US3469984A - Heat-sensitive diazotype materials - Google Patents

Description

United States Patent 3,469,984 HEAT-SENSITIVE DIAZOTYPE MATERIALS Edward C. Bialczak, Mount Prospect, 11]., assignor to Addressograph-Multigraph Corporation, Cleveland, Ohio, a corporation of Delaware No Drawing. Filed May 17, 1965, Ser. No. 456,536 Int. Cl. G03c U60, U58 U.S. C]. 96-75 6 Claims ABSTRACT OF THE DISCLOSURE A heat-sensitive diazotype material having two coatings wherein one coating contains a diazo compound and a coupling component and the other coating contains a metallic salt amine adduct, the amine being selected from the group consisting of alicyclic and heterocyclic amines.

This invention relates to heat-sensitive diazotype materials. More particularly, this invention relates to alkaline donor developers for heat-sensitive diazotype materials and diazotype materials containing such developers.

Heat-sensitive diazotype materials comprise a base member coated with a formulation containing a diazo compound and a coupling component with which the diazo compound reacts under proper conditions to form an azo dye which produces a visible image. In making a print, the diazotype material is exposed to light under a translucent master. In those areas of the diazotype material which are exposed to light, the light-sensitive diazo compound is at least partially destroyed but is unaffected in the shaded areas. The print is then developed by heating the diazotype material and causing the alkaline donor developing agent to emit ammonia or an organic amine which produces the proper pH conditions for interaction of the diazo compound and the coupling component. These react to produce a dye image in the shaded area which corresponds to the graphic material on the master.

In conventional heat-sensitive diazotype materials the alkaline donor developer is commonly a urea or thiourea compound which on decomposition at elevated temperatures yields ammonia which induces the coupling reaction to form the azo dye. Urea and thiourea compounds produce diazotype materials having a relatively poor shelf life due to precoupling of the diazo compound and the coupling component at ambient temperatures. Other heatsensitive diazotype materials which have longer shelf lives usually require higher temperatures to induce coupling. Generally, these temperatures are too high for oflice equipment and often they are so high that the diazo compound decomposes more rapidly than it reacts with the coupling component to form the azo dye. To cope with the problem of precoupling, increased amounts of acid have been used to stabilize the formulations, thus requiring increased amounts of alkaline donor to be incorporated into the formula to provide a sufiicient source of ammonia to give a suitably dense image. or example, British Patent No. 909,491 proposes the use of certain types of acids which lose their acidity on heating and thereby reduce the required quantity of alkaline donor since at developing temperatures the acid is dissipated.

It is an object of this invention to provide heat-sensitive diazotype materials wherein the alkaline donor is stable "ice at ambient temperature, decomposes to produce alkaline substances at relatively low temperature and does not contribute to precoupling. It is another object of this invention to provide heabsensitive diazotype materials which form good prints and which have extended shelf life. It is a further object to provide alkaline donor materials for heat-sensitive diazotype materials which decompose at relatively low temperatures to provide alkaline materials which induce dye formation. These and other objects are apparent from and are achieved in accordance with the following disclosure.

In accordance with the present invention, it has been discovered that primary, secondary and tertiary aliphatic amines, alicyclic amines, aromatic amines and heterocyclic amines may be reacted with the halide, sulfate and nitrate salts of the metals in Groups II, III, IV, VI, VII and VIII of the Periodic Table to form adducts or complexes which are valuable alkaline donors for diazotype materials.

The preferred metallic cations are those of Groups IIA, II-B and VIII of the Periodic Table, particularly magnesium, calcium, strontium and barium; zinc, cadmium and mercury; germanium, tin and lead; chromium, molybdenum and tungsten; manganese; and iron, cobalt and nickel. Particularly desirable are the colorless anions such as those of magnesium, calcium, zinc, cadmium and tin. Ruthenium, rubidium, palladium, osmium, iridium and platinum are operative but usually too costly for commercial purposes. Certain metallic cations such as chromium, manganese, iron, cobalt and nickel tend to form colored compounds such that when. they are applied result in a colored paper substrate which may be desirable in the circumstance where a differentiating colored paper stock is required; otherwise, a colorless metal salt would be used.

