JP3390781B2 - Injection compression molding of spectacle lenses - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method for a spectacle lens by injection molding a thermoplastic resin to obtain a spectacle lens. More specifically, the present invention relates to an injection compression molding method for spectacle lenses capable of molding a plus lens and a minus lens with high accuracy and high quality.

[0002]

BACKGROUND ART As a molding method for obtaining a lens from a thermoplastic resin, an injection compression molding method is known (for example, JP-A-2-26723 and JP-B-6-9826). For spectacle lenses, lens power + 4.00D-
A lens power range of about 8.00 D is preferably used for this molding method. In the injection compression molding method, in order to correct the shrinkage of the molten resin and obtain a uniform and high shape accuracy, the mold is clamped leaving a compression allowance inside the lens cavity, and then the inside of the lens cavity is closed. In this molding method, a molten resin is injected and filled, and then the compression margin is compressed to obtain a lens.

[0003]

By the way, the lens is
If the curvature of the front side of the lens is different from that of the rear side, the lens thickness will have a thickness deviation. There are two types, a thinner minus lens. Although the lens thickness varies depending on the optical lens design, for example, an aspherical lens having a refractive index of about 1.50 has a center thickness of 4.2 mm at +2.00 D, a peripheral thickness of 1.0 mm, and a center thickness of 1 at 4.00 D. Design values of about 0.4 mm and a peripheral thickness of about 7.9 mm can be set. However, if these lenses are compression-molded under the same conditions, the following problems occur due to the difference in shape characteristics.

In forming a minus lens, since the central portion of the lens is thinner than the peripheral portion, the flow resistance is large in the central portion of the cavity. Therefore, it is difficult for the molten resin injected into the cavity to flow in the central portion of the cavity, and since the molten resin splits and flows from the peripheral portion to the central portion, many weld marks are likely to occur in the central portion. On the other hand, in the molding of a plus lens, if the difference between the cavity volume and the filling amount of the molten resin is too large, the fluidity of the molten resin will decrease, and an unfilled portion will occur. A resin filling history called a flow mark is likely to occur in the critical portion between the unfilled portion and the filled portion.

An object of the present invention is to provide an injection compression molding method for a spectacle lens capable of molding a lens having a thickness deviation regardless of the shape characteristics of the lens, that is, a plus lens and a minus lens with high precision and high quality. To do. Another object of the present invention is to provide an injection compression molding method for a spectacle lens, which enables efficient molding of a plus lens and a minus lens from injection to release.

[0006]

[0007]

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

In the injection compression molding method for a spectacle lens according to the present invention, a movable mold that opens and closes relative to a fixed mold has a mold mounting member, and this mold mounting member faces the fixed mold. A mold body that is movably mounted is provided, and an insert that is movably fitted into an insert guide to form a lens cavity is provided inside the mold body, and the insert is held. A minus lens having a central portion with a thinner wall thickness than the peripheral portion is formed by using one molding die in which the holding member is an elastic member and is always elastically biased in a direction opposite to the fixed die and abutted on the die mounting member. And a molding method for molding a plus lens having a central part thicker than the peripheral part, wherein the mold mounting member is advanced to the fixed mold side while leaving a preset compression margin in the lens cavity. Then, the mold cavity is clamped, then molten resin is injected and filled in the lens cavity, and the set compression allowance is set by advancing the mold mounting member toward the fixed mold side at least after a time point before completion of injection of the molten resin. After compressing, the mold mounting member is retracted, the movable mold is opened from the fixed mold, and then the holding member is pressed and moved to the fixed mold side by an eject pin inserted in the mold mounting member. In the injection compression molding method of the spectacle lens for ejecting the lens molded product by the insert, the set compression allowance is set according to the types of the minus lens and the plus lens, and the set compression allowance at the time of the minus lens molding is set to the plus It is set to a value that is larger than the compression allowance set when molding the lens and that differs depending on the frequency, and is held by the eject pin when the mold mounting member retracts. By pressing move timber to the fixed mold side, said insert is advanced relative the fixed mold side with respect to the fitment member, thereafter, to open the mold the movable mold from the fixed mold,
The holding member is pressed and moved by the eject pin, and the lens molded product is projected by the insert.

