DE60213236T2 - Heat sensitive planographic printing plate precursor - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The The present invention relates to a heat-sensitive lithographic Printing plate precursor, which is an aqueous-alkaline Development requires.

GENERAL STATE OF THE ART

at lithographic printing is usually used a so-called Print master like one on a drum of a web press clamped pressure plate. The master surface carries a lithographic image and a print is obtained by first printing ink on the image applied and then the Transfer the color from the master to a receiving material, usually paper becomes. In conventional lithographic printing is both ink and fountain solution water-based on the lithographic image, made of oleophilic (or hydrophobic, i.e., ink-receptive, water-repellent) Areas 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 (i.e., 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 get where different pre-presses like the font type, Scanning, production of color separations, rastering, trapping, 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 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.

A typical radiation sensitive printing plate precursor for computer-to-film process contains a hydrophilic carrier and an image-recording layer containing radiation-sensitive compositions. For imagewise exposure a negative-working printing plate, usually with the help of a film mask in a UV contact copying machine the exposed image areas are insoluble and the non-exposed areas remain soluble in an aqueous-alkaline developer. The printing plate is then with The developer developed this in the non-exposed areas to remove contained diazonium salt or diazo resin. The illuminated Areas thus form the image areas (i.e., the printing areas) of the printing master and thus become such printing plate precursors It is also called "negative working" positive-working materials in which the exposed areas forming the non-printing areas, e.g. Plates with a novolak naphthoquinone diazide coating, which is only dissolved in the exposed areas in the developer.

Except the The above radiation-sensitive materials are also heat-sensitive Printing plate precursors very popular become. Such thermal materials have the advantage of their Daylight stability and are particularly suitable for use in the so-called computer-to-plate process, in which the plate precursor is exposed directly, i. Without any effort a movie mask. In general, the material is visually with Heat applied or exposed to infrared light and the heat generated dissolves a (physical) chemical process such as ablation, polymerization, Insolubilization by cross-linking of a polymer, coagulation the particles of a thermoplastic polymeric latex and solubilization due to the destructive effects of intermolecular interactions out.

The Coating a typical heat-sensitive lithographic printing plate precursor requiring alkaline development contains an alkali-soluble Binder and an infrared absorbing compound, the Infrared light in heat transforms. The light in heat converting compound is usually an organic dye, often a cyanine dye that acts as a dissolution inhibitor on the binder acts, i. the durability the coating increases against the alkaline developer and thereby reduces the sensitivity of the coating. As a consequence, that for the pictorial exposure a higher one Light output or longer Exposure time is required. In WO 97/39894 and EP-A 823327 are examples for such inhibitor dyes described.

EP-A 978 376 discloses that cyanine infrared-absorbing dyes having a betaine structure do not reduce the solubility of the coating in the developer. However, these dyes are sparingly soluble in an alkaline developer and often cause dye stain in non-imaging the pressure plate.

SHORT PRESENTATION THE PRESENT INVENTION

task The present invention is to provide a heat-sensitive lithographic printing plate precursor, with a high sensitivity across from Infrared light comes up and after exposure and development no Has dye stain in the non-image areas. Is solved This object is achieved by the material defined in claim 1. preferred embodiments are in the subclaims described.

The Cyanine dyes defined in claim 1 contain a bridged methine chain and three, four or five solubilizing groups. Dyes with less than three solubilizing Groups do not give the combined benefits of high sensitivity and low dye staining, while dyes with more than five solubilizing Groups have the tendency, by crystallization from the coating solution or while the drying step to precipitate out of the applied layer.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The heat-sensitive according to the invention lithographic printing plate precursor contains a hydrophilic support and a coating with one over it potted oleophilic coating. Except the oleophilic layer The coating can still with one or more additional Layers, examples of which are described below be provided.

in der

• – m und n unabhängig voneinander jeweils eine ganze Zahl zwischen 0 und 4 bedeuten,
• – Z¹ und Z² unabhängig voneinander jeweils ein oder zwei gegebenenfalls substituierte, zum Vervollständigen eines 5- oder 6-gliedrigen heterocyclischen Ringes benötigte Nichtmetallatome bedeuten,
• – Z³ zwei oder drei gegebenenfalls substituierte, zum Vervollständigen eines 5-gliedrigen oder 6-gliedrigen heterocyclischen oder carbocyclischen Ringes benötigte Nichtmetallatome bedeutet,
• – R¹, R², R⁴ und R⁵ unabhängig voneinander jeweils eine gegebenenfalls substituierte Alkylgruppe, Alkenylgruppe, Arylgruppe oder Aralkylgruppe oder eine Gruppe aus der Reihe bestehend aus -G¹, -L¹-G¹, -CN, einem Halogenatom, -NO₂, -OR_a, -CO-R_a, -CO-O-R_a, -O-CO-R_d, -CO-NR_dR_e, -NR_dR_e, -NR_d-CO-R_e, -NR_d-CO-O-R_a, -NR_d-CO-NR_eR_f, -SR_d, -SO-R_a, -SO₂-R_a, -SO₂-O-R_a und -SO₂-NR_aR_b bedeuten oder zwei angrenzende R⁴- und R⁵-Gruppen zusammen einen gegebenenfalls substituierten 5-gliedrigen oder 6-gliedrigen Ring bilden,
• – R³ ein Wasserstoffatom oder ein Halogenatom, eine -L²-G²-Gruppe, eine Alkylgruppe, eine Alkenylgruppe, eine Aralkylgruppe, eine Arylgruppe, eine Thioalkylgruppe oder eine Thioarylgruppe bedeutet, wobei all diese Gruppen gegebenenfalls substituiert sind, wobei
• – L¹ und L² eine zweiwertige Verbindungsgruppe, z.B. eine Arylengruppe oder eine Alkylengruppe, bedeuten,
• – R_a, R_b und R_c eine gegebenenfalls substituierte Alkylgruppe, Alkenylgruppe, Arylgruppe oder Aralkylgruppe bedeuten und
• – R_d, R_e und R_f ein Wasserstoffatom oder eine gegebenenfalls substituierte Alkylgruppe, Alkenylgruppe, Arylgruppe oder Aralkylgruppe bedeuten.

