JP4792748B2 - Display panel - Google Patents

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JP4792748B2
JP4792748B2 JP2005007852A JP2005007852A JP4792748B2 JP 4792748 B2 JP4792748 B2 JP 4792748B2 JP 2005007852 A JP2005007852 A JP 2005007852A JP 2005007852 A JP2005007852 A JP 2005007852A JP 4792748 B2 JP4792748 B2 JP 4792748B2
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transistor
wiring
power supply
display panel
insulating film
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JP2006195255A (en
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潤 小倉
剛 尾崎
忠久 当山
友之 白嵜
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カシオ計算機株式会社
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Description

  The present invention relates to a display panel, and more particularly to a display panel using a light emitting element.

  In recent years, as a display device using a new video display method replacing CRT (Cathode Ray Tube), a liquid crystal display using a liquid crystal panel (LCD: Liquid Crystal Display), an electroluminescence (EL) phenomenon is used. Plasma displays using an EL display and a plasma display panel (hereinafter referred to as “PDP”) have been developed.

  Among these, the EL display is roughly classified into an inorganic EL display using an inorganic compound as an electroluminescence element (hereinafter referred to as an EL element) and an organic EL display using an organic compound. Development of an organic EL display is underway from the viewpoint that it can operate at a lower voltage than an EL display.

  The driving method of the organic EL display panel used in this organic EL display includes a passive matrix driving method and an active matrix driving method. An organic EL display panel adopting the active matrix driving method has high contrast and high definition. Therefore, it is superior to the passive matrix driving method.

For example, in the conventional active matrix driving type organic EL display panel described in Patent Document 1, an organic EL element and a driving transistor in which a voltage signal corresponding to image data is applied to the gate to flow current to the organic EL element A switching transistor that performs switching for supplying a voltage signal corresponding to image data to the gate of the driving transistor is provided for each pixel. In such an organic EL display panel, when a scanning line is selected, the switching transistor is turned on, and a voltage having a level representing luminance is instantaneously applied to the gate of the driving transistor via the signal line. As a result, the driving transistor is turned on, and a driving current having a magnitude corresponding to the level of the gate voltage flows from the power source to the organic EL element via the drain-source of the driving transistor, and the organic EL element is in accordance with the magnitude of the current. Emits light with brightness. From the end of the selection of the scanning line to the next selection of the scanning line, even if the switching transistor is turned off, the level of the gate voltage of the driving transistor is maintained, and the organic EL element is driven. It emits light with a luminance corresponding to the magnitude of the current.
JP-A-8-330600

  However, in the case of the above-described organic EL display panel, there is a problem that a voltage drop or a signal delay through the wiring occurs due to the electrical resistance of the wiring that allows current to simultaneously flow through a plurality of organic EL elements such as power supply lines. . As a countermeasure for suppressing these voltage drops and signal delays, a method of reducing the resistance of the wiring by increasing the thickness or width of the wiring has been studied. However, when this wiring is formed using the gate metal, source, or drain metal of a thin film transistor such as a driving transistor for operating an organic EL element, the thickness of the electrode in the thin film transistor is designed according to the required characteristics. Therefore, in other words, it is not designed on the premise that a current flows to the light emitting element, so when trying to flow current from a wiring to a plurality of light emitting elements, a voltage drop may occur due to the electrical resistance of the wiring, A delay in the flow of current through the. In order to suppress the voltage drop and current delay, it is desirable to reduce the resistance of the wiring. For this purpose, the wiring is wide enough to allow current to sufficiently flow through the metal layer serving as the source and drain electrodes of the transistor and the metal layer serving as the gate electrode. When patterning to low resistance wiring, the area where the wiring overlaps with other wiring, conductors, etc. in plan view increases, parasitic capacitance is generated between them, and current flow is slowed down. In the case of a so-called bottom emission structure in which EL light is emitted from the transistor array substrate side, the wiring blocks the light emitted from the EL element, which reduces the aperture ratio, which is the ratio of the light emitting area. I was invited. Further, when the gate electrode of the thin film transistor is made thicker in order to reduce the resistance, not only the etching accuracy is lowered, but also a planarization film for planarizing the step of the gate electrode (for example, when the thin film transistor has an inverted staggered structure, a gate insulating film) The transistor characteristics may change significantly, and if the source and drain electrodes are made thicker, the etching accuracy of the source and drain electrodes will decrease. May adversely affect

  The present invention has been made in view of the above points, and an object thereof is to provide a display panel capable of suppressing a voltage drop and a delay of a current signal.

In order to solve the above problems, a display panel according to the invention described in claim 1 is:
A substrate,
A plurality of pixel circuits including transistors on the substrate;
An insulating film formed so as to cover the upper side of each of the transistors and having grooves along the row direction formed on the surface;
A plurality of power supply wirings embedded in the trenches and connected to the plurality of pixel circuits, respectively , and having a conductive layer different from the gate, source, and drain of the transistor ;
A plurality of conductive lines respectively formed along the extending direction of the power supply wiring on each of the plurality of power supply wirings and on the insulating film around the power supply wiring;
A ridge insulating film covering the plurality of conductive lines and formed in a lattice shape in the row direction and the column direction;
A bank formed on a portion of the protrusion insulating film extending in the column direction;
A plurality of pixel electrodes each provided on the insulating film and surrounded by the protrusion insulating film;
A counter electrode;
A light emitting layer surrounded by the protrusion insulating film between the plurality of pixel electrodes and the counter electrode;
It is characterized by comprising.

  According to the first aspect of the present invention, since the wiring is embedded in the groove formed in the protective insulating film covering the upper part of the transistors of the plurality of pixel circuits, it is possible to reduce the thickness by increasing the thickness of the wiring. It becomes possible to achieve resistance, and thereby voltage drop and current signal delay can be suppressed.

The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.
A display panel according to the present invention will be described with reference to FIGS.
First, the planar configuration of the display panel will be described.
As shown in FIG. 1, the display panel 1 in the present embodiment has pixels 3 arranged in a matrix. These pixels 3 are composed of a substantially rectangular 1-dot red sub-pixel Pr, 1-dot green sub-pixel Pg, and 1-dot blue sub-pixel Pb, and each sub-pixel Pr, Pg, Pb In the pixel 3, the red subpixel Pr, the green subpixel Pg, and the blue subpixel are arranged in a direction perpendicular to the longitudinal direction (hereinafter, horizontal direction) so that their longitudinal directions (hereinafter, vertical direction) are parallel to each other. The pixels Pb are arranged in this order.
Here, in the following description, an arbitrary subpixel of the red subpixel Pr, the green subpixel Pg, and the blue subpixel Pb is represented as a subpixel P, and the description of the subpixel P is described as a red subpixel Pr. The green subpixel Pg and the blue subpixel Pb are applied.

  In addition, as shown in FIG. 1, a signal line Yr is arranged between a column of red subpixels Pr and a column of blue subpixels Pb in the vertical direction. A signal line Yg is arranged between the vertical row of green subpixels Pg and the red row of subpixels Pr. Further, a signal line Yb is disposed between the column of blue subpixels Pb and the column of green subpixels Pg in the vertical direction. Accordingly, when attention is paid to the order of arrangement in the horizontal direction, the signal lines Yr, signal lines Yg, and signal lines Yb are repeatedly arranged in this order, and these signal lines Yr, signal lines Yg, and signal lines Yb extend in the vertical direction. These are arranged so as to be parallel to each other.

These signal line Yr, signal line Yg, and signal line Yb supply signals to all red subpixels Pr, all green subpixels Pg, and all blue subpixels Pb arranged in a line along the vertical direction. It is like that.
Here, in the following description, the signal line Y represents the signal line Yr of FIG. 1 in the case of the red subpixel Pr. In the case of the green subpixel Pg, the signal line Yg in FIG. 1 is represented. Further, in the case of the blue sub-pixel Pb, the signal line Yb in FIG. 1 is represented. The description of the signal line Y is applied to any of the signal line Yr, the signal line Yg, and the signal line Yb.

