WO1986001505A1

WO1986001505A1 - Lemon-yellow diazo compositions

Info

Publication number: WO1986001505A1
Application number: PCT/US1984/001385
Authority: WO
Inventors: Robert C. Desjarlais; Edward W. Bennett
Original assignee: James River Graphics Inc
Current assignee: James River Graphics Inc
Priority date: 1984-08-30
Filing date: 1984-08-30
Publication date: 1986-03-13
Anticipated expiration: 1987-02-28
Also published as: JPS62500099A; EP0192638A1

Abstract

A light sensitive diazo composition comprising at least one light-sensitive diazonium compound of formula (I) and at least one azo coupling component of formula (II).

Description

LEMON-YELLOW DIAZO COMPOSITIONS

BACKGROUND OF THE INVENTION

The present invention relates to diazo photoreproduction, and more particularly, to coupling compounds and diazonium compounds for use in diazo photoreproduction.

In semi-dry or two component diazotype photoreproduction, one or more coupling components are included as ingredients of a sensitizing composition. The sensitizing composition also includes a diazo sensitizer which decomposes when subjected to actinic radiation. Accordingly, after exposure, coupling between the coupling component or components and the diazo sensitizer can only occur in those areas where decomposition was not complete. Development is effected by subjecting the exposed composition to alkaline atmosphere, e.g., by bringing it into contact with ammonia vapors, to neutralize the acidic inhibitor with the concomitant formation of dyestuff in the nonexposed areas due to coupling of the residual diazo compound and the coupling components.

Although the color of the azo dye image which is obtained in any given instance depends primarily on the coupling components and the diazonium compounds which are employed, coupling components are typically described as being couplers of a given color, with the color being the color of the dye which is usually obtained when the particular coupler in question couples with a diazonium compound. For example, couplers such as monohydric phenols, catechols, catechol derivatives, resorσinols, resorcinol derivatives, diketones, acetoacetic acid derivatives, acetonitriles, cyanoacetamides and the like, usually result in yellow, orange, sepia, brown, red or maroon azo dyes. Thus, couplers from such classes of materials are conveniently referred to as yellow, orange, sepia, brown, red, or maroon couplers. On the other hand, couplers such as hydroxy naphthoic acid derivatives, dioxynaphthalene derivatives, pyronones, hydroxypyridones, and the like, usually result in blue or violet azo dyes, and thus are conveniently referred to as blue or violet couplers.

One group of highly useful coupling components are the yellow couplers, since the dyes obtained from these couplers usually have actinic absorption characteristics which permit their use as the sole coupler in a diazo composition which is employed to prepare diazotype "masters" or intermediates, and since couplers from this group can often be employed as shading components when used in conjunction with another coupler or couplers. As indicated above, compounds containing active methylene groups, compounds such as acetonitriles, derivatives of acetonitriles, and the like, have been employed as yellow couplers in diazo compositions, (c.f., for example, U.S. Patents 1,989,065; 2,531,004; 2,537,001; and 2,537,106), yet a number of these active methylene types of couplers have exhibited a tendency, when employed in two-component diazo compositions, to precouple with the diazonium compound which is present in said compositions during storage even in the presence of the stabilizers which are usually employed. This tendency to precouple prior to exposure and development has limited the use of these materials somewhat, since even a slight amount of precoupling can result in the formation of an azo dye in those areas of the diazotype material which are the background or "cleared" areas of the diazotype print. In addition to this tendency to precouple, a number of these priorart, active-methylene types of couplers also result, upon coupling, in dyes which have an undesirable reddish hue and/or which have a tendency to fade upon subsequent exposure to light.

It should be apparent from the above that, in addition to obtaining a single-color azo dye image, one should be able to obtain a mixture of azo dyes (and thus a mixture of colors) by including more than one coupling component or more than one diazonium compound in the light-sensitive diazo composition. Thus, by a proper choice of coupling components and/or diazonium compounds, one should be able to obtain a wide variety of colors in the resulting azo dyes, including black. However, the achievement of a uniform color over a wide range of image densities from a diazo composition containing more than one coupling component has proven difficult to obtain in actual practice. In order to obtain a uniform color over a wide range of image densities, it is essential to carefully match the coupling activity of the various coupling components with the diazonium compound or compounds which are employed, and that the combined absorptions of the azo dyes produced from the various couplers cover the entire visible spectrum. It is also essential that none of the azo dyes produced from the various coupling components be subject to a "color-shift" or change of shade due to a change in pH, for example, after ammonia has evaporated from the film. Otherwise, the resulting dye image of the diazotype material may shift from the neutral point.

However, in spite of the activity in this area, a need continues to exist for coupling components which give lemon-yellow colors with rapid developing diazonium compounds, are resistant to light oxidation, are resistant to oxidation to colored products, are not UV absorbers, couple very rapidly, and do not exhibit pH ammonia shift of the dyes once formed.

As will be recognized, it is of critical importance, regardless of the particular process being employed, that the print obtained possess satisfactory contrast, density, dye brightness, background clarity, etc. Thus, those areas of the light-sensitive material subjected to the actinic effects of the exposure radiation should be totally devoid of spurious discoloration. Hence, it is readily understandable that it is highly desirable that the light-sensitive diazonium compound should, ideally, yield colorless products upon light-induced decomposition.

However, many of the light-sensitive diazo compounds previously suggested for such use fail to provide optimum contrast levels, the failures in this regard being traceable to the tendency of the diazonium compound to undergo decomposition due to side reactions, with the concomitant formation of colored products. In this connection, reference may be made to the tendency of many diazonium compounds to decompose upon inadvertent heating. In other instances, it is found that a given diazo-coupler system exhibits an intolerable level of precoupling or autocoupling. Regardless of the particular mechanism responsible for such deleterious effects, the production of photocopy having the requisite sensitometric quality proves highly problematical. Because of the long exposure times typically required with diazo type photoreproduction, attempts have been made in the prior art to prepare so-called

"high speed diazos" which work considerably faster than those known previously.

In spite of these previous preparations of so-called high speed diazos, commercial products based upon such compounds have not been successful. This is believed to be largely due to their thermal instability, which is often combined with either poor dye stability to acid and light, or the predisposition background

(or minimum density) (D_min) of prints made using such compounds to rapidly discolor to an objectionable pink color. Consequently, although the diazos described in the prior art provided high speeds of reproduction, a need continues to exist for high speed diazonium salts which possess thermal stability, good dye stability to acid and light, provide a background or minimum density (D_min) which is resistant to discoloration, and develop rapidly as well as allowing a wider range of azo dye colors, especially a more neutral blue color with B.O.N. arylamides, such as

Moreover, although many of the diazo compounds promulgated provide some margin of advantage, it is invariably found that improvement in a given property, e.g., thermal stability, is accompanied by other undesirable effects, e.g., suppression in lightsensitivity, development speed, and the like.

