The present invention relates to an ink jet head, and to a method for the manufacture thereof.
Ink jet recording devices making utilization of the piezoelectric effect of piezoelectric elements to effect printing have been used as a printer, a word processing machine, a facsimile machine, etc. Some ink jet recording devices employ an ink jet head having a multi-level layered construction of thin films, like the one shown in FIGS. 14 and 15.
Referring to the ink jet head-of the figures, formed in the interior of a main body portion 108 of the head are a plurality of pressure chambers 101 which are arranged along a direction L2, and a common ink chamber 102 which has a long and narrow shape in the direction L2. Each of the plurality of pressure chambers 101 is formed into a strip-like shape having a horizontal cross section which has a long and narrow shape in a direction L1. The pressure chambers 101 are in communication through their respective ink supply passages 105 with the common ink chamber 102. Nozzle orifices 103 are formed in a front side of the ink jet head (the lower one of the sides of the ink jet head in FIG. 14). The nozzle orifice 103 is in communication through an ink discharging passage 104 with the pressure chamber 101. Each pressure chamber 101 is compartmented with an oscillation plate 112 at its back side (the upper one of the sides in FIG. 14). The oscillation plate 112 is formed of Cr (chromium) and functions as a common electrode for applying a voltage to piezoelectric elements 106. The piezoelectric element 106 is jointed to a back side of the oscillation plate 112. Mounted on a back side of the piezoelectric element 106 is an individual electrode 111. The individual electrode 111, the piezoelectric element 106 and the oscillation plate 112 together form an actuator portion 107 for applying a pressure to the ink in the pressure chamber 101. The main body portion 108 and the oscillation plate 112 are bonded together by an adhesive 120.
With the recent advancement of the resolution of recording devices to a higher degree, the miniaturization of head structures has been improved. Correspondingly, the gap between two piezoelectric elements 106 next to each other becomes shorter as shown in FIG. 15 and the thickness of a compartmenting wall 109 which compartments the pressure chamber 101 becomes thinner. Accordingly, when adhering together the main body portion 108 and the oscillation plate 112, there are some cases in which the adhesive 120 is forced out of the butt surface, as indicated by the virtual line (the two-dot chain line) of FIG. 15 and a part 114 of the forced-out adhesive adheres to a displacement portion 113 of the oscillation plate 112. This causes the displacement portion 113 of the oscillation plate 112 to decrease in its displacement amount, in addition to which the displacement portion 113 is stopped from performing a smooth displacement operation, therefore resulting in a drop in the ink discharging performance. Further, it is possible that the displacement amount of the oscillation plate 112 varies from one pressure chamber to another, resulting in poor print quality.
Bearing in mind the above-described problems with the prior art techniques, the invention was made. Accordingly, an object of the present invention is to provide such adhesion between a head main body and an oscillation plate that the adhesive will not become an obstacle to the displacement operation of the oscillation plate.
In order to achieve the object, the present invention provides an ink jet head. More specifically, the ink jet head of the present invention comprises (a) a head main body portion in which a pressure-chamber recess portion and a nozzle orifice are formed and (b) an actuator portion having (i) an oscillation plate which covers the pressure-chamber recess portion of the head main body portion so as to form, together with the head main body portion, a pressure chamber in the form of a compartment and (ii) a piezoelectric element which is rigidly fixed to the oscillation plate whereby the displacement of the oscillation plate generated by the piezoelectric effect of the piezoelectric element forces ink in the pressure chamber out of the nozzle orifice, wherein an intermediate layer is formed between the oscillation plate and the head main body portion for the prevention of adhesive adhesion to the oscillation plate and wherein the oscillation plate and the head main body portion are rigidly fixed together by an adhesive through the intermediate layer.
As a result of such arrangement, even when a part of the adhesive is forced out in adhering together the head main body and the oscillation plate, the provision of the intermediate layer between the adhesive and the oscillation plate causes the forced-out adhesive to adhere to the intermediate layer. Accordingly, the forced-out adhesive is prevented from adhering to the displacement portion of the oscillation plate, therefore ensuring that the oscillation plate satisfactorily performs its displacement operation. As a result, the variation in displacement is prevented, thereby achieving a stable ink discharging performance.
