GB2056101A - Photographic dye image- receiving element - Google Patents

Abstract

As regards the mordant used in the dye image-receiving element in colour diffusion transfer processes of reproduction, a preferred mordant is a polymer of N-vinylimidazole (which may be a homopolymer, a copolymer or a blocked polymer) which has been partially quaternised, such as with 2- chloroethanol or benzyl chloride (C6H5CH2Cl). It has been observed that certain electron transfer agents useful for releasing dyes imagewise by a redox reaction are not stable in such a receiving element on storage. There is now provided a dye image- receiving material useful in a photographic colour diffusion transfer process of reproduction comprising a layer containing a polymer of N- vinylimidazole and comprising in the said layer or another layer 4- hydroxymethyl-4-methyl-1-phenyl-3- pyrazolidone or 4-hydroxymethyl-4- methyl-1-(4'-ethyl-phenyl)-3- pyrazolidone and comprising also in the same layer as said pyrazolidone, nickel sulphate, nickel chloride, nickel nitrate, manganese sulphate, cobalt sulphate, zinc sulphate or aluminium sulphate in an amount such that the storage stability of said pyrazolidone in said element is increased.

Description

SPECIFICATION Photographic dye image-receiving element This invention relates to materials which are useful in colour diffusion transfer photography and which comprise a mordant and a silver halide developing agent.

As regards the mordant used in the dye image-receiving element in colour diffusion transfer processes of reproduction, a preferred mordant is a polymer of N-vinylimidazole (which may be a homopolymer, a copolymer or a blocked polymer) which has been partially quaternised, such as with 2chloroethanol or benzyl chloride (C6H5CH2CI). Such partially quaternised N-vinylimidazole polymers are particularly described in U.K. Specification 1,468,460 and Research Disclosure 12045 (April 1974).

Dyes mordanted by these polymers tend to have good stability to light.

In some colour diffusion transfer processes of reproduction, such as the process described in U.K.

Specification 1,496,363, it is advantageous to apply the alkaline processing composition only to the exposed photosensitive element and then laminate the element to the dry image receiving element.

The process described in U.K. 1,496,363 involves the use of certain dye releasing compounds described in U.K. Specification 1,405,662 which are first oxidised by oxidised developing agent and then hydrolysed by the alkaline processing composition to release the dye. It is preferable to incorporate the developing agent in the dye image-receiving element so that development does not begin until the two elements are laminated.

The developing agent employed is one which cross-oxidises the dye-releasing compound and it is thereby converted back to its initial form in which form it is capable of further development.

Such developing agents are usually described as electron-transfer agents (ETA's). A preferred class of ETA's (useful also in cross-oxidising other dye releasing compounds) is provided by certain 1phenyl-3-pyrazolidone derivates such as 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone (HMMP).

We have experimented with the combination of poly(N-vinylimidazole) partially ( < 10%) quaternised with 2-chloroethanol and HMMP in a layer contiguous to the polymer layer and have found that the HMMP is not stable on storage.

We have found that an increase in stability can be achieved by incorporating nickel sulphate in the mordant layer or in a gelatin layer below the mordant layer, the HMMP preferably being in the same layer as the metal salt.

The concentration of the nickel sulphate in the layer is preferably at least 5 mg/ft2. Higher concentrations increase the stability of the HMMP up to a concentration of at least 50 mg/ft2, e.g. 54 mg/ft2.

Other nickel salts which improve the stability of the HMMP are nickel chloride and nickel nitrate.

These salts may be used at concentrations from 40 to 60 mg/ft2, for example. Nickel acetate appears to reduce the stability of the HMMP, however.

We have further found that divalent metal salts of manganese, cobalt or zinc also improve the stability of the HMMP associated with the mordant layer as also do trivalent salts of aluminium. These salts may be used at concentrations from 40 to 60 mg/ft2, for example. However, diva lent salts of copper or iron reduce stability, possibly due to a redox interaction between the HMMP and the readily interconvertible valence states of the metal ions or to the low redox potential of these metal salts.

Still further we have found that the stability of 4-hydroxymethyl-4-methyl-1 -(4'-ethylphenyl)-3- pyrazolidone (HMMEP) is association with the aforementioned mordant can also be increased by a nickel salt as described for HMMP.

In addition, we have found that although the above-mentioned ETA's HMMP and HMMEP are not so unstable when the mordant is an unquaternised poly(vinylimidazole), an improvement in their stabilities can still be obtained in the same way as for the partially quaternised polymers.

