US 3615478 A
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United States Patent METHOD OF FIXING PHOTOGRAPHIC MATERIAL CONTAINING A FREE RADICAL PRODUCING COMPOUND 6 Claims, No Drawings U.S. Cl 96/48, 96/90 Int. Cl G03c 5/24 Field of Search 96/48, 90
 References Cited UNITED STATES PATENTS 3,255,013 6/l966 Dersch et al 96/67 X 3,374,094 3/1968 Waener et al.... 96/67 X 3,512,976 5/1970 Yamada et al 96/48 OTHER REFERENCES Kasor, Light-Sensitive Systems, John Wiley & Sons, TR 350 A5 C2 pg. 365 8/27/65 irimary Examiner-Norman G. Torchin Assistant Examiner-Richard E. F ichter Attorneys-J. Russell Juten, Peter F. Willig, Lionel N. White and Milford A. Juten ABSTRACT: Light-sensitive photographic material comprising a light-sensitive generator of free radicals and a color modifier capable of showing a visible color change by the acnon of such free radical lS fixed against photolytic color change by contact with a salt of hydrogen sulfide or a salt of a sulfur-containing oxygen acid.
METHOD OF FIXING PHOTOGRAPIIIC MATERIAL CONTAINING A FREE RADICAL PRODUCING COMPOUND BACKGROUND in the material, to provide a reproduction of the image. Subsequent to the desired imagewise exposure, however, it has been found necessary to fix the material against further light exposure in order to prevent undesirable background fogging and loss of image.
In the prior art, fixation of a light-sensitive photographic material of the above-specified type was accomplished by a thermal fixing method or a solvent fixing method. In the former fixing method the light-sensitive photographic material on which an image is formed by irnagewise exposure to light is heated so that the remaining light-sensitive component decomposed or sublimed. The photographic material then no longer shows color change when exposed to light.
Among the light-sensitive photographic materials which are effective for thennal fixation, there are, for example, a composition which comprises diphenyl amine and carbon tetrabromide, and one which comprises brilliant green and carbon tetrabromide. Besides the above-indicated carbon tetrabromide, aroyl trihalogenated hydrocarbons are preferred as photoactivators. As is well known, however, carbon tetrabromide is extremely toxic and volatile at an elevated temperature. During handling, therefore, a special care should be taken to prevent from inhalation of the carbon tetrabromide vapor. Aroyl trihalogenated hydrocarbon also is incon- .venient because of its lachrymatory nature and volatility. Furthermore, a light-sensitive photographic composition which is used in a thermally fixable, light-sensitive photographic material should be readily heat-decomposable or sublimable, and such light-sensitive photographic composition usually is rather unstable even at an ordinary temperature.
' Thus, a light-sensitive photographic material useful in thermal fixation has rather poor storage ability, whereas a well storable light-sensitive photographic material is not so suitable for thermal fixation.
Another fixing method is a solvent fixing process wherein a light-sensitive photographic material is treated with an appropriate solvent to remove the residual light-sensitive component so that the the photographic material becomes insensitive to further light-exposure. It is essential to use a solvent that dissolves the residual light-sensitive component well, but does not dissolve the formed image. If a solvent is used which has even a little dissolving power for the image, an unsatisfactory reproduction will be obtained due to lowered resolution resulting from the exudation of the image. Suitable solvents for solvent fixing process are very few and they are expensive, and therefore, it is a difiicult problem to find an appropriate solvent. Furthermore, the solvent-fixing process is to wash out so-called nonimage area, and so, it is required for complete washing-out to use a selected solvent in large amount or to replenish a fresh solvent from time to time. Thus, this process is rather expensive and impractical.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing method which effectively prevents postexposure fogging of the noted type of photographic material, which has no adverse influence on the quality of an image formed, and which is free from health hazard.
This object can be achieved and the drawbacks encountered in the prior art can be overcome by using a water-soluble salt of hydrogen sulfide or a water-soluble, reducing salt of a sulfur-containing oxygen acid as a fixing agent in accordance with a method of the present invention. The fixing agents are used in the form of aqueous solutions which may be applied to exposed light-sensitive photographic materials. Exposed lightsensitive photographic materials are coated with or dipped into aqueous solutions containing the fixing agents. The fixing agents used in this invention diminish the photo activity of a photoactivator remaining intact, i.e. which do not take part in image formation, by a chemical reaction in which such agents capture halogen contained in the photoactivator to render the activator inactive.
