Abstract:
A display apparatus for displaying an image to a user includes: a display panel configured to generate visible light; and an optical functional layer including: a matrix mixed with a plurality of optical functional particles that are colored, wherein the optical functional layer is at a side of the display panel such that at least a part of the visible light from the display panel would pass through the optical functional layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0122928, filed on Sep. 16, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    One or more embodiments of the present invention relate to a display apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    Display apparatuses have recently been used in various applications. Also, as thicknesses and weights of display apparatuses have decreased, display apparatuses have been more widely used. 
         [0006]    Display apparatuses include a display device that may provide an image to a user by generating at least one visible light. 
         [0007]    A display apparatus includes various members in order to improve the quality of an image that is provided to a user. Various attempts have been made to improve image quality characteristics such as a viewing angle or color reproduction. 
         [0008]    However, there are limitations to improving image quality characteristics of display apparatuses. For example, as display apparatuses have larger sizes and higher definition, it is more difficult to improve image quality characteristics. 
       SUMMARY 
       [0009]    One or more embodiments of the present invention include a display apparatus having improved image quality characteristics. 
         [0010]    Additional aspects of the present invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
         [0011]    According to one or more embodiments of the present invention, a display apparatus for displaying an image to a user includes: a display panel configured to generate visible light; and an optical functional layer including: a matrix mixed with a plurality of optical functional particles that are colored, wherein the optical functional layer is at a side of the display panel such that at least a part of the visible light from the display panel would pass through the optical functional layer. 
         [0012]    The plurality of optical functional particles may be configured to absorb visible light of at least one color, and to transmit or diffuse visible light of other colors, from among the visible light generated by the display panel. 
         [0013]    The plurality of optical functional particles may include a same tint as at least one color of visible light generated by the display panel. 
         [0014]    The plurality of optical functional particles may include a chromatic material of one color and/or a chromatic material of an other color. 
         [0015]    The chromatic material of the one color and/or the chromatic material of the other color may include a dye material. 
         [0016]    The chromatic material of the one color and the chromatic material of the other color may be mixed with each other. 
         [0017]    The chromatic material of the one color and/or the chromatic material of the other color may be formed on surfaces of the plurality of optical functional particles. 
         [0018]    The chromatic material of the one color and/or the chromatic material of the other color may be formed inside the plurality of optical functional particles. 
         [0019]    The chromatic material of the one color and the chromatic material of the other color may have different colors selected from among red, green, and blue. 
         [0020]    The plurality of optical functional particles may include at least first optical functional particles and second optical functional particles, wherein the first optical functional particles include a chromatic material of a first color or a chromatic material of a second color that is different from the first color, and wherein the second optical functional particles include a chromatic material of the first color or a chromatic material of a third color that is different from the first color. 
         [0021]    The plurality of optical functional particles may further include third optical functional particles, and the third optical functional particles may include a chromatic material of the second color or a chromatic material of the third color. 
         [0022]    The first color, the second color, and the third color may be respectively red, green, and blue. 
         [0023]    The first optical functional particles may include a red dye material and a green dye material, the second optical functional particles include a red dye material and a blue dye material, and the third optical functional particles include a green dye material and a blue dye material. 
         [0024]    The display apparatus may further include optical functional particles that are transparent or white. 
         [0025]    The matrix may include an organic material. 
         [0026]    The display apparatus may further include a polarization layer on the optical functional layer, wherein the optical functional layer is between the display panel and the polarization layer, and wherein the matrix contacts the polarization layer and the display panel. 
         [0027]    The display panel may include at least one display device, and the at least one display device may include a first electrode, a second electrode, and an intermediate layer that is disposed between the first electrode and the second electrode and may be configured to generate visible light. 
         [0028]    According to one or more embodiments of the present invention, a display apparatus for displaying an image to a user includes: a display panel that includes a plurality of subpixels configured to generate different colors of visible light; and an optical functional layer including a matrix mixed with a plurality of optical functional particles that are colored, wherein the optical functional layer is configured to absorb visible light generated by at least one subpixel of the plurality of subpixels, and to transmit or diffuse visible light generated by another subpixel of the plurality of subpixels. 
         [0029]    The plurality of subpixels may include a first subpixel, a second subpixel, and a third subpixel, wherein the first subpixel, the second subpixel, and the third subpixel may be configured to generate visible light of different colors, wherein the plurality of optical functional particles of the optical functional layer includes first optical functional particles, second optical functional particles, and third optical functional particles, wherein the first optical functional particles are configured to absorb visible light generated by the first subpixel and the second subpixel and to transmit and diffuse at least a part of visible light generated by the third subpixel, wherein the second optical functional particles are configured to absorb visible light generated by the first subpixel and the third subpixel and to transmit and diffuse at least a part of visible light generated by the second subpixel, and wherein the third optical functional particles are configured to absorb visible light generated by the second subpixel and the third subpixel and to transmit and diffuse at least a part of visible light generated by the first subpixel. 
         [0030]    The first subpixel may be configured to generate visible light having a red tint, the second subpixel may be configured to generate visible light having a green tint, and the third subpixel may be configured to generate visible light having a blue tint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    These and/or other aspects of the present invention will become apparent and more readily appreciated from the following description of the embodiments of the present invention, taken in conjunction with the accompanying drawings in which: 
           [0032]      FIG. 1  is a cross-sectional view illustrating a display apparatus according to an embodiment; 
           [0033]      FIG. 2  is an enlarged cross-sectional view illustrating a portion K of  FIG. 1 ; 
           [0034]      FIG. 3  is a cross-sectional view illustrating a modification of  FIG. 2 ; 
           [0035]      FIG. 4  is a cross-sectional view illustrating a display apparatus according to another embodiment; 
           [0036]      FIG. 5  is an enlarged cross-sectional view illustrating a portion L of  FIG. 4 ; 
           [0037]      FIG. 6  is a cross-sectional view illustrating a modification of  FIG. 5 ; 
           [0038]      FIG. 7  is a cross-sectional view illustrating a display apparatus according to another embodiment; 
           [0039]      FIG. 8  is an enlarged cross-sectional view illustrating a portion M of  FIG. 7 ; 
           [0040]      FIG. 9  is a cross-sectional view illustrating a modification of  FIG. 8 ; 
           [0041]      FIG. 10  is a cross-sectional view illustrating a display apparatus according to another embodiment; 
           [0042]      FIG. 11  is an enlarged cross-sectional view illustrating a portion N of  FIG. 10 ; 
           [0043]      FIG. 12  is a cross-sectional view illustrating a modification of  FIG. 11 ; 
           [0044]      FIG. 13  is a cross-sectional view illustrating a display apparatus according to another embodiment; 
           [0045]      FIG. 14  is an enlarged cross-sectional view illustrating a portion O of  FIG. 13 ; 
           [0046]      FIGS. 15 ,  16 A,  16 B, and  17  are graphs illustrating image quality characteristics of a display apparatus, according to an embodiment; 
           [0047]      FIG. 18  is a cross-sectional view illustrating a display apparatus according to another embodiment; 
           [0048]      FIG. 19  is an enlarged cross-sectional view illustrating a portion P of  FIG. 18 ; 
           [0049]      FIG. 20  is a cross-sectional view illustrating a modification of  FIG. 19 ; 
           [0050]      FIG. 21  is a cross-sectional view illustrating a display apparatus according to another embodiment; and 
           [0051]      FIG. 22  is an enlarged cross-sectional view illustrating a portion Q of  FIG. 21 . 
       