The coating contains in the oleophilic layer and / or in any of the additional layers an infrared-absorbing compound of the following formula I:

in the

• Each of m and n independently represents an integer between 0 and 4,
• Z ¹ and Z ² are each independently one or two unsubstituted or substituted non-metal atoms necessary to complete a 5- or 6-membered heterocyclic ring,
• Z ^{3 represents} two or three non-metal atoms which are optionally substituted and required to complete a 5-membered or 6-membered heterocyclic or carbocyclic ring,
• R ¹ , R ² , R ⁴ and R ⁵ independently of one another each represent an optionally substituted alkyl group, alkenyl group, aryl group or aralkyl group or a group consisting of -G ¹ , -L ¹ -G ¹ , -CN, a halogen atom, -NO ₂ , -OR _a , -CO-R _a , -CO-OR _a , -O-CO-R _d , -CO-NR _d R _e , -NR _d R _e , -NR _d -CO-R _e , -NR _d -CO-OR _a , -NR _d -CO-NR _e R _f , -SR _d , -SO-R _a , -SO ₂ -R _a , -SO ₂ -OR _a and -SO ₂ -NR _a R _b or two adjacent R ⁴ and R ⁵ groups together form an optionally substituted 5-membered or 6-membered ring,
• R ^{3 represents} a hydrogen atom or a halogen atom, a -L ² -G ² group, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, a thioalkyl group or a thioaryl group, all of which groups are optionally substituted, wherein
• L ¹ and L ² denote a divalent linking group, for example an arylene group or an alkylene group,
• R _a , R _b and R _{c represent} an optionally substituted alkyl group, alkenyl group, aryl group or aralkyl group and
• R _d , R _e and R _{f represent} a hydrogen atom or an optionally substituted alkyl group, alkenyl group, aryl group or aralkyl group.

In the above formula, G ¹ and G ^{2 are} solubilizing groups, ie groups which are anionic or anionic in an aqueous alkaline solution having a pH of at least 9, preferably at least 12. The total number of solubilizing groups G ¹ and G ² is three, four or five. Suitable examples of such solubilizing groups are -COOH, -OH, -PO ₃ H ₂ , -O-PO ₃ H ₂ , -SO ₃ H, -O-SO ₃ H, -SO ₂ -NH ₂ , -SO ₂ -NH-R, -SO ₂ -NH-CO-R or the salts of these groups, for example alkali metal salts or alkaline earth metal salts or mono-, di- or trialkylammonium salts, where R is an optionally substituted alkyl group, Alkenyl group, aryl group or aralkyl group. Very particularly preferred embodiments are -COOH, -SO ₃ H and -OH. The ratio of the IR-absorbing compound in the coating is generally between 0.25 and 10.0 wt .-%, particularly preferably between 0.5 and 7.5 wt .-%, based on the total weight of all non-volatile Components of the coating.

suitable Subclasses of the above dyes are as follows formulas:

In the above formulas II-XVIII, m, n, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , Z ¹ , Z ² and Z ^{3 have} the same meaning as in the above formula I. The integer o has a value between 0 and 5. R ¹⁰ means a group as defined for R ⁴ and R ⁵ .

• – R³ zumindest eine solubilisierende Gruppe enthält oder
• – R¹, R², R³, R⁴ und R⁵ jeweils eine solubilisierende Gruppe enthalten, oder
• – der Farbstoff drei solubilisierende Gruppen, von denen eine in R¹, R² und R³ enthalten ist, enthält,
• – der Farbstoff drei solubilisierende Gruppen, von denen eine in R³, R⁴ und R⁵ enthalten ist, enthält, oder
• – der Farbstoff vier solubilisierende Gruppen, von denen eine in R¹, R², R⁴ und R⁵ enthalten ist, enthält.

