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Description  |
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This invention relates to photography and more particularly to color
diffusion transfer photography employing certain nondiffusible azo
dye-releasing compounds which, as a function of development of a silver
halide emulsion layer, release a diffusible, metallizable,
pyridylazopyrazole of pyrimidylazopyrazole dye. Highly stable metal
complexes of this dye are formed in an image-receiving layer.
Azo dye developers containing metallizable groups are disclosed in U.S.
Pat. Nos. 3,081,167; 3,196,014; 3,299,041; 3,453,107; and 3,563,739. Since
it is a reactive species, however, the developer moiety of such dye
developers is capable of developing any exposed silver halide emulsion
layer that it comes into contact with, rather than just developing the
adjacent silver halide emulsion with which it is associated. Unwanted
wrong-layer development, therefore, can occur in dye developer systems
which results in undesirable interimage effects. Accordingly, it is
desirable to provide an improved transfer system in which the dye is not
attached to a "reactive" moiety, such as a developer moiety, so that such
dye can diffuse throughout the photographic film unit without becoming
immobilized in undesired areas.
In U.S. Published Patent application No. B351,673, published Jan. 28, 1975,
nondiffusible dye releasing compounds are disclosed. Among the various dye
moieties disclosed which can be released are "metal complexed dyes". No
specific structures are shown, however.
In U.S Pat. Nos. 3,931,144; 3,932,380; 3,942,987; 3,954,476; 4,001,209;
4,013,633 and 4,013,635, various nondiffusible azo dye-releasing compounds
are disclosed. The released dyes, however, are not disclosed as being
metallized or metallizable.
The April 1977 edition of Research Disclosure, pages 32 through 39,
discloses various nondiffusible dye-releasing compounds and various
metallized azo dye fragments. Such premetallized dyes are large molecules
which diffuse more slowly than unmetallized dyes, resulting in long access
times for image formation. In any event, the specific compounds employed
in the instant invention are not disclosed, however.
U.S. Pat. Nos. 3,086,005; 3,492,287 and 3,985,499 disclose various azo
dyes, U.S. Pat. Nos. 2,348,417; 2,495,244; and 2,830,042 and French Pat.
Nos. 1,124,882 and 1,200,358 disclose various dyes from azopyridines,
while U.S. Pat. Nos. 2,868,775; 2,938,895; 3,097,196; 3,691,161; and
3,875,139; British Pat. No. 899,758; and an article entitled "The Irgalan
Dyes--Neutral-Dyeing Metal-Complex Dyes" by Guido Schetty, J. Soc. Dyers
and Colourists, Volume 71, 1955, pages 705 through 724, disclose various
metal complexed dyes. Again, however neither, the specific compounds
employed in the instant invention nor the results obtained therewith are
disclosed.
It would be desirable to provide improved dye-releasing compounds
containing chelating dye moieties, so that the dye which is released
imagewise during processing can diffuse to an image-receiving layer
containing metal ions to form a metal-complexed, dye transfer image having
better hues, rapid diffusion rates and shorter access times than those of
the prior art, as well as good stability to heat, light and chemical
reagents.
A photographic element in accordance with the invention comprises a support
having thereon at least one photosensitive silver halide emulsion layer
having associated therewith a nondiffusible compound having a releasable
pyridylazopyrazole or pyrimidylazopyrazole dye moiety containing:
(a) in the ortho position of the azopyrazole moiety a metal chelating
group, a salt thereof or a hydrolyzable precursor thereof, and
(b) a ballasted carrier moiety which is capable of releasing the diffusible
azo dye under alkaline conditions such as, for example, as a function
(either direct or inverse) of development of the silver halide emulsion
layer.
In a preferred embodiment of the invention, the pyridylazopyrazole and
pyrimidylazopyrazole dye-releasing compounds may be represented by the
formula:
##STR1##
wherein:
G is a metal chelating group (any group which will donate a pair of
electrons to a metal ion) or a salt thereof (e.g., an alkali metal salt, a
quaternary ammonium salt, etc) or a hydrolyzable precursor thereof (e.g.,
a hydrolyzable acyl or ester group), e.g., hydroxy; amino; carboxy;
sulfonamido; sodium carboxylate; sulfamoyl; a hydrolyzable ester group
having the formula --OCOR, --OCOOR, --OCONR.sub.2 or --COOR, wherein each
R is an alkyl group having 1 to about 4 carbon atoms, such as methyl,
ethyl, isopropyl, butyl and the like, or an aryl group having 6 to about 8
carbon atoms, such as phenyl, etc;
A represents C or N;
Car represents said ballasted carrier moiety;
Z represents the atoms necessary to complete a pyrazole ring attached to
the azo group in the 4-position; and
t is a positive integer of 1 to 2.
