Back light module

A back light module including a back plate, a light source and a bar lens is disclosed. The bar lens includes a top and a bottom center transparent surfaces, a right and a left top total internal reflection surfaces, a right and a left first emitting surfaces, a right and a left second emitting surfaces, a right and a left bottom total internal reflection surfaces and a right and a left bottom incident surfaces. The center bottom transparent surface is located between the top center transparent surface and the light source. The connecting sequence along the right of bar lens from top center transparent surface is the right top total internal reflection surface, the right first emitting surface, the right second emitting surface, right bottom total internal reflection surface, the right incident surface and the center bottom transparent surface. The connecting sequence on the left is similar to the right.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 96131850, filed on Aug. 28, 2007. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source module. More particularly, the present invention relates to a back light module.

2. Description of Related Art

In the current society, multimedia technology is quite developed mostly benefit from the development of semiconductor device or display apparatus. As for displays, liquid crystal display (LCD) having superior features such as high definition, good space utilization efficiency, low power consumption, and free of radiation has increasingly become mainstream of the market.

LCD panel does not have the light emitting function by itself, so it is necessary to dispose a back light module under a LCD panel, so as to provide a light source to the LCD panel. Besides, Light emitting diode (LED) has advantages of high brightness, low power consumption, long life, slight heat problem etc., so recently LED array has been widely used in the back light module.

In the current backlight modules are mainly classified into two types, namely, direct-type back light module and side-edge back light module.

FIG. 1is a partial schematic cross-sectional view of a conventional back light module with a side-emitting light source. Referring toFIG. 1, a conventional back light module with a side-emitting light source10mainly includes a back plate11, an LED12, and a lens13. The LED12is disposed above the back plate11, and the lens13is disposed above the LED12. The side emitting back light module10is achieved side emitting light mixing by using the LED12together with the lens13disposed above the LED12, wherein the lens13has a proper shape. However, the conventional side emitting back light module10adopting the LED12has the following disadvantages.

1. The lens13is fabricated through plastic injection molding process which needs additional mold. It is requires to define a cavity for fitting the shape of lens13within the mold process, so the process for fabricating the lens13is quite complicated.

2. Horizontal side light emitting efficiency of the conventional side emitting back light module10is lower than the light emitting efficiency of the direct-type or the oblique-type back light module varied from the direct-type.

3. In the process of fabricating the LCD, in order to reduce the directly viewed lamp mura, it is necessary to add a light absorbing sheet placed between the LCD panel and the lens13.

4. The lens13is a kind of plastic lens, so in the fabricating process, the lens13cannot undergo the welding process in a solder pot process.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to provide a back light module having high light source uniformity.

The present invention provides a back light module including a back plate, a light source, and a bar lens. The light source is disposed on the back plate. The bar lens is disposed on the back plate and covers the light source. Particularly, the bar lens has a top center transparent surface, a right top total internal reflection surface, a right first emitting surface, a right second emitting surface, a right bottom total internal reflection surface, a right incident surface, a left top total internal reflection surface, a left first emitting surface, a left second emitting surface, a left bottom total internal reflection surface, a left incident surface, and a center bottom transparent surface. The top center transparent surface is disposed above the light source. The right top total internal reflection surface is connected to the top center transparent surface, and a first angle is formed between the right top total internal reflection surface and the back plate. The right first emitting surface is connected to the right top total internal reflection surface, and a second angle is formed between the right first emitting surface and the back plate. The right second emitting surface is connected to the right first emitting surface, and a third angle is formed between the right second emitting surface and the back plate. The right bottom total internal reflection surface is connected to the right second emitting surface, and a fourth angle is formed between the right bottom total internal reflection surface and the back plate. The right incident surface is connected to the right bottom total internal reflection surface, and a fifth angle is formed between the right incident surface and the back plate. The left top total internal reflection surface is connected to the top center transparent surface, and a sixth angle is formed between the left top total internal reflection surface and the back plate. The left first emitting surface is located on the left of the left top total internal reflection surface and connected to the left top total internal reflection surface, and a seventh angle is formed between the left first emitting surface and the back plate. The left second emitting surface is connected to the left first emitting surface, and an eighth angle is formed between the left second emitting surface and the back plate. The left bottom total internal reflection surface is connected to the left second emitting surface, and a ninth angle is formed between the left bottom total internal reflection surface and the back plate. The left incident surface is connected to the left bottom total internal reflection surface, and a tenth angle is formed between the left incident surface and the back plate. The center bottom transparent surface is connected to the left incident surface and the right incident surface, and located between the top center transparent surface and the light source.

