JPH10268097A - Radiation image storage panel including coloring agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image panel colored with dye giving superior image resolution. SOLUTION: A radiation image storage panel having a phosphor layer containing a support, medium layer and combining agent and stimulus phosphor has an average reflectivity in the wavelength zone of stimulus ray against the stimulus phosphor which is made smaller than that in the wavelength of light emitted by the stimulus phosphor. The panel exists in the support colored with triaril methane dye having at least a water alkali soluble group, phosphor layer or medium layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a radiation image storage panel having a fluorescent layer containing a binder and a stimulable phosphor dispersed therein.

BACKGROUND OF THE INVENTION In radiography, the interior of a subject is exposed to X-rays, γ-rays and high-energy elemental particle radiation, such as β-rays, electron beams or penetrating radiation which is a high-energy radiation belonging to the group of neutron radiation. Will be reproduced. To convert the transmitted radiation into visible light and / or ultraviolet radiation, luminescent substances called phosphors are used.

In a conventional radiographic system, X
X-ray radiographs are obtained by X-rays transmitted through a subject according to an image and converted into light of a corresponding intensity in a so-called intensifying screen (X-ray conversion screen). Absorb transmitted X-rays,
It is converted to visible light and / or ultraviolet radiation (photographic film is X
Line is more sensitive to direct impact).

In practice, the light imagewise emitted by the screen illuminates the photographic silver halide emulsion layer film in contact, the film being developed after exposure to a silver image consistent with the x-ray image. To form

Another development, described for example in US Pat. No. 3,589,527, discloses the property of temporarily storing a large part of the energy of an X-ray image in addition to their immediate light emission (immediate emission) during X-ray irradiation. An X-ray recording system using a photostimulable storage phosphor is described, wherein the energy is emitted by the photostimulation in the form of light that differs in wavelength characteristics from the light used for the photostimulation. . In the X-ray recording system, light emitted at the time of photostimulation is detected photo-electronically and sequentially converted into an electric signal.

The basic components of such an X-ray imaging system operated with a storage phosphor are the imaging sensors, usually plates or panels containing said phosphor, which temporarily store the X-ray energy pattern. ), A scanning laser beam for photostimulation, an opto-electronic photodetector that provides an analog signal (which is subsequently converted to a digital time series signal), usually a digital image processor (which digitally converts the image digitally). Operate), a signal recorder, such as a magnetic disk or tape, and an image recorder or an electronic signal display, such as a cathode ray tube, for modulated exposure of photographic film. Research for useful lasers for reading photostimulable latent fluorescence images is published in the journal Research Disclosure
Volume 308, No. 117, p. 991 (1989)
Has been given to.

From the foregoing description of the two X-ray recording systems operating with an X-ray converting phosphor screen in the form of a plate or panel, the plate or panel acts only as an intermediate imaging element, It is clear that no record is formed. The final image is created or reproduced on another recording medium or display. The phosphor plate or sheet can be reused repeatedly. Prior to reuse of the photostimulable phosphor panel or sheet, the residual energy pattern is blanketed with light.

In view of the image quality of the image storage panel, in particular in terms of sharpness, said sharpness is not determined by the spread of light emitted by the stimulable phosphors in the panel, but rather by the spread in the panel. Determined by the degree of spread of the stimulus line: To reduce this light spread, it can be made from a mixture of fine and coarse batches to fill the gaps between the coated coarse phosphor particles. A good bulk factor is that coarse and fine phosphor particles can cause a loss in sensitivity if the coarse and fine phosphor particles differ only slightly in sensitivity. It can be obtained by making a mixture of particles. Because of the intensifying screen, this problem
Very long ago it was already processed by Kali-Chemie,
US-A 2,129,295; 2,129,296 and 2144
040. Thus, a radiograph showing improved visualization containing a blue light absorbing (yellow) dye is described in EP-A 0
No. 028521.

[0009] In particular, the thickness of the phosphor layer can give rise to an increased unsharpness of the emitted light, for the same coverage of said phosphor particles, There is a further disadvantage when the weight ratio between the amounts of the binder and the binder is reduced.

Increasing the weight ratio of phosphor to binder to produce sharper images by reducing the amount of binder increases the brittleness and ruggedness of the coated phosphor layer, for example, in a screen. Sufficient elasticity results in unacceptable operating characteristics of the screen.

One method for obtaining thinner coated phosphor layers without changing pigment and binder coverage is described in EP-A 0 393 662.
At a temperature above the melting point or softening point of the thermoplastic elastomer,
A method of compressing a coating layer containing both components is used.

Another method that does not use the compression manufacturing method is described in WO
94/0531, in which the binding medium comprises one or more rubbery and / or elastomeric polymers, having an improved elastic modulus of the screen, a high protection against mechanical damage, a very good operation It offers ease, high pigment to binder ratio, and improved image quality, especially sharpness.

Previous literature on improving the sharpness of radiation image storage panels relates to adding colorants to the panel. For example, in U.S. Pat. No. 4,394,581, a dye or colorant is added to the panel, so that the average reflectance of the panel in the wavelength range of the stimulus line for the stimulable phosphor is such that the stimulus when stimulated The average reflectance of the panel in the wavelength band of light emitted by the phosphor is made smaller. US
-A 4491736 describes organic colorants which do not emit light at wavelengths longer than the wavelength of the stimulating rays, especially when exposed. EP-A 0 165 340 and the corresponding US-A 4,675,271 describe storage phosphor screens which exhibit better image sharpness by incorporating dyes. A similar effect brought about in the phosphor layer of the image storage panel by the introduction of dyes or colorants is furthermore described in EP-A 0 253 348 and the corresponding US-A 4,879,202 and EP-A 0288.
038.

[0014] There is, however, a continuing need for further direct work to improve sharpness.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a radiation image storage panel colored with a dye which provides excellent image resolution. Other objects and advantages will become apparent from the following description and examples.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a radiation image storage panel having a support, an intermediate layer, and a fluorescent layer comprising a binder and a stimulable phosphor dispersed therein. The average reflectance of the panel in the wavelength band of the stimulus line for the stimulable phosphor is less than the average reflectance of the panel in the wavelength band of light emitted by the stimulable phosphor when stimulated. Being colored with a coloring agent, wherein the coloring agent is a triarylmethane dye having at least one aqueous alkali-soluble group, wherein the support, the phosphor layer, or the support and the phosphorescent It is characterized in that it is present in at least one of the intermediate layers between the body layers.

