Abstract:
Disclosed herein is an electroluminescence display panel including: a pixel circuit; a signal line; a scan line; a drive power supply line; a common power supply line; a power supply line drive circuit; a high-potential power supply line; and a low-potential power supply line.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present invention contains subject matter related to Japanese Patent Application JP 2007-173590 filed in the Japan Patent Office on Jun. 30, 2007, the entire contents of which being incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a technology for enhancing the yield of EL (Electro Luminescence) display panels and has modes of as an EL display panel, a power supply line drive apparatus, and an electronic device. It should be noted that the EL display panel denotes a self-illuminant display apparatus with EL devices arranged in matrix on a substrate made of glass or other materials. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, organic EL panels on which organic EL devices are arranged in matrix have been drawing attention. This is because organic EL panels are excellent in moving picture display characteristics as well as easy in reducing apparatus weight and film thickness. 
         [0006]    Currently, two organic EL panel driving schemes are available; passive matrix driving and active matrix driving. Especially, organic EL panels based on the active matrix driving in which an active element (a thin-film transistor) and a hold capacity are arranged for every pixel circuit are under brisk development. 
         [0007]    The following shows documents associated with the active matrix driving, for example. 
         [0008]    Patent Document 1: Japanese Patent Laid-Open No. 2003-255856 
         [0009]    Patent Document 2: Japanese Patent Laid-Open No. 2003-271095 
         [0010]    Patent Document 3: Japanese Patent Laid-Open No. 2004-029791 
         [0011]    Patent Document 4: Japanese Patent Laid-Open No. 2004-093682 
         [0012]    As shown in the above-mentioned Patent Documents, the active matrix driving is of various types. Described in what follows is one of these driving schemes that controls the on state and the off state of each organic EL device by digitally driving one of two power supply lines for supplying a power supply potential to each pixel circuit. 
         [0013]    Now, referring to  FIG. 1 , there is shown an exemplary pixel circuit of the above-mentioned type. A pixel circuit  1  is made up of two N-type thin-film transistors T 1  and T 2 . Of these two transistors, the thin-film transistor T 1  is a switching transistor that controls writing of a signal line voltage Vsig to a storage capacity Cs. 
         [0014]    On the other hand, the thin-film transistor T 2  is a driving transistor that supplies drive current Ids of a magnitude corresponding to a hold voltage Vgs of a storage capacity Cs to an organic EL device D 1 . The thin-film transistors T 1  and T 2  are connected to a signal line as follows. 
         [0015]    A gate electrode of the thin-film transistor T 1  is connected to a scan line SCNL(i) (i being a serial number indicative of row position) that gives a signal line potential write timing. In  FIG. 1 , a write timing signal is indicated by SCNL(i). 
         [0016]    One main electrode of the thin-film transistor T 1  is connected to a signal line DL(j) (j being a serial number indicative of a column position) and the other main electrode is connected to a gate electrode of the thin-film transistor T 2  and an electrode of the storage capacity Cs. 
         [0017]    One main electrode of the thin-film transistor T 2  is connected to a drive power supply line DSL(i) (i being a serial number indicative of row position) and the other main electrode is connected to a positive electrode (or an anode electrode) of an organic EL device OLED. In  FIG. 1 , power supply potential of a high potential (also referred to as a high power supply potential) to be applied to a drive power supply line DSL(i) is indicated by Vcc_H and a power supply potential of low potential (also referred to as a low power supply potential) is indicated by Vcc_L 1 . 
         [0018]    It should be noted that a negative electrode (or a cathode electrode) of the organic EL device OLED is connected to a common power supply line (or a ground line). In  FIG. 1 , a power supply potential of low potential to be applied to the common power supply line is indicated by Vcc_L 2 . Meanwhile, the organic EL device OLED is a current-driven element. Therefore, it is desired to flow a current (I*n) obtained by multiplying current I flowing through one pixel circuit by the number of pixels (or n times) to the drive power supply line DSL(i) that is emitting light. 
         [0019]    Hence, a wiring resistance of the drive power supply line DSL(i) located on a route along which the power supply potential of high potential is supplied has to be relatively small. If the wiring resistance is large, a voltage drop difference occurs across the drive power supply line DSL(i) to cause problems of a luminance difference depending on the location of scan line and generating heat in the power supply line, for example. 
         [0020]    If the number of stages of scan lines making up a valid display area is V, then it is desired to flow current (I*n*V) obtained by multiplying the number of pixels (n times) of current I flowing to one pixel circuit by the number of stages (V times) to a high-potential power supply line that supplies high-potential power supply potential Vcc_H to each drive power supply line DSL(i). 
         [0021]    Consequently, it is technically necessary for both the drive power supply line DSL(i) and the high-potential power supply line to be relatively large in wiring width so as to lower the wiring resistance. The following describes these technological requirements with reference to  FIGS. 2 and 3 .  FIG. 2  shows a connection relationship between the pixel circuit  1  and a power supply line drive circuit  3 .  FIG. 3  shows a wiring pattern of a connected portion between the drive power supply lines DSL and a power supply line drive circuit  7  (or an output stage buffer circuit). 
         [0022]    The power supply line drive circuit  3  is made up of a shift register  5  that transfers a power supply line drive pulse to a next scan line for each horizontal scan interval and a buffer circuit  7  (2-stage configuration of input-stage buffer circuit and output-stage buffer circuit). 
         [0023]    The two stages of buffer circuits making up the buffer circuit  7  are each configured by a CMOS inverter circuit. In the case of  FIG. 2 , each p-channel MOS transistor is connected to a high-potential power supply line  11  and each n-channel MOS transistor is connected to a low-potential power supply line  13 . 
         [0024]    Consequently, if the power supply drive pulse is at H level, high-potential power supply potential Vcc_H is supplied to the drive power supply line DSL(i); if the power supply line drive pulse is at L level, low-potential power supply potential Vcc_L is supplied to the drive power supply line DSL(i). 
