JPS58118697A - Display panel inspector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inspection device for matrix type display panels.

In recent years, new displays have been actively developed to replace conventional CRT displays.

Among these, liquid crystal displays have attracted attention as displays that are thin, low voltage, and can be driven with low power, which is difficult to achieve with other displays, and are easy to see even in bright places. It has been announced and is about to be put into practical use.

As for the liquid crystal drive method, since it is difficult to achieve high image resolution using the time-division drive method, an active matrix drive method in which one active element is provided for each pixel is used to obtain high resolution. .

The number of pixels for a television image display is 24.
A screen size of about 2 inches with 0x220 = 52800 has been announced.

This active matrix type liquid crystal display uses a semiconductor integrated circuit board as one substrate of the display panel, and it is extremely difficult and time consuming to inspect each part of this integrated circuit board, which is approximately 2 inches in size. For example, when checking the display electrode of each pixel using a fixed card for checking the dilator, the number of bins of this fixed card is 150.
As a result, in order to check all pixels, this fixed card must be moved and inspected a large number of times, resulting in a long inspection time and strict positional accuracy, making it impractical. It is difficult. Currently, the human eye
I usually check this.

In fact, when viewed as an image on a display panel, there are two types of image defects: pixel defects and line defects.Pixel defects become more visible as the pixel size and contrast increase, but they occur randomly within the screen. 1 if distributed in
Approximately 0 to 20 pieces are allowed. On the other hand, in the case of line defects, 1
Books are also not allowed. There are two types of line defects: video signal lines and gate signal lines.

Among line defects, in addition to cases where the video signal line is short-circuited to the power supply VDD and short-circuited to the substrate potential, there are cases where the line is open and no video signal is input. If there is a short circuit on either side, there is a way to burn out the shorted part with a laser or the like, but it is difficult. In contrast, in the case of open, it is possible.

A similar thing is possible in the case of line defects in gate signal lines. Therefore, it is necessary to know the position of the line defect.

The electrical equivalent circuit of the entire liquid crystal display panel is shown in FIG. To write the TV image signal to the storage capacitor C0 of each pixel, the video signal lines XI-Xn and the gate signal lines Y1 to Yn are selected depending on the location on the screen, and the switching transistor Tr of each pixel is opened and closed. It is done as follows. The stored voltage of the storage capacitor co of each pixel becomes the voltage applied to the liquid crystal cell LC of each pixel. -Vss is the potential of the display silicon integrated circuit substrate, and VCOM is the potential of the common electrode serving as the transparent electrode.

The video signal line
2...The liquid crystal cells in the Xl and Yn portions are driven along the video signal line X1.

This video signal line X 1! The method of testing lCG pixels is to optically measure the brightness of the screen when the entire screen is set to the black level and the pixel portion located in this Xl is used as a white level signal, and the entire screen is set to the black level. By measuring the brightness of the two pixels, it is possible to determine whether there is a defect in the line of the video signal 2-in-X1 corresponding to this pixel portion.

The actual configuration of the inspection device is as shown in FIG.

To inspect the image display panel 1, first, since the display panel is of a reflective type, a light source is irradiated from an oblique direction and set at a position with the best contrast.

For example, the video signal line
When a high-level signal is input to X1, the vertical scanning circuit operates normally, and the pixels in the portion of the video signal line X1 are driven, causing this portion to shine white.

This light is focused by a condensing lens 3, converted into an electric signal by a photoelectric conversion element 4, amplified by an amplification section 5, and sent to a storage/comparison section 6. The comparison result is sent as a judgment output to the printer 8, and the video signal line number in this case is received from the line number generator 7, and the printer 8 writes and outputs it.

With this configuration, by measuring and comparing the optical signal level of a known video signal line with and without a drive signal, it is possible to determine whether there is a line defect in the video signal line. By automatically testing the video signal lines several times, it is possible to automatically know if there is a line defect in the video signal line.

Also, fix the vertical scanning signal to a certain known gate signal line, switch all of the video signal lines X1 to Xn to high level and low level in this state, and compare the optical signal levels at this time. By doing K, it is possible to determine whether there is a line defect in the gate signal line.

Now, when inspecting an uninspected display panel, we will use a display panel that is a known good product.The light level of the display screen when the entire surface is at black level and the brightness when only one video signal line is at white level. Measuring the light level and using it as a reference level for comparison in the storage/comparison section 6 leads to accurate determination.

As described above, when the output signal of the test signal generator 2 in FIG. 3 to the display panel 1 is sequentially driven from X'1 to XnK with the waveform shown in FIG. The waveform is as shown in Fig. 4b).
XI Te (7) Level comparison of L and H, judgment of X2 is T
It compares the L and H levels at X2, moves automatically while measuring and makes a comparison judgment, and when it finishes up to Xn, it sequentially measures and judges the vertical scanning signal from Yl to Yn on the gate signal line. As a result, the presence or absence of a line defect in the video signal line and the gate signal line can be determined by automatically measuring the position of the defect.

Compared to conventional methods, it has become possible to check the integrated circuit board of an active matrix display panel easily and accurately.

Here, it goes without saying that it is possible to measure each pixel one by one. Further, in the above explanation, the inspection of a reflective type liquid crystal panel has been described, but the same applies to the case of a transmissive type, and only the incident direction of the light source changes.

The display panel inspection apparatus of the present invention is not limited to liquid crystal display panels, but can also be applied to inspection of other matrix display panels such as LEDs, plasma displays, and EL.

[Brief explanation of drawings]

FIG. 1 shows an equivalent circuit of the entire liquid crystal display panel, and FIG. 2 shows the positional relationship between matrix signal lines and display pixels of this panel. Further, FIG. 3 is a configuration diagram of an inspection apparatus for an image display panel according to the present invention. FIG. 4(a) shows the input signal waveforms of the video signal lines X1 to X4 during automatic measurement, and FIG. 4(b) shows the output waveforms of the amplifying section 5 at this time. ... Video signal lines Y1 to Yn...
... Gate signal line ... Matrix display panel 2 ... Test signal generation section 3 ... Condensing lens 4
...Photoelectric conversion element 5...Amplification section 6...
Memory/comparison section co... Storage capacitor 7... Line number generation section Tr... Switching transistor 8... Printer LC music liquid crystal cell agent Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] On the matrix display panel, pixels corresponding to each vertical and horizontal signal line are displayed line by line, and the brightness of the display panel when this display is displayed and the brightness when it is not displayed. is photoelectrically converted and compared as an electrical signal, and the presence or absence of defects in the displayed pixel portion is automatically determined.The drive test signal generator of the display panel automatically converts the matrix signal lines in sequence. A display panel inspection device characterized in that the device is driven, compares and judges the brightness of a screen, confirms the location of the screen and the presence or absence of defects, and outputs the results.