JPH09254209A - Device and method for injection compression molding of lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for injection compression molding of a lens in which the high-quality lens is obtained. SOLUTION: A mixing nozzle 85 having a mixing head 93 and an auxiliary kneading cylinder 95 is used as a nozzle. The mixing head 93 is equipped with a mixing element 93B having many kneading grooves in the inside. The auxiliary kneading cylinder 95 is provided on a resin injection port side apart from the mixing head 93 and has a plurality of kneading holes 95A along the axial direction of the nozzle. Molten resin is kneaded by the mixing head 93 and temperature distribution is uniformized. Successively, when molten resin is passed through the kneading holes 95A of the auxiliary kneading cylinder 95, it is kneaded furthermore and temperature distribution is more uniformized. Thereby, since molten resin whose temperature distribution is uniformized is filled in a cavity, a linear streak or the like is not caused.

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 apparatus and a molding method for molding a lens (mainly an eyeglass lens) by injection compression molding a thermoplastic resin. More specifically, the present invention relates to a lens injection compression molding apparatus and a molding method capable of molding a high quality lens.

[0002]

BACKGROUND ART Conventionally, as a device for molding eyeglass lenses from a thermoplastic resin, a mold having a cavity for lens molding inside, a mold clamping device for clamping the mold, and a plasticizing for plasticizing a raw material resin. A device (for example, a plunger system or an in-line screw system) and an injection cylinder for introducing the molten resin plasticized by the plasticizing device and then injecting and filling the lens molding cavity of the mold through a nozzle are provided. Structured injection compression molding devices are known.

In molding an injection compression molding apparatus having such a structure, when molding a lens, a raw material resin is plasticized by a plasticizing apparatus, the molten resin is introduced into an injection cylinder and measured, and then a mold is injected through a nozzle. The lens molding cavity is injection-filled, and then the mold is clamped by the mold clamping device to compress the molten resin in the lens molding cavity to mold the lens.

[0004]

However, when a lens is molded by a conventional injection compression molding apparatus, as shown in FIG. 6, a defect in which a linear mark is left in the center portion of the molded product is observed. Striation marks are seen inside the lens rather than on the surface of the lens, and are considered to be a kind of history of resin injection. In the cavity, it is presumed that the cooling occurs from the portion closest to the mold, and the difference is generated between the surface and the thick portion inside the cavity. In other words, it is considered that this is caused by the imbalance of cooling. Therefore, optical lenses (especially eyeglass lenses) should be marked with excessively strong line marks.
Not suitable for In particular, in the case of a positive power lens having a thick central portion with respect to the peripheral edge portion or a negative power lens having a central thickness of 2 mm or more, there are many phenomena in which striation marks appear more prominently.

An object of the present invention is to provide a lens injection compression molding apparatus and a molding method which can eliminate such defects of a molded product and obtain a high quality lens.

[0006]

The inventor of the present invention conducted an experiment under different molding conditions in order to find out the cause of defects in the conventional apparatus. In this, when the molten resin was introduced into the injection cylinder and injected after a lapse of a certain period of time, a molded product having no line mark was obtained. Therefore, when the molten resin is introduced into the injection cylinder, there is a temperature difference between the outer side and the central part in contact with the inner wall of the injection cylinder. With a linear heater or band heater inserted inside),
It is presumed that the streak disappeared due to this. Therefore, the present inventor used a mixing nozzle having a function of kneading the molten resin in order to make the temperature distribution of the molten resin uniform, and was able to obtain a molded product without the above-mentioned defects.

The lens injection compression molding apparatus of the present invention comprises a mold having a lens molding cavity therein, a mold clamping device for clamping the mold, and a plasticizing device for plasticizing the raw material resin. In a lens injection compression molding apparatus including an injection cylinder for injecting and filling a lens molding cavity of the mold through a nozzle after introducing a molten resin plasticized by a plasticizing device, the nozzle,
It is characterized by using a mixing nozzle having a mixing element for kneading a molten resin therein.

