EP0978375B1 - Radiation-sensitive mixture comprising IR-absorbing, anionic cyanine dyes and recording material prepared therewith - Google Patents

Description

The invention relates to a positive-working, radiation-sensitive mixture, which is insoluble in water but soluble in aqueous alkaline solution, organic polymeric binder and an IR absorbing dye or Contains pigment. In addition, it relates to a recording material with a Carrier and a layer of this mixture and a method for producing it lithographic printing plates from the recording material. The Layer has a high sensitivity in the IR range, so that the Recording material for direct thermal imaging after the Computer-to-plate (CTP) process is suitable.

The use of dyes and pigments as IR absorbers in radiation sensitive Mixtures are known from the prior art. So the recording material according to WO 96/20429 includes a layer IR-absorbing carbon black pigments, 1,2-naphthoquinone-2-diazide sulfonic acid ester or carboxylic acid esters and a phenolic resin. The 1,2-naphthoquinone-2-diazide sulfonic acid or carboxylic acid can also directly with the hydroxyl groups Phenolic resin be esterified. The layer is first completely covered with UV rays and then exposed imagewise with IR laser beams. Through the Exposure to IR rays affects certain areas caused by UV radiation solubilized layer again insoluble. So it's about a negative working system. The processing of the material is therefore relative consuming.

A negative working mixture is also described in EP-A 0 784 233, the a) novolak and / or polyvinylphenol, b) amino compounds to Curing component a), c) a cyanine and / or polymethine dye which absorbed in the near IR range, and d) contains photochemical acid generators.

EP-A 903 225 is a light-sensitive preparation known to be a positive or when exposed to infrared rays forms a negative picture, and that from a acid-decomposable compound, an acid-crosslinking compound, an IR absorber and a polymer.

In the unpublished patent application DE 197 39 302 is a positive working, IR-sensitive mixture described that a water-insoluble, in contrast, in aqueous alkali soluble, at least swellable binder and soot particles dispersed therein, the soot particles being used for imagewise differentiation essential radiation sensitive component represent.

WO 97/39894 describes layers that inhibit solutions Additives included. The additives reduce the solubility of the layer in aqueous alkaline Developers in the unexposed areas. With these additives in addition to various pigments, they are especially cationic Compounds, especially dyes and cationic IR absorbers, such as quinoline cyanine dyes, Benzothiazole cyanine dyes or merocyanines. Will this However, layers are heated to 50 to 100 ° C for 5 to 20 s, so they lose Add their inhibitory effect and the layer becomes more soluble in aqueous alkaline Solutions.

The positive working mixture disclosed in EP-A 0 823 327 contains as an IR absorber Cyanine, polymethine, squarylium, croconium, pyrylium or Thiopyrylium dyes. Most of these dyes are cationic and show an inhibitory effect. In addition, many of them contain halogen. Under unfavorable conditions, environmentally harmful decomposition products can result arise. However, some are also revealed as Betainic as well an anionic dye (Compound S-9 on page 7). After layer drying causes this anionic dye due to its high number However, sulfonate groups generally crystallize out or precipitate out Layer components, which leads to significantly poorer properties of the IR-sensitive Shift leads and also causes a lack of layer cosmetics.

The disadvantage of the layer compositions known from the prior art is that the increase in solubility caused by reheating is reached, is reversible after storage at room temperature. Will one Pressure plate not immediately after heating (e.g. heating cabinet) processed, so the development properties change what Reproduction problems when processing the recording materials can lead. In addition, many cationic additives contain halogen, so that under unfavorable conditions environmentally harmful decomposition products can arise.

The object of the invention was a radiation-sensitive mixture and a To provide recording material of the type described in the introduction, the neither diazonium compounds nor thermosetting or acid-curing amino compounds, but also contains no silver halide compounds and besides an imagewise exposure and development no additional work step such as post-heating or post-exposure. Compared to daylight, that's supposed to Recording material to be practically insensitive.

worin

n

2 oder 3 ist,

R¹ bis R⁸

unabhängig voneinander ein Wasserstoff- oder Halogenatom, eine Sulfonat-, Carboxylat-, Phosphonat-, Hydroxy-, (C₁-C₄)Alkoxy-, Nitro-, Amino-, (C₁-C₄)Alkylamino-, Di(C₁-C₄)alkylaminogruppe oder eine (C₆-C₁₀)Arylgruppe, die gegebenenfalls ihrerseits mit einem oder mehreren Halogenatomen und/oder einer oder mehreren Sulfonat-, Carboxylat-, Phosphonat-, Hydroxy-, (C₁-C₄)Alkoxy-, Nitro-, Amino-, (C₁-C₄)Alkylamino- und/oder Di-(C₁-C₄)alkylaminogruppen substituiert ist, darstellen,

