Patent Publication Number: US-2023144694-A1

Title: Display apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a bypass continuation of PCT International Application No. PCT/KR2022/011475, which was filed on Aug. 3, 2022, and claims priority to Korean Patent Application No. 10-2021-0155089, filed on Nov. 11, 2021, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     The disclosure relates to a display apparatus having an enhanced structure of fixing an optical sheet. 
     Discussion of Related Art 
     Display apparatuses display obtained or stored electrical information by converting the electrical information to visual information, and are used in various fields such as homes or work places. 
     The display apparatus may include a display that displays images and a supporting device that supports the display. The supporting device may be formed in various shapes. For example, the supporting device may be coupled onto a wall to support the display in a wall-mounted form or provided in a stand-alone type that stands on the floor to support the display. 
     The display may be rotationally configured to be selectively positioned horizontally or vertically based on the aspect ratio of an image. 
     An optical sheet provided in the display may expand due to heat generated when the display is operated. In a case of a structure of fixing the optical sheet without considering rotation of the display, the optical sheet may expand non-uniformly due to rotation of the display, causing creases on a screen of the display. 
     SUMMARY 
     Provided is a display apparatus having a structure of fixing an optical sheet to allow the optical sheet to expand uniformly even when a display is rotated. 
     According to an aspect of the disclosure, a display apparatus includes: a liquid crystal panel; a backlight unit arranged to supply light to the liquid crystal panel; an optical sheet provided between the liquid crystal panel and the backlight unit and having a hole formed therein; and a sheet fixer configured to fix the optical sheet, wherein the sheet fixer includes: an anti-deviation projection inserted in the hole of the optical sheet to restrict movement of the optical sheet in a first direction, and a supporting projection contacting the optical sheet to restrict movement of the optical sheet in a second direction opposite the first direction. 
     The optical sheet may further include a deformable part configured to come into contact with the supporting projection, and to be structurally deformed by the supporting projection due to expansion of the optical sheet. 
     The optical sheet may expand in the second direction by structural deformation of the deformable part. 
     The anti-deviation projection may contact a first end of the hole, and the anti-deviation projection may be spaced apart from a second end of the hole by a gap in the second direction to allow expansion of the optical sheet in the second direction. 
     The anti-deviation projection may be configured to remain inserted through the hole when the anti-deviation projection moves forward or backward. 
     The anti-deviation projection may include: a first projection extending through the hole, and an anti-deviation part extending from an end of the first projection in the second direction. 
     The anti-deviation projection may include: a first projection extending through the hole, and an anti-deviation part extending from an end of the first projection in the first direction, and the anti-deviation part may have a length in the first direction that is longer than a width of the hole in the first direction. 
     The optical sheet may have a guide hole formed therein, and the guide hole is spaced apart from the hole, and the sheet fixer may further include a guide projection inserted to the guide hole and configured to guide the optical sheet during assembly of the optical sheet. 
     The guide projection may contact a first end of the guide hole, and the guide projection may be spaced apart from a second end of the guide hole by a gap in the second direction to allow expansion of the optical sheet in the second direction. 
     The supporting projection may be provided between the anti-deviation projection and the guide projection, spaced apart from the anti-deviation projection in the second direction, and spaced apart from the guide projection in the second direction. 
     The optical sheet may have a deformable hole formed therein, and the deformable hole is spaced apart from the deformable part between the hole and the guide hole in the first direction, and the deformable hole may be configured to assist structural deformation of the deformable part. 
     The display apparatus may further include a bottom chassis covering a rear side of the liquid crystal panel, and the sheet fixer may be coupled to the bottom chassis. 
     The display apparatus may further include: a middle frame provided along edges of the liquid crystal panel and configured to support the liquid crystal panel; and a light guide panel provided between the middle frame and the bottom chassis and configured to diffuse light emitted from the backlight unit, wherein a first edge of the optical sheet is fixed by being pressed by the middle frame and the light guide panel, and wherein one or more remaining edges of the optical sheet are spaced apart from the middle frame by a gap in a forward-backward direction. 
     The backlight unit may further include: a substrate facing the first edge of the optical sheet pressed by the middle frame and the light guide panel, anda plurality of light sources arranged on the substrate at intervals in a direction in which the substrate extends. 
     The sheet fixer may be elastically fitted to the bottom chassis without an extra fastening member. 
     The guide projection may include: a second projection extending forward to penetrate the guide hole, and a bending part bent downward from the second projection. 
