Radiant energy – Invisible radiant energy responsive electric signalling – With or including a luminophor
Reexamination Certificate
2000-06-28
2003-09-23
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
With or including a luminophor
C250S370110
Reexamination Certificate
active
06624421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radiation light transducer for transducing a radiation ray like an X-ray Into light, a radiation image pickup device employing the transducer, a radiation image pickup system therefor, and a process for producing the radiation light transducer. In particular, the present invention relates to a radiation light transducer having a water-impermeable member capable of transmitting a radiation ray projected from the outside, a radiation image pickup device employing the transducer, a radiation image pickup system, and a process for producing the radiation light transducer.
2. Related Background Art
A roentogen examination apparatus employed in medical diagnosis should detect precisely an abnormal portion of a patient. Usual roentogen examination apparatuses convert the X-ray transmitted through a patient body or another examination subject into visible light or the like by means of a fluorescent screen, and a film in contact with the screen is exposed to the light. Although this conventional roentogen examination is sufficient in image resolution in a practical level, it has problems such that a long time is necessary from measurement to diagnosis, and the skill and extrasensory perception is required of the rentogenograph specialist for the location of the measurement region.
In recent years, a large-area sensor typified by amorphous silicon are developed to be reliable. By utilizing the merit of the amorphous silicon and the ease of enlarging the area thereof, the amorphous silicon are being developed for real-time roentogen examination with sufficient image contrast to raise the efficiency of abnormality diagnosis of the patient.
Generally, in detection of an X-ray image by a photoelectric transducer, an X-ray visible light transducer is necessary for transducing the radiation, namely the X-ray, to visible light. In the medical field, the transducer should have a large area suitable for roentogen examination of a thorax. A conventional transducer is constructed from a readily available fluorescent screen (a plate containing powdery phosphor) for film exposure with a large-area two-dimensional photoelectric transducer.
The radiation image pickup device which has a two-dimensional photoelectric transducer and a fluorescent screen bonded thereon is explained below.
FIG. 1A
is a schematic plan view of a structure of a radiation image pickup device.
FIG. 1B
is a schematic sectional view of the device taken along line
1
B—
1
B in FIG.
1
A.
In FIG.
1
A and
FIG. 1B
, photoelectric transducer
100
comprises base plate
101
made of glass or the like, element formation region
110
having a photoelectric transducer element or the like formed on base plate
101
, and an electroconductive layer of aluminum or the like for wiring and connection electrode for electric connection with an external power source not shown in the drawing. Fluorescent screen
200
, which is an X-ray visible-light transducer for wavelength conversion, comprises base board
201
made of PET (polyethylene terephthalate) or the like, and X-ray visible-light transducing layer
210
containing a phosphor particles for transducing the X-ray transmitted through base board
201
to visible light.
Photoelectric transducer
100
and X-ray visible-light transducer
200
are prepared respectively by separate processes. They are bonded together by an adhesive not shown in the drawing and fixed to complete the radiation image pickup device
1
.
FIG. 2
is an enlarged sectional view of portion
2
indicated by a closed broken line in FIG.
15
. This example of the photoelectric transducer having a two-dimensional light-receiving region has a base plate
101
made of glass or the like having a large area, and has therein a picture element input portion comprising photoelectric transducing element portion
120
employing amorphous silicon, and thin film transistor element portion
130
, extending two-dimensionally. (Hereinafter, the thin film transistor is referred to as “TFT”.) The X-ray visible-light transducer employs a large-area fluorescent screen containing powdery phosphor.
In
FIG. 2
, photoelectric transducer
100
comprises, on base plate
101
made of glass or the like, photoelectric transducing element portion
120
; TFT element portion
130
, and element formation region
110
having wiring not shown in the drawing for driving the above elements, wiring for image signal readout, connection terminals for connection with external electric circuit, and so forth.
The respective layers constituting photoelectric transducing element portion
120
and TFT element portion
130
are constituted of lower electroconductive layer
102
composed of Cr, insulation layer
103
composed of hydrogenated noncrystalline silicon nitride layer, semiconductor layer
104
composed of an intrinsic hydrogenated noncrystalline silicon layer, n
+
layer
105
composed of n
+
type hydrogenated amorphous silicon, upper electroconductive layer
106
composed of aluminum, and semiconductor protection layer
107
composed of hydrogenated noncrystalline silicon nitride (&agr;-SiN:H) layer. These layers are formed by deposition by CVD, sputtering, vapor deposition or the like process, patterning, and are electrically tested for function confirmation.
The above materials for constituting the layers of photoelectric transducing element portion
120
and TFT element portion
130
are shown as examples only, and are not limited thereto.
X-ray visible-light transducer
200
is produced by forming X-ray visible-light transducing layer
210
by blending powdery phosphor particles
202
with binder
203
, applying the blended matter on base board
201
made of PET or a like material, curing the binder to allow phosphor particles
202
to adhere and to fix on base board
201
.
The obtained photoelectric transducer
100
and X-ray visible-light transducer
200
are bonded by adhesive
300
such as a silicone adhesive and an epoxy adhesive, and the adhesive is cured to prepare a radiation image pickup device.
This radiation image pickup device transduces the X-ray introduced from the side of base board
201
to visible light by X-ray visible-light transducing layer
210
. This visible light is introduced to element formation region
110
on base plate
101
of photoelectric transducer
100
and is transduced to electric signals. This electric signals are read out by TFT element portion
130
on base plate
101
of photoelectric transducer
100
and external drive circuit (not shown in the drawing) to obtain electric signals for two-dimensional X-ray image.
However, base board
201
of X-ray visible-light transducer
200
is made of a moisture-permeable PET (polyethylene terephthalate), and binder
203
constituting the X-ray visible-light transducing layer
210
is a permeable resin. Base board
201
is fixed to element formation region
110
of photoelectric transducer
100
by adhesive
300
with interposition of X-ray visible-light transducing layer
210
.
Therefore, when the radiation image pickup device is kept at a high humidity, base board
201
absorbs moisture, and the moisture is liable to penetrate through X-ray visible-light transducing layer
210
into element formation region
110
. The moisture in element formation region
110
may cause deterioration and variation of characteristics of the photoelectric transducing element or other parts, or may cause disconnection of wiring by corrosion, thereby causing problems in long-term environmental stability of the photoelectric transducer.
Further, X-ray visible-light transducer
200
employs a fluorescent screen prepared by cutting a large fluorescent plate into pieces of a desired size. Even if the external face of base board
201
is covered with a metal such as aluminum by bonding with an adhesive, moisture can penetrate into base board
201
from its edge side. Therefore, the penetration of moisture into element formation region
110
cannot readily be prevented completely.
In X-ray visible-lig
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Hannaher Constantine
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