CN108962109B - Detection method and detection device for display panel - Google Patents
Detection method and detection device for display panel Download PDFInfo
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- CN108962109B CN108962109B CN201810816138.7A CN201810816138A CN108962109B CN 108962109 B CN108962109 B CN 108962109B CN 201810816138 A CN201810816138 A CN 201810816138A CN 108962109 B CN108962109 B CN 108962109B
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- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
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- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/006—Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays
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Abstract
The invention discloses a detection method of a display panel, which controls the voltage of a source line to be reduced from high voltage of a source electrode to low voltage of the source electrode when a gate line is in a gate detection voltage, so that a normal pixel corresponding to a normal thin film transistor is changed from a bright picture to a dark picture, and a pixel corresponding to an abnormal thin film transistor with a TFT characteristic right shift defect still maintains the bright picture, so that the pixel corresponding to the abnormal thin film transistor is highlighted in a bright spot form in the whole black picture, and the pixel with the TFT characteristic right shift defect is accurately and effectively detected; the invention also discloses a detection device of the display panel.
Description
Technical Field
The invention relates to the technical field of display, in particular to a detection method and a detection device of a display panel.
Background
In the existing manufacturing process, the display panel is detected in multiple steps, including breaking the mother plate into multiple display panels (panels), and then inputting multiple detection signals to the display panels to perform lighting detection; and after the chip (IC) is pressed, the display module is lighted and detected again to detect defects caused by poor pressing and connecting processes or detection after breaking.
In the post-break detection (SL lighting) stage, low frequency driving is used, so defects can only be detected normally when the Thin Film Transistor (TFT) has a fully turned off semiconductor conduction channel or the thin film transistor threshold voltage is much higher than the gate turn-on voltage. Due to the process error, as shown in fig. 1, due to the film foreign matter, the transfer characteristic curve (Vg-Id curve) of one or more thin film transistors may shift right, thereby causing the threshold voltage Vth of the abnormal thin film transistor to be greater than the error allowable range. However, this type of defect is difficult to effectively detect in a blocking manner after breaking, and is usually found in module inspection, confidence verification or customer hands.
In the module detection, scanning signals are scanned line by line, a grid opening voltage Vgh and a grid threshold voltage Vgl are switched, an abnormal thin film transistor cannot well charge and discharge a pixel electrode, and defects such as bright spots or rough pictures are easily shown, so that the defect of right shift of a TFT is detected. However, the coordinate of the abnormal thin film transistor detected in the module detection stage is difficult to locate, which is inconvenient for maintenance and has failure risk in repair. Therefore, the failure to detect the right shift defect of TFT characteristics effectively after the disconnection causes waste of members and manpower, and also increases quality risk.
Disclosure of Invention
In order to solve the technical problems, the invention provides a detection method of a display panel, which achieves the effect of accurately detecting the right shift defect of the TFT characteristics by designing a group of new signal waveforms for detection.
The technical scheme provided by the invention is as follows:
the invention discloses a detection method of a display panel, wherein the display panel comprises a gate line, a source line and pixels, wherein the gate line and the source line are criss-cross, the pixels are defined by the intersection of the gate line and the source line, a thin film transistor and a pixel electrode are arranged in each pixel, the gate line inputs a scanning signal into a grid stage of the thin film transistor, the source line inputs a data signal into a source stage of the thin film transistor, and a drain stage of the thin film transistor is connected with the pixel electrode; the detection method of the display panel comprises the following steps:
step 1: in a first detection time, enabling the grid line to output a grid opening voltage to a grid of the thin film transistor, and enabling the source line to output a source electrode high voltage to a source electrode of the thin film transistor;
step 2: in the second detection time, enabling the grid line to output the grid detection voltage to the grid of the thin film transistor, and enabling the source line to continuously output the source high voltage to the source of the thin film transistor; the gate detection voltage is lower than a gate turn-on voltage and higher than a gate threshold voltage;
step 3: in the third detection time, enabling the grid line to continuously output the grid detection voltage to the grid of the thin film transistor, and enabling the source line to output the source low voltage to the source of the thin film transistor;
step 4: in the fourth detection time, enabling the grid line to output the grid threshold voltage to the grid of the thin film transistor, and enabling the source line to continuously output the source extremely-low voltage to the source electrode of the thin film transistor;
after the Step 1-Step 4 are taken as one cycle, the process enters the Step1 of the next cycle after the Step4 is finished, the display panel is simultaneously detected for a plurality of cycles, whether the pixel corresponding to the thin film transistor exists in the display panel is judged to be a bright picture, and if the pixel exists, the thin film transistor is an abnormal thin film transistor.
