EP0555457A1

EP0555457A1 - Radiographic element

Info

Publication number: EP0555457A1
Application number: EP19920918820
Authority: EP
Inventors: Wayne P. Pruett; Max A. Weaver; Elizabeth K. Priebe; Larry K. Maier; Robert E. Dickerson
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1991-08-29
Filing date: 1992-08-27
Publication date: 1993-08-18
Also published as: WO1993005443A1; CA2094143A1; JPH06501795A

Abstract

Un élément radiographique comprend un support en polyester ayant des couches d'émulsion d'halogénure d'argent à double face. Un composé de méthine absorbant la lumière ultraviolette est mélangé et ajouté au support ou dans une couche interposée entre les couches d'émulsion, en une quantité suffisante pour réduire et ramener à moins de 25 % environ le pourcentage moyen de transmission de lumière ultraviolette sur la plage de longueurs d'ondes allant de 350 nm à 395 nm environ et de sorte que le pourcentage du facteur de transmission de l'élément soit au moins de 55 % environ à une longueur d'ondes d'environ 410 nm pour une épaisseur d'élément d'environ de 0,007 pouce.An X-ray element includes a polyester backing having double sided silver halide emulsion layers. A methine compound absorbing ultraviolet light is mixed and added to the support or in a layer interposed between the emulsion layers, in an amount sufficient to reduce and reduce to less than about 25% the average percentage of transmission of ultraviolet light on the wavelength range from about 350 nm to 395 nm and so that the percentage of the element transmittance is at least about 55% at a wavelength of about 410 nm for a thickness d '' element of about 0.007 inch.

Description

RADIOGRAPHIC ELEMENT

Technical Field This invention relates to double coated silver halide radiographic elements of the type employed in combination with intensifying screens. More specifically, the invention relates to a radiographic element having an ultraviolet light -absorbing compound disposed between the silver halide layers. Background Art

Photographic elements relying on silver halide emulsions for image recording are employed in radiographic assemblies. It is known that silver halide emulsions are more responsive to light than to X rays. Accordingly, intensifying screens are used in radiographic assemblies. An intensifying screen contains a phosphor which absorbs X radiation and emits radiation in the visible spectrum or in an adjacent spectral region, ultraviolet or infrared.

It is also desirable to limit patient exposure to high levels of X radiation. Dual coated radiographic assemblies are used to allow reduced levels of X radiation to obtain a useful radiograph. Accordingly, radiographic assemblies can comprise a dual coated light sensitive radiographic element disposed between a pair of fluorescent intensifying screens. The intensifying screens, upon exposure to X radiation, emit radiation in the visible spectrum or in an adjacent spectral region, e.g. ultraviolet or infrared that exposes the silver halide emulsions and results in a recorded image in both emulsion layers.

An image sharpness limitation of dual coated radiographic elements results from a phenomenon known as "crossover". Crossover occurs when light emitted by each intensifying screen passes through the film support, exposing and giving rise to an unsharp image in the oppositely situated silver halide emulsion layer.

A variety of techniques have been tried to reduce crossover. One approach is to dissolve a filter dye in one or more of the hydrophilic colloid layers or in the support forming the radiographic element. Accordingly, in an ultraviolet light-sensitive radiographic element, an ultraviolet light absorbing compound can be situated between the emulsion layers to reduce crossover of ultraviolet radiation. A desirable characteristic of the ultraviolet light absorbing compound is that it exhibit πώiimal absorption of light at wavelengths above about 400 nm so that the amount of yellow hue in the radiographic element is thus minimized.

Another approach to improve the clarity of the exposed image by decreasing undesirable yellow hue in a radiographic element is to add a blue dye to the support to offset the yellow, thereby improving the contrast of the exposed image. This approach, however, does not sufficiently offset the yellow hue, and further improvement in decreasing the yellow hue to achieve a sharp image is desirable.

Another prior art appoach employs T-Grain ® emulsions to achieve reduction in crossover without employing dyes and ultraviolet light absorbers as above. It is desirable, however, to continue to provide an alternative to radiographic elements employing T-Grain ultraviolet light-sensitive emulsions. There is therefore still a need for improved ultraviolet light absorbing compounds for use in non-T-Grain, ultraviolet light-sensitive, radiographic elements.

The present invention solves the prior art problems noted above. It provides ultraviolet light-absorption capability sufficient to substantially reduce crossover of ultraviolet radiation to the opposite ultraviolet-sensitive emulsion layer. It achieves a desired level of ultraviolet-light absorption without imparting an undesirable yellow hue to the photographic element. Thus, by means of this invention there is provided a radiographic element that upon exposure to X radiation provides a recorded image substantially free of crossover. The invention thereby provides an exposed image that is sharper and more readable.

U.S. Pat 3,822,131 discloses a double-sided, radiographic image- recording element having an ultraviolet absorbing material between the silver halide emulsion layers to reduce crossover. The reference also discloses incorporating the ultraviolet absorbing material in the base in the range from about 50 to about 2000 parts per million and that the absorbers, are most effective at wavelengths of about 410 nm or less. The compounds of this patent are expensive and difficult to prepare. Furthermore, when added to the radiographic element in adequate levels to achieve maximum desired level of crossover they impart an unwanted yellow color.

U.S. Pat 3,849,658 discloses a radiographic image-recording element having an ultraviolet absorbing substance between the emulsion layers to reduce crossover. The ultraviolet substance is incorporated in the support in a range from about 50 to about 2000 parts per million or in a subbing layer in a range from about 25 to about 1000 parts per million. The compounds of this patent bear no structural resemblance to those of the present invention and are difficult and expensive to prepare, e.g. as set forth in U.S. Pat. 3,420,835, reqiiiiing a complicated multi-step synthetic procedure. Additionally, they contribute significant yellow color to the radiographic element when added at levels needed to achieve the maximum desired crossover reduction.

U.S. Pat. 4,617,374, 4,707,537, 4,749,773, 4,749,774, 4,845,187, and 4,994,512 disclose ultraviolet light -absorbing compounds copolymerized with polyester and polycarbonate compounds suitable for use as beverage bottles and the like. The patents do not describe the use of the compounds in

radiographic elements and in the useful loadings provided, by our invention.

Some of the preferred uv absorbers employed in this invention are within the disclosures of the above-identified references. However, the references do not describe the use of such compounds in X ray films.

Furthermore, the references do not disclose the unexpected light-absorbing activity of such compounds in X ray film (set forth in the experimental section of this specification).

Research Disclosure, Vol. 184, August 1979, Item 18431, summarizes the state of the art of constructing radiographic elements, including dual coated radiographic elements employing light-absorbing dyes to reduce crossover. Research Disclosure is published by Kenneth Mason Publications, Ltd., Ems worth, Hampshire P0107DD, England.

Research Disclosure, Vol. 248, December 1984, Item 24822, discloses a variety of structures useful as UV absorbing compounds to reduce crossover in radiographic film, including benzophenones, benzotriazoles, benzylidene malonates, salicylates, oxamides, etc. The reference, however, does not disclose the compounds of our invention. Furthermore, when compounds of this reference are used at an adequate level to reduce crossover to achieve maximum image sharpness, excessive amounts are required and/or the UV absorber imparts an objectionable yellow color. Brief Description of the Drawings

FIGURE 1 is a cross-section, not to scale, of a photographic element of the invention.

FIGURE 2 is an absorbance curve of one of the uv absorbers, Compound I, used in the invention. Compound I has an absorption maximum (λ max) at 356 nm in methylene chloride in the UV absorption spectrum. The extinction coefficient (ε) is equal to 37,105. FIGURE 3 is an absorbance curve of another uv absorber, Compound II, used in the invention. Compound II has an absorption maximum (λ max) at 364 nm in methylene chloride (ε = 45,458).

FIGURE 4 an absorbance curve of a comparison uv absorber. The compound has an absorption maximum (λ max) at 352 nm in methylene chloride (ε= 40,944).

FIGURE 5 an absorbance curve of a comparison uv absorber. The compound has an absorption maximum (λ max) at 377 nm in methylene chloride (ε = 29,380).

The structural formulas for the compounds in FIGS.2-5 are as given in the FIGURES. The curves were obtained using a methylene chloride solution in which the concentration of the compounds was about 0.1 g/l.

FIGURE 6 is a graph of ttansmittance versus spectral wavelength for test runs of poly (ethylene terephthalate) (PET) film contajxiing specified uv absorbers and for a control without uv absorber.

FIGURE 7 is a graph of percent transmittance versus spectral wavelength for test runs of PET film containing blue dye and specified uv absorbers and for a control without uv absorber.

FIGURE 8 is a graph showing film speed, percent crossover, and percent transmittance for PET film containing uv absorber used in the invention.

Disclosure of Invention

This invention comprises a radiographic element comprising a polyester support having opposed major surfaces and having an ultraviolet light- sensitive silver halide emulsion layer on each of such surfaces. Admixed in the support or in a layer interposed between the emulsion layers is an ultraviolet light absorbing methine compound.

The methine compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 25 percent, and whereby the percent transmittance of the element is at least about 55 percent at a wavelength of about 410 nm for an element thickness of about 0.007 inches. In another embodiment, the methine compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light in the stated range to less than about 12 percent Improved sharpness of the image recorded in each silver halide emulsion layer thus results. In accordance with the present invention, in one embodiment certain ultraviolet light absorbing methine compounds defined below are admixed in the polyester support material. In another embodiment, the ultraviolet light absorbing methine compound can be admixed in a hydrophilic colloid subbing layer interposed between the silver halide emulsion layers. In one embodiment in which the ultraviolet light absorbing methine compound is admixed in the support, the weight proportion of the ultraviolet light absorbing methine compound to the polyester is in the range of from about 200 to about 1600 ppm. In another such embodiment, the weight proportion of the ultraviolet light absorbing methine compound to the polyester is in the range of from about 400 to about 800 ppm.

Best Mode For Carrying Out The Invention In a preferred embodiment, this invention comprises a radiographic image-recording element, comprising:

a polyester support having opposed major surfaces; an ultraviolet light-sensitive silver halide emulsion layer on each of such surfaces; and

admixed in the support at least one ultraviolet light absorbing compound as described below.

In another embodiment the ultraviolet light absorbing compound is admixed in a subbing layer interposed between the silver halide emulsion layers.

The ultraviolet light absorbing compound has the formula:

wherein:

R₁ and R₂ are independently selected from the group consisting of:

alkyl groups having from 1 to about 20 carbon atoms, cycloalkyl groups having from about 3 to about 7 carbon atoms, and aryl groups having from 6 to about 12 carbon atoms, all of which may be substituted; alkenyl groups having from about 3 to about 10 carbon atoms; alkynyl groups having from about 3 to about 10 carbon atoms; hydrogen;

groups of the formula:

and groups of the formula:

wherein L is an organic divalent linking group;

R₃ and R₄ are selected from the group consisting of:

alkyl groups having from 1 to about 20 carbon atoms, cycloalkyl groups having from about 3 to about 7 carbon atoms, and aryl groups having from 6 to about 12 carbon atoms, all of which may be substituted;

alkenyl groups having from about 3 to about 10 carbon atoms; alkynyl groups having from about 3 to about 10 carbon atoms; and hydrogen;

X and X₁ are independently selected from -CON(R₅)R₆, -CO ₂R₆ and -

SO₂R₆, wherein:

R₅ is hydrogen or a substituted or unsubstituted alkyl group having from 1 to about 20 carbon atoms;

