DE10233631B4 - Lithographic printing plate precursor with two radiation-sensitive layers - Google Patents

Abstract

wobei R¹ und R² unabhängig voneinander jeweils ein Wasserstoffatom, einen Alkylrest oder einen Alkoxyrest darstellen,
R³ 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, das so ausgewählt ist, dass in 100 ml Wasser bei 20°C mindestens 1 g des Diazoharzes löslich ist, und
Y eine Spacergruppe ist, und
m/n eine Zahl von 0,5 bis 2 ist,
und
(c) eine zweite strahlungsempfindliche Schicht, aufgebracht auf die erste strahlungsempfindliche Schicht, umfassend mindestens ein photovernetzbares Poly(vinylacetal) enthaltend die folgenden Struktureinheiten

wobei R⁴ einen Alkylrest mit bis zu 4 C-Atomen, einen Alkylrest mit bis zu 4 C-Atomen der durch eine Säuregruppe substituiert ist, eine Phenylgruppe oder...Including radiation sensitive elements
(a) a carrier
(b) a first radiation-sensitive layer on the support comprising at least one negative-working diazo resin of the formula (1)

where R ¹ and R ² each independently represent a hydrogen atom, an alkyl radical or an alkoxy radical,
R ^{3 represents} a hydrogen atom, an alkyl radical, an alkoxy radical or a -COOR radical, where R is an alkyl radical or aryl radical,
X ^{- is} an organic or inorganic anion which is selected so that at least 1 g of the diazo resin is soluble in 100 ml of water at 20 ° C., and
Y is a spacer group, and
m / n is a number from 0.5 to 2,
and
(c) a second radiation-sensitive layer, applied to the first radiation-sensitive layer, comprising at least one photocrosslinkable poly (vinyl acetal) containing the following structural units

wherein R ^{4 is} an alkyl radical with up to 4 C atoms, an alkyl radical with up to 4 C atoms which is substituted by an acid group, a phenyl group or ...

Description

This invention relates to radiation sensitive Elements that have two radiation-sensitive layers, in particular negative working lithographic printing plate precursor with a diazo resin containing Layer and a maleimide-substituted polyvinyl acetal containing Layer; the invention also relates to a method for their Production.

The field of lithographic Pressure is based on the immiscibility of oil and water, being the oily material or the ink preferably from the image area and the water or dampening solution preferably accepted from the non-image area becomes. A properly made surface is moistened with water and then applied an ink, the background or the takes Non-image area turns on the water and repels the ink during the Image area takes on the ink and the water repels. The ink on the image area is then on the surface of a material such as paper, Tissue and the like, transferred, on which the image is to be created. In general, the But first transfer the ink to an intermediate material called a printing blanket, which then transfers the ink to the surface of the material which the image should be created; this is called offset lithography.

A commonly used type of lithographic printing plate precursor has one on a support aluminum-based, light-sensitive coating on. The coating can react to radiation by the exposed one Part so soluble will be removed during the development process. Such a record is described as positive working. A plate is reversed called negative working when the exposed part of the coating hardened by the radiation becomes. In both cases the remaining image area takes up 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 using a radiation source, part of which is from UV radiation is composed, exposed. If a positive plate is used is the area corresponding to the image on the plate the film so opaque that light does not attack the plate during the non-image area corresponding 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 on the film corresponding to the image area is clear, while the non-image area is opaque. The coating under the clear film area is cured by exposure to light during the Area not affected by light removed during development becomes. The light-cured surface a negative plate is therefore oleophilic and takes up printing ink, while the non-image area, which is the result of a developer removed coating, is desensitized and therefore is hydrophilic.

There are many different compositions for the photosensitive layer of negative working precursors of Lithographic printing plates have been described. They are also single and multi-layered Known plates. The use of negative working has long been Diazo resins known in the photosensitive layer; but also other systems have been described.

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

Further lithographic printing plate precursors, the photosensitive layer of which contain photocrosslinkable polymers with maleimide groups, for example in EP-A-0 021 019 and US-A-6,087,066 described. Other photopolymers with maleimide groups are described in US-A-3,920,618 . US-A-4,079,041 and EP-A-0 003 552 described.

Also in US-A-5,346,975 describes photosensitive compositions with maleimide group-containing polymers which are used for the preparation of lithographic printing plate precursors. The compositions may contain water-insoluble negative working diazo resins as a further component.

US-A-5,240,808 reports on photosensitive compositions for negative-working printing plate precursors which contain a polymeric compound with both photocrosslinkable groups such as maleimide groups and functional groups with P-OH bonds. Water-insoluble, negative working diazo resins are mentioned as optional components for these photosensitive compositions.

The negative working plates from US-A-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 is irrelevant.

In EP-A-1 143 301 describes a printing plate precursor that has two layers on a substrate includes; the lower layer comprises at least one diazo resin and at least one polyurethane resin with an acidic hydrogen atom and the upper layer comprises a polymer with maleimide groups.

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

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

JP-A-04-274429 describes printing plate precursors in which the photosensitive layer contains a photopolymerizable or photocrosslinkable composition and a special diazo resin. An intermediate layer containing a diazo resin can be arranged between the support and the light-sensitive layer.

