CA1038683A - Radiography - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A combination of photosensitive materials suited for radiography comprising :
(1) a photosensitive silver halide recording material, which comprises a support and incorporates at least one silver halide emulsion layer, and (2) at least one X-ray fluorescent intensifying screen material comprising a phosphor layer, characterised in that the screen contains (a) a phosphor or a phosphor mixture consisting wholly or mainly of a rare earth metal-activated lanthanum oxyhalide, said phosphor or phosphor mixture having more than half its spectral emission above 410 nm, more than half its visible light spectral emission between 400 and 500 nm, and its maximum of emission in the wavelength range of 400-500 nm and said phosphor layer having a coverage of 200 to 800 g of said lanthanum oxyhalide phosphor per sq.m, and (b) (a) dye(s) and/or pigment(s) absorbing light within the emission spectrum of said phosphor.

Description

~1038683 ~ he present invention relates to an improved combina-tion of photosensitive elements suited for use in radio-graphy and more particularly to a combination comprising~n X-ray intensifying screen of the fluorescent type and a silver halide recording element.
By the term "radiography" we designate a recording technique that makes use of penetrating radiation which in-cludes highly energetic radiation such as X-rays, ~-rays, ~-rays, and fast electrons, e.g. as obtained in an electron microscope.
It is known that the use of fluorescent screens in com-bination with silver halide emulsion materials has resulted in a reduction of the radiation dose and offers an X-ray recording system of high speed. A disadvantage, however, of the use of fluorescent screens when compared with direct X-ray recording is the reduced image sharpness especially when silver halide materials are used having on both sides of a support that is transparent for fluorescent light, a silver halide emulsion layer, each of which during the X-ray exposure stands in close contact with a fluorescent screen.
Indeed, the light emitted by one of these fluorescent screens gives rise not only to an image-wise blackening in the adjacent silver halide emulsion layer, but penetrates also in a considerable amount through the support and pro-duces an unsharp image in the oppositely situated silver halide emulsion layer. This phenomenon is called "cross-over".

GV.705 PC~

~1038683 The degree of cross-over substantially determines the image quality of the image obtained in the radiographic recording material.
~ he cross-over causes unsharpness because of the diffusion in all directions of light in the different layers and support sheet of the silver halide recording material and also because of the refraction and diffuse reflection of light taking place at the boundaries of said layers and support sheet.
It has been proposed in the United Kingdom Patent Spe-cification 821,352 filed January 3, 1957 by Photo Chemische Werke Berlin to reduce the influence of cross-over by in-corporating filtering dyes in the film support and/or the substrate layers or intermediate layers of the film. ~he colouring obtained ~ith these dyes is complementary to the colour of the fluorescent light of the particular intensi-fying screen used.
In practice this has been realized by using a blue-fluorescing calcium tungstate intensifying screen and a silver halide material containing in its support a yellow dye. ~he incorporation of a said yellow dye brings about the necessity to use a higher radiation dose, which because of the relatively weak emission power of said screens in many cases will surpass the permissible dose for medical X-ray radiography.
A urther source of image-unsharpness lies in the diffuse emission, i.e. emission in all directions of the GV.705 PC~ - 2 -~L038683 fluorescent light in the bulk materiàl of the fluorescent layer and in the diffuse reflection at the support of the screen. Indeed, only the fluorescent light rays that are impinging substantially normally to the silver halide emul-sion material offer a sharp image. Therefore, it is necessary to attenuate the non-normally emitted or reflected fluorescent radiation already in the screen material with substances that absorb said radiation. Of course this willproceed at the expense also of the strength of the normally directed light, but since the oblique radiation covers a larger path in the screen material than the normally emitted or reflected radiation,attenuation by absorption in the screen material will have a substantially larger influence on the oblique radiation.
~ he application of filtering dyes and of substances, e.g. screening dyes,in the conventional screens such as calciu~ t~lngstate screens limits the use of said screens to relatively high dosis X-ray exposures so that a great deal of ~edical X-ray photography requiring a low X-ray dose for the patient is not within the possibilities of such screens be-cause of the low emission power of the phosphor of said screens.

Accordingly this invention provides a novel radiographic combination of a fluorescent screen and a silver halide photosensitive element capable of yielding a visible image with improved resolution at still high speed.

GV.705 PCT _ 3 _ ~1 The present inventi~n also provides a particularly suitable screen-film combination for use in mammography in which high image resolution is required.
Other advantages of this invention will become apparent from an examination of the follbwing des-cription and examples.
In accordance with the present invention these advantages are attained with a combination of photosensitive elements suited for radiography comprising :
(1 ) at least one X-ray fluorescent intensifying screen material comprising a phosphor layer, which contains a phosphor or a phosphor mixture consisting wholly or main-ly of a rare earth metal-activated lanthanum oxyhalide, preferably a terbium- or terbium and ytterbium-activated lanthanum oxychloride or lanthanum oxybromide, said phosphors optionally also being activated with cerium and sai(~ phosphor or phosphor mixture having more than half its spectral emission above about 410 nm, more than half its visible light spectral emission between 400 and 500 nm and its maximum of emission in the wavelength range of 400-450 nm, said phosphor layer having a coverage of 200 to 800 g of said lanthanum oxyhalide phosphor per sq.m and a thickness preferably in the range of 60 to 250 ~m, said screen material containing (a) dye(s) and/
or pigment(s) absorbing light within the emission spec-trum of said phosphor layer, said dye(s) and/or pigment(s) GV.705 PC~ - 4 -~ P

~03~683 being present preferably between the phosphor layer and the support of the phosphor layer in an anti-reflec-tion layer, said screen material having preferably an intensification factor of at least 20 at 40 kV and at least 25 at 80 kV, and