R₆ is an alkyl group having from 1 to about 20 carbon atoms, a cycloalkyl group having from about 3 to about 7 carbon atoms, or an aryl group having from 6 to about 12 carbon atoms, all of which may be substituted; an alkenyl group having from about 3 to about 7 carbon atoms; an alkynyl group having from about 3 to about 10 carbon atoms; hydrogen; or a group having the formula

wherein Y is -CO₂-, -CON(R₅)- where R₅ is as defined above, or -SO₂-, and L, R₃, and R₄ are as defined above; and

wherein the ultraviolet light absorbing compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 25 percent, and whereby the percent transmittance of the element is at least about 55 percent at a wavelength of about 410 nm for an element thickness of about 0.007 inches. In another embodiment, the ultraviolet light absorbing compound can be employed in an amount sufficient to reduce the average percent transmission of ultraviolet light in such range to less than about 12 percent

As used herein, the term "substituted alkyl" means C₁-C₂₀ alkyl group substituted by one or more of halogen, phenyl, C₃-C₇ cycloalkyl, C₁-C₄ alkoxy, C₁-C₄ alkanoyloxy, C₁-C₄ alkoxycarbonyl, hydroxy, amino, carboxy, C₁-C₄ alkylsulfonyl, C₁ -C₄ alkylthio, phenoxy, phenylthio, cyano, succinimido, carbamoyl, sulfamoyl, C₁-C₄ alkoxycarbonyl and furyl. The term "substituted cycloalkyl" means C₃-C₇ cycloalkyl groups substituted by one or more of C₁-C₄ alkyl, C₁-C₄ alkoxy, halogen, hydroxy, C₁-C₄ alkoxycarbonyl and the like. The term "substituted aryl" means aryl groups containing 6 to about 12 carbons substituted with the substituents which may be present on the substituted alkyl groups described above. The term "C₁-C₄ alkanoyloxy" means a C₁-C₄ alkyl group bonded to a carbonyl function which is bonded to another oxygen. For example, C₂ alkanoyloxy is propionyloxy. The term "C₁-C₄ alkoxycarbonyl" means C₁-C₄ alkoxy bonded to a carbonyl function, e.g., the C₂ alkoxycarbonyl group is ethoxycarbonyl. The meaning of "reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about [X] percent", as is made clear from its context and from the below Examples, the description thereof, and the accompanying Figures, is that the transmission of ultraviolet light through the dual coated radiographic element of the invention when averaged over the stated range is less than the stated value of X.

The meaning of "whereby the percent transmittance of the element is at least about 55 percent at a wavelength of about 410 nm for an element thickness of about 0.007 inches" is readily understood by one skilled in the art The term does not limit the thickness of the element of the invention but rather defines a characteristic of the radiographic element that is, other thicker elements are also within the scope of the invention. The ttansmittance of an element will vary according to its thickness. The transmittance should vary in an

approximately linear manner for element thicknesses employed in the

radiographic art Thus, an element of the invention having a thickness of about 0.007 inches (0.18 mm) will transmit at least about 55 percent of the light of wavelength of about 410 nm. An element of the invention than such should have less transmittance, and a thinner element more transmittance, than about 55 percent at about 410 nm.

Preferred uv absorbers are those of the above formula wherein R_1, R₂, R₃ and R₄ are independently selected from hydrogen; cycloalkyl; cycloalkyl substituted with one or two of alkyl, alkoxy or halogen; phenyl; phenyl substituted with 1-3 of alkyl, alkoxy, halogen, alkanoylamino, or cyano; straight or branched lower alkenyl; straight or branched alkyl and such alkyl substituted with 1-3 of the following: halogen; cyano; succinimido; glutajimido;

phthalimido; phthalimidino; 2-pyιrolidono; cyclohexyl; phenyl; phenyl substituted with alkyl, alkoxy, halogen, cyano, or alkylsiilfamoyl; vinylsulfonyl; acrylamido; sulfamyl; benzoylsulfonicimido; alkylsulfonamido;

phenylsulfonamido; alkenylcarbonylamino; groups of the formula

wherin Y is -NH-,

-O-, -S-, or -CH₂O-; -S-R₁₄; SO₂CH₂CH₂SR₁₄; wherein R₁₄ is alkyl, phenyl, phenyl substituted with halogen, alkyl, alkoxy, alkanoylamino, or cyano, pyridyl, pyrimidinyl, benzoxazolyl, benzimidazolyl,^' benzothiazolyl, or a radical of the formulae >

-NHX₃R₁₅; -CONR₁₅R₁₅; and -SO₂NR₁₅R₁₅; wherein R₁₅ is selected form H, aryl, alkyl, and alkyl substituted with halogen, phenoxy, aryl, -CN, cycloalkyl, alkylsulfonyl, alkylthio, or alkoxy; X₃ is -CO-, -COO-, or -SO₂-; R₁₆ is selected from alkyl and alkyl substituted with halogen, phenoxy, aryl, cyano, cycloalkyl, alkylsulfonyl, alkylthio, and alkoxy; and when X₃ is -CO-, R₁₆ also can be hydrogen, amino, alkenyl, alkylamino, diallcylamino, aiylamino, aryl, or furyl; alkoxy; alkoxy substituted with cyano or alkoxy; phenoxy; or phenoxy substituted with 1-3 of alkyl, alkoxy, or halogen.

Preferably, X and X₁ are independently selected from cyano, carbamyl, N-alkylcarbamyl, N-alkyl-N-arylcarbamyl, N,N-dialkylcarbamyl, N,N- alkylarylcarbamyl, N-arylcarbamyl, N-cyclohexylcarbamyl, aryl, 2-benzoxazolyl, 2-benzothiazolyl, 2-benzimidazolyl, 1,3,4-thidiazol-2-yl, 1,3,4-oxadiazol-2-yl, alkylsulfonyl, arylsulfonyl or acyl.

