JPS6119327A - Injection compression molding method and device thereof - Google Patents

Abstract

PURPOSE:To make the form accuracy of a plastic lens high, by a method wherein at the time of cooling and curing of resin, the smaller the temperature distribution range of the resin in the inside of a cavity is, the more the molding shrinkage is unified within a softening temperature range of the resin, in a compression process after injection. CONSTITUTION:A first temperature controller 34 performs a function keeping the temperature of a stationary mold insertion piece, movable mold and movable mold insertion piece at a constant temperature T2 and the function cooling slowly the temperature of a mold from T2 to T3 after that, in an injection compression molding method making form accuracy of a plastic lens high, and a second temperature controller 35 can cool suddenly the temperature of the stationary mold insertion piece, movable mold and movable mold insertion piece. As a temperature distribution of resin in the inside of a cavity is cooled slowly up to a thermal deformation temperature emerging from a softening temperature region of the resin after the temperature distribution of the resin in the inside of the cavity has unified once in the softening temperature sphere through both the temperature controllers 34, 35, the resin is cooled while generation of an ununiform temperature of the resin to be followed by the cooling is being kept minimal.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to an injection compression molding method and apparatus for manufacturing plastic lenses using a thermoplastic plastic molding material, and in particular to an injection compression molding method and apparatus for manufacturing plastic lenses with high precision. The present invention relates to an injection compression molding method and an apparatus therefor.

(Background of the invention) In recent years, with improvements in mold manufacturing technology and molding machine control technology, P
Using Sm fat, PMM&resin or PC@fat, etc.
Relatively high-precision plastic lenses are now being manufactured.

Medium-sized, high-quality plastic lenses are used for camera viewfinder lenses and instant camera lenses. However, these plastic lenses
Shape accuracy such as lens surface accuracy and curvature radius accuracy related to the optical performance of the lens is significantly inferior to glass lenses used in imaging lenses of medium to high-end cameras.

Plastic lenses using thermoplastic resin are manufactured by injection compression molding (Plastics Age Encyclopedia).
pe-dia 1981, P148-163). In the conventional normal injection compression molding method,
190~ to the mold maintained at a constant temperature of about 40~90℃
.

After injecting molten thermoplastic resin heated to a high temperature of 260°C, the resin is cooled and solidified while applying compressive force to the resin in the mold via the insert piece that forms one side of the lens cavity. Ta.

However, when the shape of a plastic lens manufactured by such an injection pressure network forming method is measured with an accuracy on the order of microns, there is always a drawback that molding distortion such as warpage and sink marks is present.

The reason why such defects occur is considered to be due to the following reasons. In the conventional injection compression molding method described above, there is a large temperature difference between the mold and the resin injected into the mold cavity, and the high temperature molten resin injected into the cavity cools at a cooling rate of about 50 to 10"4. As a result, a large temperature difference occurs within the resin, and the resin cools and solidifies with a large temperature difference.As a result, the resin shrinks greatly and unevenly after molding. Therefore, it is thought that sink marks occur in areas of the resin that were at high temperatures, and that the imbalance of temperature throughout the resin causes warping. This is thought to be the reason why plastic lenses with the same high precision as glass lenses cannot be obtained.

The present inventors believe that the first drawback of the above-mentioned conventional injection compression molding method is large shrinkage, and have previously applied for a patent for a molding method having the following characteristics as an invention to improve this drawback. (Patent Application No. 58-105792).

(1) During the pressure holding process after the mold cavity is filled with resin from the molding machine, compressive force is applied to the resin in the cavity to preshape the resin in the cavity. At the same time, the degree of adhesion between the resin in the cavity and the mold fixing and movable inserting pieces is improved to ensure sufficient heat transfer between the resin in the cavity and the mold.

(2) Next, while maintaining this state, the resin in the cavity is temporarily cooled or left to promote internal solidification.

Thereafter, the temperature of the insert is increased to a temperature higher than the softening temperature of the resin, so that only the surface layer of the resin within the cavity is melted. The reason why only the surface layer is melted is to reduce the amount of resin shrinkage that occurs during subsequent cooling.

(3) Next, compressive force is again applied to the resin in the cavity to shape the molten surface layer.

At the same time, cooling of the fixed insertion piece and the movable insertion piece is started, and the compressive force applied to the resin in the cavity is controlled in accordance with this cooling temperature.