Preferably, the source high voltage is a source voltage of a thin film transistor corresponding to a highest gray scale of the display panel.
Preferably, the source very low voltage is a source voltage of a thin film transistor corresponding to a lowest gray scale of the display panel.
Preferably, the first detection time is 300-500 mus.
Preferably, the second detection time is 70-150 mu s.
Preferably, the third detection time is 600-1000 mus.
Preferably, the fourth detection time is 10-20 ms.
Preferably, the total time of the plurality of periods is 50ms to 3 s.
Preferably, in the plurality of periods, the polarity of the source high voltage in two adjacent periods is reversed.
The invention also discloses a detection device of the display panel, which adopts any one of the detection methods to detect the display panel.
Compared with the prior art, the invention can bring at least one of the following beneficial effects:
1. the abnormal thin film transistor with the TFT characteristic right shift defect is quickly and efficiently detected, and pixels corresponding to the abnormal thin film transistor are highlighted in the form of bright spots in the whole black picture, so that accurate positioning and subsequent repair are facilitated;
2. the detection stage can be implemented after the breaking, so that the waste of the parts caused by the backward flow of defective products is prevented;
3. the size of grid detection voltage can be flexibly adjusted according to different display panel types and technical standards, and the detection leakage is prevented;
4. only a group of signals for detection is needed to be added on the basis of the existing signal generator and other equipment, so that the cost is low and the implementation is simple and convenient.
Drawings
The present invention will be further described in the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings.
FIG. 1 is a diagram illustrating a normal transfer characteristic curve and a right-shifted transfer characteristic curve of a thin film transistor in a display panel;
FIG. 2 is a schematic structural diagram of a display panel;
FIG. 3 is a schematic diagram of waveforms of signals for detection in the method for detecting a display panel according to the present invention;
FIG. 4 is a diagram of the gate turn-on voltage, gate detection voltage, and gate threshold voltage of the present invention as compared to FIG. 1;
fig. 5 is a schematic view showing a lighting state of the display panel after lighting by using the detection method of the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled.
Fig. 2 is a display panel structure including criss-cross gate lines 01 and source lines 02, a common electrode com, and pixels defined by intersections of the gate lines 01 and the source lines 02, each of which is provided with a thin film transistor 03 and a pixel electrode 04; a Gate line 01(Gate line) inputs a scanning signal to a Gate of the thin film transistor 03, and the scanning signal is G1, G2, … …, Gn in order along a column direction; a Source line 02(Source line) inputs a data signal to a Source of the thin film transistor 03, and a drain of the thin film transistor 03 is connected to the pixel electrode 04.
When the display panel is detected, a signal for detection is input to the gate line 01, the source line 02, the common electrode com, and the like of the display panel through an external signal generator, so that the display panel is lighted, and abnormal pixels are detected through camera shooting or human eye observation.
