GB2043282A

GB2043282A - Production of prints by a dye diffusion-transfer process

Info

Publication number: GB2043282A
Application number: GB8002764A
Authority: GB
Original assignee: Ciba Geigy AG
Current assignee: Novartis AG
Priority date: 1979-01-31
Filing date: 1980-01-28
Publication date: 1980-10-01
Also published as: GB2043282B

Abstract

New prints are produced from old black and white prints by a dye diffusion- transfer process. In this process the silver image of the old print is used to imagewise render an initially non- diffusible dye diffusible in the presence of a silver-dye-bleach catalyst at a pH of less than 3.

Description

SPECIFICATION Production of prints This invention relates to a process for reproducing photographic images.

In many old photographic black and white prints the white background has become very dirty and stained and thus the use of the print either as a record or as a thing of beauty is greatly diminished. Also a great many early negatives used cellulose nitrate as the base, this base has cracked and the negatives thus have been rendered useless. One object of the present invention is to provide a process by means of which the image in old silver halide photographic print or negative material can be reproduced to form an image on a new support base.

According to the present invention there is provided a process for the reproduction of a photographic image using an assembly formed from two components, the assembly comprising a support base, a layer containing a developed silver image, a layer which contains a compound of the general formula I: D-E-F-BAL where D is a group which comprises a preformed dye, BAL is a ballasting group and E and F represent a single or double bond system which links D and BAL and which has a reduction potential above -200 mV measured against a standard hydrogen electrode at a pH of less than 3 and which bond can be reductively cleaved at a pH of less than 3 by a reducing agent which is a reduced silver dye bleach catalyst (as hereinafter defined) which is capable of acting as a reducing agent at a pH of less than 3, a dye mordant layer and a support base there being optionally inter-layers betwen the said layers, the two components of the assembly being as hereinafter defined, the process comprising: (a) Spreading on the top surface of at least one component or between the two said components a silver dye bleach solution having pH below 3 and which comprises a silver dye bleach catalyst, (b) placing the two components in intimate face-to4ace contact so forming the above defined assembly and thereby causing the silver dye bleach solution containing the silver dye bleach catalyst to diffuse into the developed silver image layer and effecting reduction of the silver dye bleach catalyst in the silver areas, (c) allowing or causing the reduced catalyst to diffuse to the layer containing the compound of formula I and in the areas corresponding to the silver image to cleave the E - F bonds of the compound of formula I thereby liberating a diffusible dye, (d) allowing or causing the diffusible dye to diffuse to the dye mordant layer (e) and there to mordant the dye to form a dye image having a peak absorption within the range of 300 800 no.

The two components of the assembly comprise either as one component a support base, a layer containing the compound of formula I and as the other component a support base and a dye mordant layer or as one component a support base and a layer containing the developed silver image and as the other component a support base, a dye mordant layer and a layer containing the compound of formula I.

Usually there is present on the layer which comprises the developed silver image a gelatin supercoat layer.

Thus in general with assemblies used in the present invention there is between the layer which contains the developed silver image and the layer which contains the compound of formula I a gelatin layer.

In the process of the present invention a direct positive reproduction of the original silver image is obtained. Thus to obviate lateral inversion of the image it is preferred that the support base on which the dye mordant layer is coated is a transparent base and there is coated over the dye mordant layer a white reflecting layer.

Thus the preferred assembly for use in the process of the present invention comprises a support base, a layer containing a developed silver image, a gelatin layer, a layer containing a compound of formula I, a white reflecting layer, a dye mordant layer and a transparent support base.

When the process of the present invention is complete the two components may be separated. There will be present a positive reproduction formed as a dye image the mordant layer of the silver image present in the original print material.

Preferably the two components used to prepare the assembly are the original print material, that is to say a support base on which is coated a layer containing the developed silver image and a gelatin supercoat layer and a sub-assembly which comprises a transparent base, a dye mordant layer, a white reflecting layer and a layer containing the compound of formula I.

However, there may be coated on the topmost layer of the original print material a coating composition which comprises the compound of formula 1. This layer is dried to form a layer which comprises the compound of formula I. In this case the other component used does not comprise a layer which contains the compound of formula 1.

By silver dye bleach catalyst is meant a compound which is used in the silver dye bleach process to accelerate the bleaching of the bleachable image dye. Certain diazine compounds are particularly suitable.

These compounds are reduced by image silver to their reduced form. In their reduced form they are able to bleach certain bleachable dyes and in particular azo dyes. In doing so they are converted to their oxidixed form which may be reduced again by the image silver. Thus the dye bleach catalyst helps in the imagewise bleaching of the azo dye in the silver dye bleach process.

Examples of suitable diazine catalysts are pyrazine compounds and preferably quinoxaline compounds, above all those which are substituted in the 2-3-, 5-, or 7- position by methyl groups, methoxy groups or acylated or non-acylated hydroxymethyl groups or acylated or non-acylated amino groups.

Further, it is possible to us pyrazines as dye bleach catalysts, such as pyrazine itself or pyrazines substituted by methyl, ethyl and/or carboxylic acid groups, such as 2-methylpyrazine, 2-ethylpyrazine, 2,3-, 2,5- or 2,6-di methyl-pyrazi ne, pyrazinecarboxylic acid, pyrazine-2,3-, -2,5- or -2,6-dicarboxylic acid or 2,3-dimethylpyrazine-2,6-dicarboxylic acid.

Usable dye bleach catalyst are also described in German Auslegeschriften 2,010,707,2,144,298 and 2,144,297, in French Patent Specification 1,489,460 and in U.S. Patent Specification 2,270,118.