         [0025]    Meanwhile, if the drive power supply line DSL(i) wide in wiring and the high-potential power supply line  11  are arranged in a crossed manner, a resultant cross area becomes wide. And, this cross appears for every drive power supply line DSL(i). Therefore, let one cross area be S, then a cross area of the entire organic EL panel becomes as large as S*V (V being the number of scan lines or the number of vertical resolutions). 
         [0026]    Thus, the wiring pattern shown in  FIG. 3  that may not avoid the increase in cross area involves a problem of causing an inter-layer short circuit due to dust or the like. This, in turn, may raise the detect rate of organic EL panels. In addition, the above-mentioned wiring pattern causes an increased capacity that is parasitic to the cross portion, thereby increasing the distortion of a potential waveform of the drive power supply line DSL(i). 
       SUMMARY OF THE INVENTION 
       [0027]    (1) Layout Pattern  1   
         [0028]    In carrying out the invention and according to one mode thereof, there is provided an EL display panel having: 
         [0029]    (a) a pixel circuit configured, arranged on a pixel array block in matrix, to drivingly control an electroluminescence element by active matrix driving; 
         [0030]    (b) a signal line configured, connected to the pixel circuit of the pixel array block in unit of row, to supply pixel data corresponding to each pixel circuit to each pixel circuit in column unit, the signal line being provided in a number equal to the number of columns; 
         [0031]    (c) a scan line configured, connected to the pixel circuit of the pixel array block, to control a timing of writing pixel data to each pixel circuit in row unit, the scan line being provided in a number equal to the number of row; 
         [0032]    (d) a drive power supply line configured, connected to the pixel circuit of the pixel array block, to control a light-on state and a light-off of the pixel circuit in row unit by two types of power supply potentials, a high potential and a low potential, the drive power supply line being provided in a number equal to the number of row; 
         [0033]    (e) a common power supply line configured, commonly connected to all pixel circuits of the pixel array, to supply the high-potential power supply potential in a fixed manner; 
         [0034]    (f) a power supply line drive circuit configured to supply one of the high-potential power supply potential and the low-potential power supply potential to corresponding the drive power supply line on the basis of a power supply drive pulse; 
         [0035]    (g) a high-potential power supply line arranged at a position where the high-potential power supply line does not cross the drive power line, the high-potential power supply line being a high-potential power supply line supplying a high-potential power supply potential to the power supply line drive circuit; and 
         [0036]    (h) a low-potential power supply line configured to supply a low-potential power supply potential to the power supply line drive circuit. 
         [0037]    (2) Layout Pattern  2   
         [0038]    In carrying out the invention and according to another mode thereof, there is provided an EL display panel having: 
         [0039]    (a) a pixel circuit configured, arranged on a pixel array block in matrix, to drivingly control an electroluminescence element by active matrix driving; 
         [0040]    (b) a signal line configured, connected to the pixel circuit of the pixel array block in unit of row, to supply pixel data corresponding to each pixel circuit to each pixel circuit in column unit, the signal line being provided in a number equal to the number of columns; 
         [0041]    (c) a scan line configured, connected to the pixel circuit of the pixel array block, to control a timing of writing pixel data to each pixel circuit in row unit, the scan line being provided in a number equal to the number of row; 
         [0042]    (d) a drive power supply line configured, connected to the pixel circuit of the pixel array block, to control a light-on state and a light-off of the pixel circuit in row unit by two types of power supply potentials, a high potential and a low potential, the drive power supply line being provided in a number equal to the number of row; 
         [0043]    (e) a common power supply line configured, commonly connected to all pixel circuits of the pixel array, to supply the low-potential power supply potential in a fixed manner; 
         [0044]    (f) a power supply line drive circuit configured to supply one of the high-potential power supply potential and the low-potential power supply potential to corresponding the drive power supply line on the basis of a power supply drive pulse; 
         [0045]    (g) a low-potential power supply line configured to supply a low-potential power supply potential to the power supply line drive circuit, the low-potential power supply line being wired at a position where the low-potential power supply line does not cross the drive power supply line; and 
         [0046]    (h) a high-potential power supply line configured to supply a high-potential power supply potential to the power supply line drive circuit, the high-potential power supply line being wired at a position where the high-potential power supply line does not cross the drive power supply line. 
         [0047]    As described and according to the invention, use of the layout patterns proposed herein can eliminate the cross between a drive power supply line that is drivingly controlled in a binary manner by a high-potential power supply and a low-potential power supply and a high-potential power supply line. This novel configuration minimizes the possibility of causing an inter-layer short circuit due to dust or the like, thereby significantly enhancing the yield of in manufacturing EL panels. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]      FIG. 1  is a circuit diagram illustrating an exemplary pixel circuit; 
           [0049]      FIG. 2  is a circuit diagram illustrating a connection relationship of pixel circuit and drive power supply circuit; 
           [0050]      FIG. 3  is a schematic diagram illustrating wiring patterns of connection portions between drive power supply line and power supply line drive circuit; 
           [0051]      FIG. 4  is a circuit diagram illustrating an exemplary configuration of a display panel of active matrix drive type; 
           [0052]      FIG. 5  is a timing chart indicative of an example of active matrix drive operation of a pixel circuit using a power supply line; 
           [0053]      FIG. 6A  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (A) of  FIG. 5 ; 
           [0054]      FIG. 6B  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (B) of  FIG. 5 ; 
           [0055]      FIG. 6C  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (C) of  FIG. 5 ; 
           [0056]      FIG. 6D  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (D) of  FIG. 5 ; 
           [0057]      FIG. 6E  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (E) of  FIG. 5 ; 
           [0058]      FIG. 6F  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (F) of FIG.  5 ; 
           [0059]      FIG. 6G  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (G) of  FIG. 5 ; 
           [0060]      FIG. 6H  is a circuit diagram illustrating a state in the pixel circuit corresponding to period (H) of  FIG. 5 ; 
