JPH04106530A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To allow the correction of a defective point by an electrical inspection in the stage before sealing of a liquid crystal and to assure reliability by insulating common capacity electrodes by each scanning line or signal line. CONSTITUTION:A selection pulse signal is impressed from the scanning line Y to the gate of a TFT 11 to selectively conduct the TFT. A video signal is inputted to the source of the TFT 11 conducted from the signal line X and is applied to and held in a liquid crystal 12 for one picture element via a picture element electrode 14. A holding capacity 13 is provided in order to suppress the voltage drop of the electrode 14 by a parasitic capacity. One end thereof is connected to the picture element electrode 14 and the other end to common capacity electrodes C1, C2, C3.... The electrodes C1, C2, C3... are insulated from each other and are separately impressed with common potentials VC1, VC2, VC3,.... The common capacity electrodes C1, C2, C3... are insulated without being shorted to each other in such a manner and, therefore, if a disconnection or shorting arises in any thereof, this disconnection or shorting is easily detected by the electrical inspection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an active matrix type liquid crystal display device.

(Conventional technology) As a conventional active matrix liquid crystal display device,
Japan Display” 89, p.

There is one published in 418-421J. FIG. 4 shows an equivalent circuit in the pixel portion of this device.

Signal lines Xi, X2. ... is the scanning line YIY2 in the column direction.
．． A plurality of ... are wired in the row direction. At the intersection of each signal line X and scanning line Y, a thin film transistor (
(hereinafter referred to as TPT) 11 are arranged in a matrix. The gate of TFTll is connected to the scanning line Y, the source to the signal line X, and the drain to the pixel electrode 14. Further, a common potential V is applied to each counter electrode 15. o
M is applied. The selection pulse signal is T from the scanning line Y.
A video signal is applied to the gate of PTll to selectively make it conductive, and a video signal is input from the signal line X to the source of TFTII, which is made conductive. The input video signal is applied to the liquid crystal 12 for one pixel via the pixel electrode 14 and held there.

In addition, due to the parasitic capacitance between the source and drain, the TF
In order to suppress the potential of the pixel electrode 14 from dropping at the moment TII is turned off, a holding capacitor jil1 is installed in parallel with the liquid crystal 12.
3 is provided. This storage capacitor 13 is provided for each pixel, with one end connected to the pixel electrode 14 and the other end connected to each scanning line Yl, Y2, . Each Y3°... is connected to a common capacitor electrode CI, 2°C3... provided in parallel.

(Problem to be Solved by the Invention) However, in the conventional device, each common capacitance electrode CI, C2
, C3, . . . are short-circuited and have a common potential vc
oM was being applied. Therefore, this common capacitance electrode CI
, C2, C3, . . . even if a short circuit or disconnection exists between them, it has been impossible to electrically detect the defective location. For this reason, inspection cannot be performed until the liquid crystal is sealed between the TPT substrate and the counter substrate and the device is operated, and there is a risk that the orientation of the liquid crystal may be disturbed if a defective portion is repaired.

The present invention has been made in view of the above circumstances, and provides a liquid crystal display device that can easily electrically detect defects such as disconnection of a common capacitor electrode, and that can contribute to improving reliability and yield. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) The liquid crystal display device of the present invention has a TPT in which a plurality of scanning lines and signal lines are arranged on a first insulating substrate, the scanning lines are scanned, and the signal lines are manually inputting signals. are arranged in a matrix at the intersections of scanning lines and signal lines, pixel electrodes to which the output of each TPT is manually input are arranged in a matrix, and counter electrodes are provided facing the first insulating substrate. A device in which a liquid crystal is sandwiched between a second insulating substrate surface on which a pixel electrode is arranged, a common capacitance electrode is provided for each scanning line or signal line, and a common capacitance electrode is provided for each scanning line or signal line, and each A storage capacitor is arranged for each pixel, and the common capacitor electrodes are insulated from each other.

Further, on the first insulating substrate, there is a driver circuit that drives the scanning line or the signal line, and during normal operation, this driver circuit applies a predetermined potential to all of the common capacitor electrodes and inspects the common capacitor electrodes for defects. In this case, predetermined potentials may be separately applied to the common capacitor electrodes.

(Function) If the common capacitance electrodes are short-circuited, it is not possible to electrically detect short-circuits or disconnections between the wirings only on the first substrate, Since it is necessary to operate the liquid crystal by sealing it between the electrodes, any modification will disturb the alignment of the liquid crystal and reduce reliability.However, since the common capacitance electrodes are insulated from each other, It is possible to electrically detect and correct defective parts at this stage, ensuring reliability.

When the driver circuit is provided on the first insulating substrate, a predetermined potential is applied to all of the common capacitor electrodes to function as a holding capacitor during normal operation of the device, and each common capacitor is used for inspection. Testing can be performed quickly and easily by applying predetermined potentials to the electrodes separately.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. First, FIG. 1 shows the configuration of a liquid crystal display device according to a first embodiment. Compared to the conventional device shown in FIG. 4, the common capacitance electrodes C1, C2, C3, . . . are insulated from each other, and the common potentials VCI, VO2, VO2 are separately applied
, . . . can be applied. Components that are the same as those of other conventional devices are given the same numbers and descriptions thereof will be omitted.