In a further preferred embodiment of the invention, the pyridylazopyrazole
and pyrimidylazopyrazole dye-releasing compounds may be represented by the
formula:
##STR2##
wherein: A represents C or N;
Car represents said ballasted carrier moiety;
t is a positive integer of 1 to 2;
G.sup.1 represents OH or NH.sub.2 ; and
R.sup.1 represents an alkylene (including substituted alkylene) group of 1
to about 8 carbon atoms or an arylene (including substituted arylene)
group of 6 to about 8 carbon atoms.
Good yellow dyes are obtained in this embodiment when the pyrazole ring is
substituted in the 3-position with a methyl group and said CAR is attached
to the pyrazole ring through a phenylene group in the 1-position. Other
substituents may also be present in either of the two rings such as alkyl
of 1 to 6 carbon atoms, alkoxy, halogens, solubilizing groups such as
sulfonamido, sulfamoyl, carboxy, sulfo, etc.
The absorption spectra of the azo dyes according to the invention, when
metallized in the image-receiving layer, are narrow banded, have bright
hues and give good color reproduction quality. This is to be contrasted
with dyes having hydroxyl radicals substituted on aryl or heterocycl
nuclei at positions ortho and ortho-prime to the azo linkage, such as
described in the above-mentioned U.S. Pat. No. 3,196,014, which generally
give rather broad spectra.
There is great latitude in selecting a CAR moiety which is attached to the
pyridylazopyrazole or pyrimidylazopyrazole dye-releasing compounds
described above. Depending upon the nature of the ballasted carrier
selected, various groups may be needed to attach or link the carrier
moiety to the dye. Such linking groups are considered to be a part of the
CAR moiety in the above definition. It should also be noted that when the
dye moiety is released from the compound, cleavage may take place in such
a position that part or all of a linking group if one is present, and even
part of the ballasted moiety may be transferred to the image-receiving
layer along with the dye moiety. In any event, the dye nucleus as shown
above can be through of as the "minimum" which is transferred.
CAR moieties useful in the invention are described in U.S. Pat. Nos.
3,227,550; 3,628,952; 3,227,552; and 3,844,785 (dye released by
chromogenic coupling); U.S. Pat. Nos. 3,443,939 and 3,443,940 (dye
released by intramolecular ring closure); U.S. Pat. Nos. 3,698,897 and
3,725,062 (dye released from hydroquinone derivatives); U.S. Pat. No.
3,728,113 (dye released from a hydroquinonylmethyl quaternary salt); U.S.
Pat. Nos. 3,719,489 and 3,443,941 (silver ion induced dye release); and
U.S. Pat. Nos. 3,245,789 and 3,980,497; Canadian Pat. No. 602,607; British
Pat. No. 1,464,104; Research Disclosure 14447, Apr. 1976; and commonly
assigned copending U.S. application Ser. No. 775,025, filed Mar. 7, 1977
of Chasman et al (dye released by miscellaneous mechanisms), the
disclosures of which are hereby incorporated by reference.
In a further preferred embodiment of the invention, the ballasted carrier
moiety or CAR as described above may be represented by the following
formula:
(Ballast-Carrier-Link) -
wherein:
(a) Ballast is an organic ballasting radical of such molecular size and
configuration as to render the compound nondiffusible in a photographic
element during development in an alkaline processing composition;
(b) Carrier is an oxidizable acyclic, carbocyclic or heterocyclic moiety
(see "The Theory of the Photographic Process", By C. E. K. Mees and T. H.
James, Third Edition, 1966, pages 282 to 283), e.g., moieties containing
atoms according to the following configuration:
a (--C.dbd.C).sub.b --
wherein:
b is a positive integer of 1 to 2; and
a represents the radicals, OH, SH, NH--, or hydrolyzable precursors
thereof; and
(c) Link represents a group which upon oxidation of said Carrier moiety is
capable of being hydrolytically cleaved to release the diffusible azo dye.
