Abstract:
A display device includes: a substrate; a static electricity shielding member formed on the substrate; a scan line formed on the substrate and transferring a scan signal; a data line and a driving voltage line intersecting the scan line, being insulated therefrom and each transferring a data signal and a driving voltage; a thin film transistor formed on the static electricity shielding member; a first sacrifice electrode connected to the static electricity shielding member; and a second sacrifice electrode positioned under the first sacrifice electrode to form a sacrifice capacitor.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 5 Jan. 2015 and there duly assigned Serial No. 10-2015-0000692. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Disclosure 
         [0003]    The present invention relates to a display device, and more specifically, to a display device preventing static electricity from disadvantageously affecting a switching element of the display device. 
         [0004]    2. Description of the Related Art 
         [0005]    An organic light emitting diode display device generally includes a cathode, an anode and an organic emission layer disposed therebetween and forms excitons by combining electrons injected from the cathode with holes injected from the anode at the organic emission layer and emits light by allowing the excitons to emit energy. 
         [0006]    The organic light emitting diode display device generally includes a plurality of pixels including an organic light emitting diode which includes a cathode, an anode, and an organic emission layer, and each pixel is provided with a plurality of transistors for driving the organic light emitting diode and a capacitor. 
         [0007]    A thickness of an insulating layer which insulates metals from one and another such as a scan line and a data line forming the transistor is typically thin as much as about 1000 Å; therefore, the insulating layer is vulnerable to static elasticity. Further, when each driving circuit has points which are vulnerable to static electricity, the static electricity is continuously generated at the points which are vulnerable to the static electricity. That is, since a separate pattern is not formed under the scan line, when the static electricity is introduced into the scan line, an outlet through which the static electricity is discharged is not present. Therefore, the static electricity is generated at a transistor adjacent to the scan line. In this case, the scan line is connected to the semiconductor layer and thus short-circuit occurs. Due to the short-circuit, dark points occur in a pixel. 
         [0008]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made in an effort to provide a display device having an advantage of guiding static electricity to a place where the static electricity does not affect a switching element. 
         [0010]    An exemplary embodiment of the present invention provides a display device including: a substrate; a static electricity shielding member formed on the substrate; a scan line formed on the substrate and transferring a scan signal; a data line and a driving voltage line intersecting the scan line, being insulated therefrom and the data line transferring a data signal and the driving voltage line transferring a driving voltage; a thin film transistor formed on the static electricity shielding member; a first sacrifice electrode connected to the static electricity shielding member; and a second sacrifice electrode positioned under the first sacrifice electrode to form a sacrifice capacitor together with the first sacrifice electrode. 
         [0011]    The thin film transistor may include: a semiconductor layer formed to overlap the static electricity shielding member; a gate electrode formed on the semiconductor layer and extending from the scan line, and a source electrode and a drain electrode formed on the gate electrode and connected to the semiconductor layer. 
         [0012]    The static electricity shielding member may be formed to be larger than the semiconductor layer. 
         [0013]    The first sacrifice electrode may be formed on the same layer as the gate electrode. 
         [0014]    The first sacrifice electrode may be made of the same material as the gate electrode. 
         [0015]    The second sacrifice electrode may be formed on the same layer as the semiconductor layer. 
         [0016]    The second sacrifice electrode may be made of the same material as the semiconductor layer. 
         [0017]    The static electricity shielding member may be made of metal, polysilicon, or oxide semiconductor. 
         [0018]    The semiconductor layer may be made of polysilicon or oxide semiconductor. 
         [0019]    The display device may further include: a buffer layer covering the static electricity shielding member, while being positioned between the static electricity shielding member and the semiconductor layer; a gate insulating layer covering the semiconductor layer, while being positioned between the semiconductor layer and the gate electrode; and an interlayer insulating layer covering the gate electrode, while being positioned between the gate electrode and the source electrode and drain electrode. 
         [0020]    The buffer layer and the gate insulating layer may include a first contact hole through which the static electricity shielding member and the first sacrifice electrode are connected to each other. 
         [0021]    The display device may further include a ground electrode connected to the second sacrifice electrode. 
         [0022]    The gate insulating layer may include a second contact hole through which the second sacrifice electrode and the ground electrode are connected to each other. 
