CA1079561A - Photopolymerisable compositions containing a polymer with a component which reduces a keto sensitizer in its excited state - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A photopolymerisable composition comprising (a) a water-soluble polymer having an amine, phosphine, arsine or stibine reducing component; (b) a monomer compatible with a solvent for (a) and which is capable of polymerizing with (a) to form a water-insoluble product; and (c) a photosensitiser;
and wherein the component (a) is capable of reducing photosen-sitiser (c) when (c) is in an excited state to effect addition polymerisation of components (a) and (b).
Also described is a process for the preparation of a polymeric material which comprises irradiating the composition with suitable radiation so as to convert the photosensitiser to an excited state. The composition is of use in the preparation of relief plates for photo-resist applications,

Description

~079561 `-This invention relates to radiation pol~merlsable composition~.
B~gian Patent ~lo.82,Q~404 describes ~hoto-polymerisa~e c~mpositions comprising ta) a wa~er-soluble or~water-dispersible.polymer or copolymer, or-.
a po~ymer or copolymer mixture in which one or more of the components is water-soluble or wa~er-dispersi~le; tb) an addition-polymerisable monomer whlch is soluble in or compatible with a solvent or dispexsing medium or (a); ana.
(c) a photo-initiator capable of ini~iating polymerisation of the monomer whereby the composition may be rendered water-insoluble by radiation.
Bqlgian Pate~t`No.789,950 descrlbes the photopoly~
merisation of ethylenically unsaturated material . ~:
-uslrlg a photo~inl~iator comprising (i~ at least one photosensitiser havi~g the struc~ure ~ ~~(X)n~~
c~ , .
where x is ~C=0, ~CR1R2 or ~CR30R4, Rl t ~ ~
may be the same or dif:Eerent, are hydxogen or hydro-carbyl groups; n ls O or 1 and the groups A9 which may be the same or different, are hydrocarbyl or substi~uted hydrocarbyl groups, the groups A beins aromatic or substituted aromatic when n is ~ and X i~ ~CR1~2 ~nd also when n is ~, and ' ~ ~ . ;

' : ' - : .

, . . .

~ ~7 ~ ~6 ~

tii) at least one reducing ayenk capable o~ reducing the photosensitiser when the photosensitiser is ~n a p~oto~exc~ted state~
We have now found that it may be advantageous to employ S as the polymer or copoLymer in the photopolymerisable composition of Patent No.820,404 a compound capable of acti~g also as the reducing age~t o Pa~ent No~789~950 ~ -in association with the photoinitiator of the latter applicationO :~
` 10 . Thus the present in~ention pro~ides a photopol~merisable ; composition comprising (a) a water-soluble or water-dispersib.~e polymer or copolymer, or a polymer or copolymer mixture in which one or more of the components is watex~soluble or water-disperslble, (b) an addition~polymeri.sable ~onomer , 15 which is soluble in or compatible with a solven~ or d~spersing ! medium for ~a); and (c) at least one photosensitiser having the s~ructure A~-(X)n-A
O
where X ls C=0, >CRlR2 or ~CR30R4, Xl to ~4; whi y the same or different are hydro~en or hydrocarbyl groups, n ls 0 or 1 and the ~roups A, which may be the same or , different are hydrocarbyl or substitu~ed hydrocarhyl groups, ; : the groups A being aromatic or subs~ituted aromatic when n is 1 and X ls >~RlR2 and also when n is 0, polymeric component (a) being capable of reducing photosensitlser (c) when said ~. :
photosens~iser is in a~ ~xcited state to effec~ addi~ion ~-_ ~ ~

- : .........

~ ~.' ' . , .

