JP5347564B2 - Molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method that can easily set an appropriate holding pressure value for suppressing the occurrence of sink. <P>SOLUTION: Appropriate holding pressure for preventing the occurrence of sink in molding can be easily determined by specifying a minimum allowable holding pressure value P1 causing no sink beforehand, and determining a molding holding pressure value Px based on the minimum allowable holding pressure value P1. The molding holding pressure value Px can thereby be accurately determined while preventing the degradation of surface shape even in the case of mass production such as with multiple cavities for the same lenses OL, that is, the degradation of optical performance due to the deformation of surface shape by excessively applying the holding pressure can be prevented. Further, sudden sink can be prevented from occurring during mass production when the holding pressure value is a value causing no sink but close to a holding pressure value causing sink. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a molding method assuming a sink-free limit holding pressure value .

  As a molding method, there is a method in which a molten resin is injected into a space (cavity) formed by the first mold and the second mold to perform molding, and the molded product is released from the mold part. To do. When a resin lens is molded by such a molding method, the molten resin is cooled after entering the mold part, and therefore the resin shrinks with cooling. When the resin shrinks in this way, there is a problem that the completed lens may be sinked and the optical performance may not be satisfied. Therefore, there is a method for preventing the lens from sinking by applying sufficient pressure (holding pressure) to the resin with an injection molding machine in order to compensate for the shrinkage of the resin (see, for example, Patent Documents 1 and 2). ).

JP-A-6-31444 JP-A-7-1534

  However, in the molding method as described above, sink marks can be reduced by applying holding pressure at the time of molding. However, in the case of mass production such as multiple production in which a plurality of lenses are produced in batch, the mold corresponding to each lens of the molding die. Since the pressure value at which sink does not occur for each mold part (the limit holding pressure value without sink) is different, it is difficult to determine the limit holding pressure value without sink. Actually, the holding pressure value is set depending on the intuition of the molding engineer, and the setting condition of the holding pressure differs depending on the molding engineer even when molding the same lens. As a result, when a holding pressure higher than an appropriate holding pressure at which no sink occurs is applied, there is a problem that the optical performance deteriorates due to excessive holding pressure and deformation of the surface shape. In addition, even if molding is performed at a holding pressure value that does not cause sink marks, if the value is close to the holding pressure value of sink marks, sudden sink marks (sudden sink marks) due to sudden changes in molding conditions occur in lenses that are in mass production. There is a problem that arises.

  Resin lenses have higher shrinkage when cooled than glass lenses, and are prone to sink. In particular, BD (Blu-Ray Disc) lenses that have been developed in recent years have a larger thickness deviation ratio than conventional CDs, DVDs, etc., and tend to cause sink marks. Very detailed judgment is required compared with the prior art.

  Accordingly, an object of the present invention is to provide a molding method capable of easily setting an appropriate holding pressure value that suppresses the occurrence of sink marks.

In order to solve the above-described problem, the molding method according to the present invention includes a step of filling a resin molding space formed in a mold part constituted by a first mold and a second mold with a molten resin, during the first mold until the mold is opened and the second mold, the molding of performing pressure-holding with holding pressure value in the filled resin, and試成forming step a plurality of times with different coercive pressure value,試成forming step Based on the wavefront aberration obtained by measuring a plurality of provisional molded products obtained in Step 1, a sinkless limit holding pressure value Pα that is a holding pressure value at which the RMS value of the wavefront aberration is virtually minimized is assumed. Among the pressure values, a step of specifying a minimum allowable pressure value P1 that is close to the limit pressure limit value Pα without sink and determining a molding pressure value Px based on the minimum allowable pressure value P1, And a main molding step of molding with. Here, the limit holding pressure value without sink means the minimum holding pressure value at which sink does not occur in the molded product after filling the resin molding space and cooling, but it is hypothetical. It is not directly used in determining the molding holding pressure value.
Furthermore, in the molding method according to the present invention, the sinkless limit holding pressure value Pα is between the minimum allowable holding pressure value P1 and the lower limit deviation holding pressure value that is 4.9 MPa lower than the minimum allowable holding pressure value P1, and the minimum The allowable pressure holding value P1 is the RMS value of the wavefront aberration of the molded product when the pressure is held and molded at the minimum allowable pressure holding value P1, and the RMS of the wavefront aberration of the molded product when the pressure is held and molded at the lower limit deviation holding pressure value. When the value is SA0, the following conditional expressions (1) to (3)
SA1 <0.1λ (1)
SA0> 0.05λ (2)
3 × SA1 <SA0 <30 × SA1 (3)
And the molding holding pressure value Px is the following conditional expression (4)
P1 + 4.9 MPa ≦ Px ≦ P1 + 19.6 MPa (4)
Meet.

