JP4725054B2 - Display device - Google Patents

Description

  The present invention relates to a display device using an organic EL element as a light emitting element, and more particularly to a top emission type display device that extracts emitted light from a side opposite to a substrate on which organic EL elements are arranged.

  An organic EL element using electroluminescence (hereinafter referred to as EL) of an organic material has an organic layer formed by laminating an organic hole transport layer and an organic light emitting layer between a lower electrode and an upper electrode. Thus, color tone is obtained by controlling the current value flowing through the organic EL element. Among display devices using such organic EL elements, in an active matrix display device, a pixel circuit including a thin film transistor and a capacitor element is provided for each pixel, and the organic EL element is driven by the pixel circuit. It has been broken.

  FIG. 9 is a block diagram illustrating an outline of a display device to which the above-described configuration is applied. This display device has a pixel array unit 22 in which pixels (pixel circuits) 21 including organic EL elements are arranged in m columns and n rows in a matrix. Here, in order to simplify the drawing, a case where the pixel array unit 22 has a pixel arrangement of 3 columns and 2 rows is shown as an example.

  In the pixel array unit 22, a scanning line 23 is wired for each row of each pixel 21, and a data line 25 is wired for each column. Around the pixel array section 22, a writing scanning circuit 26 for driving the scanning line 23 and a data line driving circuit 28 for supplying a data signal corresponding to the luminance information to the data line 25 are arranged. A power line 29 is wired for each row for each pixel 21.

  FIG. 10 is a cross-sectional view showing the layer structure of the active matrix display device 100 as described above, and the same components as those in FIG. 9 are denoted by the same reference numerals. As shown in this figure, an active matrix display device 100 includes a thin film transistor Tr constituting a pixel circuit, a capacitor element, a resistance element, etc. not shown here at positions corresponding to the respective pixels 21 on the substrate 2. Is provided. On the insulating film 3 covering these elements (the thin film transistor Tr in the drawing), each wiring connected to the transistor Tr, the source electrode wiring 4s, the drain electrode line 4d, and the signal line 25 connected to these and the power source Lines 29 and the like are provided as the same layer. In addition, another wiring (not shown) constituting the pixel circuit is formed by the conductive layer constituting the transistor Tr and the conductive layer constituting the signal line 25 and the power supply line 29.

  Further, an upper interlayer insulating film 5 is provided in a state of covering the signal line 25 and the power supply line 29 described above, and an organic EL element EL is provided on the interlayer insulating film 5.

  Each organic EL element EL includes a lower electrode 6 connected to the transistor Tr through a connection hole 5 a provided in the interlayer insulating film 5. The lower electrode 6 is used as an anode electrode (or a cathode electrode), for example, and is patterned for each pixel. Each lower electrode 6 is covered with an insulating film pattern 7 so that only the central portion is widely exposed. A portion where the lower electrode 6 is exposed from the insulating film pattern 7 is a light emitting portion, for example, a portion corresponding to the pixel 21 here.

  An organic layer 8 having at least a light emitting layer is laminated on the exposed portion of each lower electrode 6 in a patterned state. The light emitting layer provided in the organic layer 8 is made of an organic material that emits light by recombination of holes and electrons injected into the light emitting layer. An upper electrode 9 is disposed and formed above each organic layer 8 and the insulating film pattern 7 patterned in this manner in a state in which insulation is maintained between the lower electrode 6. The upper electrode 9 is used as a cathode electrode (or an anode electrode), and is formed as an electrode common to each organic EL element EL.

  The active matrix display device 100 having the above-described layer configuration is effective in securing the aperture ratio of the organic EL element EL when it is configured as a so-called top emission method in which light is extracted from the side opposite to the substrate 2. Become. Further, with such a top emission method, the aperture ratio of the organic EL element EL does not depend on the layout of the thin film transistor Tr constituting the pixel circuit. For this reason, a pixel circuit using a plurality of elements Tr can be laid out corresponding to each pixel 21.

