US2525751A - Light-sensitive diazonium salt materials - Google Patents

Description

Patented Oct. 10,

LIGHT-SENSITIVE DIAZONIUM SALT MATERIALS Paul E. Spoerri, Blue Point, and David P. Habib, Brooklyn, N. Y., assignors to L. L. Ridgway Co., Inc New York, N. Y., a corporation of Texas No Drawing. Application December 30, 1947,

Serial No. 794,824

This invention relates to light-sensitive materials, particularly to such light-sensitive materials that are of utility in the photographic printing art, and has for its object the provision of an improved light-sensitive material, an improved light-sensitive layer comprised thereof, and an improved photo-print paper surfaced therewith.

Another object is to provide a light-sensitive diazo-compound widely utilizable in the photographic printing art and a method of producing same.

Other objects will be apparent as the invention is more fully hereinafter disclosed.

In accordance with these objects, we have discovered that certain diazo-salts of 2:3 dihydroxy naphthalene-B-sulfonic acid are light-sensitive compounds; that in the presence of alkali or basic compounds the said salts decompose and undergo internal rearrangement to form a monazo dye of excellent color intensity; and that said salts are of great utility in the forming of light-sensitive layers on the surface of suitable materials such as sheet and strip materials heretofore utilized in the art of photographic printing. More specifically we have found that these said salts are excellent light-sensitive compounds for use in the forming of the light-sensitive layer on photo-print paper, all as will hereinafter be more fully disclosed.

Heretofore in the photographic printing art a large number of light-sensitive diazo-oompounds have been proposed and utilized in the forming of light-sensitive layers on the surface of sheet and strip materials such as paper, cloth or photographic film. Inthe normal use of these light-sensitive diazo-compounds it is necessary to incorporate in the light-sensitive layer a proportion of a chemical compound known in the art as a coupler compound for chemical reaction with the diazo-compound, in the presence of a basic compound, to form the monazo dye.

This practice has certain defects and difli- 14 Claims.

diffusing inorganic compounds which detrimentally affect the intensity of the color of the monazo-dye, and otherwise interfere with the obtainance of consistently uniform results. Moreover, it is exceedingly difficult to obtain in the light-sensitive layer the proper relative proportions of diazo to coupler compounds to consistently obtain the best monazo-dye reaction product on treatment with an alkaline compound.

Fhese and other difficulties have led us to discover a light-sensitive compound which on ex posure to light-radiation of a specific wave length or range of wave lengths decomposes into a compound which. is non-reactive with alkali compounds to form a monazo-dye but which when unexposed to suchspecific radiation is stable, photo-electrically and chemically, soluble in water or dilute acid solutions, and decomposable, per se, by alkaline compounds to form the desired monazo-dye. We have found this compound in the 'diazo-salts of 2:3 dihydroxynaphthalenefi-sulfonic acid. Various salts of this acid have been found suitable for use as a coupler compound for use in association with light-sensitive diazo-compounds in the forming of light-sensitive layers, but its use in this manner has been subject to the same defects and difliculties hereinabove set forth.

We have discovered that when this sulfonic acid compound is reacted with a light-sensitive diazo-compound, a diam-salt of the sulfonic acid forms and that the light-sensitivity of the basic ion of the diazo-compound is substantially unaffected by such salt formation. Moreover, when decomposed by lightradiation the diazosalt compound then becomes substantially 1m reactive towards mild alkali. The salt compound when the basic diazo-ion is not decomposed by culties which it is one of the objects of this in-g light radiation is readily decomposed by alkaline compounds with internal rearrangement to form a monazo-dye of maximum intensity. We have further found that light instability of these diazosalts of this sulfonic acid occurs mostly in the ultra-violet range of radiation. materially facilitates the handling and storage This I property tensity, such that variation in color intensity in successive prints does not occur and desired colors may be obtained through the use of various mixtures of such diazo-salts or of other dye compounds.

