JP2007094031A - Lighting inspection method for liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting inspection for a liquid crystal panel by which even a pixel generating minor defects can be detected. <P>SOLUTION: In a first inspection process, a source signal capable of alternately switching positive polarity voltage Vs(H) and negative polarity voltage Vs(L) at each prescribed time is applied to each data line 4. A gate signal having a pulse P raising from voltage Vg(L) of a level for turning off a thin film transistor 5 to voltage Vg(H) of a level for turning on the thin film transistor 5 is applied to each scanning line 3 in each time band when the positive polarity voltage Vs(H) and the negative polarity voltage Vs(L) of the source signal are applied. In this state, a liquid crystal panel is illuminated from the rear to inspect lighting (steps #5 to #15). In a second inspection process following the first inspection process, the liquid crystal panel is illuminated from the rear for a prescribed period just after turning off the application of the source signal and the gate signal to inspect lighting (steps #20 to #30). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lighting inspection method for a liquid crystal panel before mounting a driving circuit.

  In recent years, electronic devices such as personal computers, mobile phones, and portable information terminals are widely used, and a liquid crystal panel is mounted as a display screen in the electronic devices.

  Generally, the manufacturing process of a liquid crystal panel is roughly divided into an array process, a cell process, and a module process in order from the previous process.

  The array process is a process of manufacturing an array substrate that is one of the opposing substrates in the liquid crystal panel. In this array process, wiring, thin film transistors, insulating films, pixel electrodes, and the like are formed on a mother substrate that is a material. In recent years, however, a plurality of liquid crystal panels are cut out from one substrate. In this case, a mother substrate having a size much larger than the size of the desired liquid crystal panel is prepared, and the mother substrate is placed on the mother substrate. Wiring and the like are formed separately for each liquid crystal panel. In parallel with the array process, there is naturally a CF process for manufacturing a CF (color filter) substrate including a common electrode paired with the array substrate.

  In the cell process, the previously completed array substrate and CF substrate are bonded together, and then divided into individual liquid crystal panels. Then, for each liquid crystal panel, liquid crystal is injected and sealed in the gap between the opposing substrates (array substrate and CF substrate), and surface treatment is performed.

  In the module process, for each liquid crystal panel obtained through the cell process, an electronic circuit of a drive system or the like is attached or a polarizing plate is attached. Furthermore, a light source, a light guide plate, or the like as a backlight may be assembled in accordance with the final specification.

  By the way, the liquid crystal panel manufactured in this way has leakage defects between the pixel electrode and the counter electrode (common electrode) and wiring (scanning lines and data) even with advanced thin film formation technology and fine processing technology. Various defects such as line defects, disconnections, and poor thin film transistor characteristics may occur. For this reason, the liquid crystal panel obtained through the cell process is generally subjected to a lighting test before the module process, that is, before the driving circuit is mounted including the attachment of a polarizing plate.

  This lighting inspection can detect defects in the liquid crystal panel at an early stage, so that defective products can be prevented from leaking into the module process, which is a subsequent process, and unnecessary components such as a backlight are not combined with the defective liquid crystal panel. As a result, the manufacturing cost can be suppressed.

  Next, a general method of lighting inspection will be described (for example, see Patent Document 1). First, as shown in FIG. 3, the liquid crystal panel that is the object of the lighting test is mainly composed of an array substrate 1 and a CF substrate 2 in which liquid crystal is sealed between each other.

  On the array substrate 1, scanning lines 3, scanning line terminals 3a, data lines 4, data line terminals 4a, thin film transistors 5 and pixel electrodes 6 are formed. Specifically, the scanning lines 3 and the data lines 4 are arranged in a matrix with an insulating film (not shown) interposed therebetween, and in each region where the two intersect, a thin film transistor 5 and a pixel electrode 6 are formed. It is arranged adjacent to each other. The thin film transistor 5 has a gate terminal 5a, a source terminal 5b, and a drain terminal 5c. The gate terminal 5a is connected to the scanning line 3, the source terminal 5b is connected to the data line 4, and the drain terminal 5c is a pixel electrode. 6 is connected. On the other CF substrate 2, a common electrode 7 disposed to face each pixel electrode 6 is formed.

  For such a liquid crystal panel, while applying an inspection source signal from each data line terminal 4a to each data line 4, and applying an inspection gate signal from each scanning line terminal 3a to each scanning line 3, The liquid crystal panel is illuminated from the back by a backlight for inspection. At that time, a constant DC voltage is applied to the common electrode 7 from a common electrode terminal (not shown).

