JP2005241776A - Production and driving method for display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of in-element characteristic variations related to a display element. <P>SOLUTION: An electric voltage or an electric current is shut to an organic thin film light emitting layer of pixels in which a light amount is lower than in a normal element characteristics and/or a temperature is higher than in its surroundings. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display element, and more particularly to a display element composed of an organic electroluminescence (hereinafter abbreviated as EL) element, and more particularly to a highly reliable organic EL element that can be driven for a long period of time.

  Light Emitting Diode (hereinafter abbreviated as LED) and organic EL elements that have been attracting attention in recent years are attracting attention.

  The organic EL element is characterized in that planar self-emission of a thin film stack capable of high luminance emission is obtained. This EL element enables high-efficiency light emission at a low voltage by increasing the number of functional layers of organic layers (Non-Patent Document 1).

  The basic light-emitting element configuration here is a configuration of anode / hole transport layer / EL light-emitting layer / cathode. Thereafter, as shown in FIG. 8, high efficiency has been achieved by the configuration of anode / hole transport layer / EL light emitting layer / electron transport layer / cathode. Furthermore, a blocking layer is provided between the EL light emitting layer and the electron transport layer to block carriers passing through the EL light emitting layer, or between the cathode and the electron transport layer so that carriers can be injected at a low voltage. An attempt has been made to improve luminous efficiency by providing a metal thin film as an electron injection layer.

  Next, light emission driving of the organic EL element will be described.

  As a light emission control means of the organic EL element, means driven by a voltage or current as shown in FIG. 9 is known. Actually, in the simple matrix type, light emission is controlled by voltage and current.

  However, the organic EL element is a device suitable for obtaining light emission by current injection, and unlike an electric field device such as a liquid crystal display, a linear luminance characteristic can be used by passing a current through the light emitting element. For this purpose, the active matrix organic EL element has a current drive circuit composed of TFTs for each pixel.

  For example, as shown in FIG. 5, the light emission luminance signal is accumulated in the capacitor 162 by voltage input, and is applied to the gate of the TFT 163, whereby the current between the source and drain of the TFT 163 is made constant and the organic EL light emitting element 164 is supplied. How to supply. Further, Patent Document 1 and Patent Document 2 have been proposed as pixel circuits for canceling the threshold voltage of TFTs manufactured in each pixel as shown in FIG. 6 by a gate voltage determination method using an input current.

The organic EL light emitting element is a thin film laminated device, and a short circuit may occur in a part of the pixel of the element after manufacture. As a method for repairing a short circuit of such an organic EL element after manufacture, a method of repairing the short circuit part by applying a high voltage is known. In addition, in an organic EL element having a current driving circuit composed of TFTs for each pixel unit, the pixels may always be in a light emitting state due to a failure of the driving TFT.
Applied Phistics Letters, 51 '913, 913, 65,' 3610, '89 JP 2001-056667 A US Patent No. 6229506

  As described above, when an organic EL element is manufactured by thin film lamination, it often fails in a short-circuiting mode due to the extremely thin film thickness. An organic layer used in an actual EL element is as thin as several tens to several hundreds of nanometers or less, and it is industrially difficult to eliminate short-circuited pixels generated due to dust adhesion or sex film processes. FIG. 2 is an enlarged photograph of a part of one pixel. Circles indicate short-circuit points. Such a short-circuit portion is electrically present in some pixels due to dust or the like during the process. The short-circuited part is a part where a short circuit occurs between one electrode and the other common electrode.

  And this leak current due to this short circuit is not only wasted, but also generates Joule heat from the short circuit wiring as shown in FIG. FIG. 3 is a photograph of the pixel portion of FIG. 2 observed with a thermotrophy. The gradation shows the temperature distribution. When the sir is also observed with a trophy, the position of the short circuit can be clearly identified. Further, when the pixel is always in a light emitting state due to a failure of the driving TFT or the like, the same action as described above may be caused by the consumption of the conduction current or the heat generation of the current failure TFT or the overcurrent wiring.

  Therefore, not only the power consumption is increased due to the short circuit, but there is a possibility that the organic thin film layer which is relatively weak thermally is denatured and the characteristic deterioration is expanded from the short circuit part to the peripheral pixels.

