DE10338257B4 - Process for imaging two-layer radiation-sensitive elements - Google Patents

Abstract

A method of imaging a radiation-sensitive element, comprising
(a) providing a radiation-sensitive element comprising
(i) a pretreated or untreated support,
(ii) a first layer applied to the support comprising at least one aqueous solution-soluble or swellable polymeric binder and a radiation-sensitive component selected from IR absorbers or compounds having a diazo group = N ₂ , and
(iii) a cover layer comprising at least one negative-working diazonium resin,
(b) imagewise irradiating the radiation-sensitive element with radiation having a wavelength in the range of 650 to 1300 nm, when the radiation-sensitive component is an IR absorber,
or with radiation of a wavelength in the range of 300 to 450 nm, when the radiation-sensitive component is a compound having a diazo group = N ₂ ,
(c) removing the irradiated areas of the imagewise irradiated element with an aqueous alkaline developer having a pH of 12 to 14.

Description

These The invention relates to a method for imaging radiation-sensitive Elements having two layers, in particular radiation-sensitive positive-working lithographic printing plate precursor with a negative working diazonium resin containing topcoat.

The The field of lithographic printing is based on immiscibility of oil and water, being the oily one Material or ink preferably from the image area and the Water or dampening agent preferably adopted from the non-image area becomes. Is a properly prepared surface moistened with water and then applied a printing ink, the background or the takes Non-image area the water and rejects the ink while the Image area takes the ink and repels the water. The printing ink on the image area is then applied to the surface of a material, such as paper, Tissue and the like, transferred, on which the picture should be created. In general, the But first transfer ink to an intermediate material called a blanket which then transfers the ink to the surface of the material which the image should be created; This is called offset lithography.

A often used type of lithographic printing plate precursor has one on a carrier aluminum-based, photosensitive coating on. The coating can react to radiation by exposing the exposed one Part so soluble will be removed in the development process. Such a plate is called positive working. Conversely, a plate referred to as negative working when the exposed part of the coating cured by the radiation becomes. In both cases The remaining image area absorbs ink or is oleophilic and the non-image area (background) absorbs water or is hydrophilic. The differentiation between image and non-image areas takes place when exposing, with a film on the plate precursor - to ensure a good contact with vacuum - is applied. The plate is then exposed to a radiation source, part of which is UV radiation is composed, exposed. If used a positive plate is, the area corresponding to the image on the plate is on so opaque to the film, light does not attack the plate while the non-image area appropriate area on the film is clear and the light transmission on the coating, which is then more soluble is allowed. In the case of a negative plate, the reverse is true to: The area corresponding to the image area on the film is clear while the non-image area is opaque. The coating under the clear film area is hardened by the action of light, while the removed by light unaffected area during development becomes. The photohardened surface a negative plate is therefore oleophilic and absorbs ink, while the non-image area which is affected by the action of a developer removed coating, desensitized and therefore is hydrophilic.

It are many different compositions for the photosensitive layer of negative-working precursors been described by lithographic printing plates. Besides, they are single and multi-layered plates known. For a long time the use has been of negative-acting diazo resins in the photosensitive layer known; but other systems have been described as well.

US 4,845,009 describes photosensitive negative-working printing plate precursors whose photosensitive layer (1) contains a photocrosslinkable polymer having maleimide groups on the side chains and (2) a diazo resin which is soluble in organic solvents but substantially insoluble in water.

The negative working plates of US 3,808,004 comprise two layers on a support, one layer comprising a photosensitive diazo resin and the other containing a phenoxy cinnamate photopolymer; the order of the two layers does not matter.

In EP 1 143 301 A1 For example, a printing plate precursor comprising two layers on a substrate is described; the lower layer comprises at least one diazo resin and at least one polyurethane resin having an acidic hydrogen atom, and the upper layer comprises a polymer having maleimide groups.

In US 5,476,754 A there are described negative-working printing plate precursors in which a diazo resin having carboxy groups can be present in the photosensitive layer or below in a separate layer; the photosensitive layer contains photocrosslinkable polymers having acid groups and maleimide groups, these functional groups being introduced, for example, by copolymerization of maleimide group-containing monomers with acrylic acid or methacrylic acid. Also in US 5,112,743 A Diazo resins with carboxy groups are used.

JP 06-262872 A discloses a two-layer printing plate precursor with a diazo layer on the support and a non-hardenable photosensitive layer thereon, which is typically a photosensitive diazo resin and a binder resin.

US 6,451,505 B1 describes imageable elements comprising two layers on a support, wherein the lower layer can absorb actinic radiation and comprises a photothermal conversion material and the cover layer is ablatable, comprises no photothermal conversion material and is impermeable to actinic radiation.

Other thermally imageable elements having two layers on a support are shown in FIG US 6,352,811 B1 . US 6,352,812 B1 , WO 01/46318 A1 and WO 02/14071 A1.

In US 6,358,669 B1 thermally imageable elements comprising two layers on a support are disclosed. The lower layer contains a photothermal conversion material and a polymer and is soluble in aqueous alkaline developer. The overcoat is color-accepting and insoluble in aqueous alkaline developer, although the polymer contained therein is soluble with phenolic OH groups in aqueous alkaline developer. While these plates are characterized by excellent sensitivity, they usually require an additional drying step or conditioning immediately after fabrication to improve the overcoat with respect to resistance to high pH developers; this requires large special ovens.

It The object of the present invention is a method for imaging provide radiation-sensitive elements without the need an additional one Drying step and conditioning with high pH developers can be developed without the sensitivity suffers. In addition, should the radiation-sensitive elements a better resistance across from Have pressure room chemicals.

• (a) Bereitstellen eines strahlungsempfindlichen Elements, umfassend
• (i) einen gegebenenfalls vorbehandelten Träger,
• (ii) eine auf den Träger aufgebrachte erste Schicht, umfassend mindestens ein in wässrigen Lösungen lösliches oder quellbares polymeres Bindemittel und eine strahlungsempfindliche Komponente, ausgewählt aus IR-Absorbern der Verbindungen mit einer Diazogruppe =N₂, und
• (iii) eine auf die erste Schicht aufgebrachte Deckschicht, umfassend mindestens ein negativ arbeitendes Diazoniumharz,
• (b) bildweises Bestrahlen des strahlungsempfindlichen Elements mit Strahlung einer Wellenlänge aus dem Bereich von 650 bis 1300 nm, wenn die erste Schicht als strahlungsempfindliche Komponente einen IR-Absorber enthält bzw. mit Strahlung einer Wellenlänge aus dem Bereich von 300 bis 450 nm, wenn die erste Schicht als strahlungsempfindliche Komponente eine Verbindung mit einer Diazogruppe =N₂ enthält,
• (c) Entfernen der bestrahlten Bereiche des bildweise bestrahlten Elements mit einem wässrigen alkalischen Entwickler mit einem pH-Wert von 12 bis 14.

This object is achieved by a method for imaging a radiation-sensitive element, comprising:

• (a) providing a radiation-sensitive element comprising
• (i) an optionally pretreated support,
• (ii) a first layer applied to the support comprising at least one aqueous solution-soluble or swellable polymeric binder and a radiation-sensitive component selected from IR absorbers of the compounds having a diazo group = N ₂ , and
• (iii) a topcoat applied to the first layer, comprising at least one negative-working diazonium resin,
• (b) imagewise irradiating the radiation-sensitive element with radiation having a wavelength in the range from 650 to 1300 nm, when the first layer contains a IR absorber as the radiation-sensitive component or with radiation having a wavelength in the range from 300 to 450 nm, if the first layer contains a compound having a diazo group = N ₂ as the radiation-sensitive component,
• (c) removing the irradiated areas of the imagewise irradiated element with an aqueous alkaline developer having a pH of 12 to 14.

