US3390995A - Light-sensitive composition consisting of organic color-generator, photo-oxidant and organic thermally activatable reducing agent progenitor - Google Patents

Description

United States Patent LIGHT-SENSITIVE COMPOSITION CONSISTING OF ORGANIC COLOR GENERATOR, PHOTO OXI- DANT AND ORGANIC THERMALLY ACTIVATA- BLE REDUCING AGENT PROGENITOR Philip Manos, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Apr. 29, 1964, Ser. No. 363,625

9 Claims. (Cl. 96-48) ABSTRACT OF THE DISCLOSURE This invention is directed to novel light-sensitive compositions and a unique process for deactivating them by heat so that they are no longer light-sensitive. More particularly, this invention deals with a composition consisting of (1) an organic color-generator, (2) a photo-oxidant, and (3) an organic compound capable of forming a reducing agent by-heat. This novel composition quickly undergoes a color change to form a sharp image upon irradiation with a pattern of ultraviolet light. After a brief heat treatment, however, the composition is no longer light sensitive, i.e., it has become deactivated, and the image is preserved against a stable background.

Image-forming compositions and processes play an esential part in photography, thermography, and related arts dealing with the mechanisms of writing, printing, and producing images with the aid of light, heat, electricity, or combinations of these activating influences. Currently available methods of image production impose numerous limitations which are costly, inconvenient, timeconsuming, and sometimes potentially hazardous. Classical photography, for example, although efficient in the utilization of light energy, employs expensive chemicals and papers, involves multi-step processing and drying, and requires a highly skilled operator for consistently good results. Thermography requires less operator skill and less expensive paper but produces images of poor quality which are easily destroyed. Mechanical printing, while inexpensive and rapid for repetitive printing, is

decidedly more expensive and slow for sequential printing. In either the repetitive or sequential type of mechanical printing, a wet image is produced. Other photochemical image forming systems involve the use of toxic chemicals such as ammonia, cyanide derivatives, or ca-ustic materials. A new printing or imaging system which would overcome the limitations of the present methods would advance the art and be desirable.

Dry photochemical processes are known but they have certain disadvantages. For example, the dry photochemical process of US. Patent 3,079,258 suflers from the fact that the photosensitive composition remains sensitive to light. Photosensitive papers prepared according to the method of this patent cannot be handled in daylight.

Similarly, the process of US. Patent 3,042,515 produces a dry photographic film. Depending upon the particular halocarbon used, the photographic film may remain photosensitive and cannot be used in ordinary daylight. In certain cases the photographic film may be deactivated by heat but such treatment serves merely to volatilize a toxic halogenated compound such as carbon tetrabromide and thereby produces a health hazard. 7

An attempt to solve the problem of deactivation is de- 3,390,995 Patented July 2, 1968 scribed in US. Patent 3,082,086. This process depends upon the heat-promoted reaction between an organic amine which is serving as a color generator and an anhydride to render the amine inert. Anhydrides, however, are subject to hydrolysis with atmospheric moisture, and the resultant films do not have the desired storage stability. Also the time of heating to cause deactivation is unduly long. In some cases the amides which result from reaction between the amine and the anhydride are subject to further oxidation to colored material as disclosed in British Patent 917,919. In any event, this process does not work with tertiary amines. A deactivating method for printing or imaging systems which would improve upon present methods would advance the art and be desirable.

It is, therefore, an object of this invention to provide a new composition suitable for the production of visible images by exposure to light of suitable wavelength, but yet capable of being permanently deactivated toward further color formation by a thermal treatment. Another object is to provide a latent reducing agent for a photooxidant in a photosensitive composition. A still further object is to provide a novel, rapid process for deactivating a light-sensitive composition.

These objects are accomplished by the present invention defined below, described more fully in the discussion, and illustrated in the examples which follow.

This invention makes available a composition for forming an image and for preserving it in a dry, rapid, readily controlled procedure. Some of the advantages of the new composition and image-forming process over presently available image-forming systems are as follows:

Unlike photography, the process provided by the new composition is simple and at the same time rapid, and it may be conducted in but one apparatus or machine. It requires no development step to observe the image. It is dry and, therefore, does not require a wet processing treatment or complicated gadgetry to give the appearance of a dry system.

Unlike xerography, it produces images in a variety of tones, ranging over the entire density scale, and requires no intricate image developing apparatus.

Unlike thermography, the image cannot be destroyed by further exposure to the activating radiation. It also gives high-resolution images, in a variety of colors with excellent gradation of tone.

Unlike the diazo process, it is a dry process that does not require an objectionable material like ammonia, gives high resolution at greater speed, and produces positives from negatives.

Unlike the deactivation process of U.S. Patent 3,042,515, it does not volatilize a toxic halocarbon.

Unlike the deactivation process of US. Patent 3,082,086, the present deactivation process produces products with good storage stability, requires only a brief heat treatment and can be used to deactivate tertiary amines, an important class of color generators.

Unlike the products of US. Patents 2,927,025 and 3,079,258 which form images by a dry photochemical process, the products of the present invention are deactivated by heat toward further image formation or background color change.

The novel photosensitive composition of the present invention may be defined as one which contains, in intimate association, essentially non-hygroscopic, interreactant progenitors of intensely colored organic colorbodies, said progenitors being activated toward generation of intensely colored organic color-bodies by radiation of wavelength of 2000 A. to 4200 A., which can be applied in a graphic pattern and being permanently deacitvated toward generation of said intensely colored organic color-bodies when briefly heated to 80-160 C., said composition comprising (1) an essentially colorless, oxidizable, nitrogen-containing, organic color-generator which, when contained in said photosensitive composition, is stable to oxidation by atmospheric oxygen under normal room and storage conditions but which is capable of oxidation to an intensely colored species, (2) a photooxidant which, when mixed with said oxidizable colorgenerator and irradiated with light of wavelegnth of 2000 A. to 4200 A., will without further activation oxidize said color-generator to said intensely colored species, and as an essential part of the composition, (3) an organic progenitor of a reducing agent which is characterized in that, when admixed with the said color-generator and said photooxidant, but prior to said heat treatment, it does not function as a reducing agent and does not thereby prevent the photooxidative color formation but is chemically changed by said heat treatment to produce a reducing agent which prevents the photooxidative colorformation, said chemical change caused by the heat treatment being selected from the class consisting of solvolytic reactions, elimination reactions, and rearrangement reactions.

The present invention may also be defined as a novel storage-stable photosensitive composition which comprises (a) an essentially colorless, oxidizable, nitrogen-containing, organic color-generator that is stable to oxidation by atmospheric oxygen under normal room and storage conditions but is capable of oxidation to an intensely colored species, (b) a photo-oxidant that when mixed with said oxidizable color-generator and irradiated with light of wavelength from about 2000 A. to about 4200 A. will, without further activation, oxidize said colorgenerator to said intensely colored species, and (c) an organic progenitor of a reducing agent that is inert in the composition until it is heated to between 80 C. and 160 C. to form a reducing agent which prevents photooxidative color formation by the color-generator (a) and the photo-oxidant (b), said photosensitive composition being capable of activation prior to said heat treatment to form a color by exposure to light of wavelength from about 2000 A. to about 4200 A.

A preferred composition is one wherein the organic color-generator is an aminotriarylmethane having an ortho-substituent in at least two of the aryl groups, the photo-oxidant is a hexaarylbiimidazole, and the organic progenitor of a reducing agent is an acetal of hydroquinone.

Other preferred embodiments of this invention include: 1) a light-sensitive material comprising a supporting base carrying a light-sensitive composition as heretofore defined; (2) a light-sensitive material comprising a plastic film containing the present novel lightsensitive composition; and (3) paper treated With a composition defined in (1).