Thus, the provision of light-sensitive diazonium compounds with superior resistance to the formation of unwanted discoloration of print background, without adversely affecting other essential properties, continues to challenge diazotype technology.

Thus, one object of the present invention resides in the provision of light-sensitive diazonium compounds wherein the disadvantages discussed above are eliminated or at least mitigated to a substantial extent.

Another object of the present invention resides in the provision of diazo sensitizing compositions capable of providing image reproduction substantially devoid of background discoloration.

SUMMARY OF THE INVENTION In part, the present invention provides compounds of the following general formula:

wherein:

R₁, R₂, and R₃ are the same or different and are selected from the group consisting of hydrogen, a halogen atom, alkyl of about 1 to 6 carbon atoms, aralkyl of about 6 to 10 carbon atoms, aryl of about 6 to 10 carbon atoms, branched alkyl of about 1 to 6 carbon atoms, alkoxy of about 1 to 6 carbon atoms, and alkylthio, at least one of R₁, R₂, and R₃ being other than hydrogen or a halogen atom;

X is S, SO, or SO ₂; and

Y is hydrogen or a halogen atom.

These novel coupling components provide lemon-yellow colors, are resistant to light, oxidation are not UV absorbers, couple very rapidly, and do not exhibit pH ammonia shift of the dyes after formation.

The present invention also provides novel diazonium salts which possess excellent photo speed, and yet possess good thermal stability, develop rapidly, allow a wide range of azo dye colors and, importantly, provide exceptional resistance to discoloration in the Dmm. areas. In addition, the decomposition products of the diazo compounds exhibit a resistance to discoloration upon exposure to UV light, and the azo dyes resulting from the diazos are resistant to changes in pH such as acidic conditions. The diazonium salts of the present invention are of the following general formula:

wherein

R₁ is tertiary butyl or tertiary amyl, preferably in a position para to the oxygen of the phenoxy group; Y is hydrogen, alkyl, hydroxyalkyl, cyanoalkyl, cycloalkyl, aralkyl, alkoxy, aryloxy, aralkoxy, aralkylthio, arylthio, alkylthio, halogen, allyl, allyloxy, allylthio, cyanoalkoxy, hydroxyalkoxy, methoxyalkoxy, trifluoroalkyl, alkylacetylamino, morpholino, dialkyl carbonamido, and the like;

R₂ and R₃ are the same or different and are alkyl, aralkyl, allyl, cyanoalkyl, hydroxyalkyl, hydrogen, acyl, cycloalkyl, betachloroalkyl, branched alkyl, or a structure wherein R₂ and R₃ may be linked together to form a heterocyclic structure, optionally including a sulfur atom, an oxygen atom, or a substituted trivalent nitrogen atom, e.g., morpholino, piperidino, thiomorpholino, piperazino, pyrrolidino; and

X is an anion.

By substituting the phenoxy group with a strongly electron donating tertiary butyl or tertiary amyl group in the para position, compounds are produced which can be incorporated into engineering black-line films which produce prints which are neutral black, fast developing, have a stable D_min which is not subject to background discoloration such as pinking, and do not suffer from a dye shift induced by prolonged exposure to hot, dry conditions which increases the acidity of the matrix by loss of ammonia vapors. As stated above, the lemon-yellow coupling components of the present invention are compounds of the general formula:

wherein R₁, R₂, and R₃ are the same or different and are selected from the group consisting of hydrogen, a halogen atom, alkyl of about 1 to 6 carbon atoms, aralkyl of about 6 to 10 carbon atoms, aryl of about 6 to 10 carbon atoms, branched alkyl of about 1 to 6 carbon atoms, alkoxy of about 1 to 6 carbon atoms, and alkylthio, at least one of R₁, R₂ and R₃ being other than hydrogen or a halogen atom; X is S, SO, or SO₂; and Y is hydrogen or a halogen atom.

Preferred compounds within this group are those in which R₁ and R₃ are selected from methyl, ethyl, isopropyl or a halogen atom and R₂ is hydrogen; and wherein R₁ and either R₂ and R₃ are hydrogen with the other of either R₂ or R₃ being selected from other than hydrogen or a halogen atom. Particularly preferred are 2,2'-dihydroxy-3,3',6,6'-tetramethyl diphenyl sulfide (i.e., R₂ and Y are hydrogen; R₁ and R₃ are methyl; X is S); 2,2'-dihydroxy-3,3'dimethyldiphenyl sulfide (i.e., R₁, R₂ and Y are H; and R₃ is methyl); and 2,2'-dihydroxy-3,3'-diisopropyl6, 6'-dimethyldiphenyl sulfide (i.e., R₁ is methyl; R₂ is hydrogen; and R₃ is isopropyl). Such compounds can be prepared by reacting an appropriately substituted phenol with sulfur dichloride in the presence of an inert solvent. Temperatures of from about 5°C to about 35°C are preferred, with temperatures of from about 5° to about 15°C being particularly preferred with the lower-boiling inert solvents. The reaction may, if desired, be conducted under an atmosphere of a stream of dry, inert gas to facilitate the removal of the hydrogen chloride which is evolved. The resulting compounds are easily recovered as crystalline solids having relatively high melting points. The sulfoxide and sulfone derivatives of these sulfides are prepared by treating the sulfide with an appropriate amount of an oxidizing agent, such as hydrogen peroxide, chromic oxide, potassium permanganate, and the like.

Synthesis of the compounds of the present invention is facilitated by the use of starting phenols which are substituted by halogen in the position para to the hydroxy group. The predominant reaction of a phenol with sulfur dichloride is para substitution. Thus, 4-halogen substituted phenols are used to block the 4-position. This leaves the 2-position open for substitution. After this has been completed, if desired, the 4-position can be unblocked by reductive dehalogenation.

