Patent Abstract:
An OLED display including a first substrate on which a plurality of OLEDs are formed, a second substrate attached with the first substrate, a photo sensor formed on the second substrate and for detecting incident light generated by an external source, and a plurality of shield layers covering the photo sensor and for blocking (or preventing) light emitted from the OLED from being detected by the photo sensor.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2008-0066079, filed in the Korean Intellectual Property Office, on Jul. 8, 2008, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an organic light emitting diode (OLED) display. More particularly, the present invention relates to an OLED display having a touch panel. 
     2. Description of the Related Art 
     An organic light emitting diode (OLED) display includes a plurality of organic light emitting diodes (OLEDs). Each of the OLEDs includes a hole injection electrode, an organic emission layer, and an electron injection electrode, and light is emitted by energy that is generated when an exciton generated by coupling of electrons and holes falls from an exited state to a ground state within the organic emission layer. 
     Because the OLED display is a self-luminance display (due to its ability to self-generate light) and does not require a separate light source (unlike a liquid crystal display (LCD)), thickness and weight thereof can be reduced. Further, because the OLED display has desired display quality characteristics, such as low power consumption, high luminance, and high reaction speed, the OLED display is appropriate for use as a next generation display in a mobile electronic device. 
     In general, the OLED display includes a panel assembly in which a plurality of OLEDs are formed, a bezel coupled to the panel assembly at a rear side of the panel assembly, and a printed circuit board (PCB) that is electrically connected to the panel assembly through a flexible printed circuit board (FPBC). 
     As a new input method that can replace a conventional input method (e.g., mouse or keyboard), a touch screen enables direct input of data to a screen by using a hand or a pen. Particularly, the touch screen enables a user to directly perform desired work while viewing the screen, and it is easy to operate so that it has been evaluated as an ideal input method for a graphic user interface (GUI). It has been used in various fields such as mobile phones, PDAs, terminals in banks and public offices, medical equipments, and information display devices in tourist agencies and other suitable agencies. 
     The touch screen can be broadly classified as one using a resistance film method, a capacitance method, an ultrasonic wave method, or a light (infrared) method. In the resistance film method, two substrates (each of which is coated by a transparent conductive layer) face each other, and a dot spacer is interposed therebetween. 
     According to the resistance film method, an electric signal is applied to one of the transparent conductive layers for detecting a location, and a user presses an upper substrate with a finger or a pen. Then, the transparent conductive layer of the front substrate contacts the transparent conductive layer of the rear substrate so that the opposite transparent conductive layer detects the electric signal. Here, a location is detected by using the intensity of the detected electric signal. However, the resistance film method has low detection accuracy because the intensity of the signal varies in accordance with the applied pressure. Further, when the user presses the touch panel, the press load is directly delivered to an OLED panel, which may damage the OLED panel. 
     In the light method, a photo sensor is provided to detect variation of incident light and generate a corresponding electric signal, and a location is detected on the basis of the electric signal. According to the light method, the touch screen can provide high detection accuracy because a signal is generated not by pressure but only by contact. However, the light method may be influenced by light emitted from an OLED, thereby causing malfunctions. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and may contain information that does not form the prior art. 
     SUMMARY OF THE INVENTION 
     An aspect of an embodiment of the present invention is directed toward an organic light emitting diode (OLED) display having a touch screen using a photo sensor that can prevent (or reduce) malfunctions by preventing (or protecting from) interference of internal light. 
     An OLED display according to an embodiment of the present invention includes: a first substrate; a plurality of OLEDs on the first substrate; a second substrate attached with the first substrate; a photo sensor on the second substrate and for detecting incident light generated by an external source; and a plurality of shield layers covering the photo sensor and for blocking light emitted from the OLEDs from being detected by the photo sensor. 
     The shield layers may be formed in a plane that faces the OLEDs, and each of the shield layers may be a black matrix. Each of the shield layers may include a material selected from the group consisting of a metal insulator hybrid layer (MIHL), a black polymer, carbon black, and combinations thereof. 