As one specific embodiment of the present invention, but not as a limitation thereof, we will disclose the same as it has been adapted to the production of a diazo-salt of said sulfonic acid which is of particular utility in the forming of photo-print paper having a light-sensitive layer comprised of this diazo-salt.

In the art of photo-print paper, particularly direct-print paper, it is especially desirable to provide a light-sensitive layer which after exposure to light radiation of a specific wave length or range of wave lengths through a suitable marked or figured positive or negative sheet and treatment with alkali or basic compounds, produces a well-defined sharp outline of the marks or figures on the positive or negative sheet in a dark color of uniform intensity, preferably dark blue or black. The organic and inorganic salts of p-diazo-dimethylaniline in mixture association with the sulfonic acid compound above identified have heretofore been utilized in the forming of light-sensitive layers on such photo-print paper in the obtainance of such dark color outlines of the marks and figures on the positive sheet. However, such prior art use of a mixture of these two compounds has been subject to the defects and disadvantages above pointed out.

We have discovered that when an alkaline solution of the sulfonic acid coupler-compound is added to an acid solution of the diazo-compound containing suflicient free acid to provide an excess of acid over that required to neutralize the free alkali in the alkaline solution of the sulfonic acid compounds said excess providing a weakly acid pH to the combined solutions, the diazocompound and the sulfonic acid compound react to form a sparingly soluble yellow crystalline salt which has the structural formula (1) indicated below:

This diazo-salt, which may be recovered by filtration and washing with cold water, is decomposed by light radiation in the ultra-violet range but only slightlyby radiation in the visible range, without decomposition of the chemical bond between the basic and acidic ions thereof and when so decomposed is colorless and chemically stable towards weak alkali. The diazo-salt when treated with an alkaline compound, such as ammonia vapors (NI-140E), undergoes decomposition and internal rearrangement in accordance with the following reaction:

The resulting monazo-dye of this reaction is of a deep, intense blue color which is highly desirable in the photo-print art. As may be seen from the equations and structural formulas given above the diazo-salt and the final dye product does not contain any inorganic groups which in the presence of free alkali can be converted into color-diffusing or obscuring basic inorganic compounds.

As an example of the formation of this diazosalt, we first form an alkaline pH solution containing one molar weight of the sulfonic acid compound and next form an acid pH solution containing a molar reacting weight of the diazocompound and add the first solution to the second solutionrat a slow rate with vigorous stirring to maintain a uniform mixture of the two solutions as the addition of the first solution to the second solution proceeds. The free acid content of the second solution is calculated to be in excess to the free alkali content of the first solution by about 10%. The volumes of the two solutions may be widely varied without essential departure from the invention and preferably is limited to that calculated to provide for complete solution of all inorganic salts present in the combined solutions and for a readily filterable filtrate.

The diazo-salt reaction product is sparingly soluble in pure water but the solubility of the salt increases with increase in the free acid content of the solution and with increase in temperature. Initially, therefore, the diazo-salt does not precipitate out of solution but as the pH of the solution approaches the neutral point, the diazo-salt in excess of the solubility limit at the temperature of the solution precipitates out and we have found that the stirring of the solution should continue for an extended time interval after the two solutions have been mixed for equilibrium conditions to be attained therein. The pH of the final solution should approximate 6.0 to 6.5 and the temperature of the solution should be maintained low and at about room temperatures for best results. Under these conditions the diazo-salt precipitates out substantially quantitatively and recoveries of about of the theoretical yield are readily obtained. Any excess of the sulfonic acid compound should be avoided. A slight excess of the diazo-compound over the sulfonic acid compound is preferred. The diazo-salt product of this reaction, being crystalline, is relatively easy to separate from the filtrate by filtration, preferably on a suction filter with washing with limited amounts of cold water to remove the filtrate residue being the recommended practice.

As typical examples of the two solutions, the first solution consists of 15.8 grams of the ammonium or 16 grams of the sodium salt of 2:3- dihydroxynaphthalene-6-sulfonic acid dissolved in millimeters of water containing 6 grams of NaOI-I. After making up this solution, the so lution should be filtered to remove therefrom any insolubles present therein.

