JPH0826310B2 - Divalent europium-activated divalent metal fluoride-based phosphor and storage-type radiation image converter using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is activated by divalent europium.
TECHNICAL FIELD The present invention relates to a valent metal fluoride-based phosphor and a storage-type radiation image converter including the phosphor in a phosphor layer.

[Conventional technology]

A certain kind of fluorescent substance emits fluorescent light when it is irradiated with visible light or infrared light after being irradiated with X-rays, ultraviolet rays, electron beams and the like. This development is called "photostimulation". The stimulable phosphor is called a “stimulable phosphor”, and the stimulable phosphor can be used as a storage-type radiation image converter (hereinafter abbreviated as “storage-type image converter”). Is known (US Patent No.
No. 3,859,527, Japanese Patent Publication No. 61-29490, etc.).

That is, the phosphor layer of the stimulable image converter formed by forming a phosphor layer containing a stimulable phosphor on the support to absorb the radiation transmitted through the subject, then visible light or A radiation image of a subject can be obtained by irradiating infrared light and photoelectrically reading the photostimulable light emitted at this time.

By the way, as photostimulable phosphors that can be used for such an image-recording device, SrS: Ce, Sm, SrS: Eu, Sm, [(Zn, Cm
d) S: Mn, X (where X is a halogen)] and the like, sulfide-based phosphors such as La ₂ O ₂ S: Eu, Sm and the like, (Ba _1-y ,
M _y ^II ) FX: A (where M ^II is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce) , Tm, Dy, Pr, Ho, Nd, Yb, and Er, and y is a number satisfying the condition of 0 ≦ y ≦ 0.2), etc. Several fluorescent bodies such as the body are known.

[Problems to be solved by the invention]

However, it is desirable that the sensitivity of the storage-type image converter is as high as possible when it is put to practical use, and therefore, development of a new photostimulable phosphor showing high-luminance photostimulable emission continues.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel photostimulable phosphor having high brightness and a high-sensitivity storage type image converter using the same.

[Means for solving problems]

The present inventors have conducted exploratory research on various inorganic compounds in order to achieve the above object. As a result, conventionally, a divalent europium-activated alkaline earth metal fluoride as a fluorescent substance which exhibits high-luminance near-ultraviolet or blue instantaneous light emission by X-ray, electron beam, or ultraviolet ray excitation (for example, Canadian Patent No. 896,453). However, divalent europium-activated divalent metal fluoride phosphors such as these exhibit high-intensity photostimulable luminescence, and other than a small amount of fluoride,
Addition of a valent metal halide further increases the intensity of stimulated emission. Based on this finding, the inventors have found that the phosphor can be used as a storage-type image converter, and have completed the present invention.

That is, the phosphor of the present invention has a composition formula of M ^II (F _1-a , Br _a ) ₂ : xEu
²⁺ (However, M ^II is at least one of Ca, Sr, Ba and Pb,
a and x are numbers satisfying the conditions of 0 <a ≦ 0.1 and 0 <x ≦ 0.2, respectively. The same applies hereinafter. ) Is a divalent europium-activated divalent metal fluoride-based phosphor.

Further, the storage type image converter of the present invention substantially comprises a support,
It is composed of a photostimulable phosphor layer provided thereon, and this photostimulable phosphor layer is _a divalent compound represented by the composition formula M ^II (F _1-a , Br _a ) ₂ : xEu ²⁺ . It is characterized by comprising a europium-activated divalent metal fluoride-based phosphor.

 Next, the present invention will be described in detail.

To produce the M ^II (F _1-a , Br _a ) ₂ : xEu ²⁺ phosphor of the present invention i) at least one fluoride in BaF ₂ , CaF ₂ , SrF ₂ and PbF ₂ ii ) CaBr ₂ etc., Ba, Ca, Sr or Pb bromide and iii) EuF ₃ , EuCl ₃ , Eu (NO ₃ ) ₃ etc. europium compounds are stoichiometrically M ^II (F _1-a , Br _a ) ₂ : xEu ²⁺ is weighed and mixed well, then packed in a heat-resistant container and stored in a heat-resistant container, for example, in a N ₂ gas stream containing H _{2 or} in a CO gas stream at a temperature of 600 at a weak reducing atmosphere. It suffices to perform firing at 0.5 to 1200 ° C for 0.5 to 10 hours. When using a hydrous bromide as the bromide described in ii) in the above starting materials, after calcining each of the raw material mixtures of i) to iii) above in air at a temperature of 100 ° C to 200 ° C, You may bake at the temperature of 600 degreeC-1200 degreeC in a weak reducing atmosphere.

