JP2010003880A - Display and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a life reduction of an organic EL element while taking measures for luminance defects due to mixing of foreign matters. <P>SOLUTION: Taking note of a blue (B) organic EL element 21B having a shorter life than organic EL elements 21R and 21G of other colors, for example, red (R) and green (G), only one organic EL element is used for a B sub pixel 20B while multiple organic EL elements are used for R and G sub pixels 20R and 20G, while a light emission area of the B sub pixel 20B is set larger than those of the R and G sub pixels 20R and 20G. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device and an electronic device, and more particularly, to a flat-panel (flat panel) display device in which pixels including electro-optic elements are two-dimensionally arranged in a matrix (matrix shape), and an electronic device having the display device. .

  In recent years, in the field of display devices that perform image display, flat display devices in which pixels (pixel circuits) including light emitting elements are arranged in a matrix are rapidly spreading. As a flat display device, as a light emitting element of a pixel, a so-called current-driven electro-optical element whose light emission luminance changes according to a current value flowing through the device, for example, a phenomenon that emits light when an electric field is applied to an organic thin film is used. An organic EL display device using an organic EL (Electro Luminescence) element has been developed and commercialized.

  The organic EL display device has the following features. That is, since the organic EL element can be driven with an applied voltage of 10 V or less, the power consumption is low. Since the organic EL element is a self-luminous element, image visibility is higher than that of a liquid crystal display device that displays an image by controlling the light intensity from a light source (backlight) with a liquid crystal for each pixel. In addition, since an illumination member such as a backlight is not required, it is easy to reduce the weight and thickness. Furthermore, since the response speed of the organic EL element is as high as about several μsec, an afterimage at the time of displaying a moving image does not occur.

  As in the liquid crystal display device, the organic EL display device can adopt a simple (passive) matrix method and an active matrix method as its driving method. However, although the simple matrix display device has a simple structure, the light-emission period of the electro-optic element decreases with an increase in the number of scanning lines (that is, the number of pixels), thereby realizing a large-sized and high-definition display device. There are problems such as difficult.

  Therefore, in recent years, an active element in which an electric current flowing through an electro-optic element is controlled by an active element provided in the same pixel as the electro-optic element, for example, an insulated gate field effect transistor (generally, a TFT (Thin Film Transistor)). Matrix display devices have been actively developed. An active matrix display device can easily realize a large-sized and high-definition display device because the electro-optic element continues to emit light over a period of one frame.

  By the way, the organic EL element has a structure in which an organic film including a light emitting layer is sandwiched between an anode electrode and a cathode electrode. In an organic EL device using an organic EL element having such a structure as a light emitting element of a pixel, if a foreign substance is mixed in the process of forming the organic EL element, a luminance defect of the pixel occurs.

  Specifically, in the pixel circuit shown in FIG. 29, a short circuit between the anode electrode and the cathode electrode of the organic EL element 21 may be caused due to foreign matters mixed in the manufacturing process. Due to a short circuit between the electrodes of the organic EL element 21, a luminance defect called a dark spot at which the organic EL element 21 does not emit light occurs.

  Also in the substrate process of forming pixel components such as the drive transistor 22 for driving the organic EL element 21, the write transistor 23 for writing the video signal, and the storage capacitor 24 for storing the video signal on the substrate, the luminance is increased due to the mixing of foreign matter. Defects may occur. Specifically, when the drain electrode and the source electrode of the drive transistor 22 are short-circuited by a foreign substance, a current flows directly from the power source Vcc to the organic EL element 21, and thus the organic EL element 21 remains lighted. Luminance defects called so-called bright spots occur.

  In addition, when the drain electrode and the source electrode of the write transistor 23 are short-circuited due to a foreign substance, the drive transistor 23 is not completely turned off, and a current flows through the organic EL element 21. In this case, a luminance defect called a so-called half-dark point that cannot express a complete black gradation occurs. Further, when the two electrodes forming the storage capacitor 24 are short-circuited by a foreign substance, no current flows through the organic EL element 21, and a luminance defect that becomes a dark spot occurs. The occurrence of such a luminance defect due to the contamination of foreign matters in the manufacturing process becomes more prominent as the pixels become finer as the display device becomes higher in definition.

  As a countermeasure against the luminance defect due to the contamination of foreign matter, a technique has been proposed in which a plurality of pixel constituent elements including organic EL elements are provided in one subpixel (see, for example, Patent Document 1). According to this proposed technique, even if any pair of pixel constituent elements becomes defective due to a short circuit or the like, the occurrence of a luminance defect due to contamination by foreign matters is prevented by a repair technology that separates the defective pixel constituent elements. Can do.

JP 2006-133542 A

  However, since the conventional technology adopts a configuration in which a plurality of organic EL elements are provided in one subpixel, that is, a configuration in which one subpixel is divided into a plurality of light emitting portions, a process rule (for example, a wiring interval) is adopted. As a result, the opening area (light emitting area) of the organic EL element decreases. Then, in order to obtain a desired light emission luminance, the current density has to be increased, so that the lifetime of the organic EL element is reduced.

  In view of the above, an object of the present invention is to provide a display device capable of suppressing a reduction in the lifetime of an electro-optical element while taking measures against a luminance defect caused by contamination of foreign matter, and an electronic apparatus having the display device. .

A display device according to the present invention comprises:
A pixel array unit in which pixels composed of combinations of a blue sub-pixel emitting blue light and a plurality of different color sub-pixels independently emitting a plurality of different color lights other than blue light are arranged in a matrix With
The blue subpixel has one electro-optic element,
The other color sub-pixel has a plurality of electro-optic elements,
The light emission area of the blue subpixel is set larger than the light emission area of the subpixels of the other colors.

  Here, the light emission area of the sub-pixel is the opening area of the electro-optic element. Specifically, in the blue sub-pixel, the opening area of one electro-optical element is the light-emitting area of the blue sub-pixel, and in the other sub-pixels, the total area of the openings of the plurality of electro-optical elements is This is the emission area of the sub-pixels of other colors.

  For sub-pixels of other colors, since there are a plurality of electro-optic elements, when any of the electro-optic elements becomes defective, the electro-optic elements are separated, thereby causing a luminance defect due to foreign matter contamination. Can be repaired. However, since the blue sub-pixel has only one electro-optical element, it cannot be repaired for a luminance defect.

  On the other hand, the life of the electro-optical element, for example, the life in which the luminance is reduced to about half of the initial luminance (hereinafter referred to as “luminance half-life”) depends on the material, but generally, it is a blue electro-optical element. Is known to be shorter than other colors such as red or green electro-optic elements. Focusing on this point, the light emission area of the blue subpixel is set larger than the light emission areas of the subpixels of other colors.

  If the light emission area, that is, the opening area of the electro-optic element is large, the current density passed through the electro-optic element can be set lower than that when the opening area is small in obtaining the desired light emission luminance. If the current density is low, it is possible to suppress a decrease in the life of the electro-optical element. In other words, although the blue subpixel cannot be repaired with respect to the luminance defect, the life of the blue electro-optic element having a relatively short life can be increased.

  According to the present invention, since it is possible to suppress a decrease in the lifetime of a blue electro-optic element having a relatively short lifetime, the countermeasure of the luminance defect due to the contamination of foreign matter is taken and the electro-optic element of each emission color is taken. Balance lifespan.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[System configuration]
FIG. 1 is a system configuration diagram showing an outline of the configuration of an active matrix display device to which the present invention is applied. Here, as an example, an active matrix organic EL display device using, as an example, a current-driven electro-optical element whose emission luminance changes according to a current value flowing through the device, for example, an organic EL element as a light-emitting element of a pixel (pixel circuit) This case will be described as an example.

  As shown in FIG. 1, an organic EL display device 10 according to this application example includes a plurality of pixels 20 including light emitting elements, a pixel array unit 30 in which the pixels 20 are two-dimensionally arranged in a matrix, and the pixel array. The drive unit is disposed around the unit 30. The drive unit drives each pixel 20 of the pixel array unit 30. As the drive unit, for example, a write scanning circuit 40, a power supply scanning circuit 50, and a signal output circuit 60 are provided.

  Here, when the organic EL display device 10 supports monochrome display, one pixel serving as a unit for forming a monochrome image corresponds to the pixel 20. On the other hand, when the organic EL display device 10 supports color display, one pixel as a unit for forming a color image is composed of a plurality of sub-pixels (sub-pixels), and this sub-pixel corresponds to the pixel 20. More specifically, in a display device for color display, one pixel includes a sub-pixel that emits red light (R), a sub-pixel that emits green light (G), and a sub-pixel that emits blue light (B). It consists of three sub-pixels of a pixel.