Many types of organic compounds function as organic color-generators in the invention composition. All are characterized as being essentially colorless, containing nitrogen, being stable to oxidation under normal storage conditions in the photosensitive composition and being capable of producing a color in a photo-oxidative process in the presence of a photo-oxidant. The process may be a simple oxidation of the colorless compound to a colored species. The oxidation may initially produce a reactive intermediate which then undergoes a further reaction With a second component of the color-generator to produce the final colored species. In some cases the reactive intermediate combines with the photo-oxidant to produce a colored species. Mixtures of color-generators may be used. These color generation processes, and the conspounds which are adapted for them, are discussed in detail below.

Four different types of color generators are distinguished.

(A) LEUCO FORM OF DYES One type of color generator which may form part of the light-sensitive composition is the reduced form of the dye having, in most cases, one or two hydrogen atoms the removal of which together with one or two electrons produces a dye. Since the leuco form of the dye is essentially colorless, or in some instances it may be of a different color or of a less intense shade than the parent dye, it provides a means of producing an image when the leuco form is oxidized to the dye. This oxidation is accomplished by irradiating an intimate admixture of the organic color-generator and a photo-oxidant discussed below. Light of a Wavelength of from about 2000 A. to about 4200 A. initiates a redox reaction between the organic color-generator and the photo-oxidant. The result is the removal of one or two readily removable hydrogen atoms, depending on the structure of the leuco form of the particular dye chosen, with the production of a colored image against a background of unirradiated and, therefore, unchanged material. Representative dyes in the leuco form which are operative according to the present invention include:

(a) Aminotriarylmethanes, such as bis(4 benzylethylaminophenyl) (2 chlorophenyl) methane,

bis(4 dimethylaminophenyl)(4 dimethylamino-lnaphthyD-methane,

bis(p dirnethylaminophenyl) (1,3,3 trimethyl-Z-indolinylidenemethyl methane, and

bis(4 dipropylaminophenyl) (o-fluorophenyl)methane Because of their superior resistance to color development due to air oxidation, the preferred species of aminotriarylmethanes have either an alkyl group, an alkoxy group or a halogen in the position ortho to the methane carbon in at least two of the aryl groups. Specific examples of this preferred species include:

bis(4-dimethylamino-o-tolyl) (2-chlorophenyl)methane, bis(4 diethylamino-2-methoxyphenyl) (4 nitrophenyl)- methane, tris(4-dimethylamino-Z-chlorophenyl)methane, bis 4-dimethylamino-o-tolyl) (2-bromophenyl methane, bis(4-diethylamino-o-toly1)(4 benzylthiophenyl)-methane, and bis 4-diethylamino-o-tolyl -2-thienylmethane. (b) Aminoxanthenes, such as 3-amino-6-dimethylamino-Z-methyl 9 (o-chlorophenyl -xanthene, 3,6 bis(diethylamino)-9-(o-chlorophenyl)xanthene,

and 3,6 bis(dimethylamino) 9 (o-methoxycarbonylphenyl)-xanthene. (c) Aminothioxanthenes, such as 3,6 bis(dimethylamino) 9 (o-methoxycarbonylphenyl -thioxanthene, and 3,6-dianilino-9-(o-ethoxycarbonylphenyl)- thioxanthene. (d) Amino-9,IO-dihydroacridines, such as 3,6-'bis(benzylamino)-9,l0-dihydro9-methylacridine and 3,6-diamino-9-hexyl-9,IO-dihydroacridine. (e) Aminophenoxazines, such as 5-benzylamino-9-diethylamino-benzo[a]phenoxazine and 3,7-bis(diethylamino)phenoxazine. (f) Aminophenothiazines, such as 3,7-bis(dimethylamino)-4-nitrophenothiazine, 3,7-bis [N -ethyl-N-( m-sulfobenzyl) amino phenothiazine, monosodium salt and 3,7-diaminophenothiazine. (g) Aminodihydrophenazines, such as 5 3,7-bis(benzylethylamino)-5,10-dihydro-5- phenylphenazine,

3,7-bis(dimethylamino)-5 -(p-chlorphenyl)-5 ,10-

dihydrophenazine, 3,7-diamino-5,10-dihydro--rnethylphenazine, and 3,7-diamino-5,l0-dihydro-2,5,S-trimethylphenazine.

Arninodiphenylmethanes, such as 1,4-bis [bis-(p-diethylaminophenyl)methyl]- piperazine,

bis (p-diethylaminophenyl 1 -benzotriazolylmethane,

bis (p-diethylaminophenyl) (2,4-dichloroanilino methane,

bis(p-diethylaminophenyl) (octadecylamino)- methane, and 1,l-bis(p-dimethylaminophenyl)ethane.

(i) Aminohydrocinnamic acids (cyanoethanes) such as a-cyano-4-dimethylaminohydrocinnamamide, a,;8-dicyano-4-dimethylaminohydrocinnamamide, a,/3-dicyano-4-(p-chloroanilinohydrocinnamic acid, methyl ester, p-(2,2-dicyanoethyl) -N,N-dimethylaniline, and -p-(1,2,2-tricyanoethyl)-N,N-dimethylaniline.

(j) Leucoindigoid dyes, such as 7,7'-diarnino-5 ,5 '-dichloroleucothioindigo,

6,6'-dichloro-4-methylleucothioindigo,

7,7-dimethylleucoindigo,

5,5'-disulfoleucoindigo, disodium salt, and

5 ,5',7,7'-tetrachloroleucoindigo.

1,4-diamino-2,3-dihydroanthraquinones, such as l,4-bis(ethylamino)-2,3-dihydroanthraquinone, l-amino-4-methoxyanilino-2,3-dihydroanthraquinone, 1,4-diamino-2,3-dihydroanthraquinone, and 1-p-(Z-hydroxyethylamino)anilino-4-methylamino- 2,3-dihydroanthraquinone.

It is not essential that the organic color-generator have a hydrogen which is removed by oxidation to form the colored species. One class of oxidizable compounds which do not contain removable hydrogens consists of acyl derivatives of leuco dyes which contain a basic NH group. Suitable compounds which have a basic NH group and which form amides when acylated include dihydrophenazines, phenothiazines, and phenoxazines. Specific examples of such compounds are lO-acetyl-3,7-bis(dimethylamino)phenothiazine, (p chlorobenzoyl) 3,7-bis (diethylamino)phenothiazine, 5,10 dihydro 10 (pni-trobenzoyl) 5 phenyl 3,7 bis(phenylethylamino) phenazine, and 10 (p-chlorobenzoyl)-3,7-bis(naphthylmethyl) aminophenoxazine.

Also there are certain compounds related to the triarylmethane leuco dyes which contain no hydrogen atoms that are removed during the oxidative color formation, but which, nevertheless, are photo-oxidized to a colored compound. Examples of such compounds are tris(p-dimethylaminophenyl)benzylthiomethane, l-tris(p-diethylaminophenyl)methyl-2-phenylhydrazine, tris(4 diethylamino-o-tolyl)ethoxycarbonylmethane, bis(4 dipropylamino-o-tolyl)(o fluorophenyl)butoxycarbonylmethane and bis [tris (4-diethylamino-o-tolyl) methyl] disulfide.

(B) ORGANIC AMINES These are amines that can be oxidized to a colored species but do not fall into the groups of leuco dyes discussed heretofore. Organic amines of this type are disclosed in US. Patents 3,042,515, and 3,042,517. Representative examples of this type of amine are 4,4-ethylenedianiline, diphenylamine, N,N-dimethylaniline, 4,4'-methylenedianiline, triphenylamine, and N-vinylcarbazole.

