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Description  |
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TECHNICAL FIELD
This invention is in the field of photographic silver halide developer
solutions and replenishers therefor, and is specifically directed to
developer-replenisher solutions useful in low through-put machine
processing (developing) of photographic film.
BACKGROUND ART
The use of so-called "automatic processors" is conventional for developing
imagewise exposed silver halide elements such as X-ray films. The exposed
films are fed into the processor from a safelight area, i.e. one in which
the level of light is reduced below that which exposes the film further,
and is transported through various chambers containing the developer, the
fixer and the water washes. At the end of the processor, the film is dried
and exits into normal light as a finished product ready for use. This is
illustrated in U.S. Pat. No. 3,545,971 "Rapid Processing of Photographic
X-ray Film" (1966). This system is rapid and convenient and large numbers
of films can be routinely handled in this manner over long periods of time
without deleterious effects to the finished image. Of course, the
processing solutions become exhausted by the passage of the exposed silver
halide film and replenishment must be made to account for ingredient loss.
Additionally, the processing fluids, especially the developer solution,
are degraded aerobically by contact with air and anerobically when simply
left for long periods of inaction.
When large amounts of film are being processed (high throughput),
exhaustion of the developer is due almost entirely to development of the
silver halide image. The development reaction as shown in Mason's
"Photographic Processing Chemistry" Focal Press (1966) page 74, is:
2AgBr+H.sub.2 Q+Na.sub.2 SO.sub.3 .fwdarw.2Ag+HBr+NaBr+HQSO.sub.3 Na
Thus, some materials, i.e., hydroquinone and sulfite are lost while
bromide, acid, and hydroquinone monosulfonate are formed. Also, not shown
by this reaction, antifoggant may be lost. Current developer replenishers
are formulated based on this reaction as follows: The replenisher is made
higher in pH than developer and contains no bromide, so as to offset the
acid and bromide released by the development reaction. The other
ingredients are set at concentrations which allow for the expected losses,
the hydroquinone being offset by the antifoggants, without substantially
affecting the sensitometry. In this situation a replenishment rate can be
conveniently calculated based on the approximate area of film fed into the
processor.
The other situation presents a more difficult problem because when only
small amounts of film are processed (low throughput), the developer
deteriorates primarily from air oxidation and thermal reaction, and not
from development reaction; Mason's "Photographic Processing Chemistry"
supra at page 73:
H.sub.2 Q+2Na.sub.2 SO.sub.3 +O.sub.2 .fwdarw.HQSO.sub.3 Na+NaOH+Na.sub.2
SO.sub.4.
That is, hydroquinone and sulfite are lost but not bromide. Also, pH
increases, not decreases as in the development reaction. Also, since film
passage activates the replenishment, low throughput decreases
replenishment.
Current practice is to compensate for low throughput by increasing
replenishment rate significantly, e.g., as much as two-fold. This,
however, can actually accelerate the problems caused by low throughput
processing and cause sensitometric instability. It does so because the
replenisher, which is being added, in excess, has higher pH than the
developer and no bromide. The effect of this is to (1) maintain the
increasing pH of the developer caused by oxidation, and (2) dilute the
bromide content to levels so low as to cause sensitometric instability,
reflected mainly in fog and speed.
The present invention provides a replenisher formulation which is aimed at
compensating for developer changes caused by nonuse, and not by the
development reaction. Thus, the replenisher is characterized by a pH lower
than that of the developer, and it contains the maximum amount of bromide
consistent with acceptable sensitometry and contains enough antifoggant to
minimize loss during use. Now when replenishment occurs, pH will remain
constant or slightly decrease, the bromide will remain essentially
constant, and the other changes will compensate as in state of the art
formulations. That is, the developer hydroquinone, sulfite, and
antifoggant losses suffered during periods of nonuse are not sufficiently
great to cause sensitometric instability. Before this occurs replenishment
occurs, restoring these ingredients to concentrations closer to their
initial values. Thus, by maintaining the developer composition more
constant, the developer can maintain a useful lifetime equivalent to the
high throughput processors. Because of the optimal developer/replenisher
balance for low throughput, the developer is stabilized with less
replenishment than the conventional developers when attempting to process
these same low throughput conditions.
