JP2002292687A - Mold for injection-compression molding of light guide plate having wedge shape gradually reduced in thickness from one end thereof to other end thereof, and method for manufacturing light guide plate using the mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for injection-compression molding capable of molding a light guide plate having a wedge shape reduced in brightness irregularity without generating burr or the like, and a method for molding the light guide plate using the mold. SOLUTION: The mold 50 performs the injection-compression molding of the light guide plate having the wedge shape by injecting a molten resin in the product 45 formed between a fixed mold 20 and a movable mold 1, and subsequently compressing the injected resin to mold the same. The movable mold 10 consists of a movable core 11 for forming the product 45 having the wedge shape along with the fixed mold 20, a movable outer periphery core 12 for surrounding the outer periphery of the movable core 11 in a slidable manner, and the pressure source 30 provided on the movable side 13 of the mold 50 for injection- compression molding or on the movable side of an injection molding machine and pressing the end on the side of the mold opening direction of the movable outer periphery core 12 in a mold closing direction. The movable outer periphery core 12 and the mating surface 40 of the fixed mold 20 are held to a close contact state at least at the times of injection and compression.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mold for injection compression molding of a light guide plate and a method for manufacturing a light guide plate using the same.
More specifically, the injection compression of a wedge-shaped light guide plate whose thickness gradually decreases from one end to the other end without fitting the fitting portion while maintaining a state where the mating surfaces of the fixed type and the movable type are in close contact with each other. The present invention relates to a molding die and a method for producing the light guide plate molded using the molding die.

[0002]

2. Description of the Related Art Heretofore, most of a light guide plate made of a transparent resin incorporated in a backlight unit for guiding light to a liquid crystal in a liquid crystal display has been manufactured by injection molding. Many light guide plates have a wedge shape in which the thickness gradually decreases from one end to the other end (in the following description,
Even when simply describing "light guide plate" without describing "wedge-shaped light guide plate whose thickness gradually decreases from one end to the other end", "thickness gradually decreases from one end to the other end" Wedge-shaped light guide plate ”), injection molding of these light guide plates can also be performed by injection compression molding, in which molten resin is injected into the product part formed between the fixed mold and the movable mold, and then compressed. According to this molding method, the light guide plate can be made uniform and the molding time can be shortened. The production of a light guide plate by such injection compression molding could be performed using a mold described below. (1) As shown in FIG. 6, the movable mold 60 is moved in the mold closing direction by using a pressure source 80 such as hydraulic pressure or air pressure attached to the movable mold 60 of the mold 100, and is injected into the product section 95. Method of compressing and molding molten resin. (2) As shown in FIG. 7, the mating surface 90 of the movable mold 60 and the fixed mold 70 of the mold 100 is completely closed, and the injection pressure which generates a force slightly larger than the mold clamping force is applied to the product portion 95. By injecting the molten resin (the mating surface is opened by the injection pressure), the movable die 60 is moved in the mold opening direction together with the movable platen of the injection molding machine, and is moved between the fixed die 70 and the mating surface 90 of the movable die 60. A method of forming a widened space necessary for compression and increasing the clamping force after injection to form by compression, or a method of forming the mating surface 90 of the movable mold 60 and the fixed mold 70 of the mold 100 shown in FIG. A method in which the molten resin is injected into the product section 95 without being closed, and when the injection is completed, the mold 100 is closed and compressed by using the clamping force of an injection molding machine to form the molded article. (3) As shown in FIG. 8, the fixed mold 70 and the movable mold 60 do not close the mating surface 90 between the movable mold 60 and the fixed mold 70 of the mold 100 and do not allow the injection resin to leak out of the product part 95.
The molten resin is injected into the product part 95 in a state where the fitting part 91 provided in the fitting part 91 is fitted, and when the injection is completed, the mold 100 is closed and compressed using the clamping force of the injection molding machine. Or the movable mold 6 of the mold 100 shown in FIG.
Injection that generates a force slightly larger than the mold clamping force in a state where the mating surface 90 of the fixed mold 70 and the fixed mold 70 is completely closed, and the fitting portion 91 of the fixed mold 70 and the movable mold 60 is completely fitted. By injecting the molten resin under pressure, the movable mold 60 and the movable platen of the injection molding machine are moved together in the mold opening direction, and the width required for compression between the mating surfaces 90 of the fixed mold 70 and the movable mold 60 is increased. A method of creating a sealed space, compressing it with a mold clamping force after injection, and molding.

