CA1122999A - Photopolymerizable composition - Google Patents

Abstract

ABSTRACT

A photopolymerizable composition useful on printing plates comprises 1) a film forming polymer, 2) an ethylenically unsaturated polymerizable monomer.
3) a photoinitiation system, and 4) an ethylenically unsaturated, carboxylic acid substituted oligomer.

Description

~ FN 914,771 PHOTOPOI.Y~ERIZABLE COMPOSITION
Field of_the Invention This invention relates to novel photopolymerizable compositions, photoimagable recording element, and a pro-cess for imaging with photopolymerizable compositions.

Prior Art Photopolymerizable compositions have been used in photosensitive elements, such as printing plates, for a number of years. Such compositions have been.satisfactory only where contact printing of the plate and relatively long time exposures can be tolerated. Most representative of the prior art are compositions disclosed in U.S. Patents Nos. 3,218,167 and 3,887,450. In U.S. Patent No. 3,218,167 photosensitive compositions comprising 1) an ethylenically unsaturated compound (e.g., pentaerythritol polyacrylate),

2) a sensitizing dye, and 3) a thermoplastic binder (e.g., cellulose ether or polyvinyl ether). In U.S. Patent No.

3,887,450 a radiation sensitive composition is described which comprises 1) an acrylic monomer (e.g. pentaerythritol triacrylate), 2) a photosensitive dye, and 3) a binder com-prising a copolymer of styrene and a carboxyl containlng comonomer (e.g., acrylic or malelc acid). This latter com-position has the advantage of being developable (i.e. solu-ble in non-irradiated areas) by basic developers. The com-position is relatively slow, however, and must be exposedin the absence of oxygen.
Radiation sensitive elements which are oxygen in-sensitive have been produced by overcoating the elements .. ~

- 1~.22~9~

with an oxygen barrier layer as in U.S. Patent No. 3,895, 949. Here a support bearing a photopolymerizable composi-tion comprising a glycidyl acrylate adduct of a styrene/
maleic anhydride adduct, and ethylenically unsaturated monomer (e.g., pentaerythritol tetraacrylate), and a photo-initiator is overcoated with an oxygen/moisture barrier layer (e.g., a copolymer of an acrylic acid and copolymer-izable ethylenically unsaturated compound). Such elements are relatively oxygen insensitive (by reason of the bar-rier layer), and with proper selection of the barrier layercan be developed with basic solutions after exposure. These elements remain relatively slow and require the additional coating operation to provide the barrier layer. In addi-tion to the time and cost factors resulting from the over-coating operation, careful control of solvents and condi-tions in this step must be observed to avoid sensitometric damage to the photosensitive layers.
Other radiation sensitive compositions known in the art include those of U.S. Patent No. 3,827,956. This ultraviolet radiation sensitive compositlon comprises 1) an acrylic monomer (e.g., pentaerythritol triacrylate), 2) an acrylate ollgomer (e.g., the reactlon product of toluene dlisocyanate wlth two equlvalents of 2-hydroxyethyl methacrylate), and 3) a halogenated polynuclear lactone catalyst. U.S. Patents Nos. 3,297,745; 4,017,649; and

4,065,627 describe other acrylate end-capped urethane oli-gomers which can be homopolymerized or copolymerlzed with other ethylenically unsaturated compounds. These materials are photopolymerizable with relatively high radiation sen-- 1~.2Z9~?9 sitivity and low oxygen sensitivity, but they are not base soluble and have no base developable printing plate capa-bility because o~ this. These compositions also have poor bonding characteristics to metal surraces such as zinc and aluminum.

Summary of the Invention It has been found that high speed radiation sensi-tive photopolymerizable compositions with excellent adhe-sion to certain substrates, especially aluminum surraces, which compositions arè suitable for use in radiation sensi-tive printing plates and color proofing sheets can be made.
These compositions also can have extensive shelf stability and oxygen insensltivity, and the polymers produced there-from are tough and have a long service life. The composi-tions are also base soluble and can be developed in basicsolutions in printing plate processes.
The photosensitive compositions of the present invention comprise 1) an ethylenically unsaturated free radical polymerizable end-capped oligomer, the bridging oligomeric portion between the unsaturated capping groups having carboxyl group substitution thereon, 2) a polymeric binder, 3) at least one free radlcal polymerizable monomer having at least one ethylenically unsaturated ~roup, and Il) a radiation sensitive initiator system capable of ini-tiating free radical polymerization upon absorption ofelectromagnetic radiation.
A storage stable photosensitive imaging element of particular use in providing base developable printing 1~.2Z~9 plates can be made by applying the photosensitive composi-tions of the present invention to a support layer.
Particularly improved compositions comprising the photosensitive oligomers, limited classes of binder, poly-merizable monomers, and photoinitiation systems have unex-pectedly high radiation sensitivity and no oxygen or mois-ture sensitivity.

Details Of the Invention There are basically four essential ingredients of the radiation sensitive compositions o~ the present inven-tion, l) an oligomer, 2) a binder, 3) a polymerizable mon-omer, and 4 ) a photoinitiation system. All four of these materials must be present in the polymerizable composition for it to work well in photoimagable recording elements as in lithographic printing processes. Generally, the compo-sitions comprise per 100 parts total:
10 to 60 parts by weight of oligomer, lO to 60 parts by weight of binder, lO to 60 parts by weight of monomer, and 0.1 to 12.0 parts by wetgh~ of photoinitiator system. It is pre~erL-ed to have as the photoinitiator sys-tem a photosensitizer and a compound which when photosensi-tized is capable of initiating free radical polymerization.
In the practice of this invention the second compound is defined as an initiator. The photoinitiator system is more preferably present in an amount Or 0.5 to 10 parts. Pre-ferably, the photosensitive composition comprises per 100 parts total:

~zzg~9 15 to 45 parts by weight of oligomer, 15 to 35 parts by weight of binder~
25 to 50 parts by weight of monomer, 0.2 to 10 parts by weight of initiator (more preferably 2 to 8).

0.1 to 5 parts by weight of photosensitizer (more preferably 1 to 4j.
Most preferably the compositions of the present invention comprise per 100 parts total, by weight:
20 to 35 parts oligomer, 20 to 30 parts binder, 30 to 50 parts monomer, 2 to 6 parts initiator, and 1 to 3 parts photosensitizer.
Generally, the photosensitive compositions of the invention are prepared by mixing the components in a low boiling (at atmospheric pressure boiling at less than about 150C) polar solvent that is not reactive with carboxyl groups or ethylenically unsaturated groups, such as methan-ol ethanol, propanol, acetone, methylethyl ketone, tetrah-hydro~urane or mixtures thereof. There may even be water present although less than 50% by wieght of water ln the solvent is preferred. The amount of solvent used (gene-rally 0 to 98% by weight, preferably 10 to 96% by weight and in lithographic applications 85 to 95% by weight sol-vent is most preferred) depends upon the desired viscosity and desired coating thickness. It is often desirable to add a surfactant or coating aid, but these aids, including the solvent are not functionally required for practice of the invention, but are merely better modes of practice.

-6~ i~Z;~9 0.001 to 2% of surfactant, particularly silicone or fluor carbon surfactants will ususlly be sufficient.
These compositions may contain any number of addi-tional useful additives such as dyes, pigments, coating aids, surfactants, etc.
The coating weight of the compositions of the pre-sent invention is usually 0.3 to 9 g/m2, preferably 0.5 to

5 g/m2, and most preferably o.8 to 2.4 g/m2. Suitable sub-strates include resin coated paper, various transparent or opaque plastic sheet or film, metal sheets and foils (pre-ferably aluminum substrates that have been grained and an-odized).The coated substrates must be maintained in the absence of light unless the element is sensitized to a narrow range of the electromagnetic spectrum outside the range of normal light and the element is provided with a filter layer which excludes normal visible light.
The preferred utility of the photopolymerizable compositions of the present invention is as a presensitized plate for use in printing operations such as in the forma-tion of lithographic plates. This structure comprises agrained and anodized aluminum substrate coated with from 0.3 to 9 g/m2 of the compositions of the present lnvention.
Grained substrates are surfaces which have been textured or rou~hened. This treatment is well known in the art and can be effected by brush graining (roughening with an abra-sive material), chemical etching, or electrochemical grain-ing. Anodizing is the well known anodic oxidation of metal surfaces. Polymer top coat layers used in these construc-tions must be dissolvable in aqueous alkaline solutions of . , -7- ~ ZZ9~99 pH 8-13 such as the aqueous developers of the examples.
A generic structural formula for the urethane oligomers can be drawn as follows:

1l (E-D ~ R--tOCA)b wherein E is an ethylenically unsaturated, free radical polymerizable group, preferably selected from acryloyloxyalkoxy (alternatively named acryloxyalkoxy), methacryloylalkoxy (alternatively named methacryloxyalkoxy), vinylalkoxy, and allyloxy, D is the residue of polyisocyanate (preferably a diisocyanate) having at least two of its -N=C=0 groups reacted to form -NHC- groups, D bonding E to R, A is a carboxylic acid containing group, (e.g., O O
~CH2)mC ~ , -C6H4!COH, etc.), 0~1 a is a number having an average value between 2 and 20, b is a number havlng an average value between 0.3 and 10, and m = 1 to 6, R is the residue of a polyol having at least a + b hydroxyl groups and a number average molecular weight between 90 and 10,000, the residue formed by removal of hydrogen from the hydroxyl groups.