  However, one pixel is not limited to the combination of RGB three primary color subpixels, and one pixel may be configured by adding one or more color subpixels to the three primary color subpixels. Is possible. More specifically, for example, at least one sub-pixel that emits white light (W) is added to improve luminance to form one pixel, or at least one that emits complementary color light to expand the color reproduction range. It is also possible to configure one pixel by adding subpixels.

  The pixel array unit 30 includes scanning lines 31-1 to 31-m and a power supply line 32-1 along the row direction (pixel arrangement direction of pixels in the pixel row) with respect to the arrangement of the pixels 20 in m rows and n columns. ˜32-m are wired for each pixel row. Furthermore, signal lines 33-1 to 33-n are wired for each pixel column along the column direction (pixel arrangement direction of the pixel column).

  The scanning lines 31-1 to 31 -m are connected to the output ends of the corresponding rows of the writing scanning circuit 40, respectively. The power supply lines 32-1 to 32-m are connected to the output terminals of the corresponding rows of the power supply scanning circuit 50, respectively. The signal lines 33-1 to 33-n are connected to the output ends of the corresponding columns of the signal output circuit 60, respectively.

  The pixel array unit 30 serving as a display region is usually formed on a transparent insulating substrate such as a glass substrate. Thereby, the organic EL display device 10 has a flat panel structure. The drive circuit for each pixel 20 in the pixel array section 30 can be formed using an amorphous silicon TFT or a low-temperature polysilicon TFT. When the low-temperature polysilicon TFT is used, the write scanning circuit 40, the power supply scanning circuit 50, and the signal output circuit 60 can also be mounted on the display panel (substrate) 70 that forms the pixel array unit 30.

  The write scanning circuit 40 is configured by a shift register or the like that sequentially shifts (transfers) the start pulse sp in synchronization with the clock pulse ck. The writing scanning circuit 40 sequentially supplies writing scanning signals WS (WS1 to WSm) to the scanning lines 31-1 to 31-m when writing video signals to the respective pixels 20 of the pixel array section 30. Each pixel 20 of the unit 30 is scanned in order in a row unit (line-sequential scanning).

  The power supply scanning circuit 50 includes a shift register that sequentially shifts the start pulse sp in synchronization with the clock pulse ck. The power supply scanning circuit 50 synchronizes with the line sequential scanning by the write scanning circuit 40 and switches between a first power supply potential Vccp and a second power supply potential Vini lower than the first power supply potential Vccp. ) To the power supply lines 32-1 to 32-m. The light emission / non-light emission of the pixel 20 is controlled by switching the power supply potential DS to Vccp / Vini.

  The signal output circuit 60 has either a signal voltage (hereinafter also simply referred to as “signal voltage”) Vsig or a reference potential Vofs of a video signal corresponding to luminance information supplied from a signal supply source (not shown). Either one is selected as appropriate and output. The signal voltage Vsig / reference potential Vofs output from the signal output circuit 60 is written in units of rows to each pixel 20 of the pixel array unit 30 via the signal lines 33-1 to 33-n. In other words, the signal output circuit 60 employs a line-sequential writing drive configuration in which the signal voltage Vsig is written in units of rows (lines).

(Layout of organic EL display device)
FIG. 2 is a schematic plan view showing an example of the layout of the organic EL display device 10. 1, the configuration in which the write scanning circuit 40, the power supply scanning circuit 50, and the signal output circuit 60 are provided on the display panel 70 together with the pixel array unit 30 has been described as an example. Here, the layout in the case where the writing scanning circuit 40, the power supply scanning circuit 50, and the signal output circuit 60 are provided outside the display panel 70 will be described.

  In FIG. 2, auxiliary wiring 72 is provided on the outer periphery of the pixel array unit 30 on the substrate of the display panel 70 having the pixel array unit 30 serving as a display region, for example, a glass substrate 71. The auxiliary wiring 72 is electrically connected to a common power supply line 34 described later.

  The auxiliary wiring 72 is supplied with a cathode potential Vcath (described later) from an external power supply unit through a power supply TCP 73 that is electrically connected to an external power supply unit (not shown) by a TCP (Tape Carrier Package) method. Here, TCP is the name of a driver tape mounted on a flexible tape by bonding.

  A scanning signal WS is supplied to the scanning line 31 and the power supply line 32 of the pixel array unit 30 through a control signal supply TAB 74 that is electrically connected to the external writing scanning circuit 40 and the power supply scanning circuit 50 by TAB (Tape Automated Bonding). And the power supply potential DS is supplied. The control signal supply TAB 74 is provided on the left and right sides of the display panel 70, for example. Further, the signal voltage Vsig of the video signal is supplied to the signal line 32 of the pixel array unit 30 through the video signal supply TAB 75 that is electrically connected to the external signal output circuit 60.

(Pixel circuit)
FIG. 3 is a circuit diagram showing a specific circuit configuration of the pixel (pixel circuit) 20. As shown in FIG. 3, the pixel 20 includes a current-driven electro-optical element whose emission luminance changes according to a current value flowing through the device, for example, an organic EL element 21, and a drive circuit that drives the organic EL element 21. It is constituted by. The organic EL element 21 has a cathode electrode connected to a common power supply line 34 that is wired in common to all the pixels 20 (so-called solid wiring). The cathode potential Vcath is supplied to the common power supply line 34 through the auxiliary wiring 72 described above.

  The drive circuit that drives the organic EL element 21 has a drive transistor 22, a write transistor 23, and a storage capacitor 24. Here, N-channel TFTs are used as the drive transistor 22 and the write transistor 23. However, the combination of conductivity types of the drive transistor 22 and the write transistor 23 is merely an example, and is not limited to these combinations.

  Note that when an N-channel TFT is used as the driving transistor 22 and the writing transistor 23, an amorphous silicon (a-Si) process can be used. By using the a-Si process, it is possible to reduce the cost of the substrate on which the TFT is formed, and thus to reduce the cost of the organic EL display device 10. Further, when the drive transistor 22 and the write transistor 23 have the same conductivity type, both the transistors 22 and 23 can be formed by the same process, which can contribute to cost reduction.

  The drive transistor 22 has one electrode (source / drain electrode) connected to the anode electrode of the organic EL element 21 and the other electrode (drain / source electrode) connected to the power supply line 32 (32-1 to 32-m). It is connected.

  The write transistor 23 has one electrode (source / drain electrode) connected to the signal line 33 (33-1 to 33-n) and the other electrode (drain / source electrode) connected to the gate electrode of the drive transistor 22. ing. The gate electrode of the writing transistor 23 is connected to the scanning line 31 (31-1 to 31-m).

  In the drive transistor 22 and the write transistor 23, one electrode refers to a metal wiring electrically connected to the source / drain region, and the other electrode refers to a metal wiring electrically connected to the drain / source region. Say. Further, depending on the potential relationship between one electrode and the other electrode, if one electrode becomes a source electrode, it becomes a drain electrode, and if the other electrode also becomes a drain electrode, it becomes a source electrode.

  The storage capacitor 24 has one electrode connected to the gate electrode of the drive transistor 22 and the other electrode connected to the other electrode of the drive transistor 22 and the anode electrode of the organic EL element 21.

  The drive circuit of the organic EL element 21 is not limited to a circuit configuration including two transistors, the drive transistor 22 and the write transistor 23, and one capacitor element of the storage capacitor 24. For example, a circuit configuration in which one electrode is connected to the anode electrode of the organic EL element 21 and the other electrode is connected to a fixed potential, so that an auxiliary capacitor that compensates for the insufficient capacity of the organic EL element 21 is provided as necessary. It is also possible to adopt.

  In the pixel 20 configured as described above, the writing transistor 23 becomes conductive in response to a high active writing scanning signal WS applied to the gate electrode from the writing scanning circuit 40 through the scanning line 31. Thereby, the write transistor 23 samples the signal voltage Vsig or the reference potential Vofs of the video signal corresponding to the luminance information supplied from the signal output circuit 60 through the signal line 33 and writes the sampled voltage in the pixel 20. The written signal voltage Vsig or reference potential Vofs is applied to the gate electrode of the drive transistor 22 and held in the storage capacitor 24.

