US3899335A

US3899335A - Diazotype elements and processes with carbodiimide dehydrating agents to generator couplers

Info

Publication number: US3899335A
Application number: US452895A
Authority: US
Inventors: Wojciech Maria Przezdziecki
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1974-03-20
Filing date: 1974-03-20
Publication date: 1975-08-12
Anticipated expiration: 1992-08-12

Abstract

A light-sensitive, heat-developable diazotype element comprising a light-sensitive diazonium salt, a solid carbodiimide dehydrating agent, and a solid coupler precursor in the form of an aminocarboxylic acid capable of producing a diazo coupler upon dehydration; and the method of using it to produce a visible dye image wherein the element is exposed to actinic radiation and then heated to the melting point of the dehydrating agent or coupler precursor to activate the dehydrating agent, and generate the diazo coupler which in turn reacts with undecomposed (unexposed) areas of the diazonium salt to yield an imagewise dye pattern. Optionally, an alkali precursor may be utilized in the element to accelerate dye formation.

Description

United States Patent [1 1 Przezdziecki Aug. 12, 1975 [75] Inventor: Wojciech Maria Przezdziecki,

Pittsford, N.Y.

[73] Assignee: Eastman Kodak Company,

Rochester, N.Y.

[22] Filed: Mar. 20, 1974 [21] Appl. No.: 452,895

[52] US. Cl 96/49; 96/75; 96/91 R [51] Int. Cl. G03C 1/58; G03C 1/60; GO3C 5/34 [58] Field of Search 96/91 R, 75, 49

[56] References Cited UNITED STATES PATENTS 3,098,693 7/1963 Sheehan 96/111 X 3,100,704 8/1963 Coles et al. 96/11 1 3,303,028 2/1967 Aebi et a1. 96/91 R 3,307,952 3/1967 Aebi et al. 96/91 R 3,331,689 7/1967 Sosnovsky et al.. 96/91 R 3,386,827 6/1968 Aebi et al. 96/91 R 3,499,760 3/1970 Amariti et a] 96/91 R 3,563,744 2/1971 Poot 96/91 R FOREIGN PATENTS OR APPLICATIONS 983,665 2/1965 United Kingdom 96/91 R Primary ExaminerCharles L. Bowers, Jr. Attorney, Agent, or FirmD. M. Schmidt [5 7 ABSTRACT A light-sensitive, heat-developable diazotype element comprising a light-sensitive diazonium salt, a solid carbodiimide dehydrating agent, and a solid coupler precursor in the form of an aminocarboxylic acid capable of producing a diazo coupler upon dehydration; and the method of using it to produce a visible dye image wherein the element is exposed to actinic radiation and then heated to the melting point of the dehydrating agent or coupler precursor to activate the dehydrating agent, and generate the diazo coupler which in turn reacts with undecomposed (unexposed) areas of the diazonium salt to yield an imagewise dye pattern. Optionally, an alkali precursor may be utilized in the element to accelerate dye formation.

8 Claims, N0 Drawings DIAZOTYPE ELEMENTS AND PROCESSES WITH CARBODIIMIDE DEHYDRATING AGENTS TO GENERATOR COUPLERS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel light-sensitive, heatdevelopable diazotype elements, and in particular to the use of carbodiimides to generate diazo couplers in a layer comprising a diazo salt and a coupler precursor. The coupler is obtained by dehydration of the coupler precursor by the carbodiimide at an elevated temperature.

2. Prior Art In U.S. Pat. No. 3,140,180, G. Fritz describes diazotype elements containing a thermolabile pyrrole compound having a carboxylic tertiary alkyl ester group which is capable of coupling after decarboxylation by heat.

U.S. Pat. No. 3,303,028 ofC. M. Aebi et al. discloses thermodevelopable, light-sensitive diazotype compositions comprising a compound capable of being dehydrated to form a diazo coupling component in situ. The latent coupling component may be a 'y-keto alcohol, a B- or 'y-acid alcohol, a -y-lactone or mixtures thereof, which upon dehydration become compounds containing active methylene groups which are capable of entering color-forming or coupling reactions with diazonium salts. A preferred embodiment of the invention utilizes a cyanoguanidine compound as a dehydrating agent and as an alkali-precursor. In U.S. Pat. No. 3,307,952 to the same inventors provides for the formation of an unsaturated B,Bunsaturated ketone diazo coupler by heating and dehydrating a B,B'-ketoalcohol.

