US2495918A - Poly-n-vinyl lactam photographic silver halide emulsions - Google Patents

Description

Patented Jan. 31, 1950 POLY-N-VINYL LACTAM PHOTOGRAPHIC SILVER HALIDE EMULSIONS Elmer Keiser Bolton, Wilmington, DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application August 28, 1948, Serial No. 46,722

8 Claims. (01. 95-7) This invention relates to photographic emulsions and emulsion layers composed of polymers of poly-N-vinyl lactams and to photographic elements containing such emulsion layers.

Many different materials have previously been used in photographic emulsions as binding agents for light-sensitive components. The most widely used material, gelatin, is well adapted to this use because it serves as a good protective colloid for silver halides in such emulsions and, when coated ona suitable support, these emulsions form films which are permeable to the aqueous solutions used to develop photographic images. Gelatin has a number of disadvantages, however, among which may be mentioned its high cost, lack of uniformity of one batch with another, susceptibility to bacterial attack, and its susceptibilit to change in physical properties with changing humidity conditions.

It has now been found that useful photographic compositions can be made by incorporating lightsensitive material capable of forming a latent image, and especially silver halides, in a poly-N- vinyl lactam having an average molecular weight of about 10,000 to 500,000. This may be accomplished by dissolveding the poly-N-vinyl lactam in water and admixing the light-sensitive silver halidetherewith. After the light-sensitive material has been uniformly dispersed, the resulting colloidal dispersion may be further modified and coated on a support to form alight-sensitive layer.

In a practical mode of procedure, the poly-N- vinyl lactam, e. g., poly-N-vinyl caprolactam, is dissolved in water. Separate solutions are made by dissolving a soluble, ionizable halide, e. g., sodium, potassium, or ammonium chloride, bromide, or iodide, and b dissolveing separately in water a soluble, ionizable silver salt, e. g., silver nitrate. The three solutions thus formed are mixed simultaneously to disperse colloidally lightsensitive silver halide in the polymer. The resultir'ig emulsion can then be ripened, chilled, coagulated ,and washed. Unwashed emulsions can be used but, 'in general, it is desirable to remove the excess s'oluble salts, preferably by dialysis. The precipitate can then be redispersed and the emulsion modified by the addition of more of the same type of poly-N-vinyl lactam, general emulsion sensitizers, anti-fogging agents, spectral sensitizing dyes, preservatives, hardeners, and/or color formers and coated on a temporary or permanent support or on a layer of such support.

After the light-sensitive poly-N-vinyl lactam solution is prepared for coating, it may be deposited in the same .Way that gelatin-silver halide solutions are'coated upon a suitable support, e. g., metal, paper, glass,"or a transparent film such as a cellulose derivative, e. g., cellulose nitrate, cellulose acetate, or a superpolymer, e. g., polyvinyl chloride, polyethylene, nylon, etc., and dried. The resulting element can then be exposed and processed to positive or negative pictures in the same manner as ordinary gelatino-silver halide photographic elements.

The poly-N-vinyl lactams which have been found to be useful in the photographic emulsion layers of this invention can be made by adding a free radical producing catalyst, e. g., p-tertiary butyl peroxide, ma-azo-bis-isobutyronitrile, etc, to N-vinyl lactams, e. g., N-vinyl caprolactam, and heating in the absence of oxygen until the polymer is formed. The useful poly-N-vinyl lactams have an average molecular weight of about 10,000 to 500,000 and are generally soluble in Water at 5 C. to 25 C. to the extent of 5%-20% or more. They can, however, be dissolved in watercontaining small amounts (l0%-20%) of a water-soluble organic solvent, e. g., ethanol or methanol. The polymerization of N-vinyl caprolactam with a -azo-bis-isobutyronitrile and related catalysts is disclosed and claimed in Hunt U. S. application Ser. No. 655,015, filed March 16, 1946, now abandoned, and continuation-in-part application Ser. No. 2,551, filed January 15, 1948, now Patent No. 2,471,959.

The invention is further illustrated by the following examples in which parts are by weight. The photographic solutions and coatings were prepared in the absence of actinic light or radiations.

Example l A photographic emulsion containing poly-N- vinyl caprolactam having an average molecular weight of about 40,000 as the binder for silver hal ide was prepared as follows: Separate aqueous solutions containing the following constituents were made. Y

3 These three solutions were mixed simultaneously by running streams of solutions A and B from separate containers into a common reaction vessel containing solution C with rapid agitation. The resulting light-sensitive silver halide suspension in the poly-N-vinyl caprolactam was :dialyzed through a water-permeable cellophane (regenerated cellulose) membrane having a thickness .of about 0.8 mil. until the conductivity had been reduced to 800 micromhos and coatings were made on raw stock paper coated with baryta gelatin. After drying, the photographic element was exposed by focusing on it the imageo'f'a transparency negative and developed by immersion at 20 C. in a standard p-methylaminophenolhydroquinone developer having the following composition:

Parts p-Methylaminophenol sulfate .3.1 SOdiumsulfite (anhydrous) 34510 Hydroquinone 121) Sodium carbonate (anhydrous) 67,5 Potassium bromide 1;9

Water to make 1,000

.The developed picture was fixed by bathing in 1a. 25% solution of sodium vthiosulfate, freed from soluble salts by washing, and then-dried. .The re- ;sulting black and white picture had density gradations complementary to the object .scene to which the element was exposed. The developed picture formed from the :poly-N-yinyl caprolaotam showed 'speed, contrast, and fog-values comparable to that of commercial:gelatino-silverihalide emulsionsused onenlarging'papers. ,Printszon paper of this emulsion have a pleasingiwarmth :of :tone.

