US2432593A - Phloroglucide containing diazo photoprinting material - Google Patents

Description

Patented Dec. 16, 1947 PHLOROGLUCIDE CONTAINING DIAZO PHOTOPRINTING MATERIAL "James M. Straley, Easton, Pa., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 20, 1945,

Serial No. 636,250

6 Claims. (01. 95-6) This invention relates to a 'diazotype photoprinting material. More particularly, in one embodiment, it relates to a photoprinting material containing a coupling component which will couple with an undecomposed diazonium compound in the density areas, after exposure to light and upon development in an alkaline medium, to produce an azo dye image. In another embodiment, it relates to a photoprinting material containing a, coupling component which will couple with a, decomposed diazonium component in the high-light areas upon exposure to light to give an azo dye image.

Many processes have been suggested for the production of photoprinting material, such processes d ilering principally in the chemical used as the light-sensitive element and in the manner of developing a dye image. The most widely known of these processes are,those which are based upon the light sensitivity of aromatic diazo compounds. Other such processes of less importance include processes based upon the light sensitivity of the leuco compounds of the coal tar dyestufis; processes based upon the oxidizing action of o-nitro groups in aromatic systems having aliphatic side chains, as for instance, o-nitrophenyl lactic acid methyl ketone; andv processes based upon the light sensitivity of the o-nitro-diaminotriphenyl-methane bases. With the exception of the processes based upon the light sensitivity of aromatic diazo compounds, these suggested photoprinting processes have found no commercial adaptability either because of the instability of the compounds employed or the difliculty of developing the dye image from the undecomposed light-sensitive material. The

aromatic diazo compounds have found wide commercial acceptance in two well known processes which are designated respectively as the onecomponent or wet-development process, and the two-component or dry-development process.

In the one-component process, the aromatic diazo compound is incorporated into a lightsensitive layer on the carrier which may be paper,

Ioil, glass, textile material or a metallic surface.

After exposure under the original to be copied, this light-sensitive layer is developed by contact with an alkaline solution of the coupling comimage is effected after exposure by contacting the light-sensitive layer with ammonia gas. When employing a diazonium salt as the lightsensitive material, for optimum results, it is usually'necessary to limit the selection of the diazo compound to the diazo salts derived from aromatic D-diamines and o-aminonaphthols, since premature coupling of the dye components may take place if other types of diazos are used in the light-sensitive layer together with the coupling components, thus-reducing the keeping quality of the coated carrier.

In photoprinting processes of these types it is highly desirable to produce a copy which will have a distinctive color, preferably a dark shade on aclear white background, so that the image will be sharp. It is also desirable to have a material which will give gradation of shade throughout the high-light and half-tone areas.

Diazo sulfonates will not couple with a coupling component in the absence of strong actinic light. However, they may be employed in a photoprinting process as follows. A solution of a diazr) sulfonate and a coupling component is coated upon a carrier, dried, and exposed to strong actinic light under an original. The portions of the diazo sulfonate which are exposed to the actinic light are decomposed to form a diazo com pound which will couple with the coupling component to give an azo dye image. By this method, a positive is obtained from a negative, and a negative is obtained from a positive.

The coupling components must be stable, fast to light and insensitive to alkali. They should be soluble in water or in an organic solvent, yet the dyestufi produced therefrom should be'water insoluble. Only few serviceable compounds are available as coupling components, such as phenols, amines, aminophenols, pyrazolones, carbazoles, sultones, naphthols, acetoacetic acid esters and acetanilides.

An object of the present invention is to provide new photoprinting material containing a coupling component which will couple with an undecomposed diazonium salt in the density areas i after exposure to light and upon development in an alkaline medium to give an 'azo dye image.

Another object is to provide photoprinting material which contains a coupling component which will couple with the decomposed diazo sulfonate in the high-light areas upon exposure to light to give an azo dye image.

A further object is to provide a process of producing such photoprinting material.

I have discovered that a valuable photoprinting material may be obtained when phloroglucide, an ester of phloroglucide, an ether of phloroglucide, or a salt of phloroglucide is employed as a coupling component. Phloroglucide is believed to have the formula OH OH As examples of esters of phloroglucide there may be mentioned the formate, acetate, propionate, butyrate, benzoate, naphthionate and anthranilate. As examples or others of phloroglucide, there may be mentioned the methyl, ethyl, propyl, amyl, butyl, hexyl, phenyl, benzyl, naphthyl, and the like, ethers. As examples of salts of phloroglucide, there may be mentioned the sodium, potassium, calcium, barium, magnesium, copper, and the like, salts. These compounds may be further substituted for example by COOH, SOsH, N02, NHz, Cl, alkoxy, aryloxy and benzyl groups in which case, however, at least one nuclear position should be unsubstituted.

In a preferred embodiment, the process of this invention is carried out by coating a suitable base, such as paper, a cellulose or cellulose ester film, glass plate, textile material, gelatlnized surface or metallic surface with a coating preparation containing the phloroglucide or its derivatives, a light-sensitive diazonium salt, a mild acid such as citric acid, thiourea and water. The coating is effected in the usual manner by applying the coating solution to the surface of the carrier or base material with a doctor blade or by spraying. The coated material is then dried, exposed under an original positive or negative picture or drawing, and developed by treatment with ammonia or other suitable alkaline materials.