U.S. Pat. No. 3,331,689 of G. Sosnovsky et al. describes a method which comprises heating to a decarboxylating temperature a normally stable acidic composition having in intimate contact a diazonium compound and an aromatic coupler precursor which contains a carboxylic group subject to decarboxylation when heated.

C. M. Aebi et al. in their U.S. Pat. No. 3,386,827 describe the use of thermolabile diazo coupler precursors such as 3-hydroxyglutaronitrile or B-hydroxy-B-methyl glutaric acid. It is stated that: It is believed that the coupling component is produced by splitting out water, an alcohol or a phenol formed by radical R 0 and hydrogen from which the carbon to which R is attached.

U.S. Pat. No. 3,499,760 of L. Amariti et al. discloses heat developable diazotype photoprinting compositions in which a coupler containing an enolate structure is used. The system is able to couple under the influence of heat without requiring the use of alkaline solutions or vapors or alkaline generating compounds.

A. L. Poot et al. in U.S. Pat. No. 3,563,744 describe a thermodiazo copying material and process wherein a hydrazone compound decomposes upon heating to form a heterocyclic methylene base compound capable of coupling with a diazonium compound to form an azo dye image.

Most of the previous proposals for a heat developable diazo have achieved little or no commercial success, mainly because the coupler precursors and/or alkali precursors slowly decomposed, even at room temperature. Thus, decarboxylation of 2,4,6-trinitrobenzoic acid can be carried out efficiently at 150C. according to U.S. Pat. No. 3,331,689, but it is also likely to occur slowly at temperatures of 20 to 30C. with resultant premature coupling. Also, the thermal dehydration of certain carbonylcontaining coupler precursors as described, for example in U.S. Pat. No. 3,303,028, are relatively slowly generated unless an alkali precursor is utilized therewith. The alkali precursor, while speeding up the reaction, tends to decrease the storage stability of the element.

SUMMARY OF THE INVENTION The present discovery concerns improved photosensitive and thermally-developable diazotype elements which process rapidly and exhibit better storage stability than those of the prior art.

This invention relates to methods and compositions of matter for generating azo dye images from lightsensitive, heat-developable diazotype compositions comprising a light-sensitive diazonium compound, a normally solid carbodiimide dehydrating agent, and a normally solid diazo coupler precursor convertible by dehydration in reactive contact with the carbodiimide into a diazo coupler capable of reacting with said diazonium compound to form an azo dye. Preferably the coupler precursor is an aminocarboxylic acid that forms a heterocycle containing a reactive methylene radical when heated with said carbodiimide.

By the term reactive contact it is meant that the dehydrating agent and coupler precursor are contacted either in a liquid or with one of them in liquid form to produce the reaction conditions which bring about dehydration of the coupler precursor by the dehydrating agent. This latter reaction will not occur if the dehydrating agent and coupler precursor are in contact as solids.

The dehydrating agent, when brought into reactive contact with the coupler precursor by melting of one of these two components or an inert normally solid solvent" reacts with the coupler precursor to free the coupler for a conventional dye-forming reaction with the diazo salt.

SPECIFIC EMBODIMENTS OF THE INVENTION Three essential compounds are involved in the present invention and each of these components is a normally solid compound with a melting point of at least about C., and preferably above about C., in order to obtain the full benefits of the invention by avoiding premature activation of the carbodiimide dehydrating component which converts the coupler precursor into the actual coupling agent. These components are:

1. the diazo salt;

2. a carbodiimide dehydrating agent; and

3. a coupler precursor which becomes a coupler upon dehydration. Activation of the dehydrating agent occurs upon the melting of the carbodiimide or any substance in contact with it, for example, the coupler precursor or an inert normally solid material which acts as a solvent, to bring the dehydrating agent and the coupler precursor into reactive contact. v

Suitable light-sensitive diazonium compounds are well known in the art as exemplified in the aforementioned prior art patents, especially in the disclosure of U.S. Pats. Nos. 3,303,028 and 3,761,263 which are incorporated herein by reference. Mixtures of such substances may also be employed. The preferred diazo salts include l-diazo-4-( dimethylamino )benzene roborate l-diazo-4-(cyclohexylamino)benzene phosphate 1-diazo-4-(diamylamino)benzene chlorozincate l-diazo-4-( dehydroxyethylamino )-3-methylbenzene sulfate l-diazo-4-dimethylamino-3-methylbenzene chlorostannate l-diazo-4-(dimethylamino )-3-ethoxybenzene tetrafluoroborate l-diaZo-4-( diethylamino )-3-chlorobenzene one of their amino hydrogens substituted with one of a wide variety of organic radicals including aliphatic (e,g., Ndhiocarbalkoxy). cycloaliphatic (e.g., N-thiocarbamoylmorpholine), heterocyclic (e.g., N-2- benzothiazolyl), and aromatic (e.g., N-Z-pyridyl) groups which may contain sulfur, oxygen, and nitrogen atoms. Such glycines may be defined as N-organic substituted glycines capable of dehydration and which upon dehydration yield compounds having a heterocyclic ring containing both a nitrogen and an active methylene radical capable of coupling to a diazonium compound. Very good results are obtainable with hippuric acid and N-Z-pyridylglycine.