When a convex lens is molded using PMMA resin using the manufacturing method described above in the patent application, a high-precision convex lens with significantly improved lens surface accuracy can be produced compared to the conventional injection compression molding method described above. I was able to get it. The reason for this is that in the above patent, after the resin in the cavity is cooled once,
This is thought to be because the ζ-rubbing is performed to melt only the lens surface layer, so the molding shrinkage of the resin caused by cooling can be significantly reduced compared to the conventional injection compression molding method.

However, the manufacturing method of the above patent application includes the following (1) to (
Subsequent research revealed that there was a problem with 3).

(1) When a concave lens is molded, a high-precision lens like a convex lens cannot be obtained, and the lens surface precision is 10 to 20 times lower than that of a convex lens.

(2) PMM occurs when molding a convex lens using PC resin.
The lens surface precision is 5 to 10 times lower than when resin A is used.

t3) When molding a concave lens using PC resin, P
Compared to the case where a convex lens is molded using MM resin, the lens surface precision is significantly inferior (by 50 to 100 times or more).

The reasons for the above drawbacks (1) to (3) are considered to be as follows.

(A) The reason why a concave lens has inferior surface precision than a convex lens is that in a convex lens, the thickest part is at the center of the lens, but in a concave lens, the thickest part is on the outer periphery of the lens. For this reason, it is thought that the cooling contraction in the lens radial direction becomes larger than that of a convex lens.

ω) Why is the surface precision inferior when making a convex lens using PC resin compared to when using PMM resin?

In the manufacturing method of the patent application, only the lens surface layer is melted. Therefore, it is inevitable that temperature distribution occurs in the resin within the mold cavity. In addition, the heat distortion temperature is approximately 100°C for PMM resin, whereas
For PC resin, the temperature is about 130°C, and PC@Mari has a higher heat distortion temperature than PMM-containing resin.

Therefore, when heating the mold to melt only the lens surface layer, when using PC resin, it is necessary to heat the mold to a higher degree than when using PMMA resin. Therefore, the difference in temperature that occurs in the resin within the mold cavity becomes large, which increases the shrinkage of the resin that occurs as it cools and the non-uniformity of the shrinkage of each part of the resin.

(c) The reason why the lens surface precision is significantly inferior when a concave lens is molded using PC resin is thought to be that the above reasons (-) act synergistically.

(Objective of the Invention) The object of the present invention is to improve the drawbacks of the prior art (1) to (3) described above, and to improve the high performance in any combination of PMMA resin, PC resin, Pa resin, convex lens, and concave lens. An object of the present invention is to provide an injection compression molding method and an apparatus for manufacturing precision plastic lenses.

(Summary of the Invention) The present invention is characterized by a sliding piece provided on one of a fixed mold and a movable mold that are arranged opposite to each other, and a mold or a piece that faces the mold. In an injection compression molding method, resin is injected and filled into a cavity formed between the cavities, and a pressure cylinder is used to apply pressure to the insert piece to apply compressive force to the resin in the cavity. After heating the temperature distribution uniformly in the softening temperature range, we gradually cool the resin to the heat distortion temperature that takes it out of the softening temperature range, minimizing the occurrence of temperature unevenness in the resin due to cooling. Another feature of the present invention is that the fixed type, movable type, and insertion piece are heated at a constant temperature in the softening temperature range, and the resin is cooled to leave the hindlimb softening temperature range. a first temperature controller that gradually cools to a deformation temperature;
The present invention further includes a second m-even machine that rapidly cools the fixed mold, the movable mold, and the inserted pieces before the constant temperature heating and after the slow cooling.

(Embodiment of the Invention) Prior to the present invention, the present inventors had an outer diameter of 46u1, a center thickness of 1.911J, an outer diameter part thickness of 12.911J, and a radius of curvature of 2.
Injection compression mold and P for 50iu and 30iu concave lenses
Using C resin, an experiment was conducted in which the mold temperature was maintained constant and then slowly cooled.

In the experiment, the resin temperature during injection was set at 240°C, and the mold temperature maintained at a constant temperature was varied in the range of 130 to 180°C. In addition, the lens surface accuracy was measured by varying the time period during which the mold temperature was maintained constant within a range of 5 to 40 minutes.

Furthermore, after maintaining the mold temperature constant for a predetermined period of time, the lens surface accuracy was measured while changing the cooling rate for slow cooling in the range of 0.5 to to'c4.

