged so that the temperature of each part (insert, insert guide member, etc.) of the molding die 50 is set to a temperature below the Tg point according to the characteristics of the lens to be molded.
1 controls the temperature of the temperature control fluid. The resin filled in the cavity 3 is solidified and contracted as the cooling progresses in a compressed state. The movable die plate 64 is gradually advanced as the resin shrinks. When the movable die plate 64 moves forward, the fixed die plate 6
The distance between 1 and the rear plate 62 is reduced,
That is, the tie bar 63 elastically recovers, and the pressure applied to the resin in the cavity 3 decreases.

FIG. 15 shows the relationship between the mold clamping force and the extension amount of the tie bar 63 in the cooling process. Point P1 in the figure
Before injection, the lens characteristics (aspherical single focus lens, diopter -4.00D, diameter 76 mm, lens molded product center thickness 1.
1 mm), the setting operation of the set mold clamping force is shown. From there, the mold is once opened (point P2), and the filling of the molten resin is started, the mold clamping is performed, and the point P3 is set.
Is the point where the mold clamping force is the largest when the toggle links 71A and 71B are fully extended. As can be seen from this figure, the mold clamping force (pressure applied to the resin in the cavity 3) and the amount of expansion of the tie bar 63 both show the same tendency, and they are the same in the initial stage of the cooling process (section P3 to P5 in FIG. 15). Shows a slight decline, but thereafter (P5 to P6 section) shows a very gradual downward trend (state with almost no change). Also, P6 to P10
The section (1) is the initial step (primary step) of the mold release step and is the section in which the elongation amount of the tie bar is controlled. In the present invention, it has been found that the control in this section is a section in which separation is poor or lens quality is greatly affected. In the section of P6 to P8, the mold clamping force is also gradually reduced to control the elastic recovery of the tie bar, and in the section of P8 to P10, the elastic change is increased by increasing the amount of change. Next, in the subsequent sections, the mold clamping force is further reduced, and the mold is opened at a stretch, and the normal mold releasing process is continued.

In the present embodiment, the boundary between the cooling process and the mold releasing process is shown as a point P rather than a region for the sake of clarity. The relationship between the elastic recovery of the tie bar 63 due to the reduction of the mold clamping force and the cooling time can be obtained by experimental verification. Therefore, the mold clamping force is controlled by determining the proper cooling time in advance depending on the material used and the lens characteristics. That is, it is preferable to increase the cooling time as the lens power increases, the lens outer diameter increases, or the lens thickness increases. However, it goes without saying that this also greatly changes depending on the lens material.

In ST9, the releasing operation is performed. In the releasing operation, the cross head 73 of the toggle link mechanism 65 is retracted toward the rear plate 62. Cross head 7
When 3 retreats, toggle links 71A, 71 that have fully extended
B acts in a contracting direction, and the tie bar 63 elastically recovers. The movable die plate 64 coupled to the toggle links 71A and 71B has a direction in which the molding die 50 opens as the crosshead 73 retracts, that is, the rear plate 62.
However, due to the elastic recovery of the tie bar 63,
Since the rear plate 62 moves toward the fixed die plate 61, the moving amount of the movable die plate 64 and the tie bar 6
The amount of shrinkage due to the elastic recovery of No. 3 cancels each other, and apparently the gap between the fixed die plate 61 and the movable die plate 64 (that is, the insert 12 of the fixed die 2 and the insert 11 of the movable die 1). (Relative position to and) does not change so much, and the crosshead 73 continues to retreat.

FIG. 16 shows the cooling process (S3 to S6, P3 'to P6').
And the die plate spacing (the spacing between the fixed die plate 61 and the movable die plate 64) in the first mold release step (S6 to S10, P6 'to P10'). . As can be seen from this figure, the mold clamping force (pressure applied to the resin in the cavity 3) sharply decreases when entering the primary mold release process (section P6 'to P10') after the cooling process is completed. However, the distance between the fixed die plate 61 and the movable die plate 64 is determined by the initial mold release process (S6 to S10).
It also shows that there is almost no change even in the section (1). Here, the fixed die plate 61
And the movable die plate 64 (that is, the distance between the insert 12 of the fixed mold 2 and the insert 11 of the movable mold 1)
Within the difference between the thickness of the cavity for lens molding and the thickness of the molded article taken out during compression (for example, in the present embodiment,
(Within 0.3 mm).