~795~ 1 pol~me~isation of at least a proportio~ of components ~a) and (b) oE the composition Polymeric component (a) preferably compxises a reducing comp~nent having the structure s-~-B where M is an element of Group Vb of the Periodic Table of the Elements, at least one of the units B having a ~arbon atom which forms part of the polymer chain o the polymeric component (a) and at least one other of units B, being ~¦
hydrogen, hydrocarbyl, substituted hydrocarbyl, or a group 10 in ~hich two units B together with the element M form a. :~
ring system, and where the element M is attached directly to an aromatic group, at least one of the other groups B
has a - ~ - group attached to M
; , . .
Preferably polymeric component (a) comprises a :
poly- (N-vinyl pyrrolidone) and, optionally, a vinyl :
acetate component.
The reducing component of the polymer should nave a reduction potential such that in the con~entration in which it is incorporatad in the ~.~nposition it is capable of reducing the photosensitiser when ~he photo-sensitiser is in an excited state yet is incapable of reducing the photosensitiser when the latter is not excited ~y radiation The reducing component, at the conce~tration.
at which it is present in the nhotopolymerisable composition, ¦.
should have little or no inhibiting effect on polymerisation.
:~ The Peroidic Table of the Elements referred to ~- .
is that published ln "Advanced Inorganic Chemistry", second ~ ..

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~.

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edition, by F A cotton ancl G Wilkinson (Int~rscience 1966), and element M may be, for example, phosphorus or more preferably nitrog~n If desire~ M may be ~xsenic or antimon~ and throughout this specifi-cation where reference is made to specific examples of reducing components in which M is nitrogen we tend ~lso, where they are suitable, to include corresponding ex~mples in which M is phosphorus, arsenic or antimony The reducing ¢omponent may be primary,secondary or tertiary; that is, in the structure B-~-B two, one or none of the units B may be hydrogen atoms For example, the reducing component may be derived frc~ a p~imary, ; secondary or tertiary amine or phosphine ~:-One or ~ore of the groups B may be ~ydrocarbyl and the hydrocarbyl group may be, for example, alkyl, cyclo-alkyl or alkaryl. PreEerably, one or more o~ group :
is an alkyl group having from 1 to 10 carbon atoms.
Examples of suitable reducing components in :~
' which one or more of the units B is hydrocarbyl are those ~0 notionally deri~ed from propylamine, n-butylamine, ~entylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, di-n-butylamine, dipentylamine, trimethyl-amine, triethylamine, tripropylamine, tri-n-butylamine, tripen~ylamine, dimethylaminoethyl methacrylate, and :.
long chain fatty amines, e,g. Cl8H37NMe2 Thus the reducing component is conveniently introduced into the polymer by copolymerlsation.
Suitable reducing .
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comonomers in which one or more of the units B is hydro-carbyl are for example the following esters of a methacrylic acid.

2-amino ethyl

3-amino 2 hydroxypropyl 2-amino propyl

4-amino butyl

5-amino pentyl

6-aminobenzyl N-methyl amino ethyl 2-N ethyl amino ethyl 3-N propyl am~no propyL
N-methyl amino methyl 4-N-butyl amino butyl 5 N-pentyl amino pentyl NN_dimethyl amino methyl 2 N,Ndimethyl amino ethyl 3 NN-d1propyl amino propyl 4 NN-dibu~yl amino butyl ...
NN_d~pentyl amino pentyl Examples of reducing components containing aromatic groups include those notionally derived from N,N'-dimethyl aniline, N-methyl diphenylamine, p-(N,N-dimethyl amino) styrene, 2 a~ilinoethyl methacrylate, 2-p methoxy anilino-ethyl methacrylate, 2-anilino l-methyl ethyl acrylate.
One or more of the units B may be a substituted hydrocarbyl group and in particular the hydrocarbyl grou~
may carry a substituent having the structure - R2 ~ M

'~

~ ..... .. . . ., : - .. : . . -- . . . . . ::
- : - . . . ,. . : - . : . - . . , .: , - - . . -- . - : : .. . -. : - . . .

