JP2002103379A - Method for manufacturing light guide plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for manufacturing a light guide plate by which various kinds of the light guide plate with differing odd-shaped parts and sizes can be manufactured with high dimensional precision and high yield and further, at a low cost. SOLUTION: First a planar original plate 32 of a larger shape than the shape of a product of the light guide plate 10 intended for is formed by injection molding and then is fabricated using working means such as laser. Thus the odd-shaped parts 24, 26, 28 and 30 are formed by cutting to complete the light guide plate 10 intended for.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light guide plate for a lighting device used for a backlight of a liquid crystal display device or the like.

[0002]

2. Description of the Related Art A liquid crystal display device employed in a personal computer, a word processor, a liquid crystal television, a liquid crystal video, a liquid crystal DVD, a car navigation system, etc. has a backlight disposed on the back side of a liquid crystal panel and is projected from the backlight. Light is transmitted through the liquid crystal panel and dimmed, so that each dot set on the liquid crystal panel is illuminated and displayed.The backlight used in such a liquid crystal display device is a liquid crystal panel. Since it is necessary to uniformly irradiate the entire surface, generally, a flat light guide plate having a size that covers substantially the entire surface of the liquid crystal panel is used, and light projected from a cold cathode discharge lamp or the like onto the outer peripheral end surface of the light guide plate is generally used. Through the light guide plate to the entire surface of the liquid crystal panel for irradiation.

A light guide plate used in a liquid crystal display device is generally formed between a fixed mold and a movable mold, which are mounted on a mold clamping device, using an injection molding device made of a synthetic resin material. It is manufactured by injection filling a molding cavity with a molten resin material such as methacrylic resin by an injection device. Further, the light guide plate has a straight line at its outer peripheral edge for the purpose of positioning and locking with respect to the frame or the like of the liquid crystal display device, or for the purpose of avoiding an assembling bolt of the liquid crystal display device. Irregular portions such as projections and cuts having irregular shapes are formed with respect to the edge portions, and such irregular portions are also formed simultaneously with injection molding.

Further, in recent years, with the rapid spread of liquid crystal display devices, the variety of liquid crystal display devices has been remarkably increased, and accordingly, the light guide plates have the same size and differ only in the shape of the deformed portion. It is remarkable that small-scale production of many varieties, such as products and those having slightly different sizes and shapes, is performed.

However, when manufacturing a light guide plate by injection molding, it is necessary to newly prepare a molding die for providing a molding cavity shape corresponding to a deformed portion or a slight change in size even when there is a change. For this reason, there has been a problem that production cost is significantly increased when a large number of products are produced in small quantities.

In order to cope with this problem, inexpensive molding dies are used at present. However, inexpensive molding dies have insufficient accuracy in terms of dimensions and surface roughness, and also have a problem in a mold matching area. Since it is difficult to adopt a compression structure that increases the sealing performance by fitting both molds to each other, molding defects such as burrs and sink marks are likely to occur, making it difficult to ensure the product quality of the light guide plate. In many cases, the yield is less than 50%, which is a major problem.

It is conceivable to cope with the problem of poor molding by increasing the size of the mold clamping device and exerting a clamping force of 400 t or more. This is not an effective measure because not only is the increase in the molding time but also the molding cycle is inevitably lengthened.

[0008]

Here, the present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is that it is possible to easily cope with a change in a deformed portion, size, or the like. It is another object of the present invention to provide a novel light guide plate manufacturing method capable of manufacturing a plurality of types of light guide plates with high dimensional accuracy and excellent yield at low cost.

[0009]

An embodiment of the present invention which has been made to solve such a problem will be described below. The components employed in each of the embodiments described below can be employed in any combination as possible. In addition, aspects or technical features of the present invention are not limited to those described below, but are described in the entire specification and drawings, or based on the invention ideas that can be understood by those skilled in the art from the descriptions. It should be understood that it is recognized on the basis of.

That is, the features of the present invention are as follows:
When manufacturing a light guide plate having a deformed portion such as a protrusion or a cut in the outer peripheral portion, a prototype plate having a planar shape larger than a target product shape at least at a portion where the deformed portion is formed is injected with a predetermined resin material. A method for manufacturing a light guide plate, wherein the light guide plate is formed by molding, and the deformed portion is cut and formed on an outer peripheral edge of the original plate by post-processing the original plate.