The preferred binder both for the layer which contains the compound of formula I for the white reflecting layer and for the mordant layer is gelatin. However so-called gelatin extenders may be present for example those derived from synthetic colloid latexes especially acrylic latexes. Other natural or synthetic binders may be used either alone or in admixture with the gelatine, for example albumen, casein, polyvinyl alcohol and polyvinyl pyrolidone.

The support base on which the mordant layer is coated may be any of the normal bases used for photographic materials, for example if the base is transparent it may be composed of cellulose triacetate, cellulose acetatebutyrate, oriented and subbed polystyrene, polycarbonate or polyester such as polyethylene terephthalate. If the base is opaque it may be of any of the above listed film base materials which has been pigmented for example with magnesium carbonate or titanium dioxide to render its coated surface reflecting, or it may be a paper base having a baryta coating thereon or is polyethylene coated paper base. Alternatively it may be voided polyester base, i.e. polyester having sufficient small voids therein to render it light scattering enough to be opaque.

The silver dye bleach solution used may contain any of the normal ingredients of a silver dye bleach bath including a strong acid, preferably sulphuric or sulphamic acid, a silver dye bleach catalyst as hereinbefore described and an alkali metal halide or another silver halide complexing agent such as thiourea.

Two compounds of formula I of particular use in the process of the present invention are the compounds of formula ll:-

which cleaves where indicated to yield a diffusible blue dye and the compound of the formula Ill:-

which cleaves where indicated to yield a diffusible magenta dye.

The compound of formula II is used in Example I which follows and the compound of formula Ill is used in Example II which follows.

Suitable compounds of formula I for use in the process of the present invention are compounds of formula IV:

where X is N or CR4 where R4 is a hydrogen atom or an optionally substituted alkyl or aryl group, Y is S+, NR5, O or N where R5 is an optionally substituted alkyl or aryl group, R1 is a substituted aromatic or heterocyclic group containing a ballasting group, R2 and R3 are each hydrogen atoms or alkyl groups having 1 1 to 4 carbon atoms, or R2 and R3 together with the nitrogen atom complete a heterocyclic ring, or one of R2 or R3 can be hydrogen and the other of R2 or R3 can be aryl, and T1 and T2 represent hydrogen atoms, or optional annelation or further substitution Examples of such further substitution are alkyl groups and particularly methyl groups, amino groups and halogen groups.

Preferably the group R1 comprises an aromatic or heterocyclic ring containing a hydroxy or dialkylamino group ortho or para to the azo link as well as a ballasting group.

A particularly useful group R1 is the group of the formula V:

where R6 is either an alkylgroup containing at least 10 carbon atoms or a group containing such an alkyl group or an aryl-ballasting group.

An example of an aryl ballasting group is the group:

Another useful group R1 is the group of the formula VI:

where R7 and R8 are both alkyl groups having together at least 12 carbon atoms.

Compounds of formula IV may be prepared by diazotising a compound of formula VII:

to yield the diazo compound of formula VIII:-

and then coupling the diazo compound of formula VIII with a coupler of the formula Ri A+ in alkaline conditions where X, Y, R1, R2 and R3 have the meanings assigned to them above, Z is an anion and A is a cation.

The general formula VII covers several well-known classes of dyes for example, compounds of formula IV wherein X is N and Y is N+RS are azo-phenazine compounds.

Particularly suitable azo-phenazine compounds of formula IV are azo-phenazines of formula IX:

where R1, T1 and T2 have the meanings assigned to them above, T3 is a phenyl or alkyl group and Z is an anion. Preferably Z is tetrafluoroborate. Preferably T1 and T2 are methyl groups. However sometimes the compound exists in the zwitterionic form, especially when R, is a group of formula V. Preferably Ts is a phenyl group. When the azo link is cleaved a diffusible magenta phenazine dye is released.

An example of such an azo-phenazine compound is the compound of formula X:

Another example of such an azo-phenazine compound is the compound of formula Xl:-

Compounds of formula IV wherein X is N and Y is 0+ are azo-oxazine compounds.

Particularly suitable azo-oxazine compounds of formula IV are azo-oxazine compounds of formula XII:-

where Z and R1 have the meanings assigned to them above.

When the azo linkage is cleaved a diffusible blue or bluish oxazine dye is released.

An example of such an azo-oxazine compound is the compound of formula XIII:

where B is the group

and Z has the meaning assigned to it above.

Compounds of formula IV wherein X is N and Y is S+ are azo-thiazone compounds.

Particularly suitably azo-thiazine compounds of formula IV and azo-thiazine compounds of formula XIV:

where T1, T2, Z, Ri, R2 and R3 have the meanings assigned to them above.

When the azo-linkage is cleaved a blue to magenta diffusibule thiazine dye is released.

An example of such an azo-thiazine compond is the compound of formula XV:

where B and Z have the meanings assigned to them above.

Compounds of formula IV wherein X is CR4 and Y is N+R5 are azo-acridine compounds of formula XVI:

where Z, R1, R4 and R5 have the meanings assigned to them above.

When the azo linkage is cleaved a yellow diffusible acridine dye is released.

An example of such an azo-acridine compound is the compound of formula XVII:

where B and Z have the meanings assigned to them above.

Other suitable azo-acridine compounds for formula IV are azo-acridine compounds of formula XVIII:-

where R1, Tr, T2, R2, R3 and R4 have the meanings assigned to them above.