where M is an element of Group Vb of the Peri.odic Table of the Elements and the unit R2 is, for example, an alkylene chain and the units R3 which may be the same or different, are hydrogen atoms or hydrocarbyl groups, especially alkyl (particularly Cl-C4) groups.
B Examples of reducing components having the structure B-M-B in which at least one of the units B is a substituted hydrocarbyl group include notional derlvatives of the structure ~ N - (CH2) n - N \

in which n is a whole number of at least two and the groups R3, which may be the same or different, are hydrogen atom~ or hydrocarbyl, especially alkyl groups For example, the reducing component may be notionally derived from ethylene d~amine~ trimethylene diamine, tetramethylene diamine, pentamethylene diamine or hexamethylen~ diamine, or N-hydrocarbyl, especially N-alkyl derivatives thereof.
~0 Examples of such copolymerisable monomers are the following esters of ~meth)acrylic acid:-1,3 bis-(dimethylamino)isopropyl 1, 3 bis- tdiethylamino)isopropyl N-~diethylaminoethyl) N-methylami~o methyl Other suitable reducing component. include ~o~ional . derivatives of compound~ having the structure R3 \ / R3 / N (CH2~n N \

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-.. . . -. . . . - : .. - .. : . ~ . :.. . ..
. , .. : .. . . . .. :, ... .. ~. .. . . . . . . . .
, - . . . ... . - . .
.:: . .~: . . . . . , . : . - -.. : . ~ . ' ~ . --.- . -~1'0'7',956J, in wh.ich one or more of the hydrogen atoms in the -CH2 unit is suk,stituted by an - N~ 3 group, especially an -NH2 group-Ex,~mples of reducing componen~s in which th~e element M forms part of a ring system include those notionally derived from piperidine, and N~hydrocarbyl, especially N-alkyl, derivatives of piperidine fox ex,ample 1,3 bis (di-piperidinomethyl)isopropyl metha~-rylate.
Other reducing components include those notionally derived from tri,allylamine, lallyl)~-N-C~2- ~ CH2 N
~allyl?2, allyl thiourea,o-tolyl thlourea, soluble salts c,f aromatic sulphinic acids, e.g. S-benzyl iso-thiuroni~m, p-toluene sulphinate, ,and sodium diethyl dithiophosphate.
I Incorpora~ion of the reducing componen~ into the i 15 polymeric compon~ent of the composition, or preparation of ! a polymeric component containing such a reducing co~ponent I according to the invention, may be by known techniques . ..
for polymer preparation and will present no difficulty I to the skilled man. Suitable preparative ~ethods include i 20 copolymerisation of the polymeric component of the composltion with a material compri5ing the reduciny component and copolymeris,,~ble with the said polymeric component~
A particularly suitable me~hod ~o~ incorpora~ing the reduclng component is by free radical fropolymeris~tion using for instance amino alcohol esters o~ (meth)acrylic ' acid.
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The reducing component can also be introduced by reacting an existing polymer, for example poly~inyl alcohol, with an amino aldehyde. Monomers containing acid functions should not be employedO
Polycondensation techniques may also be employed where appropriate.
Suitably the concentration of the reducing component in the composition may be in the range 0.001% to 50~ by weight of addition-polymerlsable or ethylenically lo unsaturated material in the composition although concen-trations outside these ranges may be used if desired.
Preferably, the reducing component is present in a concentration of 1% to 10% by weight of the ethylenically unsaturated material in the composition.
Where o~e or more of the groups B in the reducing component B-~-B is aromatic then it is preferred to have a concentration of reducing component is the photopoly-merisable composition in the range OoOl~ to 0.5% by weight of ethylenically unsaturated material in ~he compositio~.
Typical water-soluble polymers include hydroxyethyl cellulose, polyvinyl pyridine, sulphonated polystyrene, and partially hydrolysed polyvinyl acetate.
Component (a) comprises a water-~oluble polymer either alone or in admixture or copolymerised with one or more less water-soluble polymers or monomers (as appropr~ate~, examples of which are polyacrylates, poly-alkyl acrylates (e.g. polymethyl acrylate, 2-ethyl hexyl acrylate), polyalk~l methacrylates (e.g. polymethyl _ g _ ,, ' ' ' ' ' '. .`.- - ' . . .