  As a source signal at that time, as shown in FIG. 4A, a signal in which a positive voltage Vs (H) and a negative voltage Vs (L) are alternately switched every predetermined time is used. On the other hand, as shown in FIG. 4B, the thin film transistor 5 is applied to the first half of each time zone in which the positive voltage Vs (H) and the negative voltage Vs (L) in the source signal are applied as the gate signal. A signal that periodically has a pulse P that rises from a voltage Vg (L) at a level of turning off to a voltage Vg (H) at a level of turning on the thin film transistor 5 is used.

  When such a source signal and a gate signal are applied to the source terminal 5b and the gate terminal 5a of each thin film transistor 5 through each data line 4 and each scanning line 3, respectively, the drain is only applied while the pulse P of the gate signal is applied. The supply of the source signal to the terminal is opened. Accordingly, as shown in FIG. 4C, the source signal is supplied to each pixel electrode 6 through the drain terminal while the gate signal pulse P is applied, and Vp (H) or Vp ( L) is accumulated, and the voltages Vp (H) and Vp (L) are held until the next pulse P of the gate signal is applied.

  Here, in a pixel where an excessive leak defect is generated, as shown in FIG. 4D, the voltage of the pixel electrode 6 from the time when the source signal voltages Vs (H) and Vs (L) are switched. Leaks rapidly, and in particular, the high-side voltage Vp (H) drops sharply with a steep slope. Further, in a pixel in which a defect or disconnection occurs in the scanning line 3 or the data line 4, it does not satisfy the normal high side voltage Vp (H) to be stored in the pixel electrode 6 at all. Even in a pixel in which the characteristic failure of the thin film transistor 5 has occurred, the normal high-side voltage Vp (H) cannot be stored in the pixel electrode 6.

  Then, in the case of a normally white liquid crystal panel that displays white when no voltage is applied (backlight light is transmitted through the polarizing plate), in a normal pixel, a stable and large gap between the pixel electrode 6 and the common electrode 7 is obtained. Since a potential difference is generated, this effectively acts on the liquid crystal to sufficiently change the alignment of the liquid crystal, and as a result, changes to black display (backlight is blocked by the polarizing plate). On the other hand, in a pixel in which a defect has occurred, since the potential difference between the pixel electrode 6 and the common electrode 7 is small, the change in the alignment of the liquid crystal becomes insufficient. This appears as a bright spot.

  On the other hand, in the case of a normally black liquid crystal panel that displays black when no voltage is applied, the display is inverted with respect to the normally white liquid crystal panel. That is, a normal pixel changes to white display. On the other hand, in a pixel in which a defect has occurred, black display remains as it is or an intermediate dim display, which appears as a dark spot.

  Note that even though white display is used, red, green, and blue are actually displayed by the CFs arranged corresponding to the respective pixels.

Thus, in the lighting inspection, the presence or absence of a defect can be determined by detecting a bright spot in the case of a normally white liquid crystal panel and a dark spot in the case of a normally black liquid crystal panel.
JP-A-7-209136

  However, when the source signal and gate signal shown in FIGS. 4A and 4B are used as the source signal and gate signal for lighting inspection, detection of a pixel in which an excessive leak defect has occurred is detected. Although it can be used for a while, it is difficult to detect a pixel with a slight leak failure. The reason is as follows.

  As shown in FIG. 4E, in the pixel in which a minor leak defect is generated, the voltage of the pixel electrode 6 gradually decreases from the time when the source signal voltages Vs (H) and Vs (L) are switched. Will leak. In particular, the high-side voltage Vp (H) slightly decreases with a gentle slope. That is, the voltage at the end point where the voltage Vp (H) on the higher side of the pixel electrode 6 is reduced is the voltage at the end point of the voltage Vp (H) on the higher side of the pixel electrode 6 in a normal pixel (see FIG. 4C). ) And almost no fading.

  As a result, in the case of a normally white type liquid crystal panel, the defective pixel is changed to black display or dim display, and in the case of normally black type liquid crystal panel, it is changed to white display or light display. change. Both display modes are substantially the same as the display state of normal pixels, and bright spots and dark spots are difficult to appear. Therefore, there arises a problem that it is difficult to detect a defect that relies on a bright spot or a dark spot.

  Even if such a defect is difficult to distinguish, the liquid crystal panel having this defect is a defective liquid crystal panel after all. Even if it is not determined as a defective product by such inspection, there is a risk that it will be found that the liquid crystal panel is defective when it becomes a later module process or an actual product.

