JP3221470B2 - Ink jet head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head which, when print data is received, causes ink droplets to fly and form dots on recording paper using the ink droplets.

[0002]

2. Description of the Related Art A conventional ink jet head is disclosed in Japanese Patent Publication No. 2-5173 using a piezoelectric element.
No. 4 is disclosed. This is composed of a flow path substrate in which a groove serving as a flow path is formed, a piezoelectric element, and two electrodes (an individual electrode and a common electrode) for applying a voltage to the piezoelectric element. After forming electrodes on both sides of the piezoelectric plate, the chips are cut and shaped into piezoelectric element chips, and these chips are mounted on a diaphragm corresponding to the pressure chamber.The width of the electrodes is configured to be equal to the width of the piezoelectric element. Was. An image is formed on a recording medium by discharging ink droplets by displacing a diaphragm by deformation of a piezoelectric element and increasing ink pressure in a pressure chamber.

As a method of forming piezoelectric elements arranged at high density, Japanese Patent Application Laid-Open No. 5-97437 is disclosed. In this method, a piezoelectric element is formed on a ceramic substrate by a film forming method, and is integrally formed by firing. For this reason, a large displacement can be obtained at a relatively low operating voltage, reliability is high, a response speed is fast, and a high density can be achieved. In addition, since the ceramic substrate, the piezoelectric element, and the electrode have a laminated structure, the structure is very simple.

[0004]

However, in the conventional ink jet head using the piezoelectric element, after forming electrodes on both sides of the piezoelectric plate, the chip of the piezoelectric element is cut and shaped.
These chips are mounted on a diaphragm corresponding to the pressure chamber, and it is very difficult to increase the density. For this reason, the method of forming the piezoelectric element by printing was used, but the printing of the lower electrode is relatively thin and the accuracy can be easily ensured, but the printing of the piezoelectric element has the thickness limited to the width. Since the thickness of the piezoelectric element was not sufficiently thin, the accuracy of the portion outside the shape of the piezoelectric element was extremely poor, and the deformation characteristics of the diaphragm were not uniform. In addition, when the piezoelectric element was fired, the piezoelectric element contracted, and the deformation characteristics were further deteriorated. For this reason, there is a problem that the ink speed and the amount of ejected ink differ greatly for each nozzle even when the same print pulse is input. Therefore, the present invention solves such a conventional problem, and an object thereof is to realize a high density by forming a piezoelectric element on a diaphragm by firing using a film printing technique. and by eliminating the influence of the contraction of the piezoelectric element after displacement and firing of the printing, ink-jet and uniform deformation characteristics of the diaphragm, eliminating the difference in ink velocity and the ejection amount of ink between nozzles, excellent print quality The purpose is to provide a head. Further, another object of the present invention is to
The purpose of the present invention is to propose a method of manufacturing a pad.

[0005]

In order to achieve the above object, an ink jet head according to the present invention comprises a ceramic vibrating plate, one surface of which is sealed by the vibrating plate, and the vibration of the vibrating plate. A plurality of ceramic pressure chambers arranged in a row for ejecting ink, electrodes formed on the surface of the diaphragm corresponding to the pressure chambers, and formed on the surface of the lower electrode, and the deflection In an ink jet head having a piezoelectric element for discharging ink, the piezoelectric element has a width W2 equal to the width W of the pressure chamber.
Greater than the width W3 of the electrode formed smaller than 1
It is composed .

[0006]

[0007]

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main part of an ink jet head according to the present invention, and shows a cross-sectional shape cut along a plane perpendicular to the direction of ink flow in a pressure chamber.
FIG. 2 is an external perspective view showing the ink jet head of the present invention, which is an ink jet head using three pressure generating units 20 each having 16 nozzles arranged in two vertical rows and a flow path unit 40. The number and the unit configuration are not limited to any combination.

