THERMALLY- RESPONSIVE DISPERSANTS FOR MEDIA FORMULATIONS

摘要

The invention provides a thermally-responsive dispersant for an aqueous dispersion of positively- or negatively- charged or chargeable solid or liquid particulates which comprises a compound having an anchoring moiety linked to at least one thermally-responsive polymeric stabilising moiety, other than a polyalkylene oxide, the at least one polymeric moiety having a lower affinity for the surface than the anchoring group below the thermal transition temperature, the particulates being positively- charged or chargeable when the anchoring moiety contains at least one acid and/or hydroxy group and has a net acidity or neutrality and the particulates being negatively- charged or chargeable when the anchoring moiety has at least one basic group and has a net basicity, wherein the dispersion exhibits a change in sign from negative to positive and an increase in magnitude of a rheological property, the property being viscosity at low shear and/or complex modulus at low amplitude oscillatory shear, on increasing the temperature from below to above the thermal transition temperature. The dispersant can reduce the viscosity of the dispersion when used below its thermal transition temperature, facilitating manipulations such as pouring, stirring, pumping, transporting and coating of the resulting dispersion due to improved dispersability and flowability. Once the dispersion has been manipulated into its final desired geometry, e.g. a coating, the thermally-responsive nature of the dispersant allows it to be to be destabilised by the application of sufficient heat to take the dispersant above its transition temperature, resulting in a significant increase in viscosity or the transition to from liquid- to solid-like behaviour such that the uniformity of the geometry is maintained. The presence of the dispersant in an inkjet recording element can also give rise to improved quality of a printed image as a result of reduction in coalescence or mottle.