Telephonic communications – Emergency or alarm communications – Responsive to sensed nonsystem condition
Reexamination Certificate
2000-04-03
2002-11-12
Chaudhuri, Olik (Department: 2813)
Telephonic communications
Emergency or alarm communications
Responsive to sensed nonsystem condition
C349S042000, C349S043000, C257S546000
Reexamination Certificate
active
06480577
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image display device such as a liquid crystal display device, to an image capture device such as a flat-panel image sensor, and to an active matrix substrate used in the foregoing devices and a method of manufacturing such an active matrix substrate.
BACKGROUND OF THE INVENTION
Making the most of their superior characteristics including having a large surface area, and being thin and light weight, active matrix substrates can be used not only in image display devices such as liquid crystal display devices, but also in image capture devices such as flat-panel X-ray image sensors.
The following will explain the structure of a conventional active matrix substrate with reference to
FIGS. 6 through 8
.
FIG. 6
is a plan view of a conventional active matrix substrate, showing one of a plurality of pixels provided in the active matrix substrate. Such an active matrix substrate is used to improve aperture ratio in the liquid crystal display devices such as those disclosed in Japanese Unexamined Patent Publication No. 58-172685/1983 (Tokukaisho 58-172685, published on Oct. 11, 1983) and U.S. Pat. No. 5,953,084 (issued on Sep. 14, 1999), and is structured as follows.
A plurality of scanning lines
52
and signal lines
56
are arranged in a lattice form on a glass substrate
51
(see FIGS.
7
and
8
), and a switching element and a pixel electrode
57
are provided for each area where a scanning line
52
and a signal line
56
cross. Each of the switching elements is a thin-film transistor (hereinafter referred to as “TFT”)
60
, in which a gate electrode
55
is connected to the signal line
52
, a source electrode
61
is connected to the signal electrode
56
, and a drain electrode
63
is connected to the pixel electrode
57
via a drain line
63
a
and a contact hole
57
a
. Further, below the contact hole
57
a
is provided an auxiliary capacitance line
53
.
FIGS. 7 and 8
are cross-sectional views of the foregoing conventional active matrix substrate, taken at lines D—D and E—E, respectively, of FIG.
6
. On the insulative glass substrate
51
are provided the scanning line
52
(see FIG.
6
), the gate electrode
55
, which is a branch line of the scanning line
52
, and the auxiliary capacitance line
53
. On the surfaces of these elements oxidation films
52
a
and
53
a
(anodic oxidation (AO) films) are provided by anodic oxidation. Then a gate insulating film
54
is provided on the oxidation films
52
a
and
53
a
on the scanning line
52
and the auxiliary capacitance line
53
, and on areas of the glass substrate
51
where the scanning line
52
and the auxiliary capacitance line
53
are not provided.
Then, on areas of the gate insulating film
54
lying above the gate electrode
55
, a TFT
60
, which is a switching element made up of a semiconductor domain
64
and a contact layer
65
, is provided for each pixel. The source electrode
61
of the TFT
60
is connected to the signal line
56
, which is provided on the gate insulating film
54
extending in a direction perpendicular to a direction in which the scanning line
52
extends. Further, the drain electrode
63
of the TFT
60
is connected to the drain line
63
a
provided on the gate insulating film
54
.
Over the foregoing elements is provided a protective film
58
which covers the TFT
60
(including the source and drain electrodes
61
and
63
), the signal line
56
, the drain line
63
a
, and the gate insulating film
54
. Then an inter-layer insulating film
59
and the pixel electrode
57
are provided over the foregoing elements. The pixel electrode
57
is electrically connected to the drain line
63
a
via a contact hole
57
a
which penetrates the inter-layer insulating film
59
and the protective layer
58
. Further, the drain line
63
a
lies opposite the auxiliary capacitance line
53
, but separated therefrom by the gate insulating film
54
and the oxidation film
53
a
, thus forming an auxiliary capacitance
62
.
The following will explain a flat-panel X-ray image sensor and a liquid crystal display device which use the foregoing active matrix substrate.
In a flat-panel X-ray image sensor, a device intended to replace X-ray photograph devices which use conventional photosensitive photographic film, an image is formed based on a two-dimensional distribution of X-ray quantities incident on a flat panel of the image sensor. When using such a device, an X-ray source is provided separately, and an object to be photographed is placed between the X-ray source and the image sensor.
When an active matrix substrate is used in such a flat-panel X-ray image sensor, as disclosed in Japanese Unexamined Patent Publication No. 4-212458/1992 (Tokukaihei 4-212458, published on Aug. 4, 1992), a photoelectric conversion layer, for converting X-rays to electrical charges, is provided on the pixel electrodes
57
, and the pixel electrodes
57
are used as charge-collecting electrodes. The photoelectric conversion layer is made of a semiconductor element, and this semiconductor element is provided by film formation directly on the pixel electrode
57
, or by laminating thereon a semiconductor element formed separately.
The foregoing flat-panel X-ray image sensor provided with an active matrix substrate operates as follows. A DC current is applied between the pixel electrode
57
and a counter electrode provided above the photoelectric conversion layer. The TFT
60
is OFF except when reading an image, and a charge produced in the photoelectric conversion layer by X-rays incident thereon is collected in the auxiliary capacitance
62
via the pixel electrode
57
. Reading of this charge is performed by selecting the corresponding pixel using the scanning line
52
, and allowing the charge accumulated in the auxiliary capacitance
62
to flow to the signal line
56
via the TFT
60
. Charges read out are amplified by a circuit, such as an operational amplifier, connected to the end of the signal line
56
. Then an image is formed based on the distribution of charge quantities read out from all of the pixels.
When, on the other hand, the foregoing active matrix substrate is used in a liquid crystal display device, a counter electrode is provided opposite the pixel electrodes
57
, with a liquid crystal layer therebetween. Then, by applying a potential difference between a pixel electrode
57
and the counter electrode, light passing through the liquid crystal layer is subject to a rotation of its plane of polarization corresponding to the potential difference. The direction of the plane of polarization of the light determines a quantity of light passing through a polarizing plate provided externally, thus forming an image by the intensity of light in each pixel.
In the active matrix substrate in this case, in a pixel selected by the scanning line
56
, a potential is written to the pixel electrode
57
from the signal line
56
via the TFT
60
. This produces the foregoing voltage between the pixel electrode
57
and the counter electrode.
Electrostatic capacitance parasitic in the lines provided in the active matrix substrate greatly influences the performance of the active matrix substrate. This electrostatic capacitance not only causes delay in transmission of signals inputted to the ends of these lines and of data from the pixels, but also causes the potential of non-target pixels and lines to fluctuate, and makes the potential of target lines susceptible to external influence. A further problem with this electrostatic capacitance is that it impairs the quality of images captured or displayed by the device incorporating the active matrix substrate.
In a flat-panel X-ray image sensor, image data is formed on the basis of charges accumulated in the pixel electrodes
57
, read out through the signal lines
56
. For this reason, electrostatic capacitance (signal line capacitance) between the signal lines
56
and the scanning lines
56
and auxiliary capacitance lines
53
increases the time necessary to read out the charges, and increases the noise c
Izumi Yoshihiro
Nagata Hisashi
Saito Yuichi
Chaudhuri Olik
Nixon & Vanderhye PC
Schillinger Laura
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