ES2321955T3 - METHOD FOR MANUFACTURING A THERMOSENSIBLE NEGATIVE LITHOGRAPHIC PRINT IRON PRESSURER. - Google Patents

Abstract

A method for making a heat-sensitive negative-working lithographic printing plate precursor is disclosed comprising the steps of (i) preparing a coating solution comprising hydrophobic thermoplastic polymer particles and a hydrophilic binder; (ii) applying said coating solution on a support having a hydrophilic surface or which is provided with a hydrophilic layer, thereby obtaining an image-recording layer; (iii) drying said image-recording layer; characterized in that said hydrophobic thermoplastic polymer particles have an average particle size in the range from 45 nm to 63 nm, and that the amount of said hydrophobic thermoplastic polymer particles in the image-recording layer is at least 70 % by weight relative to the dried image-recording layer.

Description

Method for manufacturing a plate precursor thermosensitive negative lithographic printing.

Field of the Invention

The present invention relates to a method to make a lithographic printing plate precursor thermosensitive negative.

       \ vskip1.000000 \ baselineskip
    

Background of the invention

Lithographic printing presses use a called a printing matrix such as a printing plate which is mounted on a cylinder of the printing press. Matrix it carries a lithographic image on its surface and you get a printing by applying ink to said image and then transferring the ink from the matrix on a receiving material, which typically It is paper. Conventionally, in the so-called lithographic printing "wet" ink is supplied as well as a solution of aqueous wetting (also called wetting liquid) to the lithographic image consisting of oleophilic (or hydrophobic, areas) is say, they accept ink and repel water) as well as areas hydrophilic (or oleophobic, that is, they accept water and repel the ink). In the so-called driographic printing, the image lithographic consists of areas that accept ink and those that are not adheres the ink (which repel the ink) and during printing In the case of ink, only ink is supplied to the matrix.

Print matrices are obtained usually through exposure and image processing  of an imaging material called the precursor of griddle. In addition to the well-known photosensitive plates, called presensitized plates, which are suitable for UV contact exposure through a photomask, also precursors of the late 90's have become very popular heat-sensitive printing plate. Such thermal materials they offer the advantage of being stable in daylight and are used especially in the so-called direct iron method, in which the plate precursor is exposed directly, that is, unused A photo mask The material is exposed to heat or light infrared and the heat generated causes a chemical (physical-) process, such as ablation, polymerization, insolubilization by crosslinking of a polymer, heat-induced or heat-induced solubilization particle coagulation of a thermoplastic polymer latex.

Although some of these thermal processes allow the plate to be manufactured without wet processing, the most popular thermal plates form an image through a difference of heat-induced solubility in a developer alkaline between exposed and unexposed areas of the coating. He coating typically comprises an oleophilic binder, by example a phenolic resin, whose dissolution rate in the developer is reduced (negative) or increased (positive) by the exposure to image mode. During processing, the solubility differential leads to the elimination of areas without image (not printed) of the coating, revealing of this hydrophilic support mode, while the image areas (which are print) of the coating remain on the support. They describe typical examples of such plates, for example, in documents EP-A 625728, 823327, 825927, 864420, 894622 and 901902. The realizations that work with negatives of said thermal materials often require a preheating stage between exposure and development, as described, for example, in EP-A 625,728.

The negative plate precursors that do not require a preheating stage can contain a layer of image recording that works by particle coalescence Heat induced of a thermoplastic polymer latex, as described, for example, in EP-A documents 770,494, 770,495, 770 496 and 770 497. These patents describe a method to make a lithographic printing plate that It comprises the steps of (1) exposing as an image an element of imaging comprising polymeric particles hydrophobic thermoplastics dispersed in a hydrophilic binder and a compound capable of transforming light into heat, (2) and revealing the element exposed as an image by application of solution wet and / or ink.

Another plate is described that works by latex coalescence in EP-A 800,928 which refers to an imaging element thermosensitive, comprising in a hydrophilic support a layer of image recording comprising an absorption compound infrared and hydrophobic thermoplastic particles dispersed in a soluble or inflatable alkaline resin containing groups Phenolic hydroxyl.

A similar plate is described in the document of US 6,427,595 describing an imaging element thermosensitive to manufacture lithographic printing plates that they comprise on a hydrophilic surface of a lithographic base a image recording layer comprising a compound capable of transform light into heat and thermoplastic polymer particles hydrophobic, which have a particle size and a polydispersity specific, dispersed in a hydrophilic binder.

A method for manufacturing a matrix is described lithographic printing comprising the stage of applying a image recording composition that includes particles hydrophobic thermoplastic polymers dispersed in a binder hydrophilic and a compound capable of transforming light into heat over an aluminum plate mounted on a plate cylinder of a friction transfer printing press in the document EP 1,048,458.

Documents EP-A 514.145 and EP-A 599,510 describe a method of formation of images by direct exposure of a radiation sensitive plate comprising a coating comprising type particles core-wrap that have a core compound insoluble in water that can be softened with heat and a compound of wrap that is soluble or inflatable in an aqueous alkaline medium. Exposure to image mode with infrared light produces coalescence of the particles, at least partially, to form an image and then non-coalescing particles are removed selectively using an aqueous alkaline developer. After, a baking stage is performed.

