Color photographic reflection print material with improved keeping properties

Color photographic print materials are described in which the surface pH is between about 4.0 and 5.3. The photographic elements have improved keeping properties under adverse conditions of storage.

This invention relates to color photography. In a particular aspect it 
relates to color photographic materials intended to provide reflection 
prints. 
Such materials are well known in the art. They generally comprise a 
reflective support bearing one or more silver halide emulsion layers and, 
optionally, subbing layers, interlayers, and overcoat layers which provide 
desired physical and/or sensitometric properties to the photographic 
material. 
Photographic materials are known to exhibit changes in their sensitometric 
properties on storage. Exposure to conditions of high heat and high 
humidity can cause deterioration in the material which will be evidenced 
as an increase in minimum density (referred to as fog) after it is 
processed to provide a viewable image. Many compounds have been suggested 
for incorporation in photographic materials to protect these materials 
against deterioration on storage. While they generally are effective for 
their intended purpose there remains a need for additional or alternative 
means for reducing deterioration of photographic materials. 
Heretofore color photographic reflection print materials have had a surface 
pH of 5.6 or greater. 
We have found that if the pH of a photographic element is between about 4.0 
and 5.3, there is a significant improvement in keeping properties when 
compared with materials coated at a higher pH. 
Thus, in accordance with this invention, there is provided a color 
photographic print material comprising a support, one or more silver 
halide emulsion layers and optionally subbing layers, interlayers, and 
overcoat layers, wherein the element has a surface pH of between 4.0 and 
5.3. 
pH is measured at the surface of the photographic element with a surface pH 
electrode. Details of an appropriate technique are shown in Example 1, 
infra. 
Surface pH is representative of the overall pH of the element. The pH of an 
individual layer can be the same as the surface pH, or it can vary from 
that value. 
The pH of the element can be adjusted by adjusting the pH of one or more 
layers, prior to coating, to a value that will provide the desired surface 
pH to the element. Preferably it is the pH of the light sensitive emulsion 
layers that is adjusted. pH can be adjusted with any suitable acidic 
solution. The anion of the acid should be innocuous. A preferred acid is 
nitric acid. 
The present invention is particularly effective when employed with elements 
which are hardened with an active hardener, such as carbamoyl pyridinium 
hardeners and bisformadinium hardeners. 
Active hardeners are described in detail in U.S. Pat. Nos. 3,880,665; 
4,055,427; 4,063,952; UK Patents 1,487,283; EP Application 0,162,308 
published Nov. 27, 1985 and U.S. Application Ser. No. 022,192 filed Mar. 
5, 1987. 
The silver halide emulsions employed in the present invention preferably 
comprise silver chloride grains which are at least 80 mole percent silver 
chloride and less than 5 mole percent silver iodide, based on total silver 
halide. In a preferred form the silver halide grains consist essentially 
of silver chloride. Silver bromide can be present in concentrations of up 
to 20 mole percent, preferably up to 5 mole percent, based on total silver 
halide. Silver iodide can be present in concentrations of less than 5 mole 
percent, preferably less than 2 mole percent, based on total silver 
halide. 
The silver halide emulsions comprise vehicles conventional in the art. 
Preferred vehicles are hydrophilic colloids which can be employed alone or 
in combination with hydrophobic materials. Preferred hydrophilic colloids 
are gelatin, e.g., alkali-treated gelatin or acid-treated gelatin, and 
gelatin derivatives such as acetylated gelatin, and phthalated gelatin. 
The silver halide emulsions can be chemically and spectrally sensitized as 
is common in the art. The emulsions, or other layers of the material, can 
contain stabilizers, antifoggants, and other components intended to 
prolong the useful life of the material prior to exposure or of the 
photographic image obtained after development. 
The material will commonly contain one or more dye-forming couplers which 
will provide the final viewable image. However, other means of forming a 
viewable image can be employed. 
The material will have a reflective support which is typically a paper 
support coated with a polyolefin and a white pigment. Alternatively the 
support can be a reflective polymeric support. 