     The supporting projection may include: a third projection extending forward to penetrate the deformable hole, and a first extension extending downward from the third projection. 
     The supporting projection may further include a second extension extending backward from the first extension. 
     The deformable hole may be configured to assist structural restoration of the deformable part. 
     The optical sheet may expand in a direction away from the first edge of the optical sheet and toward the one or more remaining edges of the optical sheet when the optical sheet is in a vertical position, and the optical sheet may expand in a direction toward the first edge of the optical sheet when the optical sheet is in a horizontal position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    illustrates an exterior of a display apparatus, according to an embodiment of the disclosure; 
         FIG.  2    is an exploded perspective view of a display apparatus, according to an embodiment of the disclosure; 
         FIG.  3    is an enlarged view of portion C of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view along A-A of  FIG.  1   ; 
         FIG.  5    is a cross-sectional view along B-B of  FIG.  1   ; 
         FIG.  6    separately illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus, according to an embodiment of the disclosure; 
         FIG.  7    is an enlarged view of portion D of  FIG.  6   ; 
         FIG.  8    illustrates a sheet fixer separated from a bottom chassis, according to an embodiment of the disclosure; 
         FIG.  9    illustrates a sheet fixer viewed from a different angle, according to an embodiment of the disclosure; 
         FIG.  10    is a front view of  FIG.  7   ; 
         FIG.  11    is a cross-sectional view along E-E of  FIG.  10   ; 
         FIG.  12    is a cross-sectional view along F-F of  FIG.  10   ; 
         FIG.  13    is a cross-sectional view along G-G of  FIG.  10   ; 
         FIG.  14    illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus when the optical sheet expands, according to an embodiment of the disclosure; 
         FIG.  15    is a cross-sectional view along H-H of  FIG.  14   ; 
         FIG.  16    is a cross-sectional view along J-J of  FIG.  14   ; 
         FIG.  17    is a cross-sectional view along K-K of  FIG.  14   ; 
         FIG.  18    separately illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus, according to an embodiment of the disclosure; 
         FIG.  19    is an enlarged view of portion L of  FIG.  18   ; 
         FIG.  20    is a cross-sectional view along M-M of  FIG.  19   ; 
         FIG.  21    is a cross-sectional view along N-N of  FIG.  19   ; and 
         FIG.  22    is a cross-sectional view along O-O of  FIG.  19   . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments and features as described and illustrated in the disclosure are merely examples, and there may be various modifications thereto. 
     Throughout the specification, like reference numerals refer to like parts or components. This specification does not describe all elements of the embodiments of the present disclosure and detailed descriptions on what are well known in the art or redundant descriptions on substantially the same configurations may be omitted. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. It is to be understood that the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. It will be further understood that the terms “comprise” and/or “comprising,” 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. 
     The terms including ordinal numbers like “first” and “second” may be used to explain various components, but the components are not limited by the terms. The terms are only for the purpose of distinguishing a component from another. Thus, a first element, component, region, layer or room discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the disclosure. Descriptions shall be understood as to include any and all combinations of one or more of the associated listed items when the items are described by using the conjunctive term “~ and/or ~,” or the like. 
     The terms “forward (or front)”, “backward (or behind)”, “left”, and “right” as herein used are defined with respect to the drawings, but the terms may not restrict the shape and position of the respective components. 
     Reference will now be made in detail to embodiments of the disclosure, which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. 
       FIG.  1    illustrates an exterior of a display apparatus, according to an embodiment of the disclosure. 
     Referring to  FIG.  1   , a display apparatus  1  is a device that is able to process image signals received from the outside and visually present the processed image. In the following description, it is assumed that the display apparatus  1  is a television (TV), but embodiments of the disclosure are not limited thereto. For example, the display apparatus  1  may be implemented in various forms, such as a monitor, a portable multimedia device, a portable communication device, and any device capable of visually presenting images, without being limited thereto. 
     The display apparatus  1  may be a large format display (LFD) installed outdoors such as on a rooftop of a building or at a bus stop. The display apparatus  1  is not, however, exclusively installed outdoors, but may be installed at any place, even indoors with a lot of foot traffic, e.g., at subway stations, shopping malls, theaters, offices, stores, etc. 
     The display apparatus  1  may receive contents including video and audio signals from various content sources and output video and audio corresponding to the video and audio signals. For example, the display apparatus  1  may receive content data through a broadcast receiving antenna or a cable, receive content data from a content reproducing device, or receive content data from a content providing server of a content provider. 