Here, there are n signal lines Y, and the signal lines Y 1 to Y n extending in the vertical direction (column direction) are m scanning lines X 1 to X extending in the horizontal direction (row direction). are orthogonal to m , m supply lines 90, 90,... and m supply lines Z 1 to Z m . In addition, m and n are each a natural number of 2 or more, and n is a multiple of 3, and the number subscripted to the scanning line X represents the arrangement order from the top in FIGS. 7 and 9 indicate the arrangement order from the top in FIG. 7 and FIG. 9, and the numbers subscripted to the signal line Y indicate the arrangement order from the left in FIG. 7 and FIG. The front side of the numbers represents the arrangement order from the top, and the back side represents the arrangement order from the left. That is, when an arbitrary natural number of 1 to m is i and an arbitrary natural number of 1 to n is j, the scanning line X i is the i-th row from the top, and the supply line Z i is the left The signal line Y j is the j-th column from the left, the sub-pixel P i, j is the i-th row from the top, the j-th column from the left, and the sub-pixel P i, j is the scanning line. It is connected to X i , supply line Z i and signal line Y j . More specifically, a plurality of scanning lines X are arranged on the upper side in the vertical direction of the pixels 3 so as to extend in the horizontal direction. On the other hand, a plurality of supply lines Z and a plurality of power supply wirings 90 are arranged in parallel to the scanning lines X on the lower side facing the scanning lines X across the pixels 3. Accordingly, when paying attention to the arrangement order in the vertical direction, the scanning lines X, the columns of the pixels 3 and the supply lines Z are repeatedly arranged in this order. These scanning lines X and supply lines Z supply signals to the subpixels Pr, Pg, and Pb arranged in one row along the horizontal direction.

Next, the circuit configuration of the subpixels Pr, Pg, and Pb will be described.
All of the subpixels Pr, Pg, and Pb are configured in the same manner. As shown in FIG. 2, each subpixel Pr, Pg, and Pb includes a switch transistor 21 and a holding transistor 22 that are all N-channel amorphous silicon thin film transistors. The pixel circuit including the driving transistor 23 and the capacitor 24 and the organic EL element 20 are provided.

  The organic EL element 20 includes a subpixel electrode 20a, an organic EL layer 20b (shown in FIG. 5), and a counter electrode 20c as pixel electrodes. Among these, the counter electrode 20 c is electrically connected to the common wiring 91.

  The switch transistor 21 has a source 21s, a drain 21d, and a gate 21g. Among these, the source 21s is electrically connected to the signal line Y, the drain 21d is electrically connected to the subpixel electrode 20a of the organic EL element 20, the source 23s of the drive transistor 23, and the electrode 24B of the capacitor 24, and the gate 21g is The gate 22g of the holding transistor 22 is electrically connected to the scanning line X.

  The holding transistor 22 includes a source 22s, a drain 22d, and a gate 22g. Among these, the source 22s is electrically connected to the gate 23g of the driving transistor 23 and the electrode 24A of the capacitor 24, the drain 22d is electrically connected to the drain 23d of the driving transistor 23 and the supply line Z, and the gate 22g is electrically connected to the switch transistor 21. The gate 21g is electrically connected to the scanning line X. Note that the drain 22d of the holding transistor 22 may be connected to the scanning line X without being electrically connected to the drain 23d of the driving transistor 23.

  The drive transistor 23 has a source 23s, a drain 23d, and a gate 23g. Among these, the source 23s is electrically connected to the sub-pixel electrode 20a of the organic EL element 20, the drain 21d of the switch transistor 21, and the electrode 24B of the capacitor 24. The drain 23d is connected to the drain 22d of the holding transistor 22 and the supply line. The gate 23g is electrically connected to the source 22s of the holding transistor 22 and the electrode 24A of the capacitor 24.

  The capacitor 24 includes electrodes 24A and 24B formed on the insulating substrate 2 so as to overlap in the vertical direction, and a dielectric interposed between the electrodes 24A and 24B. The capacitor 24 has the same layer structure in any of the subpixels Pr, Pg, and Pb.

Next, the planar configuration of the subpixel will be described.
As shown in FIG. 3, the switch transistor 21 is disposed along the signal line Y when the subpixels Pr, Pg, and Pb are viewed in plan. In addition, the holding transistor 22 is disposed at the corner of the subpixel P adjacent to the scanning line X. Further, the drive transistor 23 is disposed along the adjacent signal line Y, and the capacitor 24 is disposed along the drive transistor 23.

  In addition, when the entire display panel 1 is viewed in plan and attention is paid to the switch transistor 21, the holding transistor 22, and the driving transistor 23 in each of the subpixels Pr, Pg, and Pb, the transistors 21, 22, and 23 are arranged in a matrix. Each is arranged.

  The sub-pixel electrodes 20a of the organic EL element 20 are omitted in FIGS. 1 and 3 from the viewpoint of making the transistors 21, 22, and 23 easier to see, but these sub-pixel electrodes 20a are signal lines adjacent in the horizontal direction. It is arranged in a rectangular area surrounded by Y and the supply line Z and the scanning line X adjacent in the vertical direction. Further, since the subpixel electrode 20a is formed in a rectangular shape along the rectangular area, the entire display panel 1 is viewed in plan and attention is paid only to the subpixel electrodes 20a of the subpixels Pr, Pg, and Pb. Then, the plurality of subpixel electrodes 20a are arranged in a matrix.

Next, the layer structure of the display panel 1 will be described.
5 is a sectional view taken in the direction of the thickness of the insulating substrate 2 along the broken line VV shown in FIG. 4, and FIG. 6 is a broken line VI-VI shown in FIG. It is arrow sectional drawing cut | disconnected in the thickness direction of the insulation board | substrate 2 along line. As shown in FIG. 5, the display panel 1 includes a flexible sheet-like insulating sheet 2 having light transmittance or a plate-like insulating board 2 having rigidity. The switch transistor 21, the holding transistor 22, the driving transistor 23, and the capacitor 24 are formed to have a layer structure.

  As shown in FIG. 5, the switch transistor 21 is opposed to the gate 21g with the gate 21g formed on the upper surface of the insulating substrate 2, the gate insulating film 31 formed above the gate 21g, and the gate insulating film 31 interposed therebetween. Semiconductor film 21c, channel protective film 21p formed on the center of semiconductor film 21c, and impurity semiconductor film formed on both ends of semiconductor film 21c so as to be separated from each other and partially overlapping channel protective film 21p 21a, 21b, a drain 21d formed on the impurity semiconductor film 21a, and a source 21s formed on the impurity semiconductor film 21b.

  Note that the drain 21d and the source 21s may have a single-layer structure or a stacked structure of two or more layers.

  Although the layer structure of the holding transistor 22 is not shown, like the switch transistor 21, the gate 22g formed on the upper surface of the insulating substrate 2, the gate insulating film 31 formed on the gate 22g, and the gate The semiconductor film 22c facing the gate 22g with the insulating film 31 interposed therebetween, the channel protection film 22p formed on the central portion of the semiconductor film 22c, and formed on both ends of the semiconductor film 22c so as to be separated from each other, thereby protecting the channel Impurity semiconductor films 22a and 22b partially overlapping the film 22p, a drain 22d formed on the impurity semiconductor film 22a, and a source 22s formed on the impurity semiconductor film 22b.

  As shown in FIG. 5, the driving transistor 23 is opposed to the gate 23g with the gate 23g formed on the upper surface of the insulating substrate 2, the gate insulating film 31 formed on the gate 23g, and the gate insulating film 31 interposed therebetween. The semiconductor film 23c, the channel protective film 23p formed on the central portion of the semiconductor film 23c, and the impurity semiconductor film formed so as to be separated from each other on both ends of the semiconductor film 23c and partially overlapping the channel protective film 23p 23a, 23b, a drain 23d formed on the impurity semiconductor film 23a, and a source 23s formed on the impurity semiconductor film 23b. As shown in FIGS. 3 and 4, the driving transistor 23 is formed in a U shape so that the channel width is widened.

  Note that the drain 23d and the source 23s may have a single-layer structure or a stacked structure of two or more layers.

  The capacitor 24 includes an electrode 24A formed on the upper surface of the insulating substrate 2, a gate insulating film 31 formed as a dielectric on the electrode 24A, an electrode 24B facing the electrode 24A across the gate insulating film 31, have.

  The switch transistor 21, the holding transistor 22, the driving transistor 23, and the capacitor 24 have the same layer structure in any of the subpixels Pr, Pg, and Pb.

