Device and method for manufacturing a light diffusion lens

Abstract

Device for producing a light diffusion lens (14) by forming and laminating at least two polymer layers, comprising: a pair of shapes (15) consisting of a fixed shape (16) and a movable shape (18) forming an end part cavity (22) which defines the shape of a light diffusion lens (14); a form clamping device (62) in which the pair of forms (15) is mounted; a transport device (66) comprising a clamping device means (32, 36, 37) capable of entering and exiting the space between the pair of molds (15) in an open state, which introduces a semi-finished mold part (10, 12) for the light diffusion lens (14) into the final mold part cavity (22); a heating device (68) comprising a heating medium (35) capable of entering and exiting the space between the pair of molds (15) in an open state, which heats the solid, mold-facing surface of the inserted, semi-finished mold part (10, 12) until the surface reaches a molten state; and an injection device (64) which, after clamping the pair of molds (15), injects a casting material into the final mold cavity (22) such that the casting material covers the molten surface of the semi-finished mold part (15), wherein the pair of shapes (15) has at least one semi-finished mold cavity (20, 21) in addition to the final mold cavity (22) and wherein the solid shape (16) has a flow path (23A, 23B, 23C) that branches into a path that communicates with the final mold cavity (22) and a path that communicates with the at least one semi-finished mold cavity (20, 21).

Description

TECHNICAL FIELD

[0001] The present invention relates to a production apparatus and a production method for producing a light diffusion plate, for example for use in an automobile headlight, by injection molding. BACKGROUND

[0002] Injection molded products include a molded product constructed from a uniform laminate or a plurality of polymer layers (hereinafter referred to as an injection laminate product), for example, a molded part constructed from polymer layers in a combination of different colors and materials, or a molded part constructed from a laminate of polymer layers of the same material.

[0003] Main conventional molding methods for producing such a molded laminate part include multi-color molding and overmolding. The multi-color molding method involves injecting a plurality of polymer materials from different injection devices into a cavity in a mold, thereby laminating a plurality of polymer layers. The overmolding method involves placing an injection half-part as an insert in a cavity in a mold and then injecting a polymer material into the cavity to form a laminate.

[0004] Today, optical parts, such as plastic lenses, are commonly manufactured by injection molding. While it is conventional practice to mold plastic lenses as single-layer lenses, some thick plastic lenses exist, such as light-diffusion lenses for use in exterior lighting, automotive headlights, etc.

[0005] Such a thick light-diffusion lens must be a homogeneous transparent body free of optical defects so that light diffuses uniformly. When molding a lens composed of a laminate or multiple polymer layers, differences in physical properties, such as residual stress and internal distortion, can occur between the polymer layers, even if the same molding material is used for the layers. Therefore, it is difficult to mold a high-quality lens. Especially in the case of multi-layer molding of a laminate, a difference in the thermal behavior will arise between the polymer layers. Therefore, multi-layer molding is not suitable for molding a thick lens such as a light-diffusion lens. Therefore, nowadays, a light-diffusion lens is usually manufactured as a single-layer molded part when the lens is produced by injection molding.

[0006] However, in the case of injection molding a single-layer light-diffusion lens, defects such as depressions are likely to form in a thick region. Therefore, in a pressure-holding process, it is necessary to cool the molded part slowly over time. Accordingly, it takes a long time to mold such a lens.

[0007] In order to shorten the time for forming a lens and increase production efficiency, research is currently being conducted to form a lens that consists not of a single layer but of a laminate of multiple layers by using the overmolding process.

[0008] For example, WO 2012 / 132597 A1 has proposed a method involving forming a plurality of high cavities having different volumes in a mold, and repeatedly injecting a molten polymer while sequentially transferring an intermediate molding as an insert to a cavity having a larger volume than the intermediate molding, thereby producing a molded laminate product.

[0009] US 2004 / 0 262 791 A1 further discloses a method for pretreating inserts, in which an insert is placed in an injection mold and subjected to heat. SUMMARY OF THE INVENTION

[0010] However, the lens molding method disclosed in the above patent document, which is based on overmolding, only aims to shorten the molding time for a thick lens and optimize the production process. In the case of overmolding, a molten polymer is applied to a cooled semi-finished product, and therefore, the temperature of the molten polymer drops and its fluidity becomes low. This leads to low adhesion at the interface, resulting in non-uniform internal stress in the final product. Thus, the conventional overmolding method can only produce a low-quality plastic lens with mediocre optical properties.

[0011] The present invention has been made in view of the above problems in the prior art. Therefore, it is an object of the present invention to provide a light diffusion lens manufacturing apparatus and methods that enable efficient production of a high-quality light diffusion lens with improved optical properties.

