JP5747188B1 - Injection molding apparatus and injection molding method - Google Patents

Abstract

Provided is an injection molding apparatus capable of molding an optical element having a subwavelength structure on a surface. The injection molding apparatus includes a first mounting plate (101), an elastic member (105), a first mold member (109) attached to the first mounting plate via at least the elastic member, Two mounting plates (125), and a second mold member (113) mounted on the second mounting plate directly or via another member, and a distance between the first and second mounting plates The first mold member resists the opposing force of the elastic member by the pressure of the resin injected into the cavity formed by the first and second mold members. When the first mounting plate moves toward the second mounting plate, the first mounting plate moves together with the first mounting plate. And at least one of the first and second mold members has a sub-wavelength structure Including the surface of the mold.

Description

  The present invention relates to an injection molding apparatus and an injection molding method used for injection compression molding.

  In an injection molding apparatus, a molten resin is filled in a cavity of a mold apparatus, cooled, and solidified to form a molded product. The mold apparatus is composed of a plurality of mold members forming a cavity, and the mold clamping apparatus makes the mold closing, mold clamping, and mold opening by bringing the plurality of mold members into contact with each other or taking a distance. It is configured to be able to do. Here, the mold closing means a state from a state where the distance between the mold members is increased to a time when the parting surface of the mold member comes into contact. The mold clamping means a state in which a clamping force is applied to the mold member by bringing the parting surface of the mold member into contact.

  In order to improve the quality of a molded product, an injection molding compression method has been developed in which a resin is filled in a state where the cavity is slightly enlarged, and then the resin filled in the cavity is compressed. In the Low Links method, one of the injection molding compression methods, before injecting the molten resin into the cavity, the volume of the cavity is made larger than the volume of the molded product, and the molten resin is injected to melt into the cavity. After filling the resin, the volume of the cavity is reduced and the molten resin in the cavity is pressurized and compressed. In this case, in order to prevent the resin from leaking into the gap between the parting surfaces and generating burrs, the parting surfaces are configured to be pressed against each other by a hydraulic cylinder or a spring. The above-mentioned Low Links method is used for molding optical elements such as lenses that require high accuracy (Patent Document 1).

  On the other hand, for the purpose of preventing reflection, a method of forming a fine grating having a period equal to or shorter than the wavelength of visible light on the surface of a lens instead of a conventional multilayer film has been developed (Patent Document 2). Such a fine grating having a period equal to or shorter than the wavelength of visible light is called a sub-wavelength structure (SWS).

  By the way, when molding a lens equipped with SWS on the surface by the Low Links method, after the volume of the cavity is larger than the volume of the molded product, after injecting the molten resin and filling the cavity with the molten resin, When pressurizing and compressing the molten resin in the cavity by reducing the volume of the cavity, there is a problem in that the SWS corresponding portion of the mold surface cannot be transferred to the molten resin with high accuracy. For this reason, in order to transfer the SWS-corresponding portion of the mold surface to the resin, for example, it is necessary to install an additional heating device or the like in the injection molding device, and the molding device and the molding process must be complicated. There wasn't.

JP 2008-279784 A JP 2001-272505 A

  Therefore, there is a need for a simple injection molding apparatus and a simple injection molding method used for injection compression molding that can mold an optical element having a SWS on its surface.

  An injection molding apparatus according to a first aspect of the present invention includes a first mounting plate, an elastic member, a first mold member attached to the first mounting plate via at least the elastic member, and a second And a second mold member attached to the second attachment plate directly or via another member, and the distance between the first attachment plate and the second attachment plate The first mold member is a resin injected into a cavity formed by the first mold member and the second mold member. When the first mounting plate moves in the direction of the second mounting plate against the opposing force of the elastic member by the pressure of the elastic member, the first mounting plate moves in the direction of the second mounting plate. The first mold member and the second mold are configured to move together with the first mounting plate. At least one of the wood comprises a mold surface for the sub-wavelength structure.

