JPH09230309A - Liquid crystal image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cross talk depending on a display screen when the potential change of the common electrode arises by the method that the driving voltage of the signal line is linked with the change to correct it. SOLUTION: The device is composed from a liquid crystal panel 101 in use of a switching element, a common electrode 102, a potential supplying circuit 103, a filter circuit 104 which adjusts the potential change of the common electrode 102 to output the potential and a D/A converter type signal line driver IC 105 which has a potential input terminal 106 and, based on the input potential of the terminal 106, converts the inputted digital data to analog signals. With such constitution, the output voltage of the signal line driver IC 105 is corrected in compliance with the potential change of the common electrode 102 by optimally adjusting the potential change of the common electrode 102 by the filter circuit 104 to input the potential to the potential input terminal 106 of the signal line driver IC 105. By this, the cross talk caused by the potential change of the common electrode which depends on the display screen can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-resolution and high-quality liquid crystal image display device that can be used in televisions, monitors and the like.

[0002]

2. Description of the Related Art FIG. 13 is a block diagram of this conventional liquid crystal image display device. In FIG. 13, 101 is an active matrix liquid crystal panel, 102 is a common electrode portion of the liquid crystal panel 101, and 103 is a potential supply circuit. 1
Reference numeral 05 is a D / A converter type signal line drive IC that converts the input digital data into an analog signal based on the input reference potential, and 107 is a reference voltage circuit.

FIG. 2 is a schematic view of a liquid crystal image display device.
Reference numeral 203 denotes a scanning line of the liquid crystal panel 101, 2
Reference numeral 02 denotes a signal line.

FIG. 3 is a diagram showing a display example of a liquid crystal screen,
In FIG. 3, 301 is a black window display portion, 302 is a halftone display portion around the black window display portion 301, 303 is a signal line including the black window display portion 301, 304 is a signal line of the halftone display portion 302, Three
Reference numeral 05 is a halftone display portion on both sides of the black window display portion 301.

FIG. 4 is a diagram showing a configuration example of a pixel in the liquid crystal panel 101. In FIG. 4, 401 is a switching element and 402 is a pixel electrode.

FIG. 5 is a diagram showing an equivalent circuit of a pixel of the liquid crystal panel 101. In FIG. 5, 501 is a pixel electrode 402.
And the liquid crystal capacitance between the common electrode 102.

FIG. 7 is a diagram showing the common electrode potential waveform, the signal waveform applied to the signal line 303 of FIG. 3 and the liquid crystal applied voltage. 701 in FIG. 7 is the signal waveform of the signal line 303.
702 is an actual potential waveform of the common electrode, 703 is a signal line 3
03, the liquid crystal writing voltage of the black window display unit 301, and 704 of the signal line 303, the halftone display unit 30.
2, the liquid crystal write voltage, VDD is the power supply potential of the signal line drive IC, GND is the ground potential of the signal line drive IC, VDD / 2
Is the original potential of the common electrode.

FIG. 8 is a diagram showing the common electrode potential waveform, the signal waveform applied to the signal line 304 of FIG. 3 and the liquid crystal applied voltage. In FIG. 8, 801 is the signal waveform of the signal line 304,
Reference numeral 802 denotes a halftone display portion 305 of the signal line 304.
The liquid crystal writing voltage 803 is a liquid crystal writing voltage of the halftone display portion 302 of the signal line 304.

The operation of the liquid crystal image display device according to the conventional embodiment having the above-described structure will be described below.

The scanning line driving IC 201 is used for the liquid crystal panel 10.
One scanning line 203 for one horizontal scanning period (hereinafter referred to as 1H)
By sequentially performing selective scanning for each, the switching element 401 illustrated in FIG. 4 is sequentially ON / OFF controlled for each scanning line 203. Therefore, the output voltage of the signal line driving IC 105 is applied to the pixel electrode 402 in which the switching element is turned on. Here, it is assumed that the timing of turning on the switching element is at a timing near the final reaching voltage of the signal line, as shown by liquid crystal writing voltages 802 and 803 in FIG. The common electrode 102 has a potential supply circuit 10
3, it is assumed that VDD / 2, which is ½ of the maximum drive voltage amplitude of the signal line, is applied.