Further, the gate 21g of the switch transistor 21, the gate 22g of the holding transistor 22, the gate 23g of the driving transistor 23, the electrode 24A of the capacitor 24 and all the signal lines Yr, Yg, Yb are formed on the entire surface of the insulating substrate 2 in a single plane. The formed conductive film is formed by patterning by a photolithography method or an etching method.
Here, the gate 21g of the switch transistor 21, the gate 22g of the holding transistor 22, the gate 23g of the drive transistor 23, the electrode 24A of the capacitor 24, and the signal lines Yr, Yg, Yb are formed on a flat surface on the insulating substrate 2. The conductive film is formed by patterning by a photolithography method or an etching method. Hereinafter, the gate 21g of the switch transistor 21, the gate 22g of the holding transistor 22, the gate 23g of the drive transistor 23, the lower layer electrode 24A of the capacitor 24, and the conductive film that is the source of the signal lines Yr, Yg, Yb are hereinafter referred to as the gate. This is called a layer.

  A gate insulating film 31 is formed on the entire surface of the switch transistor 21, the holding transistor 22, the driving transistor 23, and the capacitor 24. The gate insulating film 31 includes the gate 21 g of the switching transistor 21 and the holding transistor 22. The gate 22g, the gate 23g of the driving transistor 23, the electrode 24A of the capacitor 24, and the signal lines Yr, Yg, Yb are covered.

Further, the drain 21d and source 21s of the switch transistor 21, the drain 22d and source 22s of the holding transistor 22, the drain 23d and source 23s of the drive transistor 23, the electrode 24B of the capacitor 24, all the scanning lines X, and the supply line Z are gates. The conductive film formed on the entire surface of the insulating film 31 is patterned by photolithography or etching.
Here, the drain 21d and source 21s of the switch transistor 21, the drain 22d and source 22s of the holding transistor 22, the drain 23d and source 23s of the driving transistor 23, the electrode 24B of the capacitor 24, the scanning line X, and the supply line Z are generated. Hereinafter, the conductive film is referred to as a drain layer.

As shown in FIG. 3, in the gate insulating film 31 in a plan view, one contact hole 92 is formed for each subpixel P of one dot at a position overlapping the scanning line X, and the switch transistor 21 The gate 21 g and the gate 22 g of the holding transistor 22 are electrically connected to the scanning line X through the contact hole 92.
In addition, in the gate insulating film 31, in a plan view, a contact hole 94 is formed for each dot subpixel P at a position overlapping the signal line Y, and the source 21 s of the switch transistor 21 is in contact with the contact line 94. The signal line Y is electrically connected through the hole 94.
Further, in the gate insulating film 31, a contact hole 93 is formed for each subpixel P of one dot at a position overlapping with the electrode 24 </ b> A, and the source 22 s of the holding transistor 22 is driven through the contact hole 93. The transistor 23 is electrically connected to the gate 23g and the electrode 24A of the capacitor 24.
A protective film 41 formed by patterning the same layer as the semiconductor film 23c and a protective layer formed by patterning the same layer as the channel protective film 23p are provided above the signal lines Yr, Yg, and Yb via the gate insulating film 31. The film 42 is laminated. The protective film 41 and the protective film 42 prevent the signal lines Yr, Yg, and Yb from being short-circuited to the supply line Z through the pinhole when a pinhole is formed in the gate insulating film 31. It is a protective film for.

The switch transistor 21, the holding transistor 22, the driving transistor 23, and all the scanning lines X and supply lines Z are covered with a transistor protective insulating film 32 such as silicon nitride or silicon oxide formed on a solid surface.
In addition, although mentioned later for details, the transistor protective insulating film 32 is divided | segmented into the rectangular shape in the location which overlaps with the supply line Z in planar view.

  On the upper surface of the transistor protective insulating film 32, a planarizing film 33 obtained by curing a photo-curable resin such as polyimide is laminated so as to flatten the surface, and the switch transistor 21, the holding transistor 22, the driving transistor 23, Unevenness due to the scanning line X and the supply line Z is eliminated.

When the display panel 1 according to this embodiment is used as a bottom emission type, that is, when the surface of the insulating substrate 2 on which the transistors 21, 22, and 23 are disposed is used as a display surface, the gate insulating film For the transistor protection insulating film 32 and the planarization film 33, a transparent material is used.
Here, the stacked structure from the insulating substrate 2 to the planarizing film 33 is referred to as a transistor array substrate 50.

  In the transistor protective insulating film 32 and the planarizing film 33, a first groove 34 that is long in the horizontal direction is formed at a position overlapping the supply lines Z in plan view. A second groove 35 that is long along the horizontal direction is formed at a location adjacent to the first groove 34 and overlapping with each signal line X. By the first groove 34 and the second groove 35, the transistor protective insulating film 32 and the planarizing film 33 are divided into rectangular shapes. Further, a power supply wiring 90 and a selection wiring 89 are respectively embedded in the first groove 34 and the second groove 35, and the power supply wiring 90 is above the supply line Z in the first groove 34. Are stacked. On the other hand, the selection wiring 89 is stacked on the signal line X in the second groove 35.

  The power supply wiring 90 is formed by the electroless plating method after forming the first groove 34 in the transistor protection insulating film 32 and the planarizing film 33 or by the electrolytic plating method using the supply line Z exposed from the first groove 34 as a base electrode. The conductive layer has a thickness dimension larger than that of the signal line Yr, the signal line Yg, the signal line Yb, the scanning line X, and the supply line Z. A first contact layer 96 made of aluminum or the like and a second contact layer 97 obtained by patterning a conductive layer serving as a base of the subpixel electrode 20a are provided on the power supply wiring 90. The conductive line 51 composed of the first contact layer 96 and the second contact layer 97 on the power supply wiring 90 has the same strip shape as the power supply wiring 90. The selection wiring 89 is a conductive layer formed by an electroless plating method or an electrolytic plating method using the supply line X exposed from the second groove 35 as a base electrode, and includes a signal line Yr, a signal line Yg, and a signal line. The thickness dimension is larger than that of Yb, the scanning line X, and the supply line Z. A first contact layer 101 made of aluminum or the like and a second contact layer 102 obtained by patterning a conductive layer that is a base of the subpixel electrode 20a are provided on the selection wiring 89. The conductive line 53 composed of the first contact layer 101 and the second contact layer 102 on the selection wiring 89 has the same strip shape as the selection wiring 89. The thickness dimensions of the selection wiring 89 and the power supply wiring 90 are substantially equal to the total thickness of the transistor protective insulating film 32 and the planarization film 33, and the surface of the planarization film 33 and the selection wiring 89 or the power supply wiring. The surface of 90 is almost uniform. It is preferable to include at least one of copper, aluminum, gold, or nickel.

  A plurality of subpixel electrodes 20 a are arranged in a matrix on the surface of the planarizing film 33, that is, on the upper surface of the transistor array substrate 50. Since the subpixel electrode 20a is an electrode that functions as an anode of the organic EL element 20, it is preferable that the subpixel electrode 20a has a relatively high work function and efficiently injects holes into the organic EL layer 20b.

In addition, in the case of bottom emission, the subpixel electrode 20a is transmissive to visible light. As a raw material, for example, tin-doped indium oxide (ITO), zinc-doped indium oxide, indium oxide (In 2 O 3 ), tin oxide (SnO 2 ), zinc oxide (ZnO) or cadmium-tin oxide (CTO) as a main component can be applied.

  When the display panel 1 according to this embodiment is used as a top emission type, that is, when the light emission of the organic EL layer 20b is emitted from the upper surface side of the organic EL layer 20b and displayed, the subpixel electrode 20a, It is preferable that a reflective film having high conductivity and high visible light reflectivity is formed between the planarizing film 33 or the subpixel electrode 20a itself is a reflective electrode.

  One contact hole 88 is formed in a portion of the subpixel P of 1 dot, which overlaps with the subpixel electrode 20a of the planarization film 33 and the transistor protection insulating film 32. The contact hole 88 has a conductive property. A pad 87 is embedded. As a result, the subpixel electrode 20 a is electrically connected to the electrode 24 B of the capacitor 24, the drain 21 d of the switch transistor 21, and the source 23 s of the drive transistor 23 through the contact hole 88. The conductive pad 87 is formed together with the power supply wiring 90, and particularly preferably formed by electroless plating or electrolytic plating using the upper layer electrode 24B as a base electrode. A contact layer 103 made of aluminum or the like having substantially the same shape as the contact hole 88 in plan view is provided on the conductive pad 87. The contact layer 103 is formed by patterning the same conductive film together with the first contact layer 96 of the conductive line 51 and the first contact layer 101 of the conductive line 53.

