Patent Publication Number: US-2016223851-A1

Title: Display device and manufacturing method thereof

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 4 Feb. 2015 and there duly assigned Serial No. 10-2015-0017480. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display device in which a color filter is not included, and a manufacturing method thereof. 
     2. Description of the Related Art 
     As one of the most widely used flat panel display devices recently, a liquid crystal display (LCD) device includes two display panels on which field generating electrodes such as a pixel electrode and a common electrode are formed, and a liquid crystal layer interposed between the two display panels. The LCD displays an image by generating an electric field on a liquid crystal layer by applying a voltage to the field generating electrodes, determining alignment directions of liquid crystal molecules of the liquid crystal layer by the generated field, and controlling polarization of incident light. 
     Two sheets of display panels of which the LCD consists may include a thin film transistor array panel and an opposing display panel. In the thin film transistor array panel, a gate line for transmitting a gate signal and a data line for transmitting a data signal are formed to cross each other, and a thin film transistor connected to the gate and data lines, a pixel electrode connected to the thin film transistor, and the like may be formed. In the opposing display panel, a light blocking member, a color filter, a common electrode, and the like may be formed. In some embodiments, the light blocking member, the color filter, and the common electrode may be formed on the thin film transistor array panel. 
     However, in conventional LCDs, two substrates are required and constituent elements are respectively formed on the two substrates, thereby requiring a long processing time as well as making the display device heavy, thick, and costly. 
     Recently, a technique in which a plurality of microcavities of a tunnel-shape structure are formed on one substrate and the liquid crystal is injected inside the structure to manufacture the display device has been developed. A color filter included in the display device is typically formed between the substrate and the microcavities, or is formed on the microcavities. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a display device and a manufacturing method thereof that may simplify a structure thereof and may reduce the number of manufacturing steps thereof by adding a color material to a liquid crystal material of a display device manufactured with a single substrate such that a color filter may be eliminated. 
     An exemplary embodiment of the present invention provides a display device, and the display device includes: a substrate including a plurality of pixels formed in row and column directions; a thin film transistor disposed on the substrate, and a pixel electrode connected to the thin film transistor; a first liquid crystal layer filled inside a microcavity formed on the pixel electrode; a plurality of roof layers formed to be separated from the pixel electrode with the microcavity and an injection hole therebetween; and an overcoat formed on the roof layer to cover the injection hole and encapsulate the microcavity. The first liquid crystal layer includes a liquid crystal molecule and a color material. 
     The color material may include a red, green, or blue pigment. 
     First liquid crystal layers that are adjacent in a row direction may include different color pigments, and first liquid crystal layers that are adjacent in a column direction may include the same color pigment. 
     The pigment may include an inorganic or organic pigment. 
     A second liquid crystal layer containing only liquid crystal molecules may be further included in the display device. The second liquid crystal layer may display a white color. 
     The color material may include a dichroic dye having predetermined anisotropy. 
     The dichroic dye may include a material absorbing a wavelength region corresponding to one of cyan, magenta, yellow, red, green, and blue. 
     The dichroic dye may include one or more selected from azo dyes, anthraquinone dyes, perylene dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, dioxadine dyes, polythiophene dyes, and phenoxazine dyes. 
     The color material may include a material that transmits light having a red, green, or blue wavelength, and reflect light having other wavelengths. 
     Another embodiment of the present invention provides a manufacturing method of a display device, and method includes steps of: forming a thin film transistor on a substrate; forming a pixel electrode connected to the thin film transistor on the thin film transistor; forming a sacrificial layer on the pixel electrode; forming a roof layer that includes an injection hole formed by coating and patterning an organic material on the sacrificial layer; forming a microcavity between the roof layer and the pixel electrode by removing the sacrificial layer; forming a first liquid crystal layer by injecting a first liquid crystal material in the microcavity through the injection hole; and forming an overcoat on the roof layer to cover the injection hole and encapsulate the microcavity. The first liquid crystal material includes a liquid crystal molecule and a color material. 
     The manufacturing method may further include forming a common electrode on the sacrificial layer before forming the sacrificial layer and the roof layer. 
     According to the embodiment of the present invention, it is possible to simplify a structure of the display device and may reduce the number of manufacturing steps thereof by adding a color material to a liquid crystal material of the display device manufactured with a single substrate such that a color filter may be eliminated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is a layout view of one pixel of a display device according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of  FIG. 1  taken along line II-II. 
         FIG. 3  is a cross-sectional view of  FIG. 1  taken along line III-III. 
         FIGS. 4, 6, 8, 10, and 12  are cross-sectional views of  FIG. 1  taken along line II-II according to manufacturing processes for a display device of an exemplary embodiment of the present invention. 
         FIGS. 5, 7, 9, 11, and 13  are cross-sectional views of  FIG. 1  taken along line III-III according to manufacturing processes for a display device of an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     First, a display device according to an exemplary embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . 
       FIG. 1  is a layout view of one pixel of a display device according to an exemplary embodiment of the present invention,  FIG. 2  is a cross-sectional view of  FIG. 1  taken along line II-II, and  FIG. 3  is a cross-sectional view of  FIG. 1  taken along line III-III. 
     The liquid crystal display according to the exemplary embodiment of the present invention includes an insulation substrate  110  made of a material such as glass or plastic, and a roof layer  360  formed on the insulation substrate  110 . 
