Patent Publication Number: US-2022231089-A1

Title: Display device and photomask

Description:
This application claims priority to Korean Patent Application No. 10-2021-0008826, filed on Jan. 21, 2021, 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 
     Embodiments of the invention relate to a display device and a photomask used in a manufacturing process thereof. 
     2. Description of the Related Art 
     A display device displays an image, and includes various types of display devices such as a liquid crystal display device, an organic light emitting diode display device, and the like. Such a display device is used in various electronic devices such as mobile phones, navigation units, digital cameras, electronic books, portable game machines, and various terminals. 
     The display device is formed to have a multi-layered structure. The display device may have a multi-layered structure in which a light emitting element, a touch sensor, and the like are stacked on a substrate, for example. An image may be displayed by light generated from the light emitting element passing through such layers and being emitted to the outside of the display device. 
     SUMMARY 
     Some of light generated by a light emitting element may disappear without being emitted to the outside, such as being reflected at an interlayer interface. As a result, front light emission efficiency and display quality of the display device may be deteriorated. 
     Embodiments have been made in an effort to provide a display device and a photomask used in a manufacturing process thereof, capable of improving light emission efficiency and display quality. 
     In addition, a pattern constituting the display device may include a substantially uniform pattern with a small thickness, thereby improving stability in a foldable product etc. 
     An embodiment provides a display device including a substrate, a pixel electrode disposed on the substrate, a bank layer which is disposed on the pixel electrode and in which a pixel opening overlapping the pixel electrode is defined, an encapsulation layer disposed on the pixel electrode and the bank layer, a sensing electrode disposed on the encapsulation layer, a first insulating layer which is disposed on the sensing electrode and in which an opening overlapping the pixel opening is defined, and a second insulating layer which is disposed on the first insulating layer and has a higher refractive index than a refractive index of the first insulating layer, where a side inclination angle of the first insulating layer in the opening of the first insulating layer is different depending on a position of the opening of the first insulating layer. 
     In an embodiment, an edge of the opening of the first insulating layer may include a first region and a second region in a plan view, and a side inclination angle of the first insulating layer in the first region may be smaller than a side inclination angle of the first insulating layer in the second region. 
     In an embodiment, the opening of the first insulating layer may have a polygonal shape, the first region may be a corner portion of the polygonal shape, and the second region may be a portion other than the first region. 
     In an embodiment, the opening of the first insulating layer may have the polygonal shape in which a corner portion thereof is chamfered. 
     In an embodiment, the pixel opening may be defined in the opening of the first insulating layer in a plan view. 
     In an embodiment, a distance between the pixel opening and the opening of the first insulating layer in the first region may be greater than a distance between the pixel opening and the opening of the first insulating layer in the second region. 
     In an embodiment, a ratio of the first region to the second region at the edge of the opening of the first insulating layer may be less than 1. 
     In an embodiment, the side inclination angle of the first insulating layer in the first region may be smaller than the side inclination angle of the first insulating layer in the second region by about 20 degrees or more. 
     In an embodiment, the first insulating layer in the first region may have the side inclination angle of about 70 degrees or less. 
     In an embodiment, the first insulating layer in the second region may have the side inclination angle of about 50 degrees or more and about 90 degrees or less. 
     In an embodiment, the opening of the first insulating layer may have a polygonal shape, the first region may be a central portion of each side of the polygonal shape, and the second region may be a portion other than the first region. 
     In an embodiment, a side inclination of the first insulating layer may have a straight line, a curved line, or a stepped shape. 
     An embodiment provides a photomask including a center pattern having a polygonal shape, and a peripheral pattern disposed at a corner portion of the center pattern, where the peripheral pattern extends in a direction that is parallel or perpendicular to the corner portion. 
     In an embodiment, the peripheral pattern may include a plurality of rod shapes extended in a direction that is parallel to the corner portion, and lengths of the plurality of rod shapes may be constant or may gradually increase as a distance from the center pattern increases. 
     In an embodiment, a distance between adjacent rod shapes of the plurality of rod shapes may be constant or gradually increase as the distance from the center pattern increases. 
     In an embodiment, a width of the plurality of rod shapes may be constant or may gradually decrease as the distance from the center pattern increases. 
     In an embodiment, the center pattern may be a full tone pattern, and the peripheral pattern may be a halftone pattern and may have a trapezoidal shape having a width that gradually increases as a distance from the center pattern increases. 
     An embodiment provides a display device including a substrate, a pixel electrode disposed on the substrate, a bank layer which is disposed on the pixel electrode and in which a pixel opening overlapping the pixel electrode is defined, an encapsulation layer disposed on the pixel electrode and the bank layer, a sensing electrode disposed on the encapsulation layer, a first insulating layer which is disposed on the sensing electrode and in which an opening overlapping the pixel opening is defined, and a second insulating layer which is disposed on the first insulating layer and has a higher refractive index than a refractive index of the first insulating layer, where a side inclination angle of the bank layer in the opening of the bank layer is different depending on a position of the opening of the first insulating layer. 
     In an embodiment, an edge of the pixel opening may include the first region and the second region in a plan view, and a side inclination angle of the pixel opening in the first region may be smaller than a side inclination angle of the pixel opening in the second region. 
     In an embodiment, the pixel opening may have a polygonal shape, the first region may be a corner portion of the polygonal shape, and the second region may be a portion other than the first region. 
     By the embodiments, it is possible to improve the light emission efficiency and display quality of the display device. 
     In addition, the pattern constituting the display device may be uniformly formed with a thin thickness, thereby reducing the overall thickness of the display device and stably being used for foldable products. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other exemplary embodiments, advantages and features of this disclosure will become more apparent by describing in further detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a schematic top plan view of an embodiment of a display device. 
         FIG. 2  illustrates a top plan view of an embodiment of a portion including a sensor in a display device. 
         FIG. 3  illustrates a cross-sectional view showing a portion of an embodiment of a display area in a display device. 
         FIG. 4  partially illustrates a top plan view of an embodiment of a display device. 
         FIG. 5  illustrates a cross-sectional view taken along line V-V of  FIG. 4 . 
         FIG. 6  illustrates a cross-sectional view taken along line VI-VI of  FIG. 4 . 
         FIG. 7  illustrates fluidity of a material depending on an angle of a pattern when a predetermined material is applied onto a predetermined pattern. 
         FIG. 8  illustrates an opening of a first insulating layer in a reference example of a display device. 
         FIG. 9  illustrates an opening of an embodiment of a first insulating layer in a display device. 
         FIG. 10  to  FIG. 21  illustrate top plan views showing various embodiments of a photomask for defining an opening in a first insulating layer of a display device. 
         FIG. 22  partially illustrates atop plan view of an embodiment of a display device. 
         FIG. 23  and  FIG. 24  illustrate an embodiment of some layers of a display device. 
         FIG. 25  partially illustrates atop plan view of an embodiment of a display device. 
