Soln. for hydrophobic treatment of ink jet exit - has lower and higher b.pt. constituent to control evapn. rate and give better spreading with more uniform treatment

摘要

A surface, esp. the exit plane of an ink jet printing hed, is made hydrophobic by treating it with a soln. of long chain, halogen, contg. copolymers and a crosslinking agent. The soln. contains a second solvent with a different b.pt. so that the first solvent effectively evaporates while the second solvent only evaporates after a hydrophobic layer has formed. One solvent can be tert. butyl acetate while the other solvent is gamma-butyrolactone in the ratio 10-30, pref. 20:1. The soln. (30) is sprayed from a nozzle (40) on to the surface to be treated at time to at a low viscosity la and arrives at the surface at time t1, the delay depending on the process parameters. During this time the first solvent has virtually evaporated with a corresp. increase in viscosity. When the soln. reaches the surface, the viscosity is determined by the higher b.pt. solvent which then controls spreading on the surface until crosslinking is complete at time t2. USE/ADVANTAGE - The process achieves a more uniform coating and avoids the formation of islands where the coating has missed.