Composition for the development of lithographic printing plates.

The present invention relates to a developer mixture for removing the non-image areas of exposed planographic printing plates which consist of a support provided with a light-sensitive layer.

Various methods of developing printing plates have been used in the past. For example, mixtures were used which consist of solutions of organic solvents, wetting agents, salts, acids and other substances known from the prior art.

The aim is to produce a developer mixture with which the development can be carried out within a short time. The oleophilic image areas of the printing plate should be ink-accepting and water-repellent, while the hydrophilic non-image areas should take on water and repel bold ink.

The correct selection of the organic solvents used for the developer solution is of great importance. If the solvent used for the photosensitive mixture itself is well suited, there is no sufficient distinction between the exposed and the unexposed areas. As a result, a large part of the layer components of the image areas are dissolved in the solvent or swell strongly and detach. Such printing plates are unusable. The image differentiation can be improved by adding water to lower the solvent concentration in the developer solution. During the development of printing plates, in particular of negative working printing plates, however, the resin-like binders present at the non-image areas, such as acetals, in particular polyvinyl formal, are solvated in the developer solution and detach from the layer support and clump together to form spherical, very sticky structures. Solvated particles of this type are deposited on the still solvent-dampened image areas and remain there even after drying. These "reassembled" areas can be seen with the naked eye on the developed printing plate and, moreover, are torn off from the plate by the sticky printing ink during the printing process together with the actual, underlying image area, thereby creating holes which are recognizable as image-free areas on the finished print.

To at least partially remedy this problem, many known developer mixtures use volatile solvents. It is hoped from the presence of such volatile solvents in the developer solution that rapid evaporation of the solvent prevents the image areas from becoming sticky. The use of large amounts of water-soluble solvents with a low boiling point, such as in the developer according to US Pat. No. 3,954,472, however, leads to problems with regard to health risks in the workplace, safety risks due to the low flash point and environmental pollution. By lowering the concentration of these low-boiling water-soluble solvents, these problems can be reduced to a minimum, but at the same time, development time is increased. The stickiness of the layers is reduced, but cannot be completely eliminated.

In order to shorten the time required for development when using developer solutions with a lower content of low-boiling solvents, an organic solvent is additionally used in some cases. However, such developers also have a number of disadvantages, such as, for example, toxicity, lower developer stability, unpleasant odors or inability to fully expose the background of the image at the non-image areas.

Planographic printing plates generally consist of an aluminum-based substrate which, if appropriate, has been pretreated using one of the many known processes, for example by anodic oxidation, various roughening processes or hydrophilization. A light-sensitive layer composed of light-sensitive compound, resinous binders, colorants, stabilizing acids, wetting agents and other known constituents is applied to the thus prepared substrate. Commonly used photosensitive compounds include diazonium compounds such as polymeric diazonium salt condensation products, quinonediazides and photopolymerizable mixtures. Photosensitive compounds, binders and printing plates for the production of which aromatic diazonium compounds are used are known, for example, from US Pat. Nos. 3,175,906, 3,046,118, 2,063,631, 2,667,415, 3,867,147 and 3,679,419.

Typical developer mixtures belonging to the prior art are described in US Pat. Nos. 2,754,279 and 4,381,340 and in DE-A 22 16 419.

In order to be able to achieve the best possible printing performance with the printing plates used in each case, it is customary today to use a developer mixture which is precisely matched to each individual printing plate type, ie to the binder added to the light-sensitive mixture. It is even customary to use different developers for printing plates, in the light-sensitive layer of which the same binder is contained and which differ from one another only in that the layer supports have been roughened mechanically or electrolytically.

The object of the present invention is to overcome the disadvantages of the known developers for planographic printing plates, a method for developing different types of printing plates being provided which works with only a single developer mixture. Both printing plates with substrates made of mechanically roughened aluminum and printing plates with substrates made of electrolytically roughened aluminum should be able to be developed without significant differences in development time.

It is also an object of the present invention to provide a developer for planographic printing plates, with the aid of which it is possible to produce printing plates which are essentially free of undesired redepositions. The developer mixture should also cause no foaming and less odor nuisance by solvents and also have a higher flash point. From the point of view of economy, the non-image areas should be removed quickly and easily and the developer should have a particularly long service life. The development of the developer should be very balanced overall. It should not be too aggressive, nor should long development times be required, while at the same time it should be suitable for the development of numerous different printing plates in which different light-sensitive mixtures are contained.

