Diffusion transfer photosensitive film unit for silver transfer image

There are described diffusion transfer photosensitive film units which include a novel antihalation layer comprising an antihalation material, titanium dioxide and a binder. Diffusion transfer film units prepared according to the invention provide silver images of enhanced resolution, film speed and sharpness.

This application is directed to photography and, more particularly, to 
diffusion transfer photographic film units and processes wherein a silver 
transfer reflection print is provided. The diffusion transfer photographic 
film units include a novel antihalation layer comprising an antihalation 
material, titanium dioxide and a binder. 
BACKGROUND OF THE INVENTION 
Diffusion transfer photography is well known and has been utilized to 
provide "instant" images in black and white in both a peel-apart format 
and an integral format. For example, U.S. Pat. No. 2,543,181 describes 
instant peel-apart black and white silver transfer films and U.S. Pat. No. 
4,489,152 describes instant integral black and white silver transfer 
films. 
Diffusion transfer photographic film units which include photosensitive 
silver halide for forming images typically comprise a support carrying a 
photosensitive silver halide emulsion, a silver halide solvent, a silver 
reducing agent for converting the exposed silver halide to metallic silver 
and an alkaline activator to obtain a pH at which the silver halide can be 
effectively developed. A visible image is formed in these materials by 
exposing the photosensitive silver halide to an imagewise pattern of 
activating light to form a latent image, dissolving the unexposed silver 
halide, transferring the dissolved unexposed silver halide to an 
image-receiving layer and reducing the transferred unexposed silver halide 
to form a positive image in reduced silver. 
It is well known in the art that light used to expose the photosensitive 
silver halide emulsion of a diffusion transfer photographic film unit may 
be diffusely transmitted therethrough to the support and, then be 
reflected back to the emulsion causing it to be reexposed. Given the 
distance of the support and the interfaces (of the other layers of the 
film unit between the support and the emulsion layer) from the emulsion 
layer, the reexposure of the emulsion occurs at points laterally removed 
from the initial exposure, hence, with reexposure by such reflected light, 
a "halo" appears around the site of initial exposure of the emulsion. As 
will be appreciated by one of skill in the relevant art, the halo effect 
or "halation" reduces the resolution or sharpness of the film and, 
accordingly, of the resultant image produced by such film. 
As would be understood by those of skill in the art, halation may be 
substantially prevented or reduced by absorbing any light which may be 
transmitted by the photosensitive silver halide emulsion layer. It is 
generally known in the art to prevent halation by, for example, coating 
the support of the film unit remote from where the exposure is made with 
either dyes or pigments, or coating an antihalation layer which contains 
gelatin and dyes or silver between the support of the film unit remote 
from where the exposure is made and the photosensitive silver halide 
emulsion layer. Generally, the antihalation dyes incorporated within an 
antihalation layer are either bleached, decolorized or removed from the 
layer after photographic processing, e.g., to prevent its color from 
reappearing in time as it is slowly reoxidized, while antihalation dyes or 
pigments incorporated in the support remain. 
U.S. Pat. No. 4,039,333 is directed to an antihalation layer and describes 
photographic materials for use in conventional photography which include a 
combination of at least two particular binders together with an 
antihalation material, e.g., carbon black, which provide improved 
antihalation. 
U.S. Pat. No. 4,751,174 is directed to a silver halide photographic 
material for use in conventional photography and describes the inclusion 
of a light-insensitive silver halide emulsion layer between a 
light-sensitive silver halide emulsion layer and the support which 
decreases halation. 
U.S. Pat. No. 4,957,856 is directed to a subbing layer having a decoloring 
capable antihalation function and describes a silver halide photographic 
material for use in conventional photography which includes the subbing 
layer which comprises a binder, a polymer, i.e., mordant, described 
therein, a dye described therein and a surface active agent. As reported 
therein, the particular mordant and dye combination improves the 
processing time decolorization. 
U.S. Pat. No. 4,990,432 is directed to a silver halide photographic 
light-sensitive material for use in conventional photography and which 
includes a reflective support having a transmission density of not more 
than 0.8, a silver halide emulsion layer and an antihalation layer formed 
closer to the support than the silver halide emulsion layer. As reported 
therein, the antihalation layer prevents any reflected light incident into 
the silver halide emulsion layer. 
U.S. Pat. No. 5,318,885 is directed to an antihalation layer and describes 
a photographic element for use in conventional photography which includes 
a reflective support, one or more photosensitive silver halide emulsion 
layers, and a colored, i.e., blue or gray grains of silver in the form of 
platelets, antihalation layer interposed between the support and the 
photosensitive layers. 
U.S. Pat. No. 5,665,528 is directed to a quickly decolorized new 
antihalation dye which is incorporated in an antihalation layer of a 
silver halide photographic material that is conventionally processed. 
Diffusion transfer color photographic integral-type film units are known in 
the art, such as described, for example, in U.S. Pat. No. 5,422,233, which 
include layers comprising image-forming materials, e.g., dye developers, 
interposed between an opaque support and a photosensitive silver halide 
emulsion layer, which may also function as antihalation layers given the 
light absorption ability of the dye developers. Black and white diffusion 
transfer photographic film units, by definition, do not contain such color 
image-forming materials and, therefore, generally contain some provision 
for antihalation. 
The integral black and white instant films described in U.S. Pat. No. 
4,489,152 include an opaque layer, i.e., carbon black and 
polyvinylpyrrolidone, between the silver halide emulsion layer and the 
image-receiving layer so that the film unit may be developed outside the 
camera, and a light-reflecting layer, i.e., a white layer of titanium 
dioxide, positioned between the carbon black layer and the image-receiving 
layer to provide a white background against which the silver transfer 
image may be viewed. It would be understood by those of skill in the 
relevant art that the carbon black layer disclosed therein would be able 
to function as an antihalation layer, i.e., absorb substantially all of, 
if not all of, the light which passed through the emulsion layer during 
photoexposure. 
