Abstract:
A liquid crystal display device includes a liquid crystal panel including a first substrate, a second substrate, and a liquid crystal layer disposed therebetween; and a backlight assembly including a plurality of lamps disposed in a first direction to provide light to the liquid crystal panel, and a plurality of lamp guides to fix the plurality of lamps, at least one of the lamp guides having a guide plate and a plurality of lamp fixing parts, wherein a first one of the lamp fixing parts is disposed on the guide plate at a lamp fixing part axis in a second direction perpendicular to the first direction, and wherein a second one of the lamp fixing parts is disposed on the guide plate space apart from the lamp fixing part axis.

Description:
[0001]     This application claims the benefit of Korean Patent Application No. 77771/2004 filed in Korea on Sep. 30, 2004, which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a backlight assembly and a liquid crystal display device having the same, and more particularly, to a backlight assembly with uniform brightness and a liquid crystal display device having the same.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, liquid crystal display (LCD) devices have become smaller and lighter with more powerful performance. While the widely used cathode ray tube (CRT) technology has advantages in performance and price, CRTs have disadvantages in slimness and portability.  
         [0006]     In contrast, LCD technology has advantages such as slim profile, light weight and low power consumption, thereby solving the disadvantages of CRT technology. As a result, LCDs are widely used in almost all information processing devices using a display.  
         [0007]     Backlight assemblies used for light sources in LCDs can be classified into an edge type backlight assemblies and direct type backlight assemblies according to their cylindrical lamp arrangement. An edge type backlight assembly has a lamp unit installed on the side of a light guide panel for guiding light. The lamp unit includes a lamp to emit light, lamp holders inserted on both sides of the lamp to protect the lamp, and a lamp reflection plate. The lamp reflection plate covers circumferential surface of the lamp with its side inserted on the side of the light guide panel to reflect light from the lamp to the light guide panel.  
         [0008]     Accordingly, the edge type backlight assembly having the lamp unit installed on the side(s) of the light guide panel is usually applied to relatively small-sized LCDs, such as monitors of laptop or desktop computers. The edge type backlight assembly has good light uniformity, high durability, and slim profile.  
         [0009]     Meanwhile, the direct type backlight assembly has been developed typically for 20-inch LCD displays or larger. Here, a plurality of lamps is aligned on the bottom of a diffusion plate to directly illuminate light on a front side of an LCD panel. The direct type backlight assembly is widely used for a large-sized LCD displays that require high brightness because light utilization of a direct type backlight assembly is higher than that of an edge type backlight assembly.  
         [0010]      FIG. 1  is an exploded perspective view of a related art direct type backlight assembly LCD. As shown in  FIG. 1 , a related art direct type LCD includes a liquid crystal panel  105  and a backlight assembly. The liquid crystal panel  105  includes a bottom substrate with a plurality of pixels arranged in a matrix form, a top substrate with R, G, B color filter layers and a black matrix, and a liquid crystal layer interposed between the top and bottom substrates. The backlight assembly provides light to the liquid crystal panel  105 .  
         [0011]     The backlight assembly includes a plurality of lamps  113  for emitting light toward the bottom of the liquid crystal panel  105 , a lamp holder  111  for fixing the plurality of lamps  113  with a predetermined distance, optical sheets  107 , a diffusion plate  108  disposed between the liquid crystal panel  105  and the lamps  113 , support frames  110   a  and  110   b  for fixing the optical sheets  107  and the diffusion plate  108  at both sides, and a reflection plate  117  disposed on the bottom of the lamps  113 . Two lamps  113  form a pair, and each respective pair of lamps  113  is fixed by a lamp guide  109  with a predetermined distance. Additionally, the reflection plate  117  is attached to the inside of a bottom cover  120 .  
         [0012]     That is, the liquid crystal panel  105 , the optical sheet  107 , the diffusion plate  108 , the support frames  110 A and  110 B, the lamps  113 , and the reflection plate  117  are stacked in the bottom cover  120 . Thereafter, a top case  101  is mounted to protect the stacked parts. An inverter  123  for supplying a voltage is mounted on a rear side of the bottom cover  120 , and an inverter cover shield  124  is mounted on the inverter  123 . A cover shield  121  prevents static electricity.  