  The subpixel electrode 20a is formed by planarizing a conductive film formed on the entire surface together with the second contact layer 97 of the conductive line 51 and the second contact layer 102 of the conductive line 53 by photolithography or etching. The film 33 is patterned on the upper surface. The subpixel electrode 20 a covers the contact layer 103 and is connected to the conductive pad 87. As shown in FIG. 3, the conductive line 51 is formed along the extending direction of the power supply wiring 90. The conductive line 53 is formed along the extending direction of the selection wiring 89.

  Between the adjacent subpixel electrode 20a and the subpixel electrode 20a, there is a protrusion extending in the vertical direction so as to surround the left side and the right side of each subpixel electrode 20a in plan view. When viewed in plan, an insulating film 52 is formed so as to overlap the signal lines Yr, Yg, Yb. The insulating film 52 also covers the conductive line 51. The surface 61 of the insulating film 52 is treated to exhibit liquid repellency with respect to a solution in which a material constituting at least one layer of the organic EL layer 20b formed on the surface 61 of the subpixel electrode 20a is dissolved. Since the insulating film 52 functions as a partition when the solution to be the organic EL layer 20b is applied onto the subpixel electrode 20a, the insulating film 52 is preferably formed to a thickness sufficiently higher than the height of the applied solution. .

  A bank 71 made of a photosensitive insulating resin such as polyimide is formed on the vertically extending portion of the insulating film 52 formed in a grid pattern in the horizontal direction and the vertical direction by a photolithography method. Has been. That is, the bank 71 is a protrusion extending along the vertical direction, and is superimposed on the signal lines Yr, Yg, Yb when viewed in plan. That is, the bank 71 includes a column composed of a plurality of red subpixels Pr arranged in the vertical direction and a column composed of a plurality of green subpixels Pg arranged in the vertical direction and adjacent to the column composed of the red subpixels Pr in the horizontal direction. Between the row of green subpixels Pg and the row of blue subpixels Pb adjacent to the row of these green subpixels Pg, and the row of blue subpixels Pb. A plurality of red subpixels Pr adjacent to each other in the horizontal direction are arranged between the blue subpixels Pb. The surface of the bank 71 is preferably subjected to a treatment that exhibits liquid repellency with respect to a solution in which a material constituting at least one layer of the organic EL layer 20b formed on the surface 61 of the subpixel electrode 20a is dissolved. . Further, when the height of the insulating film 52 is lower than the height of the solution that becomes the organic EL layer 20b when applied on the subpixel electrode 20a by an ink jet method or the like, the insulating film 52 and the bank 71 function as a partition. Therefore, it is preferable that the sum of the height of the insulating film 52 and the height of the bank 71 is formed sufficiently higher than the height of the solution to be applied.

  An organic EL layer 20b is formed on the subpixel electrode 20a. The organic EL layer 20b is a light-emitting layer in a broad sense and contains a light-emitting material that is an organic compound. The organic EL layer 20b has a two-layer structure in which a hole transport layer and a narrow light-emitting layer are stacked in order from the subpixel electrode 20a. Among these, the hole transport layer is made of PEDOT (polythiophene) which is a conductive polymer and PSS (polystyrene sulfonic acid) which is a dopant, and the light-emitting layer in a narrow sense is made of a polyfluorene-based light-emitting material, and the red subpixel Pr. In this case, the organic EL layer 20b emits red light. In the case of the green subpixel Pg, the organic EL layer 20b emits green light. In the case of the blue subpixel Pb, the organic EL layer 20b turns blue. Emits light.

  In addition, the organic EL layer 20b is formed in a long strip shape that is separated and independent in the horizontal direction and is continuous in the vertical direction due to the limitation by the insulating film 52 or the bank 71, and each subpixel Pr, Pg, Pb. A plurality of subpixel electrodes 20a arranged in a line in the vertical direction are covered.

  In addition, by providing the insulating film 52 and the bank 71 so as to surround the front, rear, left and right of the subpixel electrode 20a, the organic EL layer 20b is provided independently for each subpixel electrode 20a. The organic EL layers 20b may be arranged in a matrix.

  These organic EL layers 20b are formed by a wet coating method such as an inkjet method after the bank 71 is formed. When the organic EL layer 20b is formed, an organic compound-containing liquid is applied to the subpixel electrode 20a, but between the subpixel electrode 20a adjacent to the horizontal direction and the subpixel electrode 20a. Since the insulating film 52 or the bank 71 protrudes from the surface of the transistor array substrate 50, the organic compound-containing liquid applied to the subpixel electrode 20a does not leak to the adjacent subpixel electrode 20a. It has become.

  In addition to the two-layer structure described above, the organic EL layer 20b may have a three-layer structure that becomes a hole transport layer, a light-emitting layer in a narrow sense, and an electron transport layer in order from the subpixel electrode 20a. A single layer structure composed of a light emitting layer may be used. Further, in these layer structures, a laminated structure in which an electron or hole injection layer is interposed between appropriate layers may be used, or another laminated structure may be used.

  A counter electrode 20c that functions as a cathode of the organic EL element 20 is formed on the organic EL layer 20b. The counter electrode 20c is a common electrode formed in common to the subpixels Pr, Pg, and Pb, and the bank 71 is also covered with the counter electrode 20c by forming the counter electrode 20c on the entire surface.

  The counter electrode 20c is preferably formed of a material having a work function lower than that of the subpixel electrode 20a, for example, a simple substance or an alloy containing at least one of magnesium, calcium, lithium, barium, indium, and a rare earth metal. The counter electrode 20c may have a laminated structure in which layers of various materials described above are laminated, and in addition to the layers of various materials described above, a metal layer that is not easily oxidized is deposited to reduce sheet resistance. It may be a laminated structure. Specifically, a laminated structure of a high-purity barium layer having a low work function provided on the interface side in contact with the organic EL layer 20b and an aluminum layer provided so as to cover the barium layer, or a lithium layer in the lower layer Examples thereof include a laminated structure in which an aluminum layer is provided on the upper layer. In the case of a top emission structure, the counter electrode 20c may be a transparent electrode in which a thin film having a low work function as described above and a transparent conductive film such as ITO are laminated thereon.

  A common wiring 91 is provided on the lower surface of the counter electrode 20c above the bank 71 in order to reduce the sheet resistance of the upper electrode of the organic EL element 20. Therefore, the common wiring 91 is superimposed on the banks 71 provided along the column direction when viewed in plan. Further, since the common wiring 91 and the counter electrode 20c are in contact with each other, the counter electrode 20c is electrically connected to the common wiring 91 as shown in FIG. The common wiring 91 group is formed by a plating method or the like, and has a thickness dimension larger than that of each electrode of the counter electrode 20c, the switch transistor 21, the holding transistor 22, and the driving transistor 23, and is set to have a low resistance. Further, as shown in FIGS. 7 and 9, the common wiring 91 group is made conductive by the routing wiring 95 extending in the horizontal direction in the non-pixel region outside the pixel region, and the routing wiring 95 is connected to the peripheral portion of the insulating substrate 2. Are electrically connected to the plurality of terminal portions Tc. The common wiring 91 group and the counter electrode 20c are equipotential by the voltage Vcom applied from the external circuit to the terminal portion Tc. The common wiring 91 group preferably includes at least one of copper, aluminum, gold, and nickel, and all of them are thick enough to be opaque to the light emitted from the organic EL layer 20b.

  Here, when the number of pixels of the EL display panel 1 is WXGA (768 × 1366), desirable width dimensions and cross-sectional areas of the selection wiring 89, the power supply wiring 90, and the common wiring 91 are defined. FIG. 11 is a graph showing current-voltage characteristics of the drive transistor 23 and the organic EL element 20 of each subpixel P.

  In FIG. 11, the vertical axis represents the current value of the write current flowing between the drain 23 d and the source 23 s of one drive transistor 23 or the current value of the drive current flowing between the anode and cathode of one organic EL element 20. The axis is the voltage between the drain 23d and the source 23s of one driving transistor 23 (at the same time, the voltage between the gate 23g and the source 23s of one driving transistor 23). In the figure, solid line Ids max is a write current and drive current at the maximum luminance gradation (brightest display), and alternate long and short dash line Ids mid is an intermediate luminance between the highest luminance gradation and the lowest luminance gradation. The two-dot chain line Vpo is a threshold value between the unsaturated region (linear region) and the saturated region of the driving transistor 23 when the threshold voltage Vth described later is 0V, that is, the pinch-off voltage. A three-dot chain line Vds is a write current flowing between the drain 23d and the source 23s of the drive transistor 23, and a broken line Iel is a drive current flowing between the anode and the cathode of the organic EL element 20.

