JP2957614B2 - Plastic lens molding method and molding die - Google Patents

Description

The present invention relates to a method of molding a plastic lens and a molding die.

[Conventional technology]

In the injection compression molding method used for the production of high-precision optical components such as lenses, the injection molding method disclosed in Japanese Patent Application Laid-Open No. 58-94440 has been disclosed in order to obtain molded products with high dimensional accuracy and small inner diameter distortion. ing.

The outline of the injection molding method described in the publication will be described with reference to FIG. 8. The fixed mold 10 including the fixed lens insert 2 fitted to the fixed sleeve 4 and the movable lens insert 3 fitted to the movable sleeve 5 are described. In the cavity 1 formed between the fixed lens insert 2 and the movable lens insert 3 of the injection mold 8 constituted by the movable mold 11 comprising
After being filled through a runner and a gate 6 formed so as to face the outer peripheral side surface of the plastic lens, that is, formed substantially perpendicular to the optical axis of the plastic lens, the molten resin in the cavity 1 is cooled and solidified. In the process of the above, the fixed lens insert 2 or the movable lens insert 3 for molding the lens R surface is compressed in the direction shown by the arrow in FIG. 8 to inject a high-precision plastic lens without sink marks on the lens optical surface. It is intended to be molded.

[Problems to be solved by the invention]

However, in the above-described conventional injection molding method, since the compression operation of the lens to be molded is performed in the thickness direction of the lens, the amount of the molten resin injected into the cavity 1 varies, and the mold temperature varies. Or, variations in compression force and the like appear as variations in the thickness and surface accuracy of the lens to be molded, and are not suitable for molding a high-precision plastic lens particularly requiring a thickness of μm level. Was.

Therefore, the present invention has been developed to solve the above-mentioned drawbacks of the conventional injection molding method, and a plastic lens molding method and a molding die which can sufficiently cope with the molding of a high precision plastic lens. It is intended to be provided.

[Means and Actions for Solving the Problems] The plastic lens molding method of the present invention is a plastic lens injection molding die, and has a fixed side piece and a movable side piece having a molding surface of a lens optical surface, and In accordance with the shrinkage that occurs when the molten resin filled in the cavity formed by the movable sleeve that forms the outer periphery of the molded lens through the gate in a direction substantially perpendicular to the optical axis of the molded lens cools and solidifies. Then, molding is performed while applying pressure to the inner diameter side from the lens outer peripheral side of the lens to be molded, and the lens outer peripheral portion formed on the inner peripheral surface of the cavity and the outer peripheral compressed concave portion which is more concave than the outer peripheral portion are formed. Thus, the lens is formed so as not to cause sink marks on the optical surface of the lens to be molded.

A molding die for a plastic lens used in carrying out the molding method is formed by a fixed side piece and a movable side piece having a molding surface of a lens optical surface, and a movable side sleeve for molding an outer peripheral portion of a lens to be molded. A molding die for molding a plastic lens by filling a molten resin into a cavity through a gate in a direction substantially perpendicular to the optical axis of the lens to be molded, and inside the cavity for molding the outer peripheral portion of the lens to be molded. A slide mechanism for advancing the pressing portion of the lens outer peripheral compression insert having a thickness smaller than the thickness of the lens outer peripheral portion with respect to the peripheral surface in accordance with shrinkage generated when the molten resin filled in the cavity cools and solidifies. Provided on the outer diameter portion of the lens formed in the cavity, the outer peripheral surface formed by the inner peripheral surface of the cavity and the compression nest that is concave from the outer peripheral surface. It is characterized in that to form the outer peripheral compression recess which is molded in pressure part.

Further, a plastic lens molding die has a fixed side piece and a movable side piece having a molding surface of a lens optical surface,
A molding metal for molding a plastic lens by filling a molten resin into a cavity formed by a movable sleeve for molding an outer peripheral portion of the molded lens through a gate substantially perpendicular to an optical axis of the molded lens. In the mold, the pressing portion of the lens outer peripheral compression insert having a thickness smaller than the thickness of the lens outer peripheral portion is filled in the cavity with respect to the inner peripheral surface of the cavity for molding the outer peripheral portion of the lens to be molded. Provided with a slide mechanism for advancing in accordance with shrinkage that occurs when the molten resin is cooled and solidified, and a slide mechanism for compressing the optical surface of the lens to be molded in a direction in which the thickness of the lens decreases, and molded in the cavity. The outer peripheral surface of the lens is formed with an outer peripheral surface formed by the inner peripheral surface of the cavity and an outer peripheral compressed concave portion formed by a pressing portion of the compression nest that is concave more than the outer peripheral surface. It is intended to.

