Patent Publication Number: US-2022221639-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2021-0002479, filed on Jan. 8, 2021, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     Embodiments of the present inventive concept relate to a display device. More particularly, embodiments of the present inventive concept relate to a display device capable of adjusting a viewing angle. 
     2. Description of the Related Art 
     Flat panel display devices are replacing cathode ray tube display devices as display devices due to their lightweight and thin characteristics. As representative examples of such flat panel display devices, there are liquid crystal display devices and organic light-emitting element display devices. 
     In general, the display device may display an image in a wide viewing angle mode, but sometimes it may be necessary to display the image in a narrow viewing angle mode so that others cannot see the image displayed on the display device. 
     SUMMARY 
     A display device according to an embodiment may include a substrate, a first light-emitting element, and a light control layer. The substrate may include a display area and a peripheral area adjacent to the display area, and the display area may include a light-emitting area and a light-blocking area. The first light-emitting element may be disposed in the light-emitting area on the substrate, and may emit a first light having a first wavelength range. The light control layer may be disposed on the first light-emitting element, and may define an opening exposing a portion of the light-emitting area. The light control layer may include a photochromic material such that in operation a second light having a second wavelength range different from the first wavelength range applied to the light control layer discolors the light control layer. 
     In an embodiment, the display device may further include a light guide layer disposed in the display area and the peripheral area on the first light-emitting element. The second light may be incident into the light guide layer in the peripheral area. The light guide layer may transmit the second light to the display area. 
     In an embodiment, the light guide layer may contact the light control layer. A refractive index of the light guide layer may be greater than a refractive index of the light control layer. 
     In an embodiment, a first optical pattern may be formed on the light guide layer. The first optical pattern may overlap the display area. At least a portion of the second light may be output from the light guide layer to the light control layer by the first optical pattern. 
     In an embodiment, the first optical pattern may include a diffraction grating selectively diffracting a light having the second wavelength range. 
     In an embodiment, the first optical pattern may include a plurality of scattering patterns. 
     In an embodiment, the light control layer may include a first light control layer disposed under the light guide layer and a second light control layer disposed on the light guide layer. 
     In an embodiment, the display device may further include a second light-emitting element disposed in the peripheral area on the substrate. The second light-emitting element may emit the second light having the second wavelength range. 
     In an embodiment, the first light-emitting element may be driven by a first transistor, and the second light-emitting element may be driven by a second transistor different from the first transistor. 
     In an embodiment, a second optical pattern may be formed on the light guide layer. The second optical pattern may overlap the peripheral area. At least a portion of the second light emitted from the second light-emitting element may be refracted toward the display area by the second optical pattern. 
     In an embodiment, the display device may further include a second light-emitting element disposed adjacent to a side portion of the light guide layer. The second light-emitting element may emit the second light having the second wavelength range. 
     In an embodiment, the display device may further include a second light-emitting element disposed in the display area on the substrate. The second light-emitting element may emit the second light having the second wavelength range. 
     In an embodiment, the light-blocking area may surround the light-emitting area in a plan view. The second light-emitting element may be disposed in the light-blocking area on the substrate. 
     In an embodiment, the first light-emitting element may be driven by a first transistor, and the second light-emitting element may be driven by a second transistor different from the first transistor. 
     In an embodiment, the light control layer may include a first light control layer and a second light control layer disposed on the first light control layer and spaced apart from the first light control layer. 
     In an embodiment, the display device may further include a light absorption layer disposed on the light control layer. The light absorption layer may selectively absorb a light having the second wavelength range. 
     In an embodiment, the light control layer may have a slit shape in a plan view. 
     In an embodiment, the light control layer may have a lattice shape in a plan view. 
     In an embodiment, the light-emitting area may be provided in plural. The light control layer may define a plurality of openings overlapping the plurality of light-emitting area, respectively. 
     In an embodiment, the first light may be visible light, and the second light may be ultraviolet (UV) light or infrared (IR) light. 
     The display device according to embodiments may include the first light-emitting element and the second light-emitting element. The first light-emitting element may emit the first light for displaying the image. The second light-emitting element may emit the second light for switching between the wide viewing angle mode and the narrow viewing angle mode. Accordingly, the viewing angle of the display device may be adjusted without attaching a separate optical film. In addition, when the display device is in the narrow viewing angle mode, a portion of the first light having a viewing angle greater than or equal to a predetermined angle among the first light emitted from each of the pixels may be blocked, and another portion of the first light having a viewing angle less than to the predetermined angle may be emitted to outside of the display device. Accordingly, a resolution of the display device may not be reduced even in the narrow viewing angle mode. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the inventive concepts. 
         FIG. 1  is a plan view illustrating a display device according to an embodiment. 
         FIGS. 2A and 2B  are cross-sectional views illustrating an example taken along the line I-I′ of  FIG. 1 . 
         FIG. 3A  is an enlarged cross-sectional view illustrating an example of area “A” of  FIG. 2B . 
         FIG. 3B  is an enlarged cross-sectional view illustrating another example of area “A” of  FIG. 2B . 
         FIGS. 4A and 4B  are plan views illustrating a light control layer according to an embodiment. 
         FIGS. 5A and 5B  are plan views illustrating a light control layer according to another embodiment. 
         FIG. 6  is a cross-sectional view illustrating another example taken along the line I-I′ of  FIG. 1 . 
         FIGS. 7A and 7B  are cross-sectional views illustrating a display device according to another embodiment. 
         FIGS. 8A and 8B  are cross-sectional views illustrating a display device according to still another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present inventive concept provide a display device capable of adjusting a viewing angle. Additional features of the inventive concepts will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concepts. 
