Abstract:
A signal transmission circuit includes: an electro-optical substrate having electro-optical elements; a plurality of driving circuits that drives the electro-optical elements; a first connection path that electrically connects the plurality of driving circuits; and a first substrate including at least a part of the first connection path. The electro-optical substrate is formed of a substrate different from the first substrate.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present invention relates to a signal transmission circuit, to an electro-optical device, and to an electronic apparatus. In particular, the invention relates to a signal transmission circuit, to an electro-optical device, and to an electronic apparatus suitable for a case in which a plurality of circuits are cascade-connected.  
         [0003]     2. Related Art  
         [0004]     Devices having organic light-emitting diode elements (hereinafter, referred to as ‘OLED elements’) have been drawing attention as electro-optical devices that can replace liquid crystal display devices. From an electrical point of view, an OLED element operates in the same manner as a diode, and from an optical point of view, the OLED element emits light at a forward bias and the brightness of the emitted light increases as a forward bias current increases.  
         [0005]     An electro-optical device in which OLED elements are arrayed in a matrix includes a plurality of scanning lines, a plurality of data lines, and pixel circuits corresponding to intersections of the scanning lines and the data lines. That is, the pixel circuits arrayed in a matrix form a pixel region serving as a display unit. Here, each of the pixel circuits has a function of storing a value of a current supplied from the data line and supplying to the OLED element a driving current corresponding to the stored current value.  
         [0006]     Further, the electro-optical device described above includes data-line driving circuits that supply gray-scale signals, which are current signals corresponding to gray-scale levels to be displayed, to the plurality of data lines. Here, when the gray-scale signals are transmitted to the data-line driving circuits, a known common bus transmission method using a relatively simple configuration has been used.  
         [0007]     A know electro-optical device using a common bus transmission method is shown in  FIG. 13 . As shown in  FIG. 13 , an electro-optical device  600  includes an electro-optical substrate  610 , a printed circuit board  620 , and a plurality of relay FPCs  630   a  to  630   n  provided between the electro-optical substrate  610  and the printed circuit board  620 . An image region A and a data-line driving circuit  700  are formed on the electro-optical substrate  610 , the printed circuit board  620 , and the plurality of relay FPCs  630   a  to  630   n.    
         [0008]     The image region A is formed by disposing electro-optical elements serving as pixels in a matrix, and the image region A serves as a display unit. The data-line driving circuit  700  includes a plurality of driving circuits Dr 1  to DrN disposed on the electro-optical substrate  610 , a common bus  621  disposed on the printed circuit board  620 , and wiring lines  631   a  to  631   n  that are disposed on the relay FPCs  630   a  to  630   n  so as to electrically connect the driving circuits Dr 1  to DrN with the common bus  621 . An X clock signal XCLK, gray-scale data D, and a selection signal that a control circuit  650  transmits through a relay FPC  660  are transmitted to the driving circuits Dr 1  to DrN through the common bus  621  and the wiring lines  631   a  to  631   n.    
         [0009]     In the electro-optical device  600 , the gray-scale data D and the like transmitted from the control circuit  650  are transmitted to all of the driving circuits Dr 1  to DrN through the common bus  621  and the wiring lines  631   a  to  631   n . However, due to the selection signal transmitted concurrently with the gray-scale data D and the like, only a driving circuit corresponding to the selection signal is input with the gray-scale data D.  
         [0010]     However, in the electro-optical device  600 , in order to transmit the gray-scale data D and the like transmitted from the control circuit  650 , it is necessary to dispose the common bus  621  on the printed circuit board  620  such that the common bus  621  corresponds to the locations of the driving circuits Dr 1  to DrN provided on the electro-optical substrate  610 .  
         [0011]     Therefore, the shape of the printed circuit board  620  needs to correspond to the locations of the driving circuits Dr 1  to DrN provided on the electro-optical substrate  610 . Specifically, the printed circuit board  620  should have a length corresponding to a region where the driving circuits Dr 1  to DrN are provided on the electro-optical substrate  610 . Accordingly, as the number of driving circuits Dr 1  to DrN provided on the electro-optical substrate  610  increases, there has been a problem in that the printed circuit board  620  becomes longer. Further, since a main purpose of the printed circuit board  620  is to transmit the gray-scale data D and the like transmitted from the control circuit  650 , it is not efficient from a point of view of resource and material cost to make the printed circuit board  620  long.  
