JP3266502B2 - Inspection method of liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection method for a liquid crystal display device, and more particularly to an inspection method for an active matrix type liquid crystal display device in which an image signal is supplied to a pixel electrode via a switching transistor.

[0002]

2. Description of the Related Art In order to improve display contrast and response speed, an active matrix type liquid crystal display device for supplying an image signal to a pixel electrode via a switching transistor is being used frequently.

FIG. 5 is a partial equivalent circuit diagram of an active matrix type liquid crystal display device. Multiple scanning signal wirings 13
And a plurality of image signal wirings 14 intersecting each other, and a switching transistor 11 at each intersection, and a liquid crystal capacitor (not shown) sandwiched between a pixel electrode (not shown) and a counter electrode (not shown). 12 are provided. The gate electrode G of the switching transistor 11 is connected to the scanning signal line 1.
3, the switching transistor 11
Are connected to the image signal wiring 14,
The drain electrode D of the switching transistor 11 is connected to the pixel electrode of the liquid crystal capacitor 12.

A scanning signal is supplied to the gate electrode G of the switching transistor 11 from the scanning signal line 13 to turn on the switching transistor 11 and charge the liquid crystal material from the image signal line 14 via the source electrode S and the drain electrode D. Then, the switching transistor is turned off, and the charge is held in the liquid crystal material 12 until the switching transistor 11 is turned on next. During this time, the pixels of the liquid crystal material 12 are selected and displayed.

When the gate electrode G and the source electrode S of the switching transistor 11 are short-circuited, the liquid crystal material 12 of the pixel is not sufficiently charged, resulting in a display failure. When the gate electrode G and the drain electrode D and the source electrode S and the drain electrode D of the switching transistor 11 are short-circuited, the liquid crystal material 12 of the pixel is not sufficiently charged, or the charged charge leaks to display. It becomes bad.

[0006] In order to prevent such display defects beforehand in the inspection in the manufacturing process, inspection using a test probe has been conventionally performed. This conventional inspection method will be described with reference to FIG. In FIG. 6, reference numeral 15 denotes a liquid crystal display device, which includes a switching transistor T _mn (m and n are integers), a liquid crystal capacitance C _mn (m and n are integers), and a scanning signal line X.
_m (m is an integer) and image signal wiring Y _n (n is an integer). 6, 16 indicates a short-circuit defect between the gate electrode G and the drain electrode D, and 17 indicates a short-circuit defect between the source electrode S and the drain electrode D. Reference numeral 18 denotes connection means with the image signal wiring Yn, reference _numeral 19 denotes connection means with the scanning signal wiring _Xn , reference numeral 20 denotes resistance value measuring means,
1 is a test probe positioning means, 22 is a test probe, S _1m (m is an integer) is a switch provided in the connection means 19 for connection to the scanning signal wiring X _n, and S _2n (n is an integer) is an image signal wiring Y _n And a switch provided in the connection means 18. Connecting means 19 between the scanning signal lines X _n may take any electrical connection with the scanning signal lines X _n of the liquid crystal display device 15, connecting means 18 of the image signal lines Y _n is any liquid crystal display device 15 can take an image signal of the line Y _n electrically connected, test probe positioning means 21 can position the test probe 22 to the drain terminal of an arbitrary pixel. The resistance measuring means 20 is connected to the test probe 22 and the image signal lines connecting means 18 and the scanning signal lines connecting means 19, any of the scanning signal lines X _n or image signal lines Y _n and any of the switching transistor The resistance value between the drain terminals of T _mn can be measured.

First, a method for detecting a defect between a gate electrode and a drain electrode will be described. Connecting means 18 between the image signal lines Y _n is with opening switch S ₂₁ of Y ₁ terminal, the scanning signal lines connecting means 19 switch S of X ₁ terminal
Close ₁₁ . Next, the test probe positioning means 21
Positions the test probe 22 to the drain terminal of the switching transistor T _11. Then the resistance measuring means 20 for measuring the resistance between the gate electrode and the drain electrode of the switching transistor T _11. A defect can be detected from the measured resistance value. Opens the switch S ₁₁ of X ₁ terminal for the switching transistor T ₂₁ Similarly, closing the switch S ₁₂ of X ₂ terminal, positioning the test probe 22 to the drain terminal of the switching transistor T _21, the resistance The operation of measuring may be repeated. Connecting the switching transistor T _m1 to end them if one after another to the image signal wiring section 18 Y ₂
Opening the switch S ₂₂ of the terminal, this time repeating the same operation as described above for the switching transistor T _12, the resistance value may hopefully be measured. The above operation may be _repeated up to the switching transistor Tmn.

