JP2008149561A - Injection molding mold of side-light type light guide plate and side-light type light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding mold of a side-light type light guide plate which solves the problem wherein a light incident surface forming surface forming a non-planar light incident surface is worn and damaged when injection molding the side-light type guide plate having the non-planar light incident surface such as groove or dot, and can easily test a plurality of light incident surfaces by a simple mechanism. <P>SOLUTION: The light incident surface forming surface 42 for forming the light incident surface P3 of an injection molding mold 11 for the side-light type light guide plate P having the non-planar light incident surface P3 can be retracted outward from a cavity forming position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an injection mold for a sidelight-type light guide plate having a non-planar light incident surface, and a light guide plate formed by the mold, and in particular, an injection compression mold for a sidelight-type light guide plate. Further, the present invention relates to a sidelight type light guide plate formed by the mold.

Light guide plates used in liquid crystal, plasma, and organic EL display devices are broadly classified into backlight type light guide plates that receive light from the back and sidelight type light guide plates that receive light from the light incident part on the side. The The sidelight type light guide plate is also referred to as an edge light type light guide plate. Compared with the backlight type light guide plate, a light source such as an LED can be provided on the side surface, so that the display device can be made thin. However, in a side-light type light guide plate, in order to allow light to enter from one side or rarely two side surfaces, the luminance is made substantially constant at the light exit surface of the light guide plate at a portion near the light source and a portion far from the light source. There was a problem that it was difficult to do. In the present invention, the side light type light guide plate only needs to have a light source on the side surface of the light guide plate, and often includes a so-called front light type light guide plate.

In the sidelight type light guide plate, those described in Patent Document 1 to Patent Document 3 are known as devices that devise the light exit surface and the reflective surface in order to make the luminance of the portion near and far from the light source substantially constant. ing. Patent Document 1 describes an example in which the brightness is made constant by changing the width of the groove on the light exit surface from the center to the end in FIG. Patent Document 2 describes an example in which luminance unevenness is eliminated by changing a gradation pattern according to a light emission state in the vicinity of an LED. Furthermore, Patent Document 3 describes that the roughness of the exit surface is increased as the distance from the entrance surface increases.

Moreover, what was described in patent document 4 and patent document 5 is known as what devised the shape of the light-incidence surface in order to make luminance substantially constant in a sidelight type light-guide plate. Patent Document 4 describes that a radial slit is formed on the incident surface side as shown in FIG. Further, Patent Document 5 describes that the incident surface is provided with a concavo-convex formed of a continuous curved surface. The shape of the light incident surface or the like of these side light type light guide plates is determined on the assumption of light refraction for the purpose of making the luminance of the light exit surface substantially constant. However, the brightness of the light exit surface is actually affected not only by the shape of the light guide plate but also by properties such as the birefringence of the resin forming the light guide plate, molding distortion, and the like. Therefore, it was impossible to completely understand the result of actually forming the side light type light guide plate and not testing the luminance distribution.

On the other hand, as to how the light guide plate pattern is formed by using a molding die, Patent Document 1 discloses that a light guide plate prism pattern is engraved in an injection mold, and the light guide plate is formed by injection molding. Although it is described that the pattern is formed at this time, there is no further disclosure about the specific contents. In particular, there has been no conventionally disclosed method for forming fine irregularities on the light incident surface.

Japanese Patent Laying-Open No. 2005-135843 (0028, FIG. 8) JP 2004-145035 A (Claim 1, 0021, FIG. 4) Japanese Patent Laid-Open No. 10-48429 (0026, FIG. 5) JP 2004-259709 A (0046, FIG. 4) JP-A-2005-228718 (Claim 1, FIG. 1, FIG. 2)

In the present invention, in view of the above problems, an injection molding metal for a sidelight type light guide plate corresponding to various problems conceivable when injection molding a sidelight type light guide plate having a non-planar light incident surface such as a groove or a dot. The purpose is to provide a mold. In particular, the sidelight type light guide plate that solves the problem that the light incident surface forming surface that forms a non-planar light incident surface is worn or damaged, and that can test a plurality of light incident surfaces with a simple mechanism. An object of the present invention is to provide an injection mold. Another object of the present invention is to provide an injection mold for a sidelight type light guide plate that is intended to be easily released without damaging the light incident surface. In addition, in response to injection compression molding as a field of injection molding, the injection of sidelight type light guide plate corresponding to various problems that can be considered when molding the sidelight type light guide plate having the light incident surface. An object is to provide a compression mold.

An injection mold for a sidelight type light guide plate according to claim 1 of the present invention is an injection mold for a sidelight type light guide plate having a non-planar light entrance surface for molding the light entrance surface. The light incident surface forming surface is capable of moving backward from the cavity forming position.

The injection mold of the side light type light guide plate according to claim 2 of the present invention is characterized in that the light incident surface forming surface is a separate block from the other cavity forming surface. .

The injection mold of the side light type light guide plate according to claim 3 of the present invention is characterized in that, in claim 2, air is ejected from a gap adjacent to the light incident surface forming surface.

The injection mold of the sidelight type light guide plate according to claim 4 of the present invention is the injection mold according to any one of claims 1 to 3, wherein the light incident surface forming surface is arranged in parallel with the compression direction of the cavity. It is a featured groove.

A side light type light guide plate according to claim 5 of the present invention is formed by an injection mold of the side light type light guide plate according to any one of claims 1 to 4. To do.

