Abstract:
A display device includes a waveguide with a light propagating therein, and a panel including a first organic light-emitting device in a sub-pixel region and a second organic light-emitting device in a sensing region adjacent to the sub-pixel region, the first organic light-emitting device for displaying a data on the panel, and the second light-emitting device responsive to a scattering of the light from the waveguide for outputting a signal indicative of a contact on the waveguide.

Description:
This application claims priority to and the benefit of Korea Patent Application No. 10-2006-0134081 filed on Dec. 26, 2006, which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention relate to a display panel, and more particularly to an organic light-emitting diode (OLED) panel capable of recognizing touching of the display panel. 
     2. Description of the Related Art 
     The importance of flat panel displays has recently increased with the growth of multimedia. Various types of flat panel displays such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), organic light-emitting devices have been put to practical use. 
     The small-sized flat panel displays providing a large number of functions have been frequently used in conjunction with touch-screens. The related art touch-screen was manufactured in the form of a separate device attached to the surface of a display panel using a mechanical mounting device. 
     However, mechanical mounting of the touch-screen to the display panel increases the number of parts, weight, manufacturing cost, and thickness of the flat panel display. Moreover, such related art touch-screen display devices do not accurately sense touching-positions in a multi-touch operation where the display device is touched at a plurality of locations concurrently. 
     SUMMARY OF THE INVENTION 
     Accordingly, embodiments of the present invention are directed to an organic light-emitting diode panel and a touch-screen using the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art, and a liquid crystal display device using the same. 
     An object of the present invention to provide an organic light-emitting diode panel having a multi-touch recognition capability. 
     Another object of the present invention is to provide a touch-screen system having a reduced number of mechanically attached parts. 
     Another object of the present invention is to provide a touch-screen system that is light and thin. 
     Another object of the present invention is to provide a touch-screen system 
     Additional features and advantages of the invention will be set forth in the description of exemplary embodiments which follows, and in part will be apparent from the description of the exemplary embodiments, or may be learned by practice of the exemplary embodiments of the invention. These and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description of the exemplary embodiments and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a display device includes a waveguide with a light propagating therein, and a panel including a first organic light-emitting device in a sub-pixel region and a second organic light-emitting device in a sensing region adjacent to the sub-pixel region, the first organic light-emitting device for displaying a data on the panel, and the second light-emitting device responsive to a scattering of the light from the waveguide for outputting a signal indicative of a contact on the waveguide. 
     In another embodiment, an organic light emitting diode panel includes first and second substrates facing each other, thin film transistors on the first substrate, a display unit on the second substrate, the display having a plurality of sub-pixels and organic light emitting diode sensors, each sub-pixel and each organic light emitting diode sensors including first and second electrodes and an organic layer, a waveguide over the display unit, and a light source providing light into the waveguide. 
     In another embodiment, touch screen system includes a waveguide with a light substantially totally reflected therein, and a panel coupled to the waveguide, the panel including a plurality of light emitting-devices in a plurality of sensing regions adjacent to corresponding sub-pixel regions, the plurality of the light-emitting devices responsive to light scattering from the waveguide for outputting leakage currents indicative of a plurality of contacts on the waveguide, and a processor for calculating the locations of the contacts on the waveguide. 
     In a further embodiment, a method of recognizing touching on a display panel including a light emitting-device in a sensing region adjacent to a sub-pixel region and a waveguide attached thereon, the method includes propagating a light within the waveguide, applying a reverse bias to the sensing region, and detecting a leakage current from the light-emitting device produced by a scattering of the light from the waveguide in response to a contact on the waveguide. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are comprised to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG.  1 is a block diagram representation of an exemplary touch-screen system incorporating an OLED panel according to an embodiment of the present invention; 
         FIG. 2  is a plane view of an exemplary OLED panel according to an embodiment of the invention; 
         FIG. 3  is a cross-sectional view taken along line I-I′ of the exemplary OLED panel of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a first exemplary structure of a sub-pixel and an OLED sensor in an OLED panel according to an embodiment of the invention; 
         FIG. 5  is a cross-sectional view of a second exemplary structure of a sub-pixel and an OLED sensor in an OLED panel according to another embodiment of the invention; 
         FIG. 6  is an exemplary circuit diagram of the sub-pixel and the OLED sensor in the OLED panel according to an embodiment of the invention; 
         FIG. 7  is a schematic cross-sectional view of a touch detection operation of the OLED panel according to an embodiment of the invention; 
         FIG. 8  is a diagram illustrating an exemplary signal processing of a photo current generated in the OLED sensor of the OLED panel according to an embodiment of the invention; and 
         FIG. 9  is a flow chart illustrating an exemplary signal processing in a display signal processor. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made in detail to exemplary embodiments of the present invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  is a block diagram representation of an exemplary touch-screen system incorporating an OLED panel according to an embodiment of the present invention. Referring to  FIG. 1 , a touch-screen system according to an embodiment includes an OLED module  200 , which includes an OLED panel  100 , a digital board  300 , and a system  400 . 
