Backlight module and liquid crystal display with the same

[0001] The present invention relates to backlight modules used in liquid crystal displays, and particularly relates to a backlight module having a plurality of light emitting diodes (LEDs) and a plurality of reflective elements disposed between the LEDs and a liquid crystal display using the backlight module.

[0002] Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images but are also very thin. Because liquid crystal molecules in a liquid crystal display do not emit any light themselves, the liquid crystal molecules have to be lit by a light source so as to clearly and sharply display text and images. Therefore, liquid crystal displays usually require a backlight module.

[0003] Referring to FIG. 5, a typical backlight module S includes a reflective film 51, a light guide plate 52, a diffusion film 53 and a brightness enhancement film (BEF) 54 arranged in that order from bottom to top, and a light source 55. The light guide plate 52 includes a light incident surface 521, a light emitting surface 522 perpendicularly adjoining the light incident surface 521 and a bottom surface 523 opposite to the light emitting surface 522. The light source 55 is disposed adjacent to the light incident surface 521 of the light guide plate 52. The reflective film 51 is disposed below the bottom surface 523 of the light guide plate 52. The light source 55 includes a supporting plate 550 and a plurality of LEDs 551 disposed on the supporting plate 550.

[0004] In operation, light beams from the LEDs 551 enter the light guide plate 52 through the light incident surface 521, and penetrate in the light guide plate 52. A majority of the light beams emit out from the light emitting surface 522. A minority of the light beams emit out from the bottom surface 523 and reach the reflective film 51. These light beams are reflected by the reflective film 51 and are utilized again. These light beams enter the light guide plate 52 again through the bottom surface 523, and emit out from the light emitting surface 522. Then, light beams transmit through the diffusion film 53 and the BEF 54 and become uniform.

[0005] However, each of the LEDs 551 has a certain limited angle of divergence of light beams emitted therefrom. Therefore areas adjacent to the light incident surface 521 of the light guide plate 52 beyond the angles of divergence of the LEDs 551 may be relatively dark. That is, light beams emitted from the backlight module 5 may be non-uniform, and the performance of an associated LCD may be impaired.

[0006] What is needed, therefore, is a backlight module that can overcome the above-described deficiencies. What is also need is a liquid crystal display having such backlight module.

[0007] In one preferred embodiment, a backlight module includes a light guide plate, a first light source and a second light source. The first light source includes a plurality of first light emitting diodes and a plurality of first reflective members. The second light source includes a plurality of second light emitting diodes and a plurality of second reflective members. The light guide plate includes a first light incident surface and a second light incident surface opposite to the first light incident surface. The first light source and the second light source are provided adjacent to the first light incident surface and the second light incident surface, respectively. The first light emitting diodes face the second reflective members, and the second light emitting diodes face the first reflective members.

[0008] Other novel features, advantages and aspects will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

[0014] Reference will now be made to the drawings to describe the preferred embodiments in detail.

[0015] Referring to FIG. 1, a liquid crystal display 1 according to a preferred embodiment of the present invention is shown. The liquid crystal display 1 includes a liquid crystal panel 11, a backlight module 12 adjacent to the liquid crystal panel 11 and a plastic frame 13. The plastic frame 13 defines a space to accommodate the liquid crystal panel 11 and the backlight module 12.

[0016] The backlight module 12 includes a reflective film 121, a light guide plate 122, a diffusion film 123 and a brightness enhancement film (BEF) 124 arranged in that order from bottom to top, a first light source 125 and a second light source 126. The light guide plate 122 includes a first light incident surface 1220, a second light incident surface 1221 opposite to the first light incident surface 1220, a light emitting surface 1222 perpendicularly adjoining the first light incident surface 1220 and the second light incident surface 1221, and a bottom surface 1223 opposite to the light emitting surfaces 1222. The first light source 125 is disposed adjacent to the first light incident surface 1220. The second light source 126 is disposed adjacent to the second light incident surface 1221.

[0017] Referring also to FIG. 2, the first light source 125 includes a first supporting plate 1251, a plurality of first light emitting diodes (LEDs) 1252 and a plurality of first reflective elements 1253. The first supporting plate 1251 is substantially U-shaped. The first LEDs 1252 and the first reflective elements 1253 are arranged alternately on the first supporting plate 1251. The first reflective elements 1253 have convex-shaped surfaces facing the first light incident surfaces 1220.