The injection mold of the sidelight type light guide plate having a non-planar light incident surface according to claim 1 of the present invention is such that the light incident surface forming surface for forming the light incident surface is outside the cavity forming position. Therefore, even a side light type light guide plate having a non-planar light incident surface can be easily released. Further, in claim 2 of the present invention, in addition to claim 1, since the light incident surface forming surface is a separate block from other cavity forming surfaces, even if the light incident surface forming surface is worn, Only part can be replaced. In addition, by replacing the block with a block having a light entrance surface of another shape, it is possible to test the light entrance surface of various shapes, and a side light type light guide plate having an optimal light entrance surface is simple and cost-effective. It can be formed by a method that does not take.

An injection mold for a side light type light guide plate having a non-planar light incident surface according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an injection compression molding die of the sidelight type light guide plate of the present embodiment, showing a state when no clamping force is exerted. FIG. 2 is a cross-sectional view of an injection compression molding die of the side light type light guide plate of the present embodiment, showing a state where a mold clamping force is exerted. FIG. 3 is a front view of the movable mold of the injection compression molding mold of the sidelight type light guide plate of the present embodiment. FIG. 4 is a front view of a fixed mold of the injection compression molding mold of the sidelight type light guide plate of the present embodiment. FIG. 5 is a perspective view of a side light type light guide plate formed by injection compression molding of the present embodiment.

The injection compression molding die 11 for the sidelight type light guide plate of the present embodiment is an injection compression molding die for simultaneously molding one sidelight type light guide plate for mobile phones having a diagonal size of 2 inches and a thickness of 0.6 mm. Type 11. (Hereinafter, the side light type light guide plate for mobile phones is simply abbreviated as a light guide plate.) The present invention can also be performed by general injection molding in which the volume of the cavity is not changed after mold clamping. It is performed by injection compression molding which is one field in injection molding. In the injection compression molding, the interval between the movable mold 12 and the fixed mold 13 is variable between the start of molding and the end of molding. Therefore, 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 mold closed position. 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. Further, since the molten resin can be injected at a relatively low speed and low pressure, there is an advantage that no internal stress is generated particularly near the gate. 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. Such injection compression molding is particularly advantageous when a light guide plate having a thin plate thickness compared to the area of the flat portion is formed.

1 and 2 are cross-sectional views of the injection compression molding die 11 of the present invention, and are cross-sectional views taken along the line AA in FIGS. As shown in FIG. 1 to FIG. 4, the injection compression molding die 11 includes a movable die 12 as a first die and a fixed die 13 as a second die. A cavity 14 having a variable volume and thickness is formed between the molds 12 and 13. A movable mold 12 attached to a movable platen of an injection compression molding machine (not shown) is provided with a mold body 15, a core 16, and a movable frame 17. A heat insulating plate 18 is attached to the movable platen side of the mold main body 15, and an ejector air cylinder 21 for moving the protruding pin 20 forward and backward through the ejector plate 19 is disposed inside. In this embodiment, the leading end of the protruding pin 20 is provided with a biting portion 20a having a Z-shaped cross section, and the light guide plate P including the gate portion P1 and the sprue portion P2 is easily held by the protruding pin 20. The ejector air cylinder 21 may be operated by a hydraulic cylinder or a servo motor.

Concave portions 22 are formed at four positions on the surface of the mold body 15 on the fixed mold side, and springs 23 are attached in the concave portions 22 toward the fixed mold side. The fixed mold side of the spring 23 is in contact with a back plate 24 constituting the movable frame portion 17. In addition, guide holes 25 are formed at four positions on the inner side of the concave portion 22 on the surface of the mold main body 15 on the fixed mold side. A guide bar 26 provided from the back plate 24 toward the mold main body 15 is inserted into the guide hole 25. Therefore, the movable frame portion 17 including the back plate 24 provided in parallel with the mold main body portion 15 is guided by the guide bar 26 and the guide hole 25 and the distance between the two is changed by the spring 23.

A core portion 16 is fixed substantially at the center of the surface of the mold main body portion 15 on the fixed mold side. In the present embodiment, the core portion 16 has a substantially rectangular shape (a portion with a corner or a convex portion) having the same shape as the main body portion P4 of the light guide plate P. The surface of the core portion 16 that faces the fixed mold 13 is a surface that forms the light exit surface P10 and is a cavity forming surface 27 that is a mirror surface. A plurality of cooling medium channels 28 are formed in the core portion 16 in parallel with the cavity forming surface 27. 1 and 2, the core portion 16 is described as being formed from a single block, but the portion forming the cavity forming surface and the other portion may be formed from separate blocks. Further, the cavity forming surface 27 is an example of a mirror surface, but may be a groove or roughened surface.

A frame body portion 29 is disposed on the surface of the back plate 24 on the fixed mold side so as to surround the periphery of the core portion 16. Therefore, in other words, the core portion 16 is disposed in a hollow portion formed by the back plate 24 and the frame body portion 29 which are the movable frame portion 17. The entire movable frame portion 17 is movable in the mold opening / closing direction with respect to the mold main body portion 15 and the core portion 16 by the spring 23. FIG. 1 shows the state of the movable mold 12 in which the mold clamping force is not exerted and the spring 23 is extended. FIG. 2 shows the state of the movable mold 12 in which the mold clamping force is exerted and the spring 23 is contracted. FIG.

