JPH04268506A - Panel light emitting device - Google Patents

Abstract

PURPOSE:To obtain uniform panel light emission. CONSTITUTION:A cold cathode ray tube is disposed as a line light source 2 on one side face of a transparent light transmission plate 1 made of an acrylic resin and an aluminum sheet printed white is disposed as a side face reflection plate on the other side face. Dotty light diffusive transmission parts 3 are printed and formed on the rear surface of the light transmission plate in such a manner that the area rate thereof is gradually larger the furtherer from the line light source 2 up to the prescribed point between the line light source 2 and the side face reflection plate 4 and the area rate is gradually smaller the nearer the side face reflection plate from the prescribed point. The light diffusive transmission parts 3 are so printed and formed near the line light source 2 that the area rate of the light diffusive transmission parts 3 is gradually larger the nearer the end of the line light source 2 from the central part of the line light source 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called edge-light type surface emitting device which can be used as a display for thin electric lighting, thin and lightweight laptop computers, word processors, backlights for liquid crystal TVs, and the like.

0002

2. Description of the Related Art Conventionally, various types of surface emitting devices of this type have been known. For example, in some cases, the light diffusing and transmitting part has a maximum area ratio at the lowest brightness position between the linear light source and the side reflector, and then decreases in area ratio randomly from that position in both directions. . (Unexamined Japanese Patent Publication No. 2-26938
No. 2).

0003

However, a linear light source has the characteristic that it is brightest at the center and dark at both ends. Therefore, near the line light source, there was uneven brightness in the direction parallel to the tube axis of the line light source. Therefore, an object of the present invention is to provide a surface emitting device that can emit light uniformly in order to solve the above problems.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a luminance distribution not only in the direction perpendicular to the tube axis of the line light source but also in the direction parallel to the tube axis of the line light source in the vicinity of the line light source. The light guide plate was configured to uniformly emit light by considering the directional brightness distribution and changing the area ratio of the light diffusing and transmitting portion two-dimensionally near the linear light source.

That is, the surface emitting device of the present invention is a surface emitting device in which a linear light source is arranged on the side surface of a transparent light guide plate having a light diffusing and transmitting portion formed on the back surface, and the light guide plate is illuminated with light from the linear light source. , the area ratio of the light diffusing and transmitting part gradually increases as it moves away from the linear light source, and the area ratio of the light diffusing and transmitting part in the vicinity of the linear light source gradually increases as it approaches the end of the linear light source from the center of the linear light source. did.

Further, in the surface emitting device of the present invention, a linear light source is disposed on one side of a transparent light guide plate having a light diffusing and transmitting portion formed on the back surface, and a side reflection plate is disposed on the other side. In a surface light emitting device that illuminates a light guide plate with light, the area ratio of the light diffusing and transmitting portion gradually increases as the distance from the line light source increases until a predetermined point between the line light source and the side reflection plate is reached, and from the predetermined point, the side reflection The area ratio of the light diffusing and transmitting part is configured to gradually decrease as it approaches the plate, and in the vicinity of the line light source, the area ratio of the light diffusing and transmitting part gradually increases as it approaches the end of the line light source from the center of the line light source.

[0007] Furthermore, the surface emitting device of the present invention has a transparent light guide plate on which a light diffusing and transmitting portion is formed on the back surface, and line light sources are disposed on opposite sides of the plate, and the light guide plate is irradiated with light from the line light sources. In the light emitting device, the area ratio of the light diffusing and transmitting part gradually increases as the distance from the linear light source increases, and in the vicinity of the linear light source, the area ratio of the light diffusing and transmitting part gradually increases as the distance from the center of the linear light source approaches the end of the linear light source. It was configured as follows.

[0008] In each of the above configurations, it is also possible to arrange a light scattering/reflecting plate on the back surface of the light guide plate.

[0009] In each of the above configurations, a light diffusing layer may be disposed on the surface of the light guide plate.

Furthermore, in each of the above configurations, the light diffusing and transmitting portions can be configured in the form of dots or stripes.