The signal line driving IC 105 has a potential input terminal 1
A constant potential of the reference voltage circuit 107 is input to 06, and the output voltage obtained by D / A converting the input data signal based on this potential is applied to the signal line 202, thereby applying the voltage to the pixel electrode 402. Control according to the input data signal.
Here, as shown in the equivalent circuit of the liquid crystal panel pixel of FIG. 5, the pixel electrode 402 is connected to the common electrode 102 via the liquid crystal capacitor 501.
And capacitive coupling (the image signal is applied during the ON period of the switching element, and the modulation signal is applied in the reverse direction for each field during the OFF period, thereby reducing the signal driving power consumption and improving the image quality. ), The polarity of the signal waveform of the signal line 202 is inverted every 1H as shown by the signal waveform 801. Therefore, the voltage applied to the liquid crystal capacitor 501 is driven by alternating current by reversing the polarity every 1H when viewed from the potential of the common electrode 102.

Next, as shown in FIG. 3, when the liquid crystal screen display shown by the black window display portion 301 and the halftone display portion 302 around the black window display portion 301 is performed, the signal waveform of the signal line 303 is the halftone display portion 305. In the area shown by (7), the signal amplitude changes as shown by the signal waveform 701. Here, the common electrode 102 is different from the pixel electrode 402 in the liquid crystal capacitance 501.
When the potential of the signal line 202 fluctuates, the potential fluctuates in conjunction with the common electrode 102 as well, and the potential of the common electrode 102 in the region of the halftone display portion 305 is also the actual common electrode. It fluctuates as shown by the potential waveform 702.

Therefore, in the halftone display portion 302, the voltage indicated by the liquid crystal writing voltage 704 is written in the liquid crystal with respect to the potential of the common electrode 102, and in the black window display portion 301, with respect to the potential of the common electrode 102, The voltage indicated by the liquid crystal writing voltage 703 in FIG. 7 is written in the liquid crystal, and an image with a gray scale proportional to the voltage difference between the liquid crystal writing voltages 703 and 704 is displayed.

[0014]

However, in the above configuration, when a black window is displayed in the center of the halftone display screen as shown in FIG. 3, the potential waveform of the common electrode 102 is the actual common electrode. As shown by the potential waveform 702, since it fluctuates in conjunction with the black window display portion 301, the voltage actually written in the liquid crystal in the halftone display portion 305 is the liquid crystal write voltage as shown in FIG. 8
It changes as indicated by 02. As a result, halftone display portions 302 and 30 which are originally the same gradation image display,
Since the liquid crystal writing voltage of No. 5 has the amplitudes indicated by 802 and 803, the luminance difference corresponding to the potential difference between the two is generated on both sides of the black window display portion 301 as shown in FIG. Had a problem.

In view of the above point, the present invention provides the original liquid crystal writing voltage that is not affected by the variation of the liquid crystal writing voltage due to the potential variation of the common electrode depending on the displayed image, and changes the potential of the common electrode according to the potential variation of the common electrode. It is an object of the present invention to provide a high-quality liquid crystal image display device that can reduce crosstalk by correcting the output of a signal line driving IC.

[0016]

According to a first aspect of the present invention, in an active matrix liquid crystal panel having a switching element, when a potential variation of the common electrode occurs, the drive voltage of the signal line is changed to the common electrode. Since the original liquid crystal writing voltage is obtained by performing the correction in association with the potential fluctuation, crosstalk depending on the display screen can be reduced.

According to a second aspect of the present invention, the drive voltage of the signal line is continuously corrected to the potential variation of the common electrode by a filter circuit that adjustably outputs the potential variation of the common electrode. When a potential fluctuation occurs, the potential fluctuation of the common electrode is adjusted to an appropriate correction level by the constant of the filter circuit and input to the potential input terminal of the signal line drive IC, so that the output of the signal line drive IC Since the voltage can be corrected by following the potential variation of the common electrode and the voltage at the time of writing the liquid crystal can be corrected to the original voltage, crosstalk depending on the display screen can be corrected.

