Light-Sensitive Mixture and Light-Sensitive Copying Material Prepared Therefrom Wherein Image Produced Therein Is Visible Under Yellow Safety Light

The present invention relates to a light-sensitive mixture, which becomes soluble by exposure, comprising

(a) a 1,2-quinonediazide or a mixture of

(a.sup.1) a compound forming an acid on exposure and

(a.sup.2) a compound having at least one C--O--C bond cleavable by acid,

(b) a water-insoluble binder soluble in aqueousalkaline solutions,

(c) a photolytically cleavable organic halogen compound, and

(d) a dyestuff.

After exposure, the mixture shows a clearly visible color contrast between exposed and unexposed areas.

Mixtures of the generic type indicated are preferably used for preparing planographic printing plates and photoresists, and such mixtures are known, for example, from U.S. Pat. No. 3,969,118. The mixtures described there contain as the dyestuff (d) a triphenylmethane, azine or anthraquinone dyestuff and as the organic halogen compound (c) a 1,2-naphthoquinone-2-diazide-4-sulfonyl halide. After image exposure they produce an image contrast which is clearly visible in daylight or in white artificial light. However, the image contrast is less pronounced, and in some cases inadequate under the yellow safety light customarily used when working with reprographic materials.

U.S. Pat. No. 3,929,488 describes corresponding mixtures which contain certain azo dyestuffs as the dyestuffs and diazonium salts of strong acids as the acid donors. These mixtures produce only a relatively slight visual contrast in normal light and in safety light.

U.S. Pat. No. 4,163,672 and British Patent No. 2,005,855 describe similar mixtures which contain diazonium salts as the acid donors and azo, triphenylmethane, azine or anthraquinone dyestuffs as the dyestuffs. Their contrast is likewise frequently inadequate in yellow safety light.

U.S. Pat. No. 4,160,671 describes corresponding mixtures which contain trihalogenomethyls-triazines or trihalogenomethyl-2-pyrones as the acid donors and azine, triphenylmethane or anthraquinone dyestuffs as the dyestuffs. The properties of these mixtures are similar to those of the abovementioned mixtures.

It is therefore an object of the present invention to provide an improved positive-working, light-sensitive mixture of the generic type described at the outset.

In particular, it is an object of the invention to provide such a mixture which after imagewise exposure displays a contrast-rich image of the original which is clearly visible even under yellow safety light.

A further object of the invention resides in providing an improved copying material utilizing the light-sensitive mixture of the invention.

In accomplishing the foregoing objects, there has been provided in accordance with one aspect of the present invention a light-sensitive mixture, comprising (a) a 1,2-quinonediazide or a mixture of (a.sup.1) a compound forming an acid on exposure and (a.sup.2) a compound having at least one C--O--C bond cleavable by acid; (b) a water-insoluble binder soluble in aqueousalkaline solutions; (c) a photolytically cleavable organic halogen compound of one of the formulae I and II ##STR2## in which R.sup.1 denotes an aromatic radical bonded directly or via a conjugated chain, and

X denotes a halogen atom; and

(d) a dyestuff.

In accordance with another aspect of the invention, there has been provided a light-sensitive copying material comprising a support and a light-sensitive layer which becomes soluble in a developer on exposure and comprises a light-sensitive mixture as defined above.

Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments which follows.

The invention relates to a light-sensitive mixture comprising

(a) a 1,2-quinonediazide or a mixture of

(a.sup.1) a compound forming an acid on exposure and

(a.sup.2) a compound having at least one C--O--C bond cleavable by acid,

(b) a water-insoluble binder soluble in aqueousalkaline solutions,

(c) a photolytically cleavable organic halogen compound of one of the general formulae I and II ##STR3## in which R.sup.1 denotes an aromatic radical bonded directly or via a conjugated chain, and

X denotes a halogen atom, and

(d) a dyestuff.

In the mixture according to the invention, the dyestuff is an azo dyestuff containing at least one nitro group in the molecule.

