Patent Publication Number: US-2011050557-A1

Title: Backlight unit and display apparatus including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §119 and 35 U.S.C. §365 to U.S. Provisional Patent Application Ser. No. 61/237,841 filed on Aug. 28, 2009 and Korean Patent Application No. 10-2009-0080654 filed on Aug. 28, 2009, the subject matter of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the present disclosure may relate to a backlight unit and/or a display apparatus that includes a backlight unit. 
     2. Background 
     There is a need for diverse forms of display apparatuses. Accordingly, various display apparatuses such as liquid crystal display devices (LCDs), plasma display panels (PDPs), electro luminescent displays (ELDs), and/or vacuum fluorescent displays (VFDs) have become commercialized. 
     An LCD may have a liquid crystal panel that includes a liquid crystal layer, a thin film transistor (TFT) substrate, and a color filter substrate facing the TFT substrate with the liquid crystal layer therebetween. Such a liquid crystal panel, having no light source, may use light provided by a backlight unit to display an image. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Arrangements and embodiments may be described in detail with reference to the following drawings in which like reference numerals refer to like elements and wherein: 
         FIG. 1  is an exploded perspective view illustrating a display apparatus according to an embodiment; 
         FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 ; 
         FIG. 3  is an enlarged view illustrating a portion Q of  FIG. 2 ; 
         FIG. 4  is a schematic view illustrating a rear surface of a display module according to an embodiment; 
         FIG. 5  is an exploded perspective view illustrating an optical assembly of  FIG. 1 ; 
         FIG. 6  is a plan view illustrating a backlight unit according to an embodiment; 
         FIG. 7  is a plan view illustrating a light guide plate and arrayed light sources of  FIG. 5 ; 
         FIG. 8  is a bottom view illustrating a lower surface of a light guide plate (of  FIG. 5 ); 
         FIG. 9  is a cross-sectional view taken along line B-B of  FIGS. 7 and 8 ; 
         FIG. 10  is a graph illustrating density of diffusion optical elements along line B-B of  FIGS. 7 and 8 ; 
         FIG. 11  is a graph illustrating density of additional optical elements along line C-C of  FIGS. 7 and 8L ; 
         FIG. 12  is a graph illustrating a combination of density of diffusion optical elements and density of the additional optical elements along line D-D of  FIGS. 7 and 8 ; 
         FIG. 13  is a cross-sectional view illustrating a backlight unit according to an embodiment; 
         FIG. 14  is a perspective view illustrating a light guide plate of  FIG. 13 ; 
         FIG. 15  is a plan view illustrating a backlight unit according to an embodiment; 
         FIG. 16  is an enlarged view illustrating a portion S of  FIG. 15 ; 
         FIG. 17  is a cross-sectional view of a light guide plate according to an embodiment; and 
         FIG. 18  is a perspective view illustrating a bottom surface of a light guide plate according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference may now be made in detail to arrangements and embodiments, examples of which may be illustrated in the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as being 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 concept of the disclosure to those skilled in the art. In the drawings, shapes and sizes of elements may be exaggerated for clarity. 
       FIG. 1  is an exploded perspective view illustrating a display apparatus  1  according to an embodiment. Other embodiments and configurations may also be provided. 
       FIG. 1  shows that the display apparatus  1  includes a display module  200 , a front cover  300  and a back cover  400  that surround the display module  200  and a fixing member  500  (or attachment member) for fixing or attaching the display module  200  to at least one of the front cover  300  or the back cover  400 . 
     A portion of the fixing member  500  may be fixed to the front cover  300  through a coupling member such as a screw, and another portion of the fixing member  500  may support the display module  200  with respect to the front cover  300  so that the display module  200  can be fixed with respect to the front cover  300 . 
     Although the fixing member  500  is shown as having an elongated plate shape, the display module  200  may be fixed or attached to the front cover  300  or the back cover  400  through a coupling member without the fixing member  500 . 
       FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 . 
     As shown in  FIG. 2 , the display module  200  may include a display panel  210  for displaying an image, a backlight unit  100  to emit light to the display panel  210 , a bottom cover  110  providing a lower appearance of the display module  200 , a panel supporter  240  supporting the display panel  210  from the lower side, and a top cover  230  supporting the display panel  210  from the upper side and constituting a border of the display module  200 . 
     The bottom cover  110  may have a box shape with an open upper surface to receive the backlight unit  100 . A side of the bottom cover  110  may be fixed or attached to a side of the top cover  230 . For example, a coupling member such as a screw may pass through a side surface of the display module  200 , or more specifically, through a side where the bottom cover  110  overlaps the top cover  230  to fix or attach the bottom cover  110  and the top cover  230 . 
     A rear side of the bottom cover  110  may be provided with at least one driving substrate  250  to drive the display module  200  with a signal transmitted from the outside (e.g. an image signal). 
     The driving substrate  250  may be, for example, a driving part of an image panel and/or a backlight unit such as a timing controller, a T-con board, a power supply device, or a main printed circuit board (PCB), and may be fixed or attached to the rear surface of the bottom cover  110  through an adhesive member or a coupling member such as a screw. 
     The display panel  210  may include a lower substrate  211  and an upper substrate  212  attached to each other with a constant cell gap, and a liquid crystal layer may be provided between the lower substrate  211  and the upper substrate  212 . The lower substrate  211  may be provided with a plurality of gate lines and a plurality of data lines crossing the gate lines. Thin film transistors (TFTs) may be provided in crossing areas of the gate lines and the data lines. 
     The upper substrate  212  may be provided with color filters, although the structure of the display panel  210  is not limited thereto. For example, the lower substrate  211  may include color filters as well as TFTs. In addition, the structure of the display panel  210  may vary according to a method of driving the liquid crystal layer. 
     Although not shown, an edge of the display panel  210  may be provided with a gate driving printed circuit board (PCB) to supply scan signals to the gate lines, and a data driving PCB to supply data signals to the data lines. One of the upper side or the lower side of the display panel  210  may be provided with a polarized light filter (not shown). 
     The backlight unit  100  may include a plurality of optical assemblies  10  each including a light source  13 , a substrate  14 , a light guide plate  15 , a reflecting member  17 , a fixing bracket  18  and an optical sheet  220  provided between the display panel  210  and the optical assemblies  10 . 
     The optical sheet  220  may be removed, although embodiments are not limited thereto. The optical sheet  220  may include at least one of a spread sheet (not shown) or a prism sheet (not shown). 
     The spread sheet may uniformly spread light emitted from the light guide plate  15 , and the spread light may be collected to the display panel  210  through the prism sheet. The prism sheet may include one or more illumination enhancement films and at least one of a horizontal prism sheet or a vertical prism sheet may be selectively provided. The types and number of optical sheets may vary. 
     The optical assemblies  10  may be provided under the display panel  210  and the optical sheet  220  to emit light upward to the display panel  210 . 