It is accordingly an object of this invention to provide an improved
developer/replenisher system for developing exposed silver halide
photographic film. A further object is to provide a developer/replenisher
system particularly useful for machine processing of X-ray film when low
throughput of film is practised.
SUMMARY OF THE INVENTION
These and other objects are achieved in this invention by providing an
aqueous processing solution useful as a photographic developer bath for
automatic low throughput processing of silver halide photographic film,
particularly X-ray film, and as a replenisher therefor, consisting
essentially of, per liter:
______________________________________
1-phenyl-3-pyrazolidone
0.8 to 2.5 g
photographic developing
agent, or a derivative thereof
Hydroquinone developing agent
15 to 35 g
or a derivative thereof
Bromide ion 1 to 7 g
Organic antifoggant and film
0.01 to 6.0 mmole
speed restrainer
Alkaline material and buffer to
provide a pH of 10.0 .+-. 0.3;
______________________________________
with the proviso that the replenisher solution will not only contain
bromide ion but also will have a lower pH than that of the developer
solution.
Developers and replenishers made according to this invention can be used in
processing machines for low throughput of X-ray film, for example, and
will exhibit excellent stability over long periods of both use and nonuse.
This is very surprising because prior art formulations have been known to
last only a few weeks when practicing low throughput. It can be seen in
Example 2 of this specification that the preferred embodiment of this
invention lasted more than ten months under actual low throughput
conditions in a hospital X-ray processing machine.
Hence, a further embodiment of the invention is a method of automatic
processing of exposed photographic silver halide X-ray film wherein the
imagewise exposed X-ray film is developed in a photographic developer bath
comprising a photographic developer, bromide ion, an alkaline material and
buffer system to maintain the pH of the developer bath at a desired value,
an organic antifoggant and film speed restrainer, and water; the developed
X-ray film is fixed, washed and dried; and the developer bath is
replenished by replenisher solution to maintain constant the photographic
properties of the developer bath during long periods of process or
operation in which only small quantities of exposed X-ray film are
processed, i.e., under low throughput processing conditions.
DETAILED DISCLOSURE OF THE INVENTION
The processing solution of this invention can be used for both the
developer and the replenisher therefor. In the latter embodiment, wherein
the replenisher solution has a lower pH than that of the developer, it is
only necessary to add a small amount of acid, acetic acid, for example, to
adjust the pH. However, for a commercial put-up, a small amount of base
(alkaline material) is added to the developer to raise the pH of the
developer rather than adding acid to the replenisher to lower its pH. This
will be illustrated in Example 1, wherein a small amount of base is added
through the starter solution (Part D). The replenisher is added to the
developer bath as needed, based on time and/or the amount of film
processed, thus compensating for both forms of developer exhaustion. It is
surprising that this particular formulation can be used so successfully
for low throughput in automatic processors since the differences between
it and the prior art are so slight. However, as will be seen in the
Examples, the difference in performance between the formulation of this
invention and the prior art is very large.
As the photographic developing agents in the processing solution, a
combination of 1-phenyl-3-pyrazolidone (sold under the Ilford trademark
Phenidone) or a derivative thereof such as 4-methyl or 4,4-dimethyl
phenidone, and hydroquinone or a derivative thereof such as
chlorohydroquinone or bromohydroquinone is used. This combination is
particularly suited for automatic processing of X-ray films. These
ordinarily comprise a gelatino-AgBr, AgBrI, or AgClBrI emulsion on a film
support such as polyethylene terephthalate.
Any alkaline material may be used to provide the required pH, such as
sodium or potassium hydroxide, sodium or potassium carbonate, etc. The
buffer system may be any convenient system, e.g., the borate and carbonate
buffers conventionally used in X-ray developer baths are both suitable.
