DE69916773T2 - Heat-sensitive image recording material for producing positive-working planographic printing plates - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The The present invention relates to a process for producing a lithographic Pressure plate suitable heat-sensitive Image forming element with an IR-sensitive cover layer.

The The present invention particularly relates to a heat-sensitive one Image forming element for producing a lithographic printing plate with a higher one resistance the cover layer against mechanical damage.

GENERAL STATE OF THE ART

lithographic Printing is the process by which the printing of specially made Surfaces of which certain areas attract lithographic color and other areas will repel color after wetting with water. The ink attracting areas form the printing image areas, the color repellent Areas the background areas.

in the The field of photolithography becomes a photographic material in the photo-exposed areas (negative working) or in the unexposed areas Areas (positive) on a hydrophilic background imagewise oily or made bold colors attractive.

at the production of usual lithographic printing plates, also as surface litho plates or planographic printing plates, is a carrier that has an affinity to water or has such affinity obtained by a chemical processing, with a thin layer coated with a radiation-sensitive composition. As layers with a radiation-sensitive composition photosensitive polymeric layers, the diazo compounds, dichromate-sensitized hydrophilic colloids and a variety of synthetic Photopolymers included. In particular, diazosensitized layer dressings are widely used.

During the pictorial exposure the photosensitive layer becomes the exposed image areas insoluble and the non-exposed areas remain soluble. The printing plate will subsequently with a suitable liquid developed to contain that in the unexposed areas Diazonium salt or diazo resin to remove.

It are also printing plates known that a photosensitive Layer having the same imagewise exposure soluble in the exposed areas is done. While The subsequent development then becomes the exposed areas away. A typical example of such a photosensitive layer is a quinone diazide-based layer.

The above-described photographic materials used for the production the printing plates are used, one usually exposes in a camera through a photographic film that is in a lithographic Printing method to be reproduced image contains. Such an approach Although it is awkward and labor-intensive, on the other hand, however, await the obtained Printing plates with excellent lithographic quality.

It Since attempts have been made to the use of a photographic film in the above-described method can and in particular a printing plate directly on the basis of the reproducing image embodying To generate computer data. The sensitivity of the photosensitive Layer is not sufficient for a direct laser exposure. Accordingly, it has been proposed to provide the photosensitive layer with a To coat the silver halide layer. The silver halide can then be directly under computer control means be exposed to a laser. Subsequently, the silver halide layer develops and becomes a silver image on the photosensitive layer receive. This silver image then serves as a mask during a all-over Exposure of the photosensitive layer. After the full-surface exposure the silver image is removed and the photosensitive layer is developed. Such a method is described, for example, in JP-A 60-61,752, However, it has the disadvantage that a complex development and associated developing liquids needed become.

GB 1 492 070 discloses a method in which a metal layer or a carbon black-containing layer is applied to a photosensitive layer. This metal layer is then by means of a laser ablated, whereby an image mask is obtained on the photosensitive layer. The photosensitive layer is then subjected to full area ultraviolet exposure through the image mask. After removal of the image mask, the photosensitive layer is developed and a printing plate is obtained. However, this method still involves the disadvantage that the image mask must be removed in a complicated way before the development of the photosensitive layer.

on the other hand There are also methods in which for the production of printing plates Image forming elements are used, which are rather sensitive to heat are sensitive to radiation. With the as described above for Preparation of a printing plate used radiation-sensitive Image forming elements has the particular disadvantage that protected from light Need to become. Furthermore, the sensitivity to storage stability is also problematic and have a lower resolving power. The market is clearly showing a tendency towards heat-sensitive ones From printing plate precursors.

So describes, for example, Research Disclosure No. 33303, January 1992, a heat sensitive Image forming element on a support of a cross-linked hydrophilic Layer with thermoplastic polymeric particles and an infrared light absorbent pigment such. B. contains carbon black. For imagewise exposure with An infrared laser coagulates the thermoplastic polymers Particles imagewise, causing the surface of the imaging element at these areas without further development is made color attractive. As a disadvantage of this method applies the high susceptibility to damage the resulting printing plate, because the non-printing areas can at exercise a slight pressure on these areas become color-attracting. In addition, can the lithographic performance of such a printing plate below critical Conditions will be weak and is such a pressure plate accordingly a limited one have lithographic pressure margin.