U.S. Pat. No. 4,078,933 is directed to a silver halide photographic 
light-sensitive element for use in conventional photography which includes 
at least one silver halide emulsion layer and at least one hydrophilic 
colloid layer containing at least one dye wherein the dye is useful in 
antihalation and can be decolorized readily and completely. According to 
the description provided therein, to be satisfactory, the subject dyes 
must be photographically inert, have a good mordanting property, i.e., 
remain in the layer, and be decolorized or removed by dissolving during 
photographic processing, i.e., good bleachability. 
U.S. Pat. No. 4,294,917 is directed to a dye antihalation layer and 
describes a photographic silver halide material for use in conventional 
photography which includes in at least one layer a solid dispersion of a 
water-insoluble antihalation dye. As reported therein, after completion of 
the conventional photographic processing, no dye in the antihalation 
underlayer was visible and, the dye was completely and irreversibly 
destroyed in the silver halide developing solution and no discolouration 
of any of the processing solutions was visible. 
It is known in the art that use of antihalation materials may result in a 
loss of emulsion sensitivity or speed. Methods have been devised to reduce 
such losses in speed associated with the use of antihalation materials, 
by, for example, incorporating a layer of a light-reflecting pigment, such 
as, for example, titanium dioxide, e.g., in between the support containing 
the antihalation materials and the photosensitive silver halide emulsion 
layer of the film unit, or, in between the antihalation layer and the 
photosensitive silver halide emulsion layer, preferably, adjacent the 
photosensitive silver halide emulsion layer. The reflecting layer reflects 
back substantially all of the exposure light to the silver halide emulsion 
and, given the proximity of the reflecting layer to the photosensitive 
silver halide emulsion layer, causes reexposure to made in substantially 
the same point as the original exposure, hence, preventing "halo" 
formation, such as described, for example, in U.S. Pat. No. 4,563,406 
which describes a photographic support coated with, in succession, a 
colorant layer (antihalation layer), a white pigment layer and a silver 
halide emulsion layer; or, U.S. Pat. No. 4,615,966 which describes a 
diffusion transfer photographic instant film unit which includes a 
light-reflecting spacer layer disposed between a silver halide layer and 
the associated layer of image dye-providing material to increase effective 
film speed as a result of the reflection of light back to the silver 
halide. 
While such methods of preventing or reducing halation in photographic 
elements have been found to provide advantageous results as are described 
in the above-mentioned patents, nevertheless their performance in some 
photographic systems is not completely satisfactory. For example, in some 
diffusion transfer photographic systems, the use of such methods have been 
found to contribute to undesirable silver image resolution and speed loss 
thereby adversely affecting the aesthetic qualities of the final 
photograph. 
It would be desirable to have diffusion transfer photographic black and 
white film units which include suitable antihalation materials, and which, 
at the same time, provide suitable film speed and resolution in the 
finished photograph, and suitable sharpness as visually perceived. 
As the state of the art for diffusion transfer photographic film units 
continues to move forward, new techniques and materials continue to be 
developed by those of skill in the art in order to meet the performance 
criteria required of such materials. The present invention is drawn to 
novel diffusion transfer black and white photosensitive film units which 
include an antihalation layer comprising an antihalation material, 
titanium dioxide and a binder; an aqueous alkaline processing composition 
which includes a suitable amount of a light-reflecting pigment, 
preferably, titanium dioxide, to form a light-reflecting layer during 
photographic processing which provides a white background against which to 
view the final image; a silver reducing agent; and a silver halide 
solvent. 
SUMMARY OF THE INVENTION 
There is provided according to the invention a diffusion transfer 
photosensitive black and white film unit comprising: 
a photosensitive element which includes a support and carried by the 
support, in succession, an antihalation layer comprising from about 1.5% 
to about 25% by weight of an antihalation material, from about 30% to 
about 50% by weight of titanium dioxide and from about 25% to about 68.5% 
by weight of a binder, and a photosensitive silver halide layer; 
an image-receiving element in superposed relationship or adapted to be 
placed in superposed relationship with the photosensitive element so as to 
receive image silver released from the photosensitive element and thereby 
form an image, wherein the image-receiving element includes a transparent 
support and carried by the transparent support, an image-receiving layer 
comprising a silver nucleating material; 
means for providing an aqueous alkaline processing composition comprising 
an amount of a light-reflecting pigment capable of forming a 
light-reflecting layer during photographic development which provides a 
white background against which to view the final image; 
a silver reducing agent; and 
a silver halide solvent. 
In a preferred embodiment the opaque support of the photosensitive element 
carries, in succession, a polymeric acid layer, a timing layer, a spacer 
layer, an interlayer, an antihalation layer comprising from about 1.5% to 
about 25% by weight of an antihalation material, from about 30% to about 
50% by weight of titanium dioxide and from about 25% to about 68.5% by 
weight of a binder, a photosensitive silver halide layer and a topcoat 
layer; the transparent support of the image-receiving element carries, in 
succession, an image-receiving layer comprising a silver nucleating 
material, an undercoat layer comprising a silver image toning material, 
and an overcoat layer comprising a material capable of clearing the 
light-absorbing capacity of the optical filter agents incorporated in the 
aqueous alkaline processing composition; and the processing composition 
includes the silver reducing agent and the silver halide solvent. 
In operation, the film units of the present invention are exposed to an 
imagewise pattern of electromagnetic radiation through the transparent 
support of the image-receiving element and subsequently developed in the 
presence of alkali whereby there is formed in the image-receiving layer a 
visible image in metallic silver. 
More particularly, the exposed photosensitive silver halide, when developed 
with the aqueous alkaline processing composition released into the film 
unit from the pod, which is incorporated in the film unit, is reduced to 
metallic silver and remains in its original location in the film unit 
whereas the unexposed photosensitive silver halide is complexed by the 
silver halide solvent and transfers to the image-receiving layer. At the 
nucleating sites in the image-receiving layer, the soluble silver complex 
is developed and the complexed silver is reduced to metallic silver. A 
light-reflecting layer is provided to the exposed film unit from the 
processing composition during photographic processing which provides the 
white background against which the final image is viewed. 
