Patent Publication Number: US-2017357043-A1

Title: Display substrate including light exit patterns, display device including the same and method of manufacturing the same

Description:
This patent application claims priority to Korean Patent Application No. 10-2016-0073339, filed on Jun. 13, 2016, and all the benefits accruing therefrom under 35 U.S.C. §119, the content of which in its entirety is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a display device and a method of manufacturing the same. More particularly, the present disclosure relates to a display device from which a backlight unit is omitted and a method of manufacturing the display device. 
     2. Description of the Related Art 
     A flat panel display device has been developed to replace a cathode ray tube display device which has a relatively large thickness and relatively high power consumption. As the flat panel display device, an organic light emitting display device, a liquid crystal display device and a plasma display device are widely used. 
     In general, the liquid crystal display device is a non-self emissive display device and includes a display panel which generates an image with light and a backlight unit which is disposed under the display panel to provide the light to the display panel. The backlight unit occupies a significant portion of the total thickness of the liquid crystal display device. 
     SUMMARY 
     One or more exemplary embodiment provides a display device having a reduced thickness and a reduced manufacturing cost. 
     One or more exemplary embodiment provides a method of manufacturing the display device having a reduced thickness and a reduced manufacturing cost. 
     Embodiments of the invention provide a display device including a lower substrate, an upper substrate facing the lower substrate, a light source which generates and emits a light toward a side surface of the lower substrate, and an optical medium layer interposed between the lower substrate and the upper substrate and through which the light transmits to generate an image. 
     The light source emits a light toward a side surface of the lower substrate. 
     The lower substrate includes a first substrate within which the light travels from the side surface of the lower substrate to exit from an upper surface of the first substrate, and light exit patterns which are on the upper surface of the first substrate. 
     The first substrate includes an incident surface to which the light emitted from the light source is incident. 
     Each of the light exit patterns is in contact with the upper surface of the first substrate and respectively defines a first space between the light exit pattern and the upper surface of the first substrate, the first space being filled with air. 
     The first space may have a trapezoidal shape in a thickness direction of the lower substrate. 
     Each of the light exit patterns may have a refractive index equal to or greater than a refractive index of the first substrate. 
     Each of the light exit patterns may include a flat portion substantially parallel to the first substrate and spaced apart from the first substrate to dispose the first space between the flat portion and the upper surface of the first substrate, and an inclined portion which extends from the flat portion to contact the first substrate. 
     The light source may be disposed adjacent in a first direction to the incident side surface of the first substrate. The inclined portion may be provided in a plural number. The inclined portions may be respectively connected to two sides of the flat portion which are opposite to each other in the first direction. 
     An inner inclination angle respectively formed by the inclined portions with the first substrate may be from about 60° to about 70°. 
     The flat portion and the inclined portion may have a same thickness. 
     Two light exit patterns disposed adjacent to each other among the light exit patterns may define a second space filled with air therebetween. 
     Two light exit patterns disposed adjacent to each other among the light exit patterns may define a second space. The lower substrate may further include an auxiliary pattern disposed in the second space between the two light exit patterns adjacent to each other among the light exit patterns. 
     Each of the light exit patterns may have substantially a same refractive index as that of the auxiliary pattern. 
     Two light exit patterns disposed adjacent to each other among the light exit patterns may be spaced apart from each other. Each of the adjacent light exit patterns spaced apart from each other may include: a flat portion substantially parallel to the first substrate and spaced apart from the first substrate to dispose the first space between the flat portion and the upper surface of the first substrate; and an inclined portion extending inclined from the flat portion and toward to the first substrate, the inclined portion in contact with the upper surface of the first substrate, The lower substrate may further include a connection pattern between the adjacent light exit patterns spaced apart from each other. The connection pattern may connect inclined portions of the adjacent light exit patterns to each other and contact the upper surface of the first substrate. 
     The lower substrate may further include a first polarization layer which is disposed on the light exit patterns and linearly polarizes a light incident thereto. 
     The lower substrate may further include a common electrode disposed on the first polarization layer. The upper substrate may further include a second substrate, a driving layer, a pixel electrode and a second polarization layer. The driving layer may be disposed on the second substrate. The pixel electrode may be disposed on the driving layer, receive a pixel voltage from the driving layer, and generate an electric field, with the common electrode, in the optical medium layer to generate the image. The second polarization layer may be disposed on the second substrate to dispose the second substrate between the second polarization layer and the pixel electrode, and may linearly polarize a light incident thereto. 
     The upper substrate facing the lower substrate with the optical medium layer therebetween may include a second substrate, a driving layer, a pixel electrode, a common electrode and a second polarization layer. The driving layer may be disposed on the second substrate. The pixel electrode may be disposed on the driving layer and receive a pixel voltage from the driving layer. The common electrode may be disposed to face the pixel electrode, be insulated from the pixel electrode and generate an electric field, with the pixel electrode, in the optical medium layer to generate the image. The second polarization layer may be disposed on the second substrate to dispose the second substrate between the second polarization layer and the pixel electrode, and may linearly polarize a light incident thereto. 
