US2235426A

US2235426A - Sensitized photographic element and process of making the same

Info

Publication number: US2235426A
Application number: US168902A
Authority: US
Inventors: Goodman Mac
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-10-14
Filing date: 1937-10-14
Publication date: 1941-03-18
Anticipated expiration: 1958-03-18

Description

Patented Mar. 18, 1941 UNITED STATES PATENT i SENSITIZED PHOTOGRAPH) ELEMENT AND 4 j PROCESS OF MAKING THE SAME I Kerk. N. Y.

I No Drawing.

I plication October 14, 1937,

I Serial No. 168,902 7 cam.. (on. 95-7) graphic elementsincorporating color formers, by

10 virtue of the inability of properly associating or bonding such colorformers with the silver. halide Particles.

Generally, two methods have :been known, the first being that wherein color-forming compound is dispersed among the silver halide grains carried in an emulsion, whereby the color former essentially permeates the emulsion, and in hitor-miss fashion becomes associated, through sur face contact, with the silver halide particles; and

the other in which light sensitive substances are formed by precipitating silver halides in the presence of color formers as, for example, generally by reacting a soluble halide, a soluble silver salt, and a color former, in a colloid forming the 2 emulsion.

With respect to the first of these methods, little need be further stated, in view of its obvious deficiencies; with respect to the second, several factors limit the degree and amount of association of the color former to the silver halide, to such extent as to minimize the efiectiveness of this procedure for application in recording color images. Primarily, the restrictions result through the following: first, the color former being normally soluble in small quantities only, in the solution incorporating the soluble halides and silver salts of particle mass concentration far greater than that of the color former, with the result that the chemically formed insoluble silver halide crystal or grain must often form and ripen without any contact or collisions with the discrete color former particles in the reacting mixture; secondly, an aqueous medium in large quantities being required as the solvent inthe colloid in which the reaction is carried out and the color former of necessity being insoluble in such medium, the amount of physical association or afliliation of the discrete color former particles to and with the silver halide crystal nuclei as chemically formed is at. best small, since such afiiliation involves the physical intercombination of. discrete particles of two'different precipitates having no direct relationship other than being present in the solvent; lastly, the reaction involv- V ing thesoluble halide, solublesilver salt and the insoluble color former, being one wherein the' halide and the silver salts are first intended to react chemicailyto form. a silver halide precipitate, and thereafter the precipitated silver halide and discrete color former particles are intended 6 to unite physically, and the color formerdiscrete particles being essentially'and at all times during the chemical reaction aforesaid an insoluble precipitate, the amount of affiliation, surface in this case, is necessarily restricted and far from 10 the mass or molecular association necessary for the purpose, since no direct interaction of the radicals of the reagents, forming the silver halide crystals-is had with thecolor former, to place the color former particles and silver halide crys- 15 tals in the required proximity. Broadly, it is an object of this invention for the production of light sensitive halides incorporating color formers, by providing an optimum condition for inter-association of the light sensi-" tive halides and the color formers, through the reaction of media providing for a simultaneous chemical intercombination of radicles forming the silver halide and physical adsorption and, occlusion of the particle ofthe color former, 25 both chemical and physical reactions being consummated at the same situs.

Further it is an object of this invention toprovide for the formation of the light sensitive element of a photographic emulsion, wherein 0 color formers are associated with the silver halide, by reacting the silver compound of a color former with a soluble halide and forming, by presenting the color former in situ with the resulting silver halide crystals in a simultaneous 35 chemical and physical reaction, a micro-homogeneous and micro-heterogeneous complex in the nature of a silver halide crystal incorporating the color former radical or particle, such color former simultaneously at the completion of the 40 chemical reaction and subsequent ripening steps :being adsorbed and substantially occluded into the light sensitive silver halide crystal nucleus as it is formed and grows.

Specifically, it is an object of this invention'to 45 form as a light sensitive silver halide, a reaction product of a silver salt of a color former and a soluble halide in substantially molecular proportions, whereby there is formed during and by such reaction, a silver halide crystal to which there is adsorbed and in which there is occluded the color former particle or radical, from the silver salt of which color former the silver radical of the formed insoluble halide'has separated.

In general, the invention comprises a positive 55 and'efi'ective method of accomplishing the union v or bonding of a color former with a silver halide to provide a light sensitive element color recordan exchange of radicals is introduced and simultaneously therewith a physical reaction eflfectuated at the situs ofand during-the course of formation of the silver halide associating firmly by adsorption-and occlusion the color former radical or particle with the silver halide crystal nucleus produced by the chemical reaction as it ripens.

These and other advantages, capabilities and features of the invention will appear from the subjoined detailed description of one specific embodiment thereof. a

In accordance with this invention the photographic element may be either of a single emulsion or a series of emulsions in which the silver halide and color former are united or bonded in a manner that the color former is adsorbed or occluded in the silver halide crystal, being transparent and relatively colorless, the color effect desired for recording particular color values being established after exposure by and in development.

In carrying out the invention the color sensitive emulsionsfor the respective different colors are prepared as follows:

A silver salt of a color former having very slight solubility in aqueous solution is, together with an equal molecular amount of potassium bromide, disposed in a colloid serving as a carrier as, for example, gelatin, agar agar, or cellulose derivatives, there being present in the reacting mixture a small'quantity of acid. The reaction involved is the chemical combination of the silver radical from the color former salt and the bromine radical of the halide to form the insoluble light sensitive halide, the alkali oi the halide being combined with the negative radical of the acid, and the hydrogen radical of the acid being united to the color formepin replacement of the silver radical of the silver color former salt. The insoluble silver halide formed by the chemical reaction in the form of nuclei are physically bonded to the color former from which the silver has beenchemically separated, with the color former' being adsorbed and occluded to the respective silver halide nuclei as they ripen, due to the physical proximity of the color former molecules, to the latter as they are formed, with the result that the light sensitive element being in the nature of a complex silver halide-color former, is dispersed in the colloid, as the latter jells upon removal of the solvent.