       FIG. 3  is an enlarged view illustrating a portion Q of  FIG. 2 .  FIG. 4  is a schematic view illustrating a rear surface of the display module  200 . 
     As shown in  FIGS. 3 and 4 , the display apparatus  1  may include at least one cable  19  that connects the substrate  14  to the driving substrate  250  to supply a driving signal or power to the substrate  14 . 
     For example, the cable  19  may be a flexible flat cable (FFC). A first end of the cable  19  may be connected to a connector  145  provided to the lower surface of the substrate  14 , and a second end of the cable  19  may be connected to a connection part  251  of the driving substrate  250 . 
     The bottom cover  110  may be provided with assembly fixing parts  112  for fixing or attaching the optical assemblies  10 . Protrusions  111 , protruding to the front side of the display module  200 , may be adjacent to the optical assemblies  10  and have shapes corresponding to the light guide panels  15  of the optical assemblies  10 . 
     The protrusions  111  may be inclined at a predetermined angle, corresponding to a lower surface of the light guide plate  15 , which is inclined upward at a predetermined angle. The protrusions  111  may be recessed a predetermined depth forward from the rear surface of the bottom cover  110 . 
     The bottom cover  110  may be provided with at least one hole  113  through which the cable  19  passes. The hole  113  may be provided at the assembly fixing part  112 . 
     When a plurality of holes  113  are provided, the holes  113  may be arrayed at positions where the respective optical assemblies  10  connected with the cables  19  are provided at the bottom cover  110 . 
     That is, the holes  113  may be arrayed in an up-and-down direction of the bottom cover  110  on the basis of  FIG. 4 . 
     The driving substrate  250  connected to the second end of the cable  19  may be provided in the rear portion of the bottom cover  110 , and may extend in the up-and-down direction in which the holes  113  are arrayed. 
     A configuration of the optical assembly  10  may now be further described. 
       FIG. 5  is an exploded perspective view illustrating the optical assembly  10 . 
     The optical assemblies  10  may be arrayed with at least one portion fixed or attached to the bottom cover  110 , and each of the optical assemblies  10  may include the light source  13 , the substrate  14 , the light guide plate  15 , the reflecting member  17  and the fixing bracket  18 . 
     A plurality of light sources  13  may be provided. The light sources  13  may be provided in a left-and-right direction (x-axis direction) at a side surface of the light guide plate  15 . Thus, light emitted from the light sources  13  may be incident to the side surface of the light guide plate  15 . 
     The light sources  13  may include a plurality of light emitting diodes (LED). 
     The LED may be a side illumination-type LED that is configured to laterally emit light. 
     The LEDs may be provided on the upper surface of the substrate  14 , and may emit light having a wavelength ranging from about 430 nm to 480 nm. A fluorescent material may be applied on a light emitting surface of the LED to transmit light emitted from the LED. 
     Referring  FIGS. 3 and 5 , also the LEDs may emit light (L) for example, with an predetermined orientation angle (Φ) of about 90° or greater with respect to a first direction (y-axis direction). 
     The color LED may include at least one of a red LED, a blue LED, and a green LED, and the arrangement and light type of the LEDs may vary. 
     The light sources  13  may be mounted to a substrate body  141  of the substrate  14  longitudinally extending in the left-and-right direction (x-axis direction), and provided on the rear side of the substrate body  141  in a back-and-forth direction (y-axis direction). 
     The back-and-forth direction (y-axis direction) may hereafter be referred to as the first direction, and the upward direction (z-axis direction) may hereafter be referred to as a second direction, and the left-and-right direction (x-axis direction) may hereafter be referred to as a third direction. 
     The light sources  13  may be mounted to a rear area k 2  of the substrate body  141  in the back-and-forth direction, a front area k 1  may be provided in front of the rear area k 2 , and the front area k 1  may be greater than the rear area k 2 . 
     The front area k 1  may have a support space with a predetermined size for supporting at least one of the light guide plate  15  and at least one of the reflecting member  17 . In addition, as the size of the rear area k 2 , having just a width for mounting the light sources  13 , is decreased, a bezel area of the display module  200  where the rear area k 2  may be provided (i.e., the width of the border of the display module  200  may decrease). Accordingly, the width of the rear area k 2  may be minimized. 
     The forward direction of the back-and-forth direction (y-axis direction) may be the direction (+y-axis direction) of light emitted from the light sources  13 , and the rearward direction thereof may be the opposite direction (−y-axis direction) to the forward direction. 
     The first direction (y-axis direction) and the third direction (x-axis direction) may be perpendicular to each other. The substrate  14  may extend in the third direction, and the light sources  13  may be arrayed in the third direction on the substrate  14 . 
     The substrate body  141  may include through holes  142  through which coupling members  51  pass. The through holes  142  may be provided between the light sources  13 . The through holes  142  may be provided in the left and right sides of the substrate body  141  and in the middle of the substrate body  141  with the four light sources  13  on each lateral side of the middle. 
     The coupling members  51  may pass through the fixing bracket  18 , the reflecting member  17  and the substrate  14  to coordinate the configuration of the optical assembly  10  and to fix or attach the optical assembly  10  to the bottom cover  110 . 
     The light guide plate  15  may be transparent. For example, the light guide plate  15  may be formed of one of acryl-based resin such as polymethyl methacrylate (PMMA), polyethylene terephthlate (PET), poly carbonate (PC), and polyethylene naphthalate (PEN). The light guide plate  15  may be formed using an extrusion molding method. 
     The light guide plate  15  may diffuse light emitted from the light source  13  to guide the light upward. 
     More particularly, light incident forward (y-axis direction) from the light source  13  (i.e., laterally from the light source  13 ) may be refracted and diffused upward in the second direction (z-axis direction), (i.e., to the display panel  210 ) by the light guide plate  15 . The lower surface of the light guide plate  15  may be inclined upward in the forward direction to efficiently emit laterally incident light upward. 
     At least one of the lower surface of the light guide plate  15  may be placed on and supported by the front area k 1  of the substrate body  141 . 
     The light guide plate  15  may include a light incident part  15   b  having a light incident surface  151  facing the light source  13 , and a light emitting part  15   a  extending forward from the light incident part  15   b.    
     The rear side of the light guide plate  15  where the light incident surface  151  is provided may be referred to as a first side, and a front end  156  of the light guide plate  15  may be referred to as a second side. 
     A plurality of streaks of light incident from the light sources  13  into the light guide plate  15  through the light incident surface  151  may be mixed into a single streak of light through the light incident part  15   b , and then the single streak of light may be spread through the light emitting part  15   a  and emitted to the upper side of the light guide plate  15 . 
     A first side of the light emitting part  15   a  may be connected to a second side of the light incident part  15   b . Light mixed in the light incident part  15   b  may be emitted upward (i.e., through an upper surface  153  of the light emitting part  15   a ). 
     A vertical height h 2  of a light emitting surface of the light source  13  emitting light may be substantially equal to or less than a vertical height h 1  of the light incident surface  151  of the light incident part  15   b.    
