JPH08327807A - Surface light source device - Google Patents

Abstract

PURPOSE: To reproduce the shape of a light diffusing body for uniformly diffusing light from a light source without damping the light by constituting a light reflector of conical dots. CONSTITUTION: This surface light source device is constituted of a light transmission plate 2 which is made of light transmissive material and whose one side surface end is a light incident part 1, the cylindrical light source 3 such as a cold cathode tube provided proximately to the light incident part 1 of the plate 2, the light reflector 5 provided on the rear surface of the plate 2, that is, many recessed conical dots, a reflector 6 provided in contact with the light reflector 5 and made of a white sheet, and a scattering plate 4 in contact with the surface of the plate 2. By arranging the recessed conical dots in plural lines at the equal intervals all over the surface, the light made incident from the light incident part 1 of the plate 2 is reflected and radiated in respective directions, so that the light is uniformly radiated from all the surface of the scattering plate 4 and the uniform quantity of light is radiated from the entire surface.

Description

Detailed Description of the Invention

[0001]

[0001]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar light source device used for a backlight such as a liquid crystal display device and a method for manufacturing the same.

[0003]

[0002]

[0004]

2. Description of the Related Art Conventionally, various types of planar light source devices for backlight illumination have been proposed in which light emitted from a light source is guided to a display section of a display plate by a light guide plate. ~ A thing as shown in Drawing 9 is known. That is, this planar light source device is made of a light-transmissive material such as glass, acrylic resin, or polycarbonate resin, and has a light guide plate 2 whose one side end is a light incident portion 1.
A cylindrical light source 3 such as a cold cathode tube provided in the vicinity of the light incident portion 1 of the light guide plate 2, and a scattering plate 4 such as a milk-color translucent polyethylene terephthalate film attached to the surface of the light guide plate 2. A light reflector 5 provided on the back surface of the light guide plate 2 and a reflector 6 made of white polyethylene terephthalate film provided in contact with the light reflector 5.

[0005]

As shown in FIG. 9, the light reflector 5 is formed by dispersing a large number of small-sized to large-sized printed dots 7 (in the following description, the entire printed dots 7 on the back surface are shown. This is sometimes referred to as the light reflector 5). Small-diameter print dots 7 are arranged in a portion of the light guide plate 2 close to the light incident portion 1, and the print dots 7 are arranged in a row in which the diameter is gradually increased with increasing distance from the light incident portion 1.

[0006]

A large number of printing dots 7 on the surface of the light guide plate 2.
The formation of is carried out by a printing method such as screen printing using a milk white translucent printing ink containing light scattering fine powder such as titanium oxide, zinc oxide, calcium oxide, barium oxide or barium sulfate in a transparent vehicle.

[0007]

By providing the printed dots 7 of the light reflector 5 as described above, the light incident from the light incident part 1 of the light guide plate 2 is converted into the large-sized printed dots 7 as the light is separated from the light incident part 1. Therefore, a large amount of light is diffused, and the surface light source device emits a uniform amount of light from the entire surface of the scattering plate 4.

[0008]

[0006]

[0009]

In the above-described planar light source device, since the print dots 7 of the light reflector 5 are formed by a printing method such as screen printing, there is a problem in dot formation. Since the printing is performed up to 80-300 μm,
It is difficult to secure accuracy due to problems such as peeling. Further, in such a printing method, foreign matter such as dust may be mixed in during printing, which impedes the uniformity of light diffusion.

[0010]

Further, knowing how to arrange the diameters of the printing dots in order to uniformly emit light on a plane requires know-how, and time is required for an experiment for determining the distribution of the printing dots.

[0011]

The present invention has been made in view of the above points, and relates to a structure and a manufacturing method of a light guide plate of a planar light source device applied to backlight illumination of a liquid crystal display device or the like. The purpose is to accurately reproduce the shape of a light diffuser for uniform diffusion without attenuation.

[0012]

[0009]

[0013]

According to the first aspect of the present invention,
In a planar light source device in which at least one side face end of a light guide plate made of a translucent material is used as a light incident part, and a light reflector capable of reflecting light is provided on one surface of the light guide plate, the light reflector is It is characterized by being composed of conical dots.

[0014]

The invention according to claim 2 is characterized in that the apex angle of the conical dots of the light reflector is set to 80 to 100 °.