         [0023]    The ground electrode may be formed on the same layer as the gate electrode. 
         [0024]    The ground electrode may be made of the same material as the gate electrode. 
         [0025]    The ground electrode may be applied with a constant potential voltage. 
         [0026]    The display device may further include an organic light emitting diode connected to the thin film transistor. 
         [0027]    In the above-mentioned technical problems of the present invention, other features and advantages of the present invention will be described below or will be clearly understood to those skilled in the art from the technology and description. 
         [0028]    According to an exemplary embodiment of the present invention, the following effects may be obtained. 
         [0029]    According to an exemplary embodiment of the present invention, the static electricity shielding member positioned under the semiconductor layer and the parasitic capacitor Cst 2  connected to the static electricity shielding member are formed and thus the outside static electricity is previously transferred to the parasitic capacitor Cst along the static electricity shielding member before the semiconductor layer and the gate electrode are short-circuited from each other, thereby protecting the transistor. 
         [0030]    Further, other features and advantages may be newly understood based on the exemplary embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
           [0032]      FIG. 1  is an equivalent circuit diagram of a pixel of an organic light emitting diode display device according to an exemplary embodiment of the present invention. 
           [0033]      FIG. 2  is a layout view of one pixel of the organic light emitting diode display device according to the exemplary embodiment of the present invention. 
           [0034]      FIG. 3  is a cross-sectional view taken along the line III-III of  FIG. 2 . 
           [0035]      FIG. 4  is a cross-sectional view taken along the line IV-IV of  FIG. 2 . 
           [0036]      FIG. 5  is an equivalent circuit diagram of a pixel of an organic light emitting diode display device according to another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0037]    Hereinafter, several exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present invention pertains may easily practice the present invention. The present invention may be implemented in various different forms and is not limited to exemplary embodiments provided herein. 
         [0038]    Portions unrelated to the description will be omitted in order to obviously describe the present invention, and similar components will be denoted by the same reference numerals throughout the present specification. 
         [0039]    In addition, since sizes and thicknesses of the respective components shown in the accompanying drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to contents shown in the accompanying drawings. 
         [0040]    In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In addition, in the accompanying drawings, thicknesses of some of layers and regions have been 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. 
         [0041]    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. 
         [0042]    Further, a display device according to an exemplary embodiment of the present invention includes an organic light emitting diode display device, a liquid crystal display device, and the like. 
         [0043]    Hereinafter, an organic light emitting diode display device according to an exemplary embodiment of the present invention will be described with reference to  FIGS. 1 through 4 . 
         [0044]      FIG. 1  is an equivalent circuit diagram of a pixel of an organic light emitting diode display device according to an exemplary embodiment of the present invention, in which the organic light emitting diode display device is an active matrix (AM) type organic light emitting diode display device having a 2Tr 2Cap structure in which two transistors (TFTs) and two capacitors are included in one pixel. 
         [0045]    As illustrated in  FIG. 1 , the organic light emitting device according to the exemplary embodiment of the present invention includes a plurality of signal lines  121 ,  123 ,  171 , and  172  and a plurality of pixels PXs which are connected to the signal lines and are arranged in substantially a matrix form. 
         [0046]    The signal line includes a plurality of scan lines  121  which transfer scan signals (or gate signals), a plurality of data lines  171  which transfer data signals, a plurality of driving voltage lines  172  which transfer a driving voltage ELVDD, and a constant potential voltage line  123  which transfers a constant potential voltage. The scan lines  121  extend in substantially a row direction and are substantially parallel with each other and the data line  171 , the constant potential voltage line  123 , and the driving voltage line  172  extend in substantially a column direction and are substantially parallel with each other. Each pixel PX includes a switching transistor T 1 , a driving transistor T 2 , a storage capacitor Cst 1 , a sacrifice capacitor Cst 2 , and an organic light emitting diode (OLED). 
         [0047]    The switching transistor T 1  includes a control terminal, an input terminal, and an output terminal, in which the control terminal is connected to the scan line  121 , the input terminal is connected to the data line  171 , and the output terminal is connected to the driving transistor T 2 . The switching transistor T 1  transfers the data signal applied to the data line  171  to the driving transistor T 2  in response to the scan signal applied to the scan line  121 . 
