Radiographic intensifying screen and radiation image converting panel

A method for preparing a radiographic intensifying screen or a radiation image conversion panel is disclosed, comprising a support having thereon a phosphor layer, the method comprising the steps of (i) mixing a phosphor and a resin exhibiting a glass transition temperature of Tg1 to form a phosphor layer, (ii) subjecting the phosphor layer to compression, and (iii) making a glass transition temperature of the phosphor layer Tg2, wherein the Tg1 and the Tg2 meet the following requirement: Tg1<Tg2. Tg1 is within the range of -50.degree. C. to 25.degree. C., and Tg2 is 30.degree. C. to 130.degree. C.

FIELD OF THE INVENTION
 The present invention relates to a radiographic intensifying screen and
 radiation image converting panel, both having high image quality.
 BACKGROUND OF THE INVENTION
 Cited as a means for obtaining a radiographic image for medical diagnosis
 or non-destructive testing of various types of tissue and applying it to
 diagnosis and radiographic flaw detection are: radiography by a
 combination of a silver halide photographic light sensitive material and a
 radiographic intensifying screen, or a radiographic image conversion
 method by the use of a stimulable phosphor from which, after absorption of
 radiation energy, the accumulated radiation energy is emitted in the form
 of fluorescence by stimulation with electromagnetic waves such as visible
 light or infra-red rays (hereinafter referred to as stimulable phosphor).
 Diagnosis or examination with radiography is such that radiation
 transmitted through or emitted from photographic object is converted,
 through absorption by phosphor contained in the radiographic intensifying
 screen and its excitation, into visible light, which produces a
 radiographic image on a silver halide photographic light sensitive
 material. The radiographic image is formed by exposing, to radiation
 through an object, the silver halide photographic light sensitive material
 having, on one side or both sides of a support, a silver halide emulsion
 layer, which is in contact with a radiographic intensifying screen to
 radiation through an object.
 The phosphor has a high brightness and can form a radiographic image with a
 relatively small dose of radiation, so that exposure to radiation by the
 object is minimal. It is well known that sharpness and graininess of such
 images depend upon the particle size and dispersion and homogeneity of the
 phosphor, and in particular upon the filling ratio in the phosphor
 containing layer.
 The radiographic image conversion method employing stimulable phosphor
 includes the employment of a radiation image converting panel containing
 the stimulable phosphor (hereinafter, referred to as a stimulable phosphor
 panel). In this case, the radiation transmitted through or emitted from
 the object is absorbed by a stimulable phosphor contained in the panel,
 followed by stimulating time-sequentially the phosphor with
 electromagnetic waves such as visible light or infra-red rays (also known
 as stimulating light), and emitting the radiation energy accumulated in
 the phosphor, in the form of light (photo-stimulated luminescence). The
 photo-stimulated luminescence is read as electric signals and based on the
 electric signals obtained, the object or its radiographic image is
 reproduced as a visible image. The panel which has already been read is
 treated to eliminate all residual images and made ready for the next
 photograph. Thus, the conversion panel can be employed repeatedly.
 Similarly to the screen brightness, bending strength and abrasion
 resistance of the panel are also dependent upon dispersibility,
 homogeneity and filling ratio of the stimulable phosphor. Of these, the
 filling ratio of the stimulable phosphor is particularly influential.
 Means for enhancing emission characteristics of the screen and panel is in
 general to enhance the filling ratio of the phosphor.
 JP-A 3-21898 (herein, the term, JP-A means unexamined and published
 Japanese Patent Application) described, as a means for enhancing the
 filling ratio, the use of a resin having a glass transition temperature
 (hereinafter, denoted simply as Tg) of 30 to 150.degree. C. and a
 radiation image converting panel with 70% or more filling ratio of a
 stimulable phosphor, which was achieved by compressing a phosphor
 containing layer (hereinafter, also denoted as a coating layer). Since the
 radiographic intensifying screen or the radiation image converting panel
 is employed with being rubbed with a photographic film or roll at room
 temperature, the Tg of a resin to be used is preferably not less than
 30.degree. C. However, when a resin with a high Tg is employed as a
 binder, the coating layer is not easily reduced in volume during drying,
 leading to a decreased filling ratio. Further, when the resulting coated
 layer is subjected to compression, due to deteriorated softening
 characteristics, the phosphor is under pressure liable to produce defects
 or destruction of the crystal structure, resulting in lowering of the
 sensitivity. Furthermore, the compression temperature needs to be raised
 to transform the resin, producing problems such as lowered manufacturing
 efficiency.
 Accordingly, there is desired a radiographic intensifying screen or a
 radiation image converting panel with superior brightness and excellent
 image quality, and a manufacturing method thereof.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a radiographic
 intensifying screen or a radiation image conversion panel, whereby a
 radiation image with high image quality can be obtained, and a
 manufacturing method thereof.
 It was found by the inventors of the present invention that when a resin,
 having a glass transition temperature (Tg) of -50 to 25.degree. C., is
 contained as a binder resin in a phosphor layer, deformability of the
 phosphor layer during drying is improved, leading to an enhanced phosphor
 filling ratio, and further the use of a resin containing a polar group
 enhanced dispersion homogeneity and a filling ratio of the phosphor,
 leading to enhanced brightness. It was also found that when subjected to
 compression to enhance the phosphor filling ratio, the use of a resin with
 a low Tg enhanced the phosphor filling ratio even at low temperatures, and
 specifically in cases when a solvent remained in the phosphor layer in
 amounts of 1 to 30% by volume, the phosphor layer could be compressed
 under milder conditions. The above findings were applicable to the panel
 using a stimulable phosphor.
 The object of the present invention can be achieved by the following
 constitution:
 1. a method for preparing a radiographic intensifying screen comprising a
 support having thereon a phosphor layer, the method comprising the steps
 of:
 (i) mixing a phosphor and a resin having a glass transition temperature of
 Tg1 to form a phosphor layer,
 (ii) subjecting the phosphor layer to compression, and
 (iii) making a glass transition temperature of the phosphor layer Tg2,
 wherein the Tg1 and the Tg2 meet the following requirement:
EQU Tg1&lt;Tg2;
 2. the preparation method of a radiographic intensifying screen described
 in 1, wherein the Tg1 is not less than -50.degree. C. and not more than
 25.degree. C.;
 3. the preparation method of a radiographic intensifying screen described
 in 2, wherein the Tg2 is not less than 30.degree. C. and not more than
 130.degree. C.;
 4. the preparation method of a radiographic intensifying screen described
 in 3, wherein the step of (i) comprises mixing the phosphor, resin having
 the glass transition temperature of Tg1 and a hardener;
 5. the preparation method of a radiographic intensifying screen described
 in 4, wherein the hardener is a multifunctional isocyanate;
 6. the preparation method of a radiographic intensifying screen described
 in 5, wherein the amount of the isocyanate is 5 to 30% by weight, based on
 the resin;
 7. a method for preparing a radiographic intensifying screen comprising the
 steps of:
 (i) coating a coating solution containing a phosphor and a resin having a
 glass transition temperature of -50.degree. C. to 25.degree. C., and
 (ii) drying the coating solution coated on the support to form a phosphor
 layer;
 8. the preparation method of a radiographic intensifying screen described
 in 7, wherein the coating solution further contains a hardener;
 9. the preparation method of a radiographic intensifying screen described
 in 8, wherein the hardener is a multifunctional isocyanate;
 10. the preparation method of a radiographic intensifying screen described
 in 9, wherein the isocyanate is contained in an amount of 5 to 30% by
 weight, based on the resin;
 11. a method for preparing a radiographic intensifying screen comprising
 the steps of:
 (i) mixing a phosphor with a resin having a glass transition temperature of
 -50.degree. C. to 25.degree. C. to form a phosphor sheet, and
 (ii) putting the phosphor sheet onto a support;
 12. the preparation method of a radiographic intensifying screen described
 in 11, wherein in the step of (i), a hardener is further mixed;
 13. the preparation method of a radiographic intensifying screen described
 in 12, wherein the hardener is a multifunctional isocyanate;
 14. the preparation method of a radiographic intensifying screen described