In an embodiment of the present invention, the lens is a bar lens.

In an embodiment of the present invention, the first angle is between about 70 and about 80 degrees.

In an embodiment of the present invention, the second angle is between about 30 and about 40 degrees.

In an embodiment of the present invention, the third angle is between about 40 and about 70 degrees.

In an embodiment of the present invention, the fourth angle is between about 30 and about 40 degrees.

In an embodiment of the present invention, the fifth angle is between about 40 and about 70 degrees.

In an embodiment of the present invention, the sixth angle is between about 70 and about 80 degrees.

In an embodiment of the present invention, the seventh angle is between about 30 and about 40 degrees.

In an embodiment of the present invention, the eighth angle is between about 40 and about 70 degrees.

In an embodiment of the present invention, the ninth angle is between about 30 and about 40 degrees.

In an embodiment of the present invention, the tenth angle is between about 40 and about 70 degrees.

In an embodiment of the present invention, the lens further has a right connecting surface connected to the right incident surface and the right bottom total internal reflection surface.

In an embodiment of the present invention, the lens further has a left connecting surface connected to the left incident surface and the left bottom total internal reflection surface.

In an embodiment of the present invention, the material of the lens includes plastic.

In an embodiment of the present invention, the back light module further includes an optical film, and the bar lens is located under the optical film to support the optical film.

In an embodiment of the present invention, the optical film includes a diffuser sheet or a prism sheet. Based on the above mentioned, the left and the right sides of the bar lens of the present invention have incident surfaces, emitting surfaces, and total internal reflection surfaces, respectively. Therefore, light rays emitted by the light source can successfully exit after being split into left and right sides. In addition, the lens has top and bottom center transparent surfaces, so the light rays emitted upwards by the light source can successfully pass through the lens. In other words, as compared with the conventional art, the lamp mura is not easily generated in the back light module adopting the lens.

In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.

DESCRIPTION OF EMBODIMENTS

First Embodiment

FIG. 2is a schematic cross-sectional view of the back light module according to the first embodiment of the present invention. InFIG. 2, only a part of the back light module is shown for illustration. Referring toFIG. 2, a back light module100of this embodiment includes a back plate110, a light source120, and a lens130. In this embodiment, the lens130is a bar lens. The light source120is disposed on the back plate110. The bar lens130is disposed on the back plate110, and covers the light source120. Particularly, the bar lens130has a top center transparent surface140, a right top total internal reflection surface150, a right first emitting surface152, a right second emitting surface154, a right bottom total internal reflection surface156, a right incident surface158, a left top total internal reflection surface160, a left first emitting surface162, a left second emitting surface164, a left bottom total internal reflection surface166, a left incident surface168, and a center bottom transparent surface142. The top center transparent surface140is disposed above the light source120. The right top total internal reflection surface150is connected to the top center transparent surface140, and a first angle θ1is formed between the right top total internal reflection surface150and the back plate110. The right first emitting surface152is connected to the right top total internal reflection surface150, and a second angle θ2is formed between the right first emitting surface152and the back plate110. The right second emitting surface154is connected to the right first emitting surface152, and a third angle θ3is formed between the right second emitting surface154and the back plate110. The right bottom total internal reflection surface156is connected to the right second emitting surface154, and a fourth angle θ4is formed between the right bottom total internal reflection surface156and the back plate110. The right incident surface158is connected to the right bottom total internal reflection surface156, and a fifth angle θ5is formed between the right incident surface158and the back plate110.

The left top total internal reflection surface160is connected to the top center transparent surface140, and a sixth angle θ6is formed between the left top total internal reflection surface160and the back plate110. The left first emitting surface162is located on the left side of the left top total internal reflection surface160and connected to the left top total internal reflection surface160, and a seventh angle θ7is formed between the left first emitting surface162and the back plate110. The left second emitting surface164is connected to the left first emitting surface162, and an eighth angle θ8is formed between the left second emitting surface164and the back plate110. The left bottom total internal reflection surface166is connected to the left second emitting surface164, and a ninth angle θ9is formed between the left bottom total internal reflection surface166and the back plate110. The left incident surface168is connected to the left bottom total internal reflection surface166, and a tenth angle θ10is formed between the left incident surface168and the back plate110. The center bottom transparent surface142is connected to the left incident surface168and the right incident surface158, and located between the top center transparent surface140and the light source120.

