CA1097122A - Light-sensitive copying composition containing the condensation product of a diazonium salt, a water soluble copolymer and an acrylic resin - Google Patents

Abstract

LIGHT-SENSITIVE COPYING COMPOSITION

Abstract of the Disclosure This invention relates to an improvement in a negative-working light-sensitive copying composition comprising at least one condensa-tion product of a diazonium salt, at least one water-soluble synthetic polymer and at least one acrylic resin which is soluble or at least swellable in an aqueous alkaline solution, the improvement that the water-soluble synthetic polymer is a copolymer of a C3 to C16 alkyl acrylate and an N-vinyl-N-alkyl carboxylic acid amide, the alkyl and carboxylic acid groups of which contain 1 to 6 carbon atoms each. The invention also relates to a process for the preparation of a planographic printing foil using the novel light-sensitive composition.

Description

~ 39';~ ~La.<~Z ~ - 2 5 0 6 This invention relates to a negative-working light-sensitive copying composition, which is, in particular, suited for the preparation of high-quality presensitized planographic printing plates and for the production of relief images, color separations, etch resists, stencils, screen printing forms, individual copies, etc. The invention further relates to a copying material produced using this light-sensitive copy-ing composition and also to a process for the preparation of a litho-graphic printing plate.
Negative-working planographic printing plates, the copying layers of which function as stencils or etch resists after imagewise exposure -and differentiation have been in use for a long time, and they are commercially available as plates for a reversal process, sometimes called "reversal plates" or "deep etch plates", and in the form of pre-sensitized bimetal and trimetal plates. On the other hand, solutions or emulsions of light-sensitive copying compositions are available which may be used for coating single metal, bimetal and trimetal car-riers, so that a planographic printing plate desired for a particular purpose can be prepared on the spot at the processing plant.
A commercially available reversal plate is processed as Eollows:
The reversal plate which is composed of a light-hardenable copy-ing layer on a metal plate serving as a carrier is first exposed to light under a positive original. Then the unexposed and thus non-hardened image areas are removed by-wiping with a developer. The parts of the carrier surface laid bare by wiping are treated with a metal etching solution, i.e. they are deep etched. After drying, the entire surface of the plate is covered with a thin lacquer layer which is receptive to ~`
printing ink; the plate is again dried and dyed with a greasy protective ink . For removing the exposed and hardened areas of the copying layer, ':