         [0048]    The driving transistor T 2  also has a control terminal, an input terminal, and an output terminal, in which the control terminal is connected to the switching transistor T 1 , the input terminal is connected to the driving voltage line  172 , and the output terminal is connected to the organic light emitting diode (OLED). The driving transistor T 2  transfers an output current Id of which the magnitude varies in dependence upon a voltage applied between the control terminal and the output terminal. 
         [0049]    The storage capacitor Cst 1  is connected between the control terminal and the input terminal of the driving transistor T 2 . The storage capacitor Cst 1  charges the data signal applied to the control terminal of the driving transistor T 2  and maintains the charged data signal even after the switching transistor T 1  is turned off. 
         [0050]    The sacrifice capacitor Cst 2  is connected between the first sacrifice electrode connected to the constant potential voltage line  123  and the second sacrifice electrode connected to the static electricity shielding member which is positioned under the semiconductor layer of the switching transistor T 1  and the driving transistor T 2 . The sacrifice capacitor Cst 2  prevents static electricity from the outside from being transferred to the switching transistor T 1  and the driving transistor T 2 . 
         [0051]    The organic light emitting diode (OLED) has an anode connected to the output terminal of the driving transistor T 2  and a cathode connected to a common voltage ELVSS. The organic light emitting diode (OLED) emits light of which the intensity varies depending on the output current Id of the driving transistor T 2  to display an image. 
         [0052]    The switching transistor T 1  and the driving transistor T 2  may be an n-channel field effect transistor (FET) or a p-channel field effect transistor. Further, a connection relationship of the transistors T 1  and T 2 , the storage capacitor Cst 1 , and the organic light emitting diode (OLED) may be changed. 
         [0053]    Next, a detailed structure of the pixel of the organic light emitting diode display device illustrated in  FIG. 1  will be described in detail with reference to  FIGS. 2 through 4 , along with  FIG. 1 . 
         [0054]      FIG. 2  is a layout view of one pixel of the organic light emitting diode display device according to the exemplary embodiment of the present invention,  FIG. 3  is a cross-sectional view taken along the line III-III of  FIG. 2 , and  FIG. 4  is a cross-sectional view taken along the line IV-IV of  FIG. 2 . 
         [0055]    In reference to  FIGS. 2 through 4 , the organic light emitting diode display device according to the exemplary embodiment of the present invention includes the static electricity shielding member  131 , the switching transistor T 1 , the driving transistor T 2 , and the sacrifice capacitor Cst 2 . 
         [0056]    The substrate  110  may be an insulating flexible substrate which is made of glass, quartz, ceramic, plastic, or the like. 
         [0057]    The static electricity shielding member  131  is formed on the substrate  110 . The static electricity shielding member  131  is formed to overlap the switching transistor T 1  and the driving transistor T 2 . 
         [0058]    The static electricity shielding member  131  prevents static electricity introduced from the outside of the substrate  110  from being introduced into the switching transistor T 1  and the driving transistor T 2 . 
         [0059]    The static electricity shielding member  131  is formed to be larger than a switching semiconductor layer  135   a  and a driving semiconductor layer  135   b  to be described below to prevent the static electricity from being introduced into the switching semiconductor layer  135   a  and the driving semiconductor layer  135   b.    
         [0060]    In this case, the static electricity shielding member  131  may be made of metal, polysilicon, or oxide semiconductor. 
         [0061]    A buffer layer  120  which covers the static electricity shielding member  131  is formed on the substrate  110 . The buffer layer  120  may have a single layer structure made of silicon nitride (SiNx) or a double layer structure in which silicon nitride (SiNx) and silicon oxide SiO 2  are stacked. The buffer layer  120  serves to planarize a surface while preventing permeation of unnecessary components, such as impurities and moisture. 
         [0062]    The switching semiconductor layer  135   a  and the driving semiconductor layer  135   b  are formed on the buffer layer  120 , being spaced apart from each other. Further, the static electricity shielding member  131  enclosing the switching semiconductor layer  135   a  is formed on the buffer layer  120 . In  FIG. 2 , the static electricity shielding member  131  encloses the switching semiconductor layer  135   a  in a quadrangular shape but is not limited thereto, and therefore, the static electricity shielding member may enclose the switching semiconductor layer  135   a  in various shapes. 
