JP2002166452A - Method and apparatus for molding precision molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for obtaining a lengthy molding which is difficult to secure a shape precision over a whole area, a molding having a small cross-sectional area, a thin-walled molding, a molding of a complex shape, or a precision molding required for a high shape precision among precision moldings in a short molding cycle and an apparatus for the method. SOLUTION: A cavity 5 is formed from a pair of molds or a plurality of metal pieces, a resin in the cavity can be compressed by moving the movable mold or the movable metal pieces, and the apparatus for molding the precision molding. On the basis of the above-mentioned structure of the cavity at a point of time of final molding (when a molding is demolded), a clearance of at least 0.3 mm is formed in a range of at least 50% of the fringe part of the cavity, and the resin can protrude from the clearance during molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for molding a precision molded product, and to facilitate uniformity of the internal pressure of a cavity in a molding die to improve the quality of the precision molded product. This is extremely effective in manufacturing precision molded products such as optical elements and high-precision functional components in general.

[0002]

2. Description of the Related Art Precision parts such as optical elements have been increasingly made of plastic in terms of productivity and cost, and in recent years, higher precision has been required. For this reason, it has become difficult to obtain the required molding accuracy by conventional injection compression molding or the like. A molding method in which a part or the whole of a resin blank is heated to a temperature higher than the glass transition point and then compressed is disclosed (Japanese Patent Laid-Open No. 8-127).
No. 077, Japanese Unexamined Patent Publication No. 11-221834) and the like have been developed and used as a method for molding precision molded products such as optical elements. The method described in the above-mentioned Japanese Patent Application Laid-Open No. 8-1270077 discloses a method in which a temperature and a deformation speed of an optical material are regulated (Tg + 15 to Tg + 40 ° C.) in a method of heating and pressing in a cavity formed by an upper die and a lower die. In a temperature range, a pressure of 1.5 to 15 kg / cm ² (Tg: glass transition point) is applied to deform under pressure.
In the method described in Japanese Patent Application Laid-Open No. 1-221834, the shape of a preform and the molding temperature and pressure range during press molding are specified in a press molding method of an optical prism (Tg + 20 to Tg + 90 ° C., 10 to 10 ° C.). 2
(Pressure of 00 kg / cm ² ) and press-molding.

[0003] These molding methods are 1) a resin blank is supplied into a cavity, a mold is closed, the mold is heated to a high temperature, and the resin is melted and fluidized to compress and transfer the cavity shape. However, this has the following inconveniences, and since the cavity is a completely closed space, the variation in the amount of resin appears directly as a difference in the shape of the molded product. In addition, the pressure distribution is likely to occur in long molded products and the shape accuracy is likely to deteriorate, so it is necessary to heat the resin to a considerably high temperature to increase the fluidity in order to reduce this, The molding cycle is prolonged as much as the temperature is increased. other,
There is a method described in Japanese Patent Publication No. 6-20782 (a method for controlling a press force holding step of a press molding machine). In this method, a pressure control valve is controlled after a press force holding step in a molding method for pressing a molten resin. The method described in Japanese Patent Application Laid-Open No. 9-104025 (press forming method for thermoplastic resin) regulates the speed of the compression operation in the press forming method for thermoplastic resin. Is what you are doing. Further, Japanese Patent Application Laid-Open
No.-61969 (lamination molding method using plastic fluid and its mold structure) discloses a molding die for press-molding a laminated molded product, wherein an overflow passage of the plastic fluid is formed by a metal mold. The one provided so as to communicate with the outer surface of the mold and the one described in Japanese Patent Application Laid-Open No. 9-267344 (press molding method and press molding die) are used in press molding of a stampable sheet. Resin leaks from a predetermined gap (overflow portion) between the male mold and the female mold, and the leaked resin is cut and sandwiched when the mold is closed. The above publication describes, as a conventional technique, a method in which a gap of 0.05 to 0.3 mm is provided over the entire circumference to extrude gas and excess resin. Furthermore, it is extraordinary 1-393
No. 37 (a method of manufacturing a plastic lens) describes a method in which a lens material obtained by an injection molding method is melt-fluidized only in the vicinity of a surface in a mold, and then compression-molded.

On the other hand, even if there is a certain degree of variation in the weight and shape of a molding blank of a precision molded product such as a long molded product where it is difficult to obtain a high precision, a highly accurate molded product can be obtained. As a molding method, a molding method has been developed in which a part of the resin is brought into a non-contact state with a mold while being cooled to a glass transition point or lower after completion of a heating step in compression molding (Japanese Patent Application No. 2000-47574). . This is because by providing a large part where the resin and the mold do not contact each other and releasing the resin pressure, it is possible to mold the pressure distribution evenly in a shape that tends to cause pressure variations like a long molded product. As a result, a precision molded product having good shape accuracy and small internal strain can be obtained. Further, in this method, since the sensitivity to the variation in the shape of the resin blank is low, the allowable width of the variation in the shape or the weight of the resin blank is significantly larger than that of the conventional method. According to conventional common sense, it is thought that if such a large non-contact portion is provided, the pressure loss at the time of molding is too large, so that shape transfer cannot be performed. The level of pressure required for surface transfer can be sufficiently generated.