In this embodiment, the first angle θ1is preferably between about 70 and about 80 degrees. The second angle θ2is preferably between about 30 and about 40 degrees. The third angle θ3is preferably between about 40 and about 70 degrees. The fourth angle θ4is preferably between about 30 and about 40 degrees. The fifth angle θ5is preferably between about 40 and about 70 degrees. The sixth angle θ6is preferably between about 70 and about 80 degrees. The seventh angle θ7is preferably between about 30 and about 40 degrees. The eighth angle θ8is preferably between about 40 and about 70 degrees. The ninth angle θ9is preferably between about 30 and about 40 degrees. The tenth angle θ10is preferably between about 40 and about 70 degrees.

It should be illustrated that the bar lens130can change the distribution angle of the light rays emitting from the light source. In this embodiment, the material of the bar lens130is preferably plastic. In other embodiments, the material of the bar lens130can also be glass or another material. Using the glass material to fabricate the bar lens130has the advantage of simple process. It can be known fromFIG. 2that the surfaces of the bar lens130are planes, so the process of fabricating the bar lens130of this embodiment is much easier than the conventional plastic injection molding process, and the fabrication cost can be reduced by grinding and cutting glass.

A plurality of total internal reflection surfaces of the bar lens130is not necessary to perform an additional coating or depositing process on fabrication. Besides, the plurality of total internal reflection surfaces can reflect the light rays to the outside so that the back light module100adopting the bar lens130does not easily generate the lamp mura. In addition, the back light module100of this embodiment can also adopt a plurality of light sources120and a plurality of bar lenses130, so as to split more side lights, such that the display of the LCD becomes more uniform.

Second Embodiment

FIG. 3is a schematic cross-sectional view of the back light module according to the second embodiment of the present invention. Referring toFIG. 3, a back light module200of this embodiment is similar to the back light module100of the first embodiment, and the difference between the back light module200and the back light module100is that the bar lens130in the back light module200further includes a right connecting surface157and a left connecting surface167, wherein the right connecting surface157and the left connecting surface167making the light path of the light source120pass through the bar lens130more successfully. The right connecting surface157is connected to the right incident surface158and the right bottom total internal reflection surface156, and the left connecting surface167is connected to the left incident surface168and the left bottom total internal reflection surface166. Therefore, the bar lens130can further split the light emitted by the light source120to oblique light with a desired angle to the LCD panel. However, in other embodiments, the bar lens130can also separately use the right connecting surface157or the left connecting surface167. The quantity and position of the connecting surface are not limited in the present invention.

Third Embodiment

FIG. 4is a schematic cross-sectional view of the back light module according to the third embodiment of the present invention. Referring toFIG. 4, a back light module300of this embodiment is similar to the back light module100of the first embodiment, and the difference between the back light module300and the back light module100is that the back light module300of this embodiment further includes an optical film170, and the bar lens130is disposed under the optical film170to support the optical film170. Therefore, the bar lens130not only can enhance the light uniformity of the back light module300, but also can support the optical film170. In addition, the optical film170can be a diffuser sheet, a prism sheet, or another optical film.

FIG. 5is a schematic cross-sectional view of another back light module of the present invention. Referring toFIG. 5, a back light module400includes a plurality of light emitting set180and an optical film170, wherein each light emitting set180includes light sources120and a plurality of bar lens130. As shown inFIG. 5, each light emitting set180provides two light emitting paths through the bar lens130, and the light emitting paths form a light pattern190to the optical film170. In other words, the back light module400adopts the oblique-type light sources design, such that the light rays more uniformly exit onto the optical film170, so as to further enhance the light uniformity of the back light module. In addition, the quantity of the bar lens and the light source disposing manner in the back light module are not limited in the present invention.

To sum up, the present invention at least has the following advantages.

1. The surfaces of the bar lens of the present invention are planes, so the fabricating process is relatively simple.

2. The bar lens of the present invention has a plurality of total internal reflection surfaces, so as to change the light path through these total internal reflection surfaces can reduce energy loss.

3. The bar lens of the present invention can decrease the light blending distance. In other words, the lights emitted from the light source can completely blending in a shorter distance. In addition, the oblique-type design can reduce the directly viewed lamp mura, thereby improving the yield of the LCD.

4. When a plurality of bar lenses and a plurality of light sources are used together, Those two split side light emitting from the light source could be interlaced with each other through adjusting the angle of each components in the bar lens, so as to increase the uniformity of the display of the LCD.