JP4451483B2 - Light guide plate mold - Google Patents

Description

The present invention relates to a mold for a light guide plate that forms a light guide plate in a cavity formed between a fixed mold and a movable mold by injection compression molding.

As a molding die for a light guide plate, as described in Patent Document 1, a molding die is known in which a stamper is provided and transfer is performed by the stamper. However, a molding die provided with a stamper has a problem that the structure of the molding die becomes complicated because the stamper is attached. In addition, a molding die provided with a stamper has a problem that it is necessary to frequently replace a relatively expensive stamper, leading to an increase in cost, and the replacement frequency is increased, resulting in a decrease in work efficiency.

As a countermeasure to the above problem, as described in Patent Document 2, a light guide plate molding die in which a plating layer is provided on a light guide plate molding die and a gradation negative pattern or the like is formed on the plating layer is also known. Yes. However, since the molding die provided with the plating layer of Patent Document 2 is not a die used for injection compression molding, it is difficult to mold a light guide plate with a thin plate thickness, and a high-temperature molten resin is required to ensure more fluidity. It was necessary to perform molding at an ultra-high injection speed.

Further, as a countermeasure to the above-mentioned problem, as described in Patent Document 3, there is known a technique in which a plating layer is provided on a mold of a light guide plate that performs injection compression molding. If an injection compression molding die is used, the volume of the cavity can be enlarged at the time of injection, and then the molten resin can be compressed, so that it is easy to cope with the molding of a light guide plate with a thin plate thickness. However, in the injection compression molding mold, since the mold block can be moved relatively and the volume of the cavity can be changed, it is necessary to provide a gap between the mold blocks that does not cause galling. The molten resin enters and tends to generate burrs. The burrs tend to become more prominent by increasing the temperature of the molten resin, the injection speed, the clamping pressure, etc., and the burrs have a thickness of about 10 to 50 μm in the peripheral portion rather than the central portion, and the plate thickness is increased. There was a problem of thickening. Also, even if the light guide plate mold is injection compression molded, if the plate thickness is very thin and it is necessary to mold a light guide plate with a uniform thickness, the molten resin is good from the gate to the far side. Filling is more difficult, and a light guide plate having a gate side thickness of about 10 to 50 μm is apt to be formed.

Japanese Patent Laying-Open No. 2005-349646 (0014, FIG. 1) JP 2002-166446 A (0016, FIG. 1) JP 2004-202731 A (0035, FIG. 2)

In the present invention, in view of the above-described problems, a light guide plate molding die that molds a light guide plate in a cavity formed between a fixed die and a movable die by injection compression molding, without using a stamper. It is an object of the present invention to provide a light guide plate molding die that can reduce the difference in thickness between light guide plates having a thin plate thickness and a uniform plate thickness by a method with relatively low running cost.

The light guide plate molding die according to claim 1 of the present invention is a guide for forming a light guide plate having a uniform thickness in a cavity formed between a fixed die and a movable die by injection compression molding. In the optical plate mold,
A metal plating layer is formed as a cavity forming surface for forming a cavity, and the metal plating layer is formed such that the plating layer on the tip side of the cavity is thin and the plating layer on the gate side is formed at different heights. .

A molding die for a light guide plate according to a second aspect of the present invention is characterized in that, in the first aspect, the metal plating layer is formed at a different height in a post process than in the plating process.

The molding die for the light guide plate according to claim 3 of the present invention is characterized in that in claim 1 or claim 2 , the metal plating layer is provided with a pattern forming surface.

According to a fourth aspect of the present invention, in the molding die for the light guide plate according to any one of the first to third aspects, the metal plating layer is formed to a thickness of 20 to 200 μm and is shallower than the plating layer. A pattern having a depth of 5 to 100 μm is formed.

The light guide plate molding die of the present invention is a light guide plate molding die in which a main body forms a light guide plate having a uniform thickness within a cavity formed between a fixed die and a movable die by injection compression molding. A metal plating layer is formed as a cavity forming surface for forming a cavity, and the metal plating layer has a thin plating layer on the tip side of the cavity and a different thickness on the gate side, so that the light guide plate body The plate thickness difference can be reduced.

