CH513428A - Oxidation system based on 2,2',4,4'5,5'-hedaary- - ldiimidazoles - Google Patents

Abstract

Mixtures stable in air under usual conditions, but can be activated by heat, pressure, light or electron beam contain:- (A) a 2,2',4,4',5,5'-hexaaryldiimidazole in which the aryls have 1- or 2-rings opt. with substituents inert to B having Hammet p-sigma value -0.5 to +0.8 and without Zerewitinoff H; and (B) and oxidisable component, normal oxidation potential =1.35 V relative to standard calomel electrode, chosen from certain p-arylenediterarylamines,, p-phenylenediamines, iminohydrazides and N-acyl derivatives, o,o'-disubstituted phenols and organic HS-compounds. Component (A) oxidises (B) when activated by free radicals. Applications include photography, thermographic reproduction, dyeing of materials, and removal of undesirable odours.

Description

  

  
 



  Radiation sensitive composition
The invention relates to a commercially available, radiation-sensitive oxidizable mixture containing a hexaarylbiimidazole and an oxidizable agent, the oxidizable agent being a p-arylene-di-tert-amine, p-phenylenediamine mixed with a coupler, a hydrazone or an N-acyl derivative thereof in admixture with a coupler, is an o-o'-disubstituted phenol or an organic sulfhydryl compound. If the mixture is subjected to the action of heat, light or an electron beam, the hexaarylbiimidazole is converted into the corresponding triarylimidazolyl radical, which oxidizes the oxidizable agent.



   Oxidation is one of the fundamental reactions in chemistry, and a variety of methods are known to carry out oxidation reactions. Examples of oxidation reactions in which a free radical is the oxidant are: oxidation of Fe + to Fe +++ by alkoxy radicals (Walling, Free radicals in solution, John Wiley and Sons, 1957, page 33), oxidation of metallic sodium to Na + by Triphenylmethyl radicals (Fieser and Fieser, Advances in Organic Chemistry, Reinhold Publishing Corporation, 1961, page 352), oxidation of cyclohexane to cyclohexyl by phenyl radicals (Gilman, op.

   cit., in particular page 1133), and oxidation of alkanes to alkyl radicals by chlorine radicals as oxidizing agents (Florkin and Stotz, Allgemeine Biochemie, Elsevier Publishing Corporation, 1962, Volume 2, Chapter 1, on mechanisms of organic reactions by Bender and Breslow, in particular Page 204).



   Free radicals such as those noted above are highly reactive species which, because of their high degree of reactivity, are generally relatively short lived. In contrast to ordinary chemical reagents, most free radicals cannot be stored as such, but they are formed when necessary as a result of energization of a precursor by the homolytic cleavage of a covalent bond from a precursor. The radicals mentioned in the preceding paragraph are obtained, for example, in the following manner from the specified precursors: alkoxy radicals by heating a dialkyl peroxide; Triphenylmethyl radicals due to the thermal decomposition of hexaphenylethane; Phenyl radicals from heating or photolysis of benzoyl peroxide and chlorine radicals from photolysis of chlorine.

  Other known radicals can be formed from suitable precursors by these or other methods. The utility of free radicals and their precursors in the oxidation of oxidizable compounds depends on the nature and properties of the particular radical or radical precursors used. Accordingly, the oxidative power of radicals varies so that one type of radical does not oxidize an oxidizable compound that easily oxidizes another type of radical.



  For example, while triphenylmethyl radicals cannot oxidize ferric ions (Gilman Organic Chemistry, 2nd Edition, John Wiley and Sons, 1943, Volume 1, page 601), alkoxy radicals easily oxidize ferric ions to ferric ions, as mentioned above.



   Although many free radicals can be used with some success as oxidizing agents, the free radicals described so far have certain disadvantages when used generally as oxidizing agents. For example, the usefulness of many free radicals as oxidizing agents is limited by the fact that the oxidations must be carried out with the exclusion of air, since most radicals react extremely quickly and preferentially with molecular oxygen (Gould, Mechanism and Structure in Organic Chemistry, Henry Holt & Co ., 1959, pp. 692-3). This is a property of just as many so-called stable radicals such as B. 2,2-Diphenyl-1-picrylhydrazyl lUeda, Kuri and Shida, J. Phys. Chem. 36, 1676 (1962)].



   Another property that limits the applicability of many free radicals as oxidizing agents is that the radicals, once formed from their precursors, decompose or rearrange in reactions that compete with a desired oxidation reaction and therefore in poor yields of the desired oxidation product or lead to undesired by-products.

  Benzoyloxy radicals, for example, easily decompose irreversibly with the formation of phenyl radicals and carbon dioxide (Fuson, Reactions of Organic Compounds, John Wiley and Sons, 1962, page 576), tert-butoxy radicals decompose irreversibly with the formation of acetone and methyl radicals (Walling, op. Cit., Page 31) and the radical (C6H5) 3CCH2 rearranges to the less reactive (C6H5) 2CCH2C6H5 (Gould, op. Cit., Page 755). Certain other radicals are limited in their applicability because of their sensitivity to light; Triphenylmethyl, for example, has very poor photochemical stability (Walling, op. Cit, pages 533-4; Fuson, op. Cit., Page 577).

  The disadvantage of a radical, which forms harmful by-products when used as an oxidizing agent, can be demonstrated using the example of 2,2'Azobis- (2-methylpropionitrile) or other azo compounds, which when placed in a viscous medium, such as the gelatin layer of a photographic film, decompose when heated or when irradiated with ultraviolet light, generating radicals and nitrogen as by-products. The nitrogen causes bubbles in the gelatin layer and thus tarnishes the photographic film.



   A particular disadvantage of most known free radical oxidants is that once formed from the precursor they are not easily converted back to the precursor. As a result, the radicals are more likely to undergo other transformations, such as disproportionation, than to be converted back to the precursor once they have been formed. The consequence of this is that the full oxidative power of the radicals cannot be obtained in the desired reaction and, as a result, only very low yields of the desired reaction products can be obtained.



   For use as sources of oxidizing free radicals, the radical precursors should have a combination of certain properties. For many uses, for example, a radical precursor is required which is stable to the environment under normal storage conditions, but which can be activated by heat, pressure or light with the formation of radicals if required. As a result, the radical precursor should be stable at ordinary temperature, shock, air, and visible light. Examples of usually used free radical precursors that cannot be stored are hexaarylethanes, diacyl peroxides, hydrogen peroxides and diazomethane.



   An undesirable property that certain radical precursors have, especially those such as carbon tetrachloride or tetrabromide, tetrachlorobenzene, bromotrichloromethane, tetrachloroethane or hexachlorobutadiene, which are used as sources of radicals for the oxidation of hydrogen-containing compounds, is the formation of strongly acidic by-products as a result of the oxidation reaction. If the desired oxidation reaction is carried out in the presence of acid-sensitive materials, then the presence of such strong acids as the hydrogen halides is very harmful.

  Certain other radical precursors are inactivated for radical formation under moderate, acidic or basic conditions; For example, tetraphenylhydrazine, a well-known radical precursor, reacts with acids to form a mixture of colored types of ions that are difficult to convert into free radicals Ivgl. Lewis and Bigeleisen, J. Am. Chem. Soc. 64, 2808 (1942) 1.



   Other radical precursors which work well for generating radicals which are good oxidizing agents are of little practical importance because of their dangerousness. This makes handling them dangerous, either alone or in combination with other substances. Examples of such dangerous radical precursors are the volatile, very toxic halogenated hydrocarbons such as carbon tetrachloride, carbon tetrabromide and tetrachlorethylene, and explosive substances such as. B. acetyl peroxide and other peroxides (cf.