 in 13, wherein the amount of the isocyanate is 5 to 30% by weight, based
 on the resin;
 15. a radiographic intensifying screen comprising a support having thereon
 a phosphor layer containing a phosphor and a binder resin, wherein the
 phosphor layer is formed by use of a phosphor and a resing having a glass
 transition temperature of -50.degree. C. to 25.degree. C.;
 16. a radiographic intensifying screen comprising a support having thereon
 a phosphor layer containing a phosphor and a binder resin, wherein the
 phosphor layer further contains a resin having a glass transition
 temperature of -50.degree. C. to 25.degree. C.;
 17. the radiographic intensifying screen described in 16, wherein the
 phosphor layer has a glass transition temperature of 30.degree. C. to
 130.degree. C.;
 18. a radiographic intensifying screen comprising a support having thereon
 a phosphor layer, wherein the phosphor layer has a glass transition
 temperature of Tg2 and contains a resin having a glass transition
 temperature of Tg1, the Tg1 and Tg2 meeting the following requirement:
EQU Tg1&lt;Tg2;
 19. the radiographic intensifying screen described in 18, wherein the Tg1
 is not less than -50.degree. C. and not more than 25.degree. C.;
 20. the radiographic intensifying screen described in 18, wherein the Tg2
 is not less than 30.degree. C. and not more than 130.degree. C.;
 21. a method for preparing a radiation image conversion panel comprising a
 support having thereon a phosphor layer, the method comprising the steps
 of:
 (i) mixing a stimulable phosphor and a resin having a glass transition
 temperature of Tg1 to form a phosphor layer,
 (ii) subjecting the phosphor layer to compression, and
 (iii) making a glass transition temperature of the phosphor layer Tg2,
 wherein the Tg1 and the Tg2 meet the following requirement:
EQU Tg1&lt;Tg2;
 22. the preparation method of a radiation image conversion panel described
 in 21, wherein the Tg1 is not less than -50.degree. C. and not more than
 25.degree. C.;
 23. the preparation method of a radiation image conversion panel described
 in 22, wherein the Tg2 is not less than 30.degree. C. and not more than
 130.degree. C.;
 24. the preparation method of a radiation image conversion panel described
 in 21, wherein the step of (i) comprises mixing the stimulable phosphor,
 resin having the glass transition temperature of Tg1 and a hardener;
 25. the preparation method of a radiation image conversion panel described
 in 24, wherein the hardener is a multifunctional isocyanate;
 26. the preparation method of a radiation image conversion panel described
 in 25, wherein the amount of the isocyanate is 5 to 30% by weight, based
 on the resin;
 27. a method for preparing a radiation image conversion panel comprising
 the steps of:
 (i) coating a coating solution containing a stimulable phosphor and a resin
 having a glass transition temperature of -50.degree. C. to 25.degree. C.,
 and
 (ii) drying the coating solution coated on the support to form a phosphor
 layer;
 28. the preparation method of a radiation image conversion panel described
 in 27, wherein the coating solution further contains a hardener;
 29. the preparation method of a radiation image conversion panel described
 in 28, wherein the hardener is a multifunctional isocyanate;
 30. the preparation method of a radiation image conversion panel described
 in 29, wherein the isocyanate is contained in an amount of 5 to 30% by
 weight, based on the resin;
 31. a method for preparing a radiation image conversion panel comprising
 the steps of:
 (i) mixing a stimulable phosphor with a resin having a glass transition
 temperature of -50.degree. C. to 25.degree. C. to form a phosphor sheet,
 and
 (ii) putting the phosphor sheet onto a support;
 32. the preparation method of a radiation image conversion panel described
 in 31, wherein in the step of (i), a hardener is further mixed;
 33. the preparation method of a radiation image conversion panel described
 in 32, wherein the hardener is a multifunctional isocyanate;
 34. the preparation method of a radiographic intensifying screen described
 in 33, wherein the amount of the isocyanate is 5 to 30% by weight, based
 on the resin;
 35. a radiation image conversion panel comprising a support having thereon
 a phosphor layer containing a stimulable phosphor and a binder resin,
 wherein the phosphor layer is formed by use of a stimulable phosphor and a
 resing having a glass transition temperature of -50.degree. C. to
 25.degree. C.;
 36. a radiation image conversion panel comprising a support having thereon
 a phosphor layer containing a stimulable phosphor and a binder resin,
 wherein the phosphor layer further contains a resin having a glass
 transition temperature of -50.degree. C. to 25.degree. C.;
 37. the radiation image conversion panel described in 36, wherein the
 phosphor layer has a glass transition temperature of 30.degree. C. to
 130.degree. C.;
 38. a radiation image conversion panel comprising a support having thereon
 a phosphor layer, wherein the phosphor layer has a glass transition
 temperature of Tg2 and contains a resin having a glass transition
 temperature of Tg1, the Tg1 and Tg2 meeting the following requirement:
EQU Tg1&lt;Tg2;
 39. the radiation image conversion panel described in 38, wherein the Tg1
 is not less than -50.degree. C. and not more than 25.degree. C.;
 40. the radiation image conversion panel described in 38, wherein the Tg2
 is not less than 30.degree. C. and not more than 130.degree. C.
 DETAILED DESCRIPTION OF THE INVENTION
 The present invention is further described in detail.
 In the radiographic intensifying screen or the radiation image converting
 panel of the present invention, the use of a binder resin having a Tg of
 -50 to 25.degree. C. enhances form-variability of the coating layer during
 drying and increases the filling ratio of a phosphor or a stimulable
 phosphor. Furthermore, the use of a resin containing a polar group
 enhances dispersion homogeneity of the phosphor or stimulable phosphor and
 the filling ratio thereof, leading to enhanced brightness.
 When subjected to compression to enhance the filling ratio, the use of the
 resin with a low Tg as described above enables to enhance the filling
 ratio even at a low temperature. In this case, when a solvent remains in a
 phosphor layer or a stimulable phosphor layer in an amount of 0.1 to 30%
 by volume, the phosphor layer is softened, enabling compression of the
 phosphor layer under milder conditions and decreasing a load on the
 phosphor or stimulable phosphor. When the solvent remaining in the
 phosphor layer is in an amount of less than 0.1% by volume, compression
 effect is reduced and the load on the phosphor stimulable phosphor
 increases, producing problems such as lowering of brightness. When the
 remaining solvent exceeds 30% by volume, the phosphor layer is excessively
 softened and adhered to the compressing surface of a press machine or
 compression rolls, causing calender staining or destruction of the coating
 layer and lowering manufacturing efficiency.
 The phosphor layer of the screen or panel prepared by use of the resin
 having a low Tg according to the invention may possibly be deformed due to
 being rubbed with films or rolls under room temperature. The deformation
 can be prevented by hardening the layer to raise a Tg of the layer. The Tg
 of the hardened layer (or phosphor layer) is preferably 30 to 130.degree.
 C. When the Tg after being hardened exceeds 130.degree. C., the coating
 layer is liable to be cracked, easily causing coating layer destruction
 due to dropping during its use. When the Tg after being hardened is less
 than 30.degree. C., problems are produced such that when the room
 temperature is raised, uneven brightness, peeling-off of a protective
 layer or destruction of the phosphor layer or stimulable phosphor layer
 occurs.
 Means for hardening a coating layer include incorporation of a hardener and
 the use of a UV-ray hardenable resin, and hardening by use of a hardener
 is preferred. Preferred hardener is an isocyanate compound, such as
 multifunctional isocyanates is preferred. The multifunctional isocyanates
 preferably used in the invention include a di-functional isocyanate, a
 tri-functional isocyanate and tetra-functional isocyanate. Examples of the
 di-functional isocyanate include diphenylmethane-4,4'-diisocyanate (MDI),
 hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI),
 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine
 diisocyanate methyl ester, isophorone diisocyanate (IPDI),
 methylcyclohexylene-2,4(2,6)-diisocyanate,
 1,3(4)-(diisocyanatemethyl)cyclohexane and
 4,4-bis(isocyanatocyclohexyl)methane. These compounds can be synthesized
 according to conventional methods and are also commercially available.
 The phosphor layer comprises particles of the phosphor (or stimulable
 phosphor), a binder and voids. The voids are spaces in the phosphor layer,
 in which substantially none of the phosphor particles and the binder are
 present. Accordingly, the proportion of the voids in the phosphor layer
 increases with a decrease of the binder. Since the voids act as a
 light-scattering factor, diffusion of light emitted from the phosphor or
 stimulable phosphor is reduced, resulting in enhanced sharpness.