The U.S. Patent No. 4,708,925 discloses imaging elements having a radiation-sensitive surface Composition containing an alkali-soluble Novolak resin and an onium salt and optionally an IR sensitizer contains. To imagewise irradiation this imaging element with UV light - visible light - or IR radiation and a subsequent one Development stage with an aqueous-alkaline liquid a positive-working or negative-working printing plate is obtained. The printing results of a by irradiation and development of this Image forming element obtained lithographic printing plate are weak.

The EP-A-625 728 discloses an imaging element having a layer, the opposite UV and IR radiation is sensitive and both positive working as well as being negative working. This layer contains a resole resin, a novolak resin, a latent Bronsted acid and an infrared radiation absorbing substance. The printing results one by irradiation and development of this imaging element obtained lithographic printing plate are weak.

The US-P 5,340,699 is almost identical to EP-A 625 728, however with the difference that they have a procedure for obtaining a negative working, across from Infrared laser light sensitive imaging element disclosed. The IR-sensitive layer contains a resole resin, a novolak resin, a latent Bronsted acid and an infrared ray absorbing substance. The print results of one by irradiation and development of this imaging element obtained lithographic Pressure plate are weak.

In EP-A 678 380 further discloses a method in which a protective layer on a grained metal support underneath a laserablatierbaren surface layer is attached. For imagewise exposure is the surface layer completely ablated together with certain parts of the protective layer. The printing plate is then with a cleaning solution processed to remove the remainder of the protective layer and thereby the hydrophilic surface layer expose.

In EP-A 97 200 588.8 is a heat-sensitive Image-forming element for producing lithographic printing plates discloses that, on a lithographic base having a hydrophilic surface, an intermediate layer, the one in an aqueous alkaline solution soluble Contains polymer, and an IR-sensitive topcoat, wherein the penetrability and / or solubility of the topcoat in an aqueous-alkaline solution increases or decreases on exposure to infrared radiation.

EP-A 97 203 129.8 and EP-A 97 203 132.2 disclose a heat-sensitive imaging element consisting of a lithographic base having a hydrophilic surface and a cover layer, the cover layer being sensitive to infrared radiation, a solution soluble in an aqueous-alkaline solution Contains polymer and is impermeable to an alkaline developer containing silicates as SiO ₂ contains.

The three last-described heat-sensitive However, imaging elements have the disadvantage of high susceptibility to damage the topcoat. These plates are particularly susceptible to surface damage mechanical stress in combination with a vacuum treatment. These Conditions come z. B. in plate transport by suction cups before. As a result of the small contact surface resulting from a vacuum treatment a strong mechanical stress per unit area. A coating the cover layer with a protective layer will both the resolution as reduce the development latitude due to the smaller Difference in the rate of penetration of the developing fluid between exposed and unexposed areas. A solution too this problem would very appreciated become.

TASKS OF PRESENT INVENTION

task It is the object of the present invention to provide a lithographic Pressure plate suitable heat-sensitive To provide imaging element with wide development latitude.

task It is the object of the present invention to provide a lithographic Pressure plate suitable heat-sensitive To provide imaging element with high resolution.

A Another object of the present invention is to provide a heat-sensitive Image forming element for producing a lithographic printing plate with surface layers with improved durability against damage provide.

Further Objects of the present invention will become apparent from the following Description visible.

SHORT PRESENTATION THE PRESENT INVENTION

Be solved the tasks of the invention by a heat sensitive Imaging element for making a lithographic printing plate, that on a lithographic support with a hydrophilic surface a first, one soluble in an aqueous-alkaline solution Polymer-containing layer and on the same side of the lithographic carrier as the first layer contains an IR-sensitive topcoat, the impenetrable and insoluble for one alkaline developer, wherein the first layer and the topcoat can be one and the same layer, characterized in that the image forming layers have a glass transition point of at least 57 ° C exhibit.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The Cover layer is also referred to as the second layer.

Of the Freezing point (Tg) of the image forming layers is at least 57 ° C, preferably at least 59 ° C. The glass transition point of the imaging layers may be over the Drying parameters of the surface layer, in particular, the drying temperature can be adjusted.

In a first embodiment Both the first layer and the top layer are different layers. In this embodiment becomes a heat sensitive Image-forming element for producing lithographic printing plates provided on a lithographic support having a hydrophilic surface a first, one in an aqueous alkaline solution soluble Polymer-containing layer and on the same side of the lithographic carrier like the first layer one opposite IR radiation sensitive topcoat contains, the impenetrable and insoluble for one alkaline developer is.