However, as the products to which this molding method is applied are expanded to those having various shapes, it has been found that the effects may be insufficient as described below. Especially when the non-functional surface is not in contact with the mold in the cavity,
Although the pressure distribution can be considerably reduced, the pressure required for surface transfer may not be able to be secured over the entire area in a case where the shape of the functional surface portion is complicated or in a precision molded product having a small cross-sectional area. In the case of a thin molded article having a small cross-sectional area, the density distribution or shape variation of the blank greatly affects the pressure distribution, so that the uniformity of the pressure distribution may be insufficient. Therefore, it is necessary to increase the accuracy of the blank by that much, and the cost increases. In addition, if the temperature of the mold during compression is increased to make the pressure distribution uniform, there is a problem that the pressure loss is large, the pressure required for shape transfer cannot be secured, and the molding cycle becomes long. Further, in a press molding method, an excess molten resin is released from an overflow portion provided in a part of a mold (for example, Japanese Patent Application Laid-Open No. 9-267).
344 and JP-A-2000-61969), as described above. All of these molding methods have the effect of removing excess resin from the supplied resin during molding. It has not been established as a method for molding accurate precision molded products, and there are the following problems to uniform the pressure distribution in long precision molded products, etc.
Also, because the resin escapes from a part, a pressure difference occurs between the part near the overflow part and the part far from it, and uniformization tends to be insufficient.To resolve this, make the overflow part thinner and reduce the mold temperature. In addition, it is necessary to increase the fluidity of the resin, but in such a case, the molding cycle becomes extremely long. Furthermore, since the area where the resin escapes is wide, it is easy to make the pressure distribution uniform. However, since the gap is thin, the mold must be heated to a high temperature for uniform pressure, and the molding time becomes longer.
In addition, since very large burrs are generated in a wide range, there is a problem that deburring is difficult and the molding cost is increased.

[0006]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned problems, and among long precision molded products, it is difficult to secure the shape accuracy over the entire area.
The aim is to devise molding products and molding methods to obtain small cross-section molded products, thin-wall molded products, molded products with complicated shapes, precision molded products requiring extremely high shape accuracy, and obtain them in a short molding cycle. Issues.
More specifically, in addition to simply transferring the shape by compressing the resin surface in a molten state, (1) how to make the pressure distribution of the resin uniform, (2) how uniformly the shape transfer is required. The object is to generate pressure and (3) how to reduce internal stress to suppress deformation after mold release.

[0007]

[Measures taken to solve the problem]

SOLUTION: A solution means 1 is a means for solving the problem of how to make the pressure distribution of resin uniform, and a cavity is constituted by a pair of molds or a plurality of mold pieces. The movable mold or movable metal piece is moved to compress the resin in the cavity. The above cavity is premised on a precision molded product molding apparatus having a cavity configuration at the final molding time (at the time of molded product release). A gap of at least 0.3 mm or more is interposed in a range of at least 50% or more of the edge, and the resin during molding can protrude from the gap. Note that the gap is desirably 0.
5 mm or more.

[0008]

[Action] A gap is interposed in the above-mentioned range of the cavity edge,
Because the molding device allows the resin to protrude from the gap during molding, when a compressive force is applied to the resin for a certain period of time or longer, a portion thicker or higher density than the specification value of the resin blank is thinner or lower than the specification value. A higher pressure is temporarily generated than in a dense portion, so that more resin overflows. As a result, the pressure distribution in the resin is automatically made uniform. Then, after the pressure distribution is made uniform, a higher compression force is applied to uniformly generate a high pressure to transfer the shape, so that it is possible to manufacture a precision molded product having high shape accuracy. In order to actually make the entire pressure distribution uniform, the range in which the gap is interposed should be made as wide as possible, and it is necessary to allow a certain amount or more of resin to protrude.
A gap of at least 0.3 mm or more is required in a range of at least 50% or more of the cavity edge.

[0009]

According to a second aspect of the present invention, in the cavity configuration at the time of the final molding, the resin protrudes at a distance of at least 30 mm at any position on the cavity surface corresponding to the functional surface of the molded article. That is, there is a possible cavity gap. The distance is desirably within 20 mm.

[0010]

A second aspect of the present invention is a solution to the problem of how to uniformly generate a pressure required for shape transfer. Assuming a molding method using the molding apparatus of (1), it is constituted by the following elements (1) to (3) or (1) to (4). (1) After at least a part of the resin existing in the cavity is heated from a temperature lower than the glass transition point to a temperature higher than the glass transition point, the resin is cooled again to a temperature lower than the glass transition point. (2) Applying a compressive force to the resin in the cavity by moving the movable mold or movable metal piece during or after the temperature raising step and holding the resin in the cavity for a certain period of time to allow the resin to protrude from the cavity gap (uniform pressure distribution) ). (3) To transfer the functional surface by applying a higher compressive force after the step (2) (ensure shape transfer accuracy). (4) Reducing the compressive force after the step (3) (reducing pressure and releasing internal stress).

[0011]

The operations (1) to (4) are as follows. (1) By heating the resin once to a temperature higher than the glass transition point having low viscosity and applying a compressive force, the resin can be actually deformed and protruded, and the pressure distribution is made uniform and the shape is transferred. Finally, the mold is sufficiently cooled to the glass transition temperature or lower, and then the mold is released, whereby deformation at the time of mold release can be suppressed, and a highly accurate molded product can be obtained. (2) It is possible to actually apply a compressive force to the resin by moving the movable die or the movable gold piece. And by applying a compressive force for a certain period of time during or after the temperature raising step in a molding apparatus from which the resin can protrude,
The thicker or higher density portion of the resin blank is temporarily higher in pressure than the thinner or lower density portion than the specified value and more resin overflows. The pressure is further reduced and the pressure distribution in the resin is automatically made uniform. (3) Since a higher compressive force is applied after the pressure distribution is made uniform, the pressure required for shape transfer can be uniformly generated, and the shape is transferred with high accuracy. (4) By reducing the compressive force after the step (3), even when the cooling rate is increased, the pressure at the time of mold release can be suppressed to a certain pressure or less, and the mold is released with little internal stress. Therefore, a molded article with little deformation at the time of mold release and after mold release and little internal stress can be stably obtained in a short molding cycle.

