CA2038284A1

CA2038284A1 - Photopolymerizable mixture and recording material produced therefrom

Info

Publication number: CA2038284A1
Application number: CA002038284A
Authority: CA
Inventors: Rudolf Zertani; Dieter Mohr; Klaus Rode
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1990-03-20
Filing date: 1991-03-14
Publication date: 1991-09-21
Also published as: KR910017240A; DE4008815A1; PT97079A; EP0447930A3; EP0447930A2; KR100187787B1; EP0447930B1; ES2103279T3; AU631731B2; ATE155259T1; BR9101072A; DK0447930T3; AU7364991A; JPH04221958A; DE59108765D1

Abstract

Abstract of the Disclosure A photopolymerizable mixture is described which contains a polymeric binder, a compound polymerizable by a free-radical mechanism and having at least one polymerizable group and at least one photooxidizable group in the molecule, and a metallocene compound as a photoinitiator. The mixture is suitable for producing printing plates and photoresists and is distinguished by a particularly high light sensitivity, above all in the visible spectral region, and a very good thermal stability. It can be imaged with laser radiation in the visible region.

Description

-` 2~3~

PHOTOPOLYMERIZ~BLE ~IXTURE AND RECORDING
MATERIAL PRODUCED TH:EREFROM

Back~round of the Invention The invention relates to a photopolymerizable mixture which contains a polymeric binder, a polymerizable compound, in particular an acrylate or alkacrylate ester, and a photoinitiator.
It is known that the polymerization af ethylenically unsaturated compounds by a free-radical mechanism can be triggered by irradiationwith visible light in the presence of photoreducible dyes and reducing agents, for example amines (U.S.
3,097,096). However, these initiator combinations are essentially llsed only in aqueous solution or in lS combination with water-soluble binders. Initiator combinations of photoreducible dyes and other reducing agents are described in U.S. 3,597,343 and 3,488,269.
In EP-A 287,817, photopolymerizable mixtures are described which contain (meth)acrylate esters '~

.

;, , .

2 ~ 1~

with urethane groups and photooxidizable groups, in particular tertiary amino groups and, if appropriate, urea groups in the molecule, polymeric binders and, as photoinitiators, a combination of a photoreducible dye, of a radiation-sensitive trihalogenomethyl compound and of an acridine, phenazine or quinoxaline compound.
In EP-A 321,826, similar mixtures with (meth)acrylate esters are described, which do not contain any urethane groups.
In U.S. 3,717,558, metallocenes of elements of subgroups IIa to VIIIa in combination with a further photoinitiator having a carboxylic acid chloride group are described for use in photopolymerizable recording materials. These initiator combinations are highly sensitive to oxygen and hydrolysis and, as a result, are less suitable for the production of printing plates and resist materials. Further metallocenes and their use as photoinitiators in photopolymerizable mixtures are described in EP-A 119,162 and 122,223.
These are titanocenes of good stability in air, which show a spectral sensitivity in the range from W light to visible light. As ligands, they contain, inter alia, cyclopentadienyl radicals and fluorinated phenyl radicals. In EP-A 242,330 and 269,573, photopolymerizable mixtures are also described which contain a photoinitiator mixture composed of a titanocene and a liquid photoinitiator of the hydroxy- or aminoacetophenone type. In the case of these materials, the achievable light sensitivity for rapid imaging by means of a low-~ ~ - 2~3~2(g~

energy and at the same time inexpensive argon ion laser is not sufficient.
In the earlier European Patent Application 89117004.5, which is not a prior publication, photopolymerizable mixtures are described which contain: a polymeric binder; a compound polymerizable by a free-radical mechanism and having at least one polymerizable group; a photoreducible dye; a trihalogenomethyl compound cleavable by radiation; and a metallocene compound, in particular a titanocene or zirconoce~e.
As Comparison Example 2 in this application, a combination of a styrene/n-hexyl methacrylate/
methacrylic acid terpolymer of acid number lgO as binder, triethylene glycol dimethacrylate as polymerizable compound and dicyclopentadienyl-bis-pentafluorophenyl-titanium as photoinitiator is described. In the earlier German Patent Application P 40 07 428.5, which is not a prior publication, photopolymerizable mixtures of the above composition are described which contain a dicyclopentadienyl-bis-2,4,6-trifluorophenyl-titanium or -zirconium as the metallocene.

