JPH03284092A - Liquid crystal drive circuit - Google Patents

Abstract

PURPOSE:To reduce flicker by inverting the polarity of a red video signal voltage for each prescribed period with respect to a prescribed voltage against the polarity of a blue video signal voltage and applying the result to each video display picture element. CONSTITUTION:A switching circuit 13, a control circuit 14 are used to switch bipolar red video signal voltages R1, R2, bipolar green video signal voltages G1, G2, bipolar blue video signal voltages B1, B2 for each field and each video signal voltage in which the polarity of the voltages R1, R2 with respect to a common voltage is always inverted to the polarity of the voltages G1, G2 with respect to the common voltage and the polarity of the voltages B1,B2 with respect to the common voltage is fed to a source IC 16. Thus, the asymmetry of each video signal voltage and the common voltage for each field among the R video image display picture element 22, the G video image display picture element 23, and the B video image display picture element 21 is cancelled together to reduce flicker.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal drive circuit for displaying images on a liquid crystal display panel.

Conventional technology In recent years, as television receivers have become larger in screen size, higher in definition, and higher in brightness, liquid crystals have been attracting attention due to their characteristics of being small, lightweight, and low power consumption, and have been commercialized as color televisions. has been done. In this liquid crystal color television, flicker is one of the major causes of deterioration of image quality.

FIG. 12 shows the configuration of a liquid crystal television using twisted nematic mode.

In FIG. 12, 101 is a polarizing plate, 102 is a glass plate, 103 is a transparent electrode, and 104 is a liquid crystal layer.

When the voltage applied to the liquid crystal molecules in the liquid crystal layer 104 is off, the light incident on the liquid crystal layer 104 is rotated by 90 degrees due to the twist caused by the rotation of the liquid crystal molecules.
If the deflection directions of 01 are orthogonal, the incident light is transmitted, and if they are parallel, the incident light is blocked.

Conversely, if the voltage applied to the liquid crystal molecules in the liquid crystal layer 104 is on, the incident light to the liquid crystal layer 104 will be transmitted as is, so if the polarization directions of the two deflection plates 101 are orthogonal, the incident light will be transmitted. are blocked, and if they are parallel, the incident light is transmitted. In this way, liquid crystals are applied to displays such as televisions by using the rotating property of liquid crystal molecules due to applied voltage as a light shutter for incident light.

FIG. 13 shows a driving method regarding the video signal voltage applied to the liquid crystal and a predetermined reference voltage (common voltage).

In FIG. 13, 91 is a common voltage applied between the two transparent electrodes 103 in FIG. - On the other hand, the polarity of the video signal voltage with respect to the common voltage 91 is reversed every field, a voltage corresponding to the difference between the common voltage and the video signal voltage is applied to the liquid crystal molecules, and the direction of rotation of the liquid crystal molecules is changed every field. There is.

Therefore, if the video signal voltage with respect to the common voltage is asymmetric for each field, it will be perceived as flicker by the human eye.

Conventionally, to remove flicker, the DC component of the common voltage (D
C level) to a level where the video signal voltage with respect to the common voltage is symmetrical for each field.

Problems to be Solved by the Invention In general, if the video signal voltage with respect to the common voltage is symmetrical for each field, ideally no flicker should occur, but in reality, there is a slight flicker between even and odd fields. A voltage difference occurs, resulting in flicker for each field. Possible causes of flicker include insufficient on-current flowing through the TPT as a switching element of each image display pixel, and changes in off-current depending on the polarity of the image signal voltage.

Means for Solving the Problems The present invention solves the following problems by using red color (hereinafter referred to as R).
Among the three color video signal voltages of green (hereinafter referred to as G), and blue (hereinafter referred to as B), the polarity of each field with respect to the common voltage of the R video signal voltage is determined as G and B video. Apply each video signal voltage that is inverted for each field with respect to the common voltage of the signal voltage to each video display pixel, or apply the polarity of each field with respect to the common voltage of the B video signal voltage to the R and G video By applying each video signal voltage whose polarity is inverted for each field with respect to the common voltage of the signal voltage to each video display pixel, the asymmetry of each field between each video signal voltage and the common voltage is canceled out. The aim is to reduce flicker.

In addition to the above method, in a color television that projects display pixels of three image display liquid crystal panels, a video signal is applied to image display pixels adjacent to each other in at least one horizontal or vertical direction of each image display liquid crystal panel. By inverting the polarity of the voltage for each field with respect to the common voltage, the asymmetry of each field between adjacent video display pixels is offset and flicker is reduced.

Effect The present invention provides an LCD color television with the above configuration,
It becomes possible to realize an image with extremely little flicker.

Embodiment Hereinafter, a liquid crystal drive circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a circuit system in a first embodiment of the present invention.

