Radiographic element exhibiting reduced crossover

A double coated radiographic element is disclosed comprised of a dye coated between an emulsion layer and a support to reduce crossover to less than 10 percent. The dye is present in the form of microcrystalline particles, yet is capable of being decolorized in less than 90 seconds during processing.

FIELD OF THE INVENTION 
The invention relates to radiography. More specifically, the invention 
relates to double coated silver halide radiographic elements of the type 
employed in combination with intensifying screens. 
BACKGROUND OF THE INVENTION 
While silver halide photographic elements are capable of directly recording 
X ray exposures, they are more responsive to light within the visible 
spectrum. It has become an established practice to construct Duplitized 
.RTM. (double coated) radiographic elements in which silver halide 
emulsion layers are coated on opposite sides of a film support and to 
sandwich the radiographic element between intensifying screen pairs during 
imaging. The intensifying screens contain phosphors that absorb X 
radiation and emit light. This light is transmitted to the silver halide 
emulsion layer on the adjacent face of the film support. The result is 
that diagnostic radiographic imaging is achieved at significantly reduced 
X ray exposure levels. 
An art recognized difficulty with employing double coated radiographic 
elements as described above is that some light emitted by each screen 
passes through the transparent film support to expose the silver halide 
emulsion layer on the opposite side of the support to light. This results 
in reduced image sharpness, and the effect is referred to in the art as 
crossover. 
A variety of approaches have been suggested to reduce crossover, as 
illustrated by Research Disclosure, Vol. 184 August 1979, Item 18431, 
Section V. Cross-Over Exposure Control. Research Disclosure is published 
by Kenneth Mason Publications, Ltd., Emsworth, Hampshire p010 7DD, 
England. 
One approach to reducing crossover has been to dissolve a filter dye in one 
or more of the hydrophilic colloid layers forming the radiographic 
element. Such dyes must, of course, be selected to minimize residual 
density (stain) in the image bearing radiographic element. A pervasive 
problem with dissolved dyes has been their migration to the latent image 
forming silver halide grains, whether coated directly in the image forming 
emulsion layers or in underlying layers. This has resulted in loss of 
photographic speed, which, of course, runs directly counter to the general 
aim in adopting a double coated radiographic element format in the first 
instance. Thus, where this approach has been followed, a balance of 
reduced photographic speed and residual crossover has been accepted. 
Although mordants have been employed to reduce dye migration, they have 
not been effective in preventing loss of photographic speed and have 
further proved disadvantageous in increasing the bulk of the water 
permeable layers of the radiographic elements, thereby increasing the 
processing time required to produce a processed element that is dry to the 
touch. The dissolved dye approach to crossover reduction is illustrated by 
Doorselaer U.K. Pat. Spec. 1,414, 456 and Bollen et al U.K. Pat. Specs. 
1,477,638 and 1,477,639. 
To reduce dye migration to the image forming silver halide grains a variant 
approach has been to adsorb the dye to the surfaces of silver halide 
grains other than those employed in imaging. This approach reduces speed 
loss, but has the disadvantage of requiring silver halide grains to be 
present in addition to those required for latent image formation. Further, 
an added silver halide grain population increases vehicle requirements and 
correspondingly increases drying times. Millikan et al U.K. Pat. Spec. 
1,426,277 illustrates this approach applied to a specialized photographic 
imaging system in which a silver halide grain population is present in 
addition to the grain population which is relied upon to produce a latent 
image. 
The most successful approach to crossover reduction yet realized by the art 
has been to employ double coated radiographic elements containing 
spectrally sensitized high aspect ratio tabular grain emulsions or thin 
intermediate aspect ratio tabular grain emulsions, illustrated by Abbott 
et al U.S. Pat. Nos. 4,425,425 and 4,425,426, respectively. Crossover 
levels below 20 percent (but well above 10 percent) are reported. 
SUMMARY OF THE INVENTION 
In one aspect this invention is directed to a radiographic element 
comprised of a film support capable of transmitting radiation to which the 
radiographic element is responsive having opposed major faces. Processing 
solution permeable hydrophilic colloid layers are present including, 
coated on each opposed major face, at least one silver halide emulsion 
layer capable of responding to electromagnetic radiation in the visible 
portion of spectrum and at least one other hydrophilic colloid layer 
interposed between the emulsion layer and the support. A dye is dispersed 
in at least one of the interposed hydrophilic colloid layers capable of 
absorbing visible radiation to which the radiographic element is 
responsive to reduce crossover and capable of being decolorized in a 
processing solution. 
The radiographic element is characterized in that the dye is, prior to 
processing, in the form of microcrystalline particles present in a 
concentration sufficient to reduce crossover to less than 10 percent and 
is capable of being substantially decolorized in less than 90 seconds 
during processing. 
The present invention offers significant and unexpected advantages over the 
prior state of the art. Crossover is reduced below levels heretofore 
successfully achieved in the art and without desensitization of latent 
image forming silver halide grains. The extremely low crossover levels 
realized have been made possible by discovering that dyes incorporated in 
a radiographic element in the form microcrystalline particles can be 
nevertheless satisfactorily decolorized during the very short processing 
interval conventionally employed in preparing radiographic images. By 
employing the crossover reducing dyes in microcrystalline form migration 
of the dyes to latent image forming silver halide grains surfaces and 
resulting desensitization of these grains is obviated. Location of the 
microcrystalline dyes in hydrophilic colloid layers interposed between the 
emulsion layers and the support avoids competition between the dyes and 
the emulsion layers. Further, the present invention permits simpler 
radiographic element construction than is possible with radiographic 
elements employing a nonimaging silver halide grains to provide dye 
adsorption surfaces. Still further, the microcrystal line form of the dyes 
allows superior spectral adsorption profiles to be realized as compared to 
the same or chromophorically similar dyes adsorbed to silver halide grain 
surfaces. 