           [0061]      FIG. 7  is a graph indicative of a relationship of data voltage and drain current with none of threshold correction and mobility correction executed; 
           [0062]      FIG. 8  is a graph indicative of a relationship of data voltage and drain current with merely threshold correction executed; 
           [0063]      FIG. 9  is a graph indicative of a relationship of data voltage and drain current with both threshold correction and mobility correction executed; 
           [0064]      FIG. 10  is a schematic diagram illustrating a layout pattern corresponding to pattern example  1 ; 
           [0065]      FIG. 11  is a schematic diagram illustrating a layout pattern corresponding to pattern example  2 ; 
           [0066]      FIG. 12  is a schematic diagram illustrating a layout pattern corresponding to pattern example  3 ; 
           [0067]      FIG. 13  is a schematic diagram illustrating a layout pattern corresponding to pattern example  4 ; 
           [0068]      FIG. 14  is a schematic diagram illustrating a layout pattern corresponding to pattern example  5 ; 
           [0069]      FIG. 15  is a schematic diagram illustrating a layout pattern corresponding to pattern example  6 ; 
           [0070]      FIG. 16  is a schematic diagram illustrating a layout pattern corresponding to pattern example  7 ; 
           [0071]      FIG. 17  is a circuit diagram illustrating another exemplary pixel circuit; 
           [0072]      FIG. 18  is a schematic diagram illustrating a layout pattern corresponding to pattern example  8 ; 
           [0073]      FIG. 19  is a schematic diagram illustrating a layout pattern corresponding to pattern example  9 ; 
           [0074]      FIG. 20  is a schematic diagram illustrating a layout pattern corresponding to pattern example  10 ; 
           [0075]      FIG. 21  is a schematic diagram illustrating an exemplary configuration of a display module; 
           [0076]      FIG. 22  is a schematic diagram illustrating an exemplary functional configuration of electronic equipment; 
           [0077]      FIG. 23  is a schematic diagram illustrating an exemplary electronic equipment product; 
           [0078]      FIGS. 24A and 24B  are schematic diagrams illustrating an exemplary electronic equipment product; 
           [0079]      FIG. 25  is a schematic diagram illustrating an exemplary electronic equipment product; 
           [0080]      FIGS. 26A and 26B  are schematic diagrams illustrating an exemplary electronic equipment product; and 
           [0081]      FIG. 27  is a schematic diagram illustrating an exemplary electronic equipment product. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0082]    This invention will be described in further detail by way of embodiments thereof, organic EL panels of active matrix type, with reference to the accompanying drawings. It should be noted that any portion that is not illustrated or written herein is applied with known technologies in the technical field concerned. It should also be noted that the embodiments described below are illustrative only and therefore not limited thereto. 
         [0083]    (A) Structure of the Organic EL Panel 
         [0084]    Now, referring to  FIG. 4 , there is shown an exemplary structure of an organic EL panel for realizing active matrix driving of the pixel circuit  1  by driving, in a binary manner, one of two power supply lines for supplying a power supply potential to the pixel circuit  1 . 
         [0085]    An organic EL panel  21  is mainly made up of a pixel array block  23 , a scan line drive circuit  25 , a power supply line drive circuit  27  (corresponding to reference numeral  3  shown in  FIG. 2 ), and a data line drive circuit  29 . In the present embodiment, the pixel array block  23  with the pixel circuit  1  arranged in matrix in accordance with a screen resolution is for color display and arranged inside a valid screen accordance with the arrangement of luminescent color. 
         [0086]    However, if an organic EL device having a structure in which organic luminescent layers of two or more colors are laminated makes up the pixel circuit  1 , one pixel circuit  1  corresponds to two or more luminescent colors. The scan line drive circuit  25  is a circuit device configured to give, in a row unit (or a scan line unit) a write timing of a signal potential applied to signal line DL(j) to the pixel circuit  1 . 
         [0087]    It should be noted that a write timing signal is supplied to scan line SCNL(i) of a next stage for each horizontal scan interval. 
         [0088]    The power supply line drive circuit  27  is a circuit device configured to drivingly control drive power supply line DSL(i). As described with reference to  FIG. 2 , the power supply line drive circuit  27  is made up of the shift register  5  corresponding to each scan line and a power supply line drive circuit  7 . 
         [0089]    It is possible for the power supply line drive circuit  27  to be formed not merely integrally on a same substrate as the pixel array block  23 , but also as a device module discrete from the organic EL panel  21 . A detail configuration of this power supply line drive circuit  27  will be described later. 
         [0090]    The data line drive circuit  29  is a circuit device configured to drivingly control signal line DS(j). A signal voltage to be applied to signal line DL(j) is a threshold voltage Vo of corrective operation to be described later or a pixel position data voltage Vsig to be specified by a write timing signal. 
         [0091]    (B) Drive Operation of the Pixel Circuit 
         [0092]    Referring to  FIG. 5 , there is shown an exemplary active matrix driving of the pixel circuit  1  by use of a power supply line. In the drive operation example shown in  FIG. 5 , a threshold correction operation and a mobility correction operation of the thin-film transistor T 2  operating as a drive transistor are executed within one horizontal scan period ( 1 H). 
         [0093]    It should be noted that  FIG. 5  shows potential changes of scan line SCNL(i), signal line DL(j), and drive power supply line DSL(i) along the same time axis.  FIG. 5  also shows a change of gate potential Vg and a change of source potential Vs of the thin-film transistor T 2  accompanying the potential changes of these lines. Besides,  FIG. 5  shows a transition of potential changes, in 8 periods of (A) through (H) for the purpose of convenience. 
         [0094]    (i) Light Emission Period 
         [0095]    In period (A), the organic EL device OLED is in a light-emitting state. After this period, a new field of line sequential scan starts. 
         [0096]    (ii) Threshold Correction Preparation Period 
         [0097]    When a new field starts, a preparation for threshold correction is executed over periods (B) and (C). In period (B), drain current supply to the organic EL device OLED is stopped, upon which the organic EL device OLED stops emitting light. At this moment, the light-emitting voltage Vel of the organic EL device OLED undergoes a transition so as to draw toward zero. 
         [0098]    In accordance with this drop of light-emitting voltage Vel, the source potential Vs of the thin-film transistor T 2  makes a transition to almost the same potential as lower power supply potential Vcc_L for initialization. It should be noted that the gate potential Vg of the thin-film transistor T 2  is initialized to reference potential Vo that is applied along the signal line DL(j) in the following period (C). 
