Liquid crystal display apparatus

A liquid crystal display device is constituted by a pair of oppositely disposed electrode plates having thereon a group of scanning lines and a group of data lines, respectively, and a liquid crystal disposed between the pair of electrode plates so as to form a pixel at each intersection of the scanning lines and data lines. The display device is driven by sequentially selecting the scanning lines, and applying data signals to the data lines for the selected scanning lines. During the drive, the data signals applied to the data lines for pixels on a selected scanning line are determined while comprising image data for the pixels on the selected scanning line and image data for corresponding pixels on a subsequently selected scanning lines.

FIELD OF THE INVENTION AND RELATED ART 
The present invention relates to a liquid crystal display apparatus for 
computer terminals, television receivers, word processors, typewriters, 
etc., inclusive of a light valve for projectors, a view finder for video 
camera recorders, etc. 
There have been known liquid crystal display devices including those using 
twisted-nematic (TN) liquid crystals, guest-host-type liquid crystals, 
smectic (Sm) liquid crystals, etc. 
In a liquid crystal device, such a liquid crystal is disposed between a 
pair of substrates and changes an optical transmittance therethrough 
depending on voltages applied thereto. The electric field applied to the 
liquid crystal layer changes depending on the thickness of the liquid 
crystal layer, i.e., the spacing between the substrates. 
Clark and Lagerwall have disclosed a bistable ferroelectric liquid crystal 
device using a surface-stabilized ferroelectric liquid crystal in, e.g., 
Applied Physics Letters, Vol. 36, No. 11 (Jun. 1, 1980), p.p. 899-901; 
Japanese Laid-Open Patent Application (JP-A) 56-107216, U.S. Pat. Nos. 
4,367,924 and 4,563,059. Such a bistable ferroelectric liquid crystal 
device has been realized by disposing a liquid crystal between a pair of 
substrates disposed with a spacing small enough to suppress the formation 
of a helical structure inherent to liquid crystal molecules in chiral 
smectic C phase (SmC*) or H phase (SmH*) of bulk state and align vertical 
(smectic) molecular layers each comprising a plurality of liquid crystal 
molecules in one direction. 
Further, as a display device using such a ferroelectric liquid crystal 
(FLC), there is known-one wherein a pair of-transparent substrates 
respectively having thereon a transparent electrode and subjected to an 
aligning treatment are disposed to be opposite to each other with a cell 
gap of about 1-3 .mu.m therebetween so that their transparent electrodes 
are disposed on the inner sides to form a blank cell, which is then filled 
with a ferroelectric liquid crystal, as disclosed in U.S. Pat. Nos. 
4,639,089; 4,655,561; and 4,681,404. 
The above-type of liquid crystal display device using a ferroelectric 
liquid crystal has two advantages. One is that a ferroelectric liquid 
crystal has a spontaneous polarization so that a coupling force between 
the spontaneous polarization and an external electric field can be 
utilized for switching. Another is that the long axis direction of a 
ferroelectric liquid crystal molecule corresponds to the direction of the 
spontaneous polarization in a one-to-one relationship so that the 
switching is effected by the polarity of the external electric field. More 
specifically, the ferroelectric liquid crystal in its chiral smectic phase 
show bistability, i.e., a property of assuming either one of a first and a 
second optically stable state depending on the polarity of an applied 
voltage and maintaining the resultant state in the absence of an electric 
field. Further, the ferroelectric liquid crystal shows a quick response to 
a change in applied electric field. Accordingly, the device is expected to 
be widely used in the field of e.g., a high-speed and memory-type display 
apparatus. 
A ferroelectric liquid crystal generally comprises a chiral smectic liquid 
crystal (SmC* or SmH*), of which molecular long axes form helixes in the 
bulk state of the liquid crystal. If the chiral smectic liquid crystal is 
disposed within a cell having a small gap of about 1-3 .mu.m as described 
above, the helixes of liquid crystal molecular long axes are unwound (N. 