  Sax, Handbook of Hazardous Materials, Reine'gold Publishing Corporation, 1951, especially pages 5, 6, 83, 84, 369). Furthermore, such radical precursors, which are volatile under ordinary conditions, suffer from the disadvantage that they are easily lost by evaporation from mixtures in which they are contained.



   The oxidation of certain oxidizable compositions consists in the dissociation of the hexaarylbiimidazoles to triarylimidazolyl radicals being carried out in the presence of oxidizable compositions. Means for generating the triarylimidazolyl radicals are u. a.



  Heat, light and electron beams. While the oxidizable substance is being oxidized, the starting hexaarylbiimidazole is reduced to the corresponding triarylimidazole, so that the new activatable chemical exchange compositions can be referred to as oxidation-reduction compositions. The overall oxidation-reduction reaction which follows the activation of such compositions is hereinafter referred to as the oxidation reaction for the sake of simplicity.



   The biimidazoles and the oxidizing radicals they generate have advantageous properties and overcome many of the disadvantages of known systems, thereby making it possible to carry out oxidations in a practical, controlled manner. For example, the 2,2 ', 4,4', 5,5'-hexaarylbiimidazoles are stable under ordinary chemical ambient conditions until they are appropriately activated by means such as heat, heat or electron beams. This enables the oxidation reaction to be triggered at the surgeon's discretion. The biimidazoles are usually crystalline and non-volatile, compatible with a large number of substances and are not dangerous because they are not explosive and non-toxic to animals. The dissociation of the biimidazoles to the oxidizing imidazolyl radicals occurs easily even in the presence of weak acids or bases.



  When the biimidazoles are activated by light, they dissociate in high yield to form the oxidizing radicals. Both the biimidazoles and the imidazolyl radicals are practically non-reactive with air under ambient conditions. When the imidazolyl radicals are not used as oxidizing agents, they unite. in high yield with regression of the biimidazole, from which the oxidizing radicals can be generated again by suitable activation.



   The composition according to the invention contains
A) a 2,2 #, 4,4 ', 5,5'-hexaarylbiimidazole, in which the aryl groups contain one or two rings which can be substituted by substituents which are inert towards component (B) and a Hammett para- have a sigma value between -0.5 and +0.8 and are free of active hydrogen (Zerewitinoff hydrogen) are intimately mixed with
B) an oxidizable compound which has a formal oxidation potential of 1.35 volts or less, based on a standard calomel electrode, and belongs to one of the following classes of compounds:

  :
1. p-Aryleneditert.-amines, wherein the arylene groups are phenylene or diphenylene and the groups attached to the amine nitrogen are lower alkyl or lower alkylene groups;
2. p-Phenylenediamines, in which one amino group is primary and the other is tertiary and the groups connected to the tertiary nitrogen are lower alkyl groups, the p-phenylenediamines being mixed with a phenol, N, N-di (lower) alkylphenylenamine as coupling compound or an active methylene coupling compound is present;
3.

  Iminohydrazones and their N-acyl derivatives, which can be oxidized to diazonium compounds, in a mixture with a phenol or N, N-disubstituted arylamine as coupling compound or with an active methylene coupling compound;
4. o, o'-disubstituted phenols in which the substituents are halogen, lower alkyl or lower alkoxy groups and
5. organic sulfhydryl compounds.



  A) The hexaarylbiimidazoles
The constituents of the mixtures according to the invention are the 2,2 ', 4,4', 5,5'-hexaarylbiimidazoles (which are occasionally referred to below as 2,4,5-triarylimidazolyl dimers), which can be dissociated to the corresponding triarylimidazolyl radicals. The aryl groups are the same or different, preferably they are the same. They can be carbocyclic or heterocyclic and they can be free of substituents or they can carry substituents which do not interfere with the dissociation stage or the subsequent oxidation. The aryl groups are preferably phenyl, biphenyl, naphthyl, furyl or thienyl.

  Suitable substituents for the aryl groups are those which have a Hammett para sigma value of -0.5 to +0.8 and which are free of Zerewitinoff hydrogen, i.e. H. which do not contain hydrogen which reacts with methyl magnesium iodide. Typical substituents and their sigma values (in relation to hydrogen = 0.00) as described by Jaffe, Chem.



  Rev. 53, 219-233 (1953) are: methyl (-0.17), ethyl (-0.15), tert-butyl (-0.20), phenyl (0.01), styryl ( approx. -0.05), trifluoromethyl (0.55), chloromethyl (0.18), cyanomethyl (0.01), 2-carboxyethyl (-0.07), butoxy (-0.32), phenoxy (- 0.03), fluorine (0.062), chlorine (0.227), bromine (0.232), iodine (0.276), methylthio (-0.05), methylsulfonyl (0.73), nitro (0.78), ethoxycarbonyl (0 , 52), and cyano (0.63). Accordingly, the substituents can be halogen, cyano, hydrocarbon radicals (including alkyl, haloalkyl, cyanoalkyl and aryl), alkoxyl, aroxyl, alkylthio, alkylsulfonyl, arylsulfonyl and / or nitro. The aryl radicals are preferably carbocyclic, especially phenyl, while the preferred substituents have Hammett sigma values in the range from -0.4 to +0.4, especially alkyl, alkoxy, chlorine, fluorine and bromine.



   In addition, each carbon chain listed above preferably contains 1 to 6 carbon atoms. The term lower brought in this specification means such a carbon chain as lower alkyl.



   In a preferred class of biimidazoles, the 2- and 2'-aryl groups are phenyl rings which carry an ortho substituent which has a Hammett sigma value in the range from -0.4 to +0.4 and in particular fluorine, chlorine, Is bromine, lower alkyl or lower alkoxy group.



   Typical hexaarylbiimidazoles that can be used in the practice of the invention are: 2,2'-bis (o-bromophenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-bromophenyl) 4 , 4 ', 5,5'-tetraphenylbiimidazole, Z2'-bis (p-carboxyphenyl) 4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-chlorophenyl) 4,4'-5, 5'-tetrakis (p-methoxyphenyl); biimidazole, 2,2'Bis (O-chloropheny1) 4,4:

  : 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-chlorophenyl) 4,4 ', 55'-tetrakisAp-methoxyphenyWbiimidazole, Z2'-bis (p-cyanophenyl) 46', 5,5'- tetra kisXp-methoxyphenyl) -biimidazole, 2,2'-bisA2,4-dichlorophenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bisA2,4-dimethoxyphenyl) 4,4' , 5,5'-tetraphenylbiimidazole, 2,2'-bisXo-ethoxyphenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 22'Bis- (m-fluorophenyl) 4,4', 5,5 ' -tetraphenylbiimidazole, 2,2'Bis- (o-fluorophenyl) 4,4, 5,5'-tetraphenylbiimidazole, 2,2'-BisXp-fluorophenyl) 4,4 ',

   5,5'-tetraphenylbiimidazole, 2,2'-bisAo-n-hexyloxyphenyl) 4,4, 5,5'-tetraphenylbiimidazole, 2,2'-bis (on-hexyl phenyl) 4,4, 5,5 '-tetrakisAp-methoxyphenylSbiimidazole, 2,2'-Bis43,4-methylenedioxyphenyl) 4,4, 55'-tetraphenylbiimidazole, 2,2'-BisAo-methoxyphenyl) 4,4, 5,5'-tetraphenylbiimidazole, 2, 2'-BisXp-methoxyphenylS4,4-bisXo-methoxyphenyl> 5,5'-diphenylbiimidazole, 2,2'-BisXp-methoxyphenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'Bis- (m -nitropheny1> 4,4 ', 5,5' tetrakis- (2Pdimethoxyphenyltbiimidazole 2,2'-BisAp-phenylsulfonylphenyl>