(2) a photosensitive material comprising a support and at least one silver halide emulsion layer wherein preferably in said photosensitive material the combined absorption of the support and of the layers at one side of the support is such that (i) the light absorption spectrum thereof mainly (at least for 50 %) corresponds with the light emission spectrum of the fluorescent screen material in the wavelength range of 400 to 500 nm and (ii) in the range of overlap of said absorption and emission spectrum the optical density resulting therefrom is at least 0.6 on account of the inherent absorption of the silver halide emulsion layer(s) and the presence of (a) colouring substance(s) in one or more layers and/
or the support of the photosensitive material.
In the radiographic combination of X-ray fluorescent screens and silver halide radiographic materials of the present invention, the said screens may be arranged separate-ly from the radiation-sensitive silver halide material or it may form with the silver halide emulsion an integral arrangement so that on one and the same support both the silver halide emulsion and the X-ray fluorescent screens are GV.705 PC~ - 5 -1~38683 provided. The radiographic material may be a single- or double-coated radiographic material, which means that the radiographic material comprises either at only one side or at both sides of the support a radiation-sensitive silver halide emulsion layer. The same or differently~composed fluorescent screens may be provided at both sides of a single-or double-coated radiographic material.
~ he radiographic combination of fluorescent screens and radiographic materialsmay comprise the common intermediate and/or protective and/or stripping layers, which may be arranged between or over the radiation-sensitive emulsions and the fluorescent screens.
~ he lanthanum oxyhalide phosphors yield a particu-larly high emission of fluorescent light when struck by X-rays so that the use in the intensifying screen of fluores-cent light-absorbing substances imp~oving the image quality do not lower the fluorescent light emission in such a degree that low dosis medical X-ray photography would be excluded.
For use in the field of X-ray photography known as "mammography" preferably a single side coated silver halide material is used combined with one fluorescent screen in contact with the silver halide emulsion layer. In mammo-graphy very low kilovolt X-rays are normally used viz.
in the range of 20 to 40 kV applied to a molybdenum or tungsten anode X-ray tube.
Mammography has been described in the book "Rontgen-untersuchung der Brust" by W.Hoeffken and M.Lanyi (1973) GV.705 PC~ ~- 6 -Georg Thieme Verlag, Stuttgart, W-Germany.
In mammography for the purpose of high image sharpness screenless film exposures mostly have been applied up till now. Screenless exposures or in other words direct`X-ray exposures of the film require a relatively high silver halide content and X-ray dose. ~he use of phosphors as defined above makes it possible to improve the image sharpness of the screen by means of screening dyes up to a degree equal to the sharpness obtained with direct X-ray exposureswithout having to rely on the high X-ray dose characteristic for direct X-ray photography.
Phosphors or fluorescing substances used in the visible light-emitting fluorescent screens applied in the present invention are, e.g., lanthanum oxychloride acti-vated with small amounts of terbium e.g. as described in the United ~ingdom Patent Specification 1,247,602 filed October 9, 1969 by General Electric Company. Under small amounts of terbium has to be understood an amount of terbium smaller than 0.006 gram atom with respect to the lanthanum in the phosphor material.
Preferred terbium-acti~ated lanthanum oxychloride and lanthanum oxybromide phosphors are represented by the following general formula :

~ a(1 n~.Tbn3 OX
wherein :
X is chlorine or bromine GV.705 PC~ - 7 -~b 3 is trivalent terbium, and n is 0.006 to 0.0001.
~ he halogen X is preferably present in about stoichio-metric amount but may be less, e.g. only about 2.5 percent thereof.
Cerium may replace lanthanum in an amount as described in the United Kingdom Patent 1,247,602, as mentioned herein-before, e.g. in an amount of 0.1 to 0.8 mole percent based on the phosphor composition.
The preparation of terbium-activated lanthanum oxychloride and lanthanum oxybromide phosphors is described in the United Kingdom Patent 1,247,602, as described hereinbefore, French Patent Specifications 2,021,398 filed October 23, 1969 by General ~lectric Company, and 2,021,399 filed October 23, ~969 by General Electric Company, and published German Patent Applications 1,952,812 filed October 21,1969 by General ~lectric Company and 2,16~,958 filed December ~4, ~971 by General ~lectric Company.
~ he emission spectrum of a lanthanum oxybromide con-taining stoichiometric amounts of oxygen and bromine andthat has been activated with 0.002 gram atoms of terbium with respect to the lanthanum is given in the graph of the accompanying Figure~ wherein the relative emission intensity expressed in procentual values (% I) is plotted versus wavelengths expressed in nanometer (nm). ~he applied excitation radiation was 3~3 nm ultraviolet radiation.

GV.705 PC~ - 8 -~Q386W
Other particularly useful phosphors for application according to the present invention are described in the published German Patent Application 2,161,958, as mentioned hereinbefore corresponding with the Canadian Patent 927,089 filed April 11, 1972 by General Electric Company. These phosphors are terbium- and ytterbium-activated lanthanum oxychlorides or lanthanum oxybromides corresponding to the following general formula :
~a1 w yOX:TbWYby wherein :
X is chlorine or bromine, w is from 0.0005 to 0.006 mole pro mole of the oxyhalide, and y is from 0.00005 to 0.005 mole per mole of the oxyhalide.
~he presence of the ytterbium strongly reduces the after-glow effect that follows the ~-ray irradiation so that the formation of ghost images is excluded and sharper images are obtained. The preparation of this class of phosphors has been described in the published German Patent Application 2,161,958, as mentioned hereinbefore. Particularly interes-ting for the purpose of the present invention are said phosphors wherein w is 0.002.
Another phosphor composition for use according to the present invention contains a mixture of a lanthanum oxyhalide phosphor with an yttrium Qxysulphide phosphor both phosphors being activated with terbium. Yttrium oxysulphide phosphors emitting in the blue range of the visible spectrum have been described in the published German Patent Application 1,282,819 GV.705 PC~ - 9 -filed March 18, 1966 by Radio Corporation of America.
~ he selected fluorescent substance(s) is (are) in the form of a layer applied to a support or applied as a self-support-ing layer or sheet. Suited layers or sheets have a thickness of preferably 0.05 to 0.5 mm and contain the fluorescent su~stance(s) or phosphors dispersed in a binder. Such binder is, e.g., an organic high molecular weight polymer. Suitable binding agents are, e.g., cellulose nitrate, ethylcellulose, cellulose acetate, polyvinyl acetate, polystyrene, polyvinyl-butyral, polymethyl methacrylate and the like.
~ he proportion of high molecular weight polymer to fluorescent material is in general within the range of 5-15%
by weight. A preferred grain size of the fluorescent sub-stances is in the range of about 1-25 ~m.
The surface of the fluorescent material layer may be protected against moisture and mechanical damage by a coating of an organic high polymer applied to a thickness of 0.001 to 0.05 mm. Such protecting coating is, e.g., a thin film of cellulose nitrate, cellulose acetate, polymethyl methacrylate and the like.
Besides the fluorescent lighting impinging normally to the silver halide layer there is always an amount of diffuse radiation in the fluorescent screen giving rise to image unsharpness. According to the present invention the image sharpness is improved considerably by incorporating a dye that absorbs fluorescent light in the fluorescent screen material, e.g., in the phosphor layer also called fluorescent GV. 705 PC~ _ 10 -10;1S6~3 layer or in a layer called anti-reflection layer. Said dye is called here "screening dye". As the oblique radiation covers a larger path in the screen material it is attenuated by the screening dye or dyes to a greater extent than the radiation impinging normally. ~he term "screening dye"' includes here dyestuffs (i.e. coloured substances in molecular-ly divided form) as well as pigments.
~ he anti-reflection layer may be present at the rear side of the support and/or between the fluorescent layer and the support, e.g., is applied directly to the support on to a subbing layer of the support. In a particular case the screening dye or dyes are incorporated in the support.
According to another embodiment the screening dye is present in a covering layer on the fluorescent layer.
An appropriate screening dye for use in the fluorescent screens emitting in the blue part (400-500 nm) of the'visi-ble spectrum is, e.g., Tartrazine (C.I. Acid Yellow 23) and a screening dye having the following structural formula:

Na3S~ ~ Na3S~

N C=O ~0-~ ~
H3C-C - C = CH-C - C-C~3 described in the United States Patent 3,624,229 of Daniel Maurice ~immerman, August Jean Van Paesschen and Albert Emiel Van Hoof issued November 30, 1971.
~ he screening dye has not to be removed from the fluores-cent screen material and therefore may be any dye or pigment GV.705 PC~

103~683 absorbing in the emission spectrum of the fluorescent sub- -stance(s). ~hus, a black substance such as carbon black in-corporated in the anti-reflection layer of the screen material yields quite satisfactory results.
~ he screening dye(s) is (are) preferably used in the anti-reflection layer in an amount of at least 0.5 mg per sq.m.
~heir use in the anti-reflection layer in the larger amount range is not limited. Optical densities of more than 3 may be surpassed.
Very good results are obtained with the simultaneous use of screening dye(s) in the subjacent anti-reflection layer and in the layer containing the fluorescent substances.
In that case the fluorescent layer contains, e.g., the screening dye or dyes in an amount of 5 mg per sq.m. Optional-ly the screening dye(s) is (are) incorporated in the fluores-cent layer and the covering layer.
In order to diminish cross-over, at least one layer and/or the base material of the light-sensitive material of the present invention should preferably contain a dye called hereinafter "filtering dye" absorbing light in the wavelength range emitted by the fluorescent screen used in the combination. The filtering dye may be the same dye as the screening dye of the fluorescent screen but is preferably removable from the recording material during its processing.
~ he filtering dyes used in the silver halide emulsion recording material are preferably incorporated in the hydro-GV.705 PC~ - 12 -10386~
philic colloid layer between the silver halide emulsion layers or in the emulsion layers themselves. ~hey may, however, also be incorporated in one or more subbing layers and even in the support. As put forward already the filtering dyes have preferably such chemical and/or physical characteristics that they can be removed or decolourized in one of the processing baths.
According to a preferred embodiment of the present inven-tion filtering dyes absorbing in the wavelength range of about 400 to 500 nm are used in combination with fluorescent screens that substantially emit light in the wavelength range of 400 to 500 nm.
The amount of filtering dye is preferably in the range of amounts that reduces the cross-over light in such a degree that its intensity becomes smaller than 30 % of the intensity of the light impinging on an adjacent emulsion layer. ~or example 25 to 1000 mg per sq.m of filtering dye(s) are used but according to the result aimed at lower or higher amounts may be appropriate as well.
Suitable filtering dyes that can be removed from hydro-philic colloid layers are ~artrazine and the dyes described in said United States Patent 3,624,229, as me~tioned herein-before.
~he silver halide of the silver halide emulsion record-ing material may be present in a layer or coating such as a single coating or a duplitized or dual coating, i.e. in a GV.705 PC~ - 13 -1~38683 material having a silver halide emulsion layer on each side of a support. Suitable supports are those having the pro-perties of permitting their ready passage through a rapid automa~ic processor. ~he support should therefore be reason-ably flexible and preferably transparent but abie to maintain the dimensiona] stability and integrity of the various coatings thereon. ~ypical film supports are cellulose nitrate, cellulose ester, polyvinyl acetal, polystyrene, polyethylene terephthalate, and the like. Supports such as cards or paper that are coated with ~-olefin polymers, particularly polymers of ~-olefins containing two or more carbon atoms, as exem-plified by polyethylene, polypropylene, ethylene-butene co-polymers and the like, give good results.
In the radiographic combination of X-ray fluorescent screens and optionally spectrally sensitized silver halide radiographic materials of the present invention, the screens may be al-ranged separately from the radiation-sensitive silver halide material or they may form with the silver halide emulsion layer an integral arrangement so that on one and the same support both a silver halide emulsion layer and an X-ray fluorescent screen are provided.
~ he emulsions may be spectrally sensitized by any of the known procedures. They may be spectrally sensitized in the wavelength range of 400 to 500 nm by means of common spectrally sensitizing dyes in silver halide emulsions, which include cyanine dyes and merocyanine dyes as well as other dyes as described by ~.M.Hamer in "~he Cyanine Dyes and related Com-GV.705 PC~ - 14 -~03~683 pounds", Interscience Publiskers (1964). ~hese dyes are pre-ferably used in an amount in the range of 20 mg to 250 mg per mole of silver halide.
~ he silver halide in the emulsion layer(s) may comprise varying amounts of silver chloride, silver iodide, silver bromide, silver chlorobromide, silver bromoiodide, and the like, but when coated must be capable, after exposure and processing, of producing a negative silver image remaining thereon, i.e. in situ. Particularly good results are obtained with silver bromoiodide emulsions in which the average grain size of the silver bromoiodide crystals is in the range of about 0.1 to about 3 ~ . When a duplitized silver halide coating is employed, the total silver coveI,age per unit area (sq.dm) for both coatings is 'ess than about 0.080 g and preferably, each such coating contains less than a~out 0.040 g of silver per sq.~m. As these layers are applied by means well-kno~n in the art, it is desirable in the combinations of our invention that the silver halide-coating or coatings be capable of transmitting less than about 40 % and preferably less than about 30 % of the incident radiation from the screen at wavelengths longer than 410 nm when said silver halide coverage is within the above ranges.
The proper transmittance can be obtained in a variety of ways, such as e.g. by the incorporation of optically se-parating barriers, e.g. undercoates, which can be positioned between the silver halide-containing layers, by altering the GV.705 PCT - 15 -composition of said layers, by including dyes or other ma-terials, by adjusting the halide balance or by modifying the silver halide grain shape, grain size, size distribution and the like.
The image-forming silver halide emulsion may be che-mically sensitized by any of the known procedure. ~he emulsions may be digested with naturally active gelatin or with small amounts of sulphur-containing compounds such as allyl thiocyanate, allylthiourea, sodium thiosulphate, etc. ~he image-forming emulsion may be sensitized like-wise by means of reductors, e.g. tin compounds as des-cribed in the United ~ingdom Patent 789,823 filed April 29, 1955 by Gevaert Photo-Producten N.V., polyamines e.g.
diethyltriamine, and small amounts of noble metal compounds such as of gold, platinum, palladium, iridium, ruthenium, and rhodium as described by R.Eoslowsky, Z.Wiss.Phot. 46, 67-72 (1951). Representative examples of noble metal compounds are ammonium chloropalladate, potassium chloro-platinate, potassium chloroaurate and potassium aurithiG-cyanate.
Emulsion stabilizers and antifoggants may be addedto the silver halide emulsion before or after admixture of the low-speed emulsion, e.g., the known sulphinic and selenic acids or salts thereof, aliphatic, aromatic or heterocyclic mercapto compounds or disulphides, e.g.
those described and claimed in published German Patent Application 2,100,622 filed January 8, 1971 by Agfa~Gevaert A.~.
GV.705 PC~ - 16 -~.038683 preferably comprising sulpho groups or carboxyl groups, mercury compounds e.g. those described in ~elgian Patents 524,121 filed November 7, 1953 by Kodak ~td., 677,337 filed March 4, ~966 by Gevaert-Agfa N.V., 707,386 filed December 1, 1967 by Gevaert-Agfa N.V. and 709,195 filed January 11, 1968 by Gevaert-Agfa N.Y, and tetra-azaindenes as described by Birr in Z.Wiss.Phot. 47, 2-58 (1952), e.g. the hydroxy-tetra-azaindenes of the following general formula :
OH
~0 R3-~ ~N C,-R
~- ~ C N

