Field of the Invention
The present invention relates to a liquid discharge head and a liquid discharge apparatus that uses the liquid discharge head.
Description of the Related Art
A liquid discharge apparatus that records by discharging liquid onto a recording medium uses a liquid discharge head having a pressure chamber communicating with a discharge orifice and a recording element that provides energy for discharging to liquid within the pressure chamber. An inkjet recording apparatus, which is representative of liquid discharge apparatuses, discharges recording liquid which is a color material such as dye or pigment contained in a medium, process liquid for adjusting the recording liquid, and so forth, from discharge orifices. In a case where the liquid to be discharged is a recording liquid in such a liquid discharge apparatus for example, volatile components in the recording liquid near discharge orifices may evaporate, and the concentration of color material increase accordingly, leading to irregular color in the recorded image. There also are cases where the evaporation of the volatile components raises the viscosity of the liquid near the discharge orifices and within the pressure chamber, which reduces the discharge speed of the liquid, and consequently the liquid cannot accurately reach the intended position on the recording medium. One known measure to handle such an issue is to circulate liquid through the liquid discharge head, and particularly through the pressure chambers. In a case where liquid is to be circulated through the pressure chambers, channels are provided branching from a common supply channel, passing through the pressure chambers, and merging at a common recovery channel, so as to circulate liquid through the pressure chambers through these channels. Drive circuits for driving the recording elements are provided in the liquid discharge head, and in a case where the number of discharge orifices is great and the number of recording elements also is great, increased effects of heat generation by the drive circuits may also cause change in the discharge speed of the liquid, and accurate discharging of liquid as to the recording medium may be difficult. For example, PCT Japanese Translation Patent Publication No. 2003-519027 discloses an arrangement where heat generated at the drive circuits is channeled away from liquid that has circulated through the pressure chambers and transferred to the recovery channel, thereby suppressing change in viscosity of the liquid due to temperature rise, and thus suppressing change in discharge speed of the liquid.
In the configuration such as described in PCT Japanese Translation Patent Publication No. 2003-519027, in a case where the flow rate of liquid supplied from the supply channel to the pressure chambers is smaller than the flow rate of liquid discharged from the discharge orifices, the liquid from the recovery channel backs up and flow into the pressure chamber when performing discharging. This means that the liquid that has been heated by transmission of heat from the drive circuits and the like and has become less viscous flows into the pressure chambers, so discharge properties such as discharge amount and discharge speed changes. As a result, recording quality is affected, such as the density of recording being darker at portions recorded on the recording medium at the time of starting recording as compared to portions recorded later, and so forth. This is one example of discharge properties changing in accordance with a drive state of the liquid discharge head having changed (in this case here, changing from a standby circulation state to a recording stage), and recording quality also changing. On the other hand, in a case where the flow rate of liquid supplied from the supply channel to the pressure chambers is greater than the flow rate of liquid discharged from the discharge orifices, there is no backflow of liquid from the recovery channel even when performing discharging. However, the pressure drop at the at the pressure chambers and nearby channels is great in this case, so the channel width of the pressure chambers and nearby channels needs to be larger, making it difficult to dispose pressure chambers in high density an performed high-definition recording.