Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-03-13
2004-02-24
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S031000
Reexamination Certificate
active
06697035
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-094567, filed Mar. 30, 2000; and No. 2000-094875, filed Mar. 30, 2000, the entire contents of both of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a display device and, more particularly, to a moving-film display device.
Recently, low power consumption is required in large display devices or in portable display devices. One display device which accomplishes this low power consumption is a moving-film display device which drives a moving film electrode by electrostatic force. Jpn. Pat. Appln. KOKAI Publication Nos. 8-271933 and 11-95693 disclosed moving-film display devices of this type.
As shown in
FIG. 15
, a moving-film display device has a pixel matrix, i.e., an array, defined by rows and columns of a plurality of pixels. As shown in
FIG. 15
, each pixel has a moving film electrode
11
, a fixed portion
12
, and a counter electrode
13
. The moving film electrode
11
and the fixed portion
12
are connected to a signal line
41
, and the counter electrode
13
is connected to an address line
42
. The upper end portions of the moving film electrode
11
and the fixed portion
12
are colored in first and second different colors, e.g., black and white. The display color of each pixel is determined in accordance with whether or not the moving film electrode
11
bends by electrostatic force on the basis of a potential difference between the moving film electrode
11
and the counter electrode
13
(a potential difference between a signal potential and a counter potential).
As will be described later, the material of the moving film electrode
11
is so selected that the electrode
11
has hysteresis characteristics. Therefore, the moving film electrode
11
has stable states at positions where it is attracted to the fixed portion
12
and where it is attracted to the counter electrode
13
, i.e., the moving film electrode
11
has bistability similarly to, e.g., a ferroelectric liquid crystal. This allows each pixel to display an image by driving the address line
42
for applying a voltage to the counter electrode
13
and driving the signal line
41
for applying a voltage to the moving film electrode
11
and the fixed portion
12
.
A moving-film display device can also be driven by using a latch circuit
51
as shown in FIG.
16
. That is, this latch circuit
51
with memory properties has first and second switches
52
and
53
which can be turned on and off. When the first switch
52
is turned on, a moving film electrode
11
and a fixed portion
12
are given a potential from a constant-potential line
54
having a predetermined potential. When the second switch
53
is turned on, the moving film electrode
11
and the fixed portion
12
are given a potential from a ground line
55
. The constant-potential line
54
supplies a potential different from that of the ground line
55
. Since a counter electrode
13
is given a potential from the ground, the moving film electrode
11
can be selectively bent by driving the latch circuit
51
of a corresponding pixel, thereby displaying an image.
Unfortunately, these conventional moving-film display devices have the following problems.
First, in the driving method using the simple matrix circuit shown in
FIG. 15
, when one pixel is selected and applied with a signal potential, the moving film electrode must bend to come in contact with the counter electrode or the bent moving film electrode must come in contact with the fixed portion before the next pixel is driven. For example, if a signal potential is applied to a second pixel connected to the same signal line as a first pixel before the moving film electrode of the first pixel finishes moving, this signal potential for the second pixel may cause the first pixel to behave in a way different from that obtained by the signal for the first pixel. After the moving film electrode comes in contact with either electrode, the signal is stably held because the moving film electrode has hysteresis characteristics. Accordingly, the drive time of one pixel must be longer than at least the time required to move the moving film electrode. This makes it impossible to realize a high-resolution display device or a display of motion images by shortening the time for driving one pixel.
The driving method using the latch circuit as shown in
FIG. 16
requires one storage circuit for each pixel. Since this increases the number of constituent elements, the method cannot be realized at low cost. Additionally, since the structure is complicated by the use of one storage circuit for each pixel, fine pixels are difficult to form. Therefore, no small high-resolution display device can be realized.
A method of performing a gradation display in the moving-film display device will be described next. The basic operation of the moving-film display device is a binary display scheme having a state in which the moving film electrode bends and a state in which it does not. Hence, gradation display methods proposed so far are the following two methods.
The first method is a dither method which performs dot area modulation by forming one pixel from a plurality of elements, assuming that a set of the moving film electrode
11
, the fixed portion
12
, and the counter electrode
13
is one element. That is, one pixel is formed by n elements, and (n+1) gradation levels are displayed by turning on some of these elements.
The second method is a frame rate control (FRC) method which switches a display state and non-display state by dividing a time, during which an image is displayed once by supplying a signal to one pixel, into a plurality of units. That is, the time during which an image is displayed once by supplying a signal to one pixel is equally divided into n portions, and (n+1) gradation levels are displayed by turning on some of these portions.
Unfortunately, these gradation display methods have several problems.
In the dither method, one pixel is formed by a plurality of elements described above. Since, therefore, the size of one pixel cannot be unlimitedly decreased, a high-resolution display device is difficult to form. Also, even if small elements can be formed, the number of lines such as signal lines increases, and this makes the formation difficult.
In the FRC method, the time during which an image is displayed once by supplying a signal to one pixel is equally divided into n portions. Since this shortens the switching time, the signal frequency rises to make high-resolution images difficult to display. Additionally, when a large display device is formed, the wiring length increases, and this increases the possibility of occurrence of signal delays. High signal frequency of the FRC method is further problematic because the number of pixels also increases.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a moving-film display device having high resolution and capable of displaying motion images.
It is another object of the present invention to provide a display device capable of performing a gradation display even when high-resolution images are to be displayed or even when the display device is large.
According to a first aspect of the present invention, there is provided a moving-film display device comprising:
a pixel matrix defined by rows and columns of a plurality of pixels, each of the pixels comprising
first and second electrodes, one of the first and second electrodes being a moving film electrode capable of bending, at least its end portion having a colored portion, the other of the first and second electrodes being a counter electrode which opposes the moving film electrode, and
a switch connected to the first electrode;
a plurality of signal lines, each connected to the switches of pixels arranged in a raw in order to supply an image signal, for driving the first electrodes;
a signal line driver configured to selectively supp
Itoh Goh
Lang Richard
Okumura Haruhiko
Sugahara Atsushi
Anyaso Uchendu O.
Saras Steven
LandOfFree
Display device and moving-film display device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Display device and moving-film display device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Display device and moving-film display device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3320929