    
    
     DETAILED DESCRIPTION 
       [0052]    The present invention may include various embodiments and modifications, and exemplary embodiments thereof will be illustrated in the drawings and will be described herein in detail. The effects and features of the present invention and the accompanying methods thereof will become apparent from the following description of the embodiments, taken in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described below, and may be embodied in various modes. 
         [0053]    It will be understood that although the terms “first”, “second”, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These elements are only used to distinguish one element from another. 
         [0054]    As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively. 
         [0055]    As used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. 
         [0056]    It will be understood that when an element or layer is referred to as being “on”, “connected to”, “coupled to”, or “adjacent to” another element or layer, it can be directly on, connected to, coupled to, or adjacent to the other element or layer, or one or more intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on,” “directly connected to”, “directly coupled to”, or “immediately adjacent to” another element or layer, there are no intervening elements or layers present. 
         [0057]    It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. 
         [0058]    It will be understood that when a layer, region, or element is referred to as being “formed on,” another layer, region, or element, it can be directly or indirectly formed on the other layer, region, or element. That is, for example, intervening layers, regions, or elements may be present. Also, the term “exemplary” is intended to refer to an example or illustration. 
         [0059]    Sizes of elements may be exaggerated for convenience of explanation. In other words, since sizes and thicknesses of elements in the drawings are arbitrarily illustrated for convenience of explanation, the following embodiments of the present invention are not limited thereto. 
         [0060]    In the following examples, the x-axis, the y-axis and the z-axis are not limited to three axes of the rectangular coordinate system, and may be interpreted in a broader sense. For example, the x-axis, the y-axis, and the z-axis may be perpendicular to one another, or may represent different directions that are not perpendicular to one another. 
         [0061]    When a certain embodiment of the present invention may be implemented differently, a specific process order may be performed differently from the described order. For example, two consecutively described processes may be performed substantially at the same time or performed in an order opposite to the described order. 
         [0062]    As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
         [0063]    Embodiments of the present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the present invention are shown. In the drawings, the same or corresponding elements are denoted by the same reference numerals and a repeated explanation thereof will not be given. 
         [0064]      FIG. 1  is a cross-sectional view illustrating a display apparatus  100  according to an embodiment of the present invention.  FIG. 2  is an enlarged cross-sectional view illustrating a portion K of  FIG. 1 .  FIG. 3  is a cross-sectional view illustrating a modification of  FIG. 2 . 
         [0065]    Referring to  FIGS. 1 through 3 , the apparatus  100  includes a display panel  110  and an optical functional layer  120 . 
         [0066]    The display panel  110  displays an image to a user. That is, although not shown in  FIGS. 1 through 3 , the display panel  110  may include a display device that may generate visible light that is to be provided to the user. Any of various suitable devices, for example, an organic light-emitting device or a liquid crystal display (LCD) device, may be used (e.g., utilized) as the display device. Also, any of various suitable types of display devices that may generate an image may be selectively used as the display device that is included in the display panel  110 . 
         [0067]    Although not shown in  FIGS. 1 through 3 , the display panel  110  provides an image upward, that is, from the bottom to the top in  FIG. 1 . 
         [0068]    The optical functional layer  120  includes a matrix  125  and optical functional particles  121 . 
         [0069]    The matrix  125  may function as a base for the optical functional layer  120 . The matrix  125  may be formed of any of various suitable materials, for example, an insulating material. For example, the matrix  125  may be formed to include an organic material. 
         [0070]    Alternatively, the matrix  125  may be formed to include resin. 
         [0071]    Alternatively, the matrix  125  may include a polymer material, for example, acryl-based resin. 
         [0072]    Alternatively, the matrix  125  may be formed of an adhesive material. Any of various suitable adhesive materials, for example, adhesive resin, may be used as the adhesive material that is included in the matrix  125 . In this case, the optical functional layer  120  may be easily disposed on the display panel  110 . For example, as the matrix  125  contacts the display panel  110 , the optical functional layer  120  may be stably adhered to the display panel  110 . 
         [0073]    The optical functional particles  121  may be colored, instead of being transparent or non-colored. For example, the optical functional particles  121  may include a chromatic material with a red or green tint. For example, the optical functional particles  121  may include a dye material with a red or green tint. 
         [0074]    Alternatively, the optical functional particles  121  may include a chromatic material having a red tint and a chromatic material having a green tint. For example, the optical functional particles  121  may have a state where a chromatic material having a red tint and a chromatic material having a green tint are mixed with each other. 
         [0075]    For example, the optical functional particles  121  may include a dye material with a red or green tint formed on surfaces thereof. Alternatively, the optical functional particles  121  may include a dye material with a red or green tint formed not only on surfaces thereof but also inside the optical functional particles  121 . 
         [0076]    The optical functional particles  121  may be formed by using any of various suitable methods. The optical functional particles  121  may be formed by performing dyeing on organic particles, inorganic particles, or metal particles. Examples of the organic particles used to form the optical functional particles  121  may include polymelamine, polystyrene, poly(methyl methacrylate) (PMMA), and polylactide, and examples of the inorganic particles used to form the optical functional particles  121  may include silica, alumina, titania, glass, and ceramic. 
         [0077]    Although the optical functional particles  121  that are included in the optical functional layer  120  are colored, that is, include a chromatic material with a red or green tint in  FIG. 2 , the present embodiment is not limited thereto and optical functional particles that are unicolored may be optionally further included in the optical functional layer  120  as shown in  FIG. 3 . The optical functional particles  124  may be non-colored, for example, may be transparent or white. 
         [0078]    The display apparatus  100  of the present embodiment includes the optical functional layer  120  that is disposed over the display panel  110 , that is, on a side of the display panel  110  where an image is formed. 
         [0079]    Also, the optical functional layer  120  includes the matrix  125  and the optical functional particles  121  that are mixed with the matrix  125 . The optical functional particles  121  are colored. The colored optical functional particles  121  improve viewing angel characteristics of the display apparatus  100  by scattering visible light that is formed on the display panel  110 . Also, color reproduction of the display apparatus  100  may be improved by enabling the optical functional particles  121  to be colored, instead of being non-colored, that is, to have the same or substantially the same tint as a color of visible light that is formed on the display panel  110 . 
         [0080]    For example, the optical functional particles  121  may be colored to have a red or green tint. Alternatively, the optical functional particles  121  may be dyed by mixing a dye material having a red tint and a dye material having a green tint so that the optical functional particles  121  have a red or green tint. In this case, the optical functional particles  121  may absorb visible light having a red tint and visible light having a green tint from among visible light provided from the display panel  110  and may transmit or diffuse visible light having a blue tint. 
         [0081]    Accordingly, the quality of visible light having a blue tint, from among visible light that is provided from the display panel  110 , may be improved and color reproduction of the visible light with the blue tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  125  and a refractive index of the optical functional particles  121  according to a wavelength band of the visible light with the blue tint from among the visible light that is formed on the display panel  110  by forming the optical functional particles  121  by mixing a dye material having a red tint and a dye material having a green tint with each other. 
