Abstract:
A flat fluorescent lamp structure comprises a first substrate, a second substrate assembled to the first substrate to form a sealed space, at least one wall dividing the sealed space into a plurality of illuminating chambers filled with a discharge gas, wherein two terminals of each the illuminating chamber are mounted with two outside electrodes respectively for generating an electrical current through the illuminating chamber. At least one tunnel is formed therethrough to communicate the illuminating chambers. A phosphor layer is formed on a plurality of inner surfaces of the illuminating chambers, wherein the tunnel extends along a tilt direction relative to the illuminating chamber, and therebetween the entire tilt direction and the illuminating chamber form an acute angle. The entire tilt direction is formed by a first end of the tunnel directly connected with the illuminating chamber and a second end of the tunnel directly connected with another illuminating chamber adjacent to the illuminating chamber.

Description:
[0001]    This application is a continuation of co-pending U.S. application Ser. No. 11/490,083, filed Jul. 21, 2006, which claims priority on Taiwanese Patent Application No. 94146204, filed Dec. 23, 2005 and Taiwanese Patent Application No. 95113434, filed Apr. 14, 2006, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    This invention relates to a flat fluorescent lamp structure, and more particularly relates to a flat fluorescent lamp structure applied as a backlight source of a display. 
         [0004]    (2) Description of the Related Art 
         [0005]    The cold cathode fluorescent lamp (CCFL) is a common illumination device widely applied in backlight modules of liquid crystal displays. The CCFL illuminates by using plasma, which is generated by the electrons ejected from the cathode colliding with discharge gas to ionize and excite the discharge gas atom. Then, the excited atoms in the plasma release energy by the way of radiating ultra-violet (UV) illumination to back to the ground state. The UV illumination is absorbed by the phosphor layer painted on the wall of the CCFL to generate visible light. 
         [0006]    As the size of LCD increases, the backlight module thereof needs a bigger illumination surface with better brightness and uniformity. When the CCFL is applied in small size LCD, the CCFL provides illumination from an edge of a light guide to generate a planar light source. However, when the CCFL is applied in large size LCD, a direct type backlight module, which skips the light guide and applies a plurality of CCFLs to illuminate the LCD directly instead, is commonly used. 
         [0007]    Flat fluorescent lamp is another light source applied in backlight module. The flat fluorescent lamp illuminates based on the theory similar to the above mentioned CCFL but with a different structure. It is noted that a planar light source, especially the one with uniform brightness, is demanded for the illumination of LCD. The direct type backlight module, which is composed of a plurality of CCFLs, has a restriction in illuminating uniformity due to the brightness difference of the gap between neighboring CCFLs and the CCFL itself In addition, the direct type backlight module also needs higher cost and complicate assembling process. Thus, the flat fluorescent lamp is presented as a direct planar light source to meet the need of LCD. 
         [0008]      FIG. 1A  shows a top view of a typical flat fluorescent lamp,  FIG. 1B  shows a cross-section view of the flat fluorescent lamp along b-b cross-section. Referring to  FIG. 1B , the flat fluorescent lamp structure  10  has a first substrate  12  and a second substrate  14  forming a sealed space (unlabeled) filled with discharge gas  18 . Inside the flat fluorescent lamp structure  10 , the opposite surfaces of the first substrate  12  and the second substrate  14  respectively are painted or coated with phosphor layer  16 . Also referring to  FIG. 1A , the flat fluorescent lamp  1  has electrodes  11  formed on the opposite edges of the flat fluorescent lamp structure  10  to generate current. As the current is generated, the flat fluorescent lamp illuminates by the way the above mentioned CCFL does. 
         [0009]    Also referring to  FIG. 1C , which is a cross-section view along c-c cross-section of  FIG. 1A , a plurality of wall structure  13  is assembled between the first substrate  12  and the second substrate  14  to form a plurality of illuminating chambers  15 . The illuminating chambers  15  are structurally similar to a plurality of CCFLs arranged side by side. 
         [0010]    It is noted that the process of fabricating the flat fluorescent lamp structure  10  usually has the first substrate  12 , the wall structure  13 , and the second substrate  14  assembled as a whole before vacuuming the illuminating chambers  15  and injecting discharge gas  18 . In order to facilitate the vacuuming and the injecting processes, some tunnels  17  are formed through the wall structure  13  between illuminating chambers  15  to have all the illuminating chambers  15  communicating with each other. 
