JPH08313396A - Liquid crystal panel inspecting method - Google Patents

Abstract

PURPOSE: To provide an active matrix type liquid crystal panel inspecting method that can correctly detect a short-circuited place between gate wiring and source wiring in a short time and in the actual display state after a gate driving IC and a source driving IC being mounted. CONSTITUTION: Display signal voltage is applied to a plurarity of gate wiring 10 of an active matrix type liquid crystal panel 1 and a plurarity of source wiring 9a, 9b excluding specific source wiring 7, and inspecting signal voltage for changing the display luminance of a picture element row connected to the specific source wiring is applied to the specific source wiring. Whether or not the display luminance of the picture element row connected to each of a plurarity of gate wiring is changed is detected to detect a short-circuited place between the gate wiring and source wiring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting an active matrix type liquid crystal panel. More specifically, the present invention relates to an active matrix type liquid crystal panel inspection method capable of easily inspecting the presence or absence of a short circuit between a gate wiring and a source wiring in a display state and, if there is a short circuit, identifying the coordinates thereof.

[0002]

2. Description of the Related Art In recent years, an active matrix type liquid crystal display device using a thin film transistor (hereinafter referred to as a TFT) can accurately and independently transmit a necessary signal voltage to each pixel, and there is no crosstalk and contrast. Since a display with a large ratio is possible, it is used as a liquid crystal display device that requires high display capacity and high resolution display. In this active matrix type liquid crystal display device, tens to hundreds of thousands of TFTs are used. One of these TFTs has a short circuit between the gate and the source, or the source wiring and the gate wiring intersect. When a short circuit occurs at a portion, TFs connected to the gate wiring and the source wiring intersecting at that point, respectively
Pixels connected to T are not displayed, resulting in line defects.

FIG. 10 is an explanatory diagram of a method for inspecting the presence or absence of such a short circuit between a gate wiring and a source wiring. For example, a conventional active matrix type liquid crystal panel inspection method disclosed in Japanese Patent Laid-Open No. 3-123315. It is a block diagram which shows. In FIG. 10, 21 is an ohmmeter, 22 and 23 are probes, G ₁ , G ₂ , G ₃ , G ₄ , ... (generally referred to as G _i ) are gate wirings, S ₁ , S ₂ , S ₃ , S ₄ , ... (Generally referred to as S _j ) are source wirings, T _ij (i, j are 1, 2,
3, 4, ... _Are TFTs, P _ij (i, j are 1, 2, 3,
4 ...) is a pixel, and 26 is a short circuit portion between the gate wiring and the source wiring.

In the conventional inspection, before the source driving IC and the gate driving IC are connected, the probe 22 is first pressure-contacted to the source wiring S ₁ and the probe 23 is pressure-contacted to the gate wiring G ₁ to electrically connect them. After that, the resistance value between the probe 22 and the probe 23, for example, the resistance value between the source wiring S ₁ and the gate wiring G ₁ is measured by the ohmmeter 21. Next, move the probe 22 to the source wiring S ₂ ,
Similarly, the resistance value between the source wiring S ₂ and the gate wiring G ₁ is measured, and similarly, the probe is sequentially moved to the source wiring S _j to measure the resistance value.

When the resistance value between the gate wiring G ₁ and all the source wirings S _j has been measured, the probe 23 is moved and pressed against the gate wiring G ₂ , and each source is processed as in the gate wiring G _1. The resistance value with the wiring S _j is measured. By repeating this operation, the resistance value between each of the gate lines G _i and each source line S _j is measured. If the resistance value between the source wiring S _j and the gate wiring G _i is significantly lower than the resistance value of the normal portion, the source wiring S _j
And the coordinates of the gate line G _i (i, j values of S _j , G _i , for example, in FIG. 10, when the short circuit portion 26 exists, i =
3, j = 3) is detected to perform a short circuit test between the source line S _j and the gate line G _i of the active matrix type liquid crystal display device.