For example, Link may be the following groups:
##STR3##
wherein .notident. represents the position of attachment to Carrier.
The Ballast group in the above formula is not critical as long as it
confers nondiffusibility to the compound. Typical Ballast groups include
long-chain alkyl radicals linked directly or indirectly to the compound as
well as aromatic radicals of the benzene and naphthalene series indirectly
attached or fused directly to the rings, etc. Useful Ballast groups
generally have at least 8 carbon atoms such as substituted or
unsubstituted alkyl groups of 8 to 22 carbon atoms, a carbamoyl radical
having 8 to 30 carbon atoms such as --CONH(CH.sub.2).sub.4 --O--C.sub.6
H.sub.3 (C.sub.5 H.sub.11).sub.2, --CON(C.sub.12 H.sub.25).sub.2, etc, a
keto radical having 8 to 30 carbon atoms such as --CO--C.sub.17 H.sub.35,
--CO--C.sub.6 H.sub.4 (t-C.sub.12 H.sub.25), etc.
For specific examples of Ballast-Carrier-Link moieties useful as the CAR
moiety in this invention, reference is made to the November 1976 edition
of Research Disclosure, pages 68 through 74, and the April 1977 edition of
Research Disclosure, pages 32 through 39, the disclosures of which are
hereby incorporated by reference.
In a highly preferred embodiment of the invention, the ballasted carrier
moiety or CAR in the above formulas is a group having the formula:
##STR4##
wherein:
(a) Ballast is an organic ballasting radical of such molecular size and
configuration (e.g., simple organic groups or polymeric groups) as to
render the compound nondiffusible in a photographic element during
development in an alkaline processing composition;
(b) D is OR.sup.2 or NHR.sup.3 wherein R.sup.2 is hydrogen or a
hydrolyzable moiety and R.sup.3 is hydrogen or a substituted or
unsubstituted alkyl group of 1 to 22 carbon atoms such as methyl, ethyl,
hydroxyethyl, propyl, butyl, secondary butyl, tert-butyl, cyclopropyl,
4-chlorobutyl, cyclobutyl, 4-nitroamyl, hexyl, cyclohexyl, octyl, decyl,
octadecyl, dodecyl, benzyl, phenethyl, etc. (when R.sup.3 is an alkyl
group of greater than 8 carbon atoms, it can serve as a partial or sole
Ballast);
(c) Y represents the atoms necessary to complete a benzene nucleus, a
naphthalene nucleus, or a 5 to 7 membered heterocyclic ring such as
pyrazolone, pyrimidine, etc;
(d) j is a positive integer of 1 to 2 and is 2 when D is OR.sup.2 or when
R.sup.3 is hydrogen or an alkyl group of less than 8 carbon atoms; and
(e) L is a linking group which is [X--(NR.sup.4 --J).sub.q ].sub.m --or
X--J--NR.sup.4 --wherein:
(i) X represents a bivalent linking group of the formula --R.sup.5
--L'.sub.n --R.sup.5.sub.p --where each R.sup.5 can be the same or
different and each represents an alkylene radical having 1 to about 8
carbon atoms, such as methylene, hexylene and the like; a phenylene
radical; or a substituted phenylene radical having 6 to about 9 carbon
atoms, such as methoxy phenylene;
(ii) L' represents a bivalent radical selected from oxy, imino, carbonyl,
carboxamido, carbamoyl, sulfonamido, ureylene, sulfamoyl, sulfinyl or
sulfonyl;
(iii) n is an integer of 0 or 1;
(iv) p is 1 when n equals 1 and p is 1 or 0
when n equals 0, provided that when p is 1 the carbon content of the sum of
both R.sup.5 radicals does not exceed 14 carbon atoms;
(v) R.sup.4 represents a hydrogen atom, or an alkyl radical having 1 to
about 6 carbon atoms;
(vi) J represents a bivalent radical selected from sulfonyl or carbonyl;
(vii) q represents an integer of 0 or 1; and
(viii) m represents an integer of 0, 1 or 2.