During exposure, light which is diffusely transmitted through the 
photosensitive silver halide emulsion layer is partially reflected back 
into the emulsion layer at about the same point of original exposure by 
the titanium dioxide particles present in the antihalation layer which is 
positioned adjacent to the emulsion layer nearer the, e.g., opaque, 
support. 
Moreover, any light used to expose the film unit that is diffusely 
transmitted through the photosensitive silver halide emulsion layer, as 
well as through the antihalation layer and that is reflected back from 
the, e.g., opaque support, or the interfaces of the other layers between 
the antihalation layer and the, e.g., opaque support, is substantially 
absorbed by the antihalation material of the antihalation layer. The 
presence of the titanium dioxide particles within the antihalation layer 
effectively increase the path length of the reflected light such that the 
reflected light has a greater probability of interacting with one or more 
of the antihalation dyes and thus being absorbed and therefore being 
prevented from reentering the photosensitive silver halide emulsion layer 
to result in halation. 
The positioning of the light-reflecting layer with respect to the 
antihalation layer in the processed photographic laminates of the 
invention removes the need to bleach, decolorize or remove the 
antihalation material therefrom. 
It has been found that the antihalation layer utilized according to the 
present invention can minimize or virtually eliminate undesired halation 
in the photosensitive silver halide emulsion layer while providing 
suitable film speed and resolution, and suitable sharpness as visually 
perceived.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is seen a preferred embodiment of a 
diffusion transfer film unit 8 comprising a photosensitive element 38 and 
an image-receiving element 40. As illustrated, photosensitive element 38 
includes an opaque support 10, a polymeric acid layer 12, a timing layer 
14, a spacer layer 16, an interlayer 18, an antihalation layer 20, a 
photosensitive silver halide layer 22 and a topcoat 24; and 
image-receiving element 40 includes an overcoat 30, an undercoat 32, an 
image-receiving layer 34 and a transparent support 36. Each of the layers 
carried by opaque support 10 and transparent support 36 functions in a 
predetermined manner to provide desired diffusion transfer photographic 
processing as is known in the art. Also as illustrated, the alkaline 
environment required for photographic development is provided by an 
aqueous alkaline processing composition 26 which is released from the 
rupturable container or pod 28 positioned between layers 24 and 30. 
Opaque support 10 and transparent support 36 may be of any suitable 
material. Any suitable support known in the relevant art may be employed. 
Specific examples of suitable supports include synthetic polymeric films, 
such as, polyethylene terephthalate, polycarbonate, polyvinylchloride, 
polystyrene, polyethylene, polypropylene, polyimide and 
polyethylene-2,6-naphthalene dicarboxylate. The above-described supports 
can be made opaque by incorporating pigments therein such as carbon black. 
Other supports include paper supports, such as photographic raw paper, 
printing paper, baryta paper and resin-coated paper having paper laminated 
with pigmented thermoplastic resins, fabrics, glass and metals. A subcoat 
may be added to the face of the support which carries the photosensitive 
materials to increase adhesion. For example, a polyester base coated with 
a gelatin subcoat has been found to enhance adhesion of aqueous-based 
layers. As is known in the art, the opaque support 10 may include 
antihalation materials. In an embodiment of the present invention wherein 
the support of the photosensitive element is transparent, a layer 
comprising a suitable light-absorbing material, such as, carbon black, is 
coated thereon before the antihalation layer to enable photographic 
processing outside the camera in ambient light without reexposure of the 
photosensitive silver halide layer. 
Any suitable anti-reflection coating may be, and is preferably, provided on 
the outer surface of transparent support 36. Suitable anti-reflection 
coatings are widely known in the art and include those described in U.S. 
Pat. No. 3,793,022. 
Polymeric acid layer 12 reduces the environmental pH of the film unit, 
subsequent to transfer image formation. As disclosed, for example, in U.S. 
Pat. No. 3,362,819, the polymeric acid layer may comprise a nondiffusible 
acid-reacting reagent adapted to lower the pH from the first (high) pH of 
the processing composition favorable for photographic development to a 
second (lower) pH less favorable for photographic development. The 
acid-reacting reagent is preferably a polymer which contains acid groups, 
e.g., carboxylic acid or sulfonic acid groups, which are capable of 
forming salts with alkaline metals or with organic bases, or potentially 
acid-yielding groups such as anhydrides or lactones. Thus, reduction in 
the environmental pH of the film unit is achieved by the conduct of a 
neutralization reaction between the alkali provided by the processing 
composition and a layer which comprises immobilized acid-reactive sites 
and which functions as a neutralization layer. Preferred polymers such a 
neutralization layer comprise such polymeric acids as cellulose acetate 
hydrogen phthalate; polyvinyl hydrogen phthalate; polyacrylic acid; 
polystyrene sulfonic acid; and maleic anhydride copolymers and half esters 
thereof. 
Further, the polymeric acid layer can be applied, if desired, by coating 
the support layer with an organic solvent-based or water-based coating 
composition. A polymeric acid layer which is typically coated from an 
organic-based composition comprises a mixture of a half butyl ester of 
polyethylene/maleic anhydride copolymer with polyvinyl butyral. A suitable 
water-based composition for the provision of a polymeric acid layer 
comprises a mixture of a water soluble polymeric acid and a water soluble 
matrix, or binder, material. Suitable water-soluble polymeric acids 
include ethylene/maleic anhydride copolymers and poly(methyl vinyl 
ether/maleic anhydride). Suitable water-soluble binders include polymeric 
materials such as polyvinyl alcohol, partially hydrolyzed polyvinyl 
acetate, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl 
cellulose, polymethylvinylether or the like, as described in U.S. Pat. No. 
