JP3060936B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

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

FIG. 2 is a schematic diagram of a liquid crystal image display device.
In 203, scanning lines of the liquid crystal panel 101, 2
02 indicates a signal line.

FIG. 3 shows a display example of a liquid crystal screen.
3, reference numeral 301 denotes a black window display portion, 302 denotes a halftone display portion around the black window display portion 301, 303 denotes a signal line including the black window display portion 301, 304 denotes a signal line of the halftone display portion 302, 3
Reference numeral 05 denotes 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, reference numeral 401 denotes a switching element, and 402 denotes a pixel electrode.

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

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

FIG. 8 is a diagram showing a common electrode potential waveform, a signal waveform applied to the signal line 304 of FIG. 3, and a liquid crystal applied voltage. In FIG. 8, reference numeral 801 denotes a signal waveform of the signal line 304;
Reference numeral 802 denotes a halftone display portion 305 of the signal line 304.
A reference numeral 803 denotes 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 constructed as described above will be described below.

The scanning line driving IC 201 is provided for the liquid crystal panel 10.
One scanning line 203 corresponds to one horizontal scanning period (hereinafter referred to as 1H).
The switching element 401 shown in FIG. 4 is sequentially turned on / off for each scanning line 203 by sequentially performing selective scanning every time. Therefore, the output voltage of the signal line driving IC 105 is applied to the pixel electrode 402 whose switching element is turned on. Here, the switching element is turned on at a timing near the final voltage of the signal line as shown by the liquid crystal writing voltages 802 and 803 in FIG. The common electrode 102 has a potential supply circuit 10
By way of example, VDD / 2 which is 1/2 of the maximum drive voltage amplitude of the signal line is applied .

The signal line driving IC 105 includes a potential input terminal 1
A constant potential of the reference voltage circuit 107 is input to the reference numeral 06, and an output voltage obtained by D / A conversion of the input data signal based on this potential is applied to the signal line 202, so that the voltage applied to the pixel electrode 402 is reduced. Control is performed according to the input data signal.
Here, as shown in the equivalent circuit of the liquid crystal panel pixel in FIG. 5, the pixel electrode 402 is connected to the common electrode 102 via the liquid crystal capacitor 501.
(By providing an image signal during the ON period of the switching element, and applying a modulation signal in which the voltage is reversed in each field during the OFF period, thereby reducing the power consumption for driving the signal 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 AC-driven by inverting the polarity every 1 H when viewed from the potential of the common electrode 102.

Next, as shown in FIG. 3, when a liquid crystal screen is displayed on a black window display portion 301 and a halftone display portion 302 around the black window display portion 301, the signal waveform of the signal line 303 is changed to a halftone display portion 305. In the region shown by the symbol (1), the signal amplitude changes as shown by the signal waveform 701. Here, the common electrode 102 is connected to the pixel electrode 402 with the liquid crystal capacitance 501.
If the potential of the signal line 202 fluctuates, the potential of the common electrode 102 also fluctuates in conjunction with the common electrode 102. 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, the voltage is changed 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 a grayscale image 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 at the center of the halftone display screen as shown in FIG. 3, the potential waveform of the common electrode 102 is changed to the actual common electrode. As shown by the potential waveform 702, the voltage fluctuates in conjunction with the black window display portion 301, so that the voltage actually written to the liquid crystal in the region of the halftone display portion 305 is the liquid crystal write voltage as shown in FIG. 8
It changes as represented by 02. As a result, halftone display portions 302 and 30 that originally display an image of the same gradation
5 has an amplitude represented by 802 and 803, a luminance difference corresponding to the potential difference between the two occurs on both sides of the black window display portion 301 as shown in FIG. ).

In view of the above, the present invention does not receive the fluctuation of the liquid crystal writing voltage due to the fluctuation of the potential of the common electrode depending on the display image. An object of the present invention is to provide a high-quality liquid crystal image display device in which crosstalk can be reduced by correcting the output of a signal line driving IC.

[0016]

According to a first aspect of the present invention, there is provided an active matrix liquid crystal panel having a switching element, wherein one potential is supplied from a potential supply circuit to a common electrode.
A constant voltage is applied and the active matrix LCD panel
Before the potential fluctuation of the common electrode depending on the displayed image
The crosstalk of the displayed image is caused by the potential fluctuation of the common electrode.
Depending on, corrects the drive voltage of the signal line only in the potential variation
Then, by correcting the voltage in synchronization with the potential change of the common electrode, the original liquid crystal writing voltage is obtained, so that 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 change of the common electrode by a filter circuit for adjusting and outputting the potential change of the common electrode. When a potential change occurs, the potential change of the common electrode is adjusted to an appropriate correction level by the constant of the filter circuit, and is input to the potential input terminal of the signal line drive IC, so that the output of the signal line drive IC is output. Since the voltage can be corrected by following the potential fluctuation 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 driving IC having a function of shifting an output voltage in accordance with an input potential of a potential input terminal, wherein a potential of a common electrode is inputted to the potential input terminal, Signal line drive IC in conjunction with electrode potential fluctuation
By correcting the output, the original liquid crystal writing voltage is obtained, so that crosstalk depending on the display screen can be reduced.