According to this structure, when the molten resin plasticized by the plasticizer is filled in the cavity by the injection cylinder, the temperature distribution of the molten resin injected from the injection cylinder can be made uniform. Therefore, the cavity is filled with the molten resin having a uniform temperature distribution, so that it is possible to obtain a high-quality lens in which no line marks are generated.

In the above, the mixing nozzle is
It is desirable that the mixing head has a mixing element having a large number of kneading grooves therein, and an auxiliary kneading cylinder provided on the resin injection port side of the mixing head and having a plurality of kneading holes along the nozzle axial direction. . By doing so, the molten resin is first kneaded by the mixing head to make the temperature distribution uniform, and subsequently, when passing through the kneading hole of the auxiliary kneading cylinder, the property of the molten resin ejected in a spiral shape is utilized. By doing so, the temperature is further kneaded to make the temperature distribution more uniform, so that the above-mentioned drawbacks can be further reduced. here,
The injection resistance can be set to an appropriate value while maintaining sufficient kneading by changing the number of kneading holes and hole diameter of the auxiliary kneading cylinder according to the type of resin used and the lens shape. it can.

As a result, the fluidity of the molten resin is improved,
Moreover, since a sufficient injection speed can be secured, even if the mold has a structure having a plurality of lens molding cavities,
There is no unbalanced filling balance among multiple cavities, and since each cavity is filled with molten resin with a uniform temperature distribution, it is possible to obtain a high-quality lens that does not cause line marks. You can

Further, the lens molding method of the present invention includes a mold having a lens molding cavity therein, a mold clamping device for clamping the mold, and a plasticizing device for plasticizing the raw material resin. A lens for molding a lens using an injection compression molding device for a lens equipped with an injection cylinder for introducing a molten resin plasticized by a plasticizing device and then injecting and filling the lens molding cavity of the mold through a nozzle. In the molding method, a lens having a positive dioptric power with a center thickness larger than the peripheral thickness, or a lens having a negative dioptric power having a central thickness of 2 mm or more is used as the nozzle.
It is characterized by using a mixing nozzle having a mixing element for kneading a molten resin therein.

Also by this, the molten resin plasticized by the plasticizing device and introduced into the injection cylinder is kneaded by the mixing nozzle having the mixing element when being injected from the injection cylinder, and the temperature distribution is made uniform. That is, since the cavity is filled with the molten resin having a uniform temperature distribution, it is possible to obtain a high-quality lens in which no line marks are generated.

[0013]

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 shows an injection compression molding apparatus for lenses (meniscus-shaped spectacle lenses) according to this embodiment. The material of the spectacle lens molded here is a thermoplastic resin such as PMMA (polymethylmethacrylate) or PC (polycarbonate).
The injection compression molding device includes a mold clamping device 60 having an injection molding die 50 and a plasticizing device 70 for plasticizing a raw material resin.
And an injection device 80 for measuring the molten resin and injecting it into the injection mold 50.

The mold clamping device 60 comprises a fixed die plate 6
1 and a plurality of tie bars 6 on the fixed die plate 61.
A cylinder fixing plate 64 fixed via 2 and having a mold clamping cylinder 63 mounted thereon, and a movable die plate 66 provided so as to be movable up and down along the tie bar 62 and connected to a piston rod 65 of the mold clamping cylinder 63. It is configured. The injection mold 50 is attached between the fixed die plate 61 and the movable die plate 66.

In the plasticizer 70, the heater 7 is fed with the raw resin fed from the hopper 71 by the screw 72.
It is constituted by a plasticizing cylinder 74 that plasticizes at 3. The screw 72 is rotated by the hydraulic motor 75. The injection device 80 has a plunger 81 inside.
With an injection cylinder 82 and a hydraulic cylinder 8 for sliding (moving up and down) the plunger 81 of the injection cylinder 82.
And 3. A mixing nozzle 85 having a mixing element for kneading molten resin is attached to the tip (upper end) of the injection cylinder 82. Further, a band heater 86 is provided at a position above the outer periphery of the injection cylinder 82.
Is wound.