Summary of the_Invention Accordingly, it is an object of the present invention to provide a photopolymerizable mixture that is suitable for producing printing plates of high print run capacity and photoresists of high resistance to processing solutions in the hardened - ' ' ' ' , 2~2~

state, which mixture displays a high light sensitivity in the near ultraviolet and visible spectral regions.
Another object of the present invention is to provide a mixture having a simpler composition than known mixtures and having good thermal storage stability.
A further object of the present invention is to provide a mixture suitable especially for laser beam recording in the visible region.
Yet another object of the present invention is to provide a photopolymerizable recording material comprising the foregoing mixture.
In accomplishing the foregoing objectives, there has been provided, in accordance with one aspect of the present invention, a photopolymerizable mixture comprising a polymeric binder, a free-radical polymerizable compound having at least one polymerizable group and at least one photooxidizable group, and a metaIlocene photoinitiator, with the exception of a mixture of a styrene/n-hexyl methacrylate/methacrylic acid terpolymer of acid number 1~0 as the binder, triethylene glycol dimethacrylate as the polymerizable compound and di-cyclopentadienyl-bis-pentafluorophenyl-titanium as the photoinitiator.
In accordance with another aspect of the present invention there is provided a photopolymerizable recording material comprising a support and a photopolymerizable layer, wherein the photopolymerizable layer comprises a mixture as defined above.

2 8 ~

Other objects, features and advantages of the present invention will become apparent to those s~illed in the art from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.

Detailed Description of the Preferred Embodiments The metallocenes used as initiators are known as such and also as photoinitiators, for example from U.S. 3,717,558, 4,590,287 and 4,707,432, the contents of which are incorporated by reference.
Metallocenes of elements of group IVB of the periodic table, in particular compounds of titanium : and 2 irconium, are preferred. Such compounds are : 20 described in EP-A 119,162, 122,223, 186,626, 242,330, 255,486, 256,981 and 269,573, which are incorporated by reference. Of the numerous known metallocenes, in particular titanocenes, compounds of the general formula I

~1 R3 Me (I) R2 / ~ R4 are preferred. In this formula, 2 ~3 3 ~

Me is a quadridentate metal atom, especially Ti or Zr, Rl and R2 are identical or different cyclopentadienyl radicals which 5can be substituted, and R3 and R4 are identical or different phenyl radicals which can also be substituted.

The cyclopentadie.nyl groups can be 10substitut~d especially by alkyl radicals having 1 to 4 carbon atoms, chlorine ~toms, phenyl radicals or cyclohexyl radicals or linked to one another by alkylene groups. They are preferably unsubstituted or substituted by alkyl radicals or chlorine atoms.
15R3 and R4 are preferably phenyl groups which contain at least one fluorine atom in the o-position to the bond and otherwise can be substituted by halogen atoms, such as F, Cl or Br, alkyl or alkoxy groups having 1 to 4 carbon atoms or a 20polyoxyalkylene group whi~h may be e~herified or esterified. The polyoxyalkylene group has in general 1 to 6 oxyalkylene units and is preferably located in the 4-position of the phenyl radical and can be etherified or esterified by an alkyl or acyl radical 25having 1 to 18 carbon atoms; in particular, it is a polyoxyethylene group. Phenyl radicals substituted by 4 or 5 fluorine atoms are particularly preferred.
The quantitative proportion of metallocene compound is in general between about 0.01 and 10% by 30weight, preferably about 0.05 to 8% by weight, : , 2~3~
.

relative to the non-volatile constituents of the mixture.
If an increase in the sensitivity of the mixture in the visible spectral region is desired, this can be achieved by addition of a compound of the dibenzalacetone or coumarin type. This addition effects a higher resolution of the copy and a sensitization of the mixt:ure continuing into the visible spectral region up to wavelengths of about 600 nm. Suitable representatives of these compounds are 4,4'-disubstituted dibenzalacetones, e.g.
diethyl-amino-4'-methoxy-dibenzalacetone, or coumarin derivatives such as 3-acetyl-7-diethylaminocoumarin, 3-benzimidazolyl-7-diethylaminocoumarin or carbonyl-bis-~7-diethyl-aminocoumarin). The quantity of this compound is in the range from about 0 to 10% by weight, preferably from about 0.05 to 4% by weight, relative to the non-volatile constituents of the mixture.
Those polymerizable compounds are suitable for the purposes of the invention which contain at least one photooxidizable group and, if desired, at least one urethane group in the molecule. Possible photooxidizable groups are especially amino groups, urea groups, thio groups which can also be constituents of heterocyclic rings, and enol groups.
Examples of such groups are triethanolamino groups, triphenylamino groups, thiourea groups, imidazole groups, oxazole groups, thiazole groups, acetylacetonyl groups, N-phenylglycine groups and ascorbic acid groups. Polymerizable compounds 2~3~

