JP2008284867A - Method for molding light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for molding a light guide plate which can curtail a light guide plate molding cycle time by shortening the time required for a process from the start of mold opening to the completion of mold closing through the ejection of the light guide plate, when the light guide plate is molded by injection molding including injection compression molding. <P>SOLUTION: In the method for molding the light guide plate in a mold by injection molding, by arranging a mold opening/closing operation and the operation of an ejection device 23 for ejecting the light guide plate P to overlap each other, a molding cycle time in light guide plate molding can be curtailed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method of forming a light guide plate in a mold by injection molding including injection compression molding, and more particularly to a light guide plate having a diagonal size of 7 inches or less used for a mobile phone or the like. It relates to a molding method.

The thing described in patent document 1 is known as a thing regarding the shaping | molding method and taking-out method of a light-guide plate by injection molding including injection compression molding. Patent Document 1 relates to molding of a large light guide plate. Usually, when molding these large light guide plates, it takes 30 seconds or more just for molding time (time from completion of mold closing to start of mold opening after mold closing). Met. Further, the extraction method described in Patent Document 1 has a problem for shortening the molding cycle time because the light guide plate is taken out from the upper two tie bars and moved to another placement position. . Therefore, in Patent Document 1, one molding cycle time needs 40 seconds or more. Also, the molding cycle time of the small light guide plate was long because the molding time was long because of pattern transfer molding, and it also took time to take out, so usually one molding cycle time was 15 seconds. As described above, shortening the molding cycle time has been a problem.

Japanese Patent Laying-Open No. 2003-145593 (Claim 4, FIG. 2)

In the present invention, in light of the above problems, when forming a light guide plate by injection molding including injection compression molding, the time from the start of mold opening to the completion of mold closing after taking out the light guide plate is shortened, and the light guide plate is molded. It aims at providing the shaping | molding method of the light-guide plate which can aim at shortening of cycle time.

The light guide plate forming method according to claim 1 of the present invention is a light guide plate forming method in which a light guide plate is formed in a mold by injection molding. The mold opening / closing operation and the operation of a take-out device for taking out the light guide plate are performed. It is characterized in that the molding cycle time is shortened by partially overlapping .

The light guide plate forming method according to claim 2 of the present invention is the light guide plate forming method according to claim 1, wherein the take-out device is a swing arm type in which an arm provided in a direction perpendicular to a rotating shaft rotated by a motor is swung. It is characterized by that .

The light guide plate forming method according to claim 3 of the present invention is characterized in that, in claim 1 or claim 2, the mold opening operation and the arm intrusion operation are overlapped to shorten the forming cycle time .

According to a fourth aspect of the present invention, there is provided the light guide plate molding method according to any one of the first to third aspects, wherein the light guide plate is taken out by using an arm attached to the rotating shaft of the take-out device outside the mold. The time from the standby position to the release position outside the mold through the holding position near the mold is 0.15 to 1.0 seconds.

The light guide plate forming method according to claim 5 of the present invention is the light guide plate according to any one of claims 1 to 4, wherein the light guide plate formed in the mold and taken out has a diagonal dimension of 7. It is less than an inch.

The light guide plate forming method for forming the light guide plate in the mold by injection molding according to the present invention reduces the molding cycle time by partially overlapping the mold opening / closing operation and the operation of the take-out device for taking out the light guide plate. As a result , it is possible to realize a shortening of the molding cycle time which cannot be considered in the past.

An injection compression molding die for a light guide plate of the present invention will be described with reference to FIGS. FIG. 1 is a front view of the light guide plate take-out device of the present embodiment as seen from the movable platen side to the fixed platen side. FIG. 2 is a side view of the light guide plate take-out device of the present embodiment. FIG. 3 is an enlarged perspective view of a main part of the light guide plate take-out device of the present embodiment. FIG. 4 is a sectional view of an injection compression molding die for the light guide plate used in the present embodiment. FIG. 5 thru | or 7 is a chart figure which shows the injection compression molding method of the light-guide plate of this embodiment. FIG. 8 is an enlarged cross-sectional view of a sprue bush of the injection compression molding die of the light guide plate of the present embodiment. FIG. 9 thru | or FIG. 13 is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and a molding cycle time.

In the present embodiment, the light guide plate P is molded by injection compression molding, which is one field of injection molding. In injection compression molding, the distance between the movable mold and the fixed mold is variable between the start of molding and the end of molding. Accordingly, the injection compression molding includes a type called an injection press in which the movable mold is moved forward as it is after the molten resin is injected at the stop position after the mold is closed. In these injection compression moldings, the cavity is slightly open before or after the start of injection compared to when the molding is completed, so there is no need for an injection device having a high-speed injection capability, and the molten resin is kept at a relatively low speed and low pressure. Can be injected. In addition, after starting injection, the movable mold is moved in the mold clamping direction to compress the molten resin, so the flow of the molten resin can be accelerated at a position far from the gate portion of the cavity, or fine transfer can be performed satisfactorily. There is an advantage that you can. Furthermore, after the gate is cut, a normal injection mold cannot apply pressure from the injection device, but in the case of injection compression molding, the molten resin in the cavity is compressed and contracted by cooling and solidification. It can correspond to. Such injection compression molding is particularly advantageous when a light guide plate having a thin plate thickness compared to the area such as the light exit surface is formed.

As shown in FIGS. 1 and 2, an injection compression molding machine 11 includes a heating cylinder 12 a with a built-in screw and an injection device 13 having a nozzle 12 b and a mold clamping device 14 disposed on a bed 15. ing. In the mold clamping device 14, four tie bars 19 are disposed between a stationary platen 17 fixed to the bed 15 to which the stationary mold 16 is attached and a pressure receiving plate 18 disposed on the bed 15. The movable platen 21 to which the movable mold 20 is attached is movably inserted. The pressure receiving plate 18 is provided with a mold clamping cylinder 22 which is a mold opening / closing / clamping mechanism for performing mold opening / closing and clamping, and a ram 22 a of the mold clamping cylinder 22 is fixed to the back surface of the movable platen 21. The mold clamping cylinder 22 of the present embodiment is a type capable of closing the movable plate at a high speed by sending pressure oil to the booster cylinder having a small cross-sectional area by controlling a servo valve. Also, when opening the mold, it is possible to open the mold at high speed by sending pressure oil to the mold opening side oil chamber with a small cross-sectional area by controlling the servo valve. In the present embodiment, it is possible to open and close the mold in 0.3 seconds on both the mold closing and mold opening sides as the highest specification. In this embodiment, the mold opening / closing / clamping mechanism is an example of a mold clamping cylinder 22 controlled by a servo valve, but may be a toggle mechanism including a servo motor and a ball screw mechanism excellent in rising rotation drive speed and stop speed, Even in that case, the speed is realized.

