JPH08320502A - Method for inspecting liquid crystal panel - Google Patents

Abstract

PURPOSE: To provide a method for inspecting a liquid crystal panel capable of inspecting the fault of the liquid crystal panel failing to be completely removed of a short circuit wiring. CONSTITUTION: The display signal to be supplied to signal lines, the counter signal to be supplied to a counter electrode and the ON power-supply voltage and OFF power-supply voltage of scanning signals are kept constant for the liquid crystal panel from which the short circuit wiring is completely removed. The two scanning lines are shorted by the short circuit wiring. The ON power source current 1g(H)0 of the time the luminance change ΔTO of the threshold for the normal/defective condition of the wire condition is induced in the liquid crystal panel by lowering the ON power source current of the scanning signal is measured. The OFF power source current 1g(L)0 of the time the luminance change ΔTO is induced by lowering the OFF power source current of the scanning signal is measured. The liquid crystal panel is cracked by using the ON power source current 1g(H)O and OFF power source current 1g(L)0 obtd. by the measurement as reference and the respective liquid crystal panels subjected the chamfering are inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal panel inspection method using thin film transistors.

[0002]

2. Description of the Related Art In recent years, a liquid crystal panel has a wide range of applications and a severe usage environment, and it is necessary to secure higher performance and reliability by an inspection method capable of coping with this. .

A conventional method for inspecting a liquid crystal panel will be described below.

An active matrix drive type liquid crystal panel is generally composed of an upper glass substrate and a lower semiconductor integrated glass substrate. The semiconductor integrated glass substrate includes a plurality of thin film transistors arranged in a matrix and a plurality of pixel electrodes electrically connected to the thin film transistors. Each thin film transistor and the pixel electrode paired with it form a unit pixel of the liquid crystal panel. The liquid crystal panel selects a unit pixel based on a scanning signal from an external selection circuit, and applies a voltage of a display signal to the liquid crystal of the unit pixel to display an image. The external selection circuit may form an auxiliary capacitor by the pixel electrode and the common electrode or the preceding scanning signal line.

In the manufacturing process of a liquid crystal panel, a sufficient yield cannot be ensured due to problems in its structure and process. The typical yield impeding factors are:
Line defects can be mentioned. The line defect is a failure of the driving IC,
It is caused by disconnection or static electricity. In particular, line defects that occur due to deterioration of TFT characteristics due to static electricity are basically unrepairable and have become an important issue.

As a general method for preventing such line defects due to static electricity, there is a method of short-circuiting all signal wirings by short-circuiting wiring. By increasing the electric capacity by this short circuit, damage to one wiring can be dispersed. The short wiring is removed immediately before the image inspection process. As a removing method, there are a method of utilizing a chemical reaction such as etching and a method of mechanically scraping off the wiring pattern. Generally, the latter is selected in terms of workability and the like. In this case, if the short wiring is arranged near the end surface of the substrate or the split surface, the short wiring can be removed by chamfering the end surface. Normally, the chamfering amount is defined by the distance from the substrate end face or the fractured face. However, due to variations in board size, pattern, or cutting position,
It is difficult to chamfer the necessary and sufficient amount with high accuracy. Therefore, the short wiring is not completely removed, and a short circuit occurs between the wirings.

FIG. 3 is a schematic layout diagram of an active matrix drive type liquid crystal panel before cleaving a glass substrate. 1 is a display unit. Reference numeral 2 denotes a display signal line for a unit pixel, which has terminals for mounting a driving IC around the display portion. Reference numeral 3 denotes a scanning signal line for a unit pixel, which has a terminal for mounting a driving IC around the display portion.
Reference numeral 4 is a short wiring, which has a function of preventing line defects due to static electricity. 5 is a cleaving position.

FIG. 4 is a schematic circuit diagram of a liquid crystal panel when the short wiring on the scanning signal side cannot be completely removed. 6 is a thin film transistor of a unit pixel, usually M
IS transistors are used. Reference numeral 7 is a transparent pixel electrode. Reference numeral 8 is an auxiliary capacitor having a display signal holding function. Reference numeral 9 is a short wiring that could not be completely removed.

FIG. 5 is a diagram simply showing the timing of each signal of the liquid crystal panel. Vs is a display signal. Vc
Is an oncoming signal. Vg is a scanning signal, and its ON power supply voltage is Vg (H), and its OFF power supply voltage is Vg.
(L). The scanning signal Vg (1,
2, ..., N) are sequentially numbered from the top of the screen in the scanning order. However, Vg (H)> Vg (L). Here, the potential levels of the signals shown in FIG. 5 are shown in FIG.