     The lower substrate may further include a driving layer and a pixel electrode. The driving layer may be disposed on the light exit patterns. The pixel electrode may be disposed on the driving layer and receives a pixel voltage from the driving layer. The upper substrate facing the lower substrate with the optical medium layer therebetween may include a second substrate, a common electrode and a second polarization layer. The common electrode may be disposed on the second substrate, face the pixel electrode and generate an electric field, with the pixel electrode, in the optical medium layer to generate the image. The second polarization layer may be disposed on the second substrate to dispose the second substrate between the second polarization layer and the common electrode, and may linearly polarize a light incident thereto. 
     Embodiments of the invention provide a method of manufacturing the display device, including providing a lower substrate, providing an upper substrate to face the lower substrate, providing a light source unit to be disposed adjacent to a side surface of the lower substrate and providing an optical medium layer between the lower substrate and the upper substrate and through which the light transmits to generate an image. 
     The providing the lower substrate includes forming light exit patterns on an upper surface of a first substrate within which the light travels from the side surface of the lower substrate to exit from the upper surface of the first substrate. Each of the light exit patterns is in contact with the upper surface of the first substrate to define a first space between the light exit pattern and the upper surface of the substrate, the first space being filled with air. 
     The forming the light exit patterns on the upper surface of the first substrate may include forming a plurality of sacrificial layer patterns on the upper surface of the first substrate and spaced apart from each other to expose the upper surface of the first substrate; forming a transparent material layer on the sacrificial layer patterns and on the exposed upper surface of the first substrate; and removing the sacrificial layer patterns to form each of the light exit patterns in contact with the upper surface of the first substrate. 
     The removing the sacrificial layer patterns forms the first space between the light exit pattern and the upper surface of the substrate. 
     Embodiments of the invention provide a display device including a lower substrate, an upper substrate facing the lower substrate, a light source which generates and emits a light to a side surface of the lower substrate; and an optical medium layer disposed between the lower substrate and the upper substrate. 
     The light source emits a light to a side surface of the lower substrate. 
     The lower substrate includes a first substrate within which the light travels from the side surface of the lower substrate to exit from an upper surface of the first substrate, the first substrate, and light exit patterns which are on the upper surface of the first substrate. The first substrate includes an incident side surface to which the light emitted from the light source is incident. Each of the light exit patterns is in contact with the upper surface of the first substrate and respectively defines a first space between the light exit pattern and the upper surface of the first substrate, the first space filled with air. 
     The upper surface of the first substrate includes a transmission area at which the upper surface contacts the light exit patterns and a reflection area at which the upper surface is exposed to the first space. 
     According to one or more exemplary embodiment described above, an overall thickness and manufacturing cost of the display device may be reduced since the display device does not need to include a light guide plate and optical sheets as separate elements within the lower substrate to which light is incident. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other advantages of the present disclosure will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings where: 
         FIG. 1  is an exploded perspective view showing an exemplary embodiment of a display device according to the invention; 
         FIG. 2  is a top plan view of the display device in  FIG. 1  according to the invention; 
         FIG. 3  is a cross-sectional view taken along line I-I′ of  FIG. 2 ; 
         FIG. 4  is a perspective view showing an exemplary embodiment of a first substrate and light exit patterns; 
         FIG. 5  is a cross-sectional view showing the first substrate and light exit patterns of  FIG. 4  according to the invention; 
         FIG. 6  is a cross-sectional view showing a modified exemplary embodiment of the display device in  FIG. 3  according to the invention; 
         FIG. 7  is a cross-sectional view showing another modified exemplary embodiment of the display device of  FIG. 3  according to the invention; 
         FIG. 8  is a cross-sectional view showing still another modified exemplary embodiment of the display device of  FIG. 3  according to the invention; 
         FIG. 9  is a cross-sectional view showing another exemplary embodiment of a display device taken along line I-I′ of  FIG. 2  according to the invention; 
         FIG. 10  is a cross-sectional view showing still another exemplary embodiment of a display device according to the invention; 
         FIG. 11  is a flowchart showing an exemplary embodiment of a manufacturing method of a display device according to the invention; 
         FIGS. 12A to 12C  are cross-sectional views of exemplary embodiments of processes of forming light exit patterns of a first substrate according to the invention; and 
         FIG. 13  is a cross-sectional view showing an exemplary embodiment of a process of forming auxiliary patterns of a first substrate according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Like reference numerals refer to like elements throughout. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the 
     Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10% or 5% of the stated value. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Hereinafter, the invention will be explained in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view showing an exemplary embodiment of a display device  1000  according to the invention, and  FIG. 2  is a top plan view showing the display device of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the display device  1000  includes a display panel  100  and a light source unit  200 . 
     The display panel  100  generates and displays an image using a light emitted from the light source unit  200 . The display panel  100  may be a liquid crystal display panel, an electrophoretic display panel or an electrowetting display panel, but the invention is not limited thereto. Hereinafter, the liquid crystal display panel will be described as the display panel  100 . 
