Abstract:
A backlight module includes a light guide, a mixing light guide plate, and a plurality of light sources. The first light guide comprises a first side surface. The mixing light guide plate comprises an incident surface with anomalous surface and an emergent surface with fog surface. The mixing light guide plate is set on the first side surface. A plurality of light sources disposed corresponding to the incident surface, with light emitted there from and entering the mixing light guide plate through the incident surface then exits the mixing light guide plate through the emergent surface, finally, entering the light guide through the first side surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention mainly relates to a backlight module, particularly to a backlight module applied in a liquid crystal display device. 
       BACKGROUND OF THE INVENTION 
       [0002]    In recent years, the products using the liquid crystal display (LCD) has become very popular, such as notebook computers, monitors, mobile phones cameras, LCD TVs, digital cameras and personal digital assistants (PDA), etc. Their applications can be easily found everywhere. Since the LCD cannot luminesce itself, the function of the backlight module is to provide the light source, which can provide sufficient brightness and uniform light distribution on the LCD panel. Therefore, the backlight module is actually inevitable equipment for the LCD products. Furthermore, the backlight module will still be a suitable choice in the other applied field of luminescent requirement even if it is not applied to the LCD products. 
         [0003]    Traditionally, liquid crystal displays use the Cold Cathode Fluorescent Tube (CCFT) as their backlight light source, which emits white light. Since the CCFT with small diameter is very difficult to manufacture, the CCFT is restricted to be applied in liquid crystal display device of small electronic products. Moreover, the CCFT also has some drawbacks of high voltage requirement, large power consumption, electromagnetic interference and other environmental protection issues caused by the use of mercury. 
         [0004]    Therefore, the light Emitting Diode (LED) has been developed as the backlight light source of the LCD. The LED backlight light source module can generally be divided into two types. One type is using a white LED as the backlight light source, but the cost of the white light LED is high, and the other type is using the LED of red, green and blue (RGB) colors as the backlight light source, which mixes the primary colors red, green and blue light emitted by the RGB tri-color LED and then produces the white light. When the RGB tri-color LED is used as the backlight light source, the backlight module of the LCD needs additional optical components or extra space to mix red, green and blue light. 
         [0005]    The LED light source will have a great help for the LCD products because the light-emitting efficiency of LED has been dramatically improved. It is generally believed that the LED at the present stage has already possessed about half of efficiency of the CCFT. Even by year 2010, the LED light-emitting efficiency is expected to keep pace with the CCFT, of course, which is just in terms of brightness on the LED. 
         [0006]    If the high response rate of the LED characteristics is applied, so as to sequentially light up the red, blue and green LED light source with high-speed switching, which is capable to not only replace high-priced color filters in the LCD panel, but also enhance color saturation and brightness of the liquid crystal display products. In view of this, the impact of future developing trends of LED light source for LCD display products will be comprehensive and thorough. In addition to the application in the liquid crystal display products, once the LED light-emitting performance is competitive to (or exceed) CCFT, their application would then be more extensive. For example, LED light is now used in many signal sources, such as traffic signals and the turn signals of cars. If the LED luminous performance makes further progress, the most likely application is to extend to the illumination light source. The LED which has the low power consumption and low-heating characteristics will bring a huge threat to the entire present lighting source. 
         [0007]      FIG. 1  is a cross-section diagram of the conventional LED backlight system. As shown in  FIG. 1 , the backlight system includes plural light sources  10 , a reflector  11 , a mixing light guide plate  12 , a mirror  13  and a main light guide plate  14 . Among them, the light source  10  is configured in a row, and the light source  10  includes RGB tri-color LED. One LED is showed in the cross-section diagram of  FIG. 1 . The red, green and blue lights emitted from the light source  10  reflect to the mixing light guide plate  12  via the reflective mirror  11 . Then, the red, green and blue lights change their direction through the reflective surface of the mixing light guide plate  12 . Thus, the red, green and blue lights can be fully mixed into the white light by changing their direction in the mixing light guide plate  12 . Then, the mixed white light is emitted by the mixing light guide plate  12  and reflected to the main light guide plate  14  via the reflective mirror  13 . The mixed white light is transferred into the surface light source by the main light guide plate  14 , and then, the mixed white light is sent to the optical components of the back-end and finally to the LCD panel. 
