Note: Descriptions are shown in the official language in which they were submitted.
~1038683
~ he present invention relates to an improved combina-
tion of photosensitive elements suited for use in radio-
graphy and more particularly to a combination comprising~n
X-ray intensifying screen of the fluorescent type and a
silver halide recording element.
By the term "radiography" we designate a recording
technique that makes use of penetrating radiation which in-
cludes highly energetic radiation such as X-rays, ~-rays,
~-rays, and fast electrons, e.g. as obtained in an electron
microscope.
It is known that the use of fluorescent screens in com-
bination with silver halide emulsion materials has resulted
in a reduction of the radiation dose and offers an X-ray
recording system of high speed. A disadvantage, however,
of the use of fluorescent screens when compared with direct
X-ray recording is the reduced image sharpness especially
when silver halide materials are used having on both sides
of a support that is transparent for fluorescent light, a
silver halide emulsion layer, each of which during the X-ray
exposure stands in close contact with a fluorescent screen.
Indeed, the light emitted by one of these fluorescent
screens gives rise not only to an image-wise blackening
in the adjacent silver halide emulsion layer, but penetrates
also in a considerable amount through the support and pro-
duces an unsharp image in the oppositely situated silver
halide emulsion layer. This phenomenon is called "cross-over".
GV.705 PC~
~1038683
The degree of cross-over substantially determines the image
quality of the image obtained in the radiographic recording
material.
~ he cross-over causes unsharpness because of the
diffusion in all directions of light in the different layers
and support sheet of the silver halide recording material and
also because of the refraction and diffuse reflection of
light taking place at the boundaries of said layers and
support sheet.
It has been proposed in the United Kingdom Patent Spe-
cification 821,352 filed January 3, 1957 by Photo Chemische
Werke Berlin to reduce the influence of cross-over by in-
corporating filtering dyes in the film support and/or the
substrate layers or intermediate layers of the film. ~he
colouring obtained ~ith these dyes is complementary to the
colour of the fluorescent light of the particular intensi-
fying screen used.
In practice this has been realized by using a blue-
fluorescing calcium tungstate intensifying screen and a
silver halide material containing in its support a yellow
dye. ~he incorporation of a said yellow dye brings about
the necessity to use a higher radiation dose, which because
of the relatively weak emission power of said screens in
many cases will surpass the permissible dose for medical
X-ray radiography.
A urther source of image-unsharpness lies in the
diffuse emission, i.e. emission in all directions of the
GV.705 PC~ - 2 -
~L038683
fluorescent light in the bulk materiàl of the fluorescent
layer and in the diffuse reflection at the support of the
screen. Indeed, only the fluorescent light rays that are
impinging substantially normally to the silver halide emul-
sion material offer a sharp image. Therefore, it is necessary
to attenuate the non-normally emitted or reflected fluorescent
radiation already in the screen material with substances that
absorb said radiation. Of course this willproceed at the
expense also of the strength of the normally directed light,
but since the oblique radiation covers a larger path in the
screen material than the normally emitted or reflected
radiation,attenuation by absorption in the screen material
will have a substantially larger influence on the oblique
radiation.
~ he application of filtering dyes and of substances,
e.g. screening dyes,in the conventional screens such as
calciu~ t~lngstate screens limits the use of said screens to
relatively high dosis X-ray exposures so that a great deal
of ~edical X-ray photography requiring a low X-ray dose for
the patient is not within the possibilities of such screens be-
cause of the low emission power of the phosphor of said screens.
Accordingly this invention provides a
novel radiographic combination of a fluorescent screen and a
silver halide photosensitive element capable of yielding
a visible image with improved resolution at still high speed.
GV.705 PCT _ 3 _
~1
1038683
The present inventi~n also
provides a particularly suitable screen-film combination for
use in mammography in which high image resolution is required.
Other advantages of this invention will
become apparent from an examination of the follbwing des-
cription and examples.
In accordance with the present invention these advantages
are attained with a combination of photosensitive elements
suited for radiography comprising :
(1 ) at least one X-ray fluorescent intensifying screen
material comprising a phosphor layer, which contains a
phosphor or a phosphor mixture consisting wholly or main-
ly of a rare earth metal-activated lanthanum oxyhalide,
preferably a terbium- or terbium and ytterbium-activated
lanthanum oxychloride or lanthanum oxybromide, said
phosphors optionally also being activated with cerium and
sai(~ phosphor or phosphor mixture having more than half
its spectral emission above about 410 nm, more than half
its visible light spectral emission between 400 and 500
nm and its maximum of emission in the wavelength range
of 400-450 nm, said phosphor layer having a coverage of
200 to 800 g of said lanthanum oxyhalide phosphor per
sq.m and a thickness preferably in the range of 60 to
250 ~m, said screen material containing (a) dye(s) and/
or pigment(s) absorbing light within the emission spec-
trum of said phosphor layer, said dye(s) and/or pigment(s)
GV.705 PC~ - 4 -
~ P
~03~683
being present preferably between the phosphor layer
and the support of the phosphor layer in an anti-reflec-
tion layer, said screen material having preferably
an intensification factor of at least 20 at 40 kV and
at least 25 at 80 kV, and
(2) a photosensitive material comprising a support and at
least one silver halide emulsion layer wherein preferably
in said photosensitive material the combined absorption
of the support and of the layers at one side of the
support is such that (i) the light absorption spectrum
thereof mainly (at least for 50 %) corresponds with the
light emission spectrum of the fluorescent screen
material in the wavelength range of 400 to 500 nm and
(ii) in the range of overlap of said absorption and
emission spectrum the optical density resulting therefrom
is at least 0.6 on account of the inherent absorption
of the silver halide emulsion layer(s) and the presence
of (a) colouring substance(s) in one or more layers and/
or the support of the photosensitive material.