According to this molding method, minus lens molding is performed.
The compression allowance at the time is more than the compression allowance at the time of molding the plus lens.
Because it is set large, a wider cavity area
It is possible to secure the fluidity of the molten resin in the cavity.
Since it also improves the
The molten resin that has reached the inside of the bite is
It flows through the central part of the tee into the peripheral part. Therefore, the central part
Weld mark can be prevented from occurring in the lens
Since sufficient pressure is maintained in the
Image clarity is improved. Therefore, depending on the shape characteristics of the lens,
The plus lens and minus lens with high accuracy.
Can be molded to high quality. Further , when the movable die mounting member retracts, the holding member is pressed and moved by the eject pin toward the fixed die side, whereby the insert advances toward the fixed die side relative to the movable die mounting member. Therefore, there is no gap between the lens molded product in the cavity and the insert, which is the same size as the retracted amount of the mold mounting member.Therefore, it is possible to suppress the generation of excessive compressed air, and It is possible to prevent the pressure of compressed air from acting. Therefore, there is no mold release defect such as breakage of the part to be molded by the sprue or runner and deviation of the mold during mold release, and a lens molded product with high molding accuracy can be obtained.

At this time, the set pressure for molding the plus lens is set.
The compression allowance is set to the maximum compression allowance in the lens cavity.
From the large initial position to the position where there is no compression allowance
The member is advanced to the fixed mold side and clamped, and
Installed by retracting the die mounting member by the set compression amount.
Setting, setting of the minus lens molding setting of compression allowance
Is the initial position with the maximum compression allowance in the lens cavity.
From the installation to the position where the set compression margin remains
Set by advancing to the fixed mold side and clamping the mold
It is desirable to do. If you do this, minus len
The compression allowance set during molding is the compression inside the lens cavity.
From the maximum initial position to the position where the set compression amount remains
It can be set by clamping the mold, that is, gold
Setting the mold for a long distance There is no operation to open the compression amount, so set
The compression margin can be set quickly and accurately.
On the other hand, the set compression allowance when molding a plus lens is the key for the lens.
There is no compression allowance from the initial position where the compression allowance in the cavity is maximum.
After the mold is clamped to the position
If you open only the reduction amount, you can set it, so set the compression amount in the same way.
The setting can be performed quickly and with high accuracy. here,
When the movable die mounting member is retracted, the holding member is pressed and moved by the eject pin to advance the insert relatively to the fixed die side with respect to the movable die mounting member. The amount may be the same as the retreat amount (opening amount) or may be large, but smaller is more preferable.

If the amount of advance is set smaller than the amount of retreat of the die mounting member, a gap can be provided between the insert and the lens molded product, so that even when the movable mold is opened from the fixed mold, the lens molded product is released from the cavity. Does not fall out,
Prevents damage to lens moldings caused by falling off. In particular, the gap between the insert and the lens molded product is preferably 1 to 4 mm.
If the gap is less than 1 mm, the lens molded product may fall off, and if the gap is larger than 4 mm, the effect of suppressing the generation of excessive compressed air is low.

That is, when the clamping force is released after the mold is clamped, the compression allowance is set to a large amount, and therefore the mold retreats largely and sharply. Especially, the molding environment (mainly the temperature) on the convex surface side of the lens largely changes. Therefore, the releasing force strongly acts on a part of the lens surface to cause a releasing failure, or the sprue or runner portion is broken. Therefore, by setting the above-mentioned gap, it is possible to prevent the partial mold releasing action from being excessively applied to a part of the molding portion by providing an intermediate ejecting function. In particular, in the case of a plus lens, since the peripheral thickness of the lens is small, the strength of the joint with the runner is not structurally strong, so this eject method is effective.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a spectacle lens according to the present embodiment (meniscus-shaped spectacle lens; single focus,
FIG. 2 is a sectional view of the injection compression molding die used in the injection compression molding method of multifocal, progressive multifocal), and FIG. 2 is a sectional view taken along line II-II of FIG. The material of the spectacle lens molded here is a thermoplastic resin such as PMMA (polymethylmethacrylate) or PC (polycarbonate). Further, in this embodiment, low-power injection is used in order to prevent striae, optical distortion, and the like.

As shown in FIG. 1, the injection compression molding die has two eyeglass lens cavities 3 between an upper die 1 and a lower die 2 which are vertically divided in a parting line PL. It is a mold for taking two formed lenses.