On the other hand, for example, JP-A-63-182578.
In Japanese Patent Publication No. 63-123093 and Japanese Patent Publication No.
In order to detect a display defect of a pixel due to a short circuit between drains or between a source and a drain, a method of illuminating a display screen and optically inspecting is disclosed. As described above, with respect to the inspection of a point defect in which a defect appears in each pixel, the inspection can be easily performed by such an inspection method, and it is possible to specify the position of the pixel in each of the vertical and horizontal directions which is defective.

However, in the inspection for the presence or absence of a short circuit between the source wiring and the gate wiring, if there is a short circuit, it is connected to the column of pixels associated with the TFT connected to the source wiring and the gate wiring short-circuited with the source wiring. The columns of pixels associated with the TFTs are displayed as line defects. These line defects also appear, for example, when static electricity flows into the source wiring or the gate wiring, and since the line defects appear, it is not possible to immediately determine that the source wiring and the gate wiring are short-circuited.

[0008]

In a conventional method for detecting a short circuit between a gate wiring and a source wiring by measuring a resistance value between the gate wiring and the source wiring, a probe is applied to all the gate wirings and the source wirings. It is necessary to press and to measure the resistance value with a combination of matrices. Therefore, it takes a very long time to inspect a recent liquid crystal panel having more than 1000 wirings.

Further, this short-circuit inspection method uses the gate drive I
Since it is performed in the manufacturing process before the C and source driving ICs are mounted, there is also a problem that a short circuit portion or a disconnection between the gate wiring and the source wiring that occurs after this step cannot be detected.

Further, as described above, in the method of detecting an abnormality of a lighting pixel while the liquid crystal panel is turned on, it is difficult to distinguish from a line defect due to external noise such as static electricity, and a short circuit between the gate wiring and the source wiring is caused. However, there is a problem in that the line defect inspection as described above cannot be performed accurately and quickly with the light being turned on.

The present invention has been made in order to solve such a problem, and in the actual display state after the inspection time is short and the gate driving IC and the source driving IC are mounted, the gate wiring is An object of the present invention is to provide an inspection method of an active matrix type liquid crystal panel capable of accurately detecting a short-circuited portion between a source wiring and a source wiring.

[0012]

According to an inspection method of an active matrix type liquid crystal panel of the present invention, a display signal voltage is applied to a plurality of source lines other than a plurality of gate lines and a specific source line of an active matrix type liquid crystal panel. In addition to the application, an inspection signal voltage that changes the display brightness of the pixel column connected to the specific source line is applied to the specific source line, and the inspection signal voltage of the pixel column connected to each of the plurality of gate lines is applied. By detecting whether or not there is a change in display brightness, a short circuit portion between the gate wiring and the source wiring is detected.

The inspection signal voltage is a signal for blinking the display of the pixel column connected to the specific source line at a constant cycle, and whether or not the pixel column connected to any of the plurality of gate lines blinks. If there is a gate wiring that is short-circuited with a specific source wiring, the pixel column connected to the gate wiring blinks, and it is easy to discriminate at a glance.

The display signal voltage is a signal voltage having an amplitude smaller than that of the display signal having the maximum amplitude, and the pixel column connected to the source wiring other than the specific source wiring is displayed in the halftone so that the inspection is performed. Since the inspection can be performed against the background of the display state of the brightness different from the blinking display of, the blinking state can be easily recognized.

Detecting the brightness of each pixel of the liquid crystal panel with a CCD area sensor is preferable from the viewpoint of labor saving because the inspection can be performed automatically.

The source wiring to which the inspection signal voltage is applied may be sequentially changed from the ends of the plurality of source wirings.
This is preferable because it is easy to supply the inspection signal voltage to each source wiring.

It is preferable that the specific source wiring is at least two of a part of the plurality of source wirings because the inspection time can be shortened.

