JPH02140794A - Defect checking method for liquid crystal display device - Google Patents

Abstract

PURPOSE:To detect a defective picture element before assembling by immersing substrates and an electrode in an electrolyte solution and applying a negative voltage and a positive voltage to each select line of substrates and the electrode respectively and detecting a defect of the picture element electrode by the reduction action. CONSTITUTION:Substrates 22, 23, and 24 and an electrode 25 are immersed in an electrolyte solution 21, and the negative voltage and the positive voltage are applied to each of select lines 26 and 31 of substrates 22, 23, and 24 and the electrode 25 respectively, and a defect of a picture element electrode 27 is detected by the reduction action caused between the picture element electrode 27 and respective select lines 26 and 31. That is, when a voltage is applied to the picture element electrode 27 while a thin film transistor 29 is not turned on, the reduction action is caused between the picture element electrode 27 and the electrolyte solution 21 and the quantity of oxygen O included in the picture element electrode 27 is reduced. The picture electrode 27 where short- circuit 28 occurs is blackened and is easily visually detected, and this detection is possible before final assembling.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for inspecting defects in liquid crystal displays.

(Prior Art) FIG. 4 is a block diagram of a color liquid crystal display, which consists of a polarizing plate 1. An electrode side consisting of a counter substrate 2, a color filter layer 3 consisting of red, green, and blue colors, and a counter electrode 4, and a substrate side consisting of a TPT (thin film transistor) array substrate 5 and a polarizing plate 6 are arranged to face each other. However, a liquid crystal 7 is sealed between the electrode side and the substrate side, and furthermore, a diffusion plate 8 is arranged behind the polarizing plate 6, and a backlight 9 is arranged. Also, T
The FT array substrate 5 has a large number of pixel electrodes 10 arranged vertically and horizontally, thin film transistors 11 as switching elements are formed on each of these pixel electrodes 10, and selection lines 12 and 13 are formed in each of these thin film transistors 11 in the vertical and horizontal directions. It is wired. In addition,
The equivalent circuit of the above liquid crystal display is as shown in FIG.

With such a configuration, when each selection line 12.13 is selected and a voltage is applied, each selected selection line 1
The thin film transistor 11 provided where 2.13 coincides is turned on.

As a result, a voltage is applied between the pixel electrode 10 that has been turned on and the counter electrode 4, and the amount of light transmitted changes due to the action of the liquid crystal 7 during this time.

As a result, for example, if the pixel electrode 10 corresponds to red,
The light passes through the red color filter 3 and emits red light. Note that when the thin film transistor 11 is turned off,
Light no longer passes through the color filter 3 and no light is emitted.

By the way, in such a liquid crystal display, each pixel is inspected for defects. In this inspection, after a color liquid crystal display is assembled, defective pixels such as pixels that do not emit light by emitting light for each color or defective pixels that emit green light when red light is emitted are visually identified. In this case, the defective pixel is often a point defect that appears as one or a line defect that appears in multiple lines.

By the way, such a defective pixel may be caused by, for example, a short circuit 14 between the selection line 12 and the pixel electrode 10 as shown in FIG. This is due to a short circuit between the source electrode 15 and the gate electrode 16. However,
Due to such defective or defective pixels, defective pixels in a color liquid crystal display occur during the process of producing the TFT array substrate 5 before assembling the entire color liquid crystal display. Therefore, in the above defective pixel inspection method, the color liquid crystal display is inspected after the color liquid crystal display is assembled, so if a defective pixel is detected and the number of defective pixels exceeds the allowable number of defects, the assembled color liquid crystal display will be considered defective. It becomes unusable. Not only that, but the color liquid crystal display must be assembled with the defective pixel still present, making the assembly process completely wasteful. Further, the above inspection method cannot determine whether or not the color liquid crystal display can be repaired.

(Problem to be Solved by the Invention) As described above, in the above inspection method, the inspection is performed after the color liquid crystal display is assembled, so if a pixel defect is detected, the color liquid crystal display must be judged as a defective product. , which resulted in a lot of waste.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a defect inspection method for a liquid crystal display that can detect defective pixels before final assembly of the liquid crystal display.

[Structure of the invention]

(Means and effects for solving the problem) The present invention arranges a large number of pixel electrodes each provided with a switching element in the vertical and horizontal directions, and wires selection lines in the vertical and horizontal directions to these switching elements. In a defect inspection method for a liquid crystal display having a substrate made of This is a defect inspection method for liquid crystal displays that detects defects in pixel electrodes from the reduction action that occurs between the selected line and each selection line.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a defect inspection apparatus to which a liquid crystal display defect inspection method is applied. An electrolyte solution 21 is held within the water tank 20 . In this electrolyte solution 21, each TPT substrate 22, 23 of a color liquid crystal display is contained.
．． 24 is immersed, and an electrode 25 made of platinum is also immersed.