Finally, the crossover reduction advantages of the present invention are 
fully compatible with both the crossover reduction and other known 
advantages of high aspect ratio and thin, intermediate aspect ratio 
tabular grain silver halide emulsions.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, in the assembly shown a radiographic element 100 
according to this invention is positioned between a pair of light emitting 
intensifying screens 201 and 202. The radiographic element support is 
comprised of a radiographic support element 101, typically transparent or 
blue tinted, capable of transmitting at least a portion of the light to 
which it is exposed and optional, similarly transmissive subbing layer 
units 103 and 105, each of which can be formed of one or more adhesion 
promoting layers. On the first and second opposed major faces 107 and 109 
of the support formed by the subbing layer units are crossover reducing 
hydrophilic colloid layers 111 and 113, respectively. Overlying the 
crossover reducing layers 111 and 113 are light recording latent image 
forming silver halide emulsion layer units 115 and 117, respectively. Each 
of the emulsion layer units is formed of one or more hydrophilic colloid 
layers including at least one silver halide emulsion layer. Overlying the 
emulsion layer units 115 and 117 are optional protective overcoat layers 
119 and 121, respectively. All of the protective layers and hydrophilic 
colloid layers are permeable to processing solutions. 
In use, the assembly is imagewise exposed to X radiation. The X radiation 
is principally absorbed by the intensifying screens 201 and 202, which 
promptly emit light as a direct function of X ray exposure. Considering 
first the light emitted by screen 201, the light recording latent image 
forming emulsion layer unit 115 is positioned adjacent this screen to 
receive the light which it emits. Because of the proximity of the screen 
201 to the emulsion layer unit 115 only minimal light scattering occurs 
before latent image forming absorption occurs in this layer unit. Hence 
light emission from screen 201 forms a sharp image in emulsion layer unit 
115. 
However, not all of the light emitted by screen 201 is absorbed within 
emulsion layer unit 115. This remaining light, unless otherwise absorbed, 
will reach the remote emulsion layer unit 117, resulting in a highly 
unsharp image being formed in this remote emulsion layer unit. Both 
crossover reducing layers 111 and 113 are interposed between the screen 
201 and the remote emulsion layer unit and are capable of intercepting and 
attenuating this remaining light. Both of these layers thereby contribute 
to reducing crossover exposure of emulsion layer unit 117 by the screen 
201. 
In an exactly analogous manner the screen 202 produces a sharp image in 
emulsion layer unit 117, and the light absorbing layers 111 and 113 
similarly reduce crossover exposure of the emulsion layer unit 115 by the 
screen 202. It is apparent that either of the two crossover reducing 
layers employed alone can effectively reduce crossover exposures from both 
screens. Thus, only one light absorbing layer is required. In a variant 
form the crossover reducing layers on opposite sides of the support can be 
used to absorb radiation from different regions of the spectrum. For 
example, a light absorbing dye can be present in one crossover reducing 
layer while an ultraviolet (UV) absorber is present in the remaining 
crossover reducing layer. For manufacturing convenience dual coated 
radiographic elements most commonly employ identical coatings on opposite 
major faces of the support. 
Following exposure to produce a stored latent image, the radiographic 
element 100 is removed from association with the intensifying screens 201 
and 202 and processed in a conventional manner. That is, the radiographic 
element is brought into contact with an aqueous alkaline developer, such 
as a hydroquinone Phenidone.RTM. (1-phenyl-3-pyrazolidone) developer 
having a pH of 10.0, a specific form of which is illustrated in the 
examples below. The alkaline developer permeates the hydrophilic colloid 
layers, converting the silver halide emulsion layer latent image to a 
viewable silver image and simultaneously decolorizing the crossover 
reducing layers. Conventional post development steps, such as stop bath 
contact, fixing, and washing can occur. Since the crossover reducing 
layers can be decolorized in less than 90 seconds following contact with 
an aqueous alkaline processing solution of pH 10.0, the radiographic 
elements of this invention are fully compatible with conventional 
radiographic element processing, such as in an RP-X-Omat.RTM. processor. 
The radiographic elements of the present invention offer advantages in 
crossover reduction by employing one or more crossover reducing layers 
comprised a hydrophilic colloid employed as a dispersing vehicle and a 
particulate dye. The concentration of the dye present is chosen to impart 
an optical density of at least 1.00 at the peak wavelength of emulsion 
sensitivity. Since it is conventional practice to employ intensifying 
screen-radiographic element combinations in which the peak emulsion 
sensitivity matches the peak light emission by the intensifying screens, 
it follows that the dye also exhibits a density of at least 1.00 at the 
wavelength of peak emission of the intensifying screen. Since neither 
screen emissions nor emulsion sensitivities are confined to a single 
wavelength, it is preferred to choose particulate dyes, including 
combinations of particulate dyes, capable of imparting a density of 1.00 
or more over the entire spectral region of significant sensitivity and 
emission. For radiographic elements to be used with blue emitting 
intensifying screens, such as those which employ calcium tungstate or 
thulium activated lanthanum oxybromide phosphors, it is generally 
preferred that the particulate dye be selected to produce an optical 
density of at least 1.00 over the entire spectral region of 400 to 500 nm. 
For radiographic elements intended to be used with green emitting 
intensifying screens, such as those employing rare earth (e.g., terbium) 
activated gadolinium oxysulfide or oxyhalide phosphors, it is preferred 
that the particulate dye exhibit a density of at least 1.00 over the 
spectral region of 450 to 550 nm. To the extent the wavelength of emission 
of the screens or the sensitivities of the emulsion layers are restricted, 
the spectral region over which the particulate dye must also effectively 
absorb light is correspondingly reduced. 
While particulate dye optical densities of 1.00 chosen as described above 
are effective to reduce crossover to less than 10 percent, it is 
specifically recognized that particulate dye densities can be increased 
until radiographic element crossover is effectively eliminated. For 
example, by increasing the particulate dye concentration so that it 
imparts a density of 10.0 to the radiographic element, crossover is 
reduced to only 1 percent. 
