JP2003136569A - Method for injection/compression molding lens and injection/compression molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for injection/compression molding a lens by which the generation of inverted blisters and distortions can be held down to a low level and the molding cycle can be shortened, and an injection/ compression molding device. SOLUTION: This method for injection/compression molding a lens comprises the step to actuate a toggle linkage mechanism 65 and thereby, clamp a mold 50 and further, under this mold clamping state, transfer a movable die plate 64 to a position where the thickness of a cavity is larger than the thickness of a molded product as specified, the step to inject a molten resin into the cavity and seal the molten resin inside the cavity, the step to actuate the toggle linkage mechanism 65 and thereby, move a movable die plate 64 forward to a fixed die plate 61 and further, retain the relative positions of a rear plate 62 and the movable die plate 64 constantly at a position where the elongation level of a tie bar 63 reaches a previously set level, and the step to cool the molten resin for a specified time after the completion of pressurizing the resin.

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 and an injection compression molding apparatus for molding a lens by injection molding a thermoplastic resin. For example, the present invention relates to a lens injection compression molding method and an injection compression molding apparatus suitable for molding a spectacle lens in which occurrence of sink marks and distortion is reduced.

[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.

[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 and internal distortion. Therefore, a cooling process is required to uniformly cool the molten resin filled in the eyeglass lens molding cavity. In the case of a meniscus lens used as an eyeglass lens, since it is a thick-walled molded product with a difference in thickness deviation between the central portion and the peripheral portion, cooling time is required to suppress the occurrence of sink marks, shrinkage deformation, and internal distortion. Need to be long. Therefore, there is a problem that the molding cycle becomes long. Incidentally, Japanese Patent Laid-Open No. 9-2347
Japanese Patent Publication No. 74 discloses a cooling time for a minus lens (a lens whose peripheral portion is thicker than its central portion), but in the case of a diameter of 76 mm and a frequency of -4.00 D (diopter), cooling is performed. It takes 230 seconds.

An object of the present invention is to solve the above problems of the prior art, to provide an injection compression molding method and an injection compression molding apparatus for a lens capable of reducing the occurrence of sink marks and distortions and shortening the molding cycle. It is in.

[0005]

SUMMARY OF THE INVENTION A lens injection compression molding method according to the present invention comprises a tie bar connecting a pair of distance holding plates to each other, a movable die plate movably provided along the tie bar, and the pair of tie bars. A mold having a lens-forming cavity therein, which includes a pair of cavity-forming members for molding the concave-convex surface of the lens, which is provided between one of the gap-holding plates and the movable die plate; The movable die plate is provided between the other and the movable die plate, and includes an advancing and retracting mechanism for advancing and retracting the movable die plate with respect to one of the spacing plates, and by the operation of the advancing and retracting mechanism, in a state where the molding die is closed, A molding device having a structure in which the lens molding cavity is reduced when the movable die plate advances toward one of the gap holding plates. A method for injection compression molding of a lens for molding a lens made of a thermoplastic resin, wherein the advancing / retreating mechanism is actuated to close the mold, and in the mold closed state, the lens molding cavity After the cavity volume setting step of moving the movable die plate to a position where the thickness becomes a predetermined thickness thicker than the thickness of the molded product, after injecting the thermoplastic molten resin into the lens molding cavity set in the cavity volume setting step ,
A resin injection encapsulation step of enclosing the molten resin in a molding die, the advance / retreat mechanism is operated to advance the movable die plate toward one of the gap holding plates, and the extension amount of the tie bar is a lens characteristic. A resin pressurizing step of pressurizing the molten resin by holding the relative position of the other spacing plate and the movable die plate constant at a position having a preset value according to And a cooling step of subsequently cooling the molten resin for a predetermined time set in advance.

According to such a lens injection compression molding method, first, in the cavity volume setting step, the molding die is closed by the operation of the advancing / retreating mechanism, and the lens molding is performed in the closed state. The movable die plate is moved to a position where the thickness of the cavity becomes a predetermined thickness thicker 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. At the time of injection of the molten resin, the cavity for lens molding is set to be thicker than the thickness of the molded product, so there is no inappropriate resin resistance with the molding die,
The resin can be smoothly injected and filled. 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 pressurizing step, the movable die plate is advanced toward one of the gap holding plates by the operation of the advancing / retreating mechanism. At this time, since the molten resin is filled and contained in the molding die including the lens molding cavity, the tie bar is stretched, and at the position where the amount of expansion of the tie bar reaches a preset value, the other spacing plate The relative position between the movable die plate and the movable die plate is held constant. Then, the reaction force due to the extension of the tie bar acts on the molten resin in the lens molding cavity via the movable die plate. That is, the molten resin in the lens molding cavity is pressed by the reaction force due to the extension of the tie bar. 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.