In view of such a problem, in the display element of the present invention,
a. Means for detecting a pixel that is less than or equal to the amount of light of a normal pixel and / or has a higher temperature than the surroundings;
b. Means for applying a voltage between the first electrode and the second electrode of the pixel or cutting a part of a circuit for passing a current;
a. And b. 2. The method of manufacturing a display element according to claim 1, wherein a part of the circuit of the pixel is cut off using the means.

c. Means for detecting pixels that emit light or / and have a higher temperature than the surroundings even when voltage and current application are not controlled;
d. Means for applying a voltage between the first electrode and the second electrode of the pixel or cutting a part of a circuit for passing a current;
c. And d. 3. The method of manufacturing a display element according to claim 2, wherein a part of the circuit of the pixel is cut off using the means.

  b. And d. A method for manufacturing a display element, characterized in that a part of the circuit of the pixel is cut off in a flame-supporting atmosphere.

  In the display element including the organic thin-film light emitting layer between the first electrode and the second electrode arranged in a matrix on the substrate by the above means, the normal element characteristics can be obtained even when voltage or current is controlled to be applied. Of the organic thin-film light-emitting layer of a pixel whose temperature is lower than or equal to or higher than that of the surroundings, and a method of manufacturing a display element characterized by blocking a voltage or current, and a matrix arrangement on a substrate In a display element including an organic thin film light emitting layer between the first electrode and the second electrode, the voltage or the organic thin film light emitting layer of the pixel that emits light even when no current is applied and controlled, Alternatively, an attempt is made to solve the problem by using a display element manufacturing method characterized by cutting off current.

further,
e. Means for measuring and determining the amount of light by a photodetector to detect a pixel below the light amount of a normal pixel or / and at a higher temperature than the surroundings
f. Means for storing the position of the pixel;
g. Means for setting a video signal in which the voltage or current between the first electrode and the second electrode of the pixel is substantially zero;
e. And f. And / or g. A method for driving a display element, characterized in that the voltage or current of the pixel is made substantially zero using the above means.

h. Means for measuring and judging the amount of light by a photodetector to detect pixels that emit light without controlling voltage and current application;
i. Means for storing the position of the pixel;
j. Means for setting a video signal in which the voltage or current between the first electrode and the second electrode of the pixel is substantially zero;
h. And i. And / or j. A method for driving a display element in which the voltage or current of the pixel is made substantially zero by using the above means.

  f. And i. The means is stored as the pixel position in the storage device provided in the display element driving apparatus.

  g. And j. Means for writing a value at which the voltage or current is substantially zero to the pixel position of the video memory of the driving device.

  In the display element including the organic thin-film light emitting layer between the first electrode and the second electrode arranged in a matrix on the substrate by the above means, the normal element characteristics can be obtained even when voltage or current is controlled to be applied. The display element driving method is characterized in that the voltage or current is cut off from the organic thin-film light-emitting layer of the pixel whose temperature is less than or equal to or higher than the surrounding temperature, and is arranged in a matrix on the substrate In a display element including an organic thin-film light-emitting layer between a first electrode and a second electrode, even if voltage or current is not applied and controlled, the organic thin-film of a pixel having a higher temperature than the surroundings An object is to solve the problem by using a display element driving method characterized in that voltage or current is cut off from the light emitting layer.

  When manufacturing an organic EL element by thin film lamination, it often fails in a short-circuiting mode due to the extremely thin film thickness. An organic layer used in an actual EL element is as thin as several tens to several hundreds of nanometers or less, and it is industrially difficult to eliminate short-circuited pixels generated due to dust adhesion or sex film processes. Electrically, a short circuit occurs between one electrode and the other common electrode in some pixels due to dust or the like during the process. According to the present invention, the leakage current due to such a short circuit is not wasted, and the deterioration of the thermally relatively weak organic thin film layer due to the generation of Joule heat and the expansion of the characteristic deterioration from the short circuit portion to the peripheral pixels are prevented. It becomes possible.