  When the potential DS of the power supply line 32 (32-1 to 32-m) is at the first power supply potential Vccp, the drive transistor 22 has one electrode as a drain electrode and the other electrode as a source electrode in a saturation region. Operate. As a result, the drive transistor 22 is supplied with current from the power supply line 32 and drives the organic EL element 21 to emit light by current drive. More specifically, the drive transistor 22 operates in the saturation region, thereby supplying a drive current having a current value corresponding to the voltage value of the signal voltage Vsig held in the storage capacitor 24 to the organic EL element 21. The organic EL element 21 is caused to emit light by current driving.

  Further, when the power supply potential DS is switched from the first power supply potential Vccp to the second power supply potential Vini, the drive transistor 22 operates as a switching transistor with one electrode serving as a source electrode and the other electrode serving as a drain electrode. As a result, the drive transistor 22 stops supplying the drive current to the organic EL element 21 and puts the organic EL element 21 into a non-light emitting state. That is, the drive transistor 22 also has a function as a transistor that controls light emission / non-light emission of the organic EL element 21.

  The switching operation of the drive transistor 22 provides a period during which the organic EL element 21 is in a non-light emitting state (non-light emitting period), and the organic EL element 21 emits light by changing the time for applying a forward bias to the organic EL element 21. The ratio (duty) of the period and the non-light emitting period can be controlled. By this duty control, the afterimage blur caused by the light emission of the pixels over one frame period can be reduced, so that the quality of the moving image can be particularly improved.

  Here, the reference potential Vofs that is selectively supplied from the signal output circuit 60 through the signal line 33 corresponds to a potential that serves as a reference for the signal voltage Vsig of the video signal corresponding to the luminance information (for example, the black level of the video signal). Potential).

  Of the first and second power supply potentials Vccp and Vini selectively supplied from the power supply scanning circuit 50 through the power supply line 32, the first power supply potential Vccp generates a drive current for driving the organic EL element 21 to emit light. The power supply potential for supplying to The second power supply potential Vini is a power supply potential for applying a reverse bias to the organic EL element 21. The second power supply potential Vini is set to a potential lower than the reference potential Vofs, for example, a potential lower than Vofs−Vth, preferably sufficiently lower than Vofs−Vth when the threshold voltage of the driving transistor 22 is Vth. Is done.

<Pixel layout and structure>
Here, a layout of the pixel 20 and a specific structure of the pixel 20 will be described. In the case of color display support, one pixel as a unit for forming a color image is composed of a set (combination) of a plurality of subpixels, for example, RGB subpixels 20R, 20G, and 20B, as described above.

  FIG. 4 is a schematic plan view showing the overall layout of the RGB sub-pixels 20R, 20G, and 20B. As shown in FIG. 4, the RGB sub-pixels 20R, 20G, and 20B are provided adjacent to each other in the row direction. In the sub-pixels 20R, 20G, and 20B, a lower electrode (for example, an anode electrode) 211 is disposed on a substrate (glass substrate 71 in FIG. 3), and an opening (hereinafter referred to as “aperture”) of the organic EL element 21 is formed on the lower electrode 211. 21a) (denoted as “EL opening”).

  A contact portion 211 a is formed on the lower electrode 211. The lower electrode 211 is electrically connected to the source electrode of the driving transistor 22 disposed below the lower electrode 211 via a contact portion 211a. Auxiliary wiring 72 configured in the same layer as the lower electrode 211 is wired between the lower electrodes 211 in a lattice shape so as to surround the lower electrode 211. The auxiliary wiring 72 is further wired so as to surround the entire pixel array section 30 (see FIG. 3).

  The structure of the subpixels 20R, 20G, and 20B will be described in more detail with reference to FIGS.

  FIG. 5 is a diagram illustrating a specific configuration example of, for example, the R subpixel 20R among the subpixels 20R, 20G, and 20B. Here, the R sub-pixel 20R will be described as an example, but the sub-pixels 20G and 20B of the other colors have basically the same configuration as the R sub-pixel 20R. 5A is a schematic plan view focusing on the first wiring layer and the second wiring layer, and FIG. 5B is a schematic plan view focusing on the anode layer. Incidentally, FIG. 4 is a superposition of FIG. 5 (A) and FIG. 5 (B).

  FIG. 6 is a cross-sectional view showing the entire layer structure of one subpixel, and is a cross-sectional view taken along the line aa ′ of FIG. 5 and 6, the same parts as those in FIG. 4 are denoted by the same reference numerals.

  5 and 6, on the glass substrate 71, the lowermost part for forming pixel constituent elements such as a thin film transistor (driving transistor 22 and writing transistor 23) and a storage capacitor 24 constituting the sub-pixels 20R, 20G, and 20B. The first wiring layer 75 is provided. That is, the first wiring layer 75 forms part of the signal line 33, one electrode of the storage capacitor 24, and the gate electrode of the thin film transistor. An interlayer insulating film (oxide film) 76 that functions as a gate insulating film is further provided on the first wiring layer 75.

  A semiconductor thin film 77 made of amorphous silicon is formed on the interlayer insulating film (gate insulating film) 76 and crystallized. An insulating stopper layer 78 is formed in a pattern on the upper portion of the semiconductor thin film 77 serving as a channel region. An n + type semiconductor layer 79 made of, for example, silicon containing an n type impurity is formed in a state of covering the stopper layer 78. The n + -type semiconductor layer 79 and the semiconductor thin film 77 are patterned in an island shape above the gate electrode (a part of the first wiring layer 75) of the thin film transistor. As a result, the thin film transistors TFT of the drive transistor 22 and the write transistor 23 are formed.

  A second wiring layer 81 that is electrically connected to the source electrode and drain electrode of the thin film transistor TFT is further provided on the interlayer insulating film 76. Then, a passivation film 82 is formed so as to cover the second wiring layer 81, and an insulating flattening film 83 is further formed thereon. The organic EL element 21 is formed on the insulating planarizing film 83. The organic EL element 21 includes a lower electrode (for example, an anode electrode) 211, an organic layer 212, and an upper electrode (for example, a cathode electrode) 213 that are sequentially stacked from the lower layer side.

  The organic EL element 21 has a capacitance component (parasitic capacitance / equivalent capacitance) because the organic layer 212 that is a dielectric is sandwiched between the lower electrode 211 and the upper electrode 213. Specifically, the organic layer 212 employs a multilayer structure made of a low molecular weight material. More specifically, the organic layer 212 is, for example, in order from the lower electrode 211 side to the upper electrode 213 side, for example, a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer (also serving as an electron injection layer). have. In the case of color display compatibility, a material corresponding to the display color is used as the organic material of the light emitting layer.

  The periphery of the organic EL element 21 is covered with an opening defining insulating film 84 that is an insulating film pattern. Then, the auxiliary wiring 72 described above is wired as the same layer as the lower electrode 211 around the opening defining insulating film 84. The upper electrode 213 of the organic EL element 21 is solidly wired so as to cover almost the entire surface of the pixel array unit 30. Although not shown, the sealing substrate is bonded to the upper electrode 213 via a passivation film with an adhesive, and the organic EL element 21 is sealed with the sealing substrate, whereby the display panel 70 is formed. The

(Circuit operation of organic EL display device)
Next, the circuit operation of the organic EL display device 10 will be described with reference to the operation explanatory diagrams of FIGS. 8 and 9 based on the timing waveform diagram of FIG. In the operation explanatory diagrams of FIGS. 8 and 9, the write transistor 23 is illustrated with a switch symbol for simplification of the drawing. Further, the equivalent capacitance 25 of the organic EL element 21 is also illustrated.

  In the timing waveform diagram of FIG. 7, the potential (writing scanning signal) WS of the scanning line 31 (31-1 to 31-m) changes, the potential (power supply potential) of the power supply line 32 (32-1 to 32-m). ) Changes in DS and changes in the gate potential Vg and source potential Vs of the drive transistor 22 are shown. Further, the waveform of the gate potential Vg is indicated by a one-dot chain line, and the waveform of the source potential Vs is indicated by a dotted line so that the two can be identified.

<Light emission period of previous frame>
In the timing waveform diagram of FIG. 7, the time before time t1 is the light emission period of the organic EL element 21 in the previous frame (field). In the light emission period of the previous frame, the potential DS of the power supply line 32 is at the first power supply potential (hereinafter referred to as “high potential”) Vccp, and the writing transistor 23 is in a non-conduction state.

  At this time, the drive transistor 22 is designed to operate in a saturation region. As a result, as shown in FIG. 8A, the drive current (drain-source current) Ids corresponding to the gate-source voltage Vgs of the drive transistor 22 passes from the power supply line 32 through the drive transistor 22 to the organic EL element. 21 is supplied. Therefore, the organic EL element 21 emits light with a luminance corresponding to the current value of the drive current Ids.