     As shown in  FIG.  1   , the display apparatus  1  may be oriented in a horizontal direction (i.e., the display apparatus  1  may be in a horizontal position), and may include a main body  1   a  and a screen  1   b  for displaying an image I. 
     The main body  1   a  forms the exterior of the display apparatus  1 , and components for the display apparatus  1  to display the image I or perform many different functions may be included in the main body  1   a . Although the main body  1   a  of  FIG.  1    is shaped like a flat panel, the shape of the main body  1   a  is not limited thereto. For example, the main body  1   a  may have the form of a curved panel. 
     Although the main body  1   a  is shown as having a flat panel shape, the shape of the main body  1   a  is not limited thereto. The display apparatus  1  may include the main body  1   a  and a supporting device (not shown) supporting the main body  1   a  to be rotatable. Alternatively, the main body  1   a  and the supporting device may be integrally formed. In a case that the main body  1   a  is rotatable, the screen  1   b  may be positioned horizontally or vertically based on an aspect ratio of the image I. 
     The screen  1   b  may be formed on the front side of the main body  1   a  for displaying the image I. For example, the screen  1   b  may display still images or moving images. The screen  1   b  may also display two dimensional (2D) plane images, or three dimensional (3D) stereographic images using parallax of both eyes of the user. 
     The screen  1   b  may include a non-self-emitting light panel (e.g., a liquid crystal panel) capable of passing or blocking light emitted by a light source, e.g., a backlight unit (BLU). 
     A plurality of pixels P are formed on the screen  1   b , and the image I displayed on the screen  1   b  may be formed by rays emitted by the plurality of pixels P. For example, the rays emitted by the plurality of pixels P may be combined like a mosaic into the image I on the screen  1   b . 
     The plurality of pixels P may emit light in various colors and brightness. Each of the pixels P may include subpixels PR, PG, and PB to emit different colors of light. 
     The subpixels PR, PG, and PB may include a red subpixel PR to emit red light, a green subpixel PG to emit green light, and blue subpixel PB to emit blue light. The red light may be defined as having wavelengths in the range of about 620 to about 750 nm, where 1 nm is a billionth of a meter. The green light may have wavelengths in the range of about 495 to 570 nm. The blue light may have wavelengths in the range of about 450 to 495 nm. 
     By combining the red light of the red subpixel PR, the green light of the green subpixel PG, and the blue light of the blue subpixel PB, each of the pixels P may emit various brightness and colors of light. 
       FIG.  2    is an exploded perspective view of a display apparatus, according to an embodiment of the disclosure.  FIG.  3    is an enlarged view of portion C of  FIG.  2   . 
     Referring to  FIG.  2   , the display apparatus  1  according to an embodiment of the disclosure may include a BLU  50  provided to emit light, a liquid crystal panel  20  for blocking or passing the light emitted from the BLU  50 , a top chassis  10  forming front and side edges of the display apparatus  1 , a bottom chassis  40  arranged to cover the rear side of the liquid crystal panel  20 , a middle frame  30  arranged to connect between the top chassis  10  and the bottom chassis  40 , and a rear cover  90  forming a rear exterior of the display apparatus  1 . The rear cover  90  may be coupled onto the rear side of the bottom chassis  40  to form the rear exterior of the display apparatus  1 . 
     The top chassis  10 , the bottom chassis  40 , the middle frame  30 , and the rear cover  90  may form the main body  1   a  of the display apparatus  1 . 
     The display apparatus  1  may further include a light guide panel  70  provided to diffuse the light emitted from the BLU  50 , an optical sheet  60  arranged in front of the light guide panel  70 , and a sheet fixer  100  (see  FIG.  7   ) provided to fix the optical sheet  60 . 
     In an embodiment of the disclosure, the display apparatus  1  may further include a light diffuser sheet  80  arranged in front of the light guide panel  70  and the optical sheet  60  and behind the liquid crystal panel  20  to diffuse light. 
     Referring to  FIG.  3   , the BLU  50  may include a plurality of light emitting diodes (LEDs)  52  emitting monochromatic light (e.g., white light) and a substrate  51  provided for the plurality of LEDs  52  to be mounted thereon. The light guide panel  70 , the optical sheet  60 , and the light diffuser sheet  80  may refract, reflect and scatter light emitted from the LEDs  52  to convert the emitted light into a uniform surface light. 