having primary, secondary and especially tertiary amino groups are preferred.
Examples of compounds having photooxidizable groups are acrylate and alkacrylate esters of the formula II

~S R7 R(m_n)Q[~-CR2-lO-)a-CONH(X~--NHCOo)b-X2(-OOC-C=CR2,C]n (II) in which Dl Q is -N-, -~-~-N-, -N N- or ~S-, R is an alkyl group, hydroxyalkyl group or aryl group, R5 and R6 are each a hydrogen atom, an alkyl group or an alkoxyalkyl group, R7 is a hydrogen atom, a methyl group or an ethyl group, Xl is a saturated hydrocarbon group having 2 to 12 carbon atoms, X2 is a (c~ valent saturated hydrocarbon group in which up ' , 2~3~28 ~

to 5 methylene groups can be replaced by oxygen atoms, Dl and D2 are each a saturated hydrocarbon group having 1 to 5 carbon atoms, E is a saturated hydrocarbon group having 2 to 12 carbon atoms, a cycl~aliphatic group having 5 to 7 ring members and containing, if appropriate, up to two N, O
or S atoms as ring members, an arylene group having 6 to 12 carbon atoms or a heterocyclic aromatic group having 5 or 6 ring members, a is 0 or a number from 1 to 4, b is 0 or 1, c is an integer from 1 to 3, m is 2, 3 or 4 depending on the valency of Q, and n is an integer from 1 to m, it being possible for all the symbols of the same definition to be identical or different from one another. The compounds of this formula, their preparation and their use are described in detail in EP-A 287,818, corresponding to U.S. Serial No.
07/173,936, which is hereby incorporated by reference. If; in the compound of the general formula I, more than one radical R or more than one radical of the type shown in square brackets is ::

- 2 ~

bound to the central group Q, these radicals can be differant from one another.
Compounds in which all the substituents of Q
are polymerizable radicals, i.e. in which m = n, are in general preferred. In general, a is 0 in not more than one radical and ]preferably in none of the radicals. Preferably a is 1.
If R is an alkyl group or hydroxyalkyl group, this has in general 2 to 8 carbon atoms and preferably 2 to 4 carbon atoms. The aryl radical R
can in general be mononuclear or dinuclear, preferably mononuclear, and can be substituted, if desired, by alkyl groups or alkoxy groups having up to 5 carbon atoms or by halogen atoms.
If R5 and R6 are alkyl groups or alkoxyalkyl groups, these can contain 1 to 5 carbon atoms. R7 is preferably a hydrogen atom or a methyl group, especially a methyl group.
X~ is preferably a straight-chain or branched aliphatic or cycloaliphatic radical having preferably 4 to 10 carbon atoms.
X2 has preferably 2 to 15 carbon atoms, of which up to 5 can be replaced by oxygen atoms. If they are pure carbon chains, those having 2 to 12 and preferably 2 to 6 carbon atoms are in general used. x2 can also be a cycloaliphatic group having 5 to 10 carbon atoms, in particular a cyclohexylene ~roup. Dl and D2 can be identical or different and form, together with the two nitrogen atoms, a saturated heterocyclic ring having 5 to 10 and preferably 6 ring members.

~3~3~

If E is an alkylene group, this preferably has 2 to 6 carbon atoms and, as an arylene group, it is preferably a phenylene group. Cyclohexylene groups are preferred as cycloaliphatic groups, and those aromatic heterocyclic compounds are prefPrred which have N or S as hetero atoms and 5 or 6 ring members. The value of c is preferably 1.
Further suitable compounds having photooxidizable groups are compounds of the formula III

R(rn-n)Q[ (~CH2~1C)a/ (-cH2-c~-o)}~/-H~n R6 c~2 (III) OOC-CH=CH2 in which Q, R, R5, R6, R7, m and n are as defined above and Q can additionally be a group ~ -N-in which E' is a group of the formula IV

-CH2-CHOH-CX2-(O- ~ -C- ~ -o-cH2-cHoH-cH2 )c c~3 (IV) - :
' .

