Abstract:
A backlight module is provided. The backlight module includes a frame, a light source and at least an optical film. The optical film has a first side with a first positioning flange and a second positioning flange, a second side with a third positioning flange and a third side with a fourth positioning flange. The edges of the first positioning flange, the second positioning flange, the third positioning flange and the fourth positioning flange abut the edges of the frame to hold the optical film in the frame.

Description:
This application claims the benefit of Taiwan application Serial No. 93113374, filed May 12, 2004, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to a backlight module. More particularly, the present invention relates to a backlight module capable of holding an optical film without using any extra components and having additional aperture disposed on the optical film. 
     2. Description of the Related Art 
     Along with the rapid advance in the manufacturing technology and featured by the advantages of compactness, slimness, low power consumption and low radiation, liquid crystal display (LCD) has been widely applied in a variety of electronic devices such as personal digital assistant (PDA), notebook computer, digital cameral, digital video recorder, mobile phone, computer monitor and TV monitor. Since the LCD panel used in an LCD is not a self-luminous panel, a light source provided by a backlight module is needed for an LCD panel to display. 
     Referring to  FIG. 1A , a schematic diagram of a conventional backlight module is shown. In  FIG. 1A , a backlight module  10  comprises a frame  11 , a light-guide plate  12  and at least an optical film  13 . The light-guide plate  12  and the optical film  13  are both fixed in the frame  11 , wherein the bottom side of the optical film  13  is adhered onto the top surface of the light-guide plate  12  via a tape. One lateral side of he optical film  13  has two flanges  13   a  and  13   b , which respectively have apertures  13   c  and  13   d  disposed thereon. The two apertures  13   c  and  13   d  are used for two bolts  15   a  and  15   b  to pass through. After the bolts  15   a  and  15   b  have respectively passed through the apertures  13   c  and  13   d  and are bolted to the frame  11 , the optical film  13  will be fixed in the frame  11 . 
     Referring to  FIG. 1B , another schematic diagram of a conventional backlight module is shown. In  FIG. 1B , a backlight module  20  comprises a frame  21 , a light-guide plate (not shown) and at least an optical film  23 , wherein the light-guide plate and the optical film  23  are both fixed in the frame  21 . The frame  21  has hooks  21   a  and  21   b , one lateral side of the optical film  23  has the flanges  23   a  and  23   b , another lateral side of the optical film  23  has two flanges  23   e  and  23   f , which have apertures  23   c  and  23   d  disposed thereon respectively for bolts  25   a  and  25   b  to pass through. The two flanges  23   e  and  23   f  respectively have apertures  23   g  and  23   h  for being hooked to hooks  21   a  and  21   b . After the bolts  25   a  and  25   b  have respectively passed through the apertures  23   c  and  23   d  and are bolted to the frame  21 , and after the apertures  23   e  and  23   f  have respectively been hooked to the hooks  21   a  and  21   b , the optical film  23  will be fixed in the frame  21 . For a conventional optical film to be fixed in the frame parts such as tapes, bolts or hooks are indispensable. However, extra cost and processing of parts will occur. Moreover, the conventional way of fixing the optical film cannot fix the optical film within the frame firmly, causing the optical film to be folded easily or affecting the luminance quality of a backlight module severely as shown in  FIG. 1A . The conventional method is to make apertures on an optical film to form an optical film with apertures disposed thereon. However, the excavated materials, which cannot be used any more, will be wasted. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a backlight module whose design of using the cooperation between a frame and a light-guide plate to fix the optical film in three mutually perpendicular directions improves the reliability of fixing the optical film without using extra components such as tapes, bolts or hooks, so as to save parts costs. Besides, that the optical film slides into the frame to be fixed therein, improves the convenience of fixing the optical film and that the aperture-free design of the optical film reduces material waste. 
     According to the object of the present invention a backlight module comprising a frame, a light source and at least an optical film is provided. The light source is disposed within the frame. The optical film has a first side with a first positioning flange and a second positioning flange, a second side with a third positioning flange and a third side with a fourth positioning flange. The edges of the first positioning flange, the second positioning flange, the third positioning flange and the fourth positioning flange abut the edges of the frame to hold the optical film in the frame. 