3,756,815. As examples of useful polymeric acid layers, in addition to 
those disclosed in the aforementioned U.S. Pat. Nos. 3,362,819 and 
3,756,815, mention may be made of those disclosed in U.S. Pat. Nos. 
3,765,885; 3,819,371; 3,833,367 and 3,754,910. 
Timing layer 14 is used in association with polymeric acid layer 12 to 
control or "time" the pH reduction so that it is not premature and does 
not interfere with the development process but may also act as a diffusion 
control interlayer. Any suitable timing layer may be used in the film 
units of the present invention. Suitable spacer or "timing" layers useful 
for this preferred purpose are well known in the relevant art, such as, 
for example, those described in U.S. Pat. Nos. 3,421,893; 3,575,701; 
3,362,819; 4,201,587; 4,288,523; 4,297,431; 4,391,895; 4,426,481; 
4,458,001; 4,461,824; 4,457,451 and 5,593,810. It is preferred to use a 
timing layer which includes a copolymer of butyl acrylate, diacetone 
acrylamide, carbomethoxy methyl acrylate, methyl methacrylate and 
methacrylic acid in the film units of the present invention. 
Spacer layer 16 and interlayer 18 are employed as diffusion control 
interlayers and any such layers known in the art may be used in the film 
units of the invention. For example, the interlayer may include a suitable 
hardener for hardening a cross-linkable colloid such as gelatin. It is 
preferred to use an interlayer comprising a mixture of about 95 parts of a 
latex comprising 2-methyl-2-propenoic acid polymer with butyl 
2-propenoate, N-(1,1-dimethyl)-3-oxybutyl), 2-propenoimide, ethyl benzene 
and 2-propenoic acid and about 5 parts of polyacrylamide, 
1-hydroxymethyl-5,5-dimethylhydantoin and succindialdehyde. It is 
preferred that the spacer layer comprise gelatin. 
Antihalation layer 20 is intended to: (a) allow a portion of the light 
speed to expose the film unit to reflect back into the emulsion layer and 
thus boost the speed of the film and (b) attenuate reflected light from 
the, e.g., opaque support, and he interfaces of the other layers between 
the anithalation layer and the, e.g., opaque support from reentering the 
photosensitive silver halide emulsion layer and thus causing a reexposure 
laterally displaced from the original point of entry resulting in 
halation. 
As stated earlier, antihalation layer 20 comprises from about 1.5% to about 
25% by weight of an antihalation material which need not be bleached, 
decolorized or removed during photographic processing, from about 30% to 
about 50% by weight of titanium dioxide and from about 25% to about 68.5% 
by weight of a binder, preferably, gelatin. It is preferred that the 
antihalation material is any suitable antihalation dye, or combination of 
antihalation dyes, known in the art. Antihalation materials typically 
render the antihalation layer visibly colored to some extent depending 
upon the nature and amount of the specific material employed. Film unit 8 
of FIG. 1 is exposed and viewed through the transparent support of the 
image-receiving element. In addition, antihalation layer 20 is positioned 
in the photographic laminate 8a depicted in FIG. 2 between 
light-reflecting layer 28a and opaque support 10 whereas image-carrying 
layer 34a is adjacent transparent support 36 and between transparent 
support 36 and light-reflecting layer 28a. Based upon the location of 
antihalation layer 20 with respect to image-carrying layer 34a, it would 
be understood by those of skill in the relevant art that the antihalation 
material need not be decolorized or removed post-processing as it is 
shielded from view by light-reflecting layer 28a. 
Any suitable antihalation material known in the relevant art for use in 
diffusion transfer photography may be employed in antihalation layer 20, 
such as, for example, any suitable antihalation material described in U.S. 
Pat. Nos. 2,543,181; 2,653,872; 2,977,226; 3,933,798; 4,088,487; 
4,139,704; 4,140,689; 4,140,680; 4,186,001; 4,187,225; 4,210,752; 
4,258,118; 4,258,119; 4,259,493; 4,277,406; 4,277,407; 4,282,160; 
4,283,537; 4,283,538; 4,290,950; 4,290,951; 4,290,955; 4,304,833; 
4,304,834; 4,307,017; 4,310,673; 4,311,847; 4,316,950; 4,345,017; 
4,416,971; 4,429,142; and 4,617,402. As stated earlier, it is preferred to 
use an antihalation dye(s) as the antihalation material. It is 
particularly preferred to use a combination of magenta, cyan and yellow 
color filter dyes as the antihalation dyes, and a particularly preferred 
combination of such dyes is quinacridone red zeta (Violet 19), copper 
phthalocyanine and benzidine yellow, respectively. 
Suitable antihalation dyes may be commercially obtained or prepared 
according to reactions which are well known by those skilled in the art 
and such reactions will be particularly apparent from the detailed 
descriptions of the preparation of various antihalation dyes which are 
provided in the Examples. In addition, any suitable form, e.g., anatase or 
rutile, of titanium dioxide, prepared using any suitable method, may 
comprise antihalation layer 20. 
The antihalation materials and the titanium dioxide comprising antihalation 
layer 20 may be used in any amount within the ranges specified required to 
accomplish their intended purpose(s). The amount necessary in any specific 
instance is dependent upon a number of factors such as, for example, the 
specific antihalation material or form of titanium dioxide utilized, the 
type of photosensitive element and the result desired. Routine scoping 
tests may be conducted to ascertain the concentration which is appropriate 
for any given diffusion transfer black and white photographic film unit. 
As stated earlier, the antihalation layer of the present invention 
comprises from about 1.5% to about 25% by weight of an antihalation 
material, from about 30% to about 50% by weight of titanium dioxide, and 
from about 25% to about 68.5% by weight of a binder. It is preferred that 
the antihalation layer of the invention comprise from about 5% to about 
20% by weight of an antihalation material, from about 40% to about 48% by 
weight of titanium dioxide, and from about 32% to about 55% by weight of a 
binder. It is particularly preferred that the antihalation layer of the 
invention comprise about 12% by weight of an antihalation material, about 
44% by weight of titanium dioxide, and about 44% by weight of a binder. 
