JP2004191603A - Display device, and method for inspecting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active matrix type EL display device capable of confirming the operation of a TFT substrate before the film formation of an EL material, thereby improving the non-defectiveness of finished products and reducing its cost. <P>SOLUTION: A switch is provided on the tip of a pixel electrode connected to a driving TFT in a pixel part, and an inspecting wiring is connected the tip of the switch. In the inspection, the switch is turned ON, and the potential of the pixel electrode or a current value supplied to the pixel electrode is confirmed through the inspecting wiring, thereby confirming that the pixel is normally operating. Thus, it is possible to remove defective products before the EL film formation to reduce the manufacturing cost. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electronic display (electro-optical device) formed by forming a light emitting element on a substrate. In particular, the present invention relates to a display device using a semiconductor element (an element using a semiconductor thin film). Further, the present invention relates to an electronic device in which a display device using a light-emitting element is used for a display portion. Further, the present invention relates to a method for inspecting a display device using a light-emitting element.
[0002]
[Prior art]
In recent years, a technique for forming a thin film transistor (hereinafter, referred to as a TFT) on a substrate has been greatly advanced, and application development to an active matrix display device has been advanced. In particular, a TFT using a polysilicon film has higher field-effect mobility (also referred to as mobility) than a TFT using a conventional amorphous silicon film, and thus can operate at high speed. Therefore, the control of the pixels, which has been conventionally performed by the driving circuit outside the substrate, can be performed by the driving circuit formed on the same substrate.
[0003]
Such an active matrix type display device has various advantages such as manufacturing cost reduction, miniaturization of display device, increase in yield, and reduction in throughput by forming various circuits and elements on the same substrate. Can be
[0004]
Further, active matrix EL display devices having EL elements as self-luminous elements have been actively studied. An EL display device is also called an organic EL display (OELD: Organic EL Display) or an organic light emitting diode (OLED: Organic Light Emitting Diode).
[0005]
Generally, the current value flowing through the EL element and the luminance of the EL element are in a proportional relationship. For this reason, a pixel configuration different from an LCD that controls luminance by a voltage value has been proposed (see Patent Document 1).
[0006]
By the way, in a display device in which pixels are arranged in a matrix, some trouble such as disconnection or short circuit of wiring may occur in a manufacturing process. Therefore, electrical inspection is often performed during the manufacturing process (see Patent Document 2).
[0007]
[Patent Document 1]
International Publication No. 01/06484 pamphlet [Patent Document 2]
Patent No. 2618042 Specification [0008]
[Problems to be solved by the invention]
In a conventional EL display device, as shown in FIG. 4, one of a source / drain terminal of a driving TFT 400 in a pixel portion is connected to a power supply line 401, and the other terminal (pixel electrode) is connected to a light emitting element 402. Was only being done.
[0009]
Here, pixel TFTs (switching TFTs and driving TFTs) and TFTs forming driving circuits (a source signal line driving circuit and a gate signal line driving circuit) are formed over a substrate having an insulating surface. A material is formed into a film, and the driving TFT and the EL element are electrically connected.
[0010]
Therefore, in the conventional display device, before the EL material is formed, the terminal (pixel electrode) of the source / drain terminal of the driving TFT which is not connected to the power supply line is open on the circuit. It is in a state. Until an EL material is formed, a display device is completed, and a lighting test is performed, it is difficult to determine whether the driving TFT operates normally. Therefore, even if there is an abnormality in the driving TFT or a terminal portion on which the light emitting element before the driving TFT is formed and a display cannot be performed normally, it is not possible to detect until the final process, resulting in waste of the process. I was letting it.
[0011]
As described above, in the conventional EL display device, in the pre-process of forming the EL material, no abnormality can be confirmed in the driving TFT or the pixel electrode before the driving TFT, and unnecessary manufacturing cost is generated. Was.
[0012]
The present invention has been made in view of the above problems, and it is possible to provide an active matrix display device that can detect whether or not the entire display device including a pixel circuit operates normally before forming a light emitting element. As an issue.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, the inventor of the present invention inspects whether a display device including a pixel circuit operates normally before forming an EL material. It was conceived to reduce the manufacturing cost by not proceeding to the material film formation process.