According to the present invention, the amount of shrinkage generated in the process of cooling and solidifying the molten resin injected into the cavity from the molten state is molded while compensating for the volume shrinkage by compressing the lens to be molded from the outer peripheral direction. This prevents sink marks from occurring on the lens optical surface of the lens to be molded.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 to 6 show a first embodiment of the present invention.
The figure is a partially longitudinal side view of a molding die, FIGS. 2a, 2b, 2c and 3d are explanatory views showing the shape of a lens to be molded, FIG.
FIGS. A and b, FIGS. 5a and b and FIGS. 6a and b are a side view and a perspective view, respectively, showing a plastic lens molded by the molding die shown in FIG.

When plastic lenses are injection-molded, usually, in various lens shapes such as a concave lens or a convex lens, as shown in FIGS. The concave lens 20 or the convex lens 21 is formed by integrally providing the outer diameter portions 13 and 15 on the outer peripheral portion, and the outer peripheral flange portions 22 and 23 are provided on the outer periphery of the concave lens 20 or the convex lens 21 as shown in FIGS. In some cases.

Therefore, an embodiment of a molding die applied to the molding of a lens having the outer diameter portions 13 and 15 or the outer rim portions 22 and 23 such as the concave lens 20 or the convex lens 21 shown in FIGS. 2 and 3 will be described below. Will be described with reference to FIG.

The injection mold 30 in FIG. 1 is a fixed mold.
The movable mold 29 is configured to be freely openable and closable in the PL 60 with respect to 28.

In the fixed mold 28, the fixed plate 32 is fixed to the fixed side mounting plate 31, and a fixed side piece 37 having a molding surface of the lens optical surface of the lens to be molded is mounted on the fixed plate 32 via a fixed sleeve 38. And a sprue bush 33 having a sprue 34 penetrating through the mounting plate 31 and the fixing plate 32.

On the other hand, the movable mold 29 fixes the movable plate 47 to the movable mounting plate 53 via the spacer block 49 and the receiving plate 48, and the movable plate 47 includes the movable optical member 47 having the lens optical surface of the lens to be molded via the movable sleeve 41. A movable side piece 40 having a molding surface is movably mounted, and a projecting plate 50 is attached to the mounting plate 53 via a projecting plate receiver 52, and a projecting rod of the movable side piece 40 is attached via the projecting plate 50. It is configured by mounting the projection rod 51 of the runner 35 and the runner 35 movably up and down.

Further, the movable plate 47 of the movable mold 29 has an outer peripheral compression that compresses the outer peripheral portion of the molded lens in the cavity 39 formed by the fixed side piece 37, the movable side piece 40, and the movable side sleeve 41 in the inner diameter direction. An insert 42 is mounted to be able to move back and forth.

The outer peripheral compression insert 42 is shown only on the left side in FIG. 1, but is configured to be able to compress the entire circumference in the radial direction between the peripheral directions of the molten resin injected and filled in the cavity. In the above, the disk-shaped insert is divided into a plurality of parts, each insert 42 is mounted so as to be able to move back and forth in the radial direction, and each insert 42 is connected to a compression ram 43 of a hydraulic cylinder 44 for operation. The hydraulic device 46 is configured to be able to move back and forth through the switching valve 45 of the hydraulic device 46.

Further, each insert 42 is configured to be able to move back and forth while being cycled through the control unit of the hydraulic device 46.

In the case where a lens to be molded (the concave lens 20 shown in FIGS. 2a and 2b in FIG. 1) is molded by the injection mold 30 having the above configuration, the movable mold 29 is fixed to the fixed mold 28.
After the mold has been clamped through the PL60 surface, the molten resin is sprued from the molding machine nozzle (not shown) through a sprue 34, and a cavity is formed through a runner 35 and a gate 36 formed substantially perpendicular to the optical axis of the lens to be molded. Injection filling into tee 39.

Thus, shrinkage starts at the same time as the cooling and solidification of the molten resin filled in the cavity 39 is started.In response to such shrinkage, the hydraulic device 46 is operated, and When the molten resin is filled, the outer peripheral compression insert 42 positioned at the retreat end is advanced to press the molten resin in the cavity 39 toward the inner diameter side from the outer peripheral portion.

Therefore, since the molten resin in the cavity 39 is pressed toward the inner diameter side from the outer peripheral portion by the pressing of the outer peripheral compression insert 42, the occurrence of sink on the lens optical surface due to shrinkage upon cooling and solidification is prevented and the thickness is reduced. The taste can be controlled on the order of μm, and a highly accurate plastic lens can be molded.