The present invention provides another ink jet head which comprises (a) a head main body portion in which a pressure-chamber recess portion and a nozzle orifice are formed and (b) an actuator portion having (i) an oscillation plate which covers the pressure-chamber recess portion of the head main body portion so as to form, together with the head main body portion, a pressure chamber in the form of a compartment and (ii) a piezoelectric element which is rigidly fixed to the oscillation plate whereby the displacement of the oscillation plate generated by the piezoelectric effect of the piezoelectric element forces ink in the pressure chamber out of the nozzle orifice, wherein an intermediate layer having a window portion through which a displacement portion of the oscillation plate is exposed to the pressure chamber, and consisting of metal, ceramics, or resin is formed on a surface of the oscillation plate on the side of the head main body, and wherein the oscillation plate and the head main body portion are rigidly fixed together by an adhesive through the intermediate layer.
Accordingly, by the use of thin film formation technology including sputtering and CVD, the intermediate layer used for the prevention of adhesive adhesion to the displacement portion of the oscillation plate can be formed easily.
The use of copper facilitates the formation of relatively thick films, and therefore the intermediate layer is preferably formed of copper. As a result of such arrangement, it is possible to easily form the intermediate layer having a thicker film thickness capable of the prevention of adhesive adhesion to the oscillation plate without fail. Moreover, the copper is superior in workability, that is, it is easily etched. Therefore, the window portion can be formed easily.
The intermediate layer may be formed of titanium. This extends the life span of the intermediate layer because the titanium is not readily degraded even when exposed to the ink. Moreover, the degree of adhesion between titanium and chromium is high, so that, when chromium is used for the oscillation plate, the adhesion with respect to the oscillation plate is enhanced. Accordingly, there is no need for the provision of an adhesion improving layer used to improve the degree of adhesion between the intermediate layer and the oscillation plate, whereby the manufacture process can be shortened.
If the intermediate layer is formed too thin, then the adhesive is likely to adhere to the displacement portion of the oscillation plate. Taking into account this point, it is preferred that the intermediate layer is formed, having a thickness of 5 xcexcm or greater. As a result of such arrangement, it becomes possible to effectively prevent the adhesive from adhering to the displacement portion of the oscillation plate.
Furthermore, it is more preferable that the intermediate layer is formed, having a thickness of more than 7 xcexcm. This further ensures that the adhesive is prevented from adhering to the displacement portion of the oscillation plate.
On the other hand, if the intermediate layer is formed too thick, this makes it difficult to form the intermediate film having a well arranged shape. It is therefore preferable that the intermediate layer is formed, having a thickness of 30 xcexcm or less. This facilitates the formation of intermediate layers having an adequate shape.
The degree of adhesion between the intermediate layer and the oscillation plate become insufficient in some cases because of the material used. Therefore, an arrangement may be made in which an adhesion improving layer is sandwiched between the intermediate layer and the oscillation plate for the enhancement of the degree of adhesion between them. By virtue of the placement of the adhesion improving layer between the intermediate layer and the oscillation plate, the degree of adhesion between them can be enhanced, as a result of which the peeling-off of the intermediate layer can be prevented.
It is arranged such that the oscillation plate is formed of chromium, the intermediate layer is formed of copper, and the adhesion improving layer is formed of titanium. Because of such arrangement, even though the oscillation plate is formed of chromium and the intermediate layer is formed of copper, it is possible to tightly adhere the intermediate layer and the oscillation plate together because the degree of adhesion of titanium with respect to chromium is high.
In order to prevent the adhesion improving layer from being formed into an island-like shape so that the adhesion improving layer becomes a satisfactory layer, it is preferred that the adhesion improving layer is formed, having a thickness of 0.01 xcexcm or greater. As a result of such arrangement, the adhesion improving layer functions to tightly adhere the oscillation plate and the intermediate plate together.
