Photopolymerisable blends with special diaminobenzophenone compounds.

0001The invention relates to photopolymerizable mixtures with at least one photopolymerizable olefinically unsaturated compound and optionally a polymeric binder which contain special diaminobenzophenone compounds as a sensitizer, and to the use of such mixtures for mask-forming layers, for copying films and multilayer recording materials.

0002Photopolymerizable mixtures with olefinically unsaturated compounds, optionally polymeric binders and photoinitiator systems which contain diaminobenzophenone compounds as sensitizers are known. The synergistic system consisting of 4,4'-bis (dimethylamino) benzophenone (Michler's ketone) and benzophenone is a very effective photoinitiator system especially for thin photopolymerizable layers due to its high light absorption, radical formation rate and its neutral behavior towards dark storage stability. The highly absorbent Michler's ketone acts as a sensitizer for the low or low light absorbing benzophenone in the same actinic wave range. Especially in the production of copier and mask films, the use of photoinitiator systems in quite high concentrations, e.g. Michler's ketone in a concentration of over 6% by weight, is desired in order to expose the hardened mask film parts with subsequent exposure of UV-polymerizing layers under the mask film To make UV light impermeable.

0003However, the use of higher concentrations of Michler's ketone in photoinitiator systems in thin photopolymerizable layers often leads to difficulties, since Michler's ketone is unsatisfactory in its toxic properties, because of its limited solubility in many organic solvents and its limited compatibility even with some polar binders for photopolymerizable mixtures . So it happens, for example at higher concentrations of Michler's ketone in photopolymerizable mixtures for clouding stored layers, while benzophenone can also be processed in larger concentrations without problems.

0004From DE-OS 27 30 897 it is known to use derivatives of Michler's ketone in which the methyl groups in Michler's ketone are replaced, for example, by hydroxyethyl, hydroxyethoxyethyl, hydroxypropyl or hydroxypropoxypropyl groups. Although these compounds already have improved tolerability, they are not yet satisfactory in all cases. It was an object of the present invention to find diaminobenzophenone compounds as photosensitizers for photopolymerizable mixtures which, with good action as photosensitizers, have improved compatibility with prolonged storage.

0005It has now been found that photopolymerizable mixtures based on at least one photopolymerizable olefinically unsaturated compound and optionally a polymeric binder containing at least one diaminobenzophenone compound as photosensitizer have the desired properties if they are a diaminobenzophenone compound of the formula (I)<chemistry id="chem0001" num="0001"><img file="EP0143201A2_D0001.tif" /></chemistry>contain what<ul id="ul0001" list-style="none"><li>R¹ = H, C₁- to C₄-Alkyl or phenyl,</li><li>R² = H or C₁- to C₂-Alkyl,</li><li>R³ = H or C₁- to C₄Alkyl, preferably H or methyl,</li><li>C.⁴ = H, C₁- to C₄-Alkyl, _C0₂R⁷ or -CONHR⁸,</li><li>_R⁵ = _H, -_COR⁶ or -CONHR⁸,</li><li>R⁶ = C₁- to C₈-Alkyl or phenyl,</li><li>R⁷ = H or _R⁶,</li><li>R⁸ = aliphatic or aromatic radical with 2 to 22 C atoms,</li><li>x = 1, 2 or 3,</li><li>n = 0.1 to 2 mean.</li></ul>

0006The diaminobenzophenone compounds of the formula (I) used according to the invention are reaction products of alkoxylated diaminobenzophenones with α, β-olefinically unsaturated carboxylic acids, in particular maleic acid, acrylic or methacrylic acid, or their derivatives, which may also be esterified with alkanols, carboxylic acids and / or isocyanates or were converted to the amide. Reaction products of bis- (N-hydroxyethylamino) benzophenones with maleic anhydride or the anhydrides or chlorides of acrylic or methacrylic acid are preferred, the N-hydroxyalkyl groups being partially or completely esterified, with reaction of free hydroxyl groups, free carboxyl groups with alcohols, carboxylic acids or their derivatives or isocyanates.

0007The following equations give preferred examples of esterification:<chemistry id="chem0002" num="0002"><img file="EP0143201A2_D0002.tif" /></chemistry><chemistry id="chem0003" num="0003"><img file="EP0143201A2_D0003.tif" /></chemistry><ul id="ul0002" list-style="none"><li>II: 4,4'-bis (N-methyl-N-β-hydroxyethylamino) benzophenone (described in DE-OS 27 22 421)</li><li>III: Maleic anhydride</li><li>V: acrylic acid chloride</li></ul>

0008The free carboxyl group of the compound of the formula (IV) and the free hydroxyl groups of the compounds of the formulas (IV) or (VI) can also, for example, be esterified or reacted with isocyanates to give amides or urethanes.

0009Of the reaction products of the above type, the condensation products have from 1.1 to 1.4 and in particular about 1.3 moles of maleic anhydride with 1 mole of bis (N-alkyl-N-β-hydroxyethylamino) benzophenone, which are at about 110 to 140 ° C were preferably implemented in the absence of solvent, particularly proven.