The upper mold 1 is a movable mold which is vertically closed and opened with respect to the lower mold 2 which is a fixed mold, and is a mold mounting member 16
And a die body 4 movably attached to the die attachment member 16 toward the lower die 2. Mold mounting member 16
Consists of an upper member 16A and a lower member 16B. Mold body 4
Consists of an insert guide 5 and templates 6, 7. The lower mold 2 includes a mold body 8 including an insert guide 9 and a mold plate 10, and a mold mounting member 15 for mounting the mold body 8. The inserts 11 and 12 forming the cavity 3 are housed inside the insert guides 5 and 9 so as to be slidable in a direction perpendicular to the parting line PL.

The mold body 4 of the upper mold 1 is connected to the mold mounting member 16 by a bolt 17 shown in FIG. 2, and the outer periphery of the bolt 17 is located between the mold body 4 and the mold mounting member 16. The inserted disc spring 17A is interposed. The mold mounting member 16 is moved up and down by a mold clamping cylinder (not shown). A gap S is provided between the mold body 4 and the mold mounting member 16, and the mold body 4 and the mold mounting member 16 are opened and closed vertically by the gap S while being guided by the guide pins 18. It is supposed to do. An open cylinder (not shown) is arranged below the die mounting member 15, and the die mounting member 16 is pushed up by the open cylinder against the die clamping force of the die clamping cylinder to form a gap S. It is supposed to be done.

A downward hydraulic cylinder 19 is provided on the die mounting member 16 so as to be vertically movable. Piston rod 21 connected to piston 20 of hydraulic cylinder 19
Penetrates through a back insert 22 fixed to the lower surface of the cylinder 19 and has a T-shaped clamp member 23 at its tip. The T-shaped clamp member 23 is the insert 1
It is engaged with a T-shaped groove 24 formed on the upper end surface of the connector 1 so as to be freely disengaged. The die mounting member 15 is provided with an upward hydraulic cylinder 26. The piston rod 28 connected to the piston 27 of the hydraulic cylinder 26 penetrates through the die mounting member 15 and has a T-shaped clamp member 29 at its tip. The T-shaped clamp member 29 is the insert 1
It is engaged with a T-shaped groove 30 formed on the lower end surface of the member 2 so as to be disengageable.

A pressure receiving member 32 is fixed to the upper end of the hydraulic cylinder 19. When the pressure receiving member 32 is pushed down by the eject pin 34 inserted from the hole 33 formed in the die mounting member 16, the hydraulic cylinder 19, the back insert 22 and the insert 11 are also pushed down, and the lens molded product molded in the cavity 3 is obtained. The upper die 1 and the lower die 2 are projected when they are divided. Here, the back insert 22, the hydraulic cylinder 19, and the pressure receiving member 32 constitute a holding member that holds the insert 11. An eject bar 35 is vertically movable at the center of the mold mounting member 16 of the upper mold 1. A pressure receiving member 36 is fixed to the upper end of the eject bar 35. When the pressure receiving member 36 is pushed down by the eject pin 38 inserted from the hole 37 formed in the die mounting member 16, the eject bar 35 is pushed down.

The spring force of a spring 40 wound around the outer circumference of the eject return pin 39 acts upward on the pressure receiving member 32. Although not shown, the spring force of a spring wound around the outer circumference of the eject return pin acts upward on the pressure receiving member 36 as well. Therefore, when the eject pins 34, 38 rise, the pressure receiving members 32, 36
Is rising and is returning to the old place. here,
A holding member constituted by the back insert 22, the hydraulic cylinder 19 and the pressure receiving member 32 is always elastically biased in the direction opposite to the lower mold 2 by the spring 40, which is an elastic member, and is in contact with the mold mounting member 16. .

Next, the operation of this embodiment will be described. First, the inserts 11 and 12 are exchanged according to the type of lens to be molded. Insert 11, 12
When replacing the above, the upper mold 1 including the mold mounting member 16 is lifted and the mold is divided from the lower mold 2. Further, the piston rod 21 of the hydraulic cylinder 19 is lowered, the piston rod 28 of the hydraulic cylinder 26 is raised, and the T mounted on the tips of these piston rods 21 and 28.
The character clamp members 23 and 29 are projected from the insert guides 5 and 9.