The material will typically contain additional layers, such as subbing 
layers to improve adhesion to the support, and interlayers and overcoat 
layers to separate and protect the sensitive layers and to carrying 
stabilizers, filter dyes and the like. 
Further details of the components of photographic reflection print 
materials, the way they are prepared and how they are processes to obtain 
a viewable image are provided in Research Disclosure, Nov. 1979, Item No. 
18716, published by Kenneth Mason Publications, Ltd., The Old 
Harbourmaster's, 8 North Street, Emsworth, Hampshire P010 7DD, England and 
from Atwell U.S. Pat. No. 4,269,927 issued May 26, 1981.

The following examples are intended to further illustrate this invention. 
EXAMPLE 1 
Single-color photographic print materials were prepared having the 
following structure: 
Overcoat layer: 
Gelatin (1.1 g/m.sup.2), bis(vinylsulfonyl)methyl ether hardener (1.75% 
based on the total gelatin weight) 
Blue sensitive silver halide emulsion layer: 
Chemically and spectrally sensitized monodisperse silver chloride negative 
emulsion (0.34 g Ag/m.sup.2) containing yellow-dye forming coupler: 
.alpha.-(4-(4-benzyloxyphenylsulfonyl)phenoxy)-.alpha.-(pivalyl)-2-chloro- 
5-(.alpha.-(2,4-di-t-amylphenoxy)butyramido)acetanilide (1.1 g/m.sup.2) 
dispersed in di-n-butyl phthalate coupler solvent (0.27 g/m.sup.2), 
gelatin (1.7 g/m.sup.2) 
Support: 
A paper stock consisting of a mixture of hard and soft wood pulp extrusion 
overcoated with a titanium dioxide and zinc oxide pigmented polyethylene 
layer coated with 1.61 g/m.sup.2 of gelatin. 
The materials differed in pH as described in Table I below. 
For the preparation of the material, three individual coating compositions 
were involved: 
A. Composition for the overcoat layer 
B. Composition for the silver halide emulsion 
C. Composition for the yellow coupler dispersion 
Before coating, the pH of each coating composition was determined and 
adjusted to the value indicated in Table I with dilute (1:6N) nitric acid. 
The equilibrated surface pH of each element was measured using a Corning 
No. 476265 Combination Surface pH Electrode by pipetting 2 drops of 0.3M 
potassium nitrate on the coating surface, making electrode contact, and 
reading the pH after 3 min equilibration at room temperature. 
Each element was divided into two parts. One was used as a control and held 
at -18.degree. C. for two weeks, and the other was incubated at 49.degree. 
C., 50% RH for two weeks. 
Each element was solution processed at 35.degree. C. in a three-step 
process of color development (45 sec), bleach-fix (45 sec), and wash or 
stabilization (90 sec) followed by drying (60 sec) at 60.degree. C. 
The formulations for the above solutions are: 
(1) Color developer: 
______________________________________ 
Lithium salt of sulfonated polystyrene 
0.25 mL 
(30% by wt) 
Triethanolamine 11.0 mL 
N,N-diethylhydroxylamine (85% by wt) 
6.0 mL 
Potassium sulfite (45% by wt) 
0.5 mL 
Color developing agent 4-(N-ethyl-N-2- 
5.0 g 
methanesulfonylaminoethyl)-2-methyl- 
phenylenediaminesesquisulfate monohydrate 
Kodak Ektaprint 2 Stain-Reducing Agent 
2.3 g 
(a stilbene material commercially available 
from Eastman Kodak Co.) 
Lithium sulfate 2.7 g 
Potassium chloride 2.5 g 
Potassium bromide 0.025 g 
Kodak Anti-Cal No. 5 0.8 mL 
(an organic phosphonic acid material 
commercially available from Eastman 
Kodak Co.) 