Additional preferred subclasses of the dyes of our invention correspond to the embodiments of any of the above Formulas I to XVIII, wherein

• R ^{3 contains} at least one solubilizing group or
• - R ¹ , R ² , R ³ , R ⁴ and R ⁵ each contain a solubilizing group, or
• The dye contains three solubilizing groups, one of which is contained in R ¹ , R ² and R ³ ,
• - The dye contains three solubilizing groups, one of which is contained in R ³ , R ⁴ and R ⁵ , or
• - The dye contains four solubilizing groups, one of which is contained in R ¹ , R ² , R ⁴ and R ⁵ .

in der m, n, R¹, R², R³, Z¹, Z² und Z³ die diesen Symbolen in der obigen Formel I zugemessene Bedeutung haben, p und q unabhängig voneinander 0, 1 oder 2 bedeuten und R⁶ bis R⁹ unabhängig voneinander jeweils eine wie oben für R¹ und R² definierte Gruppe bedeuten. Die obigen zwei Konfigurationen anellierter Benzolgruppen sind Derivate der obigen Formel I. Ähnliche Derivate können aus den Formeln II bis XVIII hergestellt werden und solche Subklassen fallen ebenfalls innerhalb des Schutzbereichs der vorliegenden Erfindung.Other suitable subclasses correspond to formulas in which two adjacent R ⁴ and / or R ⁵ groups together form an optionally substituted benzene group. All of the above formulas I to XVIII, in which such a fused benzene group is contained, are therefore likewise dyes which are suitable for use as precursors according to the invention. Two preferred embodiments of such dyes correspond to the formulas XIX and XX

in which m, n, R ¹ , R ² , R ³ , Z ¹ , Z ² and Z ^{3 have} the meaning ascribed to these symbols in formula I above, p and q are independently 0, 1 or 2 and R ⁶ to R ⁹ each independently represent a group as defined above for R ¹ and R ² . The above two configurations of fused benzene groups are derivatives of formula I above. Similar derivatives can be prepared from formulas II to XVIII and such subclasses are also within the scope of the present invention.

When typical examples of the above formulas are the following dyes:

Of the Generation of the lithographic image by the plate precursor according to the invention is a thermally induced difference in solubility of the coating while underlying the development in the developer. The solubility difference between Image areas (i.e., printing, oleophilic areas) and non-image areas (i.e. non-printing, hydrophilic areas) of the lithographic image is characterized by a kinetic rather than a thermodynamic Effect, i. the non-image areas dissolve faster in the developer as the image areas. In a very preferred Embodiment first solve the Non-image areas of the coating completely in the developer, before the resolution Effect on the image areas begins to act. Accordingly, are the image areas by sharp edges and a high color attractiveness characterized. The time difference between the end of the resolution of Non-image areas and the beginning of the dissolution the image area is preferably longer than 10 seconds, more preferably longer than 20 seconds, and most preferably longer than 60 seconds, which means that a further development latitude is obtained. The preliminary stage can be positive or negative working, with the positive working embodiment is preferred.

Of the carrier The lithographic printing plate precursor has a hydrophilic surface or is coated with a hydrophilic surface. The carrier can a sheet-like material such as a plate or a cylindrical one Element like a sleeve-shaped plate be pushed around the printing drum of a printing press can. Preferably, the carrier a metal carrier like an aluminum carrier or a carrier stainless steel. The carrier may also be a laminate made of an aluminum foil and a plastic layer, e.g. a polyester film is constructed.

One Particularly preferred lithographic support is an electrochemical roughened and anodized aluminum support. The roughening and anodizing of aluminum is a process well known to those skilled in the art. The anodized aluminum carrier can be a processing to improve the hydrophilic properties subjected to the support surface become. So can the aluminum carrier for example, by processing the support surface with a sodium silicate solution increased Temperature, e.g. 95 ° C, be silicated. As an alternative, a phosphate processing be made with the alumina surface with optionally further processing an inorganic fluoride-containing phosphate solution becomes. Furthermore, the alumina surface can be treated with a citric acid or citrate rinsed become. This treatment may be 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, the alumina surface may be polyvinylphosphonic acid, polyvinylmethylphosphonic acid, phosphoric acid esters of polyvinyl alcohol, polyvinylsulfonic acid, polyvinylbenzenesulfonic acid, sulfuric acid esters of polyvinyl alcohol and acetals of polyvinyl alcohols obtained by Reaction with a sulfonated aliphatic aldehyde are formed, are processed. Furthermore, it is obvious that one or more of these Aftercare can be undertaken separately or in combination. more accurate 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 US-P 4,458,005.

To a further embodiment can the carrier also a flexible carrier which is coated with a hydrophilic layer, hereinafter referred to as "primer layer" is. The flexible carrier is e.g. Paper, a plastic film, a thin aluminum carrier or a laminate of these materials. Preferred examples of plastic films are a film of polyethylene terephthalate, polyethylene naphthalate, Cellulose acetate, polystyrene, polycarbonate, etc. The plastic film carrier can opaque or translucent be.

The Primer layer is preferably a crosslinked hydrophilic layer, made of a hydrophilic, with a hardener such as formaldehyde, glyoxal, Polyisocyanate or a hydrolyzed tetraalkyl orthosilicate crosslinked Binder is obtained. The latter crosslinking agent becomes special prefers. The strenght the hydrophilic primer layer can vary between 0.2 and 25 μm and is preferably between 1 and 10 microns. The hydrophilic binder for use in the primer layer is e.g. a hydrophilic (co) polymer such as homopolymers and copolymers of vinyl alcohol, acrylamide, methylolacrylamide, Methylolmethacrylamide, acrylic acid, methacrylic acid, Hydroxyethyl acrylate, hydroxyethyl methacrylate or maleic anhydride vinylmethyl ether copolymers. The hydrophilicity of the used (co) polymer or (co) polymer mixture is preferably higher or equal to the hydrophilicity of at least 60% by weight, preferably to 80% by weight hydrolyzed polyvinyl acetate. The amount hardener, in particular Tetraalkylorthosilicate, is preferably at least 0.2 parts by weight per part by weight of hydrophilic Binder, more preferably between 0.5 and 5 parts by weight, most preferably between 1 part by weight and 3 parts by weight per part by weight of hydrophilic binder.

