Substrate having a plurality of common power supply wires and a plurality of common ground wires for inkjet recording head and inkjet recording head using the same

A substrate for an inkjet recording head comprising:

• a plurality of arrays of recording elements;
• a plurality of common power supply wires, each of which extends from a position near one end portion of each array to a position near the other end portion thereof and is connected to a power supply-side electrode pad through the position near the one end portion of the array;
• and
• a plurality of common ground wires, each of which extends from a position near to the one end portion of each array to a position near to the other end portion thereof and is connected to a ground-side electrode pad through the position near the other end portion of the array,
• wherein the plurality of common power supply wires and the plurality of common ground wires are collectively wired to the power supply-side electrode pad and the ground-side electrode pad, respectively, and
• wherein each common power supply wire and each common ground wire are provided for n recording elements simultaneously driven so that a ratio RL/RH becomes less than 0.05/(0.95×n−1), the ratio RL/RH being obtained by dividing a sum RL of a resistance of the common power supply wire and that of the common ground wire by a resistance RH of the recording element in an energized state.

A substrate for an inkjet recording head comprising:

• a plurality of arrays of recording elements;
• a plurality of common power supply wires, each of which extends from a position near one end portion of each array to a position near the other end portion thereof and is connected to a power supply-side electrode pad through the position near the one end portion of the array;
• a plurality of common ground wires, each of which extends from a position near to the one end portion of each array to a position near to the other end portion thereof and is connected to a ground-side electrode pad through the position near the other end portion of the array;
• and
• means for maintaining currents flowing through heating portions constant even if a power supply voltage supplied from an outside fluctuates and/or even if an overall current value difference due to changes in the number of recording elements simultaneously driven causes fluctuations in voltage drops of the common power supply wire and the common ground wire,
• wherein the plurality of common power supply wires and the plurality of common ground wires are collectively wired to the power supply-side electrode pad and the ground-side electrode pad, respectively,
• wherein each recording element includes a heating portion for generating, in response to energization, thermal energy as energy used to eject ink and a driving element for driving the heating portion, and
• wherein the means are the driving elements constituted by MOS transistors, and the currents flowing through the heating portions are maintained constant by controlling the MOS transistors so that the MOS transistors operate in saturation regions thereof.