         [0063]    The switching semiconductor layer  135   a , the driving semiconductor layer  135   b , and a second sacrifice electrode  136  are formed on the buffer layer  120 , being spaced apart from one another. 
         [0064]    The semiconductor layer  135   a  and  135   b  and the second sacrifice electrode  136  may be made of polysilicon or oxide semiconductor, in which the oxide semiconductor may include any one of oxide which is based on titanium (Ti), hafnium (Hf), zirconium (Zr), aluminum (Al), tantalum (Ta), germanium (Ge), zinc (Zn), gallium (Ga), tin (Sn), or indium (In), and any one of zinc oxide (ZnO), indium-gallium-zinc oxide (InGaZnO4), indium-zinc oxide (Zn—In—O), zinc-tin oxide (Zn—Sn—O), indium-gallium oxide (In—Ga—O), indium-tin oxide (In—Sn—O), indium-zirconium oxide (In—Zr—O), indium-zirconium-zinc oxide (In—Zr—Zn—O), indium-zirconium-tin oxide (In—Zr—Sn—O), indium-zirconium-gallium oxide (In—Zr—Ga—O), indium-aluminum oxide (In—Al—O), indium-zinc-aluminum oxide (In—Zn—Al—O), indium-tin-aluminum oxide (In—Sn—Al—O), indium-aluminum-gallium oxide (In—Al—Ga—O), indium-tantalum oxide (In—Ta—O), indium-tantalum-zinc oxide (In—Ta—Zn—O), indium-tantalum-tin oxide (In—Ta—Sn—O), indium-tantalum-gallium oxide (In—Ta—Ga—O), indium-germanium oxide (In—Ge—O), indium-germanium-zinc oxide (In—Ge—Zn—O), indium-germanium-tin oxide (In—Ge—Sn—O), indium-germanium-gallium oxide (In—Ge—Ga—O), titanium-indium-zinc oxide (Ti—In—Zn—O), hafnium-indium-zinc oxide (Hf—In—Zn—O), all of which are composite oxides thereof. When the semiconductor layers  135   a  and  135   b  are made of the oxide semiconductor, a separate passivation layer may be added to protect the oxide semiconductor which is vulnerable to external environments, such as high temperature. 
         [0065]    The semiconductor layers  135   a  and  135   b  include a channel region which is not doped with impurities and a source region and a drain region formed by doping both sides of the channel region with impurities. Here, these impurities may be changed depending on a kind of transistor and may be N-type or P-type impurities. 
         [0066]    The switching semiconductor layer  135   a  and the driving semiconductor layer  135   b  are each divided into a channel region  1355  and a source region  1356  and a drain region  1357  which are each formed at both sides of a channel region  1355 . The channel region  1355  of the switching semiconductor layer  135   a  and the driving semiconductor layer  135   b  may include polysilicon which is not doped with impurity, that is, intrinsic semiconductor and the source region  1356  and the drain region  1357  of the switching semiconductor layer  135   a  and the driving semiconductor layer  135   b  may include polysilicon which is doped with conductive impurity, that is, impurity semiconductor. 
         [0067]    The gate insulating layer  140  is formed on the switching semiconductor layer  135   a , the driving semiconductor layer  135   b , and the second sacrifice electrode  136 . The gate insulating layer  140  may be a single layer or a plurality of layers including at least one of silicon nitride and silicon oxide. 
         [0068]    The scan line  121 , a driving gate electrode  125   b , a first storage plate of electricity  128 , a first sacrifice electrode  122 , and a ground electrode  123  are formed on the gate insulating layer  140 . The scan line  121  extends in a horizontal direction to transfer the scan signal and includes a switching gate electrode  125   a  which protrudes from the scan line  121  to the switching semiconductor layer  135   a . The driving gate electrode  125   b  protrudes from the first storage plate of electricity  128  to the semiconductor layer  135   b . The switching gate electrode  125   a  and the driving gate electrode  124   b  each overlap the channel region  1355 . 
         [0069]    The first sacrifice electrode  122  is included in the buffer layer  120  and the gate insulating layer  140  and is thus electrically connected to the static electricity shielding member  131  through a first contact hole  63  through which the static electricity shielding member  131  is exposed. 