         [0008]    However, in the above-mentioned prior art, due to the characteristic of light straight transmission, the light direction won&#39;t be changed until the light come into contact with the reflective surface of the mixing light guide plate  12 . Therefore, if red, green and blue lights need to be fully mixed, the length of the mixing light guide plate  12 , which is the path of the mixing light, must be long enough. 
         [0009]    Based on the above description of the prior art, the LED backlight module needs a good light mixing mechanism to render the LED backlight module providing a uniform color mixing and brightness. However, the light mixing mechanism provided by the conventional LED backlight module as shown in  FIG. 1  still has to be improved. In addition, while providing the LED backlight module with a better light mixing mechanism, it still has to consider the LED is a directional component, so as to avoid lowering the overall luminous efficiency of the LED backlight module while achieving a good light mixing effect. 
         [0010]    Accordingly, it still lacks a LED backlight module having both light-emitting efficiency and mixing light effectiveness to overcome the imperfect shortcoming of light mixing effect in prior art. And the newly developed technology is expected to not only improve the mixing light effect, but also be quickly and easily integrated into the existing manufacturing process of the LED backlight module for facilitating the competitiveness of the industry in cost and other aspects. 
         [0011]    Thus, the R &amp; D personnel engaged in the related fields of the LED backlight modules are devoted to solve the shortcomings that still existed in the prior art, and further improve the quality of the LED backlight module products. 
       SUMMARY OF THE INVENTION 
       [0012]    The main purpose of the present invention is to provide a backlight module with better light mixing effect. Another purpose of the present invention is to provide a backlight module that can be quickly integrated into the existing manufacturing process of the backlight module. 
         [0013]    The backlight module provided by the present invention includes a light guide plate, a mixing light guide plate and a plurality of light sources. The light guide plate has a first side surface. The mixing light guide plate has an incident surface with an anomalous surface and an emitting surface with a foggy surface. The mixing light guide plate is disposed on the first side surface of the light guide plate. A plurality of light sources disposed corresponding to the incident surface. The light emitted from the light source enters the mixing light guide plate through the incident surface, and then exits the mixing light guide plate through the emitting surface, and entering the light guide plate through the first side surface. 
         [0014]    The present invention provides a LED backlight module having both the luminous efficiency and the light mixing effect. The present invention provides a backlight module with a mixing light guide plate, having a good light mixing effect and overcoming the drawback of the inefficient luminescence of the conventional LED backlight module. Furthermore, the new technologies developed by the present invention provide excellent convenience in manufacturing, which can be quickly integrated into the existing producing process of the backlight module. Therefore, the present invention not only meets the industrial consideration on the cost and manufacturing, but also has a great progressiveness, which will facilitate the enhancement of industrial competitiveness. 
         [0015]    The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed descriptions and accompanying drawings, in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows a cross-section diagram of a conventional connecting process between an IC chip and a glass substrate. 
           [0017]      FIG. 2  shows a side cross-section diagram of the first preferred embodiment of the present invention. 
           [0018]      FIG. 3  is a diagram showing a mixing light guide plate of the first preferred embodiment of the present invention. 
           [0019]      FIG. 4  shows a side cross-section diagram of the second preferred embodiment of the present invention. 
           [0020]      FIG. 5  is a top view diagram showing the second preferred embodiment of the present invention. 
           [0021]      FIG. 6  shows another side cross-section diagram of the second preferred embodiment of the present invention. 
           [0022]      FIG. 7  is a top view diagram showing the third preferred embodiment of the present invention. 
           [0023]      FIG. 8  shows another side cross-section diagram of the third preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    The present invention will now be described more specifically with reference to the following embodiments. Besides, the present invention also can be broadly implemented in other embodiments, that is, the scope protected in the present invention will not be limited to the disclosed embodiment, which should be accorded with the broadest interpretation of the appended claims. 