         [0082]    Alternatively, viewing angle characteristics may be improved by using light scattering of the optical functional layer  120  by enabling the optical functional particles  124  that are unicolored, for example, are transparent or white, to be optionally included in the optical functional layer  120 . 
         [0083]      FIG. 4  is a cross-sectional view illustrating a display apparatus  200  according to another embodiment of the present invention.  FIG. 5  is an enlarged cross-sectional view illustrating a portion L of  FIG. 4 .  FIG. 6  is a cross-sectional view illustrating a modification of  FIG. 5 . 
         [0084]    Referring to  FIGS. 4 through 6 , the display apparatus  200  includes a display panel  210  and an optical functional layer  220 . 
         [0085]    The display panel  210  displays an image to a user. That is, although not shown in  FIGS. 4 through 6 , the display panel  210  may include a display device that may generate visible light that is provided to the user. Any of various suitable devices, for example, an organic light-emitting device or an LCD device, may be used as the display device. Also, any of various suitable types of display devices that may generate an image may be selectively used as the display device that is included in the display panel  210 . 
         [0086]    Although not shown in  FIGS. 4 through 6 , the display panel  210  provides an image upward, that is, from the bottom to the top in  FIG. 4 . 
         [0087]    The optical functional layer  220  includes a matrix  225  and optical functional particles  222 . 
         [0088]    The matrix  225  may function as a base for the optical functional layer  220 . The matrix  225  may be formed of any of various suitable materials, for example, an insulating material. For example, the matrix  225  may be formed to include resin. 
         [0089]    Alternatively, the matrix  225  may include a polymer material, for example, acryl-based resin. 
         [0090]    Alternatively, the matrix  225  may be formed of an adhesive material. Any of various suitable adhesive materials, for example, adhesive resin, may be used as the adhesive material that is included in the matrix  225 . In this case, the optical functional layer  220  may be easily disposed on the display panel  210 . For example, as the matrix  225  contacts the display panel  210 , the optical functional layer  220  may be stably adhered to the display panel  210 . 
         [0091]    The optical functional particles  222  are colored, instead of being transparent or non-colored. For example, the optical functional particles  222  may include a chromatic material with a red or blue tint. For example, the optical functional particles  222  may include a dye material with a red or blue tint. 
         [0092]    Alternatively, the optical functional particles  222  may include a chromatic material having a red tint and a chromatic material having a blue tint. For example, the optical functional particles  222  may have a state where a chromatic material having a red tint and a chromatic material having a blue tint are mixed with each other. 
         [0093]    For example, the optical functional particles  222  may include a dye material with a red or blue tint formed on surfaces thereof. Alternatively, the optical functional particles  222  may include a dye material with a red or blue tint formed not only on surfaces thereof but also inside the optical functional particles  222 . 
         [0094]    The optical functional particles  222  may be formed by using any of various suitable methods. The optical functional particles  222  may be formed by performing dyeing on organic particles, inorganic particles, or metal particles. Examples of the organic particles used to form the optical functional particles  222  may include polymelamine, polystyrene, PMMA, and polylactide, and examples of the inorganic particles used to form the optical functional particles  222  may include silica, alumina, titania, glass, and ceramic. 
         [0095]    Although the optical functional particles  222  that are included in the optical functional layer  220  include a chromatic material with a red or blue tint in  FIG. 5 , the present embodiment is not limited thereto and optical functional particles  224  that are unicolored may be optionally further included in the optical functional layer  220  as shown in  FIG. 6 . The optical functional particles  224  may be non-colored, for example, may be transparent or white. 
         [0096]    The display apparatus  200  of the present embodiment includes the optical functional layer  220  that is disposed over the display panel  210 , that is, on a side of the display panel  210  where an image is formed. 
         [0097]    Also, the optical functional layer  220  includes the matrix  225  and the optical functional particles  222  that are mixed with the matrix  225 . The optical functional particles  222  are colored. The colored optical functional particles  222  improve viewing angle characteristics of the display apparatus  200  by scattering visible light that is formed on the display panel  210 . Also, color reproduction of the display apparatus  200  may be improved by enabling the optical functional particles  222  to be colored, instead of, being non-colored, that is, to have the same or substantially the same tint as a color of the visible light that is formed on the display panel  210 . 
         [0098]    For example, the optical functional particles  222  may be colored to have a red or blue tint. Alternatively, the optical functional particles  222  may be dyed by mixing a dye material having a red tint and a dye material having a blue tint so that the optical functional particles  222  are colored to have red and blue tints. In this case. The optical functional particles  222  may absorb visible light having a red tint and visible light having a blue tint from among visible light that is provided from the display panel  210  and may transmit or diffuse visible light having a green tint. 
         [0099]    Accordingly, the quality of visible light having a green tint, from among visible light that is provided from the display panel  210 , may be improved and color reproduction of the visible light with the green tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  225  and a refractive index of the optical functional particles  222  according to a wavelength band of the visible light with the green tint from among the visible light that is formed on the display panel  210  by forming the optical functional particles  222  by mixing a dye material having a red tint and a dye material having a blue tint. 
         [0100]    Alternatively, viewing angle characteristics may be improved by using light scattering of the optical functional layer  220  by enabling the optical functional particles  224  that are unicolored, for example, are transparent or white, to be optionally included in the optical functional layer  220 . 
         [0101]      FIG. 7  is a cross-sectional view illustrating a display apparatus  300  according to another embodiment of the present invention.  FIG. 8  is an enlarged cross-sectional view illustrating a portion M of  FIG. 7 .  FIG. 9  is a cross-sectional view illustrating a modification of  FIG. 8 . 
         [0102]    Referring to  FIGS. 7 through 9 , the display apparatus  300  includes a display panel  310  and an optical functional layer  320 . 
         [0103]    The display panel  310  displays an image to a user. That is, although not shown in  FIGS. 7 through 9 , the display panel  310  may include a display device that may generate visible light that is to be provided to the user. Any of various suitable devices, for example, an organic light-emitting device or an LCD device, may be used as the display device. Also, any of various suitable types of display devices that may generate an image may be used as the display device that is included in the display panel  310 . 
         [0104]    Although not shown in  FIGS. 7 through 9 , the display panel  310  provides an image upward, that is, from the bottom to the top in  FIG. 4 . 
         [0105]    The optical functional layer  320  includes a matrix  325  and optical functional particles  323 . 
         [0106]    The matrix  325  may function as a base for the optical functional layer  320 . The matrix  325  may be formed by using any of various suitable materials, for example, an insulating material. For example, the matrix  325  may be formed to include resin. 
         [0107]    Alternatively, the matrix  325  may include a polymer material, for example, acryl-based resin. 
         [0108]    Alternatively, the matrix  325  may be formed of an adhesive material. Any of various suitable adhesive materials, for example, adhesive resin, may be used as the adhesive material that is included in the matrix  325 . In this case, the optical functional layer  320  may be easily disposed on the display panel  310 . For example, as the matrix  325  contacts the display panel  310 , the optical functional layer  320  may be stably adhered to the display panel  310 . 
         [0109]    The optical functional particles  323  are colored, instead of being transparent or non-colored. For example, the optical functional particles  323  may include a chromatic material with a green or blue tint. For example, the optical functional particles  323  may include a dye material with a green or blue tint. 
         [0110]    Alternatively, the optical functional particles  323  may include a chromatic material having a green tint and a chromatic material having a blue tint. For example, the optical functional particles  323  may have a state where a chromatic material having a green tint and a chromatic material having a blue tint are mixed with each other. 