     A color filter may be formed between the plurality of shield layers. The plurality of shield layers may be arranged in a matrix format, and the plurality of OLEDs may be formed in a matrix format. The photo sensor may be provided in a space above and between the plurality of OLEDs. 
     A touch electrode may be formed between the photo sensor and the second substrate, and may be made of a transparent conductive material. The touch electrode may include a material selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), fluorine tin oxide (FTO), antimony-doped tin oxide (ATO), and combinations thereof. 
     An OLED display according to another embodiment of the present invention includes: a first substrate; a plurality of OLEDs on the first substrate; a second substrate attached with the first substrate; a plurality of shield layers between the OLEDs and the second substrate; and a plurality of photo sensors, each of the photo sensors being covered by a corresponding one of the shield layers and between the corresponding one of the shield layers and the second substrate. 
     Each of the shield layers may be a black matrix, and a plane of the photo sensor, facing the OLED, may be covered by the shield layers. In addition, the OLED display may further include a touch electrode formed to contact the photo sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an organic light emitting diode (OLED) display according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a perspective view of a first substrate and members provided on the first substrate of  FIG. 1 . 
         FIG. 3  shows a sub-pixel circuit of the OLED display of  FIG. 1 . 
         FIG. 4  is a partially expanded cross-sectional view of the inside of the OLED display of  FIG. 1 . 
         FIG. 5  is a cross-sectional view of an OLED display according to a second exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
       FIG. 1  shows a cross-sectional view of an organic light emitting diode (OLED) display according to a first exemplary embodiment of the present invention.  FIG. 2  is a perspective view of a first substrate and members provided in the first substrate of  FIG. 1 . 
     Referring to  FIG. 1 , the OLED display according to the present exemplary embodiment includes a first substrate  20 , a plurality of OLEDs L 1  provided in a display area of the first substrate  20 , a second substrate  40  combined with (attached with or coupled to) the first substrate  20  by a sealing unit  16 , and a photo sensor  43  formed on the second substrate  40 . 
     The OLEDs L 1  are disposed in a matrix format in the first substrate  20 , and an integrated circuit chip  25  is mounted on an external side of the area where the OLEDs L 1  are provided through a chip-on-glass (COG) method. 
     A touch electrode  42 , the photo sensor  43  connected to the touch electrode  42 , and a shield layer  45  that covers the photo sensor  43  are formed on the second substrate  40 . The touch electrode  42 , the photo sensor  43 , and the shield layer  45  are formed at the internal side (i.e., a plane that faces the first substrate) of the second substrate  40 . 
     According to the present exemplary embodiment, the shield layer  45  and the photo sensor  43  are formed on the second substrate  40 , but they are not limited thereto. For example, the shield layer  45  and the photo sensor  43  may be formed on the first substrate. 
     In addition, according to the present exemplary embodiment, the first substrate  20  and the second substrate  40  are separated from each other, but they are not limited thereto. A filter may also be provided in a space between the first substrate  20  and the second substrate  40 . 
     The touch electrode  42  can be made of one or more conductive materials such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), fluorine tin oxide (FTO), and antimony-doped tin oxide (ATO). The photo sensor  43  that generates a signal by detecting a change in external light is disposed in a matrix format between the OLEDs L 1 , and are arranged (or configured) to allow light emitted from each of the OLEDs L 1  to be emitted without any interruption. 
     As shown in  FIG. 2 , the shield layer  45  is formed to cover a plane of the photo sensor  43  (which faces the first substrate  20 ) and a circumference side of the plane so as to shield influence of light emitted from the OLED L 1  to the photo sensor  43 . Therefore, a plane of the photo sensor  43 , which faces the second substrate  40 , is not covered by the shield layer  45  so that a change of light occurring at the front side of the second substrate  40  can be sensed. 