Next, a take-out device for taking out the light guide plate P molded from the injection compression molding die 51 of the injection compression molding machine 11 will be described. As shown in FIGS. 1 and 2, the take-out device is attached to a first take-out device 23 fixed to the upper surface of the fixed platen 17 on the side opposite to the operation side (opposite to the operation plate), and the bed 15 on the non-operation side. It consists of a second take-out device 24 installed on a fixed bracket 25. The first take-out device 23 is provided with a rotating shaft 26 in the mold opening / closing direction, and an arm 27 is fixed to the rotating shaft 26 in a direction orthogonal to the rotating shaft 26. The rotary shaft 26 is provided so as to be movable back and forth in the axial direction (mold opening / closing direction) by a first servo motor (not shown) and a ball screw mechanism, and the shaft is rotationally driven by a second servo motor (not shown) to operate at high speed and suddenly stop. Can be performed with high accuracy. Therefore, the first take-out device 23 is called a swing arm type take-out device. The arm 27 of the first extraction device 23 that directly extracts the light guide plate P and the like from the movable mold 20 has a predetermined thickness, and is a first member provided in a direction perpendicular to the rotation shaft 26 from the side close to the rotation shaft 26. 27a, a second member 27b provided in an inclined direction with respect to the first member 27a, and a third member provided in a substantially perpendicular direction with respect to the second member 27b. 27c consists of a substantially L-shaped arm member integrated. The portion of the third member 27 c is bent inward toward the vicinity of the cavity forming surface of the movable mold 20. The shape of the arm 27 may be another shape such as a right-angle shape having two sides or an arc shape as long as it does not interfere with the tie bar 19 or the safety door. In the present embodiment, the arm of the first take-out device is made of carbon and is reduced in weight. Or you may comprise an arm from the aluminum etc. which are 1 type of material whose specific gravity is lighter than iron. Since the weight of the main body including the motor portion is 15 to 25 kg, it has a low inertia structure. A servo motor that is a drive source employs a motor that is excellent in rising rotation driving speed and stopping speed. Therefore, after the mold opening signal is input, the time for the arm to move from the standby position to the loading position is 0.04 seconds, the suction extraction time is 0.07 seconds, and the time for the arm to move from the start of unloading rotation to the rotation stop is 0.04 seconds A total of 0.15 seconds is the fastest specification of the first take-out device before the dosing mold closing signal can be output. Note that this time is the same even when two 7-inch light guide plates are taken. Further, the time required for taking out by the first taking-out device does not exceed 1.0 seconds even if the light guide plate is difficult to release from the cavity or the mark of the suction holding part is easily attached.

As shown in FIG. 3, the third member 27c in the arm 27 of the first take-out device 23 has a plate shape having a surface on the fixed mold side and a surface on the movable mold side. Is formed with a V-groove 28 toward the base, and branch branches 29a and 29b are formed on both sides of the V-groove 28. A chuck 30 is disposed in the inner space of the V groove 28. In the chuck 30, two chuck members are opened and closed by an electromagnet type actuating device 30 a disposed on the surface of the fixed mold side closer to the base side than the joint portion of the branch branches 29 a and 29 b, and the sprue P 1 is moved. Grasp or release. A reflective detection sensor 31 is disposed on the surface on the movable mold side in the vicinity of the junction between the branch branches 29a and 29b. The detection sensor 31 detects whether or not the sprue P1 is detected and gripped, and stops the operation of the mold opening / closing and clamping mechanism when the sprue P1 is not normally gripped.

A mounting plate 32 is disposed in a direction perpendicular to the third member 27 c of the arm 27. The lengths of the upper portion and the lower portion of the mounting plate 32 relative to the third member 27c are substantially equal to the longitudinal length of the light guide plate P to be molded. An adsorption holding portion 33 for adsorbing the light guide plate P to the upper two places and the lower two places of the attachment plate 32 toward the movable mold 20 side on the surface of the attachment plate 32 on the movable mold 20 side. Is fixed. The suction holding part 33 includes a cup part 34 of a porous elastic material (sponge), a string-like spring part 35 for attaching the cup part 34 to the attachment plate 32, a pipe 36, and the like. The cup portion 34 is particularly preferably an elastomer having excellent heat resistance, and porous silicon rubber or porous fluorine rubber is used. The cup part 34 includes a disk part 34b having a suction surface 34a having a diameter of 8 to 16 mm and a thickness of about 5 mm, a V-grooved constriction part 34c behind it, and a base part 34d behind it. The base portion 34d is fixed to a string-wound spring portion 35, and the other end of the spring portion 35 is fixed to a mounting plate 32. The suction surface 34a is a flat surface in which a suction hole 34e having a diameter of about 1 mm is formed at the center and a minute small hole is formed around the suction surface 34a. The suction hole 34e is formed through the disk portion 34b, the constricted portion 34c, and the base portion 34d in the axial direction, and a pipe 36 made of a resin having flexibility is connected to the opening portion of the suction hole 34e on the base portion 34d side. It is installed. The pipe 36 passes through the inside of the spring portion 35, is fixed to the arm 27 and extends, and is connected to a vacuum device (not shown).

The second take-out device 24 installed on the bracket 25 fixed to the side surface of the bed 15 on the side opposite to the operation panel of the injection compression molding machine 11 can be driven to rotate in parallel with the mold opening / closing direction of the injection compression molding machine 11. A first rotating shaft 37 disposed on the first rotating shaft 37, and a second rotating shaft 39 disposed so as to be rotatable with respect to a fixed shaft 38 fixed in a direction perpendicular to the first rotating shaft 37. Is a two-axis transfer robot. The first rotating shaft 37 and the second rotating shaft 39 are both rotationally driven by a third servo motor and a fourth servo motor (not shown), and both perform high-speed operation and sudden stop with high accuracy. It is possible.