[0018] Referring also to FIG. 3, the second light source 126 includes a second supporting plate 1261, a plurality of second LEDs 1262 and a plurality of second reflective elements 1263. The second supporting plate 1261 is substantially U-shaped. The second LEDs 1262 and the second reflective elements 1263 are alternately arranged on the supporting plate 1261. The second reflective elements 1263 have convex-shaped surfaces facing the second light incident surface 1221.

[0019] The first reflective elements 1253 and the second reflective elements 1263 are both made of materials with a high reflective ratio. The first reflective elements 1253 and the first supporting plate 1251 can be integrally made as one piece. The second reflective elements 1263 and the second supporting plate 1262 can be integrally made as one piece.

[0020] Referring to FIG. 4, the first light source 125 and the second light source 126 are disposed adjacent to the first light incident surface 1220 and the second light incident surface 1221, respectively. The first reflective elements 1253 of the first light source 125 face the second LEDs 1262 of the second light source 126, respectively. The second reflective elements 1263 of the second light source 126 face the first LEDs 1252 of the first light source 125, respectively.

[0021] In operation, light beams emitted from the first LEDs 1252 enter the light guide plate 122 through the first light incident surface 1220, and penetrate in the light guide plate 122. A majority of the light beams emit out from the light emitting surface 1222. A minority of the light beams emit out from the bottom surface 1223. These light beams are reflected by the reflective film 121 and are utilized again. Another minority of light beams emit out from the second light incident surface 1221, and reach the second reflective elements 1263 of the second light source 126. These light beams are reflected by the second reflective elements 1263 with a certain angle of divergence. These light beams enhance the brightness in the areas between every two adjacent second LEDs 1262.

[0022] Similarly, light beams emitted by the second LEDs 1262 enter the light guide plate 122 through the second light incident surface 1221, and are converted by the light guide plate 122. A majority of the light beams emit out from the light emitting surface 1222. A minority of the light beams emit out from the bottom surface 1223. These light beams are reflected by the reflective film 121 and are utilized again. Another minority of the light beams emit out from the first light incident surface 1220, and reach the first reflective elements 1253 of the second light source 125. These light beams are reflected by the first reflective elements 1253 with a certain angle of divergence. These light beams enhance the brightness in the areas between every adjacent two first LEDs 1252.

[0023] The light beams reflected by the first reflective elements 1253 and the second reflective elements 1263 thus penetrate in the light guide plate 122, and emit out from the light emitting surface 1222. Then the light beams transmit through the diffusion film 123 and the BEF 124 and become uniform.

[0024] Unlike conventional liquid crystal displays, the liquid crystal display 1 includes a first light source 125 and a second light source 126 provided adjacent to the two opposite first light incident surface 1220 and second light incident surface 1221 of the light guide plate 122. The first light source 125 includes the first reflective elements 1253 sandwiched between the first LEDs 1252. The second light source 126 includes the second reflective elements 1263 sandwiched between the second LEDs 1262. The first LEDs 1252 face the second reflective elements 1263, and the second LEDs 1262 face the first reflective elements 1253. Light beams reflected by first reflective elements 1253 and the second reflective elements 1263 enhance the brightness and the uniformity in areas between every two first LEDs 1252 or every two second LEDs 1262. Thus, despite of a certain limited angle of divergence of light beams emitted by the first LEDs 1252 and the second LEDs 1262, the light beams emitted from the light guide plate 122 are uniform. Therefore, a brightness and a uniformity of the backlight module 12 are improved, and a display quality of the liquid crystal display 1 is improved.

[0025] Further or alternative embodiments may include the following. In a first example, the first reflective elements and the second reflective elements can have wave-shaped surfaces facing a light guide plate. In a second example, the first reflective elements and the second reflective elements can have V-shaped surfaces facing a light guide plate. In still a third example, a first supporting plate and a second supporting plate each includes a plurality of protrusions extending toward a light guide plate. In such case, a plurality of reflective films are attached to the protrusions to function as reflective elements.

[0026] It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.