         [0012]     In order to solve the problem described above, for example, techniques disclosed in JP-A-8-146449 and JP-A-2001-174843 have been proposed. In the technique disclosed in JP-A-8-146449, an electro-optical substrate, on which a plurality of driving circuits are disposed, and a flexible wiring substrate, on which a common bus connected to the driving circuits is disposed, are provided and gray-scale data or the like is supplied to each of the driving circuits through a connection point provided between the driving circuits. Further, in the technique disclosed in JP-A-2001-174843, a plurality of driving circuits and a data-line driving circuit, in which the plurality of driving circuits are electrically cascade-connected to each other, are disposed on an electro-optical substrate and gray-scale data or the like is cascade-transmitted between adjacent driving circuits.  
         [0013]     According to the technique disclosed in JP-A- 8-146449 , an area of a substrate required to dispose wiring lines may be reduced. However, since the common bus and the driving circuits are connected to each other at short sides of the driving circuits, the number of signals is limited to the number of terminals that can be provided at the short sides of the driving circuits. Accordingly, in the case when the number of signals is larger than the limited number, a problem occurs where a space between adjacent driving circuits should be widened.  
         [0014]     Further, according to the technique disclosed in JP-A-2001-174843, an area of a substrate required to dispose wiring lines may be reduced, in the same manner as the technique disclosed in JP-A-8-146449. However, since the cascade-connected driving circuits are directly disposed on an electro-optical device that is a glass substrate, a problem occurs where it is not possible to provide, for example, capacitors for stabilizing power supplied to the driving circuits. In addition, since the driving circuits are cascade-connected to each other by using relatively nigh-resistance wiring lines such as thin-film wiring lines, a voltage applied to the wiring lines drops as the driving circuits is separated from a power supply (voltage drop). As a result, there is a possibility that driving circuits disposed far from the power supply may malfunction.  
       SUMMARY  
       [0015]     An advantage of some aspects of the invention is that it provides a signal transmission circuit that can reduce an area of a substrate required to dispose wiring lines, can be used even when many signal lines are required, can suppress voltage drop in the wiring lines, and is highly reliable, an electro-optical device having the signal transmission circuit, and an electronic apparatus having the electro-optical device.  
         [0016]     According to an aspect of the invention, a signal transmission circuit includes: an electro-optical substrate having electro-optical elements; a plurality of driving circuits that drives the electro-optical elements; a first connection path that electrically connects the plurality of driving circuits; and a first substrate including at least a part of the first connection path. The electro-optical substrate is formed of a substrate different from the first substrate.  
         [0017]     In the signal transmission circuit according to the aspect of the invention, it is possible to reduce an area of a substrate required to dispose wiring lines.  
         [0018]     In the signal transmission circuit described above, preferably, the driving circuits are mounted on the electro-optical substrate.  
         [0019]     In the signal transmission circuit, it is possible to even more reduce the area of the substrate required to dispose the wiring lines.  
         [0020]     Further, in the signal transmission circuit described above, preferably, the first connection path serves as a connection path between the driving circuits adjacent to each other.  
         [0021]     In the signal transmission circuit, it is possible to even more reduce the area of the substrate required to dispose the wiring lines.  
         [0022]     Furthermore, in the signal transmission circuit described above, preferably, at least a part of the first connection path is formed on the electro-optical substrate and the first substrate.  
         [0023]     In the signal transmission circuit, it is possible to even more reduce the area of the substrate required to dispose the wiring lines.  
         [0024]     Furthermore, in the signal transmission circuit described above, preferably, each of the driving circuits has an approximately rectangular planar shape, and the at least a part of the first connection path is connected at a longitudinal side of each of the driving circuits having an approximately rectangular planar shape.  
         [0025]     In the signal transmission circuit, it is possible to connect the driving circuits so as to use even more signals.  