The radiation-sensitive according to the invention Elements can e.g. Printing plate precursor (especially precursor of lithographic printing plates), printed circuit boards for integrated circuits or Be photomasks.

in The preparation of printing plate form precursors is preferred as a carrier a dimensionally stable plate-shaped or foil-shaped Material used. As such a dimensionally stable plate or Film material is preferably used one that has been so far as a carrier for printed matter has been used. Examples of such a carrier include paper, Paper made with plastics (such as polyethylene, polypropylene, polystyrene) coated, a metal plate or foil, e.g. aluminum (including Aluminum alloys), zinc and copper plates, plastic films from, for example, cellulose diacetate, cellulose triacetate, cellulose propionate, Cellulose acetate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, Polyethylene, polystyrene, polypropylene, polycarbonate and polyvinyl acetate, and a laminate of paper or plastic film and one of above-mentioned metals or a paper / plastic film by Vaporizing has been metallized. Among these carriers is an aluminum plate or foil is particularly preferable because it is remarkable dimensionally stable and is cheap and besides shows excellent adhesion of the coating. In addition, can a composite film can be used in which an aluminum foil on a polyethylene terephthalate film is laminated.

One Metal support, in particular an aluminum support, is preferably a surface treatment, for example a roughening by brushing in the dry state, or brushes with abrasive suspensions or by electrochemical means, e.g. a hydrochloric acid electrolyte, and optionally anodic oxidation.

In addition, can to improve the hydrophilic properties of the surface of the roughened and optionally anodized in sulfuric or phosphoric acid metal support this aftertreatment with an aqueous solution of sodium silicate, calcium zirconium fluoride, polyvinyl or phosphoric acid be subjected. In the context of this invention, the term "carrier" also includes an optional one pretreated supports, the e.g. having a hydrophilizing layer on the surface.

The Details of the o.g. Substrate pretreatment are well known to those skilled in the art.

The first layer becomes a solution all components in an organic solvent or solvent mixture (for example, alcohols such as methanol, n- and iso-propanol, n- and iso-butanol; ketones such as methyl ethyl ketone, methyl propyl ketone, cyclohexanone; multifunctional Alcohols and their derivatives, such as ethylene glycol monomethyl ether and monoethyl ether, propylene glycol monomethyl ether and monoethyl ether; Esters such as methyl lactate and ethyl lactate, dixolane and mixtures thereof) applied to the optionally pretreated support and dried. For this purpose, conventional coating methods, such as roller application, knife coating, spin coating, etc., be used.

The dry layer weight of the first layer in lithographic printing plate precursors is preferably 0.5 to 4.0 g / m ² , more preferably 1 to 3 g / m ² .

The essential components of the first layer (that is, the layer applied to the support) are a polymeric binder soluble or swellable in aqueous solutions and a radiation-sensitive component selected from IR absorbers or compounds having a diazo group = N ₂ .

According to one embodiment, one or more compounds having a diazo group = N ₂ are used as the radiation-sensitive component of the first layer. Preferably, the = N ₂ group is conjugated to carbonyl groups, and more preferably the carbonyl group is attached to an aromatic or heteroaromatic ring adjacent to the diazo group.

Particularly preferred compounds having diazo groups = N ₂ are benzoquinone diazides (also short quinone diazides) and naphthoquinone diazides, with the o-isomers being particularly preferred. As used herein, the term "quinone diazide" or "naphthoquinone diazide" is intended to include derivatives thereof. Mixtures of 2 or more compounds with = N ₂ groups can also be used.

When Examples are 1,2-quinone diazides and 1,2-naphthoquinone diazides call, wherein 1,2-naphthoquinonediazides are particularly preferred. Of the 1,2-naphthoquinone diazides 1,2-naphthoquinone-2-diazide-4 and especially -5-sulfonic acid esters or amides preferred. Of these, the esters are 1,2-naphthoquinone-2-diazide-4 or -5-sulfonic acid and 2,5-dihydroxy-benzophenone, 2,3,4-trihydroxybenzophenone, 2,3,4-trihydroxy-4'-methyl-benzophenone, 2,3,4-trihydroxy-4'-methoxy-benzophenone, 2,3,4,4-tetrahydroxy-benzophenone, 2,3,4,2 ', 4'-pentahydroxy-benzophenone, 5,5'-dialkanoyl-2,3,4,2 ', 3', 4'-hexahydroxy-diphenylmethane (especially 5,5'-diacetyl-2,3,4,2 ', 3', 4'-hexahydroxy-diphenylmethane) or 5,5'-dibenzoyl-2,3,4,2 ', 3', 4'-hexahydroxy-diphenylmethane prefers. The proportion of the compounds) with a diazo group is preferably 1 to 50 wt.%, Based on the dry layer weight of the first Layer.

Next The said low molecular weight diazide compounds can also used on polymers such as novolaks, bound (naphtho) quinone diazides be as commonly known to those skilled in the art.

Examples of suitable (naphtho) quinone diazide compounds are, for example, also in EP 1 102 123 A1 and the US patents cited therein, such as US 2,766,118 ; US 3,046,110 ; and US 3,647,443 , to find. In principle, all (naphtho) quinone diazide compounds can be used, which are commonly used in positive-working conventional UV-sensitive coatings.

When the first layer contains one or more compounds having the diazide group = N ₂ as the radiation-sensitive component, an ultraviolet lamp which emits radiation having a wavelength in the range of 300 to 450 nm is used for the image-wise irradiation for imaging, as for conventional UV sensitive imageable elements is used.

According to one preferred embodiment becomes a radiation-sensitive component of the first layer or more IR absorbers used.

Under An IR absorber is a compound in the context of this invention understood that is capable of radiation from the range of 650 nm to 1300 nm to absorb and convert into heat.

Suitable IR absorbing compounds typically have an absorption maximum in the range of 650 nm to 1300 nm of the electromagnetic spectrum. Preferably, the absorption maximum is in the range of 750 to 1120 nm, more preferably in the range of 800 to 1100 nm. Preferably, the IR absorbing compound is selected from triarylamine dyes, thiazolium dyes, indolium dyes, oxazolium dyes, cyanine dyes, polyaniline dyes, polypyrrole dyes, polythiophene dyes, and phthalocyanine pigments; Of these, cyanine dyes are particularly preferred. Such IR-absorbing compounds are, for example, in US 4,327,169 . US 4,756,993 and US 5,156,938 A described.

wobei
jedes Z unabhängig für S, O, NR^a oder C(Alkyl)₂ steht;
jedes R' unabhängig einen Alkylrest, einen Alkylsulfonatrest oder einen Alkylammoniumrest bedeutet;
R'' für ein Halogenatom, SR^a, OR^a, SO₂R^a oder NR^a ₂ steht;
jedes R''' unabhängig für ein Wasserstoffatom, einen Alkylrest, -COOR^a, -OR^a, -SR^a, -NR^a ₂ oder ein Halogenatom steht; R''' kann auch ein benzokondensierter Ring sein;
A^- für ein Anion steht;
R^b und R^c jeweils ein Wasserstoffatom bedeuten oder zusammen einen carbocyclischen Fünf- oder Sechsring bilden;
R^a für ein Wasserstoffatom, einen Alkyl- oder Arylrest steht;
jedes a unabhängig 0, 1, 2 oder 3 ist,
eingesetzt.According to one embodiment, a cyanine dye of the formula (I)

in which
each Z is independently S, O, NR ^a or C (alkyl) ₂ ;
each R 'independently represents an alkyl group, an alkylsulfonate residue or an alkylammonium residue;
R '' is a halogen atom, SR ^a , OR ^a , SO ₂ R ^a or NR ^a ₂ ;
each R '''independently represents a hydrogen atom, an alkyl group, -COOR ^a , -OR ^a , -SR ^a , -NR ^a ₂ or a halogen atom; R '''may also be a benzo-fused ring;
A ^{- stands} for an anion;
R ^b and R ^c each represent a hydrogen atom or together form a carbocyclic five- or six-membered ring;
R ^{a represents} a hydrogen atom, an alkyl or aryl radical;
each a is independently 0, 1, 2 or 3,
used.