         [0013]      FIG. 2  is a partial perspective view of the lamps  113  fixed by the lamp guide  109  according to a related art. As shown in  FIG. 2 , the lamps  113  are mounted on the inside of a bottom cover. The lamps  113  are fixed by a lamp guide  109  in pairs. The lamp guide  109  includes a guide plate  109   a  and two lamp fixing parts  109   b , and each pair of the lamps is respectively fixed by the lamp part  109   b . The lamp guide  109  is mounted on the reflection plate  117  in a line and plays a role in holding the lamps when an external impact or vibration is applied.  
         [0014]      FIG. 3  is a plan view of a related art lamp guide  109 . As shown in  FIG. 3 , the lamp guide  109  includes the guide plate  109   a  and the lamp fixing part  109   b , and the lamp fixing part  109   b  is disposed on both edges of the guide plate  109   a . More specifically, the lamp fixing part  109   b  is vertically disposed on a central axis of the guide plate  109   a . In the structure of the lamp guide  109 , brightness deterioration in a region of the lamp guide  109  does not occur due to characteristics of light such as diffusion, reflection, refraction, and diffraction if there is an enough distance between the lamp and the diffusion plate.  
         [0015]     However, as the LCD becomes small-sized, light weight and slim in profile, brightness deterioration occurs in a region of the lamp guide  109  due to a close distance between the lamp and the diffusion plate. Specifically, since brightness deterioration severely occurs in the region of the lamp fixing part  109   b , a black line defect appears along with the lamp guide  109 . Therefore, the picture quality is deteriorated characterized by a non-uniform brightness over the liquid crystal panel.  
       SUMMARY OF THE INVENTION  
       [0016]     Accordingly, the present invention is directed to a backlight assembly and a liquid crystal display device having the same that substantially obviate one or more problems due to limitations and disadvantages of the related art.  
         [0017]     An object of the present invention is to provide a backlight assembly with uniform brightness over an entire region of a liquid crystal display panel by preventing brightness deterioration due to a lamp guide.  
         [0018]     Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned from practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
         [0019]     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device comprises a liquid crystal panel including a first substrate, a second substrate, and a liquid crystal layer disposed therebetween; and a backlight assembly including a plurality of lamps disposed in a first direction to provide light to the liquid crystal panel, and a plurality of lamp guides to fix the plurality of lamps, at least one of the lamp guides having a guide plate and a plurality of lamp fixing parts, wherein a first one of the lamp fixing parts is disposed on the guide plate at a lamp fixing part axis in a second direction perpendicular to the first direction, and wherein a second one of the lamp fixing parts is disposed on the guide plate space apart from the lamp fixing part axis.  
         [0020]     In another aspect, a backlight assembly comprises a plurality of lamps; an optical sheet and a diffusion plate disposed on the plurality of lamps; a reflection plate disposed on a side of the plurality of lamps opposite the diffusion plate; and a lamp guide to fix the plurality of lamps, the lamp guide including a guide plate, and a plurality of lamp fixing parts formed on the guide plate such that adjacent lamp fixing parts are shifted with respect to each other in a direction parallel to the orientation of the plurality of lamps.  
         [0021]     In another aspect, a backlight assembly comprises a plurality of lamps; an optical sheet and a diffusion plate disposed on the plurality of lamps; a reflection plate disposed on a side of the plurality of lamps opposite the diffusion plate; and a lamp guide having a guide plate slantly disposed at a predetermined angle to fix the plurality of lamps, and a plurality of lamp fixing parts formed on the guide plate.  
         [0022]     In another aspect, a liquid crystal display device comprises a liquid crystal panel including a first substrate, a second substrate, and a liquid crystal layer disposed therebetween; and a backlight assembly including a plurality of lamps disposed in a horizontal direction to provide light to the liquid crystal panel, and a plurality of lamp guides to fix the plurality of lamps, each lamp guide having a guide plate and a plurality of lamp fixing parts, wherein adjacent ones of the lamp fixing parts are horizontally shifted with respect to each other.  
