Liquid crystal display including color triads with split pixels

An active liquid crystal multi-colored display panel structure comprised of triangular triads of colored display pixels which are rotated 90.degree.. The display comprises a plurality of colored pixel electrodes arranged in rows and columns to form a matrix, wherein a row control line is provided every 1.5 rows of electrodes, and wherein three column control lines are provided for each two columns of electrodes. Thus, a matrix of 720.times.720 pixel electrodes requires 480 row control lines and 1080 column signal lines. The active liquid crystal display structure can be directly driven by a video source such that 480 active lines of video signal can be mapped directly onto the 720 rows of pixel elements. A switching circuit is provided for controlling the arrangement of R, G and B pixel signals to the column source lines. The triads of pixel elements provided are rotated 90.degree. to maintain high resolution while allowing a standard video signal to be directly mapped onto the display without additional electronics such as a ping-pong memory.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
The present invention relates to an active-matrix liquid crystal 
multi-color display panel structure, and more particularly, to a unique 
display panel structure comprised of generally triangular triads of 
colored display pixels arranged to permit 480 scan lines of data to be 
mapped directly onto 720 rows of dots while retaining a normal scanning 
sense. 
II. Discussion of the Prior Art 
Active-matrix liquid crystal multi-colored display panel structures are 
typically comprised of a matrix of colored display pixels arranged in rows 
and columns and which are controlled by semiconductor switching devices. 
The semiconductor switching devices are typically comprised of thin-film 
transistors of, for example, the amorphous-silicon field-effect design. 
Typically, multi-colored images are produced on liquid crystal display 
panels by providing colored filters in association with pixel electrodes 
across a layer of liquid crystal. Construction techniques of liquid 
crystal multi-colored display panel structures are well known in the art, 
and many control schemes can be implemented to control each of the colored 
filters. 
The pixel arrangement and control scheme can determine the image quality, 
resolution, and the unwanted generated picture artifacts associated with 
the particular pixel arrangement and control scheme. Construction of 
active-matrix liquid crystal multi-colored display panel structures and 
some of the associated artifacts are discussed in detail in U.S. Pat. No. 
4,969,718 to Noguchi, et al., which is assigned to NEC Corporation, and in 
U.S. Pat. No. 4,822,142 to Yasui and which is assigned to Hosiden 
Electronics Company, Ltd. Both patents are incorporated herein by 
reference. 
Present research and development efforts are continuously improving the 
picture quality of color images generated on display panels. Arranging 
colored pixel elements in triangular arrangements, commonly referred to as 
triads, is one known design method of improving picture quality and 
resolution. Arranging the colored pixel elements in triads is generally 
preferred over other arrangements such as linear groups or "L" shaped 
groups. 
The present invention is directed to facilitate the mapping of video data 
from a video source onto a panel which has an insufficient number of dots 
to permit a simple 1:1 mapping of the incoming data onto the display 
surface. In particular, the problem addressed is how to map a 480 active 
line color video onto a surface with 720 rows of 720 columns of pixel 
elements or dots. The video data is typically transmitted from a signal 
source, such as a digital map comprising 480 slit samples, each of which 
is in an analog data stream format. 
A display panel having a matrix display which can accommodate directly 
mapping 480 active lines of color video signals onto a display surface 
with 720 rows and 720 columns of pixel elements display while retaining 
the normal scanning sense is desirable to reduce cost and design 
complexity. A restructured panel comprising pixel electrodes and 
interconnects to the dots which permits the panel to be scanned directly, 
with no need for auxiliary memory or components is preferred. 
OBJECTS OF THE INVENTION 
It is accordingly a principal object of the invention to provide a liquid 
crystal multi-colored display panel structure which permits 480 scan lines 
to be mapped directly onto 720 rows of pixel dots while retaining the 
normal scanning sense. 
It is a further object of the present invention to provide a liquid crystal 
multi-colored display panel structure which is composed of a plurality of 
triangular triads of multi-colored display pixel electrodes to ensure a 
high quality picture with a high resolution. 
It is still yet a further object of the present invention to provide a 
liquid crystal multi-colored display panel structure which incorporates a 
practical amount of scanning control lines and column signal lines, and 
wherein the colored pixel elements are of an acceptable size to provide 
high resolution yet which can be easily manufactured. 