methacrylate~ lauryl methacrylate), dialkyl maleates (e.g. di-iso-octyl maleate, di-butyl maleate, diethyl maleate).
Selection of the ingredient(s) of component (a) will be made in the light of the requirement that it should be capable of being washed from a film of material using an aqueous liquid, preferably water, i e. that it should be water-soluble or water dispersible. Preferably also the composition is soluble in an alcohol or other convenient solvent for ease of film formation.
Our preferred component (a) comprises poly(N-vinyl-pyrrolidone), either alone or in admix~ure with polyvinyl-acetate, or a copolymer of N-vinylpyrrolidone and vinyl acetate. The polyt~-vinylpyrrolidone) and the copolymer of N-vinylpyrrolidone and vinyl acetate are both water and lower alcohol (e.g. methanol and ethanol) soluble, and we have found this advantageous because formation of the composition of the invention into a film from a solution is one of the lower alcohols (i.e. up to C4) is pref~rred~ Substitution derivatives of the components,-where suitable may also be employed, of course.
The component (a~ will usually be present in he composition in an amount forming from 50% to 95~ by weight, the water solubl~ polymer preferably foxming 30-70% of the total of (a~.
The monomer employed is one which is pxeferably, although not necessarLly, water insoluble. It i8 desirable of course tha~ the monomer be hlghly compati~le with the `~ 10 --.~ . ~ . . . :
, ~
. . . - . .. . .
- - : . :: .. . - , :

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polymeric and any other components of the composition, and capable of polymerising. with at least one of component (a) to form a water-insoluble product. Preferably the monomer comprises at least two non-conjugated ethyl~nic double bonds, and prefexably has terminal unsaturation.
As examples of suitable monomers we would ~ention (1) N (CH2CH20f ~ C a CH2) 2 ~here R = H or CH3; in which the ~enæene ring may contai~
one or more substituents which may be the same or di~erent, incl~ding alkyl groups up to 4 car~on atoms, -COOH, halogen, -COORl in which R, is a lower (e.;g. up to 4 carbon atoms~ alkyl group~ -S02 NR2 R3 or -CONR4R5 where R2, R3, R~ and R5 each represents H or a lower alkyl group.
e~g. N:N-bis-~-acryloyl oxyethyl) aniline N:N-bis~ methacryloyloxyethyl) m toluidine - ~ N:N (ac~yloyloxyethyl~-chloro aniline (2) CH2 - C - CONH(C~2)30tCH2)20(CH2)3H 2 where R - H-or CH3.
e.g. 1,2-(yacrylamidopropoxy)ethane 1,2-(yme~hacrylamidopropoxy)ethane (3) Acrylates, ; e.g. allyl methacrylate e~hylene glycol dimethacrylate ~ ~ trim~thylol propane triacrylate :

. :, .

; .............. . .
, trimethylol propane trimethacrylate pentaerythritol tetra acrylate pentaerythritol mono hydroxy triacrylate.
(4) vinyl urethanes, e.gc a reaction product of di(4-isocyanatophenyl)methane, polypropylene glycol and 2-hydroxyethyl methacrylate in mole ratio 2:1:2.
Reaction product of tolylene diisocyanate, penta-exythritol/propylene oxide adduct, and 2-hydroxyethyl methacrylate in mole ratio 4:1:4;
~5) Allyl monomers e.g. triallyl cyanurate.
The proportion of monomer in the composition will vary within wide limits but will usually lie within the range 5% to 50% by weight, preferably 10 to 25~ by weight of the composition.
It wlll be appreciated that, although not preferred, component (b) could be an oligomer, that is a short polymeric chain having up to 8~ say, 5 repeating monomeric units.
The reducing component of the polymer should naturally be one which does no~ adversely affect the ~ater-soluble or water-dispersible property of the pol~mer to an undesixable degree, and it will ~e selected accordingly.
The photosensitiser employed accordlng to the present invention may be any suitable compound. In particular according ~o the invention ~e prefer to employ .. ~.

'' ~ ,~, '. . ' ~ ;, ~. .. .

a photosensitiser as described, and in the proportions indicated~ in selgian Patent No.789,950.
In general the groups A in the photosensitiser will be aliphatic or aromatic and it is to be understood that the groups A may be the same or different, that is, for example, in the pho-tosensitiser of struc~ure I both groups A may be aromatic, or both may be aliphatic, or one group A may be aromatic and the other aliphatic provided that when n is l and X is >CRlR2, and when n is 0, ~oth groups ~ are aromatic. Howev~r, for reasons of convenience in the prepaxation of the photosensitiser the groups A are preferably the same.
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.. ~

. -.. ~ .

