DE60224642T2 - Negative-working thermal planographic printing plate precursor containing an aluminum support with a smooth surface - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The The present invention relates to a negative-working, non-ablative thermosensitive lithographic printing plate precursor with a roughened and anodised aluminum support with low surface roughness and method of making a lithographic printing plate and lithographic printing processes in which the precursor is used becomes.

GENERAL PRIOR ART

at lithographic printing using a so-called Druckmaster like a printing plate mounted on a drum of the printing press. The master surface enters lithographic image and a print is obtained by first printing ink applied to the image and then the color of the master a receiving material, usually paper, is transmitted. In conventional Lithographic wet printing both ink and fountain solution water-based on the lithographic image, made of oleophilic (or hydrophobic, i.e., ink-receptive, water-repellent) And hydrophilic (or oleophobic, i.e. hydrophilic, ink-repelling) Areas constructed, appropriate. In so-called driographic The lithographic image consists of ink-receptive and ink-repellent prints (ie color repellent) Areas and will be during of driographic printing, just apply printing ink to the master.

print Master are usually after the so-called computer-to-film process (CtF method, data-driven film production) where different Pre-press such as font selection, scanning, production of color separations, Scraping, trapping, layout and imposition done digitally and each color separation on a film exposure a graphic film is exposed. After development, the Film as a mask for the exposure of an image-forming material, as a printing plate precursor designated, used and after the development of the plate becomes obtained a printing plate, which is used as a master. Since about In 1995, the so-called computer-to-plate method (CtP method, direct digital printing plate imaging) to a significant extent in importance won. In this process, also referred to as direct-to-plate method, is waived on the production of a film and that because the digital document about a so-called platesetter transferred directly to a printing plate precursor becomes.

by virtue of their daylight resistance especially find thermal plates that are sensitive to heat or Infrared light is widely used in computer-to-plate processes. Such thermal materials can although directly with heat be applied, for example by means of a thermal head included but preferably a compound that converts absorbed light into heat, making them for Exposure with a laser, in particular infrared laser diodes suitable are. The generated in the imagewise exposure heat dissolves one (physical) chemical process such as ablation, polymerization, Insolubilization by crosslinking of a polymer, decomposition or Coagulation of thermoplastic polymer latex particles from and after any development becomes a lithographic image receive. Many thermal plate materials are based on thermal induced ablation. But there is a problem with ablative plates in that the ablation produces waste that is difficult to remove and affecting the printing process or the exposure optics of the Plattenbelichters is able to pollute. For that reason, require such ablative plates a treatment step in which the waste removed from the exposed material.

In EP 770 494 discloses a method in which an image forming material is imagewise exposed. The image-forming material contains an image-recording layer containing a hydrophilic binder, a compound capable of converting light to heat, and hydrophobic thermoplastic polymer particles. Upon exposure, the polymer particles flow together (coalesce) and the exposed areas are converted to a hydrophobic phase that forms the print areas of the master printer. The print cycle can be started immediately after the end of the exposure without any additional treatment, because the film is developed by the interaction between fountain solution and printing ink applied to the printing cylinder during the printing cycle. During the first ten or twenty revolutions of the printing press, the unexposed areas are removed from the carrier and form the non-printing areas of the plate. The wet chemical development of these materials thus takes place "invisibly" for the user during the start-up stage of the printing press, in other documents known from the prior art, such as EP-A 770 497 and US 6,001,536 , describes the (Off Press) development of similar materials with water or an aqueous liquid.

In EP 908 784 discloses a process comprising the following steps for the production of lithographic printing plates:
(i) preparing a precursor having a capping layer impermeable to a SiO ₂ -containing developer and a diazonium salt and containing at least 20% non-proteinaceous hydrophilic film-forming polymers, (ii) exposing the precursor to active light and then (iii) developing the precursor.

In EP 1 160 083 discloses a printing plate containing, on a hydrophilic support, an image-forming layer containing a hydrophilic resin, an acid precursor and at least one component selected from the group consisting of fine particles containing vinyloxy-containing compound and fine particles containing thermosetting resin.

To this day, the thermally induced coalescence is (confluence) of polymer the only thermally triggered, non-ablative imaging mechanism that requires no separate processing step with alkaline chemicals and all the requirements (Agfa Thermolite ^®) are provided for producing a first-class printing plate material, enough. Various improvements of such materials are described in e.g. B. EP-A 773,112 . EP-A 774 364 . EP-A 802 457 . EP-A 816,070 . EP-A 849 090 . EP-A 849 091 . EP-A 881 095 and EP-A 931,647 , However, none of the prior art materials that operate on the principle of thermally induced coalescence of polymer particles is suitable for making printing plates that provide excellent print stability in printing.

A Deterioration of print quality as a result of image wear, the limited circulation to a maximum of typically 25,000 printed copies. Further Reasons for the low durability of such plates are the limited mechanical ones Robustness (scratch sensitivity) and limited chemical resistance against printing press chemicals, such as plate cleaner, blanket cleaner and fountain solution ingredients.