-8- 1~.2~

The backbone of the oligomer, group R, may be any aromatic or aliphatic polyol having a molecular weight be-tween 90 and lO,000. The backbone of the oligomer may be any oligomer with the requisite molecular weight and num-ber of hydroxyl groups, but polyesterpolyols and polyoxy-alkylene polyols are preferred. Linear oligomeric polyols are useful but the branched or three-dimensional polyols such as polycaprolactone polyols are preferred. The back-bone may be prepared by any of the many well known methods of forming polyhydroxyl substituted oligomers having a mo-lecular weight between 90 and lO,000. The polyols must have a hydroxy equivalent weight of between 45 and 5,000 to be useful according to the present invention. Preferably the polyol has a hydroxy equivalent wieght between 90 and 4,000 and most preferably between 200 and 2,000.
The oligomeric backbone may be homopolymeric, co-polymeric, graft polymeric, or mixtures thereof. For ex-ample, polycaprolactone polyols may be used, or lower mo-lecular weight polycaprolactone polyols (average molecular weights of less than, for example, 500) may be ~oined by polyacids (preferably dicarboxylic acids) or by polyiso-cyanates (preferably diisocyanates) to form higher molecu-lar weight oligomer backbones.
In the synthesis of the oligomers useful in the pre-sent invention, it is preferred to ~oin the E-D substituent to the oligomeric backbone R by first separately forming an adduct of the polyisocyanate of which D is a residue by reacting one mole of the diisocyanate with one mole of an ethylenically unsaturated free radical polymericable mono-`~:

`

~,2~.C~

mer having one hydroxyl group. The adduct formed is then reacted with a hydroxyl group on the oligomer polyol back-bone (the reaction being with an isocyanate group). In an alternative method where the compound with the free radi-cal polymerizable group with one hydroxyl group and the polyisocyanate are added to the oligomeric polyhydroxy backbone before forming the E-D adduct, the polyisocyanate will act both as a polymer extender for the oligomer and as an adduct former with the free radical containing compound.
In such a reaction there would be far less control over the final product and there would be a tendency for the oligo-mer to gel. Therefore the free radical polymerizable mon-omer and the polyisocyanate (preferably diisocyanate) in an independently run synthesis form, for example, an isocyan-atoalkylacrylate, isocyanatoalkylmethacrylate, an isocyan-ato alkyl ether, or isocyanatoalkylvinyl ether adduct.
The adduct (E-D) formed in that step is then caused to react with the polyhydroxy containing backbone so that the remaining isocyanate group of the adduct reacts with some, but not all,of the hydroxyl groups on the oligomer to bond thereto.
The carboxyllc acld groups are added to the oll-gomerlc backbone preferably after addltlon of the free ra-dlcal polymerlzable moletles by reactlon of remalnlng hy~
droxyl groups on the ollgomeric backbone with a compound having free carboxyl groups. Preferably such a compound is a dicarboxylic acid or anhydrlde so that the linklng bond to the oligomeric backbone is an ester group. An isocyan-ate linkage can be formed by first making an acid-isocyanate .

~ 2Z~9 adduct.
A more specific formula representing preferred oligomeric materials is as follows:

(E-D-RltaR2--tRl-C-R3-C-oH)b wherein D, a, and b are as defined above, E ~s selected from ~CH2~nO-C-C=CH2, ~CH2~nO-I=CH2, and ~CH2~nO-CH2-CH=CH2, where R is -H or -CH3 and n is an interger of from 2 to 4 inclusive, R is the residue formed by the removal of active hydrogen atoms and hydroxyl groups from oligomeric Q-hydroxy carboxylic acids or the residue formed by the removal of active hydrogen atoms and hydroxyl groups from oligomeric diols, R is a residue, having a valence of a plus b, of an aliphatic polyol having the formula R5(oH)a+b after removal of a + b hydrogens from hydroxyl groups, or a polyol having the formula (HO ~ R5-o-D-o-R5(oH) =

after removal of a + b-l hydrogens from hydroxyl groups wherein R5 is the residue of an aliphatic polyol rad-ical formed by having the OH groups removed therefrom and having 3 to 10 valences substituted with OH groups and which can have one or two ether oxygen atoms in the aliphatic backbone, and 1~.'2Z9~9 R3 is the residue of a dicarboxylic acid having o both -C-OH groups removed therefrom.
Preferably the molecular weight of (Rlt-aR2(Ri)b is between 2QO and 5,000.
Particularly desirable aliphatic polyols from which R is formed are polyether polyols, polyester polyols, polyactone polyols, polyolefin polyols, polydiene polyols, polysiloxane polyols, poly (alkylacrylate) polyols, and poly (glycidyl ether) polyols.
A particularly desirable material is represented by the structural formula [Hoc-R3-c-o~ R7~oCNH-R6-NHCo~CH ~--OCC-CH ]

wherein R3 and R are as defined above, c is 2 to 5 inclusive, p is a number average value of 2 to 7.7, q is a number average value of 0.3 to 4, R6 is the residue of a diisocyanate having two -N=C=O groups removed therefrom and pre~erably is an aromatic resldue thereor, and R7 is an organic triyl radlcal which ls the residue of an organic polyol with at least three hydroxyl groups removed therefrom and having a molecular weight of from 90 to lO,OOO, preferably selected from aliphatic triols, tetrols and pentols, poly(oxyalkylene)triols, tetrols and pentols, poly-1~ 2~

estertriols, tetrols and pentols, polyactonetriols, tetrols and pentols, polyolefintriols, tetrols and pentols, polyacrylatetriols, tetrols and pentols, polyalkylacrylatetriols, tetrols and pentols, and polysiloxanetriols, tetrols and pentols.
Another particularly desirable material can be represented by 8~ ~ O~C~ H2)d~elR3~ oH3 f R tM ~0 (CH2)d~e7 o ll ~O:~C~CH2~dO3-elCIl'lHR6Mlllco~cH2~eocc~ h-fll2 wherein R3 and R are defined above, d is 1 to 6 inclusive, e is an average value Or 0.5 to 5 inclusive, f is an average value of 1 to 6 inclusive, R8 is the dival.ent hydrocarbon radical which is the residue of an organic polyisocyanate (prererably diisocyanate) with two lsocyanate groups re~oved there-from, R9 is an alkanepolyyl radical having a valence of h + 1 that is the residue of an alkanepolyol having h + 1 hydroxyl groups removed therefrom ( preferably having h + 1 hydroxyl groups before removal), said alka~epolyol having a molecular weight of from 100 to .2zg~

10,000 and preferebly 200 to 2,000, wherein h is an integer of from 2 to 8.
The general method of preparing the oligomers of the present invention is as follows.
STEP ONE - Preparation of a one-to-one adduct of a hydroxyalkyl (free radical polymerizable) material and a polyisocyanate, preferably a diisocyanate. This is done by reacting the two materials in a one-to-one ratio.
STEP TWO - Reaction of an organic polyol having X
number of hydroxyl groups with up to X - 1 moles of the adduct of STEP ONE. This forms a urethane oligomer having both ethylenically unsubstituted groups and at least one free hydroxyl group. Although, of course, in this reaction some individual oligomeric moieties may have all X hydroxyl groups reacted with the isocyanate, by control of the pro-portions of' isocyanate adduct and polyol, the number aver-age of free hydroxyl groups on the urethane oligomer will be at least one.
STEP THREE - The f'ree hydroxyl ~,roups on the pro-duct of STEP TWO are esterirled with a polycarboxylic acidtpreferably a dicarboxylic acid and most preferably an anhydride of a diacid). This reaction f`orms the carboxyl-substituted, ethylenically unsaturated urethane oligomer of' the invention.
The adduct of the hydroxyalkylacrylate and the diisocyanate of STEP ONE has the general formula:
O O