7~22 K-2506 r together with the lacquer and ink adhering thereto, the plate is treated with a suitable stripping solution. By this treatment the lacquer por- ~
tions adhering directly to the etched carrier are not affected. Follow- -ing wiping of the bared carrier surface, e.g., with dilute phosphoric acid, the reversal plate is ready for printing.
However, the reversal plates heretofore used show various disad-vantages during processing. Deep etching of the plate surface after developing is an expensive process step which, in addition, does not produce the required uniformity of depth and degree of roughening when large areas are treated, so that good results are not obtained with sufficient reliability.
Further, stripping of the known planographic printing plates yields relatively poor results and is time-consuming, especially when there is a very strong bond between the lacquer and the hardened copy-ing layer areas, so that an attack of the stripplng solution is made dlfflcult or even impossible. This means that aggressive mixtures of potassium permanganate and hydrogen pero~ide must be used as stripping agents.
It is, therefore, difficult to match the copying layer and the processing agents in such a manner that optimum results are obtained.
Originally, the copying layers used with reversal plates, bimetal plates and trimetal plates contained chromates as sensitizers and gum arabic, fish glue or bone glue as colloids. However, layers of this composition have the disadvantage that they possess poor storability because of the so~called "dark reaction". An identical instability is observed in chromate-sensiti7ed polyvinyl alcohol layers.
Improved storability resulted from the use of synthetic water-soluble colloids, such as polyvinyl pyrrolidone, polyvinyl alcohol, L~;~ K- 25 06 polyvinyl methyl ether etc. as binders combined with diazo resins, i.e.
condensation products of p-diazodiphenylamine and paraformaldehyde.
However, hardening obtained on exposure of these layers did not always prove adequate. The hardened image areas showed only a limited resis-tance to the great number of processing steps following exposure. Fur-ther, these layers which wera composed of solely water~soluble colloids were susceptible to finger marks, in particular in case of high atmos-pheric moisture.
In German Offenlegungsschrift No. 1,772,947, planographic printing plates for the deep etch process are described, in which special hardenable resins, e.g., a modified copolymer of acrylic acid/acrylic acid amide or a polymethacrylate are used together with diazo resin compounds serving as light-sensitive substances.
These plates have the disadvantage that after development accord-ing to the known processes it is necessary to deep etch the carrier sur-face by an additional etching step ln order to improve the adhesion of a lacquer which is applied to the carrier surface in a subsequent process-ing step and thus to ensure long runs. As a consequence, processing of the plates is time-consuming and expensive. It is also a disadvan-tage that the hardened copying layer only inadequately repels the appli-ed lacquer; it forms a relatively strong bond with this lacquer so that stripping is made difficult.
It is an object of the present invention to provide a light-sensitive copying composition which is, in particular, suited for the preparation of high-quality, presensitized negative-working planographic printing plates and which permits a simplified processing of the planographic printing plates, so that good results are repeatedly obtained. It is fur-ther an object of the invention to provide a complete and deep cleansing of the highly porous carrier surface in the course of development of the exposed planographic printing plate, so that an etching operation sepa-rate from development can be omltted.
This object is achieved by the negative-working light-sensitive copying composition of the invention. It comprises as a light-sensitive component a diazonium salt condensation product and as a binder a water-soluble synthetic polymer and an acrylic resin insoluble in water, which is soluble or at least swellable in an alkali. In addition, the copying layer may contain pigments, dyes, plasticizers, color couplers, and similar known additives.
The water-soluble synthetic polymer used for the preparation of the light-sensitive copying composition according to the invention is a copolymer of an N-vinyl-N-alkyl carboxylic acid amide, the alkyl and the carboxyllc acid radicals of which contain 1 to 6 carbon atoms each, and a C3 to C16 alkyl acrylate havlng a branched or straight-chain alkyl radical.
The following N-vinyl compounds are exemplary of the N-vinyl-N-alkyl carboxylic acid amide:
Vinyl-N-methyl formamide, vinyl-N-ethyl formamide, vinyl-N-propyl formamide, vinyl-N-butyl formamide, vinyl-N-methyl acetamide, vinyl-N-ethyl acetamide, vinyl-N propyl acetamide, vinyl-N-butyl acetamide, vinyl-N- methyl propionamide, vinyl-N -ethyl propionamide, vinyl-N-propyl propionamide, vinyl-N-butyl propionamide, vinyl~N-methyl-n-butyramide, vinyl-N-ethyl-n-butyramide, vinyl-N-propyl-n-butyr-amide, and vinyl-N-butyl-n-butyramide.
Vinyl N-methyl acetamide is preferred.
The second component of the copolymer, an alkyl acrylate, is, e.g., one of the followlng monomers:

71~ K- 2 5 0 6 n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-ethyl hexyl acrylate, and 3,5,5-trimethyl hexyl acrylate.

2-ethyl hexyl acrylate is preferred.
In general, copolymers containing N-vinyl-N-alkyl carboxylic acid amide in an amount ranging between about 80 and 99.5 per cent by weight are suitable. Particularly advantageous are copolymers contain-ing about 90 to 99 per cent by weight of vinyl-N-alkyl carboxylic acid amide .
The water-soluble synthetic polymer is, especially, a copolymer of vinyl-N-methyl acetamide and 2-ethyl hexyl acrylate. Preferably, it has a K-value of between 45 and 50, measured as a 1 per cent solution ln methanol. It is soluble in water, in acids and in organic solvents, e.g., alcohols, ketones, polyglycols and ethylene glycol methyl ether acetate; in aqueous alkaline solutions swelling is observed. It 1s, to a large extent, compatlble with the acrylic resins addltionally used according to the lnvention.
The K-value is a technical measure of the average degree of polymerization of a polymer: -K-value = 1000 k 2 0 Where:
k=t1.5 lg z - 1 + ~f1 ~ ~200/c + 2 + 1.5 lg z) 1.5 lg zl)/(150 + 3c) z = ~/~;70; '7 = viscosity of the solution, ~7O = viscosity of the solvent, c = concentration of the solution ln g/100 ml.
As acryllc reslns lnsoluble ln water, which are soluble or at least swellable in an alkali, copolymers of methacrylic acid and at least one alkyl methacrylate are suitable, with the alkyl methacrylate or at least one of the alkyl methacrylates having an alkyl group containing 1 to 15 carbon atoms. Preferably, this binder is a copolymer of methacrylic 9~ 2 K-2506 acid and a Cl to C15 alkyl methacrylate, in particular of methacrylic acid and methyl or ethyl methacrylate in weight ratios ranging between 10: 90 and 25: 75 (relative to the monomers used). Also preferred are terpolymers of methacrylic acid and two different Cl to C alkyl methacrylates, one of these being, in particular, methyl or ethyl methacrylate. Especially advantageous are terpolymers of methacrylic acid, methyl or ethyl methacrylate and a C4 to C8 alkyl methacrylate, such as n-hexyl methacrylate, e.g., in weight ratios ranging between 16: 13: 71 and 26: 15: 59 , as described in German Offenlegungs-schrift No. 2,064,080, or U. S. Patent No. 3,804,631.