BRIEF PRESENTATION OF THE PRESENT INVENTION

task The present invention is to provide a non-ablative Thermal printing plate precursor, which does not have a separate development step with alkaline chemicals requires a high circulation strength assures and meets the numerous other requirements of a lithographic Printing plate material is fair. This task is solved by Order of heat-sensitive Coating on a smooth aluminum support as defined in claim 1. The effect of having a smooth aluminum support one after the principle of thermally induced coalescence of hydrophobic thermoplastic Gives polymer particles working plate a higher circulation strength, is quite unexpected. The reason that a smooth surface, the characterized by an arithmetic mean roughness Ra less than 0.45 μm is a significant reduction in image wear during the Printing is not clear. Every expert would expect, that a rough surface ensure better adhesion to the coalesced polymer particles would as a smooth surface, but exactly the opposite has been confirmed: materials with smooth carrier with an Ra value as defined in the present invention unexpectedly ensure higher run-flat strength.

With the preferred materials of the invention It is possible to produce lithographic printing masters without visible Image wear one circulation of at least 30,000 copies, more preferably at least 60,000 Save copies. The best embodiments even give a circulation of more than 100,000 copies.

specific License plate for preferred embodiments The present invention is described in the subclaims. Further advantages and embodiments The present invention will become apparent from the following description seen.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The support of the printing plate precursor of the present invention is a roughened and anodized aluminum support having a hydrophilic surface characterized by a low surface roughness, which is referred to as arithmetic mean roughness (Ra value) or sometimes also referred to as CLA value (Center Line Average). The Ra value used in the present invention is defined in ISO 4287/1 (= DIN 4762) and in the references mentioned therein. The measurement of the Ra values mentioned in this document was carried out according to ISO 4288 and the references therein to a mechanical profilometer method using a very thin tip stylus instrument (also known are optical profiling methods which systematically give higher values than the ISO method). The Ra meter is a Talysurf 10 from Taylor Hobson Ltd. used.

Of the Ra value of the hydrophilic surface of the material according to the invention used roughened and anodized aluminum support is located below 0.45 μm, preferably less than 0.4 microns and more preferably even less than 0.3 microns. A roughened and anodized aluminum support with a hydrophilic surface with the mentioned low Ra values is referred to for brevity in the present invention as "smooth carrier". The Lower limit of the Ra value may be 0.05 μm, and is preferably 0.1 μm.

The Roughening and anodizing of lithographic aluminum supports is a well-known process. The material in the invention used roughened aluminum supports is preferably an electrochemically roughened carrier. When Acid for roasting can, for example, nitric acid be used. The acid for the Contains roughnesses preferably hydrogen chloride. Also mixtures of z. For example, hydrogen chloride and acetic acid come into question.

The ratio between the electrochemical roughening and anodizing parameters, such as electrode voltage, type and ratio of acid electrolyte or current consumption, and the lithographic quality obtained with respect to Ra and anodic weight (g / m ² Al ₂ O ₃₎ formed on the aluminum surface) is well known. More details about the relationship between different production parameters and the Ra or the anodic weight can be found in z. For example, the article entitled "Management of Change in the Aluminum Printing Industry," by FR Mayers, which will appear in the "ATB Metallurgie Journal." So experts know exactly how to adjust the various parameters to make a roughened aluminum substrate with a smooth surface In the present invention, even higher coating levels can be achieved for a given roughness Ra by adjusting the aluminum oxide ratio on the hydrophilic surface to greater than 2.5 g / m ² , especially is preferably set above 3.0 g / m ² or even above 3.5 g / m ² .

The roughened and anodized aluminum support may be subjected to post-processing to improve the hydrophilic properties of the support surface. For example, by processing the support surface with a sodium silicate solution at elevated temperature, e.g. B. 95 ° C, silicate. Alternatively, a phosphate processing may be performed wherein the alumina surface is processed with an optional further inorganic fluoride-containing phosphate solution. Further, the alumina surface may be treated with an organic acid and / or a salt of an organic acid, e.g. As carboxylic acids, hydroxycarboxylic acids, sulfonic acids or phosphonic acids, or their salts, eg. As succinates, phosphates, phosphonates, sulfates and sulfonates, rinsed. Preferred is a citric acid or citrate solution. This treatment can be carried out at room temperature or at a slightly elevated temperature between about 30 ° C and 50 ° C. Further post-processing consists of rinsing the alumina surface with a bicarbonate solution. Further, the alumina surface may be processed with polyvinylphosphonic acid, polyvinylmethylphosphonic acid, phosphoric acid esters of polyvinyl alcohol, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric acid esters of polyvinylalcohol and acetals of polyvinylalcohols formed by reaction with a sulfonated aliphatic aldehyde. Further, it is obvious that one or more of these post treatments may be performed separately or in combination. More detailed descriptions of these treatments can be found in GB-A 1 084 070 . DE-A 4 423 140 . DE-A 4 417 907 . EP-A 659 909 . EP-A 537 633 . DE-A 4 001 466 . EP-A 292 801 . EP-A 291 760 and U.S. Patent 4,458,005 ,

