DE2443785A1 - LIQUID, PHOTO-NETWORKABLE MOLDING COMPOUNDS FOR THE PRODUCTION OF RELIEF PRINTED PLATES - Google Patents

Description

Our sign O ₀ Z. Ί> 0 8IJ W / lSo 67ΟΟ Ludwigshafen, September 11th 1974

The invention relates to a liquid, photo-crosslinkable molding composition for the production of relief printing plates, which essentially consist of a photoinitiator-containing mixture of a consists of olefinically unsaturated urethane resin with polymerizable monomers and is characterized by the content on a special unsaturated polyether polyurethane resin and the content of an N-vinyl lactam as a monomer »

Negative working liquid molding compounds or coating materials for printing plates are known. These materials are mixtures of macromolecular compounds or of mixtures of macromolecular compounds and photopolymerizable olefinically unsaturated monomers or Mixtures thereof which, after exposure or irradiation, become insoluble in solvents in which they are soluble without exposure are. A good compilation of the materials used gives z. B. J. Kosar in his book "Light Sensitive Systems", John Wiley "ft Sons, New York, 1967"

Disadvantageous with the liquid molding compositions used to date for the production of relief printing plates, especially with a view to their use as letterpress printing plates, is their Tendency to be relatively slow in the presence of atmospheric oxygen to cross-link and not to form non-sticky surfaces, or to prevent this, either has to be carried out in a costly manner oxygen-free atmosphere, for example in an atmosphere of nitrogen or carbon dioxide, to be exposed imagewise or you have to image-wise exposure by a for the actinic light carry out a transparent, oxygen-impermeable layer brought into intimate contact with the polymer. .

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A photo-crosslinkable molding compound was therefore proposed for the production of flexible plates for flexographic printing to use a polyurethane prepolymer, a photosensitizer and, if desired, comprises a photopolymerizable olefinically unsaturated monomer * wherein the polyurethane prepolymer by converting a hydroxyl component, the at least 5 ether bonds and one olefinically unsaturated one Has double bond at the end groups, with a polyisocyanate component (DOS 2 115 373) ° Die However, the proposed composition has the disadvantage that the hardness of the printing plates obtained therewith are low (Shore A = 93) “You are therefore only for so-called flexographic printing and not for conventional letterpress printing, which high compressive stresses occur, suitable., Another disadvantage the composition lies in the relatively high exposure times and the remaining tackiness of the exposed surfaces «

The object of the present invention was to provide a liquid, photo-crosslinkable Molding compound for the production of relief printing plates and in particular of relief printing plates suitable for letterpress printing to find who largely meet the following liability conditions?

1) completely tack-free surfaces should also be obtained in air at imagewise exposure of the molding compositions and thus z _{o 0} B subsequent Naehbelichtung the cured image parts or expensive technical devices for exposure below attributable Säuerstoffausschluß könnenο

2) The required exposure time of the molding compounds should be as short as possible, ura long cycle times for production to be able to achieve the finished printing plate, as it is required especially in the current Zeitumgsdruek are,

3) The relief printing plates obtained should have hardnesses of Shore D = 65 in order to be able to cope with the high compressive stresses, that occur in conventional letterpress printing, none or

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to get only very slight shifts in tonal value. The imagewise hardened coating material may, however not be brittle to avoid broken points and other mechanical damage to sensitive parts of the relief image to avoid the printing plate as much as possible «,

4) The printing reliefs prepared should be sufficiently hard at temperatures up to about 8O ⁰ C, to produce by pressing suitable films or specialty boards matrices, as is common in the newspaper printing "By subsequently pouring the die with practice usual metal alloys may then several faithful duplicates of the printing plate can be obtained.

5) The printing inks commonly used should be good from the relief printing plates on the material to be printed be transferred without causing the printing plates to swell and thereby the printing result is impaired «

It has now been found that liquid containing photoinitiator. ¹ Mixtures of a certain unsaturated polymer, as it is characterized in more detail below, and an N-vinyllactam or an N-vinyllactam-containing monomer mixture are particularly suitable as molding compounds for the production of relief printing plates, in particular for letterpress printing, and largely the desired properties for their have use according to the invention.