   4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (p-sul- f # moylphenyl) 4,4', 5,5'-tetraphenylbiimidazole, 2,2'-bisX2,4,6- trimethylphenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-di4-biphenylyl4,4, 5,5'-tetraphenylbiimidazole, 2,2-di-1-naphthyl4,4', 5 , 5'-tetrakis- (p-methoxyphenyltbiimidazole, 2,2'-di-9-phenanthryl4,4 ', 5,5'-tetrakis Ap-methoxyphenylS biimidazole, 2,2'-diphenyl4,4', 5,5 ' -tetra- 4-biphenylylbiimidazole, 2,2'-diphenyl, 4,4 ', 5,5'-tetra-2,4-xylylbiimidazole, 2,2'-di-3-pyndyl4,4', 5,5 ' -tetraphenylbiimidazole,

   2,2'-di-3-thienyl, 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-di-o-tolyl4,4,5,5'-tetraphenylbiimidazole, 2,2'-di -p-tolyl, 4,4'-di-o-tolyl-5,5 '-diphenylbiimidazole, 2,2'-di-2,4-xylyl-4,4', 5,5'-tetraphenylbiimidazole, 2,2 ', 4,4', 5,5'-hexa4-biphenylylbiimidazole, 2,2 ', 4,4,5,5'-hexakis (p-benzylthiophenyWbiimidazole, 2,2', 4,4 ' , 5,5'-hexa-l-naphthylbiimidazole and 2,2 ', 4,4', 5,5'-hexaphenylbiimidazole, 2,2'-bis # o-chlorophenyW4,4 ', 5,5'-tetrakis < m-methoxyphenyl) - biimidazole, 2,2'-bisAo-chlorophenyl) -4,4 ', 5,5'-tetrakis (m-betaphenoxymethoxyphenyltbiimidazole, 2,2'-bisX2,6-dichlorophenyl) 4,4' , 5.5'-

   tetraphenylbiimidazole, 2,2'-bis-ao-nitrophenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-nitrophenyl) 4,4', 5,5'-tetrakis- (m -methoxyphenylSbiimidazole, 2,2¯Bis- (2-nitro-5-methoxyphenyl) - 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis- (o-chlorophenyl) -4> F¯bis- (p-methoxyphenyD-5,5'-diphenylbiimidazole, 2,2-bis # o-chloro-p-methoxyphenyl) 4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bisA3-pyridyl4,4', 5,5'-tetraphenylbiimidazole.



   The preferred hexaarylbiimidazole is 2,2'-bisio-chlorophenyl) 4,4 ', 5,5'-tetraphenylbiimidazole.



   The biimidazoles can be obtained in a simple manner by known processes, which are described in detail in Italian patent specification No. 707 086 and by Hayashi et al. in Bull. Chem. Soc., Japan, 33, 565 (1960). According to the preferred method, u. a.



  the corresponding triarylimidazole is oxidatively dimerized with ferricyanide in alkali, whereby the 1,2'-biimidazoles are generally obtained, although other isomers, such as. B. the 1,1'-, 1,4-, 2,2'-, 2,4'- and 4,4'-biimidazoles, can also be obtained in a mixture with the 1,2'isomer.



   For the purposes of the present invention, it is immaterial which isomer is used, provided that it is photodissociable to the imidazolyl radical as discussed above.



   Biimidazoles useful in the present invention are disclosed in South African Patent No. 3627/63, published August 12, 1963, and in British Patent No. 997,3936, published August 7, 1963.



  Published July 1965, described.



  B) The oxidizable component
The oxidizable compounds of the present invention have a formal oxidation potential of 1.35 volts or less, based on a standard calomel electrode, the sign of the potential being given in accordance with the European convention [cf. Kortum and Bockris, Textbuch der Elektrochemie, Volume 1, Elsevier, New York (1961) 1. Formal oxidation potentials are usually measured by cyclic voltammetry [cf. z. B. Sevcik, Coll. Czechoslov. Chem. Communs.



  13, 349 (1948); Mizoguchi et al., J. Am. Chem. Soc. 84: 2058 (1962); in particular Galus et al., J. Elektroanal.



  Chem. 5, 17 (1963) 1. The formal potential is the experimentally observed potential when the same formal concentrations of the oxidized and reduced forms of a substance in acetonitrile solution are present during the measurement at the electrode-solution interface [cf. z. B. Smith et al., Talanta 2, 348 (1959); Lingane, Elektroanalytische Chemie, 2nd Edition, Interscience, New York, 1958, page 58; Delahay, Instrument Analysis, MacMillan Co., New York, 1957, p. 161. Anhydrous acetonitrile is the preferred solvent for cyclic voltammetry because its dielectric constant is high and because it is an excellent solvent. Before use, it is purified by distillation and dried to reduce moisture levels to less than 100 ppm.

  The final quality index is a good blank value (flat) polarogram by cyclic voltammetry after the acetonitrile has been made 0.5 formal (= molal) with dry lithium perchlorate. In particular, the oxidizable compounds are selected from the following classes of compounds: a) p-arylene-di-tert-amines, p-R1R2N-arylene-NR3R4, in which the R groups are lower alkyl or lower alkylene groups and the arylene is a phenylene or diphenylene group is, for example, N, N, N ', N'-tetramethyl-p-phenylenediamine, N, N, N', N'-tetramethylbenzidine, 1,1 '- (4,4'-biphe, ny- len> dihexamethyleneimine or N, N, N ', N'-tetrabutylbenzidine dihydrochloride, which can be oxidized to the corresponding more strongly colored and useful Wurster salts.



   b) p-Phenylenediamines, in which one amino group is tertiary and the other is primary, for example N, N-dimethylp-phenylenediamine, N, N-diethyl-p-phenylenediamine, N, N-dipropyl-p-phenylenediamine, N, N- Dibutyl-p-phenylenediamine or N, N-dimethyltoluene-2,5-diamine, in combination with a coupling component which is less easily oxidized than the diamine, for example: i) a phenol with a free coupling site, e.g. B. in the para position, which can optionally carry halogen, alkyl and / or alkoxy substituents in other positions, e.g. B.



  Phenol, o-cresol, m-cresol, o-ethylphenol, o-chlorophenol, o-methoxyphenol, 1-naphthol or 2-methyl-1-naphthol, 7-acetylamino-1-naphthol or 2-naphthol; ii) an N, N-dialkylarylamine with a free para position, such as. B. N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-m-toluidine, and the like, as described above; iii) an active methylene coupling compound (i.e. containing an enolizable hydrogen atom, such as beta diketones (e.g. benzoylacetone), beta-ketoesters (e.g. ethyl acetoacetate, diethyl malonate), beta-ketoamides (e.g.



     4'-chloroacetoacetanilide, 2-benzoyl-m-acetanisidide) or beta-ketonitrile (e.g. 2-thenoylacetonitrile).



   The hexaarylbiimidazoles oxidize when such mixtures of compounds such as phenylenediamine / phenol, phenylenediamine / dialkylarylamine or phenylenediamine / active methylene compound are activated to indophenols, indoanilines or azomethines, all normally colored compounds that can be used for coloring various substrates. The chemistry of such oxidative condensation reactions was described by Vittum and Weissberger in J. Phot. Sci. 2, 81 (1954) and 6, 157 (1958) and von Thirtle, The Chemism of Dye Forming Development, Organic Chemical Bulletin, Volume 34, No. 3, Eastern Organic Chemical Department, Distillation Products Industries, Division of Eastman Kodak Co ., 1962.



   c) Hydrazones, in particular iminohydrazides and their N-acyl derivatives, which can be oxidized to diazonium compounds, in conjunction with a coupling component.



