CA1184055A - Photographic material comprising a timing layer including a cross-linked copolymer - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Timing layers of reduced permeability for alkali are prepared by casting a dispersion of a cross-linked copolymer of formula I in an organic solvent. Such barrier layers are useful in photographic materials for the dye diffusion transfer process, e.g. if used in combination with an acid polymer layer as a so-called neutralization system.

(-S-)x (-M-)y (-V-)z (I) in which S represents polymerized units of monomers containing carboxylic acid, sulphonic acid or phosphonic acid groups M represents polymerized units of monomers free from acid groups V represents polymerized units of cross-linking monomers x,y,z represent the percentage contents of the polymerized monomers as follows x = 2 to 15 mole %
y - 75 to 97.5 mole %
z = 0.5 to 10 mole %.

Description

This invention relates to a photographic material for the dye diffusion transfer process comprising a timing or temporary barrier layer which consists of a cross-linked copolymer applied in the form of a dispersion in an organic solvent.
It is known that intermediate layers may be used in multilayer photographic materials, particularly in photo-sensitive color photographic recording materials~ in order to keep the various developing processes taking place in the various layers spatially separate from one another. Intermediate layers of the type in question are generally layers of a hydrophilic binder, particularly gelatin, which is permeable to the developer alkali.
It is also known that intermediate layers having a timing or temporary barrier effect may be used in photographic materials to enable the developing processes taking place in the various layers to be dif`ferentiated as a function of time. Layers of this type only become permeable to diffusing aqueous alkali after a certain delay. Temporary barrier layers of the type in question are particularly important in color photographic recording materials for the dye diffusion transfer process which contain as the color providing compounds, for example so-called "dye developers" which are characterized by a certain mobility in the alkaline developer medium and are only immobllized image-wise at those places where development takes place, In addition, auxiliary layers having a timing or tempor-ary barrier effect with respect of aqueous alkali are used in combination with a layer containing an acid polymer in the form of a so-called "neutralization system". After the necessary develop-.~

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ment time, the acid polymer layer reduces to pH in the photo~raphicmaterial to be developed to a lower value at which development is effectively interrupted. The temporary barrier layer delays reduction o~ the pH to a certain extenk so that -la-development is not prematurely terminated. The use of temporary barrier layers in combination wlth an acid polymer layer as a so-called "neutralization system"
is known, for e~ample, from US Patent Nos. 2,584,030;

2,607,685; 3,419,389; 3,4~3,633; 3,362,819; 4,088,493 and 4,138,260 and from ~erman Offenleg-ungsschrift No.
2,716,505 In cases where non-diffusing color providing compounds whlch only release di~fusible dyes image-wise in consequence of development are used, it is particularly important, i~ an adequate color density is to be obtained in the transfer image, for the initial high pH required for development to be kept virtually unchanged for a certain time and then to be reduced as quickly as possible to such an extent that development of the silver halide is stopped and any subsequent diffusion of diffusible dyes is effectively prevented. Barrier layers having such a temporary barrier effect are known, for e~ample, ~rom German 0-ffenlegungsschrift No. 2,716,505 and Research Disclosure No. 18 452 (August, 1979). One o~
the hi-therto unsatisfactorily solved problems of using the temporary barrier layer according to German Offenlegungs-schrift No. 2,7:l6,505, ~hich is applied in the form o-f an aqueous dispersion (latex) to the acid polymer layer cast from organic solvent and, in principle, shows the required barrier behaviour with an activation energy for penetration by aqueous alkaline solutions o:E greater than 1~ kcal per mole, is that they only form a layer oE unsatisfactory quali-ty on the acid polymer layer. This drawback may be

3 overcome, for e~ample, by arranging be-tween the temporary barrier layer and the acid polymer layer another temporary barrier layer applied ~rom organic solution with an activa~
tion energy for penetration by aqueous alkaline solutions of less than 18 kcal per mole. By contrast, the temporary barrier layer ac^ording to Research Disclosure No. 18 452 is cast from organic phase so that there are no problems 3s~

regarding adhesion to the acid polymer layer. In this case, however, a second polymer component has to be added to obtain khe required barrier effect.
The present invention seeks to provide a photographic material for the dye diffusion transfer process comprising a timing or temporary barrier layer applied from an organic phase which shows the required temporary barrier behaviour (maintenance o:~ a high pH for a certain time, followed by a rapid reduction in the pH) and yet is simple in composition. According to the present invention, barrier layers of this type may be produced using cross-linked polymers having the composition indicated hereinafter which are applied in the form of a dispersion in an organic solvent.
According to the present invention, a photographic material for the dye diffusion transfer process comprising at least one timing layer arranged between two alkali-permeable layers is characterized in that the temporary barrier layer consists of a copolymer applied in the form of a dispersion in an organic solvent and corresponding to the following general formula:

(~S~)x (-M-)y (-V-)z (I) wherein S represents polymerized monomer of at least one monomer containing one copolymerizable ethylenically unsaturated residue and at least one carboxylic acid, sulphonic acid or phosphonic acid group;
M represents polymerized units of at least one acid group-free monomer containing one copolymerizable ethylenically unsaturated radical;
V represents polymerized units of at least one monomer containing , . . ~

at least two copolymerizable ethylenically unsaturated radicals;
this monomer is referred to hereinafter as the cross-linking compound; and x, y and z represent the percentage contents of the poly--3a-merised monomers in the copolymer (in mole percent):
x = 2 to 15 mole percent y = 75 to 97.5 mole percent z = 0.5 to lO mole percent.
Examples of monomers S are acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, maleic acid, itaconic acid, acrylamidoglycolic acid, 2~acrylamido-2-methyl propane sulfo~l~ acid, sulfoethyl acrylate, vinyl phosphonic acid and vinyl sulfonic acid.
Examples of mo~omers ~ are compounds which contain a single add~tion-polymerizable ethylenic double bond, such as acrylates, acrylamides 7 methacrylatbs~ methacrylamides, allyl compounds, vinyl esters, crotonates, styrenes and (me-th)acrylonitrile. Examples of acrylates are alkyl acry~
lates, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate J amyl acrylate, 2-ethyl hexyl acrylate, octyl acrylate, -tertO-octyl acrylate, chloroethyl acrylate, 2,2-dimethyl hydroxypropyl acrylate, 5-hydroxy pent~ acrylate, trimethylol propane monoacrylate 9 pentaerythritol monoacrylate, glycidyl acrylate, also ben~yl acrylate, methoxy benzyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate and aryl acrylates, such as phenyl acrylate. Examples of methacr~lates are alkyl methacrylates, such as methyl methacrylate, ethyl meth-acrylate, propyl methacrylate, isopropyl meth~crylate,butyl methacrylate, amyl methacrylate, he~yl methacrylate, octyl methacrylate, 4~hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate, 2,2-dimethyl-3-hydroxypropyl methacrylate, trimethylolpropane monomethacrylate, 3 pentaerythritol monomethacrylate, glycidyl methacryla-te, also cyclohexyl methacrylate, benzyl me-thacrylate, chlorobenzyl methacrylate, furfuryl methacrylate and tetrahydrofurfuryl methacrylate as well as aryl methacrylates, such as phenyl methacrylate, cresyl methacrylate and naphthyl methacrylate. Examples of acrylamides are acrylamide itself or N~monoalkyl- or N,N-dialkyl--- s acrylamides in which the alkyl group(s) is (are), foY
e~ample (a) methyl 9 ethyl, propyl, butyl, -t~butyl, heptyl, octyl, cycloheYyl, benzyl or pentyl group(s), ~or example dimethyl acrylamide, N,~-dibutyl acrylamide, hydroxyethyl-acxylamide, N-monoaryl acrylamides in which -the aryl group is, for example, a phenyl, tolyl or naphthyl group and N-hydroYyaryl acrylamides, such as hydroxyphenyl acrylamide and mixed N-alkyl-N-aryl acrylamides, for example N-methyl-N~phenyl acrylamide. Examples of meth-acrylamides are methacrylamide itself or N-monoalkyl- or N,N dial~yl-methacrylamides of which the alkyl ~roup(s) is (are), for exa~ple, (a) methyl, ethyl, t butyl, 2-ethyl he yl group(s), for example methyl methacrylamide, hydro~yethyl methacrylamide, dimethyl methacrylamide, dibutyl methacrylamide and cyclohe~yl methacrylamide 9 N-aryl methacrylamides in which the aryl group is, for example, a phenyl group, also N-hydroxyethyl-N-methyl methacrylamide, N-methyl-N-phenyl methacrylamide and Ncethyl-N-phenyl methacrylamide. ~xamples of allyl compounds are allyl esters, such as allyl acetate, allyl caproate, allyl caprylate, allyl acetoacetate, allyl laurate, allyl palmitate, allyl stearate, allyl benzoate and allyl lactate, as well as allyl cyanide and allyloYy ethanol. Examples of vinyI ethers are alkyl vinyl ethers, such as he~Yyl vinyI ether, octyl vinyl ether, decyl vinyl ether, 2-ethyl he~Yyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether, 1 methyl-2,2-dimethyl propyl vinyl ether, 2-ethylbutyl vinyl ether, hydroxyethyl vinyl ether, vinyl methyl ether, diethylene glycol vinyl ether, dimethylaminoe-thyl vinyl ether, butylaminoethyl vinyl ether, diethylaminoethyl vinyl ether, benzyl vinyl ether and tetrahydrofurfuryl vinyl ether; vinyl aryl ethers, such as vinyl phenyl ether, vinyl tolyl ethcr, vinyl chlorophenyl ether, vinyl-2,~-~5 dichlorophenyl ether, vinyl naphthyl ether and vinylanthranyl ether. Examples o~ vinyl esters are vinyl acetate, vinyl butyrate, vinyl isobutyrate, vinyl trimethyl acetate, vinyl valerate, vinyl caproate, vinyl chloro-acetate, vinyl dichloroacetate, vinyl methoxy acetate, vinyl butoxy acetate, vinyl phenyl acetate, vinyl acetoacetate, vinyl lactate, vinyl propionate, vinyl-~-phenyl butyrate, vinyl benzoate, vinyl salicylate, vinyl chlorobenzoate, vinyl tetrachlorobenzoate and vinyl naphthoate. Examples o~ styrenes are styrene itself and also alkyl styrenes, ~or example p-methyl styrene, o~
methyl styrene, 2,4~dimethyl styrene, trimethyl styrene, ~-butyl styrene, ~-hexyl styrene, a-methyl styrene, decyl ; styrene, chloromethyl styrene, trifluoromethyl styrene, etho~ymethyl styrene and acetoxy methyl styrene; alkoxy styrenes, such as ~-methoxy styrene, 4-methoxy-3-methyl styrene and dimethoxy styrene; halogen styrenes, Yor example ~-chlorostyrene, tetrachlorostyrene, pentachloro~
styrene, ~bro~ostyrene, 2,4 dibromostyrene, iluorostyrene, iodostyrene, triiluorostyrene, 2 bromo-4 trii~luoromethyl styrene and l~-fluoro-3-tri~luro-methyl styrene~
Pre~erred cross-linking compounds (monomers V) correspond to general formula (II) below:

(C~2= C)n~Rl (II) wherein n represents an integer greater than 1, pre~erably 2, 3 or ~;
Rl represents an organic radical having n bonds; and R2 represents a hydrogen atom or a methyl radical;
Rl may be, ior example, an organic radical having two or more bonds made up of alkylene, arylene, aralkylene~
cycloalkylene groups (or, in the case o~ radicals containing more bonds, o-i ~he corresponding multiple-bond analogues of these groups), also o~ ester, suIfonyl ester, amide, sulfonamide groups, ether oxygen and thioether sul~ur atoms, as well as combinations oi the groups and atoms mentioned. Rl may ~e, for e~ample, a methylene, ethylene, trimethylene, phenylène, phenylene dioxycarbonyl, I~4~-isopropylidene bis-phenyleneoxycarbonyl, methyleneoxy-carbonyl, ethylene dio~ycarbonyl, 1,2,3-propane-tri~yl-tris(oxycarbonyl),.cyclohexylene-bis (methyleneoxycarbonyl), ethylene-bis (oxyethyleneoxycarbonyl) or ethylidyne trioxy-carbonyl group.
The following are examples of suitable cross-lin~ing - compounds (monomers V): divinyl benzene; allyl acrylate;
allyl methacylate; N-allyl methacrylamide; 4,4'-isopropyli-dene diphenyl diacrylate; 1,3-butylene diacrylate; 1,3-butylene dimethacrylate; 1,4-cyclohexylene dimethylene dimethacrylate; diethylene glycol dimethacrylate;
diisopropylene glycol dimethacrylate; ethylene diacrylate;
e~hylene aimethacrylate; ethylidene diacrylate; 1,6-diacrylamidohexane, 1,6-hexamethylene diacrylate; 1-6, hexamethylene climethacrylate; N,N~-~ethylene-bis-acryla~ide;
neopentyl glycol dimethacrylate; tetra-ethylene glycol dimethacrylate; tetrame-thylene diacrylate; tetramethylene dimethacrylate; 2,2,2-trichloroethylidene dimethacrylate;
triethylene glycol diacrylate; triethylene glycol dimeth-acrylate; ethylidyne trimethacrylate; 1,2,3-propanetriyl triacrylate; vinyl methacrylate; 1,2,4-trivinyl cyclohexane and tetra-allyloxyethane.
Particularly ad~antageous cross-linking compouncls are trivinyl cyclohexane, divinyl benzene, tetra-allyloxyethane, l,L~-butylene dimethacrylate. Two or more of the above-3 mentioned monomers V may also be used alongside oneanother for the production o~ the copolymers according to the present invention.
Some copolymers typical o~ the present invention are shown below (copolymers 1 to Co~ol~mer 1:

~CH2-C~I~o 429 (CH2,~ )0 ,~C~I2 , )O, 093 ~014 CC4H9 ~ COOH ~ 1 \/\ CH-CH2 CH2-Cju ,' ``~

C op o lyme r 2:

~CH2-cH~cH2-cH3o- 4-36-~cH2-c,E)0~o95(cEI2~H3~o35 COOC4E9 ~ COOH ~CH-CH2 C op o lyme r 3: C OOH

~CH 2 -CH ) o 3 5 1 ( C~I 2 C~ ~CH 2 -C ) o 0 21 ( CH 2,~H~, 0 3 6 COOC2H5 CN C~H2 ~Q~
COOH ~
f~H-C~I2 `~
C op o 1~7mer 4:
C~H3 ~CH2-c=c-c~I2)o--3~l(c~I2-c1~o~39-(cFL2 ~ ~~ ? 2 o,o~6 ClCl COOC4Hg CO C?O
O O
C?H2 (CH2)6 C, H 2 ?O

CH-CH~, ,~ ~

(does not correspond to the present invention;
comparison).

4 ~ H2 CH)o~~og4~CH2 C~ ~,470 COOC4Hg COOH ~
.

The polymers used in accordance with the present invention may be produced by conventional emulsion polymerization processes, for example by the emulsion ~oIymerization of a monoethylenically unsa-turated monomer ! S with a polyunsaturated monomer V, (cross linki~g compound) and a monoethylenically unsaturated monomer M, preferably in the presence of an anionic sur~ace-active compound~ for e~ample sodium lauryl sulfate or in the presence o~ the sodium salt of sulfonated condensate of an alkyl phenol/ethylene oxide condensate (for example "Alipal", a product o~ General Dyestuff Corp , U.S.A,) and the like and preferably in the presence of a radical-former or radical initiator, for example in the presence o~ an initiator which forms ~ree radicals of the redo2 type, for egample in the presence of potassium persulfate-sodium metabisulfite; potassium persulfate~
Fe2+; H~02-Fe2~ and the like. Processes of the type described in US Patent No. 3,072,588, ~or e~ample~ may be used.
The copolymers may be isolated from the aqueous dispersion in the conve~tional way by flocculation and filtration or by concentrating the dispersion by evaporation.
~0 Flocculation may be carried our, for e~ample, by adding acids, salts, water-miscible solvents or by low~temperature coagulation. The copolymer precipitates as a separate phase and may be separated o~f and dried.
According to the present invention, the thus-produced copolymers are applied in the form of a dispersion in organic solvents to form temporary barrier layers Dispersions

