A liquid discharge head includes a recording element configured to generate thermal energy and a discharge orifice disposed at a position facing the recording element. A bubble is generated in liquid by the thermal energy, liquid between the bubble and the discharge orifice is discharged from the discharge orifice by the pressure of the generated bubble, and the bubble communicates with the atmosphere on the outside of the discharge orifice.

A liquid jetting apparatus includes: individual channels; and a manifold commonly provided for the individual channels. Each of the individual channels has: a nozzle; a pressure chamber arranged away from the nozzle in a predetermined direction to extend along a plane orthogonal to the predetermined direction and connected to the manifold, a connecting channel connected to the pressure chamber to form at least a part of a channel communicating the pressure chamber and the nozzle, and a circulation channel connected to the connecting channel to form a part of a channel communicating the connecting channel and the pressure chamber. The connecting channel has a throttle, and the throttle has a smaller diameter along the plane orthogonal to the predetermined direction than a diameter, of a part of the connecting channel except the throttle, along the plane orthogonal to the predetermined direction.

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 satisfy

0.0<0.44(Q.sub.2/Q.sub.1).sup.0.322(.sub.2/.sub.1).sup.0.109<1.0,

where .sub.1 is a viscosity of the first liquid, .sub.2 is a viscosity of the second liquid, Q.sub.1 is a flow rate of the first liquid, and Q.sub.2 is a flow rate of the second liquid.

A first inflow port allows a first liquid to flow into a liquid flow passage, and a second inflow port allows a second liquid to flow into the liquid flow passage. The first and second liquids flow toward a pressure chamber. There is a portion satisfying LW, where L is a length of the first inflow port and W is a length of the liquid flow passage above the first inflow port, in a direction orthogonal to a direction of flow of the first liquid in the pressure chamber and to a direction of ejection of the second liquid from an ejection port. In a case where the second liquid is ejected from bottom to top, the second liquid flows above the first liquid.

In a case where a direction of ejection of a second liquid is a direction from bottom to top, the second liquid flows above a first liquid in a pressure chamber. A substrate includes a first outflow port located downstream of the pressure chamber in a direction of flow of the first liquid and configured to allow the first liquid to flow out of a liquid flow passage. There is provided a wall located in the liquid flow passage and on a section of the substrate on a side opposite to the pressure chamber across the first outflow port, the wall including a portion located higher than a surface of a section of the substrate where the pressure chamber is located on a side opposite to the wall across the first outflow port.

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. In a state where the first liquid flows in a direction, crossing a direction of ejection of the second liquid from the ejection port, while being in contact with the pressure generation element and the second liquid flows in the crossing direction along the first liquid in the pressure chamber, the second liquid is ejected from the ejection port by causing the pressure generation element to apply a pressure to the first liquid.

A liquid discharging head includes a discharge port that discharges a liquid, a pressure chamber that communicates with the discharge port, and an energy generating element that is disposed in the pressure chamber. In the liquid discharging head, the discharge port is provided with a plurality of projections that project towards a central portion of the discharge port from an inner peripheral edge of the discharge port, and an interval between the projections at a location where the projections are closest to each other is 5 m or less.

An ejection port includes a first ejection port that is an opening portion formed on an outer surface side of a recessed portion formed in an outer surface of a nozzle plate, a second ejection port positioned on a bottom surface side of the recessed portion, the second ejection port including an opening portion that is smaller than the first ejection port, and a plurality of protrusions that extend from an outer edge portion of the first ejection port towards a center portion of the second ejection port through the second ejection port, in which a distance between tip portions of the plurality of protrusions and the substrate is larger than a distance between an outer edge portion of the second ejection port and the substrate.

A recording element board includes a discharge orifice configured to discharge liquid, a pressure chamber communicating with the discharge orifice, a recording element configured to generate thermal energy to cause bubbling of the liquid, the recording element being disposed in the pressure chamber facing the discharge orifice, and a substrate on which the recording element is formed. When the recording element is driven and the liquid of within the pressure chamber is discharged, a generated bubble communicates with the atmosphere. A discharge orifice projection region where the discharge orifice has been projected on the substrate includes a region includes a region extending beyond a heat-generating region projection region where the heat-generating region of the recording element has been projected on the substrate, the outline of the discharge orifice projection region is circumscribed by the outline of the heat-generating region projection region.

A print element substrate, comprising a base, a heater provided on the base and configured to generate heat used to discharge ink, a flow path member, which forms an ink flow path, configured to form, together with the base, a bubbling chamber in which the ink is bubbled by the heat of the heater provided in a bottom surface of the bubbling chamber, and a temperature sensor capable of detecting a temperature of the bubbling chamber, the temperature sensor being formed of the same material as the heater and provided in the same layer as the heater on the base.