     In an embodiment of the disclosure, the substrate  51  may extend along the lower edge of the bottom chassis  40 . The substrate  51  may be placed to be parallel to the ground, and the plurality of LEDs  52  mounted on the substrate  51  may emit light upward. The plurality of LEDs  52  may be arranged at certain intervals in a direction in which the substrate  51  extends. 
     In an embodiment of the disclosure, the substrate  51  may be arranged on the lower edge of the bottom chassis  40 . It is not, however, limited thereto, and the substrate  51  may be arranged on one or both side edges of the bottom chassis  40 . 
     The liquid crystal panel  20  is arranged in front of the light guide panel  70  for blocking or passing the light emitted from the BLU  50  to form the image I. 
     The front surface of the liquid crystal panel  20  may form the screen  1   b  of the aforementioned display apparatus  1 , and the liquid crystal panel  20  may include the plurality of pixels P. Each of the pixels P of the liquid crystal panel  20  may block or pass the light from the BLU  50  individually and separately from the remaining pixels P. The light that is passed through by the plurality of pixels P may form the image I displayed on the screen  1   b . 
       FIG.  4    is a cross-sectional view along A-A of  FIG.  1   .  FIG.  5    is a cross-sectional view along B-B of  FIG.  1   . 
     Referring to  FIGS.  4  and  5   , the top chassis  10  may be arranged to support the liquid crystal panel  20  by covering the front edge of the liquid crystal panel  20  and form the side exterior of the display apparatus  1 . A portion of the top chassis  10  covering the front edge of the liquid crystal panel  20  may constitute a bezel of the display apparatus  1 . The top chassis  10  may include a top chassis groove  11  formed for a first frame projection  31  of the middle frame  30  to be inserted thereto. 
     The middle frame  30  may include the first frame projection  31  arranged to be inserted to the top chassis groove  11  of the top chassis  10 , a second frame projection  32  arranged to fix the light diffuser sheet  80  by passing through a sheet hole  81  of the optical diffuser sheet  80 . Additionally, the middle frame  30  may include a third frame projection  33  and a fourth frame projections  34  provided to support the optical sheet  60 . Furthermore, the middle frame  30  may include a frame groove  35  formed for a chassis projection  41  of the bottom chassis  40  to be inserted thereto. In an embodiment of the disclosure, the middle frame  30  may be injection-molded. 
     The bottom chassis  40  may be provided to cover the rear side of the liquid crystal panel  20 . The bottom chassis  40  may include the chassis projection  41  formed with an ending portion of the bottom chassis  40  bent to be inserted to the frame groove  35  of the middle frame  30 . The bottom chassis  40  may further include a bottom chassis groove  42  (see  FIG.  8   ) formed for a fixer projection  102  of the sheet fixer  100  to be inserted thereto. 
     The liquid crystal panel  20  and the light diffuser sheet  80  arranged behind the liquid crystal panel  20  to cover the rear surface of the liquid crystal panel  20  may be arranged between the top chassis  10  and the middle frame  30 . The light diffuser sheet  80  may be formed to diffuse light and may have a thickness thinner than the light guide panel  70 . 
     Referring to  FIGS.  4  and  5   , a first buffering member  b   1  and a second buffering member  b   2  may be arranged between the liquid crystal panel  20  and the top chassis  10 . The first buffering member  b   1  and the second buffering member  b   2  may be arranged between the liquid crystal panel  20  and the top chassis  10  to distribute pressure applied to the liquid crystal panel  20 . The first buffering member  b   1  and the second buffering member  b   2  may be made of any material that is able to distribute the pressure. 
     The BLU  50  may emit light to a side of the light guide panel  70 . The substrate  51  and the side of the light guide panel  70  may be arranged to face each other. Similarly, the LEDs  52  and the side of the light guide panel  70  may be arranged to face each other. Light emitted from the LEDs  52  may enter the light guide panel  70  through the side of the light guide panel  70 , and the light that has entered the light guide panel  70  may exit through the front side of the light guide panel  70 . Point light emitted from the plurality of LEDs  52  may pass through the light guide panel  70  to be changed to surface light. 
     In an embodiment of the disclosure, the BLU  50  may include a substrate frame  53  provided to fix the substrate  51 . The substrate frame  53  may be arranged to be fixed to the bottom chassis  40  or the middle frame  30 . As the substrate frame  53  is fixed to the bottom chassis  40  or the middle frame  30 , the substrate  51  may be coupled to the inside of the display apparatus  1 . 