When R 'is an alkylsulfonate radical, an internal salt can form so that no anion A ^{- is} necessary. When R 'is an alkylammonium radical, a second counterion which is the same as or different from A ^- is necessary.
Z is preferably a C (alkyl) ₂ group.
R 'is preferably an alkyl radical having 1 to 4 carbon atoms.
R '' is preferably a halogen atom or SR ^a .
R '''is preferably a hydrogen atom.
R ^a is preferably an optionally substituted phenyl radical or an optionally substituted heteroaromatic radical.

R ^b and R ^c preferably together form a carbocyclic five- or six-membered ring. The counterion A ^- is preferably a chloride ion, trifluoromethylsulfonate or a tosylate anion.

Of the IR dyes of the formula (I), those having a symmetrical structure are particularly preferable. Examples of particularly preferred dyes are:
2- [2- [2-phenylsulfonyl-3- [2- (1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene) ethylidene] -1-cyclohexen-1-yl] ethenyl] -1,3,3-trimethyl-3H-indolium,
2- [2- [2-thiophenyl-3- [2- (1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene) ethylidene] -1-cyclohexen-1-yl] ethenyl] -1,3,3-trimethyl-3H-indolium,
2- [2- [2-thiophenyl-3- [2- (1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene) ethylidene] -1-cyclopenten-1-yl] ethenyl] -1,3,3-trimethyl-3H-indolium tosylate,
2- [2- [2-chloro-3- [2- (1,3-dihydro-1,3,3-trimethyl-2H-benzo [e] indol-2-ylidene) ethylidene] -1-cyclohexene -1-yl] -ethe nyl] -1,3,3-trimethyl-1H-benzo [e] indolium tosylate and
2- [2- [2-chloro-3- [2-ethyl- (3H-benzthiazole-2-ylidene) ethylidene] -1-cyclohexen-1-yl] ethenyl] -3-ethyl-benzthiazolium-tosylate.

Further IR absorbers suitable for the present invention are the following compounds:

If the first layer as a radiation-sensitive component an IR absorber contains is this Amount preferably at least 0.1% by weight, based on the dry layer weight the first layer, more preferably at least 1% by weight, more preferably at least 2% by weight. Usually is the amount of IR absorber is not more than 30% by weight, more preferably not more than 25% by weight, and more preferably not more than 20% by weight. There may be a single IR absorber or a mixture of two or more; in the latter case, the quantities refer on the total amount of all IR absorbers.

It is also possible to use polymers bound to IR absorbers, as long as there is a significant absorption in the range of 650 to 1300 nm. Such resins are for example in US 6124425 A and EP 1186955 A2 described.

In the context of this invention, the dry layer weight of the layer obtained with the solid material content of the composition used for the preparation of the layer equated.

Suitable polymeric binders for the first layer are in principle all polymers or polymer mixtures which are known in the field and which are soluble or swellable in aqueous systems. In the context of this invention, "polymer which is soluble or swellable in aqueous solutions" is understood as meaning a polymer or copolymer which is soluble or swellable in aqueous solutions having a pH of 8 to 13. Suitable binders are, for example, in US Pat EP 1 170 123 A2 described. Particularly noteworthy are acrylic acid copolymers, methacrylic acid copolymers, itaconic acid copolymers, crotonic acid copolymers, maleic acid copolymers, partially esterified copolymers of maleic acid, acidic cellulose derivatives and acidic polyvinyl acetals.

When polymeric binder for the first layer can For example, novolak resins are used, that is, condensation products of one or more suitable phenols, e.g. Phenol itself, m-cresol, o-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, resorcinol, pyrogallol, Phenylphenol, diphenols (e.g., bisphenol-A), trisphenol, 1-naphthol and 2-naphthol with one or more suitable aldehydes, such as formaldehyde, Acetaldehyde, propionaldehyde, benzaldehyde and furfuraldehyde and / or Ketones, e.g. Acetone, methyl ethyl ketone and methyl isobutyl ketone. The type of catalyst and the molar ratio of the reactants determined the molecular structure and hence the physical properties of the resin. An aldehyde-phenol ratio of about 0.5: 1 to 1: 1, preferably 0.5: 1 to 0.8: 1 and an acid catalyst are used to prepare those phenolic resins known as "novolacs" and have a thermoplastic character. As used in the application, the expression "in aqueous alkaline developer soluble Novolak ", as well the phenolic resins known as "resols" include those at higher levels Aldehyde phenol ratios and basic catalysts, provided they are in aqueous alkaline Developer soluble or swellable.

suitable Novolaks can are prepared by known methods or are commercially available available. Preferably the molecular weight (weight average determined with GPC using of polystyrene as standard) 1,000 to 15,000, more preferably 1,500 to 10,000.

For the first Layer suitable as binder polyvinylphenol resins are polymers of one or more hydroxystyrenes, such as o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, 2- (o-hydroxyphenyl) propylene, 2- (m-hydroxyphenyl) propylene and 2- (p-hydroxyphenyl) propylene. Such a hydroxystyrene may optionally have one or more further substituents on the phenyl ring, such as. a halogen atom (F, Cl, Br, I). It is important that the polyvinylphenol resin in watery alkaline developer soluble or swellable.

polyvinyl can be prepared by known methods. Usually one or several hydroxystyrenes in the presence of an initiator for a radical or cationic polymerization polymerized.

The Weight average molecular weight of suitable polyvinylphenol resins is preferably in the range of 1,000 to 100,000, more preferred 1,500 to 50,000.

Further, polyacrylates having sulfonamide side groups can be used as the binder for the first layer, for example, those containing structural units of the following formula (IVa) and / or (IVb): - [CH ₂ -CH (CO-X ¹ -R ⁴ -SO ₂ NH-R ⁵ )] - (IVa) - [CH ₂ -CH (CO-X ² -R ^4a -NHSO ₂ -R ^5a )] - (IVb) in which
X ¹ and X ² each represent O or NR ¹⁶ ;
R ⁴ and R ^4a each represents a substituted or unsubstituted alkylene group (preferably C ₁ -C ₁₂₎ represent, Cycloalkandiylrest (preferably C ₆ -C ₁₂₎ arylene group (preferably C ₆ -C ₁₂₎ or Aralkandiylrest (preferably C ₇ -C ₁₄₎ ;
R ⁵ and R ¹⁶ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group (preferably C ₁ -C ₁₂ ); Cycloalkyl (preferably C ₆ -C ₁₂ ), aryl (preferably C ₆ -C ₁₂ ) or aralkyl (preferably C ₇ -C ₁₄ );
R ^5a represents a substituted or unsubstituted alkyl group (preferably C ₁ -C _12), cycloalkyl (preferably C ₆ -C _12), aryl (preferably C ₆ -C ₁₂₎ or aralkyl (preferably C ₇ -C _14).