     When the height h 2  of the light sources  13  is greater than the vertical height h 1  of the light incident surface  151 , a portion of light emitted from the light emitting surfaces of the light sources  13  may not be incident to the light incident surface  151 , but may be leaked out. 
     Since the light sources  13  emit light, for example, with an predetermined orientation angle of about 90° or greater with respect to the first direction, the height h 1  of the light incident surface  151  may be greater than the height h 2  of the light sources  13 . 
     However, when the height h 1  of the light incident surface  151  is greater than two times the height h 2  of the light sources  13 , light leak prevention and light efficiency increase may not be achieved. Rather, excessive light diffusion may decrease light efficiency. 
     Thus, the height h 1  of the light incident surface  151  may be equal to the height h 2  of the light sources  13 , or the height h 1  may be less than two times the height h 2  of the light sources  13 . 
     The light incident part  15   b  may extend a predetermined distance (d 1 ) in the forward direction (y-axis direction), and the light emitting part  15   a  may extend a predetermined distance d 2  in the forward direction from the light incident part  15   b . Thus, the back-and-forth length of the light guide plate  15  including the light incident part  15   b  and the light emitting part  15   a  may be equal to a sum d 3  of the back-and-forth lengths of the light incident part  15   b  and the light emitting part  15   a.    
     A portion connecting the light incident part  15   b  to the light emitting part  15   a  may include a raised portion (or step part) due to height difference between an upper surface  152  of the light incident part  15   b  and the upper surface  153  of the light emitting part  15   a.    
     The height of the upper surface  152  of the light incident part  15   b  may be less than the height of the upper surface  153  of the light emitting part  15   a  so that the raised portion (or stair part) has a height h 5 . 
     At least one fixing bracket  18  may be in contact with the upper surface  152  of the light incident part  15   b  to press the upper surface  152  of the light incident part  15   b  downward (i.e., to the substrate body  141  and the bottom cover  110 ) so as to firmly fix or attach the light guide plate  15  to the bottom cover  110 . 
     The height h 5  of the raised portion (or stair part) may be greater than or equal to a height h 4  of the front end (also referred to as second end)  156  of the light incident part  15   b.    
     As described above, the lower surface of the light guide plate  15  may be inclined upward from the light incident part  15   b  to the light emitting part  15   a.    
     The thickness of the light guide plate  15  may gradually decrease from the light incident part  15   b  to the light emitting part  15   a.    
     When the height h 4  of the second end  156  is greater than the height h 5  of the raised portion (or stair part), the inclination angle of the lower surface of the light guide plate  15  may be decreased. This may reduce reflectance of the light guide plate  15 , thus decreasing the upward light emitting efficiency of the light emitting part  15   a.    
     In addition, light interference may occur in which light that does not pass through the upper surface  153  of the light emitting part  15   a  may be leaked into the adjacent light guide plate  15  through the second end  156 . Thus, the height h 4  of the second end  156  of the light emitting part  15   a  may be less than or equal to the height h 5  of the raised portion (or stair part). 
     When the height h 1  of the light incident surface  151  is less than the height h 5  of the raised portion (or stair part), light traveling from the light incident part  15   b  to the light emitting part  15   a  may be excessively diffused, so that a dark region is generated on the first side of the light emitting part  15   a  contacting the light incident part  15   b . Thus, the height h 1  of the light incident surface  151  may be greater than or equal to the height h 5  of the raised portion (or stair part). 
     From the relationship between the height h 1  of the light incident surface  151  and the height h 5  of the raised portion (or stair part), and from the relationship between the height h 5  of the raised portion (or stair part) and the height h 4  of the second end  156  of the light emitting part  15   a , the height h 1  of the light incident surface  151  may be equal to or greater than the height h 4  of the second end  156 . 
     The vertical height h 1  of the light incident surface  151  of the light incident part  15   b  may be less than a vertical height h 3  of a first end of the light emitting part  15   a  connected to the light incident part  15   b.    
     Thus, in the state where streaks of light incident from the light sources  13  into the light guide plate  15  through the light incident part  15   b  are mixed into a single streak of light, when the single streak of light travels to the first end of the light emitting part  15   a  having the greater cross section than that of the light incident surface  151 , the single streak of light may be spread more widely. 
     The vertical height h 4  of the front end  156  of the light emitting part  15   a  may be less than the vertical height h 1  of the light incident surface  151  of the light incident part  15   b , and less than the vertical height h 3  of the first end of the light emitting part  15   a.    
     Thus, the vertical cross section of the light emitting part  15   a  of the light guide plate  15  where light incident through the light incident surface  151  is emitted upward may be decreased, so as to improve upward emission of light. 
     The lower surface of the light guide plate  15  may be provided with the reflecting member  17  configured to reflect light upward. 
     The reflecting member  17  may include a reflecting sheet having a predetermined reflectance or greater. A portion of the reflecting member  17  contacting the lower surface of the light guide plate  15  may be greater than the lower surface of the light guide plate  15  in left-and-right width and back-and-forth width. 
     The reflecting member  17  may be greater in area than the lower surface of the light guide plate  15 . Thus, when the light guide plate  15  is provided to the lower surface of the light guide plate  15 , the light guide plate  15  may protrude from the left, right and front sides of the light guide plate  15 . 
     Fixing holes  171 , through which the light sources  13  respectively pass, may be provided in one side of the reflecting member  17  (i.e., on the rear side of the light guide plate  15 ) to fix or attach the reflecting member  17  to the substrate  14 . The fixing holes  171 , passing through the reflecting member  17 , may have sizes corresponding to the light sources  13 . Through holes  172  may be provided between the fixing holes  171  at positions corresponding to the through holes  142  of the substrate  14 . 
     The fixing bracket  18  may be provided at the first side of the light guide plate  15  (i.e., at the upper surface of the light incident part  15   b ) so as to fix or attach the light guide plate  15  to the bottom cover  110 . The fixing bracket  18  may press at least one portion of the light guide plate  15  to the bottom cover  110  to fix or attach the light guide plate  15 . 
     The fixing bracket  18  may be a cover member that covers at least one portion of the light incident part  15   b . The fixing bracket  18  may also be referred to as an attachment member. 
     The fixing bracket  18  may include a frame structure with a bent upper portion, and may be formed of synthetic resin through injection molding, or of metal. The bent upper portion of the fixing bracket  18  may be provided with through holes  181  through which the coupling members  51  pass. 
     When the fixing bracket  18  is fixed or attached to the bottom cover  110  through the coupling members  51 , the light sources  13  may be provided in the fixing bracket  18 , thus preventing light from being emitted from the light source  13  to the outside without passing through the light guide plate  15 . 
     When a first one of the optical assemblies  10  is adjacent to a second one of the optical assemblies  10 , at least one portion of the light guide plate  15  of the first optical assembly  10  may overlap, from the upper side, the fixing bracket  18  of the second optical assembly  10 . 