The coating applied to the support is heat sensitive and provides a printing plate precursor which can be handled for several hours under normal work lighting conditions (daylight, fluorescent light). The coating comprises an image-receiving layer containing hydrophobic thermoplastic polymer particles. Specific examples of suitable hydrophobic polymers are e.g. Polyethylene, poly (vinyl chloride), poly (methyl (meth) acrylate), poly (ethyl (meth) acrylate), poly (vinylidene chloride), poly (meth) acrylonitrile, poly (vinylcarbazo1), polystyrene or copolymers thereof. According to preferred embodiments, the thermoplastic polymer contains at least 50% by weight of polystyrene, more preferably at least 60% by weight of polystyrene. To achieve adequate resistance to mechanical damage and printing machine chemicals, such as the hydrocarbons used in plate cleaners, the thermoplastic copolymer preferably contains at least 5% by weight, more preferably at least 30% by weight, of units of a nitrogenous monomer or units containing as monomers Solubility parameters of more than 20 are characterized, such as (meth) acrylonitrile, or monomeric units, be contain tenent sulfonamide and / or phthalimide groups. Further suitable examples of such units of a nitrogen-containing monomer are described in EP-A 1 219 416 , A specific embodiment of the hydrophobic thermoplastic polymer is a homopolymer or copolymer of (meth) acrylonitrile and / or styrene, e.g. Example, a copolymer of styrene and acrylonitrile units in a weight ratio between 1: 1 and 5: 1 (styrene: acrylonitrile). With a ratio of 2: 1 or 3: 2 excellent results are obtained.

The Weight average molecular weight of the thermoplastic polymer particles can vary between 5,000 and 1,000,000 g / mole. The number average the particle diameter of the hydrophobic particles is preferably below 200 nm, more preferably between 10 and 100 nm. The amount hydrophobic thermoplastic polymer particles in the image recording layer is preferably between 20% by weight and 65% by weight, more preferably between 25% by weight and 55% by weight and most preferably between 30% by weight and 45% by weight.

• – wird das hydrophobe thermoplastische Polymer in einem organischen wasserunmischbaren Lösungsmittel gelöst,
• – wird die so erhaltene Lösung in Wasser oder einem wässrigen Medium dispergiert und
• – wird das organische Lösungsmittel abgedampft.

The hydrophobic thermoplastic polymer particles are contained as a dispersion in an aqueous coating liquid of the image recording layer and can be prepared according to the methods described in US 3 476 937 be prepared described methods. In a further process which is particularly suitable for the preparation of an aqueous dispersion of the thermoplastic polymer particles:

• The hydrophobic thermoplastic polymer is dissolved in an organic water-immiscible solvent,
• - The solution thus obtained is dispersed in water or an aqueous medium and
• - The organic solvent is evaporated.

The Imaging layer may further comprise a hydrophilic binder included, for. B. homopolymers and copolymers of vinyl alcohol, acrylamide, Methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, Hydroxyethyl methacrylate or maleic anhydride vinylmethyl ether copolymers. The hydrophilicity the (co) polymer or (co) polymer mixture used is preferred higher or higher equal to the hydrophilicity of at least 60% by weight, preferably to 80% by weight hydrolyzed polyvinyl acetate. Preference is given to binders with lateral Carboxylic acid groups, z. As poly (meth) acrylic acid.

The Imaging layer may contain other ingredients, like additional Binders, surfactants, colorants and development inhibitors or development accelerators, and in particular one or more compounds, the infrared light in heat to transform. Particularly useful light in heat converting compounds are, for example, infrared dyes, Carbon black, metal carbides, metal borides, metal nitrides, metal carbonitrides, Oxides with a bronze structure and conductive polymer dispersions, such as dispersions based on polypyrrole, polyaniline or polythiophene. Anionic cyanine dyes are preferred. The colorants are preferably dyes or pigments, which after development a visible Picture result.

The Coating may further include one or more additional, to the image-recording layer Contain bordering layers. Such an additional layer may, for. B. an adhesion-promoting layer between the image-recording layer and the wearer, a light absorbing layer having one or more of the above Compounds capable of converting infrared light into heat, or one during the development to be removed cover layer.

The materials of the invention are suitable for both off-press exposure and on-press exposure. The printing plate precursors according to the invention are either heated or exposed to infrared light, for example by means of a thermal head, an LED or an infrared laser. Preferred is a near infrared light having a wavelength between about 700 and about 1500 nm emitting laser, e.g. A semiconductor laser diode, an Nd: YAG laser or a Nd: YLF laser. The laser power required depends on the sensitivity of the imaging layer, the pixel dwell time of the laser beam as determined by the beam width (a typical value at 1 / e ^{2 of} the maximum intensity is between 10 and 25 μm for modern platesetters), the scanning speed and the resolution of the Exposure (ie the number of addressable pixels per unit length, often expressed in dots per inch or dpi / typical values are between 1,000 and 4,000 dpi). There are two types of common laser imagers, ie an inner drum plate setter (ITD platesetter) and an outer drum plate setter (XTD platesetter). ITD platesetters for thermal plates are usually characterized by very high scanning speeds up to 500 m / s and may require a laser power of several watts. XTD platesetter for thermal plates work at a lower scanning speed, z. Between 0.1 m / s and 10 m / s, and a typical laser power between about 200 mW and about 1 W.