         [0025]    Furthermore, in order to provide a clearer description and easier to understand the present invention, each parts in the Figures are not drawn in accordance with their relative size. Some sizes in comparison with other relevant scales have been exaggerated. In order to keep concise, irrelevant details are not completely drawn. 
         [0026]    In order to more clearly understand the above objectives, features and advantages of the present invention, the following preferred embodiments in accordance with the appended figures of the present invention will be more clearly explained as follows: 
         [0027]    Please refer to  FIGS. 2 and 3 .  FIG. 2  shows a side cross-section diagram of the first preferred embodiment of the present invention.  FIG. 3  is a detailed diagram showing a mixing light guide plate of the first preferred embodiment of the present invention. The backlight module  20  has a light guide plate  21 , a mixing light guide plate  22 , a plurality of light sources  23 , a reflector  24 , a optical film  25  and a frame  26 . The pluralities of light sources  23  have the RGB tri-color LED, placed within the reflector  24  and arranged in a row. The reflector  24  is composed of a reflective material having a reflective inner surface, which reflects the light emitted from the light sources  23  to the mixing light guide plate  22 . Besides, the inner surface of the frame  26  has a reflective layer. The mixing light guide plate  22  is placed in a first side of the light guide plate  21 . The primary tri-color red, green and blue lights from the plurality of light sources  23  enter the mixing light guide plate  22  through the incident surface  224  of the mixing light guide plate  22 , mixing into the white light within the mixing light guide plate  22 . The mixing white light is emitted to the light guide plate  21  through the emitting surface  225  of the mixing light guide plate  22 . Finally, the light guide plate  21  transforms the mixing white light from the mixing light guide plate  22  into the surface light source. The light guide plate can be a rectangular light guide plate or a wedge-shaped light guide plate. Please be noted that the mixing light guide plate  22  of the present invention is not a single material as that of prior art. The mixing light guide plate  22  is composed of the diaphanous sheet  222  which is transparent and having a foggy surface, the transparent sheet  221  and the uneven surface sheet  223  which is a transparent layer with an uneven surface, wherein the diaphanous sheet  222  is made of a ground glass or a diffractive component. The transparent sheet  221  includes a material being one selected from a group consisting of a polycarbonate, a cycloolefin copolymers (COC), a polymethyl-methacrylate and a combination thereof. The uneven surface sheet  223  includes a plurality of units having shapes being ones selected from a group consisting of zigzag shapes, waved shapes, shapes causing dark and bright bands and a combination thereof. The mixing white light of the mixing light guide plate  22  can be well mixed into an even surface light source. Since the mixing light guide plate  22  is composed of the diaphanous sheet  222  which is transparent and having a foggy surface, the transparent sheet  221  and the uneven surface sheet  223  having an uneven surface, wherein the refractive indexes of the diaphanous sheet  222 , the transparent sheet  221  and the uneven surface sheet  223  are M 1 , M 2  and M 3  respectively. Due to the differences among the refractive indexes, when the RGB tri-color lights enter the mixing light guide plate  22 , it will pass through the uneven surface sheet  223 , the transparent sheet  221  and the diaphanous sheet  222  and have different degree of refraction according to their different refractive indexes. 
         [0028]    According to the backlight module of the present invention, since the mixing light guide plate  22  is composed of the uneven surface sheet  223 , the transparent sheet  221  and the diaphanous sheet  222 , which have different refractive indexes. The primary tri-color red, green and blue lights can be refracted in the mixing light guide plate  22  to increase the probability of mixing the tri-color lights. The lights can take multiple refractions to change their directions and make the RGB tri-color lights fully mixed into white light through entering the uneven surface sheet  223 , the transparent sheet  221  and the diaphanous sheet  222 . Since the present invention has a good light mixing mechanism, which makes the light emitted from the LED backlight module with a uniform brightness and better color mixing effect. 
