JP2002020742A - Alkali halide-based fluorescent substance and radiographic transformation panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkali halide-based fluorescent substance increased in stimulated luminescent levels, and to provide a radiographic transformation panel of high sensitivity. SOLUTION: This fluorescent substance is shown by the fundamental compositional formula:CsBr:xEu (wherein, x is a numerical value satisfying the relationship: 0<x<=0.2), being a europium-activated cesium bromide-based fluorescent substance; wherein the ratio for Eu2+ and Eu3+ each contained in this fluorescent substance satisfies the relationship: 5×10-5<=Eu3+/Eu2+<=0.1 in terms of emission intensity ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkali halide phosphor and a radiation image conversion panel using the phosphor.

[0002]

2. Description of the Related Art A radiation image recording / reproducing method using a stimulable phosphor is known as an alternative to the conventional radiographic method. This method uses a radiation image conversion panel (a stimulable phosphor sheet) containing a stimulable phosphor, and transmits radiation transmitted through a subject or emitted from a subject to the stimulable phosphor of the panel. The radiation energy stored in the stimulable phosphor is absorbed by the body in a time-series manner by exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared rays. The fluorescent light is emitted as (stimulated emission light), the fluorescence is read photoelectrically to obtain an electric signal, and a radiation image of a subject or a subject is reproduced as a visible image based on the obtained electric signal. After the reading, the panel is prepared for the next photographing after the remaining image is erased. That is, the radiation image conversion panel is used repeatedly.

According to this radiographic image recording / reproducing method, a radiographic image having a large amount of information can be obtained with a much smaller exposure dose than the conventional radiographic method using a combination of a radiographic film and an intensifying screen. There is an advantage that can be. Furthermore, in contrast to the conventional radiographic method, which consumes a radiographic film for each photographing operation, the radiographic image recording / reproducing method uses a radiographic image conversion panel repeatedly, so that resource conservation and economic efficiency are reduced. Is also advantageous.

A stimulable phosphor is a phosphor that emits stimulable light when irradiated with radiation and then with excitation light. However, in practice, the stimulable phosphor has a wavelength of 400 to 900 nm due to the excitation light. Phosphors that exhibit stimulated emission in the 500 nm wavelength range are commonly used. Examples of the stimulable phosphor conventionally used in the radiation image conversion panel include an alkali halide phosphor. For example,
Japanese Patent Publication Nos. 7-84588 and 7-84589 disclose CsX and RbX (X is a halogen) phosphor. However, the valence of the activator, especially E
There is no description about the valence of u and its ratio.

The radiation image conversion panel used in the radiation image recording / reproducing method has, as a basic structure, a support and a stimulable phosphor layer provided thereon. However, when the stimulable phosphor layer is self-supporting, a support is not necessarily required. In addition, a protective film is usually provided on the upper surface of the stimulable phosphor layer (the surface not facing the support) to protect the phosphor layer from chemical deterioration or physical impact. ing.

The stimulable phosphor layer usually comprises a stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. However, there is also known a stimulable phosphor layer which does not include a binder formed by a vapor deposition method or a sintering method and is composed of only an aggregate of the stimulable phosphor. Further, there is known a radiation image conversion panel having a stimulable phosphor layer in which a polymer substance is impregnated in a gap between stimulable phosphor aggregates. In any of these phosphor layers, the stimulable phosphor is X
When irradiated with excitation light after absorbing radiation such as radiation, it has the property of stimulating luminescence, so radiation transmitted through a subject or emitted from a subject is proportional to the amount of radiation. Absorbed by the stimulable phosphor layer of the image conversion panel, a radiation image of the subject or the subject is formed on the panel as an accumulated image of radiation energy. This accumulated image can be emitted as stimulated emission light by irradiating the excitation light, and the accumulated image of radiation energy is imaged by photoelectrically reading the stimulated emission light and converting it into an electric signal. Can be realized.

As another method of the above-mentioned radiation image recording / reproducing method, Japanese Patent Application No. 11-372978 filed by the present applicant discloses a stimulable phosphor-containing stimulable phosphor layer (and a radiation-absorbing phosphor layer). A radiation image forming method using a combination of a radiation image conversion panel having a body layer) and a phosphor screen having a radiation absorbing phosphor layer containing a phosphor that absorbs radiation and emits light in the ultraviolet to visible region, and Radiation imaging materials comprising combinations thereof are described. In this method, radiation transmitted through a subject, diffracted or scattered by the subject, or emitted from the subject is first applied to a fluorescent screen or a radiation absorbing phosphor layer of a radiation image conversion panel in an ultraviolet to visible region. After that, the light is accumulated and recorded as a latent image in the stimulable phosphor layer of the panel. Next, the panel is irradiated with excitation light to photoelectrically read the stimulated emission light from the stimulable phosphor layer to convert it into an image signal, and reconstruct an image corresponding to the spatial energy distribution of radiation from the image signal. Make up. The radiation image conversion panel of the present invention also includes a panel containing both a stimulable phosphor and a phosphor that absorbs radiation and emits light in the ultraviolet to visible region as used in the above method.