When the azo linkage is cleaved a yellow diffusible acridine dye is released.

An example of such an azo-acridine compound is the compound of formula XIX:

where B has the meaning assigned to it above.

Compounds of formula IV wherein X is CR4 and Y is 0+ are azo-pyrylium compounds.

Particularly suitable azo-pyrylium compounds of formula IV are azo-pyrylium compounds of formula XX

where R1, R2, R3 and Z have the meanings assigned to them above and R8 is a substituent group.

When the azo linkage is cleaved a yellow-magenta diffusible pyrylium dye is released.

An example of such an azo-pyrylium compound is the compound of formula XXI:

where B and Z have the meanings assigned to them above.

Other compounds of formula II for use in the process of the present invention are azo-anthraquinone compounds of the general formula XXII :-

where T4 is a hydrogen atom, an hydroxy or alkoxy group, or an amino or substituted amino group, R10 is hydrogen or halogen, alkoxy, amino or substituted amino or a group conferring solubility in water and R11 is a group which comprises an azo linkage and a ballasting group or completes the hydrazo linkage and comprises a ballasting group.

It is to be understood that there may be other substituents in the anthraquinone nucleus and in particular in the benz ring to which the group - NH - R11 is not attached. Examples of such substitution include hydroxy, halogen, amino and alkoxy.

When the azo linkage is cleaved in compounds of formula XXII where T4 is a hydrogen atom a diffusible yellow or orange anthraquinone dye is liberated.

When the azo linkage is cleaved in compounds of formula XXII where T4 is an amino or alkyl amino group a a diffusible blue anthraquinone dye is liberated.

When the azo linkage is cleaved in compounds of formula XXII where T4 is an acryl amino group a diffusible red anthraquinone dye is liberated.

When the azo linkage is cleaved in compounds of formula XXII when T4 is an hydroxy or alkoxy group a diffusible magenta anthraquinone dye is liberated.

Suitable azo-anthraquinone compounds of formula XXII are azo-anthraquinone compounds of formula XXIII:

where R13 is a group containing an azo group and a ballasting group.

Compounds of formula XXIII may be prepared by diazotising a compound of formula XXIV:

to yield a diazo compound of the formula XXV:

where Z is an anion and then coupling the diazo compound of formula Vlil with a coupler of the formula R-A+ where A is a cation and R has the meaning assigned to it above, in alkaline conditions.

An example of an azo-anthraquinone compound of formula XXIII is the compound of formula XXVI:

where B is as defined above.

Another class of useful azo-anthraquinones of general formula XXIII are compounds of the formula XXVII:

where R1 has the meaning assigned to it above, R14 is an alkyl group having 1 to 4 carbon atoms or an aryl group or a hydrogen atom, and L is a linking group.

Examples of suitable linking groups include amide groups, quaternary ammonium groups, or phenyl groups, preferably substituted with groups such as a sulphonic acid group to help solubilise the anthraquinone dye which is liberated when the azo linkage is cleaved.

Compounds of formula XXVII may be prepared for example either by diazotisng a compound of the general formula XXVIII:

where R4 has the meaning assigned to it above and then coupling the resulting diazo compound with a coupler of the formula R-A+ where A is a cation and R has the meaning assigned to it above or by reacting a compound of the formula XXIX:

where R14 has the meaning assigned to it above with a preformed azo compound of the formula XXX:

where Hal is a halogen atom and R1 has the meaning assigned to it above.

An example of an azo-anthraquinone compound of formula XXVII is the compound of formula XXXI:

where B has the meaning assigned to it above.

Another example of an azo anthraquinone of formula XXVII is the compound of formula XXXI I:

Alternatively compounds of generaly formula XXVII may be made by forming the - L - group from anthraquinone and azo precursors. For instance, the compound of formula XXXII may be made by reacting a compound offormula XXIV with an azo compound offormula XXXIII:

Another group of useful azo-anthraquinones of formula XXII are azo-anthraquinones of formula XXXIV:

where R1 and R14 have the meanings assiged to them above.

Compounds of formula XXXIV may be made in a similar manner to compounds of formula XXIII, that is to say diazotisation of a compound of formula XXXV:

followed by coupling with a coupler R1-A+ where A is a cation and R1 and R14 have the meanings assigned to them above.

Another useful group of compounds of general formula XXII are hydrazo-anthraquinones of formula XXXVI :

where R14 has the meaning assigned to it above and R15 is either an alkyl group containing at least 10 carbon atoms or is a group which comprises such an alkyl group, or is a ballasting aryl group.

Hydrazo-anthraquinones of formula XXXVI may be prepared by reacting a compound of the formula XXIX with a substituted phenyl hydrazine of the formula XXXVII:-

where R15 has the meaning assigned to it above, in an alkaline medium.

An example of hydrazo-anthraquinone of formula XXXVI is the compound of formual XXXVIII:-

where B has the meaning assigned to it above.

Another group of azo compounds of formula I of use in the process of the present invention consists of the azo-phthalocyanine compounds of formula XXXIX: (M)n - Pc-(L - R16- N = N - R1)p XXXIX where M is a metal n is O or 1, Pc represents a phthalocyanine complex, L is a linking group, R, has the meaning assigned to it above, p is 1 to 4and R16 is an optionally substituted aromatic or heterocyclic ring.

Examples of M are copper, cobalt, iron, nickel, magnesium, manganese, barium and zinc.

Preferably M is copper and n is 1 andp is 2.

Preferably L is either a short linking group or comprises a solubilising moiety for example a quaternary ammonium group.