The invention of claim 3 is characterized in that the tip of the apex angle of the conical dot of the light reflector is processed into a spherical shape.

The invention of claim 4 is characterized in that the conical dots of the light reflector are formed in a convex shape.

According to a fifth aspect of the present invention, the conical dots of the light reflector are formed in a concave shape.

The invention of claim 6 is characterized in that the conical dots of the light reflector are formed on a mirror surface.

The invention of claim 7 is characterized in that the conical dots of the light reflector are formed by molding.

According to an eighth aspect of the present invention, the planar light source device according to the first aspect is characterized in that the conical dots of the light reflector are integrally formed with the light guide plate.

According to a ninth aspect of the present invention, the conical dots of the light reflector are laser-processed.

A tenth aspect of the present invention is characterized in that a groove is formed on a side surface of the light guide plate opposite to a surface on which the conical dots are formed.

[0023]

[0011]

[0024]

In the planar light source device having the above structure, the light incident from one side surface of the light guide plate is reflected by the conical dots, and the light is reflected in each direction to guide the light to the entire surface of the light guide plate, and the scattering plate 4 Light is radiated uniformly from all surfaces, and a uniform amount of light is radiated from the entire surface.

[0025]

[0012]

[0026]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show a first embodiment of the present invention,
6 to 7 show the second embodiment. Common parts are designated by the same reference numerals as those of the conventional embodiment shown in FIGS.

[0027]

FIG. 1 is a perspective view of the surface light source device of the first embodiment, and FIG. 2 is a side view. FIG. 3A is a perspective view showing an example of a pattern of a light reflector on the back surface of the light guide plate of FIG. 1, and FIG. 3B is a sectional shape view of a concave conical dot of the light reflector.

FIG. 4A is a diagram for explaining the principle of the present invention, a side view of the light reflection by the light guide plate, and FIG. 4B is a diagram for explaining the principle of the present invention. It is a side view explaining the light reflection when an edge part is divided. 5 (a) is a plan view showing light reflection at a concave conical dot, FIG. 5 (b) is a side view showing light reflection at a concave conical dot, and FIG. 5 (c) is a side view showing light reflection at a concave conical dot. It is a perspective view shown.

FIG. 6A is a perspective view of the light guide plate of the second embodiment when grooves are formed on the surface thereof, and FIG. 6B is a sectional view showing concave conical dots and grooves of the light guide plate. FIG. 7A is an explanatory diagram of light reflection in the state where there is no groove on the surface of the light guide plate, FIG. 7B is an explanatory diagram of light refraction by the groove portion, and FIG. 7C is an explanation diagram of light refraction by the groove portion. It is a figure and it is the figure which looked at the concave cone dot over a groove part.

[0030]

A first embodiment of the present invention will be described with reference to the drawings. The surface light source device of the present invention, as shown in FIGS.
A light guide plate 2 made of a light-transmissive material and having an end on one side thereof serving as a light entrance part 1, and a cylindrical light source such as a cold cathode tube provided in the vicinity of the light entrance part 1 of the light guide plate 2. 3, the light reflector 5 provided on the back surface of the light guide plate 2, that is, a large number of concave conical dots 8, the reflector 6 formed in contact with the light reflector 5 and formed of a white sheet, and the light guide plate 2. The scattering plate 4 is in contact with the surface. In the following description, when the entire conical dot 8 on the back surface of the light guide plate 2 is shown, this is referred to as a light reflector 5.

[0031]

As the material of the light guide plate 2, a translucent material such as glass, acrylic resin or polycarbonate resin is used.
The light reflector 5 provided on the back surface of the light guide plate 2 is shown in FIG.
As shown in (a) and (b), a large number of concave conical dots 8 are provided on the entire surface and are arranged in a plurality of rows at regular intervals. By providing the concave conical dots 8 on the entire surface in this manner, the light incident from the light incident portion 1 of the light guide plate 2 is reflected as shown by the arrows in FIGS. Since light is emitted, the light is uniformly emitted from the entire surface of the scattering plate 4, and a uniform amount of light is emitted from the entire surface.

