Backlight module

A backlight module, suitable for supplying a plane light source. The backlight module has a light guide plate, a reflection mask and a light compensator. The light source is disposed next to a side surface of the light guide plate, such that the light generated thereby is incident on the side surface of the light guide plate, transmitted through the bottom surface, and projecting from the top surface of the light guide plate. The reflection mask is disposed next to the sidewall of the light guide plate to cover the light source. The light compensator is disposed in the reflection mask. By disposing the light compensator with multiple reflection planes in the reflection mask or forming multiple reflection surfaces of the reflection mask, the brightness at the two comers of the light guide plate near the two sides of the light source can be compensated.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 92200124, filed on Jan. 6, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to a backlight module, and more particularly, to a backlight module that effectively compensates brightness at two corners of a light guide plate near two sides of a light source.

2. Related Art of the Invention

The advancement of multi-media has benefited from the forward looking progress of semiconductor technique or human-machine interface display. For the .display, cathode ray tube (CRT) has dominated the markets for years due to its outstanding display quality and economics. However, the environment of operating desktop terminal/monitors and the trend of power saving with environment protection in mind have manifested the problems of cathode ray tube in terms of space utilization and power consumption. Therefore, the liquid crystal display (LCD) having the characteristics of being light, thin, short, small, and low power consuming has become main stream in the market. However, as the liquid crystal molecules are not luminescent materials, a backlight is required to provide the light source of the liquid crystal panel, so as to achieve the display effect with sufficient brightness and contrast.

FIG. 1shows a top view of a conventional backlight module, andFIG. 2shows a side view of the backlight module as shown inFIG. 1. Referring toFIGS. 1 and 2, the backlight module100includes a light guide plate110, a light source120, a reflection mask130and a frame140. The light guide plate110includes a wedge light guide plate with a top surface112, a bottom surface114and a side surface116. The top surface112is designed as the projecting plane, the bottom surface114is used as the reflecting plane, while the side surface116is designed as the incident plane. The light source120such as a cold cathode fluorescent lamp (CCFL) is disposed next to the side surface116with two ends fixed on a lamp source holder150. The light beam provided by the light source120is incident onto the side surface116of the light guide plate116. Through the bottom surface114, the light beam is transmitted to the top surface112of the light guide plate110and projects therefrom. Therefore, the light projecting from the top surface112is a plane light source. The reflection mask130is disposed next to the side surface116of the light guide plate110to cover the light source120. The light beam provided by the light source120is thereby concentrated and incident on the side surface116of the light guide plate110. The frame140is used to carry the light guide plate110, the light source120and the reflection mask140, such that the light guide plate110, the light source120and the reflection mask130can be integrated into a single device.

As the cold cathode fluorescent lamp (CCFL) is currently typically used as the light source120, the brightness of the high- and low-voltage regions at the two ends of the cold cathode fluorescent lamp is normally smaller than that of the middle thereof. Therefore, the brightness at the two comers of the light guide plate110near the two sides of the lamp120(regions A and B as illustrated inFIGS. 1) is insufficient. To overcome the problem, prior art increases the length of the lamp, such that the regions with insufficient brightness extend externally to the light guide plate. The brightness at the two comers of the light guide plate is thereby increased. However, the width of the liquid crystal display is consequently increased resulting in an enlarged size. This contradicts the trends for being light, thin, short and small.

SUMMARY OF THE INVENTION

The present invention provides a backlight module in which a light compensator is disposed in the reflection mask or multiple reflection planes are formed on the reflection mask. Thereby, the brightness at the two corners of the light guide plate near the two ends of the light source is compensated, while the requirement of minimizing the volume of the liquid crystal display is fulfilled.

The backlight module provided by the present invention is suitable for use as a plane light source. The backlight module comprises a light guide plate, a light source, a reflection mask and a light compensator. The light guide plate has a top surface, a bottom surface and at least one side surface. The light source is disposed next to the side surface of the light guide plate such that the light generated by the light source is incident on the side surface, transmitted from the bottom surface to the top surface, and projecting from the top surface. The reflection mask is disposed next to the side surface of the light guide plate to cover the light source. The light compensator is disposed in the reflection mask. The light compensator has multiple reflection planes facing the two ends of the light source, such that the brightness at the two corners near the two ends of the light source is compensated.

The present invention further provides a backlight module suitable for use as a plane light source. The backlight module comprises a light guide plate, a light source, and a reflection mask. The light guide plate has a top surface, a bottom surface and at least one side surface. The light source is disposed next to the side surface of the light guide plate such that the light generated by the light source is incident on the side surface, transmitted from the bottom surface to the top surface, projecting from the top surface. The reflection mask is disposed next to the side surface of the light guide plate to cover the light source. The reflection mask has multiple reflection planes facing the two ends of the light source, such that the brightness at the two corners near the two ends of the light source is compensated.