         [0026]     Furthermore, in the signal transmission circuit described above, preferably, at least a part of a connection path provided on the first substrate has a contact region that is electrically conductive.  
         [0027]     In the signal transmission circuit, an auxiliary power line, a capacitor, or the like can be easily connected.  
         [0028]     Furthermore, in the signal transmission circuit described above, preferably, the connection path provided on the first substrate includes a power line, and a capacitor is mounted on the contact region provided on the power line.  
         [0029]     In the signal transmission circuit, it is possible to stably (smoothly) supply power to each driving circuit.  
         [0030]     Furthermore, in the signal transmission circuit described above, preferably, the connection path provided on the first substrate includes a power line, and a wiring line for a reduction of the power line impedance is mounted on the contact region provided on the power line.  
         [0031]     In the signal transmission circuit, it is possible to reduce voltage drop in the wiring lines.  
         [0032]     Furthermore, in the signal transmission circuit described above, preferably, the wiring line for a reduction of the power line impedance is commonly connected between the plurality of first substrates.  
         [0033]     In the signal transmission circuit, it is possible to easily prepare the wiring line for a reduction of the power line impedance.  
         [0034]     Furthermore, in the signal transmission circuit described above, preferably, the connection path provided on the first substrate includes a power line, and the contact region provided on the power line is connected between a plurality of the first substrates.  
         [0035]     In the signal transmission circuit, it is possible to reduce the voltage drop in the wiring lines.  
         [0036]     Furthermore, according to another aspect of the invention, an electro-optical device includes: the signal transmission circuit according to the above-mentioned aspect of the invention; and a second substrate having a control circuit that controls the signal transmission circuit.  
         [0037]     In the invention, it is possible to provide an electro-optical device that is small and highly reliable.  
         [0038]     Furthermore, according to still another aspect of the invention, an electronic apparatus includes: the electro-optical device according to the above-mentioned aspect of the invention; and a circuit that controls the electro-optical device.  
         [0039]     In the invention, it is possible to provide an electronic apparatus that is small and highly reliable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]     The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.  
         [0041]      FIG. 1  is a block diagram illustrating an electro-optical device according to a first embodiment of the invention.  
         [0042]      FIG. 2  is a timing chart illustrating scanning signals and emission control signals in  FIG. 1 .  
         [0043]      FIG. 3  is a circuit diagram illustrating a pixel circuit in  FIG. 1 .  
         [0044]      FIG. 4  is a circuit diagram illustrating a data-line driving circuit in  FIG. 1 .  
         [0045]      FIG. 5  is a circuit diagram illustrating wiring lines on a wiring substrate in  FIG. 1 .  
         [0046]      FIG. 6  illustrates a circuit diagram when wiring lines on a wiring substrate are provided with lands.  
         [0047]      FIG. 7  illustrates a circuit diagram when auxiliary power lines are connected to lands on a wiring substrate.  
         [0048]      FIG. 8  illustrates a circuit diagram when a capacitor is connected to lands on a wiring substrate.  
         [0049]      FIG. 9  is a circuit diagram illustrating a pixel circuit according to a second embodiment of the invention.  
         [0050]      FIG. 10  is a perspective view illustrating the configuration of a portable personal computer to which the electro-optical device is applied.  
         [0051]      FIG. 11  is a perspective view illustrating the configuration of a mobile phone to which the electro-optical device is applied.  
         [0052]      FIG. 12  is a perspective view illustrating the configuration of a personal digital assistant to which the electro-optical device is applied.  
         [0053]      FIG. 13  is a view schematically illustrating a known electro-optical device. 
     
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0054]     Hereinafter, exemplary embodiments of the invention will be described. The embodiments described herein are for illustrative purposes and are not intended to limit the present invention.  