OCN-R6-NHC-0(R10)OCC-CH2 1~.229~99 wherein R6, R4 and a are as defined above, and R6 is preferably tolyl, and R10 is an aliphatic group and preferably is 2)2-6 It is preferred to use diisocyanates such as tol-ylene-2,4- diisocyanate and isophorone diisocyanate because of the great differential between reactivities of the iso-cyanate groups thereon. Without this differential, the product would have to be purified or else there would be less control over the subsequent product.
Such adducts are prepared by the addition of about 0.9 to 1.1 molar equivalent of the hydroxyalkylacrylate to one mole of organic diisocyanate while stirring the reac-tion mixture. Generally, it is desirable to hold the temperature below about 30C during the addition. The reaction can be complete after stirring the mixture for 10 minutes to an hour or more. If not completed that quickly, the reaction may be completed by further heating the mix-ture at temperatures of 50 or more for at least an hour.
Since many of the reaction products are vlscous liquids or solids (the reaction product of 2-hydroxyethyl methacry-late and 2,4-toluene-diisocyanate is a solld) it is prefer-able to add 0.25 to about 35 parts by weight of a non-functional group containing solvent, such as methylethyl ketone, acetone, tetrahydrofurane or the like. The solvent can be added at the beginning of the reaction, or along with the addition of the hydroxyalkylacrylate. Although not always necessary, it is often desirable to add a cata-lyst to effect the reaction between the hydroxyl group of ' ' , ~.2 ~9 ~ 9 the hydroxyalkylacrylate and one of the isocyanate groups of the organic diisocyanate. Suitable catalysts for the reaction are well known; an example of which is dibutyltin dilaurate.
STEP TWO is accomplished by adding over a period of one to five or more hours either the product of STEP
ONE to an organic polyol as defined above while heating the mixture at about 50 to 100 or vice-versa. As for STEP ONE, a catalyst such as dibutyltin dilaurate can be used to facilitate the reaction. It is often desirable to add a polymerization inhibitor such as 2,6-di(t-butyl) -4-methylphenol to prevent premature polymerization. The ratio of diisocyanate-hydroxyalkylacrylate adduct to organ-ic polyol is chosen so that one mole of oligomer obtained by the reaction contains at least two acrylic groups but leaves at least 0.3 equivalents unreacted hydroxyl groups.
STEP THREE is carried out, generally without iso-lating the product of STEP TWO, by esterification of un-reacted hydroxyls in the product of STEP TWO with an anhy-drlde of a dicarboxylic acid. Preferably, the esterifi-cation is accomplished by adding an amount of an anhydride of a dicarboxylic acid such as preferably succinic acid anhydride or adipic acid anhydride and continuing heating 50 to 100C for 3 to about 10 hours, the higher the temper-ature, the shorter the heating time required. Depending onthe extent of carboxylation desired, there is used from about 0.3 to about 4 moles of anhydride per mole of organic polyol originally present in the reaction mixture. The esterification, however, can be preformed using in place of .

the anhydride an ester of the dicarboxylic acid, viz., the methyl or ethyl ester and by ester interchange distill of the corresponding methanol or ethanol formed. Esterifica-tion can also be preformed using other reactive deriva-tives of the dicarboxylic acid such as the diacid chlorideand removing the hydrogen chloride formed. Sometimes it is necessary to add a basic catalyst, such as lithium acetate, to increase the rate of this reaction.
Controlling the ratio of the number of acid (car-boxylic acid) groups on the oligomer to the gram molecularweight of the oligomer is an effective way of controlling the bondability of the composition to a substrate after photoinitiated reaction. With increasing acid concentra-tion, the composition is removed more easily in development.
A wide range of ratios can be used, depending upon the per-formance characteristics desired in the final product. A
composition having a ratio of molecular weight to acid groups between 67 and 17,000 is useful. It is preferred to have the ratio of molecular weight to acid groups in the oligomer between 500 and 5,000, and most preferably between 800 and 3,000.
Binders The second of the critical elements in the photo-polymerizable compositions of the present invention is the binder. This material is an organic film forming polymer having a molecular weight of at least 6,ooo, prererably 12,000 and most preferably at least 15,000. It is desira-ble, but not essential for practice of the present inven-tion, for the binder to have a labile hydrogen or easily 1~ 2~

abstractable hydrogen thereon. The polymer preferably has a molecular weight of no greater than 100,000, preferably no greater than 80,000 and most preferably no greater than 50,000, although binders with molecular weights up to 2,000,000 or 3,000,000, are known in the art. To be a la-bile or easily abstractable hydrogen, a hydrogen in the binder must be attached to a carbon atom having an adjacent heteroatom selected from N, S, Se, and O. Preferably the heteroatom is N~ S, or O. It is also preferred that the carbon having the easily abstractable hydrogen thereon is in a 5`, 6, or 7-membered heterocyclic ring comprised of C, N, S, and 0 atoms, with preferably two heteroatoms ad~acent to the carbon atom having the labile hydrogen. The carbon atom bearin~ the labile hydrogen can be primary, but is preferably secondary or tertiary. The greater the ease of abstractability the lower the proportion of binder that the composition needs, althou&h not necessarily in a linear re-lationship. Preferred binders are the polyvinyl acetals such as polyvinyl formal, polyvinyl butyral, and mixtures thereof. Poly-(vlnyl methylether), polyvinyl alcohol, hy-droxyalkylcellulose (e.~., hydroxypropylcellulose), polya-mides, polyvlnylacetate, polyvinylacetate-polyvinylchloride copolymers, polyehtyleneoxides, and polyacrylates (e.g.
polyalkylmethacrylates have also been found to work well).
The rate or quantum efficiency of double bond con-version (i.e., polymerization) and the photosensitivity of various coatings exposed in air are a function of the type of polymeric binder used. While some polymers give no in-crease in rate and photosensitivity to the composition, ~,2 many polymers have been found that give surprisingly large increases. Amongst the polymers that have been shown to give an increase in the rate of conversion of double bonds include polyvinylacetals, polyvinylalcohol, hydroxy-alkylcellulose (e.g.~ hydroxypropylcellulose), polymides,polyvinylacetate, polyvinylacetatevinylchloride, polyethyl-eneoxide, and polyalkylmethacrylates. Polymers that do not give an increase include certain aliphatic hydrocarbon resins, cellulose acetatebutyrate, certain polyurethanes such as EstaneR, and linear saturated polyesters.
It should be understood by those knowledgeable in the art that not all polymers that give a rate increase are necessarily the best binders for lithographic plate coatings although they are still useful and desirable in other imaging processes such as duplicating film and proof-ing systems. Other properties such as solubility, water sensitivity and adhesion must be considered in choosing a polymeric binder for lithographic plates.
The exact function of the binder ln the composi-tions of the present :Lnvention is, not understood. Thelabile hydrogen thereon is belleved to be desl,rable, as many materials without a :labile hydrogen do not appear ~o work as well as those w:l.th labile hydroKens, although some do ln fact work well. Oxygen barr:ler characteristics may be additionally desirable in the binder polymer but such characteristics are not known to be essential.
Monomers Another of the critical materials in the photo-polymerizable compositions of the present invention is 1~.2Z~9 the monomer. This material is a free radical polymerizable monomer having one or more ethylenically unsaturated groups, and preferably 2 to 4 ethylenically unsaturated groups such as acrylate, methacrylate, vinyl and allyl. Preferred are compounds having multiple acrylate and methacrylate groups, e.g., acrylic esters o~ low molecular weight polyols, such as trimethylolpropanetriacrylate, pentaerythritol tetraacry-late and triacrylate, etc. Preferably these monomers have a molecular weight of less than 2,000 and more preferably less than 1,000.
Suitable free radical polymerizable monomers use-ful in the compositions of the invention are well known and listed in many patents, e.g., U.S. Patent Nos. 3,8~5, 949 and 4,037,021. Preferred monomers are the polyacrylate and polymethacrylate esters of alkanepolyols, e.g., pent-aerythritol tetraacrylate, tris(2-acryloxyethyl) isocyanu-rate, tris(2-methyacryloxyethyl)-isocyanurate, 2-acetoxy-ethyl methacrylate, tetrahydrofurfuryl-methacrylate, l-aza-5-acryloxymethyl-3,7-dioxabicyclo [3Ø0] octane (ADOZ) bis[4-(2-acryloxyethyl)phenyl]dimethyl methane, dlacetone acrylamide, and acrylamidoethyl methacrylate.
Initiator The compositions Or the present invention must also have a radiatlon sensitive system capable of initiating free radical polymerization upon absorption of radiation.
Free radical initiators are materials known in the art, such as F e-Radical Chemistry, D. C. Nonhebel and J. C.
Walton, University Press (1974). Particularly suitable free radical generators can be selected from many classes of organic compounds including, for example, organic peroxides, azo compounds, aromatic dlazonium salts, aromatic iodonium salts, aromatic sulfonium salts, aromatic phos-phonium salts, quinones, benzophenones, nitroso compounds, acyl halides, aryl halides, hydrazones, mercapto compounds, pyrylium compounds, triarylimidazoles, biimidazoles, chloroalkyltriazines, etc. These materials, in general, must have photosensitizers therewith to form a photo-initiator system. Photosensitizers are well known in the art.
Additional reference in the art to free radical photoinitiator systems for ethylenically unsaturated compounds are included in U. S. Patent No. 3,887,450 (e.g., column 4), U. S. Patent No. 3,895,949 (e.g., column 7), and U. S. Patent No. 4,043,819. Preferred initiators are the onium salts as disclosed in U. S.
Patent Nos. 3,729,313; 4,058,400; and 4,058,401. Other desirable initiators are biimidazoles; and chloroalkyl-triazines as disclosed in U. S. Patent No. 3,775,113.
These references also disclose sensitizers therein.
Another good reference to photoinitiator systems is Li~ht-Sensitive Systems, J. Kosar, 1965, J. Wiley and Sons, Inc., especially Chapter 5.
Preparation I
A polycaprolactone hexol is prepared for use in forming a carboxyl substituted urethane oligomer.
63.5 grams dipentaerythritol, 228 grams epsilon-carprolactone, and 0.02 grams 2,6-di-t-butyl-4-methyl phenol (as an oxidation inhibitor)were added to a 500 ml, three-neck flask which hadbeen fitted with an overhead mechanical ' ~ , ` ~