R⁹ und R¹⁰

unabhängig voneinander eine geradkettige oder verzweigte (C₁-C₆)Alkyl-, eine (C₇-C₁₆)Aralkyl- oder eine (C₆-C₁₀)Arylgruppe, die jeweils gegebenenfalls ihrerseits mit einem oder mehreren Halogenatomen und/oder einer oder mehreren Sulfonat-, Carboxylat-, Phosphonat-, Hydroxy-, (C₁-C₄)Alkoxy-, Nitro-, Amino-, (C₁-C₄)Alkylamino- und/oder Di(C₁-C₄)alkylaminogruppen substituiert sind, darstellen,

Z¹ und Z²

unabhängig voneinander ein Schwefelatom, eine Di(C₁-C₄)alkylmethylengruppe oder eine Ethen-1,2-diylgruppe darstellen und

X⁺

ein Kation darstellt,

mit der Maßgabe, daß der Farbstoff 2 bis 4 Sulfonat-, Carboxylat- und/oder Phosphonatgruppen, insgesamt jedoch nicht mehr als zwei Sulfonatgruppen enthält.The object is achieved with a positive-working, radiation-sensitive mixture which contains an organic polymeric binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution and at least one IR-absorbing dye which is characterized in that the IR absorbent dye is an anionic cyanine dye of formula I.

wherein

n

Is 2 or 3,

R ¹ to R ⁸

independently of one another a hydrogen or halogen atom, a sulfonate, carboxylate, phosphonate, hydroxy, (C ₁ -C ₄ ) alkoxy, nitro, amino, (C ₁ -C ₄ ) alkylamino, di (C ₁ -C ₄ ) alkylamino group or a (C ₆ -C ₁₀ ) aryl group, which in turn optionally has one or more halogen atoms and / or one or more sulfonate, carboxylate, phosphonate, hydroxy, (C ₁ -C ₄ ) Alkoxy, nitro, amino, (C ₁ -C ₄ ) alkylamino and / or di (C ₁ -C ₄ ) alkylamino groups are substituted,

R ⁹ and R ¹⁰

independently of one another a straight-chain or branched (C ₁ -C ₆ ) alkyl, a (C ₇ -C ₁₆ ) aralkyl or a (C ₆ -C ₁₀ ) aryl group, each of which, in turn, in each case optionally has one or more halogen atoms and / or one or more sulfonate, carboxylate, phosphonate, hydroxy, (C ₁ -C ₄ ) alkoxy, nitro, amino, (C ₁ -C ₄ ) alkylamino and / or di (C ₁ -C ₄ ) alkylamino groups are substituted,

Z ¹ and Z ²

independently represent a sulfur atom, a di (C ₁ -C ₄ ) alkylmethylene group or an ethene-1,2-diyl group and

X ⁺

represents a cation

with the proviso that the dye contains 2 to 4 sulfonate, carboxylate and / or phosphonate groups, but in total not more than two sulfonate groups.

Z ¹ and Z ² are preferably isopropylidene groups, ie groups of the formula -C (CH ₃ ) ₂ -.

Preferred cations are alkali and alkaline earth cations, especially sodium and Potassium ions, as well as ammonium ions or mono-, di-, tri- or tetraalkylammonium ions.

Preferred are dyes with a symmetrical structure, i.e. those in which the (Partially) aromatic radicals in the formula (I) are substituted in the same way. she are also easier to access synthetically. Are therefore particularly cheap Dyes that contain two sulfonate groups. The dyes of the formula (I) surprisingly do not have any solubility-inhibiting effect on the Mixture or a layer made of it.

The (C ₁ -C ₄ ) alkoxy group mentioned is preferably a methoxy or ethoxy group, while the (C ₇ -C ₁₆ ) aralkyl group is preferably a benzyl group. The halogen atoms are generally chlorine, bromine or iodine atoms. In a first preferred embodiment, R ⁹ and R ¹⁰ each represent a group of the formula - [CH ₂ ] _n -SO ₃ -, where n is an integer from 1 to 6. In a further preferred embodiment, one of the groups R ¹ to R ⁴ or R ⁵ to R ⁸ each represents a sulfonate group. In addition to or in place of the sulfonate groups, as already stated, other of the substituents mentioned can also take place, in particular carboxylate or phosphonate groups. If amino, (C ₁ -C ₄ ) alkylamino or di (C ₁ -C ₄ ) alkylamino groups are present in the cyanine dye of the formula I, then their number is at least 2 less than that of the carboxylate, sulfonate and / or phosphonate groups to keep the dye anionic.

The IR-absorbing, anionic cyanine dyes F1 to F4 listed below are particularly suitable in the mixture according to the invention (the cationic cyanine dye F5 was used for comparison purposes and is therefore marked with *).

Surprisingly, it has been shown that the anionic IR-absorbing Cyanine dyes have no solubility-inhibiting effect on the layer, on the contrary, the dissolving or swelling rate in an aqueous alkaline Increase developer.