     Illustrative, non-limiting embodiments will be more clearly understood from the following detailed description in conjunction with the accompanying drawings. 
       FIG. 1  is a plan view illustrating a display device according to an embodiment. 
     Referring to  FIG. 1 , a display device  10  according to an embodiment may include a display area DA and a peripheral area PA. A plurality of pixels may be disposed in the display area DA. An image may be displayed in the display area DA. The peripheral area PA may be adjacent to the display area DA. For example, the peripheral area PA may be around (e.g., surround) the display area DA in a plan view. 
     The display area DA may include a plurality of light-emitting areas LA and a light-blocking area BA. In an embodiment, the light-emitting areas LA may correspond to the pixels, respectively. For example, the light-emitting areas LA may be arranged in a matrix form in a first direction DR 1  and a second direction DR 2  crossing the first direction DR 1 . For example, the second direction DR 2  may be perpendicular to the first direction DR 1 . In an embodiment, the light-blocking area BA may be around (e.g., surround) the light-emitting areas LA in a plan view. 
     First light-emitting elements (e.g., a first light-emitting element  310  of  FIG. 2A ) may be disposed in the light-emitting areas LA. Each of the first light-emitting elements may emit a first light having a first wavelength range. The first light may be visible light. For example, red light, green light, or blue light may be emitted from each of the light-emitting areas LA. In specific, a first light-emitting area in which red light is emitted, a second light-emitting area in which green light is emitted, and a third light-emitting area in which blue light is emitted may be repeatedly disposed in the display area DA. The image may be displayed by the first lights (e.g., visible light) emitted from the first light-emitting elements disposed in the display area DA. 
     In an embodiment, a black matrix may be disposed in the light-blocking area BA. The black matrix may prevent or reduce color mixing of the first lights (e.g., red light, green light, and blue light) emitted from the light-emitting areas LA adjacent to each other. 
     In an embodiment, a second light-emitting element (e.g., a second light-emitting element  320  of  FIG. 2A ) may be disposed in the peripheral area PA. The second light-emitting element may emit a second light having a second wavelength range different from the first wavelength range. For example, the second light may be ultraviolet (UV) light or infrared (IR) light. A viewing angle of the display device  10  may be adjusted by the second light. This will be described in detail later. 
     In an embodiment, the second light-emitting element disposed in the peripheral area PA may be provided in plural. The second light-emitting elements may be disposed adjacent to at least one side portion of the display area DA. 
       FIGS. 2A and 2B  are cross-sectional views illustrating an example taken along the line I-I′ of  FIG. 1 . For example,  FIG. 2A  may illustrate the display device  10  in a first mode, and  FIG. 2B  may illustrate the display device  10  in a second mode. The first mode may be a wide viewing angle mode, and the second mode may be a narrow viewing angle mode. 
     Referring to  FIGS. 1, 2A, and 2B , the display device  10  according to an embodiment may include a first substrate  100 , a first transistor  210 , a first light-emitting element  310 , a second transistor  220 , a second light-emitting element  320 , an encapsulation layer ENC, a light guide layer  500 , a light control layer  600 , a light absorption layer  700 , and a second substrate  800 . 
     The first substrate  100  may be a transparent insulating substrate. For example, the first substrate  100  may be formed of glass, quartz, plastic, or the like. 
     The first substrate  100  may include the display area DA and the peripheral area PA. The peripheral area PA may be adjacent to the display area DA. For example, in  FIGS. 2A and 2B , the peripheral area PA may be positioned in the first direction DR 1  of the display area DA. The display area DA may include the light-emitting areas LA and the light-blocking area BA. Although only one light-emitting area LA is illustrated in  FIGS. 2A and 2B , the light-emitting areas LA may be arranged in the second direction DR 2  and a third direction DR 3  opposite to the first direction DR 1 . 
     The first light-emitting element  310  may be disposed in the display area DA on the first substrate  100 . The first light-emitting element  310  may overlap the light-emitting area LA. The first light-emitting element  310  may emit a first light L 1  having the first wavelength range. The first light L 1  may be visible light. For example, the first light-emitting element  310  may emit red light, green light, or blue light. 
     The second light-emitting element  320  may be disposed in the peripheral area PA on the first substrate  100 . For example, the second light-emitting element  320  may be formed using some of dummy pixels formed in the peripheral area PA. The second light-emitting element  320  may emit a second light L 2  having the second wavelength range. The second light L 2  may include various types of light having wavelength ranges different from the first wavelength range (e.g., a visible light wavelength range). Hereinafter, an example in which the second light L 2  is UV light will be described. 
     Each of the first light-emitting element  310  and the second light-emitting element  320  may include (e.g., may be) an organic light-emitting diode, an inorganic light-emitting diode, and a quantum dot light-emitting diode, or the like. Hereinafter, an example in which each of the first light-emitting element  310  and the second light-emitting element  320  is the organic light-emitting diode will be described. For example, the first light-emitting element  310  may include a first pixel electrode  311 , a first emission layer  312 , and a first common electrode  313 . The second light-emitting element  320  may include a second pixel electrode  321 , a second emission layer  322 , and a second common electrode  323 . 
     The first light-emitting element  310  may be driven by the first transistor  210 . For example, the first transistor  210  may be disposed in the display area DA on the first substrate  100 . For example, each of the pixels may include the first transistor  210  and the first light-emitting element  310 . 
     The second light-emitting element  320  may be driven by the second transistor  220  different from the first transistor  210 . That is, the second light-emitting element  320  that emits the second light L 2  (e.g., UV light) may be driven independently from the first light-emitting element  310  that emits the first light L 1  (e.g., visible light). For example, the second transistor  220  may be disposed in the peripheral area PA on the first substrate  100 . 