The invention thus relates to liquid, photo-crosslinkable Molding compositions for the production of relief printing plates, essentially consisting of a photoinitiator-containing liquid mixture of

(A) an unsaturated polymer and

(B) a photopolymerizable monomer with an or several olefinically unsaturated double bonds or mixtures thereof,

which are characterized in that the mixture consists of:

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(A) 40 to 80 and in particular 50 to 80 percent by weight of a soluble ^, olefinically unsaturated and practically no free NCO group-containing polyurethane with a molecular weight γοη about 400 to 1 0,000 and in particular 1000 to 750O ₅ which was prepared by reaction

(A1) a soluble olefinically saturated aliphatic polyether with a molecular weight of about 300 to 4000 and in particular of about 400 to 3000, which contains 2 to 4 and preferably 3 hydroxyl groups per molecule,
with

(A2) an organic polyisocyanate with about β to J> 6 and preferably 8 to 15 carbon atoms and in particular a diisocyanate
and

(A3) a monoacrylate and / or monomethacrylate of an aliphatic diol having 2 to 10 and in particular 2 to 4 carbon atoms
and

(B) 20 to 60 and in particular 20 to 50 percent by weight of one or a mixture of photopolymerizable monomers with the proviso that 40 to 100 and in particular more than 50 to 100 percent by weight of the total amount of monomers (B) from an N-vinyl lactam with 6 to There are 8 and in particular 6 carbon atoms _ο

Another object of the invention is the use of the molding compositions mentioned for the production of relief printing forms and in particular those for direct letterpress printing, as well as a method for producing relief printing plates by imagewise exposure of a layer of the above porram compositions applied to a flat plastic or metal support and subsequent removal of the unexposed portions the layer ^ whereby, in a known manner, a brief pre-exposure of the layer or post-exposure of the developed relief printing plate can also be carried out, even if it is not necessary in many cases _e

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The olefinically unsaturated polyurethanes (A) can be prepared in a known manner by reacting the polyisocyanates (A2) with the hydroxyl-containing polyethers (A1) and hydroxy (meth) acrylates (A3), generally about equimolar amounts of NCO groups can be applied to the content of OH groups. In known manner it is naturally also possible, for "B. _e first the Dlolmono (meth) acrylate (A3) react with excess diisocyanate and then the isocyanate-functional reaction product with the hydroxyl group-containing polyether (A1), optionally with the addition of further diisocyanate to Bring reaction. The approximately simultaneous reaction of components A1, A2 and A3 is preferred.

The implementation for the production of the polyether urethanes can be solvent-free take place. However, you can also in the presence of photopolymerizable monomers (B), at least predominantly do not react with isocyanate groups under the reaction conditions, the monomers can act as a "diluent". The reaction in the presence of N-vinylpyrrolidone has proven itself. When moving in the presence of customary organic solvents which are inert to NCO groups under the reaction conditions are, the solvents are advantageously distilled off in vacuo after the reaction.

Suitable solvents are e.g. B. esters such as ethyl acetate or Ethers, such as tetrahydrofuran.

The reaction will usual catfish at temperatures of about carried out up to 70 ° C. Higher temperatures should be because of the The risk of the reaction mixture gelling should be avoided as far as possible. To speed up the reaction rate can use the usual catalysts, such as tertiary amines, or Metal compounds, such as dibutyltin dilaurate, can be used. The addition of conventional polymerization inhibitors, such as hydroquinone, methoxyphenol, hydroquinone monomethyl ether, p-chloron, Copper (I) -chiorId, methylene blue, ß-naphthylarain,

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ß-naphthol, phenol or organic nitroso compounds is appropriate in some cases _o

Suitable aliphatic polyethers (A1) for the production of Polyurethanes (A) are for example?

