DE69907867T2 - Process for making a lithographic printing plate - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for producing a lithographic printing master On-press coating an imaging composition.

GENERAL STATE OF THE ART

Used in rotary printing machines a so-called master ("master") like one on a drum printing plate clamped on the printing press. The template carries through the ink-attracting areas of the print surface and a defined image Deduction is obtained by applying ink to the printing surface and the color from the original to a substrate, usually one Paper substrate is transferred. With conventional Lithographic printing becomes both ink and fountain solution on the printing surface attached to the template. In this case, the printing surface is called lithographic surface, those made from oleophilic (or hydrophobic, i.e. color-attracting, hydrogen-absorbing) Areas and hydrophilic (or oleophobic, i.e. water-attracting, dye-ablative) areas.

Print templates are usually obtained by the so-called computer-to-film process, where different Prepress such as the choice of fonts, scanning, production of color separations, Screen, overfill, layout and imposition digitally and each color separation via an imagesetter on a graphic Film is exposed. After development, the film can be used as a mask for the Exposure of an imaging material, as a printing plate precursor designated, used and after the development of the printing plate will receive a printing plate that can be used as a template is.

In recent years, the so-called Computer-to-plate method to a noticeable degree gained in importance. In this process, also as a direct one digital printing plate imaging (computer-to-plate process), a film is not made because of that digital document about a so-called platesetters transferred directly to a printing plate prepress becomes.

With direct digital printing plate imaging The following improvements are currently being investigated:

• (i) On-press imaging. With a special type of a Computer-to-plate process is clamped onto a plate drum of a printing press Printing plate prepress via an exposed in the press exposed. This method can be referred to as a "computer-to-press" process and printing presses with built-in exposure are sometimes called digital presses. An overview of digital presses can be found in "Proceedings of the Imaging Science & Technology's 1997 International Conference on Digital Printing Technologies (Non-Impact Printing 13) ". Computer-to-press process are described in e.g. B. EP-A 770 495, EP-A 770 496, WO 94001280, EP-A 580 394 and EP-A 774 364. Typical plate material used in computer-to-press processes is based on ablation. One with ablative plates Associated problem is the production of waste, which is difficult is to be removed and interfere with the printing process or the exposure optics of the built-in imagesetter. Require other procedures a wet processing with chemicals that make up the electronic and optical components of the built-in imagesetter and other press equipment can.
• (ii) On-press coating. A printing plate prepress exists usually from a sheet-like carrier and one or more functional coatings, however, are also computer-to-press processes have been described in which a composition that is by imagewise exposure and possible development to form a lithographic surface able to hit the surface a plate drum of the press is applied. EP-A 101 266 describes the direct application of a hydrophobic layer on the hydrophilic surface a disc drum. After removing the non-printing areas a template is obtained by ablation. But ablation is at Avoid computer-to-press procedures, as discussed at the beginning. US Pat. No. 5,713,287 describes a computer-to-press method, in which a so-called switchable polymer such as tetrahydropyranylmethyl methacrylate directly on the surface a plate drum is attached. The switchable polymer has a first water-sensitive property that with imagewise exposure becomes an opposite water sensitive property. The latter process requires a curing step and the polymers are quite expensive because they are thermally unstable and consequently are difficult to synthesize.
• (iii) Thermal imaging. The majority of the above-mentioned computer-to-press processes use so-called thermal or heat-sensitive materials, that is to say printing plate precursors or compositions which can be applied to the press and contain a compound which converts absorbed light into heat. The heat generated during imagewise exposure triggers a (physical) chemical reaction such as ablation, polymerization, insolubilization by crosslinking a polymer, decomposition or coagulation of particles of a thermoplastic polymer latex. This thermal process then results in one lithographic surface consisting of ink-accepting and ink-repellent areas.
• (iv) The development of functional coatings that do not wet processing require or developable with tap water, paint or fountain solution is another important trend in the plate making market. Such materials are particularly common in computer-to-press processes he wishes, to damage or pollution of the optical and electronic elements of the built-in imagesetter due to contact with the processing liquids to prevent. In WO 90002044, WO 91008108 and EP-A 580 394 such are indeed Plates described, these are of course all ablative plates with a multilayer structure, which makes them are less suitable for On-press coating. A non-ablative plate that can be developed with tap water is described in e.g. B. EP-A 770 497 and EP-A 773 112. Such Plates are also suitable for an on-press development, either the exposed plate clamped in the printing press with water or with the paint or the fountain solution while of the first editions of the printing work are wiped.