2 ~ $ ~

in which c is as defined for formula II; a' and b' are integers from 1 to 4, The compounds of this formula, their preparation and their use are described in detail in EP-A 316,706, corresponding to U.S. Serial No.
07/270,351, which is hereby incorporated by reference.
Further suitable! compounds having photooxidizable groups are acrylate and alkacrylate esters of the formula V

Q~[(-xl CH2O)a-CONH(-Xl-NHCOO)b-X2-OOC-C=CH2]n, (V) in which Q' is D
/ ~ ~
-N-, \ D2/ or z N- , Xl is CjH2; or ClH2ll0-CONH(-Xl-NHCOO)},-XZ-OOC-C=CH2, 2~3~2~

D3 is a saturated hydrocarbon group having 4 to 8 carbon atoms, which forms a 5-membered or 6-membered ring togather with the nitrogen atom, æ is a hydrogen atom or a radical of the formula C~H~-O-CONH(-X~-NHCO)b-X2-OOC=CH2 i and k are integers from 1 to 12, n' is 1, 2 or 3 depending on the valency of Q', and R7, X~, X2, Dl, D2, a and b are as defined for formula II. All the symbols of the same definition can be identical or different from one another, and a is O
in at least one substituent on the group Q.
Of the compounds of the formula V, those are preferred which contain at least one urethane group in addition to a urea group. Urea groups are to be regarded as groups of the formula \ N - CO - N ~

in which the valencies on the nitrogen are saturated by substituted or unsubstituted hydrocarbon radicals. However, one valency on a nitrogen atom 2~&`2~

can also be bound to a further carboxamide group (CONH), so that a biuret structure results.
The symbol a in formula V is preferably 0 or 1; i is preferably a number from 2 to 10.
5The polymerizable compounds of the formula V
are prepared analogously to the compounds of the formula II. The compounds of the formula V and their preparation ars described in detail in EP-A
355,387, corresponding to U.S. Serial No.
1007/381,828, hereby incorporated by reference.
The quantitative proportion of polymerizable compounds in the photopolymerizable layer is in general about 10 to 80% by weight, preferably about 20 to 70~ by weight, relative to the non-volatile 15constituents.
Examples of binders which can be used are chlorinatedpolyethylene, chlorinated polypropylene, polyalkyl (meth)acrylates in which the alkyl group is, for example, methyl, ethyl, n-butyl, i-butyl, n-20hexyl or 2-ethylhexyl, copolymers of said alkyl (meth)acrylates with at least one monomer such as acrylonitrile, vinyl chloride, vinylidene chloride, styrene or butadiene; polyvinyl chloride, vinyl chloride/acrylonitrile copolymers, polyvinylidene 25chloride, vinylidene chloride/acrylonitrile copolymers, polyvinyl acetate, polyvinyl alcohol, polyacrylonitrile,acrylonitrile/styrenecopolymers, acrylonitrile/butadiene/styrene copolymers, polystyrene, polymethylstyrene, polyamides (for 30example nylon 6), polyurethanes, methylcellulose, ethylcellulose, acetylcellulose, polyvinyl formal and polyvinyl butyral.

~3~

Those binders are particularly suitable which are insoluble in water, soluble in organic solvents and soluble or at least swellable in aqueous-alkaline solutions.
5Binders containin~ carboxyl groups should be mentioned especially, for example copolymers of (meth)acrylic acid and/o:r unsaturated homologs thereof, such as crotonic acid, copolymers of maleic anhydride or half-esters thereof, reaction products 10of polymers containing hydroxyl groups with dicarboxylic acid anhydrides, and mixtures thereof.
Reaction products of polymers which carry H-acid groups and which were reacted wholly or partially with activated isocyanates, such as, for 15example, reaction products of polymers containing hydroxyl groups with aliphatic or aromatic sulfonyl isocyanates or phosphinic acid isocyanates, are also suitable.
Furthermore, the following are suitable:
20polymers containing hydroxyl groups, such as, for example, copolymers of hydroxyalkyl (meth)acrylates, copolymers of allyl alcohol, copolymers of vinyl alcohol, polyurethanes or polyesters, and also epoxy resins, provided that they carry a sufficient number 25of free OH groups or are modified in such a way that they are soluble in aqueous-alkaline solutions, or those polymers which carry aromatically bonded hydroxyl groups, such as, for example, condensation products of carbonyl compounds capable of 30condensation, especially formaldehyde, acetaldehyde or acetone, with phenols, or copolymers of hydroxystyrenes. Finally, copolymers of :, ~ , . . . . .