         [0070]    The gate insulating layer  140  includes a second contact hole through which the second sacrifice electrode  136  is exposed. 
         [0071]    The ground electrode  123  is connected to the second sacrifice electrode  136  through the second contact hole  64  and is applied with a constant potential voltage. The exemplary embodiment of the present invention describes that the second sacrifice electrode  136  is applied with the constant potential voltage through the ground electrode  123  which is formed on different layers but is not limited thereto, and therefore, the constant potential voltage may be directly applied to the second sacrifice electrode  136 . 
         [0072]    The first sacrifice electrode  122  forms the sacrifice capacitor Cst 2 , along with the second sacrifice electrode  136 . 
         [0073]    The static electricity introduced from the outside of the substrate  110  into the semiconductor layers  135   a  and  135   b  is first introduced the static electricity shielding member  131  prior to being introduced into the semiconductor layers  135   a  and  135   b  and is transferred to the sacrifice capacitor Cst 2  through the static electricity shielding member  131 . 
         [0074]    In the display device according to Comparative Example of the present invention which does not include the static electricity shielding member  131 , the outside static electricity is introduced into the gate insulating layer  140 , such that the gate insulating layer formed on the semiconductor layers  135   a  and  135   b  may be cracked and short-circuit between the semiconductor layers  135   a  and  135   b  and the gate electrode  121  may occur. 
         [0075]    In the display device according to the exemplary embodiment of the present invention, the static electricity shielding member  131  positioned under the semiconductor layers  135   a  and  135   b  and the parasitic capacitor Cst 2  connected to the static electricity shielding member  131  are formed and thus the outside static electricity is previously transferred to the parasitic capacitor Cst 2  along the static elasticity shielding member  131  before the semiconductor layer  135   a  and the gate electrode  121  are short-circuited from each other, thereby protecting the transistor. 
         [0076]    In this case, the scan line  121 , the driving gate electrode  125   b , the first storage plate of electricity  128 , the first sacrifice electrode  122 , and the ground electrode  123  may be made of the same material and may be formed on the same layer. The scan line  121 , the driving gate electrode  125   b , the first storage plate of electricity  128 , the first sacrifice electrode  122 , and the ground electrode  123  may be a single layer made of aluminum (Al), copper (Cu), silver (Ag), molybdenum (Mo), chromium (Cr), titanium (Ti), tantalum (Ta), indium-tin-oxide (ITO), indium-zinc-oxide (IZO), an alloy thereof, or the like or a multilayer made of a combination thereof, but the exemplary embodiment of the present invention is not limited to the above example. 
         [0077]    An interlayer insulating layer  160  is formed on the scan line  121 , the driving gate electrode  125   b , the first storage capacitor  128 , the first sacrifice electrode  122 , and the ground electrode  123   a . Similar to the gate insulating layer  140 , the interlayer insulating layer  160  may be made of silicon nitride, silicon oxide, or the like. 
         [0078]    The source contact hole  61  and the drain contact hole  62  through which the source region  1356  and the drain region  1357  are each exposed are formed on the interlayer insulating layer  160  and the gate insulating layer  140  and the storage contact hole  63  through which a portion of the first storage plate of electricity  128  is exposed is formed. 
         [0079]    The data line  171  having a switching source electrode  176   a , a driving voltage line  172  having a driving source electrode  176   b  and a second storage plate of electricity  178 , and a switching drain electrode  177   a  and a driving drain electrode  177   b  connected to the first storage plate of electricity  128  are formed on the interlayer insulating layer  160 . 
         [0080]    The data lines  171  transfer the data signal and extends in a vertical direction to intersect the gate lines  121 . The driving voltage line  172  transfers the driving voltage and extends in the same direction as the data line  171 , being separated from the data line  171 . 
         [0081]    The switching source electrode  176   a  protrudes from the data line  171  toward the switching semiconductor layer  135   a  and the driving source electrode  176   b  protrudes from the driving voltage line  172  toward the driving semiconductor layer  135   b . The switching source electrode  176   a  and the driving source electrode  176   b  are each connected to the source region  1356  through the source contact hole  61 . The switching drain electrode  177   a  faces the switching source electrode  176   a , the driving drain electrode  177   b  faces the driving source electrode  176   b , and the switching drain electrode  177   a  and the driving drain electrode  177   b  are each connected to the drain region  1357  through the drain contact hole  62 . 