Although the radiation image recording / reproducing method (and the radiation image forming method) has many excellent advantages as described above, the radiation image conversion panel used in this method has as high a sensitivity as possible. It is desired to provide an image with good image quality (sharpness, granularity, etc.).

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a europium-activated cesium bromide-based phosphor having an increased amount of stimulated emission. The present invention also provides a radiation image conversion panel having high sensitivity.

[0010]

The present inventor has studied the cesium bromide-activated phosphor based on europium, and found that the abundance ratio of Eu ²⁺ and Eu ³⁺ in Eu as an activator is a stimulating luminescence. Have been found to have a great effect on the present invention, and have reached the present invention.

The present invention provides a phosphor represented by a basic composition formula (I): CsBr: xEu (I) wherein x is a numerical value in a range of 0 <x ≦ 0.2. Europium-activated cesium bromide-based fluorescence in which the ratio of Eu ²⁺ to Eu ³⁺ contained in the phosphor is in the range of 5 × 10 ⁻⁵ ≦ Eu ³⁺ / Eu ²⁺ ≦ 0.1 in terms of emission intensity ratio. body.

The above-mentioned coefficient x in the phosphor composition described in the present specification is a numerical value corresponding to the ratio of the components of the completed phosphor. Since the composition changes before and after the firing step in the production of the phosphor, the ratio of each component of each raw material used in the production and the ratio of each component of the completed phosphor may be slightly different.

In the present specification, the emission intensity of Eu ²⁺ and Eu ³⁺ of the phosphor is defined as the peak intensity of instantaneous emission near 450 nm when the phosphor is excited at a wavelength of 346 nm, and the emission intensity of the phosphor, respectively. The peak intensity value of instantaneous emission near 595 nm when excited at a wavelength of 394 nm was used.

The present invention also provides a radiation image conversion panel including the above-mentioned europium-activated cesium bromide-based phosphor.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The europium-activated cesium bromide-based phosphor of the present invention can be produced, for example, as follows.

Cesium bromide (CsB)
r) and europium bromide (EuBr ₃ ) are prepared. These phosphor raw materials are mixed in a solid phase while stirring using various known mixers. Further, if desired, metal oxides such as aluminum oxide, silicon dioxide, and zirconium dioxide may be added and mixed in an amount of 0.5 mol or less for the purpose of improving photostimulated luminescence characteristics. Similarly, alkali metals (Li, Na, K, Rb), alkaline earth metals (Mg, Ca, Sr), and / or trivalent metals (S
A halide of c, Y, La, Al, Ga, In, or Tl) may be added and mixed in an amount of 0.5 mol or less.

An alumina crucible is used for the phosphor raw material mixture.
It is filled in a heat-resistant container such as a platinum crucible or a quartz boat, and put into a furnace core of an electric furnace for firing. The firing temperature is 100 ° C
To 620 ° C., and particularly preferably 525 ° C.
It is around ° C. As the firing atmosphere, a nitrogen atmosphere and a nitrogen atmosphere containing a small amount of oxygen or hydrogen are generally used. Oxygen is usually contained in the range of 0-2666 Pa, and hydrogen is usually contained in the range of 0-2666 Pa. Preferably, a nitrogen atmosphere and a nitrogen atmosphere containing a small amount of oxygen are used. Firing time depends on the amount of mixture charged,
Although it varies depending on the firing temperature and the temperature at which it is taken out of the furnace, it is generally suitable for 0.1 to 10 hours, preferably 0.5 to 5 hours.

The phosphor thus obtained may be subjected to various general operations in the production of the phosphor, such as pulverization and sieving, if necessary. As a result, a desired europium-activated cesium bromide-based stimulable phosphor represented by the following basic composition formula (I) is obtained. Basic composition formula (I): CsBr: xEu (I) [where x is a numerical value in the range of 0 <x ≦ 0.2]

Eu as an activator in the stimulable phosphor described above exists as Eu ²⁺ or Eu ³⁺ . However, the activator raw materials used in the production are not always incorporated into the phosphor as activator components, and the total amount of Eu varies slightly depending on the production conditions. Also, E
The abundance ratio between u ²⁺ and Eu ³⁺ varies greatly depending on conditions such as temperature and atmosphere during firing, and in other words, can be controlled by firing conditions. In general, the amount of stimulated emission of the phosphor increases as the amount of Eu ^{2+ as} the emission center increases,
In addition, it increases when Eu ³⁺ is present at a certain ratio. In the present invention, the abundance ratio of Eu ²⁺ and Eu ³⁺ is defined by the intensity ratio of the instantaneous light emission.
That is, the emission intensity of Eu ²⁺ of the phosphor is a peak intensity around 450 nm of the instantaneous emission when the phosphor is excited at the wavelength of 346 nm, and the emission intensity of Eu ³⁺ of the phosphor is the emission intensity of the phosphor at a wavelength of 394 nm. 595 of instantaneous light emission when excited
nm, and the ratio of both to Eu ²⁺
And the Eu ³⁺ abundance ratio.