According to the above molding method, the minimum allowable holding pressure value that does not cause sink marks is specified in advance, and the molding holding pressure value is determined based on the minimum allowable holding pressure value, thereby preventing the occurrence of sink marks during molding. The appropriate holding pressure can be determined easily. Thereby, even in the case of mass production such as a plurality of molded products that collectively produce a plurality of lenses, it is possible to accurately determine the molding holding pressure value while preventing the deterioration of the surface shape. That is, it is possible to prevent optical performance from being deteriorated due to deformation of the surface shape due to excessive holding pressure. Moreover, although the pressure holding value does not cause sink marks, sudden sink marks (sudden sink marks) that occur during mass production when close to the pressure holding value at which sink marks occur can be prevented. Furthermore, by holding and molding with a holding pressure value within a certain range, it is possible to prevent the occurrence of sink marks and to maintain the heat resistance of the molded product, that is, the ability to maintain the characteristics against heating.
In particular, since the minimum allowable holding pressure value P1 satisfies the conditions (1) to (3) for SA1 and SA0, the sinkless limit holding pressure is set to the minimum allowable holding pressure value corresponding to SA1. , It can be set to exist between the lower limit deviation holding pressure value corresponding to SA0. That is, it is possible to appropriately specify the minimum allowable holding pressure value. Further, when the molding holding pressure value Px satisfies the conditional expression (4), the molding holding pressure value can be reliably determined while preventing sink marks.

  In another aspect of the present invention, the minimum allowable holding pressure value is specified based on spherical aberration among the wavefront aberrations of the temporary molded product. In this case, the minimum allowable pressure value can be uniformly determined by specifying the minimum allowable pressure value based on the spherical aberration. The spherical aberration is for evaluating the performance of the lens, and is one of the evaluation items when the wavefront aberration is measured by an interferometer.

  In yet another aspect of the present invention, the molded article is a lens having at least one convex shape. In this case, it can be set as the convex lens which does not produce sink marks.

  In still another aspect of the present invention, the molded article is a lens having an NA of 0.7 or more. This type of lens is easily affected by the molding holding pressure value, but by setting the above-described molding holding pressure value, the lens as a molded product obtained in the main molding process can be made highly accurate.

In still another aspect of the present invention, when the molding holding pressure value is Px and the minimum allowable holding pressure value is P1, the following conditional expression (5)
P1 + 4.9 MPa ≦ Px ≦ P1 + 14.7 MPa (5)
Meet. In this case, it is possible to reliably determine a molding holding pressure value that can prevent oversucking pressure and sudden sinking while preventing sinking.

It is a block diagram explaining a shaping | molding system. It is a front view explaining a shaping | molding apparatus. It is a sectional side view explaining the structure of the shaping die of this embodiment. It is an expanded sectional view of the molding die of FIG. (A) is sectional drawing of the molded article shape | molded by a shaping die, (B) is a sectional side view of a lens. It is a front view explaining an example of a lens measuring device. It is a flowchart explaining a trial molding process and a main forming process. It is a flowchart explaining a shaping | molding holding pressure value determination process. It is a figure which shows the relationship between holding pressure and the RMS value of spherical aberration.

Hereinafter, a molding method according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the molding system for performing the molding method of the present embodiment includes a molding device 100, a lens measurement device 200, and a measurement processing device 300.

  As shown in FIG. 2, the molding apparatus 100 of the present molding system includes an injection molding machine 10 that is a main body part that performs injection molding to produce a molded product MP, and an attached part that takes out the molded product MP from the injection molding machine 10. And a control device 30 for comprehensively controlling the operation of each part constituting the molding device 100.

  The injection molding machine 10 includes a fixed platen 11, a movable platen 12, a mold clamping plate 13, an opening / closing drive device 15, and an injection device 16. The injection molding machine 10 clamps the molding die 40 by sandwiching a molding die 40 composed of a movable die 42 and a fixed die 41 between the movable platen 12 and the fixed platen 11. Allows molding. Here, in the injection molding machine 10, mold opening and mold closing are in the horizontal direction.

  The fixed platen 11 is fixed to the center of the support frame 14 so as to face the movable platen 12, and supports the take-out device 20 on the upper part thereof. The stationary platen 11 detachably supports the stationary mold 41. Note that the fixed platen 11 is fixed to the mold clamping plate 13 via a tie bar so that it can withstand the pressure of mold clamping during molding.

