JPH07302065A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To make defect picture elements inconspicuous by varying the blanking period voltage of video signals with a liquid crystal display device using intra- panel correction. CONSTITUTION:A black level signal is generated from the video signal polarity inversion center signal c and video signal current alternating signal d inputted from outside in a black level signal generating circuit 13. Switching of this black level signal and the video signal polarity inversion center signal c which is a white level signal is executed by an analog switch 15 in accordance with the B/W switching signal b inputted from outside. Next, switching of the output signal g of this analog switch 15 and the video signal inputted from outside is executed by an analog switch 16 in accordance with the video blanking signal a inputted from outside. An output signal h varying the timing for switching the black level voltage and the white level voltage is supplied as a source signal to a source driver 19 only in the vertical blanking period.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a bright spot correction method,
The present invention relates to a liquid crystal display device that employs a method of directly connecting a defective pixel to a source driver without applying a thin film transistor (hereinafter referred to as TFT) and applying a source voltage to the defective pixel (hereinafter referred to as in-panel correction).

[0002]

2. Description of the Related Art Conventionally, a method called C conversion has been performed in the panel correction of a TFT liquid crystal display device.
This C conversion is, as shown in the TFT equivalent circuit diagram of FIG. 4, cutting the gate input line 2 of the TFT 1 as shown by the cross mark to separate the gate bus line 3 and the pixel 4,
The picture element 4 and the source bus line 6 are connected by the line 5 without going through. This allows source bus lines 6 to 5
An average voltage of a video signal (source signal) is applied to the picture element electrode 4a via the pixel electrode 4a to make the defective picture element inconspicuous. Regarding the correction in the panel, Japanese Patent Laid-Open No. 58-184
It is disclosed in Japanese Patent No. 758, "Method for repairing defects in matrix array".

[0003]

However, in the above-described conventional in-panel correction method, defective picture elements may be conspicuous depending on the use. For example, when there is a defective picture element in a mask portion of a display having black mask portions on the upper and lower sides, the voltage applied to the defective picture element is attracted by the voltage of the display portion, so that it does not sink into black and is conspicuous. Further, in a normal display without a mask portion, when the voltage in the blanking period is at the black level, it is drawn into the voltage in the blanking period, and the average voltage is close to black.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a liquid crystal display device capable of reducing the conspicuousness of defective picture elements in any application.

[0005]

According to the liquid crystal display device of the present invention, when there is a defective pixel, the defective pixel and the source driver are not provided through a thin film transistor capable of supplying a source voltage from the source driver to the pixel. In a liquid crystal display device that is directly connected and applies the source voltage to the defective pixel to correct a bright spot, a signal generating unit for generating a video signal fixed to a black level and a video signal fixed to a white level. And a first signal for switching the video signal from the signal generating means
The switching means and the second switching means for switching to the video signal switched by the first switching means and supplying it as the source voltage only during the blanking period are provided, and the above-mentioned object is achieved thereby. Also, preferably,
The first switching unit in the liquid crystal display device of the present invention changes the switching timing of the black level voltage and the white level voltage during the blanking period. Further, preferably, in the liquid crystal display device of the present invention, the switching timing is changed by detecting the average voltage of the display period of the video signal, and by following the average voltage, the black level voltage and the white level voltage of the vertical blanking period. Change the switching timing of.

In the liquid crystal display device of the present invention, when there is a defective pixel, the defective pixel and the source driver are directly connected to each other without the thin film transistor capable of supplying the source voltage to the pixel from the source driver. A liquid crystal display device in which a bright spot is corrected by applying a voltage to the defective picture element includes a source voltage varying means for varying the source voltage in the vertical blanking period by an external signal, whereby the above The purpose is achieved. Further, preferably, the source voltage varying means in the liquid crystal display device of the present invention detects the average voltage of the video signal in the display period and varies the source voltage in the vertical blanking period so as to follow the average voltage. Further, preferably, the source voltage varying means in the liquid crystal display device of the present invention compares the average voltage of the display period of the video signal with the average voltage of the entire video signal, and according to the difference, the source of the vertical blanking period is increased. Change the voltage.

[0007]

With the above structure, the video signal fixed to the black level and the video signal fixed to the white level are generated,
The two signals are switched by the first switching unit, and the video signal supplied to the source bus line is switched by the second switching unit to a signal whose black level and white level are switched by the first switching unit only during the blanking period.