In the present invention, the above-mentioned activated bromide with europium is used.
Cesium-based phosphor is Eu²⁺And Eu ³⁺Is the emission intensity
5 × 10^-Five≦ Eu³⁺/ Eu²⁺When it is in the range of ≦ 0.1, the amount of stimulated emission increases remarkably. Like
Or Eu²⁺And Eu³⁺Is the emission intensity ratio, 1 × 10^-Four≦ Eu³⁺/ Eu²⁺≦ 1 × 10^-2 In the range.

Further, the amount of stimulated emission of the phosphor is generally
In addition, Eu which is the emission center²⁺Along with the amount of electrons in the phosphor
The number increases as the number of Br defects serving as traps increases. Departure
In the Ming, Eu²⁺Of the phosphor Eu²⁺Instant flash by
Specified by the peak intensity of the light and emitted in the same area as the reference
[(SrCaBa)_Five(PO_Four)_ThreeCl: Eu^Two
+Trade name: NP-105, manufactured by Nichia Corporation]
The emission peak of the above substance at a concentration that sufficiently absorbs the excitation light.
Standardize with peak strength (the above substance is set to 100)
By Eu²⁺Emission intensity (I_E). Eu²⁺
Emission intensity I_EIs higher, Eu²⁺Means a large amount
I do. On the other hand, the number of Br defects is determined by F
(Br^-) Coloring amount at center (I_F), X-ray irradiation
The intensity of the diffusely reflected light from the previous phosphor (I₀X for
Of the diffusely reflected light from the colored phosphor after irradiation with X-rays (I
_S) -Log (I_S/ I₀). Coloring amount I_FOften
That is, the higher the coloration, the greater the number of Br defects.
means.

The emission intensity of Eu ²⁺ phosphor I _E and F (B
r ^-) pigmenting amount I _F of center relationship: when satisfying 0.2 ≦ I _E × I _F, amount of stimulated emission significantly increases. Preferably phosphor satisfies _{0.5 ≦ I E × I F ≦} 30.0 relational expression. Especially preferably the phosphor satisfies the _{10.0 ≦ I E × I F ≦} 15.0 relational expression.

Next, in the radiation image conversion panel of the present invention, the phosphor layer contains europium-activated cesium bromide-based stimulable phosphor represented by the above basic composition formula (I). The phosphor layer is usually formed as a layer composed of columnar crystals of a stimulable phosphor by a vapor deposition method, but the phosphor layer may further contain another stimulable phosphor. Alternatively, a phosphor layer containing another phosphor such as a phosphor that absorbs radiation and emits light in the ultraviolet to visible region may be further provided. Hereinafter, a method of manufacturing the radiation image storage panel of the present invention will be described by taking, as an example, a case where the phosphor layer is formed by a vapor deposition method.

The support can be arbitrarily selected from materials known as supports for conventional radiation image storage panels.
Particularly preferred support materials are quartz, glass sheets; metal sheets made of aluminum, iron, tin, chromium and the like; resin sheets made of aramid and the like. In a known radiation image conversion panel, in order to improve sensitivity or image quality (sharpness, granularity) as the radiation image conversion panel,
It is known to provide a light reflecting layer made of a light reflecting substance such as titanium dioxide or a light absorbing layer made of a light absorbing substance such as carbon black. The support used in the present invention can also be provided with these various layers, and the configuration thereof can be arbitrarily selected depending on the desired purpose and application of the radiation image storage panel.
Further, as described in JP-A-58-200200, for the purpose of improving the sharpness of the obtained image,
The surface of the support on the side of the phosphor layer (when an auxiliary layer such as an undercoat layer (adhesion-imparting layer), a light reflecting layer or a light absorbing layer is provided on the surface of the support on the side of the phosphor layer, Fine irregularities may be formed on the surface of these auxiliary layers).

In the case of the first vapor deposition method, first, a support is placed in a vapor deposition apparatus, and the inside of the apparatus is evacuated to 1.33 × 1.
The degree of vacuum is about 0 ^-4 Pa. Next, the stimulable phosphor is heated and evaporated by a method such as a resistance heating method or an electron beam method to deposit the phosphor to a desired thickness on the surface of the support. The deposition may be performed a plurality of times, or different phosphors may be co-deposited using a plurality of resistance heaters or electron beams. Further, it is also possible to synthesize a phosphor on a support using a raw material of the stimulable phosphor and simultaneously form a phosphor layer. Further, at the time of vapor deposition, the object to be vapor-deposited (support or protective film) may be cooled or heated as necessary, or the vapor-deposited film (phosphor layer) may be heated (annealed) after vapor deposition. Is also good.