The light guide plate molding die of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a molding die for a light guide plate according to the present embodiment, showing a state after mold clamping and before starting injection. FIG. 2 is a cross-sectional view of the molding die for the light guide plate of the present embodiment, showing a state in which the volume in the cavity is enlarged at the time of injection. FIG. 3 is a cross-sectional view of the molding die for the light guide plate of the present embodiment, showing a state where the resin in the cavity is pressed and gate-cut. FIG. 4 is an enlarged cross-sectional view of the main part of the molding die for the light guide plate of the present embodiment. FIG. 5 is a chart showing the injection compression molding method for the light guide plate of the present embodiment. FIG. 6 is a cross-sectional view of the light guide plate formed by the injection compression molding method of the light guide plate of the present embodiment.

The mold 11 for the light guide plate of the present embodiment is a mold for molding a side light type light guide plate for mobile phones having a diagonal size of 3 inches and an equal plate thickness of 0.4 mm by injection compression molding. (Hereinafter, the side light type light guide plate for mobile phones is simply abbreviated as a light guide plate.) In the injection compression molding, the distance between the movable mold 12 and the fixed mold 13 is variable between the start of molding and the end of molding. The molten resin in the cavity 14 can be pressurized. Accordingly, the injection compression molding includes a type called an injection press in which the movable mold is stopped in a state where the cavity is slightly opened, and the movable mold is advanced and pressurized after injecting molten resin.

In these injection compression moldings, since the cavity is slightly opened before or after the start of injection, compared to when the molding is completed, as an example, 0.15 mm to 0.5 mm for diagonal dimensions of 2 inches to 4 inches, It is advantageous for forming a light guide plate having a very thin plate thickness of 0.3 mm to 0.8 mm for 4 inch to 6 inch and 0.5 to 2.0 mm for 6 inch to 13 inch. Since the movable mold can be moved in the mold clamping direction after the start of injection and the molten resin can be pressurized, it is not necessary to perform ultrahigh-speed injection during injection, and a light guide plate excellent in internal stress can be formed. However, even if the injection compression molding is used, as the plate thickness becomes very thin, it becomes difficult to inject and fill the molten resin into the cavity with a uniform plate thickness due to the flow loss of the molten resin and the progress of cooling and solidification.

1 to 3 are cross sections of a molding die 11 for a light guide plate of the present invention. The molding die 11 includes a movable die 12 that is a first die and a fixed die 13 that is a second die. A cavity 14 having a variable length is formed. A movable mold 12 attached to a movable platen of an injection compression molding machine (not shown) includes a mold main body 15 having a heat insulating plate 21 attached to the movable platen side, a core block 16 that is a block for pressurizing molten resin, A movable frame portion 19 and the like are provided. A substantially rectangular core block 16 that substantially matches the shape of the light guide plate P is fixed to a substantially central portion of the surface of the mold main body 15 on the fixed mold side. Since the core block 16 moves relative to a movable frame portion 19 described later, the core block 16 is formed of a hard metal member so that galling is less likely to occur. A cooling medium flow path 17 is formed inside the core block 16.

A movable frame portion 19 is attached to a surface of the mold main body portion 15 on the fixed mold side via a spring 18. The movable frame portion 19 is disposed so as to surround the periphery of the core block 16, and is movable in the mold opening / closing direction with respect to the mold main body portion 15 and the core block 16 by the spring 18. Therefore, in other words, the core block 16 is disposed in the hollow portion formed by the movable frame portion 19, and the core block 16 can move relative to the movable frame portion 19 during molding. Between the core block 16 and the movable frame portion 19, a gas flow passage 34 a having a slight gap (for example, 5 to 15 μm) for preventing the core block 16 from being squeezed and ejecting a release gas is provided. Yes. A surface of the movable frame portion 19 facing the fixed mold 13 is an abutting surface 19a (parting surface), and a part of the gate side is a runner forming surface 32. A light incident surface forming block 20 in which a light incident surface forming surface 20a of the light guide plate P is formed is detachably disposed on the side of the movable frame portion 19 opposite to the gate.