As shown in FIG. 1 to FIG. 3, the frame body portion 29 includes four frame body portions 30, 31, 32, and 33. Of these, the first frame body portion 30 and the second frame body portion 31 are movable in a direction orthogonal to the mold opening / closing direction, and the third frame body portion 32 and the fourth frame body portion 33 are not movable. The frame is fixed to the back plate 24. The moving mechanism of the first frame body part 30 positioned above the core part 16 in FIG. 3 will be described. On the upper surface of the back plate 24, an air cylinder mounting part 34 is projected and fixed toward the fixed mold side. The cylinder portions of the two air cylinders 35 are fixed to the upper surface of the air cylinder mounting portion 34. The rod portions of the air cylinders 35 are disposed downward through the holes provided in the air cylinder mounting portion 34, and the rod portions are respectively attached to the upper surface of the first frame body portion 30. ing. Therefore, the first frame body portion 30 can be moved in a direction orthogonal to the mold opening / closing direction by the operation of the air cylinder 35, and can be moved backward from the cavity forming position. The air cylinders 35, 35 of the moving mechanism may be operated by a hydraulic cylinder or a servo motor.

The moving mechanism of the second frame body portion 31 located on the right side of the core portion 16 in FIG. 3 will be described. One side of the back plate 24 on the fixed mold side has a spring mounting portion 36 facing the fixed mold side. The protrusion is fixed. Concave portions 37 and 37 are formed inside the spring attachment portion 36, and springs 38 and 38 are attached to the concave portions 37 and 37 toward the second frame body portion 31. The second frame 31 is guided by a guide groove (not shown), and a part of the back plate 24 and the fourth frame 33 serves as a stopper on the forward side and can move slightly in the left-right direction in FIG. ing. In addition, a rolling ball may be provided between the second frame body portion 31 and the core portion 16, and the second frame body portion 31 and the core portion 16 may be brought into contact with each other via the ball. The second frame 31 is always located at the cavity forming position by being biased by the springs 38 and 38. The reason why the second frame body portion 31 is movable by a spring is to prevent galling of the movable portion corresponding to the thermal expansion of the mold (particularly the core portion 16) due to the molten resin.

3, the third frame body portion 32 located on the left side of the core portion 16 is fixedly disposed at the left and right target positions with respect to the second frame body portion 31. Further, in the fourth frame body portion 33 located below the core portion 16 in FIG. 3, a gate portion forming surface 39 is formed at a position continuous with the center lower side of the cavity forming surface 27. A through hole 40 is formed at the center of the gate portion forming surface 39, and an ejector projection pin 20 is disposed in the through hole 40 so as to be movable forward and backward. The protruding pin may be disposed on the core portion. A cooling medium flow path 46 is formed around the protruding pin 20 of the fourth frame body portion 33 and in the vicinity of the gate portion forming surface 39. The cooling medium flow path 46 is mainly for cooling and solidifying the movable mold side of the gate part P1 and the sprue part P2 of the light guide plate P to be molded shown in FIG. In the present embodiment, the frame body portion 29 is divided into four parts, but it is sufficient that at least the first frame body part 30 is movable, and any number of other parts may be used. In FIG. 1, two guide bars 41 project from the back plate 24 of the movable frame portion 17 toward the fixed mold 13 below the fourth frame 33.

As shown in FIG. 3, a cavity among the surfaces of the first frame body portion 30, the second frame body portion 31, the third frame body portion 32, and the fourth frame body portion 33 that faces the fixed mold 13. 14 is opposed to the other surfaces 30a, 31a, 32a and 33a so that when the mold is brought into contact with the cavity, a burr is not formed and a slight space through which air flows is formed. Flatness is processed with high accuracy. Air passages 30b, 31b, 32b, and 33b are formed outside the opposing surfaces 30a, 31a, 32a, and 33a so as to surround the cavity 14 and a separate block 43 that will be described later. The outer portion serves as a contact surface with the fixed mold 13. Also, the inner side surface of the first frame body portion 30, the second frame body portion 31, the third frame body portion 32, and the fourth frame body portion 33 adjacent to the core portion 16 along the mold opening / closing direction is shown in FIG. Cavity forming surfaces 30c, 31c, 32c, and 33c forming the side surface P9 of the light guide plate P shown. The cavity forming surface 33c includes a surface 33e that forms the gate portion P1 of the light guide plate P. The inner side surfaces of the cavity forming surfaces 30c, 31c, 32c, 33c that are connected to the fixed platen side are opposed to the outer side surface of the core portion 16 with a slight gap at which no galling occurs.

In addition, in the cavity forming surface 30c of the first frame body portion 30, a light incident surface forming surface 42 that forms the light incident surface P3 of the light guide plate P is provided in a separate block 43, and the block 43 is a bolt. Thus, it is detachably fixed to the other part of the first frame 30. In this embodiment, the main part such as the member forming the cavity forming surface 27 of the mold, the frame portions 30, 31, 32, 33, the block 43, and the cavity forming surface of the stationary mold 13 has a Rockwell hardness of 52 or 52. It is made of 65HRC hard stainless steel (martensitic stainless steel 420J2, Elmax, etc.), and especially hardened Elmax has a Rockwell hardness of 58 to 62 and is excellent in wear resistance and is suitable. Further, the member constituting the cavity forming surface may be coated by DLC, TIN, chrome plating or the like. The hard stainless steel has a thermal conductivity of about 20 to 24 W / (m · k).

