JP2003001689A - Method for manufacturing resin molded product and optical element manufactured by this manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a resin molded product by which its high shape dimensional precision can be maintained, even when a molding cycle is shortened. SOLUTION: A molten resin is fully injected into a mold heated above a heat-deforming temperature of a resin material to be used and the resin molded product is unloaded from the mold when the temperature of the resin molded product in the mold is uniform. After that, the resin molded product is cooled slowly until its temperature is below the heat-deformation temperature of the resin material used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin molded product such as a plastic lens having a highly accurate optical mirror surface and a thick and uneven thickness, and an optical element manufactured by this manufacturing method. , A method for producing a resin molded product suitable for being applied to an optical scanning system such as a laser type digital copying machine, a laser printer or a facsimile machine, an optical device such as a video camera, and an optical element produced by the method. Regarding

[0002]

2. Description of the Related Art In recent years, resin molded products having various shapes have been used for various purposes. As a method for manufacturing the resin molded product, it is general to use an injection molding method which has a low manufacturing cost and is suitable for mass production. In this injection molding method, a resin material that has been heated and melted is injected and filled in a mold, and then, in the step of cooling and solidifying, the resin pressure and the resin temperature in the mold are made uniform, so that a desired resin molded product The accuracy of the shape and dimension and the accuracy of internal distortion are ensured. However, when the deviation of the shape of the molded product from the design value is required to be ± 1 μm or less, the required accuracy may not be satisfied even by the above injection molding method.

The cause of deterioration of accuracy in the conventional injection molding method will be described. FIG. 1 shows the temperature change of the molded product during the molding process in the injection molding method. The resin material used is, for example, a thermoplastic amorphous plastic, specifically, a cycloolefin polymer “ZEONEX (trade name)” manufactured by Nippon Zeon Co., Ltd. First, in injection molding, the desired cavity shape of the mold is transferred with high precision in the molding process (28
(0 ° C.), the resin is cooled to 135 ° C. in the mold, the mold is opened, and the resin molded product is taken out. At this time, since the difference between the temperature of the resin molded product (135 ° C.) and the ambient temperature around the mold (room temperature) is very large, the resin molded product is rapidly cooled. Therefore, in the case of a resin molded product having an uneven thickness shape, the thin portion and the thick portion have different cooling states. That is, in the thin wall portion, the cooling rate is large and the solidification progresses quickly, and in the thick portion, the cooling speed is small and the solidification is delayed. Due to this cause, the shrinkage amount is small in the thin wall portion, and the shrinkage amount is large in the thick wall portion, resulting in deterioration of the precision of the shape and dimension of the molded product. In other words, the difference between the surface temperature of the resin molded product (center position of the transfer surface) and the internal temperature (center of the thickness of the resin molded product) is small in the thin portion and large in the thick portion. This temperature difference causes a thermal stress inside the resin molded product, resulting in a decrease in shape dimension accuracy due to the thermal stress and a new strain outside the mold. Therefore, no matter how much molding was performed using the conventional high-precision resin molding method, the cavity shape was transferred to the resin-molded product side with high accuracy in the mold, and even if internal uniformity was maintained, it was taken out of the mold. The accuracy will be reduced later.

The following two methods have been considered for such a problem. The first method is to raise the temperature of the mold above the glass transition temperature of the resin material used, and to keep the cooling rate of the filled resin as low as possible in each part within the heat deformation temperature. It is a method of gradually cooling to. According to this resin molding method, since the resin is cooled while keeping the resin temperature uniform, it is possible to obtain a molded product having good shape dimensional accuracy and internal distortion.

Further, as a method of developing the above-mentioned manufacturing method and shortening the time until the molded product is taken out from the mold, there is Japanese Patent No. 2537231. That is, a step of heating a mold for molding a plastic lens to a temperature not lower than the glass transition temperature of plastic, and an injection step of injecting a plastic molten resin heated to a temperature at which the resin can flow into the cavity of the mold, A first cooling step is performed in which a cooling unit attached to the mold is operated to cool the molded plastic lens in the cavity at a cooling rate at a surface temperature close to the glass transition temperature. Following the cooling step, the mold is cooled, and when the temperature of the molded lens surface reaches the thermal deformation temperature of the plastic material, the temperature of the center of the molded plastic lens is below the glass transition point and the thermal deformation occurs. It comprises a second cooling step of cooling to a temperature equal to or higher than the temperature. This state is shown in FIG. 2 as being carried out with the molding resin material shown in FIG.

According to this method, when the surface temperature of the molded product reaches the heat distortion temperature of the plastic material, the temperature of the central portion of the molded product is below the glass transition point and above the heat distortion temperature. Is cooling down. However, since this method is a method of performing slow cooling in the mold, the number of molding cycles increases.

The second method is as follows. That is, it is described in JP-A-7-205239, and is a method of performing gradual cooling outside the mold in order to shorten the molding cycle. In this method, the mold cavity surface temperature is cooled to 10 ° C. or less higher than the heat deformation temperature of the thermoplastic resin, and then the molded product is taken out from the mold cavity and heated to the heat deformation temperature of the thermoplastic resin or more. After being placed in the furnace for 3 minutes or more, it is gradually cooled to near room temperature.