         [0082]    The switching drain electrode  177   a  extends to be electrically connected to the first storage plate of electricity  128  and the driving gate electrode  125   b  through the contact hole  63  which is formed in the interlayer insulating layer  160 . 
         [0083]    The second storage plate of electricity  178  protrudes from the driving voltage line  171  to overlap the first storage plate of electricity  128 . Therefore, the first storage plate of electricity  128  and the second storage plate of electricity  178  form the storage capacitor Cst 1  using the interlayer insulating layer  160  as a dielectric material. 
         [0084]    The switching semiconductor layer  135   a , the switching gate electrode  125   a , the switching source electrode  176   a , and the switching drain electrode  177   a  form the switching transistor T 1 , and the driving semiconductor layer  135   b , the driving gate electrode  125   a , the driving source electrode  176   b , and the driving drain electrode  177   b  form the driving transistor T 2 . 
         [0085]    A passivation layer  180  is formed on the switching source electrode  176   a , the driving source electrode  176   b , the switching drain electrode  177   a , and the driving drain electrode  177   b.    
         [0086]    A pixel electrode  710  is formed on the passivation layer  180  and the pixel electrode  710  may be made of transparent conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO) or indium oxide (In 2 O 3 ) or reflective metals such as lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), aluminum (Al), silver (Ag), magnesium (Mg), or gold (Au). The pixel electrode  710  is electrically connected to the driving drain electrode  177   b  of the driving transistor T 1  through a contact hole  181  formed on the interlayer insulating layer  160  and thus becomes an anode of an organic light emitting diode  70 . 
         [0087]    The pixel defined layer  350  is formed on the passivation layer  180  and an edge portion of the pixel electrode  710 . The pixel defined layer  350  has an opening  351  through which the pixel electrode  710  is exposed. The pixel defined layer  350  may be made of resin such as polyacrylates or polyimides, silica-based inorganic materials, and the like. 
         [0088]    An organic light emitting layer  720  is formed on the opening  351  of the pixel defined layer  350 . The organic light emitting layer is formed of a plurality of layers which include at least one of a light emitting layer, a hole-injection layer (HIL), a hole-transporting layer (HTL), an electron-transporting layer (ETL), and an electron-injection layer (EIL). When the organic light emitting layer  720  includes both of them, the hole injection layer is disposed on the pixel electrode  710  which is the anode and the hole transport layer, the light emitting layer, the electron transport layer, and the electron injection layer may be sequentially stacked thereon. 
         [0089]    The organic light emitting layer  720  may include a red organic light emitting layer which emits red light, a green organic light emitting layer which emits green light, and a blue organic light emitting layer which emits blue light, in which the red organic light emitting layer, the green organic light emitting layer, and the blue organic light emitting layer are each formed in a red pixel, a green pixel, and a blue pixel to implement a color image. 
         [0090]    Further, the organic light emitting layer  720  may implement the color image by stacking the red organic light emitting layer, the green organic light emitting layer, and the blue organic light emitting layer in all of the red pixel, the green pixel, and the blue pixel and forming a red filter, a green filter, and a blue filter for each pixel. As another example, the color image may be implemented by forming a white organic light emitting layer which emits white light in all of the red pixel, the green pixel, and the blue pixel and forming the red filter, the green filter, and the blue filter for each pixel. At the time of implementing the color image using the white organic light emitting layer and the color filters, there is no need to use a deposition mask for depositing the red organic light emitting layer, the green organic light emitting layer, and the blue organic light emitting layer on each pixel, that is, the red pixel, the green pixel, and the blue pixel. 
         [0091]    The white organic light emitting layer described in another example may be formed of a single organic light emitting layer and may be configured to emit white light by stacking the plurality of organic light emitting layers. For example, the white organic light emitting layer may also include a configuration to emit white light by combining at least one yellow organic light emitting layer with at least one blue organic light emitting layer, a configuration to emit white light by combining at least one cyan organic light emitting layer with at least one red organic light emitting layer, and a configuration to emit white light by combining at least one magenta organic light emitting layer with at least one green organic light emitting layer, and the like. 