The light sensitive diazonium compounds which can be employed in preparing the light-sensitive diazo compositions of the present invention are any of the numerous light-sensitive diazonium compounds which are available in the prior art, and the particular lightsensitive diazonium compound which is employed is not critical in the practice of this invention. Illustrative of such compounds are the stabilized salts or double salt complexes of diazonium derivatives of a phenylenediamine, for example, stabilized salts of diazonium derivatives of such compounds as N-methyl-pphenylenediamine, N-ethyl-p-phenylenediamine, Nhydroxyethyl-p-phenylenediamine, N-methyl-N-(betahydroxyethyl)-p-phenylenediamine, N-ethyl-N-(betahydroxyethyl)-p-phenylenediamine, N-butyl-N-(betahydroxyethyl)-p-phenylenediamine, N,N-di-(beta-hydroxyethyl)-p-phenylenediamine, N-benzyl-N-ethyl-pphenylenediamine, N-ethyl-2-methyl-4-aminoaniline, N,Ndimethyl-2-methyl-4-aminoaniline, N,N-dimethyl-3methyl-4-aminoaniline, N,N-diethyl-3-methyl-4aminoaniline, N-ethyl-N-(beta-hydroxyethyl)-3-methyl-4aminoaniline, N-cyclohexyl-2-methoxy-4-aminoaniline,

N,N-di(beta-hydroxyethyl)-3-methyl-4-aminoaniline, 2, 5diethoxy-4-morpholinoaniline, 2 ,5-dimethoxy-4morpholinoaniline, 2 ,5-dibutoxy-4-morpholinoaniline, 2, 5-diisopropoxy-4-morpholinoaniline, 2,5-diethoxy-4piperidinoaniline, 2,5-dimethoxy-4-piperidinoaniline, 2, 5-diisopropoxy-4-(N'-benzoyl)piperidinoaniline, Nbenzyl-2, 5-diethoxy-4-aminoaniline, 2, 6-dimethyl-4morpholinoaniline, 2 , 6-diethyl-4-morpholinoaniline, 2,6-dimethyl-4-piperidinoaniline, N,N-diethyl-2-chloro4-aminoaniline, N,N-dimethyl-2-chloro-4-aminoaniline, N-N-dibutyl-2-chloro-4-aminoaniline, 4-pyrrolidino-3methylaniline, 4-pyrrolidino-3-chloroaniline, 4-amino2,5-diethoxy-4'-methyldiphenyl sulfide, 4-amino-2,5dimethoxy-4'-methyldiphenyl sulfide, 4-amino-2, 5diethoxy-4'-methoxydiphenyl, 4-dimethylamino-2-chloro5- (4'-chloro)-phenyoxyaniline,

4-diethylamino-2-chloro-5-(4'-chloro)-phenoxyaniline and the like. The nature of the salt used to stabilize or complex the diazonium derivative is not critical, and can be, for example, a zinc chloride double salt, a cadmium chloride double salt, a tin chloride double salt, a borofluoride salt, a sulfate salt, a hexafluorophosphate salt, and the like.

A particularly preferred class of diazonium compounds for use with the couplers disclosed herein are the diazonium compounds which comprise another aspect of the present invention. The diazonium compounds are represented by the following formula:

wherein

R₁ is tertiary butyl or tertiary amyl, preferably in a position para to the oxygen of the phenoxy group;

Y is hydrogen, alkyl, hydroxyalkyl, cyanoalkyl, cycloalkyl, aralkyl, alkoxy, aryloxy, aralkoxy, aralkythio, arylthio, alkylthio, halogen, allyl, allyloxy, allyIthio, cyanoalkoxy, hydroxyalkoxy, methoxyalkoxy, trifluoroalkyl, alkylacetylamino, morpholino, dialkyl carbonamido, and the like; R₂ and R₃ are the same or different and are alkyl, aralkyl, allyl, cyanoalkyl, hydroxyalkyl, hydrogen, acyl, cycloalkyl, beta-chloroalkyl, branched alkyl, or a structure wherein R₂ and R₃ may be linked together to form a heterocyclic structure, optionally including a sulfur atom, an. oxygen atom, or a substituted trivalent nitrogen atom, e.g., morpholino, piperidino, thiomorpholino, piperazino, pyrrolidino; and

X is an anion.

Particularly preferred within this class of preferred compounds are those in which R₁ is t-butyl, R₂ and R₃ are both methyl or ethyl or combine to form a morpholino group, and Y is hydrogen, a halogen, methyl, ethyl, methoxy, morpholino, a thioether, a phenoxy group, or a substituted phenoxy group.

The diazonium compounds of the present invention are characterized by a tertiary butyl phenoxy or tertiary amyl phenoxy group which is located meta to the diazonium group. The replacement of the chloro group of the prior art by a tertiary butyl or amyl group results in a bathochromic shift of both the diazo compound and the resulting azo dyes. Thus, improved dye color and photospeed are obtained as compared to the chloro substituted compound, without any sacrifice in thermal stability.

At the same time, the nature of the group which is located para to the t-butyl or t-amyl phenoxy group is also important. The nature of this group affects the photo speed. For example, it has been found that a phenoxy substituent provides a compound having a photo speed slower than that of a compound having a chloro substituent. At the same time, the color obtained is shifted depending on this latter group. In the example above, a chloro group gives violet colors with conventional blue couplers, while a phenoxy group gives a more neutral blue.

It is believed that the group substituted para to the t-butyl or t-amyl phenoxy group, affects the photo speed and dye color of the resulting compound according to its relative electron donating ability. It is preferred that it should be less electron donating than methoxy, such as thioether, a methyl group, an ethyl group, a halogen, a hydrogen, or a phenoxy. By varying this group, one skilled in the art can obtain a compound having a desirable photospeed and thermal stability, and the desired color of the resulting azo dye. A halogen is particularly preferred because it provides an appropriate balance of photospeed, thermal stability, dye stability and dye color.

The salt forming anions employed are any of those conventionally employed in derivatives of diazotized para-phenylene diamine. Such anions include salt-forming anions such as sulfate, chloride, phosphate, tetrafluoborate, hexafluorophosphate and sulfonate, as well as preferred double salts of zinc chloride, cadmium chloride, and tin chloride.

Table I provides a list of substitutions made to prepare compounds falling within the above formula. In each case, R₁ is tertiary butyl group located in the para position on the phenoxy ring. The anion in each case is PF₆. Also provided in Table I are the waveleng³th absorbance (λ_max) and the extinction coefficient

(ε).

