GB2093205A - Diazotype material - Google Patents

Abstract

Cu(II) salts of organic carboxylic acids are effective as fade-inhibitors in one- and two-component diazotype materials. They compare favorably with known fade-inhibitors as regards effectiveness, compatability, and ease of synthesis.

Description

SPECIFICATION Diazotype material The present invention relates to diazotype materials and, more particularly, to diazotype materials having an improved stability to light.

The images in exposed and developed diazotype materials are subjected both to normal sunlight and artificial room light and often also to intense light when they are being used in projectors, microfilm readers, or other reading apparatus. They are also subject to stress as a result of irradiation during image-forming and copying processes. It is therefore important that the image dyestuffs should have a good stability to light, so that they do not fade or become bleached-out, for example as a result of oxidation induced or assisted by light. It is also important, however, that the light-fastness should not he achieved at the cost of other important properties of the diazotype material, including, for example, thermal stability, iight-sensitivity, resolution, coupling kinetics, absorption behavious, image-forming capacity, and ability to be copied.

One way of improving the light-fastness of diazotype materials is by chemical modification of the azo dyestuff and/or the coupler, for example the inclusion of certain substituents. Various azo dyestuffs that are suitable for use as image dyestuffs in diazotype materials, and which have chemical modifications in order to give them an improved light-fastness, are described in, for example, Deutsches Reich PatentschriftNr. 697051 (see also Chem. Abs. 35:5816.6),DE838 692 (see also Chem. Abs.

51:11900), and DE 864 951. In many cases, however, the use of such chemically modified azo dyestuffs entails increased synthesis costs and, moreover, the degree of light-fastness achieved is often not adequate.

Another way of improving the light-fastness of diazotype materials is by including in the material a component that will hinder fading or bleaching-out of the image dyestuff, especially when the material is to be used in a reading or exposure apparatus. Such components may be known as fade-inhibitors, bleaching-out inhibitors, light-stabilisers or, simply, stabilisers.When choosing to add a stabiliser, or indeed any extra component, to a diazo system that has proved useful, various factors have to be taken into account: the compatibility of the additional component with the remainder of the diazo system; whether the additional component will cause unacceptable fogging; the stability of the addition component during processing; the ease with which the additional component will be available or can be synthesised; and the absorption behaviour of the additional component (it should preferably absorb at a shorter wavelength than does the diazonium component).

Various stabilisers have been described in the literature: for example, various sterically hindered phenols are described in GB 1 231 270 (Eastman Kodak Co.) (corresponding to DE 17 72 981) as 'dye stabilisers'; various N,N'-diaryl-alkylenediamines are described in GB 1 248 421 (Scott Graphics, Inc.) (corresponding to DE 17 97 322) as 'background discoloration inhibitors'; and 3-anilinopyrazoles are described in DD-WP g 03 c/221 629. The degree of improvement in light-fastness achieved using such stabilisers is not, however, in general, sufficient in view of their relatively high synthesis costs.

Various phosphoric acid anilides are described as stabilisers in DD-WP G 03 c/222 062, and they can be synthesised relatively easily, but their absorption maxima lie too far within the absorption band of diazonium salts, thus restricting the use of the diazotype material and impairing the duplicating capacity of the material. It is, of course, inherent in the use of additional stabilisers that they improve the light stability of the material only until they are themselves destroyed.

Thus, many of the stabilisers already known either provide inadequate fade-inhibition, especially over a relatively long period, or are unsatisfactory as regards other criteria that have to be met.

The present invention provides a diazotype material which comprises, as a stabiliser, a copper(ll) salt of an organic carboxylic acid.

It has been found that the copper salts mentioned above have a good effectiveness as fade inhibitors, resulting in a considerable improvement in the light-fastness of the diazotype material as compared with the amount of fading occurring in a similar material without the fade inhibitor.

Furthermore, the compounds have a good compatibility with diazo systems, such that other properties, such as image-forming capacity, ability to be copied, sensitivity, and thermal stability, remain substantially unaffected. The compounds can also readily be synthesised.