  Further, when the pixel is always in a light emitting state due to a failure of the driving TFT or the like, the normal short-circuit current can be cut off, and the reactive current can be reduced and the element can be prevented from being thermally deteriorated.

(Example 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the organic EL light emitting device used in this example will be described.

  8 and 20 are diagrams showing a configuration in which a laminated organic thin film is sandwiched between an anode and a cathode, 151 is a glass substrate, 152 is a transparent anode such as ITO, 153 is a hole transport layer, 154 is a light emitting layer, Reference numeral 155 denotes an electron transport layer, and 156 denotes a cathode. By applying a positive voltage to the anode 152 side and a negative voltage to the cathode 156 side, holes 158 passing through the hole transport layer 153 and electrons 159 passing through the electron transport layer 155 form excitons in the light emitting layer 154. Emits light upon recombination.

  These light emitting elements are arranged on a matrix as shown in the organic EL light emitting element 223 of FIG. A voltage or a current is applied to the column electrode 220 and the row electrode 221, and a current flows through the organic EL light emitting element 223 sandwiched between these transparent electrodes. A voltage or a current is applied to each of the column electrode 220 and the row electrode 221 at a timing that gives a predetermined luminance in a time division manner.

  In the display element having such a matrix configuration, when a minute foreign matter such as dust adheres to the laminated film of the organic EL light emitting element 223 during the process of manufacturing the element, the pixel including the organic EL light emitting element 223 enters a short state. In this case, the current flowing through the organic EL light-emitting element 223 becomes not only invalid, but the row electrodes 221 and the connecting portions 221 generate heat, and the Joule heat promotes deterioration of the elements.

  Such pixel defects were detected using a CCD photodetector during the device manufacturing process. Even when a voltage and a current were applied, a pixel that was 1/2 or less and substantially 0 cd / m 2 could be easily identified. After completion of the organic film formation, a part 222 of the pixel circuit was cut off with a laser in a flame-supporting atmosphere. As a result, the reactive current of the non-lighting pixel composed of the organic EL light emitting element 223 and the heat generation of the row electrode 221 and the connection portion 221 are not observed.

  In addition, the apparatus shown in FIG. 1 was used for the manufacturing process for this interruption | blocking. Here, 1 is a container having a flame-supporting atmosphere, 2 is a CCD photodetector or / and a thermal detector for measuring pixel luminance such as the organic EL light emitting element 223, and 3 is a circuit of a defective pixel. It is a laser to electrically cut off a part.

(Example 2)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the organic EL light emitting device used in this example will be described.

  8 and 20 are diagrams showing a configuration in which a laminated organic thin film is sandwiched between an anode and a cathode, 151 is a glass substrate, 152 is a transparent anode such as ITO, 153 is a hole transport layer, 154 is a light emitting layer, Reference numeral 155 denotes an electron transport layer, and 156 denotes a cathode. By applying a positive voltage to the anode 152 side and a negative voltage to the cathode 156 side, holes 158 passing through the hole transport layer 153 and electrons 159 passing through the electron transport layer 155 form excitons in the light emitting layer 154. Emits light upon recombination. These light emitting elements are arranged on a matrix as shown in the display unit 180 of FIG.

  In FIG. 7, reference numeral 180 denotes a display portion in which the light emitting elements 189 are arranged in a matrix. Further, the V shift register 182, the timing conversion circuit 183, the H shift register 185, and the latch 184 are provided on the same surface as the display portion 180, and a video signal is supplied to a thin film transistor (hereinafter abbreviated as TFT) provided in the light emitting element 189. And a scanning signal is supplied. A circuit in the pixel 189 is shown in FIG. In the pixel 169, the source of the P-channel TFT 163 is connected to the power source, and the cathode of the light emitting element 164 is connected to the ground potential. The other anode is connected to the drain of the TFT 163. The gate of the N-channel TFT 161 is connected to a holding signal line for vertical scanning, the source is connected to the image signal line, and the remaining drain line is connected to the holding capacitor 162 and the gate of the TFT 163. In order to emit light from a pixel, first, a holding signal line for vertical scanning is selected, and a video signal latched by a horizontal latch circuit 184 is applied as a voltage to an image signal line. The source and drain of the TFT 161 are conducted, and the storage capacitor 162 is charged or discharged. The gate potential of the TFT 163 matches the potential of the video signal. When the vertical scanning holding signal is set to the non-selected state, the TFT 161 is turned off. At this time, the TFT 163 is separated from the image signal, but the potential is stably held by the holding capacitor 162 connected to the gate of the TFT 163. In this manner, a current corresponding to the storage capacitor 162 between the gate and the source of the TFT 163 is supplied to the light emitting element 164.