FIG. 3 is an exploded perspective view, in which a plurality of piezoelectric elements 6, a lower electrode 5, a vibration plate 4, a pressure chamber forming substrate 2 having a plurality of pressure chambers 3 corresponding to the piezoelectric elements, and a communication passage 9 are perforated. Pressure generating unit 20 constituted by the divided communication path substrate 1, an ink supply path forming substrate 13 having a plurality of ink supply holes 14, a reservoir chamber forming substrate 12 having an ink reservoir chamber 15, and a nozzle having a plurality of nozzles 16 There is a channel unit 40 constituted by the formation substrate 11 and both units are joined by an adhesive.

As a joining method, a paste adhesive is applied by a screen printing method, a transfer method, or the like, and is cured by heating.
It is also possible to use a film adhesive formed by pressing or the like. In this case, as the bonding method, the press-bonded film adhesive is laminated while being positioned using a guide hole (not shown), and then heat-pressed.

The pressure generating unit 20 is integrally formed by firing, and the steps are shown in FIGS. 4 (A) to 4 (C). In FIG. 4A, a vibration plate 4, a pressure chamber forming substrate 2 in which a portion to be a pressure chamber 3 is formed by punching, and a communication path substrate 1 in which communication paths are perforated are made of a ceramic material such as alumina or zirconia. Pressure is applied in the state of a green sheet, and firing is performed integrally at a temperature of 800 ° C to 1500 ° C.
The ceramic material is generally a material mainly containing at least one of aluminum oxide, zirconium oxide, magnesium oxide, aluminum nitride, and silicon nitride. Next, in FIG. 4B, the material of the lower electrode 5 is formed in a portion corresponding to the pressure chamber 3 by printing, and is baked. The material of the lower electrode 5 is a material mainly composed of at least one of platinum, palladium, silver-palladium, silver-platinum, and an alloy composed of platinum-palladium. Finally, in FIG. 4C, the material of the piezoelectric element 6 is similarly formed by printing and fired to finish. The material of the piezoelectric element 6 is a material mainly containing lead zirconate titanate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganese niobate, lead antimony stannate, and lead titanate. .

However, when the head is manufactured by the above-described steps, the piezoelectric element is soft when the piezoelectric element 6 is printed, and its thickness is not sufficiently thin compared to the width.
As shown in (1), the accuracy of the portion outside the piezoelectric element 6 (6-1 in FIG. 6) was very poor, and the deformation characteristics of the diaphragm 4 were reduced. In addition, the firing caused the piezoelectric element 6 to shrink, and the deformation characteristics to further deteriorate. Further, there is a possibility that the lower electrode 5 and the upper electrode 7 may be electrically short-circuited.

In the present invention, the above-mentioned problem is solved by using the following method. As shown in FIG. 6A, the lower electrode 5 is formed by printing at a portion corresponding to the pressure chamber 3, and at this time, the width of the lower electrode 5 is
And sintering. Next, as shown in FIG. 6B, the piezoelectric element 6 is also formed by printing. At this time, the width of the piezoelectric element 6 is formed to be larger than the width of the lower electrode 5, and then fired. As a result, the deformation characteristics of the diaphragm 4 were determined by the correctly formed lower electrode 5 without being affected by the printing displacement of the piezoelectric element 6 or the contraction of the piezoelectric element 6 due to firing, and the ink ejection characteristics were stabilized. Further, an electrical short between the lower electrode 5 and the upper electrode 7 was prevented.

FIG. 7 is a sectional view of a pressure chamber according to a first embodiment of the present invention, taken along a plane perpendicular to the ink flow direction. The thickness T1 of the lower electrode 5 is 5 μm in the present embodiment, but this is the optimum value. If the lower electrode 5 is thicker, the accuracy of the shape of the outer surface of the lower electrode 5 is reduced, resulting in non-uniform deformation characteristics, and the rigidity of the lower electrode 5 is increased, so that the deformation of the diaphragm 4 is reduced. As a result, the ink ejection characteristics deteriorate. Conversely, if the lower electrode 5 is made thinner, there are problems such as a reduction in deformation characteristics due to the restriction of the flow of current and a printing failure.

