JPS6120091A - Image display unit - 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 the Invention) The present invention relates to an active image display device that can achieve a high manufacturing yield even if defects occur during manufacturing.

(Prior Art) In recent years, active matrix type image display devices using display elements such as liquid crystal or electroluminescence have been developed.

FIG. 1 shows the configuration of a conventional active matrix type image display device. T21 and T
22 are field effect transistors, CIl, CI2. C2
]'! ; and C22 are display elements connected to the sources of the field effect transistors 1 to 1, respectively, and CC is a common electrode of the display elements. D old and DD2 are signal lines, which connect field effect transistors Tll, T21 and T, respectively.
I2. Connected to the drain of T22, SSI and SS
2 is a selection line, each of which is connected to a field effect transistor Tll.
, TI2 and the gates of T21 and T22. In other words, display cells (area surrounded by broken lines) each consisting of a field effect transistor and a display element are arranged in a matrix.

To perform a display, one of the selection lines SSI and SS2 is activated, and a display signal is applied to the signal lines CDI and DD2. The field effect transistor connected to the activated selection line becomes ON (conducting), and a display signal is applied to the display element via the ON field effect transistor, and the applied display signal becomes a high voltage. The display element displays brightness or darkness depending on whether it is (11) or low voltage ([4).

In such conventional image display devices, display elements and
There is only one route for applying display signals to the display element, and if any defect occurs in the selection line, signal line, or field effect transistor during manufacturing, the display signal will not be applied to the display element, making it impossible to display normally. This cannot be done and the product becomes defective. It should be noted that image display devices in recent years have become larger in area and have higher definition, and the probability of defects occurring during manufacturing is high, and conventional active matrix type image display devices have the drawback of low manufacturing yield.

(Object of the Invention) The present invention is characterized in that a plurality of routes are provided for applying display signals to a display element, and the plurality of routes are periodically switched.The purpose of the present invention is to improve the yield during manufacturing. It is in.

(Structure and operation of the invention) FIG. 2 is an embodiment showing the structure of a display cell of an active matrix type image display device according to the invention.

C1l is a display element, which is assumed to be a liquid crystal here. C
C is a common electrode of the liquid crystal, and TIIA and TIIB are field effect transistors whose sources are both connected to the display element C1l.
It is connected to the. The gate and drain of the field effect transistor T11A are connected to the selection line SIA and the signal line A, respectively, and the field effect transistor TIIB
Similarly, the gate and drain of each select line SIB
and is connected to the signal line DIR.

Next, its operation will be explained.

First, the selection line SIA is activated and a display signal is applied to the signal line SIA. As a result, the field effect transistor TIIA is turned on, and the display signal is applied to the display element C1l via the signal line (A route). Next, the selection line SEA is deactivated, SIB is activated, and a display signal is applied to the signal line front B.

As a result, field effect transistor TIIA is turned off.

Tl1n is turned on, and the display signal is applied to the display element CHI via the signal line l8 (route B). Repeat the above two application methods (A route, B route) periodically,
The display element C1l displays brightness and darkness depending on whether the display signal is a high voltage (T()) or a low voltage (L).

Next, the operation when a defect occurs in the signal line, selection line, and field effect transistor will be described.

First, a case will be described in which a defect occurs in which the signal line rllA is constantly at L. In this case, L is always applied to the display element in route A. On the other hand, in route B, the display signal is normally applied to the display element. At this time, if the display signal is L, the display element normally displays darkness. but,
When the display signal is H, high on the A route and I-1 on the B route are alternately applied to the display element. Whether the display element displays brightness or darkness in this state can be set by the threshold characteristics of the liquid crystal serving as the display element, the applied voltage, and the like. In this state, the display characteristics when displaying darkness are defined as AND characteristics, and the display characteristics when displaying brightness are defined as OR characteristics.

In the case of a defect in which the signal line is constantly at L as described above, the display can be performed normally if the display characteristic is set to the OR characteristic. Conversely, in the case of a defect where the signal line is constantly 11, the display can be performed normally by setting the display characteristic to the AND characteristic. Therefore, by setting the display characteristics to AND or OR characteristics in accordance with the mode in which many defects occur in the signal line, A.