Similarly, a photographic emulsion can .be prepared in which poly-.N-vinyl caprolactamzisused .as abinder for light-sensitive:silver'halideand a .color former. After exposing and processing .-in the usual.manner witha color developer-containing N-p-diethylaminoaniline, a photographic :element bearing a colored photographic image ,can be obtained.

Example II A photographic emulsion containing poly-N- vinyl-butyrolactam as the :binderfor silver halide was prepared -.as :follows: Separate aqueous solutions containing the following components .were made.

A AgNOs (3N) cc s5 NHOH (20%) cc 35 NHdBl :(BN) ..-gcc, .37 KI ,(O.5N cc... \6 10% soln. of poly-N-vinylbutyrolactam (average molecular weight of about 60,000) grams 120 4 valerolactam. Mixtures of two or more of such lactams can be used. The poly-N-vinyl lactams should be capable of allowing the photographic processing solutions to penetrate sufliciently to act on the exposed and unexposed light-sensitive sil- -ver halide; at the same time, they should not dissolve in photographic processing solutions. To

achieve this, they must have an average molecular weight of 10,000 to 500,000 or above.

invention is not limited to the specific light-sensitive silver halides described in the above examples. Various other simple and mixed silver halides may be used as the light-sensitive materials of this invention. Mixtures of silver chlorides, bromides, and/or iodides can be made sby adding mixtures of soluble salts of these halides in the same manner as described in Example I. Other useful soluble halides include potassium bromide, sodium iodide, sodium and potassium chlorides, etc.

.The :poly-N-vinyl lactams are useful :not only :as the binding agent for light-sensitive silver salts in radiation sensitive layers but may 'alsobeused .as a water-permeable binder for other light-sensiitive materials capable of forming a latent image such as diazonium compounds, ammonium bichromate, fu-lgides, *N-monoarylhydroxylamincs and their -nitrones, etc. 'They-mayalso be used as :the binding agent of filter layers which may have .dyes dispersed therethrough or antihalation lay ers which :have antihalation dyesor pigments dis- .persed therethrough, .and .as binding agents for non diffusing.coloiflformers which are placed adijacent to light-sensitive silver halide layers.

To the emulsions after formation and digestion can ;be added. either during :the digestion stage or before, various types :of sensitizing agents, e. g., sulfur sensitizers such as 'allyl ithioureas, thiocyanates, :or sodium thiosuliate. In addition-various types of optical sensitizing dyes which modii y the spectral characteristics of the resulting emulsion can be added.

Various "types of color formers -or dye intermediates capable of forming 'quinoneimine,

* indophenol or azomethine dyes on color-forming development can be incorporated in the emulsions. -Thus, the phenols, naphtho'ls, pyrazolones, 'acyl'acetamides, hydrindene, EN-

=homophthalimides, etc., particularly those '01 high molecular weight and which are immobile in gelatin emu'lsion layers can be 'used. Suitable color formers are described in United States Patents 2,108,602, 2,166,181 2,178,612, 2,179,228,

* 2,179,238, 2,179,239, 2,182,815, '2,1s4,303,-2,1ss,s49,

2,200,924, 2,283,276, and "2,328,652.

As compared with gelatin emulsions prepared under comparable conditions the poly-N vinyl lactam emulsions contain 'smaller size particles of silver halide and, therefore, 'give emulsions films, in lithographic film, and asportraitrma- 'teria'ls. "Infa-ctthe'illm elements of 'thisinvention can be used in systems in which elements based on gelatin or collodion have been used.

What is claimed is:

1. A photographic emulsion comprising lightsensitive silver halide grains dispersed in a poly- N -vinyl lactam having a molecular weight of about 10,000 to 500,000.

2. A photographic emulsion comprising lightsensitive silver halide grains dispersed in a poly- N-vinyl lactam having from 4 to 6 carbon atoms in the lactam ring and a molecular weight of about 10,000 to 500,000.

3. A photographic emulsion comprising lightsensitive silver halide grains dispersed in a poly- N-vinyl caprolactam having an average-molecular weight of about 10,000 to 500,000.

4. A photographic element comprising a support bearing a photographic emulsion comprising light-sensitive silver halide grains dispersed in a poly-N-vinyl lactam having a molecular weight of about 10,000 to 500,000.

5. A photographic element comprising a sup port bearing a photographic emulsion comprising light-sensitive silver halide grains dispersed in a poly-N-vinyl lactam having from 4 to 6 carbon atoms in the lactam ring and a molecular weight of about 10,000 to 500,000.

6. A photographic element comprising a support bearing a photographic emulsion comprising light-sensitive silver halide grains dispersed in a poly-N-vinyl caprolactam having an average molecular weight of about 10,000 to 500,000.

7. A photographic element comprising a transparent film support bearing a photographic emulsion comprising light-sensitive silver halide grains dispersed in a poly-N-vinyl lactam having from 4 to 6 carbon atoms in the lactam ring and a molecular weight of about 10,000 to 500,000.

8. A photographic element comprising a transparent film support bearing a photographic emulsion comprising light-sensitive silver halide grains dispersed in a poly-N-vinyl caprolactam having an average molecular weight of about 10,000 to 500,000.

ELMER KEISER BOLTON.

No references cited.

Claims (1)

1. A PHOTOGRAPHIC EMULSION COMPRISES LIGHTSENSITIVE SILVER HALIDE GRAINS DISPERSED IN A POLYN-VINYL LACTAM HAVING A MOLECULAR WEIGHT OF ABOUT 10,000 TO 500,000.