JP2007223252A - Mold for injection molding of optical element and its molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for the injection molding of an optical element capable of decreasing adverse influence on a molded article caused by shrinkage of a resin, without giving an adverse influence on flow of the resin. <P>SOLUTION: A reservoir part 15a branched from a main resin flow path 13 is formed, separately from the main resin flow path 13, for connecting a runner 8 with a cavity 3 is formed, and a fixing pin 12 as a projecting means is provided in the reservoir part 15a. Thereby, it becomes possible to relax the strain near a gate 9 without making the main resin flow path narrow, and to improve the dimensional accuracy of a molded article. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection mold for a plastic product obtained by injection molding an optical product made of plastic resin as a material to obtain a highly accurate optical element, and a molding method therefor.

  In an optical element manufactured by resin molding, resin flows in the order of the sprue of the mold, the runner, and the gate, and flows into the cavity to be molded. The molded product formed by the sprue, runner, and cavity is continuously taken out by a take-out device, and the gate portion of the molded product is cut to obtain a product.

  The mold is opened separately into a fixed mold and a movable mold, and generally remains in the movable mold with the sprue part, runner part, gate part and product part (optical element) integrated. However, when the mold is opened, the molded optical forming surface is thermally contracted, which causes warpage, deformation, and distortion of the molded product, thereby impairing optical characteristics. In particular, distortion in the vicinity of the product gate portion communicating from the sprue portion to the runner portion and the gate portion increases.

  Therefore, conventionally, the molding cycle is lengthened until the sprue or runner is completely cooled. Further, in the case of a general molded product, the shrinkage is suppressed by changing the shapes of the gate and the runner (Patent Documents 1 and 2).

FIG. 6 shows a conventional injection mold described in the patent literature.
Between each of the fixed side mold 1 and the movable side mold 2, a sprue 5 and a runner 8 are formed as a flow path for flowing resin into the cavity 3. The cavity 3 and the runner 8 are connected by a gate 9. In such an injection mold, the backflow preventing means 100 for preventing the backflow of the resin in the cavity 3 is provided in the middle of the runner 8. 10 is a sprue lock pin and 11 is a protruding pin.

By providing the backflow prevention means 100, even if the resin in the runner 8 cools and shrinks in volume, the resin in the cavity 3 is not drawn, so that distortion of the molded product does not occur.
FIG. 7 shows a schematic diagram of a general product ejection and removal method.

7A shows a mold opening process, FIG. 7B shows an ejection process, and FIG. 7C shows a removal process. In the ejection process after mold opening, the movable side insert 18, the sprue lock pin 10, The protruding pin 11 is protruded from the movable mold 2 to release the product part 19 and the runner 8 from the movable mold 2. Thereafter, in the take-out step, the molded product is taken out using the take-out device 22. The product part 19 separated from the runner 8 is shown in FIG.
JP-A-11-170306 JP-A-60-127128

  However, in the conventional mold configuration, since the resin flow path from the nozzle portion from which the resin is injected to the molded product space (cavity) is provided with the shape with a narrowed diameter and the backflow prevention means 100 for preventing the backflow of the resin, As the resin passes through the portion, the flow is disturbed. As a result, the appearance problem such as welds and the tolerance of the molding conditions are narrow with respect to the product, and there is a problem that stable molding cannot be performed.

  Further, when the molded product is taken out in the take-out process, the product part 19 is taken out in a state of sticking to the movable side insert 18, so that the runner 8 is deformed into an inverted umbrella shape by the reaction of removing the molded product from the sprue lock pin 10. The product part 19 collides with the movable lens insert, causing a problem in appearance.

  The present invention solves the above-mentioned conventional problems, and can reduce the influence on the molded product due to the shrinkage of the resin in the runner and the shrinkage of the resin in the sprue without adversely affecting the flow of the injected resin. An object of the present invention is to provide an optical element injection mold that can be expected to improve the appearance of a molded product.

  In order to solve the above-mentioned conventional problems, the mold for injection molding of the present invention is provided with a resin shrinkage prevention means at a position where the flow of the resin is not hindered when a product is molded. This resin shrinkage prevention means relieves distortion in the vicinity of the gate portion of the product. Further, by dividing the protrusion timing into the edge portion and the product portion, the product is prevented from colliding with the lens insert.

  An optical element injection mold according to claim 1 of the present invention includes a fixed-side mold and a movable-side mold that forms a cavity with the fixed-side mold in contact with the fixed-side mold. At least the movable mold of the side mold and the movable mold includes a main resin flow path including a runner and a gate continuous from the sprue formed in the fixed mold to the cavity, and In addition to the main resin flow path connecting the runner and the cavity, a reservoir branched from the main resin flow path is formed, and the fixed mold and the movable mold are separated from the reservoir. Protruding means protruding in the direction is provided.

