EP1070589A2

EP1070589A2 - Ink-jet recording head, method for fabricating same and method for ejecting ink droplets

Info

Publication number: EP1070589A2
Application number: EP00114942A
Authority: EP
Inventors: Takashi Ota
Original assignee: NEC Corp
Current assignee: Fujifilm Business Innovation Corp
Priority date: 1999-07-19
Filing date: 2000-07-18
Publication date: 2001-01-24
Also published as: EP1070589A3; CN1280917A

Abstract

An ink-jet recording head including a plurality of pressure chambers (12a, 12b, 12c) connected to one another, a plurality of first piezoelectric elements (18a, 18b, 18c) and a plurality of second piezoelectric elements (19a, 19b, 19c). Each pair of the first piezoelectric element and the second piezoelectric element is independent of the other pairs. Accordingly, since the transmission of the stress generated during the printing in the piezoelectric pair to the nearby pair is completely or almost completely prevented because the adjacent pairs are completely separated or connected with an elastic material absorbing the stress.

Description

The present invention relates to an ink-jet recording head and a method for fabricating the same, and more in detail to the ink-jet recording head for use in a printer, a facsimile and a copier and the method for fabricating the same.
An ink-jet printer described in JP-A-11(1999)-10867 includes, as shown in Fig.1, nozzles 11a, 11b, 11c for ejecting ink droplets, pressure chambers 12a, 12b, 12c connected to the nozzles 11a, 11b, 11c, respectively, supply ports (not shown) for supplying ink to the pressure chambers 12a, 12b, 12c, and piezoelectric elements 13a, 13b, 13c for generating pressures in the pressure chambers 12a, 12b, 12c, respectively.
Non-driving columns 14a, 14b, 14c which are non-driving piezoelectric elements acting as fixing members are disposed between the adjacent piezoelectric elements 13a,13b, 13c for connection with side walls 15a, 15b, 15c. The non-driving columns 14a, 14b, 14c are connected to one another at the respective bases 16.
In the ink-jet recording head having the configuration as described above, when a voltage is applied to the piezoelectric element 13b, for example, the piezoelectric element 13b elongates to compress the ink in the pressure chamber 12b, thereby ejecting an ink droplet 17 through the nozzle llb.
By moving the ink-jet recording head relative to a recording medium such as printing sheet in accordance with printing data, and driving the specified piezoelectric elements at the specified timing, characters and figures can be recorded on the recording medium.
In the conventional ink-jet recording head, the piezoelectric elements 13a, 13b, 13c are integrated at the base 16, and the piezoelectric elements 13a, 13b, 13c are fixed to the side walls 15a, 15b, 15c by way of the adjacent non-driving columns 14a, 14b, 14c. Due to the indirect fixation, the displacement of the driven piezoelectric element is also transmitted to the non-driven pressure chamber by way of the base 16 as shown in Fig.2. Accordingly, when the driven pressure chamber 12b is compressed, a cross-talk problem may occur because the non-driven pressure chambers 12a, 12c are expanded.
The speed and the diameter of the ink drop-lets decrease with the increase of the number of the nozzles simultaneously driven by the cross-talk. In other words, the speed and the diameter of the ink drop-lets change depending on the number of the nozzles simultaneously driven to shift the position to which the droplets arrive and generate the irregularity of the printing density, resulting a deterioration of the printing quality.
In a graph of Fig.3, curve B shows the fluctuation of the ejection speed of the droplets when a plurality of the pressure chambers are simultaneously driven in the conventional ink-jet recording head.
In the graph, the abscissa shows the number of the pressure chambers having the nozzles, including the subject pressure chamber to be note. The number "1" on the abscissa indicates that the nozzle only in the subject pressure chamber is driven (standard) and the speed in this case is used for normalization. The number "2" indicates that the nozzles in the subject pressure chamber and one of the two adjacent pressure chambers are driven. The number "3" indicates that the nozzles in the subject pressure chamber and both of the two adjacent pressure chambers are driven. The number "4" indicates that the nozzles in the subject pressure chamber, both of the two adjacent pressure chambers and one of the pressure chamber next to one of the two adjacent pressure chambers are driven. The number "5" indicates that the nozzles in the subject pressure chamber, both of the two adjacent pressure chambers and both of the pressure chamber next to the adjacent pressure chambers are driven, and so forth.
The ordinate of the graph indicates the speed of droplets ejected from the nozzles of the subject pressure chamber depending on the number of the pressure chambers including the nozzles simultaneously driven, taking the speed of droplets ejected from the nozzles of the subject pressure chamber as 100 % when only the nozzle of the subject pressure chamber ois driven, as described before.
As apparent from the curve B of the graph of Fig.3, the speed of the ejected droplet is reduced with the increase of the number of the pressure chambers simultaneously driven in the conventional ink-jet recording head.
JP-A-9(1997)-174836, JP-A-9(1997)-174837 and JP-A-7(1995)-57545 describe an ink-jet recording head including a vibration board, forming part of an pressure chamber, having a thinner portion and a remaining thicker portion which functions as a vibration element, for overcoming the reduction of ejection speed of the ink droplets and the generation of a cross-talk accompanied with the high integration. However, the piezoelectric element fixed between the adjacent pressure chambers is not disclosed, and accordingly an idea with respect to the influence of the piezoelectric element affecting the piezoelectric element of another pressure chamber is not disclosed.
In view of the foregoing, an object of the present invention is to provide an ink-jet recording head having an excellent printing quality by removing or reducing a cross-talk
The present invention provides, in a first aspect thereof, an ink-jet recording head including: a plurality of pressure chambers disposed in an array and each having a first wall having a nozzle for ejecting ink droplets, a second wall having a vibratable part for each pressure chamber, and a plurality of side walls in contact with the first and the second walls, each said pressure chamber receiving ink supplied through an ink supply port; a first piezoelectric element disposed for each of the pressure chambers and having a first end disposed on the vibratable part, and a second end; and a second piezoelectric element disposed for each of the pressure chambers and having a first end fixed to the side wall, and a second end; both the second end of the first and the second piezoelectric elements for each pressure chamber being integrated to form a piezoelectric pair, and adjacent piezoelectric pairs being separated by a gap.
In accordance with the first aspect of the present invention, since the transmission of the stress generated during the printing in the piezoelectric pair to the nearby pair is completely or almost completely prevented because the adjacent pair is completely separated or connected with an elastic member or material absorbing the stress. Accordingly, the cross-talk can be efficiently prevented, thereby providing the ink-jet recording head having an excellent printability.
The present invention provides, in a second aspect thereof, in addition of the configuration of the first aspect, an ink-jet recording head in which the piezoelectric element is polarized and electrically isolated.
In accordance with the second aspect of the present invention, the combination of the driving column and the depolarized and electrically isolated fixing column can suppress the transmission of the displacement generated during the printing to provide the ink-jet recording head having excellent performances. When the driving column is driven, a force is applied to the fixing column due to its reaction, and the reverse electric filed is generated in the fixing column. The reverse electric field prevents the displacement of the fixing column to elevate the stiffness. Accordingly, the cross-talk is reduced, and the variation of the ejecting speed and the diameter of ink droplets can be efficiently prevented.
The above and other objects, features and advantages of the present invention will be more apparent from the following description.

BRIEF DESCRIPTION OF DRAWINGS

Fig.1 is a sectional view of a conventional ink-jet recording head.
Fig.2 is a sectional view of the ink-jet recording head of Fig.1 when it is driven.
Fig.3 is a graph showing a change of a speed of droplet when a plurality of ink-jet recording heads are simultaneously driven.
Fig.4 is a sectional view showing an ink-jet recording head in accordance with a first embodiment of the present invention.
Fig.5 is a sectional view showing an ink-jet recording head in accordance with a second embodiment of the present invention.
Fig.6 is a sectional view showing an ink-jet recording head in accordance with a third embodiment of the present invention.
Fig.7 is a sectional view showing an ink-jet recording head in accordance with a fourth embodiment of the present invention.
Fig.8 is a sectional view showing an ink-jet recording head in accordance with a fifth embodiment of the present invention.
Fig.9 is a perspective view showing the ink-jet recording head in a practical use.
Fig.10 is a perspective view showing a principle of printing by using the ink-jet recording head of the invention.
Fig. 11 is a bottom view showing an arrangement of nozzles for the ink-jet recording head.
Fig.12 is a horizontal sectional view showing the relationship between the nozzles and ink-supply means.
Fig.13 is a perspective view showing an example of a configuration of piezoelectric elements of the ink-jet recording head.
Fig.14 is a perspective view showing an example of a piezoelectric element employable in the ink-jet recording head of the present invention.
Fig.15 is a perspective view showing contact between the piezoelectric element and a pressure chamber.
Figs.16A to 16C are graphs showing an effect of driving first and second piezoelectric elements in an opposite direction.
Figs.17A and 17B are graphs showing waveforms obtained by driving first and second piezoelectric elements in an opposite direction.
Fig.18 is a block diagram of a driving circuit for a piezoelectric element employable in the ink-jet recording head of the present invention.
Fig.19 is a block diagram of a driving waveform generating circuit for a piezoelectric element employable in the ink-jet recording head of the present invention.
Figs. 20A to 20E are perspective views consecutively showing a method for fabricating an ink-jet recording head in accordance with a first method of the present invention.
Figs. 21A to 21F are perspective views consecutively showing a method for fabricating an ink-jet recording head in accordance with a second method of the present invention.
Figs. 22A to 22E are perspective views consecutively showing a method of fabricating an ink-jet recording head in accordance with a third method of the present invention.
Figs. 23A to 23F are perspective views consecutively showing a method of fabricating an ink-jet recording head in accordance with a fourth method of the present invention.
Figs. 24A to 24E are perspective views consecutively showing a method of fabricating an ink-jet recording head in accordance with a fifth method of the present invention.
Figs. 25A to 25F are perspective views consecutively showing a method of fabricating an ink-jet recording head in accordance with a sixth method of the present invention.
Fig.26 is a partially broken perspective view showing an ink-jet recording head in accordance with a sixth embodiment of the present invention.
Fig.27 is a sectional view showing a pressure chamber in a row direction.
Fig.28 is a sectional view of the pressure chamber of Fig.27 taken in a line perpendicular to that of Fig.27.
Fig.29 is a perspective view showing one step of fabricating ink-jet recording head of the present invention.
Fig.30 is a perspective view showing another step of fabricating ink-jet recording head of the present invention.
Fig.31 is a perspective view showing a further step of fabricating ink-jet recording head of the present invention.
Fig.32 is a perspective view showing a still further step of fabricating ink-jet recording head of the present invention.
Fig.33 is a perspective view showing a yet further step of fabricating ink-jet recording head of the present invention.
Fig.34 is a perspective view showing an ink-jet recording head in accordance with a seventh embodiment of the present invention.
Fig.35 is a sectional view showing an external shape of an internal electrode for depolarizing a base section.
Fig.36 is a perspective view showing an ink-jet recording head in accordance with an eighth embodiment of the present invention.
Fig.37 is a sectional view showing the piezoelectric element and the pressure chamber of Fig.36.
Fig.38 is a perspective view showing one step of fabricating the ink-jet recording head of Fig.36.
Fig.39 is a perspective view showing another step of fabricating the ink-jet recording head of Fig.36.
Fig.40 is a perspective view showing a further step of fabricating the ink-jet recording head of Fig.36.
Fig.41 is a perspective view showing an ink-jet recording head in accordance with a ninth embodiment of the present invention.
Fig.42 is a sectional view showing the piezoelectric element and the pressure chamber of Fig.41.
Fig.43 is a perspective view showing one step of fabricating the ink-jet recording head of Fig.41.
Fig.44 is a perspective view showing another step of fabricating the ink-jet recording head of Fig.41.
Fig.45 is a perspective view showing a further step of fabricating the ink-jet recording head of Fig.41.