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- 10 ~-of the type in question are readily obtained by mi~ing the copolymers with organic solvents, preferably solvents having a swelling effect on the copolymer. Solvents of the type in question may be used either individually or even in the form of a mixture of several solvents, the choice of suitable solvents depending upon the composition of the copolymers. In many cases, polar solvents, such as dimethyl formamide, dimethyl sulfoxide, acetone, methyl ethyl ketone, tetrahydrofuran and dioxane are sui-table.
Redispersion of the copolymers according to the present invention gives organic particulate dispersions. This is evidently crucially important so far as the required barrier effect is concerned. 5urprisingly, uncross-linked copolymers which are dissolved in the organic solvents to form a clear solution cannot be processed into usable te~porary barrier layers. The particle size o~ the copolymers according to the present invention in the organic disper sions is generally from 40 to 500 nm.
According to the present invention9 the present temporary barrier layers are produced by cas-ting the above-described cross-linked copolymers in the ~orm o~ dispersions in the above-men`tioned organic solvents~ the dispersions drying to give clear layers. The thickness of the temporary barrier layers according to the present invention depends upon the req-uired barrier effect and in particular upon the barrier time, i.e. in appro~imate -terms the period of time for which the high p~I required for development remains virtually unchanged. In general, the temporary barrier layers according to the present invention are 3 from 0.5 to 10 ,um in thickness.
It has been ~ound that the thus-produced temporary barrier layers may be cast wi-thout difficulty, particularly when they are directly applied to an acid polymer layer to form the neutralization system therewith. In addition, the temporary barrier layers according to the present invention show the required temporary barrier effect with respect AG 1?29 to aqueous alkali. The temperature gradient of the barrier effect with respect to aqueous alkali may be adjusted as required within wide limits by changing the monomer ratio and the degree of cross-linking.
The following test may be used for determining suitable temporary barrier layers:
A layer support of polyethylene terephthalate is first coated with a polymeric acid layer of, for example, a copolymer of 70 parts, by weight, of acrylic acid and 30 parts, by weight, of butyl acrylate from organic solution and driedA The temporary barrier layer to be tested is then applied in the form of a dispersion in an organic solvent and likewise dried. The thus-obtained test sheet is then brought into contact on its layer side with an uncoated transparent polyethylene tereph~halate film as cover sheet via two laterally arranged spacer strips 130 ~m thick, a viscous alkali solution containing a pH-indicator being distributed between the two sheets in known manner by means of two squeezing rollers. The alkaline indicator solution may have the following composition, for example:
5 g of KOH, 3.5 g of hydroxy ethyl cellulose, for example "Natrosol HH~ , a product of the Hercules Company, 0.1 g of thymol phthalein, made up with water to 100 ml.
After a certain barrier time, the color disappears from the paste layer quickly and spontaneously. The average period of ~Trade Mark s~

time which elapses between the beginning and end of the paste decolorization process is called the "DT-value" (DT = decoloration time) measured in minutes. The temperature gradient of the barrier effect of the temporary barrier layer to be tested may be determined from the difference in the DT-values measured at different temperatures. A measure of the necessary temperature gradient is the so-called "activation energy" Ea. It may be determined in kcal per mole from the straight part of a -lla-curve in which the DT values observed are logarithmically recordecl in dependence upon the reciprocal temperature using the following equation Ea = 0.00458 T2 Tl Barrier layers having a faYourable -temporary barrier effect are characterised by an activation energy of from 15 to 30 kcal per mole.
The temporary barrier layer acco~ding to the present invention may be used in various ways in color photographic materials. For example, they may be used between two photosensitive silver halide emulsion layers in order during development to enable the development processes taking place in the two silver halide emulsion layers to be differentiated as a function of time. This embodiment merits particular consideration, for e~ample, when 90-call2d "dye developers" are used as ~he color-prcviding cOmpOUnd9. A9 iS known, these are compounds which are mobile in aqueous-alkaline medium and which are immobilized image-wise in consequence of development They contain in the same molecule a chromphoric residue which is responsible `. for image colo~- and a developer function which is used for image wise immobilization. By virtue of the presence of the developer function which is a reactive group, the developer clyes are capable of reacting as they diifuse through non-as~ociated silver halide emulsion layers, of which the development is not ye-t complete, and of being immobilized there as well, which results in a displacement of the color equilibrium in the transfer image. By means of the temporary barrier layers according -to the present invention, it is possible to ensure that, in certain silver halide emulsion layers, the high pH required for develop ment is only adjusted after the development process in ~ . _ other sil~er halide emulsion layers lying in the di~fusion path of the non-immobilised dye developers is substantially complete.
In addition, temporary barrier layers of the -type in question may have embedded in them pho-tographically active compounds, such as inhibitors for the development of silver halide which are only released on abatement of the barrier effect, i.e. after a certain delay.
In another particularly preferred application according to the present invention, the temporary barrier layers are ,, combined with so called "acid polymer layers" to form a combined neutralization systemO Such a combined neutraliz-ation system may be arranged, for e~ample, on a separate image receiving sheet for the dye diffusion transfer process providing the image-receiving sheet and the photosensitive material are to be separated after development. An image-receiving sheet of -the type in question comprises, for e~ample on a transparent or opaque layer support, an image-receiving layer in addition to the combined neutralization s~stem consisting of the acid ~olymer layer and the temporary barrier layer according to the present invention. The combinedneutralization c;ystem is preferably arranged between the layer support and the image-receiving layer in such a way ( that the temporary barrier layer according to the present invention faces the image receiving layer~ Naturally such an image-receiving sheet does not itself contain any photosensitive layers.
However, the preferred and main application of the temporary barrier layer according to the present invention 3 is its use in dye diffusion -transfer materials of the integral type, i.e. in so-called "one-sheet ma-terials", where there is no separation between the image-receiving element and the photosensitive elementO A ~olo~ photo-graphic material of this type comprises the following layer elements for example:

(l) a transparent layer support, (2) an image-receiving layer, (~ an opaque light re:Elect~ng layer ~image ~ac3cground layer), (4) a photosensitive element containing at least one photosensitive silver halide emulsion layer and at least one color-providing compouncl associated there-with, (5) a retarding layer (temporary barrier layer),

(6) an acid poly~er layer5

(7) a transparent layer support.
The integral recording material may be made up by ; producing two di~ierent parts separatley from one another, namely the photo~sitive par-t (layer elements (l) to ~4)) and the cover sheet (layer elements (5) to (7)), which are then placed with the layer sides thereof on top of one another ancl joined together, optionally using spacer strips, so -that a space is formed between the two parts for accommodating an e~actly measured quantity of a working fluid~ The layer elements (~) and (6), which -together form the neutralization system may also be arranged, but in the opposite sequence, between the layer support and the image-receiving layer of the photosensitive part, Means may be provided eOr in-troducing a working ~luid between two adjacent layers of the integral recording material, for example in the form o~ a laterally arranged con-tainer which, under the effect of mechanical forces, is designed to split open to distribute its contents between two adjacent layers O:e the material, in the presen-t case between the photosensitive part and the cover sheet.
After d~velopment is substantially complete, the acid polymer layer (layer element (6)) reduces the initia].ly high pH in the recording material in known mamler to a lower value at which there is virtually no further diffusion of dye. The time at which the pH i9 lowered and hence the end Oe develspment is controlled by the barrier layer according to the present invention (layer elemen-t (5)) in .

dependence upon the development temperatureO
As is known, an acid polymer layer is understood to be a binder layer which con-tains polymeric compounds containing acid groups, preferably s~lfo or carboxyl groups. These acid groups react with the cations of the processing flwid to ~orm salts and, in doing so, reduce its pH. The polymeric compound and hence the acld groups are of course incorporated in the above~mentioned layer in dif-fusion-resistant form. The acid polymers are ~requently derivatives o-f cellulose or ~lerivatives o~
polyvinyl compounds, although other polymeric compounds may also be used. Suitable acid polymers are, ~or example, cellulose derivatives containing a ~ree carboxyl group, ~or example cellulose dicarbo~ylic acid semi-esters containing a free carbo~xyl group, such as cellulose acetate hydrogen phthalate, cellulose acetate hydrogen glutarate, ethyl cellulose acetate hydrogen succinate, cellulose acetate hydrogen succinate hydrogen phthalateS ethers and esters o~ cellulose mo~ified with other dicarbogylic acid anhydrides or with sulfonic acid anhydrides, for example with sulfobenzoic acid anhydride, carbo~y methyl cellulose, also polystyrene sulonic acid, polyvinyl hydrogen phthalate9 polyvinyl acetate hydrogen phthalate, polyacrylic acid, optionally partly esterified, acetals o~ polyvinyl alcohol with aldehydes substituted by carbo~y or sulfo groups, such as o-, m- or ~-benzaldehyde sul~onlc acid or carboxylic acid, partially esteri~ied ethylene-maleic acid anhydride copolymers, partly esteri~ied methyl vinyl ether-maleic acid anhydride copolymers. The acid polymer layers may be applied from organic solu-tion or in the form of aqueous 3 dispersions. The acid polymer layer must contain enough acid groups to reduce -the pH of the processing composition from its initial level o~ from 11 to 14 to such an e~tent that, ultimately, the material is either substantially neutral or mildly acid (pH from 5 to ~).
In the case o~ an integral recording material, the photosensitive element (layer element (4)) is an essential _ 5~