DETAILED DESCRIPTION OF THE INVENTION In order to meet the requirements for preventing irradiation or line scattering with stimulating energy for the storage phosphor coated in the phosphor layer of the storage panel according to the invention, the wavelength range of the stimulating radiation The choice of a colorant which has as high an absorption as possible and which has as little absorption as possible in the wavelength range of the emitted radiation makes it possible to use at least one aqueous alkali-soluble group as a dye which is perfectly suitable for the aforementioned purposes. To the inventor.

Among the triarylmethane dyes in this group, the most preferred dyes have the following general formula (I), wherein R ^{1 to} R ⁸ are each independently hydrogen, substituted or unsubstituted alkyl. Represents an aryl group or a substituted or unsubstituted aryl group, provided that at least one of R ^{1 to} R ⁸ is an acid group such as a carboxylic acid group or a sulfonic acid group to impart solubility in an alkaline medium in the form of a salt. Represent.

[0019]

Embedded image

The following formulas II to IV are preferred representative examples.

[0021]

Embedded image

[0022]

Embedded image

[0023]

Embedded image

The most preferred dyes corresponding to formula (II) are
In dispersed form, provided by Hoechst AG, Germany, other blue dyes such as Valifast Blue 1605 and Zap
onFast Blue 3G (manufactured by Hoechst AG), Estr
ol Brill Blue N-3RL (manufactured by Sumitomo Chemical), Su
miacryl Blue F-GSL (manufactured by Sumitomo Chemical), D & C
Blue No.1 (manufactured by National Anilin Co., Ltd.), Spirit Blue (manufactured by Hodogaya Chemical),
Contrary to Oil Blue No. 603 (manufactured by Orient Co., Ltd.) and Kiton Blue A (manufactured by Ciba-Geigy AG)
Particularly suitable for use in storage panels according to the invention.

As shown in FIG. 1, irritating lines (500 to 7)
00 nm) and the radiation emitted by the stimulable phosphor upon stimulation (350 to 350 nm).
The ratio between the absorption signal in the wavelength range of 450 nm) and the triarylmethane used in the storage panel according to the invention, when compared to a dye such as, for example, the previously described ValifastBlue 1605 (shown in FIG. 1 as a comparative dye) The advantages of the dye are clear.

In a preferred embodiment, the intermediate light-absorbing layer containing one or more triarylmethane dyes comprises a phosphor-containing layer to avoid scattering of light at the interface between the layer containing the phosphor layer and the support. And between the support and /
Or provided in the support itself, thereby increasing the image resolution of the photostimulable phosphor screen. In particular, substituted triarylmethane dyes having relatively high solubility in polar or protic solvents such as alcohols are preferred because diffusion from the non-polar solvent to the adjacent phosphor layer does not occur. Accordingly, a preferred substituted triarylmethane dye is a triphenylmethane dye in which at least one phenyl group is substituted with one or more sulfonic acid groups, carboxylic acid groups, and the like, and the colorant further includes such an ionizable acidic group. Is a substituted triphenylmethane dye that is soluble in aqueous alkaline media.

When a preferred triarylmethane dye is present in the light absorbing intermediate layer, preferably the support further contains reflective particles to render it reflective. A support comprising, for example, TiO ₂ (anatase) particles, is thereby provided with a 45-600 nm wavelength range of 45-600 nm.
It has a reflectivity of 60% (expressed as reflectivity or% reflectivity). Otherwise example support containing BaSO ₄ particles exhibit a reflection percentage 85 to 100%. In another embodiment, the particles are incorporated into a cured layer coated on a support. Said cured layer, which should also be considered as an intermediate layer between the support and the phosphor layer, preferably contains a preferred blue triarylmethane colorant in order to obtain a storage panel according to the invention. The presence of a reflective layer, beneath the phosphor layer, whether or not containing a preferred blue colorant, favors screen speed. Although such reflectivity properties are expected to be disadvantageous for sharpness, it is surprising that this speed increase and speed compensation of speed loss due to the presence of antihalation dyes is not disadvantageous with respect to image resolution for the purposes of the present invention. Was also found here.

Another light-reflecting layer provided to enhance the output of light emitted by light stimulation is an aluminum layer (vacuum deposited). In the definition of reflectance according to the present invention, a stimulating line for said stimulable phosphor which is smaller than the average reflectance in the wavelength band of light emitted by said dye or colorant when stimulating said stimulable phosphor. Average reflectance in the wavelength band of

In another embodiment, the dye or colorant is additionally present in the phosphor layer itself: however, in order to overcome the slowdown, the dye or colorant is present more than in the interlayer and / or support. We recommend adding a small amount.

In yet another embodiment, the dye or colorant is additionally present in a protective layer coated on top of the phosphor layer: in that case, than in the phosphor layer. It is recommended to add a smaller amount of the dye, and thus a much smaller amount than the dye in the interlayer, to prevent further loss in the speed of the screen. Nevertheless, its presence is particularly useful when light transmission causes the stimulating light to enter the protective overcoat (thus resulting in unsharpness).

In the phosphor layer, an increase in the phosphor to binder volume ratio provides a further reduction in the thickness of the coating layer for the same phosphor coverage and even better sharpness. Not only does it provide higher speed or sensitivity. Improvements in special image sharpness are described in WO 94/05
31 can be realized with the thermoplastic rubber binder cited since thin phosphor layers are possible with a large phosphor to binder ratio. Rubbery binders are preferably selected because they allow for a high volume ratio of pigment to binder, provide excellent physical properties and image quality, and provide enhanced speed. In that case, a small amount of binder will not create a layer that is too brittle,
The minimum amount of binder in the phosphor layer provides sufficient structural adhesion to the layer. Especially for storage phosphor members, this factor is very important in terms of the operation of exposing said layer.
The weight ratio of phosphor to binder is preferably from 80:20 to 99: 1, and the volume ratio of phosphor to binder medium is preferably greater than 85/15. In this connection, 92/8
Larger phosphor to binder volume ratios are almost unacceptable and are about the maximum of said volume ratios. A mixture of one or more thermoplastic rubber binders can be used in the coated phosphor layer: preferably the binder medium is WO 94/005.
As described in 30, the rubber and / or elastic polymer consists essentially of one or more block copolymers having a saturated elastic central block and a thermoplastic end block. Particularly suitable thermoplastic rubbers for use as the block copolymer binder in the phosphor screens according to the present invention include KRATON-G rubber (KRATON is SHEL
L). Preferably, the phosphor layer has a binding polar functionality of at least 0.5%, a thickness in the range of 10-1000 [mu] m, and a volume ratio of 92: 8 or less.

