JPS61243487A - Active matrix substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an active matrix substrate used in active matrix liquid crystal displays and the like.

(Prior Art) Conventionally, a transistor array used for this purpose generally has a configuration as shown in, for example, Japanese Patent Laid-Open No. 59-47823. That is, as shown in FIG. 3, a thin film transistor (hereinafter referred to as TPT) (II) is provided, whose gate electrode is connected to the scanning line X+"X-, and whose source electrode is connected to the signal lines Y1 to YN. (
2B).

A liquid crystal (13) is inserted between this picture element electrode (26) and the counter ground electrode to constitute an independent picture element (14). Here, the liquid crystal (13) functions as a capacitor with equal restrictions, but depending on the case, an auxiliary capacitor may be added in parallel to it.

A transistor array having such a structure operates as follows. That is, scan lines! +, X1. X5, . . . are supplied with selection pulses P+, P! as shown in FIG. -'3...PM is applied to each of the series of TPTs (11) connected to it, for example, when scanning line x1 is in the selected state (all other scanning lines are not selected). The source and drain become conductive, and a voltage of a corresponding signal - is applied to each picture element (14) connected thereto. When the scanning line xl is switched to non-selection, the TPT (II) becomes non-conductive, so the voltage applied to the picture element (I4) remains unchanged until scanning l1iIX+ is selected again in the next frame. , retain the previous value. In this way, a liquid crystal display using a TFT array is attracting attention because it can transmit the necessary signal voltage to each picture element accurately and independently, allowing display with no crosstalk and a high contrast ratio.

(Problems to be Solved by the Invention) However, in such a configuration, as the number of running lines and signal lines increases, it becomes extremely difficult to manufacture all TFTs as good products. In particular, as shown in FIG. 5, which shows an example of the cross-sectional structure of the TFT (11), the gate (double) and the source (22)/drain (23) are stacked with at least an insulating film (20 interposed therebetween). Because of this, pinholes and other process problems may cause gate (20) and source (20)
2) or between the gate (21) and the drain (23). In particular, the gate (double)
A short circuit between the sources (23) is connected to the scan line X-
~x, 4 and all TPTs (o
), resulting in serious defects called line defects. In addition, if the drain (23) or pixel electrode (2B) is short-circuited with the gate or source due to poor photolithography, the liquid crystal cell will not maintain the normal voltage (which will cause a point defect. As a failure mode, there is a possibility that the signal line Y and the scanning line X may be short-circuited at the intersection thereof.This also causes a line defect.

The present invention was invented in view of the above problems, and even if some of the transistors are defective, even if some of the intersections of the scanning line and the signal line are short-circuited, they will not be affected by line defects. The object of the present invention is to provide a cutting matrix substrate that does not cause pixel defects based on point defects.

(Means for Solving the Problems) That is, in order to solve the above problems, the present invention firstly prepares at least two transistors for one picture element electrode, and secondly, prepares at least two transistors for one picture element electrode. The scanning line is branched into two at the intersection of the scanning lines, and thirdly, the above two transistors are arranged at the intersection of the scanning lines, so that a short circuit occurs when there is an intersection or a short circuit failure occurs in the transistor. The present invention is characterized in that it has a structure in which the scanning line branch portion can be separated from the scanning line and the picture element electrode.

(Function) As described above, the present invention first provides a charging path to one picture element corresponding to one signal line and one scanning line by using two or more transistors instead of just one transistor as in the conventional case. Since the structure has two charging paths, even if one of these transistors is defective, if the defective transistor is disconnected from the pixel electrode and scanning line, the pixel can be charged using the remaining charging path. Therefore, the above-mentioned line defects and point defects do not occur.

Next, at the intersection of the signal line and the scanning line, the scanning line is split into two, so even if either intersection is shorted, the shorted branch can be disconnected from the main scanning line. This is also not a defect. Furthermore, since the two transistors are arranged at the branching parts of the scanning lines, their drain electrodes can be shared, increasing the effective pixel area (aperture ratio), and also allowing separation and cutting in the event of a defect. The repair can be concentrated in one place, which improves the efficiency of the repair.

(Example) Hereinafter, one embodiment of the present invention will be described based on 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 effects of the present invention will be explained with reference to both figures. The layout diagram in FIG. 1 is based on the cross-sectional structure in FIG. 5. Now, at the intersection of the scanning line x1 and the signal line Yi, the scanning line x1 is branched into two. This allows two intersections (28a) and (28b) h<. Two transistors (
lla) and (jlb) are placed. The first transistor (11a) connects the signal line Yi and the picture elements C1, 2, and the second transistor (llb) connects the signal line Yj and the adjacent picture element Ci+l.
, i. Furthermore, in this embodiment, a third transistor (llc) controlled by the scanning line X is added.