In this way, the common capacitance electrodes CI, C2, C3... are insulated without being short-circuited, so if any of them is disconnected or short-circuited, it can be easily detected by electrical inspection. be able to. Since this inspection can be performed on only the TPT substrate before sealing the liquid crystal between the TPT substrate and the counter substrate, it is possible to take measures such as cutting off short circuits with laser trimming. Thereby, there is no risk of adversely affecting properties such as alignment of the liquid crystal, and it is possible to contribute to ensuring reliability and improving yield.

Next, a liquid crystal display device according to a second embodiment of the present invention will be described with reference to FIG. 2 showing its configuration. In the first embodiment, the Y driver that drives the scanning line Y and the X driver that drives the signal line X are both provided outside the device. On the other hand, this embodiment is different in that an X driver 23 and an X driver 21 are built-in.

The X driver 21 shifts the start pulse DX to the right one bit at a time in synchronization with the period of the clock pulse CLX, and switches the switching elements SW1. S
W2. . . are turned on one after another, and the video signal vID is written to each pixel. The configuration of this X driver 21 is similar to that commonly used in conventional devices.

In the X driver 23, it is necessary to change the voltage applied to each common electrode C1, C2, C3, etc. when inspecting the TPT substrate stage and when operating the device after filling the liquid crystal and assembling it. Because of this, new components have been added. A timing chart of input and output signals of this Y driver is shown in FIG. The operating waveform during normal operation is as shown in FIG. 3(a), and the waveform during inspection is as shown in FIG. 3(b).

A start pulse DY and a shift clock CLY are input to the shift register 24 in common during normal operation and inspection. The start pulse DY is shifted downward one bit at a time in synchronization with the cycle of the shift clock CLY, and the scanning lines Yl, Y2, Y3, . ... will be output sequentially.

As a result, scanning lines Yl, Y2 . Y3. As shown in the figure, the level of ... becomes high level sequentially during time T.

For each scanning line Y, a NAND circuit NR and an inverter INV are newly provided for inspection. Of the two terminals of the NAND circuit NR, one inputs the test signal TY, and the other inputs the respective scanning lines Yl, Y2 . Y3.・
... are connected, and the shifted start pulse DY is input. Here, the test signal TY is at a high level during normal operation. In this case, the start pulse DY
Regardless of the level of , a high level signal is output from the inverter INV. As a result, the common capacitance electrode C1,
C2, C3, . . . have a common potential VCI at a constant level,
When VO2, VO2,... is applied, the holding capacity 13
functions as.

During inspection, the test signal TY becomes low level. The inverter INV outputs a signal synchronized with the shift clock CLY. As a result, each common capacitance electrode C1,
It is detected whether there is a short circuit or disconnection in C2, C3, . . . . Thus, according to the second embodiment,
With the simple configuration newly provided for inspection, inspection can be performed with almost no increase in cost. As in the first embodiment, the defective location can be located faster and more reliably than in the case of inspection using a prober or the like without a built-in Y driver.

The embodiments described above are merely examples and do not limit the present invention. For example, in the embodiment, the common capacitor electrodes are arranged in parallel for each scanning line, but the same effect can be obtained even if the common capacitor electrodes are arranged for each signal line.

〔Effect of the invention〕

As explained above, according to the liquid crystal display device of the present invention, since each common capacitance electrode is insulated from each other, it is possible to electrically detect and correct defective parts before filling the liquid crystal. Therefore, the risk of disturbing the alignment of the liquid crystal can be avoided, and high reliability can be ensured.

[Brief explanation of drawings]

FIG. 1 is an equivalent circuit diagram showing the structure of a liquid crystal display device according to a first embodiment of the present invention, FIG. 2 is an equivalent circuit diagram showing the structure of a liquid crystal display device according to a second embodiment of the present invention, Figure 3 is a timing chart showing the driving waveforms of the same device;
The figure is an equivalent circuit diagram showing the configuration of a conventional liquid crystal display device. DESCRIPTION OF SYMBOLS 11... TFT, 12... Liquid crystal, 13... Storage capacitor, 14... Pixel electrode, 15... Counter electrode, 21...
・・X dry/<, 22.24...shift register,
23...Y driver, Xi, X2. X3. ...Signal line, Yl. Y2. Y3. ...Scanning line, C1, C2, CB...Common capacitance electrode, vCI"C2" CB...Common potential. Applicant's agent Mr. Sato Figure 1

Claims (1)

[Claims] 1. A plurality of scanning lines and a plurality of signal lines are arranged on a first insulating substrate, and a thin film transistor scanned by the scanning line and inputting a signal by the signal line is connected to the scanning line and the signal line. Pixel electrodes are arranged in a matrix at intersections with the lines and receive the outputs of the respective thin film transistors, and pixel electrodes are arranged in a matrix, and a counter electrode is arranged to face the first insulating substrate. In a liquid crystal display device in which a liquid crystal is sandwiched between a second insulating substrate surface, a common capacitance electrode is provided for each of the scanning lines or the signal lines, and each pixel is provided between the common capacitance electrode and the pixel electrode. 1. A liquid crystal display device, wherein a storage capacitor is arranged for each common capacitor electrode, and the common capacitor electrodes are insulated from each other. 2. A driver circuit for driving the scanning line or the signal line is provided on the first insulating substrate, and this driver circuit applies a predetermined potential to all of the common capacitance electrodes during normal operation, and 2. The liquid crystal display device according to claim 1, wherein predetermined potentials are separately applied to the common capacitor electrodes when inspecting the capacitor electrodes for defects.