Therefore, in the initial step of releasing the mold, the relative position between the insert 11 of the movable mold 1 and the insert 12 of the fixed mold 2 is maintained substantially constant, even though the pressure applied to the resin is reduced. Since the resin under pressure in the mold is gently and reasonably decompressed, even if the cooling process is shortened, the molded product will not be deformed in the mold release process, and a highly accurate lens molded product can be obtained. You can By the way, since the pressure applied to the resin in the cavity 3 can be controlled by adjusting the retreat speed of the crosshead 73, the resin in the cavity 3 is applied by adjusting the retreat speed of the crosshead 73. The pressure reduction can be controlled. As for the relationship between the retreat of the crosshead 73 and the elastic recovery of the tie bar 63, an appropriate relationship has been obtained in advance by experimental verification. Therefore, the control condition of the crosshead 73 should be determined by the material used and the lens characteristics. You can

In ST10, a molded product ejecting operation is performed. When the cross head 73 is retracted to the end, the distance between the movable die plate 64 and the fixed die plate 61 becomes maximum, the molding die 50 is divided and opened from the parting line PL, the molded product is ejected, and the molding die 5 is formed.
Separated from zero. For example, from the above series of steps,
A molded product 101 shown in FIG. 17 is obtained. This molded product 10
Reference numeral 1 denotes an eyeglass lens 102 formed by two lens forming cavities 3, a connecting portion 103 formed by a runner 49 for connecting the two eyeglass lenses 102, and a central portion of the connecting portion 103 formed by a sprue 48. The rod-shaped portion 10 extending at right angles from the lens 102 in the thickness direction of the lens 102.
4 and 4. After that, the lens 102 is dipped in a wear-resistant hard coat liquid, and then the lens 1
02 and the connecting portion 103 are separated by a cutter device. As a result, two spectacle lenses 102 coated with the coating film of the hard coat liquid can be obtained from one molded product 101 at the same time.

[Effect of Embodiment] According to this embodiment,
In the cavity volume setting step, the cavity volume (thickness) is set to a thickness thicker than the thickness of the molded product, and then in the resin injection sealing step, the molten resin is injected into the set cavity 3 and the resin is molded. The resin is sealed in the mold 50, and in this state, in the resin pressurizing step, the toggle link mechanism 65 is extended to extend the tie bar 63, and the reaction force due to the extension of the tie bar 63 is applied to the resin in the cavity 3, Since the cooling process is allowed to proceed, it is possible to reduce the occurrence of sink marks and distortion of the molded product, and also to shorten the molding cycle.

That is, in the cooling step, when the molten resin in the cavity 3 is cooled for a predetermined time, the cavity 3
The molten resin therein is gradually solidified and contracted as the cooling progresses in a compressed state. The movable die plate 64 is gradually advanced as the resin shrinks. When the movable die plate 64 moves forward, the fixed die plate 6
The distance between 1 and the rear plate 62 is reduced,
That is, the tie bar 63 is elastically recovered, and the pressure acting on the molten resin in the cavity 3 gradually decreases. Therefore, as the molten resin in the cavity 3 is gradually cooled and solidified and contracts, the pressure acting on the molten resin in the cavity 3 is gradually increased through the advancement of the movable die plate 64 and the elastic recovery of the tie bar 63. Since the temperature can be gradually lowered, the entire molded product obtained can be cooled uniformly, and as a result, the occurrence of sink marks and distortions can be reduced, and further, the cooling time and eventually the entire molding cycle can be shortened. By the way, according to the method of the present embodiment, when the diameter is 76 mm and the frequency is -4.00 D, it is possible to shift to the mold release step with a cooling time of 80 seconds.

In the mold releasing process, the insert 11 of the movable mold 1 and the fixed mold 2 are kept for a predetermined period after the cooling process is completed.
The pressure applied to the molten resin in the lens-molding cavity 3 is reduced in a state where the relative position of the mold to the insert 12 is maintained substantially constant, and then the movable mold 1 is moved with respect to the fixed mold 2.
Since the mold is opened, that is, even if the pressure applied to the resin in the lens molding cavity 3 is reduced in the initial mold releasing step, the insert 11 of the movable mold 1 and the insert 12 of the fixed mold 2 are separated from each other. Relative position is almost constant (Movable type 1
Since the change in the distance between the insert 11 and the insert 12 of the fixed mold 2 is maintained within the difference between the thickness of the lens molding cavity at the time of compression and the thickness of the taken-out molded product,
The deformation of the molded product can be suppressed. This means that the relative position between the insert 11 of the movable mold 1 and the insert 12 of the fixed mold 2 is maintained substantially constant despite the reduction of the pressure applied to the resin. Therefore, the cooling process can be shortened. Also, the molded product is less likely to be deformed in the releasing step, and a highly accurate lens molded product can be obtained. Therefore, a highly accurate lens can be obtained, and at the same time, the molding cycle can be shortened.