In the radiographic combination of X-ray fluorescent
screens and silver halide radiographic materials of the
present invention, the said screens may be arranged separate-
ly from the radiation-sensitive silver halide material or
it may form with the silver halide emulsion an integral
arrangement so that on one and the same support both the
silver halide emulsion and the X-ray fluorescent screens are
GV.705 PC~ - 5 -
1~38683
provided. The radiographic material may be a single- or
double-coated radiographic material, which means that the
radiographic material comprises either at only one side
or at both sides of the support a radiation-sensitive silver
halide emulsion layer. The same or differently~composed
fluorescent screens may be provided at both sides of a single-
or double-coated radiographic material.
~ he radiographic combination of fluorescent screens and
radiographic materialsmay comprise the common intermediate
and/or protective and/or stripping layers, which may be
arranged between or over the radiation-sensitive emulsions
and the fluorescent screens.
~ he lanthanum oxyhalide phosphors yield a particu-
larly high emission of fluorescent light when struck by
X-rays so that the use in the intensifying screen of fluores-
cent light-absorbing substances imp~oving the image quality
do not lower the fluorescent light emission in such a degree
that low dosis medical X-ray photography would be excluded.
For use in the field of X-ray photography known as
"mammography" preferably a single side coated silver halide
material is used combined with one fluorescent screen in
contact with the silver halide emulsion layer. In mammo-
graphy very low kilovolt X-rays are normally used viz.
in the range of 20 to 40 kV applied to a molybdenum or
tungsten anode X-ray tube.
Mammography has been described in the book "Rontgen-
untersuchung der Brust" by W.Hoeffken and M.Lanyi (1973)
GV.705 PC~ ~- 6 -
103B683
Georg Thieme Verlag, Stuttgart, W-Germany.
In mammography for the purpose of high image sharpness
screenless film exposures mostly have been applied up till
now. Screenless exposures or in other words direct`X-ray
exposures of the film require a relatively high silver
halide content and X-ray dose. ~he use of phosphors
as defined above makes it possible to improve the image
sharpness of the screen by means of screening dyes up to
a degree equal to the sharpness obtained with direct X-ray
exposureswithout having to rely on the high X-ray dose
characteristic for direct X-ray photography.
Phosphors or fluorescing substances used in the
visible light-emitting fluorescent screens applied in
the present invention are, e.g., lanthanum oxychloride acti-
vated with small amounts of terbium e.g. as described in
the United ~ingdom Patent Specification 1,247,602 filed
October 9, 1969 by General Electric Company. Under small
amounts of terbium has to be understood an amount of terbium
smaller than 0.006 gram atom with respect to the lanthanum
in the phosphor material.
Preferred terbium-acti~ated lanthanum oxychloride and
lanthanum oxybromide phosphors are represented by the
following general formula :
~ a(1 n~.Tbn3 OX
wherein :
X is chlorine or bromine
GV.705 PC~ - 7 -
1038683
~b 3 is trivalent terbium, and
n is 0.006 to 0.0001.
~ he halogen X is preferably present in about stoichio-
metric amount but may be less, e.g. only about 2.5 percent
thereof.
Cerium may replace lanthanum in an amount as described
in the United Kingdom Patent 1,247,602, as mentioned herein-
before, e.g. in an amount of 0.1 to 0.8 mole percent based
on the phosphor composition.
The preparation of terbium-activated lanthanum oxychloride
and lanthanum oxybromide phosphors is described in the United
Kingdom Patent 1,247,602, as described hereinbefore, French
Patent Specifications 2,021,398 filed October 23, 1969 by
General ~lectric Company, and 2,021,399 filed October 23,
~969 by General Electric Company, and published German Patent
Applications 1,952,812 filed October 21,1969 by General
~lectric Company and 2,16~,958 filed December ~4, ~971 by
General ~lectric Company.
~ he emission spectrum of a lanthanum oxybromide con-
taining stoichiometric amounts of oxygen and bromine andthat has been activated with 0.002 gram atoms of terbium
with respect to the lanthanum is given in the graph of
the accompanying Figure~ wherein the relative emission
intensity expressed in procentual values (% I) is plotted
versus wavelengths expressed in nanometer (nm). ~he applied
excitation radiation was 3~3 nm ultraviolet radiation.
GV.705 PC~ - 8 -
~Q386W
Other particularly useful phosphors for application
according to the present invention are described in the
published German Patent Application 2,161,958, as mentioned
hereinbefore corresponding with the Canadian Patent 927,089
filed April 11, 1972 by General Electric Company. These
phosphors are terbium- and ytterbium-activated lanthanum
oxychlorides or lanthanum oxybromides corresponding to the
following general formula :
~a1 w yOX:TbWYby
wherein :
X is chlorine or bromine,
w is from 0.0005 to 0.006 mole pro mole of the oxyhalide, and
y is from 0.00005 to 0.005 mole per mole of the oxyhalide.
~he presence of the ytterbium strongly reduces the after-
glow effect that follows the ~-ray irradiation so that the
formation of ghost images is excluded and sharper images are
obtained. The preparation of this class of phosphors has
been described in the published German Patent Application
2,161,958, as mentioned hereinbefore. Particularly interes-
ting for the purpose of the present invention are said
phosphors wherein w is 0.002.
Another phosphor composition for use according to the
present invention contains a mixture of a lanthanum oxyhalide
phosphor with an yttrium Qxysulphide phosphor both phosphors
being activated with terbium. Yttrium oxysulphide phosphors
emitting in the blue range of the visible spectrum have been
described in the published German Patent Application 1,282,819
GV.705 PC~ - 9 -
10386B3
filed March 18, 1966 by Radio Corporation of America.
~ he selected fluorescent substance(s) is (are) in the form
of a layer applied to a support or applied as a self-support-
ing layer or sheet. Suited layers or sheets have a thickness
of preferably 0.05 to 0.5 mm and contain the fluorescent
su~stance(s) or phosphors dispersed in a binder. Such binder
is, e.g., an organic high molecular weight polymer. Suitable
binding agents are, e.g., cellulose nitrate, ethylcellulose,
cellulose acetate, polyvinyl acetate, polystyrene, polyvinyl-
butyral, polymethyl methacrylate and the like.
