JPH0646347B2 - Active matrix substrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to an active matrix substrate used for an active matrix type liquid crystal display or the like.

(Prior Art) Conventionally, as a transistor array used for this purpose, for example, Japanese Patent Application No. 59-47623 (Japanese Patent Application Laid-Open No. 60-62623)
The configuration as shown in Japanese Patent Laid-Open No. 19236) is common. That is, as shown in FIG. 3, a thin film transistor (hereinafter referred to as a TFT) (11) having gate electrodes connected to the scanning lines X _{1 to} X _M and source electrodes connected to the signal lines Y ₁ to Y _N is provided, and its drain electrode is It is connected to the pixel electrode (26). A liquid crystal (13) is inserted between the picture element electrode (26) and the counter earth electrode to form an independent picture element (14). Where liquid crystal (1
3) equivalently acts as a capacitor, but in some cases an auxiliary capacitor may be added in parallel with it.

The transistor array having such a configuration operates as follows. That scan lines X _1, X _2, X _3, ... in the a than the fourth selection pulse P ₁ as shown in _{FIG, P 2, P 3 ... P} M is applied, respectively, for example, the scanning line X ₁ When in the selected state (all other scan lines are unselected), a series of
The source and drain of the TFT (11) become conductive, and the voltage of the signal line corresponding to each picture element (14) connected thereto is applied. When the scanning line X ₁ is switched to non-selection, the TFT (1
Since 1) is non-conductive, the voltage applied to the picture element (14) retains the previous value until the scanning line X ₁ is selected again in the next frame. As described above, a liquid crystal display using a TFT array can accurately and independently transmit a necessary signal voltage to each picture element, and therefore, it is possible to display with a large contrast ratio without crosstalk, which is attracting attention.

(Problems to be Solved by the Invention) However, in such a configuration, if the number of scanning lines and signal lines increases, it becomes extremely difficult to manufacture all the TFTs (11) as non-defective products. In particular, the TFT (11) is laminated between the gate (21) and the source (22) / drain (23) at least with the insulating film (24) interposed, as shown in FIG. Therefore, due to pinholes and other process troubles, the gate (21) and source (22) or the gate (21)
There is a risk of a short circuit between the drains (23). In particular, the gate (21) and source (23) short-circuit between the leads to abnormal operation of all of the TFT on the scan line X ₁ to X _M and the signal lines Y ₁ to Y _M connected thereto (11), a so-called line It causes serious defects such as defects. Further, when the drain (22) or the pixel electrode (26) is short-circuited with the gate or the source due to defective photolithography or the like, the liquid crystal cell does not hold a regular voltage and causes a point defect. As another important failure mode, the signal line Y and the scanning line X may be short-circuited at the intersection. This also causes line defects.

The present invention has been invented in view of the above problems, and even if some transistors are defective, even if some of the intersections of the scanning lines and the signal lines cause a short circuit defect, they are line defects or points. It is an object of the present invention to provide an active matrix substrate in which a pixel defect due to a defect does not occur.

(Means for Solving Problems) That is, in order to solve the above problems, the present invention firstly
First, at least two transistors are prepared for one pixel electrode, secondly, the scanning line is branched into two at the intersection of the signal line and the scanning line, and thirdly, the two transistors are scanned by the above-mentioned scanning. It is characterized in that the line is arranged in a branched portion so that the scanning line branching portion in which a short circuit has occurred can be separated from the scanning line and the pixel electrode when a short circuit occurs at an intersection or a transistor.