New die bodies 4 and 8 of the upper die 1 and the lower die 2
The inserts 11 and 12 mounted on the are horizontally transferred while being held by a robot arm (not shown), and the T-shaped grooves 24 and 30 of the inserts 11 and 12 are inserted into the T-shaped clamp member 2.
3, 29 are engaged. After that, the piston rod 21 of the hydraulic cylinder 19 is raised to pull up the insert 11, and the piston rod 28 of the hydraulic cylinder 26 is lowered to pull down the insert 12. This allows
The inserts 11 and 12 are fitted into the insert guides 5 and 9. In this way, in the case of molding a plus lens (lens having a central part thicker than the peripheral part), the inserts 11A and 12A shown in FIG. 4 and FIG. In the case of molding a lens thinner than the portion), inserts 11B and 12 shown in FIGS.
Replace with B respectively.

Now, in molding the lens, the operation proceeds according to the flow chart shown in FIG. First, Fig. 1
Then, the mold is closed in the state shown in FIG. That is, the upper mold 1 is lowered by the mold clamping cylinder, the mold plate 6 of the upper mold 1 contacts the mold plate 10 of the lower mold 2, and the mold spring 17A is closed without being compressed. In this state, the gap S is set to the maximum opening amount (about 15 mm), that is, the initial position where the compression margin in the cavity 3 is maximum. Next, the size difference (set compression amount) is set. At this time, the dimension difference S ₍₊₎ of 0.8 mm or less is set for molding the plus lens.
When molding a minus lens, a size difference S _(-) larger than 0.8 mm is set. That is, the set compression allowance for minus lens molding is set larger than the set compression allowance for plus lens molding.

Here, in the case of molding a plus lens, that is, when the size difference S ₍₊₎ is set to 0.8 mm or less, as shown in FIG. Is further lowered (at this time, the disc spring 17A is compressed) to completely eliminate the gap S, and then the dimension attachment cylinder 16 is used to force the die attachment member 16 against the die clamping force of the die clamping cylinder. is raised only S _(+), to set the dimensions opening amount S _(+). On the other hand, in the case of molding a minus lens, that is, when a dimension opening amount S _(-) larger than 0.8 mm is set, as shown in FIG. It is lowered to a position where the amount S _(-) is left (at this time, the disc spring 17A is compressed) and stopped at that position to set the small opening amount S _(-) .

Next, the molten resin is injected and filled. For this, molten resin is injected from the nozzle of the injection molding machine connected to the sprue bush 57, and the sprue 58 and runner 5 are injected.
It fills in the cavity 3 through 9. At this time, in the case of molding a plus lens (FIG. 4), since the thickness of the central portion of the cavity 3 (the central portion of the lens) is large, the molten resin that has reached the inside of the cavity 3 is To reach the peripheral area. On the other hand, in the case of molding a minus lens, the opening amount S (−) larger than 0.8 mm is set, that is, since the thickness of the central portion of the cavity 3 is set large, the inside of the cavity 3 is set. The molten resin that has arrived at reaches the peripheral portion through the central portion of the cavity 3 without being split. Therefore, in any case, the weld mark in the central portion is suppressed.

Next, in the case of molding a plus lens (FIG. 4)
After the injection of the molten resin is completed, the nozzle is closed to make the space including the cavity 3, the runner 59 and the sprue 58 a closed closed space, and then the pressure is applied (compressed). That is, FIG.
As shown in, the mold clamping member 16 lowers the mold mounting member 16 by the open amount S (+). On the other hand, in the case of molding a minus lens (FIG. 6), pressurization (compression) is started before completion of injection of the molten resin. Specifically, when about 90 to 95% of the molten resin to be injected is injected, pressurization is started by the mold clamping cylinder, and as shown in FIG.
6 is moved down by the open distance S (-). At this time, immediately after the injection of the molten resin is completed, the nozzle is closed to make the space including the cavity 3, the runner 59 and the sprue 58 a closed closed space.

Next, after molding the plus lens or the minus lens in this way, these lenses are ejected. To this end, the die mounting member 16 of the upper die 1 is raised by the die clamping cylinder, that is, raised from the lower die 2,
A small opening S is opened between the mold body 4. At this time, the eject pin 34 is moved down by the eject cylinder, and the ejector pin 34 pushes and moves the pressure receiving member 32 downward with respect to the die mounting member 16. This pressing movement amount is smaller than the opening amount S, and the opening amount S is, for example, 15
When it is mm, the pressing movement amount is 13 mm. In other words, when the mold mounting member 16 is raised, the insert 11
Is lowered relative to the die mounting member 16 toward the lower die 2 side.