[0018]

According to the present invention, as the inspection signal voltage, a voltage whose display luminance changes every certain period is applied to each specific source wiring, so that the source wiring to be inspected undergoes a certain luminance change, The presence or absence of abnormality of the pixel column connected to the specific source wiring can be detected separately from external noise such as static electricity, and a short-circuit portion is formed between the specific source wiring and any of a plurality of gate wirings orthogonal to each other. In some cases, the same change in brightness occurs in the pixel column connected to the gate wiring having the short-circuited portion as in the pixel row connected to the specific source wiring, so that the presence or absence of the short-circuited portion can be immediately detected. , You can know its coordinates.

[0019]

【Example】

Example 1 Next, an example of an inspection method for a liquid crystal panel according to the present invention will be described with reference to FIG.
Will be described with reference to. In FIG. 1, 1 is a liquid crystal panel, 2 is a source driving IC, 3 is a gate driving IC,
The source driving IC 2 and the gate driving IC 3 are connected to the source wiring and the gate wiring of the liquid crystal panel 1 via the connecting portions 4 and 5, respectively. Reference numeral 6 denotes a signal generating circuit for generating a display signal and a test signal, which includes a personal computer and a timing signal generating circuit.
A drive signal is supplied to the source drive IC 2 and the gate drive IC 3.

The signal generating circuit 6 generates an inspection signal voltage for blinking display as shown in FIG. 2 and a display signal voltage as shown in FIG. 3, for example. 2 to 3, the solid line indicates the source signal voltage supplied to the source wiring, and the broken line indicates the gate signal voltage supplied to the gate wiring. The inspection signal voltage of the present embodiment shown in FIG. 2 is an AC voltage signal that is converted to the maximum amplitude during the ON period shown on the left side of FIG. 2, and during the OFF period shown on the right side of FIG. Is a signal of zero amplitude, and supplies a blinking inspection signal voltage that repeats the signal voltage in the ON period and the signal voltage in the OFF period, for example, every one second so that the dark color display and the white display are alternately repeated. By switching between the full voltage for display and the zero level in this way, the screen blinks and the difference in brightness is large, so there is an advantage that inspection is easy, but switching is performed with two voltages in between. May be. The point is that the brightness of the liquid crystal panel may change between the ON period and the OFF period.

Further, the display signal voltage of the present embodiment shown in FIG. 3 is not an AC voltage having the maximum amplitude but a display signal voltage for half-tone display. This is because the inspection signal voltage is applied to a specific source line and blinks to inspect it, so that the pixels connected to other source lines are displayed in halftone (brightness between the ON state and the OFF state). This is because by setting it, it is easy to determine whether it is on or off unlike the brightness of the back.

As shown in FIG. 1, the method of inspecting a liquid crystal panel according to the present invention is such that the signal generation circuit 6 causes the source driving IC 2 and the gate driving IC 3 to generate source signals as shown in FIGS. 2 and 3, respectively. Supply voltage and gate signal voltage. In this case, as for the source signal voltage, a display signal voltage capable of performing halftone display as shown in FIG. 3 is applied to all the source wirings except one specific source wiring, Figure 2 for source wiring
The display pattern control circuit in the signal generating circuit is set so that the inspection signal voltage capable of blinking display as shown in FIG. As a result, the display signal voltage for halftone display is applied to all the source wires other than the one source wire to be inspected, and the display signal is applied together with the gate signal voltage applied from the gate driving IC 3 to each gate wire. All the pixels connected to the source wiring to which the voltage is applied via the TFT are turned on with intermediate brightness. On the other hand, in the pixel connected to the source line 7 to which the inspection signal voltage is applied via the TFT, the display blinks according to the on / off of the inspection signal voltage. Therefore, only one pixel row is illuminated in one row along the source wiring to be inspected, and all the other pixels are displayed with intermediate brightness. In this state, the source wiring is normal without any short circuit with any gate wiring. It indicates that there is. After that, the source wirings to which the test signal voltage is applied can be sequentially moved, and all the source wirings can be similarly tested.