wherein :
each of R1 and R2 represents hydrogen, an alkyl, an aralkyl, or an aryl group, and R3 represents hydrogen, an alkyl, a carboxy, or an alkoxy-carbonyl group, such as 5-methyl-7-hydroxy-s-triazolo~1,5-a~
-pyrimidine.
Other additives may be present in one or more of the hydrophilic colloid layers of the radiation-sensitive silver halide elements of the present invention, e.g. harden-ing agents such as formaldehyde, dialdehydes, hydroxy-aldehydes, mucochloric and mucobromic acid, acrolein, and glyoxal, mordanting agents for anionic colour couplers or dyes formed therefrom, plasticizers and coating aids e.g.
saponin, e.g. dialkylsulphosuccinic acid salts such as sodium diisooctyl sulphosuccinate, alkylarylpolyether-GV.705 PCl - 17 -sulphuric acids, alkylarylpolyethersulphonic acids, car-boxyalkylated polyethylene gl~col ethers or esters as described in ~rench Patent 1,537,417 filed September 18, 1967 by Agfa-Gevaert N.V. such as iso-C8H17-C6H4(0CH2CH2)8-OCH2COONa, fluorinated surfactants, e.g., those aescribed in Belgian Patent 742,680 filed December 5, 1969 by Agfa-Gevaert N.V. and the published German Patent Applications 1,950,121 filed October 4, 1969 by Dupont de ~emours and 1,942,665 filed August 21, 1969 by Ciba A.G., inert particles such as silicon dioxide, glass, starch and polymethacrylate particles.
In medical radiography it is important that the time to dispose of the recorded information be as short as possible.
~herefore the exposed radiographic silver halide materials should be processed in a minimum of time.
It is generally known that processing times and more particularly the fixing times can be shortened by using silver halide emulsions having a relatively small amount of silver halide per unit of surface. ~he use of photo-graphic materials with a small silver halide content bringsabout, however, that the maximllm density, the contrast and the resolving power of the obtained image are at a rather low level.
In this connection it is interesting to note that fine-grained silver halide emulsions have a higher covering power than coarse-grained emulsions (ref. P.Glafkidès, Photographic ~ 705 PC~ - ~8 _ Chemistry, Vol.I (1958) 89-90).
By the term "covering power" is understood in the pre-sent inventi-on the reciprocal of the photographic equivalent of developed silver, i.e. the number of grams of silver per sq.dm divided by the maximum optical density of the image (silver image density and/or colour image density~ obtained.
Fine-grained emulsions have a lower photographic speed, however, and consequently the use of such types of emulsions requires an exposure that may surpass the permissible dose applied in medical X-ray photography. ~he low speed of said fine-grained emulsions having a high covering power, e.g. at least 50, and low silver halide content i.e. equi-valent to less than 80 mg of silver per sq. &, e.g. 30 to 80 mg of silver per sq.dm, is compensated by the use of said lanthanum oxyhalide phosphor screens having a parti-cularly high intensification factor.
By "intensification factor" is to be understood a factor measured at a pre-elected density D, indicating the exposure required to produce this density when the film is exposed to ~-rays without intensifying screen, divided by the expo-sure required to produce the same density, e.g. density D = 1.00, when the film is exposed with the screen, the wavelength distribution of the radiation and the conditions of development being maintained constant.
~ or the purpose of accelerating the development the exposed photographic material is developed preferably GV.705 PGT _ 19 -~03B683 in the presence of development accelerator6. These deve-lopment accelerators can be used either in the silver halide emulsion, in adjacent layer(s) or in the developing bath. They include alkylene oxide compounds of various types, e.g. alkylene oxide condensation products or poly-mers as described in United States Patents 1,970,578 of Conrad Schoeller and Max Wittner issued August 21, 1934, 2,240,472 of Donald R. Swan issued April 29, 1941, 2,423,549 of Ralph Eings~y Blake~ William Alexander Stanton and ~erdinand Schulze issued July 8, 1947, 2,441,389 of Ralph Eingsley Blake issued May 11, 1948, 2,531,.832 of William Alexander Stanton issued ~oveDmber 28, 1950 and 2,533,990 of Ralph Eingsley Blake issued December 12, 1950 and in United Eingdom Patents 920,637 filed May 7, 1959, 940,051 filed November 1, 1961, 945,340 filed October 23, 1961, all by Gevaert Photo-Producten ~.V., 991,608 filed June 14, 1961 by Eodak Ltd. and 1,015,023 field December 24, 1962 by Gevaert Photo-Producten N.V. Other compounds accelerating the development are onium and polyonium compounds, preferably of the ammonium, phosphonium, and sulphonium type, e.g. trialkyl sulphonium salts such as dimethyl-n-nonyl sulphonium p-toluenesulphonate, tetraalkyl ammonium salts such as dodecyl trimethyl ammonium p-toluene-sulphonate, alkyl pyridinium and alkyl quinolinium salts such as 1-m-nitrobenzyl quinolinium chloride and 1-dodecyl pyridinium chloride, bis-alkylene pyridinium salts such as GV.705 PC~ - 20 -1038~83 N,N'-tetramethylene bispyridinium chloride, quaternary ammonium and phosphonium polyoxyalkylene salts especially polyoxyalkylene bispyridinium salts, examples of which can be found in the United States Patent 2,944,900 of Burt H.Carroll, Hubert S.Elins, James ~.Graham and Charles V.
Wilson issued July 12, 1960.
After radiographic exposure the radiographic silver halide elements of the present invention are developed, preferably in an energetic surface developer. ~he high energy is required in order to allow the development to proceed quickly and can be obtained by properly alkalizing the developing liquid (pH 9-~2), by using high-energy developing substances or a combination of developing sub-stances, which as a consequence of their superadditive action is very energetic.
Economy on the silver halide in the emulsion may be realized by building up the image density partly with dyes.
Such may proceed by introducing (a) colour coupler(s) into the emulsion, which at least at the stage of development form(s) (a) dye(s) with the oxiaation product of an aro-matic primary amino developing agent, e.g. of the p-phenylene-diamine type, which dye(s) absorb(s) in the visible part of the spectrum.
~ urther it is known that a relatively high maximum den-sity and contrast can be obtained even with a low amount of silver halide content per unit of surface when a colour GV.705 PC~ _ 21 -~03~
image is produced together with a silver image as is des-cribed, e.g., in the published German Patent Application (Dt-OS) 1,946,652 filed September 15, 1969 by Agfa-Gevaert A.G.
When a colour development is applied, preferably so-called 2-equivalent couplers are used to further reduce the consumption of silver. Thus only 2 instead of 4 mole-cules of exposed silver halide are necessary for the pro-duction of 1 dye molecule. Such couplers contain in the coupling position, e.g. a halogen atom such as iodine, bromine, or chlorine (see e.g. the United States Patent