(C) Z-BENZOTHIAZOLINONE HYDRAZONES AND RELATED COMPOUNDS Certain hydrazones and acyl derivatives of these hydrazones can be oxidized to diazonium compounds as described by I-Iunig and Fritsch, Ann. 609, 143 (1957). This type of hydrazone can be photo-oxidized to a diazonium compound. The resultant diazonium compound will then couple with any of a large number of coupling agents to produce an azo dye.

Compounds which are suitable for photo-oxidation to the diazo component of the color-generator are disclosed in U.S. Patent 3,076,721. Representative examples are:

3-rnethyl-2-benzothiazolinone hydrazone, 6-chloro-3-methyl-2-benzothiazolinone hydrazone, and 6-methoxy-3-methyl-2-benzothiazolinone hydrazone.

The acylated hydrazones are more difficult to oxidize than the coresponding non-acylated hydrazones. As a result, they have greater storage stability. Representative acylated hydrazones which are suitable for photooxidation to the diazo component of the color-generator are:

3-methyl-2-benzothiazolinone acetylhydazone,

3-methyl-2-benzothiazolinone p-tolylsulfonylhydrazone,

3-methyl-2-benzoselenazolinone propionylhydrazone,

3-ethyl-2-benzoxazolinone phenylsulfonylhydrazone,

5 methoxy-1,3-dimethyl-2benzimidazolinone benzoylhydrazone, and

l-methylcarbostyril phenoxyacetylhydrazone.

Compounds which may be used as the coupling component of the color-generator include:

N,N-diethylaniline, N,N-dimethyl-m-toluidine, and N- (2-cyanoethyl -N-methyl-2-naphthylamine.

In place of a separate hydrazone and coupling agent as already described, it is possible to use a composite hydrazone-coupler compound. The composite compounds supply both the diazo component and the coupler component, and thus provide the entire color-generator in one compound. Specific examples of such composite compounds a-re 3-methyl-2-benzothiazolinone l-hydroxy-2- naphthoylhydrazone and 3-methyl-2-benzothiazolinone 5- oxo-l-phenyl-3-pyraz0lylcarbonylhydrazone.

In addition to the aforementioned amines, other types of coupler can be used provided certain selection rules are followed. Specific examples of other couplers are active methylene compounds, such as acetoacetamide and 2- thenoylacetonitrile, and phenolic compounds such as mcresol, Z-naphthol, 6-sulfamido-1-naphthol and even hydroquinone.

It is essential that the coupling component be selected so that the hydrazone is photo-oxidized in preference to the coupling component. If the coupling component is a weak reducing agent not only can most hydrazones be used but even difiicult photo-oxidized compounds such as acylated hydrazones can be used. When the acylated hydrazones are employed, the photo-oxidant should be a strong oxidizing agent. If the coupling component is a moderately strong reducing agent, then the acylated hydrazones usually cannot be employed. If the coupling component is also a strong reducing agent, such as hydroquinone, it is necessary to select a hydrazone which is readily oxidized.

It is also essential to exercise care in selecting the hydrazone and reducing agent produced by the thermal treatment as hereinafter discussed. These components must be chosen so that, after thermal treatment, the reducing agent is photo-oxidized rather than the hydrazone. With difficultly oxidized compounds such as the acylated hydrazones, there usually is no problem. If the hydrazone is not acylated it usually is necessary to produce thermally a strong reducing agent such as t-butylhydroquinone or tetramethylhydroquinone.

(D) AROMATIC DIAMINES WITH COUPLING AGENT An aromatic diamine in combination with a coupling agent undergoes an oxidative condensation reaction which leads to azomethine and indoaniline dyes. More particularly, the reactants in this condensation are N,N-dialkylphenylenediamines and couplers such as active methylene compounds, anilines, phenolic compounds. The chemistry of these oxidative coupling reactions is reviewed by Vittum et al. in J. Phot. Sci., 2, 81 (1954) and ibid., 6, 157 (1958). These oxidative condensation reactions are adaptable to photochemical processes and, furthermore, such photosensitive compositions can be deactivated by the method of the present invention. Examples of N,N-dialkylphenylenediamines which are operative in the present process are N,N-dimethyl-p-phenylenediamine and N,N- diethyltoluene-2,5-diamine. Suitable couplers include 2- acetyl-4-chlrooacetanilide, 2-benzoyl-2'-methoxyacetanilide, O-ethylphenol, 2-naphthol, 7-acetylamino-1-naphthol, N,N-dimethylaniline and N,N-diethyl-m-toluidine.

Many classes of compounds function as photo-oxidants in the light-sensitive compositions of the invention. Each of the compounds is characterized by having the ability to produce a permanent color when mixed with an organic color-generator discussed above and irradiated with light of from about 2000 A. to about 4200 A. The exact means by which photo-oxidants oxidize color-generators is perhaps not fully understood for all photo-oxidants. Two classifications of photo-oxidants are proposed below but the invention gives the stated results whether or not this is the true theory involved.

The mechanism by which a particular photo-oxidant functions depends not only upon the particular photooxidant but also upon the particular color-generator and the wavelength of the activating light. Based upon the mechanism by which they act as photo-oxidants the photooxidants may be divided into two classesinitiators and acceptors. Some photo-oxidants, however, can function as either an initiator or an acceptor depending upon the wavelength of the activating light. Most photo-oxidants have a preferred mode of operation. Also some color-generators are more efiicient with a particular type of photo-oxidant and care must sometimes be exercised in selecting these two components of the composition. In addition, the pH of the system is a factor, and a change in pH may change the mechanism by which the photo-oxidant functions.

An initiator type of photo-oxidant absorbs the activating light and dissociates into free radicals. These free radicals are the active oxidizing agent which reacts with the color-generator by an oxidation-reduction mechanism to produce the colored species.

An acceptor type of photo-oxidant generally absorbs none of the activating light. If it does absorb some of the activating radiation, the absorption is dissipated in a noncolor-forming manner and does not lead to color generation. The activating radiation is, instead, absorbed by the color-generator to produce a photo-excited molecule which then undergoes an oxidation-reduction reaction with the acceptor photo-oxidant. The term acceptor is applied because the photo-oxidant accepts an electron ejected by the color-generator. It is generally believed that the colorgenerator ejects the electron (Lewis and Bigeleisen, J. Am. Chem. Soc., 65, 2419 (1943)). These ejected electrons then react very rapidly with an acceptor and the reaction is rendered irreversible.

A suitable criterion for judging whether a photo-oxidant is an acceptor or initiator is the wavelength of light which causes color formation in the light-sensitive composition. This is easily determined by the use of appropriate filters. This wavelength usually will coincide with the absorption maximum of either the color-generator or the photooxidant. For example, nearly all leuco triarylmethane dyes that contain a dialkylamino group have a strong absorption band at about 2700 A. and a weaker band, frequently appearing as a shoulder, at about 3100 A. Light having a wavelength from about 2500 A. to about 3200 A. is, therefore, effective in causing the oxidation of these leuco dyes in the presence of an acceptor type photo-oxidant.

Examples of classes of photo-oxidants which function by the initiator mechanism are the biimidazoles and the tetraarylhydrazines. Specific examples are as follows:

A. Biimidazoles:

2,2'-bis p-methoxyphenyl -4,4',5 ,5 -tetraphenyl biimidazole,

2,2'-bis p-cyanophenyl -4,4,5 ,5 '-tetrakis p-methoxyphenyl) biimidazole,

2,2-bis (m-nitrophenyl -4,4',5 ,5 '-tetrakis (2,4-

dimethoxyphenyl biimidazole,

2,2-bis 3,4,5 -trimethylphenyl -4,4',5 ,5 -tetrakis (p-methylthiophenyl biimidazole,

2,2'-bis o-methoxyphenyl -4,4,5 ,5 '-tetraphenylbiimidazole,

2,2-bis 2,4-dichlorophenyl -4,4',5 ,5 '-tetraphenylbiimidazole,

2,2-di- 1 -naphthyl-4,4',5 ,5 -tetrakis( p-methoxy pheny1)biimidazole,

2,2-bis o-bromophenyl -4,4',5 ,5 -tetraphenylbiimidazole, and

2,2-bis 2,4-dimethoxyphenyl -4,4,5 ,5 '-tetraphenylbiimidazole.

