JPH01191197A - Testing method for active matrix substrate of display panel - Google Patents

Abstract

PURPOSE:To shorten the testing time by executing the test in a state that a testing substrate is superposed on an active matrix substrate to be tested and each projecting electrode on a test electrode of the testing substrate side is brought to conductive contact with the corresponding picture element electrode of the active matrix substrate side. CONSTITUTION:On a testing substrate 50, a flexible projecting electrode 53 is provided on a position corresponding to each picture element electrode 10 on plural pieces of test electrodes 52, and when this testing substrate 50 is superposed on an active matrix substrate to be tested, the tip of this projecting electrode 53 is brought to conductive contact simultaneously with all the picture element electrodes 10 of the active matrix substrate 40. By using this testing substrate 50, it is unnecessary to move a probe one by one, and by switching electrically or electronically a scanning electrode 20 of the active matrix substrate 40 side and the test electrode 52 of the testing substrate 50 side, respectively, the test is advanced, while scanning successively all picture elements in the active matrix substrate 40, for instance, in both the vertical and the horizontal directions. In such a way, the test time can be shortened by omitting the time for moving the probe.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an active matrix substrate such as a liquid crystal display panel, that is, a scanning electrode that is provided in common to pixel electrodes for pixel display and pixel electrodes arranged in a predetermined direction. The present invention relates to a method for testing an active matrix substrate, which includes electrodes and drive elements for display driving connected between each pixel electrode and a scanning electrode, in a standalone state before being assembled into a display panel.

(Prior Art) As is well known, display panels such as the above-mentioned liquid crystal type were initially put into practical use from relatively simple structures that displayed fixed pattern images such as the dials of calculators and watches. However, as the scope of application expanded to include displaying more complex variable images such as those for televisions, matrix structures were developed in which many pixels were arranged in rows and columns within the plane. As the screen size and display density of this matrix display panel progresses, and as the number of pixels included in the screen increases, the overall display configuration, including the drive circuit, is simplified and the image quality becomes clearer. In order to maintain this level, so-called active matrix display panels have become advantageous, incorporating display driving elements such as transistors and diodes and nonlinear elements distributed within their plane. This type of drive element for display panels is incorporated into one of the pair of substrates that make up the display panel, but there is a very narrow gap of about 10 microns or less between the two substrates. Since it is necessary to fit the device inside the device, a thin film structure is used for this, and when this driving element is a transistor or diode, a thin film of amorphous silicon or polycrystalline silicon is usually used as the semiconductor film for it. The present invention relates to an active matrix substrate on the side of a display panel incorporating such a driving element. FIG. 4 shows an enlarged part of this active matrix substrate using a diode as a driving element.

The pixel electrodes 10, of which only two are shown in FIG. 4, are for displaying each pixel in the display panel, and in reality, several hundred pixel electrodes 10 are arranged in both the left and right and up and down directions in the figure, and are arranged in matrix on the active matrix substrate surface. Placed.

Scan electrodes 20 are provided for the pixel electrodes 10 arranged in a predetermined direction of this arrangement, in this example the left and right direction, and a display voltage to be applied to each pixel electrode is placed on this scan electrode. The drive element 30 is provided for each pixel electrode, and when it is a diode as in this example, diodes 30p and 30n in both positive and negative directions are provided, and both diodes are connected in antiparallel to each other. In this example, the positive direction diode 30p is formed on the scanning electrode 20 as shown in the figure and connected to the pixel electrode 10 via the connection film 7, and the negative direction diode 30p is formed on the scanning electrode 20 and connected to the pixel electrode 10 via the connection film 7.
On the other hand, 0n is formed on the pixel electrode 10 and connected to the scanning electrode 20 via the connection film 7. On the other substrate (not shown) of the display panel, the direction intersects with the scanning electrode 20.