, 2 ~

(meth)acrylamide with alkyl (meth)acrylates can also be used.
The polymers described above are suitable particularly when they have a molecular weight between about 500 and 200,000 or higher, preferably about 1000 to 100,000, and have either acid numbers between about 10 and 250, preferably from about 20 to 200, or hydroxyl numbers between about 50 and 750, preferably from about 100 to 500.
The following may be mentioned below as preferred alkali-soluble binders: Copolymers of (meth)acrylic acid with alkyl (meth)acrylates, (meth)acrylonitrile or t.he like, copolymers of crotonic acid with alkyl (meth)acrylates, (meth)acrylonitrile or the like, copolymers of vinylacetic acid with alkyl (meth)acrylates, copolymers of maleic anhydride with unsubstituted or substituted styrenes, unsaturated hydrocarbons, unsaturated ethers or esters, esterification products of the copolymers of maleic anhydride, esterification products of polymers containing hydroxyl groups with anhydrides of di- or poly-carboxylic acids, copolymers of hydroxyalkyl (meth)acrylates with alkyl (meth)acrylates, (meth)acrylonitrile or the like, copolymers of allyl alcohol with unsubstituted or substituted styrenes, copolymers of vinyl alcohol with alkyl (meth)-acrylates or other polymerizable unsaturated compounds, polyurethanes provided that they have a sufficient number of free OH groups, epoxy resins, polyesters, partially saponified vinyl acetate copolymers, polyvinyl acetals with free OH groups, , .

2~3~

copolymers of hydroxystyrenes with alkyl ~meth)acrylates or the like, phenol/formaldehyde resins, for example novolaks. The quantity of the binder in the light-s~nsitive layer is in general about 20 to 90% by weight, preferably about 30 to 80% by weight.
Depending on the planned use and depending on the desired properties, the photopolymerizable layers can contain diverse substances as additives.
Examples are: inhibitors for preventing thermal polymerization of the monomers, hydrogen donors, dyes, colored and uncolored pigments, color formers, indicators, plasticizers and chain transfer agents.
Appropriately, these constituents should be selected such that they absorb as little as possible in the actinic radiation region important for the initiation step.
Within the scope of this description, actinic radiation is to be understood as that radiation which has an energy at least corresponding to that of visible light. Visible light and long-wave W
radiation are suitable above all, but also short-wave W radiation, laser radiation, electron radiation and X-radiation. The light sensitivity extends from about 300 nm to 700 nm and thus spans a very wide range. As a result of the combination of photooxidizable monomers and metallocenes, a highly sensitive photopolymerizable mixture is obtained, whose activity is superior to that of known mixtures, particularly in the long-wave spectral region at or above 455 nm.

~3~
.

As a result of replacing the initiator combination of photoreducible dye, trihalogenomethyl compound and acridine, phenazi.ne or quinoxaline compound, which comhination is used according to EP-A 287,817 (corresponding to U.S. Serial No.
07/173,559, which is incorporated by reference) in otherwise the same photopolymerizable mixtures, mixtures of higher light sensitivity are obtained.
The mixtures according to the invention also show a considerably higher light sensitivity as compared with mixtures of conventional monomers and known initiator combinations containing metallocenes.
The following may be mentioned as possible applications of the material according to the invention: recording layers for the photomechanical production of printing forms for letterpress printing, planographic printing, gravure printing and screen printing, of relief copies, for example for producing texts in braille, of individual copies, tanning images, pigment images, and the like. The mixtures can also be used for the photomechanical production of etch resists, for example for the fabrication of nameplates, of copied circuits and for chemical milling.
The mixtures according to the invention are of particular importance as recording layers for the production of planographic printing plates and for the photoresist technique. Examples of suitable supports for the recording material according to the invention are aluminum, steel, zinc, copper and plastic films, for example of polyethylene terephthalate or cellulose ace~tate, and also screen , - . .