The present invention discloses a new set of signals for detection, which includes a gate-on voltage Vgh, a gate detection voltage Vgm, a gate threshold voltage Vgl for inputting the gate of the thin film transistor 03, a source high voltage Vsh, a source low voltage Vsl for inputting the source of the thin film transistor 03, and a common voltage Vcom for inputting the common electrode com, and the waveform of the signals for detection is as shown in fig. 3, in order to overcome the defect of the right shift of the TFT characteristics caused by the right shift of the transfer characteristic curve of the thin film transistor 03. Specifically, the detection method of the display panel comprises the following steps:
step1 (charging phase): during a first detection time T1, the gate line 01 outputs a gate turn-on voltage Vgh to the gate of the thin film transistor 03, and the source line 02 outputs a source high voltage Vsh to the source of the thin film transistor 03; the gate turn-on voltage Vgh is a preset gate voltage of the thin film transistor in the turn-on state of the display panel, and the source high voltage Vsh is a source voltage of the thin film transistor corresponding to the highest gray scale of the display panel. Each thin film transistor 03 is in an on state, the pixel electrode 04 is charged by the source line 02 through the thin film transistor 03, and pixels of normal pixels corresponding to the thin film transistors having a TFT characteristic right shift defect are all bright pictures.
The first detection time T1 is required to ensure the pixel electrode 04 is fully charged, and the first detection time T1 is about 300-500 μ s, preferably 400 μ s.
Step2 (first detection phase): during a second detection time T2, the gate line 01 outputs a gate detection voltage Vgm to the gate of the thin film transistor 03, and the source line 02 continues to output a source high voltage Vsh to the source of the thin film transistor 03; the gate detection voltage Vgm is lower than the gate turn-on voltage Vgh and higher than the gate threshold voltage Vgl, which is the preset off-state gate voltage of the thin film transistor 03.
The second detection time T2 is required to ensure that the voltage of the gate line 01 is reduced from the gate-on voltage Vgh to the gate detection voltage Vgm and stabilized at the gate detection voltage Vgm, and the second detection time T2 is about 70-150 μ s, preferably 100 μ s.
Step3 (second detection phase): during a third detection time T3, the gate line 01 continues to output the gate detection voltage Vgm to the gate of the thin film transistor 03, and the source line 02 outputs the source low voltage Vsl to the source of the thin film transistor 03; the source very low voltage Vsl is the source voltage of the TFT corresponding to the lowest gray scale of the display panel.
In fig. 4, a curve 11 is a transfer characteristic curve of the normal tft 21 (as shown in fig. 2), a curve 12 is a transfer characteristic curve of a characteristic right shift tft, which is referred to as an abnormal tft 22 (as shown in fig. 2), and the drain voltages Vd corresponding to the curves 11 and 12 are both 10V. The gate-on voltage Vgh, the gate detection voltage Vgm, and the gate threshold voltage Vgl are plotted against the curves 11 and 12 in fig. 4. The gate detection voltage Vgm is between the gate turn-on voltage Vgh and the gate threshold voltage Vgl, and the gate voltage Vg corresponding to the lowest value of the drain voltage Id in the curve 12 is denoted as Vg0The gate sense voltage Vgm is preferably equal to Vg0Or at Vg0Nearby.
However, since the characteristic right shift degrees caused by different defects are different and the characteristic right shift degree of the partial thin film transistor 03 is within an allowable error range, the gate detection voltage Vgm is obtained in such a manner that the drain current Id of the abnormal thin film transistor 22 is equal to the source low voltage Vsl when the drain voltage is the same, the gate voltage is the gate detection voltage Vgm, and the source voltage is the source low voltage Vsl2Much smaller than the drain current Id of the normal thin film transistor 211And specific values of the gate detection voltage Vgm are set through the over-leakage detection verification according to the right shift degree of the diversified TFT characteristics in the actual production and the error range allowed by the product.
Gate voltage Vg of normal thin film transistor 211When Vgm is reached, the gate detection voltage Vgm is higher than the threshold voltage Vth of the normal thin film transistor 21, as shown in fig. 41At this time, the drain current Id of the normal thin film transistor 211When the normal thin film transistor 21 is turned on, the source line 02 charges the pixel electrode 04 with the source low voltage Vsl through the normal thin film transistor 21, and the normal pixel corresponding to the normal thin film transistor 21 changes from a bright picture to a dark picture.