A computer-to-press process which has most of the advantages mentioned above as a characteristic in EP-A 698 488. An oleophilic substance is depicted by transfer a film to a drum of a rotary press, by localizing the substance is melted with a laser beam. The striped transfer film has a limited Width compared to the drum and is parallel to the drum axis transfer running course, being kept in close contact with the surface of the drum, to gradually to create a complete image on this surface. Because of this, this is System quite slow and it requires a long downtime the printing press, which results in lower productivity.

EP-A 400 595 describes a system for direct Illustration described that a printing plate drum and an agent for the selective transmission of thermally fusible particles on the surface of the Drum includes.

EP-A 368 180 describes a method for the On-press imaging of a printing drum through direct thermal transfer the image of a donor material on the printing drum.

EP-A 802 457 describes an on-press coating process in which an aqueous liquid, which is a hydrophilic binder, a compound that converts light into heat capable, and contains hydrophobic thermoplastic polymer particles the disc drum is applied, whereby a uniform continuous Layer is obtained. With imagewise exposure certain areas of the applied layer become a hydrophobic Phase converted to the printing areas of the artwork formed. Printing on the press can start immediately after exposure without additional Processing started because the layer is interacting between the fountain solution and the ink, which during the Printing process fed to the drum be developed. In this way the chemical wet development of these materials "hidden" from the user and during the First runs of the printing press. With this procedure is connected the problem that at the wet coating level there is a risk that the optical and electronic components of the built-in imagesetter damaged or become dirty. Moreover the system results in an inadequate coating quality caused by a low consistency and frequent occurrence of coating artifacts is marked. The quality the wet coating level can only be done by arranging a complex and sophisticated coating facility be improved on the press.

TASKS OF PRESENT INVENTION

Object of the present invention is a simple, consistent and high quality on-press coating process to provide for the production of a print template, wherein none Naßbeschichtungs- or wet development stage is required and be carried out at an acceptable speed can reduce the downtime of the printing press. Is solved this task according to the method defined in claim 1. Special Flag for preferred embodiments of the present invention are described in the subclaims.

Further advantages and embodiments of the present invention will become apparent from the description below and the figure below.

SUMMARY THE FIGURES

1 shows a schematic representation of a preferred embodiment according to the method of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the production process according to the invention a lithographic printing template is used on a carrier and a transfer layer containing donor material to have a hydrophilic cylindrical surface to obtain an image recording layer. The term "cylindrical Surface" can also be referred to simply as a "cylinder" herein. The transfer layer contains an imaging composition based on the donor material transfer the cylinder to form a continuous imaging layer. The transfer layer of the donor material is particularly in physical contact brought with the cylinder and the donor material continuously over the cylindrical surface guided, wherein the imaging composition is from the donor material to the cylindrical surface becomes.

The in the inventive method Imaging composition used contains hydrophobic, thermoplastic, polymeric particles dispersed in a hydrophilic binder and a connection that can convert light into heat. It has now quite unexpectedly turned out to be this Composition is easily transferable by friction. Such Friction can be generated by using the donor material at a Speed that is not the rotational speed of the cylinder is the same about the cylindrical surface promoted becomes. According to an alternative embodiment, the image recording Composition also by moistening the cylindrical surface with an aqueous solution and Promote of the donor material the cylindrical surface transmitted without friction become, d. H. by donor material at a rate which is equal to the rotational speed of the cylinder, over which cylindrical surface promoted becomes. The transmission takes place according to yet another method according to the invention the imaging composition both by pre-wetting the cylindrical surface with an aqueous solution as by friction, d. H. by donor material at a rate which is not the same as the rotational speed of the cylinder, over which wetted cylindrical surface promoted becomes.

