JPH07159623A - Light transmission plate for liquid crystal back light and metal mold producing the same - Google Patents

Abstract

PURPOSE:To improve the light emission efficiency of a light transmission plate and the uniformity of light emission over the entire surface by providing a light reflection surface with many recessed parts which are formed to a plane graphic shape expanding gradually the furtherer from a primary light source and are roughened at their bases. CONSTITUTION:The light transmission plate 7 is used and a cathode ray tube 8 which is the primary light source is installed on the side end face to be installed with the small recessed parts 5 of a square shape. A reflection sheet 9 is arranged on one surface formed with these recessed parts 5 and a diffusion sheet 10 is arranged on the other surface. The illuminance distribution in the longitudinal direction of the light transmission plate 7 is then measured. The light transmission plate obtd. by forming many projections of 50mum height of the same square shape and the same patterns on one surface of a transparent acrylic plate and the light transmission plate 7 formed by subjecting one surface of the transparent acrylic plate to white printing over the entire surface as a reflection surface are used. The light of the cathode ray tube of the same illuminance is made incident on these plates respectively from the side end faces and the illuminance distribution in the longitudinal direction is measured. As a result, the light emission efficiency is made higher by, for example, about 30% than the light emission efficiency of the conventional light transmission plates of printing type and further, the uniformity of light emission is made extremely higher than the light emission of the light transmission plate of a type formed with the projections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for a liquid crystal (LCD) backlight which irradiates a certain area with uniform brightness, a method for manufacturing the same, and a mold for molding the same.

[0002]

2. Description of the Related Art Conventionally, when it is necessary to irradiate light over a wide area in a guide display device or an interior decoration device, a plurality of fluorescent lamps are arranged in parallel to form a light source with a large area, and a diffuser plate is placed in front of this. The display panel or the decorative plate on the surface is illuminated.

Conventionally, a liquid crystal display used for a book-type personal computer, a personal word processor or the like, which irradiates light from the back surface with a surface, is required to be thin because of its portability and compactness. Therefore, a small fluorescent tube or a light emitting diode, which is a lamp of the primary light source, is arranged on the side of the light guide plate, and the brightness is made uniform by a reflective layer formed by a coating film such as printing on the reflective surface on the back surface of the light guide plate. It is made by providing. Alternatively, a method in which a large number of ridges or projection patterns are formed on the reflecting surface by a method of manufacturing a light guide plate by resin molding is also used.

[0004]

In the guide display device and the interior decoration device, since the light source is arranged on the back surface of the diffusion plate, it is necessary to always secure a space for the light source, and the entire structure should be thin. I couldn't. Also, when the reflective layer of the light guide plate in the conventional liquid crystal display module is provided by printing as described above, the effect changes depending on the ink thickness, and by carefully considering the printing method, ink drying conditions and viscosity control It is necessary to be strict, etc., and there are many that deviate from the standard, and there is a defect that the defective rate is high due to the inclusion of dust and the like.

Further, in the case of the above-mentioned molding, the cost of the protrusions and protrusions is high because the patterns of the protrusions and protrusions are formed by engraving in a mold. Further, when such projections or ridges are formed on the reflecting surface, the light from the primary light source is reflected by the edge portions of the projections or ridges, and therefore the conversion of these lights becomes a linear light source. Was there. Therefore, the luminous efficiency of the primary light source is often not fully utilized as the surface emission of the light guide plate, and it is difficult to balance the uniformity of the emission state over the front surface.

[0006]

As a result of various investigations in view of the above problems, the present invention has developed a light guide plate capable of providing a large reflection area, a method for manufacturing the same, and a mold used for manufacturing the same.

That is, in the light guide plate for a liquid crystal backlight of the present invention, the primary light source is arranged on the side end surface of the transparent plate, and one plane of the transparent plate is used as a light emitting surface and the other plane is used as a light reflecting surface. The light guide plate for a liquid crystal backlight is characterized in that the light reflecting surface is provided with a large number of recesses each having a planar figure shape that gradually expands with distance from the primary light source and whose bottom surfaces are roughened. is there.

The mold for manufacturing a light guide plate of the present invention is a base plate having a shape of a plane figure which gradually expands from one end of the surface toward the other end, and in which a large number of concave portions having a roughened bottom surface are formed. This is characterized in that the member whose surface shape is transferred is used for a mold part. In this case, it is effective to transfer the surface shape of the base plate by an electroforming method or a casting method.

Further, in the method for manufacturing a light guide plate of the present invention, a master having a large number of planar figures which gradually expand from one end to the other on the surface of the base plate is used to etch or cut the portions of these planar figures. After the bottom surface is made into a roughened concave portion by means of, the surface shape of the base plate is transferred, and the transfer member is used as a part of the mold, and the light guide plate is made of a transparent plate having the surface shape on one side by the mold. It is preferable to transfer the surface shape of the base plate by an electroforming method or a casting method.

[0010]

The shape of the plane figure provided on the light reflecting surface of the light guide plate of the present invention and gradually expanding with distance from the primary light source is circular, elliptical, triangular, quadrangular, polygonal, semicircular, crescent-shaped, etc. The shape may be a plane figure, or a combination of two or more of these plane figures may be used. By roughening the bottom surfaces of the recesses having the planar figure shape, the light from the primary light source is reflected by these roughened bottom surfaces, so that the surface emission does not occur as in the conventional line emission but the surface of the light guide plate. The luminous efficiency is improved and the uniformity of light emission is improved. It is preferable that the depth of the concave portion exhibiting such an effect is about 1 to 80 μm. Further, since the above-mentioned plane figure has a shape that gradually expands as the distance from the primary light source increases, the plane figure is larger at a position farther from the primary light source, that is, where the attenuation of light is larger, and therefore the roughened surface is wider, and the light quantity reflected by these Also becomes larger, and the uniformity of surface emission on the entire surface of the light guide plate is further improved.