In the light guide plate P of the present embodiment, light incident portions P5 slightly projecting from the main body portion P4 are formed at two locations, and the end surfaces of the light incident portions P5 are formed with grooves (vertical grooves) P3a in the plate thickness direction. It is a light incident surface P3. In the present embodiment, the difference (depth) between the peak and valley portions of the groove P3a of the light incident surface P3 is 80 μm. Accordingly, the block 43 forming the light incident surface P3 also has light incident surface forming surfaces 42 and 42 in which grooves in a direction parallel to the compression direction (mold opening / closing direction) of the cavity 14 are formed at two locations. The length in the compression direction of the portion where the groove is formed on the light incident surface forming surface 42 of the block 43 is the same as the plate thickness P6 of the light incident surface P3 of the light guide plate P. In other words, the groove is formed only in the portion exposed from the cavity forming surface 27 of the core portion 16 to the cavity side when the injection compression is completed. And the part which the side surface of the core part 16 and the side surface of the block 43 oppose at the time of completion of injection compression both consists of a plane. The reason is that forming a groove on the side surface of the core portion 16 and engaging with the groove of the block 43 requires high processing accuracy for both, and the entire side surface of the block 43 is a groove, and the entire side surface of the core portion 16 is formed. This is because, when a plane is used, burrs are generated in a gap formed by the groove and the plane.

In the present embodiment, the light incident surface forming surface 42 is formed of a groove, but is formed of a non-planar surface other than a flat surface, such as a surface on which dots or a large number of triangular pyramids or quadrangular pyramids are formed, a rough surface processed by shot blasting, or a curved surface. Anything is acceptable. And it is intended to diffuse light in the direction of the width P7 of the main body portion P4 of the light guide plate P shown in FIG. In FIG. 3, a portion between the light incident surface forming surfaces 42 and 42 is another portion of the first frame body portion 30 and has a role of positioning the block 43, but is not essential.

As shown in FIG. 3, the movable mold 12 has an air passage 44 for sucking the air in the cavity 14 before injection and ejecting the compressed air into the cavity 14 at the time of mold release including the time of depressurization. 45 is formed. The air passages 44 and 45 are connected to a vacuum device and a compressed air supply device via valves (not shown). The air passage 44 is connected to the air passage 30 b formed on the opposing surface from the hole 44 a of the first frame body portion 30. The air passage 30b is connected to air passages 31b, 32b, and 33b that are also formed on opposite surfaces. Therefore, the compressed air in the air passages 30b, 31b, 32b, 33b is a gap formed by the adjacent opposing surfaces 30a, 31a, 32a, 33a, 43a and the opposing surfaces 53a, 55a of the fixed mold 13 described later ( The air can be ejected into the cavity 14 through the parting surface), and air can be sucked from the gap. A part of the compressed air is ejected from a gap formed by the first frame body part 30 and the block 43. The air passage 45 formed in the third frame body portion 32 is connected to air passages 30d, 31d, 32d, and 33d formed between the core portion 16 and the respective frame body portions 30, 31, 32, and 33. Yes. Therefore, the compressed air in the air passages 30 d, 31 d, 32 d, and 33 d is formed by the outer surface of the core portion 16, the inner surface of each frame body portion 30, 31, 32, 33 and the light incident surface forming surface 42 of the block 43. The air can be ejected into the cavity 14 through the gap, and air can be sucked from the gap. Accordingly, the compressed air can be ejected from the gap adjacent to the light incident surface forming surface 42 toward the cavity 14.

In the present embodiment, the first frame body portion 30 can be moved backward from the cavity forming position (the position where the second frame body portion 31 is in contact with the second frame body portion 31 to form a continuous frame body). This is the reason. That is, the cavity forming surface on the movable mold side formed from the cavity forming surface 27 of the core portion 16 and the frame body portion 29 is concave, and the light guide plate P, which is a molded product after the injection compression molding is completed, is moved to the movable mold. This is because it is difficult to release from 12. In particular, it is difficult to take out the light incident surface P3 of the light guide plate P without contacting the light incident surface forming surface 42, the groove P3a of the light incident surface P3 is damaged, and the light incident surface of the mold is formed. There is a problem that the surface 42 is also worn.

Furthermore, in the present embodiment, only the block 43 having the light incident surface forming surface 42 is made detachable from the first frame body 30 for the following reason. In general, the groove or rough surface of the light guide plate P is often transferred and molded by attaching a stamper to a mold, but the light incident surface P3 has a small area and does not have a space for attaching the stamper. The light incident surface P3 is likely to be worn due to the above-described mold release or aging, but at that time, by replacing only a part of the blocks 43 instead of the entire frame portion, it is possible to reduce the cost. In the case of the light guide plate P, the luminance distribution varies depending on the light incident surface P3. However, since the block having various light incident surfaces P3 can be replaced and tested, the one having the best luminance distribution can be used. Can lead to down.

