Abstract:
A backlight unit of a display apparatus is provided. The backlight unit includes a display housing, a light source which is arranged along an inner circumference the display housing, a light guide plate through which light of the light source is transmitted, and which forms surface light, an optical sheet which is disposed on an upper side of the light guide plate to upwardly diffuse the light of the light source transmitted through the light guide plate, a plurality of first fixing units, each of which fix both the light guide plate and the optical sheet, a plurality of second fixing units which support only the light guide plate, and a support frame which is connected to the display housing to fix the optical sheet to the display housing provisionally, and has a window formed on a surface corresponding to the light guide plate to allow light to pass therethrough.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 10-2009-0045364, filed on May 25, 2009, and No. 10-2010-0044999, filed on May 13, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Apparatuses consistent with the inventive concept relate to a display apparatus, and more particularly, to a structure that fixes a light guide plate (LGP) and an optical sheet in a backlight unit (BLU) of a display apparatus. 
     2. Description of the Related Art 
     Display apparatuses employing thin-film transistor liquid crystal display (TFT-LCD) panels require backlight units (BLUs) to display images. Generally, cold cathode fluorescent lamps (CCFLs) are widely used as light sources of BLUs. However, recently, CCFLs are being replaced with light emitting diodes (LEDs) as a result of restriction on use of mercury and an increase in demand for slimmer display apparatuses. 
     BLUs may be edge-type BLUs or direct-lighting type BLUs according to the location of LEDs used as light sources of BLUs. In the case of an edge-type BLU, a light source is disposed around a light guide plate (LGP) corresponding to a frame of the BLU, and an optical sheet is disposed on a rear surface of the LGP in order to uniformly diffuse light of the light source passing through the LGP to equalize brightness of the LGP. 
     The LGP is fixed and separated from the light source by a predetermined distance to prevent the LGP which is made of resin materials from being thermally deformed by heat generated by lighting the LED. In order to fix the LGP, the LGP includes a plurality of fixing projections such as studs which are disposed at regular intervals on a housing of a display apparatus, and a plurality of support grooves into which the plurality of fixing projections are inserted. Accordingly, the LGP may be fixed by connection of the fixing projections and the support grooves. The fixing projections are sufficiently thick to support the weight of the LGP. Additionally, the support grooves are disposed to correspond to the fixing projections or at appropriate intervals, based on an amount of the LGP to be constricted, expanded or dropped down. 
     Additionally, the optical sheet needs to be attached to the LGP. The optical sheet has a predetermined pattern formed thereon to enable the light of the LED transmitted through the LGP to be appropriately diffused, so that a constant brightness of the LGP may be maintained. However, if the optical sheet is moved, a light leakage phenomenon may occur, so there is a need to accurately fix the optical sheet in an appropriate position. Accordingly, the optical sheet requires a plurality of openings, so as to be hung on a sheet hanger connected to the housing of the display apparatus. 
     Considering characteristics of edge-type BLUs, the fixing projections and sheet hanger need to be disposed proximate the light source. However, in this situation, grooves need to be formed on a portion of the LGP which faces the fixing projections and sheet hanger, so that the fixing projections and sheet hanger may pass through the grooves. Accordingly, it is impossible to avoid loss of light in the portion where the grooves are formed. Therefore, there is a need to carefully take into consideration the mounting location, the size and the number of fixing projections and sheet hanger. 
     SUMMARY 
     Exemplary embodiments may overcome the above disadvantages and other disadvantages not described above. Also, an exemplary embodiment is not required to overcome the disadvantages described above, and an exemplary embodiment of the present invention may not overcome any of the problems described above. 
     One or more exemplary embodiments provide a BLU of a display apparatus which has an improved structure to reduce the number of working processes and manufacturing cost of component parts and to minimize loss of light of the BLU. 
     According to an aspect of one or more exemplary embodiments, there is provided a BLU of a display apparatus, the BLU including a display housing, a light source which is arranged along an inner circumference the display housing, a light guide plate through which light of the light source is transmitted, and which forms surface light, an optical sheet which is disposed on an upper side of the light guide plate to upwardly diffuse the light of the light source transmitted through the light guide plate, a plurality of first fixing units, each of which fix both the light guide plate and the optical sheet, a plurality of second fixing units which support only the light guide plate, and a support frame which is connected to the display housing to fix the optical sheet to the display housing provisionally, and has a window formed on a surface corresponding to the light guide plate to allow light to pass therethrough, wherein the light source, the light guide plate, the first fixing units, and the second fixing units are disposed between the display housing and the support frame. 
     Each of the plurality of first fixing units may include a first fixing projection which is connected to a housing of the display apparatus, a first support groove which is disposed in a position corresponding to the first fixing projection, and an optical sheet opening which is disposed in a position of the optical sheet corresponding to the first support groove and through which the first fixing projection penetrates. 
     The plurality of first fixing units may be disposed symmetrically on an upper side and a lower side of the LGP. 
     Each of the plurality of second fixing units may include a second fixing projection which is connected to the housing of the display apparatus, and a second support groove which is disposed in a position corresponding to the second fixing projection. 