(Operation) As described above, according to the present invention, first, the charging path to one picture element corresponding to one signal line and one scanning line is not simply one transistor as in the conventional case but two or more transistors. Since it is configured with two charging paths, even if any of these transistors is defective, if the defective transistor is cut off from the pixel electrode and the scanning line, the pixel is charged by the remaining charging path. Therefore, the above-mentioned line defect and point defect cannot be achieved. Next, since the scanning line is branched into two at the intersection of the signal line and the scanning line, even if one of the intersections is short-circuited, if the short-circuited branch is cut off from the main scanning line, This too does not lead to defects. Further, since the two transistors are respectively arranged at the branching portions of the scanning line, their drain electrodes can be made common, the effective area of the pixel (aperture ratio) can be increased, and the separation / cutting processing can be performed when a defect occurs. The work can be concentrated in one place, and the efficiency of restoration is improved.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a layout diagram of the present invention, and FIG. 2 is an equivalent circuit diagram thereof, and the configuration and effect of the present invention will be described with reference to both drawings. The layout of FIG. 1 is based on the sectional structure of FIG. Now, at the intersection of the scanning line X _i and the signal line Y _j ,
The scan line X _i is branched into two. As a result, two intersections (2
You can do 8a) and (28b). Two transistors (11a) and (11b), which are both controlled by the scanning line X _i , are arranged in this branch portion.
The first transistor (11a) connects the signal line Y _j and the picture element C _{i, j} , and the second transistor (11 b) connects the signal line Y _j and the adjacent picture element C _{i + 1, j} . Further, in this embodiment, a third transistor (11c) controlled by the scanning line X _i is added. This connects the adjacent (i + j) and the picture element C _{i + j, j} . First, the operation when the third transistor (11c) does not exist will be described. The operating voltage waveforms applied to the scanning lines X and the signal lines Y may be exactly the same as those of the conventional example as shown in FIG. The picture element C _{i, j} is first set at the timing when the scanning line X _i -1 is selected.
For example, the voltage V _{j
Charged to i-1, j} . The voltage V _{i-1, j} is a voltage to be applied to the picture element C _{i-1, j} . Scan line X _i at the next timing
Is selected, the pixel C _{i, j} receives new information from the signal line Y _j through the transistor (11a) and receives a new voltage V _{i, j.}
Will be charged. After that, the pixel C _{i, j} holds the voltage V _{i, j} until the scanning line X _i-1 is selected again in the next frame. That is, since the picture element C _{i, j} holds the voltage V _{i, j} for most of the frame period, the liquid crystal operates according to the signal originally applied to the picture element, and the presence of the transistor (11d). Hardly affected by. If the transistor (11a) malfunctions for some reason, the transistor (11a) is cut off from the scanning line X _i and the pixel C _{i, j} . At this time, the picture element C _{i, j} has a voltage V
_{i-1, j} , that is, the voltage to be originally applied to the picture elements C _{i-1, j} is held. Therefore, picture element C _{i, j} is a transistor (11a)
Even if the pixel becomes defective, it does not become a pixel defect, and works by receiving the information of the adjacent pixel. At least when displaying an image, the correlation between information between adjacent picture elements is so strong that the picture element C _{i, j} is hardly recognized as a defect. Then the third transistor
The effect of (11c) will be described. In the example above, the transistor
When (11a) is cut off, the pixel C _{i, j} is charged with only the voltage V _{i-1, j,} but if the transistor (11c) is present, the transistor (11b) is selected at the timing when the scanning line Xi is selected. )When
(11c) becomes conductive, and the picture element C _{i, j} is adjacent to the picture element C _{i + 1, j}
At the same time, the information of the voltage V _{i, j} can be received from the signal line. Therefore, in this case, even if the transistor (11a) is defective, the picture element C _{i, j} operates at the original voltage V _{i, j} , and a completely normal display can be performed. Three transistors relating to the picture element C _i, the charge of _j as can be seen from the above description (1
Even if any one of 1a), (11b), and (11c) is defective, the pixel defect can be prevented.

(Effects of the Invention) As described above, the active matrix substrate according to the present invention is characterized in that the branching of the scanning lines and the increase in the number of transistors per picture element are combined to take advantage of the respective characteristics and generate new effects. Therefore, the effect of increasing the number of transistors is as described above, and the effect of branching the scanning line is to relieve a short circuit between the scanning line and the signal line. The effect produced when the two are combined is that, firstly, the drain lead-out portions of the two transistors can be made common, so that the area occupied by the transistors can be reduced and the pixel aperture ratio can be improved. Is. Secondly, the scanning line is branched at the intersection of the scanning line and the signal line, and the two transistors arranged at the branching portion can be positioned close to each other. That is, the efficiency of the repair process for separating the defective portion from the other is improved.

As described in detail above, the present invention can remarkably improve the yield of the active matrix substrate with a simple structure, and its practical value is very high.

[Brief description of drawings]

1 is a layout diagram of an active matrix substrate according to the present invention, FIG. 2 is an equivalent circuit diagram of FIG. 1, FIG. 3 is a conventional equivalent circuit diagram, FIG. 4 is a waveform applied to a scanning line, and FIG. [FIG. 3] is a cross-sectional view of a transistor. (11). (11a). (11b). (11c). (11d). (11e) …… thin film transistor, (13) …… liquid crystal, (14) …… picture element, (22) …… drain, (23) …… source, (25) …… semiconductor film, (26) ……
Pixel electrode, (28a). (28b) …… The intersection of the scanning line and the signal line.

Claims (3)

[Claims] 1. A plurality of scanning lines X and signal lines Y, one pixel electrode provided at each intersection of each scanning line X and signal line Y, and at least a first pixel electrode controlled by the scanning line X. And the second
The first transistor connects the signal line Y and one pixel electrode A, and the second transistor connects the signal line Y and the pixel electrode A to the scanning line X.
Each scan line X is branched at the intersection, and is connected to another pixel electrode B adjacent to each other by sandwiching
An active matrix substrate characterized in that the two transistors are respectively arranged at the branches. 2. A transistor arranged at the intersection and the branching portion, when a signal line-scanning line short-circuiting defect occurs, the shorted scanning line branching portion can be separated from the scanning line and the pixel. The active matrix substrate according to claim 1, which is characterized by the above-mentioned. 3. A scanning line arranged at a branching portion of the scanning line.
The active matrix substrate according to claim 1, wherein the drain electrode lead-out portions of the two transistors are common.