JPH06118909A - Active matrix display device and method for detecting defective drive transistor - Google Patents

Abstract

(57) [Abstract] [Purpose] An active matrix display device and a failed drive transistor capable of realizing high-quality display without display defects even when the drive transistor of each pixel constituting the active matrix display device fails. An object of the present invention is to provide a detection method that can be easily detected. [Structure] Each pixel has two electrodes, the drains of drive transistors independent of each other are connected to each display electrode, the source of each drive transistor is connected to a data electrode, and the gate is connected to a scan electrode. The source / drain of the third drive transistor whose gate is connected to the next scan electrode is connected to the display electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type display device and an improved method for detecting a defective drive transistor. In particular, even if the drive transistor of each pixel forming the active matrix display device fails, it is possible to easily detect the active matrix display device and the failed drive transistor that can realize high-quality display without display defects. And an improvement aimed at providing a detection method.

[0002]

2. Description of the Related Art In recent years, an active matrix type color liquid crystal display device having excellent image quality has been commercialized, and in the future, there is a demand for a color liquid crystal display device having higher definition.

By the way, in a high-definition active matrix type display device for color display, the number of pixels is 1280 × 3.
Since it is (R, G, B) x 1024, it is almost impossible to make about 4 million driving transistors for driving each of these pixels without defects. Therefore, various redundancy methods have been proposed for the active matrix circuit.

An active matrix type display device according to the prior art will be described below.

FIG. 4 is a main part explanatory view of a circuit configuration of a first example of an active matrix type display device according to the prior art.

Referring to FIG. 4, E10 is a display electrode of each pixel. Two drive transistors T connected in parallel to the display electrode E10
The drain of 10 · T11 is connected. The sources of the drive transistors T10 and T11 are connected to the data electrodes, and the gates are connected to the scan electrodes. One of the above two drive transistors has a preliminary purpose.

FIG. 5 is an explanatory view of the main part of the circuit configuration of the second example of the active matrix type display device according to the prior art.

See FIG. 5. In this example, one pixel is divided into two sub-pixels.
In the figure, E20 and E30 are display electrodes of divided sub-pixels. The drain of the drive transistor T20 or T30 is connected to the display electrode of each sub-pixel, the source of these drive transistors T20 and T30 is connected to the data electrode, and the gate is connected to the scan electrode.

[0009]

In the first example of the above active matrix type display device according to the prior art, when one of the drive transistors connected in parallel has a short circuit defect, the display defect of the pixel is However, since it cannot be determined which transistor is defective, it is impossible to separate the defective transistor to eliminate the display defect. In addition, in the second example of the active matrix display device according to the related art, when one of the drive transistors connected to each of the two sub-pixels is defective, the sub-pixel corresponding to the defective transistor is defective in display. Therefore, there is a drawback that perfect display cannot be realized in the display device.

An object of the present invention is to eliminate this drawback, and an active matrix which can realize a high quality display without display defects even when the drive transistor of each pixel constituting the active matrix type display device fails. (EN) Provided is a type display device and a detection method capable of easily detecting a defective drive transistor.

[0011]

The above object is achieved by the following active matrix type display device and the following method for detecting a defective drive transistor.

In the active matrix type display device, each pixel has two display electrodes (E1 and E2), and each display electrode (E1 and E2) has a drain of a driving transistor (T1 and T2) independent of each other. , The source of each drive transistor (T1 · T2) is connected to the data electrode,
The gate of each drive transistor (T1 .T2) is connected to the scan electrode, and the display electrode (E1 .E2) is connected to the source of the third drive transistor (T3) whose gate is connected to the next scan electrode. It is an active matrix type display device to which a drain is connected.

In the above structure, it is possible to provide voltage applying means for applying the voltage applied to the scan electrode and the voltage applied to the next scan electrode in an overlapping manner.

Further, a method of detecting a defective drive transistor is selected in advance by turning off all the drive transistors connected to the scan electrodes of the even (or odd) lines of the active matrix type display device. The drive transistor connected to the scan electrode of the odd (or even) line is turned on, and the presence or absence of the display defect of each pixel corresponding to the preselected odd (or even) line is inspected, The failure of the transistors corresponding to these pixels is detected, or all the driving transistors connected to the scan electrodes of the even (or odd) line of the active matrix type display device are turned off, and the odd (or The drive transistors connected to the scan electrodes of the even-numbered lines are sequentially turned on to turn on the odd-numbered (or even-numbered) lines. And inspected for display defects of each pixel corresponding to down, a detection method for detecting a failure of the corresponding transistors to these pixels.