In addition, in the part which comprises the cavity formation surface of the movable mold 12 of this embodiment, the part which can be moved with an air cylinder is only the 1st frame part 30, but a some frame part is a drive means or an angular. It may be movable outward by a combination of a pin and a spring. In addition, regarding the block 43 provided with the first frame body portion 30 and the like, the shape and number are determined according to the shape of the light incident surface of the light guide plate, and a plurality of blocks may be provided. The position at which the movable first frame part and the removable block are provided is not limited to the upper part, and may be a side part or the like. Further, the moving direction of the frame body portion is not limited as long as it can be moved backward from the cavity forming position, and may be moved not only in the direction orthogonal to the mold opening / closing direction but also to the diagonally outer side. In the present embodiment, a frame mold 29 called a so-called flat mold is used in which the frame 29 moves relative to the core 16 in the mold opening / closing direction. You may employ | adopt the metal mold | die with which a core side metal mold | die (metal mold | die which has a convex part) is fitted by the metal mold | die which has a recessed part. In that case, a light incident surface forming surface that is movable outward is formed in a part of the mold on the cabinet side.

Next, the fixed mold 13 will be described. As shown in FIGS. 1, 2, and 4, the fixed mold 13 includes a mold body 51, a cooling medium flow path forming block 52, and a first contact block. 53, a cavity forming block 54, a second contact block 55, a sprue bush 56, and the like. A heat insulating plate 57 is attached to the stationary platen side of the mold body 51, and a hole 58 into which a nozzle of an injection device (not shown) is inserted is formed in the center, and a locating ring 59 is attached around the hole 58. It has been. A cooling medium flow path forming block 52 and a second abutment block 55 that is an insert block of the sprue bush 56 are attached to the movable mold side of the mold body 51. Further, the mold body 51 is provided with a guide hole 60 into which the guide bar 41 of the movable mold 12 is inserted.

The cooling medium flow path forming block 52 has a plurality of cooling medium flow paths 61 formed in parallel with the cavity 14 therein. A first abutment block 53 having a facing surface 53 a that faces the first frame body portion 30 of the movable mold 12 is fixed to the movable mold side of the cooling medium flow path forming block 52. Similarly, a cavity forming block 54 is detachably fixed by a bolt on the movable mold side of the cooling medium flow path forming block 52 and inside the first contact block 53. The surface of the cavity forming block 54 that faces the movable mold 12 is a cavity forming surface 62 that forms the reflecting surface (back surface) P8 of the light guide plate P. In this embodiment, the surface is directly fine on the cavity forming surface 62. Unevenness has been processed. Specifically, processing is performed by shot blasting so that unevenness is increased on the side closer to the block 43 (upper side) of the fixed mold 13, and finer unevenness is higher on the reflection surface P8 closer to the light incident surface P3. To be formed. However, the cavity forming surface 62 may be formed with a groove or a mirror surface. The reason why the cavity forming surface 62 is a detachable block is the same as that of the block 43 of the light incident surface forming surface 42. By replacing only the cavity forming block 54, wear of the cavity forming surface 62 and various light guide plates P This is to cope with the test of the shape of the reflective surface. A stamper may be attached to at least one of the cavity forming surface 62 of the fixed mold 13 and the cavity forming surface 27 of the movable mold 12. Further, the light exit surface may be formed by any of the cavity forming surfaces 27 and 62, and the reflection surface may be formed.

The opposing surface 55a of the second contact block 55 is, together with the opposing surface 53a of the first contact block 53, the first frame body portion 30, the second frame body portion 31, and the third frame body portion 32 of the movable mold 12. And the fourth frame body portion 33. A cylindrical sprue bush 56 is disposed inside the second contact block 55. The sprue bush 56 faces the hole 58 of the mold main body 51 on the fixed platen side, and faces the protruding pin 20 on the movable mold side. Further, between the sprue bush 56 and the second contact block 55 on the outer peripheral side thereof, a cooling medium flow path 63 for cooling the sprue portion P2 is formed so as to surround the periphery of the sprue bush 56, Sealed by an O-ring. Further, the inner peripheral surface of the sprue bush 56 is roughened by shot blasting so that the sprue portion P2 can be easily released.

The cavity forming block 54 is formed with an air passage 64 that sucks air in the cavity 14 before injection and exerts compressed air at the time of mold release including the time of depressurization. The air passage 64 is connected to a vacuum suction device and a compressed air supply device via valves not shown. The air passage 64 is connected to an air passage 64 a formed between the cavity forming block 54 and the first contact block 53 and an air passage 64 b formed between the cavity forming block 54 and the second contact block 55. Has been. The compressed air is blown into the cavity 14 from the gap between the cavity forming block 54, the first contact block 53, and the second contact block 55 through the air passages 64a and 64b, and the air in the cavity 14 is injected before the injection. Aspirate. By making the outer edge of the cavity forming block 54 smaller than the outer shape of the light guide plate P, more compressed air can be ejected to the cavity forming surface 62 which is a transfer surface.