It is still yet another object of the present invention to provide a liquid 
crystal multi-colored display panel structure wherein the plurality of 
triads of pixel elements are arranged and controlled such that unpleasant 
display artifacts are reduced. 
SUMMARY OF THE INVENTION 
The foregoing features and objects are achieved by providing a liquid 
crystal multi-colored display panel structure having triads of colored 
display pixel electrodes which are rotated 90.degree., wherein a scanning 
control line is provided every 1.5 rows of electrodes and wherein three 
column signal lines are provided for every two columns of colored display 
pixel electrodes. This design results in one of the three colors of 
display pixel electrodes being bisected throughout the display. This 
arrangement allows 480 scan lines to be mapped directly onto 720 rows of 
pixel electrodes while retaining the normal scanning sense. No auxiliary 
memory or line storing is required, and the display panel structure can be 
manufactured using practical techniques. 
The liquid crystal multi-colored display panel structure comprises a 
substantially transparent substrate having a plurality of colored display 
pixel electrodes disposed thereon to form a matrix having columns in the 
first direction and rows in a second direction. The colored display pixel 
electrodes include three types of colors, namely the primary colors of 
red, blue and green. The colored display pixel electrodes in adjacent 
columns are offset approximately one-half distance from one another such 
that they form a plurality of generally triangular triads which are 
rotated 90.degree. from conventional and prior art arrangements. Thus, one 
side of each triad extends in the vertical direction. A plurality of 
column signal lines are disposed between the pixel columns of the matrix 
and extend in a first or vertical direction. A single signal line is 
provided between alternate adjacent columns of pixel electrodes, and a 
pair of signal lines are alternately disposed between the other adjacent 
columns, resulting in three column signal lines for every two columns of 
pixel electrodes. Thus, the resulting arrangement is an alternating 
pattern of one and two column signal lines extending between the columns 
of pixel electrodes. 
The second portion of the control structure includes a plurality of 
scanning control lines disposed every one and one-half rows of the matrix 
display and which extend in a second or horizontal direction. These 
scanning control lines extend between two pixel electrodes of two 
different colors of a triad in alternating columns, such that the scanning 
line extends across or bifurcates the third pixel electrode of the triad 
of a third color in alternating columns. Thus, each triad of pixel 
electrodes comprises one pixel electrode of a first and second color on 
opposite sides of the horizontal scanning line, while one bifurcated pixel 
electrode of the third color is defined to the left or right of the first 
two electrodes, such that the triads are interlaced. 
A plurality of switching transistors are provided, one coupled to each of 
the first and second color types of pixel electrodes, and one connected to 
at least one of the two halves of the third color type of pixel 
electrodes. The two halves of the third type of electrodes can either be 
electrically connected together such that they are both controlled by one 
transistor, or a separate transistor can be provided for each of the 
halves. Each transistor is preferably comprised of a thin-film FET having 
a first terminal or drain connected to one of the colored display 
electrodes, a second terminal or gate connected to one of the signal 
lines, and the third terminal or source connected to one of the column 
scanning lines to control conductivity between the respective first and 
second terminals. The third terminal of the switching transistors 
associated with the colored display electrodes of the first and second 
colors of each triad are defined on opposite sides of the scanning control 
line. As such, the gate or gates associated of the colored display 
electrodes of the third color type of each triad are disposed on one or 
the other of opposite sides of the respective scanning line. If both 
halves of the electrodes of the third type are electrically tied together, 
only one switching transistor is required for both halves of the pixel 
electrodes. Otherwise, a separate transistor can control the respective 
half of the pixel electrode of the third color type. It is noted that only 
one scanning control line is provided for each triad of pixel electrodes. 
Thus, only one gate pulse is required per triad and the control interface 
need not be complicated. 
In one embodiment of the invention, two of every three of the column signal 
lines are connected to the second terminals of the switching transistors 
associated with the pixels of two different color types. This provides, 
for instance, one column signal line to be connected to only those pixel 
electrodes of one color type, such as green in adjacent columns. The other 
two signal lines will each be connected to the other two types of pixel 
electrodes in adjacent columns, such as the blue and red pixel electrodes. 