0010The diaminobenzophenone compounds used according to the invention, owing to their good compatibility with conventional photopolymerizable mixtures, allow use even in higher concentrations, for example 10 to 15% by weight, based on the solids content of the mixtures, without excretion even if stored for weeks or even months at room temperature or the diaminobenzophenone compound crystallizes out.

0011It is particularly advantageous to use a further known photoactivator in addition to the diaminobenzophenone compounds in the mixtures according to the invention, such as benzoin, benzoin ether, anthraquinone, benzil, benzilmonoalkyl ketals, fluorenone, fluorene, diacetyl and in particular benzophenone or a low in the range from 300 to 380 nm absorbent benzophenone derivative, such as those with an extinction coefficient £ _{360 nm &lt;}200, whereby the molar ratios and amounts known for the combination with Michler's ketone can be used.

0012The diaminobenzophenone compounds used according to the invention surprisingly also improve the compatibility of Michler's ketone, so that it has proven to be quite advantageous to achieve a high optical density with high light sensitivity in mask films, as a photoinitiator system, a combination of a diaminobenzophenone compound used according to the invention Formula (I) with in particular about 20 to 50% by weight of Michler's ketone, based on the amount of the diaminophenone compound of the formula (I) and preferably with about 1/3 to 2/3 the sum of the amounts of Michler's ketone and diaminobenzophenone compound of the formula (I) to be used in benzophenone.

0013The photopolymerizable mixtures according to the invention contain, in a known manner, photopolymerizable olefinically unsaturated compounds such as monomers and / or oligomers which are at least partially poly-olefinically unsaturated and which, in the presence of photoinitiator systems, can quickly be converted into products which are difficult or insoluble in developers by UV radiation. The photopolymerizable olefinically unsaturated compounds which are known per se for binders which can be crosslinked with UV light and for photopolymer printing plates are suitable, the type and amount depending on the intended use of the mixtures and on the polymer binder which may also be used and with which they are compatible should be.

0014Suitable olefinically unsaturated compounds are di- and polyacrylates and methacrylates, such as can be prepared by esterifying diols or polyols with acrylic acid or methacrylic acid, such as the di- and tri (meth) acrylates of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol with a molecular weight up to about 500, 1,2-propanediol, 1,3-propanediol, neopentyl glycol (2,2-dimethylpropanediol), 1,4-butanediol, 1,1,1-trimethylolpropane, glycerin or pentaerythritol; furthermore the monoacrylates and monomethacrylates of such diols and polyols, such as, for example, ethylene glycol or di-, tri- or tetraethylene glycol monoacrylate, monomers with two or more olefinically unsaturated bonds which contain urethane groups and / or amide groups, such as those from aliphatic diols of the above mentioned type, organic diisocyanates and hydroxyalkyl (meth) acrylates produced low molecular weight compounds. Also mentioned are acrylic acid, methacrylic acid and their derivatives such as (meth) acrylamide, N-hydroxymethyl (meth) acrylamide or (meth) acrylates of monoalcohols with 1 to 6 carbon atoms.

0015Mixtures according to the invention which contain polar monomers and / or polar polymeric binders, such as urethane acrylates or epoxy acrylates, have proven very useful. With regard to suitable binder components and the use of the systems according to the invention, reference is made to DT-OS 15 22 359, 22 00 478, 23 58 948, 24 41 148, the diaminobenzophenone compounds used according to the invention being able to replace the Michler ketone described there.

0016Suitable polymeric binder components are, for example, polyurethanes, unsaturated polyesters, polyester urethanes and carboxyl-containing polymers such as copolymers of acrylic acid, methacrylic acid and in particular maleic acid or their derivatives.

0017In a known manner, the photopolymerizable mixtures according to the invention can also contain conventional additives, such as thermal polymerization inhibitors, dyes, plasticizers, etc.

0018Of particular importance is the greater solubility of the diaminobenzophenones used according to the invention when they are used for adequate curing of highly pigmented photopolymerizable systems, in particular when using highly absorbent pigments, for example in UV-curing printing inks.

0019The photopolymerizable mixtures according to the invention are particularly suitable in layer thicknesses of less than 10 μm for UV-curing printing inks, but also for offset printing plate coatings and as a photoresist material. They have proven particularly useful for mask-forming layers, for copying films and multilayer recording materials. It is thus possible to laminate a highly sensitive mask film with a high photosensitizer and initiator content with a thin polymer film as a support onto conventional UV-crosslinkable photopolymer printing plates, which can be exposed imagewise by means of an original or with a UV laser with an exposure time of a few seconds without that a photo-crosslinking of the underlying photo-crosslinkable relief-forming layer of the photopolymer printing plate occurs. After development of the mask film with, for example, aqueous alkali, the photopolymer printing plate can then be fully exposed to UV radiation through the mask layer produced and, after the mask film has been peeled off, can be developed in a customary manner into a relief form or relief printing form. Expediently, the copying films or maskable mask films over the photopolymerizable layer on the transparent carrier film carry a cover film which can be peeled off before exposure, such as one with, for example a polyester film provided with a polyamide substrate.