The amount of operation of the outer peripheral compression insert 42 is set to an amount corresponding to the volume shrinkage of the molten resin filled in the cavity 39, and the pressing force or the operation timing is adjusted in accordance with the shrinkage of the molten resin. Implemented.

Further, in the case of the concave lens 24 shown in FIGS. 4a and 4b, the configuration of the pressing portion 42a of the outer peripheral compression insert 42 can be pressed over the entire outer circumference of the outer diameter portion 16 of the concave lens 24. The outer diameter portion 16 of the concave lens 24 shows a state in which a uniform outer peripheral compression concave portion 17 is formed on the entire outer periphery.

In addition, in the case of the concave lens 25 shown in FIGS. 5A and 5B, the configuration of the pressing portion 42a of the outer peripheral compression insert 42 is changed to the outer diameter portion 1 of the concave lens 25.
In the entire circumferential direction of FIG. 8, a plurality of pressing portions are arranged, so that the outer peripheral portion of the outer diameter portion 18 of the molded concave lens 25 shows a state in which a plurality of outer peripheral compression concave portions 19 are formed, and In the concave lens 26 shown in FIGS. 6A and 6B, the outer peripheral compression nest having a circular shape is formed while each outer peripheral compression recess 19 of the concave lens 25 shown in FIG. This shows a molding state when molding is performed by the pressing portion 42a of 42, and a plurality of outer peripheral compression concave portions 28 are molded around the entire outer diameter portion 27 of the concave lens 26.

Incidentally, the concave lenses 24, 25 and 2 shown in FIG. 4 to FIG.
The configuration of the pressing portion 42a of the outer peripheral compression insert 42 of the injection molding die 30 described by 6 is not limited to the above-described configurations, but can be appropriately configured to appropriately obtain the intended operation and effect. It can be implemented.

Also, in the case of a molded lens having outer circumferential flanges 22 and 23 like the concave lens 21 and the convex 20 shown in FIGS. 3a and 3b, the distance between the lens effective diameter portions 12 and 14 and the outer diameter portions 13 and 15 is increased. This allows a greater degree of freedom in designing and designing the outer periphery compression allowance arbitrarily, and also helps prevent the deformation of the fixed side piece 37 and the movable side piece 40 during molding and compression.

As is clear from the above description, according to the present embodiment, it is possible to effectively prevent sink marks generated during injection molding, to enable injection molding of a plastic lens having high-precision transferability, and to perform lens molding at the μm level. The thickness can be controlled, and a highly accurate plastic lens can be provided.

In particular, the effective function and effect of the concave lens are confirmed, and the outer peripheral compression concave portions 17, 19, and 28 formed on the outer periphery of the lens by the outer peripheral compression insert 42 should serve as a reference for lens positioning and one-touch assembly. Has the advantage that

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention and is a partial longitudinal side view of an injection mold.

By the way, the injection mold 30 shown in FIG.
40 is configured to be operable to compress in the lens thickness direction of the molded lens, and is operated in a spacer member 49 interposed between the movable plate 47 and the movable mounting plate 53 of the movable mold 29. Hydraulic cylinder 63 for the movable side piece 40
Is connected to the ram 62 of the hydraulic cylinder 63, and the hydraulic cylinder 63 is connected to the hydraulic device 46 via the switching valve 61.

The other components are the same as those of the injection molding die 30 in the first embodiment, and the same components are denoted by the same reference numerals and description thereof will be omitted.

In the case where a plastic lens is injection-molded by the injection mold 30 having the above-described structure, the cooling resin is injected and filled into the cavity 39 at the same time as cooling and solidifying similarly to the first embodiment. In accordance with the contraction, the hydraulic cylinder 44 is operated via the hydraulic device 46 to move the outer peripheral compression insert 42.
The outer peripheral portion is pressed in the radial direction by moving the outer peripheral portion, and in association with the pressing operation, the outer peripheral compression
The hydraulic cylinder 63 is actuated (simultaneously or individually with the operation of 42) to apply a pressure in the thickness direction while moving the movable piece 40 by a required amount.

That is, molding is performed while simultaneously or individually performing compression in the outer peripheral direction and in the thickness direction in accordance with shrinkage of the molten resin filled in the cavity 39 upon cooling and solidification.