Figure 2 shows the measurement results of the former experiment, that is, the measurement results of the lens surface accuracy as the mold temperature maintenance time changes with the mold deviation to maintain a constant temperature as a parameter.
In the figure, molding was performed by slow cooling under the common conditions of cooling rate x and st4 after maintaining the mold temperature constant. From FIG. 2, it can be seen that the lens surface precision improves when the mold temperature is maintained at 140° C. and the mold temperature maintenance time is increased.

Figure 3 shows the measurement results of the latter experiment, that is, the measurement of the lens surface accuracy as the cooling rate changes with the mold temperature as a parameter after maintaining the mold/mold rigidity constant for a predetermined life. Show the results. In each case in FIG. 3, the time for maintaining the mold temperature constant was 15 minutes. From Figure 3, set the mold temperature to 14
It can be seen that the lens surface precision improves when the temperature is maintained at 0° C. and the cooling rate is reduced.

The following was found from the above experimental results. In other words, from Figure 2, the longer the time to maintain the mold at a constant flatness,
Also, from FIG. 3, it can be said that the smaller the cooling rate, the more the lens surface precision can be improved. Also, both figures 2 and 3 are 140
There is a mold temperature around ℃ that gives the best lens surface accuracy. This is because the heat deformation temperature range of the PC resin used is 130~
It is thought that this is closely related to the fact that the glass transition temperature is 142°C at 150°C.

From the experimental results shown in Figures 2 and 3, it is clear that when cooling and solidifying the resin in the compression process after injection, the smaller the temperature distribution width of the resin in the cavity within the softening temperature range of the resin, the more It is possible to derive the principle that molding shrinkage can be balanced and the shape precision of plastic lenses can be made highly accurate.

The present invention is based on this novel principle.

The present invention will be explained below by way of examples. FIG. 4 shows a mold for forming a plastic concave lens according to an embodiment of the present invention. FIG. 1 shows a block diagram of a molding control device according to an embodiment of the present invention. The same numbers in FIG. 4 and FIG. 1 indicate the same parts.

In FIG. 4, 1 is a fixed type, 2 is a fixed type insertion piece, 3 is a fixed type auxiliary plate, and 4 is a spool bush. 1 to 4
The fixed mold attachment is attached to a fixed platen (not shown) of an injection molding machine via a plate 5, and constitutes the fixed side of the lens mold.

In addition, the movable mold 6, movable mold auxiliary plate 7, spacer 8, movable mold inserting piece 9, movable mold inserting piece auxiliary plate 10, and hydraulic cylinder 11 are each attached to the movable mold via a plate 12 on the movable platen of the injection molding machine (not shown). The movable mold insertion piece 9, which is attached to the lens mold (omitted) and constitutes the movable side of the lens mold, is integrated with the insertion piece auxiliary plate 10, and compresses the resin in the cavity 13 by receiving force from the hydraulic pressure cylinder 11. do. It also works to push the plastic lens out of the mold when the mold is opened.

A surface 14 of the fixed mold insertion piece 2, a surface 15 of the movable mold 6, and a surface 16 of the movable mold insertion piece 9 form a Chianti 13 of the lens.

A spool 17 is provided in the spool bush 4 and a runner gate 18 is provided in the movable mold 6, and these form a flow path that guides the resin injected from the cylinder (not shown) of the molding machine to the cavity 13. ing.

A cooling hole 19, a heater 20, and a thermocouple 21 are installed near the surface 14 in the fixed type insert piece z. Fixed type auxiliary plate 3
A cooling hole 23 connecting the cooling hole 19 to a pipe 22 (shown in FIG. 1) is provided inside the movable mold 6. On the other hand, a heater 24, a cooling hole 25 and A thermocouple 26 is installed. A cooling hole 28 is provided in the movable auxiliary plate 7 to connect the cooling hole 25 to the piping 27 (shown in FIG. 29, a heater 30, and a thermocouple 31 are installed. The heaters 20, 24 and 30 are means for realizing the mold initial graviness T, which will be described later.In the inserting piece auxiliary plate 10, there is a cooling hole 33 that connects the cooling hole 29 to the piping 32 (shown in FIG. 1). The heat in the first temperature controller 34, which will be described later, flows to the provided cooling holes 19, 23, 25, 28, 29, and 33.
7 medium or the refrigerant in the second temperature controller 35 is sent.

An extrusion pin 36 is installed in the center of the movable mold 6 to extrude the cooled solidified resin in the spool 17 and the runner gate 18 to the outside of the mold.
6 is extruded by the extrusion rod 37 of the molding machine when the molds on the fixed side and the movable side are opened.