The diazonium compounds of the present invention are particularly suited for two-component dry processes, wherein development is achieved by the utilization of ammonia gas. In such a process, a coupling compound is generally intimately mixed with the diazo sensitizer and stabilized against premature coupling. Development is effected by coupling the diazo compound with the coupling compound by passing the material which has previously been exposed to light, through an alkaline gas, such as ammonia. By including a component in the two component layer which generates alkali on heating, coupling may be effected by heating the diazo material to generate an alkaline reagent in situ.

Suitable coupling components which can be employed in conjunction with the diazonium salts in a two component diazo reproduction process include: 6 ,7-dihydroxynaphthalene-2-sulfonic acid sodium salt 2-(m-hydroxyphenoxy) ethanol 2, 3-dihydroxynaphthalene 1, 8-dihydroxynaphthalene phloroglucinol resorcinol octylresorcinol

-resorcinol amide 3-methyl-1-phenyl-5-pyrazolone acetoacetanilide and its substitution products 2, 3-dihydroxynaphthalene-6-sulfonic acid 2,5-xylenol 2-methylresorcinol

7-hydroxy-1, 2-naphthoimidazole 2-naphthol-3,6-disulfonic acid.

Particularly preferred coupling components are betahydroxynaphthoic acid arylamides. Upon coupling with the diazos of the present invention, intense violet or blue dyes are produced.

Particularly preferred coupling components are the lemon yellow couplers disclosed herein. it should be understood that mixtures of light-sensitive diazonium compounds can be employed in the practice of the present invention without departing from the scope thereof, and that other couplers can be employed in conjunction with the yellow couplers hereinbefore described in preparing diazo compositions in accordance with the present invention without departing from the scope thereof. In this regard, of particular interest are black-line diazo compositions comprising one or more couplers from the particuuar class of lemon-yellow azo coupling components set forth above in full detail, along with one or more lightsensitive diazonium compounds and one or more BON blue azo coupling components such as 2-hydroxy-3-naphthoic acid, 2'-methoxyanilide, 2-hydroxy-3-naphthoic acid,

2', 5'-dimethylanilide, 6-methoxy-2-hydroxy-3-naphthoic acid-2'-methyl anilide, 2-hydroxy-3-napthoic acid-3'trifluoromethyl anilide, 2-hydroxy-3-naphthoic acid-2'methyl anilide, 2-hydroxy-3-naphthoic acid-2'-ethyl anilide, 2-hydroxy-3-naphthoic acid-2'-methoxy anilide and the like. A listing of preferred blue couplers is also provided in U.S. 3,619,191. Such black-line formulations provide black-line diazotype materials which are light-stable (i.e., are fade resistant) are

storage-stable (i.e., are resistant to precoupling), and are resistant to color-shift with changes in pH.

Any of the acid stabilizers which are generally employed in the art may be present to prevent the precoupling of the diazonium salt and coupling component, including organic acids such as citric acid, tartaric acid, boric acid, 5-sulfosalicylic acid, acetic acid, as well as inorganic acids, such as sulfuric acid, perchloric acid, fluoboric acid, hexafluorophosphoric acid, and the like. Other additives which are genrally included in the light sensitive diazo layer to prevent precoupling include acidic salts, such as zinc chloride, magnesium chloride, cadmium chloride, and the like.

In addition to the above stabilizing materials, other additives generally employed in diazo-type photoreproduction can be employed in conjunction with the diazonium salt of the present invention. Included in such materials are substances which increase the developing speed, such as glycerol, polyethylene glycol, and urea; surface improving substances such as finely divided silica (colloidal or non-colloidal), aluminum oxide, barium sulfate, rice starch, and the like; binders such as gelatin, gum arabic, cellulose ethers, starch derivatives, polyvinyl alcohol, dispersions of synthetic resins, such as dispersions of cationic, nonionic, and anionic polyvinyl acetate; substances intended to retard deterioration of the background of the copies such as thiourea, hindered phenolics, and the like.

The diazo compositions can be applied to any conventional support employed in diazo reproduction processes. For example, the diazo material may be applied to an opaque support such as white paper or opaque linen, or a transparent support such as tracing paper, tracing linen, cellulose ester foil, polyester foil, transparentized paper, and the like. Furthermore, the diazonium salt composition can be applied directly to the surface of the support or may be present in a hydrophilic film layer which may or may not be attached to the support by means of one or more conventional sublayers.

The novel diazonium salts of the present invention can be prepared by various routes well known to those skilled in the art. For example, 2-(4'-tert.butyl)phenoxy-5-chloro nitrobenzene can be produced by reacting 2,5-chloro-nitrobenzene with para-tert.butylphenol after which the resulting compound is converted to the corresponding amine. The amino group is then alkylated and the resulting alkylated compound is subjected to nitration in acetic acid in the presence of acetic anhydride.

Although the t-butyl or t-amyl group can be positioned at any location on the phenoxy ring, it is preferred that it be located in the para position. The tertiary butyl group is particularly well suited as a donating group due to the lack of reactivity on the adjacent carbon atom during the nitration step just prior to reduction and diazotization.

EXAMPLE I

Representative Synthesis of a Lemon-Yellow Coupler of the Present Invention

A. Preparation of 4-bromo-o-cresol.

Into a 5-liter reaction flask was charged 324 g of o-cresol (3 moles) and 1200 g of methylene chloride. The reaction was cooled to 2°C and 480g (3 moles) of bromine dissolved in 960g of methylene chloride was run in slowly over a 7-hour period. The next day, the cooling bath was removed and a heating mantle was attached. 1 liter of Isopar G (trademark of Exxon for a hydrocarbon fraction) was added and distillation of the methylene chloride was begun under water aspirator vacuum. Eventually the distillation rate slowed and the pot temperature rose to 70°C. The still head temperature dropped from 35°C to 28°C. The solution was poured into a beaker and cooled to room temperature without stirring. In the morning, the solution was cooled to -5°C and filtered. There was recovered 440g of 4-bromo-o-cresol melting at 61-64°C in 78% yield.

B. Preparation of 2,2'-dihydroxy-3,3'-dimethyl5,5'-dibromodiphenyl sulfide.

Into a 3 liter reaction flask was charged in

440g (2.35 moles) of 4-bromo-o-cresol and 700 ml of methylene chloride. The temperature dropped to 18°C.

Then 121g (1.18 moles) of freshly distilled sulfur dichloride was added fairly rapidly. HCl was evolved. The temperature was maintained at 14°C by external cooling. Hydrogen chloride gas continued to evolve with a precipitate forming during the addition of sulfur dichloride. The solution was stirred for 2 hours with cooling to 4°C after which 700 ml of hexane was added. After stirring the precipitate was filtered and washed with hexane, and then air dried overnight. There was recovered 248g of product melting at 162164°C in 52% yield.