When the azo linkage is cleaved a diffusible cyan dye is released.

A phthalocyanine complex can be shown as formula XL:

where M is the metal which may or may not be present (but when it is not present it is replaced with two H atoms) each R can be hydrogen, SO3H, S03W where W is Na, K or NH4, Cl or Br.

In the phthalocyanines of formula XL at least 1 but.no more than 4 of R of formula XL are a group of the formula XLI: -L-Ra6-N = N-R, .. XLI where L, R1 and R16 have the meanings assigned to them above.

Preferably all the groups of formula XLI attached to the phthalocyanine complex are the same but they can be different.

Phthalocyanine complexes are described in General Synthetic Procedures for Phthalocyanine Dyes in Chapter 5 of E.H. Moser and A.L. Thomas, Phthalocyanine Compounds, Reinhold, published 1963.

A preferred group L is of the formula XLII:

A particularly useful phthalocyanine of formula XL is the compound of formula XLIII:-

where B has the meaning assigned to it above.

Usually the first step in the peparation of the azo-phthalocyanine compounds of formula XLI is to prepare a compound of the formula XLIV: lMlnPc- Pe -L-R,6- p XL1V where M, n, Pc, R16 and p have the meanings assigned to them above.

The second step is to reduce the NO2 to N H2 and then diazotise the NH2. Then couple 1 mole of the diazo compound of formula XLV: (M)nPc#L#Ri6#N#N##p pX where M, n, Pc, R16, L and p have the meanings assigned to them above and X is an anion, with p moles of a coupler of the formula R1-A+ where R1 has the meaning assigned to it above and A is a cation.

In the case of the azo compounds of formula II and Ill when D also contains an azo linkthe only suitable ones are those in which the azo group in the residue D is more stable to reduction than the - N = N - linkage of azo compounds of formula II or the - NH - NH - linkage of the hydrazo compounds of formula Ill.

An example of a suitable class of azo compounds of formulae II and Ill are compounds of the general formula XLVI:

where R1 has the meaning assigned to it above, L is either a linking group or a direct link, V is a group which comprises an aromatic or heterocyclic ring, at least one of the groups L and V comprises an active methylene group.

It is thought that the group R1 renders the azo link to which it is attached more readily cleavable by the reducing compound than the other azo link in the compound. This other azo link is stabilished against reduction by the presence of the group which comprises the active methylene group attached thereto.

Examples of groups which comprise an active methylene group are pyrazolones, hydroxypyridones and the ketomethylene group - CO- CH2 - CO -.

A Agroup of suitable azo compounds of formula XLVI have the active methylene group in group V. These compounds are of the general formula XLVII:

where V1 is a group which comprises an active methylene group.

Compounds of formula XLVII may be prepared by coupling a diazo compound oftheformula XLVIII:-

where Z is an anion, with a coupler of the formula R1-A+ to yield a compound of the formula IL:

where in the above formulae R1 has the meaning assigned to it above and A is a cation, diazotising the compound of formula ILto yield the compound of formula L:

where R1 has the meaning assigned to it above and coupling the compound of formula L with a coupler of the formula V1#A+ where V1 has the meaning assigned to it above and A is a cation to yield a compound of formula XLVII.

An example of a compound of formula XLVII is the pyrazolone group-containing compound of formula LI:

where B has the meaning assigned to it above.

Another example of a compound of formula XLVII is the hydroxypyridone group-containing compound of formula LII:

where B has the meaning assigned to it above.

Another group of suitable azo compounds of formula XLVI have the group containing the active methylene group in the linking group L. These compounds are of the general formula LIII:

where T5 is at least one substituent group, K is a group which comprises an active methylene group and R has the meaning assigned to it above.

The azo compounds of formula LIII are of especial interest as the substituents T5 determine to a great extent the colour of the dye released when the azo link to which R1 is attached is broken. For example, when T5 is 4-methoxy the liberated dye is yellow. When it is 3,4-dimethoxy a darker yellow dye is liberated. When it is 4-diethylamino the dye is reddish-orange.

Compounds of formula LIII may be prepared by diazotising a compound of formula LIV:

to yield a diazo compound of formula LV:

and then coupling this compound with a coupler of the formula R1-G+ to yield a compound of formula LIII, where in the above formula T5 and A have the meanings assigned to them above, G is a cation and Z is an anion.

A particular class of compounds of formula LIII are the compounds where K is a pyrazolone. These compounds have the general formula LVI:

where T5 and R1 have the meanings assigned to them above and T6 is hydrogen or a substituent group.

An example of a compound of formula LVI is the compund of formula LVII:

where B has the meaning assigned to it above.

Compounds of formula LVI often occur in the hydrazo form which is written as formula LVIII:

where all the symbols have the meanings assigned to them above.

A suitable azoxy compound for use in the process of the present invention is the compound of formula LIX:--

This is a known compound.

The azo compounds may be incorporated in the layer of the photographic material using any of the methods employed for incorporating colour couplers into normal photographic material or azo dyes into silver dye bleach material. Such methods include aqueous solution or dispersion and oil dispersion.

Another class of useful compounds of formula I are compounds of the general formula LX: D-N =CR17-BAL LX or of the general formula LXI: D - NRi8 - CR17R15 - BAL LXI where in the above two formulae D and BAL have the meanings assigned to them above and R17, Ris and R19 each represent a hydrogen atom or an alkyl group with 1 - 3 carbon atoms, and the reduction potential of - N = CR17 - or the - NR18 - CR17Rl9 - bond is above -200 mV measured against a standard hydrogen electrode at a pH of less than 3.