         [0111]    For example, the optical functional particles  323  may include a dye material with a green or blue tint formed on surfaces thereof. Alternatively, the optical functional particles  323  may include a dye material with a green or blue tint formed not only on surfaces thereof but also inside the optical functional particles  323 . 
         [0112]    The optical functional particles  323  may be formed by using any of various suitable methods. The optical functional particles  323  may be formed by performing dyeing on organic particles, inorganic particles, or metal particles. Examples of the organic particles used to form the optical functional particles  323  may include polymelamine, polystyrene, PMMA, and polylactide, and examples of the inorganic particles used to form the optical functional particles  323  may include silica, alumina, titania, glass, and ceramic. 
         [0113]    Although the optical functional particles  323  included in the optical functional layer  320  are colored, that is, include a chromatic material with a green or blue tint, in  FIG. 8 , the present embodiment is not limited thereto and optical functional particles  324  that are unicolored may also be optionally included in the optical functional layer  320  as shown in  FIG. 9 . The optical functional particles  324  may be non-colored (e.g., achromatic colored), for example, may be transparent or white. 
         [0114]    The display apparatus  300  of the present embodiment includes the optical functional layer  320  that is disposed over the display panel  310 , that is, on a side of the display panel  310  where an image is formed. 
         [0115]    Also, the optical functional layer  320  includes the matrix  325  and the optical functional particles  323  that are mixed with the matrix  325 , and the optical functional particles  323  are colored. The colored optical functional particles  323  improve viewing angle characteristics of the display apparatus  300  by scattering visible light that is formed on the display panel  310 . Also, color reproduction of the display apparatus  300  may be improved by enabling the optical functional particles  323  to be colored, instead of being non-colored, that is, to have the same or substantially the same tint as a color of the visible light that is formed on the display panel  310 . 
         [0116]    For example, the optical functional particles  323  may be colored to have a green or blue tint. Alternatively, the optical functional particles  323  may be dyed by mixing a dye material having a green tint and a dye material having a blue tint so that the optical functional particles  323  are colored to have green and blue tints. In this case, the optical functional particles  323  may absorb visible light having a green tint and visible light having a blue tint from among visible light that is provided from the display panel  310 . 
         [0117]    Accordingly, the quality of visible light having a red tint, from among visible light that is provided from the display panel  310 , may be improved. For example, color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  325  and a refractive index of the optical functional particles  323  according to a wavelength band of the visible light with the red tint from among the visible light that is formed on the display panel  310  by forming the optical functional particles  323  by mixing a dye material having a green tint and a dye material having a blue tint. 
         [0118]    Alternatively, viewing angle characteristics may be improved by using light scattering of the optical functional layer  320  by enabling the optical functional particles  324  that are unicolored, for example, be transparent or white, to be optionally included in the optical functional layer  320 . 
         [0119]      FIG. 10  is a cross-sectional view illustrating a display apparatus  400  according to another embodiment of the present invention.  FIG. 11  is an enlarged cross-sectional view illustrating a portion N of  FIG. 10 .  FIG. 12  is a cross-sectional view illustrating a modification of  FIG. 11 . 
         [0120]    Referring to  FIGS. 10 through 12 , the display apparatus  400  includes a display panel  410  and an optical functional layer  420 . 
         [0121]    The display panel  410  displays an image to a user. That is, although not shown in  FIGS. 10 through 12 , the display panel  410  may include a display device that may generate visible light that is to be provided to the user. Any of various suitable devices, for example, an organic light-emitting device or an LCD device, may be used as the display device. Also, any of various suitable types of display devices that may generate an image may be used as the display device that is included in the display panel  410 . 
         [0122]    Although not shown in  FIGS. 10 through 12 , the display panel  410  provides an image upward, that is, from the bottom to the top in  FIG. 4 . 
         [0123]    The optical functional layer  420  includes a matrix  425  and optical functional particles. 
         [0124]    The matrix  425  may function as a base for the optical functional layer  420 . The matrix  425  may be formed of any of various suitable materials, for example, an insulating material. For example, the matrix  425  may be formed to include resin. 
         [0125]    Alternatively, the matrix  425  may include a polymer material, for example, acryl-based resin. 
         [0126]    Alternatively, the matrix  425  may be formed of an adhesive material. Any of various suitable adhesive materials, for example, adhesive resin, may be used as the adhesive material that is included in the matrix  425 . In this case, the optical functional layer  420  may be easily disposed on the display panel  410 . For example, as the matrix  425  contacts the display panel  410 , the optical functional layer  420  may be stably adhered to the display panel  410 . 
         [0127]    The optical functional particles are colored, instead of being transparent or non-colored. For example, the optical functional particles include first optical functional particles  421 , second optical functional particles  422 , and third optical functional particles  423 . 
         [0128]    The first optical functional particles  421  may include a chromatic material with a red or green tint. For example, the first optical functional particles  421  may include a dye material with a red or green tint. 
         [0129]    Alternatively, the first optical functional particles  421  may include a chromatic material having a red tint and a chromatic material having a green tint. For example, the first optical functional particles  421  may have a state where a chromatic material having a red tint and a chromatic material having a green tint are mixed with each other. 
         [0130]    For example, the first optical functional particles  421  may include a dye material with a red or green tint formed on surfaces thereof. Alternatively, the first optical functional particles  421  may include a dye material with a red or green tint formed not only on surfaces thereof but also inside the first optical functional particles  421 . 
         [0131]    The second optical functional particles  422  may include a chromatic material with a red or blue tint. For example, the second optical functional particles  422  may include a dye material with a red or blue tint. 
         [0132]    Alternatively, the second optical functional particles  422  may include a chromatic material having a red tint and a chromatic material having a blue tint. For example, the second optical functional particles  422  may have a state where a chromatic material having a red tint and a chromatic material having a blue tint are mixed with each other. 
         [0133]    For example, the second optical functional particles  422  may include a dye material with a red or blue tint formed on surfaces thereof. Alternatively, the second optical functional particles  422  may include a dye material with a red or blue tint formed not only on surfaces thereof but also inside the second optical functional particles  422 . 
         [0134]    The third optical functional particles  423  may include a chromatic material with a green or blue tint. For example, the third optical functional particles  423  may include a dye material with a green or blue tint. 
         [0135]    Alternatively, the third optical functional particles  423  may include a chromatic material having a green tint and a chromatic material having a blue tint. For example, the third optical functional particles  423  may have a state where a chromatic material having a green tint and a chromatic material having a blue tint are mixed with each other. 
         [0136]    For example, the third optical functional particles  423  may include a dye material with a green or blue tint formed on surfaces thereof. Alternatively, the third optical functional particles  423  may include a dye material with a green or blue tint formed not only on surfaces thereof but also inside the third optical functional particles  423 . 
         [0137]    The first through third optical functional particles  421 ,  422 , and  423  may be formed by using any of various suitable methods. The first through third optical functional particles  421 ,  422 , and  423  may be formed by performing dyeing on organic particles, inorganic particles, or metal particles. Examples of the organic particles used to form the first through third optical functional particles  421 ,  422 , and  423  may include polymelamine, polystyrene, PMMA, and polylactide, and examples of the inorganic particles used to form the first through third optical functional particles  421 ,  422 , and  423  may include silica, alumina, titania, glass, and ceramic. 