FIG. 2 is a graph showing the characteristics of the screen brightness of the liquid crystal panel and the thin film transistor current. Figure 2 (a)
Is a graph of the scanning signal on the ON power supply current lg (H) side, and the screen brightness is MI when the display signal Vs is MAX.
It is a figure which shows the state of the normally white system which is N (black display). lg (H) act is the ON power supply current of the scanning signal of the liquid crystal panel during actual driving. 10a is
It is a characteristic curve in the initial stage of startup of the liquid crystal panel in which the short wiring is completely removed. 10b is a characteristic curve in the initial stage of starting the liquid crystal panel, but is a characteristic curve when the short wiring is not completely removed as shown in FIG. In this case, the ON current lgon of the scanning signal for the corresponding line in the short circuit between the wirings becomes (Equation 1), and the characteristic curve of 10b shifts from 10a to 10b as shown in FIG. 2A.

[0011]

## EQU1 ## lgon = | lg (H) -lg (L) | Thus, in the conventional liquid crystal panel inspection method, 1
In both 0a and 10b, the luminance at lg (H) act showed normal performance with MIN.

FIG. 2B is a graph on the OFF power supply current lg (L) side of the scanning signal, which is of a normally white type in which the screen brightness is MIN (black display) when the display signal Vs is MAX. It is a figure which shows a state. lg (L) ac
t is OFF of the scanning signal of the liquid crystal panel during actual driving
Power supply current. 30a is a characteristic curve at the initial stage of startup of the liquid crystal panel in which the short wiring is completely removed. Three
0b is a characteristic curve in the initial stage of startup of the liquid crystal panel, but is a characteristic curve when the short wiring is not completely removed as shown in FIG. In this case, the scanning signal for the corresponding line is turned off when the wiring is short-circuited.
The current lgoff becomes (Equation 2), and the characteristic curve of 30b shifts from 30a to 30b as shown in FIG. 2 (b).

[0013]

## EQU00002 ## lgoff = | lg (L) -lg (H) | Thus, in the conventional liquid crystal panel inspection method, 3
In both 0a and 30b, the luminance at lg (L) act shows the normal performance as MIN.

[0014]

However, the above-mentioned conventional liquid crystal panel inspection method has a problem that it is not possible to detect a defect caused by a change in characteristics over time due to driving for a long time.

That is, as shown in FIG. 2A, when the characteristics of the thin film transistor change over time due to long-time driving, 10a and 10b are respectively 20a and 20b.
Shift to In this case, the ON power supply current lg of the scanning signal
In the characteristic curve 20b of the liquid crystal panel in which the short wiring in (H) act was not completely removed, the brightness exceeded the brightness change ΔTO, which is the pass / fail judgment limit. In the conventional liquid crystal panel inspection method, such an image defect could not be detected.

Similarly, as shown in FIG. 2B, when characteristics of the thin film transistor change over time due to long-time driving of the thin film transistor, 30a and 30b are respectively 40a and 40.
shift to b. In this case, in the characteristic curve 30b of the liquid crystal panel in which the short wiring in the OFF power supply current lg (L) act of the scanning signal was not completely removed, the brightness exceeded the brightness change ΔTO, which is the limit of pass / fail judgment. In the conventional liquid crystal panel inspection method, such an image defect could not be detected.

In view of the above problems of the prior art, the present invention aims to provide a liquid crystal panel inspection method capable of detecting a defect in the liquid crystal panel in which the short wiring is not completely removed. And

[0018]

The present invention according to claim 1 provides X
A first substrate on a main surface of which a unit pixel group, which is a region partitioned by scanning lines and signal lines arranged in a Y matrix, is formed, and each of the unit pixel groups connected to the scanning line. A thin film transistor forming a unit pixel; a pixel electrode connected to the signal line and electrically connected to the thin film transistor; a second substrate forming a counter electrode facing the unit pixel group; A liquid crystal composed of a plurality of liquid crystal panels including a liquid crystal enclosed in a gap facing the first substrate and the second substrate, and a short wiring that electrically short-circuits the scanning line group or the signal line group. Regarding the panel member, the display signal Vs supplied to the signal line, the counter signal Vc supplied to the counter electrode, and the scanning line for one liquid crystal panel in which the short wiring is completely removed in advance. The ON power supply voltage Vg (H) of the scan signal and the OFF power supply voltage Vg (L) of the scan signal supplied to the thin film transistor via the same are made constant, and two of the scan lines are short-circuited by a short wiring to O
The ON power supply current lg (H) 0 is measured when the N power supply current is decreased to cause a linear change in brightness ΔTO at the liquid crystal panel, and the OFF power supply current of the scanning signal is decreased. Then, the OFF power supply current lg (L) O at the time of causing the brightness change ΔTO is measured, and the ON power supply current lg (H) O of the scanning signal obtained by the measurement is measured.
And a liquid crystal panel in which the liquid crystal panel member is cleaved and the end face or the fractured face of the first substrate is chamfered using the OFF power supply current lg (L) O as a reference. Is the inspection method.