  Included are u. a. also hydrazones and N-acylhydrazones of benzothiazolinones, benzoselenazolinones, benzoazolinones, benzimidazolinones and carbostyrils, which can be represented by the following formula:
EMI4.1
 where R1 is hydrogen or at least one halogen atom or at least one alkyl or alkoxy group, R2 is an alkyl group, X is oxygen, sulfur, selenium, N-alkyl or -CH = CH- and A is an acyl, aroyl or organic sulfonyl radical.



   Hexaarylbiimidazoles oxidize upon activation in the presence of the coupling compounds of such hydrazones and N-acylhydrazones with the formation of azo dyes.



  The chemistry of the coupling reaction is from Hunig and Fritsch, Ann. 609, 143 (1957). Typical diazonium precursors are the hydrazones of 6-methoxy-3-methyl-2- (3H) -benzothiazolones, 3-methyl-2- (3H> benzothiazolones and 6-chloro-3-methyl-2- (3H) -benzothiazolones. Reactive couplers include N, N-diethylaniline, N, N-dimethyl-m-toluidine, N-2-cyanoethyl-N-methyl-1-naphthylamine, phenolic compounds such as phenol, m-cresol, 1-naphthol, 6-sulfamido-2-naphthol or hydroquinone and active methylene compounds such as acetamide, 2-thenoylacetonitrile or other beta-keto compounds described under (b) above. Other combinations of hydrazones and couplers as well as composite hydrazone coupler combinations, the disclosed below are described in U.S. Patent 3,076,721.

  Such hexaarylbiimidazole / hydrazone / coupler mixtures are particularly useful for generating images; for example by UV irradiation of a coating of the mixture on paper through a stencil or a negative.



   Photosensitive papers which contain the above-defined N-acylhydrazones generally have a longer life than those which contain the corresponding non-acylated hydrazones. Suitable N-acyl hydrazones that are useful are those disclosed in U.S. Patent 3,076,721. Typical hydrazones are 3-methyl-2-benzothiazolinone-acetylhydrazone, 3-methyl-2-benzoselenazolinone-propionylhydrazone, 2-ethyl-2-benzoxalinone-benzene-sulfonylhydrazone, 1,3-dimethyl-5-methoxy-2-benzimidazolinone-benzoyl-hydrazone, 1-methyl-acetylenephenol, 2-methyl-acetylenic-2-benzothrazone, 1-methylcarbostyrazone, and 1-methylcarbostyrazone-methyl-2-benzo-azolinone-methyl-3-benzo-azo-phenyl-2-benzothrazone -p-toluenesulfonylhydrazone. Any of the couplers described above can be used in conjunction therewith.



   When the acyl radical, A, is GCO, where G is a radical capable of coupling with the diazonium compound formed from the substituted hydrazone, such as a 1-naphthol-2-carbonyl group or a 1-phenyl-5-oxo -3-pyrazolyl-carbonyl group, then the N-acyl compound is a composite hydrazone coupler compound which contains the diazo component and the coupling component in the same molecule and which therefore, when oxidized by the present method, directly provides the colored compound. Examples of this are # methyl-2-benzothiazolinon-1-phenyl -5-oxo-3-pyrazolylcarbonylhydrazone.



   d) o, o'-disubstituted phenols, in which the substituents
Are halogen, alkyl or alkoxyl groups and the p-position to the hydroxyl group is undsubstituted.



   Examples are: 2,6-difluorophenol, 2,6-dibromophenol, 2,6-dimethylphenol, 2,6-diisopropylphenol, 2,6-di-tert-butylphenyl, 2,6-dimethoxyphenol and 2,6-di -n-butoxylphenol, which, when activated, oxidize the hexaarylbiimidazoles to the corresponding colored and useful diphenoquinones.



   e) organic sulfhydryl compounds
It includes u. a. aliphatic (including the cycloaliphatic) aromatic and heterocyclic compounds which contain one or more thio groups, including thio acids and dithio acids, which according to the present method to the corresponding
Disulfides are oxidized.



   Typical aliphatic compounds are alkane thiols, such as, for example, 1-butane thiol, ethane thiol, 2-propane thiol, alpha-toluene thiol, 1-dodecane thiol, 2,4-dimethyl-3-pentane thiol, cyclohexane thiol, 3-phenyl-2-propene-1-thiol and tetrahydro-2-naphthylenethiol; Polythiols such as
1,2-ethanedithiol, 1,6-hexanedithiol, 1,2,3-propanetrithiol, neopentanetetrathiol and polymers containing thiol groups such as the thiol-terminated alkyl disulfide polymers e.g. B. HS-1 (CH2) XSS-] 7 (CH2) x SH; substituted thiols, such as.

  B. 3-hydroxypropane-1-thiol, dithioerythritol,
2-chloroethanethiol, 2-butoxyethanethiol, 1-thiosorbitol, 2-methyl-2-mercapto4-pentanone, 1,3-dimercapto-2-propanone, bis (2-mercaptoethyl) sulfide, ethyl thioacetate, 2-mercapto-isobutyric acid , Dodecyl thio-pyruvate, diethyl mercapto-maleic acid, cysteine, phenyl-2-amino-4-methyl-4-mercaptovalerate. The aromatic thiols also include carbocyclic compounds such as benzene thiol, p-toluene thiol, 2-chloro-4-phenylbenzenethiol, 4-bromo-1-naphthalenethiol, 2,6-naphthalenedithiol, 2'-mercaptoacetophenone, 2-mercaptoanthraquinone, p-mercapto-benzoic acid ester and 4,4'-thiodibenzenethiol and heterocyclic sulfidryl compounds such as e.g.

  B. 2-mercaptoquinoline, 2- (2-mercaptoethyl) pyridine, 2-mercaptobenzothiazole, 3-furanethiol, 3-thiophenediol and 3,4-thiophenedithiol. Typical thio and dithio acids can also be used, e.g. B. thioacetic acid, dithioacetic acid, dithiobenzoic acid and thionaphthoic acid. It is also possible to use thiocarbonyl compounds which can form a mercapto group by a tautomeric shift of hydrogen; for example thiourea, which reacts as pseudothiourea.



  C) Preparation of the mixtures
An oxidizable compound of the classes defined above with a formal oxidation potential as defined above is mixed with a dissociable compound as defined above, 2,2 ', 4,4', 5,5'-hexaarylbiimidazole. The oxidizable compound and the biimidazole are intimately mixed, for example by dissolving in a solvent for both or by mechanical mixing in the dry state or in the presence of a liquid medium to form a paste, slurry or dispersion.



   The proportions of the ingredients of the compositions are not critical. For synthetic purposes, however, the yields of oxidized product are greatest when a small excess of hexaarylbiimidazole, based on the oxidizable substance, is used. Since each biimidazole molecule gives rise to two oxidizing imidazolyl radicals, each biimidazole molecule is equivalent to two oxidizable sites of the oxidizable component. For certain other reactions in which a cycle occurs or when high synthesis yields are not important, small amounts of the biimidazole in relation to the oxidizable substance are sufficient.



   It is often convenient and desirable to incorporate other components into the new chemical exchange mixtures in order to provide very intimate contact between the biimidazole and the oxidizable substances, especially when both are normally solids. Accordingly, solvents which are practically inert to the biimidazole and the oxidizable substance can be used to dissolve these components and also to provide a liquid medium for their convenient handling. Typical solvents are formamide, N, N-dimethylformamide, N, N-dimethylacetamide, hexanamide, stearamide, acetone, methanol, and ethanol.



   I-propanol, 2-propanol, butanol, ethylene glycol, polyethylene glycols, ethyl acetate, ethyl benzoate, benzene, o-dichlorobenzene, toluene, dimethyl sulfoxide, pyridine, tetrahydrofuran, dioxane, and mixtures of these compounds in various proportions, as required to achieve the desired solution .