The organic linking represented by L is bonded to the adjacent oxygen atoms through non-oxo carbon atoms, e.g., unsubstituted or substituted methylene groups, a methylidene group and an unsubstituted methylene group or a nuclear carbon atom of a carbocyclic or heterocyclic aromatic group. Thus, linking group L is selected from a wide variety of C₁-C₈ alkylene, C₃-C₈ alkenylene, C₃-C₈ alkynylene, C₃-C₇ cycloalkylene, carbocyclic and

heterocyclic arylene and combinations of such divalent groups. The alkylene linking groups may contain within their main chain hetero atoms, e.g., oxygen, sulfur, sulfonyl, nitrogen, substituted nitrogen, and/or cyclic groups such as C₃-

C₇ cycloalkylene, carbocyclic arylene, or divalent aromatic heterocyclic groups.

Examples of alkylene linking groups containing a cyclic moiety in the linking chain include:

n

The carbocyclic arylene groups may be cycloalkylene such as 1,2-, 1,3- and 1,4- cyclohexylene, 1,2-, 1,3- and 1,4-phenylene.and 2,6- and 2,7-naphthylene.

Examples of the divalent heterocyclic groups include unsubstituted and substituted triazines such as 1,3,5-triazin-2,4-diyl, 6-methoxy-1,3,5-triazin-2,4- diyl and the group having the structure:

diazines such as 2,4-pyrimidindiyl, 6-melhyl-2,4-pyrimidindiyl, 6-phenyl-2,4- pyrimidindiyl, 3,6-pyridazindiyl and 2-methyl-3-oxo-4,5-pyridazindiyl;

dicyanopyridines such as 3,5-dicyano-2,6-pyridindiyl and 4-phenyl-3,5-cyano- 2,6-pyridindiyl; quinolines and isoquinolines such as 2,4-quinolindiyl and 2,8- isoquinolinediyl; quinoxalines such as 2,3-quinoxalindiyl; and azoles such as 2,5- thiazoldiyl, 5-methylene-2-thiazolyl, 3,5-isothiazoldiyl, 5-methylene-3- isothiazolyl, 1,3,4-thiadiazol-2,5-diyl, 1,2,4-thiadiazol-3,5-diyl, 2,6- benzothiazoldiyl, 2,5-benzoxazoldiyl, 2,6-benzimidazoldiyl, 6-methylene-2- benzothiazolyl and the group having the structure:

andmaleimides such as 1-methyl-3,4-maleimidediyl and 1-phenyl-3,4- maleimidediyl. The acyclic moieties of the linking group represented by L also may be substituted for example, with hydroxy, alkoxy, halogen, alkanoyloxy, cyano, alkoxycarbonyl, aryl, aryloxy, cycloalkyl, etc. The cyclic moieties of linking group L may be substituted with alkyl as well as with the substituents already mentioned. In addition to the possible substitution described above, the nitrogen atom of the nitrogen containing alkylene groups may be substituted, for example, with alkyl, aryl, alkanoyl, aroyl, alkylsulfonyl, or carbamoyl, e.g.,

In the above definitions of L, the term "alkylene" represents a straight or branched chain divalent hydrocarbon radical which contains from one to about eight carbon atoms. The term "carbocylic arylene" refers to phenylene radicals and same substituted with C₁-C₄ alkyl, C₁-C₄ alkoxy or halogen.

In one embodiment referring to the above formula for the uv absorber, X is -CO₂R₆ and R₆ is an alkyl group having from 1 to about 10 carbon atoms, R₁ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms, and R₂ is an alkyl group having from 1 to about 10 carbon atoms.

In another embodiment, X is -CO₂R₆ wherein R₆ is an alkyl group having from 1 to about 10 carbon atoms, R₂ is an alkyl group having from 1 to about 10 carbon atoms, and R₁ has the formula:

wherein X₁ is -CO₂R₆ and R₆ is as defined hereinabove, and R₃ is an alkyl group having from 1 to about 10 carbon atoms.

In yet another embodiment R₁ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms, R₂ is an alkyl group having from 1 to about 10 carbon atoms, and X has the formula:

wherein R₃ is an alkyl group having from 1 to about 10 carbon atoms, and R₄ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms.

A suitable weight proportion of the ultraviolet light absorbing compound to the polyester is from about 200 to about 1600 parts per million. In another embodiment the weight proportion of the ultraviolet light absorbing compound to the polyester is from about 400 to about 800 parts per million.

The intensifying screens employed in the invention are capable of emitting substantially within the ultraviolet spectral range, i.e. at about 400 nm. or less. Such screens are well known in the art and are described, for example, in U.S. Pat No. 3,822,131, issued July 2, 1974, to Cleare, and Belgian Pat.703,998, issued Mar. 18, 1968, to Luckey.

The silver halide emulsion layer may contain varying amounts of silver chloride, silver iodide, silver bromide, silver chlorobromide, silver bromoiodide and the like. Conventional overcoat layers may be employed to protect the emulsion layers from damage such as abrasion and scratches.

The radiographic elements can contain additional conventional features. Referring to Research Disclosure, item 18431, cited above, the emulsion layer units can contain stabilizers, antifoggants, and antikinking agents of the type set forth in Section H, and the overcoat layers can contain any of variety of conventional addenda of the type set forth in Section IV. The outermost layers of the radiographic element can also contain matting agents of the type set out in Research Disclosure, Vol.308, Dec. 1989, Item 308119, Section XVI. Referring further to Research Disclosure, Item 308119,

incorporation of the coating aids of Section XI, and the antistatic layers of Section XIII, are each contemplated.