  In the case of such a top emission type display device, a conductive material having a high light transmittance is used for the upper electrode 9 on the side from which emitted light is extracted. Such a material has a high resistance value. On the other hand, the lower electrode 6 on the substrate 2 side is configured by using a metal having a high reflectance. For this reason, as shown in Patent Document 1 below, the auxiliary electrode 6a is provided in the same layer as the lower electrode 6, and the upper electrode 9 is connected to the auxiliary electrode 6a, thereby reducing the resistance of the upper electrode 9. Yes.

  As shown in the layout diagram of FIG. 11, such an auxiliary wiring 6 a is provided between the lower electrodes 6 in a state where insulation is maintained with respect to the lower electrodes 6 arranged in a matrix corresponding to the pixels (21). Are provided in a grid pattern.

JP 2002-318556 A

  By the way, in the active matrix display device, as shown in FIG. 11, the signal line 25 and the power supply line 29 provided in the lower layer of the lower electrode 6 and the auxiliary wiring 6a, and the scanning line 23 provided in the lower layer are provided. Therefore, the auxiliary wiring 6a is wired in parallel. For this reason, the scanning lines 23, the signal lines 25, and the power supply lines 29 are often routed along the auxiliary wiring 6a in a state where the auxiliary wiring 6a is overlapped.

  However, when wirings are provided in parallel above and below the interlayer insulating film as described above, the upper and lower wirings are easily short-circuited due to adhesion of dust to the lower layer wiring during the manufacturing process.

  In particular, the auxiliary wiring 6a has the same potential as that of the upper electrode (9), and is grounded to the GND potential, for example, while several tens of volts may be applied to the power supply line 29. For this reason, when the power supply line 29 is wired below the auxiliary wiring 6a along the auxiliary wiring 6a, a short circuit is more likely to occur due to a potential difference between these wirings. In addition, the power supply line 29 is made thicker and lower in resistance in order to prevent deterioration of uniformity due to voltage drop, and the fact that the overlapping area with the auxiliary wiring 6a is widened is also a factor that is likely to cause a short circuit. Yes. Since both the auxiliary wiring 6a and the power supply line 29 are laid out with a single wiring, the panel does not emit light even if it is short-circuited at one location. Thereby, the yield has fallen.

  Even when the signal line 25 is arranged along the auxiliary wiring 6 a below the auxiliary wiring 6 a, an irregular potential is applied to the signal line 25, and the potential difference from the auxiliary wiring 6 causes Short-circuiting between these wirings was likely to occur.

  Accordingly, an object of the present invention is to prevent a short circuit between an auxiliary wiring and a drive circuit and improve a yield in an active matrix display device including an auxiliary wiring using an organic EL element.

A display device (first to third display devices) of the present invention is connected to a drive circuit provided on a substrate, an interlayer insulating film provided on the substrate so as to cover the drive circuit, and the drive circuit. In this manner, the organic EL elements arranged on the interlayer insulating film and auxiliary wirings arranged between the organic EL elements on the interlayer insulating film are provided.
In particular, in the first display device of the present invention, among the wirings constituting the driving circuit, a wiring having the most potential difference from the potential of the auxiliary wiring and a wiring to which a non-constant potential is applied are in a region parallel to the auxiliary wiring. Wiring is not overlapped, and wiring having substantially the same potential as the auxiliary wiring is overlapped in a region parallel to the auxiliary wiring.
Further, in the second display device of the present invention, among the wirings that constitute the driving circuit, the signal lines are not overlapped in a region parallel to the auxiliary wirings, and the wirings having substantially the same potential as the auxiliary wirings are provided. The wiring is overlapped in a region parallel to the auxiliary wiring.
In the third display device of the present invention, among the wirings constituting the driving circuit, the wiring connected to the power supply potential is wired without overlapping in a region parallel to the auxiliary wiring, and is substantially the same as the auxiliary wiring. Wirings with the same potential are overlapped in a region parallel to the auxiliary wiring.

  In the display device having such a configuration, a wiring having a large potential difference with respect to the potential of the auxiliary wiring or a signal line to which a non-constant potential is applied overlaps the auxiliary wiring along the auxiliary wiring. Will not be placed. Therefore, it is difficult for a short circuit between the auxiliary wiring and the wiring arranged in this lower layer.