         [0011]    However, the existing of tunnels  17  may hinder the lighting of illuminating chambers  15 . Also referring to  FIG. 1D , which shows an equivalent circuit diagram of the flat fluorescent lamp of  FIG. 1A . The discharge gas  18  within the illuminating chambers  15  of  FIG. 1A  may be regarded as resistors R 1 , R 3 , R 5 , R 7 , and R 9  of  FIG. 1D  respectively when discharging. For the same reason, the discharge gas  18  within the tunnels  17  of  FIG. 1A  may be regarded as resistors R 2 , R 4 , R 6 , and R 8  of  FIG. 1D  respectively. The demanded current is provided by a current providing circuit, for example, power supply circuit  22 . 
         [0012]    It is understood that resistance is proportional to the ratio of length and cross-section area. The content mentioned below is based on the theory. 
         [0013]    Ordinarily, the wall structure  13  of  FIG. 1C  is formed on the first substrate  12  by using thermal forming or sand blasting technology. The tunnels  17  with a cross-section area substantially close to the cross-section area of the illuminating chambers  15  are usually preserved at the same time. Since the length of the tunnel  17  is smaller than the length of the illuminating chamber  15 . The resistance of the resistors R 2 , R 4 , R 6 , and R 8  with respect to the tunnels  17  is much smaller than the resistance of the resistors R 1 , R 3 , R 5 , R 7 , and R 9  with respect to the illuminating chambers  15 . 
         [0014]    On the other hand, the fabrication process in reality may result in variation of individual illuminating chambers  15 . That is, the resistance of the resistors R 1 , R 3 , R 5 , R 7 , and R 9  may not be the same. Thus, the non-uniformity of current distributed within the flat fluorescent lamp  1  seems unpreventable. When the non-uniformity of current becomes serious, even some illuminating chambers cannot be lighted to result in non-uniformity of lighting. Take the resistor R 1 , R 2 , and R 3  of  FIG. 1D  for example. As the resistance of resistor R 3  is small than the resistor R 1  in reality, and the resistance of serially connected resistors R 3  and R 2  is smaller than that of the resistor R 1  (R 3 +R 2 &gt;R 1 ), part of the current predicted to flow through the illuminating chamber  15  with respect to the resistor R 1  flows through the tunnel  17  with respect to the resistor R 2  and the illuminating chamber  15  with respect to the resistor R 3 . Thus, the illuminating chamber  15  with respect to resistor R 1  may not be lighted so as to result in a failure flat fluorescent lamp attending with the increasing of cost. 
         [0015]    Accordingly, in regard of the existing drawback as mentioned above, how to promote the drawback by effectively improving the non-uniformity of lighting of the flat fluorescent lamp has become an object in the present LCD industry. 
       SUMMARY OF THE INVENTION 
       [0016]    It is an object of the present invention to provide a flat fluorescent lamp structure and a flat fluorescent lamp capable of improving non-uniformity of lighting. 
         [0017]    It is another object of the present invention to provide a flat fluorescent lamp structure and a flat fluorescent lamp capable of enhancing reliability of current characteristics. 
         [0018]    It is another object of the present invention to provide a flat fluorescent lamp structure and a flat fluorescent lamp which can be uniformly lighted without the need of adding any additional vacuuming or discharge gas injecting process. 
         [0019]    A flat fluorescent lamp structure comprising a first substrate, a second substrate, a wall structure, a phosphor layer, and a discharge gas is provided in the present invention. The second substrate is oppositely assembled to the first substrate to form a sealed space. The wall structure is utilized to separate the sealed space into a plurality of illuminating chambers. A tunnel penetrates the wall structure to communicate the illuminating chambers. In addition, the tunnel divides the adjacent illuminating chamber into a first illuminating sub-chamber and a second illuminating sub-chamber connecting with each other. The phosphor layer is formed on inner surfaces of the illuminating chambers. The discharge gas is filled in the illuminating chambers. A ratio of a length and a cross-section area of the tunnel defines a first coefficient, a ratio of a length and a cross-section area of the first illuminating sub-chamber defines a second coefficient, and a ratio of a length and a cross-section area of the second illuminating sub-chamber defines a third coefficient, a ratio of the first coefficient and the second coefficient is greater than 1/20, and a ratio of the first coefficient and the third coefficient is greater than 1/20. 