  The movable platen 12 is supported by a slide guide 15a so as to be movable back and forth with respect to the fixed platen 11. The movable platen 12 detachably supports the movable mold 42. The movable platen 12 is provided with an ejector 50 on the back surface thereof. The ejector 50 can push out a runner portion (not shown) of the molded product MP in the movable mold 42 to the fixed mold 41 side by the eject pin 51, thereby enabling transfer by the take-out device 20.

  The mold clamping machine 13 is fixed to the end of the support frame 14. The mold clamping machine 13 supports the movable board 12 from the back via the power transmission part 15d of the opening / closing drive device 15 at the time of mold clamping.

  The opening / closing drive device 15 includes a slide guide 15a, a power transmission unit 15d, and an actuator 15e. The slide guide 15a supports the movable platen 12 and enables a smooth reciprocating movement in the advancing / retreating direction of the movable platen 12 with respect to the fixed platen 11. The power transmission unit 15 d expands and contracts by receiving a driving force from an actuator 15 e that operates under the control of the control device 30. As a result, the movable platen 12 moves toward and away from the fixed platen 11 and moves freely. As a result, the fixed platen 11 and the movable platen 12 move toward and away from each other, and the fixed die 41 is movable. Mold clamping and mold opening with the mold 42 are performed.

  The injection device 16 includes a cylinder 16a, a raw material reservoir 16b, a screw 16c, and a resin injection end 16d. The injection device 16 operates at an appropriate timing under the control of the control device 30, and can discharge the molten resin from the resin injection end 16d in a temperature-controlled state. The injection device 16 can detachably connect the resin injection end 16d of the cylinder 16a to the sprue portion SP (see FIG. 3) of the fixed platen 11, and is movable with the fixed mold 41 via the fixed platen 11. The molten resin can be supplied to the flow path portion FC communicating with the mold space CV (see FIG. 3) formed with the mold 42 being clamped at a desired timing.

  The temperature adjusting device 17 is a part that adjusts the temperature of the molds 41 and 42 of the injection molding machine 10. The temperature adjustment device 17 has a temperature adjustment circuit, and the temperature of the fixed mold 41 and the movable mold 42 can be adjusted. Specifically, for example, the fixed mold 41 and the movable mold 42 are heated to a necessary temperature by supplying a temperature adjusting medium to a fluid circulation path provided in the fixed platen 11 and the movable platen 12. The temperature may be adjusted using a heater or the like without using a medium.

  The take-out device 20 includes a hand 21 that can hold the molded product MP and a three-dimensional drive device 22 that moves the hand 21 three-dimensionally. The take-out device 20 operates at an appropriate timing under the control of the control device 30. The molded product MP remaining in the movable die 42 after the fixed die 41 and the movable die 42 are separated from each other and opened. It has a role of gripping and carrying it out.

  The control device 30 includes an opening / closing control unit 31, an injection device control unit 32, an ejector control unit 33, and a take-out device control unit 34. The opening / closing control unit 31 enables the molds 41 and 42 to be clamped and opened by operating the actuator 15e. The injection device controller 32 causes the resin to be injected at a desired pressure into the mold space CV formed between the molds 41 and 42 by operating the screw 16c and the like. In addition, the inside of the mold space CV is held at a constant holding pressure value during holding after resin filling. In addition, as will be described later, in the trial molding process and the main molding process, a holding pressure value corresponding to each process is appropriately set. The ejector control unit 33 operates the ejector 50 to push out the molded product MP remaining in the movable mold 42 when the mold is opened from the movable mold 42. The take-out device control unit 34 operates the take-out device 20 to grip the molded product MP remaining in the movable mold 42 after mold opening and mold release and carry it out of the injection molding machine 10.

  FIG. 3 is a cross-sectional view illustrating the structure of the molding die 40 in the molding apparatus 100 shown in FIG. The illustrated mold 40 includes a fixed mold 41 and a movable mold 42. The fixed mold 41 and the movable mold 42 can be opened and closed with the parting line PL as a boundary.

  As shown in FIG. 3, a mold space which is a resin molding space for molding the lens OL shown in FIG. 5B by performing mold clamping with a fixed mold 41 and a movable mold 42. A CV is formed, and a flow path portion FC for supplying resin to each mold space CV is formed. The mold space CV includes a main body space CV1 sandwiched between a pair of optical transfer surfaces S1 and S2, and a flange space CV2 surrounded by a pair of peripheral transfer surfaces S3 and S4. Further, the flow path portion FC is configured by a sprue portion SN, a runner portion RN, and a gate portion GN of the molded product MP, a runner portion RP, and a gate portion GP. Although not shown in the drawing, the molded product MP injection-molded by the molding die 40 includes a plurality of lenses OL, and the resin filling space corresponding to the molded product MP is formed from the sprue portion SP. The runner portion RP is branched into a plurality of portions, and the mold space CV communicates with the leading end portion of each branched runner portion RP via the gate portion GP. Each runner portion RP, each gate portion GP, and each mold space CV are arranged at equal distances from the center of each sprue portion SP.