[0014]
Note that in this specification, an electroluminescence (EL) element may be described as an example of a light-emitting element; however, a light-emitting element is not limited to an EL element, and a voltage may be applied to an electrode or a current may be applied. Any element may be used as long as the display state changes when the element flows. An EL element refers to both an element utilizing light emission (fluorescence) from a singlet excitation element and an element utilizing light emission (phosphorescence) from a triplet excitation element.
[0015]
According to the present invention, in an active matrix EL display device in which pixels are arranged in a matrix on a substrate, one of source and drain terminals of a driving TFT of each pixel is electrically connected to a power supply line, and the other is a switch. Is connected, and the inspection wiring is drawn out of the substrate via the switch.
[0016]
In the EL display device, all the switches may be simultaneously opened and closed, and terminals for controlling the switches are all connected to the same terminal, and a signal is input from outside the substrate. .
[0017]
The inspection wiring connected to the driving TFT via the switch may be shared with the wiring used in the pixel.
The inspection wiring connected to the driving TFT via the switch is such that the display device is a color display, and the power supply lines in the pixels are different for each color. And may be shared.
[0019]
According to the present invention, in the active matrix EL display device manufactured on the substrate, before operating the light emitting element, when operating one pixel at a time, the amount of current or voltage flowing through the switch is reduced. By detecting this, a defect such as a characteristic abnormality of the driving TFT, a patterning defect in a process before the light emitting element is formed, or a defect between the pixel electrode and the power supply line or the source signal line due to dust generated in the process. A method is provided for inspecting all pixels for the presence or absence of a defect such as a short circuit.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the structure of the display device of the present invention and the inspection method thereof will be described. Note that the type of a transistor used for a display device in the present invention is not limited. For example, any of a MOS transistor, an amorphous silicon TFT, a polysilicon TFT, a molecular transistor, an organic transistor, and a bipolar transistor may be used. In the case of a TFT, the structure does not need to be limited. For example, a TFT of a planar type or an inverted stagger type may be used. The polarity of the transistor is not limited, and either an N-type transistor or a P-type transistor may be used.
[0021]
The switch used for the display device in the present invention has a state where current flows between two terminals and a state where current does not flow. In the text, a flowing state is called ON, and a non-flowing state is called OFF. The two terminals are called a first terminal and a second terminal, respectively. A terminal for controlling ON and OFF is called a control terminal. However, the control terminal is not necessarily shown. The structure of the switch element is not particularly limited. For example, any of a MOS transistor, an amorphous silicon TFT, a polysilicon TFT, a molecular transistor, an organic transistor, and a bipolar transistor may be used.
Further, a known driving circuit may be used for the present invention.
[0022]
FIG. 1 shows an embodiment of the present invention. FIG. 1 shows a configuration of a pixel portion of a display device of the present invention.
[0023]
It comprises a power supply line 101, a driving TFT 100 used for driving the light emitting element, a light emitting element 102, a switch 103 used for switching between inspection and normal driving, an inspection wiring 104, and a counter electrode 105. In the inspection stage, the light emitting element 102 and the counter electrode 105 may not be provided.
[0024]
One of the source / drain terminals of the driving TFT 100 is connected to the power supply line 101, one electrode (hereinafter, referred to as a pixel electrode) of the light emitting element 102 is connected to the other terminal, and A counter electrode is connected to the other electrode, and a switch is connected between the pixel electrode and the inspection wiring. Nothing is connected to the terminal for controlling the switch in the figure, but any connection can be made as long as it can be switched between the time of inspection and the time of normal driving. Further, a terminal connected to the gate of the driving TFT is not shown in the drawing, but is not particularly limited, and differs depending on the configuration of the pixel.
[0025]
In FIG. 1, the power supply line and the driving TFT are directly connected. However, the two may be electrically connected, and a current controlling element or the like may be inserted between the two without directly connecting.