<Threshold correction preparation period>
At time t1, a new frame (current frame) for line sequential scanning is entered. Then, as shown in FIG. 8B, the second power supply potential (hereinafter referred to as the potential DS of the power supply line 32) is sufficiently lower than Vofs−Vth with respect to the reference potential Vofs of the signal line 33 from the high potential Vccp. Switch to Vini) (described as “low potential”).

  Here, the threshold voltage of the organic EL element 21 is Vthel, and the potential of the common power supply line 34 (cathode potential) is Vcath. At this time, if the low potential Vini is Vini <Vthel + Vcath, the source potential Vs of the drive transistor 22 is substantially equal to the low potential Vini, so that the organic EL element 21 is in a reverse bias state and extinguished.

  Next, when the potential WS of the scanning line 31 transits from the low potential side to the high potential side at time t2, as shown in FIG. 8C, the writing transistor 23 becomes conductive. At this time, since the reference potential Vofs is supplied from the signal output circuit 60 to the signal line 33, the gate potential Vg of the drive transistor 22 becomes the reference potential Vofs. Further, the source potential Vs of the driving transistor 22 is at a potential Vini that is sufficiently lower than the reference potential Vofs.

  At this time, the gate-source voltage Vgs of the drive transistor 22 is Vofs-Vini. Here, if Vofs−Vini is not larger than the threshold voltage Vth of the drive transistor 22, threshold correction processing described later cannot be performed, and therefore it is necessary to set a potential relationship of Vofs−Vini> Vth.

  As described above, the process of fixing (initializing) the gate potential Vg of the drive transistor 22 to the reference potential Vofs and the source potential Vs to the low potential Vini is a preparation before performing a threshold correction process described later. (Threshold correction preparation) processing. Therefore, the reference potential Vofs and the low potential Vini become the initialization potentials of the gate potential Vg and the source potential Vs of the drive transistor 22, respectively.

<Threshold correction period>
Next, at time t3, as shown in FIG. 8D, when the potential DS of the power supply line 32 is switched from the low potential Vini to the high potential Vccp, the threshold is maintained while the gate potential Vg of the drive transistor 22 is maintained. The correction process is started. That is, the source potential Vs of the drive transistor 22 starts to increase toward the potential obtained by subtracting the threshold voltage Vth of the drive transistor 22 from the gate potential Vg.

  Here, for convenience, processing for changing the source potential Vs toward the potential obtained by subtracting the threshold voltage Vth of the drive transistor 22 from the initialization potential Vofs with reference to the initialization potential Vofs of the gate electrode of the drive transistor 22 is corrected by the threshold value. This is called processing. As the threshold correction process proceeds, the gate-source voltage Vgs of the drive transistor 22 eventually converges to the threshold voltage Vth of the drive transistor 22. A voltage corresponding to the threshold voltage Vth is held in the storage capacitor 24.

  In the period for performing the threshold correction process (threshold correction period), the organic EL element 21 is cut off in order to prevent the current from flowing exclusively to the storage capacitor 24 and not to the organic EL element 21. As described above, the potential Vcath of the common power supply line 34 is set.

  Next, when the potential WS of the scanning line 31 transitions to the low potential side at time t4, the writing transistor 23 is turned off as illustrated in FIG. At this time, the gate electrode of the driving transistor 22 is electrically disconnected from the signal line 33 to be in a floating state. However, since the gate-source voltage Vgs is equal to the threshold voltage Vth of the drive transistor 22, the drive transistor 22 is in a cutoff state. Therefore, the drain-source current Ids does not flow through the driving transistor 22.

<Signal writing & mobility correction period>
Next, at time t5, as shown in FIG. 9B, the potential of the signal line 33 is switched from the reference potential Vofs to the signal voltage Vsig of the video signal. Subsequently, at time t6, the potential WS of the scanning line 31 transitions to the high potential side, so that the writing transistor 23 becomes conductive as shown in FIG. 9C, and the signal voltage Vsig of the video signal is sampled. To write in the pixel 20.

  By the writing of the signal voltage Vsig by the writing transistor 23, the gate potential Vg of the driving transistor 22 becomes the signal voltage Vsig. When the driving transistor 22 is driven by the signal voltage Vsig of the video signal, the threshold voltage Vth of the driving transistor 22 is canceled with a voltage corresponding to the threshold voltage Vth held in the storage capacitor 24. Details of the principle of threshold cancellation will be described later.

  At this time, the organic EL element 21 is in a cutoff state (high impedance state). Accordingly, the current (drain-source current Ids) flowing from the power supply line 32 to the drive transistor 22 in accordance with the signal voltage Vsig of the video signal flows into the equivalent capacitor 25 of the organic EL element 21 and charging of the equivalent capacitor 25 starts. Is done.

  As the equivalent capacitance 25 of the organic EL element 21 is charged, the source potential Vs of the drive transistor 22 rises with time. At this time, the pixel-to-pixel variation in the threshold voltage Vth of the drive transistor 22 has already been cancelled, and the drain-source current Ids of the drive transistor 22 depends on the mobility μ of the drive transistor 22.

  Here, it is assumed that the ratio of the holding voltage Vgs of the storage capacitor 24 to the signal voltage Vsig of the video signal, that is, the write gain G is 1 (ideal value). Then, the source potential Vs of the drive transistor 22 rises to the potential of Vofs−Vth + ΔV, so that the gate-source voltage Vgs of the drive transistor 22 becomes Vsig−Vofs + Vth−ΔV.

  That is, the increase ΔV of the source potential Vs of the drive transistor 22 is subtracted from the voltage (Vsig−Vofs + Vth) held in the storage capacitor 24, in other words, the charge of the storage capacitor 24 is discharged. And negative feedback was applied. Therefore, the increase ΔV of the source potential Vs becomes a feedback amount of negative feedback.

  In this way, by applying negative feedback to the gate-source voltage Vgs with a feedback amount ΔV corresponding to the drain-source current Ids flowing through the drive transistor 22, the mobility μ of the drain-source current Ids of the drive transistor 22. The dependence on can be negated. This canceling process is a mobility correction process for correcting the variation of the mobility μ of the driving transistor 22 for each pixel.

  More specifically, since the drain-source current Ids increases as the signal amplitude Vin (= Vsig−Vofs) of the video signal written to the gate electrode of the drive transistor 22 increases, the absolute value of the feedback amount ΔV of the negative feedback increases. The value also increases. Therefore, mobility correction processing according to the light emission luminance level is performed.

  Further, when the signal amplitude Vin of the video signal is constant, the absolute value of the feedback amount ΔV of the negative feedback increases as the mobility μ of the drive transistor 22 increases. Can do. Therefore, it can be said that the feedback amount ΔV of the negative feedback is a correction amount for mobility correction. Details of the principle of mobility correction will be described later.

<Light emission period>
Next, at time t7, the potential WS of the scanning line 31 shifts to the low potential side, so that the writing transistor 23 is turned off as illustrated in FIG. 9D. As a result, the gate electrode of the driving transistor 22 is electrically disconnected from the signal line 33 and is in a floating state.

  Here, when the gate electrode of the driving transistor 22 is in a floating state, the storage capacitor 24 is connected between the gate and the source of the driving transistor 22, thereby interlocking with the fluctuation of the source potential Vs of the driving transistor 22. The gate potential Vg also varies. Thus, the operation in which the gate potential Vg of the drive transistor 22 varies in conjunction with the variation in the source potential Vs is a bootstrap operation by the storage capacitor 24.

  The gate electrode of the drive transistor 22 enters a floating state, and at the same time, the drain-source current Ids of the drive transistor 22 starts to flow into the organic EL element 21, whereby the anode potential of the organic EL element 21 is set according to the current Ids. To rise.

  When the anode potential of the organic EL element 21 exceeds Vthel + Vcath, the drive current starts to flow through the organic EL element 21, and the organic EL element 21 starts to emit light. The increase in the anode potential of the organic EL element 21 is nothing but the increase in the source potential Vs of the drive transistor 22. When the source potential Vs of the drive transistor 22 rises, the gate potential Vg of the drive transistor 22 also rises in conjunction with the bootstrap operation of the storage capacitor 24.

  At this time, assuming that the bootstrap gain is 1 (ideal value), the amount of increase in the gate potential Vg is equal to the amount of increase in the source potential Vs. Therefore, the gate-source voltage Vgs of the drive transistor 22 is kept constant at Vsig−Vofs + Vth−ΔV during the light emission period. At time t8, the potential of the signal line 33 is switched from the signal voltage Vsig of the video signal to the reference potential Vofs.