As a result, originally, when the die mounting member 16 is raised by the amount S of slight opening, the amount of rise of the insert 11 which is raised by the same amount can be suppressed to a small amount.
For example, in minus lens molding, as shown in FIG.
The insert 11 is a minute gap A from the spectacle lens portion 44A of the lens molded product 44 molded in the cavity 3,
If the opening amount and the pressing movement amount are the same as the above values, 2
Separated by a gap A of mm.

Thereafter, as shown in FIG. 9, the mold mounting member 16 of the upper mold 1 and the mold body 4 are lifted by the mold clamping cylinder, and the upper mold 1 is moved.
Is opened from the parting line PL with respect to the lower mold 2. Thereafter, a part of the lens molded product 44 exposed from the lower surface of the upper mold 1 is gripped by the gripping device, and the eject pin 3
4, 38 are lowered by each eject cylinder, whereby the pressure receiving members 32, 36 are pressed and moved, and the lens molded product 44 is projected by the insert 11 and the eject bar 35. At the time of this protrusion, the lens molded product 4
Since the insert 11 is separated from the spectacle lens portion 44A of No. 4 by a slight gap A, the air entering the gap A is not compressed by the insert 11 to a large pressure, and the compressed air is compressed air. The lens molded product 44 can be ejected from the upper mold 1 without exerting a large pressure on the spectacle lens portion 44A.

That is, when the die mounting member 16 of the upper die 1 rises from the die body 4 by the opening amount S, the ejecting pin 34 does not move the pressure receiving member 32 downward, and the die mounting member 16 is moved. When the insert 11 is not moved down relatively, the spectacle lens portion 44A of the lens molded product 44
A gap having the same size as the opening amount S is formed between the insert 11 and the insert 11, and when the eyeglass lens portion 44A is projected by the insert 11, the air in this gap is largely compressed and excessive high-pressure air is generated. Although it acts on the spectacle lens portion 44A which is a precision molding portion, in the embodiment according to the present invention, since a slight gap A is formed between the spectacle lens portion 44A and the insert 11, It becomes possible to suppress the generation of excessive compressed air when the eyeglass lens portion 44A of the lens molded product 44 is ejected, and to perform the protrusion at the portion molded by the sprue 58 and the runner 59, and to the mold at the time of mold release. It is possible to secure a highly accurate molding state of the spectacle lens portion 44A without a mold release defect such as a deviation of the eyeglasses.

According to this embodiment, the opening amount S _(-) when molding the minus lens is set to the opening amount S ₍ S ₎ when molding the plus lens.
_Since it is set larger than ₍₊₎ , a wider cavity region can be secured and the fluidity of the resin in the cavity can be improved. Therefore, when molding the minus lens, the molten resin that has reached the inside of the cavity 3 flows into the peripheral portion through the central portion of the cavity 3 without shunting it, so that it is possible to prevent the occurrence of weld marks in the central portion. Therefore, the plus lens and the minus lens can be molded with high precision and high quality regardless of the shape characteristics of the lens.

At this time, it is necessary to set the opening amount S _(-) when molding the minus lens to be larger than the opening amount S ₍₊₎ when molding the plus lens, but the opening amount S is the maximum initial position. Since the opening amount S _(-) is set by lowering the die mounting member 16 of the upper mold 1 to a position where the opening amount S _(-) remains, the setting of the opening amount S _(-) is set. Can be performed quickly and with high accuracy. On the other hand, the dimension difference S ₍₊₎ when molding a plus lens is the dimension difference S _(-) when molding a minus lens.
Since it is smaller, in this case, after lowering the mold mounting member 16 of the upper mold 1 from the initial position where the opening amount S is maximum to the position where the opening amount S disappears, the opening amount S ₍₊₎ Since the open amount S ₍₊₎ is set by opening, the open amount S ₍₊₎ can be set quickly and with high precision.

Further, at the time of molding the minus lens, since the compression of the opening amount S ₍₊₎ is started before the injection of the molten resin is completed, the volume of the cavity 3 is reduced before the injection of the molten resin is completed. Therefore, a large unfilled portion rarely remains in the cavity 3 at the time of completion of injection and filling of the molten resin, and therefore, generation of flow marks can also be prevented. That is,
If the opening amount S ₍₊₎ is set to a large value, the flow of the molten resin will stop with a large unfilled portion left in the cavity at the time of completion of injection and filling of the molten resin. The problem that a resin filling history called a flow mark is likely to occur in the critical portion is conceivable, but the occurrence of the flow mark can be prevented by adopting this embodiment.