An arm 40 is fixed to the tip of the second rotating shaft 39. The arm 40 has a predetermined thickness, and is arranged at a predetermined angle with respect to the first member 40a and the first member 40a provided coaxially with the second rotation shaft 39 in order from the side closer to the second rotation shaft 39. (In the present embodiment, the second member 40b is continuously provided with an inclination with respect to the upright direction at an angle of about 60 ° toward the injection compression molding machine). The second take-out device 24 is arranged in the direction in which the suction holding portion 33 is arranged at the delivery position (release position) A2 of the first take-out device 23 and the second at the delivery position (standby position) B1 of the second take-out device 24. The direction of the member 40b coincides with that of the member 40b and can be stopped.

And the suction holding part 41 is arrange | positioned at the space | interval same as the said 1st taking-out apparatus 23 at the surface at the side of the fixed metal mold 16 of the 2nd member 40b of the arm 40. FIG. The suction holding part 41 of the second take-out device 24 is a general suction cup provided with a rubber pad, and the attachment method of the suction holding part 41 to the arm 40 is attached to the arm 40 via a spring. A flexible resin pipe (not shown) is connected to the suction hole of the cup. The resin pipe is fixed to the arm 40 through the spring and is connected to a vacuum device (not shown) in the same manner as the first take-out device 23.

On the floor surface opposite to the injection compression molding machine 11 with the second take-out device 24 interposed therebetween (further, on the side opposite to the operation side), the floor is positioned lower than the first rotating shaft 37 of the second take-out device 24. A belt conveyor 42 is provided. The belt conveyor 42 is a general one, and a rubber belt 43 having a predetermined width is intermittently driven by a motor (not shown).

As shown in FIGS. 1 and 2, a funnel-like shooter 44 having an upper opening is formed on the side of the injection device 13 of the second take-out device 24 on the side of the bed 15 on the side opposite to the operation panel of the injection compression molding machine 11. It is arranged. The shooter 44 is disposed below the delivery position (release position) A2 of the first take-out device 23 as a receiving member for collecting the sprue P1 when the first take-out device 23 releases the sprue P1. ing. 1 and 2, the pipe 45 below the shooter 44 is omitted from the middle, but the sprue P1 may be dropped into a collection box (not shown), and the pipe line extends to the upper part of the injection device. The sprue P1 may be air-conveyed by means such as air and then recycled from the inlet of the injection device. Note that the movement area of the take-out devices 23 and 24 and the movement area of the movable mold 20 are provided with safety doors and protective measures, but are not shown in the figure.

Next, the injection compression molding die 51 of the light guide plate of this embodiment will be described with reference to FIG. The injection compression molding mold 51 includes a movable mold 20 that is a first mold and a fixed mold 16 that is a second mold. Between the molds 20 and 16 that have been matched, Cavities C1 and C2 of variable volume and thickness are formed for use in injection compression molding or injection press. The movable mold 20 is provided with a mold body 52, a core 53, a movable frame 54, and the like. The core portion 53 is fixed to the mold main body portion 52, and the surrounding movable frame portion 54 is attached to the mold main body portion 52 by a spring 54a. Therefore, in the movable mold 20, the position of the core portion 53 and the movable frame portion 54 can be relatively changed in the mold opening / closing direction. Two cavity forming blocks 55 and 55 are fixed to the core portion 53, and cavity forming surfaces 55a and 55a are formed on the cavity forming blocks 55 and 55, respectively.

An ejector pin 56 of an ejector device that is advanced by a drive device (not shown) and retracted by a spring is disposed at a position facing the sprue bush 64 of the stationary mold 16 at the center of the mold body 52 and the core 53. Has been. Further, a biting portion 56 a for pulling out the sprue P <b> 1 to the movable mold 20 side is provided on the front end surface of the protruding pin 56. In addition, runner formation surfaces 57 that form runners P2 are formed from the biting portions 56a toward the respective cavity formation surfaces 55a. In addition, a gate cutter 58 that is advanced by a driving device (not shown) and retracted by a spring is disposed adjacent to the cavity forming block 55 in the movable mold 20. When the gate cutter 58 is moved forward, the gate P3 is provided so as to be cut by being crossed with the fixed gate cutter 65 of the fixed mold 16. In the movable mold 20, there are provided two channels of a cooling medium channel 59 for cooling the cavity forming surface 55 a and a cooling medium channel 60 for cooling the runner forming surface 57, the protruding pin 56 and the like. It has been.

The fixed mold 16 as the second mold includes a mold body 61, a cavity forming block 62 in which a cavity forming surface 62a is formed, an insert block 63, a sprue bush 64, a fixed gate cutter 65, and a contact block 66. Etc. The sprue bush 64 is a passage for injecting the molten resin from the nozzle 12 b, and the surface of the insert block 63 forms a runner forming surface 67. The fixed gate cutter 65 is disposed adjacent to the cavity forming block 62 so as to be fitted with the gate cutter 58. Further, in the fixed mold 16, there are two systems of channels: a cavity cooling medium channel 69 for cooling the cavity forming surface 62 a and a sprue cooling medium channel 70 for cooling the runner forming surface 67, the sprue bush 64, and the like. Is a cold runner (including sprue) type. In this embodiment, two cavities C1 and C2 are arranged in the vertical direction in the injection compression molding die 51. However, two cavities may be formed in the horizontal direction, and the number of cavities is as follows. As an example, a plurality such as 1 to 4 may be used. Then, the number and arrangement of the suction holding portions of the take-out device are made corresponding to the number and arrangement of the cavities.