     That is, at least one portion of the light emitting part  15   a  of the optical assembly  10  may be provided above the fixing bracket  18  and the light incident part  15   b  of the adjacent optical assembly  10  so that the optical assemblies  10  overlap each other. 
     The display panel  210  may have a plurality of division areas corresponding to the light guide plates  15 . The intensity of light emitted from the light guide plate  15  of the optical assembly  10  (i.e., the brightness of light emitted from the light guide plate  15 ) may be adjusted according to a gray peak value or a color coordinate signal of the corresponding division area so as to adjust the brightness of the display panel  210 . 
       FIG. 6  is a plan view illustrating the backlight unit  100 . 
     In  FIG. 6 , the fixing bracket  18  for fixing or attaching the light guide plate  15  to the bottom cover  110  is omitted. 
     As shown in  FIG. 6 , the optical assemblies  10  of the backlight unit  100  may be arrayed in an N×M matrix, where N is the number of rows arrayed along the y-axis direction, M is the number of columns arrayed along the x-axis direction, and M and N are natural numbers equal to 2 or greater. Each of the optical assemblies  10  may include the light sources  13  and the light guide plate  15 . 
     For example, the number of rows of the light guide plates  15  arrayed along the y-axis direction is N, where N is 2 or greater. The second end  156  of the light emitting part  15   a  of the light guide plate  15  in a K th  row (K is one of 1 to N−1) of the N rows may be provided above the light incident part  15   b  of the light guide plate  15  in a K+1 th  row so that the two adjacent light guide plates  15  can overlap each other in at least one portion. 
     The number of the light guide plate  15  arrayed in the longitudinal direction of the substrate  14  (i.e., the x-axis direction) may be M. 
     Although the single substrate  14  corresponds to the single light guide plate  15 , the substrate  14  may correspond to the light guide plates  15 . 
     Each of the optical assemblies  10  may be driven in an edge-type backlight manner and operate as a single light source. In this state, the optical assemblies  10  may be arrayed in a direct-type backlight manner to constitute the backlight unit  100 . Thus, the case that the LEDs are detected as a hot spot on a screen may be prevented, and thickness of the light guide plate  15  and number of optical films may be reduced to achieve slimness of the backlight unit  100 . 
     For example, the backlight unit  100  may include the nine optical assemblies  10  (M 1  to M 9 ) in a 3×3 matrix as shown in  FIG. 6 , although embodiments are not limited thereto. Thus, the matrix of the optical assemblies  10  may vary according to a screen size of a display apparatus. 
     In the current embodiment, the back-and-forth length (y-axis direction) of the light guide plate  15  is less than the left-and-right length (x-axis direction) in which the light sources  13  are arrayed. 
     Each of the optical assemblies  10  may be manufactured as a discrete assembly, and the optical assemblies  10  may be adjacent to each other to constitute a module-type backlight unit that is a backlight member configured to provide light to the display panel  210 . 
     The backlight unit  100  may be driven using an entire driving method or a local driving method such as a local dimming method and an impulsive method. The method of driving the LEDs may vary according to a circuit design, although embodiments are not limited. A color contrast ratio may increase, and a bright region and a dark region may be sharply expressed on a screen, thereby improving image quality. 
     The backlight unit  100  may operate by a plurality of division driving areas corresponding to the light guide plates  15 , and brightness of the division driving area may be linked with brightness corresponding to an image signal. Thus, the brightness in a dark portion of an image may decrease, and the brightness in a bright portion of the image may increase so as to improve a contrast ratio and sharpness of the image. 
     For example, a portion of the optical assemblies  10  (M 1  to M 9 ) may be independently driven to emit light. The light sources  13  respectively of the optical assemblies  10  may be independently controlled. 
     An area of the display panel  210  corresponding to one of the optical assemblies  10  or one of the light guide plates  15  may be divided into two or more blocks, and the display panel  210  and the backlight unit  100  may be dividedly driven in a block unit. 
     The optical assemblies  10  may be spaced predetermined distances d 4  and d 5  from each other as shown in  FIG. 6 . For example, the light guide plates  15  adjacent in the left-and-right direction (x-axis direction) may be spaced the distance d 4  from each other, and the light guide plates  15  adjacent in the back-and-forth direction (y-axis direction) may be spaced the distance d 5  from each other. 
     That is, in the state where edges of the light guide plates  15  of the adjacent optical assemblies  10  are in contact with each other and when light emitted from the light sources  13  thermally expands the light guide plates  15 , the light guide plates  15  may be out of the coordinated positions, and/or may be deformed by contact stress therebetween. 
     When the edges of the light guide plates  15  are in contact with each other, luminance of the edges having a high light emittance may be greater than the luminance of the rest of the light guide plates  15 . Thus, a mesh of bright lines corresponding to the edges of the light guide plates  15  may occur on a display screen. 
     Thus, the adjacent optical assemblies  10  may be spaced the distance d 4  in the left-and-right direction (x-axis direction) and the distance d 5  in the back-and-forth direction (y-axis direction) from each other so as to space the edges of the adjacent optical assemblies  10  apart from each other. 
     When the distances d 4  and d 5  are excessively increased, luminance of the distances d 4  and d 5  may be less than that of the rest of the light guide plate  15 . Thus, distances d 4  and d 5  between the light guide plates  15  may be within a predetermined range. 
     Accordingly, the lateral distance d 4  of the light guide plate  15  may range from about 0.1 to 5 mm, and the longitudinal distance d 5  of the light guide plate  15  may range from about 0.1 to 7 mm. 
     In this case, since the distance between the front edge of the light guide plate  15  and the light sources  13  is greater than the distance between the left edge or the right edge of the light guide plate  15  and the light sources  13 , luminance of the front edge may be less than luminance of the left and right edges. 
     The distance d 5  of the light guide plate  15  may be equal to or less than the distance d 4 . 
     Additional optical element regions and a diffusion optical element region may be provided on the lower surface (hereafter denoted  154 ) of the light guide plate  15 . The diffusion optical element region may be provided with a plurality of optical elements  155  ( FIG. 9 ) that diffuse light emitted from the light sources  13  to guide the light upward. The optical elements may be protrusions, recesses, scattering mechanisms or dimples, for example. The optical elements may also be considered patterns.  FIG. 9  shows protrusions as the optical elements. 
     A configuration of the optical elements  155 , the diffusion optical element region and the additional optical element regions may now be described. 
       FIG. 7  is a plan view illustrating the light guide plate  15  of  FIG. 5 , and the arrayed light sources  13  of  FIG. 5 .  FIG. 8  is a bottom view illustrating the lower surface  154  of the light guide plate  15  of  FIG. 5 .  FIG. 9  is a cross-sectional view taken along line B-B of  FIGS. 7 and 8 . Other embodiments and configurations may also be provided. 
     In  FIG. 7 , only the light guide plate  15  and the light sources  13  are shown, and structures such as the fixing bracket  18  are omitted. 