Typical compounds useful as fixing agents referred to above are as follows:
Sodium sulfide No.5
Sodium bisulfide NaHS Sodium polysulfide NzqS, x-Z-S) Potassium sulfide K S Potassium bisulfide KHS Calcium sulfide CaS Potassium polysulfide K S, x-Z-S) Sodium diethyl dithiocarbamate (C,H,),NCSSNa Sodium sulioxylste Na,S0
Sodium sulfite Na,SO,
Sodium hisulfite NIHSO,
Sodium thiosulfate Na,S,0,
Sodium dithionite Ns,S,0,
Sodium pyrosulfite Na,S,O,
Sodium copper sulfite NaCuSO 3 Sodium silver sulfite NaAgSO,
Potassium sulfoxylate K,SO
Potassium sulfite K,SO,
Potassium thiosulfate K,S,O,
Potassium dithionite K,S,O,
Ethylenediamine sodium sulfite NaSSCHNH(Cl-l,)
,NHCSSNa ln accordance with the present invention, any one of the above-listed compounds is prepared to an aqueous solution (about 1-30 percent concentration) which is then applied to exposed, light-sensitive photographic material. In case of coating, the amount of the aqueous solution (thls solution will be simply referred to as a fixer" hereafter) will vary depending on the type of a photoactivator used and the thickness of the light-sensitive layer, but it usually is sufficient in such an amount as used for development of a diazo-type copying paper, i.e. in an amount necessary to moisten the surface of the light-sensitive photographic material. Thus, a fixing method according to the invention can be deemed as semidry process. The fixer may be added with a binder such as cellulose derivative, vinyl polymer, synthetic rubber, etc.
In case of dipping, the required operation is quite similar to, the fixation of a silver halide photographic material. Depending on the concentration of the fixer and the film thickness of the light-sensitive layer, the required dipping time will vary, but it usually is within the range of from several seconds to several minutes. When using a coating technique in fixing, it will be better to use a fixer having a higher concentration in comparison with the case when dipping is employed. In either cases, however, drying of the photographic material by heating at a temperatureof l00l80 C. (by means of hot rolls, hot plates, etc., having a surface temperature of l00-l C.) after fixation treatment is desirable to have increased fixing effect, while it makes possible to use a fixer having a lower concentration.
Addition of 2-15 percent of a bufier agent (e.g. sodium carbonate, borax, sodium acetate, sodium dihydrogen phosphate or the like alkaline substance) into a fixer serves to increase service life of the fixer by several times compared with the nonbuifered fixer. Further in the present invention, addition of 2-l0 g. of hydroquinone, metol or similar reducing substance per cc. of a fixer is recommendable to prevent discoloration of the background and degradation of the resulting image.
As mentioned above, a fixer usable in this invention may contain one or more additives or adjuvants which are commonly known in the photographic art. Furthermore, a lightsensitive photographic material which comprises a photoactivator being capable of generating a free radical by the action of light and a color modifier showing a visible color change through the action of said free radical also may contain one or more auxiliary components.
Illustrative of photoactivators referred to are the following:
 Compounds represented by the general formula RCX wherein R is aryl, alkyl, aralkyl, aroyl, alkenyl, hydrogen or halogen, and X is halogen. For example, they include carbon tetrachloride, carbon tetrabromide, hexachloroethane, pentabromoethane, p-nitrobenzotribromide, bromotrichloroethane, hexabromoethane,
benzotrichloride, benzotribromide, jodforrn, tetrachlorotetrahydro-naphthalene, chloral, bromal, l,l,l-tribromo- 2-methyl-2-propanal, l, l ,2,2,-tetrabromoethane, 2,2,2- tribromoethanol, trichloroacetamide, dimethyl-Z-propanol, a,a,aa, trichlorotoluene. [II] Compounds represented by the general formula wherein Rx means hydrogen or 1 to 5, same or different substituents selected from the group consisting of nitro, halogen,
' alkyl, haloalkyl, acetyl, haloacetyl, alkaryl and alkoxy. They include, for example, o-nitro- 01,11,a-tribromo-acetophenone, m-nitro-a,a,a-tribromoacetophenone, p-nitro-a,a,atribromo-acetophenone, a,a,a-tribromo-acetophenone, a,a,a mtetrabromo-acetophenone, a,a,a-tribromo-3,4- dichloroacetophenone. a,a,a-tribromo-2,S-dimethylacetophenone. a,a,a-p-tetrabromo-acetophenone, a,a,a,a',a ',a'[lll] Compounds represented by the general formula R-SO,
wherein A is a heterocyclic group which may be substituted.