In FIG. 1, 11 is a video display section, 12 is a positive R video signal voltage (hereinafter referred to as R1 video signal voltage) and a negative R video signal voltage (hereinafter referred to as R2 video signal voltage) with respect to the common voltage. ) and the common voltage, the G video signal voltage (hereinafter referred to as G1 video signal voltage) is positive, the G video signal voltage is negative (hereinafter referred to as G2 video signal voltage), and the common voltage. Positive B video signal voltage (
This circuit generates a negative B video signal voltage (hereinafter referred to as B2 video signal voltage) and a negative B video signal voltage (hereinafter referred to as B2 video signal voltage). 13 is a switching circuit that switches the R1 video signal voltage, the R2 video signal voltage, the G1 video signal voltage, the G2 video signal voltage, and the B1 video signal voltage and the 82 video signal voltage for each field, and 14 is a switching circuit. 13 is a control circuit for controlling the switching timing; 15 is a driver IC (hereinafter referred to as gate IC) for controlling line sequential scanning; 16 is for sampling and holding each video signal voltage and applying it to each video display pixel. This is a driver IC (hereinafter referred to as source IC).

Switching circuit 13 shown in FIG. The control circuit 14 controls the R1 video signal voltage, the R2 video signal voltage, the G1 video signal voltage, and the G2 video signal voltage for each field.
and switching between B1 video signal voltage and B2 video signal voltage,
The polarity of R1 video signal voltage and R2 video signal voltage with respect to the common voltage is always inverted with respect to the polarity of G1 video signal voltage and 02 video signal voltage with respect to the common voltage, and the polarity of B1 video signal voltage and 82 video signal voltage with respect to the common voltage. The obtained video signal voltages are supplied to the source IC 16.

FIG. 2 is a configuration diagram of a liquid crystal panel for displaying images used in the first embodiment of the present invention.

In FIG. 2, 21 is a B image display pixel, 22 is an R image display pixel, and 23 is GIN! ll image display pixel; 24 is a TPT driven as a switching element for each image display pixel;
, 25 is a video signal storage capacitor, 26 is a liquid crystal display element, 27 is a gate) IC 15 and TFT 2 of each video display pixel.
4 is a gate bus that connects the gate, 28 is a source IC
16 and the source of the TFT 24 of each image display pixel.

FIG. 2 shows that in the video display section, B video display pixels 21, R video display pixels 22, and G video display pixels 23 are formed adjacent to each other.

FIG. 3 shows one line (m
-1) column (hereinafter referred to as (Cm-1)),! Row mth column (hereinafter referred to as (j2.m)).

! The relationship between the video signal voltage applied to the video display pixel in the row (m+1)th column (hereinafter referred to as (f, m+1)) and the common voltage is shown. In FIG. 3, (a) is a diagram showing the polarity of the B1 video signal voltage and the B2 video signal voltage applied to the B video display pixel (e, m-1) of the first embodiment with respect to the common voltage, and (b) ) is a diagram showing the polarity of the R1 video signal voltage and R2 video signal voltage applied to the R video display pixel (f, m) of the first embodiment with respect to the common voltage, and (C) is the diagram of the first embodiment ( FIG. 4 is a diagram showing the polarity of the G1 video signal voltage and the 02 video signal voltage applied to the G video display pixels (f, m+1) with respect to the common voltage.

As described above, according to this embodiment, the polarity of the R1 video signal voltage and the R2 video signal voltage applied to the R video display pixel 22 of (j2. m) with respect to the common voltage is set as El, m-1).
The B1 video signal voltage applied to the B video display pixel 21 of
2 The polarity of the video signal voltage with respect to the common voltage and (Cm, +
By always reversing the polarity of the G1 video signal voltage and the G2 video signal voltage applied to the G video display pixel 23 with respect to the common voltage in 1), the R video display pixel 22 and the G video signal voltage are
Flicker is reduced by canceling out the asymmetry of each field between each video signal voltage and the common voltage between the video display pixel 23 and the B video display pixel 21.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a configuration diagram of a liquid crystal drive circuit in a second embodiment of the present invention.