     Referring to  FIGS. 7 and 8 , at least one portion of the light guide plate  15  is provided on the front area k 1  of the substrate  14 . 
     The light sources  13  may be arrayed in the left-and-right direction (x-axis direction) and mounted or provided to the substrate  14  as described above. 
     More particularly, the light sources  13  may be spaced a first distance w 1  and a second distance w 2 , which is greater than the first distance w 1 , from each other, so as to emit light rays L to the light incident part  15   b.    
     The through hole  142  may be provided in a region corresponding to the second distance w 2 . A first light source group G 1  and a second light source group G 2  may each includes the four light sources  13  that are spaced the first distance w 1  from each other. The first light source group G 1  is spaced from the second light source group G 2  by the second distance w 2 . 
     A light source group of one of the optical assemblies  10  may be spaced the second distance w 2  from a light source group of the adjacent optical assembly  10 . 
     When the second distance w 2  between the first light source group G 1  and the second light source group G 2  is different from the first distance w 1  between the light sources  13  in one of the first light group G 1  or the second light source group G 2 , light spread may be uneven in the light guide plate  15 . 
     Thus, the light guide plate  15  may include the diffusion optical element region (hereafter denoted R 1 ) and the additional optical element regions (hereafter denoted R 2 ) that partially overlap the diffusion optical element region R 1  so as to make light spread uniform. 
     Referring to  FIGS. 7 to 9 , the lower surface  154  of the light guide plate  15  may include the diffusion optical element region R 1  and the additional optical element regions R 2  so as to efficiently emit light, incident to the light guide plate  15 , to the upper side of the light guide plate  15 . 
     The lower surface  154  of the light guide plate  15  may be provided with the optical elements  155 , such as protrusions and/or recesses. For example, the optical elements  155  may be formed in relief or intaglio on the lower surface  154  of the light guide plate  15 . 
     The optical elements  155  may be formed in relief or intaglio on the lower surface  154  through a process such as a laser cutting process. 
     For example, the optical elements  155  may have dimple shapes or line shapes extending in the left-and-right direction of the light guide plate  15 . The optical elements  155  may be spaced a distance d 7  from each other. The density of the optical elements  155  provided to the lower surface  154  may be controlled by adjusting the distance d 7 . 
     The optical elements  155  may improve light diffusion for emitting light upward from the light guide plate  15 , thus minimizing optical loss and increasing luminance of the light guide plate  15 . 
     As the density of the optical elements  155  increases, light diffusion may be improved. 
     The density of the optical elements  155  may denote a number or distances of the optical elements  155  per a unit area of the lower surface of the light guide plate  15 . 
     Thus, when one portion of the light guide plate  15  is different from another portion thereof in luminance and the amount of light, the density of the optical elements  155  may be adjusted to make the entire luminance of the light guide plate  15  uniform. 
     Although the optical elements  155  may be formed in relief or intaglio directly on the lower surface  154 , the optical elements  155  may be provided to the lower surface  154  through printing or deposition, or a discrete pattern sheet including the optical elements  155  may be provided to the lower surface  154 . 
     The lower surface  154  may include the diffusion optical element region R 1  and the additional optical element regions R 2  that divide a region provided with the optical elements  155 . 
     The diffusion optical element region R 1  and the diffusion optical element region R 2  may be provided on the lower surface  154  of the light guide plate  15 , and more particularly in the region of the lower surface  154  adjacent to the light emitting part  15   a.    
     For example, the diffusion optical element region R 1  may be the entire region of the lower surface  154  of the light guide plate  15 . The diffusion optical element region R 1  may range, e.g., from the rear edge of the light guide plate  15 , that is, from the rear edge where the light incident surface  151  of the light incident part  15   b  is provided to the front edge of the light guide plate  15 . 
     Although the diffusion optical element region R 1  may be the entire region of the lower surface  154 , the diffusion optical element region R 1  may be provided to only one portion of the lower surface  154  where the light emitting part  15   a  substantially emitting light upward is provided. 
     The optical elements  155  provided to the diffusion optical element region R 1  may be referred to as diffusion optical elements (or patterns). The density of the optical elements  155  provided to the diffusion optical element region R 1  may increase from the rear side of the light guide plate  15  to the front side thereof. 
     Light emitted from the light sources  13  spaced the second distance w 2  may be greater in area per light intensity than light emitted from the light sources  13  spaced the first distance w 1 . Thus, the region of the light guide plate  15  adjacent to the region corresponding to the second distance w 2  may have a low luminance value. 
     The lower surface  154  of the light guide plate  15  contacting the region corresponding to the second distance w 2  may be provided with the diffusion optical element region R 2  that overlaps at least a portion of the diffusion optical element region R 1 . 
     The additional optical element regions R 2  may be provided to the left end, right end and middle of the light guide plate  15 . The additional optical element regions R 2  provided to the left end and the right end of the light guide plate  15  may have shapes that are formed by removing a portion from the diffusion optical element region R 2  provided to the middle of the light guide plate  15 . 
     The diffusion optical element region R 2  provided in the middle of the light guide plate  15  may now be further described. 
     The diffusion optical element region R 2  may extend along a distance d 6  from the rear edge of the lower surface  154  to the front side of the light guide plate  15 . The distance d 6  along which the additional optical element regions R 2  extends may be equal to or greater than the distance d 1  along which the light incident part  15   b  extends, and may be less than the sum d 3  along which the light guide plate  15  extends. 
     In the same manner of the diffusion optical element region R 1 , the optical elements  155  may be provided in the additional optical element regions R 2 . The optical elements  155  provided in the additional optical element regions R 2  may be referred to as additional optical elements (or additional patterns). 
     That is, when the diffusion optical element region R 1  overlaps at least one portion of the diffusion optical element region R 2 , the density of the optical elements  155  provided in the overlapped portion may be equal to a sum of the density of the diffusion optical elements of the diffusion optical element region R 1  and the density of the additional optical elements of the diffusion optical element region R 2 . 
     A width w 3  in the left-and-right direction at the rear end of the diffusion optical element region R 2  (i.e., at the portion adjacent to the light sources  13 ) may be equal to or greater than the second distance w 2 , and may be equal to or less than a distance w 5  between centers of the two light sources  13  provided symmetrically with respect to the second distance w 2 . 
     The width w 3  of the diffusion optical element region R 2  may denote a width of the diffusion optical element region R 2  provided in the third direction. 
     The diffusion optical element region R 2  may increase in left-and-right width to the front side (i.e., in the first direction). A left-and-right width w 4  of the front end of the diffusion optical element region R 2  (i.e., of the portion of the diffusion optical element region R 2  farthest from the light sources  13 ) may be equal to or greater than the distance w 5  provided between the centers of the two light sources  13 . 
     That is, the diffusion optical element region R 2  may have a trapezoid shape that increases in width (in the third direction) from the rear side to the front side (i.e., in the first direction). The width of the portion of the diffusion optical element region R 2  adjacent to the light sources  13  may be equal to or greater than the second distance w 2  between the light sources  13 . 
