JPH03132323A - Molding method for plastic lens - Google Patents

Abstract

PURPOSE:To mold a lens of superior optical performance without weld lines and internal deformation by heating a cavity molding surface of a molding component up to the flowable temperature of resin prior to the injection filling of molten resin into a cavity. CONSTITUTION:When a molding device is ON and mold clamping is completed, a hating air feeding opening 9 is opened to communicate with a cavity 1 to actuate a selector valve 19 and a heating unit 18 and the high temperature air heated up to approximately 250 deg.C in fed into the cavity 1. Then, the heating air feeding opening 9 is closed and the cavity 1 for shaping a plastic lens is formed, and acryl resin which is heated and melted up to approximately 230 deg.C is injected from an injection molding machine into the cavity 1 and filled therein. As a cavity forming surface is constituted to heat a plastic lens-forming material up to the flowable temperature or above immediately before injection filling of molten resin, the resin filled in the cavity 1 can reach an the end section while its molten state is retained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method of molding a plastic lens such as a zoom lens (concave lens) for a video camera, and an apparatus used for carrying out the molding method, and particularly to a method for molding a plastic lens [Prior art] Plastic lenses have the advantage that they can be made with complex optical surfaces by transferring the cavity shape of a molding die. be. Therefore, an aspherical lens without spherical aberration can be easily molded, and this molding technology is being applied to many fields, such as zoom lenses for video cameras.

However, when molding a concave lens that has a difference in wall thickness between the center and peripheral parts of the lens, the filling condition becomes extremely complicated when filling the cavity with molten resin. Until the filling is completed, there are parts where the temperature of the molten resin falls below its flowable temperature, and when the molten resin in one peripheral part merges with the molten resin in the center, the merging part (of the molded product) In addition, since the temperature distribution of the molten resin is not uniform, internal distortion occurs in the molded product, which is combined with the weld twin. Therefore, the optical performance of the plastic lens was deteriorated.

By the way, as a means to prevent the occurrence of feld lines, a nine-blank approximating the lens shape is inserted into the mold in advance, and a blank is formed between this blank and the #1 mold. There is a known method in which molten resin is filled into a uniform space.Related means of this type include, for example, Japanese Patent No. F@57-175156. .

[Problem to be solved by the invention]

As mentioned above, the conventional technology of inserting a blank does not take into account the following points: 〇■ Since the blank is molded in a separate process, the number of plastic lens molding steps increases.

@ In order to form a uniform space between the blank and the mold, the structure made of the mold becomes complicated.

■ Even if it is possible to prevent the Feldline,
Internal strain occurs at the joint between the blank and the resin, making it difficult to improve optical performance.

The present invention solves the problems of the prior art described above, and provides a plastic lens molding method that can easily mold a plastic lens with excellent optical performance, especially a concave lens, without Feld lines or internal distortion, and its implementation. The object of the present invention is to provide a plastic lens molding device having a molding die with a simple structure, which can be directly used in the manufacturing process.

[Means to solve the problem]

The above object is achieved by heating the cavity forming surface that shapes the lens surface immediately before filling the molten resin and raising the temperature of the cavity forming surface to a temperature at which the molten resin can flow.
achieved.

That is, the configuration of the plastic lens molding method of the present invention uses a molding die equipped with a cavity forming member that can form a cavity for shaping a plastic lens when the mold is clamped, and the mold is in a clamped state. Molten resin is injected and filled into the cavity, and the molten resin is cooled and solidified by heat exchange between the molten resin and the molding die, thereby molding plastic resin into which the shape of the cavity is transferred. In the lens molding method, the cavity forming surface of the cavity forming member is heated to a temperature at which the resin can flow, prior to injection and filling of the molten resin into the cavity. Also, the plastic lens of the present invention The configuration of the molding apparatus is as follows: 1a1 When the mold is clamped, it has a molding die equipped with a cavity forming member capable of forming a cavity for shaping a plastic lens, and a mold for forming the cavity. The member is made of a mold material with high thermal conductivity, and 1. The cavity portion forming the lens surface is made of a thin layer of an inorganic material with low thermal conductivity, and molten resin is injected and filled into the cavity in the mold closed state. , a plastic lens molding apparatus capable of molding a plastic lens having the shape of the cavity transferred thereto by cooling and solidifying the molten resin through heat exchange between the molten resin and the molding die, the molding die having: A heated air supply hole communicating with the cavity is bored, and a mold cavity surface heating device capable of supplying high temperature air to the heated air supply hole is attached to the mold, or A mold cavity surface heating device capable of injecting high-temperature air or irradiating infrared rays onto the cavity forming surface of the cavity forming member of the mold in the open state is installed.

