Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-07-16
2002-05-21
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S031000, C345S075200, C345S055000, C345S060000, C349S041000
Reexamination Certificate
active
06392618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix device which incorporates two-dimensional matrix pixels arranged to be operated by an active matrix method, and more particularly to an active matrix device which enables a switching operation to be performed without use of a MOS semiconductor switch section and which are arranged for use in a two-dimensional image pickup device, a light modulating device, an exposing device and a display device.
2. Description of the Related Art
An active matrix device is known which incorporates two-dimensional matrix pixels which are operated by the active matrix method. The active matrix device is used in, for example, a MOS 2D image pickup device, an LCD, a thin-film EL device and an organic EL device.
An active matrix device of a type for use in the MOS 2D image pickup device incorporates a photodetecting device and a MOS transistor for switching the photodetecting device, provided for each pixel section. In the foregoing case, the active matrix device causes the photodetecting device of each pixel to photoelectrically convert light of the image so as to accumulate charges. The charges are scanned through the MOS transistors in a row-sequential manner so that the accumulated charges are extracted. Thus, serial electric signals are extracted to the outside.
The active matrix device is, as described above, used in the light modulating device, the exposing device and the display device for the LCD, the thin-film EL device and the organic EL device.
FIG. 30
shows an example of the active matrix LCD. As shown in
FIG. 30
, the active matrix device incorporates a light function device
1
, such as the light modulating device, the exposure device or the display device, and a MOS transistor
3
which are provided for each of pixels disposed in a matrix configuration. In the foregoing case, the active matrix device applies scanning pulse voltages Vg in the row-sequential manner to simultaneously turn the connected MOS transistors
3
on. In synchronization with this, data signal voltages Vb are applied to the image electrodes in the column direction. Thus, scanning is performed through the MOS transistor
3
so that charges are accumulated in the static capacitor of each pixel. After scanning of one row has been completed, the MOS transistors
3
are turned off. Thus, the charges accumulated in the capacitors are maintained. In response to data signals based on the accumulated charges, the light function devices
1
are operated so that modulation of light, exposure or display is performed.
The conventional active matrix devices is not substantially affected by the number of rows (the number of scanning lines) and capable of moving precise image with an excellent quality.
However, the active matrix device incorporating the conventional MOS semiconductor transistor of a type made of a-Si:H (amorphous silicon), poly-Si (polycrystalline silicon) or c-Si (crystal silicon) has the foregoing problems.
That is, a large number of patterning processes must be performed. Moreover, a film forming process and a process for doping impurities peculiar to the process for manufacturing the semiconductor regions must be performed. Therefore, a severe design condition has been required. As a result, the throughput and manufacturing yield deteriorate. Thus, enlargement of a device formation area cannot easily be realized with a low cost.
An attempt has been made that the patterning step is completed by a (screen) printing process in order to enlarge the device formation area and reduce the producing cost. However, the accuracy and quality under present circumstances are not sufficient. Therefore, the printing process has not been realized yet.
A TFT incorporating a glass substrate on which a-Si:H or poly-Si is formed easily encounters dispersion of electrons and positive holes which move in the semiconductor owning to lattice defects (impurities, vacancies and dislocations). Therefore, only a poor carrier mobility is permitted. Thus, a display device in the form of a precise and large-area structure which must respond at higher response suffers from reduction in the speed of response. Although use of c-Si free from considerable dispersion enables the speed of response to be raised, c-Si cannot easily be formed on the glass substrate which is a low cost substrate.
It is required to form the semiconductor films, while maintaining severe process conditions. Espetially on forming a junction, the impurity densities of both semiconductor films between which the junction is formed, must severely administered.
Since the TFT is a semiconductor device, there arises a problem in that a malfunction occurs owning to incidence of light and introduction of water, oxygen, ions and an organic material from outside. To prevent the malfunction, a light shielding film and/or a protective layer must be formed. Therefore, the design conditions and processing conditions are furthermore limited.
The following mechanically-conductive switch has been disclosed in the following document:
(1) Micromechanical Membrane Switches on Silicon, IBM J, RES. DEVELOP., VOL. 23, No. 4, JULY 1979, pp. 376-385.
In the foregoing document, as shown in
FIG. 31
which is a plan view showing a matrix device and
FIG. 32
which is a cross sectional view taken along line E—E, a mechanical switch has been suggested. That is, the matrix device operating switches comprising the transistors and non-linear devices which are replaced by plate springs are employed. Each plate spring has either end which is secured is displaced by static electric force. Thus, contact/separation of the contact point provided for the leading end of the plate spring is used. In the foregoing structure, the plate spring is formed by a thin SiO
2
film formed on a silicon substrate. The contact portion is made of a metal material such as gold.
Also a matrix type display device has been disclosed in the foregoing document. When a required data signal is written on a pixel electrode, a voltage is applied between a scanning-signal electrode and a P
+
silicon layer disposed below the scanning-signal electrode. Thus, the contact electrode, the data-signal electrode and the pixel electrode are made electrical contact with one another. As a result, a required potential is applied from the data-signal electrode to the pixel electrode. When the voltage between the scanning-signal electrode and the P
+
silicon layer is made to be zero, the contact of the foregoing electrode is separated. Thus, the data-signal electrode and the pixel electrode are made to be non-contact with each other. As a result, the potential of the pixel electrode can be maintained.
However, the mechanical switch, which has the above-mentioned structure in which either end is secured and, therefore, a cantilever spring structure is realized, has a possibility that mechanical bounds occur when contact/separation is performed. To prevent this, the structure and the operating voltage must delicately be adjusted. Therefore, the design freedom of the device is restrained.
As can be understood from the plan view, the plate spring requires a great area. Therefore, the rate of opening is reduced. To raise the speed of response by lowering the voltage for operating the switch, the length of the plate spring must be elongated. In this case, the foregoing problems become more critical.
Since the structure disclosed in the foregoing document incorporates the Si substrate, the structure is made to be an opaque structure with respect to visible light. Therefore, the foregoing structure is not suitable to serve as a transmission-type light modulating device. Moreover, enlargement of the area cannot easily be realized.
In addition, only the reflecting-type light modulating device has been disclosed. No description has been performed about the light-transmission-type modulating device and the light emitting device.
Another mechanically-conductive switch has been disclosed in the following patent.
(2) U.S. Pat. No. 4,681,403
In th
Fuji Photo Film Co. , Ltd.
Lao Lun-Yi
Sughrue & Mion, PLLC
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