 In the phosphor layer or stimulable phosphor layer of the screen or panel
 according to the invention is preferably contained a resin, as a binder,
 which contains a hydrophilic polar group. In this case, the binder resin
 contained in the phosphor or stimulable phosphor layer is preferably in an
 amount of 0.5 to 3.0% by weight of the phosphor or stimulable phosphor. In
 cases where the weight ratio of the binder to the phosphor (or stimulable
 phosphor) exceeds 3.0%, the voids in the phosphor layer decrease to reduce
 the light-scattering and the emitted light is easily diffused, resulting
 in deterioration of sharpness. In cases where the weight ratio of the
 binder is less than 0.1%; on the other hand, it is difficult for the
 binder to cover all surfaces of the particles of the phosphor or
 stimulable phosphor and to properly bind the phosphor or stimulable
 phosphor to each other. As a result, a phosphor or stimulable phosphor
 with a high filling ratio cannot be obtained. Furthermore, it is difficult
 for the binder to be uniformly present in the phosphor layer, causing the
 phosphor to be ununiform in the layer and resulting in non-uniform
 emission which causes the image to be deteriorated. It is also not
 preferred since the phosphor layer becomes brittle and is easily
 scratched.
 The filling ratio of the phosphor in the phosphor layer can be determined
 according to the following manner. At first, a protective layer of the
 screen or panel is removed and then the phosphor layer is eluted from the
 screen or panel, using an organic solvent such as methyl ethyl ketone and
 dried to remove the solvent. The resulting mixture of the phosphor and
 binder is further burned at 600.degree. C. for a period of 1 hr. to remove
 the binder and obtain the phosphor as residue (N g). The filling ratio of
 the phosphor can be calculated based on the following formula:
EQU Filling ratio of phosphor=[N/(P.times.Q.times.R)].times.100 (%)
 wherein P is a thickness of the phosphor layer (cm), Q is an area of the
 screen or panel (cm.sup.2) and R is a density of the phosphor
 (g/cm.sup.3).
 Examples of resins usable as a binder in the invention include
 polyurethane, polyester, vinyl chloride copolymer such as vinyl
 chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride
 copolymer and vinyl chloride-acrylonitrile copolymer,
 butadiene-acrylonitrile copolymer, polyamide, polyvinyl butyral, cellulose
 derivatives (e.g., nitrocellulose), styrene-butadiene copolymer, synthetic
 rubbers, phenol resin, epoxy resin, urea resin, melamine resin, phenoxy
 resin, silicone resin, and urea-formaldehyde resin. Of these resins,
 polyurethane, polyester, vinyl chloride copolymer, polyvinyl butyral and
 nitrocellulose are preferred.
 A weight-averaged molecular weight of the binder is preferably 5,000 to
 200,000.
 The binder usable in the invention is preferably a binder containing a
 hydrophilic polar group. In this case, the hydrophilic polar group
 improves dispersion of the phosphor particles, through its adsorption to
 the surface of the particles, leading to prevention of coagulation of the
 phosphor particles and enhancement of coating stability, sharpness and
 graininess. The resin containing a hydrophilic polar group according to
 the invention is one containing a hydrophilic polar group selected from
 the group consisting of --SO.sub.3 M, --OSO.sub.3 M, --COOM,
 --PO(OM).sub.2, and --OPO(OM).sub.2 (i.e., negative functional group), in
 which M is hydrogen atom or an alkali metal atom such as Li, K, Na.
 The binder resin of the phosphor layer is added with a multifunctional
 isocyanate as a hardener, preferably in an amount of 5 to 30% by weight,
 based on the binder resin.
 As a preferred example of the resin containing the hydrophilic polar group,
 polyurethane is explained further in detail. Polyurethane can be
 synthesized through reaction of a polyol with a polyisocyanate which is
 generally employed. As a polyol component is generally used
 polyesterpolyol which can be obtained through reaction of the polyol with
 a polybasic acid. According to this known method, the polyesterpolyol
 containing the hydrophilic polar group can be synthesized by using the
 polybasic acid containing the hydrophilic polar group, as a part of the
 polybasic acid.
 Examples of the polybasic acid include phthalic acid, isophthalic acid,
 terephthalic acid, adipic acid, azelaic acid, cebacic acid and maleic
 acid. Examples of the polyesterpolyol containing the hydrophilic polar
 group include , 5-sulfo-isophthalic acid, 2-sulfoisophthalic acid,
 4-sulfoisophthalic acid, 3-sulfoisophthalic acid, dialkyl
 5-sulfoisophthalate, dialkyl 2-sulfoisophthalate, dialkyl
 4-sulfoisophthalate, dialkyl 3-sulfoisophthalate and their sodium or
 potassium salt.
 Examples of the polyol include trimethylol propane, hexanetriol, glycerin,
 trimethylolethane, neo-pentylglycol, pentaerythritol, ethylene glycol,
 propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol,
 diethylene glycol and cyclohexanedimethanol.
 A polyurethane containing another hydrophilic polar group can also readily
 be synthesized according to conventional methods.
 Examples of the polyisocyanate include diphenylmethane-4,4-diisocyanate
 (MDI), hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI),
 1,5-naphthalene diisocyanate (NDI), toluidine diisocyanate (TODI), lysine
 isocyanate methyl ester (LDI) and isopholone diisocyanate (IPDI).
 As another method for synthesizing the polyurethane, it can be prepared
 through addition reaction of the following compound containing the
 hydrophilic polar group and a chlorine atom to a polyurethane containing a
 OH group.
 ClCH.sub.2 CH.sub.2 SO.sub.3 M
 ClCH.sub.2 CH.sub.2 OSO.sub.3 M
 ClCH.sub.2 PO(OM).sub.2
 ClCH.sub.2 COOM
 Furthermore, there are also commercially available polyurethane containing
 --SO.sub.3 Na group, UR8300 (available from Toyobo Co. Ltd.) and
 polyurethane containing --COOH group. TIM-6001 (available from Sanyo Kasei
 Co. ltd.).
 In addition to the resins above-described, the following resins are usable
 as a binder containing the hydrophilic polar group. Examples thereof are
 one having a weight-averaged molecular weight of 5,000 to 200,000,
 including a vinyl chloride copolymer, vinyl chloride-vinyl acetate
 copolymer, vinyl chloride-vinylidene chloride copolymer,
 butadiene-acrylonitrile copolymer, polyamide, poly(vinyl butylal),
 cellulose derivative (e.g., nitrocellulose), styrene-butadiene copolymer,
 a variety of synthetic rubber type resins, phenol resin, epoxy resin, urea
 resin, melamine resin, pheoxy resin, silicone resin, acryl type resin,
 urea-formamide resin. Among these are preferred a polyester, vinyl
 chloride type copolymer poly(vinyl butyral) and nitrocellulose.
 The vinyl chloride type resin is, for example, a vinyl chloride-vinyl
 alcohol copolymer. A vinyl chloride resin containing a hydrophilic polar
 group can be synthesized through addition reaction of the above-described
 compound containing a hydrophilic polar group and a chlorine atom to a
 copolymer containing a OH group.
 In the case of ClCH.sub.2 CH.sub.2 SO.sub.3 M, for example, it reacts with
 a vinyl alcohol copolymerizing portion, as follows:
 ##STR1##
 Alternatively, copolymerization can be done by using copolymerizable
 monomers. Thus, a reactive unsaturated monomer having a repeating unit
 with a hydrophilic polar group is introduced into a reaction vessel such
 as an autoclave with a given volume and polymerization can be done by
 using a conventional polymerization initiator including radical
 polymerization initiator such as benzoyl peroxide (BPO) and
 azobisisobutyronitrile (AIBN), redox polymerization initiator, anionic
 polymerization initiator and cationic polymerization initiator. Examples
 of the reactive monomer for introducing a sulfonic acid or its salt
 include unsaturated hydrocarbon sulfonic acids such as vinyl sulfonic
 acid, acrylsulfonic acid and p-styrenesulfonic acid and its salts.