     In an embodiment, as illustrated in  FIGS. 2A and 2B , the second light-emitting element  320  may emit the second light L 2  only in the second mode. That is, the second transistor  220  may not drive the second light-emitting element  320  when the display device  10  is in the first mode (e.g., the wide viewing angle mode), and the second transistor  220  may drive the second light-emitting element  320  when the display device  10  is in the second mode (e.g., the narrow viewing angle mode). 
     In an embodiment, each of the active layers of the first and second transistors  210  and  220  may include an oxide semiconductor, a silicon semiconductor, or the like. For example, the oxide semiconductor may include at least one oxide of indium (In), gallium (Ga), tin (Sn), zirconium (Zr), vanadium (V), hafnium (Hf), cadmium (Cd), germanium (Ge), chromium (Cr), titanium (Ti), and zinc (Zn). The silicon semiconductor may include an amorphous silicon, a polycrystalline silicon, or the like. 
     The first transistor  210  and the second transistor  220  may be covered by an insulating structure IL. For example, the insulating structure IL may include an inorganic insulating layer, an organic insulating layer, or a combination thereof. 
     The first pixel electrode  311  may be disposed on the first transistor  210 , and may be electrically connected to the first transistor  210 . The second pixel electrode  321  may be disposed on the second transistor  220 , and may be electrically connected to the second transistor  220 . Each of the first pixel electrode  311  and the second pixel electrode  321  may include a metal, an alloy, a conductive metal oxide, a conductive metal nitride, a transparent conductive material, or the like. 
     A pixel defining layer PDL may be disposed on the insulating structure IL. The pixel defining layer PDL may partially cover each of the first pixel electrode  311  and the second pixel electrode  321  on the insulating structure IL. The pixel defining layer PDL may have pixel openings exposing at least a portion of each of the first pixel electrode  311  and the second pixel electrode  321 , respectively. For example, a first pixel opening may expose a central portion of the first pixel electrode  311 , and a second pixel opening may expose a central portion of the second pixel electrode  321 . The pixel defining layer PDL may cover a peripheral portion each of the first pixel electrode  311  and the second pixel electrode  321 . The pixel defining layer PDL may include an organic insulating material. 
     The first emission layer  312  may be disposed on the first pixel electrode  311  exposed by the first pixel opening. That is, the first emission layer  312  may be disposed in the first pixel opening. The first emission layer  312  may be disposed between the first pixel electrode  311  and the first common electrode  313 . The first emission layer  312  may include an organic light emitting material that emits the first light L 1  (e.g., visible light) having the first wavelength range. 
     The second emission layer  322  may be disposed on the second pixel electrode  321  exposed by the second pixel opening. That is, the second emission layer  322  may be disposed in the second pixel opening. The second emission layer  322  may be disposed between the second pixel electrode  321  and the second common electrode  323 . The second emission layer  322  may include an organic light emitting material that emits the second light L 2  (e.g., UV light) having the second wavelength range. 
     The first common electrode  313  may be disposed on the first emission layer  312 , and may overlap the first pixel electrode  311 . The second common electrode  323  may be disposed on the second emission layer  322 , and may overlap the second pixel electrode  321 . In an embodiment, the first common electrode  313  and the second common electrode  323  may be integrally formed. In another embodiment, the first common electrode  313  and the second common electrode  323  may be separately formed. 
     The encapsulation layer ENC may be disposed on the first light-emitting element  310  and the second light-emitting element  320 . The encapsulation layer ENC may cover (e.g., may encapsulate) the first light-emitting element  310  and the second light-emitting element  320  to protect the first light-emitting element  310  and the second light-emitting element  320  from foreign substances. 
     The encapsulation layer ENC may include at least one inorganic encapsulation layer and at least one organic encapsulation layer. For example, the encapsulation layer ENC may include a first inorganic encapsulation layer, an organic encapsulation layer disposed on the first inorganic encapsulation layer, and a second inorganic encapsulation layer disposed on the organic encapsulation layer. 
     In an embodiment, a touch sensing layer TC may be disposed on the encapsulation layer ENC. The touch sensing layer TC may sense a contact or non-contact touch of a user. For example, the touch sensing layer TC may sense the touch of the user by a capacitance method. In specific, the touch sensing layer TC may sense the touch of the user by a self-capacitance method or a mutual capacitance method. In another embodiment, the touch sensing layer TC may be omitted. 
     In an embodiment, a light collecting layer CTL may be disposed on the touch sensing layer TC. For example, the light condensing layer CTL may include a plurality of micro lenses. Accordingly, a path of the first light L 1  emitted from the first light-emitting element  310  may be collected toward a fourth direction DR 4  (e.g., a thickness direction). In another embodiment, the light collecting layer CTL may be omitted. 
     The light guide layer  500  may be disposed on the encapsulation layer ENC. In an embodiment, the light guide layer  500  may be entirely disposed in the display area DA and the peripheral area PA on the encapsulation layer ENC. That is, the light guide layer  500  may be disposed on the first and second light-emitting elements  310  and  320 , and may overlap each of the first and second light-emitting elements  310  and  320 . 
     For example, as illustrated in  FIG. 2B , when the display device  10  is in the second mode (e.g., the narrow viewing angle mode), the second light L 2  (e.g. UV light) emitted from the second light-emitting element  320  may be incident into a portion of the light guide layer  500  overlapping the peripheral area PA. The light guide layer  500  may transmit (e.g., may deliver) the second light L 2  to the display area DA. 