C. Preparation of 2,2'-dihydroxy-3, 3-dimethyl-diphenyl sulfide (reductive dehalogenation) .

Into a 3 liter reaction flask was charged 128g (32 moles) of NaOH. Next was addedwith stirring 1141 ml of water. When all of the sodium hydroxide was dissolved, a pinch of zinc dust was added. Next, 258g (0.64 moles) of the brominated sulfide was added, which dissolved with stirring. Then 207g of zinc dust (3.2 moles) was added and the mixture was refluxed overnight with stirring. The mixture was filtered hot after which the zinc cake was extracted wth 100 ml of 10% NaOH (hot). The clear colorless liquors were combined, cooled, acidified with 200 ml of 36% hydrochloric acid, and then heated to liquify the product. The solution was then cooled and the solid nuggets which formed were filtered out. The nuggets were then suspended in water, heated to liquify them while keeping the solution acidic by the addition of hydrochloric acid as necessary. After cooling, the solid lumps were filtered. These were dissolved in hot Isopar G (trademark of Exxon for a hydrocarbon fraction) and the excess water distilled out. The product dissolved in hot Isopar G (trademark of Exxon for a hydrocarbon fraction) was decanted from a small amount of black tars clinging to the vessel. The decanted solution was cooled to room temperature and then to -5°C. The resulting crystals were filtered, washed with hexane and air dried, to recover 154g of product melting at 72-78°C (98% yield).

In a similar manner were prepared:

2,2'-dihydroxy-3, 3',6,6'-tetramethyl diphenyl sulfide M.P. 125-128°C.

2,2'-dihydroxy-3, 3'-diisopropyl-6, 6'-dimethyl diphenyl sulfide

M.P. 115-120°C. 2,2'-dihydroxy-3,3',4,4',6,6'-hexamethyl diphenyl sulfide

M.P. 125-135°C.

2,2'-dihydroxy-5,5'-dibromo-3, 3', 6, 6'-tetramethyl diphenyl sulfide

M.P. 171-173°C.

2,2'-dihydroxy-5,5'-dichloro-3, 3', 6, 6'-tetramethyl diphenyl sulfide M.P. 176-178°C. 2,2'-dihydroxy-5,5-dibromo-3,3',4,4',6,6'-hexamethyl diphenyl sulfide M.P. 195-205°C.

EXAMPLE II

A solution of the following was prepared:

Ingredients Amount (grams)

Methanol 78

Acetone 57

Methyl ethyl ketone 15

2-hydroxy-3-naphthoic acid-3' 1.1 acetylanilide

5-sulfosalicylic acid 2.3

6-methoxy-2-hydroxy-3-naphthoic .3 acid-2'-methyl anilide

2-chloro-4-N,N-dimethyl amino- 3.0 5-(4'-tert.-butyl)-phenoxy benzene diazonium tetrafluoborate

The mix was divided into 6 equal portions and to each was added yellow couplers of Table 1 in the amounts shown in Table 1. The solutions were bead imbibition coated onto polyester films (containing a suitable bonding layer and an overcoat of cellulose acetate propionate of approximately .25 mils thickness). The films were dried for 5 minutes at 70°C. The films were processed in the ordinary manner (i.e., using a Kodak #2 photographic step tablet as a master, the films were exposed in a Scott 716™ microprinter equipped with a

Gallium doped mercury vapor lamp followed by development in a Tecnifax™ Model 6000 ammonia developer which had an ammonia feed rate of 1.3 ml./min. of 26° Baume ammonia introduced onto a hot plate whereby ammonia gas and water vapor are delivered to the film surface).

The results obtained are shown in Table 1.

Compound IV is a yellow coupler of the present invention. Compounds I-III and VI are representative compounds of the prior art for comparison purposes.

Compound V is a known compound but has not previously been suggested as a coupler.

Table 1

Dye Color (Lower

Dye Color Density

Amount (grams) Name (D. Max Area) Area)

.18 Catechol, mono Plum-black Violet hydroxyethyl ether

II .27 1,2-bis-ortho Black Violet hydroxy phenyl cyclopropane

III .29 Meta Cresol Violet Violet Glutaric acid

IV .30 2,2' dihydroxy- Green- Plum¬

3,3' dimethylBlack Black diphenyl sulfide

V .26 2,2'dihydroxy- Greenish Violetdiphenyl sulfide Black Black VI .36 catechol, mono Black Violet hydroxyethyl ether

Based on the above results, the coupling speeds of these compounds are rated as follows:

IV > V > II > I > III

Note that Compound VI and Compound I are the same compound with the amount simply doubled. Comparing IV to VI results in a rating of IV > VI.

Since the object is to obtain as neutral a black image as possible with as little yellow coupler as possible, it is readily .seen that the compound of the present inventionis superior to the prior art. Very slow coupling compounds require large amounts of material in the mix and yet exhibit bitonal effects.

EXAMPLE III

A solution of the following was prepared:

Ingredients Amount (grams)

Methanol 52

Acetone 38

Methyl ethyl ketone 10

5-sulfosalicylic acid 1.52

2-hydroxy-3-naphthoic acid-3'-acetylanilide .74

6-methoxy-2-hydroxy-3-naphthoic acid- .20

2'-methyl anilide 2-chloro-4-N,N-dimethylamino-5- 2.00

(4'-tert.-butyl)phenoxy benzene diazonium tetrafluoborate The solution was divided into two equal portions and to each was added the yellow couplers listed in Table 2 in the amounts shown in Table 2. The solutions were coated, dried and processed as in Example II.