Apart from the copolymers and terpolymers mentioned above, theacrylic resin which is soluble or at least swellable in an alkali may be a terpolymer of (A) an unsaturated carboxylic acid, (B) a Cl to C20, preferably a C4 to C12 alkyl methacrylate and (C) a further monomer copolymerizable with (A) and (B), the corresponding homopolymer of which has a glass transition temperature of at least 80 C. These copolymers are known from German Offenlegungsschrift No . 2, 363, 806, or from U.S. PatentNo. 3,930,865.

As the component (C) of this terpolymer the following compounds are among others which are suitable:

Styrene or a substituted styrene, e.g., vinyl toluene, p-chloro-styrene, a-chlorostyrene, a-methylstyrene, vinyl ethyl-benzene, o-methoxystyrene and m-bromostyrene; vinyl naphthalene or a substituted vinyl naphthalene; a vinyl heterocycle, such as N-vinyl carbazole, vinyl pyridine, and vinyl oxazole; a vinyl cycloalkane, e.g., vinyl cyclohexane, 3,5-dimethyl-vinyl cyclohexane, acrylamide, methacryl-amide, N-alkyl acrylamide, acrylonitrile, methacrylonitrile, aryl methacrylate, aralkyl methacrylate, etc.

A preferred embodiment of the copylng composltion according to the invention contains a terpolymer in which the component (C) ls styrene, p-chlorostyrene, vinyl toluene, vinyl cyclohexane, acrylamide, meth-acrylamide, N-alkyl acrylamide, phenyl methacrylate, acrylonitrlle, methacrylonitrile or benzyl methacrylate. Of these, styrene is particu-larly preferred.
As unsaturated carboxylic aclds (A) methacrylic acid, acrylic acid, crotonic acid, sorbic acid or maleic acid or ltaconic acid or their monoesters are preferably used. Methacrylic acid is particularly preferred.