~ he proportion of high molecular weight polymer to
fluorescent material is in general within the range of 5-15%
by weight. A preferred grain size of the fluorescent sub-
stances is in the range of about 1-25 ~m.
The surface of the fluorescent material layer may be
protected against moisture and mechanical damage by a
coating of an organic high polymer applied to a thickness of
0.001 to 0.05 mm. Such protecting coating is, e.g., a thin
film of cellulose nitrate, cellulose acetate, polymethyl
methacrylate and the like.
Besides the fluorescent lighting impinging normally to
the silver halide layer there is always an amount of diffuse
radiation in the fluorescent screen giving rise to image
unsharpness. According to the present invention the image
sharpness is improved considerably by incorporating a dye
that absorbs fluorescent light in the fluorescent screen
material, e.g., in the phosphor layer also called fluorescent
GV. 705 PC~ _ 10 -
10;1S6~3
layer or in a layer called anti-reflection layer. Said dye
is called here "screening dye". As the oblique radiation
covers a larger path in the screen material it is attenuated
by the screening dye or dyes to a greater extent than the
radiation impinging normally. ~he term "screening dye"'
includes here dyestuffs (i.e. coloured substances in molecular-
ly divided form) as well as pigments.
~ he anti-reflection layer may be present at the rear
side of the support and/or between the fluorescent layer
and the support, e.g., is applied directly to the support on
to a subbing layer of the support. In a particular case
the screening dye or dyes are incorporated in the support.
According to another embodiment the screening dye is
present in a covering layer on the fluorescent layer.
An appropriate screening dye for use in the fluorescent
screens emitting in the blue part (400-500 nm) of the'visi-
ble spectrum is, e.g., Tartrazine (C.I. Acid Yellow 23) and
a screening dye having the following structural formula:
Na3S~ ~ Na3S~
N C=O ~0-~ ~
H3C-C - C = CH-C - C-C~3
described in the United States Patent 3,624,229 of Daniel
Maurice ~immerman, August Jean Van Paesschen and Albert Emiel
Van Hoof issued November 30, 1971.
~ he screening dye has not to be removed from the fluores-
cent screen material and therefore may be any dye or pigment
GV.705 PC~
103~683
absorbing in the emission spectrum of the fluorescent sub- -
stance(s). ~hus, a black substance such as carbon black in-
corporated in the anti-reflection layer of the screen material
yields quite satisfactory results.
~ he screening dye(s) is (are) preferably used in the anti-
reflection layer in an amount of at least 0.5 mg per sq.m.
~heir use in the anti-reflection layer in the larger amount
range is not limited. Optical densities of more than 3 may
be surpassed.
Very good results are obtained with the simultaneous
use of screening dye(s) in the subjacent anti-reflection
layer and in the layer containing the fluorescent substances.
In that case the fluorescent layer contains, e.g., the
screening dye or dyes in an amount of 5 mg per sq.m. Optional-
ly the screening dye(s) is (are) incorporated in the fluores-
cent layer and the covering layer.
In order to diminish cross-over, at least one layer
and/or the base material of the light-sensitive material
of the present invention should preferably contain a dye
called hereinafter "filtering dye" absorbing light in the
wavelength range emitted by the fluorescent screen used in
the combination. The filtering dye may be the same dye
as the screening dye of the fluorescent screen but is
preferably removable from the recording material during
its processing.
~ he filtering dyes used in the silver halide emulsion
recording material are preferably incorporated in the hydro-
GV.705 PC~ - 12 -
10386~
philic colloid layer between the silver halide emulsion
layers or in the emulsion layers themselves. ~hey may,
however, also be incorporated in one or more subbing layers
and even in the support. As put forward already the
filtering dyes have preferably such chemical and/or physical
characteristics that they can be removed or decolourized in
one of the processing baths.
According to a preferred embodiment of the present inven-
tion filtering dyes absorbing in the wavelength range of
about 400 to 500 nm are used in combination with fluorescent
screens that substantially emit light in the wavelength range
of 400 to 500 nm.
The amount of filtering dye is preferably in the range
of amounts that reduces the cross-over light in such a degree
that its intensity becomes smaller than 30 % of the intensity
of the light impinging on an adjacent emulsion layer. ~or
example 25 to 1000 mg per sq.m of filtering dye(s) are used
but according to the result aimed at lower or higher amounts
may be appropriate as well.
Suitable filtering dyes that can be removed from hydro-
philic colloid layers are ~artrazine and the dyes described
in said United States Patent 3,624,229, as me~tioned herein-
before.
~he silver halide of the silver halide emulsion record-
ing material may be present in a layer or coating such as a
single coating or a duplitized or dual coating, i.e. in a
GV.705 PC~ - 13 -
1~38683
material having a silver halide emulsion layer on each side
of a support. Suitable supports are those having the pro-
perties of permitting their ready passage through a rapid
automa~ic processor. ~he support should therefore be reason-
ably flexible and preferably transparent but abie to maintain
the dimensiona] stability and integrity of the various coatings
thereon. ~ypical film supports are cellulose nitrate,
cellulose ester, polyvinyl acetal, polystyrene, polyethylene
terephthalate, and the like. Supports such as cards or paper
that are coated with ~-olefin polymers, particularly polymers
of ~-olefins containing two or more carbon atoms, as exem-
plified by polyethylene, polypropylene, ethylene-butene co-
polymers and the like, give good results.
In the radiographic combination of X-ray fluorescent
screens and optionally spectrally sensitized silver halide
radiographic materials of the present invention, the screens
may be al-ranged separately from the radiation-sensitive silver
halide material or they may form with the silver halide
emulsion layer an integral arrangement so that on one and
the same support both a silver halide emulsion layer and an
X-ray fluorescent screen are provided.
~ he emulsions may be spectrally sensitized by any of the
known procedures. They may be spectrally sensitized in the
wavelength range of 400 to 500 nm by means of common spectrally
sensitizing dyes in silver halide emulsions, which include
cyanine dyes and merocyanine dyes as well as other dyes as
described by ~.M.Hamer in "~he Cyanine Dyes and related Com-
GV.705 PC~ - 14 -
~03~683
pounds", Interscience Publiskers (1964). ~hese dyes are pre-
ferably used in an amount in the range of 20 mg to 250 mg per
mole of silver halide.