A. Clark, et al., MCLC (1983), Vol. 94, p.p. 213-234). 
A liquid crystal display apparatus having a display panel constituted by 
such a ferroelectric liquid crystal device may be driven by a multiplexing 
drive scheme as described in U.S. Pat. No. 4,655,561, issued to Kanbe et 
al to form a picture with a large capacity of pixels. The liquid crystal 
display apparatus may be utilized for constituting a display panel 
suitable for, e.g., a word processor, a personal computer, a 
micro-printer, and a television set. 
A ferroelectric liquid crystal has been principally used in a binary 
(bright-dark) display device in which two stable states of the liquid 
crystal are used as a light-transmitting state and a light-interrupting 
state but can be used to effect a multi-value display, i.e., a halftone 
display. In a halftone display method, the areal ratio between bistable 
states (light transmitting state and light-interrupting state) within a 
pixel is controlled to realize an intermediate light-transmitting state. 
The gradational display method of this type (hereinafter referred to as an 
"areal modulation" method) will now be described in detail. 
FIG. 1 is a graph schematically representing a relationship between a 
transmitted light quantity I through a ferroelectric liquid crystal cell 
and a switching pulse voltage V. More specifically, FIG. 1A shows plots of 
transmitted light quantities I given by a pixel versus voltages V when the 
pixel initially placed in a complete light-interrupting (dark) state is 
supplied with single pulses of various voltages V and one polarity as 
shown in FIG. 1B. When a pulse voltage V is below threshold Vth (V&lt;Vth), 
the transmitted light quantity does not change and the pixel state is as 
shown in FIG. 2B which is not different from the state shown in FIG. 2A 
before the application of the pulse voltage. If the pulse voltage V 
exceeds the threshold Vth (Vth&lt;V&lt;Vsat), a portion of the pixel is switched 
to the other stable state, thus being transitioned to a pixel state as 
shown in FIG. 2C showing an intermediate transmitted light quantity as a 
whole. If the pulse voltage V is further increased to exceed a saturation 
value Vsat (Vsat&lt;V), the entire pixel is switched to a light-transmitting 
state as shown in FIG. 2D so that the transmitted light quantity reaches a 
constant value (i.e., is saturated). That is, according to the areal 
modulation method, the pulse voltage V applied to a pixel is controlled 
within a range of Vth&lt;V&lt;Vsat to display a halftone corresponding to the 
pulse voltage. 
However, actually, the voltage (V)-transmitted light quantity (I) 
relationship shown in FIG. 1 depends on the cell thickness and 
temperature. Accordingly, if a display panel is accompanied with an 
unintended cell thickness distribution or a temperature distribution, the 
display panel can display different gradation levels in response to a 
pulse voltage having a constant voltage. 
FIG. 3 is a graph for illustrating the above phenomenon which is a graph 
showing a relationship between pulse voltage (V) and transmitted light 
quantity (I) similar to that shown in FIG. 1 but showing two curves 
including a curve H representing a relationship at a high temperature and 
a curve L at a low temperature. In a display panel having a large display 
size, it is rather common that the panel is accompanied with a temperature 
distribution. In such a case, however, even if a certain halftone level is 
intended to be displayed by application of a certain drive voltage Vap, 
the resultant halftone levels can be fluctuated within the range of 
I.sub.1 to I.sub.2 as shown in FIG. 3 within the same panel, thus failing 
to provide a uniform gradational display state. 
In order to solve the above-mentioned problem, our research and development 
group has already proposed a drive method (hereinafter referred to as the 
four pulse method") in U.S. patent appln. Ser. No. 681,933, filed Apr. 8, 
1991. In the four pulse method, as illustrated in FIGS. 4 and 5, all 
pixels having mutually different thresholds on a common scanning line in a 
panel are supplied with plural pulses (corresponding to pulses (A)-(D) in 
FIG. 4) to show consequently identical transmitted quantities as shown at 
FIG. 4(D). In FIG. 5, T.sub.1, T.sub.2 and T.sub.3 denote selection 
periods set in synchronism with the pulses (B), (C) and (D), respectively. 
Further, Q.sub.0, Q.sub.0 ', Q.sub.1, Q.sub.2 and Q.sub.3 in FIG. 4 
represent gradation levels of a pixel, inclusive of Q.sub.0 representing 
black (0%) and Q.sub.0 ' representing white (100%). Each pixel in FIG. 4 
is provided with a threshold distribution within the pixel increasing from 
the leftside toward the right side as represented by a cell thickness 
increase. 