[0012] An apparatus for producing a light diffusion lens according to the present invention is defined in claim 1. A method for producing a light diffusion lens according to the present invention is defined in the independent claim 7. Further preferred embodiments are set forth in the subclaims.

[0013] To achieve the object, the present invention provides an apparatus for manufacturing a light diffusion lens by molding and laminating at least two polymer layers, comprising: a pair of molds consisting of a fixed mold or a movable mold, which form a final molding cavity defining the shape of a light diffusion lens; a mold clamping device in which the pair of molds are mounted; a transfer device having a chuck means capable of entering and exiting the space between the pair of molds in an open state, which introduces a semi-finished molded part for the light diffusion lens into the final molding cavity;a heating device having a heating means capable of entering and exiting the space between the pair of molds in an open state, which heats the solid shape-facing surface of the inserted semi-finished molded article until the surface enters a molten state; and an injection device that, after clamping the pair of molds, injects a molding material into the final mold cavity so that the molding material covers the molten surface of the semi-finished molded article.

[0014] The present invention also provides a method for manufacturing a light diffusion lens by molding and laminating at least two polymer layers, comprising: an insertion step of inserting a semi-finished molded article for a light diffusion lens into a final mold cavity defining the shape of the light diffusion lens and formed in a pair of molds consisting of a fixed mold and a movable mold when the pair of molds is in an open state; the heating step of allowing a heating means to penetrate into the space between the pair of molds in an open state and heating the fixed shape-exposing surface of the inserted semi-finished molded article until the surface comes into a molten state; the mold clamping step of clamping the pair of molds;the injection step of injecting a molding material into the final mold cavity so that the molding material covers the molten surface of the semi-finished mold; and the mold removal step of opening the pair of molds and removing a final molded part from the pair of molds. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A to 1C are side views showing exemplary semi-finished molded parts and an exemplary light diffusion lens manufactured by the light diffusion lens manufacturing apparatus according to a first embodiment of the present invention; Fig. 2 is a cross-sectional view of a mold for use in the light diffusion lens manufacturing apparatus according to the first embodiment; Fig. 3 is a perspective view of the light diffusion lens production apparatus according to the first embodiment; Fig. 4 is a diagram illustrating a manner in which semi-finished molded articles and a light diffusion lens are taken out from a mold, and semi-finished molded articles are inserted into the mold and heated; Fig. 5A to 5D are diagrams illustrating process steps in a light diffusion lens production method according to the first embodiment; Fig. 6A to 6C are cross-sectional views showing a primary molded part, a secondary molded part, and a light diffusing lens of a final molded part in a mold; Fig. 7 is a side view of a light diffusion lens having a four-layer laminate structure produced by the light diffusion lens production apparatus (method) according to the first embodiment of the present invention; Fig. 8 is a side view of a light diffusion lens having a five-layer laminate structure produced by the light diffusion lens production apparatus (method) according to the first embodiment of the present invention; Fig. 9 is a side view of a light diffusion lens having a two-layer laminate structure produced by a light diffusion lens production apparatus (method) according to a second embodiment of the present invention; Fig. 10 is a cross-sectional view of a mold for use in the light diffusion lens production apparatus (method) according to the second embodiment; Fig. 11A to 11D are diagrams illustrating process steps in the light diffusion lens production method according to the second embodiment; Fig. 12 is a cross-sectional view of a mold for use in a light diffusion lens production apparatus (method) according to a variation of the second embodiment; and Fig. 13A to 13D are diagrams illustrating process steps in the light diffusion lens production method according to the variation of the second embodiment. DESCRIPTION OF EMBODIMENTS

[0015] Embodiments of a light diffusion lens production apparatus and method according to the present invention will now be described with reference to the drawings. First embodiment

[0016] Fig. 1A to 1C are diagrams showing semi-finished molded parts and a light diffusion lens as a final molded part produced by a light diffusion lens production apparatus (method) according to the first embodiment.

[0017] Fig. 1A shows a primary molded part 10, which is a semi-finished molded part composed only of a first layer. The primary molded part 10 is ultimately molded into a light-diffusion lens composed of a laminate of, for example, three thermoplastic polymer (mold material) layers, for use in exterior lighting, an automotive headlight, etc.

[0018] Fig. 1B shows a secondary molded part (intermediate molded part) 12, which is formed by placing the primary molded part 10 of Fig. 1A as an insert element into a mold, and forming a second layer on the surface of the primary mold part 10. In the secondary mold part 12, the lens region is convexly curved.

[0019] Fig. Figure 1C shows a tertiary molded part which is obtained by forming a third layer on the surface of the secondary molded part 12 of Fig. 1B as an insertion element. In this embodiment, the primary mold part 10 and the secondary mold part 12 are semi-finished molded parts serving as insertion elements, and the tertiary mold part is a light diffusion lens 14 as a final molded part.

