JP2008134345A - Repair method of active matrix display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active matrix display which can efficiently be repaired with high reliability, and provide its repair method. <P>SOLUTION: This display has display components 16, pixel circuits which include transistors 26 connected to those display components to drive, and pixels arranged in a matrix on the substrate 8. The transistors are formed on the substrate and have semiconductor layers 50 including repair areas 50b. The display components are formed on the substrate with an inter-layer film in between, and have first electrodes 62 connected to the transistors and second electrodes 66 formed overlapping the first electrodes. The first electrodes have openings 63 where they overlap the repair areas of the transistors. When repairing, a laser beam is emitted from the substrate side to the repair area to cut the semiconductor layers. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a repair method for an active matrix display device.

  In recent years, the demand for flat display devices typified by liquid crystal display devices has been rapidly increased by taking advantage of the features of thinness, light weight, and low power consumption. In particular, an active matrix display device in which a pixel switch having a function of electrically separating an on pixel and an off pixel and holding a video signal to the on pixel is provided in each pixel has crosstalk between adjacent pixels. Therefore, it is used for various displays including portable information devices.

  As such a flat-type active matrix display device, an organic electroluminescence (EL) display device using an organic light emitting diode (OLED), which is a self-luminous element, has attracted attention, and research and development have been actively conducted. Has been done. The organic EL display device does not require a backlight that obstructs the reduction in thickness and weight, is suitable for moving image reproduction because of high-speed response, and further has a feature that it can be used even in a cold region because the luminance does not decrease at low temperatures.

  The organic EL display device includes a plurality of pixels provided in a matrix, and each pixel includes an organic EL element as a display element and a pixel circuit that supplies a drive current to the display element. The organic EL display device performs a display operation by controlling the light emission luminance of the display element. The pixel circuit includes, for example, a drive transistor and an output switch connected in series to the organic EL element, a pixel switch connected between the video signal line and the pixel circuit, and connected between the source and gate of the drive transistor. And a storage capacitor for holding a gate potential corresponding to the video signal. These pixel switches, drive transistors, and output switches are constituted by thin film transistors, for example.

  In such an organic EL display device, a short circuit between wirings, a gate leak of a transistor, a short circuit of a storage capacitor, or the like may occur in a manufacturing process. For example, when a gate leak of a transistor occurs, a current always flows through the display element, so that the display element always emits light and becomes a bright spot. In addition, when the storage capacitor is short-circuited, current flows excessively in the short-circuited portion, and current does not flow to the display element, resulting in a black spot (dark spot). When a black spot is generated due to a short-circuit of the storage capacitor, a few lines of pixels connected to the same signal line as this pixel are darkened, and a black tail is drawn from the black spot.

For this reason, when a black spot is detected by a lighting test after completion of the apparatus, a repair method for efficiently repairing the black spot pixel is required. In an organic EL display device, when repairing a bright spot or a black spot, it is necessary to prevent a current from flowing between the cathode and the anode of the light emitting element. For example, Patent Document 1 proposes a method of performing repair by irradiating a desired portion with laser light after completion of the apparatus.
JP 2000-208252 A

  For example, in the case where a black spot due to a short-circuit of the storage capacitor as described above and a tail that follows this occur, in the pixel where the black spot occurs, the connection between the signal line and the pixel switch, and the input side of the display element A method of cutting the connecting portion with a laser is used.

  However, when the pixel switch is disconnected from the signal line as described above, the potential of the signal line when writing to the pixel approaches a white potential, that is, OV. For this reason, the potentials of the pixels in the next several rows connected to the same signal line as this pixel also become higher and become brighter than the desired luminance. Thereby, after repair, it will be in the state which pulled the white tail from the black spot. As a result, there is a problem that the display quality is deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a repair method for an active matrix display device capable of reliably repairing a black spot.