The method of the present invention differs from the current state of the art, processes known from EP-A 698 488 that the image-recording composition not figuratively by local Transfer heating is, but is applied so that the Template a uniform, continuous layer is formed. Because the width of the donor material preferably the width of the artwork is the same, one is sufficient single revolution of the cylindrical surface to cover the entire surface of the Coating artwork, reducing downtime for coating required Press is reduced. Reaches the strength of a single Applied coating layer does not go out, so additional Revolutions needed be the desired one laydown to obtain. With the imaging composition described herein can get a sufficiently high coating thickness after just a few turns become.

After the coating step can the applied composition is subjected to heat in an imagewise manner, wherein the warmed Areas are converted into hydrophobic pressure areas. Similar to in the process described in EP-A 802 547, the non-exposed are then Areas during the first edition of the print job in a "hidden" processing stage by feeding removed from fountain solution and / or printing ink. Because the cylindrical surface a hydrophilic surface is, the unexposed areas of the artwork during the Printing wetted by means of the lithographic fountain solution. The Areas exposed to hydrophobes are color-attracting and form the printing areas of the artwork. Compared to that from EP-A 802 547 known wet coating process the method of the present invention is simpler and more practical and it ensures consistent results and fewer coating artifacts.

Except for the advantages mentioned above is the inventive method particularly suitable for performing on the press because a dry coating stage is used and therefore not an elevated one Risk of damage or contamination of the electronic or optical, in the press built-in facilities such as an imagesetter of a digital press consists. As the possible pre-wetting level and the processing level with conventional Fountain solution like an aqueous liquid are conceivable, these levels have no disturbing influence on the normal operation of electronic or optical devices the press and that because the dampening water during the press operation anyway Template supplied becomes.

According to a preferred method according to the invention, the imaging composition is transferred to the cylinder by friction. The friction can be generated by conveying the donor material over the surface of the cylinder at a speed that is not the same as the rotational speed C of the cylinder. The speed can vary in absolute magnitude as well as direction, ie the speed at which the web of the donor material is conveyed over the surface of the cylinder can be higher or lower than the rotational speed of the cylinder and the conveyance the direction of rotation of the cylinder can be the same or opposite. The designation "C not the same" also refers to the embodiment in which the speed of the rotary movement of the cylinder and the speed at which the donor material is conveyed to the cylinder have the same absolute order of magnitude but an opposite direction. C can also mean zero, which generates friction by conveying the donor material over a fixed cylinder.

In the specific embodiment of 1 becomes the donor material 1 the impression cylinder 3 fed by a roll 2 handled this material, the material 1 by means of contact rollers 4 and 5 with pressure cylinder 3 contacted and the material used 1 again on take-up reel 6 is wound up. In a known manner, feed rollers 2 and take-up reel 6 operated by means of electronically controllable motors so that during the conveyance of the donor material 1 the strip tension can be kept constant. The direction of conveyance and rotational movement of the rollers 2 and 6 and the impression cylinder 3 are in 1 indicated with arrows (vectors). In the preferred embodiment of 1 becomes the donor material 1 at a speed C (vector 7 ), which is higher than the relative movement of the cylinder 3 , and in a direction that corresponds to the direction of rotation of the cylinder 3 is opposite (vector 8th ), the pressure cylinder 3 fed. It goes without saying that the donor material 1 also in a different one than in 1 shown direction can be promoted. All the in 1 shown roles and the donor material 1 are substantially the same width (in the direction perpendicular to the plane of 1 ), whereby the entire surface of the printing cylinder is coated after a few revolutions. If the speed of the donor material is high enough in relation to the surface of the cylinder, a single revolution is sufficient to obtain a targeted coating thickness.

Of course, in addition to the embodiment of FIG 1 still other configurations are possible to generate friction between the donor material and the cylindrical surface. When using a single contact roller, a line-like contact is made between the donor material and the cylindrical surface instead of the transverse contact of 1 receive.