PREFERRED EMBODIMENTS OF THE INVENTION

Now, the present invention is more specifically described with reference to accompanying drawings.
As shown in Fig.4, an ink-jet recording head 40 in accordance with a first embodiment of the present invention includes a first, a second and a third pressure chambers 12a, 12b, 12c having first walls 31, a vibratable second wall 21, side walls 15a, 15b, 15c in contact with the first walls 31 and the second wall 21 to form closed spaces therein, and an ink supply port 32 for supplying the ink into closed spaces 31. The plurality of the pressure chambers 12a, 12b, 12c are joined with one another to form the ink-jet recording head 40. In each of the pressure chambers 12a, 12b, 12c, the vibratable second wall 21 includes vibratable parts 26 and non-vibratable parts 27 individually having a first piezoelectric element 18a, 18b, 18c and a second piezoelectric element 19a, 19b, 19c erected thereon. An end 18"a opposite to the other end 18'a of the first piezoelectric element 18a in contact with the vibratable part 26 of the second wall 21, and an end 19"a opposite to the other end 19'a of the second piezoelectric element 19a in contact with the non-vibratable part 27 or the other portion of the second wall 21, are joined with each other. Further, a pair of the first and the second piezoelectric elements 18a, 19a disposed on the first pressure chamber 12a are mounted independently of the other pairs of the piezoelectric elements 18b, 19b, 18c, 19c.
In a third embodiment and a fourth embodiment shown in Figs.6 and 7, respectively, obtained by modifying the first embodiment, the pair of the first and the second piezoelectric elements 18a and 19a mounted in the first pressure chamber 12a are joined with the other pair in the pressure chamber, for example, with the pair of the first and the second piezoelectric elements 18b and 19b mounted in the second pressure chamber 12b by a lower rigidity (elastic) region 22a, 22b (Fig.6) or 23a, 23b (Fig.7).
In the third and the fourth embodiments, the ink-jet recording head 40 includes the first wall 30 having nozzles lla and the ink supply port 32 supplying the ink are connected with each other, the plurality of the pressure chambers 12a, 12b, 12c surrounded by the vibratable second wall 21 and the side walls 15a, 15b, 15c. The ink-jet recording head 40 further includes the first piezoelectric elements 18a, 18b, 18c each one end thereof is connected to the vibratable part 26 and the second piezoelectric elements 19a, 19b, 19c, parallel to the first piezoelectric elements 18a, 18b, 18c, each one end thereof is connected to the side walls 15a, 15b, 15c by way of the second wall 21. The other ends of the first piezoelectric elements 18a, 18b, 18c and the other ends of the second piezoelectric elements 19a, 19b, 19c are joined with each other by every other higher rigidity material 20a, 20b, 20c and the lower rigidity region 22a, 22b (Fig.6) or 23a, 23b (Fig.7) between the adjacent higher rigidity material 20a, 20b, 20c.
The vibratable part 26 as shown in Figs.6 and 7 includes easily vibratable part at around the center of the second wall 21 and its periphery.
On the other hand, the non-vibratable part 27 includes non-vibratable part of the second wall 21, more concretely includes a section existing between the periphery region of the vibratable part 26 and the side walls 15a, 15b, 15c, or a section of the second wall 21 at least partially in contact with the side walls 15a, 15b, 15c, or a section of the side walls 15a, 15b, 15c not in contact with the second wall 21.
The first piezoelectric elements 18a, 18b, 18c in contact with the vibratable part 26 of the second wall 21 and second piezoelectric elements 19a, 19b, 19c in contact with the non-vibratable part 27 of the second wall 21 or part of the side walls 15a, 15b, 15c are desirably made of the same or similar material.
The lower rigidity region 22a, 22b or 23a, 23b preferably has one of a trench, a thin film and a lower rigidity material film.
A thin section is preferably formed in the second wall 21 including the vibration board, and has a trench 100 for easier vibration.
The first piezoelectric elements 18a, 18b, 18c driven during the ink droplets ejection is preferably polarized.
The first piezoelectric elements 18a, 18b, 18c are driven during the ink droplets ejection so that the vibratable part 26 of the second wall 21 is displaced toward the inner surface of the pressure chamber 12a, 12b, 12c.
The second piezoelectric elements 19a, 19b, 19c are preferably polarized and electrically isolated.
The first and the second piezoelectric elements may be driven in a direction reverse to each other.
Since the first and the second piezoelectric elements in each of the pressure chambers are completely separated from those of the other pressure chambers or connected with the lower rigidity, the displacement of the piezoelectric elements is not completely or seldom transmitted to the other pressure chambers to overcome the cross-talk.
When the second piezoelectric elements are polarized and electrically isolated, a stress is applied to the second piezoelectric elements upon the driving of the first piezoelectric elements due to the reaction thereof. The second piezoelectric elements in the polarized and electrically isolated state generate a reverse electric field which may prevent the displacement thereof by the effect of the reverse electric field. Consequently, the rigidity of the second piezoelectric elements increases, and the displacement of the first piezoelectric element is efficiently transmitted to its pressure chamber to realize the lower electric consumption and the lower cost.
The reverse direction driving of the first and the second piezoelectric elements makes the addition of the both displacements to generate a larger displacement. Accordingly, the width of the pressure chamber can be reduced, and the pressure chambers can be disposed at a higher density. The reduction of the driving voltage is also attained to decrease the cost of fabricating the driving apparatus.
The reason of the rigidity increase of the second piezoelectric element when it is polarized and electrically isolated.
The polarized piezoelectric element exhibits a piezoelectric effect and a reverse piezoelectric effect.
The polarizing treatment can be conducted by applying an electric field of 1 x 10⁶ [V/m] when, for example, "Nepec 'NPM"' N-10 which is lead zirconate and titanate-based ceramics available from Tokin Corporation, though depending on the material.
The piezoelectric effect is that of generating an electrical displacement upon application of a pressure, and the reverse piezoelectric effect is that of generating a distortion upon application of an electric field.
The piezoelectric element is elastic similar to not a few other materials, and generates the distortion upon application of a pressure.
The piezoelectric element generates an electrical displacement upon application of an electric field because it is a dielectric substance.
These relations can be expressed as follows, wherein "S" is a distortion, "T" is a stress, "D" is an electrical displacement, " S^E" is a coefficient of elasticity, "d" is a piezoelectric distortion constant, and " ε ^T E" is a dielectric constant.
Basic piezoelectric equations are as follows. S = sE T + dE D = dT + ε T E
The non-polarized piezoelectric element is elastic and dielectric, and d=0 in the above equations.
Accordingly, the coefficient of elasticity is s^E in case of no polarization.
On the other hand, when the piezoelectric element is polarized and the electrode is open, "D" becomes "0" and the coefficient of elasticity is s^D in such a case is obtained as follows by deleting "E". sD = [S/T]D=0 = sE - (d2/ε T)
In case of the above material, s^E = 18.1 x 10 ^-12 [m²/N], and s^D can be calculated as s^D = 9.73 x 10 ^-12 [m²/N] by using the s^E value.
The polarization of the piezoelectric element and the opening of the electrode make the coefficient of elasticity 0.54 time. In other words, the stiffness becomes 1.9 times.
The reason thereof is as follows. When a stress is applied to the polarized element at the electrically isolated state (D=0), an reverse electric field is generated and prevents the displacement, thereby reducing the coefficient of elasticity.
Then, examples of the piezoelectric element suitably employed as the ink-jet recording head will be described.
As described above, "Nepec 'NPM"' N-10 which is lead zirconate and titanate-based ceramics available from Tokin Corporation is an example of the material of the piezoelectric element.
The piezoelectric element can be obtained by sintering the two layers of the lead zirconate and titanate-based ceramics sandwiching an internal electrode.
Representative material constants of the "Nepec 'NPM"' N-10 are as follows. s33 E = 18.1 x 10-12 [m2/N] d33 = 635 x 10-12 [m/V] ε 33 T = 5440 x 8.854 x 10 -12 = 48.2 x 10 -9 [F/m]
Then, a more detailed structure of the ink-jet recording head in accordance with the present invention will be described.
In Fig.9 exemplifying use of the ink-jet recording head 40 in accordance with the above embodiments, a support section 93 is engaged with scanning rods 95 extending in a width direction (arrow "b") of a printer 80. The printer 80 moves in the width direction along the scanning rods 95 for responding to signals and ejects a specified amount of ink droplets on specified positions on a sheet 94 forwarded in a direction of an arrow "a" at a specified speed with suitable rollers 97, 98.
A pair of ink cartridges 90, 91 are accommodated in a container 90 of the ink-jet recording head, and a plurality of the nozzles for ejecting ink droplets are disposed on a bottom plate section 96 corresponding to the first wall 30 of the above embodiments.
In Fig.10, a situation is shown in which ink droplets 105, 106 are ejected from the ink-jet recording head 40 of the above embodiments to the sheet 94.
As shown in Fig.11, eight nozzles consisting of two columns each having four nozzles are arranged on the bottom surface of the first wall 30.
The ink supplied through the proper pipe 32 connected to an external ink supply means (not shown) is once stored in a pooling section 50 and then distributed to the respective pressure chamber 12 through each of nozzles 11 as shown in Fig.12.
As described earlier in connection with Fig.4, the ink-jet recording head of the embodiments of the present invention includes the pressure chambers 12a, 12b, 12c having the nozzles lla, 11b, 11c and the ink supply port 32 connected with each other, and surrounded by the vibratable second wall 21 and the side walls 15a, 15b, 15c. The ink-jet recording head further includes the first piezoelectric elements 18a, 18b, 18c each one end of which is connected to the vibratable second wall 21 and the second piezoelectric elements 19a, 19b, 19c, parallel to the first piezoelectric elements 18a, 18b, 18c, each one end thereof is connected to the side walls 15a, 15b, 15c by way of the second wall 21.
The other end of the first piezoelectric element 18a and the other end of the second piezoelectric element 19a are joined, the other end of the first piezoelectric element 18b and the other end of the second piezoelectric element 19b are joined, and the other end of the first piezoelectric element 18c and the other end of the second piezoelectric element 19c are joined, respectively by way of the connection materials 20a, 20b, 20c.
On the other hand, the other end of the second piezoelectric element 19a and the other end of the first piezoelectric element 18b are separated, and the other end of the second piezoelectric element 19b and the other end of the first piezoelectric element 18c are also separated.
In the ink-jet recording head having the configuration, when, for example, the first piezoelectric element 18b is driven, the piezoelectric element 18b elongates to compress the ink in the pressure chamber 12b, thereby ejecting an ink droplet 17 through the nozzle 11b.
By relatively moving the ink-jet recording head with respect to a recording medium such as printing paper in accordance with printing data, and driving the specified piezoelectric elements at the specified timing, characters and figures can be recorded on the recording medium. be driven in a direction reverse to each other.
Since the first and the second piezoelectric elements in each of the pressure chambers are completely separated from those of the other pressure chambers, the displacement of the driven piezoelectric element is not completely or seldom transmitted to the other pressure chambers to overcome the cross-talk.