The hydrophilic primer layer can also be substances containing the mechanical Strength and porosity improve the layer. For this purpose can be colloidal silica to be used. The colloidal silica can be in the form of any commercial Water dispersion of colloidal silica with for example one average particle size up to 40 nm, e.g. 20 nm, to be used. In addition, inert particles with a larger grain size than that colloidal silica be added, e.g. silica, as described in J. Colloid and Interface Sci., Vol. 26, 1968, p 62 to 69, by Stöber described, or toner particles or particles with a mean diameter of at least 100 nm, which is are particles of titanium dioxide or other heavy metal oxides. By embedding these particles, the surface of the hydrophilic primer layer with a uniform rough texture microscopic peaks and valleys, as storage for Serving water in background areas.

Special examples for suitable hydrophilic primer layers for use in the present invention are disclosed in EP-A 601 240, GB-P 1 419 512, FR-P 2 300 354, U.S. Patent Nos. 3,971,660 and 4,284,705.

The oleophilic layer contains a polymer which is soluble in aqueous-alkaline developers. Any organic polymeric binder can be used in the present invention. The organic polymeric binder is preferably a binder having acid groups whose pKa is less than 13. This ensures that the layer is soluble or at least swellable in aqueous-alkaline developers. Conveniently, the binder is a polymer or polycondensate, for example a polyester, polyamide, polyurethane or polyurea. Also particularly suitable are polycondensates and poly merisate with free phenolic hydroxyl groups, as obtained for example by reacting phenol, resorcinol, a cresol, a xylenol or a trimethylphenol with aldehydes, in particular formaldehyde, or ketones. Also suitable are condensation products of sulfamoyl or carbamoyl-substituted aromatics and aldehydes or ketones. Polymers of bismethylol-substituted ureas, vinyl ethers, vinyl alcohols, vinyl acetals or vinyl amides and polymers of phenyl acrylates and copolymers of Hydroxyphenylmaleimiden are also suitable. Furthermore, polymers having vinyl aromatic units, N-aryl (meth) acrylamides or aryl (meth) acrylates may be mentioned, these units each still having one or more carboxyl groups, phenolic hydroxyl groups, sulfamoyl groups or carbamoyl groups. Specific examples are polymers having units of 2-hydroxyphenyl (meth) acrylate, N- (4-hydroxyphenyl) - (meth) acrylamide, N- (4-sulfamoylphenyl) - (meth) acrylamide, N- (4-hydroxy-3, 5-dimethylbenzyl) - (meth) acrylamide, from 4-hydroxystyrene or from hydroxyphenylmaleimide. The polymers may additionally contain units of other monomers which have no acidic units. As such units, vinylaromatics are methyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, methacrylamide or acrylonitrile.

The Binder can be used in any amount. The Amount of binder is suitably between 40 and 99.8% by weight, preferably between 70 and 99.4% by weight, particularly preferably between 80 and 99 wt .-%, each based on the total weight of non-volatile Components of the coating. In a preferred embodiment For example, the polycondensate is a phenolic resin, such as a novolac, a resole or a polyvinylphenol. The novolak is preferably a cresol / formaldehyde novolak or a cresol / xylenol / formaldehyde novolac, the amount of novolac expediently at least 50 wt .-%, preferably at least 80 wt .-%, each based on the total weight of all binders.

The triggering behavior The oleophilic layer in the developer can be regulated by optional solubility Substances are fine tuned. In addition there are development accelerators and development inhibitors in question. These ingredients can be the oleophilic layer and / or one or more other layers be added to the coating.

at Development accelerators are compounds that as dissolution-promoting Substances act, i. are capable of the dissolution rate to increase the oleophilic layer. Exemplary can for Improving the developability in aqueous media of cyclic acid anhydrides, Phenols or organic acids be used. Examples of the cyclic acid anhydride counting phthalic anhydride, tetrahydrophthalic anhydride, 3,6-endoxy-4-tetrahydrophthalic anhydride, tetrachlorophthalic maleic anhydride, Chloromaleic anhydride, α-phenylmaleic anhydride, succinic anhydride and pyromellitic anhydride, as described in US-P 4,115,128. Examples of the phenols counting Bisphenol A, p-nitrophenol, p-ethoxyphenol, 2,4,4-trihydroxy, 2,3,4-trihydroxybenzophenone, 4-hydroxybenzophenone, 4,4 ', 4' '- trihydroxytriphenylmethane and 4,4', 3 '', 4 '' - tetrahydroxy-3,5,3 ', 5'-tetramethyltriphenylmethane and the same. Examples of the organic acids counting sulfonic acids, sulfinic, alkylsulfuric phosphonic, Phosphates and carboxylic acids, as described, for example, in JP-A 60-88,942 and JP-A 2-96,755 Examples of these organic acids counting p-toluenesulfonic acid, dodecylbenzenesulfonic p-toluenesulfinic acid, ethylsulfuric acid, phenylphosphonic acid, phenylphosphinic acid, phenylphosphate, Diphenyl phosphate, benzoic acid, isophthalic acid, adipic acid, p-toluic acid, 3,4-dimethoxybenzoic acid, 3,4,5-trimethoxy, 2,3,4-trimethoxycinnamic, phthalic acid, terephthalic acid, 4-cyclohexene-1,2-dicarboxylic acid, erucic acid, Lauric acid, n-undecanoic and ascorbic acid. The amount of cyclic acid anhydride, Phenol or organic acid in the coating is preferably between 0.05 and 20 wt .-%.