~.2;;~9~?9 stirrer and a condenser. The liquid was deoxygenated for 20 minutes by bubbling with dry nitrogen from a gas dis-persion tube. This tube was then replaced with a gas in-let adapter and the reaction mixture was heated while main-taining a slight positive pressure with nitrogen. Themixture was maintained at 170C for 5 hours under contin-ual stirring. The reaction mixture was then allowed to cool to room temperature under a nitrogen atmosphere. This material is referred to as P-I. This procedure is similar to that in U.S. Patent No. 3,169,945.

Preparation II
A urethane oligomer (hereinafter P-II) was pre-pared according to the following procedures.
A 1000 ml three-neck flask was fitted with an adapter, mechanical stirrer, thermometer, addition funnel, and drying tube. To this flask was charged 175 grams of polycaprolactone hexol P-I and 60 ml of methylethyl ketone.
A solution of 13 grams of 2,4-tolylene diisocyanate in 9 ml of methylethyl ketone was slowly dripped into the first solution wlth stirring at toom temperature. The additlon was completed in 20 minutes and the reaction mixture stirred for 90 minutes at 30C, after which time infrared spectoscopy showed that essentially all the isocyanate had reacted.
To a second flask fitted with an overhead mechan-ical stirrer, thermometer, addition funnel, and drying tube was charged 86.1 grams of 2,4-tolylene diisocyanate. To the addition funnel was added 70.2 grams 2-hydroxyethylme-thacrylate (hereafter HEMA) and 0.02 grams of the inhibitor .

1~.2Z9!~9 of the previous preparation, which was then slowly added with stirring to the diisocyanate while maintained below or at 30C. The addition was completed in 15 minutes and after 40 minutes of reaction time, a white solid formed.
The solid was dissolved in 45 ml of methylethyl ketone by heating to 45C and held at that temperature for lO min-utes to complete the reaction.
The flask containing the reaction product (adduct) of the polycaprolactone hexol (P-I) and the 2,4-tolylene diisocyanate was heated to 67C and the solution of the HEMA/2,4-tolylene diisocyanate adduct in methylethyl ketone was added slowly with stirring over a period of 2 hours.
27 grams of succinic anhydride was then added with an addi-tional 0.02 grams of the inhibitor. Heating and stirring was continued until the anhydride had completely reacted (about 5-6 hours).
The final product is a carboxyl substituted ure-thane oligomer, P-II.
Preparation III
The preparation of a second carboxyl substituted urethane oligomer ls here described.
To a 500 ml three-neck flask was charged 29.2 grams of a poly(propylene oxide)tr:lol having a molecular weight of 740, 25 ml ethyl acetate, and 0.007 grams of methylhydroquinone as a reaction inhibitor. The flask was heated ln a 65C oil bath with stirring and 13.0 grams HEMA and 17.4 grams tolylene diisocyanate were added simul-taneously from addition funnels. After addition of one half of these reactants, the reaction mixture was stirred ~ Z~9~

for another 30 minutes. Then 0.001 grams SnC12 catalyst and 0.004 grams 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexane carboxylate were added. The reaction mixture was stirred another 30 minutes and then the remainder of the HEMA and diisocyanake were added slowly. Stirring was continued overnight. Infrared analysis showed no free isocyanate groups after that time. To this reaction mix-ture was added, with stirring, 1.4 grams succinic anhy-dride. The temperature was raised to 93C and held there until the anhydride was completely reacted. The mixture was then cooled and diluted to 50% weight solution of P-III oligomer in ethyl acetate.
Preparation IV
A 250 ml flask was charged with 21.2 grams of a polycaprolactone polyol having a molecular weight of about 540, 25.1 ml of ethyl acetate and 0.007 grams methylhydro-quinone as an antioxidant. 17.4 grams of tolylene-2,4-dii-socyanate and 13.0 grams of 2-hydroxyethylmethacrylate (HEMA) were individually added to addition funnels on the flask. The polyol solution was heated to 67C and the diisocyanate and IIEMA werc added dropwise with rapid stir-ring until half of each material was added. ~t th:ls point stirring and heating were continued for 30 mlnutes. 0.002 ~rams SnC12 and 0.008 grams of` 3,~1-epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate were added and the solution stirred for another 30 minutes. The remainder of the diisocyanate and HEMA was added dropwise and then an addi-tional 5 ml of ethyl acetate was added. The mixture was stirred at 67C overnight. When isocyanate was no longer 24- 1~,2 ~ g ~ ~

detectable by in~rared analysis, 1.4 grams of succinic an-hydride was added along with 10 ml of ethyl acetate. The temperature was raised to 100C and the reaction of the an-hydride was indicated by infrared analysis as essentiallycomplete after five hours.
This resulting material, a carboxylic substituted urethane oligomer, is referred to as P-IV and is useful in the practice of the present invention.

Preparation V
A particularly useful binder material for the oli-gomers was prepared as follows. A low molecular weight polyvinyl alcohol (88% hydrolyzed polyvinylacetate) was reacted with butyraldehyde and acrolein using an acid cata-lyst, preferably sulfuric acid. The proportion of reac-tants was 100/43.2/6.4 respectively. The product was preci-pitated from water with a dilute weak basic solution (r~a-HC03). Analysis of the product showed the empirical for-mula to be close to that based on the stoichiometry of the reaction, 1l ol~l f - C - (~l3 ~C~12-~1)5. IJ(C~C~12-C~l~C~-12f~
O~ 0 0~0 CH2C~2C1~3 DC~
C~12 This material is hereinafter referred to as P-V.

~.2Z9~9 Preparations VI-XI
Six additional oligomers were prepared for eval-uation in the present invention.
P-VI was prepared by first placing 128.8 gof2,4-toluenediisocyanate into a three-neck, 250 ml flask equi-pped with a mechanical stirrer and a pressure equalizing dropping funnel. The flask was maintained at room temp-erature with a water bath. Hydroxyethylmethacrylate (106.6 g) and o.o89 butylated hydroxy toluene and 100 g methylethyl ketone were added slowly over a 30 minute per-iod. The reaction was stirred for one hour at room temper-ature. Methylethyl ketone was added and the reaction mix-ture was heated to 45C for 3 hours to complete the reac-tion.
P-I (350 g of 79% solids in methylethyl ketone) was placed into a 500 ml, three-neck flask equipped with a mechanical stirrer, pressure equalizing dropping funnel and 26.0 g 2,4-toluenediisocyanate was added over a 30 min-ute period. The temperature rose to 32C. The mixture was cooled to room temperature and stlrred over the week-end. The first reaction product from the above synthesis was added over a four hour period to this second solution which had been heated to 65C. Heating was continued for ten hours to form the second reaction product.
1.8 g of succinic anhydride and 0.1 g lithium acetate were added to 112.4 g (71% solids in methylethyl ketone) of the second reaction product and the entire mix-ture heated to 78C for twelve hours to complete the reac-tion and form oligomer P-VI.
., ~ , $~ zg~