The preferred hexaarylbiimidazoles utilized in the present invention are 2,2',4,4',5,5' hexaphenylbiimidazoles having in the 2- and 2'-phenyl rings an ortho substituent that is chlorine, bromine, fluorine, C -C alkoxy, or C -C alkyl. A particularly preferred biimidazole is 2,2'- bis(o-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole.

B. Tetraarylhydrazines:

tetraphenylhydrazine, tetra-p-tolylhydrazine, and tetrakis p-methoxyphenyl hydrazine.

Examples of classes of photo-oxidants which function by the acceptor type of mechanism are given below along with specific examples of each class of photo-oxidant.

C. Tetraacylhydrazines:

tetraacetylhydrazine, tetraformylhydrazine, and tetrabenzoylhydrazine.

D. Diacylaminobenzotriazoles:

1-diacetylaminobenzotriazole and 1-dihenzoylamino-S-chlorobenzotriazole.

E. Benzothiazole disulfides:

bis(2-benzothiazolyl) disulfide and bis(6-methoxy-2-benzothiazolyl) disulfide.

F. Triacylhydroxylamines:

N,N,O-triacetylhydroxylamine, N,N,O-tripropionylhydroxylamine, N,N,O-tribenzoylhydroxylamine, and N,N,O-tri-p-chlorobenzoylhydroxylamine.

G. Diacylaminotriazoles:

1-diacetylamino-3,S-diphenyl-1H-1,2,4-triazole, 1-dipropionylamino-3,S-diphenyl-1H-1,2,4-triazole,

and 1-dibenzoylamino-4,S-diphenyl-1H-1,2,3-triazole.

H. Alkylidene-2,5-cyclohexadien-l-ones:

2,6-dimethyl-4-(1,1,3,3-tetrafluoro-l,3-dichloroisopropylidene)-2,5-cyclohexadien-1-one.

1. Selected polymers:

polymethacrylaldehyde.

I. Diacylaminopyrazoles:

l-diacetylaminopyrazole and 1-dipropionylamino-4-chloropyrazole.

The diacylaminopyrazoles are prepared by reacting pyrazole or pyrazole substituted in one or more of the 3-, 4-, or 5-positions with alkyl, halogen, aryl, nitro or cyano groups with hydroxylamine-O-sulfonic acid in aqueous sodium hydroxide solution to form a l-aminopyrazole. The l-arninopyrazole is then reacted with the necessary acid anhydride or acid halide to form the corresponding l-diacylaminopyrazole.

K. Bibenzotriazoles:

1,Z'-bibenzotriazole, 5,5-dichloro-1,1-bibenzotriazole, and ,5 '-dimethyl-l, 1'-bibenzotriazole.

The 1,2'-bibenzotriazole and benzo ring substituted 1,2-bibenzotriazoles except those having a nitro substituent are prepared by reacting a solution of the benzotriazole in aqueous sodium hydroxide with hydroxylaminesulfonic acid to form a corresponding 2-aminobenzotriazole which is separated from its isomers by fractional crystallization. The 2-aminobenzotriazole is then mixed with o-chloronitrobenzene and heated to 160 to 205 C. for 5 hours in the presence of anhydrous sodium acetate to produce 2 (0 nitrophenylamino)benzotriazole. The product is isolated by filtration and recrystallized from ethanol. The 2-(o-nitrophenylamino)benzotriazole is catalytically reduced with hydrogen to 2-(o-aminophenylamino)benzotriazole. The 2 (o-aminophenylamino)benzotriazole is diazotized in the usual way with nitrous acid to convert the primary amine to a diazonium salt which couples with the secondary amino group to form a cyclic triazole and yield a 1,2'-bibenzotriazole.

Nitro derivatives of 1,2'-bibenzotriazoles cannot be prepared by the above procedure because the reduction of the nitro group prior to cyclization destroys any other nitro groups that are present. It is, therefore, necessary that the nitro derivatives of 1,2-bibenzotriazole be prepared by treatment of the bibenzotriazole with nitric acid.

The 1,1-bibenzotriazole and derivatives are prepared by tetraazotizing with nitrous acid o,o'-diaminoazobenzene or its derivatives to bisdiazonium salts. The resultant salts are then reduced to the l,1'-bibenzotriazole with sulfur dioxide. Derivatives bearing such substituents as alkyl, halogen, sulfo, nitro, or alkanamido are prepared from the correspondingly substituted o,o'-diaminoazobenzene.

A large class of photo-oxidants which may be utilized in the practice of this invention include those halogen compounds disclosed in US. Patent 3,042,515. The most useful halogen compounds have a bond dissociation energy to produce a first free radical of not less than about 40 kilogram calories per mol. It is disclosed in US. Patent 3,056,673 that the spectral response to these halogenated photo-oxidants is, among other things, a function of the particular halogen compound which is chosen. Iodo compounds absorb at relatively long wavelengths, bromo compounds absorb at intermediate wavelengths and chloro compounds absorb at short wavelengths. With a source of ultraviolet light such as a sun lamp the iodo compounds will function as initiators while the chloro and bromo compounds function as acceptors. The operative mechanism may be changed by utilizing another light source having a different spectral distribution. Changing the color-generator and the spectral region in which it absorbs, also can change the mechanism by which these halogenated photo-oxidants function. Specific examples of this class of photo-oxidant are:

L.-Halogen compounds:

carbon tetraiodide, iodoform, carbon tetrabromide, 1,2,3,4-tetrabromobutane, hexachloroethane, and l,2,3,4-tetrachlorobenzene.

A composition which comprises a photo-oxidant and an organic color-generator, as described above, is photosensitive and produces an image when irradiated with ultraviolet light in a graphic pattern. This image, however, is not permanent because the unirradiated areas of the image will become colored when later irradiated during the course of normal usage. A means to deactivate the photosensitive composition is needed so that the composition is no longer photosensitive. If the composition remained photosensitive it would be acted upon by ambient light to alter or destroy the image. A deactivating means has been found. It consists of incorporating into the photosensitive composition a compound which generates a reducing agent when it is heated moderately for a short time.

Several types of compounds produce reducing agents by heating. For use in the invention photosensitive compositions, such compounds must fill three requirements. First, they must be inactive as reducing agents before the heat treatment. Otherwise, they would deactivate the photosensitive composition before the required image had been formed. Second, the compound must produce a reducing agent when heated moderately and briefly. Third, the resultant reducing agent must then readily deactivate the system and prevent further color formation by the composition.

A. Type of reducing agent A variety of reducing agents may be produced by the thermal treatment, and these agents will function to deactivate the photosensitive composition. It is usually an organic reducing agent. An example of a suitable class of reducing agents is the hydroquinones, including hydroquinone and substituted hydroquinones some of which are stronger reducing agents than hydroquinone. Examples of the latter include phenylhydroquinone, t-butylhydroquinone and durohydroquinone. The hydroquinone may be partially etherified as in p-benzyloxyphenol. Hydroquinones of more highly condensed systems such as naphthalene-1,4-diol are also operable. Other polyhydroxybenzenes, such as resorcinol and pyrogallol, are operable.