         [0000]     First Embodiment  
         [0055]      FIG. 1  is a block diagram schematically illustrating the configuration of an electro-optical device according to a first embodiment of the invention. As shown in  FIG. 1 , the electro-optical device I includes an image region A, a scanning-line driving circuit  100 , a data-line driving circuit  200 , a control circuit  300 , and a power supply circuit  500 . The image region A and the scanning-line driving circuit  100  are formed on an electro-optical substrate  1  that is a glass substrate, and the data-line driving circuit  200  is formed on the electro-optical substrate  1 , and a wiring substrate that includes a plurality of flexible printed circuits (FPC) connected to the electro-optical substrate  1 . In addition, the control circuit  300  is formed on a control circuit substrate that is a printed circuit board (PCB). In addition, in the present embodiment, the wiring substrate corresponds to a first substrate and the control circuit substrate corresponds to a second substrate, respectively.  
         [0056]     In the image region A, ‘m’ scanning lines  101  and ‘m’ emission control lines  102  are formed parallel to the X direction, and ‘n’ data lines  103  are formed parallel to the Y direction perpendicular to the X direction. In addition, pixel circuits  400  each having an OLED element are provided at intersections between the scanning lines  101  and the data lines  103 . Further, a power supply voltage Vdd is supplied to each of the pixel circuits  400  through a power line L.  
         [0057]     The scanning-line driving circuit  100  generates scanning signals Y 1 , Y 2 , Y 3 , . . . , and Ym for sequentially selecting the plurality of scanning lines  101  and emission control signals Vg 1 , Vg 2 , Vg 3 , . . . , and Vgm at the same time. The scanning signals Y 1 , Y 2 , Y 3 , . . . , and Ym and the emission control signals Vg 1 , Vg 2 , Vg 3 , . . . , and Vgm are generated by sequentially transmitting a Y transmission start pulse DY in synchronization with a Y clock signal YCLK. The emission control signals Vg 1 , Vg 2 , Vg 3 , . . . and Vgm are supplied to the corresponding pixel circuits  400  through the corresponding emission control lines  102 .  
         [0058]      FIG. 2  is a view illustrating an example of a timing chart with respect to the scanning signals Y 1 , Y 2 , Y 3 , . . . , and Ym and the emission control signals Vg 1 , Vg 2 , Vg 3 , . . . , and Vgm. The scanning signal Y 1  is a pulse having a width corresponding to one horizontal scanning period  1 H, which starts from an initial timing of one vertical scanning period  1 F, and is supplied to the scanning line  101  at a first row. Subsequently, the pulse is sequentially shifted to be supplied to the scanning lines  101  at second, third, . . . , and m-th rows as the scanning signals Y 2 , Y 3 , . . . , and Ym, respectively. In general, when a scanning signal Yi supplied to the scanning line  101  at an i-th row (‘i’ is an integer in a range of 1≦i≦m) transitions to an H level, the corresponding scanning line  101  is selected. In addition, as the emission control signals Vg 1 , Vg 2 , Vg, . . . , and Vgm, for example, signals obtained by inverting logic levels of the scanning signals Y 1 , Y 2 , Y 3 , . . . , and Ym are used as the emission control signals Vg 1 , Vg 2 , Vg 3 , . . . , and Vgm.  
         [0059]     The data-line driving circuit  200  supplies gray-scale signals, which are generated on the basis of gray-scale components D 0  to D 8 , to the corresponding pixel circuits  400  located at the selected scanning lines  101  on the basis of output gray-scale data Dout. In the present embodiment, the gray-scale components D 0  to D 8  are regenerated as current signals X 1 , X 2 , X 3 , X 4 , . . . , and Xn that indicate the gray-scale brightness. Further, the gray-scale components D 0  to D 8  are components of the output gray-scale data Dout, which is digital data corresponding to pixels, and, for example, a 9-bit signal in which bit-unit signals are disposed in a predetermined arrangement in order to include as information the gray-scale level indicating the brightness of each pixel.  
         [0060]     The control circuit  300  generates various control signals, such as the Y clock signal YCLK, an x clock signal XCLK, an X transmission starting pulse DX, and the Y transmission start pulse DY, and then outputs the signals to the scanning-line driving circuit  100  and the data-line driving circuit  200 . In addition, the control circuit  300  performs an image processing, such as gamma correction, on input gray-scale data Din and then generates output gray-scale data Dout. In the output gray-scale data Dout, for example, gray-scale components D 0  to D 8 , which consist of  9  bits, are disposed in a predetermined arrangement.  