P-VII was prepared by placing 112.4 g (71~ solids in ~ethylethyl ketone) of the second reaction product in the preparation of P-VI into a 500 ml three-neck flask with stirrer and condenser and then adding 2.4 g succinic anhydride and 0.1 g lithium acetate. The mixture was heated to 78C for 12 hours until the reaction was com-plete to form P-VII.
P-~III was formed by placing 112.4 g (71% solids in methylethyl ketone) of the second reaction product in the preparation of P-VI into a 500 ml three-neck flask with stirrer and condenser with 5.5 g succinic anhydride and 0.1 g lithium acetate. The reaction mixture was then heated to 78C for 32 hours until the reaction was complete to form P-VIII.
P-IX was formed by first preparing a polycapro-lactone hexol by introducing 342 g caprolactone and 127 g dipentaerythritol into a 1000 ml reaction kettle equipped with a thermometer, mechanical stirrer and condenser.
The reaction mixture was deoxygenated by bubbling dry nitrogen through a gas dispersion tube for about 30 minutes.
The gas dispersion tube was then replaced with a gas inlet adapter and the reaction was maintained under a slight positive nitrogen pressure. The reaction mixture was heat-ed in an oil bath at 165-170C with continuous stirring for 24 hours. The product wa:, allowed to cool to room temperature while under a nitrogen atmosphere.
141.0 g of the polycaprolactone hexol and 50 g of methylethyl ketone were placed in a 1000 ml flask equipped with a pressure equali~ing dropping funnel and a mechanical 1~.2~9~9 stirrer. This solution was maintained at room temperature by using a water bath while 2,4-toluene diisocyanate (13.0 g) in 20 g of methylethyl ketone was added over a 25 minute period through the dropping funnel with contin-uous stirring. Stirring at roorn temperature was continuedfor 22 hours to form the second reaction product.
38.2 g of 2,4~toluene diisocyanate and 0.2 buty-lated hydroxytoluene were introduced into a 250 mlthree-neck flask equipped with mechanical stirrer, pressure equalizing dropping funnel and thermometer. Hydroxyethyl methacrylate (31.2 g) was added with continuous stirring over fifteen minutes at a temperature below 30C. The mixture was stirred for one hour and a white solid formed.
20 ml of methylethyl ketone was added and the mixture heat-ed to 45C for three hours to complete formation of thethird reaction product.
69.7 g of' the second reaction product and 0.02 g butylated hydroxy toulene were added to a 500 ml three-neck flask with a mechanical stirrer, condenser, and pressure equalizing dropping funnel. This solut:lon was heated to 69C with continuous stirrln~. The entire portlon of` the third reaction product was added to thls solution over one hour. Heating and stirrin~ were continued for thirteen hours to form the fourth reaction product.
13.0 g of succinic anhydride and 0.4 g of lithlum acetate were added to the fourth reaction product and the solution heated at 70C to 80C with continuous stirring to form P-IX.
P-X was prepared by first forming a polyol by 1~ 229~?~

placing 93.1 g tripentaerythritol and 303.2 g caprolactone in a 1 liter reaction kettle equipped with mechanical stir-rer, condenser, and thermometer. The reaction mixture was purged with dry nitrogen for 30 minutes, and a gas inlet tube affixed thereto. Positive nitrogen pressure was maintained over the reaction mixture as it was heated to 165-170C for 9-1/2 hours, then allowed to cool to room temperature.
300 g of this polyol and 75 g of methylethyl ketone were introduced into a 1000 ml flask equipped with stirrer, dropping funnel and thermometer. 16.4 g of 2,4-toluene diisocyanate was added through the dropping funnel over 10 minutes. The temperature of the mixture rose to between 28-32C and continued for about 3-1/2 hours to form the first reaction product. 153 g of this product (as 80% solids in methylethyl ketone) was added with 0.04 g butylated hydroxytoluene into a flask and heated to 65-70C. Over a period of 2 hours the third reaction product of preparation IX was added to this solu-tion and heated for an additional three hours.
18.5 g of succinic anhydride and 0.5 g of lithium acetate was added to the above resulting solution and the mlxture heated at 70-80C for 22 hours to product P-X.
P-XI was prepared by first forming an adduct of 25 2,4-toluene diisocyanate (26.8 g) and hydroxyethylmethacry-late (22 g) in 30 ml of methylethyl ketone with 0.02 g butylated hydroxytoluene in the same procedure used in forming the third reaction product of preparation IX. This product was added over a one hour period to the product of ~.,2zg~9 the second solution of P-VI (87.'7 g as 80% solids in meth-ylethyl ketone) and 0.02 g butylated hydroxytoluene and heated to 65-70C. Heating was continued for 7-1/2 hours at about 67C.
19.6 g of succinic anhydride and 0.4 g lithium acetate were then added to the solution and heated at 75C
for 84 hours to form P-XI.
Preparation XII
A urethane oligomer (hereinafter P-XII) was pre-pared according to the following procedure.
A 1000 ml three-neck flask with adapter fitted with an overhead mechanical stirrer, thermometer, addi-tion funnel and drying tube was charged with 180 g of a polypropylene oxide polyol of molecular weight 600 and 90 ml of methylethyl ketone. A solution of 34.8 g 2,4-toluene diisocyanate in 30 g of methylethyl ketone was added with stirring at room temperature. The addition was completed after 80 minutes and stirring was continued at room tem-perature for 90 minutes. After the addition of 0.02 g 2,6-di-t-butyl-4-methyl phenol, the temperature was increased to 45-55C for about 15 hours at which time isocyanate groups were no longer detected by infrared analysis.
To a 250 ml one-neck flask with a magnetic stirrer and drying tube was charged 95.7 g 2,4-toluene diisocyanate.
78 g of 2-hydroxyethylmethacrylate was added over a period of about 10 minutes while maintaining the temperature at less than 30C with a cold water bath. After about 40 min-utes of total reaction time a white solid formed and 45 ml of methylethyl ketone was added. The solution solidified l~..ZZ9!~3 \
-3o-on standing overnight and was redissolved by warming to about 45C.
The product from the reaction of the polyol and 2,~-toluene diisocyanate was heated to 67C and the pro-duct from the 2-hydroxyethylmethacrylate and 2,4-toluene diisocyanate was added over a period of about 30 minutes.
After 6 hours 27 g of succinic anhydride and 1.05 g of lithium acetate were added. After about 28 hours of heating at 53C to 70C the anhydride was determined to be completely reacted by infrared analysis.
Examples 1-4 A solution was prepared (in parts by weight) from 3.32 parts pentaerythritol tetraacrylate, 1.87 parts P-II, 0.17 parts triethylamine, 0.34 parts of diphenyliodonium hexafluorophosphate, 0.17 parts 4,4'-bis(dimethylamino)-benzophenone (a photosensitizer for the iodonium catalyst) and 91.62 parts of n-propanol/water azeotrope (71.8% n-propanol and 28.2% water). Aliquots of this solution were prepared and 2.50 parts by weight of different organic polymeric binders were added to the solutlon.
Alumlnum sheets whlch had been grained and ano-dlzed were coated with these solutions uslng a #14 wlre wound rod and then dried with a heat gun. The coated alu-minum was then exposed for 13 seconds ln a vacuum frame to a carbon arc having about 5000 watt output and at about 1 meter distance through a 21 step sensitivity guide and a neutral density o.51 filter. Exposed plates were developed by wiping with a weak basic aqueous solution of 0.63% so-dium metasilicate and 0.23% sodium (lower alkyl) naphtha-~.229~9 lene sulfonate.

The binders used ln the examples were:
1. P-V, 2. Poly(vinyl methyl ether), 3. Poly(vinyl formal), prepared from a poly-vinyl acetate starting material and hav-ing 85% of the acetate groups replaced by alcohol and formal groups (the poly-vinyl acetate having a viscosity of about 12 cp at 25C, as 86 grams in 1000 ml of benzene), and 4. Poly(vinyl butyral).
The following table shows the polymer retained after exposure to a certain number of steps and develop-ment by the weak basic solution.