According to a third aspect of the present invention, there is provided a signal line drive IC having a function of shifting an output voltage according to an input potential of a potential input terminal, and the potential of a common electrode is input to the potential input terminal to make a common signal. Signal line drive IC linked to potential fluctuation of electrodes
By correcting the output, the original liquid crystal writing voltage is obtained, and thus crosstalk depending on the display screen can be reduced.

The invention according to claim 4 is a signal line driving IC.
Is a D / A converter type that converts the input digital data into an analog signal based on the input reference potential. The potential variation of the common electrode is adjusted to the reference potential input terminal of the signal line drive IC. By inputting a voltage, the output potential of the signal line drive IC is corrected in conjunction with the potential variation of the common electrode, and the signal line drive voltage becomes the original liquid crystal writing voltage. Therefore, the crosstalk depends on the display screen. Can be reduced.

[0020]

FIG. 1 is a block diagram of a liquid crystal image display device according to an embodiment of the present invention.
In FIG. 1, 101 is an active matrix liquid crystal panel using switching elements, 102 is a common electrode, and 103.
Is a potential supply circuit, 104 is a filter circuit that adjusts and outputs the potential fluctuation of the common electrode 102, 105 has a potential input terminal 106, and based on the input potential of the potential input terminal,
This is a D / A converter type signal line drive IC for converting input digital data into an analog signal.

The structure of the liquid crystal panel is shown in FIG.
It is similar to that shown in FIGS.

FIG. 6 is a filter circuit diagram for adjusting and outputting the potential fluctuation of the common electrode 102. In FIG. 6, 601 is a fixed resistance type filter circuit, 602 is a calculus type filter circuit, 603 is a resistance division type filter circuit, and 604 is A gain, that is, a filter circuit capable of adjusting the increase / decrease of potential fluctuation, and a reference numeral 605, an integral type filter circuit capable of adjusting the gain.

The operation of the liquid crystal image display device of this embodiment constructed as described above will be described below.

The method of driving the liquid crystal is the same as that described in the prior art, and the scanning line driving IC 201 sequentially selects and scans the scanning lines 203 of the liquid crystal panel 101 every 1H, and the switching element 401 shown in FIG. Scan line 20
ON / OFF control is performed sequentially for every 3, and switching element 40
The output voltage of the signal line driving IC 105 is applied to the pixel electrode 402 in FIG. Here, it is assumed that the timing of turning on the switching element is at a timing near the final reaching voltage of the signal line, as indicated by liquid crystal writing voltages 802 and 803 in FIG.

The common electrode 102 has a potential supply circuit 103.
Therefore, for example, VDD which is ½ of the power supply potential of the signal line
/ 2 is applied.

The signal line driving IC 105 has a potential input terminal 1
By outputting an output voltage obtained by D / A converting the input data signal based on the potential input to 06 to the signal line 202,
The voltage applied to the pixel electrode 402 in FIG. 4 is controlled according to the input data signal. Therefore, the halftone display portion 3 shown in FIG.
02, the actual common electrode potential waveform 702 shown in FIG.
On the other hand, the voltage indicated by the liquid crystal writing voltage 704 is written in the liquid crystal, and in the black window display portion 301, the voltage indicated by the liquid crystal writing voltage 703 is written in the liquid crystal. As a result, the liquid crystal writing voltages 703 and 70
An image having a gradation proportional to the voltage difference of 4 is displayed. Here, as shown in FIG. 3, a black window display portion 301,
In the case where the liquid crystal screen display shown by the halftone display portion 302 around it is being performed, the potential waveform of the common electrode 102 is
Like the actual common electrode potential waveform 702 shown in FIG.

Next, the potential of the common electrode 102 is set to the filter circuits 601, 602, 603, 604 shown in FIG.
The output voltage optimally adjusted by any of 605 is input to the potential input terminal 106 of the signal line driving IC 105. Along with this, the signal line driving IC 105 converts the input digital signal into an analog signal based on the potential input to the potential input terminal 106. Therefore, the output of the signal line driving IC 105 is interlocked with the input potential of the potential input terminal 106. The voltage can be corrected to the original liquid crystal writing voltage that is not affected by the variation of the liquid crystal writing voltage due to the potential variation of the common electrode.