[0026]
Next, the operation of the present embodiment will be described with reference to FIG.
[0027]
First, when the panel normally operates, at this time, the switch 103 is turned off, the switch is turned off, and current does not flow. Then, the current flowing through the light emitting element is controlled by a signal input to the gate terminal of the driving TFT 100, and a gray scale is displayed. However, at this time, the driving method of the pixel does not matter. For example, a constant current driving method in which a constant current is controlled to flow through the light emitting element or a constant voltage driving method in which a constant voltage is controlled to apply to the light emitting element may be used.
[0028]
Next, the operation when inspecting the panel will be described. When the panel is inspected, the light-emitting element and the counter electrode may not be provided, and therefore, it is considered that they are not provided here. First, the switch 103 is turned on to make the switch conductive. Then, a signal is input to the pixel in the same manner as when the pixel normally operates, and the driving TFT 100 is operated. At this time, there is a light emitting element and a counter electrode, and if the switch 103 is turned off, the voltage or current value that should be applied to the light emitting element is applied to the light emitting element because the switch 103 conducts and there is no light emitting element and the counter electrode. The required voltage value or current value can be inspected through the inspection wiring. In the case of the constant voltage driving method, the voltage value may be inspected. In the case of the constant current driving method, the current value may be inspected.
[0029]
When the pixels are arranged in a matrix and the inspection wiring is shared with other pixels, all pixels except the one pixel to be inspected among the pixels sharing the inspection wiring are driven. The test TFT is turned off so that no current flows, and the driving TFT of one pixel to be inspected is driven and inspected, so that it is possible to inspect one pixel at a time and all the pixels are abnormal. Can be checked for
[0030]
FIG. 2 shows a specific example of the present embodiment.
[0031]
FIG. 2 shows a power supply line 201, a source signal line 206 for inputting a video signal to a pixel, a driving TFT 200 used for driving a light emitting element, a light emitting element 202, and a switch 203 used for switching between inspection and normal driving. , An inspection wiring 204, a counter electrode 205, a write gate signal line 207 to which a write gate signal is input, a capacitor 208 for holding a potential input by a video signal, and control of input of a video signal And a writing TFT 209. At the stage of inspection, the light emitting element 202 and the counter electrode 205 may not be provided.
[0032]
A writing gate signal line 207 is connected to a gate terminal of the writing TFT 209, a source signal line 206 is connected to one of source / drain terminals, a gate terminal of the driving TFT 200 is connected to the other, and a driving TFT 200 is connected. The power supply line 201 is connected to one of the source / drain terminals, the other electrode of the light emitting element 202 (hereinafter, referred to as a pixel electrode) is connected to the other, and the counter electrode 205 is connected to the other electrode of the light emitting element. The capacitor 208 is connected between the gate terminal of the driving TFT 200 and the power supply line 201, one terminal of the switch 203 is connected to the pixel electrode, and the inspection wiring 204 is connected to the other.
[0033]
Although a signal line for controlling the switch 203 is not illustrated here, an input method of the signal line for controlling the switch 203 is not limited. For example, the signal may be input in parallel with the source signal line or in parallel with the gate signal line.
[0034]
Although both the writing TFT 209 and the driving TFT 200 are written in a single gate structure, they may have a multi-gate structure in which two or more TFTs are connected in series, or a multi-channel structure in which two or more TFTs are connected in parallel.
[0035]
An operation and an inspection method in the pixel configuration of FIG. 2 will be described. The pixel configuration in FIG. 2 is obtained by adding a switch 203 and an inspection wiring 204 to the known configuration in FIG. For normal operation, the switch 203 is turned off to make the pixel electrode and the inspection wiring 204 non-conductive. The connection at this time is the same as that in FIG. 4, and a known driving method may be used. Next, the inspection method will be described. The light emitting element 202 and the counter electrode 205 are not provided, and the switch 203 is turned on to conduct the pixel electrode and the inspection wiring 204. Then, among the pixels sharing the inspection wiring, a video signal is input so that no current flows to the driving TFTs of all the pixels except the pixel to be inspected, and the light-emitting element and the counter electrode are applied to the pixel to be inspected. A video signal that emits light after input is input, and the driving TFT is driven. At this time, a voltage value applied to the inspection wiring from the pixel electrode via the switch 203 or a current value flowing through the inspection wiring is determined. An inspection is performed to check whether the pixel is normal.