According to the invention, the storage panel as described above may be provided with at least one antioxidant which prevents yellowing of the screen. Preferably, the antioxidant is incorporated into the phosphor layer. The coating dispersion may further contain a filler (reflective or absorbent).

As is well known, the sensitivity of a screen depends on the chemical composition of the phosphor, its crystal structure and grain size characteristics, and the weight of the phosphor coated in the phosphor layer. Image quality, especially sharpness, is determined in particular by the optical scattering phenomena in the phosphor layer, which is determined mainly by the packing density, in addition to the thickness of the phosphor layer described above. The packing density of the phosphor particles is:
It depends on their morphology and the amount of binder present in the phosphor layer.

Another factor that determines the sensitivity of the screen is the thickness of the phosphor layer, which is proportional to the amount of phosphor coated. The thickness is in the range of 10 to 1000 μm,
Preferably 50 to 500 μm, more preferably 100 to 500 μm
It is good that it is within the range of 300 μm.

Exists as the sole phosphor or, apart from differing chemical composition, as a mixture of phosphors,
The coverage of the phosphor present in one or more phosphor layers in the screen may range from about 50 g to 2500 g / m ^2.
g, more preferably from 200 g to 1750 g, even more preferably from 300 to 1500 g.
The one or more phosphor layers can have the same or different layer thicknesses and / or different weight ratio amounts of pigment to binder, and / or different phosphor particle sizes or particle size distributions. It is common knowledge that sharper images with less noise are obtained using smaller average particle size phosphor particles, but that the light emission efficiency decreases with decreasing particle size.
Thus, the best average particle size for a given application is a compromise between the desired imaging speed and image sharpness. The preferred average particle size of the phosphor particles is in the range from 2 to 30 μm, more preferably in the range from 2 to 20 μm.

In the phosphor layer, the phosphor or phosphor mixture can be covered by an object which must be obtained with the produced storage phosphor screen.
If necessary besides mixing the fine particle phosphor with the coarser particle phosphor, a grain size gradient may be created in the storage panel. In principle, this is possible by coating only one phosphor layer using the use of gravity, but in terms of reproducibility, the phosphors or phosphor mixtures according to the invention are used. At least two different storage panels coated from the containing phosphor layer may be coated in the presence of a suitable binder, wherein the layer closest to the support is a small phosphor having an average particle size of about 5 μm or less. Small phosphor particles, consisting of a mixture of particles or a mixture of different batches thereof, and having thereon a mixed particle layer having an average particle size of 8 to 20 μm for the coarse phosphor particles, may optionally be in a suitable binder. In the gaps between the large phosphor particles dispersed in the matrix. Depending on the requirements required, the stimulable phosphors according to the invention or their mixtures can be arranged in various ways in these coating configurations.

Within the scope of the present invention, the choice of phosphor or phosphor mixture is such that the radiation image storage panel is
It is clear that this is limited by having a stimulus line wavelength band located at 00 nm.

In a further preferred embodiment according to the present invention, the radiation image storage panel has a wavelength band of light, when stimulated, which is emitted by the stimulable phosphor, between 350 and 450 nm.

The radiation image storage panel according to the invention can use, for example, a divalent europium-doped barium fluorohalide phosphor, wherein the halogen-containing moiety is (1) phosphorescent as described, for example, in US Pat. No. 4,239,968. It can be stoichiometrically equivalent to a fluorine moiety as in the body, (2) eg EP-A 0021
342 or 0345904 and US-A 458703
6, it can be present in a stoichiometrically small amount relative to the fluorine moiety, or (3) e.g.
A large amount can be present stoichiometrically with respect to the fluorine moiety as described in A 4535237.

According to US Pat. No. 4,239,968,
(I) causing the visible or infrared stimulable phosphor to absorb the radiation that has passed through the subject; and (ii) stimulating the phosphor with a stimulus selected from visible and infrared and storing therein. Emitting the emitted radiation as fluorescence,
It is claimed that the phosphor is at least one phosphor selected from the group of alkaline earth metal fluorohalide phosphors, which records and reproduces a radiation image.

From the stimulus spectrum of the phosphor, it can be seen that the type of phosphor is a He-Ne laser beam (633).
nm), but has poor photostimulability below 500 nm. Stimulated light (fluorescence)
Is in the wavelength range of 350-450 nm, about 390 nm
(Publication, Radiology, 1983)
September, p. 834).

From US Pat. No. 4,239,968, it is desirable to use a visible (eg red light) stimulable phosphor rather than an infrared stimulable phosphor, because the trap of the infrared stimulable phosphor is It can be seen that the radiation image storage panels, which are narrower than those of the visible light stimulable phosphors and thus contain the infrared stimulable phosphors, exhibit a relatively rapid dark decay (fading).

In order to solve the problem, US-A
Use photostimulable storage phosphors with traps as deep as possible to avoid fading, as described in U.S. Pat. No. 4,239,968, and empty the trapped rays (short wavelength lines) with substantially higher photon energies. It is desirable to use it.

The emission intensity at a stimulation wavelength of 500 nm is 6
There have been plans to formulate phosphor compositions that exhibit a stimulation spectrum that is greater than the emission intensity at a stimulation wavelength of 00 nm. Phosphors suitable for said purpose are described in US-A 453.
5238 describes in the form of a divalent europium-activated barium fluorobromide phosphor having a stoichiometric bromine-containing moiety beyond fluorine. US-A 453523
According to 8, the photostimulation of the phosphor is between 400 and 550 nm.
Can be efficiently performed with light even in the above wavelength range.

BaF used in digital radiography
The Br: Eu ²⁺ storage phosphor has a relatively high X-ray absorption in the range of 30-120 keV (which is a suitable range for general medical radiography), but the absorption is, for example, LaOBr: Tm, Gd ₂ O ₂ S: Tb and YTaO
₄ : Smaller than the X-ray absorption of most stimulated phosphors used in screen / film radiography, such as Nb. Thus, a screen containing the light emitting luminescent phosphor will absorb a larger fraction of the irradiated X-ray dose than a BaFBr: Eu screen of the same thickness. Since the signal-to-noise ratio (SNR) of the X-ray image is proportional to the square root of the absorbed X-ray dose, the image produced with the light emitting screen will therefore have the same thickness of BaFB
The noise of the image made with the r: Eu screen will be small. The fraction with the higher X-ray dose is the thicker BaFBr:
Will be absorbed when using Eu screen. However, the use of a thick screen results in diffusion of light at large distances in the screen, which results in poor resolution. For this reason, US-A 42399
X-ray images made with digital radiography using a BaFBr screen, as described at 68, give a more noisy impression than images made with screen / film radiography.