In order to achieve the above object, a repair method for an active matrix display device according to an aspect of the present invention includes a display element and a pixel circuit for driving the display element, and is arranged in a matrix on a substrate. A plurality of pixel portions; a plurality of video signal lines connected to each column of the pixel portions; and a first signal current supplied to the pixel circuit via the video signal lines, and then via the video signal lines. A signal line driving circuit for supplying a second signal current to the pixel circuit,
Each of the pixel circuits includes a driving transistor connected in series with the display element between a high potential power source and a low potential power source to supply a driving current to the display element, a source connected to a drain of the driving transistor, An output switch having a drain connected to the display element; a pixel switch having a drain connected to the signal line; and a source connected to a source of the output switch; and a drain connected to the source of the pixel switch. And a first switch connected to the gate of the driving transistor, an electrode connected to the gate of the driving transistor, and an electrode connected to the source of the driving transistor, and holds a potential difference between the gate and source of the driving transistor An active matrix display device having a storage capacitor,
When a black spot occurs due to a short circuit of the storage capacitor, disconnect at least one of the connection between the electrode of the storage capacitor and the gate electrode of the drive transistor and the connection between the electrode of the storage capacitor and the source of the drive transistor, The connection of at least one of the source and drain of the output transistor is cut off.

  According to an aspect of the present invention, an active matrix display device that can be reliably repaired even when black spots occur due to short-circuiting of a storage capacitor and can prevent deterioration in image quality. A repair method can be provided.

Hereinafter, an organic EL display device and a repair method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 schematically shows the entire organic EL device. As shown in FIG. 1, the organic EL display device is configured as, for example, a large active matrix display device of 10 type or more, and includes an organic EL panel 10 and a controller 12 that controls the organic EL panel 10.

  The organic EL panel 10 is arranged in the form of a matrix on an insulating substrate 8 such as a glass plate, and is connected to each row of the display pixels, each of which is connected to each row of the display pixels 11 and independently. The first scanning line Sga (1 to m), the second scanning line Sgb (1 to m), and the n video signal lines X (1 to 1) connected to each column of the display pixels PX, respectively. n), a scanning line driving circuit (YDR) 14 for sequentially driving the first and second scanning lines Sga (1 to m), Sgb (1 to m) for each row of display pixels, and a plurality of video signal lines X ( 1 to n) is provided with a signal line drive circuit (XDR) 15. The scanning line driving circuit 14 and the signal line driving circuit 15 are integrally formed on the insulating substrate 8 outside the display area 11.

  Each display pixel PX that functions as a pixel portion includes a display element having a photoactive layer between opposing electrodes, and a pixel circuit 18 that supplies a drive current to the display element. The display element is, for example, a self-luminous element. In this embodiment, the organic EL element 16 including at least an organic light-emitting layer is used as a photoactive layer.

  FIG. 2 shows an equivalent circuit of the display pixel PX. The pixel circuit 18 is a current-driven pixel circuit that controls light emission of the organic EL element 16 in accordance with a video signal including a current signal. The pixel circuit 18 includes a pixel switch 20, a drive transistor 22, a first switch 24, an output switch 26, and a holding circuit. The capacitor Cs is provided. Here, the pixel switch 20, the drive transistor 22, the first switch 24, and the output switch 26 are configured by the same conductivity type, for example, a P-channel type thin film transistor. In this embodiment, all the thin film transistors constituting the pixel circuit 18 are formed in the same process and the same layer structure, and are top gate thin film transistors using polysilicon as a semiconductor layer.

  The drive transistor 22, the output switch 26, and the organic EL element 16 are connected in series in this order between a voltage power supply line Vdd as a high potential power supply and a reference voltage power supply line Vss as a low potential power supply. The reference voltage power supply line Vss and the voltage power supply line Vdd are set to potentials of −9 V and +6 V, for example. The drive transistor 22 has its first terminal, here the source, connected to the voltage power supply line Vdd. The organic EL element 16 has one electrode, here the cathode, connected to the reference voltage power supply line Vss. The source of the output switch 26 is connected to the second terminal of the driving transistor 22, here the drain. The output switch 26 has a drain connected to the anode of the organic EL element 16 and a gate connected to the corresponding second scanning line Sgb.