part of the photographic material according to the present invention. However, the photographic ma-terial according to the present invention may even be non-photosensitive~
for e~ample in the case of a cover sheet (cfo layer elements (5) to (7), for example) or in the case of a separate image-receiving sheet. Such non-photosensi-tive materials are au~iliary sheets which may be brought at any time into functional contac-t with the actual photo-sensitive recording material.
In the case of a single-dye diffusion transfer process, the photosensitive element contains a photosensitive silver halide emulsion layer, and associated therewith, a color-providing compound. The dye producing compound may be situated in a layer adjacent to -the silver halide emulsion layer or in the silver halide emulsion layer itself. In the latter case, the color o-f the image dye is preferably selected in such a way that the predominant absorption range of the color-pro~iding compound does not colncide with the predominant sensitivity range of the silver halide emulsion layer To produce multi-colored transfer images in nat~ral c~lors, however, the photosensitive element contains t~ree such associations o~ color-providing compound and photosensitive silver halide emulsion layer. In general9 the absorption range of the image dye resulting ~rom the color-providing compound will largely coincide with the spectral sensitivity range of the associated silver halide emulsion layer. In that case, however, it is favourable, in the interest3 of obtaining as high a sensitivity as possible, ~or the color providing compound to be arranged in a separate binder layer (looking in the direction of the incident ligh-t during e~posure) behind the silver halide emulsion layer or to have an absorption which is different from that of -the image dye ~"displaced image dyes" - US Patent No. 39854,945).
The developer o~idation products formed during the development of a silver halide emulsion must of course AG 1?29 act only on the assoclated color~providing compound. Because o~ this, separat~ng layers are general]y present in the photosensitive element, e~fectively preventing the developer o~idation p~oducts ~rom diffusing into other, non-associated layers. These separating layers may contain, ~or example, suitable substances l~hich react with the developer o~idation products, for example non-diffusing hydroquinone derivatives or, where the developer compound is a color developer compound, non-dif~using co~or couplers.
i The colour-providing compounds may be colored compounds which are themselves capable of diffusing and which begin to diffuse when the layers are treated with an alkaline working fluid and are only fixed by development in the expo-sed pl-aces. I~owe~er, the color-providing compounds may also be resistant to diifusion and may release a diffusing dye in the course of development.
Color-providing compounds which a priorl are ca~ble of diffusion are known, ~or eYample, ~rom German Patent 20 Nos. 1,036,640; 1,111,936 and 1,196,075~ The so~called "dye developers" described therein contain, in the same molecule a dye residue and a group which is capable of developing e~posed silver halide.
Among the hitherto known processes for the production 0~ color photographic images by the dye di~iusion transfer process, increasing significance has very recently been attributed to those which are based on the use of color-providing compounds which are incorporated in non-diffusing form and frcm which diffusible dyes or dye precursor 3 products are split o~ nage-wise during development and transferred to an image-receiving layer. Non-diffusing color provi-ding ccmpounds of ~is type (so-called dye xeleasers) are described for e~ample, in the ~ollowing publications: IJS Patent Nos.
3,227,~50; 3,44~,939 and 3,443,940; German Offenlegungs 35 schr~t Nos 1,930,215; 2,242,762; 2,402,900; 2,406,664;
2,505,248; 2,543,902; 2,613,005; 2,645t656 and 2,809,716;

- 18 ~

Belgian Patent No 861,~41.
These publicatlons describe both non~cliffusiny colo~-providing compounds of the type which produce negative dye images where conventional negative 9 ilver halide emulsions are used and al~o those of the type which produce positive dye image 9 where negative silver halide emulsions are used. In the first case, it is necessary, if positive dye images are required, either to use direct-positive silver halide emulsions or, where negative emulsions are used, to adopt one of the known reversal processes, for e~ample the silver salt difiusion process (US Patent No.
2,763,800) or by using compounds which release development inhibitors as a result of development.
In addition, in one particular embodiment, the photographic material according to the present invention, particularly when it is of the integral type, may contain one or more pigment-containing opaque layers which are permeable to aqueous liquids. These layers may perform two functions. On the one hand, they may prevent the undesirable accessoi light to photosensitive layers and, on the other hand, a pigment layer o-f the type in question ma~ form an aesthetically pleasan-t background for the dye image produced, particularly ~hen a light or white pigment, for e~ample TiO2, is used.
Integral color photographic recording materials containing a pigment layer of the type in question are known, ior e~ample, from US Patent No. ~,543,181 and German Auslegeschrift No. 1,924,430. Instead of using a preformed opaque layer, it is also posslble to provide means to enable such a layer to be formed in the course 3 o~ development. According to the two iunctions mentioned above, pigment layers of the type in question may be made up of two or more partial layers oi which one contains, for e~ample, a white pigment and the other, for e~ample, a dar~, light-absorbing pigment, for e~ample carbon black.

~9 The image-receiving layer (for e:~ample layer element (2)) consists essentially of a binder containing dye mordants for fixing the dif:Eusible acid dyes~ Preferred mordants for acid dyes are long-chain quaternary ammonium or phosphonium compounds or tertiary sulfonium compounds, for e~ample those of the type described in US Patent NosO
3,271,147 and 3,271,148. It is also possible to use certain metal salts and the hydroxides thereof which form substantially insoluble compounds with the acid dyes. In the receiving layer, the dye mordants are dispersed in one of the conventional hydrophilic binders, for example in gelatin9 polyvi~lyl pyrrolidone, completely or partially hydrolysed cellulose esters. Some binders may of course also function as mordants, for e~ample copolymers or polymer mixtures of vinyl alcohol and N-vinyl pyrrolidone of the type described, for example, in German Auslegeschrift No. 1,130,284, also those of the type which are formed by polymers of nitrogen-containing quaternary bases, for example polymers o~ N-methyl-2-vinyl pyridine, as described fo:r example, in US Patent No. 2,484,430.
Other suitable mordant bin~ers are, for example, guanyl hydrazone derivatives of alkyl vinyl ketone polymers, OI the type descri~ed, for example, in US Patent 2~o.
2,882,156, or guanyl hydrazone derivatives of acyl styrene polymers, of the type described, for example, in German Offenlegungsschrift No. 2,009,498. In general, however, other binders, for e:~ample gelatin, will be aclded to the last of the above mentionecl mordant binclers.
EIY~MP LES 1 to 5 -(Production of copolym~rs 1 to 5) Copolymer l A solution of 1 kg of water, 80 g of a 10% alkyl diphenyl ether disulfonate solution and 4 g of potassium peroxodisulphate is heated to 60C while nitrogen is passed thro-ugh. A mixture of 196 g of butyl acryla-te, 24 g of acrylic acid, ~ g of 1,2,4-trivinylcyclohexane, 172 g of AG 172_ ~ o styrene and a solution of 4 g of sodium met~hisulfite in 50 g of water are then simultaneously added dropwise over a period of 3 hours. After stirring ~or another 4 hours at 600C, a latex having a solids content o~ 12. 2% i9 obtained~
290 g of concentrated hydrochloric acid are added -to the latex obtained. The copolymer precipitated is filtered off, dried and redisper~ed in 4 kg of methyl ethyl ketone. Minor non-redispersed fractions are remo~ed from the organic dispersion by filtration.
Copolymer 2 Copolymer 2 is produced in the same way as described in E~ample 1. A mixture oi 196 g oi butyl acrylate, 24 g of acrylic acid, 200 g of styrene and 20 g oi trivinyl cyclohexane is used as monomer.