     The shield layer  45  may be formed as (or as part of) a black matrix. The black matrix improves contrast by preventing (or protecting from) light leakage, and is formed of a metal insulator hybrid layer (MIHL), a black polymer, and/or carbon black. An insulation layer of the MIHL can be made of SiO 2  and/or SiN X , and a metal component may be formed of Cr, Al, Mo, W, Ti, Ag, Cu, and/or chromium oxide. 
     When the shield layer  45  is formed as (or as part of) the black matrix, it can be easily formed during a process of forming the black matrix rather than forming a separate layer, and contrast can be improved. 
     An integrated circuit chip  47  is mounted on an external side of an area where the photo sensor  43  is formed in the second substrate  40  in order to analyze and transmit a signal input through the photo sensor  43 . 
       FIG. 3  shows a sub-pixel circuit structure of the OLED display of  FIG. 1 , and  FIG. 4  shows a partially enlarged cross-sectional view of an internal structure of the OLED display of  FIG. 1 . 
     Referring to  FIG. 3  and  FIG. 4 , a sub-pixel of the OLED display is formed of an OLED L 1  and a driving circuit. The OLED L 1  includes an anode  26 , an organic emission layer  28 , and a cathode  30 , and the driving circuit includes at least two thin film transistors T 1  and T 2  and a storage capacitor C 1 . In one embodiment, the at least two thin film transistors T 1  and T 2  include a switching transistor T 1  and a driving transistor T 2 . 
     The switching transistor T 1  is connected with a scan line SL 1  and a data line DL 1 , and transmits a data voltage input to the data line DL 1  to the driving transistor T 2  according to a switching voltage input to the scan line SL 1 . The storage capacitor C 1  is connected with the switching transistor T 1  and a power source line VDD, and stores a voltage that corresponds to a voltage difference between a voltage transmitted from the switching transistor T 1  and a voltage supplied to the power source line VDD. 
     The driving transistor T 2  is connected with the power source line VDD and the storage capacitor C 1  and supplies an output current I OLED  that proportionally corresponds to the square of a voltage difference of the voltage supplied to the power source line VDD and a threshold voltage stored in the storage capacitor C 1  to the OLED L 1 , and the OLED L 1  emits light due to the output current I OLED . The driving transistor T 2  includes a source electrode  32 , a drain electrode  34 , and a gate electrode  36 . In one embodiment, the anode  26  of the OLED L 1  is connected to the drain electrode  34  of the driving transistor T 2 . A configuration of the sub-pixel is not limited as described, and can be suitably changed. 
     The photo sensor  43  is formed on the second substrate  40  that is close to (or near) the above-stated sub-pixel. A plurality of photo sensors  43  are disposed in a matrix format on the second substrate  40 , and each photo sensor  43  is covered by the shield layer  45 . The shield layer  45  is formed as a black matrix in a space between sub-pixels. 
     Such a shield layer  45  can not only improve contrast by preventing (or protecting from) light leakage, but can also realize a touch panel function by preventing (or protecting) the photo sensor  43  from being influenced by internal light. When an external material (e.g., finger or pen) approaches, the photo sensor  43  detects the approach and generates a corresponding signal and performs a command of a corresponding location. 
       FIG. 5  shows a cross-sectional view of an OLED display according to a second exemplary embodiment of the present invention. Referring to  FIG. 5 , the OLED display according to the present exemplary embodiment includes color filter layers  48  formed between shield layers  45 . The color filter layer  48  is formed by arranging color filters of red (R), green (G), and blue (B) colors in a set or predetermined sequence in a sub-pixel area. Here, space efficiency can be improved and an image can be more stably displayed by forming the color filter layer  48  between the shield layers  45 . 
     In view of the foregoing, an OLED display according to the above-described exemplary embodiments of the present invention reduces interference of internal light by forming a shield layer in a photo sensor so that a touch screen with high sensitivity can be provided. 
     In addition, the shield layer is formed as a black matrix so that contrast of the OLED display can be improved. 
     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.

Technology Classification (CPC): 7