CA2041191A1 - Process for the production of printing forms or photoresists by imagewise irradiation of a photopolymerizable recording material - Google Patents

Abstract

Abstract of the Disclosure A process for the production of printing forms or photoresists by imagewise irradiation of a photopolymerizable recording material is disclosed.
The photopolymerizable recording material comprises a layer that contains a polymer binder, an ethylenically unsaturated compound that is polymerizable by free radicals and that contains at least one terminal ethylenic double bond, and a metallocene compound as photoinitiator. The material is heated after imagewise irradiation for a short time, exposed before, simultaneously with or after the imagewise irradiation for a short time to visible light having a wavelength of at least 400 nm without an original, and then developed. The process allows a substantial shortening of the image exposure or irradiation and is suitable in particular for the projection exposure or laser exposure of printing plates.

Description

PROCESS FOR THE PRODUCTION OF PRINTING
FORMS OR PHOTORESISTS BY IMAGEWISE
IRRADIATION OF A PHOTOPOLYMERIZABLE
RECORDING MATERIAL

Backaround of the Invention The present invention relates to a process for the production of printing forms or photoresists by imagewise irradiation of a photopolymerizable recording material containing a polymer binder, a compound polymerizable by free radicals, in particular an acrylic or alkacrylic ester, and a photoinitiator or photoinitiator combination.
DE 1,214,085 (US 3,144,331) discloses a technique for restoring the sensitivity of photopolymerizable recording materials comprising a printing plate support and a photosensitive layer, the sensitivity of which has decreased due to , : absorption of molecular oxygen. The photosensitive layer is exposed to 70 to 98% of the amount of actinic radiation necessary for initiating photopolymerization. For example, exposure takes .
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place through the transparent printing plate support, the wavelengths of the actinic radiation used being such that only 10 to 70% of the radiation is absorbed by the photopolymerizable layer. In this process, one diffuse and one imagewise exposure are in principle carried out. The diffuse or preexposure is then followed by imagewise exposure up to the full amount of radiation.
US 4,716,097 discloses a process in which a photopolymerizable layer containing a dye is first exposed to light having a wavelength above 400 nm and an intensity of at least 1500 lumen/m2 for approximately 60 minutes diffuse and then imagewise.
DE 2,412,571 describes a process for the curing of a light-curable layer of a printing plate in which blanket exposure is carried out for a short time and is followed by imagewise exposure until the layer in the exposed regions has been virtually completely cured. ~he blanket exposure lasts not more than 90% of the time necessary for curing the polymer layer, if the same intensity of radiation is used for both the preexposure and the imagewise exposure.
EP 53,708 describes a process for the production of relief copies in which the photopolymerizable layer of a recording material is subjected to imagewise exposure, is heated to elevated temperatures for a short time before or after exposure, and is then developed.
- 30 EP 284,938 describes photopolymerizable mixtures containing (meth)acrylic esters with urethane groups, tertiary amino groups and possibly '' ' ?~ ~ L~

urea groups in the molecule, polymer binders and a photoreducible dye, if desired in combination with a radiation-sensitive trihalomethyl compound, as the photoinitiator. EP 321,827 describes similar mixtures containing (meth)acrylic esters but no urethane groups.
EP 364,735 describes photopolymerizable mixtures containing - a polymer binder, - a compound polymerizable by free radicals and containing at least one polymerizable group, - a photoreducible dye, - a trihalomethyl compound which can be cleaved by radiation, and - a metallocene compound, in particular a titanocene or zirconocene.
The metallocenes used are those carrying two substituted or unsubstituted cyclopentadienyl radicals and two substituted phenyl radicals as ligands. German Patent Application P 4,007,428.5, describes further photopolymexizable mixtures of the above composition containing a dicyclopentadienyl-bis-2,4,6-trifluorophenyltitanium or -zirconium as metallocene. These mixtures have extremely high photosensitivity.
German Patent Application P 4,011,023.0 describes an after-treatment apparatus for imagewise-exposed printing plates comprising an exposure station for full-area exposure of the printing plate and a heating station. The full-area exposure is carried out using light in the spectral 2 ~
range from 500 to 700 nm. No detailed information about the composition of the photopolymerizable printing plates which are processed is given.