and R R and R individually means H. C] or Br, excepting the case where all of R,, R and R are hydrogen. They include, for example, m,cu,w-tribromoquinaldine, (0,0)- dibromoquinaldine, 2-w,w,m-tribromomethyl-4-methylquinoline, w,w-diChlromethyl-quinoline, wbromolepidine, 2w-bromomethyl-isoquinoline, 4-w,w,mtribromomethyl-pyrimidine, 4-phenyl-6-m,w,wtribromopyrimidine, 2-w,m,w-trichloromethyl-6-nitrobenzthiazole, lphenyl-3-m,w,w-trichloromethyl-5- pyrazolone, w,w,w-tribr0molepidine, bromomethylate, aw,w-dibromomethyl-4-chl0ropyridine, l-methyl- 2(chloromethyl)-benzimideazole, 2,5-ditribromomethyl- 3,4-dibromothiophene.
[VI] Compounds represented by the general formula 1, l l trichlorowherein R is unsubstituted or substituted aryl or heterocyclic group, and X X and X individually are H, C1 or Br excepting the case where all of X X and X; are hydrogen. Typical examples are hexabromo-dimethyl sulfoxide, pentabromodimethyl sulfoxide, hexabromo-dimethyl sulfone, trichloromethyl-phenyl sulfone, tribromomethyl-phenyl sulfone, trichloromethyl-p-chlorophenyl sulfone, tribomomethylp-nitrophenyl sulfone, sulfone, Z-trichloromethylbenzothiazolyl sulfone-(2), 4,6-dimethyl-pyrimidyl-2- tribromomethyl sulfone, tetrabromo dimethyl sulfone, 2,4- dichlorophenyl-trichloromethyl sulfone, 2-methyl-4- chlorophenyl-trichloromethyl sulfone, 2,5-dimethyl-4- chlorophenyl-trichloromethyl sulfone, 2,4-dichlorophenyltribromomethyl sulfone.
As color modifiers, there are known two types. A color 0 modifier of the one type is that which originally is a colorless substance capable of converting into colored state by the action of a free radical generated from a photoactivator. Such color modifier is useful in so-called negative-positive system. A color'modifier of the other type is that which originally has a color, but can be converted into bleached or differently colored state by the action of a free radical. Such color modifier is useful in so-called positive-positive system. Illustration of these color modifiers are the following; diphenylamine, dibenzylamine, triphenylamine, N-hydroxyethyl-N-ethyl aniline, p,p'-methylenebis (N,N-diethylaniline) and the like amine compounds; leuco bases of such dyes as leuco crystal violet, leuco malachite green, michleris hydrol, leuco methylene blue, etc.; and various classes of dyes, e.g. diphenylmethane dyes, triphenylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, anthraquinone dyes, iminonaphthoquinone dyes, azomethine dyes.
conventionally know sensitizers and color tone-improving agents are usable as auxiliary components. Incorporation of these additives into a light-sensitive photographic material does not injure the effectiveness of fixation according to the present invention.
In summary, a method of the present invention comprises dipping or coating exposed light-sensitive photographic material into or with an aqueous solution of the beforedefined fixing agent and then, if desired, drying said photographic material by heating. According, it is entirely free from generation of noxious vapor or from decrease in image resolution. This enables us to obtain an excellent and stable copy through simple operations.
PREFERRED EMBODIMENTS A more detailed explanation of the present invention may be had with reference to the following examples EXAMPLE 1 A baryta paper (for photographic use) is coated under red safety light with a light-sensitive solution of:
Hexabromodimethyl sulfone-S g.
Diphenyl amine-5 g.