The azo dyestuffs contained in the mixture contain at least one, and preferably 2 or more, nitro groups in the molecule. Monoazo dyestuffs, in particular those formed from substituted benzenediazonium compounds and aromatic amines as coupling components, are preferable. The azo dyestuffs, in addition to nitro groups, can also contain further substituents. Examples of preferable substituents are amino groups, particularly tertiary amino groups, halogen atoms, alkoxy groups and acylamino groups. Owing to their particularly advantageous color contrast, blue azo dyestuffs are generally preferable. The amount of azo dyestuff is in general from about 0.5 to 10%, preferably from about 2 to 7%, by weight, relative to the nonvolatile constituents of the mixture.

The organic halogen compounds used as acid donors can be s-triazine derivatives or naphthoquinonediazidesulfonyl halides of the formulae given above. These compounds are known as such as acid donors in light-sensitive mixtures and have been described in German Offenlegungsschriften No. 2,331,377 (=U.S. Pat. No. 3,969,118), No. 2,243,621 and No. 2,718,259, the disclosures of which are hereby incorporated by reference. Of the naphthoquinonediazidesulfonyl halides, the fluorides, chlorides and bromides, in particular the chlorides, are preferable. Of the s-triazine derivatives of the formula I, those are preferable in which the radical R.sup.1 is an optionally substituted naphthyl, acenaphthyl, diphenylyl or styryl radical. Suitable substituents are described in the publications mentioned. The halogen compounds are generally added in amounts of from about 1 to 20%, preferably from about 5 to 12% by weight, relative to the nonvolatile constituents.

The mixtures according to the invention can be stored, in the form of light-sensitive layers applied to a support or as solutions for preparing photoresist layers, in the dark over prolonged periods without decomposition. The image contrast obtained by means of the mixtures according to the invention is considerably more brilliant than the image contrast obtained by means of the same acid donors combined with triphenylmethane, azine or anthraquinone dyestuffs or with azo dyestuffs which do not contain nitro groups.

The mixture according to the invention contains as a further essential constituent a light-sensitive compound (a) or a light-sensitive combination of compounds (a.sup.1 +a.sup.2) the solubility of which in an aqueous alkaline developer solution is increased on exposure. The light-sensitive materials include in particular o-quinonediazides and combinations of photolytic acid donors with acid-cleavable compounds.

The o-quinonediazides preferably used are 1,2-naphthoquinone-2-diazide-4- or -5-sulfonic acid esters or amides. Of these, the esters, in particular those of 5-sulfonic acids, are particularly preferable. Suitable compounds of this type are known and have been described, for example, in German Patent No. 938,233 and in German Offenlegungsschriften No. 2,331,377 (=U.S. Pat. No. 3,969,118), No. 2,547,905, and No. 2,828,037, the disclosures of which are hereby incorporated by reference.

The amount of these o-quinonediazide compounds is in general from about 3 to 50%, preferably from about 7 to 35% by weight, relative to the nonvolatile constituents of the mixture.

Materials based on acid-cleavable compounds can also be used with beneficial effect in the mixture according to the invention.

Copying materials of this type are known and have been described, for example, in U.S. Pat. Nos. 3,779,778 and 4,101,323, German Patent No. 2,718,254 and German Offenlegungsschriften No. 2,829,512, No. 2,829,511 and No. 2,928,636, the disclosures of which are also incorporated by reference herein. They contain as acid-cleavable compounds orthocarboxylic acid derivatives, monomeric or polymeric acetals, enolethers or acylimino carbonates, of which the orthocarboxylic acid derivatives and acetals are preferable. As radiation sensitive, acideliminating compounds they predominantly contain organic halogen compounds, in particular, s-triazines substituted by halogenomethyl groups. These compounds can be identical to those used according to the invention as the acid donors (d).

Of the orthocarboxylic acid derivatives described in U.S. Pat. No. 4,101,323, in particular, the diphenoxymethyl ethers of aliphatic or aromatic hydroxy compounds, the N-diphenoxymethyl derivatives of lactams and, most preferably, the bis-1,3-dioxan-2-yl ethers of aliphatic diols are used.

Among the polyacetals described in German Patent No. 2,718,254 (equivalent to U.S. Pat. No. 4,247,611), those containing aliphatic aldehyde and diol units are preferable.

Of the polymeric ortho esters described in German Offenlegungsschrift No. 2,928,636 (equivalent to U.S. Pat. No. 4,311,782), polymers with recurring 1,3-dioxacyclohex-2-yl alkyl ether units, in which the alkyl ether group can be interrupted by ether oxygen atoms and is preferably bonded to the 5-position of the adjacent ring, are particularly preferable.

The amount of acid-cleavable compounds in the light-sensitive mixture is in general between about 8 and 60%, preferably between about 14 and 40% by weight, relative to the nonvolatile constituents of the mixture. The amount of acid-eliminating compound combined therewith is between about 0.1 and 10%, preferably between about 0.2 and 5% by weight.

Light-sensitive mixtures according to the invention preferably also contain a polymeric, water-insoluble resinous binder which is soluble in the solvents used for the mixture according to the invention and is also soluble, or at least swellable, in aqueous alkalis.

The novolak condensation resins found suitable in many positive copying materials based on naphthoquinonediazides have been found to be particularly useful and advantageous as an additive also in the case of mixtures according to the invention. They promote strong differentiation between exposed and unexposed areas of the layer on developing. This applies in particular to relatively highly condensed resins having substituted phenols, for example, cresols, as formaldehyde condensation partners. Further binders which are alkali-soluble, or swellable in alkali, and which are to be mentioned are natural resins, such as shellac and colophony, and synthetic resins, such as copolymers of styrene and maleic anhydride or copolymers of acrylic or methacrylic acid, in particular with acrylates or methacrylates.

The type and amount of alkali-soluble resin can vary according to the intended use. Proportions of the total solids content between about 95 and 35%, particularly from about 90-55% by weight, are preferable. Numerous other resins can also be used in the mixture, in addition to the abovementioned resins, with epoxy resins and vinyl polymers, such as polyvinyl acetates, polyacrylates, polyvinylacetals, polyvinyl ethers, polyvinyl pyrrolidones and copolymers of their parent monomers being preferable. The most advantageous proportion of these resins depends on application-related requirements and the effect on the developing conditions and is in general no more than about 20% by weight of the alkali-soluble resin. For special requirements, such as flexibility, adhesion, luster and coloring, the light-sensitive mixture can also contain small amounts of substances such as polyglycols, cellulose derivatives, such as ethylcellulose, wetting agents, dyestuffs, adhesion promoters and finely divided pigments and, if required, UV absorbers.

For coating a suitable support, the mixtures are generally dissolved in a solvent. The choice of solvent must be adapted to the coating method intended, the layer thickness and the drying conditions. Suitable solvents for the mixtures according to the invention are ketones, such as methyl ethyl ketone, chlorinated hydrocarbons, such as trichloroethylene and 1,1,1-trichloroethane, alcohols, such as n-propanol, ethers, such as tetrahydrofuran, alcohol-ethers, such as ethylene glycol monoethyl ether, and esters, such as butyl acetate. It is also possible to use mixtures thereof, which can additionally contain, for special purposes, solvents such as acetonitrile, dioxane or dimethylformamide. In principle, any solvent can be used which does not react irreversibly with the layer components. Partial ethers of glycols, in particular ethylene glycol monomethyl ether, are particularly preferable.

Metals are usually used as supports for layers less than about 10 .mu.m thick. For offset printing plates there can be used bright-rolled, mechanically or electrochemically roughened and, if appropriate, anodized aluminum, which can in addition also have been pretreated chemically, for example, with polyvinylphosphonic acid, silicates, phosphates or hexafluorozirconates or with hydrolyzed tetraethyl orthosilicate, and also multi-metal plates, for example, made of Al/Cu/Cr or of brass/chrome. To prepare letterpress printing plates, the mixtures according to the invention can also be applied to zinc or magnesium plates as well as to their commercially available microcrystalline alloys for powderless etching processes, and also to etchable plastics, such as polyoxymethylene. Owing to their firm adhesion and etch resistance on copper and nickel surfaces, the mixtures according to the invention are suitable for gravure or screen printing forms. The mixtures according to the invention can also be used as photoresists in the manufacture of printed-circuit boards and in chemical milling processes. Other supports, such as wood, paper, ceramic material, textile and other metals, are also possible for different applications, as is understood by those skilled in the art.

Preferable supports for layers more than 10 .mu.m thick are plastic films which, in this case, act as temporary supports for transfer layers. Polyester films, for example, made of polyethylene terephthalate, are preferable for this purpose. However, polyolefin films, such as polypropylene, are also suitable.

The support material is coated in a known manner by spin-coating, spraying, dipping, rollcoating, by means of slot dies, knife-coating or by flow coating. The coating of, for example, circuit boards, glass or ceramic material and silicon disks can also be effected by the transfer of a layer from a temporary support. Exposure is effected with light sources customary in the industry. Irradiation with electrons or lasers also represents an imaging possibility known to those skilled in the art.

The aqueous-alkaline solutions of stepped alkalinity, preferably with a pH in a range of from about 10-14, which are used for developing and which can also contain relatively small amounts of organic solvents or wetting agents remove those areas of the copying layer hit by the light and thus produce a positive image of the original.

The light-sensitive mixtures according to the invention are preferably used in the preparation of printing forms, i.e., in particular offset, autotypical gravure and screen printing forms, in photoresist solutions and in so-called dry resists.

The invention is illustrated in more detail by means of the Examples which follow and in which parts by weight (pbw) are related to parts by volume (pbv) as the g relates to the cm.sup.3. Unless otherwise indicated, percentages are percentages by weight.

A solution of

0.70 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 2 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

0.40 pbw of the esterification product of 1 mole of 2,2'-dihydroxy-1,1'-dinaphthylmethane and 2 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

6.00 pbw of a cresol-formaldehyde novolak having a softening range of 120.degree.-135.degree. C. and an average molecular weight of 1,500,

0.80 pbw of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride, and

0.40 pbw of a blue azo dyestuff obtained by coupling the diazonium salt of 2,4-dinitro-6-chlorobenzene with 2-methoxy-5-acetylamino-N,N-diethylaniline in

40 pbw of ethylene glycol monomethyl ether, and

50 pbw of tetrahydrofuran

was used to coat an electrochemically roughened and anodized aluminum plate. Before application of the light-sensitive layer, the anodized support had been treated with an aqueous solution of polyvinylphosphonic acid. The presensitized printing plate thus prepared with a layer weight of 2.30 g/m.sup.2 was imagewise exposed under a transparent positive original.

While the color of the unexposed areas of the copying layer remained deep dark blue, the color of the exposed areas of the layer changed to a color of yellow to pale brown. The image of the original was clearly visible in all details, even in the case of yellow illumination.

To prepare the printing form, the exposed printing plate was developed in a known manner with a 7.3% strength aqueous sodium metasilicate solution, whereby the exposed areas were removed. The remaining unexposed areas of the layer remained visible with good contrast to the uncolored background.

In Examples 2 to 8, which follow, the procedure of Example 1 was followed, and after exposure of the light-sensitive printing plates obtained, essentially the same good results were obtained in respect of image contrast, not only before but also after developing. In the Examples which follow, only the recipes of the coating solutions and the type of supports used are usually indicated, and further short remarks are added only occasionally.