     A plurality of pixels PX are disposed on the insulation substrate  110 . The pixels PX are disposed in a matrix form which includes a plurality of pixel columns and a plurality of pixel rows. One pixel PX is a region overlapped with one pixel electrode, and may include, for example, a first subpixel PXa and a second subpixel PXb. The first subpixel PXa is overlapped with a first subpixel electrode  191   h , and the second subpixel PXb is overlapped with the second subpixel electrode  191   l . The first subpixel PXa and the second subpixel area PXb may be disposed in a vertical direction that is an extension direction of a data line. 
     A first valley V 1  is disposed between the first subpixel PXa and the second subpixel PXb along an extension direction of a gate line, and a second valley V 2  is disposed between columns of the adjacent pixel areas. 
     The roof layer  360  is formed in the extension direction of the data line. In this case, an injection hole  307  is formed in the first valley V 1  by removing the roof layer  360  so that constituent elements disposed below the roof layer  360  may be exposed. 
     Each roof layer  360  is formed to be spaced apart from the substrate  110  between the adjacent second valleys V 2  to form a microcavity  305 . Further, each roof layer  360  is formed to be attached to the substrate  110  in the second valley V 2  to cover opposite lateral surfaces of the microcavity  305 . 
     The structure of the display device according to the exemplary embodiment of the present invention described above is just an example, and may be variously modified. For example, arrangement of the pixel PX, the first valley V 1 , and the second valley V 2  may be modified, the roof layers  360  may be connected to each other in the first valley V 1 , and each roof layer  360  may be formed to be partially separated from the substrate  110  in the second valley V 2  such that the adjacent microcavities  305  may be connected to each other. 
     In reference to  FIGS. 1-3 , a plurality of gate conductors including a plurality of gate lines  121 , a plurality of step-down gate lines  123 , and a plurality of storage electrode lines  131  are disposed on an insulation substrate  110 . 
     The gate line  121  and the step-down gate line  123  mainly extend in a horizontal direction to transmit gate signals. The gate conductor further includes a first gate electrode  124   h  and a second gate electrode  124   l  protruding upward and downward from the gate line  121 , and further includes a third gate electrode  124   c  protruding upward from the step-down gate line  123 . The first gate electrode  124   h  and second gate electrode  124   l  are connected with each other to form one protrusion. In this case, respective protruded shapes of the first, second, and third gate electrodes  124   h ,  124   l , and  124   c  may be modified. 
     The storage electrode line  131  mainly extends in a horizontal direction and transmits a predetermined voltage such as a common voltage Vcom. The storage electrode line  131  includes storage electrodes  129  protruding upward and downward, a pair of vertical portions  134  extending downward to be substantially vertical to the gate line  121 , and a horizontal portion  127  connecting ends of the pair of vertical portions  134 . The horizontal portion  127  includes a capacitive electrode  137  extended downward. 
     A gate insulating layer  140  is disposed on the gate conductors  121 ,  123 ,  124   h ,  124   l ,  124   c , and  131 . The gate insulating layer  140  may be made of an inorganic insulating material such as a silicon nitride (SiNx) and a silicon oxide (SiOx). Further, the gate insulating layer  140  may be formed as a single layer or multilayers. 
     A first semiconductor layer  154   h , a second semiconductor layer  154   l , and a third semiconductor layer  154   c  are disposed on the gate insulating layer  140 . The first semiconductor layer  154   h  may be disposed on the first gate electrode  124   h , the second semiconductor layer  154   l  may be disposed on the second gate electrode  124   l , and the third semiconductor layer  154   c  may be disposed on the third gate electrode  124   c . The first semiconductor layer  154   h  and the second semiconductor layer  154   l  may be connected to each other, and the second semiconductor layer  154   l  and the third semiconductor layer  154   c  may be connected to each other. Further, the first semiconductor layer  154   h  may be formed to be extended to the lower portion of the data line  171 . The first, second, and third semiconductor layers  154   h ,  154   l , and  154   c  may be made of amorphous silicon, polycrystalline silicon, a metal oxide, and the like. 
     Ohmic contacts (not illustrated) may be further disposed on the first, second, and third semiconductors  154   h ,  154   l , and  154   c , respectively. The ohmic contact may be made of silicide or a material such as n+hydrogenated amorphous silicon in which an n-type impurity is doped at a high concentration. 
     A data conductor including a data line  171 , a first source electrode  173   h , a second source electrode  173   l , a third source electrode  173   c , a first drain electrode  175   h , a second drain electrode  175   l , and a third drain electrode  175   c  is disposed on the first, second, third semiconductor layers  154   h ,  154   l , and  154   c.    
     The data line  171  transmits a data signal and mainly extends in a vertical direction to cross the gate line  121  and the step-down gate line  123 . Each data line  171  extends toward the first gate electrode  124   h  and the second gate electrode  124   l , and includes the first source electrode  173   h  and the second source electrode  173   l  which are connected with each other. 
     Each of the first drain electrode  175   h , the second drain electrode  175   l , and the third drain electrode  175   c  includes one wide end portion and the other rod-shaped end portion. The rod-shaped end portions of the first drain electrode  175   h  and the second drain electrode  175   l are partially surrounded by the first source electrode  173   h  and the second source electrode  173   l , respectively. One wide end portion of the second drain electrode  175   l  is further extended to form the third drain electrode  175   c  that is bent in a ‘U’-letter shape. A wide end portion  177   c  of the third drain electrode  175   c  overlaps with the capacitive electrode  137  to form a step-down capacitor Cstd, and the rod-shaped end portion is partially surrounded by the third source electrode  173   c.    
