Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-11-10
2002-12-10
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S096000
Reexamination Certificate
active
06492970
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display. More particularly, it relates to a TFT liquid crystal display that allows display of high picture quality to be embodied with the use of a low voltage driving circuit. Also, it relates to the driving circuit therefor.
Referring to FIG.
2
and
FIGS. 3A
,
3
B, the explanation will be given below concerning a conventional TFT liquid crystal display.
FIG. 2
is a block diagram for illustrating the conventional TFT liquid crystal display. Also,
FIGS. 3A
,
3
B illustrate driving waveform diagrams for the conventional liquid crystal display.
In
FIG. 2
, a reference numeral
201
denotes an interface signal including display data and a synchronization signal that are transferred from a system (not illustrated). A numeral
202
denotes an interface circuit for generating display data and control signals that drive the conventional liquid crystal display. A numeral
203
denotes a signal driving circuit for generating a tone voltage corresponding to the display data. A numeral
204
denotes a scan driving circuit for selecting scanning lines in sequence. A numeral
205
denotes a power supply circuit for generating a power supply necessary for the operation of each block. Also, a numeral
206
denotes a liquid crystal panel on which there is executed a display corresponding to the display data inputted.
Of the signals that the interface circuit
202
generates, a numeral
207
denotes a control signal that controls the signal driving circuit
203
and includes the display data and the synchronization signal. A numeral
208
denotes a control signal that controls the scan driving circuit
204
and transfers a timing signal for scanning the scanning lines in sequence. A numeral
209
denotes a liquid crystal-applying voltage alternating signal “M” that is transferred to the power supply circuit
205
.
Of the signals that the power supply circuit
205
generates, a numeral
210
denotes a tone voltage signal transferred to the signal driving circuit
203
. The tone voltage signal
210
transfers a voltage that functions as a reference voltage of the tone voltage corresponding to the display data transferred to the liquid crystal panel
206
. A numeral
211
denotes a scanning voltage signal transferred to the scan driving circuit
204
. A numeral
212
denotes an opposed electrode voltage feeding line that transfers an opposed electrode voltage “Vcom” to an opposed electrode of a liquid crystal
217
and an opposed electrode of a compensation capacitor
218
. Here, the liquid crystals
217
and the compensation capacitors
218
constitute the liquid crystal panel
206
. Moreover, a numeral
213
denotes a group of signal lines for transferring the tone voltage corresponding to the display data generated in the signal driving circuit
203
. A numeral
214
denotes a group of scanning lines for transferring a scanning voltage that switches, into a selection or a non-selection state, each of the scanning lines generated in the scan driving circuit
204
. A numeral
215
denotes pixels constituting the liquid crystal panel
206
. The pixels
215
are formed at the intersection points of the group of signal lines
213
and the group of scanning lines
214
, and thus the liquid crystal panel
206
, eventually, has a matrix structure. Also, the numbers of the pixels
215
in the horizontal and the vertical directions are equivalent to the horizontal and the vertical resolutions. Incidentally, in general, in the case of a color liquid crystal display, the three primary colors, i.e., red, green and blue colors, constitute one pixel thereof. Accordingly, when the respective color pixels are arranged in the horizontal direction, the number of the pixels in the horizontal direction becomes equal to 3 times as large as the horizontal resolution. Also, the configuration employed commonly is that the pixels
215
arranged in the horizontal direction share one scanning line of the group of scanning lines
214
and the pixels
215
arranged in the vertical direction share one signal line of the group of signal lines
213
. Furthermore, reference numerals within each of the pixels
215
denote the following components:
216
a thin film transistor (hereinafter, referred to as “TFT”), i.e., a switching element,
217
the liquid crystal,
218
the compensation capacitor,
219
a source electrode,
220
a between-gate/source parasitic capacitor configured between the scanning line (this is also referred to as “gate line”)
214
and the source electrode
219
.
In
FIGS. 3A
,
3
B, reference notations Vg(n), Vg(n+1) denote, of the group of scanning lines
214
illustrated in
FIG. 2
, driving waveforms of scanning lines that drive the nth line and the (n+1)th line, respectively. In addition, a notation Vgon denotes a selection voltage level, and a notation Vgoff denotes a non-selection voltage level. The notation Vcom indicates an ideal driving waveform of the opposed electrode voltage feeding line
212
, and a notation Vcomh denotes a high electric potential voltage level and a notation VcomL denotes a low electric potential voltage level. A notation Vd indicates the tone voltage of the group of signal lines
213
. When, with reference to the opposed electrode voltage Vcom, the tone voltage Vd is positioned on the negative polarity side, a voltage with negative polarity is applied to the pixel
215
. Conversely, when the tone voltage Vd is positioned on the positive polarity side, a voltage with positive polarity is applied to the pixel
215
. In the liquid crystal display, the electric potential difference between the opposed electrode voltage Vcom and the tone voltage Vd becomes equal to an effective voltage value applied to the liquid crystal
217
. The effective voltage value causes the liquid crystal display to operate in such a manner that the luminance thereof is varied. Moreover, in the present embodiment, the explanation will be given based on the following characteristic: If the electric potential difference between the opposed electrode voltage Vcom and the tone voltage Vd is small, the display becomes a dark display (the example: black display) and if the electric potential difference is large, the display becomes a light display (the example: white display). In
FIGS. 3A
,
3
B, the drain voltage Vd is the tone voltage executing the white display, and a notation VdWH denotes a white display drain voltage with positive polarity, and a notation VdWL denotes a white display drain voltage with negative polarity. When, with reference to the opposed electrode voltage Vcom, the drain voltage is positioned on the negative polarity side, an effective voltage value Vrms
1
is applied to the pixel. Conversely, when the drain voltage is positioned on the positive polarity side, an effective voltage value Vrms
2
is applied to the pixel.
Referring to
FIG. 2
once again, the detailed explanation will be given below concerning the operation of the conventional TFT liquid crystal display.
The interface circuit
202
inputs the display data and the synchronization signal transferred by the interface signal
201
. Then, the interface circuit
202
generates and outputs the control signal
207
to the signal driving circuit
203
, the control signal
208
to the scan driving circuit
204
, and the liquid crystal-applying voltage alternating signal M
209
to the power supply circuit
205
. The signal driving circuit
203
fetches in sequence the display data by the amount of one horizontal line, using the display data and the synchronization signal transferred by the control signal
207
. Then, after fetching the display data by the amount of one horizontal line, the signal driving circuit
203
outputs, simultaneously from the group of signal lines
213
, the tone voltage corresponding to the fetched display data by the amount of one horizontal line. The signal driving circuit
203
continues outputting the tone voltage by the amount of one horizontal line during one horizontal time-period. Also, at this time,
Furuhashi Tsutomu
Mamba Norio
Nakayoshi Yoshiaki
Ono Kikuo
Ooishi Yoshihisa
Antonelli Terry Stout & Kraus LLP
Eisen Alexander
Hitachi , Ltd.
Hjerpe Richard
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