However, in this method, the molded product is taken out from the mold cavity, placed in a furnace heated to a temperature not lower than the thermal deformation temperature of the resin material used, held for 3 minutes or more, and then gradually cooled. Regarding cooling conditions, no particular mention is made other than that the gradual cooling start temperature is equal to or higher than the heat distortion temperature of the resin material used. As an example, the cooling rate is 0.5 ° C./mi after being placed in a heating furnace at a temperature substantially matching the mold temperature (120 ° C.) at the time of taking out and holding for 15 minutes.
The sample is gradually cooled to near room temperature by n. However, in this method, a total of 2 is obtained by holding for 15 minutes and then gradually cooling from 120 ° C to 25 ° C at a cooling rate of 0.5 ° C / min.
Since it takes 05 minutes, it is a problem that productivity is poor. In addition, the increase in this slow cooling time
This will increase the cost of resin molded products.

[0009]

[Problems to be Solved by the Invention] Japanese Patent No. 2537231
In the method of molding a plastic lens described in No. 1, it is an issue to be solved that the accuracy of the lens surface roughness after taking out from the mold of molded plastic is a problem to be solved, and slow cooling in the mold is required. Since this method is performed, there is a problem that the mold is used for a long period of time, which increases the molding cycle.

In the technique disclosed in Japanese Patent Application Laid-Open No. 7-205239, a molded product is taken out of the mold cavity, placed in a furnace heated to a temperature higher than the thermal deformation temperature of the resin material used, and held for 3 minutes or more. Since it is a method of performing gradual cooling outside the mold, it is possible to shorten the time to use the mold for each molding cycle, but it requires a heating step above the heat distortion temperature of the resin material used, In addition, since the resin molded product has a long gradual cooling time, there are problems that productivity is poor and cost is increased.

[0011]

The invention according to claim 1 is
The molten resin is injected and filled in a mold heated to a temperature higher than the heat distortion temperature of the resin material used, and the resin molded product is removed from the mold with the temperature of the resin molded product in the mold being uniform. After taking out, the resin molded product was gradually cooled until the temperature of the resin molded product fell below the heat deformation temperature of the resin material used.

Therefore, the temperature difference between the surface and the inside of the resin molded product causes thermal stress inside the resin molded product, resulting in a decrease in shape and dimension accuracy due to the thermal stress and a new strain outside the mold. By gradually cooling in the cooling process, it is possible to reduce the temperature difference and maintain the high shape and dimension accuracy of the resin molded product. Also, take out the resin molded product from the mold and slowly cool it outside the mold. By carrying out, it is possible to shorten the molding cycle (cooling time in the mold), so that the next resin can be immediately injected, which can be performed by injection molding. In addition, it is possible to have a significant effect on productivity, and it is not necessary to carry out gradual cooling to room temperature (room temperature). To improve Door can be.

According to a second aspect of the invention, in the method for producing a resin molded product according to the first aspect, the resin molded product is gradually cooled at a constant slow cooling rate.

Therefore, since the slow cooling is performed at a constant rate, the temperature difference between the surface and the inside of the resin molded product can be controlled.

According to a third aspect of the present invention, in the method for producing a resin molded product according to the first or second aspect, after the resin molded product is gradually cooled, the temperature is maintained at the annealing end temperature for a certain period of time.

Therefore, the temperature difference between the surface and the inside of the resin molded product can be reduced by maintaining the temperature for the gradual cooling for a certain period of time.

According to a fourth aspect of the present invention, in the method for producing a resin molded product according to any one of the first to third aspects, the wall thickness of the portion having uneven thickness of the resin molded product is b (thin portion) to a. In the range of (thick part), the slow cooling rate of slow cooling is a / (a
+ B) (° C / min) or more, a / (ab) (° C / mi
n) so that

Therefore, the temperature difference between the surface and the inside of the resin molded product is affected by the wall thickness and uneven thickness of the resin molded product. Therefore, the slow cooling rate should be set according to the thickness and uneven thickness. Thus, a resin molded product can be obtained in an appropriate gradual cooling time, and productivity can be improved.

According to a fifth aspect of the present invention, in the method for producing a resin molded product according to any one of the first to fourth aspects, the resin molded product is housed in an apparatus capable of controlling the internal temperature, and Slow cooling was performed.

Therefore, in the slow cooling step, by using a constant temperature bath of general equipment as a device capable of controlling the internal temperature,
Equipment installation costs can be reduced.

According to a sixth aspect of the present invention, in the method for producing a resin molded article according to the fifth aspect, the device capable of controlling the internal temperature is a constant temperature bath.

Therefore, the existing equipment can be used, and no special equipment cost is required.

According to a seventh aspect of the present invention, in the method for producing a resin molded product according to any one of the first to fourth aspects, the temperature of the resin molded product is controlled so that the resin molded product has a different temperature distribution in its moving direction. The device was used for slow cooling.