When the gate voltage Vg2 of the abnormal thin film transistor 22 becomes Vgm, the gate detection voltage is detected in fig. 4The pressure Vgm is preferably equal to Vg0Or at Vg0In the vicinity, the drain current Id of the abnormal thin film transistor 22 at this time2When the abnormal thin film transistor 22 is turned off, the pixel electrode 04 cannot be charged with the source low voltage Vsl normally, and the pixel corresponding to the abnormal thin film transistor 22 is still a bright image.
The third detection time T3 is required to satisfy the requirement that the voltage on the source line 02 is decreased from the source high voltage Vsh to the source low voltage Vsl, and the pixel electrode 04 connected to the normal thin film transistor 21 is charged to the source low voltage Vsl; the third detection time T3 is about 600-1000 μ s, preferably 800 μ s.
Step4 (maintenance phase): during a fourth detection time T4, the gate line 01 outputs the gate threshold voltage Vgl to the gate of the thin film transistor 03, and the source line 02 continues to output the source low voltage Vsl to the source of the thin film transistor 03; the gate threshold voltage Vgl is a gate voltage of the tft 03 in an off state preset in the display panel.
At this time, both the normal thin film transistor 21 and the abnormal thin film transistor 22 are in an off state, and the normal pixel corresponding to the normal thin film transistor 21 maintains a dark picture and the pixel corresponding to the abnormal thin film transistor 22 maintains a bright picture.
The fourth detection time T4 is used to increase the retention time for the pixel corresponding to the abnormal thin film transistor 22 to be highlighted in the form of a bright spot on the whole black screen; the fourth detection time is about 10-20 ms, preferably 16.7 ms.
After Step4 is completed, the process proceeds to Step1 of the next cycle with steps 1 to 4 as one cycle, and the source high voltage Vsh of two adjacent cycles is reversed in polarity to prevent polarization of the liquid crystal.
And performing a plurality of periods, and detecting the display panel by enabling the observation time of human eyes to be more than 1s or enabling the exposure time of the camera to be more than 50ms, wherein the total time of the periods is in the range of 50 ms-3 s. Judging whether a pixel corresponding to the thin film transistor 03 exists in the display panel or not, wherein the pixel is a bright picture, and if the pixel exists, the thin film transistor 03 is an abnormal thin film transistor 22 (the whole lighting effect of the display panel is shown in fig. 5); if not, the display panel has no abnormal thin film transistor.
In the above detection, the common electrode com of the display panel is inputted with the preset power supply voltage Vcom, and an electric field is formed between the common electrode com and the pixel electrode 04 to control the brightness and darkness of the pixel.
It should be noted that the detection method of the present invention is applicable to both a display panel in a Gate Driver on Array (GOA) mode and a display panel in which an Integrated Circuit (IC) is used as a Gate Driver Circuit; the method is suitable for display panels using metal oxides such as IGZO as semiconductor materials, and also suitable for display panels using non-metal oxides such as a-Si and LTPS as semiconductor materials; the method is suitable for detection after breaking and also suitable for TFT characteristic detection when the array substrate is finished; and is widely applicable to display panels of various pixel structures.
The invention also discloses a detection device of the display panel, which comprises a signal generator for outputting a signal for detection to the display panel, and the detection device adopts the detection method to detect the display panel.