Under Action of during The heat generated by the exposure step melts or coagulates the heat hydrophobic thermoplastic polymer particles and thereby form a hydrophobic phase covering the printing areas of the printing plate will form. Coagulation can occur when the thermoplastic polymer particles under the influence of heat flow together (coalesce), soften or melt. The coagulation temperature Although the hydrophobic thermoplastic polymer particles is subject no specific upper limit, but should be enough under the decomposition temperature of the polymer particles are. The coagulation temperature is preferably at least 10 ° C below the temperature at which decomposition of the polymer particles occurs. The coagulation temperature is preferably more than 50 ° C, more preferably more than 100 ° C.

After exposure, the material is developed. In the present invention, the terms "development" and "processing" are used as synonyms. For development, a liquid containing a hydrophilic phase which removes the coating in the unexposed areas from the support may be applied to the coating. As such liquid, water, an aqueous liquid, a gumming, fountain solution and a single-fluid printing ink come into question. According to one embodiment, the development of the material takes place in that dampening water and / or printing ink are applied to the material, preferably first the fountain solution and then the printing ink. This method is preferably combined with an on-press exposure step. In another development process, which is also suitable for on-press development, especially on driographic presses, only single fluid ink is applied to the material. Single-fluid printing inks which are suitable for use in the process according to the invention are described in US Pat US 4,045,232 and US 4,981,517 , A suitable single-fluid ink includes a paint phase, also referred to as a hydrophobic or oleophilic phase, and a polyol phase as described in U.S. Pat WO 00/32705 , More details about the development with single fluid printing ink can be found in EP-A 1 213 140 ,

After exposure in an off-press platesetter, the material can then either on the press ("on press") by coloring with ink and / or wetting with fountain solution, as already mentioned above, or "off press", z. B. by application of water, an aqueous liquid or a gum solution can be developed. A gum solution is typically an aqueous liquid containing one or more surface-protecting compounds that protect the lithographic image of a printing plate from soiling or damage. Suitable examples of such compounds are film-forming hydrophilic polymers or surfactants. More details about the development with a gumming solution can be found in EP-A 1 342 568 ,

To Development, the plate can be dried and branded. The Plate can either before baking or during the Burning process to be dried. The burn in can at a Temperature over the coagulation temperature of the thermoplastic polymer particles, z. B. at a temperature between 100 ° C and 230 ° C, over a period of 5 to 40 minutes. So can for example the exposed and developed plates 5 minutes long at a temperature of 230 ° C, For 10 minutes at a temperature of 150 ° C or for 30 minutes at a Temperature of 120 ° C be burned. The baking temperature is preferably more than 60 ° C. The burn-in can in conventional hot air ovens or by irradiation with in the spectral infrared or ultraviolet range emitting lamps are made.

EXAMPLES

In In the examples below, the term "run length" or "run length" corresponds to the number of copies, which can be printed until the occurring due to image wear Deterioration of quality 60% of the raster of a high-quality image (200 lpi) exceeds 5%. Unless otherwise noted, all are described below Plates "on press "by order of printing ink and dampening water on the plate during the first ten to fifteen turns developed the printing press.

Example 1 (comparative example) and Example 2 (Inventive Example)

Preparation of the lithographic carrier 1

A 0.30 mm thick aluminum foil is degreased by immersing the foil in an aqueous solution containing 40 g / l of sodium hydroxide at 60 ° C. for 8 seconds and rinsing with demineralized water for 2 seconds. The film is then electrochemically electrochemically reacted at a temperature of 33 ° C. and a current density of 130 A / dm ^{2 for} 15 seconds in an aqueous solution containing 12 g / l hydrochloric acid and 38 g / l aluminum sulfate (18 hydrate) roughened. After rinsing with demineralised water for 2 seconds, the film of aluminum foil is removed by etching for 4 seconds at 70 ° C with an aqueous solution containing 155 g / l sulfuric acid, followed by rinsing with demineralized water at 25 ° C for 2 seconds. The film is then anodized at a temperature of 45 ° C. and a current density of 22 A / dm ^{2 for} 13 s in an aqueous solution containing 155 g / l sulfuric acid, then washed with demineralized water for 2 s, then at 40 for 10 s ° C with a solution containing 4 g / l polyvinylphosphonic containing, rinsed for 2 s at 20 ° C with demineralized water and finally dried. The support thus obtained has a surface roughness Ra of 0.46 μm and an anodic weight of 2.9 g / m ² Al ₂ O ₃ .

Production of the lithographic support 2

The procedure is as in the preparation of the lithographic support 1, but with the difference that the current density during roughening and anodizing to 90 A / dm ² and 30 A / dm ^{2 is} set. The support thus obtained has a surface roughness Ra of 0.22 μm and an anodic weight of 4.0 g / m ² Al ₂ O ₃ .

Production and testing of printing plates 1 and 2

It are a comparative printing plate precursor 1 and a printing plate precursor according to the invention 2 produced. For this purpose, a coating composition is prepared and applied to the above-described lithographic supports 1 and 2, respectively.