The proportion of the IR absorbing dye is generally 0.2 to 30 % By weight, preferably 0.5 to 20% by weight, particularly preferably 0.6 to 10% by weight, each based on the total weight of the solids of the mixture. By Combining suitable IR absorbing dyes can not only be narrow IR ranges are used, but the entire wavelength range of the near IR spectrum. To cover the IR range from 700 to 1200 nm, in particular from 800 to 1100 nm, are usually at least two IR-absorbing Dyes required.

The organic, polymeric binder is preferably a binder having acidic groups whose pK _s value of less than. 13 This ensures that the layer is soluble or at least swellable in aqueous alkaline developers. In general, the binder is a polymer or polycondensate, for example a polyester, polyamide, polyurethane or polyurea. Also particularly suitable are polycondensates and polymers with free phenolic hydroxyl groups, such as are obtained, for example, by reacting phenol, resorcinol, a cresol, a xylenol or a trimethylphenol with aldehydes - especially formaldehyde - or ketones. Condensation products of sulfamoyl- or carbamoyl-substituted aromatics and aldehydes or ketones are also suitable. Polymers of bis-methylol-substituted ureas, vinyl ethers, vinyl alcohols, vinyl acetals or vinyl amides as well as polymers of phenyl acrylates and copolymers of hydroxyphenyl-maleimides are also suitable. Polymers with units of vinyl aromatics, N-aryl- (meth) acrylamides or aryl- (meth) acrylates may also be mentioned, where these units may each have one or more carboxy groups, phenolic hydroxyl groups, sulfamoyl or carbamoyl groups. Specific examples are polymers with units made of (2-hydroxyphenyl) - (meth) acrylate, made of N- (4-hydroxyphenyl) - (meth) acrylamide, made of N- (4-sulfamoylphenyl) - (meth) acrylamide, from N- (4-hydroxy-3,5-dimethyl-benzyl) - (meth) acrylamide, from 4-hydroxystyrene or from hydroxyphenyl-maleimide. The polymers can additionally contain units from other monomers which have no acidic units. Such units are vinyl aromatics, methyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, methacrylamide or acrylonitrile. In this context, the term "(meth) acrylate" stands for acrylate and / or methacrylate. The same applies to "(meth) acrylamide".

The proportion of the binder is generally 40 to 99.8% by weight, preferably 70 to 99.4% by weight, particularly preferably 80 to 99% by weight, in each case based on the total weight of the non-volatile components of the mixture.

In a preferred embodiment, the polycondensation product is a Novolak, preferably a cresol / formaldehyde or a cresol / xylenol / formaldehyde novolak, the proportion of novolak preferably being at least 50% by weight is at least 80% by weight, based in each case on the total weight of all Binder.

Finally, the properties of the mixture according to the invention can also through finely divided, non-inhibitory, soluble or dispersible dyes, that practically do not absorb, influence or control in the IR range become. Triarylmethane, azine, oxazine, Thiazine and xanthene dyes. The proportion of additional where necessary Dyes present in a mixture is generally 0.01 to 30% by weight, preferably 0.05 to 10% by weight, in each case based on the total weight of the non-volatile components of the mixture.

In addition to the components mentioned, the mixture can contain other additives do not have a layer-inhibiting effect, e.g. Carbon black pigments as additional IR absorbers, Surfactants (preferably fluorine-containing surfactants or silicone surfactants), Polyalkylene oxides to control the acidity of the acidic units and low molecular weight Compounds with acidic units to increase the rate of development. However, the mixture does not contain any ingredients Exposure to radiation in the ultraviolet or visible range of the Spectrum could have an impact on daylight sensitivity.

Binder and IR-absorbing, anionic cyanine dye are common as a mixture, but can also form separate layers. Through the separate arrangement of binder and IR-absorbing, anionic dyes can often have increased photosensitivity and better stability compared to aqueous alkaline developer solutions. In this In one embodiment, the dye layer is generally over the binder layer. Due to the hardness of the dye layer, the sensitivity is at the same time the surface of the recording material is reduced. The dye layer consists in this embodiment preferably alone or several of the anionic cyanine dyes. The above, only if necessary existing non-IR-sensitive dyes are in the one below lying binder layer.

The present invention furthermore relates to a recording material with a layer support and a positive-working, IR-sensitive layer, which is characterized in that the layer consists of the mixture described. However, the mixture according to the invention can also be used for other purposes, for example as a photoresist. Another object of the invention is a recording material with a support, a layer which consists predominantly or entirely of at least one of the binders mentioned and a layer which consists essentially of at least one of the IR-absorbing, anionic dyes described or a mixture of these dyes Triarylmethane, azine, oxazine, thiazine and / or xanthene dyes (in the order given). The dye layer can also contain matting particles, for example SiO ₂ particles or pigments. Additives to improve uniformity can also be found in minor amounts.