A more suitable way to increase the X-ray absorption of the phosphor screen is by increasing the intrinsic absorption of the phosphor. In the BaFBr: Eu storage phosphor, this can be achieved by partially replacing bromine with iodine.

A BaFX: Eu phosphor containing a large amount of iodine is described, for example, in EP-A 0 143 732, the general formula of which is BaF (Br
_1-x I _x ): yEu, and 10 ⁻³ ≦ x ≦ 1.0.
In FIG. 3 of said patent application, the relative brightness of the BaFX: Eu storage phosphor is shown as a function of the iodine content. From FIG. 3 in the preceding description, x according to the general formula can be as large as 1.0, but the portion of Br replaced by I should preferably not be larger than 50%, because It is clear that replacement of a large portion of Br by I results in a low relative brightness of the light emitted when stimulated. The relative brightness of the storage phosphor should be as high as possible because the sensitivity of the storage phosphor system is proportional to the storage phosphor brightness and apart from high X-ray absorption, high system This is because sensitivity is essential for reducing image noise.
Thus, in phosphors as described in EP-A 0 143 732, the improvement in image quality is offset by a decrease in relative brightness due to the high absorption of X-rays when more than 50% of iodine is contained. .

Suitable divalent europium-activated barium fluorobromide phosphors for use according to the invention are furthermore EP-A 0 533 236 and the corresponding US-A 54
22220 and 5547807. EP-A 0 533 236 claims a divalent europium-activated stimulable phosphor in which the stimulated light is 550 nm light more than when the stimulation is performed at 600 nm light. It has great intensity when stimulated. In said phosphor it is stated that the "small part" of bromine is replaced by chlorine and / or iodine. By this small part, it must be understood that it is less than 50 atomic%.

Further divalent europium-activated barium fluorobromide phosphors suitable for use according to the invention are described in EP-A 0 533 234. EP-A 0 533 234 describes a process for preparing europium-doped alkaline earth metal fluorobromide phosphors, in which fluorine is present in a greater atomic% than bromine and clearly in a shorter wavelength band. With the stimulus spectrum shifted. Among them, the use of short wavelength light for photostimulation of a phosphor panel containing phosphor particles dispersed in a binder is advantageous for image sharpness because one kind of grating This is because the diffraction of the stimulating light in the phosphor-binder layer containing dispersed phosphor particles acting as) decreases with decreasing wavelength.

As is evident from the examples in this EP-A 0 533 234, the ultimately obtained phosphor composition, its special wavelength including a scanning light source which determines the optimum wavelength for photostimulation and thus emits light in a narrow wavelength band. Determine the sensitivity of the phosphor in the scanning system.

Another preferred photostimulable phosphor according to the aforementioned application is an alkaline earth selected from the group consisting of Sr, Mg and Ca in atomic% relative to barium in the range of 10 ^{-1 to} 20 atomic%. Contains metal. Of the alkaline earth metals, Sr is most preferred for increasing the X-ray conversion efficiency of the phosphor. Thus, in a preferred embodiment, it is recommended that the strontium be present in stoichiometric combination with barium and fluorine at a greater atomic percentage than bromine alone or bromine in combination with chlorine and / or iodine.

[0052] Other preferred photostimulable phosphors according to that application, by atomic% in the range of 10 ^-3 to 10 ^-1 atomic% relative to barium, Ce, Pr, Nd, Gd , Tb, Dy,
It contains a rare earth metal selected from the group consisting of Ho, Er, Tm, Yb and Lu. Among the rare earth metals, Gd is preferred in order to obtain a shift of the photostimulation spectrum of the phosphor to the maximum short wavelength.

The above-mentioned preferred phosphors of that patent application are also preferred for use in the present invention, provided that the wavelength band of the stimulating ray is between 500 and 700 nm as described above.

Still other preferred photostimulable phosphors for use in accordance with the present invention are based on barium, from 10 ^-1 to 10 ^-1 .
Al, Ga, In, T in atomic% in the range of 10 atomic%
It contains a trivalent metal selected from the group consisting of 1, Sb, Bi and Y. To obtain the highest short-wavelength shift of the photostimulation spectrum of the phosphor from among the trivalent metals Bi
Is preferred.

Preferred phosphors for use in accordance with the present invention are other phosphors in which fluorine is stoichiometrically present in greater than atomic percent bromine alone or in combination with bromine in combination with chlorine and / or iodine. For example, phosphors in which fluorine is present at 3-12 atomic% more than bromine or bromine in combination with chlorine and / or iodine.

An even more particularly preferred barium fluorobromide phosphor for use in accordance with the present invention is the primary dopant Eu.
^In addition to ²⁺ , EP-A 0 533 233 and the corresponding U
It contains at least Sm as a co-dopant as described in SA 5629125.

Still other useful phosphors are EP-A 0
As described in U.S. Pat. No. 736586, there is a phosphor in which Ba ions are partially substituted by Ca ions on the surface of the phosphor.

In digital radiography, for the phosphors included for use in the storage panel according to the invention, use is made of a photostimulable phosphor which can be stimulated very efficiently by light having a wavelength greater than 600 nm. It can be advantageous because then the choice of a small, reliable laser that can be used for stimulation (e.g., He-Ne, semiconductor laser, solid state laser, etc.) and the choice of laser type can be This is because the size of the device for reading (stimulating) the light screen is very large so as not to determine the size.

A more recent stimulable phosphor which gives good signal-to-noise ratio, high speed and can be stimulated at wavelengths above 600 nm is an EP application filed Oct. 10, 1996.
No. 96202816. Among them,
Provides high X-ray absorption combined with high intensity of photostimulated emission, thus having high sharpness and low noise content at the same time via reduced levels of X-ray noise and reduced levels of fluorescence noise A group of storage phosphors is described which makes it possible to construct a storage phosphor system for radiography producing images. Further, the photostimulable phosphors of the above group provide high X-ray absorption combined with a high intensity of the stimulated emission, and the photostimulated emission when stimulated with light having a wavelength above 600 nm. Shows the above high strength. The photostimulable phosphor can further be used in a panel for medical diagnosis, whereby the amount of X-rays projected to the patient can be reduced and the image quality of the diagnostic image is enhanced: above 600 nm Panels containing the phosphor in a dispersed form when photostimulated with light in the wavelength range produce images with very high signal-to-noise ratios.