     When the width w 3  of the portion of the diffusion optical element region R 2  nearest to the light sources  13  is extremely decreased to a point, the diffusion optical element region R 2  may have a triangle shape that increases in left-and-right width from the rear side to the front side. 
     The density of the additional optical elements provided in the diffusion optical element region R 2  may increase from the rear end (corresponding to the width w 3 ) to the front side. 
     Density variations of the diffusion optical elements and the additional optical elements respectively provided to the diffusion optical element region R 1  and the diffusion optical element region R 2  may now be described. 
       FIG. 10  is a graph illustrating density of the diffusion optical elements along line B-B of  FIGS. 7 and 8 .  FIG. 11  is a graph illustrating density of additional optical elements along line C-C of  FIGS. 7 and 8 .  FIG. 12  is a graph illustrating a combination of density of the diffusion optical elements and density of the additional optical elements along line D-D of  FIGS. 7 and 8 . 
       FIG. 10  is a graph illustrating optical element density in a region provided with only diffusion optical element region R 1 , and  FIG. 12  is a graph illustrating optical element density in a region provided with diffusion optical element region R 1  and diffusion optical element region R 2 . 
     Referring to  FIGS. 7 ,  8  and  10 , a diffusion optical element density distribution curve C 1  of the diffusion optical elements provided to the diffusion optical element region R 1  may gradually increase from the rear edge of the lower surface  154 , and may sharply increase in slope at a position where the light incident part  15   b  is in contact with the light emitting part  15   a  along the distance d 1 . 
     This is because the light emitting part  15   a  substantially emits light to the upper side of the light guide plate  15 , and thus increase in light diffusion efficiency may be required at the light emitting part  15   a.    
     The diffusion optical element density distribution curve C 1  may become a non-linear curve that gradually decreases in slope, and the diffusion optical element density distribution curve C 1  may have a diffusion optical element maximum density value P 1  at a position corresponding to the sum d 3  of the light guide plate  15 . 
     This is because as light emitted from the light sources  13  may pass through the light guide plate  15  toward the front side of the light guide plate  15 , the light may be diffused to be decreased in brightness per area (i.e., in luminance per area). Thus, light may be maximally diffused at the front end of the light guide plate  15  along the sum d 3 . 
     Referring to  FIGS. 7 ,  8  and  11 , an additional optical element density distribution curve C 2  of the additional optical elements provided to the diffusion optical element region R 2  may be plotted. 
     The additional optical element density distribution curve C 2  may have an additional optical element maximum density value P 2  at the rear end of the light guide plate  15 , and may decrease non-linearly in density value to have zero at a position where the diffusion optical element region R 2  ends along the distance d 6 . 
     The additional optical element maximum density value P 2  may be less than the diffusion optical element maximum density value P 1 . 
     In the rear end of the light guide plate  15  where the diffusion optical element region R 2  starts, a portion of the rear end contacting the region corresponding to the second distance w 2  may be less than the other portions of the rear end in luminance, and light spread in the light guide plate  15  may be increased forward. Thus, the region of the light guide plate  15  where the diffusion optical element region R 2  is provided may increase in luminance forward. 
     The additional optical element density distribution curve C 2  of the diffusion optical element region R 2  may decrease in optical element density forward. 
     A total optical element density distribution curve c 3  of the lower surface  154  in the state where the diffusion optical element region R 1  overlaps the diffusion optical element region R 2  may now be described. 
     Referring to  FIGS. 7 ,  8  and  12 , the total optical element density distribution curve c 3  in the region where the diffusion optical element region R 1  overlaps the diffusion optical element region R 2  may be plotted. 
     The total optical element density distribution curve c 3  may be formed by combining the diffusion optical element density distribution curve C 1  and the additional optical element density distribution curve C 2 . 
     An initial value of the total optical element density distribution curve c 3  may be equal to the additional optical element maximum density value P 2 . In the total optical element density distribution curve c 3 , a component corresponding to the additional optical element density distribution curve C 2  may be dominant until arriving at the position where the light incident part  15   b  is in contact with the light emitting part  15   a  along the distance d 1 , and the diffusion optical element density may be relatively low. 
     That is, the total pattern optical element distribution curve c 3  may decrease in optical element density from the additional optical element maximum density value P 2  until arriving at the position corresponding to the distance d 1 , and may increase in optical element density from the position corresponding to the distance d 1  since the diffusion optical element density distribution curve C 1  is dominant. 
     The total optical element density distribution curve c 3  may be the same as the diffusion optical element density distribution curve C 1  from the position where the diffusion optical element region R 2  ends along the distance d 6 , and may have the maximum value, equal to the diffusion optical element maximum density value P 1 , at the front end of the light guide plate  15  corresponding to the sum d 3 . 
     That is, when the diffusion optical element region R 1  is provided regardless of the first distance w 1  and the second distance w 2  between the light sources  13 , the additional optical element regions R 2  may be selectively added according to the first distance w 1  and the second distance w 2  between the light sources  13  so as to compensate for uneven luminance distribution due to difference between the first distance w 1  and the second distance w 2 . 
     According to the embodiment, the module-type backlight unit may include the light guide plates ide light to the display panel. The thickness of the display apparatus may be decreased, and contrast of a display image may be improved using an entire driving method or a local driving method such as the local dimming method and the impulsive method. 
     Since the backlight unit is driven using the local dimming method, an entire power consumption of the display apparatus may be reduced. 
     In addition, when the distances between the light sources are different from each other, and not the same, an uneven luminance distribution of the light guide plate due to the difference between the distances between the light sources may be prevented. 
     The diffusion optical elements and the diffusion optical element region R 1  may be referred to as a first optical element and a first optical element region, respectively. The additional optical element and the additional optical element region R 2  may be referred to as a second optical element and a second optical element region, respectively. 
     Although the diffusion optical element (i.e., the first optical element) overlaps the additional optical element (i.e., the second optical element), only the additional optical element may be provided at a position of the light emitting part  15   a  corresponding to the second distance w 2 , without the diffusion optical element. 
       FIG. 13  is a cross-sectional view illustrating a backlight unit according to an embodiment.  FIG. 14  is a perspective view illustrating the light guide plate  15  of  FIG. 13 . Other embodiments and configurations may also be provided. 
     In  FIGS. 13 and 14 , a description of similar parts as in  FIGS. 1 to 12  may be omitted. 
     Referring to  FIGS. 13 and 14 , the optical assembly  10  may include the light source  13 , the light guide plate  15 , the reflecting member  17 , and a side cover  20  for fixing or attaching the light source  13  and the light guide plate  15 . 
     The side cover  20  may provide a fixing position with respect to the bottom cover  110  and surround the light source  13  and a portion of the light guide plate  15 . The light source  13  may be provided in the side cover  20 . 
     The side cover  20  may include a first side cover  21  provided on the light source  13  and the light incident part  15   b  of the light guide plate  15 , and a second side cover  22  provided under the light incident part  15   b . The side cover  20  may be formed of plastic or metal. 