[0020] Fig. Figure 2 is a diagram showing a mold to be used in a mold clamping device of an injection molding machine to mold the light diffusion lens 14. The mold 15 includes a fixed mold 16 and a movable mold 18. The fixed mold 16 is mounted on a fixed platen 17 of the mold (device), and the movable mold is mounted on a movable platen.

[0021] The following three cavities are formed in opposite surfaces of the fixed mold 16 and the movable mold 18: a primary mold cavity 20 for forming the Fig. 1A; a secondary mold cavity 21 for forming the Fig. 1B and a final mold cavity 22 for forming the final mold, which in Fig. Light diffusion lens 14 shown in Figure 1C.

[0022] Channels 23A, 23B, 23C, which communicate with the primary mold cavity 20, the secondary mold cavity 21, and the final mold cavity 22, respectively, are formed in the fixed mold 16 so as to branch off from a gate 25. An injection nozzle 26 of the injection device described below is connected to the opening of the gate 25 so that a molten polymer (molding material) is injected into the mold.

[0023] The molten polymer is injected into the primary mold cavity 20, the secondary mold cavity 21 and the final mold cavity 22 either simultaneously or under the control of a valve gate of a hot runner, thereby forming the primary mold 10, the secondary mold 12 and the light diffusion lens 14 simultaneously.

[0024] A production apparatus for performing a light diffusion lens molding method according to this embodiment will now be described with reference to Fig. 3 described.

[0025] In Fig. 3, reference numeral 60 denotes the overall light-diffusion lens production apparatus. The light-diffusion lens production apparatus 60 includes a mold clamping device 62, an injection device 64, a first multi-axis robot 66 functioning as a transfer device for placing a semi-finished molded part for the light-diffusion lens 14 as an insert member into a cavity of the mold 15, and a second multi-axis robot 68 functioning as a heating device for heating the surface of the inserted semi-finished molded part.

[0026] The mold clamping device 62 includes a drive section 70 installed on a base 69 and having a not-shown tilting link mechanism for moving the movable plate 19 back and forth to open / close the mold and clamping the mold after closing the mold. As shown in Fig. As shown in Figure 2, the fixed mold 16 is mounted on the fixed platen 17, and the movable mold 18 is mounted on the movable platen 19. The mold 16, consisting of the fixed mold 16 and the movable mold 18, has the structure described above. Reference numeral 71 denotes tie rods, which are pulled by the tilting link mechanism after the mold is closed and generate a mold clamping force.

[0027] The injection device 64 is movably mounted on the base 69 via rails 72. The injection device 64 includes a barrel 73, a screw 74 housed in the barrel 73, a hopper 75 for feeding a polymer as a molding material into the barrel 73, and a drive 76 for rotating and reciprocating the screw 73.

[0028] An injection nozzle 26 is provided at the front end of the barrel 73. The injection device 64 advances and the injection nozzle 26 comes into contact with the fixed mold 16, as shown in Fig. 2. When a molten polymer is weighed and accumulated in the barrel 73 in front of the screw 74, the molten polymer is injected from the injection nozzle 26 into the cavities in the mold 15 by advancing the screw 74.

[0029] The first multi-axis robot 66 and the second multi-axis robot 68 will now be described.

[0030] The first multi-axis robot (transport device) 66 is engaged in the process steps of taking out a primary molded part 10, a secondary molded part 12 and a light diffusion lens 14 as a final molded part from the open mold 15, as shown in Fig. 1A to 1C, and to place another primary mold part 10 and secondary mold part 12 as insertion elements into the mold 15.

[0031] In this embodiment, a light diffusion lens 14 as a final product, which has been removed from the mold 15, is carried to a transport conveyor 78 by the first multi-axis robot 66. A primary molded part 10 and a secondary molded part 12, which have been removed from the mold 15, are temporarily placed (stored) by the first multi-axis robot 66 on a temperature adjustment stage (storage section) 80 in a robot access area, where the temperatures of the primary molded part 10 and the secondary molded part 12 are adjusted to a predetermined temperature lower than the heat distortion temperature.

[0032] As in Fig. As shown in Fig. 8, a plurality of primary mold parts 10 and a plurality of secondary mold parts 12, whose temperatures have been adjusted to a lower temperature than the heat distortion temperature, are arranged on the temperature adjustment stage 80. The first multi-axis robot 66 takes a primary mold part 10 and a secondary mold part 12, whose temperatures have reached a predetermined temperature (appropriate temperature), from the temperature adjustment stage 80 and sets them as insertion members into the movable mold 18. The primary mold part 10 is inserted into the secondary mold cavity 21 as an insertion member, and the secondary mold part 12 is inserted into the final mold cavity 22 as an insertion member.