  The optical element injection mold according to claim 2 of the present invention is the optical element injection mold according to claim 1, wherein the protrusion means is disposed in the mold release direction of the fixed side mold and the movable side mold, and the base end is the movable side. It is characterized by comprising a fixing pin fixed to the mold and having a tip protruding into the pool part.

  An optical element injection mold according to a third aspect of the present invention is the optical element injection mold according to the first aspect, wherein the protrusion means extends in a releasing direction of the fixed side mold and the movable side mold and is integrated with the movable side mold. It is characterized by comprising a convex portion protruding from the pool portion.

  An optical element injection mold according to a fourth aspect of the present invention is the optical element injection mold according to the first aspect, wherein the protrusion means is disposed in the mold release direction of the fixed side mold and the movable side mold, and the base end is the movable side. A center pin that is fixed to a mold and has a tip projecting from the pool portion, and a sleeve that guides the relative movement between the center pin and the movable side mold is provided on the movable side mold. And

  An optical element injection mold according to a fifth aspect of the present invention is the optical element injection mold according to the first aspect, wherein the cavity has a shape necessary for resin molding a lens having an edge portion, and the position of the tip of the protrusion means is A portion of the cavity formed in the movable mold is deeper than a position corresponding to the edge portion.

  According to a sixth aspect of the present invention, there is provided an optical element injection molding method comprising: a fixed mold, and a movable mold that forms a cavity with the fixed mold in contact with the fixed mold; At least the movable side mold of the mold and the movable side mold is molded by injecting resin from a sprue formed on the fixed side mold into a resin flow path composed of a runner and a gate continuous toward the cavity. In this case, a protrusion means is provided in a collecting part branched from the main resin flow path separately from the main resin flow path connecting the runner and the cavity in the mold release direction of the fixed mold and the movable mold. The resin is injected into the cavity in a protruding state, and cured while preventing the resin from contracting by the protruding means.

  The optical element injection molding method according to a seventh aspect of the present invention is the optical element injection molding method according to the sixth aspect, wherein after the resin is cured, the movable mold is moved to open the cavity, and the runner, the gate, and the cavity are used. The movable mold and the protruding means are moved relative to each other in the mold release direction while the protruding means engaged with the formed reservoir is centered and both sides thereof are restricted by the sprue lock pin and the movable insert. The first step and the sprue lock after the product part is separated from the movable side insert by further moving the sprue lock pin of the sprue lock pin and the movable side insert relative to the movable side mold. And a second step of detaching the pin from the runner.

  An optical element injection molding method according to an eighth aspect of the present invention is the optical element injection molding method according to the seventh aspect, wherein the cavity has a shape necessary for resin molding using a lens having an edge portion as a product portion, and the position of the tip of the projection means is determined. The portion of the cavity formed in the movable side mold is deeper than the position corresponding to the edge portion. In the first step, the product portion is released from the edge portion of the movable side mold. The movable side mold and the projection means are relatively moved in the mold release direction, and the runner portion that has not been released from the movable side mold is released in the second step.

  An optical element injection molding method according to a ninth aspect of the present invention is the optical element injection molding method according to the sixth aspect, characterized in that the first step and the second step proceed continuously and there is no waiting time therebetween.

  According to this configuration, the distortion in the vicinity of the gate of the molded product can be reduced, and the accuracy of the molded product can be improved. Further, it is possible to prevent damage to the lens surface that occurs during removal.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)
1 to 3 show an optical element injection mold according to Embodiment 1 of the present invention.

  In this optical element injection mold, a cavity 3 is formed between a fixed mold 1 and a movable mold 2. The fixed mold 1 is formed with a nozzle 4 penetrating the fixed mold 1 and a sprue 5 connected to the nozzle 4.

As shown in FIG. 8, the shape of the cavity 3 is a shape necessary for resin molding using the lens 7 having the edge portion 6 as a product portion.
A runner 8 and a gate 9 are formed between the sprue 5 and the cavity 3 in the movable mold 2 that can move forward and backward with respect to the fixed mold 1. Furthermore, the movable die 2 has a protruding means that protrudes in the mold releasing direction of the fixed die 1 and the movable die 2 in addition to the sprue lock pin 10 and the protruding pin 11 (see FIG. 2). A fixing pin 12 is provided.

  In this embodiment 1, two reservoirs 15a and 15b branched from the runner 8 are connected to the flow channel corners 14a, 14b, 14c and 14d in the main resin flow channel 13 from the sprue 5 to the cavity 3, respectively. Has been. The distal end of the fixing pin 12 is provided so as to protrude from the pool portion 15a.