Especially good results are obtained in the above formula when D is OH, j
is 2, Y is a naphthalene nucleus, G is OH, CAR is attached to the pyrazole
ring in the 1-position and the pyrazole ring is substituted in the
3-position with a methyl group.
Examples of the CAR moiety in this highly preferred embodiment are
disclosed in U.S. Published Patent application B351,673; U.S. Pat. No.
3,928,312; French Pat. No. 2,284,140; and German Pat. Nos. 2,406,664;
2,613,005; and 2,505,248, the disclosures of which are hereby incorporated
by reference, and include the following:
##STR5##
In another highly preferred embodiment of the invention, the ballasted
carrier moiety or CAR in the above formulas is such that the diffusible
azo dye is released as an inverse function of development of the silver
halide emulsion layer under alkaline conditions. This is ordinarily
referred to as positive-working dye-release chemistry. In one of these
embodiments, the ballasted carrier moiety or CAR in the above formulas may
be a group having the formula:
##STR6##
wherein:
Ballast is an organic ballasting radical of such molecular size and
configuration as to render the compound nondiffusible in a photographic
element during development in an alkaline processing composition;
W.sup.2 represents at least the atoms necessary to complete a benzene
nucleus (including various substituents thereon); and
R.sup.7 is an alkyl (including substituted alkyl) radical having 1 to about
4 carbon atoms.
Examples of the CAR moiety in this formula I include the following:
##STR7##
In a second embodiment of positive-working dye-release chemistry as
referred to above, the ballasted carrier moiety or CAR in the above
formulas may be a group having the formula:
##STR8##
wherein:
Ballast is an organic ballasting radical of such molecular size and
configuration as to render the compound nondiffusible in a photographic
element during development in an alkaline processing composition;
W.sup.1 represents at least the atoms necessary to complete a quinone
nucleus (including various substituents thereon);
r is a positive integer of 1 or 2;
R.sup.6 is an alkyl (including substituted alkyl) radical having 1 to about
40 carbon atoms or an aryl (including substituted aryl) radical having 6
to about 40 carbon atoms; and
k is a positive integer of 1 to 2 and is 2 when R.sup.6 is a radical of
less than 8 carbon atoms.
Examples of the CAR moiety in this formula II include the following:
##STR9##
In using the compounds in formulas I and II above, they are employed in a
photographic element similar to the other nondiffusible dye-releasers
described previously. Upon reduction of the compound as a function of
silver halide development under alkaline conditions, the metallizable azo
dye is released. In this embodiment, conventional negative-working silver
halide emulsions, as well as direct-positive emulsions, can be employed.
For further details concerning these particular CAR moieties, including
synthesis details, reference is made to commonly assigned copending U.S.
application Ser. No. 775,025 of Chasman et al, filed March 7, 1977, the
disclosure of which is hereby incorporated by reference.
In a third embodiment of positive-working dye-release chemistry as referred
to above, the ballasted carrier moiety or CAR in the above formulas may be
a group having the formula:
##STR10##
wherein:
Ballast, W.sup.2 and R.sup.7 are as defined for formula I above.
Examples of the CAR moiety in this formula III include the following:
##STR11##
For further details concerning this particular CAR moiety, including
synthesis details, reference is made to commonly U.S. assigned copending
application Ser. No. 534,966 of Hinshaw et al, filed Dec. 20, 1974, the
disclosure of which is hereby incorporated by reference.
In a fourth embodiment of positive-working dye-release chemistry as
referred to above, the ballasted carrier moiety or CAR in the above
formulas may be a group having the formula:
##STR12##
wherein:
Ballast, r, R.sup.6 and k are as defined for formula II above;
W.sup.2 is as defined for formula I above; and
K is OH or a hydrolyzable precursor thereof.
Examples of the CAR moiety in this formula IV include the following:
##STR13##
For further details concerning this particular CAR moiety, including
synthesis details, reference is made to U.S. Pat. No. 3,980,479 of Fields
et al., issued Sept. 14, 1976, the disclosure of which is hereby
incorporated by reference.
A bivalent linking group, e.g., L or X as defined above, may be used, if
desired, to link the CAR moiety described in formulas I through IV above
to the dye moiety previously described.