[0032]

4A and 4B are views for explaining the principle of the present invention. As shown in FIG. 4A, when the light emitted from the light source is cut at 45 ° at the end portion of the light guide plate 2, 100% is reflected in the L width direction. In FIG. 4B, if the reflecting surface at the end 45 ° is divided into n equal parts of k width and the parts are arranged at equal intervals in the range of W width, the width L of the reflected light can be evenly expanded to W. The amount of reflected light at this time is k * n = L.

[0033]

The present invention utilizes this principle, and the 45 ° reflection surface of this total reflection prism is divided into a light reflector of concave conical dots 6. Reflective surface B of concave conical dot 8
The diameter of the concave conical dots 8 is calculated by the number of the concave conical dots 8 arranged on the plane. The amount of reflected light at this time is reflected B
* The number of concave conical dots 8 = L, and the number and diameter of the concave conical dots 8 are determined so as to approximate L, and it is sufficient to arrange them on the entire surface.

[0034]

As shown in FIGS. 5A to 5C, the light hitting the reflecting surface B of the concave conical dot 8 is reflected in the direction H of the arrow, and the light hitting other than the reflecting surface B is inside the light guide plate 2. The concave conical dots 8 and the plane of the light guide plate 2 repeatedly reflect until they hit the reflecting surface B of the concave conical dots 8 and are reflected in the direction H of the arrow. Since it goes to the concave conical dot 8 of FIG. As described above, the light reflection by the concave conical dots 8 has a correlation with the amount of incident light, and the light amount of the light emitting surface can be estimated at the design stage.

[0035]

This concave conical dot 8 was prototyped under the following conditions, and the results were confirmed by experiments.
At 100 ° the light reflection gave the best results.

[0036]

Vertical angle: 80 to 100 ° Bottom diameter: Approx. 450 μm Height: 225 μm Dot pitch: 1.2 mm Light guide plate dimension: 200 mm * 150 mm * 3 mm (width * depth * thickness)

[0037]

Further, by processing the tip end portion of the apex angle of the concave conical dot 8 into a spherical shape, and further by mirror-finishing the entire surface of the concave conical dot 8, the attenuation of light is reduced and the accuracy is higher. Can reflect light.

[0038]

The processing of the concave conical dots 8 is performed by molding, laser processing or the like because it is required that the entire surface has a uniform shape and size. Further, the light guide plate 2 and the light guide plate 2 can be integrally molded at the same time.

[0039]

As described above, according to the first embodiment, since the light incident from one side surface of the light guide plate 2 is reflected by the concave conical dots 8 of the light reflector 5 on the back surface of the light guide plate 2, By performing light reflection with little attenuation of light quantity, it is possible to make the luminous intensity uniform over the entire irradiation surface. In addition, the amount of light emitted from the light emitting surface can be calculated at the design stage, which saves experiment time and equipment. Further, in this embodiment, the concave conical dots are used for explanation, but the convex conical dots have similar effects with respect to light reflection and can be applied.

[0040]

Next, a second embodiment of the present invention will be described. This is because the groove 9 is formed on the surface of the light guide plate 2 as shown in FIGS.
It is formed like. As described in the first embodiment, the effect of this groove is that the light incident from one side surface of the light guide plate 2 is reflected by the concave conical dots 8 of the light reflector on the back surface of the light guide plate 2, and the light of the scattering plate 4 is changed. Light is uniformly emitted from all surfaces, but by forming the grooves 9 on the surface of the light guide plate 2,
The light reflected by the concave conical dots 8 on the back surface can be split, the light is more diffused, and the entire illuminated surface can be illuminated more uniformly. Further, by forming the groove 9 on the surface of the light guide plate 2 at the same time, it is possible to further change the angle and reflect the light reflected by the concave conical dots 8 other than the reflecting surface B, so that the reflected light is further reflected. Has the effect of collecting light.

[0041]

As shown in FIG. 7A, the optical path without the groove 9 is such that the incident light is reflected by the conical dot 8 and hits the surface to be refracted, but the light is only diffused in the opposite direction, and the diffusion of the light is small. When the light is refracted in the groove 9 as shown in FIG. 7B, the optical path of the reflecting portion is changed by the portion that contacts the surface, and the light is more focused on the reflecting surface B. FIG. 7C shows the conical dot 8 over the groove 9 on the surface.
In the figure of the reflection surface B when seeing, the reflection surface B can be divided into right and left by the prism effect, and the light is more diffused,
Flat emission becomes more possible. The groove shape was checked under the following conditions, and the best result was obtained.