The cylinder mentioned above can is a plate cylinder of a rotary printing press, d. H. the transmission stage can take place directly in the press. As an alternative, the imaging composition in a suitable device for applying a layer by the method according to the invention fed to a cylinder and this cylinder can then either manually or automatically through a mechanism that finds the appropriate coating device couples to the printing press, are conveyed into a printing press. This procedure reduces the downtime of the press even more because of the coating and even the exposure level can be done off-press while doing another printing job running. After the printing process, the artwork (s) will be changed and a new print job can be started immediately.

According to a preferred embodiment the press cylinder is not directly with the image recording Coated composition, but becomes a hydrophilic carrier material clamped on the press cylinder and does not become the cylinder, but the surface of the carrier material coated with the imaging composition. The carrier material can e.g. B. be a cylindrical seamless sleeve or sheet that or that can be clamped around a press cylinder. The carrier material can e.g. B. a hydrophilic metal plate or a plastic sheet be provided with a hydrophilic layer.

A highly preferred carrier material is an electrochemically grained and anodized aluminum plate. The anodized aluminum plate can processing to improve the hydrophilic properties the plate surface be subjected. For example, the aluminum support can be processed the carrier surface with a sodium silicate solution with increased Temperature, e.g. B. 95 ° C, be silicated. As an alternative, phosphate processing be made, the aluminum oxide surface with one optionally further containing an inorganic fluoride phosphate solution is processed. Furthermore, the aluminum oxide surface with a citric acid or citrate solution rinsed become. This treatment can be done at room temperature or at light increased Temperature between about 30 ° C and 50 ° C respectively. Another interesting method is to rinse the aluminum oxide surface with a bicarbonate solution, further it is obvious that one or several of these post-treatments can be carried out separately or in combination can.

As plastic materials that can be used as a carrier material, for. As poly (ethylene terephthalate) or poly (ethylene naphthalate) to name. These materials are preferably coated with a cross-linked hydrophilic layer. A particularly suitable crosslinked hydrophilic layer can be obtained from a hydrophilic binder crosslinked with a crosslinking agent such as formaldehyde, glyoxal, polyisocyanate or a hydrolyzed tetraalkyl orthosilicate. The latter crosslinking agent is preferred. Suitable hydrophilic binders are hydrophilic (co) polymers such as, for example, homopolymers and copolymers of vinyl alcohol, acrylamide, methylolacrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate or maleic anhydride-vinyl methyl ether copolymers. The hydrophilicity of the (co) polymer or (co) polymer mixture used is preferably higher or equal to the hydrophilicity of at least 60% by weight, preferably at least 80% by weight, of hydrolyzed polyvinyl acetate. The amount of crosslinking agent, in particular tetraalkyl orthosilicate, is preferably at least 0.2 part by weight per part by weight of hydrophilic binder, is preferably between 0.5 and 5 parts by weight, particularly preferably between 1.0 part by weight and 3 parts by weight per part by weight of hydrophilic binder.

The cross-linked hydrophilic layer of the carrier material contains preferably also substances that have mechanical strength and porosity improve the layer. Colloidal silica can be used for this purpose become. The colloidal silica can be in the form of any commercially available water dispersion of colloidal silica for example with an average particle size up to 40 nm, e.g. B. 20 nm, to be used. Next to it inert particles with a larger grain size than that colloidal silica be added, e.g. B. silica, which, as in J. Colloid and Interface Sci., Volume 26, 1968, pages 62 to 69, by Stöber is made, or alumina particles or particles with an average diameter of at least 100 nm, it being are particles of titanium dioxide or other heavy metal oxides. By Embedding of these particles is obtained the surface the cross-linked hydrophilic layer with a uniform rough texture microscopic peaks and valleys, which as bearings for Serve water in background areas.

The strength of the cross-linked hydrophilic Layer of the carrier material can be between 0.2 μm and 25 μm vary and is preferably between 1 μm and 10 μm. Particular examples of usable according to the invention Suitable cross-linked hydrophilic layers are in EP-A 601 240, GB-P 1 419 512, FR-P 2 300 354, US-P 3 971 660, US-P 4 284 705 and EP-A 514 490.