Representative compounds included within the scope of the invention include
the following:
##STR14##
A process for producing a photographic transfer image in color according to
the invention comprises:
(a) treating an imagewise-exposed photographic element as described above
with an alkaline processing composition in the presence of a silver halide
developing agent to effect development of each of the exposed silver
halide emulsion layers,
(b) the dye-releasing compound then releasing the diffusible azo dye as
described above imagewise as a function of the development of each of the
silver halide emulsion layers;
(c) at least a portion of the imagewise distribution of the azo dye
diffusing to a dye image-receiving layer; and
(d) contacting the imagewise distribution of azo dye with metal ions,
thereby forming a metal-complexed azo dye transfer image.
In another preferred embodiment of the invention, a process for producing a
photographic transfer image in color according to the invention comprises:
(a) treating an imagewise-exposed photographic element as described above
wherein CAR in the compound has the formula:
##STR15##
D, Y, L and j being defined as above, with an alkaline processing
composition in the presence of a silver halide developing agent to effect
development of each of the exposed silver halide emulsion layers, thereby
oxidizing the developing agent;
(b) the oxidized developing agent thereby cross-oxidizing the dye-releasing
compound;
(c) the cross-oxidized dye-releasing compound then cleaving as a result of
alkaline hydrolysis to release the diffusible azo dye imagewise as a
function of the imagewise exposure of each of the silver halide emulsion
layers;
(d) at least a portion of the imagewise distribution of the azo dye
diffusing to a dye image-receiving layer; and
(e) contacting the imagewise distribution of azo dye with metal ions,
thereby forming a metal-complexed azo dye transfer image.
The tridentate azo dye ligand which is released from the dye-releasing
compounds in accordance with the present invention will form a
coordination complex in the image-receiving layer with polyvalent metal
ions. The metal ions can be present in the image-receiving layer itself or
in a layer adjacent thereto or the image-receiving layer can be contacted
with metal ions in a bath after diffusion of the dye has taken place.
Metal ions most useful in the invention are those which are essentially
colorless when incorporated into the image-receiving element, are inert
with respect to the silver halide layers, react readily with the released
dye to form a complex of the desired hue, are tightly coordinated to the
dye in the complex, have a stable oxidation state, and form a dye complex
which is stable to heat, light and chemical reagents. In general, good
results are obtained with polyvalent metal ions such as copper (II), zinc
(II), nickel (II), platinum (II), palladium (II) and cobalt (II) ions.
For example, it is believed that the coordination complex which is formed
from the tridentate azo dye ligand according to the invention in one of
the preferred embodiments thereof has the following structure:
##STR16##
where Z and A are defined as above, Me is metal and Lig is one or more
ligand groups depending upon the coordination number of the metal ion,
such as H.sub.2 O, Cl, pyridine, etc.
Thus, in accordance with another embodiment of the invention, a
photographic element is provided which comprises a support having thereon
a coordination complex of a polyvalent metal ion and a compound having the
formula:
##STR17##
wherein Z and A are as described previously, and G.sup.2 is a metal
chelating group, as described above. The element usually contains a
photographic mordant or image-receiving layer to bind the dye or
coordination complex thereto. The structures shown above may also, of
course, be substituted in the same manner as described above for the
starting compounds from which they are released, e.g., the pyrazole ring
may be substituted in the 3-position with a methyl group, etc.
It will be appreciated that, after processing the photographic element
described above, there remains in it after transfer has taken place an
imagewise distribution of azo dye in addition to developed silver. A color
image comprising residual nondiffusible compound may be obtained in this
element if the residual silver and silver halide are removed by any
conventional manner well known to those skilled in the photographic art,
such as a bleach bath followed by a fix bath, a bleach-fix bath, etc. Such
a retained dye image should normally be treated with metal ions to
metallize the dyes to increase their light fastness and shift their
spectral absorption to the intended region. The imagewise distribution of
azo dye may also diffuse out of the element into these baths, if desired,
rather than to an image-receiving element. If a negative-working silver
halide emulsion is employed in certain preferred photosensitive elements,
described above, then a positive color image, such as a reflection print,
a color transparency or motion picture film, may be produced in this
manner. If a direct-positive silver halide emulsion is employed in such
photosensitive elements, then a negative color image may be produced.