     In an embodiment, the second light L 2  incident into the light guide layer  500  in the peripheral area PA may be transmitted (e.g., may proceed) to the display area DA (i.e., in the third direction DR 3  of  FIG. 2B ) by total internal reflection. For example, a refractive index of the light guide layer  500  may be greater than each of refractive indices of layers that contacts an upper portion or a lower portion of the light guide layer  500  (e.g., the light control layer  600 , a planarization layer  400 , or the like). Accordingly, the second light L 2  incident into the light guide layer  500  in the peripheral area PA may be transmitted to the display area DA by total internal reflection. 
     A first optical pattern  510  and a second optical pattern  520  may be formed on the light guide layer  500 . 
     In an embodiment, the first optical pattern  510  may be formed on an upper surface or a lower surface of the light guide layer  500  overlapping the display area DA. The first optical pattern  510  may output (e.g., may emit) at least a portion of the second light L 2  transmitted inside of the light guide layer  500  to outside of the light guide layer  500  (e.g., to an upper layer or a lower layer of the light guide layer  500 ). That is, the second light L 2  transmitted (e.g., proceeding) in the third direction DR 3  inside of the light guide layer  500  by total internal reflection may be partially emitted to the outside of the light guide layer  500  by the first optical pattern  510 . Another portion of the second light L 2  that is not emitted to the outside of the light guide layer  500  may be continuously transmitted in the third direction DR 3  by total internal reflection. 
     For example, as illustrated in the drawing, the first optical pattern  510  may be provided in plural, and the plurality of first optical patterns  510  may be spaced apart at a predetermined interval in the third direction DR 3  to overlap the light control layer  600 . For another example, the first optical pattern  510  may be entirely formed in the display area DA. 
     The first optical pattern  510  may be formed in various ways. For example, the first optical pattern  510  may be implemented as a diffraction optical element, a hologram optical element, a micro pattern, or the like. 
       FIG. 3A  is an enlarged cross-sectional view illustrating an example of area “A” of  FIG. 2B .  FIG. 3B  is an enlarged cross-sectional view illustrating another example of area “A” of  FIG. 2B . 
     Referring to  FIGS. 2A, 2B, and 3A , in an embodiment, the first optical pattern  510  may include a diffraction grating having wavelength selectivity. The diffraction grating may selectively diffract a light having the second wavelength range (e.g., UV light) among lights having various wavelength ranges (e.g., visible light, UV light, and the like). The diffraction grating may not optically affect a light having a wavelength range different from the second wavelength range (e.g., visible light). For example, by adjusting a height d 1 , a width d 2 , a pitch d 3 , a formation angle, or the like of grating patterns  511   a  included in the diffraction grating, the first optical pattern  510  may be formed to have wavelength selectivity with respect to the second wavelength range (e.g., UV light wavelength range). 
     For example, as illustrated in  FIG. 2A , at least a portion of the first light L 1  (e.g., visible light) emitted from the first light-emitting element  310  may proceed to the first optical pattern  510 . The first light L 1  may have the first wavelength range different from the second wavelength range. Accordingly, the first optical pattern  510  may transmit the first light L 1  without optical change. 
     For example, as illustrated in  FIG. 2B , at least a portion of the second light L 2  (e.g., UV light) transmitted in the third direction DR 3  inside of the light guide layer  500  may proceed to the first optical pattern  510 . The second light L 2  may have the second wavelength range. Accordingly, the portion of the second light L 2  proceeding to the first optical pattern  510  may be diffracted by the first optical pattern  510 . Accordingly, the portion of the second light L 2  may not be totally reflected inside of the light guide layer  500 , and may be output (e.g., may be emitted) to the outside of the light guide layer  500 . 
     Referring to  FIGS. 2A, 2B, and 3B , in another embodiment, the first optical pattern  510  may be a micro pattern including a plurality of scattering patterns  511   b.  For example, each of the scattering patterns  511   b  may have a cross-sectional shape such as a lens, a prism, or the like. 
     For example, as illustrated in  FIG. 2B , at least a portion of the second light L 2  transmitted in the third direction DR 3  inside of the light guide layer  500  may proceed to the first optical pattern  510 . The portion of the second light L 2  proceeding to the first optical pattern  510  may be scattered by the scattering patterns  511   b.  Accordingly, the portion of the second light L 2  may not be totally reflected inside of the light guide layer  500 , and may be output (e.g., may be emitted) to the outside of the light guide layer  500 . 
     Referring back to  FIGS. 2A and 2B , in an embodiment, the second optical pattern  520  may be formed on a portion of the lower surface of the light guide layer  500  overlapping the peripheral area PA. The second optical pattern  520  may refract the second light L 2  incident in the peripheral area PA so that the second light L 2  may be totally reflected inside of the light guide layer  500 . That is, as illustrated in  FIG. 2B , the second light L 2  emitted from the second light-emitting element  320  may be refracted toward the display area DA (i.e., toward the third direction DR 3 ) by the second optical pattern  520 . 
     The second optical pattern  520  may be formed in various ways. For example, the second optical pattern  520  may be implemented as the diffraction optical element, the hologram optical element, the micro pattern, or the like. 
     The light control layer  600  may be disposed in the display area DA on the encapsulation layer ENC. That is, the light control layer  600  may be disposed on the first light-emitting element  310 . The light control layer  600  may have (e.g., may define) an opening exposing a portion of the light-emitting area LA. 
     The light control layer  600  may include a photochromic material that is discolored by a light having a specific wavelength range. In an embodiment, the photochromic material may be discolored by the second light L 2  (e.g., UV light) having the second wavelength range. The photochromic material may not be discolored by the first light L 1  (e.g., visible light) having the first wavelength range. In addition, when the photochromic material is not discolored by the second light L 2 , the photochromic material may transmit the first light L 1 . When the photochromic material is discolored by the second light L 2 , the photochromic material may absorb the first light L 1  so that the photochromic material may block transmission of the first light L 1 . For example, when the photochromic material is discolored by the second light L 2 , the photochromic material may have a transmittance of about 10% or less with respect to the first light L 1  (e.g., visible light). For example, the photochromic material may include azobenzene, spiropyran, diarylethene, or the like, but embodiments are not limited thereto. 
