JPS62151769A - Inspecting method for active matrix substrate - Google Patents

Abstract

PURPOSE:To inspect a short circuit and a leak between substrate electrodes easily and accurately by charging one electrode of an active matrix substrate at a specific potential based on the other electrode, and utilizing the difference between the potential in the charging and a potential which is certain time later. CONSTITUTION:Address lines Y1, Y2...Yn of the active matrix substrate 17 are connected in common to the negative electrode of a DC power source 22. A charging/measurement changeover switch 23 is placed on the side of the power source 22 to set a charging mode. Then, signal lines X1, X2...Xn are selected with a signal selection switch 18 for a certain time each and charged to the potential of the power source 22. The switch 23 is switched to the side of a potential measuring instrument 24 to set a measurement mode. The signal lines X1...Xn are selected with the switch 18 for a specific time each and their potentials are measured. In this measurement, even a slight leak between electrodes is measured as large potential variation, so a short circuit or slight leak between a signal line and an address line is inspected easily and securely according to how much the measured value decreases below said charging voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for inspecting an active matrix substrate for a display device on which a switch element array is formed.

[1.Technical background and problems thereof] Recently, active matrix display devices using liquid crystals and the like have been actively developed as multi-pixel display devices for displaying images and graphics. This type of display device uses an active matrix substrate on which a switch element array is formed to control the brightness or lighting/non-lighting of each pixel.

Figure 4 shows a thin film transistor (TPT) as a switch element.
) is an electrical equivalent circuit diagram of an active matrix substrate using a TFT. It is connected. TF
The gates of TI are commonly connected for each row and connected to the address line Yr.
, Y2...Yn are provided, and the drains are commonly connected for each column, and signals @taXs, X2...Xm are provided. The TFT 1, capacitor 2, pixel electrode 3, address line, and signal line are formed, for example, on a glass substrate using a one-step technique.

FIG. 5 is a cross-sectional view for explaining the structure of a liquid crystal display device as an example of a display device using the above active matrix substrate. In the same figure, 4 to 12 indicate each member in an example of an active matrix substrate, 4 is a glass substrate, 5 is a light shield made of metal such as chromium, a ground electrode also serves as 1, and 6 is an interlayer. Insulating film, 7 is TF
T is a drain electrode/signal line, 8 is a TPT source electrode/pixel electrode, and 7 and 8 are formed of a transparent conductive film such as IT◯. 9 is a semiconductor layer such as amorphous silicon,
10 is a gate insulating liquid made of silicon nitride, etc.;
1 is a TPT gate electrode made of metal such as aluminum, and 12 is a protective layer made of polyimide or the like. The overlapping portion of the pixel electrode 8 and the ground electrode 5 constitutes the capacitor 2 shown in FIG. On the other hand, 13 is a glass substrate on which a common electrode 14 made of a transparent conductive film is formed. After a liquid crystal alignment film 15 is formed on the surfaces of the side substrates 4 and 13, the peripheral portions are sealed with a gap of about 10 μl maintained, and a liquid crystal 16 is filled in the internal gap to form a liquid crystal display device.

The operation of the liquid crystal display device shown in FIG. 5 is performed as follows.

That is, in FIG. 4, address lines Y1. Y2...
-Yn is sequentially scanned and driven by a scanning signal from a Y driver, and TFTl is brought into conduction state sequentially row by row.

In synchronization with the above scanning, signal line X1. For example, when a display signal voltage from an X driver is simultaneously supplied to X2 . The liquid crystal 16 responds to this held display signal voltage.
is excited, and an image or the like is displayed.

By the way, the signal lines XI, X2...X11 and the address lines Y1... Between Y2...yn or signal line X1
．． If there is an electrical leak or short circuit between X2...→0 and the ground electrode, it will result in linear defects on the display, so these inspections are necessary when the active matrix board is completed. .

FIG. 6 is a diagram for explaining the conventional inspection method for active matrix boards, where 17 is the active matrix board explained in FIG. 4, and 18 is a changeover switch (or circuit).
, 19 is a direct current 'Rm, 20 is an ammeter (or current measuring circuit), and 21 is a current limiting resistor. Figure (a) shows the address line Y1. Connect Y2...Yn in common, and measure the electrical leakage current or short-circuit current between this and each of the signal lines Xt, X2...xIll using an ammeter (or current measurement circuit).
This is an example of the inspection method measured in 20, and the same figure (
b) is an example of an inspection method in which the electrical leakage current or short-circuit current between each of the signal lines Xt, X2...X11 and the ground electrode is measured using the N current meter (or current measuring circuit) 20. .

In a display device using an active matrix substrate, the display signal voltage is not always supplied to the signal line during the period when the address selection period is selected; The display signal voltage is supplied in a form that charges or discharges the line capacitance to the display signal voltage, and during the remaining period of the address selection period, writing to the pixel E1m may be performed using the display signal voltage held in the signal line capacitance. It happens often. In such a case, even the slightest leakage between the signal line and other electrodes is not allowed. This is because the pixel electrodes along the address line are connected to the respective signal lines via TPT during the period when the address line is selected, so the display signal voltage held on the signal line is This is because if the change occurs due to the leakage, a normal display signal voltage cannot be written to the pixel electrode. The conventional inspection method described in FIG. 6 has a problem in that the ammeter cannot capture a small amount of leakage between the electrodes, making it difficult to inspect.