Since there is a direct relationship between the dye concentration and the 
optical density produced for a given dye or dye combination, precise 
optical density selections can be achieved by routine selection 
procedures. Because dyes vary widely in their extinction coefficients and 
absorption profiles, it is recognized that the weight or even molar 
concentrations of particulate dyes will vary from one dye or dye 
combination selection to the next. 
The size of the dye particles is chosen to facilitate coating and rapid 
decolorization of the dye. In general smaller dye particles lend 
themselves to more uniform coatings and more rapid decolorization. The dye 
particles employed in all instances have a mean diameter of less than 10.0 
.mu.m and preferably less than 1.0 .mu.m. There is no theoretical limit on 
the minimum sizes the dye particles can take. The dye particles can be 
most conveniently formed by crystallization from solution in sizes ranging 
down to about 0.01 .mu.m or less. Where the dyes are initially 
crystallized in the form of particles larger than desired for use, 
conventional techniques for achieving smaller particle sizes can be 
employed, such as ball milling, roller milling, sand milling, and the 
like. 
An important criterion in dye selection is their ability to remain in 
particulate form in hydrophilic colloid layers of radiographic elements. 
While the hydrophilic colloids can take any of various conventional forms, 
such as any of the forms set forth in Research Disclosure, Vol. 176, 
December 1978, Item 17643, Section IX. Vehicles and vehicle extenders, 
here incorporated by reference, the hydrophilic colloid layers are most 
commonly gelatin and gelatin derivatives. Hydrophilic colloids are 
typically coated as aqueous solutions in the pH range of from about 5 to 
6, most typically from 5.5 to 6.0, to form radiographic element layers. 
The dyes which are selected for use in the practice of this invention are 
those which are capable of remaining in particulate form at those pH 
levels in aqueous solutions. 
Dyes which by reason of their chromophoric make up are inherently ionic, 
such as cyanine dyes, as well as dyes which contain substituents which are 
ionically dissociated in the above noted PH ranges of coating may in 
individual instances be sufficiently insoluble to satisfy the requirements 
of this invention, but do not in general constitute preferred classes of 
dyes for use in the practice of the invention. For example, dyes with 
sulfonic acid substituents are normally too soluble to satisfy the 
requirements of the invention. On the other hand, nonionic dyes with 
carboxylic acid groups (depending in some instances on the specific 
substitution location of the carboxylic acid group) are in general 
insoluble under aqueous acid coating conditions. Specific dye selections 
can be made from known dye characteristics or by observing solubilities in 
the pH range of from 5.5 to 6.0 at normal layer coating 
temperatures--e.g., at a reference temperature of 40.degree. C. 
Preferred particulate dyes are nonionic polymethine dyes, which include the 
merocyanine, oxonol, hemioxonol, styryls, and arylidene dyes. 
The merocyanine dyes include, joined by a methine linkage, at least one 
basic heterocyclic nucleus and at least one acidic nucleus. Basic nuclei, 
such as azolium or azinium nuclei, for example, include those derived from 
pyridinium, quinolinium, isoquinolinium, oxazolium, pyrazolium, pyrrolium, 
indolium, oxadiazolium, 3H- or 1H- benzoindolium, pyrrolopyridinium, 
phenanthrothiazolium, and acenaphthothiazolium quaternary salts. 
Exemplary of the basic heterocyclic nuclei are those satisfying Formulae I 
and II. 
##STR1## 
Z.sup.3 represents the elements needed to complete a cyclic nucleus 
derived from basic heterocyclic nitrogen compounds such as oxazoline, 
oxazole, benzoxazole, the naphthoxazoles (e.g., naphth[2,1-d]oxazole, 
naphth[2,3d]-oxazole, and naphth[1,2-d]oxazole), oxadiazole, 2- or 
4-pyridine, 2- or 4-quinoline, 1- or 3-isoquinoline, benzoquinoline, 1H or 
3H-benzoindole, and pyrazole, which nuclei may be substituted on the ring 
by one or more of a wide variety of substituents such as hydroxy, the 
halogens (e.g., fluoro, chloro, bromo, and iodo), alkyl groups or 
substituted alkyl groups (e.g., methyl, ethyl, propyl, isopropyl, butyl, 
octyl, dodecyl, octadecyl, 2-hydroxyethyl, 2-cyanoethyl, and 
trifluoromethyl), aryl groups or substituted aryl groups (e.g., phenyl, 
1-naphthyl, 2-naphthyl, 3-carboxyphenyl, and 4-biphenylyl), aralkyl groups 
(e.g., benzyl and phenethyl), alkoxy groups (e.g., methoxy, ethoxy, and 
isopropoxy), aryloxy groups (e.g., phenoxy and 1-naphthoxy), alkylthio 
groups (e.g., methylthio and ethylthio), arylthio groups (e.g., 
phenylthio, p-tolylthio, and 2-naphthylthio), methylenedioxy, cyano, 
2-thienyl, styryl, amino or substituted amino groups (e.g., anilino, 
dimethylamino, diethylamino, and morpholino), acyl groups, (e.g., formyl, 
acetyl, benzoyl, and benzenesulfonyl); 
Q' represents the elements needed to complete a cyclic nucleus derived from 
basic heterocyclic nitrogen compounds such as pyrrole, pyrazole, indazole, 
and pyrrolopyridine; 
R represents alkyl groups, aryl groups, alkenyl groups, or aralkyl groups, 
with or without substituents, (e.g., carboxy, hydroxy, sulfo, alkoxy, 
sulfato, thiosulfato, phosphono, chloro, and bromo substituents); 
L is in each occurrence independently selected to represent a substituted 
or unsubstituted methine group--e.g., --CR.sup.8 .dbd. groups, where 
R.sup.8 represents hydrogen when the methine group is unsubstituted and 
most commonly represents alkyl of from 1 to 4 carbon atoms or phenyl when 
the methine group is substituted; and 
q is 0 or 1. 