In this example, the opposing electrode, which is elongated in the vertical direction of the figure, is the pixel electrode 1.
When displaying on the 0 display panel, which has the same width as the 0 display panel and is arranged in the direction in which the scanning electrodes 20 extend, the scanning electrode is vertically scanned, the counter electrode is horizontally scanned, and the display voltage is changed between the two electrodes to be positive or negative at each scanning period. The display panel is driven by alternating current. In a pixel specified by vertical and horizontal scanning, the scanning electrode 2
A positive display voltage is applied to 0, and the diode 30p in the positive direction
conducts and transfers this display voltage from the scan electrode 20 to the pixel electrode 1.
0, and in the next scan period, a negative display voltage is applied to the scan electrode 20, the negative direction diode 30n becomes conductive, and this display voltage is transmitted to the pixel electrode.

Figure 5 shows the structure of this active matrix substrate.
The insulating substrate 1 is usually made of transparent glass, and the surface of the insulating substrate 1 is first coated with ITO (indium).
After depositing a transparent conductive film 2 such as tin oxide), the pixel electrode 10 and the scanning electrode 20 are patterned. The diode 30p on the scanning electrode 20 as a driving element is
It consists of a semiconductor IP 14 made of amorphous silicon in a pin configuration, for example, which is sandwiched between a pair of light-shielding films 3.5 made of chrome, etc., and an insulating film made of silicon nitride or the like is placed on top of it, as shown in FIG. , 30n in common. The connection film 7 is provided so that one end thereof is in conductive contact with the light shielding film 5 on the top of the diode through the window 6a of the insulating film 6, and the other end is in conductive contact with the pixel electrode 10. The active matrix substrate configured in this way is combined with the other substrate, the front substrate is bonded to each other at the periphery, and a display medium such as liquid crystal is filled in the gap between both substrates to form a display panel. Ru.

However, since hundreds of thousands of pixels are incorporated into one active matrix substrate, some defective pixels may occur among them. The main defects are short circuits and disconnections, and the former include, for example, contact between the connecting film 7 and the lower light-shielding film 3 due to a defect in the insulating film 6, and the conductive film 2.
Pixel electrode 10 and scanning electrode 20 due to poor patterning
The latter includes a rupture of the connecting film 7 and a disconnection of the scanning electrode 20. Generally, short circuits are considered to be more serious defects, but since it is difficult to completely eliminate serious defects, active matrix substrates with a predetermined number of defective pixels, for example 10 or less, are considered good products. The presence or absence of defects and the number of defects can be easily determined by assembling the active matrix substrate into a display panel and performing a display test, but even if the active matrix substrate is found to be defective after assembly, it is possible to determine The active matrix board has no choice but to be discarded together with the other board, and all the work required for assembly and the mating board are wasted.For this reason, active matrix boards are tested on their own before being assembled into a display panel. It will be done. The most difficult thing in this test is how to connect each pixel electrode to the test circuit, and the procedure for this conventional test will be explained with reference to FIG.

First, all the scanning electrodes 20 on the illustrated active matrix substrate 4o are connected in common at their connecting portions 20a at the ends of the substrate, and then connected to one end of a test circuit consisting of a test voltage source 71 and a current measuring device 72. -Each pixel electrode 10
In order to connect the probe to the other end of this test circuit, a probe 60 is used, and the probe 60 is brought into contact with each pixel electrode 10 while automatically sequentially moving in both left and right and up and down directions P and Q, and measurements are taken each time. However, in this conventional method, the test must be carried out while the probe or grain probe is in contact with each pixel electrode, so that the current flowing through the active matrix substrate may not be included in the active matrix substrate. As the number of pixels increases, it takes more time to move the probe, which increases the testing time.For example, when pixels are arranged in 200 rows and 400 columns, the total number of pixels can be as high as 80,000. However, since it takes about 1 hour to test 2000 pixels, it will take as long as 40 hours to test all the pixels on the active matrix substrate.Therefore, from an economic point of view, 1710 pixels on the active matrix substrate The only option is to perform a sampling test on the following pixels.

Furthermore, this conventional testing method has a problem in reliability of conductive contact between the probe and the pixel 1a pole. Since the separation and conductive contact of the probe from each pixel electrode is manipulated at high speed,
Contact resistance tends to fluctuate slightly, but since it is necessary to determine whether the number of defective pixels on one active matrix substrate is, for example, 10 or less, the number of pixels is about 80,000 or more as mentioned above. When contact resistance is 0.01%
If the probability fluctuates as above, the test will become completely unreliable.