The coupling components of the present invention are particularly suited to non-aqueous coatings, such as those obtained from resinous solutions. Organic solutions of high volatility such as alcohols, ethers and ketones, may also be employed in the place of water. Such diluents may be employed to make up the coating solution in cases where the base material or carrier is such that the diluent exerts no appreciable solvent action on the carrier material. High temperature drying may thus be avoided.

In another manner of carrying out this process, only the light-sensitive diazonium salt is added to the mild acid solution and coated onto the carrier. The exposure under a suitable positive is effected as above, but the image is developed by bathing the exposed element in analkaline bath containing the coupling component necessary to combine with the undecomposed diazonium salt to form a dye in the unexposed areas.

In still another manner of carryingmut this process, a diazonium sulfonate may be employed as the light-sensitive material. A solution of a diazo sulfonate and a coupling component is coated on a suitable carrier, dried, and exposed to 4 stabilizers, preservatives, extenders, color intensiflers and light-sensitive intensiflers.

The colors produced by this process are intensely dark, and are similar to those obtained when phloroglucinol is employed-as the coupling component. However, unlike phloroglucinol, the two-component diazotype coatings using phloroglucide or its derivatives as the coupling component produce a dlazotype photoprinting material which will not precouple during long storage prior to use. Undesirable background color in the prints subsequently made from such diazotypes is accordingly eliminated.

The following examples illustrate methods of carrying out the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.

Example 1 whose backgrounds showed no appreciable disstrong actinic light under a suitable positive or 'to the coating solution in any of the modifications of this process, which materials may function as coloration.

When an equivalent amount of phloroglucinol was substituted for the phloroglucide in the above paper, and the coated paper stored under the same conditions as above upon exposure and development, there were obtained prints having badly discolored backgrounds indicating that a high degree of coupling had taken place during storage.

When methyl 2,4,6-trihydroxybenzoate (as disclosed in U. S. P. 2,286,656) is used instead of phloroglucide, and the coated paper stored under the same conditions, the results are similar to those experienced with phloroglucinol.

Example 2 In the process of Example 1, 1.5 grams of naphthalene-2-diazo-l-oxide-fi-sulfonic acid is substituted for the 1.6 grams of p-diethylaminobenzenediazonium chloride-zinc chloride. Similar intense violet images on excellent clear white backgrounds are obtained.

Storage of the unexposed paper of this example for twenty hours at 38 C. and relative humidity, followed by subsequent exposure and development, gave prints whose backgrounds showed no appreciable discoloration.

Example 3 A coating solution of 0.3 gram of phloroglucide, 5 grams maleic acid, and 0.7 gram of pdiethylaminobenzenediazonium borofluoride (in 3 cc. formic acid) was dissolved in 50 cc. of a 12% acetone solution of cellulose acetate butyrate. This solution was coated onto cellulose acetate foil and onto paper. Upon exposure to ultraviolet light under a suitable positive and development with ammonia vapors, intense, almost black prints, on colorless background were obtained.

Storage under the conditions in Example 1, exposing and developing, gave pictures in which the whites were clear and showed no appreciable staining resulting from preooupling.

means when phioroglucinol was substituted for the phloroglucide in the same papers, prints were obtained, after similar storage as above, in which the unexposed portions could scarcely be distinguished from the exposed surfaces.

Phlorogiucide acetate gives the same good results as are obtained from phloroglucide.

Example 4 Paper was coated with a solution of 2.1 grams of 4 benzoylamino 2,5 diethoxy benzenediazonium chloride-zinc chloride double salt, 10 grams citric acid, and 5.4 grams thiourea in 100 cc. of water. The dried coating was exposed to ultraviolet light and sponged with a solution of 2 grams phloroglucide dissolved in 100 cc. of water made alkaline with sodium hydroxide. Dark prints on a white background were obtained.

Example 5 A solution of grams of citric acid, 5.4 grams of thiourea, and 1.5 grams of p-phenylaminobenzenediazonium sulfate in 98 cc. of water was added to a solution of 0.6 gram phloroglucide in 4 In any of the foregoing examples, any of the esters, ethers or salts of pholoroglucide, such as phloroglucide acetate. monomethyl ether of phloroglucide and sodium phloroglucide, can be substituted for the phloroglucide to produce the same results as are obtained when using phioroglucide. Diazosulfonates may also be substituted for the diazo compounds when negative prints are desired. A typical diazo sulfonate coating solution contains 3.5 grams of 4-benzoylamino- 2,5-dimethoxybenzene diazo sulfonate and 2 grams of the monomethyl ether of phloroglucide in cc. of a 1% sodium hydroxide solution. After drying such a coating on a suitable base. exposing under a negative to ultraviolet light and developing with ammonia gas, an excellent positive picture can be obtained.

I claim:

1. A photoprinting material containing a lightsensitive diazo compound and a phloroglucide compound as the azo dye component.

2. A photoprlnting material containing a lightsensitive diazo compound and phloroglucide.

3. A photoprinting material containinga lightsensitive diazo compound and an ester of phloroglucide.

4. A photoprinting material containing a lightsensitive diazo compound and an ether of phloroglucide.

5. A photoprinting material containing a lightsensitive' diazo compound and phloroglucide acetate.

6. A photoprinting material containing a lightsensitive diazo compound and phloroglucide methyl ether. 1

' JAMES M. STRALEY.