A toggle link mechanism 65 is used as a mechanism for moving the movable die plate 64 forward and backward with respect to the fixed die plate 61, and the toggle link mechanism 65 is extended to close the molding die 50, and When the toggle link mechanism 65 is operated to the maximum extension position and the volume of the cavity 3 is set to the minimum volume (minimum thickness), the fixed die plate 61 and the fixed die plate 61 are adjusted so that the extension amount of the tie bar 63 becomes a desired value. Since the distance to the rear plate 62 is adjusted, the operation control in the resin pressing step can be simplified.

That is, when the toggle link mechanism 65 is operated to the extension operation limit position and the volume of the cavity 3 is set to the minimum volume, the extension amount of the tie bar 63 becomes a preset desired value (for example, ΔL). In addition, if the distance between the fixed die plate 61 and the rear plate 62 is adjusted, the toggle link mechanism 65 need only be moved to the extension operation limit position in the resin pressurizing step. The amount of expansion of the tie bar 63 in the resin pressurizing step is the amount of expansion (ΔL) in the mold clamping force adjusting step, and the amount of expansion of the tie bar 63 (α) because the molding die 50 cannot be completely closed due to the resin volume in the cavity 3. Therefore, if the elongation amount (ΔL) is set in consideration of the elongation amount (α) in the mold clamping force adjusting step, the toggle link mechanism 65 is extended in the resin pressing step. All you have to do is move it to the limit position.

In the mold clamping force adjusting step, the rear plate 62 is moved toward and away from the fixed die plate 61. Therefore, the normal mold thickness adjusting device 67 is used.
The rear plate 62 can be moved toward and away from the fixed die plate 61. Further, in the resin injection and sealing step, when the resin is filled in the cavity 3 and the resin is sealed, the nozzle shut pin 91 is projected into the sprue 48 to close the nozzle passage for injecting the thermoplastic resin. It suffices to simply project the nozzle shut pin 91 into the nozzle passage, and immediately after the injection of the molten resin into the cavity 3 is completed, the injected and filled thermoplastic resin can be contained therein. Therefore, even when the resin pressurizing step is started immediately before the completion of injection, the backflow of the resin can be prevented.

[Modification] The present invention is not limited to the structure and method described in the above embodiment, and includes the following examples. In the above embodiment, as a mechanism for moving the movable die plate 64 forward and backward with respect to the fixed die plate 61,
Although the toggle link mechanism 65 is used, it is not limited to this.
In short, it is provided between the rear plate 62 and the movable die plate 64, and the movable die plate is fixed to the fixed die plate 61.
A mechanism for moving the movable die plate forward and backward with respect to the fixed die plate 61, and at the position where the extension amount of the tie bar reaches a preset value, the rear plate 62 and the movable die plate 64 are Any structure may be used as long as it is a mechanism capable of holding the relative position of the.

Further, in the above-mentioned embodiment, the mold structure 45 includes two lens molding cavities 3, but it may be only one lens molding cavity or three or more lens molding cavities. May be included.

In the above embodiment, the compression is started immediately before the completion of the injection of the molten resin. However, for example, after the injection of the molten resin is completed depending on the type of the lens (minus lens or plus lens), The injection may be started. Further, in the above-described embodiment, when adjusting the distance between the rear plate 62 and the fixed die plate 61, the rear plate 62 is moved toward and away from the fixed die plate 61, but this may be reversed.

Further, in the above-mentioned embodiment, the injection compression molding apparatus for the spectacle lens has been described, but the invention is not limited to the spectacle lens and can be used for other lenses in general.

[0058]

According to the lens injection compression molding method of the present invention, it is expected that the deformation of the molded product at the time of mold release can be suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an injection compression molding apparatus to which a method according to an embodiment of the present invention is applied.

FIG. 2 is a sectional view showing a molding die according to the same embodiment.

