JP5899532B2 - Active matrix substrate - Google Patents

Description

  The present invention relates to an active matrix substrate, and more particularly to an inspection circuit for a display panel using an active matrix substrate having an electrostatic protection function.

  With the recent demand for higher-quality display devices, liquid crystal display panels and organic electroluminescence (EL) display panels have attracted attention as thin and low power consumption display panels. These display panels include a plurality of pixels arranged two-dimensionally.

  For example, in an active matrix organic EL display panel, a thin film transistor (TFT) is provided at the intersection of a plurality of scanning lines and a plurality of data lines, and a storage capacitor element (capacitor) and a driving transistor are provided in the TFT. A gate, a compensation circuit, and the like are connected. Then, the TFT is turned on through the selected scanning line, and a data signal or the like from the data line is input to the driving transistor, the holding capacitor element and the compensation circuit, and the organic EL element emits light by the driving transistor, the holding capacitor element and the compensation circuit. Control brightness and light emission timing. With this configuration of the pixel drive circuit, the active matrix organic EL display panel can emit the organic EL element until the next scanning (selection), so that the luminance of the display is reduced even if the duty ratio is increased. There is no such thing.

  However, since the active matrix organic EL display panel has a complicated pixel drive circuit configuration, electrical defects such as variations in characteristics of pixel drive circuit elements and short-circuiting or opening of wirings occur. In order to compensate for such characteristic variations and improve the manufacturing yield, it is necessary to sufficiently perform an array inspection of the active matrix substrate in the middle of the manufacturing process and a display operation inspection of the display panel before mounting the mounted component at the time of completion. is there. At the time of such an inspection, for example, when an external measurement device and an active matrix substrate or a display panel as a measurement object are connected, or when an external measurement device or the like is not connected in each manufacturing process, the active matrix substrate There is a case where static electricity flows into the pixel circuit and the pixel circuit is destroyed.

  Patent Document 1 discloses a configuration for inspecting signal line disconnection while protecting a liquid crystal display panel from electrostatic breakdown. Specifically, inspection voltages that are placed around the display area and outside the electrostatic protection circuit are simultaneously input to all pixels to inspect the lighting state of each pixel on which the liquid crystal element is formed. To do. By inspecting the lighting state, a signal line disconnection inspection is performed without electrostatic breakdown.

JP 2011-154161 A

  However, the inspection method of the display device described in Patent Document 1 is an active matrix substrate in which only a driving circuit is formed without forming a light emitting element in order to check the lighting state of a pixel by applying an inspection voltage. It cannot be applied to inspection of signal lines, scanning lines, and driving circuits.

  In addition, each pixel of the active matrix substrate is formed with a capacitor for maintaining light emission. In the above inspection method in which the inspection voltage is applied to a plurality of pixels at the same time, it is not possible to specify a pixel exhibiting an abnormal capacity. Have difficulty.

  In view of the above problems, an object of the present invention is to provide an active matrix substrate capable of selecting a pixel to be inspected with a simple circuit while ensuring an electrostatic protection function.

  In order to achieve the above object, an active matrix substrate according to one embodiment of the present invention includes a substrate, a plurality of signal lines disposed on the substrate, an inspection terminal provided on the substrate, and the plurality of terminals. Corresponding to each of the plurality of first thin film transistors, each of the plurality of first thin film transistors switching between conduction and non-conduction between the corresponding signal line and the inspection terminal, and corresponding to each of the plurality of first thin film transistors. And a plurality of selection signal input terminals to which a selection signal for selecting a signal line to be electrically connected to the inspection terminal and a pair of diodes connected in antiparallel are provided. A plurality of second electrostatic protection elements including a protection element, a pair of diodes arranged in correspondence with each of the plurality of selection signal input terminals, and connected in antiparallel, and a discharge destination of static electricity Static electricity Each of the plurality of first thin film transistors, wherein one of a source electrode and a drain electrode is connected to the corresponding signal line, and the other of the source electrode and the drain electrode is connected to the inspection terminal, And the first electrostatic protection element is connected to the electrostatic discharge line, the gate electrode is connected to the corresponding selection signal input terminal, and the corresponding second electrostatic protection element is used. It is connected to an electrostatic discharge line.

  According to the active matrix substrate of the present invention, since the pixel circuit can be inspected for each pixel, the defective pixel can be specified. In addition, since the electrostatic protection circuit also serves as the pixel selection circuit, the circuit for inspecting the pixels can be simplified and the area can be reduced.

It is a block diagram which shows the electrical structure of the conventional active matrix substrate which can test | inspect a pixel circuit. 1 is a block diagram showing an electrical configuration of an active matrix substrate according to Embodiment 1 of the present invention. FIG. 3 is a circuit diagram for explaining a discharge path when positively charged static electricity flows into the active matrix substrate according to the first embodiment of the present invention. FIG. 3 is a circuit diagram illustrating a discharge path when negatively charged static electricity flows into the active matrix substrate according to the first embodiment of the present invention. It is a circuit diagram explaining the state in the case of selecting a test pixel in the active matrix substrate according to the first embodiment of the present invention. It is a block diagram which shows the electric constitution of the active matrix substrate which concerns on Embodiment 2 of this invention. It is a graph explaining an example of the effect by one Example of pixel capacity inspection in the present invention. 1 is an external view of a thin flat TV incorporating an active matrix substrate of the present invention.

(Knowledge that became the basis of the present invention)
The inventor has found that the following problems occur with respect to the active matrix substrate described in the “Background Art” section.

  When the inspection of the display device described in Patent Document 1 is applied to the pixel circuit inspection of an active matrix substrate in which a pixel circuit is already formed but a light emitting element is not yet formed, a circuit configuration as shown in FIG. 1 is obtained. .