When the second piezoelectric elements are polarized and electrically isolated, a stress is applied to the second piezoelectric elements upon the driving of the first piezoelectric elements due to the reaction thereof. The second piezoelectric elements in the polarized and electrically isolated state generate a reverse electric field which may prevent the displacement thereof by the effect of the reverse electric field. Consequently, the rigidity of the second piezoelectric elements increases, and the displacement of the first piezoelectric element is efficiently transmitted to its pressure chamber to realize the lower electric consumption and the lower cost.
The reverse direction driving of the first and the second piezoelectric elements, for example, the elongating action of the first piezoelectric and the contracting action of the second piezoelectric element makes the addition of the both displacements to generate a larger displacement. Accordingly, the width of the pressure chamber can be reduced, and the pressure chambers can be disposed at a higher density. The reduction of the driving voltage is also attained to decrease the cost of fabricating the driving apparatus.
Next, a preferred embodiment of the ink-jet recording head 40 will be described referring to Figs.13 to 15.
In Fig.13 showing of the overall configuration of the ink-jet recording head of Fig.4, a plurality of the piezoelectric element units 101 are, independently of each other, arranged in an array on the surface of the vibratable second wall 21. In each of the piezoelectric element units, the other ends of the first and the second piezoelectric elements not connected to the surface of the vibratable second wall 21 are joined with each other by way of the suitable connection materials 20.
The piezoelectric element units 111 are not only arranged in line on the surface of the vibratable second wall 21, but also arranged parallel to each other in an array corresponding to the nozzles of Fig.13.
An embodiment of the piezoelectric element unit 101 shown in Fig.14 includes external electrodes 85a, 85b, 86a, 86b and internal electrodes 87, 88 embedded in the unit.
Since an electric filed is not applied to the both ends, in a longitudinal direction, of the pressure chamber of the piezoelectric element units 111, the both end portions correspond to the non-vibratable parts and referred to as inactive sections 77, 78. The middle section between the inactive sections 77, 78 receiving an electric field by way of the external electrodes is referred to as an active section 79 which expands and contracts responding to the degree of a voltage applied.
Since, in the piezoelectric element units 18 of the piezoelectric element units 111, the inactive sections 77, 78 are bonded to and supported by the side walls of the pressure chamber by means of adhesive means 81, 82 shown in Fig.15, the vibration of the inactive sections 77, 78 is suppressed. However, the inactive sections 77, 78 are not necessarily bonded to the side wall of the pressure chamber.
The active section 79 is preferably joined to the vibratable second wall 21 by means of a suitable adhesive means 80.
The base end of the second piezoelectric element 19 of the piezoelectric element unit 111 is joined directly to the top surface of the side wall 15 or indirectly to the entire top surface of the side wall 15 by way of the vibratable second wall 21 by means of the uniform and continuous adhesive means 80.
The first piezoelectric element 18 may be intermittently jointed to the top surface of the vibratable second wall 21 on the pressure chamber 12 in the longitudinal direction of the pressure chamber 12.
An example of the configuration of the piezoelectric element unit 111 employable in the ink-jet recording head 40 of the first embodiment is as follows.
Interlayer distance: 40 x 10^-6 [m]
Number of layers: 10
Sectional area of active section 79: 0.242 x 10^-6 [m²]
Sectional area of inactive section 77, 78: 0.0924 x 10^-6 [m²]
Height of piezoelectric element: 0.75 x 10^-3 [m]
Height of connection material: 1.25 x 10^-3 [m]
Displacement of piezoelectric element: 6.88 X 10^-9 [m]
Width of pressure chamber: 0.32 x 10^-3 [m]
Depth of pressure chamber: 2.2 x 10^-3 [m]
Height of pressure chamber: 0.14 x 10^-3 [m]
Pitch in width direction of pressure chamber: 0.508 x 10^-3 [m]
The test already described in connection with Fig.3 was similarly conducted to the ink-jet recording head 40 of the first embodiment. The result thereof is shown in the graph of Fig.3 as a line A.
As apparent from comparison between the lines A and B in the graph, even if the plurality of the nozzles were simultaneously driven, the spray speed of the ink droplets electing from one nozzle was always substantially constant by using the ink-jet recording head 40 of the embodiment, and exhibited a sufficient stability compared with that of the conventional one.
Accordingly, the use of the ink-jet recording head of the first embodiment completely avoids the generation of the cross-talk which may occur in the conventional ink-jet recording head.
The ink-jet recording head 40 in accordance with a second embodiment of the present invention shown in Fig.5 includes the connection materials 20a, 20b, 20c for the first piezoelectric element 18a, 18b, 18c and the second piezoelectric element 19a, 19b, 19c, and the connection materials are separated elements from these piezoelectric elements.
In the ink-jet recording head 40 having the configuration, the difference of the materials between the connection materials and the piezoelectric elements can produce advantages such that, for example, a lower-cost fabrication of the ink-jet recording head can be intended by employing, as the material of the connection materials 20, a lower-cost material than that of the piezoelectric element 18, 19, and efficiency elevation can be expected by employing, as the material of the connection materials 20, a higher rigidity material.
The difference between the first and the third embodiments is that the other end of the second piezoelectric element 19a and the other end of the first piezoelectric element 18b, and the other end of the second piezoelectric element 19b and the other end of the first piezoelectric element 18c are completely separated for the first embodiment, and these are not completely separated and joined with each other by the lower rigidity material 22a, 22b.
Further, the difference between the second and the fourth embodiments is similar to that between the first and the third embodiments, that is, the two ends of the adjacent first and second piezoelectric elements are completely separated in the second embodiment, and these are not completely separated and joined with each other by the lower rigidity material in the fourth embodiment.
In the ink-jet recording head 40 in accordance with a fifth embodiment shown in Fig.8, the first piezoelectric elements 18a, 18b, 18c, and the second piezoelectric elements 19a, 19b, 19c and the connection materials 20a, 20b, 20c are connected to a thin plate member 25, and the ends of the first and the second piezoelectric elements are not completely separated and joined with each other by the lower rigidity material 24a, 24b.
In accordance with the third to the fifth embodiments of the present invention, the first and the second piezoelectric elements in each of the pressure chambers are joined with the piezoelectric elements of the other pressure chambers with the lower rigidity. Accordingly, the displacement generated in the driven piezoelectric elements in the pressure chamber is seldom transmitted to the other pressure chamber, thereby overcoming the occurrence of the cross-talk.
In these embodiments, the piezoelectric element units 111 joined with one another can be treated as a whole to improve the productivity such as the handling and the position adjustment.
Substantially no difference of the characteristics among the ink-jet recording heads of the third to the fifth embodiments is observed. However, the ink-jet recording head of the third embodiment can be fabricated most easily among the three. In the fabrication of the ink-jet recording heads of the fourth and the fifth embodiments, an additional reverse operation and an additional bonding operation are required, respectively to increase the number of the steps.
The voltage and the effect obtained by driving the first and the second piezoelectric elements in the opposite direction will be described referring to Figs.16A to 16C and Figs.17A and 17B.
Fig.16A shows a voltage waveform for driving only the first piezoelectric element, and the maximum voltage of about 28 V is required.
On the other hand, Fig.16B and Fig.16C show voltage waveforms required for driving the first piezoelectric element and that for driving the second piezoelectric element, respectively, when the first and the second piezoelectric elements are driven in the direction opposite to each other.
As apparent from Figs.16A and 16B compared with Fig.16A, the required voltage for simultaneously driving the first and the second piezoelectric elements in the opposite direction is about half that for driving only the first piezoelectric element. Accordingly, the reduction of the required voltage for driving the ink-jet recording head can be realized by the driving in the opposite direction.
Figs.17A and 17B show voltage waveforms required for driving the first piezoelectric element and that for driving the second piezoelectric element, respectively, when the first and the second piezoelectric elements are driven in the direction opposite to each other by applying about 28 V similarly to the case of Fig.16A.
In cases of Figs.17A and 17B, reduction of the voltage is not expected. However, the heights of the first and the second piezoelectric elements can be decreased to miniaturize the ink-jet recording head itself and reduce the fabrication cost.
A driving circuit shown in Fig. 18 can be used for the ink-jet recording head 40 for driving the first and the second piezoelectric elements, and a driving waveform generating circuit 121 employable in the driving circuit is shown in Fig. 19.
The driving waveform generating circuit 121 includes a constant current circuit for first-charging 210, a constant current circuit for second-charging 211, a constant current circuit for first-discharging 212, a constant current circuit for second-discharging 210, transistors Tr1 and Tr2, resistors R1, R2, R3, R4, R5 and R6, a capacitor "C" and a current amplifying circuit 214. To the driving waveform generating circuit 121 are supplied timing signals T1, T2, T3 and T4 from a timing signal generating circuit not shown.
The constant current circuit for first-charging 210 includes transistors Q1 and Q2 and a resistor R10. To a control terminal Tc of the constant current circuit for first-charging 210 is connected the collector of the transistor Tr1 by way of the resistor R2. The emitter of the transistor is connected to ground and the timing signal T1 is input to the base thereof by way of the resistor R1.
An output terminal To of the constant current circuit for first-charging 210 is connected to a first terminal of the capacitor "C". The constant current circuit for first-charging 210 is made active by the timing signal T1 having a high level (hereinafter referred to as "H level") and outputs a current having a specified dimension.
The configuration of the constant current circuit for second-charging 211 is substantially the same as that of the constant current circuit for first-charging 210, and the characteristics of the transistors Q1 and Q2 and the resistance value of the resistor R10 are the same. To a control terminal Tc of the constant current circuit for second-charging 211 is connected the collector of the transistor Tr2 by way of the resistor R4. The emitter of the transistor Tr2 is connected to ground and the timing signal T2 is input to the base thereof by way of the resistor R3.
An output terminal To of the constant current circuit for first-charging 211 is connected to the first terminal of the capacitor "C". The constant current circuit for second-charging 211 is made active by the timing signal T1 having the H level, and outputs a current having the same dimension as that of the constant current circuit for first-charging 210.
The constant current circuit for first-discharging 212 includes transistors Q3 and Q4 and a resistor R20. To a control terminal Tc of the constant current circuit for first-discharging 212 is input the timing signal T3 by way of the resistor R5.