Potassium carbonate 25.0 g 
Water to total of 1 liter, pH adjusted to 10.12 
______________________________________ 
(2) Bleach-fix: 
______________________________________ 
Ammonium thiosulfate 58. g 
Sodium sulfite 8.7 g 
Ethylenediaminetetraacetic acid ferric 
ammonium salt 40. g 
Acetic acid 9.0 mL 
Water to total 1 liter, pH adjusted to 6.2 
______________________________________ 
(3) Stabilizer: 
______________________________________ 
Sodium citrate 1 g 
Dearside 45 ppm 
(a biocide produced by Rohm and Haas) 
Water to total 1 liter, pH adjusted to 7.2 
______________________________________ 
After processing, the Status A blue density of each control and incubated 
coating was read and the change in D-min (no exposure density) was 
calculated. The data in Table I illustrate that coatings with an 
equilibrated surface pH value of 5.3 or below have improved raw stock 
keeping. 
TABLE I 
______________________________________ 
Coating 
Composition Status A Blue 
pH Density 
Coating A B C Surface pH 
Control 
.DELTA. 
______________________________________ 
C-1 (control) 
6.0 5.9 5.3 5.7 0.07 +0.23 
C-2 (control) 
6.0 5.9 5.3 5.7 0.07 +0.25 
C-3 (control) 
6.0 5.9 5.3 5.7 0.07 +0.21 
C-4 (comparison) 
6.0 5.0 5.3 5.6 0.07 +0.25 
C-5 (comparison) 
6.0 5.0 5.0 5.5 0.07 +0.23 
E-1 5.0 5.0 5.0 5.3 0.07 +0.20 
E-2 4.5 5.0 5.0 5.1 0.07 +0.16 
E-3 4.5 5.9 5.0 5.2 0.07 +0.16 
E-4 4.5 5.9 5.3 5.3 0.07 +0.18 
______________________________________ 
EXAMPLE 2 
This example is similar to Example 1 but provides data for multicolor 
elements where all individual emulsion, coupler, interlayer, and overcoat 
coating compositions were individually adjusted for pH. Details are shown 
in Table II below. 
The following layers were coated in order on a commercial paper stock: 
7. Overcoat layer: 
Gelatin (1.4 g/m.sup.2) 
6. UV absorbing layer: 
A mixture of hydroxyphenylbenzotriazoles (0.38 g/m.sup.2), gelatin (0.66 
g/m.sup.2) 
5. Red sensitive layer: 
Chemically and red spectrally sensitized monodisperse silver chloride 
negative emulsion (0.23 g Ag/m.sup.2) and cyan-dye forming coupler C (0.45 
g/m.sup.2) in di-n-butyl phthalate coupler solvent (0.25 g/m.sup.2), 
gelatin (1.1 g/m.sup.2) 
4. UV absorbing layer: 
A mixture of hydroxyphenylbenzotriazoles (0.38 g/m.sup.2), gelatin (0.66 
g/m.sup.2) 
3. Green sensitive layer: 
Chemically and green spectrally sensitized monodisperse silver chloride 
negative emulsion (0.29 g Ag/m.sup.2) and magenta-dye forming coupler M 
(0.45 g/m.sup.2) in di-n-butyl phthalate coupler solvent (0.22 g/m.sup.2), 
gelatin (1.2 g/m.sup.2) 
2. Interlayer: 
Gelatin (0.76 g/m.sup.2) 
1. Blue Sensitive layer: 
Chemically and blue spectrally sensitized monodisperse silver chloride 
negative emulsion (0.34 g Ag/m.sup.2) and yellow-dye forming coupler Y 
(1.1 g/m.sup.2) in di-n-butyl phthalate coupler solvent (0.27 g/m.sup.2), 
gelatin (1.5 g/m.sup.2) 
Support: A paper stock consisting of a mixture of hard and soft wood pulp 
extrusion overcoated with a titanium dioxide and zinc oxide pigmented 
polyethylene layer. 