The column signal lines will control the pixel electrodes of a triad 
addressed by the scanning control line. In operation, as the rows of pixel 
electrodes of the display are scanned from top to bottom, when scanning 
the odd rows, a column signal line will control one color, such as red. 
When scanning the even rows, the same signal line will control the blue 
color pixel electrodes. Again, the third of every three column signal 
lines control electrodes of only one color, such as green, regardless of 
whether an even or odd row of pixels is being scanned. 
In another embodiment of the present invention, each of the column signal 
lines is connected to the second terminal of the switching transistors 
associated with the electrodes of two different color types. Thus, when 
scanning odd rows, each column signal line will control pixel electrodes 
of one color of each triad, and when scanning even rows, the same column 
signal line will control pixel electrodes of each triad of the other 
color. The scanning control line which is scanned determines which 
electrode is controlled. The column signal lines provide a variable 
voltage to each of the scanned pixel electrodes to generate a field in the 
liquid crystal between the respective pixel electrodes and the common 
electrode to control the passage of light therethrough. Light having the 
appropriate wavelength selected for the color filter associated with the 
particular color display is, thus, passed through the color filter so that 
a picture element in any of a total of eight different colors can be 
produced by a triad of pixels respectively assigned to the three primary 
colors. Thus, a full color picture can be produced which is composed of 
picture elements with steplessly varied color tones. 
The display panel structure includes control circuitry for connecting and 
coordinating the column signals between a control signal bus and the 
signal lines, which is dependent on whether an odd or even row of pixels 
is being scanned. A row drive circuit is connected to the scanning control 
lines for driving each of the plurality of scan lines in synchronism with 
the horizontal scanning cycle of a video signal, and a column drive 
circuit is connected to the column signal lines for supplying a video 
signal to each of the signal lines wherein the input of the column drive 
circuit is connected to a control circuit which provides the video signals 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a liquid crystal display device which 
comprises a pair of transparent substrates 10 and 12 and a liquid crystal 
14 sealed therebetween. A plurality of transparent square display 
electrodes are provided on the inner surface of one of the transparent 
substrates 10 and 12. A transparent common electrode 18 is provided on the 
entire inner surface of the other substrate 12 opposite electrodes 16. The 
display electrodes 16 are arranged in rows and columns and are actively 
controlled by thin film transistors attached to them. The thin film 
transistors are controlled by row or scanning drive lines and column 
signal drive lines. A more detailed description of a typical prior art 
colored liquid crystal display device is described in U.S. Pat. No. 
4,822,142 which is hereby incorporated by reference. 
Referring to FIG. 2, the preferred embodiment of an active-matrix liquid 
crystal multi-colored display panel structure is generally shown at 20. 
Display 20 is manufactured using well-known techniques, such as techniques 
used to create the structure shown in FIG. 1. However, the preferred 
embodiment of the present invention is vastly different from prior art 
displays in that the arrangement and interconnection of the display 
electrodes, the row scanning and column signal drive lines, and the 
arrangement of the thin film transistors is unique compared to prior art 
arrangements. In FIG. 2, display electrodes 16 are arranged in rows and 
columns to form a display matrix as shown. The pixel electrodes 16 are 
comprised of one of three colors, namely, the primary colors of red, blue 
or green. The pixel electrodes 16 are arranged in a pattern producing a 
plurality of generally triangular interleaved triads of colored display 
pixels. Each triad comprises one pixel of each of the three primary 
colors. These color groups or triads are represented by the dotted 
triangular grouping identified at 22. Each of the triads 22 form a 
triangle shape and have an apex shown at 24. Apex 24 is always centered 
over a respective row or scanning control line 26. All triads 22 are 
oriented and interleaved such that the apex 24 of the triads 22 are 
disposed on either the right side or the left side of the triangle as one 
observes the display with the column drive lines extending in the vertical 
direction as shown in FIG. 2. Hence, electrodes 16 in adjacent columns are 
offset from one another one-half pitch distance, which is half the height 
of an electrode 16. 
The arrangement of pixel electrodes into triads is well known for providing 
a picture of enhanced resolution which is free from image moires. However, 
the arrangement of the triads 22 in accordance with the present invention 
is unique from the prior art because each triad 22 is rotated 90.degree. 
such that one side 28 of each triad 22 extends in the vertical direction. 