   Polymeric substances, especially translucent and film-forming polymers, can also serve as binders, carriers and oxidation media; accordingly, oxidizable compounds, biimidazole, polymer, with or without mutual solvents, mixed, then extruded, cast, pressed or otherwise formed into supported or unsupported films or molded articles. Polymeric materials that have been found suitable are polyvinyl alcohol, ethyl cellulose, polyvinyl chloride, polystyrene, polyvinyl acetate, polymethyl methacrylate, cellulose acetate, cellulose butyrate, copolymers of vinyl monomers, gelatin, and polyethylene. Other suitable inert materials that can be used include: a. Glasses, resins or waxes.



   Usually, the amount ranges from about 0.5 to about 500 parts by weight per part of the sum of the weight of the oxidizable compound and the hexaarylbiimidazole.



   The radiation-sensitive compositions according to the invention can serve as coatings, impregnating agents or additives for various substrates, such as are frequently used in the graphic arts and for jewelry purposes. The substrates can be rigid or flexible, solid or porous, opaque or for
Be transparent to light. You can use paper from silk to heavy cardboard boxes; Films made from plastics and polymeric materials, such as B. regenerated cellulose, cellulose acetate, cellulose nitrate, polyethylene, polymethyl methacrylate, polyvinyl chloride, glass, wood and metals.

   Substrates in which a photosensitive composition is dissolved, or which the compositions on the side facing away from the light source as
Wearing coating must be permeable to the wavelength of the radiation used to activate the biimidazole.



   For the stability of these compositions for long-term storage, methods can be used which keep the biimidazole and the oxidizable substance in a physically separate, chemically interacting relationship, as described in U.S. Patents 2,063,654-7, 3,076,721 and 3,094,417 or encapsulate one or both of the reacting substances as small particles in protective envelopes such as those described in U.S. Patents 2,800,457-8 and 3,015,128.



   When the compositions are exposed to heat, light or electron beams, the biimidazole component dissociates to its free radical form. The free radical then reacts with the oxidizable mixture and oxidizes it.



   If the oxidation occurs as a result of the action of heat on the compositions of the invention, then the compositions are simply heated by any heating means such as e.g. B. ovens, infrared lamps, heated metal plates and the like, heated to or above the dissociation temperature of the biimidazole. In general, the biimidazoles dissociate at temperatures below approx. 1800, but above approx. 60 C.



   The biimidazoles characteristically absorb short-wave light with wavelengths in the range from 2000 to 4200 A, such as e.g. B. ultraviolet light, and they can be photodissociated to triarylimidazolyl radicals by such light, especially that rich in wavelengths between 2500 and 2750 Å. Therefore, when the oxidation is effected by exposing the compositions to light, then such wavelengths are used. Photoactivation is the preferred method for triggering oxidation, since biimidazole dissociation often has a quantum yield of approx.



  1.0, indicating that for every quantum of radiation absorbed, one biimidazole molecule dissociates. In general the yield of oxidation product, i.e. H. in the triarylimidazolyl oxidizable substance reaction, also high. Any light source can be used to activate the photosensitive compositions and initiate color formation. In general, light sources that deliver radiation in the range between about 2000 and about 4200 Å are particularly valuable. Examples are Jupiter lamps (artificial sunsets), electronic flash cannons, germicidal lamps, UV lamps that specifically deliver short wavelength light (2537), and lamps that deliver long wavelength light (3663).

  Depending on the intensity of the light, the distance of the light source from the photosensitive composition, the type and amount of the photosensitive composition available and the desired intensity of the color in the image, the exposure time to the light varies from a fraction of a second to several minutes. It is also possible to use coherent light beams, for example nitrogen pulse lasers, argon-ion lasers and neon-II-ion lasers, the emission of which falls within the UV absorption bands of the triarylimidazolyl dimer or overlaps them.



   Ultraviolet radiation emitting cathode ray tubes, which can be used extensively in printout systems for writing on photosensitive materials, are also useful for oxidizing the compositions to their colored form. These generally contain as an inner coating a fluorescent material emitting UV radiation as a means for converting electrical energy into light energy and a fiber optic faceplate as a means for directing the radiation onto the photosensitive target. For these purposes, the phosphors should emit strongly below 420 nm (4200) so that they overlap the near UV absorption range of the new image-forming compositions. Typical phosphors include a. the types P4B (emitting at 300 to 550 nm, peak at 410 nm), P16 (330 to 460, peak at 380 nm) and P22B (390 to 510, peak at 450 nm).



  (The Association of the Electron Industries, New York, New York, assigns P-numbers and provides descriptive information about the phosphors; phosphors with the same P-numbers have practically identical characteristic properties).



   The spectral sensitivity of the biimidazoles can be extended to visible light, which the biimidazoles do not normally absorb, by incorporating visible light absorbing, energy converting agents into the compositions, e.g. B. Erythrosin B, Rose Bengal, or other phthalein dyes, diethyl orange, acridine orange or similar acridine dyes, 3,3'-diethyl #, 56,5'-dibenzoxacarbo-cyanine-p-toluenesulfonate, 3,3'-diethyloxase enacarbocyanine iodide, 3,3'-di-n-butyl-9methylthiacarbocyanine iodide, 3,3'-diethylthiaselenacarbocyanine iodide, 3,3'-diethylselenacarbocyanine iodide, or similar carbocyanine dyes, may be incorporated.



   The hexaarylbiimidazoles can also be activated by ionizing radiation. For these purposes, electron beams with a wide range of electron energies can be used, for example beams with average electron energies with a lower limit of approx. 15 kilovolts and an upper limit of approx. 1.7 MeV.



   In this process, the reaction time for the oxidation of an oxidizable compound is not critical. Depending on the activating agents and on the structures of the hexaarylbiimidazole and the oxidizable compound, it can be in the range of a fraction of a second, for example 1 to 500 milliseconds up to several hours and longer, e.g. B. take about 24 hours. With high-energy activation agents, such as the light of a flash photoly source, the oxidation takes place within a few milliseconds.



  When less energetic agents are used and when high yields of the product of the oxidation reaction are required, it is preferred to use longer reaction times.



   The triarylimidazolyl free radical generated by the above-described agents can be represented by the following formula
EMI6.1
 where A, B and D stand for the aryl groups described above and the dotted circle denotes 5 delocalized electrons which saturate the valences of the carbon and nitrogen atoms of the imidazolyl ring, 4 of these electrons being combined in pairs (which can be represented as two conjugated double bonds) and the fifth electron is redundant. In other words, the triarylimidazolyl radical contains an unpaired electron that is delocalized within the conjugated system.

   The dissociation of the biimidazole to the free radical can be discovered not only through the oxidative ability of the radicals thus formed, but also through the paramagnetic electron resonance, UV spectra and visible spectra. The biimidazoles can exist as isomers which differ in how the imidazolyl units are connected to one another and which also differ in their spectra and in their sensitivity to heat and pressure. However, all such isomers dissociate into the same triarylimidazolyl radical. White and Sonnenberg (Abstracts, 144.



  At the. Chem. Soc. Meeting, Los Angeles, March 31 to March 15.



  April 1963, pages 55M-56M) describe, for example, 2,2 ', 4,4', 5,5'-hexaphenylbiimidazole isomers. One, referred to in this specification as isomer A, is more thermally resistant to dissociation to 2,4,5-triphenylimidazolyl radicals than the other isomer B. Thus, isomer A, when dissolved in most organic solvents at room temperature, gives a very faint color and a correspondingly weak ESR signal. Whereas isomer B gives an intense purple to pink color and a very strong ESR signal.



  Accordingly, for oxidations at low temperatures (e.g. at temperatures of dry ice-acetone mixtures) isomer B is preferred as the latent oxidizing agent, while isomer A is preferred at room temperatures and above.