Despite the multitude of known ones negative printing plate precursors still exist Need for printing plate precursors, which is characterized by high sensitivity, rapid developability and good storage stability distinguish and printing plates with high circulation resistance deliver.

It is therefore the task of the present Invention to provide radiation sensitive elements that high sensitivity and rapid developability at the same time good storage stability show and enable long runs when used as printing plates. Another task is to provide a method for Manufacture of such elements.

• (a) einen Träger
• (b) eine erste strahlungsempfindliche Schicht auf dem Träger umfassend mindestens ein negativ arbeitendes Diazoharz der Formel (1)
  
  wobei R¹ und R² unabhängig voneinander jeweils ein Wasserstoffatom, einen Alkylrest oder einen Alkoxyrest darstellen, R³ 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, das so ausgewählt ist, dass in 100 ml Wasser bei 20°C mindestens 1g des Diazoharzes löslich ist, und Y eine Spacergruppe ist, und m/n eine Zahl von 0,5 bis 2 ist, und
• (c) eine zweite strahlungsempfindliche Schicht, aufgebracht auf die erste strahlungsempfindliche Schicht, umfassend mindestens ein photovernetzbares Poly(vinylacetal) enthaltend die folgenden Struktureinheiten
  
  
  wobei R⁴ einen Alkylrest mit bis zu 4 C-Atomen, einen Alkylrest mit bis zu 4 C-Atomen, der durch eine Säuregruppe substituiert ist, eine Phenylgruppe oder eine Phenylgruppe an die eine Säuregruppe gebunden ist, eine Phenylgruppe mit oder ohne Säuregruppe mit 1 bis 2 weiteren Substituenten ausgewählt aus Halogenatomen, Amino-, Methoxy-, Ethoxy-, Methyl- und Ethylgruppe, oder eine Gruppe -Z-NR⁵-CO-Q-COOH bedeutet, wobei Z eine aliphatische, aromatische oder araliphatische Spacergruppe bedeutet, R⁵ ein Wasserstoffatom oder ein aliphatischer, aromatischer oder araliphatischer Rest und Q eine gesättigte oder ungesättigte ketten- oder ringförmige Spacergruppe ist, k eine ganze Zahl von 1 bis 3 ist, R⁶ und R⁷ jeweils unabhängig voneinander ein Wasserstoffatom oder eine Methylgruppe bedeuten und R⁸ und R⁹ unabhängig voneinander Wasserstoff oder Alkylreste mit höchstens 4 Kohlenstoffatomen oder R⁹ und R⁸ zusammen mit den beiden Kohlenstoffatomen, an die sie gebunden sind, einen 5- oder 6-gliedrigen carbocyclischen Ring darstellen, wobei die Einheit (C) mit verschiedenen Resten R⁴ unabhängig voneinander mehrmals enthalten sein kann und die Einheit (D) mit verschiedenen Resten R⁶–R⁹ und k unabhängig voneinander mehrmals enthalten sein kann und mindestens einen Photosensibilisator für Photocycloaddition, wobei diese zweite strahlungsempfindliche Schicht keine Diazoverbindung enthält.

The first task is solved comprehensively by radiation-sensitive elements

• (a) a carrier
• (b) a first radiation-sensitive layer on the support comprising at least one negative-working diazo resin of the formula (1)
  
  where R ¹ and R ² each independently represent a hydrogen atom, an alkyl radical or an alkoxy radical, R ^{3 represents} a hydrogen atom, an alkyl radical, an alkoxy radical or a radical -COOR, where R is an alkyl radical or aryl radical, X ^- an organic or inorganic Anion is selected so that at least 1 g of the diazo resin is soluble in 100 ml of water at 20 ° C., and Y is a spacer group, and m / n is a number from 0.5 to 2, and
• (c) a second radiation-sensitive layer, applied to the first radiation-sensitive layer, comprising at least one photocrosslinkable poly (vinyl acetal) containing the following structural units
  
  
  where R ^{4 is} an alkyl radical with up to 4 C atoms, an alkyl radical with up to 4 C atoms which is substituted by an acid group, a phenyl group or a phenyl group to which an acid group is attached, a phenyl group with or without an acid group with 1 to 2 further substituents selected from halogen atoms, amino, methoxy, ethoxy, methyl and ethyl group, or a group -Z-NR ⁵ -CO-Q-COOH, where Z is an aliphatic, aromatic or araliphatic spacer group, R ^{5 is} a hydrogen atom or an aliphatic, aromatic or araliphatic radical and Q is a saturated or unsaturated chain or ring-shaped spacer group, k is an integer from 1 to 3, R ⁶ and R ⁷ each independently represent a hydrogen atom or a methyl group and R ⁸ and R ⁹ independently of one another are hydrogen or alkyl radicals having a maximum of 4 carbon atoms or R ⁹ and R ⁸ together with the two carbon atoms to which they are attached represent a 5- or 6-membered carbocyclic ring, where the unit (C) with different radicals R ⁴ can be contained several times independently of one another and the unit (D) with different radicals R ⁶ -R ⁹ and k can be contained several times independently of one another and at least one photosensitizer for photocycloaddition, this second radiation-sensitive layer containing no diazo compound.