[Object of the Invention] The present invention solves the above problems and provides an active matrix substrate inspection method that enables easy and reliable inspection of even the slightest leak between arbitrary electrodes of an active matrix substrate. purpose.

[Summary of the Invention] The present invention is a method for inspecting short-circuits or leakage between electrodes of an active matrix substrate for a display device in which at least a switch element and a pixel electrode are provided at each intersection of a plurality of signal lines and an address line. When performing this, the method includes means for charging one electrode to a predetermined potential with respect to the other electrode, and means for measuring the potential of the charged electrode after a predetermined time has elapsed after charging. The degree of short circuit or leakage between the electrodes can be determined from the difference in potential after the lapse of time.

FIG. 1(a) is a circuit diagram for explaining an embodiment of the board inspection method. This is an example of a case where the presence or absence of short circuit or leakage is inspected.
The addresses MJYx, Y2, . . This charging/measurement switch 23
The second fixed terminal 232 of is connected to the potential measuring device 24,
The movable terminal 230 of the charging/measurement changeover switch 23 is connected to the movable terminal 180 of the signal line selection switch 18, and the fixed terminals 181, 182, . . .
18I11 are connected to the signal lines X1°×2 . . . Xll+ of the active matrix board 17, respectively.

FIG. 1(b) is an example of a case where the presence or absence of short circuit or leakage between the signal lines Xs, X2, . . . . . . xl and the ground electrode is inspected. The ground electrode of the active matrix substrate 17 is connected to the negative electrode of the active matrix substrate 122. In FIG. 1(b), the same parts as those in FIG. 1(a) are given the same reference numerals, and the explanation thereof will be omitted. FIG. 2 is a waveform diagram for explaining the operation of the circuit of FIG. 1. That is, in the case of FIG. 1(a), the charge/measurement changeover switch 23 is first turned to the power supply 22 side to set the charge mode.Next, the signal line selection switch 18 is used to select Xl, X2,
...The signal line Xt as shown in the period T1 of Xll.

×2...xIi is sequentially selected for each predetermined time t, and N source 2
Charge to the potential Ea of 2. All signal lines Xt.

When the charging of ×2...→0 is completed, the charging/measurement changeover switch 23 is turned to the potential measuring device 24 side to set the measurement mode. Next, use the signal line selection switch 18 to select Xs,
As shown in the T2 period of X2...X1ll, the signal line
I, X2, . . . The degree of short circuit or leakage between the signal line and the address line can be determined based on how much the measured value has decreased with respect to the previous charging voltage EO.

FIG. 3 shows this state, where tl indicates a charging period of a certain signal line, and T2 indicates a potential measurement period of that signal line. Further, T3 is a charging period when re-measurement is performed if necessary. During the charging period t1, the potential Ea of the power supply 22
The potential of the signal line, which has been charged up to 1, decreases over time. Actual @a indicates a normal potential change of the signal line, and although there is a slight decrease due to the input impedance of the potential measuring device 24, a value close to the charging potential EO is maintained at 2 during the measurement period. The broken line indicates a change in the potential of the signal line with slight leakage between it and the address line, which is considerably lower than the charging potential Ea during the measurement period t2. A one-dot chain line C indicates a change in the potential of a signal line in which a state close to a normal path state exists between the signal line and the address line, and the signal line potential in the measurement period t2 has decreased to 0 volts. In the inspection method according to the present invention, by setting the time from charging to measurement after considering the signal line guest and the input impedance of the potential measuring device, even a small leakage can be treated as a large potential change. It can be measured.

The case of Fig. 1(a) has been explained above, but in the case of Fig. 1(b), the other electrode for testing for short circuits or leakage with the signal line is simply replaced by the ground electrode instead of the address line. Inspection can be performed using the same operation as in the case of FIG.
Charging/measurement switch 23, signal line selection switch 18
The electric potential measuring device 24 and the like can be collectively configured as an electronic circuit, and by setting a threshold value for the measured value in the electric potential measuring device 24, it is also possible to make automatic pass/fail judgment.

[Effects of the Invention] As explained above, according to the present invention, even a slight leakage between electrodes can be measured as a large potential change. This has the advantage of being easy and reliable.

[Brief explanation of drawings]

Figure 1 is a circuit diagram for explaining one embodiment of the present invention, Figures 2 and 3 are waveform diagrams for explaining the operation of Figure 1, and the fourth factor is for explaining the active matrix board. FIG. 5 is an electrical equivalent circuit diagram using the active matrix substrate shown in FIG. 4; FIG. 6 is a cross-sectional view for explaining an example of a display device, and FIG. FIG. 17... Active matrix board, 18... Signal line selection switch, 22... Power supply, 23... Charging/measurement changeover switch, 24... Potential measuring device, ×1 to XI・
...Signal line, Y1-Yn...Address line. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a method for inspecting an active matrix substrate for a display device, in which at least a switch element and a pixel electrode are provided at each intersection of a plurality of signal lines and an address line, one of the electrodes of the active matrix substrate is provided. The method includes means for charging the other electrode to a predetermined potential using the electrode as a reference, and means for measuring the potential of the charged electrode after a predetermined time has elapsed after charging. A method for inspecting an active matrix substrate, characterized by determining the degree of short circuit or leakage between the electrodes.