         [0099]    Executing these two initializing operations complete the initialization setting of the hold voltage of the hold capacity Cs. Namely, the hold voltage of the hold capacity Cs is initialized to a voltage (Vo−Vcc_L) larger than the threshold voltage Vth of the thin-film transistor T 2 . This is a threshold correction preparing operation. 
         [0100]    (iii) Threshold Correcting Operation 
         [0101]    Subsequently, a threshold correcting operation is executed for period (D). In this period (D) too, the reference potential Vo is given to the gate potential Vg. In this state, a high power supply potential Vcc_H is applied to the drive power supply line DSL(i). 
         [0102]    As a result, the drain current flows to the signal line DL(j) through the hold capacity Cs to lower hold voltage Vgs of the hold capacity Cs. Accordingly, the source potential Vs of the thin-film transistor T 2  rises. 
         [0103]    It should be noted that the drop of the hold voltage Vgs of the hold capacity Cs stops when the hold voltage Vgs reaches the threshold voltage Vth upon which the thin-film transistor T 2  cuts off. Thus, the threshold correcting operation for setting the hold voltage Vgs of the hold capacity Cs to the threshold voltage Vth unique to the thin-film transistor T 2  is completed. 
         [0104]    (iv) Signal Potential Write and Mobility Correction Preparing Operation 
         [0105]    When a threshold correcting operation has been completed, a preparation for signal write and mobility correction is executed over periods (E) and (F). It should be noted that this preparing operation may be omitted. In period (E), the drive potential of scan line SCNL(i) is switched to low to float the thin-film transistor T 2 . 
         [0106]    In period (F), the data voltage Vsig corresponding to pixel data is applied to the signal line DL(j). This period (F) is provided in consideration of a delay in the rise of the signal line potential due to the effect of the capacity component parasitic to the signal line DL(j). The existence of this period allows a write operation to be started with the potential of the signal line DL(j) stabilized in the next period (G). 
         [0107]    (v) Signal Potential Write and Mobility Correcting Operation 
         [0108]    In period (G), a signal potential write operation and a mobility correcting operation are executed. Namely, the drive potential of the scan line SCNL(i) is switched to high, applying the data potential Vsig to the gate potential of the thin-film transistor T 2 . When the data potential Vsig is applied, the hold voltage Vgs held in the hold capacity Cs makes a transition to Vsig+Vth. Thus, because the hold voltage Vgs gets larger than the threshold voltage Vth, the thin-film transistor T 2  is turned on. 
         [0109]    When the thin-film transistor T 2  has been turned on, the drain current starts flowing to the organic EL device OLED. However, in the stage where the drain current starts flowing, the organic EL device OLED is still in a cutoff state (or high impedance). Therefore, in proportion to the mobility of the thin-film transistor T 2 , the drain current flows so as to charge parasitic capacity C 0  of the organic EL device OLED. 
         [0110]    The anode potential of the organic EL device OLED (namely, the source potential Vs of the thin-film transistor T 2 ) rises by the charge voltage ΔV of this parasitic capacity C 0 . By this charge voltage ΔV, the hold voltage Vgs of the hold capacity Cs lowers. Namely, the hold voltage Vgs changes to Vsig+Vth−ΔV. Thus, an operation in which the hold voltage Vgs is corrected by the charge voltage ΔV of the parasitic capacity C 0  corresponds to the mobility correcting operation. 
         [0111]    It should be noted that a bootstrap operation of the hold capacity Cs raises the gate potential Vg of the thin-film transistor T 2  by the same rise as that of the source potential Vs. To be more precise, the gate potential Vg rises by a potential obtained by multiplying the rise of the source potential Vs by gain g (&lt;1). 
         [0112]    (vi) Light-Emitting Period 
         [0113]    In period (H), the drive potential of the scan line SCNL(i) is changed to low to put the gate electrode of the thin-film transistor T 2  into a floating state. At this moment, the thin-film transistor T 2  supplies a drain current equivalent to hold voltage Vgs after mobility correction (=Vsig+Vth−ΔV) to the organic EL device OLED. 
         [0114]    Consequently, the organic EL device OLED starts light emission. At this moment, the anode potential (the source potential Vs of the thin-film transistor T 2 ) of the organic EL device OLED rises to the light-emitting voltage Vel in accordance with the magnitude of the drain current. At this moment, the gate potential Vg of the thin-film transistor T 2  also rises by the light-emitting voltage Vel by the bootstrap operation of the hold capacity Cs. The gate potential Vg rises by a potential obtained by multiplying the rise of the source potential Vs by gain g (&lt;1). 
         [0115]    (C) Changes of Connection State and Potential in Pixel Circuit 
         [0116]    The following schematically describes the potential state changes inside the pixel circuit  1  corresponding to the period described with reference to  FIG. 5 . The following description is made by use of same reference numbers as the corresponding periods. Namely, the following description is made with reference to  FIGS. 6A through 6H . It should be noted that, with  FIGS. 6A through 6H , the thin-film transistor T 1  that operates as a sampling transistor is indicated as a switch and the parasitic capacity of the organic EL device OLED is explicitly indicated as C 0 . 
         [0117]    (i) Light-Emitting Period 
         [0118]      FIG. 6A  shows corresponds to an operation state of period (A) shown in  FIG. 5 . In period (A) that is a light-emitting period, high power supply potential Vcc_H for light emitting is applied to the drive power supply line DSL (i). At this moment, the thin-film transistor T 2  supplies drain current Ids corresponding to the hold voltage Vgs (&gt;Vth) of the hold capacity Cs to the organic EL device OLED. The light-emitting state of the organic EL device OLED continues until the end of period (A). 
         [0119]    (ii) Threshold Correction Preparing Period 
         [0120]      FIG. 6B  corresponds to an operation state of period (B) shown in  FIG. 5 . In period (B), the potential of the drive power supply line DSL(i) is switched from the light-emitting high power supply potential Vcc_H to the low power supply potential Vcc_L. This switching blocks the supplying of drain current Ids. 