FIG. 3 is a sectional view taken along line III-III in FIG.

4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is a flowchart showing a lens forming procedure in the embodiment.

FIG. 6 is a diagram showing a relationship between a lens power and a mold clamping force when setting a resin pressurizing condition in the same embodiment.

FIG. 7 is a diagram for explaining a resin pressurizing condition setting step in the embodiment.

FIG. 8 is a view showing a state of a cavity at the time of mechanical END mold clamping in a resin pressure condition setting step in the same embodiment.

FIG. 9 is a diagram showing the entire apparatus when the mold is closed along the parting line in the same embodiment.

FIG. 10 is a view showing a cavity when the mold is closed by a parting line in the same embodiment.

FIG. 11 is a diagram showing the entire apparatus when the cavity volume is set in the same embodiment.

FIG. 12 is a diagram showing a cavity when a cavity volume is set in the same embodiment.

FIG. 13 is a diagram showing the entire apparatus when resin is pressed in the same embodiment.

FIG. 14 is a view showing a cavity at the time of resin pressurization in the same embodiment.

FIG. 15 is a diagram showing a relationship between a mold clamping force and a tie bar elongation amount in a cooling step in the same embodiment.

FIG. 16 is a diagram showing a relationship between a mold clamping force and a die plate spacing in a cooling process and a primary mold releasing process in the same embodiment.

FIG. 17 is a perspective view showing a molded product obtained in the same embodiment.

[Explanation of symbols]

1 Movable Mold 2 Fixed Mold 3 Lens Molding Cavity 4 Mold Body 11 Insert (Lens Concave Surface Molding Cavity Forming Member) 12 Insert (Lens Convex Surface Molding Cavity Forming Member) 16 Mold Mounting Member 45 Mold Composition 48 Sprue (Resin Flow Path) ) 49 runner (resin flow path) 50 molding die 61 fixed die plate (one spacing member) 62 rear die plate (other spacing member) 63 tie bar 64 movable die plate 65 toggle link mechanism (advancing and retracting mechanism) 67 die thickness Adjusting device (spacing adjusting means) 68 Extension amount detection sensor (tie bar extension amount detecting means) 85 Injection nozzle 91 Nozzle shut pin (blocking member)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Tanagawa             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. (72) Inventor Tetsuya Uchida             2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Ho             Within Ya Co., Ltd. F-term (reference) 4F202 AA21 AA28 AH74 AM32 AR02                       AR07 CA11 CB01 CK07 CK90                       CL32 CN05 CN24                 4F206 AA21 AA28 AH74 AR02 AR07                       JA03 JL02 JN25 JN34 JN41                       JN43 JQ81 JQ83 JT05

Claims (7)