Coating solution:

1.0 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 3 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

6.0 pbw of a phenol-formaldehyde novolak having a softening range of 110.degree. to 120.degree. C.,

0.8 pbw of 2-(4-ethoxynaphth-1-yl)-4,6-bistrichloromethyl-s-triazine,

0.4 pbw of the azo dyestuff indicated in Example 1,

40.0 pbw of ethylene glycol monomethyl ether, and

50.0 pbw of tetrahydrofuran.

Copying layer support: electrochemically roughened and anodized aluminum plate corresponding to Example 1.

Color of the exposed areas changed from deep dark blue to pale yellow brown.

Coating solution:

1.0 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 3 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

6.2 pbw of the novolak indicated in Example 1,

0.8 pbw of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride,

0.3 pbw of a blue azo dyestuff obtained by coupling the diazonium salt of 2,4-dinitro-6chlorobenzene with 2-methoxy-5-acetylamino-N-cyanoethyl-N-hydroxyethylaniline,

40.0 pbw of ethylene glycol monomethyl ether, and

50.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate corresponding to Example 1.

Color of the exposed areas changed from deep dark blue to yellow brown.

Coating solution:

0.8 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 2 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

0.5 pbw of the esterification product of 1 mole of 2,2'-dihydroxy-1,1'-dinaphthylmethane and 2 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

6.0 pbw of the phenol-formaldehyde-novolak indicated in Example 2,

0.7 pbw of 2,4-bis-trichloromethyl-6-p-methoxystyryl-s-triazine,

0.2 pbw of a blue dyestuff obtained by coupling the diazonium salt of 2,4-dinitro-6-chlorobenzene with 2-ethoxy-5-acetylamino-N,N-bis-(acetoxyethyl)-aniline,

40.0 pbw of ethylene glycol monomethyl ether, and

50.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate corresponding to Example 1.

Color of the exposed areas changed from dark blue to yellow brown.

Coating solution:

1.0 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 3 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

5.6 pbw of the novolak indicated in Example 1,

0.6 pbw of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride,

0.2 pbw of an azo dyestuff obtained by coupling the diazonium salt of 4-nitrobenzene with diphenylamine,

40.0 pbw of ethylene glycol monomethyl ether, and

50.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate corresponding to Example 1.

Pale brown color of the exposed areas changed to deep violet to dark blue.

Coating solution:

1.0 pbw of the esterification product of 1 mole of 2,3,4-trihydroxybenzophenone and 3 moles of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride,

6.0 pbw of the phenol-formaldehyde novolak indicated in Example 2,

0.9 pbw of 2-(acenaphth-5-yl)-4,6-bis-trichloromethyl-s-triazine,

0.4 pbw of the azo dyestuff indicated in Example 1,

40.0 pbw of ethylene glycol monomethyl ether, and

50.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate corresponding to Example 1.

Color of the exposed areas changed from deep dark blue to pale brown.

Coating solution:

1.2 pbw of a 50% strength solution of a polyorthoester in toluene, prepared from 7,7-bishydroxymethyl-5-oxanonan-1-ol and trimethyl orthoformate,

0.3 pbw of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride,

0.2 pbw of the cresol-formaldehyde novolak indicated in Example 1,

0.1 pbw of the azo dyestuff indicated in Example 1,

20.0 pbw of ethylene glycol monomethyl ether, and

20.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate.

Color of exposed areas changed from dark blue to yellow brown.

Coating solution:

0.6 pbw of a polyacetal prepared from triethylene glycol and 2-ethylbutyraldehyde,

0.2 pbw of 2,4-bis-trichloromethyl-6-(4-phenylphenyl)-s-triazine,

3.0 pbw of the novolak indicated in Example 1,

0.1 pbw of the azo dyestuff indicated in Example 1,

20.0 pbw of ethylene glycol monomethyl ether, and

30.0 pbw of tetrahydrofuran.

Support: electrochemically roughened and anodized aluminum plate.

Color of the exposed areas changed from dark blue to pale brown.