         [0138]    Although the first through third optical functional particles  421 ,  422 , and  423  included in the optical functional layer  420  include a chromatic material in  FIG. 11 , the present embodiment is not limited thereto and optical functional particles  424  that are unicolored may be optionally further included in the optical functional layer  420  as shown in  FIG. 12 . The optical functional particles  424  may be non-colored, for example, may be transparent or white. 
         [0139]    The display apparatus  400  of the present embodiment includes the optical functional layer  420  that is disposed over the display panel  410 , that is, on a side of the display panel  410  where an image is formed. 
         [0140]    Also, the optical functional layer  420  includes the matrix  425  and the first through third optical functional particles  421 ,  422 , and  423  that are mixed with the matrix  425 . The first through third optical functional particles  421 ,  422 , and  423  are colored. The first through third colored optical functional particles  421 ,  422 , and  423  improve viewing angle characteristics of the display apparatus  400  by scattering visible light that is formed on the display panel  410 . Also, color reproduction of the display apparatus  400  may be improved by enabling the first through third optical functional particles  421 ,  422 , and  423  to be colored, instead of being non-colored, that is, to have the same or substantially the same tint as a color of the visible light that is formed on the display panel  410 . 
         [0141]    For example, the first optical functional particles  421  may be colored to have a red or green tint. Alternatively, the first optical functional particles  421  may be dyed by mixing a dye material having a red tint and a dye material having a green tint so that the first optical functional particles  421  are colored to have red and green tints. In this case, the first optical functional particles  421  may absorb visible light having a red tint and visible light having a green tint from among visible light that is provided from the display panel  410  and may transmit or diffuse visible light having a blue tint. 
         [0142]    Accordingly, the quality of visible light having a blue tint, from among visible light that is provided from the display panel  410 , may be improved and color reproduction of the visible light with the blue tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  425  and a refractive index of the first optical functional particles  421  according to a wavelength band of the visible light with the blue tint from among the visible light that is formed on the display panel  410  by forming the first optical functional particles  421  by mixing a dye material having a red tint and a dye material having a green tint. 
         [0143]    For example, the second optical functional particles  422  may be colored to have a red or blue tint. Alternatively, the second optical functional particles  422  may be dyed by mixing a dye material having a red tint and a dye material having a blue tint so that the second optical functional particles  422  are colored to have red and blue tints. In this case, the second optical functional particles  422  may absorb visible light having a red tint and visible light having a blue tint from among visible light that is provided from the display panel  410  and may transmit or diffuse visible light having a green tint. 
         [0144]    Accordingly, the quality of visible light having a green tint, from among visible light that is provided from the display panel  410 , may be improved and color reproduction of the visible light with the green tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  425  and a refractive index of the second optical functional particles  422  according to a wavelength band of the visible light with the green tint from among the visible light that is formed on the display panel  410  by forming the second optical functional particles  422  by mixing a dye material having a red tint and a dye material having a blue tint. 
         [0145]    For example, the third optical functional particles  423  may be colored to have a green or blue tint. Alternatively, the third optical functional particles  423  may be dyed by mixing a dye material having a green tint and a dye material having a blue tint so that the third optical functional particles  423  are colored to have green and blue tints. In this case, the third optical functional particles  423  may absorb visible light having a green tint and visible light having a blue tint from among visible light that is provided from the display panel  410  and may transmit or diffuse visible light having a red tint. 
         [0146]    Accordingly, the quality of visible light having a red tint, from among visible light that is provided from the display panel  410 , may be improved and color reproduction of the visible light with the red tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  425  and a refractive index of the third optical functional particles  423  according to a wavelength band of the visible light with the blue tint from among the visible light that is formed on the display panel  410  by forming the third optical functional particles  423  by mixing a dye material having a green tint and a dye material having a blue tint. 
         [0147]    The first through third optical functional particles  421 ,  422 , and  423  may include all of the optical functional particles  121  of  FIGS. 1 and 2 , the optical functional particles  222  of  FIGS. 4 and 5 , and the optical functional particles  323  of  FIGS. 7 and 8 . However, the present embodiment is not limited thereto, and the first through third optical functional particles  421 ,  422 , and  423  may include only two from among the optical functional particles  121  of  FIGS. 1 and 2 , the optical functional particles  222  of  FIGS. 4 and 5 , and the optical functional particles  323  of  FIGS. 7 and 8 . 
         [0148]    Alternatively, viewing angle characteristics may be improved by using light scattering of the optical functional layer  420  by enabling the optical functional particles  424  that are unicolored, for example, are transparent or white, to be optionally further included in the optical functional layer  420 . 
         [0149]      FIG. 13  is a cross-sectional view illustrating a display apparatus  500  according to another embodiment of the present invention.  FIG. 14  is an enlarged cross-sectional view illustrating a portion O of  FIG. 13 . 
         [0150]    Referring to  FIGS. 13 and 14 , the display apparatus  500  includes a display panel  510 , an optical functional layer  520 , and a polarization layer  530 . 
         [0151]    The optical functional layer  520  includes a matrix  525  and optical functional particles. 
         [0152]    The display panel  510  and the optical functional layer  520  of  FIGS. 13 and 14  correspond to the display panel  410  and the optical functional layer  420  of  FIGS. 10 and 11 , and thus a detailed explanation thereof will not be given. Although not shown in  FIGS. 13 and 14 , the description of  FIGS. 1 through 3 , the description of  FIGS. 4 through 6 , the description of  FIGS. 7 through 9 , and/or the description of  FIG. 12  may apply to the optical functional layer  520 . 
         [0153]    The optical functional layer  520  is disposed between the polarization layer  530  and the display panel  510 . For example, the matrix  525  of the optical functional layer  520  may contact one surface of the display panel  510  and one surface of the polarization layer  530 , and thus the display panel  510 , the optical functional layer  520 , and the polarization layer  530  may be stably adhered to one another. 
         [0154]    Also, like in the previous embodiments of the present invention, image quality characteristics of the display apparatus  500  may be improved by improving viewing angle effect and color reproduction by using light scattering of the optical functional layer  520 . 
         [0155]    As described above in the previous embodiments of the present invention, the optical functional particles may be formed by using any of various suitable chromatic materials. 
         [0156]    For example, the optical functional particles may be formed by using various suitable dyes or pigments. 
         [0157]    When the optical functional particles are formed to include a chromatic material having a red tint, the optical functional particles may be formed by using a dye having a red tint such as C.I. Pigment Red 7, 9, 14, 41, 48:1, 48:2, 48:3, 48:4, 81.1, 81.2, 81.3, 97, 122, 123, 146, 149, 168, 177, 178, 180, 184, 185, 187, 192, 200, 202, 208, 210, 215, 216, 217, 220, 223, 224, 226, 227, 228, 240, 246, 254, 255, 264, or 272. Alternatively, a dye with a yellow or orange tint may also be used together. 
         [0158]    When the optical functional particles are formed to include a chromatic material having a green tint, the optical functional particles may be formed by using a dye having a green tint such as C.I. Pigment Green 7, 10, 36, or 37. 
         [0159]    When the optical functional particles are formed to include a chromatic material having a blue tint, the optical functional particles may be formed by using a dye having a blue tint such as C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:5, 16, 22, 60, or 64. Alternatively, a dye with a purple tint such as C.I. Pigment Violet 1, 19, 23, 27, 29, 30, 32, 37, 40, 42, or 50 may also be used. 
         [0160]    Also, one or more selected from, for example, AcidRed138 (see the following chemical formula), Green3 (see the following chemical formula), and Blue97 (see the following chemical formula), may be used as a chromatic material used to form the optical functional particles. 
       Acid Red 138: 
       [0000]    
       