[0015]

In the active matrix type display device according to the present invention, the two display electrodes E1 and E2 of each pixel are connected to the data electrode through the mutually independent drive transistors T1 and T2. Since the source / drain of the third driving transistor T3 whose gate is connected to the next scanning electrode is connected to the electrodes E1 and E2, if either of the driving transistors T1 and T2 is a defective transistor, This defective transistor, eg T
Even if 1 is disconnected, the third drive transistor T3
By turning on a healthy transistor, eg T2
Since the voltage of the display electrode E2 connected to is applied to the display electrode E1 via the third drive transistor T3,
The pixels of the display electrodes E1 and E2 can display normally.

Further, the above-mentioned third drive transistor T3
Is a defective transistor, if it is an open defect, the driving transistors T1 and T2 connected to the display electrodes E1 and E2 operate independently of each other, and the pixel displays normally, and the driving transistor T3 If is a short-circuit defect, the pixel will display normally if the defective transistor T3 is cut off.

Further, in the method of detecting a defective drive transistor according to the present invention, all the drive transistors connected to the scan electrodes of the even (or odd) lines are turned off and the odd (or even) drive transistors are turned off. Since the drive transistor connected to the scan electrode of the th line is turned on, the two sub-pixels forming each pixel corresponding to the odd (or even) line are driven by the drive transistors T1 and T2. Driven independently. Therefore, for example, when the drive transistor T1 is defective, the sub-pixel of the display electrode E1 connected to this transistor T1 has a defective display, so that the defective transistor can be easily detected.

In addition, the above-mentioned third drive transistor T3
Is a short-circuit defect, an abnormal voltage is applied to the display electrodes E1 and E2, so that the display electrode E1 pixel and the display electrode E2 pixel both display defects.
It is possible to discriminate the failure of the driving transistor T3.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An active matrix type display device according to an embodiment of the present invention and a method of detecting a defective drive transistor will be described below with reference to the drawings.

FIG. 1 is an explanatory view of a main part of a circuit configuration of an active matrix type display device according to an embodiment of the present invention.

In FIG. 1, E1 and E2 are the display electrodes of each of the two sub-pixels forming one pixel. T1 is a drive transistor (for example, a TFT) whose drain is connected to the display electrode E1, the source is connected to the data electrode, and the gate is connected to the scan electrode. T2 is the drain connected to the display electrode E2 and the source. Is a drive transistor (eg, TFT) connected to the data electrode and the gate is connected to the scan electrode. T3 is a third driving transistor whose gate is connected to the next scanning electrode and whose source / drain are connected to the above-mentioned display electrodes E1 and E2.

Next, the operation of the active matrix type display device according to this embodiment will be described. FIG. 2 is a waveform diagram of the voltage applied to the gate of the drive transistor. (A) of the figure shows the voltage of the scan electrode of the Nth line to which the gates of the drive transistors T1 and T2 are connected, and (b) of the figure shows the scan of the (N + 1) th line to which the gate of the drive transistor T3 is connected. The voltage of the electrode. As shown in the figure, the voltage of the scan electrode on the Nth line and the voltage of the scan electrode on the N + 1th line overlap. Therefore, in the period t1, the transistors T1 and T2 are on and the transistor T3 is off. In the period t2, the transistors T1.T2.T3 are in the ON state. In the period t3, the transistors T1 and T2 are off and the transistor T3 is on. Therefore, for example, even if the driving transistor T1 is a defective transistor, the voltage applied to the display electrode E2 by the driving transistor T2 is the third driving transistor T3.
Since it is also applied to the display electrode E1 via the display, a normal display without display defects can be realized.

When the third drive transistor T3 has an open defect, the drive transistors T1 and T2 connected to the display electrodes E1 and E2 only operate independently of each other, and the pixel has a normal display. If the third drive transistor T3 has a short circuit defect, the defective transistor is detected by the following detection method, and if it is separated from the bus line / display electrode by a laser cutter or the like, the pixel displays normally.

Next, a method of detecting a defective drive transistor according to the present invention will be described. First, a non-selection voltage is applied to the scan electrodes of even (or odd) lines to turn off all the drive transistors connected to these scan electrodes. Then odd (or even)
For the second line, the selection voltage is applied by simultaneously applying the selection voltage to the scan electrodes of the preselected line or sequentially applying the selection voltage to the scan electrodes of the odd (or even) lines. The drive transistor connected to the scan electrode of the selected line is turned on. For example, when the driving transistor T1 is defective and the driving transistor T2 is normal, the pixels of the display electrode E2 display normally corresponding to the data voltage, but the pixels of the display electrode E1 display defective and the pixels of the display electrode E2 are displayed. Since the display is different from the display of the pixel, the defective drive transistor can be easily detected. If the third drive transistor T3 has a short circuit defect, an abnormal voltage is applied to the display electrodes E1 and E2, so that the pixel of the display electrode E1 and the pixel of the display electrode E2 are both defective. Therefore, it is possible to determine the failure of the third drive transistor T3.