FIG. 9 shows a common electrode potential waveform when the fixed resistance type filter circuit 601 and the resistance division type filter circuit 603 shown in FIG. 6 are used in the filter circuit 104 of FIG. 1 in the embodiment of the present invention, and FIG. Signal line 30 shown
4 is a diagram showing a signal waveform applied to No. 4 and a liquid crystal applied voltage.

In FIG. 9, reference numeral 901 denotes the signal line 3 shown in FIG.
A signal waveform 04, a liquid crystal writing voltage 902 in the halftone display portion 305 region of the signal line 304, and a liquid crystal writing voltage 903 in the halftone display portion 302 of the signal line 304, where 902 = 903 Amplitude. Therefore, the fixed resistance filter circuit 6 is added to the filter circuit 104.
When 01 and the resistance division type filter circuit 603 are used, the signal waveform of the signal line 304 is corrected in association with the potential waveform of the common electrode to obtain the original liquid crystal writing voltage which is not affected by the fluctuation of the liquid crystal writing voltage. be able to.

10 is a block diagram of the filter circuit 104 of FIG. 1 according to the embodiment of the present invention, and FIG.
4 is a diagram showing a common electrode potential waveform when 02 is used, a signal waveform applied to a signal line 304 shown in FIG. 3, and a liquid crystal applied voltage.

In FIG. 10, 1001 is a signal waveform of the signal line 304, 1002 is a liquid crystal writing voltage in the halftone display portion 305 region of the signal line 304 of FIG. 3, and 1003 is a halftone of the signal line 304 of FIG. The liquid crystal write voltage of the display portion 302 is shown, where the amplitude is 1002 = 1003. Therefore, when the calculus-type filter circuit 602 is used as the filter circuit 104, the signal waveform of the signal line 304 can be corrected only by the final voltage at the time of writing the liquid crystal in association with the potential variation of the common electrode.

FIG. 11 shows the common electrode potential waveform when the filter circuit 604 shown in FIG. 6 capable of adjusting the phase and gain is used in the filter circuit 104 of FIG. 1 in the embodiment of the present invention, and the signal shown in FIG. FIG. 6 is a diagram showing a signal waveform applied to a line 304 and a liquid crystal applied voltage.

In FIG. 11, 1101 is a signal waveform of the signal line 304 when the signal waveforms have different polarities, 1102 is a liquid crystal writing voltage in the halftone display portion 305 region of the signal line 304, 1103 is a signal line 304. , Shows the liquid crystal writing voltage of the halftone display portion 302, where 11
The amplitude is 02 = 1103. Therefore, the filter circuit 1
When a filter circuit 604 whose gain can be adjusted is used for 04, even if the signal waveform of the signal line 304 and the polarity of the potential fluctuation of the common electrode 102 are different, the signal waveform of the signal line 304 is linked to the potential fluctuation of the common electrode. Can be corrected.

FIG. 12 shows the common electrode potential waveform when the integral type filter circuit 605 shown in FIG. 6 is used in the filter circuit 104 of FIG. 1 in the embodiment of the present invention, and the signal shown in FIG. FIG. 6 is a diagram showing a signal waveform applied to a line 304 and a liquid crystal applied voltage.

In FIG. 12, 1201 is a signal waveform of the signal line 304 in the case where the polarities of the signal waveforms are different, 1202 is a liquid crystal writing voltage in the halftone display portion 305 region of the signal line 304, 1203 is a signal line 304. , Shows the liquid crystal writing voltage of the halftone display portion 302, where 12
The amplitude is 02 = 1203. Therefore, the filter circuit 1
Integral filter circuit 605 whose gain can be adjusted to 04
When using, the signal waveform of the signal line 304 and the common electrode 1
Even when the polarity of the potential fluctuation of 02 is different, the final voltage at the time of writing the liquid crystal can be corrected in association with the potential fluctuation of the common electrode.

Therefore, the effective voltage applied to the liquid crystal capacitor 501 is adjusted by optimizing the constant of any one of the filter circuits shown in FIG. 6 so that the output voltage of the signal line driving IC 105 changes according to the potential fluctuation of the common electrode 102. Since the liquid crystal writing voltage can be corrected so that the original liquid crystal writing voltage amplitude is obtained, it is possible to cancel the crosstalk due to the potential variation of the common electrode depending on the display image.