The invention relates to an aqueous developer mixture for removing the non-image areas of a photosensitive substance located on a carrier after their exposure, the developer mixture containing organic solvents and salts, the characteristic feature of which is that it<ul id="ul0001" list-style="none"><li>a) 5 to 30% by weight of benzyl alcohol,</li><li>b) 1 to 20% by weight of an alkali, preferably sodium, xylene sulfonate and / or alkali, preferably sodium, cumene sulfonate,</li><li>c) 5 to 40 wt .-% of an alkali, preferably potassium, toluenesulfonate, and d) supplemented to 100 wt .-% water.</li></ul>

If appropriate, the developer can also contain salts, antioxidants and an anionic or nonionic wetting agent.

In the manufacture of photosensitive materials, such as. B. planographic printing plates, a sheet-like carrier is first pretreated and optionally, for example, from aluminum alloys suitable for the production of planographic printing plates such as Alcoa 3003 or Alcoa 1100 and optionally in the usual way, for example by mechanical or electrolytic roughening and / or etching and / or anodic oxidation also with a mixture such as Polyvinylphosphonic acid has been treated, which is suitable as a hydrophilizing agent for planographic printing plates, coated with a photosensitive, a polymeric diazonium salt, a quinonediazide or a mixture containing a photopolymer. This mixture can also contain resinous binders such as polyvinyl acetate or polyvinyl formal resins, novolaks, polyurethanes, polyvinyl acetates or styrene-maleic anhydride copolymers, colorants, stabilizing acids, wetting agents, exposure indicators or other known additives.

The light-sensitive sheet-like material is then exposed by means of a radiation source through a mask or transparent template, and the exposed plate is developed to remove the non-image areas.

The photosensitive mixture is usually prepared as a mixture in a solvent system that is compatible with all other components. The layer support is coated with this light-sensitive mixture and the solvent is evaporated.

The diazonium compounds which are used most frequently in the context of this invention for the preparation of light-sensitive mixtures correspond to the general formula A-N₂⁺X⁻, in which A is an aromatic or heterocyclic radical and X is the anion of an acid.

The light-sensitive diazonium materials suitable for the abovementioned purposes include, in particular, higher molecular weight mixtures which, for. B. can be obtained by the condensation of certain aromatic diazonium salts in an acidic medium with certain aromatic carbonyl compounds such as formaldehyde, as described, for example, in US Pat. Nos. 2,063,631 and 2,667,415. A group of diazonium compounds used with preference is described in US Pat. No. 3,849,392. Particularly preferred among the diazonium salts is the polycondensation product of 3-methoxy-4-diazodiphenylamine sulfate and 4,4'-bismethoxymethyldiphenyl ether which is known from US Pat. No. 3,849,392 and precipitated as mesitylene sulfonate.

Suitable photopolymerizable mixtures are known to the person skilled in the art.

The present invention provides a method for developing such exposed, light-sensitive materials, in which a developer is used to remove the non-image areas, which contains the mentioned components in aqueous solution. The developer obtained according to the invention preferably has a flash point of at least 111 ° C (200 ° F), in particular at least 122 ° C (220 ° F).

The alkali, preferably potassium, toluenesulfonate component is based in the aqueous mixture in an amount of 5 to 40% by weight, in particular 15 to 35% by weight, and preferably 20 to 30% by weight, in each case on the total weight of the mixture.

The alkali, preferably sodium, xylene and / or alkali, preferably sodium, cumene sulfonate component is in the aqueous mixture in an amount of 1 to 20% by weight, in particular 3 to 15% by weight, and preferably from 4 to 10% by weight, based in each case on the total weight of the mixture.

The benzyl alcohol component is contained in the aqueous mixture in an amount of 5 to 30% by weight, in particular 8 to 25% by weight, and preferably 10 to 15% by weight, in each case based on the total weight of the mixture.

The mixture preferably also contains at least one salt from the group of potassium and sodium phosphates, nitrates, chlorides, borates, acetates, sulfates, citrates, sulfites, tartrates, oxalates, formates and propionates, -succinates, -glutamates and -benzoates. The salt component is in the developer in an amount of 0.1 to 10% by weight, preferably 0.1 to 3% by weight and in particular 0.1 to 1% by weight, in each case based on the weight of the developer , available.