         [0061]     Next, the pixel circuit  400  will be described.  FIG. 3  is a circuit diagram illustrating the pixel circuit  400 . The pixel circuit  400  shown in  FIG. 3  corresponds to the i-th row, and a power supply voltage Vdd is supplied to the pixel circuit  400 . The pixel circuit  400  includes four TFTs  401  to  404 , a capacitive element  410 , and an OLED element  420 . In a process of manufacturing the TFTs  401  to  404 , a polysilicon layer is formed on a glass substrate by using laser annealing. In addition, in the OLED element  420 , a light-emitting layer is interposed between an anode and a cathode. Further, the OLED element  420  emits light with brightness corresponding to a forward current. For the light-emitting layer, an organic EL (electroluminescent) material corresponding to the color of light to be emitted is used. In a process of manufacturing the light-emitting layer, the organic EL material is discharged from an inkjet-type head and is then dried.  
         [0062]     The TFT  401  serving as a driving transistor is a p-channel transistor, and the TFTs  402  to  404  serving as switching transistors are n-channel transistors. A source electrode of the TFT  401  is connected to a power line L and a drain electrode of the TFT  401  is connected to a drain electrode of the TFT  403 , a drain electrode of the TFT  404 , and a source electrode of the TFT  402 .  
         [0063]     One end of the capacitive element  410  is connected to the source electrode of the TFT  401  and the other end of the capacitive element  410  is connected to a gate electrode of the TFT  401  and a drain electrode of the TFT  402 . A gate electrode of the TFT  403  is connected to the scanning line  101  and a source electrode of the TFT  403  is connected to the data line  103 . Furthermore, a gate electrode of the TFT  402  is connected to the scanning line  101 . Further, a gate electrode of the TFT  404  is connected to the emission control line  102  and a source electrode of the TFT  404  is connected to the anode of the OLED element  420 . The emission control signal Vgi is supplied to the gate electrode of the TFT  404  through the emission control line  102 . In addition, the cathode of the OLED element  420  serves as a common electrode for the entire pixel circuit  400  and serves as a low (reference) potential in a power supply.  
         [0064]     In the configuration described above, since the n-channel TFT  402  is turned on when the scanning signal Yi transitions to an H level, the TFT  401  serves as a diode in which the gate and drain electrodes of the TFT  401  are connected to each other. Further, when the scanning signal Yi transitions to an H level, the n-channel TFT  403  is also turned on in the same manner as the TFT  402 . As a result, a currant Idata of the data-line driving circuit  200  flows through a path of the power line L→TFT  401 →TFT  403 →data line  103 , and at the same time, charge corresponding to the potential of the gate electrode of the TFT  401  is accumulated in the capacitive element  410 .  
         [0065]     On the other hand, when the scanning signal Yi transitions to an L level, the TFTs  402  and  403  are turned off. At this time, since the input impedance of the gate electrode of the TFT  401  is extremely high, a state in which charge is accumulated in the capacitive element  410  does not change. Therefore, the gate-to-source voltage of the TFT  401  is held as a voltage When the current Idata flows. In addition, when the scanning signal Yi transitions to an L level, the emission control signal Vgi changes to an H level. Accordingly, the TFT  404  is turned on and an injection current Ioled corresponding to a voltage of the gate of the TFT  401  flows between the source and the drain of the TFT  401 . That is, the injection current Ioled flows through a path of the power line L→TFT  401 →TFT  404 →OLED element  420 .  
         [0066]     Here, the injection current Ioled flowing through the OLED element  420  is determined by the gate-to-source voltage of the TFT  401 , and the gate-to-source voltage of the TFT  401  is a voltage held by the capacitive element  410  when the current I data flows through the data line  103  due to the H-level scanning line Yi. For this reason, when the emission control signal Vgi transitions to an H level, the injection current Ioled flowing through the OLED element  420  is approximately equal to the current Idata. Thus, the pixel circuit  400  is a circuit using an active current programming method because the brightness of emitted light is determined by the current Idata.  