Summary of the Invention It is therefore an object of the invention to provide a process for the production of printing forms, in particular planographic printing forms, or photoresists by imagewise exposure of a photopolymerizable recording material which already has very high photosensitivity and to propose suitable processins steps, by means of which the energy requirement during exposure of the image can be reduced substantially, thus achieving a correspondingly higher photosensitivity in practice.
These and other objects according to the present invention are achieved by a process for the production of printing forms or photoresists, comprising the steps of imagewise irradiating a photopolymerizable recording material comprising a photopolymerizable layer containing a polymer binder, an ethylenically unsaturated compound that is polymerizable by free radicals and that contains at least one terminal ethylenic double bond, and a metallocene compound that forms free radicals upon 2S irradiation; heating the recording material after the imagewise irradiation for a short time; and then developing the recording material; wherein the material is also blanket-exposed to visible light having a wavelength of at least 400 nm for a short time.

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,' , i ' ~ ' Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Detailed Descri~tion of the Preferred Embodiments According to the invention, a process for the production of printing forms or photoresists by imagewise irradiation of a photopolymerizable recording material is proposed. The photo-polymerizable layer contains a polymer binder, an ethylenically unsaturated compound polymerizable by free radicals and containing at least one terminal ethylenic double bond, and a polymerization initiator or initiator combination that forms free radicals upon irradiation. The material is heated after the imagewise irradiation for a short time and then developed.
The process according to the invention uses a metallocene compound as the radical-forming polymerization initiator and entails exposing the material before, simultaneously with, or after the imagewise irradiation for a short time to visible light having a wavelength of at least 400 nm without .~;

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an original. This latter exposure is termed "blanket-exposure" in this description The heating and exposure without an original can advantageously be carried out in an apparatus such as that described in German Application P 4,011,023Ø The sequence of the exposure steps is as desired; preferably the material is first subjected to imagewise exposure or irradiation, then exposed without an original and finally heated.
lo The imagewise irradiation can preferably be carried out by projection using standard copying light or laser radiation. Examples of projection light sources which can be used are mercury vapor lamps, xenon lamps, metal ha~ide lamps, flashlight lamps, c~rbon arc lamps and the like, it being possible for the intensity and/or duration of exposure to be kept low. Suitable laser light sources are in particular lasers emitting in the visible spectral range, for example, at 488 and 514 ~0 nm. For this purpose, for example, argon ion lasers having a relatively low output, for example, 10 to 25 mW, can advantageously be used. The dosage of imagewise irradiation is preferably in the range from about 5 to 50% of the dosage necessary for complete curing of the layer without further treatment. The remainder of the amount of energy re~uired is supplied according to the invention by the combination of diffuse exposure, i.e., without an original, followed by heating.
; 30 For exposure without an original, a light - source of relatively low output, for example, a fluorescent lamp, is used, which emits a very high proportion of light having a wavelength of more than 500 nm. The emission range is generally between about 400 and 700, preferably between about 450 and 650, nm. The layer surface should generally be exposed to an intensity of about lo to 80 lux. The doses have to be selected so that complete curing is effected in combination with the image exposure and heat treatment on the image areas to be cured. It must be ensured that the non-image areas do not become cured by the diffuse exposure in combination with the heating to such an extent that they are no longer completely soluble in the developer. The desired image differentiation can be achieved with ` an image exposure or irradiation in the above-mentioned range of about 5 to 50% of the amount of radiation required.
Heating is carried out as the last treatment step before development in a manner known per se.
To this end, the completely exposed material is heated to ~ temperature in the range from about 60 t~ 140C, preferably from about 80 to 120C, in particular from about 90 to 110C, for approximately seconds to 2 minutes. In most cases, the treatment time required is in the range between about 30 and 80 seconds. During this treatment, the temperature must be measured when printing plates on metal supports, in particular aluminum, are heated.
This is advantageously done on the back of the plate, for example, using commercially-available temperature test strips. Heating can take place by air circulation, by contact heating or by infrared radiation.