  A mold space CV, which is a space sandwiched between both molds 41 and 42, corresponds to the shape of a lens OL (see FIG. 5B) as an optical element of the molded product MP. The lens OL is made of resin, and includes a center portion OLa as an optical function portion having an optical function, and an annular flange portion OLb extending from the center portion OLa in the outer diameter direction. The center portion OLa corresponds to the main body space CV1, and the flange portion OLb corresponds to the flange space CV2. The lens OL is an objective lens for an optical pickup device having an NA of 0.70 or more, for example, and has a convex shape with a high thickness deviation ratio (a state in which the thickness of the optical element has changed abruptly). In the case of this embodiment, the lens OL is compatible with BD, DVD, and CD. For example, the lens OL is a lens that satisfies NA of 0.85 or more for a light beam having a wavelength for BD.

  As shown in FIG. 4, the fixed mold 41 includes a circular optical transfer surface S1 corresponding to the optical surface OS1 of the lens OL and a flange portion FL1 of the lens OL on the mold surface facing the movable mold 42. The annular peripheral transfer surface S3 that surrounds the outer periphery of the optical transfer surface S1, the gate recess S5 that corresponds to the gate portion GP, and the groove shape that corresponds to the runner portion RP Runner recess S7. Further, a sprue portion SP for injecting resin is formed in the center of the fixed mold 41 (see FIG. 3).

  As in the case of the fixed mold 41, the movable mold 42 has a circular optical transfer surface S2 that is a portion corresponding to the optical surface OS2 of the lens OL on the mold surface facing the fixed mold 41, and the lens OL. A portion corresponding to the flange portion FL2, an annular peripheral transfer surface S4 surrounding the outer periphery of the optical transfer surface S2, a gate recess S6 corresponding to the gate portion GP, and a portion corresponding to the runner portion RP. A groove-like runner recess S8 is provided.

  As shown in FIG. 6, the lens measuring device 200 of the present molding system includes an interference measuring device that measures the wavefront aberration of the lens ML to be measured using interference. Note that the test lens ML as a measurement target is a lens OL (see FIG. 5B) separated from the molded product MP molded by the molding apparatus 100 of FIG.

  The interferometer shown in the figure is composed of a Twiman-Green type interferometer. As an optical system portion, a laser diode 61, a collimator lens 62, a beam splitter 64, a reflection source 65, a reference plane mirror 66, and a reference A surface driving unit 67, an imaging lens 68, and an imaging device 69 are provided. In addition, this interference measurement apparatus includes a control device 77 that comprehensively controls the operation of the optical system portion. The control device 77 includes peripheral devices such as a laser driver for the laser diode 61, an image processing device for the imaging device 69, and a drive circuit for the reference plane drive unit 67 in addition to a computer for arithmetic processing. Note that the wavelength of the measurement light emitted from the laser diode 61 can be set to, for example, 404 nm, 655 nm, 785 nm, and the like, and the wavelength of the measurement light can be changed by switching the laser diode 61.

  The illumination light from the laser diode 61 is collimated by the collimator lens 62, then branched by the beam splitter 64, and enters the reference plane mirror 66 and the lens ML to be measured held by the holder 71. The illumination light that has passed through the test lens ML is reflected by the reflection source 65, travels backward along the optical axis OA, and enters the beam splitter 64 again as inspection light. On the other hand, the reference light reflected by the reference plane mirror 66 travels back along the optical path along the optical axis OA, and is synthesized by the beam splitter 64 with the inspection light that has passed through the lens ML to be tested. The interference light combined by the beam splitter 64 enters the imaging device 69 via the imaging lens 68. At this time, the reference plane mirror 66 is displaced in the direction of the optical axis OA by the reference plane driving unit 67, so that a so-called fringe scan is performed, and an image signal output from the imaging device 69 is analyzed in synchronization with the scan and is referred to. With reference to the flat mirror 66 and the like, a change in wavefront due to the lens ML to be measured is measured. That is, wavefront aberration reflecting a deviation from the design value of the optical surface and refractive index of the lens ML to be measured can be obtained as a measured value (specifically, root mean square (RMS)). Note that the wavefront aberration of the test lens ML includes spherical aberration, astigmatism, coma aberration, and the like. However, in this embodiment, when the test lens ML is a convex lens, a shape change due to sinking is caused at the top of the lens. Considering that it is likely to appear as a projection deficiency, the performance evaluation of the lens ML to be measured is mainly performed using spherical aberration.