[0036]
As shown in FIG. 3, the pixel may have a configuration in which an erasing TFT 311 and an erasing gate signal line 310 for controlling the erasing TFT are added between the power supply line and the gate terminal of the driving TFT.
[0037]
When the display device is a color display and has a plurality of types of power supply lines, as shown in FIG. 5, a configuration may be adopted in which the inspection wiring and the power supply line of the adjacent pixel are shared. As described above, when the power supply line and the inspection line are shared, and if they are arranged as shown in FIG. 5, the inspection of the pixel connected to the middle green power supply line g in the three columns is performed. In this case, the power supply line r connected to the switch 503 in the pixel is used as a test wiring, and no power is supplied.
[0038]
Although not shown, when there are a plurality of types of power supply lines in color display, the inspection wiring and the power supply lines of adjacent pixels may be shared in the circuit configuration of the pixel in FIG.
[0039]
【Example】
Hereinafter, examples of the present invention will be described.
[0040]
[Example 1]
In this example, among the configurations of the display device described in the embodiment, a pixel configuration illustrated in FIG. 5 will be described. FIG. 6 illustrates a configuration example of a display device. A display portion 612 in which a plurality of pixels 613 are arranged in a matrix of m rows and n columns is provided over a substrate 611, and a signal line driver circuit 614 and a row selection line driver circuit 615 are provided around the display portion 612. are doing. The source signal lines 606 denoted by S1 to Sn are connected to the pixels 613 corresponding to the columns, and are connected to the signal line driver circuit 614. The write gate signal lines 607 denoted by G1 to Gm are connected to the pixels 613 corresponding to the rows, and are connected to the row selection circuit 615. The signal line driver circuit 614 and the row selection circuit 615 are connected to the FPC contact section 616. The three power supply lines 601r, 601g, 601b, and the switch drive signal line 617 are directly connected to the pixel from the FPC contact portion 615. Although a clock signal line and a power supply line actually exist, they are omitted here.
[0041]
When the semiconductor device is mounted on an electronic device as a display device and used, a flexible cable or the like is attached to the FPC contact portion 616 and connected to a power source or a signal source.
[0042]
When an inspection is performed during the manufacturing process, a contact probe 621 including a plurality of needles is brought into contact with the FPC contact portion 316, and is electrically connected to the inspection device 622. The inspection device 622 includes an external drive circuit 623 and a measurement device 624. The external drive circuit 623 supplies power and signals to the semiconductor device to be inspected. The measuring device 624 measures a voltage value or a current value of a power supply line used as a test wiring. From the measurement result, it is checked whether each pixel is operating normally.
[0043]
[Example 2]
As an electronic device using the display device of the present invention, a video camera, a digital camera, a goggle-type display (head-mounted display), a navigation system, a sound reproducing device (car audio, audio component, etc.), a notebook personal computer, a game device, A portable information terminal (mobile computer, mobile phone, portable game machine or electronic book, etc.), an image reproducing apparatus equipped with a recording medium (specifically, a recording medium such as a digital versatile disc (DVD) is reproduced, and the image is reproduced. Device equipped with a display capable of displaying). In particular, it is desirable to use a self-luminous display device for a portable information terminal in which a screen is often viewed from an oblique direction, since a wide viewing angle is important. FIG. 7 shows specific examples of these electronic devices. Note that the electronic device shown here is merely an example, and is not limited to these applications.
[0044]
FIG. 7A illustrates a display, which includes a housing 2001, a support base 2002, a display portion 2003, a speaker portion 2004, a video input terminal 2005, and the like. The display device of the present invention can be used for the display portion 2003. According to the present invention, the display shown in FIG. 7A is completed. Since the display device of the present invention is a self-luminous type, it does not require a backlight and can be a display portion thinner than a liquid crystal display. The display includes all information display devices for personal computers, TV broadcast reception, advertisement display, and the like.