Next, the injection compression molding method of the light guide plate P by the injection compression molding machine 11 of the present embodiment will be described with reference to the chart of FIG. In the present embodiment, the light guide plate P having a diagonal size of 3 inches and a plate thickness of 0.4 mm is formed with a forming cycle time of 4.4 seconds. The breakdown is as follows: mold opening time 0.5 seconds, removal time 0.4 seconds, mold closing time 0.5 seconds. The time from mold opening start to light guide plate P removal to mold closing completion is 1.4. In seconds. The time from the start of mold opening to the completion of mold closing after taking out the light guide plate P is preferably within 2.2 seconds (0.75 to 2.2 seconds), and more preferably within 1.5 seconds ( 0.75 to 1.5 seconds) is more desirable. Of the time from the start of mold opening through the removal of the light guide plate P to the completion of mold closing, the fastest 0.75 seconds is the mold opening / closing / clamping mechanism by the servo mechanism and the swing type take-out apparatus by the servo motor as described above. Is the shortest time that can be realized by using. The maximum 2.2 seconds of the time from the start of mold opening to the completion of mold closing after taking out the light guide plate P is 0.6 seconds for mold opening and mold closing, respectively, as will be described later. The time is 1.0 second. The case where the take-out time is required for 1.0 seconds is the purpose of eliminating the trace of the light guide plate held by releasing the release by air or contacting the light guide plate formed at a very low speed. Furthermore, even if the mold opening / closing time is extended, the molding cycle time is extended, resulting in poor production efficiency, and the residence time of the molten resin in the heating cylinder of the injection device becomes too long, or the nozzle is cooled and cold. There is a problem that slag is generated. The time from the completion of mold closing to the start of mold opening after injection is 3.0 seconds, and the breakdown is: injection delay time (pressure increasing time) 0.1 seconds, injection time 0.05 seconds, pressure holding time 0 .45 seconds and cooling time of 2.4 seconds (substantially cooling starts from the start of injection). However, the time from the completion of mold closing to the start of mold opening after injection varies in the range of 1.75 to 6 seconds depending on the shape of the light guide plate (area, plate thickness, transfer surface shape). In order to shorten the time, it is desirable that the time be within 4 seconds (1.75 to 4.0 seconds).

If the size of the light guide plate P is within this range, the molding cycle time is not affected so much. However, if the molding cycle time is further reduced, the cooling time of the sprue P1 is particularly insufficient, and the sprue is insufficiently solidified. A defect or the like in which the sprue does not come off occurs. 6 and 7 are charts showing the injection compression molding method of the light guide plate of this embodiment. FIG. 6 shows an example of a molding cycle time of 2.5 seconds, and FIG. 7 shows an example of a molding cycle time of 6 seconds. ing. The breakdown when the molding cycle time is 2.5 seconds is as follows. As shown in the chart of the light guide plate injection compression molding method of FIG. 6, the mold opening and closing time (including the extraction time and intermediate time) is 0.75 seconds. Injection delay time (pressure increase time) 0.1 seconds, injection time 0.05 seconds, pressure holding time 0.4 seconds, cooling time 1.2 seconds (1.75 seconds from mold closing completion to mold opening start) is there. If the size of the light guide plate P is within this range, the molding cycle time is not affected so much. However, if the molding cycle time is further reduced, the cooling time is insufficient, and the thickest sprue P1 is insufficiently solidified. In this case, there is a defect that the sprue P1 cannot be removed. Further, as shown in FIG. 7, a light guide plate having a transfer pattern with a diagonal dimension of 3 inches and a plate thickness of 0.6 mm (uniform plate thickness) can be formed by injection compression molding with a molding cycle time of 6.0 seconds. The cooling time is 3.9 seconds.

As described above, the diameter and taper angle (draft angle) θ of the sprue P1 shown in FIG. 8 have the most influence as factors determining the cooling time in the molding cycle time in the present invention. In this embodiment, the diameter of the nozzle hole (not shown) of the nozzle of the injection device is 1.5 mm. The diameter of the injection hole 64a on the nozzle hole side of the sprue bush 64 needs to be larger than the diameter of the nozzle hole so that the resin at the tip of the nozzle can be satisfactorily removed when the sprue is pulled out. It is desirable to use holes. 9 to 13 use an injection compression molding die of a light guide plate that takes two light guide plates P with a diagonal dimension of 2.8 inches and a plate thickness of 0.4 mm, and cool the cavity forming surfaces 55a and 62a. The temperature of the cooling water in the cooling medium passages 59 and 69 is 90 ° C., the nozzle temperature is 325 ° C., the heating cylinder front temperature is 355 ° C., the heating cylinder middle temperature is 370 ° C., the heating cylinder rear temperature is 360 ° C., and the injection speed is 300 mm / sec. This is the result of testing.

FIG. 9 shows data when the sprue bushing 64 having a diameter of the injection hole 64a of 1.6 mm, a taper angle θ of 1 ° and a length of 25 mm shown in FIG. In this example, when the cooling temperature of the sprue bush 64 is 70 ° C. and 80 ° C., if the molding cycle time becomes long (more than 5 seconds), the injection hole 64a of the sprue bush 64 and the nozzle hole of the nozzle are overcooled. As a result, there was a problem that the next injection could not be performed or cold slag was mixed with the molded product. Even when the cooling temperature of the sprue bushing 64 was 90 ° C., it became defective in 6 seconds or more. Accordingly, the diameter of the injection hole 64a of the sprue bush 64 is 1.6 mm, so that the practical range is extremely narrow, and if it is less than that, a practical setting adjustment cannot be made.

FIG. 10 shows data when the sprue bushing 64 having a diameter of the injection hole 64a of 2.0 mm, the taper angle θ shown in FIG. 8 of 1 °, and a length of 25 mm is used. In this example, even at each cooling temperature, when the molding cycle time is 2 seconds, the cooling of the sprue P1 may not catch up and sprue breakage may occur. However, it is not economical to extend the molding cycle time more than necessary. And if the molding cycle time is extended too much, the nozzle is cooled and the fluidity of the molten resin is lowered, and the residence of the molten resin in the heating cylinder becomes too long, and the resin deteriorates (yellowing or black spots). Problems also arise. As for the temperature of the cooling water, when the temperature is 40 ° C., cold slag begins to mix with the molded product, and thus it is preferably 50 ° C. or higher. In the case of 120 ° C., sprue breakage occurs in 4 seconds, so the cooling temperature used for molding is desirably 110 ° C. or lower.

FIG. 11 shows data when the sprue bushing 64 having a diameter of the injection hole 64a of 2.3 mm, the taper angle θ shown in FIG. 8 of 1 °, and a length of 25 mm is used. In this example, when the cooling temperature is 70 ° C., sprue breakage occurs when the molding cycle time is 3 seconds, and when the cooling temperature is 80 ° C. and 90 ° C., sprue breakage occurs even when the molding cycle time is 5 seconds.