Many phenolic compounds are strong enough reducing agents to function as a reducing agent for the photooxidant. Suitable examples include 2,4,6-trimethylphenol, 2,6,di-tert-butyl-p-cresol and 2,4,6-tri-tert-butylphenol.

Other suitable reducing agents include hydroxylamines such as N,N-dimethylhydroxylamine and N,N-dibutylhydroxylamine; certain oxidizable hydroxy acids such as tartaric acid; certain nitrogen-containing compounds such as semicarbazide and those hydrazines which react with Fehlings solution such as hydrazine and phenylhydrazine.

Some, but by no means all, amines can function as a reducing agent. An example is aniline.

To effect deactivation, it is necessary that the reducing agent be formed in situ within the photosensitive composition. This is achieved by heating the reducing agent progenitor and thereby effecting formation of the reducing agent by means of one of the following three types of reactions.

(1) Solvolytic Reactions-Solvolytic reactions are particularly well suited for deactivating a photosensitive composition once the required image has been formed on the supporting substrate. With a paper substrate enough moisture is present to effect a hydrolytic reaction of a reducing agent progenitor. Thus, at an elevated temperature is formed a compound which deactivates the photosensitive composition and preserves the alreadyformed image. When an acid catalyst for the hydrolytic reaction is needed, it may be supplied by an acid salt of a basic color generator, e.g., the acid salt of a leuco triphenylmethane dye containing amino groups. Representative and illustrative compounds that undergo hydrolysis with mild heating to produce a reducing agent for the invention compositions are:

(a) Acetals as exemplified by p-bis(2-tetrahydropyra nyloxy benzene.

(b) Orthoesters as exemplified by the tris(p-methoxyphenyl) ester of orthoformic acid.

now-Q-oomn 11.0

znoQ-oom no- -oon.

(c) Orthocarbonates as exemplified by the tetrakis-(pmethoxyphenyl) ester of orthocarbonic acid.

(d) Carbonates as exemplified by o-phenylene carbonate.

OH U C0: \OH

(e) Semicarbazones as exemplified by ethyl methyl ketone semicarbazone.

(f) Schiifs bases as exemplified by N-benzylidineaniline.

Other compounds will produce a reducing agent upon hydrolysis. One example of these is the resin obtained from formalaniline and formaldehyde. Another example is the acetal-ester derivative of tartaric acid having the structure acid l l O OH 2, 3-dihydr0-1, 4-

1, 4-naphthaleuediol naphthoquinone O O H H l l 4a, 5, 8, 8a-tetrahydr0- 5, 8-dihydro-1, 4-

1, 4-naph thaquinone naphthalenediol (3) Elimination reactions-It is possible that the hydroquinone-bis-(dihydropyran) adduct can produce a reducing agent by an elimination reaction as shown below:

acid I The wavelength of the radiation which activates color formation varies with both the photo-oxidant and the color-generator employed. In general, the wavelength of the activating radiation will be within the range 2000 A. to 4200 A. Suitable means for providing such radiation include sun lamps, electronic flash guns, germicidal lamps and ultraviolet lamps providing specifically light of long wavelength (3663 A.) and lamps providing light of short wavelength (2537 A.). The range of activating radiation may be extended to longer wavelengths by adding certain dyes to the photosensitive composition. Such dyes function as sensitizers as is well known in the art. See, for instance, C. E. Kenneth Mees, The Theory of the Photographic Process, The Macmillan Company, 1952, pp. 317- 493.

The amount of color-generator determines the depth of color which will be obtained with a given photosensitive composition. The photo-oxidant is, therefore, measured in proportion to the color-generator. Most color-generators, such as the leuco triarylmethane dyes, will require a molar equivalent of photo-oxidant for complete conversion to the colored form. Less than molar equivalents of photo-oxidant are operable but wasteful of color-generating material. Thus, ratios of photo-oxidant to color-generator from about 1:10 to about :1 are operable. The preferred range is form 1:1 to 2:1.

The progenitor of the reducing agent is measured in proportion to the photo-oxidant. Many, but not all, photooxidants require an equivalent molar amount of a reducing agent. Thus, molar equivalents of the photo-oxidant and reducing agent progenitor are desirable provided that one mole of progenitor produces one mole of reducing agent and that this one mole of reducing agent deactivates one mole equivalent of photo-oxidant. If the latter two conditions are not met, the ratio must be adjusted in accordance with the stoichiometry of the reactions involved for complete deactivation. A very large molar excess of reducing agent progenitor may unduly lower the photographic speed of the composition. In those compositions in which one mole of reducing agent progenitor can deactivate one mole of photo-oxidant a molar ratio of photooxidant to reducing agent progenitor of from abut 5:1 to 1:20 is operable, but a ratio of 1:1 to 1:2 is preferred.

The heat to deactivate the photosensitive composition may be applied by various means. When the photosensitive composition is in sheet form direct contact with a heated object is suitable. Pressure is useful in facilitating the transfer of heat, particularly if the heated object is a good heat conductor like a metal. Ovens are convenient for providing heat especially when large objects are to be heated. Convection means, such as blowers which discharge warm air, are often satisfactory. Radiation means, such as infrared lamps, are also suitable as long as the radiation is free from ultraviolet light.

In most cases heating the photosensitive composition or its substrate to between 80 C. and C. is adequate. Reducing agent progenitors which can be deactivated below 80 C. are apt to be deficient in storage stability at room temperature. Deactivation temperatures over 160 C. are generally avoided lest the image or the substrate be adversely affected. This precaution is usually necessary when the photosensitive composition is borne by a heat-sensitive substrate such as cellulose. Heating time will vary with the heating means, the temperature and the particular progenitor of the reducing agent. With efficient heating methods heating periods between 0.5 and 60 seconds are usually adequate. Periods between 1 and 15 seconds are preferred.

The photosensitive compositions of the present invention may be applied as a coating or impregnant to various substrates. Frequently the substrates will be materials used in the graphic arts and in decorative applications. The substrates may be rigid or flexible; solid, porous or even liquid; either opaque or transparent to ultraviolet light. They may include paper ranging from tissue paper to heavy cardboard; films of plastics and polymeric materials such as regenerated cellulose, cellulose acetate, cellulose nitrate, polyethylene, polymethyl methacrylate, polyvinyl chloride; textile fabrics; glass; wood and metals. Opaque as well as transparent substrates may be. used. Substrates in which the photosensitive composition is dissolved or which bear the composition as a coating on the side away from the ultraviolet light source used for image formation must be transparent to a portion of the ultraviolet range of radiation useful for image formation.

The novel light-sensitive compositions heretofore described are significantly useful in a variety of applications. Among these are:

(1) Printing applications.Very soft paper, as for example, tissue paper can be easily imaged when it has been treated with the subject photosensitive composition, by projecting an image onto the treated surface. The image may then be made permanent by a brief heat treatment.

. (2) Radiation dosimeters.Paper or plastic film may be impregnated or coated with the subject photosensitive compositions and these may be used to determine easily the quantity of solar radiation that falls on a particular 14 diethylamino-o-tolyl)methane trihydrochloride and 0.4% 2,2-bis(o-chlorophenyl)-4,4',5,5 tetraphenylbiimidazole followed by drying under an infrared lamp. The photosensitive paper is then dipped into a 0.5% benzene solution of a progenitor of a reducing agent and again dried briefly under the lamp. The paper is folded so that a part of it is exposed for 10 seconds to a 275 watt sun lamp at a distance of 10 inches whereupon an intense blue color forms. The whole paper is then heated for 5 seconds between the plates of a hydraulic press maintained at 125 C. and the unirradiated portion of the paper exposed to the sun lamp for seconds.