[0045]
FIG. 7B illustrates a digital still camera, which includes a main body 2101, a display portion 2102, an image receiving portion 2103, operation keys 2104, an external connection port 2105, a shutter 2106, and the like. The display device of the present invention can be used for the display portion 2102. According to the present invention, a digital still camera shown in FIG. 7B is completed.
[0046]
FIG. 7C illustrates a laptop personal computer, which includes a main body 2201, a housing 2202, a display portion 2203, a keyboard 2204, an external connection port 2205, a pointing mouse 2206, and the like. The display device of the present invention can be used for the display portion 2203. According to the present invention, a notebook personal computer shown in FIG. 7C is completed.
[0047]
FIG. 7D illustrates a mobile computer, which includes a main body 2301, a display portion 2302, a switch 2303, operation keys 2304, an infrared port 2305, and the like. The display device of the present invention can be used for the display portion 2302. According to the present invention, the mobile computer shown in FIG. 7D is completed.
[0048]
FIG. 7E illustrates a portable image reproducing device (specifically, a DVD reproducing device) including a recording medium, which includes a main body 2401, a housing 2402, a display portion A 2403, a display portion B 2404, and a recording medium (such as a DVD). A reading unit 2405, operation keys 2406, a speaker unit 2407, and the like are included. The display portion A 2403 mainly displays image information, and the display portion B 2404 mainly displays character information. The display device of the present invention can be used for these display portions A, B 2403, and 2404. Note that the image reproducing device provided with the recording medium includes a home game machine and the like. According to the present invention, the DVD reproducing device shown in FIG. 7E is completed.
[0049]
FIG. 7F illustrates a goggle-type display (head-mounted display), which includes a main body 2501, a display portion 2502, and an arm portion 2503. The display device of the present invention can be used for the display portion 2502. Further, according to the present invention, the goggle type display shown in FIG. 7F is completed.
[0050]
FIG. 7G illustrates a video camera, which includes a main body 2601, a display portion 2602, a housing 2603, an external connection port 2604, a remote control receiving portion 2605, an image receiving portion 2606, a battery 2607, a voice input portion 2608, operation keys 2609, and the like. . The display device of the present invention can be used for the display portion 2602. According to the present invention, the video camera shown in FIG. 7G is completed.
[0051]
Here, FIG. 7H illustrates a mobile phone, which includes a main body 2701, a housing 2702, a display portion 2703, a sound input portion 2704, a sound output portion 2705, operation keys 2706, an external connection port 2707, an antenna 2708, and the like. The display device of the present invention can be used for the display portion 2703. Note that the display portion 2703 can display white characters on a black background to reduce current consumption of the mobile phone. According to the present invention, the mobile phone shown in FIG. 7H is completed.
[0052]
If the light emission luminance of the light emitting material increases in the future, the light including the output image information can be enlarged and projected by a lens or the like and used for a front-type or rear-type projector.
[0053]
In addition, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the response speed of the light-emitting material is extremely high, the display device of the present invention is preferable for displaying moving images.
[0054]
Further, in the display device of the present invention, since the light emitting portion consumes power, it is desirable to display information so that the light emitting portion is reduced as much as possible. Therefore, when a display device is used for a portable information terminal, particularly a display portion mainly for character information such as a mobile phone or a sound reproducing device, the display device is driven so that character information is formed by a light emitting portion with a non-light emitting portion as a background. It is desirable to do.
[0055]
As described above, the applicable range of the present invention is extremely wide, and the present invention can be used for electronic devices in all fields. Further, the electronic apparatus of the present embodiment can use the configuration shown in the first embodiment.
【The invention's effect】
According to the present invention, it is possible to easily inspect whether all the pixel circuits operate normally. Thus, the defective product can be removed before the light emitting element is formed, and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of a pixel portion of the present invention.
FIG. 2 is a diagram showing a circuit configuration of a pixel portion of the present invention.