[0012]

Embodiment 1 (corresponding to claim 5) This embodiment 1
The maximum temperature of the resin in the cavity in the steps (2) to (4) of Solution 2 is set to a temperature higher by 3 ° C. to 25 ° C. than the glass transition point of the resin. Note that the maximum temperature of the resin in the cavity is desirably 5 ° C. to 15 ° C. higher than the glass transition point of the resin.

[0013]

Embodiment 2 (corresponding to claim 6) The embodiment 2 is that in the above-mentioned step (2) of the solution 2,
It is to maintain the pressure in the resin of not more than MPa for 10 seconds or more.

[0014]

Embodiment 3 (corresponding to claim 7) The embodiment 3 is that in the step (3) of the solution 2, the pressure is not less than 3 MPa and not more than 30.
It is to maintain a pressure of not more than MPa and at least 2 MPa higher than the maximum pressure in the step (2) for 5 seconds or more.

[0015]

Embodiment 4 (corresponding to claim 8) The embodiment 4 is that in the step (4) of the solution 2, the pressure is not less than 1 MPa and not more than 20.
That is, the pressure is reduced to a pressure of not more than MPa and at least 2 MPa lower than the maximum pressure in the step (3).

[0016]

Embodiment 5 (corresponding to claim 9) In Embodiment 5, the amount of resin protruding from the cavity gap during the above-mentioned steps (2) to (4) of Solution 2 is the cavity volume at the end of molding. That is, it should be 1% or more and 40% or less. The amount of the resin protruding from the cavity gap is desirably 3 to 3 times the cavity volume at the end of molding.
20%.

[0017]

(Sixth Embodiment) In a sixth embodiment of the present invention, in the molding method according to the second aspect, the movable die or the movable metal piece is advanced by controlling its position or speed based on preset conditions. Thus, a compressive force is applied to the resin in the cavity.

[0018]

Embodiment 7 (corresponding to claim 11) Embodiment 7 relates to the molding method according to Solution 2, wherein the resin pressure in the cavity or the force applied to the movable mold or movable metal piece is detected and the detection is performed. The compression force is applied to the resin in the cavity by moving the movable die or the movable gold piece forward or backward based on the obtained information and a preset pressure condition.

[0019]

Solution 3 (corresponding to claim 12) Solution 3 is a solution to the problem of how to reduce internal stress to suppress deformation after mold release. In the step 4), the movable mold or the movable gold piece is
Stopping for 0 second or more, and further protruding the resin from the cavity gap to reduce the resin pressure in the cavity.

[0020]

[Function] After the high-pressure is generated in the resin and the shape is transferred, the movable mold or movable piece is stopped for a certain period of time when the resin temperature is still high, so that the resin protrudes from the entire cavity gap and the pressure distribution is almost uniform. The total pressure will automatically drop when held. As a result, the internal stress is reduced, the pressure at the time of mold release is suppressed, and a highly accurate molded product with little deformation at the time of mold release and after mold release can be obtained. Also, the pressure drop width changes depending on the increase or decrease of the stop time, so that the pressure at the time of mold release can be adjusted. However, it takes 10 seconds or more to actually obtain the effect of the pressure drop by protruding the resin.

[0021]

A fourth aspect of the present invention is a solution to the problem of how to reduce internal stress and suppress deformation after mold release. In step 4), the movable mold or the movable metal piece is retracted to reduce the resin pressure in the cavity.

[0022]

[Function] After a high pressure is generated in the resin and the shape is transferred, the movable resin or the movable piece is retracted at a stage where the resin temperature is still high and the viscosity of the resin is low and the resin can follow the movement of the mold or the piece. Is quickly reduced. as a result,
The internal stress is reduced, the pressure at the time of release is suppressed, and a highly accurate molded product with little deformation at the time of release and after release is obtained.

[0023]

Embodiment 1 (corresponding to claim 14) This embodiment 1
Is an embodiment of the molding method of Solution 2 to Solution 4 for increasing the precision of the molded article. After the above-mentioned step (4), the molded article shape specification, the shrinkage ratio of the resin used, and the mold release The movable mold or movable metal piece is moved to a predetermined position calculated from the cavity temperature, and is stopped at that position until the molded product is released.

[0024]

Embodiment 2 (corresponding to claim 15) Embodiment 2
In the molding method according to the seventh embodiment of the solution means 2, the stop position of the movable die or the movable piece in the molding method according to the first embodiment is retracted from the final position in the step (3).

[0025]

Embodiment 3 (corresponding to claim 16) Embodiment 3
Is an embodiment of the molding method of Solution 2 to Solution 4, wherein the maximum value of the resin pressure in the cavity at the time of mold release is set to 0.3.
That is, it was set to 10 MPa to 10 MPa. The maximum value of the resin pressure in the cavity is preferably 0.5 MPa
５5 MPa.

[0026]

Embodiment 4 (corresponding to claim 17) This embodiment 4
Is an embodiment of the molding method according to Solution 2 to Solution 4, wherein the maximum temperature of the resin in the cavity at the time of mold release is set to a temperature lower by 3 ° C. to 30 ° C. than the glass transition temperature of the resin. The maximum temperature of the resin in the cavity at the time of mold release is preferably a temperature lower by 5 ° C. to 20 ° C. than the glass transition temperature of the resin.