         [0121]    As a result, the gate potential Vg and the source potential Vs of the thin-film transistor T 2  lower in cooperation with the lowering of the light-emitting voltage Vel of the organic EL device OLED. Then, the source potential Vs lowers to nearly the same level as the low power supply potential Vcc_L applied to the drive power supply line DSL(i). It should be noted that the low power supply potential Vcc_L is sufficiently lower than the reference potential Vo for initialization to be applied to the signal line DL(j). 
         [0122]      FIG. 6C  corresponds to an operation state of period (C) shown in  FIG. 5 . In period (C), the potential of scan line CSNL(i) changes to high. Consequently, the thin-film transistor T 1  is turned on, upon which the gate potential Vg of the thin-film transistor T 2  is set to the reference potential Vo for initialization applied to the signal line DL(j). 
         [0123]    When period (C) ends, the hold voltage Vgs of the hold capacity Cs is initialized to a voltage greater than the threshold voltage Vth of the thin-film transistor T 2 . At this moment, a high potential is applied to the common power supply line to which the cathode electrode of the organic EL device OLED is connected, thereby reversely biasing the organic EL device OLED. Consequently, the drain current Ids flows to the signal line DL(j) through the hold capacity Cs and the thin-film transistor T 1 . 
         [0124]    (iii) Threshold Correcting Operation 
         [0125]      FIG. 6D  corresponds to an operation state of period (D) shown in  FIG. 5 . In period (D), the potential of the drive power supply line DSL(i) is switched from the low power supply potential Vcc_L for initialization to the high power supply potential Vcc_H for light emitting. It should be noted that the thin-film transistor T 1  for sampling is maintained in the on state. 
         [0126]    As a result, merely the source potential Vs starts rising with the gate potential Vg of the thin-film transistor T 2  kept at the initializing reference potential Vo. At any point of time up to the end of period (D), the hold voltage Vgs of the hold capacity Cs reaches the threshold voltage Vth. Consequently, the thin-film transistor T 2  turns off. The source potential Vs at this moment goes lower than the gate potential Vg (=Vo) by the threshold voltage Vth. 
         [0127]    (iv) Preparing Operation for Signal Potential Write and Mobility Correction 
         [0128]      FIG. 6E  corresponds to an operation state of period (E) shown in  FIG. 5 . In Period (E), the potential of the scan line SCNL(i) changes to low. Consequently, the thin-film transistor T 2  is turned off to put the gate electrode of the thin-film transistor T 2  as a drive transistor into a floating state. 
         [0129]    However, the cutoff state of the thin-film transistor T 2  is maintained. Therefore, the drain current Ids does not flow.  FIG. 6F  corresponds to an operation state of period (F) shown in  FIG. 5 . In period (F), the potential of signal line DL(j) changes from the initialization reference potential Vo to the data potential Vsig. It should be noted however that the thin-film transistor T 1  that functions as a sampling transistor remains in the off state. 
         [0130]    (v) Signal Potential Write and Mobility Correction 
         [0131]      FIG. 6G  corresponds to an operation state of period (G). In period (G), the potential of scan line SCNL(i) changes to high. Consequently, the sampling transistor T 1  is turned on, upon which the gate electrode of the thin-film transistor T 2  goes to signal potential Vsig. 
         [0132]    Also, in period (G), the power supply line DSL(i) changes to the light-emitting high power supply potential Vcc_H. As a result, the thin-film transistor T 2  is turned on, upon which the drain current Ids flows. However, the organic EL device OLED is initially in the cutoff state (or the high impedance state). Hence, the drain current Ids flows not into the organic EL device OLED but into the parasitic capacity Cs as shown in  FIG. 6G . 
         [0133]    As the parasitic capacity Cs is charged, the source potential Vs of the thin-film transistor T 2  starts rising. Then, the hold voltage Vgs of the hold capacity Cs goes Vsig+Vth−ΔV. Thus, the sampling of signal potential Vsig and the correction by charge voltage ΔV are executed in parallel. It should be noted that, as the data potential Vsig is larger, the drain current Ids gets larger, thereby making the absolute value of charge voltage ΔV larger. 
         [0134]    Consequently, the mobility correction in accordance with any light-emitting level is made practicable. It should be noted that, if the signal potential Vsig is constant, as mobility μ of the thin-film transistor T 2  is larger, the absolute value of charge voltage ΔV gets larger, thereby making a feedback larger. 
         [0135]    (vi) Signal Potential Write and Mobility Correction 
         [0136]      FIG. 6H  corresponds to an operation state of period (H) shown in  FIG. 5 . The potential of scan line SCNL(i) changes to low again. Consequently, the thin-film transistor T 1  is turned off to put the gate electrode of the thin-film transistor T 2  into a floating state. 
         [0137]    It should be noted that the potential of the power supply line DSL(i) is maintained at the light-emitting high power supply potential Vcc_HH, so that the drain current Ids corresponding to the hold voltage Vgs (=Vsig+Vth−ΔV) of the hold capacity Cs is continuously supplied to the organic EL device OLED. This supply of the drain current causes the organic EL device OLED to start emitting light. At the same time, light-emitting voltage Vel corresponding to the magnitude of the drain current Ids occurs between both the electrodes of the organic EL device OLED. 
         [0138]    Namely, the source voltage Vs of the thin-film transistor T 2  rises. Also, a bootstrap operation of the hold capacity Cs 1  causes the gate potential Vg to rise by the amount of rise of the source potential Vs. Consequently, the hold capacity Cs comes to hold the same hold voltage Vgs (=Vsig+Vth−ΔV) as that before the bootstrap operation. As a result, the light-emitting operation caused by the drain current Ids with the mobility corrected is continued. 
         [0139]    (B-3) Correction Effect 
         [0140]    Here, the effect of correction is confirmed.  FIG. 7  shows the current-voltage characteristic of the thin-film transistor T 2 . Especially, the drain current Ids at the time when the thin-film transistor T 2  is operating in a saturation region is given by the following equation. 