         [0092]    A common electrode  730  is formed on the pixel defined layer  350  and the organic emission layer  720 . The common electrode  730  may be made of transparent conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO) and indium oxide (In 2 O 3 ) or reflective metals such as lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), aluminum (Al), silver (Ag), magnesium (Mg), and gold (Au). The common electrode  730  becomes a cathode of the organic light emitting diode  70 . The pixel electrode  710 , the organic emission layer  720 , and the common electrode  730  form the organic light emitting diode  70 . 
         [0093]      FIG. 5  is an equivalent circuit diagram of a pixel of an organic light emitting diode display device according to another exemplary embodiment of the present invention, in which the organic light emitting diode display device is an active matrix (AM) type organic light emitting diode display device having a 3Tr 3Cap structure in which three transistors (TFTs) and three capacitors are included in one pixel. 
         [0094]    As illustrated in  FIG. 5 , a gate of the first transistor Q 1  is connected to a current scan signal scan[n], the input terminal is connected to a data signal Data[t], and the output terminal is connected to a first node N 1 . 
         [0095]    The gate of the driving transistor Qd which is the second transistor Q 2  is connected to the second capacitor C 2  at a second node N 2 , the input terminal is connected to a first power supply, for example, a driving voltage ELVDD at a fourth node N 4 , and the output terminal is connected to the anode electrode of the organic light emitting diode (OLED) and an input terminal of a third transistor Q 3  at a third node N 3 . 
         [0096]    The gate of the third transistor Q 3  is connected a global control signal GC(t) for compensating for a threshold voltage of the driving transistor Qd, the input terminal is connected to the output terminal of the driving transistor Qd at the third node N 3 , and the output terminal is connected to the gate of the driving transistor Qd and the second capacitor C 2  at the second node. 
         [0097]    One terminal of a first capacitor C 1  is connected to one terminal of the second capacitor C 2  and an output terminal of the first transistor Q 1  at the first node N 1  and the other terminal thereof is connected to the first power supply required to supply a current to the organic light emitting diode at the fourth node N 4 , for example, the driving voltage ELVDD. 
         [0098]    One terminal of the second capacitor C 2  is connected to the output terminal of the first transistor Q 1  and one terminal of the first capacitor C 1  at the first node N 1  and the other terminal thereof is connected to the gate of the driving transistor Qd and the output terminal of the third transistor Q 3  at the second node N 2 . 
         [0099]    The sacrifice capacitor Cst 2  is connected between the first sacrifice electrode connected to the constant potential voltage line  123  and the second sacrifice electrode connected to the static electricity shielding member which is positioned under the semiconductor layer of the first transistor Q 1 , the second transistor Q 2 , and the third transistor Q 3  at a fifth node N 5 . The sacrifice capacitor Cst 2  prevents static electricity from the outside from being transferred to the first transistor Q 1 , the switching transistor Q 2 , and the third transistor Q 3 . 
         [0100]    The anode (pixel electrode) of the organic light emitting diode (OLED) is connected to the output terminal of the driving transistor Qd and the input terminal of the third transistor Q 3  at the third node N 3  and the cathode (common electrode) thereof is connected to a second power supply, for example a common voltage ELVss. 
         [0101]    The first transistor Q 1  is a switching transistor which responds to a current scan signal scan[n] to transfer the data signal Data[t] to the corresponding data line and controls a light emission amount of the organic light emitting diode (OLED) to transfer the data signal Data[t]. 
         [0102]    The driving transistor Qd which is the second transistor Q 2  is the driving transistor Qd which responds to the data signal (Data[t]) transferred to the gate through the first transistor Q 1  to supply the driving current of the organic light emitting diode (OLED). 
         [0103]    The third transistor Q 3  is a threshold voltage compensation transistor which responds to the global control signal GC[t] to compensate for a threshold voltage of the driving transistor Qd. 
         [0104]    The first capacitor C 1  is a capacitor for storing a data signal applied to the gate of the driving transistor Qd. 
         [0105]    The second capacitor C 2  is a capacitor for controlling the threshold voltage of the driving transistor Qd. 
         [0106]    The sacrifice capacitor Cst 2  prevents the outside static electricity from being introduced into the first transistor Q 1 , the second transistor Q 2 , and the third transistor Q 3 . 
         [0107]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.