     Hereinafter, operations of the display device  10  in the first mode and the second mode will be described with reference to  FIGS. 2A and 2B . 
     In  FIG. 2A , when the display device  10  is in the first mode, the first transistor  210  may drive the first light-emitting element  310 , and the second transistor  220  may not drive the second light-emitting element  320 . Accordingly, the first light L 1  (e.g., visible light) may be emitted from the first light-emitting element  310 , and the second light L 2  (e.g., UV light) may not be emitted from the second light-emitting element  320 . Accordingly, the light control layer  600  may not be discolored. Accordingly, the light control layer  600  may transmit the first light L 1 . That is, the first light L 1  emitted from the light-emitting area LA may not blocked by the light control layer  600 , and may be emitted to outside of the display device  10  through the second substrate  800 . Accordingly, the display device  10  may have a wide viewing angle. 
     In  FIG. 2B , when the display device  10  is switched to the second mode, the second transistor  220  may drive the second light-emitting element  320 . Accordingly, the second light L 2  may be emitted from the second light-emitting element  320 . As described above, the second light L 2  emitted from the second light-emitting element  320  may be transmitted to the display area DA through the light guide layer  500 . In addition, a portion of the second light L 2  transmitted inside of the light guide layer  500  may be output (e.g., may be emitted) to the outside of the light guide layer  500  (e.g., to the light control layer  600 ) by the first optical pattern  510 . Accordingly, the light control layer  600  may be discolored. Accordingly, a portion of the first light L 1   a  proceeding to the light control layer  600  among the first light L 1  emitted from the light-emitting area LA may be blocked by the light control layer  600 . Another portion of the first light L 1   b  proceeding to openings OP 1  and OP 2  among the first light L 1  emitted from the light-emitting area LA may not be blocked by the light control layer  600 , and may be emitted to outside of the display device  10  through the second substrate  800 . That is, when the display device  10  is in the second mode, the light control layer  600  may block the portion of the first light L 1   a  having a viewing angle greater than or equal to a predetermined angle among the first light L 1  emitted from the light-emitting area LA. Accordingly, the display device  10  may have a narrow viewing angle. 
     When the display device  10  is switched to the first mode again, the second transistor  220  may not drive the second light-emitting element  320 . Accordingly, the second light L 2  may not be emitted from the second light-emitting element  320 , and the light control layer  600  may be restored to have its original color. Accordingly, the light control layer  600  may transmit the first light L 1  again, and the display device  10  may have the wide viewing angle again. 
     In an embodiment, as illustrated in  FIGS. 2A and 2B , the light control layer  600  may include a first light control layer  610  and a second light control layer  620  spaced apart from each other in a fourth direction DR 4 . For example, the light guide layer  500  may be disposed between the first light control layer  610  and the second light control layer  620 . That is, the first light control layer  610  may be disposed under the light guide layer  500 , and the second light control layer  620  may be disposed on the light guide layer  500 . In some embodiments, the light control layer  600  may be a single layer. 
     When the first and second light control layers  610  and  620  are disposed to be spaced apart from each other in the fourth direction DR 4 , a degree of decrease of the viewing angle of the display device  10  in the second mode may be relatively easily adjusted. For example, the degree of decrease of the viewing angle (e.g., a light emitting distribution of the first light L 1 ) may be determined according to a ratio of a width of each of the openings OP 1  and OP 2  respectively formed in the first and the second light control layers  610  and  620  to a separation distance of the openings OP 1  and OP 2 . In specific, as the ratio of the width to the separation distance increases, the degree of decrease of the viewing angle of the display device  10  in the second mode may be increased. That is, as the ratio of the width to the separation distance increases, the light emitting distribution of the first light L 1  in the second mode may be decreased. 
     The light control layer  600  may be adjacent to the light guide layer  500 . For example, the first light control layer  610  may contact the lower surface of the light guide layer  500 , and the second light control layer  620  may contact the upper surface of the light guide layer  500 . In this case, each of refractive indices of the first and second light control layers  610  and  620  may be less than the refractive index of the light guide layer  500 . However, embodiments are not limited thereto. In another embodiment, the light control layer  600  may be spaced apart from the light guide layer  500 . 
       FIGS. 4A and 4B  are plan views illustrating a light control layer according to an embodiment. For example,  FIG. 4A  may correspond to  FIG. 1 .  FIG. 4B  may be an enlarged view of a portion of the light control layer  600   a  of  FIG. 4A . 
     Referring to  FIGS. 1, 2A, 2B, 4A, and 4B , in an embodiment, the light control layer  600   a  may have a slit shape in a plan view. For example, the light control layer  600   a  may include a plurality of stripe patterns arranged in the first direction DR 1 , each of the stripe patterns extending in the second direction DR 2 . That is, the openings OP formed in the light control layer  600   a  may be arranged in the first direction DR 1 , each of the openings OP extending in the second direction DR 2 . Each of the openings OP may overlap the light-emitting areas LA arranged in the second direction DR 2 . According to an embodiment, in the second mode (e.g., the narrow viewing angle mode), a viewing angle of the display device  10  in the first direction DR 1  may be decreased, but a viewing angle in the second direction DR 2  may not be decreased. Alternatively, in order to decrease the viewing angle of the display device  10  in the second direction DR 2 , the light control layer  600   a  may be formed such that the stripe patterns are arranged in the second direction DR 2 . 