  In the molding system shown in FIG. 1, the measurement processing device 300 is configured by a computer that processes and stores data. The measurement processing apparatus 300 is managed by a molding engineer.

  The measurement processing device 300 analyzes the measurement result obtained by the lens measurement device 200, transmits the processing result to the injection device control unit 32 of the molding device 100, and transmits feedback information specifying the molding conditions. That is, in the measurement processing device 300, the molding conditions when the lens OL is trial-molded or main-molded by the molding device 100, and the spherical surface obtained by measuring the obtained lens OL, that is, the test lens ML, by the lens measuring device 200. It has a function of making it possible to contrast with aberrations and assisting a molding engineer in setting and correcting molding conditions by the molding apparatus 100. Specifically, the minimum allowable pressure holding value P1 related to the lens OL, that is, the molding die 40 is specified from the spherical aberration of the plurality of lenses OL obtained by the plurality of trial moldings by the processing in the measurement processing device 300. A molding holding pressure value Px suitable for the molding die 40 can be determined. A processing method in the measurement processing apparatus 300 will be described later.

  7 and 8 are flowcharts conceptually illustrating the operation of the present molding system, that is, the molding method of the present embodiment.

  First, a trial molding process is performed as a pre-stage for specifying the minimum allowable holding pressure value. The basic molding process of the molded product MP other than the holding pressure value is the same as the main molding process described later.

  First, as shown in FIG. 7, the temperature adjusting device 17 of the molding apparatus 100 is operated to heat both molds 41 and 42 to a temperature suitable for molding (step S10).

  Next, the opening / closing drive device 15 is operated to advance the movable platen 12 to start mold closing (step S11). By continuing the closing operation of the opening / closing drive device 15, the movable platen 12 moves to the fixed platen 11 side to the die contact position where the fixed die 41 and the movable die 42 come into contact with each other, and the die closing is completed. By further continuing the closing operation of the device 15, mold clamping is performed to clamp the fixed mold 41 and the movable mold 42 with necessary pressure (step S12).

  After the mold clamping, the injection device 16 is operated in the injection molding machine 10 to apply the heated molten resin to the mold space CV between the clamped fixed mold 41 and the movable mold 42 and the necessary pressure. Injection is performed (step S13). As a result, a filling process is performed in which the mold space CV between the clamped fixed mold 41 and the movable mold 42 is filled with resin. For example, PC (polycarbonate), POM (polyacetal), or COP (cycloolefin polymer) is used as the resin.

  After the filling process, the injection molding machine 10 keeps the resin pressure in the mold space CV at a necessary level (step S14). At this time, an appropriate holding pressure value is set.

  In the molding die 40, the mold space CV and the flow path portion FC are appropriately heated by the temperature adjusting device 17, and the molten resin supplied from the injection device 16 is gradually cooled. It waits for solidification to be completed (step S15).

  After completion of molding, the mold clamping is finished, and the opening / closing drive device 15 is operated to perform mold opening for retracting the movable platen 12 (step S16). Along with this, the movable mold 42 moves backward, and the fixed mold 41 and the movable mold 42 are separated. As a result, the molded product MP, that is, the lens OL is released from the fixed mold 41 while being held by the movable mold 42.

  Next, in the injection molding machine 10, the ejector 50 is operated to eject the molded product MP (step S17). Specifically, the sprue SN of the molded product MP and the like are released from the movable mold 42 by the ejection by the eject pin 51.

  After the molded product MP is released from the movable mold 42, the take-out device 20 is operated, and the proper position of the projected molded product MP is gripped by the hand 21 and carried out to the outside (step S18).

  The molded product MP is cut at the gate portion GN, and the lens OL is separated from the molded product MP (step S19).

  The trial molding process as described above is repeated a plurality of times by setting the holding pressure value to a different value and matching other conditions. That is, it is possible to obtain a large number of lenses OL formed by changing only the holding pressure value.

  After the trial molding process, a process of specifying the minimum allowable pressure holding value and determining the molding pressure holding value is performed based on a large number of lenses OL molded in the trial molding process.

  First, as shown in FIG. 8, the lens OL is set as the lens ML to be measured at the aberration measurement position on the holder 71 of the lens measuring apparatus 200 (step S20). Note that the moving work is assumed to be performed by an operator, but automatic conveyance can also be performed.