  Here, the voltage VP1 is a pinch-off voltage of the driving transistor 23 at the maximum luminance gradation, and the voltage VP2 is applied to the driving transistor 23 in the saturation region when the threshold voltage Vth of the driving transistor 23 exceeds 0V. The voltage VELmax (voltage VP4−voltage VP3) has a current value according to the write current of the maximum luminance gradation. This is the voltage between the anode and the cathode when light is emitted with the driving current of the maximum luminance gradation. The voltage VP2 ′ is a drain-source voltage when the drive transistor 23 receives an intermediate luminance gradation write current, and the voltage (voltage VP4′−voltage VP3 ′) is an organic EL element 20 having an intermediate luminance gradation. This is an anode-cathode voltage when light is emitted with a drive current having an intermediate luminance gradation between a write current and a current value according to the current value.

  In order to drive both the drive transistor 23 and the organic EL element 20 in the saturation region, “the voltage Vcom during the light emission period of the common wiring 91” is subtracted from “the voltage VH during the light emission period of the selection wiring 89 or the power supply wiring 90”. The value VX satisfies the following formula (1).

VX = Vpo + Vth + Vm + VEL (1)
Here, Vth (equal to VP2−VP1 in the case of the highest luminance) is a threshold voltage at which the drain-source current of the driving transistor 23 starts flowing, and VEL (equal to VELmax in the case of the highest luminance) is the organic EL element 20. As for the anode-cathode voltage, Vm, the threshold voltage Vth is shifted in the positive direction (rightward in FIG. 11) due to the margin of the voltage difference due to the increase in resistance of the organic EL element 20 over time and the deterioration of the drive transistor 23 over time. The allowable voltage is set so as to include a margin and the like.

  As is clear from FIG. 11, the higher the luminance gradation of the voltage VX, the higher the voltage Vpo required between the drain and source of the transistor 23 and the voltage VEL required between the anode and cathode of the organic EL element 20. Becomes higher. Accordingly, the higher the luminance gradation, the lower the allowable voltage Vm, and becomes VP3−VP2 at the maximum luminance gradation.

  The organic EL element 20 generally deteriorates with time regardless of the low-molecular EL material and the high-molecular EL material, and increases in resistance. It has been confirmed that the anode-cathode voltage after 10,000 hours is about 1.4 times the initial voltage. That is, the voltage VEL increases with time even at the same luminance gradation. For this reason, the higher the allowable voltage Vm at the beginning of driving, the more stable the operation over a long period of time. Therefore, the voltage VX is set so that the voltage VEL is 8V or higher, more preferably 13V or higher.

  This allowable voltage Vm includes not only a voltage difference due to high resistance over time but also a voltage drop caused by the selection wiring 89 or the power supply wiring 90.

  If the voltage drop is large due to the influence of the wiring resistance of the selection wiring 89 and the power supply wiring 90, the power consumption of the EL display panel 1 is remarkably increased. For this reason, it is particularly preferable that the voltage drops of the selection wiring 89 and the power supply wiring 90 are each set to 1 V or less.

The pixel width Wp, which is the length of one pixel in the row direction, the number of pixels in the row direction (1366), the extension from the first lead-out wiring to one wiring terminal outside the pixel region, As a result of considering the extended portion from the first routing wiring to the other wiring terminal, when the panel size of the EL display panel 1 is 32 inches and 40 inches, the total length of the first routing wiring is 706.7 mm and 895, respectively. Set to 2 mm. Here, when the line width WL of the selection wiring 89, the line width WL of the power supply wiring 90, and the line width WL of the common wiring 91 are widened, the area of the organic EL layer 20b is structurally reduced and further overlapped with other wirings. In order to generate a capacitance and cause a further voltage drop, it is desirable to suppress the width WL of the selection wiring 89, the width WL of the power supply wiring 90, and the line width WL of the common wiring 91 to each one fifth or less of the pixel width Wp. Considering this, when the panel size of the EL display panel 1 is 32 inches and 40 inches, the width WL is within 34 μm and within 44 μm, respectively. In addition, the maximum film thickness Hmax of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is 1.5 times the minimum processing dimension 4 μm of the transistors 21 to 23, that is, 6 μm in consideration of the aspect ratio. Thus, the maximum cross-sectional area Smax of the selection lines 89, feed interconnection 90 and common interconnection 91 is 32-inch 40-inch respectively 204Myuemu 2, a 264μm 2.

  For such a 32-inch EL display panel 1, in order to reduce the maximum voltage drop of the selection wiring 89, the power supply wiring 90, and the common wiring 91 when all lights up so that the maximum current flows, to 1 V or less, FIG. 12, the wiring resistivity ρ / cross-sectional area S of each of the selection wiring 89, the power supply wiring 90, and the common wiring 91 needs to be set to 4.7 Ω / cm or less. FIG. 13 shows the correlation between the cross-sectional area and current density of each of the selection wiring 89, the power supply wiring 90, and the common wiring 91 of the 32-inch EL display panel 1. Note that the resistivity allowed at the maximum cross-sectional area Smax of the selection wiring 89, the power supply wiring 90, and the common wiring 91 described above is 9.6 μΩcm at 32 inches and 6.4 μΩcm at 40 inches.

  For the 40-inch EL display panel 1, in order to reduce the maximum voltage drop of the selection wiring 89, the power supply wiring 90, and the common wiring 91 when all lights up so that the maximum current flows, to 1 V or less, FIG. As shown in FIG. 4, the wiring resistivity ρ / cross-sectional area S of each of the selection wiring 89, the power supply wiring 90, and the common wiring 91 needs to be set to 2.4 Ω / cm or less. In FIG. 15, the cross-sectional area of each of the selection wiring 89, the power supply wiring 90, and the common wiring 91 of the 40-inch EL display panel 1 is correlated with the current density.

  The failure life MTF that does not operate due to the failure of the selection wiring 89, the power supply wiring 90, and the common wiring 91 satisfies the following formula (2).

MTF = A exp (Ea / K b T) / ρJ 2 (2)
Here, Ea is the activation energy, K b T = 8.617 × 10 −5 eV, ρ is the resistivity of the selection wiring 89, the power supply wiring 90, and the common wiring 91, and J is the current density.

The failure lifetime MTF of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is limited by an increase in resistivity or electromigration. When the selection wiring 89, the power supply wiring 90, and the common wiring 91 are set to Al (Al alone or an alloy such as AlTi or AlNd) and the MTF is estimated at an operating temperature of 85 ° C. for 10,000 hours, the current density J is 2.1. It is necessary to make x10 4 A / cm 2 or less. Similarly, when the selection wiring 89, the power supply wiring 90, and the common wiring 91 are set to be Cu-based, it is necessary to make 2.8 × 10 6 A / cm 2 or less. It is assumed that materials other than Al in the Al alloy have a lower resistivity than Al.
In consideration of these matters, in the 32-inch EL display panel 1, the Al-based selection wiring 89, the power supply wiring 90, and the common wiring 91 so that the power supply wiring 90 and the common wiring 91 do not fail in 10,000 hours in the fully lit state. As shown in FIG. 13, each cross-sectional area S of 57 μm 2 or more is required. Similarly, the cross-sectional areas S of the Cu-based selection wiring 89, power supply wiring 90 and common wiring 91 are shown in FIG. Thus, 0.43 μm 2 or more is required.

In the 40-inch EL display panel 1, each of the Al-based selection wiring 89, the power supply wiring 90, and the common wiring 91 so that the selection wiring 89, the power supply wiring 90, and the common wiring 91 do not break down in 10,000 hours in the fully lit state. As shown in FIG. 15, the cross-sectional area S of 92 μm 2 or more is required. Similarly, the cross-sectional areas S of the Cu-based selection wiring 89, the power supply wiring 90, and the common wiring 91 are each required to be 0.69 μm 2 or more as shown in FIG.

In the Al-based selection wiring 89, the power supply wiring 90, and the common wiring 91, if the Al-based resistivity is 4.00 μΩcm, the 32-inch EL display panel 1 has the wiring resistivity ρ / cross-sectional area S as described above. Since it is 4.7 Ω / cm or less, the minimum cross-sectional area Smin is 85.1 μm 2 . At this time, since the wiring width WL of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is within 34 μm as described above, the minimum film thickness Hmin of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is 2.50 μm. It becomes.