     The optical sheet  60  may be arranged to cover the front side of the light guide panel  70 . The optical sheet  60  may be arranged between the third and fourth frame projections  33  and  34  of the middle frame  30  and the light guide panel  70 . The optical sheet  60  may be fixed by the sheet fixer  100 . The optical sheet  60  may be provided to enhance properties of light output from the light guide panel  70 . 
     Referring to  FIG.  4   , a gap may be formed in an upper portion of the display apparatus  1  between the optical sheet  60  and the third frame projection  33 . The third frame projection  33  may be provided to prevent the optical sheet  60  from falling out forward. The third frame projection  33  may contact the optical sheet  60  such that the third frame projection does not apply pressure on the optical sheet  60 . With this structure, when the optical sheet  60  expands, the third frame projection  33  may not hinder expansion of the optical sheet  60 . The optical sheet  60  may expand upward. 
     Referring to  FIG.  5   , in a lower portion of the display apparatus  1 , a third buffering member  b   3  may be arranged between the fourth frame projection  34  and the optical sheet  60 . 
     The third buffering member  b   3  may apply pressure onto the optical sheet  60 . Specifically, in a lower portion of the display apparatus  1 , the optical sheet  60  may be coupled to the inside of the main body  1   a  by being pressed by the third buffering member  b   3  and the light guide panel  70 . In the lower portion of the display apparatus  1 , pressure may be constantly applied onto the optical sheet  60 . 
     In the upper portion of the display apparatus  1 , when the optical sheet  60  and the light guide panel  70  are not pressed by the third frame projection  33 , a portion of the light emitted from the LEDs  52  may not enter the light guide panel  70 . That is, the light may leak out of the light guide panel  70 . To prevent this, the optical sheet  60  and the light guide panel  70  may be pressed by the third buffering member  b   3  in the lower portion of the display apparatus  1  where the BLU  50  is arranged. As the optical sheet  60  and the light guide panel  70  are pressed by the third buffering member  b   3  in a lower portion of the display apparatus  1 , leakage of light emitted from the LEDs  52  may be prevented. 
     The middle frame  30  may include the fourth frame projection  34  that serves as a positioning guide to which the third buffering member  b   3  may be attached. The third buffering member  b   3  may be made of any material that is able to distribute the pressure. 
     When the display apparatus  1  is in the horizontal position, even though a lower portion of the optical sheet  60  is pressed by the third buffering member  b   3 , when the optical sheet  60  vertically expands, the optical sheet  60  may expand downward because the downward gravitational force on the optical sheet  60  is greater than a frictional force on the optical sheet  60  caused by being pressed by the third buffering member  b   3 . When the display apparatus  1  is in a vertical position (i.e., rotated clockwise or counterclockwise by 90° or 270° with respect to the horizontal position), the up-down direction is turned to the left-right direction, therefore the downward gravitational force on the optical sheet  60  does not act in the same direction (with respect to the horizontal position) on the portion pressed by the third buffering member  b   3 . In the vertical position, an ending portion of one side of the optical sheet  60  is constrained by the third buffering member  b   3 , so that the optical sheet  60  may expand toward an ending portion of the other side of the optical sheet  60 . In a case that the ending portion of the other side of the optical sheet  60  is constrained without a gap between a hole  61  and an anti-deviation projection  110  arranged in the ending portion of the other side of the optical sheet  60 , the optical sheet  60  may crease when the optical sheet  60  expands. This may cause distortion of the image I. 
     According to the disclosure, the third frame projection  33  may not constrain an upper end of the optical sheet  60 . This may allow the optical sheet  60  to expand upward. Although not shown, the third frame projection  33  may be provided to prevent the side ends of the optical sheet  60  from being deviated. Specifically, the third frame projection  33  may prevent the side ends of the optical sheet  60  from falling out forward but may not constrain the side ends of the optical sheet  60  (similar to the upper end of the optical sheet  60 ). Accordingly, the optical sheet  60  may also expand toward one or both sides. In an embodiment of the disclosure, the optical sheet  60  may expand upward and toward the left and right sides. This may prevent the optical sheet  60  from creasing when the optical sheet  60  expands. Furthermore, this may prevent the optical sheet  60  from creasing even if the display apparatus  1  is rotated. 
       FIG.  6    separately illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus, according to an embodiment of the disclosure.  FIG.  7    is an enlarged view of portion D of  FIG.  6   .  FIG.  8    illustrates a sheet fixer separated from a bottom chassis, according to an embodiment of the disclosure.  FIG.  9    illustrates a sheet fixer viewed from a different angle, according to an embodiment of the disclosure. 
