Patent Document

CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority under 35 USC § 119 to Korean Patent Application No. 2004-67751 filed on Aug. 27, 2004, the content of which is herein incorporated by reference in its entirety for all purposes.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a backlight assembly and a liquid crystal display (LCD) apparatus having the backlight assembly. More particularly, the present invention relates to a backlight assembly that is capable of reducing the leakage current of a lamp, and an LCD apparatus having the backlight assembly.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, there has been much technical progress made with information-processing devices. As a part of this progress, much progress has also been made to display apparatuses that interface the data that is processed by the information-processing devices to convert the data to a user-recognized format.  
         [0006]     An LCD apparatus, which is known for advantages such as light weight, small size, full-color, high resolution, etc., has been widely used in display apparatuses. The LCD apparatus converts variations of optical characteristics of a liquid crystal (LC) cell into visual variations. Since the LCD apparatus does not generate light on its own, a backlight assembly is employed in the LCD apparatus to act as the light source. The LCD apparatus displays an image by using the light from the backlight assembly.  
         [0007]     The backlight assembly is classified as either a direct illumination type or an edge illumination type in accordance with positions of the light source. The direct illumination type backlight assembly includes a light source positioned under an LCD panel. Light emitted from the light source is directly irradiated onto an entire surface of the LCD panel. Since the direct illumination type backlight assembly utilizes more light sources than those of the edge illumination type backlight assembly, the direct illumination type backlight assembly generally has a higher luminance than the edge illumination type backlight assembly.  
         [0008]     The direct illumination type LCD apparatus includes an LCD panel displaying an image and a backlight assembly providing the LCD panel with light.  
         [0009]      FIG. 1  is a partial cross sectional view illustrating a conventional backlight assembly.  
         [0010]     Referring to  FIG. 1 , a conventional backlight assembly includes a lamp  10 , a light-diffusing member  30  placed over the lamp  10 , a bottom chassis  50  located under the lamp  10 , and a reflection plate  20  on the bottom chassis  50 . Electrons move in the lamp  10  so that a current flows in the lamp  10 . Meanwhile, since the bottom chassis  50  includes a conductive material, the lamp  10  and the bottom chassis  50  form a capacitor so that a leakage current is generated from the lamp  10 . In general, the capacitance of the capacitor is inversely proportional to the distance between electrodes.  
         [0011]      FIG. 15  is a graph illustrating luminance variations with respect to a length of the lamp from a first end to which a high voltage is applied to a second end to which a low voltage is applied. In  FIG. 15 , line I represents the luminance of the lamp  10  when a distance between the lamp  10  and the bottom chassis  50  is about one millimeter. Line II indicates the luminance of the lamp  10  when a distance between the lamp  10  and the bottom chassis  50  is about three millimeters. Line III represents the luminance of the lamp  10  when a distance between the lamp  10  and the bottom chassis  50  is about five millimeters. Line IV indicates the luminance of a separate lamp that is not assembled with a bottom chassis. As shown, the first ends of each of the lamps  10  have luminance levels higher than the first end of the separate lamp (IV). This is caused by increasing a current that is applied to the first ends of the lamps  10  to obtain a tubular current of about six milliamperes at the second ends of the lamps.  
         [0012]     As shown in  FIG. 15 , the leakage current, which is indicated by the luminance drop with the length of the lamp, is reduced proportionally to an increase in the distance L 1  between the lamp  10  and the bottom chassis  50 . Thus, to obtain substantially the same tubular current at the second end of the lamp  10  as at the first end of the lamp  10 , the initially applied high voltage is proportionally increased, as is the distance L 1  between the lamp  10  and the bottom chassis  50 . Thus, the distance L 1  between the lamp  10  and the bottom chassis  50  is an important parameter for controlling the leakage current.  
         [0013]     To prevent or reduce the leakage current of the lamp  10 , the distance L 1  between the lamp  10  and the bottom chassis  50  is increased. However, the lengthening of the distance L 1  causes an increase of a thickness of the LCD apparatus. Thus, a method that allows a reduction in the lamp current leakage without undesirably increasing the thickness of the LCD apparatus is desired.  