The amino compounds of formula LXI are the dihydro derivatives of the imino compounds of formula LX, thus for ease of reference the term "imino compounds" as used hereinafter also covers the derived amino compounds and refers to compounds of formulae LX and LXI.

Particularly useful compounds of formula LX and of formula LXI are compounds of the general formula LXII:

or of the general formula LXIII :-

where in the above two formulae T1, T2, R2, R3, R18, X and Y have the meanings assigned to them above, and Z is a group which comprises both an activating group (as hereinafter described) which contains at least one double bond system and also a ballasting group.

The compounds of formula LXIII are the partially oxidised compounds of formula LXII.

By activating group is meant an electron-withdrawing group which activates the - NRis - CH2 - or - N = CH bond and renders it more susceptible to reduction cleavage. Examples of suitable activating groups which contain a double bond system are aromatic rings and groups which contain a carbonyl group.

A particularly useful group Z is the group of the general formula LXIV:

where R20 comprises a ballasting group containing at least 10 carbon atoms and R21 represents optional further substitution, e.g. alkyl groups or halogen atoms.

Another useful group Z is of the general formula LXV:

where R20 and R21 have the meanings assigned to them above.

Afurther useful group Z is of the general formula LXVI:

where R21 has the meaning assigned to it above.

The general formulae LXII and LXII I cover several well-known classes of dyes. For example when X is N and Y is OC the compounds of formulae LXII and LXIII are oxazine compounds. Particularly useful dyes are of formula LXVII:

where X is an anion and R2 and R3 are as defined above. An example of such an oxazine compound is the compound of formula LXVIII:-

An oxazine compound of formula LXIII is the compound of formula LXIX

Compounds of formula LXII wherein X is N and Y is NR5+ are phenazine dyes. Particularly useful phenazine compounds of formula LXII are the dyes of formula LXX:

where R2, R3, T1, T2, X and Z have the meanings assigned to them above and R22 is a hydrogen atom, alkyl or aryl group, and is preferably a phenyl group. An example of such a phenazine compound is the compound of formula LXXI:

Compounds of formula LXII where X is N and Y is S+ are thiazone dyes. Useful thiazine compounds have the formula LXXII:

where T1, T2, R2, R3 and Z have the meanings assigned to them above and T2 preferably comprises a methyl group.An example of such a thiazine compound is the compound of formula LXXIII:-

Compounds of formula LXII may be prepared by treating a dye of formula LXXIV:

with an alkali and a suitable alkylating agent of formula LXXV:

LXXV where G is a leaving group, and X, Y, Z, R2, R3, R18, T1 and T2 have the meanings assigned to them above. An example of a leaving group is Br.

In the azo compounds of formulae II and Ill of use in the process of the present invention D is linked to the azo group by a covalent bond. Also in the imino and amino compounds of formulae LX and LXI D is linked to the imino and amino groups by a covalent bond. However in another class of azo dyes of particular use in the process of the present invention the group which contains the preformed dye consists of a preformed dye D1 linked to the remainder of the group D by an ionic bond.

Compounds of this type are of the general formula LXXVI: (D1)nl(A)n2 - (R23)n3 - N = N - BAL LXXVI where A is a charged group which may be positively or negatively charged, D1 is a residue of a diffusible dye which carries a charge opposite in sign to the charge carried by A, R23 is an optionally substituted aromatic or heterocyclic ring which is present unless A is charged heterocyclic group, n1 is 1 or 2, n2 is 1 or 2, n3 is O or 1 and BAL has the meaning assigned to it above. Examples of substitution in R23 include alkyl groups and halogen atoms.

Thus in the above formula LXXVI the group (D1)n1(A)n2 - (R23)n3 is the group D of formula I.

Examples of group A which are positively charged are a quaternary ammonium group, a quaternary phosphonium or arsonium group and a guanidinium group.

Examples of group Awhich are negatively charged are a sulphonic acid anion group, a phosphonic acid anion group and an alkyl sulphate group.

Examples of suitable classes of dyes for the residue of the diffusible dye D' are phthalocyanines, anthraquinones and azines, including oxazines and thiazines, and acridines. Also indigo dyes, oxonols, pyrylium dyes, azo and azoxy dyes are useful.

When A in formula LXXVI is anionic the compounds of formula LXXVI may be prepared from compounds of formula LXXVII: Mn 1±(A)n2- (R23)n3- N = N - BAL LXXVII LXXVII where A, R23, BAL, nn, n2 and n3 have the meanings assigned to them above and M is a cation, by reaction with a cationic or basic dye such as those described in the Colour Index.

Mixed solutions of a suitable cationic or basic dye and a compound of formula LXXVII result in a precipitation of a compound of formula LXXVI. The precipitated compound can then be purified.

Alternatively the mixed solution may be an aqueous gelatin solution and in this case a gelatin suspension of the compound of formula LXXVI is produced which can then be added to a photographic coating solution to coat onto a film base.

However the compounds of formula LXXVI may be prepared in situ in a coated gelatin layer. In this case a gelatin coating which comprises a compound of formula LXXVII is prepared and a solution of a cationic dye applied thereto. A compound of formula LXXVI is then produced in situ in the coated gelatin layer.

In similar manner when A is cationic compounds of formula LXXVI may be prepared from compounds of formula LXXVIII: X l (A)n2 - (R23)n3- N LXXVIII ... LXXVIII where A, R23, BAL, nl, n2 and n3 have the meanings assigned to them above and X is an anion, using soluble anionic or acid dyes such as those listed in the Colour Index.