The invention discloses a detection method of a display panel aiming at the defect of right shift of TFT characteristics caused by the right shift of a transfer characteristic curve of a thin film transistor 03, which controls the voltage of a source electrode line 02 to be reduced from a source electrode high voltage Vsh to a source electrode low voltage Vsl when a gate line 01 is at a gate detection voltage Vgm so as to change a normal pixel corresponding to a normal thin film transistor 21 from a bright picture to a dark picture and maintain the pixel corresponding to an abnormal thin film transistor 22 to be still in the bright picture, thus the pixel corresponding to the abnormal thin film transistor 22 is highlighted at a bright point in the whole black picture, and the accurate positioning and the subsequent repair are convenient. The detection method can be implemented in a detection stage after segmentation, so that the waste of the parts due to the backward flow of defective products is prevented; the size of the grid detection voltage can be flexibly adjusted according to different display panel types and technical standards, and the detection leakage is prevented; only a group of signals for detection is needed to be added on the basis of the existing signal generator and other equipment, so that the cost is low and the implementation is simple and convenient.
It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that various modifications and adaptations can be made by those skilled in the art without departing from the principle of the present invention, and should be considered as the scope of the present invention.
Claims (10)
1. A detection method of a display panel comprises criss-cross gate lines and source lines, and pixels defined by the intersection of the gate lines and the source lines, wherein each pixel is internally provided with a thin film transistor and a pixel electrode;
the detection method of the display panel is characterized by comprising the following steps of:
step 1: enabling the grid line to output a grid opening voltage to a grid of the thin film transistor and enabling the source line to output a source electrode high voltage to a source electrode of the thin film transistor within first detection time, wherein the first detection time ensures that a pixel electrode is fully charged;
step 2: in the second detection time, enabling the grid line to output the grid detection voltage to the grid of the thin film transistor, and enabling the source line to continuously output the source high voltage to the source of the thin film transistor; the grid detection voltage is lower than the grid starting voltage and higher than the grid threshold voltage, and the second detection time ensures that the voltage of the grid line is reduced from the grid starting voltage to the grid detection voltage and is stabilized at the grid detection voltage;
step 3: enabling the gate line to continuously output a gate detection voltage to the gate of the thin film transistor and enabling the source line to output a source low voltage to the source of the thin film transistor within a third detection time, wherein the third detection time meets the condition that the voltage on the source line is reduced from a source high voltage to a source low voltage and a pixel electrode connected with a normal thin film transistor is charged to the source low voltage;
step 4: enabling the gate line to output a gate threshold voltage to a gate of the thin film transistor and enabling the source line to continuously output a source extremely low voltage to a source electrode of the thin film transistor within a fourth detection time, wherein the fourth detection time is used for increasing the maintaining time of a pixel corresponding to an abnormal thin film transistor which is highlighted on the whole black picture in a bright spot mode;
after the Step 1-Step 4 are taken as one cycle, the process enters the Step1 of the next cycle after the Step4 is finished, the display panel is simultaneously detected for a plurality of cycles, whether the pixel corresponding to the thin film transistor exists in the display panel is judged to be a bright picture, and if the pixel exists, the thin film transistor is an abnormal thin film transistor.
2. The method for inspecting a display panel according to claim 1, wherein:
and the high source voltage is the source voltage of the thin film transistor corresponding to the highest gray scale of the display panel.
3. The method for inspecting a display panel according to claim 1, wherein:
and the low source voltage is the source voltage of the thin film transistor corresponding to the lowest gray scale of the display panel.
4. The method for inspecting a display panel according to claim 1, wherein: the first detection time is 300-500 mu s.
5. The method for inspecting a display panel according to claim 1, wherein: the second detection time is 70-150 mu s.
6. The method for inspecting a display panel according to claim 1, wherein: the third detection time is 600-1000 mu s.
7. The method for inspecting a display panel according to claim 1, wherein: the fourth detection time is 10-20 ms.
8. The method for inspecting a display panel according to claim 1, wherein: the total time of the plurality of periods is 50ms to 3 s.
9. The method for inspecting a display panel according to claim 1, wherein: in the multiple periods, the polarity of the high voltage of the source electrode in two adjacent periods is reversed.
10. A display panel detection device, which adopts the detection method of any one of claims 1 to 9 to detect the display panel.
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