         FIG. 26  illustrates a cross-sectional view taken along line XXVI-XXVI of  FIG. 25 . 
         FIG. 27  illustrates a cross-sectional view taken along line XXVII-XXVII of  FIG. 25 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention will be described more fully hereinafter with reference to the accompanying drawings, in which 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 invention. 
     To clearly describe the invention, parts that are irrelevant to the description are omitted, and like numerals refer to like or similar constituent elements throughout the specification. 
     Further, since sizes and thicknesses of constituent members shown in the accompanying drawings are arbitrarily given for better understanding and ease of description, the invention is not limited to the illustrated sizes and thicknesses. In the drawings, the thicknesses of layers, films, panels, regions, etc., are exaggerated for clarity. In the drawings, for better understanding and ease of description, the thicknesses of some layers and areas are exaggerated. 
     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. Further, in the specification, the word “on” or “above” means disposed on or below the object portion, and does not necessarily mean disposed on the upper side of the object portion based on a gravitational direction. 
     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. 
     In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
     Further, in the specification, the phrase “in a plan view” means when an object portion is viewed from above, and the phrase “in a cross-sectional view” means when a cross-section taken by vertically cutting an object portion is viewed from the side. 
     “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%, 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 invention 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 invention, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, a display device in an embodiment will be described with reference to  FIG. 1  and  FIG. 2 . 
       FIG. 1  illustrates a schematic top plan view of an embodiment of a display device, and  FIG. 2  illustrates a top plan view of an embodiment of a portion including a sensor in a display device. 
     As illustrated in  FIG. 1 , the display device in the illustrated embodiment includes a substrate  100  and a pad portion  30 . 
     The substrate  100  includes a display area DA and a non-display area NA. The display area DA is an area in which pixels including a light emitting diode and a transistor display an image thereon, and the non-display area NA is an area in which an image is not displayed. The non-display area NA may surround a periphery of the display area DA. The non-display area NA is an area including the pad portion  30  in which pads PAD for applying driving signals to pixels are formed or provided. 
     A plurality of pixels (not illustrated) each including a transistor, a light emitting diode, or the like may be disposed in the display area DA. The pixels may be arranged in various forms, for example, may be arranged in a matrix form. A sensing area TA including a plurality of sensing electrodes  520  and  540  in  FIG. 2  may be further disposed above the display area DA to recognize a touch. 
     In the non-display area NA, a driving voltage line (not illustrated), a driving low voltage line (not illustrated), and the pad portion  30  may transfer driving signals such as voltages and signals to pixels formed or disposed in the display area DA. In addition, a plurality of sensing wires  512  and  522  (refer to  FIG. 2 ) may be further disposed in the non-display area NA. The sensing wires  512  and  522  may be connected to the sensing electrodes  520  and  540 . The sensing wires  512  and  522  and the sensing electrodes  520  and  540  will be further described below with reference to  FIG. 2 . 
     The pad portion  30  is disposed in a portion of the non-display area NA, and includes a plurality of pads PAD. Voltages, signals, etc., may be applied to a plurality of voltage lines (not illustrated) connected to the display area DA through the pads PAD, and the sensing wires  512  and  522  (refer to  FIG. 2 ). A flexible printed circuit board (“FPCB”) (not illustrated) may be attached to the non-display area NA. The FPCB may be electrically connected to the pad portion  30 . The FPCB and the pad portion  30  may be electrically connected by an anisotropic conductive film. The FPCB may include an integrated chip (not illustrated), and a driving signal outputted from the driving integrated circuit may be supplied to each pixel through the pads PAD of the pad portion  30 . 
     As illustrated in  FIG. 2 , the substrate  100  further includes a sensing area TA in which the sensing electrodes  520  and  540  are formed or disposed at an upper portion of the display area DA, and a peripheral area PA surrounding the sensing area TA. In an embodiment, the sensing area TA may include the display area DA and a partial area of the non-display area NA of  FIG. 1 , and the peripheral area PA may include a remaining area excluding the sensing area TA. However, this is merely an example, and positions of the sensing area TA and the peripheral area PA may be variously changed. In an embodiment, the sensing area TA may include a portion of the display area DA, and the peripheral area PA may include a remaining area of the display area DA excluding the sensing region TA, and anon-display area NA, for example. In an alternative embodiment, the sensing area TA may include a display area DA and a non-display area NA. 
     The sensing area TA may include the sensing electrodes  520  and  540 . The sensing electrodes  520  and  540  may include a plurality of first sensing electrodes  520  and a plurality of second sensing electrodes  540 . 
     The first sensing electrodes  520  and the second sensing electrodes  540  may be electrically separated from each other. In an embodiment, the first sensing electrodes  520  may be sensing input electrodes, and the second sensing electrodes  540  may be sensing output electrodes. However, the invention is not limited thereto, and the first sensing electrodes  520  may be the sensing output electrodes, and the second sensing electrodes  540  may be the sensing input electrodes. 
     The first sensing electrodes  520  and the second sensing electrodes  540  may be alternately distributed so as to not overlap each other in the sensing area TA, and may be disposed in a mesh form. The first sensing electrodes  520  may be disposed in plural in a column direction and may be disposed in plural in a row direction, and the second sensing electrode  540  may also be disposed in plural in the column direction and may be disposed in plural in the row direction. The first sensing electrodes  520  may be connected to each other in the column direction by a plurality of first sensing electrode connectors  521 , and the second sensing electrodes  540  may be connected to each other in the row direction by a plurality of second sensing electrode connectors  541 . 
     The first sensing electrodes  520  and the second sensing electrodes  540  may be disposed in a same layer. In an embodiment, the first sensing electrodes  520  and the second sensing electrodes  540  may be disposed in different layers. The first sensing electrodes  520  and the second sensing electrodes  540  may have a rhombus shape, but the invention is not limited thereto. The first sensing electrode  520  and the second sensing electrode  540  may have a polygonal shape such as a quadrangle or a hexagon, or a circular or elliptical shape, and may be embodied in various shapes such as having a protrusion to improve sensitivity of a sensor. The first sensing electrodes  520  and the second sensing electrodes  540  may be formed or provided as a transparent conductor or an opaque conductor. In an embodiment, the first sensing electrodes  520  and the second sensing electrodes  540  may include a transparent conductive oxide (“TCO”), and the TCO may include at least one of an indium tin oxide (“ITO”), an indium zinc oxide (“IZO”), a zinc oxide (ZnO), a carbon nanotube (“CNT”), and graphene, for example. In addition, a plurality of openings may be defined in the first sensing electrodes  520  and the second sensing electrodes  540 . The openings defined in the sensing electrodes  520  and  540  serve to allow light emitted from a light emitting diode to be emitted to the front without interference. 
