Planar display structure with LED light source

A planar display structure with LED light source includes a plane light source constituted by a plurality of LEDs and a light guide plate, wherein the light guide plate has a plurality of recesses that the above LEDs can be put into.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a planar display structure, and more particularly to a planar display structure with LED (light emitting diode) light source.

2. Description of the Prior Art

Presently many display devices need to use plane light sources, such as transmissive-type/reflective-type liquid crystal display (LCD) or scanner so that the development of plane light source art is fast and attentive. The light source mainly used by LCD device is constituted by line light source formed with LED or cold cathode fluorescent lamp (CCFL). The light rays emitted from the light source at a lateral end of wedge light guide plate are guided almost vertically into the panel by the wedge light plate. The above structure is referred to U.S. Pat. No. 6,309,080, surface light source device and liquid crystal display. It has a main disadvantage that the light rays emitted from plane light source are not well distributed, in other words, the illumination of the portion of wedge light guide plate near the light source is higher than the other portion. Besides, the unsteady matter of CCFL that shortens the lift cycle of device is a drawback, too.

A method to solve the above problems is referred to US patent publication number 20020047837, which uses a array constituted by EL (electro-luminescent) components to replace plane light source that guides vertically the light rays into the panel by-light guide plate.

LED is a lighting component with low electricity and high illumination, and it has the steady lighting matter and long life cycle, too. It is very suitable for plane light source with LED as light source. Please refer toFIG. 1, a conventional structure of plane light source with LED light source is shown. The array constituted by LED102on a substrate100is used as plane light source. A light guide plate104is placed above the LED array102so that the light rays emitted from LEDs102can be well distributed. There are sequentially a first diffusor sheet106, a prism sheet108, and a second diffusor sheet110on the light guide plate104for the light rays emitted from the emitting surface of light guide plate104can be further well distributed. The above structure of plane light source is used as a back light source of LCD panel120.

However, the aforementioned structure of plane light source has many drawbacks. First, the light rays emitted into the light-receiving surface of light guide plate104are not distributed. As shown inFIG. 1, the illumination of the section A of light guide plate104is darker than the section over LED102because the illuminating area of each LED is finite. A method that shortens the distance between two LEDs to decrease the area of the section A of light guide plate104can solve this problem. When the distance B inFIG. 1is shortened, in other words, it will need the additional LEDs in the condition of same illuminated area. So this method is helpless to reduce manufacturing cost.

It is another method can solve the above problem to enlarge the thickness of light guide plate. As shown inFIG. 2, the area of the section A of light guide plate105is zero while the thickness of light guide plate is increased to a predetermined value. However, it is disadvantageous for minimizing volume and diminishing weight of electric devices. Besides, the manufacturing cost of light guide plate105is increased, too.

The utilization of light rays is not best in the conventional structure of light source because some of the light rays emitted from LEDs are reflected by light guide plate when the light rays enter into light guide plate. As shown inFIG. 1andFIG. 2, the light rays C emitted from LEDs102will be reflected by the light guide plate104and105so that the utilization of light rays is worse. The above phenomenon still exists when the additional LEDs is used or the thickness of light guide plate is enlarged.

SUMMARY OF THE INVENTION

In the light of the state of the art described above, it is an object of the present invention to provide a light guide plate with a plurality of recesses that the LEDs can be put into which is immune to the problems of the conventional planar light structure described above and which can decrease the whole thickness of planar display structure because the light rays emitted from light guide plate are well distributed while the thickness of light guide plate is not enlarged.

It is also an object of this invention to decrease the numbers of LEDs for the distance between LEDs is not changed.

It is another object of this invention to increase the utilization of light rays of light guide plate.

It is a further object of this invention to decrease the ratio of reflected or fully reflected light rays for a plurality of slanted portions (V-cuts) on the inner surface of recess can guide the light rays emitted from LEDs into light guide plate in the predetermined angle.

In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a planar display structure with LED light source which comprises a plane light source constituted by a plurality of LEDs (light emitting diode); and a light guide plate having a plurality of recesses, wherein each LED can be put into a recess.