   A particular advantage of the biimidazole / oxidizable substance systems is that the oxidation reaction can be controlled so that it only occurs at a time that is favorable for the surgeon. The simple mixing of the oxidizable compound with the biimidazole does not result in an immediate oxidation reaction unless the means described above are used which bring about activation of the biimidazole.



   The hexaarylbiimidazoles and the imidazolyls formed therefrom are relatively unreactive towards oxygen. This can be shown by passing oxygen through a benzene solution of the biimidazole while it is irradiated with UV light.



  Even after 30 hours of uninterrupted irradiation and oxidation, imidazolyl radicals, which are formed by the photolytic dissociation of the biimidazole, are still present in high concentrations. This stability towards oxygen can also be demonstrated, for example, by the identical reaction rates of the imidazolyls with aromatic amines in the presence or in the absence of air. This lack of reactivity to oxygen is very advantageous since it makes the need for a protective gas atmosphere superfluous and also enables the composition according to the invention to be handled, stored and used in air.



   The compositions of the present invention and the oxidation process are useful in such diverse fields as organic synthesis including dye manufacture, photography, thermography and pattern drawing. The compositions are also useful in tracking thresholds of light, heat, electron beams and combinations of these agents through the chemical changes, including color changes, that they undergo when activated by such agents.



   The present composition is particularly useful for the formation of colored light-evoked images and provides a dry, silver-free, photographic process capable of printing images on various substrates such as paper and similar fibrous sheet materials different colors and shades. Apparatus useful for performing the color photographic printing process are described in U.S. Patents 2,214,365 and 2,655,802.

  Even very soft papers, such as tissue paper treated with a mixture of hexaarylbiimidazole and a color-forming oxidizable system, can easily be printed by applying the desired graphic pattern to the treated paper and by exposing it to the action of the color-forming radiation .



   The compositions of the invention are also useful in thermographic imaging processes.



  Heat-sensitive copier papers, for example, obtained by treating a paper with a mixture of a hexaarylbiimidazole and a practically colorless, but color-forming, oxidizable compound or a mixture of compounds as described above, are simply heated to image-forming temperatures in order to produce a colored image to develop a desired pattern made, for example, with matrices in conjunction with an infrared lamp. By changing the oxidizable, color-forming compound, the color can be varied over a wide range.



  U.S. Patents 2,740,895 and 3,089,952 describe typical methods and apparatus for the thermographic application of heat.



   Although the oxidation process is particularly valuable for the formation of color, it can also be used to prevent color formation in imaging systems such as those described above by adding a non-color-forming, oxidizable substance such as e.g. B. a sulfhydryl compound which is more easily oxidized than the color forming oxidizable compound is incorporated into the composition. This oxidation can be used to convert polythiols to polydisulfide polymers.



   Preferred embodiments of the invention are explained in more detail below with the aid of examples.



   example 1
One method of performing the oxidation process is that of Porter, Proc. Roy. Soc. (London) A200, 284 (1950) and Lindquist, Arkiv. Kem. 16, 79-138 (1961) described flash photolysis.



   The cylindrical quartz cell reaction vessel of the flash photolysis apparatus is filled with a methanol solution containing 1.01 x 10-4 molar of N, N, N ', N'-tetramethyl-p-phenylendiamine dihydrochloride and 2 x 10-4 molar of 2.2' -Bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole.



  The reaction vessel is irradiated with a flash tube through a filter that lets through UV light with a wavelength of 3660 Å, which is only absorbed by the biimidazole. As a result of the light activation of the biimidazole, the N, N, N ', N'-tetramethyl-p-phenylenediamine in Wursters blue is oxidized. Lewis and Lipkin, J. Am. Chem. Soc.



  64, 2801 (1942)], which is identified by its color and its spectra. The N, N, N ', N'-tetramethyl-p-phenylenediamine dihydrochloride has a formal oxidation potential of 0.96 volts. Using the flash photolysis technique, the rate of conversion of the 2 (o-chlorophenyl) 4,5-diphenylimidazolyl radical is measured by the rate of decrease in intensity of the characteristic absorption peak of this radical at 3900 Å, and the rate of formation of Wurster's blue is measured by the The speed of the increase in intensity of its characteristic absorption peak measured at 6200 Å.

   The rate constant for the conversion of the radical is 7 x 107 liters / mole x 6, and the rate constant for the formation of Wurster's blue is identical to this value. It follows that the imidazolyl only reacts with the diamine.



   Similarly, the 2Ao-chlorophenyl) 4,5-diphenylimidazolyl radical N, N, N ', N' formed by UV irradiation of Z2'-bis (o-chlorophenyl) 4,4 ', 5,5'-tetraphenylbiimidazole -Tetramethylbenzidine and N, N, N ', N'-tetrabutylbenzidine.



   The presence of air during photolysis does not change the reaction rate constants. In contrast to the behavior of most free radicals, this shows the non-reactivity of the imidazolyl radicals towards oxygen.



   Example 2
A solution made in the dark of 1.3 g of 2,6-di-tert-butylphenol, 1.5 g of 2,2'Bis- (o-chloropheny1) 4,4: 5,5¯ 'tetraphenylbiimidazole in 100 ml of benzene is placed 152.4 mm under a 275 watt Jupiter lamp. When the solution is irradiated for an hour, the initially colorless solution turns bright yellow. Evaporation of the yellow solution on a steam bath gives a mixture of dark red and light yellow crystals. The mixture of crystals is treated with petroleum ether to dissolve the red crystals, and then the yellow crystals are filtered off.

  Addition of methanol to the filtrate precipitates 0.29 g of crude 3,3 ', 5,5'-tetra-tert-butyl-4,4'-diphenoquinone. After purification by crystallization from a mixture of petroleum ether and methanol, the red crystals are then at 200 ° C. and melt within a range from 245.0 to 245.5 C. This melting range is identical to that of an authentic sample of 3.3 ', 5, 5'-Te tra-tert-butyl -4,4'-diphenoquinone, prepared by the method of Hart et al., J. Am. Chem. Soc. 73, 3179 (1951) is identical. The identity of the product is confirmed by its IR, UV spectrum and the visible spectrum.



   The oxidation potential of 2,6-di-tert-butylphenol is 1.15 volts. If the original solution is kept in the dark at room temperature, it remains unchanged.



   Example 3
Example 2 is repeated with 2,6-dimethoxyphenol, a purple precipitate of 3,3 ', 5,5'-tetra-methoxy4,4'-diphenoquinone, usually called ceruliquinone, being obtained. The formal oxidation potential of 2,6-dimethoxyphenol is 0.88 volts. The original solution remains unchanged in the dark at room temperature.



   Example 4
2,6-dimethoxyphenol and mexaphenylbiimidazole, isomer A, in approximately equal amounts by weight, are heated in benzene solution for 5 minutes at a temperature of 50 to 80 ° C., whereby ceruliquinone is obtained.



   The original, unheated solution remains unchanged when it is stored in the dark at room temperature.



   Example 5
If approx. 1 g each of 2,6-dimethoxyphenol and hexaphenylbiimidazole, isomer B, are added to approx. 100 ml of benzene, the reaction takes place at room temperature (approx.



  30 C) with the formation of ceruliquinone.



   Example 6
In subdued light, 0.635 g of 3-methyl-2-benzothiazolone hydrazone hydrochloride, 0.468 g of 'N, N-dimethyl aniline hydrochloride and 1.0 g of 2,2'-bis (o-chlorophenyl) 4,4', 5,5'- tetraphenylbiimidazole added to 100 ml of methanol. The clear, colorless solution obtained is irradiated for 10 minutes with a 275 watt Jupiter lamp. The solution is diluted with 100 ml of water and extracted three times with 50 ml of petroleum ether each time. The petroleum ether extracts are discarded and the aqueous methanol solution is evaporated on a steam bath, cooled to room temperature and filtered. The filtrate is saturated with sodium chloride.