     The first sensing electrodes  520  may be electrically connected to each other by the first sensing electrode connectors  521  (also referred to as bridges), and the second sensing electrodes  540  may be electrically connected to each other by the second sensing electrode connectors  541 . When the first sensing electrodes  520  are connected to each other in a first direction, the second sensing electrodes  540  may be connected to each other in a second direction intersecting the first direction. When the first sensing electrodes  520  and the second sensing electrodes  540  are disposed in a same layer, one of the first sensing electrode connectors  521  and the second sensing electrode connectors  541  may be disposed at the same layer as that of the first sensing electrodes  520  and the second sensing electrodes  540 , and the other one may be disposed at a different layer from that of the first sensing electrodes  520  and the second sensing electrodes  540 . As a result, the first sensing electrodes  520  and the second sensing electrodes  540  may be electrically separated. The sensing electrode connector disposed in the different layer may be disposed at an upper layer or a lower layer of the first sensing electrodes  520  and the second sensing electrodes  540 , and in embodiments described below, descriptions will be made focusing on an embodiment in which the sensing electrode connector is disposed on the lower layer, i.e., a layer closer to the substrate. 
     The sensing wires  512  and  522  are respectively connected to the first sensing electrodes  520  and the second sensing electrodes  540  in the peripheral area PA. The sensing wires  512  and  522  may include the first sensing wires  512  and the second sensing wires  522 . The first sensing wire  512  may be connected to the second sensing electrodes  540  disposed in the row direction, and the second sensing wire  522  may be connected to the first sensing electrodes  520  disposed in the column direction. In an embodiment, the first sensing wire  512  and the second sensing wire  522  may be electrically connected to some of the pads PAD included in the pad portion  30  of  FIG. 1 . 
     In  FIG. 2 , a sensor of a mutual-cap type that senses a touch using two sensing electrodes  520  and  540  is illustrated. However, in an embodiment, it may be formed or provided as a sensor of self-cap type that senses a touch using only one sensing electrode. 
     Hereinafter, a display device in an embodiment will be further described with reference to  FIG. 3  illustrating a cross-sectional view in the display area DA. 
       FIG. 3  illustrates a cross-sectional view showing an embodiment of a portion of a display area in a display device. 
     As illustrated in  FIG. 3 , in the display device in the illustrated embodiment, the display area DA may include a substrate  100 , a semiconductor layer  131 , a transistor TFT including a gate electrode  124 , a source electrode  173 , and a drain electrode  175 , a gate insulating layer  120 , a first inter-insulating layer  160 , a second inter-insulating layer  180 , a pixel electrode  191 , an emission layer  370 , a bank layer  350 , a common electrode  270 , and an encapsulation layer  400 . Herein, the pixel electrode  191 , the emission layer  370 , and the common electrode  270  may constitute a light emitting diode LED. In addition, the display device further includes the sensing area TA disposed at an upper portion of the display area DA, and the sensing area TA includes a first sensing insulating layer  510 , the sensing electrodes  520  and  540 , and the second sensing electrode connectors  541 . In addition, the display device may further include a first insulating layer  550  and a second insulating layer  560  disposed above the sensing area TA. 
     The substrate  100  may include a material having a rigid characteristic such as glass, or a flexible material such as plastic or polyimide that is bendable. A buffer layer  111  for flattening a surface of the substrate  100  and blocking penetration of impurity elements may be further disposed on the substrate  100 . In an embodiment, the buffer layer  111  may include an inorganic material, and for example, may include an inorganic insulating material such as a silicon nitride (SiN x ), a silicon oxide (SiO x ), and a silicon oxynitride (SiO x N y ). The buffer layer  111  may have a single layer structure or a multi-layered structure of the material. A barrier layer (not illustrated) may be further disposed on the substrate  100 . In this case, the barrier layer may be disposed between the substrate  100  and the buffer layer  111 . The barrier layer may include an inorganic insulating material such as a silicon nitride (SiN x ), a silicon oxide (SiO x ), and a silicon oxynitride (SiO x N y ). The barrier layer may have a single layer structure or a multi-layered structure of the material. 
     The semiconductor layer  131  may be disposed on the substrate  100 . The semiconductor layer  131  may include any one of amorphous silicon, polycrystalline silicon, and an oxide semiconductor. In an embodiment, the semiconductor layer  131  may include low temperature polysilicon (“LTPS”), or may include an oxide semiconductor material including at least one of zinc (Zn), indium (In), gallium (Ga), tin (Sn), and a combination thereof, for example. In an embodiment, the semiconductor layer  131  may include an indium-gallium-zinc oxide (“IGZO”). The semiconductor layer  131  may include a channel region, a source region, and a drain region into which it is classified depending on whether or not doped with impurities. The source region and the drain region may have a conductive characteristic corresponding to a conductor. 
     The gate insulating layer  120  may cover the semiconductor layer  131  and the substrate  100 . In an embodiment, the gate insulating layer  120  may include an inorganic insulating material such as a silicon nitride (SiN x ), a silicon oxide (SiO x ), and a silicon oxynitride (SiO x N y ). The gate insulating layer  120  may have a single layer structure or a multi-layered structure of the material. 
     The gate electrode  124  may be disposed on the gate insulating layer  120 . In an embodiment, the gate electrode  124  may include a metal such as copper (Cu), molybdenum (Mo), aluminum (Al), silver (Ag), chromium (Cr), or tantalum (Ta), or a metal alloy thereof. The gate electrode  124  may be formed or provided as a single layer or a multilayer. A region of the semiconductor layer  131  that overlaps the planar gate electrode  124  may be a channel region. 
     The first inter-insulating layer  160  may cover the gate electrode  124  and the gate insulating layer  120 . In an embodiment, the first inter-insulating layer  160  may include an inorganic insulating material such as a silicon nitride (SiN x ), a silicon oxide (SiO x ), and a silicon oxynitride (SiO x N y ). The first inter-insulating layer  160  may have a single layer structure or a multi-layered structure of the material. 
     The source electrode  173  and the drain electrode  175  are disposed on the first inter-insulating layer  160 . The source electrode  173  and the drain electrode  175  may be connected to the source region and the drain region of the semiconductor layer  131  through openings defined in the first inter-insulating layer  160  and the gate insulating layer  120 , respectively. Accordingly, the semiconductor layer  131 , the gate electrode  124 , the source electrode  173 , and the drain electrode  175  described above constitute one transistor TFT, e.g., one thin film transistor. In an embodiment, the transistor TFT may include only the source region and the drain region of the semiconductor layer  131  instead of the source electrode  173  and the drain electrode  175 . 
     In an embodiment, the source electrode  173  and the drain electrode  175  may include a metal such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), tantalum (Ta), or the like, or a metal alloy thereof. The source electrode  173  and the drain electrode  175  may be formed or provided as a single layer or a multilayer. The source electrode  173  and the drain electrode  175  in an embodiment may be configured as a triple layer including an upper layer, an intermediate layer, and a lower layer, the upper layer and the lower layer may include titanium (Ti), and the intermediate layer may include aluminum (Al). 