The photographic element in the above-described process can be treated with
an alkaline processing composition to effect or initiate development in
any manner. A preferred method for applying processing composition is by
use of a rupturable container or pod which contains the composition. In
general, the processing composition employed in this invention contains
the developing agent for development, although the composition could also
just be an alkaline solution where the developer is incorporated in the
photographic element, image-receiving element or process sheet, in which
case the alkaline solution serves to activate the incorporated developer.
A photographic film unit which can be processed in accordance with this
invention is adapted to be processed by passing the unit between a pair of
juxtaposed pressure-applying members, such as would be found in a camera
designed for incamera processing, and comprises:
(1) a photographic element as described above;
(2) a dye image-receiving layer; and
(3) means for discharging an alkaline processing composition within the
film unit, such as a rupturable container which is adapted to be
positioned during processing of the film unit so that a compressive force
applied to the container by the pressure-applying members will effect a
discharge of the container's contents within the film unit;
the film unit containing a silver halide developing agent.
In the embodiment described above, the dye image-receiving layer may itself
contain metal ions or the metal ions may be present in an adjacent layer,
so that the tridentate azo dye ligand which is released will form a
coordination complex therewith. The dye thus becomes immobilized in the
dye image-receiving layer and metallized at the same time. Alternatively,
the dye image in the dye image-receiving layer may be treated with a
solution containing metal ions to effect metallization. The formation of
the coordination complex shifts the absorption of the dye to the desired
hue, usually to longer wavelengths, which have a different absorption than
that of the initial dye-releasing compound. If this shift is large enough,
then the dye-releasing compound may be incorporated in a silver halide
emulsion layer without adversely affecting its sensitivity.
The dye image-receiving layer in the above-described film unit can be
located on a separate support adapted to be superposed on the photographic
element after exposure thereof. Such image-receiving elements are
generally disclosed, for example, in U.S. Pat. No. 3,362,819. When the
means for discharging the processing composition is a rupturable
container, it is usually positioned in relation to the photographic
element and the image-receiving element so that a compressive force
applied to the container by pressure-applying members, such as would be
found in a typical camera used for in-camera processing, will effect a
discharge of the container's contents between the image-receiving element
and the outermost layer of the photographic element. After processing, the
dye image-receiving element is separated from the photographic element.
The dye image-receiving layer in the above-described film unit can also be
located integral with the photographic element between the support and the
lowermost photosensitive silver halide emulsion layer. One useful format
for integral receiver-negative photographic elements is disclosed in
Belgian Pat. No. 757,960. In such an embodiment, the support for the
photographic element is transparent and is coated with an image-receiving
layer, a substantially opaque light-reflective layer, e.g., TiO.sub.2, and
then the photosensitive layer or layers described above. After exposure of
the photographic element, a rupturable container containing an alkaline
processing composition and an opaque process sheet are brought into
superposed position. Pressure-applying members in the camera rupture the
container and spread processing composition over the photographic element
as the film unit is withdrawn from the camera. The processing composition
develops each exposed silver halide emulsion layer and dye images are
formed as a function of development which diffuse to the image-receiving
layer to provide a positive, right-reading image which is viewed through
the transparent support on the opaque reflecting layer background. For
other details concerning the format of this particular integral film unit,
reference is made to the above-mentioned Belgian Pat. No. 757,960.
Another format for integral negative-receiver photographic elements in
which the present invention can be employed is disclosed in Belgian Pat.
No. 757,959. In this embodiment, the support for the photographic element
is transparent and is coated with the image-receiving layer, a
substantially opaque, light-reflective layer and the photosensitive layer
or layers described above. A rupturable container containing an alkaline
processing composition and an opacifier is positioned adjacent the top
layer and a transparent top sheet which has thereon a neutralizing layer
and a timing layer. The film unit is placed in a camera, exposed through
the transparent top sheet and then passed through a pair of
pressure-applying members in the camera as it is being removed therefrom.
The pressure-applying members rupture the container and spread processing
composition and opacifier over the negative portion of the film unit to
render it light-insensitive. The processing composition develops each
silver halide layer and dye images are formed as a result of development
which diffuse to the image-receiving layer to provide a positive,
right-reading image which is viewed through the transparent support on the
opaque reflecting layer background. For further details concerning the
format of this particular integral film unit, reference is made to the
above-mentioned Belgian Pat. No. 757,959.
