Back to results
US 6,187,224 B1Granted
Optical brightening agent
AssigneeAxiva GmbH
InventorsWilli Kreuder, Josef Salbeck
Life of this patent
Estimating the term…
Abstract
An optical brightener comprising one or more spiro compounds of the formula (I), where K1 and K2, which are identical or different, are conjugated systems, and ψ is C, Si, Ge, Sn or Pb, is notable for high fluorescence quantum yields and a high temperature stability.
Claims13
A method of optically brightening which comprises adding to a material to be optically brightened one or more spiro compounds of the formula
- where
- K1 and K2, which are identical or different, are conjugated systems, and ψ is C, Si, Ge, Sn or Pb.
An optical brightener which contains a material and
- a. which has a fluoroescence quantum yield of ≧40% in solid form, and
- b. an emission maximum in the range from 380 to 750 nm, measured at room temperature, decreases by no greater than 25%, relative to an initial state, after the material, applied in a thickness of no greater than 1 μm to a quartz substrate, has been heated to 250° C. in an inert atmosphere at a pressure no greater than 1 mbar for 30 min.
Dependencies are inferred from the claim text.