The organic antifoggant may be any organic antifoggant and film speed
restrainer. Such organic antifoggants are commonly employed in X-ray
developer baths and include compounds of the benzimidazole, benzotriazole,
benzothiazole, indazole, tetrazole, mercaptotetrazole and thiazole group,
as well as anthraquinone sulfonic acid salts. Two or more organic
antifoggants may be used. It is preferred to use a mixture of two
antifoggants such as 5-nitroindazole and benzotriazole.
A range of bromide ion can be used successfully in this invention and
provides excellent stability. 1 to 10 g/liter of KBr, for example, will
provide sufficient bromide ion. NaBr may also be employed. Optimum amounts
depend on replenishment rate and specific formula.
These essential ingredients, when dissolved in water at the concentrations
set forth above, enable the photographic solution of the invention to
function as a developer bath and a shelf-stable replenisher.
Other materials may be included in the processing solution, such as gelatin
hardening agents, aerial oxidation restrainers, sequestering agents,
surfactants, dyes etc., as well known in the art. See, e.g., U.S. Pat. No.
3,545,971 and "Photographic Processing Chemistry", supra, page 149 et seq.
Conventionally, all of the ingredients of the developer are prepared in
concentrated form in water. Separate portions of the concentrates are
furnished users so that interaction between ingredients is lessened while
in this concentrated state. Then, the user makes up the developer solution
by measuring various amounts from each part and diluting with water to
achieve the desired solution. The pH is then adjusted, e.g., to
10.0.+-.0.3, and the solution charged to the processing tank, e.g., of the
type described in U.S. Pat. No. 3,545,971, such as an "X-Omat Processor",
in the amount required by the system. Development time is determined
empirically or by the processor. Replenishment will be carried out at a
rate per unit area of exposed film to provide processing of a large
quantity of exposed film without change in sensitometric properties of the
film, and will be determined empirically, as is known. As a guide, when
using an X-Omat Processor to process X-ray film, a suitable replenishment
rate will be about 55 ml per 240 square inches of exposed film for
development to normal radiographic density, using the processing solution
of the invention.
Some processors have a standby replenishment mode. This works as follows:
if no film is passed in a given time, the processor goes into a standby
mode which deactivates the drive train and dryer and reduced water supply.
After a given time, it comes back on for several minutes and then shuts
off again. After a specified number of cycles, it replenishes a
predetermined amount. This replenishment is not effective with current
developer/replenisher formulations but very effective with this invention
since more of the correct replenisher is used.
After development in the processing solution of the invention, the silver
halide film is fixed, preferably in an acid fixer, and washed and dried in
the usual manner. If a processing machine is used, these steps will be
determined by the machine.
The following examples are illustrative of the invention, with Example 1
being the best mode contemplated by the inventor of carrying out the
invention.
EXAMPLE 1
The following solutions were prepared in order to formulate a
developer/replenisher (I) according to the present invention, and to
compare it with a conventional developer/replenisher (II):
______________________________________
Ingredients Amt. (g)
______________________________________
Part A
Dist. Water 250
Ethylenediaminetetraacetic
8
Acid (EDTA)
Sodium Bisulfite (43% aq.)
383
Hydroquinone 100
KBr 13
KOH (45% aq.) 323
K.sub.2 CO.sub.3 (47% aq.)
116
Distilled Water to
1 liter
Part B
Acetic Acid 560
Triethylene Glycol
240
Phenidone 60
5-nitroindazole 6.4
2.66 m moles
Benzotriazole 8.0
Sodium Bisulfite (anhydr.)
5
Distilled Water to
1 liter
Part C
Dist. Water 500
Glutaraldehyde (50% aq.)
300
Sodium Bisulfite (anhydr.)