The amount of color formed by irradiation prior to thermal treatment measures whether or not the reducing agent progenitor has either inhibited color formation or produced its offspring prematurely. A control having no reducing agent progenitor is necessary to make this evaluation. The amount of color formed by irradiation after thermal treatment measures how effectively the reducing agent progenitor has deactivated the photosensitive paper.

Table I shows the results of the evaluation of several generators of reducing agents which are derivatives of hydroquinone and related phenolic compounds.

TABLE I.'DEACTIVATION BY HYDROQUINONE AND PROGENITORS OF HYDROQUINONE AND OTHER PHENOLIC COMPOUNDS N 0. Deactivating Agent Color Formation Color Formation Before Heating After Heating 1 None Excellent (intense Excellent.

color). 2 Hydroquinone None None. 3. p-bis(tetrahydro-Z-pyranyloxy)benzene. Excellent Do. 4. p-bis(1-ethoxyethoxy)-benzene Good Do. 5. p-bis(1-benzyloxyethoxy)-henzene do D0. 6- 1,4-bis(tetrahydro2,pyranyloxy)-2-chloro-benzene Excellent. Very slight. 7- 1,4-bis(tetrahydro-2-pyranyloxy)-2-t-butyl-benzeue. do. Slight. 8 2,5-bis( tetrahydro-2,pyranyloxy)biphenyl do. Do. 9 1,4-di-t-butyl-2,5-bis-(tetrahydro-Z-pyranyloxy)benzene do. Do. 10 1,4-bis(tetrahydro-Z-pyranyloxy)tetrachloro-benzene. do. Very slight. ll Polymer containing repeating units of do Do.

t E --CHgO-CHOOCHOCH2 from hydroquinone and 1,2-bis (vinyloxy)ethane.

12.- l-m ethoxy-4 (tetrah ydro-Z-pyranyloxy) benzene -do Do. 13-- 0-(tetrahydro-Z-pyranyloxy)phenol Slight. 14.. 2,6-bis(tetrahydro-2-pyranyloxy)phenol Good one. 15 Tris(p-methoxyphenyl)-orthoiormate Very slight 16 2,6-bis(l-ethoxyethoxy)-phenol G None.

surface. A brief heat treatment than makes the record permanent.

(3) Pattern lay-out for metal working.--The photosensitive composition may be applied to a metal surface when suitably formulated as a paint or a lacquer. The metal surface may then be marked by irradiation through a suitable template and the image so produced may be made permanent by a brief thermal treatment. The image may correspond to holes which are to be drilled or other operations of metal working and manufacture. This technique is particularly valuable when the metal to be marked has an irregular shape.

(4) Blue prints-When applied to paper or plastic films, the light compositions of this invention can find application in diazo printout equipment, where they can be made to give readily a variety of shades, with different speeds and sensitivities. After a brief thermal treatment,

it is possible to utilize the paper or film in ordinary room light and even in outside daylight, rather than have to handle it in the dark.

Representative examples illustrating the present invention follow.

EXAMPLE 1 Photosensitive paper is prepared by dipping unsized formamide solution containing (by weight) 0.4% tris(4- composition has already lost its photosensitivity (No. 2

of Table I). With acetals of hydroquinone, substituted hydroquinones and other phenolic compounds, however, the photosensitive composition gives sharp images on ultraviolet light exposure and is readily deactivated by moderate heating to preserve the initial image during subsequent light exposure (Nos. 3-16 of Table 1). Although the deactivating agents numbered 13, 14, and 16 in Table I have a hydroxyl group, which might be expected to have a reducing action, these compounds do not unduly deactivate the photosensitive composition prior to the heat treatment. Such inactivity is believed to result from the steric hindrance from the tetrahydro-Z-pyranyloxy or 1- ethoxyethoxy groups in positions adjacent to the hydroxyl group [Parham and Anderson, J. Am. Chem. Soc., 70, 4178 (1948)].

The melting or boiling point and elemental analysis of the new compounds shown in Table I are given in Table II.

TABLE IL-PROPE RTIES OF NEW COMPOUNDS IN TABLE I No. Calculated Found from M.P., C. B.P., C./ Table I mm. Percent Perrclent Percent Percent Preparation of progenitors of phenolic compounds.- Into a wide-mouth flask are placed 55 g. (0.5 mole) of a hydroquinone and 100 g. (1.2 mole) of A -dihydropyran. The mixture is heated with stirring to about 60 C. An exothermic reaction occurs resulting in elevation of the temperature of about 105 to 110 C. and complete solution of the hydroquinone. Stirring is continued until the temperature drops to about 80 C. The flask is cooled to room temperature, and then placed in an ice bath. The contents crystallize to a compact mass. The product is transferred to a vacuum filter where the excess dihydropyran is removed and crude product is rinsed with icecold methanol. A recrystallization from a mixture of acetone and methanol affords 112 g. (80% yield) of pure p-bis(tetrahydro-Z-pyranyloxy)benzene melting at 128- 130 C.

The other products listed in Table I and described in Table II are prepared in a similar way except that 5 drops of 37% hydrochloric acid are used to start the exothermic reaction. After the reaction is complete, the reaction mixture is neutralized with a few drops of 28% ammonium hydroxide. Ethyl vinyl ether, benzyl vinyl ether, and 1,2- bis(vinyloxy)ethane as Well as A -dihydropyran are used to form the phenol adducts.

The tris(p-methoxyphenyl) orthoformate (No. of Table I) is prepared by heating together 37.2 g. (3 mole) of p-methoxyphenol with 14.8 g. (1 mole) of triethyl orthoformate in the presence of a few drops of concentrated sulfuric acid. When the ethanol evolution ceases the reaction mass is cooled, and the resulting solid is Washed with ice-cold petroleum ether. There is obtained 19 g. of a solid melting at about 30 C. which infrared analysis identifies as the desired tris(p-methoxyphenyl) orthoforrnate.

By the above test procedure the progenitors of reducing agents shown in Table III interfere very little with color formation before the heat treatment and deactivate the photosensitive composition after the heat treatment.

TABLE III.ADDITIONAL DEACTIVATORS BY THE METHOD OF EXAMPLE 1 Compound: No. Semicarbazone of heptaldehyde 17 Semicarbazone of methyl ethyl ketone 18 Semicarbazone of diisobutyl ketone 19 N-benzylideneaniline 20 N-p-chlorobenzylideneaniline 21 N-benzylidene-l-naphthylamine 22 EXAMPLE 2 Both filter paper and rag bond paper are dipped into a solution of 0.54 g. bis(4-diethylamino-o-tolyl) (p-benzylthiophenyl)methane, 0.99 g. 2,2 bis(o chlorophenyl)- 4,4,5,5'-tetraphenylbiimidazole, 0.21 g. of the tin chloride complex, M.P. 235237 C., having the formula SnCl 2 (CH NCHO and 0.50 g. of 4a,5,8,8a-tetrahydro-1,4-naphthoquinone (prepared according to the procedure of J. Chem. Soc., 3293 (1958)) in ml. of acetone. The papers are air dried and then exposed through a template to the light of a (General Electric UH3) 360-watt medium pressure ultraviolet lamp. The imaged paper is then passed at a speed of 15 ft./min. between metal plates set 0.025 in. apart and heated to about 150 C. After this'heat treatment further exposure to ultraviolet light does not cause color to form on either paper in the previously unirradiated parts of the image.

EXAMPLE 3 Both filter paper and sized rag bond paper are dipped into a solution of 0.27 g. of bis(4-diethylamino-o-tolyl) (p-benzylthiophenyl)methane, 0.33 g. of 2,2-bis(o-chl0r0- phenyl)-4,4,5,5'-tetraphenylbiimidazole, 0.11 g. of

SnCL, 2 (CH NCHO and 0.50 g. of 2,3 dihydro 1,4, naphthoquinone. The papers are dried and exposed as in Example 2 with the same results.