FIG. 12 shows data when the sprue bushing 64 having a diameter of the injection hole 64a of 2.6 mm, a taper angle θ shown in FIG. 8 of 1 °, and a length of 25 mm is used. In this example, the diameter of the runner connection portion 64c is 3.47 mm, and it takes time to cool and solidify this portion. In this example, when the cooling temperature is 70 ° C., sprue breakage occurs when the molding cycle time is 5 seconds, and when the cooling temperature is 80 ° C. and 90 ° C., sprue breakage occurs even when the molding cycle time is 6 seconds. . Therefore, when the diameter of the injection hole 64a is 2.6 mm, it can be said that it is the upper limit diameter among the above-described cases where the desired molding cycle time is within 6 seconds as described above.

In addition, FIG. 13 uses a sprue bush 64 having a diameter of the injection hole 64a of 1.6 mm, 2.0 mm, 2.3 mm, 2.6 mm, a taper angle θ of 1.5 °, and a length of 25 mm, It is the data at the time of testing by setting a cooling temperature as 70 degreeC. In this example, the diameter of the runner connection portion 64c is 2.9 mm, 3.3 mm, 3.6 mm, and 3.9 mm corresponding to the above, respectively, and there is a problem that the cooling and solidification of this thickest part is particularly delayed. is there. In the example in which the diameter of the injection hole 64a is 2.6 mm, the diameter of the runner connection portion 64c is 3.9 mm, and the taper angle θ is 1.5 °, when the cooling temperature is 70 ° C., the molding cycle time becomes 5 seconds. Sprue breakage occurred, and spur elongation and bending were observed even in 6 seconds, and it was judged unsuitable for practical use. Further, in the case of the other injection hole 64a having the diameter, the molding failure occurred unless the molding cycle time that is the shortest was extended as compared with the case where the taper angle θ of the inner hole 64b of the sprue bush 64 was 1 °. Therefore, when the molding cycle time is within 6 seconds, the sprue bush 64 having the inner hole 64b with a diameter of 3.6 mm of the runner connection portion 64c that is most delayed in cooling is judged to have the maximum diameter in the practical range.

The preferable taper angle θ of the inner hole 64b of the sprue bush 64 is preferably increased by 0.5 to 2.0 ° from the injection hole 64a toward the runner connection portion 64c. However, if the diameter of the runner connection portion 64c exceeds 3.6 mm, the cooling and solidification in the vicinity of the runner connection portion 64c is delayed even when the molding cycle time is 6 seconds (cooling time 3.9 seconds), and the sprue P1 is cut when the mold is opened. May occur. Once the sprue P1 remains in the sprue bush 64, continuous molding is interrupted, and a skilled worker needs to work in a narrow space to take out the sprue P1 and possibly damage the mold. is there. The wall thickness 64d of the portion where the cooling medium flow path 70 is provided in the small diameter portion of the sprue bush 64 is preferably about 15 to 30 mm.

For this reason, in this embodiment, the cavity cooling medium flow path 59 for cooling the cavity forming surface 55 a of the movable mold 20, the cooling medium flow path 60 for cooling the vicinity of the runner forming surface 57 and the protrusion pin 56, and the fixed mold 16. Glass transition of polycarbonate, which is a resin molded by a temperature controller, to cavity cooling medium flow path 69 for cooling cavity forming surface 62a, runner forming surface 67, sprue cooling medium flow path 70 for cooling sprue bushing 64, and the like. A cooling medium (cooling water) whose temperature is controlled to about 50 to 110 ° C., which is 40 to 100 ° C. lower than the temperature Tg, is flowing. Note that the temperature of the cooling medium in the sprue cooling medium flow path 70 may be set lower than the others to promote the cooling of the sprue P1 that takes the longest time for cooling and to prevent stringing.

The temperature of the front zone (zone closest to the nozzle) of the heating cylinder 12a is set to 340 ° C., and the molten resin of polycarbonate is measured. When polycarbonate is used, the temperature setting of the front zone of the heating cylinder 12a is preferably set to 330 to 380 ° C. Then, the mold clamping cylinder 22 as a mold opening / closing / clamping mechanism is operated, and the movable mold 20 attached to the movable platen 21 is brought into contact with the fixed mold 16 attached to the fixed platen 17 to close the mold. Is done. Next, the mold clamping force is increased to 50 to 200 kN to perform mold clamping. As a result, the mold main body portion 52 of the movable mold 20 and the movable frame portion 54 are brought into contact with each other by overcoming the resilience of the spring 54 a, and the movable frame portion 54 is finally retracted from the core portion 53. Become. A runner P2 including a variable thickness gate P3 and variable thickness cavities C1 and C2 connected to the gate P3 are formed between the fixed mold 16 and the movable mold 20. At this time, it is desirable to suck the air in the cavities C1 and C2 from the viewpoint of the molten resin flow into the cavities C1 and C2. In this embodiment, the nozzle of the injection device (not shown) is always in contact with the sprue bush 64 in order to shorten the molding cycle time.

Next, when a predetermined delay time elapses, the molten resin is injected from the nozzle 12b of the injection device 13 (not shown) through the sprue bush 64 at an injection speed of 100 to 400 mm / sec. The movable platen 21 and the core portion 53 of the movable mold 20 are retracted again by the pressure during injection. As a result, the movable frame portion 54 of the movable mold 20 is positioned relatively forward of the core portion 53, and the interval between the cavity forming surface 62a of the fixed mold 16 and the cavity forming surface 55a of the movable mold 20 is Compared with the position where the mold clamping force is initially exerted as shown in FIG. Further, when the core 53 of the movable mold 20 is retracted, the molten resin can be injected into the cavities C1 and C2 in which the cross-sectional area of the gate P3 is increased, and the flow loss of the molten resin can be reduced. As a result, since the molten resin can be injected at a relatively low speed and low pressure, there is an advantage that internal stress is not generated particularly near the gate of the light guide plate P.