106
Water to 1 liter
Part D
Dist. Water 500
KOH (45% aq.) 200
KBr 171
Water to 1 liter
To make developer I:
250cc A
25cc B pH 10.2
25cc C
Water to 1 liter
23.4cc D
To make replenisher
250cc A pH 10.0
25cc B
25cc C
Water to 1 liter
______________________________________
For comparison, a conventional high throughput medical X-ray developer II
was prepared. The most significant difference was that Part A' (of
developer II) contained no KBr, and Part D' contained 130 g acetic
acid/liter instead of 200 g KOH 45% aqueous/liter. Developer II had a pH
of 10.15, and replenisher II a pH of 10.35 (compared to pH 10.0 for
replenisher I).
In an actual hospital situation, samples of exposed, high speed medical
X-ray film were processed (ca. 15-20 sheets of 8".times.10" film/day)
using developers I and II, which were charged to a CRONEX QC-1 Medical
X-ray Automatic Processor (E. I. du Pont de Nemours and Company,
Wilmington, DE). The respective replenisher solutions were supplied to the
replenisher tank thereof. The activities of the systems were checked by
processing control strips of X-ray film exposed through a .sqroot..sub.2
21-step wedge on a Cronex.RTM. Electroluminescent (ELS) Sensitometer (E.
I. du Pont de Nemours and Company, Wilmington, DE). Two strips per day
(one in the morning and one in the afternoon) were processed and the
sensitometry checked to see whether the processor and its solutions were
performing well. Processing time (dry-to-dry) was about 21/2 minutes at
92.degree. F. The processor was equipped with a conventional ammonium
thiosulfate fixer solution.
In the case of developer/replenisher II, above, high fog and lower speed
was noted after about 2 weeks of use and the machine was shut-down and the
solutions drained therefrom. In the case of developer/replenisher I,
above, the fog and speed remained constant after more than 4 weeks of
continued, low throughput use, demonstrating good long life performance.
EXAMPLE 2
Developer/replenisher I of Example 1 was operated for more than 101/2
months at low throughput at St. Joseph's Hospital in Phoenix, Ariz. in a
Cronex QC-1 processor under essentially the same conditions as Example 1.
The same formula was also run over four weeks at high throughput, thus
demonstrating that developer/replenishers of this invention exhibit
excellent stability over long periods of time in both high and low
throughput.
EXAMPLE 3
In order to differentiate this invention over another prior art
developer/replenisher formulation, the example given in Mertz, U.S. Pat.
No. 4,046,571 "Processing Solution For Use As Photographic Developer Bath
and Replenisher Therefor" (1977), Cols. 3, 4 and 5 was repeated. In this
reference, the organic antifoggant and film speed restrainer is defined as
being between 7-26 m mole/liter of solution, as compared to 2.66 m
mole/liter in Part B of Example 1. Corresponding Part B of the Mertz
example containing 3.6 g/liter of 5-chlorobenzotriazole and 5 g/liter of
5-nitrobenzimidazole was difficult to prepare and required heating to ca.
120.degree. F. Preparation of the working strength developer/replenisher
as described was also difficult and required constant heating to keep all
the solids dissolved. For this reason the solutions could not be tested in
a commercial, automatic processor. Instead, control strips of X-ray film
were tray processed in this developer and took about 3 times as long to
process as those processed in developer solution I of Example 1, above.
EXAMPLE 4
The following solutions were prepared:
______________________________________
Ingredients Amt. (g)
______________________________________
Part A
Dist. Water ca. 3785 (1 gal)
EDTA 75
Sodium Bisulfite 1428
Hydroquinone 946
KOH (45% aq.) 3075
KOH (solid) 1383
Sodium Bicarbonate 315
KBr 113
Dist. Water to 9.46 liters
(2.5 gals)
Part B
Triethylene Glycol 402
Acetic Acid 270
Phenidone 60
5-nitroinidazole 6
Benzotriazole 8
Dist. Water to 1 liter
Part C
Water 500
Glutaraldehyde (50% Aq.)
267
Sodium Bisulfite (anhydr.)
106
Dist. Water to 1 liter
A developer solution was made up as follows:
Dist. Water 26.5 l.