     The second inter-insulating layer  180  may be disposed on the source electrode  173  and the drain electrode  175 . The second inter-insulating layer  180  covers the source electrode  173 , the drain electrode  175 , and the first inter-insulating layer  160 . The second inter-insulating layer  180 , which is for planarizing a surface of the substrate  100  provided with the transistor TFT, may be an organic insulating layer, and may include at least one material of a polyimide, a polyamide, an acrylic resin, benzocyclobutene, and a phenol resin. 
     The pixel electrode  191  may be disposed on the second inter-insulating layer  180 . The pixel electrode  191  is also referred to as an anode, and may be formed or provided as a single layer including a transparent conductive oxide film, a metal material, or as multiple layers including them. In an embodiment, the transparent conductive oxide layer may include an ITO, a poly-ITO, an IZO, an indium gallium zinc oxide (“IGZO”), an indium tin zinc oxide (“ITZO”), or the like. In an embodiment, the metal material may include silver (Ag), molybdenum (Mo), copper (Cu), gold (Au), and aluminum (Al). 
     A via hole  81  exposing the drain electrode  175  may be defined in a second inter-insulating layer  180 . The drain electrode  175  and the pixel electrode  191  may be physically and electrically connected through the via hole  81  of the second inter-insulating layer  180 . Accordingly, the pixel electrode  191  may receive an output current to be transferred from the drain electrode  175  to the emission layer  370 . 
     The bank layer  350  may be disposed on the pixel electrode  191  and the second inter-insulating layer  180 . The bank layer  350  is also referred to as a pixel defining layer (“PDL”), and a pixel opening  351  overlapping at least a portion of the pixel electrode  191  is defined in the bank layer  350 . In this case, the pixel opening  351  may overlap a central portion of the pixel electrode  191 , and may not overlap an edge portion of the pixel electrode  191 . As a result, a size of the pixel opening  351  may be smaller than that of the pixel electrode  191 . The bank layer  350  may define a formation position of the emission layer  370  such that the emission layer  370  may be disposed on a portion thereof where an upper surface of the pixel electrode  191  is exposed. The bank layer  350  may be formed or provided as an organic insulator including at least one material of a polyimide, a polyamide, an acryl resin, benzocyclobutene, and a phenol resin. In an embodiment, the bank layer  350  may be formed or provided as a black pixel define layer (“BPDL”) including a black pigment. 
     The emission layer  370  may be disposed within the pixel opening  351  defined by the bank layer  350 . The emission layer  370  may include an organic material that emits light such as red, green, and blue light. The emission layer  370  emitting red, green, and blue light may include a low molecular weight or high molecular weight organic material. In  FIG. 3 , the emission layer  370  is illustrated as a single layer, but in practice, an auxiliary layer such as an electron injection layer, an electron transport layer, a hole transport layer, and a hole injection layer may be included above and below the emission layer  370 , where the hole injection layer and the hole transport layer may be disposed below the emission layer  370 , and the electron transport layer and the electron injection layer may be disposed above the emission layer  370 . 
     The common electrode  270  may be disposed on the bank layer  350  and the emission layer  370 . In an embodiment, the common electrode  270  may be also referred to as a cathode, and may include a transparent conductive layer including an ITO, an IZO, an IGZO, an ITZO, etc. In addition, the common electrode  270  may have a translucent characteristic, and in this case, it may constitute a micro-cavity together with the pixel electrode  191 . According to such a micro-cavity structure, light of a predetermined wavelength is emitted to an upper part by the characteristics and spacing between both of the electrodes, and as a result, red, green, or blue light may be displayed. 
     The encapsulation layer  400  may be disposed on the common electrode  270 . The encapsulation layer  400  may include at least one inorganic layer and at least one organic layer. In the illustrated embodiment, the encapsulation layer  400  may include a first inorganic encapsulation layer  410 , an organic encapsulation layer  420 , and a second inorganic encapsulation layer  430 . However, this is merely an example, and numbers of inorganic and organic layers constituting the encapsulation layer  400  may be variously changed. The first inorganic encapsulation layer  410 , the organic encapsulation layer  420 , and the second inorganic encapsulation layer  430  may be disposed in a portion of the non-display area NA and the display area DA. In an embodiment, the organic encapsulation layer  420  may be formed or provided around the display area DA, and the first inorganic encapsulation layer  410  and the second inorganic encapsulation layer  430  may be formed or provided up to the non-display area NA. The encapsulation layer  400 , which is for protecting the light emitting diode LED from moisture or oxygen that may be introduced from the outside, may directly contact first ends of the first inorganic encapsulation layer  410  and the second inorganic encapsulation layer  430 . 
     A buffer layer  501  may be disposed on the encapsulation layer  400 . The buffer layer  501  may include an inorganic insulating layer, and an inorganic material included in the inorganic insulating layer may be at least one of a silicon nitride, an aluminum nitride, a zirconium nitride, a titanium nitride, a hafnium nitride, a tantalum nitride, a silicon oxide, an aluminum oxide, a titanium oxide, a tin oxide, a cerium oxide, and a silicon oxynitride. In an embodiment, the buffer layer  501  may be omitted. 
     A second sensing electrode connector  541 , the first sensing insulating layer  510 , and the plurality of sensing electrodes  520  and  540  may be disposed on the buffer layer  501 . One of the first sensing electrode connectors  521  and the second sensing electrode connector  541  may be disposed in a same layer as that of the sensing electrodes  520  and  540 , and the other may be disposed at a different layer from that of the sensing electrodes  520  and  540 . Hereinafter, an example in which the second sensing electrode connector  541  is disposed at a different layer from that of the sensing electrodes  520  and  540  will be described. 
     The second sensing electrode connector  541 , the first sensing insulating layer  510 , and the sensing electrodes  520  and  540  may constitute a sensing sensor. The sensing sensor may be classified into a resistive type, a capacitive type, an electro-magnetic type, and an optical type. The sensing sensor in an embodiment may be a capacitive type of sensor. 
     The second sensing electrode connector  541  may be disposed on the buffer layer  501 , and the first sensing insulating layer  510  may be disposed on the buffer layer  501  and the second sensing electrode connector  541 . The first sensing insulating layer  510  may include an inorganic insulating material or an organic insulating material. An inorganic insulating material may include at least one of a silicon nitride, an aluminum nitride, a zirconium nitride, a titanium nitride, a hafnium nitride, a tantalum nitride, a silicon oxide, an aluminum oxide, a titanium oxide, a tin oxide, a cerium oxide, and a silicon oxynitride. An organic insulating material may include at least one of an acrylic resin, a methacrylic resin, a polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin, and a perylene resin. 