  As described above, according to the display device of the present invention, it is difficult to cause a short circuit between the auxiliary wiring arranged between the organic EL elements and the wiring constituting the driving circuit arranged below the auxiliary wiring. Thus, the display device can reliably emit light over the entire surface, and the yield can be improved.

  Embodiments of a display device according to the present invention will be described below in detail with reference to the drawings.

<First Embodiment>
FIG. 1 is a circuit diagram of a first embodiment of an active matrix organic EL display device to which the present invention is applied. In the display device 1 shown in this figure, a plurality of pixels 21 are arranged in a matrix in the pixel array section 22 as described with reference to the block diagram of FIG. 9 in the previous technical background. The pixel circuit provided in each pixel 21 in the display device 1 includes, for example, an organic EL element EL having a cathode electrode connected to the ground potential GND and a drain having an organic EL element EL as shown in FIG. A drive transistor Tr1 connected to the anode electrode and having a source connected to the power supply line 29 having a positive potential (Vcc), a capacitive element Cs connected between the gate of the drive transistor Tr1 and the positive power supply potential Vcc, a source Has an n-channel write transistor Tr2 having a gate connected to the gate of the drive transistor Tr1, a gate connected to the scanning line 23, and a drain connected to the data line 25, respectively. Note that the connection state of the source and the drain of the write transistor Tr2 may be reversed depending on the voltage setting.

  FIG. 2 is a timing chart for explaining the operation of such a pixel circuit. As shown in this figure (timing chart), in the pixel circuit of FIG. 1, the write signal WS is applied to the selected scanning line 23 and the gate potential of the write transistor Tr2 is controlled, so that the data line 25 is applied. The signal voltage thus written is written to the gate of the drive transistor Tr1. At this time, the gate potential of the driving transistor Tr1 is stably held by the capacitive element Cs for one field (1f) period until the next scanning line 23 is selected. During this time, a current corresponding to the gate-source voltage of the drive transistor Tr1 flows to the organic EL element EL, and the organic EL element EL continues to emit light with a luminance corresponding to the current value.

  FIG. 3 is a cross-sectional view showing the layer structure of the active matrix display device 1 as described above, and the same components as those in FIG. 1 are denoted by the same reference numerals.

  The basic layer configuration of the active matrix type display device 1 shown in this figure is the same as that described with reference to the cross-sectional view of FIG. 10 in the above technical background, and detailed description thereof is omitted here. However, here, as described with reference to FIG. 1, the power supply line 29 is connected to a positive potential (Vcc). Further, the lower electrode 6 of the organic EL element EL is used as an anode electrode, and the upper electrode 9 is used as a cathode electrode. For this reason, the auxiliary wiring 6a composed of the same layer as the lower electrode 6 is also connected to the ground potential GND similarly to the cathode electrode. The power supply line 29 is a wiring having the most potential difference from the potential of the auxiliary wiring 6a connected to the ground potential GND among the wirings constituting the driving circuit.

  The display device 1 of the first embodiment shown in FIG. 3 differs from the display device (100) shown in FIG. 10 in that the signal line 25 and the power supply line 29 are arranged below the auxiliary wiring 6a. There is no place. That is, the signal line 25 and the power supply line 29 are arranged below the lower electrode 6 or between the lower electrode 6 and the auxiliary wiring 6a.

  FIG. 4 shows a layout diagram of the lower electrode 6 and the auxiliary wiring 6a and the wiring layer underneath. As shown in this figure, the lower electrode 6 is arranged in a matrix corresponding to the pixel (21), and the auxiliary wiring 6a is insulated from the lower electrode 6 while maintaining the insulating property. 6 are provided in a grid pattern. The signal line 25 and the power supply line 29 are wired under the upper electrode 6 or under the gap between the upper electrode 6 and the auxiliary wiring 6a while partially crossing the auxiliary wiring 6a. In the first embodiment, the wiring composed of the same layer as the signal line 25 and the power supply line 29 is not arranged below the auxiliary wiring 6a in parallel with the auxiliary wiring 6a.