Particularly preferred are terpolymers of (A), (B) and ~C) in the weight ratios of 25: 67: 8 to 35: 53: 12.
It is further possible that the blnder copolymer contalns, apart from t~he components (A), (B) and (C), another alkyl methacrylate which is copolymerlzable with these components and which may contain in its alkyl group a number of carbon atoms different from (B). As a matter of ~ -fact, all of the components (A), (B), and (C) may be present by several of their representatives.
Binders comprising four monomeric units are, e.g., preferred when a fine adlustment of certain properties, such as adhesion of the copying composition to newly developed alloys, is required.
C)f the acrylic resins mentioned, which are soluble or at least swellable ln an alkali, the polymers with acld numbers ranging between 60 and 200 and molecu~lar weights ranglng between 20,000 and 50,000 are partlcularly suitable.
Suitable light-sensitive copdensed diazonium compounds are in particular condensates of diazotized p-amino diarylamines with com-pounds containing carbonyl groups, e.g., aldehydes, preferably form-aldehyde, or with aldehyde donors, e.g. paraformaldehyde. These and similar compounds are disclosed in German Patent No. 1,214,086, or U. S. Patent No. 3,235,334 and in U. S. Patents Nos. 2,922,715 and 2,946,683. Particularly preferred are condensation products of diazo-tized p-amino diphenylamine and paraformaldehyde, which are free from metal salts, corresponding to German Patent No. 1,214,086, or U. S.
Patent No. 3,235,384. Further, the diazonium condensates described in German Offenlegungsschriften Nos. 2,024,242; 2,024,244, and 2,041,395, are suitable. These condensationproducts comprise at least one unit each of the general types A(-D) and B, which are inter-connected by bivalent intermediate members derived from a carbonyl compound capable of condensation.
As the components A(-D)n and B practically any compounds may be used which are capable of reaction, by condensation, with active carbonyl compounds, in an acld medlurn and which are not decomposed by the conditions of the condensation reaction.
Where:
A is a radical of a compound containin~ at least two isocyclic or heterocyclic aromatic rings and which, in an acid medium, is in at least one position of its molecule condensable with an active carbonyl com-pound, D is a diazonium salt group which is linked to an aromatic carbon atom of A, n is an integer between 1 and 10, B is a radical of a compound free from diazo groups, which is, in an acid medium, in at least one position ~` ~9~;22 K-2506 of its molecule eapable of condensation with an active carbonyl compound, in particular a radical of an aromatic amine, a phenol, a phenol ether, an aromatic thioether, an aromatic hydrocarbon, an aromatic heterocyclic compound or an organic acid a mide .
The anion of the diazonium salt is preferably derived from an ali-phatic monosulfonic acid having from 1 to 6 carbon atoms. Condensates of a 3-alkoxy-diphenylamine-4-diazonium salt and a derivative of di-lû phenyl ether, diphenyl sulfide, diphenyl methane or diphenyl are equally preferred.
A great number of examples of dlazo condensates of these kinds are given in German Offenlegungsschriften Nos . 2, 024, 242; 2, 024, 244;
and 2,041,395, already mentioned.
The preferred part-by-weight ranges of the individual components of the eopying eomposltlon are approxlmately as follows:
0.2 to 1.5 parts by weight of a diazo condensate, 0.1 to 5.0 parts by weight of the aerylie resin, - :
0.5 to 4.0 parts by weight of the water-soluble synthetie polymer and, if required, 0 .01 to 0.175 part by weight of a dye.
The added dyes preferably act as contrast agents. Blue dyes are best suited which, together with the yellow diazonium condensate, im-part a green color to the eopying layer. This eombination has the ad-vantage that upon exposure a elear image contrast is obtained, whieh substantially reduees or even eliminates the risk of a double exposure in praetice .
Suitable dyes are compounds which are soluble in organic sol- ;~
vents, e.g., those belonging to the class of azo or triphenyl methane ~ ~7~Z K-2506 dyes . A preferred dye is a coupling product of 2 ,4-dinitro-6-chloro-benzene diazonium salt with 2-methoxy-5-acetylamino-N-cyanoethyl-N-hydroxyethyl aniline.
The negative-working copying materials are produced in known manner. The coating solution composed of the components of the copy-ing composition and a suitablè solvent or solvent mixture is applied by casting, spraying, immersion, application with rollers etc., so as to form a film on the intended carrier, which is subsequently dried.
The carrier materials used for the reversal plate are generally zinc or aluminum or laminates of zinc and polyester. In order to obtain long runs it is advantageous to use a metal carrier with improved adhe-sion, e.g., mechanically, chemically or electrolytically roughened and anodized aluminum with an aluminum oxide weight of at least 3 g/m2.
The process for the preparation of a planographic printlng form using the copying material according to the invention is, in detail, as fol.loWs:
The copying material is exposed in the actinic range under a posi-tive original and is developed with a suitable developer.
Preferred developers are aqueous allcaline solutions, e.g., of alkali phosphates, alkali silicates or alkali borates, to which small quantities of miscible organic solvents may be added, if required. The pH value of the solutions is preferably between 8 and 10. For special compositions small additions of suitable anionic wetting agents, such as sodium lauryl sulfate or ammonium alkyl sulfate, have proved suc-cessful. It is also possible to use solely developer mixtures composed of deionized-water and an organic solvent miscible wlth water, -with the addition of small quantities of wetting agents, if required.
After thoroughly rinsing with water, the plate is completely dried and, if necessary, the film edges or defective areas are corrected by ~97~ 2 K-2506 means of a masking lacquer. In order to ensure long runs, the subse-quently applied lacquer is preferably dried for 10 minutes at 50 to 60 C and, if necessary, the plate is treated with a protective ink. Then, any surplus lacquer and ink are removed by brisk brushing under water and subsequently the hardened portions of the copying layer are removed by treating-with a stripper.
As strippers, aqueous alkaline solutions likewise may be used.
They differ from the corresponding developers in that they have higher pH values.
Finally, the surface of the plate is acidified or made hydrophilic, preferably using dilute phosphoric acid, and, if required, it is coated or preserved with a protective ink. Then the plate is ready for printing.
If the above procedure is appropriately modified the copying com-position according to the invention, among others, also may be used for the preparation of a printing form on a multi-metal carrler, e.g. a tri-metal carrier.
For this purpose, the presensitized planographic printing plate comprising the copying composition according to the invention and a multi-metal carrier, e.g., a chromium/copper/aluminum carrier, is ex-posed under a positive original; the non-hardened image areas are re-moved by treatment with a developer; the bared carrier surface is etched with a chromium etching solution until the copper appears; the copper surface is preferably activated by treatment with compounds producing oleophilic properties and, finally, the image areas hardened by the light are removed with an alkaline solution. Following treatment of the image-wise modified carrier surface, preferably with dilute phosphoric acid, the planographic printing plate is ready for printing.
Carriers composed of copper/aluminum or brass/chromium are gen-erally used for bimetal plates, whereas for trimetal plates carriers of -- 11 ~