The present invention overcomes the difficulties of such conventional testing methods, and
The present invention aims to provide a method for testing active matrix substrates that can test all the pixels within a short time even though the number of pixels included in the active matrix substrate is large, and that can improve the reliability of the results. , elongated test electrodes extending in a direction that intersects the scan electrodes are arranged side by side along the direction in which the scan electrodes extend, and the tips of the test electrodes are placed in conductive contact with each pixel electrode at positions corresponding to each pixel electrode. Using a test board with flexible protruding electrodes,
This test substrate is overlapped with the active matrix substrate to be tested, and each protruding electrode on the test electrode on the test substrate side is brought into IX conductive contact with the corresponding pixel electrode on the active matrix substrate side, and the active matrix substrate side is scanned. This is achieved by applying a test voltage between the electrodes and the test electrode on the test substrate side while scanning the electrodes, and testing the active matrix substrate for each pixel.

[Effect]

The test board used in the test method according to the present invention may be used for multiple tests as described in the above configuration. ! A flexible protruding electrode made of conductive rubber, for example, was provided in place of a conventional probe at a position corresponding to each pixel electrode on the electrode, and this test substrate was superimposed on the active matrix substrate to be tested. At this time, the tips of the protruding electrodes are brought into conductive contact with all the pixel electrodes of the active matrix substrate at the same time.

By using this test board, the present invention eliminates the need to move the probes one by one, and electrically or electronically switches the scanning electrodes on the active matrix board side and the test electrodes on the test board side. By sequentially scanning all pixels on the board, for example in both the vertical and horizontal directions, the time required to move the conventional probe is completely eliminated, reducing the test time by 1 to 2 orders of magnitude compared to conventional methods. It was successfully shortened. Additionally, the conductive contact between the protruding electrode and its corresponding pixel electrode remains in place throughout the test period after the test substrate is stacked with the active matrix substrate, allowing the probe to contact each pixel one by one as in the past. Since there is no contact or separation with the electrode, the present invention utilizes this to maintain the contact resistance of this conductive contact unchanged, and has succeeded in significantly improving the conductivity of the test results.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 3. FIG. 1 shows an active matrix substrate 40 indicated by thick lines and a test substrate 50 indicated by thin lines.
The test circuit is shown in a superimposed state, and the test circuit is also illustrated.

On the active matrix substrate 40 in FIG. 1, there are a large number of pixel electrodes 10 arranged in rows and columns, a scanning electrode 20 provided in common to the pixel electrodes arranged in the row direction in this example, and a scanning electrode 20 for each pixel electrode. A driving element 30 is shown connected between the electrode and the scanning electrode, and the driving element 30, which is shown as a small square in the figure, is a two-terminal element such as a diode in this example. If the driving element is a three-terminal element, scanning electrodes are also provided in the column direction, but testing can be performed with one of the scanning electrodes in both row and column directions connected to the test circuit and the other set at a predetermined potential. , the procedure is not much different from the case where the drive element is a two-terminal element.

On the test substrate 50 superimposed on the active matrix substrate 40, test electrodes 52 which are elongated in a direction orthogonal to the scanning electrodes 20 on the active matrix substrate side are arranged on an insulating substrate in the direction in which the scanning electrodes extend. Furthermore, flexible protrusions 1tF153 are provided on each test electrode 52 at positions corresponding to the pixel electrodes 10 on the active matrix substrate side, arranged in the vertical direction in the figure. This situation is clearly shown in the perspective view of FIG. In this FIG. 2, an active matrix substrate 40
and the test board 50 are shown separated from each other,
In the figure, the correspondence between the protruding electrodes 53 arranged on the test electrodes 52 on the lower surface of the test substrate 50 and the pixel electrodes 10 on the upper surface of the active matrix substrate 40 is indicated by thin arrows in the vertical direction of the figure. Further, FIG. 3, which is a cross section taken along the line X--X in FIG. 2, shows a state in which the active matrix substrate 40 and the test substrate 50 are overlapped.