         [0023]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:  
         [0025]      FIG. 1  is an exploded perspective view of a direct type backlight assembly according to the related art;  
         [0026]      FIG. 2  is a partial perspective view of lamps fixed by a lamp guide according to the related art;  
         [0027]      FIG. 3  is a plan view of a lamp guide according to the related art;  
         [0028]      FIG. 4  is a perspective view of a liquid crystal display (LCD) device according to an exemplary embodiment of the present invention;  
         [0029]      FIG. 5  is an enlarged view of region A in the exemplary LCD device of  FIG. 4 ;  
         [0030]      FIG. 6  is a plan view of a lamp guide according to an exemplary embodiment of the present invention; and  
         [0031]      FIGS. 7 and 8  are plan views of a lamp guide according to other exemplary embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]     Reference will now be made in detail to the 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.  
         [0033]      FIG. 4  is a perspective view of a liquid crystal display (LCD) device according to an exemplary embodiment of the present invention, and  FIG. 5  is an enlarged view of region in  FIG. 4 . As shown in  FIGS. 4 and 5 , the LCD device includes a liquid crystal panel  205  and a backlight assembly. The liquid crystal panel  205  includes a bottom substrate with a plurality of pixels, a top substrate with R, G, B color filter layers, and a liquid crystal layer between the two substrates. A backlight assembly is mounted with a lamp guide  209  to provide light to the liquid crystal panel  205 .  
         [0034]     The backlight assembly includes a plurality of optical sheets  207 , a diffusion plate  208 , a plurality of lamps  213 , and a reflection plate  217 . Here, the reflection plate  217  is mounted on a bottom cover  220 , and the lamps  213  are disposed inside the bottom cover  220  at a predetermined distance from the reflection plate  217 . The lamps  213  are mounted on power terminals  203   a  and  203   b  disposed on the both sides of the bottom cover  220 . Additionally, the power terminals  203   a  and  203   b  are respectively fixed by support frames  210   a  and  210   b . Moreover, three lamps  213  form a set, and each set of lamps is fixed by a corresponding lamp guide  209 . The lamp guide  209  plays an important role in arranging each lamp  231  in a set with an equal distance between the lamps  231 .  
         [0035]     As shown in  FIG. 5 , the lamp guide  209  includes a guide plate  209   a  and three lamp fixing parts  209   b  on the guide plate  209   a . Additionally, a diffusion plate support part  230  is formed projecting from the guide plate  209   a , for example, between the lamp fixing parts  209   b  to maintain the separation between the lamps  213  and the diffusion plate  208 . Specifically, the lamp fixing parts  209   b  are disposed on a left side, a center, and a right side with respect to a central axis of the guide plate  209   a . Consequently, the lamp brightness deteriorated by the lamp fixing part  209   b  is compensated by adjacent lamps  213 . Here, more than two lamp fixing parts  209   b  can be formed on the lamp guide  209 .  
         [0036]      FIG. 6  is a plan view illustrating a structure of a lamp guide according to an embodiment of the present invention. As shown in  FIG. 6 , a lamp guide  209  fixing lamps with a predetermined equal distance between the lamps includes three lamp fixing parts  209   b  on a rectangular guide plate  209   a . While three lamp fixing parts  209   b  are shown, two lamp fixing parts  209   b  can be formed on the lamp guide  209 . Also, more than three lamp fixing parts  209   b  can be formed on the lamp guide  209 .  
         [0037]     In  FIG. 6 , the guide plate  209   a  is perpendicular to lamps  213  fixed and arranged by the lamp fixing part  209   b  with an equal distance. The lamp fixing parts  209   b  on the guide plate  209   a  are formed on left, middle, and right, respectively, with respect to a central axis perpendicular to the guide plate  209   a . Consequently, when light is emitted from lamps fixed by the lamp fixing parts  209   b , deterioration of brightness can be substantially prevented in a region of the lamp fixing parts  209   b.    
