1. Field of the Invention
This invention relates to an ink jet recording head wherein some of the pressure generation chambers communicating with nozzle openings for jetting ink drops are formed of a diaphragm and the diaphragm is formed on a surface with a piezoelectric element for jetting ink drops by displacement of the piezoelectric element, and an ink jet recorder comprising the ink jet recording head.
2. Description of the Related Art
The following two types of ink jet recording heads, each wherein a part of a pressure generation chamber communicating with a nozzle opening for jetting an ink drop is formed of a diaphragm and the diaphragm is deformed by a piezoelectric element for pressurizing ink in the pressure generation chamber for jetting an ink drop from the nozzle opening, are commercially practical: One uses a piezoelectric actuator in a vertical vibration mode in which a piezoelectric element is expanded and contracted axially and the other uses a piezoelectric element in a deflection vibration mode.
With the former, the volume of the pressure Generation chamber can be chanced by abutting an end face of the piezoelectric element against the diaphragm and heads appropriate for high-density printing can be manufactured. However, in this example, a difficult step of dividing the piezoelectric element into comb-like teeth which match the arrangement pitch of the nozzle openings and positioning and fixing the piezoelectric element divisions in the pressure generation chambers are required and the manufacturing process is complicated.
In contrast, with the latter, the piezoelectric element can be created and attached to the diaphragm by executing a comparatively simple process of putting a green sheet of a piezoelectric material matching the form of the pressure generation chamber and calcining it, but a reasonable area is required because deflection vibration is used. Accordingly, high-density arrangement is difficult to make.
On the other hand, to solve the problem of the latter recording head. Japanese Patent Laid-Open No. Hei 5-286131 proposes an art wherein uniform piezoelectric material layer is formed over the entire surface of a diaphragm according to a film formation technique and is divided to a form corresponding to a pressure generation chamber according to a lithography technique for forming a piezoelectric element independently for each pressure generation chamber.
This eliminates the need to place the piezoelectric element on the diaphragm and the piezoelectric element can be created by an accurate and simple technique of lithography method. In addition, the piezoelectric element can be thinned and high-speed drive is enabled.
However, in the manufacturing method according to the lithograph method and the thin-film technique described above, after thin film patterning, pressure generation chambers are formed. At that time, a diaphragm is deflected to the pressure generation chamber side by the effect of easing the internal stresses of the upper electrode and piezoelectric layers and the deflection remains as the initial deformation of the diaphragm. Particularly, if the lower electrode is overetched, the deflection amount is large and the diaphragm deformation amount by driving a piezoelectric actuator becomes smaller than the calculation value. The possible reason is that the diaphragm is deflected by the effect of easing the internal stresses of the upper electrode and piezoelectric layers (and the lower electrode) in the tension direction and thus a plastic deformation area is reached beyond an elastic deformation area. In addition to a diaphragm containing a silicon oxide film, a diaphragm containing a zirconium oxide film as a highly rigid diaphragm is proposed as the diaphragm, but similar initial deformation occurs in any diaphragms.