     The OLED panel  100  includes a display part which includes a plurality of sub-pixels and a plurality of OLED sensors. A waveguide and a light source are positioned over the display part. 
     The OLED panel  100  is connected to a scan driver  210 , a data driver  220 , and a readout integrated circuit (IC)  230 . The scan driver  210  and the data driver  220  apply driving signals to the OLED panel  100 . The readout IC  230  measures a photo current generated in the OLED sensor of the OLED panel  100 . In other words, the OLED module  200  includes the OLED panel  100 , the scan driver  210 , the data driver  220 , and the readout IC  230 . 
     The digital board  300  is connected to the OLED module  200 . The digital board  300  may comprise a timing controller, an analog to digital converter (ADC) for processing a signal output to the readout IC  230 , and a display signal processor (DSP). The timing controller generates control signals for controlling the scan driver  210  and the data driver  220 . 
     The digital board  300  is connected to the system  400  such as a computer. A signal passing through the display signal processor of the digital board  300  is transmitted to the system  400  through a system interface, and the system  400  performs an operation corresponding to the transmitted signal. 
       FIG. 2  is a plane view of an exemplary OLED panel according to an embodiment of the invention.  FIG. 3  is a cross-sectional view taken along line I-I′ of the exemplary OLED panel of  FIG. 2 . Referring to  FIGS. 2 and 3 , the OLED panel  100  includes a display P, a waveguide  170  positioned over the display P, and a light source  180  positioned at an edge of the waveguide  170 . 
     The display P includes a plurality of sub-pixels  150  and a plurality of OLED sensors (S)  155 . In  FIG. 3 , the OLED sensors  155  are positioned between pixels  160  each including red (R), greed (G), and blue (B) sub-pixels  150 . However, the configuration of the pixel  160  or the OLED sensor  155  is not limited thereto. The pixel  160  or the OLED sensor  155  may be formed in other forms depending on the color gamut or the sensing level. In an embodiment, the pixel  160  may include a white sub-pixel in addition to the red (R), greed (G), and blue (B) sub-pixels  150 . In another embodiment, each pixel  160  may at least two of the red (R), greed (G), blue (B), white sub-pixels. 
     The waveguide  170  is positioned on the upper portion of the display P. The waveguide  170  may be formed of glass or plastic with high transmissivity. The light source  180  is positioned at an edge of the waveguide  170 . Although  FIG. 2  has illustrated four light sources  180  positioned at four edges of the waveguide  170 , the light source  180  is not limited thereto. If necessary, the number of light sources or the positions of the light sources may vary. 
     The light source  180  may be a light-emitting diode (LED). Light generated in the light source  180  enters the waveguide  170  through the side surface of the waveguide  170 . The light enters in a direction perpendicular to the side surface of the waveguide  170 . The light is totally reflected inside the waveguide  170 , and stays inside the waveguide  170 . 
     When the waveguide  170  is contacted by a material each having a different refractive index from the waveguide  170 , the waveguide  170  may need be spaced apart from the display P using a mechanical device because of the break of the total reflection inside the waveguide  170 . 
     If the waveguide  170  and the display P are formed of materials having a substantially equal refractive index, total reflection can be maintained inside the waveguide  170  even when the waveguide touches the display P. For example, a substrate positioned on an uppermost portion of the display P can to be formed of a material with a refractive index substantially equal to the refractive index of the material used in the waveguide  170 . 
       FIG. 4  is a cross-sectional view of a first exemplary structure of a sub-pixel and an OLED sensor in an OLED panel according to an embodiment of the invention.  FIG. 5  is a cross-sectional view of a second exemplary structure of a sub-pixel and an OLED sensor in an OLED panel according to another embodiment of the invention. Referring to  FIG. 4 , the sub-pixel  150  includes a thin film transistor (T) positioned on a first substrate  500  and a light-emitting diode (OLED) electrically connected to the thin film transistor (T). 