         disodium 5-(acetylamino)-3-[(4-dodecylphenyl)azo]-4-hydroxynaphthalene-2,7-disulphonate 
       
     
         [0000]    
       
                 
         
             
             
         
       
     
       Green 3: 
       [0000]    
       
         1,4-bis(p-tolylamino)anthraquinone 
       
     
         [0000]    
       
                 
         
             
             
         
       
     
       Blue 97: 
       [0000]    
       
         1,4-Bis[(2,6-diethyl-4-methylphenyl)amino]anthraquinone; 1,4-Bis(2,6-diethyl-4-methylanilino)anthraquinone; or N,N′-Bis(2,6-diethyl-4-methylphenyl)-1,4-diaminoanthraquinone 
       
     
         [0000]    
       
                 
         
             
             
         
       
     
         [0164]    Also, the optical functional particles may be formed by using any of various suitable methods. For example, a method of dipping unicolored particles in the chromatic material may be performed. Alternatively, any of various other suitable coating methods may be used. 
         [0165]      FIGS. 15 ,  16 A,  16 B, and  17  are graphs for explaining image quality characteristics of a display apparatus, according to an embodiment of the present invention. 
         [0166]      FIG. 15  will be first explained. In  FIG. 15 , the X-axis represents a wavelength of visible light and the Y-axis represents a refractive index. 
         [0167]    Graph C of  FIG. 15  shows a relationship between a refractive index and a wavelength of visible light for a matrix of an optical functional layer according to any of the previous embodiments of the present invention. For example, the graph C shows a relationship between a refractive index and a wavelength of visible light that is formed on a display panel. Referring to the graph C of  FIG. 15 , a refractive index decreases as a wavelength of visible light increases. 
         [0168]    A graph A of  FIG. 15  shows a relationship between a refractive index and a wavelength of visible light for optical functional particles of an optical functional layer according to any of the previous embodiments of the present invention, for example, the first through third optical functional particles  421 ,  422 , and  423  of the optical functional layer  420  of  FIGS. 10 and 11 . For example, the graph A of  FIG. 15  shows a relationship between a refractive index and a wavelength of visible light that is formed on a display panel. Referring to the graph A of  FIG. 15 , a refractive index decreases as a wavelength of visible light increases. 
         [0169]    A graph B of  FIG. 15  shows a relationship between a refractive index and a wavelength of visible light for optical functional particles of an optical functional layer when the optical functional particles are unicolored, instead of being colored, that is, are transparent or white. For example, the graph B of  FIG. 15  shows a relationship between a refractive index and a wavelength of visible light that is formed on a display panel. Referring to the graph B of  FIG. 15 , a refractive index decreases as a wavelength of visible light increases. 
         [0170]    Referring to  FIG. 15 , there is a difference of a refractive index between a matrix and optical functional particles. Also, the difference of the refractive index varies according to a wavelength of visible light. For example, in the graph B compared to the graph A of  FIG. 15 , a difference of a refractive index between an optical functional layer and a matrix greatly varies according to a wavelength of visible light and in the graph A, a difference of a refractive index between an optical functional layer and a matrix is almost constant. That is, when optical functional particles of the present embodiment are used, since a difference of a refractive index between a matrix and an optical functional layer is almost constant irrespective of a wavelength of visible light, a change in color reproduction according to the wavelength of visible light may be reduced, thereby improving image quality characteristics. 
         [0171]      FIGS. 16A and 16B  are detailed graphs of  FIG. 15 . 
         [0172]    First,  FIG. 16A  shows a difference between the graphs B and C of  FIG. 15 , that is, a difference of a refractive index between an optical functional layer and a matrix of the graph B by precisely adjusting scales of the X-axis and the Y-axis compared to  FIG. 15 . Referring to  FIG. 16A , a difference of a refractive index between an optical functional layer and a matrix greatly varies according to a wavelength of visible light. For example, a difference of a refractive index between an optical functional layer and a matrix decreases as a wavelength of visible light increases. 
         [0173]      FIG. 16B  shows a difference between the graphs A and C of  FIG. 15 , that is, a difference of a refractive index between an optical functional layer and a matrix by precisely adjusting scales of the X-axis and the Y-axis compared to  FIG. 15 . Referring to  FIG. 16B , a difference of a refractive index between an optical functional layer and a matrix slightly varies according to a wavelength of visible light. A difference of a refractive index between an optical functional layer and a matrix is almost constant irrespective of a wavelength of visible light. 
         [0174]      FIG. 17  is a color coordinate system illustrating color reproduction characteristics of a display apparatus when an optical functional layer is used. A graph A shows color coordinate characteristics of the display apparatus when optical functional particles of the optical functional layer are unicolored, instead of being colored, that is, are transparent or white. A graph B shows color coordinate characteristics of the display apparatus when the optical functional particles of the optical functional layer are colored, that is, when the optical functional layer according to any of the previous embodiments of the present invention, for example, the optical functional layer  420  of  FIGS. 10 and 11 , is included. A graph C shows reference color coordinate characteristics. 
         [0175]    When the optical functional layer according to the previous embodiments of the present invention is included as shown in  FIG. 17 , the color display apparatus may have color coordinate characteristics that are almost the same as the reference color coordinate characteristics. 
         [0176]      FIG. 18  is a cross-sectional view illustrating a display apparatus  600  according to another embodiment of the present invention.  FIG. 19  is a cross-sectional view illustrating a portion P of  FIG. 18 . 
         [0177]    Referring to  FIGS. 18 and 19 , the display apparatus  600  includes a display panel  610  and an optical functional layer  620 . 
         [0178]    The display panel  610  displays an image to a user. The display panel  610  may include a display device  650  that may generate visible light that is to be provided to the user. Any of various suitable devices may be used as the display device  650 . In the present embodiment, it is assumed that the display device  650  is an organic light-emitting device. 
         [0179]    The display panel  600  will be explained in detail. The display panel  600  includes a substrate  601 , the display device  650 , and an encapsulation member  670 . 
         [0180]    The substrate  601  may be formed of any of various suitable materials. For example, the substrate  601  may be formed of a transparent glass material having SiO 2  as a main component. Alternatively, the substrate  601  may be formed of a transparent plastic material. 
         [0181]    The display device  650  is formed on the substrate  601 , and includes a first electrode  651 , a second electrode  652 , and an intermediate layer  653 . For example, the first electrode  651  is formed on the substrate  601 , the second electrode  652  is formed on the first electrode  651 , and the intermediate layer  653  is formed between the first electrode  651  and the second electrode  652 . 
         [0182]    Although not shown in  FIGS. 18 and 19 , a buffer layer (not shown) may be further formed on the first electrode  651  and the substrate  601 . The buffer layer may provide a planarized surface on the substrate  601 , and may prevent or reduce moisture or gas from penetrating the substrate  601 . 
         [0183]    The first electrode  651  may function as an anode and the second electrode  652  may function as a cathode. However, polarities of the first electrode  651  and the second electrode  652  may be reversed. 
         [0184]    When the first electrode  651  functions as an anode, the first electrode  651  may include ITO, IZO, ZnO, or In 2 O 3  having a high work function. According to the purposes and design conditions, the first electrode  651  may further include a reflective film formed of silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), ytterbium (Yb), or calcium (Ca). 
         [0185]    When the second electrode  652  functions as a cathode, the second electrode  652  may be formed of a metal such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, or Ca. Alternatively, the second electrode  652  may include ITO, IZO, ZnO, or In 2 O 3  in order to allow light to pass therethrough. 
         [0186]    The intermediate layer  653  includes at least one organic light-emitting layer. Also, the intermediate layer  653  may include at least one selected from a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL), in addition to the organic light-emitting layer. 
         [0187]    When a voltage is applied to the first electrode  651  and the second electrode  652 , the intermediate layer  653  (i.e., the organic light-emitting layer of the intermediate layer  653 ) generates visible light. 
         [0188]    The encapsulation member  670  is disposed on the display device  650  to protect the display device  650 . The encapsulation member  670  may protect the display device  650  from external impact, and reduce or prevent penetration of an external material or moisture. 
         [0189]    The encapsulation member  670  may be formed of any of various suitable materials. For example, the encapsulation member  670  may be formed of a transparent glass material having SiO 2  as a main component. 
         [0190]    Alternatively, the encapsulation member  670  may be formed of a glass material through which light may pass. 
         [0191]    Alternatively, the encapsulation member  670  may be formed by using an inorganic film or an organic film. 
         [0192]    Alternatively, the encapsulation member  670  may be formed by stacking at least one organic film and at least one inorganic film. In this case, the encapsulation member  670  may be formed by selectively alternately stacking the at least one organic film and the at least one inorganic film. 
         [0193]    Although not shown in  FIGS. 18 and 19 , the display panel  610  provides an image upward, that is, toward the optical functional layer  620  in  FIG. 19 . 