When the die mounting member 16 of the upper die 1 is lifted from the lower die 2, the holding member holding the insert 11 provided in the die body 4 of the upper die 1 is ejected by the eject pin 34 to the lower die. Since the insert 11 is moved downward by pushing to the lower mold 2 side relative to the mold mounting member 16, it is possible to suppress generation of compressed air when the lens molded product 44 is projected by the insert 11. This protrusion becomes possible, and since the pressure of the air compressed to a high pressure does not act on the lens molded product 44, the protrusion work can be performed while ensuring the molding accuracy of the lens molded product 44 molded with high accuracy.

Further, the mold mounting member 16 of the upper mold 1 is the mold body 4
When the insert pin 11 is moved relative to the mold mounting member 16 by pressing the pressure receiving member 32 downward by the eject pin 34 when the insert 11 is moved upward by a distance S from
Since the descending amount is made smaller than the ascending amount of the die mounting member 16 (the opening amount S), the insert 11 and the lens molded product 44 are
A gap can be provided between the eyeglass lens unit 44A and the eyeglass lens unit 44A. Therefore, even when the upper mold 1 is opened from the lower mold 2, the lens molded product 44 does not drop off from the cavity 3, and damage to the lens molded product 44 due to the falling off can be prevented.

Further, in this embodiment, the insert 11
There are two cavities 3 formed by, for example, the holding member of the insert 11 including the back insert 22, the hydraulic cylinder 19, and the pressure receiving member 32 is elastically biased upward by the spring 40 independently for each insert 11. Therefore, even if the spring 40 of each insert 11 has a different spring force, the structure is not affected by the difference. However, the eject pin 34 is provided for each insert 11, that is, a holding member for these inserts 11. Since they are provided for each of them, these holding members that are independent of each other can be pressed downwardly by the eject pin 34 as required, and the two eyeglass lens parts of the lens molded product 44 can be formed by the two inserts 11. 44A can be projected.

In the above-described embodiment, the set compression allowance is set by the amount of the dimension difference formed between the mold body 4 and the mold mounting member 16, but other molds may be used. . For example, by using a mold having a structure in which a cavity core projecting in the cavity 3 is provided, a set compression allowance is set from the position of this cavity core, and then the cavity core is projected into the cavity 3 for compression. Good.

Further, in the above-described embodiment, the size difference is set to 0.8 mm or less for the plus lens and 0.8 mm or more for the minus lens. It may be arbitrarily determined according to the characteristics. In the above-described embodiment, the compression of the opening amount S _(-) is started at the time of injecting the molten resin by about 90 to 95% during the molding of the minus lens. Volume, resin type,
It may be arbitrarily determined according to the characteristics of the lens.

Further, in the above-described embodiment, when the mold mounting member 16 of the upper mold 1 is lifted from the mold main body 4 by the dimension opening amount S and when the mold main body 4 is separated from the lower mold 2 and opened. According to the above, the eject pin 34 is moved downward in a two-step manner. However, the opening movement of the die mounting member 16 by the die clamping cylinder and the die opening movement from the lower die 2 of the die body 4 are continuously performed. If so, the eject pin 34 is continuously moved downward, whereby the die mounting member 16
It is also possible to increase the descending amount of the insert 11 with respect to the above and directly eject the lens molded product 44.

[0046]

According to the injection compression molding method for a spectacle lens of the present invention, the set compression allowance during minus lens molding is set to be larger than the set compression allowance during plus lens molding. It is possible to prevent the weld mark from being generated, and it is possible to mold the plus lens and the minus lens with high precision and high quality regardless of the shape characteristics of the lens.

Further, when the movable die mounting member is retracted from the fixed die, the holding member holding the insert provided in the movable die main body is pressed and moved to the fixed die side by the eject pin, Since the insert is advanced toward the fixed mold side relative to the mold mounting member, when the lens molded product is projected by the insert, this projection can be performed while suppressing generation of compressed air. Therefore, since the pressure of the air compressed to high pressure does not act on the lens molded product,
The protrusion work can be performed while ensuring the molding accuracy of the lens molded product molded with high accuracy. Therefore, it is possible to efficiently perform from injection to release.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an injection molding die used in an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a flowchart showing a molding procedure in the same embodiment.

FIG. 4 is a diagram showing a state before injection and filling of a molten resin at the time of molding a plus lens in the embodiment.