     The plurality of second fixing units may support the upper side, the lower side, a left side and a right side of the LGP. Additionally, the plurality of second fixing units may be disposed symmetrically at one position between the plurality of first fixing units on the upper side of the LGP and the opposite position between the plurality of first fixing units on the lower side of the LGP, and disposed symmetrically at two positions on the left side of the LGP and two positions on the right side of the LGP. 
     The first fixing projection and the second fixing projection may be configured with the same component part. 
     The first fixing projection may include a first portion which supports the optical sheet, and a second portion which supports the LGP. In this situation, the first portion and the second portion may have different diameters. 
     As described above, according to the exemplary embodiments, the LGP and the optical sheet are supported at the same position, and thus it is possible to minimize loss of light in a position where the fixing units are mounted. Additionally, it is possible to reduce the number of times the support grooves of the LGP are cut and the number of times the optical sheet openings are punched through the optical sheet, thereby reducing the cost required to manufacture component parts. 
     Furthermore, component parts for supporting the LGP and the optical sheet may be used in common, and it is thus possible to reduce the cost of component parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will be more apparent by describing certain exemplary embodiments with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a backlight unit (BLU) of a display apparatus according to an exemplary embodiment; 
         FIGS. 2 and 3  are perspective views illustrating a first fixing projection and a second fixing projection; 
         FIG. 4  is an exploded perspective view illustrating the first fixing projection of  FIG. 2  assembled with a displaying housing; 
         FIG. 5  is a view illustrating a BLU of a display apparatus according to a first exemplary embodiment; and 
         FIG. 6  is a view illustrating a BLU of a display apparatus according to a second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Certain exemplary embodiments will now be described in greater detail with reference to the accompanying drawings. 
     In the following description, the same drawing reference numerals are used for the same elements even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the invention. Thus, it is apparent that the exemplary embodiments can be carried out without those specifically defined matters. Also, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail. 
       FIG. 1  schematically illustrates a BLU of a display apparatus according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1 , the BLU includes a display housing  1 , a support plate  2 , a light source  10 , a light guide plate (LGP)  20 , an optical sheet  30 , a first fixing unit  100  and a second fixing unit  200 . 
     The display housing  1  accommodates a control board and a plurality of electronic components to drive the BLU. The support plate  2  is connected to an upper side of the display housing  1 . 
     The light source  10 , the LGP  20 , the optical sheet  30  and the first and the second fixing units  100  and  200 , which configure the BLU, are disposed in a space formed between the support plate  2  and the display housing  1 . 
     The display housing  1  and the support plate  2  are connected to each other such that the light source  10 , the LGP  20 , the optical sheet  30 , and the first and the second fixing units  100  and  200  are prevented from being detached and are fixed in their respective positions. 
     The light source  10  includes a plurality of light emitting diodes (LEDs), which are disposed at regular intervals on an edge portion of the LGP  20  on a printed circuit board (PCB). 
     The LGP  20  is made of transparent materials so that light generated by the light source  10  may be transmitted therethrough. The LGP  20  is spaced apart by a predetermined distance from the light source  10 . 
     The optical sheet  30  is attached to the LGP  20 , and diffuses the light, which is generated by the light source  10  and is transmitted through the LGP  20 , and enables brightness of the LGP  20  to be equalized. 
     The first fixing unit  100  fixes both the LGP  20  and the optical sheet  30 . As shown in  FIG. 5  and  FIG. 6 , the first fixing unit  100  includes a first fixing projection  110 , an optical sheet opening  120  and a first support groove  130 . 
     According to a first exemplary embodiment, as shown in  FIG. 2 , the first fixing projection  110  includes a first body  110   a  to support the optical sheet  30 , a second body  110   b  to support the LGP  20 , and a projection support plate  110   c  to fix the mounting location of the first fixing projection  110 . 
     As shown in  FIG. 4 , the first fixing projection  110  is penetratingly connected to a mounting recess  1   a  and a mounting hole  1   b  formed on a rear surface of the display housing  1 . The mounting hole  1   b  may have a diameter corresponding to a diameter of the second body  110   b . Accordingly, the first and the second bodies  110   a  and  110   b  passing through the mounting hole  1   b  support the optical sheet  30  and the LGP  20 , respectively, and control locations of the optical sheet  30  and the LGP  20 . 
     A diameter of the second body  110   b  of the first fixing projection  110  is sufficiently thick to support the weight of the LGP  20 . In the case of a BLU using an edge-type LED light source, since the first fixing projection  110  is disposed proximate the light source  10 , interference of light may be reduced as the diameter of the first fixing projection  110  becomes smaller. Accordingly, it is desirable to form the first fixing projection  110  with as small a diameter as possible. The first fixing projection  110  may be made of opaque materials and may be colored with black, in order to prevent a light leakage phenomenon. Additionally, at least two first fixing projections  110  may be mounted on an upper side and a lower side of the LGP  20 , respectively, and may be disposed at four vertically symmetrical positions as shown in  FIG. 1 . 
