Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-06-23
2004-10-26
Liang, Regina (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S089000, C345S097000, C345S098000, C345S690000
Reexamination Certificate
active
06809717
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a display apparatus, particularly by a liquid crystal display apparatus including a liquid crystal device for use in light-valves for flat-panel displays, projection displays, printers, etc., and a driving method for the (liquid crystal) display apparatus.
As a type of a nematic liquid crystal display device used heretofore, there has been known an active matrix-type liquid crystal device wherein each pixel is provided with an active element (e.g., a thin film transistor (TFT)).
As a nematic liquid crystal material used for such an active matrix-type liquid crystal device using a TFT, there has been presently widely used a twisted nematic (TN) liquid crystal as disclosed by M. Schadt and W. Helfrich, “Applied Physics Letters”, Vol. 18, No. 4 (Feb. 17, 1971), pp. 127-128.
In recent years, there has been proposed a liquid crystal device of In-Plain Switching mode utilizing an electric field applied in a longitudinal direction of the device, thus improving a viewing angle characteristic being problematic in TN-mode liquid crystal displays. Further, a liquid crystal device of a super twisted nematic (STN) mode without using the active element (TFT etc.) has also be known as a representative example of the nematic liquid crystal display device.
Accordingly, the nematic liquid crystal display device includes various display or drive modes. In any mode however, the resultant nematic liquid crystal display device has encountered a problem of a slow response speed of several ten milliseconds or above.
In order to solve the above-mentioned difficulties of the conventional types of nematic liquid crystal devices, a liquid crystal device using a liquid crystal exhibiting bistability (“SSFLC”, Surface Stabilized FLC), has been proposed by Clark and Lagerwall (Japanese Laid-Open Patent Application (JP-A) 56-107216, U.S. Pat. No. 4,367,924). As the liquid crystal exhibiting bistability, a chiral smectic liquid crystal or a ferroelectric liquid crystal (FLC) having chiral smectic C phase (SmC*) is generally used. Such a chiral smectic (ferroelectric) liquid crystal has a very quick response speed because it causes inversion switching of liquid crystal molecules by the action of an applied electric field on spontaneous polarizations of their liquid crystal molecules. In addition, the chiral smectic liquid crystal develops bistable states showing a memory characteristic and further has an excellent viewing angle characteristic. Accordingly, the chiral smectic liquid crystal is considered to be suitable for constituting a display device or a light valve of a high speed, a high resolution and a large area.
In recent years, as another liquid crystal material, an antiferroelectric liquid crystal showing tristability (tristable states) has caught attention. Similarly as in the ferroelectric liquid crystal, the antiferroelectric liquid crystal causes molecular inversion switching due to the action of an applied electric field on its spontaneous polarization, thus providing a very high-speed responsiveness. This type of the liquid crystal material has a molecular alignment (orientation) structure wherein liquid crystal molecules cancel or counterbalance their spontaneous polarizations each other under no electric field application, thus having no spontaneous polarization in the absence of the electric field.
The above-mentioned ferroelectric and antiferroelectric liquid crystal causing inversion switching based on spontaneous polarization are liquid crystal materials assuming smectic phase (chiral smectic liquid crystals). Accordingly, by using these liquid crystal materials capable of solving the problem of the conventional nematic liquid crystal materials in terms of response speed, it has been expected to realize a smectic liquid crystal display device.
As described above, the (anti-)ferroelectric (or chiral smectic) liquid crystal having a spontaneous polarization has been expected to be suitable for use in displays exhibiting a high-speed response performance in the near future.
In the case of the above-mentioned device (cell) using the (anti-)ferroelectric liquid crystal exhibiting bistability or tristability, however, it has been difficult to effect a gradation display in each pixel based on its display principle.
In recent years, in order to allow a mode of controlling various gradation levels, there have been proposed liquid crystal devices using a specific chiral smectic liquid crystal, such as a ferroelectric liquid crystal of a short pitch-type, a polymer-stabilized ferroelectric liquid crystal or an anti-ferroelectric liquid crystal showing no threshold (voltage) value. However, these devices have not been put into practical use sufficiently.
On the other hand, with respect to a liquid crystal display apparatus, it has been clarified by recent studies that it is difficult to attain a sufficient human-sensible high-speed motion picture response characteristic only by simply increasing a response speed of a liquid crystal portion of a conventional liquid crystal device (using a nematic TN or STN) mode)(as described in, e.g., “Shingaku Giho” (Technical Report of IEICD), EID 96-4 (1996-06, p. 19).
According to results of these studies, it has been concluded that a scheme wherein a time aperture (opening) rate is decreased to at most 50% by using a shutter or a double-rate display scheme is effective in improving motion picture qualities as a scheme by which a human-sensible high-speed motion picture responsiveness is provided.
However, in the conventional nematic (display) mode, the response speed of a liquid crystal is insufficient, thus failing to be applied to the above motion picture display schemes. Further, in order to realize the high-speed motion picture display as described above by using the conventionally proposed high-speed responsive chiral smectic liquid crystal devices including those using a ferroelectric liquid crystal of a short pitch-type or a polymer-stabilized type and a threshold-less antiferroelectric liquid crystal, any (chiral) smectic mode is accompanied with difficulties, such as complicated driving method and peripheral circuits, thus leading to an increase in production cost. Even when a time aperture rate is completely set to 50% or below, the entire display device (apparatus) is also correspondingly decreased in brightness of 50% or below. As a result, it is clear that the resultant display device causes a lowering in (display) luminance.
In recent years, it has been desired to effect full-color display using a liquid crystal device. As one of methods for effecting full-color display, there has been known a method wherein a liquid crystal device is irradiated with respective color lights (e.g., red light, green light and blue light) in succession to effect switching of liquid crystal molecules under the respective color light irradiations. Even in such a liquid crystal device, however, if the time aperture rate is decreased to at most 50% as described above, the resultant liquid crystal device is similarly accompanied with a (display) luminance lowering problem.
More specifically,
FIG. 19
is a block diagram of a conventional liquid crystal apparatus.
Referring to
FIG. 19
, the liquid crystal apparatus includes a liquid crystal device (panel)
80
, a color light source
101
capable of emitting respective color lights (of red (R), green (G) and blue (B)) and a color light source driving unit
102
for driving the color light source
101
based on synchronizing signals.
The liquid crystal device
80
shown in FIG.
19
includes 480 scanning lines supplied with scanning (data) signals X
001
to X
480
, respectively, through a Y-driver
92
. These X- and Y-drivers
91
and
92
are driven by applying a drive voltage carrying drive signals. The synchronizing signals supplied to the color light source driving unit are separated from the drive signals.
FIG. 20
is a time chart for illustrating a driving method of the conventional liquid crystal apparatus shown in FIG.
19
.
Referring to
FIG. 2
Asao Yasufumi
Isobe Ryuichiro
Mori Shosei
Moriyama Takashi
Terada Masahiro
Canon Kabushiki Kaisha
Dinh Duc Q
Fitzpatrick ,Cella, Harper & Scinto
Liang Regina
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