         [0067]     Next, the present embodiment is characterized by the configuration of the data-line driving circuit  200 , which is shown in  FIG. 4 . As shown in  FIG. 4 , the data-line driving circuit  200  according to the present embodiment is formed on the electro-optical substrate  1  and a plurality of wiring substrates F 1  to Fn connected to the electro-optical substrate  1 . Specifically, a plurality of driving circuits Dr 1 , Dr 2 , . . . , and DrN are disposed parallel to one another on the electro-optical substrate  1 , and lines L 1  to Ln, which are first connection lines through which adjacent driving circuits are cascade-connected to each other, are disposed on the electro-optical substrate  1  and the wiring substrates F 1  to Fn such that each of the lines L 1  to Ln is connected between two of the driving circuits and goes through a corresponding one of the wiring substrates F 1  to Fn connected to the electro-optical substrate  1 . In addition, as shown in  FIG. 5 , the lines L 1  to Ln are formed of a plurality of wiring lines W 1  to Wm, and the X clock signal XCLK, the output gray-scale data Dout, or the like can be transmitted through the lines L 1  to Ln. In addition, the wiring substrates F 1  to Fn according to the present embodiment are connected to an end surface of the electro-optical substrate  1  between the driving circuits. In addition, in the present embodiment, even though all of the wiring lines W 1  to Wm forming each of the lines L 1  to Ln are disposed on the wiring substrates F 1  to Fn, all of the wiring lines W 1  to Wm are not necessarily disposed on the wiring substrates F 1  to Fn. For example, parts of the wiring lines W 1  to Wm may be disposed on the wiring substrates F 1  to Fn.  
         [0068]     Here, one end of each of the plurality of wiring lines W 1  to Wm forming the lines L 1  to Ln is connected to a terminal located at a longitudinal side of each of the driving circuits Dr 1 , Dr 2 , . . . , and DrN, respectively. Further, the pluralities of wiring lines W 1  to Wm forming the lines L 1  to Ln are disposed on the electro-optical substrate  1  and the wiring substrates F 1  to Fn so as to go through, from the terminals, an end portion of the electro-optical substrate  1  and the wiring substrates F 1  to Fn disposed between the driving circuits, respectively. Then, each of the wiring lines W 1  to Wm is connected to a terminal located at a longitudinal side of an adjacent one of the driving circuits. In addition, the wiring lines W 1  to Wm disposed on the electro-optical substrate  1  and the wiring line W 1  to Wm disposed on the wiring substrates F 1  to Fn are correspondingly connected through connection terminals that are provided at end portions of the substrates for the respective wiring lines W 1  to Wm.  
         [0069]     Thus, since the wiring lines W 1  to Wm can be disposed on the wiring substrates F 1  to Fn connected to the electro-optical substrate  1 , it is possible to reduce the area of the electro-optical substrate  1 . Further, since the wiring lines W 1  to Wm can be connected to the longitudinal sides of the driving circuits Dr 1  Dr 2 , . . . , and DrN, the driving circuits can be cascade-connected to each other so as to enable the use of even more signals. Furthermore, since a material having low electrical resistance, such as copper or aluminum, can be used as a material of wiring lines on the wiring substrates F 1  to Fn, the voltage drop can be suppressed.  
         [0070]     Further, in the present embodiment, since flexible substrates are used as the wiring substrates F 1  to Fn, it is possible to make the electro-optical device I small by bending the wiring substrates F 1  to Fn in the direction of a bottom surface of the electro-optical substrate  1 . As a result, it is possible to improve the value of the electro-optical device I as a product due to the miniaturization.  
         [0071]     Furthermore, in the case when problems, such as contact failure or short-circuits, occur on the wiring line W 3  disposed on the wiring substrate Fi, it s possible to solve the problems by only exchanging the wiring substrate Fi. Accordingly, the productivity of the electro-optical device Ican be improved, and as a result, it is possible to reduce a cost of manufacturing the electro-optical device I.  
