Abstract:
A backlight unit containing one or more light sources and fabrication method are provided. Each light source has a tube with a first bent side connected to a first end and a second bent side connected to a second end. First and second electrodes are disposed on the tube between the bent sides and their corresponding ends. The backlight unit further includes a first plate having oppositely spaced edge regions. Each edge region has holes. A first portion of each light source is disposed above the first plate and a second portion of each light source is disposed below the first plate. The first and second common electrodes are electrically connected to the first and second electrodes disposed on the tube.

Description:
[0001]     This application claims the benefit of priority under 35 U.S.C. § 119 to Korean Patent Application No. 16503/2005, filed on Feb. 28, 2005.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a light source and to a backlight unit minimizing the presence of non-emitting regions.  
         [0004]     2. Description of the Related Art  
         [0005]     A liquid crystal display (LCD) device provides low power consumption and excellent color reproduction. However, because the liquid crystal panel displaying images in a LCD device does not emit light, an LCD device is a non-luminous display device. Accordingly, the LCD device requires a backlight unit disposed under the liquid crystal panel to irradiate light.  
         [0006]     A fluorescent lamp can be used in a backlight unit. A glass tube in the fluorescent lamp is filled with mercury and inert gas, and an inner wall of the glass tube is coated with phosphors. Electrodes are disposed on both ends of the glass tube. Accordingly, when an electric field is applied to the electrodes, electrons are generated. As the electric field increases, electrons are accelerated within the glass tube. The accelerated electrons ionize mercury atoms. Ultraviolet (UV) rays are radiated by the ionized mercury atoms and light is generated through the phosphors.  
         [0007]     The backlight units are classified as edge type backlight units or direct type backlight units depending on the location of the fluorescent lamp relative to the liquid crystal panel. An edge type backlight unit provides light to the side of a liquid crystal panel and is used for smaller LCD devices (e.g., portable phone, PDA, etc.). A direct type backlight unit directly provides light to the bottom of a liquid crystal panel and is used in medium- to large-size LCD devices (e.g., notebook computer, TV, etc.). A direct type backlight unit provides more brightness than an edge type backlight unit.  
         [0008]     Fluorescent lamps may be classified as cold cathode fluorescent lamps (CCFLs) or external electrode fluorescent lamps (EEFLs) depending on location of their electrodes. Electrodes are embedded into the fluorescent lamp of a CCFL, but are disposed in the outside of the fluorescent lamp in an EEFL.  
         [0009]      FIG. 1  is a sectional view of a related art EEFL. In this case, both ends of the glass tube  1  are sealed. First and second electrodes  4   a  and  4   b  are attached around the outer periphery of the glass tube  1  at each end.  
         [0010]     In the EEFL depicted in  FIG. 1 , brightness and efficiency can be optimized by changing the length of the external electrodes depending on the length and diameter of the fluorescent lamp. With a longer EEFL, optimal lengths of the first and second external electrodes  4   a  and  4   b  will also be longer. Moreover, in a larger LCD, EEFLs tend to be longer and the external electrodes  4   a  and  4   b  tend to be lengthened.  
         [0011]     The non-emitting A region corresponding to the EEFL depicted in  FIG. 1  is particularly influenced by the lengths of the external electrodes  4   a  and  4   b  and by the size of the LCD device. Accordingly, as the size of the LCD device increases, there is a greater tendency for the first and second external electrodes  4   a  and  4   b  to be lengthened and for the non-emitting A region to be widened. Driver circuits, various lines, and external electrodes  4   a  and  4   b  are disposed in the non-emitting A regions. The non-emitting A regions are non-display regions, which are unable to display images. Accordingly, as the LCD device becomes larger in size and the non-emitting A regions are widened, the display region is reduced, resulting in decreased use efficiency of the LCD device.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention is directed to a light source and a backlight unit containing the same, which obviate limitations and disadvantages in the related art. Accordingly,  
         [0013]     The present invention provides a light source minimizing non-emitting regions in the backlight unit of an LCD device.  