  A blue-black, crystalline solid forms on standing. The visible spectrum of a methanol solution of this solid is identical to that of 3-methyl-24p-dimethylamino phenylazole) benzothiazolium chloride, which was prepared by the method of Hunig and Fritsch, Ann.



  609, 143 (1957).



   Example 7
Example 6 is repeated with hydroquinone as the coupling component instead of the N, N-dimethylaniline hydrochloride, 3-methyl-2- (2,5-dihydroxyphenylazole) benzothiazolium chloride being obtained.



   Example 8
This example illustrates the use of the light activated oxidative coupling reaction of the type described in the previous example to produce a colored image on paper.



   To 50 ml of a solution which contains 80 parts by volume of methanol and 20 parts by volume of N, N-dimethylformamide, 0.198 g of 3-methyl-6-methoxy-2-benzothiazolone hydrazone, 0.151 g of N, N-dimethylaniline hydrochloride and 0.650 g of 2.2 '-Bis- (o-chlorophenyl) 4,4, 5,5'-tetraphenylbiimidazole added. Unsized paper is impregnated with the resulting solution, and the wet paper is dried by IR heating. The dried, impregnated paper, which is stored in the dark, is practically no different in appearance from untreated paper.



  Exposure to the light of a 275 watt Jupiter lamp on a sheet of the treated paper results in the formation of an intense blue color of 3-methyl-6-methoxy-2- (p-dimethylaminophenylazole) benzothiazolium chloride. Another sheet of the treated paper is exposed to the Jupiter lamp through a mask for one minute, so that the paper is exposed to UV light through a stencil. Without a further development stage, an image corresponding to the template is formed on the paper.



   Example 9
The procedure of Example 8 is applied to paper with a solution of 0.196 g of 3-methyl-6-methoxy-2benzothiazolonhydrazone, 1.3 g of phenol and 1.3 g of 2,2'-bis (o-chlorophenyl) 4, Impregnate 4, 5, -tetraphenylbiimidazole in 50 ml of a mixture of 20 parts by volume of N, N-dimethylformamide and 80 parts by volume of benzene. After drying, the paper is exposed to UV light under a graphic template, which produces a purple image as a result of the oxidative formation of 3-methyl-6-methoxy-2 (p-hydroxyphenyl-azo) -benzothiazolium salt.



   Example 10
Under subdued light, 0.136 g of N, N-diethyl-pphenylenediamine, 0.151 g of 2-thenoylacetonitrile and 0.65 g of 2,2'-bisAo-chlorophenyl) 4,4,5'-tetraphenylbiimidazole to 50 ml of a mixture of 20 Added parts by volume of N, N-dimethylformamide and 80 parts by volume of methanol. Unsized paper is dipped in this solution and then dried. The action of UV light with a wavelength of 2500 to 4050 Å through a stencil on the practically colorless paper produces an intense red-violet image. The N, N-diethyl-p-phenylenediamine has a formal oxidation potential of 0.66 volts.



   Example 11
0.272 g of N, N-dimethyl-p-phenylenediamine (formal oxidation potential = 0.66 volt), 0.094 g of phenol and 0.66 g of 2.2 are added to 50 ml of a mixture of 20 parts by volume of N, N-dimethylformamide and 80 parts by volume of methanol '-Bis- (o-chlorophenyl) -4,4', 5,5'-tetraphenylbiimidazole added. Unsized paper is impregnated with the resulting solution and then dried by IR heating.



  These operations are all performed in subdued lighting. If the dry, treated paper is exposed to the light of a Jupiter lamp, it turns blue.



   Example 12
A paper sample, which has been produced as in Example 11, but has not been exposed to bright light, is cut to approx.



   Heated to 175 ° C, which resulted in the formation of the blue indoaniline dye of the following formula
EMI9.1
 a blue color is obtained.



   Example 13
Instead of phenol, N, N-dimethylaniline is used in Example 12. Paper that has been impregnated with the solution obtained turns red when it is irradiated with UV light or when it is heated to 175 ° C. for several minutes.



   Example 14
A mixture of 2.7 g of 1-butanethiol, 3.3 g of 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole and 20 ml of benzene is added under a protective gas atmosphere of dry nitrogen stirred and heated to boiling under reflux. The boiling solution is irradiated in a pyrex glass flask from a distance of 51 mm with a 275 watt Jupiter lamp. The initially clear, yellow solution turns wine red and then gradually changes to a light brown color. After 20 hours, the irradiation is stopped and the solution is cooled to room temperature. A precipitate which separates out is filtered off. This precipitate, Schm.-P. 193.0-194.5 C, is identified as 2 (o-chlorophenylY45-diphenylimidazole by IR spectral analysis.

  A high concentration of butyl disulfide is found in the filtrate by gas chromatography; no disulfide is present in the starting material. The formal oxidation potential of 1-butanethiol is 0.73 volts.



   Example 15
A mixture of 0.44 g of thiophenol (formal oxidation potential = 0.9 volts), 1.2 g of 2,2 ', 4,4,5,5'-hexaphenylbiimidazole (isomer A) is applied under a protective gas atmosphere of dry nitrogen. and stirred 15 ml of benzene under reflux and heated to boiling. After heating with stirring for 20 hours, the reaction mixture is cooled to room temperature and filtered to remove the precipitate that has formed.



  It is determined by IR spectral analysis that the solid, Schm.-P. 190.0-191.5 C, is identical to an authentic sample of 2,4,5-triphenylimidazole. Gas chromatographic analysis of the filtrate shows a high concentration of phenyl disulfide.



   The foregoing typical examples can be varied within the scope of the disclosure of the entire description herein, as would be understood by one skilled in the art, with virtually the same results being obtained.



   PATENT CLAIM I
Commercially available, radiation-sensitive composition which (A) is a 2,2 ', 4,4', 5,5'-hexaarylbiimidazole, in which the aryl groups contain one to two rings which can be substituted with substituents which are inert towards component (B) and which have a Hammett para sigma value between -0.5 and +0.8 and which are free from Zerewitinoff hydrogen, in intimate mixture with (B) an oxidizable compound that has a formal oxidation potential of 1, 35 volts or less based on a standard calomel electrode and is selected from one of the following classes of compounds:

  :
1. p-arylene-di-tert-amines, wherein the arylene groups are phenylene or diphenylene groups and the groups attached to the amine nitrogen are lower alkyl or lower alkylene groups;
2. p-Phenylenediamines with a primary and a tertiary amino group, in which the groups connected to the tertiary nitrogen are lower alkyl groups, in a mixture with a phenol or N, N-di (lower) aWylphenylenamine as a coupling compound or in a mixture with one active methylene coupling compound
3.

  Hydrazones and their N-acyl derivatives, which can be oxidized to diazonium compounds, in a mixture with a phenol or N, N-disubstituted arylamine as coupling compound or in a mixture with an active methylene coupling compound;
4. 0,0'-disubstituted phenols in which the substituents are halogen atoms, lower alkyl groups or lower alkoxy groups and
5. organic sulfhydryl compounds.



   SUBCLAIMS
1. Composition according to claim I, in which the aryl groups of the biimidazole are phenyl groups and the 2- and 2'-phenyl groups are substituted in the ortho position by a substituent which is inert towards component B and has a Hammett para-sigma value between - 0.4 and +0.4.



   2. Composition according to dependent claim 1, characterized in that the 4-, 4'-, 5- and 5'-phenyl groups of the biimidazole are unsubstituted and that the 2- and 2'-phenyl groups of the biimidazole are in the ortho position with fluorine, Chlorine, bromine, lower alkyl or lower alkoxy groups are substituted.



