US3809906A

US3809906A - Radiographic colour material

Info

Publication number: US3809906A
Application number: US00303385A
Authority: US
Inventors: Doorselaer M Van
Original assignee: Agfa Gevaert NV
Current assignee: Agfa Gevaert NV
Priority date: 1971-11-05
Filing date: 1972-11-03
Publication date: 1974-05-07
Anticipated expiration: 1991-05-07
Also published as: DE2254306A1; JPS5841502B2; CA1000101A; FR2158575B1; FR2158575A1; GB1414455A; IT970200B; JPS4855730A; DE2254306C2; BE790862A

Abstract

A radiographic silver halide colour emulsion for the production of a radiographic monochromic dye image by the steps of radiographic exposure and colour development, said exposure proceeding in contact with an X-ray intensifying screen emitting for at least 50 percent light of the wavelength region beyond 410 nm and having a main emission maximum in the green region of the spectrum, the said emulsion comprising a mixture of a silver halide emulsion capable of producing a visible image upon said exposure and colour development, and a relatively low speed silver chloride-containing emulsion, the speed of which is insufficient to produce a visible image by the said exposure and development, and incorporating at least one colour coupler producing by coupling with an oxidized aromatic primary amino colour developing agent a monochromic dye image, characterized in that said emulsion is spectrally sensitized for the wavelength region comprised between 480 and 600 nm.

Description

United States Patent 1191 Van Doorselaer [54] RADIOGRAPHIC COLOUR MATERIAL [75] Inventor: Marcel Karel Van Doorselaen' s-Gravenwezel, Belgium [73] Assignee: AGFA-Gevaert, N.V., Mortsel,

Belgium [22] Filed: Nov. 3, 1972 [21] Appl. No.2 303,385

. [30] Foreign Application Priority Data Nov. 5, 1971 Great Britain 5 1628/71 521 U.s. cl...... 250/472, 250/475- [51] Int. Cl. G03b 41/16 [58] .Field of Search 250/65 R, 65 F, 83 PH FOREIGN PATENTS OR APPLICATIONS 2,120,950 7/1972 France 250/651 1111 3,809,906 14 1 May 7,' 1974 Primary Examiner-James W, Lawrence Assistant Examiner-C. E. Church Attorney, Agent, or Firm'A. W. Breiner [5 7] ABSTRACT A radiographic silver halide colour emulsion for the production of a radiographic monochromic dye image by the steps of radiographic exposureand colour development, said exposure proceeding in contact with an X-ray intensifying screen emitting for at least 50 percent light of the wavelength region beyond 410 nm and having a main emission maximum in the green region of the spectrum, the said emulsion comprising a mixture of a silver halide-emulsion capable of producing a visible image upon said exposure and colour development, and a relatively low speed silver chloridecontaining emulsion, the speed of which is insufficient -to produce a visible, image by the said exposure and development, and incorporating at least one colour coupler producing by coupling with an oxidized aromatic primary amino colour developing agent a monochromic dye image, characterized in that said emulsion is spectrally sensitized for the: wavelength region comprised between 480 and 600 nm'.

1 1 Claims, No Drawings The present invention relates to green-sensitized radiographic silver halide colour emulsions for radiographic exposure in contact with intensifying screens, the luminescent substances of which have a high emission in the green spectral wavelength region.

In medical radiography it is often highly important to dispose of the recorded information as quickly as possible. Therefore, the exposed radiographic silver halide materials should. be processed in a minimum of time.

It is known to employ for black-and-white radiographic recording materials automatic processing machines, in which processing occurs at elevated temperatures and the photographic materials are guided automatically and at a constant speed from one processing unit to the other in such a way that the overall processing time takes less than 2 minutes.

According to the published German Pat. No. 1,946,652 monochromic radiographic images are produced, optionally together with a silver. image in radiographic elements, which preferably comprisea colourless support and at least one silver halide emulsionlayer, each such layer containing at least one colour coupler producing by coupling with an oxidized aromatic primary amino developing agent a monochromic dye image mainly absorbing in the red and green spectral regions.

Radiographic colour images, which have certain advantages'over black-and-white radiographs, e.g., in that they offer more visual retrieval of information and have a lower silver halide content, normally cannot be producedwith satisfactory quality by rapid colour processing at elevated temperature because the gradation, especially in the higher densities, is much lower than that obtainable at ambient temperatures, which results in colour images of unsatisfactory quality.

According to the Belgian Pat. No. 777,581, it was found possible to obtain for radiographic colour elements of the type described above, upon exposure and rapid colour processing at elevated temperature, as

compared with normal development at ambient temperature, improved speed values and the same or even improved values for the gradation, by adding to the radiographic image-forming silver halide emulsion, prior to coating, a silver chloride-containing emulsion having such a sufficiently low speed that no visible image is produced therein under the conditions of exposure and development of the radiographic image-forming silver halide emulsion.

Further, it is known to expose radiographic silver hal ide materials in contact with intensifying screens comprising luminescent substances emitting in the U.V. or blue region of thespectrum. For medical purposes, the

intensifying fluorescence screens used together with the radiographic silver halide materials are in practice almost exclusively screens that comprise calcium 'tugnstate or lead/barium sulphate as phosphor, because the skilled art worker has never questioned the superiority of these screens over the large variety of screens comprising other types of U.V.- or blue-emittingphosphors. Moreover, the radiographic silver halide emulsions used .have their optimum sensitivity in the U.V. and blue regions of the spectrum.

X-ray exposure of photographic materials in contact with intensifying, luminescent screens emitting beyond radiographic material that can be used for medical purposes and that leads to the formation of radiographic colour images thus offering an increased perceptibility of the recorded information. i

A second object of the present invention is to provide a radiographic colour material that can be processed automatically after exposure at elevated temperaturein less than 2 minutes. i Y

Another object of the present invention is toprovide a radiographic material, the spectral sensitivity of which has been extended beyond the U.V.-blue region of the spectrum so that it can be used for exposure in contact with intensifying screens comprising luminescent substances emitting in the green region of the spectrum. i

Other objects will become apparent from the following description.

These and other objects have been accomplished by the invention described hereinafter. We have found that a rapid-developable radiographic colour emulsion of the type described in the Belgian Pat. No." 777,581 is extraordinarily suitable for being spectrally sensitized in the green region of the spectrum. We also found that with such spectrally sensitized radiographic colour material,;when used together with green-light-emitting intensifying screens, an optimum relationship between speed and image quality can be obtained;

In accordance with the present invention a radiographic colour emulsion is provided for radiographic exposure in contact with an X-ray intensifying screen emitting for at least 50 percentligm of the wavelength region beyond 410 nm, and having a main fluorescence emission maximum in the green region of the spectrum, the said emulsion comprising a mixtureof a silver halide emulsion, capable of producing a visible image upon said exposure and colour development, and a sliver chloride-containing emulsion, the speed of which is insufficient .to producea visible image upon the said exposure and development, and incorporating at least i one colour coupler producing by coupling with an oxidized aromatic primary amino developing-agent a monochromic dye image, wherein the said emulsion is spectrally sensitized for the green wavelength region comprised between 480 and 600 nm. g

i The invention further provides a radiographic recording combination, which comprises a radiographic silver halide material having a support and a greensensitized radiographic colour emulsion as described above, and an intensifying screen, which during radiographic exposure is in contact with the said emulsion,

the said intensifying screen comprising luminescent material spectrally emittingfor atleast 50 percent in the wavelength region beyond 410 nm and having a the green reand oxychlorideactivated with terbium or dysprosium, lanthanum and gadolinium oxysulphides activated with terbium or with terbium and dysprosium, or with europium or europium and samarium and yttrium and lutetium Oxysulphide activated with one of the above rare earth elements. Rare earth luminescent materials have been extensively described in the recent literature for which we refer, e.g., to German Pat. No. 1,282,819; French Pat. Nos. 1,504,341, 1,580,544 and 2,021,397; French Patent of Addition 94,579 to 1,473,531; US. Pat. Nos. 3,418,246, 3,418,247 and 3,546,128; and to K. A. Wickersheim et a], Rare Earth Oxysulphide X-ray Phosphors," in the proceedings of the IEEE Nuclear Science Symposium, San Francisco, Oct. 29-31,

1969 and to Wang et a1, X-ray Image intensifier Tubes Using Rare Earth Oxysulphide Phosphors, IEEE Transactions on Nuclear Science Vol. NS-l7 (1970) 49 56. These novel rare earth luminescent materials especially the gadolinium and lanthanum oxysulphides and oxyhalides activated with other selected rare earths, e.g., erbium, terbium and dysprosium have a high X-ray stopping power or average absorption and high emission density and makes it possible for radiologists to use substantially lower X-ray dosage levels.

1n the radiographic combination of X-ray intensifying screens and green-sensitized radiographic colour materials of the present invention, the said screens may be arranged separately from the radiation-sensitive silver halide material or it may formwith the silver halide emulsion an integral arrangement so that on one and the same support both the silver halide emulsion and the X-ray intensifying screen are provided. The radiographic material may be a singleor 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. The intensifying screens may be provided at both sides of a single or double coated radiographic material. The radiographiccombination ofintensifying screens and radiographic colour materials may further comprise the common intermediate and/or protective and/or stripping layers, which may be arranged between or over the radiation sensitive emulsions and the intensifying screens.

As noted above, in order to permit rapid-processing at elevated temperature of the exposed radiographic silver halide material, the radiographic silver halide emulsion is formed by adding to the image-forming silver halide emulsion a silver chloride-containing emulsion having such a sufficiently low speed that no visible image is produced therein under the conditions of exposure and development of the radiographic imageforming silver halide emulsion;

As can be learned from Belgian Pat. No. 777,581, the blue-light sensitivity of the image-forming silver halide emulsion is preferably at least 100 times the blue-light sensitivity of the silver chloride-containing emulsion. Though the amount of low speed silver chloridecontaining emulsion to be added to the image-forming silver halide emulsion may vary within very wide limits, the ratio of low speed silver chloride to image-forming silver halide, expressed in parts by weight of silver ni-.

trate, is preferably comprised between 1:50 and 1:1. The low-speed silver chloride-containing emulsion is preferably a fine-grain silver chloride-containing emulsion having a particle size in the range from 50 to 500 nm. Though it is preferred to use a pure silver chloride emulsion as low speed emulsion it is also possible to use an emulsion of mixed silver halides comprising silver chloride, e.g., a silver chlorobromide emulsion.

The radiographic silver halide emulsion according to the presentinvention, which comprises a mixture of image-forming silver halide and non-image forming silver chloride, is spectrally sensitized for the wavelength region comprised between 480 nm and 600 nm. The

spectral sensitization maximum is preferably comprised between 520 nm and 560 nm. In those instances where the emulsion, after exposure, is to be processed under normal dark-room red safelight conditions, the spectral sensitization of the radiographic silver halide emulsion of the present invention should be such that the sensitivity of the emulsion for the dark-room illumination is kept as low as possible. If necessary or desired, selectively working desensitizing dyes could be incorporated in the emulsion to lower the sensitivity for the darkroom illumination.

The emulsions can be spectrally sensitized by any of the accepted procedures. They can be spectrally sensitized by means of any of the common spectrally sensitizing dyes used in silver halide emulsions, particularly.

silver halide colour emulsions, which include cyanine dyes and'merocyanine dyes as well as other dyes as described by F.M. Hamer in The Cyanine Dyes and related Compounds, lnterscience Publishers (1964)] The image-forming radiographic silver halide emulsion may comprise different types of silver halide, e.g., silver chloride, silver bromide, silver chlorobromide, and silver chlorobromoiodide.

The image-forming silver halide emulsion is preferably a medium or high speed image-forming silver halide emulsion in which the silver halide is predominantly silver bromide, e.g., pure silver bromide emulsions and silver bromoiodide emulsions, the iodide content of which is less than 10 mole percent. The average silver halide grain size is preferably comprised between 500 nm and 1200 nm.

The total silver halide content in the mixed silver halide emulsion is generally such that after coating on a suitable support the amount of silver halide, expressed support. 1

The monochromic radiographic dye image preferably has its main absorption in the red region (600-700 nm) of the visible spectrum and it absorbs in the green region (500-600 nm) of the visible spectrum for at least 30 percent in respect of the red region. In other words cyan dye images with a fairly large sideabsorption in the-green region and blue dye images are favoured.

For this purpose, phenol or a-naphthol type colour couplers 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 green and having an absorption maximum in the spectral wavelength range of 550 to 700, are particularly suitable.

Phenol couplers having such properties correspond, e.g., to the following general formula:

RiHN

wherein R and R each represent a carboxylic acid acyl or sulphonic acid acyl group includingsaid groups in substituted state, e,'g., an aliphatic carboxylic acidacyl' group, an'aromaticcarboxylic acid acyl group, an

heterocycliccarboxylic acid acyl group, e.g., a 2-furoyl 5 group ora 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, aphenyl carbamyl aliphatic carboxylic acid acyl group, or a tolyl carboxylic acid acyl group.

For such types of phenol colour couplers and their preparation referencecan be made to US. Pat. Nos. 2,772,162 and 3,222,176, and to the British Pat. No. 975,773.'

The image-forming silver halide emulsion can be chemically sensitized by any of the accepted procedures, The emulsions can be digested with naturally active gelatin or with small amounts of sulphur containing compounds such as allyl thiocyanate, ally] thiourea, so-

dium thiosulphate,-etc. The image formingemulsion' can also be sensitized. by means of reductors, e.g., tin

compounds as described in the UK. Pat. No. 789,823, polyamines, e.g.,diethyltriamine, and small amounts of noble metal compounds such as gold, platinum, pallacarboxyl groups, mercury compounds for example those described in Belgian Pat. Nos. 524,121, 677,337, 40

707,386-and1 709,195 and tetra-azaindenes as describedby Bir'r in Z.wiss.Phot; .47, 2-58*( 1952), e.g., the hydroxy tetraazaindenes of the following general each of R, and R repres kyl, an aralkyl, oran aryl group, and

R representsa hydrogen atom, an alkyl, a carboxy, or an alkoxycarbonyl' group, such as 5 -methyl-7- hydroxy-s triazolofl ,5 -a pyrimidine.

Other additives, e.g., hardening agents such as formaldehyde, dialdehydes, hydroxy aldehydes, mucochloric and mucobromic acid, acrolein, and glyoxal, mordanting agentsfor anionic colour couplers or dyes formed therefrom, e.g., as described in British conts a hydrogen atom, an al- 5 potassium chloroaurate, and potassium auritbiocyasulphonic acids, carbo ryalltylated polyethyleneglycol 1 *ethers or esters as described" in French Pat. No.

iso-C,,H -C H 1,537,417 such as (OCH CH OCHCOONa, fluorinated surfactants,

eg, those described in Belgian Pat No. 742,680 and 1,950,121 and the published German Pat. Nos. 1,942,665, inert particles suchassilicon dioxide, gl'as,

starch and polymethylmethacrylate particles can be present in one or more of the hydrophilic colloid layers, of the radiation-sensitive silver halideelemjentsof thepresent invention.

The green-sensitized radiation-sensitive, emulsions.

according to the present invention can be coated on a wide variety of supports, e.g., films of cellulosenitra'te, cellulose esters, polyvinylacetal, polystyrene, polyethylene terephthalate and other polyester materials as well as a-olefin-coated papers, e.g., paper coated with polyethylene or polypropylene. U.V.-absorbing compounds may be incorporated inthe support orin h ydrophilic colloid intermediate layers of the radiographic element.

The radiographic silver halide colour elements of the present inventionare developed, afterradiographic exposure, preferably in an energetic surface developer. The highenergy is requiredin order to allow the development to proceed quickly. It can be obtainedby properly alkalizing the developing liquid (pH 9-12), by

using highenergy developing substances or acombination of developing substances, which' 'as a consequence of their superadditive action is very energetic.'Aromatic .p'rimary amino colour-developing agents, e.g.,

N,N-dialkyl-p-phenylene diamines and derivatives thereof, e.g., N,N-diethyl-p-plienylene diamine, N- butyl-N-sulphobutyl-p-phenylene diamine, 2-amino-5- diethylaminotoluene' hydrochloride and 4"amino-N- ethyl-N(B-methane sulphonamidoethyl)-m-toluidine sesquisulphate monohydrate and N-hydroxyethyLN- ethyl-p-phenylene diamine can be used together with black-and-whitedeveloping agents, e.g., l-phenyl-3- pyrazolidinone and p-monomethylaminophenolwhich are known to'have a superadditi've effect on colour development (see L.F.A. Mason, Jl.Phot.Sci. 11 (1963 )1 136l39),and other p-aminopheno l derivatives for example thoseaccording to FrenchPat. No. 1,283,420 such as 3-methyl-4-hydroxy-N,N-diethylaniline,- 3- methyl-4 hydroxy-N-ethyl-N-B-hydroxyethylaniline,

l-methyl- B-hydrorcyethyl-6-hydroxy-l,2,3,4-

tetrahydroquinoline, N-(4'-hydroxy-3 -methylphenyly pyrrolidine, etc. It is also possible to use combinations of aromatic primary amino colour developing agents to pending application Ser. No. 42381/71, plasticizers and 6 coatingfaids, e.g., saponin, e.g., dialkylsulphosuccinic acid salts such as sodium diisooctylsulphosuccinate, alkylaryl polyether sulphuric acids, alkylarylpolyetherobtain an increased rate of colour development (see, e.g., German Pat. No; 954,311 and French Pat. No. 1,- 299,899); favourableeffect s are, e.g., obtained by the use of N-ethyl-N-Z-hydroxyethyLp-phenylene diamine together with N-butyl-N-sulphobutyl p=phenylene diamine, Z-amino-5-diethylamino-toluene hydrochloride 0'! N,N-'diethyl-p-phenylene diamine hydrochloride. A

superadditive colour development effect is also obtained, whenza tetraalkyl p-phenylene diamine deriva- 'tive is used together with an aromatic primary amino colour developing agent.

For the purpose of accelerating the development, the

exposed photographic material is developed preferably in the presence of development accelerators. These development accelerators can be used either in thesilver halide emulsion or in the developing bath. They include -hydroxy-l ,2,3,4 tetrahydroquinoline, l-

alkylene oxide compounds of various types, e.g., alkylene oxide condensation products or polymers as described in US. Pat. Nos. 1,970,578, 2,240,472 2,423,549, 2,441,389, 2,531,832 and 2,533,990 and in UK. Pat. Nosv 920,637, 940,051, 945,340, 991,608 and 1,015,023. Other development accelerating compounds are onium and polyonium compounds preferably of the ammonium, phosphonium, and sulphonium type for example trialkyl sulphonium salts such as dimethyl-n-nonyl sulphonium p-toluene sulphonate, tetraalkyl ammonium salts such as dodecyl trimethyl ammonium p-toluene sulphonate, alkyl pyridinium and alkyl quinolinium salts such as l-m-nitrobenzyl quinolinium chloride and l-dodecyl pyridinium chloride, bisalkylene pyridinium salts such as N,N-tetramethylene bispyridinium chloride, quaternary ammonium and phosphonium polyoxyalkylene salts especially polyoxyalkylene bispyridinium salts, examples of which can be found in U.S. Pat. No. 2,944,900, etc.