1~ ~9~1ZZ K- 2 5 0 6 aluminum/copper/chromium or steel/copper/chromium are generally used .
In addition, printed circuits may be prepared using the copying composition according to the invention. In this case, processing is carried out as is usual for the preparation of bimetal plates: Following exposure under a negative original the material is developed and then etched and stripped. Carriers used for the preparation of printed cir-cuits may be laminates of copper and a moulding material of phenolic resin, or copper and a glass fiber reinforced epoxy resin or copper and a polyimide.
As compared to the conventional copying compositions and negative-working planographic printing plates the copylng compositions and plates according to the present invention as well as the method suggested for their processing have the following advantages:
The copying layer may be developed wlthout residue by means of aqueous solutions which contain only very small amounts of organic compounds and which, in addition, are ecologically acceptable. As a consequence, no deep etching of the carrier surface is required after development the copying layer is not susceptible to finger marks, it is extremely well suited for storing, and in the light-hardened conditlon it may be stripped without residue using aqueous alkaline solutions.
In contrast to the stripping method at present employed in the graphic trade, involving the use of potassium permanganate and H2O2 mixtures, this stripping method is to a higher degree ecologically accept-able and is thus less problematic.
The copying composition and the copying material prepared with this copying composition as-well as the method for processing this material are further illustrated by the examples which follow. Unless 97~ 2 K-2506 otherwlse stated, the percentages and quantities specified in the exam-ples are by weight. The relation between parts hy weight and parts by volume corresponds to that between g and ml.
Example 1 To an electrochemically roughened and anodized aluminum surface wlth an oxide layer of 3 g/m2 a solut~on of the following composition is applied:
1.34 parts of a terpolymer containin~ 62.5 per cent of n-hexyl methacrylate, 12.5 per cent of methyl methacrylate and 25 per cent of methacrylic acid having an acid number of 155, 4 parts of a copolymer contalnlng 98 per cent of N-vlnyl-N-methyl acetamide and 2 per cent of 2-ethyl-hexyl acrylate havlng a K-value of 45 to 50, measured as a 1 per cent solution ln methanol, 0.53 part of a polycondensate of p-diazodlphenylamine and paraformaldehyde, as described in Example 1 of German Patent No. 1,214,086, or U. S.
Patent No. 3,235,384. (For this purpose, approximately 42 parts of an 85 per cent phos-phoric acid, 3.3 parts of paraformaldehyde and 23 parts of diphenylamine-4-dla~onium chloride are stirred in at room temperature. The resulting viscous solution ls stirred for 30 minutes at room temperature, Subsequently, lt ls heated to 4 0 C~ C durin~ 24 hours . ) :;

71~;~

0.04 part of a dye obtained by coupling 2,4-dlnitro-6-chloro-benzene diazonlum salt wlth 2-methoxy-5 -acetylamlno-N-cyanoethyl-N -hydroxyethyl-anillne, 4.06 parts of methyl ethyl ketone, and 90 . 03 parts of ethylene glycol monomethyl ether.
The solution is applled by casting or whirler-coating in such a manner that a dry layer weighing 2.8 to 3 g/m2 is obtained.
Subsequently, the platè is drled for 2 minutes at 100C. Follow-ing an exposure of 35 seconds under a positive original with a Xenokop (capacity 8 kW, distance 80 cm, model BIKOP of Messrs. ~limsch, Neu-Isenburg) the exposed plate is developed for one minute, using a plush pad, with a developer of the following composition:

3 parts of n-propanol, 0.05 part of sodium lauryl sulfate as a wetting agent; and ~96 . 95 parts of deionized water, so that a negative image of the orl~inal ls obtained.
After thoroughly rlnslng with water, the plate is dried for 10 min-utesat50C.
Subsequently, possible film edges or defective areas are correct-ed, e.g., by means of "Abdeckfarbe-Rot" of Messrs. EGGEN-Hannover, Followin~ drylng of the correcting agent, e.g., under a hot-air blower, the plate is coated with a lacquer. Any commercially available lac-quers may be used, such as "Ha~olac" of Messrs. Hauslelter (Munich), "EGGEN-Stabil-Lack" of Messrs. EGGEN-Hannover, "Rubilac 9" of Messrs. IMG ~Verona~ Italy) and "Krause-Alu-Emaille-Lack" of Messrs.
`~ Krause tBielefeld).
The lacquer ls dried for 10 minutes at 50 to 60 C in a drying chamber. Then, various protective inks may be applled, such as .