1 to 3, the lower portion of the core block 16 is connected to the runner forming surface 32 of the movable frame portion 19 through the gate P3. In the gate P3, a gate cutter member 24 is disposed across the inside of the mold main body 15 and the boundary portion between the core block 16 and the movable frame portion 19. The gate cutter member 24 is made of a hard metal member and is made of a material different from that of the core block 16. A slight gap that does not cause galling is also formed between the gate cutter member 24 and the core block 16 as in the gas flow passage 34a shown in FIG.

Further, a projecting pin 23 that is moved back and forth through the ejector plate 22 of the ejector device is disposed over the inside of the mold main body portion 15 and the movable frame portion 19. And the front-end | tip of the protrusion pin 23 faces the runner formation surface 32, and the biting part 23a is provided in the cross-sectional Z-shape so that the sprue P1 and the runner P2 can be easily held. A cooling medium flow path 33 is formed around the protrusion pin 23 and in the vicinity of the gate cutter member 24 for cooling the runner P2 and the sprue P1 on the movable mold 12 side. The core block 16 and the runner forming surface 32 may be formed from the same block, and the volume of the runner P2 may be changed.

Next, the fixed mold 13 will be described. As shown in FIGS. 1 to 3, the fixed mold 13 attached to the fixed plate of the injection compression molding machine includes a mold body 41, a cavity forming block 42, an insert block. 43, a sprue bush 44, a gate cutter member 45, a contact block 46, and the like. A heat insulating plate 47 is attached to the fixed plate side of the mold main body 41, and a hole 48 into which a nozzle of an injection device (not shown) is inserted is formed. A locating ring 49 is attached around the hole 48. A cavity forming block 42 is attached to the movable mold side of the mold body 41.

A groove-like gas flow passage 53 is formed so as to surround the periphery of the cavity forming block 42. The gas flow passage 53a is formed in a slight gap (for example, 3 to 10 μm) between which the resin does not enter between the cavity forming block 42 and the contact block 46.

Further, an insert block 43 is disposed in the mold main body 41 together with the cavity forming block 42. The insert block 43 is provided with a sprue bush 44 provided with a hole whose diameter is increased toward the movable platen at the center thereof. A cooling medium flow path 51 for cooling the sprue P1 and the runner P2 is formed around the sprue bush 44. A runner formation surface 54 is formed on the surface of the insert block 43 facing the movable mold 12 from the tip of the sprue bush 44 toward the cavity formation surface. A gate cutter member 45 made of a hard metal member is fixed between the insert block 43 and the cavity forming block 42.

As shown in FIG. 4 which is an enlarged cross-sectional view of the main part, the metal plating layers 25 and 30 are formed on the flat surfaces 16a and 42a, which are the cavity-side surfaces of the core block 16 and the cavity forming block 42, as cavity forming surfaces, respectively. Is formed. In the present embodiment, the metal plating layers 25 and 30 are each formed by electroless nickel phosphorus plating. The electroless nickel phosphorus plating is excellent in adhesion and has a coefficient of thermal expansion of 13 × 10 ⁻⁶ cm / ° C. And since it has a thermal expansion coefficient close to that of the stainless steel hard metal material of the core block 16 and the cavity forming block 42, the durability is exhibited even under conditions where the temperature changes drastically such as injection compression molding. In addition to nickel phosphorus plating, the metal plating layers 25 and 30 may be nickel plating, nickel alloy plating, nickel phosphorus alloy plating, or the like, and the plating method may be electroplating.

In the present embodiment, the metal plating layer 25 of the core block 16 is formed by the following procedure. First, in a plating step, a plating layer having a thickness of 100 μm is uniformly formed on the entire flat surface 16 a of the core block 16. Then, in the next cutting step and polishing step, the entire surface of the central portion excluding the 1 mm wide portion in the vicinity of the gas flow passage 34a in the metal plating layer 25 is cut to a thickness of 50 μm. Then, in the subsequent step of the next plating step, the central portion and the portion not cut near the gas flow passage 34a are polished, and the central portion as shown in FIG. The protrusion 25b that is higher than the center and smoothly joined to the central portion is formed. As shown in FIG. 6, the protruding portion 25 b forms a burr escape portion Pc lower than the surface of the light guide plate main body Pa (the light exit surface Pb in the present embodiment) around the light guide plate P at the time of molding. By forming the burr Pd, it is possible to prevent a burr having a height higher than that of the light exit surface Pb. The protrusion 25b is formed to have a width (width from the outer side toward the center side in the plane) of 50 to 2000 μm and a height of 20 to 100 μm, and the gas flow passage 34a side is sharp as shown in FIG. It doesn't have to be a thing. In the present invention, the “height” indicates a distance from the base surface (in this embodiment, the flat surface 16a) in a direction orthogonal to the mold opening / closing direction, and is a general vertical height. Absent.