  In the series of circuit operations described above, each processing operation of threshold correction preparation, threshold correction, signal voltage Vsig writing (signal writing), and mobility correction is executed in one horizontal scanning period (1H). Further, the signal writing and mobility correction processing operations are executed in parallel during the period from time t6 to time t7.

(Threshold cancellation principle)
Here, the principle of threshold cancellation (that is, threshold correction) of the drive transistor 22 will be described. The drive transistor 22 operates as a constant current source because it is designed to operate in the saturation region. As a result, a constant drain-source current (drive current) Ids given by the following equation (1) is supplied from the drive transistor 22 to the organic EL element 21.
Ids = (1/2) · μ (W / L) Cox (Vgs−Vth) ² (1)
Here, W is the channel width of the drive transistor 22, L is the channel length, and Cox is the gate capacitance per unit area.

  FIG. 10 shows the characteristics of the drain-source current Ids versus the gate-source voltage Vgs of the drive transistor 22.

  As shown in this characteristic diagram, if no cancellation process is performed for the variation of the threshold voltage Vth of the drive transistor 22 for each pixel, the drain-source current corresponding to the gate-source voltage Vgs when the threshold voltage Vth is Vth1. Ids becomes Ids1.

  On the other hand, when the threshold voltage Vth is Vth2 (Vth2> Vth1), the drain-source current Ids corresponding to the same gate-source voltage Vgs is Ids2 (Ids2 <Ids). That is, when the threshold voltage Vth of the drive transistor 22 varies, the drain-source current Ids varies even if the gate-source voltage Vgs is constant.

On the other hand, in the pixel (pixel circuit) 20 having the above configuration, as described above, the gate-source voltage Vgs of the drive transistor 22 at the time of light emission is Vsig−Vofs + Vth−ΔV. Therefore, when this is substituted into the equation (1), the drain-source current Ids is expressed by the following equation (2).
Ids = (1/2) · μ (W / L) Cox (Vsig−Vofs−ΔV) ²
(2)

  That is, the term of the threshold voltage Vth of the drive transistor 22 is canceled, and the drain-source current Ids supplied from the drive transistor 22 to the organic EL element 21 does not depend on the threshold voltage Vth of the drive transistor 22. As a result, even if the threshold voltage Vth of the drive transistor 22 varies from pixel to pixel due to variations in the manufacturing process of the drive transistor 22 and changes over time, the drain-source current Ids does not vary. The brightness can be kept constant.

(Principle of mobility correction)
Next, the principle of mobility correction of the drive transistor 22 will be described. FIG. 11 shows a characteristic curve in a state where a pixel A having a relatively high mobility μ of the drive transistor 22 and a pixel B having a relatively low mobility μ of the drive transistor 22 are compared. When the driving transistor 22 is composed of a polysilicon thin film transistor or the like, it is inevitable that the mobility μ varies between pixels like the pixel A and the pixel B.

  Consider a case where the signal amplitude Vin (= Vsig−Vofs) of the same level is written to both the pixels A and B, for example, in the gate electrode of the drive transistor 22 in a state where the mobility μ varies between the pixel A and the pixel B. In this case, if the mobility μ is not corrected at all, it is between the drain-source current Ids1 ′ flowing through the pixel A having a high mobility μ and the drain-source current Ids2 ′ flowing through the pixel B having a low mobility μ. There will be a big difference. Thus, when a large difference occurs between the pixels in the drain-source current Ids due to the variation in mobility μ from pixel to pixel, the uniformity of the screen is impaired.

  Here, as is clear from the transistor characteristic equation of Equation (1), the drain-source current Ids increases when the mobility μ is large. Therefore, the feedback amount ΔV in the negative feedback increases as the mobility μ increases. As shown in FIG. 11, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel B having a low mobility.

  Therefore, by applying negative feedback to the gate-source voltage Vgs with the feedback amount ΔV corresponding to the drain-source current Ids of the drive transistor 22 by the mobility correction processing, the negative feedback is increased as the mobility μ is increased. become. As a result, variation in mobility μ for each pixel can be suppressed.

  Specifically, when the feedback amount ΔV1 is corrected in the pixel A having a high mobility μ, the drain-source current Ids greatly decreases from Ids1 ′ to Ids1. On the other hand, since the feedback amount ΔV2 of the pixel B having a low mobility μ is small, the drain-source current Ids decreases from Ids2 ′ to Ids2, and does not decrease that much. As a result, since the drain-source current Ids1 of the pixel A and the drain-source current Ids2 of the pixel B are substantially equal, the variation in mobility μ from pixel to pixel is corrected.

  In summary, when there are a pixel A and a pixel B having different mobility μ, the feedback amount ΔV1 of the pixel A having a high mobility μ is larger than the feedback amount ΔV2 of the pixel B having a low mobility μ. That is, the larger the mobility μ, the larger the feedback amount ΔV, and the larger the amount of decrease in the drain-source current Ids.

  Therefore, by applying negative feedback to the gate-source voltage Vgs with a feedback amount ΔV corresponding to the drain-source current Ids of the driving transistor 22, the current value of the drain-source current Ids of the pixels having different mobility μ. Is made uniform. As a result, variation in mobility μ for each pixel can be corrected. That is, the process for applying negative feedback to the gate-source voltage Vgs of the drive transistor 22 with the feedback amount ΔV corresponding to the current flowing through the drive transistor 22 (drain-source current Ids) is the mobility correction process.

  Here, in the pixel (pixel circuit) 20 shown in FIG. 2, the relationship between the signal voltage Vsig of the video signal and the drain-source current Ids of the drive transistor 22 depending on the presence or absence of threshold correction and mobility correction is shown in FIG. I will explain.

  In FIG. 12, (A) does not perform both threshold correction and mobility correction, (B) does not perform mobility correction, and performs only threshold correction, (C) performs threshold correction and mobility correction. Each case is shown. As shown in FIG. 12A, when neither threshold correction nor mobility correction is performed, the drain-source current Ids is caused by variations in the threshold voltage Vth and the mobility μ for each of the pixels A and B. A large difference occurs between the pixels A and B.

  On the other hand, when only the threshold correction is performed, as shown in FIG. 12B, although the variation in the drain-source current Ids can be reduced to some extent, the variation in the mobility μ for each of the pixels A and B. The difference in the drain-source current Ids between the pixels A and B due to this remains. Then, by performing both the threshold correction and the mobility correction, as shown in FIG. 12C, the drain between the pixels A and B due to the variation of the threshold voltage Vth and the mobility μ for each of the pixels A and B. -The difference in the current Ids between the sources can be almost eliminated. Therefore, the luminance variation of the organic EL element 21 does not occur at any gradation, and a display image with good image quality can be obtained.

  Further, the pixel 20 shown in FIG. 2 has the function of bootstrap operation by the storage capacitor 24 described above in addition to the correction functions of threshold correction and mobility correction. Obtainable.

  That is, even if the source potential Vs of the drive transistor 22 changes with the time-dependent change of the IV characteristic of the organic EL element 21, the gate-source potential Vgs of the drive transistor 22 is set by the bootstrap operation by the storage capacitor 24. Can be kept constant. Therefore, the current flowing through the organic EL element 21 does not change and is constant. As a result, since the light emission luminance of the organic EL element 21 is kept constant, even if the IV characteristic of the organic EL element 21 changes with time, it is possible to realize image display without luminance deterioration associated therewith.

[Repair technology]
In the organic EL display device 10 as the premise of the present invention described above, as described above, the step of forming the organic EL element 21, the substrate on which the drive transistor 22, the write transistor 23, and the storage capacitor 24 are formed. When a foreign substance is mixed in the process, various luminance defects are generated. Examples of the luminance defect include a dark spot due to a short circuit between the electrodes of the organic EL element 21 and a short circuit between the electrodes of the storage capacitor 24, a bright spot due to a short circuit between the electrodes of the drive transistor 22, and a half dark spot due to a short circuit between the electrodes of the write transistor 23. It is done. When the luminance defect of these pixel units occurs, the yield of the display panel 70 decreases.

  As a technique for suppressing a decrease in the yield of the display panel 70 due to the luminance defect, there is a repair technique for the luminance defect. The repair technique for this luminance defect will be described below with reference examples.