Examples of compounds capable of dehydration to l-diazo-2-carboxy-4-(diethylamino)benzene phosyield a heterocyclic ring containing an active methylphate ene group capable of coupling with a diazo salt are:

PRECURSOR COUPLER S C=O )HOOCCH NHCSNOO HO OQN H A 2 2 N N thiocurbamoylmorpholine- Z-N-morpholinylthiazol-S-one glycine h) RSSCNHCH COOH H O Hg N-dithiocurbalkoxyglycmes RS N Z-alkyl-thiwthiuol-S-ones c) ROSCNHCFLCOOH H. ,O SC=O RO- 7H N N-thiocurhalkoxyglycines Z-alkoxythiazol-S-ones S a) 1 CNHCH COOH H,o N/

N-Z-Benzothiuzolylglycine l-diazo-4-morpholinobenzene tetrafluoroborate l-diazo-4-morpholino-3-methoxybenzene tetrafluoroborate l-diazo-4-morpholino-2-ethoxy-5-methoxybenzene chlorozincate l-diazo-4-morpholino-2,S-dibutoxybenzene sulfate l-diazo-2,5-diethoxy-4-benzoylaminobenzene phosphate as well as those employed in the examples hereinafter. In some cases, this choice will be based upon one or more of such factors as the hue of the dye image, its brightness and resistance to fading as well as the cost of the diazo compound.

A more detailed description of useful diazonium salts and couplers is contained in US. Pat. No. 3,761,263 to Fleming et al. issued Sept. 25, 1973 which is incorporated herein by reference.

A variety of normally solid coupler precursors may be utilized as long as they are capable of being dehydrated, preferably rapidly, by the carbodiimide when brought into reactive contact therewith by melting of the carbodiimide, the coupler precursor or a normally solid solvent" (as described hereinafter), to yield diazo coupling compounds. The coupler generated should desirably be substantially colorless and should, of course, be capable of coupling with the contiguous diazo salt, preferably in a rapid manner. As will be described below, coupling can be accelerated by rendering the reaction medium alkaline. Aminocarboxylic acids in general are suitable, especially glycines having C=N N 2c H 0 Benzothia7.o[ 23-11 I-( 4H )-imidazol-5-one wherein R and R may each individually represent substituted and unsubstituted organic radicals which include alkyl (e.g. methyl, ethyl, etc.), cycloalkyl (e.g. cyclohexyl), aralky, aryl and amine radicals and R may also be a hydrogen atom. Among the many compounds suitable for the purposes described herein are:

DA-dehydrating agent DA-l dinaphthylcarbodiimide DA-2 dicyclohexylcarbodiimide DA-3 N-phenyl-N '-cyclohexylcarbodiimide DA-4 di-pdimethylaminophenylcarbodiimide DA-5 Ntert-Butyl-N'-( triphenylmethyl )carbodiimide DA-o l-Ethyl-3( 3-dimcthylaminopropyl )-carbodiimide hydrochloride In applying the aforesaid components to various substrates of an absorbent nature (e.g., paper or cloth), it is often sufficient to merely dissolve the solid substances in a solvent, such as a conventional volatile organic solvent or mixtures thereof, that is subsequently evaporated to deposit the solute in and on the substrates. When an impermeable substrate (e.g., a metal or polymeric sheet, polyethylene coated paper, etc.) is to be coated, the use of a vehicle or carrier which comprises a film-forming material is usually necessary. Techniques for accomplishing such coating are well known in the art. Among the many suitable conventional film-forming materials or binders suitable for this purpose are such resins as cellulose esters, acrylates, methacrylates, as well as polyvinyl alcohol, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, etc. Conventional diazo binders and supports, in addition to the foregoing, are well known in the art and further discussion of such materials here would serve no useful purpose.