         [0194]    The optical functional layer  620  includes a matrix (not shown) and optical functional particles (not shown). The optical functional layer  620  may correspond to one of the optical functional layers  120 ,  220 ,  320 ,  420 , and  520  of the previous embodiments of the present invention, and thus a detailed explanation thereof will not be given. 
         [0195]    The display panel  610  may include a thin-film transistor (TFT) that transmits a necessary signal to the display device  650  in order to drive the display device  650 , which will be explained in detail with reference to  FIG. 20 . 
         [0196]      FIG. 20  is a cross-sectional view illustrating a modification of  FIG. 19 . Referring to  FIG. 20 , the display panel  610  includes the substrate  601 , the display device  650 , a TFT, and the encapsulation member  670 . 
         [0197]    The TFT includes an active layer  603 , a gate electrode  605 , a source electrode  607 , and a drain electrode  608 . 
         [0198]    A detailed explanation will now be made. 
         [0199]    A buffer layer  602  may be formed on the substrate  601 . The buffer layer  602  that prevents or substantially prevents impurity elements from penetrating the substrate  601  and provides a planarized surface on the substrate  601  may be formed of any of various suitable materials. The buffer layer  602  is an optional element and thus may be omitted in some embodiments. 
         [0200]    The active layer  603  is disposed on the buffer layer  602  and may have a pattern (e.g., a predetermined pattern). The active layer  603  may be formed of an inorganic semiconductor material such as silicon. Alternatively, the active layer  603  may be formed of an organic semiconductor material or an oxide semiconductor material. 
         [0201]    The gate insulating film  606  is formed on the active layer  603 . The gate insulating film  606  may be formed of any of various suitable insulating materials, for example, oxide or nitride. 
         [0202]    The gate electrode  605  is formed on a gate insulating film  606  to correspond to the active layer  603  (e.g., a predetermined portion of the active layer  603 ). The gate electrode  605  may be formed of a material having high conductivity. For example, the gate electrode  605  may include Au, Ag, Cu, Ni, Pt, Pd, Al, or molybdenum (Mo), or an alloy such as Al:Nd or Mo:W. However, the present embodiment is not limited thereto, and the gate electrode  605  may be formed of any of various other suitable materials. 
         [0203]    An interlayer insulating film  609  is formed to cover the gate electrode  605 . 
         [0204]    The source electrode  607  and the drain electrode  608  are formed on the interlayer insulating film  609 . The source electrode  607  and the drain electrode  608  are formed to contact the active layer  603  (e.g., predetermined portions of the active layer  603 ). 
         [0205]    A passivation layer  643  is formed to cover the source electrode  607  and the drain electrode  608 . Although not shown in  FIG. 20 , an insulating film may be further formed on the passivation layer  643  to planarize the TFT. 
         [0206]    Although not shown in  FIG. 20 , at least one TFT, that may be coupled (e.g., electrically connected, connected, or electrically coupled) to the display device  650 , may also be provided, and at least one capacitor that may be coupled to the display device  650  or the TFT may also be provided. 
         [0207]    The first electrode  651  is formed on the passivation layer  643 . The first electrode  651  is coupled to one of the source electrode  607  and the drain electrode  608 . For example, the first electrode  651  is coupled to the drain electrode  608 . 
         [0208]    A pixel-defining film  660  is formed on the first electrode  651  to expose a portion of the first electrode  651  (e.g., a predetermined portion of the first electrode  651 ). 
         [0209]    The intermediate layer  653  is formed on the first electrode  651 . The intermediate layer  653  includes an organic light-emitting layer. Alternatively, the intermediate layer  653  may further include at least one selected from an HIL, an HTL, an ETL, and an EIL, in addition to the organic light-emitting layer. 
         [0210]    The second electrode  652  is formed on the intermediate layer  653 . 
         [0211]    The encapsulation member  670  is disposed on the display device  650  to protect the display device  650 . 
         [0212]    The display apparatus  600  of the present embodiment and the modification thereof include the optical functional layer  620  that is disposed over the display panel  610 , that is, on a side of the display panel  610  where an image is formed. 
         [0213]    Also, color reproduction of the display apparatus  600  may be improved by using the optical functional layer  620 . 
         [0214]      FIG. 21  is a cross-sectional view illustrating a display apparatus  700  according to another embodiment of the present invention.  FIG. 22  is an enlarged cross-sectional view illustrating a portion Q of  FIG. 21 , 
         [0215]    Referring to  FIGS. 21 and 22 , the display apparatus  700  includes a display panel  710 , an optical functional layer  720 , and a polarization layer  730 . 
         [0216]    The display panel  710  includes at least one subpixel. The subpixel may include at least one display device  750 . Any of various suitable devices may be used as the display device  750 . In the present embodiment, it is assumed that the display device  750  is an organic light-emitting device. 
         [0217]    The display panel  710  will be explained in detail. The display panel  700  includes one or more subpixels SP 1 , SP 2 , and SP 3  that are formed on a substrate  701  and an encapsulation member  770 . Each of the subpixels SP 1 , SP 2 , and SP 3  may include the display device  750 . 
         [0218]    The substrate  701  may be formed of any of various suitable materials. For example, the substrate  701  may be formed of a transparent glass material having SiO 2  as a main component. Alternatively, the substrate  701  may be formed of a transparent plastic material. 
         [0219]    The subpixels SP 1 , SP 2 , and SP 3  are disposed on the substrate  701 . 
         [0220]    The subpixel SP 1  includes a first electrode  751 , a second electrode  752 , and an intermediate layer  753 R. For example, the first electrode  751  is formed on the substrate  701 , the second electrode  752  is formed on the first electrode  751 , and the intermediate layer  753 R is formed between the first electrode  751  and the second electrode  752 . 
         [0221]    Although not shown in  FIGS. 21 and 22 , a buffer layer (not shown) may be further formed on the first electrode  751  and the substrate  701 . The buffer layer may provide a planarized surface on the substrate  701  and may prevent or reduce moisture or gas from penetrating the substrate  701 . In this case, the buffer layer may be formed on the substrate  701  to be shared by the subpixels SP 1 , SP 2 , and SP 3 . 
         [0222]    The intermediate layer  753 R includes at least one organic light-emitting layer. Also, the intermediate layer  753 R generates visible light having a red tint. The intermediate layer  753 R may include at least one selected from an HIL, an HTL, an ETL, and an EIL, in addition to the organic light-emitting layer. 
         [0223]    The subpixel SP 2  includes the first electrode  751 , the second electrode  752 , and an intermediate layer  753 G. For example, the first electrode  751  is formed on the substrate  701 , the second electrode  752  is formed on the first electrode  751 , and the intermediate layer  753 G is formed between the first electrode  751  and the second electrode  752 . 
         [0224]    The intermediate layer  753 G includes at least one organic light-emitting layer. Also, the intermediate layer  753 G may generate visible light having a green tint. The intermediate layer  753 G may include at least one selected from an HIL, an HTL, an ETL, and an EIL, in addition to the organic light-emitting layer. 
         [0225]    The subpixel SP 3  includes the first electrode  751 , the second electrode  752 , and an intermediate layer  753 B. For example, the first electrode  751  is formed on the substrate  701 , the second electrode  752  is formed on the first electrode  751 , and the intermediate layer  753 B is formed between the first electrode  751  and the second electrode  752 . 
         [0226]    The intermediate layer  753 B includes at least one organic light-emitting layer. Also, the intermediate layer  753 B may generate visible light having a blue tint. 
         [0227]    The intermediate layer  753 B may include at least one selected from an HIL, an HTL, an ETL, and an EIL, in addition to the organic light-emitting layer. 
         [0228]    Although the second electrode  752  is separately formed for each of the subpixels SP 1 , SP 2 , and SP 3  in  FIG. 22 , the present embodiment is not limited thereto and the second electrode  752  may be commonly formed in the subpixels SP 1 , SP 2 , and SP 3 . 
         [0229]    The first electrode  751  and the second electrode  752  correspond to those described in the previous embodiments of the present invention, and thus a detailed explanation thereof will not be given. 
         [0230]    The encapsulation member  770  is disposed over the display devices  750  to protect the subpixels SP 1 , SP 2 , and SP 3 . The encapsulation member  770  may protect the display devices  750  from external impact, and may reduce or prevent penetration of an external material or moisture. 
         [0231]    The encapsulation member  770  corresponds to that described in the previous embodiments of the present invention, and thus a detailed explanation thereof will not be given. 
         [0232]    Although not shown in  FIGS. 21 and 22 , the display panel  710  provides an image upward, that is, toward the optical functional layer  720  in  FIG. 22 . 
         [0233]    The optical functional layer  720  includes a matrix  725  and optical functional particles. 
         [0234]    The matrix  725  may function as a base for the optical functional layer  720 . The matrix  725  may be formed of any of various suitable materials, for example, an insulating material. For example, the matrix  725  may be formed to include resin. 
         [0235]    Alternatively, the matrix  725  may include a polymer material, for example, acryl-based resin. 
         [0236]    Alternatively, the matrix  725  may be formed of an adhesive material. Any of various suitable adhesive materials, for example, adhesive resin, may be used as the adhesive material that is included in the matrix  725 . Accordingly, the optical functional layer  720  may be easily disposed on the display panel  710 . For example, as the matrix  725  contacts the display panel  710 , the optical functional layer  720  may be stably adhered to the display panel  710 . 