[Claims] 1. A molding die including a fixed die and a movable die that moves back and forth with respect to the fixed die, and provided with a lens forming cavity including a pair of cavity forming members for forming a lens uneven surface between the die. A method of injection compression molding of a lens for molding a lens made of a thermoplastic resin, wherein the mold is closed, and in this mold closed state, the thickness of the lens molding cavity is smaller than the thickness of the molded product. A cavity volume setting step of moving the movable cavity forming member to a position where a thick predetermined thickness is obtained, and a thermoplastic molten resin is injected into the lens molding cavity set in the cavity volume setting step, and then the molten resin A resin injection encapsulation step of encapsulating the mold in the mold, and moving the cavity forming member of the movable mold toward the cavity forming member of the fixed mold. And a resin pressurizing step of compressing the molten resin injected into the lens molding cavity, a cooling step of cooling the molten resin for a predetermined time after the resin pressurizing step is finished, and after the cooling step is finished, An initial mold releasing operation for lowering the pressure applied to the molten resin in the lens molding cavity while maintaining the relative position of the movable mold cavity forming member and the fixed mold cavity forming member substantially constant for a predetermined period.
And a mold release step of thereafter performing a main mold release operation of opening the movable mold with respect to the fixed mold, the injection compression molding method of the lens. 2. The lens injection compression molding method according to claim 1, wherein in the cooling step, a relative position between the movable mold cavity forming member and the fixed mold cavity forming member is set for a preset predetermined time. An injection compression molding method for a lens, characterized in that the pressure applied to the molten resin in the lens molding cavity is gradually reduced at a rate slower than the pressure reduction rate in the mold releasing step while being kept constant. 3. The method of injection compression molding of a lens according to claim 1, wherein in at least an initial mold releasing step of the mold releasing step and the cooling step, the cavity forming member and the fixed mold of the movable die are used. The pressure applied to the molten resin in the lens molding cavity is reduced while maintaining the change in the distance from the cavity forming member within the difference between the thickness of the lens molding cavity during compression and the thickness of the ejected molded product. A method for injection compression molding of a lens, comprising: 4. The lens injection compression molding method according to claim 1, wherein a pair of spacing plates are connected to each other by a tie bar, and the movable die plate is movable along the tie bar. The movable die is attached to the movable die plate, and the fixed die is attached to one of the pair of gap holding plates, and the fixed die is provided between the other of the pair of gap holding plates and the movable die plate. On the other hand, a toggle link mechanism for advancing and retracting the movable die is provided, and the toggle link mechanism is extended to close the molding die, and the toggle link mechanism is operated to the extension operation limit position. Is set to the minimum volume, so that the amount of extension of the tie bar becomes a desired value, Comprising a mold clamping force adjustment step of adjusting the release, as in the resin pressurizing step, injection compression molding method of a lens, characterized in that operating the toggle link mechanism to the expansion operation limit position. 5. The method for injection compression molding of a lens according to claim 4, wherein in the mold clamping force adjusting step, the other space holding plate is adjusted by moving the space holding plate closer to or separated from the one space holding plate. A method for injection compression molding of a characteristic lens. 6. The lens injection compression molding method according to claim 1, wherein in the resin injection encapsulation step, a molten resin is injected into the lens molding cavity, and then the lens is molded. An injection compression molding method for a lens, characterized in that a blocking member is projected into a sprue communicating with a molding cavity via a runner to close a nozzle passage for injecting a molten resin. 7. A tie bar connecting a pair of spacing plates to each other, a movable die plate movably provided along the tie bar, and between one of the pair of spacing plates and the movable die plate. A movable die plate that is provided between the movable die plate and a molding die that has a lens molding cavity that includes a pair of cavity forming members that are provided for molding the lens uneven surface, and the other of the pair of gap holding plates and the movable die plate. An advancing / retreating mechanism for advancing / retreating with respect to one of the spacing plates, the molding die being fixed to the one spacing plate, having a cavity forming member for forming the lens molding cavity therein, A movable die fixed to a movable die plate, the movable die forming the lens forming cavity therein. A mold body having a cavity forming member, a mold mounting member fixed to the movable die plate and movably holding the mold body toward the fixed mold, and a mold mounting member interposed between the mold mounting member and the mold body. An elastic member, and the mold mounting member and the mold main body are configured to be openable and closable by a predetermined distance by the elastic member, and when the molding die is closed by the operation of the advancing and retracting mechanism, the movable member is movable. A method for injection compression molding of a lens, wherein a lens made of a thermoplastic resin is molded using a molding device having a structure in which the cavity for molding the lens is reduced when the die plate advances toward one of the spacing plates. Actuating the mechanism to close the mold, and
In this mold closed state, the cavity volume setting step of moving the cavity forming member of the movable die to a position where the thickness of the lens molding cavity becomes a predetermined thickness thicker than the thickness of the lens molded product, and set in the cavity volume setting step. After injecting the thermoplastic molten resin into the lens molding cavity, the resin injection encapsulation step of enclosing the molten resin in the molding die, and by operating the advancing and retracting mechanism, fixed to the movable die plate The movable mold cavity forming member is advanced toward the fixed mold cavity forming member fixed to one of the space holding plates, and the other space is held at a position where the thickness of the lens molding cavity is equal to or less than the thickness of the lens molded product. Hold the relative position between the plate and the movable die plate constant and inject into the lens molding cavity. A resin pressurizing step of compressing the molten resin obtained, a cooling step of cooling the molten resin for a predetermined period of time after the resin pressing step is finished, and the other interval holding which is held constant after the cooling step is finished. By operating the advancing / retreating mechanism in a direction of reducing the distance between the plate and the movable die plate, the relative position of the cavity forming member of the movable die and the cavity forming member of the fixed die is substantially constant for a predetermined period in the initial mold release. While maintaining
An initial mold releasing operation for lowering the pressure applied to the molten resin in the lens molding cavity, and a mold releasing step for thereafter performing a main mold releasing operation for opening the movable mold with respect to the fixed mold. A method for injection compression molding of a lens, comprising: