Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1998-12-14
2002-02-19
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S070000, C347S047000, C347S044000
Reexamination Certificate
active
06347862
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ink-jet heads for use in ink-jet recorders.
BACKGROUND OF THE INVENTION
Recently, printers incorporating ink-jet recorders come into wide use as printers for personal computers and the like because of their high printing performance, handling ease, inexpensiveness and the like. There are a variety of ink-jet recorders of this type: some of them jet ink droplets utilizing pressure waves which are caused by bubbles formed in ink by thermal energy; some of them suck and jet ink droplets utilizing static electric power; some of them jet ink droplets utilizing pressure waves which are caused by vibrators such as piezoelectric elements, and the like.
Generally, the ink-jet recorders using piezoelectric elements comprise, for example, compression chambers communicating with ink-supply chambers and ink outlets communicating with the compression chambers, wherein the compression chambers are provided with vibration plates bonded with piezoelectric elements. In such a structure, when a given voltage is applied to the piezoelectric elements to expand or contract them, the piezoelectric elements vibrate bending themselves to compress the ink in the compression chambers, thereby jetting ink droplets from the outlets. Today, while color ink-jet recorders are coming into wide use, improvement on the printing performance, particularly high resolution and high-speed printing are demanded. Therefore, there are seen many trials to realize high resolution and high-speed printing by using multi-nozzle heads which are achieved by fine processing of ink heads. To finely process ink heads, it becomes necessary to miniaturize piezoelectric elements for use in jetting ink droplets.
In the meantime, the piezoelectric films of piezoelectric elements are formed by molding powder of PbO, ZrO
2
and TiO
2
into sheets and baking the molded sheets, and therefore, it is difficult to form piezoelectric thin films with a thickness of, for example, 20 &mgr;m or less. For this reason, fine processing of piezoelectric films is accompanied by difficulties, which leads to difficulties in miniaturizing the piezoelectric elements. Further, in the above piezoelectric films formed by baking the powder, as their thickness is becoming smaller, the affection of the thickness on the grain boundary is becoming serious, so that sufficient piezoelectric characteristics can not be obtained. As a result, there is a problem in that the piezoelectric films formed by baking the powder can not provide sufficient piezoelectric characteristics to jet ink droplets when the thickness of the films is 15 &mgr;m or less. Therefore, miniaturized ink heads having characteristics necessary for jetting ink droplets have not been realized.
DISCLOSURE OF THE INVENTION
Objects of the present invention are to provide structures for ink-jet heads having ink outlets which are formed at a high density, by developing thin film materials which have high piezoelectric characteristics in spite of very small thickness and forming piezoelectric films, vibration plates and the like therefrom with very small thickness for constituting piezoelectric elements, thereby making it possible to utilize fine processing techniques which have been applied to the field of the semiconductor processing, and also to provide methods for producing ink-jet heads having such structures.
A first ink-jet head according to the present invention comprises a body having ink outlets and compression chambers respectively communicating with each of the ink outlets, and piezoelectric vibration sections, each being provided on a part of each of the compression chambers and including a piezoelectric film containing Pb, Ti and Zr, and electrodes provided on both sides of the piezoelectric film, whereby each of the piezoelectric vibration sections generates flexural vibration to thereby jet ink droplets from each of the ink outlets, characterized in that the above piezoelectric film comprises a first layer having a perovskite structure containing Sr or Ba, and a second layer formed in contact with the first layer, having a perovskite structure containing Pb, Ti and Zr.
As mentioned above, by forming the second layer in contact with the first layer having a perovskite structure containing Sr or Ba, the second layer containing Zr can be formed thinner, having a higher quality and a larger piezoelectric constant. With this configuration, the first ink-jet head of the present invention can be made very small in size and light in weight.
A second ink-jet head according to the present invention comprises a body having ink outlets and compression chambers respectively communicating with each of the ink outlets, and piezoelectric vibration sections, each being provided on a part of each of the compression chambers and including a piezoelectric film containing Pb, Ti and Zr, and electrodes provided on both sides of the piezoelectric film, whereby each of the piezoelectric vibration sections generates flexural vibration to thereby jet ink droplets from each of the ink outlets, characterized in that the above piezoelectric film comprises a first layer and a second layer, each having a perovskite structure and being formed in contact with each other, and that the content of Zr in the first layer is smaller than that in the second layer.
As mentioned above, by composing the piezoelectric film of the first layer and the second layer which are formed in contact with each other, the second layer containing comparatively more amount of Zr can be formed thinner, having a good quality and a larger piezoelectric constant. With configuration, the second ink-jet head of the present invention can be made very small in size and light in weight.
A third ink-jet head according to the present invention comprises a body having ink outlets and compression chambers respectively communicating with each of the ink outlets, and piezoelectric vibration sections, each being provided on a part of each of the compression chambers and including a piezoelectric film containing Pb, Ti and Zr, and electrodes provided on both sides of the piezoelectric film, whereby each of the piezoelectric vibration sections generates flexural vibration to thereby jet ink droplets from each of the ink outlets, characterized in that the above piezoelectric film comprises a first layer containing no Zr and a second layer containing Zr, each having a perovskite structure and being formed in contact with each other. Thus, the second layer can have a better quality and a higher piezoelectric constant in comparison with the above second ink-jet head.
In the second and third ink-jet heads of the present invention, to form the first layers simply and at low temperatures, it is preferable for the first layers to contain La.
Also, in the first to the third ink-jet heads of the present invention, it is preferable for the second layers to have a Zr/Ti ratio within a range of 30/70 to 70/30 so as to further increase the piezoelectric constants of the above piezoelectric films.
Also, in the first to the third ink-jet heads of the present invention, it is more preferable for the above piezoelectric films to be single crystal so that the piezoelectric constants which the materials constituting the piezoelectric films inherently possess can be effectively utilized.
Also, in the first to the third ink-jet heads of the present invention, it is preferable for the above piezoelectric films to be formed with a thickness of 10 &mgr;m or less so that the piezoelectric films can be finely processed.
Also, in the first to the third ink-jet heads of the present invention, it is more preferable for the above piezoelectric films to be formed with a thickness within a range of 1 to 3 &mgr;m so that the piezoelectric films can be finely processed, and simultaneously that the ink heads can have sufficient ink-jetting powers and sufficiently reliable piezoelectric films. In this case, it is preferable for the first layers to be formed with a thickness within a range of 50 to 100 nm so that the second layers can be formed
Fujii Satoru
Kamada Takeshi
Kanno Isaku
Takayama Ryoichi
Barlow John
Shah Manish S.
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