Merocyanine dyes link one of the basic heterocyclic nuclei described above 
to an acidic keto methylene nucleus through a methine linkage, where the 
methine groups can take the form --CR.sup.8 .dbd. described above. The 
greater the number of the methine groups linking nuclei in the polymethine 
dyes in general and the merocyanine dyes in particular the longer the 
absorption wavelengths of the dyes. 
Merocyanine dyes link one of the basic heterocyclic nuclei described above 
to an acidic keto methylene nucleus through a methine linkage as described 
above. Exemplary acidic nuclei are those which satisfy Formula III. 
##STR2## 
where G.sup.1 represents an alkyl group or substituted alkyl group, an 
aryl or substituted aryl group, an aralkyl group, an alkoxy group, an 
aryloxy group, a hydroxy group, an amino group, or a substituted amino 
group, wherein exemplary substituents can take the various forms noted in 
connection with Formulae VI and VII; 
G.sup.2 can represent any one of the groups listed for G.sup.1 and in 
addition can represent a cyano group, an alkyl, or arylsulfonyl group, or 
a group represented by 
##STR3## 
or G.sup.2 taken together with G.sup.1 can represent the elements needed 
to complete a cyclic acidic nucleus such as those derived from 
2,4-oxazolidinone (e.g., 3-ethyl-2,4-oxazolidindione), 
2,4-thiazolidindione (e.g., 3-methyl 2,4-thiazolidindione), 
2-thio-2,4-oxazolidindione (e.g., 3-phenyl-2-thio-2,4-oxazolidindione), 
rhodanine, such as 3-ethylrhodanine, 3-phenylrhodanine, 
3-(3-dimethylaminopropyl)rhodanine, and 3-carboxymethylrhodanine, 
hydantoin (e.g., 1,3-diethylhydantoin and 3-ethyl 1-phenylhydantoin), 
2-thiohydantoin (e.g., 1-ethyl-3-phenyl-2-thiohydantoin, 
3-heptyl-1-phenyl-2-thiohydantion, and arylsulfonyl-2-thiohydantoin), 
2-pyrazolin-5-one, such as 3-methyl-1-phenyl-2-pyrazolin-5-one and 
3-methyl-1-(4-carboxyphenyl)-2-pyrazolin-5-one, 2-isoxazolin-5-one (e.g., 
3-phenyl-2-isoxazolin-5-one), 3,5-pyrazolidindione (e.g., 
1,2-diethyl-3,5-pyrazolidindione and 1,2-diphenyl-3,5-pyrazolidindione), 
1,3-indandione,1,3-dioxane-4,6-dione, 1,3-cyclohexanedione, barbituric 
acid (e.g., 1-ethylbarbituric acid and 1,3-diethylbarbituric acid), and 
2-thiobarbituric acid (e.g., 1,3-diethyl-2-thiobarbituric acid and 
1,3-bis(2-methoxyethyl)-2-thiobarbituric acid). 
Useful hemioxonol dyes exhibit a keto methylene nucleus as shown in Formula 
III and a nucleus as shown in Formula IV. 
##STR4## 
where G.sup.3 and G.sup.4 may be the same or different and may represent 
alkyl, substituted alkyl, aryl, substituted aryl, or aralkyl, as 
illustrated for R ring substituents in Formula I or G.sup.3 and G.sup.4 
taken together complete a ring system derived from a cyclic secondary 
amine, such as pyrrolidine, 3-pyrroline, piperidine, piperazine (e.g., 
4-methylpiperazine and 4-phenylpiperazine), morpholine, 
1,2,3,4-tetrahydroquinolone, decahydroquinoline, 
3-azabicyclo[3,2,2]nonane, indoline, azetidine, and hexahydroazepine. 
Exemplary oxonol dyes exhibit two keto methylene nuclei as shown in Formula 
III joined through one or higher uneven number of methine groups. 
Useful arylidene dyes exhibit a keto methylene nucleus as shown in Formula 
III and a nucleus as shown in Formula V joined by a methine linkage as 
described above containing one or a higher uneven number of methine 
groups. 
##STR5## 
where G.sup.3 and G.sup.4 are as previously defined. 
A specifically preferred class of oxonol dyes for use in the practice of 
the invention are the oxonol dyes disclosed in Factor and Diehl U.S. Ser. 
No. 73,257, filed July 13, 1987, commonly assigned, cited above. These 
oxonol dyes satisfy Formula VI. 
##STR6## 
wherein R.sup.1 and R.sup.2 each independently represent alkyl of from 1 
to 5 carbon atoms. 
Exemplary of specific preferred oxonol dyes are those set forth below in 
Table I. 
TABLE I 
__________________________________________________________________________ 
##STR7## 
wherein 
Dye R.sup.1 R.sup.2 
__________________________________________________________________________ 
1/0 CH.sub.3 CH.sub.3 
2/0 C.sub.2 H.sub.5 
C.sub.2 H.sub.5 
__________________________________________________________________________ 
A specifically preferred of arylidene dyes for use in the practice of the 
invention are the arylidene dyes disclosed in Diehl and Factor U.S. Ser. 
No 945,634, filed Dec. 23, 1986, commonly assigned, cited above. These 
arylidene dyes satisfy Formula VII. 