     The sensing electrodes  520  and  540  may be disposed on the first sensing insulating layer  510 . The sensing electrodes  520  and  540  may include the first sensing electrodes  520  and the second sensing electrodes  540 . The first sensing electrodes  520  and the second sensing electrodes  540  may be electrically insulated. An opening exposing an upper surface of the second sensing electrode connector  541  may be defined in the first sensing insulating layer  510 , and the second sensing electrode connector  541  is connected to the second sensing electrodes  540  through the opening of the first sensing insulating layer  510  to electrically connect two adjacent second sensing electrodes  540 . The first sensing electrode connector  521  connecting the first sensing electrodes  520  is formed or provided in a same layer as that of the first sensing electrodes  520  and the second sensing electrodes  540 . 
     The sensing electrodes  520  and  540  may include a conductive material having good conductivity. In an embodiment, the sensing electrodes  520  and  540  may include a metal such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), tantalum (Ta), or the like, or a metal alloy thereof, for example. The sensing electrodes  520  and  540  may be configured as a single layer or a multilayer. In this case, an opening may be defined in the sensing electrodes  520  and  540  so that light emitted from the light emitting diode is emitted upward without interference. In an embodiment, the sensing electrodes  520  and  540  may be configured as a triple layer including an upper layer, an intermediate layer, and a lower layer, where the upper layer and the lower layer may include titanium (Ti), and the intermediate layer may include aluminum (Al). 
     A second sensing insulating layer  530  may be disposed on the sensing electrodes  520  and  540  and the first sensing insulating layer  510 . The second sensing insulating layer  530  may include an inorganic insulating material or an organic insulating material. In an embodiment, an inorganic insulating material may include at least one of a silicon nitride, an aluminum nitride, a zirconium nitride, a titanium nitride, a hafnium nitride, a tantalum nitride, a silicon oxide, an aluminum oxide, a titanium oxide, a tin oxide, a cerium oxide, and a silicon oxynitride. In an embodiment, an organic insulating material may include at least one of an acrylic resin, a methacrylic resin, a polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin, and a perylene resin. 
     A first insulating layer  550  is disposed on the second sensing insulating layer  530 . The first insulating layer  550  may include a light-transmitting organic insulating material having a low refractive index. In an embodiment, the first insulating layer  550  may include at least one of an acrylic resin, a polyimide resin, a polyamide resin, and Alq 3  [Tris(8-hydroxyquinolinato)aluminum], for example. The first insulating layer  550  may have a relatively smaller refractive index than that of a second insulating layer  560  to be described later. In an embodiment, the first insulating layer  550  may have a refractive index of about 1.40 to about 1.59, for example. 
     An opening  551  is defined in the first insulating layer  550 . The opening  551  refers to a portion where the second sensing insulating layer  530  is not covered by the first insulating layer  550 . The opening  551  of the first insulating layer  550  may overlap the pixel opening  351 . 
     A distance S 1  between the pixel opening  351  and the opening  551  of the first insulating layer  550  indicates a shortest distance between an edge of the pixel opening  351  and an edge of the opening  551 . The edge of the pixel opening  351  refers to a point where an edge of the bank layer  350  contacts the pixel electrode  191 . The edge of the opening  551  refers to a point where the edge of the first insulating layer  550  contacts the second sensing insulating layer  530 . 
     The second insulating layer  560  may be disposed on the second sensing insulating layer  530  and the first insulating layer  550 . The second insulating layer  560  may include a light-transmitting organic insulating material having a high refractive index. The second insulating layer  560  may have a relatively larger refractive index than that of the first insulating layer  550 . In an embodiment, the second insulating layer  560  may have a refractive index of about 1.60 to about 1.80, for example. 
     The second insulating layer  560  may be disposed within the opening  551  of the first insulating layer  550 . In this case, the second insulating layer  560  is in contact with a side surface of the first insulating layer  550 . Furthermore, the second insulating layer  560  may also be disposed on an upper surface of the first insulating layer  550  so as to contact the upper surface of the first insulating layer  550 . 
     Although not illustrated, a polarization layer including a linear polarizer and a retarder may be further disposed on the sensing area TA. In addition, a cover window for protecting the sensing area TA and the display area DA may be further disposed on the sensing area TA. In this case, an adhesive layer may be further disposed between the polarization layer and the cover window. 
     The sensing area TA may include the first insulating layer  550 , in which the opening  551  is defined, and the second insulating layer  560  disposed in the opening  551  of the first insulating layer  550 , thereby improving front visibility and light emission efficiency of the display device. That is, at least a portion of the light generated from the light emitting diode LED may be totally reflected at an interface between the first insulating layer  550  and the second insulating layer  560 , thereby condensing light to the front. 
     Light L generated from the emission layer  370  may be emitted in various directions, and enters the sensing area TA with various incident angles. In this case, at least some of the light L incident on the second insulating layer  560  of the sensing area TA is reflected at the interface between the first insulating layer  550  and the second insulating layer  560 . In particular, when an incident angle of the light L incident on the second insulating layer  560  is greater than a critical angle, the incident light L may be totally reflected at the interface between the first insulating layer  550  and the second insulating layer  560 . That is, the light L that is incident on the second insulating layer  560  having a relatively large refractive index may travel to the first insulating layer  550  having a relatively small refractive index, and may be totally reflected at the interface between the first insulating layer  550  and the second insulating layer  560 . 
     In this case, the interface between the first insulating layer  550  and the second insulating layer  560  may form a straight line parallel to the substrate  100  at a predetermined angle. The interface between the first insulating layer  550  and the second insulating layer  560  may be a side surface of the first insulating layer  550 . Accordingly, the side surface of the first insulating layer  550  may be inclined at a predetermined inclination angle θ with respect to the upper surface of the second sensing insulating layer  530 . That is, the side inclination angle θ of the first insulating layer  550  refers to an angle defined by the side surface of the first insulating layer  550  with respect to the upper surface of the second sensing insulating layer  530  in the opening  551  of the first insulating layer  550 . 
     In the display device in an embodiment, the side inclination angle θ of the first insulating layer  550  in the opening  551  of the first insulating layer  550  may be different depending on a position. Hereinafter, the inclination angle θ of the side surface of the first insulating layer  550  depending on a position of the opening  551  of the first insulating layer  550  will be described with reference to  FIG. 4  to  FIG. 6 . 
       FIG. 4  partially illustrates a top plan view of an embodiment of a display device,  FIG. 5  illustrates a cross-sectional view taken along line V-V of  FIG. 4 , and  FIG. 6  illustrates a cross-sectional view taken along line VI-VI of  FIG. 4 .  FIG. 4  illustrates an embodiment of a pixel opening and an opening of the first insulating layer of the display device.  FIG. 5  and  FIG. 6  illustrate an embodiment of some layers of a display device.  FIG. 5  and  FIG. 6  illustrate an embodiment of the pixel electrode  191  and layers disposed thereon. That is, layers disposed under the pixel electrode  191  are omitted. 
     As illustrated in  FIG. 4 , the opening  551  of the first insulating layer  550  of the display device in an embodiment may have a substantially polygonal shape in a plan view. 