The developing solutions can also comprise any of the usual additional ingredients, e.g., sodium sulphite and hydroxylamine or derivatives thereof, hardening agents, antifoggants, for instance, benzotriazole, nitrobenzimidazole, S-nitro-indazole, halides such as potassium bromide, silver halide solvents, toning and intensifying compounds, solvents, 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, etc.

Since the silver image need not be removed, the development step need not be followed by a bleaching step so that a processing as simple as that for producing black-and-white radiographs can be applied.

The exposed radiographic colour elements of the present invention are preferably processed in an automatic processing apparatus for X-ray films, in which the photographic material can be guided automatically and at a constant speed from one processing unit to the other.

The following example illustrates the present invention.

Example A radiographic colour material was prepared in the following way.

To 155 g ofa high speed silver bromoiodide emulsion (9 mole percent silver iodide), which comprises an amount of silver halide equivalent to 23.9 g of silver nitrate and 15.5 g of gelatin, and which has an average silver halide grain size of 800 nm, 22.5 ml ofa 0.5 percent methanolic solution of the following sensitizing dye were added:

aatsac ,LJZEIQQTPSOF The low speed silver chloride emulsion was prepared by adding 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[l,5-a]pyrimidine so that no chemical ripening occurred. The mean grain size of the silver chloride emulsion was 220 nm.

The mixture was molten by heating for 1 hour at 38 C whereupon were added:

a. 14.5 g of the colour coupler having the formula from an aqueous alkaline solution, g

h. an aqueous acetic acid solution in the amount necessary to neutralize the emulsion (pl-I 7),

c. 5-methyl-7-hydroxy-s-triazolo[ l,5-a]pyrimidine as emulsion stabilizer,

d. saponine as coating aid, and

e. mucochloric acid as hardening agent.

The emulsion was diluted to make 920 ml and then coated on both sides of a subbed polyethylene terephthalate support, the total surface of which is 10 sq.m. (2 X 5 sq.m). On both sides a gelatin anti-abrasion layer of 0.0015 mm was provided, whereupon the radiographic colour material formed was dried.

The spectrally sensitized material has a sensitization maximum at about 540 nm. 7

A non-spectrally sensitized material prepared in identical circumstances but without the addition of the spectrally sensitizing dye as well as the spectrally sensitized material were arranged between two fluorescent intensifying screens comprising as luminescent material gadolinium oxysulphide activated with terbium-and the radiographic elements formed were exposed to 60 kV X-ray radiation through a lead bar test object in order to determine the relationship between speed and MTF- value.

After removal of the intensifying screens, the radiographic colour materials were colour-processed automatically, which includes colour-development (24 sec at 41C), fixing (20 sec at 41 C), rinsing (25 sec at 41 C) and drying (20 sec at 55 C).

The developing bath used had a pHof 10.6 and comprised per litre: 8 g of N-hydroxyethyl-N-ethyl-pphenylene diamine, 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.

The measurements of the relationship between MTF- value and speed occurred by means of a microdensitometer and showed that for a same MTF-value, the spectrally sensitized material has a markedly higher speed than the non-spectrally sensitized material, namely about 320 percent.

It was also found that the combined use of the above luminescent screens with the spectrally sensitized radiographic colour material of the invention yields a more favourable relationship between MTF-value and speed than the combined use of a non-spectrally sensitized radiographic colour element with conventional calcium tungstate screens.

I claim:

l. A radiographic silver halide colour emulsion for the production of a radiographic monochromic dye image by the steps of radiographic exposure and colour development, said exposure proceeding in contact with an X-ray intensifying screen emitting for at least 50 percent light of the wavelength region beyond 410 nm and having a main emission maximum in the green region of the spectrum, the said emulsion comprising a mixture of a silver halide emulsion capable of producing a visible image upon said exposure and colour development, and a relatively low speed silver chloridecontaining emulsion, the speed of which is insufficient to produce a visible image by the said exposure and development, and incorporating at least one colour coupler producing by coupling with an oxidized aromatic primary aminocolour developing agent a monochro mic dye image, characterized in that said emulsion is spectrally sensitized for the wavelength region comprised between 480 and 600 nm.

2. A radiographic silver halide emulsion according to claim 1 wherein the spectral sensitization maximum is comprised between 520 and 560 nm. N

3. A radiographic silver halide emulsion according to 1 claim 1, wherein the said non-image forming silver chloride-containing emulsion is a pure silver chloride emulsion.

4. A radiographic silver halide emulsion according to claim 1, wherein the ratio of non-image forming silver chloride to image forming silver halide is comprised between 1250 and 1:1.

5. A radiographic silver halide emulsion according to claim 1, wherein the colour coupler has its main absorption in the red region (600-700 nm) of the visible spectrum and absorbs in the green region (500600 nm) of the visible spectrum for at least 30 percent in I respect of the red region.

6. A radiographic silver halide emulsion according to claim 5, whereinthe said colour coupler is a phenol or oz-naphthol colour coupler.

7. A radiographic silver halide emulsion according to claim 6, wherein the colour coupler is a phenol colour coupler of the formula:

RzHN

wherein each of R and R is a carboxylic or sulphonic acid acyl group.

8. A radiographic recording element comprising the combination of a radiographic silver halide material having a support and on at least one side thereof a spectrally sensitized silver halide emulsion according to claimJ with at least one X-ray intensifying screen, which during radiographic exposure isin contact with the said emulsion, the said intensifying screen comprising luminescent material spectrally emitting for at least 50 percent in the wavelength region beyond 410 nm and having a main fluorescence emission maximum in the green region of the spectrum.

9. A radiographic recording element accordingto claim 1, wherein the said luminescent material is a rare earth oxysulphide or oxyhalide activated with other selected rare earths.

10. A radiographic recording element according to claim 9, wherein the said luminescent material is a gadolinium or lanthanum oxysulphide or oxyhalide activated with erbium, terbium, or dysprosium or with terbium and dysprosium or is anyttrirum or lutetium oxysulphide activated with a rare earth element.

11. A radiographic recording element according to claim 8 wherein the said luminescent material has a main fluorescence emission peak in the region comprised between 520 and 560 nm.

Claims

2. A radiographic silver halide emulsion according to claim 1 wherein the spectral sensitization maximum is comprised between 520 and 560 nm.
3. A radiographic silver halide emulsion according to claim 1, wherein the said non-image forming silver chloride-containing emulsion is a pure silver chloride emulsion.
4. A radiographic silver halide emulsion according to claim 1, wherein the ratio of non-image forming silver chloride to image forming silver halide is comprised between 1:50 and 1:1.
5. A radiographic silver halide emulsion according to claim 1, wherein the colour coupler has its main absorption in the red region (600-700 nm) of the visible spectrum and absorbs in the green region (500-600 nm) of the visible spectrum for at least 30 percent in respect of the red region.
6. A radiographic silver halide emulsion according to claim 5, wherein the said colour coupler is a phenol or Alpha -naphthol colour coupler.
7. A radiographic silver halide emulsion according to claim 6, wherein the colour coupler is a phenol colour coupler of the formula:
8. A radiographic recording element comprising the combination of a radiographic silver halide material having a support and on at least one side thereof a spectrally sensitized silver halide emulsion according to claim 1 with at least one x-ray intensifying screen, which during radiographic exposure is in contact with the said emulsion, the said intensifying screen comprising luminescent material spectrally emitting for at least 50 percent in the wavelength region beyond 410 nm and having a main fluorescence emission maximum in the green region of the spectrum.
9. A radiographic recording element according to claim 1, wherein the said luminescent material is a rare earth oxysulphide or oxyhalide activated with other selected rare earths.
10. A radiographic recording element according to claim 9, wherein the said luminescent material is a gadolinium or lanthanum oxysulphide or oxyhalide activated with erbium, terbium, or dysprosium or with terbium and dysprosium or is an yttrium or lutetium oxysulphide activated with a rare earth element.
11. A radiographic recording element according to claim 8 wherein the said luminescent material has a main fluorescence emission peak in the region comprised between 520 and 560 nm.