The Covering layer according to the invention contains an IR dye or an IR pigment, and preferably a binder resin. Although it can use a mixture of IR dyes or IR pigments However, the use of a single IR dye is preferred or IR pigments. Preferred IR dyes are IR cyanine dyes. Particularly useful IR cyanine dyes are cyanine dyes with at least two acid groups, particularly preferably at least two sulfonic acid groups. Especially preferred are cyanine dyes having two indolenine and at least two sulfonic acid groups. Very particular preference is given to compound I of the following structure:

Particularly useful IR absorbing pigments are carbon black, metal carbides, metal borides, metal nitrides, metal carbonitrides, bronze structure oxides, and bronze family related oxides, but without the A component, e.g. B. WO _2.9 . It is also possible to use conductive polymer dispersions, such as conductive polypyrrole or polyaniline-based polymer dispersions. The lithographic performance achieved, and in particular the print run stability, depends on the thermal sensitivity of the imaging member. In this regard, it has been found that very good and favorable results can be achieved with soot.

Of the Proportion of the IR-absorbing dyes or pigments is preferably between 1 and 99 parts by weight, more preferably between 50 and and 95 parts by weight, based on the total amount of IR-sensitive Top layer.

The Cover layer may preferably be a water-insoluble binder Polymer such as a cellulose ester, a copolymer of vinylidene chloride and acrylonitrile, poly (meth) acrylates, polyvinyl chloride, silicone resins, etc. contain. Preferred as a binder is nitrocellulose resin.

The total amount of the topcoat preferably varies between 0.05 and 10 g / m ² , more preferably between 0.1 and 2 g / m ² .

In the cover layer is during the pictorial exposure a difference in penetrability and / or solubility the topcoat in an aqueous-alkaline Solution, in this case in the alkaline according to the invention Developer, causes.

In The present invention provides penetrability and / or solubility while the imagewise IR exposure so elevated, that the imaged parts during the development are removed without the non-imaged parts to solubilize and / or damage.

The Development with the aqueous-alkaline solution preferably takes place within a period between 5 and 120 s.

In the present invention, there is present between the topcoat and the lithographic support a first layer which is soluble in an aqueous alkaline developing solution preferably having a pH of between 7.5 and 14. While this first layer is preferably adhered to the cover layer, other layers may be interposed between the cover layer and the first layer. The alkali-soluble binders used in this layer are preferably hydrophobic binders such as those used in conventional positive or negative working PS plates, e.g. B. Novolakpolymere, hydroxystyrene units containing polymers, carboxyl-substituted polymers, etc. Typical examples of these polymers are described in DE-A 40 07 428, DE-A 40 27 301 and DE-A 44 45 820. The hydrophobic. Used in the present invention Binder is further characterized by insolubility in water and partial solubility / swellability in an alkaline solution and / or by partial solubility in water when combined with a cosolvent.

Further this is in an aqueous alkaline solution soluble Layer preferably one opposite to visible Light and UV light desensitized layer. The layer is preferably thermosetting. These preferably opposite Visible light and UV desensitized layer contains none radiation-sensitive ingredients such as diazo compounds, photo acids, photoinitiators, Quinone diazides, sensitizers, etc., which are in the wavelength range absorb between 250 nm and 650 nm. This way a can across from Daylight insensitive printing plate can be obtained.

The contains first layer preferably also a low molecular acid, preferably a carboxylic acid, especially preferably a benzoic acid, most preferably a 3,4,5-trimethoxybenzoic acid or a benzophenone.

The ratio between the total amount of the low molecular weight acid or the benzophenone and the polymer in the first layer preferably varies between 2:98 and 40:60, more preferably between 5:95 and 20:80. The total amount of the first layer preferably varies between 0, 1 and 10 g / m ² , more preferably between 0.3 and 2 g / m ² .

in the Image-forming element of the present invention may be the lithographic carrier for all embodiments an anodised aluminum support be. A particularly preferred lithographic support is an electrochemically grained and anodised aluminum support. The anodised 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, z. B. 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. Further, the alumina surface may be rinsed with a citric acid or citrate solution. This treatment may be at room temperature or at an easy elevated temperature between about 30 ° C and 50 ° C respectively. Another interesting method is to rinse the aluminum oxide surface with a bicarbonate solution. Furthermore, 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 these post-treatments can be made separately or in combination can. More detailed descriptions of these treatments can be found in GB-A 1 084 070, DE-A 44 23 140, DE-A 44 17 907, EP-A 659 909, EP-A 537 633, DE-A 001 466, EP-A 292 801, EP-A 291 760 and US-P-4 458 005.