##STR8## 
A represents a substituted or unsubstituted acidic nucleus having a 
carboxyphenyl substituent selected from the group consisting of 
2-pryazolin-5-ones free of any substituent bonded thereto through a 
carboxyl group, rhodanines; hydantoins; 2-thiohydantoins; 
4-thiohydantoins; 2,4-oxazolidindiones; 2-thio-2,4-oxazolidindiones; 
isoxazolinones; barbiturics; 2-thiobarbiturics and indandiones; 
R represents hydrogen, alkyl of 1 to 4 carbon atoms or benzyl; 
R.sup.1 and R.sup.2, each independently, represents alkyl or aryl; or taken 
together with R.sup.5, R.sup.6, N, and the carbon atoms to which they are 
attached represent the atoms needed to complete a julolidene ring; 
R.sup.3 represents H, alkyl or aryl; 
R.sup.5 and R.sup.6, each independently, represents H or R.sup.5 taken 
together with R.sup.1 ; or R.sup.6 taken together with R.sup.2 each may 
represent the atoms necessary to complete a 5 or 6 membered ring; and 
m is 0 or 1. 
Exemplary of specific preferred arylidene dyes are those set forth below in 
Tables II and III. 
TABLE II 
__________________________________________________________________________ 
##STR9## 
x 
Ring .lambda.-max 
.epsilon.-max 
Dye R.sup.1, R.sup.2 
R.sup.3 
R.sup.4 
# Site 
n (nm) 
(10.sup.-4) 
__________________________________________________________________________ 
1/A 
CH.sub.3 
H CH.sub.3 
1 4 0 466 3.73 
2/A 
C.sub.2 H.sub.5 
H CH.sub.3 
1 4 0 471 4.75 
3/A 
n-C.sub.4 H.sub.9 
H CH.sub.3 
1 4 0 475 4.50 
4/A 
CH.sub.3 
H COOCH.sub.2 H.sub.5 
1 4 0 508 5.20 
5/A 
##STR10## 
CH.sub.3 
CH.sub.3 
1 4 0 430 3.34 
6/A 
CH.sub.3 
H CH.sub.3 
2 3,5 
0 457 3.78 
7/A 
C.sub.2 H.sub.5 
H CH.sub.3 
2 3,5 
0 475 4.55 
8/A 
n-C.sub.4 H.sub.9 
H CH.sub.3 
2 3,5 
0 477 4.92 
9/A 
##STR11## 
H CH.sub.3 
2 3,5 
0 420 3.62 
10/A 
##STR12## 
CH.sub.3 
CH.sub.3 
2 3,5 
0 434 3.25 
11/A 
CH.sub.3 
H CH.sub.3 
1 4 1 516 4.62 
12/A 
##STR13## 
H CH.sub.3 
1 4 0 420 3.94 
13/A 
CH.sub.3 
H 
##STR14## 
1 4 0 573 5.56 
14/A 
CH.sub.3 
H COOEt 1 4 1 576 5.76 
15/A 
CH.sub.3 
H CH.sub.3 
2 3,5 
1 506 3.90 
16/A 
CH.sub.3 
H COOEt 1 4 0 502 4.83 
17/A 
CH.sub.3 
H COOEt 2 3,5 
1 560 5.25 
18/A 
C.sub.2 H.sub.5 
H COOEt 1 4 0 512 6.22 
19/A 
CH.sub.3 
H CF.sub.3 
1 4 0 507 4.58 
20/A 
CH.sub.3 
H Ph 1 4 0 477 4.54 
21/A 
CH.sub.3 
H 
##STR15## 
1 4 0 506 5.36 
__________________________________________________________________________ 
TABLE III 
______________________________________ 
##STR16## 
x .lambda.-max 
.epsilon.-max 
Dye R.sup.3 
R.sup.4 # Rng. Site 
(nm) (10.sup.-4) 
______________________________________ 
22/A H CH.sub.3 1 4 500 5.82 
23/A H CH.sub.3 2 3,5 502 5.47 
______________________________________ 
As indicated above, it is specifically contemplated to employ a UV 
absorber, either blended with the dye in each of crossover reducing layers 
111 and 113 or confined to one crossover reducing layer with the dye being 
confined to the other crossover reducing layer. Any conventional UV 
absorber can be employed for this purpose. Illustrative useful UV 
absorbers are those disclosed in Research Disclosure, Item 18431, cited 
above, Section V, or Research Disclosure, Item 17643, cited above, Section 
VIII.C., both here incorporated by reference. Preferred UV absorbers are 
those which either exhibit minimal absorption in the visible portion of 
the spectrum or are decolorized on processing similarly as the crossover 
reducing dyes. 
Apart from the crossover reducing layers 111 and 113 described above, the 
remaining features of the dual coated radiographic elements can take any 
convenient conventional form. Such conventional radiographic element 
features are illustrated, for example, in Research Disclosure. Item 18431, 
cited above and here incorporated by reference. Other conventional 
features common to both silver halide radiographic elements and 
photographic elements are disclosed in Research Disclosure. Item 17643, 
cited above. 
Radiographic elements according to this invention having highly desirable 
imaging characteristics are those which employ one or more tabular grain 
silver halide emulsions. 
Preferred radiographic elements according to the present invention are 
those which employ one or more high aspect ratio tabular grain emulsions 
or thin, intermediate aspect ratio tabular grain emulsions. Preferred 
tabular grain emulsions for use in the radiographic elements of this 
invention are those in which tabular silver halide grains having a 
thickness of less than 0.5 .mu.m (preferably less than 0.3 .mu.m and 
optimally less than 0.2 .mu.m) have an average aspect ratio of greater 
than 5:1 (preferably greater than 8:1 and optimally at least 12:1) and 
account for greater than 50 percent (preferably greater than 70 percent 
and optimally greater than 90 percent) of the total projected area of the 
silver halide grains present in the emulsion. Preferred blue and minus 
blue spectral sensitizing dyes as well as optimum chemical and spectral 
sensitizations of tabular silver halide grains are disclosed by Kofron et 
al U.S. Pat. No. 4,439,520. 