Specifically, in the case of using the electron beam method, first, a tablet (pellet) is prepared by compressing the stimulable phosphor or its raw material mixture as an evaporation source under pressure. The compression pressure varies depending on the type and state of the phosphor, but is generally in the range of 800 to 1000 kg / cm ² . At the time of compression, it may be heated to a temperature in the range of 30C to 200C. After pressurizing and compressing, the obtained tablets are preferably subjected to a degassing treatment. This allows a relative density of 80
% Or more and 98% or less, preferably 90% or more and 96% or less, and the phosphor can be uniformly evaporated from the tablet surface.

Next, a stimulable phosphor tablet as an evaporation source and a support as an object to be deposited are placed in a deposition apparatus, and the inside of the apparatus is evacuated to 1.33 × 10 ^-2 to 1.33. × 1
The degree of vacuum is about 0 ^-4 Pa. At this time, an inert gas such as an Ar gas or a Ne gas may be introduced while maintaining the degree of vacuum at this level. The distance between the evaporation source and the support is 5-
It is set appropriately within a range of 150 cm. Next, the acceleration voltage from the electron gun is 1.5 kV or more and 5.0 kV or less, preferably 2.
An electron beam is generated at 0 kV or more and 4.0 kV or less, and the electron beam is irradiated to the evaporation source. The irradiation of the electron beam causes the stimulable phosphor, which is the evaporation source, to be heated, evaporated, scattered, and deposited on the surface of the support. The deposition rate of the phosphor, that is, the deposition rate, is generally in the range of 0.1 to 1000 μm / min, preferably in the range of 1 to 100 μm / min. After the deposition is completed, the deposited film may be subjected to a heat treatment, for example, in a temperature range of 50 ° C. to 600 ° C. in a nitrogen atmosphere (which may contain a small amount of oxygen or hydrogen) for 1 to 3 hours.

In the case of the second sputtering method, a support is first placed in a sputtering apparatus, and the inside of the apparatus is once evacuated to a degree of vacuum of about 1.33 × 10 ⁻⁴ Pa. An inert gas such as an Ar gas or a Ne gas is introduced as a gas to a gas pressure of about 0.133 Pa. Then
Discharge is performed using the stimulable phosphor as a target, and the phosphor is scattered by the impact of the ionized gas to deposit the phosphor to a desired thickness on the surface of the support. Sputtering may be performed a plurality of times, or a plurality of targets made of different phosphors may be used simultaneously or sequentially to form a phosphor layer. Further, it is also possible to simultaneously or sequentially sputter using a plurality of stimulable phosphor materials to synthesize a phosphor on a support and simultaneously form a phosphor layer. If necessary, reactive sputtering may be performed by introducing O ₂ gas and H ₂ gas into the apparatus. Further, at the time of sputtering, an object to be deposited (a support or a protective film) may be cooled or heated as necessary, or the phosphor layer may be subjected to a heat treatment (annealing treatment) after completion of the sputtering.

In this way, a phosphor layer in which the columnar crystals of the stimulable phosphor have grown substantially in the thickness direction is obtained. The phosphor layer does not contain a binder and consists only of a stimulable phosphor,
Voids (cracks) exist between the columnar crystals of the stimulable phosphor. The thickness of the phosphor layer varies depending on the characteristics of the target radiation image conversion panel, the means and conditions of the vapor deposition method, etc., but is usually in the range of 100 μm to 1 mm, preferably in the range of 200 μm to 700 μm. is there. Note that the phosphor layer does not necessarily need to be formed by vapor phase growth of the phosphor directly on the support as described above. For example, the phosphor layer may be separately formed on a temporary support such as a glass plate, a metal plate, or a plastic sheet. After forming the phosphor layer by vapor-phase growth of the body, a method of bonding the phosphor layer on the support using an adhesive or the like may be used.

Alternatively, the phosphor layer may be composed of the above-mentioned stimulable phosphor and a binder containing and supporting the stimulable phosphor in a dispersed state. An additive such as a coloring agent may be included. In that case, the phosphor layer can be formed on the support by the following known method. First, a stimulable phosphor and a binder are added to an appropriate organic solvent and mixed well to prepare a coating solution in which the phosphor is uniformly dispersed in a binder solution. Various types of resin materials are known for the binder, and in the formation of the radiation image conversion panel of the present invention, any known resin material, mainly those known binder resins, may be appropriately selected and used. Can be. The mixing ratio between the binder and the phosphor in the coating solution is generally 1: 1 to 1: 100.
(Weight ratio), and particularly preferably in the range of 1: 8 to 1:40 (weight ratio). The prepared coating solution is then uniformly applied on the surface of the support to form a coating film. This coating operation can be performed by using ordinary coating means, for example, a doctor blade, a roll coater, a knife coater, or the like.

