JPH0646346B2 - 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. 60-1).
9236) is generally used. That is, as shown in FIG. 2, 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). Liquid crystal here (13)
Acts equivalently 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 is, the selection pulses P ₁ , P ₂ , P ₃ ... P _M as shown in FIG. ₃ are applied to the scanning lines X ₁ , X ₂ , X ₃ , ... X _M , respectively. _{When 1} is in the selected state (all other scan lines are unselected), the series of TFTs (11) connected to this becomes conductive between the source and drain, and corresponds to each picture element (14) connected to it. The voltage of the signal line to be applied is applied. When the scan line X ₁ is switched to non-selection, the TFT
Since (11) becomes 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. In this way, a liquid crystal display using a TFT array is capable of accurately and independently transmitting a required signal voltage to each picture element, so that it is possible to display with a high contrast ratio without crosstalk, which is drawing 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 electrode or the pixel electrode is short-circuited with the gate electrode or the source electrode due to defective photolithography or the like, the liquid crystal cell does not hold a regular voltage and causes a point defect.

The present invention has been made in view of the above problems, and provides an active matrix substrate that does not cause a pixel defect based on a line defect or a point defect even if some switching elements are defective. The purpose is to do.

(Means for Solving the Problems) That is, according to the present invention, a first switch element that connects each picture element (referred to as picture element A) to a signal line, a picture element A, and an adjacency adjacent to the picture element A. It is characterized in that a second switch element that is connected to the picture element B is provided, and the first and second switch elements are controlled by the same scanning line.

(Operation) With the above configuration, in the present invention, the first switch element simultaneously transmits information from the signal line to the picture elements A and B.
Focusing on the picture element A, the picture element A always has two charging paths from the signal line. Therefore, even if the switching element that constitutes the charging path happens to be defective, if the defective switching element is separated from the scanning line and the picture element, the operation of the picture element A is ensured by the remaining charging path, resulting in a picture element defect. Can be prevented.

As a method of adding the redundant circuit as described above, it is conceivable that transistors are simply added in parallel to the configuration of the conventional example, but in this case, even if a dot or line defect occurs, either transistor is defective. It is difficult to determine if there is and difficult to repair. Two scan lines and two per pixel
A configuration in which one transistor is provided and two transistors are controlled by different scanning lines is also conceivable, but in this case, the effective area ratio (aperture ratio) of the picture element is significantly reduced, which is not desirable.

(Example) Hereinafter, the Example of this invention is described based on drawing. The transistor used in this embodiment is not particularly limited, for example, the one whose sectional structure is shown in FIG. 4, and a MOS transistor or a thin film transistor can be used.
Further, as the selection pulse applied to the scanning line, the one shown in FIG. 3 can be used as in the conventional example. Now, the charging path from Y _j to the picture element C _{i, j in} Fig. 1 is the transistor (11a).
There are two direct routes, and an indirect route by transistors (11c) and (11d). The former is scan line X _i , the latter is scan line
It is controlled by X _i-1 . When both operate normally, the one selected later, that is, the voltage V _{i, j} charged through the direct path, controls the operation of the pixel C _{i, j} . This means that the operation is the same as before, and the existence of the transistors (11b) and (11c) does not affect the normal operation of the picture elements C _{i, j} .

Next, when the transistor (11a) is defective, the transistor (11a) and the transistor (11b) are simultaneously disconnected from the pixel C _{i, j} and the scanning line X _i or the signal line Y _j . In this way, the picture element C _{i, j} is scanned by the scanning line one timing before the original.
Voltage V through the indirect path when X _i-1 is selected
_It is charged with the voltage _{i-1, j} and held for one frame. Therefore, in this case, the picture element C _{i, j} operates with the same signal as the adjacent picture element C _{i-1, j,} and the transistor (11a)
Even if the pixel is defective, it does not lead to a pixel defect. If the probability that a transistor on a substrate becomes defective is P, the probability of occurrence of pixel defects is close to P in the conventional example. However, in the case of this embodiment according to the present invention, a pixel defect does not occur unless two transistors related to a specific pixel become defective at the same time, and the occurrence probability of the pixel defect is on the order of P × P. . P
Is generally much smaller than 1, so it is easy to understand that the yield improvement effect of the substrate is remarkable.

(Effects of the Invention) As described in detail above, the present invention has a simple configuration and causes pixel defects such as line defects and point defects even if some of the switch elements, which are constituent elements, are defective. Without such a situation, the yield of the active matrix substrate can be significantly improved, and its practical value is great.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an active matrix substrate according to the present invention, FIG. 2 is a circuit diagram of a conventional example, FIG. 3 is a voltage waveform diagram applied to a scanning line, and FIG. 4 is a sectional view of a thin film transistor. (11), (11a-d) …… transistor, (13) …… liquid crystal,
(14) …… Picture element, (22) …… Source, (23) …… Drain, (2
5) …… Semiconductor film, (26) …… Pixel electrode.

Claims (4)

[Claims] 1. A plurality of scanning lines X and signal lines Y, one pixel electrode A provided at each intersection of each scanning line X and signal line Y, and a first pixel line controlled by the scanning line X. And a second switch element, the first switch element connecting the signal line Y and the picture element electrode A, and the second switch element connecting the picture element electrode A and the adjacent picture element electrode B. An active matrix substrate characterized by the above. 2. The active matrix according to claim 1, wherein the terminal portions of the first and second switch elements are separable from the scanning lines, signal lines or picture element electrodes. substrate. 3. The first and second switch elements are MO
The active matrix substrate according to claim 1, wherein the active matrix substrate is formed by an S transistor. 4. The active matrix substrate according to claim 1, wherein the first and second switch elements are formed by thin film transistors.