         [0072]     Furthermore, as shown in  FIG. 6 , the wiring lines W 1  to Wm on the wiring substrates F 1  to Fn may be provided with lands R 1  and R 2  that are contact regions such that an auxiliary power line, a capacitor, or the like can be connected to the lands R 1  and R 2 .  FIG. 6  is a circuit diagram when the wiring lines W 1  and W 2  on the wiring substrate Fj are respectively provided with the lands R 1  and R 2 . Here, the contact region is not limited as long as the wiring lines can be electrically connected to the auxiliary power line or the like. In the present embodiment, as shown in  FIG. 6 , the wiring lines W 1  and W 2  are respectively provided with the lands R 1  and R 2  as contact regions. In addition, the lands R 1  and R 2  are formed by enlarging the width of a part of each of the wiring lines W 1  and W 2  connected to the lands R 1  and R 2 , and the lands R 1  and R 2  can be electrically connected to, for example, an auxiliary power mine.  
         [0073]     Specifically, for example, as shown in  FIG. 7 , the lands R 1  and R 2  may be respectively provided for a power line VSS and a ground line VCC, which are power lines provided to supply power to the driving circuits Dr 1 , Dr 2 , . . . , and DrN, among the wiring lines W 1  Wm provided on the wiring substrates F 1  to Fn. Further, a bypass wiring line for VSS enhancement, which serves as a wiring line for power line enhancement, may be connected to the land R 1 , and a bypass wiring line for VCC enhancement, which also serves as a wiring line for power line enhancement, may be connected to the land R 2 . The bypass wiring line for VSS enhancement is connected to a cathode of a power supply (not shown), and the bypass wiring line for VCC enhancement is connected to an anode of the power supply (not shown). In addition, through the land R 1 , a negative voltage is applied to the power line VSS and a positive voltage is applied to the ground line VCC. Accordingly, the voltage drop between the power line VSS and the ground line VCC can be suppressed. In addition, as a power supply connected to the bypass wiring line for VSS enhancement and the bypass wiring line for VCC enhancement, a power line of the control circuit  300  or an external power supply may be used.  
         [0074]     With the configuration described above, since it is possible to reduce the voltage drop between the power line VSS and the ground line VCC, it is possible to improve (stabilize) a capability of supplying power to each driving circuit. Accordingly, it is possible to improve reliability or operation margin of the signal transmission circuit and electro-optical device using the signal transmission circuit. In addition, in the present embodiment, even though the bypass wiring line for VSS enhancement and the bypass wiring line for VCC enhancement are respectively connected to the power line VSS and the ground line VCC by using the lands R 1  and R 2  through which the bypass wiring line for VSS enhancement and the bypass wiring line for VCC enhancement can be easily connected to the power line VSS and the ground line VCC, the bypass wiring line for VSS enhancement and the bypass wiring line for VCC enhancement may be directly connected to the power line VSS and the ground line VCC, respectively.  
         [0075]     Further, as shown in  FIG. 8 , the lands R 1  and R 2  may be respectively provided for the power line VSS and the ground line VCC among the wiring lines W 1  to Wm forming the lines L 1  to Ln, and then a capacitor C 1  may be connected between the lands R 1  and R 2 . By providing the capacitor C 1  as described above, it is possible to stabilize the capability of supplying power to each of the driving circuits Dr 1  to DrN. As a result, the reliability of the signal transmission circuit and electro-optical device using the signal transmission circuit can be improved. Furthermore, in the present embodiment, even though the capacitor C 1  is connected between the power line VSS and the ground line VCC by using the lands R 1  and R 2  through which the power line VSS and the ground line VCC can be easily connected to each other, the capacitor C 1  may be directly connected between the power line VSS and the ground line VCC.  
         [0076]     Furthermore, since the lands are provided, it is possible to check the state of a signal by probing the lands. Accordingly, the evaluation on the electro-optical device I can be performed quickly and accurately. As a result, a period of time required for development and design is shortened, which reduces cost.  