Next, a method for detecting a defect between the source electrode and the drain electrode will be described. In this case, the scanning signal wiring X
with the connection means 19 between the _n opens the switch S ₁₁ of X ₁ terminal, connection between the image signal lines Y _n means 18 Y ₁
Closing the switch S ₂₁ of the terminal. Then test probe positioning means 21 for positioning the test probe 22 to the drain terminal of the switching transistor T _11. Next, the resistance value measuring unit 20 measures the resistance between the source electrode and the drain electrode of the switching transistor T _11. A defect can be detected from the measured resistance value. Similarly, opening the switch S ₁₂ of X ₂ terminal for the switching transistor T _21, to position the test probe 12 to the drain terminal of the switching transistor T _21, may be repeated operation of measuring the resistance value. Connecting means 18 and the next image signal lines Y _n be terminated until the switching transistor T _m1 is Y ₁
Opening the switch S ₂₂ of the terminal, this closes the switch S ₂₂ may if we measure the resistance value by repeating the same operation as described above for the switching transistor T _12. It may be repeated the above operation until the switching transistor T _mn.

[0009]

However, in the above configuration, since the test probe 22 is used, the test probe 22 is directly connected to the switching transistor T.
₁₁ must be in contact with the through T _mn pixel electrodes connected to the source terminal and the drain terminal of, may damage the element surface. In addition, defect detection leakage due to poor contact of the test probe 22 is likely to occur. In addition, since it is necessary to detect a defect while moving the test probe 22, there is a problem that an enormous amount of time is required for the positioning time.

The present invention has been made in view of the above problems, and has as its object to provide a method of inspecting a liquid crystal display device which can easily perform an inspection of the liquid crystal display device in a non-contact manner.

[0011]

According to a first aspect of the present invention, there is provided an inspection method for a liquid crystal display device, wherein a plurality of scanning signal lines and a plurality of image signal lines are provided so as to intersect with each other. An image signal supplied from the image signal wiring is provided based on a scanning signal having an ON period for maintaining the scanning signal wiring at a predetermined voltage or higher and an OFF period for maintaining the scanning signal wiring at a predetermined voltage or lower while providing a pixel electrode at the intersection. In the inspection method for a liquid crystal display device provided with a switching transistor that performs display by supplying to the pixel electrode, an on period of the scan signal is set to be longer than when the display is performed, and an off period of the scan signal is set to Inspect the charging failure of the pixel electrode portion in the same manner as when performing display.

According to a second aspect of the present invention, a plurality of scanning signal lines and a plurality of image signal lines are provided to intersect with each other, a pixel electrode is provided at the intersection, and the scanning signal line is provided. A switching signal for supplying an image signal supplied from the image signal wiring to the pixel electrode based on a scanning signal having an ON period for maintaining the wiring at a predetermined voltage or higher and an OFF period for maintaining the wiring at a predetermined voltage or lower. In an inspection method of a liquid crystal display device provided with a transistor,
The on-period of the scanning signal is set to be the same as that when the display is performed, and the off-period of the scanning signal is set longer than when the display is performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The configuration of the liquid crystal display device to be inspected by the liquid crystal display device inspection method according to the present invention is the same as the configuration of the liquid crystal display device shown in FIGS.

FIG. 1 is an equivalent circuit diagram of a switching transistor portion and a pixel portion in a liquid crystal display device to be inspected. 1 is a scanning signal line, 2 is an image signal line,
Is a switching transistor, 4 is a pixel electrode, and 5 is a counter electrode.

FIG. 2 is a waveform diagram of a scanning signal, an image signal, and a voltage applied to a liquid crystal material. In Figure 2, the V _G scanning signal supplied from the scanning signal line 1 to the gate electrode G of the switching transistor 3, V _S is the image signal supplied from the image signal line 2 to the source electrode S of the switching transistor . In FIG. 2, t is the time when the switching transistor 3 is on, and T is the time when the switching transistor 3 is off. When a predetermined voltage is applied to the scanning signal wiring in a state where a predetermined positive voltage is applied to the image signal wiring 2, a positive voltage starts to be applied to the liquid crystal material, and the liquid crystal remains after the switching transistor 3 is turned off. A positive voltage is continuously applied to the material.

Next, when a predetermined voltage is applied to the scanning signal wiring 1 in a state where a predetermined negative voltage is applied to the image signal wiring 2, a negative voltage starts to be applied to the liquid crystal material, and the scanning signal wiring is started. The negative voltage is continuously applied to the liquid crystal material even after the application of the predetermined voltage is stopped. Alongside these to ON for a predetermined period of time (t) of the scanning signal V _G to and in other periods (T) off, the period t in which the scanning signal V _G is on
A by applying a positive polarity and negative polarity video signal V _S of alternately applying positive and negative voltages alternately to the liquid crystal material.