When the screw position of the injection device 13 reaches a predetermined holding pressure switching position, the injection control is switched to the holding pressure control. Even after switching to the holding pressure control, the mold clamping cylinder 22 performs mold clamping with a high clamping force, and after the switching to the holding pressure control, the clamping force is reduced after a certain time. Alternatively, the mold clamping force may be decreased simultaneously with the holding pressure switching. In the present embodiment, the gate cutter 58 is advanced by 0.45 to 0.8 mm by a driving device (not shown) almost simultaneously with the decrease in the mold clamping force, and the gate P3 is cut. At this time, the gate cutter 58 of the movable mold 20 and the fixed gate cutter 65 of the fixed mold 16 are crossed to cut the gate P3. Needless to say, the molten resin of the gate P3 is not completely solidified when the gate is cut.

Then, after the gate P3 is cut by the gate cutter 58, the gate cutter 58 is held at the advanced position. As a result, the holding pressure does not completely reach the molten resin in the cavities C1 and C2 from the injection device 13 side, but the movable mold 20 is advanced by driving the mold clamping cylinder 22 to move into the cavities C1 and C2. Since the molten resin can be compressed, sink marks do not occur even when shrinkage occurs due to cooling, and good transfer molding can be performed. In the meantime, the molten resin used for the next molding is measured in the heating cylinder 12a of the injection device 13. Before the end of the cooling time, the air passage between the movable frame portion 54 and the cavity forming block 55 of the movable mold 20, the air passage between the cavity forming block 62 and the contact block 66 of the stationary mold 16, etc. Supply of release air (air blow) to C1 and C2 is started. Next, the mold clamping cylinder 22 is operated to perform pressure release and mold opening in order. In this embodiment, the cooling time from the completion of the pressure holding to the start of mold opening (including the pressure release) is 2.4 seconds.

Next, the mold clamping cylinder 22 is operated, and the movable platen 21 and the movable mold 20 are moved to open the mold. When the mold opening is started, the sprue P1 including the runner P2 is biting into the biting portion 56a at the tip of the projecting pin 56 of the movable mold 20. Therefore, the sprue P1 is extracted from the sprue bush 64 of the fixed mold 16. The light guide plate P is also opened from the concave mold shape while being held on the cavity forming surface 55a of the movable mold 20. Accordingly, both the sprue P1 including the gate-cut runner P2 and the light guide plate P are held in a state separated from the movable mold 20 and moved in the mold opening direction. Simultaneously with the mold opening, the blowing of the mold release air is stopped in the fixed mold 16. In this embodiment, from the start of mold opening of the movable mold 20 to completion of mold opening is performed in 0.5 seconds, this mold opening time can be changed between 0.3 and 0.6 seconds. The mold opening stroke (substantially equal to the interval between the fixed mold 16 and the movable mold 20 when the mold opening is completed) is 60 to 100 mm.

Then, in response to the mold opening completion signal transmitted when the mold opening is completed, the rotating shaft 26 of the first take-out device 23 is rotated counterclockwise in FIG. 1, and the arm 27, the suction holding portion 33 and the like are moved from the standby position A3. It is moved to a position facing the light guide plate P in the vicinity of the opened movable mold 20 and stopped. Next, the rotary shaft 26 moves 15 to 30 mm in the mold opening direction, and the arm 27, the suction holding portion 33 and the like are moved to the holding position A1. As a result, the suction surface 34 a of the cup portion 34 of the suction holding portion 33 is brought into contact with the reflection surface transferred and molded by the cavity forming surface 62 a of the fixed mold 16 of the light guide plate P. Note that the air suction to the suction holding portion 33 of the first take-out device 23 is activated simultaneously with the start of the operation of the take-out device 23, so that the suction is performed simultaneously with the contact of the suction surface 34a. The suction force at that time is about −50 to −120 kpa, and is a relatively weak suction force so as not to leave a mark on the light guide plate P immediately after molding. Further, since the cup portion 34 of the suction holding portion 33 is made of a porous elastic material (sponge), the entire suction surface 34a is attracted to the light guide plate P, so that the light guide plate P is not further marked. Furthermore, in this embodiment, since the molding cycle time is as short as 4.4 seconds, the heat of the molded light guide plate P is transmitted to the cup portion 34 and the temperature is above a certain level. Therefore, this point is also an element with no trace on the light guide plate P.

Further, at the same time when the first take-out device 23 moves to the holding position A1, the detection sensor 31 determines whether or not the sprue P1 extracted from the sprue bush 64 is normally located between the chuck members of the chuck 30 inside the V-groove 28. Detected. When the sprue P1 is detected by the detection sensor 31, the chuck 30 is closed by the electromagnet actuator, and the sprue P1 including the runner P2 is held by the chuck 30. When the light guide plate P is sucked by the suction holding portion 33 and the sprue P1 including the runner P2 is gripped by the chuck 30, the rotation shaft 26 and the arm 27 of the first takeout device 23 slightly move again in the mold closing direction. Then, the light guide plate P is released from the cavity forming surface 55a, and the sprue P1 including the runner P2 is removed from the biting portion 56a at the tip of the protruding pin 56. Supply of release air in the movable mold 20 is also performed during release of the light guide plate P and the sprue P1 including the runner P2 by the first take-out device 23, and assists release of the light guide plate P and the like. . Note that the light guide plate P may be further easily removed by opening a part of the movable frame portion of the movable mold outward or by advancing the cavity forming surface.

Next, the rotating shaft 26 of the first take-out device 23 is rotated clockwise in FIG. 1, and the position indicated by the two-dot chain line (the position where the first take-out device 23 and the second take-out device 24 overlap in FIG. 1). When the arm 27 is swung, the rotation shaft 26 stops rotating. Then, the rotation shaft 26 of the first take-out device 23 is moved again in the mold opening direction, and the arm 27 and the suction holding portion 33 are moved to the delivery position (release position) A2. In the present embodiment, the time required for taking out the light guide plate P and the sprue P1 from the start of the operation of the first take-out device 23 and moving to the delivery position (release position) A2 is 0.4 seconds. In the meantime, cooling of the light guide plate P proceeds.

The second extraction device 24 stands by with the arm 40 stopped at the position indicated by the solid line in FIG. 1 so that the light guide plate P can be received from the first extraction device 23 at the delivery position (release position) A2. The suction holding portion 41 of the second extraction device 24 is sucked with air before the light guide plate P is brought into contact therewith. It should be noted that the suction holding unit 41 of the second take-out device 24 is strongly sucked with a lower degree of vacuum than the suction holding unit 33 of the first take-out device 23. Then, the first extraction device 23 moves in the mold opening direction, and the surface formed by the cavity forming surface 55 a of the movable mold 20 in the light guide plate P (the light exit surface in this embodiment) is the second extraction device 24. When the suction holding unit 41 comes into contact and is sucked, the suction holding unit 33 of the first take-out device 23 stops air suction, and immediately after that, the first take-out device 23 moves backward, and the light guide plate P 2 to the take-out device 24.

