Patent GB-966297-A (GB)
Title: Light-sensitive polymers their preparation and use
IPC: C08G79/04
Filed: 1960-07-21
Abstract: A light-sensitive polymer is made by condensing in the presence of an alkaline catalyst, e.g. sodium hydroxide or an amine such as triethylamine, tri-n-butyl amine and tri-isoamylamine, a mixture of a dialdehyde, the two aldehyde groups of which are bonded to one or two aryl nuclei, and a ketone having two reactive methylene groups bonded to the carbonyl group in solution in an organic solvent.  The condensation reaction is preferably carried out at ambient or slightly elevated temperatures. Quaternary salts such as benzyl triethyl ammonium chloride or hydroxide may also be used as catalysts.  The condensation may be stopped by the addition of excess acetic acid. The polymer may then be precipitated by pouring the reaction mixture into a large volume of methanol or water and the product purified by solution in dioxane and reprecipitation in methanol or water.  Aldehydes which may be used include dialdehydes and bisaldehydes in which the two aldehyde groups are separated by an aromatic nucleus, preferably nuclei of the benzene series.  The aromatic nucleus may be substituted or unsubstituted.  The dialdehyde may be an a , o -di(o-formylphenoxy) alkane, e.g. 1, 3-di(o-formylphenoxy) propane, 1, 3-bis(21-methoxy-61-formylphenoxy) propane and terephthaldehyde. The ketone may be aliphatic, alicyclic or aromatic, e.g. acetone, cyclohexanone and p-diacetylbenzene. Mixtures of the dialdehydes and ketones may also be used.  The light-sensitive groups in the polymers are styryl ketone groups having the formula I: <FORM:0966297/C3/1> in which R is H or a hydrocarbon group, and constitute links in the polymer chain. Examples of repeating units obtainable are represented by formulae II and III: <FORM:0966297/C3/2> wherein each R is H or both R's together complete, with the -CO-, a cyclohexanone ring; <FORM:0966297/C3/3> wherein x is an integer. In the preferred polymers of the invention the number of repeating units of formulae I to III in the polymer chain is at least 5.  The condensation of 1, 3-di-(o-formylphenoxy) propane with acetone preferably in the presence of aqueous sodium hydroxide and tetrahydrofurfuryl alcohol and dioxane yields a polymer which may be represented by formula IV: <FORM:0966297/C3/4> or with p-diacetyl benzene preferably in the presence of dioxane and trimethyl benzyl ammonium hydroxide a polymer which may be represented by formula V: <FORM:0966297/C3/5> In formulae IV and V, p is at least 5, preferably at least 10. The method of the present invention is preferably carried out so as to produce film-forming polymers. The polymer may be dissolved in a solvent e.g. dioxane, and the solution coated on a support, and the solvent is then removed, and the layer may be formed over a hardened caesin layer containing a zinc salt coated on a rosin sized paper support.  A light-image may be recorded by a method wherein a layer of a light-sensitive polymer is exposed to a light image until the most exposed parts of the layer become insoluble in a solvent for the unexposed polymer, the unexposed parts of the layer are then dissolved in said solvent and the solution removed from the layer.