  FIG. 1 is a block diagram showing an electrical configuration of a conventional active matrix substrate capable of inspecting a pixel circuit. The active matrix substrate 500 shown in the figure includes a plurality of pixels 501 arranged in a matrix, a plurality of scanning lines 512 arranged for each pixel row, and a plurality of data lines 511 arranged for each pixel column. In the display area. Further, the active matrix substrate 500 includes guard lines 513, ESD diodes 521 and 522 and pads 531 arranged for each data line, and inspection terminals 532 around the display area.

  The guard line 513 is an electrostatic discharge line arranged so as to surround the display area.

  The pad 531 is a terminal that ensures electrical connection between the active matrix substrate 500 and an external measuring device or drive circuit when the peripheral portion of the active matrix substrate 500 is cut by a cutting line at the final stage of the manufacturing process.

  The inspection terminal 532 is arranged for each of a plurality of adjacent pixel columns, and is connected to a plurality of data lines 511 arranged corresponding to the plurality of pixel columns in the process up to the cutting. The external measuring device collectively outputs inspection voltages to the plurality of data lines 511 via the inspection terminals 532, stops the output, and after a predetermined period has elapsed, from the plurality of data lines 511, A pixel voltage corresponding to the pixel capacitance is measured.

  Each of the ESD diodes 521 and 522 includes a thin film transistor in which a gate electrode and a source electrode are short-circuited.

  In the ESD diode 521, the drain electrode and the data line 511 are connected, and the gate electrode and the source electrode and the guard line 513 are connected. With the above connection, the ESD diode 521 causes a forward current to flow from the data line 511 to the guard line 513 when a voltage higher than the built-in voltage is applied to the data line 511 with the guard line 513 as a reference (data line 511). To release a positive charge in the direction of the guard line 513).

  The built-in voltage is a threshold voltage of the diode, and is a voltage at which a forward current is substantially generated (exponentially increases) in the current-voltage characteristic of the diode.

  In the ESD diode 522, the drain electrode and the guard line 513 are connected, and the gate electrode and the source electrode are connected to the data line 511. With the above connection, the ESD diode 522 has a forward current in the direction from the guard line 513 to the data line 511 when a negative voltage having an absolute value equal to or greater than the built-in voltage is applied to the data line 511 with the guard line 513 as a reference. (Negative charge is released from the data line 511 toward the guard line 513).

  Due to the arrangement of the ESD diodes 521 and 522, when static electricity flows into the active matrix substrate 500 from the inspection terminal 532 during the manufacturing process, the positive charge becomes the inspection terminal 532 → the data line 511 → the ESD diode 521 → the guard line 513. It is released by the route. On the other hand, the negative charge is discharged through the path of the inspection terminal 532 → the data line 511 → the ESD diode 522 → the guard line 513. Accordingly, static charges do not flow into the display region, so that the pixel is prevented from being destroyed.

  In the mass production stage, from the viewpoint of manufacturing cost and mass productivity, high-speed inspection is required in units of a plurality of pixel circuits, and so-called bundle inspection in which a plurality of pixel circuits are inspected collectively is employed. For this reason, as shown in FIG. 1, one inspection terminal 532 is arranged in common with a plurality of adjacent data lines 511.

  According to the above-described bundle inspection, the number of inspection steps in the manufacturing process can be reduced, and a display panel having a short circuit of wiring and a defect of a pixel circuit can be selected. For example, an inspection voltage is applied from the inspection terminal 532 to a data line block including a plurality of pixels, and the application voltage is stopped and a pixel voltage from the data line block is applied to the inspection terminal 532 after a predetermined period has elapsed. Read from. Then, the pass / fail judgment of the data line block is made by calculating the combined capacity of the data line block by comparing the inspection voltage and the pixel voltage.

  However, in the above bundling inspection, it is only possible to determine whether the data line block is good or bad, and it is difficult to identify defective pixels.

  In order to solve such a problem, an active matrix substrate according to one embodiment of the present invention includes a substrate, a plurality of signal lines arranged on the substrate, an inspection terminal provided on the substrate, One each corresponding to each of the plurality of signal lines, a plurality of first thin film transistors for switching conduction and non-conduction between the corresponding signal line and the inspection terminal, and each of the plurality of first thin film transistors Correspondingly, a plurality of selection signal input terminals that are arranged one by one and to which a selection signal for selecting a signal line to be conducted with the inspection terminal is input, and a first that includes a pair of diodes connected in antiparallel An electrostatic protection element, a plurality of second electrostatic protection elements including a pair of diodes arranged in correspondence with each of the plurality of selection signal input terminals and connected in antiparallel, and a discharge destination of static electricity Become Each of the plurality of first thin film transistors includes one of a source electrode and a drain electrode connected to the corresponding signal line, and the other of the source electrode and the drain electrode connected to the inspection terminal. And connected to the electrostatic discharge line via the first electrostatic protection element, a gate electrode is connected to the corresponding selection signal input terminal, and via the corresponding second electrostatic protection element And is connected to the electrostatic discharge wire.

  According to this aspect, since the pixel circuit on the substrate connected to the signal line can be individually inspected for each signal line, the defective pixel can be specified. The static electricity flowing into the signal line is allowed to flow into the pixel circuit by an electrostatic protection circuit including a first thin film transistor, a first electrostatic protection element, and a second electrostatic protection element that can select the signal line. Without discharging to the electrostatic discharge line. Therefore, since a part of the electrostatic protection circuit also serves as the selection circuit, the inspection circuit for individually inspecting the pixel circuit can be simplified and reduced in area.

  The discharge path of the static electricity flowing into the signal line from the external connection terminal is signal line → first thin film transistor → first electrostatic protection element → static discharge line. The first thin film transistor and the first electrostatic protection element are in series. Contains a route connected to. Thus, in order for the discharge current to flow through the discharge path, the electrostatic voltage is required to be larger than the sum voltage of the threshold voltage of the first thin film transistor and the built-in voltage of the first electrostatic protection element. From the opposite viewpoint, when a voltage is applied to each pixel via a signal line, it is possible to increase a voltage margin for preventing current from leaking into the discharge path. For example, it is convenient when the pixel voltage is to be inspected by increasing the inspection voltage, or when it is desired to increase the data voltage in order to ensure luminance in the image display stage after the display panel is completed.