According to the method of the present invention, a deformed portion having an arbitrary shape can be formed by post-processing on the original plate obtained by injection molding, and the position and shape of the deformed portion are different. Since a plurality of types of light guide plates can be injection-molded using the same molding die, the manufacturing cost of the light guide plate can be greatly improved. In addition, a light guide plate having a slightly different outer peripheral shape and dimensions is also manufactured by cutting the outer peripheral edge of the original plate in a different shape at the time of forming a deformed portion using an original plate injection-molded with the same molding die. It becomes possible.

In addition, since the deformed portion provided on the outer peripheral edge of the light guide plate is cut and formed after the injection molding, molding such as burrs and sink marks on the outer peripheral edge of the light guide plate, which is generated at the time of injection molding. The defective portion can also be cut off when forming the deformed portion. If the outer peripheral edge of the light guide plate where molding defects easily occur is cut by post-processing, product defects caused by molding defects can be eliminated without the need for expensive molds or large mold clamping devices. Can be reduced or avoided, thereby improving the product yield.

Further, the light guide plate is required to have high dimensional accuracy in order to uniformly guide the light emitted from the light source over the entire surface with the highest possible efficiency. Although it was necessary to set the mold shape by trial and error in consideration of the cooling shrinkage caused by the difference in the thickness dimension, etc., the method of the present invention also requires the light guide plate to cut and form the irregularly shaped portion. Can also be cut and formed. Therefore, high dimensional accuracy can be imparted to the light guide plate without requiring an expensive mold, and improvement in product quality can be realized easily and at low cost.

In short, the method of the present invention is, as can be seen from the history, the injection molding which has been improved mainly for the purpose of simplifying the production by giving the final product shape simultaneously with the molding. On the other hand, the idea of completely reversing, dare to adopt post-processing after molding, which had only been considered to be reduced in the past, and to actively use such post-processing, is a major technical issue. It has the origin of thought. And, when manufacturing a light guide plate of a specific structure having a deformed part such as a projection or a notch on the outer peripheral part of the lock, based on such an idea of reversal, post-processing that was conventionally taboo in injection molding For the first time, aggressive use made it possible to produce a plurality of types of light guide plates with high dimensional accuracy and excellent yield at low cost.

In the post-processing by the method of the present invention,
Any shape can be used as long as it can form a deformed part of the desired shape on the original plate with sufficient accuracy and good workability. In addition to machining, cutting using ultrasonic waves, electron beam and water jet It is also possible to adopt a cutting process using a method.

In the method of the present invention, a cutting process using a laser can be preferably employed in the post-processing of the original plate. That is, if the cutting process by laser is adopted, the outer peripheral edge of the light guide plate can be cut quickly in an arbitrary shape, and adverse effects on quality and workability due to processing powder and the like can be avoided. As the laser, conventionally known laser processing such as a CO ₂ laser or a YAG laser can be appropriately employed.

In laser processing, the surface roughness and the like of the cut surface can also be adjusted by adjusting the power of the laser and the like. Therefore, for example, the incidence efficiency at the end face of the light guide plate can be reduced. It is also easy to adjust the surface roughness of the outer peripheral surface in order to improve it.

Further, in the method of the present invention, in the post-processing of the original plate, a cutting process by machining using a milling machine or the like can be suitably adopted. In particular, if machining is employed, since the influence of heat on the cut surface of the original plate is avoided, the quality and shape of the light guide plate, for example, the shape of the edge portion, etc., can be more highly managed. .

In particular, the present invention is advantageously employed when manufacturing a plurality of types of light guide plates having different external shapes by performing the post-processing on a plurality of the original plates having the same dimensions. Therefore, it is possible to easily cope with high-mix low-volume production while maintaining excellent product quality and with good cost performance.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described in detail with reference to the drawings.