     According to another object of the present invention, a backlight frame structure is provided. The backlight frame structure includes an accommodating area and a number of frame sides. The accommodating area is configured to receive one or more optical film having a first side with a first positioning flange and a second positioning flange, a second side with a third positioning flange and a third side with a fourth positioning flange. The frame sides abut the edges of the first positioning flange, the second positioning flange, the third positioning flange and the fourth positioning flange to hold the optical film in the frame. 
     Other objects, features, and advantages of the present invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram of a conventional backlight module; 
         FIG. 1B  is another schematic diagram of a conventional backlight module; 
         FIG. 2  and  FIG. 3  are two partial explosion diagrams of the backlight module according to a preferred embodiment of the invention; 
         FIG. 4  is an assembly diagram of the backlight module illustrated in  FIG. 2 ; 
         FIG. 5  is an assembly diagram of the backlight module illustrated in  FIG. 3 ; 
         FIG. 6  is a schematic diagram of an optical film with two semi-circular positioning flanges; and 
         FIG. 7  is a schematic diagram of an optical film with two pentagonal positioning flanges. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 2  and  FIG. 3 , two partial explosion diagrams of the backlight module according to a preferred embodiment of the invention are shown. In  FIG. 2  and  FIG. 3 , a backlight module  30  comprises a frame  31 , a light-guide plate  32  and at least an optical film  33 . The frame  31  further comprises a number of frame sides, such as two opposite frame sides  31   a  and  31   b  and another two opposite frame sides  31   c  and  31   d . The frame sides  31   a  and  31   b  are connected to the frame sides  31   c  and  31   d . The frame sides  31   a  to  31   d  form an accommodating area  80  configured to receive the light-guide plate  32  and at least an optical film  33 . The light-guide plate  32  is disposed on the accommodating area  80  of the frame  31 . The luminance of the backlight module  30  comes from a light source (not shown in  FIG. 2  and  FIG. 3 ), wherein the light source, which is disposed on the frame  31 , is located underneath a surface or beside a lateral side of the light-guide plate  32 . 
     The optical film  33  comprises a light-emitting surface  33   a  and four positioning flanges  33   f ,  33   g ,  33   h  and  33   i , wherein the four positioning flanges  33   f  to  33   i  are located on the peripheral of the light-emitting surface  33   a . The light-emitting surface  33   a  has four sides  39   a  to  39   d . The side  39   a  is opposite to the side  39   d . The side  39   b  is opposite the side  39   c . The sides  39   a  and  39   d  are connected to the sides  39   b  and  39   c . The position flanges  33   f  and  33   g  are disposed on the side  39   a . The position flanges  33   h  and  33   i  are disposed on the side  39   b  and  39   c  respectively. The extension direction of the positioning flange  33   f  is substantially the same as the extension direction of the position flange  33   g . The extension direction of the positioning flange  33   f  is shown as y direction. The extension direction of the positioning flange  33   h  and the extension direction of the position flange  33   i  are inversed. The extension direction of the positioning flange  33   h  is shown as x direction and the extension direction of the position flange  33   i  is shown as x direction. The position flanges  33   f  and  33   g  are substantially identical the feet structure of the optical film  33 , and the position flanges  33   h  and  33   i  are substantially identical the shoulder structure of the optical film  33 . 
     The two positioning flanges  33   f  and  33   i  are located at the two sides of a line L 2  formed between the two positioning flanges  33   g  and  33   h . The four positioning flanges  33   f  to  33   i  abut the edges of the frame  31 , such as the frame sides  31   a ,  31   c  and  31   d , to hold the optical film  33  in the frame  31  in three mutually perpendicular directions, when the optical film  33  slides into accommodating area  80  of the frame  31  via the edges of the frame 3 l. For example, the optical film  33  slides into accommodating area  80  of the frame  31  via the frame side  31   b . Of which, one of the three mutually perpendicular directions is the normal direction of the optical film  33 , z direction for instance. In this embodiment of the invention, the rectangular positioning flanges  33   f ,  33   g ,  33   h  and  33   i  are exemplified for illustrating the optical film  33  mounted to the frame  31 . Moreover, the shape of the optical film  33  approximates a reconcile or a polygon in practical applications, and is exemplified by the rectangular. In other embodiment, one side with two positioning flanges is adjacent another two opposite sides when the optical film has a number of sides. Each of the two opposite sides has a positioning flange. 