An input terminal Ti of the constant current circuit for first-discharging 212 is connected to the first terminal of the capacitor "C". The constant current circuit for first-discharging 212 is made active by the timing signal T3 having the H level, and inputs a current from the input terminal Ti.
The constant current circuit for second-discharging 213 includes transistors Q5 and Q6 and a resistor R30. To a control terminal Tc of the constant current circuit for second-discharging 213 is input the timing signal T4 by way of the resistor R6.
An input terminal Ti of the constant current circuit for second-discharging 213 is connected to the first terminal of the capacitor "C". The constant current circuit for second-discharging 213 is made active by the timing signal T4 having the H level, and inputs a current from the input terminal Ti.
The first terminal of the capacitor "C" is connected to an input terminal of the current amplifying circuit 214 in addition to the respective output terminals To of the constant current circuit for first-charging 210 and the constant current circuit for second-charging 211 and to the respective input terminals Ti of the constant current circuit for first-discharging 212 and the constant current circuit for second-discharging 213. The charge stored in the capacitor "C" is charged by current flowing from the constant current circuit for first-charging 210 and the constant current circuit for second-charging 211 by making these circuits active. The capacitor "C" is discharged by current flowing out from the capacitor by making the constant current circuit for first-discharging 212 and the constant current circuit for second-discharging 213.
The current amplifying circuit 214 includes transistors Q7 and Q8 and amplifies current flowing through the first terminal of the capacitor "C". The signal amplified by the current amplifying circuit 214 is supplied to a waveform extracting circuit 122.
Then, an operation of the driving waveform generating circuit 121 will be exemplified.
The constant current circuit for first-charging 210 is made active by the timing signal T1 having the H-level, and outputs, from the output terminal To, a current from a power source through the resistor R10 and the transistor Q2. Thereby, the capacitor "C" is charged at a speed in accordance with a time constant of a CR circuit formed by the resistor R20 and the capacitor "C" in the constant current circuit for first-charging 210.
When the timing signal T1 becomes a low level (hereinafter referred to as "L-level"), the output of the current from the constant current circuit for first-charging 210 is stopped and the charge stored in the capacitor "C" is maintained as it is until the timing signal T3 becomes the H-level. Thereby, a first retention section is formed which maintains the level of a terminal part of a first starting section for a specified period of time, for example, a period of time "t2".
When the timing signal T3 becomes the H-level, the constant current circuit for first-charging 210 is made active, and the charge stored in the capacitor "C" flows to ground through the transistor Q4 and the resistor R20. Thereby, the capacitor "C" is charged at a speed in accordance with a time constant of a CR circuit formed by the resistor R20 and the capacitor "C" in the constant current circuit for first-discharging 212.
When the timing signal T3 becomes the L-level, the input of the current into the constant current circuit for first-discharging 212 is stopped and the charge stored in the capacitor "C" is maintained as it is until the timing signal T2 becomes the H-level.
The constant current circuit for second-charging 211 is made active by the timing signal T1 having the H-level, and outputs, from the output terminal To, a current from a power source through the resistor R10 and the transistor Q2. Thereby, the capacitor "C" is charged at a speed in accordance with a time constant of a CR circuit formed by the resistor R10 and the capacitor "C" in the constant current circuit for second-charging 211.
Since the constant current circuit for first-charging 210 and the constant current circuit for second-charging 211 are have the same configuration, the time constants of these circuits are the same. As a result, the first starting section and a second starting section have the same slope. In order to differentiate the slopes of the first starting section and the second starting section, the value of the resistor R10 in the constant current circuit for first-charging 210 and the value of the resistor R10 of the constant current circuit for second-charging 211 are differentiated.
When the timing signal T3 becomes the L-level, the input of the current into the constant current circuit for first-discharging 212 is stopped and the charge stored in the capacitor "C" is maintained as it is.
The constant current circuit for second-discharging 213 is made active by the timing signal T4 having the H-level, and the charge stored in the capacitor "C" flows to ground through the transistor Q6 and the resistor R30. Thereby, the capacitor "C" is discharged at a speed in accordance with a time constant of a CR circuit formed by the resistor R10 and the capacitor "C" in the constant current circuit for second-discharging 213.
The current flowing through the first terminal of the capacitor "C" by the charging and the discharging of the capacitor is amplified by the current amplifying circuit 214 and is output as a driving waveform.
The detailed configuration of the waveform extracting circuit 122 will be described referring to a block diagram of Fig.18. Although the waveform extracting circuit 122 usually generates signals for driving several hundreds of piezoelectric elements, the description will proceed with the circuit which generates signals for driving four piezoelectric elements 113a, 113b, 113c, 113 d for a simplification's sake.
The waveform extracting circuit 122 includes a system controlling circuit 123, shift circuits 124a, 124b, 124c, 124d, latch circuits 125a, 125b, 125c, 125d, level-conversion circuits126a, 126b, 126c, 126d and switching circuits 127a, 127b, 127c, 127d.
The system controlling circuit 123 controls the whole driving apparatus. The system controlling circuit 123 generates clock signals which are then supplied to the shift circuits 124a to 124d, and further generates latch signals which are then supplied to the latch circuits 125a to 125d. The system controlling circuit 123 supplies serial printing data externally received to the shift circuit 124a, and further supplies an initiation signal for ordering the initiation of the driving waveform, upon generation thereof, to the driving waveform generating circuit 121.
Each of the shift circuits 124a to 124d includes a D-type flip-flop of, for example, 1 bit. The shift circuit 124a stores the printing data supplied from the system controlling circuit 123 synchronized with a clock signal. The shift circuits 124b to 124d store the printing data from the previous stages of the shift circuits 124a to 124c synchronized with the clock signals. Thereby, the shift circuits 124a to 124d form a shift register of 4 bits which sequentially shifts the printing data from the system controlling circuit 123 synchronized with the clock signals. The printing data stored in each of the shift circuits 124a to 124d are supplied to the latch circuits 125a to 125d.
Each of the latch circuits 125a to 125d latches the printing data from each of the shift circuits 124a to 124d synchronized with the latch signals from the system controlling circuit 123. The printing data latched in the latch circuits 125a to 125d are supplied to each of the level-conversion circuits 126a to 126d.
The level-conversion circuits 126a to 126d formed by, for example, amplifiers convert the level of the signals from each of the latch circuits 125a to 125d and supply the converted signals to the switching circuits 127a to 127d. Thereby, the gate controlling signals having the sufficient level for controlling each of the switching circuits 127a to 127d are supplied thereto.
The switching circuits 127a to 127d are formed by gate circuits for driving and non-driving in accordance with the gate controlling signal. To the input terminals of the switching circuits 127a to 127d are input driving waveforms from the driving waveform generating circuit 121, and to the gate control terminal are input the controlling signals from the level-conversion circuits 126a to 126d. The output terminals of the switching circuits 127a to 127d are connected to the other terminals of the piezoelectric elements 113a to 113d. The signals from the switching circuits 127a to 127d are supplied, as the driving signals, to the piezoelectric elements 113a to 113d. The other terminals of the piezoelectric elements 113a to 113 d are connected to ground.
First to fifth methods of fabricating the ink-jet recording head will be described referring to Figs.20A to 25F.
In Figs.21A to 20F showing a series of steps of a second method for fabricating the ink-jet recording head of the embodiment of the present invention, the ink-jet recording head includes the plurality of the pressure chambers, connected with one another, formed by the first wall 30 having nozzles for ejecting ink droplets, vibratable second wall and the side walls in contact with the first wall 30 and the vibratable second wall.
At first, a piezoelectric material block 300 to have the first piezoelectric elements 18 and the second piezoelectric elements 19 is formed (Fig.20A), and after the piezoelectric material block 300 is reversed (Fig.20B), trenches 301 having a depth from the surface of the piezoelectric material block 300 to the connection region 20 are formed at a specified interval to leave remaining regions 302 having at least two electrode sections 76 (Fig.20C).
Then, separating trenches 303 are formed in each of the remaining regions 302 of the piezoelectric material block 300 to provide the piezoelectric element units 304 (Fig.20D). After each of the piezoelectric element units 304 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is reversed, the first and the second piezoelectric elements 18, 19 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively, to complete the ink-jet recording head 40 (Fig.20E).
In accordance with the first method shown in Figs.20A to 20E, the request of the increase and the decrease of the number of the pressure chambers can be easily responded because each of the separated piezoelectric element units 304 is bonded to the second wall 21.
In Figs.21A to 21F showing a series of steps of a second method for fabricating the ink-jet recording head of the embodiment of the present invention, at first, a piezoelectric material block 300 to have the first piezoelectric elements 18 and the second piezoelectric elements 19 is formed (Fig.21A), and after the piezoelectric material block 300 is reversed, the connection region 20 side of the piezoelectric material block 300 is temporarily fixed to a proper substrate 305 (Fig.21B).
Then, trenches 306 having a depth from the surface of the piezoelectric material block 300 to the connection region 20 are formed at a specified interval to leave remaining regions 307 having at least two electrode sections 76 (Fig.21C).
Then, disconnecting trenches 308 are formed in each of the remaining regions 307 of the piezoelectric material block 300, between the adjacent trenches 306 (Fig.21D).
Then, the thus obtained piezoelectric element units 304 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is bonded such that the first and the second piezoelectric elements 18, 19 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively (Fig.21E). Thereafter, the substrate 305 is peeled off from the connection region 20 to complete the ink-jet recording head 40 (Fig.21F).
In accordance with the second method shown in Figs.21A to 21F, the piezoelectric material block 300 temporarily fixed to the substrate 305 can be treated as an integrated member until the bonding of the piezoelectric material block 300 to the second wall 21 to elevate the productivity such as the handling and the position adjustment.
In the second method, upon the bonding of the piezoelectric unit to the second wall 21, the piezoelectric units are completely separated from one another and the cross-talk is not generated.
In Figs.22A to 22F showing a series of steps of a third method for fabricating the ink-jet recording head of the embodiment of the present invention, at first, a piezoelectric material block 300 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is formed (Fig.22A). After the piezoelectric material block 300 is reversed (Fig.22B), first trenches 301' having a depth from the first and the second piezoelectric elements 18, 19 side to the connection region 20 are formed at a specified interval to leave remaining regions 302 having at least two electrode sections 76 (Fig.22C).