This connects the adjacent picture elements C:+4 and C+ ringing. First, the operation when the third transistor (llc) is not present will be explained. The operating voltage waveforms applied to the scanning line X and the signal line Y may be exactly the same as in the conventional example shown in FIG. The picture element CH,; first receives information from the signal line Y> through a transistor (Ild) at the timing when the scanning line xI-1 is selected, and outputs a voltage, for example, V + -+ z J
is charged to. This voltage Vt-H.

λ is a voltage that should originally be applied to the picture element C1-1,; When scanning line X is selected at the next timing, picture element C
j and i receive new information from the signal line Yj through the transistor (lla) and are newly charged to a voltage V;,4. Thereafter, the picture element Ci, or the voltage vi, is held until the scanning line x knee 1 is selected again in the next frame.

In other words, for most of the frame period, the picture element C'*h holds the voltage V+;, so the liquid crystal operates according to the signal that should originally be applied to that picture element, and the transistor (l
ld) is hardly affected by the presence of ld). If the transistor (Ita) malfunctions for some reason, this transistor (Ia) should be connected to the scanning line X:
and picture element C5, ;

At this time, the picture element C'pk has a voltage of V, as can be seen from the previous explanation.
``r k s, that is, the voltage that should originally be applied to the picture element Ci-+, ; is held.Therefore, even if the transistor (lla) becomes defective in the picture element "x J", it will not become a picture element defect, It works by receiving information about neighboring pixels. At least when displaying an image, the correlation of information between adjacent picture elements is quite strong, so the picture element Ci, ↓ is hardly recognized as a defect. Next, the effect of the third transistor (Ilc) will be explained. In the previous example, when the transistor (lIa) is cut off, the picture elements C;, ; are charged only with the voltage V;
At the timing when 1 is selected, the transistors (llb) and (Ilc) become conductive, and the picture element C1, ; together with the adjacent picture element C: + + I) can receive the voltage Vi and the information from the signal line. I can do it. Therefore, in this case, even if the transistor (lla) is defective, the picture elements ci and j will operate at the original voltages v+ and J, and a completely normal display can be performed. ° As can be seen from the above explanation, there are three transistors (ll
a) Even if any one of (llb), (llc) is defective, picture element defects can be prevented.

(Effects of the Invention) As explained above, the active matrix substrate according to the present invention is characterized by combining the branching of scanning lines and the increase in the number of transistors per picture element, making the best use of each feature and generating new effects. The effect of increasing the number of transistors is as described in 1-, and the effect of branching the scanning lines is to relieve short circuits between the scanning lines and signal lines even if they occur. The effect that occurs when the two are combined is that firstly, the drain lead-out part of the two transistors can be made common, and therefore the area occupied by the transistor can be reduced, and the ratio between pixels can be improved. That's true. Second, the scanning line is branched at the intersection of the scanning line and the signal line, and the two transistors placed at the branch can be positioned close to each other, which makes it easier to identify the location of the defect when they are defective. This improves the efficiency of the repair process that separates defective parts from others.

As described in detail above, the present invention can significantly improve the yield of active matrix substrates with a simple configuration, and its practical value is extremely high.

[Brief explanation of the drawing]

Fig. 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. 5 is a cross-sectional view of a transistor. (11), (lla), (llb) 11C), (ll
d), (lle)--thin film transistor, ('13)
...Liquid crystal% (14)...Picture element, (22)...Drain, (23)...Source, (2S)...Semiconductor film, (28)...Picture element electrode, ( 28a), (28b)
...Intersection of scanning line and signal line. αυ(lla~11e)...Thin film transistor wire...
・Drain 伜...Source Figure 3

Claims (3)

[Claims] (1) a plurality of scanning lines X and signal lines Y, and one picture element electrode provided corresponding to each intersection of each scanning line X and signal line Y;
At least a first transistor and a second transistor are controlled by the scanning line X, and the first transistor is controlled by the signal line Y.
and one picture element electrode A, and the second transistor couples the signal line Y and another picture element electrode B adjacent to the picture element electrode A across the scanning line X. configured,
An active matrix substrate characterized in that each scanning line X is branched at the intersection, and the two transistors are disposed at each branch. (2) When a short-circuit between the signal line and the scanning line occurs in the transistors arranged at the intersection and the branch, the short-circuited scanning line branch can be separated from the scanning line and the picture element. An active matrix substrate according to claim 1. (3) The active matrix substrate according to claim 1, wherein the drain electrodes of the two transistors arranged at the branched portions of the scanning lines are made common.