JPH06100891B2 - Liquid crystal display device defect inspection method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method for a liquid crystal display device including an active matrix substrate and a common electrode substrate.

2. Description of the Related Art In recent years, with the miniaturization of industrial equipment, there has been a demand for a thin flat-panel display device that replaces a CRT, which has been a conventional display device. Among various types of flat panel display devices, a display device using liquid crystal has attracted attention as a display device for portable equipment because it consumes less power and can be driven by a battery. Liquid crystal display devices for displaying images and characters are roughly classified into a simple matrix system and an active matrix system using a thin film transistor, etc., but a liquid crystal display device using the active matrix system accurately and independently requires a necessary signal voltage. Since it can be transmitted to each picture element, there is no crosstalk, and a display with a large contrast ratio is possible, which is drawing attention. However, in the active matrix method, it is necessary to make several hundreds of thousands of transistors on the entire screen, and how to eliminate defects in the active matrix substrate including these transistors is a technical issue.

As a thin film transistor used in an active matrix type liquid crystal display device, for example, as shown in JP-A-60-192369, the structure is as shown in FIG. That is, the gate electrode of the transistor 51 is the gate line
The source electrodes are connected to X _{1 to} X _M , the source electrodes are connected to Y ₁ to Y _N , and the drain electrodes are connected to the pixel electrodes 52. Then, the liquid crystal 53 is inserted between the picture element electrode and the counter common electrode to form an independent picture element 54. Among the defects of the thin film transistor having the structure as shown in FIG. 2, the short circuit defect causes a serious deterioration of the display image quality.
The short circuit between the gate electrode and the source electrode of the transistor causes a so-called line defect in which all the pixels connected to the gate line and the source line including the short circuit portion do not light up. On the other hand, a short circuit between the gate electrode and the drain electrode and a short circuit between the source electrode and the drain electrode are so-called point defects that affect only the pixel to which the transistor including the defect is connected.
Here, in the case of the line defect inspection, which is a short circuit between the gate electrode and the source electrode, the defect inspection can be performed relatively easily because the gate line and the source line of the active matrix substrate are short-circuited. And drain electrode,
Alternatively, in the case of inspecting a point defect that is a short circuit between the source electrode and the drain electrode, there is no effective method other than performing a defect inspection by directly contacting each electrode with a test probe or the like.

Problems to be Solved by the Invention As described above, there is no effective means for inspecting a point defect of a liquid crystal display device except for directly inspecting a transistor on an active matrix substrate using a test probe.
However, the method using the test probe may damage the surface because the test probe is brought into direct contact with the transistor or the pixel electrode.Because all the transistors must be inspected while moving the test probe, It takes a huge amount of time. When an image is displayed on the entire surface after liquid crystal is injected and sealed, it is easy to confirm the presence or absence of point defects, but it is practically impossible to count the coordinates of the picture elements in order to check the position. . For the reasons described above, it has been the reality that the point defect inspection of the liquid crystal display device is hardly performed.

The present invention has been made in view of the above points, and an object thereof is to provide an inspection method for easily inspecting a point defect of a liquid crystal display device.

Means for Solving the Problems In order to solve the above problems, the present invention provides an active matrix type liquid crystal display device in which an electric signal is supplied to an arbitrary gate line or source line to turn on a defective pixel. As to detect the position of the picture element.

The present invention has the above-described configuration, and inspects a point defect in the entire liquid crystal display device by supplying a signal to the gate line and the source line from the outside and detecting the defect position in the liquid crystal display device in which liquid crystal is injected and sealed. Can be performed efficiently.

Embodiment A defect inspection method for a liquid crystal display device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a defect inspection method for a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, X _{1 to} X _M are gate lines and Y _{1 to} Y _N
Is a source line, T _{11 to} T _MN is a transistor, C _{11 to} C _MN is a pixel, 11 is an AC electric signal source of a gate line, 12 is an AC electric signal source of a source line, and 21 and 22 are electric signals. It is a switch to do. Reference numeral 31 indicates a short-circuited portion between the gate electrode and the drain electrode of the transistor, and 32 indicates a short-circuited portion between the source electrode and the drain electrode.

