Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-09-10
2003-07-29
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S087000, C345S102000, C349S162000
Reexamination Certificate
active
06600470
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to driving devices for driving liquid-crystal panels for use with a TFD (Thin Film Diode) driving method, a TFT (Thin Film Transistor) driving method, and a simple-matrix driving method, and to a liquidcrystal device comprising a liquid-crystal panel and a driving device. More particularly, the present invention relates to an device for driving a transflective liquid-crystal panel which comprises a polarizer, a transflector, and a light source. The device being capable of serving dual purposes of a reflective-type such that a display is produced by reflecting external light, and of a transmissive-type such that a display is produced by transmitting light-source light.
2.Description of Related Art
In a conventional transmissive-type liquid-crystal panel using TN (Twisted Nematic) liquid-crystal, STN (Super-Twisted Nematic) liquid-crystal, and the like, generally, relatively satisfactory brightness is obtained by light-source light. On the other hand, in order that the contrast ratio to be sufficient, a construction is employed in which a shading film called a black mask or a black matrix is formed in a net form around an opening area opposing each pixel on an opposite substrate in order to separate each of the adjacent pixels, preventing mixing of colors between the pixels when a color display using color filters is produced, and further, the contrast ratio is increased regardless of a color display and a black-and-white display.
FIGS. 20 and 21
respectively show an enlarged sectional view and an enlarged plan view of the opposite substrate within a screen display area where a shading film which separates each pixel is formed in this manner and color filters of RGB are formed in each pixel. In
FIG. 20
, RGB color filters
501
are formed on the surface of an opposite substrate
500
on a side facing the liquid crystal in such a way that the RGB color filters
501
correspond to each pixel. A shading film
502
made of a shading metal or a shading organic film is formed in the spacing of the opening area of each pixel, that is, in the boundary of the color filters
501
. Further, a transparent electrode
504
is formed on the color filters
501
via an overcoat (OC) layer
503
, which transparent electrode
504
forms a data line or scanning line (in the case of a liquid-crystal panel of a TFD active-matrix driving method, a simple-matrix driving method, or the like), an opposite electrode (in the case of a liquid-crystal panel of a TFT active-matrix driving method), and the like.
As its planar layout, there are the mosaic arrangement, the delta arrangement, and the stripe arrangement, as shown in
FIGS. 21A
,
21
B, and
21
C, respectively. In
FIGS. 21A
,
21
B, and
21
C, shading film
502
a,
502
b,
and
502
c
are formed in the boundary areas (that is, the hatched areas in the figures) of the color filters
501
a,
501
b,
and
501
c,
respectively.
In this type of transmissive-type liquid-crystal panel, the shading films which separate each pixel in this manner makes it possible to generally obtain a very high contrast ratio of, for example, about 100:1. Here, the “contrast ratio” refers to the ratio of the display luminance when a driving voltage is not applied to a liquid crystal, to the display luminance when a driving voltage is applied in the normally white mode, or in the normally black mode.
On the other hand, in a conventional reflective-type liquid-crystal panel using a TN liquid-crystal or a STN liquid-crystal, since the brightness of a display depends on the intensity of external light, generally, a display which is as approximately bright as the brightness in the case of a transmissive-type display cannot be obtained. That is, in a reflective-type liquid-crystal device, insufficient brightness is considered to be more problematical than an insufficient contrast ratio. For this reason, it is a common practice that a shading film is not formed on an opposite substrate like in the case of the above-mentioned transmissive-type liquid-crystal panel.
FIGS. 22 and 23
respectively show an enlarged sectional view and an enlarged plan view of an opposite substrate within a screen display area where a shading film is not formed in this manner and RGB color filters are formed in each pixel. Components which are the same as those in
FIGS. 20 and 21
are given the same reference numerals, and accordingly, descriptions thereof have been omitted.
In the reflective-type liquid-crystal panel, since a shading film which separates each pixel in this manner is not formed, the amount of light which passes through the opposite substrate is increased by an amount corresponding to that in which light is not shielded by the shading film, causing the display to be bright. However, because there is no shading film, mixing of colors occurs when a color display using color filters is made. Also, since leakage of light (loss of white) occurs in the spacing (non-opening area) between opening areas for adjacent pixels regardless of color display and black-and-white display, a contrast ratio of, for example, about 10:1 is obtained.
In the manner as described above, in the case of a reflective-type liquid-crystal panel which produces a display using external light, in a dark environment, the display darkens and becomes difficult to see with a decrease in the amount of light. In contrast, in the case of a transmissive-type liquid-crystal panel, such as the above mentioned, which produces a display using a light source such as a backlight, power consumption is increased by an amount corresponding to the light source regardless of whether it is a bright environment or a dark environment, and the transmissive-type liquid-crystal panel is not suitable, in particular, for a portable display device which is operated by a battery.
Therefore, in recent years, a transflective liquid-crystal panel which can be used for both a reflective-type and a transmissive-type has been developed. This transflective liquid-crystal panel produces, mainly in a bright environment, a reflective-type display by controlling the amount of light which is output from the display screen for each pixel by using an optical element, such as a liquid crystal, a polarized-light separator, and so on, disposed on the light path while external light which enters from the display screen is reflected by a transflective film provided inside the device, whereas, mainly in a dark environment, a transmissive-type display is produced by controlling the amount of light which is output from the display screen for each pixel by using an optical element, such as a liquid crystal, a polarized-light separator, and so on, described above, while light-source light is emitted by a built-in light source, such as a backlight, from the rear side of the transflective film.
A liquid-crystal panel driving device for driving various types of liquid-crystal panels, such as a reflective-type, a transmissive-type, or a transflective-type, constructed in the above manner generally comprises driver circuits, such as data-line driving circuits, and scanning-line driving circuits, which supply a data signal and a scanning signal to a plurality of data lines and a plurality of scanning lines, disposed on a substrate on which liquid-crystal elements are formed, respectively, in such a manner as to correspond to display data. This driver circuit is formed on a substrate on which liquid-crystal elements are formed, or provided externally to the liquidcrystal panel. Also, such a liquid-crystal panel driving device comprises a driver control circuit for controlling the driver circuit by supplying, to the driver circuit, (i) various control signals for controlling a voltage value and a supply timing in a data signal and a scanning signal, and (ii) a data signal of a predetermined format, which corresponds to display data and which is based on display data, and the like. Such a liquid-crystal panel driving device further comprises a control power supply circuit for supplying various contro
Chow Dennis-Doon
Oliff & Berridg,e PLC
Seiko Epson Corporation
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