Base on the idea described above, wherein the LEDs are on a substrate.

Base on the aforementioned idea, wherein the substrate is selected from the group consisting of PCB (printed circuit board) and FPC (flexible printed circuit board).

Base on the idea described above, wherein the recess can cover the lighting portion of the LED.

Base on the aforementioned idea, wherein the recess can cover the whole LED.

Base on the idea described above, wherein the inner surface of the recess is dealt with a diffusion process.

Base on the aforementioned idea, wherein the diffusion process forms a plurality of slanted portions (V-cuts) on the inner surface of the recess.

Base on the idea described above, wherein the cross-section view of the recess is selected from the group consisting of circle, ellipse, and polygon.

Base on the aforementioned idea, wherein the pattern of array constituted by the LEDs is selected from the group consisting of rectangle-type and interlacing-type.

Base on the idea described above, wherein the light-emitting surface of the light guide plate is dealt with a diffusion process.

Base on the aforementioned idea, wherein the diffusion process forms a plurality of slanted portions (V-cuts) on the light-emitting surface of the light guide plate.

Base on the idea described above, wherein the LEDs and the light guide plate are made with the design of All-in-One.

Base on the aforementioned idea, wherein the LEDs are constituted by the lighting units that have red, green, and blue LEDs.

Base on the idea described above, wherein the LED is a white LED.

There is provided according to a general aspect of the present invention a back light source of LCD display device which comprises a substrate; a plane light source constituted by a plurality of LEDs located on the substrate; a light guide plate on the substrate and the LEDs including a plurality of recesses that the LEDs can be put into, wherein the inner surface of the recess and the light-emitting surface of the light guide plate are dealt with a diffusion process; a first diffusor sheet on the light guide plate; a prism sheet on the first diffusor sheet; and a second diffusor sheet on the prism sheet.

Base on the idea described above, wherein the substrate is selected from the group consisting of PCB (printed circuit board) and FPC (flexible printed circuit board).

Base on the aforementioned idea, wherein the recess can cover the lighting portion of the LED.

Base on the idea described above, wherein the recess can cover the whole LED.

Base on the aforementioned idea, wherein the diffusion process forms a plurality of slanted portions (V-cuts) on the inner surface of the recess and the light-emitting surface of the light guide plate.

Base on the idea described above, wherein the cross-section view of the recess is selected from the group consisting of circle, ellipse, and polygon.

Base on the aforementioned idea, wherein the pattern of array constituted by the LEDs is selected from the group consisting of rectangle-type and interlacing-type.

Base on the idea described above, wherein the LEDs are constituted by the lighting units that have red, green, and blue LEDs.

Base on the aforementioned idea, wherein the LED is a white LED.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Some sample embodiments of the present invention will now be described in greater detail. Nevertheless, it should be recognized that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.

Next, a planar display structure with LED light source is illustrated according to this invention. Please refer toFIG. 3, a plane light source is constituted by a plurality of LEDs12on a substrate10. The substrate10can be printed circuit board (PCB) or flexible printed circuit board (FPC). The LEDs12are welded on the substrate10and electrically connected to power supply by the circuit on the substrate10. A light guide plate14is placed above the substrate10and the LEDs12, and the upper edge surface of light guide plate14is a light-emitting surface142. The lower edge surface of the light guide plate14is a light receiving surface141.

There are a plurality of recesses15on the lower edge surface of light guide plate14. Each recess is used to cover the lighting portion of LED12. This structure can make the light rays emitted from LEDs12to be well distributed so that the thicker light guide plate is not needed while the lighting portion of LED12is fully covered. Besides, additional LEDs are not needed for increasing the illumination because the distance between LEDs remains the original length. It is another advantage that the ratio of reflected or fully reflected light rays by the light guide plate14are substantially decreased while the light rays emitted from LEDs12enter into the light guide plate14, in other words, the utilization of light rays is increased. The thickness of whole planar display structure can be reduced because the lighting portion of LED12is put into the recess15of light guide plate. The above structure with the well-distributed property for light rays can directly use as back light source of LCD panel30.