The photostimulable phosphor is within the range of the following formula: _{Ba 1-xyp-3q-z} Sr x M y 2+ M 2p 1+ M 2q 3+ F
_2-ab Br _{a Ib} : zEu

In the formula, M ¹⁺ is Li, Na, K, Rb and Cs
At least one alkali metal selected from the group consisting of: M ²⁺ is at least one divalent metal selected from the group consisting of Ca, Mg, and Pb; M ³⁺ is Al, G
a, In, Tl, Sb, Bi, Y or trivalent lanthanide,
For example, La, Ce, Pr, Nd, Sm, Gd, Tb, D
at least one trivalent metal selected from the group consisting of y, Ho, Er, Tm, Yb and Lu; 0 ≦ x ≦ 0.
30,0 ≦ y ≦ 0.10,10 ⁻⁶ ≦ z ≦ 0.2,0 ≦ p
≦ 0.3, 0 ≦ q ≦ 0.1, 0.05 ≦ a ≦ 0.76
0.20 ≦ b ≦ 0.90 and a + b <1.00.

In a preferred embodiment, 0.06 ≦
x ≦ 0.20 and 0.85 ≦ a + b ≦ 0.96,
In a more preferred embodiment, 0.06 ≦ x ≦ 0.
20, 0.85 ≦ a + b ≦ 0.96, and M ¹⁺ is Cs
Or Rb, M ²⁺ is Pb, and 10 ⁻⁴ ≦ y ≦ 10
⁻³ , 10 ⁻⁴ ≦ p ≦ 10 ⁻¹ and q = 0.

A very useful and preferred method for the preparation of stimulable phosphors is described in Research Disclosure Vol.
8, Feb. 1994, p. 93, item 35841, which is incorporated herein by reference.

Even in the presence of co-dopants which affect the location of the stimulation spectrum, such as, for example, samarium or alkali metals, which are added in small amounts to the raw material mixture of the substrate material as described in EP-A 0 533 234 A solution has been proposed in U.S. Pat. No. 5,551,034 to make a phosphor having a composition of and therefore a constant stimulation spectrum for use in a storage phosphor panel.

Among them, a method for recording and reproducing a transmitted radiation image comprising the following steps has been proposed:

(I) causing the stimulable storage phosphor to absorb the transmitted radiation passed through or emitted by the subject and store the energy of the transmitted radiation; (ii) stimulating the phosphor Stimulating with light to release at least a portion of the stored energy as fluorescence; (iii) detecting the stimulating light;
The phosphor comprises a mixture of two or more divalent europium-doped barium fluorohalide phosphors, each made of at least one of which is characterized by the stimulation spectrum properties of the co-doped phosphor. It is characterized by containing a co-dopant which is determined jointly.

More particularly suitable divalent europium fluorobarium bromide phosphors for use according to the invention are:
Corresponds to empirical formula (I) of EP-A 0 533 236 and contains, in addition to the main dopant Eu ²⁺ , at least one alkali metal, preferably sodium or rubidium, as co-dopant. Preferred photostimulable phosphors according to that application contain samarium in barium in the range of 10 ^-3 to 10 at%. Another preferred photostimulable phosphor according to that application is 1 bar against barium.
Li, Na, K, Rb at atomic% in the range of 0 ^-2 to 1 atomic%
And an alkali metal selected from the group consisting of Cs.

In practice, for example, the highest in the stimulation spectrum for a lithium-melted stimulating europium-activated barium fluorohalide phosphor is between 520 and 5
It can be found between 50 nm, but for cesium-fused phosphors, the highest is 570-63.
Located between 0 nm. The highest for the stimulation spectrum of the phosphor can be found at intermediate wavelengths after making the mixture. The stimulation spectrum of the mixture is 5
It is further characterized in that the emission intensity at 00 nm stimulation is always lower than the emission intensity at 600 nm. The resulting broadening of the stimulation spectrum is another advantage resulting from the method of making the mixture, in that the storage panel incorporating the stimulable phosphor is sensitive to a broad band of stimulation wavelengths in the visible range of the wavelength spectrum. . As a result, a storage panel comprising a layer with a phosphor mixture as described above can offer versatile applicability in terms of stimulation with different stimulus light sources. The different stimulus sources that can be applied include the Research Discl
osure No. 308117 (December 1989).

The radiographic screen according to the present invention can be manufactured by the following manufacturing method.

The phosphor layer is EP-A 0510753.
The use of solvents for the binder of the phosphor-containing layer as well as the use of useful dispersants, useful plasticizers, useful fillers and primer or interlayer compositions described extensively in Can be applied to the support.

The phosphor particles may be mixed with the dissolved rubber and / or elastomeric polymer at a suitable mixing ratio to form a dispersion. The dispersion is uniformly applied to the substrate by known coating methods such as, for example, doctor blade coating, roll coating, gravure coating or wire bar coating, and dried to fluoresce by X-ray irradiation. A layer (hereinafter referred to as a fluorescent layer) is formed. Another mechanical action, such as compression, to reduce the void ratio is not required within the scope of the present invention.

Not only useful dispersants for improving the dispersibility of the phosphor particles dispersed in the coating dispersion but also various additives that can be added to the phosphor layer, for example, phosphorous in the phosphor layer Plasticizers for increasing the bond between the phosphor particles and the binder and light-reflecting or absorbing fillers and / or colorants according to the invention are described in EP-A 0 510 753.

Useful plasticizers include phosphates such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalates such as diethyl phthalate and dimethoxyethyl phthalate; and salts such as ethyl phthalyl ethyl glycolate and butyl phthalyl butyl glycolate. Glycolates; include polymeric plasticizers, such as polyesters of aliphatic dicarboxylic acids and polyethylene glycols such as polyesters of succinic acid and diethylene glycol and polyesters of adipic acid and triethylene glycol.

The stimulable phosphor preferably protects against the effects of moisture by chemically or physically attaching a hydrophobic or hydrophobizing substance thereto. Suitable substances for this purpose are, for example, US-A 4,138,361.
It is described in.

In the composition of the storage panel, to improve the bond between the support and the phosphor layer, or to improve the sensitivity of the screen or the sharpness and resolution of the resulting image, the support and the phosphor Between the phosphor-containing layers, one or more additional layers having a primer or interlayer composition are optionally provided. For example, an undercoat or adhesive layer can be provided by a coated polymeric material on the side of the support on the phosphor layer side.