Compounds of formula LXXVIII may be prepared by diazotising a compound of formula LXXIX: Hn1 (A)n2 - (R23)n3- NH2 LXXIX when A, R23, ni, n2 and n3 have the meanings assigned to them above to yield a compound of formula LXXX: Hn1 (A)n2#(R23)n3#N2+ .. LXXX and then coupling this diazo compound with a coupler R1-M+ where R1 is as defined above and M is a cation.

A particularly useful compound of formula LXXVII is the compound of formula LXXXI:

where R1 is as defined above.

Most preferably R1 has the formula LXXXII:

Suitable basic dyes for the preparation of the compound of formula LXXVIII are basic dyes of the general formula LXXXIII:

where T1, T2, R2, R3, X, Y and X- are as defined above, and R24 and R25 are hydrogen, alkyl groups with 1 - 3 carbon atoms, or optionally substituted aryl groups.

Compounds of formula LXXXIII wherein X is N and Y is NR+5 are phenazine compounds.

Particularly suitable phenazine compounds of formula LXXXIII are phenazines of formula LXXXIV:

where T1, T2 and R22 are as defined above. Preferably R22 is a phenyl group. X is an anion.

An example of such a phenazine compound is the compond of formula LXXXV:

where B is as defined above.

When the azo link is cleaved a magenta dye is liberated.

Compounds of formula LXXXIII wherein X is N and Y is 0+ are oxazine compounds.

Particularly suitable oxazine compounds of formula LXXXIII are oxazine compounds of formula LXXXVI:

where Xis an anion.

An example of such an oxazine compound of formula LXXVII is the compound of formula LXXXVII:

where B is the group as defined above.

When the azo link is cleaved a diffusible bluish dye is obtained.

Compounds of formula LXXXIII where X is N and Y is S+ are thiazine compounds.

Particularly suitable thiazine compounds are those of formula LXXXVIII:

where T1, T2, X#, R2, R3, R24 and R25 have the meanings assigned to them above.

An example of such a thiazine compound of formula LXXVII is the compound of formula LXXXIX:

where B has the meaning assigned to it above.

When the azo link is cleaved a blue dye is liberated.

Compounds of formula LXXXIII where X is CR4 and Y is N+R5 are acridine compounds.

Particularly suitable acridine compounds are those of formula XC:

where X R4 and R5 have the meanings assigned to them above.

An example of such an acridine compound of formula LXXVII is the compound of formula XCI:-

where B has the meaning assigned to it before.

When the azo linkage is cleaved a diffusible yellow acridine dye is released.

Compounds of formula LXXXIII where X is CR4 and Y is 0+ are pyrylium compounds.

Particularly suitable pyrylium compounds are compounds of formula XCII:

where R2, R3, R24, R25 and X- have the meanings assigned to them above and R26 is a substituent group.

An example of a rhodamine compound of formula LXXVIII is the compound of formula XCIII:

where B is as defined above.

When the azo linkage of dye XCIII is cleaved a magenta diffusible rhodamine dye is released.

Another class of basic dyes which are suitable for the preparation of the compounds of the general formula LXXVII are basic anthraquinone dyes of the general formula XCIV:

where Rio, T4, X and L are as defined above and R27, R28 and R29 are alkyl or aryl groups.

It is to be understood that further substitution may be present in the anthraquinone nucleus, particularly in the ring which is not already substituted. Alternatively R27, R28 and R29 may comprise a ring system or systems.

An example of such an anthraquinone compound of formula LXXVI is the compound of formula XCV:

where B has the meaning assigned to it above.

Another class of cationic dyes which is suitable for the preparation of the compounds of formula LXXVI is cationic phthalocyanine dyes.

A phthalocyanine complex can be shown as formula XCVI:-

where M represents a metal which may or may not be present and each R can be hydrogen, SO3H, SO3W where W is an alkaline metal and at least one R has the formula + L - NR27R28R29 where L, R27, R28 and R29 have the meanings assigned to them above.

Preferably M is Cu. An example of such a phthalocyanine compound of formula LXXVI is the compound of formula XCVII:

where B has the meaning assigned to it above and Pc represents the phthalocyanine nucleus of formula XCVI.

Compounds of formula LXVI may be prepared by diazotising an amine of formula A - N Hp where A is either a heterocyclic ring which can be quaternised or presents either an aromatic or heterocyclic ring to which is attached a group which can be converted to a cationic group, and then coupling the resultant diazonium compound of the formula A - N = N+ with a coupler of the formula W+ BAL- where W and BAL have the meanings assigned to them above and then forming the cationic compound by reaction with a quaternising reagent, e.g. methyl iodide.

An example of such a reaction is when A is Thus

An example of such a compound is the compound of formula XCVIII:

where B has the meaning assigned to it above.

An example of a group A which can be converted to a cationic group is the group of formula IC:

which may be converted to quaternary ammonium groups, phosphonium or arsonium groups by reaction with p-toluene-sulphonyl chloride and an amine or phosphine or arsine, thus:

An example of such a compound is the compound of formula C:

where B has the meaning assigned to it above.

Diamines of the formula NH2 - F - NH2 where F is a linking group are also of use as they can be converted to guanidinium compounds. For example:

where R' is hydrogen or alkyl.