     The display panel  100  includes a lower (display) substrate  110 , an upper (display) substrate  120 , and an optical medium layer  130 . Where the liquid crystal display panel is described as the display panel  100 , the optical medium layer is a liquid crystal layer  130 . The lower substrate  110  faces the upper substrate  120 . The image displayed by the display panel  100  is perceived by a user through the upper substrate  120 . The liquid crystal layer  130  is interposed between the lower substrate  110  and the upper substrate  120 . The lower substrate  110  includes or defines an upper surface thereof facing the upper substrate  120 , a lower surface thereof opposite to the upper surface, and side surfaces each connecting the upper and lower surfaces to each other. The upper substrate  120  may have a similar configuration. Each of the upper and lower substrates  110  and  120  may include or define four side surfaces thereof. 
     The display panel  100  includes two sides defining lengths thereof extending in a first direction DR 1  and two sides defining lengths thereof extending in a second direction DR 2  crossing the first direction DR 1 , when viewed in the top plan view. In the following embodiments, long (e.g., length) sides of the display panel  100  extend in the first direction DR 1  and short (e.g., width) sides of the display panel  100  extend in the second direction DR 2 . In addition, a thickness direction of the display panel  100  is referred to as a “third direction DR 3 .” The first, second and third directions DR 1 , DR 2  and DR 3  may be perpendicular to each other, but the invention should not be limited thereto or thereby. 
     The display panel  100  includes or defines a display area DA and a non-display area NDA when viewed in the top plan view. The display area DA is an area where the image is displayed, and the non-display area NDA is an area where no image is displayed. 
     The display panel  100  includes gate lines GL 1  to GLn, data lines DL 1  to DLm, and a pixel PX provided in plurality. The gate lines GL 1  to GLn are insulated from the data lines DL 1  to DLm while crossing the data lines DL 1  to DLm. In  FIG. 2 , each of the gate lines GL 1  to GLn defines a length thereof which extends in the first direction DR 1 , and each of the data lines DL 1  to DLm defines a length thereof which extends in the second direction DR 2 , but the invention should not be limited thereto or thereby. In an alternative exemplary embodiment of the top plan view of the display device  1000 , for instance, each of the gate lines GL 1  to GLn may have a curved shape at a portion thereof instead of having a total straight line shape, and each of the data lines DL 1  to DLm may have a curved shape at a portion thereof instead of having a total straight line shape. In an exemplary embodiment, the gate lines GL 1  to GLn and the data lines DL 1  to DLm may respectively define a pixel area PA provided in plurality, but the invention should not be limited thereto or thereby. The pixel area PA may be a display unit of the display device  1000  which generates and displays the image. 
     The pixels PX are arranged in the pixel areas PA, respectively. Each of the pixels PX is connected to a gate line among the gate lines GL 1  to GLn and a data line among the data lines DL 1  to DLm to display the image. Each of the pixels PX may display one of red, green and blue colors, but the invention should not be limited thereto or thereby. That is, each of the pixels PX may display another color, e.g., a white color, other than the red, green and blue colors. In  FIG. 1 , each of the pixels PX has a quadrangular shape in the top plan view, but the planar shape of the pixels PX should not be limited to the quadrangular shape. Each of the pixels PX may have various shapes, such as a polygonal shape, a circular shape, an oval shape, etc. in the top plan view. 
     The light source unit  200  is disposed adjacent to a side surface  111  of the lower substrate  110 . The light source unit  200  includes a light source LG provided in plurality and a driving circuit board PB. The light sources LG are mounted on the driving circuit board PB. Each of the light sources LG may be, but not limited to, a light emitting diode package. Each of the light sources LG receives a source voltage from the driving circuit board PB to generate the light. 
     The light generated from the light sources LG travels toward the side surface  111  of the lower substrate  110 . 
     The light sources LG are arranged along the side surface  111  of the lower substrate  110 . The light sources LG are spaced apart from each other in the second direction DR 2 . 
     According to another exemplary embodiment of the present disclosure, the light source unit  200  may be provided in a plural number within the display device  1000 , and the light source units may be disposed adjacent to two or more side surfaces among the four side surfaces of the lower substrate  110 , respectively. 
       FIG. 3  is a cross-sectional view taken along line I-I′ of  FIG. 2 . Particularly,  FIG. 3  shows an exemplary embodiment of the display panel  100  and the light source LG of the display device  1000 . 
     Referring to  FIG. 3 , the lower substrate  110  includes a first (base) substrate SB 1 , a light exit pattern OP provided in plurality, a first polarization layer PL 1 , and a common electrode CE. The plurality of light exit patterns OP may be referred to as a light exit pattern layer. 
     The first substrate SB 1  may be a transparent substrate, such as a glass substrate, a plastic substrate, a silicon substrate, etc. The first substrate SB 1  includes or defines an upper surface S 1 , a lower surface S 2  and an incident surface S 3 . The incident surface S 3  is connected to the upper surface Si and the lower surface S 2 . 