The donor material contains one carrier and a transfer layer containing the imaging composition. Between the carrier and the imaging layer may optionally have one or more Intermediate layers inserted become.

The carrier of the donor material can a metal foil, paper or a plastic foil such as a poly (ethylene terephthalate) foil, a cellulose acetate film, a polystyrene film, a polycarbonate film etc. The plastic film carrier can be opaque or translucent his. The use of a polyester film carrier is particularly preferred.

The transfer layer of the donor material contains a hydrophilic binder, for example synthetic homo- or Copolymers such as a poly (vinyl alcohol), a poly (meth) acrylic acid Poly (meth) acrylamide, a polyhydroxyethyl (meth) acrylate, a polyvinyl methyl ether or natural Binders such as gelatin, a polysaccharide such as e.g. B. dextran, pullulan, Cellulose, gum arabic and alginic acid.

The transfer layer of the donor material contains also hydrophobic thermoplastic polymer particles, preferably with a coagulation temperature above 35 ° C and particularly preferably above 50 ° C. coagulation may result from softening or melting of the thermoplastic polymer Particles under the influence of heat enter. The coagulation temperature of the thermoplastic hydrophobic polymeric particles are not subject to any specific upper limit, however, it should be enough are below the decomposition temperature of the polymeric particles. The Coagulation temperature is preferably at least 10 ° C below that Temperature at which decomposition of the polymer particles occurs. The polymeric particles become a temperature above the coagulation temperature exposed, they coagulate and form a hydrophobic agglomerate in the hydrophilic layer, causing the hydrophilic layer to adhere to them Make insoluble in tap water or an aqueous liquid becomes. Specific examples of hydrophobic polymeric particles for use in the present Invention are e.g. B. polyethylene, polystyrene, poly (vinyl chloride), Poly (methyl (meth) acrylate), poly (ethyl (meth) acrylate), poly (vinylidene chloride), Polyacrylonitrile, poly (vinyl carbazole), etc. or copolymers thereof. Polystyrene is very particularly preferred. The weight average of the Molecular weight of the polymers can be between 5,000 and 1,000,000 g / mol vary. The particle size of the hydrophobic Particles can be between 0.01 μm and 50 μm, particularly preferably between 0.05 μm and 10 μm and very particularly preferably between 50 nm and 80 nm vary. The amount of hydrophobic thermoplastic polymeric particles in the imaging layer is preferably between 20 and 95% by weight, particularly preferably between 40 and 95 % By weight and very particularly preferably between 70 and 90% by weight.

The polymeric particles are as one Dispersion in the aqueous casting liquid of the image-forming layer and can be according to the in US-P 3,476 937 described methods can be prepared. In another, for the Preparation of an aqueous dispersion the thermoplastic polymer particles particularly suitable processes:

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

Infrared absorbing components are preferably used as suitable light to heat converting compounds, although the absorption wavelength is not of great importance as long as the absorption of the compound used falls within the wavelength range of the light source used for imagewise exposure. Particularly useful compounds are, for example, dyes and in particular infrared dyes, carbon black, metal carbides, metal borides, metal nitrides, metal carbonitrides, oxides with a bronze structure and oxides with a structure related to the bronze family, but without the A component, e.g. B. WO _2.9 . Conductive polymeric dispersions can also be used, such as conductive polymeric dispersions based on polypyrrole or polyaniline.

The transfer layer of the donor material can also contain other ingredients such as anionic, cationic, Contain non-ionic or amphoteric surfactants. Perfluoro surfactants are preferred. Nonionic perfluoro surfactants are particularly preferred. These surfactants can used alone or preferably in combination.

According to a preferred method according to the invention is preferably the imaging element using a Lasers or an LED diode subjected to a scanning heating. Most notably preference is given to using one in the infrared range (IR range), especially in the near infrared, d. H. in the wavelength range between 700 and 1,500 nm, emitting laser. Are particularly preferred Semiconductors (diodes) lasers emitting in the near infrared range.