Still other useful integral formats in which this invention can be employed
are described in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646;
3,647,437; and 3,635,707. In most of these formats, a photosensitive
silver halide emulsion is coated on an opaque support and a dye
image-receiving layer is located on a separate transparent support
superposed over the layer outermost from the opaque support. In addition,
this transparent support also preferably contains a neutralizing layer and
a timing layer underneath the dye image-receiving layer.
Another embodiment of the invention uses the image-reversing technique
disclosed in British Pat. No. 904,364, page 19, lines 1 through 41. In
this process, the dye-releasing compounds are used in combination with
physical development nuclei in a nuclei layer contiguous to the
photosensitive silver halide negative emulsion layer. The film unit
contains a silver halide solvent, preferably in a rupturable container
with the alkaline processing composition.
The film unit or assembly used in the present invention may be used to
produce positive images in single- or multicolors. In a three-color
system, each silver halide emulsion layer of the film assembly will have
associated therewith a dye-releasing compound which releases a dye
possessing a predominant spectral absorption within the region of the
visible spectrum to which said silver halide emulsion is sensitive
(initially of after forming the coordination complex), i.e., the
blue-sensitive silver halide emulsion layer will have a yellow or
yellow-forming dye-releaser associated therewith, the green-sensitive
silver halide emulsion layer will have a magenta or magenta-forming
dye-releaser associated therewith, and the red-sensitive silver halide
emulsion layer will have a cyan or cyan-forming dye-releaser associated
therewith, at least one of the dye-releasers being a compound in
accordance with the present invention. The dye-releaser associated with
each silver halide emulsion layer may be contained either in the silver
halide emulsion layer itself or in a layer contiguous to the silver halide
emulsion layer.
The concentration of the dye-releasing compounds that are employed in the
present invention may be varied over a wide range, depending upon the
particular compound employed and the results which are desired. For
example, the dye-releasers of the present invention may be coated in
layers by using coating solutions containing between about 0.5 and about 8
percent by weight of the dye-releaser distributed in a hydrophilic
film-forming natural material or synthetic polymer, such as gelatin,
polyvinyl alcohol, etc, which is adapted to be permeated by aqueous
alkaline processing composition.
Depending upon which CAR is used in the present invention, a variety of
silver halide developing agents can be employed. In certain embodiments of
the invention, any silver halide developing agent can be employed as long
as it cross-oxidizes with the dye-releasers described herein. The
developer may be employed in the photosensitive element to be activated by
the alkaline processing composition. Specific examples of developers which
can be employed in this invention include:
N-methylaminophenol
Phenidone (1-phenyl-3-pyrazolidone)
Dimenzone (1-phenyl-4,4-dimethyl-3-pyrazolidone) aminophenols
1-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone
N,n-diethyl-p-phenylenediamine
N,n,n',n'-tetramethyl-p-phenylenediamine
3-methyl-N,N-diethyl-p-phenylenediamine
3-methoxy-N-ethyl-N-ethoxy-p-phenylenediamine, etc.
The non-chromogenic developers in this list are preferred, however, since
they avoid any propensity of staining the dye image-receiving layer.
In a preferred embodiment of the invention, the silver halide developer
employed in the process becomes oxidized upon development and reduces
silver halide to silver metal. The oxidized developer then cross-oxidizes
the dye-releasing compound. The product of cross-oxidation then undergoes
alkaline hydrolysis, thus releasing an imagewise distribution of
diffusible azo dye which then diffuses to the receiving layer to provide
the dye image. The diffusible moiety is transferable in alkaline
processing composition either by virtue of its self-diffusivity or by its
having attached to it one or more solubilizing groups, for example, a
carboxy, sulpho, sulphonamido, hydroxy or morpholino group.