0020Unless otherwise stated, the parts and percentages given in the examples below relate to the weight. Parts by volume are by weight like liters to kilograms.

example 1

1.1 Preparation of a reaction product from 4,4'-bis (N-methyl-N-β-hydroxyethylamino) benzophenone and maleic anhydride

0021164 Parts of 4,4'-bis (N-methyl-N-β-hydroxyethylamino) benzophenone and 63.7 parts of maleic anhydride are mixed in a reaction vessel and stirred in the absence of solvent for 10 minutes at 130 ° C. The viscous reaction product is poured onto an aluminum foil and the glassy, ​​hard mass is crushed after solidification.

0022Analysis:<ul id="ul0003" list-style="none"><li>calc. (for ^C.₂₄,₂^H₂₆,₆^N₂⁰₆,9) _C.: 63.7% H: 5.8% N: 6.1%</li><li>found C: 62.9% H: 5.9% N: 6.0%</li></ul>

1.2 Production of a mask-forming layer

0023A filtered is applied to a 125 µm thick polyethylene terephthalate film pretreated by corona discharge, which was first provided with a 2 to 3 µm thick polyamide substrate layer, then with a 10 µm thick layer of polyvinyl alcohol (degree of saponification 88 mol%, viscosity 18 cP) Solution of 180 parts of a copolymer of 40% n-butyl acrylate, 35% styrene and 25% methacrylic acid, 120 parts of 1,1,1-trimethylolpropane triacrylate, 48 Parts of the reaction product prepared according to 1.1, 12 parts of Michler's ketone, 30 parts of benzophenone, 6.3 parts of a nitrosamine in 900 parts of methyl ethyl ketone, the 50 parts of a saturated solution of the dye 3-amino-5-nitro-2,1-benzisothiazole → N - (2-Methoxycarbonylethyl) -N-ethylaniline in methyl ethyl ketone were added, layered in such a way that a 6 pm thick layer is formed after drying. A 12 µm thick transparent polyethylene terephthalate film is laminated onto this. The photopolymerizable layer can be stored for months at room temperature without the photosensitizer crystallizing out.

1.3 Use of the mask-forming layer in the production of a relief printing plate

0024The mask-forming layer produced according to 1.2 is laminated with the 12 μm thick polyester film down onto a commercially available high-pressure photopolymer plate which can be photocrosslinked by irradiation with UV light. To produce the printing plate, the 125 μm thick polyester film with the polyamide substrate is peeled off and the photopolymerizable mixture of the mask film is exposed imagewise for about 3 seconds. After the polyvinyl alcohol layer has been washed off, the unexposed portions of the photopolymerizable layer of the mask film are washed out with aqueous alkali (pH = 11), and the high-pressure photopolymer plate is then exposed over the entire area through the resulting mask film for 3 to 5 minutes. After the mask has been removed, the high-pressure photopolymer pla_tte developed in the usual way and processed into relief printing.

Example 2

2.1 Preparation of a reaction product from 4,4'-bis (N-methyl-N-β-hydroxyethylamino) benzophenone and acrylic acid chloride

0025130.4 parts of 4,4'-bis (N-methyl-N-β-hydroxyethylamino) benzophenone, 0.2 part of hydroquinone and 91 parts of triethylamine are dissolved in 300 parts by volume of dimethylformamide in a reaction vessel. 58 parts of acrylic acid chloride are slowly added in portions to the solution, which is cooled to 0 ° to 5 ° C., and the mixture is then stirred at 25 ° C. for 15 hours. After adding 800 parts by volume of methylene chloride, the solution is stirred into 1000 parts by volume of water, the lower phase is separated off and washed twice with 500 parts by volume of water each. Then it is washed with 600 parts by volume of 5% aqueous sodium carbonate solution. After adding 0.2 parts of hydroquinone, the solvent is removed in a water jet vacuum and the residue is dried in a vacuum of 0.1 torr at 30 ° C. There remain 115.6 parts of a viscous reaction product which, according to NMR analysis, represents the compound of formula (VI) with n about 1.2.

NMR analysis (solvent CDC13): signals at 3.06 ppm (100%);

00263.57 ppm (broad, 22.6%); 3.62 ppm (broad, 48%); 3.8 ppm (broad, 22.6%); 4.37 ppm (broad, 48%); 5.84 (doublet, 19.4%); 6.10 ppm (multiplet, 19.4%); 6.38 ppm (doublet, 19.4%); 6.65 to 6.8 ppm (multiplet, 74.2%); 7.6 to 7.8 ppm (multiplet, 74.2%).

2.2 Production of a mask-forming layer

0027The procedure is as in Example 1.2, but instead of 48 parts of the reaction product prepared according to 1.1 and 12 parts of Michler's ketone, 40 parts of the reaction product prepared according to 2.1 are used. The resulting layers can be stored for many weeks at room temperature without crystallization.