Then, second trenches 309 having a depth deeper than that of the first trench 301' are formed in the remaining regions 302 between the first trenches 301' and between the electrode sections (Fig.22D).
After each of the piezoelectric material block 300 is reversed, the first and the second piezoelectric elements 18, 19 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively, to complete the ink-jet recording head 40 having the lower rigidity region 22 between the first and the second piezoelectric elements 18, 19 (Fig.22E).
In accordance with the third method shown in Figs.22A to 22E, the first and the second trenches 301', 309 can be formed by using a dicing saw and only by changing the cutting depth of the dicing saw to form the lower rigidity region 22 by adjusting these depths. The piezoelectric material block 300 can be treated as an integrated member to elevate the productivity such as the handling and the position adjustment.
In Figs.23A to 23F showing a series of steps of a fourth method for fabricating the ink-jet recording head of the embodiment of the present invention, at first, a piezoelectric material block 300 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is formed (Fig.23A). After the piezoelectric material block 300 is reversed, the connection region 20 side of the piezoelectric material block 300 is temporarily fixed to a proper substrate 305 (Fig.23B).
Then, first trenches 310 having a depth from the first and the second piezoelectric elements 18, 19 side of the piezoelectric material block 300 to the connection region 20 are formed at a specified interval to leave remaining regions 311 having at least two electrode sections 76 (Fig.23C).
Then, second trenches 312 for disconnection are formed in each of the remaining regions 311, between the adjacent trenches 310 and between the electrode sections 76, to form the piezoelectric material block 300 having the first and the second piezoelectric elements 18, 19 connected with each other by way of the lower rigidity region 22 without dividing the piezoelectric material block 300 (Fig.23D).
After each of the piezoelectric element units 304 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is reversed, the first and the second piezoelectric elements 18, 19 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively (Fig.23E). Then, the substrate 305 is peeled off from the connection region 20 to complete the ink-jet recording head 40 having the lower rigidity region between the first and the second piezoelectric elements 18, 19 (Fig.23F).
In accordance with the fourth method shown in Figs.23A to 23F, even if the rigidity is reduced when the piezoelectric material block is reinforced for high density integration, the piezoelectric material block 300 can be treated as an integrated member to elevate the productivity such as the handling and the position adjustment, by temporarily fixing the piezoelectric material block 300 to the substrate.
In Figs.24A to 24E showing a series of steps of a fifth method for fabricating the ink-jet recording head of the embodiment of the present invention, at first, a piezoelectric material block 300 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is formed (Fig.24A). After the piezoelectric material block 300 is reversed (Fig.24B), first trenches 313 having a depth from the first and the second piezoelectric elements 18, 19 side of the piezoelectric material block 300 to the connection region 20 are formed at a specified interval between the electrode sections 76 (Fig.24C).
After the first and the second piezoelectric elements 18, 19 of the piezoelectric material block 300 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively (Fig.24D), second trenches 314 are formed at every other position on the connection region 20 corresponding to the first trenches 313 to form the connection region made of the lower rigidity material 22 to complete the ink-jet recording head 40 (Fig.24E).
In accordance with the fifth method shown in Figs.24A to 24E, the process substantially the same as the conventional process can be utilized until the comb-like piezoelectric material block is bonded to the vibratable second wall 21, and only a step of forming the trenches for bonding the piezoelectric element units by the lower rigidity material is added after the bonding of the piezoelectric material block to the vibratable second wall 21. Accordingly, the ink-jet recording head 40 can be fabricated without large modification of the conventional method.
In Figs.25A to 25F showing a series of steps of a sixth method for fabricating the ink-jet recording head of the embodiment of the present invention, at first, a piezoelectric material block 300 including the first and the second piezoelectric elements 18, 19 and the connection region 20 is formed (Fig.25A). After the piezoelectric material block 300 is reversed, the connection region 20 side of the piezoelectric material block 300 is temporarily fixed to the substrate 305 (Fig.25B).
Then, first trenches 315 having a depth from the first and the second piezoelectric elements 18, 19 side of the piezoelectric material block 300 to the connection region 20 are formed (Fig.25C).
Then, the piezoelectric material block 300 is reversed with the substrate 305, and the first and the second piezoelectric elements 18, 19 are bonded to the vibratable part of the vibratable second wall 21 and to the non-vibratable part of the vibratable second wall 21 or the side wall 15, respectively (Fig.25D).
After the substrate 305 is peeled off from the connection region 20 (Fig.25E), second trenches 316 are formed at every other position on the connection region 20 corresponding to the first trenches 315 to form the connection region made of the lower rigidity material 22 to complete the ink-jet recording head (Fig.25F).
In accordance with the sixth method shown in Figs.25A to 25F, the piezoelectric material block 300 temporarily fixed to the substrate 305 can be treated as an integrated member to elevate the productivity such as the handling and the position adjustment, even if the piezoelectric material block is reinforced for high density integration
In the second, the fourth and the sixth methods described above, the temporary fixation and the release between the piezoelectric elements and the substrate can be performed by using an adhesive and foamed release sheet which loses the adhesion and is released when heated to a higher temperature (about 100 °C).
In the above methods, the step of forming the electrode sections is not especially restricted. For example, a step of screen-printing silver paste on a position on the piezoelectric material block where an external electrode is to be formed and sintering the silver paste may be used. Another step of sputtering aluminum or gold on the position on the piezoelectric material block where an external electrode is to be formed by using a metal mask may be used.
In Fig. 26 showing a sixth embodiment of the present invention, only a part of an ink-jet recording head having a significant number of the same configurations extending in a horizontal direction is shown. Although, in Fig.26, a piezoelectric material block 401 and an ink flowing unit 402 are separated, these units are, in reality, joined with each other in a positional relationship described later. A vibration plate 403 of the ink flowing unit 402 is partially broken for illustrating the interior thereof.
The ink-jet recording head in Fig.26 includes nozzles 404 for ejecting ink droplets into the ink flowing unit 402, and pressure chambers 405 arranged in a row in correspondence to each of the nozzles 404, supply ports 406 for supplying the ink to each of the pressure chambers 405, an ink pool 407 for the ink supply connected to the respective pressure chambers 405 by way of each of the supply ports and to an ink tank (not shown), and a plate made of an elastic material which covers the surface of the ink flowing unit 402 opposite to the surface having the nozzle 404, for example, the vibration plate 403 made of stainless steel.
The piezoelectric material block 401 includes driving columns 408 for generating a pressure in correspondence with each of the pressure chambers 405 and fixing columns 409, which are non-driven piezoelectric elements, for fixing the piezoelectric material block 401 to the ink flowing unit 402. The driving columns 408 and the fixing columns 409 alternately arranged in a row are integrated by way of a base section 410.
As shown in Fig.27, the fixing columns 409 alternately arranged with the driving columns 408 are joined to side walls 411 of the pressure chambers 405 in correspondence with the driving columns 408 by way of the vibration plate 403. The driving columns 408 are joined to the central parts between the adjacent side walls of the corresponding pressure chambers 405. The driving columns 408 and the fixing columns 409 are mainly made of a piezoelectric material such as lead zirconate and titanate-based ceramics. A plurality of flat internal electrodes 412a, 412b, 412c, 412d arranged at a specified interval and parallel to the vibration plate 403 are disposed in the driving columns 408 and the fixing columns 409.
Each of the piezoelectric elements and driving columns block 401 includes a pair of side surfaces 413a, 413b opposing to each other and extending nearly perpendicular to the internal electrodes and perpendicular to the row direction. The internal electrodes 412a, 412c are disposed such that the ends thereof are exposed to one of the side surfaces 413a different from the other side surfaces 413b to which the adjacent internal electrodes 412b, 412d are exposed. Each of the driving columns 408 and the fixing columns 409 includes a pair of external electrodes 414, 415 on the opposing side surfaces 413a, 413b, respectively. Each of the external electrodes 414, 415 is alternately connected to the internal electrodes in the corresponding driving columns 408 and fixing columns 409. The external electrodes 414, 415 extend to a top surface 416 opposite to the surface where the driving columns 408 and the fixing columns 409 are mounted.
The fixing column 409 functioning as a non-driving piezoelectric element for fixation is polarized, similarly to the driving column 408, by applying a specified polarization voltage between the corresponding external electrodes 414, 415 for a specified period of time.
When a stress is applied to the driving column 409 obtained by polarizing the piezoelectric element, a reverse electric field is generated which may prevent the displacement thereof by the effect of the piezoelectric field depending on the polarization direction. If, accordingly, two electrodes are present opposing to the direction of the electric field, a difference of voltage is generated between the electrodes. Since, however, the electrodes are electrically isolated in the embodiment, the voltage difference is maintained. Accordingly, the reverse electric field is maintained to prevent the displacement thereof by the maintained stress, that is, reduces distortion due to the stress.
The effect of reducing the distortion is again described using piezoelectric basic equations showing relations between a stress and an electric field and between a stress and an electric displacement.
The piezoelectric basic equation can be expressed as follows, wherein "S" is a distortion, "T" is a stress, "D" is an electrical displacement obtained by diving an amount of charges by an area, " s" is a coefficient of elasticity when having no influence due to the electric field, that is, not polarized or depolarized but short-circuiting an electrode, "E" is an electric filed, "d" is a piezoelectric distortion constant, and " ε " is a dielectric constant. S = s x T + d x E D = d x T + ε x E
When the electrode is open to make the electric displacement D =0, the coefficient of elasticity polarized and electrically isolated state "s"' is obtained as follows by deleting the electric filed "E" from the above two equations. s' = S/T = s - d2 / ε
When the coefficient of elasticity "s"' having no influence due to the electric field of, for example, the lead zirconate and titanate-based ceramics is s=18.1 x 10^-12 (m² /N), the piezoelectric distortion constant "d"= 635 x 10^-12 (m/V) and the dielectric constant " ε " = 48.2 x 10^-9 (F/ m), the coefficient of elasticity ("s"') under the polarized and electrically isolated state is s' = 9.73 x 10^-12 (m²/N). That is, the obtained coefficient of elasticity is 0.54 time that under the non-polarized state or the polarized and short-circuited state, and the stiffness is 1.94 times.