Within the scope of the term aliphatic groups we include cycloaliphatic groUpS and aliphatic groups carrying aromatic subs~ituents, that is, alkaryl groupS. Similarly, within the scope of the term aromatic group we include S groups carrying alkyl substi~uents, that ls~ aralkyl grouPs.
The aromatic group may be a benzenoid aromatic group, e.g. the phenyl group, or it may be a non-ben~enoid cyclic group which is recognised ln the art as possessing the chaxacteristics of a benzenoid aromatic group.
The groups A, especially when aromatic, may carry substituent groups other than hydrocarbyl, e. g. halogen or alkoxy, provided the photos~nsikiser containing the substituents groups is not present ln the photopolymerisable composition in such a concentration as to result in substantial inhibition of pol~merisation of the ethylen-ically unsaturated material in the composition.
In the photosensitlser having the structure I the group X preferably has the structure ~C=0 or ~CR30R4 where R3 and R4 are a~ hereinbe~ore described.
The groups ~1' R2~ R3 and R4 ma~ be hydrogen or hydrocarbyl groups, for example alkyl. Preferably the groups Rl to R4 are hydrogen.
In the photosensitiser having the structure I the groups A may be further linked tog~ther by a direct link, or by a ~ivalen~ group, e.g. a dlvalent hydrocarbyl group, that is~ in addition to the link through the group ~ ~ ~ tX~n - the groups B may be further lLnked so as to . - , ,. , : . . : : .

:- . : : - ~ . - :
, : . :

~ ~ 7 ~ 5 ~ ~

forn~ ~ cyelic ring system. -~or example, wh~re the groups A are aromatic the photosensitiser may have the structure (Y)m ~ - (X~ ~ II

in which X and n are as hereinbefore described, Y is ~CH2, or hydrocarbyl derivative thereof, and m is o, 1 or 2. Preferably, the group Y is linked ~o the aromatic groups in positions ortho ~o the group - ~ - (X)n -The groups A togethex may orm a fused aromatic rlng system.
Particularly preferred photosensiti~ers on account of the rapid rates at which the ethylenically unsaturated ma~exial may be polymerised are a-diketones having the structure I in which X ls >C=0 and n is 1. In general r the a-diketone~ are capable of being excited by radia~ion in the visible region of the spectrum, that is, by light : having a wavelength greater than 400 m~, e.g. in thP
. . .~15 w velength:~ange 403 m~ to 500 m~, although ultraviolet radiation or a mixture o~ ultraviolet radiation and viæible light, ma~ be used. Suitable -diketone photo-sensltisers include biacetyl in which both groups A are methyl, bqnzil in which both groups A are phenyl, ~--dlketon~s ln which buth of the groups A are fused aromtic, e.g. a-naphthil and B naphthil, and ~-diketones in which : ~ the groups A are aralkyl groups~ e.g. p-tolil. As an ~ `: example of a suitakle a-diketone pho~osensitiser in which :: , ~ 15 , ~ : : . ;- . . . . . ... . .