[0033] In this embodiment, in addition to the first multi-axis robot 66, which performs the operation of removing the semi-finished products and a finished product from the mold and inserting the semi-finished products into the mold, the second multi-axis robot (heating device) 68 is installed, which performs the operation of heating the primary mold part 10 and the secondary mold part 12, the semi-finished products that have been inserted into the movable mold 18. An infrared heater 35 or the like is provided as a heating means at the front end of an arm of the second multi-axis robot 68.

[0034] Process steps in a light diffusion lens molding process performed by the thus constructed light diffusion lens production apparatus will now be described sequentially with reference to the Fig. 5A to 5D.

[0035] In the light-diffusion lens production apparatus according to this embodiment, the molding of a primary molded part 10, the molding of a secondary molded part 12, and the molding of a light-diffusion lens 14 as the final molded part are performed in parallel to optimize the production process. For easier understanding of the process steps, a description will start at a time when the immediately preceding cycle of molding a primary molded part 10, a secondary molded part 12, and a light-diffusion lens 14 is completed.

[0036] First illustrated Fig. 5A illustrates the step of opening the movable mold 18 from the fixed mold 16 after completion of a pressure transfer step. At this time, the primary mold part 10, the secondary mold part 12, and the light diffusion lens 14 remain in the movable mold 18.

[0037] Fig. 5B illustrates the step of removing the primary molded part 10, the secondary molded part 12, and the light diffusion lens 14 from the movable mold 18. In this embodiment, the arm of the first multi-axis robot 66 includes a second-stage chuck 32. The first-stage chuck 36 is a chuck for attracting and holding a primary molded part 10 and a secondary molded part 12 that have been placed on the temperature adjustment stage 80 and whose temperatures have been adjusted to a predetermined temperature. The second-stage chuck 37 is a chuck for attracting and holding a primary molded part 10, a secondary molded part 12, and a light diffusion lens 14 as the final molded part, and removing them from the movable mold 18.

[0038] In this embodiment, the first multi-axis robot 66, while holding the primary mold part 10 and the secondary mold part 12 with the first-stage chuck 36, allows the chuck 32 to enter the space between the fixed mold 16 and the movable mold 18 of the open mold. The first multi-axis robot 66 then attracts and holds the primary mold part 10, the secondary mold part 12, and the light diffusion lens 14 with the second-stage chuck 37, and removes them from the movable mold 18.

[0039] Next, as in Fig. 5C, the first multi-axis robot 66 rotates the chuck 32 by 180° and places the primary molded part 10 and the secondary molded part 12, which have been held by the first-stage chuck 36, into the secondary molded part cavity 21 and the final molded part cavity 22, respectively, as insertion members.

[0040] By using the chuck 32 having the two front / back chucks as described above, the removal of the semi-finished molded parts and the light diffusion lens 14 and the setting of the semi-finished products as insertion elements into the movable mold 18 can be successively performed in the same process step.

[0041] Thereafter, the primary molded part 10 and the secondary molded part 12 that have been removed are transported to the temperature adjustment stage 80, where their temperatures are adjusted to a predetermined temperature and they wait until they are introduced into the mold 5. When a polycarbonate (PC) polymer is used as a molding material, the heat distortion temperature is 130°C to 140°C, although it may vary slightly depending on the quality and grade of the polymer. In the case of an acrylic polymer (e.g., PMMA), the heat distortion temperature is 70°C to 100°C. Depending on the type of molding material, the temperatures of the primary molded part 10 and the secondary molded part 12 are adjusted to a temperature slightly lower than the heat distortion temperature.

[0042] In this embodiment, the light diffusion lens 14 is applied as a final molded part to the Fig. 3 shown transport conveyor 78.

[0043] Fig. Figure 5D shows the step of heating semi-finished molded parts, the most important step in the light diffusion lens 14 production process according to this embodiment. The heated objects are the primary molded part 10, which has been placed on an insertion element in the secondary molding cavity 21, and the secondary molded part 12, which has been placed as an insertion element in the final molding cavity 22.

[0044] The Fig. The second multi-axis robot 68 shown in Fig. 3 allows the infrared heater 35 or the like, which is provided as an (external) heating means at the front end of the arm, to penetrate into the space between the fixed mold 16 and the movable mold 18 of the open mold.