[0027]

Embodiment 5 (corresponding to claim 18) This embodiment 5
Is an embodiment of the molding method according to Solution 2 to Solution 4, wherein a resin blank having a substantially final molded product shape is inserted into the cavity to perform compression molding.

[0028]

Embodiment 6 (corresponding to claim 19) This embodiment 6
Is an embodiment of the molding method according to Solution 2 to Solution 4, wherein compression molding is performed after supplying the molten resin onto the open cavity or into the closed cavity.

[0029]

Next, Embodiments 1 and 2 will be described with reference to FIGS. The object to be molded according to Examples 1 and 2 is the long lens 1 shown in FIG. 1 and its size is 5 mm × 5 mm × 80 mm, and the resin material is a polyolefin resin (glass transition point: 1
40 ° C.). The long lens 1 shown in FIG.
Are molded and taken out by the molding apparatus shown in FIG. At the edge of the cavity 5 formed by the fixed metal piece 3 and the movable metal piece 4 of the molding device 2, there is a cavity gap 6 in the entire range excluding both ends in the longitudinal direction of the molded product (the whole). The movable metal piece 4 is pushed down and compressed until the cavity gap at the end of molding becomes 0.9 mm. Therefore, the resin protruding portions 7 having a thickness of about 0.9 mm are formed on both side surfaces of the molded product. The transfer processing of the functional surface (lens surface) of the molded product is performed by the above-described compression operation by moving the movable gold piece. The heating of the molding apparatus is performed by a heater (not shown) installed in the apparatus.

[0030]

Example 1 [Method] A blank having a substantially final shape previously molded by injection molding was inserted into a molding apparatus, the mold was closed, and the resin surface was heated to a glass transition point (Tg) or higher and then cooled.
When the resin is sufficiently cooled to a temperature below the glass transition point, the molded article is released from the mold and taken out. Here, cavity 5
Was raised to a maximum of 152 ° C. (Tg + 12 ° C.), and demolding was performed at 128 ° C. (Tg-12 ° C.). The heating rate was about 15 ° C./min, and the cooling rate was 4 ° C./min. When the temperature rise is almost completed, the movable gold piece is moved to start resin compression.
Thereafter, the movable gold piece is moved in the following order to compress the resin and adjust the pressure. The pressure control of the movable gold piece is performed by feeding back resin pressure information detected by a pressure sensor embedded in the apparatus. 1) After the gold piece is advanced to a position where pressure is generated in the cavity, the pressure is controlled to maintain a pressure of 3 MPa for 20 seconds. By holding the resin at a relatively low pressure for a certain period of time, the entire cavity is reliably filled with the resin and the pressure distribution is made uniform. Even when there is shape variation in the blank, a portion thicker than the others is temporarily pressurized stronger than the others, and the resin is extruded more, so that the pressure distribution is automatically made uniform. Note that the width of the cavity gap 6 gradually decreases as the resin protrudes, but at this time, the width is about 1.5 mm.
It is. 2) Then, the pressure is controlled to maintain a pressure of 10 MPa for 10 seconds. Since the high pressure is uniformly applied to the functional surface when the pressure distribution in the resin is substantially uniform, the transfer of the optical surface is reliably performed without local distortion. 3) Then, the state where the pressure is reduced to 6 MPa by pressure control is maintained for 15 seconds. At this time, the pressure is reduced so that the residual pressure is in a predetermined pressure range at the time of demolding, and the overall internal stress is reduced by lowering the pressure before cooling to below the glass transition point. . 4) Next, the position is controlled to move the movable mold or movable piece to a specified position calculated from the molded product shape specification, the shrinkage ratio of the resin used, and the cavity temperature at the time of mold release. Here, as a result, a slight advance was made, and the final cavity gap was 0.9 mm. 5) Thereafter, the pressure naturally dropped due to the shrinkage of the resin due to cooling and the slight protrusion of the resin from the cavity gap, and the pressure at the time of mold release was about 1 MPa. The final resin protrusion amount was about 5% of the cavity volume. In addition, as a comparative example, FIG.
A compression molding experiment was performed in a completely closed cavity space with no cavity gap using a molding apparatus as shown in FIG. Figure 2 shows the basic temperature and pressure patterns.
This is the same as Example 1 shown in (a), but in this case, since the pressure distribution was hardly reduced with the same molding temperature pattern, the maximum temperature during molding was set to 170 ° C. (Tg + 30).
℃) to perform molding.