US 6,692,890 describes an element from which radiation images can be formed comprising a Anodized hydrophilic aluminum base with a surface that comprises pores and an imaging layer comprising polymeric particles coated at the base where the ratio of said pores with respect to the average diameter of the particles Polymers vary from about 0.4: 1 to 10: 1.

EP-A 1,243,413 describes a method for manufacturing a plate precursor of thermosensitive negative lithographic printing comprising the stages of (i) applying on a lithographic basis that has a hydrophilic surface an aqueous dispersion comprising particles hydrophobic thermoplastics and particles of a polymer B having a softening temperature lower than the temperature of glass transition of said hydrophobic thermoplastic particles and (ii) heat the image recording layer to a temperature that is higher than the softening temperature of polymer B e below the glass temperature of thermoplastic particles hydrophobic

US 5,948,591 describes an element heat-sensitive to manufacture a lithographic printing plate comprising on a base that has a hydrophilic surface a image recording layer that includes an absorption agent infrared, hydrophobic thermoplastic particles and a copolymer that it contains acetal groups and hydroxyl groups that have reacted to less partially with a compound with at least two groups carboxyl

A problem associated with the plates of negative impressions that work according to the mechanism of Coalescence of heat-induced latex, is to provide both a high run length during printing as a high sensitivity during exposure. A length of high circulation exposing the printing plate to a high dose of heat (infrared light) -that is to say a high energy density- so that a high degree of coalescence of the particles occurs latex on exposed areas, adhere firmly to the support and therefore become resistant to development when removed Support the unexposed areas. However, the use of a high Energy dose involves a slow iron that takes a while of prolonged exposure and / or a high power laser. When by on the other hand a low heat dose is applied, the degree of Coalescence is reduced and exposed areas degrade quickly during the printing process and as a result Get a reduced run length.

Summary of the invention

An object of the present invention is provide a method for manufacturing a plate precursor of thermosensitive negative lithographic printing based on the latex coalescence that has a high sensitivity and that gives as result a printing plate with a run length improved in the press and excellent printing properties without tacked

This object is performed using a method to manufacture a negative lithographic printing plate precursor thermosensitive comprising the stages of:

(i) prepare a coating solution that it comprises hydrophobic thermoplastic polymer particles and a hydrophilic binder;

(ii) apply said coating solution in a support that has a hydrophilic surface or that is provided of a hydrophilic layer, thereby obtaining a layer of image recording;

(iii) drying said recording layer of image;

characterized in that said particles hydrophobic thermoplastic polymers have an average size of particle in the range of 45 nm to 63 nm,

and why the amount of said particles hydrophobic thermoplastic polymers in the recording layer of image is at least 70% by weight in relation to the layer of dried image recording.

Preferred embodiments of the present Inventions are defined in the dependent claims.

It was surprising to discover that a precursor to printing plate, comprising latex particles with a average particle size in a range of 45 nm to 63 nm in a amount of at least 70% by weight, provides an iron printing with a substantially increased press life and improved sensitivity In addition, the printing plate used in The present invention provides prints with a quality of excellent image and without tacking.

Detailed description of the invention

Hydrophobic thermoplastic particles are present in an image recording layer of the lithographic printing plate precursor coating used in the present invention. The average particle size is between 45 nm and 63 nm, more preferably between 45 nm and 60 nm, more preferably between 45 nm and 59 nm, even more preferably between 45 nm and 55 nm and more preferably between 48 nm and 52 nm . In this document, the particle size is defined as the particle diameter, measured by Photonic Correlation Spectrometry, also known as quasi-elastic or dynamic light scattering. This technique is a convenient method for measuring particle size and the measured particle size values fit well with the particle size measured with transmission electron microscopy (TEM) as described by Stanley D. Duke et al . in Calibration of Spherical Particles by light scattering, in Technical Note-002B, May 15, 2000 (revised on 1/3/2000 from an article published in Particulate Science and Technology 7, pp. 223-228 (1989) .

The amount of polymer particles hydrophobic thermoplastics present in the recording layer of Coating image is at least 70% by weight, preferably at least 75% by weight and, more preferably, at less than 80% by weight. The amount of polymer particles hydrophobic thermoplastics in the image recording layer of the Coating is preferably between 70% by weight and 85% in weight and, more preferably, between 75% by weight and 85% by weight. The percentage by weight of thermoplastic polymer particles hydrophobic is determined in relation to the weight of all components in the image recording layer.