Therefore, according to the present embodiment, by compressing in the thickness direction and the outer peripheral direction, in addition to the operation and effect of the first embodiment, even if the thickness has a large degree of change (even if the uneven thickness is large). Compression can be performed evenly and reasonably, and molding of a high-quality plastic lens free of stress at a thin portion and sink at a thick portion at the time of compression during molding can be accurately performed.

That is, in molding a lens having a large thickness deviation,
When the amount of compression is matched to the amount of sink in the thin part, the thick part becomes sink, and when the amount of compression is matched to the amount of sink in the thick part, a large amount of stress is generated in the thin part, and the optical properties of the molded lens deteriorate significantly. However, in the case of the present embodiment, high-precision molding of a plastic lens can be achieved while eliminating such a disadvantage.

〔The invention's effect〕

According to the present invention, it is possible to prevent sink marks due to shrinkage of molten resin during injection molding, and to mold a high-quality plastic lens having high-precision transferability on the lens optical surface and dimensional accuracy in the thickness direction at the μm level. I can do it if possible.

[Brief description of the drawings]

1 to 6 show a first embodiment of the present invention. FIG. 1 is a partially longitudinal side view of a molding die, and FIGS. 2a, b, c, d and 3a, 3b. Is an explanatory view showing the shape of the lens to be molded, FIG.
a, b, FIGS. 5a, b and 6a, b are side and perspective views, respectively, showing a plastic lens molded by the molding die shown in FIG. 1, and FIG. FIG. 8 shows an example, and is a partially longitudinal side view of an injection mold, and FIG. 8 is an explanatory view showing a conventional plastic lens injection molding method. 16,18,27… Effective diameter part 17,19,28… Outer peripheral compression concave part 24,25,26 …… Concave lens 28 …… Fixed mold 29 …… Movable mold 30 …… Injection mold 37 …… Fixed Side piece 39 Cavity 40 Movable side piece 42 Peripheral compression nest 43 Compression ram 44 Hydraulic cylinder 45 Switching valve 46 Hydraulic device 61 Switching valve 62 Ram 63 …… Hydraulic cylinder

Claims (3)

(57) [Claims] 1. A mold for injection molding a plastic lens, comprising a fixed side piece and a movable side piece having a molding surface of a lens optical surface, and a movable side sleeve for molding an outer peripheral portion of a lens to be molded. In the cavity,
In accordance with the shrinkage that occurs when the molten resin filled through the gate in the direction substantially perpendicular to the optical axis of the molded lens cools and solidifies, it is molded while applying pressure from the lens outer peripheral side to the inner diameter side of the molded lens. By forming an outer peripheral portion of the lens formed on the inner peripheral surface of the cavity and an outer peripheral compressed concave portion which is more concave than the outer peripheral portion on the outer periphery of the lens, molding so as not to cause sink on the optical surface of the lens to be molded. Molding a plastic lens. 2. A mold for injection molding a plastic lens, comprising a fixed side piece and a movable side piece having a molding surface of a lens optical surface, and a movable side sleeve for molding an outer peripheral portion of a lens to be molded. In the cavity,
In accordance with the shrinkage that occurs when the molten resin filled through the gate in a direction substantially perpendicular to the optical axis of the molded lens is cooled and solidified, the entire outer peripheral portion of the lens is moved from the outer peripheral side of the molded lens to the inner side. Molding is performed by applying pressure from a plurality of locations in the circumferential direction, and forming an outer peripheral portion of the lens formed on the inner peripheral surface of the cavity and an outer peripheral compressed concave portion which is more concave than the outer peripheral portion on the outer periphery of the lens. A method of molding a plastic lens, characterized in that molding is performed so as not to cause sink marks on the optical surface of the lens. 3. The optical axis of the lens to be molded is formed in a cavity formed by a fixed side piece and a movable side piece having a molding surface of a lens optical surface, and a movable side sleeve for molding an outer peripheral portion of the lens to be molded. A molding die for molding a plastic lens by filling a molten resin through a vertical gate, wherein the thickness of the outer peripheral portion of the lens is greater than the inner peripheral surface of the cavity for molding the outer peripheral portion of the lens to be molded. A slide mechanism is provided for advancing the pressing portion of the lens outer peripheral compression insert having a small thickness in accordance with shrinkage generated when the molten resin filled in the cavity cools and solidifies, and is formed in the cavity. Forming an outer peripheral compression concave portion formed on the outer peripheral surface of the lens at an outer peripheral surface formed by the inner peripheral surface of the cavity and a pressing portion of the compression nest that is concaver than the outer peripheral surface. Mold the plastic lens to symptoms.