The preferred amines are those having basic characteristics, that is, having basic dissociation constants of the order of 1x10" or greater. Such amines can form complexes or adducts with the metallic salts discussed herein.

The aliphatic amines are preferably alkylamines of the general formula wherein n is a positive integer from 1 to 20, inclusive, and x is a positive integer from 1 to 3, inclusive. Among the alkylamines which are suitable are:

Methylamine Propylamine Dimethylamine Dipropylamine Trimethylam ine Isopropylamine Ethylamine Butylamine Diethylamine Isobutylamine Triethylamine Ses-butylamine Amylamine Methylbutylamine Hexylamine Ethylpropylamine Isohexylamine Ethyloctylamine Heptylamine Methyllaurylamine Octylamine Ethylcetylamine Dioctylamine Dimethyldodecylamine Nonylamine Diethyldecylamine Decylamine Dimethyllaurylamine Laurylamine Dipropyllaurylamine Cetylamine Diethylcetylamine Stearylamine Dimethylstearylamine Methylethylamine Other aliphatic amines of the unsaturated type can be used. Preferred are those of the general formulas wherein n is a positive integer from 3 to 20, inclusive and x is a positive integer from 1 to 3, inclusive. Among such amines are:

Allylamine Crotylamine Diallylamine Propargylamine Triallylamine Alicylic amines of the general formulas are also operative: [(IhCGmHhNHa-X wherein n is a positive integer from 3 to 9, inclusive, and x is a positive integer from 1 to 3, inclusive; and

wherein n is a positive integer from 3 to 9, inclusive, and x is a positive integer from 1 to 2, inclusive. Preferred of this class of amines are cyclohexylamine and dicyclohexylamine. Other operative amines include:

Cyclobutylamine Butylcyclohexylamine Dicyclobutylamine Methylcyclobutylamine Cycloheptylamine Ethylcyclobutylamine Cyclooctylamine Dimethylcyclobutylamine Cyclodecylamine Diethylcyclopentylamine Propylcyclopentylamine Butylcyclobutylamine Ethylcycloheptylamine Methylcyclooctylamine Ethylcyclodecylamine Methylcyclohexylamine Dimethylcyclohexylamine Ethylcyclohexylamine Diethylcyclohexylamine Propylcyclohexylamine The heterocyclic amines which are operative in this invention can have one of the following general formulas:

wherein the symbol S signifies that the ring is saturated, R, R and R" can represent hydrogen or lower alkyl of 1 to 5 carbon atoms, and R and R together or R and R" together can represent a bivalent hydrocarbon radical forming one or two additional carbocyclic rings. Among such heterocyclic amines are:

It is desirable that the alkaline donor incorporated into the heat sensitive diazotype formulation be stable at room temperatures; be soluble in water to the same degree as urea, thiourea and derivatives; and provide sulficient basicity at lower temperatures to neutralize the acid stabilizers so that the diazo compound can couple and produce azo dye images. It is important that the alkaline donors respond at temperatures in the range of 50- C. and release the amine when the diazotype material is heated to such temperature.

The light sensitive diazo compounds which are useful in two-component diazotype systems can also be used to advantage in thermally responsive diazotype materials. Examples of such compounds are the diazonium salts obtained by the diazotization of the following amines:

p-Amino-N,N-diethylaniline p-Amino-N-ethylaniline p-Amino-N-ethyl-N-fl-hydroxyethylaniline p-Amino-N-methyl-N-B-hydroxyethylaniline p-Amino-N,N-di- (B-hydroxyethyl) aniline p-Amino-m-ethoxy-N,N-diethylaniline p-Amino-N-ethyl-o-toluidine p-Amino-N-ethyl-m-toluidine p-Amino-N,N-diethyl-m-toluidine p-Amino-N-ethyl-N-B-hydroxy'ethyl-m-toluidine N-p-amino henylmorpholine l-amino-2,5-diethoxy-4-morpholinobenzene The preferred diazo compound is the zinc chloride double salt of 4-morpholinobenzenediazonium chloride.