Thermoplastic polymer particles hydrophobes are preferably selected from polyethylene, chloride poly (vinyl), (meth) polymethyl acrylate, (meth) polyethyl acrylate, polyvinylidene chloride, poly (meth) acrylonitrile, polyvinylcarbazole, polystyrene or copolymers thereof. According to a preferred embodiment, thermoplastic polymer particles they comprise polystyrene or derivatives thereof, mixtures that comprise polystyrene and poly (meth) acrylonitrile or derivatives thereof or copolymers comprising polystyrene and poly (meth) acrylonitrile or derivatives thereof. The Last copolymers may comprise at least 50% by weight of polystyrene, and more preferably at least 65% by weight of polystyrene. To get enough chemical resistance organic such as hydrocarbons used in cleaners plates, thermoplastic polymer particles comprise preferably at least 5% by weight of nitrogen, which contains units as described in EP 1,219,416, more preferably at least 30% by weight of nitrogen containing units, such as (meth) acrylonitrile. According to the most preferred embodiment, the polymer particles Thermoplastics consist essentially of styrene units and acrylonitrile in a weight ratio between 1: 1 and 5: 1 (styrene: acrylonitrile), for example, in a 2: 1 ratio.

The weight average molecular weight of the thermoplastic polymer particles may vary from 5,000 to 1,000,000 g / mol.

Thermoplastic polymer particles hydrophobic present in the image recording layer can be applied on the lithographic basis in the form of a dispersion in an aqueous coating liquid and can be prepared by methods described in US 3,476,937 or EP 1,217,010. Another method especially suitable for preparing a dispersion Aqueous of thermoplastic polymer particles comprises:

- dissolve the hydrophobic thermoplastic polymer in a water immiscible organic solvent,

- disperse the solution obtained in this way in water or in an aqueous medium and

- remove the organic solvent by evaporation.

The image recording layer comprises additionally a hydrophilic binder which is preferably soluble in an aqueous developer that has a pH ≥ 10. They are examples of suitable hydrophilic binders homopolymers and copolymers of vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, acrylate of hydroxyethyl, hydroxyethyl methacrylate and copolymers of maleic anhydride / vinyl methyl ether.

The printing plate precursor holder Lithographic has a hydrophilic surface or is provided with a hydrophilic layer The support can be such a sheet material such as an iron or it can be a cylindrical element such as a sleeve that can slide around a printing cylinder of a printing press. Preferably, the support is a metal support such as aluminum or stainless steel. The support it can also be a laminate comprising an aluminum foil and a plastic layer, for example, a polyester film.

A particularly preferred lithographic support It is a support of grained aluminum and electrochemically anodized. Preferably, the aluminum is grained by electrochemical graining and it is anodized by anodizing techniques that use acid phosphoric or a mixture of sulfuric acid / phosphoric acid. Be methods of graining as well as of anodizing aluminum

By graining (or making rough) the support of aluminum, the adhesion of the printed image is improved so much as the moisturizing characteristics of the areas without image. Varying the type and / or concentration of the electrolyte and the voltage applied in the graining stage, different types can be obtained of grains

By anodizing the aluminum support, it Improves its abrasion resistance and hydrophilic nature. The microstructure as well as the thickness of the Al 2 O 3 layer is determine by anodizing stage, the anodic weight (g / m 2 of AL 2 O 3 formed on the aluminum surface) It varies between 1 and 8 g / m2.

The support of grained and anodized aluminum can be treated later to improve the properties hydrophilic surface. For example, the oxide surface of Aluminum can be silicated by treating its surface with a solution of sodium silicate at elevated temperature, for example, 95 ° C. How alternatively, a phosphate treatment can be applied which implies treat the surface of aluminum oxide with a solution of phosphate that may additionally contain an inorganic fluoride. In addition, the aluminum oxide surface can be cleared with a organic acid and / or a salt thereof, for example, acids carboxylic, hydroxycarboxylic acids, sulfonic acids or phosphonic acids, or their salts, for example, succinates, phosphates, phosphonates, sulfates and sulfonates. A solution of citric acid or citrate. This treatment can be carried out at room temperature or it can be carried out at a temperature slightly elevated from about 30 ° C to 50 ° C. A treatment additional interesting involves clarifying the oxide surface of aluminum with a bicarbonate solution. Additionally, the Aluminum oxide surface can be treated with acid polyvinylphosphonic acid, polyvinylmethylphosphonic acid, acid esters phosphoric of polyvinyl alcohol, polyvinyl sulfonic acid, acid polyvinylbenzenesulfonic acid esters of alcohol sulfuric acid polyvinyl and acetals of polyvinyl alcohols formed by reaction with a sulfonated aliphatic aldehyde. It is also clear that one or more of these subsequent treatments can be carried out alone or in combination In documents GB 1084070, DE 4423140, DE 4417907, EP 659909, EP 537633, DE 4001466, EP A 292801, EP A 291760 and US 4458005 more detailed descriptions of these are provided. treatments

According to another embodiment, the support it can also be a flexible support, provided with a layer hydrophilic, hereinafter referred to as "base layer". The support flexible is, for example, paper, plastic film, aluminum fine or a laminate thereof. They are preferred examples of film of plastic a polyethylene terephthalate film, film polyethylene naphthalate, cellulose acetate film, film polystyrene, polycarbonate film, etc. The support of Plastic film can be opaque or transparent.