The mixing nozzle 85 has a cylindrical nozzle body 91, as shown in FIG. Nozzle body 9
In one, the attachment 92, in order from the tip (upper end),
The mixing head 93 and the sleeve 94 are detachably inserted. The attachment 92 has an injection hole 92A having a diameter of about 3 mm along the central axis direction.
And a storage hole 92B having a diameter larger than the diameter of the injection hole 92A. Storage hole 92B
An auxiliary kneading cylinder 95 is housed inside. As shown in FIG. 3, the tip surface of the auxiliary kneading cylinder 95 has a diameter of about 1 mm.
About four kneading holes 95A are formed in parallel with the auxiliary kneading cylinder 95 at 90 degree intervals on the same circumference centered on the axis. The mixing head 93 includes a sleeve 93.
A, and a mixing element 93B which is housed in the sleeve 93A and arranged on the outer peripheral surface so as to intersect with each other and which has a plurality of spiral grooves and a large number of parallel grooves parallel to the shaft.

FIG. 4 is a sectional view of the injection molding die 50, and FIG. 5 is a sectional view taken along line VV of FIG. Same injection mold 50
As shown in FIG. 4, an upper mold (movable mold) 1 and a lower mold (fixed mold) 2 which are divided into upper and lower parts on a parting line PL are provided, and two spectacle lens moldings are provided between them. A cavity 3 is formed. The mold body 4 of the upper mold 1 is
It is composed of an insert guide member 5 and templates 6 and 7. The mold body 8 of the lower mold 2 includes an insert guide member 9 and a mold plate 10. Inside the insert guide members 5 and 9, the inserts 11 and 12 forming the cavity 3 are formed.
Are stored so as to be slidable in a direction perpendicular to the parting line PL.

The mold body 8 of the lower mold 1 is fixed to a mold mounting member 15 fixed on the fixed die plate 61. The mold body 4 of the upper mold 1 includes a bolt 1 shown in FIG. 5 on the mold mounting member 16 including an upper member 16A and a lower member 16B.
7 and the mold body 4 and the mold mounting member 1
6 and a disc spring 17 inserted around the outer periphery of the bolt 17.
A is installed. The die mounting member 16 is fixed to the movable die plate 66, and a downward die clamping force of the die clamping cylinder 63 is applied.

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 guided by the guide pins 18 and are separated by the gap S. It is designed to open and close up and down. Also,
An open cylinder (not shown) is arranged below the die mounting member 15, and the die mounting member 1 is provided by this open cylinder.
The gap S is formed by pushing up 6 against the mold clamping force of the mold clamping cylinder.

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 rod 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,
The lenses molded in the cavity 3 are the upper mold 1 and the lower mold 2.
It is designed to stick out when the mold is divided. The eject pin 3 is provided at the center of the upper die 4 and the die mounting member 16.
5 is arranged so as to be vertically movable. Eject pin 35
A pressure receiving member 36 is fixed to the upper end of the. When the pressure receiving member 36 is pushed down by the eject rod 38 inserted from the hole 37 formed in the die mounting member 16, the eject pin 35 is pushed down.

A 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 rods 34, 38 rise, the pressure receiving members 32, 3
6 has risen and is returning to the old place.

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.
Character clamp members 23 and 29 to insert guide member 5 and
6 to project.

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. Then, 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 guide members 5 and 6. Thus, in the case of molding a plus lens, an insert having a cavity 3 having a center wall thickness larger than that of a peripheral portion is formed, and in the case of molding a minus lens, a cavity 3 having a center wall thickness smaller than that of a peripheral portion. Replace each with an insert having.