.
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the groups A are non-benzenoid aromatic there may be mentioned furil in which the groups A have the struckure ~ ~ e.g. 2:2'-furil. In ~he a-diketone photo-sensitiser the groups ~ may carry non~hydrocarbyl groups, S for exampl~, the photosensitiser may be p,p'-dialkoxy benzil, e.g. p,p'-dimethoxy benzil, or p,p'-dihalobenzil, eOg. p,p'-dichloxobenzil, or p-nitrobenzil.
In the photosensitiser having the structure I, n may be zero in which case the groups A are aromatic or subs~ituted aromatic. An example of such a photosensitiser is benzophenone in which both the groups A are phenyl.
Further suitable photosensitisers include those having the structure I in which n is l and X is >CR30R4.
For example, ~he photosensitiser may be ben~oin in which R3 and R4 and H and both the grou~s A are phenyl, an alkyl benzoin in which R3 is hydrogen and R4 is alkyl, e.g.
methyl, a-naphthoin and ~-naphthoi~ in which both the groups A are fused aro~atic, p,p'-dialkoxy benzoin, e.g.
p,pl-dime~hoxy benzoin, and p,p'-dihalobenzoin, e.g.
p,p'-di~hlorobenzoin, in which the groups A oarry non-hydrocarbyl groups, and furoin in which the groups A are non-benzenoid aromatic and have the structure e.g 2,2'-furoin.
In the photosensitiser the groups A may b~ linked together by a direct link or by a divalent hyd~ocarbyl group to form a cyclic ring system~ For example where the groups A are aliphatic the photosensitiser may be c~mphorquinone.

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Where the photosensitisar has the structure II
suitable photosensitisers include fluorenone in which n and m are both zero and the aromatic groups A are linked by a direct link ortho to the group - C - (X)n -, and phenanthraquinone in which X is >C=0', n is 1, and m is 0, the aromatic groups A being linked by a direct link ortho to the group - C ~ (X)~ ~. The photosensitiser may be acenaphthene quinone in which the groups A in structure I together form a fused aromatic ring system.
~he photosensitlser may, for example, be present in the photopolymerisable composition ln a concentration in the range 0.001% to 10% by weight of the ethylenically unsaturated material in the composition although concen-trations outside these ranges may be preferred.
The method of mixing.of the photosensistiser with the ethylenlcally unsaturated material may have a bearing on the succesR or otherwise of achieving the desired concen~rations of photos~nsitiser and reducing agent : therein.
- 20 Thus, where the photosensi~iser is no~ suficiently soluble in the ethylenically unsa~ura~ed matexial, or where one or the other may be dissolved only with difficulty, we have found that dissolution of the photo-sensltlser may be assisted by addition to the ethylenically unsaturated material of a small amount of a diluent in . whlch the photosensitiser is soluble and which is :
mlscible with the ethylenically unsaturated material.

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Suitably, the photosensitiser may be intxoduced into the ethylenically unsaturated material in the form of a solution in such a diluent.
According to a further embodiment of the lnvention there i5 provided a process for the preparation o a polymeric material which comprises irradiating a photo-polymerisable composition as herein described with radiation having a wavelength which i5 capable of being absorbed by the photosensitiser so as to convert the photosensitiser to an excited state.
The radiation may be visible light or ultraviolet radiation or radiation which includes within its spectrum radiation of both visible and ultraviolet wavelengths.
Suitably, the radiation may have a wavelength in the range 230 m~ ~o 600 m~. Sunlight may be used as ,the sourcP o~ radiation although the wavelength of radiation to be used will be determined by the particular photo-sen~itiser in the composition, the radiation being of a wavelength such a~ ~o be absorbed by the photosensitiser so as to convert the photosensitiser to an excited state.
A suitable wavelength may be chosen by means of simple experiment e.g. by measuring the electronic absorption spectrum of the photosensitiser.
In general, polymerisation of the ethylenically unsaturated material proceeds readily at ambient temperature when the composition 1s irradiated with radiation having a wavelength which converts the photosensitiser to an - ~

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-, ' . ' : '. ~ .. ' :
- . . - ~ . : . .

3L~7~356,1 excited state. However, the rate of poly~erisation may in general be increased by effecting the polymerisation at a temperature above ambient.
The invention provides photopolymerisable compositions which may be developed (that is, unexposed areas removed) by treatmen~ with water or an aqueous liquid, and the compositions may be employed for example in the preparation of coated sheet materialsl carrying a layer of the composit~on. Such sheet material~ may be employed for ` example as printing plates. Other uses for the compositions include photo-resist applications.
According to anokher aspect of the invention there-for, we provide a carrier having dep~sited thereon a photopolymerisable composition as hereinbefore described.
Preferably the carrier will be a sheet together with a - layer of the composition deposited upon at least one surface thereof. A particular application o~ such a sheet product is in the production of relief plates whlch are capable, af~er suitable processing, of being used both for direct or offset letterpress printing flexo printing, flexo-printing or as pattern plates as described fully in Belgian Patent No.820,404, and accordingly another a~pect of the lnvention provides a " ~ ., , . , ,, "
method of preparing reIief pl tes ~y selectivi~y exposing - - - . .. . . .
a composition according to the invention to appropriate radiation, fsr example through a negative, and developing the exposed composition (convenien~ly in the form of a sheet upon a substrate).