The preferred radiographic elements of this invention are those which 
employ one or more of the crossover reducing layers described above in 
combination with tabular grain latent image forming emulsions. Preferred 
radiographic element and tabular grain silver halide emulsion features are 
disclosed in Abbott et al U.S. Pat. Nos. 4,425,425 and 4,425,426 and 
Dickerson U.S. Pat. No. 4,414,304, here incorporated by reference. 
Radiographic elements can be constructed according to this invention in 
which tabular grain silver halide emulsion layers are coated nearer the 
support than nontabular grain silver halide emulsion layers to reduce 
crossover, as illustrated by Sugimoto European Patent Application 
0,084,637. By employing tabular grain emulsions, which in themselves 
reduce crossover in combination with the crossover reducing layers 
provided by this invention radiographic elements exhibiting extremely low 
crossover levels can be achieved while also achieving high photographic 
speed, low levels of granularity, high silver covering power, and rapid 
processing capabilities deemed highly desirable in radiography. 
EXAMPLES 
The invention is further illustrated by the following examples. 
EXAMPLES 1 THROUGH 6 
The following examples compare the performance of double coated 
radiographic elements exposed using blue emitting thulium activated 
lanthanum oxybromide phosphor intensifying screens. The radiographic 
elements were identical, except for the choice of the crossover reducing 
materials employed between the emulsion layer and the support on each 
major surface. 
The dye satisfying the requirements of the invention was Dye 1/A shown 
above in Table II. The dye was employed in a particulate form, the mean 
diameter of the dye particles being 0.08 .mu.m. 
Tartrazine Yellow (C.I. Acid Yellow 23-C.I. 13.065), hereinafter referred 
to as C-1, was selected as a control exemplary of dyes which are water 
soluble and nonbleachable taught by the art to be used as a crossover 
reducing dye in a double coated radiographic element. To reduce wandering 
of the dye a cationic mordant poly(1-methyl-2-vinylpyridinium p-toluene 
sulfonate (hereinafter referred to as M-1) was used with the dye in a 
weight ratio of 5 parts of mordant per part of dye. 
Carey Lea Silver, hereinafter referred to as CLS, was selected as a control 
exemplary of a particulate material which is neither water soluble nor 
bleachable under conditions compatible with silver imaging. 
A series of double coated radiographic elements identical, except for the 
choice and concentration of crossover reducing material listed below in 
Table IV, were prepared as follows: 
Onto each side of a blue tinted polyester film support was coated a gelatin 
hydrophilic colloid layer containing the crossover reducing material. The 
gelatin coating coverage was 0.11 g/m.sup.2. 
One control element was constructed with the same hydrophilic colloid 
layers, but without a crossover reducing material being present. This 
element is referred to as C-0. 
An emulsion layer was coated over each hydrophilic colloid layer. The blue 
recording silver bromide emulsion layer was coated at a coverage of 2.2 
g/m.sup.2 silver and 2.2 g/m.sup.2 gelatin. 
Over each emulsion layer was coated a gelatin overcoat at a coverage of 
0.91 g/m.sup.2. 
The hydrophilic colloid layers (including the emulsion layers) were 
hardened with bis(vinylsulfonylmethyl) ether at 1.0% of the gelatin 
weight. 
To permit crossover determinations, samples of the dual coated radiographic 
elements were exposed with a single intensifying screen placed in contact 
with one emulsion layer. Black paper was placed against the other emulsion 
side of the sample. The X-radiation source was a picker VTX653 3-phase 
X-ray machine, with a Dunlee High Speed PX1431-CQ-150 kVp 0.7/1.4 mm focus 
tube. 
Exposure was made at 70 kVP, 32 mAs, at a distance of 1.40 m. Filtration 
was with 3 mm Al equivalent (1.25 inherent+1.75 al); Half Value Layer 
(HVL--2.6 mm Al. A 26 step Al wedge was used, differing in thickness by 2 
mm per step. 
Processing of the exposed film was in each instance undertaken using a 
processor commercially available under the trademark Kodak RP X Omat film 
Processor M6A-N. The developer employed exhibited the following formula: 
______________________________________ 
Hydroquinone 30 g 
Phenidone .RTM. 1.5 g 
KOH 21 g 
NaHCO.sub.3 7.5 g 
K.sub.2 SO.sub.3 44.2 g 
Na.sub.2 S.sub.2 O.sub.5 
12.6 g 
NaBr 35 g 
5-Methylbenzotriazole 
0.06 g 
Glutaraldehyde 4.9 g 
Water to 1 liter/pH 10.0. 
______________________________________ 
The film was in contact with the developer in each instance for less than 
90 seconds. 
The density of the silver developed in each of the silver halide emulsion 
layers, the emulsion layer adjacent the intensifying screen and the 
non-adjacent emulsion layer separated from the intensifying screen by the 
film support was determined. By plotting density produced by each emulsion 
layer versus the steps of the step-wedge (a measure of exposure), a 
sensitometric curve was generated for each emulsion layer. A higher 
density was produced for a given exposure in the emulsion nearest the 
intensifying screen. Thus, the two sensitometric curves were offset in 
speed. At three different density levels in the relatively straight line 
portions of the sensitometric curves between their toe and shoulders the 
difference in speed (.DELTA. log E) between the two sensitometric curves 
was measured. These differences were then averaged and used in the 
following equation to calculate percent crossover: 
##EQU1## 
Percent crossover is reported in Table IV below. Relative speed reported 
in Table IV is the speed of the emulsion layer nearest the support. 
TABLE IV 
______________________________________ 
Crossover Reducer Relative Stain 
(D/sq. m) % Crossover 
Speed (FIG. 2) 
______________________________________ 
None 20 70 C-0 
(.07) 1/A (Example) 
11 59 
(.07) CLS (Control) 
3 59 
(.07) C-1 (Control) 
9 52 
(.14) 1/A (Example) 
6 56 E-1/A 
(.14) CLS (Control) 
3 61 CLS 
(.14) C-1 (Control) 
5 51 C-1 
______________________________________ 
All of the crossover reducing materials of Table IV were shown capable of 
reducing crossover below 10 percent. 