Copolymer 3 i9 produced in the same way as described in E~ample 1. A monomer mixture of 15 g o~ itaconic acid, 25 g o-f di~inyl benzene, 170 g of acrylonitrile a~d 190 g oi ethyl acrylate is used.
Copolymer 4 Copolymer 4 is produced by the method described in Example 1. A monomer mi~ture of 35 g of carboxy ethyl acrylate, 30 g of he~ane diol diacrylate, 135 g of 2,3-dichl~robutadiene and 200 g of butyl methacryla-te i9 u3ed.

(does not correspond to the present invention) Copolymer 5 is produced in the same way as described in Example 1 using a monomer mixture of 200 g of butyl 3 acrylate, 24.4 g of acrylic acid and 175.5 g of styrene.
E~AMPLE 6 A copolymer o~ 70 parts, by weight, of acrylic acid and 30 parts, by weight, of butyl acrylate is applied from methanolic sol-ution to a layer support of polyethylene terephthalate to give a coating of 15 g/m2.
Copolymer 2 according to the present inven-tion was 55.
~ 21 -then cast in -the form of a dispersion in methyl ethyl ketone to gi~e a coating of 6 5 g/m .
A 10 ~1 drop of lN KOH is applied to the test sheet .
thus-produced, a pH-surface electrode (Ingold type HA 403) is attached and the pH~reduction curve is recorded by a connected x/y-recorder (Figure 1, curve 1). The curve shows a distinct klnk after a barrier time of 2 minutes and then falls away steeply.
COMPARISON E~ IPLE
If the uncrosslinked copolymer 59 which, apart from the missing monomer V, has virtually the same monomer ratio as the above copolymer 2, is cast as described above onto the acid polymer layer and i~ the pH-reduction is recorded under the same measuring conditions, a much flatter pH-reduction curve is obtained with no pronounced barrier time and no sharp kink (Figure 1, curve 3).
When processed with integral photosensitive elements, of the type used as instant-picture materials, for example in accordance with German O~fenlegungsschrift No. 2,652,464, Example 19, cover sheets having a flat pEI reduction like this give color images with much higher minimal densities, i e. higher color fogging in the white areas of the image, which seriously impairs the quality of the image.
( EXAMPLE 7 Longer barrier times are obtained, for e~ample, by using copolymers having a lower degree of cross-linking (the monomer ratio ~I/S may be retained).
If a barrier layer consisting o~ the more weakly cross-linked copolymer 1 is prepared in the same way as described in E~ample 1 and cast directly onto the acid polymer layer, barrier layers characterized by a much longer barrier -time are obtained, even with considerably reduced layer thicknesses. 'rhus, a layer thickness o~
1.4 g/m2 gives a barrier time of 8.2 minutes (figure 1, curve 2).

I~yers containing copolymer 3 cast in the form of a dispersion in an organic solven-t shows similar barrier behaviour with respect to alkaliO I~ copolymer 3 is cast in a thickness of 3,5 g/m2 onto an acid polymer layer according to Example 6 and if the barrier e~fect oi this layer is tested with lN KOH in the same way as described above uslng a pH-surface electrode, a barrier time of 4.2 minutes and a steep reduction in pH are observed (Figure 1, curve 4).

____.
(A) The photosensitive part A of a photographic film unit was produced by successiv~e~ly applying the following layers to 150 ~m thick transparent support of polyester film.
The quantities indicated are each based on 1 square metre.
The structural formulae oi compounds (I) to (I~) are shown in the attached supplement.
ordant layer of 2.7 g oi a polymeric mordant of copoly-(styrene-NrN-dimethyl-N-benzyl-methacrylamidobenzylammoniumchlroide divinylbenzene), molar ratio 49:49:2; 2.7 g of gelatin.
2. A white pigment layer of 18 g of titanium dio~ide; 2.6 g o~ gelatin.
3. A black pigment layer of 1.9 a of carbon black; 2.1 g of gelatin.-4. A cyan dye layer of 0,35 g oi compound I; 0.35 g of gelatin.
5, A red~sensitized silver halide emulsion layer containing a non-fogged, direct-positive silver chloride bromide emulsion oi l.OS g of silver (0.01 mole); 1~42 g of gelatin;
0.19 g of the potassium salt of sec-octadecyl hydro-quinone sulfonic acid; 0.025 mg oi l-p~formyl hydrazinophenyl-3-phenyl-2-thiourea; 0.25 mg of 2 mercapto~5- sulfobenzimidazole.

35~
- 23 ~

6. ~n intermediate layer of 0,5 g of 2-acetyl-5-sec octadecyl hydroquinone~ 0.75 g of gelatin.
7. A magenta dye la~er of 0.45 g of compound II; 0.45 g oe gelatin.