       SUMMARY OF THE INVENTION  
       [0014]     The present invention provides a backlight assembly that is capable of reducing a leakage current of a lamp. The present invention also provides an LCD apparatus having the above-mentioned backlight assembly.  
         [0015]     A backlight assembly in accordance with one aspect of the present invention includes a lamp and a metal container. The lamp generates light. The metal container receives the lamp. The metal container includes a bottom plate having a first region and a second region. The lamp is disposed over the first region. A distance between a virtual plane, which is parallel to the bottom plate and passes through a center of the lamp, and the first region of the bottom plate is larger than a distance between the virtual plane and the second region of the bottom plate.  
         [0016]     A backlight assembly in accordance with another aspect of the present invention includes a plurality of lamps emitting a first light. An optical member converts the first light into a second light having enhanced optical characteristics. A receiving member receives the lamps and the optical member. The receiving member has protrusions that are aligned with the lamps. The protrusions protrude away from the lamps.  
         [0017]     A backlight assembly in accordance with still another aspect of the present invention includes a plurality of lamps emitting a first light. An optical member converts the first light into a second light having enhanced optical characteristics. A reflection plate is positioned under the lamps. The reflection plate reflects the first light toward the optical member. A bottom chassis is placed under the reflection plate to receive the reflection plate and the lamps. The bottom chassis includes a bottom face and sidewalls extending from edges of the bottom face. Also, the bottom chassis has recesses that are formed at surface portions of the bottom chassis that are aligned with each of the lamps.  
         [0018]     A liquid crystal display apparatus in accordance with still another aspect of the present invention includes a plurality of lamps emitting a first light. An optical member converts the first light into a second light having enhanced optical characteristics. A receiving member receives the lamps and the optical member. The receiving member has protrusions corresponding to the lamps. The protrusions protrude away from the lamps. A liquid crystal display panel assembly displays an image using the second light. A top chassis is combined with the receiving member to fix the liquid crystal display panel assembly to the receiving member.  
         [0019]     A liquid crystal display apparatus in accordance with yet still another aspect of the present invention includes a plurality of lamps emitting a first light. An optical member converts the first light into a second light having enhanced optical characteristics. A reflection plate is positioned under the lamps to reflect the first light to the optical member. A bottom chassis is placed under the reflection plate to receive the reflection plate and the lamps. The bottom chassis includes a bottom face and sidewalls extending from edges of the bottom face. Also, the bottom chassis has recesses that are formed at surface portions of the bottom chassis that are aligned with each of the lamps. A liquid crystal display panel assembly displays an image using the second light. A top chassis is combined with the bottom chassis to fix the liquid crystal display panel assembly to the bottom chassis.  
         [0020]     According to the present invention, the distance between the lamps and the receiving member is increased without also increasing the thickness of the LCD apparatus. As a result, the capacitance of the capacitor that forms between the lamps and the receiving member is maintained at a low level and the leakage current of the backlight assembly may be decreased. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The above and other features and advantages of the present invention will become more apparent by describing in detailed exemplary embodiments thereof with reference to the accompanying drawings, in which:  
         [0022]      FIG. 1  is a partial cross sectional view illustrating a conventional backlight assembly;  
         [0023]      FIG. 2  is a partial cross sectional view illustrating a backlight assembly in accordance with an exemplary embodiment of the present invention;  
         [0024]      FIG. 3A  is an enlarged cross sectional view illustrating a portion “A” in  FIG. 2  in accordance with an exemplary embodiment of the present invention;  
         [0025]      FIG. 3B  is an enlarged cross sectional view illustrating a portion “A” in  FIG. 2  in accordance with another exemplary embodiment of the present invention;  
         [0026]      FIG. 4A  is an enlarged cross sectional view illustrating a portion “A” in  FIG. 2  in accordance with still another exemplary embodiment of the present invention;  
         [0027]      FIG. 4B  is an enlarged cross sectional view illustrating a portion “A” in  FIG. 2  in accordance with still another exemplary embodiment of the present invention;  
         [0028]      FIG. 5  is a partial cross sectional view illustrating a backlight assembly in accordance with another exemplary embodiment of the present invention;  
         [0029]      FIG. 6A  is an enlarged cross sectional view illustrating a portion “B” in  FIG. 2  in accordance with an exemplary embodiment of the present invention;  
         [0030]      FIG. 6B  is an enlarged cross sectional view illustrating a portion “B” in  FIG. 2  in accordance with another exemplary embodiment of the present invention;  
         [0031]      FIG. 7A  is an enlarged cross sectional view illustrating a portion “B” in  FIG. 2  in accordance with still another exemplary embodiment of the present invention;  
         [0032]      FIG. 7B  is an enlarged cross sectional view illustrating a portion “B” in  FIG. 2  in accordance with still another exemplary embodiment of the present invention;  
         [0033]      FIG. 8  is an exploded perspective view illustrating an LCD apparatus in accordance with an exemplary embodiment of the present invention;  
         [0034]      FIG. 9A  is a cross sectional view taken along a line III-III′ in  FIG. 8 .  