 Furthermore, acryl or methacrylsulfoalkyl ester such as
 2-acrylamido-2-methylpropanesulfonic acid, (metha)acrylsulfonic acid ethyl
 ester, (metha)acrylsulfonic acid propyl ester and their salts and ethyl
 2-sulfoacrylate are cited.
 In cases where a carboxylic acid or its salt (i.e. --COOM group) is
 introduced, (metha)acrylic acid or maleic acid may be usable. In cases
 where phosphoric acid or its salt is introduced, (metha)acrylic
 acid-2-phosphoric acid eater may be usable.
 As commercially available products of these compounds are cited, for
 example, vinyl chloride-vinyl acetate copolymer containing -SO.sub.3 K
 group, MR110 (produced by Nihon Zeon Co. Ltd.) and polyester containing
 -SO.sub.3 Na group, Biron 280 (produced by Toyobo Co. Ltd.).
 The hydrophilic polar group can be identified by means of, e.g., NMR
 (Nuclear Magnetic Resonance) and quantitatively determined by
 wavelength-dispersion type fluorescent X-ray analysis (WDX). As an
 exemplary means of measuring the content of the hydrophilic polar group,
 the content of an SO.sub.3 M group can be determined according to the
 following manner. Various amounts of sulfur (S) at a purity of 99.9999%
 are added to a matrix resin, with a given amount of a phosphorus
 (P)-containing compound as an internal standard material. Fluorescent
 X-ray intensities of S to P are measured with respect to each sample by
 the WDX to prepare a calibration curve for the content of sulfur. Next, to
 a sample is added a given amount of P-containing compound, which was
 subjected to WDX analysis to determine the P-content.
 The content of the hydrophilic polar group is preferably 10.sup.-7 to
 10.sup.-3 and more preferably 10.sup.-7 to 10.sup.-4 mol per gram of the
 binder contained in the phosphor or stimulable phosphor layer.
 A resin not containing a hydrophilic polar group may be contained in the
 binder. Examples of the resin are one having a weight-averaged molecular
 weight of 5,000 to 200,000, including urethane-vinyl chloride copolymer,
 vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride
 copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile
 copolymer, polyamide, polyvinyl butyral, cellulose derivative (e.g.,
 nitrocellulose), styrene-butadiene copolymer, a variety of types of
 synthetic rubber resin, phenol resin, epoxy resin, urea resin, melamine
 resin, phenoxy resin, silicone resin, acryl resin and urea-formamide
 resin. Among these, polyurethane-polyester, vinyl chloride type copolymer,
 polyvinyl butyral and nitrocellulose are preferably used. In this case,
 the content of the hydrophilic polar group is also preferably 10.sup.-7 to
 10.sup.-3 mol per gram of the binder contained in the phosphor or
 stimulable phosphor layer.
 Examples of the phosphors preferably usable in the radiographic
 intensifying screen of the invention include the following: tungstate
 phosphor (e.g., CaWO.sub.4, MgWO.sub.4, CaWO.sub.4 :Pb, etc.); terbium
 activated rare earth sulfide phosphor (e.g., Y.sub.2 O.sub.2 S:Tb,
 Gd.sub.2 O.sub.2 S:Tb, La.sub.2 O.sub.2 S:Tb, (Y,Gd).sub.2 O.sub.2 S:Tb,
 (Y,Gd).sub.2 O.sub.2 S:Tb,Tm, etc.); terbium activated rare earth
 phosphate phosphor (e.g.,YPO.sub.4 :Tb, GdPO.sub.4 :Tb, LaPO.sub.4 :Tb,
 etc.); terbium activated rare earth oxyhalide phosphor (e.g.,LaOBr:Tb,
 LaOBr:Tb,Tm, LaOCl:Tb, LaOCl:Tb,Tm, LaOCl:Tb,Tm, LaOBr:Tb, GdOBr:Tb,
 GdOCl:Tb, etc.); thulium activated rare earth oxyhalide phosphor (e.g.,
 LaOBr:Tm, LaOCl:Tm, etc.); barium sulfate phosphor (e.g., BaSO.sub.4 :Pb,
 BaSO.sub.4 :Eu.sup.2+, (Ba,Sr)SO.sub.4 :Eu.sup.2+, etc.); bivalent
 europium activated alkali earth phosphate phosphor [e.g., (Ba.sub.2
 PO.sub.4).sub.2 :Eu.sup.2+, (Ba.sub.2 PO.sub.4).sub.2 :Eu.sup.2+, etc.];
 bivalent europium activated alkali earth metal fluorohalide phosphor
 [e.g.,BaFCl:Eu.sup.2+, BaFBr:Eu.sup.2+, BaFCl:Eu.sup.2+.Tb,
 BaFBr:Eu.sup.2+.Tb, BaF.sub.2 BaClKCl:Eu.sup.2+, (Ba,Mg)F.sub.2
 BaClKCl:E.sup.2+ etc.];iodide phosphor (e.g., CsI:Na, CsI:Tl, NaI, KI:Tl,
 etc.); sulfide phosphor [e.g., ZnS:Ag, (Zn,Cd)S:Ag, (Zn,Cd)S:Cu,
 (Zn,Cd)S:Cu.Al, etc.]; hafnium phosphate phosphor (e.g., HfP.sub.2 O.sub.7
 :Cu, etc.); tantalate phosphor (e.g., YTaO.sub.4, YTaO.sub.4 :Tm,
 YTaO.sub.4 :Nb, [Y,Sr]TaO.sub.4-x :Nb, LuTaO.sub.4, LuTaO.sub.4 :Nb,
 (Lu,Sr)TaO.sub.4-x :Nb, GdTaO.sub.4 :Tm, Gd.sub.2 O.sub.3 TaO.sub.4 :Tm,
 Gd.sub.2 O.sub.3 Ta.sub.2 O.sub.5 B.sub.2 O.sub.3 :Tb, etc.]. However,
 phosphors usable in the invention are not limited to these compounds. Any
 phosphor capable of emitting visible or near-ultra violet light upon
 exposure to radiation, can be used.
 Examples of the stimulable phosphors preferably usable in the radiation
 image converting panel according to the invention include the following:
 alkali earth metal halide phosphor (e.g., BaFBr:Eu, BaFI:Eu, BaFBr.sub.1-x
 I.sub.x :Eu, BaFCl:Eu, BaFBr:Ce, BaBrI:Eu, BaBrClEu, SrFBr:Eu, BaBr.sub.2
 :Eu etc.); alkali metal halide phosphor (e.g., RbBr:Tl, RbI:Tl, CsI:Na,
 RbBr:Eu, RbI:Eu, CsI:Eu, etc.); sulfide phosphor (e.g., SrS:Ce,Sm,
 SrS:Eu,Sm, CaS:Eu,Sm, etc.); barium aluminate phosphor (e.g.,
 BaO.xAl.sub.2 O.sub.3 :Eu, etc.); alkali earth metal silicate phosphor
 (e.g., MgO.xSiO.sub.2, etc.), rare earth oxyhalide phosphor (e.g.,
 LaOBr:Bi, Tb,Pr, etc.); and phosphate phosphor [e.g., (3Ca.sub.3
 (PO.sub.4).sub.2 CaF.sub.2 :Eu, etc.). However, the stimulable phosphor
 used according to the invention is not limited to these compound. There
 may be usable any phosphor which, after absorbing radiation energy, is
 capable of emitting the accumulated radiation energy in the form of
 fluorescence (stimulated luminescence), through stimulating with visible
 light or infrared rays (stimulating light).
 As to a method for preparing the radiographic intensifying screen or
 radiation image converting panel, first one is that a coating solution
 containing a binder and phosphor, or a coating solution containing a
 binder and stimulable phosphor (hereinafter referred to as a phosphor
 coating solution or stimulable phosphor coating solution) is coated on a
 support to form a phosphor layer.
 A second one is that a sheet comprised of the binder and phosphor, or the
 binder and stimulable phosphor is formed and then put onto the support,
 followed by a process of adhesion to the support at not lower than a
 softening or melting temperature of the binder.
 As a method for forming the phosphor layer on the support are cited the
 above two types of methods. However, any method whereby the phosphor layer
 is uniformly formed on the support, may be adopted. Impingement coating
 may be usable.
 In the first preparing method, the phosphor layer is formed by coating the
 coating solution in which the phosphor or stimulable phosphor is
 homogeneously dispersed in a binder, on the support and drying it.