     In an embodiment, the opening  551  of the first insulating layer  550  may have a quadrangular shape in a plan view, for example. In this case, the opening  551  of the first insulating layer  550  may have a polygonal shape with a corner portion chamfered in a plan view. The corner portion of the opening  551  of the first insulating layer  550  may be chamfered in a straight line or a curved line. However, the planar shape of the opening  551  of the first insulating layer  550  is not limited thereto, and may be variously changed. In an embodiment, the opening  551  of the first insulating layer  550  may have a circular shape or an oval shape, for example. 
     An edge of the opening  551  of the first insulating layer  550  may include a first region R 1  and a second region R 2  in a plan view. The first region R 1  may be a corner portion of the polygonal shape defining the opening  551  of the first insulating layer  550 , and the second region R 2  may be a portion other than the first region R 1 . A ratio of the first region R 1  to the second region R 2  at the edge of the opening  551  of the first insulating layer  550  may be less than 1. 
     As illustrated in  FIG. 5  and  FIG. 6 , the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be different from a side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 .  FIG. 5  illustrates the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1 , and  FIG. 6  illustrates the side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 . 
     The side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be smaller than the side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 . In an embodiment, the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be lower by 20 degrees or more than the side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 , for example. In the first region R 1 , the side inclination angle θ 1  of the first insulating layer  550  may be designed to be about 50 degrees, and in the second region R 2 , the side inclination angle θ 2  of the first insulating layer  550  may be designed to be about 70 degrees. In this case, assuming that a process error is at most 20 degrees, the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be about 30 degrees or more and about 70 degrees or less. The side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be about 30 degrees or less. In addition, in the second region R 2 , the side inclination angle θ 2  of the first insulating layer  550  may be about 50 degrees or more and about 90 degrees or less. 
     The opening  551  of the first insulating layer  550  may overlap the pixel opening  351 . A planar shape of the pixel opening  351  may be similar to that of the opening  551  of the first insulating layer  550 . The pixel opening  351  may have a substantially polygonal shape in a plan view. The pixel opening  351  may be defined inside the opening  551  of the first insulating layer  550  in a plan view. That is, the size of the opening  551  of the first insulating layer  550  may be larger than that of the pixel opening  351 . 
     The distance S 1  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the first region R 1  may be different from a distance S 2  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the second region R 2 . In an embodiment, the distance S 1  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the first region R 1  may be larger than the distance S 2  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the second region R 2 , for example. However, the invention is not limited thereto, and the distance S 1  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the first region R 1  may be the same as the distance S 2  between the pixel opening  351  and the opening  551  of the first insulating layer  550  in the second region R 2 . 
     Hereinafter, an effect of forming the side inclination angle θ of the first insulating layer  550  differently depending on the position will be described with further reference to  FIG. 7  to  FIG. 9 . 
       FIG. 7  illustrates fluidity of a material depending on an angle of a pattern when a predetermined material is applied onto a predetermined pattern.  FIG. 8  illustrates an opening of a first insulating layer in a reference example of a display device, and  FIG. 9  illustrates an embodiment of an opening of a first insulating layer in a display device. In  FIG. 8  and  FIG. 9 , a movement path of a material for forming a second insulating layer around an opening of the first insulating layer is illustrated. 
     As illustrated in  FIG. 7 , when a predetermined material is applied onto a predetermined pattern having an inclination angle α of about 0 degree, i.e., no inclination angle, the material may be smoothly spread. An initial angle at a point where a droplet is dropped is about 65 degrees, and it may be seen that it spreads smoothly from the point where the droplet is dropped. It may be seen that, when a predetermined material is applied onto a predetermined pattern having an inclination angle α of about 10 degrees, fluidity of the material is lowered compared to the case of about 0 degree. That is, the material applied onto the pattern moves to a point of the inclined portion, and then stops. When the inclination angle α of the predetermined pattern is more than about 20 degrees, the fluidity of the material is further lowered, so that the material applied onto the pattern cannot enter the inclined portion. That is, when the inclination angle α of the pattern is increased, the fluidity of the material applied onto the pattern may be lowered, thereby preventing the material from entering the inclined portion. 
     In the reference example of the display device, the side inclination angle of the first insulating layer may be constant, and in this case, the side inclination angle may be about 70 degrees or more. After the first insulating layer is formed or provided, a material for forming the second insulating layer may be applied to form the second insulating layer thereon. In this case, the material for forming the second insulating layer applied onto the first insulating layer may move in various directions. As illustrated in  FIG. 8 , in the reference example of the display device, the material for forming the second insulating layer may not enter the opening  551  of the first insulating layer due to a high side inclination of the first insulating layer. The first insulating layer may include a plurality of openings  551 , and the material for forming the second insulating layer may not be disposed in some of the openings  551 . Accordingly, in the reference example of the display device, the second insulating layer may not be entirely uniformly formed or disposed on the substrate. In this case, a method of thickly forming the second insulating layer may be considered in order to uniformly form the second insulating layer, and as a result, a thickness of the display device may be increased. In addition, other problems may occur in a post-process, and when applied to a foldable product, there are problems such as deterioration of impact resistance. 
     In the display device in the embodiment, the material for forming the second insulating layer may smoothly enter the opening  551  of the first insulating layer by forming a relatively low side inclination angle of the first insulating layer in the first region R 1 . That is, the movement path of the material for forming the second insulating layer may be formed or provided by the low inclination angle of the first insulating layer in the first region R 1 . The openings  551  may be defined in the first insulating layer, and the material for forming the second insulating layer may be entirely disposed in the openings  551 . Accordingly, in the display device in the embodiment, the second insulating layer may be uniformly formed or provided with a thin thickness. Accordingly, an overall thickness of the display device may be reduced, problems occurring in post-processing may be solved, and it may be stably used for foldable products. 
     In addition, in the display device in the embodiment, light that is incident on the interface between the first insulating layer and the second insulating layer may be totally reflected and condensed to the front of the display device by forming a relatively high side inclination angle of the first insulating layer in the second region R 2 . That is, it is possible to improve light emission efficiency at the front of the display device. 
     In this case, a ratio of the first region R 1  to the second region R 2  at an edge of the openings  551  of the first insulating layer may be variously changed. In this case, the ratio of the first region R 1  to the second region R 2  may be less than 1. When the ratio of the first region R 1  to the second region R 2  is set too low, the movement path of the material for forming the second insulating layer may be reduced, so that uniform formation of the second insulating layer may be difficult. When the ratio of the first region R 1  to the second region R 2  is set too high, the light emission efficiency of the front of the display device may be relatively lowered. Accordingly, the ratio of the first region R 1  to the second region R 2  may be appropriately selected so as to increase the front emission efficiency of the display device while uniformly forming the second insulating layer. In an embodiment, the ratio of the first region R 1  to the second region R 2  may be about 1% or more and about 20% or less, for example. 