Moreover, since the center part of the metal plating layer 25 becomes the mirror surface 25a by the grinding | polishing process, the light emission surface Pb of the light-guide plate main body Pa formed of the said mirror surface 25a is a flat surface. However, a pattern may be formed on the mirror surface portion at the center by cutting or the like.

Similarly to the core block 16 of the movable mold 12, the metal plating layer 30 made of electroless nickel phosphor plating is also applied to the flat surface 42a on the cavity side in the cavity forming block 42 of the fixed mold 13 according to the following procedure. It is formed with. First, in the plating step, a metal plating layer 30 having a thickness of 100 μm is formed uniformly on the entire flat surface 42a. In the cutting process and the polishing process, which are subsequent to the plating process, the metal plating layer 30 has a thin plating layer on the side close to the light incident surface forming surface 20a (light incident surface forming surface side). It is cut and polished so that the plating layer on the near side (gate side) becomes thick. In this embodiment, cutting and polishing are performed so that the light incident surface forming surface side has a thickness of 50 μm and the gate side has a thickness of 80 μm. Therefore, the cavity forming block 42 is formed with a cavity forming surface of the metal plating layer 30 that is 30 μm higher on the gate side than the light incident surface forming surface side at the tip of the cavity 14. The V-groove 31 is cut to a depth of 5 to 50 μm on the entire surface of the cavity forming surface of the metal plating layer 30 to form a pattern forming surface 30a. The pattern formation surface 30a is a surface on which the reflection surface Pe of the light guide plate P is formed. The edge of the metal plating layer 30 may not be provided with a pattern as with the movable mold 12. The V-groove 31 on the pattern forming surface 30a is formed so that the groove interval becomes narrower from the light incident surface forming surface side toward the gate side.

The cutting blade that forms the V-groove 31 of the pattern forming surface 30a is a hard metal, cermet material, or diamond-based cutting blade that is harder than the HRC hardness 30 to 32 side of the electroless nickel phosphorus plating, and the nickel phosphorus plating Excellent workability. The thickness of the pattern forming surface 30a formed by the metal plating layer 30 is required to be thicker than the depth of the pattern such as the V groove 31 to be formed, but is preferably 20 to 200 μm. The pattern formed on the metal plating layer 30 is easy in terms of processing the V-groove 31, but may be a pattern such as other prisms, holograms, dots, and satin. The depth of the pattern is preferably 5 to 100 μm in a range shallower than the metal plating layer 30. The method for forming the pattern forming surface 30a may be laser cutting, sand blasting, or the like in addition to cutting. In the present invention, the projecting portion Pf having a triangular cross section of the reflecting surface Pe formed by the V-groove 31 or the like is not called a light guide plate body Pa. The light guide plate body Pa of the present invention refers to a portion of the light guide plate P having an equal plate thickness (including a very slight plate thickness error).

Further, in the core block 16 and the cavity forming block 42, when the mirror surface 25a, the projecting portion 25b, and the pattern forming surface 30a are worn, or when the assumed brightness is not obtained when the light guide plate P is made as a test prototype. It is possible to peel or re-polish the metal plating layers 25 and 30 so that the re-polished surface becomes a desired mirror surface or pattern-formed surface again, and the entire blocks 16 and 42 need not be replaced.