The base layer is preferably a layer crosslinked hydrophilic obtained from a hydrophilic binder crosslinked with a hardening agent such as formaldehyde, glyoxal, polyisocyanate or a hydrolyzed tetra-alkyl borosilicate. The last one is particularly preferred The thickness of the hydrophilic base layer can vary in the range of 0.2 to 25 µm and preferably is 1 at 10 µm. The hydrophilic binder for use in the base layer is, for example, a hydrophilic (co) polymer such as homopolymers and copolymers of vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylic acid, methacrylic acid, acrylate of hydroxyethyl, hydroxyethyl methacrylate and copolymers of maleic anhydride / vinyl methyl ether. The hydrophilicity of (co) polymer or mixture of (co) polymers used is preferably the same or greater than the hydrophilicity of acetate of hydrolyzed polyvinyl to a degree of at least 65% by weight, preferably 80% by weight. The amount of agent of hardening in particular tetra-alkylortosilicate, is preferably from al less 0.2 parts per part by weight of hydrophilic binder, more preferably between 0.5 and 5 parts by weight, more preferably between 1 part and 3 parts by weight.

According to another embodiment, the base layer may additionally comprise Al 2 O 3 and a binder optional. The deposition methods for Al_ {2} O_ {3} on the Flexible support can be (i) physical vapor deposition including spray reagents, RF spray, laser pulsed PVD and evaporation of aluminum, (ii) chemical deposition of steam both under vacuum and non-vacuum conditions, (iii) chemical deposition of solution, which includes coating by spray, dip coating, coating centrifugation, chemical bath deposition, adsorption and reaction Selective ion layer, liquid phase deposition and non electrolytic deposition. Al 2 O 3 powder can be prepared using different techniques that include pyrolysis to flame, ball mill grinding, precipitation, synthesis hydrothermal, aerosol synthesis, emulsion synthesis, synthesis sol-gel (solvent based), synthesis of gel-solution (water based) and phase synthesis soda. The particle size of Al_ {2} O_ {3} powders it can vary between 2 nm and 30 µm; more preferably between 100 nm and 2 µm.

The hydrophilic base layer may contain additionally substances that increase mechanical strength and porosity of the layer. Silica can be used for this purpose. colloidal The colloidal silica used may be in the form of any dispersion of colloidal silica in water available in the market that has for example a particle size of up to 40 nm, for example, 20 nm. Furthermore, inert particles of larger than colloidal silica, for example, prepared silica according to Stöber, as described in J. Colloid and Interface Sci., Vol. 26. 1968, pages 62 to 69 or alumina particles or particles that have an average diameter of at least 100 nm, which are particles of titanium dioxide or other metal oxides heavy

Particular examples of base layers are described. hydrophilic suitable for use in accordance with the present invention in EP 601240, GB 1419512, FR 2300354, US 3971660 and US 4284705.

An optimal ratio between pore diameter of the surface of the aluminum support (if present) and the average particle size of thermoplastic particles hydrophobic can increase the press life of the plate printing and can improve the turning behavior of impressions This proportion of the average pore diameter of the aluminum support surface with respect to the average size of particle of thermoplastic particles present in the layer of image recording of the coating, preferably varies from 0.05: 1 to 0.8: 1, more preferably from 0.10: 1 to 0.35: 1.

Preferably, the coating also It contains a compound that absorbs infrared light and transforms the energy absorbed in heat. The amount of absorption agent infrared in the coating is preferably between 0.25 and 25.0% by weight, more preferably between 0.5 and 20.0% in weight. The infrared absorption compound may be present in the image recording layer and / or in an optional layer. In the embodiment, the infrared absorption agent is present in the coating image recording layer, its concentration is preferably of at least 6% by weight, more preferably of at minus 8% by weight, relative to the weight of all components in the image recording layer. IR absorption compounds Preferred are dyes such as cyanine, merocyanine, indoaniline, oxonol, pyrilium and squaryl dyes or pigments such as carbon black. Examples of IR absorbers are described suitable, for example, in EP-A documents 823327, 978376, 1029667, 1053868, 1093934; WO 97/39894 and 00/29214. A preferred compound is the following cyanine dye IR-1:

one

To protect the surface of the coating, in particular of mechanical damage, it can also be applied optionally a protective layer. Generally the protective layer comprises at least one water soluble polymeric binder, such such as polyvinyl alcohol, polyvinylpyrrolidone, acetates of partially hydrolyzed polyvinyl, gelatin, carbohydrates or hydroxyethylcellulose, and can be produced in any way known as an aqueous solution or dispersion that can contain, if necessary, small quantities, ie less than 5% by weight based on the total weight of the coating solvents for the protective layer of organic solvents. The thickness of the protective layer can conveniently be any quantity, advantageously up to 5.0 µm, preferably 0.05 to 3.0 µm, particularly preferably from 0.10 to 1.0 µm.

The coating may also contain of the image recording layer one or more additional layers. Apart from the additional layers already described above - that is an optional light absorption layer comprising one or more compounds that are capable of transforming infrared light into heat and / or a protective layer such as, for example a cover layer which is removed during processing - the coating can additionally comprising for example a layer that improves the adhesion between the image recording layer and the support.