Gelatin is the preferred binder. 
It is preferred to provide the components of the antihalation layer of the 
invention in an amount calculated to provide a coated coverage in the 
range of from about 1500 mg/M.sup.2 to about 2200 mg/m.sup.2. In a 
preferred embodiment antihalation layer 20 includes about 400 mg/m.sup.2 
to about 1000 mg/.sup.2 of titanium dioxide. 
Photosensitive silver halide layer 22 may comprise any suitable 
photosensitive silver halide known in the art such as silver chloride, 
bromide, iodobrornide, chlorobromide, etc., and it may be prepared in situ 
or ex situ by any known method. It is preferred to use silver iodobrornide 
as the photosensitive silver halide. Any type of silver halide emulsion 
may be utilized, such as, for example, core shell, tabular, as well as, 
any of the variety of silver halide crystal shapes known in the art, e.g., 
cubic or octahedral. 
The photosensitive silver halide comprising photosensitive silver halide 
layer 22 is typically prepared as an emulsion which is typically an 
aqueous emulsion, and any conventional silver halide precipitation 
techniques may be employed in the preparation of the emulsions. The silver 
halide emulsions may be spectrally sensitized by any suitable spectral 
sensitization technique to extend the photographic sensitivity to 
wavelengths other than those absorbed by the unsensitized silver halide. 
Examples of typical suitable sensitizing materials include cyanine dyes, 
merocyanine dyes, styryl dyes, hemicyanine dyes and oxanole dyes. In 
addition to spectral sensitization, the silver halide emulsions may be 
chemically synthesized using any known suitable chemical sensitization 
technique. Many chemical sensitization methods are known in the art. The 
film units of the present invention may include more than one 
photosensitive silver halide layers. 
The silver halide emulsion is generally added to photosensitive silver 
halide layer 22 in an amount calculated to provide a coated coverage in 
the range from about 0.5 to about 15.0 mmol/m.sup.2, and preferably from 
about 1.0 to about 8.0 mmol/m.sup.2. 
Any suitable silver halide solvent may be used in the film units of the 
present invention such as, for example, sodium or potassium thiosulfate, 
sodium thiocyanate and uracil. Also, a silver halide solvent precursor may 
be used. 
Any suitable silver reducing agent may be used in the film units of the 
present invention, and these may be selected from among those commonly 
used in diffusion transfer photographic film units, such as, for example, 
reductic acid and its derivatives; hydroxylamine and its derivatives; 
hydroquinone and its derivatives, e.g., 2-chlorohydroquinone; aminophenol 
derivatives, e.g., 4-aminophenol and 3,5-dibromophenol; catechol and its 
derivatives, e.g., 3-methoxycatechol; phenylenediamine derivatives, e.g., 
N,N-diethyl-p-phenylenediamine; and 3-pyrazolidone derivatives, e.g., 
1-phenyl-3-pyrazolidone and 4-hydroxymethyl-1-phenyl-3-pyrazolidone. The 
preferred silver reducing agents are 1-phenyl-3-pyrazolidone, commercially 
available under the tradename Phenidone, 
4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone, commercially available 
under the tradename Dimezone-S, and graphidones. Also preferred are 
aminoreductones, such as, for example, those disclosed in U.S. Pat. No. 
5,427,905. It is particularly preferred to use 
di(methoxyethyl)hydroxylamine as the silver reducing agent. 
The reducing agents may be used singly or in combination and are generally 
employed in amounts ranging from about 0.5 to about 20.0 mmol/m.sup.2, and 
preferably from about 8.0 to about 15.0 mmol/m.sup.2. 
The silver reducing agent(s) and the silver halide solvent(s) may be 
incorporated in photosensitive silver halide layer 22 together with the 
photosensitive silver halide, in a separate layer or layers of the film 
unit or, preferably, in processing composition 26 contained within 
rupturable container 28. 
Photosensitive silver halide layer 22 and other layers of the film unit, 
specifically, photosensitive element 38 and image-receiving element 40, 
contain various materials as binders. Any suitable binder may be used in 
the layers of the film unit of the invention. Suitable binders include 
water-soluble synthetic high-molecular weight compounds, such as, for 
example, polyvinyl alcohol and polyvinylpyrrolidone, and synthetic or 
natural high-molecular weight compounds, such as, for example, gelatin, 
gelatin derivatives, cellulose derivatives, proteins, starches and gum 
arabic. A single binder or a mixture of binders may be used. Gelatin is 
the preferred binder for use in each layer. The amount of binder used in 
each layer is generally from about 0.5 to about 5.0 g/m.sup.2, preferably 
from about 0.5 to about 2.0 g/m.sup.2. 
The layers of the film unit of the present invention which contain a 
crosslinkable colloid as a binder, e.g., gelatin, can be hardened by using 
any suitable organic and inorganic hardeners, such as, for example, those 
described in T. H. James, The Theory of the Photographic Process, 4th Ed., 
MacMillan, 1977, pp. 77-87. The hardeners can be used alone or in 
combination. It is preferred that the film units according to the present 
invention contain a hardener in interlayer 18. Any suitable hardener may 
be used in the film units of the present invention; however, aldehyde 
hardeners, e.g., 1-hydroxymethyl-5,5-dimethylhydantoin (Dantoin), 
succinaldehyde and glyoxal, have been found to be particularly useful when 
gelatin is employed as the binder. The hardeners are generally used in 
amounts ranging from about 1 to about 10% by weight of the gelatin coated 
and, preferably, about 6%. 