The additional layers can be coated on the support as a backing layer or as a layer inserted between the support and the intermediate layer, between the intermediate layer and the phosphor-containing layer. Some of the additional layers may be applied in combination.

In preparing a phosphor screen having a subbing layer between the substrate and the layer containing the phosphor, the subbing layer is pre-applied onto the substrate and then the phosphor dispersion is applied to the subbing layer. Apply and dry to form a fluorescent layer.

When using a phosphor in combination with a binder to produce a screen or panel according to the invention,
The phosphor particles are tightly dispersed in a solution of the binder, then coated on a support and dried. The coating of the phosphor binder layer of the present invention can be performed by any conventional method, for example by spraying, dip coating, or doctor blade coating. After coating, the solvent of the coating mixture is removed by evaporation, for example by drying in a stream of hot (60 ° C.) air.

Sonication can be applied to improve the packing density and to degas the phosphor-binder combination.
Prior to any application of the protective coating, phosphor - binder layer, can improve the packing density and calendered (i.e. g number of phosphor for dry coating 1 cm ^3).

After applying the coating dispersion to the support, the coating dispersion is gradually heated and dried in order to complete the formation of the phosphor layer. Prior to coating, it can be subjected to sonication to remove as much air entrained in the phosphor coating composition as possible.

After the formation of the phosphor layer, a protective layer is generally provided on top of the fluorescent layer.

With the desirable and surprising properties of excellent image sharpness and ease of scanning, the relative features of roughness and thickness of the protective coating on the screens of the present invention are EP-
A0510754.

According to a preferred embodiment, the coating of the protective layer is effected here by screen printing (silk screen printing).

The protective coating composition is as described in EP-A 051
It is preferably applied by means of a rotary screen printing apparatus as described in detail in EP 0 753. Radiation-curable compositions that are very useful for forming protective coatings include as major components: (1) a crosslinkable prepolymer or oligomer;
It contains (2) a reactive diluent monomer and, in the case of UV curable, (3) a photoinitiator.

Examples of suitable prepolymers for use in the radiation-curable composition applied to the storage panel according to the invention include: unsaturated polyesters, such as polyester acrylates; urethane-modified unsaturated polyesters, such as Urethane-polyester acrylate. Liquid polyesters having an acrylic end group, such as unsaturated copolyesters having an acrylic end group, are disclosed in published EP-A 207257 and Radiat. Phys. Che.
m. Vol. 33, No. 5, 443-450 (1989). The latter liquid copolyester is substantially free of low molecular weight unsaturated monomers and other volatiles and is of very low toxicity (the journal Adha
esion 1990 Heft 12, page 12). The production of a very wide variety of radiation-curable acrylic polyesters is G
erman Offenlengungsschrift No. 2838691. Mixtures of two or more of the above prepolymers may be used. For a survey of UV curable coating compositions, see, for example, the journal "Coating" 9/88, pp. 348-35.
3 is given.

When radiation curing is carried out with ultraviolet radiation (UV), the presence of a photoinitiator in the coating composition and the prepolymers and their prepolymers which cause polymerization of the monomers and curing of the coated protective layer composition Acts as a catalyst to initiate the desired crosslinking.

A photosensitizer can be present to enhance the effect of the photoinitiator. Suitable photoinitiators for use in the UV curable coating composition are organic carbonyl compounds such as benzoin ether compounds such as benzoin isopropyl, isobutyl ether; benzyl ketal compounds; ketoxime esters; benzophenone compounds such as benzophenone, o Benzoylmethylbenzoate; acetophenone compounds such as acetophenone, trichloroacetophenone, 1,1-dichloroacetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone; thioxanthones such as 2-chlorothioxanthone, -Ethylthioxanthone; and 2-hydroxy-2-methyl-
It belongs to the group of propiophenone, 2-hydroxy-4'-isopropyl-2-methylpropiophenone, 1-hydroxycyclohexylphenyl ketone and the like.

A particularly preferred photoinitiator is 2-hydroxy-
2-methyl-1-phenyl-propan-1-one, which is trade name DAROCUR 1173,
It is marketed by E. Merck of Darmstadt, Germany. The aforementioned photopolymerization initiators can be used alone or as a mixture of two or more. Examples of suitable photosensitizers include, for example, GB-A 1314556, 1486911, US-
There are certain aromatic amino compounds as described in US Pat. No. 4,255,513 and merocyanine and carbostyril compounds as described in US Pat. No. 4,282,309.

When using ultraviolet radiation as a curing source,
The photoinitiator to be added to the coating solution also absorbs, to a lesser or greater extent, the light emitted by the phosphor, which results in radiation, especially when using phosphors that emit UV or blue light. It will impair the sensitivity of the photographic screen.
Electron beam curing can therefore be more effective.

The protective coating of the storage panel according to the invention, following the coating step, gives the uncured or slightly cured coating through the nip of a pressure roller to give an embossed structure, in which case it contacts said coating The roller has a micro-relief structure, for example, which gives the coating an embossed structure so as to obtain a relief part as described for example in EP-A 455309 and 456318.

A preferred method for forming a patterned structure in a plastic coating by means of an engraving chill roll is described in US-A-A.
3,959,546.

According to another embodiment, the patterned or embossed structure is formed using a radiation-curable liquid coating composition (Hepler viscosity at a coating temperature of 25 ° C. is 450-20,000 mPa.s.). It can be obtained beforehand in the coating stage by applying the pasty coating composition with a gravure roller or screen printing device that operates.

Radiation curing takes place immediately or almost immediately after application of the liquid coating to avoid flattening of the embossed structure under the effects of gravity viscosity and surface shear. The rheological behavior or flow properties of the radiation-curable coating composition can be controlled by so-called flow agents. For that purpose, lower alkyl (C1-C1
Alkyl acrylate ester copolymers containing C2) and higher alkyl (C6-C18) ester groups can be used as shearing agents to reduce viscosity. Addition of a pigment, such as colloidal silica, increases the viscosity.

The radiation-curable coating composition of the radiographic product of the present invention may contain various other optional compounds such as a compound for reducing electrostatic charge accumulation, a plasticizer, a matting agent, a lubricant, an antifoaming agent and the like. -A It can be contained as described in 0510753. In that document, not only devices and methods for curing, but also X-ray conversion screen phosphors,
A non-limiting investigation of the photostimulable phosphor and the binder of the phosphor containing layer is also provided.

