Abstract:
A backlight module is provided. The backlight module comprises a light source, a reflection panel, a back bezel, and an upper filtering apparatus. The reflection panel has a first upper portion, which is essentially disposed at an outer side of the light source, and is used to reflect lights projecting from the light source. The back bezel has a second upper portion which is essentially disposed at an outer side of the reflection panel. At least one of the first upper portion and the second upper portion forms an upper opening. The filtering apparatus covers the openings. The filtering apparatus is capable of changing the distribution of the temperature of the light source to allow more efficient lamp activity. As a result, luminance is increased and lamp life extended.

Description:
This application claims priority to Taiwan Patent Application No. 095134029 filed on Sep. 14, 2006, the disclosures of which are incorporated herein by reference in its entirety. 
   CROSS-REFERENCES TO RELATED APPLICATIONS 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a backlight module. More particularly, the present invention relates to a backlight module with an upper filtering apparatus so that a larger proportion of a light source can operate under a better working temperature. 
   2. Description of the Related Arts 
   In recent years, techniques of manufacturing liquid crystal display (LCDs) have been quickly developed to equip many electronic products, such as personal digital assistants, notebooks, digital cameras, digital camcorders, mobile phones, computer monitors, LCD TVs, etc, with LCDs. An LCD requires the light source of a backlight module to display. Consequently, the quality of the light source of the backlight module is highly related to the quality of the LCD. 
   Based on the light source positioning in backlight modules, backlight modules can be roughly classified into edge type backlight modules and direct-type backlight modules. Lamps of an edge type backlight module are disposed on one side of an LCD panel. The lamp lights are propagated into a light guiding plate disposed in the rear of the LCD panel to guide reflection and refraction of the incident lights, using the light guiding plate as a medium. 
   The direct type backlight module comprises a back bezel, a reflection panel, a plurality of lamps, a diffuser, and an optical film set. The back bezel forms a container. The reflection panel is disposed inside the container. The lamps are arranged in the container and are disposed on the inner side of the reflection panel. The diffuser is disposed on the inner side of the lamps, while the optical film set is disposed on the inner side of the diffuser. The optical film set usually comprises a prism, a diffuser sheet, or a brightness enhancement film. The LCD panel is disposed on the inner side of the optical film set. The assembly of these components results in a complete LCD. 
   The temperature of a lamp surface influences the quality of a direct type backlight module greatly. Understandably, different types of lamps have different ranges of optimal working temperatures. If there are more lamps with temperatures that fall within the range, the luminance of the backlight module is more uniform, resulting in a longer lamp life. However, the heat generated by the lamps increases the temperature inside the backlight module, so fewer lamps are able to operate at their optimal working temperatures. Furthermore, since hot air rises, lamps disposed in the upper areas suffer from higher temperatures. This causes serious damages to the overall lighting quality and lifetime of the lamps. 
   In the prior art, an opening is disposed on the back bezel of a backlight module to release hot air. Although this method can reduce heat, no more adjustments can be made after the opening is disposed. Furthermore, external dust and extraneous particles may easily fall inside the backlight module through the opening, reducing the quality of the backlight module. 
   In response to the above-mentioned concerns, an invention that (1) reduces the hot air in a direct type backlight module, (2) prevents external particles from entering and changing the temperature distribution of the lamps and, (3) increases both the overall light efficiency of the light sources and the usage life is greatly needed in this field. 
   SUMMARY OF THE INVENTION 
   The primary objective of this invention is to provide a backlight module that reduces the concentration of hot air in the upper portion of the apparatus and to prevent external particulates from entering. This backlight module comprises a light source, a reflection panel, a back bezel, and an upper filtering filter. The reflection panel has a first upper portion and is essentially disposed at an outer side of the light source to reflect lights projecting from the light source. In addition, the back bezel has a second upper portion and is essentially disposed at an outer side of the reflection panel, wherein at least one of the first upper portion and the second upper portion is formed with an upper opening, and the upper filtering device covers the upper opening. 
   Another objective of this invention is to provide a back bezel for a backlight module of an LCD to reduce the concentration of hot air at an upper portion and to prevent external particulates from entering. The backlight module comprises a light source and a reflection panel. The reflection panel is essentially disposed at an outer side of the light source to reflect lights projecting from the light source and having a first upper portion, wherein the back bezel is essentially disposed at an outer side of the reflection panel. The back bezel has a second upper portion and an upper filtering device. At least one of the first upper portion and the second upper portion is formed with an upper opening to allow the accumulated hot air to escape. The upper filter device covers the upper opening. 