         [0038]     As shown in  FIG. 6 , among the three lamp fixing parts  209   b , a middle lamp fixing part  209   b  is formed on a central axis, and the other lamp fixing parts  209   b  are formed on a left side and a right side of the central axis, respectively. Alternatively, the middle fixing part  209   b  can be formed to the left or the right of the central axis, and the other lamp fixing parts  209   b  can be formed on the central axis.  
         [0039]     Accordingly, since the lamp fixing parts  209   b  of the related art are aligned on the central axis, a brightness deterioration occurs. However, according to the present invention, the brightness deterioration can be prevented because the lamp fixing parts  209   b  on the lamp guide are formed on the central axis, or a right or a left side of the central axis, respectively.  
         [0040]     To prevent brightness deterioration, the lamp fixing parts  209   b  are formed non-aligned with respect to the central axis of the guide plate  209   a . Consequently, the brightness deterioration in a region of the middle lamp fixing part  209   b  is compensated from adjacent lamps fixed by the other lamp fixing parts  209   b . That is, the light from lamps  213  fixed by the off-centered lamp fixing parts  209   b  are diffused and reflected on a region of the centered lamp fixing parts  209   b  to compensate for the brightness deterioration. Similarly, the brightness deterioration of the off-centered lamps is compensated by the light from adjacent lamps fixed by the centered lamp fixing part  209   b.    
         [0041]     In accordance with the present invention, uniform brightness can be obtained without a black line defect because the brightness deterioration caused by the lamp fixing parts  209   b  of the lamp guide  209  can be compensated from adjacent lamps. Accordingly, the deterioration of the brightness in a dark region where the light is screened by the lamp fixing part  209   b  can be substantially prevented by applying the lamp guide  209  of the present invention.  
         [0042]      FIGS. 7 and 8  are plan views of a lamp guide according to other exemplary embodiments of the present invention.  
         [0043]     Lamp fixing parts  209   b  are formed in a central region of a lamp guide plate  209   a  in  FIG. 7 , but the lamp guide plate  209   a  is formed with a predetermined angle in relation to a central axis. Consequently, brightness compensation can be obtained from lamps  213  fixed by each lamp fixing part  209   b . That is, a central axis is defined parallel to the lamp fixing parts  209   b  on the guide plate  209   a . As such, the lamp fixing parts  209   b  except the lamp fixing part  209   b  in the bottom of the guide plate  209   a  is off-centered with respect to the central axis. However, the central axis is still perpendicular to the lamps fixed by the lamp fixing part  209   b.    
         [0044]     The brightness deterioration of the lamp fixing part  209   b  can be substantially prevented by the adjacent lamps because only one lamp fixing part  209   b  is aligned on the central axis perpendicular to the lamps fixed by the lamp fixing part  209   b . That is, uniform brightness can be obtained through a structure in which brightness deterioration caused by the lamp fixing parts  209   b  can be compensated by adjacent lamps.  
         [0045]     More than two lamp fixing parts  209   a  can be formed on the lamp guide  209  having the guide plate  209   a  slanted with a predetermined angle. Even though the number of the lamp fixing parts  209   b  increases, only one lamp fixing part  209   b  is provided on the central axis so that the brightness compensation can be obtained.  
         [0046]     Even though a lamp guide  209  illustrated in  FIG. 8  is somewhat similar to that illustrated in  FIG. 6 , the lamp fixing parts  209   b  in  FIG. 8  are formed not to be on the central axis of the guide plate  209   a . In this structure, when the central axis is parallelly displaced, there are two lamp fixing parts  209   b  on the central axis but brightness deterioration does not occur due to the distance between these two lamp fixing parts  209   b  as well as the lamp  213  disposed between these two lamp fixing parts  209   b.    
         [0047]     As described in detail above, brightness deterioration caused from a region of the lamp guide in the backlight assembly can be substantially prevented by changing the positions of the lamp fixing parts on the lamp guide or the structure of the lamp guide. Consequently, uniform brightness can be obtained in the backlight assembly and the liquid crystal display device.  
         [0048]     It will be apparent to those skilled in the art that various modifications and variations can be made in the backlight assembly and the liquid crystal display device having the same of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.