         [0014]     In one aspect of the present invention, a light source is provided. The light source has a glass tube with a first bent side connected to a first end and a second bent side connected to a second end. First and second electrodes are disposed on the glass tube between the bent sides and their corresponding ends.  
         [0015]     In another aspect, a backlight unit is provided having a first plate containing oppositely spaced edge regions. Each edge region has a plurality of holes. First and second common electrodes are disposed below the first plate. A plurality of light sources are provided, each light source has a glass tube with a first bent side connected to a first end and a second bent side connected to a second end. First and second electrodes are disposed on the glass tube between the bent sides and their corresponding ends. A first portion of each light source is disposed above the first plate and a second portion of each light source is disposed below the first plate. The first and second common electrodes are electrically connected to the first and second electrodes disposed on the glass tubes.  
         [0016]     In another aspect, a method of making a backlight unit includes: providing a backlight unit with a first plate containing oppositely spaced edge regions, each edge region having a plurality of holes; disposing first and second common electrodes below the first plate; and providing the backlight unit with a plurality of light sources in accordance with the present invention; disposing a first portion of each light source is above the first plate and a second portion of each light source below the first plate; and electrically connecting the first and second common electrodes to the first and second electrodes disposed on the glass tubes.  
         [0017]     In a further aspect, a method of preventing non-emitting regions from being determined by a light source in an LCD device includes providing an LCD device with a backlight unit containing light sources in accordance with the present invention and supplying a driving voltage so that a non-emitting region is not determined by the light sources.  
         [0018]     The foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the claimed invention. Advantages, objects, and features of the invention will be apparent from the description which follows. Objectives and advantages of the present invention may be realized or attained using the embodiments exemplified in the specification, claims and appended drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The accompanying drawings illustrate aspects and principles of the present invention.  
         [0020]      FIG. 1  is a sectional view of a related art EEFL;  
         [0021]      FIG. 2  is a sectional view of an EEFL according to an embodiment of the present invention;  
         [0022]      FIG. 3  is a partial sectional view of a backlight unit using the EEFL depicted in  FIG. 2 ;  
         [0023]      FIG. 4  is a sectional view of an EEFL according to another embodiment of the present invention; and  
         [0024]      FIG. 5  is a partial sectional view of a backlight unit using the EEFL depicted in  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     Reference will now be made in detail to preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
         [0026]      FIG. 2  is a sectional view of an EEFL according to an embodiment of the present invention. In  FIG. 2 , the EEFL  110  includes a glass tube  101  and first and second external electrodes  104   a  and  104   b . The glass tube  101  is filled with a discharge gas and an inner wall of the glass tube  101  is coated with phosphor. Each end of the glass tube  101  is bent in a curved C-shape. The first and second external electrodes  104   a  and  104   b  have a predetermined length and are attached to each of the curved C-shaped ends in the glass tube  101 . Except for the region where the external electrodes  104   a  and  104   b  reside, the rest of the glass tube  101  serves as a complete light-emitting region.  
         [0027]      FIG. 3  is a partial sectional view of a direct type backlight unit employing the EEFL depicted in  FIG. 2 . In  FIG. 3 , light emitted from a plurality of EEFLs  110  is directly irradiated in a forward direction. The EEFLs  110  are fixed to a bottom case  111  with edge regions containing a plurality of holes  103  spaced apart at a predetermined distance from one another.  
         [0028]     Toward each end of the bottom case  111 , first and second common electrodes  107  are electrically connected to the first and second electrodes  104   a  and  104   b  in each EEFL  110 . To the extent that the first and second electrodes  104   a  and  104   b  are outside of the bottom case  111  and light can be emitted from the portion of the EEFL tube inside the bottom case  111 , the EEFL tube inside the bottom case fails to produce non-emitting regions.  
