JPH0478512A - Injection molding method for plastic lens - Google Patents

Abstract

PURPOSE:To mold a plastic lens small in an external waviness in one injection stage without constraining the edge shape of the lens by sliding one side of the cavities of the top and bottom forces to perform mold matching and injecting resin and thereafter matching the outside diameters of the cavities and moving one side of the nested boxes of the top and bottom forces and compressing, cooling and curing resin. CONSTITUTION:The cavities 6, 7 of the top and bottom forces 6, 7 are formed of both the nested box 3 of a top force and the nested box 5 of a bottom force. Mold matching is performed in a state wherein both top force plate 1 and a slide 4 are slid in a range wherein the said cavities 6, 7 are not completely separated. At this time, the external peripheral edge part of the cavity 7 of the nested box 5 of the bottom force is engaged with the gate 2 of the top force plate 1. In this state, resin 8 is filled into the cavities 6, 7 from the gate 2. After filling is completed, both the top force plate 1 and the slide 4 are relatively moved in the horizontal direction to separate the gate 2 from the cavity 7. Moreover slippage of the outside diameters of the cavities 6, 7 is prevented. While resin 8 in the cavities 6, 7 is compressed by moving the nested box 3 of the top force or the nested box 5 of the bottom force, it is cooled and cured.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to injection molding of plastic lenses.

[Conventional technology]

Conventionally, the following important inventions have been disclosed for injection molding of plastic lenses.

For example, in the invention described in JP-A-57-72822, a preform is inserted into a mold,
A method of forming multiple layers on the outer periphery has been proposed.

Furthermore, in the invention described in Japanese Patent Application Laid-Open No. 61-258719, an invention has been proposed in which a gate is provided in communication with the cavity or between the gate and the launch to separate the gate from the runner.

[Problem to be solved by the invention]

However, the above-mentioned prior art has the following major drawbacks.

That is, the invention described in JP-A-57-72822 requires a preform molding step and a preform inserting step, resulting in a longer takt time and higher cost. Furthermore, the preform must be fixed, which imposes restrictions on the edge shape.

Further, in the invention described in Japanese Patent Application Laid-Open No. 61-258719, a large temperature difference occurs between the center part and the outer peripheral part of the lens, which tends to cause waviness on the lens surface of the molded product during cooling and hardening.

Furthermore, in each of the above-mentioned inventions, since the gate is installed on the side surface of the lens, the shape of the edge of the lens is restricted.

The present invention was developed in view of the above-mentioned shortcomings in the prior art, and provides an injection molding method for plastic lenses that does not restrict the edge shape of the lens and can mold plastic lenses with small waviness in a -degree injection process. With the goal.

[Means and effects for solving the problem] The present invention, when injection molding a plastic lens, aligns the molds by shifting the outer diameter of either the upper mold cavity or the lower mold cavity within a range that does not separate the cavity spaces. After the resin is injected from the outer diameter gap, the outer diameters of the upper mold cavity and lower mold cavity are aligned, and at least one of the upper mold insert and the lower mold insert is moved to fill the cavity. In this method, the resin is cooled and hardened while being compressed.

FIG. 1 is a conceptual diagram of an apparatus used in the injection molding method for plastic lenses according to the present invention.

1 is an upper mold plate, and a gate 2 is formed on this upper mold 11, and an upper mold insert 3 is fitted therein.

A lower mold insert 5 is fitted into the slide 4 that comes into contact with the upper mold plate l.

At this time, mold matching is performed with the upper mold plate 1 and the slide 4 shifted to the extent that the upper and lower mold cavities 6.7 formed by the upper mold insert 3 and the lower mold insert 5 are not completely separated. The outer peripheral edge of the lower mold cavity 7 of the lower mold insert 5 is engaged with the gate 2 of the upper mold plate 1. In this state, from gate 2, resin 8
is filled into the upper and lower mold cavities 6.7. After filling is completed, the upper mold plate 1 and the slide 4 are moved relatively in the horizontal direction to separate the lower mold cavity 7 and the gate 2, and also to remove the difference in outer diameter between the upper mold cavity 6 and the lower mold cavity 7. Then, the upper mold insert 3 or the lower mold insert 5 is moved in the vertical direction to compress and harden the resin 8 in the upper and lower mold cavities 6°7.

(Example) Hereinafter, an example of the injection molding method for a plastic lens according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIGS. 2a and 2b show a first embodiment of the present invention, in which FIG. 2a is a longitudinal sectional view and FIG. 2 is a partial sectional view.

11 is a molding device used in the injection molding method of the present invention, and this molding device 11 includes a lower mold 12 and an upper mold 1 placed on the lower mold 12.
It is composed of 3.

The lower mold 12 has a spacer block 15 on the lower mounting plate 14.
A receiving plate 16 and a lower mold plate 17 are arranged in series. A protruding plate 18 is installed inside the spacer block 15 so as to be movable up and down, and the protruding rod 1 has its lower end fitted into the protruding plate 18.
9 and a protruding pin 20 are provided upright. A slide plate 21 is provided on the protruding plate 18 so as to be movable up and down, and a lower end thereof is fitted into the slide plate 21, and a wedge 22 having a slope 22a formed on the upper part is erected. 17 has a slide 23 that can move horizontally on the upper surface of the receiving plate 1.6
is installed inside. A wedge 22 is attached to one end of the slide 23.
An inclined surface 23a is formed to engage with the inclined surface 22a of the lower mold plate 17, and an elastic member 24 fixed in the lower mold plate 17 is in contact with the other end surface 23b so as to be pressed against the wedge 22 at all times. Furthermore, a lower mold insert 25 whose lower part protrudes and contacts the upper end of the rod 19 is fitted into the slide 23 and is movable up and down.