Therefore, in the slow cooling step, the resin molded product is
For example, by using a device that can be internally moved by a belt conveyor, etc., and the temperature distribution is controlled in the moving direction, it is possible to continuously gradually cool a resin molded product molded into a desired shape. Therefore, a highly accurate resin molded product can be obtained with high productivity.

According to an eighth aspect of the present invention, in the method for producing a resin molded product according to any one of the first to fourth aspects, a temperature-controlled member is brought into contact with the resin molded product, whereby I tried to cool.

Therefore, since the temperature-controlled member is brought into contact with the resin molded product, the amount of heat can be efficiently transmitted to the resin molded product.

According to a ninth aspect of the present invention, in the method for producing a resin molded article according to the eighth aspect, the hand portion of the take-out machine of the plastic molding device is a temperature-controlled member.

Therefore, by applying the temperature-controlled member to the hand section of the take-out machine, the number of steps in the manufacturing process can be reduced, and a highly accurate resin molded product can be obtained with high productivity.

The invention according to a tenth aspect is the first to ninth aspects.
In the method for manufacturing a resin molded product according to any one of 1, a device capable of controlling an internal temperature between a die for molding into a desired molded product shape and a device for gradually cooling the molded resin molded product. The temperature of the resin molded product was controlled when the resin molded product was taken out of the mold.

Therefore, the space between the die for molding into the desired shape of the resin molded product and the device for slow cooling is covered with the device capable of controlling the internal temperature, so that the surface of the resin molded product is The temperature difference with the inside can be controlled.

The invention described in claim 11 is the invention according to claims 1 to 1.
0. In the method for producing a resin molded product according to any one of 0, in a state in which the surface temperature of the resin molded product is maintained within a temperature range of at least ± 5 ° C. as compared with the temperature immediately after being taken out from the mold. The slow cooling process was started.

Therefore, the surface temperature of the resin molded product is at least ±
By maintaining the temperature range within 5 ° C, it is possible to reduce the temperature difference between the surface and the inside of the resin molded product before the start of slow cooling, and the accuracy of the shape and dimension of the resin molded product decreases. Can be prevented.

The invention according to claim 12 is the invention according to any one of claims 1 to 1.
An optical element such as a lens, a mirror or a prism manufactured by the method for manufacturing a resin molded product according to 1.

Therefore, the optical element manufactured by the method for manufacturing a resin molded product according to any one of claims 1 to 11 has good shape uniformity and internal uniformity, and is excellent in optical performance.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. First, FIG. 3 shows an outline of a manufacturing process of a resin molded product. FIG. 3 shows the relationship between the elapsed time in the manufacturing process of the resin molded product and the molded product temperature. As the resin material used, the thermoplastic amorphous material is used as in the case of FIG. 1 and FIG. Plastic, specifically, cycloolefin polymer "ZEONEX (trade name)" manufactured by Nippon Zeon Co., Ltd. First, a molding step of accurately transferring (280 ° C.) a desired cavity shape of a mold in the molding step is performed. That is, a desired shape is formed from a resin in a molten state or a resin in a blank state (this depends on the molding method but is not particularly limited). Then, an in-mold cooling step of cooling the injection-molded resin to 135 ° C. in the mold is performed, and then the mold is opened by opening the resin while the temperature of the resin molded product in the mold is uniform. Take out the molded product. After that, gradual cooling is performed until the temperature of the resin molded product taken out of the mold reaches the heat deformation temperature of the resin material used, in this case, 123 ° C. or less (gradual cooling process outside the mold). Next, when the temperature of the resin molded product becomes equal to or lower than the thermal deformation temperature, a molded product taking-out step of taking out the resin molded product from the apparatus is executed.

Therefore, in the manufacturing method shown in FIG. 1, which does not include the slow cooling step, the molding cycle is short, but there is a drawback in that the shape and dimension accuracy is deteriorated due to rapid cooling of the resin molded product. In the manufacturing method in which the slow cooling step is provided in the mold as shown in FIG. 2, the shape and dimension accuracy is good, but the molding cycle (cooling time in the mold) becomes long, which leads to an increase in the cost of the resin molded product. However, according to the present embodiment, since the gradual cooling step is provided, the shape and dimension accuracy of the resin molded product is high, and the defect of the manufacturing method shown in FIG. 1 is solved. Further, since the slow cooling process is the slow cooling outside the mold, the molding cycle consisting of the molding process and the slow cooling process inside the mold may be short, and the drawbacks of the manufacturing method shown in FIG. The cost of can be reduced.

[0037]

[Example 1] Before explaining various concrete examples, common points of the examples are the resin molded product shape, material,
The method for annealing outside the mold, the shape evaluation method, and the temperature measurement method will be described.