EXAMPLE 4 A paint is prepared by mixing 0.1 g. (.0002 mole) of tris(4-diethylamin0-o-tolyl)methane, 0.076 g. (.0004 mole) of p-toluenesulfonic acid monohydrate, 0.066 g. (.0001 mole) of 2,2-bis(o-chlorophenyl)-4,4,5,5'-tetraphenylbiimidazole, and .056 g. (.0002 mole) of compound No. 3 from Table I and 0.20 g. of pigmentary grade TiO with 20 ml. of a 70:30 by weight methanol-trichloroethylene vehicle containing 15% by weight of soluble nylon resin. This paint is applied to aluminum, steel, and glass. When in place of the 20 ml. of vehicle containing nylon there is used 45 ml. of the same solvent mixture, there is obtained a thinner formulation which is sprayed through an atomizer onto the same substrates. After air drying, the coated materials are irradiated through a stencil with ultraviolet light supplied by a 360-Watt UV lamp. The image is made permanent by heating in an oven at C. for 30 seconds. The coating is resistant to abrasion, but after it has served its purpose, it can be readily removed after softening with methanol.

This formulation is also applied as a coating to paper. The coated paper is imaged and deactivated as in Example 2.

EXAMPLE 5 Photosensitive paper is prepared by dipping unsized paper into a 4:1 (by volume) methanol-N,N-dimethylformamide solution containing by Weight 0.4% tris(pdiethylaminophenyl)methane trihydrochloride and a photo-oxidant as indicated in Table IV. The photosensitive paper is briefly dried under an infrared lamp, dipped into a 0.5% benzene solution of p-bis(tetrahydro-2-pyranyloxy)benzene and dried as before. This photosensitive paper is then irradiated, heated, and found to be deactivated as in Example 1.

17 TABLE IV.-EFFECTIVE PHOTOOXIDANTS FOR HEAT DEACTIVATABLE LIGHT-SENSITIVE COMPOSITION OF EXAMPLE Amount used, percent in Photooxidant: Methanol-DMF Solution (1) N,N,O-triacetylhydroxylamine 0.4 (2) 1,1-bibenzotriazole 0.6 (3) l,2-bibenzotriazole 0.6 (4) Bis(2-benzothiazolyl) disulfide 0.4 (5) Bis (p-methoxyphenyl) -4,4',5,5-

tetraphenylbiimidazole 0.4 (6) 4-bromobipheny1 0.4 (7) Carbon tetrabrornide 0.4 (8) Carbon tetraiodide 0.4 (9) l-diacetylaminobenzotriazole 0.4 (10) 1-diacetylamino-3,S-diphenyl- 1H,l,2,4-triazole 0.4 (11) 1-diacetylamino-4-chloropyrazole 0.6 (12) 4(1,3-dichloro-1,1,3,3-tetrafluoroisopropylidene)-2,S-cyclohexadien-1-one 0.4 13 2,2-di-o-tolyl-4,4,5,5 -tetraphenylbiimidazole 0.4 (14) Hexachloroethane 0.4 (15) 2,2,4,4',5,5'-hexaphenylbiimidazole 0.4 (16) Polymethacrylaldehyde 0.8 (17) Tetraacetylhydrazine 0.6 (18) Tetraphenylhydrazine 0.4

EXAMPLE 6 (1) Photosensitive paper is prepared by dipping unsized paper into a 4:1 (by volume) methanol-N,N-dimethylformamide solution containing by weight 0.30% thenoylacetonitrile, 0.27% N,N-diethyl-p-phenylenediamine and 1.30% 2,2'-bis-(o-chlorophenyl)-4,4,5,5'- tetraphenylbiimidazole. The photosensitive paper is briefly dried under an infrared lamp, dipped into a 0.5% benzene solution of p-bis(tetrahydro-Z-pyranyloxy)benzene and again dried under the lamp. This photosensitive paper is irradiated in a graphic pattern and then deactivated with heat as in Example 1, except that the heating period is 10 seconds at 140 C. The irradiated portion of the paper remains red-violet, while the unirradiated portion becomes essentially colorless during subsequent exposure to ultraviolet light.

(2) When the N,N-diethyl-p-phenylenediamine in the above photosensitive paper is replaced by 0.52% N,N- dimethyl-p-phenylenediamine and the 2-thenoylacetonitrile is replaced with 0.18% phenol a blue color is obtained on exposure to the ultraviolet light and the unirradiated portions of the paper are deactivated against color formation by the heat treatment.

EXAMPLE 7 A photosensitive paper is prepared by dipping unsized paper into 4:1 (by volume) methanol-N,N-dimethylformamide solution containing 0.5 2,2'-bis(o-chlorophenyl)-4,4,5,5-tetraphenylbiimidazole, 0.5% of 6-methoxy-3-methyl-2-benzothiazolinone hydrazone, 0.4% N,N- dimethylaniline and 0.2% of a SnCl '2 N,N-dimethyl formamide complex, M.P. 235237 0, followed by drying under an infrared lamp. This photosensitive paper is then dipped into a 1% benzene solution of 1,4-di-t-butyl- 2,5-bis(1-ethoxyethoxy)benzene, M.P. 67-67.5 C. (prepared as described in Example 1) and dried under an infrared lamp. When this paper is exposed through a stencil to the light of a 275 watt sunlamp, a blue image is produced. When the paper bearing the image is heated for 10 seconds between the plates of a hydraulic press maintained at 140 C; the paper'is deactivated against coloration by ultraviolet light, i.e., no color appears in the previously irradiated portions of the pattern upon subsequent irradation with the light.

EXAMPLE 8 (1) Photosensitive paper is prepared by dipping unsized paper into a 4:1 (by volume) methanol-N,N-dimethylformamide solution containing by weight 0.5%

ethyl tris(p-dimethylaminophenyl)acetate, 0.5% 2,2'-bis (o-chlorophenyl) -4,4,5 ,5 '-tetraphenylbiimidazole, 0.25 of the complex, having the formula SnCl -2(CH NCHO. The photosensitive paper is briefly dried under an infrared lamp, dipped into a 0.5% benzene solution of 1,4-di-tbutyl-2,5-bis(tetrahydro-Z-pyranyloxy)benzene and again dried under the lamp. This photosensitive paper is irradiated to produce a blue-violet color and then deactivated as in Example 1. The color and unirradiated areas of the papers remain unchanged upon further irradiation.

- "(2) In the above composition, when the ethyl tris(pdimethylaminophenyl)acetate is replaced by 0.5% 10- benz oyl-3,7-bis(dimethylamino)pheno-thiazine a blue color appears upon irradiation and after heat treatment the paper is no longer photosensitive.

--(3) When the substituted ethyl acetate is replaced with 0.3% p-(1,2,2-tricyanoethyl)-N,N-dimethylaniline an orange color is formed by the exposure to ultraviolet light. The color and unirradiated areas of the paper remain unchanged upon further irradiation following the heat treatment.

(4) When the. above ethyl acetate derivative is still further replaced by 0.5% l-phenyl-Z-tris(p-diethylaminophenyl)-methylhydrazine the irradiated areas turn violet. Following heating and further irradiation the color remains unchanged and no color appears in the unirradiated areas of the paper.

(5) If, in the above photosensitive composition, 0.5% bis(p-dimethylaminophenyl)phenylmethane is used as the color-generator the color of the irradiated portions of the paper is green. Heating briefly under a sun lamp effectively deactivatives against further color formation by irradiation.