• (1) Bereitstellen eines Trägers
• (2) Aufbringen einer wässrigen Lösung umfassend mindestens ein negativ arbeitendes wasserlösliches Diazoharz wie vorstehend definiert,
• (3) Trocknen
• (4) Aufbringen einer nicht-wässrigen Lösung umfassend mindestens ein wie vorstehend definiertes photovernetzbares Poly(vinylacetal) und mindestens einen Photosensibilisator für Photocycloaddition, wobei die Lösung frei von Diazo-Verbindungen ist,
• (5) Trocknen und
• (6) gegebenenfalls Aufbringen einer wasserlöslichen Deckschicht.

The second problem is solved by a process comprising:

• (1) Providing a carrier
• (2) applying an aqueous solution comprising at least one negative working water-soluble diazo resin as defined above,
• (3) drying
• (4) applying a non-aqueous solution comprising at least one photocrosslinkable poly (vinyl acetal) as defined above and at least one photosensitizer for photocycloaddition, the solution being free from diazo compounds,
• (5) drying and
• (6) optionally applying a water-soluble top layer.

welches wasserlöslich ist.In the radiation-sensitive element according to the invention there is a first radiation-sensitive layer on the carrier. This comprises at least one negative-working diazo resin of the formula (1)

which is water soluble.

In formula (1), R ¹ and R ² each independently 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 ). R ¹ is preferably H or -OCH ₃ , particularly preferably -OCH ₃ ; R ² is preferably H or -OCH ₃ , particularly preferably -OCH ₃ .

R ³ 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, where 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 ^{3 is} H-.

X ^- is an organic or inorganic anion that must be selected so that at least 1 g of the diazo resin, preferably at least 10 g, is soluble in 100 ml of water at 20 ° C. Preferred anions are sulfate, dihydrogen phosphate, tetrachlorozincate, of which dihydrogen phosphate and tetrachlorozincate are particularly preferred.

Y is a spacer group which is 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 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 particularly preferably 1.

For the preparation of the diazo resin usable monomeric diazo compounds include, for example: 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, 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 are, for example, formaldehyde, 4,4'-bis-methoxy-methyldiphenyl ether, acetaldehydes, propionaldehyde, butyraldehyde and benzaldehyde, but are not limited thereto. Formaldehyde and 4,4'-bis-methoxy-methyldiphenyl ether are particularly preferred. The production conditions for the diazo resins are well known to the person skilled in the art; it is exemplary at this point US-A-3849392 directed.

Particularly preferred diazo resins are those by co-condensation of formaldehyde and 4-phenylaminobenzene diazonium salt (1: 1 condensation product) or 4,4'-bis-methoxymethyldiphenyl ether and 4-phenylamino-2-methoxybenzene diazonium salt (1: 1 condensation product) were manufactured.

It is essential for the present invention that the diazo resin is water-soluble, which means that at least 1 g of the diazo resin dissolves in 100 ml of water at 20 ° C. Diazo resins with a ge less water solubility ie better solubility in organic / non-polar solvents lead to a significantly longer exposure and development time as well as poor shelf life and are therefore not used according to the invention. Diazo resins with a solubility of at least 10 g / 100 ml of water at 20 ° C. are preferred.

The first radiation sensitive Layer is carried out on the carrier, which may have been pretreated in the customary manner Apply an aqueous solution and get drying. For the application can be conventional coating methods such as. Knife coating, spin coating etc. used become. The watery solution in addition to the at least one diazo resin, one or more Contain additives, selected from stabilizing acids (e.g. phosphoric acid, phosphorous acid, diphosphoric, Oxalic acid, boric acid, p-toluenesulphonic acid, benzosulphonic acid, p-hydroxybenzenesulphonic acid, 2-methoxy-4-hydroxy-5-benzoylbenzenesulphonic acid, malic acid, citric acid, tartaric acid, dipicolinic acid, 5-nitro-naphthalene-1-phosphoric acid, 4-chlorophenoxymethylphosphonic acid, 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 amount of stabilizing acids is preferably 0 to 3 wt .-% based on the dry layer weight, especially preferably 0.2 to 3% by weight. The surfactants can be in an amount of e.g. 0 to 5 wt .-%, particularly preferably 0.05 to 1% by weight can be used. Thickeners are common in an amount of e.g. 0 to 2% by weight, particularly preferably 0.1 up to 0.5 wt .-% used. Plasticizers can e.g. 0 to 2% by weight, especially preferably 0.25 to 2 wt .-% are used. The contrast dyes and pigments can in a proportion of e.g. 0 to 15% by weight, particularly preferably 2 to 7% by weight can be used. The set of exposure indicators is preferably 0 to 5% by weight, particularly preferably 0.3 to 2% by weight.

It is preferred that the first radiation sensitive layer next to the diazo resin and possibly polymeric Additives no other polymeric binders such as e.g. polyurethanes, Contains polyvinyl acetals or acrylic polymers.

The aqueous solution to be applied preferably contains 80 to 100% by weight of the diazo resin (s), particularly preferably 85 up to 98% by weight. The total amount of additives is preferably 0 to 20% by weight, particularly preferably 2 to 15% by weight.

Although water miscible organic solvent (e.g. methanol, ethanol, propylene glycol monomethyl ether) could be (e.g. 5 to 50% by weight), it is preferred that only water be used as the solvent is used.

