Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-10-27
2004-01-20
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000, C345S092000, C345S098000, C345S099000
Reexamination Certificate
active
06680722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display panel driving method, a display panel driver circuit, and a liquid crystal display device, which are capable of inverting a polarity of a data signal which is applied to respective picture elements of a display panel every predetermined time, i.e., executing the alternating current drive and, more particularly, an active matrix type liquid crystal display panel driving method, a liquid crystal panel driver circuit, and a liquid crystal display device.
2. Description of the Related Art
In recent years, as a display for OA devices such as the notebook computer (mobile PC), etc. as well as various devices such as the digital video camera, the telephone, etc., the liquid crystal display device is rapidly spreading. Such liquid crystal display device is still inferior in screen size, picture quality, cost, etc. to the displaying means such as the CRT (cathode ray tube), etc., nevertheless its excellent features such as low power consumption, light weight, space saving, etc. are watched with interest.
The active matrix type liquid crystal display panel has such a structure that a liquid crystal is sealed between two glass substrates. A plurality of picture element electrodes, which are arranged in the horizontal direction and the vertical direction, and a plurality of switching elements, which turn ON/OFF the voltage applied to the picture element electrodes, are formed on one glass substrate. As the switching element, a thin film transistor (abbreviated as a “TFT” hereinafter) is often employed.
Also, color filters and opposing electrode are formed on the other glass substrate. These two glass substrates are arranged such that a face on which the picture element electrodes are formed and a face on which the opposing electrode are formed are opposed to each other. Three color filters, i.e., red (R), green (G), blue (B) filters are formed as the color filters. The R, G, B color filters are arranged in predetermined sequence to correspond to respective picture element electrodes. The substrate having the TFTs thereon is called a TFT substrate, and the substrate having the opposing electrode thereon is called an opposing substrate.
In addition, a pair of polarizing plates are arranged so as to put the TFT substrate and the opposing substrate, between which the liquid crystal is sealed, between them. Normally, polarizing axes of a pair of polarizing plates are arranged to intersect orthogonally with each other.
FIG. 1
is a block diagram showing an example of a liquid crystal display device in the prior art. As shown in
FIG. 1
, the liquid crystal display device comprises a liquid crystal display panel
501
, a data driver include a plurality of data driver IC
502
, a gate driver include a plurality of gate driver IC
503
, an input controlling portion
505
, and a reference voltage power supply
506
.
A plurality of picture elements (not shown) which are arranged in a matrix, a plurality of data bus lines
502
a
and a plurality of gate bus lines
503
a
, and a plurality of TFTs (not shown) which are connected between the picture elements and the data bus lines
502
a
and the gate bus lines
503
a
respectively are provided to the liquid crystal display panel
501
. The data driver
502
outputs data signals (display data) to the data bus lines
502
a
. The gate driver
503
outputs a predetermined scanning signal to the gate bus lines
503
b in sequence at timings which are in synchronism with the horizontal synchronizing signal. The TFTs are turned ON when the predetermined scanning signal is supplied to the gate bus lines
503
a
to transmit the data signals, which are supplied to the data bus lines
502
a
, to picture element electrodes.
The input controlling portion
505
receives signals such as image signals, synchronizing signals, operating clocks, etc. from a display control information source (referred to as a “personal computer” hereinafter)
504
such as a personal computer, and then outputs the image signals to the data driver
502
at predetermined timings and also supplies the clock signals to the gate driver
503
. The reference voltage power supply
506
supplies reference voltages, which is applied to the picture elements, to the data driver
502
.
FIG. 2
is a block diagram showing a configuration of the input controlling portion
505
of the liquid crystal display device in the prior art.
The input controlling portion
505
is composed of an input interface (I/F) portion
511
, an input data latch circuit
512
, and a data output circuit.
513
. The input I/F portion
511
receives display control information (the image signal, the horizontal, and vertical synchronizing signal, the operation control signal, etc.) from the personal computer
504
, and transmits predetermined signals to the input data latch circuit
512
, the data output circuit
513
, etc. The input data latch circuit
512
holds temporarily the image signals (R, G, B). Also, the data output circuit
513
performs timing control, waveform shaping, etc. of the image signal, and then outputs them to the data driver
502
.
In such configuration, the image data which are received via the input I/F portion
511
are output to the data driver
502
at a predetermined timing via the input data latch circuit
512
and the data output circuit
513
. Based on an inverting period of the reference voltage supplied from the reference voltage power supply
506
, the data driver
502
inverts the polarity of the data signal, which is applied to the picture element, at a predetermined period.
Where the wording “inverting period of the reference voltage” means such an inverting period that the reference voltage being applied between the picture element electrode and the opposing electrode in the liquid crystal display panel repeats a positive polarity voltage and a negative polarity voltage invertedly relative to a common voltage alternatively. Normally, such inverting period of the reference voltage is set to a constant inverting period.
As described above, the active matrix type liquid crystal display panel can be driven by the alternating current voltage. For example, the voltage whose polarity can be changed into a positive polarity (+) and a negative polarity (−) every predetermined time interval with respect to the voltage, which applied to the opposing electrode, is supplied to the picture element electrode. It is preferable that the voltage being applied to the liquid crystal should have a positive voltage waveform and a negative voltage waveform symmetrically. However, even if the alternating current voltage which has the positive voltage waveform and the negative voltage waveform symmetrically is applied to the picture element electrodes, the positive voltage waveform and the negative voltage waveform which are applied actually to the liquid crystal are not formed in a symmetrical manner. Therefore, a transmittance of light obtained when the positive voltage is applied and a transmittance of light obtained when the negative voltage is applied become different. As a result, a luminance is varied in a period of the alternating current voltage being applied to the picture element electrode to thus cause a flicker. This phenomenon is called a flicker.
In the prior art, a method of changing the voltage applied to the opposing electrode, a method of setting the polarity of the voltage applied to the adjacent picture element electrodes differently in the horizontal direction and the vertical direction, and a method of increasing the frequency of the polarity inversion are known as a method of suppressing such flicker. For example, such technologies have been disclosed in Patent Application Publication (KOKAI) Sho 62-113129, Patent Application Publication (KOKAI) Hei 2-34818, Patent Application Publication (KOKAI) Hei 6-149174, Patent Application Publication (KOKAI) Hei 7-175448, and Patent Application Publication (KOKAI) Hei 9-204159.
In case the voltages which has the different polarity are applied to th
Furukoshi Yasutake
Hayashimoto Seiji
Hiraki Katsuyoshi
Ito Takae
Katagawa Koichi
Fujitsu Display Technologies Corporation
Greer Burns & Crain Ltd.
Lewis David L.
Shalwala Bipin
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