Here, the first switching means changes the switching timing between the black level voltage and the white level voltage for the source voltage in the vertical blanking period. This variable switching timing detects the average voltage during the video signal display period,
The switching timing of the black level voltage and the white level voltage in the vertical blanking period is changed so as to follow the average voltage.

For example, when the display screen has a mask portion and the display mask portion has a defective pixel, the switching timing of the black level voltage and the white level voltage can be varied by changing all the source voltages in the blanking period to the black level. If the defect picture element is fixed to, and the defective picture element is brought close to the black level, the defective picture element becomes inconspicuous. If the display screen does not have a mask portion but only the display portion, the switching timing of the black level voltage and the white level voltage can be changed to bring the applied voltage to the defective pixel close to the peripheral voltage, The element becomes less noticeable. That is, if the duty ratio of the source signal in the blanking period is set to, for example, 50% and the voltage applied to the defective pixel is brought close to an intermediate value, the defective pixel becomes inconspicuous. In this way, the switching timing of the black level voltage and the white level voltage can be changed to change the average voltage applied to the pixel electrodes, so that the defective pixels can be made inconspicuous in any application. Becomes

Further, even if the source voltage changing means is provided and the source voltage in the vertical blanking period is changed by a signal from the outside, the defective pixel is changed in the same manner as the change timing of switching between the black level voltage and the white level voltage. Can be made inconspicuous. The variable source voltage detects the average voltage during the display period of the video signal and changes the source voltage during the vertical blanking period so as to follow the average voltage. Further, the source voltage varying means compares the average voltage of the video signal during the display period with the average voltage of the entire video signal and feeds it back, and varies the source voltage during the vertical blanking period according to the difference.

[0011]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention, which is a normally white TF in which the polarity of a video signal is inverted every vertical period.
This is the case when applied to a T liquid crystal display device. In FIG.
The video signal polarity inversion center signal generating circuit 11 and the video signal alternating signal generating circuit 12 are the black level signal generating circuit 1.
3, the video signal polarity inversion center signal c and the video signal alternating signal d are supplied to the black level signal generation circuit 13
Entered in. The analog switch 15 to which the black level signal generating circuit 13, the video signal polarity reversal center signal generating circuit 11 and the B / W switching signal generating circuit 14 are connected is connected to the analog switch 16, and the black from the black level signal generating circuit 13 is connected. The level signal f and the video signal polarity inversion center signal c as a white level signal are switched by the B / W switching signal b and output to the analog switch 16. The analog switch 16 to which the analog switch 15, the video blanking signal generation circuit 17, and the video signal generation circuit 18 are connected is connected to the source driver 19, and the output signal g and the video signal e from the analog switch 15 are transferred to the video blanking signal a. And the output signal h is output to the source driver 19. The source driver 19 and the gate driver 20 are used for the TFT-LCD panel 2
1 is driven for liquid crystal display.

FIG. 2 is a signal waveform diagram of each main part of the liquid crystal display device of FIG. 1, where (A) shows a mask portion above and below the display screen, and (B) shows a normal mask portion. The case of display is shown. As shown in FIG. 2, in the black level signal generation circuit 13, the video signal AC is converted around the video signal polarity inversion center signal c output from the video signal polarity inversion center signal generation circuit 11 of the liquid crystal drive signal generation circuit. The amplitude of the signal d is amplified to the maximum amplitude that can be applied to the liquid crystal, and the output signal f which is a black signal is generated. The inverted center signal c is used as it is as a white signal. These black signal and white signal are converted to the analog switch 15
Switch with. The output signal g from the analog switch 15 and the video input signal e are switched by the analog switch 16 based on the video blanking signal a. That is, only during the vertical blanking period when the video blanking signal a is at a high level, the video signal is switched to the video signal switched by the analog switch 15 and supplied to the gate driver 20 as the source voltage. The signal e is supplied to the gate driver 20 as a source voltage.

Therefore, by changing the timing of the B / W switching signal b for switching the analog switch 15 by the circuit described above, the duty ratio between the white level voltage and the black level voltage in the blanking period is changed, and the defect picture is displayed. The effective value of the voltage applied to the element can be changed.

3 (A) and 3 (B) are shown in FIG.
(B) It is a figure which shows each screen display example. As shown in FIG. 3A, the display screen has mask portions 23 above and below the central display portion 22, and when a defective pixel exists in this display mask portion, the defective pixel is made as close to black as possible. This makes the defective picture element inconspicuous. Therefore, by fixing the B / W switching signal b shown in FIG. 2A to the black side and fixing the signal in the blanking period to black, Bring the picture elements closer to black.