         [0029]     A plurality of insertion holders  109  is integrally formed in the bottom case to electrically connect pairs of electrodes toward each end of an EEFL  110 . Each insertion holder  109  has three elastic clips. In each insertion holder  109 , three elastic clips open and close so as to secure the first and second electrodes  104   a  and  104   b  of the EEFL  110 . The EEFLs  110  pass through holes  103  in the bottom case  111  and are connected to the insertion holders  109  of the first and second common electrodes  107  attached to the rear side of the bottom case  111 . Thus, the insertion holders  109  for the first and second common electrodes  107  fix and electrically connect the EEFLs  110 .  
         [0030]     An inverter  113  helps generate a driving voltage for the EEFLs  110 . The inverter  113  is attached to a rear side of the bottom case  111  and is spaced apart from the first and second common electrodes  107  by a predetermined distance. The inverter  113  and the first and second common electrodes  107  are electrically connected by a lamp wire  117 . Accordingly, the driving voltage from the inverter  113  is applied to the first and second common electrodes  107  through the lamp wire  117  and then supplied to the first and second external electrodes  104   a  and  104   b  connected to insertion holders  109 . In this manner, a predetermined light is generated.  
         [0031]     Because the external electrodes  104   a  and  104   b  are thinner than the inverter  113 , the thickness of the backlight unit is not changed, even when the external electrodes  104   a  and  104   b  are disposed on the rear side of the bottom case  111 .  
         [0032]     Since both sides of the EEFL  110  are bent, it may be difficult for the EEFL  110  to pass through the holes  103 . Therefore, any suitable method for passing EEFLs through the bottom case  111  may be used. For example, the bottom case  111  may be divided into a plurality of portions, including divided bottom cases  111  coupled together after passing the EEFLs  110  through holes  103  in divided bottom case  111  portions.  
         [0033]     In  FIG. 3 , supporter sides  115  are attached to edge regions toward each end the bottom case  111  so as to not plug the holes. Reflective plates (not shown) may be provided in the bottom of the bottom case  111  and in the inner side of the supporter sides  115  to reflect light emitted from the EEFLs  110 . The reflective plates make the emitted light travel in a forward direction.  
         [0034]     An optical sheet  119  is spaced from the EEFLs  110  at a predetermined distance. The optical sheet  119  controls emission of light in a forward direction from the EEFLs  110 . Accordingly, the optical sheet  119  may include a diffusion sheet for diffusing light, a prism sheet for concentrating the diffused light to travel in parallel, and a protection sheet for protecting the diffusion sheet and the prism sheet. A panel guide member  105  fixed to the top of the supporter side  115  fixes the optical sheet  119 .  
         [0035]     Since the first and second external electrodes  104   a  and  104   b  of the EEFL  110  are disposed outside of the bottom case  111 , non-emitting regions are not formed from the EEFL  110  disposed inside the bottom case  111 . Accordingly, even though the LCD device may be larger and the first and second external electrodes  104   a  and  104   b  may be longer, non-emitting regions are not formed from EEFLs  110  inside the bottom case  111 . By effectively removing non-emitting regions that would have been formed by the first and second external electrodes  104   a  and  104   b  according to the related art EEFL  1 , display regions are effectively expanded.  
         [0036]     Although a non-emitting B region may not be determined by EEFLs  110  in a backlight unit according to the present invention, non-emitting B regions may be determined by the width of the supporter side  115  and/or the panel guide member  105 . Accordingly, non-emitting regions can be further reduced by narrowing the supporter side  115  and/or the panel guide member  105 .  
         [0037]      FIG. 4  is a sectional view of an EEFL according to another embodiment of the present invention. In  FIG. 4 , the EEFL  210  includes a glass tube  201  and first and second external electrodes  204   a  and  204   b . The glass tube  201  is filled with a discharge gas and an inner wall of the glass tube  201  is coated with phosphor. Each end of the glass tube  201  is bent in a rectangular C-shape. The first and second external electrodes  204   a  and  204   b  have a predetermined length and are attached to each of the rectangular C-shaped ends in the glass tube  201 . Except for the region where the external electrodes  104   a  and  104   b  reside, the rest of the glass tube  101  serves as a complete light-emitting region.  