In FIG. 4, 31 is a liquid crystal panel for displaying R video, 32
3 is a liquid crystal panel for displaying G video, 33 is a liquid crystal panel for displaying B video, 34 is an R video display section, 35 is a G video display section, 36
is the B video display section. As shown in the figure, the switching circuit 13. The control circuit 14 switches the R1 video signal voltage and the R2 video signal voltage, the Gl video signal voltage and the 62 video signal voltage, and the B1 video signal voltage and the 82 video signal voltage for each field, and switches the R1 video signal voltage and the R2 video signal voltage. Each video signal voltage is such that the polarity of the signal voltage with respect to the common voltage is always inverted with respect to the polarity of the G1 video signal voltage and 02 video signal voltage with respect to the common voltage, and the polarity of the 81 video signal voltage and 82 video signal voltage with respect to the common voltage. It is supplied to the first source IC 41 and the second source IC 42. Image display pixel R (+, j) (hereinafter similarly referred to as G ci, j) in the i row and j column of the R image display liquid crystal panel, B
The polarity for each l field with respect to the common voltage of R1 video signal voltage and R2 video signal voltage applied to By always inverting the polarity of each field with respect to the common voltage of B1 and 82 video signal voltages applied to B(i, j), each video signal is Flicker is reduced by canceling out the asymmetry of each field between the voltage and the common voltage.

FIG. 5 is a configuration diagram of a liquid crystal panel for displaying images used in a second embodiment of the present invention.

In FIG. 5, 41 is a driver IC (hereinafter referred to as a first source IC) that samples and holds the video signal voltage and applies the video signal voltage to odd-numbered video display pixels in the row direction, and 42 is the video signal voltage. a driver IC (hereinafter referred to as a second source IC), which samples and holds a video signal voltage and applies a video signal voltage to even-numbered video display pixels in the row direction;
are the first source IC41 and the second source IC42
and the source of the TFT 24,
By always reversing the polarity of the common voltage of the video signal voltage applied to horizontally adjacent video display pixels of each video display liquid crystal panel for each l field, the common voltage of the video signal voltage between adjacent video display pixels is This shows that flicker is reduced by canceling out the asymmetry for each l field.

(i, j-1), (i.

When the video signal voltage is applied from the first source IC 41 to the video display pixel (j+1), the video signal voltage is applied from the second source IC 42 to the video display pixel (i, j). From the configuration diagram of the circuit system in Figure 4, the first source I
Since the polarity of each field with respect to the common voltage of the video signal voltage supplied from C41 and the second source IC42 is reversed, the polarity of the video signal voltage applied to horizontally adjacent video display pixels with respect to the common voltage is By constantly reversing the polarity for each field, the asymmetry of the video signal voltage for each field with respect to the common voltage between adjacent video display pixels is canceled out, and flicker is reduced.

FIG. 6 is an overall configuration diagram of a second embodiment of the present invention. 51 is a projector for projecting a display image, 52 is a second mirror, 53 is a third mirror, 54 is a screen, and the R light, G light, and B light projected from the projector 51 are transmitted to the second mirror 5.
The light is reflected by the second and third mirrors 53 and projected onto the screen 54.

FIG. 7 is a configuration diagram of a projector in a second embodiment of the present invention. In FIG. 7, 61 is a condensing optical system, 62 is R
63 is a G-reflecting dichroic mirror, 64 is a B-reflecting dichroic mirror, 65 is a first mirror, 66 is an R projection lens system, 67 is a G projection lens system, and 68 is a B projection lens system. The white light emitted from the condensing optical system 61 is converted into R light, G light, and B light by an R reflection dichroic mirror 62, a G reflection dichroic mirror 63, and a B reflection dichroic mirror 64, respectively.
The light is decomposed into light, passes through the R image display section 34, the G image display section 35, and the B image display section 36, and is reflected by the first mirror 65, after which it is transmitted to the R projection lens system 66 and the G projection lens system 67, respectively. , B projection lens 68 and is projected.

FIG. 8 shows R(
It shows the relationship between the video signal voltage and common voltage for each field of i, j) and G, j).

Moreover, FIG. 9 shows R(i,
This shows the relationship between the video signal voltage and the common voltage for each field of R(i, j+1) and R(i, j+1).

In this embodiment, after reversing the polarity of each field of the R video signal voltage with respect to the common voltage, the polarity of each field with respect to the common voltage of the two color video signal voltages of G and B is reversed. Assuming that the voltage is applied to the video display pixels or each video display liquid crystal panel, the circuit configuration shown in FIGS. The same effect can be obtained even if the polarity of the two-color video signal voltage with respect to the common voltage is reversed for each field and then applied to each video display pixel or each video display liquid crystal panel.

Note that in the embodiments described above, the polarity of the video signal voltage applied to the horizontally adjacent video display pixels of each video display liquid crystal panel with respect to the common voltage is always reversed for each field. The polarity of the video signal voltage applied to the vertically adjacent video display pixels of each video display liquid crystal panel with respect to the common voltage may be always reversed for each field.