     The light source LG is disposed adjacent to the incident surface S 3  of the first substrate SB 1  in the first direction DR 1 . The light emitted from the light source LG is incident to the incident surface S 3  of the first substrate SB 1 . The first substrate SB 1  has a refractive index of about 1.5. 
       FIG. 4  is a perspective view showing an exemplary embodiment of the first substrate SB 1  and the light exit patterns OP. 
     Referring to  FIGS. 3 and 4 , the light exit patterns OP are disposed on the first substrate SB 1 . Each of the light exit patterns OP provides a first space ASC defined therein. The first space ASC may be filled with air. 
     Each of the light exit patterns OP includes a flat portion OP 1  and an inclined portion OP 2  provided in plural. The flat portion OP 1  is flat. The flat portion OP 1  is arranged parallel to and spaced apart from the first substrate SB 1 . A plane of the flat portion OP 1  may be defined in the first and second directions DR 1  and DR 2 , and the plane may be parallel to the upper surface of the first substrate SB 1 . In the illustrated exemplary embodiment, the flat portion OP 1  has a quadrangular shape when viewed in the top plan view. 
     The inclined portions OP 2  respectively extend from the flat portion OP 1 . The light exit pattern OP may include a pair of inclined portions OP 2  with respect to one flat portion OP 1 , but the invention should not be limited thereto or thereby. The inclined portions OP 2  are respectively connected to two sides of the flat portion OP 1  which oppose each other in the first direction DR 1  with respect to the flat portion OP 1 . The inclined portions OP 2  make contact with the first substrate SB 1 . Distal ends of the inclined portions OP 2  make contact with the first substrate SB 1 . The inclined portions OP 2  are disposed to be inclined with respect to the first substrate SB 1 . One of the flat portion OP 1  and the inclined portions OP 2  may be considered as extending to define the other one of the flat portion OP 1  and the inclined portions OP 2 . 
     The first space ASC is surrounded by the flat portion OP 1 , the pair of inclined portions OP 2  extended from the flat portion OP 1 , and the first substrate SB 1 . The first space ASC has a trapezoidal shape when viewed in a plane defined by the first direction DR 1  and the third direction DR 3 . 
     In the illustrated exemplary embodiment, the first space ASC may be extended to penetrate the light exit patterns OP in the second direction DR 2 . 
     In the illustrated exemplary embodiment, light exit patterns OP may be adjacent to each other in the first direction DR 1 . Among a first and second light exit pattern OP adjacent to each other in the first direction DR 1 , an inclined portion OP 2  of light exit pattern OP may make contact with an inclined portion OP 2  of the other light exit pattern OP. 
     The flat portion OP 1  has a thickness T 1  that is equal to a thickness T 2  of each of the inclined portions OP 2 . The thicknesses T 1  and T 2  may be taken in a direction normal to an inner surface of the light exit pattern OP and/or to an outer surface of the light exit pattern OP which is opposite to an inner surface thereof at the first space ASC. 
     The light exit patterns OP include a transparent material. The light exit patterns OP have a refractive index equal to or greater than the refractive index of the first substrate SB 1 . In the illustrated exemplary embodiment, the light exit patterns OP have the refractive index of about 1.5. The light exit patterns OP include a silicon nitride layer or a silicon oxide layer. 
     Referring to  FIG. 3  again, the first polarization layer PL 1  is disposed on the light exit patterns OP. 
     The first polarization layer PL 1  linearly polarizes the light incident thereto. The first polarization layer PL 1  may be a wire-grid polarization plate (“WGP”). Although not shown in figures, the first polarization layer PL 1  may include a base layer, a wire grid pattern and an insulating layer. The base layer, the wire grid pattern and the insulating layer may be sequentially stacked on the light exit patterns OP. The wire grid pattern includes a metal material and extends parallel to a plane surface defined by the first direction DR 1  and the second direction DR 2 . The insulating layer covers the wire grid pattern. 
     The first polarization layer PL 1  has a refractive index equal to or greater than the refractive index of the light exit patterns OP. 
     In the illustrated exemplary embodiment, a second space BSC may be provided between the first polarization layer PL 1  and the light exit patterns OP. In detail, the second space BSC may be a space surrounded by the inclined portions OP 2  and the first polarization layer PL 1 . The second space BSC may be filled with air. 
     The common electrode CE is disposed on the first polarization layer PL 1 . The common electrode CE includes a transparent electrode. The common electrode CE receives a common voltage having a constant level. 
     Although not shown in figures, the lower substrate  110  may further include a reflection layer disposed under the first substrate SB 1 . The reflection layer reflects the light incident thereto from the first substrate SB 1  toward the light exit patterns OP. 
     The upper substrate  120  includes a second substrate SB 2 , a driving layer (or element) DRV, a pixel electrode PE and a second polarization layer PL 2 . 
     The second substrate SB 2  may be a transparent substrate, such as a glass substrate, a plastic substrate, a silicon substrate, etc. 
     The driving layer DRV includes a gate electrode GE, a gate insulating layer GI, a semiconductor pattern SM, a first source-drain electrode SE, a second source-drain electrode DE and a passivation layer PAS. 