         [0038]      FIG. 5  is a partial sectional view of a backlight unit employing the EEFL depicted in  FIG. 4 . The backlight unit in  FIG. 5  is similar to the background unit described in  FIG. 3  and may employ similar or comparable elements described therein.  
         [0039]      FIG. 5  depicts an EEFL  210  fixed to a bottom case  211 . The direct type backlight unit depicted in  FIG. 5  includes a plurality of EEFLs  210  spaced apart at a predetermined distance from one another. The EEFL  210  includes a glass tube  201  having an inner wall coated with phosphor. The first and second external electrodes  204   a  and  204   b  are attached to an outside of the glass tube  201  at each end.  
         [0040]     A bottom case  211  includes two edge regions having plurality of holes  203 . Each EEFL  210  passes through a pair of holes  203  in the bottom case  211 . Because the bottom case  211  includes a plurality of paired holes  203 , a plurality of EEFLs  210  can be disposed in the bottom case  211 .  
         [0041]     First and second common electrodes  207  are attached at a rear side toward each end of the bottom case  211 , and are electrically connected to the first and second electrodes  204   a  and  204   b  in each EEFL  210 . A plurality of insertion holders  209  are integrally formed toward each end of the bottom case to electrically connect external electrodes  204   a  and  204   b  with first and second common electrodes  207  corresponding thereto.  
         [0042]     The first and second common electrodes  207  are electrically connected to an inverter  213  by a lamp wire  217 . The inverter  213 , attached to a rear side of the bottom case  211 , is spaced apart from the first and second common electrodes  207 .  
         [0043]     In  FIG. 5 , supporter sides  215  are attached to edge regions toward each end of the bottom case  211  so as to not plug the holes. Reflective plates (not shown) may be provided in the bottom of the bottom case  211  and in the inner side of the supporter sides  215  so as to reflect light emitted from the EEFLs  210 .  
         [0044]     An optical sheet  219  is spaced from the EEFLs  210  at a predetermined distance. The optical sheet  219  controls emission of light in a forward direction from the EEFLs  210 . A panel guide member  205  fixed to the top of the supporter side  215  fixes the optical sheet  219 .  
         [0045]     Since the first and second external electrodes  204   a  and  204   b  of the EEFL  210  are disposed outside of the bottom case  211 , non-emitting regions are not formed from the glass tube  201  of EEFL  210  disposed inside the bottom case  211 . Accordingly, even though the LCD device may be larger and the first and second external electrodes  204   a  and  204   b  may be longer, non-emitting regions are not formed from EEFLs  210  inside the bottom case  211 . By effectively removing non-emitting regions that might have been formed by the first and second external electrodes  204   a  and  204   b  according to a related art EEFL  1 , display regions are effectively expanded.  
         [0046]     Although a non-emitting C region may not be determined by EEFLs  210  in a backlight unit according to the present invention, non-emitting C regions may be determined by the width of the supporter side  215  and/or the panel guide member  205 . Accordingly, non-emitting regions can be further reduced by narrowing the supporter side  215  and/or the panel guide member  205 .  
         [0047]     In accordance with the present invention, the display region of the LCD device can be effectively expanded by precluding external electrodes from forming non-emitting regions. In particular, the present invention minimizes non-emitting regions by bending the EEFL and disposing the first and second external electrodes of the EEFL outside of the bottom case.  
         [0048]     In related art EEFLs, electrode lengths increase and non-emitting regions widen as an LCD device becomes larger in size. When using the EEFLs of the present invention, however, display regions are not reduced when an LCD device increases in size. Accordingly, the display region improvement accompanying the present invention results in improved use efficiency in an LCD device.  
         [0049]     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, the present invention intends to cover such modifications and variations provided they come within the scope of the specification and the appended claims and their equivalents.