To a further embodiment of the present invention the lithographic support with a hydrophilic surface a flexible carrier, such as B. a paper carrier or a plastic film that is cross-linked to all embodiments coated hydrophilic layer is. A particularly suitable crosslinked hydrophilic layer can from a hydrophilic, with a crosslinking agent such as formaldehyde, Glyoxal, polyisocyanate or a hydrolyzed tetraalkyl orthosilicate crosslinked binder can be obtained. The latter crosslinking agent is particularly preferred.

When hydrophilic binders are hydrophilic (co) polymers 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 in question. 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 at least 80% by weight hydrolyzed polyvinyl acetate.

The Amount of crosslinking agent, in particular tetraalkyl orthosilicate, is preferably at least 0.2 parts by weight per part by weight of hydrophilic binder, is preferably between 0.5 and 5 parts by weight, especially preferably between 1.0 part by weight and 3 parts by weight per part by weight hydrophilic binder.

A crosslinked hydrophilic layer in a lithographic support used in this embodiment also preferably contains substances that enhance the mechanical strength and porosity of the layer improve. Colloidal silica may be used for this purpose. The colloidal silica may be in the form of any commercial aqueous dispersion of colloidal silica having, for example, an average particle size of up to 40 nm, e.g. B. 20 nm, are used. In addition, inert particles having a larger grain size than the colloidal silica may be added, e.g. Silica, prepared as described in J. Colloid and Interface Sci., Vol. 26, 1968, pages 62 to 69, by Stober, or particles of toner or particles having an average diameter of at least 100 nm, which are particles of Titanium dioxide or other heavy metal oxides. By embedding these particles, the surface of the cross-linked hydrophilic layer is given a uniform rough texture with microscopic peaks and valleys serving as reservoirs for water in background areas.

The Strength a crosslinked hydrophilic layer in one of this embodiment used lithographic support can be between 0.2 μm and 25 μm vary and is preferably between 1 .mu.m and 10 .mu.m.

Special examples for usable according to the invention suitable crosslinked hydrophilic layers are described in EP-A 601 240, GB-P 1 419 512, FR-P 2 300 354, US-P 3 971 660, US-P 4,284,705 and EP-A 514,490.

When flexible carrier a lithographic support according to this embodiment in particular one prefers a plastic film, z. B. Subbed Polyethylene terephthalate film, a subbed polyethylene naphthalate film, a cellulose acetate film, a polystyrene film, a polycarbonate film etc. The plastic film carrier can be opaque or translucent be.

Particularly preferred is a polyester film support coated with an adhesion-promoting layer. Particularly suitable adhesion-enhancing layers for use according to the invention comprise a hydrophilic binder and colloidal silica, as described in EP-A 619 524, EP-A 620 502 and EP-A 619 525. The amount of silica in the adhesion-promoting layer is preferably between 200 mg / m ² and 750 mg / m ² . Further, the ratio of silica to hydrophilic binder is preferably greater than 1, and the specific surface area of the colloidal silica is preferably at least 300 m ² / g, more preferably at least 500 m ² / g.

In a second embodiment For example, the first layer and the second layer are one and the same layer. In this embodiment becomes a heat sensitive Image-forming element for the production of lithographic printing plates provided on a lithographic support having a hydrophilic surface Contains cover layer, the opposite IR radiation is sensitive, a soluble in an aqueous-alkaline solution Contains polymer and impenetrable and insoluble for one alkaline developer is.

The IR-sensitive layer of the present invention contains a IR dye or an IR pigment and a soluble in an aqueous alkaline solution Polymer. It may be a mixture of IR dyes or IR pigments be used, but it is preferred to use a single IR dye or IR pigments. As suitable IR dyes and IR pigments are those in the first embodiment of the present invention Call mentioned invention.

The IR dyes are preferably in an amount between 1 and 60 Parts by weight, more preferably between 3 and 50 parts by weight, based on the total amount of IR-sensitive topcoat, in the cover layer included.