3,006,759 of Anthony ~oria, Warren A.Reckhow and Ilmari .Salminen issued October 31, 1961). The density of the image is thus realised by addition of the densities of the silver image(s) combined with the dye image(s).
For improving the information content retrieval those phenol or ~-naphthol type colour couplers are particularly suitable that on colour development of the silver halide with an aromatic primary amino developing agent form a quinoneimine dye mainly absorbing in the red and also absorbing in the green and having an absorption maximum in the spectral wavelength range of 550 to 700 (ref., e.g.
to the published German Patent Application (Dt-OS) 1,946,652 as mentioned hereinbefore).
Phenol couplers suited for that purpose correspond, e.g. to the following general formula :

GV.705 PCT - 22 -- 1038~;83 OH
~ -NHR2 R1H~- bJ' wherein :
eacn of R1 and R2 represents a carboxylic acid acyl or sulphonic acid acyl group including said groups in sub-stituted state, e.g. an aliphatic carboxylic acid acyl group, an aromatic carboxylic acid acyl group, an hetero-cyclic carboxylic acid acyl group, e.g. a 2-furoyl group or a 2-thienoyl group, an aliphatic sulphonic acid acyl group, an aromatic sulphonic acid acyl group, a sulphonyl thienyl group, an aryloxy-substituted aliphatic carboxylic acid acyl group, a phenyl carbamyl aliphatic carboxylic acid acyl group, or a tolyl carboxylic acid acyl group.
~or such types of phenol colour couplers and their preparation reference may be made to United States Patents 2,772,162 of Ilmari F.~alminen and Charles R.Barr issued November 27, 1956 and 3,222,176 of Jan Jaeken issued December 7, 1965 and to United Kingdom Patent 975,773 filed September

4, 1961 by Gevaert Photo-Producten N.V.
When colour images are prepared together with silver images normally aromatic primary amino colour developing agents are used, e.g. ~ dialkyl-p-phenylenediamines and derivatives thereof, e.g. N,~-diethyl-p-phenylenediamine, N-butyl-~-sulphobutyl-p-phenylenediamine, 2-amino-5-di-ethylaminotoluene hydrochloride, 4-amino-N-ethyl-~
methane sulphonamidoethyl)-m-toluidine sesquisulphate GV.705 PC~ - 23 -monohydrate and N-hydroxy-ethyl-N-ethyl-p-phenylenediamine.
~he colour developer may be used together with black-and-white developing agents e.g. 1-phenyl-3-pyrazolidinone and p-monomethylaminophenol, which are known to have a super-additive effect on colour development (see L.~.A. Mason, J.Phot.Sci. 11 (1963) 136-139), and other p-aminophenol derivatives, e.g.those according to French Patent 1,283,420 filed February 16, 1961 by Ilford Ltd. such as 3-methyl-4-hydroxy-~,~-diethylaniline, 3-methyl-4-hydroxy-~-ethyl-~-~-hydroxyethylaniline, 1-methyl-6-hydroxy-1,2,3,4-tetra-hydroquinoline, 1-~-hydroxyethyl-6-hydroxy-1,2,3,4-tetra-hydroquinoline and N-(4-hydroxy-3'-methylphenyl)-pyrrolidine.
It is also possible to use combinations of aromatic primary amino colour developing agents to obtain an increased rate of colour development (see e.g. German Patent 954,311 filed December 5, 1953 by Agfa A.G. and ~rench Patent 1,299,899 filed September 8, 1961 by ~gfa ~.G.) ; favourable effects are obtained, e.g., by the use of N-ethyl-N-2-hydroxyethyl-p-phenylenediamine together with ~-butyl-N-sulphobutyl-p-phenylenediamine, 2-Pmino-5-diethylamino-toluene hydrochlo-ride or N,N-diethyl-p-phenylenediamine hydrochloride.
~ he developing solutions may also comprise any of the usual additional ingrediënts, e.g. sodium sulphite and hydroxylamine or derivatives thereof, hardening agents, antifoggants, e.g. benzotriazole~ 5-nitro-benzimidazole~