Referring to FIG. 1, in the assembly shown a radiographic element 100 according to this invention is positioned between a pair of ultraviolet light- emitting intensifying screens 102 and 104. The radiographic element 100 is comprised of a support 106, typically transparent or blue tinted, capable of transmitting at least a portion of the light to which it is exposed and optional, similarly transmissive under layer or sub layer units 108 and 110. in the depicted embodiment, on the first and second opposed major faces 112 and 114 of the support formed by under layer units 108 and 110 are crossover reducing layers 116 and 118, respectively, each layer having admixed therein an ultraviolet light- absorbing compound of the invention. Silver halide ultraviolet light-sensitive emulsion layers 120 and 122 are respectively disposed on crossover reducing layers 116 and 118.

In another embodiment of the invention in which the ultraviolet light absorbing compound of the invention is admixed in the support, silver halide emulsion layers 120 and 122 are disposed on faces 112 and 114 respectively without such under layer units 108 and 110 respectively interposed therebetween. In use, the assembly is imagewise exposed to X radiation. The X radiation is principally absorbed by intensifying screens 102 and 104, which promptly emit ultraviolet light as a direct function of X ray exposure.

Considering first the light emitted by screen 102, the light recording, ultraviolet light-sensitive, latent image-forming layer unit 120 is positioned adjacent this screen to receive the light which it emits. Because of the proximity of screen 102 to emulsion layer unit 120 only minimal light scattering occurs before latent image-forming absorption occurs in emulsion layer 120. Hence light emission from screen 102 forms a sharp image in emulsion layer 120. However, not all of the light emitted by screen 102 is absorbed within emulsion layer 120. This remaining light, unless otherwise absorbed, will reach remote emulsion layer unit 122, resulting in a highly unsharp image being formed in this remote emulsion layer unit. Both crossover reducing layers 116 and 118 are interposed between screen 102 and emulsion layer 122 and are capable of intercepting and attenuating this remaining light. Both of these layers thereby contribute to reducing crossover exposure of emulsion layer 122 by screen 102. In an exactly analogous manner, screen 104 produces a sharp image in light recording, ultraviolet light- sensitive emulsion layer unit 122, and ultraviolet light-absorbing layers 108 and 110 similarly reduce crossover exposure of emulsion layer unit 120 by the ultraviolet light emitted by screen 104.

Following exposure to produce a stored latent image, radiographic element 100 can be removed from association with intensifying screens 102 and 104 and processed in a suitable readily available processor of a type well known in the art.

The radiographic elements of the present invention make possible the unique combination of advantages set forth above by employing an ultraviolet light-absorbing compound of the invention as described above admixed in a crossover reducing layer or in the support

The preparation and the properties of the radiographic element of the invention is illustrated by the following examples. Descriptions and/or preparation of some ultraviolet light-absorbing compounds of the invention may be found in U.S. Pat Nos. 4,617,374, 4,749,774, and 4,994,512. The preparation of some of the ultraviolet light-absorbing compounds of the invention is also illustrated by the following examples. PREPARATION OF COMPOUNDS The intermediate aldehydes useful in preparing the compounds used in the practice of the invention are known or are prepared by known methods. For example, intermediate aldehydes A (below) are prepared by well- known reactions such as those described in H. Szmant "Organic Building Blocks of the Chemical Industry", John Wiley and Sons, New York (1989), pp 234 and 514). In one method, catechol is monoalkylated by reacting with suitable alkylating agents such as alkyl halides, alkyl sulfates, and alkyl phosphates, and the like, to give catechol monoalkyl ethers, which undergo the Reimer-Tieman reaction to give intermediate aldehydes A, as follows:

(A)

Aldehydes A may also be prepared by reacting piperonal with HBr to give 3,4-dihydroxybenzaldehyde which may be alkylated with suitable alkylating agents to produce A as follows:

Piperonal

These aldehydes A may be used directly to prepare UV absorbing compounds useful in the practice of the invention or may be reacted further to produce useful, more highly substituted benzaldehydes, as in Example 1 of U.S. Pat No. 4,707,537 (supra), and as in the examples below.

Methods of preparation of bis-aldehydes useful in preparing bis- methine compounds useful in the practice of the invention are described in U.S. Pat No.s 4,749,774 (supra) and 4,994,512 (supra).

Methods useful in reacting the intermediate aldehydes with the active methylene compounds are well known and are described in the above patents and the examples below. Example 1

Preparation of Methyl 2-Cyano-3-(4-Hydroxy-3-Methoxyphenyl)-2-Propenoate

A mixture of vanillin (7.60 g, 0.05 mol), methyl cyanoacetate (4.95 g, 0.05 mol), ethanol (50 mL), piperidine (12 drops) and acetic acid (6 drops) is heated at reflux for 3 hours with stirring and then cooled. The pale yellow product crystallizes and additional ethanol (25 mL) is added to promote stirring and 5% HCl (10 mL) is added to neutralize any phenol salt present. The product methyl 2-cyano-3-(4-hydroxy-3-methoxyphenyl)-2-propenoate, is collected by filtratiori, washed with ethanol and dried in air. A yield of 9.4 g (80.6%) is obtained. The identity of the product is supported by mass spectroscopy analysis and is shown below as compound I.

Example 2 Preparation of 4-(Benzyloxy)-3-Methoxy-Benzaldehyde Sodium hydroxide (2.4 g) is dissolved in water (50 mL) by stirring. Vanillin (7.60 g, 0.05 mol) and α-chloro-toluene (7.60 g, 0.06 mol) are added and the reaction mixture is heated at reflux with stirring for 16 hours. The product is extracted from the aqueous mixture using methylene chloride (10 mL). When the solvent is removed under vacuum an oil results which crystallizes when treated with isopropyl alcohol and stirred. Mass spectrometry supports the following structure:

Example 3

Preparation of Methyl 3-(4-Benzyloxy-3-Methoxyphenyl)-2-Cyano-2-Propenoate A m ixture of 4-(benzyloxy)-3-methoxybenzaldehyde (1.21 g,

0.005 mol), methyl cyanoacetate (0.50 g, 0.005 mol) methanol (10.0 mL) and piperidine (5 drops) is heated and stirred at reflux for 1 hour and cooled. The product 3-(4-benzyloxy-3-methoxyphenyl)-2-cyano-2-propenoate is collected by filtration, washed with methanol and dried in air. The yield is 1.50 g (93%) of product having an absorption maximum at 364 nm in methylene chloride solution. The identity of the product is supported by mass spectrometry.

Example 4 Preparation of Methyl 2-Cyano-3-[4-(2-Hydroxyethoxy)-3-methoxyphenyl]-2- Propenoate

A mixture of 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde (0.98 g, 0.005 mol), ( see Example 1 of U.S. Pat No.4.707,537, supra) methyl cyanoacetate (0.50 g, 0.005 mol), piperidine (3 drops) and methanol (10 mL) is heated and stirred at reflux for 1 hour and cooled. The pale yellow product is collected by filtration, washed with methanol and dried in air. A yield of 1.0 g (72%) of product is obtained which has the following structure as supported by mass spectrometry:

The compound has an absorption maximum at 365 nm in methylene chloride.

Example 5 Preparation of Ethyl 2-Cyano-3-(3-Hydroxy-4-Methoxyphenyl-2-Propenoate

A mixture of 3-hydroxy-4- methoxybenzaldehyde (isovanillin) (1.52 g, 0.01 mol), ethyl cyanoacetate (1.13 g, 0.01 mol), ethanol (20.0 mL) and piperidine (5 drops) is heated at reflux for 1 hour. The reaction mixture is cooled and acidified to pH of about 4-5 with 10% HCl to produce the product which is collected by filtration, washed with ethanol and air dried. A yield of 1.36 g (55%) of product is obtained which corresponds to the following structure as supported by mass spectrometry:

The compound has an absorption maximum (λ max) at 354 nm in methylene chloride solution. Example 6

Preparation of Methyl 2-Cyano-3-(3,4-Dimemoxyphenyl)2-Propenoate A mixture of 3,4-dimethoxybenzaldehyde (4.15 g, 0.025 mol), methyl cyanoacetate (2.48 g, 0.025 mol), methanol (100 mL) and piperidine (10 drops) is heated at reflux for 2 hours. The reaction rmxture is then cooled and the product collected by filtration, washed with methanol and dried in air (yield - 6.0 g, 97%). The following structure is supported by mass spectrometry:

The compound has an absorption maximum at 361 nm in methylene chloride. Example 7

Preparation of Ethyl 2-Cyano-3-(4-Carbethoxymethoxy-3-Methoxyphenyl)-2- Propenoate A rnixture of 4-carbethoxymethoxy-3-methoxybenzaldehyde (23.8 g, 0.10 mol), ethyl cyanoacetate (11.3 g, 0.10 mol), ethanol (150 mL) and piperidine (2 mL) is heated at reflux for 4 hours. The reaction mixture is allowed to cool, and the solid is collected by filtration, washed with ethanol and dried in air. A yield of 31.3 g (93%) of product is obtained which has the following structure as supported by mass spectrometry:

An absorption maximum at 355 nm is observed when the product is dissolved in methylene chloride.

Example 8

Preparation of 3-[4(2-Hydroxyethoxy)-3-Methoxyphenyl]-2-Methylsulfonyl-2- Propene Nitrile

A mixture of 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde (0.98 g, 0.005 mol), (see Example 1 of U.S. Pat No.4,707,537, supra),

methylsulfonylacetonitrile (0.60 g, 0.005 m), ethanol (10 mL) and piperidine (5 drops) is heated at reflux for 1 hour, during which time the product crystallizes. The reaction mixture is allowed to cool and the very pale yellow product is collected by filtration, washed with ethanol and dried in air. The yield of product is 1.05 g (70.9%). Mass spectrometry supports the following structure:

In methylene chloride the product has an absorption maximum at 362 nm. Example 9

Preparation of 2-Cyano-3-(4-Hydroxy-3-Memoxyphenyl)-2-Propenamide A reaction mixture of vanillin (1.52 g, 0.01 mol), α- cyanoacetamide (0.84 g, 0.01 mol), ethanol (25 mL) and piperidine (6 drops) is heated at reflux for 1 hour and then allowed to cool to room temperature. The reaction mixture is acidified to pH of about 3-4 by addition of a few drops of concentrated HCl. The product which is collected by filtration, washed with ethanol and dried in air has the following structure supported by mass spectrometry:

The yield of product is 1.5 g (68.8%). In methylene chloride the product has an absorption maximum of 352 nm.

Example 10 A reaction mixture of vanillin (1.96 g, 0.01 mol), 1,2-ethanediyl bis(α-cyanoacetate) (3.04 g, 0.02 mol), N,N-dimethylformamide (10 mL) and piperidine acetate (0.2 g) is heated and stirred at 90-95°C for 1.5 hour, allowed to cool to room temperature, and drowned into methanol (100 mL). The pH is adjusted to 3-4 by addition of cone. HCl and the solid product is collected by filtration, washed with methanol and dried in air. A yield of 2.1 g of product having the structure

as evidenced by NMR and mass spectrum analyses is obtained. In methylene chloride the compound has an absorption maximum of 365 nm and an extinction coefficient of 40,490.

Example 11

To a solution of vanillin (4-hydroxy-3-methoxybenzaldehyde, 91.2 g, 0.60 mol) dissolved in water (500 mL) containing sodium hydroxide (24.0 g, 0.60 mol) is added 1,2-dibromoethane (56.7 g, 0.30 mol) and the reaction mixture is stirred and heated to reflux for 8 hours and then allowed to cool. The product, 4,4'-[(1,2-ethanediyl)bis(oxy)bis(3-methoxybenzaldehyde)], is collected by filtration, washed with water and dried in air. A yield of 67.5 g (68%) of a slightly gray solid is obtained. The identity of the product is supported by mass spectroscopy analysis.