         [0000]     Second Embodiment  
         [0077]     Even though a circuit using an active current programming method has been used as the pixel circuit  400  in the first embodiment, a circuit using a passive current method may be used.  FIG. 9  is a view illustrating a circuit using a passive current method. A pixel circuit  400 A shown in  FIG. 9  corresponds to an i-th row, and the power supply voltage Vdd is supplied to the pixel circuit  400 A. The pixel circuit  400 A includes an OLED element  420 A. The OLED element  420 A has the same structure as the OLED element  420  in the first embodiment and is manufactured by using the same manufacturing process as the OLED element  420  in the first embodiment.  
         [0078]     As such, even when the circuit using the passive current method is used as the pixel circuit  400 , it is possible to obtain the same effects as in the first embodiment.  
         [0000]     Other Embodiments  
         [0079]     In the first and second embodiments, the driving circuits have been formed on the electro-optical substrate of the electro-optical device I, on which pixel circuits are arranged in a matrix as described above, and the plurality of wiring substrates F 1  to Fn connected to the electro-optical substrate; however, the invention is not limited thereto. For example, it is possible to form driving circuits on an electro-optical substrate of an electro-optical device (for example, a writing head used for an optical printer or an electronic copying machine), on which pixel circuits are arranged in a line shape, and a plurality of wiring substrates connected to the electro-optical substrate. Alternatively, the driving circuits may be formed on an electro-optical substrate of an electro-optical device, which is made of an organic light-emitting material using monomer, polymer, dendrimer, or the like, and a plurality of wiring substrates connected to the electro-optical substrate. Alternatively, the driving circuits may be formed on an electro-optical substrate of an electro-optical device using liquid crystal and a plurality of wiring substrates connected to the electro-optical substrate. In any cases described above, the same effects as in the first and second embodiments can be obtained.  
         [0000]     Applications  
         [0080]     Next, an electronic apparatus to which the electro-optical device I according to the above embodiment is applied will be described.  FIG. 10  is a view illustrating the configuration of a portable personal computer to which the electro-optical device I is applied. A personal computer  2000  includes the electro-optical device I serving as a display unit and a main body  2010 . The main body  2010  includes a power switch  2001  and a keyboard  2002 . Since the electro-optical device I uses the OLED elements  420 , it is possible to display a screen that has a wide viewing angle and can be easily viewed.  
         [0081]      FIG. 11  is a view illustrating the configuration of a mobile phone to which the electro-optical device I is applied. A mobile phone  3000  includes a plurality of operation buttons  3001 , a plurality of scroll buttons  3002 , and the electro-optical device I serving as a display unit. By operating the scroll buttons  3002 , a screen displayed on the electro-optical device I is scrolled.  
         [0082]      FIG. 12  is a view illustrating the configuration of a personal digital assistant (PDA) to which the electro-optical device I is applied. A personal digital assistant  4000  includes a plurality of operation buttons  4001 , a power switch  4002 , and the electro-optical device I serving as a display unit. By operating the power switch  4002 , various information items, such as an address list or a schedule, are displayed on the electro-optical device I.  
         [0083]     Furthermore, the electro-optical device I can be preferably applied to a liquid crystal display device or display devices using self-luminous elements, such as a field emission display (FED) device, a surface-conduction-type emission display (SED) device, or a ballistic electron emission display (BSD) device.  
         [0084]     Further, an electronic apparatus to which the electro-optical device I is applied includes a television having a large screen, a computer monitor, a display and illumination device, a mobile phone, a game device, an electronic paper, driving operation panel, a video camera, a digital still camera, a liquid crystal television, a view-finder-type or monitor-direct-view-type video tape recorder, a car navigation apparatus, a pager, an electronic diary, a desktop calculator, a word processor, a workstation, a video phone, a POS terminal, an apparatus having a touch panel, and the like, as well as those shown in FIGS.  10  to  12 . In addition, the electro-optical device I can be applied as display units of these various electronic apparatuses. In addition, the electro-optical device I can be effectively applied to a printer or a scanner that uses an electro-optical device as a light source.  
         [0085]     The entire disclosure of Japanese Patent Application No. 2005-234047, filed Aug. 12, 2005 is expressly incorporated by reference herein.