  According to the injection molding apparatus of this aspect, a pressure corresponding to a force equal to or greater than the opposing force of the elastic member is applied to the molten resin while the molten resin is filled in the cavity. Accordingly, if the opposing force of the elastic member is appropriately determined, at least one of the first mold member and the second mold member is used for the sub-wavelength structure while the cavity is filled with the molten resin. The shape of the mold can be transferred to the molten resin. For this reason, before the skin layer of molten resin grows, transfer to the molten resin having a fine structure can be performed with high accuracy.

  According to the first embodiment of the first aspect of the present invention, the elastic member is attached to the concave portion of the surface of the first attachment plate or the other member facing the first mold member. When the first mounting plate moves in the direction of the second mounting plate after injection, the first mold member comes into contact with the periphery of the concave portion of the surface so that the first mounting plate is moved. It is configured to move together with the plate.

  According to the present embodiment, with the simple structure described above, the first mold member is made to resist the opposing force of the elastic member by the pressure of the resin injected into the cavity. When the first mounting plate moves in the direction of the second mounting plate, the first mounting plate can move integrally with the first mounting plate.

  According to the second embodiment of the first aspect of the present invention, the elastic member is a spring.

  According to the present embodiment, a desired counter force can be easily realized by selecting a spring having a predetermined spring constant.

  An injection molding method according to a second aspect of the present invention includes a first attachment plate, an elastic member, a first mold member attached to the first attachment plate via at least the elastic member, and a second And a second mold member attached to the second attachment plate directly or via another member, and the distance between the first attachment plate and the second attachment plate An injection compression molding method using an injection molding apparatus configured to be able to change the temperature of the molten metal injected during injection into a cavity formed by the first mold member and the second mold member While the volume of the cavity is increased by shrinking the elastic member by the pressure of the resin, the shape of the fine structure portion of the first mold member corresponding to the sub-wavelength structure is transferred to the molten resin. Performing the first step after the injection The plate includes a step of compressing the resin in the cavity is moved in a direction to reduce the volume of the cavity of the second mounting plate together with the first mold member.

  According to the injection molding method of this aspect, the elastic member is contracted by the pressure of the molten resin injected into the cavity formed by the first mold member and the second mold member during injection. As a result, the shape of the fine structure portion corresponding to the sub-wavelength structure of the first mold member is transferred to the molten resin while increasing the volume of the cavity. For this reason, before the skin layer of molten resin grows, transfer to the molten resin having a fine structure can be performed with high accuracy.

It is a figure which shows the structure of the injection molding apparatus by one Embodiment of this invention used for injection compression molding. It is a flowchart for demonstrating the injection compression molding method by the injection molding apparatus by one Embodiment of this invention. It is a figure which shows the state which the volume of the cavity increased sufficiently of the injection molding apparatus by one Embodiment of this invention. It is a figure which shows the state which contracted the hydraulic cylinder of the injection molding apparatus by one Embodiment of this invention, and made the volume of the cavity small. It is a figure which shows an example of a structure of the lens provided with SWS on the surface. It is a figure which shows the structure of the conventional injection molding apparatus used for injection compression molding. It is a flowchart for demonstrating the injection compression molding method by the conventional injection molding apparatus. It is a figure which shows the state which step S2050 completed of the conventional injection molding apparatus.

  FIG. 6 is a diagram showing a configuration of a conventional injection molding apparatus 100A used for injection compression molding. The injection molding apparatus 100A includes a first mounting plate 101, a first receiving plate 103A, a hydraulic cylinder 107, a first mirror piece (first mold member) 109A, a first mold plate 111, and a second mirror surface. It includes a piece (second mold member) 113, a second mold plate 115, a second receiving plate 117, ejector plates 119 and 121, a spacer block 123, and a second mounting plate 125. A cavity 301 into which resin is injected is formed between the first mirror surface piece 109A and the second mirror surface piece 113. 6 and 8, the cavity 301 is indicated by hatching. The first mounting plate 101, the first receiving plate 103A, the hydraulic cylinder 107, and the first mirror surface piece 109A are connected to each other and fixed. FIG. 6 shows a state where the hydraulic cylinder 107 is extended. As the hydraulic cylinder 107 extends, the distance between the first receiving plate 103A and the first template 111 increases, and the volume of the cavity 301 increases.