  Next, the lens measuring apparatus 200 is operated to perform wavefront measurement on the lens ML to be tested, that is, the lens OL, and to measure wavefront aberration including spherical aberration and the like of the lens OL (step S21). Specifically, the control device 77 emits measurement light of a specific wavelength from the laser diode 61, analyzes the image signal from the imaging device 69 while displacing the reference plane mirror 66 by the reference surface driving unit 67, and each lens. Obtain the RMS value of wavefront aberration for OL.

  The above steps S20 and S21 are repeated for each lens OL obtained in the trial molding process, and the wavefront aberration of the lens OL under each holding pressure setting condition is measured. In the present embodiment, in particular, spherical aberration among wavefront aberrations is used to evaluate the shape accuracy of the optical surface of the lens OL for setting the pressure holding setting condition.

  Next, in the measurement processing apparatus 300, the minimum allowable holding pressure value P1 is specified (step S22) and the forming holding pressure value Px is determined (steps S23 and S24) from the measurement result in step S21.

  The specification of the minimum allowable holding pressure value P1 utilizes the fact that the spherical aberration of the lens OL of the molded product MP mainly changes when the holding pressure value is changed. For a general objective lens, the relationship between the RMS value of spherical aberration and the pressure holding value is as shown in FIG.

As shown in FIG. 9, there is a hypothetical holding pressure value that does not cause sinking, that is, a non-sinking limit holding pressure value Pα among certain holding pressure values. That is, the limit pressure value Pα without sink is a pressure value at which the RMS value of the spherical aberration of the lens OL after molding is minimized. When the holding pressure value is increased from the sinkless limit holding pressure value Pα, the RMS value of the spherical aberration of the lens OL after molding increases gradually as the holding pressure value increases. In addition, as the pressure holding value is lowered from the limit holding pressure value Pα without sink, a sink occurs on the lens OL surface, so that the RMS value of the spherical aberration of the lens OL after molding increases rapidly as the pressure holding value decreases. To do. Using the phenomenon in which the RMS value of the spherical aberration rapidly increases, the minimum allowable holding pressure value P1 is obtained from the measurement result of the RMS value of the spherical aberration with respect to the plurality of lenses OL held and molded with a plurality of holding pressure values set in advance. Is specified (step S22). The minimum allowable holding pressure value P1 is the lower limit deviation holding value that is 4.9 MPa (50 kgf / cm ² ) lower than the minimum allowable holding pressure value P1 by setting SA1 as the spherical aberration RMS value when holding and molding at the minimum allowable holding pressure value P1. Conditional expressions (1) to (3) below when the RMS value SA0 of spherical aberration in the case of holding and molding with a pressure value P0 is used.
SA1 <0.1λ (1)
SA0> 0.05λ (2)
3 × SA1 <SA0 <30 × SA1 (3)
It satisfies. When the conditional expressions (1) to (3) are satisfied, the sinkless limit holding pressure value Pα is assumed to be between the minimum allowable holding pressure value P1 and the lower limit deviation holding pressure value P0. The minimum allowable holding pressure value P1, the lower limit deviation holding pressure value P0, and the sinkless limit holding pressure value Pα are different depending on the type of resin, the shape of the mold space CV, and the like.

After specifying the minimum allowable holding pressure value P1, the range of the forming holding pressure value Px is determined (step S23). For example, the following conditional expression (4)
P1 + 4.9 MPa ≦ Px ≦ P1 + 19.6 MPa (4)
(Step S24). The molding holding pressure value Px satisfying the conditional expression (4) is a holding pressure equal to or larger than the limit holding pressure value Pα without sink, and can be molded so as to prevent the sinking of the lens OL after molding. It becomes.

As described above, the molding pressure value Px is set within an allowable range from the lower limit allowable pressure value P1 + 4.9 MPa (P1 + 50 kgf / cm ² ) to the upper limit allowable pressure value P1 + 19.6 MPa (P1 + 200 kgf / cm ² ). Is done.

Further, from the viewpoint of further emphasizing the prevention of deformation of the surface shape of the lens OL and the occurrence of sudden sink marks, in step S23, the range of the molding holding pressure value Px is set to, for example, the following conditional expression (5):
P1 + 4, 9 MPa ≦ Px ≦ P1 + 14.7 MPa (5)
It is better to decide to satisfy. That is, the molding pressure value Px is set within an allowable range from the lower limit allowable pressure value P1 + 4.9 MPa (P1 + 50 kgf / cm ² ) to the upper limit allowable pressure value P1 + 14.7 MPa (P1 + 150 kgf / cm ² ). .