Accordingly, in accordance with the configuration of the embodiment, the displacement of the driving column 408 driven is suppressed by the fixing column 409, and the displacement is hardly transmitted to the non-driven pressure chamber by way of the base section 410 and the driving column non-driven to significantly reduce a cross-talk.
The displacement of the driving column 408 driven is efficiently transmitted to the pressure chamber 405 even if a nearby driving column integrated by way of the base section 410 is driven. As a result, the driving voltage can be reduced so as to decrease a cost of fabricating the driving circuit.
Then, a method for fabricating the ink-jet recording head will be described.
As shown in Fig.29, the internal electrode 412a is formed on the top surface of a piezoelectric material sheet 417 such that one of the both ends of the internal electrode 412a is exposed to one side surface 413a, and the other end is not exposed to the other side surface, and another piezoelectric material sheet 417 is placed thereon. Another internal electrode 412b having the opposite orientation to the underlying internal electrode 412a is disposed on the piezoelectric material sheet 417. Then, after a further piezoelectric material sheet 417 is placed thereon, a further internal electrode 412c having the opposite orientation to the underlying internal electrode 412b is disposed on the piezoelectric material sheet 417. The repetition of the layering can form a stacked member of the piezoelectric material sheet 417 having the ends alternately exposed to one and the other of the both side surfaces.
Then, a piezoelectric material block 408 to become the base section 410 is disposed on the stacked member, as shown in Fig.30, and sintered.
Next, silver alloy sheets are screen-printed on the both side surfaces and the top surface 416 thereof ands sintered, thereby connecting the alloy sheets with the exposed ands of the internal electrodes to form the external electrodes 414, 415 extending to the top surface 416. The external electrodes 414, 415 are symmetrically disposed as shown in Fig.31.
Then, trenches 419 between the adjacent external electrodes are formed such that the stacked portions of the piezoelectric material sheets 417 having the internal electrodes are separated to form the driving columns 408 to be joined with the vibration plate 403 and the fixing columns 409 to be joined with the vibration plate 403 on the side walls in each of the pressure chambers 405 of the ink flowing unit 402.
The stacked piezoelectric material is subjected to the position adjustment with the ink flowing unit 402 and bonded with each other such that the driving column 408 overlies the pressure chamber 405 and the fixing column 409 overlies the side wall 411.
Then, as shown in Fig.33, the external electrodes 414, 415 are in contact with probes 420, and a specified voltage is applied to a place between the corresponding external electrodes for a specified period of time by means of a polarization voltage applying circuit 421, to sufficiently polarize the driving column 408 and the fixing column 409 made of the piezoelectric material.
Since the polarization treatment before the trench formation weakens the polarization state due to heat generation during the trench formation, the polarization treatment is desirably conducted after the trench formation.
When the heat is applied during the bonding between the stacked piezoelectric material member and the ink flowing unit 402, the polarization is preferably conducted after the bonding.
An FPC for applying a driving signal to the driving column 408 is bonded to the piezoelectric material block 401. Electrodes pads are placed on positions of the FPC corresponding to the external electrodes 414, 415 of the driving column 408, and the electrodes corresponding to the FPC fixed on the top surface 416 of the base section 410 and to the piezoelectric material block 401 are bonded to each other. However, no electrode pads are disposed on the FPC corresponding to the external electrodes 414, 415 of the fixing column 409, and the the external electrodes 414, 415 of the fixing column 409 are not connected with the driving circuit to be kept electrically isolated.
A seventh embodiment of the present invention shown in Fig.34 is different from the sixth embodiment in that an external electrode for depolarizing the base section 422 is disposed on a region excluding the external electrodes 414, 415. An external electrode for depolarizing the base section 423 may be disposed which is connected with either of the pair of the external electrodes 414, 415 of the fixing column 409 over the trench 419. The external electrode for depolarizing the base section 422 is formed as shown in Fig.34 such that the electrode 422 covers the region excluding the external electrodes 414, 415 and is not connected with the external electrodes 414, 415. The external electrode for depolarizing the base section 423 having a similar shape to that of the external electrode for depolarizing the base section 422 shown by dotted lines in Fig.35 includes an end exposed to a portion where the external electrode 424 corresponding to at least one of the fixing columns 409 among the external electrodes on the side surface 413a of the piezoelectric material block, and connected with the external electrode 424.
In the depolarization treatment of the present embodiment, similarly to the sixth embodiment, after a specified voltage is applied to places between the external electrodes 414, 424 of the driving column 408 and the fixing column 409 and the corresponding external electrodes 415 for a specified period of time, a voltage is applied between the external electrode for depolarizing the base section 422 and the external electrode 424 connected to the external electrode for depolarizing the base section 423 for depolarizing the base section 410. In case that the interval between the external electrode for depolarizing the base section 422 and the external electrode for depolarizing the base section 423 is broader than that between the internal electrodes, a higher voltage is desirably applied for obtaining a specified electric field strength depending on the interval.
In an eighth embodiment of the present invention shown in Fig.36, a plurality of piezoelectric elements 430 are fixed to the ink flowing unit 402 separated from one another. Each of the piezoelectric elements 430 corresponds to each of the pressure chambers 405, and the piezoelectric elements 430 are separated from one another. As shown in Fig.37, a driving column 431 is connected with the vibration plate 403 on the pressure chamber 405, and fixing columns 432, 433 are connected to the vibration plate 403 at positions where the vibration plate 403 is fixed to a substrate member constituting the pressure chamber 405 at the both ends of the pressure chamber 405. In the present embodiment, in place of the fixing column between the pressure chambers, the fixing columns, together with the driving column, fixed to the base section are disposed on the both ends of the pressure chamber perpendicular to the row direction thereof.
The piezoelectric element 430 includes the driving column 431, the fixing columns 432, 433 disposed on the both sides thereof, and a base section for integrating these columns. As shown in Fig.38, the piezoelectric element 430 further includes the plurality of the internal electrodes 412a, 412b, 413c, 413d formed in the driving column 431 parallel to one another, and the internal electrodes 412a, 412b, 413c, 413d are alternately exposed to inner surfaces of gaps 435, 436 for separating the fixing columns 432, 433 at the both sides of the driving column 431. Intermediate electrodes are formed on the entire inner surface of the gaps 435, 436 by means of plating or sputtering for connecting the internal electrodes exposed to the gaps 435, 436. External electrodes 439, 440 connected to the internal electrodes of the fixing column are formed on the surface of the fixing columns 432, 433 opposite to the driving column. Each of the external electrodes 439, 440 extends to a top surface of a base section 434 opposite to a place where the piezoelectric element 430 is bonded to the vibration plate 403. When a voltage is applied to the external electrodes 439, 440, the voltage is applied to the internal electrodes of the driving column 431 by way of the internal electrodes of the fixing columns 432, 433 and the intermediate electrodes.
An external electrode for depolarizing the base section 441 is disposed on a region excluding the external electrode on the top surface of the base section 434, and an internal electrode for depolarizing the base section 442 connected with one of the pair of the external electrodes 439, 440 overlies the gaps 435, 436.
Then, a method for fabricating the ink-jet recording head will be exemplified.
As shown in Fig.38, a stacked piezoelectric material 443 is formed by stacking piezoelectric material sheets 445 having an electrode 444 thereon. The electrodes of the piezoelectric material sheets are overlapped in the central portion between the pair of the side surfaces, and the electrodes are overlapped near the side surface in an every other fashion disposing the piezoelectric material sheet between the adjacent electrodes. A piezoelectric material sheet 447 having an electrode 446 of a maximum dimension is layered on the stacked piezoelectric material sheets such that one end surface of the electrode is exposed and the other end surface is not exposed. A piezoelectric material block 448 having no electrodes is layered thereon, and these are sintered and integrated.
Then, as shown in Fig.39, the gaps 435, 436 are formed in the alternately overlapped portions of the electrodes having the two piezoelectric material sheet layers therebetween by using a dicing saw or a wiring saw. The gaps 435, 436 separated from an active region 449, where the internal electrodes are overlapped at a specified width in the central portion, by a specified distance in the width direction are formed in a uniform depth extending the overall block. The depth of the gap is formed not to reach to the uppermost electrode 446.
Then, as shown in Fig.40, intermediate electrodes 437, 438, external electrodes 439, 440 and an external electrode for depolarizing the base section 441' are formed on the inner surfaces of the gaps 435, 436, on the both surfaces of the stacked piezoelectric material 443, and on a region on the top surface of the stacked piezoelectric material 443 excluding the external electrodes 439, 440, respectively, by means of plating, sputtering or screen-printing, and bonded to the ink flowing unit 402. At this stage, a masking member such as resist is formed on the regions where the internal electrode and the external electrode are not formed for masking thereof, and the masking member may be peeled off after the electrode film is formed.
The stacked piezoelectric material 443 is subjected to the position adjustment with the ink flowing unit 402 and bonded with each other such that the central portions of the pressure chambers 405 perpendicular to the row direction thereof is matched with the intermediate position between the gaps 435, 436, and the central portions of the pressure chambers 405 in the row direction thereof is matched with the external electrodes 439, 440. After the bonding, the stacked piezoelectric material 443 is divided to form the piezoelectric elements 430.
In the polarizing treatment similarly to the seventh embodiment, after the division and the separation of the stacked piezoelectric material 443 and application of a specified voltage between the external electrodes 439, 440 for a specified period of time, a voltage is applied between the external electrode for depolarizing the base section 441 of the stacked piezoelectric material and the external electrode 439 connected to the internal electrode for depolarizing the base section 442 for depolarizing the. base section 434. In case that the interval between the external electrode for depolarizing the base section 441 and the internal electrode for depolarizing the base section 442 is broader than that between the internal electrodes of the driving column 431, a higher voltage is desirably applied for obtaining a specified electric field strength depending on the interval. A polarization voltage applying circuit employable in the present embodiment includes a further probe in contact with the external electrode for depolarizing the base section 441' of the separated piezoelectric elements in addition to those employed in the sixth embodiment, and polarizes the base section 434 by applying a voltage between the external electrode for depolarizing the base section 441' and the external electrode 439.