  FIG. 7 is a flowchart for explaining an injection compression molding method by the conventional injection molding apparatus 100A.

  In step S2010 of FIG. 7, mold clamping is started. Specifically, the following operations are performed in a state where the first template 111 and the second template 115 are brought into contact with each other through a parting line (PL).

  In step S2020 of FIG. 7, the hydraulic cylinder 107 is extended to move the first mounting plate 101, the first receiving plate 103A, and the first mirror piece 109A so as to increase the volume of the cavity 301. FIG. 6 is a diagram illustrating a state in which step S2020 has been completed in the conventional injection molding apparatus 100A.

  In this state, the distance between the vertex of the concave surface in contact with the cavity 301 of the first mirror surface piece 109 and the surface in contact with the cavity 301 of the second mirror surface piece 113, that is, the height of the cavity 301 is, for example, 23 .6 liters.

  In step S2030 of FIG. 7, injection is started and molten resin is injected into the cavity 301.

  In step S2040 of FIG. 7, it is determined whether the molten resin has filled the cavity 301 based on the pressure of the molten resin in the cavity 301. After the resin fills the cavity 301, the process proceeds to the next step S2050.

  In step S2050 of FIG. 7, the hydraulic cylinder 107 is contracted to move the first mounting plate 101, the first receiving plate 103A, and the first mirror piece 109A so as to reduce the volume of the cavity 301. By this operation, the molten resin in the cavity 301 is pressurized and compressed.

  FIG. 8 is a diagram showing a state in which step S2050 has been completed in the conventional injection molding apparatus 100A. The first receiving plate 103A and the first template 111 are in contact with each other, and the volume of the cavity 301 is reduced as compared with the volume shown in FIG.

  In this state, the distance between the vertex of the concave surface in contact with the cavity 301 of the first mirror surface piece 109 and the surface in contact with the cavity 301 of the second mirror surface piece 113, that is, the height of the cavity 301 is, for example, 23 It is a millimeter.

  That is, in step S2050 of FIG. 7, the hydraulic cylinder 107 is contracted so that the height of the cavity 301 is changed from 23.6 millimeters to 23 millimeters, and as a result, the molten resin filled in the cavity 301 is compressed. .

  In step S2060 of FIG. 7, the resin in the cavity 301 is cooled.

  In step S2070 of FIG. 7, mold opening is performed. Specifically, the ejector plates 119 and 121 to which the ejector pins 122 are attached are pushed up by an ejector device (not shown) to take out the molded product.

  FIG. 5 is a diagram showing an example of the configuration of a lens having a SWS on the surface. The inside of the two dotted lines is the effective range of the lens 201. In the effective range of the lens 201, SWS are formed on the surfaces A and B. In order to form these SWSs, the first specular piece 109A and the second specular piece 113 have a fine structure corresponding to these SWSs. The SWS of the lens 201 is formed by transferring the shape of the fine structure portion to the molten resin.

  By the way, in order for the shape of the fine structure portion to be transferred to the molten resin, it is necessary for the molten resin to enter the fine structure portion against the surface tension, and for this purpose, the pressure of the molten resin must be higher than a predetermined value. There is. In steps S2030 to S2040 described above, the pressure of the molten resin applied to the surfaces of the first mirror surface piece 109A and the second mirror surface piece 113 corresponds to the SWS of the surface while the cavity 301 is filled with the molten resin. The shape of the fine structure portion to be reached does not reach the predetermined value transferred to the molten resin. Therefore, the shape of the fine structure portion corresponding to the SWS of the first mirror surface piece 109A and the second mirror surface piece 113 is not transferred to the molten resin while the cavity 301 is filled with the molten resin. In step S2050, when the molten resin filled in the cavity 301 is compressed, the pressure of the molten resin applied to the surfaces of the first mirror surface piece 109A and the second mirror surface piece 113 is a microstructure corresponding to the SWS on the surface. The shape of the part reaches the predetermined value transferred to the molten resin. However, at this stage, a skin layer grows on the surface of the molten resin. As a result, since the viscosity of the resin is increased, the deformation start pressure is increased, and even when the pressure of the molten resin reaches the predetermined value, transfer to the molten resin having a fine structure is not performed with high accuracy.