After forming the coating on the support as described above, the coating is dried to complete the formation of the phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the mixing ratio of the binder and the phosphor, etc., but is generally in the range of 20 μm to 1 mm, preferably in the range of 50 μm to 500 μm. is there. In this case as well, the phosphor layer does not necessarily need to be formed by directly coating on the support. For example, after coating and drying on a temporary support to form a phosphor layer, the phosphor layer is pressed onto the support. Or,
Alternatively, the support and the phosphor layer may be joined using an adhesive or the like.

A radiation image conversion panel is provided on the surface of the phosphor layer.
For convenience in transporting and handling of materials and avoiding property changes
It is desirable to provide a protective film on the substrate. The protective film is
Has little effect on the incidence of light or emission of photostimulated light
It is desirable to be transparent and
The radiation image conversion panel from physical impacts and chemical influences.
Chemically stable and moisture proof so that it can be protected in minutes
It is desirable to have high physical properties and high physical strength. Security
For the protective film, use an inorganic compound such as magnesium fluoride.
And the evaporation method such as the electron beam method.
1.33 × 10 ^-2~ 1.33 × 10^-FourPa, evaporation source
5 to 150 cm distance from the object to be deposited, acceleration voltage 1.5 to
Under the condition of 5.0 kV and a deposition rate of about 1 μm / min,
By forming, it can be provided on the phosphor layer.

Alternatively, the protective film may be formed by applying a solution prepared by dissolving a transparent organic polymer such as a cellulose derivative or polymethyl methacrylate in a suitable solvent onto the phosphor layer. Alternatively, an organic polymer film such as polyethylene terephthalate or a protective film forming sheet such as a transparent glass plate may be separately formed and provided on the surface of the phosphor layer using an appropriate adhesive. Further, a protective film formed of a coating film of a fluorine-based resin soluble in an organic solvent, in which a perfluoroolefin resin powder or a silicone resin powder is dispersed and contained, may be used.
The thickness of the protective film is generally in the range of about 0.1 to 20 μm.

Although the radiation image conversion panel of the present invention is obtained as described above, the configuration of the panel of the present invention may include various known variations. For example, for the purpose of improving the sharpness of the obtained image, at least one of the above-mentioned layers may be colored with a coloring agent that absorbs excitation light but does not absorb stimulating light (Japanese Patent Publication No. No. 59-23400).

[0035]

EXAMPLES Example 1 Production of CsBr: 0.01Eu Phosphor After weighing 15 g (0.07 mol) of cesium bromide and 0.2761 g (7.0 × 10 ⁻⁴ mol) of europium bromide, Mix with a mixer. The obtained mixture was placed in a quartz container, placed on the core of an electric furnace, evacuated initially, nitrogen gas was introduced to atmospheric pressure, and baked at a temperature of 525 ° C. for 1 hour. Then, after evacuation was performed for 5 minutes, oxygen gas was introduced into the chamber at 133 Pa, and nitrogen gas was further introduced to atmospheric pressure, followed by firing at the same temperature for 1 hour. After firing, the furnace was evacuated and the fired product was cooled to room temperature in a vacuum. The fired product was taken out and pulverized in a mortar to obtain europium-activated cesium bromide phosphor particles represented by the composition formula described above.

Example 2 Manufacture of Phosphor In the same manner as in Example 1, except that 266 Pa of oxygen gas was introduced instead of 133 Pa after the intermediate evacuation in the firing step, europium activation was performed. Cesium bromide phosphor particles were obtained.

Example 3 Manufacture of Phosphor Example 1 was the same as Example 1 except that firing was performed in a nitrogen atmosphere for 2 hours without intermediate evacuation in the firing step.
In the same manner as described above, europium-activated cesium bromide phosphor particles were obtained.

Example 4 Production of Phosphor In Example 1, after evacuating to an intermediate vacuum in the firing step, europium activation was performed in the same manner as in Example 1 except that 399 Pa was introduced instead of 133 Pa. Cesium bromide phosphor particles were obtained.

Example 5 Production of Phosphor In Example 1, after initial evacuation in the firing step, hydrogen gas was introduced at 39.9 Pa, nitrogen gas was further introduced to atmospheric pressure, and the temperature was raised to 500 ° C. In this manner, europium-activated cesium bromide phosphor particles were obtained in the same manner as in Example 1 except that firing was completed for 2 hours.

Example 6 Production of Phosphor In Example 1, after evacuating to an intermediate vacuum in the firing step, europium was activated in the same manner as in Example 1 except that oxygen gas was introduced at 1330 Pa instead of 133 Pa. Cesium bromide phosphor particles were obtained.

Comparative Example 1 Production of CsBr: 0.0001 Eu Phosphor 15 g (0.07 mol) of cesium bromide and 0.0028 g (7.0 × 10 ⁻⁶ mol) of europium bromide were weighed and then mixed. And mixed. The resulting mixture was placed in a quartz container, placed on the core of an electric furnace, evacuated initially, nitrogen gas was introduced to atmospheric pressure, and baked at a temperature of 550 ° C. for 2 hours. After firing, the furnace was evacuated and the fired product was cooled to room temperature in a vacuum. The fired product was taken out and pulverized in a mortar to obtain europium-activated cesium bromide phosphor particles represented by the composition formula described above.