  The drive transistor 22 outputs a light emission current having a current amount corresponding to the video signal to the organic EL element 16. The output switch 26 is controlled to be on (conducting state) and off (non-conducting state) by a control signal Sb (1 to m) from the second scanning line Sgb, and the connection between the driving transistor 22 and the organic EL element 16 is not connected. Control the connection.

  The holding capacitor Cs is connected between the first terminal and the control terminal of the driving transistor 22, here, between the source and the gate, and holds the gate control potential of the driving transistor 22 determined by the video signal. In other words, the storage capacitor Cs has a pair of electrodes arranged opposite to each other with an insulating layer interposed therebetween, one electrode being connected to the gate of the driving transistor 22 and the other electrode being connected to the source of the driving transistor 22. Yes.

  The pixel switch 20 is connected between the corresponding video signal line X (1 to n) and the drain of the driving transistor 22, and the gate thereof is connected to the corresponding first scanning line Sga. That is, the pixel switch 20 has a drain connected to the video signal line and a source connected to the drain of the driving transistor. The pixel switch 20 takes in a signal current as a gradation current from the corresponding video signal line X (1 to n) in response to the control signal Sa (1 to m) supplied from the first scanning line Sga.

  The first switch 24 is connected between the drain and gate of the drive transistor 22, and the gate thereof is connected to the first scanning line Sga. The drain of the first switch 24 is connected between the drain of the driving transistor 22 and the source of the pixel switch 20. The first switch 24 is on / off controlled in accordance with a control signal Sa (1 to m) from the first scanning line Sga, controls connection / disconnection between the gate and drain of the drive transistor 22, and holds capacitance. Regulates current leakage from Cs.

Next, the configuration of the drive transistor 22 and the organic EL element 16 will be described in detail with reference to FIG. FIG. 3 shows a cross section of the display pixel Px including the organic EL element 16.
The P-channel type thin film transistor constituting the first drive transistor 22a includes a semiconductor layer 50 made of polysilicon formed on the insulating substrate 8. The semiconductor layer includes a source region 50a, a drain region 50b, and a source / drain region. It has a channel region 50c located between them. A gate insulating film 52 is formed over the semiconductor layer 50, and a gate electrode G is provided on the gate insulating film so as to face the channel region 50c. An interlayer insulating film 54 is formed over the gate electrode G, and a source electrode (source) S and a drain electrode (drain) D are provided on the interlayer insulating film. The source electrode S and the drain electrode D are respectively connected to the source region 50a and the drain region 50b of the semiconductor layer 50 through contacts formed through the interlayer insulating film 54 and the gate insulating film 52, respectively. The drain electrode D of the first drive transistor 22a is connected to the output switch 26 via a wiring formed on the interlayer insulating film 54 and the first switch 24a. Note that the thin film transistors constituting the pixel switch 20, the first holding switch 23a, the second holding switch 23b, the first switch 24a, the second switch 24b, and the output switch 26 are also formed in the same structure as described above. The second drive transistor 22b is also formed in the same structure as described above, but an LDD region may be further added.

  A plurality of wirings including the video signal lines X (1 to n) are provided on the interlayer insulating film 54. A protective film 56 is formed on the interlayer insulating film 54 so as to cover the source electrode S, the drain electrode D, and the wiring. On the protective film 56, a hydrophilic film 58 and a partition film 60 are laminated in this order.

  The organic EL element 16 has a structure in which an organic light emitting layer 64 containing a luminescent organic compound is sandwiched between an anode 62 and a cathode 66. The anode 62 is made of a transparent electrode material such as ITO (indium tin oxide) and is provided on the protective film 56. Of the hydrophilic film 58 and the partition wall film 60, the part facing the anode 62 is removed by etching. An anode buffer layer 63 and an organic light emitting layer 64 are formed on the anode 62, and a cathode 66 made of silver / aluminum alloy is laminated on the organic light emitting layer 64 and the partition wall film 60.