  Therefore, the present invention has been made in view of the above problems, and provides a lighting inspection method for a liquid crystal panel that can be reliably detected at the stage of the liquid crystal panel even in a pixel in which a minor defect has occurred. It is intended.

  In order to achieve the above object, a method for inspecting lighting of a liquid crystal panel according to the present invention includes a scanning line, a data line, and pixels provided in each region where the scanning line and the data line intersect with each other. An electrode, a thin film transistor provided adjacent to each pixel electrode, having a gate terminal connected to the scanning line, a source terminal connected to the data line, and a drain terminal connected to the pixel electrode; and a liquid crystal for each pixel electrode. A lighting inspection method for a liquid crystal panel including a common electrode disposed so as to be opposed to each other, and includes a first inspection step and a second inspection step described below. In the first inspection process, a source signal in which a positive voltage and a negative voltage are alternately switched every predetermined time is applied to each data line, and a positive voltage and a negative voltage in the source signal are applied to each scanning line. The liquid crystal panel is illuminated from the back side and inspected while applying a gate signal having a pulse that opens the supply of the source signal to the drain terminal in each time zone when the voltage of. In the second inspection process, following the first inspection process, the liquid crystal panel is illuminated from the back for a predetermined period immediately after the application of the gate signal is cut off.

  In this way, in the first inspection process, the pixel in which a defect other than a slight leak failure is generated appears as a bright spot in the case of a normally white liquid crystal panel, and the normally black type. In the case of a liquid crystal panel, it appears as a dark spot. Therefore, by detecting the bright spot or dark spot, it is possible to determine the presence or absence of a defect other than a minor leak defect. In the subsequent second inspection process, in the case of a normally white type liquid crystal panel, the pixel in which a minor leak defect has occurred is immediately returned to white display immediately after the gate signal application is turned off. In the case of a black liquid crystal panel, black display is instantaneously returned immediately after the gate signal application is turned off. Therefore, the presence or absence of a minor leak defect can be determined by detecting the location. As a result, it is possible to reliably determine the presence or absence of defects including minor leak defects.

  According to the lighting inspection method for a liquid crystal panel of the present invention, even a pixel having a minor defect can be reliably detected.

  Below, one Embodiment of the lighting test method of the liquid crystal panel of this invention is explained in full detail, referring drawings. FIG. 1 is a flowchart showing a flow of a lighting inspection of a liquid crystal panel according to an embodiment of the present invention, and FIG. 2 is a time chart of signals in a second inspection process in the lighting inspection. Here, FIG. 2A shows the voltage of the pixel electrode in a normal pixel, and FIG. 2B shows the voltage of the pixel electrode in a pixel in which a minor leak defect has occurred.

  The liquid crystal panel which is the object of the lighting inspection in the present embodiment is the same as the liquid crystal panel shown in FIG.

  As shown in FIG. 1, in the lighting inspection in this embodiment, first, as a first inspection process, an inspection source signal is applied to each data line 4 from each data line terminal 4a to the liquid crystal panel. At the same time, the liquid crystal panel is irradiated from the back surface by the backlight for inspection while applying the gate signal for inspection from each scanning line terminal 3a to each scanning line 3 (steps # 5 and # 10).

  In this case, either the source signal and the gate signal may be turned on or the backlight may be turned on first or simultaneously. As the light source of the backlight, a cold cathode tube or a light emitting diode is used. At that time, a constant DC voltage is applied to the common electrode 7 from the common electrode terminal.

  As the source signal at that time, a signal in which the positive voltage Vs (H) and the negative voltage Vs (L) are alternately switched every predetermined time is used as in the source signal shown in FIG. . In this signal, for example, the positive voltage Vs (H) and the negative voltage Vs (L) are alternately switched every 1/60 [s (seconds)] (= 16.7 [ms]).

  On the other hand, as the gate signal, the positive voltage Vs (H) and the negative voltage Vs (L) in the source signal are applied in the first half of each time zone, as in the gate signal shown in FIG. A signal having a pulse P periodically rising from a voltage Vg (L) at a level for turning off the thin film transistor 5 to a voltage Vg (H) at a level for turning on the thin film transistor 5 is used. This signal has, for example, a period of 1/60 [s] (= 16.7 [ms]) and a pulse P width of 10 to 25 [μs].