FIG. 5 is a view showing a state after the molten resin is compressed at the time of molding the plus lens in the embodiment.

FIG. 6 is a view showing a state before injection and filling of a molten resin at the time of molding a minus lens in the same embodiment.

FIG. 7 is a view showing a state after the molten resin is compressed at the time of molding the minus lens in the embodiment.

FIG. 8 is a view showing a state in which, in the embodiment, the upper die mounting member is lifted from the die main body by an opening amount, and the upper die insert is moved downward relative to the die mounting member by an eject pin. FIG.

9 is a view showing a state in which the upper die and the lower die are opened from the state of FIG.

[Explanation of symbols]

1 Upper mold (movable mold) 2 Lower mold (fixed mold) 3 Cavity 4 Mold body 5,9 Insert guide 10,11 Insert 16 Mold mounting member 19,22,32 Hydraulic cylinder which constitutes a holding member,
Back insert and pressure receiving member 34, 38 Eject pin 40 Spring (elastic member) 44 Lens molded product 58 Sprue 59 Runner S Maximum opening amount (maximum compression allowance) S (+) Plus lens opening amount (setting compression allowance) ) S (-) Minus lens opening distance (compression allowance)

Continuation of the front page (56) References JP-A 61-66623 (JP, A) JP-A 2-26723 (JP, A) JP-A 7-117088 (JP, A) JP-A 55-27300 (JP , A) JP 62-268620 (JP, A) JP 63-216719 (JP, A) JP 62-83121 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB) (Name) B29C 45/40-45/57 B29C 45/64-45/76 B29D 11/00

Claims (4)

(57) [Claims] 1. A movable die which opens and closes with respect to a fixed die includes a die mounting member and a die body movably attached to the die mounting member toward the fixed die. An insert that is movably fitted into an insert guide to form a lens cavity is provided inside the main body, and a holding member that holds this insert is an elastic member that is always elastic in a direction opposite to the fixed mold. A molding method for molding a minus lens having a central wall thickness smaller than that of a peripheral portion and a plus lens having a central wall thickness thicker than that of a peripheral portion by using one molding die that is urged and brought into contact with the mold mounting member. The mold attachment member is advanced to the fixed mold side while leaving a preset compression margin in the lens cavity, and the mold is clamped, and then the molten resin is filled in the lens cavity. After injection filling, at least before the completion of injection of the molten resin, the set compression allowance is compressed by advancing the mold mounting member toward the fixed mold side, and thereafter, the mold mounting member is retracted to move the fixed mold. After the mold is opened from the mold, the injection compression molding method for the spectacle lens in which the holding member is pressed and moved to the fixed mold side by the eject pin inserted in the mold mounting member and the lens molded product is projected by the insert. In the above, the set compression allowance is set according to the types of the minus lens and the plus lens, and the set compression allowance during minus lens molding is set to a value larger than the set compression allowance during plus lens molding and different depending on the frequency. Set, and when the holding member is pressed and moved to the fixed mold side by the eject pin when the mold mounting member is retracted, the inserter is moved. To the fixed mold side relative to the mold mounting member, and thereafter, the movable mold is opened from the fixed mold, the holding member is pressed and moved by the eject pin, and the lens is inserted by the insert. An injection compression molding method for a spectacle lens, which comprises ejecting a molded product. 2. The injection compression molding method for a spectacle lens according to claim 1 , wherein the setting of the compression allowance at the time of molding the plus lens is performed by changing the compression allowance from the initial position where the compression allowance in the lens cavity is maximum. It is set by advancing the mold mounting member to the fixed mold side to the position where it disappears and clamping the mold, and further retracting the mold mounting member by the set compression allowance. The spectacles characterized by being set by advancing the mold mounting member toward the fixed mold side and clamping the mold from an initial position where the compression margin in the lens cavity is maximum to a position where the set compression margin remains. Injection compression molding method for lenses. 3. A injection compression molding method of a spectacle lens according to claim 1 or claim 2, when advancing the insert relatively the stationary mold side with respect to the fitment member, the said insert An injection compression molding method for a spectacle lens, characterized in that the die mounting member is advanced by a smaller amount than the amount of retreat at the time of retreating, and a gap is provided between the insert and the lens molded product. 4. The injection compression molding method for an eyeglass lens according to claim 3 , wherein the gap between the insert and the lens molded product is 1 to 4 mm.