The protruding electrodes 53 on the test substrate 50 shown in FIGS. 2 and 3 are hemispherical protrusions made of conductive silicone rubber, and are made, for example, as follows.

First, the insulating substrate 51 for the test substrate 50 is made of, for example, a glass substrate like the active matrix substrate 40 (on top of which a thin film of ITO or metal is coated on the entire surface with a thickness of 0.1 After depositing to a thickness of ~0.5 microns, it is patterned into the shape shown in FIG.

As the conductive silicone rubber for the protruding electrode 53, for example, TCM8401 manufactured by Toshiba Silicone Co., Ltd. is used.
Using a metal mask with a large number of holes with a diameter of about 0.15 m at a pitch of about 0.3 cranes, which corresponds to the arrangement pitch of the pixel electrodes of the active matrix substrate, in a thin copper plate with a thickness of about 1 fi, paste-like The silicone rubber is adhered onto the test electrode 52 by a rubbing method, formed into a hemispherical shape by a type of glue flow effect during heating and oxidation, and then cured to form a protruding electrode as shown in Fig. 3. 53. Alternatively, using a normal photoresist as a mask, first apply this photoresist to a thickness of 30 microns or more over the entire surface of the insulating substrate 51 on which the test electrode 52 has been formed, and then pattern it onto the test electrode 52. Similarly, at a pitch of about 0.3 cranes, 0.
For example, TCM8403 manufactured by the above-mentioned company is used as the silicone rubber for the protruding electrode from which a window with a diameter of about 25 nm is cut out.After filling the inside of the window with this silicone rubber using the same rubbing method, it is heated and cured. IAji photoresist
By removing 1, a cylindrical protruding electrode of conductive silicone rubber is obtained.

All of the protruding electrodes 53 formed in this way have flexibility, and even if there is a slight difference in height, they deform slightly and protrude when the test substrate 50 is pressed toward the active matrix substrate. Reliable conductive contact between the electrode 53 and the pixel electrode IO can be obtained. As shown in FIG.
A stopper 54 having an appropriate height is provided at the peripheral edge between the active matrix substrate 40 and the active matrix substrate 40, and from the state where the tip of the protruding electrode 53 slightly contacts the pixel electrode 10 as shown in the figure, the pressure is further increased by δ. By pressing down, the protruding electrode 53 can be deformed and its conductive contact with the pixel electrode 10 can be ensured.

Returning to FIG. 1, the test voltage source 71 that generates the test voltage E
In this embodiment, there is a changeover switch 7 for changing the polarity.
1a-t-provide. The measuring device 72 may be a normal high-sensitivity current measuring device, but if the measured current is 10-" to 10-1^
Since it takes about 100m5 to measure with a normal microcurrent, it is desirable to use one with the fastest measurement speed possible.The 0 selection switch 73 should also be an electronic multi-point switch with fast operation speed. The terminals are connected to each connection portion 52a of the pixel electrode 52 of the test substrate 50. A selection terminal of this selection switch 73 is connected to one end of a test circuit consisting of a test voltage [71] and a measuring device 72. In this embodiment, the scanning electrode 30 of the active matrix substrate 40 is connected to each switching terminal of a multi-point changeover switch 74 via its connecting portion 20a, and each of the switched terminals on one side of the changeover switch 74 is commonly connected. connected to the other end of the test circuit at the top. The other terminal to be switched of the changeover switch 74 is connected to the terminal to be selected of a selection switch 75, and the selection terminal of this selection switch 75 is connected to the other end of the test circuit.

An example of a procedure for testing the active matrix substrate 40 using the test circuit configured as described above will be described below. In this test, a 10-bit horizontal selection command sh was sent from a control circuit such as a computer (not shown) to the selection switch 73 so that, for example, 640 pixels arranged in a row could be selected.
However, a 1-bit switching command S is sent to the changeover switch 74.
For the other selection switch, cheer 5, a 9-bit vertical selection command Sν is issued to select, for example, 400 pixels arranged in the column direction, and represents the test result from the measuring device 72. It is assumed that a test signal TS is applied to this control circuit.