[0045] In the primary molded part 10 and the secondary molded part 12 as semi-finished molded parts, the area to be heated is the surface to which a polymer layer is to be laminated in the next step, that is, the entire surface facing the solid mold 16. The surfaces of the primary molded part 10 and the secondary molded part 12 are heated to a temperature higher than the melting temperature of the polymer as a molding material, so that only the surfaces of the molded part enter a molten state. The melting temperature is about 240°C when the thermoplastic polymer as a molding material is a polycarbonate (PC) polymer and about 160°C in the case of an acrylic (PMMA) polymer. The upper limit of the heating temperature is equal to the melting temperature. When the surfaces of the primary molded part 10 and the secondary molded part 12 have entered a molten state, the second multi-axis robot 68 retracts the infrared heater 35 from the mold.

[0046] Next, form 15 is closed and clamped. After that, the Fig. 3 is connected to the mold 15 and the filling step (injection filling step) of injecting a polymer (molding material) into the mold 15 is carried out.

[0047] In this embodiment, all cavities in the mold 15, i.e., the primary mold cavity 20, the secondary mold cavity 21, and the final mold cavity 22, are simultaneously filled with a molten polymer material through the filling step. In this embodiment, the same polymer is injected into the cavities from a single injection device.

[0048] Fig. 6A shows a cross section of a primary mold part 10 in the primary mold part cavity 20, Fig. 6B shows a cross section of a secondary mold part 12 in the secondary mold part cavity 21 and Fig. Figure 6C shows a cross-section of a light diffusion lens 14 in the final mold cavity 22.

[0049] As in Fig. As shown in Figure 6A, the primary molded part 10 constructed from a single polymer layer is formed in the primary molded part cavity 20 by filling the molten polymer.

[0050] On the other hand, as in Fig. As shown in Fig. 6B, the molten polymer is filled into the secondary mold cavity 21 in which the primary mold 10 has been placed as an insertion member; therefore, a second polymer layer is laminated onto the surface of the primary mold 10. Since the surface of the primary mold 10 has been heated and becomes a molten state, the injected molten polymer can adhere to the interface with the primary mold 10 in a homogeneously fused state. Further, there is no decrease in the temperature of the molten polymer upon contact with the surface of the primary mold 10. Therefore, the molten polymer is filled into the secondary mold cavity 21 while maintaining good fluidity without partial solidification.

[0051] The injected molten polymer is thus filled into the secondary mold cavity 21 while maintaining sufficient adhesion and fluidity at the interface with the primary mold 10. Accordingly, pressure is uniformly transferred within the molten polymer. This can prevent the occurrence of the phenomenon of high residual stress in one region, such as a region near a gate, and lower residual stress in the other region. Therefore, in a pressure transfer step performed after the filling step, in which the molten polymer is solidified while pressure is applied to the polymer, non-uniform residual stress is prevented from remaining in the second layer, thereby achieving a uniform stress distribution.

[0052] Similar to Fig. As shown in Figure 6C, the molten polymer is filled into the final mold cavity 22 in which the secondary mold 12 has been placed as an insert; a third polymer layer is laminated onto the surface of the secondary mold 12.

[0053] Also, in the final mold cavity 22, the surface of the secondary mold 12 has been heated and has entered a molten state, and therefore, the injected molten polymer can adhere to the interface with the secondary mold 12 in a homogeneously bonded state. The injected molten polymer is thus filled into the final mold cavity 22 while maintaining sufficient adhesion and fluidity at the interface with the secondary mold 12. Accordingly, a pressure is uniformly maintained within the molten polymer. Therefore, in a pressure transfer step performed after the filling step in which the molten polymer is solidified while maintaining the pressure, a non-uniform residual stress can be prevented from remaining in the third layer, thereby achieving a uniform stress distribution.

[0054] The lamination of the light diffusion lens 14 is preferably performed in such a manner that, as in this embodiment, the protrusion of the convex curve of the lens gradually increases from the primary mold part 10, which forms the bottom portion of the light diffusion lens 14. Such a lamination manner can stabilize the position of a semi-finished molded part when it is transported to the temperature adjustment stage 80 and can facilitate the placement of the semi-finished molded part on the temperature adjustment stage 80.

[0055] Upon completion of the filling step, the process proceeds to the pressure transfer step described above while maintaining the pressure. After the molten polymer in the primary mold cavity 20, the secondary mold cavity 21, and the final mold cavity 22 has solidified, the mold opening step described in Fig. 5A and the one in Fig. The mold part removal step shown in Figure 5B is performed. The same casting cycle is then repeated successively.

[0056] As described above, according to this embodiment, the surface of the primary molded part 10, the first semi-finished product, is heated to a molten state before the second layer is laminated onto the primary molded part 10, and similarly, the surface of the secondary molded part 12, the next semi-finished product, is heated to a molten state before the third layer is laminated onto the secondary molded part 12. This makes it possible to mold the light diffusion lens 14, the final molded product, which is a high-quality plastic lens with excellent optical properties and a uniform stress distribution despite its large thickness. Furthermore, the primary molded part 10, the secondary molded part 12, and the light diffusion lens 14, the final molded product, can be molded simultaneously in parallel using the same mold 15. Thus, the light diffusion lens 14 can be produced with high efficiency.

