Patent Publication Number: US-2022236470-A1

Title: Optical film and display device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. 119 from Korean Patent Application No. 10-2021-0011380, filed on Jan. 27, 2021 in the Korean Intellectual Property Office, the contents of which are herein incorporated by reference in their entirety. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present disclosure are directed to an optical film and a display device that includes the same. 
     2. Discussion of the Related Art 
     The importance of display devices has steadily increased with the development of multimedia technology. Accordingly, various types of display devices, such as a liquid crystal display (LCD) device, an organic light emitting display (OLED) device, etc., have been developed. Such display devices have been incorporated to various mobile electronic devices, such as portable electronic devices such as a smart phone, a smart watch, or a tablet PC, etc. 
     The display quality of a display device may deteriorate due to incident light that is reflected from the display device. To address this situation, studies have been conducted to reduce reflection of external light by providing an optical film on a display surface of a display device. 
     SUMMARY 
     Embodiments of the present disclosure provide an optical film that can reduce light leakage by reducing reflectance of light at a side, and a display device including the same. 
     In accordance with an optical film according to embodiments, light leakage can be reduced by reducing the reflectance of light at a side, and by providing a first optical compensation layer that compensates for distortion of an optical axis when viewed from the side. 
     Further, in accordance with a display device according to embodiments, it is possible to enhance display quality by reducing light leakage. 
     According to an embodiment of the disclosure, an optical film comprises a polarizing layer, a first optical compensation layer that is disposed under the polarizing layer and is a biaxial plate, a second optical compensation layer that is disposed under the first optical compensation layer and is a quarter wave plate, and a third optical compensation layer that is disposed under the second optical compensation layer and is a positive C plate. The first optical compensation layer has an optical axis angle of 86 to 94 degrees with respect to a transmission axis of the polarizing layer. 
     In an embodiment, the first optical compensation layer has an in-plane retardation value (Ro) from 170 nm to 270 nm. 
     In an embodiment, the first optical compensation layer has a refractive index ratio (Nz) from 0.5 to 2.5. 
     In an embodiment, the first optical compensation layer has a retardation value (Rth) from 4 nm to 84 nm in a thickness direction. 
     In an embodiment, the transmission axis of the polarizing layer is at 0 degrees and an optical axis of the second optical compensation layer is at 45 degrees. 
     In an embodiment, the optical film further comprises at least one of a first protective member disposed on the polarizing layer or a second protective member disposed between the polarizing layer and the first optical compensation layer. 
     In an embodiment, the optical film further comprises a first adhesive member disposed between the first optical compensation layer and the second optical compensation layer, and a second adhesive member disposed between the second optical compensation layer and the third optical compensation layer. 
     In an embodiment, the second optical compensation layer is in contact with a bottom surface of the first optical compensation layer. 
     In an embodiment, the first optical compensation layer is in contact with a bottom surface of the polarizing layer. 
     According to an embodiment of the disclosure, a display device comprises a display panel, and an optical film disposed on the display panel. The optical film includes a polarizing layer, a first optical compensation layer that is disposed under the polarizing layer and is a biaxial plate, a second optical compensation layer that is disposed under the first optical compensation layer and is a quarter wave plate, and a third optical compensation layer that is disposed under the second optical compensation layer and is a positive C plate. The first optical compensation layer has an optical axis angle of 86 to 94 degrees with respect to a transmission axis of the polarizing layer. 
     In an embodiment, the third optical compensation layer is closer to the display panel than the polarizing layer, and is in contact with the display panel. 
     In an embodiment, the display device further comprises a cover window disposed in front of the optical film, a polymer film layer disposed behind the display panel, and a cushion layer disposed behind the polymer film layer. 
     In an embodiment, the first optical compensation layer has an in-plane retardation value (Ro) from 170 nm to 270 nm. 
     In an embodiment, the first optical compensation layer has a refractive index ratio (Nz) from 0.5 to 2.5. 
     In an embodiment, the first optical compensation layer has a retardation value (Rth) from 4 nm to 84 nm in a thickness direction. 
     In an embodiment, the transmission axis of the polarizing layer is at 0 degrees and an optical axis of the second optical compensation layer is at 45 degrees. 
     In an embodiment, the display device further comprises at least one of a first protective member disposed on the polarizing layer or a second protective member disposed between the polarizing layer and the first optical compensation layer. 
     In an embodiment, the display device further comprises a first adhesive member disposed between the first optical compensation layer and the second optical compensation layer, and a second adhesive member disposed between the second optical compensation layer and the third optical compensation layer. 
     In an embodiment, the second optical compensation layer is in contact with a bottom surface of the first optical compensation layer. 
     According to an embodiment of the disclosure, an optical film comprises a polarizing layer; a first optical compensation layer that is disposed under the polarizing layer and is a biaxial plate; a second optical compensation layer that is disposed under the first optical compensation layer and is a quarter wave plate; and a third optical compensation layer that is disposed under the second optical compensation layer and is a positive C plate. The first optical compensation layer has an in-plane retardation value (Ro) from 170 nm to 270 nm, the first optical compensation layer has a refractive index ratio (Nz) from 0.5 to 2.5, and the first optical compensation layer has a retardation value (Rth) from 4 nm to 84 nm in a thickness direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a display device in an unfolded state according to an embodiment. 
         FIG. 2  is a perspective view of a display device in a folded state according to an embodiment. 
         FIG. 3  is a cross-sectional view of a display device in an unfolded state according to an embodiment. 
         FIG. 4  is a cross-sectional view of a display device in a folded state according to one embodiment. 
         FIG. 5  is a cross-sectional view of a display panel according to an embodiment. 
         FIG. 6  is a cross-sectional view of an optical film according to an embodiment. 
         FIG. 7  is a cross-sectional view of an optical film according to a comparative example. 
         FIG. 8  illustrates polarization of light that has passed through the optical film of the comparative example, as a Poincare sphere, when viewed from the front. 
         FIG. 9  illustrates polarization of light that has passed through an optical film of the comparative example, with a Poincare sphere, when viewed from the side. 
         FIG. 10  is a cross-sectional view of an optical film according to one embodiment. 
         FIG. 11  illustrates polarization of light that has passed through an optical film of an embodiment, with a Poincare sphere, when viewed from the side. 