  In the organic EL element 16 having such a structure, when the holes injected from the anode 62 and the electrons injected from the cathode 66 are recombined inside the organic light emitting layer 64, the organic molecules constituting the organic light emitting layer are formed. Is excited to generate excitons. The excitons emit light in the process of radiation deactivation, and the light is emitted from the organic light emitting layer 64 to the outside through the transparent anode 62 and the insulating substrate 8.

  The case where the anode electrode 62 is connected to the drain of the driving transistor 22 and the cathode electrode 66 is connected to the reference voltage power supply line Vss through the output switch 26 has been described. However, the cathode electrode 66 is connected to the drain of the driving transistor 22 and the anode electrode is connected. 62 may be connected to the reference voltage power supply line Vss.

  The cathode 66 may be light transmissive, and light may be extracted to the outside from the surface facing the insulating substrate 8. Further, a reverse lamination type in which the anode 62 is disposed on the insulating substrate 8 side with respect to the cathode 66 may be employed. In either case, it is necessary to form the light emitting surface side with a transparent conductive material. For example, when the cathode 66 is disposed on the light emitting surface side, the alkaline earth metal and the rare earth metal are thin enough to have light transmittance. This can be achieved by forming.

  On the other hand, the controller 12 shown in FIG. 1 is formed on a printed circuit board disposed outside the organic EL panel 10 and controls the scanning line driving circuit 14 and the signal line driving circuit 15. The controller 12 receives a digital video signal and a synchronization signal supplied from the outside, and generates a vertical scanning control signal for controlling the vertical scanning timing and a horizontal scanning control signal for controlling the horizontal scanning timing based on the synchronizing signal. The controller 12 supplies the vertical scanning control signal and the horizontal scanning control signal to the scanning line driving circuit 14 and the signal line driving circuit 15, respectively, and outputs the digital video signal in synchronization with the horizontal and vertical scanning timings. To supply.

  The scanning line driving circuit 14 includes a shift register, an output buffer, and the like, sequentially transfers a horizontal scanning start pulse supplied from the outside to the next stage, and supplies a control signal, that is, a control signal to the display pixels PX in each row via the output buffer. Signals Sa (1 to m) and Sb (1 to m) are supplied. Accordingly, the first and second scanning lines Sga (1 to m) and Sgb (1 to m) are respectively controlled by the control signal Sa (1 to m) and the control signal Sb (1 to 1) in one horizontal scanning period different from each other. m).

  The signal line driving circuit 15 converts the video signal sequentially obtained in each horizontal scanning period into an analog format under the control of the horizontal scanning control signal to obtain a signal current Idata, and in parallel with the plurality of video signal lines X (1 to n). Supply.

  The operation of the pixel circuit 18 is divided into a video signal writing operation and a light emission operation. As shown in FIG. 2, in the video signal writing operation, the control signals Sa1 and Sb1, in which the pixel switch 20 and the first switch 24 are turned on (conductive state) and the output switch 26 is turned off (non-conductive state), here The control signal Sa1 is output at a low level and the control signal Sb1 is output at a high level. Thereby, the pixel switch 20 and the first switch 24 are turned on (conductive state), the output switch 26 is turned off (non-conductive state), and the video signal writing operation is started.

  In the video signal writing period, the video signal current Idata supplied from the signal line driving circuit 15 to the corresponding video signal line X (1 to n) is supplied to the selected display pixel PX via the pixel switch 20. In the display pixel PX, the pixel switch 20 and the first switch 24 are in the on state, and the captured video signal current Idata is supplied to the driving transistor 22 to set the driving transistor 22 in the writing state. As a result, a write current flows from the voltage power supply line Vdd to the video signal line X1 through the drive transistor 22, and the gate-source potential of the drive transistor 22 corresponding to the current amount of the video signal current Idata is written to the storage capacitor Cs.