The invention is used to produce the recording material Mixture dissolved in a solvent mixture that with the components of the Mixture does not react irreversibly. The solvent is on the intended Coating process, the layer thickness, the composition of the layer, and to coordinate the drying conditions. Are suitable as solvents generally ketones, such as methyl ethyl ketone (= butanone), chlorinated hydrocarbons, such as trichlorethylene or 1,1,1-trichloroethane, alcohols such as methanol, Ethanol, propanol, ethers, such as tetrahydrofuran, glycol monoethers, such as ethylene glycol monoalkyl ether, Propylene glycol monoalkyl ether and esters such as butyl acetate or propylene glycol monoalkyl ether acetate. Mixtures can also be used which also use solvents such as acetonitrile, dioxane, May contain dimethylacetamide, dimethyl sulfoxide or water. For the production the double layer (binder layer + dye layer) can for the both coating processes the same or different solvents be used.

The support in the recording material according to the invention is preferably an aluminum foil or a composite of an aluminum and a Polyester film. The aluminum surface is preferably roughened, anodized and with a compound having at least one phosphonic acid or phosphonate unit contains, hydrophilized. Before roughening, degreasing and Pickling with bases and mechanical and / or chemical pre-roughening respectively.

A solution of the invention is then placed on this layer support Mixture applied and dried. The thickness of the IR sensitive layer is generally 1.0 to 5.0 µm, preferably 1.5 to 3.0 µm. In the case of the double layer the thickness of the binder layer is generally 1.0 to 5.0 μm, preferably 1.5 to 3.0 µm, while the dye layer compared is significantly thinner and generally a thickness of only 0.01 to 0.3 μm is preferred 0.015 to 0.10 microns.

To protect the surface of the recording material, especially from mechanical action, a top layer can also be applied become. It generally consists of at least one water-soluble polymeric binders such as polyvinyl alcohol, polyvinyl pyrrolidone, partially saponified Polyvinyl acetates, gelatin, carbohydrates or hydroxyethyl cellulose and will prepared from an aqueous solution or dispersion, which if necessary small amounts, i.e. less than 5% by weight based on the total weight the coating solvent for the top layer, on organic solvents may contain. The thickness of the cover layer is up to 5.0 μm, preferably 0.1 to 3.0 µm, particularly preferably 0.15 to 1.0 µm.

Finally, the present invention also relates to a method for Production of a planographic printing form in which the recording material according to the invention irradiated imagewise with infrared radiation and then in a conventional aqueous alkaline developer at a temperature of 20 to 40 ° C is developed. When developing, the water-soluble that may be present Cover layer also removed.

Commonly used developers can be used for the development of positive plates. Silicate-based developers which have a ratio of SiO ₂ to alkali oxide of at least 1 are preferred. This ensures that the aluminum oxide layer of the carrier is not damaged. Preferred alkali oxides are Na ₂ O and K ₂ O, and mixtures thereof. In addition to alkali silicates, the developer can contain further components, such as buffer substances, complexing agents, defoamers, organic solvents in small amounts, corrosion inhibitors, dyes, surfactants and / or hydrotropes.

Development is preferred at temperatures of 20 to 40 ° C in machine Processing plants carried out. Alkali silicate solutions are used for regeneration used with alkali contents from 0.6 to 2.0 mol / l. These solutions can have the same silica / alkali ratio as the developer own (usually it is lower) and also contain other additives. The required amounts of regrind must be based on the used Development devices, daily plate throughputs, image parts etc. coordinated are and are generally 1 to 50 ml per square meter of recording material. The addition can be regulated, for example, via the conductance measurement take place as described in EP-A 0 556 690.

The recording material according to the invention can then, if necessary post-treated with suitable correcting agents or preservatives become.

To increase the resistance of the finished printing form and thus to Increasing the possible print run can temporarily increase the layer Temperatures are warmed ("baking"). This also increases the Resistance of the printing form to washing-out agents, correction agents and UV-curable agents Printing inks. Such a thermal aftertreatment includes in the DE-A 14 47 963 (= GB-A 1 154 749).

The following examples explain the subject matter of the invention in detail. In the examples, Gt stands for part (s) by weight. Percentage and quantity ratios unless otherwise stated, are to be understood in weight units. Comparative compounds or comparative examples are marked with an asterisk (*) marked.