[0003]

However, (1)
According to the molding method using the mold, the movable mold must be pressed with a high pressure to move the movable mold in the mold closing direction while resisting the injection pressure, resulting in an increase in the size of the pressure source and, consequently, the size of the mold itself. It was not suitable for space saving.
According to the molding method using the mold of (2), since the mating surface is in an open state before compression, the injected molten resin leaks out, and there is a possibility that a defect such as a burr may occur in the light guide plate. .
According to the molding method using the mold of (3), when the mold is opened and the light guide is taken out, when the mold is closed, it is difficult to position the fitting portion, and the mold is painful due to galling or the like. There was a problem that it was easy.

In view of the above, the present invention has been made in view of the above circumstances, and it is possible to prevent inconveniences such as burrs or the like from being generated on a light guide plate while maintaining the advantages of the above-described injection compression molding, and suitable for saving space. It is an object of the present invention to provide a mold for injection compression molding of a light guide plate capable of preventing pain of the mold, and a method of manufacturing a light guide plate formed by using the mold.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems and completed the present invention. That is, the present invention provides a method for injecting a wedge-shaped light guide plate in which a molten resin is injected into a product portion formed between a fixed mold and a movable mold, and then the thickness of the molded resin is gradually reduced from one end to the other end. In the compression molding die, the movable mold has a movable nest that forms a wedge-shaped product part between the fixed mold and a movable outer nest that slidably surrounds the outer periphery of the movable nest. A pressure source provided on a movable side of the injection compression molding die or a movable side of an injection molding machine, and for pressing an end of the movable outer peripheral nest on the mold opening direction side in a mold closing direction; A mold for injection compression molding of a wedge-shaped light guide plate whose thickness gradually decreases from one end to the other end, wherein the mating surface of the nest and the fixed mold is maintained at least at the time of injection and compression. (Claim 1).

According to the invention having the above construction, the mating surfaces of the movable mold (movable outer nest) and the fixed mold can be kept in close contact with each other at the time of injection and compression, so that there is no leakage of the molten resin and burrs are generated on the light guide plate. There is no defect to do. Further, since there is no need to fit the fitting portions of the movable mold and the fixed mold, the mold is not damaged by galling or the like. Furthermore, a pressure source for pressing the end of the movable outer nest on the mold opening direction side in the mold closing direction is provided on the movable side of the injection compression molding die or the movable side of the injection molding machine, so that a simple configuration ensures reliable and efficient operation. The mating surface of the movable mold (movable outer peripheral nest) and the fixed mold can be kept in close contact with each other.

A light guide plate is characterized in that the light guide plate is formed by using an injection compression molding die for a wedge-shaped light guide plate whose thickness gradually decreases from one end to the other end. A method (claim 2). According to the invention having this configuration, it is possible to manufacture a light guide plate with less luminance unevenness without generating burrs and the like.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a mold for injection compression molding of a light guide plate according to the present invention and a method for manufacturing a light guide plate formed by using the same will be described with reference to the drawings.

FIGS. 1 to 3 are schematic cut-away longitudinal sectional views of a mold (hereinafter, referred to as the present mold) 50 for injection compression molding of a light guide plate of the present invention, and FIG. 4 is a schematic cut-away lateral view. . Main mold 50
Is composed of a movable mold 10 composed of a movable nest 11 and a movable outer peripheral nest 12, a fixed mold 20, a movable-side mounting plate 13, a fixed-side mounting plate 21, and a hydraulic device 30 provided on the movable-side mounting plate 13. It is configured.

The movable insert 11 is a substantially prismatic body having an end on the mold closing direction side forming a tapered surface, and forms a wedge-shaped product portion 45 with the end of the fixed mold 20 in a longitudinal sectional view. The end of the movable nest 11 on the mold opening direction side is fixed to a square-plate-shaped movable-side mounting plate 13. The movable side mounting plate 13 is fixed to a movable platen of an injection molding machine (not shown).