When the molding holding pressure value Px is selected from the holding pressure values within the allowable range P1 + 4.9 to P1 + 19.6 MPa as described above, an automatic process such as selecting an intermediate value within the allowable range is also possible. Further, it is also possible for the molding engineer to appropriately select a numerical value in accordance with the situation within an allowable range.
The molding holding pressure value is a pressure value set in the molding machine and is different from an actual pressure value applied to the lens portion of the molded product. Therefore, when the present technology is used for in-mold pressure control or the like, it is necessary to set the pressure value in consideration of the correlation between the in-mold pressure value and the set pressure value of the molding machine.

  After the molding holding pressure value Px is determined, the processing result is transmitted to the injection device control unit 32 of the molding apparatus 100 by the measurement processing device 300, and the molding holding pressure value Px is set as the holding pressure value in the main molding process. .

  In the main molding step, as described above, the molding steps (steps S10 to S19) similar to the trial molding step are performed except for the holding pressure value. That is, in the main molding step, the mold space CV after resin filling is held at the molding pressure value Px at the time of holding pressure (step S14).

  Hereinafter, specific examples of the present embodiment will be described.

Table 1 shows the spherical aberration, the occurrence of sink marks, and the state of excessive holding pressure of the lens OL formed by holding at each holding pressure value. In Table 1, regarding the evaluation of the occurrence of sink marks, when the sink rate is 0.001% or less, it is judged as “◎”, and when it is 0.1% or less, it is judged as “◯”, and several tens of percent The following cases are determined as “Δ”, and the case of approximately 100% is determined as “x”. Further, regarding the evaluation of the over-holding pressure state, when the spherical aberration is 0.01λ or less, it is determined as “◎”, and when it is 0.01λ to 0.02λ, it is determined as “◯”, and 0.02λ to The case of 0.03λ is determined as “Δ”, and the case of 0.03λ or more is determined as “x”. The molding holding pressure values Px, P1 + 50, P1 + 100, P1 + 150, P1 + 200, and P1 + 250 kgf / cm ² correspond to P1 + 4.9, P1 + 9.8, P1 + 14.7, P1 + 19.6, and P1 + 24.5 MPa, respectively.

As can be seen from Table 1, the molded retaining pressure value Px is P1 + 4.9MPa (P1 + 50kgf / cm 2) or more P1 + 19.6MPa (P1 + 200kgf / cm 2) If you coercive pressure molding below, sink into the lens OL does not occur. Further, when molding is carried out by holding pressure at a holding pressure value Px of P1 + 4.9 MPa (P1 + 50 kgf / cm ² ) or more and P1 + 14.7 MPa (P1 + 150 kgf / cm ² ) or less, it is possible to prevent characteristic deterioration caused in the lens OL due to overholding pressure. .

  Moreover, when it shape | molds by hold | maintaining pressure at P1 + 2.45MPa, the incidence rate of a sudden sink is 0.1% or less. On the other hand, when molding is performed by holding at P1 + 9.8 MPa, the incidence of sudden sink marks is 0.001% or less.

  According to the molding method of the embodiment described above, the minimum allowable holding pressure value P1 that does not cause sink marks is specified in advance, and an allowable range set based on the minimum allowable holding pressure value P1 (for example, P1 + 4.9 to P1 + 19.6 MPa). ), It is possible to easily determine an appropriate holding pressure that prevents the occurrence of sink marks during molding. Thereby, even if it is a shape where the central part of the molded product MP is thick and easily sinks like a convex lens shape, it is possible to mold the molded product MP that is unlikely to cause sinks.

  Conventionally, when examining the molding holding pressure value for molding a molded product that does not cause sink marks, it has been common to judge sensuously by looking at the bending of the interference fringes when using an interferometer. If the change tendency of the RMS value of spherical aberration is used as in the present embodiment, the molding holding pressure value Px can be easily determined. Thereby, even in the case of mass production such as a plurality of lenses OL, the molding holding pressure value Px can be accurately determined from the viewpoint of ensuring the prevention of sink marks.

  Conventionally, in order to avoid the occurrence of sink marks, it is possible to apply a higher holding pressure than the limit holding pressure without sink by applying a high holding pressure without considering the relationship between the holding pressure value and spherical aberration. There were many. If the molding holding pressure value Px is determined on the basis of the minimum allowable holding pressure value P1 in which sink marks are unlikely to occur as in the present embodiment, the optical performance is prevented from being deteriorated due to deformation of the surface shape due to excessive holding pressure. be able to. Moreover, although the pressure holding value does not cause sink marks, sudden sink marks (sudden sink marks) that occur during mass production when close to the pressure holding value at which sink marks occur can be prevented.

