Patent Publication Number: US-9405056-B2

Title: Backlight assembly and display apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 13/908,920, filed on Jun. 3, 2013, which is a continuation of U.S. patent application Ser. No. 13/038,278, filed on Mar. 1, 2011 (U.S. Pat. No. 8,469,577, issued on Jun. 25, 2013), which claims priority to Korean Patent Application No. 10-2010-0026435 filed on Mar. 24, 2010, the contents of the prior applications being herein incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to flat panel displays. More particularly, the present invention relates to a backlight assembly capable of uniformly emitting a light and a display apparatus having the backlight assembly. 
     2. Description of the Related Art 
     In general, a display apparatus that is suitable for use in a small-size electronic information apparatus, such as a notebook computer or a mobile communication system, typically employs an edge-illumination type backlight unit. The edge-illumination type backlight unit includes a light source that emits a light, and a guide member that guides the light through a display panel. In the edge-illumination type backlight unit, the light source is disposed adjacent to a side portion of the guide member so as to supply the light to the guide member. The guide member guides light from its side portion to its upper portion, in order to allow the light to travel to the display panel. 
     SUMMARY 
     Exemplary embodiments of the present invention provide a backlight assembly capable of providing more uniform illumination. 
     Exemplary embodiments of the present invention provide a display apparatus having the backlight assembly to improve its display quality. 
     According to exemplary embodiments, a backlight assembly includes at least two light guide plates, a light source, and a diffusion member. Each of the light guide plates includes a light incident surface and a light exiting surface and the light guide plates are spaced apart from each other so as to form a gap therebetween. The light source is disposed adjacent to at least one side portion of the light guide plates to emit light to the light incident surfaces. The diffusion member covers the gap, the diffusion member configured to diffuse light received from the light source. 
     According to exemplary embodiments, a display apparatus includes light guide plates, a light source, a display panel, and a diffusion member. 
     The light guide plates are spaced apart from each other so as to form a gap therebetween, and each of the light guide plates includes a light incident surface and a light exiting surface. The light source is disposed adjacent to at least one side portion of the light guide plates, so that light from the light source is directed toward the light incident surfaces. The display panel is positioned to receive light exiting through the light exiting surface, so as to facilitate display of an image. The diffusion member is positioned between the display panel and the light guide plates, and covers the gap so as to diffuse light directed toward the display panel. 
     According to exemplary embodiments, a display apparatus includes light guide plates, a light source, a display panel, and an optical member. 
     The light guide plates are spaced apart from each other so as to form a gap therebetween, and each of the light guide plates includes a light incident surface and a light exiting surface. The light source is disposed adjacent to at least one side portion of the light guide plates, and is configured to direct light toward the light incident surfaces. The display panel is positioned to receive light from the light exiting surface, to facilitate display of an image. The optical member covers the gap, so that light passing through the gap also passes through, and is diffused by, the optical member. 
     According to the above, the display apparatus includes the diffusion member to cover the upper portion of the light sources disposed between the light guide plates. Thus, the diffusion member may diffuse the light traveling to the display panel through between the light guide plates, thereby preventing the display quality of the display apparatus from being deteriorated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other advantages of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1  is an exploded perspective view showing a display apparatus according to an exemplary embodiment of the present invention; 
         FIG. 2  is an exploded perspective view showing a coupling relation between a first light source part, a second light source part, a third light source part, a light guide part, and a diffusion plate of  FIG. 1 ; 
         FIG. 3  is a perspective view showing a first light source part of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along a line I-I′ of  FIG. 2 ; 
         FIG. 5A  is a plan view showing a diffusion member of  FIG. 4 ; 
         FIG. 5B  is a cross-sectional view taken along a line II-II′ of  FIG. 5A ; 
         FIG. 6  is a sectional view showing a display apparatus employing a diffusion member according to another exemplary embodiment of the present invention; 
         FIG. 7  is a sectional view showing a display apparatus employing a light source part and a diffusion plate according to another exemplary embodiment of the present invention; 
         FIG. 8  is a perspective view showing a coupling relation between a light source part and a light guide part according to another exemplary embodiment of the present invention; 
         FIG. 9  is a sectional view showing a display apparatus employing a light source part and a diffusion plate according to another exemplary embodiment of the present invention; 
         FIG. 10  is a plan view showing a coupling relation between a light guide part, a light source part, and diffusion members according to another exemplary embodiment of the present invention; and 
         FIG. 11  is a sectional view showing a display apparatus according to another exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms, “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view showing a display apparatus according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a display apparatus  500  includes a backlight assembly  200 , a display panel  400 , a bottom chassis  310 , and a top chassis  380 . 