In FIG. 1, 34 is a heater 38 and a first cooler 39.
and a program controller 40.
It is a temperature controller in which a heat medium (oil) is placed. The program controller 40 is connected to the thermocouples 21, 26, and 31 via a temperature recorder 41, and depending on the temperature detected by any one of the thermocouples 21, 26, and 31, the heater 38 and the first cooler 39 are activated. It also has a program control function that keeps the temperature of the heat medium in the first temperature controller 34 constant, and a program control function that allows cooling at a constant cooling rate over time. .

The heat medium in the first temperature controller 34 has a mold temperature T2 to T, which will be described later.
It is a means of sharing the scope of . This heat medium passes through the solenoid valve 42 that opens and closes the feed pipes 22, 27 and 32, and the cooling hole 23-1 through the pipes 22, 27 and 32, respectively.
9. Enters 28-25 and 33-29, passes through return pipes 43.44 and 45, and returns to return pipe 43.44.
It circulates through a solenoid valve 46 that opens and closes 45 and returns to the first temperature controller 34.

With the above functions, the first temperature controller 34 is connected to the fixed type inserting piece 2.
, the temperature of the movable mold 6 and the movable mold insertion piece 9 is kept at a constant tin degree T,
After that, the mold temperature can be gradually cooled from T to T8.

35 is a second temperature controller, which is composed of a heater 47 and a second cooler 48. In the second temperature controller 35, a refrigerant (oil) of the same substance as the heating medium in the first temperature controller 34 is contained.
Contains. The refrigerant in the second warming machine 35 is a means for sharing the mold temperature T, ~T, which will be described later, and the rapid transition from T3 to T4.

This refrigerant passes through the feed pipe 49, passes through the solenoid valve 50 that opens and closes the pipe 49, passes through the pipes 22.27 and 32, and then passes through the cooling holes 23-19, 28-25 and 33-, respectively.
29, passes through piping 43, 44 and 45, returns piping 51, and a solenoid valve 52 that opens and closes piping 51, and then goes to the second
It circulates through the path that returns to the temperature controller 35.

With the above functions, the second changing machine 35 is able to adjust the fixed type insertion piece 2.
, the temperature of the movable mold 6 and the movable mold insertion piece 9 can be rapidly cooled.

53 is a hydraulic generator, 54 is an oil feed pipe, 55 is an oil return pipe, and 56 is a solenoid valve that opens and closes the feed pipe 54. The oil in the oil pressure generator 53 can be circulated through the solenoid valve 56, the feed pipe 54, and the hydraulic cylinder 11, and returns to the return pipe 55.

Also, 57a, 57b and 57c are for fixed type, respectively.
This is a heater controller for movable types and insert pieces.

These heater controllers are wired with heaters 20.24 and 30 and thermocouples 21, 26 and 31, and temperature recorder 41 is wired with thermocouples 21.26 and 31.
Displays each detected temperature.

The heater controllers 57a, 57b and 57e
has a function of turning on or off the power to the heaters 20, 24 and 30, respectively, when the detected temperatures of the thermocouples 21, 26 and 31 are below or above the temperature set for each thermocouple. are doing.

58, 59, 60 and 61 are each connected to the control panel of the molding machine (not shown) by a timer installed in each control device, and the time is measured at the same time as the start of molding, and the time when the operation of each control device starts. and 3 points when the operation stops.

Now, FIG. 5 shows a control sequence during the injection compression molding process of a plastic lens according to this embodiment. Also, the 6th
The figure shows a thermocouple 21 during the injection compression molding process according to this embodiment.
The detected temperature curve of any one of 26 and 31 is h,
The estimated maximum temperature curve of the resin in the cavity 13 is indicated by k, and the estimated minimum temperature curve is indicated by t. The resin temperature at each part within the cavity 13 changes between the curve and t.

Next, the injection compression process of the plastic lens according to this example will be explained using FIGS. 5 and 6. In Figure 5.6,
To is the resin temperature at the time of injection. T1 is the initial mold temperature at the start of molding, and in this example, when making a concave lens, the high temperature is used to melt and erase the weld lines that are created by the flow of resin that branches and merges in the cavity during injection. 175: 0 mold initial temperature set above ℃ T
, the heater controller 57a maintains the temperature detected by the thermocouples 21, 26 and 31 at T1.
.