         FIG. 12  is a cross-sectional view of an optical film according to an embodiment. 
         FIG. 13  is a cross-sectional view of an optical film according to an embodiment. 
         FIG. 14  is a cross-sectional view of an optical film according to an embodiment. 
         FIG. 15  is a cross-sectional view of an optical film according to an embodiment. 
         FIG. 16  illustrates reflectance according to a viewing angle of a display device according to the comparative example. 
         FIG. 17  is a graph of front reflectance of a display device according to the comparative example. 
         FIG. 18  illustrates LAB color space coordinates of reflected light according to an omnidirectional viewing angle in a display device according to the comparative example. 
         FIG. 19  shows colors of reflected light according to a viewing angle in a dark state of a display device according to the comparative example. 
         FIG. 20  illustrates reflectance according to a viewing angle of a display device according to an embodiment. 
         FIG. 21  is a graph of front reflectance of a display device according to an embodiment. 
         FIG. 22  illustrates LAB color space coordinates of reflected light according to an omnidirectional viewing angle in a display device according to an embodiment. 
         FIG. 23  shows colors of reflected light according to a viewing angle in a dark state of a display device according to an embodiment. 
         FIG. 24  shows the reflectance according to viewing angle in sample #1. 
         FIG. 25  shows the reflectance according to viewing angle in sample #2. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the disclosure are shown. This disclosure may, however, be embodied in different forms and should not be construed as limited to embodiments set forth herein. 
     It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. The same reference numbers may indicate the same components throughout the specification. 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a display device in an unfolded state according to an embodiment.  FIG. 2  is a perspective view of a display device in a folded state according to an embodiment. 
     Referring to  FIG. 1 , a display device  10  according to an embodiment can be incorporated into a smartphone, a mobile phone, a tablet PC, a personal digital assistant (PDA), a portable multimedia player (PMP), a television, a game machine, a wristwatch-type electronic device, a head-mounted display, a monitor of a personal computer, a laptop computer, a car navigation system, a car&#39;s dashboard, a digital camera, a camcorder, an external billboard, an electronic billboard, a medical device, an inspection device, various household appliances such as a refrigerator or a washing machine, or an Internet-of-Things device. 
     Further, the display device  10  according to an embodiment can be a foldable display device. For purposes of exposition, it will be assumed that the display device  10  is incorporated into a smartphone, but embodiments are not limited thereto. 
     In  FIGS. 1 and 2 , a first direction DR 1  is a direction parallel to one side of the display device  10  in a plan view and may be, for example, a horizontal direction of the display device  10 . A second direction DR 2  is a direction parallel to a side in contact with the one side of the display device  1  in a plan view, and may be, for example, a vertical direction of the display device  10 . A third direction DR 3  is a thickness direction of the display device  10  and is normal to plane defined by the first direction DR 1  and the second direction DR 2 . 
     In an embodiment, the display device  10  has a rectangular shape in a plan view. The display device  10  has a rectangular shape with right-angled or rounded corners in a plan view. The display device  10  includes two short sides parallel to the first direction DR 1  and two long sides parallel to the second direction DR 2 , in a plan view. 
     In an embodiment, the display device  10  includes a display area DA and a non-display area NDA. In a plan view, the shape of the display area DA corresponds to the shape of the display device  10 . For example, when the display device  10  has a rectangular shape in a plan view, the display area DA also has a rectangular shape. 
     In an embodiment, the display area DA includes a plurality of pixels that display an image. The plurality of pixels are arranged in a matrix. Each of the plurality of pixels may have a rectangular, rhombic, or a square shape in a plan view, but embodiments are not limited thereto. For example, in other embodiments, each of the plurality of pixels may have a quadrilateral shape other than a rectangular, rhombic, or square shape, a polygonal shape other than a quadrilateral shape, a circular shape, or an elliptical shape. 
     In an embodiment, the non-display area NDA does not include pixels and does not display an image. The non-display area NDA is disposed around the display area DA. The non-display area NDA surrounds the display area DA as shown in  FIGS. 1 and 2 , but embodiments are not limited thereto. In other embodiments, the display area DA is partially surrounded by the non-display area NDA. 
     In an embodiment, the display device  10  can maintain both a folded state and an unfolded state. As shown in  FIG. 2 , the display device  10  can be folded in an in-folding manner in which the display area DA is disposed on the inside thereof. When the display device  10  is in-folded, the top surfaces of the display device  10  face each other. Alternatively, for another example, the display device  10  can be folded in an out-folding manner in which the display area DA is disposed on the outside thereof. When the display device  10  is out-folded, the bottom surfaces of the display device  10  face each other. 
     In an embodiment, the display device  10  is a foldable device. As used herein, the term “foldable device” refers to a device which can be folded and is used to mean not only a folded device but also a device that can have both a folded state and an unfolded state. Further, the folding typically includes folding at an angle of about 180 degrees. However, embodiments of the present disclosure are not limited thereto, and in other embodiments, the folding angle may exceed 180 degrees or be less than 180 degrees. For example, the folding angle may be equal to or greater than 90 degrees and less than 180 degrees, or the folding angle may be equal to or greater than 120 degrees and less than 180 degrees. In addition, a folded state also includes when folding is performed out of an unfolded state, even if complete folding is not performed. For example, even if the device is folded at an angle of 90 degrees or less, as long as the maximum folding angle is 90 degrees or more, the device is considered as being in a folded state to distinguish from the unfolded state. During folding, the radius of curvature may be 5 mm or less, may be in the range of 1 mm to 2 mm, or may be about 1.5 mm, but embodiments are not limited thereto. 
     In an embodiment, the display device  10  includes a foldable area FDA, a first non-foldable area NFA 1 , and a second non-foldable area NFA 2 . The foldable area FDA is where the display device  10  is folded, and the first and second non-foldable areas NFA 1  and NFA 2  are where the display device  10  is not folded. 
     In an embodiment, the first non-foldable area NFA 1  is disposed on one side, such as an upper side, of the foldable area FDA. The second non-foldable area NFA 2  is disposed on the other side, such as a lower side, of the foldable area FDA. The foldable area FDA can be bent to a predetermined curvature. 
     In an embodiment, the foldable area FDA of the display device  10  is located at a specific location. One or two or more foldable areas FDA can be located at a specific location(s) in the display device  10 . In another embodiment, the location of the foldable area FDA is not specified in the display device  10  and can be freely set in various areas. 