The diazotype material according to the invention may be a one-component or two-component diazotype material. Both types of diazotype material are well known: one-component diazotype material contains a diazonium compound in the absence of a coupler, and the coupler is provided by the developing solution, in the 'semi-wet' development process; whereas two-component diazotype mateial contains both the diazonium compound and the coupler and is developed by a 'dry' development process.

The copper(ll) salt used as a stabiliser according to the invention may be a copper(ll) salt of any organic carboxylic acid. The carboxylic acid may be saturated or unsaturated; substituted or unsubstituted; straight-chained, branched or cyclic; aliphatic or aromatic; carbocylic or heterocyclic; and may, for example, be a monocarboxylic, dicarboxylic or tricarboxylic acid. Advantageously, however, the carboxylic acid is a monocarboxylic acid, preferably an aliphatic monocarboxylic acid, and especially a straight-chain saturated aliphatic monocarboxylic acid.

Examples of suitable organic carboxylic acids are straight-chain saturated aliphatic monocarboxylic acids, especially those having not more than 12 carbon atoms, for example ethanoic acid (acetic acid), propanoic acid (propionic acid), butanoic acid (butyric acid), pentanoic acid (valeric acid), hexanoic acid (caproic acid), decanoic acid (capric acid), and dodecanoic acid (lauric acid); branched saturated aliphatic monocarboxylic acids, especially those having from 4 to 10 0 carbon atoms, for example, 2,2-dimethylpropanoic acid (pivalic acid) and 2-methylbutanoic acid (methylethylacetic acid); straight-chain unsaturated aliphatic monocarboxylic acids, for example propynoic acid (propiolic acid) and cis-9-octadecenoic acid (oleic acid); branched unsaturated aliphatic monocarboxylic acids, for example 2-methylpropenic acid (methacrylic acid); aromatic monocarboxylic acids, for example benzenecarboxylic acid (benzoic acid) and o-hydroxybenzoic acid (salicylic acid); araliphatic monocarboxylic acids, for example phenylacetic acid and a-phenyl-hydrnxyacetic acid (mandelic acid); cyclic aliphatic monocarboxylic acids, for example cyclohexaneca rboxylic acid; heterocyclic carboxylic acids, for example 4-pyridinecarboxylic acid (isonicotinic acid); saturated aliphatic dicarboxylic acids, for example propanedioic acid (malonic acid) and hexanedioic acid (adipic acid); unsaturated aliphatic dicarboxylic acids, for example cis-butenedioic acid (maleic acid); aromatic dicarboxylic acids, for example 1 ,2-benzenedicarboxylic acid (phthalic acid); hydroxycarboxylic acids, for example 2-hydroxypropanoic acid (a-hydrnxyprnpionic acid, lactic acid); halocarboxylic acids, for example chloroacetic acid and 2,3-dichloropropanoic acid (,ss-dichloropropionic acid); keto acids, for example 2-oxopropanoic acid (r-ketopropionic acid, acetylformic acid, pyruvic acid); and tricarboxylic acids, for example 2 hydroxy-1 ,2,3-propanetricarboxylic acid (citric acid).

The copper(ll) salts of the organic carboxylic acids may be prepared in known manner, for example as described in ''Gmelins Handbuch der anorganischen Chemise', vol. Cu.

A diazotype material according to the invention may be prepared in a conventional manner, The copper salt may simply be mixed with the diazonium compound to be used and, in the case of a twocomponent diazotype material, the coupler to be used, and any further auxiliaries (such as a stabilising acid), in a solution of a polymeric binder. The coating composition thus obtained may then be applied to the surface of a support material.

The diazotype material according to the invention may include any known diazonium compound(s), for example 2-aminobenzenediazonium salts, 4-aminobenzenediazonium salts, and 4thiobenzenediazonium salts.