         [0237]    Also, due to the adhesiveness of the matrix  725 , the polarization layer  730  that is disposed on the optical functional layer  720  may be stably adhered to the optical functional layer  720 . 
         [0238]    The optical functional particles are colored, instead of being transparent or non-colored. For example, the optical functional particles include first optical functional particles  721 , second optical functional particles  722 , and third optical functional particles  723 . 
         [0239]    The first optical functional particles  721  may include a chromatic material with a red or green tint. For example, the first optical functional particles  721  may include a dye material with a red or green tint. 
         [0240]    Alternatively, the first optical functional particles  721  may include a chromatic material having a red tint and a chromatic material having a green tint. For example, the first optical functional particles  721  may have a state where a chromatic material having a red tint and a chromatic material having a green tint are mixed with each other. 
         [0241]    For example, the first optical functional particles  721  may include a dye material with a red or green tint formed on surfaces thereof. Alternatively, the first optical functional particles  721  may include a dye material with a red or green tint formed not only on surfaces thereof but also inside the first optical functional particles  721 . 
         [0242]    The second optical functional particles  722  may include a chromatic material with a red or blue tint. For example, the second optical functional particles  722  may include a dye material with a red or blue tint. 
         [0243]    Alternatively, the second optical functional particles  722  may include a chromatic material having a red tint and a chromatic material having a blue tint. For example, the second optical functional particles  722  may have a state where a chromatic material having a red tint and a chromatic material having a blue tint are mixed with each other. 
         [0244]    For example, the second optical functional particles  722  may include a dye material with a red or blue tint formed on surfaces thereof. Alternatively, the second optical functional particles  722  may include a dye material with a red or blue tint formed not only on surfaces thereof but also inside the second optical functional particles  722 . 
         [0245]    The third optical functional particles  723  may include a chromatic material with a green or blue tint. For example, the third optical functional particles  723  may have a state where a chromatic material having a green tint and a color material having a blue tint are mixed with each other. 
         [0246]    For example, the third optical functional particles  723  may include a dye material with a green or blue tint formed on surfaces thereof. Alternatively, the third optical functional particles  723  may include a dye material with a green or blue tint formed not only on surfaces thereof but also inside the third optical functional particles  723 . 
         [0247]    The first through third optical functional particles  721 ,  722 , and  723  may be formed by using any of various suitable methods. The first through third optical functional particles  721 ,  722 , and  723  may be formed by performing dyeing on organic particles, inorganic particles, or metal particles. Examples of the organic particles used to form the first through third optical functional particles  721 ,  722 , and  723  may include polymelamine, polystyrene, PMMA, and polylactide, and examples of the inorganic particles used to form the first through third optical functional particles  721 ,  722 , and  723  may include silica, alumina, titania, glass, and ceramic. 
         [0248]    Also, any of various suitable dyes described in the previous embodiments of the present invention may be used during dyeing performed in order for the first through third optical functional particles  721 ,  722 , and  723  of the optical functional layer  720  to be colored. 
         [0249]    Also, the first through third optical functional particles  721 ,  722 , and  723  may be formed by using any of various suitable methods. For example, a method of dipping organic particles, inorganic particles, or metal particles in any of various suitable chromatic materials described in the previous embodiments of the present invention may be performed. Alternatively, any of various other suitable coating methods may be used. 
         [0250]    Although the first through third optical functional particles  721 ,  722 , and  723  included in the optical functional layer  720  include a chromatic material in  FIG. 22 , the present embodiment is not limited thereto and optical functional particles (not shown) that are unicolored may be further included in the optical functional layer  720 . In this case, the optical functional particles that are unicolored may be non-colored, for example, may be transparent or white. 
         [0251]    The polarization layer  730  may be disposed over the optical functional layer  720 . Alternatively, the polarization layer  730  may be disposed on the optical functional layer  720  to be adhered to, that is, to contact the optical functional layer  720 . 
         [0252]    The display apparatus  700  of the present embodiment includes the optical functional layer  720  that is disposed over the display panel  710 , that is, on a side of the display panel  710  where an image is formed. 
         [0253]    Also, the optical functional layer  720  includes the matrix  725  and the first through third optical functional particles  721 ,  722 , and  723  that are mixed with the matrix  725 . The first through third optical functional particles  721 ,  722 , and  723  are colored. The first through third colored optical functional particles  721 ,  722 , and  723  improve viewing angle characteristics of the display apparatus  700  by scattering visible light that is formed on the display panel  710 . Also, color reproduction of the display apparatus  700  may be improved by enabling the first through third optical functional particles  721 ,  722 , and  723  to be colored, instead of being non-colored, that is, to have the same or substantially the same tint as a color of the visible light that is formed on the display panel  710 . 
         [0254]    For example, the first optical functional particles  721  may be colored to have a red or green tint. Alternatively, the first optical functional particles  721  may be dyed by mixing a dye material having a red tint and a dye material having a green tint by enabling the first optical functional particles  721  to be colored to have red and green tints. In this case, the first optical functional particles  721  may absorb visible light having a red tint that is provided from the subpixel SP 1  of the display panel  710  and visible light having a green tint that is provided from the subpixel SP 2 , and may transmit or diffuse visible light having a blue tint that is provided from the subpixel SP 3 . 
         [0255]    Accordingly, the quality of visible light having a blue tint from among visible light that is provided from the display panel  710  may be improved. For example, color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  725  and a refractive index of the first optical functional particles  721  according to a wavelength band of the visible light with the blue tint from among the visible light that is formed on the display panel  710  by forming the first optical functional particles  721  by mixing a dye material having a red tint and a dye material having a green tint. 
         [0256]    Also, the second optical functional particles  722  may be colored to have a red or blue tint. Alternatively, the second optical functional particles  722  may be dyed by mixing a dye material having a red tint and a dye material having a blue tint by enabling the second optical functional particles  722  to be colored to have red and blue tints. In this case, the second optical functional particles  722  may absorb visible light having a red tint that is provided from the subpixel SP 1  of the display panel  710  and visible light having a blue tint that is provided from the subpixel SP 3 , and may transmit or diffuse visible light having a green tint that is provided from the subpixel SP 2 . 
         [0257]    Accordingly, the quality of visible light having a green tint from among visible light that is provided from the display panel  710  may be improved. For example, color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  725  and a refractive index of the second optical functional particles  722  according to a wavelength band of the visible light with the green tint from among the visible light that is formed on the display panel  710  by forming the second optical functional particles  722  by mixing a dye material having a red tint and a dye material having a blue tint. 
         [0258]    Also, the third optical functional particles  723  may be colored to have a green or blue tint. Alternatively, the third optical functional particles  723  may be dyed by mixing a dye material having a green tint and a dye material having a blue tint to be colored to have green and blue tints. In this case, the third optical functional particles  723  may absorb visible light having a green tint that is provided from the subpixel SP 2  of the display panel  710  and visible light having a blue tint that is provided from the subpixel SP 3 , and may transmit or diffuse visible light having a red tint that is provided from the subpixel SP 1 . 
         [0259]    Accordingly, the quality of visible light having a red tint, from among visible light that is provided from the display panel  710 , may be improved and color reproduction of the visible light with the red tint may be improved. Color reproduction may be improved by reducing a change in a difference between a refractive index of the matrix  725  and a refractive index of the third optical functional particles  723  according to a wavelength band of the visible light with the red tint from among the visible light that is formed on the display panel  710  by forming the third optical functional particles  723  by mixing a dye material having a green tint and a dye material having a blue tint. 
         [0260]    Although not shown in  FIGS. 21 and 22 , the display panel  710  may further include a TFT that transmits a necessary signal to the display device  750  in order to drive the display device  750 . 
         [0261]    As described above, according to the one or more of the previous embodiments of the present invention, a display apparatus having improved image quality characteristics may be provided. 
         [0262]    While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. Accordingly, the true technical scope of the present invention is defined by the technical spirit of the appended claims and their equivalents.