         [0020]    A flat fluorescent lamp comprising a first substrate, a second substrate, at least an electrode, a phosphor layer, and a discharge gas is also provided in the present invention. The second substrate is oppositely assembled to the first substrate to form a plurality of illuminating chambers and at least a tunnel, wherein the tunnel is communicated with the neighboring illuminating chambers and a cross-section area of the tunnel is smaller than that of the illuminating chamber. The electrode is connected to the illuminating chambers. The phosphor layer is formed on inner surfaces of the illuminating chambers. The discharge gas is filled in the illuminating chambers. In addition, a ratio of a length and a cross-section area of the tunnel defines a first coefficient, a ratio of a length and a cross-section area of the first illuminating sub-chamber defines a second coefficient, and a ratio of a length and a cross-section area of the second illuminating sub-chamber defines a third coefficient, the first coefficient may be greater than the second coefficient or the third coefficient. Moreover, a ratio of the first coefficient and the second coefficient and of the first coefficient and the third coefficient is greater than 1/20 or greater than 20. 
         [0021]    It is noted that the resistance with respect to the tunnel is much greater than the resistance with respect to the illuminating chamber in accordance with the present invention. Thus, the current provided by the electrodes would not flow into the high-resistance tunnel to make sure the flat fluorescent lamp can be uniformly lighted. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which: 
           [0023]      FIG. 1A  is a top view of a typical flat fluorescent lamp; 
           [0024]      FIG. 1B  is a cross-section view along b-b cross-section of the flat fluorescent lamp of  FIG. 1A ; 
           [0025]      FIG. 1C  is a cross-section view along c-c cross-section of the flat fluorescent lamp of  FIG. 1A ; 
           [0026]      FIG. 1D  is a equivalent circuit diagram of the flat fluorescent lamp of  FIG. 1A ; 
           [0027]      FIG. 2A  is a top view of a flat fluorescent lamp in accordance with the present invention; 
           [0028]      FIG. 2B  is a cross-section view of the flat fluorescent lamp of  FIG. 2A ; 
           [0029]      FIG. 2C  is a cross-section view along c-c cross-section of a preferred embodiment of the flat fluorescent lamp of  FIG. 2A ; 
           [0030]      FIG. 2D  is a cross-section view along c-c cross-section of another preferred embodiment of the flat fluorescent lamp of  FIG. 2A ; 
           [0031]      FIG. 2E  is a equivalent circuit diagram of the flat fluorescent lamp of  FIG. 2A ; 
           [0032]      FIG. 2F  is a cross-section view along e-e cross-section of a preferred embodiment of the flat fluorescent lamp of  FIG. 2A ; 
           [0033]      FIG. 3A  is a top view of another preferred embodiment of the flat fluorescent lamp in accordance with the present invention; 
           [0034]      FIG. 3B  is a top view of another preferred embodiment of the flat fluorescent lamp in accordance with the present invention; and 
           [0035]      FIG. 4  is a cross-section view along e-e cross-section of another preferred embodiment of the flat fluorescent lamp of  FIG. 2A . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]      FIG. 2A  shows a top view of a flat fluorescent lamp in accordance with the present invention, and  FIG. 1B  shows a cross-section view along b-b cross-section of the flat fluorescent lamp. As shown, the flat fluorescent lamp structure  40  has a first substrate  42 , a wall structure  43 , a second substrate  44 , a phosphor layer  46 , a tunnel  47 , and a discharge gas  48 . The flat fluorescent lamp  4  has electrodes  41  formed on the opposite edges of the flat fluorescent lamp structure  40  to generate current. The discharge gas  48  may be inert gas selected from the group consisting of Xe, Ne, Ar, and combinations thereof. 
         [0037]    As shown in  FIG. 2B , the second substrate  44  is oppositely assembled to the first substrate  42  to form a sealed box and also a sealed space  49 . Within the seal space  49 , the phosphor layer  46  is formed on the inner surfaces of the first substrate  42  and the second substrate  44 . A sidewall  421  is formed surrounding the space between the first substrate  42  and the second substrate  44 , and it may formed on an upper surface of the first substrate  42  as a preferred embodiment. When oppositely assembling the first substrate  42  and the second substrate  44 , a sealant  51  may be placed on the top of the sidewall  421  to provide reliable connecting and sealing quality. 
         [0038]    The structure or assembling procedure of the first substrate  42 , wall structure  43 , and the second substrate  44  has many varieties. For example, a plurality of concaves may be directly formed on the first substrate  42 , which is understood as forming the wall structure  43  on the first substrate  42  integrally. In addition, the flat fluorescent lamp structure  40  of  FIG. 2D  features a specific designed first substrate  42  to replace the usage of wall structure  43  as shown in  FIG. 2C , but the proposed function and object of the two cases are identical. Therefore, it is noted that the wall structure  43 , the first substrate  42 , and the second substrate  44  may not definitely be separated parts. The wall  43 , the first substrate  42 , and the second substrate  44  may be formed into one piece, or the wall  43  and the first substrate  42  may be formed into one piece. The naming for these elements is for clarifying individual function but not for restricting the present invention. 