FIG. 1 shows Ca (F _1-a , Br _a ) ₂ : 0.005Eu ²⁺ , which is one of the divalent europium-activated divalent metal fluoride-based phosphors of the present invention, Br / F + Br. Is a graph exemplifying the relationship between the ratio (a value) and stimulated emission intensity, where the vertical axis represents 80 KVp for each phosphor.
Is a relative value of the stimulated emission intensity upon irradiation with light of 633 nm obtained by dispersing the light from the xenon lamp after irradiating the X-ray. As can be seen from Fig. 1, CaF ₂ : 0.0
By substituting a part of F in the matrix of 05Eu ²⁺ fluorescent substance with Br, the stimulated emission intensity of the obtained fluorescent substance is remarkably increased, but when this ratio (a value) becomes larger, the stimulated emission is increased. The emission intensity rather decreases, and if the value a exceeds 0.1, the original CaF _{2 is} 0.
Since it is lower than that of the Eu ²⁺ fluorescent substance (point A in the figure), the value a is preferably in the range of 0 <a ≦ 0.1, particularly 1 × 10 ⁻⁵ ≦ a ≦ 3 × 10 ^−2. Is more preferably in the range.

FIG. 2 shows the concentration of Eu ²⁺ (x value) in the Ca (F _0.999 , Br _0.001 ) ₂ : xEu ²⁺ phosphor which is one of the divalent europium-activated fluoride phosphors of the present invention. Is a graph exemplifying the relationship between the stimulated emission intensity and the stimulated emission intensity, and the vertical axis is the stimulated emission intensity (arbitrary scale) obtained in the same manner as in the case of FIG. The x value is 0.
When it exceeds 2, the stimulated emission intensity of the obtained phosphor is remarkably lowered, which is not preferable in practical use. Therefore, as can be seen from FIG. 2, the concentration of Eu ²⁺ (x value) is in terms of the stimulated emission intensity. 0 <
It is desirable that x ≦ 0.2, especially 5 × 10 ⁻⁵ ≦ x ≦ 1 × 1
It is preferably 0 ^-2 .

FIG. 3 shows one of the phosphors of the present invention, Ca (F _0.999 , Br
It is a stimulated emission spectrum obtained by spectrally stimulating stimulated emission of a _0.001 ) F ₂ : 0.005Eu ²⁺ phosphor. As can be seen from FIG. 3, this phosphor exhibits stimulated emission having a peak of emission spectrum at about 425 nm, but when excited by X-rays or ultraviolet rays of 254 nm, it exhibits instantaneous emission having almost the same emission spectrum. .

Although not illustrated, the composition formula M ^II (F _1-a , Br _a ) ₂ : xEu
^{Even when} M ^II is a divalent metal element other than Ca in the phosphor of the present invention represented by ²⁺ , the X / F + X ratio (a value) and stimulated emission when F is partially replaced by Br. The relationship between the intensity, the relationship between the concentration of Eu ² and the stimulated emission intensity, and the stimulated emission spectrum are
It was confirmed that it was almost similar to the case where M ^II and X were Ca and Br, respectively (FIGS. 1, 2, and 3).

On the other hand, in order to manufacture the storage type image converter of the present invention, for example, it is manufactured as described above on a support made of horizontally placed paper, plastic such as polyethylene terephthalate, metal thin plate such as aluminum, glass plate, etc. Of the present invention
M ^II (F _1-a , Br _a ) ₂ : xEu ^{2+ A} phosphor coating solution obtained by mixing a phosphor and a nitrification cotton together with a solvent is uniformly applied and dried on a support. Form a phosphor layer of about 300μ. Then, if necessary, a transparent plastic thin film such as a polyethylene terephthalate film may be laminated on this phosphor layer, or a coating solution obtained by dissolving it in a resin such as nitrification cotton or acrylic cellulose may be applied and dried. A transparent protective film is formed on the phosphor layer to form a storage type image converter.
The storage-type image converter of the present invention is a conventional storage-type image converter except that the M ^II (F _1-a , Br _a ) ₂ : xEu ²⁺ phosphor of the present invention is used as the fluorescent layer. It has the same structure, and the manufacturing method is not limited to the above-mentioned method, and it can be manufactured by a method similar to the conventional method.

〔Example〕

After thoroughly mixing each of the 7 types of fluorescent materials shown, put them in a quartz crucible, bake them for 6 hours in an electric furnace maintained at 1000 ° C while flowing CO gas, and then take them out of the furnace and air cool. 7 types of fluorescent materials [1] to [7]
Was manufactured.