  When such a source signal and a gate signal are applied to the source terminal 5b and the gate terminal 5a of each thin film transistor 5 through each data line 4 and each scanning line 3, respectively, the drain is only applied while the pulse P of the gate signal is applied. The supply of the source signal to the terminal is opened. Accordingly, each pixel electrode 6 in a normal pixel is supplied with a source signal through the drain terminal while the gate signal pulse P is applied, as in FIG. 4C, and Vp (H). Alternatively, the voltage Vp (L) is accumulated, and the voltages Vp (H) and Vp (L) are substantially held until the next pulse P of the gate signal is applied.

  On the other hand, in the pixel in which an excessive leak defect is generated, the voltage of the pixel electrode 6 is changed from the time when the source signal voltages Vs (H) and Vs (L) are switched, as in FIG. Leakage is abrupt, and in particular, the higher voltage Vp (H) decreases sharply. Further, although not shown in the figure, in a pixel in which the scanning line 3 or the data line 4 is missing or disconnected, the normal high side voltage Vp (H) to be stored in the pixel electrode 6 is not satisfied at all. Even in a pixel in which the characteristic failure of the thin film transistor 5 has occurred, the normal high-side voltage Vp (H) cannot be stored in the pixel electrode 6.

  Further, in the pixel in which the minor leak defect is generated, the voltage of the pixel electrode 6 is compared from the time when the source signal voltages Vs (H) and Vs (L) are switched, as in FIG. In particular, the voltage Vp (H) on the high side slightly decreases with a gentle slope. That is, the voltage at the end point where the voltage Vp (H) on the higher side of the pixel electrode 6 is reduced is the voltage at the end point of the voltage Vp (H) on the higher side of the pixel electrode 6 in a normal pixel (see FIG. 4C). ) And almost no fading.

  Then, in the case of a normally white liquid crystal panel, a normal pixel changes to black display when a voltage is applied. On the other hand, in a pixel in which a minor leak defect is generated, the display is changed to a black display or a dim display having substantially the same display mode as a normal pixel. In other pixels in which defects have occurred, white display remains as it is or light-bright display, which appears as a bright spot.

  On the other hand, in the case of a normally black liquid crystal panel, the display is inverted with respect to the normally white liquid crystal panel. That is, a normal pixel changes to white display. On the other hand, in a pixel in which a minor leak defect is generated, the display is changed to a white display or a light display with the same display mode as that of a normal pixel. In other pixels where defects have occurred, black display remains dark or dark, and this appears as a dark spot.

  4 (c), (d), and (e) show ideal signal waveforms in order to facilitate understanding of the invention. For example, in the case of (c), the voltage Vp (H) is constant until the next gate signal pulse P is applied. However, in an actual pixel electrode, the voltage drops slightly until the next gate signal pulse P is applied. The same applies to (d) and (e) of FIG. However, this voltage decrease is much more gradual than the slope indicating the voltage decrease in the defective pixel shown in (d) and (e) of FIG.

  And as shown in FIG. 1, it progresses to step # 15 and performs a test | inspection. In this inspection, the presence of defects other than minor leak defects is detected by detecting bright spots for normally white liquid crystal panels and dark spots for normally black liquid crystal panels. Can be determined. That is, in this inspection, the presence or absence of a minor leak defect that is difficult to determine is not determined.

  Thus, the first inspection process is completed, and subsequently, the process proceeds to a second inspection process for determining the presence or absence of a minor leak defect. Specifically, the process proceeds to step # 20, where the application of the source signal and the gate signal is turned off and suddenly cut off, and the inspection by observation is executed immediately after that until a predetermined time has elapsed (steps # 25, # 30). ).

  When a DC voltage is applied to the common electrode 7, the voltage may be turned off at the same time as the source signal and the gate signal are turned off. On the other hand, the backlight remains on and the LCD panel continues to be illuminated. However, the backlight may be turned off once after the inspection in the first inspection process (step # 15), and the backlight may be turned on again immediately before the application of the source signal and the gate signal is turned off (step # 20). Absent.

  At that time, when the application of the source signal and the gate signal is instantaneously turned off, as shown in FIG. 2A, the voltage Vp of the pixel electrode 6 in a normal pixel gradually decreases and is about 3 [s]. To "0 (zero)". On the other hand, the voltage Vp of the pixel electrode 6 in a pixel in which a minor leak defect has occurred is rapidly reduced as compared with a normal pixel, and reaches “0” instantaneously of about 0.5 [s].