The second solution consists of 15 grams of the double zinc chloride salt of p-diazo-dimethylaniline dissolved in 125 milliliters of water containing 1.5 grams of the sodium salt Of naphthalene tri-sulfonic acid and 2 grams of ammonium chloride. This solution after being made up also should be filtered to remove the insolubles and the filtrate should be acidified with 8 grams of sulfuric acid, or enough free acid to p vide about a 10% excessof the free acid over that required to neutralize the free alkali of the first solution.

The two solutions are mixed together by pouring the first solution into the second solution slow- 1 with vigorous stirring while maintaining the temperature of the acid mixture of solutions at a temperature approximating room or atmospheric temperatures and after complete mixing the vigorous stirring is continued for about one-half hour.

As a typical example of a coating solution containing the diazo-salt product of the present invention, which is utilizable in the art of forming photo-print paper, th following mixture of in- In the forming of this solution the tartaric acid is added to the water and the acid solution is warmed sufficiently to dissolve the diazosalt product therein. The glycerine is then added to the acidified diazo-salt solution; The tartaric acid increases the solubility of the diazosalt in the water and stabilizes it in solution. The glycerine assists in the retention of the solution on the surface of the photo-print paper. If desired, suitable amounts of a thickener such as gelatin or casein may be incorporated in the solution to facilitate application of the solution onto the surface of sheet and strip materials,

such as paper, cloth or photographic (cellulose acetate) film, and the like.

The application of this solution to the surface of photo-print paper is in accordance with standard practices, and, per se, forms no part of the present invention. Following coating the photoprint paper may be stored and handled in accordance with prior art practice with the advantage that the diazo-salt of the present invention being chemically stable and substantially inert except towards alkaline compounds and being substantially insensitive to light radiation above the ultra-violet wave band, is much easier to store and handle and remains radiationsensitive towards ultra-violet radiation longer than prior art photo-print paper usually does.

After exposure of the coated sheet to ultraviolet radiation in the usual manner through a transparent positive or negative sheet the yellow color of the sheet in the area subjected to ultraviolet radiation is de-colorized leaving a picture in yellow representative of the picture on the transparent positive or negative sheet through which the radiation is passed. On subjecting the photo-print paper to moist ammonia (NHrOI-I) vapors the yellow figure changes to a dark, intense blue color by decomposition and internal rearrangement of the diazo-salt into a monazodye in accordance with the equation given above.

The advantages of the diazo-salt product of the present invention over previous lightsensitive diazo-compounds are believed to be apparent to those skilled in the art from the above disclosure. However, it is believed most important to point out that the preservation of the l to 1 ratio of diazo-compound to coupler compound in the diazo-salt product in those areas not decomposed by the light radiation insures a color of constant and consistent intensity in the monazo-dye product formed by alkali decomposition. Further, decomposition of the basic ,diazo-ion'by light radiation inactivates the diazo-salt for alkaline reaction to form a monazo-dye, thus maintaining the 1 to 1 ratio of diazo to coupler ions in the undecomposed areas. Finally, the absence of inorganic groups in the diazo-salt of the present invention, particularly those containing basic metallic ions forming insoluble hydroxides or oxy-compounds in the presence of alkaline compounds, eliminates the possibility of color diffusion due to these reaction products.

In addition by its process of manufacture and precipitation from acid pH solution the diazosalt is substantially free of associated organic compounds and tarry residues.

In place of the p-diazo-dimethylaniline compound, above given, any other water or acid soluble salt of this diazo-compound may be employed in the manufacture of the diazo-salt of the present invention. Various other light-sensitive diazo-compounds also may be substituted for the p-diazo-dimethylaniline compound in the manufacture of light-sensitive diazo-salts of this sulfonic acid compound without essential depar ture from the invention, where monazo-dyes of different colors are desired. In substitution for the sulfonic acid compound above identified, varifunctioning as a coupler compound with diazocompounds may be substituted without essential departure from the invention, where color variations in the monazo dye product of alkaline reaction with the diaZo-salt, are desired.