Drying the treated substrate in unheated or gently heated circulating air may be necessary with a low melting component present in instances where the carbodiimide dehydrating agent is in contact with the coupler precursor, in order to avoid activating the coupler prematurely. However, premature activation can be coupler precursor 6 occurs. Third, the novel system is not sensitive to ambient humidity conditions until the fusion of one of the substances present occurs due to the nature of the mechanism of the conversion of the precursor into an active coupling agent by heating. Fourth, some carbodiimides, although excellent dehydrating agents at their melting point or in solution, have excellent solid EXAMPLE 1 dehydrating agent coupler avoided by keeping these two components apart by separately depositing them on the substrate with a resin film between them or by depositing one of these components on the substrate and the other on a separate developing sheet that is placed on the substrate coating only shortly before dye image formation is desired.

For the formation of an image on a substrate coated or impregnated with a light-sensitive, heat-developable diazonium compound either alone or in combination with either the coupler precursor or the dehydrating carbodiimide, a latent image is formed by conventional exposure of the substrate through a photographic positive or other image pattern to actinic radiation, such as visible (if a suitable sensitizer is used) or ultraviolet light, are lamps, etc. Next, the latent image is developed by heating the treated substrate while all three of the reactive substances are in intimate contact with one another (e.g., by laying a developing sheet onto a coating of diazo salt) to a suitable temperature to convert the precursor into a coupler by dehydration and to couple the coupler with undecomposed diazo compound in the unexposed areas to form a visible image colored by the resulting dye in such areas. Temperatures suitable for such dehydration and coupling will vary for different specific reactive components, and they may be easily determined by routine experimentation. As a guide, temperatures of the order of 1 10 to 130C. have given excellent results with a number of the compositions described above and in the examples below.

The coupler-generating system of the instant invention provides important advantages. First, there is improved stability, since the coupler is not formed prematurely. The coupling agent is formed or released only when the melting point of one of the solid components is reached in the composition or coating. Second, activation of the active components of these compositions results in extremely rapid development of the dye image, even though the system is inert until such melting Filter paper is imbibed with a solution of 0. l-g hippuric acid and O.l-g 2,5-diethoxy-4-morpholinobenzene diazonium tetrafluoroborate in 5 ccs of a mixture of equal volumes of Z-Butanone and methanol. Since the above diagrammed dehydrating reaction occurs at a somewhat elevated room temperature using the dicyclohexylcarbodiimide, a second sheet of filter paper is imbibed with a solution of O.l-g dicyclohexylcarbodiimide in 5 ccs of Z-butanone to produce a developing sheet; then both sheets are dried.

The first sheet is exposed for 7 sec. to ultraviolet light through a positive in the Kalcard 200 Exposer after which it was passed, in contact with the developing sheet, through heated rollers set at l 10C. Coupling of the nondestroyed (unexposed) diazo occurs rapidly to form red colored areas.

EXAMPLE ll 10.0 g. Hippuric Acid 0. l 8 g. 2,5-Diethoxy 4-Morpholinobenzene diazonium tetrafluoroborate 0.10 g.

To a wet thickness of about 4 mils 2. A developing sheet is prepared by coating a paper support with:

A 10% by weight solution of cellulose acetate butyrate in solvent as in (1) above 10.0 g. Dicyclohexylcarbodiimide 0.2 l g.

To a wet thickness of about 4 mils After gently drying the coatings at a temperature of EXAMPLE VI about 40C for about minutes, the coated film l) is A red image is obtained when another Specimen of exposed to ultraviolet light for 30 see. through a posi- Sheet 2 of Example v is used with another Sheet 1 of tive in the Kalcard 200 Exposer and then passed in Example Iv contact with the developing sheet (2) containing the 5 dehydrating agent through heated rolls set at 110C. EXAMPLE VII The undecomposed. dmzo coupies fi h pi The following single sheet of three layer material is formed by dehydration of the hippuric acid. giving a p p da-rk red Image Layer 3 as Sheet 2 of Example V XA P I" m Layer 2 5% Vistanex MM L-l40*(polyisobutylene in ligroin) coupler precursor dehydrating coupler agent I l N NHCH COOH R--N=C=NR pl] I O=C CH2 R:

Niz-pyfidylglycine Dinaphthylcarhodiimide The following coatings are prepared: 25 Layer 1 as Sheet 1 of Example III *A product of the Enjay Chemical Company.