As shown, one complete pixel electrode 16 of triad 22 lies on the other 
side of the respective scanning control line 26, while the third pixel 
electrode 16 of the triad proximate apex 24 is divided or bifurcated by 
control line 26 with one-half of the bifurcated pixel electrode 16 
situated on each side of control line 26. Thus, only one of the three 
pixel electrodes 16 which form each triad 22 is divided or intersected by 
a control scanning line 26. None of the pixel electrodes 16 is intersected 
by any of the column signal control lines 30. As shown in FIG. 2, several 
column signal control lines 30 are provided. Specifically, there are three 
control lines 30 for each triad 22. In other words, there are three 
control lines for each two columns of pixel electrodes 16, yielding 50% 
more signal control lines 30 than columns of pixel electrodes 16. While 
this arrangement necessitates a higher interconnect density in the 
horizontal direction and also requires additional gray scale driver 
electronics, current and improving technologies for integrated driver 
electronics, such as chip-on glass or direct transistor deposition 
techniques can provide the necessary higher interconnect densities at a 
reasonable cost. 
Still referring to FIG. 2, a first triad group T.sub.1, and a second triad 
group T.sub.2 are shown and are shaded for illustration purposes. Triad 
groups T.sub.1 and T2 are also consistently shown in FIG. 3 as will be 
discussed shortly. Triads 22, typified by triad T.sub.1, are all arranged 
with apex 24 to the right in odd rows of triads and in even rows, such as 
triad T.sub.2, the apex 24 is positioned to the left. This arrangement 
allows the triads in adjacent rows to interleave and provide a high 
density of pixel electrodes 16 per unit area. High density, of course, 
translates into high resolution pictures without undesirable display 
artifacts. 
One key feature of the present invention is that only one scanning control 
line 26 is required per triad 22. Hence, only one gate pulse needs to be 
provided, allowing for less complex driving electronics. A control line 26 
is provided only every 1.5 rows of pixel electrodes 16. This design is 
advantageous over prior art displays because the pixel electrodes 16 can 
be larger in area than pixel electrodes in displays having a scanning line 
for every row of pixel electrodes and manufacture is simplified. Moreover, 
prior art displays having a scanning control line for every other row of 
pixel electrodes are inferior because the smaller electrodes of the 
present invention provide higher image quality and resolution. Thus, the 
present invention is unique from the prior art due to the unique design 
arrangement of the scanning control lines and the column signal control 
lines and the rotated triads to achieve a display panel capable of high 
quality images yet which can be directly driven by the control 
electronics. 
Referring to FIG. 3, the relation of the display electrodes 26 to the 
column signal drive lines 30, row or scanning drive lines 26, thin film 
transistors 40 and drive/control circuitry 42 is illustrated. For purposes 
of illustration and clarification, consecutive row or scanning control 
lines 26 have been labeled L.sub.1, L.sub.2, L.sub.3 . . . from top to 
bottom, and wherein column signal control lines 30 are referenced left to 
right as C.sub.1, C.sub.2, C.sub.3 . . . Triads T.sub.1 and T.sub.2 
correspond to the triads discussed in relation to FIG. 2. Each of pixel 
electrodes 16 are controlled by a respective thin film switching 
transistor 40, as will be discussed in greater detail shortly. Circuit 42 
provides controls and drives the column control signals, consisting of 
pixel information, to the three-color display element sets forming the 
pixel array, as will now be described in detail. 