In a preferred embodiment, the developer according to the invention can also contain smaller amounts of other constituents which facilitate the processing of the printing plate. Such constituents are, for example, antioxidants, nonionic or anionic wetting agents and other known substances, such as, for example, agents for preventing foam formation. Antioxidants are used to mainly prevent conversion of the benzyl alcohol into benzaldehyde.

Antioxidants suitable according to the invention include, for example, 2,6-di-tert-butyl-p-cresol (available under the name Ionol from Shell Chemical Co., Houston, Texas), tetra-kis [methylene (3, 5-di-tert-butyl-4-hydroxy-hydrocinnamate)] - methane (available under the name Irganox 1010 from Ciba Geigy) and 3,4,5-trihxdroxybenzoic acid propyl ester (as propyl gallate from Alderich Chemical Co., Milwaukee, Wisconsin, available).

The antioxidant optionally used is preferably used in an amount of 0.005 to 0.2% by weight, in particular 0.01 to 0.05% by weight, in each case based on the total weight of the mixture.

The mixture further preferably contains at least one anionic or nonionic wetting agent which is present in the developer mixture in an amount of 0.1 to 2% by weight, preferably 0.5 to 1% by weight, based in each case on its total weight. Suitable, preferably used wetting agents correspond to the general formula<chemistry id="chem0001" num="0001"><img file="EP0212263A2_D0001.tif" /></chemistry> in the n = 4 - 40 and R = H = OH = C₈H₁₇ = C₉H₁₉ = C₁₀H₂₁ or = CH₃ (CH₂)_m-O- (CH₂CH₂O)_{n '}CH₂CH₂OH mean where m = 9-30 n '= 4 -20.

The preferred Netzmilleln include: Nonylphenoxy polyoxyethylene ethanol, Polyoxyethylene monosorbitan oleate, Tridecyl alcohol polyoxyethylene ethanol, Isooctylphenoxypolyoxyethyleneethanol, Decyl alcohol polyoxyethylene ethanol, Decylphenoxypolyoxyethylene ethanol, Isooctylphenoxypolyoxyethylene ethanol and Isooctylphenoxyethylene ethanol.

A detailed description of these wetting agents is contained in US-A4381340.

Particularly preferred wetting agents according to the invention are octylphenoxypolyethoxyethanol (available under the name Triton TX-100 from Rohm &amp; Haas, Philadelphia, Pa.) And tridecyl alcohol polyoxyethylene ethanol (under the name Trycol OP 407 available from Emery Industries, Inc., Cincinnati, Ohio). .

The anionic wetting agents include ammonium, potassium and sodium laurysulfate, as well as sodium tridecyl ether sulfate. The mixture also contains water in an amount sufficient to produce an effective developer.

With the developer according to the invention, it is possible to remove the non-image areas of a light-sensitive material practically completely within a maximum of 2 minutes without noticeable parts of the image areas being removed in the process. Virtually nothing of the material from the removed non-image areas is re-attached to the reproduction material.

The invention is illustrated by the following examples, but without being restricted to these:

Example 1:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R)whose aluminum carrier material has been roughened electrolytically are exposed imagewise in a known manner by means of actinic radiation. (Plates of this type are available from American Hoechst Corp., Somerville, New Jersey.) Their photosensitive layer contains a polyvinyl formal resin and a diazonium salt, as described in US-A 3,849,392. The exposed plates are developed in a commercially available processor with the following developer mixture: 10.50% by weight of benzyl alcohol, 29.00% by weight sodium xylene sulfonate and 60.50% water by weight.

The N-500 plate can be developed with a satisfactory result, while the image on the N-25 plate is completely washed off by the developer.

Example 2:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R)whose aluminum carrier material has been roughened electrolytically are exposed imagewise in a known manner by means of actinic radiation. The exposed plates are developed in a commercially available processor with the following developer mixture: 10.50% by weight of benzyl alcohol, 29.00% by weight of potassium toluenesulfonate and 60.50% water by weight.

The N-25 type plate can be developed with a satisfactory result, while the N-500 type plate cannot be properly developed. Aggregations are found in the grid area.

Example 3:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R)whose aluminum carrier material has been roughened electrolytically are exposed imagewise in a known manner by means of actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 10.50% by weight of benzyl alcohol, 6.00% by weight sodium xylene sulfonate, 23.00% by weight of potassium toluenesulfonate and 60.50% water by weight.