Such polyacrylates and starting monomers and comonomers for their preparation are described in detail EP 0 544 264 A1 (Pp. 3 to 5).

To the polyacrylates of the formula (IVa) and (IVb) analogous polymethacrylates can also as a binder for the first layer can be used.

wobei
X³ ein substituierter oder unsubstituierter Alkandiylrest (vorzugsweise C₁-C₁₂), Cycloalkandiylrest (vorzugsweise C₆-C₁₂), Arylenrest (vorzugsweise C₆-C₁₂) oder Aralkandiylrest (vorzugsweise C₇-C₁₄) ist, und
X⁴ ein substituierter oder unsubstituierter Arylenrest (vorzugsweise C₆-C₁₂) ist.Also, polyacrylates having pendant sulfonamide groups which additionally contain a urea moiety in the side chains can be used as the binder for the first layer. Such polyacrylates are for example in EP 0 737 896 A2 described and have the following structural unit (IVc)

in which
X ³ is a substituted or unsubstituted alkylene group (preferably C ₁ -C ₁₂₎ Cycloalkandiylrest (preferably C ₆ -C ₁₂₎ arylene group (preferably C ₆ -C ₁₂₎ or Aralkandiylrest (preferably C ₇ -C _14), and
X ^{4 is} a substituted or unsubstituted arylene radical (preferably C ₆ -C ₁₂ ).

To The polyacrylates of the formula (IVc) analogous polymethacrylates can also used according to the invention become.

wobei
X³ und X⁴ wie vorstehend definiert sind.Also in EP 0 737 896 A2 mentioned polyacrylates of the formula (IVd) with urea moiety and phenolic OH can be used here as a binder for the first layer:

in which
X ³ and X ^{4 are} as defined above.

To The polyacrylates of the formula (IVd) analogous polymethacrylates can also used according to the invention become.

The Weight average molecular weight of suitable poly (meth) acrylates with sulfonamide side groups and / or phenolic side groups is preferably 2,000 up to 300,000.

wobei
Y ausgewählt wird aus -(CR⁶R⁷)_k- und -CR⁸=CR⁹- wobei
k eine ganze Zahl von 1 bis 6 ist,
jedes R⁶ und R⁷ unabhängig aus einem Wasserstoffatom und einem C₁-C₆ (vorzugsweise C₁-C₄)-Alkylrest ausgewählt wird (wenn k>1 ist, müssen nicht alle R⁶ gleich sein und genauso müssen nicht alle R⁷ gleich sein), und
R⁸ und R⁹ unabhängig voneinander ausgewählt sind aus einem Wasserstoffatom und einem C₁-C₆ (vorzugsweise C₁-C₄) Alkylrest oder R⁸ und R⁹ zusammen mit den beiden Kohlenstoffatomen, an die sie gebunden sind, einen gegebenenfalls substituierten Aryl- oder Heteroarylrest bilden.Carboxylic acid derivatives of a cellulose polymer suitable as binders for the first layer are, for example, reaction products of a cellulose polymer such as a cellulose alkanoate and a carboxylic acid or especially an acid anhydride, the carboxylic acid or anhydride preferably having the formula (V) or (Va)

in which
Y is selected - (CR ⁶ R ⁷ ) _k - and -CR ⁸ = CR ⁹ - in which
k is an integer from 1 to 6,
each R ⁶ and R ^{7 is} independently selected from a hydrogen atom and a C ₁ -C ₆ (preferably C ₁ -C ₄ ) alkyl radical (when k> 1, not all R ^6's need to be the same, and similarly, not all R ^7's must be the same) be the same), and
R ⁸ and R ^{9 are} independently selected from a hydrogen atom and a C ₁ -C ₆ (preferably C ₁ -C ₄ ) alkyl radical or R ⁸ and R ⁹ together with the two carbon atoms to which they are attached, an optionally substituted aryl or form heteroaryl radical.

wobei R¹⁰ bis R¹⁵ jeweils unabhängig aus einem Wasserstoffatom und einem C₁-C₆-Alkylrest ausgewählt werden.Y is particularly preferred, selected from: -CR ¹⁰ R ¹¹ -CR ¹² R ¹³ -; -CR ¹⁴ = CR ¹⁵

wherein R ¹⁰ to R ^{15 are} each independently selected from a hydrogen atom and a C ₁ -C ₆ alkyl group.

Such carboxylic acid derivatives of a cellulose polymer are, for example, in EP 1 101 607 A1 described in sections [0024] to [0037].

Especially to mention would be here the commercially available Derivatives such as cellulose acetate phthalate (CAP), cellulose acetate hydrogen phthalate (CAHP), cellulose acetate trimellitate (CAT), cellulose acetate propionate and cellulose acetate butyrate.

entspricht, B in einem Mengenanteil von 1 bis 30 mol% vorliegt und der Formel

entspricht, C in einem Mengenanteil von 5 bis 60 mol% vorliegt und der Formel

entspricht, D in einem Mengenanteil von 5 bis 60 mol% vorliegt und der Formel

entspricht, und E in einem Mengenanteil von 1 bis 40 mol% vorliegt und der Formel

entspricht, wobei
X eine aliphatische, aromatische oder araliphatische Spacergruppe bedeutet,
R¹ ein Wasserstoffatom oder ein aliphatischer, aromatischer oder araliphatischer Rest ist,
R², R³ und R Alkylreste mit Kohlenstoffzahlen zwischen 1 und 18 darstellen und
Y¹ eine gesättigte oder ungesättigte ketten- oder ringförmige Spacergruppe ist.Polyvinyl acetals suitable as binders for the first layer are, for example, in DE 195 24 851 A1 described. These are copolymers comprising the units A, B, C, D and E, wherein A is present in a proportion of 10 to 60 mol% and the formula

B is present in a proportion of 1 to 30 mol% and the formula

corresponds to, C is present in a proportion of 5 to 60 mol% and the formula

corresponds to, D is present in a proportion of 5 to 60 mol% and the formula

and E is present in a proportion of from 1 to 40 mol% and of the formula

corresponds, where
X represents an aliphatic, aromatic or araliphatic spacer group,
R ^{1 is} a hydrogen atom or an aliphatic, aromatic or araliphatic radical,
R ² , R ³ and R represent alkyl radicals having carbon numbers between 1 and 18 and
Y ^{1 is} a saturated or unsaturated chain or ring-shaped spacer group.