Table 2

(Lower

Dye Color Density

Amount-(grams) Name (D. Max Area) Area) IV .60 2,2'-dihydroxy- Green- Plum¬

3,3'-dimethylBlack Black diphenyl sulfide

VII .66 2,2'-dihydroxy- Yellow- Green¬

3, 3', 6, 6'-tetraBlack Black methyl-diphenyl sulfide

It is immediately evident that Compound VII couples much faster than Compound IV. In fact, reduction of the amount of Compound VII in the same formulation to .28 to .30 gms resulted in a continuous neutral black over a wide range of densities indicating that Compound VII couples twice as fast as Compound IV. If instead of Compound VII, there is used 2,2'-dihydroxy-3,3'diisopropyl-6, 6'-dimethyldiphenyl sulfide in an equimolar amount, similar results would be obtained, although the color would be a slight plum-black with a yellow dye which is not as stable to UV light as the preferred compounds. If 2, 2'-dihydroxy-5, 5'-dibromo3, 3', 6,6'-tetramethyl diphenyl fulfide is used, similar results are obtained. EXAMPLE IV

Solutions of the following were prepared:

Component Amount (grams) Function Acetone 18.79 Solvent Methanol 18.79 ''

Methyl cellosolve 4.18 ''

Eastman CAP-482-20 Cellulose 5.01 Polymer

Acetate Propionate 5-Sulfosalicylic acid .57 Acid Thiourea .12 Antioxidant

Tryptophan .05 ''

Riechold Stabilite Antioxidant .28 "

49-470 2-hydroxy-3-naphthoic acid .50 Blue -2'-ethyl anilide coupler

2,2'-dihydroxy-3, 3',6, 6' .36 Yellow tetramethyl diphenyl sulfide . coupler 2,2',4,4'-tetrahydroxydiphenyl .03 Sepia sulfide coupler 4-Morpholino-2,5-diisopropoxy 1.01 Diazo benzene diazonium tetrafluoborate Tributyl citrate .10 Development Accelerator

The solution measured 1000 centipoise viscosity and was coated onto a 7 mil polyester film containing a suitable bonding layer using a #30 wire wound Mayer rod. The film was dried for 3 minutes at 85°C in a convection oven. Next the film was cut into rectangular pieces (105 x 148 mm) and processed in an Addressograph/Multigraph OP-50^R Bruning diazo microfiche duplicator at exposure setting 7. To illustrate the independence of temperature on the color of the diazo microfiche, these films were developed at 140°F (60°C), 160°F (71°C), and 180°F (82°C), respectively. The results are as follows:

Prints Aired

Temp. Temp. Initial of (°F) (°C) Color Ammonia

140 60 Green- Green¬

Black Black

160 71 Green- Green¬

Black Black

180 82 Green- Green¬

Black Black

The results indicate the excellent developing latitude of this coupling component. If, instead of the 2,2'dihydroxy-3, 3',6,6'-tetramethyl diphenyl sulfide, there is used 2,2',4,4'-tetrahydroxy-3, 3'-dimethyl diphenyl sulfide (or sulfoxide) a severe colorshift of the yellow dye is observed from deep plum-black when first developed, to a slightly plum-black when aired of ammonia.

Similarly, use of the morpholine amide of 1hydroxy-2-naphthoic acid would result in the same general results as with the above tetrahydroxy compounds. In addition, both of the tetrahydroxy compounds described above would not result in a film of the same color at 140°F (60°C), 160°F (71°C), or 180°F but instead would be blue-black at 180°F (82°C) and reddish brown at 140°F (60°C) developing temperature. EXAMPLE V

Representative Synthesis of a Tertiary Butyl Compound of the Present Invention

A. 2-(4'-tert.-butyl)phenoxy-5-chloro-nitrobenzene. 43.5 grams of sodium hydroxide was dissolved in 65 grams of water. During the cooling of the resulting heated liquid, 350 ml of DMSO was added. To this was added 163.5 gm (1.09 moles) of 4-tertiary butylphenol. The resulting solution was warmed to 70°C to obtain a clear solution. To this was added

210 gm (1.09 moles) of 2,5-dichloronitrobenzene. The solution was then heated to 130°C and the reaction proceeded quickly. The solution was heated overnight at 115°C, after which it was poured into ice water. Pale yellow solids formed which were washed twice with hot water, and then with hot, dilute (approximately 5%) sodium hydroxide solution. The solids were filtered, washed with water, and then recrystallized from isopropanol to yield 287 gm (86% yield) of solids having a melting point of 71-74°C.

B. Reduction of 2- (4 '-tert.-butyl)phenoxy-5-chloronitrobenzene.

213.9 gm of the above compound were stirred with 806 ml of ethanol and 400 gm of sodium dithionite. The resulting solution was heated to 55°C after which

806 ml of water was slowly added. At 65°C, the reaction became very vigorous and exothermic, at which time the water addition was stopped and the reaction vessel was removed from the heating source and placed in an ice water bath. The reaction proceeded for about 20 minutes, after which the addition of water was resumed while maintaining the heat at 65°C. After the addition of water was complete, the reaction was heated to a boil to drive off the ethanol. The recovered solids were filtered and then added to a small amount of ethanol to dissolve slightly, after which 135 ml of 36% HCl was added. The solution was refluxed for 4 hours during which an oil gradually formed which was allowed to stand in the beaker overnight. By morning, semisolids had appeared and with the resumption of boiling and stirring, solids formed. The solution was cooled to 10°C and filtered. The filtered solids were suspended in dilute sodium hydroxide, heated to liquify, and then followed by cooling with the reformation of solids. The solids were filtered and reslurried in hot dilute sodium hydroxide to liquify the product and dissolve any sulfamate. The slurry was cooled and filtered, washed with water, and air dried, yielding pinkish-colored nuggets. The yield was 171 gm (89% yield), having a melting point of 74-77°C. A single spot was seen by TLC, and the material couples yellow with diazo.

C. Alkylation.

To 89 .7 gm of the amine of step B was added 133 gm of trimethyl phosphate. The solution was heated to 180°C at which time the reaction became exothermic, raising the temperature to 210°C. The reaction was cooled and then 60 gm of granular potassium carbonate was added and the resulting solution refluxed for two hours. The solution was again cooled and 28.5 gm of sodium hydroxide dissolved in water was added. The solution was then heated to reflux for two hours. At this time the condenser was removed while heating was continued to allow the methanol to evaporate. After standing for 48 hours, the pH was basic and a solid mass formed. This was extracted with methylene chloride. The methylene chloride was evaporated on a flash evaporator during which the oil solidified yielding 88.1 gm of a solid having a melting point of 52-55°C. An IR scan of the resulting product indicated an absence of N-H bonds.

D. Nitration in acetic acid in the presence of acetic anhydride. The dimethylated amine of step C (18.79 gm) was stirred with 50 ml of acetic acid during which most of the amine dissolved. To this was added 6.5 gm of acetic anhydride after which 6.4 gm of nitric acid was added rapidly. The temperature rose to 31°C and then subsided again. The resulting solution was cooled to between 5 to 10°C and then filtered. The resulting crystals were washed with acetic acid, followed by isopropanol, and then hexane. The resulting crystals were recrystallized from ethanol and some acetone. The crystal slurry was cooled to room temperature, and then to minus 5°C. Bright irridescent yellow crystals (70% yield) 15 gm, having a melting point of 123-125°C were obtained after filtration and drying.

