Liquid ejection head, liquid ejection apparatus, and manufacturing method of liquid ejection head

A liquid ejection head comprising:

• a channel unit including a channel substrate provided with a channel section which includes pressure chamber cavity rows formed by arranging a plurality of pressure chamber cavities to be pressure chambers in rows, a nozzle substrate provided with a plurality of nozzle orifices formed so as to correspond to the pressure chambers, respectively, and a sealing plate which seals an opening of the channel section of the channel substrate, wherein the nozzle substrate is joined with one surface of the channel substrate and the sealing plate is joined with the opposite surface of the channel substrate so that the channel unit has a series of liquid channels from a common liquid chamber to the nozzle orifices via the process chambers;
• wherein a first reference hole and a second reference hole are disposed in a frame region formed outside a channel section forming region at one side of an arrangement direction of the pressure chamber cavity rows, and a third reference hole and a fourth reference hole are formed in the frame region at the opposite side of the arrangement direction of the pressure chamber cavity rows, wherein the first reference hole, the second reference hole, and the fourth reference hole have a polygonal shape whose sides are equal to each other in length, wherein the third reference hole has a polygonal shape whose sides are different in length, in which dimension of shorter sides of the third reference hole is equal to dimension of the sides of the other reference holes other than the third reference hole, and wherein each of the nozzle substrate and the sealing plate is provided with a first through-hole, a second through-hole, a third through-hole, and a fourth through-hole at positions corresponding to the first reference hole, the second reference hole, the third reference hole, and the fourth reference hole of the channel substrate.