First, FIG. 1 shows a specific example of a light guide plate manufactured by the method of the present invention. This light guide plate 1
0 has a thin, substantially rectangular flat plate shape as a whole,
The plate has a substantially wedge cross-sectional shape whose thickness gradually decreases from the upper end to the lower end in the figure. One plate surface (front surface) is a projection surface 12 facing the rear surface of the liquid crystal panel, and the other plate surface (rear surface) is an inclined reflection surface 14. Although not explicitly shown in FIG. 1, light emitted from a cold cathode discharge lamp or the like which is spaced apart from the top end surface (incident end surface) 16 which is the thickest is transmitted from the incident end surface 16 into the light guide plate 10. And is guided over the entire inside of the light guide plate 10 and projected from the projection surface 12 toward the liquid crystal panel.

An upper end surface (projection surface) 16 and a lower end surface 18 are disposed on the outer peripheral edge portion of the light guide plate 10 so as to be opposed to each other in a pair at upper and lower sides and left and right sides in the figure, and extend in parallel with each other. A surface 20 and a right end surface 22 are formed, and each has a planar shape substantially orthogonal to the projection surface 12. Furthermore, on the left and right end surfaces 20 and 22, only light guide plates 1 and 26, which are located at intermediate portions in the longitudinal direction, are formed as substantially rectangular block-shaped protrusions projecting on the end surfaces.
It is integrally formed with the same thickness dimension as 0. The left end face 20 has a cutout portion 28 which is located below the indentation portion 24 at the middle portion in the longitudinal direction and is inwardly cut in an arc shape over the entire light guide plate 10 in the thickness direction. Is formed. Furthermore, the left and right end surfaces 20,
22 at the corner between the small notch 3
0, 30 are formed over the entire light guide plate 10 in the thickness direction.

For example, the notches 24 and 26 formed on the left and right end surfaces 20 and 22 are fitted to engagement portions provided on a frame or the like of a liquid crystal display device (not shown), and are attached to both ends of the lower end surface 18. The formed notches 30, 30
The light guide plate 10 can be positioned and set at a predetermined position of the housing of the liquid crystal display device by locking the light guide plate to a locking projection provided on the frame or the like. Further, in a frame or the like of the liquid crystal display device, assembling bolts and the like, which are provided so as to protrude to the area where the light guide plate 10 is provided, escape by the cutouts 28 formed in the left end surface 20 so that the light guide plate 10 Can be assembled.

The notches 24, 26, notches 28, and notches 30, 30 are all appropriately employed according to the structure of the frame of the liquid crystal display device to which the light guide plate 10 is to be assembled. The shape is designed, and the specific shape thereof is not limited at all. Needless to say, the formation position and the number of the formation can be appropriately changed. Needless to say, only one or two of the notches and notches may be employed.

Subsequently, the light guide plate 1 having such a structure is used.
0, a specific example of the manufacturing method according to the present invention will be described.

First, as shown in FIGS. 2 and 3, a prototype plate 32 having a larger planar shape than the intended light guide plate 10 is formed by injection molding. This original plate 32
Has the same wedge-shaped cross-sectional shape as the target light guide plate 10, and only the planar shape corresponds to the target light guide plate 10.
Is different. In particular, in the present embodiment, the original plate 32 is formed so that the left and right end surfaces 34 and 36 which spread in parallel with each other.
And a main body portion 42 having a rectangular flat plate shape having upper and lower end surfaces 38 and 40, and a runner portion 44 protruding from a central portion in the longitudinal direction of the upper end surface 38 of the main body portion 42. In this case, the original plate 32 has a width between the left and right end surfaces 34 and 36 and a height between the upper and lower end surfaces 38 and 40.
It is set larger than the target product size of the light guide plate 10.

The original plate 32 is integrally formed by injection molding using an injection molding apparatus which has been widely used in molding a synthetic resin material. Since the structure of the injection molding apparatus and the molding operation using the same are well known, detailed description is omitted here, but generally,
The fixed mold and the movable mold mounted on the fixed plate and the movable plate of the mold clamping device are clamped, and the molding cavity formed between the two molds is heated and melted by an injection device with a methacrylic resin or the like. By injecting and filling an appropriate resin material from the runner formed in the mold through the gate, cooling and solidifying, the mold is opened and the molded product is taken out.
The target original plate 32 is formed. In addition, in such injection molding, for example, injection compression molding, which has been conventionally employed for molding a CD (compact disk), is advantageous in transferring a pattern onto the surface of the original plate 32 with high accuracy. Can be suitably adopted.