The tip of the fixed pin 12 is formed so as to be deeper than the position 16 corresponding to the edge portion 6 in the portion of the cavity 3 formed on the movable mold 2.
As shown in FIG. 1, in a state where the fixed mold 1 and the movable mold 2 are clamped, the resin 17 is injected from the nozzle 4, and the two reservoirs 15 a and 15 b are filled with the resin from the runner 8. At the same time, the cavity 3 is filled with resin through the gate 9. The tip of the sprue lock pin 10 and the tip of the fixing pin 12 are inserted into the resin.

  In addition, as shown in FIG. 2, the protrusion pin 11 is retracted to a position facing the flow path corner portions 14a, 14b, 14c, and 14d so as not to protrude into the main resin flow path 13 until the filled resin is cured. And waiting.

  Therefore, the main resin flow path 13 that connects the runner 8 and the cavity 3 is provided with the backflow prevention means 100 having a shape that narrows the diameter of the resin flow path as seen in the conventional example shown in FIG. The resin flow into the cavity 3 is not disturbed, and the resin can be filled into the cavity 3 smoothly.

  Further, during the cooling process after the filling is completed, the shrinkage of the molded product can be suppressed by the fixing pin 12 protruding to the reservoir portion 15a, and even if the resin of the runner 8 and the sprue 5 undergoes volume shrinkage, it enters the cavity 3. It is possible to prevent the influence of the above, and to provide a molded product with good quality and high accuracy. As a result of the experiment, the total wavefront aberration of the lens as a product separated from the molded product was improved from 40 mλ to 25 mλ.

3 (a), 3 (b), 3 (c), and 3 (d) show a specific process of taking out the molded product after the cooling process is completed.
FIG. 3A shows a state immediately after the mold opening. Next, in the first step shown in FIG. 3B, the movable side insert 18, the sprue lock pin 10, and the protruding pin 11 are protruded from the movable side mold 2.

  Thus, the molded product 20 including the sprue portion, the runner portion, the product portion 19 and the like is regulated by the sprue lock pin 10 and the movable side insert 18 on both sides with the fixed pin 12 engaged with the reservoir portion 15a as the center. However, the fixed mold 1 and the movable mold 2 are protruded in the mold release direction. In this first step, the sprue lock pin 10 and the movable side insert are arranged so that the product part 19 is not released from the movable side insert 18 until the product part 19 is released from the edge part of the movable side mold 2. 18 is sticking out.

  In this first step, the tip of the fixed pin 12 is gradually pulled out of the pool portion 15a by the protrusion of the sprue lock pin 10 and the movable side insert 18, but in the end state of the first step, the tip of the fixed pin 12 is The portion engaged with the pool portion 15a remains.

  In the second step shown in FIG. 3 (c), the sprue lock pin 10 out of the sprue lock pin 10 and the movable side insert 18 is further protruded from the movable side mold 2, and the product portion 19 is moved from the movable side insert 11. Release.

  After releasing the product part 19 from the movable side insert 18 in this way, the sprue part 21 of the cured product 20 as shown in FIG. , The runner portion 23 of the molded product 20 is detached from the sprue lock pin 10. At the timing when the molded product 20 is detached from the sprue lock pin 10, the product portion 19 is already separated from the movable side insert 18, so that the product portion hits the insert and is damaged by the reaction when it is taken out. Can be avoided.

Here, the first process and the second process have been described separately, but the first process and the second process can be performed continuously so that there is no waiting time between them.
Moreover, in this Embodiment, a 1st process and a 2nd process progress continuously, and there is no waiting time in between.

Moreover, although the fixed pin 12 has a round cross section substantially the same as the runner width, it may be square, long, or oval.
The fixing pin 12 is disposed closer to the center of the lens molded product than half of the distance from the center of contraction to the center of the lens molded product.

  As described above, according to the molding method in which the protrusion portion is provided on the reservoir portion 15a that does not hinder the flow of the resin and the projection timing is divided into the edge portion and the product portion, the distortion in the vicinity of the gate of the molded product is reduced. Therefore, the accuracy of the molded product can be improved. Further, it is possible to prevent damage to the lens surface that occurs during removal. Therefore, it is useful for applications of optical elements such as lenses.

  In the first step of this embodiment, the movable side insert 18, the sprue lock pin 10, and the protruding pin 11 are protruded from the movable side mold 2, but the movable side insert 18, the sprue lock pin 10, the protruding pin 11, The same can be done by moving the movable mold 2 relative to each other.

(Embodiment 2)
4 (a) and 4 (b) show another embodiment.
In the first embodiment, the fixing pin 12 is provided in the reservoir portion 15a as a protruding means protruding in the mold release direction of the fixed side mold 1 and the movable side mold 2. However, in FIG. The mold 1 and the movable mold 2 are arranged in the mold release direction, the base end is fixed to the movable mold 2, and the distal end protrudes from the collecting portion 15 a. Is provided with a sleeve 25 for guiding relative movement between the center pin 24 and the movable mold 2. FIG. 4B shows a perspective view of the center pin 24 and the sleeve 25. Others are the same as (Embodiment 1).