In one embodiment of the present invention, the light guide plate includes a wedge light guide plate. The bottom surface of the light guide plate preferably includes a step surface or a surface with multiple recesses to scatter the light provided by the light source. The light source includes, for example, a cold cathode fluorescent lamp.

The light compensator includes a first guide member and a second guide member. The first and second guide members are disposed in the reflection mask with first and second reflection surfaces, respectively. The first and second reflections faces the two ends of the light source to compensate the brightness at the two corners near the two ends of the light source. The first and second reflection surfaces preferably include step surfaces or multiple recesses.

According to one embodiment of the present invention, the light compensator includes a first reflection plate and a second reflection plate disposed in the reflection mask. The first and second reflection plates face two ends of the light source to compensate the brightness at the two corners near the two ends of the light source. In addition, the first and second reflection plates include step surfaces or multiple recesses thereon.

To enhance the irradiance of the backlight module, a diffusion sheet and a prism sheet are further incorporated. The diffusion sheet is disposed on the top surface of the light guide plate, and the prism sheet is disposed on the diffusion sheet. A framer is used to integrate the light guide plate, the light source, the reflection mask and the light compensator into a single unit.

According to the above, the present invention installs a light compensator in the reflection mask or forms multiple reflection surfaces directly on the reflection mask, such that the brightness at the two corners of the light guide plate near the two ends of the light source is enhanced. The light guide plate can thus provide a uniform plane light source, while the minimized volume of the liquid crystal display is maintained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

First Embodiment

FIG. 3shows a top view of a backlight module provided in the first embodiment, andFIG. 4shows a side view of the backlight module. Referring toFIGS. 3 and 4, the backlight module200comprises a light guide plate210, a light source220, a reflection mask230, a frame240and a light compensator260. The light guide plate210is wedge-shaped preferably. For example, The light guide plate210has a top surface212, a bottom surface214and a side surface216. The top surface212is designed as a projecting plane, the bottom surface214is designed as a reflection plane, and the side surface216is designed as an incident plane. The bottom surface214includes a step surface or multiple recesses thereon, such that the light incident thereon is scattered and/or reflected.

The light source220includes a cold cathode fluorescent lamp, for example. The light source220is disposed next to the side surface216with the two ends fixed on a lamp holder250. The light provided by the light source220is incident into the side surface216of the light guide plate210, transmitted from the bottom surface214to the top surface212, and projecting from the top surface212. Therefore, the light projecting from the top surface212includes a plane light source.

The reflection mask230is disposed next to the side surface216to cover the light source220. The light provided by the light source220is thus concentrated thereby to be incident on the side surface216of the light guide plate210. In addition, to integrate the light guide plate210, the light source220, the reflection mask230and the light compensator260into a single unit, a frame240is used to carry the above devices.

To increase the irradiance of the backlight module200, a diffusion sheet270and a prism sheet280are used. The diffusion sheet270is disposed on the top surface212of the light guide plate210, and the prism sheet280is disposed on the diffusion sheet270.

The present invention installs a light compensator260in the reflection mask230. The light compensator260includes two guide members each having a reflection plane262facing the two ends of the light source220, respectively. The reflection planes262include stepped surface262aor multiple recesses262bthereon to scatter the light provided by the light source220. As the reflection planes262are facing the two ends of the light source220, the light emitted from the middle part of the light source220is reflected or scatter towards two corners (regions C and D) of the light guide plate210near the two ends of the light source220, so that the brightness at the two corners is compensated. Therefore, the plane light source provided from the top surface212of the light guide plate is made uniform. It is appreciated that the number of the guide members262is not limited to two, and the guide members262can be integrated into a single member with a length similar to that of the light source220.

In addition, the light compensator can also be replaced with two reflection plates disposed in the reflection mask and facing the two ends of the light source. The reflection plate includes a step surface or multiple recesses thereon for scattering the incoming light, so as to compensate the brightness at the two corners of the light guide plate near the two ends of the light source.

Second Embodiment

FIG. 5shows the backlight module provided in a second embodiment of the present invention. Referring toFIG. 5, the overall structure of the backlight module300is similar to that provided in the first embodiment. The backlight module300differs from the backlight module200by forming a plurality of reflection planes332directly on the reflection mask330. The reflection planes332face the two ends of the light source320with stepped surfaces or multiple recesses to scatter the incoming light provided by the light source. The brightness at the two comers of the light guide plate310(regions E and F) near the two ends of the light source320is thereby compensated.

According to the above, the present invention has at least the following advantages.

1. The backlight module compensates the brightness at the two comers of the light guide plate near the two ends of the light source, such that the top surface of the light guide plate provides a uniform plane light source.

2. In addition, to enhance the brightness at the two comers of the light guide plate near the two ends of the light source, the backlight module provided by the present invention does not increase the overall volume, such that the thin, light, short and small characteristics of liquid crystal display is retained.

Other embodiments of the invention will appear to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples are considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.