The Alkali-soluble polymers used in this layer are preferred hydrophobic and color attracting polymers like those in conventional positive or negative working PS plates are used, for. As carboxyl-substituted polymers, etc. Particularly preferred a phenolic resin such as a hydroxystyrene units-containing polymer or a novolac polymer. Very particular preference is given to a novolak polymer. typical examples for These polymers are described in DE-A 40 07 428, DE-A 40 27 301 and DE-A 44 45 820. The hydrophobic. Used in the present invention Polymer is also insoluble in water and at least partial solubility / swellability in one alkaline solution and / or by at least partial solubility in water when combined marked with a cosolvent.

Further, this IR-sensitive layer is preferably a visible-light and UV-light-desensitized layer. The layer is further preferably thermosetting. This preferably visible light and UV desensitised layer contains no radiation-sensitive ingredients such as diazo compounds, photo acids, photoinitiators, quinone diazides, sensitizers, etc. which are in wavelength range between 250 nm and 650 nm. In this way, an insensitive to daylight pressure plate can be obtained.

The Contains IR-sensitive layer preferably also a low molecular acid, preferably a carboxylic acid, especially preferably a benzoic acid, very particularly preferably 3,4,5-trimethoxybenzoic acid, or a benzophenone, especially preferred is trihydroxybenzophenone.

The ratio between the total amount of the low molecular acid or the benzophenone and the polymer in the IR-sensitive layer preferably varies between 2:98 and 40:60, more preferably between 5:95 and 30:70. The total amount of the IR-sensitive layer varies preferably between 0.1 and 10 g / m ² , more preferably between 0.3 and 2 g / m ² .

In The IR-sensitive layer is exposed during imagewise exposure a difference in penetrability and / or solubility the IR-sensitive layer in the alkaline developer according to the invention causes.

to Making a lithographic printing plate becomes the heat-sensitive one Imaging element exposed imagewise and developed.

The Image-wise exposure according to the invention is a pictorial scanning exposure using an infrared (IR) and / or near infrared range, d. H. in the wavelength range between 700 and 1500 nm, emitting laser. Very particularly preferred are near infrared emitting laser diodes. The exposure of the imaging member can be used with both shorter and longer lasers Pixel dwell time are made. Preference is given to using lasers a pixel dwell time between 0.005 μs and 20 μs.

After imagewise development, the heat-sensitive imaging element is developed by rinsing with an aqueous-alkaline solution. As aqueous-alkaline solutions for use in the present invention, those used for developing conventional positive-working presensitized printing plates, preferably containing SiO ₂ as silicates and preferably having a pH between 11.5 and 14 are used. Thus, the imaged portions of the overcoat, whose permeability in the aqueous alkaline solution is increased during exposure, are removed, whereby a positive-working printing plate is obtained.

In The composition of the present invention is also used Developer of the utmost importance.

Out For this reason, in order to achieve development processing that has one long period is stable, qualities such as the strength of the Alkalis and the ratio Of the silicates in the developer particularly important. In such conditions The inventors of the present invention have found that only using the developer of the above composition Fast processing at high temperature is possible, the amount of supplied Refilling solution low is and stable development over a long period of time at least 3 months without replacing the developer can.

The developers and replenishers for the developer used in the present invention are preferably aqueous solutions containing as the main component alkali metal silicates and alkali metal hydroxides of the formula MOH or their oxide of the formula M ₂ O, wherein the developer is SiO ₂ and M ₂ O in a molar ratio between 0.5 and 1.5 and a SiO ₂ ratio between 0.5 and 5 wt .-%. As the alkali metal silicates, for example, sodium silicate, potassium silicate, lithium silicate and sodium metasilicate are preferred. On the other hand, as alkali metal hydroxides, sodium hydroxide, potassium hydroxide and lithium hydroxide are preferred.

The used according to the invention Developers can simultaneously contain other alkaline agents. Examples of such Other alkaline agents include inorganic alkaline agents such as Ammonium hydroxide, tertiary Sodium phosphate, secondary Sodium phosphate, tertiary Potassium phosphate, secondary Potassium phosphate, tertiary Ammonium phosphate, secondary Ammonium phosphate, sodium bicarbonate, sodium carbonate, potassium carbonate and ammonium carbonate, and organic alkaline agents such as mono-, Di- or triethanolamine, mono-, di- or trimethylamine, mono-, di- or Triethylamine, mono- or diisopropylamine, n-butylamine, mono-, di- or triisopropanolamine, ethyleneimine, ethylenediimine and tetramethylammonium hydroxide.