Optionally, the coating may contain additionally additional ingredients. These ingredients can be present in the image recording layer or in another layer optional. For example, they are well known components of Additional binder lithographic coatings, particles Polymers such as crosslinking agents or spacers, surfactants such as perfluorinated surfactants, particles of silicon or titanium dioxide, development inhibitors, development accelerators or dyes. They are advantageous, especially  the addition of coloring agents such as dyes or pigments that provide a visible color to the coating and they remain in the exposed areas of the coating after the processing stage In this way, areas with images that do not are removed during the processing stage form an image visible on the printing plate and at this stage it is already done Possible examination of the revealed printing plate. Are examples typical of said contrast dyes tri-o dyes amino substituted diarylmethane, for example, violet crystal, Methyl Violet, Victoria Pure Blue, Flexoblau 630, Basonylblau 640, auramine and malachite green. They are also contrast dyes suitable dyes that are analyzed deeply in the detailed description of EP-A 400,706. Also interesting are dyes that, combined with additives specific, color only the coating but that They color intensely after exposure.

In accordance with the method herein invention, first a coating solution is prepared that it comprises the hydrophobic thermoplastic polymer particles and the hydrophilic binder described above, then applied said coating solution on a support (as described above), thus obtaining a recording layer of image, and then said image recording layer is dried.

The printing plate precursor used in the The present invention can be exposed as an image directly with heat, for example, by means of a thermal head, or indirectly by infrared light, preferably light near infrared The infrared light is preferably transformed in heat by a compound that absorbs IR light, as has been previously described. Preferably, the plate precursor of thermosensitive lithographic printing used in the present invention It is not sensitive to visible light. More preferably, the coating is not sensitive to ambient daylight, that is, visible (400-750 nm) and near UV light (300-400 nm), at an intensity and time of exposure corresponding to operating conditions normal, so that the material can be handled without the need for A safe light environment.

The used printing plate precursors in the present invention they can be exposed to infrared light by means of, for example, LED or an infrared laser. Preferably, the light used for exposure is a laser that emits near infrared light that has a wavelength in the range from about 700 to about 1500 nm, per For example, a semiconductor laser diode, an Nd: YAG or Nd: YLF laser. The Laser energy required depends on the sensitivity of the layer of image recording, the residence time per pixel of the ray laser, which is determined by the point diameter (typical value of modern flatbed video recorders at 1 / e2 intensity maximum: 10-25 µm), the scan speed and the resolution of the exposure apparatus (i.e. the number of addressable pixels per unit of linear distance, expressed with  frequency in dots per inch or dpi; typical value: 1000-4000 dpi).

Normally two types of devices are used Laser exposure: internal drum plate (ITD) filmmakers and external (XTD). Typically the ITD plate recorders for thermal plates are characterized by a very high speed of scanning of up to 1500 m / s and may require a laser energy of several watts La Agfa Galileo T (trademark of Agfa Gevaert N. V.) is a typical example of an ironing machine that uses the ITD technology. XTD plate ironing machines thermal having a typical laser energy of approximately 20 mW at approximately 500 mW operate at a scan speed lower, for example 0.1 to 20 m / s. Both the family of Creo Trendsetter plate makers (Creo trademark) as the family of Agfa-Xcalibur plate presses (trademark of Agfa Gevaert N. V.) use XTD technology.

Due to the heat generated during the stage of exposure, hydrophobic thermoplastic polymer particles are fuse or coagulate to form a hydrophobic phase that corresponds to the printing areas of the printing plate. Coagulation may be the result of induced coalescence. by heat, softening or melting of the polymer particles thermoplastics There is no specific upper limit for coagulation temperature of hydrophobic polymer particles thermoplastics, however the temperature must be sufficiently below the decomposition temperature of polymeric particles. Preferably, the temperature of coagulation is at least 10 ° C lower than the temperature at which decomposition of polymer particles occurs. The coagulation temperature is preferably greater than 50 ° C, more preferably higher than 100 ° C.

After exposure, the material can be revealed supplying the coating with an aqueous alkaline solution, so that areas without image of the coating are removed. This stage developing with an aqueous alkaline developing solution can be combined with mechanical rubbing, for example by brush rotary. During the development stage, it is also removed preferably any water soluble protective layer present. A preferred developer solution is a developer with a pH of at at least 10, more preferably at least 11, more preferably at minus 12. Preferred development solutions are solutions buffer such as, for example, silicate based developers or development solutions comprising phosphate buffers. They are advantageous silicate based developers that have a ratio of silicon dioxide to metal oxide alkaline of at least 1 because they ensure that the layer of alumina (if present) of the substrate. Metal oxides Preferred alkalines include Na 2 O and K 2 O, and mixtures of the same. A particularly preferred developer solution silicate-based is a developer solution that comprises sodium or potassium metasilicate, that is, a silicate where the ratio of silicon dioxide to metal oxide Alkaline is 1.

In addition to alkali metal silicates, the developer may optionally contain additional components, such as buffer substances, complexing agents, defoamers, organic solvents in small quantities, inhibitors of corrosion, colorants, surfactants and / or hydrotropic agents known in the art.