     The first gate electrode  124   h , the first source electrode  173   h , and the first drain electrode  175   h  form a first thin film transistor Qh together with the first semiconductor layer  154   h , the second gate electrode  124   l , the second source electrode  173   l , and the second drain electrode  175   l  form a second thin film transistor Ql together with the second semiconductor layer  154   l , and the third gate electrode  124   c , the third source electrode  173   c , and the third drain electrode  175   c  form the third thin film transistor Qc together with the third semiconductor layer  154   c.    
     The first semiconductor layer  154   h , the second semiconductor layer  154   l , and the third semiconductor layer  154   c  are connected to each other to form a linear shape, and may have substantially the same planar shape as the data conductors  171 ,  173   h ,  173   l ,  173   c ,  175   h ,  175   l , and  175   c  and the ohmic contacts therebelow, except at channel regions between the source electrodes  173   h ,  173   l , and  173   c  and the drain electrodes  175   h ,  173   l , and  175   c.    
     In the first semiconductor layer  154   h , an exposed portion which is not covered by the first source electrode  173   h  and the first drain electrode  175   h  is disposed between the first source electrode  173   h  and the first drain electrode  175   h . In the second semiconductor layer  154   l , an exposed portion which is not covered by the second source electrode  173   l  and the second drain electrode  175   l  is disposed between the second source electrode  173   l  and the second drain electrode  175   l . In addition, in the third semiconductor layer  154   c , an exposed portion which is not covered by the third source electrode  173   c  and the third drain electrode  175   c  is disposed between the third source electrode  173   c  and the third drain electrode  175   c.    
     A first passivation layer  180   a  is disposed on the data conductors  171 ,  173   h ,  173   l ,  173   c ,  175   h ,  175   l , and  175   c  and the semiconductor layers  154   h ,  154   l , and  154   c  exposed between the respective source electrodes  173   h ,  173   l , and  173   c  and the respective drain electrodes  175   h ,  175   l , and  175   c . The first passivation layer  180   a  may be made of an organic insulating material or an inorganic insulating material, and may be formed as a single layer or multilayers. 
     Next, a second passivation layer  180   b  and a light blocking member  220  are disposed on the first passivation layer  180   a.    
     The light blocking member  220  is disposed in a region at which the thin film transistor is disposed. The light blocking member  220  is disposed on a boundary portion of the pixel PX and on the thin film transistor to prevent light leakage thereon. The second passivation layer  180   b  may be disposed in each of the first subpixel PXa and the second subpixel PXb, and the light blocking member  220  may be disposed in the first subpixel PXa and the second subpixel PXb. 
     The light blocking member  220  extends along an extending direction of the gate line  121  and the step-down gate line  123  to be extended upward and downward. The light blocking member  220  may cover a region in which the first thin film transistor (Qh), the second thin film transistor (Ql), and the third thin film transistor (Qc) are disposed, or may extend along the data line  171 . In other words, the light blocking member  220  may be disposed in the first valley V 1  and the second valley V 2 . The second passivation layer  180   b  and the light blocking member  220  may be partially overlapped with each other. 
     In the first passivation layer  180   a , the second passivation layer  180   b , and the light blocking member  220 , a plurality of first contact holes  185   h  and a plurality of second contact holes  185   l  are formed to expose the wide end portion of the first drain electrode  175   h  and the wide end portion of the second drain electrode  175   l.    
     A first insulating layer  240  is disposed on the second passivation layer  180   b  and the light blocking member  220 , and a pixel electrode  191  is disposed on the first insulating layer  240 . The pixel electrode  191  may be made of a transparent metal material such as indium tin oxide (no) and indium zinc oxide (IZO). 
     The pixel electrode  191  includes a first subpixel electrode  191   h  and a second subpixel electrode  191   l  that are separated from each other with the gate line  121  and the step-down gate line  123  therebetween and disposed above and below the pixel PX based on the gate line  121  and the step-down gate line  123  to be adjacent to each other in the extending direction of the data line. In other words, the first subpixel electrode  191   h  and the second subpixel electrode  191   l  are separated from each other with the first valley V 1  therebetween, the first subpixel electrode  191   h  is disposed in the first subpixel PXa, and the second subpixel electrode  191   l  is disposed in the second subpixel PXb. 
     The first subpixel electrode  191   h  and the second subpixel electrode  191   l  are connected to the first drain electrode  175   h  and the second drain electrode  175   l  through the first contact hole  185   h  and the second contact hole  185   l , respectively. Accordingly, when the first thin film transistor Qh and the second thin film transistor Ql are turned on, the first thin film transistor Qh and the second thin film transistor Ql receive data voltages from the first drain electrode  175   h  and the second drain electrode  175   l.    
     An overall shape of each of the subpixel electrode  191   h  and the second subpixel electrode  191   l  is a quadrangle, and the subpixel electrode  191   h  and the second subpixel electrode  191   l  include cross stems including horizontal stems  193   h  and  193   l  and vertical stems  192   h  and  192   l  crossing the horizontal stems  193   h  and  193   l , respectively. Further, the first subpixel electrode  191   h  and the second subpixel electrode  191   l  include a plurality of minute branches  194   h  and  194   l , and projections  197   h  and  197   l  protruding downward or upward from edge sides of the subpixel electrodes  194   h  and  194   l , respectively. 