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The invention is illustrated by the following examples:-Example 1 Preparation of Polymer A mixture of vinyl acetate (100 gm), vinyl pyrrolidone (100 gm), dimethylamino ethyl methacrylate (4 ~m) and azobis iso-butyronitrile (2 gm) was added to ref~uxing industrial methylated spirits (160 gm). The mixture was refluxed in a nitrogen atmosphere ~or a total of 14 hours. A viscous straw coloured solution was obtained.
_ _ The above solution ~100 gm) was mixed with ethylene glycol dimethacrylate (11 gm), benzil (1.65 gm) and dimethyl phthalate (5.5 gm). The mi~tu~e was spread on to a steel shee~ and dri`ed by heating at 60C for 1 hour and 85C for 1 hour to yield a coating 0.5 mm thick.
The dried plate was exposed through a negative to ultra violet radiation for 5 mins and then washed for 4 minutes with a spray of water to give a relief image. After drying ; at 105C for 10 minutes the plate was suitable for use as a let~erpress printing plate. The plate was ~uite flexi~le and after processing could be ormed round a roller of 4 cm diamster.
Exam~le 2 167 parts of 60% solution o~ copoly(vlnyl acetate/vinyl pyrrolidone), made by polymerislng a mixture of equal weights of vinyl pyxrolidone and vinyl acetate in industrial methylated spirits, was mixed with 20 paxts of ethylene glycol dimeth-acrylate, 10 parts of dlmethyl phthalate, 2 parts dimethyl ..... _ . ................. . . .....

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amino ethyl methacrylate and 2 parts benzilO A portion of the solution was used to prepare a printin~ plate as described in Example 1. After exposure and wash-out, the plate cracked on being formed round a 4 cm diameter roller.

Plates were prepared as described ln ~xample 1 using different photoini~ia~ors at various concentrations ln the following basic composition:-vinyl pyrrolidone:vinyl aceta~e-dimethyl~minoethyl methacrylate polymer ~50:50:2) 100 pts ethylene glycol dime~hacrylate ~0 pts Cereclor - 50LV* 10 pts The dxied plates were exposed to W radiation through a "By Chrome"*screen tint negativeO The exposur~
times quoted are those which were requirea to retain th~
5~ dots on the plate after processin~ as described in Example 1. . . .
. ~oncentration of gxposure ~ ~ (m 3 t-Bu~yl anthraquinone 0O01 6 4 1I n n n O o l 6 1~ n n n 10 O . 7 5 6 ~ 1. 0 10 ' 25 7 Fluorenone 0.01 ~12 8 n n n O. 1 S
9 ~ 00 5 5 10 . ~ 1 . 0 5 . *Trade Mark .

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. . . Concentration of Exposure Exam~le Photolnltlator ~) ~mins 11 Ben20phenone 3.0 5 12 A plate was made using vinyl pyrrolidone:vinyl acetate copolymer (50:50) in place of the copolymer in the composition of Example 11.
An exposure of 12 minutes was found to be necessary ~o retain the 5~ dots.
~K~o~le~ 7 Plates were prepared as described as in Example 1 but using polymer with different amounts of reducing agent in the composition.
vinyl pyrrolldone:vinyl acetate:dimethylamino ethyl methacrylate (50:50:various) 100 pts ethyle~e glycol dimethacrylate 20 pts Cereclor -50 LV 10 pts t-Butyl anthraquinone 0.75 pks ~ - EXposur~ time .
` 20 13 0 1~
14 ~ ~.0 8 5.0 10 16 7.5 12 1:7 10.0 >lS
. - 25 The plates were:exposed to UV radiation th~ough a By Chrome screen tlnt negative and the exposure time indicated is that required to retain the 5~ dots on the plate after processing.