[Molded Product Shape] In this embodiment, the following three patterns are formed. 1. Resin molded product shape 1 (Fig. 4) Central lens thickness: 14 mm, end lens thickness: 6 m
m, short length: 15 mm, long length 260 mm 2. Resin molded product shape 2 (Fig. 5) Central lens thickness: 6 mm, end lens thickness: 14 m
m, short side length: 15 mm, long side length 260 mm 3. Resin molded product shape 3 (Fig. 6) Convex lens, outer diameter 25φ, maximum lens thickness 14 mm, minimum lens thickness 6 mm

Here, the resin molded product shape 1 and the resin molded product shape 2 are optical elements applied to an optical device such as an optical scanning system of a laser type digital copying machine, a laser printer or a facsimile machine, a video camera and the like. Is. The resin molded product shape 3 is an optical element such as a plastic lens applied to a taking lens for a lens shutter camera or a single lens reflex camera.

As the measurement result, the shape measurement result of FIG. 4 will be described. However, the present invention does not depend on the shape of the molded product, but all shapes having a thick and uneven thickness and capable of being gradually cooled can be obtained. Applied to.

Further, with respect to the transfer surface (lens surface) shape which requires a highly accurate shape and dimension, it can be applied to any shape such as a flat surface, a spherical surface, an aspherical surface, a free curved surface.

[Material] In this embodiment, the following three types of amorphous plastics are used.

1. Resin material 1 Thermoplastic amorphous plastic Cycloolefin polymer “ZEONEX” manufactured by Nippon Zeon Co., Ltd. Heat distortion temperature (deflection temperature under load) 123 ° C. Test method ASTM D648 Glass transition temperature 138 ° C. Test method DSC Mold softening resin The temperature is kept at 135 ° C., which is lower than the temperature (less than the glass transition temperature for amorphous resin), and then the molten resin at 290 ° C. is injection-filled into the cavity of this mold. Then, the mold is released and gradually cooled while the temperature of the molded product in the mold is uniform.

2. Resin material 2 Thermoplastic amorphous plastic Polycarbonate (PC) Heat distortion temperature 121 ° C Glass transition temperature 145 ° C The mold is heated and kept at 142 ° C, which is lower than the softening temperature of resin (less than glass transition temperature for amorphous resin). Then, the molten resin at 300 ° C. is injected and filled into the cavity of the mold. Then, the mold is released and gradually cooled while the temperature of the molded product in the mold is uniform.

3. Resin material used 3 Thermoplastic crystalline plastic Polymethylmethacrylate (PMMA) Heat distortion temperature 99 ° C Glass transition temperature 100 ° C Mold is heated to 97 ° C, which is lower than the softening temperature of resin (less than glass transition temperature for amorphous resin). Hold and then injection-fill the molten resin at 300 ° C. into the cavity of this mold. Then, the mold is released and gradually cooled while the temperature of the molded product in the mold is uniform. However, regarding PMMA,
Since there was no temperature difference between the glass transition temperature and the heat distortion temperature, the glass was gradually cooled to room temperature, but the effect of slow cooling was not confirmed. Further, since PMMA has a saturated water absorption of about 2% and a large dimensional change rate after taking out, the highly accurate shape and dimension characteristic of the present invention cannot be expected.

This embodiment is carried out on the above-mentioned three kinds of amorphous plastics. As the measurement result, the shape measurement result of Zeonex which is the resin material 1 used will be explained.

However, the present invention does not depend on the resin material used, but is applied to all resin materials that can obtain the effect of slow cooling regardless of crystallinity or amorphousness. That is, any resin molded product that is molded at a mold temperature of not less than the thermal deformation temperature of the resin material can be applied.

[Slow cooling method] For the slow cooling, a general-purpose constant temperature bath was used. The followability between the ambient temperature and the set temperature in the constant temperature bath was adjusted by changing the angle of the damper. In addition, the slow cooling process,
After the molded product was taken out of the mold, it was started within at least 10 seconds (time when exposed to the outside air). this is,
This means that the surface temperature of the molded product is within a range of ± 5 ° C (see FIG. 7, claim 10). As is clear from FIG. 7, the longer the pre-annealing holding time, the lower the shape dimension accuracy. After the molded product is taken out of the mold, the slow cooling step is started 12 seconds later. In this case, the precision of the shape and dimension of the molded product was reduced (short-shaped PV2μ
m). The upper and lower limits of the temperature range are set to ± 5 ° C because the difference in temperature between the surface and the interior of the thermal stress on the molded product poses a problem. Becomes

A method other than housing the resin molded product in a device such as a thermostatic chamber whose internal temperature can be controlled and slowly cooling it will be described later as Examples 2, 3, and 4.

[Shape Evaluation Method] The shape was measured by a stylus type three-dimensional measuring machine to evaluate the amount of deviation from the design value of the molded product. To be precise, the amount of deviation from the coordinate value of the sub-scanning (horizontal) direction (Y direction in FIG. 4) and the design value of the molded product in the lens thickness direction (Z direction of FIG. 4) is the coordinate value of the main scanning (longitudinal) direction ( X in Figure 4
The PV value of the graph plotted for each direction was evaluated (see FIG. 8). This is because the effect of the slow cooling of the present invention is
Since the purpose is to reduce the thermal stress inside the molded product, the larger the lens thickness, the more rapidly the shape is cooled down, resulting in a large decrease in the shape and dimension accuracy. This is the relationship between the lens shape shown in FIG. 8A and the shape measurement result shown in FIG. 8B. That is, the difference from the design value between the case of rapid cooling and the case of slow cooling is 3 μm in the case of rapid cooling and 0.5 μm in the case of slow cooling, and the difference is clear.