     The pixel electrode  191  is divided into four subregions by the horizontal stems  193   h  and  193   l  and the vertical stems  192   h  and  192   l . The minute branches  194   h  and  194   l  obliquely extend from the horizontal stems  193   h  and  193   l  and the vertical stems  192   h  and  192   l , and the extending direction thereof may form an angle of about 45° or 135° with the gate line  121  or the horizontal stems  193   h  and  193   l . Further, extending directions of the minute branches  194   h  and  194   l  of the two adjacent subregions may be perpendicular to each other. 
     In the exemplary embodiment, the first subpixel electrode  191   h  further includes an outer stem surrounding the outside, and the second subpixel electrode  191   l  further includes horizontal portions disposed at an upper end and a lower end, and left and right vertical portions  198  disposed at left and right sides of the first subpixel electrode  191   h . The left and right vertical portions  198  may prevent capacitive coupling, that is, coupling between the data line  171  and the first subpixel electrode  191   h.    
     The layout form of the pixel, the structure of the thin film transistor, and the shape of the pixel electrode described above are just exemplified, and the present invention is not limited thereto and may be variously modified. 
     A second insulating layer  250  is disposed on the pixel electrode  191 , and a common electrode  270  is disposed on the pixel electrode  191  to be spaced apart from the pixel electrode  191  by a predetermined distance. A microcavity  305  is formed between the pixel electrode  191  and the common electrode  270 . In other words, the microcavity  305  is surrounded by the pixel electrode  191  and the common electrode  270 , and is differentiated per one pixel. A width and an area of the microcavity  305  may be variously modified according to a size and resolution of the display device. 
     The common electrode  270  may be made of a transparent metal material such as indium tin oxide (ITO) and indium zinc oxide (IZO). A predetermined voltage may be applied to the common electrode  270 , and an electric field may be generated between the pixel electrode  191  and the common electrode  270 . 
     A first alignment layer  11  is formed on the second insulating layer  250 . A second alignment layer  21  is disposed below the common electrode  270  to face the first alignment layer  11 . 
     The first alignment layer  11  and the second alignment layer  21  may be formed with vertical alignment layers and made of alignment materials such as polyamic acid, polysiloxane, and polyimide. The first and second alignment layers  11  and  21  may be connected to each other at the edge of the pixel PX. 
     A liquid crystal layer made of liquid crystal molecules  310  is formed in the microcavity  305  disposed between the pixel electrode  191  and the common electrode  270 . The liquid crystal molecules  310  have negative dielectric anisotropy, and may stand up in a direction perpendicular to the substrate  110  while the electric field is not applied. That is, the liquid crystal molecules  310  may be vertically aligned. 
     The liquid crystal layer of the display device according to the exemplary embodiment of the present invention includes a liquid crystal material including the liquid crystal molecules  310  and color materials  311 ,  312 , and  313  mixed with the liquid crystal material. The color materials  311 ,  312 , and  313  are mixed with the liquid crystal material, and each of the color materials  311 ,  312 , and  313  may be a pigment representing at least one of primary colors of red, green, and blue. 
     Accordingly, the pigments  311 ,  312 , and  313  with different colors are respectively applied to the microcavities  305 , such that light passing through each of the microcavities  305  may represent a color corresponding to each of the pigments  311 ,  312 , and  313 . That is, when colors of the pigments  311 ,  312 , and  313  are respectively red, green, and blue, the liquid crystal layers included in the microcavities  305  may respectively represent the red, green, and blue colors. 
     The pigments  311 ,  312 , and  313  may be an inorganic pigment or an organic pigment, but are not limited thereto, and thus may be any pigment that is able to represent a predetermined color. 
     Further, a microcavity  305  representing a white color may be formed by not including any of the pigments  311 ,  312 , and  313 . 
     The color materials  311 ,  312 , and  313  may include dichroic dyes having anisotropy in absorption of light, instead of the pigments with the colors described above. 
     Colors represented by the dichroic dyes  311 ,  312 , and  313  are determined by a spectrum with respect to colors that are not absorbed by the dichroic dyes  311 ,  312 , and  313 , that is, complementary colors. Accordingly, when any pixel is intended to display one of primary colors of red, green, and blue, the dichroic dye  311 ,  312 , or  313  included in the liquid crystal layer corresponding to the pixel may be a material absorbing light of a wavelength region corresponding to one of cyan, magenta, and yellow. For example, each of liquid crystal layers corresponding to a red pixel, a green pixel, and a blue pixel may include a liquid crystal material in which a cyan dichroic dye, a magenta dichroic dye, and yellow dichroic dye  311 ,  312 , and  313  are respectively mixed. In this case, the cyan dichroic dye may absorb light of a wavelength region of 600-700 nm, the magenta dichroic dye may absorb light of a wavelength region of 500-580 nm, and the yellow dichroic dye may absorb light of a wavelength region of 430-490 nm. 
     Unlike this, when any pixel displays one of cyan, magenta, and yellow, the dichroic dye  311 ,  312 , or  313  included in the liquid crystal layer corresponding to the pixel may be a material absorbing light of a wavelength region corresponding to one of red, green, and blue. 
     Further, a microcavity  305  representing a white color may be formed by including the pigments  311 ,  312 , and  313  with only primary colors of red, green, and blue. 
