US Patent 10974507 Liquid ejection head, liquid ejection apparatus, and liquid ejection module

A liquid ejection head includes a pressure chamber that allows a first liquid and a second liquid to flow inside, a pressure generation element that applies pressure to the first liquid and an ejection port that ejects the second liquid. The first liquid and the second liquid that flows on a side closer to the ejection port than the first liquid flow in contact with each other in the pressure chamber. The first liquid and the second liquid flowing in the pressure chamber satisfy0.0<0.44(Q2/Q1)−0.322(η2/η1)−0.109<1.0,where η1 is a viscosity of the first liquid, η2 is a viscosity of the second liquid, Q1 is a flow rate of the first liquid, and Q2 is a flow rate of the second liquid.