Finally, in the cooling step, the molten resin is cooled for a predetermined time set after the completion of the resin pressurizing step.
Then, the molten resin in the lens molding cavity is cooled in a compressed state, and gradually solidifies and contracts as the cooling progresses. 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 gradually cools and solidifies and contracts, it acts on the molten resin in the lens molding cavity through the advancement of the movable die plate and elastic recovery of the tie bar. The pressure being applied can be gradually reduced. 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. Incidentally, according to the method of the present invention, the diameter is 76 m.
In the case of m and frequency -4.00D, it is possible to shift to the mold release step with a cooling time of 80 seconds.

In the above structure, the molding die is a fixed die having a cavity forming member which is fixed to the one spacing plate and which forms the lens molding cavity, and a movable die which is fixed to the movable die plate. And a mold main body having a cavity forming member for forming the lens molding cavity therein, and the movable mold fixed to the movable die plate and movably holding the mold main body toward the fixed mold. A mold mounting member and an elastic member interposed between the mold mounting member and the mold body, and the elastic member is configured to be capable of opening and closing the mold mounting member and the mold body by a predetermined gap. Is desirable. With this configuration, in the cavity volume setting step, the fixed die and the movable die are closed by the operation of the advancing / retreating mechanism, and when the movable die plate is advanced in the mold closed state, the elastic member is compressed. While the mold is being closed, the mold mounting member and the mold body approach each other,
The thickness of the lens molding cavity can be set to a predetermined thickness that is thicker than the thickness of the molded product. That is,
By simply moving the movable die plate forward by operating the advancing / retreating mechanism, the molding die is closed, and in this mold closed state, the thickness of the lens molding cavity can be set to a predetermined thickness.

Further, a toggle link mechanism is used as the advancing / retreating mechanism, the toggle link mechanism is extended, the molding die is closed, and the toggle link mechanism is operated up to the extension operation limit position. In a state where the cavity is set to the minimum volume, a mold clamping force adjusting step of adjusting the distance between the pair of spacing plates is provided so that the extension amount of the tie bar becomes a desired value. It is preferable to operate the toggle link mechanism to the extension operation limit position. In this way, the toggle link mechanism is used as the advancing / retreating mechanism, 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. With the lens molding cavity set to the minimum volume, there is a mold clamping force adjustment process that adjusts the distance between the pair of spacing plates so that the amount of tie bar expansion reaches the desired value. The operation control in can be simplified.

That is, 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 extension amount of the tie bar becomes a preset desired value (for example, ΔL). If the distance between the pair of distance holding plates is adjusted, the toggle link mechanism only has to be moved to the extension operation limit position in the resin pressurizing step. The amount of elongation of the tie bar in the resin pressurizing process is equal to the amount of elongation (ΔL) in the mold clamping force adjusting process,
This amount is the sum of the amount of expansion (α) of the tie bar that comes from the mold that cannot be completely closed due to the volume of resin in the lens molding cavity. Therefore, consider the amount of expansion (α) in the mold clamping force adjustment process. If you set the amount of elongation (ΔL),
In the resin pressing step, the toggle link mechanism only has to be operated to the extension operation limit position. 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 when 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 approach and separate 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 via 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.

In the lens injection compression molding apparatus of the present invention, a tie bar that connects a pair of spacing plates to each other, a movable die plate movably provided along the tie bars, and one of the pair of spacing plates. And a movable die plate, which is provided between the movable die plate and the movable die plate, and has a lens molding cavity including a pair of cavity forming members for molding the concave-convex surface of the lens, and the other of the pair of spacing plates and the movable die. A toggle link mechanism provided between the movable die plate and the plate for moving the movable die plate forward and backward with respect to one of the gap holding plates, and the movable die in a state where the mold is closed by the operation of the toggle link mechanism. When the plate advances toward one of the spacing plates, the lens molding cavity shrinks. An expansion compression molding apparatus, wherein the tie bar extension amount detecting means for detecting the extension amount of the tie bar and the tie bar extension amount detecting means in the state where the toggle link mechanism is operated to the extension operation limit position are detected. And a space adjusting means for adjusting the distance between the pair of space holding plates so that the amount of expansion of the space becomes a desired value.

According to this lens injection compression molding apparatus,
In an injection compression molding machine that performs mold clamping with a toggle link mechanism, the tie bar extension amount detection means for detecting the extension amount of the tie bar and the tie bar extension amount detection means when the toggle link mechanism is operated to the extension operation limit position are detected. The above-mentioned injection compression molding method of the present invention can be realized by providing the interval adjusting means for adjusting the distance between the pair of interval holding plates so that the expansion amount of the tie bar to be a desired value.

[0016]

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 includes a fixed die plate 61 and a rear plate 62 as a pair of space holding 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. The tie bar 63 is provided with an extension amount detection sensor 68 as a 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). Note that the toggle link mechanism has various mechanisms such as a double link mechanism and is structurally complicated, but 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 of 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 periphery 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 includes 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 when the disc spring 71A is closed without compression to the movable die plate 64, 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 the completion of injection filling. That is, the nozzle shut pin 91 is projected into the sprue 48 to close the passage tip of the injection nozzle 85. 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. 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 drop relatively greatly in the initial stage of the cooling process, but after that, Indicates a very gradual downward trend (state in which there is almost no change). Since the proper relationship between the elastic recovery of the tie bar 63 and the cooling time is required by experimental verification, the cooling time can be determined by the material used and the lens characteristics.