         [0035]      FIG. 9B  is a cross sectional view illustrating an LCD apparatus in accordance with another exemplary embodiment of the present invention;  
         [0036]      FIG. 10A  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0037]      FIG. 10B  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0038]      FIG. 11A  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0039]      FIG. 11B  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0040]      FIG. 12A  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0041]      FIG. 12B  is a cross sectional view illustrating an LCD apparatus in accordance with still another exemplary embodiment of the present invention;  
         [0042]      FIG. 13  is a perspective view illustrating a bottom chassis of an LCD apparatus in  FIG. 8 ;  
         [0043]      FIG. 14  is a perspective view illustrating a bottom chassis of an LCD apparatus in accordance with an exemplary embodiment of the present invention; and  
         [0044]      FIG. 15  is a graph illustrating luminance variations in accordance with a length of a lamp of the backlight assembly in  FIG. 1   
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0045]     The present invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity.  
         [0046]     It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.  
         [0047]     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.  
         [0048]     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.  
         [0049]     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.  
         [0050]     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.  
         [0051]      FIG. 2  is a partial cross sectional view illustrating a backlight assembly in accordance with an exemplary embodiment of the present invention,  FIGS. 3A, 3B ,  4 A, and  4 B are enlarged cross sectional views illustrating the portion “A” of  FIG. 2  in accordance with different exemplary embodiments of the present invention.  
         [0052]     Referring to  FIG. 2 , a backlight assembly  300  includes a lamp  310 , a reflection plate  320 , a light diffusing member  330  and a bottom chassis  350 . The light-diffusing member  330  is positioned over the lamp  310 . The bottom chassis  350  is placed under the lamp  310 . Also, the reflection plate  320  is placed on the bottom chassis  350 .  
         [0053]      FIG. 3A  is an enlarged cross sectional view illustrating a portion “A” in  FIG. 2 .  
         [0054]     Referring to  FIG. 3A , the reflection plate  320  includes a non-conductive material. Also, the bottom chassis  350  has a protrusion  355  downwardly protruding from the bottom chassis  350 . That is, the protrusion  355  protrudes in a direction opposite to the lamp  310 . Here, the protrusion  355  is vertically aligned with the lamp  310 .  
         [0055]     In the backlight assembly shown in  FIG. 3A , the protrusion  355  has a quadrangular shape. Here, the reflection plate  320  includes a non-conductive material and the reflection plate  320  does not function as an electrode of a capacitor. Thus, the distance between the electrodes of the capacitor corresponds to a distance R between a center point C of the lamp  310  and an upper face of the protrusion  355 . Also, the protrusion  355  has a width L 2  corresponding to a distance between two points M and M′. Here, the points M and M′ correspond to points between the bottom chassis  350  and the protrusion  355 . Meanwhile, when the number of the lamp  310  is at least two, the number of the protrusion  355  matches the number of the lamps  310 .  
         [0056]     Alternatively, as shown in  FIG. 3B , a protrusion  357  may have an arch shape. Here, the protrusion  357  has a point K on an upper face of the protrusion  357  that is located farthest from the center point C of each of the lamps  310 . Also, the point K of the protrusion  357  and the center point C of the lamp  310  are positioned on substantially the same vertical line I-I′. To guarantee a sufficient distance R between the lamp  310  and the protrusion  357 , the protrusion  357  having the arch shape has the distance R as a curvature radius from the center point C of the lamps  310 . Each of the protrusions  357  has a width corresponding to a distance between two intersection points at which parts of a circle intersects the bottom chassis  350 . The partial circle has a radius between the point K of the protrusions  357  and the center point C of the lamps  310 . The point K of the protrusions  357  is located farthest from the center point C of each of the lamps  310 .  