     Hereinafter, a photomask for defining an opening of a first insulating layer of a display device in an embodiment will be described with reference to  FIG. 10  to  FIG. 21 . 
       FIG. 10  to  FIG. 21  illustrate top plan views showing various embodiments of a photomask for defining an opening in a first insulating layer of a display device. 
     The first insulating layer of the display device in the embodiment may include a negative type of photosensitive material. First, the material for forming the first insulating layer is entirely applied, and after the photomask is matched, an exposure process is performed. In this case, a portion exposed to light remains in the first insulating layer, and a portion masked by a pattern of the photomask is removed to define an opening. However, the invention is not limited thereto, and the first insulating layer of the display device in the embodiment may include a positive type of photosensitive material. In this case, the pattern of the photomask for defining the opening of the first insulating layer may be reversely formed or provided. 
     As illustrated in  FIG. 10 , a photomask  900  for defining an opening of a first insulating layer of a display device in an embodiment may include a center pattern  910  having a substantially polygonal shape and a peripheral pattern  920  disposed adjacent to a corner portion of the center pattern  910 . 
     The center pattern  910  may have a polygonal shape, e.g., a quadrangular shape. In this case, the corner portion of the center pattern  910  may be chamfered in a straight line or a curved line. 
     The peripheral pattern  920  may be disposed at each corner portion of the center pattern  910 . When the center pattern  910  has the quadrangular shape, the peripheral pattern  920  may be disposed at each of the four corner portions of the center pattern  910 . That is, four peripheral patterns  920  may be disposed adjacent to one center pattern  910 . 
     The peripheral patterns  920  may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, a length of the rods may gradually increase as they move away from the center pattern  910 . A width of the rods may be constant. 
     As illustrated in  FIG. 11  to  FIG. 21 , the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may include the center pattern  910  and the peripheral pattern  920 . A shape of the center pattern  910  in the photomask  900  illustrated in  FIG. 11  to  FIG. 21  is substantially the same as that of the photomask illustrated in  FIG. 10 , and a shape of the peripheral pattern  920  may be different from that of the photomask illustrated in  FIG. 10 . Hereinafter, various shapes of the peripheral pattern  920  will be described. 
     As illustrated in  FIG. 11 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, the rods may have a constant length. A width of the rods may be constant. 
     As illustrated in  FIG. 12 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, a length of the rods may gradually increase as they move away from the center pattern  910 . A width of the rods may be constant. A distance between adjacent rods may gradually increase as a distance from the center pattern  910  increases. 
     As illustrated in  FIG. 13 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, the rods may have a constant length. A width of the rods may be constant. A distance between adjacent rods may gradually increase as a distance from the center pattern  910  increases. 
     As illustrated in  FIG. 14 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, a length of the rods may gradually increase as they move away from the center pattern  910 . A width of the rods may gradually decrease as they move away from the center pattern  910 . A distance between adjacent rods may increase as the distance from the center pattern  910  increases. 
     As illustrated in  FIG. 15 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, the rods may have a constant length. A width of the rods may decrease as the distance from the center pattern  910  increases. A distance between adjacent rods may increase as the distance from the center pattern  910  increases. 
     As illustrated in  FIG. 16 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, the rod shape may be formed or provided in a shape that is bent at least once. A length of the rods may be constant. A width of the rods may be constant. A distance between adjacent rods may increase as the distance from the center pattern  910  increases. 
     As illustrated in  FIG. 17 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged side by side. In this case, the rods may extend in a direction that is perpendicular to the corner portion of the center pattern  910 . The length of the rods may be constant, and the width of the rods may be constant. 
     As illustrated in  FIG. 18 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of rod shapes is arranged to have a fan shape. In this case, a first end of the rods is gathered at a point that is adjacent to the corner portion of the center pattern  910 , and a second end of the rods is spaced apart at a predetermined interval. A length and a width of the rods may be constant. 
     As illustrated in  FIG. 19 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may have a rod shape. In this case, one rod shape may be disposed so as to be adjacent to each corner portion of the center pattern  910 . The rods may extend in a direction that is perpendicular to the corner portion of the center pattern  910 . 
     As illustrated in  FIG. 20 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may be formed or provided in a form in which a plurality of quadrangles has a triangular shape. In this case, a number of quadrangles may increase as the distance from the corner portion of the center pattern  910  increases. 
     As illustrated in  FIG. 21 , the peripheral pattern  920  of the photomask  900  for defining the opening of the first insulating layer of the display device in the embodiment may have a trapezoid shape. In this case, the peripheral pattern  920  may gradually have a wider width as the distance from the center pattern  910  increases. In this case, the center pattern  910  may be a full-tone pattern, and the peripheral pattern  920  may be a half-tone pattern. 
     The opening of the first insulating layer of the display device in an embodiment may be defined by various photomasks  900  as illustrated in  FIG. 10  to  FIG. 21 . In this case, an opening corresponding to the shape of the substantially center pattern  910  may be defined, and the opening may have relatively low inclination. 
     Next, a display device in an embodiment will be described with reference to  FIG. 22 . 
     Since the display device in the embodiment illustrated in  FIG. 22  is substantially the same as the display device in the embodiment shown in  FIG. 1  to  FIG. 6 , a description of the same parts will be omitted. In the illustrated embodiment, the positions of the first region and the second region are different from those of the previous embodiment, and this will be further described below. 
       FIG. 22  partially illustrates a top plan view of a display device.  FIG. 22  illustrates a pixel opening and an opening of the first insulating layer of the display device. 
     As illustrated in  FIG. 22 , the opening  551  of the first insulating layer of the display device in an embodiment may have a substantially polygonal shape in a plan view. In an embodiment, the opening  551  of the first insulating layer may be defined in a quadrangular shape, and each corner portion of the quadrangle may be chamfered in a straight line or a curved line, for example. 
     An edge of the opening  551  of the first insulating layer may include a first region R 1  and a second region R 2  in a plan view. The first region R 1  may be a central portion of each side of a quadrangle defining the opening  551  of the first insulating layer  550 , and the second region R 2  may be a portion other than the first region R 1 . The second region R 2  may include each corner portion of the quadrangle defining the opening  551  of the first insulating layer and a periphery thereof. In this case, the ratio of the first region R 1  to the second region R 2  may be less than 1. 
     A side inclination angle of the first insulating layer in the first region R 1  may be smaller than a side inclination angle of the first insulating layer in the second region R 2 . In the previous embodiment, the first region R 1  may be disposed at each corner portion of the quadrangle, and in the illustrated embodiment, the first region R 1  may be disposed at a central portion of each side of the quadrangle. 
