METHOD OF MARKING AN ARTICLE

摘要

An article of manufacture, for example wire or cable, security items such as a credit card, or food packaging, has a surface formed from a polymer, the polymer incorporating a quantity of a compound of general formula (I) wherein: R1 and R4, which may be the same or different, each is a straight-chain, branched-chain or cyclic alkyl group or an aryl group, which groups may be unsubstituted or substituted and may include one or more hetero atoms; R2 is a straight-chain, branched-chain or cyclic alkyl group or an aryl group which may be unsubstituted or substituted and may include one or more hetero atoms, but which does not include any eliminatable alpha -hydrogen atoms; and R3 which may be fused with or separate from R2 or which may be fused with or separate from R4, is a straight-chain, branched-chain or cyclic alkyl group or an aryl group which may be unsubstituted or substituted and may include one or more hereto atoms; provided that, when water is eliminated from the compound of general formula (I) to form a cyclopentadieneone, the groups R1 to R4 together have sufficient conjugated unsaturation to produce an absorption band in the visible spectrum. The compound of formula (I) is thermally stable at temperatures required to melt process polymers, but will eliminate water when subjected to an excimer laser to form a visible mark.