[Results] The resin is protruded from the large cavity gap to make the pressure uniform, the shape is transferred with a uniform pressure, and the pressure is appropriately controlled to release the resin in a state where the internal stress is small and sufficiently cooled. By molding, a molded product of high precision and stable quality was obtained. Specifically, there was little deformation after mold release, and shape accuracy was reliably obtained up to the end of the molded product. On the other hand, in the comparative example, the accuracy was hardly stabilized particularly at the end portions, and the yield was poor. In addition, thickness is 5%
A molded product with almost the same accuracy can be obtained even when molding is performed using blanks of different degrees, and the allowable range of blank accuracy is much wider than the conventional method (about 0.5% in the comparative example).
Further, the molded product has high accuracy and has very little variation. This is presumably because both the resin pressure and the position of the gold piece are controlled. (By the way, in the conventional example, the final position control of the gold piece or movable mold was performed by hitting the most advanced position, or the specified pressure. Therefore, in the former, the residual pressure at the time of mold release is large, and the residual pressure fluctuates with each molding, so that the shrinkage or deformation after the mold release varies, and the height of the molded product is increased. In the latter, the residual pressure is constant, but the final position of the movable mold or movable mold itself varies depending on the blank used, and the accuracy of the molded product also varies. ). Also, molded products have low internal stress,
Low birefringence. In addition, the maximum temperature of the resin during molding is Tg
The molding could be performed at + 12 ° C., which is lower than the conventional examples (the conventional examples disclosed in JP-A-8-127577 and JP-A-11-221834). This leads to shortening of the molding cycle, and at the same time, it is possible to suppress the occurrence of burrs at unexpected portions and extend the life of the molding apparatus. In addition, when a molding experiment was attempted while changing the maximum temperature from Tg to Tg + 30 ° C., Tg
In the range of + 5 ° C. to Tg + 20 ° C., a highly accurate molded product can be obtained stably. At Tg + 3 ° C. or lower, surface transferability is deteriorated. At Tg + 25 ° C. or higher, pressure loss due to resin protrusion is too large. As a result, the pressure required for shape transfer could not be secured over the entire surface. However, since the fluidity of the resin increases and the pressure loss increases as the molding temperature increases, the experiment was performed using a thicker blank. In the above conventional example, the temperature is from Tg + 15 ° C. to Tg + 40 ° C. as disclosed in JP-A-8-127077.
No. 221834, Tg + 20 ° C. to Tg + 90
° C, which makes it possible to lower the molding temperature and shorten the molding cycle as compared with these molding methods, and at the same time, to suppress the occurrence of burrs at unexpected portions, thereby extending the life of the molding apparatus.
Regarding the resin temperature at the time of mold release, if the temperature is too close to the glass transition point, the resin is still soft and some deformation occurs at the time of mold release, and if the inside of the mold is cooled to a temperature too low, the molding cycle will be long On the contrary, since internal strain occurs and causes birefringence and deformation, a temperature range of at least 3 ° C. to 30 ° C. lower than the glass transition temperature is required. It was confirmed that a temperature range lower by 20 ° C. The experiment was performed with the pressure range also changed. The compressive force in the pressure distribution uniforming step (step 2 of claim 3) is 2 MPa to 15 MPa.
It was confirmed that by setting the pressure to MPa, the resin was allowed to protrude to stably uniform the entire pressure distribution. 1M
If the pressure is less than Pa, the amount of protrusion of the resin is small.
If it is more than the above, the amount of resin protruding more than necessary will be a factor of cost increase, and it will be necessary to enlarge the equipment to withstand high pressure, which will be a factor of cost increase, and the internal stress will increase. Not suitable as a condition. In addition, it was confirmed that in the shape transfer step (step 3 of claim 3), 3 MPa or more is required for stable transfer, and that the pressure needs to be higher than in the pressure distribution uniforming step. A pressure increase of at least about 2 MPa is required,
As a result, a further pressure distribution reducing effect can be obtained simultaneously with the shape transfer. It should be noted that the more complicated the shape of the molded product, the higher the pressure or the higher the temperature, the more it is necessary to facilitate the transfer. However, increasing the pressure to 30 MPa or more reduces the amount of the protruding resin and reduces the size of the molding device as described above. It is not suitable from the viewpoints of improvement of the durability, improvement of the durability and reduction of the internal stress. In addition, in order to prevent deformation after mold release and obtain a molded product with small internal strain, the residual pressure at the time of mold release is 0.5MPa to 5MPa.
It has been confirmed that a range of at least about 0.3 MPa and not more than 0.3 MPa is appropriate. Therefore, a relatively high pressure is generated in the shape transfer process, and the residual pressure at the time of release is kept within the above range without lengthening the cooling time, and at the same time, the internal stress is reduced as a whole. In the step (step 4 of claim 4), the resin pressure is set to 2 MPa.
It has been confirmed that it is appropriate to lower the pressure to a range of 15 MPa or less. Since the pressure gradually decreases during cooling, the pressure condition slightly changes depending on the cooling time and the shape of the molded product. However, if the pressure is at least 1 MPa or less, the residual pressure at the time of releasing from the mold is out of the above range, and the sink is easily generated. 20M
When the pressure is Pa or more, the residual pressure at the time of mold release increases, and deformation tends to occur after mold release due to residual stress, problems such as increased birefringence occur, and the molding cycle is significantly lengthened by extending the cooling time. The problem arises. In addition, molding was performed while varying the time for applying pressure, but at least 5 seconds or more in the shape transfer step and at least 10 seconds or more in the pressure equalizing step are required to reliably exert the above-mentioned effects. It turned out to be. A molding experiment to examine the effect of the cavity gap was performed while simultaneously changing the blank thickness so that the same pressure was generated in the first pressure equalization step.
If the width is less than m, thin burrs will be greatly extended, and it will be necessary to cut them, leading to increased costs. As it is necessary to raise the molding temperature as a problem such as a longer molding cycle occurs, at least 0.3 mm or more,
It has been found that it is desirable to secure a width of 0.5 mm or more.