  For example, the built-in voltage of the diode included in each of the plurality of second electrostatic protection elements may be larger than the threshold voltage of each of the plurality of first thin film transistors.

  When the selection signal voltage is less than or equal to the threshold voltage of the first thin film transistor, the first thin film transistor is not turned on, and when the selection signal voltage is greater than or equal to the built-in voltage of the second electrostatic protection element, 2 Current flows to the electrostatic discharge line via the electrostatic protection element, and the first thin film transistor is not brought into a conducting state. According to this aspect, since the built-in voltage is higher than the threshold voltage, the first thin film transistor can be reliably brought into a conducting state by setting the selection signal voltage to be equal to or higher than the threshold voltage and equal to or lower than the built-in voltage. It becomes possible to select the data line with high accuracy.

  Further, for example, the diode included in each of the first electrostatic protection element and the plurality of second electrostatic protection elements includes a thin film transistor in which one of a source electrode and a drain electrode and a gate electrode are short-circuited. Also good.

  According to this aspect, the diodes included in the first electrostatic protection element and the second electrostatic protection element can be formed by the same process as the first thin film transistor and the thin film transistor constituting the pixel circuit, and the manufacturing process is simplified. it can.

  Further, for example, a plurality of second thin film transistors that are arranged one by one corresponding to each of the plurality of signal lines and that switch between conduction and non-conduction between the corresponding signal line and the electrostatic discharge line, and A plurality of non-selection signal input terminals which are arranged one by one in correspondence with each of the second thin film transistors and to which a non-selection signal for conducting the corresponding signal line and the electrostatic discharge line is input; A third electrostatic protection element including a pair of diodes arranged one by one corresponding to each of the non-selection signal input terminals and connected in antiparallel, each of the plurality of second thin film transistors including a source electrode And one of the drain electrodes is connected to the corresponding signal line, the other of the source electrode and the drain electrode is connected to the electrostatic discharge line, and a gate electrode is connected to the corresponding non-selection signal. Other than a signal line connected to the input terminal and connected to the electrostatic discharge line set to a fixed potential via the corresponding third electrostatic protection element and conducting to the inspection terminal by the selection signal The signal line may be set to the fixed potential by the non-selection signal.

  According to this aspect, in the inspection of the pixel circuit connected to the signal line, the application of the inspection voltage to the selected signal line and the measurement of the pixel voltage after stopping the application are performed, and the fixed potential is applied to the non-selected signal line. It can be done while introducing. Therefore, by causing the non-selected signal line to act as a shield, the induction noise to the selected signal line is reduced, so that the inspection accuracy can be increased while ensuring the electrostatic protection function.

  For example, the built-in voltage of the diode included in each of the plurality of third electrostatic protection elements may be larger than the threshold voltage of each of the plurality of second thin film transistors.

  When the non-selection signal voltage is lower than or equal to the threshold voltage of the second thin film transistor, the second thin film transistor is not turned on. When the non-selection signal voltage is higher than the built-in voltage of the third electrostatic protection element, the non-selection signal input terminal Current flows through the third electrostatic protection element to the electrostatic discharge line, and the second thin film transistor does not enter the conductive state. According to this aspect, since the built-in voltage is larger than the threshold voltage, the non-selection signal voltage is set to be equal to or higher than the threshold voltage and equal to or lower than the built-in voltage, so that the second thin film transistor can be reliably turned on. It becomes possible.

  For example, the diode included in each of the plurality of third electrostatic protection elements may be formed of a thin film transistor in which one of the source electrode and the drain electrode and the gate electrode are short-circuited.

  According to this aspect, the diode included in the third electrostatic protection element can be formed in the same process as the first and second thin film transistors and the thin film transistor constituting the pixel circuit, and the manufacturing process can be simplified.

  Further, for example, the plurality of signal lines are divided into m (m is an integer of 2 or more) signal line blocks, and the inspection terminal and the first electrostatic protection element are the signal lines. It may be provided for each block.

  In the mass production stage, from the viewpoint of manufacturing cost and mass productivity, high-speed inspection is required in units of a plurality of pixel circuits, and so-called bundle inspection in which a plurality of pixel circuits are inspected collectively is employed. According to this aspect, since the signal lines are blocked into m (m is an integer of 2 or more) signal line blocks, an inspection voltage is output from the inspection terminal to the selected signal line, Further, the pixel voltage is detected from the signal line. At this time, the inspection voltage can be applied only to the selected signal line by the conduction or non-conduction of the first thin film transistor, and the inspection voltage is collectively applied to all the signal lines belonging to the signal line block. Can also be applied.

  Hereinafter, an active matrix substrate according to one embodiment of the present invention will be described with reference to the drawings. In the following drawings, the same reference numerals are used for the same components.

  Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements that constitute a more preferable embodiment.

(Embodiment 1)
In the present embodiment, the active matrix substrate is arranged in correspondence with each of the plurality of signal lines arranged on the substrate, the inspection terminals provided on the substrate, and the plurality of signal lines. A plurality of first thin film transistors that switch between conduction and non-conduction between the signal line to be inspected and the inspection terminal, and one signal line that is arranged corresponding to each of the plurality of first thin film transistors and that conducts to the inspection terminal is selected. Corresponding to each of the plurality of selection signal input terminals, a first electrostatic protection element including a pair of diodes connected in antiparallel, and each of the plurality of selection signal input terminals. A plurality of second electrostatic protection elements including a pair of diodes arranged one by one and connected in antiparallel, and an electrostatic discharge line as a discharge destination of static electricity. In each of the plurality of first thin film transistors, one of the source electrode and the drain electrode is connected to the corresponding signal line, the other of the source electrode and the drain electrode is connected to the inspection terminal, and the first electrostatic protection It is connected to the electrostatic discharge line through the element, the gate electrode is connected to the corresponding selection signal input terminal, and is connected to the electrostatic discharge line through the corresponding second electrostatic protection element.