         [0000]        Ids =(½)·μ·( W/L )· Cox ·( Vgs−Vth ) 2   (1) 
         [0141]    In the above-mentioned relation, μ is representative of mobility. W is representative of gate width. L is representative of gate length. Cox is representative of gate oxide film capacitance per unit area. As seen from the above-mentioned transistor characteristics relation, when the threshold voltage Vth fluctuates, the drain current Ids fluctuates if the hold voltage Vgs is constant.  FIG. 7  shows a relationship between the data voltage Vsig and the drain current Ids at a time when neither threshold correction nor mobility correction is executed. 
         [0142]    In the case of the above-mentioned example of correcting operation, however, the hold voltage Vgs at the time of light emission is given by Vsig+Vth−ΔV. Therefore, the equation (1) above can be represented as follows. 
         [0000]        Ids =(½)·μ·( W/L )· Cox ·( Vsig−ΔV ) 2   (2) 
         [0143]    As seen from equation (2), threshold voltage Vth is deleted from the equation. Namely, it is understood that the dependence on the threshold voltage Vth was removed by the above-mentioned correcting operation. 
         [0144]    This denotes that, if there exist a variation in the threshold voltage Vth of the thin-film transistor T 2  that constitutes the pixel circuit  1 , such a variation will not affect the drain current Ids.  FIG. 8  shows a relation between the data voltage Vsig and the drain current Ids at a time when merely the threshold correction is executed. 
         [0145]    It should be noted that, with pixels having different motilities μ, the drain currents Ids thereof will take different values if the data voltage Vsig is the same. In the case of  FIG. 8 , pixel A is greater in mobility μ than pixel B. Hence, if the data voltage Vsig is the same, the drain current Ids of pixel A is greater than the drain current Ids of pixel B. However, the charge voltage ΔV occurring in the parasitic capacity C 0  in the same correction period depends on mobility μ. 
         [0146]    Namely, the charge voltage ΔV of the pixel having greater mobility μ is greater than the charge voltage ΔV of the pixel having smaller mobility μ. In equation (2) above, the charge voltage ΔV acts on the direction in which the drain current Ids lowers. As a result, the effect of the variation in the mobility μ appearing in the drain current Ids is suppressed. Namely, as shown in  FIG. 9 , the same drain current Ids can flow to any data current Vsig. 
         [0147]    (D) Layout Pattern Examples 
         [0148]    (D-1) Pattern Example  1   
         [0149]    The following describes a layout pattern of the high-potential power supply line  11  that is suitable when a pixel array block is made up of the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0150]      FIG. 10  shows a layout pattern that is proposed as the pattern example  1 . In this pattern example, the low-potential power supply line  13  that is not desired to increase the wiring width thereof is arranged on the valid pixel area side so as to cross the drive power supply line DSL(i). On the other hand, the high-potential power supply line  11  that is desired to increase the wiring width thereof is arranged so as to cross the output wiring of the preceding buffer circuit that constitutes the power supply line drive circuit  27 . 
         [0151]    In pattern example  1 , the waveform of power supply drive pulse may also remain blunt due to the parasitic capacitance at the cross between the high-potential power supply line  11  thick in wiring width and the output wiring of the preceding buffer circuit. However, if the waveform of the supply line drive pulse is made blunt, the blunt waveform can be reshaped in the subsequent output buffer circuit. Therefore, the driving of the drive power supply line DSL(i) will not be affected. 
         [0152]    Also, use of a positional relation in which there is no cross between the high-potential power supply line  11  and the drive power supply line DSL(i) can make smaller the cross area between wirings that may generate a large potential alternately. This configuration can minimize the possibility of causing a inter-layer short circuit due to dust or the like, thereby significantly improving the yield of the production of organic EL panels. 
         [0153]    (D-2) Pattern Example  2   
         [0154]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0155]      FIG. 11  shows a layout pattern proposed as the pattern example  2 . The pattern example  2  is a variation of the pattern example  1 . Namely, merely the positional arrangement of the low-potential power supply line  13  that need not be increased in wiring width is changed in the pattern example  2 . 
         [0156]    In the case of the pattern example  2 , the low-potential power supply line  13  and the drive power supply line DSL(i) are arranged so as not to cross each other. To be more specific, the low-potential power supply line  13  is arranged so as to overlap the output buffer of the power supply line drive circuit  27 . 
         [0157]    In this wiring example, the number of layers increases from 2 to 3; however, the cross portion between the digitally driven power supply line DSL(i) and the low-potential power supply line  13  can be eliminated. As a result, this configuration can still decrease the possibility of an inter-layer short circuit due to dust or the like, thereby still significantly improving the yield of the production of organic EL panels. 
         [0158]    (D-3) Pattern Example  3   
         [0159]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0160]      FIG. 12  shows a layout pattern proposed as the pattern example  3 . The pattern example  3  is another variation of the pattern example  1 . Namely, merely the positional arrangement of the low-potential power supply line  13  not desired to increase the wiring width thereof is changed. 
         [0161]    In the case of pattern example  3 , the low-potential power supply line  13  is arranged so as not to cross the drive power supply line DSL(i). To be more specific, the low-potential power supply line  13  is arranged at an intermediate position between the output buffer circuit of the power supply line drive circuit  27  and the drive power supply line DSL(i). Namely, the low-potential power supply line  13  is arranged so as to cross an extraction wire for connecting the output terminal of the output buffer circuit with the drive power supply line DSL(i). 
         [0162]    In this wiring example, the low-potential power supply line  13  crosses the digitally driven wiring (the extraction wire); however, the cross area is also small because this extraction wire is small in wiring width. As a result, this configuration can still further decrease the possibility of an inter-layer short circuit due to dust or the like, thereby still further significantly improving the yield of the production of organic EL panels. 
         [0163]    (D-4) Pattern Example  4   
         [0164]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0165]      FIG. 13  shows a layout pattern proposed as the pattern example  4 . The pattern example  4  is still another variation of the pattern example  1 . Namely, merely the positional arrangement of the low-potential power supply line  13  not desired to increase the wiring width thereof is changed. 
