Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-26
2002-12-17
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S100000
Reexamination Certificate
active
06496172
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving method suitable for a display which uses a display material such as a liquid crystal and in which display pixels are arranged in a matrix form, and particularly to an alternating current driving method of a liquid crystal panel.
2. Description of the Related Art
In recent years, a technique for manufacturing a semiconductor device in which a semiconductor thin film is formed on an insulating substrate, such as a thin film transistor (TFT), has been rapidly developed. The reason thereof resides in that the demand for a liquid crystal display device (typically, an active matrix type liquid crystal display device) has been increased.
The active matrix type liquid crystal display device displays an image in such a manner that an electric charge going in and out of each of several tens to millions of display pixels arranged in a matrix form is controlled by a switching element of each of the display pixels.
In the present specification, the display pixel indicates a device mainly constituted of a switching element, a pixel electrode connected to the switching element, a liquid crystal, and an opposite electrode disposed opposite to the pixel electrode through the liquid crystal. However, the display pixel in the case of a liquid crystal panel using IPS driving, the display pixel indicates a device mainly constituted of a switching element, a pixel electrode connected to the switching element, a liquid crystal, and a common electrode disposed on the same substrate.
In addition, the common potential in the present specification indicates the potential of the opposite electrode of the display pixel or the potential of the common electrode.
FIG. 2
is a schematic view showing a liquid crystal display device.
FIG. 3A
is a schematic structural view of an active matrix circuit in a liquid crystal panel
101
in FIG.
2
.
In
FIG. 2
, the liquid crystal panel
101
includes a plurality of (N) scanning lines (corresponding to scanning lines A, B, C, D, . . . in
FIG. 3A
) extending in parallel to each other in the horizontal direction (lateral direction), a plurality of (M) signal lines (corresponding to signal lines (
1
), (
2
), (
3
), (
4
), . . . in
FIG. 3A
) extending in parallel to each other in the vertical direction (longitudinal direction) and crossing the scanning lines at right angles, M×N switching elements (TFTS etc.) respectively disposed in the vicinity of each of the crossing portions of the scanning lines and the signal lines, and a pixel electrode
111
connected to each of the switching elements.
In the liquid crystal panel
101
, one end of the scanning line is connected to a gate electrode of each of the switching elements
110
, and the other end is connected to a gate driver circuit
104
(scanning line driver circuit). On the other hand, one end of the signal line is connected to a source electrode of each of the switching elements
110
and the other end is connected to a source driver circuit
105
(signal line driver circuit).
FIG. 3B
shows a display pattern (display pixels of four rows by six columns (A
1
to D
6
)) as a part of a display region.
FIG. 3B
corresponds to the pixel electrodes
111
in FIG.
3
A. That is, the display pixel A
1
is mainly constituted of the switching element
110
disposed at the crossing point of the scanning line A and the signal line (
1
) in
FIG. 3A
, the pixel electrode
111
connected to the switching element, an opposite electrode provided opposite to the pixel electrode, and a liquid crystal existing between the pixel electrode and the opposite electrode.
For simplification,
FIG. 3
shows only the scanning lines A to D, the signal lines (
1
) to (
6
), and the display pixels of four rows by six columns (A
1
to D
6
) forming a part of the display region.
A typical example of display operation of the panel will be described in brief with reference to
FIGS. 3A and 3B
.
First, in accordance with a signal from a shift register circuit or the like (not shown) in the source driver circuit, only a part (pixel A
1
) of the lateral direction (horizontal direction) line of picture information (panel input image signal
203
) is selectively sampled in the signal line (
1
), and its signal potential is applied to the entire of the signal line (
1
). Then a signal potential (turning on the TFT disposed in the vicinity of the crossing place) is applied only to the scanning line A. Only the switching element disposed in the vicinity of the place where the signal line (
1
) and the scanning line A cross with each other is turned on, so that the signal potential of the signal line (
1
) is applied to the pixel electrode. The liquid crystal is driven by the applied signal potential and the amount of transmitted light is controlled, so that a part (picture corresponding to A
1
) of the picture information is displayed on the display pixel A
1
.
Next, while the state in which the display pixel A
1
displays is kept by an auxiliary capacitance or the like, at the next instant, only a part of the lateral direction (horizontal direction) line of the image signal is selectively sampled, and its signal potential is applied to the signal line (
2
) adjacent to the signal line (
1
). In this way, similarly to the display pixel A
1
, a part (picture corresponding to A
2
) of the picture information is displayed on the display pixel A
2
.
Such a display operation is sequentially carried out, so that a part (A
1
, A
2
, A
3
, A
4
, . . . ) of the picture information is sequentially displayed on the first pixel row (row A) in the lateral direction. During this, the scanning line A is applied with a signal which turns on the switching element disposed in the vicinity of each of the places where the scanning line crosses the signal lines.
Subsequently, when writing in all pixels of the first pixel row A in the lateral direction is ended, a signal potential (turning on a switching element disposed in the vicinity of a crossing place) is applied only to the scanning line B. Only a part (pixel B
1
) of the image signal is sampled in the signal line (
1
) and its signal potential is held. In the same way, only the pixel row (row B) corresponding to the second row in the lateral direction is sequentially written. Such a display operation is carried out by the number of pixel rows (N rows), so that one picture (frame) is displayed on the display region.
In addition, after one picture (frame) is displayed, in the liquid crystal display using TFTs or the like as switching elements, in order to prevent deterioration of the liquid crystal material, to eliminate display blur, and to keep display quality, signal potentials in which positive and negative polarities are inverted in one frame (one picture) are normally applied (alternating current driving) to the respective display pixels, while common potential is used as a reference.
These display operations are sequentially repeated and a plurality of pictures are obtained, so that images are displayed on the display region
106
.
Next, the alternating current driving method briefly described in the above will be described in more detail. Incidentally, polarity patterns of display pixels (four rows by six columns) in conventional typical alternating current driving methods are shown in
FIGS. 15A
to
15
B and FIG.
16
A. The polarity patterns of
FIGS. 15A and 15B
and
FIG. 16A
correspond to the display pattern (display pixels of four rows by six columns (A
1
to D
6
)) shown in FIG.
2
B.
In the drawings (
FIG. 1
,
FIGS. 15A and 15B
,
FIG. 16A
, and
FIG. 17A
) showing polarity patterns in the present specification, the common potential is made a reference, and in the case where a signal potential applied to a display pixel is positive, “+” is shown, and in the case of negative, “−” is shown.
In addition, as a scanning system, there is interlaced scanning in which scanning lines of one picture (one frame) are divided into two (two fields) and scanning is carried out, and non-interlaced scannin
Anyaso Uchendu O.
Robinson Eric J.
Robinson Intellectual Property Law Office PC
Saras Steven
Semiconductor Energy Laboratory Co,. Ltd.
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