  Thereby, since the pixel circuit on the substrate connected to the signal line can be individually inspected for each signal line, the defective pixel can be specified. The static electricity flowing into the signal line is discharged to the electrostatic discharge line without flowing into the pixel circuit by the electrostatic protection circuit constituted by the first thin film transistor, the first electrostatic protection element, and the second electrostatic protection element. . Therefore, since a part of the electrostatic protection circuit also serves as the selection circuit, the inspection circuit for individually inspecting the pixel circuit can be simplified and reduced in area.

  Hereinafter, the first embodiment will be described with reference to the drawings.

  FIG. 2 is a block diagram showing an electrical configuration of the active matrix substrate according to Embodiment 1 of the present invention. The active matrix substrate 1 in the figure is arranged in a display area on the substrate, a plurality of pixels 10 arranged in a matrix, data lines 11 as signal lines arranged for each pixel column, and arranged for each pixel row. And a scanning line 12 as a signal line, and an ESD selection unit around the display area.

  The pixels 10 are arranged on the active matrix substrate 1 and at the intersections of the data lines 11 and the scanning lines 12, and all the pixels 10 constitute an m-row × n-column matrix. The pixel 10 includes, for example, a selection transistor in which a gate electrode is connected to the scanning line 12 and a drain electrode is connected to the data line 11, a driving transistor in which a gate electrode is connected to the source electrode of the selection transistor, and driving A capacitor connected to the gate electrode and the source electrode of the transistor; In the final stage of the manufacturing process, an organic light emitting layer is formed on the active matrix substrate 1 having the selection transistor, the drive transistor, and the capacitor, so that the organic EL element is connected to the source electrode of the drive transistor. The

  With the above configuration, for example, in the active matrix substrate 1 during the manufacturing process, the inspection voltage is supplied from the outside to the pixels 10 connected to the scanning line 12 to which the positive voltage scanning signal is applied via the data line 11. As a result, the capacitor is charged. After the inspection voltage is stopped and a predetermined period has passed, the holding voltage of the capacitor is measured as a pixel voltage via the data line 11, and the capacitance value is calculated from the inspection voltage and the pixel voltage. Can be judged.

  The ESD selection unit includes a guard line 13, a selection thin film transistor 21 disposed for each data line 11, ESD diodes 22 and 23, a pad 31, a selection signal input terminal 33, and an ESD diode disposed for each data line block. 24 and an inspection terminal 32. Here, the data line block requires a high-speed inspection in units of a plurality of pixel circuits, and thus is a signal line block including a plurality of groups of data lines 11 set to execute the above-described bundle inspection. That's it.

  The guard line 13 is an electrostatic discharge line that is disposed so as to surround the display area and serves as a discharge destination of static electricity. The guard line 13 is made of, for example, a low resistance material such as metal.

  The pad 31 is a terminal that ensures electrical connection between the active matrix substrate 1 and an external measuring device or an external drive circuit when the peripheral portion of the active matrix substrate 1 is cut by a cutting line in the final stage of the manufacturing process. is there.

  The selection thin film transistor 21 is a first thin film transistor that is arranged corresponding to each of the plurality of data lines 11 and switches between conduction and non-conduction between the corresponding data line 11 and the inspection terminal 32. In the selection thin film transistor 21, one of the source electrode and the drain electrode is connected to the corresponding data line 11. The other of the source electrode and the drain electrode is connected to the inspection terminal 32 and is connected to the guard line 13 via the ESD diode 24. The gate electrode is connected to the selection signal input terminal 33 and connected to the guard line 13 via the ESD diode 23. With the above connection, for example, when a selection signal (H) is applied to the selection signal input terminal 33, the selection thin film transistor 21 becomes conductive, and the corresponding data line 11 and the inspection terminal 32 become conductive. The plurality of selection thin film transistors 21 belonging to the same data line block together with the selection signal input terminal 33 constitute a selection circuit for switching between conduction and non-conduction between the corresponding data line 11 and the inspection terminal 32.

  The selection signal input terminal 33 is arranged corresponding to each of the plurality of data lines 11 and is a terminal to which a selection signal for connecting the corresponding data line 11 and the inspection terminal 32 is input.

  The inspection terminal 32 is arranged for each of a plurality of pixel columns (data line blocks), and the source electrode of the thin film transistor for selection 21 arranged corresponding to the plurality of data lines 11 in the manufacturing process up to cutting at the cutting line. And the other of the drain electrodes. The data line 11 is divided into data line blocks for every m (m is an integer of 2 or more). An external measuring device such as an array tester outputs an inspection voltage to the selected data line 11 via the inspection terminal 32 and the selection thin film transistor 21, and also stops outputting the inspection voltage to a predetermined value. After the period elapses, the pixel voltage is detected from the data line 11. At this time, the external measuring device can apply the inspection voltage only to the selected data line 11 by the conduction or non-conduction of the selection thin film transistor 21, and all the data belonging to the data line block can be applied. It is also possible to apply the inspection voltage to the line 11 at once.

  One ESD diode 24 is arranged for each data line block, and is a first electrostatic protection element including a pair of diodes connected in antiparallel. The ESD diode 24 includes a thin film transistor in which one of a source electrode and a drain electrode and a first gate electrode are short-circuited and the other of the source electrode and the drain electrode and a second gate electrode are short-circuited. Thereby, the ESD diode 24 has a circuit configuration in which two diodes are connected in parallel in opposite directions. One terminal of the ESD diode 24 is connected to the other of the inspection terminal 32 and the source electrode and the drain electrode of the selection thin film transistor 21 in the corresponding data line block, and the other terminal is connected to the guard line 13. .