     The dichroic dyes  311 ,  312 , and  313 , for example, may include one or more selected from azo dyes, anthraquinone dyes, perylene dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, dioxadine dyes, polythiophene dyes, and phenoxazine dyes, but are not limited thereto. 
     An appropriate concentration of the dichroic dyes  311 ,  312 , and  313  mixed with the liquid crystal material may be varied depending on an absorption capacity of light of the dichroic dyes  311 ,  312 , and  313 . 
     The dyes  311 ,  312 , and  313  are not limited to those described above, and may include materials which pass through light of some specific wavelengths and which reflect light of the other wavelengths. In other words, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a red color may include a material that passes through only light of a red wavelength band and reflects light of the remaining wavelength band. Further, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a green color may include a material that passes through only light of a green wavelength band and reflects light of the remaining wavelength band. In addition, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a blue color may include a material that passes through only light of a blue wavelength band and reflects light of the remaining wavelength band. 
     According to the exemplary embodiment of the present invention, since the color of the pixel is implemented by the color pigment or the dichroic color dye that is included in the liquid crystal layer, or by the material that passes through light of some specific wavelengths, a color filter is not required. Accordingly, a photolithography process for forming the color filter is not required, thereby simplifying a structure of the display device, and reducing manufacturing processes, time, and cost. 
     The first subpixel electrode  191   h  and the second subpixel electrode  191   l  to which the data voltage is applied generate an electric field together with the common electrode  270  to determine directions of the liquid crystal molecules  310  of the microcavity  305  between the two electrodes  191  and  270 . As such, luminance of light passing through the liquid crystal layer varies according to the determined directions of the liquid crystal molecules  310 . 
     A third insulating layer  340  may be further formed on the common electrode  270 . The third insulating layer  340  may be made of an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon nitride oxide (SiOxNy), and may be removed if necessary. 
     A roof layer  360  is formed on the third insulating layer  340 , and may be made of an organic material. The microcavity  305  is formed below the roof layer  360 , and the roof layer  360  is hardened by a curing process to maintain a shape of the microcavity  305 . That is, the roof layer  360  is formed to be spaced apart from the pixel electrode  191  with the microcavity  305  therebetween. 
     The roof layer  360  is formed in each pixel PX and the second valley V 2  along an extending direction of the data line, and is not formed in the first valley V 1 . That is, the roof layer  360  is not formed between the first subpixel area PXa and the second subpixel area PXb. The microcavity  305  is formed below each roof layer  360  in the first subpixel PXa and the second subpixel PXb. In the second valley V 2 , the microcavity  305  is not formed below the roof layer  360 , but is formed to be attached to the substrate  110 . Accordingly, a thickness of the roof layer  360  disposed at the second valley V 2  may be larger than a thickness of the roof layer  360  disposed in the first subpixel PXa or the second subpixel PXb. An upper surface and both sides of the microcavity  305  are formed to be covered by the roof layer  360 . 
     An injection hole  307  exposing a portion of the microcavity  305  is formed in the common electrode  270 , the third insulating layer  340 , and roof layer  360 . The injection holes  307  may be formed to face each other at the edge of the first subpixel PXa and the second subpixel PXb. For example, the injection holes  307  may be formed at a lower side of the first subpixel PXa and an upper side of the second subpixel PXb to expose lateral surfaces of the microcavity  305 . Since the microcavity  305  is exposed through the injection hole  307 , an aligning agent or a liquid crystal material may be injected into the microcavity  305  through the injection hole  307 . 
     An overcoat  390  is disposed on the roof layer  360 . The overcoat  390  covers the injection hole  307  that exposes a portion of the microcavity  305  to the outside. The overcoat  390  seals the microcavity  305  such that the liquid crystal molecules  310  contained in the microcavity  305  may not be discharged outside. Since the overcoat  390  contacts the liquid crystal molecules  310 , the overcoat  390  may be made of a material that does not react with the liquid crystal molecules  310 . 
     The overcoat  390  may be formed to cover the entire surface of the substrate  110 . 
     Although not illustrated, polarizers may be further formed on the upper and lower surfaces of the display device. The polarizers may be formed as a first polarizer and a second polarizer. The first polarizer may be attached to the lower surface of the substrate  110 , and the second polarizer may be attached to the overcoat  390 . 
     A manufacturing method of the display device according to the exemplary embodiment of the present invention will now be described with reference to  FIGS. 4 to 13 . 
       FIGS. 4, 6, 8, 10, and 12  are cross-sectional views of  FIG. 1  taken along line II-II according to manufacturing processes for the display device of the exemplary embodiment of the present invention, and  FIGS. 5, 7, 9, 11, and 13  are cross-sectional views of  FIG. 1  taken along line III-III according to manufacturing processes for the display device of the exemplary embodiment of the present invention. 
     First, as shown in  FIGS. 4 and 5 , a gate line  121  and a step-down gate line  123  that extend in one direction are formed on a substrate  110  that is formed of glass or plastic, and a first gate electrode  124   h , a second gate electrode  124   l , and a third gate electrode  124   c  are formed to protrude from the gate line  121 . 
     Further, a storage electrode line  131  may be formed together to be spaced apart from the gate line  121 , the step-down gate line  123 , and the first, second, and third gate electrodes  124   h ,  124   l , and  124   c.    