The layers 1 to 7 were hardened with bis(vinylsulfonyl)methyl ether at 
12.8% of the total gelatin weight. Coupler identifications are: 
C=Cyan dye forming coupler: 
(2-(.alpha.-(2,4-di-tert-amylphenoxy)butyramido-4,6-dichloro-5-ethyl 
phenol 
M=Magenta dye forming coupler: 
1-(2,4,6-trichlorophenyl)-3-(2-chloro-5-(.alpha.-(4-hydroxy-3-tert-butylph 
enoxy)-tetradecanoamido)anilino)-5-pyrazolone 
Y=Yellow dye forming coupler: 
.alpha.(4-(4-benzyloxyphenyl-sulfonyl)phenoxy)-.alpha.-(pivalyl)-2-chloro- 
5-(.gamma.-(2,4-di-tamylphenoxy)butyramido)acetanilide 
Each coated layer had its own single coating composition except layers 5, 
3, 1 which consisted of two separate compositions for each of the emulsion 
and coupler as in Example 1. Each of the ten compositions for coating was 
adjusted with (1:6N) nitric acid to the indicated pH. 
The equilibrated surface pH of each finished coating was measured after 5 
weeks keeping at room temperature as described in Example 1. 
Each finished coating as a) used as a control and held at -18.degree. C. 
for 6 months, or b) incubated at 26.degree. C., 50% RH for 6 months. 
Each element was solution processed at 35.degree. C. in a three-step 
process of color development (45 sec), bleach-fix (45 sec), and 
stabilization (90 sec) followed by drying (60 sec) at 60.degree. C. as 
described in Example 1. 
After processing, the Status A blue, green and red densities of each 
control and incubated coating were read and the change in D-min (no 
exposure density) was calculated. 
The data in Table II illustrate that coatings with an equilibrated surface 
pH of 5.3 or below have improved raw stock keeping. 
TABLE II 
__________________________________________________________________________ 
Coating Status A Density 
Composition 
Measured 
Control .DELTA. After Incubation 
Coating Adjusting to pH 
Surface pH 
R G B R G B 
__________________________________________________________________________ 
C-10 (control) 
6.0* 5.9 0.075 
0.090 
0.105 
+0.015 
+0.010 
+0.027 
E-10 5.0 5.3 0.089 
0.081 
0.109 
+0.004 
+0.013 
+0.015 
E-11 4.0 4.2 0.075 
0.078 
0.098 
+0.001 
+0.009 
+0.011 
__________________________________________________________________________ 
*The pH of the magenta coupler dispersion only was pH 5.3 
EXAMPLE 3 
This example is similar to Example 2 with regard to coating compositions 
and evaluation procedure except in place of the bis(vinylsulfonyl)methyl 
ether hardener, a more active hardener, 
1-(4'-morpholinocarbonyl)pyridinium-4-ethyl sulfonate, was used. 
The data in Table III illustrate that coatings of lower surface pH have 
improved raw stock keeping. The coating with an equilibrated surface pH of 
4.5 showed the greatest improvement. From a comparison between the data 
for the coating with an equilibrated surface pH of 5.6, and the data for 
the other two coatings, it is apparent that a value of 5.3 or below would 
provide good results. 
TABLE III 
__________________________________________________________________________ 
Coating Status A Density 
Compositions Control .DELTA. After Incubation 
Coating Adjusting to pH 
Surface pH 
R G B R G B 
__________________________________________________________________________ 
C-20 (control) 
6.0* 6.4 0.083 
0.103 
0.206 
+0.009 
+0.016 
+0.016 
C-21 (comparison) 
5.0 5.6 0.076 
0.090 
0.134 
+0.006 
+0.005 
+0.012 
E-20 4.0 4.5 0.075 
0.086 
0.099 
+0.001 
+0.004 
+0.008 
__________________________________________________________________________ 
*The pH of the magenta coupler dispersion only was pH 5.3 
The invention has been described in detail, with reference to preferred 
embodiments thereof, but it will be understood that modifications can be 
effected within the spirit and scope of the invention.