  The ESD diode 23 is a second electrostatic protection element that is disposed corresponding to the data line 11 and includes a pair of diodes connected in antiparallel. The ESD diode 23 includes a thin film transistor in which one of a source electrode and a drain electrode and a first gate electrode are short-circuited, and the other of the source electrode and the drain electrode and a second gate electrode are short-circuited. Thereby, the ESD diode 23 has a circuit configuration in which two diodes are connected in parallel in opposite directions. The ESD diode 23 has one terminal connected to the gate electrode of the selection thin film transistor 21 and the selection signal input terminal 33, and the other terminal connected to the guard line 13.

  Due to the connection relationship between the selection thin film transistor 21 and the ESD diodes 23 and 24, the other of the source electrode and the drain electrode of the selection thin film transistor 21 and the gate electrode are connected via the ESD diode 24, the guard line 13, and the ESD diode 23. Has been. Therefore, when static electricity having a positive charge is applied from one of the source electrode and the drain electrode of the selection thin film transistor 21, the selection thin film transistor 21 is short-circuited between the other of the source electrode and the drain electrode and the gate electrode. It functions as an ESD diode.

  The ESD diode 22 is disposed corresponding to the data line 11 and is configured by a thin film transistor in which one of a source electrode and a drain electrode and a gate electrode are connected to each other. In the ESD diode 22, the other of the source electrode and the drain electrode and the guard line 13 are connected, and one of the source electrode and the drain electrode and the gate electrode are connected to the corresponding data line 11. With the above connection, when static electricity having a negative charge is applied to the pad 31 or the data line 11, the ESD diode 22 functions as an electrostatic protection element. The ESD diode 22 applies a forward current from the guard line 13 to the data line 11 when a negative voltage whose absolute value is greater than or equal to the built-in voltage is applied to the data line 11 with respect to the guard line 13. A negative charge is released to the line 13.

  Next, it will be described that the ESD selection unit having the above circuit configuration has an electrostatic protection function.

  FIG. 3 is a circuit diagram for explaining a discharge path when positively charged static electricity flows into the active matrix substrate according to the first embodiment of the present invention. This figure shows a discharge path when static electricity having a positive charge flows into the active matrix substrate 1 through the pad 31, the inspection terminal 32 or the selection signal input terminal 33.

  As described above, the other of the source electrode and the drain electrode of the selection thin film transistor 21 and the gate electrode are diode-connected through the ESD diode 24, the guard line 13, and the ESD diode 23. With the above connection, when positively charged static electricity flows from the pad 31, the positive charge does not pass through the display area through the path of the pad 31 → the data line 11 → the selection thin film transistor 21 → the ESD diode 24 → the guard line 13. Released at. In this case, the condition is that the electrostatic voltage having a positive charge is larger than the addition voltage of the threshold voltage of the selection thin film transistor 21 and the built-in voltage of the ESD diode 24. In this respect, it is clear that the electrostatic voltage is sufficiently larger than the added voltage.

  When static electricity having a positive charge flows from the inspection terminal 32, the positive charge is discharged through the inspection terminal 32 → the ESD diode 24 → the guard line 13 without passing through the display area. In this case, the condition is that the electrostatic voltage having a positive charge is larger than the built-in voltage of the ESD diode 24. In this respect, it is clear that the electrostatic voltage is sufficiently larger than the built-in voltage.

  Further, when static electricity having a positive charge flows from the selection signal input terminal 33, the positive charge is discharged through the selection signal input terminal 33 → the ESD diode 23 → the guard line 13 without passing through the display area. In this case, the condition is that the electrostatic voltage having a positive charge is larger than the built-in voltage of the ESD diode 23. In this respect, it is clear that the electrostatic voltage is sufficiently larger than the built-in voltage.

  As described above, when positively charged static electricity flows into the active matrix substrate 1 via the pad 31, the inspection terminal 32 or the selection signal input terminal 33, the selection thin film transistor 21 and the ESD diodes 23 and 24. Functions as an electrostatic protection circuit. This prevents the static electricity from flowing into the display area and destroying the pixel circuit.

  Further, as described above, the discharge path for the inflow of static electricity from the data line 11 including the pad 31 and the like is the pad 31 → the data line 11 → the selection thin film transistor 21 → the ESD diode 24 → the guard line 13; A path in which the thin film transistor 21 and the ESD diode 24 are connected in series is included. Thus, in order for the discharge current to flow through the discharge path, the electrostatic voltage is required to be larger than the sum voltage of the threshold voltage of the selection thin film transistor 21 and the built-in voltage of the ESD diode 24. It is clear that the electrostatic voltage is larger than the added voltage, but from the opposite viewpoint, when a voltage is applied from the pad 31 to each pixel 10 via the data line 11, no current leaks into the discharge path. Therefore, a large voltage margin can be obtained. For example, it is convenient when it is desired to increase the inspection voltage to perform pixel inspection, or when it is desired to increase the data voltage in order to ensure luminance in the image display stage after the display panel is completed.

  FIG. 4 is a circuit diagram for explaining a discharge path when negatively charged static electricity flows into the active matrix substrate according to the first embodiment of the present invention. This figure shows a discharge path when static electricity having negative charges flows into the active matrix substrate 1 via the pad 31, the inspection terminal 32 or the selection signal input terminal 33.

  When static electricity having a negative charge flows from the pad 31, the discharge current flows through the path of the guard line 13 → the ESD diode 22 → the data line 11 → the pad 31 without passing through the display area. In this case, the absolute value of the negatively charged electrostatic voltage is required to be larger than the built-in voltage of the ESD diode 22. In this respect, it is clear that the absolute value of the electrostatic voltage is sufficiently larger than the built-in voltage.

  When static electricity having a negative charge flows from the inspection terminal 32, the discharge current flows through the path of the guard line 13 → the ESD diode 24 → the inspection terminal 32 without passing through the display area. In this case, it is a condition that the absolute value of the negatively charged electrostatic voltage is larger than the built-in voltage of the ESD diode 24. In this respect, it is clear that the absolute value of the electrostatic voltage is sufficiently larger than the built-in voltage.