     Next, a gate insulating layer  140  is formed on the entire surface of the substrate  110  including the gate line  121 , the step-down gate line  123 , the first, second, and third gate electrodes  124   h ,  124   l , and  124   c , and the storage electrode  131  by using an inorganic insulating material such as a silicon oxide (SiOx) or a silicon nitride (SiNx). The gate insulating layer  140  may be formed with a single layer or multilayers. 
     Next, a first semiconductor layer  154   h , a second semiconductor layer  154   l , and a third semiconductor layer  154   c  are formed by depositing a semiconductor material such as amorphous silicon, polycrystalline silicon, and a metal oxide on the gate insulating layer  140  and then patterning the deposited semiconductor material. The first semiconductor layer  154   h  may be disposed on the first gate electrode  124   h , the second semiconductor layer  154   l  may be disposed on the second gate electrode  124   l , and the third semiconductor layer  154   c  may be disposed on the third gate electrode  124   c.    
     Next, a data line  171  extending in the other direction is formed by depositing a metal material and then patterning the deposited metal material. The metal material may be formed as a single layer or multilayers. 
     Further, a first source electrode  173   h  protruding upward the first gate electrode  124   h  from the data line  171  and a first drain electrode  175   h  spaced apart from the first source electrode  173   h  are formed together. Further, a second source electrode  173   l  connected with the first source electrode  173   h  and a second drain electrode  175   l  spaced apart from the second source electrode  173   l  are formed together. Further, a third source electrode  173   c  extended from the second drain electrode  175   l  and a third drain electrode  175   c  spaced apart from the third source electrode  173   c  are formed together. 
     The first, second, and third semiconductor layers  154   h ,  154   l , and  154   c , the data line  171 , the first, second, and third source electrodes  173   h ,  173   l , and  173   c , and the first, second, and third drain electrodes  175   h ,  175   l , and  175   c  may be formed by sequentially depositing a semiconductor material and a metal material and simultaneously patterning the semiconductor material and the metal material. In this case, the first semiconductor layer  154   h  may be extended to the lower portion of the data line  171 . 
     The first, second, and third gate electrodes  124   h ,  124   l , and  124   c , the first, second, and third source electrodes  173   h ,  173   l , and  173   c , and the first, second, and third drain electrodes  175   h ,  175   l , and  175   c  form first, second, and third thin film transistors (TFTs) Qh, Ql, and Qc together with the first, second, and third semiconductor layers  154   h ,  154   l , and  154   c , respectively. 
     Next, a first passivation layer  180   a  is formed on the data line  171 , the first, second, and third source electrodes  173   h ,  173   l , and  173   c , the first, second, and third drain electrodes  175   h ,  175   l , and  175   c , and the semiconductor layers  154   h ,  154   l , and  154   c  exposed between the respective source electrodes  173   h ,  173   l , and  173   c  and the respective drain electrodes  175   h ,  175   l , and  175   c . The first passivation layer  180   a  may be made of an organic insulating material or an inorganic insulating material, and may be formed with a single layer or multilayers. 
     Next, a second passivation layer  180   b  is formed to be disposed in respective pixels PX above the first passivation layer  180   a . The second passivation layer  180   b  may be formed in the first subpixel PXa or the second subpixel PXb, and may not be formed in the first valley V 1 . 
     Next, a light blocking member  220  is formed on each boundary portion of the pixels PX above the first passivation layer  180   a , and on the thin film transistors. The light blocking member  220  may also be formed in the first valley V 1  disposed between the first subpixel PXa and the second subpixel PXb. 
     Hereinabove, it is described that the light blocking member  220  is formed after forming the second passivation layer  180   b , but the present invention is not limited thereto, and the light blocking member  220  may be first formed and then the second passivation layer  180   b  may be formed. 
     Next, a first insulating layer  240  made of an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon nitride oxide (SiOxNy) is formed on the second passivation layer  180   b  and the light blocking member  220 . 
     Next, a first contact hole  185   h  is formed by etching the first passivation layer  180   a , the light blocking member  220 , and the first insulating layer  240  to expose a portion of the first drain electrode  175   h , and a second contact hole  185   l  is formed to expose a portion of the second drain electrode  175   l.    
     Next, a first subpixel electrode  191   h  is formed in the first subpixel PXa and a second subpixel electrode  191   l  is formed in the second subpixel PXb by depositing and patterning a transparent metal material such as indium tin oxide (ITO) and indium zinc oxide (IZO) on the first insulating layer  240 . The first subpixel electrode  191   h  and the second subpixel electrode  191   l  are separated from each other with the first valley V 1  therebetween. The first subpixel electrode  191   h  is connected with the first drain electrode  175   h  through the first contact hole  185   h , and the second subpixel electrode  191   l  is connected with the second drain electrode  175   l  through the second contact hole  185   l.    
     Horizontal stems  193   h  and  193   l  and vertical stems  192   h  and  192   l  crossing the horizontal stems  193   h  and  193   l  are formed in the first subpixel electrode  191   h  and the second subpixel electrode  191   l , respectively. Further, a plurality of minute branches  194   h  and  194   l  are formed to obliquely extend from the horizontal stems  193   h  and  193   l  and the vertical stems  192   h  and  192   l.    
     Next, a second insulating layer  250  is formed on the pixel electrode  191  and the first insulating layer  240 . 
     As shown in  FIGS. 6 and 7 , a photosensitive organic material is coated on the second insulating layer  250 , and a sacrificial layer  300  is formed by a photo process. 