(7 gal.)
NaBr 120 g
Sodium Bisulfite (anhydr.)
270 g
Potassium Carbonate (anhydr.)
312 g
Sodium Carbonate 200 g
Part A, above 4.75 l.
(5 quarts)
Part B, above .95 l.
(1 quart)
Part C, above .95 l.
(1 quart)
Dist. Water to 37.85 l.
(10 gallons)
pH 10.17 .+-. 0.05
______________________________________
Five gallons (approx. 19 liters) of this developer were charged to the
processor described in Example 1. About 60 grams of acetic acid were added
to the remaining 19 liters to give a pH of 10.0.+-.0.05 and this was used
as the replenisher. The processor was also charged with standard ammonium
thiosulfate fixer and set at 92.degree. F. Two samples of exposed X-ray
film (high speed CRONEX 4, E. I. du Pont de Nemours and Company),
14.times.17 inch size, were processed (developed) and the sensitometry of
the system checked with control strips as described in Example 1. The
processor was then allowed to stand by for the remainder of the day. About
2,000 cc of replenisher was added by the machine during this time. At the
end of the 8 hour day, the machine was shutdown. The processor was run for
10 days in this manner. No substantial change was noted in the
sensitometry of the control strips used to check developer activity,
indicating that this formula was very stable to low throughput of silver
halide film and resistant to anerobic and aerobic degradation.
EXAMPLE 5
The formula of Example 2 (pH about 10.2) was used in this example, as both
developer and replenisher, in the processor of Example 1. Under low
throughput conditions (7 to 10 sheets of X-ray film/day) it served for
more than five weeks. At the end of this period of time, control strips
processed in this machine showed that the activity of the developer was
well within limits and produced excellent results. A conventional
developer of the prior art deteriorated badly in less than two weeks under
these conditions and required shut-down and cleaning of the automatic
processor followed by re-charging with fresh solution.
EXAMPLE 6
A developer/replenisher solution identical to that described in Example 1
was prepared, except that the level of antifoggant was increased to 5.32 m
mole per liter (0.32 g/l of 5 nitro-indazole and 0.40 g/l of
benzotriazole). All other ingredients and conditions remained the same as
described in Example 1. The activity of this solution was checked by
processing control strips of medical X-ray photographic film therein.
Sensitometric results indicate that this developer will perform
satisfactorily under low throughput conditions, i.e., that this solution
will remain stable for long periods of nonuse.
EXAMPLE 7
Example 6 was repeated except that the level of antifoggant was raised to
7.0 m mole per liter (0.42 g/l of 5-nitroindazole and 0.53 g/l of
benzotriazole). Although film strips processed in this solution were
satisfactory as regards sensitometry, solids precipitated from the
solution. It was obvious from this fact that it would be impossible to
keep this solution in an automatic processor.
EXAMPLES 8, 9 AND 10
A developer/replenisher solution identical to that described in Example 1
was prepared except for the level of antifoggant. Three samples were
prepared from this, and the antifoggant changed in each one as follows:
______________________________________
Antifoggant Level.sup.(1)
Example m mole/l g/l
______________________________________
8 0.98 0.16
9 1.96 0.32
10 3.92 0.48
______________________________________
.sup.(1) 5-nitroindazole
Film strips processed in these solutions were comparable,
sensitometrically, to those processed in the preferred embodiment,
indicating that these three levels of antifoggant will perform within this
invention.
EXAMPLES 11, 12 AND 13
A developer/replenisher solution identical to that described in Example 1
was prepared, except that the level of antifoggant was changed as follows:
______________________________________
Antifoggant Level.sup.(1)
Example m mole/l g/l
______________________________________
11 0.05 0.01
12 0.15 0.025
13 0.31 0.05
______________________________________
.sup.(2) 1-phenyl-5-mercaptotetrazole
Sensitometric results indicate that this developer will perform
satisfactorily under low throughput conditions, i.e., that this solution
will remain stable for long periods of nonuse.
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