(Reference Example 1)
FIG. 13 is a circuit diagram illustrating a pixel circuit using the repair technique according to Reference Example 1. In the repair technique according to Reference Example 1, for example, three organic EL elements 21-1, 21-2, and 21-3 are used as electro-optical elements, and these organic EL elements 21-1, 21-2, and 21-3 are used. Are commonly driven by a single drive circuit 25.

  In the repair technique according to the reference example 1, when any one of the three organic EL elements 21-1, 21-2, and 21-3 is defective due to a short circuit between electrodes due to a foreign matter, the defective organic By disconnecting the EL element 21-1 / 21-2 / 21-3 from the drive circuit 25, the pixel 20 is prevented from becoming a complete dark spot (repair for luminance defect).

  Here, as shown in FIG. 14A, if the current value flowing through the organic EL elements 21-1, 21-2, 21-3 is I, the organic EL elements 21-1, 21-2, 21 -3 current value of I / 3 flows individually. As a result, the light emission luminance corresponding to the current value I is obtained in total for the organic EL elements 21-1, 21-2 and 21-3.

  On the other hand, among the three organic EL elements 21-1, 21-2, and 21-3, for example, when the organic EL element 21-1 is defective due to a short circuit between electrodes due to foreign matter, as shown in FIG. In addition, the organic EL element 21-1 is separated from the drive circuit 25 by cutting the wiring of the part a. Then, since the current value flowing through the remaining organic EL elements 21-2 and 21-3 becomes I / 2, the light emission luminance corresponding to the current value I can be ensured. However, since the current density of the remaining organic EL elements 21-2 and 21-3 is increased, the deterioration of the organic EL elements 21-2 and 21-3 is accelerated, so that the luminance half-life is shortened. . Here, the luminance half-life refers to a lifetime in which the luminance of the organic EL element is reduced to about half of the initial luminance.

(Reference Example 2)
FIG. 15 is a circuit diagram illustrating a pixel circuit using the repair technique according to Reference Example 2. In the repair technique according to Reference Example 2, for example, three organic EL elements 21-1, 21-2, and 21-3 are used as electro-optical elements, and these organic EL elements 21-1, 21-2, and 21-3 are used. Is driven independently by three drive circuits 25-1, 25-2 and 25-3.

  In the repair technique according to the second reference example, the signal voltage Vsig of the video signal is stored in the storage capacitors 24-1, 24-2, 24-3 by 1/3 by the write transistors 23-1, 23-2, 23-2. Is done. Then, assuming that the current value flowing through the entire EL elements 21-1, 21-2, 21-3 according to the signal voltage Vsig is I, each of the organic EL elements 21-1, 21-2, 21-3 is individually A current value of I / 3 flows. As a result, the light emission luminance corresponding to the current value I is obtained in total for the organic EL elements 21-1, 21-2 and 21-3.

  Here, of the three organic EL elements 21-1, 21-2, and 21-3, for example, when the organic EL element 21-3 is defective due to a short circuit between electrodes due to foreign matter, the wiring of the part b By being disconnected from the drive circuit 25-3 by the cutting, the repair for the dark spot is performed. When the driving transistor 22-3 becomes defective due to a short circuit between electrodes due to foreign matter, the bright line is repaired by cutting the wiring of the part c. When the writing transistor 23-3 is defective due to a short circuit between electrodes due to a foreign substance or the like, the wiring of the part d is cut to repair the half-dead point. When the storage capacitor 24-3 becomes defective due to a short-circuit between electrodes due to a foreign substance or the like, the wiring at the site e is cut to repair the dark spot.

  According to the repair technique according to the reference example 2, even when a defect due to a foreign substance occurs in any pixel constituent element, the defective element can be separated, so that the pixel 20 is prevented from becoming a complete luminance defect. be able to. Even if any element of the drive transistor 22 and the write transistor 23 is defective and separated, the signal voltage Vsig / 3 is stored in the storage capacitors 24-1, 24-2, 24-3, respectively. Therefore, since the current value flowing through the organic EL elements 21-1, 21-2, and 21-3 is I / 3, the light emission luminance according to the current value I can be secured, and the luminance before and after the repair. Half-life does not change.

  However, as in Reference Examples 1 and 2, by adopting a configuration in which a plurality of organic EL elements are provided in one subpixel, that is, a configuration in which one subpixel is divided into a plurality of light emitting portions, a process rule (for example, Due to the wiring interval, the opening area (light emitting area) of the organic EL element decreases. Then, in order to obtain a desired light emission luminance, the current density has to be increased, so that the lifetime of the organic EL element is reduced.

[Characteristics of this embodiment]
The present invention has been made in view of the above points. In the present invention, the luminance half life of the organic EL element 21 depends on the material, but in general, the life of the B organic EL element 21B is different from that of other colors, for example, R and G organic EL elements 21R and 21G. Focus on short and short.

  FIG. 16 shows the relationship of the luminance half-life to the aperture ratios of the R, G, and B organic EL elements 21R, 21G, and 21B. If the aperture ratio is low for all colors, it is necessary to increase the current density in order to obtain a predetermined luminance. If the current density increases, the luminance half-life is shortened. As is apparent from the characteristic diagram of FIG. 16, the B organic EL element 21B is shorter than the R and G organic EL elements 21R and 21G. Incidentally, the organic EL element 21R of R is relatively longest.

  In view of the luminance half-life that differs depending on the emission color, in one embodiment of the present invention, there is one organic EL element for the B subpixel 20B, and a plurality of organic EL elements for the R and G subpixels 20R and 20G. On the other hand, the light emission area of the B subpixel 20B is set larger than the light emission areas of the R and G subpixels 20R and 20G.

  Here, the light emitting areas of the sub-pixels 20R, 20G, and 20B are the opening area of the organic EL element. Specifically, in the B sub-pixel 20B, the opening area of one electro-optic element is the light emission area of the B sub-pixel 20B, and in the R and G sub-pixels 20R and 20G, the openings of the plurality of organic EL elements. The total partial area is the light emitting area of the R and G subpixels 20R and 20G.

  Further, the drive circuit including the drive transistor 22, the write transistor 23, and the storage capacitor 24 has the following configuration. That is, the B sub-pixel 20B employs a configuration in which one organic EL element is driven by one drive circuit. The R subpixel 20R adopts a configuration in which a plurality of organic EL elements are commonly driven by a single drive circuit. The configuration of the R sub-pixel 20 </ b> R corresponds to the repair technique according to the reference column 1. The G sub-pixel 20G employs a configuration in which a plurality of organic EL elements are independently driven by a plurality of drive circuits with a one-to-one correspondence. The configuration of the G sub-pixel 20G corresponds to the repair technique according to the reference column 2.

(Example)
FIGS. 17A and 17B are diagrams showing an embodiment of one pixel, where FIG. 17A is a schematic plan view showing an EL element side layout, and FIG. 17B is a schematic plan view showing a substrate side layout. Here, the B sub-pixel 20B has one organic EL element, and the R and G sub-pixels 20R and 20B have, for example, three organic EL elements, as in Reference Examples 1 and 2. An example will be described. Having three organic EL elements is equivalent to dividing the light emitting area of each sub-pixel into three. That is, it can be said that providing a plurality of organic EL elements in one sub-pixel divides one sub-pixel into a plurality of light-emitting portions (light-emitting regions) (pixel division).

  As shown in FIG. 17A, the B sub-pixel 20B has one organic EL element 21, and the R and G sub-pixels 20R and 20G each have three organic EL elements 21-1 and 21-2. , 21-3. At this time, on the EL element side on which the organic EL element 21 is formed, assuming that the widths in the row direction (subpixel arrangement direction) of the subpixels 20R, 20G, and 20B are Ir, Ig, and Ib, respectively, Ir <Ig <Ib The widths Ir, Ig, and Ib are set so that

  Here, the opening area (that is, the light emission area) of the organic EL element 21 of the B sub-pixel 20B is Sb. Also, the opening areas of the organic EL elements 21-1, 21-2, 21-3 of the R subpixel 20R are Sr1, Sr2, Sr3, and the organic EL elements 21-1, 21-21 of the G subpixel 20G are used. Each opening area of 2, 21-3 is defined as Sg1, Sg2, Sg3.

  At this time, the opening area Sb of the organic EL element 21 of the B subpixel 20B is equal to the total opening area Sg of the organic EL elements 21-1, 21-2, and 21-3 of the G subpixel 20G (= Sg1 + Sg2 + Sg3). ) To be larger than Further, the total opening area Sg of the organic EL elements 21-1, 21-2, 21-3 of the G subpixel 20G is equal to the organic EL elements 21-1, 21-2, 21- of the R subpixel 20R. 3 is set to be larger than the total opening area Sr (= Sr1, Sr2, Sr3).