This can be achieved by adjusting the settings of 57b and 57c.

T- allows the resin in the mold cavity 13 to be compressed and shaped by applying pressure with the piece 9, and also to equalize the resin temperature.
± in the range of heat distortion temperature of resin ~ (heat distortion temperature + 40℃)
This is the mold temperature that should be maintained at a constant temperature within 5° C. for 0.5 minutes or more. It is experimentally known that the accuracy deteriorates when the temperature exceeds (heat distortion temperature +40° C.).

By the way, the heat deformation temperature (temperature at which it can be considered that it has been softened by heat) of the resin used for plastic lenses is approximately 9 for PS resin.
5℃, PMMA resin about 100℃, PC resin about 130℃
It is ℃.

When the mold temperature shifts from T1 to T, the heating by the heaters 20, 24, and 30 is stopped, the temperature is maintained at T2, and the heat medium in the first @conditioner 34 is circulated into the mold. This can be achieved by doing so.

In FIG. 6, in order to shorten the molding cycle, heater 20.
After stopping the heating by 24 and 30 (time t1),
The second temperature controller 3 is maintained at a low temperature of 10 to 20°C in advance.
The refrigerant in 5 is circulated into the mold for a short time to rapidly cool the mold (
Time t, ~ t2) o After that, the heat medium in the first temperature controller 34 was circulated into the mold (time t2 ~ t4). The mold temperature T3 is the temperature at which the resin is considered to have completely escaped the softening range. It is suitable that the temperature is within the range of (heat distortion temperature -20°C).

To maintain the mold temperature at T2 and then slowly cool it to T3 (times t3 to 1.), the program controller 40 is set in two stages, initially T is kept constant, then the slow cooling gradient is set, This can be achieved by circulating the heat medium in the first temperature controller 34 within the mold. Note that this gradual cooling gradient is preferably set to 5° outside and downwind. O12 is the mold temperature at which the plastic lens is taken out after cooling the resin. Shifting the mold temperature from T3 to T4 (time t, to 16) can be achieved by circulating the refrigerant in the second temperature regulator 35 for a predetermined period of time.

Also, the mold temperature is transferred from T4 to T1 (time t,
~18) stops the circulation of the refrigerant in the second temperature controller 35, and sets the temperature T1 in advance to the temperature controller 57a.
, 57b and 57e heaters 20° 24 and 3
It is very possible to start the heating of 0.Next, the fifth part of
In Fig. 6, tO is the time when molding starts, and Ot is the time when the operation of the molding machine shifts from injection to holding pressure.
The electromagnetic valves 50 and 5 of the second temperature controller 35 containing the refrigerant stop the heat generation and set the temperature to 10 to 20°C in advance.
2 and quench the mold for a short time. At the same time, movable type insertion piece 9
The solenoid valve 5 of the hydraulic generator 53
6 Open O When the resin pressure in the cavity 13 falls below the pressure of the hydraulic cylinder 11 that operates the movable mold inserting piece 9, the movable mold inserting piece 9 is used to remove the plastic lens from the mold. The resin in the cavity 13 continues to be compressed until time t6 immediately before opening.

At t2, in order to uniformly shift the temperature of the resin in the cavity 13 to T2, the solenoid valve 5 of the second temperature controller 35 that was rapidly cooling is activated.
0 and 52 are closed and the solenoid valves 42 and 46 of the first temperature controller 34 are opened, with the temperature of the heating medium being maintained at T2 in advance. At t3, the temperature detected by the thermocouple 21°26.31 reaches T.

t4 is a point at which the constant temperature heating control that kept the mold temperature constant at T2 is stopped and the process is shifted to slow cooling control.

At t5, when the temperatures detected by the thermocouples 21, 26 and 31 become below T3, the solenoid valves 42 and 46 of the first temperature controller 34 are closed to stop slow cooling, and the second At Ot6, the solenoid valves 50 and 52 of the temperature controller 35 are opened again to start rapid cooling of the mold, and at the time when the pressurization by the insertion piece 9 is stopped, the mold is opened and the cooled and solidified plastic lens is placed in the mold. It is set just before taking it outside.

t7 is for returning the mold temperature to the initial temperature T again after taking out the plastic lens from the mold.

It is now time to start heating heaters 20, 24 and 30 again. t, is the end of one cycle when the mold@blood is returned to T, for the next cycle.