When molding the lens, the mold is closed in the state shown in FIGS. That is, the upper mold 1 is lowered by the mold clamping cylinder 63, 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 in a non-compressed state. In this state, the gap S is set to the maximum open amount (about 15 mm). Next, the size difference (compression allowance) is set. At this time, in forming the plus lens, the dimension opening amount S of 0.8 mm or less is set. When molding a minus lens, the dimension difference S is larger than 0.8 mm.
Set. That is, the compression margin at the time of molding the minus lens is set to be larger than the compression margin at the time of molding the plus lens.

Next, the molten resin is injected and filled. For this purpose, the molten resin plasticized by the plasticizing device 70 is introduced into the injection cylinder 82 of the injection device 80 for measurement, and then the plunger 81 is lifted up to raise the mixing nozzle 8.
5, the cavity 3 is filled through the spool 48 of the spool bush 47 and the runner 49. Here, when the molten resin passes through the mixing nozzle 85, the molten resin is first kneaded by the mixing head 93 to make the temperature distribution uniform, and subsequently, the kneading hole 95A of the auxiliary kneading cylinder 95.
When passing through the outlet of the kneading hole 95A, that is,
In the space of the storage hole 92B, a fine spiral is blown out from each kneading hole 95A, and the injection hole 92 is discharged from the storage hole 92B.
By narrowing to A, the temperature is further kneaded and the temperature distribution is made more uniform. As a result, the flowability of the molten resin is improved, so that the filling balance between the left and right cavities 3 does not become unbalanced, and the cavities 3
Since the molten resin having a uniform temperature distribution is filled in, a high-quality lens free of line marks and the like can be obtained.

Next, a plus lens is molded, for example, plus 2.00 diopters (outer diameter 75 mm, center thickness 4.
In the case of molding of 2 mm and edge thickness of 1.00 mm), the nozzle 85 is closed after completion of injection and filling of the molten resin (for the closing mechanism, see Applicant's Japanese Utility Model Publication No. 7-27140).
No. 5, Japanese Patent Publication No. 5-44893 and Japanese Patent Publication No. 5-30608), followed by pressurization (compression)
I do. On the other hand, in the case of molding a minus lens, pressurization (compression) is started before completion of injection and filling of 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 63. Finally, the nozzle 85 is closed. In this way, after molding the plus lens or the minus lens, these lenses are ejected.

Therefore, according to this embodiment, since the mixing nozzle 85 having the mixing element for kneading the molten resin therein is used, the molten resin plasticized by the plasticizing device 70 is injected into the injection cylinder 82 of the injection device 80. By this, when the cavity 3 is filled, the temperature distribution of the molten resin injected from the injection cylinder 82 can be made uniform. Therefore, since the cavity 3 is filled with the molten resin having a uniform temperature distribution, it is possible to obtain a high-quality lens in which no line marks are generated.

Further, the mixing nozzle 85 comprises a mixing head 93 having therein a mixing element 93B having a large number of kneading grooves, and an auxiliary kneading cylinder 95 having a plurality of kneading holes 95A along the nozzle axial direction. Because
The molten resin is kneaded by the mixing head 93 to make the temperature distribution uniform, and subsequently, the kneading holes 95 of the auxiliary kneading cylinder 95.
When it passes through A, it is further kneaded to make the temperature distribution more uniform, so that it can be kneaded in a state where there is no temperature distribution. Moreover, by changing the number and diameter of the kneading holes 95A of the auxiliary kneading cylinder 95, the injection resistance can be changed together with the kneading degree of the molten resin. Therefore, by setting these values to appropriate values, sufficient kneading can be achieved. It is possible to secure a sufficient injection speed while maintaining

As a result, since the fluidity of the molten resin is improved, the filling balance in the left and right cavities 3 does not become unbalanced, and the molten resin having a uniform temperature distribution is provided in each cavity 3. Since it is filled, it is possible to obtain a high-quality lens in which no line mark is generated.