         [0029]    Please refer to  FIG. 4-6 .  FIG. 4  shows a side cross-section diagram of the second preferred embodiment of the present invention.  FIG. 5  is a top view diagram showing the second preferred embodiment of the present invention.  FIG. 6  shows another side cross-section diagram of the second preferred embodiment of the present invention. The frame  36  covers a first light source  33 , a reflector  34 , a first wedge-shaped light guide plate  32 , a optical film  35  and a light guide plate  31 . The inner surface of the frame  36  has a reflective layer. The first light source  33  including the RGB tri-color LED are set in the reflector  34  and set in the side of the first wedge-shaped light guide plate  32 . The reflector  34  has a reflective inner surface, which will reflect the light emitted from the first light source  33  to the first wedge-shaped light guide plate  32 . The first wedge-shaped light guide plate  32  placed on a first side of the light guide plate  31 , having a second side  37  and a third side  38  and the area of the second side is greater than the area of the third side. In addition, the first side is substantially perpendicular to the second side and the third side. The first wedge-shaped light guide plate  32  is composed of the diaphanous sheet, the transparent sheet and the uneven surface sheet (not shown in figure), having different refractive indexes. Among them, the diaphanous sheet is against to the first side of the light guide plate  31 . The uneven surface diaphanous sheet is installed at the second side  37  relatives to the light source. Since the diaphanous sheet, the diaphanous sheet and the uneven surface diaphanous sheet have different refractive indexes, the red, green and blue lights from the first light source  33  will be mixed to form the white light in the first wedge-shaped light guide plate  32 . Due to the differences among the refractive indexes, when the RGB tri-color lights enter the mixing light guide plate  22 , which will pass through the uneven surface sheet  223 , the transparent sheet  221  and the diaphanous sheet  222  and refract according to different refractive indexes. Finally, the mixed white light from the first wedge-shaped light guide plate  32  will be transformed into the surface light source through the light guide plate  31 . 
         [0030]    Please refer to  FIGS. 7 and 8 .  FIG. 7  is a top view diagram showing the third preferred embodiment of the present invention.  FIG. 8  shows another side cross-section diagram of the third preferred embodiment of the present invention. The frame  36  encloses the first light source  33 , the second light source  33 ′, the reflector  34 , the first wedge-shaped light guide plate  32 , the second wedge-shaped light guide plate  32 ′, the optical film  35  and the light guide plate  31 . The inner surface of the frame  36  has a reflective layer. The first light source  33  and the second light source  33 ′ including the RGB tri-color LED are set in the reflector  34 . The reflector  34  has a reflective inner surface, which will reflect the light emitted from the first light source  33  and the second light source  33 ′ to the first wedge-shaped light guide plate  32  and the second wedge-shaped light guide plate  32 ′. The first wedge-shaped light guide plate  32  and the second wedge-shaped light guide plate  32 ′ placed on a first side of the light guide plate  31 . The first wedge-shaped light guide plate  32  has a second side  37  and a third side  38  and substantially perpendicular to the first side of the light guide plate  31  and the area of the second side is greater than the area of the third side. The second wedge-shaped light guide plate  32 ′ has a fourth side  38 ′ and a fifth side  37 ′ and substantially perpendicular to the first side of the light guide plate  31  and the area of the fifth side  37 ′ is greater than the area of the fourth side  38 ′. Please refer to  FIG. 8 , the third side  38  of the first wedge-shaped light guide plate  32  is opposite to the fourth side  38 ′ of the second wedge-shaped light guide plate  32 ′ and the area of the third side is substantially equal to the area of the fourth side. Because the structures of the first wedge-shaped light guide plate  32  and the second wedge-shaped light guide plate  32 ′ are the same as the wedge-shaped light guide plate of the second embodiment of the present invention, therefore, which will not be recited again. The first light source  33  is set in the second side  37  of the first wedge-shaped light guide plate  32 . The second light source  33 ′ is set in the fifth side  37 ′ of the second wedge-shaped light guide plate  32 ′. The red, green and blue lights from both the first light source  33  and the second light source  33 ′ are mixed into the white light within the first wedge-shaped light guide plate  32  and second wedge-shaped light guide plate  32 ′. Finally, the mixed white light from the first wedge-shaped light guide plate  32  and the second wedge-shaped light guide plate  32 ′ will be transformed into the surface light source through the light guide plate  31 . 
         [0031]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.