5-nitro-indazole, halides such as potassium bromide, silver GV.705 PC~ - 24 -~038683 halide solvents, toning and intensifying compounds, sol-vents, e.g. dimethylformamide, dimethylacetamide and N-methyl-pyrrolidone for chemical ingredients that are difficult to dissolve in the preparation of the developing solutions or that tend to precipitate upon standing.
~ he radiation-sensitive emulsions for use in the pre-sent invention may be coated on a wide variety of supports e.g. films of cellulose nitrate, cellulose esters, poly-vinylacetal, polys~yrene, polyethylene terephthalate and other polyester materials as well as ~-olefin-coated papers e.g. paper coated with polyethylene or polypropylene.
Preferred supports comprise a linear condensation poly-mer, blue coloured polyethylene terephthalate being an example thereof.
~ he supports ~sed in the present recording materials may be coated with subbing layers for improving the adhesion of (a) gelatino-silver halide emulsion layer(s) thereto.
~ he mech~nical strength of melt-extruded supports of the polyester type can be improved by stretching. In some cases as described in the United Eingdom Patent 1,234,755 filed September 28, 1967 by Gevaert-Agfa N.V. the support may carry a subbing layer in the stretching stage.
Suited subbing layers are known to those skilled in the art of silver halide photography. With regard to the use of hydrophobic film supports reference is made to the composition of subbing layers aescribea in said United GV.705 PC~ - 25 -103868~
Kingdom Patent 1,234,755.
According to said Patent a hydrophobic film support has 1) a layer which is directly a& erent to t~e said hydrophobic film support and comprises a copolymer ~ormed from 45 to 99.5 % by weight of at least one of the chlorine-containing monomers vinylidene chloride and vinyl chloride, from 0.5 to 10 % by weight of at least an ethylenically unsaturated hydrophilic monomer, and from 0 to 54.5 % by weight of at least one other copolymerisable ethylenically unsaturated monomer ; and 2) a layer comprising in a ratio of 1:3 to 1:0.5 by weight a mixture of gelatin and a co-polymer of ~0 to 70 % by weight of butadiene with at least one copolymerisable ethylenically unsaturated monomer.
~ he exposed radiographic elements of the present invention are preferably processed in an automatic processing apparatus for X-ray films in which the photographic material may be guided automatically and at a constant speed from one processing unit to the other, but it will be understood by those skilled in the art that the radiographic image-recording elements disclosed herein can also be processedapart from the above mentioned automatic processing apparatus in a variety of ways, such as b~ using the manual conventional multi-tank methods well known in the art.
~ or common emulsion preparation processes and the use of particular emulsion ingredients reference is made in general to the Product Licensing Index of December 1971 in which the following terms are dealt within more details :
GV.705 PCT - 26 -- 10386~3 I/II Emulsion type and preparation of said element III Chemical sensitization IV Development modifiers V Antifoggants and stabilizers VI Developing agents VII Hardeners VIII Binding agents or polymers for silver halide layers and other layers IX Antistatic layers X Supports XI Plasticizers and lubricants XII Coating aids XV Spectral sensitization agents for silver halides XXIII Colour material ingredients XVI Absorbing and filter dyes XXI Physical development systems, and XVII and XVIII Addition agents and coating procedures.
The following examples illustrate the present invention.
E~amPle 1 A radiographic colour material was prepared in the following way.
To 155 g of a high-speed silver bromoiodide emulsion (9 mole % silver iodide), which comprises 15.5 g of gelatin and an amount of silver halide equivalent to 23.9 g of silver nitrate and which has an average silver halide grain-size of 800 nm 200 g of a low-speed silver chloride emulsion comprising 16.8 g of gelatin and an amount of GV.705 PC~ - 27 -~038683 silver chloride equivalent to 24 g of silver nitrate were added.
~ he low-speed silver chloride emulsion was prepared by admixing an aqueous solution of silver nitrate to an aqueous gelatin/sodium chloride solution, precipitating the gelatin emulsion with ammonium sulphate, washing and peptizing. Gelatin was then added as well as 5-methyl-7-hydroxy-s-triazolo~1,5-a~p~rimidine so that no chemical ripening occured. ~he mean grain-size of the silver chloride emulsion was 220 nm.
~ he mixture was molten by heating for 1 h at 38C
whereupon were added :
a) 14.5 g of the colour coupler having the formula :