     More specifically, a buffer layer  505  is positioned on the first substrate  500  including glass, plastic or metal. A gate electrode  510  and a semiconductor layer  520  corresponding to a portion of the gate electrode  510  are positioned on the buffer layer  505 . The semiconductor layer  520  may include amorphous silicon or polysilicon. Although not shown, an ohmic contact layer may be positioned on the semiconductor layer  520 . A gate dielectric layer  515  is positioned between the gate electrode  510  and the semiconductor layer  520 . A source electrode  530   a  and a drain electrode  530   b  are positioned on a portion of the semiconductor layer  520 . 
     A passivation layer  535  is positioned on the first substrate  500  including the source electrode  530   a  and the drain electrode  530   b . The passivation layer  535  includes a via hole  540  for exposing a portion of the drain electrode  530   b.    
     A first electrode  545  is positioned on the first substrate  500  including the passivation layer  535 . The first electrode  545  is electrically connected to the drain electrode  530   b  through the via hole  540 . 
     A bank layer  550  is positioned on the first substrate  500  including the first electrode  545 . The bank layer  550  includes an opening  555  exposing a portion of the first electrode  545 . 
     An emitting layer  560  is positioned inside the opening  555  of the bank layer  550 . The emitting layer  560  may include an organic material. The emitting layer  560  performs light-emission by receiving an electron and a hole and then forming an exciton. Although not shown, a hole injecting/transporting layer and an electron injecting/transporting layer for efficiently transporting electrons and holes may be further positioned on upper and lower portions of the emitting layer  560 , respectively. 
     The emitting layer  560  may be formed by doping a guest material on a host material. Each sub-pixel  150  can emit red (R) light, green (G) light or blue (B) light depending on a material used in the emitting layer  560 . A second electrode  565  is positioned on the emitting layer  560 . 
     The first electrode  545  may be a cathode for supplying electrons to the emitting layer  560 , and can be made of a metal, such as aluminum (Al) or magnesium (Mg) having a low work function and high reflectivity. The second electrode  565  may be an anode for supplying holes to the emitting layer  560 , and can be made of a conductive metal, such as transparent indium-tin-oxide (ITO) having a high work function. 
     The first electrode  545  of each sub-pixel  150  and the first electrode  545  of each OLED sensor  155  are positioned to be spaced apart from each other. The second electrode  565  of each sub-pixel  150  and the second electrode  565  of each OLED sensor  155  are patterned to be spaced apart from each other. 
     This is to apply voltages of different polarities to the sub-pixel  150  and the OLED sensor  155 . The second electrode  565  of the sub-pixel  150  may be formed of a common electrode, which is patterned to be spaced apart from the second electrode  565  of the OLED sensor  155 . 
     The first substrate  500 , on which the thin film transistor (T) and the light-emitting diode (OLED) are positioned, is attached to a second substrate  570  to protect the thin film transistor (T) and the light-emitting diode (OLED) from the outside air. 
     The sub-pixel  150  may have a different structure from the structure illustrated in  FIG. 4 . 
     Referring to  FIG. 5 , a buffer layer  605  is positioned on a first substrate  600 , and a thin film transistor (T) is positioned on the buffer layer  605 . The thin film transistor (T) includes a gate electrode  610 , a semiconductor layer  620  corresponding to a portion of the gate electrode  610 , a gate dielectric layer  615  positioned between the gate electrode  610  and the semiconductor layer  620 , and a source electrode  630   a  and a drain electrode  630   b  positioned on a portion of the semiconductor layer  620 . A passivation layer  635  is positioned on the thin film transistor (T) to expose the drain electrode  630   b.    
     An OLED is positioned on a second substrate  670 . More specifically, a first electrode  675  is positioned on the second substrate  670 . The first electrode  675  may be a common electrode formed on a front surface of the second substrate  670 . A bank layer  680  is positioned on the second substrate  670  including the first electrode  675 . The bank layer  680  includes an opening  685  exposing a portion of the first electrode  675 . An emitting layer  690  is positioned inside the opening  685 . A contact spacer  695  is positioned in a portion of the bank layer  680  spaced apart from the opening  685 . A second electrode  700  is positioned on the contact spacer  695  and the emitting layer  690 . 
     The first substrate  600 , on which the thin film transistor (T) is formed, is attached to the second substrate  670 , on which the light-emitting diode (OLED) is formed, with a sealant. The thin film transistor (T) is electrically connected to the light-emitting diode (OLED) through the contact spacer  695 . 
     An organic light-emitting display including the OLED panel according to an embodiment is a top-emission type organic light-emitting display. In other words, the first electrode  675  may be a transparent electrode, and the second electrode  700  may be a reflective electrode. For example, the first electrode  675  may include a transparent conductive layer and be an anode with a high work function. The second electrode  700  may be a cathode including a metal with a low work function. 