[Effect]

Supplying high-temperature air into the cavity of a molding die that is in a closed state, or injecting high-temperature air or irradiating infrared rays to the cavity forming surface of a cavity forming member of a molding die that is in an open state. to heat the cavity forming surface. The cavity forming surface is rapidly heated by heat exchange with high-temperature air, and the temperature of the cavity forming surface rises to the temperature at which the resin can flow.〇The molten resin injected and filled into the heated cavity through the surface is heated. The cavity is filled up to t while maintaining a fluid state to the end of the cavity. Since the molten resin is in a fluid state, no internal strain occurs in the molten resin. Also.

At the part where the resin joins at the part facing the runner fist gate, the resin to be joined is in a fluid state, so it is completely integrated, and the generation of weld lines can be prevented. Let's explain by example.

Figure 1 shows the first part of the plastic lens molding apparatus of the present invention.
FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention.

The outline of this molding apparatus will be explained using FIG. 1. This is a fixed insert piece 2 related to a cavity forming member that can form a cavity 1 for shaping a plastic lens when the mold is clamped.゜Fixed type 5. It has a molding die M equipped with a movable insert piece 41 and a movable die 5. Molten resin is injected and filled into the cavity 1 in the mold clamped state, and by heat exchange between the molten resin and the inner cavity forming member. By cooling and solidifying the molten resin, a plastic lens having the shape of the cavity 1 transferred thereto can be molded, and the mold M is provided with a heated air supply hole 9 communicating with the cavity 1. Then, in the mold M,
A supply hole opening/closing unit 25 capable of opening and closing the heated air supply hole 9; a heated air supply unit 26 capable of supplying high temperature air to the heated air supply hole 9; and a supply hole opening/closing unit 25. This is a plastic lens molding apparatus equipped with a mold cavity surface heating device H having a controller 17 capable of controlling a heated air supply unit 26.

This will be explained in detail below.

1 is a cavity for shaping a plastic lens, and this is a fixed insert piece 2 related to a cavity forming member.
．． Fixed type 3. Movable entering piece 4. The fixed insert piece 2 and the movable insert piece 4 are formed by a movable mold 5. As shown in FIG. 4, the cavity 1 is formed by a thin layer 27 of ceramic having low thermal conductivity. That is, thermal conductivity: 2&
The cavity surfaces of the fixed insert piece 2 and the movable insert piece 4 made of a copper alloy having a thermal conductivity of 7. OX 10-6Kcal/samm・℃
The cavity 1 is constructed by welding a ceramic member having a thickness of 1.0 mm.

Cough cavity 1 has runner gate 8. Via the sprue 7, the nozzle hole 6 also communicates with the injection molding machine (not shown). Therefore, the molten resin is supplied to the cavity 1 through these flow paths. Fixed input pieces 2. The movable entry piece 4 is provided with a round temperature control groove 10 that adjusts the temperature of the mosquito entry piece to v4. The temperature control groove 10 is connected to a mold temperature control device 12 via a heat medium supply path 11.

The mold temperature controller 12 has a heating medium supply path 11. By circulating a heat medium through the temperature control port 10), the input piece can be maintained at a constant temperature at all times. A heated air supply hole is provided at a position communicating with the cavity 1 and facing the runner gate 8. is provided. The heated air supply hole 9 has a structure that it can be opened and closed by a sliding block 13 connected to a sliding unit 14. The sliding unit 14 is connected to a hydraulic pressure source 16 via a directional control valve 15, and the sliding unit 14. Directional control valve 15. The hydraulic pressure generation source 16 constitutes a supply hole opening/closing unit 25.