The dry layer weight of the first radiation-sensitive layer is preferably 0.05 to 1 g / m ² , particularly preferably 0.1 to 0.5 g / m ² .

In the radiation-sensitive according to the invention Element is directly on the first radiation sensitive Layer a second radiation sensitive layer.

• (i) mindestens ein polymeres Bindemittel, das durch Bestrahlung zur Photocycloaddition fähig ist,
• (ii) mindestens einen Photosensibilisator für Photocycloaddition

und gegebenenfalls mindestens eine weitere Komponente wie z.B. Verdickungsmittel, oberflächenaktive Substanzen, sowie Weichmacher, Kontrastfarbstoffe und -pigmente (z.B. Rhodaminfarbstoffe, Methylviolet, Anthrachinonpigmente, Phthalocyaninfarbstoffe und -pigmente) und Belichtungsindikator wie z.B. Phenylazodiphenylamin,
wobei das Bindemittel (i) die Einheiten A, B, C und D umfasst:

wobei R⁴ einen Alkylrest mit bis zu 4 C-Atomen, der gegebenenfalls durch eine Säuregruppe substituiert ist, oder eine Phenylgruppe an die gegebenenfalls eine Säuregruppe gebunden ist, wobei die Phenylgruppe gegebenenfalls 1 bis 2 weitere Substituenten ausgewählt aus Halogenatomen, Amino-, Methoxy-, Ethoxy-, Methyl- und Ethylgruppe aufweist, oder eine Gruppe -Z-NR⁵-CO-Q-COOH bedeutet, wobei Z eine aliphatische, aromatische oder araliphatische Spacergruppe bedeutet, R⁵ ein Wasserstoffatom oder ein aliphatischer, aromatischer oder araliphatischer Rest und Q eine gesättigte oder ungesättigte ketten- oder ringförmige Spacergruppe ist,
k eine ganze Zahl von 1 bis 3 (vorzugsweise 3) ist,
R⁶ und R⁷ jeweils unabhängig voneinander ein Wasserstoffatom oder eine Methylgruppe bedeuten und
R⁸ und R⁹ unabhängig voneinander Wasserstoff oder Alkylreste mit höchstens 4 Kohlenstoffatomen oder R⁹ und R⁸ zusammen mit den beiden Kohlenstoffatomen, an die sie gebunden sind, einen 5- oder 6-gliedrigen carbocyclischen Ring darstellen.The second radiation sensitive layer contains:

• (i) at least one polymeric binder which is capable of photocycloaddition by irradiation,
• (ii) at least one photosensitizer for photocycloaddition

and optionally at least one further component such as, for example, thickeners, surface-active substances, and plasticizers, contrast dyes and pigments (for example rhodamine dyes, methyl violet, anthraquinone pigments, phthalocyanine dyes and pigments) and exposure indicators such as, for example, phenylazodiphenylamine,
wherein the binder (i) comprises the units A, B, C and D:

wherein R ^{4 is} an alkyl radical with up to 4 C atoms, which is optionally substituted by an acid group, or a phenyl group to which an acid group is optionally bonded, the phenyl group optionally 1 to 2 further substituents selected from halogen atoms, amino, methoxy , Ethoxy, methyl and ethyl group, or a group -Z-NR ⁵ -CO-Q-COOH, where Z is an aliphatic, aromatic or araliphatic spacer group, R ^{5 is} a hydrogen atom or an aliphatic, aromatic or araliphatic radical and Q is a saturated or unsaturated chain or ring-shaped spacer group,
k is an integer from 1 to 3 (preferably 3),
R ⁶ and R ⁷ each independently represent a hydrogen atom or a methyl group and
R ⁸ and R ⁹ independently of one another are hydrogen or alkyl radicals having a maximum of 4 carbon atoms or R ⁹ and R ⁸ together with the two carbon atoms to which they are attached form a 5- or 6-membered carbocyclic ring.

This unit (C) can be contained several times with different radicals R ⁴ independently of one another. The unit (D) can be contained several times with different radicals R ⁶ -R ⁹ and k independently of one another.

Examples of Z are -CH ₂ - and -CH ₂ CH ₂ -. Examples of Q are -CH = CH-, -CH ₂ -CH ₂ - and 1,2-C ₆ H ₄ -.

Examples of particularly preferred R ⁴ are -CH ₂ -N (CH ₃ ) CO-CH = CH-COOH and 1,4-C ₆ H ₄ -COOH.

R ⁶ and R ⁷ in unit (D) are preferably both hydrogen atoms.

R ⁸ and R ⁹ are preferably -CH ₃ or R ⁸ and R ⁹ together form a C ₄ H ₈ ring, CH ₃ is particularly preferred.

The proportions of the units (A) to (D) in the binder are not particularly limited, it is but preferred that the unit (A) in an amount of 0.5 up to 20% by weight (particularly preferably 0.5 to 12% by weight), Unit (B) from 10 to 40% by weight (particularly preferably 15 to 35 % By weight), unit (C) from 10 to 50% by weight (particularly preferably 5 to 20% by weight) and unit (D) from 25 to 70% by weight (particularly preferred 45 to 70 wt .-%), each based on the total weight of the acetal polymer.