Farbstoff 1 On the above-described lithographic supports, an image-recording layer is coated from an aqueous coating solution at a wet-thickness of 30 g / m ² . After drying, the image-recording layer contains 600 mg / m ² of an anionic surfactant-stabilized copolymer of styrene and acrylonitrile (weight ratio 60/40) having an average particle size of 65 nm, 60 mg / m ^{2 of} the infrared dye I and 120 mg / m ² polyacrylic acid (Glascol D15 from Allied Colloids, molecular weight 2.7 × 10 ⁷ g / mol).

Dye 1

The resulting printing plate precursors are exposed on a CREO TRENDSETTER (Creo, Burnaby, Canada platesetter) at 330 mJ / cm ² and 150 ppm. Subsequent to the exposure, the plates are clamped in a MO printing press (available from Heidelberger Druckmaschinen AG) and a printing cycle is carried out using K + E800 printing ink and a 10% isopropanol solution containing 4% Combifix XL as the fountain solution.

To 25,000 copies occurs a deterioration in the quality of the image on the plate obtained with printing plate precursor 1 up and down a circulation of 30,000 copies, the image wear comes over the above-mentioned criterion out. The plate obtained with printing plates precursor 2 is no image wear visible, even not when the press is stopped after 100,000 copies.

Example 3 Example According to the Invention and Example 4 (comparative example)

Production of the lithographic carrier 3

An aluminum continuous web 0.30 mm thick and 500 mm wide is degreased by immersing the web in an aqueous solution containing 10.4 g / l sodium hydroxide at 38 ° C. for 35 seconds and then demineralizing water for 30 seconds rinsed. The aluminum sheet is then electrochemically electrocolded at a temperature of 29 ° C. and a current density of 826 A / m ^{2 for} 30 seconds in an aqueous solution containing a mixture of 9.5 g / l hydrochloric acid and 21 g / l acetic acid roughened. The carrier thus obtained has an arithmetic mean roughness Ra of 0.24 μm. After rinsing with demineralised water for 30 seconds, the film of the aluminum web is removed by etching at 43 ° C for 35 seconds with an aqueous solution containing 124 g / l phosphoric acid and then rinsing the web with demineralized water for 30 seconds. Subsequently, the aluminum web is anodized at a temperature of 48.5 ° C with DC voltage at a current density of 1173 A / m ^{2 for} 30 seconds in an aqueous, 137 g / l sulfuric acid containing solution to form an anodized film with an Al ₂ O ₃ Content of 3.4 g / m ² . The aluminum web is then washed with demineralised water for 30 seconds and subsequently post-processed at 52 ° C. for 15 seconds with a solution containing 2.2 g / l polyvinylphosphonic acid, rinsed with demineralised water for 30 seconds and finally dried.

Production of the lithographic carrier 4

The procedure is the same as in the production of the lithographic support 3, but with the difference that the current density when roughening is set to 2,125 A / dm ² . The carrier thus obtained has a surface roughness Ra of 0.53 μm. The anodic weight is the same as the carrier 3.

Production and testing of printing plates 3 and 4

For the production the printing plate precursors 3 and 4 become the same coating composition as above for the preparation of the printing plate precursors 1 and 2 described applied. Also the exposure, the on-press development and the printing process done in the same way.

With Plate 4 is a run height achieved by 30,000 copies while on plate 3 after 50,000 copies, d. H. when the test of Overlay resistance is stopped, no image wear visible is.

Examples 5 to 9

Preparation of the lithographic supports 5 to 9

A Continuous track made of aluminum with a thickness of 0.30 mm and a width of 500 mm is replaced by 35 seconds Dipping the web into a watery, Degreased 10 g / l of sodium hydroxide solution at 39 ° C and then with 30 s rinsed with demineralised water. The aluminum web will follow at a temperature of 30 ° C and a current density as shown in Table 1 for 30 seconds in an aqueous Solution, containing a mixture of 8.1 g / l hydrochloric acid and 21.7 g / l acetic acid, with AC electrochemically roughened. After rinsing for 30 seconds with demineralized water is the coating of the aluminum sheet through 35 second etching at 43 ° C with an aqueous, 128 g / l phosphoric acid containing solution and then the web is demineralized for 30 s Water rinsed. Subsequently, will the aluminum web at a temperature of 50 ° C with DC at a current density as shown in Table 1 for 30 seconds in an aqueous, 154 g / l sulfuric acid containing solution anodized. Then the aluminum sheet is demineralized for 30 seconds Washed water and then 15 seconds at 53 ° C post-processed with a solution containing 2.45 g / l polyvinylphosphonic acid, Rinsed with demineralised water for 30 seconds and finally dried.

Production and testing of printing plates 5 to 9

For the production the printing plate precursors 5 to 9 will be the same coating composition as above for the preparation of the printing plate precursors 1 and 2 described on the carriers 5 to 9 applied. Also the exposure, the on-press development and the printing process done in the same way.