Therefore, the operation of the supply hole opening/closing unit 25 can be controlled by the controller 17. Further, the heated air supply hole 9 is connected to the heating unit 18.
The heating unit 1B is connected to the air supply source 20 via the switching valve 19, and the switching valve 19. The heating air supply unit 26 is configured by the air supply source 20, and the heating unit 18. The switching valve 19 is connected to a controller 17, which can also control the operation of the heated air supply unit 26.

The 10th plastic lens molding method of the present invention uses a plastic lens molding apparatus constructed like this.
! ! An example will be explained.

In this embodiment, a concave meniscus lens is molded using acrylic resin as a lens material.

The shape and dimensions of the lens are such that the lens surface has a radius of curvature of 40
When turning on the mouth forming device, which has a spherical shape of 80 mm, center wall thickness of 2 mm, and outer diameter of 50 mm,
When the movable mold 5 moves forward and the dividing planes of the fixed mold 5 and the movable m5 coincide and the mold clamping operation is completed, the sliding w knit 14
operates, the sliding block 13 retreats, the heated air supply hole 9 opens, and the supply hole 9 and the cavity 1 communicate with each other.
Next, the switching valve 19. The heating unit 18 is activated and 25
High temperature air heated to 0°C is supplied into the cavity 1. Then fill cavity 1 and runner gate 8. Thin ceramic layer 27 forming the cavity surface is discharged from the nozzle hole 6 through the sprue 7
is exposed to high-temperature air, and the temperature increases to 220''C in about 20 seconds by heat exchange with the high-temperature air.

The high temperature air effect causes heat to be stored in the thin layer portion, and the copper alloy entry piece member is not affected by the high temperature air.

Next, switching pulp 19. The operation of the heating unit 18 is stopped, and the supply of high temperature air is stopped. Furthermore, sliding unit 1
4 operates to close the heating error supply hole 9 with the sliding block 13 and form the cavity 1 for shaping the plastic lens. ◎Next 11C, the acrylic resin heated and melted at 250°C is heated and melted at 250°C, and the injection molding is performed. The resin filled into cavity 1 is injected and filled from the machine into cavity 1.

Since the temperature of the cavity forming surface is higher than the melting temperature of the resin, the resin reaches the end of the cavity 1 while maintaining its molten state. At the position facing the runner gate 8, the molten resins merge and join together, but since the resin in contact with the cavity forming surface and the resin at the center of flow are both in a molten state, these resins do not flow into the merging area. The weld line can be prevented from forming by being integrated into the entire body.

In addition, since no temperature distribution occurs in the molten resin filled, a uniform molten state can be achieved, and internal strain can also be prevented from occurring.

On the other hand, a 60° C. heat medium is continuously supplied to the temperature control groove 10 into the inside of the insert piece related to the cavity forming member. Therefore, the molten resin in the cavity 1 is cooled by heat exchange with the input piece, and a desired plastic lens is obtained.

According to the above-described embodiment, the cavity forming surface is heated to a temperature higher than the flowable temperature of the plastic lens molding material immediately before injection and filling of the molten resin, so that the resin filled into the cavity is melted. It reaches the end of the cavity while maintaining its condition ◎This prevents the internal distortion that conventionally occurs, as well as the generation of weld lines, which has the effect of improving the optical performance of the plastic lens. There is.

Other embodiments will be described below.

FIG. 2 shows the second part of the plastic lens molding apparatus of the present invention.
◎ In this Fig. 2, the same numbers as those in Fig. 1 are the same parts @ and y/ is the same mold as the conventional one ( The one shown in FIG. 1 is a molding plate μ having heated air supply holes 9
).21 is a nozzle unit for injecting high-temperature air, and 22 is a nozzle unit 21 for injecting high-temperature air. The moving unit 17A that can be positioned near the cavity forming surface of the movable figure 4 is a controller that can control the heated air supply unit 26. ．． koy).

- This is a metal cavity surface heating device consisting of 17 members and 26 heating air supply units.

A second embodiment of the plastic lens molding method of the present invention will be described using a plastic lens molding apparatus having such a VC configuration.