The development is preferably carried out at temperatures of 20 to 40ºC in automated processing units  as usual in the art. For regeneration, they can be used conveniently alkali metal silicate solutions that they have alkali metal contents of 0.6 to 2.0 mol / l. These solutions can have the same proportion of oxide of silica / alkali metal than the developer (however, it is usually minor) and similarly contain optionally additives additional. The necessary quantities of regenerated material must adapt to used development devices, daily capacity of plate processing, image areas, etc. and in general they are 1 to 50 ml per square meter of plate precursor. May regulate the addition of regenerator, for example, by measuring the developer conductivity as described in the document EP-A 0.556.690.

The development stage may be followed by a rinsing stage and / or a gumming stage. The gumming stage involves the subsequent treatment of the printing plate Lithographic with a rubber solution. A rubber solution is typically an aqueous liquid comprising one or more compounds surface protectors that are capable of protecting the image lithographic printing plate against contamination or damage. Suitable examples of said polymeric compounds are film-forming hydrophilic or surfactants.

If necessary, the plate precursor can be subsequently treated with a corrective or preservative agent suitable as is known in the art. To increase resistance of the finished printing plate and therefore increase the run length, the layer may briefly heat up to high temperatures ("baked"). The iron can dry before baking or drying during the same baking process. During the baking stage, the iron can be heated to a temperature that is higher than the glass transition temperature of the thermoplastic particles, for example between 100 ° C and 230 ° C, over a period of 40 minutes to 5 minutes. A temperature of Preferred baking is greater than 60 ° C. For example, the plates exposed and developed can be baked at a temperature of 230 ° C for 5 minutes, at a temperature of 150 ° C for 10 minutes or at a temperature of 120 ° C for 30 minutes. Baking can be carried out in conventional hot air ovens or by irradiation with lamps emitting in the infrared spectrum or ultraviolet. As a result of this baking stage, the resistance of the printing plate to plate cleaners, Correction agents and UV-curable printing inks. Saying subsequent heat treatment is described, among others, in the DE 1,447,963 and GB 1,154,749.

The printing plate obtained in this way can be used for the so-called conventional wet transfer ( offset) printing , in which ink and an aqueous wetting liquid are supplied to the plate. Another suitable printing method uses so-called single-fluid ink without a wetting liquid. Suitable single-fluid inks have been described in US 4,045,232; US 4,981,517 and US 6,140,392. In a more preferred embodiment, the single-fluid ink comprises an ink phase, also called hydrophobic or oleophilic phase, and a polyol phase as described in WO 00/32705.

       \ vskip1.000000 \ baselineskip
    

Examples

Example one

Preparation of the lithographic substrate

A 0.30 mm aluminum foil was degreased thickness by dipping the paper in an aqueous solution containing 40 g / l of sodium hydroxide at 60 ° C for 8 seconds and rinsed with demineralized water for 2 seconds. Afterwards, the paper electrochemically for 15 seconds using a current alternated in an aqueous solution containing 12 g / l of acid hydrochloric and 38 g / l aluminum sulfate (18-hydrate) at a temperature of 33 ° C and a current density of 130 A / dm 2. After rinsing with water demineralized for 2 seconds, the foil was treated then with demotion by chemical attack with an aqueous solution that it contained 155 g / l of sulfuric acid at 70 ° C for 4 seconds and was Rinse with demineralized water at 25 ° C for 2 seconds. Subsequently the paper was subjected to anodic oxidation for 13 seconds in an aqueous solution containing 155 g / l of acid sulfuric acid at a temperature of 45 ° C and a current density of 22 A / dm 2, then washed with demineralized water for 2 seconds and was subsequently treated for 10 seconds with a solution containing 4 g / l polyvinylphosphonic acid at 40 ° C, was rinsed with demineralized water at 20 ° C for 2 seconds and dry.

The support obtained in this way had a surface roughness Ra of 0.21 µm and an anodic weight of 4 g / m 2 of Al 2 O 3.

Preparation of printing plate precursors 1-6

Plate precursors were produced from print 1 to 6 applying a coating solution on the lithographic substrate described above. Table 1 defines The coating composition. The average sizes of particle of styrene / acrylonitrile copolymers with a Brookhaven BI-90 analyzer, available in the Market in Brookhaven Instrument Company, Holtsville, NY, United United, and are indicated in Table 2. The coating was applied to from an aqueous coating solution and a weight was obtained 0.84 g / m2 dry coating.

TABLE 1

2

Image formation and precursor processing of printing plate 1-6

Iron precursors were exposed 1-6 with a Creo Trendsetter 2344T (40 W) (camcorder of irons, trademark of Creo, Burnaby, Canada), which It operates at 200 mJ / cm2 and 150 rpm.

After imaging, the precursors of plates were processed on an Agfa VA88 processor (brand commercial of Agfa), which operates at a speed of 1 m / min and at 22 ° C, using Agfa PD91 (trademark of Agfa) as a solution for developed (based on silicate).

PD91 is a buffer solution comprising potassium metasilicate, Genapol C200 (surfactant available in the market at Clariant GmbH, Frankfurt am Main Germany) and Librateric AA30 (surfactant commercially available from Libra Chemicals Limited, Manchester, United Kingdom) and has a pH = 13.

After development, the plates were gummed with RC795 (trademark of Agfa).