In addition, in the 40-inch EL display panel 1 including the Al-based selection wiring 89, the power supply wiring 90, and the common wiring 91, the wiring resistivity ρ / cross-sectional area S is 2.4Ω / cm or less as described above. The cross-sectional area Smin is 167 μm 2 . At this time, since the wiring width WL of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is within 44 μm as described above, the minimum film thickness Hmin of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is 3.80 μm. .

On the other hand, if the Cu-based selection wiring 89, the power supply wiring 90, and the common wiring 91 have a Cu-based resistivity of 2.10 μΩcm, the 32-inch EL display panel 1 has the wiring resistivity ρ / cut as described above. Since the area S is 4.7 Ω / cm or less, the minimum cross-sectional area Smin is 44.7 μm 2 . At this time, as described above, since the wiring width WL of the selection wiring 89, the power supply wiring 90 and the common wiring 91 is within 34 μm, the minimum film thickness Hmin of the selection wiring 89, the power supply wiring 90 and the common wiring 91 is 1.31 μm. It becomes.

In addition, in the 40-inch EL display panel 1 including the Cu-based selection wiring 89, the power supply wiring 90, and the common wiring 91, the wiring resistivity ρ / cross-sectional area S is 2.4Ω / cm or less as described above. The cross-sectional area Smin is 87.5 μm 2 . At this time, as described above, since the wiring width WL of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is within 44 μm, the minimum film thickness Hmin of the selection wiring 89, the power supply wiring 90, and the common wiring 91 is 1.99 μm. It becomes.

  From the above, in order to operate the EL display panel 1 normally and with low power consumption, it is preferable to set the voltage drop in the selection wiring 89, the power supply wiring 90, and the common wiring 91 to 1 V or less. In order to achieve this, if the selection wiring 89, the power supply wiring 90 and the common wiring 91 are an Al-based 32-inch panel, the thickness dimension H is 2.50 μm to 6 μm, the width dimension WL is 14.1 μm to 34.0 μm, resistance The ratio is 4.0 μΩcm to 9.6 μΩcm, and when the selection wiring 89, the power supply wiring 90, and the common wiring 91 are 40-inch panels in which the selection wiring 89, the power supply wiring 90, and the common wiring 91 are Al-based, the thickness The dimension H is 3.80 μm to 6 μm, the width dimension WL is 27.8 μm to 44.0 μm, and the resistivity is 4.0 μΩcm to 9.6 μΩcm.

In general, in the case of the Al-based selection wiring 89, the power supply wiring 90, and the common wiring 91, the thickness dimension H is 2.50 μm to 6 μm, the width dimension WL is 14.1 μm to 44 μm, and the resistivity is 4.0 μΩcm to 9.6 μΩcm. Become.
Similarly, when the selection wiring 89, the power supply wiring 90, and the common wiring 91 are Cu-based 32-inch panels, the thickness dimension H is 1.31 μm to 6 μm, the width dimension WL is 7.45 μm to 34 μm, and the resistivity is 2. In the case of a 40-inch panel in which the selection wiring 89, the power supply wiring 90 and the common wiring 91 are Cu-based, and the selection wiring 89, the power supply wiring 90 and the common wiring 91 are Cu-based, the thickness dimension H is 1 μΩcm to 9.6 μΩcm. 1.99 μm to 6 μm, width dimension WL is 14.6 μm to 44.0 μm, and resistivity is 2.1 μΩcm to 9.6 μΩcm.

In general, in the case of the Cu-based selection wiring 89, the power supply wiring 90, and the common wiring 91, the thickness dimension H is 1.31 μm to 6 μm, the width dimension WL is 7.45 μm to 44 μm, and the resistivity is 2.1 μΩcm to 9.6 μΩcm. Become.
Therefore, when an Al-based material or a Cu-based material is applied as the selection wiring 89, the power supply wiring 90, and the common wiring 91, the thickness dimension H of the selection wiring 89, the power supply wiring 90, and the common wiring 91 of the EL display panel 1 is 1. .31 μm to 6 μm, width dimension WL is 7.45 μm to 44 μm, and resistivity is 2.1 μΩcm to 9.6 μΩcm. Of course, if the material is equivalent to the Al-based material or Cu-based material, or has a resistivity between the Al-based material and the Cu-based material, the thickness dimension H in this range is not necessary even if it is not the Al-based material or the Cu-based material. The width dimension WL may be sufficient.

  A sealing protective insulating film 56 is formed on the upper surface of the counter electrode 20c. The sealing protective insulating film 56 covers the entire counter electrode 20c and the common wiring 91, thereby preventing the common wiring 91 and the counter electrode 20c from being deteriorated.

  When the display panel 1 according to this embodiment is used as a top emission type, the counter electrode 20c and the sealing protective insulating film 56 are made transparent by forming the counter electrode 20c and the sealing protective insulating film 56 into a thin film. By using such a material, it is possible to improve visible light transmittance of the counter electrode 20c and the sealing protective insulating film 56.

A method for driving the EL display panel 1 configured as described above will be described.
The driving method of the EL display panel 1 is roughly divided into a driving method by a passive matrix method and a driving method by an active matrix method. In this embodiment, two kinds of driving methods by an active matrix method will be described.

First, in the structure of the first display panel 1, as shown in FIG. 7, the selection driver 111 to which the scanning lines X 1 to X m are respectively connected is disposed on the first peripheral portion of the insulating substrate 2. A second peripheral edge in which the power supply driver 112 to which the power supply wirings 90, 90,... (Supply lines Z 1 to Z m ) that are electrically insulated from each other are connected is a peripheral part facing the first peripheral part of the insulating substrate 2. It is arranged in the part.
The first display panel 1 is driven by the active matrix method as follows. That is, as shown in FIG. 8, the scanning lines X 1 to X by the connected selection driver 111 m, the order from the scanning line X 1 to scan line X m (the next scan line X m scanning lines X 1) The scanning lines X 1 to X m are sequentially selected by sequentially outputting high level shift pulses. In addition, a write power supply voltage VL for applying a write current is applied to the drive transistors 23 connected to the supply lines Z 1 to Z m via the power supply lines 90 during the selection period, and the drive transistors 23 are used during the light emission period. A power supply driver 112 that applies a drive power supply voltage VH for causing a drive current to flow through the organic EL element 20 is connected to each power supply wiring 90. This feeding driver 112, to synchronize the selection driver 111, the counter electrode of the forward (following the supply lines Z 1 of the supply line Z m) to the low level (the organic EL element 20 to supply line Z m from the supply line Z 1 The supply lines Z 1 to Z m are sequentially selected by sequentially outputting the write power supply voltage VL having a lower level than the voltage of the first voltage. Further, when the selection driver 111 selects each of the scanning lines X 1 to X m , the data driver sends a write current (current signal) that is a write current between the drain and source of the drive transistors 23 in a predetermined row. Through all the signal lines Y 1 to Y n . The counter electrode 20c and the common wiring 91 group are connected to the outside by the lead wiring 95 and the wiring terminal Tc, and are maintained at a constant common potential Vcom (for example, ground = 0 volts).