   The difference between this invention and the prior art is that an opening is formed at the appropriate places in the backlight module to allow hot air to flow through the device quickly. Since there is an upper filtering device, external particulates are not able to enter the device. Understandably, the best position for the opening is in the upper portion of the backlight module. When the hot air is released, more lamps are able to work within their optimal temperature ranges, resulting in better luminance and a longer backlight module life. 
   The embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a lateral cross-sectional view of a backlight module without its filtering device covered in the first embodiment of the present invention; 
       FIG. 1B  is an enlarged lateral cross-sectional view of a first upper portion of the first embodiment; 
       FIG. 1C  is a top cross-sectional view of  FIG. 1B ; 
       FIG. 1D  is a lateral cross-sectional view of an upper filtering device of the first embodiment, 
       FIG. 1E  is a top cross-sectional view of  FIG. 1D ; 
       FIG. 1F  is an enlarged lateral cross-sectional view of a first upper portion with a covered filtering device of the first embodiment; 
       FIG. 1G  is a top cross-sectional view of  FIG. 1F ; 
       FIG. 1H  is a lateral cross-sectional view of a backlight module with a covered filtering device of the first embodiment; 
       FIG. 2A  is a lateral cross-sectional view of a filtering device with a slot; 
       FIG. 2B  is a lateral cross-sectional view of a first upper portion of a filtering device with a slot; 
       FIG. 2C  is a top cross-sectional view of another upper portion; 
       FIG. 3  is a lateral cross-sectional view of the second embodiment; 
       FIG. 4  is a lateral cross-sectional view of the third embodiment; 
       FIG. 5  is a diagram of a distribution of a lamp surface temperature; 
       FIG. 6  is a comparison diagram of a lamp surface temperature of a backlight module with or without a filtering device. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A first embodiment of the present invention is a backlight module with an upper filtering device covering an upper opening of an upper portion of a reflection panel. Referring to  FIG. 1A , the backlight module  10  comprises 8 Cold Cathode Fluorescent Lamps (CCFLs)  11 , a reflection panel  12 , and a back bezel  13 . The indication of the arrow means the referenced outward direction. The reflection panel  12  is disposed at an outer side of the 8 CCFLs  11 , while the back bezel  13  is disposed at an outer side of the reflection panel  12 . The reflection panel  12  has a first upper portion  121  with an upper opening  122 . In addition, the back bezel  13  has a second upper portion  131 . 
     FIG. 1B  is an enlarged lateral cross-sectional view of the first upper portion  121  and the corresponding upper opening  122  of this embodiment.  FIG. 1C  is a top cross-sectional view of  FIG. 1B . Looking at  FIG. 1C , the upper opening  122  completely extends along the first upper portion  121 . Meanwhile, the first upper portion  121  comprises four screw holes  125 . 
     FIG. 1D  is a lateral cross-sectional view of the upper filtering device  14  of this embodiment.  FIG. 1E  is a top cross-sectional view of  FIG. 1D . In this embodiment, a filter area of the upper filtering apparatus  14  is close to an area of the upper opening  122 . The filter is single layered and is made of copper with a 0.1 mm mesh. The upper filtering device is disposed with four screw holes  144  corresponding to the screw holes  125  of the first upper portion  121 , respectively. 
   Next, the filtering device  14  is fixed to the first upper portion  121  by screws.  FIG. 1F  is a lateral cross-sectional view of the upper opening  122  covered by the upper filtering device  14 .  FIG. 1G  is a top cross-sectional view of  FIG. 1F . Referring to  FIG. 1G , four screws  145  fix the upper filtering device  14  onto the first upper portion  121  to cover the upper opening  122 .  FIG. 1H  depicts a lateral cross-sectional view of the backlight module covered with the upper filtering device  14 . Similarly, the indication of the arrow means the referenced outward direction. 
   With the above arrangements, hot air in the backlight module  15  covered by the upper filter device  14  can be released. Consequently, more lamps can operate in their optimal working temperature ranges, resulting in better luminance of the back light module  15 . In addition, lifetimes of lamps  11  are increased. 
   It is necessary to emphasize that the objective of this invention is to control the hot air in the backlight module and the temperature distribution caused by heat generated from the lamps through the filtering device. Consequently, a fixing manner, a material, a size, a shape, a quantity, a mesh size, a number of the filter stacks used in the upper opening, as well as a number, a shape and a position of the filtering device are not used to limit the range of this invention. Any other substitution is applicable as shown in the following examples. 
   For example, instead of being screwed on, the filtering device can be substituted by a filtering device with a slot  FIG. 2A  is a lateral cross-sectional view of the filtering apparatus  24  with a slot. By using the slot, the filtering device  24  can be fixed onto the first upper portion  121  by sliding as depicted in  FIG. 2B . By using this approach, the filtering device can be easily replaced easily or taken out for cleaning. 