However, when the switching transistor 3 in the display section of the liquid crystal display device is not normal, such a situation arises that it is impossible to alternately apply such positive and negative voltages to the liquid crystal material. The following two cases can be considered as causes of such a situation. First,
Is the scanning signal V _G is supplied to the transistor 3 is turned on switching, is charged from the source electrode S, the switching transistor 3 is also immediately leaked off is the leakage condition that can not hold a charge by the liquid crystal material .
Next, the scanning signal V _G is supplied switching transistor 3 is not fully charged from the source electrode S is also turned on, a charging fault condition can not hold a charge by the liquid crystal material.

[0018] In the inspection method of a liquid crystal display device according to the present invention is to the same as when performing the normal display of the on-period t of the scanning signal V _G, performs normal display of the off period T of the scanning signal V _G Black display is performed by setting the period to 2T, which is twice the time, and the luminance at that time is measured and compared with the luminance in the normal state to make a determination. Thus, the off period T of the scanning signal V _G
Is set to a period 2T, which is twice as long as that for normal display, and the black display is performed, the period for leaking is doubled, and if there is a leak, this leak defect can be detected extremely accurately.

Further, with doubling of the period 2t when performing display the on period t of the scanning signal V _G of the normal, setting the OFF period T of the scanning signal V _G to the same as when performing a normal display Black display is performed, and the luminance at that time is measured and compared with the luminance in a normal state to make a determination. Thus, when black display is performed by setting the ON period t of the scanning signal V _G to twice the period 2t when performing normal display, the period to be charged is doubled, there is a charging failure If it is, this charging failure state can be detected extremely accurately.

[0020] In the above embodiment, although the off period T of the ON period t and the scanning signal of the scanning signal V _G was stated to be two-fold, respectively, it is not limited to this embodiment, at least usually If the period is longer than the period in the display state, the leak state or the charging failure state can be detected with higher accuracy. If there is no need to distinguish between the leakage state or insufficiently charged state may be long both the on period t and OFF period T of the scanning signal V _G.

[0021]

As described above, according to the inspection method for a liquid crystal display device according to the present invention, the on-period of the scanning signal is made longer than when displaying, and the off-period of the scanning signal is displayed. Inspection of the charging failure of the pixel electrode portion is performed in the same manner as described above, and the ON period of the scanning signal is set to be the same as when displaying, and the OFF period of the scanning signal is set longer than when displaying the pixel electrode portion. By inspecting the leak failure, it is possible to grasp whether or not the switching transistor in the display unit has an abnormality before the driving IC is mounted. In addition, no special equipment is required for performing this test, and the test can be performed simply by adding a signal generator program.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram illustrating one pixel portion of a liquid crystal display device.

FIG. 2 is a waveform diagram showing a scanning signal, an image signal, and a voltage applied to a liquid crystal material.

FIG. 3 is a waveform diagram of a signal used at the time of a leak failure inspection.

FIG. 4 is a waveform diagram of a signal used at the time of a charge failure test.

FIG. 5 is an equivalent circuit diagram of a conventional liquid crystal display device.

FIG. 6 is a view for explaining a conventional method of inspecting a liquid crystal display device.

[Explanation of symbols]

1 ... scanning signal wiring, 2 ... image signal wiring, 3 ...
.Switching transistors, 4... Pixel electrodes, 5
... Counter electrode

Claims (2)

(57) [Claims] A plurality of scanning signal lines and a plurality of image signal lines are provided to intersect with each other, a pixel electrode is provided at the intersection, and an ON period for maintaining the scanning signal lines at a predetermined voltage or higher and a voltage lower than a predetermined voltage. An inspection method for a liquid crystal display device provided with a switching transistor for performing display by supplying an image signal supplied from the image signal wiring to the pixel electrode based on a scan signal having an off period to be maintained,
A liquid crystal display, wherein an on-period of the scanning signal is made longer than when the display is performed, and an off-period of the scanning signal is made the same as when the display is performed, to check for a charging failure of the pixel electrode portion. Display device inspection method. 2. A plurality of scanning signal wirings and a plurality of image signal wirings are provided crossing each other, a pixel electrode is provided at the crossing portion, and an ON period for maintaining the scanning signal wirings at a predetermined voltage or higher and a voltage lower than a predetermined voltage. An inspection method for a liquid crystal display device provided with a switching transistor for performing display by supplying an image signal supplied from the image signal wiring to the pixel electrode based on a scan signal having an off period to be maintained,
The on-period of the scanning signal is set to be the same as that when the display is performed, and the off-period of the scanning signal is set longer than when the display is performed, to inspect the pixel electrode unit for a leak failure. Inspection method for liquid crystal display.