According to a fourth aspect of the present invention, there is provided a signal line driving IC.
Is a D / A converter type that converts input digital data into an analog signal based on an input reference potential, and adjusts a potential fluctuation of a common electrode to a reference potential input terminal of the signal line driving IC. By inputting a voltage, the output potential of the signal line drive IC is corrected in conjunction with the potential change of the common electrode, so that the signal line drive voltage becomes the original liquid crystal write voltage. Can be reduced.

[0020]

FIG. 1 is a block diagram of a liquid crystal display according to an embodiment of the present invention.
In FIG. 1, reference numeral 101 denotes an active matrix liquid crystal panel using switching elements; 102, a common electrode;
Is a potential supply circuit, 104 is a filter circuit for adjusting and outputting potential fluctuations of the common electrode 102, 105 is a potential input terminal 106, and based on an input potential of the potential input terminal,
This is a D / A converter type signal line driving IC for converting input digital data into an analog signal.

The structure of the liquid crystal panel is shown in FIG.
This is the same as 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, reference numeral 601 denotes a fixed resistance type filter circuit, 602 denotes a calculus type filter circuit, 603 denotes a resistance division type filter circuit, and 604 denotes a resistance division type filter circuit. A filter circuit that can adjust the gain, that is, the level of the potential fluctuation, and 605 is an integral filter circuit that can adjust the gain.

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

The driving method of 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. To scan line 20
ON / OFF control is performed sequentially for every 3
The output voltage of the signal line driving IC 105 is applied to the pixel electrode 402 in FIG. Here, the timing of turning on the switching element is performed at a timing near the final voltage of the signal line as shown by the liquid crystal writing voltages 802 and 803 in FIG .

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

The signal line driving IC 105 is connected to the potential input terminal 1
By outputting an output voltage obtained by D / A converting the input data signal based on the potential input to the signal line 202 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 potential waveform 702 of the actual common electrode shown in FIG.
In contrast, the voltage indicated by the liquid crystal writing voltage 704 is written in the liquid crystal, and the voltage indicated by the liquid crystal writing voltage 703 is written in the liquid crystal in the black window display portion 301. As a result, the liquid crystal writing voltages 703 and 70
The image of the gradation proportional to the voltage difference of No. 4 is displayed. Here, as shown in FIG. 3, a black window display portion 301,
When the liquid crystal screen display shown by the surrounding halftone display portion 302 is performed, the potential waveform of the common electrode 102 is shown in FIG.
As shown in an actual common electrode potential waveform 702 shown in FIG.

Next, the potential of the common electrode 102 is changed to the filter circuits 601, 602, 603, 604 and 604 shown in FIG.
The output voltage optimally adjusted by any one of 605 is input to the potential input terminal 106 of the signal line driving IC 105. Accordingly, 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, so that the output of the signal line driving IC 105 interlocks with the input potential of the potential input terminal 106. The voltage can be corrected to the original liquid crystal writing voltage which does not receive the fluctuation of the liquid crystal writing voltage due to the fluctuation of the potential 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 for the filter circuit 104 of FIG. 1 in the embodiment of the present invention, and FIG. Signal line 30 shown
FIG. 4 is a diagram illustrating a signal waveform applied to a liquid crystal 4 and a liquid crystal applied voltage.

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

FIG. 10 shows a calculus type filter circuit 6 shown in FIG. 6 in addition to the filter circuit 104 shown in FIG. 1 according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating a common electrode potential waveform in the case of using No. 02, a signal waveform applied to the signal line 304 illustrated in FIG. 3, and a liquid crystal applied voltage.

In FIG. 10, reference numeral 1001 denotes a signal waveform of the signal line 304, 1002 denotes a liquid crystal writing voltage in the half tone display portion 305 of the signal line 304 of FIG. 3, and 1003 denotes a half tone of the signal line 304 of FIG. It shows the liquid crystal writing voltage of the display portion 302, where the amplitude becomes 1002 = 1003. Therefore, when the calculus filter circuit 602 is used as the filter circuit 104, the signal waveform of the signal line 304 can be corrected only for the final voltage at the time of writing the liquid crystal in conjunction with the potential change of the common electrode.

FIG. 11 shows a common electrode potential waveform and a signal shown in FIG. 3 when the filter circuit 604 capable of adjusting the phase and the gain shown in FIG. 6 is used for the filter circuit 104 shown in FIG. 1 in the embodiment of the present invention. FIG. 3 is a diagram illustrating a signal waveform applied to a line 304 and a liquid crystal applied voltage.