~ he silver halide in the emulsion layer(s) may comprise
varying amounts of silver chloride, silver iodide, silver
bromide, silver chlorobromide, silver bromoiodide, and the
like, but when coated must be capable, after exposure and
processing, of producing a negative silver image remaining
thereon, i.e. in situ. Particularly good results are obtained
with silver bromoiodide emulsions in which the average grain
size of the silver bromoiodide crystals is in the range of
about 0.1 to about 3 ~ . When a duplitized silver halide
coating is employed, the total silver coveI,age per unit area
(sq.dm) for both coatings is 'ess than about 0.080 g and
preferably, each such coating contains less than a~out 0.040 g
of silver per sq.~m. As these layers are applied by means
well-kno~n in the art, it is desirable in the combinations
of our invention that the silver halide-coating or coatings
be capable of transmitting less than about 40 % and preferably
less than about 30 % of the incident radiation from the
screen at wavelengths longer than 410 nm when said silver
halide coverage is within the above ranges.
The proper transmittance can be obtained in a variety
of ways, such as e.g. by the incorporation of optically se-
parating barriers, e.g. undercoates, which can be positioned
between the silver halide-containing layers, by altering the
GV.705 PCT - 15 -
1038683
composition of said layers, by including dyes or other ma-
terials, by adjusting the halide balance or by modifying the
silver halide grain shape, grain size, size distribution and
the like.
The image-forming silver halide emulsion may be che-
mically sensitized by any of the known procedure. ~he
emulsions may be digested with naturally active gelatin
or with small amounts of sulphur-containing compounds such
as allyl thiocyanate, allylthiourea, sodium thiosulphate,
etc. ~he image-forming emulsion may be sensitized like-
wise by means of reductors, e.g. tin compounds as des-
cribed in the United ~ingdom Patent 789,823 filed April 29,
1955 by Gevaert Photo-Producten N.V., polyamines e.g.
diethyltriamine, and small amounts of noble metal compounds
such as of gold, platinum, palladium, iridium, ruthenium,
and rhodium as described by R.Eoslowsky, Z.Wiss.Phot. 46,
67-72 (1951). Representative examples of noble metal
compounds are ammonium chloropalladate, potassium chloro-
platinate, potassium chloroaurate and potassium aurithiG-
cyanate.
Emulsion stabilizers and antifoggants may be addedto the silver halide emulsion before or after admixture
of the low-speed emulsion, e.g., the known sulphinic and
selenic acids or salts thereof, aliphatic, aromatic or
heterocyclic mercapto compounds or disulphides, e.g.
those described and claimed in published German Patent
Application 2,100,622 filed January 8, 1971 by Agfa~Gevaert A.~.
GV.705 PC~ - 16 -
~.038683
preferably comprising sulpho groups or carboxyl groups,
mercury compounds e.g. those described in ~elgian Patents
524,121 filed November 7, 1953 by Kodak ~td., 677,337 filed
March 4, ~966 by Gevaert-Agfa N.V., 707,386 filed December
1, 1967 by Gevaert-Agfa N.V. and 709,195 filed January 11,
1968 by Gevaert-Agfa N.Y, and tetra-azaindenes as described
by Birr in Z.Wiss.Phot. 47, 2-58 (1952), e.g. the hydroxy-
tetra-azaindenes of the following general formula :
OH
~0 R3-~ ~N C,-R
~- ~ C N
wherein :
each of R1 and R2 represents hydrogen, an alkyl, an aralkyl,
or an aryl group, and
R3 represents hydrogen, an alkyl, a carboxy, or an alkoxy-
carbonyl group, such as 5-methyl-7-hydroxy-s-triazolo~1,5-a~
-pyrimidine.
Other additives may be present in one or more of the
hydrophilic colloid layers of the radiation-sensitive
silver halide elements of the present invention, e.g. harden-
ing agents such as formaldehyde, dialdehydes, hydroxy-
aldehydes, mucochloric and mucobromic acid, acrolein, and
glyoxal, mordanting agents for anionic colour couplers or
dyes formed therefrom, plasticizers and coating aids e.g.
saponin, e.g. dialkylsulphosuccinic acid salts such as
sodium diisooctyl sulphosuccinate, alkylarylpolyether-
GV.705 PCl - 17 -
1038683
sulphuric acids, alkylarylpolyethersulphonic acids, car-
boxyalkylated polyethylene gl~col ethers or esters as
described in ~rench Patent 1,537,417 filed September 18,
1967 by Agfa-Gevaert N.V. such as iso-C8H17-C6H4(0CH2CH2)8-
OCH2COONa, fluorinated surfactants, e.g., those aescribed
in Belgian Patent 742,680 filed December 5, 1969 by Agfa-
Gevaert N.V. and the published German Patent Applications
1,950,121 filed October 4, 1969 by Dupont de ~emours and
1,942,665 filed August 21, 1969 by Ciba A.G., inert particles
such as silicon dioxide, glass, starch and polymethacrylate
particles.
In medical radiography it is important that the time
to dispose of the recorded information be as short as possible.
~herefore the exposed radiographic silver halide materials
should be processed in a minimum of time.
It is generally known that processing times and more
particularly the fixing times can be shortened by using
silver halide emulsions having a relatively small amount
of silver halide per unit of surface. ~he use of photo-
graphic materials with a small silver halide content bringsabout, however, that the maximllm density, the contrast and
the resolving power of the obtained image are at a rather
low level.
In this connection it is interesting to note that fine-
grained silver halide emulsions have a higher covering power
than coarse-grained emulsions (ref. P.Glafkidès, Photographic
~ 705 PC~ - ~8 _
1038683
Chemistry, Vol.I (1958) 89-90).
By the term "covering power" is understood in the pre-
sent inventi-on the reciprocal of the photographic equivalent
of developed silver, i.e. the number of grams of silver per
sq.dm divided by the maximum optical density of the image
(silver image density and/or colour image density~ obtained.