Next, the source wiring 9a and the gate wiring 10a
The display state when the short-circuited portion 8a is present between and will be described. If there is the short-circuit portion 8a, the equivalent circuit of the pixel can be expressed as shown in FIG. That is, the insulation resistance between the source wiring 9a and the gate wiring 10a is reduced and a current path is formed through the short-circuit portion 8a, so that a sneak current flows from the source wiring 9a to the gate wiring 10a. Therefore, the gate signal voltage applied to the gate wiring 10a changes under the influence of the source signal voltage of the source wiring 9a. That is, when the blinking signal voltage as shown in FIG. 2 is applied to the source wiring 9a, the gate wiring 10a
The gate signal voltage of is transformed into a waveform as shown in FIG. 6 as compared with the signal voltage of the normal gate wiring (see FIG. 5). Source-drain current _Id-s and gate of TFT
The relationship with the bias voltage V _gs between the sources is generally as shown in FIG. 7, and in the intermediate region of V _on -V _off , log I _ds and V _gs are partial linear expressions (linear relationship).
Can be approximated by.

The source and drain of the TFT on the gate wiring 10a during the ON period of the blinking inspection signal voltage,
The signal voltages SV, DV and GV of the gates are as shown in FIG. 8, and the charges injected into the pixel via the drain during the positive polarity period in FIG. 8 are represented by the formula (1).

[0025]

[Equation 1]

Similarly, the charge injected into the pixel via the drain during the negative polarity period of FIG. 8 is expressed by the equation (2).

[0027]

[Equation 2]

Here, the positive polarity period indicates when the drain voltage is positive, and the negative polarity period indicates when the drain voltage is negative. I _on3> I _on1, I _off3 than 7>
Since I _off1 , Equation (1)> Equation (2) holds and the charge injected into the pixel during the positive polarity period becomes larger than the charge injected into the pixel during the negative polarity period, and as a result, the potential of the pixel increases. The time average value changes to the higher potential side, and the luminance of the pixel connected to the gate wiring having the short circuit portion becomes dark during the on period.

On the other hand, during the off period of the blinking inspection signal voltage, the gate signal is the same in both the positive polarity period and the negative polarity period, and the charge injected into the pixel is expressed by the following equation (3) in both periods.
Will be constant as given by.

[0030]

(Equation 3)

As described above, the potential of the pixel column connected to the gate wiring 10a via the TFT is different between the ON period and the OFF period of the flashing inspection signal voltage, and as a result, the gate wiring 10a is connected to the gate wiring 10a via the TFT. The luminance of the connected pixel column blinks in synchronization (synchronization) with the blinking inspection signal voltage applied to the source wiring 9a intersecting the gate wiring 10a via the short-circuit portion 8a. That is, when a blinking state for inspection appears in a pixel column orthogonal to the pixel line along the source line being inspected, the gate line 10a connected to the pixel column and the source line 9a inspected are connected. It is possible to detect the presence of the short circuit portion 8a in the meantime. Gate wiring 10a connected to this blinking pixel column
The address (display coordinates) of the short-circuit portion 8a can be calculated by displaying the cursor at the position and calculating the coordinates of the display cursor by software. Source wiring 9
The coordinates of a may be calculated from the coordinates of the display cursor as in the case of calculating the coordinates of the gate wiring 10a, or may be calculated from the coordinates of the source wiring 9a to which the inspection signal voltage is input. it can.

Another gate wiring 10b is formed by the same method.
It is possible to calculate the coordinates of another short circuit portion 8b existing between the source wiring 9b and the source wiring 9b.

Second Embodiment In the first embodiment, the change in the luminance of the pixel column connected to the gate wiring 10a caused by the application of the inspection signal voltage to the gate wiring 10a and the source wiring 9a having the short circuit portion 8a is used. Then, the defective gate wiring 10a was visually detected, but the defective gate wiring 10a can be detected by converting an optical signal into an electric signal, for example, by a CCD area sensor or the like. The effect that the short circuit inspection of the matrix type liquid crystal panel can be automated is added. When inspecting with a CCD area sensor, for example, as shown in the block diagram in FIG. 9,
The sensor 11 may be provided directly on the front surface of the liquid crystal panel 1 (see FIG. 9).
(A)), the sensor 11 is arranged via the convex lens 12 and the slit 13 (FIG. 9B), and the output of the signal processing circuit 14 for photoelectrically converting the output of the sensor 11 is used as the arithmetic processing circuit 1.
By performing image processing according to 5, line defects can be automatically detected.