[Temperature Measurement Method] The surface temperature of the molded product was measured by fixing the thermocouple with a heat transfer tape at the center position of the transfer surface on the convex side of the molded product (main scanning coordinate value 0, sub-scanning coordinate value 0).

Regarding the internal temperature of the molded product, a thermocouple was fixed at the center position of the lens thickness of the molded product (main scanning coordinate value 0, sub scanning coordinate value 0) (the gap was filled with a copper alloy paste of a high heat transfer material). It was measured.

<Example 1-1> It was carried out for the lower limit value (° C) of the slow cooling temperature range (slow cooling rate 1 ° C / min). Factor Slow cooling temperature range lower limit level 135, 130,
125, 120, 110, 100 Here, the lower limit value of 100 ° C. and the slow cooling rate of 1 ° C./min are set as the standard slow cooling conditions. The execution results are shown in FIG. 9. From these results, if the lower limit value of the annealing temperature range is 123 ° C. or less,
It was confirmed that it is possible to prevent the deterioration of the shape accuracy due to the rapid cooling of the resin molded product. This is below the thermal deformation temperature of the resin material used, and it is speculated that the decrease in shape accuracy due to rapid cooling is due to the thermal stress acting inside the molded product at the thermal deformation temperature or above (corresponding to claims 1 and 2).

<Example 1-2> The cooling was carried out at a slow cooling rate (° C / min) within a predetermined temperature range (lower limit value 100 ° C). Factor Annealing rate Level 0.3, 0.6, 1, 2,
3, 4, 5 The execution results are shown in FIG. 10. From the results, if the slow cooling rate in the predetermined temperature range is 0.7 ° C./min or more and 5 ° C./min or less, the resin molded product is rapidly cooled. It was confirmed that shape deterioration can be prevented. Also, slow cooling rate 0.6
Comparing the results of 1 and 1, it can be seen that the shape accuracy of 0.6 is lowered. It is presumed that this is because the amount of relaxation of the internal strain of the molded product increased due to the increase of the slow cooling time, and the shape of the transfer surface was changed.

FIG. 11 shows the measurement results of the internal temperature and the surface temperature of the resin molded product when it is rapidly cooled after taking out the mold from the mold. It is considered that thermal stress acts inside the resin molded product due to the difference between the internal temperature and the surface temperature of the resin molded product as shown in FIG. When this thermal stress exceeds the strength of the molded product, the accuracy of the shape dimension decreases. However, the strength of the molded product naturally changes depending on the shape of the resin molded product, the resin material used, the temperature, and the like.

<Example 1-3> Examples 1-1 and 1
From the result of -2, as a slow cooling condition for the purpose of shortening the slow cooling cycle, the lower limit value of the slow cooling temperature range was set to 120 ° C,
The slow cooling rate (° C./min) was performed again. Factor Annealing rate Level 0.3, 0.6, 1, 1.
5, 2, 3, 4, 5 The execution results are shown in FIG. 12. From these results, it was confirmed that when the slow cooling rate was increased at the lower limit of 120 ° C. of the slow cooling temperature range, the dimensional accuracy was lowered. The cause is that the difference between the internal temperature and the surface temperature of the molded product at the end of the slow cooling (7.25 ° C. in the resin molded product of the present example) increases due to the subsequent rapid cooling, and becomes slightly smaller than the heat deformation temperature of 120 ° C. It is considered that even at the lower temperature, the dimensional accuracy was reduced.

Here, the shape of the resin molded product of this embodiment will be described. In this embodiment, the end portion is 6 mm, and the central portion is 14 mm.
The molded product has a thick and uneven thickness, and from the thick portion a and the thin portion b, a / (a + b) = 0.7, a / (ab) =
1.75, which is 0.7-1.75 (° C /
min). It has been confirmed that, within this slow cooling rate, there is no deterioration in the dimensional accuracy of the molded product that has been gradually cooled at 120 ° C., which is below the heat distortion temperature (corresponding to claim 3).

<Example 1-4> Examples 1-1 and 1
-2, from the results of Example 1-3, the lower limit of the slow cooling temperature range was set to 12 as the slow cooling condition for the purpose of shortening the slow cooling cycle.
0 ° C, slow cooling with slow cooling rate set to 5 ° C / min,
Then, it hold | maintained at 120 degreeC for 3 minutes. Here, the holding time was set to 3 minutes because it was 120 at the slow cooling rate of 1 ° C./min.
It is the time required until the temperature difference between the surface temperature and the internal temperature at the temperature of ° C (1.8 ° C in the molded product of this example) becomes equal to or less.