Steps Example Solid Ghost The "ghost" values indicate the lowest exposure from which photopolymer was retained on the plate. The "solid" values indicate the exposure level at which the developed image density can no lon~er be differentiated from the background andis believed to be cured to the de-sired level.
The numbers of the steps consecutively indlcate an increase of about 40% in filtering strength. The high-er the step number remaining after development, the corres-pondingly higher sensitivity of the composition exposed and developed.
;,' ~.2Z~9 Example 5 The usefulness of the compositions of the present invention in conventional newspaper printing operations ~as evaluated here.
A solution was prepared having 17.2 grams pentae-rythritol tetraacrylate, 13.5 grams P-II (70% by weight in methylethyl ketone), 171.6 grams of polyvinyl formal in a

6% by weight solution in the azeotrope, 295 grams of the n-propanol/water azeotrope, 4.3 grams of 20% triethylamine 5 3.7 grams of red pigment (Pigment Red 48, C115865 in the Color Index) in a composition of 1:2 weight ratio to poly-vinyl formal (as described above), 1.74 grams diphenyllo-donium hexafluorophosphate and 0.65 grams 4,4'-bis(dimethy-lamino)benzophenone photosensitizer. This composition was coated on grained anodized aluminum using a squeeze roll coater fitted with a rubber gravure sleeve. The coating weight was about 1.72 grams/m2. The coating was exposed in a vacuum frame by a carbon arc for 40 seconds through a neutral density 0.5 filter and a newspaper negative. The coatlng was developed with the aqueous developing solution of Examples 1-4 and then gummed with a standard substrac-tive plate gum. The resulting printing plate was mounted on a high speed web press using direct lithographic tech-niques and produced 95,000 newspaper impression without de-gradation of the image line copy or half-tones.
Exam~le 6 A solution was prepared from 7.72 grams of P-V, 327.4 grams of the n-propanol/water azeotrope, 12.8 grams of pentaerythritol tetraacrylate, 10.3 grams of a 69% by i~..Z~9~

weight solution of P-II in the azeotrope, 3.2 grams of a 20% solution of triethylamine in the azeotrope, 15.7 grams of Pigment ~ed 48 dispersed in P-V and the azeotrope (4 8 88), 1.3 grams of diphenyliodonium hexafluorophosphate and o.65 grams of the benzophenone sensitizer of' the pre-vious examples. This solution was coated onto grained ano-dized aluminum using a squeeze roll caoter fitted with a rubber gravure sleeve at a coating weight of about 1.72 grams/m . The coatings were exposed from a pasteup with a laser imaging system, using primarily the 351 and 364 nm lines of an argon ion laser, (at 4 milliJoules/cm2 exposure) and developed with the mild basic aqueous developing solu-tion of the previous examples, and gummed with a commercial substractive plate gum. The printing plates were mounted on a web offset press and produced high quality impressions.

Example 7 A solution was prepared from 12.8 grams of poly-vinyl formal from a 6% by weight solution in the n-propanol/
wate,r azeotrope, 1.28 ~rams of pentaerythrlto] tetraacry-late, 1.42 ~rams of P-IIIas a 50% by weight solution in ethyl acetate, 24 grams Or the azeotropic solution, 0.28 grams of Plgment Red 48 in polyvinyl formal (1:2 wei~ht ratio), 8 drops of a 20% solutlon of triethylamine in the azeotrope, 0.13 grams of' dip~lenyliodonium hexafulorophos-phate and o.o65 grams o* the benzophenone sensitizer ofthe previous examples.
This solution was coated onto grained anodized aluminum using the #14 wire wound rod. After exposure (from a 5000 watt output carbon arc for 13 second through -34- l~.Z~9 neutral density 0.51 filter) and development with the weak basic solution of the previous examples, a solid image at step 6 was obtained~ and a ghost image at step 7 was ob-tained.

Example 8 A solution was prepared from 1.54 grams of P-V, 2.56 grams of pentaerythritol tetraacrylate, 2.06 grams of P-II as a 70% by weight solution in methylethyl ketone, o.64 grams of triethylamine as a 20% by weight solution in the azeotrope, 4.7 grams of a dispersion of Pigment Red 48 in P-V and the azeotrope (4:8:88), 65.6 grams of the azeotrope, 0.25 grams of diphenyllodonium hexafluorophos-phate, and 0.13 grams of 4,4'-bis(dimethylamino)benzophen-one. This solution was coated with a #14 wire wound rod onto a substrate comprising polyethylene film with a top coat of TiO2 and CaCO3 in a polyurethane binder. This coating was air dried with a heat gun and overcoated with a 10% solution of low molecular weight (88% hydrolyzed polyvinyl acetate) poly(vinyl alcohol) with a small amount of inert surfactant as a coating aid. A #10 wire wound rod was used to coat this solution. The dried coating was exposed in a vacuum frame to a carbon arc for 13 seconds through a 0.5 neutral density filter, a half-tone negative, and a sensitivity guide. The exposed coating was developed with an aqueous solution of o.63% sodium metasilicate and 0.23% sodium (lower alkyl)naphthalene sulfonate. A strong magenta image on a white background was obtained. Solid 3 and ghost 5 steps were visible and sharp 3-97% dots of at least a 110 line screen were obtained.

~..2zg~9 Examples 9-15 The following examples show the necessity and in-teraction o~ the different components of the system of the present invention. The effect of poly(vinyl alcohol) top-coats, normally used in the art as an oxygen barrier, wasalso investigated.
Solutions were prepared with di~ferent combina-tions of representative additives. P-V was used as the binder, P-II as the carboxyl containing free radical poly-merizable oligomer, pentaerythritol tetraacrylate as thefree radical polymerizable monomer, diphenyliodonium hexa-fluorophosphate (as 0.04 parts by weight) as the free radical initiator, N ~ N \ C7H15, here~nafter re~erred to as CEBI-I (0.01 parts by weight) as sensitizer, and poly (vinyl alcohol) as a topcoat. The solu~lons havin~, the compositions noted below in the table were coated on grained and anodized aluminum to g:lve dry coating weigllts of ~rom 1. o6 to 1.61 grams/m2. Where a topcoat was present, the poly(vinyl alcohol) was applled at about the same coat-ing weight as the base coat. In the examples the solutions were made from isopropanol or methanol-methylethyl ketone-water solvents. Triethylamine was added in all examples in amounts equivalent to the acid in P-II.

z,~ 9 The dried samples were exposed through a 21 step sensitivity guide for 2 seconds with a 16,000 foot candle tungsten source. The exposed samples were developed by wiping with an aqueous solution of 0.35% sodium metasili-cate and 0.25% sodium (lower alkyl)naphthalene sulfonate.Exam~le_No. P-V P-II Monomer Top Coat Steps 9 0.3 0.0 0.4 No 0.3 0.4 0.0 No 11 0.0 0.5 0.4 No 0 12 0.0 0.5 0.4 Yes10 13 0.3 0.2 0.4 No 9 14 0.3 0.4 0.2 No10-11 0.3 0.4 0.2 Yes14 As can be seen from these results, the absence f any one of the three lngredients (blnder, oligomer, or monomer) produces poor or useless photopolymerizable com-posltions. When a top coat is put on the composition with-out the binder (Example 12), the oxygen sensitivity of the system is reduced and it polymerizes well. Surprising]y, systems having the three components of the present inven-tion work as well as the top coated system (Examples 13 and 14), and when the systems of the present invention ar-e combined with a top coat, even f`urther improved re-sults are obtained (Example 15). These results are sur-prising and hlghly desirable.

Example 16 A solution was prepared from 4 parts poly)m-dial-lylphthalate), 2 parts P-II, 4 parts pentaerythritol tetraacrylate, 5 parts methanol, 0.4 parts diphenylio-donium hexafluorophosphate, 0.1 part CEBH, 0.4 parts of Phthalocyanine Blue GS, and methylethyl ketone to 100 parts. This was coated onto grained and anodized aluminum to give a dry coating weight of about 1.34 grams/m2.
This was overcoated with poly~vinyl alcohol) at about the same coating weight as the base coat. The coating was air dried, then exposed and developed as in Examples 9-15.
The photopolymer was retained through step 12.

Example 17 The same procedure as in Example 16 was used ex-cept that 4 parts of tris-methacryloxyethyl isocyanurate was substituted for the pentaerythritol tetraacrylate.
The photopolymer was again retained through step 12.

Examples 18-21 A solution was prepared from 0.3 grams P-V, 0.4 grams pentaerythritol tetraacrylate, 0.22 grams P-II, 0.04 grams diphenyliodonium hexafluorophosphate, 0.02 grams of CEBH, 1.28 grarns methylethyl ketone, 0.47 grams water, 7.36 grams isopropanol, and 6 drops of a 20% by weight solution of triethylamine in n-propanol. The solution was coated w.tth wire wound rods onto grained and anodized aluminum at coating weights of 0.95, 1.36 and 2.0ll grams/m2. Some of the coatings were overcoated with a 10% by weight solution of poly(vinyl alcohol) using a #8 wire wound rod. The coatings were exposed using an argon laser at 488 nm and developed by wiping with a pad and an aqueous solution of a 0.35% sodium metasilicate and 0.25% sodium (lower alkyl)naphthalene sulfonate. The l~.Z29~9 laser beam was passed through a 21 step sensitivity guide.
The exposure values (in milliJoules/cm ) listed are the exposures needed to give a solid step 6 for the various coating weights.

Example Goating Weight g/m2 Top Coat Exposure 18 .95 Yes 1.8 19 1.36 Yes 1.8 1.36 No 10-14 21 2.04 No 10 As can be seen, the top coat improves the compo-sitions, but the uncoated materials are still of excellent speed and quality even when exposed in the presence of air.
Examples 22-32 Solutions were prepared as in Example 16 except that different photolnitiation systems were evaluated.
Exposure was to a mercury vapor lamp having an output of 500 watts/inch at a distance of about 34 cm through an interference filter having a maximum transmission at 366 nm and a 21 step sensitivity guide. The table indicates the relative sensitivity of the system for the minimum exposure required to give retained photopolymer with development as in Example 16.