         [0166]    In the case of the pattern example  4 , the low-potential power supply line  13  is arranged so as not to cross the drive power supply line DSL(i). To be more specific, the low-potential power supply line  13  is arranged at an intermediate position between the output buffer circuit of the power supply line drive circuit  27  and the high-potential power supply line  11 ( i ). 
         [0167]    In this wiring example, like the case of the high-potential power supply line  11  thick in wiring width, the waveform of power supply drive pulse may also remain blunt due to the parasitic capacitance at the cross between the low-potential power supply line  13  and the output wiring of the preceding buffer circuit. 
         [0168]    However, because the wiring width of the low-potential power supply line  13  is small and the parasitic capacity is low, and, if the waveform get blunt, the blunt waveform can be reshaped, thereby involving no problem in operation. Obviously, in this case can also improve the yield of the production of organic EL panels. 
         [0169]    (D-5) Pattern Example  5   
         [0170]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0171]      FIG. 14  shows a layout pattern proposed as the pattern example  5 . The pattern example  5  is yet another variation of the pattern example  1 . Namely, merely the positional arrangement of the high-potential power supply line  11  is changed. 
         [0172]    To be more specific, the high-potential power supply line  11  is arranged so as to overlap the output buffer circuit of the power supply line drive circuit  27 . 
         [0173]    In this wiring example, the number of wiring layers increases from 2 to 3; however, the cross portion between the digitally driven power supply line DSL(i) and the low-potential power supply line  13  can be eliminated. As a result, this configuration can still decrease the possibility of an inter-layer short circuit due to dust or the like, thereby still significantly improving the yield of the production of organic EL panels. 
         [0174]    (D-6) Pattern Example  6   
         [0175]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0176]      FIG. 15  shows a layout pattern proposed as the pattern example  6 . The pattern example  6  is a different variation of the pattern example  1 . To be more specific, the low-potential power supply line  13  is arranged so as to overlap the high-potential power supply line  11  arranged in front of the output buffer circuit of the power supply line drive circuit  27 . 
         [0177]    In this wiring example, a high voltage is applied between the power supply lines; however, this high voltage is a static voltage, so that an effect of the waveform to the operation of the drive power supply line DSL(i) need not be considered. In addition, because the power supply line need not be offset-arranged on the plane, the area of the organic EL panel can be reduced if slightly. 
         [0178]    (D-7) Pattern Example  7   
         [0179]    The following also describes a layout pattern example of the high-potential power supply line  11  that is suitable when a pixel array block is made up by the pixel circuit  1  having the configuration shown in  FIG. 1 . 
         [0180]      FIG. 16  shows a layout pattern proposed as the pattern example  7 . In the pattern example  7 , the high-potential power supply line  11  and the low-potential power supply line  13  are arranged in a manner opposite to the pattern example  1 . However, if the high-potential power supply line  11  crosses the drive power supply line DSL(i), the above-mentioned technical problems may not be solved. 
         [0181]    Therefore, the extraction wire connected the output terminal of the output buffer circuit of the power supply line drive circuit  27  to the drive power supply line DSL(i) is elongated so as to be crossed with the high-potential power supply line  11 . 
         [0182]    In this wiring example, the high-potential power supply line  11  crosses the digitally driven wiring (namely, the extraction wire); however, the cross area is also small because this extraction wire is small in wiring width. As a result, this configuration can still further decrease the possibility of an inter-layer short circuit due to dust or the like, thereby still further significantly improving the yield of the production of organic EL panels. 
         [0183]    (D-8) Pattern Example  8   
         [0184]    The following describes a layout pattern example of the high-potential power supply line  11  and the low-potential power supply line  13  that is suitable when the pixel array block is constituted by a pixel circuit  31  having the configuration shown in  FIG. 17 . The pixel circuit  31  in this example is made up of the thin-film transistor T 2  with the drive transistor is of p type. Accordingly, the other electrode of the hold capacity Cs is connected to the common power supply line that supplies high power supply potential Vcc_H to all pixels. 
         [0185]    It should be noted that, in the case of  FIG. 17 , the drive power supply line DSL(i) corresponds to a power supply line to which the cathode electrode of the organic EL device OLED is connected. Therefore, in the case of  FIG. 17 , the operation in the pixel circuit  31  is controlled by digitally driving the drive power supply line DSL(i) to which the cathode electrode is connected. 
         [0186]    Obviously, in this case too, the common signal line to which high power supply potential Vcc_H is applied is relatively large in wire width in preparation for the supply of a large current. Also, the signal width of the drive power supply line DSL(i) is large to cope with the drawing of a large current. 
         [0187]      FIG. 18  shows a layout pattern proposed as the pattern example  8 . In the pattern example  8 , not merely the high-potential power supply line  11  but also the low-potential power supply line  13  have to have a relatively thick wiring width, so that these power supply lines have to be arranged so as not to cross the drive power supply line DSL(i). 
         [0188]    Namely, in the case of  FIG. 18 , the high-potential power supply line  11  is arranged so as to be crossed with the output wiring of the preceding buffer circuit constituting of the power supply line drive circuit  27 , while the low-potential power supply line  13  is arranged so as to be overlapped on the top layer of the preceding buffer circuit constituting the power supply line drive circuit  27 . This arrangement minimizes the possibility of a short circuit due to dust or the like, thereby significantly improving the yield of the production of organic EL panels. 
         [0189]    (D-9) Pattern Example  9   
         [0190]    The following describes a layout pattern example of the high-potential power supply line  11  and the low-potential power supply line  13  that is suitable when the pixel array block is constituted by the pixel circuit  31  having the configuration shown in  FIG. 17 . 
         [0191]      FIG. 19  shows a layout pattern proposed as the pattern example  9 . In the pattern example  9 , the high-potential power supply line  11  and the low-potential power supply line  13  are arranged so as to be overlapped with each other at a preceding position of the output buffer of the power supply line drive circuit  27 . Either of these power supply lines may be the other in overlapping. It should be noted that, in this case, a parasitic capacity is generated at the portion in which the power supply lines having thick wire width overlap with each other. However, this parasitic capacity will not affect the power supply drive pulse because these power supply lines supply fixed potentials. 