     Referring to  FIGS.  6 ,  7 ,  8  and  9   , in the display apparatus  1  according to an embodiment of the disclosure, the optical sheet  60  may be fixed by the sheet fixer  100 . The sheet fixer  100  may be elastically fitted to the bottom chassis  40  without an extra fastening member. The sheet fixer  100  may be provided in the plural to be arranged at certain intervals along an upper edge of the bottom chassis  40 . For example, there may be three sheet fixers  100 . It is not, however, limited thereto, and the number of sheet fixers may be changed depending on the size of the optical sheet  60 . 
     The optical sheet  60  may include the hole  61 , a guide hole  62 , and a deformable hole  63  arranged side by side. The hole  61 , the deformable hole  63  and the guide hole  62  may also be referred to as first, second, and third holes. 
     The optical sheet  60  may include a deformable part  64  arranged above the deformable hole  63 . The deformable part  64  and the deformable hole  63  may be arranged between the hole  61  and the guide hole  62 . 
     The sheet fixer  100  may include the fixer projection  102  arranged to be inserted to the bottom chassis groove  42  of the bottom chassis  40 , and an elastic projection  104  formed to be elastically coupled to the bottom chassis  40 . The fixer projection  102  and the elastic projection  104  may each be provided in the plural. The elastic projection  104  may be formed to be deformable. The sheet fixer  100  may be coupled to the bottom chassis  40  by elastic resilience of the elastic projection  104 . 
     The sheet fixer  100  may include a first body  101  arranged to face the upper surface of the bottom chassis  40 , and a second body  103  extending downward from the first body  101 . The fixer projection  102  may be formed with a portion of the first body  101  sunken downward, and the elastic projection  104  may be formed by extending backward from the second body  103 . 
     The sheet fixer  100  may include the anti-deviation projection  110 , a supporting projection  130 , and a guide projection  120 . The anti-deviation projection  110 , the supporting projection  130 , and the guide projection  120  may also be referred to as first, second, and third projections. 
     The anti-deviation projection  110  may be inserted to the hole  61  and the guide projection  120  may be inserted to the guide hole  62  to restrict downward movement of the optical sheet  60 . The supporting projection  130  may restrict upward movement of the optical sheet  60  by contacting the deformable part  64 . 
       FIG.  10    is a front view of  FIG.  7   .  FIG.  11    is a cross-sectional view along E-E of  FIG.  10   .  FIG.  12    is a cross-sectional view along F-F of  FIG.  10   .  FIG.  13    is a cross-sectional view along G-G of  FIG.  10   . 
     Referring to  FIGS.  10 ,  11 ,  12 , and  13   , structures of the optical sheet  60  and the sheet fixer  100  when the optical sheet  60  is not expanded will now be described in detail. 
     Referring to  FIGS.  10  and  11   , the anti-deviation projection  110  may include a first projection  111  protruding forward from the second body  103 , and an anti-deviation part  112  bent upward from the first projection  111 . 
     When the anti-deviation projection  110  is inserted to the hole  61 , the first projection  111  may come into contact with an upper end  61   a  of the hole  61 . As the optical sheet  60  moves downward by gravity, the first projection  111  comes into contact with the upper end  61   a  of the hole  61  to restrict downward movement of the optical sheet  60 . 
     The anti-deviation part  112  may be provided to prevent the anti-deviation projection  110  from passing through the hole  61  as the optical sheet  60  moves forward or backward. In other words, the anti-deviation part  112  may be arranged to remain inserted through the hole  61  even when the optical sheet  60  moves forward or backward. As shown in  FIGS.  4  and  5   , the edges of the optical sheet  60  may be prevented from falling out forward by the third frame projection  33  or the fourth frame projection  34 . The anti-deviation part  112  may be arranged to prevent the optical sheet  60  from falling out of the sheet fixer  100  before the display apparatus  1  is assembled. 
     In an embodiment, the anti-deviation part  112  may be bent upward from an end of the first projection  111 . As described above, the optical sheet  60  may move downward due to gravity until the first projection  111  and the upper end  61   a  of the hole  61  come into contact with each other. When the optical sheet  60  moves forward while the first projection  111  is in contact with the upper end  61   a  of the hole  61 , the anti-deviation part  112  and the optical sheet  60  come into contact with each other, thereby preventing deviation of the optical sheet  60 . 