The movable outer nest 12 has a rectangular cylindrical shape whose both ends are open, and is slidably fitted on the outer periphery of the movable nest 11. The movable outer nest 12 is
Can be slid on the outer periphery of the light guide plate 15 after molding is completed.
It can be used to extract 0. As shown in FIG. 4, four hydraulic devices 3 each having a known configuration are provided at four corners of the movable side mounting plate 13 to which the movable nest 11 is fixed.
0, the tip of the plunger 31 of each hydraulic device 30 is in contact with the end of the movable outer nest 12 on the mold opening direction side. The end of the movable outer nest 12 on the mold closing direction side abuts on the end of the fixed mold 20 on the mold opening direction side to form a mating surface 40. An end of the fixed die 20 on the mold closing direction side is fixed to a fixed-side mounting plate 21, and the fixed-side mounting plate 21 is fixed to a fixed platen of an injection molding machine (not shown). Note that the number of hydraulic devices 30 provided in the movable-side mounting plate 13 is not limited to the above four, and can be increased or decreased as appropriate.

Next, the main mold 5 constructed as described above is used.
The operation of 0 will be described. First, in the mold closed state, as shown in FIG. 1, the end face of the movable nest 11 on the mold opening direction side and the end face of the movable outer nest 12 are flush, and the end of the movable outer nest 12 on the mold closing direction side. Are in close contact with the fixed mold 20. A wedge-shaped product part 45 is formed between the movable die 10 and the fixed die 20.

When the movable nest 11 is slightly moved in the mold opening direction by slightly moving the movable platen of the injection molding machine in the mold opening direction as shown in FIG. Is injected, and the product part 45 is filled with a molten resin. With the movement of the movable nest 11 in the mold opening direction, the hydraulic device 30 provided inside the movable side mounting plate 13 operates, and the plunger 31 presses the end of the movable outer nest 12 on the mold opening direction side. Even when the movable nest 11 moves in the mold opening direction, the movable outer nest 12 does not separate from the fixed mold 20, and the mating surface 40 between the movable outer nest 12 and the fixed mold 20 can be maintained in a close contact state. Note that the movement of the movable nest 11 in the mold opening direction is not limited to the case where the injection molding machine is operated as described above, and the movable nest 11 is melted at an injection pressure slightly larger than the mold clamping force of the injection molding machine. A configuration in which the resin is injected into the product part 45 may be adopted.

The pressure of the hydraulic device 30 for pressing the end of the movable outer peripheral nest 12 does not need to withstand the injection pressure, and it is sufficient to simply bring the movable outer peripheral nest 12 into close contact with the mating surface 40 with the fixed mold 20. A small pressing force is sufficient, and FIG.
It is not necessary to increase the size of the hydraulic device 30 as in the above-described conventional mold shown in FIG. 1 and thus the mold 50 itself can be reduced in size. Further, since the injection of the molten resin can be performed in a state where the mating surface 40 of the movable outer nest 12 and the fixed mold 20 is closed,
There is no problem that the molten resin does not leak out and burrs or the like are generated on the light guide plate 150. Further, since there is no need to fit the fitting portion between the movable mold 10 and the fixed mold 20, no pain occurs in the main mold 50 due to galling or the like.
It should be noted that the pressure source may not be provided in the main mold 50 itself or the injection molding machine itself, but may be externally attached thereto. Further, not only the end of the movable outer nest 12 on the mold opening direction side but also a portion other than the end such as the outer periphery of the movable outer nest 12 may be pressed in the mold closing direction. Further, the movable outer peripheral nest 12 is engaged with the fixed mold 20 so that the movable outer
The light guide plate 150 may be disengaged when the light guide plate 150 is taken out.

When the injection of the molten resin is completed, the movable nest 11 is closed by the mold clamping force of the injection molding machine as shown in FIG. The wedge-shaped light guide plate 150 whose thickness gradually decreases from one end to the other end is manufactured. The light guide plate 150 manufactured by the present mold 50 not only does not generate burrs and the like as described above, but also is manufactured by injection compression molding, so that the pressure holding time and the cooling time are increased to avoid sink marks. Since it is not necessary to perform the molding, the molding time can be shortened, and since the molding is performed with a constant stress, luminance unevenness can be reduced.