Next, the molding method of the present invention will be described with reference to the chart of FIG. In this embodiment, the light guide plate P having a diagonal size of 3 inches and a plate thickness of 0.4 mm is molded by the injection compression molding method in a molding cycle time of 4.4 seconds. The breakdown is as follows: mold opening / closing time (including removal time) 1.4 seconds, pressure increasing time 0.1 seconds, injection time 0.05 seconds, pressure holding time 0.45 seconds, cooling time 2.4 seconds (substantially Cooling starts from the start of injection). For this reason, in this embodiment, the cooling medium flow path 17 for cooling the mirror surface 25a (cavity forming surface) of the movable mold 12, the cooling medium flow path 33 for cooling the vicinity of the protrusion pin 23 and the runner forming surface 32, and the fixed mold 13 are used. Polycarbonate, which is a resin molded by a temperature controller, into the cooling medium flow path 50 for cooling the pattern forming surface 30a (cavity forming surface), the cooling medium flow path 51 for cooling the vicinity of the sprue bush 44 and the runner forming surface 54 A cooling medium (cooling water) whose temperature is controlled to about 50 to 120 ° C., which is 30 to 100 ° C. lower than the glass transition temperature Tg.

The front zone of the injection device (zone closest to the nozzle) is set to 350 ° C., and the molten resin of polycarbonate is measured. In addition, as for the temperature setting of the front zone of the said injection apparatus at the time of using a polycarbonate, it is desirable to set temperature to 320-380 degreeC. Then, a mold clamping device (not shown) is operated, the movable mold 12 attached to the movable plate is brought into contact with the fixed mold 13 attached to the fixed plate, and the mold clamping force is increased to 50 to 200 kN to mold the mold. Tighten. As a result, as shown in FIG. 1, the mold main body 15 and the movable frame portion 19 of the movable mold 12 are brought into contact with each other by overcoming the elastic force of the spring 18, and the movable frame portion is brought into contact with the core block 16. 19 is the last position to retreat. A cavity 14 having a variable thickness is formed between the fixed mold 13 and the movable mold 12.

Next, molten resin is injected from a nozzle of an injection device (not shown) through the sprue bush 44 at an injection speed of 250 to 500 mm / sec. The mold main body 15 and the core block 16 of the movable platen and the movable mold 12 are moved back to the positions shown in FIG. 2 by the pressure at the time of injection. As a result, the movable frame portion 19 of the movable mold 12 is positioned relatively forward of the core block 16, and the pattern forming surface 30 a of the cavity forming block 42 of the fixed mold 13 and the core block 16 of the movable mold 12 are arranged. The distance from the mirror surface 25a is widened by about 50 to 200 μm at each point as compared with the position where the mold clamping force is first exerted as shown in FIG. As a result, the molten resin can be injected and filled into the cavity 14 without performing ultra-high speed injection.

Immediately before or at the same time as the holding pressure switching, the mold clamping device is operated to increase the pressure rapidly, and the core block 16 is rapidly advanced. As a result, the molten resin in the cavity 14 is compressed and compensated for the decrease in the flow rate, and is filled toward the tip side of the cavity 14. However, the temperature of the molten resin has started to be lower than that at the start of injection, and in the state where the skin layer has already begun to be formed on the gate side of the cavity 14, compression is performed and the molten resin is caused to flow toward the cavity tip side. Therefore, even if injection compression molding is used, the plate thickness near the tip of the cavity 14 tends to be thinner than the plate thickness near the gate P3. In the present embodiment, as described above, the metal plating layer 30 is formed thicker toward the gate side. As a result, the pattern formation surface 30a that is the cavity formation surface is high. In proportion to this, the sectional area of the cavity 14 is slightly larger in the vicinity of the light incident surface on the tip side. Therefore, even if the flow rate decreases toward the tip of the cavity 14 due to the temperature of the injected molten resin starting to decrease, the molded light guide plate P has a light incident surface Pg vicinity. The thickness of the light guide plate body Pa in the vicinity of the surface Ph cut by the gate cutter 24 is calculated to be substantially the same.

In addition, the molten resin is movable with the core block 16 in particular, depending on at least one of the conditions such as when the temperature of the molten resin is high and the fluidity is high, when the injection speed is higher than a predetermined value, when the compression pressure by the mold clamping device is high It enters as a burr between the gas flow passages 34 a between the frame portions 19. However, in the present embodiment, since the metal plating layer 25 of the core block 16 is provided with the protruding portion 25b that forms the burr escape portion Pc, the height of the portion where the burr Pd can be formed is set to the light exit surface Pb of the light guide plate body Pa. Can be lower. Therefore, the plate thickness of the light guide plate P having a thin plate thickness and a uniform plate thickness can be made more uniform (excluding the protruding portion Pf due to the V groove or the like), and the burr Pd can be broken and adhere to other portions. Can be less.