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Surprisingly, it has been found that the process according to the invention results in tha desired increase in sensitivity only in very specific photopolymerizable materials. Thus, it has been shown that adequate reexposure and reheating achieves virtually no increase in sensitivity, if a known photopolymerizable material is used which contains 9-phenylacridine as the photoinitiator and trimethylolethane triacrylate as the monomer. If, however, a metallocene, in particular a titanocene or zirconocene, is used as the photoinitiator, an increase in photosensitivity by several degrees is achieved by the same treatment.
The metallocenes used as initiators are known as such and also as photoinitiators, for example, from US 3,717,558, 4,590,287 and 4,707,432.
Preferably, metallocenes of elements from subgroup IV of the periodic table of the elements, in particular compounds of titanium and zirconium, are uced. Compounds o~ this type are de6cribed in EP 364,735. Of the large number of known metallocenes, in particular titanocenes, compounds ; of the general formula l ~ R3 Me "' R ~ ~ R4 are preferred. In this formula, , , .
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Me is a tetravalent metal atom, in particular Ti or Zr, Rt and R2 are identical or different cyclopentadienyl radicals, which maybe substituted, and R3 and R4 are identical or different phenyl radicals which may also be substituted.

The cyclopentadienyl groups can be substituted, in particular by alkyl radicals having 1 to 4 carbon atoms, chlorine atoms, phenyl or cyclohexyl radicals or linked to one another by alkylene groups. They are preferably unsubstituted or substituted by alkyl radicals or chlorine atoms.
lS R3 and R4 are preferably phenyl groups which contain at least one fluorine atom in the ortho position relative to the bond. The other carbons can be substituted by halogen atoms, such as F, Cl or Br, alkyl or alkoxy groups having 1 to 4 carbon atoms, a polyoxyalkylene group which may be etheri~ied or esterified, or a heterocyclic group, fox example, a pyrrolyl radical. The polyoxy-alkylene group generally has 1 to 6 oxyalkylene units and is preferably in the 4 position of the phenyl radical. It can be etherified or esterified by an alkyl or acyl radical having 1 to 18 carbon atoms; it is in particular a polyoxyethylene group.
The relative amount of metallocene compound is generally between about 0~01 and 10, preferably between about 0.05 and 8, % by weight, relative to the photopolymerizable layer.
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~"` ' , ' ,, The photopolymerizable layer can contain a photoreducible dye as a further photoinitiator constituent. Suitable dyes are in particular xanthene, benzoxanthene, benzothioxanthene, thiazine, pyronine, porphyrin or acridine dyes.
Suitable xanthene and thiazine dyes are described, for example, in EP 287,817. Suitable benzoxanthene and benzothioxanthene dyes are described in DE 2,025,291 and in ~P 321,828.
An example of a suitable porphyrin dye is hematoporphyrin and an example of a suitable acridine dye is acriflavinium chloride hydrochloride.
Examples of xanthene dyes are Eosin B (C.I.
No. 45400), Eosin J (C.I. No. 45380), Eosin alcohol-soluble (C.I. 45386), Cyanosine (C.I. No. 45410), Rose Bengal, Erythrosine (C.I. No. 45430), 2,3,7-trihydroxy-9-phenylxanthen-6-one and Rhodamin 6 G
(C.I. No. 45160).
Examplee of thiazine dyes are thionine (C.I.
No. 52000), Azure A (C.I. No. 52005) and ~zure C
(C.I. No. 52002).
Examples of pyronine dyes are Pyronine B
(C.I. No. 45010) and Pyronine GY (C.I. No. ~5005).
The amount of photoreducible dye is generally between about 0.01 and 10, preferably between about 0.05 and 4, % by weight of the layer.
To increase the photosensitivity, the photopolymerizable layers can additionally contain compounds having trihalomethyl groups which can be cleaved photolytically, these compounds being known per se as free radical-forming photoinitiators for 9 ~
photopolymerizable mixtures. In particular, compounds containing chlorine and bromine, in particular chlorine as a halogen have proved suitable as coinitiators of this type. The 5trihalomethyl groups can be bound to an aromatic carbo- or heterocyclic ring directly or via a through-conjugated, e.g., vinylogous, chain.
Preference is given to compounds having a triazine ring in the parent structure which in turn 10preferably carries two trihalomethyl groups, in particular to those described in EP 137,452, DE
2,718,259 and DE 2,243,621. Compounds with a different parent structure, which absorb in the shorter W wavelength region, for example, phenyl 15trihalomethyl sulfones or phenyl trihalomethyl ketones, for example, phenyl tribromomethyl sulfone, are also suitable. The halogen compounds are generally used in an amount of about 0.01 to 10, preferably about 0.05 to 4, % by weight of the layer.
20The photopolymerizable layers can contain, if desired, acridine, phenazine or quinoxaline compounds as ~urther initiator constituents. These comp~unds are known as photoinitiators and described in DE 2,027,467 and 2,03~,861. The total amount of 25polymerization initiators is generally about 0.05 to 20, preferably about 0.1 to 10, % by weight.
Polymerizable compounds which are suitable for the purposes of the invention are known and described, for example, in US 2,760,863 and 303,060,023. Preferred examples are acrylic and methacrylic esters of di- or polyhydric alcohols, such as ethylene glycol diacrylate, polyethylene ~;