A mixture of 4,4'-[(1,2-ethanediyl)bis(oxy)bis(3- methoxybenzaldehyde)] (49.5 g, 0.15 mol), methyl cyanoacetate (30 g, 0.30 mol), N,N-dimemylformaτnide (500 mL), piperidine (3 mL) and acetic acid (1 mL) is heated with stirring at about 100° C. for 2 hours. The reaction mixture is allowed to cool to room temperature and the pale yellow solid which forms is collected by filtration and washed with methanol. The crude product is reslurried in 500 mL of boiling methanol, collected by filtration, washed with methanol and dried in air. A yield of 59.4 g (81%) of dimethyl 3,3'-[(1,2-ethanediyl)bis(oxy)bis(3- methoxy-4,1-phenylene)-bis(2-cyano-2-propenoate)] having the formula:

and designated as compound II is obtained.

Additional examples of methine compounds which may be used in the preparation of the X-ray elements of the invention are set forth in the following tables in which the compounds of each table conform to the structural formula immediately preceding each such table. These compounds may be prepared according to the procedures described above.

SUBSTITUTE SHEET

Examples 134-143

Preparation of polyester support with uv absorber:

A 7 mil thick clear poly (ethylene terephthalate) ("PET") support is prepared as a control, and 7 mil thick PET supports for films of the invention are prepared as follows :

Poly (ethylene terephthalate) granules (I.V. between about 0.55 and about 0.70 dl/g=about 0.63 as measured in a 60:40 percent by weight solution of phenol and chlorobenzene at 25° C) are vacuum dried and dry blended with 800 ppm by weight of a uv light-absorbing compound (identified below). The blend is dried overnight (16 hours) in a vacuum oven at 110° C. After drying, the material is melt blended and extruded into 7 mil film on a 1 inch Killion extruder (25 to 1 L/D).

Film support 1: Control PET 7 mil thick film sample (containing no uv absorbing compound).

Film support 2: contains the compound of EX. 1 hereinafter identified as

"Compound I).

FIG. 2 is the characteristic absorption curve of compound I.

Film support 3 contains the compound of EX.11 hereinafter identified as

"Compound II".

FIG.3 is the characteristic absorption curve of compound II. Film support 4 (Comparison) contains an ultraviolet light-absorbing compound having the structure

(III)

FIG.4 is the characteristic absorption curve of compound III. Film support 5 (Comparative example)

contains an ultraviolet light-absorbing compound of the invention having the structure

FIG. 5 is the characteristic absorption curve of compound IV.

Additional 7 mil thick PET film supports are also prepared with the above compounds and also containing 250 ppm by weight of a blue dye, 1,4- bis(2,6-diethylanilino)-anthraquinone, ad mixed with each such PET support.

Transmission spectra are obtained for each sample using standard techniques. The results are shown in FIGs. 6 and 7 and Table 9 as follows:

Colorimetry data is obtained using standard techniques and the results are shown in Table 10, below. The term "B*" is the Tone value.

FIG.S 6 and 7 of percent transmission for the same weight proportion of each uv absorber in the PET support, with and without 250 ppm by weight of 1,4-bis(2,6-diethylanilino)-anthraquinone blue dye, show that the supports containing compound I and compound II exhibit better absorption in the ultraviolet range of about 350 nm to about 395 nm than does compound III at the same weight proportion of 800 ppm. The supports containing compounds I and II also show less unwanted absorption in the visible range above 400 nm. As a result, the poly (ethylene terephthalate) supports containing compounds I and II can employ a lower weight percent of uv absorber than a support containing compound III for a similar amount of uv absorption. A support containing an ultraviolet light-absorbing compound of the invention therefore exhibits less undesirable yellow hue than a support containing compound III.

The colorimetry results in Table 10 can be interpreted in that the more negative the value of the tone (B*), the colder is the tone and hence the more desirable is the support A "Just Noticeable Difference" (JND) is 0.7. Thus in Table 10 there is no noticeable difference between support 2 and 3, and the good tone of the support containing compound I is not noticeably different than the support containing compound II which also exhibits good tone. When the colorimetry results of film supports 2 and 3, containing compounds I and II, respectively, are compared to film supports 4 and 5, respectively, it is noted that the film supports which contain the prior art compounds have significantly more objectionable yellow color, i.e. a more positive value of B*. The same results are obtained even when the blue toner dye is added (film supports 7 and 8 as compared to film supports 9 and 10, respectively, in Table 10). Example 144

The 7 mil PET supports of EXS. 1 and 11 respectively containing compound I and compound H are each coated with a standard silver halide emulsion layer on each side of the support and are each assembled into a radiographic element of the invention. Each element is tested for stated loadings of absorber compound for speed, percent crossover, and percent transmittance in the wavelength ranges of 350-395 nm and 400-430 nm and the results shown in Table 11, below, and in FIG. 8. Table 11 shows the percent transmittance in the stated wavelength ranges for the stated absorber loadings. FIG. 8 graphs speed, percent crossover, and percent transmittance at 380 nm.

Both radiographic elements exhibit good crossover reduction while maintaining good film speed, and exhibited good transmittance, especially in the range of about 400 ppm to about 800 ppm.

Industrial Applicability

The radiographic image-recording element of the invention provides a substantially yellow-free image recording material useful in medical and other applications. The exposed, developed image is easier to read because it provides better contrast and a sharper image than other radiographic elements. This in turn should lead to improved information- collection from the imaged material, as for example improving diagnostic capability in medical applications.

