1. Technical Field
The present invention relates to liquid ejecting heads and liquid ejecting apparatuses and is particularly useful when applied to the case where a drive waveform of the liquid ejecting head is appropriately selected depending on the temperature of a liquid to be ejected in order to control ejection properties of the liquid.
2. Related Art
A typical example of liquid ejecting heads that eject liquid droplets includes, for example, an ink jet recording head having a flow channel forming substrate on which pressure generating chambers are formed and a piezoelectric actuator disposed on one side of the flow channel forming substrate so as to correspond the pressure generating chambers and is configured such that the displacement of the piezoelectric actuator causes a pressure to be applied to the pressure generating chambers, thereby ejecting ink droplets through nozzles that are formed so as to penetrate a nozzle plate in the thickness direction.
In this type of ink jet recording head, the ejection properties of ink depend on the viscosity of the ink, and the viscosity depends on the temperature of the ink. Therefore, a drive waveform has been controlled by appropriately selecting and/or changing the drive waveform that drives the piezoelectric actuator depending on a temperature measured by a thermistor.
Such a thermistor, however, is disposed on a circuit board as one of electronic components. In this configuration, the thermistor measures an atmospheric temperature, which may be significantly different from the actual temperature of ink ejected from the nozzles.
In order to improve the ejection properties of ink, it is important to measure the temperature of ink to be ejected with a higher accuracy. Accordingly, various configurations have been proposed as a solution to measure the temperature of ink to be ejected through the nozzles with a higher accuracy, such as that disclosed in JP-A-2004-345109 and JP-A-2006-205735.
JP-A-2004-345109 describes that the recording head is formed by bonding a heat generating substrate and a flow channel substrate, and a temperature sensor is embedded in the heat generating substrate.
Further, JP-A-2006-205735 describes that an insulation film is disposed on a lower electrode that is formed on the flow channel forming substrate, and a thermistor which is a temperature detection sensor is disposed on the top of the insulation film so as to be insulated from the lower electrode via the insulation film.
In the configuration described in JP-A-2004-345109, since the temperature sensor is embedded in the heat generating substrate while being in contact with ink, the insulation property of the electrode or the like seems not to be ensured. Further, in the configuration described in JP-A-2006-205735, since the temperature detection sensor is disposed on the top of the insulation film so as to be insulated from the lower electrode formed on the flow channel forming substrate via the insulation film, problems occur in that the configuration of this portion becomes complicated and the accuracy of the measurement is reduced by measuring the ink temperature via the lower electrode film and the insulation film.
In addition, such problems exist not only in the ink jet recording head that eject ink, but also in the liquid ejecting head that eject liquid other than ink.