In association with the diazo-salt of the present invention, we employ, also, an amount of a permanent yellow dye which is suificient to impart a substantially black color to the monazo-dye product formed by reaction of the diazo-salt with an alkaline compound. In general, this amount of yellow dye approximates 30%.

Various modifications of and departures from the invention will occur to those skilled in the art and all those are contemplated by us as may fall within the scope of the following claims.

What we claim is:

1. A light-sensitive compound consisting of a diaZo-salt of 2:3 dihydroxynaphthalene-G-sulfonic acid.

2. A light-sensitive compound consisting of the p-diazo-dimethylaniline salt of 2:3, dihydroxynaphthalene-G-sulfonic acid.

3. A light-sensitive layer comprised of a dia zosalt of 2:3 dihydroxynaphthalene-fi sulfonic acid.

4. A light-sensitive layer comprised of the pdiazo-dimethylaniline salt of 2:3 dihydroxynaphthalene-G-sulfonic acid.

5. Photo-print paper having a light-sensitive layer on the surface thereof comprised of a diazosalt of 2:3 dihydroxynaphthalene-6-sulfonic acid.

6. .Photo-print paper having a light-sensitive layer on the surface thereof comprised of the pdiazo-dimethylaniline salt of 2:3 dihydroxynaphthalene-B-sulfonic acid.

7. A coating composition for forming lightsensitive layers on the surface of sheet and strip materials, said composition consisting of a weakly acid aqeous solution of a light-sensitive diazosalt of 2:3 dihydroxynaphthalene-6-sulfonic acid.

8. The coating composition of claim '7, said solight-sensitive salt being the p-diazo-dimethylaniline salt of said sulfonic acid.

11. Photo-print paper having a light-sensitive layer comprised of the coating composition of claim 7. I

12. The method of forming a diazo-salt of 2:3 dihydroxynaphthalene-S-sulfonic acid which comprises adding an alkaline pH solution of the sulionic acid compound to an acid pH solution of a diaZo-compound slowly and with vigorous stirring and while maintaining an acid pH in the mixture of solutions and continuing the stirring of the acid pH mixture of the solutions for an extended time interval While the temperature of the solution cools to atmospheric temperatures and equilibrium conditions are attained therein and separating the precipitated salt product from the solution.

13. The method of forming the p-diazo-dimethylaniline salt of 2:3 dihydroxynaphthalenefi-sulfonic acid which comprises forming an alkaline pI-I solution of the sulfonic acid compound and an acid pH solution of the diazo-compound, said acid solution containing an excess of free acid over that required to neutralize the free alkali content of the alkaline solution, mixing the alkaline pH solution with the acid pH solution at a slow rate and with vigorous agitation sufiicient to maintain a uniform dispersion of the alkaline pH solution in the acid pH solution, continuing the agitation of the solution for an extended time interval after the alkaline pH solution has been all added to the acid pH solution to permit the mixture of solutions to cool down to room temperatures and to attain equilibrium conditions therein, and separating therefrom the precipitated salt product obtained thereby.

14. The method of claim 13, wherein the two said solutions contain molar reacting weights of the sulfonic acid compound and diazo-compound, respectively, and the volumes of the two solutions are at least suflicient to hold in solution on admixture substantiall all soluble reaction products except the precipitated salt product.

. PAUL E. SPOERRI.

DAVID P. HABIB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES K. H. Saunders, The Aromatic Diazo Compounds and Their Technical Application, pp. 164 171 (1936). V 1

Claims (2)

1. A LIGHT-SENSITIVE COMPOUND CONSISTING OF A DIAZO-SALT OF 2:3 DIHYDROXYNAPHTHALENE-6-SULFONIC ACID.

6. PHOTO-PRINT PAPER HAVING A LIGHT-SENSITIVE LAYER ON THE SURFACE THEREOF COMPRISED OF THE PDIAZO-DIMETHYLANILINE SALT OF 2:3 DIHYDROXYNAPHTHALENE-6-SULFONIC ACID.