Method of protecting heater surface of ink-jet printer, ink-jet recording apparatus, recording unit and method of prolonging service life of ink-jet recording head

摘要

The outermost surface protection layer of the heater of an ink-jet recording head containing at least metal or oxide thereof is protected against erosion by suppressing or preventing the dissolution of the outermost surface protection layer. The heater is adapted to apply thermal energy to a liquid composition to be ejected. The liquid composition contains a liquid medium, alkali metal ions and a compound expressed by general formula H₂N—(CHY)_n—(CH₂)_m—X, X representing a carboxyl group or a sulfonic acid group, Y representing a hydrogen atom, a carboxyl group or a sulfonic acid group, n representing 0 or 1, m representing an integer from 0 to 2. The liquid composition is heated so as to satisfy the relation as defined by the formula 1.10≦E_op/E_th≦1.90, E_op representing the amount of energy applied to the heater per unit time in order to cause the recording head to eject the liquid composition, E_th representing the minimum amount of energy required by the recording head per unit time to eject ink.