       \ vskip1.000000 \ baselineskip
    

Print results

The plates were mounted in a press GTO46 printing (available from Heildelberger Druckmaschinen AG), and a print job was started using K + E Novavit 800 ink Skinnex (trademark of BASF Drucksysteme GmbH) and FS101 at 3% (trademark of Agfa) in 10% isopropanol as a liquid wet.

The lithographic properties of the plates by visual inspection of the aspect of the tack on the areas without image of the plates and the quality of the coating in terms of run length (Table 2). A excellent resistance to roll length (++) means that after 100,000 prints the 1% brightness of a screen of 200 lpi still reproduces in print and good resistance  to the length of the roll (+) means that after 100,000 prints the 2% brightness of a 200 lpi screen is still Play in print. Insufficient resistance to roll length (-) means that after 1,000 prints degradation of the brightness of a 200 lpi screen occurs.

TABLE 2 Results of the run length and appearance of the tacked in areas without plate image

3

The results in Table 2 demonstrate that the plates comprising a latex with an average particle size below 45 nm show tacked in the plate areas without printing, and plates comprising a latex with a size mean particle of 77 nm or greater have a run length reduced Plates comprising a medium sized latex 45 nm particle show only a slight tendency to turn and it is not seen turned in plates with particles of 50 nm or 61 nm.

       \ vskip1.000000 \ baselineskip
    

Example 2

Preparation of the lithographic substrate

The lithographic substrate preparation is performed according to Example 1.

Preparation of printing plate precursors 7-10

Plate precursors 7 to 10 were produced applying a coating on the lithographic substrate described previously. Table 3 defines the composition of the covering. The average particle sizes of the particles were measured. styrene / acrylonitrile copolymers with a Brookhaven analyzer BI-90, commercially available in Brookhaven Instrument Company, Holtsville, NY, United States, and indicated in Table 4. The coating was applied from a solution of aqueous coating and a dry coating weight of  0.84 g / m2.

TABLE 3 Dry coating composition (% in weight)

4

Image formation and precursor processing of printing plate 7-10

Iron precursors were exposed 7-10 with a Creo Trendsetter 2344T (40 W) (camcorder of irons, available in Creo, Burnaby, Canada), which works at 150 rpm and variable energy densities up to 250 mJ / cm2.

After imaging, the plates are they processed on an Agfa VA88 processor, which runs at a speed 1 m / min and at 25 ° C, and using Agfa PD91 (trademark of Agfa) as developing solution (based on silicate).

PD91 is a buffer solution comprising potassium metasilicate, Genapol C200 (surfactant available in the market at Clariant GmbH, Frankfurt am Main Germany) and Librateric AA30 (surfactant commercially available from Libra Chemicals Limited, Manchester, United Kingdom) and has a pH = 13.

After development, the plates were gummed with RC795 (trademark of Agfa).

       \ vskip1.000000 \ baselineskip
    

Print results

The plates were mounted in a press GTO46 printing (available from Heildelberger Druckmaschinen AG) and a print job was started using K + E Novavit 800 ink Skinnex (trademark of BASF Drucksysteme GmbH) and Combifix XL 4% with 10% isopropanol as a wetting liquid.

       \ vskip1.000000 \ baselineskip
    

       \ vskip1.000000 \ baselineskip
    

       \ vskip1.000000 \ baselineskip
    

(Table goes to page next)

       \ newpage
    

The sensitivity of the precursors was determined of iron and are summarized in Table 4.

TABLE 4 Sensitivity of the plates 7-10

5

       \ vskip1.000000 \ baselineskip
    

The results show that at the average size of 41 nm particle flocculation occurs and that at the average size of 79 nm particle, the sensitivity is too low (sensitivity >> 250 mJ / cm2). Plates with a particle size 51 nm or 63 nm show high sensitivity.

       \ vskip1.000000 \ baselineskip
    

Example 3

Preparation of the lithographic substrate

The lithographic substrate preparation is performed according to Example 1.

Preparation of printing plate precursors 11-16

Plate precursors were produced from print 11 to 16 applying a coating on the substrate lithograph described above. Table 5 defines the coating composition. The coating was applied from of an aqueous coating solution and a weight of 0.84 g / m2 dry coating.

       \ vskip1.000000 \ baselineskip
    

       \ vskip1.000000 \ baselineskip
    

       \ vskip1.000000 \ baselineskip
    

(Table goes to page next)

TABLE 5 Dry coating composition (% in weight)

6

Image formation and precursor processing of printing plate 11-16

Iron precursors were exposed 11-16 with a Creo Trendsetter 2344T (40 W) (plate maker available in Creo, Burnaby, Canada), which It operates at 260 mJ / cm2 and 150 rpm.

After imaging, the plates are they processed on an Agfa VA88 processor, which runs at a speed 1 m / min and at 25 ° C, and using Agfa PD91 (trademark of Agfa) as developing solution (based on silicate).

PD91 is a buffer solution comprising potassium metasilicate, Genapol C200 (surfactant available in the market at Clariant GmbH, Frankfurt am Main, Germany) and Librateric AA30 (surfactant commercially available from Libra Chemicals Limited, Manchester, United Kingdom) and has a pH = 13.

