Patent ID: 7285231

Claim:
An immersion liquid for water-immersion microscopy, having a refractive index of water, when measured at a temperature of 23° C. and a light wavelength of 546.1 nm, having a kinematic viscosity of greater than 20 mm 2 /s measured at a temperature of 20° C., and having a transmission of more than 70% at a layer thickness of 10 mm at wavelengths in the range between 350 nm and 850 nm, and said immersion liquid comprising a mixture of at least two different functional perfluoropolyethers, at least one of said two different functional perfluoropolyethers being selected from the group consisting of HO(CH 2 CH 2 O) n CH 2 —CF 2 O(CF 2 CF 2 O) p (CF 2 O) q CF 2 —CH 2 (OCH 2 CH 2 ) n OH and HOCH 2 CH(OH)CH 2 OCH 2 —CF 2 O(CF 2 CF 2 O) p (CF 2 O) q CF 2 —CH 2 OCH 2 CH(OH)CH 2 OH wherein n is in each case in the range from 1 to 3, and p and q are in each case in the range from 3 to 12.