Our research and development group has also proposed a drive method (a 
so-called "pixel shift method", as disclosed in U.S. patent appln. Ser. 
No. 984,694, filed Dec. 2, 1991 and entitled "LIQUID CRYSTAL DISPLAY 
APATUS"), requiring a shorter writing time than in the four pulse 
method. In the pixel shift method, plural scanning lines are 
simultaneously supplied with different scanning signals for selection to 
provide an electric field intensity distribution spanning the plural 
scanning lines, thereby effecting a gradational display. According to this 
method, a variation in threshold due to a temperature variation can be 
absorbed by shifting a writing region over plural scanning lines. 
An outline of the pixel shift method will now be described below. 
A liquid crystal cell (panel) suitably used may be one having a threshold 
distribution within one pixel. Such a liquid crystal cell may for example 
have a sectional structure as shown in FIG. 6. The cell shown in FIG. 6 
has an FLC layer 55 disposed between a pair of glass substrates 53 
including one having thereon transparent stripe electrodes 53 constituting 
data lines and an alignment film 54 and the other having thereon a 
ripple-shaped film 52 of, e.g., an insulating resin, providing a saw-teeth 
shape cross section, transparent stripe electrodes 52 constituting 
scanning lines and an alignment film 54. In the liquid crystal cell, the 
FLC layer 55 between the electrodes has a gradient in thickness within one 
pixel so that the switching threshold of FLC is also caused to have a 
distribution. When such a pixel is supplied with an increasing voltage, 
the pixel is gradually switched from a smaller thickness portion to a 
larger thickness portion. 
The switching behavior is illustrated with reference to FIG. 7A. Referring 
to FIG. 7A, a panel in consideration is assumed to have portions having 
temperatures T.sub.1, T.sub.2 and T.sub.3. The switching threshold voltage 
of FLC is lowered at a higher temperature. FIG. 7A shows three curves each 
representing a relationship between applied voltage and resultant 
transmittance at temperature T.sub.1, T.sub.2 or T.sub.3. 
Incidentally, the threshold change can be caused by a factor other than a 
temperature change, such as a layer thickness fluctuation, but an 
embodiment of the present invention will be described while referring to a 
threshold change caused by a temperature change, for convenience of 
explanation. 
As is understood from FIG. 7A, when a pixel at a temperature T.sub.1 is 
supplied with a voltage Vi, a transmittance of X% results at the pixel. 
If, however, the temperature of the pixel is increased to T.sub.2 or 
T.sub.3, a pixel supplied with the same voltage Vi is caused to show a 
transmittance of 100%, thus failing to perform a normal gradational 
display. FIG. 7C shows inversion states of pixels after writing. Under 
such conditions, written gradation data is lost due to a temperature 
change, so that the panel is applicable to only a limited use of display 
device. 
In contrast thereto, it becomes possible to effect a gradational display 
stable against a temperature change by display data for one pixel on two 
scanning lines S1 and S2 as shown in FIG. 7D. 
The drive scheme will be described in further detail hereinbelow. 
(1) A ferroelectric liquid crystal cell as shown in FIG. 12 having a 
continuous threshold distribution within each pixel is provided. It is 
also possible to use a cell structure providing a potential gradient 
within each pixel as proposed by our research and development group in 
U.S. Pat. No. 4,815,823 or a cell structure having a capacitance gradient. 
In any way, by providing a continuous threshold distribution within each 
cell, it is possible to form a domain corresponding to a bright state and 
a domain corresponding to a dark state in mixture within one pixel, so 
that a gradational display becomes possible by controlling the areal ratio 
between the domains. 
The method is applicable to a stepwise transmittance modulation (e.g., at 
16 levels) but a continuous transmittance modulation is required for an 
analog gradational display. 
(2) Two scanning lines are selected simultaneously. The operation is 
described with reference to FIG. 8. FIG. 8A shows an overall 
transmittance--applied voltage characteristic for combined pixels on two 
scanning lines. In FIG. 8A, a transmittance of 0-100% is allotted to be 
displayed by a pixel B on a scanning line 2 and a transmittance of 
100-200% is allotted to be displayed by a pixel A on a scanning line 1. 
