Photographic chemistry

A photographic chemistry comprised of a solution containing a mixture of different chemicals which cooperate to minimize the need for long film exposure times to achieve high film quality and contrast. The photographic chemistry includes a number of alkalies in a pH range from about 8 to 14, a developer in solution with the alkalies, a solvent mixed with the alkalies and the developer, a modified alkanolamide in solution with the alkalies, the developer and the solvent, and a hydrotrope mixed with the modified alkanolamide. Other chemicals that can be used in the photographic chemistry include an emulsion penetrant, a cleaner for various components of film processing equipment, a chelating agent, and an enzyme to enhance the reactions of the various chemicals in the photographic chemistry. A specific mixture of chemicals is disclosed.

This invention relates to improvements in photographic developers and, more 
particularly, to an improved photographic chemistry which allows increased 
effective emulsion speeds and a relatively long gray range in films 
developed by the use of the photographic chemistry. 
BACKGROUND OF THE INVENTION 
Conventional photographic chemistries have limitations which are well 
known. Such limitations require that a photographic film be exposed for a 
sufficiently long time so that conventional photographic chemistries can 
develop the film to provide the desired contrast and other results to 
permit the proper analysis of the developed film to obtain the desired 
information therefrom. In the case of X-rays, long exposure times are 
harmful to human beings and precautions should be taken to assure that a 
patient does not receive an unnecessary overexposure of X-rays. However, a 
safer exposure to X-rays is, in many cases, not sufficient to assure that 
the X-ray film, when developed by using conventional photographic 
chemistries, has the proper information recorded on it. Either the 
information cannot be obtained from the film or higher exposure of the 
patient to the X-rays is required. 
Another drawback concerning the use of conventional photographic 
chemistries is that they do not contain ingredients which properly clean 
certain components, such as rollers, automatic film processing equipment 
sufficiently to prevent frequent maintenance of such equipment. As a 
result, photographic developing processes must be interrupted for such 
maintenance to clean the equipment so that the equipment can be placed in 
operation once again as soon as possible.

SUMMARY OF THE INVENTION 
The present invention is directed to a photographic chemistry which 
operates to develop exposed silver halides in a photographic emulsion, 
which halides were previously not capable of being developed with 
conventional photographic chemistries because of underexposure of the 
halides (to a light or other radiation source). Thus, the present 
invention is a distinct advance over conventional photographic chemistries 
because it allows increased effective emulsion speeds and a longer gray 
range than is obtainable with conventional chemistries. As a result, high 
quality photographic images may be obtained even with minimum exposure 
times. This is an especially advantageous feature when the photographic 
chemistry of this invention is used to develop a photographic emulsion 
used in non-invasive diagnostic imaging (such as X-rays), because the 
dosage can be reduced over that conventionally used to thereby minimize 
the harmful effects on a patient being subjected to X-rays. 
Other advantages of the photochemistry of the present invention is it 
provides a developer which is functional at a lower temperature than that 
at which conventional developers operate (especially in rapid-processors 
used in the medical profession), resulting in a longer operating life of 
the chemistry itself. By keeping the developer at a lower operating 
temperature than conventional chemistries, the developer will last longer 
because of less oxidation. An additional benefit is a reduction of energy 
costs from heating the developer itself, keeping the processor temperature 
lower all the way through, and shorter exposures by the X-ray generator, 
as well as less potential damage to film emulsions which may normally be 
caused by excessive heat and swelling. Conventional photochemistries for 
rapid processing must include a hardener in the developer (such as 
glutaraldehyde) to prevent these problems. This invention makes that 
unnecessary. 
The photochemistry of the present invention further provides an improved 
developer which operates to clean process machine parts and tends to 
preserve the integrity of rollers of process machines. Using conventional 
photochemistries the rollers soak up solution and film/developer residues, 
and mineral or organic contaminants can form in the tank, on the rollers 
and film guides, thus necessitating the replacement of rollers and 
thorough cleaning more often than with the chemistry of the present 
invention. The higher conventional operating temperatures also contribute 
to the processor problems. By keeping the temperature lower and keeping 
the processor cleaner as with the present invention, roller life is 
prolonged to a considerable degree and some machine breakdowns may be 
avoided. The present invention is further advantageous because it lacks 
the toxicity normally associated with conventional chemistries which use 
glutaraldehyde and unreacted aldehydes as hardeners in the developer, 
which the present invention does not need. 