     The backlight assembly  200  includes a first light source part  20 , a second light source part  26 , a third light source part  29 , a light guide part  10  including a first light guide plate  11  and a second light guide plate  16 , a diffusion member  30 , a reflection plate  110 , a diffusion plate  120 , and optical sheets  130 . 
     The first to third light source parts  20 ,  26  and  29  generate a light used to display an image on the display panel  500 . The light guide part  10 , including the first and second light guide plates  11  and  16 , guides the light generated by the first to third light source parts  20 ,  26 , and  29  toward the display panel  400 . 
     In more detail, the first light source part  20  is disposed between the first light guide plate  11  and the second light guide plate  16 , and the light generated by the first light source part  20  travels to both the first light guide plate  11  and the second light guide plate  16 . In addition, the second light source part  26  is disposed to face the first light source part  20  with the first light guide plate  11  positioned inbetween, so that the light generated by the second light source part  26  is directed into the first light guide plate  11 . The third light source part  29  is disposed to face the first light source part  20  with the second light guide plate  16  positioned inbetween, and thus the light generated by the third light source part  29  is directed toward the second light guide plate  16 . 
     According to the present exemplary embodiment, the first light source part  20 , the second light source part  26 , and the third light source part  29  may be independently operated, so the amount of the light provided to the first light guide plate  11  may be different from the amount of the light provided to the second light guide plate  16 . Consequently, the amount of the light provided to the display panel  400  through the first and second light guide plates  11  and  16  may be varied according to the image in a display area of the display panel  400 . This allows the display apparatus  500  to implement various methods that employ position-dependent backlight lighting, such as local dimming. 
     The diffusion member  30  is disposed between the first and second light guide plates  11  and  16 , and covers an upper side of the first light source part  20  so as to direct light from the first light source part  20  into the light guide plates  11 ,  16 . In  FIG. 1 , the diffusion member  30  covers only the first light source part  20 . However, the invention is not limited to this configuration, and it should not be limited thereto or thereby. That is, the diffusion member  30  may be provided in a plural member in order to cover any or all of the first to third light source parts  20 ,  26 , and  29 . 
     For ease of explanation, the light generated by the first light source part  20  that travels between the first and second light guide plates  11  and  16  is referred to as leakage light. In general, excessive leakage light results in a displayed image that has uneven brightness distribution. However, according to the present exemplary embodiment, the diffusion member  30  is disposed between the first and second light guide plates  11  and  16  to cover the upper side of the first light source part  20 , thus preventing or reducing leakage light. Thus, the brightness distribution of the image displayed on the display panel  400  may be made more even, resulting in better image quality. 
     The reflection plate  110  includes a material to reflect the light, such as polyethylene terephthalate (PET), aluminum, etc. The reflection plate  110  is disposed on a bottom surface of the bottom chassis  310 , and reflects the light generated by the first, second, and third light source parts  20 ,  26 , and  29  back up to the display panel  400 . Therefore, the amount of the light traveling to the display panel  400  may be increased by the reflection plate  110 . 
     The diffusion plate  120  is disposed between the light guide part  10  and the display panel  400 . The diffusion plate  120  diffuses the light exiting from the light guide part  10  and the light diffused by the diffusion member  30 . Thus, light may be more uniformly provided to the display panel  400 . 