More specifically, as one pixel is constituted by one scanning line, a 
transmittance of 200% is displayed when both the pixels A and B are wholly 
in a transparent state by scanning two scanning lines simultaneously. 
Herein, two scanning lines are selected for displaying one gradation data 
but a region having an area of one pixel is allotted to displaying one 
gradation data. This is explained with reference to FIG. 8B. 
At temperature T.sub.1, inputted gradation data is written in a region 
corresponding to 0% at an applied voltage V.sub.0 and in a region 
corresponding to 100% at V.sub.100. As shown in FIG. 8B, at temperature 
T.sub.1, the range (pixel region) is wholly on the scanning line 2 (as 
denoted by a hatched region in FIG. 8B). When the temperature is raised 
from T.sub.1 to T.sub.2, however, the threshold voltage of the liquid 
crystal is lowered correspondingly, the same amplitude of voltage causes 
an inversion in a larger region in the pixel than at temperature T.sub.1. 
For correcting the deviation, a pixel region at temperature T.sub.2 is set 
to span on scanning lines 1 and 2 (a hatched portion at T.sub.2 in FIG. 
8B). 
Then, when the temperature is further raised to temperature T.sub.3, a 
pixel region corresponding to an applied voltage in the range of V.sub.0 
-V.sub.100 is set to be on only the scanning line 1 (a hatched portion at 
T.sub.3 in FIG. 8B). 
By shifting the pixel region for a gradational display on two scanning 
lines depending on the temperature, it becomes possible to retain a normal 
gradation display in the temperature region of T.sub.1 -T.sub.3. 
(3) Different scanning signals are applied to the two scanning lines 
selected simultaneously. As described at (2) above, in order to compensate 
for the change in threshold of liquid crystal inversion due to a 
temperature range by selecting two scanning lines simultaneously, it is 
necessary to apply different scanning signals to the two selected scanning 
lines. This point is explained with reference to FIG. 7. 
Scanning signals applied to scanning lines 1 and 2 are set so that the 
threshold of a pixel B on the scanning line 2 and the threshold of a pixel 
A on the scanning line 1 varies continuously. Referring to FIG. 7B, a 
transmittance-voltage curve at temperature 1 indicates that a 
transmittance up to 100% is displayed in a region on the scanning line 2 
and a transmittance thereabove and up to 200% is displayed in a region on 
the scanning line 1. It is necessary to set the transmittance curve so 
that it is continuous and has an equal slope spanning from the pixel B to 
the pixel A. 
As a result, even if the pixel A on the scanning line 1 and the pixel B on 
the scanning line 2 are set to have identical cell shapes as shown in FIG. 
9B, it becomes possible to effect a display substantially similar to that 
in the case where the pixel A and the pixel B are provided with a 
continuous threshold characteristic (cell at the right side of FIG. 7B). 
If a cell including pixels each having a threshold distribution as shown in 
FIG. 6 is supplied with a voltage waveform as shown in FIG. 10A&lt;a 
gradation level formed by application of a writing pulse V.sub.1 is 
affected by application of subsequent alternating pulses .+-.Vc. 
The value .vertline.Vc.vertline. is below an inversion threshold at a pulse 
width of 40 .mu..mu.m (FIG. 10A), so that, if the pulses .+-.Vc are 
applied not immediately after the writing but in the absence of the pulse 
V.sub.1, the reset state given by the pulse V.sub.0 is displayed as it is 
without being accompanied with any change (crosstalk). The quantity or 
level of change (hereinafter referred to as "crosstalk") affecting the 
written level varies depending on the peak value of Vc even if V.sub.1 and 
V.sub.0 are the same. More specifically, the crosstalk quantity increases 
as the value .vertline.Vc.vertline. increases as shown in FIG. 10B, 
amounting to 20% or more at .vertline.Vc.vertline.=5 volts. As a result, 
in case where some alternating signals are applied after a writing pulse, 
it is difficult to drive a matrix electrode cell by a line-sequential 
writing drive (FIG. 10C). 