In the embodiment described above, the mixing nozzle 85 has the mixing head 93 and the auxiliary kneading cylinder 95 inside, but it may have a structure having only the mixing head 93. Also, the configuration of the mixing head 93 is not limited to the structure described in the above-described embodiment, and any other structure may be used as long as it has a structure capable of kneading molten resin. Further, it is desirable to use the auxiliary kneading cylinder 95 by arbitrarily changing the length of the main body, the number of kneading holes 95A or the hole diameter depending on the type of resin used and the lens shape. Further, when more kneading is required, for example, in the case of molding a plus lens having a relatively thick central portion, the sleeve 94 inserted in the mixing nozzle 85 is replaced with the same as the mixing head 93. You may make it insert the mixing head of a structure.

Further, in the above-mentioned embodiment, the band heater 86 is provided on the outer circumference of the injection cylinder 82, but instead of this, a linear heater or the like may be inserted into the injection cylinder 82. Alternatively, both may be provided. Further, although the compression allowance at the time of molding is set by the opening amount formed between the mold body 4 and the mold mounting member 16, other molds may be used. For example, a mold having a structure in which a cavity core protruding into the cavity 3 is provided, a compression allowance is set from the position of the cavity core, and then the cavity core is projected into the cavity 3 for compression is also used. 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. Further, in the above-described embodiment, when the minus lens is molded, the compression of the opening amount S is started when the molten resin is injected by about 90 to 95%.
The% at this time may be arbitrarily determined according to the volume of the cavity 3, the type of resin, the characteristics of the lens, and the like.

Further, in the above-described 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.

[0035]

According to the lens injection compression molding apparatus and molding method of the present invention, since the mixing nozzle having the mixing element for kneading the molten resin is used, the temperature distribution of the molten resin can be made uniform, resulting in high quality. You can get a nice lens.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing a mixing head nozzle of the same embodiment.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a cross-sectional view showing an injection molding die of the same embodiment.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is a diagram of a lens showing conventional problems.

[Explanation of symbols]

 1 Upper Mold 2 Lower Mold 3 Eyeglass Lens Molding Cavity 50 Injection Molding Mold 60 Mold Clamping Device 70 Plasticizing Device 82 Injection Cylinder 85 Mixing Nozzle 93 Mixing Head 93B Mixing Element 95 Auxiliary Mixing Cylinder 95A Mixing Hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location // B29L 11:00

Claims (4)

[Claims] 1. A mold having a cavity for molding a lens therein, a mold clamping device for clamping the mold, a plasticizing device for plasticizing a raw material resin, and a melting plasticized by the plasticizing device. In a lens injection compression molding apparatus having an injection cylinder for injecting and filling resin into a lens molding cavity of the mold through a nozzle, a mixing having a mixing element for kneading a molten resin therein as the nozzle. A lens injection compression molding device characterized by using a nozzle. 2. The lens injection compression molding apparatus according to claim 1, wherein the mixing nozzle includes a mixing head having therein a mixing element having a large number of mixing grooves, and a resin injection port side of the mixing head. An injection compression molding apparatus for a lens, comprising: an auxiliary kneading cylinder provided with a plurality of kneading holes along the nozzle axis direction. 3. The lens injection compression molding apparatus according to claim 1 or 2, wherein the lens molding cavity is a meniscus-shaped eyeglass lens molding cavity. apparatus. 4. A mold having a cavity for molding a lens inside, a mold clamping device for clamping the mold, a plasticizing device for plasticizing a raw material resin, and a melting plasticized by the plasticizing device. In a lens molding method of molding a lens using an injection compression molding device for a lens equipped with an injection cylinder for injecting and filling resin into a lens molding cavity of the mold through a nozzle, A mixing nozzle having a mixing element for kneading a molten resin therein is used as the nozzle for molding a lens having a positive power with a larger thickness deviation or a lens having a negative power having a center thickness of 2 mm or more. And the lens molding method.