The vinyl alcohol / vinyl acetate copolymers, which are used as starting material in the production of the maleimide group-containing polyacetals, are preferably hydrolyzed to 70 to 98 mol% and usually have a weight-average molecular weight M _w of 20,000 to 130,000 g / mol. Which copolymer is used as the starting material for the synthesis depends on the later intended use of the radiation-sensitive element. Polymers with a weight average molecular weight M _w of 35,000 to 130,000 g / mol and a degree of hydrolysis of the vinyl acetate structural unit of 80 to 98 mol% are preferably used for offset printing plates.

The maleinimide-modified polyvinyl acetals are produced in two synthesis steps. In egg In the first step, monomeric imido acetals are prepared from amino aldehyde acetals and substituted maleic anhydrides and substituted or unsubstituted tetrahydrophthalic anhydrides. The second step is the acetalization of polyvinyl alcohol with the monomeric imidoacetals and R ⁴ CHO or its acetates with C1 to C6 alcohols. Both steps can either be carried out separately or in a one-pot process. Maleimide-modified polyvinyl acetals suitable for the present invention and their preparation are described in detail, for example, in US-A-6,087,066 respectively. DE-C-198 47 616 described.

Another essential component of the second radiation-sensitive layer is a sensitizer for photocycloaddition. All of the sensitizers known in the art which permit photocycloaddition can be used for this. For example, here in DE-A-26 26 769 and DE-A-42 31 324 mentioned sensitizers, such as xanthone, acetophenone, benzaldehyde, carbazole, triphenylamine, hexachlorobenzene, 4,4-diphenylcyclohexadienone, 1,2-dibenzoylbenzene, benzophenone, 1,4-diacetylbenzene, fluorene, anthrone, benzanthrone, 2-nitralin, fluorine 4-nitrodiphenyl, 4-cyanobenzophenone, thioxanthone (also alkyl- or halogen-substituted), phenylglyoxal, anthraquinone, quinoline, phenanthrene, flavon, Michler's ketone, 4-acetyldiphenyl, 2-acetonaphthene, acridine yellow, 1-naphthylphenolketol 1-naphthaldehyde, coronene, benzil, fluorenone, fluorescine (acid), p-nitrostilbene, 5-nitroacenaphthene, 4-nitroaniline, naphthothiazoline, 1-acetylamino-4-nitronaphthalene, quinones, benzothiazoline derivatives, naphthothiazole derivatives, benzetofumaryl derivative, ketacofin derivative, ketacofin derivative and thiapyrylium salts.

Of these, thioxanthione and Thioxanthone derivatives with C1-C12 alkyl, C1-C12 alkoxy and halogen substituents preferred, particularly preferred are thioxanthone and derivatives which contain alkoxy and chlorine at the same time.

The weight fraction of the sensitizers is preferably 2 to 15 wt .-% based on the dry layer weight the second radiation-sensitive layer, particularly preferred 2 to 8% by weight.

The weight fraction of the photocrosslinkable Acetal copolymer in the second radiation sensitive layer is preferably 50 to 95 wt .-% based on the layer weight, particularly preferably 60 to 90% by weight.

In addition to acetal copolymer and sensitizers the second radiation-sensitive layer can contain additives such as surface-active Agents, thickeners, plasticizers, contrast dyes and pigments as well as exposure indicators in the same amounts as the front for the first contain radiation-sensitive layer described.

Inorganic and / or organic particles can also be present in the second radiation-sensitive layer, which support the application of the vacuum when exposing lithographic printing plate precursors. Suitable particles are, for example, aluminum oxide, titanium dioxide, silicon dioxide or organic particles made of polyethylene, polypropylene, polystyrene or polyamide; they are described in, for example, together with information for suitable particle sizes EP 161592 . EP 527369 and US-A-4599299 , Their amount can be 0 to 20% by weight of the layer, particularly preferably 0 to 10% by weight.

It is also possible in the second radiation-sensitive layer one or more polymeric binders to be used that are not sensitive to radiation. examples are Acrylic polymers, polyvinyl acetals such as polyvinyl butyral and polyvinyl formal or polyvinyl pyrrolidone.

Their amount is preferably 0 to 35% by weight the layer, particularly preferably 0 to 20% by weight.

It is essential for the present Invention that the second radiation sensitive layer has no diazo compounds contains such as. the above for the first radiation-sensitive layer described diazo resins and monomeric diazo compounds. It has been found that diazo compounds like diazo resins in the second radiation-sensitive layer Reduce photosensitivity of the element according to the invention.

The dry layer weight of the second radiation-sensitive layer is preferably 0.5 to 10 g / m ² , particularly preferably 0.8 to 3 g / m ² .

It is preferred that the dry layer weight the first layer ("diazo layer") is less than that the second layer ("acetal layer").

The second radiation sensitive Layer becomes a solution the ingredients in an organic solvent or solvent mixture (e.g. acetone, methyl ethyl ketone, methyl propyl ketone, methyl amyl ketone, Diethyl ketone, methyl hexyl ketone, diacetone alcohol, cyclohexanone, methyl cyclohexanol, 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) applied to the first layer and dried. Therefore can use conventional coating methods such as knife coating, spin coating etc. are used.