The characteristics of a liquid crystal device referred to above with 
reference to FIGS. 10A-10C are identical to those used in Example 
described hereinafter inclusive of the cell structure and materials. The 
crosstalk may be attributable to instability of FLC immediately after the 
switching. When the light quantity change through FLC immediately after 
switching was examined and the result was as shown in FIG. 11A, showing a 
continual change in light quantity for some time and resulting in a 
certain stable quantity level. The stabilization of optical response 
required a time (hereinafter referred to as "relaxation time") of about 
200 .mu.s. 
When a drive waveform as shown in FIG. 11C was used to examine the 
relationship between the relaxation time and the crosstalk, a graph as 
shown in FIG. 11B was obtained. The waveform shown in FIG. 11C includes a 
writing pulse V.sub.ON and a reset pulse -V.sub.0. FIG. 11B shows a change 
in final transmittance when crosstalk pulses .+-.Vc were applied after 
lapse of time T after the fall down of the V.sub.ON pulse. FIG. 11B shows 
that the crosstalk quantity varies depending on the value of T even if 
.vertline.Vc.vertline. is fixed at 5 volts and the effect of the pulses 
.+-.Vc is substantially lost under the condition of T.gtoreq.relaxation 
time (=200 .mu.s). The crosstalk quantity (change in transmittance) can 
change depending on the number of crosstalk pulses after the V.sub.ON 
pulse in the case of a drive waveform as shown in FIG. 12A. FIG. 12B 
however shows that the crosstalk quantity is not affected if the total 
time of the number of the pulses exceeds the relaxation time, i.e., 
showing that N.gtoreq.Z (.gtoreq.200 .mu.s) provides a substantially 
constant final transmittance. 
Accordingly, in the case of gradational display, it is an important problem 
how to treat non-selection signals applied after a switching pulse. As a 
measure, it is possible to prevent the crosstalk by not applying such 
non-selection signals for a period corresponding to the relaxation time 
after the writing. This however requires a long one line-selection time 
and is not suitable for other than a static picture display, thus being 
impractical. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide a practical 
liquid crystal display apparatus capable of obviating the crosstalk caused 
by application of non-selecting signals after writing. 
As a result of our study, it has been found possible to suppress the 
crosstalk (i.e., change in written gradation level) in a line-sequential 
scanning of an FLC panel by applying appropriate data signals based on 
estimated crosstalk quantity caused by detected contents of data written 
on a subsequent scanning line. 
More specifically, according to the present invention, there is provided a 
liquid crystal display apparatus, including: 
a liquid crystal display device comprising a pair of oppositely disposed 
electrode plates having thereon a group of scanning lines and a group of 
data lines, respectively, and a liquid crystal disposed between the pair 
of electrode plates so as to form a pixel at each intersection of the 
scanning lines and data lines, and 
drive means including means for sequentially selecting the scanning lines, 
means for applying data signals to the data lines for the selected 
scanning lines, and control means for determining the data signals applied 
to the data lines for pixels on a selected scanning line while comparing 
image data for the pixels on the selected scanning line and image data for 
corresponding pixels on a subsequently selected scanning lines. 
These and other objects, features and advantages of the present invention 
will become more apparent upon a consideration of the following 
description of the preferred embodiments of the present invention taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Examination of the crosstalk encountered in gradational display using a 
ferroelectric liquid crystal (FLC) device has revealed the following 
characteristics. 
Referring to FIG. 10C, if the change in crosstalk quantity from the same 
gradation level (at Vc=0 volt) according to increased .+-.Vc is examined, 
it is seen that different crosstalk quantities are observed at 30.degree. 
C. and 35.degree. C. The applied voltages VON (=V.sub.1) at that time were 
16 volts at 30.degree. C. and 11.7 volts at 35.degree. C. However, if the 
varying crosstalk voltages Vc were normalized by a bias ratio 
R=Vc/V.sub.ON, the transmittance change according to the varying crosstalk 
voltage could be represented by a substantially signal line regardless of 
the temperature difference as shown in FIG. 13. 