In Table 1, the current roughnesses (AR) and the anodization (AD), the surface roughness Ra, the anodic weight (AG) of the lithographic supports 5 to 9, and those with the plates 5 to 9 are targeted circulation number listed. Table 1 Example no. Current density AR (A / m ² ) Ra (μm) Current density AD (A / m ² ) AG (g / m ² ) circulation 5 (see) 2740 0.53 2350 4.8 11,000 6 (required) 1300 0.28 2350 4.8 55,000 7 (required) 1300 0.28 1750 3.5 50,000 8 (required) 1300 0.28 2900 6.3 70,000 9 (required) 1000 0.21 2350 4.8 > 90,000

From the data for Examples 5, 6 and 9 in Table 1 it turns out that for a given anodic weight (4.8 g / m ² ) a significant increase in the run length is achieved by reducing the Ra value. For a given Ra value (Examples 6 to 8: 0.28 μm), a further improvement in the run length is achieved by increasing the anodic weight. With plate 9, after 90,000 copies, ie when the printing cycle is stopped, no image wear is still visible.

Examples 10 to 12

Production of printing plate precursors 10 and 11

It become the same lithographic carrier and the same coating as used in Example 1 or Example 2, with the difference however, that the thermoplastic polymer is a homopolymer of styrene with a mean particle size of 70 nm is.

Production and testing of printing plates 10 to 12

The printing plates 10 and 11 are produced by exposure and development of the printing plate precursors 10 and 11, respectively, according to the procedure described in the previous examples, with the difference that the on-press development and the test of the printing endurance using K + E800. Printing ink and a 4% Combifix XL containing 10% isopropanol solution as fountain solution on a GTO printing press (Heidelberger printing machines) are made. Pressure plate 12 is prepared analogously to the procedure for the plates 10 and 11 from precursor 2. Table 2 Example no. Ra (μm) polymer circulation 10 (see) 0.46 Styrene homopolymer 21,500 11 (required) 0.22 Styrene homopolymer 85,000 12 (required) 0.22 Styrene / acrylonitrile copolymer > 100,000

Out The data in Table 2 prove that a further increase in the achievable run height by Incorporation of a nitrogen-containing unit, such as acrylonitrile, is achieved in the hydrophobic thermoplastic polymer.

Examples 13 to 15

exam chemical resistance the printing plates 10 to 12

• Prüfung 1: die bildmäßig belichteten Platten werden in eine GTO-Druckpresse (Heidelberger Druckmaschinen) eingespannt, wonach unter Verwendung von K+E800-Druckfarbe und einer 4% Combifix XL enthaltenden 10%igen Isopropanollösung als Feuchtwasser eine Auflage von 500 Kopien gedruckt wird. Danach wird eine Druckfläche jeder Platte mit zwei typischen Druckmaschinenflüssigkeiten (Meter-X, ein Druckwalzenreiniger auf Kohlenwasserstoffbasis von ABC Chemicals Corp. Ltd., Großbritannien, und Normakleen, ein Plattenreiniger auf Basis eines Petroldestillats von Agfa) behandelt. Dazu werden Baumwolltupfer verwendet, die mit der betreffenden Flüssigkeit getränkt und über die Oberfläche gerieben werden. Der Schaden auf den behandelten Oberflächen wird bewertet (vgl. Tabelle 3: 0 = kein Bildschaden, X = starker Bildschaden, XX = völlig gelöschtes Bild).

Tabelle 3 Platte Nr. Ra (μm) Polymer Bildschaden Meter-X Normakleen 10 (vergl.) 0,46 Styrolhomopolymer XX XX 11 (erf.) 0,22 Styrolhomopolymer XX XX 12 (erf.) 0,22 Styrol/Acrylnitril-Copolymer 0 0

• Prüfung 2: die bildmäßig belichteten Platten werden in eine GTO-Druckpresse (Heidelberger Druckmaschinen) eingespannt, wonach unter Verwendung von K+E800-Druckfarbe und einer 4% Combifix XL enthaltenden 10%igen Isopropanollösung als Feuchtwasser eine Auflage von 500 Kopien gedruckt wird. Danach wird ein Tropfen jeder der gleichen, wie in Prüfung 1 verwendeten Flüssigkeiten auf eine Druckfläche der Platten angebracht. Anschließend lässt man den Tropfen 4 Minuten trocknen. Danach wird eine neue Auflage von 200 Kopien gedruckt (statt des Wischens von Prüfung 1 wird also in Prüfung 2 eine zweite Auflage gedruckt). Nach dem zweiten Druckzyklus werden die mit der Flüssigkeit behandelten Flächen ausgewertet (vgl. Tabelle 4: 0 = kein Bildschaden, X = starker Bildschaden, XX = völlig gelöschtes Bild).

Tabelle 4 Platte Nr Ra (μm) Polymer Bildschaden Meter-X Normakleen 10 (vergl.) 0,46 Styrolhomopolymer XX X 11 (erf.) 0,22 Styrolhomopolymer XX X 12 (erf.) 0,22 Styrol/Acrylnitri1-Copolymer 0 0

• Prüfung 3: die Beschichtung der bildmäßig belichteten Platten wird in einer nicht-belichteten Fläche mechanisch angekratzt. Danach werden die Platten analog den Prüfungen 1 und 2 in eine Presse eingespannt und wird eine Auflage von 1.000 Kopien gedruckt. Die Druckmaschine wird gestoppt und es wird ausgewertet, ob die auf die Platten angebrachten Kratzer auf den zuletzt gedruckten Kopien sichtbar sind (Farbanziehung in Nicht-Bildbereichen infolge Kratzerbildung).