The present invention includes a developer comprised of a mixture of 
different chemicals, some of which may appear to perform the same function 
in the photographic chemistry itself. The present invention has a number 
of alkalies ranging from slightly alkaline to highly alkaline, and it is 
important that they be balanced in a stair-step progression. Such alkalies 
are so balanced in the photochemistries of the present invention. As 
examples of the various alkalies in the photographic chemistry of the 
present invention and their relative pH's, the following alkalies could be 
used: 
______________________________________ 
sodium sulfite pH 8-9 
modified alkanolamides 
pH 9-10 
potassium carbonate pH 10-11.5 
potassium silicate pH 10.5-11.7 
potassium hydroxide pH up to 14 
______________________________________ 
With the alkalies in the stair-step fashion as set forth above, fast 
high-accutance formulas for panchromatic films can be obtained. As an 
example, with the present developer, it is possible to process Kodak 
Panatomic-X (ASA 32) at E.I.s (exposure indexes) over 400 ASA with better 
results than with conventional photochemistries (at normal exposure 
levels). In the balancing of alkalies, a rule of thumb is that at least a 
minimum of 1% solution of each alkali in the stair-step is desired except 
the modified alkanolamide which may be as low as 0.00001%. 
In Table 1, there is a representative photographic chemistry of the present 
invention. It is comprised initially of three solutions. The first 
solution, Solution I, is prepared, followed by the preparation of the 
second solution, Solution II. Then Solutions I and II are mixed together. 
The remaining chemicals are added to the mixture of Solutions I and II in 
the order listed. The result is a representative example of the 
photographic chemistry of the present invention. 
Private tests conducted in the clinic of Dr. B. Peck Lau, M.D. Radiation 
Oncology and Nuclear Medicine Medical Clinic, Inc., Fresno, Calif., have 
shown that the present invention permits a 50% reduction in radiation to 
patients for diagnostic X-rays compared directly to state-of-the-art rapid 
processor X-ray chemistry (Kodak brand used for comparison). Higher 
reductions are possible with the present invention in conjunction with 
technique modification (kVp-mAs level variations by the radiologist), 
amounting to over 80% reduction in field tests, depending on 
film/screen/chemistry/technique combinations in use (varies greatly from 
clinic to clinic). 
Among the chemicals in the photographic chemistry of the present invention 
is diacetone alcohol (4-Hydroxy-4-methyl-2-pentanone). This chemical is 
used as a solvent and a cleaner. It is further used as an intermediate 
between other chemicals so as to make other chemicals compatible with each 
other. Furthermore, diacetone alcohol serves as a penetrant so that the 
quicker penetration of the emulsion by the chemicals, the quicker the 
charge-barrier effect (emulsion minus charge vs. chemical minus charge) is 
penetrated. 
Dimethyl formamide (DMF; N,N-dimethylformamide) is included in the 
photochemistry of the present invention because it serves as a "universal" 
solvent, inasmuch as it is a dipolar aprotic solvent that is miscible with 
water and most organic solvents. It is a penetrant and an emulsion 
hardener and protector, and it is used also as a chemical compatibility 
regulator. 
Acetone (Dimethylketone; 2-propanone) is also included in the 
photochemistry of the present invention. It serves as a cleaner of 
processing machines, a new use in combination with the other chemicals of 
the photographic chemistry of the present invention. Acetone further acts 
as an organic developing agent solvent and emulsion penetrant, thus 
carrying developing agents rapidly into the emulsion with little or no 
regard for the charge-barrier effect. 
The modified alkanolamide in the developer of the present invention is 
unique in combination with the other chemicals of the developer. Such a 
modified alkanolamide can be cocamide diethanolamine (Coco DEA). It serves 
as a pH builder and stabilizer, a wetting agent and detergent which is 
biodegradable, but necessitating the use of an hydrotrope in high builder 
level formulae, i.e., phosphates used to raise the pH levels of a 
solution. For instance, a useable modified alkanolamide is Clindrol 202 
CGN, manufactured and sold by the Clintwood Chemical Company, Chicago, 
Ill. 
Sodium xylenesulfonate (dimethylbenzenesulfonic acid, sodium salt) is a 
typical hydrotrope for use with the modified alkanolamide. A suitable 
hydrotrope is SXS-40, manufactured and sold by Pilot Industries of Los 
Angeles, Calif. The hydrotrope level depends upon the amount of modified 
alkanolamide used, the amount and types of pH builders and other solvents 
in solution, and whether the formula is a pre-mix or concentrate for use 
in the marketplace. 
These criteria establish that the range of hydrotrope may be from 0.01% of 
the total solution to 50% or more, depending on the type of application 
(concentrate or pre-mix). The hydrotrope defined by sodium xylenesulfonate 
operates as a compatibility agent so that other chemicals are compatible 
with water (in the presence of other generally non-compatible chemicals). 
It also acts as a surfactant and as a cleaning agent. As a surfactant, it 
increases the penetrating ability of the solution and controls foam levels 
so that the flow of the developer is increased while turbulence in the 
developer is decreased (in rapid processors). 
