Backlight module with light reflector having plural reflection capability and liquid crystal display using same

An exemplary backlight module (200) includes a light guide plate (210) having a light incident surface (211), and a light source assembly (220) provided adjacent to the light incident surface of the light guide plate. The light source assembly includes a light source (221) and a light reflector (225). The light source includes a first portion and a second portion. A brightness of light emitted from the first portion is less than that of light emitted from the second portion. The light reflector is configured for reflecting light beams emitted from the light source toward the light incident surface of the light guide plate. The light reflector includes a first region (226) corresponding to the first portion of the light source and a second region (227) corresponding to the second portion of the light source. A reflection capability of the first region is greater than that of the second region.

FIELD OF THE INVENTION

The present invention relates backlight modules, and particularly to a backlight module which includes a light reflector having plural regions with different reflection capabilities.

GENERAL BACKGROUND

An LCD has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions. An LCD generally includes a liquid crystal panel, a driving circuit for driving the liquid crystal panel, and a backlight module for illuminating the liquid crystal panel.

Referring toFIG. 4, a typical backlight module100includes a light guide plate110having a light incident surface111, a light source assembly114, and a frame116for accommodating the light guide plate110and the light source assembly114.

The light source assembly114includes a light source117, a pair of fixing blocks119, and a light reflector118. The light source117can be a cold cathode fluorescent lamp (CCFL), and is positioned adjacent to the light incident surface111of the light guide plate110. High and low voltages are applied to the two ends of the CCFL so that the CCFL lights up. The light reflector118has a generally U-shaped cross-section, and thus can accommodate the light source117. The fixing blocks119are configured to fix the light source117to the light reflector118. The light reflector118can reflect light beams toward the light guide plate110, thereby increasing light utilization of the backlight module100.

Generally, the brightness of the two ends of the CCFL is lower than the brightness of a middle portion of the CCFL. Thus the light guide plate110receives non-uniform incident light beams from the light source assembly114, and the brightness of light output by the backlight module100may also be non-uniform. Accordingly, a liquid crystal display using the backlight module100may have impaired display quality.

Alternatively, the light source117can instead be a plurality of light emitting diodes (LEDs). In general, lower powered LEDs are used, in order to limit the amount of heat produced and limit power consumption. Therefore the brightness of this kind of backlight module100may be too low.

What is needed, therefore, is a new backlight module that can overcome the above-described deficiencies. What is also needed is an LCD using such backlight module.

SUMMARY

In one preferred embodiment, a backlight module includes a light guide plate having a light incident surface, and a light source assembly provided adjacent to the light incident surface of the light guide plate. The light source assembly includes a light source and a light reflector. The light source includes a first portion and a second portion. A brightness of light emitted from the first portion is less than a brightness of light emitted from the second portion. The light reflector is configured for reflecting light beams emitted from the light source toward the light incident surface of the light guide plate. The light reflector includes a first region corresponding to the first portion of the light source and a second region corresponding to the second portion of the light source. A reflection capability of the first region is greater than a reflection capability of the second region.

Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIG. 1, a liquid crystal display2according to a first embodiment of the present invention is shown. The liquid crystal display2includes a liquid crystal panel290, and a backlight module200for illuminating the liquid crystal panel290. The backlight module200includes a light guide plate210, a light source assembly, a reflective plate230, an optical film assembly240, and a frame250for accommodating the above components.

The light guide plate210includes a light incident surface211, a top light emitting surface212adjoining the light incident surface211, and a bottom surface213. The optical film assembly240is positioned adjacent the light emitting surface212, and includes a diffusing film241, a lower brightness enhancement film (BEF)242, and an upper brightness enhancement film (BEF)243arranged in that order from bottom to top. The reflective plate230is located adjacent the bottom surface213of the light guide plate210.

The light source assembly220includes a light source221, a pair of fixing blocks223, and a light reflector225. The light source221can be a linear light source, such as a cold cathode fluorescent lamp (CCFL). The light source221includes a middle portion (not labeled) and two end portions (not labeled). The light reflector225has a generally U-shaped cross-section so as to accommodate the light source221. The fixing blocks223are configured to fix the light source221to the light reflector225. The light reflector225can reflect light beams toward the light guide plate210, thereby increasing light utilization of the backlight module200.

Referring also toFIG. 2, the light reflector225defines a first region226and a second region227both at an inner surface (not labeled) thereof. The first region226is located at two ends of the light reflector225, and corresponds to the end portions of the light source211. The second region227is located at the middle of the light reflector225, and corresponds to the middle portion of the light source221. The light reflector225further includes a first reflective material coated on the first region226and a second reflective material coated on the second region227. A reflection index of the first reflective material is greater than a reflective index of the second reflective material. The first reflective material can be ALSET SAS-B230 (which is manufactured by Mitsubishi Plastics Inc.). The second reflective material can be ALSET AL E60V (which is also manufactured by Mitsubishi Plastics Inc.).

In operation, after light beams are emitted from the light source221, part of the light beams reach the first and second regions226,227of the light reflector225and are reflected toward the light incident surface211of the light guide plate210. Because the light reflector225has a higher reflection capability at the first region226corresponding to the end portions of the light source221which have a lower brightness, and has a lower reflection capability at the second region corresponding to the middle portion of the light source221which has a higher brightness, the light guide plate210can receive substantially uniform light beams from the light source assembly220. Thus, the brightness of the backlight module200is substantially uniform, and therefore the display quality of the liquid crystal display2is improved.

Referring toFIG. 3, a light reflector325of a backlight module of a liquid crystal display according to a second embodiment of the present invention is similar to the light reflector225. However, the light reflector325includes a reflective material coated only on a first region326thereof. The reflective material has a reflection index higher than that of the light reflector325itself. The liquid crystal display has advantages similar to those described above in relation to the liquid crystal display2of the first embodiment.

Further or alternative embodiments may include the following. In a first example, the first reflective material can be an enhanced specular reflective material. This material has a reflection index of 98%. In a second example, the first and second reflective material can be sputtered on the light reflector225. In a third example, the light source221can instead include a plurality of light emitting diodes (LEDs). In such case, some of the LEDs may be low powered, in order to limit the amount of heat produced and limit power consumption. The first region226having the first reflective material formed thereon corresponds to the low powered LEDs, and the second region227having the second reflective material formed thereon corresponds to high powered LEDs. In a fourth example, the light reflector325accommodates a light source which includes a plurality of LEDs. In such a case, the first region336having the reflective material formed thereon corresponds to low powered LEDs of the light source.