E. Reduction and Diazotization.

4.0 gm of calcium chloride was dissolved in 15 ml of water. To this was added 40 ml of ethanol, followed by 16gm of zinc dust, after which heating was begun. When the solution reached 60°C, the nitro compound from step D was slowly added which resulted in an exothermic reaction raising the solution to 80°C. The solution was refluxed for one hour and then filtered while still hot. The amine phased out as an oil. 16 grams of hydrochloric acid was added without any precipitate appearing. The ethanol was evaporated leaving an oil which solidified upon the addition of water. The precipitate was allowed to stand for 48 hours and then filtered. The resulting solids were dissolved in 40 ml of 36% hydrochloric acid and then filtered through a sintered glass filter. To the resulting clear amber solution was added 20 ml of water forming solids having a light tan color. These were cooled to 8°C and diazotized with 40% sodium nitrite solution until a positive test for nitrous acid was obtained. A deep orange clear solution was formed. To this was added 6.8 gm of zinc chloride dissolved in water resulting in the formation of solids which were filtered and washed with hexane. The solids were slurried in hexane and filtered producing a zinc salt having a decomposition point of 148-149°C. The zinc salt of the diazo was dissolved in warm water and then filtered to remove impurities. To the solution was added 65% hexafluorophosphoric acid. The resulting solids were filtered, washed with hexane and then recrystallized by dissolving in a minimum of acetone, adding ethyl acetate equal to the acetone, and then hexane. The yield was 10.3 gm (50% yield) having a melting point of 117-118°C (decomposition). The spectra showed a λ max of 4010A, with an extinction coefficient of 23,278.

EXAMPLE VI A solution was prepared by combining the following ingredients:

Ingredient Amount (grams)

Methanol 52

Acetone 38

Methyl ethyl ketone. 10

Blue coupler (2-hydroxy-3-naphthoic 2.08 acid-3'-acetylanilide) 5-Sulfosalicylic acid 2.18

2-chloro-4-N,N-dimethylamino-5- 3.2

(4'tert.-butyl)phenoxy benzene diazonium hexafluorophosphate

The resulting solution was coated onto cellulose propionate subbed polyethylene terephthalate and' dried in an oven at 70°C for five minutes. The sensitized films were processed in the following well-known manner. Using a Kodak #2 photographic step tablet as a master, the films were exposed in a Scott 716 microprinter equipped with a gallium-doped mercury vapor lamp, followed by development in a Tecnifax Model 6000 ammonia developer which had an ammonia feed rate of 1.3 m./min. introduced onto a hot plate whereby ammonia gas and water vapor are delivered to the film surface. The maximum density of the unexposed area was 2.55 while the minimum density was .04 in the exposed area, as measured with a MacBeth TR 524 densitometer with a visual filter. Density measurements reported in the remainder of the present application were also made by the same densitometer.

To illustrate the advantages of the present invention over the prior art, the following comparative Examples VII and VIII are provided.

EXAMPLE VII

A solution of the following was prepared:

Ingredient Amount (grams)

Methanol 52

Acetone 38

Methyl Ethyl Ketone 10 5 Sulfosalicylic Acid 2.18 2-hydroxy-3-naphoic acid-2' ethylanilide 2.91 The solution was divided into two equal parts. To one part (part A) was added 2.27 gm of 2-chloro-4-N,N-dimethyl amino-5-(4'chloro)phenoxy benzene diazonium hexafluorophosphate ( λ_max 3950Å). To the other part (part B) was added 2.38 gm of 2-chloro-4-N,N-dimethylamino-5(4'-tert.-butyl) phenoxy benzene diazonium hexafluorophosphate ( λ_{m a x} 4010 Å) . The solutions were bead imbibition coated onto polyester films containing a suitable bonding layer and covered with an overcoat of a layer of cellulose acetate propionate of approximately .25 mils thickness. The films were dried for 5 minutes at 70°C. The sensitized films were processed in the following ordinary manner. Using a Kodak #2 photographic step tablet as a master, the films were exposed in a Scott 716 microprinter equipped with a gallium doped mercury vapor lamp, followed by development in a Tecnifax Model 6000 ammonia developer which had an ammonia feed rate of 1.3 ml. /min. introduced onto a hot plate whereby ammonia gas and water vapor are delivered to the film surface. The following results were obtained.

Film A Film B

Optimum Exposure 33 seconds 30 seconds Dye Color Violet Blue Visual Density 2.90 2.94

Thus by substituting the chloro group on the phenoxy ring of the prior art with a tert.-butyl group, a 10% improvement in photo speed is obtained, in addition to a blue dyestuff color which is well suited for obtaining neutral black dyestuff colors. One skilled in the art could readily envision appropriate yellow and yelloworange coupling components to admix in the solution of part B to achieve neutral black dyestuff colors. The thermal stability of B was found to be equivalent to A by forced sensitizer aging tests for 3 days at 50°C . If, instead of (A) or (B), there is used 4morpholino-2,5-diethoxy benzene diazonium hexafluorophosphate ( λ_max 3970Å) at 2.11 gm, the following is obtained:

Optimum Exposure 35 seconds Dye Color Neutral Blue Visual Density 3.0

Although a good neutral blue is obtained with this diazo, the development rate was much slower than that of (A) or (B) and the background areas (D _Min areas) soon exhibit an objectionable pinkish discoloration compared to (A) or (B). In addition, the photospeed is slower than both (A) and (B) . The development rate of (A) is equivalent to (B).