Other suitable polyvinyl acetals are, for example, in DE 198 47 616 A1 . US 5,700,619 B1 and US 6596460 B1 described.

wobei F in einem Anteil von 5 bis maximal 50 mol% vorliegt und R¹⁷ und R²⁰ so gewählt wird, dass das Homopolymer von F alkalilöslich ist, G in einem Anteil von 20 bis 70 mol% vorliegt und R¹⁸, R²² und R²³ so gewählt wird, dass das Homopolymer von G eine hohe Glasübergangstemperatur (>100°C) aufweist, und H in einem Anteil von 10 bis 50 mol% vorliegt und R¹⁹ und R²¹ so gewählt sind, dass das Homopolymer von H wasserlöslich ist und Einheit F von Einheit H verschieden ist.In addition, the in DE 199 36 331 A1 described copolymers are used as binders in the first layer; these copolymers consist of the units F, G and H.

wherein F is present in a proportion of 5 to a maximum of 50 mol% and R ¹⁷ and R ²⁰ are chosen such that the homopolymer of F is alkali-soluble, G is present in a proportion of 20 to 70 mol% and R ¹⁸ , R ²² and R ²³ is chosen so that the homopolymer of G has a high glass transition temperature (> 100 ° C), and H is present in a proportion of 10 to 50 mol% and R ¹⁹ and R ²¹ are selected so that the homopolymer of H is water-soluble and unit F of unit H is different.

Preferably R ^{17 is} a hydrogen atom, an aryl radical having at least one substituent selected from a hydroxyl and carboxyl group, and optionally also at least one substituent selected from halogen atom, (C ₁ -C ₁₂ ) -alkyl radical and -NO ₂ , an arylsulfonamide radical or a (C ₁ -C ₁₂ ) -alkyl radical having at least one carboxyl group.

R ²⁰ and R ²¹ are independently of each other preferably a hydrogen atom, a halogen atom or a (C ₁ -C ₁₂ ) alkyl radical.

R ¹⁸ is preferably a hydrogen atom, an aryl group optionally having one or more substituents selected from halogen atom, alkyl group, -NO ₂ and -OH, an alkyl group, a cycloalkyl group, an arylsulfonamide group or a sulfonamide group.

R ²² and R ²³ are each independently preferably hydrogen, halogen, (C ₁ -C ₄ ) alkyl or phenyl.

R ¹⁹ is preferably a hydrogen atom, a (C ₁ -C ₁₂ ) -alkyl radical having at least one hydroxy group and optionally also one or more substituents selected from halogen atom and -NO ₂ , a (C ₃ -C ₈ ) -cycloalkyl radical compound having at least one hydroxy group and optionally also one or more substituents selected from halogen atom and -NO ₂ , an aryl group having at least one hydroxy group and optionally one or more substituents selected from halogen atom, (C ₁ -C ₁₂ ) alkyl and -NO ₂ ; a (C ₁ -C ₁₂ ) alkylsulfonamide radical, an arylsulfonamide radical, -NH (CH ₂ ) _t O -alkyl (where t is an integer of 1 to 20), -NHR ²⁴ (wherein R ^{24 is} a hydrogen atom, (C C ₁ -C ₁₂ ) -alkyl or aryl) or a (C ₁ -C ₁₂ ) -alkoxy radical which optionally has at least one hydroxyl group.

enthalten, wobei R²⁵ ein gegebenenfalls substituierter Cycloalkyl- oder Alkylrest ist, x für 0 oder 1 steht und A ein gegebenenfalls substituierter Alkandiylrest ist oder durch die Formel -CHR²⁶CH₂- wiedergegeben wird, wobei R²⁶ ein Wasserstoffatom, Halogenatom, eine Hydroxygruppe oder ein gegebenenfalls substituierter Alkyl-, Alkoxy- oder Phenylrest ist.Other possible binders for the first layer are in US Pat. No. 6,475,698 B1 described. These are polymers containing the unit (VI)

wherein R ^{25 is} an optionally substituted cycloalkyl or alkyl radical, x is 0 or 1 and A is an optionally substituted alkanediyl radical or represented by the formula -CHR ²⁶ CH ₂ -, wherein R ^{26 is} a hydrogen atom, halogen atom, a hydroxy group or an optionally substituted alkyl, alkoxy or phenyl radical.

Preferred binders for the first layer are the copolymers of DE 199 36 331 A1 (That is, the above copolymers with the units F, G and H) and the in US Pat. No. 6,475,698 B1 described polymers having the above-described structural unit (VI).

in the With regard to possible inking problems during the printing process it is preferred that the polymer used has an acid number of <200 mg KOH / g or in the use of polymer mixtures, the arithmetic Means of the individual acid numbers <200 mg KOH / g. An acid number is preferred between 80 and 140 mg KOH / g, more preferably <100 mg KOH / g.

It can but also polymers without acid number be used if by special functional groups, such as e.g. Polyether functions as side chains, sufficient developability in aqueous-alkaline solutions is available.

Of the Proportion of polymeric binder (single polymer or polymer blend) in the first layer is preferably 50 to 98% by weight, particularly preferably 70 to 95% by weight, based on the dry layer weight of the first layer.

In addition to The above compounds may optionally contain additives and / or Coating aids may be present in the first layer.

So The first layer may be dyes or pigments that have high absorption in the visible spectral range, included to increase the color contrast. Particularly suitable are those which are good in the coating used solvents or solvent mixture solve or can be introduced as a pigment in disperse form. To The suitable contrast dyes include, among others. rhodamine, Triarylmethane dyes, such as Victoria blue R and Vikoriareinblau BO, crystal violet and methyl violet, anthraquinone pigments, azo pigments and phthalocyanine dyes or pigments. The dyes are in the first layer, preferably in a proportion of 0.5 to 30 % By weight, more preferably 5 to 20% by weight, based in each case on the Dry layer weight, included.

The Layer may further contain plasticizer. Suitable plasticizers are u.a. Dibutyl phthalate, triaryl phosphate, dioctyl phthalate, didodecyl phthalate, Dibutyl sebacate, glycerol triacetate and mixtures thereof. Becomes a plasticizer used, the amount thereof is preferably in the range of 0.25 to 2% by weight, based on the dry layer weight.

In addition, surface-active Agents (e.g., anionic, cationic, amphoteric or nonionic Surfactants or mixtures thereof). Suitable examples are siloxane-containing polymers, fluorine-containing polymers, polymers with Ethylene oxide and / or propylene oxide groups, sorbitol tristearate and Alkyl di (aminoethyl) glycine. Their amount is preferably 0 to 10% by weight, based on the dry layer weight, more preferably 0.2 to 5% by weight.

Further optional constituents of the first layer are, for example, inorganic fillers, for example Al ₂ O ₃ and SiO ₂ . They are preferably in an amount of 0 to 20 wt.%, Based on the dry layer weight, particularly preferably 0.1 to 5 wt.%.

wobei R^1a und R^2a unabhängig voneinander jeweils ein Wasserstoffatom, einen Alkylrest oder einen Alkoxyrest darstellen,
R^3a ein Wasserstoffatom, einen Alkylrest, einen Alkoxyrest oder einen Rest -COOR darstellt, wobei R ein Alkylrest oder Arylrest ist,
X^- ein organisches oder anorganisches Anion ist,
Y² eine Spacergruppe ist, und
m/n eine Zahl von 0,5 bis 2 ist.The essential component of the topcoat is a negative-working diazo resin, as has long been known for conventional UV-sensitive coatings of printing plate precursors. Suitable diazo resins are, for example, diazo resins of the formula (II)

wherein R ^1a and R ^2a independently of one another each represent a hydrogen atom, an alkyl radical or an alkoxy radical,
R ^{3a represents} a hydrogen atom, an alkyl radical, an alkoxy radical or a radical -COOR, where R is an alkyl radical or aryl radical,
X ^{- is} an organic or inorganic anion
Y ^{2 is} a spacer group, and
m / n is a number from 0.5 to 2.