In active matrix substrates, short-circuit defects are also serious defects and their incidence is usually high, so the primary purpose of testing is to eliminate defective products based on the number of short-circuit defects. For this purpose, the changeover switch '71a attached to the test voltage source 71 is fixed, for example, in the state shown in the figure, and the polarity of the test voltage E is kept constant, and the changeover switch 74 is set in the state shown in the figure by the switching command Sc, and the changeover switch 74 is set in the state shown in the figure. After all the scanning electrodes 20 of the matrix board 40 are brought into a common connection state, a horizontal selection command sh is sent to the selection switch 73 to sequentially connect each test electrode 52 of the test board 50 to the test circuit while scanning it. At this time, if there is even one short-circuit defect in the pixels arranged in the vertical direction in the figure on the active matrix substrate 40 corresponding to a certain test electrode 52, the test result will indicate that there is a short-circuit defect, but the control circuit will detect the presence of the defect. While memorizing the test electrode number, add up the total number of defective test electrodes, and when this total exceeds the allowable number (for example, IO), immediately stop the test and mark the active matrix board under test as defective. .

If the total number of defective test electrodes is 10 or less after scanning all the test electrodes 8i52, place the changeover switch 74 in the opposite position to that shown in the figure according to the changeover command Sc, and then set the previously memorized defect. A horizontal selection command sh corresponding to the test electrode number of YES is sent to the selection switch 73 to select that test electrode, and a vertical selection command Sv is sent to the selection switch 75 to sequentially select the test circuit while scanning the scanning electrode 20. While connected, all pixels aligned in the vertical direction corresponding to the test electrode are tested for the presence or absence of short circuits. As a result of conducting a similar test on all the test electrodes that had previously been found to have short circuits, if the sum of the pixels with short circuits was 10 or less, the active matrix substrate was considered to be good for short circuit defects. When the value exceeds this value, the test is stopped at that point and the active matrix board is considered a defective product.

In the test for disconnection defects, it is impossible to perform a batch test on the test electrodes as in the short-circuit defect test, so with the changeover switch 74 placed in the opposite switching position from that shown, horizontal selection commands are sequentially sent to the selection switches 73 and 75. sh and vertical selection command Sν, respectively, to the active matrix substrate 4.
While scanning the pixels within 0 in both the left and right and up and down directions, each pixel is tested for the presence or absence of a disconnection. In this case as well, when the total number of pixels with disconnection defects exceeds the allowable number, the test is stopped and the active matrix board under test is determined to be a defective product. In addition, if the drive element 30 is a diode, it is necessary to test for the presence or absence of a disconnection with respect to the test voltage E in both the positive and negative directions.
When each pixel in the active matrix substrate 40 is scanned, the changeover switch 71a is switched each time to test each pixel for the presence or absence of disconnection with respect to test voltages in both positive and negative directions. In this way, it is necessary to perform the open circuit defect test on all pixels in the active matrix board, and the test time therefore takes about IO times that of the short circuit defect test. Therefore, it is recommended to use a high-speed measuring instrument 72. This is especially desirable, but fortunately the measuring device only needs to know whether the current is 0 or not, so it can be made exclusively for that purpose and the operating speed can be increased. In this case, it is advantageous to be able to use the measuring device 72 by switching between the open circuit defect test and the short circuit defect test. If a dedicated high-speed measuring instrument is used to detect disconnection defects in this way, the disconnection defect test can be completed in about 3 to 5 times the time of the short circuit defect test.