From the results of the implementation, it was confirmed that the above gradual cooling cycle could prevent the deterioration of the shape dimensional accuracy (specifically, the lateral shape PV = 0.3 μm). This holding time is provided to reduce the temperature difference between the surface temperature and the internal temperature of the molded product and to prevent the deterioration of the shape dimension accuracy due to thermal stress. It can be changed appropriately according to the required accuracy (corresponding to claim 4).

The time required for the slow cooling step will be added here. In order to manufacture the molded article of this example with a highly precise shape and dimension (here, the short side shape PV 0.5 μm) under the slow cooling conditions described in Example 1-4, it is necessary to set the temperature from 135 ° C. to 120 ° C. Slowly cool at ℃ / min,
After that, when a holding time of 3 minutes is added, a total annealing time of 6 minutes is obtained.

Next, as a comparative example, JP-A-7-2052
As in the prior art (gradual cooling out of the mold) described in Japanese Patent No. 39, from 135 ° C to 25 ° C (normal temperature), 0.5 ° C / min.
When cooled slowly with, keep the mold temperature at the time of removal for 15 minutes,
The annealing time at a constant annealing rate is 205 minutes, and when these are added up, the annealing time is 220 minutes.

Therefore, by using the slow cooling method of this embodiment, the slow cooling time can be greatly shortened,
It is possible to improve the productivity in the slow cooling step and reduce the cost of the molded product.

<Example 1-5> As Example 1-5, after passing through the holding section (min) in the upper limit value of the slow cooling temperature range (in this case, the mold temperature at the time of taking out the resin molded product is substantially the same) Then, the standard gradual cooling step was performed. Factor Retention time Level 0, 15, 30, 60, 12
0 The result of the operation is shown in FIG. 7, and it was confirmed from this result that the shape accuracy is lowered by keeping the molded product at the upper limit of the annealing temperature range for a long time. It is expected that this is because the internal strain of the resin molded product was alleviated by holding at a high temperature such as the upper limit of the predetermined temperature range. From this result, it can be said that the slow cooling rate in the slow cooling step needs to be increased within a range in which the strength of the molded product does not lose heat stress.

[0064]

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the step of molding the resin material into the desired shape of the resin molded product 2 in the mold 1 is carried out by the injection molding method. Since it is characterized by the condition of, regardless of the molding method,
In addition to injection molding, it can be applied to various molding methods such as injection compression / press molding, gas assist molding and extrusion molding. Here, it is assumed that the mold temperature is substantially the same as the upper limit temperature at which the slow cooling is performed and is controlled at a constant temperature. After injecting the molten resin into the mold 1, the resin is cooled. Then, after taking out the resin molded product 2 from the mold 1, the resin molded product 2
Is stored in a device whose internal temperature can be controlled (general-purpose constant temperature bath 3, oven, etc.) and gradually cooled (Claims 5 and 6).
Alternatively, the resin molded product 2 can move inside, and the temperature distribution is controlled in the moving direction. By slow cooling, the accuracy of the shape and dimension of the resin molded product 2 is prevented from decreasing ( 14 and claim 7).

By using the constant temperature bath 3 of general-purpose equipment as an apparatus capable of controlling the internal temperature in the gradual cooling step, it is possible to obtain a molded article with extremely high accuracy even if the low-cost equipment is introduced.

In the step of carrying out slow cooling, the resin molded product 2 can be molded into a desired shape by using the device 5 in which the inside can be moved by the belt conveyor 4 etc. and the temperature distribution is controlled in the moving direction. The resin molded product 2 thus obtained can be continuously annealed, and the highly accurate resin molded product 2 can be obtained with high productivity. Further, the device 5 whose temperature distribution is controlled in the moving direction does not require such precise temperature control, and the strength of the molded product does not exceed the thermal stress acting on the inside of the resin molded product 2. Since it suffices to reduce the temperature difference between the surface and the inside of the resin molded product 2, it is not necessary to introduce precise equipment. That is, it is possible to sufficiently cope with it by changing the number of turns of the heater according to the temperature distribution and changing the output.

[0067]

Third Embodiment A third embodiment of the present invention will be described with reference to FIG. The present embodiment is a method of manufacturing a resin molded product 2 in which a temperature-controlled member is applied to the hand portion 6 of a take-out machine of a resin molding device (corresponding to FIG. 15, claims 8 and 9). By bringing the temperature-controlled member, that is, the take-out machine hand portion 6 into contact with the resin molded product 2, the amount of heat can be efficiently transmitted to the resin molded product 2. Further, by applying to the hand portion 6 of the take-out machine, after the mold is opened, the resin molded product 2
It is possible to perform the process of taking out and the process of slow cooling at the same time, and by reducing the number of steps in the plastic manufacturing process,
A highly accurate resin molded product 2 can be obtained with high productivity.

[0068]

Fourth Embodiment A fourth embodiment of the present invention will be described. Mold 1 for molding into a desired molded product shape, and devices 3 and 5 for slow cooling
Is covered with a device (not shown) capable of controlling the internal temperature, and the surface temperature of the resin molded product 2 is at least ± 5 ° C. as compared with the temperature immediately after taken out from the mold 1. The resin molded product 2 can be moved to the step of performing slow cooling while being maintained within the temperature range of less than, and it is possible to prevent the deterioration of the shape precision of the molded product due to rapid cooling (corresponding to claims 10 and 11). .