Next, an injection compression molding method using the injection compression molding die 11 of the present embodiment will be described. As described above, the present invention can be realized by a general injection molding method, but an injection compression molding method, which is one of the fields, is an optimal embodiment. In this embodiment, a light guide plate having a diagonal size of 2 inches and a thickness of 0.6 mm is formed in a molding cycle time of 4 seconds. The breakdown is as follows: mold opening / closing time (including removal time and intermediate time) 1.35 seconds, injection time 0.05 seconds, pressure holding time 0.4 seconds, cooling time 2.2 seconds (substantially cooling from the start of injection) It has started). For this reason, in this embodiment, the cooling medium flow path 28 of the core part 16 of the movable mold 12, the cooling medium flow path 46 in the vicinity of the protruding pin 20 and the gate part forming surface 39, and the cooling medium flow path forming block of the fixed mold 13. A cooling medium (cooling water) whose temperature is controlled to 100 ° C. by a temperature controller is supplied to the cooling medium flow path 61 of 52 and the cooling medium flow path 63 in the vicinity of the sprue bush 56. The temperature of the cooling water is preferably 80 to 110 ° C., and preferably 40 to 70 ° C. lower than the glass transition temperature Tg of polycarbonate, which is a resin to be molded. In the conventional general light guide plate molding die, the vicinity of the gate portion P1 or the vicinity of the sprue portion P2 is not cooled. However, in the present embodiment, the gate portion P1 and the sprue portion P2 are also cooled at substantially the same temperature as the cavity forming surfaces 27 and 62. In the present invention, the gate portion P1 has a temperature difference of minus 20 ° C. to plus 20 ° C. with respect to the cavity forming surfaces 27 and 62, thereby ensuring the fluidity of the molten resin at the time of injection and the gate of the light guide plate P. The aim is to reduce the molding cycle time by eliminating the difference in plate thickness between the near portion P11 and the far gate portion P12. Further, by changing the temperature of the cooling medium flow path 28 of the movable mold 12 and the temperature of the cooling medium flow path 61 of the fixed mold 13, the warp, the birefringence, etc. of the light guide plate P can be adjusted.

Further, the temperature of the front zone (zone closest to the nozzle) of the injection apparatus is set to 310 ° C., and the molten resin of polycarbonate is measured. When polycarbonate is used, the temperature of the front zone of the injection device is preferably set to 300 to 350 ° C. Then, a mold clamping device (not shown) is operated to bring the movable mold 12 in the state shown in FIG. 1 attached to the movable plate into contact with the fixed mold 13 attached to the fixed plate, and perform the mold clamping. . At this time, a frame-shaped portion formed by the first contact block 53 and the second contact block 55 of the fixed mold 13, the first frame body portion 30, the second frame body portion 31 of the movable mold 12, The frame part 29 including the third frame part 32 and the fourth frame part 33 is brought into contact with each other, and the cavity 14 including the gate part forming surface 39 connected to the sprue part P2 is formed therein. When the cavity 14 is formed, the valve is opened so that the air passages 44, 45, 64 are connected to the vacuum suction device, and the air in the cavity 14 is sucked. Needless to say, the nozzle of the injection device is in contact with the sprue bush 56 at that time. The suction of the air in the cavity 14 has the purpose of improving the flow of the molten resin at the time of injection.

With respect to the clamping force before the injection is started after the mold contact, the mold main body portion 15 of the movable mold 12 and the back plate 24 of the movable frame portion 17 are in contact with each other by overcoming the elastic force of the spring 23. The mold clamping force is 50 to 100 kN in this embodiment. Then, as shown in FIG. 2, when the back plate 24 is brought into contact with the mold main body portion 15, the frame body portion 29 is in a position where the frame portion 29 is finally retracted with respect to the core portion 16. Next, molten resin is injected from a nozzle of an injection device (not shown) through the sprue bush 56 at an injection speed of 100 to 200 mm / sec. The mold body 15 and the core 16 of the movable platen and the movable mold 12 are moved back to the positions as shown in FIG. 1 again by the pressure at the time of injection. As a result, the movable frame portion 17 of the movable mold 12 moves forward relative to the core portion 16, and the distance between the cavity forming surface 62 of the fixed mold 13 and the cavity forming surface 27 of the movable mold 12 is increased. Molten resin can be injected into the cavity 14. At this time, the plate thickness of the cavity 14 is increased by about 50 to 200 μm at the maximum as compared with the position where the clamping force shown in FIG. 2 is exerted.

When the screw position reaches a predetermined holding pressure switching position by the injection device, the injection control is switched to the holding pressure control. The mold clamping force is reduced to 20 to 50 kN before or after the holding pressure switching or simultaneously with the holding pressure switching. Then, the cavity forming surface 27 of the movable mold 12 is moved to the fixed mold side, and the molten resin in the cavity 14 (solidification proceeds from the cavity forming surfaces 27 and 62 side) is compressed. The ratio of the movement amount in the mold opening direction and the movement amount in the compression direction compresses the movement amount corresponding to 1/3 to the movement amount in the mold opening direction. The positional relationship of the light incident surface forming surface 42 of the block 43 with respect to the cavity forming surface 27 of the core 16 after completion of the compression is such that only the light incident surface forming surface 42 on which the groove is formed is exposed to the cavity 14. is there. In the present embodiment, since the molten resin is compressed by the movement of the movable mold 12, the transfer of grooves and dots can be further improved as compared with normal injection molding. However, on the other hand, there is a problem that the groove of the light incident surface forming surface 42 of the block 43 and the groove P3a of the light incident surface P3 of the light guide plate P are well meshed so that the mold release becomes difficult. In addition, the amorphous resin such as polycarbonate used in the present embodiment has a problem that it has excellent moldability but is difficult to release because it has a small shrinkage rate during molding.

Therefore, in this embodiment, the valve connected to the air passages 44, 45, 64 from the compressed air supply source (not shown) is opened before the mold opening is started (before the pressure is released), and the air passages 44, 45, 64 and the air passages are opened. Compressed air is supplied to 30b, 31b, 32b, 33b, 64a, 64b and the like. However, since the movable mold 12 has not yet been depressurized in the first stage, the compressed air is filled in the air passages 44, 45, 64 and the air passages 30b, 31b, 32b, 33b, 64a, 64b, etc. Does not erupt in large quantities. As this compressed air, air at normal temperature is used, but it also contributes to the promotion of cooling of the light guide plate by ejecting the compressed air from before the mold release to the time of the pressure release and the time of the mold release. Further, the warpage of the light guide plate P can be adjusted by adjusting the timing of supplying air to the air passages 44, 45 and 64 and the supply amount of air.