     In an embodiment, the display device  10  can be folded in the second direction DR 2 . Accordingly, the length of the display device  10  in the second direction DR 2  is reduced by approximately half, so that a user can conveniently carry the display device  10 . 
     In an embodiment, the direction in which the display device  10  is folded is not limited to the second direction DR 2 . For example, the display device  10  can be folded in the first direction DR 1 . In this case, the length of the display device  10  in the first direction DR 1  is reduced by approximately half. 
       FIGS. 1 and 2  illustrate that each of the display area DA and the non-display area NDA overlaps the foldable area FDA, the first non-foldable area NFA 1 , and the second non-foldable area NFA 2 , but embodiments of the present disclosure are not limited thereto. For example, each of the display area DA and the non-display area NDA overlaps at least one of the foldable area FDA, the first non-foldable area NFA 1 , and the second non-foldable area NFA 2 . 
       FIG. 3  is a cross-sectional view of a display device in an unfolded state according to an embodiment.  FIG. 4  is a cross-sectional view of a display device in a folded state according to an embodiment. 
     Referring to  FIGS. 3 and 4 , in an embodiment, the display device  10  includes a display panel  100 , a front laminated structure  200  on a front side of the display panel  100 , and a rear laminated structure  300  on a rear side of the display panel  100 . The laminated structures  200  and  300  include at least one bonding member  251  to  253  and  351  to  354 , respectively. Here, the front side of the display panel  100  refers to a side in which the display panel  100  displays an image, and the rear side refers to a side that is opposite to the front side. One surface of the display panel  100  is located on the front side, and the other surface of the display panel  100  is located on the rear side. 
     In an embodiment, the display panel  100  displays an image. Examples of the display panel  100  include not only a self-light emitting display panel such as an organic light emitting display (OLED) panel, an inorganic electroluminescence (EL) display panel, a quantum dot light emitting display (QED) panel, a micro-LED display panel, a nano-LED display panel, a plasma display panel (PDP), a field emission display (FED) panel or a cathode ray tube (CRT) display panel, but also a light receiving display panel such as a liquid crystal display (LCD) panel or an electrophoretic display (EPD) panel. Hereinafter, for simplicity of exposition, an organic light emitting display panel will be described as an example of the display panel  100 , and an organic light emitting display panel incorporated into an embodiment will be simply referred to as the display panel  100 , unless a special distinction is required. However, embodiments are not limited to an organic light emitting display panel, and other embodiments incorporate other display panels mentioned above or known in the art and within the same scope of technical spirit. 
     In an embodiment, the display panel  100  further includes a touch member. The touch member is provided as a panel or film separate from the display panel  100  and attached onto the display panel  100 , but may also be provided in the form of a touch layer inside the display panel  100 . For simplicity of exposition, an embodiment in which a touch member is provided inside the display panel  100  and included in the display panel  100  will be described, but embodiments of the present disclosure are not limited thereto. 
       FIG. 5  is a cross-sectional view of a display panel according to an embodiment. 
     Referring to  FIG. 5 , in an embodiment, the display device  10  includes the display panel  100 . The display panel  100  includes a base substrate  11 , a first electrode  12 , a pixel defining layer  13 , a light emitting layer  14 , a second electrode  15 , an encapsulation layer  20  and a touch sensor  40 . 
     In an embodiment, the base substrate  11  is an insulating substrate. The base substrate  11  is flexible, and includes a flexible polymer material. The polymer material may be one or more of polyimide (PI), polyethersulphone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylenenaphthalate (PEN), polyethyleneterephthalate (PET), polyphenylenesulfide (PPS), polyallylate, polycarbonate (PC), cellulosetriacetate (CAT), or cellulose acetate propionate (CAP), or a combination thereof. 
     In an embodiment, the first electrode  12  is disposed on the base substrate  11 . In an embodiment, the first electrode  12  is an anode electrode. In addition, a plurality of components can be further disposed between the base substrate  11  and the first electrode  12 . The plurality of components can include, for example, a buffer layer, a plurality of conductive wires, an insulating layer, and a plurality of thin film transistors. 
     In an embodiment, the pixel defining layer  13  is disposed on the first electrode  12 . The pixel defining layer  13  includes an opening that exposes at least a portion of the first electrode  12 . 
     In an embodiment, the light emitting layer  14  is disposed on the first electrode  12 . The light emitting layer  14  is disposed in the opening of the pixel defining layer  13 . In one embodiment, the light emitting layer  14  emits one of red light, green light, or blue light. The wavelength of red light is about 620 nm to 750 nm, and the wavelength of green light is about 495 nm to 570 nm. Further, the wavelength of blue light is about 450 nm to 495 nm. The light emitting layer  14  is formed of a single layer. Alternatively, in other embodiments, the light emitting layer  14  includes a plurality of organic light emitting layers that are laminated together, such as a tandem structure. In other embodiments, the light emitting layer  14  emits white light. When the light emitting layer  14  emits white light, the light emitting layer  14  includes a red organic light emitting layer, a green organic light emitting layer, and a blue organic light emitting layer that are laminated together. 
     In an embodiment, the second electrode  15  is disposed on the light emitting layer  14  and the pixel defining layer  13 . The second electrode  15  entirely formed on the light emitting layer  14  and the pixel defining layer  13 . In some embodiments, the second electrode  15  is a cathode electrode. 
     In an embodiment, the first electrode  12 , the second electrode  15 , and the light emitting layer  14  constitute a light emitting element EL. 
     In an embodiment, the encapsulation layer  20  is positioned on the light emitting element EL. The encapsulation layer  20  seals the light emitting element EL and prevents external moisture, etc., from entering the light emitting element EL. 
     In an embodiment, the encapsulation layer  20  is a thin film encapsulation film, and includes one or more organic films and one or more inorganic films. For example, the encapsulation layer  20  includes a first inorganic film  21  positioned on the second electrode  15 , an organic film  22  positioned on the first inorganic film  21 , and a second inorganic film  23  positioned on the organic film  22 . 
     In an embodiment, the first inorganic film  21  prevents moisture or oxygen, etc., from infiltrating into the light emitting element EL. The first inorganic film  21  includes one or more of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, or silicon oxynitride (SiON), etc. 