Suitable dyes for the formation of compounds of formula LXXVI where A carries a positive charge include dyes of the azo, anthraquinone and phthalocyanine classes. A suitable azo dye has the structure Cl:

Thus the compound of formula LXXVI made using the compounds of formula C and formula CI is of the formula CII:

An example of such a phthalocyanine complex is the compound of formula CIII:

where Pc is the complex of formula XCVI and four of R groups are SO3-.

It is to be understood that sometimes the diffusible dye is in a reduced form, which can be written as DH2, and is preferably oxidised to its full colour density either in its passage to the receiving layer or in the receiving layer. This oxidation may occur in the presence of air or be caused by an oxidant present in the receiving layer or in an extra processing step, for example raising the pH of the assembly.

An example of a suitable mordant is sodium cellulose sulphate and also charged polymer particles derived from a latex of a polymer containing units of an anionically charged monomer. The anionically charged monomer may be sodium ethene sulphonate and the remainder of the polymer, because it serves only to carry the charge, can be composed of a variety of monomers, e.g. vinyl acetate, styrene and vinylidene chloride. Other suitable charged monomers include allyl sulphonic acid and acrylic acid, The anionically charged polymer latex is prepared using initiators such as persulphate salts and surfactants such as sodium lauryl sulphate. Suitable binders for the charged latex particles include gelatin and casein.

Certain other charged compounds which are substantive to gelatin layers can also be used as mordants.

For example some optical brightening agents and surfactants.

In the process as hereinbefore set forth the processing is carried out in acid conditions and thus preferably in order to preserve the dye image in the receiving layer the pH of the receiving layer is raised either during the process or as a final step in the process. For example there may be present a neutralising layer in the assembly through which the diffusing dye passes. Or there may be a neutralising layer located between the mordant layer and the support. However the assembly after the dye has been fixed in the mordant layer may be treated with a base to neutralise the acid or when the mordant layer and support are separated from the remainder of the photographic assembly this image portion of the assembly may be treated alone with a base.

The preferred pigment to use in the white reflecting layer is titanium dioxide.

The white reflecting layer used in the Examples which follow was prepared as follows: Titanim dioxide (mean particle size 1.5F) 15 9 Gelatin (4% aqueous solution) 50 ml Sodium dodecyl sulphate (28% aqueous solution) 0.3 ml Aryl alkyl polyethylene oxide condensate 3.0 ml (6% solution in 50/50 ethanol/water) dispersed using a homogeniser or ultrasonic mixer coated to give a layer containing 27 g.m TiO2.

The process of the present invention is of especial use for the preparation of direct positive reproductions of positive black and white silver halide prints. It is also of use for the reproduction of negatives to produce a negative on new base.

Sometimes the silver image in the photographic material used in the process of the present invention becomes a little degraded. In order to regenerate it the photographic material may be treated with a solution of black and white photographic developer, for example an aqueous solution of hydroquinone and metol in daylight conditions to ensure re-exposure of all the rehalogenated silver.

Example 1 The following component was prepared: 1. On to a transparent colourless film base (150 microns) there was coated the following layers.

2. A dye receiving layer containing as mordant a charge copolymer of styrene and butyl acrylate (1:1) (1.5 g solids m#2) and gelatin (4.0 gum~2).

3. A white reflecting layer as just set forth.

4. A layer containing the dye of formula II (as just set forth) 0.1 gum~2 in gelatin 1.0 gum~2.

There was coated all over layer 4 of this component a silver dye bleach solution of the following composition: Sulphamic acid 79 Distilled water 42.5 ml To this solution was added 5 ml of a solution consisting of 2- ethoxy ethanol 120 ml 2,3- dimethyl quinoxaline 3.6 g acetic acid (glacial) 4 potassium iodide 129 distilled water 7.6 ml The second component was a black and white print containing a silver image and covered with a gelatin supercoat, was then pressed into close contant with the silver dye bleach solution coated component as just prepared.

After 1 minute the two components of the assembly were separated and the portion which now contained a blue dye image in the mordant layer was washed with water. A dense blue positive reproduction of the original silver image was obtained which could be viewed through the transparent base.

Example 2 The following component was prepared: 1. Support base as Example 1 onto which was coated: 2. A dye receiving layer as Example 1.

3. A white reflecting layer as Example 1 The second component was prepared by coating on to the gelatin supercoat layer of a black and white silver image print material a layer containing the compound of formula 1110.159-2 as an oil dispersion in gelatin 2.5 g m~2.

The oil dispersion was made as follows: Compound of formula III 0.1 g Tricresyl phosphate 0.4 ml Dichloromethane 1.6 ml The dichloromethane was evaporated off and the residue mixed with 6% gelatin solution 13 ml Water 5 ml and treated ultrasonically for 5 minutes. The coating solution contained The above dispersion 3 ml 6% gelatin solution 3 ml Hardener 1 ml Saponin (wetting agent) 0.5 ml Water 2.5 ml On contacting the two components of the assembly with a silver dye bleach solution as for Example 1 for 1 minute and then washed with water a positive magenta image of the original silver image was obtained in the dye receiving layer which could be viewed through the base.

Example 3 Example of the use of an azo dye as the image dye.

The first component was prepared as in Example 2.

The second component was prepared as described in Example 2, but using the bis-azo compound of formula LI. After processing with a solution as described in Example 1 but with a contact time of 4 minutes a bright yellow positive image was obtained in the receiving layer, which could be viewed through the base.

Example 4 Example of the use of an anthraquinone dye as the image dye.

The first component was prepared as in Example 2.

The second component was prepared as in Example 2 but using an azo-anthraquinone compound of formula XXVI as the dye releasing compound. After processing with a solution as described in Example 1 a positive blue image was obtained in the receiving layer, which could be viewed through the base.