In using the dye-releasing compounds according to the invention which
produce diffusible dye images as a function of development, either
conventional negative-working or direct-positive silver halide emulsions
may be employed. If the silver halide emulsion employed is a
direct-positive silver halide emulsion, such as an internal-image emulsion
designed for use in the internal image reversal process or a fogged,
direct-positive emulsion such as a solarizing emulsion, which is
developable in unexposed areas, a positive image can be obtained in
certain embodiments on the dye image-receiving layer. After exposure of
the film unit, the alkaline processing composition permeates the various
layers to initiate development of the exposed photosensitive silver halide
emulsion layers. The developing agent present in the film unit develops
each of the silver halide emulsion layers in the unexposed areas (since
the silver halide emulsions are direct-positive ones), thus causing the
developing agent to become oxidized imagewise corresponding to the
unexposed areas of the direct-positive silver halide emulsion layers. The
oxidized developing agent then cross-oxidizes the dye-releasing compounds
and the oxidized form of the compounds then undergoes a base-catalyzed
reaction to release the dyes imagewise as a function of the imagewise
exposure of each of the silver halide emulsion layers. At least a portion
of the imagewise distributions of diffusible dyes diffuse to the
image-receiving layer to form a positive image of the original subject.
After being contacted by the alkaline processing composition, a
pH-lowering layer in the film unit or image-receiving unit lowers the pH
of the film unit or image receiver to stabilize the image.
Internal-image silver halide emulsions useful in this invention are
described more fully in the November 1976 edition of Research Disclosure,
pages 76 through 79, the disclosure of which is hereby incorporated by
reference.
The various silver halide emulsion layers of a color film assembly employed
in this invention can be disposed in the usual order, i.e., the
blue-sensitive silver halide emulsion layer first with respect to the
exposure side, followed by the green-sensitive and red-sensitive silver
halide emulsion layers. If desired, a yellow dye layer or a yellow
colloidal silver layer can be present between the blue-sensitive and
green-sensitive silver halide emulsion layers for absorbing or filtering
blue radiation that may be transmitted through the blue-sensitive layer.
If desired, the selectively sensitized silver halide emulsion layers can
be disposed in a different order, e.g., the blue-sensitive layer first
with respect to the exposure side, followed by the red-sensitive and
green-sensitive layers.
The rupturable container employed in certain embodiments of this invention
can be of the type disclosed in U.S. Pat. Nos. 2,543,181; 2,643,886;
2,653,732; 2,723,051; 3,056,492; 3,056,491 and 3,152,515. In general, such
containers comprise a rectangular sheet of fluid- and air-impervious
material folded longitudinally upon itself to form two walls which are
sealed to one another along their longitudinal and end margins to form a
cavity in which processing solution is contained.
Generally speaking, except where noted otherwise, the silver halide
emulsion layers employed in the invention comprise photosensitive silver
halide dispersed in gelatin and are about 0.6 to 6 microns in thickness;
the dye-releasers are dispersed in an aqueous alkaline solution-permeable
polymeric binder, such as gelatin, as a separate layer about 0.2 to 7
microns in thickness; and the alkaline solution-permeable polymeric
interlayers, e.g., gelatin, are about 0.2 to 5 microns in thickness. Of
course, these thicknesses are approximate only and can be modified
according to the product desired.
Scavengers for oxidized developing agent can be employed in various
interlayers of the photographic elements of the invention. Suitable
materials are disclosed on page 83 of the November 1976 edition of
Research Disclosure, the disclosure of which is hereby incorporated by
reference.
Any material can be employed as the image-receiving layer in this invention
as long as the desired function of mordanting or otherwise fixing the dye
images is obtained. The particular material chosen will, of course, depend
upon the dye to be mordanted. Suitable materials are disclosed on pages 80
through 82 of the November 1976 edition of Research Disclosure, the
disclosure of which is hereby incorporated by reference.
Use of a pH-lowering material in the film units employed in this invention
will usually increase the stability of the transferred image. Generally,
the pH-lowering material will effect a reduction in the pH of the image
layer from about 13 or 14 to at least 11 and preferably 5 to 8 within a
short time after imbibition. Suitable materials and their functioning are
disclosed on pages 22 and 23 of the July 1974 edition of Research
Disclosure and pages 35 through 37 of the July 1975 edition of Research
Disclosure, the disclosures of which are hereby incorporated by reference.
A timing or inert spacer layer can be employed in the practice of this
invention over the pH-lowering layer which "times" or controls the pH
reduction as a function of the rate at which alkali diffuses through the
inert spacer layer. Examples of such timing layers and their functioning
are disclosed in the Research Disclosure articles mentioned in the
paragraph above concerning pH-lowering layers.
The alkaline processing composition employed in this inventi | | |