  In the display device 1 configured as described above, the power supply line 29 having a large potential difference with respect to the potential of the auxiliary wiring 6a or a signal line to which a non-constant potential is applied is provided below the auxiliary wiring 6a connected to the ground potential GND. 25 are not arranged in parallel with the auxiliary wiring 6a. For this reason, there is no short circuit between the auxiliary wiring 6a and the wiring arranged in the lower layer. Therefore, for example, it is possible to prevent a problem in which all the pixels of the display device 1 do not emit light due to a short circuit between the auxiliary wiring 6a and the power supply line 29, both of which are laid out with a single wiring. Thus, the yield of the semiconductor device 1 can be improved.

Second Embodiment
FIG. 5 is a block diagram showing an outline of the display device of the second embodiment. This display device 1 ′ is a pixel array in which pixels (pixel circuits) 31 including organic EL elements that emit light of red (R), green (G), and blue (B) are arranged in m columns and n rows in a matrix. A portion 32 is provided. Here, for simplification of the drawing, a case where the pixel array section 32 has a pixel array of 6 columns and 2 rows is shown as an example.

  In the pixel array section 32, a scanning line 33 and a first drive line 34 are wired for each row of each pixel 31, and a second drive line 35 is wired for each pixel of the same emission color in each row. In addition, an auto-zero line 36 is wired for each row for each pixel 31, and a data line 37 is wired for each column. Around the pixel array section 32, a write scanning circuit 38 for driving the scanning line 33, a first driving scanning circuit 39 for driving the first driving line 34, and a second driving scanning for driving the second driving line 35 are provided. A circuit 40, an auto zero circuit 41 for driving the auto zero line 36, and a data line driving circuit 42 for supplying a data signal corresponding to the luminance information to the data line 37 are arranged. In this example, the writing scanning circuit 38 and the first driving scanning circuit 39 are arranged on one side (right side in the figure) across the pixel array section 32, and the second driving scanning circuit 40 and the auto zero circuit 41 are arranged on the opposite side. It has been configured.

  A power line 43 is wired for each row of each pixel 31.

  FIG. 6 is a circuit diagram of a pixel circuit (unit pixel circuit) in the active matrix organic EL display device 1 ′. As shown in this figure, the pixel circuit 31 in the display device 1 ′ includes a drive transistor Tr1, capacitors (pixel capacitors) Cs1 and Cs2, and switching transistors Tr2 to Tr6 as circuit elements in addition to the organic EL element EL. It has become. The drive transistor Tr1 and the switching transistors Tr2 to Tr6 are N-channel field effect transistors, for example, N-channel TFTs (thin film transistors).

  The organic EL element EL has a cathode electrode connected to the first power supply potential (in this example, the ground potential GND). The drive transistor Tr1 is a drive transistor that drives the organic EL element EL to emit light. The drain of the drive transistor Tr1 is the second power supply potential (in this example, the power supply line 43 connected to the positive potential Vcc), and the source is the organic EL element EL. A source follower circuit is formed by being connected to each anode electrode. The capacitive element Cs1 is a pixel capacitor, and one end is connected to the gate of the drive transistor Tr1, and the other end is connected to a connection node N11 between the source of the drive transistor Tr1 and the anode electrode of the organic EL element EL.

  The transistor Tr2 has a source connected to the data line 37 and a gate connected to the scanning line 33. One end of the capacitive element Cs2 is connected to the drain of the transistor Tr2, and the other end is connected to a connection node N12 between the gate of the driving transistor Tr1 and one end of the capacitive element Cs1. The transistor Tr3 has a drain connected to the connection node N11, a source connected to the third power supply potential Vss (for example, the ground potential GND), and a gate connected to the first drive line 34. Note that a negative power supply potential may be used as the third power supply potential Vss.

  The transistor Tr4 has a drain connected to the positive potential Vcc, a source connected to the drain of the drive transistor Tr1, and a gate connected to the second drive line 35. The transistor Tr5 has a drain connected to the connection node N13 between the drain of the drive transistor Tr1 and a source of the transistor Tr4, a source connected to the connection node N12, and a gate connected to the auto-zero line 36. The transistor Tr6 has a drain connected to the fourth power supply potential Vofs, a source connected to the drain of the transistor Tr2, and a gate connected to the auto-zero line 36. Of the above transistors, the transistors Tr2, Tr5, Tr6 may have the source and drain connected in reverse depending on the voltage setting.