After development, the plates were gummed with RC795 (trademark of Agfa).

       \ vskip1.000000 \ baselineskip
    

Print results

The plates were mounted in a press GTO46 printing (available from Heildelberger Druckmaschinen AG), and a print job was started using K + E Novavit 800 ink Skinnex (trademark of BASF Drucksysteme GmbH) and FS101 at 3% (trademark of Agfa) with 10% isopropanol as a liquid wet.

       \ newpage
    

The appearance of spots (Dmin) and tackled in the areas without image of the plate and is summarized in the Table 6.

TABLE 6 Stain results (Dmin) and tacked

7

       \ vskip1.000000 \ baselineskip
    

The results show that a concentration Latex 65% by weight in the coating does not provide a Good image quality. Plates with a concentration of latex Over 65% by weight do not show spots or tacks.

       \ vskip1.000000 \ baselineskip
    

Example 4

Preparation of the lithographic substrate

The lithographic substrate preparation is performed according to Example 1.

       \ vskip1.000000 \ baselineskip
    

Preparation of printing plate precursors 17-20

Plate precursors were produced from print 17 to 20 applying a coating on the substrate lithograph described above. Table 7 defines the coating composition. The coating was applied from of an aqueous coating solution and a weight of 0.84 g / m2 dry coating.

TABLE 7 Dry coating composition (% weight)

8

       \ vskip1.000000 \ baselineskip
    

Image formation and precursor processing of 17-20 printing plate

Iron precursors were exposed 17-20 with a Creo Trendsetter 2344T (40 W) (plate maker available in Creo, Burnaby, Canada), which It works at 150 rpm.

After imaging, the plates are they processed on an Agfa VA88 processor, which runs at a speed 1 m / min and at 25 ° C, using Agfa PD91 (trademark of Agfa) as developing solution (based on silicate).

PD91 is a buffer solution comprising potassium metasilicate, Genapol C200 (surfactant available in the market at Clariant GmbH, Frankfurt am Main Germany) and Librateric AA30 (surfactant commercially available from Libra Chemicals Limited, Manchester, United Kingdom) and has a pH = 13.

After development, the plates were gummed with RC795 (trademark of Agfa).

       \ vskip1.000000 \ baselineskip
    

Print results

The plates were mounted in a press GTO46 printing (available from Heildelberger Druckmaschinen AG), and a print job was started using K + E Novavit 800 ink Skinnex (trademark of BASF Drucksysteme GmbH) and FS101 at 3% (trademark of Agfa) with 10% isopropanol as a liquid wet.

       \ newpage
    

The appearance of spots and tackling was determined in the imageless areas of the plate and is summarized in Table 8.

TABLE 8 Stain results (Dmin) and tacked

9

The results show that a concentration Latex 65% by weight is not enough to get a good image quality. Plates with a latex concentration of 75% by weight or 83% by weight demonstrate high sensitivity No spots or tacks.

Claims (10)

1. A method of manufacturing a precursor of thermosensitive negative lithographic printing plate that It comprises the stages of: (i) prepare a coating solution that it comprises hydrophobic thermoplastic polymer particles and a hydrophilic binder; (ii) apply said coating solution on a support that has a hydrophilic surface or that is provided with a hydrophilic layer, thereby obtaining a layer image recording; (iii) drying said recording layer of image; characterized in that said hydrophobic thermoplastic polymer particles have an average particle size in the range of 45 nm to 63 nm, and why the amount of said hydrophobic thermoplastic polymer particles in the layer of Image recording is at least 70% by weight in relation to the image recording layer dried 2. A method according to claim 1, in which the hydrophobic thermoplastic polymer particles they have an average particle size in the range of 45 nm to 55 nm. 3. A method according to any of the previous claims, wherein the amount of particles hydrophobic thermoplastic polymers in the recording layer of image is at least 75% by weight in relation to the layer of image recording 4. A method according to any of the previous claims, wherein the amount of particles hydrophobic thermoplastic polymers in the recording layer of image is less than or equal to 85% by weight in relation to the layer of image recording 5. A method according to any of the previous claims, wherein the polymer particles hydrophobic thermoplastics comprise polyethylene, chloride poly (vinyl), (meth) polymethyl acrylate, polyethyl methacrylate, polyvinylidene chloride, poly (meta) acrylonitrile, polyvinylcarbazole, polystyrene or copolymers thereof. 6. A method according to claim 5, in which the hydrophobic thermoplastic polymer particles comprise polystyrene or a copolymer comprising polystyrene and poly (meth) acrylonitrile. 7. A method according to any of the previous claims, wherein the hydrophilic binder is soluble in an aqueous developer having a pH ≥ 10. 8. A method according to any of the previous claims, wherein the recording layer of image further comprises an infrared absorption agent in an amount of at least 6% by weight in relation to the layer of image recording 9. A method according to any of the previous claims, wherein the coating comprises additionally one or more compounds that provide an image visible after exposure as an image and developing. 10. A method according to any of the previous claims, wherein the coating comprises additionally one or more compounds that provide an image visible after exposure as an image but before revealed.