  When static electricity having a negative charge flows from the selection signal input terminal 33, the discharge current flows through the path of the guard line 13 → the ESD diode 23 → the selection signal input terminal 33 without passing through the display area. In this case, it is a condition that the absolute value of the negatively charged electrostatic voltage is larger than the built-in voltage of the ESD diode 23. In this respect, it is clear that the electrostatic voltage is sufficiently larger than the built-in voltage.

  As described above, when static electricity having a negative charge flows into the active matrix substrate 1 via the pad 31, the inspection terminal 32 or the selection signal input terminal 33, the ESD diodes 22, 23, and 24 Functions as a protection circuit. This prevents the static electricity from flowing into the display area and destroying the pixel circuit.

  Next, it will be described that the ESD selection unit having the above circuit configuration has a pixel selection function.

  FIG. 5 is a circuit diagram for explaining a state in the case where an inspection pixel is selected in the active matrix substrate according to the first embodiment of the present invention.

  When inspecting the capacity of a specific pixel, an inspection voltage is applied to the pixel from the external measurement device via the data line 11, and the application is stopped. After a predetermined period of time, the pixel voltage held in the pixel is , It is necessary to detect via the data line 11. Specifically, it is necessary to apply the inspection voltage from the data line 11 to which the inspection target pixel is connected in a state where the pixel row to which the inspection target pixel belongs is selected by the scanning line 12.

  However, since the inspection terminal 32 is connected in common to all the selection thin film transistors 21 in the data line block, the data line 11 to which the inspection target pixel is connected via the inspection terminal 32 by the external measuring device is connected. It is impossible to choose. On the other hand, the ESD selection unit included in the active matrix substrate 1 includes a selection signal input terminal 33 connected to the gate electrode of the thin film transistor for selection 21 disposed corresponding to the data line 11. By applying a selection signal from the external measurement device via the selection signal input terminal 33, only the selection thin film transistor 21 arranged on the data line 11 to which the pixel to be inspected is connected can be made conductive. is there. Therefore, in a state where the pixel row to which the pixel to be inspected belongs is selected by the scanning line 12, the selection thin film transistor 21 arranged in the data line 11 to which the pixel to be inspected is connected is set in a conductive state and is inspected from the inspection terminal 32. By applying the voltage, it is possible to detect the pixel voltage of the pixel to be inspected after the application is stopped and a predetermined period has elapsed.

  Note that the inspection voltage applied to the inspection target pixel from the inspection terminal 32 is required to be smaller than the built-in voltage of the ESD diode 24. This is because when the inspection voltage is equal to or higher than the built-in voltage, a current flows from the inspection terminal 32 to the guard line 13 via the ESD diode 24, and an accurate inspection voltage is not applied to the inspection target pixel.

  The selection voltage applied from the selection signal input terminal 33 to the gate electrode of the selection thin film transistor 21 is required to be higher than the threshold voltage of the selection thin film transistor 21 and lower than the built-in voltage of the ESD diode 23. In other words, the condition is that the built-in voltage of the ESD diode 23 is larger than the threshold voltage of the selection thin film transistor 21. When the selection voltage is equal to or lower than the threshold voltage, the selection thin film transistor 21 does not become conductive. When the selection voltage is equal to or higher than the built-in voltage, the guard line 13 is connected from the selection signal input terminal 33 via the ESD diode 23. This is because a current flows into the selection thin film transistor 21 and the selection thin film transistor 21 does not become conductive.

  As described above, as illustrated in FIGS. 3 to 5, the ESD selection unit included in the active matrix substrate 1 according to the present embodiment can inspect the pixel circuit connected to the data line for each pixel. Identification becomes possible. The static electricity flowing into the data line 11 is discharged to the guard line 13 without flowing into the pixel circuit by the electrostatic protection circuit constituted by the selection thin film transistor 21 and the ESD diodes 22, 23 and 24. Therefore, since a part of the electrostatic protection circuit also serves as the selection circuit, the inspection circuit for individually inspecting the pixel circuit can be simplified and reduced in area.

(Embodiment 2)
In the present embodiment, in addition to the configuration of the active matrix substrate according to the first embodiment, one is arranged corresponding to each of the plurality of signal lines, and conduction and non-conduction between the corresponding signal lines and the electrostatic discharge lines are not performed. A plurality of second thin film transistors that switch conduction, and a plurality of non-selection signals that are arranged corresponding to each of the plurality of second thin film transistors and that make the corresponding signal line and electrostatic discharge line conductive. And a third electrostatic protection element including a pair of diodes arranged one by one corresponding to each of the plurality of non-selection signal input terminals and connected in antiparallel. In each of the plurality of second thin film transistors, one of a source electrode and a drain electrode is connected to a corresponding signal line, the other of the source electrode and the drain electrode is connected to an electrostatic discharge line, and a gate electrode is A signal other than a signal line connected to the selection signal input terminal and connected to the electrostatic discharge line set to a fixed potential via the corresponding third electrostatic protection element and conducting to the inspection terminal by the selection signal The line is set to a fixed potential by a non-selection signal.

  As a result, when the inspection voltage is applied to the pixel via the selected signal line and the pixel voltage is inspected via the signal line after a predetermined period after the application is stopped, the inspection voltage is applied to the signal line. The pixel voltage can be detected while introducing a fixed potential to the non-selected signal line. Therefore, the non-selection signal line acts as a shield to reduce the induction noise to the selection signal line, and the inspection accuracy can be increased.

  FIG. 6 is a block diagram showing an electrical configuration of the active matrix substrate according to Embodiment 2 of the present invention. The active matrix substrate 2 in FIG. 1 includes a plurality of pixels 10 arranged in a matrix, data lines 11 arranged for each pixel column, and scanning lines arranged for each pixel row in a display area on the substrate. 12 and an ESD selection unit around the display area.

  The active matrix substrate 2 according to the present embodiment is different from the active matrix substrate 1 according to the first embodiment only in the circuit configuration of the ESD selection unit. In the following, description of the same points as in the active matrix substrate 1 will be omitted, and description will be made focusing on differences in circuit configuration.