The radiation-sensitive elements according to the invention can, for example, printing form precursors (in particular precursors of lithographic printing plates), printed circuit boards for integrated circuits or photomasks his.

In the manufacture of printing plate form precursors as a carrier preferably a dimensionally stable plate or foil-shaped Material used. As such a dimensionally stable plate or Foil material is preferably one that has been used previously as a carrier for printed matter has been used. Examples of such a support include paper, Paper made with plastics (such as polyethylene, polypropylene, polystyrene) is 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 a plastic film and one of the above metals or a paper / plastic film made by Evaporation has been metallized. Among these carriers is an aluminum plate or foil is particularly preferred because it is remarkable dimensionally stable and is cheap and besides shows an excellent adhesion of the coating. Besides, can a composite film can be used with an aluminum foil is laminated on a polyethylene terephthalate film.

A metal carrier, in particular an aluminum carrier, is preferably a surface treatment, for example roughening by brushing when dry, or brushing with abrasive suspensions or electrochemically, e.g. a hydrochloric acid electrolyte, and optionally subjected to anodic oxidation.

It can also improve the hydrophilic properties of the surface of the roughened and optionally metal support oxidized in sulfuric or phosphoric acid an aftertreatment with an aqueous solution of sodium silicate, calcium zirconium fluoride, polyvinylphosphonic acid or phosphoric acid be subjected. In the context of this invention, the term “carrier” also includes, if appropriate pretreated carrier, e.g. has a hydrophilizing layer on the surface.

The details of the above substrate pretreatment are sufficient for the expert known.

In a few cases, the additional application of a water-soluble cover layer to the second radiation-sensitive layer can be advantageous. The polymers suitable for the top layer include, inter alia, polyvinyl alcohol, polyvinyl alcohol / polyvinyl acetate copolymers, polyvinylpyrrolidone, polyvinylpyrrolidone / polyvinyl acetate copolymers and gelatin. The layer weight of the cover layer can be, for example, 0.1 to 4 g / m ² , and particularly preferably 0.3 to 2 g / m ² . However, the printing plate precursors according to the invention have excellent properties even without a top layer. The top layer can also contain matting agents (ie organic or inorganic particles with a particle size of 2 to 20 μm), which facilitate the flatness of the film during contact exposure.

The printing plate precursors thus produced become exposed to UV radiation in the manner known to the person skilled in the art and subsequently with a commercially available aqueous developed alkaline developer. The developed plates can be made in the usual way treated with a preservative ("gum"). The preservatives are watery solutions of hydrophilic polymers, wetting agents and other additives.

For certain applications, it is also advantageous to increase the mechanical strength of the printing layers by heat treatment or combined use of heat and UV light. Before this treatment, the plate is first treated with a solution which protects the non-image areas in such a way that the heat treatment does not cause these areas to become colored. A suitable solution for this is, for example, in US-A-4,355,096 described. However, printing plates which were produced using printing plate precursors according to the invention show outstanding properties even without heat treatment.

Lithographic printing plate precursor according to the present Ending are characterized by fast development time, high sensitivity to light and good shelf life out; the developed printing plates show excellent abrasion resistance, which makes long runs possible are.

The invention is illustrated by the following Examples closer explained.

Production Example 1 (Preparation of N- (4,4-diethoxy-butyl) -2,3-dimethyl-maleimide; Precursor for the production of the photosensitive polymer)

138.72 g of 2,3-dimethyl maleic anhydride were dissolved in 600 ml of toluene in a three-necked flask equipped with a stirrer, dropping funnel and water separator. A solution of 161.25 g of 4-aminobutyraldehyde diethylacetal in 100 ml of toluene was slowly added dropwise. The solution was stirred at 20 ° C for 30 minutes and then heated under reflux for 1 hour. The solvent was removed under reduced pressure to give 283.1 g of a yellowish oil. The product obtained has the following formula (2)

Production Example 2 (Poly (vinyl acetal) 2)

In a three-necked flask equipped with stirrer, dropping funnel and reflux condenser were charged 18.0 g of Mowiol 10/98 ^® (a polyvinyl alcohol available from Clariant) are dissolved in 180 ml of DMSO at 60 ° C. After adding 2.25 ml of hydrochloric acid (30%), a solution of 32.64 g of the compound prepared in Preparation 1 and 4.71 g of 4-formylbenzoic acid in 45 ml of DMSO was slowly added and the mixture was stirred at 60 ° C. for 16 hours. The viscous solution was diluted with 120 ml of DMSO and the polymer was precipitated in water, filtered, washed three times with water and finally dried at 40 ° C., whereby 39.9 g of yellowish-white pearls were obtained.

Production Example 3 (Poly (vinyl acetal) 3)

In a three-necked flask equipped with stirrer, dropping funnel and reflux condenser were charged 18.0 g of Mowiol 10/98 ^® (a polyvinyl alcohol available from Clariant) are dissolved in 180 ml of DMSO at 60 ° C. After adding 2.25 ml of hydrochloric acid (30%), a solution of 30.75 g of the compound prepared in Preparation Example 1 and 5.85 g of 4-formylbenzoic acid in 45 ml of DMSO was slowly added and the mixture was stirred at 60 ° C. for 16 hours. The viscous solution was diluted with 120 ml of DMSO and the polymer was precipitated in water, filtered, washed three times with water and finally dried at 40 ° C., whereby 39.6 g of yellowish-white pearls were obtained.