Tabelle 5 Platte Nr. Ra (μm) Polymer Sichtbare Kratzer auf den Kopien 10 (vergl.) 0,46 Styrolhomopolymer sehr viel 11 (erf.) 0,22 Styrolhomopolymer wenig 12 (erf.) 0,22 Styrol/Acrylnitril-Copolymer keine The plates 10 to 12 prepared as described above are tested in three tests for their chemical resistance.

• Test 1: The imagewise exposed plates are clamped in a GTO printing press (Heidelberger Druckmaschinen), after which a print run of 500 copies is printed using K + E800 printing ink and a 10% isopropanol solution containing 4% Combifix XL as fountain solution. After that, a Printing surface of each plate was treated with two typical printing machine fluids (Meter-X, a hydrocarbon-based printing roller cleaner from ABC Chemicals Corp. Ltd., UK, and Normakleen, a Petroleum distillate plate cleaner from Agfa). For this purpose cotton swabs are used, which are soaked with the liquid in question and rubbed over the surface. The damage on the treated surfaces is evaluated (see Table 3: 0 = no image damage, X = severe image damage, XX = completely erased image).

Table 3 Plate no. Ra (μm) polymer image damage Meter-X Normakleen 10 (see) 0.46 Styrene homopolymer XX XX 11 (required) 0.22 Styrene homopolymer XX XX 12 (required) 0.22 Styrene / acrylonitrile copolymer 0 0

• Test 2: the imagewise exposed plates are clamped in a GTO printing press (Heidelberger Druckmaschinen), after which a print run of 500 copies is printed using K + E800 printing ink and a 10% isopropanol solution containing 4% Combifix XL as fountain solution. Thereafter, a drop of each of the same liquids used in Test 1 is applied to a printing surface of the plates. Then let the drops dry for 4 minutes. Thereafter, a new edition of 200 copies will be printed (instead of wiping Exam 1, a second edition will be printed in Exam 2). After the second printing cycle, the areas treated with the liquid are evaluated (see Table 4: 0 = no image damage, X = severe image damage, XX = completely erased image).

Table 4 Plate no Ra (μm) polymer image damage Meter-X Normakleen 10 (see) 0.46 Styrene homopolymer XX X 11 (required) 0.22 Styrene homopolymer XX X 12 (required) 0.22 Styrene / Acrylnitri1 copolymer 0 0

• Test 3: the coating of the imagewise exposed plates is mechanically scratched in a non-exposed area. Thereafter, the plates are clamped in a press analogously to the tests 1 and 2 and an edition of 1,000 copies is printed. The press is stopped and it is evaluated whether the scratches applied to the plates are visible on the last printed copies (color attraction in non-image areas due to scratching).

Table 5 Plate no. Ra (μm) polymer Visible scratches on the copies 10 (see) 0.46 Styrene homopolymer very much 11 (required) 0.22 Styrene homopolymer little 12 (required) 0.22 Styrene / acrylonitrile copolymer none

Examples 16 and 17

Production of the lithographic support 16

The steps described in Example 2 are repeated, except for the roughening step: the aluminum foil is heated for 4 seconds at a temperature of 40 ° C by means of alternating current with a current density of 36 A / dm ² in an aqueous, 12.4 g / l nitric acid and 67 g / l aluminum nitrate (9-hydrate) containing solution electrochemically roughened. The nitric acid roughened carrier thus obtained has an Ra value of 0.38 μm.

Production and testing of printing plates 16 and 17

For the preparation of the printing plate precursor 16, the same coating composition as in Example 2 is applied to the support 16 prepared as described above. Plates 16 and 17 are prepared by exposing plate precursors 16 and 2, respectively, to a Creo Trendsetter (Creo, Burnaby, Canada platesetter) at 330 mJ / cm ² and 150 ppm. After imaging, plates 16 and 17 are clamped in a MO printing press (available from Heidelberger Druckmaschinen AG) and a printing cycle is initiated using K + E800 ink and a 10% isopropanol solution containing 4% Combifix XL as the fountain solution.

Identical patterns of plates 16 and 17 are clamped in a Speedmaster SM-74 press (available from Heidelberger Druckmaschinen AG), followed by printing using K + E700 Novavit Speed ink and a 4% Varnfount fountain solution. Table 6 Plate no. Acid used for roughening press Color deposit on the blanket cylinder 16 (required) Chlorsäure NOT A WORD No 17 (required) nitric acid NOT A WORD No 16 (required) Chlorsäure SM-74 No 17 (required) nitric acid SM-74 Yes

at none of the plates is during of printing the circulation of 100,000 copies to observe image deterioration. In plate 17 (nitric acid roughening) settles during the Printing ink on the blanket cylinder of the SM-74 printing press while off on plate 16 (chlorination with chloric acid) over the entire printing cycle No ink deposits on the blanket cylinder of the SM-74 printing press can be observed.