971~;2 "Schutzfarbe S" (EGGEN), "Haco-Pos. Fettfarbe" (Hausleiter) or "RC
43" (KALLE). Prior to stripping, any surplus lacquer and greasy ink are removed by brushing in water.
The light-hardened stencil is then stripped using a solution of the following composition:
9 parts of completely softened water, 5.3 parts of sodium metasilicate 9 H2O, 3.4 parts of tert. sodium phosphate 12 H2O, and 0.3 part of sec. sodium phosphate.
Subsequently, the plate is acidified-with a 1 per cent phosphoric acid and then preserved.
On a (Multilith 1850) printing machine approximately 150,000 flawless prints without loss of tone vaLue were produced.
Example 2 A solution of:
1.78 parts of a terpolymer binder of styrene, n-hexyl methacrylate and methacrylic acid in a ratio of 10: 60: 30, having an acid number of 195 to 200, 3.56 parts of a copolymer as described in Example 1, part of a diazonium mixed condensate of 1 mole of 3-methoxy-diphenylamine-4~diazonium sulfate and 1 mole of 4,4'-bis-methoxy methyl-diphenyl-ether, prepared in an 85 per cent phosphoric acld ~ ;~
and isolated as methane sulfonate, 0.1 part of the dye described in Example 1, in 94 parts of ethylene glycol monomethyl ether, is applied to an electrochemically roughened and anodized aluminum 7~'~Z

plate wlth the aid of a casting device in such a manner that after drying in a stream of warm air a layer weighing about 2.5 g/m2 is obtained.
Subsequently, the plate is exposed for approximately 30 seconds under a positive original using a metal halide lamp with a capacity of 5 kW, positioned at a distance of 140 cm.
The image areas which are not cross-linked are washed out using a plush pad with a developer of the following composition:
0.8 part of polyethylene glycol 200, 0.6 part of sodium lauryl sulfate, and 98.6 parts of deionized water.
After thoroughly rinsing with water, the plate is dried for 10 min-utes at 50 C. The plate is further processed as described in Example 1, preferably using "Abdecklack-Rot" of Messrs. EGGEN as a masking lacquer and "EGGEN-Kopierlack-Stabll" as a lacquer.
The light-hardened stencil is strlpped using the same solution as in Example 1. Up to 150,000 copies are printed with these plates.
Example 3 A solution of:

4 parts of a terpolymer of n-hexyl methacrylate, methyl methacrylate and methacrylic acid in a ratio of ; 62.5 :12.5 :25, having an acid number of about 160, 1 part of a copolymer as described in Example 1, 1 part of a polycondensate of p-diazo-diphenylamine with paraformaldehyde, a s described in Exam-ple 1, 0.075 part of the dye described in Example 1, in 15 parts of methyl ethyl ketone, and 70 parts of ethylene glycol monomethyl ether, is whirler-coated on a trimetal plate composed of Fe/Cu/Cr in such a manner that a layer weighing about 2 g/m is obtained. The plate is dried for 2 minutes at 100 C.
Subsequently, the coated plate is exposed for 150 seconds under a positive original using a Xenokop (capacity 8 kW, distance 80 cm, model BIKOP of Messrs. Klimsch, Neu-Isenburg), and developed with a developer of the following composition:
70 parts of completely softened water, 25 parts of n-propanol,

5 parts of MgSO4 7 H2O, and 0.5 part of lauryl polyglycol ether.
The plate is rinsed with water and dried with the aid of a fan.
The developed plate is then treated with a solution of:
17.4 per cent of calcium chloride, 35.3 per cent of zinc chloride, 2.1 per cent of hydrogen chloride and 45.2 per cent of water, until the copper in the developed image areas is entirely bared. It is again rinsed with water and the light-hardened stencil (etch resist) is re-moved-wlth a stripper, as described in Example 2.
After rubbing the plate with a conventional activator, such a~
sulfuric acid or mercapto compounds, in order to render the copper ~ ^-surface oleophilic, the plate is rinsed with-water and then a greasy - ink is applied.
Example 4 ' ~` A solution of:
part of a terpolymer of n-he~yl methacrylate, methyl methacrylate and methacrylic acid in a ratio of 62.5: 12.5: 25, having an acid number of about 160, - 17 ~