The mordanted water soluble dye C-1 and the CLS both gave unacceptable 
results, since in neither instance did bleaching occur on processing. 
Further, the dye C-1 by reason of its wandering characteristic reduced 
photographic speed significantly, even though it was incorporated with a 
mordant to prevent wandering. 
The dye 1/A was entirely decolorized during processing. From FIG. 2 it can 
be seen that the density of the element after processing was essentially 
similar to the element lacking a crossover reducing material. At the same 
time the capability of crossover reduction below 10 percent was 
demonstrated. Some loss of photographic speed was observed, but it is to 
be noted that, since the purpose of a crossover reducing agent is to 
prevent a portion of the light emitted by the screens from exposing the 
emulsion layers, some reduction in photographic speed is inherent in 
crossover reduction. 
This example demonstrates the satisfactory performance of a bleachable 
particulate dye to reduce crossover without producing dye stain in the 
processed radiographic element and with only minimal impact on imaging 
speed. The control crossover reducing materials were unacceptable because 
of their high dye stain, and the control dye was unacceptable in producing 
an increased loss in imaging speed. Further, the control dye required the 
further incorporation of a mordant, which added to the drying load on the 
processor. Without the mordant being present the imaging speed loss would 
have been significantly higher. 
EXAMPLES 7 THROUGH 12 
The procedure of Examples 1 through 6 was repeated, except that magenta 
dyes were substituted for testing, green sensitized radiographic emulsions 
were employed, and green emitting intensifying screens, Kodak Lanex 
Regular.RTM. screens, were employed. 
The dye satisfying the requirements of the invention was Dye 4/A shown 
above in Table II. The dye was employed in a particulate form, the mean 
diameter of the dye particles being 0.2 .mu.m. 
Acid Magenta (C.I. Acid Violet 19-C.I. 42,685), hereinafter referred to as 
C-2, was selected as a control exemplary of dyes which are water soluble 
and bleachable taught by the art to be used as a crossover reducing dye in 
a double coated radiographic element. To reduce wandering of the dye the 
cationic mordant M-1 was employed in a 5 parts mordant to 1 part dye 
weight ratio. 
1,3-Bis[1-(4-sulfonylphenyl)-3-carboxy-2-pyrazolin-5-one-4] trimethine 
oxonol, disodium salt, hereinafter referred to as C-3, was selected as a 
control exemplary of magenta dyes which are water soluble and 
nonbleachable. Dye C-3 differed from dye 10 disclosed on page 5 of U.K. 
Pat. Spec. No. 1,414,456 only in that the nuclei were joined by 3 methine 
groups instead of 5 (to shift absorption into the desired green spectral 
region). To reduce wandering of the dye cationic mordant M-1 was again 
employed in a 5 parts mordant to 1 part dye weight ratio. 
The results are summarized below in Table V. 
TABLE V 
______________________________________ 
Crossover Reducer Relative Stain 
(D/m.sup.2) % Crossover 
Speed (FIG. 3) 
______________________________________ 
None 19 113 C-0 
(.045) 4/A (Example) 
11 101 
(.045) C-2 (Control) 
19 92 
(.045) C-3 (Control) 
14 98 
(.09) 4/A (Example) 
7 97 E-4/A 
(.09) C-2 (Control) 
15 87 C-2 
(.09) C-3 (Control) 
10 91 C-3 
______________________________________ 
From Table V it is apparent that the control crossover reducing dyes were 
inferior, both in terms of relatively lower crossover reduction and in 
terms of relatively greater speed loss imparted. The dyes 4/A and C-2 
exhibited essentially similar bleaching characteristics. The dye C-3 
produced a significantly higher dye stain. 
APPENDIX 
A-1. Preparation of 
1,3-Bis[1-(4-carboxyphenyl)-3-methyl-2-pyrazolin-5-one-4]trimethine oxonol 
(Dye 1/O) 
1-(p-Carboxyphenyl)-3-methylpyrazolone (21.8 g), ethanol (100 ml), and 
triethylamine (14.6 g or 20 ml) were combined and boiled under reflux for 
30 minutes. The mixture was chilled and then combined with 200 ml 
methanol, then 40 ml concentrated hydrochloric acid. A red precipitate 
formed immediately. The mixture was stirred at room temperature for 15 
minutes and filtered. The precipitate was washed with 300 ml ethanol, 1000 
ml methanol, 1000 ml ether, and then air dried to yield a dry weight of 
12.4 g. 
The precipitate containing the dye was then purified through a number of 
washing and dissolution/recrystallization steps. The precipitate was first 
slurried in 500 ml refluxing glacial acetic acid, cooled to room 
temperature, filtered, washed with 250 ml acetic acid, 250 ml H.sub.2 O, 
250 ml methanol, and then dried. It was then dissolved in 100 ml hot 
dimethylsulfoxide and cooled to 40.degree. C. 300 ml methanol was added, 
upon which a red precipitate formed, which was filtered, washed with 
methanol, acetone, and ligroin, and dried. This precipitate was dissolved 
in 200 ml methanol and 6 ml (4.38 g) triethylamine and heated to reflux. 
4.8 ml of concentrated hydrochloric acid was added and a fine red 
precipitate was formed. The so1ution was filtered while hot and the 
precipitate was washed with methanol and acetone and dried. The 
precipitate was then dissolved in a refluxing mixture of 200 ml ethanol 
and 6.0 ml (4.38 g) triethylamine. 9.0 g of sodium iodide dissolved in 50 
ml methanol was added. Upon cooling to room temperature, a red precipitate 
formed. The mixture was chilled in ice for one hour, then filtered. The 
precipitate was washed with ethanol, ligroin and dried to yield the sodium 
salt of the dye. 
