Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2000-01-04
2003-02-11
Le, Que T. (Department: 2811)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C257S676000, C257S443000, C349S150000, C250S214100
Reexamination Certificate
active
06518557
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a two-dimensional image detector, which includes connecting terminals (input/output terminals, mainly input terminals in a display device) for connecting electrode wires of an active-matrix substrate to the outside, and which is connected to the outside via an anisotropic conductive adhesive, and further concerns an active-matrix substrate and a display device. To be specific, the present invention relates to an active-matrix substrate which can be readily connected to the outside at a low temperature and maintain a resistance value at a fixed value, a two-dimensional image detector using the same, and a display device.
BACKGROUND OF THE INVENTION
Conventionally, a two-dimensional image detector for radiation has been known with the following construction: semiconductor sensors, each being provided with a semiconductor layer, a pixel electrode, and others for detecting an X-ray and generating electric charge (electron-hole pair, namely, with photoconductivity), are two-dimensionally disposed in a matrix form (in column and row directions), each of the pixel electrodes is provided with a switching element, and the electrical switches are successively turned on for each raw and the electric charge is read for each column.
A specific structure and principle of such a two-dimensional image detector are described in “D. L. Lee, et al., ‘A New Digital Detector for Projection Radiography’, SPIE, 2432, pp. 237-249, 1995” (published in 1995), “L. S. Jeromin, et al., ‘Application of a-Si Active-Matrix Technology in a X-ray Detector Panel’, SID 97 DIGEST, pp. 91-94, 1997” (first edition is published in May, 1997), and Japanese Laid-Open Patent Publication No. 342098/1994 (Tokukaihei 6-342098, published on Dec. 13, 1994).
The following explanation describes the structure and principle of a typical two-dimensional image detector for radiation.
FIG. 6
is a schematic diagram showing the construction of the two-dimensional image detector for radiation. Further,
FIG. 7
is a schematic diagram showing a sectional structure for one pixel of the two-dimensional image detector for radiation.
As shown in
FIGS. 6 and 8
, the two-dimensional image arc detector for radiation is provided with an active-matrix substrate
51
having electrode wires (gate electrode group
52
consisting of a plurality of gate electrodes G
1
, G
2
, G
3
, . . . , and Gn and source electrode group
53
consisting of a plurality of source electrodes S
1
, S
2
, S
3
, . . . , and Sn) in an XY matrix form, a TFT(thin film transistor)
54
and a storage capacitor(Cs)
55
, on a glass substrate. Moreover, input/output terminals are disposed on ends(not shown) of the active-matrix substrate
51
. Furthermore, a photoconductive film
56
, a dielectric layer
57
, and an upper electrode
58
are formed on virtually the entire surface of the active-matrix substrate
51
.
The storage capacitor
55
has a construction in which a Cs electrode
59
is opposed via an insulating film
61
to a pixel electrode
60
connected with a drain electrode of the thin-film transistor
54
.
For the photoconductive film
56
(amorphous semiconductor layer), a semiconductive material is used to generate electric charge (electron-hole pair) by exposure to radiation such as an X-ray. According to the aforementioned literatures, amorphous selenium(a-Se) is used as a semiconductor material, which has high dark resistance and favorable photoconductivity and can form a large film by evaporation. The photoconductive film(a-Se)
56
is formed with a thickness of 300~600 &mgr;m by using a vacuum evaporation method.
Further, an active-matrix substrate, which is formed in a manufacturing process of a liquid crystal display device, can be applied to the aforementioned active-matrix substrate
51
. For example, the active-matrix substrate used for an active matrix liquid crystal display device (AMLCD: Active Matrix LCD) is provided with the TFT made of amorphous silicon(a-Si) or polysilicon(p-Si), an XY matrix electrode, and a storage capacitor. Therefore, only if a few changes are made in arrangement, the active-matrix substrate can be used for the two-dimensional image detector for radiation.
The following explanation describes a principle of operations of the two-dimensional image detector for radiation having the above-mentioned structure.
Electric charge (electron-hole pair) is generated in the photoconductive film
56
when the photoconductive film
56
such as an a-Se film is exposed to radiation. As shown
FIGS. 6 through 8
, the photoconductive film
56
and the storage capacitors(Cs)
55
are electrically connected in series with each other; thus, when voltage is applied between the upper electrode
58
and the Cs electrode
59
, electric charge (electron-hole pair) generated in the photoconductive film
56
moves to a positive electrode side and a negative electrode side. As a result, the storage capacitors(Cs)
55
stores electric charge. Further, an electron blocking layer
62
made of a thin insulating layer is formed between the photoconductive film
56
and the storage capacitor(Cs)
55
. The electron blocking layer
62
acts as a blocking photodiode for preventing electric charge from being injected from one side.
With the above-mentioned effect, the thin-film transistor(TFT)
54
is turned on in response to input signals of gate electrodes G
1
, G
2
, G
3
, . . . , and Gn so that the electric charge stored in the storage capacitors(Cs)
55
can be applied to the outside from source electrodes S
1
, S
2
, S
3
, . . . , and Sn. The gate electrode group
52
and the source electrode group
53
, the TFT
54
, the storage capacitors
55
, and the like are made in a matrix form; therefore, it is possible to obtain two-dimensional image information of an X-ray by on lines sequentially scanning signals inputted to gate electrodes G
1
, G
2
, G
3
, . . . , and Gn.
Additionally, in the case when the used photoconductive film has photoconductivity for a visible ray and an infrared ray as well as for the radiation such as an X-ray, the above-mentioned two-dimensional image detector for radiation acts as a two-dimensional image detector for detecting the visible ray and the infrared ray. For example, the a-Se film has favorable photoconductivity to a visible ray, and an image sensor with a high sensitivity has been developed by using an avalanche effect of applying a high electric field.
Incidentally, the two-dimensional image detector for radiation is provided (packaged) with a “driving circuit” (driving IC) for applying a driving voltage for the switching element (TFT) to the gate electrode group
52
and the source electrode group
53
on ends of the active-matrix substrate
51
, and a “reading circuit” (reading IC) for reading information on an image. Upon mounting (packaging) these circuits, TCP (Tape Carrier Package) method and COG (Chip on Glass) method are mainly used.
FIG.
9
(
a
) shows an example of an arrangement of package in accordance with TCP method. In TCP method, a wire pattern is formed by copper foil and the like on a TCP substrate
67
having a base film made of a material such as polyimide, and electric members including a driving IC
65
and a reading IC
66
are mounted thereon. One end of the TCP substrate
67
is connected to input/output terminals (not shown) disposed on ends of the active-matrix substrate
51
, and the other end is connected to an external circuit substrate (PWB: Printed Wiring Board)
68
.
Further, FIG.
9
(
b
) shows an example of an arrangement in accordance with COG method. In this method, the driving IC
65
and the reading ID
66
are directly mounted and connected onto the active-matrix substrate
51
(namely, glass substrate) of the two-dimensional image detector for radiation. Additionally, power and a signal is inputted and outputted to the driving IC and the reading IC
66
by using an FPC (Flexible Printed Circuit) substrate
69
. Moreover, as an application of COG method, it is possible to form the driving IC
65
and the reading IC
66
in a mon
Izumi Yoshihiro
Teranuma Osamu
Le Que T.
Luu Thanh X.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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