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. In this embodiment, the gate cutter member 24 of the movable mold 12 is advanced slightly faster or substantially simultaneously with the holding pressure switching, and the gate P3 in which the molten resin is not completely solidified is cut, and the gate cutter member 24 is held in the forward position. As a result, the holding pressure does not reach the molten resin in the cavity 14 completely from the injection apparatus side, but the molten resin in the cavity 14 is compressed by advancing the movable mold 12 by driving the mold clamping device. Therefore, even if there is shrinkage due to cooling, sink marks do not occur and good transfer molding can be performed. When the pressurization is completed, the core block 16 is advanced to the position indicated by the one-dot chain line in FIG. During the cooling process, the molten resin used for the next molding is measured on the injection device side. When a predetermined time has elapsed, compressed air for mold release is applied to the cavity 14 via the gas flow passages 34 and 34 a between the movable frame portion 19 of the movable mold 12 and the core block 16.

Next, the mold clamping device is operated to perform pressure release and mold opening in order. When the mold is opened, the light guide plate P, the sprue P1 and the runner P2 are separately taken out while being held on the movable mold 12 side. On the movable mold 12 side, the spring 18 of the movable frame portion 19 is further extended, and the movable frame portion 19 is advanced relative to the mold main body portion 15 and the core block 16. Further, the compressed air is ejected through a gas flow passage 34 a between the core block 16 and the movable frame portion 19. When the mold is opened, the ejector pin 23 of the ejector device is advanced, and the runner P2 is released from the runner forming surface 32. When the mold is opened, the take-out robot is actuated to take out the light guide plate P and the like.

Next, another embodiment corresponding to claim 2 will be described with reference to FIG. The same parts as those in the embodiment shown in FIG. 1 and the like are denoted by the same reference numerals, and detailed description thereof is omitted. In another embodiment shown in FIG. 7, as a plating step, a first plating layer 61 of electroless nickel phosphorus plating is formed on the flat surface 16 a of the core block 16 to a thickness of 50 μm. Then, after applying a plating inhibitor that prevents the formation of plating on the pattern forming surface 61a at the center of the plating layer, electroless nickel phosphorous plating is performed again, and the vicinity of the gas flow passage 34a and the gate cutter member 24 The second plating layer 62 is formed to a thickness of 50 μm only on the periphery of the substrate. By performing the plating process in this manner, the protrusion 63 having a height different from that of the pattern formation surface 61a of the first plating layer 61 can be formed by the second plating layer 62 without post-processing. The protrusion 63 forms a burr Pd having a height lower than that of the light guide plate main body Pa, so that the thickness difference of the light guide plate main body Pa can be reduced. The pattern forming surface 61a is subjected to cutting of the V-groove 61b and the like after removing the plating inhibitor.

Further, regarding the metal plating layer 30 having a different thickness on the fixed mold 13 side, the thickness of the plating layer may be changed by overlapping the plating layers in multiple layers or by partially changing the time of the plating process. And when plating layers are stacked in multiple layers, polishing processing is performed later to eliminate the step, but if the plating process is performed in this way, the portion to be cut is smaller than when the plating layer is uniformly formed and then cut. Can also be reduced. By forming the metal plating layer 30 to have different thicknesses, the pattern formation surface 30a can be formed higher on the gate side and lower on the light incident surface formation surface side. Accordingly, when the light guide plate P having a thin plate thickness and a uniform plate thickness is formed in the cavity 14 provided with the pattern forming surfaces 30a having different heights, the plate thickness difference of the light guide plate body Pa can be reduced. .

Further, in another embodiment shown in FIG. 7, in the process up to the plating process, first, the first flat surface 16a, 42a is directly cut, or the first is used as a base by using a method other than plating such as spraying. A layer may be formed. Thereafter, the metal plating layer can be formed at different heights.