Polyethylene glycols of the formula

HO (CH ₂ CH ₂ O) _n H

(where η is an integer from 6 to 90) Polypropylene glycols of the formula

HO (CH ₂ CHO) _n H CH ₃

(where η is an integer from 5 to 70) Polytetramethylene glycols of the formula

HO (CH ₂ CH ₂ CH ₂ CH ₂ O) _n H

(where η is an integer from 4 to 55) polyoxyethylated glycerols of the formula

CH ₂ O (CH ₂ CH ₂ O) ₁ H

CHO (CH ₂ CH ₂ O) _1n H

CH ₂ O (CH ₂ CH ₂ O) _n H

(where l _s m and η each mean zero or a positive integer and equation 1 ■ ¥ m + η = an integer from 5 to 90)

polyoxypropylated glycerols of the formula

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CH ₂ O (CH ₂ CHO) ₁ H

CH ₃

CH ₂ O (CH ₂ CHO) _n H
CEL

(in which 1, m and η have the meanings given above) polyoxyethylated triraethylolpropanes of the formula

CH ₂ O (CH ₂ CH ₂ O) ₁ H CH CH ₂ C-CH ₂ O (CH ₂ CH ₂ O) _1n H. CH ₂ O (CH ₂ CH ₂ O) _n H

(in which 1, m and η have the meanings given above) polyoxypropylated trimethylolpropanes of the formula

CH ₂ O (CH ₂ CHO) ₁ H

I ^CH 3

CH ₂ O (CH ₂ CHO) _n H

CH ₃

(in which 1, m and η have the meanings given above)

Bi- and trifunctional copolyethers are also suitable Based on propylene oxide and ethylene oxide, such as hydroxy compounds of the formula

(where 1, m and η are each a positive integer of at least 1 mean and the equation 1 + m + η = a whole

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Number from 1 to 10)

These hydroxyl-containing polyethers can either be used for can be used alone or in the form of mixtures,

For the preparation of the polyether polyurethanes (A) suitable organic polyisocyanates (A2) are, for. Bo 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-disocyanato-diphenylmethane, Xylylene diisocyanate, 4,4'-phenylcyclohexylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, Isophorone diisocyanate, hexamethylene diisocyanate, Biurets based on z. B. Hexamethylene diisocyanate and mixtures of polyisocyanates «Preferred are aliphatic diisocyanates, by which aliphatic and cycloaliphatic diisocyanates are understood.

Examples of suitable monoesters of acrylic acid or methacrylic acid and an aliphatic diol (A ^) are 1,4-butanediol monoacrylate, Ethylene glycol monoacrylate, 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate «Also mixtures of these Hydroxyl compounds (A3) can be used for the production of the polyether urethane (A), In addition, dioders Tri (meth) acrylates of aliphatic triols or tetraols, such as 1,1,1-trimethylolpropane diacrylate or dimethacrylate and pentaerythritol triacrylate or pentaerythritol triacrylate can be used.

The photopolymerizing monomers contained in the molding compositions according to the invention in addition to the unsaturated polyurethane (A) or mixtures of monomers should be at least 40 and preferably to more than 50 percent by weight of N-vinyl lactam, such as N-vinylcaprolactam or especially N-vimylpyrrolidone exist. Molding compounds, at denea over 50 to about 100 percent by weight the amount of monomers (B) consisted of N-vinylpyrrolidone, have proven to be very effective as comonomers in amounts up to 50 and up to 50 percent by weight of the monomer amount are particularly preferred suitable esters of acrylic acid and / or methacrylic acid, such as methyl methacrylate, n-butyl acrylate or methacrylate, 2-hydroxypropyl acrylate, butanediol-1,4-diacrylate or diethylene glycol dimethacrylate. Monomers of the aromatic allyl type

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2U3785

Compounds such as diallyl phthalate can also be used favorably. Also suitable in smaller amounts are amides of (meth) acrylic acid, such as acrylamide or N-methylol (meth) acrylamide, as long as the resulting mixtures remain liquid. Aliphatic vinyl ethers, for example, are also quite suitable Diols with 2 to 8 carbon atoms, such as butanediol 1,4-divinyl ether and also vinyl esters of aliphatic monocarboxylic acids, such as Vinyl acetate or vinyl propionate in smaller amounts. Mixtures of photopolymerizable monomers can of course also be used are used and the properties of the molding compounds in the desired manner for certain due to their type and quantity Applications can be modified. Advantageous monomers are the isocyanate group-free reaction products of organic ones and preferably aliphatic polyisocyanates, such as those mentioned above as components A2, with hydroxyl groups (Meth) acrylates, such as those above as components A3 mentioned, e.g. B. the reaction products from 1 mole of isophorone diisocyanate and 2 moles of 1,4-butanediol monoacrylate or propylene glycol monoacrylate. Molding compositions according to the invention which contain 20 to 50 percent by weight of the Total amount of monomers contained in these monomers, with these are also produced simultaneously in the same reaction vessel during the production of the unsaturated polyurethanes can. In the case of particularly suitable molding compositions, the proportion of these monomers is about 10 to 35 percent by weight the amount of polyurethane.