  As described above, it is difficult to form the SWS of the surface A of the lens 201 by transferring the SWS corresponding portions of the first specular piece 109A and the second specular piece 113 to the resin. Therefore, it is difficult to mold the lens 201 having SWS on its surface by the conventional injection compression method shown in FIG.

  FIG. 1 is a diagram showing a configuration of an injection molding apparatus 100 according to an embodiment of the present invention used for injection compression molding. The injection molding apparatus 100 includes a first mounting plate 101, a first receiving plate 103, an elastic member 105, a hydraulic cylinder 107, a first mirror piece (first mold member) 109, a first template 111, A second mirror surface piece (second mold member) 113, a second mold plate 115, a second receiving plate 117, ejector plates 119 and 121, a spacer block 123, and a second mounting plate 125 are included. The elastic member 105 is attached between the first receiving plate 103 and the first mirror piece 109. Here, the elastic member is a member such as a spring, rubber, or cushion that contracts while generating a counter force when receiving a force from another, and returns to the original state when the force is removed. In the present embodiment, the elastic member 105 is a spring. As the elastic member 105 expands and contracts, the distance between the first receiving plate 103 and the first mirror piece 109 can change. A cavity 301 into which resin is injected is formed between the first mirror surface piece 109 and the second mirror surface piece 113. In FIG. 1, FIG. 3 and FIG. 4, the cavity 301 is indicated by hatching. The first mounting plate 101, the first receiving plate 103, and the hydraulic cylinder 107 are connected and fixed to each other.

In this embodiment, four lenses having a diameter of 60 millimeters are molded simultaneously. There are also 6 cylinders with a diameter of 50 millimeters. A pressure of 150 kg · f / cm ² is applied to each cylinder.

  Here, the side where the ejector plates 119 and 121 are installed is called a movable side, and the side where the ejector plates 119 and 121 are not installed is called a fixed side. In the present embodiment, a member described as “first” corresponds to a member on the fixed side, and a member described as “second” corresponds to a member on the movable side. In the present embodiment, the elastic member 105 coupled to the mirror piece is attached to a fixed member (first receiving plate 103). In another embodiment, the elastic member 105 coupled to the mirror piece may be attached to the movable member.

  FIG. 2 is a flowchart for explaining an injection compression molding method by the injection molding apparatus 100 according to an embodiment of the present invention.

  In step S1010 of FIG. 2, mold clamping is started. Specifically, the following operations are performed in a state where the first template 111 and the second template 115 are brought into contact with each other through a parting line (PL).

  In step S1020 of FIG. 2, the hydraulic cylinder 107 is extended so that the first mounting plate 101 and the first receiving plate 103 have a distance between the first receiving plate 103 and the first template 111. Move to a predetermined size.

  In step S1030 of FIG. 2, it is confirmed that the first mirror piece 109 is moved by the elastic member (spring) 105 so as to reduce the volume of the cavity 301. FIG. 1 is a diagram illustrating a state in which step S1030 has been completed in an injection molding apparatus 100 according to an embodiment of the present invention.

  In this state, the distance between the vertex of the concave surface in contact with the cavity 301 of the first mirror surface piece 109 and the surface in contact with the cavity 301 of the second mirror surface piece 113, that is, the height of the cavity 301 is, for example, 23 It is a millimeter.

  In step S 1040 of FIG. 2, injection is started and molten resin is injected into the cavity 301. When a predetermined amount of molten resin is injected into the cavity 301, the surface of the first mirror piece 109 in contact with the cavity 301 receives the pressure of the molten resin in the cavity 301. As a result, the elastic member (spring) 105 contracts and the first mirror piece 109 retracts in the direction of the first receiving plate 103. Here, the injection pressure of the molten resin is 0.9 megapascal (MPa).

