JP2594358B2 - Image display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal image display device formed using a thin film transistor on an insulating substrate.

2. Description of the Related Art A conventional image display device will be described below. FIG. 3 shows a conventional configuration diagram. There is a driving circuit including a vertical scanning circuit 11 and a horizontal scanning circuit 12. At each output of the horizontal scanning circuit 12, a transfer transistor switch group 13 controlled by an output of the horizontal scanning circuit 12 is formed. The pixel units 14 are arranged in a two-dimensional matrix and are driven by an active matrix system. A horizontal gate line, which is an output of the vertical scanning circuit 11, is formed of polysilicon, and a vertical signal line is formed of aluminum (AL), and is written to a pixel portion in a dot-sequential manner.

However, in such a conventional configuration, when there is a short circuit between the vertical signal lines, it is very difficult to find the short circuit between the vertical signal lines, and usually, the signal lines are confirmed one by one. Alternatively, there is a drawback that pixels must be displayed through a liquid crystal process.

The present invention has been made in view of the above-described disadvantages, and provides an image display device capable of determining the presence and location of a short circuit before a liquid crystal process when a short circuit occurs between vertical signal lines.

Means for Solving the Problems In order to solve the above problems, the image display device of the present invention is provided with a test switch group at each of odd-numbered and even-numbered ends of a vertical signal line, so that each of the vertical signal lines can be tested. Are connected to the control terminal of the test switch group, and the source and the drain of the test switch group are commonly connected.

Operation According to the above configuration, an inspection switch is provided at each of the odd-numbered ends of the vertical signal lines passing through the pixel portion, and a NOR circuit can be formed by connecting the switches in series with the resistors. A similar NOR circuit is formed at the even-numbered terminal. A pulse shorter than a selection period of each output of the horizontal scanning circuit is input to an input terminal of a transfer transistor switch group controlled by an output of the horizontal scanning circuit.
If there is a short circuit between the vertical signal lines, the outputs of the NOR circuits at the ends of the odd-numbered and even-numbered vertical signal lines have the same waveform where there is a short circuit.

The present invention is based on the above-described principle, and provides an image display device capable of easily checking the presence or absence of a short circuit between vertical signal lines and its position.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of an image display device according to an embodiment of the present invention. 1 is a vertical scanning circuit, 2 is a horizontal scanning circuit, 3 is a transfer transistor switch group, 4 is a pixel section, 5 is an odd-numbered signal line inspection switch group, 6 is an even-numbered signal line inspection switch group, and 7 is Denotes a horizontal gate line, and 8 denotes a vertical signal line. The isolation is an active matrix method and has a switching thin film transistor. The traveling section of the horizontal scanning circuit 2 is provided with a transfer transistor switch group 3 controlled by the output of the horizontal scanning circuit 2, and performs signal transmission to the pixel section 4 by dot sequential writing due to AL defeat.

Next, a method for checking a short circuit between the vertical signal lines passing through the pixel unit 4 of the image display device of the present invention will be described. 2 (a) and 2 (b) show a configuration diagram and a voltage waveform diagram at each point. A, B, and C indicate output waveforms of the horizontal scanning circuit 2, and D indicates a test pulse input to the transfer transistor switch group 3. Each vertical signal line 8 is connected to the gates of the test switch groups 5 and 6 for odd-numbered and even-numbered signal lines, and the switch group in each stage has a common source and drain.
Further, the odd-numbered and even-numbered inspection switch groups 5 and 6 each constitute a NOR circuit with a resistor. The resistance R is set to be larger than the ON resistance of the transistor used for the inspection switch and smaller than the OFF resistance.

Here, it is assumed that, for example, the vertical signal lines indicated by arrows in the figure are short-circuited. First, assuming that there is no short circuit between the vertical signal lines 8, the output waveform observed at E is output only during the period in which the odd-numbered stage of the horizontal scanning circuit 2 is selected in the test pulse input to D. Similarly, the waveform observed at F is output only during the selection period of the even-numbered stages. That is, D
The test pulse input to the E is distributed to E and F. However, if there is a short circuit between the vertical signal lines as indicated by the arrow in the figure, the odd-numbered and even-numbered circuits will always be short-circuited, and the output of E and F will be the same at the short-circuited point, It can be seen that there is a short circuit at the same output. The same test can be performed when three or more vertical signal lines 8 are short-circuited. In this case, only the period during which the output of E and F has the same waveform becomes longer.

As described above, an inspection switch group is provided at the end of each of the odd-numbered and even-numbered vertical signal lines of the image display device, a NOR circuit is formed by resistors, and the output waveform is observed. Short lines between vertical signal lines and their positions, which were unknown until each line was examined or an image was displayed through the liquid crystal process, can be easily known before the liquid crystal process. In addition, since the inspection switch group is formed of a thin film transistor in the embodiment, it can be manufactured at the same time when the horizontal and vertical scanning circuits are formed, so that it is not necessary to newly add a process.

In this embodiment, the transistors are used as the inspection switch group. However, other configurations may be used. The resistor may be externally mounted or built-in, or a resistor may be used as a transistor. Further, the transfer transistor switch group may be an n-channel transistor or a p-channel transistor, or may be a transfer gate having a CMOS-TFT configuration.

Effect of the Invention As described above, the present invention provides an inspection switch group at the odd-numbered vertical signal line terminal,
A NOR circuit is formed, and a test circuit is provided also at the even-numbered vertical signal line terminal, and a NOR circuit is formed by resistors. According to such a configuration, it is possible to easily find out the short circuit between the vertical signal lines, which has been difficult in the past, before the liquid crystal process simply by checking the output signals of the odd-numbered and even-numbered NOR circuits. The practical effect is great.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image display device according to an embodiment of the present invention, FIGS. 2 (a) and 2 (b) are configuration diagrams of an inspection example of a short circuit in an embodiment of the present invention, a voltage waveform diagram, and FIG. FIG. 9 is a configuration diagram of a conventional image display device. 1, vertical scanning circuit 2, horizontal scanning circuit 3, transfer transistor switch group 4, pixel unit 5, inspection switch group for odd-numbered signal lines, 6 for even-numbered signal lines Inspection switch group 7, horizontal gate line 8, vertical signal line.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Eiji Fujii, Inventor Kazuma 1006 Kadoma, Osaka Prefecture Inside Matsushita Denshi Kogyo Co., Ltd. (56) References JP-A-63-52121 (JP, A) JP-A-63-116190 (JP, A) JP-A-3-18891 (JP, A)

Claims (1)

(57) [Claims] 1. A horizontal scanning circuit and a vertical scanning circuit formed by a thin film transistor on an insulating substrate, a pixel arranged in a two-dimensional matrix, and a vertical line for supplying a video signal to pixels in each column formed by a conductive film. A signal line and a horizontal gate line, an output section of the horizontal scanning path includes a transfer switch group for transferring a video signal controlled by an output pulse of the horizontal scanning circuit to a vertical signal line, The terminal is connected to the control terminal of the test switch group, the source and drain of the test switch group at the end of the odd-numbered vertical signal line are common, and the terminal is connected to the terminal of the even-numbered vertical signal line. An image display device, wherein a source and a drain of the certain test switch group are common to each other.