Table 1 summarizes the characteristics of the photocrosslinkable polymers together.

Table 1

Examples 1-2 and Comparative Examples 1-11 (manufacture of lithographic printing plates)

An electrochemical substrate was used roughened and anodized aluminum foil covered with an aqueous solution of polyvinylphosphonic acid had been treated. The exact composition of the coating solutions used can be seen in Table 3. As a solvent for the photocrosslinkable Layer was a mixture of 25 vol% methyl ethyl ketone, 45 vol% Methanol and 30 vol% ethylene glycol monomethyl ether used, where a 5% by weight solution was produced. The amounts in Table 3 are% by weight provided not stated otherwise. The diazo resin intermediate layer was made from a 3% by weight aqueous solution or a 3 wt .-% solution a mixture of methyl ethyl ketone, methanol and ethylene glycol monomethyl ether (25:45:30 vol%) applied. The applied photocrosslinkable Coating was at 90 ° C for 4 min dried. The diazo resin intermediate layer was dried at 90 ° C. for 5 minutes. The dry layer weight of the photocrosslinkable layer and the Diazo intermediate layer are also given in Table 3. The diazo resins used are Table 2 shows their solubility in water at 20 ° C.

Table 2

The printing plate precursors were placed under a silver film halftone step wedge with a density range of 0.15 to 1.95, the density increments being 0.15, as a negative original with a metal halide lamp (MH burner, available from W. Sack) at 300 mJ / cm ² exposed.

The exposed printing plate precursor was treated for 30 seconds with a developer solution A which contained the following constituents:
3.4 parts by weight of Rewopol NLS 28 ^® (30% solution of sodium lauryl sulfate in water, available from REWO)
1.8 parts by weight of 2-phenoxyethanol
1.1 parts by weight of diethanolamine
1.0 part by weight of Texapon 842 ^® (42% solution of octyl sulfate in water from Henkel)
0.6 part by weight of Nekal BX Paste ^® (sodium salt of an alkyl naphthalene sulfonic acid from BASF)
0.2 parts by weight of 4-toluenesulfonic acid
91.9 parts by weight of water.

Then the developer solution was again Rubbed on the surface with a tampon for 30 seconds and then the rinsed entire plate with water. After this treatment, only the exposed parts remained the plate. The plate was used to evaluate the light sensitivity blackened with a printing ink when wet; was used Einschwärzfarbe 304 from Kodak Polychrome Graphics.

For the production of a printing plate became, as stated above, a copy layer on the aluminum foil applied, exposed, developed and the developed plate after rinsing doctored with water and with an aqueous solution of 5% phosphoric acid and 6% gum arabic grated. The plate thus produced was in a sheet-fed offset printing press clamped. It became an "abrasive" black ink used and printing continued until the plate wears became visible.

To simulate a natural Aging was a second plate of each formulation for 60 minutes at 90 ° C saved, and then exposed the plate in the same manner as described above and diluted with a 1: 1 with water developer solution A developed.

To assess the developability of the plate, the following test was carried out to measure the drop test value:
10 drops of the developer were applied to an unexposed piece of a plate at time intervals of 5 seconds. 5 seconds after the last drop of the developer was applied to the plate surface, the plate was rinsed with cold water with no mechanical treatment. The time in seconds it took to get a clean plate surface in the developer-treated area is called "development time in the drip test".

The results summarized in Table 3 show the following:
The photosensitivity of the printing plates according to the invention is significantly higher than that of printing plates in which no diazo resin intermediate layer is used (see comparative example 1).

The print run achieved with the printing plates according to the invention is higher than that of printing plates in which the diazo resin is not separate Layer was applied but in the photocrosslinkable acetal layer exists (see comparative examples 2 and 11)

By using a diazo resin with a water solubility of> 1g per 100 ml at 20 ° C the development time required is evident in the intermediate layer shortened compared to water-insoluble Diazo resins (see Comparative Examples 3 and 4 compared to Example 2).

The printing plates according to the invention are faster developable and enable a higher one Print run as printing plates, in which radiation-sensitive in both Layers of a diazo resin is present (see Comparative Example 8).

From a comparison of example 1 and 2 with comparative example 7 it becomes clear that through the use of an acetal copolymer with maleimide groups with simultaneous two-layer Building a higher Run length as well as a higher one Sensitivity / resolution is achieved compared to an acrylic acid copolymer with maleimide groups. As a comparison of comparative examples 2 and 6 shows, this is one However, improvement through the use of acetal copolymers is not generally applicable, so that the printing plates according to the invention achieved surprising results are.

For example, from EP-A-1 143 301 known use of a combination of polyurethane and diazo resin in the intermediate layer shows a slower development and a substantially lower print run stability (see comparative example 9) compared to printing plates according to the invention (see example 2).

Comparative Example 10 shows that the use of a cinnamoyl resin (such as in US-A-3,387,976 disclosed) leads to non-developable two-layer printing plates instead of the acetal copolymer used according to the invention.

In summary, it can be said that the printing plates according to the invention in terms of Developability, shelf life, Sensitivity and durability show a significant improvement.