Fine-grained emulsions have a lower photographic speed,
however, and consequently the use of such types of emulsions
requires an exposure that may surpass the permissible dose
applied in medical X-ray photography. ~he low speed of
said fine-grained emulsions having a high covering power,
e.g. at least 50, and low silver halide content i.e. equi-
valent to less than 80 mg of silver per sq. &, e.g. 30 to
80 mg of silver per sq.dm, is compensated by the use of
said lanthanum oxyhalide phosphor screens having a parti-
cularly high intensification factor.
By "intensification factor" is to be understood a factor
measured at a pre-elected density D, indicating the exposure
required to produce this density when the film is exposed
to ~-rays without intensifying screen, divided by the expo-
sure required to produce the same density, e.g. density
D = 1.00, when the film is exposed with the screen, the
wavelength distribution of the radiation and the conditions
of development being maintained constant.
~ or the purpose of accelerating the development the
exposed photographic material is developed preferably
GV.705 PGT _ 19 -
~03B683
in the presence of development accelerator6. These deve-
lopment accelerators can be used either in the silver
halide emulsion, in adjacent layer(s) or in the developing
bath. They include alkylene oxide compounds of various
types, e.g. alkylene oxide condensation products or poly-
mers as described in United States Patents 1,970,578 of
Conrad Schoeller and Max Wittner issued August 21, 1934,
2,240,472 of Donald R. Swan issued April 29, 1941,
2,423,549 of Ralph Eings~y Blake~ William Alexander Stanton
and ~erdinand Schulze issued July 8, 1947, 2,441,389 of
Ralph Eingsley Blake issued May 11, 1948, 2,531,.832 of
William Alexander Stanton issued ~oveDmber 28, 1950 and
2,533,990 of Ralph Eingsley Blake issued December 12, 1950
and in United Eingdom Patents 920,637 filed May 7, 1959,
940,051 filed November 1, 1961, 945,340 filed October 23,
1961, all by Gevaert Photo-Producten ~.V., 991,608 filed
June 14, 1961 by Eodak Ltd. and 1,015,023 field December
24, 1962 by Gevaert Photo-Producten N.V. Other compounds
accelerating the development are onium and polyonium
compounds, preferably of the ammonium, phosphonium, and
sulphonium type, e.g. trialkyl sulphonium salts such as
dimethyl-n-nonyl sulphonium p-toluenesulphonate, tetraalkyl
ammonium salts such as dodecyl trimethyl ammonium p-toluene-
sulphonate, alkyl pyridinium and alkyl quinolinium salts
such as 1-m-nitrobenzyl quinolinium chloride and 1-dodecyl
pyridinium chloride, bis-alkylene pyridinium salts such as
GV.705 PC~ - 20 -
1038~83
N,N'-tetramethylene bispyridinium chloride, quaternary
ammonium and phosphonium polyoxyalkylene salts especially
polyoxyalkylene bispyridinium salts, examples of which can
be found in the United States Patent 2,944,900 of Burt
H.Carroll, Hubert S.Elins, James ~.Graham and Charles V.
Wilson issued July 12, 1960.
After radiographic exposure the radiographic silver
halide elements of the present invention are developed,
preferably in an energetic surface developer. ~he high
energy is required in order to allow the development to
proceed quickly and can be obtained by properly alkalizing
the developing liquid (pH 9-~2), by using high-energy
developing substances or a combination of developing sub-
stances, which as a consequence of their superadditive
action is very energetic.
Economy on the silver halide in the emulsion may be
realized by building up the image density partly with dyes.
Such may proceed by introducing (a) colour coupler(s) into
the emulsion, which at least at the stage of development
form(s) (a) dye(s) with the oxiaation product of an aro-
matic primary amino developing agent, e.g. of the p-phenylene-
diamine type, which dye(s) absorb(s) in the visible part of
the spectrum.
~ urther it is known that a relatively high maximum den-
sity and contrast can be obtained even with a low amount of
silver halide content per unit of surface when a colour
GV.705 PC~ _ 21 -
~03~
image is produced together with a silver image as is des-
cribed, e.g., in the published German Patent Application
(Dt-OS) 1,946,652 filed September 15, 1969 by Agfa-Gevaert
A.G.
When a colour development is applied, preferably so-
called 2-equivalent couplers are used to further reduce
the consumption of silver. Thus only 2 instead of 4 mole-
cules of exposed silver halide are necessary for the pro-
duction of 1 dye molecule. Such couplers contain in the
coupling position, e.g. a halogen atom such as iodine,
bromine, or chlorine (see e.g. the United States Patent
3,006,759 of Anthony ~oria, Warren A.Reckhow and Ilmari
.Salminen issued October 31, 1961). The density of the
image is thus realised by addition of the densities of the
silver image(s) combined with the dye image(s).
For improving the information content retrieval those
phenol or ~-naphthol type colour couplers are particularly
suitable that on colour development of the silver halide
with an aromatic primary amino developing agent form a
quinoneimine dye mainly absorbing in the red and also
absorbing in the green and having an absorption maximum
in the spectral wavelength range of 550 to 700 (ref., e.g.
to the published German Patent Application (Dt-OS) 1,946,652
as mentioned hereinbefore).
Phenol couplers suited for that purpose correspond,
e.g. to the following general formula :
GV.705 PCT - 22 -
- 1038~;83
OH
~ -NHR2
R1H~- bJ'
wherein :
eacn of R1 and R2 represents a carboxylic acid acyl or
sulphonic acid acyl group including said groups in sub-
stituted state, e.g. an aliphatic carboxylic acid acyl
group, an aromatic carboxylic acid acyl group, an hetero-
cyclic carboxylic acid acyl group, e.g. a 2-furoyl group
or a 2-thienoyl group, an aliphatic sulphonic acid acyl
group, an aromatic sulphonic acid acyl group, a sulphonyl
thienyl group, an aryloxy-substituted aliphatic carboxylic
acid acyl group, a phenyl carbamyl aliphatic carboxylic acid
acyl group, or a tolyl carboxylic acid acyl group.