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glycol dimethacrylate, acrylates and methacrylates of trimethylolethane, trimethylolpropane, pentaerythritol and dipentaerythritol, and of polyhydric alicyclic alcohols or N-substituted acryl- and methacrylamides. Reaction products of mono- or diisocyanates with partial esters of polyhydric alcohols are also advantageously used.
Monomers of this type are described in DE 2,064,079, 2,361,041 and 2,822,190.
Polymerizable compounds containing at least one photooxidizable and, if desired, at least one urethane group in the molecule are particularly preferred. Suitable photooxidizable groups are in particular amino groups, urea groups, thio groups, which can also be constituents of heterocyclic rings, enol groups and carboxyl groups in combination with olefinic double bonds. Examples of groups of this type are triethanolamino, triphenylamino, thiourea, imidazole, oxazole, thiazole, acetylacetonyl, N-phenylglycine and ascorbic acid groups. Polymerizable compounds having primary, secondary and in particular tertiary amino groups are preferred.
Examples of compounds containing photooxidizable groups are acrylic and alkacrylic esters of the formula I

R(~"_n~Q~ (-C~2-CO-~a-CONH~X~ b-X2(-OOC-C~C~)C~n 2 ~
in which Q is Dl / \
-N-, -N-r-N-, -N N- or -5-R is an alkyl, hydroxyalkyl or aryl group, R5 and R6 are each a hydrogen atom, an alkyl group or alkoxyalkyl group, R7 is a hydrogen atom, a methyl or ethyl group, Xl is a saturated hydrocarbon group having 2 to 12 carbon atoms, X2 is a (c+l)-valent saturated hydrocarbon group in which up to S
methylene groups can be replaced by oxygen atoms, Dt and D2 are each a saturated hydrocarbon group having 1 to 5 carbon atoms, ;~ E is a saturated hydrocarbon group of 2 to 12 carbon atoms, a cycloaliphatic group of 5 to 7 ring members, which, if desired, can contain up to two N, O or S atoms as ring members, an arylene ~ gro~p of 6 to 12 carbon atoms or a ; heterocyclic aromatic group of 5 or 6 ring members, a is O or a number from 1 to 4, b is O or 1, ~ c is an integer from 1 to 3, :~ ~
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m is, depending on the valency of Q, 2, 3 or 4, and n is an integer from 1 to m, it being possible for all symbols of the same definition to be identical to or different from one another. The compounds of this formula, and their preparation and use are described in detail in EP 287,818. If in the compound of the general formula I more than one radical R or more than one radical of the type indicated in square brackets is bound to the central group Q, these radicals can be different from one another.
Compounds in which all substituents of Q are polymerizable radicals, i.e., in which m is n, are generally preferred. In general, a is 0 in not more than one radical, and preferably in no radical.
Preferably a is 1.
If R is an alkyl or hydroxyalkyl group, this group generally has 2 to 8, preferably 2 to 4, carbon atoms. The aryl radical R can generally be substituted on one or two rings, preferably on one ring, and may be substituted by ~lkyl or alkoxy groups of up to 5 carbon atoms or halogen atoms.
If R5 and R6 are alkyl or alkoxyalkyl groups, they can contain 1 to 5 carbon atoms. R7 is preferably a hydrogen atom or a methyl group, in particular a methyl group.
X~ is preferably a straight-chain or branched aliphatic or cycloaliphatic radical of, preferably, 4 to 10 carbon atoms. X~ preferably has 2 to 15 carbon atoms, up to 5 of which can be replaced by . . .