   With regards to the type of material, a stainless steel, a nylon, a polypropylene, a glass fiber, or any combination of the above can replace the above-mentioned copper. Because the filtering device may be disposed above the upper opening  122  of the first upper portion  121  of the reflection panel  12 , a light collecting ability of the original reflection panel  12  can be kept if the filtering device is made of a light reflection material. The mesh size may range from 0.1 mm to 0.5 mm. Likewise, the filter stacks could be single-layered or multiple-layered. If there are multiple filter stacks, each mesh layer can be staggered to achieve a better result for isolating the suspended particulates, while still maintaining heat circulation. Certainly, there is no limitation in selecting the mesh size and the material. 
   For the number, shape and position of the upper opening, various opening shapes may be adopted.  FIG. 2C  is a top cross-sectional view of another upper portion  221 . In the figure, the first upper portion  221  forms two upper openings  222  and  223 . This diagram shows that the shape and the fixing manner of the filtering device are adjustable. In addition, the upper opening can be disposed on the upper portion of the back bezel corresponding to the opening of the reflection panel. 
     FIG. 3  depicts a second embodiment of this invention disposing a backlight module comprising two upper filtering devices and a lower filtering device. The backlight module  3  comprises a Cold Cathode Flat Fluorescent Lamp (CCFFL)  31 , a reflection panel  32 , a back bezel  33 , a first upper filtering device  34 , a second upper filtering device  35 , and a lower filtering device  36 . The reflection panel  32  has a first upper portion  321  and a first lower potion  322 , wherein the first upper portion  321  forms a first upper opening, while the first lower portion  322  forms a lower opening. The back bezel  33  has a second upper portion  331  and a second lower portion  332 , wherein the second upper portion  331  forms a second upper opening. 
   The first upper filtering device  34  is slid into the first upper opening. The second upper filtering device  35  is also slid into the second upper opening. The lower filtering device  36  is screwed at the lower opening. 
   Similarly, a fixing manner, a material, a size, a shape, a quantity, a mesh size, a number of filter stacks of the filter device, as well as a number, a shape and a position of the upper opening are not used for limiting this invention. Any other suitable substitution is applicable. 
     FIG. 4  is a lateral cross-sectional view of a third embodiment of this invention which is a back bezel  4 . The back bezel  4  is suitable for a backlight module of an LCD. An upper portion  41  of the back bezel  4  forms an upper opening. The back bezel  4  comprises an upper filtering device  411  covered on the upper opening. Consequently, while the back bezel  4  is assembled with the backlight module, hot air inside the backlight module can be released from the upper filtering device  411  of the back bezel  4 . Similar to the first and second embodiments as stated above, in this embodiment the ways to implement the upper filtering device  411  onto the back bezel  4  can be of different forms to achieve the desired purposes. 
     FIG. 5  is a diagram of a lamp surface temperature distribution, wherein the horizontal direction axis represents the lamp surface temperature, while the vertical direction axis represents the luminance. A dotted line  51  indicates a position of the lamp surface temperature of about 59° C., while a dotted line  52  indicates a lamp surface temperature of about 63° C. According to  FIG. 5 , the optimal luminance range for lamps ranges from 59° C. to 63° C. regardless of a current of the lamp. That is, the luminance of the lamp is higher and more uniform when the lamp is in its optimal operating range. Because an objective of this invention is to increase the light emitting efficiency and life, the ratio of more efficient lamps should also increase. In other words, if more lamps work in a temperature range of around 65° C. to 75° C., the light emitting efficiency of the whole backlight module can be increased and a relative heating degree among the lamps can be balanced to indirectly extend the life of the lamps. 
     FIG. 6  is a comparison diagram of the lamp surface temperature of a backlight module with or without a filtering device (curve A and B, respectively). The horizontal direction axis represents the numbering of the lamps from top to bottom, while the vertical direction axis represents the lamp surface temperature. For a more detailed description, two backlight modules are deposed with 20 lamps, wherein the lamp with number  1  is located at the highest position of the backlight module, and the lamp with number  20  is located at the lowest position. In the figure, an average temperature of the lamps of the backlight module deposed with the filtering device decreases about 3° C. In other words, most lamps have a surface temperature ranging from 59° C. to 63° C. Based on this finding, it is not hard to imagine that the lamps may have better light emitting efficiency, longer lifetime and uniform luminance. 
   From the above descriptions, the filtering device disposed on the back bezel or/and the reflection panel can reduce hot air in the backlight module, increase the light source luminance and uniformity, and also increase lamp life. 
   The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements, based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.