         [0039]    The first substrate  42 , the second substrate  44 , and the sidewall  421  are formed of a material comprising glass. As a preferred embodiment of the present invention, the second substrate  44 , which is selected as an illuminating surface of the flat fluorescent lamp structure  40 , is formed of a transparent material. In addition, the first substrate  42  may be painted with reflecting material or assembled with a reflector to increase illumination efficiency. 
         [0040]    Referring to  FIG. 2C , which shows a cross-section view of the flat fluorescent lamp of  FIG. 2A  along c-c cross-section, the wall structure  43  divides the sealed space  49  into a plurality of illuminating chambers  45 . Also referring to  FIG. 2A , the tunnels  47  penetrates through the wall structure  43  to communicate the illuminating chambers  45 . By using the preset opening  425  on the sidewall  421 , the seal space  49  as a whole can be vacuumed. Then, the discharge gas  48  is filled into the illuminating chambers  45  through the opening  425 , and following the opening  425  is sealed to finish the fabrication process. 
         [0041]    As shown in  FIG. 2C , the phosphor layer  46  may be formed on the inner surfaces of the illuminating chambers  45 . That is, besides the formation of phosphor layer  46  on the first substrate  42  and the second substrate  44 , the phosphor layer  46  may be also formed on the surface of the wall structure  43 . In addition, in the embodiment as shown in  FIG. 2C , the wall structure  43 , which is formed of a material identical to that of the first substrate  42 , is formed on the first substrate  42  before assembling to the second substrate  44 . As the first substrate  42  is assembled to the second substrate  44 , the sealant  51  is placed on the top of the wall structure  43  to connect the second substrate  44  and the wall structure  43 . The discharge gas  48  may be an inert gas selected from Xe, Ne, or Ar. 
         [0042]    Also referring to  FIG. 2B  in views of  FIG. 2A , the demanded current in the flat fluorescent lamp structure  40  is provided by outside electrodes  41 , which are connected to the illuminating chambers  45 . As shown in  FIG. 2B , the outside electrodes  41  are assembled on the outer surface of the first substrate  42  or the second substrate  44  and discharge through the two substrates  42  and  44 . Thus, the glass material of the first substrate  42  or the second substrate  44  may be regarded as a capacitor. In addition, the power supply circuit  52  provides the demanded current as shown in the equivalent circuit diagram of  FIG. 2E . 
         [0043]    In addition, also referring to  FIG. 2A , the illuminating chamber  45  at the left end is divided by the adjacent tunnel  47  into a first illuminating sub-chamber  45   a   1  and a second illuminating sub-chamber  45   a   2 . The discharge gas  48  within the first illuminating sub-chamber  45   a   1  and the second illuminating sub-chamber  45   a   2  forms chamber resistance respectively when discharging. Therefore, as shown in  FIG. 2E , the first illuminating sub-chamber  45   a   1  and the second illuminating sub-chamber  45   a   2  may be regarded as resistors r 11  and r 12 , respectively. For the same reason, the adjacent tunnel  47  may be regarded as a resistor r 2 . In order to solve the problem of non-uniformity of lighting existed in the typical flat fluorescent lamp  1  as shown in  FIGS. 1A to 1D , the idea provided in the present invention focuses on enormously increasing tunnel resistance corresponding to the resistor r 2 , to have the tunnel resistance greater than the chamber resistance corresponding to the resistors r 11  and r 12 . 
         [0044]    According to the function about resistance R=ρ·L/A , the resistance R of the tunnel  47  is proportional to the length L of the tunnel  47  as shown in  FIG. 2A , but inversely proportional to the cross-section area A of the tunnel  47  as show in  FIG. 2F , which shows a cross-section view along e-e cross-section. The equivalent coefficient of resistance ρ of the tunnel  47  is related to the ionization of gas within the tunnel  47 . Let a ratio of the length L and the cross-section area A of the tunnel  47  defines a first coefficient, a ratio of the length L 1  as shown in  FIG. 2A  and the cross-section area A′ as shown in  FIG. 2C  of the first illuminating sub-chamber  45   a   1  defines as a second coefficient, and a ratio of the length L 2  and the cross-section area A′ of the second illuminating sub-chamber  45   a   2  defines a third coefficient. In order to have the flat fluorescent lamp uniformly lighted, the resistance of the tunnel should be greater than the resistance of the chamber. As s preferred embodiment, both a ratio of the first coefficient and the second coefficient and a ratio of the first coefficient and the third coefficient are greater than 1/20 to make sure individual illuminating chambers  45  are successfully lighted. In another preferred embodiment, both the ratio of the first coefficient and the second coefficient and the ratio of the first coefficient and the third coefficient are greater than 20. 