In each selection period, the potential of the data driver side, feed interconnections 90, 90, ... and the supply lines Z 1 to Z m output to the and below the write feed voltage VL the write feed voltage VL below the common potential Vcom Is set to Therefore, at this time, since the organic EL element 20 does not flow to the signal lines Y 1 to Y n , as shown in FIG. 2, a write current (write current) having a current value corresponding to the gradation is generated by the data driver. As indicated by an arrow A, the signal lines Y 1 to Y n flow through the sub-pixels P i, j from the power supply wiring 90 and the supply line Z i between the drain and source of the drive transistor 23 and between the drain and source of the switch transistor 21. A write current (write current) directed to the signal line Y j flows through the via. Thus, the current value of the current flowing between the drain and source of the drive transistor 23 is uniquely controlled by the data driver, and the data driver writes the write current (write current) according to the gradation input from the outside. Set the current value. While the write current (write current) is flowing, i-th row of P i, 1 to P i, the voltage between the gate 23g- source 23s of the driving transistor 23 of the n each signal line Y 1 to Y The write current (write current) flowing between the drain 23d and the source 23s of the drive transistor 23 regardless of the current value of the write current (write current) flowing through n , that is, the change in the Vg-Ids characteristic of the drive transistor 23 with time. The capacitor 24 is forcibly set so as to meet the current value of the current, and the capacitor 24 is charged with a charge having a magnitude according to the level of this voltage, so that the current value of the write current (write current) becomes the gate 23g of the drive transistor 23. -It is converted into the voltage level between the sources 23s. In the subsequent light emission period, the scanning line X i becomes a low level, and the switch transistor 21 and the holding transistor 22 are turned off. However, the charge on the electrode 24A side of the capacitor 24 is confined by the holding transistor 22 in the off state and floats. Even when the voltage of the source 23s of the drive transistor 23 is modulated when the voltage shifts from the selection period to the light emission period, the potential difference between the gate 23g and the source 23s of the drive transistor 23 is maintained as it is. In this light emission period, the potential of the supply line Z i and the power supply wiring 90 connected thereto becomes the drive power supply voltage VH, which is higher than the potential Vcom of the counter electrode 20c of the organic EL element 20, thereby connecting to the supply line Z i and the supply line Z i. A drive current flows from the power supply wiring 90 to the organic EL element 20 through the drive transistor 23 in the direction of arrow B, and the organic EL element 20 emits light. Since the current value of the drive current depends on the voltage between the gate 23g and the source 23s of the drive transistor 23, the current value of the drive current in the light emission period is equal to the current value of the write current (drawing current) in the selection period.

As shown in FIG. 9, the second display panel 1 has a structure in which a selection driver 111 to which the scanning lines X 1 to X m are connected is disposed on the first peripheral edge of the insulating substrate 2, The lead-out wiring 99 formed integrally with the power supply wirings 90, 90,... So as to be electrically connected to each other is a peripheral portion facing the first peripheral portion of the insulating substrate 2. It arrange | positions at the 2nd peripheral part. The routing wiring 99 receives clock signals from both the terminal portion 90d and the terminal portion 90e located at the third peripheral portion and the fourth peripheral portion orthogonal to the first peripheral portion and the second peripheral portion, respectively. . The active matrix driving method of the second display panel 1 is as follows. That is, as shown in FIG. 10, the external oscillation circuit outputs a clock signal to the power supply wirings 90, 90,... And the supply lines Z 1 to Z m through the terminal portion 90d and the terminal portion 90e through the wiring 99. To do. The scanning lines X 1 to X m by sequentially outputting the high-level shift pulse sequentially (the next scan line X m scanning lines X 1) from the scanning line X 1 by the selection driver 111 to the scan line X m Are sequentially selected, but when the selection driver 111 outputs one of the scanning lines X 1 to X m outputting a high level, that is, on-level shift pulse, the clock signal of the oscillation circuit becomes low level. Further, when the selection driver 111 selects each of the scanning lines X 1 to X m , the data driver sends a drawing current (current signal) that is a write current to all the signal lines via the drain-source of the driving transistor 23. Flow from Y 1 to Y n . The counter electrode 20c and the power supply wiring 90 are kept at a constant common potential Vcom (for example, ground = 0 volts).

In the selection period of the scan line X i, from the shift pulse to the i-th scanning line X i is output, the switch transistor 21 and holding transistor 22 are turned on. In each selection period, the potential of the data driver side, feed interconnections 90, 90, ... and the low level of the supply lines Z 1 to Z m and the clock signal following a low level of the clock signal output to the following common potential Vcom Is set to Therefore, at this time, since the organic EL element 20 does not flow to the signal lines Y 1 to Y n , as shown in FIG. 2, a write current (drawing current) having a current value corresponding to the gradation is indicated by an arrow as shown in FIG. As shown in A, it flows to the signal lines Y 1 to Y n , and in the subpixel P i, j , the power supply wiring 90 and the supply line Z i pass through the drain-source of the drive transistor 23 and the drain-source of the switch transistor 21. Thus, a write current (drawing current) directed to the signal line Y j flows. In this way, the current value of the current flowing between the drain and source of the drive transistor 23 is uniquely controlled by the data driver, and the data driver is capable of writing current (drawing current) according to the gradation input from the outside. Set the current value. While the write current (drawing current) is flowing, the voltage between the gate 23g and the source 23s of each driving transistor 23 of the i- th row P i, 1 to P i, n is the signal line Y 1 to Y n , respectively. Current value of the write current (extraction current) flowing through the transistor 23, that is, the current value of the write current (extraction current) flowing between the drain 23d and the source 23s of the drive transistor 23 regardless of the change over time of the Vg-Ids characteristic of the drive transistor 23 The capacitor 24 is forcibly set to meet the voltage level, the capacitor 24 is charged with a charge, and the current value of the write current (drawing current) is between the gate 23g and the source 23s of the drive transistor 23. Is converted to the voltage level. In the subsequent light emission period, the scanning line X i becomes a low level, and the switch transistor 21 and the holding transistor 22 are turned off. However, the charge on the electrode 24A side of the capacitor 24 is confined by the holding transistor 22 in the off state and floats. Even when the voltage of the source 23s of the drive transistor 23 is modulated when the voltage shifts from the selection period to the light emission period, the potential difference between the gate 23g and the source 23s of the drive transistor 23 is maintained as it is. During this light emission period, during which the row is not a selection period, that is, the clock signal is high when the potential of the power supply wiring 90 and the supply line Z i is higher than the potential Vcom of the counter electrode 20 c of the organic EL element 20 and the power supply wiring 90. During the level, the drive current flows in the direction of arrow B from the higher potential power supply line 90 and the supply line Z i to the organic EL element 20 through the drain-source of the drive transistor 23, and the organic EL element 20 emits light. . Since the current value of the drive current depends on the voltage between the gate 23g and the source 23s of the drive transistor 23, the current value of the drive current in the light emission period is equal to the current value of the write current (drawing current) in the selection period. Further, in the light emission period, during the selection period of any row, that is, when the clock signal is at a low level, the potential of the power supply wiring 90 and the supply line Z i is equal to or lower than the potential Vcom of the counter electrode 20c and the power supply wiring 90. Therefore, no drive current flows through the organic EL element 20 and no light is emitted.

  In any driving method, the switch transistor 21 functions to turn on (selection period) / off (light emission period) the current between the source 23s of the driving transistor 23 and the signal line Y. Yes. The holding transistor 22 is in a state in which a current can flow between the drain 23d and the source 23s of the driving transistor 23 during the selection period, and holds the voltage applied between the gate 23g and the source 23s of the driving transistor 23 during the light emission period. It comes to function as a thing. Then, when the supply line Z and the power supply line 90 are at a high level during the light emission period, the drive transistor 23 drives the organic EL element 20 by causing a current having a magnitude corresponding to the gradation to flow through the organic EL element 20. It comes to function as a thing.

As described above, the magnitude of the current flowing through each of the power supply wirings 90, 90,... Is the sum of the magnitudes of the drive currents flowing through the n organic EL elements 20 connected to the one line of supply lines Z i . When the selection period for moving image driving with the number of pixels equal to or greater than VGA is set, the parasitic capacitance of each of the power supply wirings 90, 90,... Increases, and the gate electrode or source of a thin film transistor such as the transistors 21 to 23, In the wiring composed of a thin film constituting the drain electrode, the resistance is too high to cause a write current (that is, a drive current) to flow through the n organic EL elements 20, but in this embodiment, the subpixels P 1,1 to P m , the gate electrode and the source of the n thin film transistors, each feed interconnections so constitute respective feed lines 90, 90, ... of the different conductive layer and the drain electrode 90, 90, ... voltage by Below is reduced to allow flow shorter a selection period without delay sufficient write current (pull-out current). Further, since the resistance of the power supply wirings 90, 90, ... is reduced by increasing the thickness of the power supply wirings 90, 90, ..., the width of the power supply wirings 90, 90, ... can be reduced. Therefore, in the case of bottom emission, the decrease in pixel aperture ratio can be minimized.