  A timing signal and a video signal are supplied from the display control unit 186 to these display driving devices.

  In a display element having such a matrix configuration, when a minute foreign matter such as dust adheres to the laminated film of the organic EL light emitting element 189 during a process during the manufacture of the element, the pixel including the organic EL light emitting element 189 enters a short state. In this case, the current flowing through the organic EL light emitting element 189 becomes not only invalid, but the wiring to the TFT 163 and the light emitting element 164 generates heat, and the Joule heat promotes the deterioration of the element.

  Such pixel defects were detected using a CCD photodetector during the device manufacturing process. Even when a voltage and a current were applied, a pixel that was 1/2 or less and substantially 0 cd / m 2 could be easily identified. After the organic film was formed, a part of the wiring circuit from the TFT 163 to the light emitting element 164 of the pixel 189 was cut off with a laser in a flame-supporting atmosphere. As a result, the reactive current of the non-lighting pixel composed of the organic EL light emitting element 163 and the heat generation of the wiring are not observed.

(Example 3)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the organic EL light emitting device used in this example will be described.

  8 and 20 are diagrams showing a configuration in which a laminated organic thin film is sandwiched between an anode and a cathode, 151 is a glass substrate, 152 is a transparent anode such as ITO, 153 is a hole transport layer, 154 is a light emitting layer, Reference numeral 155 denotes an electron transport layer, and 156 denotes a cathode. By applying a positive voltage to the anode 152 side and a negative voltage to the cathode 156 side, holes 158 passing through the hole transport layer 153 and electrons 159 passing through the electron transport layer 155 form excitons in the light emitting layer 154. Emits light upon recombination. These light emitting elements are arranged on a matrix as shown in the display unit 180 of FIG.

  In FIG. 7, reference numeral 180 denotes a display portion in which the light emitting elements 189 are arranged in a matrix. Further, the V shift register 182, the timing conversion circuit 183, the H shift register 185, and the latch 184 are provided on the same surface as the display portion 180, and a video signal is supplied to a thin film transistor (hereinafter abbreviated as TFT) provided in the light emitting element 189. And a scanning signal is supplied. A circuit in the pixel 189 is shown in FIG. FIG. 6 shows an example of a drive circuit having a function of compensating for variation in TFT characteristics of each pixel. Here, the light emitting element 173 emits light with a constant current.

The operation of this drive circuit will be described with reference to the timing chart of FIG. First, the luminance signal idata is set. Thereafter, Vg ₁ becomes low level and the P-channel TFT 174 is turned on. At the same time, Vg ₂ becomes high level, the N-channel TFT 175 is turned on, and the current of data flows between the source and the drain of the TFT 171, and the P-channel TFT 172 is turned off to block the current to the light emitting element 173. During this time, the capacitor 177 accumulates the gate voltage of the TFT 171 in which the current of data is passed between the source and the drain. Through the series of operations described above, the P-channel TFT 171 performs a constant current operation by copying data. Therefore, when the gate voltage of the P-channel TFT 12 is indicated by Vg ₂ in FIG. 11, when the TFT 172 is turned on, the same amount of current as that of data flows to cause the light emitting element 173 to emit light.

  In the display element having such a matrix configuration, the display unit 180 is damaged during the process of manufacturing the element, and the TFT 171 and the TFT 172 of the pixel driving circuit including the organic EL light emitting element 189 are short-circuited. In this case, the organic EL light emitting element 189 is always in a lighting state due to a current flowing from the power source. This current not only becomes ineffective, but the wiring from the TFT 171 to the light emitting element 173 generates heat, and the Joule heat promotes deterioration of the element.