[0011]

[Operation] According to the above configuration, the area ratio of the light diffusing and transmitting portion gradually increases as the distance from the line light source increases, so that in the vicinity of the line light source, the light is emitted in a direction perpendicular to the tube axis of the line light source. The majority of the light is guided to the center of the light guide plate through repeating total reflection with equal angle of incidence and reflection inside the transparent light guide plate, while the remaining light is diffused and transmitted through a small area. is scattered and guided to the surface side of the light guide plate. In addition, in the part far from the linear light source, that is, the part where the light intensity is the weakest, most of the light is scattered by the large-area light diffusing and transmitting part and guided to the surface side of the light guide plate, while the remaining light is
Inside the transparent light guide plate, the incident angle and reflection angle are equal, and the light undergoes repeated total reflection and is guided to the vicinity of the side of the light guide plate.

[0012] Also,
In the vicinity of the line light source, the area ratio of the light diffusing and transmitting portion gradually increases as it approaches the end of the line light source from the center of the line light source. Most of the light irradiated in the direction undergoes repeated total reflection inside the transparent light guide plate, where the angle of incidence and reflection angle are equal, and is guided to the vicinity of the end of the linear light source, while the remaining light is small in terms of area. The light is scattered by the light diffusing and transmitting portion and guided to the surface side of the light guide plate. In addition, near the end of the linear light source, most of the light is scattered by the large-area light diffusing and transmitting part and guided to the surface side of the light guide plate, while the remaining light is reflected inside the transparent light guide plate depending on the incident angle. The light is guided to the vicinity of the side of the light guide plate by repeating total reflection at the same angle.

[0013]

Embodiments Next, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 4. 1 and 2 show a surface emitting device with one light source. A line light source 2 is arranged on one of a pair of opposing side surfaces of the transparent light guide plate 1, and a side reflection plate 4 is arranged on the other side. In a surface emitting device with such a configuration, the front side of the light guide plate 1 is irradiated with the light from the line light source 2 and the light reflected by the side reflector 4, so the line light source 2 and the side reflector 4 are The area ratio of the light diffusing and transmitting part 3 gradually increases as the distance from the linear light source 2 increases until a predetermined point between the two, and the area ratio of the light diffusing and transmitting part 3 gradually decreases as the distance from the predetermined point approaches the side reflector 4. A light diffusing and transmitting section 3 is formed on the back surface of the light guide plate 1. In addition, since the linear light source 2 has the characteristic that the center part is brightest and both ends are dark, the area ratio of the light diffusing and transmitting part 3 gradually increases near the linear light source 2 as it approaches the end part of the linear light source 2 from the center part of the linear light source 2. The light diffusing and transmitting portion 3 is formed so as to be as follows. Further, a light diffusion layer 5 was arranged on the surface of the light guide plate 1.

FIGS. 3 and 4 show a surface emitting device with two light sources. Line light sources 2 are arranged on both opposing sides of the transparent light guide plate 1 . In a surface emitting device having such a configuration, the front side of the light guide plate 1 is irradiated with light from the linear light source 2, so that the area ratio of the light diffusing and transmitting portion 3 gradually increases as the distance from the linear light source 2 increases. A light diffusing and transmitting section 3 is formed on the back surface of the light guide plate 1. In addition, since the linear light source 2 has the characteristic that the center part is brightest and both ends are dark, the area ratio of the light diffusing and transmitting part 3 gradually increases near the linear light source 2 as it approaches the end part of the linear light source 2 from the center part of the linear light source 2. The light diffusing and transmitting portion 3 is formed so as to be as follows. Further, a light diffusion layer 5 was arranged on the surface of the light guide plate 1.

The material of the light guide plate 1 is preferably a rectangular plate made of transparent plastic and having a thickness of about 2 to 30 mm.
For example, a transparent acrylic plate with a length of 240 mm, a width of 170 mm, and a thickness of 6 mm is used. The side surface of the light guide plate 1 is preferably polished to a smooth surface, and a line light source is disposed on the side surface of the light guide plate 1. Preferred materials for the light guide plate 1 include acrylic resin, glass, polycarbonate, and polyvinyl chloride.