When a predetermined mold clamping time elapses, the mold clamping device performs pressure relief. The compressed air that has filled the air passage 64 and the air passages 64 a and 64 b on the side of the fixed mold 13 due to the depressurization is a gap between the cavity forming block 54, the first contact block 53, and the second contact block 55. Is applied to the gap between the cavity forming surface 62 and the reflecting surface P8, etc., and helps to release the reflecting surface P8 on which fine irregularities of the light guide plate P are formed with respect to the fixed mold 13. At the same time, the compressed air that has filled the air passage 44 and the air passages 30b, 31b, 32b, and 33b is also a gap (parting surface) between the facing surfaces 30a, 31a, 32a, 33a, and 43a and the facing surfaces 53a and 55a. To the gap between the cavity forming surface 62 and the reflecting surface P8, and similarly helps to release the reflecting surface P8. On the movable mold 12 side, the compressed air that has been filled in the air passage 45 and the air passages 30d, 31d, 32d, and 33d is formed into a cavity from the gap between the core portion 16 and the frame portions 30, 31, 32, and 33. The gap between the surface 27 and the light exit surface P10 of the light guide plate P, the gap between the light incident surface forming surface 42 and the light incident surface P3, and the gap between the cavity forming surfaces 30c, 31c, 32c, 33c, 33e and the side surface P9. Helps release the light guide plate P from the movable mold 12.

Thereafter, the movable platen and the movable mold 12 are moved in the mold opening direction by the mold clamping device. At this time, the light guide plate P formed in the cavity 14 is easily pulled out of the sprue bush 56 by the rough surface processing of the inner surface of the sprue bush 56 or the tip end of the protruding pin 20. Thus, the mold design is such that the sprue portion P2 is not cut. Therefore, there is no problem even if the temperature of the cooling medium flowed to the cooling medium flow path 46 near the gate part P1 of the sprue part P2 or the cooling medium flow path 63 near the sprue part P2 is relatively high. On the movable mold 12 side, the compressed air filled in the air passages 44 and 45 is further released from the cavity forming surfaces 30c, 31c, 32c, 33c and 33e and the side surface P9 by opening the mold. It is ejected to the outside through a gap or the like to help release the light guide plate P. At the same time as or slightly behind the mold opening, air is supplied to the rod side chamber of the air cylinder 35 of the moving mechanism, and the first frame body portion 30 including the block 43 faces outward (upward in FIGS. 1 to 3). The light guide plate P is moved away from the portion including the light incident surface P3. The movement amount at this time is at least 1 mm or more, preferably 2 mm or more. At this time, it is desirable to provide the light incident surface P3 other than the lower side and move the portion corresponding to the first frame body sideward or upward to prevent the light guide plate from dropping unexpectedly.

Next, a gripping portion of an unillustrated unloader grips the sprue portion P2, and the ejector air cylinder 21 is actuated to project the projecting pin 20, projecting the back side of the sprue portion P2 and the gate portion P1 and the sprue portion P2. The light guide plate P connected to is completely released from the movable mold 12 and is taken out and moved to another placement position. Therefore, in the present invention, when the light incident surface forming surface 42 and the light incident surface P3 are already separated from each other by compressed air or cooling contraction, the first frame body portion 30 is moved outward both in other cases. The light guide plate P can be taken out by the extractor without bringing the light incident surface P3 of the light guide plate P into contact with the cavity forming surface such as the light incident surface forming surface 42, and the light incident surface P3 and the light incident surface forming surface 42 are damaged. Never do.

Then, when the light guide plate P is taken out from the movable mold 12, the air cylinder 35 of the moving mechanism is actuated again to advance the first frame body portion 30 and the block 43, and the second frame body portion 31, By bringing the three frame body parts 32 into contact with each other and returning to the cavity forming position, the continuous frame body parts 29 are formed again by the first frame body part 30 and the like. Then, the movable platen and the movable mold 12 are moved forward again by the mold clamping device, and the next molding is performed. However, the molding cycle time of this embodiment is 4 seconds and the molding cycle time of the conventional light guide plate is several ten seconds. Compared to that, it was a revolutionary short time. The reason for this is that the cavity forming surface 62 of the fixed mold 13, the sprue bush 56, the cavity forming surface 27 of the movable mold 12, and the gate portion forming surface 39 are controlled by a cooling medium, respectively. Since it is a mold, there is no need to cool a relatively thick runner part like multiple molds, and it is possible to shorten the holding time by using injection compression molding and using a single mold. It is done. Then, by forming one light guide plate P at the same time with a single die, it is necessary to consider the filling balance of the resin as in the case of simultaneously forming a plurality of light guide plates with a plurality of die. Since only the molding conditions of one light guide plate can be pursued, the generation of defective products is almost eliminated.