The coupler used in a two-component diazotype material according to the invention, or the coupler provided by the developing solution in the case of a one-component diazotype material according to the invention, may be any known coupler that contains a hydroxy group in the o-position relative to the coupling-active position (which is usually the alpha-position, as would be known by a person skilled in the art), for example a 2-hydroxy-3-naphthylamide, a 2,3-dihydroxynaphthalene, resorcinol, and ,e-naphthol.

The polymeric binder used in the diazotype material according to the invention may be any binder conventionally used in the manufacture of diazotype materials. Examples of suitable binders are cellulose derivatives, vinyl chloride/vinyl acetate copolymers, polystyrene, alkyl acrylate/acrylic acid copolymers, and polyethylene oxides.

The diazotype material according to the invention may contain conventional auxiliaries including, for example, a stabilising acid (for example, p-toluenesulphonic acid), a development accelerator, and a plasticiser.

The support material for the light-sensitive layer in a diazotype material according to the invention may be, for example, a polymer film (for example, polyethylene terephthalate or cellulose triacetate), paper (including transparent paper), glass, or metal.

The examples summarised in the table below illustrate the diazotype material according to the invention.

In each example, a diazo system of the following c9mposition: 4.5 x 10-2 mole of a diazonium salt, as specificed in the table, 5.3 x 10-2 mole of a coupler, as specified in the table, (except in Example 34, in which the specified coupler was present in the developing solution), 1.7 x 10-2 mole of p-toluenesulphonic acid, (Examples 1 to 33) or of sulphosalicylic acid (Example 34), N x 10-2 mole of a copper(ll) salt of an organic carboxylic acid, the particular acid and the value of N being specified in the table, and 1000 ml of a solution of 10% by weight (Examples 1 to 33) or 7.5% by weight (Example 34) of cellulose acetate in CH3OH/CH2Cl2 or in acetone/CH2Cl2, was prepared and poured onto a polyethylene terephthalate support of 10~15 m2 area, to form a transparent film. The diazotype material thus formed was developed in a basic medium according to the 'dry' development process (Examples 1 to 33), or in a phloroglucinol/coupler developing solution according to the 'wet' development process (Example 34), to give an image dyestuff. The developed material was subjected to a xeno test for 1 5 hours (irradiation for 1 5 hours by a xenon lamp (which simulates daylight) - see J. Voegt, "Die Stabilität vom Kunststoffen gegenuber Licht und Warm", Springer-Verlag, 1 966). The optical density of the image dyestuff of the film was measured before and after irradiation, as a measure of the amount of fading that occurred during the xeno test. The results are given in the table.

In each case, the procedure was repeated, for comparison purposes, using an identical diazo system but without the copper(ll) salt as fade inhibitor.

The diazonium salts used are indicated in the table by Roman numerals as follows: 2,5-dihydroxy-4-morpholinobenzenediazonium tetrachloroborate II - 2,5-dibutoxy-4-morpholinobenzenediazonium tetrachlorozincate IIl-4-(N,N-bis-cyanoethyl-amino)-2-propylbenzenediazonium sulphate.

The couplers used are indicated in the table by Arabic numerals as follows: (1) 2-hydroxy-3-naphthoic acid o-anisidide (2) 2-hydroxy-3-naphthoic acid 2,4-dimethoxy-5-chloroanilide (3) 2-hydroxy-3-naphthoic acid 2-methyl-4-chloroanilide (4) 2-hydroxy-3-naphthoic acid 2-methyl-4-methoxyanilide (5) 2-hydroxy-3-naphthoic acid 2-methyl-4-nitroanilide (6) resorcinol (7) p-naphthol In the case where a mixture of two couplers was used, the two couplers were used in equal amounts.

The examples and the results obtained are summarised in the following table.