Acetone- 100 cc. and then dried. The thus obtained light-sensitive photographic material is superposed with a photographic negative bearing an original image and the resulted assembly is exposed to light from an 800 watt mercury lamp at a distance of 5 cm. for 5 seconds. A dark blue negative image is obtained on white background.
Then, the photographic material having the negative image is dipped into a fixer of:
Sodium hydrogen sulfite- 10 g.
Water-100 cc. for 1 minute, to obtain a reproduction which is entirely stable to light exposure.
In another run, the fixer used further contains 5 g. of hydroquinone. In this case, the resulting fixed reproduction showed a clean, white background even when stored over a long period.
In the same manner as in example 1, a light-sensitive solution of:
Acetone-100 cc. is coated on a photographic paper which is then dried. The light-sensitive photographic material thus obtained is subjected to light exposure in the same manner as in example 1 and then passed through a wet-diazotype-developing machine in which a fixer of:
Sodium sulfitel 5 g.
Water-100 cc. is applied in an amount just sufficient to moisten the surface of said photographic material. A blue image which is stable against further light exposure is obtained.
When the moistened photographic material, after applica tion of the fixer, is dried by heating at 50 C. for 7 seconds, the similar blue image is obtained. in this case, there may be substituted for the above fixer:
Sodium sulfite-7 g.
Water- 100 cc.
EXAMPLE 3 As in example I, a light-sensitive solution of the following formulation is coated on baryta paper:
Carbon tetrachloride-5 g.
Cellulose acetate-l g.
Acet0ne 100 cc. The resulting lighbsensitive photographic material is subjected to light exposure in the same manner as in example 1. whereupon a blue image is obtained. Then, the image-bearing photographic material is dipped for 1 minute in a fixer of the following formulation:
Sodium bisulfide-S g.
Waterl 00 cc. The image becomes stable against further light exposure.
Addition of 7 g. of sodium carbonate to the above fixer serves to increase the service life of said fixer as much as five times.
EXAMPLE 4 On a white base paper, the surface of which is pretreated with a 10 percent aqueous solution of polyvinyl chloride (polymerization degree 600), a light-sensitive solution of the following formulation is coated:
Tribromomethyl phenyl sulfone-S g.
Cellulose acetatel g.
The light-sensitive photographic material is a bluish green color and useful in positive-positive system, i.e., bleach-out. Exposure of the photographic material to light yields a clear bluish green image, which can be stabilized in the same manner as in example 2 by using a fixer of the following formulation:
Sodium bisulfide-S g.
Water- I 00 cc. The resulted image does not show any color change by further light exposure.
EXAMPLE 5 g. Diphenyl aminel 0 g. Acridine Orange-0.l g.
Acetone-1 00 cc. The light-sensitive photographic material obtained is sensitive over the wide range of wavelength including a visible region, since it includes a photo-sensitizing dye. The photographic material is subjected to light exposure by imagewise irradiation at a distance of 30 cm. and for 15- 1) seconds by means of a slide projector, with a 500 w. tungsten lamp as light source, having an image-bearing photographic negative placed therein. A clear blue image is obtained. The imaged photographic material is then treated by using the same apparatus and fixer as used in example 2, to obtain stabilized image which is entirely safe against further light exposure.
The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described exam ples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.
What is claimed is:
1. In the method of forming an image which comprises providing an imaging material comprising a photoactivator capable of generating a halogen free radical by the action of light and a color modifier capable of producing a visible color change by the action of said halogen free radical; exposing said material imagewise to light thereby effecting imagewise halogen free radical generation and a coincident visible color change; and fixing the resulting image; the improvement which comprises a fixing method wherein said material, after light exposure, is contacted with an aqueous solution of a sulfur compound selected from the group consisting of watersoluble salts of hydrogen sulfide and water-soluble salts of sulfur-containing oxygen acids for a time sufficient to inactivate said photoactivator.
2. The improvement according to Claim 1 comprising the further step of drying the material thus contacted at a temperature between about l 80 C.
3. The improvement according to Claim 1 wherein said material is coated with said solution.
4. The improvement according to Claim 1 wherein said material is dipped into said solution.
5. The improvement according to claim I wherein said solution further comprises up to about 10 percent of a hydroxy benzene reducing agent.
6. The improvement according to claim 2 wherein said drying step comprises contacting said material with a surface heated to about C.