Of major importance in the present invention is the molar ratio [SiO ₂ ] / [M ₂ O] in the developer, which is usually between 0.6 and 1.5, preferably between 0.7 and 1.3. If the molar ratio is less than 0.6, noticeable scattering of the effect is observed, while at a molar ratio of more than 1.5, rapid development is difficult to obtain and the photosensitive layer on the non-image areas is unlikely to be completely peeled off or removed , In addition, the SiO ₂ ratio in the developer and in the replenisher is preferably between 1 and 4% by weight. Such limitation of the SiO ₂ ratio makes it possible to stably obtain lithographic printing plates having good end qualities even when a large amount of printing plates of the invention are processed for a long period of time.

In a particularly preferred embodiment, the developer used is an aqueous solution of an alkali metal silicate with a molar ratio [SiO ₂ ] / [M ₂ O] of between 1.0 and 1.5 and an SiO ₂ ratio of between 1 and 4% by weight. In this case, of course, a replenisher solution must be used whose alkaline strength is greater than or equal to the alkaline strength of the developer used. In order to limit the amount of the replenisher to be supplied, it is preferable that the molar ratio [SiO ₂ ] / [M ₂ O] of the replenisher is less than or equal to the molar ratio [SiO ₂ ] / [M ₂ O] of the developer or the SiO ₂ Ratio is high when the molar ratio of the developer is equal to the molar ratio of the replenisher.

In The developers and replenishers used in the present invention may each be if necessary, organic solvents with a solubility at the same time in water at 20 ° C not more than 10% by weight. Examples of such organic solvents are carboxylic acid esters such as ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzyl acetate, Ethylene glycol monobutyl acetate, butyl lactate and butyl levulinate, ketones such as ethyl butyl ketone, methyl isobutyl ketone and cyclohexanone, alcohols such as ethylene glycol monobutyl ether, ethylene glycol benzyl ether, ethylene glycol monophenyl ether, Benzyl alcohol, methylphenylcarbinol, n-amyl alcohol and methylamyl alcohol, alkyl-substituted aromatic hydrocarbons such as xylene, halogenated Hydrocarbons such as methylene dichloride and monochlorobenzene. These Organic solvents can be used alone or used in combination. In the present invention, benzyl alcohol becomes particularly prefers. These organic solvents Be the developer or the replenisher for the developer in general in a maximum amount of 5% by weight and preferably 4% by weight.

Also, a surfactant can be embedded in the developers and replenishers used in the present invention to improve their development properties. Examples of such surfactants include salts of higher alcohol (C ₈ -C ₂₂ ) sulfuric acid esters such as sodium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, Teepol B-81 (trademark of Shell Chemicals Co., Ltd.) and disodium alkyl sulfates. Salts of phosphoric acid esters with aliphatic alcohol, such as sodium salt of cetyl alcohol phosphate, alkylarylsulfonic acid salts, such as sodium dodecylbenzenesulfonate, sodium salt of isopropylnaphthalenesulfonate, sodium salt of dinaphthalenedisulfonate and sodium salt of metanitrobenzenesulfonate, sulfonic acid salts of alkylamides such as C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ CH ₂ SO ₃ Na and Sulfonic acid salts of dibasic aliphatic acid esters such as sodium dioctylsulfosuccinate and sodium dihexylsulfosuccinate. These surfactants can be used alone or in combination. Particularly preferred are sulfonic acid salts. These surfactants can be used in an amount which is generally not more than 5% by weight, preferably not more than 3% by weight.

to Improvement of the development stability of in the present invention used developers and replenishers can work simultaneously the following compounds are used.