     The first side cover  21  may be coupled to the second side cover  22  through a first fixing member  51  to prevent the shaking of the light source  13  and the light guide plate  15  due to external shock, and more particularly to prevent the shaking along the second direction (z-axis). 
     The second side cover  22  may support the inclined surface of the light guide plate  15  to firmly maintain alignment of the light guide plate  15  with the light source  13  and protect the light guide plate  15  and the light source  13  from external shock. 
     The light incident part  15   b  of the light guide plate  15  may include a protrusion  30  protruding with a predetermined height ‘a’. The protrusion  30  may be provided to at least two points in the x-axis direction on the upper surface of the light incident part  15   b  of the light guide plate  15 . 
     The shape of the protrusion  30  may vary. For example, the protrusion  30  may have a rectangular parallelepiped shape. The protrusions  30  may be caught by the first side cover  21  to prevent the shaking of the light guide plate  15  along the x-axis and the y-axis. 
     An edge  30   a  of the protrusion  30  may be rounded to prevent a case that a crack is formed at the protrusion  30  by shock due to movement of the light guide plate  15 . 
     The height ‘a’ of the protrusion  30  may range from about 0.3 mm to 0.6 mm from the upper surface of the light incident part  15   b . The protrusion  30  may have a width ‘b’ ranging from about 2 mm to 5 mm along the x-axis. The protrusion  30  may have a width ‘c’ ranging from about 1 to 3 mm along the y-axis. 
     The protrusion  30  may be provided between neighboring LEDs  11  and adjacent to a light incident surface  16  on the upper surface of the light incident part  15   b  so as to prevent optical interference of light emitted from the LEDs  11  due to the protrusion  30  integrally formed with the light guide plate  15 . 
     The LEDs  11  may be spaced a predetermined distance from each other. The LEDs  11  may be provided in an oblique direction with respect to the protrusion  30  to minimize optical effect due to the protrusion  30  of the light guide plate  15 . Accordingly, the distance between the LEDs  11  around the protrusion  30  may be greater than the distance between the other LEDs  11 . 
     The distance between a portion of the LEDs  11  may be greater than the distance between the other LEDs  11  to secure a coupling space of the first side cover  21  and the second side cover  22  and minimize optical effect due to coupling force for pressing the light guide plate  15 . 
     The first side cover  21  may have first holes  41  at positions corresponding to the protrusions  30  of the light incident part  15   b.    
     The first holes  41  may be larger than the protrusions  30  such that the protrusions  30  are fitted and caught to the first holes  41 . The protrusion  30  provided in the first hole  41  may partially have a predetermined gap that may be a margin for preventing torsion of the light guide plate  15  when the light guide plate  15  is expanded by environmental change such as a sharp temperature increase. In this case, the rest of the protrusion  30  without the predetermined gap may be in contact with the first side cover  21  to increase fixing force thereof. 
     At least one second hole  42  may be further provided in the first side cover  21 . The second side cover  22  may have at least one third hole  43  at a position corresponding to the second hole  42 . 
     The backlight unit  100  as described above may be provided in the bottom cover  110  having a box shape with an open top. 
       FIG. 15  is a plan view illustrating the backlight unit  100  according to an embodiment.  FIG. 16  is an enlarged view illustrating a portion S of  FIG. 15 . Other embodiments and configurations may also be provided. 
     The current embodiment is the same as the embodiment of  FIG. 6  except for a structure configured to fix or attach the light guide plate  15 , which may be further described. 
     Referring to  FIGS. 15 and 16 , the backlight unit  100  may include a fixing member  52  that is configured to simultaneously fix or attach the adjacent light guide plates  15  to a bottom cover. 
     More particularly, the light incident parts  15   b  adjacent to each other may be respectively provided with recesses  158  that are symmetric to each other. 
     One of the light guide plates  15  may be referred to as a first light guide plate, and another one may be referred to as a second light guide plate. 
     When the recesses  158  of the light incident parts  15   b  are adjacent to each other, the width of the recesses  158  may be greater than the width of a head of the fixing member  52 . 
     The height of the head may be less than or equal to the depth of the recess  158  (i.e., a distance between the upper surface of the light incident part  15   b  and a surface of the recess  158 ). This may prevent the head from protruding out of the recess  158 . 
     The fixing member  52  may be a cover member that covers at least one portion of the light incident part  15   b.    
     The recesses  158  may be provided with a through hole  159  through which a portion of the fixing member  52  may pass. 
     When the light guide plates  15  are adjacent to each other, the fixing member  52  may be inserted into the through hole  159  defined by the light guide plates  15 , and may be fixed or attached to the bottom cover. The head of the fixing member  52  may be provided at the recesses  158  to simultaneously press the light guide plates  15  to the bottom cover so that the fixing member  52  fixes or attaches the light guide plates  15  to the bottom cover. 
     The recess  158  provided in the first light guide plate  15  may be referred to as a first insertion part, and the recess  158  provided in the second light guide plate  15  may be referred to as a second insertion part. 
     The distance between a first light source  131  provided at a first end of the light guide plate  15  in the left-and-right direction and a second light source  132  adjacent to the first light source  131  and provided at a second end of the adjacent light guide plate  15  in the left-and-right direction may be equal to the second distance w 2 . 
     The second light source  132  and a third light source  133 , which are adjacent to each other at the light guide plate  15  in the left-and-right direction, may be spaced apart from each other by the first distance w 1 . 
     The second distance w 2  may be greater than the first distance w 1  as described with respect to  FIG. 7 . 
     That is, since the structure for fixing or attaching the light guide plates  15  (i.e., the fixing member  52 ) is provided at the position where the light guide plates  15  are adjacent to each other, the first light source  131  and the second light source  132  may be spaced the second distance w 2 , which is greater than the first distance w 1 , from each other to secure the space where the fixing member  52  is provided. 
     Accordingly, an optical element structure for compensating for uneven luminance distribution due to difference between the first distance w 1  and the second distance w 2  may be the same as  FIG. 8 . Thus, a description thereof will be omitted. 
       FIG. 17  is a cross-sectional view of a light guide plate according to an embodiment. Other embodiments and configurations may also be provided. 
     The  FIG. 17  embodiment may be similar to the  FIG. 6  embodiment except for a scattering-mechanism formed on the bottom surface  154  (or lower surface) of the light guide plate  15 , as will be further described. 
     As shown in  FIG. 17 , a scattering-mechanism, which is an optical element  155 , may be formed in protruding shapes on the bottom surface  154  of the light guide plate  15 . 
       FIG. 18  is a perspective view illustrating a bottom surface of a light guide plate according to an embodiment. Other embodiments and configurations may also be provided. 
     The  FIG. 18  embodiment may be the same as the  FIG. 6  embodiment except for a scattering-mechanism formed on the bottom surface  154  of the light guide plate  15 , as may be further described. 