Claims (18)

Radiation-sensitive elements comprising (a) a support (b) a first radiation-sensitive layer on the support comprising at least one negative-working diazo resin of the formula (1)

wherein R ¹ and R ² each independently represent a hydrogen atom, an alkyl radical or an alkoxy radical, R ^{3 represents} a hydrogen atom, an alkyl radical, an alkoxy radical or a radical -COOR, where R is an alkyl radical or aryl radical, X ^- an organic or inorganic Anion is selected so that at least 1 g of the diazo resin is soluble in 100 ml of water at 20 ° C, and Y is a spacer group, and m / n is a number from 0.5 to 2, and (c) one second radiation-sensitive layer, applied to the first radiation-sensitive layer, comprising at least one photocrosslinkable poly (vinyl acetal) containing the following structural units

wherein R ^{4 is} an alkyl radical with up to 4 carbon atoms, an alkyl radical with up to 4 carbon atoms which is substituted by an acid group, a phenyl group or a phenyl group to which an acid group is attached, a phenyl group with or without an acid group with 1 to 2 further substituents selected from halogen atoms, amino, methoxy, ethoxy, methyl and ethyl group, or a group -Z-NR ⁵ -CO-Q-COOH, where Z is an aliphatic, aromatic or araliphatic spacer group, R ⁵ a hydrogen atom or an aliphatic, aromatic or araliphatic radical and Q is a saturated or unsaturated chain or ring-shaped spacer group, k is an integer from 1 to 3, R ⁶ and R ⁷ each independently represent a hydrogen atom or a methyl group and R ⁸ and R ⁹ independently of one another are hydrogen or alkyl radicals having at most 4 carbon atoms or R ⁹ and R ⁸ together with the two carbon atoms to which they are attached represent a 5- or 6-membered carbocyclic ring, where the unit (C) with different radicals R ⁴ can be contained several times independently of one another and the unit (D) with different radicals R ⁶ -R ⁹ and k can be contained several times independently of one another and at least one photosensitizer for photocycloaddition, this second radiation-sensitive layer containing no diazo compound. Radiation sensitive element according to claim 1, wherein the first radiation sensitive layer also at least an additive selected from stabilizing acids, surfactants Agents, thickeners, contrast dyes and pigments, Includes exposure indicators and plasticizers. Radiation sensitive element according to claim 1 or 2, the first radiation sensitive layer other than that at least one diazo resin no other polymeric binders contains. Radiation sensitive element according to one of claims 1 to 3, the second radiation-sensitive layer also at least an additive selected from surface active Agents, thickeners, plasticizers, contrast dyes and - contains pigments and exposure indicators. Radiation sensitive element according to one of claims 1 to 4, wherein the radiation-sensitive element additionally a water-soluble cover layer on the second radiation sensitive layer. Radiation sensitive element according to claim 5, the top layer being organic and / or inorganic particles with 2 to 20 μm Contains particle size. Radiation sensitive element according to one of claims 1 to 6, the dry layer weight of the first radiation sensitive Layer is less than that of the second radiation-sensitive Layer. Radiation sensitive element according to one of claims 1 to 7, being the carrier is an aluminum foil. Radiation sensitive element according to claim 8, wherein the aluminum foil before coating at least one treatment selected from mechanical and chemical roughening, anodizing and accidental with a hydrophilizing layer. A radiation sensitive element according to any one of claims 1 to 9, wherein the anion X ^{- is} a dihydrogen phosphate or tetrachlorozincate. Radiation sensitive element according to one of claims 1 to 10, wherein in the photocrosslinkable poly (vinyl acetal) the unit (A) in a proportion of 0.5 to 20% by weight, the unit (B) in an amount of 15 to 35% by weight, the unit (C) in an amount from 10 to 50% by weight and the unit (D) in a proportion of 25 to 70% by weight, based in each case on the total weight of the acetal copolymer, is present. Process for producing a radiation sensitive Elements as in one of the claims 1-11 defined, full: (1) providing a carrier, (2) Applying one aqueous solution comprising at least one negative working water-soluble Diazo resin as defined in claim 1 or 8, (3) drying (4) Apply a non-aqueous solution comprising at least one photocrosslinkable poly (vinyl acetal) such as defined in claim 1 or 9 and at least one photosensitizer for photocycloaddition, being the solution is free of diazo compounds, and (5) drying. Method according to claim 12, in addition comprising applying a water-soluble top layer. The method of claim 12 or 13, wherein the aqueous solution in Step (2) no other polymeric binders besides the diazo resin contains. Method according to one of claims 12 to 14, wherein it is at the carrier is an aluminum foil that has at least one treatment selected from mechanical and chemical roughening, anodizing and accidental with a hydrophilizing layer. A method according to any one of claims 12 to 15, wherein the aqueous solution also at least an additive selected from stabilizing acids, surfactants Agents, thickeners, contrast dyes or pigments, exposure indicators and plasticizers. Radiation sensitive element available after the method of any one of claims 12 to 16. Lithographic printing plate obtainable by a process full: (a) Providing a radiation sensitive Elements as in one of the claims 1-11 and 17 defined (b) imagewise exposing the radiation sensitive Elements with UV radiation and (c) Developing the exposed Elements with an aqueous alkaline developer.