         [0045]    In practice, the present invention achieves the limitations about the ratio of the first coefficient and the second coefficient or the third coefficient by elongating the length L of the tunnel or decreasing the cross-section area A of the tunnel The detail of the adjusting method is mentioned below. 
         [0046]    Except the above mentioned embodiment, the three illuminating chambers  45  located in the center of  FIG. 2A  depict another preferred embodiment. As shown, each of the illuminating chamber  45  located in the center is divided by two adjacent tunnels  47  located at the both sides into three illuminating sub-chambers. Take the second illuminating chamber  45  counted from the left for example. As shown, the illuminating chamber  45  is divided by the tunnels  47  into three illuminating sub-chambers  45   b   1 ,  45   b   2 , and  45   b   3  corresponding to the resistors r 31 , r 32 , and r 33  as shown in  FIG. 2E . The two adjacent tunnels  47  are corresponding to the resistors r 2  and r 4 . As mentioned in the above paragraph, the tunnel is corresponding to the defined first coefficient. A ratio of the length L 3 , L 4 , and L 5  of the illuminating sub-chambers  45   b   1 ,  45   b   2 , and  45   b   3  as shown in  FIG. 2A  and a cross-section area A″ thereof as shown in  FIG. 2C  defines a fourth coefficient. The resistance of the tunnel corresponding to the resistors r 2  and r 4  should be greater than that of the chamber corresponding to the resistors r 31 , r 32 , and r 33 . As a preferred embodiment, a ratio of the first coefficient and the fourth coefficient is greater than 1/20 to make sure individual illuminating chambers  45  are successfully lighted. In another preferred embodiment, the ratio of the first coefficient and the fourth coefficient is greater than 20. 
         [0047]    The embodiments for elongating the length L of the tunnel or decreasing the cross-section area A of the tunnel are described below in detail. In regarding of elongating the length L of the tunnel, as shown in  FIG. 2A , without changing the thickness of the wall structure  43 , this embodiment has the tunnel  47  penetrate through the wall structure  43  along a tilt direction to increase the length L of the tunnel The varieties of the above mentioned method, such as adapting different tilt angle or having the tunnel  47  penetrating the wall structure  43  along different cross-section surfaces, are included in the present invention. 
         [0048]      FIG. 3A  shows a top view of another preferred embodiment for elongating the length L of the tunnel As shown, the tunnel  47  has a bend to increase the overall length L of the tunnel  FIG. 3B  shows a top view of a similar embodiment, which uses two bends to form an N-type tunnel It is understood that various embodiments using the same idea to increase the length of the tunnel  47  are available in accordance with the present invention. 
         [0049]    The method of decreasing the cross-section area of the tunnel may be understood by comparing the flat fluorescent lamp structure of  FIG. 2A  and  FIG. 1A . In the typical flat fluorescent lamp structure as shown in  FIG. 1A , the width of the tunnel  17  is close to the width of the illuminating chamber  15 , whereas, a narrower tunnel  47  is used in the present invention as shown in  FIG. 2F  to decrease cross-section area of the tunnel Referring to another embodiment as shown in  FIG. 4 , which shows a cross-section view along e-e cross-section of  FIG. 2A , the height h of the tunnel  47  is only part of the total height H of the wall structure  43  so as to decrease cross-section area of the tunnel. 
         [0050]    As a result, the flat fluorescent lamp structure  40  provided in the present invention keeps the tunnel  47  to facilitate single vacuuming process and single discharge gas  48  filling process. In addition, since the equivalent resistance of individual chambers (r 11 , r 12 , r 13 , r 31 , r 32 , r 33 , r 51 , r 52 , r 53 , r 71 , r 72 , r 73 , r 91 , and r 92  in  FIG. 2E ) and the equivalent resistance of tunnels (r 2 , r 4 , r 6 , and r 8  in  FIG. 2E ) when applying current to the illuminating chamber  45  and the tunnel  47  are properly arranged in the present invention to have the resistance of tunnel greater than that of the chamber, the current predicted to flow through the illuminating chambers  45  would not make a detour along the tunnel  47  so as to make sure that all the illuminating chambers  45  are lighted. Therefore, the present invention not only facilitates the enhancement of fabrication yield of the flat fluorescent lamp but also prevents the abandon of products, which is good for saving cost. In addition, the present invention does not need additional process is particularly welcome to the industry. 
         [0051]    While the embodiments of the present invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the present invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the present invention.