Alternate rows of scanning drive lines 26 are driven in synchronism with 
the horizontal sync pulses H.sub.syn by the conventional arrangement of a 
row register 44 and a row drive circuit 46. More specifically, all the odd 
rows labeled L.sub.1, L.sub.3 . . . are first successively driven in 
synchronism with the horizontal sync pulses, and then the even row drive 
lines, L.sub.2, L.sub.4 . . . are driven to complete a picture on the 
display in an interlaced manner. A switching circuit 50, forming a subset 
of circuit 42 connects the input signal lines R, G and B to control signal 
busses 52, 54 and 56 as shown. When the odd rows of triads are being 
scanned by the driving electronics via lines L.sub.1, L.sub.3 . . . , 
switching circuit 50 routes the signals R, G and B, labeled as inputs 51, 
to color signal busses 52, 54, and 56, respectively. Thus, signal control 
line C.sub.1 provides red pixel information to each of the adjacent red 
pixel electrodes 16, signal control line C.sub.2 provides green pixel 
information to each of the adjacent green pixel electrodes, and signal 
control line C.sub.3 provides blue pixel information to each of the 
adjacent blue pixel electrodes 16. Subsequently, when even rows of triads 
are stroke scanned, via scanning lines, L.sub.2, L.sub.4 . . . , switching 
circuit 50 provides the R, G and B pixel information to color signal 
busses 56, 52 and 54, respectively. Thus, in the preferred embodiment, 
each signal control line C.sub.1, C.sub.2, C.sub.3 . . . can provide pixel 
information of two different colors to adjacent columns of electrodes 16 
as controlled by bus switching circuit 50. 
A tertiary counter 60 is provided between terminal 72 providing the 
H.sub.syn horizontal sync pulse and switching circuit 50. Counter 60 
counts to .sub.240 (half the number of total scan lines) as the row 
control electronics completes scanning the 240 odd rows of control lines 
26. Counter 60 provides switching circuit 50 a control signal on line 61 
to initiate the rearrangement of the R, G and B pixel signals to color 
signal busses 52, 54 and 56 before the subsequent scanning of the even 
rows of control signals 26. Thus, to generate one complete frame on the 
display 20, the odd row control lines 26 labeled L.sub.1, L.sub.3 . . . 
are scanned first, and then the even control lines 26, labeled L.sub.2, 
L.sub.4 . . . are scanned. Switching circuit 50 rearranges the R, G and B 
inputs labeled 51 to color signal busses 52, 54 and 56 only twice every 
generated frame on the pixel array 20. 
To generate an image on display 20, pixel information is first loaded from 
the respective colored signal bus 52, 54 and 56 into column registers 62. 
A clock signal, CLK, having three times the dot frequency of the input 
colored video signal is supplied as a shift clock from a clock terminal 68 
to a shift register 70. The horizontal sync pulse H.sub.syn is supplied as 
data from the terminal 72 to the first stage of the shift register 70 at 
the start of each horizontal scanning cycle period. Colored pixel data 
from the individual stages of the column register 62 are fetched 
successively in response to the respective output of the shift stages of 
the shift register 70. Thus, as the odd or even row drive lines 26 are 
successively driven in synchronism with the horizontal sync pulses 
H.sub.syn by the conventional arrangement of row registers 44 and row 
drive circuit 46, pixel data will be provided by the respective column 
register 62 via a column driver 71 to the respective column control line 
30. 
Multiple parallel column register 62 can be provided, such that while a 
gate pulse is active for one of the row control lines 26, (such as control 
line L.sub.1), the pixel data for the electrodes of the next scan line 
(such as line L.sub.3), is being sampled and placed into sample and hold 
registers of the column registers 62. Thus, when the pixel data is 
provided on source lines C.sub.1, C.sub.2, C.sub.3 . . . , as one row of 
triads of pixels is being scanned, data for the next row of triads to be 
scanned is being routed to color signal busses 52, 54 and 56 which is to 
be subsequently loaded into column registers 62. This arrangement allows 
the display electrodes 16 to be directly driven without auxiliary memory 
or line storage capabilities. 