The present invention provides still another ink jet head which comprises (a) a head main body portion in which a pressure-chamber recess portion and a nozzle orifice are formed and (b) an actuator portion having (i) an oscillation plate which covers the pressure-chamber recess portion of the head main body portion so as to form, together with the head main body portion, a pressure chamber in the form of a compartment and (ii) a piezoelectric element which is rigidly fixed to the oscillation plate whereby the displacement of the oscillation plate generated by the piezoelectric effect of the piezoelectric element forces ink in the pressure chamber out of the nozzle orifice, wherein a projection portion for mounting the oscillation plate on the head main body portion is formed on a surface of the oscillation plate opposite to the head main body portion.
An arrangement may be made, in which the oscillation plate and the head main body portion are rigidly fixed together by an adhesive through the projection portion.
Accordingly, the projection portion which is a part of the oscillation plate functions as the foregoing intermediate layer. As a result of such arrangement, the intermediate layer is no longer to be formed separately from the oscillation plate. Moreover, there is no need to attach the intermediate layer to the oscillation plate.
The present invention provides a method of manufacturing an ink jet head in which an oscillation plate is displaced by the piezoelectric effect of a piezoelectric element and the displacement of the oscillation plate forces ink in a pressure chamber out of a nozzle orifice, the method comprising the steps of (a) forming on a surface of the oscillation plate an intermediate layer, (b) forming an opening in a position of said intermediate layer corresponding to a displacement portion of the oscillation plate, and (c) with the opening of said intermediate layer brought into agreement in position with a pressure-chamber recess portion of the head main body portion, adhering together the intermediate layer and the head main body portion.
As a result of such arrangement, the oscillation plate and the head main body portion are rigidly adhered together by adhesive through the intermediate layer. Accordingly, even when a part of the adhesive is forced out in adhering the oscillation plate and the head main body portion together, the forced-out adhesive will adhere to the intermediate layer, whereby adhesive adhesion to the displacement portion of the oscillation plate is prevented.
The present invention provides another method of manufacturing an ink jet head in which an oscillation plate is displaced by the piezoelectric effect of a piezoelectric element and the displacement of the oscillation plate forces ink in a pressure chamber out of a nozzle orifice, the method comprising the steps of (a) forming on a surface of the oscillation plate an adhesion improving layer, (b) forming on a surface of the adhesion improving layer an intermediate layer, (c) forming an opening in at least a position of the intermediate layer corresponding to a displacement portion of the oscillation plate, and (d) with the opening of the intermediate layer brought into agreement in position with a pressure-chamber recess portion of the head main body portion, adhering together the intermediate layer and the head main body portion.
As a result of such arrangement, the adhesion improving layer is formed between the oscillation plate and the intermediate layer, wherein the intermediate layer is rigidly secured to the oscillation plate through the adhesion improving layer. Thus, the oscillation plate and the head main body portion are tightly secured together by an adhesive through the intermediate layer. Accordingly, even when a part of the adhesive is forced out in adhering the oscillation plate and the head main body portion together, the forced-out adhesive will adhere to the intermediate layer, whereby adhesive adhesion to the displacement portion of the oscillation plate is prevented.
As described above, in accordance with the present invention, the intermediate layer is formed between the oscillation plate and the head main body portion, so that the adhesive is prevented from adhering to the displacement portion of the oscillation plate in adhering the actuator portion and the head main body portion together. This accordingly enables the oscillation plate to perform a displacement operation in a smooth manner, thereby achieving an improved ink discharging performance.
The intermediate layer is formed of copper, thereby facilitating the formation of a relatively thick film well-arranged in shape. This therefore makes it possible to form, in an easy manner, a layer suitably used for the prevention of adhesive adhesion to the oscillation plate. Moreover, it is possible to easily form the window portion for the displacement portion of the oscillation plate.
The arrangement that the intermediate layer is formed of titanium makes it possible to make the intermediate layer less readily degraded when exposed to ink. Moreover, if the oscillation plate is formed of chromium, this makes it possible to enhance the degree of adhesion between the intermediate layer and the oscillation plate.
By virtue of the provision of the adhesion improving layer between the intermediate layer and the oscillation plate, the degree of adhesion between the intermediate layer and the oscillation plate can be enhanced, therefore preventing the peeling-off of the intermediate layer without fail.