The width W1 of the pressure chamber 3 is 420 μm, the width W2 of the lower electrode 5 is 340 μm, and the width W3 of the piezoelectric element 6 is 380.
μm. The ratio W2 / W1 of the width W2 of the lower electrode 5 to the width W1 of the pressure chamber 3 is 0.8 or more. The displacement efficiency of the diaphragm 4 is maximized when the ratio of the width W2 of the lower electrode 5 to the width W1 of the pressure chamber 3 and W2 / W1 are around 0.9, but there are errors such as manufacturing variations. For this reason, the ratio of the width W2 of the lower electrode 5 to the width W1 of the pressure chamber 3, W2 / W1, is set to 0.8 or more, and preferably around 0.9. In the case of this embodiment, since the piezoelectric element 6 is joined to the diaphragm 4 via the lower electrode 5, the functioning width of the width W3 of the piezoelectric element 6 is actually the width W2 of the lower electrode 5. Therefore, the width W3 of the piezoelectric element 6
The optimum value is about 10% wider than the width W2 of the lower electrode 5 in consideration of variations in printing, shrinkage after baking, and the like. The ratio of the width of the lower electrode 5 to the width of the piezoelectric element 6, W2 / W3
Is around 0.9.

In the second embodiment of the present invention shown in FIG. 8, the piezoelectric element 6 is merely joined to the diaphragm 4 via the lower electrode 5, and the piezoelectric vibrator 6 has a width W3. beneath
Although the width is larger than the width W2 of the electrode 5, its periphery is denoted by reference numeral 8.
A state protruding from the lower electrode 5 like a region indicated by -1,
That is, it is in an overhang state. This allows
The piezoelectric vibrator 6 comes into contact with the diaphragm 4 via the partial electrode 4
That the piezoelectric vibrator 6 directly contacts the diaphragm 4
Therefore, the deformation characteristics of the diaphragm 4 become uniform, and the ink ejection characteristics are improved.

In the third embodiment of the present invention shown in FIG. 9, the gap between the baked piezoelectric elements 6 may be filled with an insulating material 8. With this shape, the electric influence between the adjacent piezoelectric elements 6 is prevented, so that the electric crosstalk is improved. Further, the insulation between the lower electrode 5 and the upper electrode 7 is improved, and the electrical characteristics are also improved.

In the fourth embodiment of the present invention shown in FIG. 10, the lower electrode 5 and the insulating material 8 may be formed into a single sheet. With this shape, the piezoelectric element 6 is not bonded to the vibration plate 4, so that the deformation characteristics of the vibration plate are further improved, and the ink ejection characteristics are stabilized.

In the fifth embodiment of the present invention shown in FIG. 11, the diaphragm 4 can be provided with a groove in which the lower electrode 5 and the piezoelectric element 6 can be laminated. This shape allows the lower electrode 5
In addition, the printing accuracy of the piezoelectric element 6 is improved, the displacement characteristics of the diaphragm 4 become uniform, and the ink ejection characteristics can be stabilized.

[0021]

As described above, in the present invention,
The width W2 of the piezoelectric element is smaller than the width W1 of the pressure chamber.
The width of the formed electrode is larger than W3.
Therefore, electrodes that can be formed with higher accuracy than piezoelectric elements
As long as the piezoelectric element is formed as specified, the piezoelectric element
The surrounding area can be vibrated as a displacement area, and printing variations
Influence of deformation characteristics due to shrinkage of piezoelectric element due to burning and firing
And uniform deformation characteristics of the diaphragm in each pressure chamber.
Ink can be stably ejected.

[0022]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pressure chamber according to a first embodiment of the present invention, taken along a plane perpendicular to the ink flow direction.

FIG. 2 is a perspective view showing the appearance of the present invention.

FIG. 3 is an exploded perspective view showing the configuration of the present invention.

FIG. 4 is a view showing a conventional process of manufacturing an integral firing type inkjet head.

FIG. 5 is a cross-sectional view of a printing state of a conventional piezoelectric element in a plane perpendicular to the direction of ink flow in a pressure chamber.

FIG. 6 is a diagram showing a manufacturing process of the first embodiment of the present invention.

FIG. 7 is a cross-sectional view of a pressure chamber according to the first embodiment of the present invention in a plane perpendicular to the ink flow direction.