     Since the side inclination angle of the first insulating layer in the first region R 1  is relatively low, the light emission efficiency toward the front in the first region R 1  may be relatively low. In the previous embodiment, a corner portion having a relatively far distance between the pixel opening  351  and the opening  551  of the first insulating layer may be set as the first region R 1 , thereby minimizing a decrease in light emission efficiency. When the distance between the pixel opening  351  and the opening  551  of the first insulating layer is substantially the same in all regions, a position of the first region R 1  may not significantly affect the light emission efficiency. Accordingly, the position of the first region R 1  may be variously changed. In an embodiment, as in the illustrated embodiment, the first region R 1  may be disposed at the central portion of each side of the quadrangle defining the opening  551  of the first insulating layer, or may be disposed at a point that is inclined to one side from the central portion, for example. 
     Next, a display device in an embodiment will be described with reference to FIG.  23  and  FIG. 24 . 
     Since the display device in the embodiment illustrated in  FIG. 23  and  FIG. 24  is substantially the same as the display device in the embodiment shown in  FIG. 1  to  FIG. 6 , a description of the same parts will be omitted. The illustrated embodiment differs from the previous embodiment in that the inclination of the side surface of the first insulating layer is made in a stepped shape, and will be further described below. 
       FIG. 23  and  FIG. 24  illustrate an embodiment of some layers of a display device. As illustrated in  FIG. 23  and  FIG. 24 , the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be different from a side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 . The side inclination angle θ 1  of the first insulating layer  550  in the first region R 1  may be smaller than the side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 .  FIG. 23  illustrates the side inclination angle θ 1  of the first insulating layer  550  in the first region R 1 , and  FIG. 24  illustrates the side inclination angle θ 2  of the first insulating layer  550  in the second region R 2 . 
     In the previous embodiment, the inclination of the side surface of the first insulating layer  550  may be formed or provided in a continuous straight line or curved shape. In the illustrated embodiment, the inclination of the side surface of the first insulating layer  550  may have a step shape. When the inclination of the side surface of the first insulating layer  550  has the step shape, the inclination angle of the side surface of the first insulating layer  550  may be an angle defined between a virtual line connecting successively disposed steps and an upper surface of the second sensing insulating layer  530 . 
     The shape of the inclined portion of the side surface of the first insulating layer  550  is not limited thereto, and the shape of the photomask for patterning the first insulating layer  550 , an exposure amount, an exposure time, a material constituting the first insulating layer  550 , a type of developer, or the like may be variously changed. 
     Next, a display device in an embodiment will be described with reference to  FIG. 25  to  FIG. 27 . 
     Since the display device in the embodiment illustrated in  FIG. 25  to  FIG. 27  is substantially the same as the display device in the embodiment shown in  FIG. 1  to  FIG. 6 , a description of the same parts will be omitted. The illustrated embodiment differs from the previous embodiment in that the inclination of the side surface of the bank layer is different depending on a position thereof, and will be further described below. 
       FIG. 25  partially illustrates a top plan view of an embodiment of a display device in an embodiment,  FIG. 26  illustrates a cross-sectional view taken along line XXVI-XXVI of  FIG. 25 , and  FIG. 27  illustrates a cross-sectional view taken along line XXVII-XXVII of  FIG. 25 .  FIG. 25  illustrates an embodiment of a pixel opening and an opening of the first insulating layer of the display device.  FIG. 26  and  FIG. 27  illustrate an embodiment of some layers of a display device. 
     As illustrated in  FIG. 25 , the pixel opening  351  of the display device in the embodiment may have a substantially polygonal shape in a plan view. In an embodiment, the pixel opening  351  may have a quadrangular shape in a plan view, for example. In this case, the pixel opening  351  may have a polygonal shape having a chamfered corner in a plan view. In this case, the corner portion of the pixel opening  351  may be chamfered in a straight line or a curved line. However, the planar shape of the pixel opening  351  is not limited thereto, and may be variously changed. In an embodiment, the pixel opening  351  may have a circular shape or an oval shape, for example. 
     An edge of the pixel opening  351  may include a first region R 11  and a second region R 22  in a plan view. The first region R 11  may be a corner portion of the polygonal shape forming the pixel opening  351 , and the second region R 22  may be a portion other than the first region R 11 . A ratio of the first region R 11  to the second region R 22  at the edge of the pixel opening  351  may be less than 1. 
     As illustrated in  FIG. 26  and  FIG. 27 , a side inclination angle θ 11  of the bank layer  350  in the first region R 11  may be different from a side inclination angle θ 22  of the bank layer  350  in the second region R 2 .  FIG. 26  illustrates the side inclination angle θ 11  of the bank layer  350  in the first region R 1 , and  FIG. 27  illustrates the side inclination angle θ 22  of the bank layer  350  in the second region R 2 . 
     The side inclination angle θ 11  of the bank layer  350  in the first region R 11  may be smaller than the side inclination angle θ 22  of the bank layer  350  in the second region R 2 . In an embodiment, the side inclination angle θ 11  of the bank layer  350  in the first region R 11  may be lower by 20 degrees or more than the side inclination angle θ 22  of the bank layer  350  in the second region R 22 , for example. In the first region R 11 , the side inclination angle θ 11  of the bank layer  350  may be designed to be about 50 degrees, and in the second region R 22 , the side inclination angle θ 22  of the bank layer  350  may be designed to be about 70 degrees. In this case, assuming that a process error is at most 20 degrees, the side inclination angle θ 11  of the bank layer  350  in the first region R 11  may be about 30 degrees or more and about 70 degrees or less. The side inclination angle θ 11  of the bank layer  350  in the first region R 11  may be about 30 degrees or less. In addition, in the second region R 22 , the side inclination angle θ 22  of the bank layer  350  may be about 50 degrees or more and about 90 degrees or less. 
     The encapsulation layer  400  may be formed or disposed on the bank layer  350 , and the encapsulation layer  400  may include an organic encapsulation layer  420 . The side surface of the bank layer  350  has a constant inclination angle, and in the case of having a high inclination angle, the material for forming the organic encapsulation layer  420  may not enter the pixel opening  351  of the bank layer  350 . 
     In the display device in the embodiment, the material for forming the bank layer  350  may smoothly enter the pixel opening  351  of the bank layer  350  by forming a relatively low side inclination angle of the bank layer  350  in the first region R 11 . That is, a movement path of the material for forming the encapsulation layer may be formed or provided by the low inclination angle of the bank layer  350  in the first region R 11 . A plurality of pixel openings  351  may be defined in the bank layer  350 , and the material for forming the encapsulation layer may be entirely disposed in the pixel openings  351 . Accordingly, in the display device in an embodiment, the encapsulation layer may be uniformly formed or provided with a thin thickness. Accordingly, an overall thickness of the display device may be reduced, problems occurring in post-processing may be solved, and it may be stably used for foldable products. 
     In the display device in an embodiment, the side inclination angle θ of the first insulating layer  550  in the opening  551  of the first insulating layer  550  may be constant. However, the invention is not limited thereto, and the side inclination angle of the first insulating layer  550  in the opening  551  of the first insulating layer  550  may be different according to a position. 
     While this invention has been described in connection with what is presently considered to be practical 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 invention.