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. For example, the metal plating layer 30 whose height increases from the light incident surface forming surface side toward the gate side (thickness increases) is provided in both the fixed mold and the movable mold, or only in the movable mold. It may be provided. Further, the metal plating layer 25 provided with the protruding portions 25b in the peripheral portion may be provided in both the fixed mold and the movable mold or only in the fixed mold. Further, the metal plating layers 25 and 30 may be such that the central part gradually increases in height toward the gate side, and the peripheral part is provided with a protruding part. In addition, when one of the metal plating layers 25 and 30 is provided in one mold, the metal plating layer may not be provided in the other mold. The cavity forming surface of the metal plating layer 25 may be a pattern forming surface, and the cavity forming surface of the metal plating layer 30 may be a mirror surface or a rough surface. Further, regardless of the presence or absence of a pattern in the metal plating layers 25 and 30, the surface hardness may be increased to about 1.5 to 2 times by heat treatment at 300 to 700 ° C. for about 0.5 to 2 hours. Other coatings may be applied to the surface. Alternatively, the surface of the core block 16 and the cavity forming block 42 may be directly processed to provide a cavity forming surface having a height higher on the gate side than on the protrusion for preventing burr and on the light incident surface forming surface side. In that case, the combined use with the pattern forming surface may or may not be performed.

The light guide plate P that is simultaneously molded by the molding die has been described with respect to one example, but may be a plurality of two or more. And it is easier to maintain the parallelism of the fixed mold and the movable mold by providing a sprue bush at the center and arranging two or four cavities symmetrically on both sides. The light guide plate of the present invention is not limited in size and shape, and a light diffusing plate, a lens with incident and outgoing light, and other optical thin plates are also included in the category of the light guide plate. The present invention can also be used when a wedge-shaped light guide plate or the like having a different plate thickness is formed to a thickness as designed. As for the resin used, the type of resin such as polycarbonate, methacrylic resin, and cycloolefin polymer resin is not limited as long as the resin has excellent optical performance.

The molding die may be a so-called inlay die in which the convex portion of the other die is fitted into the concave portion of the fixed die or the movable die which is one die. Further, the injection compression molding may be performed only by the core compression of a hydraulic cylinder provided in the mold regardless of the mold clamping device. Furthermore, a mold using a mold that opens and closes in the vertical direction may be used.

It is sectional drawing of the shaping die of the light-guide plate of this embodiment, Comprising: It is a figure which shows the state before a start of injection after mold clamping. It is sectional drawing of the shaping die of the light-guide plate of this embodiment, Comprising: It is a figure which shows the state in which the volume in a cavity was expanded at the time of injection | emission. It is sectional drawing of the shaping die of the light-guide plate of this embodiment, Comprising: It is a figure which shows the state by which resin in the cavity was pressurized and the gate was cut. It is an expanded sectional view of the principal part of the shaping die 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 sectional drawing of the light-guide plate shape | molded by the injection compression molding method of the light-guide plate of this embodiment. It is an expanded sectional view of the principal part of the shaping die of the light-guide plate of another embodiment.

DESCRIPTION OF SYMBOLS 11 Molding die 12 Movable die 13 Fixed die 14 Cavity 16 Core block 16a, 42a Flat surface 19 Movable frame part 25, 30 Metal plating layer 30a, 61a Pattern formation surface 34, 34a, 53, 53a Gas flow path P guide Light plate Pa Light guide plate body

Claims (4)

In the mold of the light guide plate in which the main body molds the light guide plate with a uniform thickness within the cavity formed between the fixed mold and the movable mold by injection compression molding,
A metal plating layer is formed as a cavity forming surface for forming the cavity,
The metal plating layer is a light guide plate molding die characterized in that the plating layer on the front end side of the cavity is thin and the plating layer on the gate side is formed to have a different thickness . 2. The light guide plate molding die according to claim 1, wherein the metal plating layer is formed at a different height in a later process than in the plating process. Wherein the metal plating layer, the molding die of the light guide plate according to claim 1 or claim 2, characterized in that the pattern forming surface is provided. The metal plating layer is formed to a thickness of 20 to 200 [mu] m, any one of claims 1, characterized in that the depth of the pattern of 5~100μm is formed a shallow range from the plating layer according to claim 3 2. A molding die for the light guide plate according to item 1.

Images