       FIGS. 5A and 5B  are plan views illustrating a light control layer according to another embodiment. For example,  FIG. 5A  may correspond to  FIG. 1 .  FIG. 5B  may be an enlarged view of a portion of the light control layer  600   b  of  FIG. 5A . 
     Referring to  FIGS. 1, 2A, 2B, 5A, and 5B , in another embodiment, the light control layer  600   b  may have a lattice shape in a plan view. That is, the openings OP formed in the light control layer  600   b  may be arranged in a matrix form in the first direction DR 1  and the second direction DR 2 . The openings OP may overlap the light-emitting areas LA, respectively. For example, an area of each of the openings OP in a plan view may be less than an area of each of the light-emitting areas LA. According to another embodiment, in the second mode (e.g., the narrow viewing angle mode), both the viewing angle of the display device  10  in the first direction DR 1  and the viewing angle in the second direction DR 2  may be decreased. 
     Referring back to  FIGS. 2A and 2B , in an embodiment, the display device  10  may further include a planarization layer  400 . The planarization layer  400  may include a first and second planarization layers  410  and  420 . The first planarization layer  410  may be disposed under the light guide layer  500 . The first planarization layer  410  may provide a substantially flat lower surface. The second planarization layer  420  may be disposed on the light guide layer  500 . The second planarization layer  420  may provide a substantially flat upper surface. Each of the first and second planarization layers  410  and  420  may include an organic material. Each of refractive indices of the first and second planarization layers  410  and  420  may be less than the refractive index of the light guide layer  500 . In another embodiment, the planarization layer  400  may be omitted. 
     The light absorption layer  700  may be disposed on the light control layer  600 . The light absorption layer  700  may be entirely disposed in the display area DA and the peripheral area PA on the light control layer  600 . The light absorption layer  700  may selectively absorb the second light L 2  (e.g., UV light) having the second wavelength range. That is, the light absorption layer  700  may block the second light L 2  from being emitted to the outside of the display device  10 . The light absorption layer  700  may transmit the first light L 1  (e.g., visible light) having the first wavelength range. 
     The second substrate  800  may be a transparent substrate. For example, the second substrate  800  may be formed of glass, quartz, plastic, or the like. The second substrate  800  may transmit the first light L 1  emitted from the light-emitting area LA. 
       FIG. 6  is a cross-sectional view illustrating another example taken along the line I-I′ of  FIG. 1 . 
     Referring to  FIGS. 1 and 6 , in an embodiment, the light control layer  600  may include a plurality of openings overlapping the light-emitting area LA. For example, the first light control layer  610  may include first openings OP 1   a  and OP 1   b  spaced apart from each other in the third direction DR 3 . The second light control layer  620  may include second openings OP 2   a  and OP 2   b  spaced apart from each other in the third direction DR 3 . The first openings OP 1   a  and OP 1   b  may overlap the second openings OP 2   a  and OP 2   b,  respectively. 
     In some embodiments, the display device  10  may display the image in the first mode implementing the wide viewing angle or the second mode implementing the narrow viewing angle. Accordingly, the viewing angle of the display device  10  may be adjusted. In addition, when the display device  10  is in the second mode, a portion of the first light L 1   a  having a viewing angle greater than or equal to a predetermined angle among the first light L 1  emitted from each of the pixels disposed in the display area DA may be blocked, and another portion of the first light L 1   b  having a viewing angle less than to the predetermined angle may be emitted to outside of the display device  10 . Accordingly, a resolution of the display device  10  may not be reduced even in the second mode. In addition, the second light-emitting element  320  may emit the second light L 2  for switching between the first mode and the second mode. The second light-emitting element  320  may be disposed in the peripheral area PA of the display device  10 . In some embodiments, the second light-emitting element  320  may be formed using some of the dummy pixels formed in the peripheral area PA. Accordingly, the display device  10  capable of adjusting the viewing angle may be manufactured without affecting the display area DA. In addition, the viewing angle of the display device  10  may be adjusted without attaching a separate optical film for adjusting the viewing angle of the display device  10 . 
       FIGS. 7A and 7B  are cross-sectional views illustrating a display device according to another embodiment. For example,  FIG. 7A  may illustrate a display device  11  in a first mode, and  FIG. 7B  may illustrate the display device  11  in a second mode. The first mode may be a wide viewing angle mode, and the second mode may be a narrow viewing angle mode. 
     Referring to  FIGS. 7A and 7B , the display device  11  according to another embodiment may include a first substrate  100 , a first transistor  210 , a first light-emitting element  310 , a second light-emitting element  1320 , an encapsulation layer ENC, a light guide layer  500 , a light control layer  600 , a light absorption layer  700 , and a second substrate  800 . The display device  11  according to another embodiment described with reference to  FIGS. 7A and 7B  may be substantially the same as or similar to the display device  10  described with reference to  FIGS. 1 to 6  except for the second light-emitting element  1320  and omitting the second transistor. Therefore, repeated descriptions will be omitted or simplified. 
     The first light-emitting element  310  may be disposed in the display area DA on the first substrate  100 . The first light-emitting element  310  may overlap the light-emitting area LA. The first light-emitting element  310  may emit the first light L 1  having the first wavelength range. The first light L 1  may be visible light. For example, the first light-emitting element  310  may emit red light, green light, or blue light. 
     The second light-emitting element  1320  may be disposed outside of a display panel. The second light-emitting element  1320  may be disposed adjacent to at least one side portion of the light guide layer  500 . For example, as illustrated in  FIGS. 7A and 7B , the second light-emitting element  1320  may be disposed adjacent to a side portion of the light guide layer  500  in the first direction DR 1 . A light-emitting surface  1321  of the second light-emitting element  1320  may face a side surface  501  of the light guide layer  500 . For example, the second light-emitting element  1320  and the display panel may be accommodated by a housing (not illustrated). 