The molding compositions or coating materials according to the invention are used in a known manner to increase their sensitivity to radiation photoinitiators or sensitizers added in amounts of about 0.1 to 10 percent by weight. Such sensitizers are for example o (-ketaldonyl alcohols, such as benzoin and benzoin ethers, O ^ -substituted benzoin compounds, such as eC-methylolbenzoin and o (-methylolbenzoin ether, o <-methylbenzoin or p (-phenylbenzoin. Also so-called triplet sensitizers, as, for example, N. Turro in his book "Molecular Photochemistry?" * W. A. Benjamin, Inc., New York, 1967 Page 132 describes are suitable.

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Also other common auxiliaries and additives, such as Polymerization inhibitors, plasticizers and / or coloring · = Substances can optionally ^ but not necessarily the invention Form masses for the production of relief printing plates are added,

To produce laminates for the production of relief printing forms, the photocrosslinkable molding compositions according to the invention can be applied in a manner known per se, for example with the aid of a doctor blade, to dimensionally stable substrates, such as metal plates or plastic films, in the desired layer thickness. In the case of layer thicknesses of over JO / um, the use of an adhesion promoter ₉ as described, for example, in DOS 1 572 3O3 or in DOS 1 597 515 is recommended.

By imagewise exposure of the laminates thus obtained through a negative original, depending on the performance of the used Light source can last up to several minutes, the exposed area is fixed in an imagewise fashion by a Photo-crosslinking »For development, the unexposed and thus non-crosslinked image parts of the layer are removed, which is useful with the help of a solvent (developer) or, mechanically, by blowing off or blowing out and applying absorbent materials can be made «A kind of mechanical Removal of the uncrosslinked sloe components (dry development) is z. Bo in the Belgian patent specification 803 682.

In addition to high-energy W-containing lamps, such as carbon arc lamps, mercury vapor lamps, xenon lamps or fluorescent tubes, including low-heat light sources, such as fluorescent tubes with a high blue component ^ are used.

The molding compositions according to the invention and the process according to the invention are suitable both for the production of relief forms for letterpress printing and for dry offset printing (indirect letterpress printing). They point towards familiar

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ORlQiNAL INSPECTED

th liquid systems for printing plate production have the advantage that relief forms with very short exposure times can be achieved with a high degree of definition. Even if air is exposed, printing plates can be quickly removed Manufacture with tack-free surfaces, with the resulting Reliefs are sufficiently hard and yet not brittle when properly exposed. They also have good transmission capabilities for printing inks without being more swollen by them. The molding compositions according to the invention In addition, they generally do not require the full-tone standard of other liquid masses for printing plates Pre-exposure. Post-exposure of the developed relief printing plate is useful in some cases and for special ones Requirements for the properties of the printing plates are favorable. In the case of dry development, post-exposure is advisable to harden any remaining resin residue leads to tack-free in a very short time even in the presence of atmospheric oxygen without the use of special techniques Surfaces.

The parts and percentages mentioned in the examples and comparative tests below relate to the weight, if not stated otherwise.

example 1

a) By reacting 1 mol of a polyether polyol (A1) from Trimethylol propane and 1,2-propylene oxide of molecular weight of 7 ^ 0 with 4 moles of hexamethylene diisocyanate and subsequent reaction with 5 moles of 2-hydroxypropyl acrylate a polyurethane (molecular weight about 1600) was produced. 75 parts of the polyurethane were mixed with 25 parts N-vinylpyrrolldone, 1 part benzoin methyl ether and 0.05 part of the potassium salt of N-nitrosocyclohexylhydroxylamine mixed.