  That is, when the lifetime of the organic EL elements 21R, 21G, and 21B of R, G, and B is 21R> 21G> 21B, the opening area Sr, Sg, and Sb of the organic EL elements 21R, 21G, and 21B is Sr <Sg. Each opening area Sr, Sg, Sb is set so that <Sb. Here, for the R organic EL element 21R, the opening areas Sr1, Sr2, and Sr3 of the organic EL elements 21-1, 21-2, and 21-3 are set to be the same. For the G organic EL element 21G, the opening areas Sg1, Sg2, and Sg3 of the organic EL elements 21-1, 21-2, and 21-3 are set to be the same.

  On the other hand, on the substrate side on which the drive circuit 25 is formed, the subpixels 20R and 20B have one drive circuit, and the subpixel 20G has three drive circuits. On the substrate side, similarly to the EL element side, the widths Ir, Ig, and Ib in the row direction of the sub-pixels 20R, 20G, and 20B are set to satisfy Ir <Ig <Ib. That is, the layout area of the subpixels 20R, 20G, and 20B is the largest for the subpixel 20B and the smallest for the subpixel 20R.

  FIG. 18 shows a layout of one entire pixel. FIG. 18 is an overlay of FIG. 17 (A) and FIG. 17 (B). Regarding the sub-pixel 20G, each of the regions of the drive circuits 25-1, 25-2, and 25-3 and the organic EL elements 21-1, 21-2, and 21-3 have a corresponding positional relationship. On the other hand, for the sub-pixel 20R, the three organic EL elements 21-1, 21-2, and 21-3 are positioned almost above the area of one drive circuit 25.

<R sub-pixel>
FIG. 19 shows an overall layout of the R subpixel 20R, and FIG. 20 shows a substrate side layout. 19, FIG. 20, the same code | symbol is attached | subjected and shown to FIG. 5, FIG.

  19 and 20, a lowermost first wiring layer 75 for forming circuit elements such as a drive transistor 22, a write transistor 23, and a storage capacitor 24 constituting the sub-pixel 20R is provided. The first wiring layer 75 forms part of the signal line 33, the gate electrodes of the drive transistor 22 and the write transistor 23, one electrode of the storage capacitor 24, and the like.

  A second wiring layer 81 is provided on the first wiring layer 75 via an interlayer insulating film (interlayer insulating film 76 in FIG. 6). The second wiring layer 81 is electrically connected to the source electrode and the drain electrode of the drive transistor 22 and the write transistor 23, and the other electrode of the storage capacitor 24, the scanning line 31, the power supply line 32, and the signal line 33. Form a part of

  The first wiring layer 75 and the second wiring layer 81 are electrically connected by contact portions 91, 92, 93. In addition, as shown in FIG. 21, the lower electrode (eg, anode electrode) 211-1 of the organic EL element 21-1 is electrically connected to the first and second wiring layers 75 and 81 by the contact portion 92-1. Connected. Similarly, the lower electrodes 211-2 and 211-3 of the organic EL elements 21-2 and 21-3 are electrically connected to the first and second wiring layers 75 and 81 at the contact portions 92-2 and 92-3. Connected.

  Here, for example, when the organic EL element 21-3 becomes defective, if the wiring of the first wiring layer 75 between the contact portions 93, 94-2 and the contact portion 94-3 is cut by, for example, laser light irradiation. Good. As a result, the defective organic EL element 21-3 is disconnected from the drive circuit 25, and repair for the defective organic EL element 21-3 is performed.

  Here, the electrical connection between the organic EL elements 21-1, 21-2, 21-3 and the drive circuit 25 is the first wiring layer formed in the same process as the gate electrodes of the drive transistor 22 and the write transistor 23. 75 wirings are used. Therefore, at the time of repair, the wiring can be easily cut from the back side of the display panel 70 by laser beam irradiation.

<G subpixel>
FIG. 22 shows the overall layout of the G sub-pixel 20G, and FIG. 23 shows the substrate-side layout. 22 and 23, the same parts as those in FIGS. 19 and 20 are denoted by the same reference numerals.

  22 and 23, three drive circuits 25-1, 25-2, and 25-3 are provided on the substrate side corresponding to the three organic EL elements 21-1, 21-2, and 21-3. Yes. Specifically, by the first wiring layer 75, a part of the signal line 33, the gate electrode of the drive transistor 22-1 and the write transistor 23-1, and one electrode of the storage capacitor 24-1 of the drive circuit 25-1. Etc. are formed. The same applies to the drive circuits 25-2 and 25-3.

  Further, the second wiring layer 81 forms part of the other electrode of the storage capacitors 24-1, 24-2 and 24-3, the scanning line 31, the power supply line 32 and the signal line 33. The second wiring layer 81 is electrically connected to the source and drain electrodes of the drive transistors 22-1 2-22-2-3 and the write transistors 23-1, 23-2, 23-3.

  The first wiring layer 75 and the second wiring layer 81 are electrically connected by contact portions 91, 92-1, 92-2, and 92-3. Further, the second wiring layers 81-1, 81-2, 81-3 of the driving circuits 25-1, 25-2, 25-3, and the lower electrodes 211- of the organic EL elements 21-2, 21-3, respectively. 1, 211-2 and 211-3 are electrically connected by contact portions 93-1, 93-2 and 93-3.

  The equivalent circuit of the G sub-pixel 20G described above is the same as that of the reference example 2 in FIG. Therefore, of the three organic EL elements 21-1, 21-2, and 21-3, for example, when the organic EL element 21-3 becomes defective due to a short circuit between electrodes due to foreign matter, the wiring at the part b is cut. Thus, the dark spot is repaired by separating from the drive circuit 25-3. When the driving transistor 22-3 becomes defective due to a short circuit between electrodes due to a foreign substance, the bright spot is repaired by cutting the wiring at the part c. When the writing transistor 23-3 is defective due to a short circuit between electrodes due to a foreign substance, repair of the half-dead point is performed by cutting the wiring of the part d. When the storage capacitor 24-3 becomes defective due to a short circuit between electrodes due to foreign matter, repair of the dark spot is performed by cutting the wiring of the part e.

  Similar to the case of the reference example 2, even when a defect caused by a foreign substance occurs in any pixel constituent element, the defective element can be separated, so that the sub-pixel 20G is prevented from becoming a complete luminance defect. Can do. Even if any of the drive transistors 22-1, 22-2, 22-3 and the write transistors 23-1, 23-2, 23-3 is defective and separated, the organic EL elements 21-1, 21 are separated. The value of the current flowing through −2 and 21-3 is I / 3. Therefore, it is possible to ensure the light emission luminance corresponding to the current value I. In addition, the luminance half-life before and after repair does not change.

[Operational effects of this embodiment]
As described above, since the R and G sub-pixels 20R and 20B have the plurality of organic EL elements 21-1, 21-2, and 21-3, the organic EL elements 21-1, When any of 21-2 and 21-3 becomes defective, the organic EL element is separated. As a result, it is possible to repair a luminance defect caused by contamination of foreign matter. However, since the B sub-pixel 20B has only one organic EL element 21, it is not possible to repair the luminance defect.

  On the other hand, paying attention to the fact that the B organic EL element 21B is shorter than the R and G organic EL elements 21R and 21G, the light emission area Sb of the B subpixel 20B is set to the light emission of the subpixels 20R and 20G of other colors. It is set larger than the areas Sr and Sg. If the light emission area, that is, the opening area of the organic EL element 21 is large, the current density flowing in the organic EL element 21 can be set lower than that when the opening area is small in obtaining the desired light emission luminance. If the current density is low, a decrease in the lifetime of the organic EL element 21 can be suppressed.

  That is, regarding the B sub-pixel 20B, although it is impossible to repair the luminance defect, it is possible to extend the life of the B organic EL element having a relatively short life. As a result, it is possible to balance the lifetime of the organic EL element 21 for each luminescent color while taking measures against luminance defects caused by contamination with foreign matter. In particular, for the R sub-pixel 20R having the longest lifetime, the lifetime of the organic EL element 21 can be more reliably balanced for each emission color by setting the emission area to be the smallest. .

[Modification]
In the above embodiment, the driving circuit of the organic EL element 21 is basically described as an example of the pixel configuration including the two transistors of the driving transistor 22 and the writing transistor 23. However, the present invention is not limited to this pixel configuration. The application is not limited to. For example, various pixel configurations such as a pixel configuration having a switching transistor for selectively writing the reference potential Vofs to the gate electrode of the drive transistor 22 are conceivable.