 In the second preparing method, on the other hand, the phosphor sheet which
 is to form the phosphor layer is prepared by temporarily coating the
 phosphor coating solution or stimulable phosphor coating solution on a
 support or subbed support and drying, followed by peeling the layer off
 from the support. Thus, the binder and the phosphor or stimulable phosphor
 particles are added in an appropriate solvent and mixed with stirring by
 means of a disperser or a ball mill to form a coating solution in which
 the phosphor or stimulable phosphor is homogeneously dispersed in the
 binder.
 Examples of the solvent for the coating solution include lower alcohols
 such as methanol, ethanol, n-propanol and n-butanol; chloro-containing
 hydrocarbons such as methylene chloride and ethylene chloride; ketones
 such as acetone, methyl ethyl ketone and methyl isobutyl ketone; cyclic
 hydrocarbon compounds such as toluene, benzene, cyclohexane, cyclohexanone
 and xylene; esters of a lower fatty acid and lower alcohol, such as methyl
 acetate, ethyl acetate and butyl acetate; and ethers such as dioxane,
 ethylene glycol monomethyl ester, ethylene glycol monoethyl ester.
 The coating solution may contain a dispersing agent and plasticizer for the
 purpose of enhancement of dispersion of the phosphor or binding power
 between the binder and phosphor after forming the layer, respectively.
 Examples of the dispersing agent include phthalic acid, stearic acid,
 caproic acid and a hydrophobic surfactant. Examples of the plasticizer
 include phosphate esters such as triphenyl phosphate, tricresyl phosphate
 and diphenyl phosphate; phthalate esters such as diethyl phthalate and
 dimethoxyethyl phthalate; glycolate esters such as ethyl phthalylethyl
 glycolate and butyl phthalylbutyl glycolate; polyesters of polyethylene
 glycol and dibasic fatty acid, such as polyester of triethylene glycol and
 adipic acid and polyester of diethylene glycol and succinic acid.
 The thus-prepared coating solution containing the phosphor or stimulable
 phosphor and the binder is uniformly coated on the temporary support to
 form a coating layer of the coating solution. A means for coating is, for
 example, a doctor blade, roll coater, knife-coater, extrusion coater and
 so forth.
 Support or temporary support made of glass, wool, cotton, paper or metal
 may be usable and those which are capable of being converted in the form
 of flexible sheet or roll are preferred in terms of handleability as
 information recording material. In view thereof are preferred plastic
 films such as cellulose acetate film, polyester film, polyethylene
 terephthalate film, polyamide film, polyimide film, triacetate film and
 polycarbonate film; metal sheets such as aluminum foil and aluminum alloy
 foil; and paper including paper for general use, paper for use in printing
 such as coated paper and art paper, photographic base paper such as baryta
 paper and resin-coated paper, paper sized with polysaccharide as described
 in Belgian Patent 784,615, pigment paper containing pigment such as
 titanium dioxide, and paper sized with poly(vinyl alcohol).
 In the second preparing method, coat on a temporary support or
 subbed-support is peeled off from the support to form a phosphor layer
 sheet. Therefore, it is preferred that the surface of the support is
 previously coated with a releasing agent so that the phosphor layer is
 easily peelable.
 To strengthen binding between the support and phosphor layer, a sub layer
 may be provided by coating polyester or gelatin on the surface of the
 support to enhance adhesion. There may be provided a light-reflecting
 layer comprised of light-reflecting material such as titanium dioxide or a
 light-absorbing layer comprised of light-absorbing material such as carbon
 black, for the purpose of enhancement of sensitivity and image quality
 (e.g., sharpness, graininess, etc.).
 The phosphor layer according to the invention may be compressed.
 Compression of the phosphor layer leads to an increase of a filling
 density of the phosphor and improvements in sharpness and graininess.
 Compression can be made by the use of a pressing machine or calendering
 roll. In the case of the first preparing method, the phosphor and support
 are compressed together as such. In the case of the second preparing
 method, the obtained phosphor sheet is put on the support and compressed
 at not lower than a softening temperature or melting temperature of the
 binder to cause the phosphor sheet to adhere to the support. Thus, the
 phosphor sheet can be expanded to further thinner thickness by employing
 the method of compression-adhering, instead of previously fixing the sheet
 to the support.
 Conventionally, the radiographic intensifying screen and the radiation
 image converting panel each have a transparent protective layer provided
 on the surface of the phosphor layer for physical and chemical protection
 thereof. In the invention, the transparent protective layer is preferably
 provided. The thickness thereof is in general within a range of 2 to 20
 .mu.m.
 The protective layer can be formed by coating, on the surface of the
 phosphor layer, a solution prepared by dissolving in an appropriate
 solvent a cellulose derivative such as cellulose acetate or
 nitrocellulose, or a synthetic polymer material such as polymethyl
 methaacrylate, polyethylene terephthalate, poly(vinyl butyral), poly(vinyl
 formal), polycarbonate, poly(vinyl acetate), copoly(vinyl chloride-vinyl
 acetate). These polymer materials may be used singly or in combination
 thereof. In cases when coating the protective layer, a cross-linking agent
 may be added thereto immediately before coating. The protective layer may
 be formed by adhering a sheet comprised of poly(ethylene terephthalate),
 poly(ethylene naphthalate), polyethylene, poly(vinylidene chloride) or
 polyamide with an adhesive.
 The protective layer according to the invention is preferably formed with a
 coating layer containing an organic solvent-soluble fluoro resin. The
 fluoro resin is referred to as fluorine containing olefin (i.e.,
 fluoroolefin) polymer or copolymer having as a copolymerizing component a
 fluorine containing olefin. The protective layer formed of fluoro resin
 coating may be cross-linked. The fluoro resin coating protective layer has
 such an advantage that stain due to fat resulted from touching with hands
 or photographic materials, or due to plasticizer bled out of the
 photographic material is not liable to penetrate into the internal portion
 of the protective layer, so that the stain can easily be wiped off. The
 fluoro resin may be used in combination with another polymer material for
 the purpose of improving layer strength.
 The protective layer is preferably a transparent synthetic resin layer with
 a thickness of 10 .mu.m or less and provided on the phosphor layer. The
 use of such a thin protective layer, particularly in the case of the
 intensifying screen, shortens the distance from the phosphor to a silver
 halide emulsion layer, contributing to improvement in sharpness of the
 resulting radiographic image.

EXAMPLES
 Embodiments of the present invention are explained further in detail based
 on examples, but the invention is not limited to these examples.
 Example 1
 Preparation of Screen
 To phosphor Gd.sub.2 O.sub.2 S:Tb (av. particle size 4.3 .mu.m), a resin as
 shown in Table 1 was added as a binder and mixed according to the formula
 shown in Table 2 (expressed as percentage by weight, based on phosphor);
 and further thereto, a mixed solvent of methyl ethyl ketone and toluene
 (in a ratio of 1:1) was added so as to have a viscosity of 20 Ps with
 stirring in a ball mill for 6 hrs. to obtain a coating solution of the
 phosphor.
 TABLE 1
 Molecular Hydrophilic
 weight Tg polar group
 Resin (Mn) (.degree. C.) Group mol/g
 Polyurethane a 1.8 .times. 10.sup.4 -60 --
 Polyurethane b 2.3 .times. 10.sup.4 -45 --
 Polyurethane c 3.2 .times. 10.sup.4 -20 --
 Polyurethane d 3.2 .times. 10.sup.4 -20 SO.sub.3 Na 1 .times.
 10.sup.-8
 Polyurethane e 3.2 .times. 10.sup.4 -20 SO.sub.3 Na 1 .times.
 10.sup.-6
 Polyurethane f 3.2 .times. 10.sup.4 -20 SO.sub.3 Na 1 .times.
 10.sup.-4
 Polyurethane g 3.2 .times. 10.sup.4 -20 SO.sub.3 Na 1 .times.
 10.sup.-2
 Polyurethane h 3.2 .times. 10.sup.4 -20 SO.sub.3 K 1 .times.
 10.sup.-4
 Polyurethane i 3.2 .times. 10.sup.4 -20 OSO.sub.3 Na 1 .times.
 10.sup.-4
 Polyurethane j 3.2 .times. 10.sup.4 -20 COOH 1 .times.