  Depending on the configuration in the display region, for example, in the active matrix substrate 2 in the middle of the manufacturing process, an inspection voltage is applied to the pixels 10 connected to the scanning lines 12 to which a positive scanning signal is applied via the data lines 11 from the outside. By being supplied, the capacitor is charged. After the application of the inspection voltage is stopped and a predetermined period elapses, it is possible to determine the quality of the capacitor by measuring the holding voltage of the capacitor through the data line 11.

  The ESD selection unit includes the guard line 13, the fixed potential terminal 35, the selection thin film transistor 21 and the non-selection thin film transistor 42, the ESD diodes 23 and 25, the pad 31, the selection signal input terminal 33, and the non-display arranged for each data line. A selection signal input terminal 34, and an ESD diode 24 and an inspection terminal 32 arranged for each data line block are provided.

  The guard line 13 is connected to the fixed potential terminal 35. As a result, a fixed potential is set to the guard line 13 via the fixed potential terminal 35.

  The non-selection thin film transistor 42 is a second thin film transistor that is arranged corresponding to each of the plurality of data lines 11 and switches between conduction and non-conduction between the corresponding data line 11 and the guard line 13. The non-selection thin film transistor 42 is obtained by changing the connection relationship of the ESD diode 22 of the active matrix substrate 1 according to the first embodiment. In the non-selection thin film transistor 42, one of the source electrode and the drain electrode is connected to the corresponding data line 11. The other of the source electrode and the drain electrode is connected to the guard line 13. The gate electrode is connected to the non-selection signal input terminal 34 and is connected to the guard line 13 via the ESD diode 25. With the above connection, for example, when a non-selection signal (H) is applied to the non-selection signal input terminal 34, the non-selection thin film transistor 42 becomes conductive, and the corresponding data line 11 and guard line 13 become conductive.

  The non-selection signal input terminal 34 is arranged corresponding to each of the plurality of data lines 11 and receives a non-selection signal for conducting the corresponding data line 11 and the guard line 13 from an external measurement device such as an array tester. Terminal.

  The ESD diode 25 is a third electrostatic protection element including a pair of diodes arranged corresponding to the data line 11 and connected in antiparallel. The ESD diode 25 is composed of a thin film transistor in which one of a source electrode and a drain electrode and a first gate electrode are short-circuited, and the other of the source electrode and the drain electrode and a second gate electrode are short-circuited. Thereby, the ESD diode 25 has a circuit configuration in which two diodes are connected in parallel in opposite directions. The ESD diode 25 has one terminal connected to the gate electrode of the non-selection thin film transistor 42 and the non-selection signal input terminal 34, and the other terminal connected to the guard line 13.

  Here, in FIG. 6, among the three data lines 11 belonging to the same data line block, the central data line 11 is the selected data line to which the inspection target pixel is connected, and the other data lines are the non-selected data. Assume it is a line. In addition, the selection thin film transistor 21 and the non-selection thin film transistor 42 drawn in bold represent a conductive state, and the selection thin film transistor 21 and the non-selection thin film transistor 42 drawn in a broken line represent a non-conductive state. At this time, the pixel capacity inspection is performed in the following procedure, for example.

  First, the fixed potential Fix is applied from the fixed voltage source to the fixed potential terminal 35. Thereby, the potential of the guard line 13 is set to the fixed potential Fix.

  Next, a scanning signal is applied from the gate signal source to the scanning line 12 to which the inspection target pixel is connected. Thereby, each pixel of the pixel row to which the inspection target pixel belongs and the data line 11 are brought into conduction.

  Next, a predetermined non-selection signal is applied from the selection signal source to the non-selection signal input terminal 34. Specifically, the non-selection signal (H) is applied to the non-selection signal input terminals 34 corresponding to the data lines 11 at both ends among the three non-selection signal input terminals 34. Thereby, the non-selected data line and the guard line 13 are brought into conduction, and the potential of the non-selected data line is set to the fixed potential Fix.

  Next, a predetermined selection signal is applied from the selection signal source to the selection signal input terminal 33. Specifically, the selection signal (H) is applied to the selection signal input terminal 33 corresponding to the central data line 11 among the three selection signal input terminals 33. As a result, the selected data line and the inspection terminal 32 become conductive.

  Next, an inspection voltage is applied from the external measuring device to the inspection terminal 32.

  Next, the application of the inspection voltage is stopped, and after a predetermined period, the pixel voltage is measured from the inspection terminal 32 by an external measurement device, and the capacitor capacity of the inspection target pixel is calculated from the measured voltage value.

  In the pixel capacitance inspection performed in this way, the application of the inspection voltage to the selected data line and the measurement of the pixel voltage after stopping the application are performed while introducing the fixed potential Fix to the non-selected data line. By causing the selected data line to act as a shield, the induction noise to the selected data line can be reduced, and the inspection accuracy can be increased while ensuring the electrostatic protection function. Note that the fixed voltage source, the selection signal source, and the external measurement device may be configured as one inspection device.

  On the other hand, in pixel inspection in which the non-selected data line is not set to a fixed potential, a test voltage is applied to the selected data line while the non-selected data line is left in a high impedance state, and then the selected data is Since the pixel voltage is measured from the line, the non-selected data line cannot be used as a shield, and the inspection accuracy is likely to deteriorate due to induced noise.

  FIG. 7 is a graph for explaining an example of the effect of one embodiment of the pixel capacity inspection according to the present invention. The graph of the figure shows the frequency distribution of the calculated capacitance value when the pixel capacitance inspection is performed in a state where a fixed potential is applied to the non-selected data line in the active matrix substrate 2 according to the second embodiment (Example). The frequency distribution of the calculated capacitance value when the pixel capacitance inspection is performed in a state where no fixed potential is applied to the non-selected data line (comparative example) is shown. This frequency distribution is obtained by actually measuring an active matrix substrate having a pixel capacitance design value of 1.5 pF.