     The second light-emitting element  1320  may emit the second light L 2  having the second wavelength range different from the first wave length range. For example, the second light may be UV light or IR light. 
     The second light-emitting element  1320  may emit the second light L 2  only in the second mode. That is, the second light L 2  may not be emitted from the second light-emitting element  1320  in the first mode, and the second light L 2  may be emitted from the second light-emitting element  1320  in the second mode. In the second mode, the second light L 2  may be emitted from the light-emitting surface  1321  of the second light-emitting element  1320  in the third direction DR 3 , and may be incident into the light guide layer  500  through the side surface  501  of the light guide layer  500 . The second light L 2  incident into the light guide layer  500  may be transmitted (e.g., may proceed) to the display area DA (i.e., in the third direction DR 3  of  FIG. 7B ) by total internal reflection. 
     A first optical pattern  510  may be formed on the light guide layer  500 . In an embodiment, the first optical pattern  510  may be formed on an upper surface or a lower surface of the light guide layer  500  overlapping the display area DA. The first optical pattern  510  may output (e.g., may emit) at least a portion of the second light L 2  transmitted inside of the light guide layer  500  to outside of the light guide layer  500  (e.g., to an upper layer or a lower layer of the light guide layer  500 ). That is, the second light L 2  transmitted (e.g., proceeding) in the third direction DR 3  inside of the light guide layer  500  by total internal reflection may be partially emitted to the outside of the light guide layer  500  by the first optical pattern  510 . Another portion of the second light L 2  that is not emitted to the outside of the light guide layer  500  may be continuously transmitted in the third direction DR 3  by total internal reflection. 
     In the display device  11  according to another embodiment, an optical pattern (e.g., the second optical pattern  520  of  FIG. 2A ) may not be formed on a portion of the lower surface of the light guide layer  500  overlapping the peripheral area PA. 
     Hereinafter, operations of the display device  11  in the first mode and the second mode will be described with reference to  FIGS. 7A and 7B . 
     In  FIG. 7A , when the display device  11  is in the first mode, the first light L 1  (e.g., visible light) may be emitted from the first light-emitting element  310 , and the second light L 2  (e.g., UV light) may not be emitted from the second light-emitting element  1320 . Accordingly, the light control layer  600  may not be discolored. Accordingly, the light control layer  600  may transmit the first light L 1 . That is, the first light L 1  emitted from the light-emitting area LA may not blocked by the light control layer  600 , and may be emitted to outside of the display device  11  through the second substrate  800 . Accordingly, the display device  11  may have a wide viewing angle. 
     In  FIG. 7B , when the display device  11  is switched to the second mode, the second light L 2  may be emitted from the second light-emitting element  1320 . As described above, the second light L 2  emitted from the second light-emitting element  1320  may be transmitted to the display area DA through the light guide layer  500 . In addition, a portion of the second light L 2  transmitted inside of the light guide layer  500  may be output (e.g., may be emitted) to the outside of the light guide layer  500  (e.g., to the light control layer  600 ) by the first optical pattern  510 . Accordingly, the light control layer  600  may be discolored. Accordingly, a portion of the first light L 1   a  proceeding to the light control layer  600  among the first light L 1  emitted from the light-emitting area LA may be blocked by the light control layer  600 . Another portion of the first light L 1   b  proceeding to openings OP 1  and OP 2  among the first light L 1  emitted from the light-emitting area LA may not be blocked by the light control layer  600 , and may be emitted to outside of the display device  11  through the second substrate  800 . That is, when the display device  11  is in the second mode, the light control layer  600  may block the portion of the light L 1   a  having a viewing angle greater than or equal to a predetermined angle among the first light L 1  emitted from the light-emitting area LA. Accordingly, the display device  11  may have a narrow viewing angle. 
     When the display device  11  is switched to the first mode again, the second light L 2  may not be emitted from the second light-emitting element  1320 , and the light control layer  600  may be restored to have its original color. Accordingly, the light control layer  600  may transmit the first light L 1  again, and the display device  11  may have the wide viewing angle again. 
       FIGS. 8A and 8B  are cross-sectional views illustrating a display device according to still another embodiment. For example,  FIG. 8A  may illustrate a display device  12  in a first mode, and  FIG. 8B  may illustrate the display device  12  in a second mode. The first mode may be a wide viewing angle mode, and the second mode may be a narrow viewing angle mode. 
     Referring to  FIGS. 8A and 8B , the display device  12  according to still another embodiment may include a first substrate  100 , a first transistor  210 , a first light-emitting element  310 , a second transistor  2220 , a second light-emitting element  2320 , an encapsulation layer ENC, a light control layer  600 , a light absorption layer  700 , and a second substrate  800 . The display device  12  according to still another embodiment described with reference to  FIGS. 8A and 8B  may be substantially the same as or similar to the display device  10  described with reference to  FIGS. 1 to 6  except for the second transistor  2220 , the second light-emitting element  2320 , and omitting the light guide layer. Therefore, repeated descriptions will be omitted or simplified. 
     The display device  12  may include (e.g., have) the display area DA and the peripheral area PA. The plurality of pixels may be disposed in the display area DA. The display area DA may include the plurality of light-emitting areas LA and the light-blocking area BA. The light-emitting areas LA may correspond to the pixels, respectively. For example, the light-emitting areas LA may be arranged in a matrix form in the first direction DR 1  and the second direction DR 2 . The light-blocking area BA may be around (e.g., surround) the light-emitting areas LA in a plan view. 