 10.sup.-4
 Polyurethane k 3.7 .times. 10.sup.4 0 -- --
 Polyurethane l 3.9 .times. 10.sup.4 20 -- --
 Polyurethane m 4.5 .times. 10.sup.4 45 -- --
 Polyurethane n 6.0 .times. 10.sup.4 80 -- --
 Polyester a 1.9 .times. 10.sup.4 -60 -- --
 Polyester b 2.6 .times. 10.sup.4 -45 -- --
 Polyester c 3.5 .times. 10.sup.4 -20 -- --
 Polyester d 3.5 .times. 10.sup.4 -20 SO.sub.3 Na 1 .times.
 10.sup.-4
 Polyester e 3.8 .times. 10.sup.4 0 -- --
 Polyester f 4.3 .times. 10.sup.4 20 -- --
 Polyester g 5.2 .times. 10.sup.4 45 -- --
 Polyester h 7.3 .times. 10.sup.4 80 -- --
 Polyvinylbutyral 11.0 .times. 10.sup.4 65 -- --
 Polyurethane o 3.2 .times. 10.sup.4 -32 -- --
 Polyurethane p 3.2 .times. 10.sup.4 -28 -- --
 Polyurethane q 3.2 .times. 10.sup.4 18 -- --
 Polyurethane r 3.2 .times. 10.sup.4 23 -- --
 Next, a hardener, Colonate HX (available from Nippon Polyurethane Corp.)
 was further added thereto in an amount as shown in Tables 2 and 3 (% by
 weight, based on phosphor), immediately before coating. Then, on a white
 250 .mu.m polyethylene terephthalate support containing titanium dioxide,
 the above coating solution was coated by use of a knife-coater to form a
 phosphor layer with 150 .mu.m in dry thickness.
 After non-compressive samples (Samples 1 to 17, 30 to 38 and 47) were aged
 at 60.degree. C. for 24 hr., a polyester type adhesive was coated on one
 side of a polyethylene terephthalate film at a thickness of 10 .mu.m and
 the adhesive side thereof was brought into contact with the phosphor layer
 side to provide a protective layer. Separately, after samples containing a
 residual solvent as shown in Table 2 were each compressed by a press at
 60.degree. C. and 50 kg/cm.sup.2 for 5 min., compressed samples (Samples
 18 to 29 and 39 to 46) were aged at 60.degree. C. for 24 hr., and a
 protective later was coated thereon in a manner described above. Thus,
 radiographic intensifying screen samples were obtained, as shown in Table
 2 (Samples 1 to 47).
 Measurement of Tg of Resin and Phosphor Layer
 On a 50 .mu.m transparent polyethylene terephthalate film was coated with a
 knife-coater a resin layer (10 .mu.m in dry thickness) to obtain a sample
 for measuring Tg of the resin. Similarly, on a 50 .mu.m transparent
 polyethylene terephthalate film was coated a phosphor layer with a dry
 thickness of 150 .mu.m and after being dried, was aged at 60.degree. C.
 for 24 hr. to obtain a sample for measuring Tg of the phosphor layer. The
 obtained samples were each measured with respect to tangent of loss angle,
 tan.delta. (E=E=j) using Solid Analyzer RSAII (available from Rheometer
 Co. Ltd.) at a measuring frequency of 10 Hz, measured at a strain of 0.05%
 and a temperature of -11 to 200.degree. C. (using liquid nitrogen). Then,
 the 50 .mu.m transparent polyethylene terephthalate film was measured and
 used for correction as a base line, and a peak temperature of the thus
 obtained data was defined as Tg. In the case of a coating layer having
 plural peaks, the highest peak temperature was defined as Tg.
 Measurement of Unhardened Resin Content
 A part of the binder resin remained in the phosphor layer without being
 hardened with a hardener. The amount of unhardened resin in the phosphor
 layer can be determined in the following manner. Initially, a
 cross-section of the phosphor layer was measured by a IR spectrometer to
 identify the kind of the resin. The phosphor layer was cut into small
 pieces and refluxed with a solvent (methyl ethyl ketone) for 30 min to
 extract unhardened resin. Thereafter, the mixture was filtered, the
 solvent was removed from the filtrate and the residue was dried to obtain
 the unhardened resin. The content of the unhardened resin was shown as a
 percentage by weight, based on total binder resin.
 Measurement of Phosphor Filling Ratio
 The filling ratio of the phosphor in the phosphor layer can be determined
 according to the following manner. Initially, a protective layer of the
 screen or panel is removed and then the phosphor layer is eluted from the
 screen, using methyl ethyl ketone and dried to remove the solvent. The
 resulting mixture of the phosphor and binder is further calcined at
 600.degree. C. for a period of 1 hr. to remove the binder and obtain the
 phosphor as residue (N g). The filling ratio of the phosphor can be
 calculated based on the following formula:
EQU filling ratio of phosphor=[N/(P.times.Q.times.R)].times.100 (%)
 wherein P is a thickness of the phosphor layer (cm), Q is the area of the
 screen or panel (cm.sup.2) and R is the density of the phosphor
 (g/cm.sup.3).
 Evaluation of Brightness:
 Screen samples each were cut out in pieces of 1.times.1 cm and sample
 pieces were each exposed to X ray (tube voltage of 80 kVp, tube current of
 50 mA and exposure time of 0.1 sec.). Produced emissions were condensed
 with an optical fiber and photoelectrically transferred through a
 photomultiplier and the resulting brightness was measured. The brightness
 is shown as a relative value, based on the brightness of screen Sample 1
 being 100.
 Bending Test
 On a support, coated with a peeling agent, was coated a phosphor layer with
 a dry thickness of 150 .mu.m. Compressed samples were each further
 compressed at the residual solvent content shown in Table 2. After being
 dried, the phosphor layer was peeled and cut into a rectangular piece of
 1.times.5 cm. The phosphor layer was bent in the longitudinal direction
 and evaluated based on the following criteria.
 A: No destruction of the phosphor layer occurred until being folded.
 C: Destruction occurred immediately upon being bent.
 B: An intermediate level of the above, and commercially acceptable.
 Abrasion Resistance Test
 Onto a sample stand of a surface tester HEIDON-14 (available from Shintoh
 Kagaku Co. Ltd.) was adhered a 10.times.10 cm screen sample with a
 protective layer. The screen sample was rubbed 1000 times at a speed of 1
 cm/sec. with a 1.times.1 cm X-ray film, SR-G (available from Konica Corp.)
 which was loaded at 5 g/cm.sup.2, and evaluated based on the following
 criteria.
 A: No flaw observed after rubbing
 C: Many flaws observed after rubbing
 B: An intermediate level of the above and commercially acceptable.
 Obtained results are summarized in Table 2.
 TABLE 2
 Unhard- Fill-
 Abra-
 Sam- Hard- Residual Tg of ened ing
 sion
 ple Screen Resin ener solvent phosphor resin ratio
 Bright- Bending resist- Re-
 No. No. (%) (%) (%) layer (.degree. C.) (wt %)