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 acts to cancel each other, and the cross head 73 moves backward with the apparent gap between the fixed die plate 61 and the movable die plate 64 remaining largely unchanged. to continue.

FIG. 16 shows the relationship between the die clamping force and the die plate spacing (the spacing between the fixed die plate 61 and the movable die plate 64) in the cooling step and the primary demolding step. As can be seen from this figure, the mold clamping force (pressure applied to the resin in the cavity 3) sharply decreases in the primary mold release process after the cooling process, but the fixed die plate 61 and the movable die The distance between the plate 64 and the plate 64 is shown to remain unchanged during the primary mold release process. The pressure applied to the resin in the cavity 3 can be controlled by controlling the retreat speed of the crosshead 73 to control the decrease in the pressure applied to the resin in the cavity 3. 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 in the cooling time 80.

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 constructing body 45 includes two lens forming cavities 3, but it may be only one lens forming cavity or three or more lens forming 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 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.

[0052]

According to the injection compression molding method and the injection compression molding apparatus of the present invention, it is expected that the occurrence of sink marks and distortions can be reduced and that the molding cycle can be shortened.

[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 the relationship between the mold clamping force and the amount of extension of the tie bar 63 in the 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) 71A Disc spring (elastic member) 85 Injection nozzle 91 Nozzle shut pin (blocking member)

Claims (6)

[Claims] 1. 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 provided between the movable die plate and a molding die having a lens molding cavity including a pair of cavity forming members for molding the lens uneven surface, and the movable die plate. An advancing and retracting mechanism for advancing and retracting the plate with respect to one of the gap holding plates, and when the movable die plate advances toward one of the gap holding plates in a state where the mold is closed by the operation of the advancing and retracting mechanism. Using a molding machine with a structure in which the lens molding cavity is reduced, a lens made of thermoplastic resin is molded. An injection compression molding method, wherein the advancing / retreating mechanism is operated to close the molding die, and
In this mold closed state, a cavity volume setting step of moving the movable die plate 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 set in the cavity volume setting step. Resin injection and encapsulation process of injecting thermoplastic molten resin into the mold cavity and then enclosing the molten resin in the mold, and moving the movable die plate toward one of the gap holding plates by operating the advancing and retracting mechanism. When the tie bar is moved forward and the expansion amount of the tie bar reaches a value set in advance according to the lens characteristics, the relative position between the other spacing plate and the movable die plate is held constant and the molten resin is added. And a cooling step of cooling the molten resin for a predetermined time set in advance after the resin pressing step. Injection compression molding method of a lens according to claim. 2. The lens injection compression molding method according to claim 1, wherein the molding die has a cavity forming member that is fixed to the one spacing plate and internally forms the lens molding cavity. And a movable die fixed to the movable die plate, the movable die having a cavity forming member inside which forms the lens forming cavity, and the die body fixed to the movable die plate. A mold mounting member that holds the mold movably toward the fixed mold, and an elastic member interposed between the mold mounting member and the mold body, and the elastic member keeps the mold mounting member and the mold body constant. The method of injection compression molding of a lens, wherein the gap can be opened and closed only. 3. The lens injection compression molding method according to claim 1 or 2, wherein a toggle link mechanism is used as the advancing / retreating mechanism, and the toggle link mechanism is extended to close the molding die. In addition, when the toggle link mechanism is operated to the extension operation limit position and the lens forming cavity is set to the minimum volume, the distance between the pair of spacing plates is adjusted so that the extension amount of the tie bar becomes a desired value. The method for injection compression molding of a lens, comprising: a mold clamping force adjusting step for adjusting the above, wherein in the resin pressurizing step, the toggle link mechanism is operated to an extension operation limit position. 4. The method for injection compression molding of a lens according to claim 3, wherein in the mold clamping force adjusting step, the other spacing holding plate is adjusted to approach and separate from one spacing holding plate. A method for injection compression molding of a characteristic lens. 5. 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. 6. 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 mold provided between the movable die plate and a molding die that is provided with a lens molding cavity that includes a pair of cavity forming members for molding the concave-convex surface of the lens; And a toggle link mechanism for moving the die plate forward and backward with respect to one of the gap holding plates,
An injection compression molding apparatus for a lens having a structure in which a lens molding cavity is reduced when the movable die plate advances toward one of the gap holding plates in a state where the molding die is closed by the operation of the toggle link mechanism. In the state where the tie bar extension amount detecting means for detecting the extension amount of the tie bar and the toggle link mechanism are operated to the extension operation limit position, the extension amount of the tie bar detected by the tie bar extension amount detecting means is desired. An injection compression molding apparatus for a lens, comprising: a space adjusting means for adjusting a distance between the pair of space holding plates so that the value becomes a value.