Approx.
Absorption Relative Ex. Photoinitiation System at 366 nm Exposure 22 4,4'-bis(dimethylamino) 0.3 0.26 benzophenone 2-o-chlorophenyl-4,5-di (m-methoxyphenyl)imidazole dimer 2-o-chlorophenyl-4,5-di-phenylimidazole dimer 2-mercaptobenzoxazole 23 Same as Example 22 0.01 o.88 24 4,4'-bis(dimethylamino) 0.1 2.2 benzophenone diphenyliodonium hexaflu-orophosphate tetraphenyl benzidine 0.2 3.3 diphenyliodonium hexaflu-orophosphate 26 tetraphenyl benzidine 0.1 4.8 diphenyliodonium hexaflu-orophosphate 27 tetraphenyl benzidine 0.02 13 diphenyliodonium hexaflu-orophosphate 28 2,4-bis(trichloromethyl)-6- 0.2 6.6 (4-methoxylstyryl)-s-triazlne 29 3-carboxymethyl-5(3-ethyl 0.02 13 -2-benzothiazolinylidene) -2-(3-heptyl-4-oxo-2-thio -5-thiazolinylidene)-4-thiazolidone diphenyliodonium hexaflu-orophosphate chlorothioxanthone 0.2 diphenyliodonium hexaflu-orophosphate Approx.
Absorption Relative Ex. Photoinitiation System at 366 nm Exposure 31 ethyldimethoxy antracene 0.02 40 diphenyliodonium hexaflu-orophosphate 32 4,4'-bis(dimethylamino)-benzophenone 0.1 40 Examples 33-39 A stock solution was prepared by mixing 5.13 grams pentaerythritol tetraacrylate, 4.03 grams P-II, 25.5 grams of a 10% by weight solution Or polyviny formal in the azeotropic solution of n-propanol and water, 119 grams of methylethyl ketone and 1.5 grams of a 20% by weight solution of triethylamide in the azeotrope. To aliquots of 20 grams of this solution were added various photoinitiation systems. The photoinitiation systems and amount of each are shown in the following table. The solutions were then coated on a grained anodized aluminum substrate with a #L4 wlre wound rod and drled with a heat gun. The result:Lng coating,s were exposed for 13 seconds to a carbon arc through a 21 step sensltivity guide and a 0.5 density filter. The exposed coatings were developed by wiping with an aqueous solution of o.63%
by weight sodium metasilicate and 0.23% by weight of sodium (lower alkyl)naphthalene sulfonate. The number of solid steps observed after gumming and inking were re-corded. As in previous examples, the higher the number of steps retained, the greater the sensitivity of the coating.

Weight Solid Ex.Photoinitiation System (Grams) Steps 33 4,4'-bis(dimethylamino)benzophenone 0.035 0 34 4,4'-bis(dimethylamino)benzophenone 0.035 7 diphenyliodonium hexafluorophosphate 0.070

7-diethylamino-4-methylcoumarin 0.035 0 36 7-diethylamino-4-methylcoumarin 0.035 4 diphenyliodonium hexafluorophosphate 0.070 37 2,4-bis(trichloromethyl)-6-(4- 0.070 2 methoxystyryl)-s-trazine 38 2,4-bis(trichloromethyl)-6-(4- 0.14 3 methoxystyryl)-s-triazine 39 4,4'-bis(dimethylamino)benzophenone 0.035 11 2-o-chlorophenyl-4,5-di(m-methoxy- 0.10 phenyl)-imidizole dimer 2-o-chlorophenyl-4,5-diphenyl 0.10 imidizole dimer 2-mercaptobenzoxazole 0.07 None of these compositions had top coats.

Examples 40 and 41 Two addit.tonal monomers were evaluated in the compositions of the present inventlon. Two solutions (A and B) were prepared havin~ the following composition:
Grams P-II (64% in methylethyl ketone) 3.12 polyvinylformal (10% in the n- 7.6 propanol-water azeotrope) P-V (12.9% in n-propanol (62%), 4.18 isopropanol (10%, and water (28%) disperson of Pigment Red 48 and 10.0 polyvinyl formal (10% in the above azeotrope) in a 2/1 parts by weight ratio resin/pigment 1~2~9 4,4'-bis(dimethylamino)benzo- 0.19 phenone diphenyliodonium hexafluorophos- 0.37 phate triethylamine (20% by weight in o.96 the azeotrope n-propanol-water azeotrope 70.0 To solution A was added 3.67 grams of pentaerylthritol tetraacrylate and to solution B was added 3.67 grams of tris(2-acryloxyethyl isocyanurate~. `The solutions were~~ ~~
then coated onto grained and anodized aluminum using a number 18 wire wound rod and dried for one minute at 65C.
The coated plates were then exposed with a 2 kilowatt dia-zotype lamp for 2, 5, and 10 seconds in air. The exposed plates were developed by washing with an aqueous solution of 3% sodium metasilicate, 3% n-propanol, 0.3% sodium dod-ecyl diphenylether disulfonate, and 0.3% of an alkyl naph-thalene sulfonate. The number of solid and ghost steps remaining after development are given in the followin~
table.

2 Sec. 5 Sec. 10 Sec.
Coating Solid/~host Solid/Ghost Solid/Ghost A 4-5 5-7 6-~

Examples 42 and 43 The usefulness of the compositions of the present invention with lower intensity exposure porcesses was ex-amined. The compositions as weight percentages were as follows:

~4 2~9 Percenta~e Solids ComponentSolution A Solution B

pentaerythritol tetraacrylate43.1 32.3 P-II 23.7 18 P-V 6.25 17.2 polyvinyl formal (10% in the azeo- 15.2 17.7 trope pigment dispersion (of Example 40) 3.09 2.8 tri.ethylamine (20% in the azeotrope) 2.15 1.6 10 diphenyliodonium hexafluorophosphate 4.30 8 4,4'-bis(dimethylamino)benzophenone 2.14 2 Solution A was dried for one minute at 180F with a coating welght of 200 mg/ft . Solution B was dried with a heat gun at a coating wei~ht of 170 mg/ft2. The substrate in both cases was grained and anodized aluminum. A c.onventional micro~ilm en].arger was used and the plates were exposed with between 10 and 30 milliwatts/cm2 irradiance by a mer-cury xenon lamp through a 21 step sensitlvity ~uide in contact with the plate. ~xposure was made in alr. The exposed plates were developed by washing wlth an aqueous solution Or 5.25% metaslllcate, 6.37% n-propanol, 8.25%
glycerol and 0.075% alkyl naphthalene sulfonate. The re-sults are reported below.

Exposure Time . Steps Plate Seconds Solid/Ghost .

8 5-7 1~.2~9~9 Exposure Time Steps P]ate Seconds Solid/Ghost L~ 6-8 When identical plates were imaged (A for 3 seconds and B for 1 second) with line copy and half tones on an aluminum sheet, 10,000 high quality impressions were ob-tained with no image loss.

Examples 44-50 A standard solution was prepared having the following weight percentages of ingredients in the n-pro-panol-water azeotrope:

pentaerythritol tetraacrylate 43.2 P-V 6.35 polyvinyl formal (10% in the 15.1 azeotrope) Pigment Red 48 3.1 triethylamine 2.15 diphenyliodonium ilexafluoro- 4.1J
phosphate 4~LI~-bis(dimethylamlno)benzo- 2.2 phenone To seven aliquots of this solution were added 23.5 percent by weight o~ the oligomers P-II and P-VI through P-XI.
The solutions were coated on grained and anodized alumlnum using a number 18 wire wound rod and dried for one minute at 65C.
The dry coatings were exposed in air through a 21 step sensitivity guide with a mercury metal halide diazo bul~
and developed by wiping with the aqueous developing solu--29g~
_1~5_ tion of Example 40. The results are shown in the follo-wing table.

Steps Example Oligomer Solid/Ghost The above examples show the effect of varying the ratio of aci.d groups to molecular weight of the oligomer. The first two compositions (Examples 44 and 45) had ratios of acid groups to molecular weight of approximately l:4300 and l:3600 respectively and were more difficult to develop than preferred and had a tendency to hold the ink on the background, A stronger or more vlgorous developer could correct that tendency. The ollgomer oI' Example 50 had an acid to molecular wei~ht ratio of` about l:750 and developed a lLttle to easily, wit~l much of the photoreact,ed material bein~ removed, All composJt:Lons were useful and could be polymerized in air, however. Examples 46 through 49 worked exceptionally well and had a ratio of the number of acid groups to molecular weight of between about l:800 and l:3000, with Example 48 having a ratio of about l:1200.
Compositions without any acid groups do not adhere well to the substrate. Development does not differentiate between exposed and unexposed areas with both being removed indis-~ 2 ~ ~ ~9 criminately. Compositions without ethylenic unsaturation do not photoreact and also do not bind to the plate sur-face.