 (%) ness strength ance mark
 1 1 Polyurethane a (3.5) 20 -- 15 3.0 70
 100 B C Comp.
 2 2 Polyurethane b (3.5) 20 -- 35 2.7 70
 101 A A Inv.
 3 3 Polyurethane c (3.5) 20 -- 40 3.9 65
 98 A B Inv.
 4 4 Polyurethane c (2.0) 20 -- 50 1.2 72
 104 A A Inv.
 5 5 Polyurethane c (3.5) -- -- -20 100 67
 95 B C Comp.
 6 6 Polyurethane d (3.5) 20 -- 40 2.8 68
 99 A B Inv.
 7 7 Polyurethane e (3.5) 20 -- 40 3.5 73
 105 A A Inv.
 8 8 Polyurethane f (3.5) 20 -- 45 3.1 75
 109 A A Inv.
 9 9 Polyurethane g (3.5) 20 -- 45 2.5 69
 100 A B Inv.
 10 10 Polyurethane h (3.5) 20 -- 50 3.1 74
 107 A A Inv.
 11 11 Polyurethane i (3.5) 20 -- 40 2.4 73
 104 A A Inv.
 12 12 Polyurethane j (3.5) 20 -- 40 2.8 72
 103 A A Inv.
 13 13 Polyurethane k (3.5) 20 -- 50 2.8 63
 97 B A Inv.
 14 14 Polyurethane l (3.5) 20 -- 80 2.6 61
 96 B A Inv.
 15 15 Polyurethane m (3.5) -- -- 45 100 59
 88 A A Comp.
 16 16 Polyurethane n (3.5) -- -- 80 100 57
 87 B A Comp.
 17 17 Polyurethane n (3.5) 20 -- 145 3.3 55
 85 C B Comp.
 18 18 Polyurethane a (3.5) 20 5 20 3.0 75
 107 C C Comp.
 19 19 Polyurethane b (3.5) 20 5 40 2.7 75
 110 A B Inv.
 20 20 Polyurethane c (3.5) 20 5 45 3.3 74
 108 A A Inv.
 21 21 Polyurethane f (3.5) 20 5 50 3.1 77
 111 A A Inv.
 22 22 Polyurethane k (3.5) 20 5 65 2.7 73
 107 A A Inv.
 23 23 Polyurethane l (3.5) 20 5 80 2.6 72
 104 B A Inv.
 24 24 Polyurethane l (3.5) 40 5 140 2.6 60
 88 C B Comp.
 25 25 Polyurethane m (3.5) -- 1 50 100 60
 80 A A Comp.
 26 26 Polyurethane n (3.5) -- 1 85 100 58
 76 C B Comp.
 27 27 Polyurethane c (3.5) 20 0.05 40 3.0 67
 97 A B Inv.
 28 28 Polyurethane c (2.0) 20 10 45 2.7 75
 109 A A Inv.
 29 29 Polyurethane c (3.5) 20 35 -- -- --
 -- -- -- Comp.
 30 30 Polyester a (3.5) 20 -- 15 2.8 63
 92 A C Comp.
 31 31 Polyester b (3.5) 20 -- 40 2.5 63
 91 B B Comp.
 32 32 Polyester c (3.5) 20 -- 40 3.2 63
 94 A A Inv.
 33 33 Polyester c (2.0) 20 -- 45 1.5 70
 100 A A Inv.
 34 34 Polyester d (3.5) 20 -- 45 2.8 73
 104 A A Inv.
 35 35 Polyester e (3.5) 20 -- 70 3.3 64
 95 A A Inv.
 36 36 Polyester f (3.5) 20 -- 80 3.3 62
 93 A A Inv.
 37 37 Polyester g (3.5) -- -- 45 100 55
 78 B A Comp.
 38 38 Polyester h (3.5) -- -- 80 100 54
 82 C B Comp.
 39 39 Polyester a (3.5) 20 5 15 3.1 72
 105 C B Comp.
 40 40 Polyester b (3.5) 20 5 40 2.9 72
 106 A A Inv.
 41 41 Polyester c (3.5) 20 5 40 3.0 72
 107 A A Inv.
 42 42 Polyester d (3.5) 20 5 45 2.8 75
 110 A A Inv.
 43 43 Polyester e (3.5) 20 5 70 3.1 70
 101 A A Inv.
 44 44 Polyester f (3.5) 20 5 80 3.2 68
 98 A A Inv.
 45 45 Polyester g (3.5) -- 5 45 100 59
 79 B A Comp.
 46 46 Polyester h (3.5) -- 5 80 100 58
 75 C B Comp.
 47 47 Polyvinylbutyral (3.5) -- -- 65 100
 59 88 C A Comp.
 48 48 Polyurethane c (2.0) 4.5 -- 5 80 72
 103 B B Inv.
 49 49 Polyurethane c (2.0) 5.5 -- 35 40 72
 104 B A Inv.
 50 50 Polyurethane c (2.0) 28 -- 60 0.3 71
 102 A A Inv.
 51 51 Polyurethane c (2.0) 33 -- 65 0.1 70
 101 B A Inv.
 52 52 Polyurethane o (2.0) 20 -- 35 1.5 68
 98 B A Inv.
 53 53 Polyurethane p (2.0) 20 -- 40 1.4 67
 98 A A Inv.
 54 54 Polyurethane q (2.0) 20 -- 80 1.4 66
 97 A A Inv.
 55 55 Polyurethane r (2.0) 20 -- 85 1.3 63
 93 B A Inv.
 56 56 Polyurethane b (2.0) 15 -- 25 8 70
 100 B A Inv.
 As can be seen from Tables 2, screen samples of the present invention were
 superior in brightness, as compared to comparative screen samples.
 Furthermore, raising the Tg of the phosphor layer led to improvements in
 bending resistance and abration resistance.
 Example 2
 Preparation of Panel
 To stimulble phosphor BaFBr:Eu (av. particle size 3.8 .mu.m) was added a
 resin as a binder, as shown in Table 1 and mixed according to the formula
 shown in Tables 3 (expressed as percentage by weight, based on phosphor);
 and further thereto, a mixed solvent of methyl ethyl ketone and toluene
 (in a ratio of 1:1) was added so as to have a viscosity of 20 Ps with
 stirring in a ball mill for 6 hrs. to obtain a coating solution of the
 phosphor.
 Next, a hardener, Colonate HX (available from Nippon Polyurethane Corp.)
 was further added thereto in an amount as shown in Table 3 (% by weight,
 based on phosphor), immediately before coating. Then, on a white 250 .mu.m
 polyethylene terephthalate support containing titanium dioxide, the above
 coating solution was coated by use of a knife-coater to form a phosphor
 layer with 150 .mu.m in dry thickness.
 After non-compressive samples (Samples 101 to 117, 130 to 138 and 147) were
 aged at 60.degree. C. for 24 hr., a polyester type adhesive was coated on
 one side of a polyethylene terephthalate film at a thickness of 10 .mu.m
 and the adhesive side thereof was brought into contact with the stimulable
 phosphor layer side to provide a protective layer. Separately, after
 samples containing a residual solvent as shown in Table 3 were each
 compressed by a press at 60.degree. C. and 50 kg/cm.sup.2 for 5 min.,
 compressed samples (Samples 118 to 129 and 139 to 146) were aged at
 60.degree. C. for 24 hr., and a protective later was coated thereon in a
 manner described above. Thus, radiation image conversion panel samples
 were obtained, as shown in Table 3 (Samples 101 to 147).
 Measurement of Tg of Phosphor Layer
 On a 50 .mu.m transparent polyethylene terephthalate film was coated with a
 knife-coater a stimulable phosphor layer with a dry thickness of 170
 .mu.m, provided that compressed samples were subjected to compression and
 after being dried, was aged at 60.degree. C. for 24 hr. to obtain a sample
 for measuring Tg of the stimulable phosphor layer. The obtained samples
 were each measured with respect to tangent of loss angle, tans (E"/E')
 using Solid Analyzer RSAII (available from Rheometer Co. Ltd.) at a
 measuring frequency of 10 Hz, measured at a strain of 0.05% and a
 temperature of -11 to 200.degree. C. (using liquid nitrogen). Then, the 50
 .mu.m transparent polyethylene terephthalate film was measured and used
 for correction as a base line, and a peak temperature of the thus obtained
 data was defined as Tg. In the case of a coating layer having plural
 peaks, the highest peak temperature was defined as Tg.
 Measurement of Unhardened Resin Content
 A part of the binder resin remained in the phosphor layer without being
 hardened with a hardener. The amount of unhardened resin in the phosphor
 layer can be determined in the following manner. Initially, a
 cross-section of the phosphor layer was measured by a IR spectrometer to
 identify the kind of the resin. The phosphor layer was cut into small
 pieces and refluxed with a solvent (methyl ethyl ketone) for 30 min to
 extract unhardened resin. Thereafter, the mixture was filtered, the
 solvent was removed from the filtrate and the residue was dried to obtain
 the unhardened resin. The content of the unhardened resin was shown as a
 percentage by weight, based on total binder resin.