~7~2;2 K- 2 5 0 6 4 parts of a copolymer containing 91 per cent of N-vinyl-N-methyl acetamide and 9 per cent of 2-ethyl hexyl acrylate, having a K-value of 70, measured as a 1 per cent solution in methanol, 0.8 part of a polycondensate of p-diazo diphenylamine with paraformaldehyde, according to Example 1, 0.175 part of the dye described in Example 1, in 3 .2 parts of methyl ethyl ketone, and 1090.83 parts of ethylene glycol monomethyl ether, is appll0d to an electrochemically roughened and anodlzed aluminum plate with an oxide layer of 10 g/m by castlng or whirler-coating in such a manner that a layer weighing 2 .2 g/m2 is obtained.
The plate is then dried for 2 minutes at 100C. Following expo-sure for about 30 seconds under a positlve original using the lamp de-scribed in Example 2 positioned at a clistance of 140 cm, the unexposed image areas are washed out with a 1 per cent phosphoric acid, and the plate is rinsed with water.
The deve.loped plate is dried for 10 minutes at 50C, and is then 20further processed as described in Example 1. ~:
70,000 to 80,000 flawless prints are obtained.
Example 5 A solution of: -1. 78 parts of a copo.lymer of methyl methacrylate/
methacrylic acid in a-weight ratio of 90: 10, having an acid number of 65 and an average molecular weight of 30, 000, 3.56 parts of a copolymer as described in Example 1, ' . .

7~L~2Z K-2506 0.40 part of a polycondensate of p-diazo diphenylamine and paraformaldehyde as described in Example 1, 0 . 04 part of the dye described in Example 1, in 60 parts of ethylene glycol monomethyl ether is whirler-coated on an electrochemically roughened and anodized alumi-num plate in such a manner that a layer weighing approximately 2 . 8 g/m2 is obtained . The plate is dried for two minutes at 100 C . Fol-lowing an exposure of 45 seconds under a positive original by means of a Xenokop (capacity 8 kW, distance 80 cm, model BIKOP of Messrs.
Klimsch, Neu-Isenburg) the exposed plate is developed during 45 sec-onds, using a plush pad, with a developer composed of:
5 parts of n-propanol, and 95 parts of deionized water, so that a negative image of the original is obtained.
The plate ls further processed as described in Example 1.
Example 6 A solution of the following composition:
1.34 parts of a copolymer of methyl methacrylate/
methacrylic acid in a weight ratio of 80: 20, having an acid numberof 120 and an average molecular weight of 3 5, 000, 4 parts of a copolymer as described in Example 1, 0.5 part of a polycondensate of p-diazo diphenylamine and paraformaldehyde as described in Example 1, 0 . 04 part oi the dye described in Example 1, in 65 parts of ethylene glycol monomethyl ether, is applied to an electrochemically roughened and anodized aluminum plate in such a manner tha~ a layer weighing approximately 3 g/m2 is obtained .

~9~2 ~-2506 The plate is further processed as described in Example 1. The exposed plate is treated with the following developing solution:
3 parts of n-propanol, 0.06 part of sodium lauryl sulfate 0. 01 part of antifoaming solution T (see Karsten Lack-rohstofftabellen, 5th Edition, page 415).
The plate is further processed as described in Example 1.
Approximately 100,000 prints are obtained.
Example 7 A plate of a coppe~phenoplast laminate cleaned with pumice ;~
powder and thoroughly rinsed with water is first dried with a blower and then dried for 10 minutes at 100C.
Subsequently, the plate 1s whirler-coated with a solution of:
4.25 parts of a terpolymer of n-hexyl methacrylate, methyl methecrylate and methacrylic acid in a ratio of 62.5 :12.5 :25, havlng an acid number of about 160, 0.75 part of a copolymer as described in Example 1, 0.4 part of a polycondensate of p-diazodiphenylamine and paraiormaldehyde, as described in Example 1, 0.04 part of the dye as described in Example 1, in 60 parts of ethylene glycol monomethyl ether, in such a manner that a layer weighing approximatély 4 g/m2 is obtained .
The layer is pre-dried for 1 minute in warm air, and the plate is then placed for 2 minutes in a drying chamber at a temperature of 100 C.