Effects of the Invention As described above, according to the present invention, it is possible to realize a liquid crystal color television with extremely little flicker in displayed images.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a liquid crystal drive circuit according to a first embodiment of the present invention, FIG. 2 is a block diagram of a liquid crystal panel for video display according to a first embodiment of the present invention, and FIG. (i, j-1) in Example 1. Waveform diagram showing the relationship between the video signal voltage applied to the video display pixels (i, j), ci, j+1) and the common voltage, 4th
The figure is a block diagram of a liquid crystal drive circuit according to a second embodiment of the present invention, FIG. 5 is a block diagram of a liquid crystal panel for displaying an image according to a second embodiment of the present invention, and FIG. A configuration diagram of a liquid crystal color television using a liquid crystal drive circuit according to an embodiment, FIG. 7 is a configuration diagram of a projector according to a second embodiment of the present invention, and FIG. ij)
FIG. 9 is a waveform diagram showing the relationship between the video signal voltage and the common voltage for each field of C(i, j), and FIG. 10 and 11 are waveform diagrams showing the relationship between the video signal voltage and the common voltage for each field of FIG. 13, which is a configuration diagram of the liquid crystal television used, is a waveform diagram showing the relationship between the video signal voltage applied to the liquid crystal and the common voltage. 13... Switching circuit, 14...
Control circuit, 15... Gate IC, 16...
...Source IC, 21...B video display pixel, 2
2...R video display pixel, 23...G video display pixel, 24...TFT, 26...
-Liquid crystal display element, 31... Liquid crystal panel for R video display, 32... Liquid crystal panel for G video display, 33
...B liquid crystal panel for video display, 41...
・First source IC142...Second source■
C151...Projector, 54...Screen, 61...Condensing optical system, 62...
R reflective dichroic mirror, 63...G reflective dichroic mirror, 64...B reflective dichroic mirror, 65...first mirror, 66...
...Projection lens system for R, 67...Projection lens system for G, 68...Projection lens system for B.

Claims (5)

[Claims] (1) A video display section consisting of a switching element and a liquid crystal display element, in which red video display pixels, green video display pixels, and blue video display pixels are formed in a matrix, a red video signal voltage, a blue video signal voltage, and a green video signal voltage. a circuit unit that inverts the polarity of the video signal voltage with respect to a predetermined voltage at predetermined intervals, and inverts the polarity of the red video signal voltage with respect to the predetermined voltage every predetermined period with respect to the green video signal voltage and the blue video A liquid crystal drive circuit characterized in that each of the video signal voltages whose polarity is inverted for each of the predetermined periods with respect to the predetermined voltage of the signal voltage is applied to each of the video display pixels. (2) A video display section consisting of a red video display liquid crystal panel, a green video display liquid crystal panel, and a blue video display liquid crystal panel in which video display pixels each consisting of a switching element and a liquid crystal display element are formed in a matrix; a circuit that inverts the polarity of a video signal voltage, a blue video signal voltage, and a green video signal voltage with respect to a predetermined voltage at predetermined intervals; , a liquid crystal drive characterized in that each of the video signal voltages inverted with respect to the polarity of the green video signal voltage and the blue signal voltage with respect to the predetermined voltage for each of the predetermined periods is applied to each of the video display panels. circuit. (3) A video display section consisting of a switching element and a liquid crystal display element, in which red video display pixels, green video display pixels, and blue video display pixels are formed in a matrix, a red video signal voltage, a blue video signal voltage, and a green video signal voltage. a circuit unit that inverts the polarity of the video signal voltage with respect to a predetermined voltage at predetermined intervals, and inverts the polarity of the blue video signal voltage with respect to the predetermined voltage every predetermined period with respect to the red video signal voltage and the green video signal voltage. A liquid crystal drive circuit characterized in that each of the video signal voltages whose polarity is inverted for each of the predetermined periods with respect to the predetermined voltage of the signal voltage is applied to each of the video display pixels. (4) A video display section consisting of a red video display liquid crystal panel, a green video display liquid crystal panel, and a blue video display liquid crystal panel in which video display pixels each consisting of a switching element and a liquid crystal display element are formed in a matrix; a circuit that inverts the polarity of a video signal voltage, a blue video signal voltage, and a green video signal voltage with respect to a predetermined voltage at predetermined intervals; , wherein each of the video signal voltages inverted with respect to the predetermined voltages of the red video signal voltage and the green video signal voltage at each predetermined period is applied to each of the video display panels. drive circuit. (5) A video signal voltage including a first video signal voltage sample and hold circuit and a second video signal voltage sample and hold circuit that sample and hold the video signal voltage, the polarity of which is always reversed for each predetermined period with respect to the predetermined voltage. is supplied to the first video signal voltage sample and hold circuit and the second video signal voltage sample and hold circuit, and the first video signal is supplied to video display pixels adjacent to each other in at least one horizontal or vertical direction. Claim 2 or Claim 4, wherein the video signal voltage is applied from different video signal voltage sample and hold circuits of the voltage sample and hold circuit and the second video signal voltage sample and hold circuit. LCD drive circuit.