     As shown in  FIG. 1 , the diffusion plate  120  is disposed on supporting members  40  each protruding from the light guide part  10 , and thus the diffusion plate  120  may be spaced apart from the light guide part  10  by the supporting members  40 . 
     The optical sheets  130  are disposed between the diffusion plate  120  and the display panel  400 . The optical sheets  130  may include prism sheets that concentrate the light exiting from the diffusion plate  120  to improve a front brightness, as well as diffusion sheets that diffuse the light exiting from the diffusion plate  120 . 
     The display panel  400  may be a liquid crystal display. The display panel  400  receives the light generated by the backlight assembly  200  in order to display an image. The display panel  400  includes a first substrate  410 , a second substrate  420  facing the first substrate  410 , and a liquid crystal layer (not shown) interposed between the first substrate  410  and the second substrate  420 . 
     The first substrate  410  may include a plurality of pixel electrodes (not shown) and a plurality of thin film transistors electrically connected to the pixel electrodes in one-to-one correspondence. Each thin film transistor switches a driving signal applied to each pixel electrode. In addition, the second substrate  420  may include color filter layers corresponding to the pixel electrodes and an opposite electrode that forms an electric field with the pixel electrodes to control an arrangement of liquid crystal molecules of the liquid crystal layer. 
     The bottom chassis  310  includes a bottom portion, as well as sidewalls extending from the bottom portion to provide a receiving space in which the backlight assembly  200  and the display panel  400  are received. In addition, the top chassis  380  is coupled to the bottom chassis  310  to help fix the backlight assembly  200  and the display panel  400  to the bottom chassis  310 . 
       FIG. 2  is an exploded perspective view showing a coupling relation between first light source part  20 , second light source part  26 , third light source part  29 , light guide part  10 , and diffusion plate  120  of  FIG. 1 .  FIG. 3  is a perspective view showing a first light source part of  FIG. 2 , and  FIG. 4  is a cross-sectional view taken along line I-I′ of  FIG. 2 . 
     Referring to  FIGS. 2 to 4 , the light guide part  10  includes the first light guide plate  11  and the second light guide plate  16  that are arranged in a first direction D 1 , and the diffusion plate  120  is disposed on the first and second light guide plates  11  and  16 . In addition, at least one of the first, second, and third light source parts  20 ,  26 , and  29  is disposed adjacent to at least one side portion of each of the first and second light guide plates  11  and  16 . 
     In this embodiment, the first light guide plate  11  has a plate-like shape. More specifically, the first light guide plate  11  includes a first light incident surface  12 A, a second light incident surface  12 B opposite to the first light incident surface  12 A, and a first light exiting surface  13  connecting the first light incident surface  12 A and the second light incident surface  12 B. 
     The second light guide plate  16  also has a plate-like shape. The second light guide plate  16  includes a third light incident surface  17 A, a fourth light incident surface  17 B opposite the third light incident surface  17 A, and a second light exiting surface  18  connecting the third light incident surface  17 A and the fourth light incident surface  17 B. 
     The first light source part  20  is disposed between the first light guide plate  11  and the second light guide plate  16 . The first light source part  20  includes a first printed circuit board  23 , first auxiliary light sources  21 , and second auxiliary light sources  22 . The first printed circuit board  23  is disposed between the first and second light guide plates  11  and  16  and extends in a third direction D 3  substantially perpendicular to the first direction D 1  along a space between the first and second light guide plates  11  and  16 . Opposite ends of a widthwise direction of the first printed circuit board  23  are disposed under the first light guide plate  11  and the second light guide plate  16 , respectively. 
     The first auxiliary light sources  21  and the second auxiliary light sources  22  are electrically connected to the first printed circuit board  23 . In addition, the first auxiliary light sources  21  and the second auxiliary light sources  22  are alternately arranged on the first printed circuit board  23  in the third direction D 3 . While this embodiment shows an alternate arrangement of light sources  21  and  22 , the invention encompasses any other arrangement as well. 