     The first electrode  675  of each sub-pixel  150  and the first electrode  675  of each OLED sensor  155  are positioned to be spaced apart from each other so that the first electrode  675  of each sub-pixel  150  is electrically insulated from the first electrode  675  of each OLED sensor  155 . The second electrode  700  of each sub-pixel  150  and the second electrode  700  of each OLED sensor  155  are patterned to be spaced apart from each other. This is to apply voltages of different polarities to the sub-pixel  150  and the OLED sensor  155 . The first electrode  675  of the sub-pixel  150  may be formed of a common electrode, which is patterned to be spaced apart from the first electrode  675  of the OLED sensor  155 , for simplification of interconnection processes. 
       FIG. 6  is an exemplary circuit diagram of the sub-pixel and the OLED sensor in the OLED panel according to an embodiment of the invention. Referring to  FIG. 6 , the sub-pixel  150  of the OLED panel includes a switching transistor Ti, a capacitor Cst 1 , a driving transistor T 2 , and a light-emitting diode OLED 1 . The switching transistor T 1  receives a scan signal from a scan line (Sn), and transmits a data signal received from a data line Dm. The capacitor Cst 1  receives the transmitted data signal and stores it. The driving transistor T 2  generates a driving current corresponding to a difference between the data signal stored in the capacitor Cst 1  and a reference voltage Vss. The light-emitting diode OLED 1  emits light corresponding to the driving current. A first electrode of the light-emitting diode OLED 1  is connected to a source voltage VDD, and a second electrode of the light-emitting diode OLED 1  is connected to the reference voltage Vss. Therefore, the sub-pixel emits light of various gray levels depending on a magnitude of the data signal. 
     The OLED sensor  155  includes a switching transistor M 1 , a capacitor Cst 2 , a driving transistor M 2 , and a light-emitting diode OLED 2 . The switching transistor M 1  receives a scan signal from the scan line (Sn), and transmits a data signal received from a data line D sensor . The capacitor Cst 2  receives the transmitted data signal and stores it. The driving transistor M 2  is turned on by the data signal stored in the capacitor Cst 2 . A first electrode of the light-emitting diode OLED 2  is connected to a source voltage VDD, and a second electrode of the light-emitting diode OLED 2  is connected to the reference voltage Vss. 
     The sub-pixel  150  and the OLED sensor  155  can be formed by the same fabrication processes except for that the second electrode of the sub-pixel  150  and the second electrode of the OLED sensor  155  are formed to be spaced apart from each other. In other words, in the OLED panel according to an embodiment, the sub-pixel  150  for achieving an image and the OLED sensor  155  for touch sensing are concurrently formed in an array form on the same plane. Accordingly, the OLED panel according to an embodiment is manufactured to be light and thin at low manufacturing cost while including a touch sensing function. Further, since the sub-pixel  150  and the OLED sensor  155  are formed in an array form over the entire surface of the OLED panel according to an embodiment, it is possible to sense several touch positions. In other words, multi-touch sensing is possible. 
       FIG. 7  is a schematic cross-sectional view of a touch detection operation of the OLED panel according to an embodiment of the invention. Referring to  FIGS. 6 and 7 , when light enters the waveguide  170  by turning on the light source  180  (shown in  FIG. 3 ), the light entering the waveguide  170  is substantially totally reflected and stays inside the waveguide  170 . 
     The switching transistor T 1  of the sub-pixel  150  is turned on by applying a scan signal to the scan line Sn such that a data signal is applied through the data line Dm of the sub-pixel  150 . The capacitor Cst 1  stores the data signal. The driving transistor T 2  generates a driving current corresponding to a difference between the data signal stored in the capacitor Cst 1  and the reference voltage Vss, and transmits the driving current to the light-emitting diode OLED 1 . Since a positive bias is applied to the sub-pixel  150 , the light-emitting diode OLED 1  emits light corresponding to the driving current. The display P displays an image corresponding to the data signal. 
     The switching transistor Ml of the OLED sensor  155  is turned on by applying a scan signal to the scan line Sn such that a data signal is applied through the data line D sensor  of the OLED sensor  155 . The capacitor Cst 2  stores the data signal. The driving transistor M 2  is turned on by the data signal stored in the capacitor Cst 2  such that the first electrode of the light-emitting diode OLED 2  is connected to the reference voltage Vss. Since a reverse bias is applied to the OLED sensor  155 , a current does not flow in the OLED sensor  155 . 
