Backlight module

A backlight module including a housing, a first reflector plate, a light guide plate, a second reflector plate and at least one light bar is provided. The first reflector plate is disposed on a bottom of the housing, and the light guide plate is disposed within the housing. The light guide plate includes a first optical surface, a second optical surface and a light emitting surface, and the first optical surface is adjacent to the first reflector plate. The second reflector plate is adjacent to the second optical surface of the light guide plate. The light bar is disposed between the first reflector plate and the light guide plate, and the light bar is opposite to the second optical surface.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 98203480, filed Mar. 6, 2009. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a backlight module, in particular, to a direct-type backlight module having an edge-type light emitting structure.

2. Description of Related Art

As a liquid crystal display (LCD) panel does not emit lights itself, a backlight module is required to provide a sufficient intensity and evenly distributed light source to display an image. A structure of a conventional backlight module mainly includes two types, namely, an edge-type backlight module and a direct-type backlight module.

In the edge-type backlight module, a light source is placed at certain edges around the light guide plate, and then the lights are guided, so as to provide uniform light emission, which is edge-type light emission. As the space at the edges is somewhat limited, the numbers of cold cathode fluorescent lamps (CCFLs) or light emitting diode (LED) light bars capable of being arranged therein to provide a light source is restricted. Thus, if the edge-type backlight module is used in a large-scale display, a phenomenon of insufficient luminance occurs, which fails to satisfy the demand of a high brightness. In the direct-type backlight module, a light source is disposed below a LCD panel directly, which is upward-type light emission. Although this type of backlight module provides sufficient backlight brightness, the evenness of the light provided thereby is poor. Therefore, a large light source diffusion space is further needed and the structure of the backlight module is rather thick, such that the thin-type design thereof cannot be realized.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a direct-type backlight module having an edge-type light emitting structure, which not only has an advantage of a high luminance of a direct-type backlight module, but also has thin-type and power-saving advantages of an edge-type backlight module.

As embodied and broadly described herein, the present invention provides a backlight module. The backlight module includes a housing, a first reflector plate, a light guide plate, a second reflector plate, and at least one light bar. The first reflector plate is disposed on a bottom of the housing, and the light guide plate is disposed within the housing. The light guide plate has a first optical surface, a second optical surface, and a light emitting surface, and the first optical surface is adjacent to the first reflector plate. The second reflector plate is adjacent to the second optical surface of the light guide plate. The light bar is disposed between the first reflector plate and the light guide plate, and the light bar is opposite to the second optical surface.

The backlight module further includes at least one optical film. The optical film is disposed adjacent to the light emitting surface of the light guide plate. In the backlight module, the optical film includes a diffusion film and a brightness enhancement film.

In the backlight module, the first optical surface includes a pattern.

In the backlight module, the second optical surface includes a plurality of slot structures. A cross section of the slot structures is V-shaped, ellipse-shaped or trapezium-shaped.

In the backlight module, a notch is respectively formed at two sides of the first reflector plate, so as to accommodate the light bar. The light bar is an LED light bar or a CCFL.

To make the above and other objectives, features, and advantages of the present invention more comprehensible, embodiments are illustrated in detail in the following with reference to the accompanying drawings.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a side view of a backlight module according to an embodiment of the present invention. Referring toFIG. 1, a backlight module1mainly includes a housing11, a first reflector plate12, a light guide plate13, a second reflector plate14, at least one light bar15, and at least one optical film16.

The first reflector plate12is disposed on a bottom of the housing11. The light guide plate13is disposed within the housing11. Preferably, the housing11is a backplate. The light guide plate13is moulded through a plastic injection molding process, so that the light guide plate13can be easily manufactured. The light guide plate13mainly serves as a medium for guiding lights. The light guide plate13has a first optical surface131, a second optical surface132, and a light emitting surface133. The first optical surface131of the light guide plate13is adjacent to the first reflector plate12. The second reflector plate14is adjacent to the second optical surface132of the light guide plate13.

One of the differences between the light guide plate13of the present invention and a conventional light guide plate is that a cutting angle is respectively formed at two sides of the light guide plate13, such that an angle of less than 90° is included between the first optical surface131and the second optical surface132.

The light bar15is used to provide a light source required by the whole backlight module1, which may be an LED light bar or a CCFL. If the light bar15is an LED light bar, the number of the LEDs may be determined depending upon the actual requirements. Moreover, the LEDs may be RGB LEDs or white-light LEDs.

FIG. 2is a schematic view of a relative position between a light bar and a first optical surface of a light guide plate according to an embodiment of the present invention. Referring to bothFIGS. 1 and 2, at least one light bar15is disposed between the first reflector plate12and the light guide plate13. Moreover, the light bars15are opposite to the second optical surface132. At positions adjacent to the first optical surface131of the light guide plate13, a notch121is respectively formed at two sides of the first reflector plate12to accommodate the light bars15respectively. The light bars15may be disposed around an upper side of the first optical surface131of the light guide plate13at the same time, as shown inFIG. 2. Alternatively, the light bars15may also be partially disposed around the first optical surface131according to the actual demands.

Referring toFIG. 1, the optical film16is disposed adjacent to the light emitting surface133of the light guide plate13. The optical film16includes a diffusion film and a brightness enhancement film. The first optical surface131of the light guide plate13has a pattern1311. The second optical surface132has a plurality of slot structures1321. A cross section of the slot structures1321may be V-shaped, ellipse-shaped or trapezium-shaped.

Lights emitted from the light bars15are mixed through the slot structures1321of the second optical surface132of the light guide plate13. Particularly, when the light bars15are LED light bars and the adopted LEDs are RGB LEDs, the slot structures1321may achieve an especially desirable light mixing function.

The pattern1311of the first optical surface131of the light guide plate13is used to modulate a density of lights emitted from the light bars15, and enables lights entering the light guide plate13to be effectively utilized, so as to reduce the loss of light energy, and enhance the light utilization efficiency. Therefore, the light guide plate13has preferred light emitting luminance and light emitting evenness.

The first reflector plate12and the second reflector plate14respectively assist the pattern1311on the first optical surface131and the slot structures1321on the second optical surface132to reflect light rays, so as to prevent the light leakage, and provide the light source reusing function.

In view of the above, in the backlight module according to the present invention, by realizing the evenness of a light source on a light emitting surface through reflection and refraction, the backlight module not only has an advantage of a high luminance of a direct-type backlight module, but also has advantages of thin-type and power-saving of an edge-type backlight module. Moreover, the number of adopted CCFLs or LED light bars is reduced in the present invention, thereby achieving the effects of low cost and high luminance.