A coating composition, a process for producing it and substrate coated therewith are described. The light source may be an existing dental light curing system, thereby permitting the existing light curing system to be used as dental bleaching system. The fluid bed cooler includes an inlet for the hot polymer and inlets for the gas used for agitating the polymer. %, in relation to the copolymer, of emulsifiers with an HLB value of at least 14 must be contained therein. The cathode and anode of the fourth diode are respectively connected to the second input terminal and the second output terminal.