In this embodiment, when the mold is opened, a fixed input piece 2 is inserted from the nozzle unit 21. High temperature air is injected onto the cavity forming surface of the movable figure 4 to heat the cavity forming surface. The subsequent steps, that is, injection and filling of the molten resin into the cavity and cooling of the molten resin, are the same as in the previous embodiment, and provide the same effects.

FIG. 3 shows the third part of the plastic lens molding apparatus of the present invention.
FIG. 2 is a schematic configuration diagram showing an embodiment of the present invention.

In FIG. 3 of this section, the same parts as in FIG. 2 are denoted by the same numbers. And 2! 1 is a lamp unit for emitting infrared rays, and 24 is this lamp unit 2.
H// is a power supply unit that can control the energy supplied to the lamp unit 25. Mobile unit 22. This is a mold cavity surface heating device consisting of a power supply unit 24.

Third implementation 1' of the plastic lens molding method of the present invention using the glass lens molding apparatus configured as described above! Explain l.

In this embodiment, when the mold is opened, the fixed input piece 2. is inserted from the lamp unit 25. The cavity forming surface of the movable figure 4 is heated by irradiating the cavity forming surface with infrared rays.The subsequent steps are the same as those in the above embodiment.P] It is the effect of Qin.

〔Effect of the invention〕

As described in detail above, the present invention provides a plastic lens molding method that can easily mold a plastic lens with excellent optical performance, especially a concave lens, without weld lines or internal distortion, and a method that can be used directly to implement the method. be done. A plastic lens molding device having a mold with a simple structure can be provided.

[Brief explanation of the drawing]

1 to 5 are schematic configuration diagrams showing first to third embodiments of the plastic lens molding apparatus of the present invention, respectively.
FIG. 4 is a schematic diagram showing the structure of the cavity. 1... Cavity, 2... Fixed insert piece, 3... Fixed type, 4... Movable insert piece, 5... Movable type, 9... Heated air supply hole, 17, 17A...・Controller, 21
... nozzle unit), 22 ... moving unit, 25
... Lamp unit, 25 ... Supply hole opening/closing unit, 26 ... Heated air supply unit, H, H/, H
//...Mold cavity surface heating device, M, M'
...Molding mold.

Claims (1)

[Claims] 1. Cavity for shaping a plastic lens (
The fixed insert piece (2) and the movable insert piece (4) forming 1) are made of a metal material having a thermal conductivity of 26.0×10^-^6Kcal/s・mm・℃ or more, and the lens Using a mold (M) whose cavity surface forming the surface is made of an inorganic material having a thermal conductivity of 7.0 x 10^-^7Kcal/s・mm・℃ or less, By injecting and filling a molten resin into the cavity (1) and cooling and solidifying the molten resin through heat exchange between the molten resin and the molding die (M), a plastic having the shape of the cavity (1) transferred thereto is produced. In a plastic lens molding method for molding a lens, prior to injection and filling of the molten resin into the cavity (1), the cavity molding surface of the molded member of the cavity (1) is heated to a temperature at which the resin can flow. A plastic lens molding method characterized by: 2. Cavity for shaping plastic lenses (
Claim 1) wherein the molding die (M) is composed of insert pieces (2) and (4) made of a copper alloy, and the cavity surface is composed of a thin layer of ceramic having a thickness of 1 mm or less. Plastic lens molding method described in. 3. The molding die (M) has a structure in which a heated air supply hole (9) is formed to communicate with the cavity (1), and when the mold is closed, the heated air supply hole (9) is used to connect the cavity (1) with the heated air supply hole (9). The plastic lens molding method according to claim 1, characterized in that the cavity forming surface of the cavity (1) forming member is heated by supplying high temperature air to the inside. 4. The plastic lens molding method according to claim 1, wherein the forming surface of the cavity (1) is heated by blowing high temperature air to the cavity forming surface of the member forming the cavity (1) in the mold open state. 5. The plastic lens molding method according to claim 1, wherein the cavity forming surface of the cavity forming member is heated by irradiating infrared rays onto the cavity forming surface of the cavity forming member in an open state.