This invention has been described above with particular reference to preferred embodiments. A skilled practitioner familiar with the detailed description above, can make many substitutions and modifications without departing from the scope and spirit of the appended claims.

Claims

1. A radiographic image-recording element comprising:

a polyester support having opposed major surfaces;

an ultraviolet light-sensitive silver halide emulsion layer on each of said surfaces; and

admixed in said support at least one ultraviolet light absorbing compound having the formula:

wherein:

R₁ and R₂ are independently selected from the group consisting of: alkyl groups having from 1 to about 20 carbon atoms, cycloalkyl groups having from about 3 to about 7 carbon atoms, and aryl groups having from 6 to about 12 carbon atoms, all of which may be substituted;

alkenyl groups having from about 3 to about 10 carbon atoms; alkynyl groups having from about 3 to about 10 carbon atoms; hydrogen;

groups of the formula:

and groups of the formula:

wherein L is an organic divalent linking group;

R₃ and R₄ are selected from the group consisting of:

X and X₁ are independently selected from -CON(R₅)R₆, -CO₂R₆ and - SO₂R₆, wherein:

R₅ is an alkyl group having from 1 to about 20 carbon atoms, a cycloalkyl group having from about 3 to about 7 carbon atoms, or an aryl group having from 6 to about 12 carbon atoms, all of which may be substituted; an alkenyl group having from about 3 to about 7 carbon atoms; an alkynyl group having from about 3 to about 10 carbon atoms; hydrogen; or a group having the formula

wherein Y is -CO ₂-, -CON(R₅)- where R₅ is as defined above, or -SO₂-, and L, R₃, and R₄ are as defined above; and wherein said ultraviolet light absorbing compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 25 percent and whereby the percent transmittance of said element is at least about 55 percent at a wavelength of about 410 nm for an element thickness of about 0.007 inches.

2. The radiographic image-recording element of Claim 1 , wherein:

X is -CO₂R₆ and R₆ is an alkyl group having from 1 to about 10 carbon atoms,

R₁ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms, and

R₂ is an alkyl group having from 1 to about 10 carbon atoms.

3. The radiographic image-recording element of Claim 1, wherein:

X is -CO₂R₆ wherein R₆ is an alkyl group having from 1 to about

10 carbon atoms,

R₂ is an alkyl group having from 1 to about 10 carbon atoms, and

R₁ has the formula:

4. The radiographic image-recording element of Claim 1, wherein:

R₁ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms,

R₂ is an alkyl group having from 1 to about 10 carbon atoms, and X has the formula: wherein R₃ is an alkyl group having from 1 to about 10 carbon atoms, and

R₄ is hydrogen, an alkyl group having from 1 to about 10 carbon atoms, or a substituted alkyl group having from 1 to about 10 carbon atoms.

5. The radiographic image-recording element of Claim 1, wherein said ultraviolet light absorbing compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 12 percent

6. The radiographic image-recording element of Claim 1, wherein the weight proportion of said ultraviolet light absorbing compound to said polyester is from about 200 to about 1600 parts per million.

7. The radiographic image-recording element of Qaim 1, wherein the weight proportion of said ultraviolet light absorbing compound to said polyester is from about 400 to about 800 parts per million.

8. A radiographic image-recording element comprising:

a polyester support having opposed major surfaces; an ultraviolet light-sensitive silver halide emulsion layer on each of said surfaces; and

admixed in a layer interposed between between said emulsion layers an ultraviolet light absorbing compound having the formula:

wherein:

groups of the formula:

and groups of the formula:

wherein L is an organic divalent linking group;

R₃ and R₄ are selected from the group consisting of:

alkenyl groups having from about 3 to about 10 carbon atoms; alkynyl groups having from about 3 to about 10 carbon atoms; and hydrogen; X and X₁ are independently selected from -CONOR₅)R₆, -CO₂R₆ and - SO₂R₆, wherein:

R₆ is an alkyl group having from 1 to about 20 carbon atoms, a cycloalkyl group having from about 3 to about 7 carbon atoms, or an aryl group having from 6 to about 12 carbon atoms, all of which may be substituted; an alkenyl group having from about 3 to about 7 carbon atoms; an alkynyl group having from about 3 to about 10 carbon atoms; hydrogen;, or a group having the formula

wherein Y is -CO₂-, -CON(R₅)- where R₅ is as defined above, or -SO₂-, and L, R₃, and R₄ are as defined above;

and wherein said ultraviolet light absorbing compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 25 percent and whereby the percent ttansmittance of said element is at least about 55 percent at a wavelength of about 410 nm for an element thickness of about 0.007 inches.

9. The radiographic image-recording element of Claim 8, wherein:

R₂ is an alkyl group having from 1 to about 10 carbon atoms. 10. The radiographic image-recording element of Claim 8, wherein:

X is -CO₂R₆ wherein R₆ is an alkyl group having from 1 to about

10 carbon atoms, R₂ is an alkyl group having from 1 to about 10 carbon atoms, and R₁ has the formula:

11. The radiographic image-recording element of Claim 8, wherein:

R₂ is an alkyl group having from 1 to about 10 carbon atoms, and

X has the formula:

wherein R₃ is an alkyl group having from 1 to about 10 carbon atoms, and

12. The radiographic image-recording element of Claim 8, wherein said ultraviolet light absorbing compound is present in an amount sufficient to reduce the average percent transmission of ultraviolet light over the range of wavelength of from about 350 nm to about 395 nm to less than about 12 percent.

13. The radiographic image-recording element of Claim 8, wherein the weight proportion of said ultraviolet light absorbing compound to said polyester is from about 200 to about 1600 parts per million.

14. The radiographic image-recording element of Claim 8, wherein the weight proportion of said ultraviolet light absorbing compound to said polyester is from about 400 to about 800 parts per million.