  The reaction force of the elastic member, for example, the spring constant is determined by the molten resin applied to the surfaces of the first mirror piece 109 and the second mirror piece 113 during the injection of the molten resin, that is, during the retraction of the first mirror piece 109. Is determined so that the shape of the fine structure corresponding to the SWS on the surface exceeds a predetermined value transferred to the molten resin. Specifically, in the present embodiment, the elastic member 105 includes two springs having a spring constant of 16.1 kg · f / mm.

  By appropriately determining the spring constant as described above, the fineness of the first specular piece 109 and the second specular piece 113 is obtained while the cavity 301 is filled with the molten resin (between steps S1040 and S1050). The shape of the structural part is transferred to the molten resin.

  In step S1050 of FIG. 2, it is determined whether or not the volume of the cavity 301 is sufficiently increased by the pressure of the molten resin in the cavity 301.

  FIG. 3 is a view showing a state in which the volume of the cavity 301 is sufficiently increased in the injection molding apparatus 100 according to the embodiment of the present invention. The spring 105 attached between the first receiving plate 103 and the first mirror piece 109 contracts, and the opposing surfaces of the first receiving plate 103 and the first mirror piece 109 are in contact with each other. Here, the spring 105 is attached to the concave portion of the surface of the first receiving plate 103 that faces the first template 111, and the first receiving plate 103 has a first contracted state when the spring is contracted. The periphery of the concave portion on the surface facing the template plate 111 is configured to contact the surface of the first template plate 111.

  In this state, the distance between the vertex of the concave surface in contact with the cavity 301 of the first mirror surface piece 109 and the surface in contact with the cavity 301 of the second mirror surface piece 113, that is, the height of the cavity 301 is, for example, 23 .6 millimeters.

  In step S1060 of FIG. 2, the hydraulic cylinder 107 is contracted to move the first receiving plate 103 so that the distance from the first template 111 becomes small. At this time, the spring 105 attached between the first receiving plate 103 and the first mirror piece 109 contracts, and the opposing surfaces of the first receiving plate 103 and the first mirror piece 109 are in contact with each other. Therefore, the mirror surface piece 109 also moves in the direction of the first template 111 together with the first receiving plate 103. As a result, the volume of the cavity 301 is reduced and the resin in the cavity is compressed. Finally, the hydraulic cylinder 107 is contracted until the opposing surfaces of the first receiving plate 103 and the first template 111 come into contact with each other.

  FIG. 4 is a diagram illustrating a state in which the volume of the cavity 301 is reduced by contracting the hydraulic cylinder 107 of the injection molding apparatus 100 according to the embodiment of the present invention. The opposing surfaces of the first receiving plate 103 and the first template 111 are in contact with each other.

  In this state, the distance between the vertex of the concave surface in contact with the cavity 301 of the first mirror surface piece 109 and the surface in contact with the cavity 301 of the second mirror surface piece 113, that is, the height of the cavity 301 is, for example, 23 It is a millimeter.

  That is, in step S1060 of FIG. 2, the hydraulic cylinder 107 is contracted so that the height of the cavity 301 is changed from 23.6 millimeters to 23 millimeters, and as a result, the molten resin filled in the cavity 301 is compressed. .

  In step S1070 of FIG. 2, the resin in the cavity 301 is cooled.

  In step S1080 of FIG. 2, mold opening is performed. Specifically, the ejector plates 119 and 121 to which the ejector pins 122 are attached are pushed up by an ejector device (not shown) to take out the molded product.

  In the prior art, after the molten resin is filled in the cavity (from step S2030 to the end of step S2040), the mirror surface SWS microstructure is not transferred to the molten resin, and after the molten resin is filled into the cavity. (After the end of step S2040), the compression of the molten resin and the transfer of the fine structure of the mirror surface SWS to the molten resin are performed simultaneously (step S2050).