A positive voltage (+) is applied to the electrode 25 so that it acts as an anode, and a negative voltage (-) is applied to the vertical selection line 26 shown in FIG. is used to act as a cathode.

Next, an inspection method using the apparatus configured as described above will be explained.

Each TPT substrate 22, 23, 24 is immersed in the electrolyte solution 21, and the electrode 25 is immersed in the same electrolyte solution 21. In this state, a positive voltage (+) is applied to the electrode 25.
is applied and each TFTM board 22, 23, 24 (
7) A negative voltage (-) is applied to each vertical (7) selection i26. In this case, the electrode 25 and each TPT substrate 22,
The voltage applied between 23 and 24 is set to a predetermined value.

Here, if there is a short circuit 28 between the pixel electrode 27 and the vertical selection line 26 as shown in FIG.
A voltage is applied to. Then, a reduction action occurs between the pixel electrode 27 and the electrolyte solution 21, and the amount of oxygen O contained in the pixel electrode 27 decreases. As a result, the pixel electrode 2
7 changes color due to this reduction, and its color becomes black.

FIG. 3 shows each pixel electrode 30 with defects appearing in the TPT substrate 22. FIG.

Next, application of the negative voltage to the vertical selection line 26 is stopped, and at the same time, a positive voltage is applied to the horizontal selection line 26. As a result, if there is a short circuit between the pixel electrode 27 and the horizontal selection line 31, a reduction effect occurs in the same manner as described above, and the pixel electrode 27 changes color.

In this way, in the above embodiment, the TPT substrate 22,
23 and 24 are immersed in the electrolyte solution 21, and in this state, a negative voltage is applied to each selection line 26 and 31, and the electrode 25 to which a positive voltage has been applied is immersed in the electrolyte solution 21, and the pixel electrode 27 and each Since defects in the pixel electrode are detected from the reduction action that occurs between the selection line 26 and 31, short circuit 2
The pixel electrode 27 where 8 has occurred becomes black and can be easily detected visually, and this detection can be made before the color liquid crystal display is finally assembled. Therefore, the short circuit can be repaired before final assembly of the color liquid crystal display. Furthermore, if the number of defective pixel electrodes 30 is greater than the allowable number of defects, or if defective pixels are located at locations where they should not be present, a color liquid crystal display will no longer be assembled using a defective TPT substrate. . Therefore, waste in manufacturing color liquid crystal displays can be greatly reduced.

Furthermore, in the above inspection method, since a voltage is applied to each selection line 26.31, the inspection can be performed in a state close to the usage state, and by increasing the voltage value applied to the electrode 25 and each selection line 26.31, Even the slightest short circuit can be detected.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, in the above embodiment, a color liquid crystal display was inspected for defects, but the present invention can also be applied to defect inspections for black and white liquid crystal displays. Further, the switching element is not limited to a thin film transistor, but may be a two-terminal element such as an MIM. Also, electrode 2
5 and the selection line 26 may be applied before immersion in the voltage solution.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide a defect inspection method for a liquid crystal display that can detect defective pixels before final assembly of the liquid crystal display.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the defect inspection method for a liquid crystal display according to the present invention, in which FIG. 1 is a block diagram of a defect inspection apparatus to which the method is applied, and FIG. 2 is a diagram showing the detection operation. Figure 3 is a diagram showing the test results, Figure 4 is a configuration diagram of a color liquid crystal display, Figure 5 is an equivalent circuit diagram of the display, and Figure 6 is a diagram showing a short circuit state. . 20... Water tank, 21... Electrolyte solution, 22.23° 24... TPT substrate, 25... Electrode, 26.31.
. . . Selection line, 27 . . . Pixel electrode, 29 . . . Thin film transistor. Applicant's Representative Patent Attorney Takehiko Suzue

Claims (1)

[Claims] A defect inspection method for a liquid crystal display having a substrate having a plurality of pixel electrodes each provided with a switching element arranged in the vertical and horizontal directions, and each selection line in the vertical and horizontal directions being wired to the switching elements, the substrate and immersing said electrode in an electrolyte solution; at the latest after this immersion state, applying a negative voltage to each selection line of said substrate and applying a positive voltage to said electrode, which occurs between said pixel electrode and each said selection line; A method for inspecting defects in a liquid crystal display, characterized in that defects in the pixel electrode are detected from a reduction effect.