| 摘要 |
1515174 Developing printing plates AMERICAN HOECHST CORP 18 July 1975 [22 July 1974 29 Jan 1975] 30266/75 Headings G2C and G2X The unhardened areas of an imagewise exposed printing plate having a negative working copying layer containing a diazonium salt condensation product are removed by an aqueous solution containing a) 1 to 50 wt. per cent of a water-miscible organic solvent and b) a minor proportion of a water-soluble colloid, the developer having a pH between 3 and 11. The colloid serves to preserve the plate. Organic solvents specified are isopropanol, n-propanol, ethanol, butanol,γ-butyrolactone, #-hydroxypropyl ether, butoxy ethanol and diacetone alcohol. The colloid is dextrim, gum arabic, larch gum, or sodium carboxymethylcellulose. The developer may also contain i) an organic or inorganic acid or salt e.g. nitric, sulphuric, phosphoric, toluene-sulphonic or phosphonic acid or magnesium, sodium, potassium and ammonium sulphates, nitrates, phosphates, bicarbonates, acetates and tartrates. ii) a surfactant iii) a dyestuff and iv) an anti-foaming agent. A thin film of developer is left on the processed plate after treating. The developer is used at a temperature substantially at its cloud point. Apparatus for treating the plate is shown in the Figure. The plate passes through a softening chamber 4 where it is coating with developer from feed lines 7 and 8. It is then sprayed with additional developer by sprays 9, 10 before being rubbed by brushes 12, 13 which rotate contrary to the movement of the plate. The brush axles 14, 15 are hollow and supply additional developer. The plate then passes through optionally movable rubbing pads 20, 21 supplied with developer through lines 22, 23. The upper brush 12 and pad 20 are floatingly supported. Finally the plate is coated with a thin film of developer by sprays 28, 29 and dried by pipes 32, 33 which direct hot air on to the plate. In an alternative embodiment the rotating brushes are replaced by flat brushes which move to and fro Fig. 2 (not shown). |