Both the plate of the type N-500 and the plate of the type N-25 can be developed without residue and result in printing forms with good printing properties. The layer is removed in the form of tiny particles during development.

Example 4:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R), whose aluminum support material has been electrolytically roughened, are exposed in a known manner using actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 5.50% by weight of benzyl alcohol, 6.00% by weight sodium xylene sulfonate, 23.00% by weight of potassium toluenesulfonate and 60.50% water by weight.

Both the N-25 plate and the N-500 plate can be developed perfectly, if not very easily. The layer is removed during development in larger pies. The reason for this is that component a) was used at the lowest limit with regard to the effectiveness of the developer.

Example 5:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R), whose aluminum support material has been electrolytically roughened, are exposed in a known manner using actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 25.50% by weight of benzyl alcohol, 6.00% by weight sodium xylene sulfonate, 23.00% by weight of potassium toluenesulfonate and 45.50% water by weight.

Both the N-25 plate and the N-500 plate can be easily and flawlessly developed.

Example 6:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R), whose aluminum support material has been electrolytically roughened, are exposed in a known manner using actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 10.50% by weight of benzyl alcohol, 10.00% by weight sodium xylene sulfonate, 19.00% by weight potassium tolulsulfonate, 0.20% by weight sodium benzoate, 0.75% by weight TX-100, 0.01% by weight of ionol and 49.44 wt% water.

Both the N-25 plate and the N-500 plate can be developed perfectly. The layer is removed in the form of tiny particles during development.

Example 7:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R), whose aluminum support material has been electrolytically roughened, are exposed in a known manner using actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 10.50% by weight of benzyl alcohol, 6.00% by weight sodium xylene sulfonate, 23.00% by weight of potassium tolulsulfonate, 0.20% by weight sodium benzoate, 0.80% by weight TX-100, 0.01% by weight of ionol and 59.49 wt% water.

Both the N-25 plate and the N-500 plate can be developed without residue and result in printing forms with good printing properties. The layer is removed in the form of tiny particles during development.

Example 8:

A coating solution is prepared from the following mixture: 0.447 g phosphoric acid (85%), 2.790 g polyvinyl acetate (Mowilith 60, manufacturer Hoechst AG), 5.581 g polystyrene / maleic acid semi-ester (Sripset 540, manufacturer Monsanto) , 0.030 g p-phenylazodiphenylamine, 0.056 g of Acetol-Feuerrot 3GLS (from Sandoz) and 5.023 g diazonium compound according to US-A 3 849 392.

The constituents mentioned are successively added to 450 g of ethylene glycol monomethyl ether with vigorous stirring. After all the components have been dissolved, the solution is filtered off and applied to an aluminum surface roughened and hydrophilized in an abrasive suspension. After the layer has dried, exposure is carried out through a negative template in such a way that a sufficient number of hardened steps is obtained under a 21-step Stauffer wedge serving as a template. The exposed plate is developed with the aqueous developer from Example 7. The unexposed areas are removed perfectly, while the exposed areas remain as a sharp image.

Example 9:

An 8 "× 25" plate of the aluminum alloy 1100 suitable for printing is degreased with an aqueous alkaline degreasing solution and electrochemically roughened with an alternating current of 900 Coulomb in a medium made of nitric acid and aluminum nitrate. The roughened plate is rinsed well and anodized in a sulfuric acid bath, the aluminum serving as the anode. The current strength and voltage is chosen so that an oxide layer of 2.8 g / m² is formed. The anodized plate is rinsed well and hydrophilized by immersion in a polyvinylphosphonic acid solution. The plate is then rinsed well again and dried. Now it is spin coated with a solution of the following composition: 4.54% by weight of a terpolymer of polyvinyl acetate, polyvinyl alcohol and polyvinyl formal (trade name Formvar 12/85), 2.01% by weight dipentaerythritol monohydroxy pentacrylate, 2.01% by weight of a diacrylated urethane oligomer which is obtained by first reacting 1,6-hexanediol with adipic acid to give a polyester, the molar ratio of adipic acid to 1,6-hexanediol being greater than 1: 1, and then the polyester obtained is reacted with dicyclohexylmethane-4,4'-bis-diisocyanate, the molar ratio of diisocyanate to polyester being 2: 1. The product obtained is reacted with 2-hydroxyethyl acrylate, the molar ratio of acrylate to reaction product of diisocyanate and polyester being 2: 1, 1.22% by weight of the polycondensation product of 3-methoxy-4-diazo-diphenylamine sulfate and 4,4-bis-methoxymethyldiphenyl ether, isolated as mesitylene sulfonate, 3.20% by weight of 2-stilbenyl-4,6-di (trichloromethyl) triazine and 87.02 wt% ethylene glycol monomethyl ether.