     In the non-display area NDA, the gate electrode GE is disposed on the second substrate SB 2 . The gate insulating layer GI is disposed on the gate electrode GE. The gate insulating layer GI includes an organic insulating material or an inorganic insulating material. The semiconductor pattern SM is disposed on the gate insulating layer GI to overlap with the gate electrode GE. The first source-drain electrode SE is connected to one end of the semiconductor pattern SM, and the second source-drain electrode DE is connected to an opposing end of the semiconductor pattern SM. 
     The passivation layer PAS is disposed on the first source-drain electrode SE and the second source-drain electrode DE in the non-display area NDA. The passivation layer PAS may include an organic insulating material or an inorganic insulating material, but should not be limited thereto or thereby. In the illustrated exemplary embodiment, the passivation layer PAS may include a black matrix (not shown) and a color filter (not shown). Referring to  FIG. 3 , the passivation layer PAS as the color filter is disposed to overlap with the pixel electrode PE in the display area DA and assigns a color to the light incident thereto. the passivation layer PAS as the black matrix is disposed to overlap with the gate electrode GE, the first source-drain electrode SE and the second source-drain electrode DE in the non-display area NDA, and disposed to overlap the gate lines GL 1  to GLn and the data lines DL 1  to DLm in the display area DA (refer to  FIG. 2 ), and blocks the light incident thereto. The passivation layer PAS disposed in one of the display area DA and the non-display area NDA may extend in the first and/or second directions to define the passivation layer PAS disposed in the other one of the display area DA and the non-display area NDA. 
     The passivation layer PAS includes a contact hole CH defined therethrough to expose a portion of the second source-drain electrode DE. 
     The pixel electrode PE is disposed on the passivation layer PAS and connected to the second source-drain electrode DE at the contact hole CH. The pixel electrode PE receives a pixel voltage from the second source-drain electrode DE in the display area DA. The pixel electrode PE is disposed in both the display area DA and the non-display area NDA, such that the pixel voltage received at the non-display area NDA may be transmitted to the display area DA. 
     The second polarization layer PL 2  is disposed to face the pixel electrode PE such that the second substrate SB 2  is disposed between the second polarization layer PL 2  and the pixel electrode PE within the upper substrate  120 . 
     The second polarization layer PL 2  linearly polarizes the light incident thereto. The first polarization layer PL 1  has a transmission axis (or an absorption axis) substantially perpendicular to a transmission axis (or an absorption axis) of the second polarization layer PL 2 . The first polarization layer PL 1  may be provided in a film shape, and the first polarization layer PL 1  may be a wire-grid polarization plate. 
     The liquid crystal layer  130  as the optical medium layer includes a plurality of liquid crystal molecules. An alignment state of the liquid crystal molecules is changed due to an electric field generated by the pixel electrode PE and the common electrode CE, thereby controlling a transmittance of the light traveling through the liquid crystal layer  130 . 
     The display device  1000  may further include a sealing member SL. The sealing member SL may seal the liquid crystal layer  130  in cooperation with the lower substrate  110  and the upper substrate  120 . In addition, the sealing member SL maintains a distance between the lower substrate  110  and the upper substrate  120  in the thickness direction DR 3 . 
       FIG. 5  is a cross-sectional view showing the first substrate and the light exit patterns of  FIG. 4  according to the invention. 
     Hereinafter, a path of the light incident to the incident surface S 3  of the first substrate SB 1  will be described with reference to  FIG. 5 . 
     The first substrate SB 1  includes a transmission area TA and a reflection area RA each defined at the upper surface Si thereof and provided in plural across the upper surface S 1 . 
     The transmission area TA may correspond to an area where the inclined portions OP 2  of the light exit patterns OP make contact with the upper surface Si of the first substrate SB 1 . The reflection area RA may correspond to an area where the first substrate SB 1  makes contact with the first space ASC or is exposed at the first space ASC. 
     Among the light incident to the incident surface S 3  of the first substrate SB 1 , a light L 1  is incident to an inner area of the first substrate SB 1  from the light source LG and travels within the first substrate SB 1 . The light L 1  incident to the reflection area RA may be totally reflected due to a difference in refractive index between the first substrate SB 1  and the air within the first space ASC. Light may not be transmitted at the reflection area RA. A reflected light L 2  which travels within the first substrate SB 1  to be incident to the lower surface S 2  of the first substrate SB 1  may be further reflected. Where the lower surface S 2  of the first substrate SB 1  makes contact with the air, the light L 2  incident to the lower surface S 2  of the first substrate SB 1  may be totally reflected. Also, with the reflection layer disposed on the lower surface S 2  of the first substrate SB 1 , the reflected light L 2  incident to the lower surface S 2  of the first substrate SB 1  may be reflected by the reflection layer to further travel within the first substrate SB 1 . 
     Since the light exit pattern OP has a similar refractive index as that of the first substrate SB 1 , a reflected light L 3  passes through the first substrate SB 1  to be incident to the transmission area TA. The reflected light L 3  incident to the transmission area TA is totally reflected by the inclined portions OP 2  of the light exit pattern OP and travels upward in a direction away from the light exit pattern OP. Light may not be reflected at the transmission area TA. 