[0069]

According to the first aspect of the present invention, the molten resin is injection-filled in a mold heated to a temperature not lower than the heat deformation temperature of the resin material used, and the temperature of the resin molded product in the mold is made uniform. In this state, the resin molded product is taken out of the mold, and then gradually cooled until the temperature of the resin molded product falls below the thermal deformation temperature of the resin material used. The temperature difference of causes the generation of thermal stress inside the resin molded product, which reduces the accuracy of shape and dimension due to thermal stress and causes new strain outside the mold. It is possible to reduce the number of molds and maintain high shape and dimension accuracy of the resin molded product. Also, by removing the resin molded product from the mold and performing slow cooling outside the mold, the molding cycle (inside the mold) Cooling time)
The following resin can be immediately injected, which can have a great effect on productivity in resin molding using injection molding. Furthermore, since it is not necessary to perform slow cooling to room temperature (room temperature), it is sufficient to reach the heat distortion temperature of the resin material used,
There is an effect that the productivity of the resin molded product can be improved.

According to the second aspect of the invention, in the method for producing a resin molded article according to the first aspect, the resin molded article is gradually cooled at a constant slow cooling rate. This has the effect of controlling the temperature difference between the surface and the inside of the resin molded product.

According to a third aspect of the present invention, in the method for producing a resin molded product according to the first or second aspect, after the resin molded product is gradually cooled, the temperature is maintained at the annealing end temperature for a certain period of time. Holding at the end temperature for a certain period of time has the effect of reducing the temperature difference between the surface and the inside of the resin molded product.

According to a fourth aspect of the present invention, in the method for producing a resin molded product according to any one of the first to third aspects, the wall thickness of a portion of the resin molded product having an uneven thickness is from b (thin portion) to a. In the range of (thick part), the slow cooling rate of slow cooling is a / (a
+ B) (° C / min) or more, a / (ab) (° C / mi
n) or less, the temperature difference between the surface and the inside of the resin molded product is affected by the wall thickness and uneven thickness of the resin molded product. Therefore, slow cooling according to the wall thickness and uneven thickness is performed. By setting the speed, it is possible to obtain a resin molded product in an appropriate gradual cooling time and to improve the productivity.

According to a fifth aspect of the present invention, in the method for producing a resin molded product according to any one of the first to fourth aspects, the resin molded product is housed in an apparatus capable of controlling the internal temperature, and Since the gradual cooling is performed, there is an effect that the facility introduction cost can be reduced by using a constant temperature bath of general-purpose equipment as a device capable of controlling the internal temperature in the gradual cooling process.

According to the sixth aspect of the present invention, in the method for producing a resin molded article according to the fifth aspect, the device capable of controlling the internal temperature is a constant temperature bath, so that the existing device can be used. It has the effect that no special equipment cost is required.

According to a seventh aspect of the present invention, in the method for producing a resin molded article according to any one of the first to fourth aspects, the temperature of the resin molded article is controlled so that the resin molded article has a different temperature distribution in the moving direction. Since the device is used for slow cooling, in the slow cooling process, the resin molded product can be internally moved by, for example, a belt conveyor, and the temperature distribution is controlled in the moving direction. The resin molded product molded into a desired shape can be continuously annealed, and a highly accurate resin molded product can be obtained with high productivity.

According to an eighth aspect of the present invention, in the method for producing a resin molded article according to any one of the first to fourth aspects, a temperature-controlled member is brought into contact with the resin molded article so that Since the cooling is performed, the temperature-controlled member is brought into contact with the resin molded product, so that the amount of heat can be efficiently transmitted to the resin molded product.

According to the ninth aspect of the present invention, in the method for producing a resin molded product according to the eighth aspect, since the hand portion of the take-out machine of the plastic molding apparatus is a temperature-controlled member, the temperature-controlled member is taken out. By applying it to the hand part of the machine, it is possible to reduce the number of steps in the manufacturing process, and it is possible to obtain a highly accurate resin molded product with high productivity.

The invention as defined in claim 10 is defined by claim 1 through claim 9.
In the method for manufacturing a resin molded product according to any one of 1, a device capable of controlling an internal temperature between a die for molding into a desired molded product shape and a device for gradually cooling the molded resin molded product. Since the temperature of the resin molded product is controlled when the resin molded product is taken out of the mold, the mold for molding into the desired resin molded product shape and the slow cooling are used. By covering the inside of the resin molding product with a device capable of controlling the internal temperature, it is possible to control the temperature difference between the surface and the inside of the resin molded product.

