TECHNOLOGY FOCUS - POLYMERS - Preferred Materials: Solutions or dispersions, preferably containing 0.25-10 wt% organic semiconductor, especially solutions of polymeric semiconductors.Preferred Semi-conductors: Soluble poly-p-arylene-vinylenes, polyfluorenes, poly-spiro-bifluorenes, poly-p-phenylenes, substituted polythiophenes, substituted polypyridines, substituted polypyrroles, substituted copolymers of the above, or optionally substituted polyvinylcarbazoles or triarylamine polymers.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Solvents: Mixtures of solvents with different boiling points, preferably only solvents with b.pts. at least 100degreesC, especially at least 3 different solvents with different b.pts., preferably 100-150degreesC, 130-180degreesC and 170 to below 200degreesC respectively. Suitable solvents comprise o-xylene, 2,6-lutidine, 2-fluoro-m-xylene, 3-fluoro-o-xylene, 2-chlorobenzotrifluoride, DMF, 2-chloro-6-fluorotoluene, 2-, 3- or 4-fluoroanisole, anisole, 2,3-dimethylpyrazine, 3-trifluoromethylanisole, 2-, 3- or 4-methylanisole, phenetole, 4-fluoro-3-methylanisole, 2- or 3-fluorobenzonitrile, 4-fluoroveratrole, 2,6-, 2,4-, 2,5- or 3,5-dimethylanisole, N,N-dimethylaniline, 1-fluoro-3,5-dimethoxybenzene, N-methyl-pyrrolidone, 2-, 3- or 4-fluorobenzotrifluoride, benzotrifluoride, dioxane, trifluoro-methoxybenzene, 2- or 3-fluoropyridine, toluene, 2-, 3- or 4-fluorotoluene, 2,5-di-fluorotoluene, pyridine, 1-chloro-2,4- or -2,5-difluorobenzene, 2-, 3- or 4-chloro-fluorobenzene, chlorobenzene and p- or m-xylene.    TECHNOLOGY FOCUS - IMAGING AND COMMUNICATION - Preferred Method: Ink jet printing. EXAMPLE - A test solution with a concentration of 9 g/l and a viscosity of 8-15 mPa.s (at 40 s-1) was obtained by dissolving a p-phenylene-vinylene terpolymer (Mw = 1 x 106; Mn = 310000; see WO 99/24526) in a mixture of 2,5-dimethylanisole, anisole and o-xylene (20:25:55 v/v/v). Increasing the concentration of this solution to 22 g/l by evaporation resulted in an increase in viscosity to 10000 mPa.s; if a mixture of 2,5-dimethylanisole, 4-methylanisole and o-xylene was used (10:60:30 v/v/v), the concentration could be increased to 30 g/l with an increase in viscosity to ca. 8000 mPa.s. With pure anisole as the solvent, the solution showed a viscosity of less than 1000 mPa.s at 30 g/l (much slower thickening).