As the linear light source 2, a fluorescent lamp, a cold cathode ray tube, or the like is arranged. As an example, if the light guide plate 1 is a transparent acrylic plate with the above dimensions, the linear light source 2 has a tube length of 240 m.
It is preferable to use a cold cathode ray tube with a diameter of 6 mm and to provide this cold cathode ray tube on the side surface of the light guide plate 1. Further, it is possible to arrange a curved reflective plate 7 to cover the linear light source 2, and reflect the light from the linear light source 2 toward the light guide plate 1 using the mirror surface on its inner surface, so that the light can be used effectively. preferable.

On the other hand, the light diffusing and transmitting portion 3 is formed on the back surface of the light guide plate 1 by screen printing using matte ink in dot-like gradation. This light diffusing and transmitting section 3 is
For example, they may be circular dots, and the area may be changed by changing the diameter, or the number may be changed depending on the position. Further, the light diffusing and transmitting portion 3 is formed using a printing method such as gravure printing, offset printing, or screen printing, or a transfer method using ink containing a pigment having light diffusing properties such as calcium carbonate or silica. The light that reaches this light diffusing and transmitting section 3 from the linear light source 2 is diffused here and goes in many directions, such as toward the front side of the light guide plate 1 and further away from the linear light source 2 on the light guide plate 1. The light diffusing and transmitting portion 3 is not limited to a circular shape, and may be formed in an arbitrary shape in the form of a dot. Alternatively, they may be formed in stripes. In addition,
In the case of a single-lamp type, the above-mentioned predetermined location in the light diffusing and transmitting section 3 refers to the luminance distribution with respect to the distance from the light source of a known surface emitting device in which a light source and a reflecting plate are respectively disposed on opposite sides of a light guide plate. This is the position where the measured brightness is at its minimum. When forming the light diffusing and transmitting portion 3, it is formed so that the area ratio (density) becomes maximum at the predetermined location. At this time, in order to suppress unevenness in brightness as much as possible, the area ratio of the light diffusing and transmitting portion 3 is made to change continuously and smoothly.

Further, it is preferable that the light diffusing layer 5 coated with a light diffusing substance be disposed over the entire surface of the light guide plate 1 so as not to come into close contact with it. By not bringing the light diffusion layer 5 into close contact with the light guide plate 1, total reflection is ensured inside the light guide plate 1, and light can be sufficiently reflected inside the light guide plate 1 with little loss. A specific example of the light diffusion layer 5 is light diffusion film D204 manufactured by Kimoto Co., Ltd. Further, as the light diffusion layer 5, in addition to the structure described above, a film having a diffusive property itself or a material having a similar effect such as a milky white resin plate may be arranged.

Further, as the side reflection plate 4, the following is preferable. (1) White PET film such as Tetron Film U2 manufactured by Teijin, W900J manufactured by Diafoil, or E60 manufactured by Toray Industries. This thickness is preferably 188 to 250 μm. (2) White painted or white printed aluminum plate. The thickness is preferably 100 to 500 μm. (3) Metal plates with mirror surfaces, metal foils such as aluminum, or films and plates with metal vapor deposition.

On the other hand, when the side reflection plate 4 is disposed as a reflection layer in direct contact with the side surface of the light guide plate 1, the following method is available. That is, it is preferable to directly coat or print white on the side surface of the light guide plate 1, or to perform vapor deposition directly on the side surface of the light guide plate 1.

[0021] Furthermore, if necessary, a light scattering reflector plate 6 may be installed.
It may be arranged on the back surface of the light guide plate 1. That is, when a reflective layer is arranged as a separate body from the light guide plate 1, the reflective layer described in (1) to (3) above is preferable as in the case of the side reflector plate 4. Alternatively, the inner surface of the case housing the light guide plate 1 and the linear light source 2 may be painted or printed white to form a reflective layer.

Comparative Experimental Example The results of a comparative experiment between a conventional surface-emitting device with one light source and a surface-emitting device with one light source according to the present invention are shown in FIGS. 5 and 6.
Shown below. In addition, FIG. 5 and FIG. 6 are AA' line shown in FIG.
Each figure shows the luminance distribution on the BB' line. Further, the horizontal axis shows the position on the light guide plate, the vertical axis shows the brightness, the dotted line shows the conventional example, and the solid line shows the comparative experimental example.