Examples 18 and 19

plate 18 is prepared analogously to Example 2, with the difference, however, that the exposed plate is "off press" with an RC520 burn-in rubber coating developed by Agfa (HWP450 developing device, immersion time 1 minute, room temperature).

plate 19 is similar made, with the difference, however, that the developed plate additionally 2 minutes at 270 ° C is burned.

Both Plates are placed in a MO printing press (Heidelberger Druckmaschinen AG) and using K + E800 printing ink and a 4% Combifix XL containing 10% isopropanol solution as fountain solution in one Pressure cycle evaluated.

From 150,000 copies begins the picture quality at the non-branded Plate 18 on, worsen, while in the case of the burned Plate 19 no image wear is visible. Even after 300,000 copies are still observed in plate 19 no image deterioration and the overlay strength test is stopped.

Claims (20)

A negative working lithographic printing plate precursor comprising: a roughened and anodized aluminum support having a hydrophilic surface; and a heat sensitive coating attached to the hydrophilic surface comprising hydrophobic thermoplastic polymer particles capable of forming a hydrophobic phase through thermally induced coalescence of the polymer particles of the coating, characterized in that the hydrophilic surface has a surface roughness expressed as arithmetic mean roughness Ra of less than 0.45 μm. Printing plate precursor according to claim 1, characterized in that that the hydrophilic surface a surface roughness expressed as arithmetic mean roughness Ra of less than 0.4 μm. Printing plate precursor according to claim 1, characterized in that that the hydrophilic surface a surface roughness expressed as arithmetic mean roughness Ra of less than 0.3 μm. Printing plate precursor according to one of the preceding claims, characterized in that the hydrophilic surface of the aluminum support contains more than 2.5 g / m ^{2 of} alumina. Printing plate precursor according to one of the preceding claims, characterized in that the hydrophilic surface of the aluminum support contains more than 3.5 g / m ^{2 of} alumina. Printing plate precursor according to one of the preceding Claims, characterized in that the hydrophobic thermoplastic polymer is a homopolymer or copolymer of (meth) acrylonitrile and / or styrene. Printing plate precursor according to one of the preceding Claims, characterized in that the hydrophobic thermoplastic polymer pendant Contains sulfonamide and / or phthalimide groups. Printing plate precursor according to one of the preceding Claims, characterized in that the heat-sensitive coating furthermore, a hydrophilic polymeric binder having pendant carboxylic acid groups contains. Printing plate precursor according to one of the preceding Claims, characterized in that the heat-sensitive coating and an anionic infrared-absorbing cyanine dye contains. Printing plate precursor according to one of the preceding Claims, characterized in that the heat-sensitive coating a visible light-absorbing dye or a contains visible light absorbing pigment. Printing plate precursor according to one of the preceding Claims, characterized in that the hydrophilic surface by Treatment with (i) an organic acid and / or a salt of a organic acid or with (ii) a polymer selected from the group consisting of polyvinylphosphonic acid, polyvinylmethylphosphonic acid, phosphoric acid esters of polyvinyl alcohol, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric acid esters of polyvinyl alcohol and the reaction product of polyvinyl alcohol made hydrophilic with a sulfonated aliphatic aldehyde. Printing plate precursor according to one of the preceding Claims, characterized in that the color attractiveness of the hydrophobic phase during a print run of at least 60,000 allowed printed copies. Printing plate precursor according to one of the preceding Claims, characterized in that the color attractiveness of the hydrophobic Phase during a print run of at least 100,000 allowed printed copies. A marked by the following steps Method for producing a lithographic printing plate: - imagewise heating or Infrared exposure of a printing plate precursor according to any one of the preceding Claims, wherein the coalescing of the hydrophobic thermoplastic polymer particles triggered in exposed areas will, and - Development the heated one or exposed plate precursor by applying a hydrophilic Phase-containing liquid on the coating, with the coating in unexposed Areas away from the carrier being, being as a liquid Water, an aqueous Liquid, a gum, fountain solution or single fluid ink used becomes. Method according to claim 14, characterized in that that made the steps of exposure and development be while the printing plate precursor on a cylinder of a lithographic printing machine is stretched. The method of claim 14, further comprising the step in which the developed plate precursor is at a temperature of more than 60 ° C is burned. A marked by the following steps lithographic printing process: - Production of a lithographic A printing plate according to the method defined in claim 14, 15 or 16 and - To Print of at least 60,000 copies with the resulting lithographic Printing plate. A marked by the following steps lithographic printing process: - Production of a lithographic A printing plate according to the method defined in claim 14, 15 or 16 and - To Print of at least 100,000 copies with the thus obtained lithographic Printing plate. A marked by the following steps lithographic printing process: - Production of a lithographic A printing plate according to the method defined in claim 14, 15 or 16 and - To Print of at least 300,000 copies with the thus obtained lithographic Printing plate. Using a roughened and anodized aluminum support with a hydrophilic surface and a surface roughness expressed as arithmetic mean roughness Ra less than 45 μm in a negative working lithographic printing plate precursor with a heat-sensitive surface attached to the hydrophilic surface A coating containing hydrophobic thermoplastic polymer particles which are able to over a thermally induced coalescence of the polymer particles to form hydrophobic phase in the coating, to increase the with the exposure and development of the printing plate precursor obtained printing plate achievable run height.