Further, as shown in FIG. 3B, in the case where the display screen does not have the mask portion 23 but only the display portion 22, if the applied voltage of the defective pixel is brought close to the voltage around it, the defective pixel is Is less noticeable. Therefore, as shown in FIG. 2B, the duty ratio of the B / W switching signal b in the blanking period is set to, for example, 50%, and the voltage applied to the defective pixel is brought close to an intermediate value to make the defective pixel inconspicuous. To do.

In this embodiment, the case where the source voltage is changed in the vertical blanking period and the switching timing of the black level voltage and the white level voltage is changed, but the source voltage in the vertical blanking period is changed by an external signal. Variable source voltage varying means may be provided, and in this case, the source voltage varying means detects the average voltage of the video signal during the display period and varies the source voltage of the vertical blanking period so as to follow the average voltage. To do. The source voltage varying means may compare the average voltage of the video signal during the display period and the average voltage of the entire video signal to perform feedback, and vary the source voltage during the vertical blanking period according to the difference. .

For example, if the output signal g input to the analog switch 16 in FIG. 1 is used as the output signal of the voltage varying means, the output of the voltage varying means is output by the analog switch 16 at the next stage during the vertical blanking period. The signal can be supplied to the source driver 19. The output signal of the voltage varying means outputs a black level signal when, for example, a defective picture element exists in the display mask portion, and when there is no mask portion on the display screen and only the display portion, the output signal around the defective picture element is Output close to the voltage. In this way, by changing the source voltage during the blanking period, the average voltage is changed,
The defective picture element can be made inconspicuous in any application.

[0019]

As described above, according to the present invention, in any application, the effective value of the voltage applied to the defective pixel is varied by utilizing the blanking period to make the defective pixel inconspicuous. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to an embodiment of the present invention.

2A and 2B are signal waveform diagrams of respective main parts of the liquid crystal display device of FIG. 1, where FIG. 2A shows a case where a mask portion is displayed above and below, and FIG. 2B shows a case where normal display is performed without a mask portion. ing.

3A and 3B are diagrams showing screen display examples of FIGS. 2A and 2B, respectively.

FIG. 4 is a TFT equivalent circuit diagram showing C conversion in panel correction of a conventional TFT liquid crystal display device.

[Explanation of symbols]

 11 video signal polarity inversion center signal generation circuit 12 video signal alternating signal generation circuit 13 black level signal generation circuit 14 B / W switching signal generation circuit 15, 16 analog switch 17 video blanking signal generation circuit 18 video signal generation circuit 19 source driver

Claims (6)

[Claims] 1. When there is a defective pixel, the defective pixel and the source driver are directly connected without passing through a thin film transistor capable of supplying a source voltage from the source driver to the pixel, and the source voltage is supplied to the defective pixel. In a liquid crystal display device in which a bright spot is corrected by applying to a signal, a signal generating means for generating a video signal fixed to a black level and a video signal fixed to a white level, and a video signal from the signal generating means are switched. A liquid crystal display device comprising: a first switching unit; and a second switching unit that switches to a video signal switched by the first switching unit and supplies it as the source voltage only during a blanking period. 2. The liquid crystal display device according to claim 1, wherein the first switching means changes a switching timing of a black level voltage and a white level voltage during the blanking period. 3. The switching timing is changed by detecting an average voltage during a display period of a video signal and changing a switching timing between a black level voltage and a white level voltage during a vertical blanking period so as to follow the average voltage. The liquid crystal display device according to claim 2. 4. When there is a defective pixel, the defective pixel and the source driver are directly connected without passing through a thin film transistor capable of supplying a source voltage from the source driver to the pixel, and the source voltage is supplied to the defective pixel. A liquid crystal display device in which a bright spot is corrected by applying to the liquid crystal display device, the liquid crystal display device having a source voltage varying means for varying the source voltage during a vertical blanking period by an external signal. 5. The liquid crystal display according to claim 4, wherein the source voltage varying means detects an average voltage during a display period of a video signal and varies the source voltage during the vertical blanking period so as to follow the average voltage. apparatus. 6. The source voltage varying means compares an average voltage of a video signal during a display period with an average voltage of the entire video signal, and varies the source voltage during the vertical blanking period according to the difference. 4. The liquid crystal display device according to 4.