On the other hand, in the upper mold 13, an upper mold plate 27 is provided on the lower surface of the ball mounting plate 26. The upper mold plate 27 is fitted with and fixed to the upper mold insert 2, and is provided with a spool bush 29 which is fitted into the ball mounting plate 26 and the upper mold plate 27. A gate 30 is formed on the lower surface of the upper mold plate 27.

In the injection molding method using the molding apparatus 11 having the above configuration, first, resin 31 is injected from the gate 30 in the state shown in FIG. , 25a are filled with resin 31.

After filling, the slide plate 21 is raised by a rod (not shown) of the molding device, and the wedge 22 is raised. As a result, the slope 23a of the slide 23 that engages with the slope 22a of the wedge 22 is pushed to the left, the slide 23 moves to the left, and as shown in FIG.
b coincides with the axis 1128b of the upper mold insert 28.

Next, the protruding plate 18 is raised by a rod (not shown) of the molding device, and the lower mold insert 25 is raised via the protruding rod 19. By raising the lower mold insert 25, the filled resin 3I is compressed and cooled and hardened. Then, the compression by the lower mold insert 25 is returned to O to open the mold, and the protruding plate 18 is raised again to eject the molded product.

Thereafter, when the force for raising the protrusion Fi1B and the slide plate 21 is returned to 0, the slide 23 moves to the right due to the pressing force of the elastic member 24, pushes back the wedge 22, and presses the slide plate 21 against the protrusion plate 18. Then, the mold is closed and the state shown in FIG. 2a is returned. The above steps constitute one cycle, and the molding is repeated.

According to this embodiment, the gate and the molded product can be separated within the mold. In addition, there is no need for a gate connected to the cavity.
By filling the resin 31 in a state where the axis 25b is shifted from the axis 25b, the thickness of the resin 31 at the time of filling becomes thinner. Therefore, the temperature difference in the resin 31 between the center of the cavity and its outer periphery when filling is completed is reduced, and the waviness of the lens surface of the molded product due to uneven shrinkage due to the temperature difference is reduced.

(Second example) FIG. 3 is a partial plan view showing a second embodiment of the present invention.

This embodiment differs in that a runner 32 is provided along the outer periphery of the lower mold insert 28 instead of the gate 30 in the first embodiment, and a plurality of gates 33 are arranged from this runner 32. The other configurations are the same, and the same components are given the same numbers and their explanations will be omitted.

The operation of this embodiment is the same as that of the first embodiment, and the explanation of the operation will be omitted.

According to this embodiment, the same effects as in the first embodiment can be obtained, and since a plurality of gates 33 can be provided regardless of the shape of the cavity, the stress strain of the gates 33 can be dispersed. It also has the effect of making it difficult to form flow marks due to welding or air taming.

(Third Embodiment) Figures 4a, b, and C show a third embodiment of the present invention, in which Figure 4a is a partial sectional view, Figure 4 is a partial plan view, and Figure 4C is a partial sectional view.
is a side view of the lens.

In this embodiment, when molding a lens 34 with a flange, the amount of misalignment between the upper mold insert 28 and the lower mold insert 25 in the first embodiment is limited, and the amount of misalignment between the upper and lower mold inserts 28 and 28 is opposite to each other. 25
They are different in that they are molded into a keyhole that does not fit within the effective surface of the lens, but they have the same structure, so the same numbers will be given and explanations of the structure and operation will be omitted.

According to this embodiment, the same effect as the first embodiment can be obtained, and when the axes 28a and 25a of the upper and lower mold inserts 28 and 25 are aligned on the same axis after cooling for a while after completion of filling, the lens The weld 35 generated on the weld 34 can be removed from the effective surface.

[Effects of the Invention] As explained above, according to the injection molding method for a plastic lens according to the present invention, there is no need for a gate connected to a cavity, so the shape of the molded product can be determined without being restricted by the gate. . Furthermore, since the gate and the molded product are separated within the mold, the gate cutting step can be omitted.

Furthermore, since the thickness of the resin at the time of completion of filling is thinner than the thickness of the molded product, the temperature difference between the resin at the center of the lens and its outer periphery becomes smaller. Therefore, a thick lens with small waviness on the lens surface can be molded by one injection.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an apparatus used in the injection molding method for plastic lenses according to the present invention, FIGS. 2 a and b show the first embodiment, and FIG. 2 a is a longitudinal sectional view. A partial sectional view, FIG. 3 is a partial plan view showing the second embodiment, and FIG. 4 a
, b and C show the third embodiment; FIG. 4a is a partial sectional view, FIG. 4 is a partial plan view, and FIG. 4C is a side view of the lens. 1.27...Upper mold plate 2.30.33--Gate 3.28...Upper mold insert 4.23...Slide 5.25...Lower mold insert 6...Top Mold cavity 7...Lower mold cavity 8.31...Resin 11...Molding device 12...Lower mold 13...Upper mold 14...Lower mounting plate 15...Spacer bronc 16 ... Receiving fabric 17 ... Lower template plate 18 ... Projection plate 19 ... Projection rod 20 ... Projection pin 21 ... Slide plate 22 ... Wedge 24 ... Elastic member 26 ...・Lower mounting plate 29...Spool bush 32...Lunch 34...Lens 35...Weld

Claims (1)

[Claims] (1) When injection molding a plastic lens, the outer diameter of either the upper mold cavity or the lower mold cavity is shifted within a range that does not separate the cavity space, and the molds are matched, and the resin is injected from the shifted portion of the outer diameter. After that, the outer diameters of the upper mold cavity and the lower mold cavity are aligned, and at least one of the upper mold insert and the lower mold insert is moved to compress and harden the resin filled in the cavity. Characteristic plastic lens injection molding method.