Embodiment 3 In the above-mentioned Embodiments 1 and 2, the source wiring 7 to which the inspection signal voltage is applied is sequentially moved one by one. However, the inspection signal voltage is simultaneously applied to a plurality of source wirings, The number of source lines to which a blinking signal is input is reduced by the change in the luminance of the pixel to be inspected to narrow down the number of pixels to be inspected. be able to. In this case, when blinking appears in the pixel row in the gate wiring direction, it is necessary to return the source wirings to which the inspection signal is applied to one by one, but the inspection signal voltage is applied to the specific source wiring to be inspected. It can be applied and the inspection time can be shortened, and it is effective when there are few abnormalities and the number of source wirings is large.

[0035]

According to the present invention, since the abnormality is detected by detecting the brightness change of the pixel column, it is not necessary to press the probe to the source wiring terminal or the gate wiring terminal under pressure, and the source wiring and the gate wiring are eliminated. It is possible to perform the inspection in the display state while distinguishing the line defect caused by the short circuit of the line defect from the line defect caused by the external noise such as static electricity. as a result,
It is possible to detect the short circuit location of the source wiring and the gate wiring in a short time with certainty, and it is possible to detect the short circuit location of the source wiring and the gate wiring after mounting the source driving IC and the gate driving IC. The property is improved.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a method for inspecting a liquid crystal display device of the present invention.

FIG. 2 is a timing chart showing an example of an inspection signal voltage used in the method of the present invention.

FIG. 3 is a timing chart showing an example of a display signal voltage used in the method of the present invention.

FIG. 4 is an equivalent circuit diagram in the case where one pixel of the liquid crystal panel has a short circuit portion.

FIG. 5 is a timing chart showing an example of a signal voltage of a gate wiring.

FIG. 6 is a timing chart showing the signal voltage of the gate wiring when there is a short circuit between the gate and the source.

FIG. 7 is a diagram showing a V _gs -I _ds characteristic of a TFT.

FIG. 8 is a timing chart showing the voltage of each part of the TFT on the gate wiring when there is a short circuit between the gate and the source.

FIG. 9 is a block explanatory diagram when a display defect is inspected using a CCD sensor.

FIG. 10 is a diagram illustrating a conventional liquid crystal panel inspection method.

[Explanation of symbols]

 1 liquid crystal panel 6 signal generation circuit 8a, 8b short-circuit part 9a, 9b source wiring 10a, 10b gate wiring

Claims (6)

[Claims] 1. A display signal voltage is applied to a plurality of source wirings other than a plurality of gate wirings and a specific source wiring of an active matrix liquid crystal panel, and the specific source wiring is connected to the specific source wiring. Applying the inspection signal voltage that changes the display brightness of the pixel row,
A method of inspecting a liquid crystal panel, which detects a short-circuited portion between a gate wiring and a source wiring by detecting whether or not there is a change in display brightness of a pixel column connected to each of the plurality of gate wirings. 2. The inspection signal voltage is a signal for blinking a display of a pixel column connected to the specific source wiring at a constant cycle, and blinking of a pixel column connected to any one of the plurality of gate wirings. The inspection method according to claim 1, wherein the presence or absence of the above is detected. 3. The display signal voltage is a signal voltage having an amplitude smaller than that of the maximum amplitude display signal voltage, and a pixel column connected to a source line other than a specific source line is displayed in halftone. Or the inspection method described in 2. 4. The brightness of each pixel of the liquid crystal panel is measured by a CCD.
The inspection method according to claim 1, 2 or 3, which is detected by an area sensor. 5. The inspection method according to claim 1, 2, 3, or 4, wherein the source lines to which the inspection signal voltage is applied are sequentially changed from the ends of the plurality of source lines. 6. The specific source line is at least two of a part of the plurality of source lines.
The inspection method described in 2, 3, 4 or 5.