In the description of the present embodiment, the piezoelectric element 430 includes the external electrode for depolarizing the base section 441' formed on the region of the top surface of the base section 434 excluding the external electrode, and the internal electrode for depolarizing the base section 442 connected with one of the pair of the external electrodes 439, 440 overlying the gaps 435, 436. However, the piezoelectric element 430 may include, without the internal electrode for depolarizing the base section 442, the external electrode for depolarizing the base section 441' as a pattern similar to that of the uppermost internal electrode among the plurality of the internal electrodes formed in the driving column 431 at a constant interval between the adjacent electrodes on the region excluding the external electrode on the top surface of the base section 434. In this case, the layering of the piezoelectric material sheet 47 having the electrode 446 thereon is unnecessary, and the piezoelectric material block 448 having no electrodes is layered thereon. Accordingly, the number of the fabrication steps is reduced to facilitate the fabrication.
Although the intermediate electrodes 437, 438 and the external electrodes 439, 440 are connected by way of the plurality of the internal electrodes in the above description, the connection may be performed by employing at least one internal electrode.
In a ninth embodiment of the present invention shown in Fig.41, no internal electrodes are disposed in fixing columns 451, 452 of a piezoelectric element 450. External electrodes for driving 453, 454 are formed on a base section 455, and two internal electrodes 456, 457 having both end surfaces exposed to the gap 435 or the gap 436 and to the top surface of the base section 455 are formed in the base section 455. Further, the present embodiment is different from the eighth embodiment in that external electrodes for depolarizing the fixing columns 451, 452 are formed on both side surfaces of the piezoelectric element 430. In the present embodiment, no internal electrodes are formed overlying the gaps 435, 436.
As shown in Fig.41, the plurality of the piezoelectric elements 450 are separated and fixed on the ink flowing unit 402. Each of the piezoelectric elements 450 corresponds to each of the pressure chambers 405, and the piezoelectric elements 450 are separated from one another. An external electrode for depolarizing the base section 460 is formed on the region excluding the external electrodes 453, 454 on the top surface of the base region 455.
In the piezoelectric elements 450 shown in Fig.42 similarly to the eighth embodiment, the fixing columns 451, 452 bonded by the driving column 431 and the base section 455 in the direction perpendicular to the row direction thereof are fixed to the vibration plate 403 at positions where a substrate member 462 constitutes the pressure chamber 405 at the both ends perpendicular to the row direction thereof. The piezoelectric elements 450 for driving the pressure chambers 405 are separated. In the present embodiment similarly to the eighth embodiment, in place of the fixing column between the pressure chambers, the fixing columns 451, 452, together with the driving column 431, fixed to the base section 455 are disposed on the both ends of the pressure chamber perpendicular to the row direction thereof.
In the piezoelectric element 450 of the present embodiment similarly to the eighth embodiment, the plurality of the internal electrodes 412a, 412b formed in the driving column 431 parallel to one another at a constant interval are alternately exposed to inner surfaces of the gaps 435, 436 separating the fixing columns 451, 452 at the both sides of the driving column 431. In the present embodiment, the two internal electrodes 456, 457 having both end surfaces exposed to the gap 435 or the gap 436 and to the top surface of the base section 455 are formed in the base section 455. The intermediate electrodes 437, 438 are formed on the nearly entire inner surfaces of the gaps 435, 436 by plating or sputtering, and connect the internal electrodes exposed to the gaps.
In the present embodiment, the external electrodes for driving 453, 454 connected to the internal electrodes 456, 457 are formed only on the top surface of the base section 455 opposite to the driving column 431 and the fixing columns 451, 452 for integrally bonding the driving column 431 and the fixing columns 451, 452. When a voltage is applied to the external electrodes 453, 454, the voltage is applied to the internal electrodes 412a, 412b by way of the internal electrodes 456, 457 of the base section 455 and the intermediate electrodes 437, 438.
The piezoelectric element 450 further includes an external electrode for depolarizing the base section 459 formed in a region between the external electrodes 453, 454 of the top surface of the base section 455. In the present embodiment, by applying a voltage between the uppermost electrode 461 among the internal electrodes formed in the driving column 431 and the external electrode for depolarizing the base section 459, the part of the base section 455 between these electrodes can be polarized.
External electrodes for depolarizing fixing column 458, 459 are formed on the side surfaces of the piezoelectric element 450. These electrodes are opposed to the intermediate electrodes 437, 438 formed in the gaps and the external electrodes 456, 457 connected thereto. Accordingly, by applying a voltage between the external electrodes 453, 454 for driving connected to the internal electrodes 456, 457 and the external electrodes for depolarizing fixing column 458, 459, an electric field can be generated at overall fixing columns 451, 452 and the both ends of the base section 455.
Then, a method for fabricating the ink-jet recording head of the present embodiment will be described.
As shown in Fig.43, a stacked piezoelectric material 463 is prepared by stacking piezoelectric material sheet 465 having an electrode 464 on the top surface thereof. The electrodes 464 of the piezoelectric material sheet are overlapped the central portion by a specified width between the pair of the side surfaces, and the electrodes are alternately shifted in a horizontal direction, and no electrodes are formed near the side surfaces.
Internal electrodes 467, 468 are formed on the overall side surfaces of a piezoelectric material block 466 having a width wider than the overlapped with of the electrodes 464 and narrower than the maximum alternate shifting width, and a pair of piezoelectric material blocks 469 are attached to the side surfaces thereof. These are sintered for integration.
Then, as shown in Fig.44, the gaps 435, 436 are formed in the stacked portions of the piezoelectric material sheet 465 by using a dicing saw or a wiring saw. The gaps 435, 436 separated from an active region 449, where the internal electrodes are overlapped at a specified width in the central portion, by a specified distance in the width direction are formed in a uniform depth extending the overall block. In the present embodiment, the depth of the gap is controlled such that the end surfaces of the electrodes are exposed to the inner surfaces of the gaps, and the gap is formed at a depth smaller than that from the bottom surface of the block to the uppermost electrode among the electrodes 464.
Then, as shown in Fig.45, the intermediate electrodes 437, 438, external electrodes 453, 454 and an external electrode for depolarizing the base section 460 are formed on the inner surfaces of the gaps 435, 436, on the top surface of the stacked piezoelectric material at a specified interval, and on the top surface between the external electrodes 453, 454, respectively, by means of plating, sputtering or screen-printing such that the external electrodes 453, 454 are connected to the internal electrodes 456, 457 , and bonded to the ink flowing unit 402. At this stage, a masking member such as resist is formed on the regions where the internal electrode and the external electrode are not formed for masking thereof, and the masking member may be peeled off after the electrode film is formed.
The position adjustment of the stacked piezoelectric material 463 is conducted such that the central portions of the pressure chambers 405 in the row direction thereof and the direction perpendicular thereto agree with the intermediate portions of the gaps 435, 436 and the intermediate portions of the pressure chambers 405 in the column direction agree with the external electrodes 453, 454. The pressure chambers are fixed to the vibration plate 403. After the bonding, the stacked piezoelectric material 463 is divided to form a plurality of the piezoelectric elements.
In the depolarization treatment of the present embodiment, similarly to the eighth embodiment, after the stacked piezoelectric material is divided for separation and a specified voltage is applied between the external electrodes 453, 454 for a specified period of time, a voltage is applied between the external electrode for depolarizing the base section 460 of the piezoelectric element 450 and the external electrode connected to the uppermost internal electrode 461 nearest to the external electrode for depolarizing the base section 460 among the external electrodes of the driving column 431, thereby polarizing the central portion of the base section 455. In case that the interval between the external electrode for depolarizing the base section 460 and the uppermost internal electrode 461 is broader than that between the internal electrodes of the driving column 431, a higher voltage is desirably applied for obtaining a specified electric field strength depending on the interval.
In the present embodiment, by applying a voltage between the external electrodes 453, 454 of the piezoelectric element 450 and the external electrodes for depolarizing fixing column 458, 459, the overall fixing columns 451, 452 and the both ends of the base section 455 are polarized. In case that the interval between the external electrodes 153, 154 and the external electrodes for depolarizing fixing column 458, 459 is broader than that between the internal electrodes of the driving column 431, a higher voltage is desirably applied for obtaining a specified electric field strength depending on the interval.
In the present embodiment, the external electrode for depolarizing the base section 460 is mounted. However, the electrode may not be used and the base section may not be polarized.
In place of the absence of the external electrode for depolarizing the base section 460, the presence of the external electrode for depolarizing the base section 460 and the absence of the external electrodes for depolarizing fixing column 458, 459 are possible. In these cases, the stiffness is inferior to that of the ninth embodiment, however the number of steps is reduced to facilitate the fabrication.
Although the direction of the internal electrodes in the driving column and the fixing column is parallel to the vibration plate in the above embodiments, the direction may be perpendicular to the vibration plate.
Although no internal electrodes are disposed between the pair of the electrodes which polarize the fixing column and the base section, internal electrodes alternately connected to one electrode similarly to the interior of the driving column may be disposed.
Although the driving columns and the fixing columns are fixed to the single base section in the sixth and the seventh embodiments, these may be separately fixed to a plurality of the base sections. Although the piezoelectric elements are divided such that each piezoelectric element belongs to each pressure chamber in the eighth and the ninth embodiments, the piezoelectric elements corresponding to the plurality of the pressure chambers my be connected to the base section.
Since the above embodiments are described only for examples, the present invention is not limited to the above embodiments and various modifications or alternations can be easily made therefrom by those skilled in the art without departing from the scope of the present invention.

