JPH1158464A - Mold structure for surface illuminant light guide and its molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold structure and a method thereof for replacing a stamper securely and with high accuracy, safely and efficiently without replacing a mold. SOLUTION: In a mold for molding a surface illuminant light guide, an ejector block 11 provided with the gradient of same angle of a light guide plate end face 15 is brought into contact with the light guide plate end face 15, and also the light guide plate 14 is molded as a part of an end face forming cavity 5 when the light guide plate 14 is molded by the cavity. When the molding is completed and mold opening is started, the ejector block 11 is protruded forward, and the light guide plate end face 15 is extruded on an ejector block inner side face 12 being brought into contact with the light guide plate end face 15 to release the light guide plate 14 from the cavity. The ejector block 11 is provided with a hook-shaped section 13 and the stamper 17 is clamped between the hook-shaped section 13 and end face forming cavities 6a and 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-light emitting display device,
For example, the present invention relates to a molding die structure of a light guide for a surface light source used for a backlight that irradiates a liquid crystal display device with light from the back thereof, and a molding method thereof.

[0002]

2. Description of the Related Art A backlight unit as a light source for irradiating a liquid crystal display device which is a non-light emitting display device from behind,
On the back of the liquid crystal panel, a fluorescent tube as a light source and a light guide plate for irradiating light from a light source incident from the side to the entire surface of the diffusion panel are provided.

[0003] A prism pattern is formed on the light exit plate surface of the light guide plate at the time of molding the light guide plate in order to improve the luminance distribution. The processing of this prism pattern is performed by using a mold in which a pattern opposite to the desired pattern is engraved. As a method of creating these molds, a plate-shaped mold obtained by electroforming from a master is used. As a method of fixing an object (hereinafter referred to as a stamper) to a mold cavity surface to form an optical pattern, for example, as disclosed in Japanese Patent Application Laid-Open No. H8-6017, "Mold Structure of Light Guide for Backlight Unit" , Stamper, screwed to the mold member,
As disclosed in Japanese Patent Application Laid-Open No. Hei 9-131770, "Method for Forming Light Guide Plate and Die Used for the Same", there is a device mounted on a mold member by vacuum suction.

[0004]

Generally, the prism pattern of the stamper is as thin as about several mm in thickness and the prism shape is, for example, a pitch of 31 μm.
Since it is very fine with a height of 31 μm, as the molding is repeated, the wear of the pattern and the
In case of deformation, scratches or breakage, the stamper must be replaced with a mold. Since this stamper exchange is performed during molding, it must be quickly and reliably performed to increase the processing efficiency.

[0005] For such a reason, Japanese Unexamined Patent Publication No.
The technology described in Japanese Patent No. 6017 discloses loosening screws,
Time is required for operations such as tightening and the like, and time is required for replacing the stamper. In addition, if the tightening of the screw is uncertain and the screw is loosened, the position of the stamper may shift or come off, resulting in poor molding or breakage of the stamper.

Further, the technique described in Japanese Patent Application Laid-Open No. 9-131770 has a problem that the suction force is incomplete due to the state of the stamper suction surface (dirt, deformation, etc.), and the fixed stamper comes off. Failure occurs. In addition, equipment for vacuum suction is required, which complicates the apparatus and increases the cost.

In general, when a molded product is released from the mold, the stamper flat surface is protruded by an ejector pin or a sleeve and released from the mold. There is a possibility that the mark protrudes upward and is deformed, which adversely affects the luminance distribution of the light guide plate.

[0008]

According to the present invention, there is provided an apparatus and method for molding a light guide plate, comprising: an ejector block for extruding a light guide when the mold is released from a mold for molding a light guide for a surface light source. Wherein the ejector block forms a part of a mold cavity for molding the light guide, and the light guide is extruded by the ejector block.

Further, the ejector block has a gradient at the same angle as the draft of the light guide, and extrudes the light guide at the gradient when the mold is released from the mold.

In a mold for molding a light guide for a surface light source, an ejector block for extruding the light guide when the mold is released, and a fine pattern for improving brightness on a light exit surface of the light guide. A stamper is formed on the ejector block to lock the stamper, and the stamper is fixed by the hook at the time of mold clamping.

Further, the ejector block gradient and the ejector block hook-shaped portion are shared by one ejector block.

In a method of molding a light guide for a surface light source, a stamper is fixed at the hook-like portion of the ejector block when the mold is clamped, and the ejector block is inclined at a gradient when the mold is released. And extruding the light guide.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, an injection mold A is formed by a fixed mold 1 and a movable mold 2. The movable mold 2 includes a movable mold plate 3 and a cavity 4. The cavity 4
Bottom forming cavity 5 and end surface forming cavities 6a, 6b
Consisting of Recessed grooves 9 (four upper and lower locations) are formed in the upper and lower end faces 7, 8 of the bottom surface forming cavity 5 in the mold opening direction, and ejector blocks 11 (four locations) are inserted into the respective recessed grooves 9 so as to be able to advance and retreat. It is ejected in the mold opening direction by an ejector block ejecting device (not shown) provided behind the movable mold plate 3.