[0032]

Embodiment 2 [Method] In Embodiment 2, the same molded product is molded under the same molding apparatus and the same temperature conditions as in Embodiment 1.
However, in contrast to the first embodiment, the movement of the movable gold piece was performed by controlling the position and speed in a stepwise manner, and the compression process was performed as follows. 1) After the gold piece is advanced to the position where pressure is generated in the cavity, the speed is reduced to about half, the metal piece is advanced to the specified position, and stopped for 3 seconds. Specifically, during this period, 2.5 to 3.5
The position and speed are adjusted so that the pressure can be maintained for 20 seconds at a pressure of MPa. As a result, the pressure distribution is made uniform as in step 1) of the first embodiment. 2) Then control the speed to the next specified position and move forward,
Stop for 3 seconds. Again, between 9.5 and 10.5M
Position and speed conditions were specified in advance so that the pressure of Pa could be maintained for 10 seconds. This ensures that the shape is transferred without any local distortion as in step 2) of the first embodiment. 3) Then, hold at the final position of the above 2) for 20 seconds. By holding the resin for about 0.7 mm with a cavity gap protruding in a high temperature state and releasing the pressure for a certain period of time,
The pressure is reduced to 8 MPa to reduce the overall internal stress. 4) Next, the position is controlled to move the movable mold or movable piece to a specified position calculated from the molded product shape specification, the shrinkage ratio of the resin used, and the cavity temperature at the time of mold release. Here, the resin pressure is reduced, and at the same time, the resin pressure is reduced by about 2 MPa to about 6 MPa. Reducing the pressure of the resin by retracting the gold pieces in this way is a method of reducing the pressure by extruding the resin at a high temperature as in the above step 3), and extending the cooling time to reduce the pressure until the mold release. Since the pressure can be reduced directly faster than the method of increasing the width, high pressure is generated in the shape transfer process without sacrificing the molding cycle and the residual pressure at the time of release is reduced, so that a highly accurate molded product can be produced. It becomes possible to mold. However, if the metal piece is retreated too rapidly, the resin cannot follow the metal piece, and instead, a pressure distribution or internal stress may be generated, which may deteriorate the precision of a molded product. 5) Thereafter, the pressure naturally dropped due to the shrinkage of the resin due to cooling and the slight protrusion of the resin from the cavity gap, and the pressure at the time of mold release was about 1 MPa as in Example 1. The final protrusion amount of the resin was about 5% with respect to the cavity volume as in Example 1.

[Results] The resin was protruded from the large cavity gap to make the pressure uniform, the shape was transferred with a uniform pressure, the pressure was appropriately controlled, and the mold was released with a small internal stress. As in the case of No. 1, a molded product of higher precision and more stable quality than the conventional example was obtained. Basically, the control method of the movable gold piece movement is simply changed from the pressure control to the step control of the position and the speed, and the same compression is performed by programming the gold piece movement program so that a desired pressure pattern is obtained in advance. Since the effect can be obtained, the accuracy of the obtained molded article is substantially equal. Also, in the second embodiment, unlike the first embodiment, a step of stopping the position of the gold piece in a high temperature state and executing the step of protruding the resin to reduce the pressure is performed. Since it is reduced, the internal stress can be reduced at the same time, which is effective as a process for obtaining a precision molded product with little internal distortion and birefringence. However, if the pressure is reduced only by this process, the molding time becomes longer, so if it is used together with the method of retreating the gold piece position and directly reducing the pressure, the molding cycle can be effectively reduced without sacrificing the molding cycle. The pressure during mold release can be optimized.

[0034]

Third Embodiment The object to be molded according to the first and second embodiments is a two-dimensional lens array shown in FIG. The two-dimensional lens array 51 has 15 × 15 lenses with a diameter of 3 mm arranged at a pitch of 5 mm. However, FIG.
FIG. 6 shows 3 * 3 planes for simplification. The resin material of the lens array 51 is a polyolefin resin (glass transition point Tg: 140 ° C.). FIG. 6 schematically shows a molding apparatus according to the third embodiment. As shown in the figure, a resin escape portion is set in a groove shape in the vertical and horizontal directions around each lens cavity, and is formed in a lattice shape. The groove communicates with the outside so as to escape. The groove width is 1 mm, and the cavity clearance at the end of molding formed between the upper and lower dies 52 and 53 is also 1 mm. The heating of the molding apparatus is performed by a heater (not shown) installed in the apparatus.

[Molding Method] The temperature condition and the pressure condition were almost the same as those in Example 1, and the movable mold was moved under pressure control except for stopping at the final position. The final pressure at the time of mold release was about 2 MPa, and the final resin protrusion amount was about 6% with respect to the cavity volume.

[Results] In particular, in the molding of a two-dimensional lens array, it is necessary to minimize variations in the shape accuracy of each lens, and it has been difficult to achieve stable and accurate molding until now. The molded product of high quality with high accuracy and stable quality can be obtained by uniformizing the pressure, transferring the shape with uniform pressure, and controlling the pressure appropriately and releasing the mold with small internal stress. Was. There is a molding method that presses the sheet, and consequently protrudes the resin at the end of the sheet. However, especially in high-precision precision molded products such as a two-dimensional lens array, the internal pressure distribution is sufficiently uniformed. In order to perform high-precision molding, it is necessary to provide a resin escape portion in the vicinity of each functional surface as in the present invention and to perform a temperature and pressure process as in the present invention. It is valid. As described above, in the first, second, and third embodiments, the molding is performed by the specific molding method. However, if the non-contact portion with the mold is provided on the resin surface, the molding method of the present invention can be realized. Since it is good, in either case, molten resin filling molding or heat compression molding using a blank may be used. Also,
The resin is not limited to the polyolefin resin, but may be a thermoplastic resin or another resin as long as the molding method can be applied. Furthermore, the target precision molded product and the shape of the molded product are not limited to optical components as long as the present molding method can be applied.

[0037]

The operation and effect of the present invention are summarized as follows for each of the main claims.

1. The apparatus for molding a precision molded product according to claim 1 has a cavity gap necessary to protrude the resin during molding to make the pressure distribution uniform, so that a precision molded product having a shape which was conventionally difficult to achieve high precision. In this case, a highly accurate molded product having a small internal stress and good shape accuracy can be stably obtained in a short molding cycle. Further, in the molding using the resin blank, it is possible to improve the productivity by increasing the allowable width with respect to the weight and the shape variation of the resin blank.