The sodium salt of the dye was dissolved in 200 ml water with rapid 
stirring. 6.0 ml concentrated hydrochloric acid was added and a fluffy red 
precipitate formed. The mixture was filtered and the precipitate was 
washed with water, methanol, acetone, and ligroin, and dried to yield Dye 
1/O. 
A-2. Preparation of 
1-(3,5-Dicarboxyphenyl)-4-(4-dimethylaminobenzylidene)-3-methyl-2-pyrazoli 
n-5-one (Dye 6/A) 
A solution of sodium nitrite (35.8 gm, 0.52 mol) in water (75 ml) was added 
to a slurry of 5-aminoisophthalic acid (90.6 gm, 0.50 mol) in 4.8 molar 
HCl (500 ml) at 0.degree. C. over 15 minutes with stirring. Stirring was 
continued for one hour at 0.degree.-5.degree. C. and the slurry was then 
added to a solution of sodium sulfite (270 gm, 2.2 mol) in water (1.21) 
all at one time, with stirring, at 2.degree. C. The resulting homogeneous 
solution was heated at 50.degree.-60.degree. for 45 minutes. Concentrated 
HCl (60 ml) was added and the reaction mixture was heated further at 
90.degree. C. for one hour. After cooling to RT another portion of 
concentrated HCl (500 ml) was added. The solid was isolated by filtration 
and washed on a funnel with acidified water, EtOH and ligroin in 
succession. The off-white solid was dissolved in a solution of NaOH (76 
gm, 1.85 mol in 600 ml water). This solution was subsequently acidified 
with glacial acetic acid (166 ml, 3.0 mol) to yield a thick slurry. This 
was isolated by filtration, washed on the funnel with water, EtOH and 
ligroin in succession, and thoroughly dried in a vacuum oven at 80.degree. 
C., and 10 mm Hg. The mp was above 300.degree. C. The NMR and IR spectra 
were consistent with the structure for 5-hydrazino-1,3-benzenedicarboxylic 
acid. The product gave a positive test for hydrazine with Tollens' 
reagent. 
A slurry composed of the product 5 hydrazino-1,3-benzenedicarboxylic acid 
(64.7 gm, 0.33 mol), ethylacetoacetate (50.7 gm, 0.39 mol) and glacial 
acetic acid (250 ml) was stirred and refluxed for 22 hours. The mixture 
was cooled to RT and the product which had precipitated was isolated by 
filtration, washed with water, EtOH, Et.sub.2 O, and ligroin in succession 
and thoroughly dried in a vacuum oven at 80.degree. and 10 mm Hg. The mp 
of the solid was above 310.degree. C. The NMR and IR spectra were 
consistent with the assigned structure. The product gave a negative test 
with Tollens' reagent. The C,H and N elemental analyses were in agreement 
with those calculated for the empirica1 Formula for 
1-(3,5-dicarboxyphenyl)-3-methyl-2-pyrazoline-5-one. 
A slurry composed of 1-(3,5-dicarboxyphenyl)-3-methyl-2-pyrazoline-5-one 
(44.6 grams, 0.17 mol), 4-dimethylaminobenzaldehyde (26.9 grams, 0.18 mol) 
and EtOH (500 mL) was heated at reflux for three hours. The reaction 
mixture was chilled in ice and the resulting crude orange product was 
isolated by filtration and washed with EtOH (200 mL). The product was 
purified by three repetitive slurries of the solid in acetone (1.4 1) at 
reflux and filtering to recover the dye. The mp of the product was above 
310.degree. C. The NMR and IR spectra were consistent with the structure 
assigned. The C, H and N elemental analyses were in agreement with those 
calculated for the empirical formula for the dye. 
A-3. Preparation of 
(1-(4-Carboxyphenyl)-4-(4-dimethylaminobenzylidene)-3-methyl-2-pyrazolin-5 
-one (Dye 1/A) 
A slurry composed of 1-(4-carboxyphenyl)-3-methyl-2-pyrazolin-5-one (21.8 
gm, 0.10 mol), 4-dimethylaminobenzaldehyde (14.9 gm, 0.10 mol) and EtOH 
(250 ml) was heated at reflux for two hours. The reaction mixture was 
cooled to RT resulting in a crude orange product which was isolated by 
filtration. The product was then washed with ether and dried. The product 
was purified further by making a slurry of the solid in EtOH (700 ml) at 
refluxing temperature and filtering the slurry to recover the dye. The 
treatment was repeated. The mp of the product was above 310.degree. C. The 
NMR and IR spectra were consistent with the structure assigned. The C,H, 
and N elemental analyses were in agreement with those calculated for the 
empirical formula. 
A-4. Preparation of 
1-(4-Carboxyphenyl)-4-(4-dimethylaminocinnamylidene)-3-methyl-2-pyrazolin- 
5-one (Dye 11/A) 
1-(4-Carboxyphenyl)-3-methyl-2-pyrazolin-5-one (2.18 gm, 0.010 mol), 
4-dimethylaminocinnamaldehyde (1.75 gm, 0.010 mol) and glacial acetic acid 
(10 ml) were mixed together to form a slurry. It was heated to reflux with 
stirring, held at reflux for five minutes and then cooled to RT. EtOH (20 
ml) was added to the reaction mixture which was heated again to reflux, 
held there for five minutes and cooled to RT. The product was isolated by 
filtration, washed in succession with ethanol and ligroin, and dried. The 
reaction was repeated twice on the same scale and the products obtained 
were all combined. They were treated further by first slurrying in 
refluxing EtOH (150 ml), isolating the solid by filtration while hot, and 
then slurrying in refluxing MeOH (200 ml) and isolating it again, while 
hot, by filtration. The mp was 282.degree.-284.degree. C. The NMR and IR 
spectra were consistent for the structure assigned. The C,H and N 
elemental analyses were in agreement with those calculated for the 
empirical formula of the dye. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.