Generally, a number of coupling components may be employed. However, in this regard, some caution must be exercised because of the tendency of diazo compounds to precouple; that is, the color formation takes place before the diazotype material is imaged and processed. The preferred coupling component that may be employed to produce the dye image is 2,4-dihydroxynaphthalene-G-sulfonic acid. Other known couplers may be employed such as resorcinol, acetoacetanilide, 4-chlororesorcinol and diacetoacetylethylenediamine. However, it has been shown that precoupling is a particular problem with many couplers and the shelf life of the coated sheet turns out to be quite poor. Therefore, the right coupler is an important component.

In the presence of the alkaline donors hereinbefore described, the diazo salts and the couplers would, in and of themselves, tend to give a color reaction prematurely. To prevent precoupling and premature dye formation, there is added an acid component to keep the pH below the level required for coupling. Sulfonic acid derivatives, such as m-benzenedisulfonic acid, are employed as the preferred acid components. Other acids may be used to produce the desired pH such as:

Oxalic acid Citric acid Tartaric acid Lactic acid In addition to the acid components, there are added to the diazo formulation certain heavy metal salts such as the sulfates of zinc and cadmium. The inclusion of the heavy metal salts tends to prevent precoupling of the components at near room temperature.

By appropriate combinations of alkaline metallic saltamine donors and acids, such as those listed above, it is possible to develop pH ranges between 5 and 12 which will induce reaction between any combination of diazo compound and coupling component.

The alkaline donor reaction products formed between metal cations and amines have been characterized as complexes 0r adducts. Analyses indicate that in some instances the metal cation in combination with an amine forms a complex compound. There is evidence that other metal cations and amines form adducts. In either case, when exposed to temperatures of a range of 50l50 C., they undergo dissociation to release free amine as distinct from the decomposition producing free ammonia experienced by the urea and thiourea alkaline donors. Accordingly, it is believed that this may account for the lower response temperatures of the adducts or complexes. Further, it has been observed that the base release temperatures or the activation temperatures of the amine metal salt complexes and adducts are substantially reduced by the incorporation of compounds such as thiourea, acetamide, thioacetamide, urea, ethylureaand methylthiourea in quantities approximately equal to the weight of the donor. The activation temperature of the heat-sensitive diazotype material may be lowered as much as 20 C. by their incorporation.

The complexes and adducts of this invention, when exposed to heat, undergo dissociation to yield the corresponding-amines which react with the free acid in the formulation. One possible explanation may be that the urea compounds readily form stable compounds with the metal salts, more so than with the amines, thereby displacing'amines from the less stable complex or adduct structure. Since there may be other explanations for the accelerating effect of the urea compounds, it is intended that the invention not be limited by the mechanism of the reactions.

In summary, it is seen that the alkaline donors of the invention; tend to lower the temperature to which the diazotype materials are subjected, simplify the equipment, produce more intense copy since the high temperatures which would degrade the diazo salts are avoided and increase the self life of diazotype materials.

With certain metallic salts, the amines form complexes of definite composition and physical properties. For instance, zinc chloride forms a complex with two moles of an amine such as cyclohexylamine which is of definite composition. With other metallic salts the amines form solid adducts which are not of well-established composition. These adducts, however, are useful as'alkaline donors for diazotype materials and serve the same purpose as the complexes.

