Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-06-16
2001-11-13
Tran, Huan (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S068000, C347S071000
Reexamination Certificate
active
06315400
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet recording head and an ink-jet recording device wherein a piezoelectric element is formed in a part of a pressure generating chamber communicating with a nozzle aperture for jetting an ink droplet via a diaphragm so that an ink droplet is jetted by the displacement of the piezoelectric element.
2. Description of the Related Art
For an ink-jet recording head wherein a part of a pressure generating chamber communicating with a nozzle aperture for jetting an ink droplet is constituted by a diaphragm and an ink droplet is jetted from the nozzle aperture by deforming the diaphragm by a piezoelectric element and pressurizing ink in the pressure generating chamber, two types are used, such as a piezoelectric actuator in a longitudinal vibration mode for extending or contracting a piezoelectric element axially, and a piezoelectric actuator in a flexural vibration mode are used.
For the former, the volume of a pressure generating chamber can be varied by touching the end face of a piezoelectric element to a diaphragm and a head suitable for high density printing can be manufactured. However, on the other hand, there is a problem that a difficult process for cutting a piezoelectric element in the form of the tooth of a comb in accordance with the arrangement pitch of nozzle apertures, and work for positioning and fixing the cut piezoelectric element over a pressure generating chamber are required, and its manufacturing process is complicated.
In the meantime, for the latter, a piezoelectric element can be fixed on a diaphragm in a relatively simple process by sticking a green sheet which is a piezoelectric material in accordance with the shape of a pressure generating chamber and burning it. However, on the other hand, there is a problem that area to some extent is required because flexural vibration is utilized and a high density arrangement is difficult.
In the meantime, to solve the problem of the recording head equivalent to the latter, as disclosed in Japanese published unexamined patent application No. Hei 5-286131, a recording head wherein a piezoelectric element is independently formed for every pressure generating chamber by forming a uniform piezoelectric material layer on the whole surface of a diaphragm by a thin film technique and cutting the piezoelectric material layer in a shape corresponding to each pressure generating chamber by lithography, is proposed.
Accordingly, there is an advantage that work for sticking a piezoelectric element on a diaphragm is not required, and not only a piezoelectric element can be fixed by a precise and convenient method such as lithography, but the piezoelectric element can be thinned and high speed driving is enabled.
In this case, a piezoelectric element corresponding to each pressure generating chamber can be driven by providing at least only an upper electrode for every pressure generating chamber with a piezoelectric material layer provided on the whole surface of a diaphragm. However, it is desirable because of a problem of the quantity of displacement per unit driving voltage and stress upon a piezoelectric layer in a part across a part opposite to a pressure generating chamber and the outside, that a part except at least one end of a piezoelectric layer and an upper electrode respectively constituting a piezoelectric element is not continuously extended outside a pressure generating chamber. However, there is a problem that in such a structure, a crack is readily made in a piezoelectric layer particularly crossing a boundary.
If a substantial driving part of a piezoelectric element is provided apart from over a peripheral wall and corresponding to each pressure generating chamber, structure wherein a piezoelectric element corresponding to each pressure generating chamber is generally covered with an insulating layer, a window (hereinafter called a contact hole) for forming a connection to a lead electrode for supplying voltage for driving each piezoelectric element is provided to the insulating layer corresponding to each pressure generating chamber and the connection of each piezoelectric element and a lead electrode is formed in a contact hole, is proposed. However, the above structure has as a problem that stress is concentrated in the vicinity of a contact hole and breaking and, other problems are readily caused.
For the above ink-jet recording head, to enhance the efficiency of the displacement of a diaphragm by the driving of a piezoelectric element, a structure in which a diaphragm in a part corresponding to both sides of a piezoelectric element is thinned, is proposed. However, when displacement is increased as described above, the above problem is promoted. Further, there is also a problem that breaking such as a crack is readily caused in the vicinity of the peripheral wall of a pressure generating chamber of a diaphragm or in the vicinity of a contact hole.
These problems are readily caused particularly in the case where a piezoelectric material layer is formed by a film forming technique. The reason is that as a piezoelectric material layer formed by film forming technique is very thin, its rigidity is lower, compared with a piezoelectric material layer on which a piezoelectric element is stuck.
SUMMARY OF THE INVENTION
The present invention is made in view of such a situation and the object is to provide an ink-jet recording head and an ink-jet recording device wherein peeling, a crack and other problems in the vicinity of the peripheral wall of a pressure generating chamber of a piezoelectric element and a crack and other problems of a diaphragm are prevented and durability can be secured.
A first embodiment of the present invention to solve the above problems relates to an ink-jet recording head based upon an ink-jet recording head provided with a diaphragm constituting a part of a pressure generating chamber communicating with a nozzle aperture and a piezoelectric element formed on the diaphragm and provided with a piezoelectric active part of the above piezoelectric element in an area opposite to the above pressure generating chamber and characterized in that a vibration regulating part for partially regulating at least a part of the vibration of the above diaphragm is provided in the vicinity of a boundary with the peripheral wall of the above pressure generating chamber.
According to such a first embodiment, the vibration of the diaphragm in the vicinity of a part in which a crack and other problems are readily caused is partially regulated by the vibration regulating part without extremely reducing the whole excluded volume and a crack and peeling are prevented.
A second embodiment of the present invention relates to an ink-jet recording head based upon the first embodiment and characterized in that the above diaphragm is provided with a thin part thinner than the thickness of a part corresponding to the above piezoelectric active part in a part at least on both sides in the direction of the width of the piezoelectric active part and along the edge of the above pressure generating chamber.
According to such a second embodiment, a crack and etc. is prevented from being caused due to the increase of the quantity of displacement by the vibration regulating part because of the thin part.
A third embodiment of the present invention relates to an ink-jet recording head based upon the first or second embodiment and characterized in that the above vibration regulating part is provided outside and on both sides of the end in the longitudinal direction of the above piezoelectric active part.
According to such a third embodiment, vibration at the end of the piezoelectric active part is regulated and a crack and peeling at the end are prevented.
A fourth embodiment of the present invention relates to an ink-jet recording head based upon the second embodiment and characterized in that the above vibration regulating part is provided outside the end in the longitudinal direction of the above piezoelectric active part and the above
Miyata Yoshinao
Sakai Shinri
Takahashi Tetsushi
Do An H.
Seiko Epson Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tran Huan
LandOfFree
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