The invention described in claim 11 is according to any one of claims 1 to 1.
0. In the method for producing a resin molded product according to any one of 0, in a state in which the surface temperature of the resin molded product is maintained within a temperature range of at least ± 5 ° C. as compared with the temperature immediately after being taken out from the mold. Since the gradual cooling process was started, the surface temperature of the resin molded product is maintained within a temperature range of at least ± 5 ° C as compared with the temperature immediately after being taken out from the mold, so that the gradual cooling is performed. Before starting, it is possible to reduce the temperature difference between the surface and the inside of the resin molded product, and it is possible to prevent deterioration of the shape and dimension accuracy of the resin molded product.

The twelfth aspect of the present invention provides the first aspect.
Since it is an optical element such as a lens, a mirror, a prism, etc. manufactured by the method for manufacturing a resin molded product as described in 1, there is an effect that the shape uniformity is good and the internal uniformity is good and the optical performance is excellent.

[Brief description of drawings]

FIG. 1 is a graph of a conventional example showing a resin temperature change in a manufacturing process without a slow cooling process after molding.

FIG. 2 is a graph of a conventional example showing a resin temperature change in a manufacturing process including a slow cooling process of gradually cooling in a mold after molding.

FIG. 3 is a graph in the first example showing a main part of the present invention showing a change in resin temperature in a manufacturing process including a slow cooling step of gradually cooling outside the mold after molding.

FIG. 4 is a perspective view showing an example of a resin molded product.

FIG. 5 is a perspective view showing another example of a resin molded product.

FIG. 6 is a side view showing still another example of the resin molded product.

FIG. 7 is a graph showing the influence of holding time before slow cooling on shape dimension accuracy.

8A and 8B show state changes between a case of rapid cooling and a case of slow cooling; FIG. 8A is a graph showing a lens shape, FIG. 8B is a graph showing a shape measurement result, and FIG. It is a graph which shows the difference of the thermal stress when annealed.

FIG. 9 is a graph showing the influence of the gradual cooling end temperature on the shape dimension accuracy.

FIG. 10 is a graph showing the influence of the slow cooling rate on the shape and dimension accuracy.

FIG. 11 is a graph showing changes in the surface temperature and the internal temperature of the resin molded product over time immediately after molding.

FIG. 12 is a graph showing the influence of the slow cooling rate on the shape and dimension accuracy.

FIG. 13 is a cross-sectional view using a constant temperature bath showing a second embodiment of the present invention.

FIG. 14 is a cross-sectional view of an apparatus in which the temperature distribution is controlled in the moving direction according to the third embodiment of the present invention.

FIG. 15 is a sectional view showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 mold 2 resin molded products

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Watanabe Jun             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Kiyotaka Sawada             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 4F202 AA21 AA28 AH74 AH76 AH78                       CA11 CB01 CM11 CM90                 4F206 AA21 AA28 AH74 AH76 AH78                       JA07 JN41 JW15 JW16

Claims (12)

[Claims] 1. A resin molded product obtained by injection-filling a molten resin into a mold heated to a temperature not lower than the thermal deformation temperature of the resin material used, and maintaining the temperature of the resin molded product in the mold uniform. Is taken out of the mold, and then gradually cooled until the temperature of the resin molded product becomes equal to or lower than the thermal deformation temperature of the resin material used, the method for producing a resin molded product. 2. The method for producing a resin molded product according to claim 1, wherein the resin molded product is slowly cooled at a constant slow cooling rate. 3. The gradual cooling of the resin-molded article, after which the gradual cooling end temperature is maintained for a certain period of time.
A method for producing the resin molded article described. 4. The gradual cooling rate of gradual cooling is a / (a + b) when the wall thickness of the portion having uneven thickness of the resin molded product is in the range of b (thin wall portion) to a (thick wall portion). (℃ / min) or more a
/ (Ab) (° C / min) or less, The method for producing a resin molded article according to any one of claims 1 to 3. 5. The resin molded product according to claim 1, wherein the resin molded product is housed in an apparatus capable of controlling an internal temperature and the resin molded product is gradually cooled. Method. 6. The method for producing a resin molded product according to claim 5, wherein the device capable of controlling the internal temperature is a constant temperature bath. 7. The gradual cooling is performed by a device whose temperature is controlled so that the resin molded product is moved and has different temperature distributions in the moving direction. Method for manufacturing resin molded products of. 8. The resin molded product according to claim 1, wherein the resin molded product is gradually cooled by bringing a temperature-controlled member into contact with the resin molded product. Manufacturing method. 9. The method for producing a resin molded product according to claim 8, wherein the temperature-controlled member is a hand part of a take-out machine of a plastic molding device. 10. Between a die for forming into a desired shape of a molded product and an apparatus for gradually cooling the molded resin molded product,
10. The temperature of the resin molded product is controlled when the resin molded product is taken out of the mold by being covered with a device capable of controlling the internal temperature. Kaichi's method for manufacturing resin molded products. 11. The gradual cooling step is started in a state where the surface temperature of the resin molded product is maintained within a temperature range of at least ± 5 ° C. as compared with the temperature immediately after being taken out from the mold. The method for producing a resin molded product according to any one of claims 1 to 10, characterized in that. 12. An optical element such as a lens, a mirror or a prism, which is manufactured by the method for manufacturing a resin molded product according to any one of claims 1 to 11.