The modified alkanolamide, in addition to its foregoing properties, further 
acts as a solvent, as a surfactant, as a cleaner, and as a buffer. As a 
buffer, it neutralizes acids introduced into solution (from development 
by-products, step-reactions) so as to cause the solution not to abruptly 
change activity or pH upon such intrusion (of acid or alkali). The 
balancing of the alkalis and other ingredients of the present invention 
provides a developer which is, in effect, a balanced alkali buffer system. 
Potassium silicate in the solution is used as a cleaner and as an alkali or 
pH builder. It also preserves the integrity of the emulsion subjected to 
the developer of the present invention and tends to give low fog, high 
contrast images. A number of chemicals of the present invention are 
incompatible with potassium silicate and should be put into solution as 
indicated in Table I. A suitable potassium silicate is one denoted as 
Kasil No. 1 made by Philadelphia Quartz Company, Philadelphia, Pa. 
Another chemical that can be used in the developer of the present 
invention, although not used in a solution as shown in Table 1, is 
dimethyl sulfoxide (DMSO; methyl sulfoxide). It is a solvent and a 
penetrant as well as a lubricant. It conditions rollers in rapid 
processors and preserves the film emulsion. It also reduces the opacity of 
the emulsion base fog. 
Methanol is used in the present invention as a solvent, a cleaner, a 
buffering agent and an intermediate compatibility agent. It also aids in 
preventing excessive emulsion swelling and softening while allowing the 
penetration of developing agents, for which it is also a solvent. 
Ethylenediamine tetraacetic acid, tetrasodium salt (EDTA Na.sub.4), in the 
form of Versene 100, a commercially available solution of EDTA Na.sub.4 
(40%), is used as a chelating (sequestering) agent, which is not an 
uncommon use, except in conjunction with uncommon photochemical 
ingredients. 
Potassium carbonate is a pH builder or accelerator which is used as well 
for its higher photochemical activity and solution concentration ability 
(over the Na form), in its particular pH range. Potassium hydroxide, a pH 
builder, is used in the present invention to alter the mole ratio of the 
potassium silicate. This mole ratio (Kasil #1) is 2.50:1 SiO.sub.2 
:K.sub.2 O and is adjusted by the addition of potassium hydroxide to 
approximately 1:1. 
Enzymes are used as organic catalysts as follows: they can be either 
amylolytic or proteolytic enzymes, a combination of amylolytic and 
proteolytic enzymes, and/or other enzymes which catalyse the myriad 
step-reaction activities of the present invention in the process of 
developing silver halides. Suitable enzymes of this type are made by Emkay 
Chemical Company of Elizabeth, N.J. 
To obtain high emulsion speed in the present invention, dependence is made 
on the balancing of alkalies, on solvents, on surfactants, and on 
catalysts. This feature is achieved by the use of the combination of 
modified alkanolamides, diacetone alcohol, dimethyl formamide, potassium 
silicate, and enzymes with other chemicals. No other prior developers have 
used these chemicals in combination with each other, or proven a drastic 
exposure reduction (such as a decrease in X-ray radiation exposure to 
patients) because of such use. 
TABLE 1 
______________________________________ 
(to make 4 liters) 
______________________________________ 
Solution I 
HOH 2.9 liters 
Potassium Silicate, 50% sol. 
(2.50:1 SiO.sub.2 :K.sub.2 O mole ratio) 
50 ml 
Sodium Sulfite (Anhydrous) 
395 gms 
Ethylenediamine tetraacetic 
acid, tetrasodium salt 
(EDTA Na.sub.4) 40% sol. 
25 ml 
Potassium Hydroxide 50% sol. 
75 ml 
Potassium Carbonate 160 gms 
Hydroquinone 36 gms 
Solution II 
HOH at 125.degree. F.+ 
300 ml 
Sodium Sulfite 5 gms 
p-Methylaminophenol sulfate (Elon) 
10 gms 
(Add Sol. II to Sol. I; then add:) 
Methanol 200 ml 
Phenidone A 10 gms 
Isopropyl Alcohol (Anhydrous) 
10 ml 
Benzotriazole 1% sol. 50 ml 
Sodium xylenesulfonate, 40% sol. 
100 ml 
modified alkanolamide 80 ml 
Diacetone Alcohol 10 ml 
Dimethyl Ketone (Acetone) 
10 ml 
Dimethylformamide 5 ml 
Enzymes (such as a standard 
mixture of amylolytic enzymes 
and catalysts, etc., used in 
the fabric cleaning industry; 
and/or proteolytic enzymes, etc.) 
2 ml 
______________________________________