In formula (II), R ^1a and R ^2a independently of one another each represent a hydrogen atom, an alkyl radical (preferably C ₁ -C ₁₈ , particularly preferably C ₁ -C ₁₀ ) or an alkoxy radical (preferably C ₁ -C ₁₈ , particularly preferably C ₁ -C ₁₀ ). Preferably, R ^{1a is} H or -OCH ₃ , more preferably -OCH ₃ ; R ^2a is preferably H or -OCH ₃ , more preferably -OCH ₃ .

R ^3a is selected from a hydrogen atom, an alkyl radical (preferably C ₁ -C ₁₈ , particularly preferably C ₁ -C ₁₀ ), an alkoxy radical (preferably C ₁ -C ₁₈ , particularly preferably C ₁ -C ₁₀ ), and the radical COOR, wherein R is an alkyl radical (preferably C ₁ -C ₁₈ , particularly preferably C ₁ -C ₁₀ ) or aryl radical (preferably phenyl). It is preferred that R ^{3a is} H-.

X is an organic or inorganic anion. Preferred anions are the anion of tetraphenylboronic acid, the anion more aromatic Carboxylic acids, the anion of aromatic sulfonic acids, the anion of a polyfluoroalkylcarboxylic or sulphonic acid, chloride, Hexafluorophosphate, tetrafluoroborate, sulphate, dihydrogenphosphate, Tetrachlorozinc, particularly preferably the tosylate or Mesitylensulfonatanion.

Y ² is a spacer group introduced into the diazo resin by co-condensation of a monomeric diazo compound with a compound selected from aliphatic aldehydes, aromatic aldehydes, phenol ethers, aromatic thioethers, aromatic hydrocarbons, aromatic heterocycles, and organic acid amides. Examples of Y ² are -CH ₂ - and -CH ₂ -C ₆ H ₄ -OC ₆ H ₄ -CH ₂ -.

m / n is 0.5 to 2, preferably 0.9 to 1.1, and more preferably 1.

For the production of the diazo resin usable monomeric diazo compounds e.g. 4-diazodiphenylamine, 4'-hydroxy-4-diazodiphenylamine, 4'-methoxy-4-diazodiphenylamine, 4'-ethoxy-4-diazodiphenylamine, 4'-n-propoxy-4-diazodiphenylamine, 4'-i-propoxy-4-diazodiphenylamine, 4'-methyl-4-diazodiphenylamine, 4'-ethyl-4-diazodiphenylamine, 4'-n-propyl-4-diazodiphenylamine, 4'-i-propyl-4-diazodiphenylamine, 4'-n -butyl-4-diazodiphenylamine, 4'-hydroxymethyl-4-diazodiphenylamine, 4'-β-hydroxyethyl-4-diazodiphenylamine, 4'-γ-hydroxypropyl-4-diazodiphenylamine, 4'-methoxymethyl-4-diazodiphenylamine, 4'-ethoxymethyl-4-diazodiphenylamine, 4'-β-methoxyethyl-4-diazodiphenylamine, 4'-β-ethoxyethyl-4-diazodiphenylamine, 4'-carbomethoxy-4-diazodiphenylamine, 4'-carboxyethoxy-4-diazodiphenylamine, 4'-carboxy-4-diazodiphenylamine, 4-diazo-3-methoxy-diphenylamine, 4-diazo-2-methoxy-diphenylamine, 2'-methoxy-4-diazodiphenylamine, 3-methyl-4-diazodiphenylamine, 3-ethyl-4-diazodiphenylamine, 3'-methyl-4-diazodiphenylamine, 3-ethoxy-4-diazodiphenylamine, 3-hexyloxy-4-diazodiphenylamine, 3-β-hydroxyethoxy-4-diazodiphenylamine, 2-methoxy-5'-methyl-4-diazodiphenylamine, 4-diazo-3-methoxy-6-methyldiphenylamine, 3,3'-dimethyl-4-diazodiphenylamine, 3'-n-butoxy-4-diazodiphenylamine, 3,4'-dimethoxy-4-diazodiphenylamine, 2'-carboxy-4-diazodiphenylamine, 4-diazodiphenyl ether, 4'-methoxy-4-diazodiphenyl ether, Of 4'-methyl-4-diazodiphenyl ether, 3,4'-dimethoxy-4-diazodiphenyl ether, 4'-Carboxy-4-diazodiphenyl ether, 3,3'-dimethyl-4-diazodiphenyl ether, 4-diazodiphenyl sulfide, 4'-methyl-4-diazodiphenyl sulfide and 4'-methyl-2,5-dimethoxy-4-diazodiphenyl sulfide, but are not limited to this.

Preferred reactants for the diazo compounds include, but are not limited to, formaldehyde, 4,4'-bis-methoxymethyldiphenyl ether, acetaldehyde, propionaldehyde, butyraldehyde, and benzaldehyde. Particularly preferred are formaldehyde and 4,4'-bis-methoxy-methyldiphenyl ether. The production conditions for the diazo resins are well known to the person skilled in the art; it is an example at this point US 3849392 directed.

Especially preferred diazo resins are those obtained by co-condensation of Formaldehyde and 4-phenylaminobenzenediazonium salt (1: 1 condensation product) or 4,4'-bis-methoxymethyldiphenyl ether and 4-phenylamino-2-methoxybenzenediazonium salt (1: 1 condensation product) were manufactured.

A hybrid system of diazonium polycondensation product ("diazo resin") and radically polymerizable system may also be used The radically polymerizable system is composed of photoinitiators absorbing in the range of 300 to 800 nm, preferably 300 to 450 nm, and radically polymerizable components Suitable photoinitiators are preferably the parent compounds or derivatives of acetophenone, benzophenone, (trichloromethyl) -1,3,5-triazine, benzoin, benzoin ethers, benzoine ketals, xanthone, thioxanthone, acridine or hexaarylbisimidazole The free-radically polymerizable constituent is preferably an acrylic It may be in solid or liquid form, with solid and viscous forms being preferred are eligible to count for example, trimethylolpropane triacrylate and methacrylate, pentaerythritol triacrylate and methacrylate, dipentaerythritol monohydroxypentaacrylate and methacrylate, dipentaerythritol hexaacrylate and methacrylate, pentaerythritol tetraacrylate and methacrylate, di (trimethylolpropane) tetraarylate and methacrylate, diethylene glycol diacrylate and methacrylate, triethylene glycol diacrylate and methacrylate or tetramethylene glycol diacrylate and methacrylate. Suitable oligomers or prepolymers are urethane acrylates and methacrylates, epoxy acrylates and methacrylates, polyester acrylates and methacrylates, polyether acrylates and methacrylates or unsaturated polyester resins. The photoinitiators and free-radically polymerizable constituents are to be composed in a manner known to the person skilled in the art, and combinations of different photoinitiators and different radically polymerizable components are also possible. Such hybrid systems preferably contain 1 to 50% of diazonium polycondensation products, 0.5 to 20% of photoinitiators and 5 to 80% of radically polymerizable constituents based on the Hybrid system.