In a preferred embodiment contains the coating also developer resistance agent, also as a development inhibitor denotes, i. one or more ingredients that dissolve the unexposed Areas during to delay development capital. The dissolution-inhibiting Effect is preferably reduced by the heating, so that the resolution the exposed areas is not delayed and thereby a large difference in resolution between exposed and non-exposed areas. Such developer resistance agents can the oleophilic layer or another layer of the material be added.

The compounds described in for example EP-A 823 327 and WO 97/39894 act as dissolution inhibitors as a result of their interaction, eg by formation of a hydrogen bond, with the alkali-soluble binder (s) in the coating. Inhibitors of this type typically contain a hydrogen bonding group such as nitrogen atoms, onium groups, carbonyl groups (-CO- groups), sulfinyl groups (-SO - groups) or sulfonyl (-SO ₂ --Gruppen) and a large hydrophobic moiety such as one or more aromatic nuclei.

Further suitable inhibitors improve the resistance to the developer by delaying the Penetration of the aqueous-alkaline Developer in the oleophilic layer. Such compounds can be found in the oleophilic layer itself as described in e.g. EP-A 950 518, or in a development barrier layer located on the oleophilic layer, as described in e.g. EP-A 864 420, EP-A 950 517, WO 99/21725 and WO 01/45958, be included. In the positive working embodiment contains the barrier layer is preferably a polymeric material that is insoluble in or impenetrable for the developer is, e.g. Acrylic polymers or acrylic copolymers, polystyrene, Styrene-acrylic copolymers, polyesters, polyamides, polyureas, polyurethanes, Nitrocelluloses, epoxy resins and silicones. In this embodiment can the solubility the barrier layer in the developer or the penetrability of the developer into the barrier layer by exposure to heat or exposure to infrared light be reduced.

Preferred examples of inhibitors of the latter type include water-repellent polymers such as a polymer having siloxane and / or perfluoroalkyl units. In a typical embodiment, the precursor contains a barrier layer comprising a water repellent polymer in a suitable amount between 0.5 and 25 mg / m ² , preferably between 0.5 and 15 mg / m ² and most preferably between 0.5 and 10 contains mg / m ² . Depending on the hydrophobic / oleophobic degree of the compound, higher or lower amounts are also suitable. If the water-repellent polymer is also color-repelling, for example when using polysiloxanes, the use of amounts above 25 mg / m ² can lead to a weak color attraction of the unexposed areas. On the other hand, an amount less than 0.5 mg / m ^{2 may} result in unsatisfactory developer resistance. The polysiloxane may be a linear, cyclic or complex crosslinked polymer or copolymer. The term "polysiloxane compound" includes any compound containing more than one siloxane group -Si (R, R ') - O- in which R and R' represent an optionally substituted alkyl or aryl group Preferred siloxanes are phenylalkylsiloxanes and dialkylsiloxanes. The number of siloxane groups in the (co) polymer is at least 2, preferably at least 10, more preferably at least 20. It can be below 100, preferably below 60. In another embodiment, the water-repellent polymer is a block copolymer or graft copolymer of a poly (alkylene oxide) and A suitable copolymer contains about 15 to 25 siloxane units and 50 to 70 alkylene oxide units Preferred examples include copolymers with phenylmethylsiloxane and / or dimethylsiloxane and ethylene oxide and / or propylene oxide such as Tego Glide 410, Tego Wet 265, Tego Protect 5001 or Silikophen P50 / X, all by Tego Chemie, Essen, Deu Germany, be distributed. As a result of its bifunctional structure, such a copolymer acts as a surfactant during coating, thereby automatically positioning itself at the interface between the coating and the air, forming a separate topcoat, even when applied as part of the coating solution of the oleophilic coating. At the same time, such surfactants act as spreading agents, which improves the coating quality. The water repellent polymer may also be applied to the oleophilic layer from a second solution. In this embodiment, it may be advantageous to use in the second casting solution a solvent that is incapable of dissolving the ingredients contained in the first layer, thereby providing a highly concentrated water-repellent phase on the material.

Optional Furthermore, a protective layer can be attached to the surface of the Protect coating especially against mechanical damage. The protective layer contains in the Usually at least one water-soluble polymeric binder, such as polyvinyl alcohol, polyvinylpyrrolidone, partially hydrolyzed polyvinyl acetates, gelatin, carbohydrates or hydroxyethyl cellulose, and may be any known Technique can be made, such as from an aqueous solution or dispersion, if necessary small amounts of organic solvents contains i.e. less than 5% by weight, based on the total weight of the protective layer used coating solvents. The strenght the protective layer can correspond to any value, is expediently to 5.0 μm and is preferably between 0.1 and 3.0 microns, more preferably between 0.15 and 1.0 μm.