[0057] Furthermore, in this embodiment, the primary molded part 10 and the secondary molded part 12 as semi-finished molded parts are temporarily placed (stored) on the temperature adjustment stage (storage section) 80 capable of temperature adjustment. This can prevent the primary molded part 10 and the secondary molded part 12 from fully solidifying as semi-finished molded parts intended to serve as insertion elements, making it possible to smoothly perform heating in the later heating step.

[0058] While the above-described embodiment refers to the molding of a light diffusion lens 14 constructed from a laminate of three layers, a light diffusion lens 14 constructed from a laminate of four or five layers can also be molded using a mold having cavities that define the shapes of the molded parts at different lamination stages.

[0059] Fig. Figure 7 shows a light diffusion lens 14 constructed from a four-layer laminate. In this light diffusion lens 14, a secondary mold part 50 and a tertiary mold part 51 are intermediate mold parts between the primary mold part 10 and the final mold part. Each semi-finished mold part serves as an insertion element during the molding of a product at the next lamination stage: the primary mold part 10 serves as an insertion element during the molding of the secondary mold part 50; the secondary mold part 50 serves as an insertion element during the molding of the tertiary mold part 51; and the tertiary mold part 51 serves as an insertion element during the molding of the final mold part.

[0060] Fig. Figure 8 shows a light diffusion lens 14 constructed from a five-layer laminate. In this light diffusion lens 14, a secondary mold part 50, a tertiary mold part 51, and a quarter mold part 52 are intermediate mold parts between the primary mold part 10 and the final mold part. Each semi-finished mold part serves as an insertion element in the molding of a product in the next lamination stage. The primary mold part 10 serves as an insertion element in the molding of the secondary mold part 50; the secondary mold part 50 serves as an insertion element in the molding of the tertiary mold part 51; the tertiary mold part 51 serves as an insertion element in the molding of the quarter mold part 52; and the quarter mold part 52 serves as an insertion element in the molding of the final mold part.

[0061] The above is a description of a process for molding a light diffusion lens 14 constructed from a laminate mold of 3, 4, or 5 polymer layers. The description begins at a time when the immediately preceding cycle of molding semi-finished products and a light diffusion lens 14 is completed.

[0062] At the start of a first molding cycle, no semi-finished molded part has yet been formed to be used as an insertion element. Therefore, the semi-finished molded parts are prepared in a preliminary molding process, which is different from the final molding process described above, and are subjected to temperature adjustment as described above before the first molding cycle. The first molding cycle starts by placing the thus prepared semi-finished molded parts into the cavities for molding products in the next lamination stage. Second embodiment

[0063] In the first embodiment described above, a final molded article 14, which is a light diffusing lens composed of a laminate of three or more layers, is molded in such a manner that a secondary molded article 12 is lamination-molded using a primary molded article 10 of an insertion member, and the secondary molded article 12 is then used as an insertion member.

[0064] On the other hand, in the second embodiment described below, a light diffusion lens having a two-layer laminate structure is molded using a primary molding 10 made of an insertion member.

[0065] Fig. Figure 9 shows a light-diffusion lens 14 produced by a production apparatus (method) according to the second embodiment. As in the first embodiment, a primary mold 10 serving as an insertion element forms the bottom portion of the lens: a convexly curved lens portion is formed by laminating a thermoplastic polymer layer onto the primary mold 10.

[0066] Fig. Figure 10 is a diagram showing a mold for use in molding the light diffusion lens. The same reference numerals as those used for the first Fig. 2 are used to refer to the same components, and a detailed description thereof will be omitted.

[0067] In the Fig. In the mold 40 shown in Figure 10, a final mold cavity 44 defining the shape of a light diffusing lens 14 is formed by opposing surfaces of a fixed mold 41 and a movable mold 42. A channel 43 communicates with the final mold cavity 44. A primary mold part 10 is to be inserted into the final mold cavity 44. The primary mold part 10 has been molded in another injection molding machine, and its temperature has been adjusted.

[0068] A casting process using the mold 40 will now be described with reference to Fig. 11A to 11D.

[0069] Fig. Figure 11A illustrates the step of opening the movable mold 42 from the fixed mold 41 after completion of the previous molding cycle. A light diffusion lens 14, a final molded part produced in the previous molding cycle, is waiting to be removed from the mold.