The solution for the Covering layer can in addition to the at least one diazo resin still one or contain several additives and / or coating aids, for Example selected from stabilizing acids (e.g. Phosphoric acid, phosphorous acid, diphosphoric, oxalic acid, boric acid, p-toluenesulfonic acid, benzenesulfonic, p-hydroxybenzenesulfonic acid, 2-Methoxy-4-hydroxy-5-benzoylbenzenesulfonic acid, malic acid, citric acid, tartaric acid, dipicolinic acid, 5-nitro-naphthalene-1-phosphoric acid, 4-chlorophenoxymethylphosphonic acid, phenylmethylpyrazolone sulfonate sodium salt, 2-phosphonobutanetricarboxylic acid-1,2,4, 1-1,2,2-Phosphonoethantricarbonsäure and 1-hydroxyethane-1,1-disulfonic acid and mixtures thereof), surface-active Agents (e.g., anionic, cationic or neutral surfactants), thickeners (e.g., carboxymethyl cellulose), plasticizers (e.g., dibutyl phthalate, Triaryl phosphate, dioctyl phthalate and mixtures thereof), exposure indicators (e.g., 4-phenylazodiphenylamine) and contrast dyes and pigments (e.g., rhodamine dyes, Methyl violet, anthraquinone pigments, and phthalocyanine dyes and -pigments). The cover layer may also have a like contain the above-defined IR absorber; this is not necessary.

The Amount of stabilizing acids is preferably 0 to 3 wt .-% based on the dry layer weight the cover layer, more preferably 0.2 to 3 wt .-%. The surface active Means can be in a quantity of e.g. 0 to 5 wt .-%, particularly preferably 0.05 to 1 wt .-% can be used. Thickeners are usually in an amount of e.g. 0 to 2 wt .-%, particularly preferably 0.1 used to 0.5 wt .-%. Plasticizers may e.g. 0 to 2% by weight, especially preferably 0.25 to 2 wt .-% are used. The contrasting dyes and -pigments can in a proportion of e.g. 0 to 15% by weight, more preferably 2 used to 7 wt .-%. The amount of exposure indicators is preferably 0 to 5 wt .-%, particularly preferably 0.3 to 2 wt .-%.

The Cover can except the diazo resin also contain other polymers. These polymers should in alkaline developers with high pH (about pH 11 to 14) be soluble. These polymers can for example selected be from the above for the first layer of polymeric binders.

The to be applied solution contains preferably 10 to 100% by weight of the diazo resin (s), based on Solids, more preferably 20 to 60 wt .-%. The amount of additional Polymers in the coating solution is preferably 40 to 80% by weight.

The dry layer weight of the cover layer is preferably 0.1 to 2 g / m ² , more preferably 0.2 to 1.2 g / m ² .

It it is preferred that the dry layer weight of the first layer is larger than that of the second layer ("top coat" or "diazo layer").

The second layer (cover layer) is also made of a solution of Ingredients in an organic solvent or solvent mixture (e.g., acetone, methyl ethyl ketone, methyl propyl ketone, methyl amyl ketones, Diethyl ketone, methyl hexyl ketone, diacetone alcohol, cyclohexanone, methylcyclohexanol, Methanol, ethanol, n- and iso-propanol, n- and iso-butanol, ethylene glycol monomethyl ether, Propylene glycol monomethyl ether, propylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, Ethylene glycol acetate, propylene glycol acetate, propylene glycol monomethyl acetate, Propylene glycol monobutyl ether, 3-methyl-3-methoxybutanol, ethyl acetate, butyl acetate, Methyl lactate, and ethyl lactate, tetrahydrofuran, acetamide, dimethylformamide, N-methylpyrrolidone, toluene) was applied to the first layer and dried. Therefore can usual coating methods such as knife coating, roller application, spin coating etc. be used. Preferably, for the coating solution for Producing the topcoat using a solvent (mixture), that does not dissolve the first layer.

The imageable elements thus produced are processed with semiconductor lasers or emitting laser diodes emitting in the range of 650 to 1300 nm, if in the first layer one or more IR absorbers are radiation-sensitive Component is used. Such a laser radiation is digital over a Computer controllable, that is, it can either be or off, so that a pictorial exposure of the plates over a digitized information storage in the computer becomes possible. The IR-sensitive invention Compositions are therefore suitable for so-called computer-to-plate (ctp) to create printing plates. It may well known to those skilled Exposure units are used with IR lasers.

When the first layer contains a (naphtho) quinone diazide as a radiation-sensitive component, For imagewise radiation, a conventional UV radiation source emitting radiation of a wavelength in the range of 300 to 450 nm is used.

The Development of imagewise irradiated Elements, such as e.g. Printing plate precursor, carried out with an aqueous alkaline developer for positive-working systems that have a pH of 12 to 14. It can be commercially available positive developers can be used, which have a pH of 12 to 14.

Drawing lithographic printing plate precursors through developability with high pH developers, high Radiation sensitivity and good resistance to pressure chamber chemicals out.

The The invention will be explained in more detail with reference to the following examples.

Examples

Comparative Example 1

An electrochemically roughened and anodized aluminum foil was subjected to treatment with an aqueous solution of polyvinyl phosphoric acid (PVPA). The thus pretreated support was coated with the following solution:
3 g of NW 1428 (negative diazo resin obtained by condensation of 3-methoxydiphenylamine-4-diazonium sulfate and 4,4'-bis-methoxymethyldiphenyl ether isolated as mesitylenesulfonate, available from Clariant)
20 g of a mixed solvent of Dowanol ^® PM (propylene glycol methyl ether, available from Dow Chemical) and methanol (weight ratio 70:30)

The coating was dried at 90 ° C for 10 minutes; the dry layer weight was 0.7 g / m ² .

One Part of the coated plate was exposed to developer without exposure 1 (Goldstar, undiluted; available by Kodak Polychrome Graphics) for 30 s, a second part 30 seconds with developer 2 (Developer 956, undiluted, available from Kodak Polychrome Graphics). The layer loss became gravimetric by weighing the plate before and after the developer treatment. The results are together with the characteristics of the developers 1 and 2 are shown in Table 1.

Table 1

This Trial showed that when using a developer with very high pH (i.e., 11.5 or higher) an azo coupling takes place which renders the coating insoluble.

example 1

A pretreated aluminum support as described in Comparative Example 1 was coated with the following coating solution:
10 g copolymer of N-phenylmaleimide, methacrylamide and methacrylic acid (50:35:15 mol%)
1.8 g of IR Trump dye
45 g mixture of methyl lactate, methanol and dioxolane (15: 42.5: 42.5% by weight)

The coating was dried at 90 ° C for 10 minutes; the dry layer weight was 1.83 g / m ² .

A second coating solution was prepared by dissolving 3 g NW 1428 in 20 g of a mixed solvent of Dowanol ^® PM and methanol (weight ratio 70:30). This was applied to the dried first layer; the dry layer weight of the overcoat layer after drying at 90 ° C for 10 minutes was 0.7 g / m ² .

Of the obtained printing plate precursors was exposed imagewise with a Creo Trendsetter exposure unit (Wavelength: 830 nm; 9.5 W; 160 rpm).