Topcoat 24 is intended to be an anti-abrasion, anti-blocking or protective 
layer and may be of any suitable material known to accomplish that purpose 
such as, for example, gelatin in combination with a cross-linking material 
to prevent the gelatin from being softened during processing. Other 
materials such as polyacrylamide, polyvinylpyrrolidone and polyvinyl 
alcohol may be used in the topcoat. In addition, as is well known in the 
relevant art, other suitable materials may also be included in the topcoat 
layer of the present invention, such as, for example, tinuvin and silica, 
e.g., Silcron G100. It is preferred to use gelatin as the topcoat 
material. It is particularly preferred to use gelatin and 
polymethylmethacrylate (about 0.2 micron) as the topcoat material. It is 
also particularly preferred to use gelatin and silica as the topcoat 
material. 
Overcoat 30 is intended to reduce the light-absorbing capacity of an 
optical filter agent(s) during photographic processing. The optical filter 
agent(s) are included in processing composition 26. The overcoat may 
comprise any suitable material known to perform such a function. It is 
preferred that the overcoat comprise nonylphenoxypolyoxyethylene, 
polyoxyethylene stearate and polyvinylpyrrolidone as disclosed in 
copending, commonly assigned U.S. patent application, Ser. No. 08/890,500 
which was filed on Jul. 9, 1997. 
Undercoat 32 is intended to (1) impart suitable adhesiveness to the film 
unit of the invention to prevent the coming apart of the film unit with 
time post-processing and (2) to tone the silver image of image-carrying 
layer 34a. Many suitable materials or, in effect, "glues," are known in 
the art to provide such adhesiveness, such as, for example, a carboxylated 
styrene-butadiene polymer latex as the glue, such as, for example, that 
which is commercially available under the tradename DL219. Materials 
suitable to tone the silver transfer image of the present invention to, 
e.g., enhance the stability of the silver image, are widely known in the 
art and any such material may be used in the undercoat. It is preferred to 
use a species formed from the combination of HAuCl.sub.3.3H.sub.2 O and 
thiocyanate salts as the toning agent. In addition, it is particularly 
preferred to include polyvinylpyrrolidone in the undercoat. 
Image-receiving layer 34 comprises any suitable material which is adapted 
to effect catalytic reduction of solubilized silver halide. The 
composition of silver precipitating layers is well known in the art, and a 
wide variety of silver precipitating materials, or nuclei, may be used in 
a wide variety of matrix, or binder, materials. Such silver precipitating 
nuclei include heavy metals and heavy metal compounds such as the metals 
of Groups IB, IIB, IVA, VIA and VIII, and the reaction products of metals 
of Group IB, IIB, IVA and VIII with elements of Group VIA. Typical 
suitable silver precipitating nuclei are disclosed in U.S. Pat. Nos. 
2,698,237 and 4,489,152 including metallic sulfides and selenides. Also 
suitable as silver precipitating agents are heavy metals such as silver, 
gold, platinum and palladium. Noble metals are typically preferred and are 
generally provided in a binder matrix as colloidal particles. The matrix, 
or binder, material may comprise a colloidal material such as gelatin, 
carboxymethylcellulose, a siliceous material and mixtures thereof. A 
particularly preferred image-receiving layer comprises colloidal palladium 
dispersed in colloidal silicas. Typically, the silver precipitating agents 
are present in a range of from about 1 to about 10 mg/m.sup.2 and the 
binder material in the range of from about 5 to about 500 mg/m.sup.2. A 
preferred binder to nuclei ratio is about 100:1. It is particularly 
preferred in the film units of the present invention that the 
image-receiving layer of the present invention comprise colloidal 
palladium dispersed in colloidal silica, a latex copolymer, 
polytetrafluoroethylene beads, 2-mercaptothiazoline, 2,4-dithiouracil, a 
gelatin dispersion of colloidal palladium nuclei and water, as disclosed 
in U.S. Pat. No. 4,489,152. 
Rupturable container 28 is a pressure-rupturable container. Such pods and 
like structures are common in the art and generally define the means for 
providing the processing composition to the photosensitive element and the 
image-receiving element. Any suitable rupturable container may be 
incorporated in the film units of the present invention. 
Processing composition 26 is distributed to the film unit of the invention 
from rupturable container 28 after exposure of photosensitive silver 
halide layer 22. Suitable processing compositions are widely known in the 
diffusion transfer art, and any suitable processing composition may be 
used in the film units of the present invention. The processing fluid 
typically contains a film-forming polymer adapted to provide viscosity 
suitable for distributing the processing fluid in a thin layer of 
substantially uniform thickness between the superposed sheet-like elements 
of the film unit. A preferred polymer is t-butyl acrylamide copolymer, 
although other polymers such as hydroxyethyl cellulose and sodium 
carboxymethyl cellulose also are suitable. Processing composition 26 
includes an alkali, such as sodium or potassium hydroxide. As stated 
earlier, the silver reducing agent(s) and the silver halide solvent(s) may 
be included in the processing composition of the present invention. In 
addition, development restrainers, antifoggants, toning agents and any 
other suitable photographic additives for use in diffusion transfer 
photographic film units may be included in the processing composition of 
the present invention or, in one or more of the layers of the film unit of 
the present invention. 
Referring now to FIG. 2, which shows a preferred photographic laminate 8a 
of the present invention formed by the processing of the film unit of FIG. 
1, layers designated by numerals used to designate layers in FIG. 1 
represent the same layers. Also, layers in FIG. 2 which are designated by 
numerals used to designate layers in FIG. 1 but now also include an "a" 
next to the numeral are intended to illustrate that these layers are not 
the same layers as in FIG. 1, but rather, that these layers have undergone 
some type of change from their initial state. More specifically, 
photosensitive silver halide layer 22 has been exposed and developed and, 
therefore, is designated developed silver halide layer 22a; polymeric acid 
layer 12 has neutralized the alkalinity of processing composition 26 and, 
therefore, is designated polymeric acid layer 12a; timing layer 14 has 
undergone hydrolysis to effect the pH drop, hence, is designated timing 
layer 14a; image-receiving layer 34 has received the silver transfer image 
and, therefore, is designated image-carrying layer 34a; and undercoat 
layer 32 has toned the silver transfer image residing in image-carrying 
layer 34a and, therefore, is designated 32a. 