The coated and dried plate is exposed through a negative template using actinic radiation so that a fully covered step 7 is obtained on a 21-step Stauffer wedge. The plate can be developed with the developer of Example 7 with good results.

Example 10:

An 8 "× 25" plate of the aluminum alloy 1100 suitable for printing is degreased with an aqueous alkaline degreasing solution and electrochemically roughened with an alternating current of 900 Coulomb in a medium made of nitric acid and aluminum nitrate. The roughened plate is rinsed well and anodized in a sulfuric acid bath, the aluminum serving as the anode. The current strength and voltage is chosen so that an oxide layer of 2.8 g / m² is formed. The anodized plate is rinsed well and hydrophilized by immersion in a polyvinylphosphonic acid solution. The plate is then rinsed well again and dried. Now it is spin coated with a solution of the following composition: 4.54% by weight of a resinous binder which is obtained by firstly adding 75.0 g of Vinol 523, a polyvinyl alcohol / polyvinyl acetate copolymer with approx. 75 up to 80% by weight of hydroxyl groups and an average molecular weight of about 70,000, dissolved in a solution of 225 g of water and 200 g of ethanol and allowed to react at a temperature of 70 ° C for 16 hours, then with 10.13 g of hydrochloric acid %) and finally, with vigorous stirring, add 37.66 g of propionaldehyde, the temperature being set to 60 ° C. Using conventional analytical methods, it is found that the resulting product contains 13.6% acetate, 9.8% hydroxyl and 76.7% acetal groups. 80 % of the acetal groups are six-membered ring-shaped acetals and 16% are intermolecular acetals, 2.01% by weight dipentaerythritol monohydroxy pentacrylate, 2.01% by weight of a diacrylated urethane oligomer obtained by first reacting 1,6-hexanediol with adipic acid to a polyester, the molar ratio of adipic acid to 1,6-hexanediol being greater than 1: 1, and then the one obtained Polyester is reacted with dicyclohexylmethane-4,4'-bis-diisocyanate, wherein the molar ratio of diisocyanate to polyester is 2: 1. The product obtained is reacted with 2-hydroxyethyl acrylate, the molar ratio of acrylate to reaction product of diisocyanate and polyester being 2: 1, 1.22% by weight of the polycondensation product of 3-methoxy-4-diazodiphenylamine sulfate and 4,4-bis-methoxymethyldiphenyl ether, isolated as mesitylene sulfonate, 3.20% by weight of 2-stilbenyl-4,6-di (trichloromethyl) triazine and 87.02 wt% ethylene glycol monomethyl ether

The coated and dried plate is exposed through a negative exposure template using actinic radiation so that a fully covered step 7 is obtained on a 21-step Stauffer wedge. With the developer of Example 7, the plate can be developed with good results.

Example 11:

A positive pressure plate of the type Enco P7S^(R) is used; these printing plates consist of an aluminum support which is coated with a light-sensitive mixture of a novolak resin and an ester of naphthoquinone- (1,2) -diazide- (2) -sulfonic acid- (5) and 1,2,3-trihydroxybenzophenone as a light-sensitive compound is. The plate is exposed imagewise in a conventional manner using a working test template. It can be developed with the de-icing agent of Example 7 with good results.

Example 12:

An Enco N-25 printing plate^(R), the aluminum carrier material of which was mechanically roughened in an abrasive suspension, and a pressure plate of the type Enco N-500^(R), whose aluminum support material has been roughened electrolytically, are exposed imagewise in a known manner by means of actinic radiation. The exposed plates are developed in a commercially available developing device with the following developer mixture according to the invention: 10.32% by weight of benzyl alcohol, 6.00% by weight sodium cumene sulfonate, 23.00% by weight potassium toluenesulfonate, 0.20% by weight sodium benzoate, 0.60 wt% TX-100 and 59.88 wt% water

Both printing plates can be developed with good results.