  Such pixel defects were detected using a CCD photodetector during the device manufacturing process. It was possible to easily identify a pixel that was always lit when only the EL element was turned on without applying voltage or current. After the organic film was formed, a part of the wiring circuit from the TFT 171 to the light emitting element 173 of the pixel 189 was cut off with a laser in a flame-supporting atmosphere. As a result, the ineffective current of the always-lit pixel composed of the organic EL light emitting element 163 and the heat generation of the wiring are not observed.

Example 4
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, the structure of the organic EL light emitting device used in this example will be described.

  8 and 20 are diagrams showing a configuration in which a laminated organic thin film is sandwiched between an anode and a cathode, 151 is a glass substrate, 152 is a transparent anode such as ITO, 153 is a hole transport layer, 154 is a light emitting layer, Reference numeral 155 denotes an electron transport layer, and 156 denotes a cathode. By applying a positive voltage to the anode 152 side and a negative voltage to the cathode 156 side, holes 158 passing through the hole transport layer 153 and electrons 159 passing through the electron transport layer 155 form excitons in the light emitting layer 154. Emits light upon recombination. These light emitting elements are arranged on a matrix as shown in the display unit 180 of FIG.

  In FIG. 7, reference numeral 180 denotes a display portion in which the light emitting elements 189 are arranged in a matrix. Further, the V shift register 182, the timing conversion circuit 183, the H shift register 185, and the latch 184 are provided on the same surface as the display portion 180, and a video signal is supplied to a thin film transistor (hereinafter abbreviated as TFT) provided in the light emitting element 189. And a scanning signal is supplied. A circuit in the pixel 189 is shown in FIG. FIG. 6 shows an example of a drive circuit having a function of compensating for variation in TFT characteristics of each pixel. Here, the light emitting element 173 emits light with a constant current.

The operation of this drive circuit will be described with reference to the timing chart of FIG. First, the luminance signal idata is set. Thereafter, Vg ₁ becomes low level and the P-channel TFT 174 is turned on. At the same time, Vg ₂ becomes high level, the N-channel TFT 175 is turned on, and the current of data flows between the source and the drain of the TFT 171, and the P-channel TFT 172 is turned off to block the current to the light emitting element 173. During this time, the capacitor 177 accumulates the gate voltage of the TFT 171 to which the current of data is passed between the source and the drain. Through the series of operations described above, the P-channel TFT 171 performs a constant current operation by copying data. Therefore, when the gate voltage of the P-channel TFT 12 is indicated by Vg ₂ in FIG. 11, when the TFT 172 is turned on, the same amount of current as that of data flows to cause the light emitting element 173 to emit light.

  In the display element having such a matrix configuration, the display unit 180 is damaged during the process of manufacturing the element, and the TFT 171 and the TFT 172 of the pixel driving circuit including the organic EL light emitting element 189 are short-circuited. In this case, the organic EL light emitting element 189 is always in a lighting state due to a current flowing from the power source. This current not only becomes ineffective, but the wiring from the TFT 171 to the light emitting element 173 generates heat, and the Joule heat promotes deterioration of the element.

  A code corresponding to current 0 is always stored in the pixel memory 121 corresponding to the current control of the organic EL light emitting element 189 of the video memory 120 of FIG. As a result, the ineffective current of the always-lit pixel composed of the organic EL light emitting element 163 and the heat generation of the wiring are not observed.