     A gap may be formed in the vertical direction between the anti-deviation projection  110  and a lower end  61   b  of the hole  61 . Specifically, a gap may be formed in the vertical direction between the first projection  111  and the lower end  61   b  of the hole  61 . With the gap formed in the vertical direction between the anti-deviation projection  110  and the hole  61 , the anti-deviation projection  110  may not hinder expansion of the optical sheet  60 . 
     Referring to  FIGS.  10  and  12   , the supporting projection  130  may be arranged to come into contact with the deformable part  64  of the optical sheet  60 . The deformable part  64  may form a portion of the edges of the optical sheet  60 . The deformable part  64  may be formed to be structurally deformed by the supporting projection  130  when the optical sheet  60  expands. For example, the deformable part  64  may be bent when the optical sheet  60  expands. 
     The supporting projection  130  may include a third projection  131  protruding forward from the second body  103 , a first extension  132  extending downward from the third projection  131 , and a second extension  133  extending backward from the first extension  132 . With this double bending structure of the supporting projection  130 , there may be no pointed projection formed from the front of the sheet fixer  100 . Accordingly, the assembly worker may protect his/her hands from being wounded by a possible end protruding from the supporting projection  130 . 
     In an embodiment of the disclosure, the deformable hole  63  may be formed below the deformable part  64  of the optical sheet  60 . The deformable hole  63  may be provided to supplement structural deformation of the deformable part  64 . As the deformable hole  63  is deformed in shape, structural deformation or bending of the deformable part  64  may be easily made. The deformable hole  63  may facilitate not only deformation of the deformable part  64  but also restoration of the deformable part  64 . For example, the deformable hole  63  may facilitate a spring-like action of the deformable part  64 . That is, when the optical sheet  60  expands in an upward direction (e.g., due to heat generated by the BLU  50 ), potential energy is stored in the compression/deformation of the deformation part  64  into the space provided by the deformable hole  63 ; and when the optical sheet  60  contracts (e.g., due to cooling when the BLU  50  is switched off), the potential energy of the deformation part  64  is released causing the optical sheet  60  to contract in a downward direction and restoring the deformable part  64 . 
     The deformable part  64  may be arranged between the hole  61  and the guide hole  62 . The deformable part  64  may connect a surrounding portion of the hole  61  to a surrounding portion of the guide hole  62 . The deformable part  64  may also be referred to as a bridge. 
     Referring to  FIGS.  10  to  13   , the guide projection  120  may be arranged to be inserted to the guide hole  62 . The guide projection  120  may be inserted to the guide hole  62  to guide the assembling position of the optical sheet  60 . Even when the guide projection  120  is inserted to the guide hole  62 , the guide projection  120  may be pulled out from the guide hole  62  when the optical sheet  60  or the sheet fixer  120  moves forward or backward. 
     The guide projection  120  may include a second projection  121  protruding forward from the second body  103 , and a bending part  122  bent downward from the second projection  121 . 
     Like the first projection  111 , the second projection  121  may be arranged to come into contact with an upper end  62   a  of the guide hole  62 . A gap may be formed between the second projection  121  and a lower end  62   b  of the guide hole  62 . Due to the gap between the second projection  121  and the guide hole  62 , expansion of the optical sheet  60  may not be hindered by the guide projection  120 . 
     In an embodiment of the disclosure, the bending part  122  may prevent the guide projection  120  from passing through the guide hole  62  due to forward movement of the optical sheet  60  when the optical sheet  60  expands. Furthermore, the bending part  122  may prevent the assembly worker from being wounded on his/her hand by a possible end protruding forward from the second projection  121 . 
       FIG.  14    illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus when the optical sheet expands, according to an embodiment of the disclosure.  FIG.  15    is a cross-sectional view along H-H of  FIG.  14   .  FIG.  16    is a cross-sectional view along J-J of  FIG.  14   .  FIG.  17    is a cross-sectional view along K-K of  FIG.  14   . 
     Referring to  FIGS.  14  to  17   , structures of the optical sheet  60  and the sheet fixer  100  when the optical sheet  60  expands will now be described in detail. 
     Referring to  FIG.  14   , the optical sheet  60  may expand due to heat generated when the display apparatus  1  operates. As described above, when the optical sheet  60  expands, the optical sheet  60  may expand upward because the lower end of the optical sheet  60  is fixed by being pressed by the fourth frame projection  34 . Hence, the optical sheet  60  may appear to be slightly moved upward. However, for convenience of explanation,  FIGS.  15  to  18    illustrate the optical sheet  60  assumed to have expanded, but actual features may be different from what are shown in  FIGS.  15  to  18   . 