Fade Inhibitor Degree of fading Example Cu(ll) salt of Amount Diazonium Coupler with without No. N(x 10-2 mole) salt inhibitor inhibitor 1. propionic acid 2.36 1 (1)+(6) 0% 24% 2. propionicacid 2.13 11 (1) 5% 51% 3. propionic acid 3.55 11 (6) 0% 29% 4. propionic acid 4.73 11 (7) 0% 90% 5. propionic acid 9.47 11 (5) 8% 50% 6. propionicacid 2.13 11 (2) 3% 51% 7. propionic acid 2.13 11 (3) 14% 49% 8. butyricacid 2.09 1 (1)+(6) 0% 24% 9. hexanoicacid 1.72 11 (1) 0% 51% 10. hexanoic acid 1.72 11 (6) 0% 26% 11. hexanoic acid 1.72 11 (5) 15% 43% 12. acetic acid 2.73 1 (1)+(6) 2% 42% 13. lauric acid 2.21 11 (1) 10% 47% 14. pivalicacid 3.77 1 (1)+(6) 3% 27% 15. pivalicacid 2.26 11 (1) 0% 51% 16. pivalic acid 1.50 11 (7) 0% 30% 17. pivalic acid 2.26 11 (2) 0% 50% 18. pivalic acid 1.50 11 (3) 0% 39% Fade inhibitor Degree of fading Example Cu(ll) salt of Amount Diazonium Coupler with without No.N(x 10-2 mole) salt inhibitor inhibitor 19. pivalic acid 2.26 11 (4) 9% 34% 20. oleicacid 1.90 11 (1) 8% 51% 21. oleicacid 1.90 II (6) 0% 26% 22. oleicacid 1.90 11 (3) 8% 39% 23. benzoicacid 0.655 11 (1) 11% 51% 24. phenylacetic acid 0.90 1 (1)+(6) 5% 24% 25. phenylacetic acid 1.50 11 (7) 0% 9096 26. chloraceticacid 3.01 11 (1) 8% 47% 27. malonicacid 1.24 11 (1) 17% 51% 28. maleicacid 1.35 11 (1) 19% 51% 29. phthalicacid 1.20 11 (1) 17% 51% 30. citric acid 1.25 11 (1) 20% 51% 31. pyruvicacid 1.50 11 (1) 20% 51% 32. lactic acid 1.81 11 (1) 18% 51% 33. isonicotinicacid 1.23 11 (1) 18% 51% 34. propionicacid 2.11 Ill (1)* 25% 51% * Coupler present in developing solution - one-component diazotype material.

Claims (7)

1. A diazotype material which comprises, as a stabiliser, a copper(ll) salt of an organic carboxylic acid.

2. A diazotype material as claimed in claim 1, wherein the organic carboxylic acid is one of those acids specifically mentioned herein.

3. A diazotype material as claimed in claim 1 or claim 2, which comprises, as a diazonium component, a 2-aminobenzenediazonium salt, a 4-aminobenzenediazonium salt, or a 4thiobenzenediazonium salt.

4. A diazotype material as claimed in claim 1 or claim 2, which comprises, as a diazonium component, 2,5-dihydroxy-4-morpholinobenzenediazonium tetrachloroborate, 2,5-dibutoxy-5- morpholinobenzenediazonium tetrachlorozincate, or 4-(N,N-bis-cyanoethylamino)-2propylbenzenediazonium sulphate.

5. A diazotype material as claimed in any one of claims 1 to 4, which is a two-component diazotype material and comprises, as a coupler, a 2-hydroxy-3-naphthylamide, a 2,3dihydroxynaphthalene, resorcinol, orp-naphthol.

6. A diazotype material as claimed in any one of claims 1 to 4, which is a two-component diazotype material and comprises, as a coupler, 2-hydroxy-3-naphthoic acid o-anisidide, 2-hydroxy-3-naphthoic acid 2,4-dimethoxy-5-chloroanilide, 2-hydroxy-3-naphthoic acid 2-methyl-4-chloroa nilide, 2-hydroxy-3-naphthoic acid 2-methyl-4-methoxyanilide, or 2-hydroxy-3-naphthoic acid 2-methyl-3-nitroanilide.

7. A diazotype material as claimed in claim 1, substantially as described in any one of Examples 1 to 34 herein.