Next, the original plate 32 obtained by injection molding is subjected to a cutting process on the outer peripheral edge, and the outer peripheral edge is cut along a line shown by a virtual line in FIG. Then, the light guide plate 10 having the desired outer peripheral edge shape is finished. That is, the light guide plate 10
The left and right end surfaces 20, 22 and the upper end surface 16 are formed.

At the left and right edge portions, the notch portions 24 and 26 and the cut portions 28 formed there, and the lower end surface 1
8 is cut along a line along the outline of the notches 30, 30 formed at the corners with the right and left end faces 2.
At the same time as the formation of 0 and 22, the notch portions 24 and 26, the cut portions 28, and the notch portions 30 and 30 are integrally formed on the left and right end surfaces 20 and 22.

The upper edge is cut straight over the entire length to cut off the runner portion 44 protruding from the upper surface 38 and to remove the distortion and the like of the upper surface 38 to obtain a flat surface. An upper end surface 16 is formed as an incident surface.

The cutting of the original plate 32 is advantageously performed by, for example, laser processing using laser light. Although a specific laser processing method is not described in detail here, various known laser cutting techniques using a conventionally known CO ₂ laser or YAG laser can be applied. That is, by employing laser processing for the cutting of the original plate 32, the notches 24, 26, the cuts 28, the notches 30, 30, and the like can be easily and quickly formed in any shape. In addition, the equipment cost can be reduced as compared with electron beam processing, water jet processing, etc., and a reduction in processing accuracy such as thermal distortion can be avoided as compared with plasma processing or the like. Therefore, there is an advantage that the material is hardly restricted.

According to the above-described method of manufacturing the light guide plate 10, upon injection molding, the original plate 32 may be formed using a molding die having a simple rectangular flat plate-shaped molding cavity. When the light guide plate 10 is obtained by post-processing, the notch portions 24, 26, the notch portions 28, the notch portions 30, 3,
0 and the like can be formed at any position and shape.

Therefore, the notches 24, 26 and the cuts 28,
It is possible to manufacture a plurality of types of light guide plates having different positions, shapes, and the like of the notches 30, 30 by using a single molding die, and it is easy to change the design of the outer shape of the light guide plate 10 and the like. Therefore, a light guide plate of high-mix low-volume production can be easily manufactured at low cost.

Also, the notches 24, 2
It is not necessary to form the molding cavity of the cutting cavity 6, the cutout 28, and the cutouts 30, 30. Since the shape of the molding cavity is extremely simplified, the cost of the molding die itself can be suppressed.

Further, as shown in FIG. 2, the outer peripheral edge, where molding defects such as burrs 46 and sink marks 48 tend to occur during injection molding, are cut off during post-processing after injection molding. Is formed, even if such a molding defect occurs during injection molding, excellent quality can be stably secured in the light guide plate 10 as a product.

Since the adverse effect of the injection molding defect on the product quality is avoided, it is not necessary to employ an unnecessarily large mold clamping device, for example, in order to prevent the generation of burrs. It is possible to carry out injection molding in a short molding cycle and at low cost by using.

In the present embodiment, since the outer shape is given to the light guide plate 10 by post-processing (cutting), including the incident surface 16 where particularly high dimensional accuracy is required, cooling shrinkage and the like are performed. Therefore, it is possible to avoid a decrease in dimensional accuracy due to the deformation of the mold, and it is not necessary to perform an extremely troublesome work of trially setting the shape of the molding cavity in consideration of the heat shrinkage after molding as in the related art.

Further, as described above, if the cutting of the original plate 32 is performed by laser processing, it is possible to control the properties of the cut surface by adjusting the power of the laser beam. Therefore, for example, improvement of the incident efficiency by adjusting the surface roughness of the cut surface can be easily realized by adjusting the power of the laser beam without requiring special finishing such as polishing.

Further, since the outer peripheral surface of the light guide plate 10 is formed by cutting the original plate 32, the runner portion 44 protruding from the outer peripheral edge of the original plate 32 is also removed. Special processing such as cutting of the portion 44 and subsequent polishing is not required.