1. Anfertigung der Grundrezeptur;

2. Zugabe der zu untersuchenden Zusätze zu der Grundrezeptur;

3. Aufbringen der aus dieser Rezeptur hergestellten Beschichtungslösungen auf einen geeigneten Träger, so daß nach dem Trocknen eine Schichtdicke von 1,9 +/- 0,1 µm entsteht;

4. Bestimmung der Abtragsrate mittels Küvettenentwicklung in einem Zeitraum von 30 sec bis 6 min;

5. War die Abtragsrate niedriger als bei einer mitvermessenen Grundrezeptur, so besaß der Zusatz eine lösevermittelnde Eigenschaft und entsprach dem erfindungsgemäßen Aufzeichnungsmaterial;

6. Wies der Zusatz eine inhibierende Wirkung auf, so wurde eine Probe bei 50 bis 160°C für 5 bis 20 s nacherwärmt und die Abtragsrate, wie unter Punkt 4. beschrieben, durchgeführt. Dabei wurde ein möglicher Schichtverlust durch die Nacherwärmung berücksichtigt. Blieb die inhibierende Wirkung im Vergleich zur Grundrezeptur erhalten, so entsprach dies ebenfalls dem erfindungsgemäßen Aufzeichnungsmaterial.

First of all, the solution-inhibiting or solution-imparting properties of the IR dyes were determined by determining the layer removal rate before and after imagewise heating in an aqueous alkaline developer as follows:

1. Preparation of the basic recipe;

2. addition of the additives to be examined to the basic formulation;

3. Applying the coating solutions prepared from this recipe to a suitable carrier, so that after drying a layer thickness of 1.9 +/- 0.1 µm arises;

4. Determination of the removal rate by means of cuvette development over a period of 30 seconds to 6 minutes;

5. If the removal rate was lower than in the case of a co-measured basic formulation, the additive had a solubilizing property and corresponded to the recording material according to the invention;

6. If the additive had an inhibiting effect, a sample was reheated at 50 to 160 ° C. for 5 to 20 s and the removal rate was carried out as described under point 4. A possible layer loss due to reheating was taken into account. If the inhibitory effect was retained in comparison to the basic formulation, this also corresponded to the recording material according to the invention.

example 1

A basic recipe consisting of 1a * 4.87 Gt meta- / para- cresol / formaldehyde novolak, 20.00 pbw Ethylene glycol monoalkyl ether / methyl ethyl ketone (6: 4) and 2.00 pbw distilled water, to which one of the following dyes was added: 1b * 0.04 pbw cationic cyanine dye F 5 *, 1c 0.04 pbw anionic cyanine dye F 1, 1d 0.04 pbw anionic cyanine dye F 2, 1e 0.04 pbw anionic cyanine dye F 3, 1f * 0.04 pbw ®Flexoblau 630, a cationic dye from BASF AG,

The coating solutions thus prepared were roughened in hydrochloric acid, anodized in sulfuric acid and hydrophilized with polyvinylphosphonic acid Aluminum foils applied. After drying at 100 ° C. for 2 min Layer thickness at 1.9 +/- 0.1 µm.

Determination of the removal rates without reheating

Development was carried out in a cuvette at a temperature of 23 ° C. using a potassium silicate developer containing K ₂ SiO ₃ (normality 0.8 mol / l in water) and 0.2% by weight of O, O ^' bis-carboxymethyl polyethylene glycol-1000 and 0.4 wt .-% pelargonic acid contained. The development time was 30 to 360 seconds. Küvettenentwicklungszeit
[S] Removal rates without reheating [g / m ² ] 1a * 1b * 1c 1d 1e 1f * 1g 30 0.02 0.01 0.11 0.09 0.10 0.05 0.05 60 0.11 0.05 0.29 0.23 0.23 0.07 0.18 120 0.34 0.23 0.68 0.48 0.51 0.18 0.45 240 0.59 0.43 1.12 0.81 0.91 0.60 0.86 360 0.96 0.61 1.81 1.43 1.85 0.81 1.51

The table shows that in Examples 1b * and 1f * the layer removal in Compared to example 1a * is reduced, i.e. that the cationic cyanine dye F5 * as well as the Flexoblau 630 have a solubility-inhibiting effect on the Exercise shift. The anionic cyanine dyes in the invention Examples 1c, 1d, 1e and 1g, on the other hand, result in increased layer removal by the aqueous alkaline developer.

Determination of the removal rates with reheating

Küvettenentwicklungszeit
[S] Removal rate after 20 s reheating at 50 ° C 1b * 1f * 30 0.05 0.02 60 0.15 0.03 120 0.44 0.18 240 0.85 0.52 360 1.21 0.75

The relatively low post-heating therefore caused practically no change in the removal rates compared to the non-post-heated recording materials. Küvettenentwicklungszeit
[S] Removal rate after 5 s at 160 ° C Removal rate after 20 s at 160 ° C 1b * 1f * 1b * 1f * 30 0.10 0.01 0.10 0.01 60 0.20 0.05 0.19 0.04 120 0.28 0.19 0.36 0.22 240 0.65 0.60 0.98 0.59 360 1.09 0.73 1.46 0.70

Table 1c shows that only Comparative Example 1b *, which is a cationic IR-absorbing dye contains an increase in solubility after reheating experienced in an aqueous alkaline developer. In example 1f * however, the solubility-inhibiting effect is retained.