FIG. 3 is a diagram showing a circuit configuration of a pixel portion of the present invention.
FIG. 4 is a diagram showing a circuit configuration of a conventional pixel portion.
FIG. 5 is a diagram showing a circuit configuration of a pixel portion of the present invention.
FIG. 6 is a diagram showing an embodiment of the present invention.
FIG. 7 illustrates an example of an electronic device to which the present invention can be applied.

Claims (9)

In a display device in which a plurality of pixels are arranged in matrix on a substrate, each of the plurality of pixels includes a transistor, a switch, and a light-emitting element, and a first wiring is electrically connected to a first terminal of the transistor. Connected, a first terminal of the switch is connected to a second terminal, a first terminal of the switch is electrically connected to a second wiring, and the light emitting element is connected to a second terminal of the transistor. A display device, which is connected. 2. The display device according to claim 1, wherein the first wiring is a power supply line, and the second wiring is an inspection wiring and is connected to an inspection terminal at an end of the substrate. The display device according to claim 1, wherein the first wiring is a power supply line, and the second wiring is shared with a power supply line of an adjacent pixel different from the first wiring. In a display device in which a plurality of pixels are arranged in a matrix on a substrate, each of the plurality of pixels includes a first transistor, a second transistor, a light-emitting element, a capacitor, a switch, a power supply line, a source signal line, It has an inspection wiring and a gate signal line, the gate signal line is connected to a gate terminal of the first transistor, the source signal line is connected to one of a source / drain terminal of the first transistor, and the other Is connected to the gate terminal of the second transistor, one of the source and drain terminals of the second transistor is connected to the power supply line, the other is connected to the light emitting element, the gate of the second transistor The capacitor is formed between a terminal and the power supply line, and the power supply is selected from among source / drain terminals of the second transistor. To the side not connected to the feed line terminal, said switch being connected to the opposite terminal of the switch, the display device, wherein the inspection wire is connected. In a display device in which a plurality of pixels are arranged in a matrix on a substrate, each of the plurality of pixels includes a first transistor, a second transistor, a light-emitting element, a capacitor, a switch, a power supply line, a source signal line, Inspection wiring, a first gate signal line, a second gate signal line, a third transistor, the first gate signal line is connected to the gate terminal of the first transistor, the first The source signal line is connected to one of the source / drain terminals of the transistor, one of the source / drain terminals of the second transistor is connected to the other, and the second gate is connected to the gate terminal of the second transistor. A signal line is connected, and the source / drain terminal of the second transistor is connected to both the source / drain terminal of the first transistor. The power supply line is connected to a terminal that is not connected, and of the source and drain terminals of the first transistor, the terminal on the side not connected to the source signal line and the source and drain of the second transistor. Of the terminals, a gate terminal of the third transistor is connected to a connection portion with a terminal not connected to the power supply line, and one of a source / drain terminal of the third transistor is connected to the power supply line. And the other is connected to the light emitting element, the capacitor is formed between the gate terminal of the third transistor and the power supply line, and among the source and drain terminals of the third transistor, The switch is connected to a terminal not connected to the power supply line, and the inspection wiring is connected to the other of the switches. Display devices. 6. The display device according to claim 4, wherein the inspection wiring is shared with a power supply line of an adjacent pixel. 7. The display device according to claim 1, wherein the transistor is a polysilicon TFT. In a display device in which a plurality of pixels are arranged in a matrix on a substrate, each of the plurality of pixels includes a transistor, a switch, and a light-emitting element, and the first wiring is electrically connected to a first terminal of the transistor. Connected to the first terminal of the switch to the second terminal, electrically connected the first terminal of the switch and the second wiring, the second terminal of the transistor In the display device, wherein a light-emitting element is connected, the switch is closed and turned on, a voltage is supplied to the power supply line, and a signal is input to the transistor, a voltage value of the second wiring, Alternatively, a method of inspecting a display device, comprising reading a current value supplied to the second wiring and inspecting whether a pixel operates normally. An electronic apparatus using the display device according to any one of claims 1 to 7.

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