Patent GB-825795-A (GB)
Title: Photopolymerisable compositions and elements and process of making reliefs therefrom
IPC: G03F7/033
Filed: 1957-08-08
Abstract: A photopolymerizable composition comprises 10-60% by weight of an addition polymerizable ethylenically unsaturated compound, 40-90% of a polyvinyl alcohol derivative having a molecular weight greater than 10,000 and containing lateral free oxyacid groups or corresponding salt groups which is soluble to the extent of at least 10% in 2% aqueous ammonia and has the oxyacid or salt groups linked to the main polymer chain through ester and/or ether, including acetal, oxygen, and 0.01 to 5% by weight of the unsaturated compound of an addition polymerization initiator activatable by actinic light which is compatible with the other ingredients of the composition and is not active thermally at temperatures below 80-85 DEG  C., such as diacetyl, benzil, benzoin, pivaloin, benzoin methyl and ethyl ethers, and alphamethyl, alpha-phenyl and alpha-allyl benzoins.  Specified polymerizable unsaturated compounds are methyl methacrylate, mixtures of styrene with diethyl maleate or fumarate, methyl and hydroxyethyl vinyl benzoate, N(b -hydroxyethyl) methacrylamide, N,N-bis-(b -hydroxyethyl) acrylamide, b  - acetamidoethyl methacrylate, b  - methacrylamido ethyl propionate and, in particular, polyunsaturated monomers such as esters of acrylic and methacrylic acids with polyhydric alcohols (listed), methylene bisacrylamide and methacrylamide, ethylene bismethacrylamide, 1,6 - hexamethylene bisacrylamide, diethylene triamine tris - methacrylamide, divinyl succinate, adipate, phthalate and terephthalate, divinyl benzene-1,3-disulphonate, divinyl butane-1,4-disulphonate, sorbaldehyde, b  - methacrylamidoethyl methacrylate, N - (b  - hydroxyethyl) - b -(methacrylamido) ethyl acrylate and N,N-bis-(b -methacrylyloxyethyl) acrylamide.  The polyvinyl alcohol derivatives may be derived from polyvinyl alcohol itself or a hydrolysed copolymer of a vinyl ester with a minor amount of another monomer, e.g. N-vinyl phthalimide, N-vinyl pyrrolidone, N-vinyl-N-methylformamide, ethylene, styrene, butadiene, vinyl fluoride, methyl, ethyl and benzyl vinyl ethers and allyl glycidyl ether.  The oxyacid derivatives may be prepared in various ways, e.g. the polyvinyl alcohol may be provided with acidic groups, either carboxylic or sulphonic, by esterification or acetalization with alcohols or aldehydes containing acid groups.  Amongst many such derivatives specified the examples refer to the preparation and use of polyvinyl acetate/acrylal/(sodio o-sulpho) benzal, polyvinyl alcohol/acetate/(sodio o-sulpho) benzal, polyvinyl hydrogen phthalate, polyvinyl alcohol/acetate/hydrogen maleate, polyvinyl formal/hydrogen phthalate, polyvinyl acetate/benzal/(sodio o-sulpho) benzal and polyvinyl alcohol/acetate/hydrogen dodecenyl succinate. The compositions may also contain silica, bentonites, powdered glass, polyvinyl alcohol, acetate, butyrate, formal and butyral, polyglycerol phthalate and maleate, polyvinyl sorbate and sorbal, triacetin and bis-(acetamidopropoxy) ethane.  The compositions are used in the preparation of relief images whereby a plate comprising the photopolymerizable composition is exposed to actinic light through a negative and undeveloped portions of the plate are removed by aqueous, preferably basic, solutions. Specifications 535,341, 575,626, [both in Group IV], 600,023, 741,441, 741,470, [both in Group XX], and 792,840 are referred to.