  In the prior art, after the cavity is filled with the molten resin, the mirror piece SWS microstructure is transferred to the molten resin at the stage of compressing the molten resin, so that after the skin layer grows on the surface of the molten resin Transfer to a resin having a fine structure is performed. Since the viscosity of the resin increases due to the growth of the skin layer on the surface, the deformation start pressure increases, and the transfer to the resin having a fine structure is not performed with high accuracy.

  On the other hand, in the present invention, while the molten resin is filled into the cavity (between steps S1040 and S1050), the SWS of the mirror surface piece is transferred to the molten resin, and thereafter the molten resin is transferred. Is compressed (step S1060).

  As described above, in the present invention, since the fine structure of the SWS of the mirror piece is transferred to the molten resin while the cavity is filled with the molten resin, the SWS fine of the mirror piece is grown before the resin skin layer grows. The structure can be transferred to a resin having a fine structure by bringing the molten resin into contact with the structure at a pressure equal to or higher than a predetermined value. For this reason, it is possible to transfer the mirror surface SWS to the resin having the fine structure with high accuracy.

Claims (3)

Directly attached to the first mounting plate, the elastic member, the first mold member attached to the first mounting plate via at least the elastic member, the second mounting plate, and the second mounting plate Or a second mold member attached via another member, wherein the elastic member is attached to a concave portion of the surface facing the first mold member, and the first attachment plate and the first An injection compression molding apparatus for molding a lens having a sub-wavelength structure on at least one surface, the distance between the two mounting plates being changeable,
Prior to injection, the first mold member causes the second member by the elastic member to reduce the volume of the cavity formed by the first mold member and the second mold member. During the injection, the first mold member is displaced in the direction of the mold member, and the first mounting plate resists the opposing force of the elastic member by the pressure of the molten resin injected into the cavity. moves in the direction of increasing the volume of the cavity, for the post-injection compression, the first mounting plate, when moving in the direction of the second mounting plate, the elastic member In the contracted state, the first mold member is configured to contact the surface and move integrally with the first mounting plate to mold a lens, and the first mold member At least one of the member and the second mold member has a surface of the mold for the sub-wavelength structure. Look,
The elastic coefficient of the elastic member is such that the first mold member moves in the direction of the first mounting plate against the opposing force of the elastic member due to the pressure of the molten resin injected into the cavity. In this case, an injection compression molding apparatus is set such that the fine structure portion corresponding to the subwavelength structure is transferred to the molten resin . The injection compression molding apparatus according to claim 1, wherein the elastic member is a spring. Directly attached to the first mounting plate, the elastic member, the first mold member attached to the first mounting plate via at least the elastic member, the second mounting plate, and the second mounting plate Or a second mold member attached via another member, wherein the elastic member is attached to a concave portion of the surface facing the first mold member, and the first attachment plate and the first An injection compression molding method for molding a lens having a subwavelength structure on at least one surface by using an injection compression molding apparatus configured to change a distance between two mounting plates. ,
Prior to injection, the first mold member is moved to the second mold by the elastic member so as to reduce the volume of the cavity formed by the first mold member and the second mold member. Displacing in the direction of the mold member;
While increasing the volume of the cavity by contracting the elastic member by the pressure of the molten resin injected into the cavity formed by the first mold member and the second mold member during injection, Transferring the shape of the microstructure portion corresponding to the sub-wavelength structure of the first mold member to a molten resin;
For compression after injection , the first mounting plate is moved together with the first mold member while the elastic member is contracted while the first mold member is in contact with the surface. to compress the resin in the cavity to reduce the volume of the cavity is moved in the direction of the second mounting plate, viewed including the steps of performing molding of a lens, a,
The elastic coefficient of the elastic member is such that the first mold member moves in the direction of the first mounting plate against the opposing force of the elastic member due to the pressure of the molten resin injected into the cavity. In this case, the injection compression molding method is set such that the fine structure portion corresponding to the subwavelength structure is transferred to the molten resin .

Images