         [0057]      FIG. 4A  is an embodiment in which the reflection plate  320  includes a conductive material and functions as the electrode of the capacitor. Thus, a protrusion  325  having a quadrangular shape downwardly protrudes from the reflection plate  320 . The protrusion  325  of the reflection plate  320  makes contact with the protrusion  355  having the quadrangular shape of the bottom chassis  350 .  
         [0058]     Alternatively, as shown in  FIG. 4B , an arch-shaped protrusion  327  downwardly protrudes from the reflection plate  320 . The protrusion  327  of the reflection plate  320  makes contact with the protrusion  357 , which forms an arch-shaped portion of the bottom chassis  350 .  
         [0059]      FIG. 5  is a partial cross sectional view illustrating a backlight assembly in accordance with an exemplary embodiment of the present invention, and is substantially the same as the backlight assembly of  FIG. 2  except for the region indicated as “B.”  FIGS. 6A, 6B ,  7 A, and  7 B are enlarged cross sectional views illustrating the portion “B” of  FIG. 2  in accordance with different exemplary embodiments of the present invention.  
         [0060]     Referring to  FIG. 5 , a backlight assembly  400  includes a lamp  410 , a reflection plate  420 , a light diffusing member  430  and a bottom chassis  450 . The light-diffusing member  430  is positioned over the lamp  410 . The bottom chassis  450  is placed under the lamp  410 . Also, the reflection plate  420  is placed on the bottom chassis  450 .  
         [0061]      FIG. 6A  is an enlarged cross sectional view illustrating the portion “B” in  FIG. 5  in accordance with an exemplary embodiment of the present invention.  
         [0062]     In the embodiment of  FIG. 6A , the reflection plate  420  includes a non-conductive material. The bottom chassis  450  has a recess  455  that is formed at a surface portion of the bottom chassis  450  facing the lamp  410 . In the present embodiment, the recess  455  has a quadrangular shape. Here, since the reflection plate  420  includes a non-conductive material, the reflection plate  420  does not function as an electrode of a capacitor. Thus, the distance between the electrodes of the capacitor corresponds to a distance R between a center point C of the lamp  410  and an upper face of the recess  455  (e.g., point N). The recess  455  has a width L 3  corresponding to a distance between two curved points M and M′. Here, the curved points M and M′ lie at the interface between the bottom chassis  450  and the recess  455 . Meanwhile, when the number of the lamp  410  is at least two, the number of the recess  455  matches the number of the lamps  410 .  
         [0063]     Alternatively, as shown in  FIG. 6B , a recess  457  may have an arch shape. Here, to guarantee a sufficient distance R between the lamp  410  and the recess  457 , the recess  457  having the arch shape has the distance R as a curvature radius. Each of the recesses  457  has a width corresponding to a distance between two intersection points at which a partial circle intersects the bottom chassis  450 . The partial circle has a radius between the point K of the recesses  457  and the center point C of the lamps  410 . The point K of the recesses  457  is located farthest from the center point C of each of the lamps  410 . The point K of the recess  457  and the center point C of the lamp  410  are positioned on a substantially same vertical line II-II′.  
         [0064]     In the embodiment of  FIG. 7A , the reflection plate  420  includes a conductive material and functions as the electrode of the capacitor. Thus, a protrusion  425  having a quadrangular shape downwardly protrudes from the reflection plate  420 . The protrusion  425  of the reflection plate  420  makes contact with the upper face of the recess  455  having the quadrangular shape of the bottom chassis  450 .  
         [0065]     Alternatively, as shown in  FIG. 7B , a protrusion  427  having an arch shape downwardly protrudes from the reflection plate  420 . The protrusion  427  of the reflection plate  420  makes contact with the arch-shaped recess forming the upper face of the bottom chassis  450 .  