         [0192]    (D-10) Pattern Example  10   
         [0193]    The following describes a layout pattern example of the high-potential power supply line  11  and the low-potential power supply line  13  that is suitable when the pixel array block is constituted by the pixel circuit  31  having the configuration shown in  FIG. 17 . 
         [0194]      FIG. 20  shows a layout pattern proposed as the pattern example  10 . In the pattern example  10 , the high-potential power supply line  11  is arranged in front of the output buffer of the power supply line drive circuit  27  and the low-potential power supply line  13  is arranged so as to be crossed with the extraction wire connecting the output buffer of the power supply line drive circuit  27  to the drive power supply line DSL(i). 
         [0195]    It should be noted that the positions of the high-potential power supply line  11  and the low-potential power supply line  13  may be replaced with each other. In this wiring example too, the cross area between the drive power supply line DSL(i) and the power supply line can be made small. Therefore, this arrangement minimizes the possibility of short circuit due to dust or the like, thereby significantly improving the yield of the production of organic EL panels. 
         [0196]    (D-11) Others 
         [0197]    It should be noted that the above-mentioned layout patterns are illustrative and therefore it is practicable to use other layouts. 
         [0198]    (E) Other Embodiments 
         [0199]    (E-1) Product Examples 
         [0200]    (a) Drive IC 
         [0201]    In the above, embodiments in which the pixel array block and the drive circuit are formed on one panel. It is also practicable to manufacture the scan line drive circuits  25 , the power supply line drive circuit  27 , and the data line drive circuit  29  separately from the pixel array block  23  and separately distribute organic EL panels formed with the pixel array block  23 . For example, these drive circuits may be manufactured as drive ICs (Integrated Circuits) to be mounted on each organic EL panel formed with the pixel array block  23 . 
         [0202]    (b) Display Module 
         [0203]    The organic EL panel  21  in the above-mentioned embodiments may also be distributed in the form of a display module  41  having an external view shown in  FIG. 21 . 
         [0204]    The display module  41  has a construction in which an opposite block  43  is laminated on the surface of a support base  45 . With the opposite block  43 , a color filter, a protection film, and a light-resistant film are arranged on the surface of a base that is made of glass or another transparent material. 
         [0205]    It should be noted that the display module  41  may have an FPC (Flexible Printed Circuit)  47  or the like for interfacing between the outside and the support base  45 . 
         [0206]    (c) Electronic Devices 
         [0207]    The organic EL panels in the above-mentioned embodiments may be distributed in the form of a product mounted on electronic devices.  FIG. 22  shows a conceptual configuration example of an electronic device  51 . The electronic device  51  is made up of an organic EL panel  53  and a system control block  55 . Contents of processing to be executed by the system control block  55  depend on the product form of the electronic device  51 . 
         [0208]    It should be noted that the electronic device  51  is not limited to devices of a particular field as long as the electronic device  51  has capabilities of displaying images or video that generated inside the electronic device  51  or supplied from the outside. For the electronic device  51  of this type, a television receiver is assumed, for example.  FIG. 23  shows an exemplary external view of a television receiver  61 . 
         [0209]    On the front side of a housing of the television receiver  61 , a display screen  67  made up of a front panel  63  and a filter glass  65  is arranged. The portion of the display screen  67  corresponds to the organic EL panel described above with reference to embodiments. 
         [0210]    In addition, for the electronic device  51  of this type, a digital camera is assumed, for example.  FIG. 24  show external views example of a digital camera  71 .  FIG. 24A  shows the front side (the side of a subject to be taken).  FIG. 24B  shows an external view example of the rear side (the side of photographer). 
         [0211]    The digital camera  71  has a protection cover  73 , a taking lens block  75 , a display screen  77 , a control switch  79 , and a shutter button  81 . The portion of the display screen  77  corresponds to the organic EL panel described above with reference to embodiments. 
         [0212]    Besides, for the electronic device  51  of this type, a video camera is assumed, for example.  FIG. 25  shows an external view example of a video camera  91 . The video camera  91  has a taking lens  95  for taking a subject on the front side of a body  93 , a shooting start/stop switch  97 , and a display screen  99 . Of these components, the portion of the display screen  89  corresponds to the organic EL panel described above with reference to embodiments. 
         [0213]    Moreover, for the electronic device  51  of this type, a portable terminal device is assumed, for example.  FIG. 26  show external views example of a mobile phone  101 , for example, as a portable terminal device. The mobile phone  101  shown in  FIG. 26  is of folding type.  FIG. 26A  shows an external view example in which the mobile phone is in the opened state.  FIG. 26B  shows an external view example in which the mobile phone is in the closed state. 
         [0214]    The mobile phone  101  has an upper housing  103 , a lower housing  105 , a link block  107  (a hinge block in this example), a display screen  109 , an auxiliary display screen  111 , a picture light  113 , and a taking lens  115 . Of these components, the portions of the display screen  109  and the auxiliary display screen  111  correspond to the organic EL panel described above with reference to embodiments. 
         [0215]    Also, for the electronic device  51  of this type, a computer is assumed, for example.  FIG. 27  shows an external view example of a note-type computer  121 . The note-type computer  121  has a lower housing  123 , an upper housing  125 , a keyboard  127 , and a display screen  129 . Of these components, the portion of the display screen  129  corresponds to the organic EL panel described above with reference to embodiments. 
         [0216]    In addition to the above-mentioned devices, audio players, game machines, electronic books, and electronic dictionaries, for example, are assumed for the electric device  51 . 
         [0217]    (C-2) Other Display Device Examples 
         [0218]    The above-mentioned driving method is also applicable to other than the organic EL panel. For example, the above-mentioned driving method is applicable to inorganic EL panels, LED-type display panels, and EL light-emitting type display panels with light-emitting elements having diode structure arranged on the screen. 
         [0219]    (C-3) Others 
         [0220]    While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purpose, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims. 
         [0221]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factor in so far as they are within the scope of the appended claims or the equivalents thereof.