b) On a steel sheet 20 × 20 cm in size coated with an adhesive lacquer in accordance with DOS 1 597 515 is used as a spacer

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a metal ring 15 cm inside diameter and 0.5 mm Placed height. The resulting flat container is filled with the specified liquid photosensitive mixture filled and covered with a 10 / µm thick polyester film. By placing a raster negative in a commercially available copier (Pa. Moll "Piccolo", equipped with 8 low-pressure fluorescent tubes from Philips, TLA 20 W / 05) exposed. After peeling off the polyester film and washing out the unexposed parts of the image with ethanol, small letterpress plates are obtained. Like the comparative A compilation of some properties of the molding compositions and printing plates in Table 1 shows the result non-sticky sheets that only swell slightly in organic solvents (printing inks).

Comparative experiment A

The procedure is exactly as in Example 1, except that instead of 25 parts of N-vinyl pyrrolidone, 20 parts of 2-hydroxypropyl acrylate are used and 5 parts of acrylamide mixed in as photopolymerizable monomers.

The properties of the molding compounds and printing plates are shown in Table 1.

Example 2

A mixture of 75 parts of a polyurethane that by Implementation of 1 mol of the polyether specified in Example 1a) (A1) with 4 moles of isophorone diisocyanate and then Reaction with 1.2 moles of 2-hydroxypropyl methacrylate and 4 moles of 2-hydroxypropyl acrylate and 25 parts N-Vinylpyrrolidon are 1 part Benzoinraethylather and 0.05 part of the potassium salt of N-nitrosocyclohexylhydroxy1-amine mixed in.

These molding compositions are processed into printing plates as indicated in Example 1b). The properties of the molding compositions and printing plates are shown in Table 1 _β The molding compositions

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are characterized by a particularly short exposure time as well as a high degree of hardness and very little swelling from it made relief printing plates in ethyl glycol acetate.

Example 3

The procedure is exactly as indicated in Example 2, but the liquid mixture contains instead of 25 parts of N-vinylpyrrolldon 16 parts of N-vinylpyrrolidone, 5 parts of 2-hydroxypropyl acrylate and 4 parts of acrylamide. Some properties Table 1 shows the molding compounds and printing plates.

The table clearly shows the enormous increase in photosensitivity when using N-vinylpyrrolidone as a monomer additive. The oxygen sensitivity of photocrosslinking on the surface is also strongly depressed, as the stickiness test shows. Sensitivity too compared to organic solvents (printing inks!) is special when only N-vinylpyrrolidone is used low, as the last column in Table 1 shows.

Comparative experiment B

The procedure is as indicated in Example 3, but contains the liquid mixture as added monomers 20 parts of 2-hydroxypropyl acrylate and 5 parts of acrylamide. Some properties Table 1 shows the molding compounds and printing plates.

Comparative experiment C

A mixture of 90 parts of a prepolymer according to Examples 1 to 3 of DOS 2 115 373 * prepared from 2 moles Tolylene diisocyanate, 1 mole of a polyether polyol with a molecular weight of 1000 and 2.2 moles of hydroxyethyl aorylate and 1 0 parts of methyl methacrylate, 1 part of benzoin methyl ether and 0.015 part of p-benzoquinone is processed into printing plates as indicated in Example 1b). Like the in The properties given in Table 1 show that printing plates with a tacky surface result in organic

Solvents (printing inks!) Swell quite strongly.

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Table 1

Some properties of the molding compositions and printing plates according to the examples 1 to 3 and comparative tests A to C

Exposure time (min)

a)

Surface tack

Pendulum hardness
after king
(lake)

Swelling ^c '
in HUO in AGAe

a) Until the complete formation and anchoring of a 1 cm 5 $ grid field (JO lines / cm)

b) Surface tack of a full tone area after 10 minutes of exposure without covering with a polyester film

c) Weight increase after storage in water (HpO) or ethyl glycol acetate for 24 hours (AGAc)

example 1 2 tack free 46 10.4 11.7 O Comparison
attempt A 7.5 slightly sticky - 6.2 35.8 CO
CX) Example 2 2 tack free 90 8.5 11.2 ^ Example 3 7.5 tack free 79 7.7 42.3 O
CO Comparison
attempt B 12th slightly sticky 80 6.0 47.1 ex" Comparison
try C 30th very sticky
pulls strings 9.6 14th 71.8

enco - ■

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Example 4

1 00 parts of the polyether urethane (A) mentioned in Example 2 with 55 parts of N-vinylpyrrolidone and 2 parts of benzoin methyl ether mixed.