When the metallic salt-amine complexes or adducts are applied to sheet materials in the production of diazotype materials, the complexes or adducts are dispersed in fine particulate form in an organic solvent such as toluene and the resulting suspension applied to the sheet material by conventional coating procedures. The adducts or complexes are usually present in the suspensions or dispersions at concentrations of 5% to 20% by weightQthe range from 9% to 11% being preferred. After the solvent evaporates, the complexes or adducts form a thin coating of fine crystalline or solid particles which can release an organic amine when activated by heat.

In the photosensitive coating formulations for sheet materials, the amount of diazo compound is usually conventional. It generally constitutes 2% to 6% of the formulation with 4% being preferred. Equivalent quantities of coupling reagent are employed, following conventional practice. The coating formulations are applied in amounts which will provide about 15 grams of diazo compound for 3,000 square feet of surface.

The invention is disclosed in more detail by the following examples which are provided for purposes of illustration only. It will be understood by those skilled in the art that various combinations of diazo compounds, coupling components and alkaline donor developers can be used. It will also be understood that the amounts of ingredients in formulations and the operating conditions may be varied within this disclosure without departing from the invention.

EXAMPLE 1 A heat-activated alkali donor developing agent comprising the complex formed by treating zinc chloride with cyclohexylamine in 1:2 molar ratio Was presented as follows:

Parts by wt. Zinc chloride 15.5 Cyclohexylamine 22.5 Isopropyl alcohol 62.0

The zinc chloride was dissolved in the isopropyl alcohol. The cyclohexylamine was added to the alcohol solution of zinc chloride slowly and with stirring to dissipate heat developed in the ensuing exothermic reaction. Stirring was continued for several hours to eifect complete crystallization of metal-amine complex. The complex was recovered by vacuum filtration and was air dried for 48 hours and pulverized. Yields of 92-97% complex with melting point of 211-216 C. and nitrogen analyses of 8.02-8.17% (theoretical-8.37%) were obtained. This particular alkaline donor is a complex having the structure:

Utilization of this complex as an alkali donor developing agent can be carried out in various ways. One way involves incorporation of the complex on the surface of twocomponent diazotype papers as described below.

Photosensitive coating: Parts by wt. Water Citric acid 0.5 Thiourea 8 Sodium salt of 2,3-dihydroxynaphthalene-6-sulfonic acid 3 2,5 diethoxy-4-morpholinobenzene diazonium chlorozincate 4 The photosensitive coating is applied to the paper substrate by conventional coating techniques such as by wire wound rod and air dried.

Alkali donor coating: Parts by wt.

Zinc chloride-cyclohexylamine complex 10.0 Methyl methacrylate resin 4.5 Toluene 85.5

The resin was dissolved in the toluene and the metalamine complex dispersed in the resin solution. This alkaline donor dispersion was applied over the dried photosensitive coating by a conventional coating technique and air dried. The solvent-based alkaline donor coating forms a separate layer and does not intermingle with the previously applied aqueous photosensitive diazo layer.

The treated diazo paper was used to make thermally developed copies by exposing it to actinic light under a transparent original and subsequently developing the exposed sheet by subjecting it to a temperature of C. for five seconds on a heated rotating aluminum drum. Clear and legible copies of the original were formed. It was also observed that the diazo paper treated in accordance with the present invention exhibited good shelf life.

EXAMPLES 2-7 The complexes listed below illustrate various metal salts and amines that function well as heat-activated alkali donor developing agents. These are utilized according to the procedure described in Example 1. With the exception of the stannous chloride-amine complex, each mole of metal salt complexed with two moles of amine. Stannous chloride complexed with four moles of amine. The close agreement between nitrogen found and the theoretical values substantiates existence of the complex structure shown in Example 1. Nitrogen analysis results indicate the following structure for the tin-amine complexes:

Solvent (parts by Weight) Parts by weight Cyclohexylamine Zinc chloride Dieyclohexylamine Zinc chloride Quinoline;

Preparation of complexes recovered from ethyl alcohol was carried out by dissolving the halide salt in the specified proportion of alcohol and then stirring this solution together with cyclohexylamine in alcohol. When complex crystallization was complete, the mixture was cooled and filtered. After drying at 60-70 C., the complex was ready to use.