     The optical sheet  30  may be made of resin film material and thus may be lighter than the LGP  20 . Accordingly, a diameter of the first body  110   a  to be hooked into the optical sheet opening  120  may be smaller than the diameter of the second body  110   b  supporting the LGP  20  which is relatively heavier than the optical sheet  30 . 
     The optical sheet opening  120  may be formed integrally with the optical sheet  30 , and may be provided in the form of a penetrating hole having a predetermined size. The optical sheet opening  120  may have a size corresponding to the first fixing projection  110 , as shown in  FIG. 2 . 
     Referring to  FIG. 1 , the first support groove  130  may be formed on the LGP  20  in the form of a trench having a width and a depth corresponding to the diameter of the first fixing projection  110 , but there is no limitation thereto. Accordingly, the first support groove  130  may be formed have a width and a depth which are larger than the diameter of the first fixing portion  110  by a predetermined amount, taking into consideration thermal expansion of the LGP  20  occurring due to heat generated by the light source  10 . 
     The first fixing projection  110 , the optical sheet opening  120  and the first support groove  130  may function to fix the location of the LGP  20  and the optical sheet  30  while supporting the weight of the LGP  20  and the optical sheet  30 . For example, four first fixing units  100  may be provided such that four first fixing projections  110 , four optical sheet openings  120  and four first support grooves  130  are provided at four positions of the BLU, respectively. That is, as shown in  FIG. 1 , two of the first fixing units  100  are disposed symmetrically at two positions on the upper side of the LGP  20 , and two of the first fixing units  100  are disposed symmetrically at two positions on the lower side of the LGP  20 . However, the exemplary embodiments are not limited to four first fixing units  100  and other numbers of first fixing units may be utilized. Alternatively or additionally, although not shown, the first fixing units  100  may be provided at positions on a left side and a right side of the LGP  20 . 
     The second fixing unit  200  is similar to or the same as the first support groove  130  and the second body  110   b  of the first fixing unit  100 . That is, as shown in  FIG. 5 , the second fixing unit  200  includes a second fixing projection  210  and a second support groove  230  and is similar to the first fixing unit  100  from which the first body  110   a  to support the optical sheet  30  is removed. Accordingly, the second fixing projection  210  shown in  FIG. 3  is connected to the display housing  1  and supports the LGP  20 . The second fixing projection  120  has a same diameter as the diameter of the second body  110   b  of the first fixing projection  110 . 
     As shown in  FIG. 1 , six second fixing units  200  may be provided such that six second fixing projections  210  may be formed at six positions of the BLU, that is, a first position between the two first fixing projections  110  on the upper side of the LGP  20 , a second position between the two first fixing projections  110  on the lower side of the LGP  20 , a third position and fourth positions on a left side of the LGP  20 , and a fifth position and sixth position on a right side of the LGP  20 . However, the exemplary embodiments are not limited to six second fixing units  100  and the number of second fixing units  200  may increase according to a size of the LGP  20 . 
     The second support groove  230  may be formed on the LGP  20  to have a width and a depth corresponding to the diameter of the second fixing projection  210 . The second support groove  230  may be configured in the trench form which is the same as the first support groove  130  described above. 
     In this situation, the optical sheet opening  120  may have a size corresponding to the diameter of the first fixing projection  110  and second fixing projection  210 . The optical sheet opening  120  is configured in the form of a quadrangle as shown in  FIGS. 1 ,  5  and  6 , but there is no limitation to such a quadrangle. Alternatively, the optical sheet opening  120  may be configured in the form of a circle, triangle or loop, although not shown in the drawings. In other words, any component part capable of having the shape of a penetrating hole in which the first fixing projection  110  is inserted may be used as the optical sheet opening  120 . 
     Accordingly, the first fixing projection  110  and second fixing projection  210  may be used in common, and thus it is possible to more conveniently assemble the BLU and reduce the number of component parts of the BLU. 
     According to another exemplary embodiment, the first fixing projection  110  may include a first portion  110   a  for supporting the optical sheet  30 , and a second portion  110   b  for supporting the LGP  20 . 
     Since the optical sheet  30  is lighter in weight than the LGP  20 , the first portion  110   a  which is inserted in the optical sheet opening  120  may be smaller in diameter than the second portion  110   b  for supporting the LGP  20  which is relatively heavier in weight than the optical sheet  30 . 
     In this situation, the optical sheet opening  120  may be formed with a sufficient width or diameter to allow the first portion  110   a  to penetrate the optical sheet opening  120 . However, even when the optical sheet opening  120  has a diameter corresponding to the second portion  110   b  as described above with reference to  FIGS. 1 and 2 , there is no problem to use the optical sheet opening  120 . 
     Additionally, although not shown in the drawings, the first portion  110   a  may be provided in any form capable of supporting the optical sheet  30 , for example a circle, triangle or loop. 
     As described above, the first fixing projection  110  can support both the LGP  20  and the optical sheet  30  at once, and therefore it is possible to reduce not only the cost required to manufacture the LGP  20  but also the number of component parts caused by component part commonality, as compared with related fixing methods. 
     The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.