Optionally, the coating and in particular the oleophilic layer may further contain additional ingredients. Examples of preferred ingredients for improving the print run resistance and chemical resistance of the plate are additional binders, in particular sulfonamide-containing and phthalimide-containing polymers. Examples of such polymers are those described in EP-A 933 682, EP-A 894 622 and WO 99/63407. It is also possible to add colorants, such as dyes or pigments, which give the coating a visible color and remain in the unexposed areas of the coating and, after exposure and development, allow the formation of a visible image. Typical examples of such contrasting dyes are the amino-substituted tri- or diarylmethane dyes, eg, Crystal Violet, Methyl Vi olet, Victoria Pure Blue, Flexo Blue 630, Basonyl Blue 640, Auramine and Malachite Green. Other well known ingredients of lithographic coatings suitable for use in the printing plate precursor of the present invention are surfactants, particularly perfluorosurfactants, particles of silicon or titanium dioxide, polymer particles such as matting agents, and spacers.

to Production of the lithographic printing plate precursor may be any known technique are applied. By way of example, the above ingredients in a solvent mixture that is not irreversible reacted with the ingredients and preference, on the intended Coating process, the layer thickness, the composition of the Layer as well as the drying conditions is tuned to be solved. To suitable solvents counting Ketones, such as methyl ethyl ketone (butanone), and chlorinated hydrocarbons, such as trichlorethylene or 1,1,1-trichloroethane, alcohols, such as methanol, Ethanol or propanol, ethers, such as tetrahydrofuran, glycol monoalkyl ethers, such as ethylene glycol monoalkyl ethers, e.g. 2-methoxy-1-propanol, or Propylene glycol monoalkyl ethers and esters, such as butyl acetate or propylene glycol monoalkyl ether acetate. It can also be used a mixture, which also special for Purposes solvent such as acetonitrile, dioxane, dimethylacetamide, dimethyl sulfoxide or May contain water.

To the Order one or more casting solutions the hydrophilic surface of the carrier Any coating technique can be used. In the event of a multilayer coating can either separate each layer applied sequentially and dried or can different casting solutions simultaneously be applied. In the drying step, the volatile solvent removed from the coating until a self-supporting and yourself dry feeling Coating is obtained. All the solvent does not have to necessarily during the drying step are removed (sometimes this is even not even possible). In this case, the residual amount of solvent as additional Composition variable considered by the composition can be made more optimal. The drying usually takes place by having hot air, usually at a temperature of at least 70 ° C, preferably 80-150 ° C and especially preferably 90-140 ° C, over the Coating blows. The drying time can usually be between 15 and 600 seconds lie.

The pictorial exposure of the material may be either directly by the application of heat, e.g. by means of a thermal head, or indirectly with infrared light, preferably near infrared light, with the infrared light preferably by means of an infrared light absorbing as described above Connection in heat is converted. The heat-sensitive lithographic invention Printing plate precursor is preferably not sensitive to visible Light, i. an exposure with visible light does not cause any significant effect on the dissolution rate the coating in the developer. Very particularly preferred is the Coating insensitive to Ambient daylight, i. visible light (400-750 nm) and near infrared light (300-400 nm), where the light intensity and the exposure time set under normal working conditions Values, so that the material is not a darkroom for its handling requires. Under "insensitive" to daylight is understood that exposure to ambient daylight no noticeable change the speed of the resolution the coating in the developer causes. In a preferred, across from Daylight resistant embodiment contains the coating does not contain radiation-sensitive components, such as (Quinone) diazide or diazo (nium) compounds, photoacids, photoinitiators, Sensitizers, etc., that in sunlight or office light absorb near infrared light and / or visible light and at the same time the solubility change the coating in the light exposed areas.

The printing plate precursor according to the invention can be exposed by means of, for example, an LED or a laser with infrared light. Very particularly preferred for the exposure is a near infrared light with a wavelength between about 750 and about 1500 nm emitting laser, for example a semiconductor laser diode, a Nd: YAG laser or a Nd: YLF laser. The required laser power depends on the sensitivity of the image recording layer, the pixel dwell time which is determined by the beam width of the laser beam (a typical value at 1 / e ² of maximum intensity of modern plate 10 to 25 microns), the scan 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).

It are two types more common Laser imager, i. an inner drum plate setter (ITD platesetter) and an outer drum plate setter (XTD) plate-. ITD plate-setters for thermal plates usually by very high scanning speeds up to 500 m / s and sometimes need a laser power of several watts. XTD platesetter for thermal plates with a typical laser power between about 200 mW and about 1 W operate at a lower scanning speed between e.g. 0.1 and 10 m / s.

The known platesetters are suitable for use as off-press imagesetters. This option has the advantage of reducing press downtime. XTD platesetter configurations are also suitable for on-press exposure, which has the advantage of immediate registration in a multi-color press. More detailed technical information on on-press platesetter are eg in US 5,174,205 and US 5,163,368 described.

In the development step, the non-image areas of the coating are removed by immersion in a conventional aqueous-alkaline developer, optionally in combination with mechanical wiping, eg by means of a rotary brush. During development, all possible water-soluble protective layers are removed. To avoid damaging the (possible) toner layer of the substrate, preferred are silicate-based developers having a silica to alkali metal oxide ratio of at least 1. Preferred alkali metal oxides include Na ₂ O and K ₂ O and mixtures thereof. In addition to alkali metal silicates, the developer, as well known to those skilled in the art, may further contain other ingredients such as buffering agents, chelating agents, defoaming agents, small amounts of organic solvents, corrosion inhibitors, dyes, surfactants and / or hydrotropes. The development is preferably carried out at a temperature between 20 ° C and 40 ° C in a conventional, known to those skilled in development machines. Suitable solutions for the regeneration are alkali metal silicate solutions having an alkali metal content between 0.6 and 2.0 mol / l. These solutions may have the same silica / alkali metal oxide ratio as the developer (but usually lower) and optionally also contain other ingredients. The required amounts of regenerating material are to be matched to the processing equipment used, the daily plate throughputs, the image areas, etc., and are generally between 1 and 50 ml per square meter of recording material. The addition can be controlled, for example by measuring the conductivity, as described in EP-A 0 556 690.