Light-reflecting layer 28a is formed by the solidification of the stratum 
of processing composition 26 distributed after exposure. Evaporation of 
water from the applied layer of processing composition results in 
solidified light-reflecting layer 28a which permits the viewing 
thereagainst of image-carrying layer 34a through transparent support 36. 
Light-reflecting layer 28a comprises an amount of a light-reflecting 
pigment sufficient to provide a suitable white background against which 
the final image is viewed, such as, for example, that amount delivered 
from a processing composition which includes, for example, from about 30% 
to about 60% by weight of a light-reflecting pigment, preferably, titanium 
dioxide, which would be understood by those of skill in the relevant art 
to result in a coating of from about 20,000 to about 40,000 mg/m.sup.2 of 
titanium dioxide. In addition, light-reflecting layer 28a serves to 
laminate together developed silver halide layer 22a and image-carrying 
layer 34a to provide a final photographic laminate, such as, the preferred 
laminate 8a depicted in FIG. 2 herein. 
It should be noted that the film units of the invention may include other 
materials which are well known in the art for use in such film units. Such 
other materials include, for example, antifoggants, releasable 
antifoggants, antistatic agents, coating aids such as surfactants, 
activators and the like. 
The invention will now be described further in detail with respect to a 
specific preferred embodiment by way of an example, it being understood 
that these are intended to be illustrative only and the invention is not 
limited to the materials, procedures, amounts, etc. recited therein. All 
parts and percentages recited are by weight unless otherwise stated. 
EXAMPLE 
Two diffusion transfer photographic film units were prepared. More 
specifically, a "control" photosensitive element was prepared by coating 
the following layers, in succession, onto an opaque, i.e., carbon black 
filled, subcoated polyethylene terephthalate film of approximately 4 mil 
thickness: 
1. a polymeric acid layer comprising about 28,520 mg/m.sup.2 of a mixture 
of about 4 parts of a half-butyl ester of poly(ethylene/maleic anhydride) 
copolymer and about 1 part of polyvinyl butyral; 
2. a timing layer comprising a 49.1/30.0/10.0/7.2/3.7 copolymer of butyl 
acrylate/diacetone acrylamidelcarbomethoxy methyl acrylate/methyl 
methacrylate/methacrylic acid, in water, coated at a coverage of about 
7500 mg/m.sup.2 ; 
3. a spacer layer comprising about 1600 mg/m.sup.2 of gelatin; 
4. an interlayer comprising about 3000 mg/m.sup.2 of a mixture of about 95 
parts of a latex comprising 2-methyl-2-propenoic acid polymer with butyl 
2-propenoate, N-(1,1-dimethyl)-3-oxybutyl), 2-propenoimide, ethyl benzene 
and 2-propenoic acid and about 5 parts of polyacrylamide, about 345 
mg/m.sup.2 of 1-hydroxymethyl-5,5-dimethylhydantoin and about 10 
mg/m.sup.2 of succindialdehyde; 
5. an antihalation layer comprising about 800 mg/m.sup.2 of gelatin and 
about 220 mg/m.sup.2 of about 80/100/40 of benzidine yellow/quinacridone 
red zeta Violet 19)/copper phthalocyanine; 
6. a photosensitive silver halide layer comprising about 650 mg/m.sup.2 of 
silver iodobromide (1.0 microns) and about 2000 mg/m.sup.2 of gelatin; and 
7. a topcoat layer comprising about 467 mg/n.sup.2 of gelatin and about 600 
mg/m.sup.2 of polymethylmethacrylate (about 0.2 micron). 
The photosensitive element utilized in the "test" diffusion transfer 
photographic film unit was the same as described above except that layer 
5, i.e., the antihalation layer, further included about 800 mg/m.sup.2 of 
titanium dioxide. 
The image-receiving element used in each of the film units described above 
was prepared by coating the following layers, in succession, onto a 
transparent polyethylene terephthalate film of approximately 3.5 mil 
thickness: 
1. an image-receiving layer comprising about 1.4 mg/sq.m of colloidal 
palladium using a coating solution comprising about 60.13 g of a colloidal 
silica dispersion (about 30% silica), about 5.7 g of a 60.6/29/6.3/3.7/0.4 
latex copolymer of butylacrylate, diacetone acrylamide, styrene, 
methacrylic acid and acrylic acid, about 2.35 g of about 0.5 micron 
polytetrafluoroethylene beads, about 0.034 g of 2-mercaptothiazoline, 
about 0.017 g of 2,4-dithiouracil, about 4.55 g of a gelatin dispersion of 
colloidal palladium nuclei (about 0.62% palladium) and about 875 g of 
water; 
2. an undercoat layer comprising about 100 mg/m.sup.2 of 
polyvinylpyrrolidone, about 60 mg/m.sup.2 of a 60.6/29/6.3/3.7/0.4 latex 
copolymer of butylacrylate, diacetone acrylamide, styrene, methacrylic 
acid and acrylic acid, and about 3 mg/m.sup.2 of gold delivered as a 
species derived from HAuCl.sub.3.3H.sub.2 O and potassium thiocyanate; and 
3. an overcoat layer comprising about 15 mg/M.sup.2 of 
polyvinylpyrrolidone, about 43 mg/m.sup.2 
nonylphenoxypoly(ethyleneoxy)ethanol and about 42 mg/m.sup.2 of an 
ammoniated 1/1/0.1/0.1 tetrapolymer of diacetone acrylamide, methylacrylic 
acid, butylacrylate and styrene. 