  Moreover, although the sink-free limit holding pressure value Pα differs depending on the shape of the resin and the mold space CV, the molding holding pressure value Px can be easily determined because the minimum allowable holding pressure value P1 is used as a reference. it can.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above-described embodiment, the present invention may be used not only when two or four lenses OL are molded from one molded product MP, but also when four or more lenses OL are molded.

  Even if the resin material of the lens OL is changed, the minimum allowable holding pressure value P1 is specified in the same manner as in the embodiment, and the allowable range set based on the minimum allowable holding pressure value P1 (for example, P1 + 4.9 to P1 + 19.6 MPa). By determining the molding holding pressure value Px in (), it is possible to mold the lens OL that is unlikely to cause sink marks.

  Moreover, in the said embodiment, the shape of mold space CV provided in the shaping die 40 etc. which are comprised with the fixed metal mold | die 41 and the movable metal mold | die 42 is not restricted to what is illustrated, It can be made into various shapes. That is, the shape of the mold space CV is merely an example, and can be appropriately changed according to the use of the lens OL. For example, it can be used when molding an imaging lens for a portable camera.

  Recently, imaging lenses, portable camera lenses, and the like have become as large as pickup lenses, and the molding method of the present invention can be applied to molding optical components such as imaging lenses. The same optical performance improvement effect as that of the pickup lens can be obtained. Furthermore, the same effect can be obtained when the present invention is applied to molding precision products other than optical components.

  In the above embodiment, the injection molding machine 10 may be, for example, a hydraulic type or an electric type as long as it can open and close the molding die 40 and the like.

  DESCRIPTION OF SYMBOLS 10 ... Injection molding machine, 11 ... Fixed board, 12 ... Movable board, 15 ... Opening / closing drive device, 16 ... Injection device, 17 ... Temperature control device, 20 ... Extraction device, 30 ... Control device, 40 ... Molding die, 41 ... fixed mold, 42 ... movable mold, 100 ... molding device, 200 ... lens measuring device, 300 ... measurement processing device, CV ... mold space, FC ... flow path part, GP ... gate part, RP ... runner part, SP ... Sprue part, OL ... Lens, MP ... Molded product, GN ... Gate part, RN ... Runner part, SN ... Sprue part, PL ... Parting line, Pα ... Sinkless limit holding pressure value, P0 ... Lower limit deviation holding pressure value , P1 ... Minimum allowable holding pressure value

Claims (5)

After filling the melted resin in the resin molding space formed in the mold part constituted by the first mold and the second mold, until the mold opening between the first mold and the second mold During the time, a molding process for holding pressure at a holding pressure value in the filled resin, a test molding step for performing a plurality of times at different holding pressure values,
Based on the wavefront aberration obtained by measuring a plurality of provisional molded products obtained in the trial molding step, a sinkless limit pressure holding value Pα that is a pressure holding value at which the RMS value of the wavefront aberration is virtually minimized is assumed. A step of identifying a minimum allowable pressure value P1 close to a sinkless limit pressure value Pα among the different pressure values, and determining a molding pressure value Px based on the minimum allowable pressure value P1 ;
A main molding step of molding under the molding holding pressure value;
Equipped with a,
The sinkless limit holding pressure value Pα is between the minimum allowable holding pressure value P1 and a lower limit deviation holding pressure value that is 4.9 MPa lower than the minimum allowable holding pressure value P1.
The minimum allowable holding pressure value P1 is the RMS value of the wavefront aberration of the molded product when holding and molding at the minimum allowable holding pressure value P1, and the molded product when holding and molding at SA1 and the lower limit deviation holding pressure value. When the RMS value of the wavefront aberration is SA0, the following conditional expressions (1) to (3)
SA1 <0.1λ (1)
SA0> 0.05λ (2)
3 × SA1 <SA0 <30 × SA1 (3)
The filling,
The molding holding pressure value Px is defined by the following conditional expression (4)
P1 + 4.9 MPa ≦ Px ≦ P1 + 19.6 MPa (4)
The molding method characterized by satisfy | filling . The molding method according to claim 1 , wherein the minimum allowable holding pressure value is specified based on spherical aberration among wavefront aberrations of the provisional molded product. The molded article, forming method according to claim 1 or 2, characterized in that at least one of a lens convex. The molded article, forming method according to claim 1, characterized in that a NA0.7 or more lenses. When the molding holding pressure value is Px and the minimum allowable holding pressure value is P1, the following conditional expression (5)
P1 + 4.9 MPa ≦ Px ≦ P1 + 14.7 MPa (5)
The molding method according to any one of claims 1 to 4 , wherein:

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