The Printing plate precursor according to the invention if necessary subsequently, as known to those skilled in the art, with a suitable correction means or preservatives are post-treated. To increase the resistance the finished printing plate and thus to increase the possible Print layer, the layer can be briefly heated to elevated temperatures ( "Burning"). This increases also the resistance the pressure plate opposite Washes, correction agents and UV-curable inks. Such thermal aftertreatment is i.a. in DE-A 14 47 963 and GB-A 1 154 749 described.

Except the The above aftertreatment may be the development of the printing plate precursor also a rinsing step, a drying step and / or a gumming step.

The printing plate thus obtained is suitable for conventional, so-called wet offset printing, in which printing ink and fountain solution are applied to the plate. In another suitable printing method so-called single-fluid printing ink is used without fountain solution. 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 . US 4,981,517 and US 6,140,392 , In a most preferred embodiment, the single-fluid ink contains a paint phase, also referred to as a hydrophobic or oleophilic phase, and a polyol phase as described in WO 00/32705.

EXAMPLES

solubility the infrared dyes

• – der Extinktionskoeffizient der Farbstoffe wird mit einem HP8453 UV/VIS/NIR-Spektralfotometer in Methanol gemessen,
• – es wird eine übergesättigte Lösung der Farbstoffe in a) 2-Methoxy-1-propanol (MOP) und b) Wasser/NaOH (pH = 9) angesetzt. Nach Filtrierung wird das Verhältnis des gelösten Farbstoffes durch Auflösung mit Methanol unter Verwendung des im vorigen Schritt bestimmten Extinktionskoeffizienten bestimmt.
  

Tabelle 1: Löslichkeit der Infrarot-Farbstoffe

• * Triethylamin wird zugesetzt, um den Farbstoff aufzulösen.
• ** unlöslich bei einem pH von 9/NaOH wird zugesetzt, bis ein pH von 11,7 erreicht wird.

The solubility of the infrared dyes IR-1 to IR-5 and a comparative dye Cl (commercially available from FEW Chemicals GmbH) is determined as follows:

• The extinction coefficient of the dyes is measured with an HP8453 UV / VIS / NIR spectrophotometer in methanol,
• - It is a supersaturated solution of the dyes in a) 2-methoxy-1-propanol (MOP) and b) water / NaOH (pH = 9) set. After filtration, the ratio of the dissolved dye is determined by dissolution with methanol using the extinction coefficient determined in the previous step.
  

Table 1: Solubility of the infrared dyes

• * Triethylamine is added to dissolve the dye.
• ** insoluble at a pH of 9 / NaOH is added until a pH of 11.7 is reached.

manufacturing of the carrier

A 0.30 mm thick aluminum foil is degreased by immersing the foil in an aqueous solution containing 5 g / l of sodium hydroxide at 50 ° C and rinsed with demineralized water. The film is then electrochemically grained with AC 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 hydrobromic acid and 5 g / l aluminum ions. to obtain a surface topography with a center-line arithmetic mean Ra of 0.5 μm.

To flush with demineralized water, the aluminum foil with a aqueous, 300 g / l sulfuric acid containing solution 180 s at 60 ° C etched and subsequently 30 s at 25 ° C rinsed with demineralised water.

Subsequently, the film is 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, 3.00 g / m ² Al ₂ O ₃ containing oxidation film, then washed with demineralized water, then first with a solution containing polyvinylphosphine and then with a solution containing aluminum trichloride, then rinsed with demineralized water for 120 s at 20 ° C and dried.

Examination of inhibiting ability the dyes

A novolak layer (Alnovol SPN452 from Clariant, a 40.5% strength by weight solution in methoxypropanol) and the dyes mentioned in Table 2 are applied to the abovementioned support. To 1 minute drying at 130 ° C, the samples contain 0.9 g / m ² novolak. A series of unexposed samples are then immersed in Agfa EP26 developer at 20 ° C with a dipping time varying for each pattern. After completion of the immersion, the pattern is removed from the developer, rinsed immediately with water and dried, after which the degree of dissolution of the coating in the developer is measured by comparing the weight of the sample before and after development. Once the coating has completely dissolved in the developer, no further weight loss is measured with an even longer immersion time, ie from the moment of complete dissolution of the layer, which is referred to in the present invention as "dissolution time", forms in the curve, in If the dissolution time of the pattern containing the infrared dye is longer than the dissolution time of the pattern containing no infrared dye, the infrared dye clearly acts as an inhibitor (inhibitor) Dissolution time of the infrared dye-containing pattern not longer than the dissolution time of the reference pattern, the infrared dye has no inhibitory effect and thus causes no reduction in the solubility of the oleophilic layer in the developer.

Table 2

The Examples 2-6 contain a dye according to the invention and have the same or shorter dissolution times on Reference Example 1 containing no dye. In the case of of Comparative Example 7, a longer dissolution time is observed than in the materials of the invention.