The figure for demonstrating the manufacturing method of this invention. The figure which shows the non-lighting pixel by a short circuit. The figure which shows the heat_generation | fever of 4 non-lighting pixels by a short circuit. FIG. 6 is an example for explaining a method for driving a display element of the present invention. FIG. 6 is a diagram showing a configuration of a current driving circuit of an active matrix display element. It is a figure which shows the structure of the TFT correction | amendment type | mold current drive circuit of an active matrix type display element. The figure which shows the drive device of the conventional active matrix type display element. The figure which shows the structure of an organic electroluminescent light emitting element. The figure which shows the light emission principle of an organic electroluminescent light emitting element. The figure which shows a simple matrix type organic electroluminescent light emitting element. FIG. 5 is a diagram for explaining operation timing of a pixel circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container of flame support gas atmosphere 2 Detector 3 Laser 120 Video memory 121 Pixel memory 151 Glass substrate 152 Anode 153 Hole transport layer 154 Light emitting layer 155 Electron transport layer 156 Cathode 157 Power source 158 Hole 158 Electron 161 N-type TFT
162 Capacitor 163 P-type TFT
164 Light Emitting Element 171 P-type TFT
172 P-type TFT
173 Light-emitting element 174 P-type TFT
175 N-type TFT
180 Display Unit 182 V Shift Register 183 Timing Conversion Circuit 184 Latch 185 H Shift Register 186 Display Control Device 187 Controller 188 Timing Generator 220 Column Electrode 221 Row Electrode 220 Contact Electrode 230 Light Emitting Element

Claims (11)

  In a display element including an organic thin-film light emitting layer between a first electrode and a second electrode arranged in a matrix on a substrate, even if voltage or current application control is performed, / And a voltage or an electric current is interrupted | blocked with respect to the organic thin film light emitting layer of the pixel whose temperature is higher than the periphery. The manufacturing method of the display element characterized by the above-mentioned.   In a display element including an organic thin film light emitting layer between a first electrode and a second electrode arranged in a matrix on a substrate, an organic thin film of a pixel that emits light even when voltage or current is not applied and controlled A method for manufacturing a display element, wherein voltage or current is cut off from a light emitting layer. In the display element,
a. Means for detecting a pixel that is less than or equal to the amount of light of a normal pixel and / or has a higher temperature than the surroundings;
b. Means for applying a voltage between the first electrode and the second electrode of the pixel or cutting a part of a circuit for passing a current;
a. And b. 2. The method of manufacturing a display element according to claim 1, wherein a part of the circuit of the pixel is cut off using the means. In the display element,
c. Means for detecting pixels that emit light or / and have a higher temperature than the surroundings even when voltage and current application are not controlled;
d. Means for applying a voltage between the first electrode and the second electrode of the pixel or cutting a part of a circuit for passing a current;
c. And d. 3. The method of manufacturing a display element according to claim 2, wherein a part of the circuit of the pixel is cut off using the means.   b. And d. 3. The method of manufacturing a display element according to claim 1, wherein said means is used in a flame-supporting atmosphere and blocks a part of the circuit of the pixel.   In a display element including an organic thin-film light emitting layer between a first electrode and a second electrode arranged in a matrix on a substrate, even if voltage or current application control is performed, / And a method for driving a display element, wherein voltage or current is cut off from an organic thin film light emitting layer of a pixel whose temperature is higher than that of the periphery.   In a display element including an organic thin-film light emitting layer between a first electrode and a second electrode arranged in a matrix on a substrate, light is emitted even when voltage or current is not controlled, and / or from the periphery A method for driving a display element, wherein voltage or current is cut off from an organic thin film light emitting layer of a pixel having a high temperature. In the display element,
e. Means for measuring and determining the amount of light by a photodetector to detect a pixel below the light amount of a normal pixel or / and at a higher temperature than the surroundings;
f. Means for storing the position of the pixel;
g. Means for setting a video signal in which the voltage or current between the first electrode and the second electrode of the pixel is substantially zero;
e. And f. And / or g. The method of driving a display element according to claim 7, wherein the voltage or current of the pixel is made substantially zero using the means. In the display element,
h. Means for measuring and judging the amount of light by a photodetector to detect pixels that emit light without controlling voltage and current application;
i. Means for storing the position of the pixel;
j. Means for setting a video signal in which the voltage or current between the first electrode and the second electrode of the pixel is substantially zero;
h. And i. And / or j. 9. The method of driving a display element according to claim 8, wherein the voltage or current of the pixel is made substantially zero by using the means.   f. And i. 9. The display element driving method according to claim 7, wherein said means is stored as the pixel position in a storage device provided in the display element driving apparatus.   g. And j. 9. The display element driving method according to claim 7, wherein said means writes a value at which the voltage or current becomes substantially zero at the pixel position of the video memory of the driving device.

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