     In an embodiment, when the user touches the waveguide  170 , totally reflected light in the predetermined position is scattered in a rear surface of the waveguide  170 . This phenomenon is called frustrated total internal reflection (FTIR). Accordingly, when light is totally reflected in a first medium, the light will be scattered when the first medium comes into contact with a second medium having a different refractive index. The OLED panel according to an embodiment uses FTIR. In other words, the OLED sensor  155  senses light scattered by FTIR when the user touches the waveguide  170 . 
     The light is scattered at the position touched by the user and enters the OLED sensor  155  to which the reverse bias is applied. The light entering the OLED sensor  155  having light receiving characteristics generates a free electrons and holes inside the emitting layer. Accordingly, the scattered light entering the OLED sensor  155  at the touch position causes a leakage current, i.e., a photo current to flow in the OLED sensor  155 . The amount of the leakage current depends on the amount of light entering the OLED sensor  155  at the touch position. 
     The photo current is transmitted to the digital board  300  through an output line O sensor  of the OLED sensor  155  of  FIG. 6  and the readout IC  230  of  FIG. 1 . The digital board  300  processes the photo current, and then transmits the processed photo current to the system  400 . The system  400  performs an operation corresponding to the applied signal. 
     As described above, the OLED panel according to an embodiment drives the sub-pixel  150  and the OLED sensor  155  using the same driving method, thereby simultaneously performing the image display and the touch sensing. Accordingly, since the OLED panel does not have a separate driving circuit of the OLED sensor  155  for touch sensing, the OLED panel is manufactured by the simple manufacturing processes at low cost. 
       FIG. 8  is a diagram illustrating an exemplary signal processing of a photo current generated in the OLED sensor of the OLED panel according to an embodiment of the invention. Referring to  FIG. 8 , a photo current generated in the OLED sensor  155  is output to the readout IC  230 . The readout IC  230  converts the photo current into a voltage, amplifies the voltage, and supplies the amplified voltage to an analog to digital converter (ADC)  310  positioned on the digital board  300  of  FIG. 1 . The ADC  310  converts the supplied voltage into a digital signal, and then transmits the digital signal to a display signal processor  320 . 
       FIG. 9  is a flow chart illustrating an exemplary signal processing in a display signal processor. Referring to  FIG. 9 , a signal is input to the display signal processor  320  in step S 810 . The display signal processor  320  performs a reference mapping process on the input signal in step S 820 . 
     The reference mapping process corrects the input signals to adjust a characteristic of each OLED sensor  155  because each OLED sensor  155  of the OLED panel has different noise characteristics. 
     Next, the display signal processor  320  smoothes noises of the corrected signals, and clearly defines boundaries of the signals by detecting edge portions of the signals in step S 830 . 
     Since the OLED sensors and the sub-pixels are arranged in an array form, the OLED sensor recognizes signals not in coordinate information but in image form information. Accordingly, the above process is performed to analyze a pattern of the image information. Since the signal is recognized not in coordinate information but in image form information, the OLED panel can perform multi-touch sensing. 
     The display signal processor  320  detects regions of signal intensity greater than a threshold value, and determines the detected regions as touch positions in step S 840 . 
     In other words, since a photo current is likely to be partially generated by user&#39;s hand shape as well as user&#39;s finger, regions whose signal intensity is greater than the threshold value are detected and the detected regions are determined as touch positions. 
     The display signal processor  320  gives a target identification (ID) to each of the detected regions in step S 850 . 
     The display signal processor  320  calculates middle coordinates of each region in step S 860 . The display signal processor  320  transmits the calculated middle coordinates to the system  400  in step S 870 . The system  400  performs an operation corresponding to the transmitted middle coordinates. 
     As described above, in the OLED panel according to an embodiment and the touch-screen system including the OLED panel, the sub-pixel and the OLED sensor are simultaneously formed in the array form using light receiving characteristics of the OLED sensor. Accordingly, the thin and light flat panel displays can be achieved, and manufacturing yield can improve due to a reduction in time and cost. 
     Further, since the OLED sensor is arranged in the array form, the OLED sensor receives touch information of an image form. Therefore, multi-touch sensing can be performed. 
     The OLED panel according to an embodiment and the touch-screen system are manufactured to be light and thin while reducing time and cost. Further, multi-touch sensing is possible. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in embodiments of the present invention. Thus, it is intended that embodiments of the present invention cover the modifications and variations of the embodiments described herein provided they come within the scope of the appended claims and their equivalents.