As described above, when the resin is cooled and solidified in the compression process after injection, the smaller the temperature distribution of the resin in the cavity within the softening temperature range of the resin, the more uniform the molding shrinkage can be, and the higher the temperature. It is based on the principle that high-precision plastic lenses can be obtained ◇ Therefore, the thermal deformation temperature of the resin is between the set temperature T2 of the mold and T, and the mold temperature is maintained at T2. ,−
The time between t and t is long enough to make the resin temperature distribution in the cavity uniform, and the cooling rate during slow cooling between t and '-t, when the mold temperature is transferred from T2 to T3, is enough to make the resin temperature distribution in the cavity uniform. A condition for the establishment of the present invention is that the temperature is sufficiently gentle so as not to increase non-uniformity in temperature.

Therefore, 13-1. Between and 1. -1. It is necessary to set a sufficiently long time for both periods.

On the other hand, T is closer to T2, %+ Tl'l Tt and T4 are lower, jO-tl + jl-jl +
t, -tll+LB-t4 + t, t,...
It goes without saying that the shorter each of +t7-t8 is, the shorter the molding cycle is and the more advantageous it is in terms of production efficiency. Therefore, the mold setting temperature T, ~T4%
When actually setting the operation start or stop times t1 to t of each control device, it is naturally necessary to consider molding cycle requirements as well as accuracy requirements.

Next, the resin temperature and mold setting temperature T. - A detailed setting procedure for T4 and operation start or stop times t1 to t8 will be explained. First, it is necessary to find conditions that improve the overall quality of plastic lenses, including residual stress, including shape accuracy, surface gloss, and transparency.

Regarding shape accuracy, while observing the conditions for establishing the present invention, %T1 and T2 are set to a high temperature, T3 and T4 are set to a low temperature, and each interval from t to t7 is set to a long value. It is recommended to set it to . According to experiments, the sum of t, ~t8 is 1
If it is about 2 hours, it will never be too long and the quality of the plastic lens will deteriorate. After finding the conditions that satisfy the overall quality of the plastic lens above, each interval at t and ~t can be shortened6. towards・“°・1・・7・o-I″H), ”low“　I
9T3 is changed in small increments closer to T at appropriate time or temperature intervals. If this is done, the shape accuracy of the plastic lens will eventually fall below an allowable value.

After finding the value just before the shape accuracy of the plastic lens falls below the allowable value for each of TO-T41tl to t8, the same procedure is repeated several times in a cyclical manner. In this way, T0 to T4+tI to t8 all converge to specific values. T by the above procedure. -T41 tl
~tll can be appropriately compared from the viewpoint of the molding cycle.Next, the results of specific examples based on this example are shown in Table 1.

Specific example: The shape of a human lens has an outer diameter of 47jlJ and a center thickness of 1
．． 9m, outer diameter thickness 12.7Tu1. The concave lens has a radius of curvature of 250u to 30IIj and is made of PC resin.

When this lens is manufactured by the method of the patent application mentioned above,
Although only a surface accuracy with a deviation of 130 to 100 μm was obtained, when manufactured under the manufacturing conditions shown in Table 1 according to this specific example, the lens surface accuracy could be increased to 3.0 to 1.0 μm, resulting in a dramatically higher level of accuracy. We were able to obtain a highly accurate plastic lens.

Further, the lens shape of specific example B has an outer diameter of 47u1, a center thickness of 14.5 m, and an outer diameter of 1.0 mm. , radius of curvature 88 and 31
This is a convex lens made of PC resin.

On the other hand, the lens shape of specific example C is 1. Outer diameter 21mm, center thickness 1.8NJ1, outer diameter thickness 5.81111. radius of curvature 2
It is a concave lens between 3m5 and 17m and is made of PMMA resin.

In any of these cases, the lens surface accuracy should be 2.0 to 1.
．． It was possible to suppress the thickness to 0 μm and obtain a highly accurate plastic lens.

In Table 1, during compression molding, the mold temperature is maintained at a constant temperature above the heat deformation temperature between 1 and -1 for 4 minutes in Example A, in the evening in Example B, and 1 minute in Example C. It is.

1, -1. Later slow cooling section 1. -1. The number of concrete examples is 6.
minutes, specific example B is 10 minutes, and specific example C is 4 minutes.

1, -1. The cooling rate during slow cooling in Specific Example A was 1.7
'C4, specific example B is 3°0'C4, specific example C is 5.09
It's outside.