     As shown in  FIG. 18 , an diffusion optical element region R 2  may start from the side of the light incident part  15   b  (i.e., adjacent to the light emitting part  15   a ) and may be elongated with a predetermined length in the first direction. 
     Thus, any optical elements  155  or scattering-mechanisms may not be formed on a part of the bottom surface  154  (i.e., corresponding to the light emitting part  15   a ), and the optical elements or scattering-mechanism may just be provided on the other part of the bottom surface  154  (i.e., corresponding to the light incident part  15   b ). 
     According to the above described embodiments, a module-type backlight unit may include the light guide plates that provide light to the display panel. A thickness of the display apparatus may be decreased, and contrast of a display image may be improved using the entire driving method or the local driving method such as the local dimming method and the impulsive method. 
     Since the backlight unit is driven using the local dimming method, an entire power consumption of the display apparatus may be reduced. 
     In addition, when distances between the light sources are different from each other, and not the same, an uneven luminance distribution of the light guide plate due to difference between the distances may be prevented. 
     Embodiments may provide a backlight unit and a display apparatus including the backlight unit to improve quality of a display image. 
     In one embodiment, a backlight unit may include a substrate and a plurality of light sources arrayed on the substrate, the light sources emitting light with a predetermined orientation angle with respect to a first direction, the light sources including first through third light sources adjacent to each other. The backlight unit may further include a light guide plate including: a light incident part having a light incident surface to which streaks of light respectively emitted from the light sources are laterally incident, and a light emitting part emitting the incident streaks of light upward and having a side adjacent and connected to the light incident part. A first distance between the first light source and the second light source is less than a second distance between the second light source and the third light source. 
     In another embodiment, a backlight unit may include a bottom cover, a substrate at the bottom cover, a plurality of light sources arrayed on the substrate, the light sources emitting light with a predetermined orientation angle with respect to a first direction, the light sources including first through third light sources adjacent to each other. The backlight unit may further include N (N is 2 or greater) light guide plates including: a light incident part having a light incident surface to which streaks of light respectively emitted from the light sources are laterally incident, and a light emitting part emitting the incident streaks of light upward and having a side adjacent and connected to the light incident part. The light emitting part of a K th  (K is one of 1 to N−1) light guide plate of the N light guide plates may have a distant end from the light incident part, and the distant end may be provided on an upper side of the light incident part of a K+1 th  light guide plate. A first distance between the first light source and the second light source may be less than a second distance between the second light source and the third light source. 
     In another embodiment, a display apparatus may include a display panel, a backlight unit on a rear side of the display panel, the backlight unit including a plurality of driving areas that are independently drivable, and a driving part on a rear side of the backlight unit, the driving part driving at least one of the display panel and the backlight unit. The backlight unit may includes a bottom cover, a substrate at the bottom cover, and a plurality of light sources arrayed on the substrate, the light sources emitting light with a predetermined orientation angle with respect to a first direction, the light sources including first through third light sources adjacent to each other. The backlight unit may further include a light guide plate including: a light incident part having a light incident surface to which streaks of light respectively emitted from the light sources are laterally incident, and a light emitting part emitting the incident streaks of light upward and having a side adjacent and connected to the light incident part. A first distance between the first light source and a second light source is less than a second distance between the second light source and a third light source 
     A backlight unit comprises: at least one light guide plate having a light incident part to receive light from a first direction and a light emitting part adjacent to the light incident part to emit light received from the light incident section in a second direction, the first and second directions being different directions, a first portion of the light emitting part closer to the light incident part in the first direction has a first prescribed thickness, and a second portion of the light emitting part farther from the light incident section in the first direction has a second prescribed thickness, the first prescribed thickness being different from the second prescribed thickness; and a plurality of light sources arranged in a third direction, the light sources configured to emit light toward the first direction, the light sources including a first light source, a second light source and a third light source, wherein the second light source is adjacent to the first light source and the third light source, wherein a first distance between the first light source and the second light source is different from a second distance between the second light source and the third light source. A backlight unit comprises: at least one light guide plate having a light incident part to receive light from a first direction and a light emitting part adjacent to the light incident part to emit light received from the light incident section in a second direction, the first and second directions being different directions, a lower surface of the light incident part having a first plurality of optical elements and a lower surface of the light emitting part having a second plurality of optical elements; and a plurality of light sources in a third direction, the light sources configured to emit light toward the first direction. 
     A display apparatus having the backlight unit of above, wherein the display apparatus comprises: a display panel; and a driving circuit to drive at least one of the display panel or the backlight unit, the backlight unit provided between the display panel and the driving circuit. The N×M array of light guide plates is divided into a plurality of areas, the light guide plates in at least one area emit light independently from the light guide plates in at least one other area such that a brightness of the at least one area is different from brightness of the at least one other area. 
     The present disclosure also provides a “green” technology for display devices. Presently, the backlight is generally turned on continuously, even when the display of the entire screen is not desirable. For example, the prior art display allows control of the resolution of the entire display screen but not the size of the display screen. However, in certain instances, a smaller screen area may be desirable for lower resolution images. The size of the display area can be controlled based on the present disclosure. For example, instead of viewing images and programs in 42 inch display, the display screen size can be reduce to 32 inches by turning off the light sources for appropriate number of light guide plates located at the periphery of the display device. As can be appreciated, the location and size of the display area can be controlled based on program or user needs. As can be appreciated, multiple configuration may be possible based on turning on or off the light sources for appropriate number of light guide plates (light guide panels or light guide modules or assemblies) based on application and user configuration. 
     This application is related to Korean Applications Nos. 10-2008-0049146 filed on May 27, 2008, 10-2008-0061487 filed on Jun. 27, 2008, 10-2008-0099569 filed on Oct. 10, 2008, 10-2009-0035029 filed on April 22, 200910-2009-0036472 filed Apr. 27, 2009, 10-2009-0052805 filed on Jun. 15, 2009, 10-2009-0061219 filed Jul. 6, 2009, 10-2009-0071111 filed Aug. 2, 2009, 10-2009-0072449 filed Aug. 6, 2009, 10-2009-0075120 filed on Aug. 14, 2009, 10-2009-0098844 filed on Oct. 16, 2009, and 10-2009-0098901 filed on Oct. 16, 2009, whose entire disclosures are incorporated herein by reference. Further, this application is related to U.S. Provisional Patent Application Nos. 61/219,480 filed on Jun. 23, 2009; 61/229,854 filed on Jul. 30, 2009; 61/230,844 filed on Aug. 3, 2009; and 61/233,890 filed on Aug. 14, 2009 and U.S. application Ser. Nos. 12/453,885 filed on May 22, 2009, 12/618,603 filed on Nov. 13, 2009, 12/632,694 filed on Dec. 7, 2009, and LGE-162, LGE-163, HI-0400, HI-0412, HI-0413, HI416 and HI-0420 all filed on Mar. 19, 2010, whose entire disclosures are incorporated herein by reference. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.