[0019]

According to the first aspect of the present invention, the ON power source current lg (H) O and the OFF power source current lg of the scanning signal are previously set.
(L) O is calculated. That is, for the one liquid crystal panel from which the short wiring has been completely removed, the display signal Vs supplied to the signal line, the counter signal Vc supplied to the counter electrode, and the thin film transistor supplied via the scanning line. The ON power supply voltage Vg (H) of the scan signal and the OFF power supply voltage Vg (L) of the scan signal are set to be constant. Then, two of the scanning lines are short-circuited by a short wiring.
After the short circuit, the ON power supply current of the scanning signal is lowered to change the brightness of the liquid crystal panel to the linear quality judgment limit Δ.
The ON power supply current lg (H) O at the time of generating TO is measured. Further, the OFF power supply current of the scanning signal is reduced to measure the OFF power supply current lg (L) O when the brightness change ΔTO is caused.

Next, the ON power supply current lg (H) O and the OFF power supply current lg of the scanning signal obtained by the measurement
Using (L) O as a reference, each liquid crystal panel in which the liquid crystal panel member is cleaved and the end face or the fractured face of the first substrate is chamfered is inspected.

[0021]

An embodiment of the present invention will be described below with reference to the drawings.

The structure of the liquid crystal panel member which is the object of one embodiment for carrying out the liquid crystal panel inspection method of the present invention will be described. That is, the liquid crystal panel member is connected to the first substrate on which a unit pixel group, which is a region partitioned by the scanning lines and signal lines arranged in an XY matrix, is formed on one main surface, and the scanning lines. A thin film transistor that constitutes each unit pixel of the unit pixel group, a pixel electrode connected to the signal line and electrically connected to the thin film transistor,
A second electrode forming a counter electrode facing the unit pixel group
Substrate, a liquid crystal sealed in a gap facing the first substrate and the second substrate, and a short wiring that electrically short-circuits the scanning line group or the signal line group. .

Here, a method of obtaining the ON power supply current and the OFF power supply current of the scanning signal, which are required in advance in the liquid crystal panel inspection method of the present embodiment, will be described. FIG.
[Fig. 4] is a graph showing characteristics of screen brightness and thin film transistor current of a liquid crystal panel. FIG. 1A shows the scan signal O
It is a graph on the N power source current lg (H) side, and shows a display signal Vs.
FIG. 8 is a diagram showing a state of a normally white method in which the screen luminance is MIN (black display) when is MAX. lg
(H) act is the ON power supply current of the scanning signal of the liquid crystal panel during actual driving. 10a is a characteristic curve at the initial stage of startup of the liquid crystal panel in which the short wiring is completely removed. FIG. 1B shows the OFF power supply current lg of the scanning signal.
It is a graph on the (L) side, and is a diagram showing a state of the normally white method in which the screen brightness is MIN (black display) when the display signal Vs is MAX. lg (L) act
Is the OFF power supply current of the scanning signal of the liquid crystal panel during actual driving. 30a is a characteristic curve at the initial stage of startup of the liquid crystal panel in which the short wiring is completely removed.

At this time, the display signal Vs supplied to the signal line,
Counter signal Vc supplied to the counter electrode, ON power supply voltage Vg of the scan signal supplied to the thin film transistor via the scan line
(H) and the OFF power supply voltage Vg (L) of the scanning signal are kept constant, and as shown in FIG. 4, the two scanning lines are intentionally short-circuited by the short wiring. However, in the state of the liquid crystal panel before the intentional short circuit, it is assumed that the short wiring is completely removed.

Due to this short circuit, 10a in FIG.
0b shifts to 30b from 30a in FIG. 1 (b). With respect to the shifted 10b and 30b, the ON power supply current Ig (H) act and the OFF power supply of the scanning signal at the time of actual driving are respectively generated so as to cause the linear quality change limit brightness change ΔTO in the liquid crystal panel. Current Ig (L) ac
t is lowered. And the characteristic curve of 10b and △ TO
The value of Ig (H) that intersects the straight line of is defined as Ig (H) O, and the value of Ig (H) O intersects the characteristic curve of 30b
Let the value of (L) be Ig (L) o.

Ig (H) O and I thus obtained
Let g (L) o be the ON power supply current and the OFF power supply current of the scanning signal when inspecting the liquid crystal panel member.

From FIG. 1, Ig (H) O and Ig (H) O
Each of (L) 0 has the relationship of (Equation 3).