  From the comparison result of the frequency distribution in the graph of FIG. 7, it is clear that the variation in the calculated capacitance value according to the example is smaller than the variation in the calculated capacitance value according to the comparative example. The average error of the calculated capacity value with respect to the design value was 5.8% in the comparative example and 1.3% in the example. From this, it can be seen that a higher inspection accuracy can be obtained in the capacity inspection of the active matrix substrate 2 than in the comparative example.

  While the first and second embodiments have been described above, the active matrix substrate according to the present invention is not limited to the first and second embodiments described above. Other embodiments realized by combining arbitrary components in the first and second embodiments, and various modifications conceivable by those skilled in the art without departing from the gist of the present invention to the first and second embodiments. Modifications obtained in this manner and various devices incorporating the active matrix substrate according to the present invention are also included in the present invention.

  For example, in Embodiments 1 and 2, one embodiment of the present invention has been described as an active matrix substrate in a manufacturing process, but an active matrix substrate on which a light-emitting element such as an organic EL element is formed is also within the scope of the present invention. There is a similar effect.

  In the above-described embodiment, although described as n-type transistors that are turned on when the voltage level of the gate electrode of each TFT is HIGH, these are formed by p-type transistors and the gate electrode wiring Even with an active matrix substrate having a reversed polarity, the same effects as those of the above-described embodiment can be obtained.

  In the first and second embodiments, the circuit configuration for selecting the data line 11 while protecting the display area from the inflow of static electricity to the data line 11 has been described. However, the display area is protected from the inflow of static electricity to the scanning line 12. However, a circuit configuration for selecting the scanning line 12 is also included in the scope of the present invention.

  Further, for example, in the active matrix substrate according to the present invention, a thin flat TV as shown in FIG. 8 is formed in a state in which the light emitting element is formed and a peripheral portion is cut along a cutting line in the final stage of the manufacturing process. Built in. By incorporating the active matrix substrate according to the present invention, a thin flat TV having an electrostatic protection function and capable of setting a wide range of data voltage values is realized.

  The active matrix substrate of the present invention is particularly useful as a substrate in the manufacturing process stage of an active type organic EL flat panel display in which pixel circuits are individually inspected while having an electrostatic protection function.

1, 2, 500 Active matrix substrate 10, 501 Pixel 11, 511 Data line 12, 512 Scan line 13, 513 Guard line 21 Thin film transistor for selection 22, 23, 24, 25, 521, 522 ESD diode 31, 531, Pad 32, 532 Inspection terminal 33 Selection signal input terminal 34 Non-selection signal input terminal 35 Fixed potential terminal 42 Non-selection thin film transistor

Claims (7)

A substrate,
A plurality of signal lines arranged on the substrate;
Inspection terminals provided on the substrate;
A plurality of first thin film transistors arranged one by one corresponding to each of the plurality of signal lines, and switching between conduction and non-conduction between the corresponding signal line and the inspection terminal;
A plurality of selection signal input terminals which are arranged one by one corresponding to each of the plurality of first thin film transistors and to which a selection signal for selecting a signal line to be conducted with the inspection terminal is input;
A first electrostatic protection element comprising a pair of diodes connected in anti-parallel;
A plurality of second electrostatic protection elements including a pair of diodes arranged one by one corresponding to each of the plurality of selection signal input terminals and connected in anti-parallel;
It has an electrostatic discharge wire that is the electrostatic discharge destination,
Each of the plurality of first thin film transistors includes:
One of the source electrode and the drain electrode is connected to the corresponding signal line,
The other of the source electrode and the drain electrode is connected to the inspection terminal, and is connected to the electrostatic discharge line via the first electrostatic protection element,
An active matrix substrate, wherein a gate electrode is connected to the corresponding selection signal input terminal and connected to the electrostatic discharge line via the corresponding second electrostatic protection element. The active matrix substrate according to claim 1, wherein a built-in voltage of the diode included in each of the plurality of second electrostatic protection elements is larger than a threshold voltage of each of the plurality of first thin film transistors. The diode included in each of the first electrostatic protection element and the plurality of second electrostatic protection elements is formed of a thin film transistor in which one of a source electrode and a drain electrode and a gate electrode are short-circuited. The active matrix substrate as described. A plurality of second thin film transistors arranged one by one corresponding to each of the plurality of signal lines and switching between conduction and non-conduction between the corresponding signal line and the electrostatic discharge line;
A plurality of non-selection signal input terminals which are arranged one by one corresponding to each of the plurality of second thin film transistors and to which a non-selection signal for conducting the corresponding signal line and the electrostatic discharge line is input;
A third electrostatic protection element including a pair of diodes arranged one by one corresponding to each of the plurality of non-selection signal input terminals and connected in reverse parallel;
Each of the plurality of second thin film transistors includes:
One of the source electrode and the drain electrode is connected to the corresponding signal line,
The other of the source electrode and the drain electrode is connected to the electrostatic discharge line,
A gate electrode connected to the corresponding non-selection signal input terminal, and connected to the electrostatic discharge line set at a fixed potential via the corresponding third electrostatic protection element;
The active matrix substrate according to claim 1, wherein a signal line other than a signal line that is electrically connected to the inspection terminal by the selection signal is set to the fixed potential by the non-selection signal. The active matrix substrate according to claim 4, wherein a built-in voltage of the diode included in each of the plurality of third electrostatic protection elements is larger than a threshold voltage of each of the plurality of second thin film transistors. 5. The active matrix substrate according to claim 4, wherein a diode included in each of the plurality of third electrostatic protection elements is configured by a thin film transistor in which one of a source electrode and a drain electrode and a gate electrode are short-circuited. The plurality of signal lines are divided into signal line blocks for each m (m is an integer of 2 or more),
The active matrix substrate according to claim 1, wherein the inspection terminal and the first electrostatic protection element are provided for each signal line block.

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