     For example,  FIGS. 8A and 8B  may correspond to each of the pixels. That is, each of the pixels may include the first transistor  210 , the first light-emitting element  310 , the second transistor  2220 , and the second light-emitting element  2320 . In addition, in  FIGS. 8A and 8B , a width of the light-emitting area LA is illustrated to be less than a width of the light-blocking area BA, but the width of the light-emitting area LA may be greater than the width of the light-blocking area BA. 
     The first light-emitting element  310  may be disposed in the display area DA on the first substrate  100 . The first light-emitting element  310  may overlap the light-emitting area LA. The first light-emitting element  310  may emit the first light L 1  having the first wavelength range. The first light L 1  may be visible light. For example, the first light-emitting element  310  may emit red light, green light, or blue light. 
     The second light-emitting element  2320  may be disposed in the display area DA on the first substrate  100 . The second light-emitting element  2320  may be spaced apart from the first light-emitting element  310 . For example, the second light-emitting element  2320  may overlap the light-blocking area BA. The second light-emitting element  2320  may emit the second light L 2  having the second wavelength range different from the first wave length range. For example, the second light may be UV light or IR light. 
     The first light-emitting element  310  may be driven by the first transistor  210 . The second light-emitting element  2320  may be driven by the second transistor  2220  different from the first transistor  210 . That is, the second light-emitting element  2320  that emits the second light L 2  (e.g., UV light) may be driven independently from the first light-emitting element  310  that emits the first light L 1  (e.g., visible light). For example, the first transistor  210  and the second transistor  2220  may be disposed in the display area DA on the first substrate  100 . 
     The light control layer  600  may be disposed in the display area DA on the encapsulation layer ENC. That is, the light control layer  600  may be disposed on the first and the second light-emitting elements  310  and  2320 . The light control layer  600  may have (e.g., may define) an opening exposing a portion of the light-emitting area LA. 
     The light control layer  600  may include a photochromic material that is discolored by a light having a specific wavelength range. In an embodiment, the photochromic material may be discolored by the second light L 2  (e.g., UV light) having the second wavelength range. The photochromic material may not be discolored by the first light L 1  (e.g., visible light) having the first wavelength range. In addition, when the photochromic material is not discolored by the second light L 2 , the photochromic material may transmit the first light L 1 . When the photochromic material is discolored by the second light L 2 , the photochromic material may absorb the first light L 1 . 
     In an embodiment, as illustrated in  FIGS. 8A and 8B , the light control layer  600  may include a first light control layer  610  and a second light control layer  620  spaced apart from each other in the fourth direction DR 4 . For example, a light collecting layer CTL may be disposed between the first light control layer  610  and the second light control layer  620 . However, embodiments are not limited thereto, and various functional layers capable of transmitting the first light L 1  such as a touch sensing layer TC may be disposed between the first light control layer  610  and the second light control layer  620 . In some embodiments, the light control layer  600  may be a single layer. 
     In the display device  12  according to still another embodiment, each of the pixels may include the first light-emitting element  310  and the second light-emitting element  2320 . Accordingly, the second light L 2  for switching between the first mode and the second mode may be emitted from each of the pixels disposed in the display area DA. Accordingly, a light guide layer (e.g., the light guide layer  500  of  FIG. 2A ) for transmitting the second light L 2  to the display area DA may be omitted. 
     Hereinafter, operations of the display device  12  in the first mode and the second mode will be described with reference to  FIGS. 8A and 8B . 
     In  FIG. 8A , when the display device  12  is in the first mode, the first transistor  210  may drive the first light-emitting element  310 , and the second transistor  2220  may not drive the second light-emitting element  2320 . Accordingly, the first light L 1  (e.g., visible light) may be emitted from the first light-emitting element  310 , and the second light L 2  (e.g., UV light) may not be emitted from the second light-emitting element  2320 . Accordingly, the light control layer  600  may not be discolored. Accordingly, the light control layer  600  may transmit the first light L 1 . That is, the first light L 1  emitted from the light-emitting area LA may not blocked by the light control layer  600 , and may be emitted to outside of the display device  12  through the second substrate  800 . Accordingly, the display device  12  may have a wide viewing angle. 
     In  FIG. 8B , when the display device  12  is switched to the second mode, the second transistor  2220  may drive the second light-emitting element  2320 . Accordingly, the second light L 2  may be emitted from the second light-emitting element  2320 . Accordingly, the light control layer  600  may be discolored. Accordingly, a portion of the first light L 1   a  proceeding to the light control layer  600  among the first light L 1  emitted from the light-emitting area LA may be blocked by the light control layer  600 . Another portion of the first light L 1   b  proceeding to openings OP 1  and OP 2  among the first light L 1  emitted from the light-emitting area LA may not be blocked by the light control layer  600 , and may be emitted to outside of the display device  12  through the second substrate  800 . That is, when the display device  12  is in the second mode, the light control layer  600  may block the portion of the first light L 1   a  having a viewing angle greater than or equal to a predetermined angle among the first light L 1  emitted from the light-emitting area LA. Accordingly, the display device  12  may have a narrow viewing angle. 
     When the display device  12  is switched to the first mode again, the second transistor  2220  may not drive the second light-emitting element  2320 . Accordingly, the second light L 2  may not be emitted from the second light-emitting element  2320 , and the light control layer  600  may be restored to have its original color. Accordingly, the light control layer  600  may transmit the first light L 1  again, and the display device  12  may have the wide viewing angle again. 
     Although certain embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concepts are not limited to such embodiments, but rather to the broader scope of the appended claims and various obvious modifications and equivalent arrangements as would be apparent to a person of ordinary skill in the art.