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oxygen atoms. If pure carbon chains are involved, those having 2 to 12, preferably 2 to 6, carbon atoms are generally used. x2 can also be a cycloaliphatic group of 5 to 10 carbon atoms, in particular a cyclohexylene group. Dl and D2 can be identical or different and, together with the two nitrogen atoms, form a saturated heterocyclic ring having 5 to 10, preferably 6, ring members.
If E is an alkylene group, it preferably has 2 to 6 carbon atoms, and as an arylene group it is preferably a phenylene group. Preferred cyclo-aliphatic groups are cyclohexylene groups, preferred aromatic heterocycles are those having N or S as hetero atoms and 5 or 6 ring members. The value of c is preferably 1.
Further suitable compounds containing photooxidizable groups are compounds of the formula II

2(~_"1~ ~2-f)~- ~ ~2 ~ - N~"
R6 ¦ 2 IR7 ( I I ) OOC--CH~CN2 in which Q, R, R5, R6, R7, m and n have the abovementioned meaning and Q can additionally be a group ,. . . .
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-N-E'-~-in which E' is a group of the formula III

-C~-C~oH-cH2-~o~ >-o-c~2-cH~H-a~2-~c (II~) in which c has the meaning as in formula I; a' and S b' are integers f rom 1 to 4.
The compounds of this formula, their preparation and use are described in detail in EP
316,706.
Further suitable compounds having photooxidizable groups are acrylic and alkacrylic esters of the formula IV

Q~ x~ c~2o)a~CC~ -xl-NHCoo)~, x2-~ c~ v) in which Q' is -N-, ,:, ' 2 ~

Dl ~--/ \ or D3 N-, -N N- \ I~
D2/ z Xl is CjH2;
or ClH2~. IO-CON~(-%~ 00)2,-X~-OOC-C-CH2, D3 is a saturated hydrocarbon group having 4 to 8 carbon atoms which, together with the nitrogen atom, forms a 5- or 6-membered ring, Z is a hydrogen atom or a radical of the formula R~
O--CO~ D~ C~b--X --OOc C~2 i and k are lntegers from 1 to 12, n' is, depending on the valency of Q', 1, 2 or 3, and R7, X~, X2, Dl, D2, a and b have the meaning given under formula I, it being possible for all symbols of the same definition to be identical to or '~

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of the compounds of the formula IV, those are preferred which contain at least one urethane group apart from a urea group.
The symbol a in formula IV is preferably 0 or 1; i is preferably a number from 2 to 10.
The polymerizable compounds of the formula IV
are prepared analogously to the compounds of the formula I. The compounds of the formula IV and their preparation are described in detail in EP
355,387.
The percentages of polymerizable compounds in the photopolymerizable layer is generally about 10 to 1580, preferably about 20 to 60, % by weight, relative to the non-volatile components.
Examples of binders which can be used are chlorinated polyethylene, chlorinated polypropylene, polyalkyl (meth)acrylates, in which the alkyl group is, for example, methyl, ethyl, n-butyl, i-butyl, n-hexyl or 2-ethylhexyl, copolymers of the 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 chloride, vinylidene chloride/acrylonitrile copolymers, polyvinyl acetate, polyvinyl alcohol, polyacrylonitrile,acrylonitrile/styrenecopolymers, acrylonitrile/butadiene/styrene copolymers, poly-styrene, polymethylstyrene, polyamides, for example, nylon-6, polyurethanes, methyl cellulose, ethyl "~
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,~' -cellulose, acetyl cellulose, polyvinyl formal and polyvinyl butyral.
Binders that are insoluble in water, soluble in organic solvents and soluble or at least swellable in aqueous-alkaline solutions are particularly suitable.
Carboxyl group-containing binders, for example, copolymers comprising (meth)acrylic acid and/or unsaturated homologues thereof, such as crotonic acid, copolymers of maleic anhydride or its monoesters, reaction products of hydroxyl-containing polymers with dicarboxylic anhydrides and mixtures thereof, should be mentioned in particular.
Reaction products of polymers carrying groups with acidic hydrogen, which have been completely or partially reacted with activated isocyanates, such as, for example, reaction products of hydroxyl-containing polymers with aliphatic or aromatic sulfonyl isocyanates or phosphinyl isocyanates, are also suitable.
Hydroxyl-containing polymers are also suitable, such as, for example, hydroxyalkyl ~meth)acrylate copolymers, allyl alcohol copolymers, vinyl alcohol copolymers, polyurethanes or polyesters, and epoxy resins, as long as they carry a sufficient number of free OH groups or are modified in such a manner that they are soluble in aqueous-alkaline solutions. Polymers of this kind carrying aromatically-bound hydroxyl groups can be used, such as, for example, condensation products of condensable carbonyl compounds, in particular formaldehyde, acetaldehyde or acetone, with phenols ,:

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or hydroxystyrene copolymers. Finally, copolymers of (meth)acrylamide with alkyl (meth)acrylates can also be used.
The polymers described above are particularly suitable if they have a molecular weight between about 500 and 200,000 or more, preferably between about 1,000 and 100,000, and either acid numbers between about 10 and 250, preferably between about 20 and 200, or hydroxyl numbers between about 50 and 750, preferably between about 100 and 500. The amount of binder in the photosensitive layer is generally about 20 to 9o, preferably about 40 to 80, % by weight.
Depending on the intended use and the desired properties, a wide range of substances can be present as additives in the photopolymerizable layers. These additives are inhibitors for preventing thermal polymerization of the monomers, hydrogen donors, dyes, colored and uncolored pigments, color formers, indicators, plasticizers and chain transfer agents. These components are advantageously selected to have the lowest possible absorption in the actinic radiation region important for the initiation process.
In the context of this description, actinic radiation is understood to mean any radiation having an energy that corresponds at least to that of visible light. In particular, visible light and long-wave W radiation, but also short-wave W
radiation, laser radiation, electron and X-ray radiation are suitable. The photosensitivity ranges from about 300 nm to 700 nm.

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Possible applications for the ~p~e~
according to the invention include the photomechanical production of printing forms for relief printing, offset printing, intaglio printing, screen printing, relief copies, for example, production of texts in braille, individual copies, tanning images,pigment images, and the like.
Furthermore, the process can be used for the photomechanical production of etch resists, for example, for manufacturing name tags, printed circuits and for chemical milling. The preparation of planographic printing plates and the photoresist technique are of particular importance.
Examples of suitable supports are aluminum, steel, zinc, copper and plastic sheets, for example, those made of polyethylene terephthalate or cellulose acetate, and screen printing supports, such as perlon gauze. In many cases, it is advantageous to subject the surface of the support 20 to a pretreatment (chemically or mechanically), wit~
the aim of properly adjusting the adhesion of the layer, to improve the lithographic properties of the surface of the support or to reduce the reflectance of the support in the actinic region of the copying layer (antihalation).
It is generally advantageous to protect the photopolymerizable materials during the photopolymerization substantially against the effect of oxygen in the air. In the case where the mixture is applied in the form of thin copying layers, it is recommended that a suitable top film which has low permeability to oxygen be applied. This film may be -self-supporting and removed before development of the copying layer. For this purpose, for example, polyester films are suitable. The top film can also be made of a material which is soluble in the developer liquid or can at least be removed at the uncured areas during the development. Examples of materials which are suitable for this are polyvinyl alcohol, polyphosphates, sugars, and the like. Top coats of this type generally have a thickness of about 0.1 to 10, preferably about 1 to 5, ~m.
For development, the materials are treated with a suitable developer solution, for example, with organic solvents, but preferably with a weakly alkaline-aqueous solution, in which the unexposed portions of the layer are removed and the exposed areas remain on the support. The developer solutions can con~ain a small portion, preferably less than about 5% by weight, of water-miscible organic solvents. They can further contain wetting agents, dyes, salts and other additives. The development removes the entire top coat together with the unexposed areas of the photopolymerizable layer.
Working examples of the invention are given below. Parts by weight (pbw) relate to parts by volume (pbv) as the gram relates to cubic ; centimeters. Percentages and amounts are by weight, unless stated otherwise.

ExamPles 1-7 (comparative examPles) 2. Q ~
Electrochemically roughened and anodized aluminum having an oxide layer of 3 gtm2 that 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 these operations were carried out under red light:

2.84 pbw of a 22.3% strength solution of a terpolymer comprising styrene, n-hexyl methacrylate and methacrylic acid (10:60:30) and having an acid number of 190 in methyl ethyl ketone, 1.49 pbw of the monomer according to Table 1, 0.04 pbw of Eosin alcohol-soluble (C.I. 45386), 0.03 pbw of 2,4-bis-trichloromethyl-6-(4-styrylphenyl)-s-triazine~ and 0.01 pbw of dicyclopentadienyl-bis(pentafluoro-phenyl)titanium, in 22 pbw of propylene glycol monomethyl ether.
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The mixture was applied by spin-coating 50 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 through-circulation drying oven. The plate was then coated with a 15% strength aqueous solution of polyvinyl alcohol (12% of residual acetyl groups, K
value 4). After drying, a top coat having a weight of 2.5 to 4 g/m2 was obtained. The printing plate obtained was exposed to a 2 kW metal halide lamp at a distance of 110 cm under a 13-step exposure wedge 30 at density increments of 0.15. To test the ....
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sensitivity of the printing plates in visible light, a 3 mn ~chick heat-ab6orption glass filter from Schott with an edge transmitt~nce of 4ssnm and a si lver fil~ havin~
uniform blàckening (density 1.4 ) and uniform absorption over the effective spectral range as a gray filter were mounted on the exposure wedge. The plates were exposed for 10 seconds and then heated to lOO~C for one minute. They were then developed using a developer of the following composition:

120 pbw of sodium metasilicate x 9 H20 ~
2.13 pbw of strontium chloride, 1.2 pbw of nonionic wetting agent (coconut fatty alcohol/poly-oxyethylene ether having about 8 oxyethylene units), and 0.12 pbw of antifoam, in 4000 pbw of fully deionized water.

The plates were coated with fatty printing ink. The fully crosslinked wedge steps given in Table 2 were obtained.

.
, ?, Table 1 Example No. Monomer 1 Reaction product of 1 mol of triethanolamine with 3 mol of isocyanatoethyl methacrylate, 2 Reaction product of 1 mol of N,N'-bis(~-hydroxyethyl)piperidine 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 2,2,4-trimethylhexamethylene diisocyanate with 2 mol of 2-hydroxyethyl methacrylate, Reaction product of 1 mol of hexamethylene diisocyanate with 1 mol of 2-hydroxyethyl methacrylate and 0.33 mol of triethanolamine, 6 Trimethylolethane triacrylate, 7 Reaction product of 1 mol of hexamethylene diisocyanate with 0.5 mol of 2-hydroxyethyl methacrylate and 0.25 mol of 2-piperidinoethanol.
~' Exam~les 8-14 The printing plates described in Examples 1 ~ to 7 were produced as described there and subjected ,.,~
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to imagewise exposure. They were then reexposed over the entire area with diffuse light from a fluorescent lamp emitting light of about 400 to 700 nm, the spectral portion below 500 nm of which was absorbed by a filter, at a light intensity of 15 lux for 20 seconds, followed by heating as in Examples 1 to 7 and development. The number of the wedge steps obtained is shown in Table 2.
Table 2 _ Example No. Gray Filter Wedge Steps I
8 yes 9 - 11 ~ ~ l~

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* no image :~ -26-Exa~le lS

A solution of the following composition was spin-coated onto the supports mentioned in Examples 1 to 7 under the same conditions as there, in such 5 a manner that a coating weight of 2.5 g/m2 was obtained:

2.84 pbw of the terpolymer solution mentioned in Example 1, 1.49 pbw of the monomer according to Example 7, 0.04 pbw of Eosin alcohol-soluble (C.I. 45386), 0.03 pbw of 2,4-bis(trichloromethyl)-6-(4-styrylphenyl)-s-triazine, and 0.01 pbw of dicyclopentadienyl bis(2,4,6-trifluorophenyl) titanium, in 22 pbw of propylene glycol monomethyl ether.

After applying a top coat comprising polyvinyl alcohol, the plate was exposed in the same manner as in EY.amples 1 to 7 for 5 seconds and then developed. To test the sensitivity of the printing plates in visible liaht, ~ 3 mm thick heat-absorption glass filter from Schott with an edge transmittance of 455nm and a silver film having uniform blackening (density 1.1) as gray filter were mounted on the exposure ~edge.
Eight to nine fully-crosslinked wedge steps were obtained. In a further experiment, the plate was exposed to diffuse reexposure as mentioned in Examples 8-14. Eleven to twelve fully-crosslinked wedge steps were obtained.

:

'~, In both cases, the printing plates were developed without leaving a residue and gave more than 150,000 excellent prints.

Exam~le 16 A photopolymerizable printing plate produced as in Example 7 was irradiated in a commercially-available film exposure apparatus ~y means of an argon ion laser (~ = 488 nm~ with 182 ~J/cm2 and processed without reexposure as in Example 7. More than 150,000 excellent prints were obtained.
The same plate was reexposed after laser irradiation with 375 lux seconds as described in Example 14. It was found that under these conditions an irradiation energy of only 32 ~J/cm2 was required to completely cure the plat~. Again more than 150,000 prints were obtained.
In a further experiment, reexposure using 500 1UX seconds was carried out, requiring only 18 ~J/cm2 for the laser imaging.