The operation of the present embodiment configured as described above will be described below with reference to the drawings. In FIG. 1, the switch 21 is closed and the signal source 11 for outputting a signal of a magnitude capable of keeping the liquid crystal sufficiently transmitting light is gated.
Consider the case of connecting to X ₁ . In this case, the source lines Y _{1 to} Y _N
Is in the open state, the pixel connected to the gate line X ₁ is in the non-lighting state unless the active matrix is defective. However, for example, if the transistor T ₁₂ connected to the gate line X ₁ has a short-circuited portion 31 between the gate electrode and the drain electrode, the pixel C ₁₂ has a signal-source 11 through the short-circuited portion 31.
Signal is added and the picture element C ₁₂ is turned on. Normally, when the gate electrode and the drain electrode of the transistor are short-circuited, when the display is performed, the picture element of the defective portion is turned off. This is because the gate line is scanned during display, and the off time is much longer than the on time of the transistor, so the charge once charged to the pixel is discharged through the short-circuited part. The reason is that On the other hand, in this embodiment, the gate line is not scanned and is fixed, so that the picture element is always supplied with electric charge and is in a lighting state.

Also, consider a case where the switch 22 is closed, the signal source 12 is connected to the source line Y ₁ , and all the gate lines are opened. In this case as well, the transistor does not operate unless the active matrix has a defect, and therefore all the picture elements connected to the source line Y ₁ are in the non-lighting state. However, for example, if the transistor T ₂₁ connected to the source line Y ₁ has a short circuit portion 32 between the source electrode and the drain electrode, the short circuit portion 32 is provided in the pixel C _21.
Since the signal from the signal source 12 is constantly applied via the picture element C _{21, the} picture element C ₂₁ is turned on.

Here, the reason why the signals supplied to the gate lines and the source lines are alternating current is that some liquid crystal materials do not operate unless they are driven by alternating current.

When an arbitrary gate line or source line is selected and an electric signal is supplied as described above, a pixel (for example, a pixel) in which the gate electrode and the drain electrode of the transistor are in a short circuit state
C ₁₂ ) and the picture element (for example, picture element C ₂₁ ) in which the source electrode and the drain electrode are in a short circuit state are turned on. Therefore, the defect inspection of the liquid crystal display device can be easily carried out by detecting the defective picture element in the lighting state by using the optical means.

A phototransistor or the like may be used as the means for optically detecting the picture element that has been turned on due to a short-circuit defect, or it may be visually performed. For example, when visually inspecting, if an electric signal is supplied to an arbitrary gate line or source line to turn on a defective pixel and then a signal is supplied to the gate line, an arbitrary source is added. If a signal is supplied to the source line in addition to the line, the signal is supplied to any gate line. Then, the transistor at the intersection of the gate line and the source line supplying the signal is in an operating state, and the pixel connected to the transistor is in a lighting state. The position of the defective pixel can be easily detected by moving the gate line or the source line to which a signal is additionally supplied to match the pixel at the intersection in the lighting state with the defective pixel. it can.

Although the above description has been made in the case where the transistor portion has a short circuit defect, the defect inspection can be performed in the same manner when the gate line and the pixel electrode or the source line and the pixel electrode are in a direct short circuit state.

EFFECTS OF THE INVENTION As is clear from the above description, the present invention relates to an active matrix type liquid crystal display device with an arbitrary gate line,
By supplying an electric signal to the source line to turn on the defective pixel and then detecting the position of the defective pixel by optical means, the defect inspection of the liquid crystal display device can be performed easily and efficiently. You can do it well.

[Brief description of drawings]

FIG. 1 is a block diagram showing a defect inspection method of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a thin film transistor array used in an active matrix type liquid crystal display device. X _{1 to} X _M …… Gate line, Y _{1 to} Y _N …… Source line, T _{11 to} T _MN …
… Transistor, C _{11 to} C _MN …… Picture element, 11,12 …… Electrical signal source, 21,22 …… Switch, 31 …… Short part of gate electrode and drain electrode, 32 …… Source electrode and drain electrode Short circuit part.

Claims (2)

[Claims] 1. An active matrix type liquid crystal display device, wherein a pixel which is connected to the gate line or the source line and is in a lighting state when an electric signal is supplied to the arbitrary gate line or the source line is optically operated. A method for inspecting a defect of a liquid crystal display device, which is characterized in that the defect is detected by a mechanical means. 2. A gate line or a source line at the time of defect inspection is supplied with a signal having a magnitude capable of keeping liquid crystal sufficiently transmitting light. A method for inspecting a defect of the liquid crystal display device described.