  In the above embodiment, the case where the present invention is applied to an organic EL display device using an organic EL element as the electro-optical element of the pixel 20 has been described as an example. However, the present invention is not limited to this application example. . Specifically, the present invention relates to a display device using a current-driven electro-optical element (light emitting element) such as an inorganic EL element, an LED element, a semiconductor laser element or the like whose emission luminance changes according to a current value flowing through the device. Applicable to all.

[Application example]
The display device according to the present invention described above can be applied to display devices of electronic devices in various fields that display video signals input to electronic devices or video signals generated in electronic devices as images or videos. Is possible. As an example, the present invention can be applied to various electronic devices shown in FIGS. 24 to 28, for example, digital cameras, notebook personal computers, portable terminal devices such as mobile phones, and display devices such as video cameras.

  The display device according to the present invention includes a module-shaped one having a sealed configuration. For example, a display module formed by attaching a facing portion such as transparent glass to the pixel array portion 30 is applicable. The transparent facing portion may be provided with a color filter, a protective film, and the like, and further the above-described light shielding film. Note that the display module may be provided with a circuit unit for inputting / outputting a signal to the pixel array unit from the outside, an FPC (flexible printed circuit), and the like.

  Specific examples of electronic devices to which the present invention is applied will be described below.

  FIG. 24 is a perspective view showing an appearance of a television set to which the present invention is applied. The television set according to this application example includes a video display screen unit 101 including a front panel 102, a filter glass 103, and the like, and is created by using the display device according to the present invention as the video display screen unit 101.

  25A and 25B are perspective views showing the external appearance of a digital camera to which the present invention is applied. FIG. 25A is a perspective view seen from the front side, and FIG. 25B is a perspective view seen from the back side. The digital camera according to this application example includes a light emitting unit 111 for flash, a display unit 112, a menu switch 113, a shutter button 114, and the like, and is manufactured by using the display device according to the present invention as the display unit 112.

  FIG. 26 is a perspective view showing the external appearance of a notebook personal computer to which the present invention is applied. A notebook personal computer according to this application example includes a main body 121 including a keyboard 122 that is operated when characters and the like are input, a display unit 123 that displays an image, and the like, and the display device according to the present invention is used as the display unit 123. It is produced by this.

  FIG. 27 is a perspective view showing the appearance of a video camera to which the present invention is applied. The video camera according to this application example includes a main body part 131, a lens 132 for photographing an object on the side facing forward, a start / stop switch 133 at the time of photographing, a display part 134, etc., and the display part 134 according to the present invention. It is manufactured by using a display device.

  28A and 28B are external views showing a mobile terminal device to which the present invention is applied, for example, a mobile phone. FIG. 28A is a front view in an opened state, FIG. 28B is a side view thereof, and FIG. (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. A cellular phone according to this application example includes an upper casing 141, a lower casing 142, a connecting portion (here, a hinge portion) 143, a display 144, a sub-display 145, a picture light 146, a camera 147, and the like. Then, by using the display device according to the present invention as the display 144 or the sub display 145, the mobile phone according to this application example is manufactured.

1 is a system configuration diagram showing an outline of a configuration of an organic EL display device to which the present invention is applied. It is a schematic plan view which shows an example of the layout of the organic electroluminescence display which concerns on this application example. It is a circuit diagram which shows the circuit structure of the pixel of the organic electroluminescence display which concerns on this application example. It is a schematic plan view which shows the whole layout about a RGB subpixel. 2A and 2B are diagrams illustrating a specific configuration example of one subpixel, in which FIG. 1A is a schematic plan view focusing on a first wiring layer and a second wiring layer, and FIG. 2B is a schematic plan view focusing on an anode layer. . FIG. 5 is a cross-sectional view showing the entire layer structure of one subpixel, and is a cross-sectional view taken along the line aa ′ in FIG. 4. It is a timing waveform diagram with which it uses for description of the circuit operation | movement of the organic electroluminescence display which concerns on this application example. It is explanatory drawing (the 1) of the circuit operation | movement of the organic electroluminescence display which concerns on this application example. It is explanatory drawing (the 2) of the circuit operation | movement of the organic electroluminescence display which concerns on this application example. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the threshold voltage Vth of a drive transistor. It is a characteristic view with which it uses for description of the subject resulting from the dispersion | variation in the mobility (mu) of a drive transistor. FIG. 10 is a characteristic diagram for explaining the relationship between the signal voltage Vsig of the video signal and the drain-source current Ids of the drive transistor depending on whether threshold correction and mobility correction are performed. It is explanatory drawing (the 1) about the repair technique which concerns on the reference example 1. FIG. It is explanatory drawing (the 2) about the repair technique which concerns on the reference example 1. FIG. It is explanatory drawing about the repair technique which concerns on the reference example 2. FIG. It is a characteristic view which shows the relationship of the lifetime with respect to the aperture ratio of the organic EL element of R, G, B. It is a figure which shows one Example about one pixel, (A) is a schematic plan view which shows EL element side layout, (B) is a schematic plan view which shows a board | substrate side layout. It is a schematic plan view which shows the layout of the whole one pixel. It is a top view which shows the whole layout of R subpixel. It is a schematic plan view which shows the board | substrate side layout of R subpixel. It is a figure which shows the state of the electrical connection of the 1st, 2nd wiring layer in the R subpixel, and the lower electrode of an organic EL element. It is a top view which shows the whole layout of the subpixel of G. It is a schematic plan view which shows the substrate side layout of the subpixel of G. It is a perspective view which shows the external appearance of the television set to which this invention is applied. It is a perspective view which shows the external appearance of the digital camera to which this invention is applied, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. 1 is a perspective view illustrating an appearance of a notebook personal computer to which the present invention is applied. It is a perspective view which shows the external appearance of the video camera to which this invention is applied. BRIEF DESCRIPTION OF THE DRAWINGS It is an external view which shows the mobile telephone to which this invention is applied, (A) is the front view in the open state, (B) is the side view, (C) is the front view in the closed state, (D) Is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. It is explanatory drawing about a brightness | luminance defect.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Organic EL display device, 20 ... Pixel, 20R, 20G, 20B ... Sub-pixel, 21, 21-1, 21-22, 21-3 ... Organic EL element, 22, 22-1, 22-2, 22- 3... Drive transistor, 23, 23-1, 23-2, 23-3... Write transistor, 24, 24-1, 24-2, 24-3... Storage capacitor, 30. 31-m) ... scanning line, 32 (32-1 to 32-m) ... power supply line, 33 (33-1 to 33-n) ... signal line, 34 ... common power supply line, 40 ... write scanning circuit 50 ... Power supply scanning circuit, 60 ... Signal output circuit, 70 ... Display panel

Claims (8)

A pixel array unit in which pixels composed of combinations of a blue sub-pixel emitting blue light and a plurality of different color sub-pixels independently emitting a plurality of different color lights other than blue light are arranged in a matrix With
The blue subpixel has one electro-optic element,
The other color sub-pixel has a plurality of electro-optic elements,
The light emitting area of the blue subpixel is larger than the light emitting area of the other color subpixel. The other color sub-pixels include at least a red sub-pixel that emits red light and a green sub-pixel that emits green light,
The display device according to claim 1, wherein a light emission area of the red sub-pixel is smaller than a light emission area of the blue sub-pixel. The display device according to claim 2, wherein the red sub-pixel has one drive circuit that drives a plurality of electro-optic elements in common. The display device according to claim 3, wherein each of the plurality of electro-optical elements has the same opening area in the red sub-pixel. In the red sub-pixel, the plurality of electro-optical elements and the one driving circuit are electrically connected by wiring of a first wiring layer formed in the same process as a gate electrode of a transistor constituting the driving circuit. The display device according to claim 3. The display device according to claim 2, wherein the green subpixel includes a plurality of drive circuits that independently drive the plurality of electro-optic elements. The display device according to claim 6, wherein each of the plurality of electro-optic elements has the same opening area in the green sub-pixel. A pixel array unit in which pixels composed of combinations of a blue sub-pixel emitting blue light and a plurality of different color sub-pixels independently emitting a plurality of different color lights other than blue light are arranged in a matrix With
The blue subpixel has one electro-optic element,
The other color sub-pixel has a plurality of electro-optic elements,
An electronic apparatus having a display device, wherein a light emission area of the blue subpixel is larger than a light emission area of the other color subpixel.

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