Unless there is a defect in route B, the display is performed normally and the manufacturing yield can be improved.

Note that the far end of the signal line from the drive circuit is grounded (connected to the power supply) via a resistor or a field effect transistor with a clock pulse applied to the gate, so that if the wire is disconnected, it will not remain electrically floating and will remain steady. Therefore, it is possible to set r, (11). Therefore, if the display characteristics of the display element are changed to OR (AND) characteristics in response to this, the manufacturing yield will be greatly improved.

Next, a defect in which the selection line is constantly inactive or a defect in which the field effect transistor is constantly turned off will be explained. In this case, it is equivalent to the case where there is no route including the defect described in item 2. Therefore, by using the present invention, normal display can be performed without the above defects having any adverse effect on the display. Note that, similarly to the signal line, by grounding the far end of the selection line via a resistor or the like, it is possible to constantly deactivate the selection line in the event of a disconnection. Therefore, by using the present invention, the manufacturing yield of active matrix type image display devices can be greatly improved. Also, if you cut the defective route using a laser etc.
Manufacturing yields are further improved.

FIG. 3 shows an example in which the display cells shown in FIG. 2 are arranged in a matrix. CIl~C24 are display elements, TIIA-T24A and TIIB-T24B are field effect transistors, DIA-D4A and DAB-
D4B is a signal line, which is connected to the drains of the field effect transistors on the A side and B side, respectively, and connects SIA, S
2A, S1B, and 52Fl are selection lines connected to the gates of the A-side and B-side field effect transistors, respectively.

The operation of this embodiment is similar to that shown in FIG. First, select line SIA is activated, signal lines A-D4A and field effect transistors T11A, Tl2A, T13A, Tl4 are activated.
Display elements C11, C12, C1, 3, C14 via A
Apply a display signal to. Next, the selection line S2A is activated, and the signal lines A to D4A and the field effect transistor T are activated.
2] A display signal is applied to the display elements C2], C22, C23, and C24 via A, T22A, T23A, and T24A.

In this way, the display signal for one screen (frame) is applied to the display element via route A, and for the next screen, the display signal is similarly applied to the display element via route B, and so on.For odd frames, the display signal is applied to the display element via route A. , for even-numbered frames, display signals are alternately applied to the display elements using the B route. At this time, if the display characteristics of the display element are set to OR characteristics, defects such as the signal line being constantly inactivated, the selection line being constantly inactive, and the field effect transistor constantly being turned off may occur. Even if this occurs, the display will not be adversely affected in any way and normal display can be performed.

FIG. 4 shows an embodiment of the present invention in which the signal lines of adjacent display cells in FIG. 3 are shared.

D1 to D5 are connected to the drains of (field effect type transistors of adjacent display cells respectively on i-segment lines) transistors.

The operation of this embodiment is similar to that shown in FIG. 3, except that the same signal line is used for both the A route and the B route in a time-sharing manner. That is, for example, the signal 1iD2 display signal is A
In the route B, the voltage is applied to the display element C12 via the field effect transistor T12A, and in the B route, it is applied to the display element C1l via the field effect transistor TIIB. In this configuration, the number of signal lines is halved compared to that in FIG. 3, so the probability of defect occurrence is low and manufacturing yield can be improved.

FIG. 5 shows an example in which the arrangement of the selection lines in FIG. It is the result of reducing the probability that

FIG. 6 shows an embodiment in which the selection lines in FIG. 5 are shared, in which the selection lines of adjacent display cells are shared, and the selection lines Sl, S2, . This is designated as S3.

This configuration differs from the other embodiments described above in that display signals are applied to the display elements through both routes A and B within the same frame. However, in odd-numbered frames, the A route and B route are applied in this order, and in even-numbered frames -0-, the B route and A route are applied in that order. Sunao) Chi,
In an odd frame, the selection line S1 is first activated, and a display signal is applied to the display element C1l through the A route.