Example 2

Coating solutions were made from 0.87 pbw meta - / para- cresol / formaldehyde novolak, 0.10 pbw Polyhydroxystyrene (M _w 4,000), 4.50 pbw tetrahydrofuran, 1.80 pbw Ethylene glycol monomethyl ether, 2.70 pbw Methanol and 0.03 pbw of the respective IR absorber (see Table 2). number IR absorbers 2a * Without absorber 2 B* Carbon black pigment type HCC d.Fa. Grolman 2c F1 2d F2 2e F3

The coating solutions were roughened in hydrochloric acid, in sulfuric acid anodized aluminum foils hydrophilized with polyvinylphosphonic acid applied. After drying for 2 min at 100 ° C, the layer thickness was 2 µm.

These recording materials were then in an outer drum imagesetter exposed to infrared radiation. For this purpose, an Nd-YAG laser with a wavelength was used of 1064 nm and a power of 7.0 W, a write speed of 120 revolutions of the drum per min and a beam width of 10 µm used.

Development was carried out in a conventional automatic processor at a throughput speed of 0.8 m / min and a temperature of 23 ° C. using a potassium silicate developer, the K ₂ SiO ₃ (normality 0.8 mol / l in water) and 0.2% by weight. -% O, O'-bis-carboxymethyl-polyethylene glycol-1000 and 0.4 wt .-% pelargonic acid contained.

Table 3 shows the image reproduction of halftone dots of a test wedge. number Play the percentage grid points Rendering of the open grid depths 2a * no stay no stay 2 B* 4 97 2c 3 98 2d 3 99 2e 2 98

The table shows that recording materials without an IR absorber are not developed can be. In the recording material containing the carbon black pigment (Experiment 2b *) the reproduction of the percentage grid points was clear worse, the rendering of the open screen depth was also less good.

Example 3

A coating solution was made from 0.60 pbw meta- / para- cresol / formaldehyde novolak, 0.10 pbw F 2, 6.00 pbw Tetrahydrofuran and 4.00 pbw Ethylene glycol monoalkyl.

The solution was either used as such (Example 3a) or it was 0.20 pbw of an esterification product from 1 mol 2,3,4-trihydroxybenzophenone and 1.5 mol of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride were added (example 3b *).

The coating solutions without or with diazo compound were dissolved in hydrochloric acid roughened, anodized in sulfuric acid and with polyvinylphosphonic acid hydrophilized aluminum foils applied. After drying for 2 min 100 ° C the layer thickness was 2 µm.

The recording materials were then exposed in an outer drum imagesetter exposed to infrared radiation. For this purpose, an Nd-YAG laser with a wavelength was used of 1064 nm and a power of 7.0 W, a write speed of 120 rpm and a beam width of 10 µm (before the IR exposure were the plates 0 minutes, 1 hour, 1 day or 1 week Exposed to daylight).

Development was carried out in a conventional automatic processor at a throughput speed of 0.8 m / min and a temperature of 23 ° C. using a potassium silicate developer, the K ₂ SiO ₃ (normality 0.8 mol / l in water) and 0.2% by weight. -% O, O'-bis-carboxymethyl-polyethylene glycol-1000 and 0.4 wt .-% pelargonic acid contained. Developmental behavior after exposure to daylight number 0 min exposure 1 hour exposure 1 week exposure 3a By default By default By default 3b * By default total shift removal ----

The table shows that the diazo-containing layer is completely developed was removed if daylight had previously been on the Recording material had acted. The recording material according to the invention was, however, insensitive to daylight and could also be still process easily if it is daylight for 1 week (or more) was exposed.

Example 4

This example shows the advantage of IR dyes with and without indicator dyes compared to soot-sensitive recording materials in Regarding mechanical surface attack.

Coating solutions were made from 0.72 pbw meta / para cresol formaldehyde novolak, 0.10 pbw Copolymer of (2-hydroxyphenyl) methacrylate and methyl methacrylate (M _w 4,000), 0.05 pbw 2,4-dihydroxy-benzophenone, 0.02 pbw Flexoblau 630 from BASF (only in layers 4b and 4d), 0.08 pbw F 3 (only in layers 4a and 4b), 0.04 pbw Carbon black pigment type HCC d. Grolman (only in layers 4c * and 4d *).

These solutions were roughened in hydrochloric acid, in sulfuric acid anodized aluminum foils hydrophilized with polyvinylphosphonic acid applied. After drying for 2 minutes at 100 ° C., the layer thickness was 2 μm.

The recording materials were then exposed in an outer drum imagesetter exposed to infrared radiation. This was also the case in the previous Examples used Nd-YAG lasers with a power of 7.0 W, one Writing speed of 120 rpm and a beam width of 10 µm used.

Before development, the recording materials were subjected to a hardness tester pretreated. A rubber wheel with a diameter of about rolled 1 to 2 cm and a width of the tread of about 1 mm above the one to be tested Material. With the help of weights, the contact pressure became as from the table clearly set.