     To have the optical film  33  firmly disposed in the frame  31 , the frame  31  further comprises two positioning recesses  31   e  and  31   f  and two indentations  31   g  and  31   h , wherein the two positioning recesses  31   e  and  31   f  and the two indentations  31   g  and  31   h  correspond to the positioning flanges  33   f  to  33   i . The two positioning recesses  31   e  and  31   f  are disposed at the two sides on the inner wall of the frame sides  31   a . As shown in  FIG. 2 , the recesses (i.e.  31   e ) project into the frame and face to the accommodating area of the frame (the inner sides of the frame member). One inner wall of the positioning recess  31   e  is connected to the inner wall of the frame side  31   c , while one inner wall of the positioning recess  31   f  is connected to the inner wall of the frame side  31   d . The inner wall of the frame sides  31   c  and that of the frame side  31   d  have the indentations  31   g  and  31   h  disposed respectively, wherein the indentations  31   g  and  31   h  are adjacent to the frame sides  31   b . Of which, the positioning recess  31   e  and the indentation  31   h  are located at the two sides of the line L 1  formed between the positioning recess  31   f  and the indentation  31   g . Furthermore, the optical film  33  can slide into or from the frame  3 l via the frame edges side  31   b.    
     Referring to  FIG.3 , the frame member  31   d  includes an indentation having two portions connected to each other, one portion of the indentation is formed in part of the upper side of the frame member  31   d  and in part of the inner side of the frame member  31   d , and the other portion  31   h  of the indentation formed in the inner side of the member  31   d  and projecting therein so as to receive one of the positioning flanges  33   i  and  33   h . When the optical film  33  in  FIG. 2  and  FIG. 3  slide into the frame  31  via the frame sides  31   b  along the y direction, the positioning flanges  33   f  and  33   g  are inserted to the positioning recesses  31   e  and  31   f  respectively, and the positioning flanges  33   h  and  33   i  respectively slide into the frame  31  along the tracks  36   a  and  36   b  in the frame  31  to be embedded into the indentation  31   g  and  31   h  respectively as shown in  FIG. 4  and  FIG. 5 . The optical film  33  abut against the contact edges of the frame members configuring the recess  31   e  and  31   f  at the frame member  31   a , and against inner sides of the indentations  31   g  and  31   h , so as to hold the optical film  33  in the frame  31  in x and y direction. In addition, it is noted that at least part of inner wall of recess covers at least part of the positioning flange so as to hold the optical film in the frame. For example, the inner wall of recesses  31   e  and  31   f  cover the positioning flanges  33   f  and  33   g . It allows the optical film  33  to be hold in the frame  31  in z direction. By doing so, the optical film  33  be firmly fixed in the frame  31  in x, y, and z directions, preventing the optical film  33  from being folded and peeled off so as to maintain the luminance quality of the backlight module  30 . The optical film  33  can be removed from the accommodating  80  of the frame  31  via the frame side  31   b.    
     Anyone who understands the technology of the invention will realize that the technology is not limited to the preferred embodiment. For example, the structure of the frame sides  31   a  to  31   d  can be formed in one block. Under the premise that the edges of the positioning flanges abut the edges of the frame, the positioning flanges can be of a variety of shapes. As illustrated in  FIG. 6 , the optical film  60  has four semi-circular positioning flanges  61   a  to  61   d  whose edges abut the edges of the frame, so as to hold the optical film  60  in the frame firmly in three mutually perpendicular directions. As illustrated in  FIG. 7 , the optical film  70  has four pentagonal positioning flanges  71   a  to  71   d  whose edges abut the edges of the frame so as to hold the optical film  70  in the frame firmly in three mutually perpendicular directions. 
     Moreover, when a plurality of the optical films are to be disposed on the frame, the invention can disposed four positioning flanges on the periphery of the topmost optical film only instead of disposing four positioning flanges on the periphery of each optical film. Such practice also fixes the optical films in the frame firmly. Besides, if the optical films are used to be disposed within the frame in order to fix the optical films within the frame, instead of forming the four positioning flanges at a lateral side of each of the optical films, the invention only need to form four positioning flanges at a lateral side of the topmost optical film. 
     The backlight module disclosed in the above embodiment of the present invention uses the cooperation between the frame and the light-guide plate to fix the optical film in x, y and z directions so as to improve the reliability of fixing the optical film without using extra components such as tapes, bolts or hooks, so as to save parts costs. Besides, that the optical film slides into the frame to be fixed therein, improves the convenience of fixing the optical film and that the aperture-free design of the optical film reduces material waste. 
     While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.