2. In the molding apparatus according to claim 2, there is a cavity gap where the resin can protrude near any position on the cavity surface corresponding to the molded product functional surface.
Even in a precision molded product having a shape that has conventionally been difficult to achieve high precision, a highly accurate molded product having small internal stress and good shape precision can be stably obtained in a short molding cycle. Further, in the molding using the resin blank, it is possible to improve the productivity by increasing the allowable width with respect to the weight and the shape variation of the resin blank.

3. The method of molding a precision molded product according to claim 3 is
After the resin is protruded from the cavity gap to make the pressure distribution in the cavity uniform, the high pressure is uniformly generated on the functional surface, the shape is transferred securely, and the mold is released after being cooled sufficiently. It was possible to stably produce high-precision molded products with good shape accuracy even in precision molded products of difficult shapes, and there was shape and weight variation in blanks in molding using resin blanks Even in the case of thicker parts, the pressure is temporarily stronger than the others, and more resin is extruded and the pressure distribution is automatically uniformed. The operation and effect that productivity can be improved can be exhibited.

4. The method for molding a precision molded product according to claim 4 is
After the high pressure is generated on the functional surface and the shape is transferred securely, the internal stress in the resin is reduced and the mold is released after being sufficiently cooled. Therefore, a high-precision molded product having a small internal stress and good shape accuracy can be stably manufactured in a short cycle.

5. By molding under the temperature condition of claim 5, the balance between the fluidity of the resin and the cavity gap is optimized, so that the above-mentioned effects can be actually exerted.

6. By molding under the pressure condition of claim 6, the resin protrudes from the cavity gap, the pressure distribution in the cavity is made uniform, and the above-mentioned effect can be actually exerted.

7. By molding under the pressure condition of claim 7, the shape of the functional surface is reliably transferred, so that the above-described effects can be actually exerted.

8. By molding under the pressure conditions of claim 8, the internal stress in the resin is reduced as a whole, and the pressure at the time of mold release can be optimized without sacrificing the molding cycle. Can be demonstrated.

9. By molding under the conditions of claim 9, the resin pressure distribution in the cavity is actually reduced, and the above-described effects can be exerted.

10. By applying a compressive force to the resin in the cavity by the control method according to the tenth aspect, pressure can be applied to the resin in the cavity in an optimal pattern, and the above-described effects can be actually exerted.

11. By applying a compressive force to the resin in the cavity by the control method according to claim 11, the pressure can be applied to the resin in the cavity in an optimal pattern by a simple control device, and the above-described operation and effect can be actually exerted. .

12. By molding under the conditions of claim 12, the resin pressure distribution in the cavity and the overall internal stress are actually reduced, and the above-mentioned effects can be exerted.

13. By molding under the control conditions of claim 13, the resin pressure distribution in the cavity and the overall internal stress are actually reduced, and the above-mentioned effects can be exerted.

14. By molding under the control conditions of claim 14, both the pressure in the resin and the final position of the movable metal piece or movable mold are controlled, so that a precision molded product having extremely high shape accuracy even in the height direction of the molded product is obtained. be able to.

15. By molding under the control conditions of claim 15, both the pressure in the resin and the final position of the movable metal piece or the movable mold are controlled, and the resin pressure is reduced by retreating the position of the movable metal piece or the movable mold. Therefore, it is possible to obtain a precision molded product having very good shape accuracy in the height direction of the molded product in a short molding cycle.

16. By molding under the pressure condition of claim 16, the deformation at the time of release and after release can be reduced, and the internal stress in the resin can be reduced, so that the above-mentioned effects can be actually exerted.

17. By molding under the temperature condition of claim 17, deformation at the time of release and after release can be reduced, and the internal stress in the resin can be reduced, so that the above-mentioned effects can be actually exerted.

18. According to the molding method of the eighteenth aspect, since the supplied resin is close to the shape of the final molded product in advance, the pressure distribution can be easily made uniform, and the above-mentioned effects can be exhibited in a short molding cycle.

19. By molding by the molding method of the nineteenth aspect, a highly accurate precision molded product can be obtained in only one molding step, and the productivity can be improved.

20. The precision molded product according to claim 20 is a high quality precision molded product having a small internal stress and good shape accuracy because the pressure distribution is made uniform by the resin overflowing from a certain range or more during molding. Utilizing this makes it possible to produce higher-performance or lower-priced units and products.

21. Since the precision molded article according to claim 21 is molded by the molding method having the above-described operation and effect, it is obtained at a low cost while being of high quality. Units and products can be manufactured.

22. The precision molded product according to claim 22 is a high quality precision molded product having a low internal stress and good shape accuracy because the pressure is sufficiently uniformized during the molding. You can make expensive units and products.

23. By using the resin of claim 23, it is easy to apply a molding method having the above-described effects, and by using this molding method, a high-quality, low-cost precision molded product can be obtained. It can be molded, so that a high-performance and low-cost unit or product can be manufactured.

24. Since the precision molded product of claim 24 is a high-quality and low-cost optical element, by using this, a high-performance and low-cost optical unit or optical product can be manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view of a long lens according to Embodiments 1 and 2. FIG.

FIG. 2A is a cross-sectional view schematically showing a periphery of a cavity in a molding apparatus according to Examples 1 and 2,
(B) is the same sectional view of a comparative example (conventional example).

FIG. 3 is a diagram showing a graph of a temperature / pressure and a gold piece position control pattern in the pressure control in the molding method of the first embodiment.