  FIG. 7 is a timing chart for explaining the operation of such a pixel circuit. The pixel circuit of FIG. 6 drives each line 33 to 36 as shown in the timing chart by driving each circuit 38 to 41. As a result, the gate-source potential Vgs of the drive transistor Tr1 is kept constant at Vgs = Vini + Vth. For this reason, the electric current which flows into the organic EL element EL does not change. Therefore, even if the IV characteristic of the organic EL element EL deteriorates, the constant current Ids always flows, so that the luminance of the organic EL element EL does not change. Further, the threshold voltage Vth of the drive transistor Tr1 is canceled by the action of the transistor Tr5 during the threshold cancellation period, and a constant current Ids that is not affected by the variation of the threshold voltage Vth can be flowed, so that a high-quality image is obtained. be able to.

  FIG. 8 is a cross-sectional view showing the layer structure of the active matrix display device 1 ′ as described above, and the same components as those in FIG. 6 are denoted by the same reference numerals.

  The basic layer configuration of the active matrix type display device 1 ′ shown in this figure is the same as that described with reference to the cross-sectional view of FIG. 3 in the first embodiment, and detailed description thereof is omitted here. To do. However, here, as described with reference to FIG. 6, a positive potential (Vcc) is applied to the power supply line 43. Further, the lower electrode 6 of the organic EL element EL is used as an anode electrode, and the upper electrode 9 is used as a cathode electrode. For this reason, the auxiliary wiring 6a composed of the same layer as the lower electrode 6 is also connected to the ground potential GND similarly to the cathode electrode. The power supply line 43 is the wiring having the most potential difference from the potential of the auxiliary wiring 6a connected to the ground potential GND among the wirings constituting the driving circuit.

  As in the first embodiment, the display device 1 ′ of the second embodiment shown in FIG. 8 is different from the display device (100) shown in FIG. The auxiliary wiring 6a is not disposed below the auxiliary wiring 6a. That is, the signal line 37 and the power supply line 43 are arranged below the lower electrode 6 or below the lower electrode 6 and the auxiliary wiring 6a, as in the first embodiment.

  In the second embodiment, the power line connected to the third power supply potential Vss (here, Vss) and the fourth power supply potential Vofs are on the same layer as the signal line 37 and the power supply line 43. A connected power line (here, Vofs) is wired. As described above with reference to FIG. 6, the third power supply potential Vss, for example, the ground potential GND is set. The fourth power supply potential Vofs is maintained at a predetermined potential of, for example, several volts. For this reason, these power supply lines Vss and Vofs are wirings having substantially the same potential as the auxiliary wiring 6a connected to the ground potential GND among the wirings constituting the driving circuit. Note that the wiring having the same potential as that of the auxiliary wiring 6a is determined by comparing the potentials of a plurality of wirings constituting the pixel circuit, and the wiring having the same potential as that of the auxiliary wiring 6a and the wiring having the smallest potential difference are used. Selected.

  Therefore, in the second embodiment, these power supply lines Vss and Vofs are wired in parallel to the auxiliary electrode 6a so as to overlap the auxiliary electrode 6a. If there is enough wiring space, these power supply lines Vss and Vofs may not be arranged below the auxiliary wiring 6a in parallel with the auxiliary electrode 6a.

  In the display device 1 ′ having the above configuration, only the power supply lines Vss and Vofs having substantially the same potential as the auxiliary electrode 6 a are wired in parallel with the auxiliary wiring 6 a below the auxiliary wiring 6 a connected to the ground potential GND. Has been. Under the auxiliary electrode 6a, the power supply line 43 having a large potential difference with respect to the potential of the auxiliary wiring 6a and the signal line 37 to which a non-constant potential is applied are not arranged in parallel with the auxiliary wiring 6a. . For this reason, as in the first embodiment, it is possible to improve the yield of the semiconductor device 1.