On the inner surface 12 of the ejector block, a gradient is formed at the same angle as the draft angle of the end face 15 of the molded product (hereinafter referred to as a light guide plate) 14. The light guide plate 14 is released from the cavity 4 by extruding the end face 15 by the inner surface 12 of the ejector block. The ejector block 11 has a hook 13
Is formed, and when the ejector block 11 retreats,
The stamper 17 is sandwiched between the hook portion 13 and the bottom surface forming cavity 5, and the stamper 17 is
Pressed against. At the center of each end face of the bottom forming cavity 5, a stamper positioning block 20 (up and down four places) for positioning the stamper 17 is provided at the center of the end face of the bottom forming cavity 5 in the groove 10 (up and down 4) formed in the mold opening direction. Location). The stamper 17 has a notch 18 formed in the width dimension of the stamper positioning block 20 in consideration of thermal contraction and thermal expansion, and the stamper notch 18 is fitted to the stamper positioning block 20. . End face forming cavity 6a,
6b, which is fixed to the movable mold plate 3, constitutes a part of the cavity of the light guide plate 14, and is removed by replacing the stamper 17, repairing the movable mold, or the like.

The fixed mold 1 includes a fixed mold plate 21 and a reflecting surface forming core 22 for forming a reflecting surface of the stamper 10. The fixed side mold plate 21 has a gate portion (not shown), and a molten thermoplastic resin is filled into the cavity at a high pressure.

The stamper 17 is formed by forming an original plate by photolithography or the like, and then formed into a thin plate having a thickness of about several mm by electroforming plating so as to cover the pattern of the original plate. Therefore, the fine pattern 19 (for example, prism angle 90 degrees, pitch 31
μm and a height of 31 μm). Then, at the time of molding, the light guide plate fine pattern 16 (a reversed pattern of the concavo-convex state of the fine pattern 19) is formed. Stamper 17
When the mold is closed, the ejector block 11 is retracted, so that the ejector block 11 is sandwiched between the bottom surface forming cavity 5 and the ejector block hook 13.

Next, the main operation of this embodiment will be described with reference to FIGS.

(1) The injection mold A is attached to a predetermined position of an injection molding machine (not shown).

(2) The movable mold 2 is retracted, the mold is opened, and the ejector block 11 is set in a protruding state.

The procedure for replacing the stamper 17 with the movable mold 2 will be described below.

When the stamper is removed, (3) the end face forming cavities 6a and 6b are removed from the movable mold plate.
(2 places each). (See FIG. 2) (4) The stamper notch 17 is removed from the stamper positioning block 13 and the stamper positioning block 1 is removed.
The stamper is pulled out from between the hook 3 and the hook 13 of the ejector block, and the stamper is taken out of the mold. (Refer to FIG. 3) When attaching a stamper, (5) At the same time as fitting the stamper end face into the hook-shaped portion 13 of the upper and lower ejector blocks, the stamper notch 17 is fitted into the stamper positioning block 13 to form the stamper cavity 5. The upper mold is positioned at a predetermined position.
(See FIG. 3) (6) The end face forming cavities 6a and 6b (four places) are attached, and the stamper 17 is fixed. (Refer to FIG. 2.) The replacement of the stamper is thus completed.

Next, the molding process in this embodiment will be described step by step with reference to FIGS.

(1) The movable mold 2 is moved to the fixed mold 1 to join them. At this time, the ejector block 11 is retracted in the mold opening direction, so that the end face of the stamper is clamped by the hook-like portion 13 of the ejector block, thereby preventing the stamper from moving due to molding pressure or the like during molding. The inner surface 12 of the ejector block has the same angle of inclination as the outer surface of the light guide plate, and the end face forming cavities 6a,
As in 6b, a cavity is formed.

(2) After completion of mold clamping, a gate portion (not shown) provided in a fixed mold of a thermoplastic resin, which has been brought into a fluid state by heating and melting in an injection cylinder (not shown). ) Is injected into the cavity 4.