     In an embodiment, the organic film  22  is positioned on the first inorganic film  21 . The organic film  22  improves flatness. The organic film  22  is formed of a liquid organic material, such as an acrylic resin, a methacrylic resin, polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin or a perylene resin, etc. The organic material is disposed on the base substrate  11  through vapor deposition, printing and coating, and may be subjected to a curing process. 
     In an embodiment, the second inorganic film  23  is positioned on the organic film  22 . The second inorganic film  23  performs substantially the same or a similar function as the first inorganic film  21 , and is made of a material substantially the same as or similar to that of the first inorganic film  21 . The second inorganic film  23  completely covers the organic film  22 . In some embodiments, the second inorganic film  23  and the first inorganic film  21  contact each other in the non-display area NDA and form an inorganic-inorganic junction. However, embodiments of the structure of the encapsulation layer  20  are not limited thereto, and in other embodiments, the laminated structure of the encapsulation layer  20  can vary. Alternatively, in other embodiments, the encapsulation layer  20  is formed of a glass substrate, etc. 
     In an embodiment, the touch sensor  40  is disposed on the encapsulation layer  20 . In an embodiment, the touch sensor  40  is located directly on the encapsulation layer  20 . That is, the encapsulation layer  20  functions as a base portion of the touch sensor  40 . 
     In an embodiment, the touch sensor  40  includes a touch element layer  41  and a protective layer  43 . The touch element layer  41  includes a touch electrode and touch signal lines connected to the touch electrode. In an embodiment, the touch electrode includes a metal, and has a mesh shape. That is, the touch electrode is formed of a metal mesh pattern, thereby improving flexibility of the touch element layer  41 . 
     In an embodiment, the protective layer  43  is positioned on the touch element layer  41  and protects the touch element layer  41 . In an embodiment, the protective layer  43  includes an organic material, such as an acrylic polymer. When the protective layer  43  is made of an organic material, the touch sensor  40  is more flexible. 
     Referring back to  FIGS. 3 and 4 , in an embodiment, the front laminated structure  200  is disposed on the front side of the display panel  100 . The front laminated structure  200  includes an optical film  230 , a cover window  220 , and a cover window protection layer  210  that are sequentially laminated forward from the display panel  100 . 
     In an embodiment, the optical film  230  polarizes light passing therethrough. The optical film  230  reduces reflection of external light. In an embodiment, the optical film  230  includes a polarizing layer (see item  400  in  FIG. 6 ) and a plurality of optical compensation layers (see items  450 ,  460 , and  490  in  FIG. 6 ). A detailed description thereof will be provided below. 
     In an embodiment, the cover window  220  is disposed on the front side of the optical film  230 . The cover window  220  protects the display panel  100 . The cover window  220  is made of a transparent material. The cover window  220  includes, for example, glass or plastic. 
     In an embodiment, when the cover window  220  includes glass, the glass is ultra-thin glass (UTG) or thin glass. When the glass is ultra-thin glass or thin glass, it is flexible so that it can be curved, bent, folded, or rolled. The thickness of the glass may be, for example, in the range of 10 μm to 300 μm, in particular, in the range of 10 μm to 100 μm, or may be about 50 μm. The glass of the cover window  220  includes one or more of a soda-lime glass, an alkali aluminosilicate glass, a borosilicate glass, or a lithium alumina silicate glass. The glass of the cover window  220  includes chemically strengthened or thermally strengthened glass to increase rigidity. Chemical strengthening can be achieved through an ion exchange process in alkaline salts. The ion exchange process can be performed two or more times. In addition, the cover window  220  can be obtained by coating glass thin films on both surfaces of a polymer film. 
     In an embodiment, when the cover window  220  includes plastic, the cover window  220  is more flexibile for being folded. Examples of plastics applicable to the cover window  220  include, but are not limited to, polyimide, polyacrylate, polymethylmethacrylate (PMMA), polycarbonate (PC), polyethylenenaphthalate (PEN), polyvinylidene chloride, polyvinylidene difluoride (PVDF), polystyrene, ethylene vinylalcohol copolymer, polyethersulphone (PES), polyetherimide (PEI), polyphenylene sulfide (PPS), polyarylate (PAR), triacetyl cellulose (TAC), or cellulose acetate propionate (CAP). The plastic cover window  220  can include one or more of the plastic materials mentioned above. 
     In an embodiment, the cover window protection layer  210  is disposed on the front side of the cover window  220 . The cover window protection layer  210  can prevent scattering, absorb impacts, prevent scratches, prevent fingerprint smudges and glare on the cover window  220 . The cover window protection layer  210  includes a transparent polymer film. The transparent polymer film includes at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyimide (PI), polyarylate (PAR), polycarbonate (PC), polymethyl methacrylate (PMMA), or cycloolefin copolymer (COC) resin. 
     In an embodiment, the front laminated structure  200  includes front bonding members  251  to  253  that bond adjacent laminated members. For example, a first bonding member  251  is disposed between and bonds the cover window protection layer  210  and the cover window  220 , a second bonding member  252  is disposed between and bonds the cover window  220  and the optical film  230 . A third bonding member  253  is disposed between and bonds the optical film  230  and the display panel  100 . That is, the front bonding members  251  to  253  attach the layers to one surface of the display panel  100 . The first bonding member  251  is a protection layer bonding member that attaches the cover window protection layer  210 , the second bonding member  252  is a window bonding member that attaches the cover window  220 , and the third bonding member  253  is an optical film bonding member that attaches the optical film  230 . The front bonding members  251  to  253  are all optically transparent. 
     In an embodiment, the rear laminated structure  300  is disposed on the rear side of the display panel  100 . The rear laminated structure  300  includes a polymer film layer  310 , a cushion layer  320 , and a plate  330 , and a heat dissipation portion  340  that are sequentially laminated rearward from the display panel  100 . 
     In an embodiment, the polymer film layer  310  is disposed on the rear side of the display panel  100 . The polymer film layer  310  includes a polymer film. The polymer film layer  310  includes, for example, at least one of polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polysulfone (PSF), polymethylmethacrylate (PMMA), triacetylcellulose (TAC), or cycloolefin polymer (COP), etc. The polymer film layer  310  includes a functional layer on at least one surface thereof. The functional layer includes, for example, a light absorbing layer. The light absorbing layer includes a light absorbing material such as a black pigment or dye. The light absorbing layer is formed by coating or printing black ink on a polymer film. 