 Measurement of Phosphor Filling Ratio
 The filling ratio of the stimulable phosphor in the stimulable phosphor
 layer can be determined according to the following manner. Initially, a
 protective layer of the panel is removed and then the phosphor layer is
 eluted from the screen or panel, using methyl ethyl ketone and dried to
 remove the solvent. The resulting mixture of the phosphor and binder is
 further calcined at 600.degree. C. for a period of 1 hr. to remove the
 binder and obtain the stimulable phosphor as residue (N' g). The filling
 ratio of the phosphor can be calculated based on the following formula:
EQU filling ratio of phosphor=[N'/(P'.times.Q'.times.R')].times.100 (%)
 wherein P' is a thickness of the phosphor layer (cm), Q' is the area of the
 screen or panel (cm.sup.2) and R' is the density of the phosphor
 (g/cm.sup.3).
 Evaluation of Brightness
 Panel samples each were cut out in pieces of 1.times.1 cm and sample pieces
 were each exposed to X ray (tube voltage of 80 kVp, tube current of 50 mA
 and exposure time of 0.1 sec.) and excited by scanning with semiconductor
 laser light (oscillating wavelength of 680 nm and beam diameter of 100
 .mu.m). Stimulated emissions were condensed with an optical fiber and
 photoelectrically transferred through a photomultiplier and brightness was
 measured. The brightness was shown as a relative value, based on the
 brightness of Sample 101 being 100.
 Bending Test
 On a support, coated with a peeling agent, was coated a stimulable phosphor
 layer with a dry thickness of 150 .mu.m. Compressed samples were each
 further compressed at the residual solvent content shown in Table 3. After
 being dried, the phosphor layer was peeled and cut into a rectangular
 piece of 1.times.5 cm. The phosphor layer was bent in the longitudinal
 direction and evaluated based on the following criteria.
 A: No destruction of the stimulable phosphor layer occurred until being
 folded.
 C: Destruction occurred immediately upon being bent.
 B: An intermediate level of the above, and commercially acceptable.
 Abrasion Resistance Test
 Onto a sample stand of a surface tester HEIDON-14 (available from Shintoh
 Kagaku Co. Ltd.) was adhered a 10.times.10 cm screen sample with a
 protective layer. The screen sample was rubbed 1000 times at a speed of 1
 cm/sec. with a 1.times.1 cm X-ray film, SR-G (available from Konica Corp.)
 which was loaded at 5 g/cm.sup.2, and evaluated based on the following
 criteria.
 A: No flaw observed after rubbing
 C: Many flaws observed after rubbing
 B: An intermediate level of the above and commercially acceptable.
 Obtained results are shown in Table 3.
 TABLE 3
 Resid- Tg of Unhard- Fill-
 Abra-
 Sam- Pa- Hard- ual phosphor ened ing
 sion
 ple nel ener solvent layer resin ratio
 Bright- Bending resist-
 No. No. Resin (%) (%) (%) (.degree. C.) (wt %) (%)
 ness strength ance Remark
 101 1 Polyurethane a (5.0) 20 -- 20 3.1 70
 100 B C Comp.
 102 2 Polyurethane b (5.0) 20 -- 35 2.7 71
 100 A A Inv.
 103 3 Polyurethane c (5.5) 20 -- 45 4.1 64
 97 A B Inv.
 104 4 Polyurethane c (2.0) 20 -- 50 1.3 72
 103 A A Inv.
 105 5 Po1yurethane c (5.0) -- -- -20 100 66
 93 B C Comp.
 106 6 Polyurethane d (5.0) 20 -- 40 2.8 67
 98 A B Inv.
 107 7 Polyurethane e (5.0) 20 -- 45 3.6 74
 105 A A Inv.
 108 8 Polyurethane f (5.0) 20 -- 50 3.3 75
 108 A A Inv.
 109 9 Polyurethane g (5.0) 20 -- 45 2.7 69
 101 A B Inv.
 110 10 Polyurethane h (5.0) 20 -- 50 3.2 74
 107 A A Inv.
 111 11 Polyurethane i (5.0) 20 -- 40 2.6 72
 103 A A Inv.
 112 12 Polyurethane j (5.0) 20 -- 45 2.9 73
 104 A A Inv.
 113 13 Polyurethane k (5.0) 20 -- 50 2.7 62
 95 A A Inv.
 114 14 Polyurethane l (5.0) 20 -- 85 2.9 61
 95 B A Inv.
 115 15 Polyurethane m (5.0) -- -- 45 100 60
 85 B A Comp.
 116 16 Polyurethane n (5.0) -- -- 85 100 57
 82 C A Comp.
 117 17 Polyurethane n (5.0) 20 -- 150 3.5 56
 81 C C Comp.
 118 18 Polyurethane a (5.0) 20 5 25 3.2 75
 106 B C Comp.
 119 19 Polyurethane b (5.0) 20 5 45 2.8 76
 110 A B Inv.
 120 20 Polyurethane c (5.0) 20 5 45 3.3 74
 109 A A Inv.
 121 21 Polyurethane f (5.0) 20 5 55 3.1 77
 112 A A Inv.
 122 22 Polyurethane k (5.0) 20 5 70 2.9 73
 107 A A Inv.
 123 23 Polyurethane l (5.0) 20 5 80 2.8 72
 104 B A Inv.
 124 24 Polyurethane l (5.0) 40 5 145 2.6 59
 84 C C Comp.
 125 25 Polyurethane m (5.0) -- 1 50 100 59
 80 A A Comp.
 126 26 Polyurethane n (5.0) -- 1 90 100 57
 77 C B Comp.
 127 27 Polyurethane c (5.0) 20 0.05 45 3.1 67
 94 A A Inv.
 128 28 Polyurethane c (5.0) 20 10 50 3.0 75
 109 A A Inv.
 129 29 Polynrethane c (5.0) 20 35 -- -- 3
 -- -- -- Comp.
 130 30 Polyester a (5.0) 20 -- 20 3.1 63 91
 A C Comp.
 131 31 Polyester b (5.0) 20 -- 45 2.7 62 91
 C B Comp.
 132 32 Polyester c (5.0) 20 -- 40 3.3 63 91
 A A Inv.
 133 33 Polyester c (2.5) 20 -- 50 1.4 70
 100 A A Inv.
 134 34 Polyester d (5.0) 20 -- 45 2.9 73
 104 A A Inv.
 135 35 Polyester e (5.0) 20 -- 80 3.5 64 94
 A A Inv.
 136 36 Polyester f (5.0) 20 -- 90 3.4 63 95
 A A Inv.
 137 37 Polyester g (5.0) -- -- 45 100 56 79
 C A Comp.
 138 38 Polyester h (5.0) -- -- 85 100 55 78
 C B Comp.
 139 39 Polyester a (5.0) 20 5 25 3.2 73
 106 B C Comp.
 140 40 Polyester b (5.0) 20 5 45 2.8 72
 106 A A Inv.
 141 41 Polyester c (5.0) 20 5 40 3.1 73
 107 A A Inv.
 142 42 Polyester d (5.0) 20 5 50 3.0 75
 111 A A Inv.
 143 43 Polyester e (5.0) 20 5 80 3.3 71
 102 A A Inv.
 144 44 Polyester f (5.0) 20 5 90 3.2 69 98
 A A Inv.
 145 45 Polyester g (5.0) -- 5 50 100 59 77
 C A Comp.
 146 46 Polyester h (5.0) -- 5 85 100 56 74
 C B Comp.
 147 47 Polyvinylbutyral (5.0) -- -- 65 100 59
 86 C A Comp.
 148 48 Polyurethane c (2.0) 4.5 -- 10 80 71
 101 B B Inv.
 149 49 Polyurethane c (2.0) 5.5 -- 35 30 70
 103 B A Inv.
 150 50 Polyurethane c (2.0) 28 -- 60 0.4 71
 100 A A Inv.
 151 51 Polyurethane c (2.0) 33 -- 65 0.2 69
 100 A A Inv.
 152 52 Polyurethane o (2.0) 20 -- 40 1.5 68
 95 B A Inv.
 153 53 Polyurethane p (2.0) 20 -- 45 1.4 67
 95 A A Inv.
 154 54 Polyurethane q (2.0) 20 -- 85 2 59
 94 A A Inv.
 155 55 Polyurethane r (2.0) 20 -- 90 1.6 57
 92 B A Inv.
 156 56 Polyurethane b (2.0) 15 -- 25 6 68
 95 B A Inv.
 As can be seen from Table 3, panel samples of the present invention were
 superior in brightness, as compared to comparative panel samples. Further,
 raising the Tg of the phosphor layer led to improvements in bending
 resistance and abration resistance.