, Since it is desired to form different color sensitive emulsions, silver salts of various color formers may be applied to establish the respective color values capable of production by exposure and development and following are examples of i the same.

To produce an emulsion for the red color, a

' silver nitrophenyl acetonitrile is reacted with potassium bromide and a dilute acid such as nitric acid, the reaction being as follows:

Where the dotted line in the formula on the right hand side of the equation, between the nitro phenyl aceto nitrile and the Ag bromide, indicates the close association of the respective molecules.

To produce an emulsion tor the blue color silver pentabrom alpha naphthoi is reactedwith potassium bromide and nitric acid in accordance with the following reaction:

Br Br v Br he Br r AgBr To produce an' emulsion for the yellow color,

silver aceto-acet-2,- 4 dichloranilide is-reacted with potassium bromide and dilute nitric acid in accordance with the following reaction:

cmcocmconOm Ag+BrH Agllr Furthermore, it is not necessary for the reacting substances to be present in molecular proportions. For example, it may be desired for given purposes to produce an emulsion containing Pa complex light sensitive medium and consisting of adsorbed and occluded silver halidecolor former-silver salt of color former; Thus, 2 parts of the silver salt of the color former may be used with 1 part each of potassium bromide and nitric acid, or 2 parts of the silver salt of the color former and one part of the acid halide.

Cl Cl CIIa.CO,CH2.CO.N (.I CHz.CO.CHz.CO.N Cl ,0

Ag s

+BrH 5 IM; ngBr '01 omcocmcoxQm 1 C cmcocmcogQm These silver halide and color formers complexes which provide'fonthe production of definite colors on exposure and development may be sensitized for specific regions of the spectrum in the ways well'known in the art.

Thus, the emulsion for red may be opticallyv sensitized for green by treatment, during or after the production of the emulsion, with an appropriate green sensitizing dye as erythrosine; The emulsion for blue may be optically sensitized for red by treatment with an appropriate red sensitizing dye as pinacyanol; the emulsion for yellow being natively sensitive for blue and thus need not be especially treated.

By thus mixing emulsions for each of the three colors,'which have been appropriately sensitized, a mixed emulsion is produced which may be coated as a single layer on a carrier, forming a photographic light sensitive element for the production of the three colors. The single emulsion alternately may be coated in three layers one upon another, on a carrier, thus producing the more familiar element for three colors.

After exposure the emulsions are treated with or Farmers reducer.

' the color former and the silver halide are sub- These color images are superior to those produced by other processes by virtue of the fact that'the color former is constantly in contact with the silver halide crystal at its formation and during its period of ripening and growth and the ratio of mass particles of respectively s'tantially molecular; the color former. at the instant of liberation and the instant of formation of the nucleus of silver halide being present in molecularly dispersed form at the crystal face of the halide for simultaneous adsorption and occlusion as the silver halide nucleus grows through ripening. It is to be understood in this process that with the ionic exchange of radicals there are produced two insoluble substances at one situs, and since one of the insolubles, the silver halide, is of a nature once its nucleus has formed as to enlarge its crystal form on ripening in a duration of time; and since the color former particles are absorbableand are at thesitus of the formation of the silver halide nucleus, the physical phase of the interaction between the respective silver halide and color former commences immediately and 'is carried on progressively with the resultant effect, that there is no difier'ential separation of the particles but rabheran agglomeration, that is, a building up of the particles of one precipitate by absorbing the immediately available particles of the other.

Wherever in the specification the words color former have been used, it is to be understood that the expression refers to a color forming silver halide crystal having adsorbed and occluded thereon a color forming development component through chemical and physical interaction, which consists in reacting in solution a pre-formed silver salt of a color forming development component with a soluble halide.

2. A-method of making a light sensitive complex for photographic purposes, incorporating a silver halide crystal having adsorbed and eluded thereon a color forming development componentthrough chemical and physical interaction, which consists in reacting in solution and inrmolecular proportions a pro-formed silver salt ofa color forming development component with a soluble halide.

3. The methodof making a light sensitive photographic element, which consists in precipitating in a colloid medium, a silver halide-color forming development component complex through reaction of a pre-formed silver salt of a color forming development component with a soluble halidein acid solution.

4. The method of making a light sensitive photographic element, which consists in forming at one and the same situs by chemical and physical union, a complex incorporating a silver halide having adsorbed and occluded thereon an organic color forming development component by reacting in" solution the pre-formed silver salt (if a color forming development component with a soluble halide in-a colloidal medium serving as a carrier.

5. In the preparation of a light sensitive photographic medium,.the process which comprises reacting in solutiona pro-formed soluble halide with a silver salt of a color forming development component in a colloidal medium serving as a carrier, to form at one and the same situs through precipitation and ripenin a complex salt in the nature of a silver halide crystal having a color forming development component adsorbed and occluded thereto.

6. In the preparation of a light sensitive prises reacting in solution-in molecular proportions within a colloidal medium serving as a carrier, a soluble halide and apre-formed silver salt of a color forming development component for precipitating out and forming by subsequent ripening, a complex salt incorporating a silver halide crystal having the color forming development component bound thereto by adsorption and occlusion in substantially molecular proportions.

7. In the preparation of a light sensitive photographic medium, the process which comprises reacting in solution in acolloidal medium serving as a carrier a soluble halide and a preformed silver salt of a color forming development component for producing at the same situs by simultaneous chemical and physical interaction, a macro-homogeneous and microheterogeneous complex in the nature of asilver' halide crystal incorporating a color forming development component.

' MAC GOODMAN.