Further, the sprue P1 including the runner P2 gripped by the chuck 30 of the first take-out device 23 opens at the delivery position (release position) A2, and drops into the lower shooter 44. The chuck 30 may be opened and the sprue P1 may be dropped at the same time as the delivery of the light guide plate P. If there is a possibility that the sprue P1 may come into contact with the light guide plate P when the sprue P1 is dropped, the first takeout is performed. The light guide plate P may be delivered from the device 23 to the second take-out device 24, and the take-out device 23 may be retracted in the mold closing direction. Then, after delivering the light guide plate P to the second take-out device 24 and dropping the sprue P1, the arm 27 of the first take-out device 23 is moved to a standby position A3 indicated by a one-dot chain line in FIG. The standby position A3 is in a range that is not affected by heat from the mold that does not interfere with the moving region of the movable mold 20, and the position closer to the movable mold 20 can contribute to shortening the molding cycle time.

Further, at the same time as the first take-out device 23 moves backward after delivering the light guide plate P, the second take-out device 24 is driven to rotate the first rotating shaft 37 counterclockwise in FIG. A fixed shaft 38 fixed in a direction perpendicular to the first rotating shaft 37 is swung. At the same time, the second rotating shaft 39 rotatably attached to the fixed shaft 38 is also rotated by 90 °, and is inclined and connected to the first member 40a of the arm 40 as the second rotating shaft 39 rotates. The second member 40b is also rotated 90 ° so that the suction holding portion 41 and the held light guide plate P are directed downward. When the arm 40 is swung to the release position B2 indicated by the two-dot chain line in FIG. 1, the rotation of the first rotating shaft 37 is stopped and the swinging of the arm 40 is stopped. Next, air suction to the suction holding unit 41 is stopped, the light guide plate P is released with the reflection surface facing downward, and dropped onto the rubber belt 43 of the belt conveyor 42. In the present embodiment, the two light guide plates P are dropped in a direction orthogonal to the moving direction of the rubber belt 43. However, since the light guide plate P is dropped by a small distance on the rubber belt 43, the light guide plate P is not damaged. Absent.

Then, the second take-out device 24 that has released the light guide plate P rotates the first rotary shaft 37 and the second rotary shaft 39 in the opposite manner, and is returned to the delivery position (standby position) B1 again. Further, the belt conveyor 42 is intermittently driven so that the next light guide plate P can be placed, and the rubber belt 43 is fed forward by a predetermined dimension. The light guide plate P is further cooled on the rubber belt 43, and is then packed manually or by a robot.

The first take-out device 23 and the second take-out device 24 are connected to and controlled by a controller for a take-out device (not shown) disposed in the injection compression molding machine 11. The controller for the take-out device is connected to a controller of an injection compression molding machine 11 (not shown). Accordingly, in response to the mold opening start signal from the injection compression molding machine 11, the air suction of the first extraction device 23 is activated, and in response to the mold opening completion signal, the first extraction device 23 starts the rotation of the arm 27. Further, in response to the operation of the arm 27 of the first extraction device 23, the air suction of the second extraction device 24 is started and the operation of the arm 40 is performed. In response to the movement of the first take-out device 23 to the delivery position (release position) A2 outside the movable mold 20, a mold closing start signal is transmitted and the mold closing operation is performed. In this embodiment, the time from the start of mold closing of the movable mold 20 to the completion of mold closing is 0.5 seconds, but this mold closing time can be changed between 0.3 and 0.6 seconds. For example, in some cases, it is better not to pursue the maximum mold opening speed and mold closing speed from the viewpoint of the durable life of the injection compression molding machine 11 and the injection compression molding mold 51 and the stability of measurement.

In the present embodiment, the reason why the take-out devices 23 and 24 are swing arm type and the light guide plate P is delivered between the two take-out devices 23 and 24 at the delivery position is first to shorten the cycle. is there. In this embodiment, the time required for the take-out device to take out the light guide plate or the like (the mold opening is completed, the arm 27 of the first take-out device 23 starts to operate from the standby position A3, and the light guide plate P is taken out from the holding position A1. After that, the time from the moving region of the movable mold 20 to the delivery position (release position) A2) is 0.4 seconds. However, the time is assumed to be in the range of 0.15 to 1.0 seconds, and when a shortening of the molding cycle time is strongly desired, the time can be 0.15 to 0.4 seconds. Further, in order to make the mark of the suction holding part 33 less likely to adhere to the light guide plate P having a high temperature after molding, the speed at which the suction holding part 33 is brought into contact with the light guide plate P can be lowered, It is conceivable to wait for the release air blowing (air blow) to be performed. In that case, it is desirable to extend the required time to about 1.0 second.

Furthermore, by partially overlapping the mold opening / closing operation of the movable mold 20 and the operation of the take-out device 23, the molding cycle time can be further reduced by about 0.3 to 0.5 seconds. For example, by detecting the movable mold 20 moved to the position immediately before the completion of mold opening and operating the arm 27 of the take-out device 23, the mold opening operation and the arm 27 intrusion operation are overlapped, and the molding cycle time is shortened. You can also. Further, the movement of the arm 27 and the suction holding part 33 from the movable region of the movable mold 20 to the outside is detected by a limit switch or the like, and a mold closing start signal is transmitted before reaching the delivery position A2, thereby closing the mold. It is also possible to shorten the molding cycle time by overlapping the operation and the retracting operation of the arm 27.