Still referring to FIG. 3, a thin film switching transistor 40, comprised 
of a FET, is provided for each red and green pixel electrode 16. FET 40 is 
also provided for each of the two blue pixel electrodes 16 of each triad 
22. It is noted that the arrangement of electrodes could be interchanged 
such that it is the green electrodes or the red electrodes 16 which are 
divided in half. Hence, limitation to the exact orientation of colored 
electrodes by color is not to be inferred. As each control line 26 is 
scanned, the respective switching transistors 40, having a gate terminal 
connected thereto, are rendered conductive. The source terminal of each 
switching transistor 40 is connected to an adjacent control line 30, and 
the drain terminal of each switching transistor 40 is connected to the 
adjacent respective pixel electrode 16. Thus, as the respective switching 
transistor 40 is rendered conductive by the adjacent control line 26, the 
pixel information, or voltage on the respective adjacent column signal 
line 30, is provided through the conductive FET to the respective pixel 
electrode 16. Thus, pixel information provided on the signal control lines 
30 are presented only to the pixel electrodes 16 adjacent the scanned row 
control line 26. The pixel information for the bifurcated blue pixel 
electrodes 16 is provided to each of the pixel electrodes, via the 
respective adjacent switching transistor 40. Referring to FIG. 4, an 
alternative embodiment of the present invention is shown. Here, column 
signal line C.sub.2, is only coupled, via a respective switching 
transistor 40, to each of the green pixel electrodes 16 in each adjacent 
column of pixel electrodes. The other two column signal control lines 
C.sub.1 and C.sub.3 are coupled to two different colors of pixel 
electrodes in adjacent columns of pixel electrodes 16. As shown, both 
signal control line C.sub.1 and C.sub.3 are coupled via switching 
transistors 40 to each of the blue and red pixel electrodes 16 in adjacent 
columns. When signal control line C.sub.1 is providing pixel information 
to the red pixel electrodes 16 of the adjacent columns, signal control 
line C.sub.3 is providing pixel information to the blue pixel electrodes 
16. Thus, as the odd row control lines 26 are scanned, pixel information 
for the red pixel electrodes is provided on control line C.sub.1, green 
pixel information is provided on signal control line C.sub.2, and blue 
pixel information is provided on signal control line C.sub.3. When the 
even row control lines 26 are scanned, switching circuit 50 reverses the 
connections of the R and B source lines 51 to the corresponding color 
signal busses 52 and 56 such that signal column line C.sub.1 provides blue 
pixel information to the blue pixels 16 and signal column line C.sub.3 
provides pixel information to the red pixel electrodes 16 in the adjacent 
columns. This arrangement somewhat simplifies the switching circuit 50 and 
control arrangement shown in FIG. 3. One column control, such as C.sub.2, 
line is always dedicated to one color of pixel electrodes 16, wherein the 
other two column signal control lines alternately control the red and blue 
pixel electrodes 16. Again, whether an odd or even row control line 26 is 
being scanned dictates whether switching circuit 50 is routing the red 
pixel signals on R to color signal bus 52 or 56, and whether the blue 
pixel signals on B are being routed to color signal bus 56 or 52. 
Another alternative embodiment of the present invention is shown in FIG. 5. 
Here, each of the two blue pixel electrodes 16 for a particular triad 22 
are electrically connected together via a conductive bridge (80). Only one 
switching transistor 40 is required to provide pixel information from the 
respective signal control line 30 to each of the blue pixel electrodes. 
Thus, only one switching transistor 40 is required for each of the three 
colors of pixel electrodes in a triad 22. In other words, only three 
switching transistors 40 are required for each triad 22. 
Referring now back to FIG. 3, one of the principal features of the present 
invention is that 480 row control lines 26 are used for 720 pixel 
electrodes 16 in each column, with the bifurcated blue electrode being 
considered one electrode. Thus, a standard 480 active line colored video 
signal can be directly mapped onto a display panel structure having 720 
columns of electrodes 16. Further, the 720 pixel electrodes 16 in each 
row, wherein each triad 22 comprises electrodes of two adjacent columns, 
are partitioned such that there are a total of 360 triads of pixels 16 in 
each row which also corresponds to the number of pixel samples per line of 
the video source. Thus, the video source having 480 active colored signal 
control lines with 360 signal source samples can be directly mapped onto 
the display of the present invention. No auxiliary memory or line storage 
components are required. The rotation of the triads 22 by 90.degree. 
provides for a unique display without requiring a "ping-pong" memory. High 
resolution is maintained, the control electronics remain simple and 
manageable, and the current manufacturing techniques can be implemented. 
It is noted that the present matrix architecture could be employed in other 
matrix technologies as well including, but not limited to, EL displays, 
plasma displays, and field emission displays. Hence, limitation to an LCD 
display is not to be inferred. 
This invention has been described herein in considerable detail in order to 
comply with the Patent Statutes and to provide those skilled in the art 
with the information needed to apply the novel principles and to construct 
and use such specialized components as are required. However, it is to be 
understood that the invention can be carried out by specifically different 
equipment and devices, and that various modifications, both as to the 
equipment details and operating procedures, can be accomplished without 
departing from the scope of the invention itself.