  If the power supply lines Vss and Vofs having substantially the same potential as the auxiliary electrode 6a are not arranged in parallel with the auxiliary electrode 6a so as to overlap with the auxiliary electrode 6a, a short circuit between the auxiliary wiring 6a and the lower wiring is performed. Furthermore, it can prevent reliably. Therefore, the yield of the semiconductor device 1 can be improved more reliably.

It is a circuit diagram which shows the structure of the pixel circuit in the display apparatus of 1st Embodiment. 3 is a timing chart for explaining the operation of the pixel circuit in the display device of the first embodiment. It is sectional drawing which shows the structure of the display apparatus of 1st Embodiment. FIG. 3 is a layout diagram of an organic EL element and a lower electrode in the display device according to the first embodiment, and wirings underneath. It is a block diagram which shows schematic structure of the display apparatus of 2nd Embodiment. It is a circuit diagram explaining the pixel circuit of the display apparatus of 2nd Embodiment. 12 is a timing chart for explaining the operation of the pixel circuit in the display device according to the second embodiment. It is sectional drawing which shows the structure of the display apparatus of 2nd Embodiment. It is a block diagram which shows an example of schematic structure of a display apparatus. It is sectional drawing which shows the structure of the conventional display apparatus. FIG. 10 is a layout diagram of an organic EL element and a lower electrode in a conventional display device, and a wiring underneath.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 '... Display apparatus, 2 ... Board | substrate, 5 ... Interlayer insulating film, 6 ... Lower electrode, 6a ... Auxiliary wiring, 9 ... Upper electrode, 25, 37 ... Signal line, 29, 43 ... Power supply line (Auxiliary wiring) Wiring having the most potential difference from the potential), EL ... organic EL element, Vss, Vofs ... power supply line (wiring having substantially the same potential as the auxiliary electrode 6a)

Claims (7)

A driving circuit provided on the substrate, an interlayer insulating film provided on the substrate so as to cover the driving circuit, and an organic EL arrayed and formed on the interlayer insulating film in a state of being connected to the driving circuit In a display device having an element and an auxiliary wiring arranged between the organic EL elements on the interlayer insulating film,
Of the wirings constituting the drive circuit ,
The wiring having the most potential difference from the potential of the auxiliary wiring and the wiring to which a non-constant potential is applied are wired without overlapping in a region parallel to the auxiliary wiring ,
A display device in which a wiring having substantially the same potential as that of the auxiliary wiring is overlapped in a region parallel to the auxiliary wiring . The display device according to claim 1,
The wiring erratic potential is applied, Ru signal line der
Viewing equipment. The display device according to claim 1 or 2,
The wiring having the most potential difference from the potential of the auxiliary wiring is a wiring connected to the power supply potential.
Display device. The display device according to any one of claims 1 to 3 ,
The auxiliary line is formed of a lower electrode in the same layer constituting the organic EL element, and it is connected to the upper electrode constituting the organic EL device
Viewing equipment. The display device according to any one of claims 1 to 4 ,
Emitting light in the organic EL device, it is picked from the opposite side to the substrate
Viewing equipment. A driving circuit provided on the substrate, an interlayer insulating film provided on the substrate so as to cover the driving circuit, and an organic EL arrayed and formed on the interlayer insulating film in a state of being connected to the driving circuit In a display device having an element and an auxiliary wiring arranged between the organic EL elements on the interlayer insulating film,
Of the wirings constituting the drive circuit ,
The signal line is wired without overlapping in a region parallel to the auxiliary wiring ,
A display device in which a wiring having substantially the same potential as that of the auxiliary wiring is overlapped in a region parallel to the auxiliary wiring . A driving circuit provided on the substrate, an interlayer insulating film provided on the substrate so as to cover the driving circuit, and an organic EL arrayed and formed on the interlayer insulating film in a state of being connected to the driving circuit In a display device having an element and an auxiliary wiring arranged between the organic EL elements on the interlayer insulating film,
Of the wirings constituting the drive circuit ,
The wiring connected to the power supply potential is wired without overlapping in a region parallel to the auxiliary wiring ,
A display device in which a wiring having substantially the same potential as that of the auxiliary wiring is overlapped in a region parallel to the auxiliary wiring .

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