The time required to equalize the resin temperature in the mold cavity and the cooling rate for cooling while maintaining an even temperature distribution are shown in Table 1, and are used for the lens shape and molding to be molded. Naturally, it varies depending on the size of the resin and mold. Therefore, the present invention is not limited to the manufacturing conditions shown in Table 1, and the mold temperature is maintained at a constant spirituality T within the resin softening temperature range.
The temperature to be maintained at 2 or the interval 1. −． 1 slow cooling section 1. −
1. .

1, -1. It goes without saying that the cooling rate between can be adjusted depending on the lens shape, resin, mold size, etc.The specific example shown in Table 1 is a lens using PMM & resin and PC resin. It goes without saying that the present invention is not limited thereto and can be applied to molding a plastic lens of any shape using any type of resin.

Naturally, the present invention can also be applied to injection molding of plastic parts other than lenses that require high shape accuracy.

(Effects of the Invention) According to the present invention, the temperature distribution during solidification of the plastic during injection compression molding can be made uniform, so the molding shrinkage of the plastic lens at the time when the temperature stabilizes at room temperature after molding can be equalized.
Even on the micron order, it is possible to manufacture plastic lenses with high shape accuracy and minimal sink marks and warpage.

In particular, the effect is more pronounced for lenses with significant shape asymmetry such as concave lenses with large differences in wall thickness. Outer diameter thickness 12.7. In the case of a concave lens using PC resin, the surface precision was dramatically improved to 3.0 to 1.0 μm, whereas the conventional method had a deviation of 130 to 100 μm.

According to the present invention, the optical performance of plastic lenses can be brought significantly closer to the optical performance of glass lenses, and the applications of plastic lenses, which are lighter and lower cost than glass lenses, can be further expanded.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a molding control device according to an embodiment of the present invention, Figs. 2 and 3 are graphs showing experimental data explaining the present invention in detail, and Fig. 4 is a block diagram of a molding control device according to an embodiment of the present invention. 5 is a sequence diagram of injection compression molding control according to an embodiment of the present invention, and FIG. 6 is a temperature one-hour curve diagram for explaining the operation of an embodiment of the present invention. It is. 1... Fixed type, 2... Fixed type insertion piece, 6... Movable type, 9... Movable type insertion piece, 11... Hydraulic fringe,
13...Cavity, 19,25.29...Cooling hole, 21.26.31...Thermocouple, 20,24,30.
...Heater, 34...First temperature controller, 35...Second
temperature controller, 53--hydraulic generator, 57a, 57b. 57c... Heater controller, 40... Program controller Figure 2 Figure 24 Figure 5 Figure 6

Claims (4)

[Claims] (1) In a cavity formed between a sliding piece provided in either a fixed mold or a movable mold placed facing each other, and the opposing mold or piece. In an injection compression molding method in which resin is injected and filled, and a pressure cylinder is used to apply pressure to the insert piece to apply compressive force to the resin in the cavity, the temperature distribution of the resin in the cavity is adjusted once in the softening temperature range. After homogenization, the resin is slowly cooled to a heat distortion temperature that takes it out of the resin's softening temperature range, thereby cooling the resin while minimizing the occurrence of temperature unevenness in the resin due to cooling. Characteristic injection compression molding method. (2) The fixed mold, the movable mold, and the insertion piece are held within the temperature range of the heat deformation temperature of the resin to (heat deformation temperature + 40°C) ±
The injection compression according to claim 1, wherein the temperature distribution of the resin in the cavity is made uniform in the softening temperature range by once maintaining a constant temperature within 5°C. Molding method. (3) (Heat distortion temperature of resin + 40℃) ~ (Heat distortion temperature -
The injection compression according to claim 1, wherein the fixed mold, the movable mold, and the insertion piece are slowly cooled at a cooling rate of 5° C./min or less in a temperature range of 20° C. Molding method. (4) In a cavity formed between a sliding piece provided in either a fixed mold or a movable mold placed opposite to each other, and the opposing mold or insertion piece. In an injection compression molding apparatus that injects and fills resin and applies pressure to the inserting piece using a pressure cylinder to apply compressive force to the resin in the cavity, the fixed mold, movable mold, and inserting piece are heated to the softening temperature. The first step is heating at a constant temperature in
An injection compression molding apparatus comprising: a temperature controller; and a second temperature controller that rapidly cools the fixed mold, the movable mold, and the inserted pieces before the constant temperature heating and after the slow cooling.