. , : - 22 -: :

,, ~ . ... - - . --: ~ : . . .. .
- ,- . .. : . , ~L0~561 Exam~le_18 A plate was prepared as in Example 1 but replacing the ethylene glycol dimethacryla~e by polyethylene glycol dimethacrylate (Sartomer 210 - available ~rom Sartomer Resins~ Inc). The processed pla~e showed good flexibility and could be ormed round a roller of 4 cm diameter.
Example 19 A plate was made using the polymer described in Example 1~ The composition was:
polymer 100 pts eth~lene glycol dimethacryl~te 20 pts di-isobutyl phthalate 20 pts fluorenone 1 pt :1 15 The plate was exposed through. a negative to W
radiation for 5 minutes. The unexposed areas of polymer were removed by washing with a water spray for 4 minutes.
~ After drying~ the plate was used on a rotary newpaper `, - press. After 300,000 impressio~s the prints were still ¦ 20 of good quality.

: *Trade Mark ' ~ ' .

~ 23 -. , ~

Claims (15)

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

1. A photopolymerisable composition comprising (a) a water-soluble polymer or copolymer comprising a reducing component which is an amine, phosphine, arisen or stibine group having the structure B-?-B where M is nitrogen, phosphorus, arsenic or antimony, at least one of units B
having a carbon atom which forms part of the polymer chain and at least one other of units B being hydrogen, hydro-carbyl, substituted hydrocarbyl, or a group in which both remaining units B together with M form a ring system (b) a monomer which is soluble in or compatible with a solvent or dispersing medium for (a) and polymerizes with (a) to form a water-insoluble product; and (c) at least one photo-sensitiser having the structure where X is C=O, > CR1R2 or > CR3OR4, R1 to R4, which are the same or different, are hydrogen or hydrocarbyl groups, n is 0 or 1 and the groups A, which are the same or different, are hydrocarbyl, substituted hydrocarbyl, or heterocyclic groups, and in which groups A are linked together by a direct link or by a divalent hydrocarbyl group, or in which the groups A together form a fused aromatic ring system, the groups A being aromatic or substituted aromatic when n is 1 and X is> CR1R2, and also when n is O; component (a) reduces photosensitiser (c) when said photosensitiser is in an excited state to effect additon polymerisation of at least a proportion of components (a) (b) of the composition.

2. A composition according to Claim 1 in which component (a) comprises N-vinyl pyrrolidone units.

3. A composition according to Claim 1 or 2 in which component (a) is in admixture with one or more less water soluble polymers or is a copolymer including additionally units of such polymers.

4. A composition according to Claim 1 or 2 in which component (a) is a copolymer comprising N-vinyl pyrrolidone and vinyl acetate units.

5. A composition according to Claim 1 in which at least one of the units B is alkyl, cycloalkyl or alkaryl.

6. A composition according to Claim 5 in which at least one of the units B is an alkyl group having from 1 to 10 carbon atoms.

7. A composition according to Claim 1 in which (a) is a copolymer comprising vinyl pyrrolidone, vinyl acetate and an ester of acrylic acid or methacrylic acid.

8. A composition according to Claim 7 in which the ester is alkyl acrylate or methacrylate.

9. A composition according to Claim 7 in which the ester has the structure B - ? - B

in which one of groups B is where X

is a group having the structure CnH2n where n is an integer selected from 1 to 5, the remaining groups B being H or alkyl.

10. A composition according to Claim 9 in which the ester is dimethylaminoethylmethacrylate.

11. A composition according to Claim 1 in which at least one of units B is an aromatic group.

12. A composition according to Claim 1 containing from 15% to 95% by weight of component (a).

13. A composition according to Claim 12 contain-ing 15 to 66 5% by weight of component (a).

14. A composition according to Claim 1, 8 or 9 in which the photosensitiser is fluorenone.

15. A film comprising a composition according to Claim 1 deposited on a support or carrier therefor.