~or such types of phenol colour couplers and their
preparation reference may be made to United States Patents
2,772,162 of Ilmari F.~alminen and Charles R.Barr issued
November 27, 1956 and 3,222,176 of Jan Jaeken issued December
7, 1965 and to United Kingdom Patent 975,773 filed September
4, 1961 by Gevaert Photo-Producten N.V.
When colour images are prepared together with silver
images normally aromatic primary amino colour developing
agents are used, e.g. ~ dialkyl-p-phenylenediamines and
derivatives thereof, e.g. N,~-diethyl-p-phenylenediamine,
N-butyl-~-sulphobutyl-p-phenylenediamine, 2-amino-5-di-
ethylaminotoluene hydrochloride, 4-amino-N-ethyl-~
methane sulphonamidoethyl)-m-toluidine sesquisulphate
GV.705 PC~ - 23 -
1038683
monohydrate and N-hydroxy-ethyl-N-ethyl-p-phenylenediamine.
~he colour developer may be used together with black-and-
white developing agents e.g. 1-phenyl-3-pyrazolidinone and
p-monomethylaminophenol, which are known to have a super-
additive effect on colour development (see L.~.A. Mason,
J.Phot.Sci. 11 (1963) 136-139), and other p-aminophenol
derivatives, e.g.those according to French Patent 1,283,420
filed February 16, 1961 by Ilford Ltd. such as 3-methyl-4-
hydroxy-~,~-diethylaniline, 3-methyl-4-hydroxy-~-ethyl-~-
~-hydroxyethylaniline, 1-methyl-6-hydroxy-1,2,3,4-tetra-
hydroquinoline, 1-~-hydroxyethyl-6-hydroxy-1,2,3,4-tetra-
hydroquinoline and N-(4-hydroxy-3'-methylphenyl)-pyrrolidine.
It is also possible to use combinations of aromatic primary
amino colour developing agents to obtain an increased rate
of colour development (see e.g. German Patent 954,311 filed
December 5, 1953 by Agfa A.G. and ~rench Patent 1,299,899
filed September 8, 1961 by ~gfa ~.G.) ; favourable effects
are obtained, e.g., by the use of N-ethyl-N-2-hydroxyethyl-
p-phenylenediamine together with ~-butyl-N-sulphobutyl-p-
phenylenediamine, 2-Pmino-5-diethylamino-toluene hydrochlo-
ride or N,N-diethyl-p-phenylenediamine hydrochloride.
~ he developing solutions may also comprise any of the
usual additional ingrediënts, e.g. sodium sulphite and
hydroxylamine or derivatives thereof, hardening agents,
antifoggants, e.g. benzotriazole~ 5-nitro-benzimidazole~
5-nitro-indazole, halides such as potassium bromide, silver
GV.705 PC~ - 24 -
~038683
halide solvents, toning and intensifying compounds, sol-
vents, e.g. dimethylformamide, dimethylacetamide and N-methyl-
pyrrolidone for chemical ingredients that are difficult to
dissolve in the preparation of the developing solutions or
that tend to precipitate upon standing.
~ he radiation-sensitive emulsions for use in the pre-
sent invention may be coated on a wide variety of supports
e.g. films of cellulose nitrate, cellulose esters, poly-
vinylacetal, polys~yrene, polyethylene terephthalate and
other polyester materials as well as ~-olefin-coated papers
e.g. paper coated with polyethylene or polypropylene.
Preferred supports comprise a linear condensation poly-
mer, blue coloured polyethylene terephthalate being an
example thereof.
~ he supports ~sed in the present recording materials
may be coated with subbing layers for improving the adhesion
of (a) gelatino-silver halide emulsion layer(s) thereto.
~ he mech~nical strength of melt-extruded supports of
the polyester type can be improved by stretching. In
some cases as described in the United Eingdom Patent
1,234,755 filed September 28, 1967 by Gevaert-Agfa N.V. the
support may carry a subbing layer in the stretching stage.
Suited subbing layers are known to those skilled in
the art of silver halide photography. With regard to the
use of hydrophobic film supports reference is made to the
composition of subbing layers aescribea in said United
GV.705 PC~ - 25 -
103868~
Kingdom Patent 1,234,755.
According to said Patent a hydrophobic film support
has 1) a layer which is directly a& erent to t~e said
hydrophobic film support and comprises a copolymer ~ormed
from 45 to 99.5 % by weight of at least one of the chlorine-
containing monomers vinylidene chloride and vinyl chloride,
from 0.5 to 10 % by weight of at least an ethylenically
unsaturated hydrophilic monomer, and from 0 to 54.5 % by
weight of at least one other copolymerisable ethylenically
unsaturated monomer ; and 2) a layer comprising in a ratio
of 1:3 to 1:0.5 by weight a mixture of gelatin and a co-
polymer of ~0 to 70 % by weight of butadiene with at least
one copolymerisable ethylenically unsaturated monomer.
~ he exposed radiographic elements of the present
invention are preferably processed in an automatic processing
apparatus for X-ray films in which the photographic material
may be guided automatically and at a constant speed from
one processing unit to the other, but it will be understood
by those skilled in the art that the radiographic image-
recording elements disclosed herein can also be processedapart from the above mentioned automatic processing apparatus
in a variety of ways, such as b~ using the manual conventional
multi-tank methods well known in the art.
~ or common emulsion preparation processes and the use
of particular emulsion ingredients reference is made
in general to the Product Licensing Index of December 1971
in which the following terms are dealt within more details :
GV.705 PCT - 26 -
- 10386~3
I/II Emulsion type and preparation of said element
III Chemical sensitization
IV Development modifiers
V Antifoggants and stabilizers
VI Developing agents
VII Hardeners
VIII Binding agents or polymers for silver halide
layers and other layers
IX Antistatic layers
X Supports
XI Plasticizers and lubricants
XII Coating aids
XV Spectral sensitization agents for silver halides
XXIII Colour material ingredients
XVI Absorbing and filter dyes
XXI Physical development systems, and
XVII and XVIII Addition agents and coating procedures.