  Next, the control signal Sa1 becomes a high level (off potential), and the pixel switch 20 and the first switch 24 are turned off. Thereby, the video signal writing operation is completed. Subsequently, the control signal Sb1 becomes low level, and the output switch 26 is turned on. Thereby, the light emission operation starts. As shown in FIG. 4, in the light emission period, the drive transistor 22 is maintained in a conductive state by the gate control voltage written in the storage capacitor Cs, and the light emission current having a current amount corresponding to the video signal current Idata from the voltage power supply line Vdd. Is supplied to the output switch 26 side. This light emission current is supplied to the organic EL element 16 after passing through the output switch 26. Thereby, the organic EL element 16 emits light, and the light emission operation is started. The organic EL element 16 maintains the light emission state until the control signal Sb1 becomes the off potential again after one frame period.

Next, a repair method when a defect such as a black spot occurs in the organic EL display device configured as described above will be described.
First, after completion of the organic EL display device, a lighting test is performed. Among the pixels determined to be deficient by this lighting test, the pixel in which a short circuit between the electrodes of the storage capacitor Cs occurs causes no current to flow through the organic EL element, resulting in a black dot. In this case, as shown in FIG. 5, the pixels of the next several lines connected to the same video signal line as the pixel in which the black spot is generated become slightly darker, and the black spot is drawn from the black spot. It becomes a draw sunspot.

  In this case, as shown in FIG. 6, at least one of the storage capacitors Cs in which a short circuit has occurred while maintaining a circuit passing through the drive transistor 22 and the pixel switch 20 between the power supply voltage line Vdd and the video signal line X1. The connection of the electrode and the connection of at least one of the source and drain of the output transistor 16 are disconnected. That is, at least one of the connection between the electrode of the storage capacitor Cs and the gate electrode of the drive transistor 22 and the connection between the other electrode of the storage capacitor and the source of the drive transistor are disconnected. Further, at least one of the connection between the drain of the output transistor 16 and the organic EL element 16 and the connection between the source of the output transistor and the drain of the drive transistor 22 are disconnected. The organic EL element is floated.

  The disconnection is performed by irradiating a laser beam from the light emitting surface side of the insulating substrate 8 and laser cutting the wiring or the semiconductor layer of the transistor. As the laser light, a green laser, for example, a YAG laser or a YLF laser having a wavelength of 500 to 560 nm is used. The reason why the green laser is used is that the infrared laser easily transmits through the semiconductor layer 50 made of polysilicon, and the damage to the lower layer film due to thermal processing is large. In the ultraviolet laser, the glass substrate or the undercoat is used. It is mentioned that a high energy laser is necessary to cut the semiconductor layer. In the case of cutting a semiconductor layer that is cut by irradiation with laser light, the light emitting layer is preferably arranged so as not to overlap with the metal wiring, and a cross-sectional structure covered with an oxide film, a nitride film, or the like is desirable.

  By the above repair, the connection of the electrode of the storage capacitor Cs is disconnected and the organic EL element is floated, so that the black spot following the black spot pixel can be eliminated and a single black spot can be obtained as shown in FIG. At this time, by maintaining a circuit that passes through the drive transistor 22 and the pixel switch 20 between the power supply voltage line Vdd and the video signal line X1, the potential of the repaired pixel is maintained lower than the white potential. Can do. Therefore, the potentials of the pixels in the next several lines connected to the same video signal line as the black spot pixels do not approach OV, and the occurrence of a white tail following the black spot can be prevented and a single black spot can be obtained. . Therefore, it is possible to reliably repair the black spots without deteriorating the display quality.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  For example, when a short-circuit occurs in the storage capacitor, the connection between both electrodes may be disconnected without being limited to one electrode of the storage capacitor. The laser used may be a short wavelength laser with a wavelength of 400 nm or less.