The edges of the screen, which can be particularly scratched by many operations, have edges (sides) made of a polymer material essentially formed from the moisture-cured polymer composition made according to EP-A 0 541 146. Can be enhanced by covering.

Support materials for radiographic screens according to particular embodiments of the present invention include plastic films such as cellulose acetate, polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, polystyrene, polyester, polyethylene terephthalate, polyethylene naphthalate, polyamide, Polyimide, cellulose triacetate and polycarbonate;
Metal sheets such as aluminum foil and aluminum alloy foil; ordinary paper; baryta paper; resin-coated paper; pigment paper containing titanium dioxide and the like; and paper sized with polyvinyl alcohol and the like are preferable.

Examples of preferred supports include transparent or blue or black colored polyethylene terephthalate (eg supplied by Toray Industries, Tokyo, Japan).
LUMIRROR C, type X30), comprising polyethylene terephthalate filled with TiO ₂ or BaSO _4. For example, a metal such as aluminum or bismuth may be deposited by, for example, a vapor deposition method to obtain a radiation-reflective polyester support.

These supports can have different thicknesses depending on the material of the support and generally have a thickness of 50 to 1000 μm, more preferably 80 to 50 μm, depending on the handling characteristics.
It can be 0 μm. Furthermore, a glass support and a metal support are also included.

Usually, the screens described above are used for medical X-ray diagnostic applications, but according to a particular embodiment, the radiographic screens of the present invention have a higher energy X-ray than in medical X-rays. It can also be used in non-destructive inspection (NDT) of metal objects using X-rays or gamma rays. In particular, in said applications, furthermore glass and metal supports are used, the latter being described, for example, in US Pat.
High atomic weight ones are preferred, as described in 09 and 3389255.

According to a particular embodiment for industrial radiography, the image sharpness of the phosphor screen is determined by the phosphor screen between the phosphor-containing layer and the support.
Or on the back side of the support, Research Disclosure 1979
September 18th, item 18502, by incorporating a pigment-binder layer containing a non-fluorescent pigment which is a metal compound such as a lead salt or oxide.

To obtain a reasonable signal-to-noise ratio (S / N), the stimulating light should be prevented from being detected together with the fluorescence emitted upon photostimulation of the storage phosphor. Accordingly, a suitable filter means is used to prevent stimulating light from entering the detection means, such as a photomultiplier tube. This is because the intensity ratio of the stimulating light is significantly greater than that of the stimulated emitted light, ie in the range of 10 ⁴ : 1 to 10 ⁶ : 1 (see column 5 of published EP-A 0007105). Due to differences in intensity, very selective filters should be used. Suitable filter means or filter combinations can be selected from the group of cut-off filters, transmission band filters and band reject filters. A survey by filter type and spectral transmission grade is available from A Wiley-Interscience Publi in New York.
cation-John Wiley & Sons (1973), Wo
odlief Thomas, Jr ed., SPSE Handbook of Photogra
phicScience and Engineering, pp. 264-326.

The fluorescence emitted by the light stimulus is preferably a converter that converts light energy into electron energy.
For example, it is detected photoelectronically by a phototube (photomultiplier) which provides a sequential electrical signal which can be digitized and stored. After storage, these signals can be subjected to digital processing. Digital processing includes, for example, image contrast enhancement, spatial frequency enhancement, image color reduction, image color addition, and contool definition of specific image portions.

According to one embodiment for the reproduction of a recorded X-ray image, the optionally processed digital signal is converted into an analog signal, which is modulated, for example by an acousto-optical modulator, into a writing laser beam. used. The modulated laser beam is then used to scan a photographic material, for example, a silver halide emulsion film on which an X-ray image, optionally imaged, is reproduced.

According to another embodiment, a digital signal obtained from an analog-to-digital conversion of an electrical signal corresponding to light obtained via light stimulation is displayed on a cathode ray tube. Before display, the signal may be processed by a computer. Conventional image processing techniques can be applied to reduce the signal-to-noise ratio of the image and to enhance the image quality of the coarse or fine image features of the radiograph.

The present invention is illustrated by, but not limited to, the following examples. Important points related to image quality as reflected in the S-SWR measurement method will be described later in Examples.

EXAMPLES Definitions and Methods Used.

Sensitivity S to stimulable phosphor screen
Of square wave response and SWR

S and SWR were measured on a photostimulable phosphor screen coated with BaSrFBr: Eu ²⁺ phosphor with an image scanner made with a He-Ne laser. The beam of the 10 mW red He-Ne laser is focused on a small point (FMWH) of 140 μm by an optical element including a beam expander and a collimating lens. A mirror galvanometer is used to scan this small laser spot across the width of the phosphor sample. During this scanning process, the phosphor is stimulated and the emitted light is captured by an array of aligned optical fibers. A photomultiplier tube was placed at the other end of the optical fiber mounted in the circle.

To attenuate the stimulating light, an optical filter, type BG3 from SCHOTT, is placed between the fiber and the photomultiplier. In this way, only the light emitted by the phosphor is measured. The small current of the photomultiplier is first amplified by an I / V converter and digitized by an A / D converter.

The measurement device thus prepared is connected to an HP 9826 computer and an HP 6944 multiplex programmer to control the measurement. When starting this method, close the electronic shutter and tighten the laser. 50mm × 120
A phosphor sample of mm dimensions is excited with an 85 kV X-ray source equipped with an aluminum filter having a thickness of 21 mm. The radiation dose is measured with a FARMER dosimeter. X
A thin lead raster containing six different spatial frequencies is mounted between the source and the phosphor layer to modulate x-ray radiation. The frequency used is 0.50, 1.0 for 1 mm.
0, 2.00 and 3.00 line pairs. After exposure, the sample is placed in a laser scanner. To read one line, open the shutter and move the galvanometer linearly. During the scanning process, the emitted light is measured continuously with an A / D converter at a sampling rate frequency of 100 kHz and multiplexed. Store in the memory card in the programmer. Thus, one scan contains 100,000 pixels. Once the scan is complete, close the shutter again and reposition the galvanometer to its original position.

The scan line data is transferred from the memory card in the multiplex programmer to a computer that analyzes the data. The first correction takes into account the sensitivity change of the distanced scan lines. The calibration scan was therefore pre-measured on a truly homogeneously exposed phosphor sample. The second correction takes into account the X-ray dose by dividing said value by the X-ray dose.