According to the present invention there is provided a dye image-receiving element useful in a photographic colour diffusion transfer process of reproduction comprising a layer containing a polymer of N-vinylimidazole partially quaternised with 2-chloroethanol or benzyl chloride and comprising in the said layer or another layer 4-hydroxymethyl-4-methyl-1 -phenyl-3-pyrazolidone or 4-hydroxymethyl-4 methyl-1 -(41-ethylphenyl)-3-pyrazolidone and comprising also in the same layer as said pyrazolidone, nickel sulphate, nickel chloride, nickel nitrate, manganese sulphate, cobalt sulphate, zinc sulphate or aluminium sulphate in an amount such that the storage stability of said pyrazolidone in said element is increased.

EXAMPLE 1 Two coatings A and B were prepared, of the structures set out below.

B A Layer II Layer I

Mordant (200) Mordant (200) Gelatin (200) Gelatin (200) Hardener (20) Hardener (20) Surfactant (60) Surfactant (60) NiSO4 (54) ETA (50) ETA (50) Gelatin (100) Gelatin (100) Hardener (10) Hardener (10) Surfactant (25) Surfactant (25) Support /// Support Numbers in parentheses after each component refer to the coating weight of that component in mg.ft-2 = 929cm~2. A deionised pig-skin gelatin was used in all layers.

'Surfactant' = nonylphenoxy-poly-glycidol.N-10 'Hardener' = 'Araldite' Diluent DY022, active component: butanediol-diglycidylether = BGE.

ETA = 4-methyl-4-.hydrnxymethyl- 1 -phenyl-3-pyrazolidone.

Mordant = poly(vinylimidazole) partially quaternised ( < 10%) with 2-chloroethanol A resin-coated paper support was used for each coating.

The gelatin layer I was coated and dried before applying the polymeric mordant layer ll. Each coating melt was adjusted in pH to 5.5 with dilute hydrochloric acid before coating. A 10% solution of the ETA was prepared in N2-bubbled 50% aqueous methanol and added to the requisite melts immediately prior to coating.

After two weeks hardening sample strips of both coatings were hung in an oven maintained at 1 200F and 75% RH for 3 days. Check samples were maintained in a refrigerator for this period.

Polargraphic analysis of the ETA level in the incubated and check samples gave the following results: Check Incubated Loss on Incubation A 44 mg/ft2 8 mg/ft2 82% B 47 mg/ft2 34 mg/ft2 28% The polarographic method of analysis employed a Bruker E3 10 modular pulse polarograph operated in the differential pulse mode. Polarograms were run in pH 7.0 buffer [ KH2PO4 + K2HPO4, 0.1 M total salt conc. ] scanning between~300 mv and + 100 mv (S.C.E.). Analytical solutions were prepared by cutting 3 discs (0.75 in. diameter) from each coating and leaching the E.T.A. into a known volume of buffer solution for 5 minutes. The buffer solution was deoxygenated by bubbling nitrogen through it before use, and bubbling was continued during the soak. Comparison of the polyarographic signal from the test solution with a calobration plot gave the E.T.A. concentration and hence the coating weight could be computed. The calibration plot was obtained from a series of standard solutions of the E.T.A. dissolved in deoxygenated buffer solution.

EXAMPLE 2 A second pair of coatings was prepared as for Example 1 except that the nominal E.T.A. coating weight was reduced to 30 mg/ft2. Coating C contained no NiSO4 while coating D contained 54 mg/ft2 NiSO4 in the gelatin layer I. Analysis of the E.T.A. level in incubated (2 days, 75% RH, 1 200F) and nonincubated samples gave the following results.

Check Incubated Loss on Incubation C C 25.5 mg/ft2 5.1 mg/ft2 80% D 25.2 mg/ft2 12.0 mg/ft2 52% Both Examples 1 and 2 show less ETA decomposition for the coatings containing NiSO4 in the gelatin layer layer.

EXAMPLE 3 Coatings were prepared of the general structure shown below:

Mordant (200) Hardener (10) Gelatin (200) Surfactant (60) CH2O (10) Gelatin (100) Hardener (2.5) ETA (25)' Surfactant (25) CH2O (2.5) Support Layer II Layer I Numbers in parentheses refer to the coating weight of each component in mg/ft#2. A deionised acid processed pig-skin gelatin was used throughout. The hardening effect of formaldehyde (CH2O) in each layer was reinforced by the addition of a second cross-linking agent, Hardener (= 'Araldite' diluent DYO22, in which the active component is butanediol-diglycidylether).The surfactant employed throughout was nonylphenoxy-poly-glycidol N-1 0. Mordant is poly(N-vinyiimidazole) partially (approx.

10%) quaternized with chioroethanol and ETA is 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone.

The pH of each coating melt was adjusted to 5.5 prior to coating by adding dilute hydrochloric acid. A resin-coated paper support was employed.