[Evaluation of Phosphor] Regarding the stimulable phosphor described above, the emission intensity ratio between Eu ²⁺ and Eu ³⁺ was determined as follows.
And I _E × I _F (Eu ²⁺ emission intensity × F (Br ⁻ ) center coloring amount) were determined, and evaluation was made based on the stimulated emission amount.

(1) Emission Intensity Ratio of Eu ²⁺ and Eu ³⁺ (Eu ³⁺ / Eu ²⁺ ) First, spectral correction of a spectrofluorometer (F-4500, manufactured by Hitachi, Ltd.) is used. went. Excitation wavelength correction: Rhodamine B, whose quantum efficiency for each wavelength is almost constant, is injected into a quartz cell, and the excitation spectrum at an emission wavelength of 640 nm is measured by the above-mentioned spectrofluorometer at a voltage of 400 V of the photomultiplier tube on the excitation side. Slit 5.0 nm, emission side slit 20 nm, scanning speed 60
The measurement was performed under the condition of nm / min, and the correction coefficient of the excitation wavelength was determined so that the spectrum intensity at each wavelength became constant.

Correction of emission wavelength: The scattering spectrum of a glass diffusion element whose scattering intensity for each wavelength is substantially constant is measured by the spectrofluorometer at a voltage of 400 V of a photomultiplier tube.
V, slit 5.0 nm on excitation side, slit 2 on emission side
The excitation and emission spectrometers were simultaneously scanned under the conditions of 0 nm and a scanning speed of 60 nm / min, and the measurement was performed. The emission wavelength correction coefficient was determined so that the scattering spectrum intensity at each wavelength was constant.

Next, the phosphor particles of the sample were packed in a holder whose window material was made of quartz, and the instantaneous emission of Eu ²⁺ of the phosphor was measured by the above-mentioned spectrofluorometer. The measurement was performed at a voltage of 400 V of the photomultiplier, a slit of 2.5 nm on the excitation side,
Excitation was performed at a wavelength of 346 nm under the conditions of a slit on the emission side of 2.5 nm and a scanning speed of 60 nm / min, and an emission spectrum was obtained. The emission peak intensity around 450 nm of the obtained emission spectrum was read. Next, the instantaneous emission spectrum of Eu ³⁺ of the phosphor was measured under the same measurement conditions at a wavelength of 394.
After excitation at 550 nm, the emission peak intensity around 595 nm was read. After correcting the excitation light intensity and the emission intensity at each wavelength based on the above-mentioned correction coefficient, respectively, Eu relative to the emission peak intensity of Eu ²⁺ obtained is obtained.
The ratio of the ³⁺ emission peak intensities was defined as the Eu ³⁺ / Eu ²⁺ emission intensity ratio.

(2) I _E × I _F (Eu ²⁺ emission intensity × F (B
r ⁻ ) Center coloring amount) Measurement of Eu ²⁺ emission intensity _IE : Phosphor particles are packed in a holder made of quartz as a window material, and instantaneous emission by Eu ²⁺ of the phosphor is performed by the above-mentioned spectrofluorometer. Was measured. The measurement was performed at a voltage of 400 V of the photomultiplier, a slit of 2.5 nm on the excitation side,
Excitation was performed at a wavelength of 346 nm under the conditions of a slit on the emission side of 2.5 nm and a scanning speed of 60 nm / min, and an emission spectrum was obtained. The emission peak intensity around 450 nm of the obtained emission spectrum was read. Next, materials showing light emission in the region _{[(SrCaBa) 5 (PO 4} ) 3 Cl: Eu 2+,
(Trade name: NP-105, manufactured by Nichia Chemical Co., Ltd.)], packed in the same holder, similarly excited at a wavelength of 370 nm, measured the emission spectrum, and read the emission peak intensity around 450 nm. The emission peak intensity of the phosphor is expressed as a relative value when the emission peak intensity of the substance is 100, and Eu ²⁺
The emission intensity _IE was used.

[0047] F (Br ^-) Measurement of pigmenting amount I _F of the central: phosphor particles 200mg black cylindrical holder (recess opening diameter 1
(0 mm, depth 250 μm). A very weak probe light having a wavelength of 633 nm is irradiated to the phosphor surface of the holder opening, and diffused reflected light from the phosphor is passed through an optical filter (O-50, manufactured by Hoya Glass Co., Ltd.) to a photomultiplier tube ( R-1848, manufactured by Hamamatsu Photonics KK), and the intensity (I ₀ ) of diffusely reflected light from the phosphor was measured. Next, an X-ray of 40 kVp and 30 mA was applied to the phosphor for 20 minutes.
And the intensity (I _S ) of the diffusely reflected light from the phosphor at that time was measured in the same manner. Calculates _{-log (I S / I 0)} , F - centering the pigmenting amount I _F (Br).