Further, according to the manufacturing method as described above, the outer peripheral edge of the original plate 32 is cut by post-processing,
Any of various light guide plates having an outer shape and size smaller than the original plate 32 can be manufactured, and therefore, for example, as shown by phantom lines in FIG. The light guide plates 10a and 10b of different sizes can be manufactured using the same size original plate 32 injection-molded. In FIG. 4, in order to facilitate the understanding, in the light guide plates 10 a and 10 b of two different sizes, the corresponding portions of the light guide plate (10) in the embodiment are respectively described. The same reference numerals as those of the embodiment are denoted by a and b, respectively.

The embodiment of the present invention has been described in detail above, but this is merely an example, and the present invention is not to be construed as being limited to the specific description in the embodiment.

For example, in the above-described embodiment, the case where the cutting process of the original plate 32 is performed by laser processing has been described. However, it is of course possible to perform the cutting process by laser processing or by mechanical processing. In particular, when the original plate 32 is cut and machined by using a milling machine or the like using an end mill, the influence of heat can be avoided more than by laser processing. For example, the front and back surfaces 12 and 14 and the outer peripheral surfaces 16 and 18 can be avoided. , 20, and 22 can be further sharpened. Further, it is of course possible to adopt a different processing method according to the cut portion. For example, only the left and right end surfaces 20 and 22 having a complicated shape are cut by laser processing, and the upper end surface 16 is machined. You may cut by processing.

In the above-described embodiment, the left and right edges and the upper edge of the original plate 32 are cut after molding. However, the shape of the target light guide plate 10 is taken into consideration. For example, it is also possible to apply post-processing only to one edge, or to apply post-processing to all four edges. More specifically, as shown in FIG. 5, for example, by injection molding a prototype plate 50 whose height in the vertical direction is the same as the height of the target light guide plate 10, The light guide plate 10 can be manufactured by cutting only the left and right side edges. In this case, as shown in the figure, it is preferable that the runner portion 44 is also set at one of the left and right edges to be cut off.
Finishing processes such as cutting and polishing of the steel are not required. In FIG. 5, in order to facilitate the understanding, the same reference numerals as those of the light guide plate (10) in the above-described embodiment denote the same parts as those of the light guide plate (10) in the above-described embodiment. I will attach it.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements, and the like can be made, and unless such embodiments depart from the spirit of the present invention.
Both are included in the scope of the present invention,
Needless to say.

[0045]

As is clear from the above description, in the present invention, when manufacturing a special product called a light guide plate,
Injection molding, which has the basic development concept of giving the desired product shape at the same time as molding, uses a single molding die by actively combining the post-processes with the reverse idea. By injection molding, it was possible to manufacture a plurality of types of light guide plates having different shapes, different sizes, and the like with high dimensional accuracy and at low cost.

In particular, in the past, a yield of only about 50% was obtained, and a large actual problem in the light guide plate manufacturing industry which had to be injection molded by a large mold clamping device while accepting a decrease in the molding cycle. Can be completely eliminated by the present invention, and there is a great technical effect of the present invention.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a specific example of a light guide plate manufactured by the method of the present invention.

FIG. 2 is a front explanatory view of a prototype plate for explaining a method of manufacturing the light guide plate shown in FIG. 1 according to the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an explanatory diagram for explaining a method of manufacturing a plurality of types of light guide plates using the prototype plate shown in FIG. 2;

FIG. 5 is an explanatory front view corresponding to FIG. 2 for explaining another specific example of the method for manufacturing a light guide plate according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 light guide plate 16 upper end surface 18 lower end surface 20 left end surface 22 right end surface 24, 26 embossed portion 28 cutout portion 30 cutout portion 32, 50 original plate

Claims (3)

[Claims] When manufacturing a light guide plate having a deformed portion such as a protrusion or a cut in an outer peripheral portion, a prototype plate having a planar shape larger than a target product shape at least in a portion where the deformed portion is formed is removed by a predetermined method. And forming the deformed portion on the outer peripheral edge of the original plate by post-processing the original plate. 2. The method for manufacturing a light guide plate according to claim 1, wherein the post-processing of the original plate is performed using a laser. 3. The light guide plate according to claim 1, wherein a plurality of types of light guide plates having different external shapes are manufactured by performing the post-processing on a plurality of the original plates having the same dimensions. Manufacturing method.