In addition to the coating shown three other coatings were prepared containing various quantities of nickel sulphate added to Layer I. ETA concentrations in each coating were measured by the polarographic method (described in Example 1) after incubation at 1 200F and 75% RH, and compared with the equivalent value from refrigerated check samples. During incubation sarnples were suspended open to the atmosphere inside a chamber maintained at the required humidity and temperature.

The results are shown in the following table.

ETA Concn. (mg. fit.2) NiSO4 Coating Wt. lncu ETA Loss (mg. tt:2) Refrig. Check Incubation on Incubation 0 16.6 5.5 67% 5 16.5 10.0 39% 20 17.6 11.5 35% 50 16.2 12.2 25% The results show increasing ETA stabilization with increasing salt level, but even at low levels of nickel sulphate (5 mg.ft-2) a useful improvement is obtained.

EXAMPLE 4 Coatings were prepared of the same general structure as shown in Example 3. Various salts of nickel (II) were incorporated into Layer I, giving equal concentrations of Ni++ ion in each case (19 mg.ft-2). ETA stability was measured for each coating as in Example 3, and the results are shown in the table below.

ETA conc. (mg. ft.2) Salt Loss of Salt Coating Wt. ETA on Additive (mg. ftr2) Check Incubated Incubation Nil - 16.6 5.5 67% NiSO4 50 16.2 12.2 25% NiCI2 42 30.0 27.0 10% Ni(NO3)2 59 23.2 18.8 19% Ni(OAc)2 57 1 16.5 2.4 85% Nickel nitrate and especially nickel chloride appear to be more effective stabilizers for the ETA than nickel sulphate but nickel acetate destabilises the compound.

EXAMPLE 5 A series of coatings was produced to the general structure shown in Example 3, but with a number of different metal sulphates incorporated into Layer I at equivalent molar concentrations. ETA stability was assessed for each coating, as described in Example 1. The results are indicated in the table below.

ETA Conc. (mg. ft.) Metal MSO4 ~ ETA Sulphate Coating Wt. | Loss on (MSO4) (mg. ftr2) Refrig. check Incubated Incubation None - 22.1 6.8 69% Al2 (S04)3 55 22.7 11.8 48% MnSO4 49 19.3 9.4 51% FeSO4 49 Too Small Too Small - To Measure To Measure CoSO4 50 19.7 12.5 37% NiSO4 50 23.1 12.9 44% CuSO4 51 Too Small Too Small I To Measure To Measure ZnSO4 j 52 21.4 12.6 31% With the exception of iron and copper, all the added metal ions increase the stability of ETA.

Cuprous sulphate and ferrous sulphate catalyse ETA decomposition (probably via a redox mechanism) so effectively that it does not survive in the coating melt.

EXAMPLE 6 Three pairs of coatings were prepared, as below with different ETAs in each pair. The three ETAs were 4-methyl-4-hydroxymethyl- 1 -phenyl pyrazolidone (ETAI), 4-methyl-4-hydroxymethyl- 1 -(4'-ethylphenyl)-3-pyrazolidone (ETA2) and 1 -phenyl-3-pyrazolidone (ETA3).Other terms and abbreviations in the coating plan below are as described in Example 3.

Mordant (200) Mordant (200) Gel (200) Gel (200) CH2O (10) CH2O (10) BGE (10) BGE (10) Surfactant (60) Surfactant (60) Gel (100) Gel (100) ETA (25) Nisi, (50) Hardener (2.5) ETA (25) CH2O (2.5) | | Hardener (2.5) Surfactant (25) CH2O (2.5) Surfactant (25) Support ; /// Support //T Support

ETA stability in each coating was measured as in Example 3. The results (presented in the table below) show that ETA 3 is intrinsically less stable than ETA 1 and ETA 2 and that it is not possible to stabilise ETA 3 by adding nickel salt to the system. The basic stability of ETA 2 is apparently slightly greater than that of ETA 1 but stabilization with NiSO4, although possible, is less efficient than in the case of ETA 1.

% ETA Loss on Incubation ETA NiSO4 absent NISO, present ETA1 69 44 ETA3 78 82 ETA2 63 54

EXAMPLE 7 Coatings of different mordants were prepared according to the following coating plan:

Mordant (200) Gelatin (200) CH2O (10) Hardener (10) Surfactant (60) Gelatin (100) ETA (30) CH2O (2.5) Hardener (2.5) Surfactant (25) Layer II Layer The terminology and abbreviations are as described in Example 3.The mordants used were poly(4-vinylpyridine) (PVP); poly(N-vinylimidazole) (PVI), poly(N-vinylimidazole) partially (approx. 10%) quaternised with benzyl chloride (PVlbc); and poly(N-vinylimidazole) partially (approx. 10%) quaternised with chloro-ethanol (PVI,,). PVP was dissolved in dilute HCI and the pH of this coating melt was slightly lower than the standard value of 5.5 used for all other melts.