In FIG. 3, the non-selection voltage is applied to all the scan electrodes of the even-numbered lines to turn off all the drive transistors connected to these scan electrodes, and the scan electrodes of the odd-numbered lines are sequentially turned on. It is a figure which shows the scanning voltage waveform at the time of applying a selection voltage.

[0026]

As described above, in the active matrix type display device according to the present invention, each pixel has 2 pixels.
The display electrodes are connected to the drains of the drive transistors independent of each other, the sources of the drive transistors are connected to the data electrodes, and the gates are connected to the scan electrodes. The source / drain of the third drive transistor whose gate is connected to the next scan electrode is connected to each display electrode, and, for example, the voltage applied to the scan electrode and the voltage applied to the next scan electrode are overlapped. Since the driving transistor connected to each display electrode is defective, even if one of the driving transistors is a defective transistor, by turning on the third driving transistor, the other healthy transistor is turned on. The voltage of the connected display electrode is applied to the display electrode connected to one of the defective transistors via the third driving transistor. , The pixels of each display electrode is capable of both normal display.

Further, in the method of detecting a defective drive transistor according to the present invention, all the drive transistors connected to the scan electrodes of the even (or odd) line are turned off and the odd (or even) line is driven. Since the driving transistors connected to the scan electrodes of the preselected line of the lines are turned on at the same time, or the driving transistors connected to the scan electrodes of the odd (or even) number lines are turned on sequentially. , Two sub-pixels forming each pixel corresponding to the odd-numbered (or even-numbered) line are independently driven by respective drive transistors. Therefore, when one of the drive transistors is defective, the sub-pixel of the display electrode connected to this drive transistor has a defective display, and the defective transistor can be easily detected.

Therefore, according to the present invention, an active matrix type display device and a defective drive transistor which can realize high quality display without display defects even when the drive transistor of each pixel constituting the active matrix type display device fails. It is possible to provide a detection method that can be easily detected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part of a circuit configuration of an active matrix display device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a voltage applied to a gate of a driving transistor.

FIG. 3 is a waveform diagram of voltage applied to scan electrodes when a defective drive transistor is detected.

FIG. 4 is a circuit configuration diagram of a first example of an active matrix display device according to a conventional technique.

FIG. 5 is a circuit configuration diagram of a second example of an active matrix type display device according to a conventional technique.

[Explanation of symbols]

E1 / E2 display electrode (present invention) T1 / T2 drive transistor (present invention) T3 third drive transistor E10 / E20 / E30 display electrode (prior art) T10 / T11 / T20 / T30 drive transistor (prior art)

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Yoshioka 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (4)

[Claims] 1. Each pixel has two display electrodes (E1 and E2)
The display electrodes (E1 and E2) are connected to the drains of the drive transistors (T1 and T2) independent of each other, and the sources of the drive transistors (T1 and T2) are connected to the data electrodes and Transistor (T1 ・ T2)
Of the display electrode (E1.
E2) has a gate connected to the next scanning electrode
An active matrix type display device characterized in that the source and drain of a driving transistor (T3) of the above are connected. 2. The active matrix type display device according to claim 1, further comprising voltage applying means for applying the voltage applied to the scan electrode and the voltage applied to the next scan electrode in an overlapping manner. 3. A method of detecting a defective drive transistor for detecting a fault of a drive transistor of each pixel constituting the active matrix display device according to claim 1, wherein a scan electrode of an even (odd) line is used. All the connected driving transistors are turned off, and the driving transistors connected to the scan electrodes of the preselected odd (even) lines are turned on to correspond to the preselected odd (even) lines. A method of detecting a defective drive transistor, which comprises inspecting each pixel for a display defect and detecting a failure of a transistor corresponding to the pixel. 4. A method of detecting a defective drive transistor for detecting a fault of a drive transistor of each pixel constituting the active matrix type display device according to claim 1, wherein a scan electrode of an even (odd) line is used. All the connected drive transistors are turned off, the drive transistors connected to the scan electrodes of the odd (even) lines are sequentially turned on, and there is a display defect in each pixel corresponding to the odd (even) lines. Is detected to detect a failure of a transistor corresponding to the pixel, a method of detecting a defective drive transistor.