There is provided a liquid discharge head including a channel unit. The channel unit includes: first and second individual channel groups including a plurality of first and second individual channels; two supply manifolds and two return manifolds; and bypass channels communicating with the two supply manifolds or with the two return manifolds. A relationship of |P1|>|P2| is satisfied, wherein P1 is a first pressure of the supply manifold provided commonly for the first individual channel group, P2 is a second pressure of the supply manifold provided commonly for the second individual channel group, −P1 is a third pressure of the return manifold provided commonly for the first individual channel group, and −P2 is a fourth pressure of the return manifold provided commonly for the second individual channel group.

A liquid ejecting head includes: a first nozzle array and a second nozzle array through which a non-fluorescent- colored liquid is discharged; and one or more fluorescent nozzle arrays through which respective fluorescent-colored liquids are discharged. Further, the fluorescent nozzle arrays are arranged between the first nozzle array and the second nozzle array.

A liquid ejecting head includes a first-nozzle-row set in which a pair of first-nozzle-rows is disposed in a second direction intersecting a first direction so that the first-nozzle-rows are symmetrical about a reference line extending in the first direction and a second-nozzle-row set in which a pair of second-nozzle-rows is disposed in the second direction so that the second-nozzle-rows are symmetrical about the reference line. In the second direction, the distance between the second-nozzle-rows is longer than the distance between the first-nozzle-rows. First nozzles constituting the first-nozzle-row set communicate with a first liquid supply source via a first supply flow path. Second nozzles constituting the second-nozzle-row set communicate with a second liquid supply source via a second supply flow path. Compliance capacity of the second supply flow path is larger than compliance capacity of the first supply flow path.

An ink jet recording method includes an ink attachment step, in which an aqueous ink composition is ejected from a recording head and attached to a recording medium, and a treatment liquid attachment step, in which a treatment liquid containing a flocculant is ejected from a recording head and attached to the recording medium. The recording head for ejecting the treatment liquid has a circulation channel in which the treatment liquid is circulated.

An ink jet recording method includes an ink attachment step, in which an aqueous ink composition is ejected from a recording head and attached to a recording medium, and a treatment liquid attachment step, in which a treatment liquid containing a flocculant is ejected from a recording head and attached to the recording medium. The recording head for ejecting the treatment liquid has a circulation channel in which the treatment liquid is circulated.

An ink jet method includes: a discharging step of discharging a radiation-curable ink jet composition onto a recording medium at an ink weight per dot of 22 ng/dot or less by using an ink jet head having a nozzle density of 600 npi or more and configured to discharge the radiation-curable ink jet composition; and an irradiating step of irradiating, with radiation, the radiation-curable ink jet composition attached to the recording medium. The radiation-curable ink jet composition contains polymerizable compounds containing a monofunctional monomer and a multifunctional monomer. The monofunctional monomer includes a nitrogen-containing monofunctional monomer. The amount of the monofunctional monomer is 90 mass % or more relative to the total amount of the polymerizable compound. The amount of the nitrogen-containing monofunctional monomer is from 1 to 15 mass % relative to the total amount of the polymerizable compounds.

An ink jet method includes: a discharging step of discharging a radiation-curable ink jet composition onto a recording medium at an ink weight per dot of 22 ng/dot or less by using an ink jet head having a nozzle density of 600 npi or more and configured to discharge the radiation-curable ink jet composition; and an irradiating step of irradiating, with radiation, the radiation-curable ink jet composition attached to the recording medium. The radiation-curable ink jet composition contains polymerizable compounds containing a monofunctional monomer and a multifunctional monomer. The monofunctional monomer includes a nitrogen-containing monofunctional monomer. The amount of the monofunctional monomer is 90 mass % or more relative to the total amount of the polymerizable compound. The amount of the nitrogen-containing monofunctional monomer is from 1 to 15 mass % relative to the total amount of the polymerizable compounds.

a part of a first head is positioned in the second part, a part of a second head is positioned in the third part, a part of a third head is positioned in the fifth part, a part of a fourth head is positioned in the sixth part, and a first color is cyan and a third color is magenta.

There is provided a printing apparatus including: a head unit including two first heads and a second head; a support unit arranged to face the head unit and has a support surface; and a sensor arranged between a first virtual line extending in a conveyance direction so as to pass an end of a nozzle group area, of one of the two first heads, defined on a side of other of the two first heads and a second virtual line extending in the conveyance direction so as to pass an end of a nozzle group area, of the other of the two heads, defined on a side of the one of the two first heads, and arranged, in the conveyance direction, upstream of a nozzle group of the second head, the sensor including a projecting member which projects toward the supporting surface with respect to a nozzle surface.

There is provided a printing apparatus including: a head unit including two first heads and a second head; a support unit arranged to face the head unit and has a support surface; and a sensor arranged between a first virtual line extending in a conveyance direction so as to pass an end of a nozzle group area, of one of the two first heads, defined on a side of other of the two first heads and a second virtual line extending in the conveyance direction so as to pass an end of a nozzle group area, of the other of the two heads, defined on a side of the one of the two first heads, and arranged, in the conveyance direction, upstream of a nozzle group of the second head, the sensor including a projecting member which projects toward the supporting surface with respect to a nozzle surface.