Although the basic configuration of the present mold 50 has been described above, the injection compression molding die for the light guide plate of the present invention is not limited to the above-described structure unless departing from the gist of the present invention. Various forms can be changed and embodied. (1) The movable nest and the movable outer nest are not limited to the above-described embodiments, but can be variously changed according to the desired configuration of the light guide plate. (2) The mold for injection compression molding of the light guide plate of the present invention can be appropriately provided with various protrusion mechanisms, runner mechanisms, temperature control mechanisms, and the like, which are usually employed in the mold field. (3) The pressure source is not particularly limited as long as the movable outer nest can be pressed in the mold closing direction. In addition to hydraulic pressure, pneumatic pressure, biasing force of a spring, a servomotor, or the like can be used. (4) The pressure source is not limited to the case where the pressure source is provided inside the movable mounting plate, and may be provided on a movable outer nest, a movable platen of an injection molding machine, or the like. (5) The movable outer nest may be manufactured by dividing it into a plurality of blocks, and assembling each block when assembling the mold. With such a configuration, the movable outer nest can be efficiently manufactured. (6) The pressing of the movable outer nest into the fixed mold may be performed at least at the time of injection and at the time of compression, but may be configured to be constantly pressed. (7) The outer peripheral surface of the product part and the outer peripheral surface of the movable nest need not be flush with each other, and the inner diameter of the product part may be larger than the inner diameter of the movable nest. With this configuration, it is possible to add a molded product pushing function to the movable outer nest.

[0017]

Since the present invention is configured as described in detail above, it has the following effects. ADVANTAGE OF THE INVENTION According to the metal mold | die for the injection compression molding of the light guide plate of this invention, since the malfunction which burrs etc. generate | occur | produce in a light guide plate can be avoided and the molding time can be shortened, generation | occurrence | production of a defective light guide plate is suppressed. This can contribute to efficient production of the light guide plate. Further, since the mold is not damaged by galling or the like, it can contribute to the maintenance of the mold. Further, the size of the mold itself that can achieve the above-described effects can be reduced, which contributes to space saving.

Further, according to the method of manufacturing a light guide plate of the present invention, a uniform light guide plate free from burrs and the like can be manufactured with a reduced molding time, and a high quality light guide plate with less luminance unevenness can be manufactured. .

[Brief description of the drawings]

FIG. 1 is a schematic cut longitudinal sectional view showing a mold for injection compression molding of a light guide plate of the present embodiment in a mold closed state.

FIG. 2 is a schematic longitudinal sectional view showing a mold for injection compression molding of the light guide plate of the present embodiment at the time of injection.

FIG. 3 is a schematic longitudinal sectional view showing a mold for injection compression molding of the light guide plate of the present embodiment during compression.

FIG. 4 is a schematic cross-sectional view showing a mold for injection compression molding of the light guide plate of the present embodiment.

FIG. 5 is a perspective view showing a light guide plate manufactured by using a mold for injection compression molding of the light guide plate of the present embodiment.

FIG. 6 is a schematic longitudinal sectional view showing a conventional die.

FIG. 7 is a schematic cut longitudinal sectional view showing a conventional mold.

FIG. 8 is a schematic cut longitudinal sectional view showing a conventional mold.

[Explanation of symbols]

 10, 60 Movable mold 11 Movable nest 12 Movable outer nest 13 Movable mounting plate 20, 70 Fixed type 21 Fixed mounting plate 30, 80 Hydraulic device (pressure source) 31 Plunger of hydraulic device 40, 90 Fitting surface 45, 95 Product part 91 Fitting part 50, 100 Injection compression molding die for light guide plate 150 Light guide plate

Continuation of the front page (72) Inventor Kenji Ozawa 177, 17-jo, Jinan-cho, Motosu-gun, Gifu Pref.

Claims (2)

[Claims] Injection compression of a wedge-shaped light guide plate in which the thickness of the molded product is reduced gradually from one end to the other end after the molten resin is injected into a product part formed between the fixed mold and the movable mold. In the molding die, the movable mold is a movable nest that forms a wedge-shaped product portion between the fixed mold and a movable outer nest that slidably surrounds the outer periphery of the movable nest. A pressure source provided on a movable side of the injection compression molding die or a movable side of the injection molding machine, and configured to press an end of the movable outer peripheral insert in a mold opening direction in a mold closing direction; A wedge-shaped light guide plate having a thickness gradually reduced from one end to the other end, the mold being used for injection compression molding, wherein the mating surfaces of the fixed mold and the fixed mold are maintained at least at the time of injection and compression. 2. A light guide plate according to claim 1, wherein the thickness of the light guide plate is gradually reduced from one end to the other end by using a mold for injection compression molding of a wedge-shaped light guide plate. Method.