Examples of such compounds are neutral salts such as NaCl, KCl and KBr as described in JN-A 58 75 152, chelating agents such as EDTA and NTA as described in JN-A 58 190 952 (US Pat. No. 4,469,776), complexes such as [Co (NH ₃ ) ₆ ] C ₁₃ , as described in JN-A 59 121 336 (US Pat. No. 4,606,995), ionizable compounds of elements of group IIa, IIIa or IIIb of the Periodic Table, such as those in JN-A 55 25 100 described, anionic or amphoteric surfactants such as sodium alkylnaphthalenesulfonate and N-tetradecyl-N, N-dihydroxythylbetain, as described in JN-A 50 51 324, tetramethyldecyndiol, as described in US-A 4,374,920, nonionic surfactants as described in JN -A 60 213 943 describes cationic polymers such as quaternary methyl chloride products of p-dimethylaminomethyl polystyrene as described in JN-A 55 95 946, the more amphoteric polyelectrolytes such as a copolymer of vinylbenzyltrimethylammonium chloride and sodium acrylate as described in JN-A 56 142 528, inorganic Reduction salts such as sodium sulfite, wi in JN-A 57 192 952 (US Pat. No. 4,467,027), and alkali-soluble mercapto compounds or thioether compounds such as thiosalicylic acid, cysteine and thioglycolic acid, inorganic lithium compounds such as lithium chloride as described in JN-A 58 95 444, organic lithium compounds such as lithium benzoate, as described in JN-A 50 34 442, organometallic surfactants containing Si, Ti or similar substances, as described in JN-A 59 75 255 organoboron compounds, as described in JN-A 59 84 241 (US-A 4,500,625 ), quaternary ammonium salts such as Te traalkylammonium oxides as described in EP-A 101 010, and bactericides such as sodium dehydroacetate as described in JN-A 63 226 657.

in the Inventive development processing method may be any means for supplying a replenisher for developers to be used. examples for Such preferred methods are a method in which a replenisher with time interruptions or continuously as a function of Amount of processed PS plates and time is supplied as described in JN-A-55-115 039 (GB-A-2 046 931), a process in which a sensor is arranged to detect the extent to which the Photosensitive layer in the middle region of a development zone solved and the refill solution is proportional to the proven extent of disentanglement the photosensitive layer is supplied as in JN-A-58-95 349 (US-A 4 537 496), and a method in which the Impedance value of a developer determined and the determined impedance value is processed by a computer to perform the supply of a replenishment solution, such as in GB-A 2 208 249.

The Pressure plate according to the invention can also be in the form of a seamless sleeve-shaped printing plate in one Pressure cycle can be used. In this application, the pressure plate soldered together to form a cylindrical shape by means of a laser. These cylindrical pressure plate whose diameter is equal to the diameter of Print drum is the same, is pushed onto the printing drum, instead by conventional means than in conventional Way prepared printing plate arranged on the printing press to become. More details about sleeve-shaped printing plates can be found in "Graphical Nieuws ", publisher Keesing, 15, 1995, pages 4 to 6.

To Development of a pictorial exposed Image forming element with an aqueous-alkaline solution and Drying can the resulting printing plate without further processing be used as a printing plate. However, the pressure plate can to improve the durability even at a temperature between 200 ° C and 300 ° C over a Period of 30 seconds to 5 minutes are burned. The imaging element can also be a full-surface After exposure to UV radiation, the image is subjected to harden and thus the circulation to increase the pressure plate.

The The present invention will now be apparent from the following examples illustrated but not limited thereto. All Parts and percentages mean parts by weight unless otherwise stated.

EXAMPLE 1

manufacturing of the lithographic 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.

Production of heat-sensitive Image forming element 1

On top of the lithographic support described above, a layer of an 8.6% by weight solution in tetrahydrofuran / methoxypropanol (ratio 55/45) is first cast in a wet layer thickness of 14 μm. The layer thus obtained contains 88% ALNOVOL SPN452 ^™ (marketed by Clariant, Germany) and 12% 3,4,5-trimethoxybenzoic acid and is dried at 120 ° C for 40 s.

On this layer sheds one then in a wet layer thickness of 20 μm the IR-sensitive layer of a 0.272 wt .-% solution in Methyl ethyl ketone / methoxypropanol (ratio 50/50). This layer is dried for at least 42 seconds at a temperature of at least 100 ° C.

The IR-sensitive layer thus obtained contains 35 mg / m ^{2 of} the infrared absorbing dye I, 12.5 mg / m ^{2 of} FLEXO-BLAU 630 ^™ , 2.0 mg / m ^{2 of} TEGO WET 265 and 5.0 mg / m ² TEGO GLIDE 410 ^™ (both are siloxane surfactants from Goldschmitt, Germany).
FLEXO-BLUE 630 is marketed by BASF, Ludwigshafen, Germany.

EXAMPLE 2

It becomes the same carrier as used in Example 1.

It the same coatings are used as in Example 1, but with the difference that the IR-sensitive layer 42 s at 110 ° C is dried.