     When the optical sheet  60  expands, the deformable part  64  and the deformable hole  63  may be deformed in structure by the supporting projection  130 . For example, as shown in  FIG.  17   , the deformable part  64  may be bendable. 
     Furthermore, when the optical sheet  60  expands, the anti-deviation projection  110  may come into contact with the lower end  61   b  of the hole  61  and the guide projection  120  may come into contact with the lower end  62   b  of the guide hole  62 . 
     Referring to  FIG.  15   , when the optical sheet  60  expands, the first projection  111  may come into contact with the lower end  61   b  of the hole  61 . It is not, however, limited thereto, and the optical sheet  60  may expand less than necessary to contact the lower end  61   b  of the hole  61 . 
     Referring to  FIG.  16   , when the optical sheet  60  expands, the deformable part  64  may be bent by the supporting projection  130 . This may cause a lower end  64   b  of the deformable part  64  to come into contact with the deformable hole  63 . It is not, however, limited thereto, and the lower end  64   b  of the deformable part  64  may expand less than necessary to contact the deformable hole  63 . 
     Referring to  FIG.  17   , when the optical sheet  60  expands, the second projection  121  may come into contact with the lower end  62   b  of the guide hole  62 . It is not, however, limited thereto, and the optical sheet  60  may expand less than necessary to contact the lower end  62   b  of the guide hole  62 . 
       FIG.  18    separately illustrates an optical sheet, a sheet fixer, and a bottom chassis in a display apparatus, according to an embodiment of the disclosure.  FIG.  19    is an enlarged view of portion L of  FIG.  18   .  FIG.  20    is a cross-sectional view along M-M of  FIG.  19   .  FIG.  21    is a cross-sectional view along N-N of  FIG.  19   .  FIG.  22    is a cross-sectional view along O-O of  FIG.  19   . 
     Referring to  FIGS.  18  to  22   , a sheet fixer  200  in accordance with an embodiment of the disclosure will now be described. The sheet fixer  200  may have the same function and purpose as the aforementioned sheet fixer  100  except for a partial structure. As the other structures are identical between the sheet fixer  200  and the aforementioned sheet fixer  100 , overlapping descriptions thereof will not be repeated. 
     In an embodiment of the disclosure, the sheet fixer  200  may include a first body  201  arranged to face the upper surface of the bottom chassis  40 , a fixer projection  202  formed with a portion of the first body  201  sunken, a second body  203  extending downward from the first body  201 , and an elastic projection protruding backward from the second body  203 . 
     Furthermore, the sheet fixer  200  may include an anti-deviation projection  210 , a supporting projection  230 , and a guide projection  220 . 
     Referring to  FIGS.  19  and  20   , the sheet fixer  200  according to an embodiment of the disclosure may include the anti-deviation projection  210 . The anti-deviation projection  210  may be inserted to the hole  61  to prevent the sheet fixer  200  from falling out of the hole  61 . In other words, the anti-deviation projection  210  may be inserted to the hole  61  to prevent the optical sheet  60  from falling out of the sheet fixer  200 . 
     In an embodiment of the disclosure, the anti-deviation projection  210  may include a first projection  211  protruding forward from the second body  203 , and an anti-deviation part  212  extending downward from an end of the first projection  211 . 
     The anti-deviation part  212  may be formed to have a vertical length larger than the vertical size of the hole  61 . With this structure, when the anti-deviation part  212  is inserted to the hole  61 , the optical sheet  60  may be prevented from being separated from the sheet fixer  200  because the anti-deviation part  212  is stuck in the hole  61  even when the optical sheet  60  or the sheet fixer  200  is moved forward or backward. 
     Referring to  FIGS.  19  and  21   , the supporting projection  230  may include a third projection  231  protruding forward from the second body  203 , and an extension  232  extending upward from an end of the third projection  231 . The extension  232  may prevent the assembly worker from being wounded on his/her hand by a possible end protruding forward from the third projection  231 . 
     Referring to  FIGS.  19  and  22   , the guide projection  220  may include a second projection  221  protruding forward from the second body  203 , and a bending part  222  extending downward from an end of the second projection  221 . The bending part  222  may prevent the assembly worker from being wounded on his/her hand by a possible end protruding forward from the second projection  221 . 
     According to the disclosure, a display apparatus having a structure of fixing an optical sheet to allow the optical sheet to expand uniformly even when a display is rotated may be provided. 
     While some embodiments of the disclosure have been described above, it will be understood that various modifications can be made without departing from the scope of the disclosure.