     Meanwhile, the light generated by the first auxiliary light sources  21  travels in a direction different from a direction in which the light generated by the second auxiliary light sources  22  travels. In detail, the first auxiliary light sources  21  direct their light generally in the first direction D 1 , as shown by the arrows extending from light sources  21  in  FIG. 2 . As a result, the light generated by the first auxiliary light sources  21  is incident to the first light guide plate  11  through the first light incident surface  12 A. The second auxiliary light sources  22  direct their light generally in a second direction D 2  opposite to the first direction D 1  (as shown by the arrows extending from light sources  22 ), so that the light generated by the second auxiliary light sources  22  is incident to the second light guide plate  16  through the third light incident surface  17 A. 
     The second light source part  26  is disposed adjacent to the second light incident surface  12 B to provide the light to the first light guide plate  11 . The second light source part  26  includes a second printed circuit board  24  and third auxiliary light sources  25 . The second printed circuit board  24  extends in the third direction D 3  along the second light incident surface  12 B, and one end of a widthwise direction of the second printed circuit board  24  is disposed under the first light guide plate  11 . The third auxiliary light sources  25  are electrically coupled to the second printed circuit board  24  and arranged on the second printed circuit board  24  generally along the third direction D 3 . The light generated by the third auxiliary light sources  25  is incident to the first light guide plate  11  generally through the second light incident surface  12 B. 
     In addition, the third light source part  29  is disposed adjacent to the fourth light incident surface  17 B to direct light into the second light guide plate  16 . The third light source part  29  includes a third printed circuit board  27  and fourth auxiliary light sources  28 . The third printed circuit board  27  extends in the third direction D 3  along the fourth light incident surface  17 B, and one end of a widthwise direction of the third printed circuit board  27  is disposed under the second light guide plate  16 . The fourth auxiliary light sources  28  are electrically coupled to the third printed circuit board  27  and arranged on the third printed circuit board  27  generally along the third direction D 3 . The light generated by the fourth auxiliary light sources  28  is incident to the second light guide plate  16  generally through the fourth light incident surface  17 B. 
     As described above, the light guide part  10  receives the light from the first to third light source parts  20 ,  26 , and  29 , and the light incident to the light guide part  10  travels to the diffusion plate  120  through the first light exiting surface  13  and the second light exiting surface  18  after the light incident to the light guide part  10  is reflected by various surfaces and structures that can include a guide pattern (not shown) formed on a rear surface of the light guide part  10 . 
     The diffusion member  30  can be formed of a polymer material, such as polymethylmethacrylate (PMMA), polycarbonate (PC), etc., and extends generally in the third direction D 3 . The diffusion member  30  is disposed at a position corresponding to a space between the first light guide plate  11  and the second light guide plate  16 , so as to cover the first light source part  20 . In addition, the diffusion member  30  partially overlaps the first light guide plate  11  and the second light guide plate  16  so as to cover the first light incident surface  12 A and the third light incident surface  17 A. The diffusion member  30  diffuses that light generated by the first light source part  20  which is directed up toward the diffusion plate  120 , rather than into either the first light guide plate  11  or the second light guide plate  16 . 
     As described above, the first auxiliary light sources  21  are disposed such that their light emitting surfaces ES face the first light incident surface  12 A in order to provide their light primarily to the first light guide plate  11 . The first auxiliary light sources  21  may be spaced apart from the first light guide plate  11  with an air layer AL therebetween, in order to accommodate expansion of the first light guide plate  11  due to temperature, humidity, or the like. As a result, a portion of the light emitted from the light emitting surfaces ES may be a first light L 1  that travels to the diffusion plate  120  through the space between the first and second light guide plates  11  and  16  rather than through the first light incident surface  12 A, or may be a second light L 2  that travels to the diffusion plate  120  through the space between the first and second light guide plates  11  and  16  after reflection off of the first light incident surface  12 A. Since the first light L 1  and the second light L 2  are both diffused by the diffusion member  30 , the ability of light escaping from between the light guide plates  11  and  16  to contribute to uneven lighting of the display is reduced. Display quality is thus increased. 