EXAMPLE 3

It becomes the same carrier as used in Example 1.

It the same coatings are used as in Example 1, but with the difference that the IR-sensitive layer 42 s at 120 ° C is dried.

EXAMPLE 4

It becomes the same carrier as used in Example 1.

It the same coatings are used as in Example 1, but with the difference that the IR-sensitive layer 42 s at 130 ° C is dried.

EXAMPLE 5

It becomes the same carrier as used in Example 1.

It the same coatings are used as in Example 1, but with the difference that the IR-sensitive layer 42 s at 140 ° C is dried.

detection the freezing point

at In these materials, the coating is scraped off the aluminum substrate. The Tg of this material is on a Sciko SSC 5200 DSC device measured. These measurements will increase the heating rate 20 ° C / minute set. The measurements are carried out in a temperature range of -20 ° C to 120 ° C.

detection the susceptibility to damage across from suckers

In an experimental device with original suction cups of a laser exposure the following check is carried out. 12 suckers are put under a vacuum of 85 kPa. After 30 s that will be Vacuum of 3 suction cups canceled. After 60 seconds, the vacuum is lifted by 3 more suction cups. After 2 and 5 minutes, the vacuum of the 3 following suction cups or the last 3 suckers canceled. Subsequently the plate is at a speed of 1 m / min. in a EP26 solution in an NPX development unit developed.

To Drying causes visual damage to the damage caused by the suction cups rated with a numeral.

Then be the 12 digits added.

Exposure of the heat-sensitive Imaging element

All of the above-mentioned materials are imaged with a Creo 3244 ^™ Outer Drum printing plate setter at 2400 dpi and the performances shown in the table below.

Development of the imagewise exposed element

To Exposure of the imaging element becomes the element in a aqueous alkaline developer solution developed. This development occurs at a speed from 1 m / min. and a temperature of 25 ° C in a TECHNIGRAPH NPX-32 processor equipped with OZASOL EP262A (OZASOL EP262A is sold by Agfa) and water in the rinsing zone and OZASOL RC795 rubber is filled in the gum area.

Determination of susceptibility to damage across from suckers

Alles the printing plates are according to the above-described Test procedure checked, about the susceptibility to damage across from suckers to investigate. The lower the value obtained, the lower the susceptibility to damage across from Suction cups.

To the Getting a faultless transport by suction cups is a maximum of 15 acceptable.

Claims (9)

A heat-sensitive imaging element for making a lithographic printing plate comprising on a lithographic support having a hydrophilic surface a first aqueous alkaline solution-soluble polymer-containing layer and on the same side of the lithographic support as the first layer an IR-sensitive cover layer; which is impenetrable and insoluble to an alkaline developer, wherein the first layer and the overcoat layer can be one and the same layer and the first layer and the overcoat layer are the image-forming layers, characterized in that the image-forming layers have a glass transition point of at least 57 ° C. thermosensitive Image forming element for producing a lithographic printing plate according to claim 1, characterized in that the image-forming layers have a glass transition point of at least 59 ° C. thermosensitive Image forming element for producing a lithographic printing plate according to claim 1 or 2, characterized in that in a aqueous alkaline solution soluble Polymer is thermosetting. thermosensitive Image forming element for producing a lithographic printing plate according to claim 3, characterized in that the polymer is a polymer from the group consisting of novolak, polyhydroxystyrene and a carboxyl-substituted polymer. Heat-sensitive imaging element for producing a lithographic printing plate according to one of claims 1 to 4, characterized in that the layer containing the polymer becomes soluble containing compound for the polymer. thermosensitive Image forming element for producing a lithographic printing plate according to claim 5, characterized in that the solubilizing Compound one of the group consisting of low molecular weight acids and benzophenones. thermosensitive Image forming element for producing a lithographic printing plate according to one of the claims 1 to 6, characterized in that the lithographic base with a hydrophilic surface an electrochemically grained and anodized aluminum substrate. thermosensitive Image forming element for producing a lithographic printing plate according to one of the claims 1 to 6, characterized in that the lithographic base with a hydrophilic surface a flexible, a hardened one hydrophilic binder containing carrier. thermosensitive Image forming element for producing a lithographic printing plate. according to one of the claims 1 to 8, characterized in that the imaging element an infrared absorbing dye or an infrared light contains absorbent pigment.