     In an embodiment, the cushion layer  320  is disposed on the rear side of the polymer film layer  310 . The cushion layer  320  absorbs external impacts and prevents damage to the display panel  100 . The cushion layer  320  may be formed of a single layer or a plurality of laminated layers. The cushion layer  320  includes, for example, an elastic material such as polyurethane or polyethylene resin. In an embodiment, the cushion layer  320  is made of a foam material similar to a sponge. 
     In an embodiment, the plate  330  is disposed on the rear side of the cushion layer  320 . The plate  330  is a support member that bonds the display device  10  to a case. The plate  330  is made of a rigid material. In an embodiment, the plate  330  is made of a single metal or metal alloy such as stainless steel (SUS). 
     In an embodiment, the heat dissipation portion  340  is disposed on the rear side of the plate  330 . The heat dissipation portion  340  diffuses heat generated from the display panel  100  or other portions of the display device  10 . The heat dissipation portion  340  includes a metal plate. The metal plate includes a thermally conductive metal, such as copper or silver. The heat dissipation portion  340  may be a heat dissipation sheet that includes graphite or carbon nanotubes. 
     Although embodiments are not limited thereto, the heat dissipation portion  340  is separated by the foldable area FDA to facilitate folding of the display device  10  as illustrated in  FIGS. 3 and 4 . For example, a first metal plate can be disposed in the first non-foldable area NFA 1 , and a second metal plate can be disposed in the second non-foldable area NFA 2 . The first metal plate and the second metal plate are physically separated from each other with respect to the foldable area FDA. 
     In an embodiment, the rear laminated structure  300  includes rear bonding members  351  to  354  that bond adjacent laminated members. For example, a fourth bonding member  351  is disposed between and bonds the display panel  100  and the polymer film layer  310 , a fifth bonding member  352  is disposed between and bonds the polymer film layer  310  and the cushion layer  320 , a sixth bonding member  353  is disposed between and couples the cushion layer  320  and the plate  330 , and a seventh bonding member  354  is disposed between and bonds the plate  330  and the heat dissipation portion  340 . That is, of the rear bonding members  351  to  354  that attach the layers on the other surface of the display panel  100 , the fourth bonding member  351  is a polymer film layer bonding member that attaches the polymer film layer  310 , the fifth bonding member  352  is a cushion layer bonding member that attaches the cushion layer  320 , the sixth bonding member  353  is a plate bonding member that attaches the plate  330 , and the seventh bonding member  354  is a heat dissipation portion bonding member that attaches the heat dissipation portion  340 . When the heat dissipation portion  340  is separated with respect to the foldable area FDA, the seventh bonding member  354  may also be separated in the same way, but may also be continuous as illustrated in  FIG. 3  without being separated by the non-foldable areas NFA 1  and NFA 2 . 
     In an embodiment, when the display device  10  displays an image only on the front surface, the rear bonding members  351  to  354  are not necessarily optically transparent, unlike the front bonding members  251  to  253 . 
     As described above, in an embodiment, the optical film  230  is disposed in front of the display panel  100  and absorbs external light incident on the front of the display panel  100 , thereby preventing reflection thereof. Hereinafter, the optical film  230  that can prevent light leakage by reducing reflectance in a lateral direction will be described. 
       FIG. 6  is a cross-sectional view of an optical film  230  according to an embodiment. 
     Referring to  FIG. 6 , the optical film  230  according to an embodiment includes a polarizing layer  400 , a first optical compensation layer  450 , a second optical compensation layer  460 , and a third optical compensation layer  490 . 
     In an embodiment, the polarizing layer  400  converts natural light or polarized light into arbitrarily polarized light. For example, it can convert external light incident on the display device  10  into linearly polarized light. The polarizing layer  400  can stretch in one direction. The stretching direction of the polarizing layer  400  is an absorption axis, and a direction perpendicular thereto is a transmission axis. In an embodiment, the transmission axis of the polarizing layer  400  is at 0 degrees. The polarizing layer  400  is disposed farthest from the display panel  100  of the constituent layers of the optical film  230  and converts external light incident from the outside into linearly polarized light. 
     In an embodiment, the polarizing layer  400  is made of a polymer material whose main component is a polyvinyl alcohol (PVA) resin that contains iodine or a dichroic dye. However, embodiments of the present disclosure are not limited thereto, and in other embodiments, the polarizing layer  400  can be an O-type polarizer prepared by aligning a liquid crystal composition that contains a dichroic material and a liquid crystal compound in a predetermined direction, or an E-type polarizer prepared by aligning lyotropic liquid crystals in a predetermined direction, etc. 
     In an embodiment, a first protective member  410  and a second protective member  420  are disposed above the polarizing layer  400  and under the polarizing layer  400 , respectively. The first protective member  410  is disposed on the top surface of the polarizing layer  400  in the third direction DR 3 . The second protective member  420  is disposed on the bottom surface of the polarizing layer  400  in a direction opposite to the third direction DR 3 . 
     In an embodiment, the first and second protective members  410  and  420  protect the polarizing layer, and are formed of a typical retardation-free protection film. The first protective member  410  and the second protective member  420  can be formed of, for example, one or more of triacetyl cellulose (TAC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), or cycloolefin (COP), etc. 
     In an embodiment, the first optical compensation layer  450  is disposed under the polarizing layer  400 . The first optical compensation layer  450  compensates for distortion of the axis of the polarizing layer  400 , which is generated in an off-axis. For example, the first optical compensation layer  450  improves black visibility of the side. 
     In an embodiment, the first optical compensation layer  450  includes at least one of a cycloolefin polymer (COP), a cycloolefin copolymer (COC), polycarbonate (PC), polystyrene (PS), methyl methacrylate-styrene (MS), polymethyl methacrylate (PMMA), or triacetyl cellulose (TAC). In addition, the first optical compensation layer  450  includes a liquid crystal compound, for example, a liquid crystal compound that has a nematic liquid crystal phase. The liquid crystal compound is a liquid crystal polymer or a liquid crystal monomer of a polymerizable mesogenic compound. The liquid crystal compound may be a discotic liquid crystal compound or a rod-like liquid crystal compound. The first optical compensation layer  450  may be fabricated as a film type or a liquid crystal type depending on the material. 