The different blocks are divided and the amplitude for each spatial frequency is calculated, this time using Fourier analysis. The amplitude of the first block having a spatial frequency of 0.025 line pairs per mm is taken as the sensitivity of the stimulable phosphor screen. Other values are representative of the square wave response for screen resolution (SWR: SWR1 represents the response on one line pair for 1 mm; SWR2 represents the response on two line pairs for 1 mm) ) Is the result for the curve.

Screen Composition Antihalation Undercoat Layer: Solution A: MOWILITH CT5 (from HOECHST AG) 300 g ethanol 700 g CYMEL 300 60 g p-toluenesulfonic acid 12 g Solution B ^* : Dye-1 0.750 g ethanol 150 g sodium hydroxide 0.08 g * Sixteen hours after its preparation, solution B is filtered to give a reddish brown solution.

Coating solution: 33.3 g of solution A 3.0 g of solution B 63.6 g of ethanol

By dip coating at a speed of 4 m / min on a polyethylene terephthalate support having reflective (containing BaSO ₄ particles) or absorbing (containing carbon black particles) (see also Table 1). The coating solution was coated. After drying, heat curing was performed at 80 ° C. overnight.

Properties of the antihalation layer thus obtained. 0.22 absorption at a wavelength of 633 nm (HeNe laser emission wavelength). No substantial absorption is measured at the emission wavelength of the stimulable phosphor (having its maximum emission at 390 nm).

Phosphor layer composition: BAEROSTAB M36 (from Baerloecher GmbH) 1.5 g DISPERSE AYD 9100 (from Daniel Produkts Company) 0.75 g KRATON FG19101X (from Shell Chemicals) 12.5 g BaSrFBr: Eu (average particle size) : 7 μm) 270 g BaSrFBr: Eu (average particle size: 3 μm) 30 g

Preparation of the phosphor lacquer composition: BAEROSTA
B M36, DISPERSE AYD 9100 and KRATON FG19101X
Was dissolved with stirring in 61.5 g of a solvent mixture of 100-120 washed benzene, toluene and butyl acrylate in a volume ratio of 50:30:20 with stirring. Thereafter, a phosphor was added, and the mixture was further stirred at a speed of 1700 rpm for 10 minutes.

The composition was doctor-blade coated on a subbed 175 μm thick polyethylene terephthalate support at a coating speed of 2.5 m / min and dried at room temperature for 30 minutes. The coated phosphor plate was dried at 90 ° C. in a drying stove to remove as much volatile solvent as possible.

It has proved that a layer composition having good curable properties has been obtained. Furthermore, no diffusion of the colorant from the intermediate antihalation layer between the support and the phosphor layer to the phosphor layer was found: this is because certain dyes dissolve in ethanol but phosphor Advantageously, it is insoluble in the solvents present in the coating composition of the layer.

Table 1 shows the coating compositions for the stimulable phosphor. For each screen sample, the following data for the composition is tabulated in the respective tables.

(A) Sample No. (Material No.); (B) Support: expressed as% reflectance: 0 to 10% corresponds to a support having carbon black dispersed in the support material; 85 ~ 100% is the BaSO dispersed therein
_This corresponds to a support having ₄ . (C) Presence of anti-halation undercoat layer (AHU):
Yes (Y) or no (N). (D) Phosphor coating weight (PCW) (70 to 90 mg /
cm ² ). (E) The presence of the dye in the phosphor layer (without N) and, if present, the amount. (F) Screen speed (the higher the number, the greater the sensitivity). (G) The respective SWR1 and SWR2 values.

[0123]

[Table 1]

As is evident from the data relating to speed and sharpness, the highest (most preferred) values are those for Material Nos. 1 and 2
(Both have an antihalation primer coat and a reflective support): an increased amount of coated phosphor increases the speed and there is no significant decrease in sharpness. As in Material No. 6 without a reflective layer, the addition of a small amount of an anti-halation dye to the phosphor layer alone provides a reasonably good relationship between speed and sharpness.

[Brief description of the drawings]

FIG. 1 shows a comparison between the absorption signals measured on the irritant line between the dye used in the present invention and a comparative dye.

Claims (6)

[Claims] 1. A radiation image storage panel comprising a support, an intermediate layer, and a phosphor layer comprising a binder and a stimulable phosphor dispersed therein, said stimulus phosphor being stimulated. The panel such that the average reflectance of the panel in the line wavelength band is less than the average reflectance of the panel in the wavelength band of light emitted by the stimulable phosphor upon stimulation of the stimulable phosphor. Wherein the coloring agent is a triarylmethane dye having at least one aqueous alkali-soluble group, wherein the support, the phosphor layer or the support and A radiation image storage panel, characterized in that it is present in an intermediate layer between the phosphor layers. 2. The method according to claim 1, wherein the coloring agent has the general formula (I): Wherein R ^{1 to} R ⁸ each independently represent hydrogen, a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that at least one of R ^{1 to} R ⁸ represents an acidic group. The radiation image storage panel according to claim 1, wherein the radiation image storage panel is a phenylmethane dye. 3. The method according to claim 2, wherein the coloring agent has the formula (II): The radiation image storage panel according to claim 1, having a structure corresponding to (1). 4. The radiation image storage panel according to claim 1, wherein the support has a reflectivity of 45 to 60% at a wavelength in the range of 350 to 600 nm. 5. The radiation image storage panel according to claim 1, wherein the intermediate layer has a reflectance of 85 to 100% at a wavelength in the range of 350 to 600 nm. Wherein said stimulable phosphor has the formula _{Ba 1-xyp-3q-z} Sr x M y 2+ M 2p 1+ M 2q 3+ F 2-ab Br a
I _b : zEu (where M ¹⁺ is at least one alkali metal selected from the group consisting of Li, Na, K, Rb and Cs;
²⁺ is at least one divalent metal selected from the group consisting of Ca, Mg and Pb; M ³⁺ is Al, Ga, In,
Tl, Sb, Bi, Y or trivalent lanthanides such as L
a, Ce, Pr, Nd, Sm, Gd, Tb, Dy, H
at least one trivalent metal selected from the group consisting of o, Er, Tm, Yb and Lu; 0 ≦ x ≦ 0.30,
0 ≦ y ≦ 0.10, 10 ⁻⁶ ≦ z ≦ 0.2, 0 ≦ p ≦ 0.
3,0 ≦ q ≦ 0.1,0.05 ≦ a ≦ 0.76,0.2
6. A composition according to claim 1, wherein 0 ≦ b ≦ 0.90 and a + b <1.00.
Item radiation image storage panel.