Subsequently was a portion of the exposed printing plate precursor in a "Mercury Processor "-Entwicklungseinheit developed using Goldstar ("Positive Developer") from Kodak Polychrome Graphics as developer has been. A second part of the exposed printing plate precursor was Developed using Developer 956 ("Negative Developer").

in Using Goldstar became a clear picture with clean background areas receive. When using Developer 956 remained in the exposed areas still coating in the unexposed areas on the carrier, this means, there was no picture. This proves that when using a developer with a pH ≥11 an image is obtained while a developer with a pH <11 to no differentiation between image and non-image areas leads.

reference example

(Preparation of 1.8 mol% N 13 tosylated novolac)

dry m-cresol / formaldehyde novolak resin (129 g) was added with stirring in Dissolved 325 g of acetone and the solution at 10 ° C cooled. About one 1 minute period was p-toluenesulfonyl chloride (3.56 g) was added. Subsequently was over for 1 hour at 10 ° C triethylamine (2.09 g). The The reaction mixture was stirred at a temperature ≤ 15 ° C for 1 hour. About one For 1 minute, acetic acid (1.36 g) was added at 10 ° C and the reaction mixture then stirred for 15 minutes.

One Mixture of 3.0 kg of ice and 3.0 kg of water was placed in a 7.5 liter beaker given. 5 g of acetic acid with stirring added and the mixture stirred for about 1 minute. About 25% of the reaction mixture was added and the mixture stirred for about 20 minutes. Then you left that Mixture stand for 20 minutes and decanted the supernatant.

Approximately 1.9 kg of water was added to the remaining precipitate and the mixture then at 16 ° C for 5 minutes touched. One left the Deposit the solid and decant the supernatant. This approach was repeated with the remaining 3 parts of the reaction mixture.

Of the Precipitate was then combined and dried. There were 123 g tosyliertes novolak resin, wherein about 1.8 mol% of the hydroxy groups converted into tosyl groups.

Comparative Example 2

A pretreated aluminum support as described in Comparative Example 1 was coated with the following coating solution:
3 g of N 13-tosylated novolak (1.5 mol%) (prepared as described in the Reference Example)
20 g of mixed solvent of Dowanol ^® PM and methanol (weight ratio 70:30)

After drying for 10 minutes at 90 ° C, a dry film weight of 0.7 g / m ^{2 was} obtained.

One Part of the coated carrier was placed in Goldstar developer for 1 min; after rinsing with water and drying, the layer weight loss was found to be 70%.

One other part of the coated support was baked at 130 ° C. for 30 minutes, before the layer weight loss is determined in the same way has been; the loss here was less than 10%.

This Comparative example shows that in non-inventive plates (i.e., plates without diazo topcoat), a baking step is required is to constancy across from to reach a strong alkaline positive developer.

Example 2

It An aluminum support as described in Comparative Example 1 was used and this with the coating solution for the first described in Example 1 Coated layer.

Subsequently, another coating solution was prepared and applied to the dried first layer; this coating solution (according to Example 10 of US 6,352,812 B1 ) contained:
2.13 g polyvinyl acetal with carboxyl function (prepared according to Preparation Example 11 of US 5,700,619 A )
2.13 g of Nega 107 (negative diazo resin prepared by polycondensation of 3-methoxydiphenylamine-4-diazonium sulfate and 4,4'-bismethoxymethyldiphenyl ether isolated as mesitylenesulfonate salt, available from Panchim)
0.15 g EC2117 IR dye (absorption maximum: 830 nm) and
50 ml solvent mixture (2-methoxyethanol, methanol and methyl ethyl ketone, 35:25:40)

The second layer (cover layer) had a dry layer weight of 0.56 g / m ² .

Of the obtained printing plate precursors was equipped with a Creo Trendsetter exposure unit (wavelength: 830 nm; 9.5 W; 160 rpm).

in Development with Goldstar developer got a good picture.

Example 3

An aluminum support as described in Comparative Example 1 was used, and it was coated with the coating solution described below to obtain a dry film weight of 2.0 g / m ² .

Coating solution:
7 parts by weight of CF novolac
2 parts by weight of 2,1-naphthoquinonediazole-4-sulfonic acid ester of a CF novolak
0.11 parts by weight crystal violet
0.05 parts by weight of triazine B
30 parts by weight of isobutyl acetate
30 parts by weight of methyl isobutyl acetate
20 parts by weight of methyl ethyl ketone
9 parts by weight of ethyl glycol

Subsequently, the coating solution described in Example 2 was used to prepare a cover layer with 0.54 g / m ² dry layer weight.

The printing plate precursor thus prepared was imagewise irradiated with ultraviolet ray (300 mJ / cm ² ) and then with "4005" developer (developed by Kodak Polychrome Graphics (pH = 13.4): a good positive image was obtained and a clean background.

Claims (10)

A process for imaging a radiation-sensitive element comprising (a) providing a radiation-sensitive element comprising (i) a pretreated or untreated support, (ii) a first layer applied to the support comprising at least one aqueous solution-soluble or swellable polymeric binder and a radiation-sensitive component selected from IR absorbers or compounds having a diazo group = N ₂ , and (iii) a cover layer comprising at least one negative-working diazonium resin, (b) image-wise irradiating the radiation-sensitive element with radiation having a wavelength in the range from 650 to 1300 nm, when the radiation-sensitive component is an IR absorber, or with radiation of a wavelength in the range of 300 to 450 nm, when the radiation-sensitive component is a compound having a diazo group = N ₂ , (c) removing the irradiated areas of the imagewise irradiated element with an aqueous alkaline developer having a pH of 12 to 14. Method according to claim 1, wherein the first layer one or more IR absorbers as radiation-sensitive Component contains. The method of claim 2, wherein the IR absorber is a compound of formula (I)

wherein each Z is independently S, O, NR ^a or C (alkyl) ₂ ; each R 'independently represents an alkyl group, an alkylsulfonate residue or an alkylammonium residue; R '' is a halogen atom, SR ^a , OR ^a , SO ₂ R ^a or NR ^a ₂ ; each R '''independently represents a hydrogen atom, an alkyl group, -COOR ^a , -OR ^a , -SR ^a , -NR ^a ₂ or a halogen atom, or a benzo-fused ring; A ^{- stands} for an anion; R ^b and R ^c each represent a hydrogen atom or together form a carbocyclic five- or six-membered ring; R ^{a represents} a hydrogen atom, an alkyl or aryl radical; and each a is independently 0, 1, 2 or 3. The method according to claim 1, wherein the first layer contains one or more compounds having a diazo group = N ₂ as a radiation-sensitive component. Method according to one the claims 1 to 4, wherein the first layer also comprises at least one component, selected from colorants, plasticisers, surface-active agents, inorganic fillers, Leuco dyes and exposure indicators. Method according to one the claims 1 to 5, wherein the cover layer also comprises at least one component, selected from colorants, plasticisers, surface-active agents, thickeners, Exposure indicators and alkali-soluble polymers. A process according to any one of claims 1 to 6, wherein the polymeric binder of the first layer is at least one polymer selected from novolacs, resoles, polyvinylphenol resins, acidic butene lyvinyl acetals, acid cellulose derivatives, methacrylic acid copolymers, acrylic acid copolymers and maleic acid copolymers. A process according to any one of claims 1 to 7, wherein the at least one negative diazonium resin is a diazonium resin of formula (II)

wherein R ^1a and R ^2a each independently represent a hydrogen atom, an alkyl group or an alkoxy group, R ^{3a represents} a hydrogen atom, an alkyl group, an alkoxy group or a group -COOR, wherein R is an alkyl group or aryl group, X ^- an organic or inorganic Anion is, Y ^{2 is} a spacer group, and m / n is a number from 0.5 to 2. Method according to one the claims 1 to 8, wherein the carrier is an aluminum plate or foil acts. Method according to claim 9, wherein the aluminum plate or foil prior to coating at least one Treatment, selected from roughening, anodizing and hydrophilizing.