Stimulable phosphor and radiation image conversion panel by...

Details Stimulable phosphor and radiation image conversion panel by... Stimulable phosphor and radiation image conversion panel by...

1999-04-19

2001-01-23

Koslow, C. Melissa (Department: 1755)

Compositions

Inorganic luminescent compositions

Compositions containing halogen; e.g., halides and oxyhalides

C252S30140R, C427S064000, C427S215000, C427S214000

Reexamination Certificate

active

06177030

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a stimulable phosphor, a preparation method of the stimulable phosphor and radiation image conversion panel by the use of the stimulable phosphor, and in particular to a stimulable phosphor which are little in deterioration of performance due to moisture sorption and usable in acceptable conditions over a long period of time, a preparation method of the stimulable phosphor and radiation image conversion panel by the use of the stimulable phosphor.
BACKGROUND OF THE INVENTION
Radiographic images such as X-ray photographic images are generally employed for medical diagnoses. To obtain X-ray photographic images is generally employed conventional X-ray photography. Thus, X-rays, having passed through a photographic object, are allowed to be irradiated onto a phosphor layer (fluorescent screen) to produce visible light, and the visible light produced is irradiated onto a conventionally used silver salt film, which is further developed to obtain the images. Recently, there is known a method of taking out images directly form a phosphor layer without the use of the silver salt film. The radiation, having passed through an object, is allowed to be absorbed in the phosphor, then the phosphor is excited by light or heat energy to release the radiation energy stored in the phosphor as fluorescence, and the resulting fluorescence is detected to form images. Exemplarily, there is known a radiation image conversion method using a stimulable phosphor, as disclosed in U.S. Pat. No. 3,859,527 and JP-A 55-12144 (hereinafter, the term, JP-A means a Unexamined and Published Japanese Patent Application).
In the method, a radiation image conversion panel (in other words, an image storage phosphor sheet) comprising a stimulable phosphor is employed, and the method comprises the steps of causing the stimulable phosphor of the panel to absorb radiation which passed through an object or having radiated from an object, sequentially exciting the stimulable phosphor with a electromagnetic waves such as visible light or infrared rays (hereinafter referred to as “stimulating rays”) to release the radiation energy stored in the phosphor as light emission (stimulated emission), photoelectrically detecting the emitted light to obtain electrical signals, and reproducing the radiation image of the object as a visible image from the electrical signals.
In the radiation image recording and reproducing methods described above, a radiation image is advantageously obtained with a sufficient amount of information by applying radiation to an object in a considerably smaller dose, as compared to conventional radiography employing a combination of a radiographic film and a radiographic intensifying screen.
The stimulable phosphor, after being exposed to radiation, exhibits stimulated emission upon exposure to the stimulating ray. In practical use, phosphors are employed, which exhibit an emission within a wavelength region of 300 to 500 nm stimulated by stimulating light at wavelengths of 400 to 900 nm.
Examples of the stimulable phosphor used in the radiation image conversion panel include,
(1) a rare earth activated alkaline earth metal fluorohalide phosphor represented by the formula of (Ba
1−x
,M
2+
x
)FX:yA, as described in JP-A 55-12145, in which M
2+
is at least one of Mg, Ca, Sr, Zn and Cd; X is at least one of Cl, Br and I; A is at least one of Eu, Tb, Ce, Tm, Dy, Pr, Ho, Nd, Yb, and Er; x and y are numbers meeting the conditions of 0≦x≦0.6 and 0≦y≦0.2; and the phosphor may contain the following additives:
X′, BeX″ and M
3
X
3