     In an embodiment, the first optical compensation layer  450  is a retardation plate, such as a biaxial plate, and has refractive indices of nx, ny, and nz in a spatial coordinate system. Typically, optical characteristics of a retardation layer are represented by characteristics with respect to 550 nm wavelength light that can be easily obtained, unless otherwise mentioned about the wavelength of a light source. The optical characteristics of the retardation layer are defined by its refractive indices. 
     In an embodiment, the first optical compensation layer  450  has a refractive index ratio Nz defined by Equation 1, below. 
         Nz =( nx−nz )/( nz−ny )  Equation 1
 
     Here, nx is a refractive index of an axis of the first optical compensation layer having the largest refractive index in a planar direction  450 , ny is a refractive index in a planar direction perpendicular to the nx axis, and nz is a refractive index in the thickness direction. 
     In the first optical compensation layer  450  of an embodiment of the present disclosure, the refractive indices nx, ny, and nz in three directions may satisfy a relationship of nx&gt;ny, nz. According to Eq. 1, the refractive index ratio Nz of the first optical compensation layer  450  may range from 0.5 to 2.5. 
     In an embodiment, the first optical compensation layer  450  has an in-plane retardation value Ro defined by Equation 2, below, while satisfying the refractive index ratio Nz. 
         Ro =( nx−ny )* d   Equation 2
 
     Here, d is the thickness of the first optical compensation layer  450 . 
     In an embodiment, the thickness of the first optical compensation layer  450  ranges from 1 to 100 μm, but embodiments are not limited thereto. The in-plane retardation value Ro of the first optical compensation layer  450  ranges from 0 to 300 nm, and may range from 170 to 270 nm. The in-plane retardation value Ro of the first optical compensation layer  450  is selected from a range that satisfies the refractive index ratio Nz. 
     In an embodiment, a retardation value Rth of the first optical compensation layer  450  in the thickness direction is determined from Equation 3, below, based on the refractive index ratio Nz and the in-plane retardation value Ro described above. 
         Rth =[( nx−ny )/2− nz ]* d   Equation 3
 
     According to Eq. 3, the retardation value Rth of the first optical compensation layer  450  in the thickness direction ranges from 0 to 200 nm, and may range from 4 to 84 nm. The retardation value Rth of the first optical compensation layer  450  in the thickness direction is selected from within the above-described range. 
     In an embodiment, an angle between the transmission axis of the polarizing layer  400  and an optical axis of the first optical compensation layer  450  ranges from 86 to 94 degrees. That is, the optical axis of the first optical compensation layer  450  is tilted from 86 to 94 degrees with respect to the transmission axis of the polarizing layer  400 . In an embodiment, the first optical compensation layer  450  described above can compensate for distortion of the optical axis at the side. A detailed description thereof will be provided below. 
     In addition, in an embodiment, the second optical compensation layer  460  is disposed under the first optical compensation layer  450 . The second optical compensation layer  460  converts linearly polarized light incident received from the first optical compensation layer  450  into circularly or elliptically polarized light. The second optical compensation layer  460  is a quarter (λ/4) wave plate. In an embodiment, an optical axis (slow axis) of the second optical compensation layer  460  is at 45 degrees. The second optical compensation layer  460  is made of the materials listed above with regard to the first optical compensation layer  450 . 
     In an embodiment, the third optical compensation layer  490  is disposed under the second optical compensation layer  460 . The third optical compensation layer  490  is in direct contact with the top surface of the display panel  100 . The third optical compensation layer  490  retards the phase of circularly or elliptically polarized light incident received from the second optical compensation layer  460 . The third optical compensation layer  490  is a positive C plate. The third optical compensation layer  490  is made of the materials listed above with regard to the first optical compensation layer  450 . 
     In an embodiment, a first adhesive member  470  is disposed between the first optical compensation layer  450  and the second optical compensation layer  460 . Further, a second adhesive member  480  is disposed between the second optical compensation layer  460  and the third optical compensation layer  490 . 
     In an embodiment, the first and second adhesive members  470  and  480  include an acrylic copolymer that has a superior elastic modulus and adhesive property, and can prevent delamination by reducing generation of fine bubbles. In an embodiment, the first and second adhesive members  470  and  480  are pressure sensitive adhesives (PSA). The first and second adhesive members  470  and  480  not only serve as adhesives, but also protect the compensation layers or the display panel  100  from external impacts, because they have a predetermined elasticity. 
     Since the optical film  230  according to an embodiment includes the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 , reflection of external light that is incident on the side from the outside can be reduced. Hereinafter, an action of reducing reflection of external light by the optical film  230  will be described in detail with reference to other drawings. 
       FIG. 7  is a cross-sectional view of an optical film according to a comparative example.  FIG. 8  is illustrates polarization of light that has passed through the optical film of a comparative example, as a Poincaré sphere viewed from the front.  FIG. 9  illustrates polarization of light that has passed through the optical film of a comparative example, as a Poincaré sphere viewed from the side.  FIG. 7  will be described by using the same reference numbers to refer to substantially the same components of the optical film described with reference to  FIG. 6 . 
     Referring to  FIG. 7 , an optical film according to a comparative example includes the polarizing layer  400 , the second optical compensation layer  460  that is the quarter wave plate, and the third optical compensation layer  490  that is the positive C plate, which are stacked. 
     Referring to  FIG. 8  in conjunction with  FIG. 7 , when viewed from the front, external light incident on the optical film is converted into 0 degree linearly polarized light in the polarizing layer  400  and is located at a position {circle around (1)}. Since the linearly polarized light transmitted through the polarizing layer  400  is converted into right-handed circularly polarized light by being phase-shifted half a wavelength by a quarter wavelength retardation value and the 45 degree optical axis (slow axis) of the second optical compensation layer  460 , it is located at S3 (target point, position {circle around (2)}). Since the third optical compensation layer  490  does not cause retardation from the front, the right-handed circularly polarized light remains at S3 (position {circle around (3)}). The right-handed circularly polarized light at S3 is reflected from the display panel  100  and has its phase changed to be left-handed circularly polarized light. Then, it is converted into 90 degree linearly polarized light in the second optical compensation layer  460 , and is finally absorbed by the polarizing layer  400 . Therefore, when viewed from the front, external light is absorbed by the optical film, so that reflected light may be reduced. 