[0028]

## EQU3 ## lg (H) O = lg (H) act-Δlg (H) O lg (L) O = lg (L) act-Δlg (L) O where lg (H) O> 0, lg (L) O> 0.

Next, Ig (H) O and Ig (L) O are
O of the scanning signal when inspecting the liquid crystal panel member, respectively.
The operation of this embodiment when used as the N power supply current and the OFF power supply current will be described. First, the liquid crystal panel member is cut and divided into a plurality of liquid crystal panels. The end face or the fractured face of the divided first substrate of each liquid crystal panel is chamfered to remove the short wiring. In the work of removing the short wiring, the short wiring may not be completely removed in some cases, which causes the liquid crystal panel having the short wiring with a predetermined defective rate. Each chamfered liquid crystal panel has an ON power source current lg of the scanning signal.
The (H) O and OFF power supply current lg (L) O are used as a reference and tested.

ON power supply current lg (H) O of the scanning signal
The OFF power supply current lg (L) O will be described in more detail. As shown in FIG. 1 (a), if Ig (H) O is used as the ON power supply current of the scanning signal at the time of inspecting the liquid crystal panel, for 10a in which the short wiring is completely removed, Ig (H) O The brightness is located below the straight line of ΔTO, and this liquid crystal panel is judged to be normal.
However, the short wiring was not completely removed. 10
Regarding b, the luminance in Ig (H) O is located on the straight line of ΔTO, and this liquid crystal panel is determined to be defective.

As shown in FIG. 1 (b), if Ig (L) O is used as the OFF power supply current of the scanning signal at the time of inspecting the liquid crystal panel, Ig (L) for 30a from which the short wiring is completely removed. ) The brightness at O is below the line of ΔTO, and this liquid crystal panel is judged to be normal. However, for 30b in which the short wiring was not completely removed, the luminance at Ig (L) O was ΔTO.
Is located on a straight line, and this liquid crystal panel is determined to be defective.

[0032]

As is apparent from the above, the present invention makes it possible to detect a liquid crystal panel having a short wiring without completely removing the short wiring, and as a result, driving the liquid crystal panel for a long time. Even if the characteristics change over time due to the above, there is an effect that a good image quality can be secured.

As a result, the reliability of the liquid crystal panel on the market can be significantly improved, and the liquid crystal panel inspection method of the present invention is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a graph showing characteristics of screen brightness of a liquid crystal panel and thin film transistor current.

FIG. 2 is a graph showing characteristics of screen brightness of a liquid crystal panel and thin film transistor current.

FIG. 3 is a schematic layout diagram of an active matrix driving type liquid crystal panel before cleaving a glass substrate.

FIG. 4 is a schematic circuit diagram of a liquid crystal panel when the short wiring on the scanning signal side cannot be completely removed.

FIG. 5 is a diagram simply showing the timing of each signal of the liquid crystal panel.

6 is a diagram showing the potential level of each signal shown in FIG.

[Explanation of symbols]

 1 Display Part 2 Display Signal Line 3 Scanning Signal Line 4 Short Wiring 5 Break Position 6 Thin Film Transistor 7 Pixel Electrode 8 Auxiliary Capacitor 9 Short Wiring Not Completely Removed

Claims (1)

[Claims] 1. A first substrate having a unit pixel group, which is an area partitioned by scanning lines and signal lines arranged in an XY matrix, formed on one main surface, and is connected to the scanning lines. A thin film transistor forming each unit pixel of the unit pixel group, a pixel electrode connected to the signal line and electrically connected to the thin film transistor, and a second electrode forming a counter electrode facing the unit pixel group. A substrate and the first
A liquid crystal panel comprising a plurality of liquid crystal panels, each of which has a liquid crystal sealed in a space facing the substrate and the second substrate, and a short wiring which electrically short-circuits the scanning line group or the signal line group. Regarding the member, the display signal V to be supplied to the signal line with respect to one liquid crystal panel from which the short wiring has been completely removed in advance.
s, a counter signal Vc supplied to the counter electrode, and a scan signal O supplied to the thin film transistor through the scan line.
The N power supply voltage Vg (H) and the OFF power supply voltage Vg (L) of the scanning signal thereof are kept constant, two of the scanning lines are short-circuited by a short wiring, and the ON power supply current of the scanning signal is reduced to reduce the liquid crystal. The ON power supply current lg (H) O at the time of causing a linear change in brightness ΔTO at the panel to judge the quality
Is measured, the OFF power supply current of the scanning signal is reduced to measure the OFF power supply current lg (L) O when the brightness change ΔTO is generated, and the ON of the scanning signal obtained by the measurement is measured. Power supply current l
Using g (H) O and the OFF power supply current lg (L) O as a reference, each liquid crystal panel in which the liquid crystal panel member is cleaved and the end face or the fractured face of the first substrate is chamfered is inspected. Characteristic liquid crystal panel inspection method.