As described above, according to this embodiment, the potential fluctuation of the common electrode is optimally adjusted by the filter circuit,
By inputting to the potential input terminal of the signal line drive IC, the output voltage of the signal line drive IC can be corrected according to the potential variation of the common electrode, and the crosstalk due to the potential variation of the common electrode depending on the display image. You can cancel.

In the embodiment of the present invention, 105 is D /
Although the A converter type signal line drive IC is used, similar effects can be obtained even if the analog signal line drive IC has a potential input terminal and has a function of shifting the output voltage according to the input potential of the potential input terminal. Things are clear. Further, when the signal line driver IC 105 has a function of shifting the output voltage to the polarity opposite to the input potential of the potential input terminal 106, the filter circuits 604 and 605 are filter circuits using an inverting amplifier and similar effects can be obtained. Can be obtained.

The potential of the common electrode 102 is set to VDD / 2, which is ½ of the signal line power supply voltage. However, the common voltage inversion driving method in which the potential of the common electrode is inverted at a predetermined voltage amplitude and cycle. It goes without saying that the same effect can be obtained. Further, a driving method of the liquid crystal panel is a capacitive coupling driving method (for example, described in Japanese Patent Laid-Open No. 2-157815).
It goes without saying that the same effect can be obtained in.

[0040]

As described above, according to the embodiment of the present invention, the potential variation of the common electrode is optimally adjusted by the filter circuit and is simply input to the potential input terminal of the signal line driving IC. Since the output voltage of the signal line driving IC can be optimally corrected by following the potential variation of the common electrode, it is possible to cancel crosstalk due to the potential variation of the common electrode depending on the display image, and at low cost. A high-quality liquid crystal image display device can be easily realized, and its practical effect is very large.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram of a liquid crystal image display device.

FIG. 3 is a front view showing an example of displaying a liquid crystal screen.

FIG. 4 is a block diagram of a pixel in a liquid crystal panel

FIG. 5 is an equivalent circuit diagram of a pixel of a liquid crystal panel.

FIG. 6 is a filter circuit diagram according to an embodiment of the present invention.

FIG. 7 is a waveform diagram of a voltage applied to a conventional signal line and a liquid crystal.

FIG. 8 is a waveform diagram of a conventional signal line and liquid crystal applied voltage.

FIG. 9 is a waveform diagram of signal lines and liquid crystal applied voltage according to an embodiment of the present invention.

FIG. 10 is a waveform diagram of a signal line and a liquid crystal applied voltage according to an embodiment of the present invention.

FIG. 11 is a waveform diagram of a signal line and a liquid crystal applied voltage in the example of the invention.

FIG. 12 is a waveform diagram of a signal line and a liquid crystal applied voltage in the example of the invention.

FIG. 13 is a block diagram of a conventional liquid crystal image display device.

[Explanation of symbols]

 101 liquid crystal panel 102 common electrode 103 potential supply circuit 104 filter circuit 105 signal line drive IC 106 potential input terminal 107 reference voltage circuit 201 scanning line drive IC 202 signal line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Tsurugi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An active matrix liquid crystal panel having a switching element, wherein when a potential variation of a common electrode occurs, a driving voltage of a signal line is corrected in association with a potential variation of the common electrode. Display device. 2. The liquid crystal image display according to claim 1, wherein the drive voltage of the signal line continuously corrects the potential fluctuation of the common electrode by a filter circuit which adjustably outputs the potential fluctuation of the common electrode. apparatus. 3. A signal line drive IC having a function of shifting an output voltage according to an input potential of a potential input terminal, the potential of a common electrode being input to the potential input terminal, and interlocked with potential fluctuation of the common electrode. The liquid crystal image display device according to claim 1 or 2, wherein the output of the signal line driving IC is corrected. 4. The signal line drive IC is a D / A converter type which converts input digital data into an analog signal based on an input reference potential, and the signal line drive I
4. The output potential of the signal line driving IC is corrected in association with the potential variation of the common electrode by inputting a voltage obtained by adjusting the potential variation of the common electrode to the reference potential input terminal of C, wherein The liquid crystal image display device described.