The present invention is not enumerated one by one, but is not limited to that of the above-described embodiment, and it goes without saying that those skilled in the art also apply modifications made in accordance with the spirit of the present invention. is there. The swing arm type first take-out device may be at least as long as the arm swings, and the entire arm does not move in the mold opening / closing direction, and only the suction holding portion at the tip of the arm moves in the mold opening / closing direction. You may be made to do. In addition, the second take-out device may be transferred so as to be movable in the mold opening / closing direction without making the first take-out device movable in the mold opening / closing direction, in which case the mold is transferred to the first take-out device. In order to adsorb the light guide plate, a mechanism may be separately provided in the mold or the movable plate may be slightly advanced. The placement positions of the first take-out device and the second take-out device can also be changed on the bed, on the fixed plate, on the placement table on the floor, or the like. Furthermore, in the present invention, the first take-out device is taken out in a state where the light guide plate and the sprue are separated to the release position outside the mold, and the second take-out device is not essential. For example, the rotation drive shaft may be further increased on the arm of the swing arm type first take-out device, and the light guide plate may be placed in a horizontal state at the release position so as to be directly released and placed on the conveyor. The suction holding portion of the first take-out device may be a normal rubber pad or a multi-stage bellows type, and the material may be urethane rubber or nitrile rubber, and is not limited. As the take-out device, a horizontally-moving take-out device that moves in a horizontal direction between a holding position near the movable mold and a release position outside the mold may be used. In that case, the time required for taking out is 0.8 to 2.2 seconds. Also for the horizontal movement type take-out device, an adsorption holding unit that adsorbs the light guide plate and a chuck that holds the sprue are provided, and the light guide plate and the sprue are held in a separated state. The adsorption holding unit is preferably a porous elastic material such as silicon rubber.

In the present embodiment, the injection compression molding die for the light guide plate for a mobile phone having a diagonal size of 3 inches has been described, but the size of the light guide plate is 1.5 inches to 7 inches in diagonal size (7. 7 in terms of area). 5cm containing ² or more 150 cm ² or less of those, or those of the area having no corners at the four corners) of what is desirable. A plurality of die is often used for a diagonal dimension of 5 inches or less, and a single die is often used for 6 to 7 inches. The shape of the light guide plate may be a light guide plate having a uniform thickness or a wedge-type light guide plate whose thickness decreases from the light incident surface side toward the other side, and transmits light such as a backlight. If it is a thing, a light-diffusion plate, a lens, etc. shall fall into the category of a light-guide plate. As for the resin used for forming the light guide plate, polycarbonate (as an example, Idemitsu Kosan's Taflon LC1500) has been described. However, other resins may be used as long as they have excellent optical performance. Resin etc. are mentioned. Since the temperature of the molten resin and the glass transition temperature differ depending on the resin, it goes without saying that the timing of gate cut, the temperature of the cooling medium, the molding cycle time, and the like are also different.

Moreover, since the light guide plate P of this embodiment has a plate thickness of 0.4 mm, an injection compression molding method is used in this embodiment, but when the plate thickness is about 0.2 to 0.4 mm, an injection press method is used. Can also be considered. The injection press increases pressure from a state where the mold clamping force is already low or close to 0 with the cavity spacing already wide at the mold closed position, and injection is performed at a relatively low speed and low pressure even when the plate thickness is very thin. can do. FIG. 14 is a chart showing a light guide plate injection press method, in which a light guide plate having a transfer pattern with a diagonal dimension of 3 inches and a plate thickness of 0.3 mm (equal plate thickness) is formed in a molding cycle time of 4.2 seconds. An example is shown. The cooling time in this case is 2.2 seconds. Further, in the present embodiment, the injection compression molding die attached to the injection compression molding machine in which the mold is opened and closed in the horizontal direction has been described. However, the mold may be opened and closed in the vertical direction.

In the above embodiment, a type called a flat mold in which the position of the movable frame portion 54 can be changed relative to the core portion 53 has been described, but the convex portion of one mold is in the concave portion of the other mold. The present invention can also be applied to a type called an inlay mold that is fitted and a cavity having a variable volume is formed therebetween. In this embodiment, the gate is completely cut by the gate cutter in the mold, but the chuck of the take-out device has an action of moving the sprue with respect to the light guide plate, an action of cutting, etc. The light guide plate and the sprue may be separated and taken out by the take-out device.

It is the front view which looked at the extraction device of the light guide plate of this embodiment from the movable platen side to the fixed platen side. It is a side view of the taking-out apparatus of the light-guide plate of this embodiment. It is a principal part expansion perspective view of the taking-out apparatus of the light-guide plate of this embodiment. It is sectional drawing of the injection compression molding metal mold | die of the light-guide plate used for this embodiment. It is a chart figure which shows the injection compression molding method of the light-guide plate of this embodiment. It is a chart figure which shows the injection compression molding method of the light-guide plate of this embodiment. It is a chart figure which shows the injection compression molding method of the light-guide plate of this embodiment. It is an expanded sectional view of the sprue bush of the injection compression molding die of the light guide plate of this embodiment. It is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and molding cycle time. It is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and molding cycle time. It is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and molding cycle time. It is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and molding cycle time. It is a figure which shows the relationship between the sprue shape of the injection compression molding metal mold | die of the light-guide plate of this embodiment, and molding cycle time. It is a chart figure which shows the injection press method of the light-guide plate of another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Injection compression molding machine 16 Fixed metal mold | die 17 Fixed disk 20 Movable metal mold | die 21 Movable disk 23 1st taking-out apparatus 24 2nd taking-out apparatus 30 Chuck 33 Adsorption holding part 42 Belt conveyor A1 Holding position A2 Delivery position (release position)
A3 Standby position B1 Delivery position (standby position)
B2 release position P light guide plate P1 sprue P2 runner P3 gate

Claims (5)

In the light guide plate molding method of forming the light guide plate in the mold by injection molding,
A molding method for a light guide plate, characterized in that a molding cycle time is shortened by partially overlapping a mold opening / closing operation and an operation of a take-out device for taking out the light guide plate. The light guide plate forming method according to claim 1, wherein the take-out device is a swing arm type in which an arm provided in a direction perpendicular to a rotation shaft rotated by a motor is swung. 3. The method for forming a light guide plate according to claim 1, wherein the mold opening operation and the arm intrusion operation are overlapped to shorten the molding cycle time. The extraction of the light guide plate takes 0.15 to the time until the arm attached to the rotating shaft of the extraction device reaches the release position outside the mold from the standby position outside the mold through the holding position near the mold. The method for forming a light guide plate according to any one of claims 1 to 3, wherein the method is performed in 1.0 second. The light guide plate forming method according to any one of claims 1 to 4, wherein the light guide plate formed in the mold and taken out has a diagonal dimension of 7 inches or less.

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