  As a result, in the case of a normally white liquid crystal panel, the normal pixel gradually returns to white display immediately after the application of the source signal and the gate signal is turned off, according to the decrease in the voltage Vp of the pixel electrode 6. In a pixel in which a minor leak defect is generated, the display is quickly returned to white. In other words, both normal pixels and pixels that have minor leak defects will eventually return to white display, but the time it takes to return to the white display will be minor leak defects. The pixel in which the occurrence is much faster than the normal pixel.

  On the other hand, in the case of a normally black liquid crystal panel, the normal pixel gradually returns to black display immediately after the source signal and gate signal are turned off, and a slight leak defect occurs. In the case of pixels, the black display is instantaneously returned. In other words, both normal pixels and pixels that have minor leak defects will eventually return to black display, but the time it takes to return to black display will be minor leak defects. The pixel in which the occurrence is much faster than the normal pixel.

  As a specific method of turning off the source signal and the gate signal as described above, the switch for turning off the source signal and the gate signal is attached to a general liquid crystal panel lighting inspection device. This is possible. Further, although both the source signal and the gate signal are turned off, a configuration in which only the gate signal is turned off may be employed. This is because the signal application to the pixel electrode 6 is stopped by turning off the gate signal. In particular, a general lighting inspection apparatus is provided with a volume so that the pulse width of the gate signal can be freely changed. Therefore, the gate signal may be turned off instantaneously by turning this volume, or a switch different from this volume may be provided.

  In this inspection (step # 30), in the case of a normally white liquid crystal panel, the point where the white display is instantaneously returned immediately after the application of the source signal and the gate signal is turned off is determined as a normally black liquid crystal panel. In the case of a panel, the presence or absence of a minor leak defect can be determined by detecting a point where the display returns instantaneously to black immediately after application of the source signal and gate signal is turned off.

  When the specified time has passed immediately after the application of the source signal and the gate signal is turned off, the second inspection process is finished, and the process proceeds to step # 35 to turn off the backlight and stop the illumination on the liquid crystal panel. The specified time here is the time for instantaneously returning to white display or black display after the application of the source signal and the gate signal is turned off, that is, the voltage Vp of the pixel electrode 6 in the pixel in which a slight leak defect has occurred. The time from when the signal and the gate signal are applied to “0” is sufficient.

  This completes the lighting inspection.

  In this way, in the lighting inspection, the presence or absence of defects other than minor leakage defects can be determined in the first inspection process, and the presence or absence of minor leakage defects can be determined in the subsequent second inspection process. The presence or absence of a defect including a defective defect can be reliably determined.

  In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, as the gate signal used in the first inspection process in the lighting inspection, the pulse P rises in each time zone in which the positive voltage Vs (H) and the negative voltage Vs (L) in the source signal are applied. Any signal that opens the supply of the source signal to the drain terminal can be used.

  The present invention is useful for lighting inspection of a liquid crystal panel before mounting a drive circuit.

It is a flowchart which shows the flow of the lighting test | inspection of the liquid crystal panel which is one Embodiment of this invention. It is a time chart of the signal in the 2nd inspection process in lighting inspection. It is a circuit diagram of the liquid crystal panel which is the object of the lighting inspection. It is a time chart of the signal in the lighting test | inspection of the conventional liquid crystal panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Array substrate 2 CF substrate 3 Scan line 3a Scan line terminal 4 Data line 4a Data line terminal 5 Thin film transistor 5a Gate terminal 5b Source terminal 5c Drain terminal 6 Pixel electrode 7 Common electrode

Claims (1)

Scan lines and data lines formed in a matrix while being insulated from each other,
A pixel electrode provided in each region where the scanning line and the data line intersect;
A thin film transistor provided adjacent to each pixel electrode, having a gate terminal connected to the scanning line, a source terminal connected to the data line, and a drain terminal connected to the pixel electrode;
A liquid crystal panel lighting inspection method comprising a common electrode disposed opposite to each pixel electrode with a liquid crystal interposed therebetween,
A source signal in which a positive voltage and a negative voltage are alternately switched every predetermined time is applied to each data line, and a positive voltage and a negative voltage in the source signal are applied to each scanning line. A first inspection step of performing an inspection by illuminating the liquid crystal panel from the back while applying a gate signal having a pulse for opening the supply of the source signal to the drain terminal in each time zone;
A lighting inspection of a liquid crystal panel, comprising: a second inspection step for inspecting the liquid crystal panel by illuminating the liquid crystal panel from the back surface for a predetermined period immediately after the application of the gate signal is cut off after the first inspection step. Method.

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