Exam~le 17 The coating solution from Example 7 was spin-coated onto a biaxially-oriented 35 ~m thick polyethylene terephthalate support so that a coating weight of 15 g/m2 was obtained after drying. The layer was then dried at 100C for three minutes in a through-circulation drying oven. The layer was then laminated onto a cleaned support composed of a ~ 3. CI~J .~
board n~ade of an insulating materlal and clad with a 35 um copper layer, at 115 C and 1 . 5 mlmin .
l~e layer was exposed for 30 seconds to a 2 kW metal halide lamp ~distance 140 an) under a heat-absorption qlass filter 455 nm, as described in Example l, using a step wedge as the original, and reexposed followed by heating as described in Examples 1 to 7. After removing the polyethylene terephthalate support, the layerwas developed for 20 seconds with 0.8~ strength sodium carbonate solution in a spraying processor.
Eight fully-crosslinked wedge steps were obtained.
The crosslinked layer was resistant to iron(III) chloride solution which is common in printed circuit technology. The resistance to etching was good.

ExamPle ~8 (Com~arative Exam~le) The following coating solution was applied to the support described in Examples 1 to 7 and dried:

1.4 pbw of a methacrylic acid/methyl methacry-late mixed polymer having an acid number of 115, 1.4 pbw of trimethylolethane triacrylate, O.2 pbw of dihydroxyethoxyhexane, and 0.05 pbw of 9-phenylacridine, in 13 pbw of 2-methoxyethanol The plate was exposed to a 5,000 W metal ; halide lamp under a step wedge for 35 seconds, followed by heating as in Example l. Six to seven fully-crosslinked wedge steps were obtained. In a ' -' .
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-further experiment, the same plate was only exposed for 15 seconds, subjected to diffuse reexposure after the image exposure with 300 lux seconds and then heated. No image was obtained. ~iffuse re-exposure with 300 lux seconds after an unchangedimage exposure of 35 seconds likewise gave 6 to 7 fully-crosslinked wedge steps.

Claims (13)

1. A process for the production of printing forms or photoresists, comprising the steps of:
imagewise irradiating a photopoly-merizable recording material comprising a photopolymerizable layer containing a polymer binder, an ethylenically unsaturated compound that is polymerizable by free radicals and that contains at least one terminal ethylenic double bond, and a metallocene compound that forms free radicals upon irradiation;
heating the recording material after the imagewise irradiation for a short time; and then developing the recording material, wherein the material is also blanket-exposed to visible light having a wavelength of at least 400 nm for a short time.

2. The process as claimed in claim 1, wherein the material is subjected to imagewise exposure with an irradiation energy corresponding to about 5 to 50% of the energy necessary to completely cure the layer.

3. The process as claimed in claim 1, wherein the imagewise irradiation is carried out using laser light.

4. The process as claimed in claim 1, wherein the imagewise irradiation is carried out by projection exposure using actinic light.

5. The process as claimed in claim 1, wherein the imagewise-exposed material is additionally heated to a temperature in the range from about 60 to 140°C.

6. The process as claimed in claim 1, wherein the material is additionally heated for about 10 to 120 seconds.

7. The process as claimed in claim 6, wherein the additional heating and blanket exposure are of such an intensity that the image areas are completely cured and the non-image areas remain completely soluble in the developer.

8. The process as claimed in claim 1, wherein the photopolymerizable recording material is first subjected to imagewise irradiation, then blanket exposed and then heated.

9. The process as claimed in claim 1, wherein the photopolymerizable layer additionally comprises a photoreducible dye as a coinitiator.

10. The process as claimed in claim 1, wherein the compound polymerizable by free radicals contains at least one photooxidizable group.

11. The process as claimed in claim 9, wherein the photopolymerizable layer additionally comprises a trihalomethyl compound which can be cleaved by radiation.

12. The process as claimed in claim 1, wherein the metallocene is selected from the group consisting of a titanocene and a zirconocene.

13. The process as claimed in claim 9, wherein the photoreducible dye is selected from the group consisting of a xanthene, thiazine, pyronine, porphyrin and acridine dye.