In FIG. 11, reference numeral 1101 denotes a signal waveform of the signal line 304 when the polarity of the signal waveform is different, 1102 denotes a liquid crystal writing voltage in the halftone display portion 305 area of the signal line 304, and 1103 denotes a signal writing voltage of the signal line 304. , The liquid crystal writing voltage of the halftone display portion 302, where 11
02 = 1103. Therefore, filter circuit 1
When the filter circuit 604 capable of adjusting the gain is used for the signal line 04, the signal waveform of the signal line 304 is interlocked with the potential change of the common electrode even when the polarity of the potential fluctuation of the common electrode 102 differs from the signal waveform of the signal line 304. Can be corrected.

FIG. 12 shows a common electrode potential waveform and a signal shown in FIG. 3 in the case where an integration type filter circuit 605 capable of adjusting the gain shown in FIG. 6 is used as the filter circuit 104 in FIG. 1 in the embodiment of the present invention. FIG. 3 is a diagram illustrating a signal waveform applied to a line 304 and a liquid crystal applied voltage.

In FIG. 12, reference numeral 1201 denotes a signal waveform of the signal line 304 when the polarity of the signal waveform is different, 1202 denotes a liquid crystal writing voltage in the halftone display portion 305 of the signal line 304, and 1203 denotes a signal writing voltage of the signal line 304. , The liquid crystal writing voltage of the halftone display portion 302,
02 = 1203. Therefore, filter circuit 1
04: Integral type filter circuit 605 whose gain can be adjusted
Is used, 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 conjunction with the potential fluctuation of the common electrode.

Therefore, the effective voltage applied to the liquid crystal capacitor 501 is optimized according to the constant of one of the filter circuits shown in FIG. And the liquid crystal writing voltage can be corrected so as to have the original liquid crystal writing voltage amplitude, so that the crosstalk due to the potential fluctuation of the common electrode depending on the displayed image can be canceled.

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 change of the common electrode, and crosstalk due to the potential change of the common electrode depending on the display image Can be canceled.

In the embodiment of the present invention, reference numeral 105 denotes D /
Although the A-converter type signal line driving IC is used, the same effect can be obtained by an analog signal line driving IC having a potential input terminal and having a function of shifting an output voltage according to an input potential of the potential input terminal. The thing is obvious. 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 same effect can be obtained by using the filter circuits 604 and 605 as filter circuits using inverting amplifiers. Can be obtained.

The potential of the common electrode 102 is set to VDD / 2, which is 1/2 of the signal line power supply voltage.

[0040]

As described above, according to the embodiment of the present invention, the potential fluctuation of the common electrode is optimally adjusted by the filter circuit, and the potential 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 change of the common electrode, crosstalk due to the potential change of the common electrode depending on the displayed image can be canceled, and the cost can be reduced. A high-quality liquid crystal image display device can be easily realized, and its practical effect is very large.

[Brief description of the 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 configuration 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 conventional signal line and a liquid crystal applied voltage.

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

FIG. 9 is a waveform diagram of a signal line and a liquid crystal applied voltage in an embodiment of the present invention.

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

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

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

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

[Explanation of symbols]

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

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Tsurugi 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-9-265279 (JP, A) JP-A-3-3 12633 (JP, A) JP-A-4-109218 (JP, A) JP-A-5-323279 (JP, A) JP-A-8-5989 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/133 G09G 3/36

Claims (4)

(57) [Claims] In an active matrix liquid crystal panel having a switching element, a common voltage is supplied from a potential supply circuit.
A constant voltage is applied to the poles,
Crosstalk of the display image when the potential variation of the common electrode which is dependent on the panel of the display image occurs, before the common electrode
The driving voltage of the signal line is changed according to the potential fluctuation.
A liquid crystal image display device characterized in that the crosstalk is reduced by correcting the crosstalk only by using only the correction . 2. An active mask having a switching element.
In a trix liquid crystal panel, the common
A constant voltage is applied to the poles,
The potential fluctuation of the common electrode depending on the display image of the
Crosstalk of the display image when the Flip, by a filter circuit in which only the potential change is moderate output is directly input of said common electrode in response to the potential variation of the common electrode,
A liquid crystal image display device wherein the crosstalk is reduced by correcting a drive voltage of a signal line. 3. A signal line driving IC having a function of shifting an output voltage according to an input potential of a potential input terminal, wherein an adjusted output of a filter circuit is input to the potential input terminal, and a common electrode Signal line drive IC in conjunction with potential fluctuation
The output of the common electrode according to the potential fluctuation of the common electrode.
3. The method according to claim 1 , wherein the drive voltage of the signal line is corrected to reduce crosstalk .
Liquid crystal image display device according to. 4. The signal line driving IC is of a D / A converter type for converting input digital data into an analog signal based on an input reference potential.
The adjusted output of the filter circuit is connected to the reference potential input terminal of C.
When the power is input, the output potential of the signal line drive IC is corrected in conjunction with the potential change of the common electrode, and the drive voltage of the signal line is reduced .
3. The liquid crystal image display device according to claim 1 , wherein the pressure is corrected to reduce crosstalk .