Example 5 Example of the use of an ionic dye-releasing compound.

The first component was prepared as in Example 2. The second component was prepared as in Example 2, but using an azo-rhodanine dye releasing compound of formula XCIII. After processing with a solution as in Example 1 a bright magenta positive rhodanine dye image was seen in the receiving layer, suitable for viewing as a print through the base.

Example 6 Example of the use of pyrazine as the catalyst.

The first component was prepared as in Example 2.

The second component was prepared as in Example 2, but using an azo-phenazine dyestuff of formula Xl.

The two components were contacted as in Example 1, but using a processing solution of the solution of the following composition: Pyrazine 0.5g Potassium iodide 0.5g Hydrochloric acid (0.5M) 100 ml.

After processing for 1 minute the two components were separated and a magenta positive image was seen in the receiving layer.

Example 7 Example of the use of sodium cellulose sulphate as the mordant.

The first component was prepared by coating sequentially onto: 1. Support base as in Example 1 2. A coating solution of sodium cellulose sulphate of the following composition:- Gelatin 6% solution 5 ml Water 2.75 ml Sodium cellulose sulphate 1% solution 0.5 ml Hardener 3% solution 1 ml Wetting agent 1% solution 0.25 ml 3. A reflecting layer as layer 3 of Example 1.

The above component was contacted with a second component as in Example 6, using a processing solution as in Example 1. After processing for 1 minute a magenta image was seen in the receiving element. Example 8 Example of the use of an optical brightener in the receiving element. The optical brightener used had the formula CIV:

The first component was prepared as follows: 1. Support base as Example 1 onto which was coated: 2. A dye receiving layer made by coating the following solution: :- Compound CIV (above) 99 in 2-ethoxyethanol 250 ml added to gelatin 60g in water 1000 ml Hardener 3 9 Saponin G wetting agent 1.5 9 Made up to 2000 ml and adjusted to pH 5.

3. A reflecting layer as layer 3 of Example 1.

This receiving element was contacted with a dye-releasing component as in Example 6, and treated with a processing solution as in Example 1. A positive magenta dye image was seen in the receiving layer.

Claims

1. A process for the reproduction of a photographic image using as assembly formed from two components, the assembly comprising a support base, a layer containing a developed silver image, a layer which contains a compound of the general formula I: D-E-F-BAL where D is a group which comprises a preformed dye, BAL is a ballasting group and E and F represent a single or double bond system which links D and BAL and which has a reduction potential above -200 mV measured against a standard hydrogen electrode at a pH of less than 3 and which bond can be reductively cleaved at a pH of less than 3 by a reducing agent which is a reduced silver dye bleach catalyst (as hereinbefore defined) which is capable of acting as a reducing agent at a pH of less than 3 a dye mordant layer and a support base there being optionally inter-layers between the said layers, the two components of the assembly being as hereinafter defined, the process comprising: (a) spreading on the top surface of at least one component or between the two said components a silver dye bleach solution having a pH below 3 and which comprises a silver dye bleach catalyst, (b) placing the two components in intimate face-to-face contact so forming the above defined assembly and thereby causing the silver dye bleach solution containing the silver dye bleach catalyst to diffuse into the developed silver image layer and effecting reduction of the silver dye bleach catalyst in the silver areas, (c) allowing or causing the reduced catalyst to diffuse to the layer containing the compound of formula I and in the areas corresponding to the silver image to cleave the E -F bonds of the compound of formula I thereby liberating a diffusible dye, (d) allowing or causing the diffusible dye to diffuse to the dye mordant layer, (e) and there to mordant the dye to form a dye image having a peak absorption within the range of 300 800 nm.

2. A process according to claim 1 wherein the assembly comprises a support base, a layer containing a developed silver image, a gelatin layer, a layer containing a compound of formula I, a white reflecting layer, a dye mordant layer and a transparent support base.

3. A process according to either claim 1 or claim 2 wherein the silver dye bleach catalyst is a quinoxaline compound substituted in the 2-, 3-, 5-, 6- or 7- position by methyl groups, methoxy groups or acylated or non-acylated hydroxymethyl groups or acylated or non-acylated amino groups.

4. A process according to either claim 1 or claim 2 wherein the silver dye bleach catalyst is pyrazine itself or a pyrazine substituted by methyl, ethyl and/or carboxylic acid groups, such as 2-methylpyrazine, 2-ethylpyrazine, 2,3-, or 2,6-dimethylpyrazine, pyrazinecarboxylic acid, pyrazine-2,3-, -2,5- or 2,6 dicarboxylic acid or 2,3-dimethyl pyrazine-5,6-dicarboxylic acid.

5. A process according to any one of claims 1 to 4 wherein the silver dye bleach solution comprises the silver dye bleach catalyst, a strong acid and, as the silver halide complexing agent, an alkali metal halide.

6. A process according to claim 5 wherein the strong acid is sulphamic acid.

7. A process according to any one of claims 1 to 6 wherein the compound of formula I is a azo-tricyclic compound of formula IV, an azo-anthraquinone compound of formula XXII, an azo-phthalocyanine compound of formula XXXIX, an azo-azo compound of formula XLVI, a compound of formula LX, a compound of formula LXI, an amino-tricyclic compound of formula LXIII, an amino-tricyclic compound of formula LXII or an azo compound of formula LXXVI.

8. A process for the reproduction of a silver image in photographic material substantially as hereinbefore described with reference to the foregoing example.