     An inner angle Θ 1  defined in the light exit patterns OP among inclination angles formed between the inclined portions OP 2  and the first substrate SB 1  may be in a range from about 60° to about 70°. A front exit angle of a light exiting to the outside of the light exit patterns OP may become closer to 0° depending on the inclination angles of the inclined portions OP 2 . The front exit angle may be defined by an angle formed between a direction in which the light travels and a direction perpendicular to the first substrate SB 1 . 
     As illustrated in  FIG. 5 , the light guided inside the first substrate SB 1  finally exits from the first substrate SB 1  in a direction away from the first substrate SB 1  through the light exit patterns OP. In addition, the light exit patterns OP control the front exit angle of the light exiting to the outside of the first substrate SB 1  to become closer to about 0°, and thus the light exit patterns OP may replace an optical sheet of a conventional display device. 
     One or more exemplary embodiment of the display device  1000  according to the invention does not include a light guide plate and optical sheets of the conventional display device. Thus, an overall thickness of the display device  1000  may be reduced and a manufacturing cost of the display device  1000  may be reduced as compared to the thickness and cost of the convention display device. 
       FIG. 6  is a cross-sectional view showing a modified exemplary embodiment of a display device  1001  according to the invention. 
     The display device  1001  shown in  FIG. 6  has substantially the same structure and function as those elements of the display device  1000  shown in  FIG. 3  except for an auxiliary pattern AXP. 
     A lower substrate  110 -A may further include the auxiliary pattern AXP provided in plural. The auxiliary patterns AXP are disposed in a second space BSC. The auxiliary patterns AXP make contact with inclined portions OP 2  of light exit patterns OP at the second space BSC. 
     The auxiliary patterns AXP include a transparent material. The auxiliary patterns AXP have a refractive index equal to or greater than a refractive index of a first substrate SB 1 . The auxiliary patterns AXP and the light exit patterns OP may have substantially the same refractive index. In the illustrated exemplary embodiment, the refractive index of the auxiliary patterns AXP is about 1.5. The auxiliary patterns AXP include a silicon nitride layer or a silicon oxide layer. The refractive indices of these elements may be defined by the material thereof. 
     The auxiliary patterns AXP and the light exit patterns OP allow the light guided within the first substrate SB 1  to travel upward in a direction away from the first substrate SB 1 . Among lights guided by the inclined portions OP 2  of the light exit patterns OP, a light incident to an interface between the second space BSC and the inclined portions OP 2  passes through the auxiliary patterns AXP and exits upward above from the auxiliary patterns AXP without being totally reflected. 
       FIG. 7  is a cross-sectional view showing another modified exemplary embodiment of a display device  1002  according to the invention. 
     The display device  1002  shown in  FIG. 7  has substantially the same structure and function as those elements of the display device  1000  shown in  FIG. 3  except for a light exit pattern OPX and a connection pattern OPC. 
     The light exit pattern OPX and the connection pattern OPC are provided in plural on the first substrates SB 1 . Each of the light exit patterns OPX includes a flat portion OPX 1  and inclined portions OPX 2  which are respectively connected to ends of the flat portion OPX 1 . The flat portion OPX 1  is the same as the flat portion OP 1  described with reference to  FIGS. 1 to 5 , and thus detailed descriptions on the flat portion OPX 1  will be omitted. 
     In the illustrated exemplary embodiment, light exit patterns OPX may be adjacent to each other in the first direction DR 1 . Among a first and second light exit pattern OPX adjacent to each other in the first direction DR 1 , the inclined portions OPX 2  of the first and second light exit patterns OPX may be spaced apart from each other in the first direction DR 1 . The other features of the inclined portions OPX 2  are the same as those of the inclined portions OP 2  described with reference to  FIGS. 1 to 5 , and thus detailed descriptions thereof will be omitted. 
     A lower substrate  110 -B may further include the connection patterns OPC. The connection patterns OPC respectively connect inclined portions OPX 2  of the first and second light exit patterns OPX to each other. In the thickness direction DR 3 , the connection patterns OPC are disposed to be closer to a first substrate SB 1  than the flat portion OPX 1 . The connection patterns OPC make contact with the first substrate SB 1 . When viewed in the top plan view, the connection patterns OPC may not be overlapped with the flat portion OPX 1 . 
     The connection patterns OPC may include the same material as the light exit patterns OPX. The light exit patterns OPX and the connection patterns OPC may have an integrally formed shaped. That is, one among the connection pattern OPC, the flat portion OPX 1  and the inclined portion OPX 2  may extend to define one or all of the remaining among the connection pattern OPC, the flat portion OPX 1  and the inclined portion OPX 2 . 
     In  FIG. 7 , labels TA 1  and RA 1  are respectively used to indicate boundaries of a transmission area and a reflection area, and to indicate dimensions of the transmission area and the reflection area in the first direction DR 1 . According to the display device  1002  shown in  FIG. 7 , a ratio (TA 1 :RA 1 ) of the dimension of the transmission area TA 1  to the dimension of the reflection area RA 1  may be set freely to allow the light exit patterns OPX and the connection patterns OPC to make contact with the first substrate SB 1  and to vary a length of the connection patterns OPC in the first direction DR 1 . 