   3. Composition according to dependent claim 1, characterized in that the oxidizable compound is a p-arylene-di-tert-amine of group B list.



   4. Composition according to dependent claim 1, characterized in that the oxidizable compound is a p-phenylenediamine of group B 2, mixed with (a) a phenol with a free coupling-accessible site which is substituted with halogen, lower alkyl or lower alkoxy can be; (b) an N, N-di # lower drig) alkylphenylenamine with a free point accessible to the coupling; (c) a beta-diketone; (d) a beta keto ester; (e) a beta-ketoamide or (f) a beta ketonitrile.

** WARNING ** End of DESC field could overlap beginning of CLMS **.



   

 

Claims (1)

** WARNING ** Beginning of CLMS field could overlap end of DESC **. colorless paper gives an intense red-violet image. The N, N-diethyl-p-phenylenediamine has a formal oxidation potential of 0.66 volts. Example 11 0.272 g of N, N-dimethyl-p-phenylenediamine (formal oxidation potential = 0.66 volt), 0.094 g of phenol and 0.66 g of 2.2 are added to 50 ml of a mixture of 20 parts by volume of N, N-dimethylformamide and 80 parts by volume of methanol '-Bis- (o-chlorophenyl) -4,4', 5,5'-tetraphenylbiimidazole added. Unsized paper is impregnated with the resulting solution and then dried by IR heating. These operations are all performed in subdued lighting. If the dry, treated paper is exposed to the light of a Jupiter lamp, it turns blue. Example 12 A paper sample, which has been produced as in Example 11, but has not been exposed to bright light, is cut to approx. Heated to 175 ° C, which resulted in the formation of the blue indoaniline dye of the following formula EMI9.1 a blue color is obtained. Example 13 Instead of phenol, N, N-dimethylaniline is used in Example 12. Paper that has been impregnated with the solution obtained turns red when it is irradiated with UV light or when it is heated to 175 ° C. for several minutes. Example 14 A mixture of 2.7 g of 1-butanethiol, 3.3 g of 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole and 20 ml of benzene is added under a protective gas atmosphere of dry nitrogen stirred and heated to boiling under reflux. The boiling solution is irradiated in a pyrex glass flask from a distance of 51 mm with a 275 watt Jupiter lamp. The initially clear, yellow solution turns wine red and then gradually changes to a light brown color. After 20 hours, the irradiation is stopped and the solution is cooled to room temperature. A precipitate which separates out is filtered off. This precipitate, Schm.-P. 193.0-194.5 C, is identified as 2 (o-chlorophenylY45-diphenylimidazole by IR spectral analysis. A high concentration of butyl disulfide is found in the filtrate by gas chromatography; no disulfide is present in the starting material. The formal oxidation potential of 1-butanethiol is 0.73 volts. Example 15 A mixture of 0.44 g of thiophenol (formal oxidation potential = 0.9 volts), 1.2 g of 2,2 ', 4,4,5,5'-hexaphenylbiimidazole (isomer A) is applied under a protective gas atmosphere of dry nitrogen. and stirred 15 ml of benzene under reflux and heated to boiling. After heating with stirring for 20 hours, the reaction mixture is cooled to room temperature and filtered to remove the precipitate that has formed. It is determined by IR spectral analysis that the solid, Schm.-P. 190.0-191.5 C, is identical to an authentic sample of 2,4,5-triphenylimidazole. Gas chromatographic analysis of the filtrate shows a high concentration of phenyl disulfide. The foregoing typical examples can be varied within the scope of the disclosure of the entire description herein, as would be understood by one skilled in the art, with virtually the same results being obtained. PATENT CLAIM I Commercially available, radiation-sensitive composition which (A) is a 2,2 ', 4,4', 5,5'-hexaarylbiimidazole, in which the aryl groups contain one to two rings which can be substituted with substituents which are inert towards component (B) and which have a Hammett para sigma value between -0.5 and +0.8 and which are free from Zerewitinoff hydrogen, in intimate mixture with (B) an oxidizable compound that has a formal oxidation potential of 1, 35 volts or less based on a standard calomel electrode and is selected from one of the following classes of compounds: : 1. p-arylene-di-tert-amines, wherein the arylene groups are phenylene or diphenylene groups and the groups attached to the amine nitrogen are lower alkyl or lower alkylene groups; 2. p-Phenylenediamines with a primary and a tertiary amino group, in which the groups connected to the tertiary nitrogen are lower alkyl groups, in a mixture with a phenol or N, N-di (lower) aWylphenylenamine as a coupling compound or in a mixture with one active methylene coupling compound 3. Hydrazones and their N-acyl derivatives, which can be oxidized to diazonium compounds, in a mixture with a phenol or N, N-disubstituted arylamine as coupling compound or in a mixture with an active methylene coupling compound; 4. 0,0'-disubstituted phenols in which the substituents are halogen atoms, lower alkyl groups or lower alkoxy groups and 5. organic sulfhydryl compounds. SUBCLAIMS 1. Composition according to claim I, in which the aryl groups of the biimidazole are phenyl groups and the 2- and 2'-phenyl groups are substituted in the ortho position by a substituent which is inert towards component B and has a Hammett para-sigma value between - 0.4 and +0.4. 2. Composition according to dependent claim 1, characterized in that the 4-, 4'-, 5- and 5'-phenyl groups of the biimidazole are unsubstituted and that the 2- and 2'-phenyl groups of the biimidazole are in the ortho position with fluorine, Chlorine, bromine, lower alkyl or lower alkoxy groups are substituted. 3. Composition according to dependent claim 1, characterized in that the oxidizable compound is a p-arylene-di-tert-amine of group B list. 4. Composition according to dependent claim 1, characterized in that the oxidizable compound is a p-phenylenediamine of group B 2, mixed with (a) a phenol with a free coupling-accessible site which is substituted with halogen, lower alkyl or lower alkoxy can be; (b) an N, N-di # lower drig) alkylphenylenamine with a free point accessible to the coupling; (c) a beta-diketone; (d) a beta keto ester; (e) a beta-ketoamide or (f) a beta ketonitrile. 5. Composition according to dependent claim 1, da characterized in that the oxidizable compound is an iminohydrazide or an N-acyl derivative thereof, which is oxidizable to a diazonium compound, in admixture with (a) a phenol with a free position accessible to the coupling, which is represented by halogen, lower alkyl or lower Alkoxy may be substituted; (b) an N, N-di- (lower) alkylphenylenamine with a free position accessible to the coupling; (c) a beta-diketone; (d) a beta-keto ester; (e) a beta-ketoamide or (f) a beta-ketonitrile. 6. Composition according to dependent claim 1, characterized in that the oxidizable compound is an o, o -disubstituted phenol, in which the substituents are halogen, lower alkyl or lower alkoxy. 7. Composition according to dependent claim 1, characterized in that the oxidizable compound is a sulfhydryl compound. 8. Composition according to dependent claim 1, characterized in that it contains a solvent which is inert towards the constituents of the composition. 9. Composition according to dependent claim 1, characterized in that it contains a polymeric binder. PATENT CLAIM II Use of the radiation-sensitive composition according to claim I for the production of images, characterized in that a substrate is coated with the composition and that the composition is exposed to the action of heat, light or electron beams. Protection is only claimed for this process insofar as it does not concern any finishing of raw or processed textile fibers that is suitable for the textile industry. SUBCLAIMS 10. Use according to claim II, characterized in that the composition is exposed to the action of light with wavelengths between 2000 and 4200 Å. 11. Use according to claim II, characterized in that the composition is heated to a temperature between the dissociation temperature of the hexarylbiimidazole and the decomposition temperature of the component of the composition with the lowest decomposition temperature.