H3c-(cH2)12-cH=cH-cH2-cH-coNH- ~ -OH O
b~2coox ~ -NHCO-from an aqueous alkaline solution, b) sufficient aqueous acetic acid solution to neutralize the emulsion (pH 7), 0 c) 5-methyl-7-hydroxy-s-triazolo~1,5-a]pyrimidine as emulsion stabilizer, d) saponin as coating aid, and e) mucochloric acid as hardening agent.
~ he emulsion was diluted to make g20 ml and then coated on both sides of a subbed polyethylene terephthalate support, the total surface of which was 10 sq.m. (2 x 5 sq.m). On both sides a gelatin antistress layer of 0.0015 mm GV.705 PC~ - 28 -103~tiB3 was provided whereupon the radiographic colour material formed was dried.
The above prepared material was arranged between two fluorescent intensifying screens comprising as luminescent material ~anthanum oxybromide activated with terbium (0.002 gram atoms with respect to the lanthanum) and con-taining stoichiometric amounts of oxygen and bromine.
The phosphor layer of the fluorescent screens contained 500 g per sq.m of said lanthanum oxybromide dispersed in cellulose nitrate as binder. The weight ratio of phosphor to binder was 92.5 to 7.5. In each screen an anti-reflection layer was situated between the phosphor layer and the paper support sheet of the screen material. The anti-reflection layer contained per sq.m 4 g of carbon black dispersed in cellulose nitrate. The weight ratio of carbon black to the binder was 10 to 90.
~ he radiographic combination of screen materials and silver halide material was exposed to 80 kV-peak X-ray radiation passing through 6 mm of aluminium for filtering purposes and through a test original being a lead line grid test object in order to determine the relationship between speed and modulation transfer function value (MTF-value).
After removal of the intensifying screens the radio-graphic colour material was automatically colour-processed, which includes colour-development (24 s at 4~C), fixing GV.705 PCT - 29 - -~038683 (20 s at 41C), rinsing (25 s at 41~C) and drying (20 s at 55C).
~ he developing bath used had a pH of 10.6 and comprised per litre :
8 g of N-hydroxyethyl-N-ethyl-p-phenylenediamine, 1.5 g of hydroxylamine, 4 g of anhydrous sodium sulphite, 1 g of potassium bromide, and 65 g of anhydrous potassium carbonate.
Fixing occurred by means of a sodium thiosulphate fixing solution.
~ he measurements of the relationship between M~F-value and speed occurred by means of a microdensitometer.
It was established that the combined use according t~
the invention of the above luminescent screens with said radiographic colour material yields a more favourable relationship between MTF value and speed than the combined use of a same radiographic colour element with conventional fluorescent calcium wolframate screens, viz. a speed four times as high as for the same MT~-value.
ExamPle 2 A silver bromoLodide X-ray emulsion (1.5 mole % of silver iodide) was prepared in such a way that it contained silver halide grains with an average grain size of 0.60 ~m and comprised per kg 74 g of gelatin and an amount of silver halide corresponding to 190 g of silver nitrate.
As stabilizing agents the emulsion contained per kg 545 mg GV.705 PC~ - ~0 -of 5-methyl-7-hydroxy-s-triazolo~1,5-a~ yrimidine, 6.5 mg of 1-phenyl-5-mercaptotetrazole, and 0.45 mg of mercury cyanide. ~he covering power obtainable with said emulsion was 60.
The above emulsion was coated on both sides of a double-side subbed polyethylene terephthalate support in such a way that on each side of the support a silver halide emulsion layer was obtained containing an amount of silver halide equivalentto 6 g of silver nitrate per sq.m.
~ach emulsion layer was coated with a gelatino anti-stress layer at a coverage of 1 g per sq.m.
~ he material prepared was arranged between the same two fluorescent intensifying screens as described in Example 1 and the radiographic combination formed was exposed to 60 kV X-ray radiation through a lead line grid test object in order to determine speed and modulation transfer function value.
After removal of the fluorescent screens the radio-graphic materials was processed in an automatic 90 seconds processing machine ; the development occurred for 23 s at 35C in ~gfa-Gevaert's hardening developer G 138, which comprises hydroquinone and 1-phenyl-3-pyrazolidinone as developing agents and glutaraldehyde as a hardener.
It was established that the combined use of the above fluorescent screens with the above radiographic silver halide material yielded a more favourable relationship GV.705 PC~ - 31 -~038683 between MTF value and speed than the combined use of the same radiographic element with conventional calcium wol-framate screens, viz. a speed four times as high as for a same MT~-value.
EXamPle 3 A silver bromoiodide X-ray emulsion (1.5 mole % of silver iodide) was prepared analogously to that of Example 2 but so that it contained silver halide grains with an average grain size of 0.65 ~m. ~he covering power obtain-able with said emulsion in the developing conditions definedhereinafter was 60. Then it was applied to a support and coated with an antistress layer as described in Example 2.
- Composition of the fluorescent screen material I.
The fluorescent screen used according to the invention was prepared as follows :
92.2 g of LaOBr:0.002 Tb:0.0005 Yb phosphor particles pre-pared according to the methoa aescribed in the published German Patent Application 2,161,958, as mentioned hereinbefore, were dispersed in a solution of 7.8 g of ELVACI~E 2044 (trade name of du Pont de Nemours, Wilmington, Del., USA, for a high-molecular weight poly-n-butyl methacrylate) in 21.7 g of toluene.
~ he obtained dispersion was filtered through a filter having passages with a mean diameter of 75 )um and was de-aerated by subjecting it to reduced pressure of 100 mbar (100 cm of water). The average grain size of the phosphor GV.705 PCT - 32 -10386~3 particles was 5 ~ . The content of solids of the obtained dispersion was 82.1 % by weight.
~ he dispersion was coated onto an anti-reflection layer, which was applied to a subbed polyethylene terephtha-late resin support of 250 ~m. The subbing layer was produced ~rom a latex on the basis of a copolymer of vinyl chloride, vinylidene chloride, n-butyl acrylate and itaconic acid (weight ratio : 63/30/5/2).
~ he anti-reflection layer contained per sq.m ~ g of carbon black dispersed in cellulose nitrate. ~he weight ratio of carbon black to the binder was 10 to 90.
The coating of the phosphor dispersion was effected in such a way that 35 mg of phosphor were applied per sq.cm.
- Composition of the fluorescent screen material II.
Calcium wolframate phosphor screen particles of the commercial type (manufactured by Riedel-de Haën, Seelze (Hannover), W.Germany) used in CaW04 screens were incorporated in an intensifying screen binder layer as described for fluorescent screen material I. The phosphor layer was applied at a same phosphor coverage per sq.m as described for screen material I on the above anti-reflection layer.
- Exposure.
~ he light-sensitive material was exposed with a 80 kV
X-ray radiation filtered through a 6 mm aluminium sheet and modulated with a test object being a line screen made of lead wherein the width of the bars of the screen gradually diminishes, and their spatial frequency (number per mm) GV.705 PC~ - 3~ -1~3~3 gradually increases from one side of the test object to the other. By applying such a test object in the exposure it is posslble to obtain an objective value for the sharpness independently of subaect contrast by determining the "square wave response function" (SWRF) (ref.Amer.J. Roentgenol.
106 (1969) pages 650-6~4).
Each of a first and a second strip of light-sensitive materials called material A and B respectively was exposed between two fluorescent screen materials I and two fluores-cent screen materials II respectively arranged in contactwith the opposite sides of the light-sensitive material.
The exposed materials were processed in an automatic 90 seconds processing machine the development occurring for 23 s at 35C in Agfa-Gevaert's hardening developer G 138 containing hydroquinone and 1-phenyl-3-pyrazolidione as~
developing agents and glutaraldehyde as hardener.
~ he s~uare wave response function of the test materials was derived from the measurements obtained by scanning the line pattern obtained in these materials with a microdensito-meter.
The relative square wave response factor ~value of thefunction) at a spatial frequency respectively of one and two line pairs per mm for the different combinatiGns of light-sensitive materials and screens as defined above is listed in the following table.

GV.705 PC~ - 34 -~able 10~83 Combination of light Speed Square wave response , sensitive material s~5-log10E factor at :
and screen for denslty 1 line 2 llne _ _ 1.00 pair per mm Pairs per mm ¦
A, I 3.57 0-71 0.45 B, II 3.09 0.70 0.43 Example 4 A silver bromoiodide ~-ray emulsion (1.5 mole % of sil-ver iodide) was prepared in such a way that it contained silverhalide grains with an average grain size of 0.70 pm. ~he emulsion contained a stabilizing agent as defined in Example ~ and was coated at only one side of a subbed polyethylene terephthalate film support, which carried a common anti-reflection layer at the rear side. Coating of the emulsion proceeded in such a way that an amount of silver halide equivalent to 8 g of silver nitrate per sq.m was applied.
~ he obtained photographic silver halide material was used for mammography and for that purpose exposed to X-rays while being in contact with the fluorescent screen layer of a fluorescent screen material whose fluorescent layer incorporated in ELVACI~ 2044 (trade name) as binder the lanthanum oxybromide phosphor of Example 3 at a coverage of 250 g per sq.m and ~sscreening dye "ZAPON ECH~ GELB CGG"
(C.I. ~8,820) in an amount of 0.0379 % by weight with respect to the phosphor.