A second set of coatings was prepared in which NiSO4 (50 mg.ft-2) was included in the gelatin layer I. ETA concentrations in incubated and refrigerated samples of each coating were measured as described in Example 3 and the results are collected in the following table.

Measured ETA Coating Wt. ETA Loss on Incubation Mordant NiSO4 Refrigerated Incubated (o/o) PVP NO 12.0 12.0 | 0 PVP YES 14.0 13.6 3% PVI NO 28.2 14.3 49% PVI YES 24.7 14.1 | 43% PVI bc NO 24.7 5.0 80% PVI bc YES 32.0 13.9 56% PVI ce NO 24.6 6.2 75% PVI ce YES 25.5 12.1 53%

ETA is quite stable in the PVP coatings, but considerably less so in the PVI coatings. Addition of NiSO4 slightly increases ETA stability of PVI. Both of the partially quaternised polymers show rather worse ETA stability than the unquaternised parent polymer, but significant improvements are obtained by the addition of NiSO4.

EXAMPLE 8 Another set of mordant coatings was prepared according to the following diagram (see Example 3 for explanation of terms).

A B

Mordant (200) Mordant (200) Gel (200) Gel (200) Hardener (20) Hardener (20) Surfactant (60) Surfactant (60) Gel (100) ] Gel (100) ETA (30) NiSO4 (54) CH2O (10) CH2O (10) Hardener (10) ETA (30) Surfactant (25) Hardener (10) Surfactant (25) Support Support C D

Mordant (200) Mordant (200) Gel (200) Gel (200) Hardener (20) Hardener (20) Surfactant (60) Surfactant (60) ETA (30) ETA (30) Gel (100) Gel (100) CH2O (10) NiSO4 (54) Hardener . (10j CH2O (10) Surfactant (25) Hardener (10) Surfactant (25) Support Support E F

Mordant (200) Mordant (200) Gel (200) Gel (200) ETA (30) ETA (30) CH2O (10) NiSO4 (50) Hardener (10) CH2O (10) Surfactant (60) Hardener (10) Surfactant (60) Support Support Coatings A and B follow the pattern of the earlier Examples, with the ETA and NiSO4 (in B) included in a lower (gel) layer. Coatings C and D include the ETA in the upper (mordant) layer but the NiSO4 included in D is retained in the gel layer. Coatings E and F are single layer coatings with the ETA and NiSO4 (in F) coated in the same layer as the mordant.

ETA stability was measured by the incubation technique described in Example 3, and yielded the following results:

Measured Coating Wt (mg.ft.-2) % ETA Loss on Coating Refrigerated I ncu bated I Incubation A 18.2 4.2 77 B 17.0 9.0 47 C 21.0 2.2 90 D 20.8 6.6 68 E 23.1 5.9 74 F 18.8 13.2 30 The gain in ETA stability associated with NiSO4 is maintained in all three coating formats. The best results was achieved in the single layer format of coatings E and F while separating the metal salt and ETA into different layers gives the worst results.

Claims (8)

1. A dye image-receiving material useful in a photographic colour diffusion transfer process of reproduction comprising a layer containing a polymer of N-vinylimidazole and comprising in the said layer or another layer 4-hydroxymethyl-4-methyl-1 -phenyl-3-pyrazolidone or 4-hydroxymethyl-4 methyl-1-(4'ethylphenyl)-3-pyrazolidone and comprising also in the same layer as said pyrazolidone, nickel sulphate, nickel chloride, nickel nitrate, manganese sulphate, cobalt sulphate, zinc sulphate or aluminium sulphate in an amount such that the storage stability of said pyrazolidone in said element is increased.

2. A material according to claim 1 wherein in said polymer some of the polymerised Nvinylimidazole units are quaternised with 2-chloroethanol or benzyl chloride.

3. A material according to claim 2 wherein less than 10% of said units are quaternised.

4. A material according to any of claims 1 to 3 which contains nickel sulphate in said polymercontaining layer or in a gelatin layer below said polymer-containing layer.

5. A material according to claim 4 which contains from 54 to 580 milligrams nickel sulphate per square metre of material.

6. A material according to any of claims 1 to 3 which contains from 430 to 646 milligrams of nickel chloride or nickel nitrate per square metre of material.

7. A material according to any of the preceding claims which contains from 161 to 592 milligrams of said pyrazolidone per square metre of material.

8. A photographic colour diffusion transfer process of reproduction wherein a colour image is formed by diffusion transfer in a material according to any of the preceding claims.