  In the display device to be repaired, the semiconductor layer of the thin film transistor is not limited to polysilicon but can be composed of amorphous silicon. The self-luminous elements constituting the display pixels are not limited to organic EL elements, and various display elements capable of self-luminance are applicable.

FIG. 1 is a plan view schematically showing an organic EL display device according to an embodiment of the present invention. FIG. 2 is a plan view showing an equivalent circuit of display pixels in the organic EL display device. FIG. 3 is a cross-sectional view showing a display pixel. FIG. 4 is a plan view showing an equivalent circuit of the display pixel in the light emission period. FIG. 5 is a plan view schematically showing a display state in which a black drawing black spot is generated due to a short of the storage capacitor. FIG. 6 is a plan view showing a cutting position of the display pixel at the time of repair. FIG. 7 is a plan view schematically showing a display state after repair.

Explanation of symbols

8 ... Insulating substrate, 10 ... Organic EL panel, 12 ... Controller,
14 ... scanning line driving circuit, 15 ... signal line driving circuit, 16 ... organic EL element,
18 ... Pixel circuit, 20 ... Pixel switch, 22 ... Drive transistor,
24 ... 1st switch, 26 ... Output switch, 50 ... Semiconductor layer,
50a ... source region, 50b ... drain region,

Claims (3)

A display element and a pixel circuit for driving the display element; a plurality of pixel portions arranged in a matrix on a substrate; and a plurality of video signal lines connected to each column of the pixel portion; A signal line driving circuit for supplying a first signal current to the pixel circuit via the video signal line and then supplying a second signal current to the pixel circuit via the video signal line;
Each of the pixel circuits includes a driving transistor connected in series with the display element between a high potential power source and a low potential power source to supply a driving current to the display element, a source connected to a drain of the driving transistor, An output switch having a drain connected to the display element; a pixel switch having a drain connected to the signal line; and a source connected to a source of the output switch; and a drain connected to the source of the pixel switch. And a first switch connected to the gate of the driving transistor, an electrode connected to the gate of the driving transistor, and an electrode connected to the source of the driving transistor, and holds a potential difference between the gate and source of the driving transistor An active matrix display device having a storage capacitor,
When a black spot occurs due to a short circuit of the storage capacitor, disconnect at least one of the connection between the electrode of the storage capacitor and the gate electrode of the drive transistor and the connection between the electrode of the storage capacitor and the source of the drive transistor,
A repair method for an active matrix display device, in which at least one of a source and a drain of the output transistor is disconnected. A display element having an organic light emitting layer disposed between the electrodes, and a pixel circuit for driving the display element, and a plurality of pixel portions disposed in a matrix on the substrate; A plurality of video signal lines connected to each column, and a first signal current is supplied to the pixel circuit via the video signal line, and then a second signal current is supplied to the pixel circuit via the video signal line A signal line driving circuit that
Each of the pixel circuits includes a driving transistor connected in series with the display element between a high potential power source and a low potential power source to supply a driving current to the display element, a source connected to a drain of the driving transistor, An output switch having a drain connected to the display element; a pixel switch having a drain connected to the signal line; and a source connected to a source of the output switch; and a drain connected to the source of the pixel switch. And a first switch connected to the gate of the driving transistor, an electrode connected to the gate of the driving transistor, and an electrode connected to the source of the driving transistor, and holds a potential difference between the gate and source of the driving transistor An active matrix display device having a storage capacitor,
A connection between at least one electrode of the storage capacitor while maintaining a circuit passing through the drive transistor and a pixel switch between the high-potential power source and a signal line when a black spot occurs due to a short circuit of the storage capacitor; and A repair method for an active matrix display device, in which at least one of a source and a drain of the output transistor is disconnected.   3. The repair method for an active matrix display device according to claim 1, wherein the connection is cut by irradiating laser light having a wavelength of 500 to 560 nm.

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