Plate precursor materials

The solutions in Table 3 below are in a wet layer thickness of 22 microns at a speed of 10.8 m / min. and applied at a drying temperature of 135 ° C in a coating line on the above-mentioned carrier. The materials are then exposed at between 90 mJ / cm ² and 220 mJ / cm ² varying energy density settings (exposure intensity on the image plane) with a Creo Trendsetter 3244 (830 nm). Thereafter, the plates at a speed of 0.96 m / min. developed using Agfa DP300 developer at 25 ° C in an Agfa Autolith PN85 processor and finally gummed with Agfa Ozasol RC795. The sensitivity to infrared light of the various compositions corresponds to the minimum energy density adjustment required to achieve a 50% reduction in the light absorption of the coating in areas exposed to 50% area coverage (Q200 lpi) done on the developed plate at the maximum wavelength of the contrast dye.

• * Alvonol SPN452 ist eine 40,5%ige Lösung in Dowanol PM (erhältlich durch Clariant)
• ** 1 gew.-%ige Lösung des folgenden nicht-hemmenden Farbstoffes in Methoxypropanol:
  
• *** Tensid erhältlich durch Tego Chemie, Essen, Deutschland/1 gew.-%ige Lösung in Methoxypropanol.

It can be seen from the results in Table 3 that the non-inhibiting dyes IR-1 to IR-5 give higher sensitivity than the inhibiting infrared dye C1. Table 3

• * Alvonol SPN452 is a 40.5% solution in Dowanol PM (available from Clariant)
• ** 1% strength by weight solution of the following non-inhibiting dye in methoxypropanol:
  
• *** Surfactant available from Tego Chemie, Essen, Germany / 1% by weight solution in methoxypropanol.

Claims (10)

A heat-sensitive lithographic printing plate precursor comprising (i) a support having a hydrophilic surface or a support provided with a hydrophilic surface and (ii) a support coated over the support comprising (a) an oleophilic aqueous alkali-soluble polymer-containing polymer Layer and (b) an infrared absorbing compound of the following formula:

in which m and n are each independently an integer between 0 and 4, Z ¹ and Z ² are each independently one or two unsubstituted or substituted, necessary to complete a 5-membered or 6-membered heterocyclic ring non-metal atoms, Z ^{3 represents} two or three non-metal atoms which are optionally substituted and required to complete a 5-membered or 6-membered heterocyclic or carbocyclic ring; R ¹ , R ² , R ⁴ and R ⁵ are each independently an optionally substituted alkyl group, alkenyl group, aryl group or Aralkyl group or a group consisting of the group consisting of -G ¹ , -L ¹ -G ¹ , -CN, a halogen atom, -NO ₂ , -OR _a , -CO-R _a , -CO-OR _a , -O-CO -R _d , -CO-NR _d R _e , -NR _d R _e , -NR _d -CO-R _e , -NR _d -CO-OR _a , -NR _d -CO-NR _e R _f , -SR _d , -SO-R _a , -SO ₂ -R _a , -SO ₂ -OR _a and -SO ₂ -NR _a R _b or two adjacent R ⁴ and R ⁵ groups together e in which optionally substituted 5-membered or 6-membered ring form, R ^{3 represents} a hydrogen atom or a halogen atom, a -L ² -G ² group, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, a thioalkyl group or a thioaryl group wherein all these groups are optionally substituted, wherein - L ¹ and L ² denote a divalent linking group, - R _a , R _b and R _{c represent} an optionally substituted alkyl group, alkenyl group, aryl group or aralkyl group and - R _d , R _e and R _{f represents} a hydrogen atom or an optionally substituted alkyl group, alkenyl group, aryl group or aralkyl group, characterized in that the infrared-absorbing compound contains solubilizing groups G ¹ and G ² in a total of three, four or five, the solubilizing groups being anionic or in an aqueous-alkaline solution having a pH of at least 9 become anionic. A printing plate precursor according to claim 1, characterized in that R ^{3 contains} at least one of these solubilizing groups. A printing plate precursor according to claim 1, characterized in that R ¹ , R ² , R ³ , R ⁴ and R ⁵ each contain one of these solubilizing groups. A printing plate precursor according to claim 1, characterized in that the infrared absorbing compound contains three solubilizing groups, one of which is contained in R ¹ , R ² and R ³ . A printing plate precursor according to claim 1, characterized in that the infrared absorbing compound contains three solubilizing groups, one of which is contained in R ³ , R ⁴ and R ⁵ . A printing plate precursor according to claim 1, characterized in that the infrared-absorbing compound contains four solubilizing groups, one of which is contained in R ¹ , R ² , R ⁴ and R ⁵ . A printing plate precursor according to any one of the preceding claims, characterized in that Z ¹ and Z ^{2 are} -C (CH ₃ ) ₂ -. A printing plate precursor according to any one of the preceding claims, characterized in that Z ^{3 is} - (CH ₂ ) ₂ - or - (CH ₂ ) ₃ -. A printing plate precursor according to the preceding claims 1 and 6, characterized in that R ^{3 is} -Cl or an optionally substituted -SC ₆ H ₅ group. A printing plate precursor according to any one of the preceding Claims, characterized in that the solubilizing group is a carboxyl group, a sulfo group or a hydroxyl group or a derivative thereof Salt is.