(3) Stimulated Luminescence Amount 200 mg of phosphor particles were uniformly packed in a black cylindrical holder (recess opening diameter 10 mm, depth 250 μm). In the dark room, an X-ray generator (MG)
164, made by Philips)
Vp X-rays were passed through a 3 mm thick Al filter for 100
Irradiated with mR. Twenty seconds later, the semiconductor laser (ML-
1016R, manufactured by Mitsubishi Electric Corporation), a laser beam having a wavelength of 660 nm is uniformly spread on the phosphor surface and irradiated with excitation energy of 4.3 J / m ² , and the stimulated emission light emitted from the phosphor surface is Optical filter (B-410, Hoya Glass Co., Ltd.)
Manufactured by Hamamatsu Photonics KK, and the amount of stimulated emission was measured.

The emission spectrum of Eu2 ⁺ and the emission spectrum of Eu3 ⁺ of the CsBr: 0.01Eu phosphor are shown in FIGS. 1 and 2, respectively. In addition, the obtained results are shown in FIGS.

FIG. 1 is a graph showing the emission spectrum of Eu ²⁺ of the CsBr: 0.01Eu phosphor (Example 1).
FIG. 2 shows Eu of the CsBr: 0.01Eu phosphor (Example 1).
It is a graph which shows the emission spectrum of ³⁺ . FIG.
It is a graph which shows the relationship between ^{3 +} / Eu2 ⁺ luminescence intensity ratio and the amount of photostimulated luminescence. FIG. 4 shows I _E × I _F (Eu ²⁺ emission intensity × F (B
r ^-) center pigmenting amount) and a graph showing the relationship between amount of stimulated emission.

[0051]

[Table 1]

[0052]

[Table 2] Eu ²⁺ Eu ³⁺ Eu ³⁺ / Eu ²⁺ photostimulated luminescence amount luminescence intensity luminescence intensity luminescence intensity ratio 例 Example 1 56 0.010 1.9 × 10 ⁻⁴ 37.7 Example 2 51 0.014 2.8 × 10 ⁻⁴ 45.2 Example 3 55 0.022 4.0 × 10 ⁻⁴ 47.6 Example 4 47 0.029 6.1 × 10 ⁻⁴ 43.1 Example 5 11 0.044 3.9 × 10 ⁻³ 16.9 Example 6 2 0.073 3.1 × 10 ⁻² 12.6} ─────────────────────────────── Comparative Example 1 2 2.6 × 10 ^-5 1.3 × 10 ^-5 1 .5─────────────────────────────── ─

[0053]

TABLE 3 TABLE _{3 ──────────────────────────────── I E I F I E} × I F stimulated emission Amount ──────────────────────────────── Example 1 56 0.1799 10.0 37.7 Example 2 51 0.2639 13.5 45.2 Example 3 55 0.2362 13.0 47.6 Example 4 47 0.2245 10.6 43.1 Example 5 11 0.1679 1.9 16.9 Example 6 2 0.2635 0.6 12.6 比較 Comparative Example 1 2 0.1237 0.1 1.5 ────────────────────────────────

As is clear from FIG. 3 and Table 2, Eu
²⁺And Eu³⁺Is 5 × 10 in emission intensity ratio^-Five~ 0.1
Activated cesium bromide fired with europium of the present invention in the range of
The light bodies (Examples 1 to 6) are phosphors for comparison (Comparative Examples).
Compared with 1), the amount of stimulated emission is significantly increased.
u²⁺/ Eu³⁺Emission intensity ratio is 1 × 10^-Four~ 1 × 10^-2Range of
When it was in the box, an extremely large amount of stimulated emission was exhibited. This
Eu like²⁺And Eu ³⁺Is as shown in Table 1.
In particular, it is preferable to set the firing temperature and firing atmosphere during firing of the phosphor raw material.
It can be achieved by appropriate adjustment.

[0055] Further, as apparent from FIGS. 4 and Table 3, Eu ²⁺ emission intensity of the phosphor I _E and F (Br ^-) in the case the product of the center pigmenting amount I _F is 0.2 or more ( Example 1
6), the amount of stimulated emission is much higher than that of the comparative phosphor (Comparative Example 1), and especially the product _IE × _IF is 10.0.
In the cases described above (Examples 1 to 4), an extremely large amount of stimulated emission was exhibited.