Preparation of complexes recovered from water was carried out by dissolving the halide salt in the specified proportion of water and then stirring this solution together with the amine. When complex crystallization was complete, the mixture was cooled and filtered. After washing the complex with water, it was dried at 6070 C.

Thermal diazo development and shelf life obtained with the foregoing alkaline donors was similar to that obtained with the complex described in Example 1.

EXAMPLES 814 The heat-activated alkaline donor developing agents of Examples 8-14 are adducts which are distinguished from the complexes previously described in Examples 17 by virtue of structure. The adducts of the metal salts and amines listed below, combined in 1:2 molar proportions and prepared as described in Examples 2-7, were utilized in diazotype materials according to the procedure given in Example 1. These substances have been found to perform well as alkaline donors.

Metal salt, 1 mole: Amine, 2 moles:

Cadmium chloride Cyclohexylamine Calcium chloride Cyclohexylamine Magnesium chloride Cyclohexylamine Zinc chloride Ethylamine Zinc chloride Morpholine Zinc chloride Piperidine Zinc chloride Pro pylamine Thermal diazo development and shelf life obtained with the above alkaline donors were similar to those Obtained with the complex of Example 1.

EXAMPLE In this example heat-sensitive diazotype material was prepared by including the heat responsive alkaline donor in a separate or distinct layer which was precoated onto Alkaline donor N-analysis Found Yield Percent Theory 2,5 diethoxy p morpholinobenzenediazonium chlorozincate The precoat solution was applied, dried and overcoated with the photosensitive solution. Coating was carried out by roller application with excess solution doctored off by the conventional air knife system. After drying, the treated paper was used to make thermally developed diazo copies by the procedure of, and with similar results to, Example 1.

I claim:

1. A heat-sensitive diazotype material comprising a base sheet coated with the combination of a diazo compound, a coupling component in a first coating, and an alkaline donor metallic salt amine adduct in a second coating. wherein the metallic salt is selected from the group fconsisting of halides, sulfates and nitrates of metals of Groups II, III, IV, VI, VII, and VIII of the Periodic Table and the amine is selected from the group consisting of alicyclic, and heterocyiclic amines, said adduct having solubilities in water and in toluene not greater than 1% by weight.

2. A heat-sensitive diazotype material comprising a base sheet coated with a diazo compound and a coupling component in a first coating and an alkaline donor metallic salt-amine adduct of salts of the group consisting of halides, sulfates and nitrates of magnesium, calcium, zinc, cadmium, tin, chromium, manganese, iron, cobalt and nickel with an alicyclic amine in a second coating thereon. 1

3. A heat-sensitive diazotype material comprising a base sheet coated with a diazo compound and a coupling component in a first coating and an alkaline donor metallic salt-amine adduct of salts of the group consisting of halides, sulfates and nitrates of magnesium, calcium, zinc, cadmium, tin, chromium, manganese, iron, cobalt and nickel with a heterocyclic amine in a second coating thereon.

4. A heat-sensitive diazotype material as defined by claim 2 wherein the metallic salt-amine adduct is a zinc halide adduct of cyclohexylamine.

5. A heat-sensitive diazotype material as defined by claim 2 wherein the metallic salt-amine adduct is a zinc halide adduct of dicyclohexylamine.

6. A heat-sensitive diazotype material as defined by claim 2 wherein the metallic salt-amine adduct is a tin halide adduct of cyclohexylamine.

References Cited UNITED STATES PATENTS 3,076,707 2/1963 Lawton et al. 96-75 FOREIGN PATENTS 1,325,692 3/1963 France.

1,377,477 9/1964 France.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner US. Cl. X.R.