       FIG. 8  is a cross-sectional view showing still another modified exemplary embodiment of a display device  1003  according to the invention. 
     The display device  1003  shown in  FIG. 8  has substantially the same structure and function as those elements of the display device  1000  shown in  FIG. 3  except for a position of a common electrode CE. 
     The common electrode CE may be included in an upper substrate  120 - 1  without being included in a lower substrate  110 - 1 . The common electrode CE is disposed to face a pixel electrode PE within the upper substrate  120 - 1 . An insulating layer INS of the upper substrate  120 - 1  is disposed between the common electrode CE and the pixel electrode PE to insulate the common electrode CE from the pixel electrode PE. 
     Referring to  FIG. 8 , the pixel electrode PE is disposed between a second substrate SB 2  and the common electrode CE, but should not be limited thereto or thereby. According to another exemplary embodiment, the common electrode CE may be disposed between the second substrate SB 2  and the pixel electrode PE. 
     A horizontal electric field may be formed in a liquid crystal layer  130  by voltages respectively applied to the pixel electrode PE and the common electrode CE of the upper substrate  120 - 1 . An alignment state of liquid crystal molecules in the liquid crystal layer  130  may be controlled by the horizontal electric field. 
       FIG. 9  is a cross-sectional view showing another exemplary embodiment of a display device  1004  taken along line I-I′ of  FIG. 2  according to the invention. 
     The display device  1004  shown in  FIG. 9  has substantially the same structure and function as those elements of the display device  1000  shown in  FIG. 3  except for a structure of a lower substrate  110 - 2  and an upper substrate  120 - 2 . 
     The lower substrate  110 - 2  includes a first substrate SB 1 , light exit patterns OP, a first polarization layer PL 1 , a driving layer DRV and a pixel electrode PE. 
     The driving layer DRV is disposed on the first polarization layer PL 1 . The pixel electrode PE is disposed on the driving layer DRV. 
     The upper substrate  120 - 2  includes a second substrate SB 2 , a common electrode CE, and a second polarization layer PL 2 . The common electrode CE is disposed on the second substrate SB 2  to face the pixel electrode PE with respect to the liquid crystal layer  130 . The second substrate SB 2  is disposed between the common electrode CE and the second polarization layer PL 2 . 
     However, the invention should not be limited thereto or thereby. In an alternative exemplary embodiment, for instance, the common electrode CE may be included in the lower substrate  110 - 2  without being included in the upper substrate  120 - 2 . Where the common electrode CE and the pixel electrode PE are included in the lower substrate  110 - 2 , similar to that discussed for  FIG. 8 , an insulating layer (not shown) may be disposed on the pixel electrode PE, and the common electrode CE may be disposed on the insulating layer (not shown). 
     In other alternative exemplary embodiments, any of the varying structures of the auxiliary pattern AXP or the connection pattern OPC within  FIGS. 6-8  may be applied to the illustrated exemplary embodiment in  FIG. 9 . 
     According to the display device  1004  shown in  FIG. 9 , even though the lower substrate  110 - 2  includes the driving layer DRV and the pixel electrode PE and the upper substrate  120 - 2  includes the common electrode CE, opposite to the display device  1000  shown in  FIG. 3 , the display device  1004  may have a similar function as that of the display device  1000  shown in  FIG. 3 . 
       FIG. 10  is a cross-sectional view showing still another exemplary embodiment of a display device  1005  according to the invention. 
     Referring to  FIG. 10 , the display device  1005  includes a display panel  100 - 3 , a light source unit  200 -A, a bottom chassis BC, a flexible printed circuit board FPC, a printed circuit board PTB and a module frame MF. 
     The display panel  100 - 3  may be one of the display panels described with reference to 
       FIGS. 1-9 . The display panel  100 - 3  includes a lower substrate  110 - 3  and an upper substrate  120 - 3 . The upper substrate  120 - 3  has an overall size greater than that of the lower substrate  110 - 3  when viewed in the top plan view. The upper substrate  120 - 3  may extend further than an outer edge of the lower substrate  110 - 3 , as illustrated in  FIG. 10 . Since the lower substrate  110 - 3  and the upper substrate  120 - 3  are described with reference to  FIGS. 1-9 , details thereof will be omitted. 
     The light source unit  200 -A has the same structure and function as those elements of the light source unit  200  shown in  FIGS. 1 to 3 , and thus detailed descriptions of the light source unit  200 -A will be omitted. 
     The bottom chassis BC includes and defines an accommodating space therein. The display panel  100 - 3  and the light source unit  200 -A are accommodated in the accommodating space. The bottom chassis BC includes a bottom portion BC 1  and a sidewall portion BC 2 . 
     The light source unit  200 -A is disposed on the sidewall portion BC 2  of the bottom chassis BC. The lower substrate  110 - 3  is disposed on the bottom portion BC 1 . 