′″, as described in JP-A 56-74175 (in which X′, X″ and X′″ are respectively a halogen atom selected from the group of CL, Br and I; and M
3
is a trivalent metal);
a metal oxide described in JP-A 55-160078, such as BeO, BgO, CaO, SrO, BaO, ZnO, Al
2
O
3
, Y
2
O
3
, La
2
O
3
, In
2
O
3
, SiO
2
, TiO
2
, ZrO
2
, GeO
2
, SnO
2
, Nb
2
O
5
or ThO
2
;
Zr and Sc described in JP-A 56-116777;
B described in JP-A 57-23673; As and Si described in JPA 57-23675;
M.L (in which M is an alkali metal selected from the group of Li, Na, K, Rb and Cs; L is a trivalent metal Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, In, and Tl) described in JP-A 58-206678;
calcined tetrafluoroboric acid compound described in JPA 59-27980;
calcined, univalent or divalent metal salt of hexafluorosilic acid, hexafluorotitanic acid or hexafluorozirconic acid described in JP-A 59-27289;
NaX′ described in JP-A 59-56479 (in which X′ is at least one of Cl, Br and I);
a transition metal such as V, Cr, Mn, Fe, Co or Ni, as described in JP-A 59-56479;
M
1
X′, M′
2
X″, M
3
X′″ and A, as described in JP-A 59-75200 (in which M
1
is an alkali metal selected from the group of Li, Na, K, Rb and Cs; M′
2
is a divalent metal selected from the group of Be and Mg; M
3
is a trivalent metal selected from the group Al, Ga, In and Tl; A is a metal oxide; X′, X″ and X′″ are respectively a halogen atom selected from the group of F, Cl, Br and I);M
1
X′ described in JP-A 60-101173 (in which M
1
is an alkali metal selected from the group of Rb and Cs; and X′ is a halogen atom selected from the group of F, Cl, Br and I);
M
2
′X′
2
.M
2
′X″
2
(in which M
2
′ is at least an alkaline earth metal selected from the group Ba, Sr and Ca; X′ and X″ are respectively a halogen atom selected from the group of Cl, Br and I, and X′≠X″); and
LnX″
3
described in Japanese Patent Application No. 60106752 (in which Ln is a rare earth selected from the group of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; X″ is a halogen atom selected from the group of F, Cl, Br and I);
(2) a divalent europium activated alkaline earth metal halide phosphor described in JP-A 60-84381, represented by the formula of M
2
X
2
.aM
2
′
2
:xEu
2+
(in which M
2
is an alkaline earth metal selected from the group of Ba, Sr and Ca; X and X′ is a halogen atom selected from the group of Cl, Br and I and X≠X′; a and x are respectively numbers meeting the requirements of 0≦a≦0.1 and 0≦x≦0.2);
the phosphor may contain the following additives;
M
1
X″ described in JP-A 60-166379 (in which M
1
is an alkali metal selected from the group of Rb, and Cs; X″ is a halogen atom selected from the group of F, Cl, Br and I;
KX″, MgX
2
′″ and M
3
X
3
″″ described in JP-A 221483 (in which M
3
is a trivalent metal selected from the group of Sc, Y, La Gd and Lu; X″, X′″ and X″″ are respectively a halogen atom selected from the group of F, Cl Br and I;
B described in JP-A 60-228592;
an oxide such as SiO
2
or P
2
O
5
described in JP-A 60-228593;
LiX″ and NaX″ (in which X″ is a halogen atom selected from the group of F, Cl, Br and I;
SiO described in JP-A 61-120883;
SnX
2
″ described in JP-A 61-120885 (in which X″ is a halogen atom selected from the group of F, Cl, Br and I;
CsX″ and SnX
2
′″ described in JP-A 61-235486 (in which X″ and X′″ are respectively a halogen atom selected from the group of F, Cl, Br and I;
CsX″ and Ln
3+
described in JP-A 61-235487 (in which X″ is a halogen atom selected from the group of F, Cl, Br and I; Ln is a rare earth element selected from the group of Sc, Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;
(3) a rare earth element activated rare earth oxyhalide phosphor represented by the formula of LnOX:xA, as described in JP-A 55-12144 (in which Ln is at least one of La, Y, Gd and Lu; A is at least one of Ce and Tb; and x is a number meeting the following condition, 0<x<0.1);
(4) a cerium activated trivalent metal oxyhalide phosphor represented by the formula of M
3
OX:xCe, as described in JP-A 58-69281 (in which M
3
is an oxidized metal selected fro

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