FIG. 4 is a diagram showing a graph of a temperature / pressure and a gold piece position control pattern in position and speed control in the molding method according to the second embodiment.

FIG. 5 is a perspective view of a two-dimensional lens array according to a third embodiment.

FIG. 6 is a schematic exploded perspective view of a two-dimensional lens array forming apparatus according to a third embodiment.

[Explanation of symbols]

 1: Long lens 2: Long lens molding device 3: Fixed metal piece 4: Movable metal piece 5: Cavity 6: Cavity gap 7: Resin protrusion 51: Two-dimensional lens array 52: Movable metal piece 53: Fixed metal Piece 54: Resin protrusion

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 CA11 CB01 CK18 CK43 CK52 CK83 CK85 CN01 CN05 CN15 4F206 JA03 JM05 JM11 JN25 JN33 JQ81

Claims (24)

[Claims] A cavity is formed by a pair of molds or a plurality of metal pieces, and a movable mold or a movable metal piece moves to compress a resin in the cavity. In the cavity configuration of (1), there is a gap of at least 0.3 mm or more in a range of at least 50% or more of the cavity edge portion, and the resin during molding can protrude from the gap. apparatus. 2. In the cavity configuration at the time of final molding,
2. The molding apparatus according to claim 1, wherein a cavity gap through which resin can protrude exists within at least 30 mm at any position on the cavity surface corresponding to the molded article functional surface. 3. A molding method using the molding apparatus according to claim 1, wherein the molding apparatus has the following characteristics. 1) At least a part of the resin present in the cavity is heated from a temperature lower than the glass transition point of the resin to a temperature higher than the glass transition point, and then cooled again to a temperature lower than the glass transition point. 2) During or after the temperature raising step By moving a movable mold or a movable metal piece to the resin, a compressive force is applied to the resin in the cavity and the resin is held for a certain period of time to protrude from the cavity gap. 3) After the step 2), a higher compressive force is applied. Transfer the functional surface. 4. A method for molding a precision molded article according to claim 3, which is a molding method using the molding apparatus according to claim 1. 4) Reducing the compressive force after the step 3) in claim 3. 5. The maximum temperature of the resin in the cavity in the steps 2) to 4) according to claim 3 or 4, is a temperature higher by 3 ° C. to 25 ° C. than the glass transition point of the resin. The molding method according to claim 3 or 4, wherein 6. The molding method according to claim 3, wherein in the step 2) in claim 3, the pressure in the resin of 1 MPa to 20 MPa is maintained for 10 seconds or more. 7. The method according to claim 3, wherein 3M
7. The molding method according to claim 3, wherein a pressure of not less than Pa and not more than 30 MPa and a pressure higher than the highest pressure in step 2) by at least 2 MPa is maintained for 5 seconds or more. 8. The method according to claim 4, wherein in the step (4), the pressure is reduced to 1 MPa or more and 20 MPa or less and at least 2 MPa lower than the maximum pressure in the step (3). The molding method according to claim 7. 9. An amount of resin protruding from the cavity gap during the steps 2) to 4) according to claim 3 or 4 is 1% to 40% of a cavity volume at the final molding time.
9. The molding method according to claim 3, wherein: 10. A compressive force is applied to the resin in the cavity by controlling the position or speed of the movable mold or movable metal piece and moving it forward based on preset conditions. The molding method according to claim 9. 11. A resin pressure in the cavity or a force applied to the movable mold or movable metal piece is detected, and the movable mold or movable metal piece is moved based on the detected information and a preset pressure condition. By moving forward or backward,
10. The molding method according to claim 3, wherein a compressive force is applied to the resin in the cavity. 12. The method according to claim 3, wherein said movable die or movable gold piece is stopped for 10 seconds or more in said step 4) to further protrude the resin from the cavity gap to reduce the resin pressure in the cavity. The molding method according to claim 11. 13. The molding method according to claim 3, wherein in the step (4), the movable die or the movable metal piece is retracted to reduce the resin pressure in the cavity. 14. After the above steps 3) and 4), the movable mold or movable metal piece is moved to a specified position calculated from the molded product shape specification, the shrinkage ratio of the resin used, and the cavity temperature at the time of mold release. 14. The molding method according to claim 3, further comprising stopping the molded article at that position until the molded article is released. 15. The molding method according to claim 14, wherein the stop position of the movable die or the movable piece is retracted from the final position in the step (3). 16. The molding method according to claim 3, wherein the maximum value of the resin pressure in the cavity at the time of mold release is 0.3 MPa or more and 10 MPa or less. 17. The molding method according to claim 3, wherein the maximum temperature of the resin in the cavity at the time of mold release is a temperature lower by 3 ° C. to 30 ° C. than the glass transition temperature of the resin. 18. The molding method according to claim 3, wherein a compression molding is performed by inserting a resin blank having a substantially final molded product shape into said cavity. 19. The molding method according to claim 3, wherein the compression molding is performed after supplying the molten resin onto the open cavity or into the closed cavity. 20. A precision molded product characterized in that a portion or a trace of the resin protruding from the cavity with a thickness of at least 0.3 mm or more is present in at least 50% or more of a cavity edge trace. 21. A precision molded article formed by the molding method according to claim 3. 22. The precision molded article according to claim 20, wherein a portion or a trace of the resin protruding within at least 30 mm exists at any position on the functional surface of the precision molded article. 23. A precision molded product according to claim 20, wherein the material is an amorphous thermoplastic resin. 24. The precision molded article according to claim 20, wherein the precision molded article is an optical element having at least one mirror surface.