Development was carried out in a conventional automatic processor at a throughput speed of 0.8 m / min and a temperature of 23 ° C. using a potassium silicate developer, the K ₂ SiO ₃ (normality 0.8 mol / l in water) and 0.2% by weight. -% O, O'-bis-carboxymethyl-polyethylene glycol-1000 and 0.4 wt .-% pelargonic acid contained.

Table 5 shows the results after the recording materials were treated with the hardness tester. Depending on the mechanical sensitivity of the coating surface, traces of imprints (referred to in the table as "traces") appear on the material. example Impact on the impeller [N] 0.5 1 2 5 4a - traces traces traces 4b - - - traces 4c * traces traces traces traces 4d * - - traces traces

Recording materials with an additional indicator dye are less sensitive to mechanical influences. The table also shows that IR sensitized Layers are less sensitive to imprints than soot-pigmented ones.

On the IR-sensitive layer of the recording material according to Example 4a then an aqueous solution of a polyvinyl alcohol (K value 4; residual acetyl group content 12%) applied and dried in accordance with EP-A 0 290 916. After drying, the thickness of the cover layer produced in this way was 0.2 μm. When testing this material (Example 4e) in the manner described there were no more traces of imprint.

Example 5

Example 5 shows the influence of IR absorber mixtures on recording materials.

A coating solution was made from 0.85 pbw meta - / para- cresol / formaldehyde novolak, 0.06 pbw Styrene / acrylate copolymer (M _w 6,500; acid number 205), 4.50 pbw tetrahydrofuran, 1.80 pbw Ethylene glycol monomethyl ether and 2.70 pbw Methanol.

Were mixed with this solution 0.04 pbw Dye F 1 (Example 5a) or 0.04 pbw Dye F 1 and 0.04 pbw Carbon black pigment type HCC d. Grolman (Example 5b) or 0.04 pbw Carbon black pigment type HCC from Grolman (Example 5c *).

The respective coating solutions were applied to aluminum foils, which was previously roughened in hydrochloric acid, anodized in sulfuric acid and with Polyvinylphosphonic acid had been hydrophilized. After drying for 2 min 100 ° C the layer thickness was 2 µm.

a) einem Außentrommelbelichter; dabei wurde ein Laser mit einer Wellenlänge von 830 nm und einer Leistung von 5,0 W, einer Schreibgeschwindigkeit von 120 U/min und einer Strahlbreite von 10 µm eingesetzt,

b) einem Innentrommelbelichter; dabei wurde ein Nd-YAG-Laser mit einer Wellenlänge von 1064 nm, einer Leistung von 8,0 W, einer Schreibgeschwindigkeit von 367 m/s und einer Strahlbreite von 10 µm eingesetzt.

The recording materials were then exposed with the following laser systems:

a) an outer drum imagesetter; a laser with a wavelength of 830 nm and a power of 5.0 W, a writing speed of 120 rpm and a beam width of 10 µm was used,

b) an inner drum imagesetter; an Nd-YAG laser with a wavelength of 1064 nm, a power of 8.0 W, a writing speed of 367 m / s and a beam width of 10 µm was used.

Development was carried out in a conventional automatic processor at a throughput speed of 1.0 m / min and a temperature of 23 ° C. using a potassium silicate developer, the K ₂ SiO ₃ (normality 0.8 mol / l in water) and 0.2% by weight. -% O, O'-bis-carboxymethyl-polyethylene glycol-1000 and 0.4 wt .-% pelargonic acid contained. example Development behavior after laser exposure at 830 nm Development behavior after laser exposure at 1064nm 5a just background free not developable 5b Background free Background free 5c * Background free Background free

The table shows that by appropriately mixing IR absorbers Sensitization in the entire range from 830 nm to 1064 nm is possible.

Example 6 :

A coating solution was made from 4.87 Gt meta - / para- cresol / formaldehyde novolak, 20.00 pbw Ethylene glycol monomethyl ether and 2.00 pbw Butanone.

The solution was applied to the support described in Example 5 and dried (2 min; 100 ° C). The layer thickness was then 2 µm.

Solutions of the anionic were then applied to the binder layer thus produced Cyanine dyes F1 (example 6a), F2 (example 6b) and F3 (example 6c) applied in water / isopropanol (1: 1) and dried so that the layer thickness was 0.02 µm each.

Then, as described in the previous example, the mechanical Sensitivity of the surface of the recording material was examined. In none of Examples 6a to 6c showed traces of the impeller.