Further, as shown in FIG. 14, the relationship between the crosstalk 
quantity (reduction in transmittance) and the bias ratio R (=Vc/V.sub.ON) 
could be represented as a substantially single linear relationship without 
depending on the writing levels (values of V.sub.ON). Further, as shown in 
FIG. 15, if the signs of alternating pulses .+-.Vc after the V.sub.ON 
pulse were altered, the sign of the crosstalk quality was also altered. 
More specifically, in the case where V.sub.ON was positive, the 
application sequence of +Vc pulse and then -Vc pulse resulted in an 
enhancement in the written level, and the application sequence of -Vc 
pulse and then +Vc pulse resulted in an reduction in the written level. 
As described above, (1) the crosstalk quantity is determined by the bias 
ratio and does not depend on the temperature or the gradation level, and 
(2) the change in light quantity (transmittance) due to the crosstalk 
remarkably depends on the pattern of subsequent pulses following the 
writing pulse V.sub.ON. These characteristics indicate that it is possible 
to completely compensate for the crosstalk quantity and design data 
signals (inclusive of pulse widths and amplitudes) for one frame or 
several lines while taking the crosstalk quantity into consideration, in 
case where the above-mentioned pixel shift method is applicable and 
subsequent display data are known Based on the above knowledge, the 
present invention provides an FLC data line based on a system capable of 
recognizing subsequent data and arranging data signals for one frame based 
thereon. It is also possible to design data signals for not only one frame 
but also a subsequent frame. it is also effective to preliminarily set 
subsequent signals at a prescribed value. 
EXAMPLE 1 
As a first embodiment, a liquid crystal cell having a sectional structure 
as shown in FIG. 6 was prepared. The lower glass substrate 53 was provided 
with a saw-teeth shape cross section by transferring an original pattern 
formed on a mold onto a UV-curable resin layer applied thereon to form a 
cured acrylic resin layer 52. 
The thus-formed UV-cured uneven resin layer 52 was then provided with 
stripe electrodes 51 of ITO film by sputtering and then coated with an 
about 300.ANG.-thick alignment film (formed with "LQ-1802", available from 
Hitachi Kasei K.K.). 
The opposite glass substrate 53 was provided with stripe electrodes 51 of 
ITO film on a flat inner surface and coated with an identical alignment 
film. 
Both substrates (more accurately, the alignment films thereon) were rubbed 
respectively in one direction and superposed with each other so that their 
rubbing directions were roughly parallel but the rubbing direction of the 
lower substrate formed a clockwise angle of about 6 degrees with respect 
to the rubbing direction of the upper substrate. The cell thickness 
(spacing) was controlled to be from about 1.0 .mu.m as the smallest 
thickness to about 1.4 .mu.m as the largest thickness. Further, the lower 
stripe electrodes 51 were formed along the ridge or ripple (extending in 
the thickness direction of the drawing) so as to provide one pixel width 
having one saw tooth span. Thus, rectangular pixels each having a size of 
300 .mu.m.times.200 .mu.m were formed. 
Then, the cell was filled with a chiral smectic liquid crystal A showing 
the following phase transition series and properties. 
TABLE 1 
______________________________________ 
(liquid crystal A) 
______________________________________ 
1 STR1## 
- Ps = -5.8 nC/cm.sup.2 (30.degree. C.) 
Tilt angle = 14.3 deg. (30.degree. C.) 
.DELTA..epsilon. .apprxeq. -0 (30.degree. C.) 
______________________________________ 
FIG. 16 is a block diagram of a control system for a display apparatus 
according to the present invention, and FIG. 19 is a time chart for 
communication of image data therefor. Hereinbelow, the operation of the 
apparatus will be described with reference to these figures. 
A graphic controller 102 supplies scanning line address data for 
designating a scanning electrode and image data PD0-PD3 for pixels on the 
scanning line designated by the address data to a display drive circuit 
constituted by a scanning line drive circuit 104 and a data line drive 
circuit 105 of a liquid crystal display apparatus 101. In this embodiment, 
scanning line address data (A0-A15) and display data (D0-D1279) must be 
differentiated. A signal AH/DL is used for the differentiation. The AH/DL 
signal at a high (Hi) level represents scanning line address data, and the 
AH/DL signal at a low (Lo) level represents display data. 