3 ~

printing supports such as perlon gauze. In many cases, it is advantageous to subject the support surface to a pretreatment (chemical or mechanical) which has the object of adjusting the adhesion of the layer to the correct level, improving the lithographic properties of the support surface or reducing the reflectivity of the support in the actinic region of the copying layer (antihalo protection).
The light-sensitive materials are produced in a known manner. Thus, the layer constituents can be taken up in a solvent, and the solution or dispersion can be applied to the intended support by casting, spraying, dipping, roller application and the like, and th~n dried. Due to the broad spectral sensitivity of the recording material according to the invention, all light sources familiar to those skilled in the art can be used, for example tube lamps, pulsed xenon lamps, metal halide-doped mercury vapor high-pressure lamps and carbon arc lamps.
Furthermore, with the light-sensitive mixtures according to the inven~ion, exposure in conventional projection apparatus and enlarging apparatus under the light of the metallic filament lamp and contact exposure with ordinary incandescent lamps are possible. The exposure can also be carried out with the coherent light of a laser. Lasers of the correct power are suitable for the purposes of the present invention, for example argon ion lasers, krypton ion lasers, dye lasers, helium/cadmium lasers and helium/neon lasers, which emit in ` ~3~8~

particular between 250 and 650 nm. The laser beam can be controlled by means of a predetermined program~ed line motion and/or scanning motion.
It is in general advantageous to protect the mixtures during the light polymerization effectively against the action of atmospheric oxygen. In the case of the use of the mixture in the form of thin copying layers, it is advisable to apply a suitable cover film of low oxygen permeability. This can be self-supporting and can be peeled off before the copying layer is developed. Polyester films, for example, are suitable for this purpose. The cover film can also be composed of a material which dissolves in the developer fluid or can be removed during the development at least in the non-hardened areas.
Examples of materials suitable for this purpose are polyvinyl alcohol, polyphosphates, sugars and the like. Such covering layers have in general a thickness from about 0.1 to 10 ~m, preferably about 1 to 5 ~m. The further processing of the materials is carried out in the known manner.
For development, they are treated with a suitable developer solution, for example with organic solvents, but preferably with a weakly alkaline aqueous solution, the unexposed areas of the layer being removed and the exposed areas remaining on the support. The developer solutions can contain a small proportion, preferably less than 5% by weight, of water-miscible organic solvents. They can also contain wetting agents, dyes, salts and other additives.

2~3~

During the development, the entire covering layer is removed together with the unexposed areas of the photopolymerizable layer.
Illustrative examples of the invention are given below. Parts by weight (p.b.w.) and parts by volume (p.b.v.) here have the same relationship as the g and the ccm. Unless otherwise stated, percentage and quantity data are to be understood as weight units.

ExamPle 1 (comparison examE~

Electrochemically roughened and anodized aluminum with an oxide layer of 3 g/m2, which had been pretreated with an aqueous solution of polyvinylphosphonic acid, was used as the support for printing plates. The support was coated with a solution of the following composition. All the operations were here carried out under red light:

2.84 p.b.w. of a 22.3% solution of a 10:60:30 styrene/n-hexyl methacrylate/
methacrylic acid terpolymer of acid number 190 in methyl ethyl ketone, 1.49 p.b.w. of trimethylolethane triacrylate, 0.07 p.b.w. of phenylmethanesulfonyl chloride and 0.02 p.b.w. of dicyclopentadienyltitanium dichloride in 11 p.b.w. of butanone and 11 p.b.w. of butyl acetate.

. ~ ' ' ;,:

2~3~
.

