Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2001-07-09
2003-05-20
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S2140RC, C345S204000
Reexamination Certificate
active
06566643
ABSTRACT:
Japanese Patent Application No. 2000-209564, filed Jul. 11, 2000, is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electro-optical device, a method of driving the electro-optical device, and an electronic apparatus using the electro-optical device.
2. Description of Related Art
At present, in TFT (thin-film transistor) liquid crystal devices, for example, AC voltage driving methods such as frame inversion driving, line inversion driving, and dot inversion driving are used. Among those driving methods, the dot inversion driving method is a driving method capable of preventing flicker and a luminance gradient. As shown in
FIG. 12A
, the dot inversion driving method is such that the phase is inverted on a pixel-by-pixel basis. The operation of a liquid crystal device using the dot inversion method will be described below by using one particular pixel P(
1
,
1
) as an example.
FIG. 12B
shows how the voltage V
P(1, 1)
of the pixel P (
1
,
1
) varies with time in a case where a data signal voltage +V
1
or −V
1
is applied to the pixel P (
1
,
1
). Symbols t
1
, t
2
, . . . represent the starts of frame periods f
1
, f
2
, . . . and symbol H
1
represents one horizontal scanning period (selection period).
In the frame period f
1
, when the data signal voltage +V
1
is applied to the pixel P (
1
,
1
), the pixel voltage V
P (1, 1)
increases along a charging characteristic curve C
a1
, reaches the data signal voltage +V
1
at a time point t
a1
in the selection period, and is stabilized thereafter. In the frame period f
2
, when the data signal voltage −V
1
is applied to the pixel P (
1
,
1
), the pixel voltage V
P (1, 1)
decreases along a charging characteristic curve C
a2
, reaches the data signal voltage −V
1
at a time point t
a2
in the selection period, and is stabilized thereafter. Since this liquid crystal device employs the dot inversion driving method, the data signal voltage is changed between +V
1
and −V
1
(the polarity is reversed). Every time the frame period is changed, a voltage change of about 2V
1
should occur in the pixel P (
1
,
1
). To cause the voltage change of 2V
1
in the pixel P (
1
,
1
) every time the frame period is changed, charging from −V
1
to +V
1
or from +V
1
to −V
1
should be effected. In the liquid crystal panel, charging to a voltage corresponding to the wiring capacitance of each data line also occurs. This results in a problem that charging a pixel to a predetermined voltage in the selection period becomes more difficult as the distance between the source of the data signal voltages such as a data line driving circuit and the pixel to be charged becomes longer or the screen size of the liquid crystal device becomes larger. This phenomenon is more remarkable when the voltage change to be caused by charging each pixel is larger.
SUMMARY OF THE INVENTION
According to the present invention, in a case where an electro-optical device is driven by the dot inversion driving method, the amplitude of data signal voltages supplied to each pixel can approximately be halved. An objective of the invention is to provide an electro-optical device capable of reducing the power consumption and charging each pixel sufficiently within the selection period, as well as a driving method of such an electro-optical device and an electronic apparatus using such an electro-optical device.
To solve the above problems, the present invention provides an electro-optical device comprising: a plurality of data line pairs extending in a first direction, each of the data line pairs including a first data line to which a data signal of a first polarity is supplied and a second data line to which a data signal of a second polarity is supplied;
a plurality of scanning lines extending in a second direction that intersects the first direction;
a plurality of pixels arranged at intersections of the data lines pairs and the scanning lines;
a scanning line driving circuit which supplies each of the scanning lines with a scanning signal for selecting one of the scanning lines in a selection period; and
a data line driving circuit which includes a data line switching circuit and supplies the first and second data lines of the data line pairs with the data signals of the first and second polarities, respectively,
wherein the data line switching circuit selects one of the first and second data lines of each of the data line pairs alternately along the second direction in a t-th selection period (t is a natural number) of a k-th (k is a natural number) frame period, and then in the (t+1)-th selection period, selects the other of the first and second data lines of each of the data line pairs which has not been selected in the t-th selection period.
The invention also provides a method of driving an electro-optical device,
wherein the electro-optical device comprises:
a plurality of data line pairs extending in a first direction, each of the data line pairs including a first data line to which a data signal of a first polarity is supplied and a second data line to which a data signal of a second polarity is supplied;
a plurality of scanning lines extending in a second direction that intersects the first direction;
a plurality of pixels arranged so as to correspond to intersections of the data lines pairs and the scanning lines;
a scanning line driving circuit which supplies each of the scanning lines with a scanning signal for selecting one of the scanning lines in a selection period; and
a data line driving circuit which supplies the first and second data lines of the data line pairs with the data signals of the first and second polarities, respectively; and
wherein the data line driving circuit selects one of the first and second data lines of each of the data line pairs alternately along the second direction in a t-th selection period (t is a natural number) of a k-th (k is a natural number) frame period, and then in the (t+1)-th selection period, selects the other of the first and second data lines of each of the data line pairs which has not been selected in the t-th selection period.
REFERENCES:
patent: 6025835 (2000-02-01), Aoki et al.
Le Que T.
Oliff & Berridg,e PLC
Seiko Epson Corporation
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