Next, each of these seven types of phosphors [1] to [7]
90 parts by weight, 10 parts by weight of nitrified cotton, and 80 parts by weight of an equal mixture of butyl acetate and acetone were sufficiently mixed to prepare 7 types of phosphor coating liquids, and each phosphor coating liquid was carbon black. Was applied to a support of polyethylene terephthalate having a thickness of 250μ kneaded so that the coating weight after drying would be 100 mg / cm ^2, and after drying, a solution of cellulose acetate was applied onto this phosphor layer. Seven types of storage-type image converters [I] to [VII] were manufactured by coating and drying so that the film thickness after drying was about 10 μm.

On the other hand, for comparison, instead of the fluorescent substances [1] to [7], CaF ₂ : 0 / 0005Eu ²⁺ fluorescent substance (fluorescent substance [R1]), CaF ₂ : 0.
0005Eu ²⁺ fluorescent substance (fluorescent substance [R2]), BaF ₂ : 0.0005Eu
²⁺ (fluorescent substance [R3]) and SrS: 0.0001Eu ³⁺ , 0.0001Sm ³⁺
(Fluorescent body [R4]) Four types of storage type image converters [RI], [RII], and [RIII] similar to the storage type image converters [I] to [VII] except that a fluorescent body is used. And [RIV] were produced.

11 types of storage-type image converters [I], [II] ... [VII], [RI], [RII] ... [RIV] manufactured in this way
After irradiating with 80KVp X-rays, each was irradiated with light of 633nm obtained by dispersing light from xenon, and the stimulated emission intensity at that time was measured. The results shown in the table below were obtained. Also showed higher intensity stimulated emission than the conventional storage-type image converters [RI], [RII], [RIII] and [RIV] using a phosphor.

[Effects of the Invention] The divalent europium-activated divalent metal fluoride-based phosphor of the present invention and the storage-type image converter using the same as the phosphor layer were irradiated with X-rays, ultraviolet rays, electron beams, or the like. When it is subsequently excited with visible light or infrared light, it exhibits stimulated luminescence with high brightness.

[Brief description of drawings]

FIG. 1 shows one of the phosphors of the present invention, Ca (F _1-a , Br _a ) ₂ : 0.
3 is a graph illustrating the relationship between Br / F ratio + Br (a value) and stimulated emission intensity of the phosphor in 005Eu ²⁺ . FIG. 2 shows Ca (F _0.999 , Br, which is one of the phosphors of the present invention.
₃ is a graph illustrating the relationship between the concentration (x value) of Eu ²⁺ and the stimulated emission intensity of the phosphor in _0.001 ) ₂ : xEu ²⁺ . FIG. 3 shows one of the phosphors of the present invention, Ca (F _0.999 , Br
₃ is a graph illustrating a stimulated emission spectrum of _0.001 ) ₂ : 0.005Eu ²⁺ .

Claims (4)

[Claims] 1. A composition formula M ^II (F _1-a , Br _a ) ₂ : xEu ²⁺ (where M ^II is calcium, strontium, barium,
And at least one of lead, and a and x are 0 <
It is a number that satisfies the conditions of a ≦ 0.1 and 0 <x ≦ 0.2. ) A divalent europium-activated divalent metal fluoride-based phosphor represented by: 2. The values a and x are each 1 × 10 ⁻⁵ ≦ a ≦ 3.
2. The number according to claim 1, wherein the number satisfies the conditions of ^{x10 -2} and 5 ^{x10 -5 ≤x≤1} x10 ^-2.
-Valent europium-activated divalent metal fluoride-based phosphor. 3. A storage-type radiation image converter substantially composed of a support and a stimulable phosphor layer provided on the support, wherein the stimulable phosphor layer has a composition formula M ^II. (F _1-a , Br _a ) ₂ : xEu ²⁺ (where M ^II is calcium, strontium, barium,
And at least one of lead, and a and x are 0 <
It is a number that satisfies the conditions of a ≦ 0.1 and 0 <x ≦ 0.2. ) A storage type radiation image converter comprising a divalent europium-activated divalent metal fluoride-based phosphor represented by 4. A and x are each 1 × 10 ⁻⁵ ≦ a ≦ 3.
The storage-type radiation image converter according to claim 3, wherein the number is a number satisfying the conditions of ^{x10 -2} and ^{5x10 -5} ≤x≤1x10 ^-2 .