The application was carried out by whirler-coating in such a way that a dry weight of 2.4 to 2.8 g/m2 was obtained. The plate was then dried for two minutes at 100C in a circulating-air drying cabinet. The plate was then coated with a 15%
aqueous solution of polyvinyl alcohol (12% of residual acetyl groups, K value 4). After drying, a covering layer of a weight of 2.5 to 4 g/m2 was obtained. The printing plate obtained was exposed by means of a 2 kW metal halide lamp at a distance of 110 cm for 20 seconds under a 13-step exposure wedge with density increments of 0.15. For testing the sensitivity of the printing plates in visible light, a 3 mm thick edge filter made by Schott, having an edge transparency of 455 nm, was mounted on the exposure wedge. After the exposure, the plate was heated for one minute to lOO~C. It was then developed using a developer of the following composition:

120 p.b.w. of sodium metasilicate x 9 H2O, 2.13 p.b.w. of strontium chloride, 1.2 p.b.w. of nonionic wetting agent (coconut fatty alcohol polyoxyethylene ether with about 8 oxyethylene units) and 0.12 p.b.w. of antifoam in 4000 p.b.w. of deionized water.

The plate was inked with fatty printing ink.
The fully crosslinked wedge steps indicated in Table 2 were obtained.

.
' 2~2~

Examples 2 to 8 A solution of the following composition was applied by whirler-coating to the support indicated in Example 1 under the same conditions as indicated therein, in such a way that a layer weight of 2.5 y/m2 was obtained in each case:

2.84 p.b.w. of the terpolymer solution indicated in Example 1, 1.49 p.b.w. of monomer according to Table 1 and 0.06 p.b.w. of dicyclopentadienyl-bis-pentafluoro phenyl-titanium in 22 p.b.w. of propylene glycol monomethyl ether.

The plate was then coated as in Example 1 with a polyvinyl alcohol layer and, as therein, exposed and developed. After inking with fatty printing ink, the fully crosslinked wedge steps indicated in Table 2 were obtained.

2 ~ $ ~

Table 1 No. Monomers used 1. Reaction product of 1 mol of triethanolamine with 3 mol of isocyanatoethyl methacrylate, 2. Reaction product of 1 mol of N,N'-bis-~-hydroxyethylpiperidine with 2 mol of isocyanatoethyl methacrylate, 3. Reaction product of 1 mol of triethanolamine with 3 mol of glycidyl methacrylate, 4. Reaction product of 1 mol of hexamethylene diisocyanate with 1 mol of 2-hydroxyethyl methacrylate and 0.33 mol of triethanolamine, 5. Trimethylolethane triacrylate, 6. Reaction product of 1 mol of hexamethylene diisocyanate with 0.5 mol of 2-hydroxyethyl methacrylate and 0.25 mol of 2-piperidine-ethanol, 7. Pentaerythritol triacrylate.

. ~ ;
, 2 ~ $ ~

Table 2 Exposure results after 20 seconds exposure time Example Monomer Wedge steps Wedge steps filter _ 4 _ 3-4 1-2 7 6 >13 11-13 8 (V) 7 1-2 *
1 (V) 3-4 - _1-2 *no image V = comparison example Exam~le 9 The coating solution from Example 7 was applied by whirler--coating to a biaxially stretched, 35 ~m thick polyethylene terephthalate film in such a way that a layer weight of 30 g/m2 was obtained after drying. The layer was further dried for three minutes at 100C in a circulating-air drying cabinet. The layer was then Iaminated at 115C at 1.5 m per minute to a cleaned support which was composed of an insulating material plate with a 35 ~m copper coating.
The layer was exposed for 30 seconds by means of a 5 kW metal halide lamp (140 cm distance) under ~: .

2 ~3 3 ~ Ç~

a 455 nm edge filter, as described in Example 1, with a step wedge as the original and, after peeling off the film, developed for 20 seconds with 0.8%
soda solution in a spray processor. 4 fully crosslinked wedge steps were obtained. The crosslinked layer was resistant to the iron (III) chloride solution conventional in circuit board technology. The etch resistance was good.

Example 10 A solution of the following composition was applied by whirler-coating to the support indicated in Example 1 under the same conditions as therein, in such a way that a Iayer weight of 2.5 g/m2 was obtained:

2.84 p.b.w. of the terpolymer solution indicated in Example 1, 1.49 p.b.w. of monomer 6 according to Table 1, 0.01 p.b.w. of dicyclopentadienyl-bis-pentafluoro-phenyl-zirconium in 11.0 p.b.w. of butanone and 11.0 p.b.w. of butyl acetate.