     Referring to  FIG. 9  in conjunction with  FIG. 7 , when viewed from the side, external light incident on the optical film is converted into linearly polarized light distorted due to distortion of the absorption axis of the polarizing layer  400  and is located at a position {circle around (1)}. The linearly polarized light transmitted through the polarizing layer  400  is converted into right-handed circularly polarized light by being phase-shifted half a wavelength by the quarter wavelength retardation value and the 45 degree optical axis (slow axis) of the second optical compensation layer  460 . However, it fails to be located at S3 (target point), but is located at a position {circle around (2)} before S3 due to distortion of the optical axis. Subsequently, the phase-shift of the light incident on the third optical compensation layer  490  is corrected by the retardation value Rth of the third optical compensation layer  490  in the thickness direction, so that the right-handed circularly polarized light is located at a position {circle around (3)}. The incomplete right-handed circularly polarized light at the position {circle around (3)} is reflected from the display panel  100  and has its phase changed to be incomplete left-handed circularly polarized light. Then, it is converted into incomplete linearly polarized light in the second optical compensation layer  460 . A portion of the incomplete linearly polarized light is absorbed by the polarizing layer  400 , while the other portion is transmitted to be visibly recognized as light leakage. 
     However, since the optical film  230  according to an embodiment includes the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 , it is possible to reduce light leakage by reducing reflected light when viewed from the side. 
       FIG. 10  is a cross-sectional view of an optical film according to an embodiment.  FIG. 11  illustrates polarization of light that has passed through an optical film of an embodiment, with a Poincaré sphere viewed from the side. 
     Referring to  FIGS. 10 and 11 , in an embodiment, when viewed from the side, external light incident on the optical film  230  is converted into linearly polarized light that is distorted due to the distortion of the absorption axis of the polarizing layer  400  and is located at a position {circle around (1)}. The linearly polarized light transmitted through the polarizing layer  400  is located at a position {circle around (2)}) by being compensated for the position due to the distortion of the absorption axis of the polarizing layer  400  by a retardation value and a 90 degree optical axis of the first optical compensation layer  450 . Then, it is converted into right-handed circularly polarized light by being phase-shifted half a wavelength by the quarter wavelength retardation value and the 45 degree optical axis of the second optical compensation layer  460 . However, the right-handed circularly polarized light fails to be located at S3 (target point), but is located at a position {circle around (3)} before S3 due to the distortion of the optical axis. Then, the phase-shift is corrected by the retardation value Rth of the third optical compensation layer  490  in the thickness direction, so that the right-handed circularly polarized light is located at S3 (target point, position {circle around (4)}). The right-handed circularly polarized light at the position {circle around (4)} is reflected from the display panel  100  and has its phase changed to be left-handed circularly polarized light. Then, it is converted into 90 degree linearly polarized light in the second optical compensation layer  460 . The linearly polarized light is absorbed by the polarizing layer  400 , thereby reducing reflected light and reducing light leakage. 
       FIG. 12  is a cross-sectional view illustrating an optical film according to an embodiment. 
     Referring to  FIG. 12 , the optical film  230  according to an embodiment includes the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 . This embodiment differs from an embodiment of  FIG. 6  described above in that it omits the second protective member  420  disposed between the polarizing layer  400  and the first optical compensation layer  450 . Hereinafter, a description will be given of different configurations and a description of the same configurations will be omitted. 
     In an embodiment, the polarizing layer  400  is disposed on the first optical compensation layer  450 . The first optical compensation layer  450  is in direct contact with the bottom surface of the polarizing layer  400 , which is disposed in a direction opposite to the third direction DR 3 . The first optical compensation layer  450  is directly coated on or adhered to the bottom surface of the polarizing layer  400 . Since the second protective member  420  of  FIG. 6  does not have a retardation property, it does not affect the polarization of light. Therefore, by omitting the second protective member  420 , the process can be simplified and the thickness of the optical film  230  can be decreased. 
       FIG. 13  is a cross-sectional view of an optical film according to an embodiment. 
     Referring to  FIG. 13 , the optical film  230  according to an embodiment may include the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 . This embodiment differs from an embodiment of  FIG. 6  described above in that it omits the first protective member  410  disposed on the polarizing layer  400 . Hereinafter, a description will be given of different configurations and a description of the same configurations will be omitted. 
     In an embodiment, the polarizing layer  400  is disposed at the top layer of the optical film  230 . That is, no optical layer is disposed on the polarizing layer  400 . As described above, since the first protective member  410  of  FIG. 6  does not have a retardation property, it does not affect the polarization of light. Therefore, by omitting the first protective member  410 , the process can be simplified and the thickness of the optical film  230  can be decreased. 
       FIG. 14  is a cross-sectional view of an optical film according to an embodiment. 
     Referring to  FIG. 14 , the optical film  230  according to an embodiment includes the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 . This embodiment differs from an embodiment of  FIG. 6  described above in that it omits the first protective member  410  disposed on the polarizing layer  400  and the second protective member  420  disposed between the polarizing layer  400  and the first optical compensation layer  450 . Hereinafter, a description will be given of different configurations and a description of the same configurations will be omitted. 
     In an embodiment, the top layer of the optical film  230  is the polarizing layer  400 , and the first optical compensation layer  450  is disposed in direct contact with the bottom surface of the polarizing layer  400 . Since neither of the first protective member  410  and the second protective member  420  of  FIG. 6  have a retardation property, they do not affect the polarization of light. Therefore, by omitting the first protective member  410  and the second protective member  420 , the process can be simplified and the thickness of the optical film  230  can be decreased. 
       FIG. 15  is a cross-sectional view of an optical film according to an embodiment. 
     Referring to  FIG. 15 , the optical film  230  according to an embodiment includes the polarizing layer  400 , the first optical compensation layer  450 , the second optical compensation layer  460 , and the third optical compensation layer  490 . This embodiment differs from an embodiment of  FIG. 6  described above in that it omits the first adhesive member  470  disposed between the first optical compensation layer  450  and the second optical compensation layer  460 . Hereinafter, a description will be given of different configurations and a description of the same configurations will be omitted. 