After the imagewise exposure, the Develop the imaging layer, preferably by starting the printing work. In a preferred embodiment, the Fountain water supply Dampening rollers on those with the imaging composition coated cylinders and then the inking rollers lowered. Usually after about 10 revolutions of the cylinder get the first clear and usable deductions.

The fountain solution usable according to the invention are subject to no particular limitation and it can commercial Fountain water can be used. Suitable fountain solutions are aqueous liquids usually with an acidic pH which is an alcohol like isopropanol contain.

In addition to the pre-wetting level, transfer level, Exposure level and hidden development level can be additional Stages in the inventive method to be built in. Before coating by transfer, the surface of the Cylinders according to the known manual or automatic processes be cleaned, such as by wiping with a cloth, cotton swab or a brush, Air bubbles, vacuum suction, rinsing with a liquid by spraying or order, or by means of cleaning rollers, e.g. B. by means of the Devices known to those skilled in the art for cleaning the blanket cylinder an offset press. additionally this can be done before applying the imaging composition a primer layer is applied to the surface of the cylinder become. The undercoat can improve the imaging Composition or used to improve the hydrophilic nature of the surface become.

EXAMPLES

example 1

manufacturing of the carrier material

A 0.20 mm thick aluminum plate is degreased by immersing the plate in an aqueous solution containing 5 g / l of sodium hydroxide at 50 ° C. and then rinsed with demineralized water. The plate is then electrochemically grained with alternating current at a temperature of 35 ° C. and a current density of 1200 A / m ² in an aqueous solution containing 4 g / l hydrochloric acid, 4 g / l hydrochloric acid and 5 g / l aluminum ions, to obtain a surface topography with an arithmetic mean roughness (Ra) of 0.5 μm. After rinsing with demineralized water, the aluminum plate is etched with an aqueous solution containing 300 g / l of sulfuric acid for 180 s at 60 ° C. and then rinsed with demineralized water at 25 ° C. for 30 s. The plate is then anodized at a temperature of 45 ° C, a voltage of about 10 V and a current density of 150 A / m ² for about 300 s in an aqueous solution containing 200 g / l of sulfuric acid to give an anodic, 3.0 To obtain g / m ² alumina-containing oxidation film. Finally, the plate is rinsed with demineralized water, post-processed with a solution containing a polyvinylphosphonic acid and then with a solution containing aluminum trichloride, then rinsed with demineralized water for 120 s at 20 ° C. and dried.

manufacturing of the donor material

To 7.5 g of a 20% by weight dispersion of stabilized with a surfactant (1.5 wt .-%, based on the polymer) Polystyrene (with a particle diameter of 60 nm) in demineralized 20 g of a 1% strength by weight solution of the following compound are added to water

Then 66.5 g of demineralized water and 6 g of a 5% by weight solution of CARBOPOL ^™ WS801 (a polyacrylic acid available from Goodrich) are added to the solution thus obtained. The solution thus obtained is cast in a wet layer thickness of 60 μm onto a polyester film with a thickness of 100 μm and then dried at 60 ° C. for at least 5 minutes.

manufacturing the print template

The carrier material mentioned above is as in 1 illustrates on the plate cylinder of a Heidelberg equipped with a device for friction-induced transmission. GTO46 offset printing press, the condition being noted that only a single contact roller is arranged, through which a line-like contact is obtained between the donor material and the carrier material. The donor material is conveyed in the same direction as the direction of rotation of the cylinder, but at a reduced speed, ie at 80% of the press speed (3400 copies / hour), with a pressure on the contact roller of 3 bar over the plate cylinder. Contact is interrupted after a press run.

The printing element is then exposed imagewise with an IR diode laser with a wavelength of 830 nm and a power of 400 mJ / cm ² . The dampening rollers are used for the development 5 Brought into contact with the printing element for a number of revolutions, after which the ink application system is started. Very good print quality is obtained from the first copies. A print run of 10,000 copies can be achieved without loss of print quality.

Example 2

The same support material and donor material and the same press as described in Example 1 are used. Before the donor material and carrier material are brought into contact, the latter is wetted for 3 revolutions by contact with the dampening system of the press. In this example, the pressure on the contact roller is brought back to 0.6 bar. To 1 The transferred image recording layer is allowed to dry under ambient conditions of temperature and humidity. Finally, the same imaging, development and printing process as described in Example 1 is used and comparable results are obtained.