After application of a covering layer of polyvinyl alcohol, the plate was exposed for 20 seconds and then developed, in the same way as in Example 1. The exposure was carried out under a 455 -26~

8 1~

nm edge filter. 4 to 5 fully crosslinked wedge steps were obtained.

Example 11 Solutions of the following composition were applied by whirler-coating to the support indicated in Example 1 under the same conditions as therein, in such a way that a layer weight of 2.5 g/m2 was obtained in each case:

2.84 p.b.w. of the terpolymer solution indicated in Example 1, 1.49 p.b.w. of monomer 1 according to Table 1, 0.01 p.b.w. of dicyclopentadienyl-bis-2,4,6-trifluorophenyltitanium and 22 p.b.w. of propylene glycol monomethyl ether.

After application of a covering layer of polyvinyl alcohol, the plates were exposed for 10 seconds and then developed, in the same way as in Example 1. The exposure was carried out under a 3 mm thick edge filter with the edge transparency at 455 nm. 8 - 9 fully crosslinked wedge steps were obtained.

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Claims

1. A photopolymerizable mixture comprising a) a polymeric binder, b) a free-radical polymerizable compound having at least one polymerizable group and at least one photooxidizable group, and c) a metallocene photoinitiator, with the exception of a mixture of a styrene/n-hexyl methacrylate/methacrylic acid terpolymer of acid number 190 as the binder, triethylene glycol dimethacrylate as the polymerizable compound and di-cyclopentadienyl-bis-pentafluorophenyl-titanium as the photoinitiator.

2. A mixture as claimed in claim 1, wherein said metallocene is composed of a central metal atom and four ligands having an aromatic electron system.

3. A mixture as claimed in claim 2, wherein said metal atom is an atom from group IVB of the periodic table of the elements.

4. A mixture as claimed in claim 3, wherein said metal atom is a titanium atom or zirconium atom.

5. A mixture as claimed in claim 2, wherein two of said ligands are substituted or unsubstituted cyclopentadienyl radicals.

6. A mixture as claimed in claim 2, wherein two of said ligands are phenyl radicals which are unsubstituted or substituted by halogen atoms or polyoxyalkylene radicals.

7. A mixture as claimed in claim 5, wherein two of said ligands are phenyl radicals which are unsubstituted or substituted by halogen atoms or polyoxyalkylene radicals.

8. A mixture as claimed in claim 6, wherein said halogen atoms are fluorine atoms.

9. A mixture as claimed in claim 7, wherein said halogen atoms are fluorine atoms.

10. A mixture as claimed in claim 1, wherein said metallocene compound (c) is present in an amount from about 0.01 to 10 wt% relative to the non-volatile constituents of the mixture.

11. A mixture as claimed in claim 10, wherein said metallocene compound (c) is present in an amount from about 0.05 to 8 wt% relative to the non-volatile constituents of the mixture.

12. A mixture as claimed in claim 1, wherein said compound (b) which is polymerizable by a free-radical mechanism contains an amino group, urea group, thio group or enol group as said photooxidizable group.

13. A mixture as claimed in claim 1, wherein said binder is insoluble in water and soluble in aqueous alkaline solutions.

14. A mixture as claimed in claim 1, which contains 10 to 80% by weight of polymerizable compound, 20 to 90% by weight of polymeric binder and 0.01 to 10% by weight, relative to the non-volatile constituents of the mixture, of metallocene.

15. A mixture as claimed in claim 1, further comprising (d) a dibenzalacetone or coumarin compound as a sensitizer.

16. A mixture as claimed in claim 15, wherein said compound (d) is present in an amount from about 0 to about 10 wt% relative to the non-volatile constituents of the mixture.

17. A mixture as claimed in claim 16, wherein said compound (d) is present in an amount from about 0.05 to 4 wt% relative to the non-volatile constituents of the mixture.

18. A mixture as claimed in claim 1, consisting essentially of the recited components.

19. A mixture as claimed in claim 15, consisting essentially of the recited components.

20. A photopolymerizable recording material comprising a support and a photopolymerizable layer, wherein said photopolymerizable layer comprises a mixture as claimed in claim 1.

21. A recording material as claimed in claim 20, further comprising, on said photopolymerizable layer, a transparent layer of low permeability for atmospheric oxygen, which layer is soluble in a developer fluid for said photopolymerizable layer.