[0070] Next, transported as in Fig. 11B shows that lining 32 is a primary molded part 10 from the Fig. 3 shown temperature adjustment stage 80 between the fixed mold 41 and the movable mold 42 and, while holding the primary mold part 10, it attracts and holds the light diffusion lens 14 as a final mold part, and removes it from the movable mold 42. Next, as in Fig. 11C, the overall chuck 32 rotates 180° and places the primary molded part 10, which is held by the first-stage chuck 36, as an insertion element in the cavity 44. Thereafter, the light diffusion lens 14 is transported to the transfer conveyor 78 as a final molded part.

[0071] Next, as in Fig. As shown in Figure 11D, the infrared heater 35 penetrates the space between the fixed mold 41 and the movable mold 42 and heats the surface of the primary molded part 10 until it reaches a molten state. The mold is then closed and clamped. Thereafter, as shown in Fig. 10, the injection nozzle 26 of the injection device 64 is connected to the mold and a casting material is filled into the cavity 44.

[0072] In the above-described embodiment, the primary mold part 10 formed in another molding apparatus is used as an insertion member. However, as in the first embodiment, a primary mold part 10 and a light diffusion lens 14 as a final mold part can be simultaneously molded using one mold as shown in Fig. 12 shown.

[0073] In the Fig. In the mold 50 shown in Figure 12, a primary mold cavity 53 defining the shape of a primary mold 10 and a final mold cavity 54 defining the shape of the light diffusing lens 14 are formed by opposing surfaces of a fixed mold 51 and a movable mold 52. Channels 56a, 56b branching from a channel 55 and communicating with the primary mold cavity 53 and the final mold 54 are formed in the fixed mold 51.

[0074] A molding process using the mold 50 will now be described with reference to Fig. 13A to 13D.

[0075] Fig. Figure 13A illustrates the step of opening the movable mold 52 away from the fixed mold 51 after completion of the previous molding cycle. A primary molded part 10 and a light diffusing lens 14 as a final molded part, which were produced in the previous molding cycle, are waiting to be removed from the mold.

[0076] Next, as in Fig. 13B, the first-stage chuck 36 of the chuck 32 transports a temperature-adjusted primary molded part 10 from the temperature adjustment stage 80 to a position between the fixed mold 51 and the movable mold 52, while the second-stage chuck 37 holds the light diffusion lens 14 as a final molded part and removes it from the movable mold 52. Next, as shown in Fig. 13C, the overall chuck 32 rotates 180° and places the primary molded part 10 held by the first-stage chuck 36 as an insertion member into the final molded part cavity 54. Thereafter, the primary molded part 10 that is molded and the light diffusion lens 14 as the final molded part are transported to the transport conveyor 78.

[0077] Next, as in Fig. As shown in Figure 13D, the infrared heater 35 penetrates the space between the fixed mold 51 and the movable mold 52 and heats the surface of the primary molded part 10 until it enters a molten state. The mold is then closed and clamped. Thereafter, as shown in Fig. As shown in Figure 12, the injection nozzle 26 of the injection device 64 is connected to the mold, and the same polymer molding material is simultaneously filled into the primary mold cavity 53 and the final mold cavity 54. In this way, the primary mold 10 as a semi-finished molded part and the light diffusion lens 14 as a final molded part can be molded in parallel and simultaneously.

[0078] As described above, the surface of the primary molded part 10, the first semi-finished product, is heated to a molten state before the next, second layer is laminated onto the primary molded part 10. This allows the light diffusion lens 14, the final molded part, to be formed as a high-quality plastic lens with excellent optical properties and a uniform stress distribution.

[0079] While a light diffusion lens production apparatus and method according to the present invention has been described with reference to preferred embodiments in which a lens constructed from a laminate of 2, 3, 4, or 5 polymer layers is molded, the present invention may also be applied to a molding process involving molding and laminating more than five polymer layers to form a light diffusion lens.