The following examples illustrate the present invention.
E~amPle 1
A radiographic colour material was prepared in the
following way.
To 155 g of a high-speed silver bromoiodide emulsion
(9 mole % silver iodide), which comprises 15.5 g of gelatin
and an amount of silver halide equivalent to 23.9 g of
silver nitrate and which has an average silver halide
grain-size of 800 nm 200 g of a low-speed silver chloride
emulsion comprising 16.8 g of gelatin and an amount of
GV.705 PC~ - 27 -
~038683
silver chloride equivalent to 24 g of silver nitrate were
added.
~ he low-speed silver chloride emulsion was prepared
by admixing an aqueous solution of silver nitrate to an
aqueous gelatin/sodium chloride solution, precipitating
the gelatin emulsion with ammonium sulphate, washing and
peptizing. Gelatin was then added as well as 5-methyl-7-
hydroxy-s-triazolo~1,5-a~p~rimidine so that no chemical
ripening occured. ~he mean grain-size of the silver
chloride emulsion was 220 nm.
~ he mixture was molten by heating for 1 h at 38C
whereupon were added :
a) 14.5 g of the colour coupler having the formula :
H3c-(cH2)12-cH=cH-cH2-cH-coNH- ~ -OH O
b~2coox ~ -NHCO-
from an aqueous alkaline solution,
b) sufficient aqueous acetic acid solution to neutralize
the emulsion (pH 7),
0 c) 5-methyl-7-hydroxy-s-triazolo~1,5-a]pyrimidine as
emulsion stabilizer,
d) saponin as coating aid, and
e) mucochloric acid as hardening agent.
~ he emulsion was diluted to make g20 ml and then
coated on both sides of a subbed polyethylene terephthalate
support, the total surface of which was 10 sq.m. (2 x 5
sq.m). On both sides a gelatin antistress layer of 0.0015 mm
GV.705 PC~ - 28 -
103~tiB3
was provided whereupon the radiographic colour material
formed was dried.
The above prepared material was arranged between two
fluorescent intensifying screens comprising as luminescent
material ~anthanum oxybromide activated with terbium
(0.002 gram atoms with respect to the lanthanum) and con-
taining stoichiometric amounts of oxygen and bromine.
The phosphor layer of the fluorescent screens contained
500 g per sq.m of said lanthanum oxybromide dispersed in
cellulose nitrate as binder. The weight ratio of phosphor
to binder was 92.5 to 7.5. In each screen an anti-reflection
layer was situated between the phosphor layer and the paper
support sheet of the screen material. The anti-reflection
layer contained per sq.m 4 g of carbon black dispersed in
cellulose nitrate. The weight ratio of carbon black to
the binder was 10 to 90.
~ he radiographic combination of screen materials
and silver halide material was exposed to 80 kV-peak
X-ray radiation passing through 6 mm of aluminium for
filtering purposes and through a test original being a
lead line grid test object in order to determine the
relationship between speed and modulation transfer function
value (MTF-value).
After removal of the intensifying screens the radio-
graphic colour material was automatically colour-processed,
which includes colour-development (24 s at 4~C), fixing
GV.705 PCT - 29 - -
~038683
(20 s at 41C), rinsing (25 s at 41~C) and drying (20 s
at 55C).
~ he developing bath used had a pH of 10.6 and comprised
per litre :
8 g of N-hydroxyethyl-N-ethyl-p-phenylenediamine,
1.5 g of hydroxylamine,
4 g of anhydrous sodium sulphite,
1 g of potassium bromide, and
65 g of anhydrous potassium carbonate.
Fixing occurred by means of a sodium thiosulphate fixing
solution.
~ he measurements of the relationship between M~F-value
and speed occurred by means of a microdensitometer.
It was established that the combined use according t~
the invention of the above luminescent screens with said
radiographic colour material yields a more favourable
relationship between MTF value and speed than the combined
use of a same radiographic colour element with conventional
fluorescent calcium wolframate screens, viz. a speed four
times as high as for the same MT~-value.
ExamPle 2
A silver bromoLodide X-ray emulsion (1.5 mole % of
silver iodide) was prepared in such a way that it contained
silver halide grains with an average grain size of 0.60 ~m
and comprised per kg 74 g of gelatin and an amount of
silver halide corresponding to 190 g of silver nitrate.
As stabilizing agents the emulsion contained per kg 545 mg
GV.705 PC~ - ~0 -
1038683
of 5-methyl-7-hydroxy-s-triazolo~1,5-a~ yrimidine, 6.5 mg
of 1-phenyl-5-mercaptotetrazole, and 0.45 mg of mercury
cyanide. ~he covering power obtainable with said emulsion
was 60.
The above emulsion was coated on both sides of a double-
side subbed polyethylene terephthalate support in such a
way that on each side of the support a silver halide emulsion
layer was obtained containing an amount of silver halide
equivalentto 6 g of silver nitrate per sq.m.
~ach emulsion layer was coated with a gelatino anti-
stress layer at a coverage of 1 g per sq.m.
~ he material prepared was arranged between the same
two fluorescent intensifying screens as described in Example
1 and the radiographic combination formed was exposed to
60 kV X-ray radiation through a lead line grid test object
in order to determine speed and modulation transfer function
value.
After removal of the fluorescent screens the radio-
graphic materials was processed in an automatic 90 seconds
processing machine ; the development occurred for 23 s
at 35C in ~gfa-Gevaert's hardening developer G 138, which
comprises hydroquinone and 1-phenyl-3-pyrazolidinone as
developing agents and glutaraldehyde as a hardener.
It was established that the combined use of the above
fluorescent screens with the above radiographic silver
halide material yielded a more favourable relationship
GV.705 PC~ - 31 -
~038683
between MTF value and speed than the combined use of the
same radiographic element with conventional calcium wol-
framate screens, viz. a speed four times as high as for
a same MT~-value.