Example 3

The same support material and donor material and the same press as described in Example 1 are used. In this example, the plate cylinder is additionally provided with a free-running adhesive cleaning roller, a product distributed by Teknek LLC (USA) Teknek ^TM -Reinigungskopf CH2 ie, equipped. Before the donor material and the carrier material are brought into contact, the press is first run for 10 revolutions with the adhesive roller touching the carrier material. After this cleaning step, the procedure for exposure and development is analogous to Example 1. The lithographic quality of the copies is very comparable with the quality obtained in Examples 1 and 2. The pre-cleaning stage, however, brings the number of point errors caused by dust adhering to the image-receiving material to almost zero.

Example 4

It will be the same backing material and donor material and the same press as described in Example 1 used. In this example, the plate cylinder is also included a free-running rubber cleaning roller (with a Shore hardness of 40) with a lint-free absorbent, from Veratec USA expelled Hyton Cover is provided. In front Bring the donor material and carrier material into contact Press first Run 10 revolutions, wetting the plate over the dampening unit and contact between the coated Rubber roller and the backing material created. Subsequently becomes the exaggerated Rubber roll from the carrier material tilted away. After this cleaning stage is used for exposure and development proceeded analogously to Example 1. The lithographic quality of the copies is very comparable to the quality obtained in Examples 1 and 2. By however, the pre-cleaning level becomes the number of times the image is taken Dust adhering to the material caused point errors almost to zero brought back.

Claims (10)

A method of making a lithographic artwork, in the following steps a hydrophilic cylindrical surface ( 3 ) is provided with a continuous imaging layer - a donor material ( 1 ) containing a support and a layer containing an imaging composition is brought into physical contact with the cylindrical surface ( 3 ) and - the donor material ( 1 ) is over the cylindrical surface ( 3 ), whereby the imaging composition of the donor material ( 1 ) on the cylindrical surface ( 3 ) is transferred, characterized in that the image-recording composition contains hydrophobic thermoplastic polymer particles dispersed in a hydrophilic binder and a compound which converts light to heat. A method according to claim 1, characterized in that the transfer of the imaging composition is obtained by friction, the friction being obtained by - rotating the cylindrical surface ( 3 ) at a speed C, which can be zero, and - conveying the donor material ( 1 ) over the cylindrical surface ( 3 ) is generated at a speed that is not equal to C. A method according to claim 1 or 2, characterized in that the cylindrical surface ( 3 ) is wetted with an aqueous liquid before the donor material ( 1 ) in physical contact with the cylindrical surface ( 3 ) is brought. A method according to any one of the preceding claims, characterized in that the cylindrical surface ( 3 ) is cleaned before the donor material ( 1 ) in physical contact with the cylindrical surface ( 3 ) is brought. A method according to any one of the preceding claims, characterized in that the donor material ( 1 ) is a web-like material that extends over the cylindrical surface ( 3 ) is promoted by the donor material ( 1 ) unwound from a supply roll and after physical contact with the cylindrical surface ( 3 ) is rewound on a take-up reel. A method according to any one of the preceding claims, characterized in that the cylindrical surface ( 3 ) is the surface of a hydrophilic carrier material stretched on a cylinder of a rotary printing press. A method according to any one of the preceding claims, characterized in that the width of the donor material ( 1 ) the width of the lithographic artwork is essentially the same. A method for producing a lithographic printing master characterized by the following steps (i) providing a hydrophilic cylindrical surface ( 3 ) with a continuous image recording layer according to one of the preceding claims, (ii) imagewise exposure of the image recording layer, and (iii) removing the unexposed areas of the imaging layer by removing the cylindrical surface ( 3 ) Fountain solution or printing ink. A method according to claim 8, characterized in that the image recording layer is exposed with an infrared laser. A method according to claim 8 or 9, characterized in that that the Stages (i), (ii) and (iii) in a rotary printing press with built-in Laser imagesetter performed become.