Example 51 A solution was prepared like those in Examples 44-50 using P-XII in place of the oligomers in the above examples. Coatings were exposed and developed as in Ex-amples 44-50. Only one ghost step and no solid steps were obtained. Prolonged exposure gave more retained steps.

Examples 52-57 A solution was prepared for the comparison of different binder materials. The solution comprised in parts by weight:

pentaerythritol tetraacrylate 41.3 15 P-II 22.5 polyvinyl formal 9.95 Pigment Red 4~ 2.94 triethylamlne 2.05 diphenyliodonium hexaf`luoro- 4.2 20 phosphate 4,4'-bis(d1methylalllino)ben~o- 2.1 phenone selected binders 14.9 The binders selected were 25 52. P-V
53. low molecular weight hydroxypropyl cellulose 54. polyvinyl butyral (MW 38,000-45,000) "2zg~9 55. polyamide (ElvamideR nylong resin supplied by DuPont Co.) 56. polyvinyl formal 57. no resin The solutions were coated onto salt plates (clear crystals of sodium chloride), dried, and the infrared spectrum determined. The coatings were exposed in air to radiation from a 2 kilowatt mercury metal halide diazo bulb for various times at various irradiances. The infrared spec-trum was determined after the exposure and the percentageof double bonds converted by the exposure was calculated on the basis of the absorption at 810 cm 1. The results appear below.

Percentage of Dou~le Bonds 15Exam~leConverted at 9 mW/cm Irradiance Examples 58-69 A solution was prepared for the comparlson of different binder materials. The solutlon compr:lsed ln parts by wei~ht:
pentaerythrltol tetraacrylate 43.1 P-II 23.7 polyvinyl formal 15.0 Pigment ~ed 48 3.0 triethylamine 2.2 diphenyliodonium hexafluoro- 4.4 phosphate 4,4'-bis(dimethylamino)benzo- 2.2 phenone selscted polymeric binders 6.3 The binders selected were 58. P-V
59. polyvinylpyrolidone 60. polyvinyl ~ormal 61. copolymer of vinyl chloride (81%) and vinyl acetate (19%) 62. polyvinyl acetate 63. polyethylene oxide (MW - 4,000,000) 64. polymethylmethacrylate (low molecular weight, inherent viscosity - 0.2) 65. low molecular weight polyolefin resin 66. linear saturated polyester resin 67. thermoplastic aromatic polyurethane 68. cell.ulose acetate butyrate 69. no resin.
The results o~ infrared analysis after coating of these compositions as i.n Examples 52-57 and exposure to 9 milli-Watts/cm irradiance appears below.
Doubl.e l30nd Converslon Examp.le __ %
5~ 3 63 2~1 6~ 15 In examp:Les 52-69, exposure time was 10 seconds.

Claims (16)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A photopolymerizable composition comprising 1) 10% to 60% by weight of an organic film forming polymer, 2) 10% to 60% by weight of a free radical polymerizable monomer having at least one ethylenically unsaturated group, and 3) 0.1% to 12% by weight of a photoinitiator system capable of initiating free radical polymerization upon absorption of electro-magnetic radiation, said photopolymerizable composition characterized by further comprising a photopolymerizable composition comprising 4) 10% to 60% by weight of an oligomer of the formula where E is an ethylenically unsaturated, free radical polymerizable group, D is the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form groups bonded to E and R, R is the residue of a polyol having at least a + b hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, said polyol having a number average molecular weight between 90 and 10,000, A is a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10.

2. The photopolymerizable composition of claim 1 wherein E is selected from the class consisting of acryloyloxyalkoxy, methacryloyloxyalkoxy, vinylalkoxy, and allyloxy groups, D is the residue of a diisocyanate, A is selected from the group consisting of and , and m is an integer of from 1 to 6 inclusive.

3. The photopolymerizable composition of claim 2 wherein E is selected from the class consisting of acryloyloxyalkoxy and methacryloyloxyalkoxy, and said free radical polymerizable monomer has 2 to 4 ethylenically unsaturated groups selected from the class consisting of acryloxy and methacryloxy.

4. The photopolymerizable composition of claim 3 wherein R is the residue of a polyesterpolyol having a hydroxy equivalent weight between 90 and 4,000.

5. The photopolymerizable composition of claim 4 wherein said film forming polymer is selected from the group consisting of polyvinyl acetals, polyvinylalcohol, polyvinylpyrolidone, polyamides, hydroxyalkylcelluloses, polyvinylacetate, and copolymers of polyvinylchloride and polyvinylacetate.

6. The photopolymerizable composition of claim 3 comprising 10 to 96% by weight of a solvent which is not reactive with carboxyl groups or ethylenically unsaturated groups.

7. The photopolymerizable composition of claim 1 wherein said oligomer is represented by the formula:

wherein E is an ethylenically unsaturated free radical polymerizable group selected from acryloyl-oxyalkoxy and methacryloyloxyalkoxy, D is the residue of a diisocyanate having its two isocyanate groups reacted to form groups bonded to E and R1, R1 is the residue formed by the removal of active hydrogen atoms and hydroxyl groups from oligomeric .OMEGA.-hydroxy carboxylic acids or the residue formed by the removal of active hydrogen atoms and hydroxyl groups from oligomeric diols, R2 is the residue of an aliphatic polyol having the formula R5 (OH)a+b after removal of a+b hydrogens from hydroxyl groups and having a valance of a+b, or the residue of an aliphatic polyol having the formula after removal of (a+b-1) hydrogens from hydroxyl groups and R5 is the residue of an aliphatic polyol radical formed by having the OH groups of the polyol removed therefrom and having 3 to 10 valences substituted with OH groups, R3 is the residue formed by removal of two groups from a dicarboxylic acid, a is a number having an average value of from 2 to 20, and b is a number having an average value of from 0.3 to 10, wherein the molecular weight of is between 200 and 5,000.

8. The photopolymerizable composition of claim 7 comprising 15 to 45% by weight of oligomer, 15 to 35% by weight of organic film forming polymer, 25 to 50% by weight of free radical polymerizable monomer, and a photoinitiator system comprising in parts by weight of the polymerizable composition 2 to 8% of initiator and 1 to 4% photosensitizer.

9. The photopolymerizable composition of claim 7 comprising 85 to 95% by weight of a solvent which is not reactive with carboxyl groups or ethylenically unsaturated groups.

10. The photopolymerizable composition of claim 1 wherein said oligomer is represented by the formula:

wherein R3 is the residue formed by the removal of two groups from a dicarboxylic acid, R4 is H or CH3, c is 2 to 5 inclusive, p is a number average value of from 2 to 7.7, q is a number average value of from 0.3 to 4, R6 is the residue formed by the removal of two iso-cyanate groups from a diisocyanate, and R7 is an organic polyol radical which is the resi-due of an organic polyol with at least three hydroxyl groups removed therefrom and having a molecular weight of from 90 to 10,000.

11. The photopolymerizable composition of claim 10 wherein said film forming polymer is a polyvinyl acetal.

12. The photopolymerizable composition of claim 1 wherein said oligomer is of the formula wherein R3 is the residue formed by removal of two groups from a dicarboxylic acid, R4 is H or CH3, R6 and R8 are independently the residues formed by the removal of two isocyanate groups from a diisocyanate, d is 1 to 6 inclusive, e is an average value of 0.5 to 5 inclusive R9 is an alkanepolyol radical having a valence of h + 1 that is the residue of an alkanepolyol having h + 1 hydroxyl groups removed therefrom, said alkanepolyol having a molecular weight of from 100 to 10,000, f is an integer of 1 to 6, and h is an integer of 2 to 8.

13. A substrate having coated on at least one face thereof a photo-polymerizable composition according to claim 1.

14. The substrate having a coating of claim 13 wherein said substrate is grained and anodized aluminum and the composition is present in an amount of from 0.3 to 9 g/m2.

15. The substrate having a coating of claim 14 having an additional polymer top coat comprising an organic polymer which is soluble in an aqueous alkaline solution of pH 8-13 coated over said photopolymerizable composition.

16. A polymerizable oligomer of the formula wherein E is an ethylenically unsaturated, free radical polymerizable group, D is the residue of a polyisocyanate having at least two of its isocyanate groups reacted to form groups bonded to E and R, R is the residue of a polyol having at least a + b hydroxyl groups, the residue formed by removal of hydrogen from the hydroxyl groups, said polyol having a number average molecular weight between 90 and 10,000, A is a carboxylic acid containing group, a is a number having an average value between 2 and 20, and b is a number having an average value between 0.3 and 10.