For each of the film units, the photosensitive element was placed in a 
superposed relationship with the image-receiving element with their 
respective supports outermost and a rupturable container retaining an 
aqueous alkaline processing composition fixedly mounted at the leading 
edge of the superposed elements, by pressure-sensitive or heat-sensitive 
tapes to make a film unit, so that, upon application of compressive force 
to the container to rupture the marginal seal of the container, the 
contents thereof would be distributed between the superposed elements. The 
chemical composition of the aqueous alkaline processing composition 
utilized for the processing of the film units is set forth in TABLE I. 
TABLE I 
______________________________________ 
COMPONENT TS BY WEIGHT 
______________________________________ 
potassium hydroxide 6.6 
titanium dioxide 42.8 
uracil 2.7 
di(methoxyethyl)hydroxylamine 
1.2 
2-mercaptothiazoline 
0.003 
optical filter agent.sup.1 
1.4 
triethanolamine 0.2 
3,4,5,6-tetrahydropyrimidine 2-thiol 
0.001 
potassium thiosulfate 
0.02 
optical filter agent.sup.2 
0.3 
colloidal silica 0.6 
optical filter agent.sup.3 
0.13 
t-butyl acrylamide copolymer 
1.0 
water balance to 100 
______________________________________ 
1 
##STR1## 
2 
##STR2## 
3 
##STR3## 
Each film unit, after exposure to a sensitometric target, was passed 
through a pair of rollers set at a gap spacing of about 0.007 mm, at room 
temperature. The final images were viewed through their respective 
transparent supports of their respective image-receiving elements. 
The minimum (D.sub.min) and maximum (D.sub.max) reflection densities of the 
silver image of both film units were read on a MacBeth Densitometer, and 
the data are reported in TABLE II. 
TABLE II 
______________________________________ 
FILM UNIT D.sub.max 
D.sub.min 
______________________________________ 
Control 195 0.19 
Test 193 0.21 
______________________________________ 
It can be seen from the D.sub.max values reported in TABLE II that both the 
"control" and the "test" film units provide a silver image of suitable 
density in their respective image-carrying layers. As would also be 
appreciated by one of skill in the art from the D.sub.min data reported in 
TABLE II, the antihalation layer prepared according to the present 
invention provides substantially the same suitable background as the 
control. Hence, a diffusion transfer photographic film unit prepared 
according to the present invention provides an acceptable photograph, 
i.e., a final photograph of suitable silver image density and background. 
In addition, the film of each of the "control" and "test" diffusion 
transfer photographic film units was measured and would be well understood 
by those of skill in the relevant art to represent the relative exposure 
necessary to produce a 0.6 visual density, i.e., the amount of light to 
provide a greyish image discemable to the viewer's eye. Moreover, as will 
be appreciated by those of skill in the art, an increase in speed was 
measured by calculating the log relative exposure (in meter candle second 
(mcs) at constant exposure) necessary to produce the 0.6 visual density. 
Briefly, both the "control" and the "test" film units of this example were 
exposed with the same amount of light, i.e., about 0.5 mcs, through a 
filter of gradations, and then processed as described above. The film 
speed data are reported in TABLE III, and one stop is equal to about 30 
units of film speed. 
TABLE III 
______________________________________ 
FILM UNIT FILM SPEED 
______________________________________ 
Control about 122 
Test about 146 
______________________________________ 
As will be appreciated by those of skill in the art from the data reported 
in TABLE III, an antihalation layer prepared according to the present 
invention provides a faster film, i.e., the film speed for the "test" film 
unit is about 146 and the film speed for the "control" film unit is about 
122; hence, the differential is about 23 which represents slightly less 
than a two-fold increase in film speed or a gain of about one stop. 
In addition, the resolution, i.e., a measurement of the number of lines 
that can be resolved by the "control" and "test" diffusion transfer 
photographic film units was measured in "line pairs per millimeter." 
Briefly, as would be well understood by those of skill in the art, the 
film units were exposed to different amounts of light, specifically, plus 
and minus about 0.5 stop or about 15 units, with a visual readout 
incorporated therein, namely, an Air Force Resolution 3 Bar Target, and 
processed as described above. The resultant diffusion transfer film units 
were examined using a stereoscope for their ability to resolve the line 
pairs. As would be well understood, the greater the number of line pairs, 
the higher the resolving power, or visually perceived sharpness, of the 
film. The resolution data are reported in TABLE IV. 
TABLE IV 
______________________________________ 
FILM UNIT LINE PAIRS PER MILLIMETER 
______________________________________ 
Control about 8 
Test about 10.1 
______________________________________ 
As will be appreciated by those of skill in the art from the data reported 
in TABLE IV, an antihalation layer prepared according to the present 
invention provides an image of increased resolution, i.e., the resolution 
for the "test" film unit is about 10.1 and the resolution for the 
"control" film unit is about 8. In addition, when viewed by the 
photographer, the final image of the "test" film unit provides an image of 
perceptively greater sharpness than the image provided by the "control" 
film unit. Hence, film units prepared according to the present invention 
provide suitable resolution, e.g., suitable antihalation, and suitable 
film speed, and, in fact, an increase in film speed. 
As will be understood by those of skill in the art from the data reported 
in TABLES m and IV, the "test" film unit provides an increase in film 
speed along with an image of enhanced resolution. Those of skill in the 
art will understand that an increase in film speed through the 
incorporation of a layer according to the present invention may also bring 
about other distinct but interrelated advantages. For example, where such 
a film speed increasing layer is incorporated in the film unit, it will be 
understood by those of skill in the art that a concomitant decrease in 
silver halide grain size is then permissible. In other words, as would be 
appreciated by one of skill in the art, decreasing the grain size should 
result in a "slower" emulsion which will offset the film speed increase 
due to the incorporation of the film speed increasing layer, but will also 
result in less granularity as visually perceived from viewing the final 
image. 
Although the invention has been described in detail with respect to various 
preferred embodiments thereof, those skilled in the art will recognize 
that the invention is not limited thereto but rather that variations and 
modifications can be made which are within the spirit of the invention and 
the scope of the appended claims.