The scanning line address data is extracted from the image data PD0-PD3 in 
a drive control circuit 111 in the liquid crystal display apparatus 101 
outputted to the scanning line drive circuit 104 in synchronism with the 
timing of driving a designated scanning line. The scanning line address 
data is inputted to a decoder 106 within the scanning line drive circuit 
104, and a designated scanning electrode within a display panel is driven 
by a scanning signal generation circuit 107 via the decoder 106. On the 
other hand, display data is introduced to a shift register 108 within the 
data line drive circuit 105 and shifted by four pixels as a unit based on 
a transfer clock pulse. When the shifting for 1280 pixels on a horizontal 
one scanning line is completed by the shift register 108, display data for 
the 1280 pixels are transferred to a line memory 109 disposed in parallel, 
memorized therein for a period of one horizontal scanning period and 
outputted to the respective data electrodes from a data signal generation 
circuit 110. 
Further, in this embodiment, the drive of the display panel 103 in the 
liquid crystal display apparatus 101 and the generation of the scanning 
line address data and display data in the graphic controller 102 are 
performed in a non-synchronous manner, so that it is necessary to 
synchronize the graphic controller 102 and the display apparatus 101 at 
the time of image data transfer. The synchronization is performed by a 
signal SYNC which is generated for each one horizontal scanning period by 
the drive control circuit 111 within the liquid crystal display apparatus 
101. The graphic controller 102 always watches the SYNC signal, so that 
image data is transferred when the SYNC signal is at a low level and image 
data transfer is not performed after transfer of image data for one 
scanning line at a high level. More specifically, referring to FIG. 16, 
when a low level of the SYNC signal is detected by the graphic controller 
102, the AH/DL signal is immediately turned to a high level to start the 
transfer of image data for one horizontal scanning line. Then, the SYNC 
signal is turned to a high level by the drive control circuit 111 in the 
liquid crystal display apparatus 101. After completion of writing in the 
display panel 103 with lapse of-one horizontal scanning period, the drive 
control circuit 111 again returns the SYNC signal to a low level so as to 
receive image data for a subsequent scanning line. 
FIG. 17 is a waveform diagram showing a set of driven signal waveforms used 
in this embodiment including scanning signals applied to scanning lines 
S.sub.1, . . . , S.sub.3, . . . , data signals applied to a data line I, 
and a combined voltage signal applied to a pixel at S.sub.1 -I. 
In this embodiment, a gradation drive scheme according to the pixel shift 
method was adopted, so that adjacent two scanning lines were supplied with 
scanning signals having mutually reverse polarities at corresponding 
phases. 
Referring to FIG. 17, the respective pulses were characterized by 
parameters of dt.sub.1 =40 .mu.sec, dt.sub.2 =27 .mu.sec, dt.sub.3 =13 
.mu.sec, .vertline.V.sub.1 .vertline.=20.0 volts, .vertline.V.sub.2 
.vertline.=17.2 volts, Vi=3.4 volts to -3.4 volts, and .vertline.V.sub.4 
.vertline.=4.0 volts. 
The data signal modulation was effected as voltage modulation so as to 
provide 0% at (V.sub.2 +Vi)=13.8 volts, 100% at (V.sub.2 +V.sub.i)=20.6 
volts and a halftone at an intermediate voltage. In FIG. 17, the data 
signal is represented as a signal at a period A applied to a data line I 
including a gradation data -carrying pulse having an amplitude Vi and a 
pulse width dt.sub.1 and auxiliary pulses on both sides each having a 
pulse width 1/2.multidot.dt.sub.1 for removing the DC component. The 
relationship between the voltage V.sub.LC (=V.sub.2 +Vi) applied to a 
pixel (i.e., liquid crystal layer) and the resultant transmittance T (%) 
was as shown below: 
______________________________________ 
V.sub.LC 
1.38 14.4 15.0 15.6 16.2 16.8 17.5 
T(%) 0 10 20 30 40 50 60 
______________________________________ 
18.2 19.0 19.8 20.6 
70 80 90 100 
______________________________________ 
The influence of the crosstalk is most pronounced for a time up to 100 
.mu.sec from the falling down of the writing pulse (FIG. 10B) and, in the 
case of repetitive pulses, up to 30 cycles (6 pulses) have a significant 
influence but pulses thereafter have little influence (FIG. 12B). 