EXAMPLE 9 (1) Photosensitive paper is prepared by dipping unsized paper into a 1:1 (by volume) benzene-N,N-dimethy1- formamide solution containing by weight 0.82% 1,2-dibromo-1,1,2,2-tetrachloroethane, 0.33% bis(p-diethylaminophenyl)-phenylmethane and 1.0% .p-bis(tetrahydro- 2-pyranyloxy)benzene and briefly drying under an infrared lamp. The paper is irradiated through a template for 10 seconds at a distance of 6 inches from a 275 watt sunlamp. The paper, bearing a green image, is then deactivated toward further color formation by heating for 10 seconds between the metal plates of a hydraulic press maintained at C.

(2) When the bis(p-diethylaminophenyl)phenylmethane of the above composition is replaced with 0.92% diphenylamine and the treated paper is irradiated in the same way a black image forms. This image remains in clear outline after further irradiation following heating in the press.

(3) When the procedures of this example are followed with the inclusion in the solution of 2% cellulose diacetate as a minder essentially the same results are obtained.

The preceding representative examples may be varied within the scope of the present total specification disclosure, as understood and practiced by one skilled in the art, to achieve essentially the same results.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A storage-stable photosensitive composition which comprises (a) an essentially colorless, oxidizable nitrogen-containing, organic color-generator that, when contained in said composition, is stable to oxidation by atmospheric oxygen under normal room and storage conditions but is capable of oxidation to an intensely colored species, ('13) a photooxidant that when mixed with said oxidizable color-generator and irradiated with light of 19 Wavelength from about 2000 A. to about 4200 A. will, without further activation, oxidize said color-generator to said intensely colored species, and (c) a thermally activatable progenitor of a non-color-forming reducing agent which is a stronger reducing agent for the photoactivated oxidant than is the color generator and thereby prevents photooxidative color formation, said progenitor being (i) convertible to said color-preventing reducing agent at temperatures 80 to 160 C., (ii) inert at temperatures below the conversion range and (iii) inert to the photooxidant when said composition is irradiated with said light for ac tivating the photooxidant, and said progenitor being selected from the class consisting of 1) compounds hydrolyzable to the reducing agent at said temperatures, and (2) compounds rearrangeable to the reducing agent at said temperatures, with the proviso that when the progenitor is of the hydrolyzable type (1) there is present in said composition water in amount sufiicient for said hydrolysis to take place; said photosensitive composition being capable of activation prior to said heat treatment to form color by exposure to light of wavelength from about 2000 A. to about 4200 A.

2. The composition of claim 1 wherein component (a) is selected from the class consisting of (1) a le'uco dye having one to two removable hydrogens, the removal of which forms a diflferently colored compound; (2) an N-acyl derivative of a leuco dye defined in (a) (1) above; (3) a triarylmethane wherein the single remaining methane bond is substituted with benzylthio, 2-phenylhydrazino, alkoxycarbonyl or disulfide; (4) an organic amine; (5) a Z-benzothiazolinone hydrazone or N- acyl derivative thereof, oxidizable to a diazonium compound, in combination with a coupling compomint; and (6) an N,N-dialkylphenylenediamine in combination with a coupling component; wherein component (b) is selected from the class consisting of (1) a hexaarylbiimidazole, ('2) a tetraarylhydrazine, (3) a diacylamiobenzotriazole, (4) a henzothiazole disulfide, (5) a triacylhydroxylamine, (6) a diacylaminotriazole, (7) an a1kylidene-2,5-cyclohexadiene-l-one, (8) polymethacrylaldehyde, (9) a diacylaminopyrazole, (10) a bibenzotriazole, (11) a halogen compound having a bond dissociation energy to produce a first free radical of not less than about 40 kilogram calories per mole, and (12) tetraacyl'hydrazine; and wherein component (c) is selected from the class consisting of 1) acetals hydrolyzable to yield phenols, (2) acetals hydrolyzable to yield hydroxylarnines, (3) acetals hydrolyzable to yield hydroxycarboxylic acids which are reducing acids for said activated photooxidant, (4) carboxyesters hydrolyzable to yield phenols, (5 carboxyesters hydrolyzable to yield hydroxylamines, (6) carboxyesters hydrolyzable to yield hydroxycarboxylic acids defined in (3), (7) hydrazones hydrolyzable to hydrazines which reduce Fehlings solution, (8) semicarbaz-ones hydrolyzable to semicarbazides which reduce Fehlings solution, (9) Schiifs bases which hydrolyze to anilines, (10) Schii'fs bases which hydrolyze to naphthyl amines,

20 (11) formalaniline formaldehyde resin hydrolyzable to aniline, and (12) hydroquinone tautomers wherein the hydro hydrogen atoms are bonded to nuclear carbon atoms adjacent to the doubly bonded quinone oxygen atoms, which tautomers rearrange on heating at said temperatures to the corresponding hydroquinones wherein the hydro hydrogens are hydroxylic hydrogens.

3. The composition of claim 2 wherein component (0) is selected from the class consisting of p-bis 2-tetrahydropyranyloxy) benzene,

tris(p-methoxyphenyl)ester of orthoformic acid,

tetrakis(p-methoxyphenyl)ester of orthocarbonic acid, o-phenylene carbonate,

ethyl methyl ketone semicarbazone,

N-benzylidine aniline,

the resin of formalaniline and formaldehyde,

the acetal-ester of tartaric acid,

2,3-dihydro-1,4-napthoquinone,

4a,5,8,8a-tetrahydro-1,4-naphthaquinone,

hydroquinone-bis(dihydropyran) adduct,

p-bis l-ethoxyethoxy) benzene,

p-bis 1-benzyloxyethoxy)benzene,

1,4-bis tetrahydro-Z-pyranyloxy) -2-chlorobenzene,

1,4-bis tetrahydro-Z-pyranyloxy -2-t-'butylbenzene,

2,5 -bistetrahydro-Z-pyranyloxy) biphenyl,

1,4,di-t-buty1-2,5-bis(tetrahydro-Z-pyranyloxy)benzene,

1,4-bis tetrahydro-Z-pyranyloxy) tetrachlorobenzene, polymer of hydroquinone and 1,2-bis(vinyloxy)ethane, 1-methoxy-4-(tetrahydro-Z-pyranyloxy)benzene,

otetrahydro-Z-pyranyloxy phenol,

2,6-'bis( l-ethoxyethoxy) phenol,

2,6-bis(tetrahydro-Z-pyranyloxy)phenol,

semicarbazone of heptaldehyde,

semicarbazone of diisobutyl ketone,

N-p-chl-orobenzylideneaniline,

N-benzylidene-l-napthylamine, and

1,4-di-t-butyl-2,5-bis l-ethoxyethoxy benzene.

4. The composition of. claim 2 wherein component (c) is selected from the class consisting of an acetal of hydroquinone and an acetal of a substituted hydroquinone.

5. A storage-stable photosensitive composition according to claim 1 wherein said (a) is an aminotriarylmcthane' having substituent in at least two of the aryl groups that is located ortho to the methane carbon atom and is selected from the class consisting of alkyl, alkoxy and halogen, said (b) is a hexaaryl-biimidazole and said (0) is an acetal of hydroquinone.

6. A light-sensitive material comprising a supporting base carrying a photosensitive composition as defined in claim 1.

7. A light-sensitive material comprising a plastic film containing a composition as defined in claim 1.

8. Paper treated with a composition as defined in claim 1. a

9. The process of deactivating a photosensitive composition as defined in claim 1 wherein said composition is heated at a temperature between C. and C References Cited UNITED STATES PATENTS 3/1963 Sprague 9690 8/1964 Workman 96-91