As shown inFIG. 3, the light guide plate14has side surfaces143at edges of the light receiving surface141and the light emitting surface142. The side surfaces143each has an area significantly smaller than the area of each of the light emitting surface142and the light receiving surface141. There is no LED positioned with light received through the side surfaces143.

There are sequentially a first diffusor sheet16, a prism sheet18, and a second diffusor sheet20on the light guide plate14. This structure can make the light rays emitted from the light-emitting surface of light guide plate104to be further well distributed. It is proper to use the aforementioned structure as back light source of LCD panel30, too.

It is another preferred embodiment according to the present invention as shown inFIG. 4. The depth of recess15located on the light guide plate14-1is deep enough to put the whole LED12into the recess15so the substrate10can be adhered on the light guide plate14-1. Not only this design has the advantages of first embodiment according to the present invention, but also the thickness of whole planar display structure can be further reduced for the purpose of minimizing volume.

FIG. 5is the top view of light guide plate14according to the present invention. The geometrical pattern of recess15on light guide plate14can be circle, ellipse or other shapes to make the LED, which is put into the recess15, has best illuminant effect for light guide plate14only. The LED can be a white LED or one lighting unit that includes red, green, and blue LEDs. Of course, any lighting devices that emit white light can replace the above LED.

Please refer toFIG. 6, a cross section view of recess15according to the present invention is shown. The cross section of recess15can be a portion of circle, ellipse, polygon or other shapes to make the LED, which is put into the recess15, has best illuminant effect for light guide plate14or the light rays, which are emitted from the LED, enter into the light guide plate14in the proper angle for reducing the ratio of reflected or fully reflected light rays. Besides, the inner surface of recess15can be dealt with a diffusion process, which forms convex/concave dots or a plurality of slanted portions (V-cuts) thereon, so the light rays emitted from the LED easily enter into the light guide plate14for decreasing the ratio of reflected or fully reflected light rays. Similarly, the light-emitting edge surface of light guide plate14can be too dealt with a diffusion process, which forms convex/concave dots or a plurality of slanted portions (V-cuts) thereon, for the light rays are easily guided out from the light-emitting surface of light guide plate14.

FIG. 7shows the arranged figure of recesses15or the pattern of array constituted by LEDs in interlacing-type according to the present invention. It is the pattern of interlacing-type with two different lines inFIG. 7. However, the recesses or LEDs in interlacing-type with three or more different lines can be use in the present invention. The above arrangements of recesses15are all rectangle-type, but an irregular pattern of recesses15can be used, too.

Please refer toFIG. 8, the length of long axis (as the dash line in FIG.) of recess15on light guide plate14is between from about 0.1 to about 10 cm and the length of short axis of recess15is between from about 0.1 to about 10 cm. Two depths of recess15can be chosen, one is between from about 0 to about 5 cm, and the other is between from about 0 to about 10 cm.

Besides, the LEDs and the light guide plate in the present invention can be made with the design of All-in-One.

There are many advantages to put LED into the recess on the lower surface of light guide plate. First, the light rays emitted from the light-emitting surface of light guide plate are well distributed because the whole lighting portion of LED is covered, in other words, the thicker light guide plate is not needed. Next, additional LEDs are not used for increasing the illumination because the distance between LEDs remains the original length. Besides, the ratio of reflected or fully reflected light rays by the light guide plate are substantially decreased while the light rays emitted from LEDs enter into the light guide plate so the illumination is increased for the utilization of light rays is high.

When the depth of recess on the light guide plate is deep enough to put the whole LED into the recess so the substrate can be adhered on the light guide plate. The thickness of whole planar display structure can be further reduced to finish the purpose of minimizing volume.

Convex/concave dots or a plurality of slanted portions (V-cuts) on the inner surface of recess can make the light rays emitted from the LED easily enter into the light guide plate14in the proper angle for decreasing the ratio of reflected or fully reflected light rays. This design makes the LED in the recess to have best illumination for light guide plate.