     Meanwhile, the supporting members  40  may be disposed on, or extend from, an upper surface of each of the first and second light guide plates  11  and  16 . The supporting members  40  protrude from the upper surfaces (i.e., light exiting surfaces  13  and  18 ), thereby maintaining an air gap, or a spacing of the diffusion plate  120  apart from the first and second light guide plates  11  and  16 . This air layer acts to further diffuse light exiting through the first and second light exiting surfaces  13  and  18  and traveling to the diffusion plate  120 . 
       FIG. 5A  is a plan view showing a diffusion member of  FIG. 4 , and  FIG. 5B  is a cross-sectional view taken along a line II-II′ of  FIG. 5A . 
     Referring to  FIGS. 4, 5A, and 5B , the diffusion member  30  includes an incident surface  33  facing the first and second auxiliary light sources  21  and  22 , and an optical pattern OP disposed on the incident surface  33 . The optical pattern OP includes a light reflection part  31  and a light transmission part  32 . 
     According to the present exemplary embodiment, the light reflection part  31  may be a reflection layer including a light reflection material and being disposed on the incident surface  33 . The light transmission part  32  may be openings in the light reflection part  31 . The light transmission part  32  may be formed by removing portions of the light reflection part  31 . Thus, as shown in  FIG. 5B , the first light L 1  passes through the light transmission part  32 , and the second light L 2  is reflected off the light reflection part  31 , and is directed back toward the light guide plates  11 ,  16 . As a result, the amount of the light diffused by the diffusion member  30  may be adjusted by altering an area ratio of the light reflection part  31  to the light transmission part  32 . That is, the relative surface areas of light reflection part  31  and transmission part  32  can be adjusted so as to adjust the amount of light diffused by diffusion member  30  to any desired amount. 
       FIG. 6  is a sectional view showing a display apparatus employing a diffusion member according to another exemplary embodiment of the present invention. The display apparatus according to this exemplary embodiment has substantially the same structure and function as those of the display apparatus shown in  FIGS. 1 to 5 , except for a diffusion member  35 A. Therefore, in  FIG. 6 , the same reference numerals denote the same elements shown in  FIGS. 1 to 5 , and thus detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 6 , a diffusion member  35 A includes diffusion beads BD. The diffusion beads BD may be distributed within the diffusion member  35 A, and/or on its surface. 
     The diffusion beads BD may include a material such as silicon dioxide (SiO 2 ) or titanium dioxide (TiO 2 ), thereby improving diffusion characteristics of the diffusion member  35 A. The diffusion beads BD may thus act to further improve diffusion of the light L 1  and L 2 , thus further enhancing image quality. 
       FIG. 7  is a sectional view showing a display apparatus employing a light source part and a diffusion plate according to another exemplary embodiment of the present invention. The display apparatus according to this exemplary embodiment has largely the same structure and function as those of the display apparatus shown in  FIGS. 1 to 5  except for a diffusion member  35 B. Therefore, in  FIG. 7 , the same reference numerals denote the same elements shown in  FIGS. 1 to 5 , and thus detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 7 , a diffusion member  35 B includes a light diffusion part  38  and a supporting part  39  that, in cross-section, collectively form a general T-shape. The light diffusion part  38  may be formed of an optically transmissive material such as polycarbonate (PC). The light diffusion part  38  makes contact with a lower surface of the diffusion plate  120  to diffuse light escaping from between the first and second light guide plates  11  and  16 . In addition, the supporting part  39  is connected to the light diffusion part  38  and disposed between the light diffusion part  38  and the first light source part  20 , so as to support the light diffusion part  38 . 