(Embodiment 3)
FIG. 5 shows yet another embodiment.
In the first embodiment, the fixed pin 12 is provided in the reservoir portion 15a as a protruding means that protrudes in the mold release direction of the fixed mold 1 and the movable mold 2. However, in FIG. When the pool portion 15a is formed, the protruding means is formed integrally with the movable die 2 by the convex portion 26 extending in the mold release direction of the fixed die 1 and the movable die 2 by, for example, uncarving. ing. Others are the same as (Embodiment 1).

  The quality of an optical element such as a lens is improved, which can contribute to the improvement of the performance of various devices using the optical element.

Mold sectional view in (Embodiment 1) of the present invention Runner layout diagram in the same embodiment Process drawing of product ejection and removal method in the embodiment Sectional view of mold and perspective view of main part in (Embodiment 2) of the present invention Mold sectional view in (Embodiment 3) of the present invention Cross section of conventional mold Process diagram of general product ejection and removal methods Enlarged perspective view of product example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed side metal mold 2 Movable side metal mold 3 Cavity 4 Nozzle 5 Sprue 7 Lens which has edge part 6 Runner 9 Gate 10 Sprue lock pin 11 Protrusion pin 12 Fixing pin (protrusion means)
13 Main resin flow paths 14a, 14b, 14c, 14d Flow path corners 15a, 15b Reservoir 26 Protrusion (projection means)
24 Center pin (protruding means)
25 sleeve

Claims (9)

A movable side mold that forms a cavity with the fixed side mold and the fixed side mold in contact with the fixed side mold;
At least the movable mold of the fixed mold and the movable mold is provided with a main resin flow path comprising a runner and a gate continuous from the sprue formed in the fixed mold to the cavity. ,
And forming a reservoir branched from the main resin flow path separately from the main resin flow path connecting the runner and the cavity,
An optical element injection mold in which a protrusion means protruding in the mold release direction of the stationary mold and the movable mold is provided in the pool portion. The protrusion means comprises a fixed pin that is disposed in a releasing direction of the fixed mold and the movable mold, has a base end fixed to the movable mold, and a distal end protruding into the pool portion. 2. An optical element injection mold according to 1. 2. The optical element injection molding die according to claim 1, wherein the projecting means comprises a convex portion that extends in a releasing direction of the fixed side mold and the movable side mold and protrudes integrally with the movable side mold and protrudes into the pool portion. Type. Protruding means is constituted by a center pin disposed in the mold release direction of the fixed side mold and the movable side mold, a base end fixed to the movable side mold, and a distal end protruding to the pool portion,
2. The optical element injection mold according to claim 1, wherein the movable mold is provided with a sleeve for guiding relative movement between the center pin and the movable mold. The cavity has a shape necessary for resin-molding a lens having an edge portion, and the position of the tip of the protrusion means is from a position corresponding to the edge portion of the portion formed on the movable mold of the cavity. The optical element injection mold according to claim 1, which is deepened. A movable side mold that forms a cavity with the fixed side mold and the fixed side mold in contact with the fixed side mold; and at least the movable side mold of the fixed side mold and the movable side mold When injecting the resin from the sprue formed on the fixed side mold into the resin flow path consisting of the runner and gate continuous to the cavity, and mold the mold,
A state in which a protruding means protrudes in a release direction of the stationary mold and the movable mold in a pool portion branched from the main resin flow path separately from the main resin flow path connecting the runner and the cavity. An optical element injection molding method in which a resin is injected into the cavity and cured while the resin is prevented from contracting by the protruding means. After the resin is cured, the movable side mold is moved to open the cavity, and the projecting means engaged with the reservoir formed by the runner, the gate, and the cavity is centered on both sides thereof. A first step of relatively moving the movable mold and the protrusion means in the mold release direction while being regulated by a sprue lock pin and the movable insert;
The sprue lock pin is moved from the runner after the sprue lock pin of the movable side insert is further moved relative to the movable side mold to release the product from the movable side insert. The optical element injection molding method according to claim 6, further comprising a second step of separating. The cavity has a shape necessary for resin molding using a lens having an edge portion as a product portion, and the position of the tip of the protrusion means corresponds to the edge portion of the cavity formed on the movable mold. In the first step, the movable mold and the protruding means are relatively moved in the mold release direction until the product section is released from the edge of the movable mold.
The optical element injection molding method according to claim 7, wherein in the second step, the runner portion that has not been released from the movable mold is released. 7. The optical element injection molding method according to claim 6, wherein the first step and the second step proceed continuously, and there is no waiting time between them.

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