     The flexible printed circuit board FPC is attached to the upper substrate  120 - 3  and bent downward below the bottom chassis BC. The flexible printed circuit board FPC electrically connects the display panel  100 - 3  and the printed circuit board PTB to each other. The flexible printed circuit board FPC includes a base film  11  and an integrated circuit chip  12  which is formed or disposed on the base film  11 . 
     The printed circuit board PTB is disposed under the bottom portion BC 1  of the bottom chassis BC. The printed circuit board PTB generates and/or transmits signals to drive the display panel  100 - 3 . The printed circuit board PTB provides a driving signal to the upper substrate  120 - 3 . The printed circuit board PTB includes a driving substrate (not shown) and a plurality of circuit parts (not shown) mounted on the driving substrate (not shown). The flexible printed circuit board FPC may transmit driving and control signals between the display panel  100 - 3  and the printed circuit board PTB. 
     The module frame MF accommodates therein the display panel  100 - 3 , the light source unit  200 -A, the bottom chassis BC, the flexible printed circuit board FPC and the printed circuit board PTB. 
     The module frame MF includes a bottom frame portion MF 1  and a sidewall frame portion MF 2 . The bottom frame portion MF 1  has a flat shape. The sidewall frame portion MF 2  extends from an edge of the bottom frame portion MF 1  in the third direction DR 3 . The sidewall frame portion MF 2  covers a side surface of the upper substrate  120 - 3 . 
       FIG. 11  is a flowchart showing an exemplary embodiment of a manufacturing method of a display device according to the invention. 
     Referring to  FIG. 11 , the method of manufacturing the display device includes forming a lower substrate including light exit patterns (S 10 ), forming an upper substrate (S 20 ), forming a liquid crystal layer (S 30 ), and arranging a light source unit at one side surface of the lower substrate (S 40 ). 
     While the structure of  FIG. 3  is used for description in the method of manufacturing the display device, the method may be respectively applied to any of the structures of the upper and lower substrates described herein. 
     Referring to  FIGS. 3 and 11 , the forming of the lower substrate (S 10 ) includes forming the light exit patterns OP on the first substrate SB 1 , forming the first polarization layer PL 1  on the light exit patterns OP, and forming the common electrode CE on the first polarization layer PL 1 . The first polarization layer PL 1  may be formed using a deposition process and a patterning process. 
     The forming of the upper substrate (S 20 ) includes forming the driving layer DRV on the second substrate SB 2 , forming the pixel electrode PE on the driving layer DRV, and forming the second polarization layer PL 2  on the second substrate SB 2 . 
     In the forming of the liquid crystal layer (S 30 ), the liquid crystal is provided between the upper substrate  120  and the lower substrate  110 . Then, the sealing member SL is formed between the lower substrate  110  and the upper substrate  120  to seal the liquid crystal between the lower substrate  110  and the upper substrate  120 . The lower substrate  110  and the upper substrate  120  may be coupled to each other by the sealing member SL. 
     In the arranging of the light source unit (S 40 ), the light source LG is disposed adjacent to the incident surface S 3  of the first substrate SB 1 . 
       FIGS. 12A to 12C  are cross-sectional views of exemplary embodiments of processes of the forming light exit patterns on the first substrate within the forming of the lower substrate (S 10 ). 
     Referring to  FIGS. 3 and 12A , a sacrificial layer SCR is formed on the first substrate SB 1 . The sacrificial layer SCR is formed by depositing an insulating material and patterning the insulating material using a photolithography process. The sacrificial layer SCR may include convex patterns protruded from an upper surface of the first substrate SB 1 . Inclined surfaces of the convex patterns may have a lateral inclination angle of from about 60° to about 70° with respect to the upper surface of the first substrate SB 1 . In a subsequent process, the sacrificial layer SCR is removed to form a first space ASC. 
     Referring to  FIG. 12B , the light exit patterns OP are formed on the sacrificial layer SCR. The light exit patterns OP have substantially the same refractive index as that of the first substrate SB 1  and include a transparent material. A shape of the light exit patterns OP corresponds to that of the sacrificial layer SCR. The shape of the light exit patterns OP may be the convex shape. 
     Referring to  FIG. 12C , the sacrificial layer SCR is removed. The first space ASC is formed inside each of the light exit patterns OP by removing the sacrificial layer SCR. The first space ASC may be filled with the air. 
       FIG. 13  is a cross-sectional view showing an exemplary embodiment of a process of forming the auxiliary patterns. 
     The forming of the lower substrate (S 10 ) shown in  FIG. 11  may further include forming the auxiliary patterns AXP on the light exit patterns OP. 
     The auxiliary patterns AXP may be formed between the adjacent inclined portions OP 2  of adjacent light exit patterns OP. The auxiliary patterns AXP may have substantially the same refractive index as that of the light exit patterns OP and include a transparent material. 
     Although the exemplary embodiments of the invention have been described, it is understood that the invention should not be limited to these exemplary embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the invention as hereinafter claimed.