     The sacrificial layer  300  is formed to be connected along a plurality of columns. That is, the sacrificial layer  300  is formed to cover each pixel PX and to cover the first valley V 1  disposed between the first subpixel PXa and the second subpixel PXb. 
     Next, a common electrode  270  is formed by depositing a transparent metal material such as indium tin oxide (ITO) and indium zinc oxide (IZO) on the sacrificial layer  300 . 
     Next, a third insulating layer  340  may be formed on the common electrode  270  by using an inorganic insulating material such as a silicon nitride, a silicon oxide (SiOx), and a silicon nitride oxide (SiOxNy). 
     Next, the roof layer  360  is formed by coating and patterning an organic material on the third insulating layer  340 . In this case, the organic material disposed in the first valley V 1  may be patterned to be removed. As a result, the roof layers  360  may be formed to be connected to each other along a plurality of pixel rows. 
     In the meantime, the roof layers  360  are not disposed in the first valley areas, and the roof layers  360  are spaced apart from each other with the valley area therebetween. Accordingly, a roof layer adjacent to a valley area is formed to have an inclined surface. 
     Next, as shown in  FIGS. 8 and 9 , the third insulating layer  340  and the common electrode  270  are patterned by using the roof layer  360  as a mask. First, the third insulating layer  340  is dry etched by using the roof layer  360  as a mask, and then the common electrode  270  is wet etched. 
     Next, as shown in  FIGS. 10 and 11 , the sacrificial layer  300  is completely removed by supplying a developer or a striper solution on the substrate  110  in which the sacrificial layer  300  is exposed, or by using an ashing process. 
     When the sacrificial layer  300  is removed, the microcavity  305  is formed at a region at which the sacrificial layer  300  was disposed. 
     The pixel electrode  191  and the common electrode  270  are spaced apart from each other with the microcavity  305  therebetween, and the pixel electrode  191  and the roof layer  360  are spaced apart from each other with the microcavity  305  therebetween. The common electrode  270  and the roof layer  360  are formed to cover an upper surface and both lateral surfaces of the microcavity  305 . 
     The microcavity  305  is exposed to the outside through a region in which the roof layer  360 , the third insulating layer  340 , and the common electrode  270  are removed, which is referred to as the injection hole  307 . The injection hole  307  is formed along the first valley V 1 . For example, the injection holes  307  may be formed to face each other at edges of the first subpixel PXa and the second subpixel PXb. That is, the injection hole  307  may be formed to expose lateral surfaces of the microcavity  305  to correspond to a lower side of the first subpixel PXa and an upper side of the second subpixel PXb. In other embodiments, the injection hole  307  may be formed along the second valley V 2 . 
     Subsequently, the roof layer  360  is cured by applying heat to the substrate  110 . This is for the purpose of maintaining the shape of the microcavity  305  by the roof layer  360 . 
     Subsequently, when an alignment agent including an alignment material is dripped on the substrate  110  by a spin coating method or an inkjet method, the alignment agent is injected into the microcavity  305  through the injection hole  307 . When a curing process is performed after the aligning agent is injected into the microcavity  305 , a solution component is vaporized and the alignment material remains at an inner wall surface of the microcavity  305 . 
     Accordingly, the first alignment layer  11  may be formed on the pixel electrode  191 , and the second alignment layer  21  may be formed below the common electrode  270 . The first alignment layer  11  and the second alignment layer  21  are formed to face each other with the microcavity  305  therebetween, and are formed to be connected to each other at the edge of the pixel PX. 
     In this case, the first and second alignment layers  11  and  21  may be aligned in a direction that is perpendicular to the insulating substrate  110 , except for the lateral surface of the microcavity  305 . The first and second alignment layers  11  and  21  may be aligned in a direction that is parallel to the insulating substrate  110  by additionally irradiating UV to the first and second alignment layers  11  and  21 . 
     Subsequently, when the liquid crystal material formed of the liquid crystal molecules  310  is dripped on the substrate  110  by an inkjet method or a dispensing method, the liquid crystal material is injected into the microcavity  305  through the injection hole  307 . 
     The liquid crystal material of the display device according to the exemplary embodiment of the present invention includes the liquid crystal molecules  310  and the color materials  311 ,  312 , and  313  mixed with the liquid crystal molecules. The color materials  311 ,  312 , and  313  are mixed with the liquid crystal material, and each of the color materials  311 ,  312 , and  313  may be a pigment representing at least one of primary colors of red, green, and blue. 
     Accordingly, the pigments  311 ,  312 , and  313  with different colors are respectively applied to the microcavities  305 , such that light passing through each of the microcavities  305  may represent a color corresponding to each of the pigments  311 ,  312 , and  313 . That is, when colors of the pigments  311 ,  312 , and  313  are respectively red, green, and blue, the liquid crystal layers included in the microcavities  305  may respectively represent the red, green, and blue colors. 
     The pigments  311 ,  312 , and  313  may be an inorganic pigment or an organic pigment, but is not limited thereto, and thus may be any pigment that is able to represent a predetermined color. 
     Further, a microcavity  305  representing a white color may be formed by including the pigments  311 ,  312 , and  313  with only primary colors of red, green, and blue. 
     The color materials  311 ,  312 , and  313  may include dichroic dyes having anisotropy in absorption of light, instead of the pigments with the colors described above. 