Claims

[1] An apparatus for producing a light diffusing lens (14) by molding and laminating at least two polymer layers, comprising: a pair of molds (15) consisting of a fixed mold (16) and a movable mold (18) forming a final mold cavity (22) defining the shape of a light diffusion lens (14); a mold clamping device (62) in which the pair of molds (15) is mounted; a transport device (66) having a chuck means (32, 36, 37) capable of entering and exiting the space between the pair of molds (15) in an open state, which introduces a semi-finished molded part (10, 12) for the light diffusion lens (14) into the final molded part cavity (22); a heating device (68) comprising a heating means (35) capable of entering and leaving the space between the pair of molds (15) in an open state, which heats the solid, mold-facing surface of the inserted semi-finished molded part (10, 12) until the surface enters a molten state; and an injection device (64) which, after clamping the pair of molds (15), injects a casting material into the final mold cavity (22) so that the casting material covers the molten surface of the semi-finished molded part (15), wherein the pair of molds (15) has at least one semi-finished mold cavity (20, 21) in addition to the final mold cavity (22), and wherein the fixed mold (16) has a flow path (23A, 23B, 23C) branching into a path communicating with the final mold cavity (22) and a path communicating with the at least one semi-finished mold cavity (20, 21). [2] An apparatus for producing a light diffusion lens (14) according to claim 1, wherein the pair of molds (15) comprises, as the at least one semi-finished mold cavity (20, 21), a primary mold cavity (20) and at least one cavity (21) for an intermediate mold (12) between a primary mold (10) and a final mold (14). [3] An apparatus for producing a light diffusing lens (14) according to claim 2, wherein the at least one intermediate mold cavity (21) consists of at least two cavities (21) both defining the shape of an intermediate mold (12) on the next lamination stage. [4] An apparatus for producing a light diffusion lens (14) according to any one of claims 1 to 3, wherein the heating means (35) of the heating device (68) is capable of simultaneously heating the surfaces of semi-finished products (10, 12) which have been introduced into the at least one semi-finished mold cavity (21) and the final mold cavity (22). [5] An apparatus for producing a light diffusion lens (14) according to any one of claims 1 to 3, further comprising a storage section (80) for temporarily storing the semi-finished molded part(s) (10, 12) taken out of the pair of molds (15) by the transfer device (66) and adjusting the temperature of the semi-finished molded part(s). [6] The apparatus for producing a light diffusion lens (14) according to claim 5, wherein the chuck means of the transfer device (66) is capable of successfully performing the operation of taking out the semi-finished molded part(s) (10, 12) and the final molded part (14) from the pair of molds (15) and the operation of inserting the temperature-adjusted semi-finished molded part(s) (10, 12) transferred from the storage section (68) into the cavity(s) (20, 21, 22). [7] A method for producing a light diffusing lens (14) by molding and laminating at least two polymer layers, comprising: the inserting step of inserting a semi-finished molded part (10) for a light diffusion lens (14) into a final mold cavity (44) defining the shape (40) of the light diffusion lens (14) and formed in a pair of molds (41, 42) consisting of a fixed mold (41) and a movable mold (42) when the pair of molds (41, 42) is in an open state; the heating step of allowing a heating means (35) to enter the space between the pair of molds (41, 42) in an open state and heating the solid mold-facing surface of the inserted semi-finished molded article (10) until the surface comes into a molten state; the shape clamping step of clamping the pair of shapes; the injection step of injecting a casting material into the final mold cavity (44) so ​​that the casting material covers the molten surface of the semi-finished molded part (10); and the molded part removal step of opening the pair of molds (41, 42) and removing a final molded part (14) from the pair of molds (41, 42). [8] A method for producing a light diffusing lens (14) according to claim 7, wherein the pair of molds (41, 42) has at least one semi-finished mold cavity (53) in addition to the final mold cavity (54), and wherein in the injection step, the molding material is simultaneously injected into the final mold cavity (54) and into at least one semi-finished mold cavity (53) from a single injection device. [9] A method for producing a light diffusion lens (14) according to claim 8, wherein the pair of molds (41, 42) has, as the at least one semi-finished mold cavity (53), a primary mold cavity and at least one cavity for an intermediate mold between a primary mold (10) and a final mold (14), and wherein in the inserting step, the primary mold (10) is inserted into the intermediate mold cavity and the intermediate mold is inserted into the final mold cavity (54). [10] A method of producing a light diffusion lens (14) according to claim 9, wherein the at least one intermediate mold cavity consists of at least two cavities, both of which define the shape of an intermediate mold at the next lamination stage, and wherein in the inserting step, the primary mold (10) and the intermediate parts are all inserted into a cavity which defines the shape of the mold at the next lamination stage. [11] A method for producing a light diffusion lens (14) according to any one of claims 7 to 10, wherein in the heating step, the surfaces of semi-finished products introduced into the at least one semi-finished mold cavity (53) and the final mold cavity (54) are heated simultaneously. [12] A method for producing a light diffusion lens (14) according to any one of claims 7 to 10, wherein the semi-finished molded part(s) taken out from the pair of molds (41, 42) by the transfer device (66) in the mold-part taking-out step are temporarily stored in a storage section (80), where the temperature of the semi-finished molded part is adjusted and the semi-finished molded parts are inserted into the cavity(s) after completion of the temperature adjustment. [13] A method for producing a light diffusion lens (14) according to claim 12, wherein the removal of the semi-finished molded part(s) and the finished molded part (14) in the molded part removal step and the introduction of the temperature-adjusted semi-finished product(s) which have been transported from the storage section (80) into the cavity(s) in the introduction step are successively performed in the next cycle.

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