EXAMPLE VIII

A solution of the following was prepared: Ingredient Amount (grams)

Butyl Acetate 9.9

Ethanol 21.45

Acetone 12.65

Eastman CAP 504 - .2 (Cellulose Acetate 5.4 Propionate)

Eastman CAP 482 - 20 (Cellulose Acetate .6

Propionate)

5-Sulfosalicylic Acid .78

Zinc Chloride .20 Thiourea .06 Antioxidant (hindered phenol) .20 6-methoxy-2-hydroxy-3-napthoic .10 acid-2'-methyl anilide 2-hydroxy-3-naphthoic acid-3'- .38 acetyl anilide 2,2'-dihydroxy-3, 3'-6, 6'-tetramethyl .34 diphenyl sulfide Masking Dyes .64

The solution was divided into two equal parts. To one part (part A) was added 0.48 gm of 2-chloro-4-N,Ndimethyl-amino-5-(4'-chloro) phenoxy benzene diazonium tetrafluoborate. To the other part (part B) was added 0.50 gm of 2-chloro-4-N,N-dimethyl-amino-5- (4'-tert.-butyl) phenoxy benzene diazonium tetrafluoroborate. The solutions were coated onto a polyester film containing a suitable bonding layer using a #28 wire wound Mayer rod, then dried 5 minutes at 70°C in a convection oven. The other side of the polyester film was coated with a silica dispersed into a suitable polymer matrix and dried. The films were each cut to proper size and processed as in Example VI to yield prints of A and B:

Print A Print B

D_max Color Plum-Black Greenish

Black

Lower Density Color Plum-Violet Neutral

Black EXAMPLE IX

A solution of the following prepared:

Ingredient Amount (grams) Methanol 52 Acetone. 38

Ethyl Acetate 10 Masking Dyes 1.10

Wingstay L (trademark of Goodyear Tire .40 and Rubber Co.) Thiourea .12

Zinc Chloride .4 5-Sulfosalicylic Acid 1.54

2-hydroxy-3-naphthoic acid-3'-trifluoromethyl 1.00 anilide 2,2'-dihydroxy-3,3',6,6'-tetramethyl .66 diphenyl sulfide

The solution was divided into two equal parts, part A and part B. To part A was added 1.0 gm of 2-chloro-4-N,Ndimethylamino-5-(4'-tert.-butyl) phenoxy benzene diazonium tetrafluoroborate. To part B was added .9 gm of 2chloro-4-N,N-dimethyl amino-5-(4'methyl) phenoxy benzene diazonium tetrafluoroborate. The resulting solutions were bead imbibition coated onto clear polyester films, dried, and processed as in Example VII. The resulting print obtained from film coated from part A was a more neutral black color than that from part B. This was especially evident when the prints were placed side by side in a microfilm reader. In a microfilm reader, film from part A looks neutral in color while film from part B has an undesirable plum color. While the invention has been described in terms of various preferred embodiments, one skilled in the art will appreciate that various modifications, substitutiions, omissions, and changes may be made without departing from the spirit thereof. Accordingly, it is intended that the scope of the present invention be limited solely by the scope of the following, claims.

Claims

1. A compound of the following formula:

wherein

R₁, R₂, and R₃ are the same or different, and are selected from the group consisting of hydrogen, a halogen atom, alkyl of about 1 to 6 carbon atoms, aralkyl of about 6 to 10 carbon atoms, aryl of about 6 to 10 carbon atoms, branched alkyl of about 1 to 6 carbon atoms, alkoxy of about 1 to 6 carbon atoms, and alkylthio, at least one of R₁, R₂, and R₃ being other than hydrogen or a halogen atom;

X is S, SO, or SO₂; and Y is hydrogen.

2. A compound as claimed in claim 1 wherein R ₁, R₂, and R₃ are the same or different and are eitl hydrogen or alkyl of about 1 to 6 carbon atoms.

3. A compound as claimed in claim 1 wherein

R₃ is methyl, ethyl, or isopropyl.

4. A compound as claimed in claim 1 wherein R₁ is methyl, ethyl, or isopropyl; and R₃ is methyl or ethyl.

5. A compound as claimed in claim 1 wherein

R₁ and R₃ are methyl or ethyl.

6. 2,2'-dihydroxy-3,3',6,6'-tetramethyl diphenyl sulfide.

7. 2,2'-dihydroxy-3,3'-dimethyl diphenyl sulfide.

8. 2,2'-dihydroxy-3,3'-diisopropyl-6,6'dimethyl diphenyl sulfide.

9. A diazonium compound of the following formula;

wherein R₁ is tertiary butyl or tertiary amyl;

is hydrogen, alkyl, hydroxyalkyl, cyanoalkyl, cycloalkyl, aralkyl, alkoxy, aryloxy, aralkoxy, aralkylthio, arylthio, alkylthio, halogen, allyl, allyloxy, allylthio, cyanoalkoxy, hydroxyalkoxy, methoxyalkoxy, trifluoroalkyl, alkylacetylamino, morpholino, or dialkyl carbonamido;

R₂ and R₃ are the same or different, and are alkyl, aralkyl, allyl, cyanoalkyl, hydroxyalkyl, hydrogen, acyl, cycloalkyl, beta-chloroalkyl, branched alkyl, or a structure wherein R₂ and R₃ may be linked together to form a heterocyclic structure; and

X is an anion.

10. The diazonium compound of claim 9 wherein R₁ is located in the para position on the phenoxy group.

11. The diazonium compound of claim 9 wherein

Y is hydrogen, methyl, ethyl, a halogen, a thioether, a phenoxy group, or a substituted phenoxy group.

12. The diazonium compound of claim 9 wherein R₂ and R₃ are methyl or ethyl, or are combined to form a morpholino, piperidino, thiomorpholino, piperazino, or pyrrolidino ring.

13. The diazonium compound of claim 9 wherein

R₁ is in the para position, R₂ and R₃ are methyl, and

Y is chloro or phenoxy.

14. The diazonium compound of claim 9 wherein R₁ is in the para position, R₂ and R₃ are methyl, Y is chloro and X is tetrafluoroborate.

15. The diazonium compound of claim 9 wherein R₂ and R₃ are ethyl.

16. A light-sensitive diazo composition which comprises at least one light-sensitive diazonium compound, and at least one azo coupling component as claimed in claim 1.

17. The composition of claim 16 wherein the diazonium compound is at least one of the compounds claimed in claim 9.

18. A light-sensitive diazotype photoreproduction material comprising a support member coated with a light-sensitive composition as claimed in claims 16 or 17.

19. The photoreproduction material of claim 18 wherein the support member is a film substrate.

20. A diazo dyestuff of the -following formula:

A • B

the dyestuff being formed by the coupling of a diazo sensitizer represented by A, with a compound as claimed in claim 1 represented by B.

21. The dyestuff of claim 20 wherein A and B are as claimed in claim 17.

22. A process for diazotype photoreproduction comprising the exposure of the photoreproduction material of claim 18 to actinic light, and developing the photoreproduction material to form a positive azo dye image by treatment with ammonia.