     In the present exemplary embodiment, since the light diffusion part  38  is integrally formed with the supporting part  39 , and the light diffusion part  38  and the supporting part  39  may be formed of the same material, both parts  38 ,  39  may act to diffuse light. The invention encompasses any shape of parts  38 ,  39 , and is not limited to the T-shape shown. However, it is preferred that neither of these parts  38 ,  39  is shaped to extend between light source  21  and light guide plate  11 . That is, it is preferable that neither part  38 ,  39  interferes with the direct transmission of light from light source  21  to light guide plate  11 . In addition, although not shown in  FIG. 7 , the supporting part  39  may be disposed on either one or both of the first auxiliary light sources  21  and second auxiliary light sources  22 . 
     According to the present exemplary embodiment shown in  FIG. 7 , the supporting part  39  is disposed between the light diffusion part  38  and the first auxiliary light sources  21  to support the diffusion plate  120 . Therefore, the diffusion plate  120  may be spaced apart from the first and second light guide plates  11  and  16  by a thickness of the supporting part  39 , and thus the diffusion member  35 B may also perform a function like that of the supporting members  40  shown in  FIG. 4 . Accordingly, some embodiments of the invention do not employ supporting members  40 . 
       FIG. 8  is a perspective view showing a coupling relation between a light source part and a light guide part according to another exemplary embodiment of the present invention. In  FIG. 8 , the same reference numerals denote the same elements in  FIGS. 1 to 5 , and thus detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 8 , the diffusion member  30  is coupled to the first light guide plate  11  and the second light guide plate  16  by coupling members  90 . The coupling members  90  may be provided at either one or both ends of a lengthwise direction of the diffusion member  30 , as desired. The coupling member  90  acts to more securely couple the diffusion member  30  to the first and second light guide plates  11  and  16 . 
       FIG. 9  is a sectional view showing a display apparatus employing a light source part and a diffusion plate according to another exemplary embodiment of the present invention. 
     The display apparatus shown in  FIG. 9  includes a first optical member  85  instead of employing the diffusion member  40  shown in  FIGS. 1 to 5 , and further includes a second optical member  81  and a third optical member  82 . The display apparatus shown in  FIG. 9  has largely the same structure and function as those of the display apparatus of  FIGS. 1 to 5  except for the first, second, and third optical member  85 ,  81 , and  82 . Accordingly, the same reference numerals in  FIG. 9  denote the same elements in  FIGS. 1 to 5 , and thus detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 9 , the first optical member  85  includes a first optical portion  82 , a second optical portion  83 , and a third optical portion  84 . The first optical portion  82  is disposed between the first light guide plate  11  and the first auxiliary light sources  21 , and the second optical portion  83  is disposed between the second light guide plate  16  and the second auxiliary light sources  22  (refer to  FIG. 3 ). In addition, the third optical portion  84  is connected with the first and second optical portions  82  and  83 , and has a generally rounded shape on its upper face that makes contact with the lower surface of the diffusion plate  120 . 
     The second optical member  81  is disposed between the first light guide plate  11  and the third auxiliary light sources  25 . Similar to the first optical member  85 , the second optical member  81  has a rounded shape on its upper face that makes contact with the lower surface of the diffusion plate  120 . Likewise, the third optical member  82  is disposed between the second light guide plate  16  and the fourth auxiliary light sources  28 , and has a rounded shape on its upper face making contact with the lower surface of the diffusion plate  120 . 
     In the present exemplary embodiment, each of the first, second, and third optical members  85 ,  81 , and  82  may be made of any suitable optically transmissive material. However, they may preferably be formed of a material having a refractive index of about 1.2 to about 1.6, along with elasticity and light transmittance similar to those of silicone. Thus, when the first and second light guide plates  11  and  16  include a material having a refractive index of about 1.2 to about 1.6 such as polymethylmethacrylate (PMMA) or polycarbonate (PC), the difference in refractive index between the first light guide plate  11  and a space between the first light guide plate  11  and the first auxiliary light sources  21  may be reduced. That is, it is preferable for the first optical member  85  to have a refractive index substantially the same as that of the first light guide plate  11 , so that the air layer AL that existed in previous embodiments (and which had a refractive index different from plate  11 ) is filled by a material with the same refractive index as plate  11 . As a result, a third light L 3  generated by the first auxiliary light sources  21  is further diffused by optical member  85 . 