FIG. 8 is a sectional view of a pressure chamber according to a second embodiment of the present invention in a plane perpendicular to the ink flow direction.

FIG. 9 is a sectional view of a pressure chamber according to a third embodiment of the present invention in a plane perpendicular to the ink flow direction.

FIG. 10 is a cross-sectional view of a pressure chamber according to a fourth embodiment of the present invention in a plane perpendicular to the ink flow direction.

FIG. 11 is a cross-sectional view of a pressure chamber according to a fifth embodiment of the present invention, taken along a plane perpendicular to the ink flow direction.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 communication path substrate 2 pressure chamber forming substrate 3 pressure chamber 4 diaphragm 5 lower electrode 6 piezoelectric element 7 upper electrode 8 insulating material 9 communication path 11 nozzle forming substrate 12 reservoir forming substrate 13 supply path forming substrate 14 ink supply hole 15 ink reservoir Chamber 16 Nozzle 20 Pressure generation unit 40 Flow passage unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/16

Claims (15)

(57) [Claims] 1. A ceramic vibrating plate, a plurality of ceramic pressure chambers arranged in a row in which one surface is sealed by the vibrating plate and ink is ejected by vibration of the vibrating plate, and An electrode formed on the surface of the diaphragm corresponding to the chamber, and an ink jet head comprising a piezoelectric element formed on the surface of the lower electrode and discharging the ink by flexural displacement, wherein the piezoelectric element is An inkjet head having a width W2 larger than a width W3 of the electrode formed smaller than a width W1 of the pressure chamber. 2. The ink jet head according to claim 1, wherein the piezoelectric element has a width W2 smaller than a width W1 of the pressure chamber. 3. The width W3 of the electrode and the width W1 of the pressure chamber.
2. The ink jet head according to claim 1, wherein the ratio is 0.8 to 0.9. 4. The ink jet head according to claim 1, wherein the piezoelectric element is joined to the electrode with its peripheral edge overhanging from the electrode. 5. The ink jet head according to claim 1, wherein an electric insulating layer is formed between the electrodes. 6. The ink-jet head according to claim 1, wherein the piezoelectric element is laminated with an unfired piezoelectric material on the electrode and then fired and joined to the electrode. 7. The ink jet head according to claim 1, wherein upper electrodes are formed on surfaces of the plurality of piezoelectric elements. 8. The ink jet head according to claim 1, wherein an electric insulating layer is formed between the electrodes, and an upper electrode is formed on a surface of the plurality of piezoelectric elements. 9. A ceramic vibrating plate, a plurality of ceramic pressure chambers arranged in a row in which one surface is sealed by the vibrating plate and ink is discharged by vibration of the vibrating plate, and A method for manufacturing an inkjet head comprising: an electrode formed on the surface of the vibration plate corresponding to a chamber; and a piezoelectric element formed on the surface of the lower electrode and discharging the ink by bending displacement. Forming an electrode having a width W3 smaller than the width W1 of the pressure chamber on the surface of the vibration plate; and forming a layer of piezoelectric material on each of the electrodes with a width W2 larger than the width W3 of the electrode. And baking the piezoelectric material layer to form a plurality of piezoelectric elements. 10. The method according to claim 9, wherein the width W2 of the piezoelectric element is smaller than the width W1 of the pressure chamber. 11. The method according to claim 9, wherein the layer of the piezoelectric material is formed by laminating a green sheet of the piezoelectric material. 12. The method according to claim 9, wherein the layer of the piezoelectric material is formed by printing a piezoelectric material. 13. The method according to claim 9, further comprising the step of forming upper electrodes on the surfaces of the plurality of piezoelectric elements. 14. The method according to claim 9, further comprising the step of forming an electric insulating layer between the plurality of piezoelectric elements. 15. A step of forming an electric insulating layer between a plurality of said piezoelectric elements, and a step of forming an electric insulating layer between said plurality of said piezoelectric elements.
The method for manufacturing an ink jet head according to claim 9, further comprising a step of forming an upper electrode on a surface of the formed electric insulating layer and the piezoelectric element .