This mixture is drawn onto an aluminum plate provided with an intermediate lacquer and brought to a layer thickness of about 500 μm using known aids. The layer is then covered with a polyester film with a thickness of 10 μm and exposed imagewise through a transparent image carrier in a vacuum frame. A pre-exposure does not take place. The exposure times are: for tone value 3 % 55 seconds. and for tone value 5 % 45 see at J2. L / cm and for point 300 / around diameter 50 see.

The imagewise exposed printing plate is developed by removing the cover sheet with ethanol as a solvent for the uncrosslinked parts, nachbelichtet 4 minutes under fluorescent tubes and post-treated for 3 minutes at 100 ⁰ C.

A printing plate with good printing properties is obtained, which has the following properties:

Shore D hardness 80

Ball indentation hardness (p / mm) oonn

(according to DIN 50 351) ^ ^yuu

Tensile strength (kp / cm ² ) 480

Elongation at break (#) 17

Rebound load ± 2ity (%) 44 Pendulum tack (see) 84

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Claims (6)

Claims (A) 40 to 80 percent by weight of an olefinically unsaturated and practically no free NCO groups containing polyurethane having a molecular weight of about 400 to 1 0,000 which has been prepared by implementing a - (A1) soluble olefinically saturated aliphatic polyether with a molecular weight of about 300 to 4000, which contains 2 to 4 hydroxyl groups per molecule,
with (A2) an organic polyisocyanate with about 6 to 36 carbon atoms
and (A3) a monoacrylate and / or monomethacrylate. an aliphatic diol with 2 to 10 carbon atoms and (B) 20 to 60 percent by weight of one or a mixture of photopolymerizable monomers with the proviso, that 40 to 100 percent by weight of the total amount of monomers consists of an N-vinyllactam with 6 to 8 carbon atoms * 2. Liquid, photo-crosslinkable molding compositions according to claim 1, characterized in that the polyurethane (A) through 609814/0981 " ¹⁷ " - η - Ο.Ζ. 30th Implementation of the polyether (Al) with the isocyanate group-containing Reaction product from approximately equal molar quantities Diisocyanate (A2) and monoester (A3) was produced. 3. Liquid, photo-crosslinkable molding compositions according to claim 1 or 2, characterized in that the N-vinyl lactam is N-vinyl pyrrolidone. 4. Liquid, photo-crosslinkable molding compositions according to one of claims 1 to 3, characterized in that the polyurethane (A) was prepared from an aliphatic diisocyanate as component (A2). 5. Use of the molding compositions according to the preceding claims for the production of printing plates for letterpress and dry offset printing. 6. Process for the production of relief printing plates by imagewise exposure of a layer of a photoinitiator applied to a flat plastic or metal support containing liquid mixture consisting essentially of (A) an unsaturated polymer and (B) a photopolymerizable monomer with a or more olefinically unsaturated double bonds or mixtures thereof and then Removing the unexposed parts of the layer, characterized in that the liquid mixture consists of (A) 40 to 80 percent by weight of an olefinically unsaturated and practically no free NCO group Polyurethane having a molecular weight of about 1,000 to 10,000, which has been made by Implementation of a (A1) soluble olefinically saturated aliphatic polyether with a molecular weight of about 8098U / 0981 - 19 - - -Ϊ8 - 0.Ζ.30 815 500 to 4000, of 2 to 4 hydroxyl groups per Molecule contains, (A2) an organic polyisocyanate with about 6 to 6 carbon atoms
and (A3) a monoacrylate and / or monomethacrylate of an aliphatic diol with 2 to 10 carbon atoms and (B) 20 to 50 percent by weight of one or a mixture of photopolymerizable monomers with the proviso that 40 to 100 percent by weight of the total amount of monomers from an N-vinyllactam with 6 to 8 carbon atoms consists. BASF Aktiengesellschaft 6098U / 0981