     It is also preferable that the optical members  81 ,  82 ,  85  be made of an elastic material, so as to accommodate expansion of the light guide plates  11 ,  16  due to temperature/humidity. Thus, as above, it is preferable for the optical members  81 ,  82 ,  85  to be made of a material having compliance and sufficient light transmittance, such as a silicone or similar materials. 
     According to the present exemplary embodiment shown in  FIG. 9 , the first to third optical members  85 ,  81 , and  82  make contact with the lower surface of the diffusion plate  120 , so that the diffusion plate  120  may be spaced apart from the first and second light guide plates  11  and  16 . Therefore, the first to third optical members  85 ,  81 , and  82  may be used instead of the supporting members  40  shown in  FIG. 4 . 
       FIG. 10  is a plan view showing a coupling relation between a light guide part, a light source part, and diffusion members of a display apparatus according to another exemplary embodiment of the present invention. The display apparatus shown in  FIG. 10  has largely the same structure and function as those of the display apparatus shown in  FIGS. 1 to 5 , except for a first auxiliary diffusion member  30 A and a second auxiliary diffusion member  30 B. Therefore, in  FIG. 10 , the same reference numerals denote the same elements shown in  FIGS. 1 to 5 , and thus detailed descriptions of the same elements will be omitted. 
     Referring to  FIG. 10 , a first auxiliary diffusion member  30 A is disposed to cover an upper side of the second light source part  26 . Thus, the first auxiliary diffusion member  30 A may diffuse light from the third auxiliary light sources  25 . In addition, a second auxiliary diffusion member  30 B is disposed to cover an upper side of the third light source part  29 . As a result, the second auxiliary diffusion member  30 B may diffuse light from the fourth auxiliary light sources  28 . That is, the diffusion members  30 A,  30 B act similarly to diffusion member  30 , diffusing light that would otherwise leak out through the corresponding gaps between light guide plates. 
     Accordingly, the display apparatus of this embodiment enhances the brightness uniformity at both the middle, as well as each side of, the display area. The invention contemplates use of diffusion members over any one or more of the gaps between light guide plates. 
       FIG. 11  is a sectional view showing a display apparatus according to another exemplary embodiment of the present invention. In  FIG. 11 , the same reference numerals denote the same elements in  FIGS. 1 to 4, 5A, and 5B . In  FIG. 11 , for the convenience of explanation, the first light guide plate  11 , the second light guide plate  16 , the diffusion  30 , the diffusion plate  120 , the first light source part  20 , and a supporting member  41  have been shown. 
     Referring to  FIG. 11 , the supporting member  41  is disposed between the first light guide plate  11  and the second light guide plate  16 . The upper surface of supporting member  41  makes contact with the lower surface of the diffusion plate  120 . Thus, the supporting member  41  may maintain a space between diffusion plate  120  and first and second light guide plates  11  and  16 . 
     In the present exemplary embodiment, the supporting member  41  is disposed between one of the first auxiliary light sources  21  and one of the second auxiliary light sources  22 , and makes contact with the lower surface of the diffusion plate  120  after passing through an opening formed through the diffusion member  30 . In addition, the supporting member  41  may be positioned at outermost positions of the first and second auxiliary light sources (i.e., at outer edges of the display area) so as to minimize any reduction in effectiveness of the diffusion member  30 . 
     Although the exemplary embodiments of the present invention have been described, it is understood that the present invention should not be limited to these exemplary embodiments but various changes and modifications can be made by one of ordinary skill in the art within the spirit and scope of the present invention as hereinafter claimed.