Similarly, the magnitude of the drive current flowing through the common wiring 91 during the light emission period is the same as the magnitude of the write current (drawing current) flowing through the power supply wiring 90 during the selection period, but the common wiring 91 includes the subpixel P 1. , 1 to P m, n , the conductive layer different from the conductive layer constituting the gate electrode, the source and the drain electrode of the thin film transistor is used, so that the thickness of the common wiring 91 can be reduced. Further, even when the counter electrode 20c itself is thinned to have a higher resistance, the voltage of the counter electrode 20c can be made uniform in the plane. Therefore, even if the same potential is applied to all the subpixel electrodes 20a, the light emission intensity of any organic EL layer 20b becomes substantially equal, and the in-plane light emission intensity can be made uniform. Further, when the EL display panel 1 is used as a top emission type, the counter electrode 20c can be made thinner, so that light emitted from the organic EL layer 20b is not easily attenuated while being transmitted through the counter electrode 20c. Furthermore, since the common wiring 91 is provided between the subpixel electrodes 20a adjacent in the horizontal direction in plan view, a decrease in the pixel aperture ratio can be minimized.

Furthermore, since the common wiring 91 group is disposed above the signal lines Y 1 to Y n disposed in the non-pixel region between the sub-pixel electrodes 20a and 20a, it is not necessary to reduce the area of the sub-pixel electrode 20a.

  In the display panel 1 of the two driving methods described above, in the display panel 1, the power supply wirings 90, 90,... Since the potential is equalized by the clock signal from the external oscillation circuit via the terminal 90d and the terminal portion 90e, current can be promptly supplied from the organic EL elements 20, 20,. .

The common wirings 91, 91,... Of the first and second EL display panels 1 are connected to each other by the lead wirings 95, 95 provided at the third peripheral edge and the fourth peripheral edge of the insulating substrate 2, and the common voltage Vcom. Is applied. Common wiring 91, ... and the lead wiring 95, 95, the scanning lines X 1 to X m, the signal lines Y 1 to Y n, and is electrically insulated from the supply lines Z 1 to Z m.

[Modification 1]
In this embodiment, each of the transistors 21, 22, and 23 is an N-channel field effect transistor, but is not limited to this embodiment, and may be a P-channel field effect transistor. In this case, in the circuit configuration shown in FIG. 2, the relationship between the sources 21s, 22s, and 23s of the transistors 21, 22, and 23 and the drains 21d, 22d, and 23d is reversed. For example, when the drive transistor 23 is a P-channel field effect transistor, the drain 23d of the drive transistor 23 is conducted to the subpixel electrode 20a of the organic EL element 20, and the source 23s is conducted to the supply line Z. In addition, the waveform of the drive signal has an opposite phase.

[Modification 2]
In the present embodiment, the signal line Y is patterned from the gate layer. However, the present invention is not limited to this embodiment, and the signal line Y may be patterned from the drain layer. In this case, the scanning line X and the supply line Z are patterned from the gate layer, and the signal line Y is an upper layer than the scanning line X and the supply line Z.

[Modification 3]
Further, in the present embodiment, three transistors 21, 22, and 23 are provided for each dot subpixel P. However, the present invention is not limited to this embodiment, and one or more transistors are provided for each dot subpixel P. It may be a display panel that is provided and can be driven by an active matrix method using these transistors.

[Modification 4]
Furthermore, in the present embodiment, the pixel 3 is composed of three subpixels Pr, Pg, and Pb. However, the present invention is not limited to this embodiment, and includes a subpixel composed of intermediate colors of red, green, and blue. It may be configured.

[Modification 5]
In each of the above embodiments, the counter electrode 20c is the cathode of the organic EL element 20, and the subpixel electrode 20a is the anode of the organic EL element 20. However, the counter electrode 20c is the anode of the organic EL element 20, and the subpixel electrode 20a may be used as the cathode of the organic EL element 20.
[Modification 6]
In each of the above embodiments, each selection line 89 is connected to both the switch transistor 21 and the holding transistor 22, but the switch transistor selection line connected to the gate 21 g of the switch transistor 21 for each row, and the switch transistor It may be constituted by a holding transistor selection wiring which is separated from the selection wiring and connected to the gate 22g of the holding transistor 22 for each row.

It is a top view which shows the pixel in the display apparatus which concerns on this invention. 3 is an equivalent circuit diagram of a subpixel P. FIG. 3 is a plan view showing an electrode of a subpixel P. FIG. It is a top view which shows the pixel in the display apparatus which concerns on this invention. It is arrow sectional drawing cut | disconnected in the thickness direction of the insulated substrate 2 along the broken line VV in FIG. FIG. 5 is a cross-sectional view taken along the arrow line VI-VI in FIG. 4 and cut in the thickness direction of the insulating substrate 2. It is the schematic plan view which showed the wiring structure of the display panel. FIG. 8 is a timing chart for explaining a method of driving the display panel of FIG. 7. It is the schematic plan view which showed the wiring structure of the display panel. 10 is a timing chart for explaining a method of driving the display panel of FIG. 4 is a graph showing current-voltage characteristics of a drive transistor 23 and an organic EL element 20 in a subpixel P. 6 is a graph showing the correlation between the maximum voltage drop of each of the power supply wiring 90 and the common wiring 91 and the wiring resistivity ρ / cross-sectional area S in the 32-inch EL display panel 1. It is a graph which shows correlation with each cross-sectional area of the electric power feeding wiring 90 in the 32-inch EL display panel 1, and the common wiring 91, and a current density. It is a graph which shows the correlation with each maximum voltage drop of the electric power feeding wiring 90 and the common wiring 91 in 40-inch EL display panel 1, and wiring resistivity (rho) / sectional area S. FIG. It is a graph which shows correlation with each cross-sectional area of the electric power feeding wiring 90 and the common wiring 91 in 40-inch EL display panel 1, and a current density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display panel 2 Insulating substrate 20a Subpixel electrode 20b Organic EL layer 20c Counter electrode 21 Switch transistor 22 Holding transistor 23 Drive transistor 21d, 22d, 23d Drain 21s, 22s, 23s Source 21g, 22g, 23g Gate 31 Transistor protection insulating film 34 First groove 35 Second groove 50 Transistor array substrate 71 Bank 89 Selection wiring 90 Power supply wiring 91 Common wiring Pr, Pg, Pb Subpixel

Claims (12)

  1. A substrate,
    A plurality of pixel circuits including transistors on the substrate;
    An insulating film formed so as to cover the upper side of each of the transistors and having grooves along the row direction formed on the surface;
    A plurality of power supply wirings embedded in the trenches and connected to the plurality of pixel circuits, respectively, and having a conductive layer different from the gate, source, and drain of the transistor;
    A plurality of conductive lines respectively formed along the extending direction of the power supply wiring on each of the plurality of power supply wirings and on the insulating film around the power supply wiring;
    A ridge insulating film covering the plurality of conductive lines and formed in a lattice shape in the row direction and the column direction;
    A bank formed on a portion of the protrusion insulating film extending in the column direction;
    A plurality of pixel electrodes each provided on the insulating film and surrounded by the protrusion insulating film;
    A counter electrode;
    A light emitting layer surrounded by the protrusion insulating film between the plurality of pixel electrodes and the counter electrode;
    A display panel comprising:
  2. The display panel according to claim 1, wherein the transistor includes a drive transistor in which one of a source and a drain is connected to the power supply wiring.
  3.   The transistor includes a switch transistor that allows a write current to flow between the drain and source of the driving transistor, and a holding transistor that holds a voltage between the gate of the driving transistor and one of the source and drain during a light emission period. The display panel according to claim 2.
  4. The embedded in the groove, further comprising the connected selection line to at least one of the switching transistor and the holding transistor,
    The display panel according to claim 3, wherein the power supply wiring is connected to one of a source and a drain of the driving transistor .
  5. The display panel according to claim 4 , wherein the pixel electrode is provided on the other of the source and the drain of the driving transistor.
  6.   The display panel according to claim 1, wherein the conductive line includes a contact layer formed by patterning a conductive layer serving as a base of the pixel electrode.
  7. The display panel according to claim 1, wherein the power supply wiring includes a transistor conductive layer that is the same as at least one of a gate, a source, and a drain of the transistor.
  8.   The display panel according to claim 1, wherein the insulating film includes a transistor protective insulating film that directly covers the transistor.
  9.   The display panel according to claim 8, wherein the insulating film includes a planarizing film provided on the transistor protective insulating film.
  10.   The display panel according to claim 1, further comprising a common wiring disposed on the bank between the adjacent pixel electrodes and connected to the counter electrode.
  11. The display panel according to claim 10, wherein an extending direction of the common wiring is orthogonal to an extending direction of the power supply wiring.
  12.   The display panel according to claim 10, wherein the common wiring is formed of a conductive layer different from the counter electrode.
JP2005007852A 2005-01-14 2005-01-14 Display panel Active JP4792748B2 (en)

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