Sheet 1 N-Z-pyridylglycine 0.23 g- The material is exposed for 4 seconds using an IBM A by weight solution of cellulose acetate 30.0 g. Mi o Co i M d [ID d th processed on a butyrate in 80/20 weight ratio of acetone/methanol heated block at 130C for seconds. A stable brown positive image is obtained. 1 g The above composltlon ls coated at 4 ml] wet thlckness While the invention has been described in detail with on subbed polyethyiene tcrephthalate particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the inven- Sheet 2 Dinaphthylcarhodiimide 0.55 g.

p-( Diethylamino) benzene diazonium tetrafluoroborate (128 I aim:

A 10% by weight solution of cellulose acetate 4 .0 g. butyrate in 80/20 weight ratio of acetone/methanol l. A method of forming an azo dye image comprising a the step of:

This formulation is coated at 4 mil wet thickness on 1. imagewise exposing to actinic radiation a supsubbed poly( ethylene terephthalate). Subsequent to 40 d layer comprising drying the Coatings, Sheet 2 is lmagewise exposed for a. a light-sensitive diazonium compound; and

2 seconds to ultraviolet light using an IBM Micro b. at least one compound selected from at least one Copier Model IID and then passed through rollers at b not b h f l 10C. in contact with Sheet 1. A stable, reddish posii, a solid carbodiimide dehydrating agent having tive image is obtained, indicating formation of a couh f l pler by dehydration. The color of the image is intensified by fuming with moist ammonia after the aforesaid RN=C=NR heat treatment. 1

wherein R is an organic radical of the group consisting EXAMPLE IV of alkyl, cycloalkyl, aralkyl, and aryl groups and amino derivatives thereof, and R is of the group consisting of hydrogen and said organic radicals, and

ii. an N-organic substituted glycine convertible by dehydration, when placed in reactive contact with carbodiimide, into a heterocyclic EXAMPLE V active methylene coupler reactive with said diazonium compound to form an azo dye; and

Example III is repeated except that N-2- pyridylglycine is replaced in Sheet 1 with 0.29 g. of hippuric acid as the coupler precursor. A yellow image is obtained.

Example III is again repeated with dinaphthylcarbodiimide replaced in Sheet 2 with 0.56 g. of I (below) as an aminocarbodiimide dehydrating agent of the following structural formula:

contact with a layer comprising the other of (i) and (ii) to a temperature sufficient to cause said acid and said carbodiimide dehydrating agent to come dehydrating agm'n into reactive contact thereby initiating formation (CHK)2 N N=C=N N (CH3)2 said azo dye image by reaction of said coupler with unexposed portions of said diazoniurn compound.

2. A divdimethylamimphenylcarbodiimide method according to claim 1 wherein said gly cine is selected from the group consisting of l A reddish-blue Positive image is Produced y P N-dithio-carbalkoxyglycines and N-thiocarbalkoxyglying as in Example III. cines' 2. heating said imagewise exposed layer while in of said coupler by dehydration and production of 3. A method according to claim 1 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide,

N-phenyl-N -cyclohexylcarbodiimide. di-pdimethylaminophenylcarbodiimide, N-tert-butyl-N'- I (triphenylmethyl)-carbodiimide and l-ethyl-3(3- dimethylaminopropyl )-carbodiimide hydrochloride.

4. A light-sensitive heat-developable diazotype imaging element comprising,

a a layer comprised of a normally solid carbodiimide dehydrating agent having the formula wherein R is an organic radical of the group consisting of alkyl, cycloalkyl, aralkyl and aryl groups and amino derivatives thereof, and R is of the group consisting of hydrogen and said organic radicals, and

b. a layer comprised of a an N-organic substituted glycine convertible by dehydration, when in reactive contact with said carbodiimide, into a coupler having a heterocyclic ring containing both a nitrogen atom and a couplingreactive methylene radical, capable of coupling with a diazonium compound, wherein (a) and (a') are separate layers, one of said layers (a) and (b) further including a light-sensitive diazonium compound. 5. An element according to claim 4 wherein said glycine is selected from the group consisting of N-dithio-carbalkoxyglycines and N-thiocarbalkoxyglycines. t v 6. An element according to claim 4 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide, N-phenyl-N '-cyclohexylcarbodiimide, di-pdimethylaminophenylcarbodiimide, N-tert-butyl-N- (triphenylmethyl )-carbodiimide and l-ethyl-3( 3- dimethylaminopropyl)-carbodiimide hydrochloride.