8. ~ green-sensitised silver halide emulsion layer containing a non-fogged~ direct positive silver chloride bromide emulsion of 1.08 g of silver~ 1.42 g o~ gelatin; 0,19 g of the potassium salt of sec-octadecyl hydroquinone sulfonic acid; 0.03 mg of l-~formyl hydrazinophenyl-3 phenyl-2-thiourea; 0.25 mg of 2-mercapto-5-sulfobenzimidazole.

9. An intermediate layer identical with layer No, 6,

10, A yellow dye layer of 0.62 g of compound III; 0.62 g of gelatin,

11. ~ blue-sensitive silver halide emulsion layer containing a non-fogged, direct-positive silver chloride bromide emulsion of 1.08 g Oe silver; 1.42 g o~ gelatin; 0.08 mg o~ 1-p-formyl hydra~inophenyl-3-phenyl-2-thiourea; 0.19 g of the potassium salt of sec-octadecyl hydroquinone sulphonic acid; 0.125 mg of 2-mercapto-5_sulfobenz-imidazole.

12, A protective layer o~
o.6 g of gelatin.

13. A hardening layer of o.o6 g of the hardener compound (IV); 0.6 g o~ gelatin.
(B) The co~er~ sheet B containing the neutralization element consisting of an acid polymer layeranda temporary barrier layer according to the present invention was produced by successively applying the following two layers to a 100 ~lm thick transparent support of polyester film:
1. ~ neutrali~ation layer of 17 g o-~ copolymer of 70 parts of acrylic acid and 30 parts of butyl acrylate (c~. French Patent No. 2~290,699).

2. A temporary barrier layer of 0.9 g of copolymer 1 dispersed in methyl ethyl ketone.
(C) A cover sheet C which, instead of copolymer 1, contained the uncross-linked copolymer 5 in a thickness of o 7 g/m2 as the temporary barrier layer was used for comparison.
One sheet each of the photosensitive part A and the cover sheet B and of the comparison cover sheet C were applied to one another with the layer side thereof with two laterally arranged spacer strips 100 ~m thick in between, a bag filled with developer paste being arranged at one end and a trap for surplus developer being arranged at the other end. The thus-formed set was exposed through an original (grey wedge and color separation) and sub-sequently passed through a pair of squeezing rollers, the developer paste being distributed between the photosensitive part and the cover sheet. The developer paste had the following composition:
743 g of H2O
160 g of carbon black ("Printex 200"*, a Degussa product) 1.6 g Of Na2SO3 sicc.
2.75 g of 5-mercaptobenztriazole 8 . 4 g of 2,2-hydroxyme~hyl-methyl-phenidone 0.3 g of tert.-butyl hydroquinone 0.2 g of methyl hydroquinone 1.0 g of cyclohexanol g of carboxy methyl cellulose 47 g of KOH
5.2 g of potassium fluoride After the development time, a positive image of the s~

ori~inal was visible through the transparent support on the TiO2 layer as the image background.
Much less color fogging in the white areas of the image was observed in the case of the sample containing cover sheet B
than in the case of the sample containing -24a-~. ...

cover sheet C, commensurate with the s-teeper reduction in pH ~or equ~lly good ma~imal densities.
The results are shown in Table 1 below.
Table 1 D min. D ma .
blue green red blue green red Sample containing 0045 0.43 0.32 2.11 2.13 1.91 cover sheet B

Sample containing 0.80 0~74 0.50 2.11 2.18 1.91 cover sheet C

s Formula Supplement ~O-N ~ _ (I) SO~ S02-NH N=N ~ 102 CH

~ ~ SO ~I/CH-CH3 OH \ -CH3 CO-N ~ 18 37(n) C~3H37(n) /CH3 (I~) I '502-NH--C{~EI3 =~-OH C 3 CO-N~ 1 37 (n) NH (III) S02 ~ ~,N=C ~ ~ Cl C-CH-N=N~ ) ~ (C~2)2-S039 (IV)

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a photographic material for the dye diffusion transfer process containing at least one timing layer arranged between two alkali-permeable layers the improvement according to which the timing layer consists of a cross-linked copolymer applied in the form of a dispersion in an organic solvent and corresponding to the following general formula:

(-S-)x (-M-)y (-V-)z wherein S represents polymerized monomer of at least one monomer containing one co-polmerizable ethylenically unsaturated residue and at least one carboxylic acid, sulphonic acid or phosphonic acid group;
M represents polymerized monomer units of at least one acid group-free monomer containing one copolymerizable ethylenically unsaturated residue;
V represents polymerized monomer units of at least one organic cross-linking compound selected from monomer compounds containing at least two copolymerizableethylenically unsaturated residues;
and x, y and z represent the percentage contents of the polymerized monomers in the copolymer (in mole percent):
s = 2 to 15 mole percent y =75 to 97.5 mole percent z = 0.5 to 10 mole percent

2. A photographic material as claimed in Claim 1, in which the timing layer adjoins an acid polymer layer and, together with it, forms a combined neutralization system.

3. A photographic material as claimed in Claim 2, in which the combined neutralization system is arranged on a transparent support.

4. A photographic material as claimed in Claim 1, in which the timing layer is arranged between an acid polymer layer and an image-recording layer.

5. A photographic material as claimed in Claim 1, in which the combined neutralization system consisting of the acid polymer layer and the timing layer is part of an integral color photographic recording material.