〔Effect of the invention〕

As described above, in the present invention, a pixel electrode for display of each pixel, a scan electrode provided in common for the pixel electrodes arranged in a predetermined direction, and a display drive connected between each pixel electrode and the scan electrode. When testing an active matrix substrate equipped with a drive element for use with a drive element, elongated test electrodes extending in a direction intersecting with the scan electrodes are arranged in parallel along the direction in which the scan electrodes extend, and each pixel electrode on the test electrodes corresponds to the test electrode. Using a test board with flexible protruding electrodes whose tips can make conductive contact with each pixel electrode, place this test board on the active matrix board to be tested, and insert the test electrodes on the test board side. Each of the protruding electrodes on the top is brought into conductive contact with the corresponding pixel electrode on the active matrix substrate side, and a test voltage is applied between both electrodes while scanning the scan electrode on the active matrix substrate side and the test electrode on the test substrate side. Since the active matrix substrate is tested for each pixel, there is no need to mechanically move the probe to and from the pixel electrode of the active matrix substrate one by one as in the conventional method. Since it is possible to test each pixel in the active matrix substrate while scanning the scanning electrode and the test electrode on the test substrate side purely electrically or electronically as appropriate, the test time can be significantly shortened compared to conventional methods. For example, when there are 80,000 pixels in an active matrix substrate, it would take 40 hours to test all the pixels with the conventional method, but with the method of the present invention, short circuit defect testing can be done in one time.
The wire breakage test can be completed within 1 hour. In addition, all tests can be completed with the protruding electrodes on the test substrate in conductive contact with the pixel electrodes on the active matrix substrate in the original state when the two substrates are stacked, so contact The reliability of the test results can be improved by conducting the test in a state where the resistance is much more stable.

Furthermore, as can be seen from the description of the embodiments, the method of the present invention is particularly advantageous for testing short-circuit defects, which are considered to be serious defects in display panels.
By testing about 3% of the number of pixels in the active matrix substrate, it is possible to efficiently check for short-circuit defects in all pixels within a short period of time.

[Brief explanation of the drawing]

1 to 3 relate to the present invention, and FIG. 1 shows a superimposed active matrix substrate and a test substrate in an embodiment of the method for testing an active matrix substrate of a display panel according to the present invention, together with an example of a related test circuit. FIG. 2 is a perspective view showing the active matrix board and the test board in a state where they are slightly spaced apart from each other, and FIG. 3 is a sectional view of the two boards in a superimposed state. 4 and 5 show an example of the structure of an active matrix substrate that is a target of the method of the present invention, with FIG. 4 being a partially enlarged top view, and FIG. 5 being a sectional view of the main part thereof. . FIG. 6 is a configuration circuit diagram of an active matrix substrate and a test circuit showing the gist of a conventional active matrix substrate testing method. In FIG. 4: Semiconductor film, 6: 'dA edge film, 6a: Insulating film window, 7: Connection film, 10: Pixel electrode, 20: Scanning electrode, 20a: Scanning electrode connection part, 30: Drive element, 30p, 30n : Cross-sectional view in the positive and negative directions as a driving element, 40 Near active matrix substrate, 50: Test substrate, 51: Insulating substrate, 52
: test electrode, 52a: connection part of test electrode, 53: protruding electrode, 54: stopper, 60: tip or probe, 7
1: Test voltage source, 71a: Test voltage polarity changeover switch, 72: Current measuring device, 73: Selection switch, 74
: Changeover switch, 75: Selection switch, δ: Pressing distance, E
: Test voltage, SC: Switching command, Sh: Horizontal selection command, S
v: Vertical selection command, TS: Test signal. Board Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1) Connection between each pixel electrode and the scanning electrode and a scanning electrode provided in common for the display pixel electrodes of each pixel arranged in a matrix on the display panel and the pixel electrodes arranged in a predetermined direction. A method for testing an active matrix substrate comprising a drive element for driving a display according to the present invention, wherein elongated test electrodes extending in a direction intersecting with the scan electrodes are arranged in a row along the direction in which the scan electrodes extend; Using a test substrate with flexible protruding electrodes whose tips can conductively contact each pixel electrode at positions corresponding to each pixel electrode, this test substrate is superimposed on the active matrix substrate to be tested. With each protruding electrode on the test electrode on the test board side in conductive contact with the corresponding pixel electrode on the active matrix board side, both electrodes are scanned while scanning the scan electrode on the active matrix board side and the test electrode on the test board side. 1. A method for testing an active matrix substrate of a display panel, comprising testing the active matrix substrate for each pixel by applying a test voltage between them.