In order to mold the light guide plate having such a shape by using a mold, a mold having a pattern of such a shape engraved can be used. In the present invention, such a mold is obtained. An electroforming method or a casting method was used for this.

An example of the electroforming method will be described. First, iron,
The surface of a metal base material such as aluminum or brass is covered with, for example, a master having a large number of circles that expand from one end to the other end as shown in FIG. To the base material (1)
A large number of cylindrical recesses (2) are formed on the surface, and the bottom surfaces of these recesses are made rough by etching. Next, the surface of the base material (1) is subjected to electroforming by laminating a metal plating (4) as shown in FIG. Then, by removing the portion of the laminated plating material (4) from the base material (1), the shape of the surface of the base material is transferred to the surface of the laminated plating material (4). The transferred laminated plating material is finished into a mold part for molding.

An example of the above casting method will be described with reference to FIG.
A molten metal such as an epoxy resin, a beryllium alloy, or a Zn alloy is poured onto the surface of the base material having the above surface shape to transfer the shape of the surface of the base material to the cast material. Then, using the transferred casting material, a mold part for molding is manufactured in the same manner as above.

[0014]

EXAMPLE A surface shape of a base material made of an aluminum alloy in which a large number of recesses (5) each having a square shape whose bottom surface is roughened by etching are provided as shown in FIG. 5 by gradually expanding from one end to the other end. Was transferred to a brass laminated plating material by the above electroforming method to prepare a mold part (6) of a resin molding mold as shown in FIG. Then, using such a mold, a light guide plate having a size of 150 mm × 210 mm × thickness of 2 mm was produced from transparent acrylic resin as a raw material. On one side of this light guide plate, there was formed a large number of recesses each having a square shape and a roughened bottom surface, the square shape gradually expanding with increasing distance from the one end face side having a length of 150 mm where the primary light source is arranged. Further, the depth of these recesses was 50 μm.

Using such a light guide plate (7) of the present invention, as shown in FIG. 7, a cathode tube (8) which is a primary light source is installed on a side end face where a small square recess is arranged, and these recesses are formed. The reflection sheet (9) was provided on one surface on which (5) was formed, and the diffusion sheet (10) was provided on the other surface, and the luminance distribution in the longitudinal direction of the light guide plate (7) was measured. Also, the same square shape and the same pattern as above with a height of 50 μm on one side of the transparent acrylic plate.
Using a light guide plate with a large number of protrusions formed on it and a transparent acrylic plate on one side of which a white print is applied as a reflective surface,
The light distribution of the light guide plates in the longitudinal direction was measured by injecting the light of the cathode tubes having the same brightness from the side end faces, and the results are shown in FIG.

According to FIG. 8, the light guide plate A of the present invention has a luminous efficiency improved by about 30% or more as compared with the conventional print type light guide plate B, and the light emitting plate A emits light more than the conventional protrusion type light guide plate C. It can be seen that the uniformity is greatly improved.

[0017]

As described above, according to the present invention, the luminous efficiency of the light guide plate is improved, and further, the uniformity of the light emission is improved over the entire surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a master for etching a base material used in the present invention.

FIG. 2 is an explanatory view showing the above base material.

FIG. 3 is an explanatory view illustrating an electroforming method and a casting method on the above base material.

FIG. 4 is an explanatory view showing a laminated plated material obtained by the electroforming method and the casting method of the above.

FIG. 5 is an explanatory diagram showing a graphic pattern on the surface of a base material used in an example.

FIG. 6 is an explanatory view showing an example of a mold part used in the present invention.

FIG. 7 is an explanatory diagram showing a usage state of a light guide plate.

FIG. 8 is a diagram showing a measurement result in an example.

[Explanation of symbols]

 1 Base Material 2 Recess 3 Rough Surface 4 Laminated Material (Electroformed Material and Cast Material) 5 Square Recess 6 Mold Component (Cavity) 7 Light Guide Plate 8 Cathode Tube 9 Reflection Sheet 10 Diffusion Sheet

Claims (7)

[Claims] 1. A light guide plate for a liquid crystal backlight in which a primary light source is disposed on a side end surface of a transparent plate, and one surface of the transparent plate has a light radiating surface and the other surface has a light reflecting surface. A light guide plate for a liquid crystal backlight, comprising a large number of concave portions each having a roughened bottom surface, the reflection surface having a shape of a plane figure that gradually expands as the distance from the primary light source increases. 2. A base plate having a large number of concave portions having a roughened bottom surface, the member having a surface shape which is gradually expanded from one end to the other end of the surface and to which the surface shape is transferred is gold. A mold for manufacturing a light guide plate, which is used as a mold part. 3. The mold for producing a light guide plate according to claim 2, wherein a member whose surface shape is transferred by electroforming is used. 4. The mold for producing a light guide plate according to claim 2, wherein a member whose surface shape is transferred by a casting method is used. 5. A master having a large number of planar figures that gradually expand from one end to the other on the surface of the base plate is used to etch or grind the portions of these planar figures to roughen the bottom surface of the base plate to form concave portions. After that, the surface shape of the base plate is transferred, the transfer member is used as a part of a mold, and a light guide plate made of a transparent plate having the surface shape on one side is obtained by the mold. Manufacturing method of light guide plate for light. 6. The method of manufacturing a light guide plate according to claim 5, wherein the surface shape is transferred by electroforming. 7. The method of manufacturing a light guide plate according to claim 5, wherein the surface shape is transferred by a casting method.