[0042]

Radius: 800 to 1000 μm Groove width: 500 to 700 μm Depth: 5 to 10 μm Groove pitch: 1000 to 1200 μm

[0043]

Further, since the groove is required to be formed in a uniform shape on the entire surface of the light guide plate as in the case of the conical dot 8, molding or laser processing is used. In addition, the conical dot 8 is integrally molded at the same time,
It is also possible to mold the entire light guide plate 2 and, at times, integrally mold it with the conical dots 8.

[0044]

[0028]

[0045]

As described above, according to the present invention, the light incident from one side surface of the light guide plate is reflected by the conical dots on the back surface of the light guide plate, and is provided in the groove on the surface of the light guide plate. Since the light diffuser efficiently reflects and diffuses the light, the light can be reflected and diffused with less attenuation of the light intensity with higher accuracy, and the intensity of the light on the irradiation surface can be made uniform. It has a noticeable effect on light lighting. In addition, it is a feature that the trial calculation of the light quantity of the light emitting surface is possible at the design stage, and the experiment time and equipment can be saved.

[Brief description of drawings]

FIG. 1 is a perspective view of a planar light source device according to a first embodiment.

FIG. 2 is a side view of the planar light source device of FIG.

3 (a) is a perspective view showing an example of a pattern of a light reflector on the back surface of the light guide plate of FIG. 1, and FIG. 3 (b) is a sectional shape view of a concave conical dot of a light diffuser. Is.

FIG. 4 (a) is a side view for explaining the principle of light reflection by the light guide plate, and FIG. 4 (b) is a diagram for explaining the same principle. Light when the end of the light guide plate is divided. It is a side view explaining reflection.

5 (a) is a plan view showing light reflection on a concave conical dot, FIG. 4 (b) is a side view showing light reflection on a concave conical dot, and FIG. 4 (c) is a concave cone dot. The perspective view which shows the light reflection of.

FIG. 6 (a) is a perspective view when a groove is formed on the surface of the light guide plate of the second embodiment, and FIG. 6 (b) is a sectional view showing the concave conical dot and groove of the light guide plate. is there.

7A is an explanatory view of light reflection at a groove on the surface of the light guide plate of the second embodiment, FIG. 7B is an explanatory view of light refraction at the groove portion, and FIG. It is an explanatory view of refraction of light by a groove, and is a figure which saw a concave conical dot over a groove part.

FIG. 8 is a sectional view of an example of a conventional planar light source device.

9 is a plan view of a pattern of a light reflector on the back surface of the light guide plate of FIG.

[Explanation of symbols]

 1: Light incident part 2: Light guide plate 3: Light source (cathode tube etc.) 4: Scattering plate 5: Light reflector 6: Reflector plate 7: Printing dot 8: Concave conical dot 9: Groove on the surface of the light guide plate

Claims (10)

[Claims] 1. A planar light source device in which at least one side end of a light guide plate made of a translucent material is used as a light incident part, and a light reflector capable of reflecting light is provided on one surface of the light guide plate, A planar light source device, wherein the light reflector is composed of conical dots. 2. The planar light source device according to claim 1, wherein the conical dots of the light reflector have an apex angle of 80 to 100 °. 3. The planar light source device according to claim 1, wherein the tip of the apex angle of the conical dot of the light reflector is processed into a spherical shape. 4. The planar light source device according to claim 1, wherein the conical dots of the light reflector are formed in a convex shape. 5. The planar light source device according to claim 1, wherein the conical dots of the light reflector are formed in a concave shape. 6. The planar light source device according to claim 1, wherein the conical dots of the light reflector are formed on a mirror surface. 7. The planar light source device according to claim 1, wherein the conical dots of the light reflector are formed by molding. 8. The planar light source device according to claim 1, wherein the conical dots of the light reflector are integrally molded with the light guide plate. 9. The planar light source device according to claim 1, wherein the conical dots of the light reflector are laser-processed. 10. The planar light source device according to claim 1, wherein a groove is formed on a side surface of the light guide plate opposite to a surface on which the conical dots are formed.