GV.705 PC~ - 35 -103~683 The grain size of the phosphor particles averaged 2.5 ~m.
The fluorescent screen layer was applied to an anti-reflection layer as described in Example 3, which was coated onto a subbed polyethylene terephthalate support.
In the X-ray exposure for mammographic purposes an X-ray apparatus known as "SENOGRAPH"*(marketed by Compagnie ~Ténérale de Radiologie filiale du groupe ~homson-Brandt ;
France) was used. The X-ray tube was operated at 30 kV
and the X-rays filtered with a 30 ~m plate of mol~ybdenum and a 30 mm plate of polymethyl methacrylate.
Compared with "direct" (screenless) X-ray mammography which operates with a high silver halide content film having a silver halide coverage equivalent to 36 g of silver nitrate per sg.m, the present screen-film combination offered a speed ~ times as high with higher image contrast.
By applying a developer as described in Example 3 the development time necessary for reaching a same maximum density with the present screen film combination was only 1/15 part of the development time needed for said high silver halide content film.

~ Trade Mark GV.705 PC~ - 36 -

Claims (27)

The embodiments of the invention in which an exclusive property or privilege is claimed, are defined as follows :

1. A combination of photosensitive materials suited for radiography comprising :
(1) at least one X-ray fluorescent intensifying screen material comprising a phosphor layer, which contains a phosphor or a phosphor mixture consisting wholly or mainly of a rare earth metal-activated lanthanum oxyhalide, said phosphor or phosphor mixture having more than half its spectral emission above 410 nm, more than half its visible light spectral emission between 400 and 500 nm, and its maximum of emission in the wavelength range of 400-450 nm, said phosphor layer having a coverage of 200 to 800 g of said lanthanum oxyhalide phosphor per sq.m, and said screen material containing (a) dye(s) and/or pigment(s) absorbing light within the emission spectrum of said phosphor layer, and (2) a photosensitive silver halide recording material, which comprises a support and incorporates at least one silver halide emulsion layer.

2. The combination of claim 1, wherein the X-ray fluorescent screen material contains an amount of said dyes and/or pigments and of said phosphors such that the inten-sification factor of the screen is at least 20 at 40 kV
and at least 25 at 80 kV.

3. The combination of photosensitive materials according to claim 1, wherein in the silver halide recording material the combined absorption of the support and of the layers at one side of the support is such that (i) the light absorption spectrum thereof mainly (at least for 50 %) corresponds with the light emission spectrum of the fluorescent screen material in the wavelength range of 400 to 500 nm and (ii) the said combined absorption is such that in the range of overlap of said absorption and emission spectrum the optical density resulting therefrom is at least 0.6 on account of the inherent absorption of the silver halide emulsion layer(s) and the presence of a colouring substance(s) in one or more layers and/or the support of the recording material.

4. The combination of claim 1, wherein the screen contains as phosphor one or more lanthanum oxybromides or oxychlorides activated with terbium and ytterbium.

5. The combination of claim 1, wherein said screen con-tains as phosphor one or more lanthanum oxyhalides activated with terbium and that have their emission maximum in the 400-450 nm range.

6. The combination of claim 5, wherein said phosphor corresponds to the following general formula :
La(1-n)?Tbn3+OX

wherein :
X is chlorine or bromine Tb3+ is trivalent terbium, and n is 0.006 to 0.0001, and wherein the halogen X is present in the range of between about the stoichiometric amount and about 2.5 percent thereof.

7. The combination of claim 6, wherein in the general formula n is equal to 0.002.

8. The combination of claim 4, wherein said phosphor corresponds to the following general formula :
La1-w-yOX:TbwYby wherein :
X is chlorine or bromine, w is from 0.0005 to 0.006 mole of the oxyhalide, and y is from 0.00005 to 0.005 mole per mole of the oxyhalide.

9. The combination of claim 8, wherein w is 0.002 mole and y is 0.0005 mole.

10, The combination of claim 1, wherein the phosphor layer contains a mixture of said lanthanum oxyhalide and an yttrium oxysulphide phosphor activated with terbium.

11. The combination of materials according to claim 1, wherein the intensifying screen contains the fluorescent particles dispersed in a binder within the range of 85-95 % by weight and the thickness of the fluorescent layer is in the range of 60 to 250 pm.

12. The combination according to claim 1, wherein the intensifying screen contains fluorescent particles having a grain size within the range of about 1-25 µm

13. The combination according to claim 1, wherein said silver halide is coated on both sides of the support and is capable of producing a negative visible image having a covering power of about more than 50, said silver halide being present in each coating in a corresponding equivalent amount of less than about 4 g of silver per sq.m.

14. he combination according to claim 1, wherein the silver halide is a silver bromoiodide having an average grain size in the range of about 0.1 to 5 µm.

15. The combination according to claim 1, wherein the silver halide emulsion layer(s) contain(s) a colour coupler for forming a dye with an oxidized-p-phenylenediamine developing agent.

16. The combination of claim 15, wherein the colour coupler is a phenol or an .alpha.-naphthol colour coupler, which on colour development of the silver halide with an aromatic primary amino developing agent forms a quinone-imine dye mainly absorbing in the red and partly absorbing in the green and having an absorption maximum in the spectral wavelength range of 550 to 700 nm.

17. The combination of claim 15, wherein the colour coupler is a phenol, which corresponds to the following general formula :

wherein :
each of R1 and R2 represents a carboxylic acid acyl or sulphonic acid acyl group including said groups in substituted state.

18. The combination described in claim 13, wherein the silver halide layers contain together an amount of silver halide equivalent to about 3 to 8 g of silver per sq.m.

19. The combination of claim 1, wherein the photosensitive material on both sides of its support has been coated with a silver halide emulsion layer and between said silver halide emulsion layers and/or in said emulsion layers (a) filtering dye(s) is (are) present that can be decolourized in one of the processing baths for the photo-sensitive silver halide material.

20. The combination of claim 1, wherein the photosensitive material contains a support con-taining a filtering dye.

21. The combination according to claim 1, wherein the photosensitive material contains a filtering dye or mixture of dyes that absorb in the wave-length range of 400 to 500 nm.

22. The combination of claim 21, wherein said filtering dyes are used in a hydrophilic colloid layer.

23. The combination according to claim 1, wherein the fluorescent screen is arranged separately from the photo-sensitive material containing the silver halide.

24. The combination according to claim 1, wherein the fluorescent screen forms an integral arrangement with the photosensitive material containing the silver halide.

25. The combination according to claim 1, wherein the X-ray fluorescent intensifying screen material contains said dye(s) and/or pigments in an anti-reflection layer adjacent to the phosphor layer.

26. The combination according to claim 1, wherein the dye(s) and/or pigment(s) are present in the layer containing the fluorescent substance(s).

27. The combination according to claim 25, wherein dye(s) and/or pigment(s) is (are) present in an anti-reflection layer applied to a support and subjacent to the fluorescent layer.