Ink jet recording head, ink jet recording device and head manufacturing method

An ink jet recording head, comprising:

• at least one individual passage communicating with a nozzle for jetting ink droplets;
• a common liquid chamber communicating with each individual passage;
• an ink chamber for supplying ink to the common liquid chamber;
• and
• a communicating passage connecting the common liquid chamber with the ink chamber, wherein:
• when the jetting rate D of the ink jet recording head is D≧0.05, for a bubble having a diameter d that satisfies the following expression (3), the communicating passage having the minimum cross section S that satisfies the following expression (4) is formed:
• d≧2Np (3)
• {(n×V×f×D/S)2×Cd×ρ×π×d2}/8<(ρ×g×π×d3)/6 (4)
• where n denotes the number of nozzles, V denotes the volume of an ink droplet jetted from the ink jet recording head, f denotes a maximum printing frequency, Cd denotes a resistance coefficient, ρ denotes the density of ink, g denotes a gravitational constant and Np denotes pitch between nozzles.

An ink jet recording head, comprising:

• at least one individual passage communicating with a nozzle for jetting ink droplets;
• a common liquid chamber communicating with each individual passage;
• an ink chamber for supplying ink to the common liquid chamber;
• and
• a communicating passage connecting the common liquid chamber and the ink chamber, wherein:
• the communicating passage is formed to enable at least a bubble in size that causes a printing defect to be moved from the common liquid chamber to the ink chamber;
• plural communicating passages each of which connects one common liquid chamber to a ink chamber are provided;
• the recording head comprises k pieces of communicating passages, where k is an integer not less than 2, and
• when the jetting rate D of the ink jet recording head is D≧0.05, for a bubble having a diameter d that satisfies the following expression (5), at least one communicating passage that satisfies the following expression (6) is formed:
• {((n×V×f×D/Si)×(Li4/ΣLi4))2×Cd×ρ×π×d2}/8<(ρ×g×π×d3)/6 (5)
• d<Li (6)
• where n denotes the number of nozzles, V denotes the volume of an ink droplet jetted from the ink jet recording head, f denotes a maximum printing frequency, Si denotes the minimum cross section of an ith communicating passage, Li denotes the minimum width of the ith communicating passage, ΣLi4 denotes the sum of the fourth power value of the minimum width of all communicating passages (=L14+L24+ . . . +Lk4), Cd denotes a resistance coefficient, ρ denotes the density of the ink and g denotes a gravitational constant.

An ink jet recording head, comprising:

• at least one individual passage communicating with a nozzle for jetting ink droplets;
• a common liquid chamber communicating with each individual passage;
• an ink chamber for supplying ink to the common liquid chamber;
• and
• a communicating passage connecting the common liquid chamber and the ink chamber, wherein:
• the communicating passage is formed to enable at least a bubble in size that causes a printing defect to be moved from the common liquid chamber to the ink chamber;
• plural communicating passages each of which connects one common liquid chamber to a ink chamber are provided;
• the recording head comprises k pieces of communicating passages, where k is an integer not less than 2, and
• when the jetting rate D of the ink jet recording head is D≧0.05, for a bubble having a diameter d that satisfies the following expression (7), at least one communicating passage that satisfies the following expression (8) is formed:
• d≧2Np (7)
• {((n×V×f×D/Si)×(Li4/ΣLi4))2×Cd×ρ×π×d2}/8<(ρ×g×π×d3)/6 (8)
• where n denotes the number of nozzles, V denotes the volume of an ink droplet jetted from the ink jet recording head, f denotes a maximum printing frequency, Si denotes the minimum cross section of an ith communicating passage, Li denotes the minimum width of the ith communicating passage, ΣLi4 denotes the sum of the fourth power value of the minimum width of all communicating passages (=L14+L24+ . . . +Lk4), Cd denotes a resistance coefficient, ρ denotes the density of the ink, g denotes a gravitational constant and Np denotes pitch between nozzles.

An ink jet recording head, comprising:

• at least one individual passage communicating with a nozzle for jetting ink droplets;
• a common liquid chamber communicating with each individual passage;
• an ink chamber for supplying ink to the common liquid chamber;
• and
• a communicating passage connecting the common liquid chamber and the ink chamber, wherein:
• the communicating passage is formed to enable at least a bubble in size that causes a printing defect to be moved from the common liquid chamber to the ink chamber;
• plural communicating passages each of which connects one common liquid chamber to a ink chamber are provided;
• at least one of the plural communicating passages is provided upward in a gravitational direction in the common liquid chamber;
• and
• at least another one communicating passage is provided in a direction substantially perpendicular to an upward direction in a gravitational direction.

A method of manufacturing an ink jet recording head, comprising:

• producing a heater element substrate with head units to which plural heater elements are provided;
• producing plural passage substrates with head units in each of which an individual passage formed corresponding to one or plural heater elements for jetting ink droplets, a common liquid chamber for supplying ink to plural individual passages and plural communicating passages for supplying ink from an ink tank to the common liquid chamber are formed such that each of the plural communicating passages enables at least a bubble that causes a printing defect to be moved from the common liquid chamber to the ink tank;
• at least one of the plural communicating passages is provided upward in a gravitational direction in the common liquid chamber;
• and at least another one communicating passage is provided in a direction substantially perpendicular to an upward direction in a gravitational direction;
• producing head chips by mating the heater element substrate and the passage substrate and dicing per head unit;
• forming a nozzle on a first end face of a head chip;
• forming an electrical signal input-output terminal on a second end face of the head chip opposite the first end face;
• and
• simultaneously forming an opening of the communication passage by the dicing step.