Next, the selection line S2 is activated, and a display signal is applied to the same display element C11 via the B route to rewrite. (At this time.

A display signal is applied to the display element C21 through route A. ) This operation is performed sequentially to select the selection lines Sl, S2 . By sequentially activating S3, a display signal on route B is applied as a result in odd frames. Conversely, in even frames, the selection line S4. S3. S2. By activating Sl in order, a display signal on route A is applied to the display element.

As a result, as in the previous embodiment, the B route is used for odd frames and even frames.

The display signals of route A can be applied alternately.

FIG. 7 is a diagram showing the configuration of another embodiment of the present invention in which a display signal application route switching transistor is provided.

In all of the above-mentioned embodiments, the application route of the display signal was switched by the selection line, but as shown in FIG. The same effect can be obtained even if field effect transistors TIIE and Tll0 to which route switching signals E and 0 are applied to their gates are added between C11 and routes are switched using the route switching signals.

All of the above explanations have been made regarding the case where there are two routes for applying display signals, but the same effect can be expected even if three or more routes are provided and the routes are sequentially switched. Note that when three or more routes are provided, the effect when one of the routes becomes defective is smaller than when there are two routes. Therefore, even if a plurality of routes become defective, it is possible to prevent the display from being affected in any way. In addition, in the above explanation, it is assumed that the display signal is I (or L) to indicate whether the display element is bright or dark, but in order to change the voltage applied to the display element to alternating current, the common electrode is 1/2 Van, and the display signal is VDD or Ov for bright and 1/2 Van for dark.
The operation is the same for 2vDD.

Although the above explanation assumes that a liquid crystal is used as the display element, the present invention can also be applied to cases where other elements other than liquid crystals, such as electroluminescence (EL), are used, and similar effects can be achieved. can be expected.

Note that when a plurality of display signal application routes are provided in one display element as in the present invention, defects can be easily inspected by inspecting continuity between the routes. That is, in FIG. 6, the selection lines Sl and S2 are simultaneously activated and deactivated,
By inspecting conduction and non-conduction between the signal lines 02 and 02, the quality of the signal lines DI and D2, selection lines Sl and S2, and field effect transistors TIIA and TIIB can be inspected. This makes it possible to conduct detailed inspections of each display cell, which could conventionally be carried out only in display tests after completion, on the thin film transistor substrate before forming the liquid crystal layer. Thereby, manufacturing costs can be reduced.

(Effects) As explained above, according to the present invention, a plurality of display signal application routes to the display element are provided and are periodically switched and used, so that defects may occur in some of the display signal application routes during manufacturing. Even if this occurs, it hardly affects the display, which has the advantage of providing good display. Therefore, by applying the present invention to large-area, high-definition image display devices that have a high probability of producing defects during manufacturing, there is an advantage that the manufacturing yield can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a conventional active matrix type image display device, FIG. 2 is an embodiment diagram showing the configuration of a display cell of an active matrix type image display device according to the present invention, and FIG. An embodiment in which the display cells shown in the figure are arranged in a matrix, FIG. 4 is an embodiment of the present invention in which the signal lines of adjacent display cells in FIG. 3 are shared, and FIG. FIG. 6 shows an example in which the selection line in FIG. 5 is shared, and FIG. 7 shows an example in which a display signal application route switching transistor is provided. FIG. 7 is a diagram showing the configuration of another embodiment. TIIA-T24A, TIIB-T24B...Field effect transistor, C11-C24...Display element, C
C...Liquid crystal 115 = common electrode, old ~ D5. DIA-D4A, DIFI-D4
B...Signal line, 5l-53, SEA, S2A, SIR
, S2B... selection line.

Claims (1)

[Claims] In an active matrix image display device in which display cells each consisting of a display element and a field effect transistor are arranged in a matrix, a field effect transistor for applying a display signal to the display element and a method for selecting the field effect transistor A plurality of input routes each consisting of a selection line and a signal line for transmitting a display signal to the field effect transistor are provided for one display element, and the input routes are periodically switched and used. Image display device.