.; .,., . - ., . ' ~1~97~ K--2506 Following an exposure of 60 seconds under a negative original using a Xenokop (capacity 8 kW, distance 80 cm, model BIKOP) the unexposed image areas are removed with a developer of the following composition:
220 parts of deionized water, 35 parts of n-propanol,

6.5 parts of MgSO4 7H2O, and 0 . 7 part of lauryl polyglycol ether.
After thoroughly rinsing with water the layer is sub~ected to a compressed air stream, and subsequently the bared copper is etched in an etching machine using a ferric chloride solution of 42 Be, with the hardened image areas serving as an etch resist.
Following stripping of the cross-linked layer areas with acetone the desired cLrcuit path image is obtained.
It will be obvLous to those skllled in the art that many modifica-tions may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications .

Claims (16)

WHAT IS CLAIMED IS:

1. In a negative-working light-sensitive copying composition com-prising at least one condensation product of a diazonium salt, at least one water-soluble synthetic polymer and at least one acrylic resin which is soluble or at least swellable in an aqueous alkaline solution, the improvement that the water-soluble synthetic polymer is a co-polymer of a C3 to C16 alkyl acrylate and an N-vinyl-N-alkyl carboxy-lic acid amide, the alkyl and carboxylic acid groups of which contain 1 to 6 carbon atoms each.

2. A copying composition in accordance with claim 1 in which the water-soluble polymer is a copolymer of N-vinyl-N-methyl aceta-mide and 2-ethyl hexyl acrylate.

3. A copying composition in accordance with claim 1 in which the acrylic resin is a copolymer of methacrylic acid and at least one C1 to C15 alkyl methacrylate.

4. A copying composition in accordance with claim 3 in which the acrylic resin is a copolymer of methacrylic acid and methyl methacry-late or ethyl methacrylate.

5. A copying composition in accordance with claim 3 in which the acrylic resin is a terpolymer of methacrylic acid, methyl methacrylate or ethyl methacrylate, and a C4 to C15 alkyl methacrylate

6. A copying composition in accordance with claim 5 in which the alkyl methacrylate is butyl methacrylate or hexyl methacrylate.

7. A copying composition in accordance with claim 1 in which the acrylic resin is a copolymer of (A) an unsaturated carboxylic acid, (B) a C1 to C20 alkyl methacrylate and (C) a further monomer copolym-erizable with (A) and (B), the corresponding homopolymer of which has a glass transition temperature of at least 80°C.

8. A copying composition in accordance with claim 7 in which the acrylic resin is a copolymer of methacrylic acid, n-hexyl methacrylate, and styrene.

9. A copying composition in accordance with claim 1 in which the acrylic resin has an acid number between 60 and 200.

10. A copying composition in accordance with claim 1 in which the acrylic resin has a molecular weight ranging between 20,000 and 50,000.

11. A copying composition in accordance with claim 1 in which the weight ratio of water-soluble synthetic polymer and acrylic resin is within the limits of 10:90 and 90:10.

12. A copying composition in accordance with claim 1 in which the composition further contains pigments, dyes, plasticizers or color couplers.

13. In a light-sensitive copying material composed of a carrier and a light-sensitive layer comprising at least one condensation product of a diazonium salt, at least one water-soluble synthetic polymer and at least one acrylic resin insoluble in water, which is soluble or at least swellable in an alkali.
the improvement that the water-soluble synthetic polymer is a co-polymer of a C3 to C16 alkyl acrylate and an N-vinyl-N-alkyl carboxy-lic acid amide, the alkyl and carboxylic acid groups of which contain 1 to 6 carbon atoms each.

14. A process for the preparation of a planographic printing form using a light-sensitive copying material in accordance with claim 13, compris-ing exposing the copying material under a positive original, removing the non-hardened image areas by treatment with a developer, coating the imagewise bared carrier surface with an alkali-resistant ink-receptive lacquer, dyeing the entire surface with a protective ink and subsequently treating it with water while brushing, and removing the light-hardened image areas with an alkaline solution.

15. A process according to claim 14 including rendering the bared carrier surface hydrophilic.

16. A process for the preparation of a planographic printing form which comprises exposing a light-sensitive layer, on a multi-metal carrier composed of chromium/copper/aluminum, under a positive original, said light-sensitive layer comprising at least one condensation product of a diazonium salt, at least one copolymer of a C3 to C16 alkyl acrylate and an N-vinyl-N-alkyl carboxylic acid amide, the alkyl and carboxylic acid groups of which contain 1 to 6 carbon atoms each, and at least one acrylic resin which is soluble or at least swellable in an aqueous alkaline solution, removing non-hardened image areas by treatment with a developer, etching the bared carrier surface with a chromium etching solution until the copper appears, and removing light-hardened image areas with an alkaline solution.