Claims (16)

1. A positive-working, radiation-sensitive mixture which contains an organic, polymeric binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution and at least one IR-absorbing dye, wherein the IR-absorbing dye is an anionic cyanine dye of the formula (I)

   

   in which

   n

   is 2 or 3,

   R¹ to R⁸

   independently represent a hydrogen or halogen atom, a sulphonate, carboxylate, phosphonate, hydroxyl, (C₁-C₄)alkoxy, nitro, amino, (C₁-C₄)alkylamino or di(C₁-C₄)alkylamino group or a (C₆-C₁₀)aryl group which in turn may be substituted by one or more halogen atoms and/or one or more sulphonate, carboxylate, phosphonate, hydroxyl, (C₁-C₄)alkoxy, nitro, amino, (C₁-C₄)alkylamino and/or di-(C₁-C₄)alkylamino groups,

   R⁹ and R¹⁰

   independently represent a straight-chain or branched (C₁-C₆)alkyl, a (C₇-C₁₆)aralkyl or a (C₁₀-C₁₀)aryl group, each of which in turn may be substituted by one or more halogen atoms and/or one or more sulphonate, carboxylate, phosphonate, hydroxyl, (C₁-C₄)alkoxy, nitro, amino, (C₁-C₄)alkylamino and/or di(C₁-C₄)alkylamino groups,

   Z¹ and Z²

   independently represent a sulphur atom, a di(C₁-C₄)alkylmethylene group or an ethene-1,2-diyl group and

   X⁺

   is a cation,

   with the proviso that the dye contains from 2 to 4 sulphonate, carboxylate and/or phosphonate groups but altogether not more than two sulphonate groups.
2. The radiation-sensitive mixture according to claim 1, wherein the cation is an alkali or alkaline earth cation, preferably a sodium or potassium ion, an ammonium ion or a mono-, di-, tri- or tetraalkylammonium ion.
3. The radiation-sensitive mixture according to claim 1 or 2, wherein the binder contains acidic groups having a pK_s value of less than 13.
4. The radiation-sensitive mixture according to claim 3, wherein the binder is a polycondensate of phenols or sulphamoyl- or carbamoyl-substituted aromatics with aldehydes or ketones, a reaction product of diisocyanates with diols or diamines or a polymer having units of vinylaromatics, N-aryl(meth)acrylamides or aryl (meth)acrylates, these units each furthermore containing one or more carboxyl groups, phenolic hydroxyl groups, sulphamoyl groups or carbamoyl groups.
5. The radiation-sensitive mixture according to claim 3, wherein the polycondensate is a novolak, preferably a cresol/formaldehyde or a cresol/xylenol/formaldehyde novolak, the amount of novolak preferably being at least 50% by weight, particularly preferably at least 80% by weight, based on the total weight of all binders.
6. The radiation-sensitive mixture according to any of claims 1 to 5, wherein the amount of the binder is from 40 to 99.8% by weight, preferably from 70 to 99.4% by weight, particularly preferably from 80 to 99% by weight, based in each case on the total weight of the nonvolatile components of the mixture.
7. The radiation-sensitive mixture according to any of claims 1 to 6, wherein the IR-absorbing dye results in no increase in solubility after a brief post-bake.
8. The radiation-sensitive mixture according to any of claims 1 to 7, wherein the amount of the IR-absorbing anionic cyanine dye is from 0.2 to 30% by weight, preferably from 0.5 to 20% by weight, particularly preferably from 0.6 to 10% by weight, based in each case on the total weight of the dyes of the mixture.
9. The radiation-sensitive mixture according to any of claims 1 to 8, wherein it contains two or more different anionic cyanine dyes of the formula I in order to cover the near IR wavelength range, i.e. the IR range from 700 to 1200 nm, in particular from 800 to 1100 nm.
10. The radiation-sensitive mixture according to any of claims 1 to 9, wherein it additionally contains a carbon black pigment.
11. A recording material having a substrate and a radiation-sensitive layer, wherein the layer comprises a radiation-sensitive mixture according to any of claims 1 to 11.
12. A recording material having a substrate, a layer which essentially comprises an organic, polymeric binder which is insoluble in water but soluble or at least swellable in aqueous alkaline solution, and a dye layer, wherein the dye layer essentially comprises at least one of the anionic cyanine dyes according to claim 1.
13. The recording material as claimed in claim 11 or 12, wherein an overcoat comprising at least one water-soluble polymeric binder is present on the radiation-sensitive layer or on the dye layer, the overcoat having a thickness of up to 5.0 µm, preferably from 0.5 to 3.0 µm.
14. The recording material according to claim 13, wherein the water-soluble polymeric binder is polyvinyl alcohol, polyvinylpyrrolidone, partially hydrolyzed polyvinyl acetate, gelatine, a carbohydrate or hydroxyethylcellulose.
15. The recording material according to any of claims 11 to 13, wherein the substrate comprises an aluminium foil.
16. A process for the preparation of a printing plate, in which a radiation-sensitive recording material according to any of the preceding claims is exposed imagewise to infrared radiation and then developed with an aqueous alkaline solution, wherein the recording material corresponds to one or more of claims 12 to 15.