In this embodiment, the light guide plate P having a diagonal size of 2 inches and a plate thickness of 0.6 mm is formed in a molding cycle time of 4 seconds as described above. In the present invention, the diagonal size is 1 inch to 4 inches and the plate thickness is One light guide plate having a uniform thickness of 0.3 to 1.0 mm can be molded in a molding cycle time of 2.5 to 6 seconds. The breakdown when the molding cycle time is 2.5 seconds is: mold opening / closing time (including removal time and intermediate time) 0.85 seconds, injection time 0.05 seconds, pressure holding time 0.4 seconds, cooling time 1.2 Seconds. If the size of the small 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 sprue is lost due to insufficient solidification of the sprue. There will be no defects. Although it is possible to extend the molding cycle time, there is a problem in economical efficiency. Therefore, even a mold having a complicated transfer surface or a wedge mold can be molded in about 6 seconds, which is the upper limit.

The molded light guide plate P is separated and finished at the gate portion P1, and is incorporated into the display device as a side light type light guide plate. However, the side light type light guide plate does not exclude the case where a prism sheet or the like is separately attached. The light guide plate P molded in this embodiment is a non-defective product having a difference between the plate thickness P6 of the gate vicinity portion P11 and the gate distant portion P12 within 10 μm. When the light guide plate P was tested in combination with an LED or the like as a light source, the uniformity and the light emission surface were equally divided into nine, and both the average brightness of each part cleared the target and showed good results.

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. In the present embodiment, the injection compression molding die for the light guide plate for a mobile phone having a diagonal size of 2 inches has been described, but other small light guide plates (1 inch to 10 inches) may be manufactured. Nowadays, a display screen for a mobile phone is enlarged for television reception or the like, and a light guide plate for a display device used for another electronic dictionary, car navigation, or the like may be used. Further, the small light guide plate may be a light guide plate having a uniform thickness or a wedge-type light guide plate in which the plate thickness decreases from the light incident surface side toward the other side. Furthermore, the light guide plate of the present invention is not limited to a small light guide plate, and may be a large light guide plate as long as the light incident surface is a non-planar sidelight type light guide plate.

Further, in the present embodiment, the single-piece injection compression molding mold for molding one light guide plate for a mobile phone at the same time has been described, but a plurality of light guide plates such as four may be formed at the same time. However, when molding a plurality of sheets at the same time, it is necessary to solve problems such as molding cycle time and yield by a separate method. When four sheets are formed at the same time, it is necessary to provide a mechanism for moving the light incident surface forming surface in two directions such as up and down and left and right. In the present embodiment, the injection compression molding die attached to the injection 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.

Furthermore, in this embodiment, since the light guide plate P of this embodiment has a plate thickness of 0.6 mm, an injection compression molding method is used. However, when the plate thickness is 0.3 to 0.5 mm, an injection press method is used. It is possible to do it. In the injection press, the gap between the cavities is already widened at the mold closing position, so even a very thin plate can be injected at a relatively low speed and low pressure. After injection, the movable mold is moved forward and compressed. . Moreover, it is desirable that the mold clamping speed at that time be high.

Further, as the resin used for molding, an example of polycarbonate has been described, but other resins may be used as long as they are excellent in optical performance. Examples thereof include methacrylic resins and cycloolefin polymer resins. Since the temperature of the molten resin and the glass transition temperature differ depending on the resin, it goes without saying that the temperature of the cooling medium and the molding cycle time are also different.

It is sectional drawing of the injection compression molding metal mold | die of the sidelight type light-guide plate of this embodiment, and is a figure which shows a state when the mold clamping force is not exerted. It is sectional drawing of the injection compression molding metal mold | die of the sidelight type light-guide plate of this embodiment, Comprising: It is a figure which shows the state to which the clamping force was exerted. It is a front view of the movable metal mold | die of the injection compression molding metal mold | die of the sidelight type light-guide plate of this embodiment. It is a front view of the fixed metal mold | die of the injection compression molding metal mold | die of the sidelight type light-guide plate of this embodiment. It is a perspective view of the sidelight type light guide plate shape | molded by the injection compression molding die of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Injection compression mold 12 Movable mold 13 Fixed mold 14 Cavity 15,51 Mold main body part 16 Core part 17 Movable frame part 27,30c, 31c, 32c, 33c, 62 Cavity formation surface 28,46,61, 63 Cooling medium flow path 30 1st frame part 31 2nd frame part 32 3rd frame part 33 4th frame part 30a, 31a, 32a, 33a, 43a, 53a, 55a Opposing surface 42 Light incident surface forming surface 43 block 30b, 30d, 31b, 31d, 32b, 32d, 33b, 33d, 44, 45, 64, 64a, 64b air passage 53 first contact block 54 cavity forming block 55 second contact block 56 sprue bush P guide Light plate P3 Light incident surface P3a Groove P8 Reflective surface P10 Light emission surface

Claims (5)

An injection mold of a sidelight type light guide plate having a non-planar light incident surface,
An injection mold for a sidelight type light guide plate, wherein a light incident surface forming surface for molding the light incident surface is movable backward from a cavity forming position. The injection mold of the sidelight type light guide plate according to claim 1, wherein the light incident surface forming surface is a block separate from other cavity forming surfaces. The injection mold of the sidelight type light guide plate according to claim 1 or 2, wherein air is ejected from a gap adjacent to the light incident surface forming surface. The injection molding of the sidelight type light guide plate according to any one of claims 1 to 3, wherein the light incident surface forming surface is a groove disposed in parallel with a compression direction of the cavity. Mold. The sidelight type light-guide plate shape | molded by the injection mold of the sidelight type light-guide plate of any one of the said Claim 1 thru | or 4.

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