Example 7 Production of Radiation Image Conversion Panel (1) Production of Evaporation Source 100 g (0.47 mol) of cesium bromide and 1.8404 g (4.7 × 10 ⁻³ mol) of europium bromide were used. After crushing and mixing in a mortar, the mixture was further stirred and mixed for 15 minutes with a stirring vibrator. The obtained mixture was placed in a furnace, evacuated for 3 minutes, and then nitrogen gas was introduced to atmospheric pressure, followed by firing at 525 ° C. for 2 hours in a nitrogen atmosphere. After firing, the furnace was evacuated for 15 minutes to cool the fired product. Next, the obtained europium-activated cesium bromide (CsBr: 0.01 Eu) stimulable phosphor was crushed in a mortar, and then the pressure was 950 kg / cm.
Pressing and compression at ² produced tablets for vapor deposition. The tablets were further degassed by evacuation at 150 ° C. for 2 hours.

(2) Formation of Phosphor Layer As a support, an aluminum sheet was washed with methyl ethyl ketone and then with ultraviolet ozone, then dried naturally in a clean booth, and a glass sheet and a quartz sheet were washed with alkali, respectively. What was dried naturally in the clean booth was prepared. These supports were sequentially placed in a vapor deposition apparatus, and after the above-mentioned vapor deposition source was placed at a predetermined position in the apparatus, the inside of the apparatus was evacuated to 4.0 × 10 ^-4 P
The degree of vacuum was a. Next, an electron source was irradiated with an electron beam having an accelerating voltage of 4.0 kV and a current of 28 mA for 16 minutes by an electron gun to deposit a stimulable phosphor on the support at a rate of 25 μm / min. Thereafter, the irradiation of the electron beam was stopped, the inside of the apparatus was returned to the atmospheric pressure, and the support was taken out of the apparatus. Phosphor layers having a structure in which columnar crystals of a phosphor having a width of about 30 μm and a length of about 400 μm are densely formed almost vertically in an aluminum sheet, a glass sheet, and a quartz sheet (layer thickness: 40)
0 μm). In this way, a radiation image conversion panel including the support and the phosphor layer was manufactured.

[0058]

According to the present invention, the stimulable luminescence of the europium-activated cesium bromide-based phosphor is reduced by setting the abundance ratio of the activators Eu ²⁺ and Eu ³⁺ to a specific range. Can be significantly increased. Therefore, the radiation image conversion panel of the present invention containing this phosphor exhibits high sensitivity. In particular, when the phosphor layer is formed by a vapor deposition method, a radiation image conversion panel that has higher sensitivity and provides a high-quality radiation image can be obtained. For this reason, the radiation image conversion panel of the present invention is particularly advantageous when used in a method for recording and reproducing a radiation image for medical diagnosis.

[Brief description of the drawings]

FIG. 1 is a graph showing the emission spectrum of Eu ²⁺ of the CsBr: 0.01Eu phosphor of the present invention.

FIG. 2 is a graph showing the emission spectrum of Eu ³⁺ of the CsBr: 0.01Eu phosphor of the present invention.

FIG. 3 is a graph showing the relationship between the Eu ³⁺ / Eu ²⁺ emission intensity ratio and the amount of stimulated emission.

FIG. 4 is a graph showing the relationship between I _E × I _F and the amount of stimulated emission.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G083 AA03 BB01 CC02 CC03 DD01 DD02 DD11 DD12 DD14 DD15 EE03 4H001 CA02 CF02 XA35 XA55 YA63

Claims (7)

[Claims] 1. A phosphor represented by a basic composition formula (I): CsBr: xEu (I) wherein x is a numerical value in a range of 0 <x ≦ 0.2. A europium-activated cesium bromide-based phosphor in which the ratio of Eu ²⁺ to Eu ³⁺ contained in the body is in the range of 5 × 10 ⁻⁵ ≦ Eu ³⁺ / Eu ²⁺ ≦ 0.1 in terms of emission intensity ratio. 2. The europium according to claim 1, wherein the ratio between Eu ²⁺ and Eu ³⁺ is in the range of 1 × 10 ⁻⁴ ≦ Eu ³⁺ / Eu ²⁺ ≦ 1 × 10 ⁻² in terms of emission intensity ratio. Activated cesium bromide phosphor. 3. The phosphor of Eu²⁺Emission intensity I_EAnd F (B
r^-) Coloring amount at center I _FIs the relational expression: 0.2 ≦ I_E× I_F The europium activation according to claim 1 or 2, which satisfies the following.
Cesium bromide phosphor. 4. A phosphor raw material mixture containing at least cesium bromide and europium bromide at 100 ° C. to 620 ° C.
The method according to any one of claims 1 to 3, which is produced by calcining in a nitrogen atmosphere or a nitrogen atmosphere containing a small amount of oxygen or hydrogen at a temperature in the range of 0 ° C for 0.1 to 10 hours. Active cesium bromide phosphor with europium. 5. A radiation image conversion panel comprising the europium-activated cesium bromide-based phosphor according to any one of claims 1 to 4. 6. The radiation image conversion panel according to claim 5, further comprising a phosphor layer formed of europium-activated cesium bromide-based phosphor formed by a vapor deposition method. 7. The radiation image conversion panel according to claim 5, further comprising a phosphor layer made of a binder that supports and supports the europium-activated cesium bromide-based phosphor.