Accordingly, while it can depend to some extent on the alignment state of 
the liquid crystal, the influence of crosstalk can be minimized by 
detecting the data for 1-2 lines after application of a pulse AA shown at 
S1 - I in FIG. 17. 
More specifically, if the potential immediately after the pulse after the 
period A is fixed as shown for a period B (or known in anyway), the 
influence of the crosstalk can be removed substantially by controlling the 
applied voltage for a line concerned based on data for one subsequent 
line. For example, if alternating pulses of .+-.3 volts and 20 .mu.s are 
applied after the application of the pulse AA, the writing voltage for an 
n-th line may be determined from writing data for a subsequent (n+1)-th 
line in the following manner. That is, in a data conversion circuit within 
the graphic controller 102 shown in FIG. 16, image data for 1 frame is 
stored in a frame memory (I) and then, based on the image data, conversion 
data for displaying an image corresponding to the image data under the 
influence of the crosstalk is derived starting from a final scanning line 
and is stored in a frame memory (2). The converted data for the final 
scanning line is obtained by applying a constant data signal for a one 
horizontal scanning period. In this way, the conversion data is 
sequentially obtained up to the starting line and is stored in the image 
memory (II) as described above. Such conversion data can be obtained 
regardless of a particular scanning scheme. The above data conversion is 
effected for respective data lines. 
More specifically, the conversion of "image data" into "image data taking 
the crosstalk into account" may be performed in a manner as illustrated in 
FIG. 18 for each data line, i.e., for determining conversion data for a 
pixel n.sub.j on a j-th scanning line from image data for a pixel, 
n.sub.j+1 on a j+1-th scanning line and the same data line, in the 
following manner. 
FIG. 18 is a flow chart for illustrating an operation in the data 
conversion circuit as a comparison-determination circuit used in the 
present invention. As shown in FIG. 18, the following steps are performed 
sequentially. 
(1) Image data X for n.sub.j is obtained. 
(2) Data signal V.sub.j for displaying X without considering crosstalk is 
determined [TABLE I]. 
(3) Display data T for the input Vj is determined (T is initially set to X) 
[TABLE I]. 
(4) Crosstalk quantity ST is determined from a data signal V.sub.j+1 and Vj 
determined in step (2). 
(5) A relationship between T determined in step (3) and X given in step (1) 
is examined. According to judgment 1, if T+.delta.T=.times.(YES), the 
voltage for n.sub.j is determined at Vj which is stored in the frame 
memory (II), and the process for determining V.sub.j+1 for a subsequent 
line is started. If the answer to the judgment 1 is NO, the judgment 2 (if 
T+.delta.T&gt;X) is performed and, if the answer is YES, Vj'=Vj+.delta.V 
(fixed value) is substituted for Vj (i.e., Vj=Vj'). 
If the answer to the judgment 2 is NO, Vj'=Vj+.delta.V (fixed value) is 
substituted for Vj. 
(6) Then, the steps (3)-(5) are repeated until the judgment 1 is answered 
by YES. 
According to the above process, it is possible to write one picture as 
desired corresponding to input image data. Herein, TABLE (I) contains data 
giving a relationship between transmittance and input data signal in the 
absence of crosstalk, and TABLE (II) contains data for deriving crosstalk 
quantity from data signal V.sub.j+1 for a subsequent line and writing 
signal V.sub.ON =V.sub.2 .+-.Vj. 
TABLE (II) in this embodiment was given by the following equation: 
EQU T=26.7.times.V.sub.j+1 /(V.sub.2 +Vj)-1.3, 
wherein V.sub.2 (=V.sub.S) denotes a scanning signal voltage, Vj denotes a 
data signal voltage and V.sub.j+1 denotes a data signal voltage for a 
subsequent line. 
As described hereinabove, according to the present invention, it has become 
possible to realize a good quality of gradational display free from 
crosstalk.