         [0066]      FIG. 8  is an exploded perspective view illustrating an LCD apparatus in accordance with an exemplary embodiment of the present invention.  FIGS. 9A, 9B ,  10 A, and  10 B are cross sectional views of different exemplary embodiments taken along a line III-III′ in  FIG. 8 .  FIG. 13  is a perspective view illustrating a bottom chassis of an LCD apparatus in  FIG. 8 , and  FIG. 14  is a perspective view illustrating a bottom chassis of an LCD apparatus in accordance with an exemplary embodiment of the present invention.  
         [0067]     Referring to FIGS.  8  to  10 B, an LCD apparatus  1000  includes an LCD panel assembly  200  displaying an image, and a backlight assembly  300  providing a light to the LCD panel assembly  200 .  
         [0068]     The LCD panel assembly  200  includes an LCD panel  210 , a first printed circuit board (PCB)  220 , a second PCB  230 , a first tape carrier package (TCP)  240  electrically connected to the first PCB  220 , and a second TCP  250  electrically connected to the second PCB  230 . The backlight assembly  300  further includes a middle chassis  550  and a top chassis  500 .  
         [0069]     The LCD panel  210  includes a thin film transistor (TFT) substrate  211 , a color filter substrate  213  facing the TFT substrate  211 , and an LC layer (not shown) interposed between the TFT substrate  211  and the color filter substrate  213 .  
         [0070]     The TFT substrate  211  includes a glass substrate on which TFTs are arranged in a matrix pattern. The TFT substrate  211  includes source terminals electrically connected to data lines and gate terminals electrically connected to gate lines. Pixel electrodes including transparent ITO are formed on drain terminals.  
         [0071]     The color filter substrate  213  is positioned over the TFT substrate  211 . The color filter substrate  213  has at least one color pixel member including a red pixel portion, a green pixel portion and a blue pixel portion. When the light rays pass through the color pixel member, the color of the light may change. The color pixel member may be formed in the color filter substrate  213  by a thin film process. A front face of the color filter substrate  213  is covered with a common electrode including a transparent conductive material such as ITO.  
         [0072]     The first and second PCBs  220  and  230  are connected to the first and second TCP  240  and  250 , respectively. The first and second PCBs  220  and  230  receive external image signals and then provide the gate line and the data line with drive signals. In order to operate the LCD device  1000 , the first and second PCBs  220  and  230  generate gate and data drive signals, respectively. In addition, the first and second PCBs  220  and  230  generate a plurality of timing signals enabling the gate drive signal and the data drive signal to be applied to the gate line and the data line at a desired timing. The gate drive signal and the data drive signal may be applied to the gate line and the data line through the first TCPs  240  and  250 , respectively.  
         [0073]     Here, the backlight assembly  300  includes the bottom chassis having the protrusion  355  in  FIG. 13  or the protrusion  357  in  FIG. 14 . The backlight assembly  300  is illustrated in detail with reference to FIGS.  2  to  4 B. Thus, any further illustrations with respect to the backlight assembly  300  are omitted herein.  
         [0074]      FIGS. 11A, 11B ,  12 A, and  12 B are cross sectional views illustrating an LCD apparatus in accordance with various exemplary embodiments of the present invention,.  
         [0075]     The LCD apparatus of  FIGS. 11A, 11B ,  12 A, and  12 B includes elements substantially identical to those of the LCD apparatus in  FIG. 8  except for a bottom chassis and a reflection plate. Thus, same reference numerals refer to the same elements and any further illustrations with respect to the same elements will be omitted.  
         [0076]     The LCD apparatus  1100  in  FIG. 11A  includes the bottom chassis  450  having the quadrangular recess  455 . The LCD apparatus in  FIG. 11B  includes the bottom chassis  450  having the arch recess  457 . The LCD apparatus  1100  in  FIG. 12A  includes the bottom chassis  450  having the quadrangular recess  455  and the reflection plate  420  having the quadrangular protrusion  425 . Also, the LCD apparatus in  FIG. 12B  includes the bottom chassis  450  having the arch recess  457  and the reflection plate  420  having the arch protrusion  427 .  
         [0077]     According to the present invention, a receiving member has the protrusion or the recess aligned with the lamps so that the distance between the receiving member and the lamps may be lengthened. As a result, a capacitor may not be formed between the receiving member and the lamps and a leakage current of the lamps may be reduced.  
         [0078]     Having described the exemplary embodiments of the present invention and its advantages, it is noted that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by appended claims.

Technology Category: 3