EXamPle 3
A silver bromoiodide X-ray emulsion (1.5 mole % of
silver iodide) was prepared analogously to that of Example 2
but so that it contained silver halide grains with an
average grain size of 0.65 ~m. ~he covering power obtain-
able with said emulsion in the developing conditions definedhereinafter was 60. Then it was applied to a support and
coated with an antistress layer as described in Example 2.
- Composition of the fluorescent screen material I.
The fluorescent screen used according to the invention
was prepared as follows :
92.2 g of LaOBr:0.002 Tb:0.0005 Yb phosphor particles pre-
pared according to the methoa aescribed in the published
German Patent Application 2,161,958, as mentioned hereinbefore,
were dispersed in a solution of 7.8 g of ELVACI~E 2044
(trade name of du Pont de Nemours, Wilmington, Del., USA,
for a high-molecular weight poly-n-butyl methacrylate) in
21.7 g of toluene.
~ he obtained dispersion was filtered through a filter
having passages with a mean diameter of 75 )um and was de-
aerated by subjecting it to reduced pressure of 100 mbar
(100 cm of water). The average grain size of the phosphor
GV.705 PCT - 32 -
10386~3
particles was 5 ~ . The content of solids of the obtained
dispersion was 82.1 % by weight.
~ he dispersion was coated onto an anti-reflection
layer, which was applied to a subbed polyethylene terephtha-
late resin support of 250 ~m. The subbing layer was produced
~rom a latex on the basis of a copolymer of vinyl chloride,
vinylidene chloride, n-butyl acrylate and itaconic acid
(weight ratio : 63/30/5/2).
~ he anti-reflection layer contained per sq.m ~ g of
carbon black dispersed in cellulose nitrate. ~he weight
ratio of carbon black to the binder was 10 to 90.
The coating of the phosphor dispersion was effected in
such a way that 35 mg of phosphor were applied per sq.cm.
- Composition of the fluorescent screen material II.
Calcium wolframate phosphor screen particles of the
commercial type (manufactured by Riedel-de Haën, Seelze
(Hannover), W.Germany) used in CaW04 screens were incorporated
in an intensifying screen binder layer as described for
fluorescent screen material I. The phosphor layer was
applied at a same phosphor coverage per sq.m as described
for screen material I on the above anti-reflection layer.
- Exposure.
~ he light-sensitive material was exposed with a 80 kV
X-ray radiation filtered through a 6 mm aluminium sheet and
modulated with a test object being a line screen made of
lead wherein the width of the bars of the screen gradually
diminishes, and their spatial frequency (number per mm)
GV.705 PC~ - 3~ -
1~3~3
gradually increases from one side of the test object to the
other. By applying such a test object in the exposure it is
posslble to obtain an objective value for the sharpness
independently of subaect contrast by determining the "square
wave response function" (SWRF) (ref.Amer.J. Roentgenol.
106 (1969) pages 650-6~4).
Each of a first and a second strip of light-sensitive
materials called material A and B respectively was exposed
between two fluorescent screen materials I and two fluores-
cent screen materials II respectively arranged in contactwith the opposite sides of the light-sensitive material.
The exposed materials were processed in an automatic
90 seconds processing machine the development occurring for
23 s at 35C in Agfa-Gevaert's hardening developer G 138
containing hydroquinone and 1-phenyl-3-pyrazolidione as~
developing agents and glutaraldehyde as hardener.
~ he s~uare wave response function of the test materials
was derived from the measurements obtained by scanning the
line pattern obtained in these materials with a microdensito-
meter.
The relative square wave response factor ~value of thefunction) at a spatial frequency respectively of one and
two line pairs per mm for the different combinatiGns of light-
sensitive materials and screens as defined above is listed
in the following table.
GV.705 PC~ - 34 -
~able 10~83
Combination of light Speed Square wave response ,
sensitive material s~5-log10E factor at :
and screen
for denslty 1 line 2 llne
_ _ 1.00 pair per mm Pairs per mm ¦
A, I 3.57 0-71 0.45
B, II 3.09 0.70 0.43
Example 4
A silver bromoiodide ~-ray emulsion (1.5 mole % of sil-
ver iodide) was prepared in such a way that it contained silverhalide grains with an average grain size of 0.70 pm. ~he
emulsion contained a stabilizing agent as defined in Example
~ and was coated at only one side of a subbed polyethylene
terephthalate film support, which carried a common anti-
reflection layer at the rear side. Coating of the emulsion
proceeded in such a way that an amount of silver halide
equivalent to 8 g of silver nitrate per sq.m was applied.
~ he obtained photographic silver halide material was
used for mammography and for that purpose exposed to
X-rays while being in contact with the fluorescent screen
layer of a fluorescent screen material whose fluorescent
layer incorporated in ELVACI~ 2044 (trade name) as binder
the lanthanum oxybromide phosphor of Example 3 at a coverage
of 250 g per sq.m and ~sscreening dye "ZAPON ECH~ GELB CGG"
(C.I. ~8,820) in an amount of 0.0379 % by weight with
respect to the phosphor.
GV.705 PC~ - 35 -
103~683
The grain size of the phosphor particles averaged 2.5
~m.
The fluorescent screen layer was applied to an anti-
reflection layer as described in Example 3, which was
coated onto a subbed polyethylene terephthalate support.
In the X-ray exposure for mammographic purposes an
X-ray apparatus known as "SENOGRAPH"*(marketed by Compagnie
~Ténérale de Radiologie filiale du groupe ~homson-Brandt ;
France) was used. The X-ray tube was operated at 30 kV
and the X-rays filtered with a 30 ~m plate of mol~ybdenum
and a 30 mm plate of polymethyl methacrylate.
Compared with "direct" (screenless) X-ray mammography
which operates with a high silver halide content film having
a silver halide coverage equivalent to 36 g of silver
nitrate per sg.m, the present screen-film combination
offered a speed ~ times as high with higher image contrast.
By applying a developer as described in Example 3 the
development time necessary for reaching a same maximum
density with the present screen film combination was only
1/15 part of the development time needed for said high
silver halide content film.
~ Trade Mark
GV.705 PC~ - 36 -