7. A light-sensitive heat-developable diazotype composition for use with a coupler precursor capable of forming a coupler upon dehydration; the composition comprising, an admixture of a light-sensitive diazonium compound, and

a normally solid carbodiimide dehydrating agent having the formula wherein R is an organic radical of the group consisting of alkyl, cycloalkyLaralkyl and aryl groups and amino derivatives thereof, and R is of the group consisting of hydrogen and said organic radicals.

8. A composition according to claim 7 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide,

N-phenyl-N '-cyclohexylcarbodiimide, di-pdimethylaminophenylcarbodiimide, N-tert-butyl-N (triphenylmethyl)-carbodiimide and l-ethyl-3( 3- dimethylaminopropyl )-carb0diimide hydrochloride.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3, 99,335

DATED August 12, 1975 INVENTOR(S) W.J. Przezdziecki It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 9, line 22, "couplingreactive" should read --couplingreactive--; line 24, "(a')" should read -(b).

gigncd and Sealed this thirteenth Day of April1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting ()jll'r'cer Commissioner of Pare/11s and Trademarks

Claims

1. IMAGEWISE EXPOSING TO ACTINIC RADIATION A SUPPORTED LAYER COMPRISING A. A LIGHT-SENSITIVE DIAZONIUM COMPOUND, AND B. AT LEAST ONE COMPOUND SELECTED FROM AT LEAST ONE BUT NOT BOTH OF I. A SOLID CARBODILIMIDE DHYDRATING AGENT HAVING THE FORMULA

1. A METHOD OF FORMING AN AZO IMAGE COMPRISING THE STEP OF:

2. HEATING SAID IMAGEWISE EXPOSED LAYER WHILE IN CONTACT WITH A LAYER COMPRISING THE OTHER OF (I) AND (II) TO A TEMPERATURE SUFFICIENT TO CAUSE SAID ACID AND SAID CARBODIIMIDE DHYDRATING AGENT TO COME INTO REACTIVE CONTACT THEREBY INITIATING FORMATION OF SAID COUPLER BY DEHYDRATION AND PRODUCTION OF SAID AZO DYE IMAGE BY REACTION OF SAID COUPLER WITH UNEXPOSED PORTIONS OF SAID DIAZONIUM COMPOUND.

2. A method according to claim 1 wherein said glycine is selected from the group consisting of N-dithio-carbalkoxyglycines and N-thiocarbalkoxyglycines.

2. heating said imagewise exposed layer while in contact with a layer comprising the other of (i) and (ii) to a temperature sufficient to cause said acid and said carbodiimide dehydrating agent to come into reactive contact thereby initiating formation of said coupler by dehydration and production of said azo dye image by reaction of said coupler with unexposed portions of said diazonium compound.

3. A method according to claim 1 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide, N-phenyl-N''-cyclohexylcarbodiimide, di-p-dimethylaminophenylcarbodiimide, N-tert-butyl-N''-(triphenylmethyl)-carbodiimide and 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride.

4. A LIGHT-SENSITIVE HEAT-DEVELOPABLE DIAZOTYPE IMAGING ELEMENT COMPRISING. A. A LAYER COMPRISED OF A NORMALLY SOLID CARBODIIMIDE DEHYDRATING AGENT HAVING THE FORMULA

5. An element according to claim 4 wherein said glycine is selected from the group consisting of N-dithio-carbalkoxyglycines and N-thiocarbalkoxyglycines.

6. An element according to claim 4 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide, N-phenyl-N''-cyclohexylcarbodiimide, di-p-dimethylaminophenylcarbodiimide, N-tert-butyl-N''-(triphenylmethyl)-carbodiimide and 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride.

7. A LIGHT-SENSITIVE HEAT-DEVELOPEABLE DIAZOTYPE COMPOSITION FOR USE WITH A COUPLER PRECURSOR CAPABLE OF FORMING A COUPLER UPON DEHYDRARION, THE COMPOSITION COMPRISING, AN ADMIXTURE OF A LIGHT-SENSITIVE DIAZONIUM COMPOUND, AND A NORMALLY SOLID CARBODIIMIDE DEHYDRATING AGENT HAVING THE FORMULA

8. A composition according to claim 7 wherein said carbodiimide is selected from the group consisting of dinaphthylcarbodiimide, dicyclohexylcarbodiimide, N-phenyl-N''-cyclohexylcarbodiimide, di-p-dimethylaminophenylcarbodiimide, N-tert-butyl-N''-(triphenylmethyl)-carbodiimide and 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide hydrochloride.