     In an embodiment, the first optical compensation layer  450  is disposed on the second optical compensation layer  460 . The second optical compensation layer  460  is disposed in direct contact with the bottom surface of the first optical compensation layer  450 , which is disposed in the direction opposite to the third direction DR 3 . The second optical compensation layer  460  is directly coated on or adhered to the bottom surface of the first optical compensation layer  450 . Since the first adhesive member  470  of  FIG. 6  does not have a retardation property, it does not affect the polarization of light. Therefore, by omitting the first adhesive member  470 , the process can be simplified and the thickness of the optical film  230  can be decreased. 
     Hereinafter, embodiments will be described in more detail through fabrication examples and experimental examples. 
     Fabrication Example 1: Fabrication of Display Devices 
     A display device of a comparative example was fabricated by attaching the optical film of the comparative example illustrated in  FIG. 7  to a display panel, and a display device of an embodiment was fabricated by attaching the optical film of an embodiment illustrated in  FIG. 6  to a display panel. Here, in the comparative example, an optical film was fabricated in which a third optical compensation layer, a second optical compensation layer, and a polarizing layer are sequentially stacked on the display panel. In an embodiment, an optical film was fabricated in which a third optical compensation layer, a second optical compensation layer, a first optical compensation layer, and a polarizing layer are sequentially stacked on the display panel. In this case, the refractive index ratio Nz, the in-plane retardation value Ro, and the retardation value Rth in the thickness direction of the first optical compensation layer of an embodiment were 0.7, 220 nm, 44 nm, respectively. An angle between the optical axis and the transmission axis of the polarizing layer was 90 degrees. The optical axis of the polarizing layer was at 0 degrees and the optical axis of the second optical compensation layer was at 45 degrees. 
     Experimental Example 1: Measurement of Reflectance and Color of Reflected Light 
     A reflectance according to a viewing angle, a reflectance from the front (10 degree viewing angle), a color of reflected light according to an omnidirectional viewing angle, and a color of reflected light according to a viewing angle in a dark state were measured with respect a display device according to each of the comparative example and an embodiment described above. In both cases, a simulation tool used for the measurement was TechWiz LCD 1D. 
       FIG. 16  illustrates a reflectance according to a viewing angle of the display device according to the comparative example.  FIG. 17  is a graph of front reflectance (10 degree viewing angle) of the display device according to the comparative example.  FIG. 18  illustrates LAB color space coordinates of reflected light according to an omnidirectional viewing angle in the display device according to the comparative example.  FIG. 19  shows colors of reflected light according to a viewing angle in a dark state of the display device according to the comparative example.  FIG. 20  illustrates a reflectance according to a viewing angle of a display device according to an embodiment.  FIG. 21  is a graph of front reflectance (10 degree viewing angle) of a display device according to an embodiment.  FIG. 22  is a diagram illustrating LAB color space coordinates of reflected light according to an omnidirectional viewing angle in the display device according to the embodiment.  FIG. 23  shows colors of reflected light according to a viewing angle in a dark state of a display device according to an embodiment. 
     Referring to  FIGS. 16 and 20 , in the display device according to the comparative example, the reflectance increased in a 0 degree direction, 75 degree direction, 180 degree direction, and 255 degree direction from the front. On the other hand, in a display device according to the embodiment, the reflectance was generally low. 
     Referring to  FIGS. 17 and 21 , the display device according to the comparative example exhibited a reflectance ranging from 0.00062 to 0.00063 (a.u.) from the front (10 degree viewing angle), and a display device according to an embodiment exhibited a reflectance ranging from 0.00060 to 0.00063 (a.u.). Thus, there was no difference in the front reflectance. 
     Referring to  FIGS. 18 and 22 , the LAB color space coordinates of the reflected light according to the omnidirectional viewing angle in the display device according to the comparative example had a* values in a range of −4 to 4 and b* values in a range of −1 to 3. On the other hand, in a display device according to an embodiment, the LAB color space coordinates had a* values in a range of −1 to 4 and b* values in a range of −2 to 0. That is, it can be seen that the coordinates were shown to be relatively darker because the dispersion was narrower and closer to the center. 
     Referring to  FIGS. 19 and 23 , the color of reflected light according to the viewing angle in the dark state of the display device according to the comparative example was black from the front, but it was yellowish in the vicinity of the 0 degree direction, 75 degree direction, 180 degree direction, and 255 degree direction. On the other hand, a display device according to an embodiment showed black from the front, and also showed darker black in the 0 degree direction, 75 degree direction, 180 degree direction, and 255 degree direction. 
     Experimental Example 1 described above shows that a display device that includes an optical film of an embodiment, which has the first optical compensation layer, can decrease light leakage by reducing reflectance of external light from the front and side surfaces. 
     Fabrication Example 2: Fabrication of Display Device Samples 
     Sample #1 was fabricated by setting a tilt angle of the optical axis of the first optical compensation layer of the above-described embodiment to 86 degrees, and sample #2 was fabricated by setting the tilt angle of the optical axis thereof to 94 degrees. 
     Experimental Example 2: Measurement of Reflectance 
     A reflectance according to a viewing angle in each of samples #1 and #2, which were fabricated in Fabrication Example 2, was measured. 
       FIG. 24  shows the reflectance according to the viewing angle in sample #1.  FIG. 25  shows the reflectance according to the viewing angle in sample #2. 
     Referring to  FIGS. 24 and 25  in conjunction with  FIG. 20 , sample #1, in which the first optical compensation layer has an optical axis angle of 86 degrees, exhibited a reflectance of 0.832%, increasing by 1,171% compared to 0.071% of an embodiment. Sample #2, in which the first optical compensation layer has an optical axis angle of 94 degrees, exhibited a reflectance of 0.916%, increasing by 1,290% compared to an embodiment. 
     These results indicate that the tilt angle of the optical axis of the first optical compensation layer may be 90 degrees, and the reflectance is sufficiently improved in the range of 86 to 94 degrees. 
     As described above, an optical film and a display device that includes the same according to embodiments have reduced light leakage by reducing reflectance of external light when viewed from the side. 
     In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to disclosed embodiments without substantially departing from the principles of embodiments of the present disclosure. Therefore, disclosed embodiments of the disclosure are used in a generic and descriptive sense only and not for purposes of limitation.