(3) When the molten resin injected into the cavity 4 is cooled and the light guide plate is completely solidified, the movable mold 2 retreats from the fixed mold 1 to start mold opening, and at the same time, the ejector block 11 forms the bottom surface. The light guide plate 14 is released from the cavity 4 by protruding from the cavity 5 and projecting the light guide plate outer surface 15 at the ejector block inner surface 12. When the mold is released (the ejector block 11 is
The ejector block hook 13 does not hold the stamper end face, but the end face forming cavity 6 holds the entire periphery of the stamper end, so that the stamper does not fall out. (See FIG. 2) In the present embodiment, the ejector block 11 has a role of protruding the light guide plate 14 when releasing the mold and a role of holding the end face of the stamper when clamping the mold. (See FIGS. 4 and 5) In this embodiment, as shown in FIG.
When exchanging, even if the outer peripheral end surface forming cavity 6 is removed, the stamper 17 is not caught by the hook-like portion 13 of the upper and lower ejector blocks, and the stamper 17 does not fall out of the cavity and is not damaged or damaged.

Generally, in order to release the light guide plate from the mold, as shown in FIG. 6, the outer peripheral surface of the light guide plate 114 is formed by the ejector pins 102 or a sleeve ( (Not shown).
In this case, since the ejector pins must be provided at the outer peripheral position where they do not interfere with the prism surface, the area must be secured. Therefore, the overall size of the light guide plate becomes large. In addition, since the protrusion is left near the prism of the light guide plate, the luminance distribution may be adversely affected.

As a technique for fixing a stamper to a mold, Japanese Patent Application Laid-Open Nos. Hei 8-6017 and Hei 9-13177 are known.
There is a technique described in Japanese Patent Application Laid-Open Publication No. H07-15095, in which the former is a method of fixing a stamper with a screw, and this method may loosen if the screw is incompletely fixed. Further, since a hole for fixing with a screw must be provided on the outer periphery of the stamper, the area must be secured. Therefore, the entire light guide plate becomes large. In the latter, since the stamper is attracted by vacuum, it is affected by the state of the stamper surface (dirt, deformation, etc.), the fixing of the stamper is uncertain, and it is difficult to secure a constant positioning state.

As shown in FIG. 6, there is also a technique of directly fixing the bottom surface of the cavity (bottom forming cavity) with the double-sided adhesive tape 103, but it is not reliable, and if the stamper is scratched or damaged due to molding trouble or the like. In addition, repairs and replacements must be performed by the mold manufacturer, and it takes days to troubleshoot.

In comparison with the above-mentioned prior art, the present application
Not only can the stamper be securely fixed in place with high precision, but also when ejecting the end face forming cavity, the ejector block plays the role of preventing falling down and the double safety function allows the It is less likely to drop and damage or damage the stamper.

[0031]

According to the present invention, the stamper is securely fixed to the mold, and a high-quality, high-precision light guide plate can be obtained by molding. Further, the stamper can be replaced reliably and with high accuracy without replacing the mold, and the stamper can be replaced rationally and economically.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main configuration of an injection mold in one embodiment of the present invention.

FIG. 2 is a perspective view of a movable mold portion of the injection mold.

FIG. 3 is also a diagram showing an end face forming cavity 6a,
It is a perspective view which shows the state of the stamper when 6b is removed.

FIG. 4 is an explanatory diagram showing a state of each part when the injection molding die is closed.

FIG. 5 is an explanatory view showing a state of each part when the injection molding die is opened.

FIG. 6 is a drawing showing a conventional technique, and is an explanatory view showing an example in which a stamper is attached to a bottom surface forming cavity with a double-sided adhesive tape.

[Explanation of symbols]

 Reference Signs List 14 Light guide plate (light guide for surface light source) A Injection molding die (die) 11 Ejector block 4 Cavity (mold cavity) 15 Light guide draft angle 19 Fine pattern for brightness improvement 17 Stamper 12 Ejector block gradient 13 Ejector Block hook

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B29L 11:00

Claims (5)

[Claims] 1. A mold for molding a light guide for a surface light source,
When the mold is released, the mold has an ejector block that pushes out the light guide, the ejector block constitutes a part of a mold cavity for molding the light guide, and the light guide is formed by the ejector block. A mold structure of a light guide for a surface light source, which is extruded. 2. An ejector block according to claim 1, wherein said ejector block has a gradient of the same angle as said light guide draft, and extrudes said light guide at said gradient when said mold is released. Mold structure of light guide for surface plateau. 3. A mold for molding a light guide for a surface light source,
An ejector block for extruding the light guide when the mold is released, and a stamper for forming a fine pattern for improving brightness on the light emitting surface of the light guide, wherein the stamper is engaged with the ejector block. To stop, form a hook-shaped part,
A mold structure for a light source for a surface light source, wherein a stamper is fixed by the hook-shaped portion during mold clamping. 4. A mold apparatus for a light source for a surface light source, wherein said ejector block gradient and said ejector block hook-shaped portion are shared by one ejector block. 5. A method for molding a light guide for a surface light source, comprising:
A method for forming a light guide for a surface light source, comprising fixing a stamper and extruding the light guide at the same ejector block gradient when releasing the mold.