     Colors represented by the dichroic dyes  311 ,  312 , and  313  are determined by a spectrum with respect to colors that are not absorbed by the dichroic dyes  311 ,  312 , and  313 , that is, complementary colors. Accordingly, when any pixel is intended to display one of primary colors of red, green, and blue, the dichroic dye  311 ,  312 , or  313  included in the liquid crystal layer corresponding to the pixel may be a material absorbing light of a wavelength region corresponding to one of cyan, magenta, and yellow. For example, each of liquid crystal layers corresponding to a red pixel, a green pixel, and a blue pixel may include a liquid crystal material in which a cyan dichroic dye, a magenta dichroic dye, and yellow dichroic dye  311 ,  312 , and  313  are respectively mixed. In this case, the cyan dichroic dye may absorb light of a wavelength region of 600-700 nm, the magenta dichroic dye may absorb light of a wavelength region of 500-580 nm, and the yellow dichroic dye may absorb light of a wavelength region of 430-490 nm. 
     Unlike this, when any pixel displays one of cyan, magenta, and yellow, the dichroic dye  311 ,  312 , or  313  included in the liquid crystal layer corresponding to the pixel may be a material absorbing light of a wavelength region corresponding to one of red, green, and blue. 
     Further, a microcavity  305  representing a white color may be formed by including the pigments  311 ,  312 , and  313  with only primary colors of red, green, and blue. 
     The dichroic dyes  311 ,  312 , and  313 , for example, may include one or more selected from azo dyes, anthraquinone dyes, perylene dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, dioxadine dyes, polythiophene dyes, and phenoxazine dyes, but are not limited thereto. 
     An appropriate concentration of the dichroic dyes  311 ,  312 , and  313  mixed with the liquid crystal material may be varied depending on an absorption capacity of light of the dichroic dyes  311 ,  312 , and  313 . 
     The dyes  311 ,  312 , and  313  are not limited to those described above, and may include materials which pass through light of some specific wavelengths and which reflect light of the other wavelengths. In other words, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a red color may include a material that passes through only light of a red wavelength band and reflects light of the remaining wavelength band. Further, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a green color may include a material that passes through only light of a green wavelength band and reflects light of the remaining wavelength band. In addition, a liquid crystal layer filled inside a microcavity  305  corresponding to a pixel representing a blue color may include a material that passes through only light of a blue wavelength band and reflects light of the remaining wavelength band. 
     According to the exemplary embodiment of the present invention, since the color of the pixel is implemented by the color pigment or the dichroic color dye that is injected into the liquid crystal layer, or by the material that passes through light of some specific wavelengths, a color filter is not required. Accordingly, a photolithography process for forming the color filter is not required, thereby simplifying a structure of the display device, and reducing manufacturing processes, time, and cost. 
     In a vertical direction of the microcavity  305 , the liquid crystal material including corresponding color materials  311 ,  312 , and  313  that can display corresponding colors is injected into the microcavity  305  through the injection holes  307  formed at opposite sides of the microcavity  305 . In a horizontal direction of the microcavity  305 , the liquid crystal materials including different kinds of color materials  311 ,  312 , and  313  that can display different colors are repeatedly injected into the adjacent microcavities  305  through the injection holes  307  with a predetermined cycle (e.g., repetition of red, green, and blue). A nozzle injecting the liquid crystal materials including the different kinds of color materials  311 ,  312 , and  313  may drip the liquid crystal material including the color materials  311 ,  312 , and  313 , for example, moving in a vertical direction. In this case, the injecting process for each color may be sequentially performed with a time interval such that the liquid crystal materials including the different kinds of the color materials  311 ,  312 , and  313  may not be mixed, the injecting processes may be simultaneously performed by adjusting a spread of the liquid crystal material including the color materials  311 ,  312 , and  313 , or the two injecting processes may be combinatorially performed. 
     Next, as shown in  FIGS. 12 and 13 , the overcoat  390  is formed at the entire surface of the substrate  110  by depositing a material that does not react with the liquid crystal molecules  310  on the roof layer  360 . The overcoat  390  is formed to cover the injection hole  307  where the microcavity  305  is exposed outside to seal the microcavity  305 . 
     Although not illustrated, polarizers may be further formed on the upper and lower surfaces of the display device. The polarizers may be formed as a first polarizer and a second polarizer. The first polarizer may be attached to the lower surface of the substrate  110 , and the second polarizer may be attached to the overcoat  390 . 
     As described above, according to the exemplary embodiments of the present invention, it is possible to simplify a structure of the display device and may reduce the number of manufacturing processes thereof by adding a color material to a liquid crystal material of the display device manufactured with a single substrate such that a color filter may be removed. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     DESCRIPTION OF SYMBOLS 
       11 : first alignment layer  21 : second alignment layer 
       110 : insulation substrate  121 : gate line 
       124   h : first gate electrode  124   l : second gate electrode 
       124   c : third gate electrode  131 : storage electrode line 
       140 : gate insulating layer  171 : data line 
       191 : pixel electrode  191   h : first subpixel electrode 
       191   l : second subpixel electrode  220 : light blocking member 
       180 : passivation layer  240 : first insulating layer 
       270 : common electrode  300 : sacrificial layer 
       305 : microcavity  307 : injection hole 
       310 : liquid crystal molecule  250 : second insulating layer 
       370 : third insulating layer  390 : overcoat 
       311 ,  312 ,  313 : dye