As a result of the experiment, as shown in FIGS. 5 and 6, in the surface emitting device of the present invention, the light diffusing and transmitting section 3 is
Since the area ratio of the light diffusing and transmitting portion 3 is formed to gradually increase from the center of the linear light source 2 to the end of the linear light source 2, the brightness is reduced near the end of the linear light source 2 compared to the conventional one. This results in a more uniform surface emission.

[0024] Note that the above configuration is just one implementation, and the present invention is not limited to these embodiments. For example, light guide plate 1
The shape of may be a polygon other than a quadrilateral, such as a triangle or a hexagon. Furthermore, the number of linear light sources 2 may be three or more.

[0025]

Effects of the Invention The surface light emitting device of the present invention is a surface light emitting device in which a line light source is arranged on the side surface of a transparent light guide plate having a light diffusing and transmitting portion formed on the back surface, and the light guide plate is illuminated with light from the line light source. , the area ratio of the light diffusing and transmitting part gradually increases as it moves away from the linear light source, and the area ratio of the light diffusing and transmitting part in the vicinity of the linear light source gradually increases as it approaches the end of the linear light source from the center of the linear light source. did.

Therefore, in the vicinity of the line light source, by changing the area ratio of the light diffusing and transmitting portion in the direction parallel to the line light source, the amount of light guided to the light guide plate surface side increases as it approaches the end of the line light source. The brightness unevenness caused by the linear light source characteristic of being brightest in the center and dark at both ends has been eliminated. Also,
A linear light source with a tube length shorter than the width of the light guide plate can also be used.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of a surface emitting device of the present invention.

FIG. 2 is a sectional view showing an embodiment of the surface emitting device of the present invention.

FIG. 3 is a plan view showing another embodiment of the surface emitting device of the present invention.

FIG. 4 is a sectional view showing another embodiment of the surface emitting device of the present invention.

FIG. 5 is a graph showing the luminance distribution on the AA' line of a comparative experimental example of the present invention.

FIG. 6 is a graph showing the luminance distribution on the BB' line of a comparative experimental example of the present invention.

[Explanation of symbols]

1 Light guide plate 2 Line light source 3 Light diffusion transmitting part 4 Side reflector 5 Light diffusion layer 6 Light scattering reflector 7 Curved reflector

Claims (6)

[Claims] Claim 1: In a surface emitting device in which a linear light source is arranged on the side surface of a transparent light guide plate with a light diffusing and transmitting portion formed on the back surface, and the light guide plate is illuminated with light from the linear light source, the light decreases as the distance from the linear light source increases. A surface emitting device characterized in that the area ratio of the light diffusing and transmitting part gradually increases, and in the vicinity of the linear light source, the area ratio of the light diffusing and transmitting part gradually increases from the central part of the linear light source to the end of the linear light source. [Claim 2] A linear light source is arranged on one side of a transparent light guide plate with a light diffusing and transmitting part formed on the back side, and a side reflection plate is arranged on the other side, and the light guide plate is irradiated with light from the linear light source. In a surface light emitting device, the area ratio of the light diffusing and transmitting portion gradually increases as the distance from the line light source increases until a predetermined location between the linear light source and the side reflector, and the area ratio of the light diffusing and transmitting portion increases as the distance from the predetermined location approaches the side reflector. A surface light-emitting device characterized in that the area ratio of the light diffusing and transmitting portion gradually decreases, and the area ratio of the light diffusing and transmitting portion gradually decreases near the line light source as it approaches the end of the line light source from the center of the line light source. 3. In a surface emitting device in which a line light source is arranged on both opposing sides of a transparent light guide plate with a light diffusing and transmitting portion formed on the back surface, and the light guide plate is illuminated with light from the line light source, the light guide plate is arranged away from the line light source. A surface light emitting device characterized in that the area ratio of the light diffusing and transmitting part gradually increases as the area approaches the linear light source, and the area ratio of the light diffusing and transmitting part gradually increases from the center of the line light source to the end of the line light source in the vicinity of the line light source. 4. The surface emitting device according to claim 1, further comprising a light scattering and reflecting plate arranged on the back surface of the light guide plate. 5. The surface emitting device according to claim 1, further comprising a light diffusing layer disposed on the surface of the light guide plate. 6. The surface emitting device according to claim 1, wherein the light diffusing and transmitting portion has a dot shape or a stripe shape.