For drop-on-demand(DOD)inkjet printing,stable and single ink droplet fo rmation without satellite dots is the key to improve the print quality.The formation of stable and single droplet is influenced by filament break...For drop-on-demand(DOD)inkjet printing,stable and single ink droplet fo rmation without satellite dots is the key to improve the print quality.The formation of stable and single droplet is influenced by filament break up and the polymer chain’s coil-stretch transition behavior.In this paper,the droplet formation behaviors of polyfluorene(PFO)ink at various driving voltages(V),polymer chain’s coil-stretch transition mechanism and its effects on single ink droplet formation are investigated.It indicates that when 5863 V,Wi>0.5,the PFO molecular chain is stretched because of the high hydrodynamic forces,resulting unwanted satellite droplets.When 55<V<58V,the droplet shrinks into the nozzle,which indicates that the kinetic energy supplied by the deformation of the piezoelectric transducer isn't enough to force thedroplet to be jetted from the nozzle.展开更多
Polymer thin film with uniform thickness and flat surface profile is the key point for polymer light emitting diodes(PLEDs) by inkjet printing. However, the coffee ring effect is usually observed due to the mismatch b...Polymer thin film with uniform thickness and flat surface profile is the key point for polymer light emitting diodes(PLEDs) by inkjet printing. However, the coffee ring effect is usually observed due to the mismatch between the evaporation of the solvent and the decrease of solution volume, which promotes the formation of radial flow from the interior of the drop to the edge. In this paper, coffee ring effects of inkjet printed poly(spirobifluorene) films were proposed to be restrained by decreasing capillary force by adding co-solvent with high boiling point and high viscosity to the main solvent. The low evaporation rate of the co-solvent can reduce the driving force of the radial flow; meanwhile the high viscosity of the co-solvent can increase the resistance of the radial flow. Thus, polymer films with improve uniformity can be obtained due to the suppression of the radial flow. The device performance was greatly improved under the condition of proper film thickness and film uniformity and the maximum luminous efficiency of devices with inkjet printed poly(spirobifluorene) can reach 80% of the spin-coated devices.展开更多
Inkjet printing is a new fabricating method that can realize the precise film deposition. For polymer inks, the coil-stretch transition of polymer chains always impacts the ink droplet formation and a beads-on-a strin...Inkjet printing is a new fabricating method that can realize the precise film deposition. For polymer inks, the coil-stretch transition of polymer chains always impacts the ink droplet formation and a beads-on-a string structure filament is formed, thus generating unwanted satellite droplets. This review provides a short introduction of the dynamic process of the droplet formation. Then fluid theological requirements for a printable polymer ink are summarized. Finally the strain hardening phenomenon of polymer chains in the filament formation and its impact on polymer ink-jetting are discussed. The research of viscoelastic polymer inks shows that rheological parameters and viscoelasticity are two key factors that determine the printability of polymer inks.展开更多
基金the National Natural Science Foundation of China(Nos.51873212,91833306)National Key R&D Program of"Strategic Advanced Electronic Materials"(Nos.2016YFB0401301,2017YFB0404402)。
文摘For drop-on-demand(DOD)inkjet printing,stable and single ink droplet fo rmation without satellite dots is the key to improve the print quality.The formation of stable and single droplet is influenced by filament break up and the polymer chain’s coil-stretch transition behavior.In this paper,the droplet formation behaviors of polyfluorene(PFO)ink at various driving voltages(V),polymer chain’s coil-stretch transition mechanism and its effects on single ink droplet formation are investigated.It indicates that when 5863 V,Wi>0.5,the PFO molecular chain is stretched because of the high hydrodynamic forces,resulting unwanted satellite droplets.When 55<V<58V,the droplet shrinks into the nozzle,which indicates that the kinetic energy supplied by the deformation of the piezoelectric transducer isn't enough to force thedroplet to be jetted from the nozzle.
基金financially supported by the National Natural Science Foundation of China (Nos. 21574130, 51473161, 51873212)the Ministry of Science and Technology of China (No. 2015CB655001)National Key R&D Program of "Strategic Advanced Electronic Materials" (Nos. 2016YFB0401301, 2016YFB04011001)
文摘Polymer thin film with uniform thickness and flat surface profile is the key point for polymer light emitting diodes(PLEDs) by inkjet printing. However, the coffee ring effect is usually observed due to the mismatch between the evaporation of the solvent and the decrease of solution volume, which promotes the formation of radial flow from the interior of the drop to the edge. In this paper, coffee ring effects of inkjet printed poly(spirobifluorene) films were proposed to be restrained by decreasing capillary force by adding co-solvent with high boiling point and high viscosity to the main solvent. The low evaporation rate of the co-solvent can reduce the driving force of the radial flow; meanwhile the high viscosity of the co-solvent can increase the resistance of the radial flow. Thus, polymer films with improve uniformity can be obtained due to the suppression of the radial flow. The device performance was greatly improved under the condition of proper film thickness and film uniformity and the maximum luminous efficiency of devices with inkjet printed poly(spirobifluorene) can reach 80% of the spin-coated devices.
基金supported by the National Natural Science Foundation of China(Nos. 51473161,21574130)the National Basic Research Program of China (973 Program, No. 2015CB655001)National Key R&D Program of "Strategic Advanced Electronic Materials"(Nos.2016YFB0401301,2016YFB0401100)
文摘Inkjet printing is a new fabricating method that can realize the precise film deposition. For polymer inks, the coil-stretch transition of polymer chains always impacts the ink droplet formation and a beads-on-a string structure filament is formed, thus generating unwanted satellite droplets. This review provides a short introduction of the dynamic process of the droplet formation. Then fluid theological requirements for a printable polymer ink are summarized. Finally the strain hardening phenomenon of polymer chains in the filament formation and its impact on polymer ink-jetting are discussed. The research of viscoelastic polymer inks shows that rheological parameters and viscoelasticity are two key factors that determine the printability of polymer inks.