Claims

An ink-jet recording head (40) comprising:

a plurality of pressure chambers (12a, 12b, 12c) disposed in an array and each having a first wall (30) having a nozzle (11a, 11b, 11c) for ejecting ink droplets, a second wall (21) having a vibratable part for each pressure chamber (12a, 12b, 12c), and a plurality of side walls (15a, 15b, 15c) in contact with the first and the second walls (30, 21), each said pressure chamber (12a, 12b, 12c) receiving ink supplied through an ink supply port (32); and

a first piezoelectric element (18a, 18b, 18c) disposed for each of the pressure chambers (12a, 12b, 12c) and having a first end disposed on the vibratable part, and a second end;

a second piezoelectric element (19a, 19b, 19c) disposed for each of the pressure chambers (12a, 12b, 12c) and having a first end fixed to the side wall (15a, 15b, 15c), and a second end;

characterized in that:
both the second ends of the first and the second piezoelectric elements (18, 19) for each pressure chamber (12a, 12b, 12c) are integrated to form a piezoelectric pair, and adjacent piezoelectric pairs are separated by a gap.
The ink-jet recording head (40) as defined in claim 1, wherein the first piezoelectric element (18a, 18b, 18c) and the second piezoelectric element (19a, 19b, 19c) are made of substantially the same material.
The inkjet recording head (40) as defined in claim 1 or 2, wherein the second wall (21) includes a trench (100).
The ink-jet recording head (40) as defined in any of claims 1 to 3, wherein an overall surface of the second piezoelectric element (19a, 19b, 19c) is connected, directly or by way of the second wall (21), to a top surface of the side wall (15a, 15b, 15c) in a longitudinal direction of the pressure chamber (12a, 12b, 12c), and the first piezoelectric element (18a, 18b, 18c) is intermittently connected to a top surface of the vibratable second wall (21) of the pressure chamber (12a, 12b, 12c) in a longitudinal direction of the pressure chamber (12a, 12b, 12c).
The ink-jet recording head (40) as defined in any of claims 1 to 4, wherein the first piezoelectric element (18a, 18b, 18c) is driven during the ink droplets ejection so that the vibratable part of the second wall (21) is displaced toward the inner surface of the pressure chamber (12a, 12b, 12c).
The ink-jet recording head (40) as defined in any of claims 1 to 5, wherein the first piezoelectric element (18a, 18b, 18c) is driven in a polarized state.
The ink-jet recording head (40) as defined in any of claims 1 to 6, wherein the second piezoelectric element (19a, 19b, 19c) is polarized and electrically isolated during the ink droplets ejection.
The ink-jet recording head (40) as defined in any of claims 1 to 7, further comprising a means for generating an electric signal for driving the first and the second piezoelectric element (18, 19) in an opposite direction.
An ink-jet recording head (40) comprising:

a plurality of pressure chambers (12a, 12b, 12c) disposed in an array and each having a first wall (30) having a nozzle (11a, 11b, 11c) for ejecting ink droplets, a second wall (21) having a vibratable part for each pressure chamber (12a, 12b, 12c), and a plurality of side walls (15a, 15b, 15c) in contact with the first and the second walls (30, 21), each said pressure chamber (12a, 12b, 12c) receiving ink supplied through an ink supply port (32);

a first piezoelectric element (18a, 18b, 18c) having a first end disposed on the vibratable part, and a second end for each of the pressure chambers (12a, 12b, 12c); and

a second piezoelectric element (19a, 19b, 19c) having a first end fixed to the side wall (15a, 15b, 15c) of each of the pressure chambers (12a, 12b, 12c), and a second end;

characterized in that:
the second ends of the first and the second piezoelectric elements (18, 19) for the respective pressure chambers (12a, 12b, 12c) are coupled together by an elastic member (22a, 22b).
The ink-jet recording head (40) as defined in claim 9, wherein the elastic member (22a, 22b) is formed by one means selected from a plate having a trench, a thin film and a lower rigidity material.
An ink-jet recording head (40) characterized by comprising:

a plurality of pressure chambers (12a, 12b, 12c) disposed in an array and each having a first wall 30) having a nozzle (lla, 11b, 11c) for ejecting ink droplets, a second wall (21) having a vibratable part and a non-vibratable part for each pressure chamber (12a, 12b, 12c), and a plurality of side walls (15a, 15b, 15c) in contact with the first and the second walls (30, 21) of the pressure chamber (12a, 12b, 12c) receiving ink supplied through an ink supply port (32);

a plurality of first piezoelectric elements (18a, 18b, 18c) disposed on the vibratable part of the second wall (21); and

a plurality of second piezoelectric elements (19a, 19b, 19c) disposed on the non-vibratable part of the second wall (21) or overlying the side wall (15a, 15b, 15c).
The ink-jet recording head (40) as defined in claim 11, wherein the first and the second piezoelectric elements (18, 19) are formed by making trenches (100) in a piezoelectric member.
A method for ejecting ink droplets characterized by comprising the steps of:
driving a first piezoelectric element (18a, 18b, 18c) and a second piezoelectric element (19a, 19b, 19c) in an opposite direction in response to a specified electric signal in an ink-jet recording head (40) including a plurality of pressure chambers (12a, 12b, 12c), disposed in an array, formed by a first wall (30) having a nozzle (11a, 11b, 11c) for ejecting the ink droplets, a second wall (21) having a vibratable part for each pressure chamber (12a, 12b, 12c), and a plurality of side walls (15a, 15b, 15c) in contact with the first and the second walls (30, 21), each said pressure chamber (12a, 12b, 12c) receiving ink supplied through an ink supply port (32).
The method as defined in claim 13, wherein the first piezoelectric element (18a, 18b, 18c) is driven during the ink droplets ejection so that the vibratable part of the second wall (21) is displaced toward the inner surface of the pressure chamber (12a, 12b, 12c).
The method as defined in claim 13 or 14, wherein the first piezoelectric element (18a, 18b, 18c) s driven in a polarized state.
The method as defined in any of claims 13 to 15, wherein the second piezoelectric element (19a, 19b, 19c) is polarized and electrically isolated.
The method as defined in any of claims 13 to 16, wherein the end of the first piezoelectric element (18a, 18b, 18c) opposite to that in contact with the vibratable part and the end of the second piezoelectric element (19a, 19b, 19c) opposite to that in contact with the non-vibratable part or part of the side wall (15a, 15b, 15c) in each of the pressure chambers (12a, 12b, 12c) are connected with each other.
The method as defined in any of claims 13 to 17, wherein the pair of the first and the second piezoelectric elements (18, 19) in the pressure chamber (12a, 12b, 12c) are independent of the other pairs in the other pressure chambers.
A method for fabricating an ink-jet recording head (40) including:

a plurality of pressure chambers (12a, 12b, 12c) disposed in an array and each having a first wall (30) having a nozzle (11a, 11b, 11c) for ejecting ink droplets, a second wall (21) having a vibratable part for each pressure chamber (12a, 12b, 12c), and a plurality of side walls (15a, 15b, 15c) in contact with the first and the second walls (30, 21), each pressure chamber (12a, 12b, 12c) receiving ink supplied through an ink supply port (32); and

a plurality of piezoelectric pairs having a first piezoelectric element (18a, 18b, 18c) disposed on the vibratable part of the second wall (21) for each pressure chamber (12a, 12b, 12c) and a plurality of second piezoelectric elements (19a, 19b, 19c) fixed to the second wall (21), and having an end opposite to the second wall (21) or the side wall (15a, 15b, 15c) and connected to an end of the first piezoelectric element (18a, 18b, 18c) opposite to the second wall (21);

characterized by comprising the steps of:

forming a piezoelectric material block (300) including a piezoelectric element section and a connection region;

forming first trenches (301') having a depth from the first and the second piezoelectric elements side to a connection region of a piezoelectric material block (300) for separately forming the piezoelectric pair; and

bonding the first and the second piezoelectric elements (18, 19) to the second wall (21) or the side wall (15a, 15b, 15c).
The method as defined in claim 19 further comprising the steps of:

temporarily fixing the connection region side of the piezoelectric material block (300) to a substrate (305) between the piezoelectric material block forming step and the first trench forming step; and

peeling off the substrate (305) from the piezoelectric material block (300).
The method as defined in claim 19 or 20 further comprising the steps of:
forming second trenches (309) having a depth deeper than that of the first trench (301') between the first trenches (301').
The method as defined in claim 19 further comprising the steps of:

temporarily fixing the connection region side of the piezoelectric material block (300) to a substrate (305) between the piezoelectric material block forming step and the first trench forming step;

forming second trenches (309) having a depth deeper than that of the first trench (301') between the first trenches; and

peeling off the substrate (305) from the piezoelectric material block (300).
The method as defined in any of claims 19 to 22 further comprising the steps of:
forming additional trenches, in every other fashion, in the thinner portions of the connection region.
The method as defined in claim 19 further comprising the steps of:

temporarily fixing the connection region side of the piezoelectric material block (300) to a substrate (305) between the piezoelectric material block forming step and the first trench forming step;

peeling off the substrate (305) from the piezoelectric material block (300); and

forming additional trenches, in every other fashion, in the thinner portions of the connection region.
The method as defined in any of claims 19 to 24, wherein the piezoelectric material block (300) is integrally formed by the piezoelectric element section and the connection region.
The method as defined in any of claims 19 to 24, wherein the piezoelectric material block (300) is formed by bonding the piezoelectric element section and the connection region by using an adhesive.
The method as defined in any of claims 19 to 24, wherein the piezoelectric material block (300) is formed by an integral member including the piezoelectric element section and the connection region, and a thin plate member bonded thereto by using an adhesive.
An ink-jet recording head comprising:

a plurality of pressure chambers (405) disposed in an array and each having a first wall having a nozzle (404) for ejecting ink droplets, a second wall (403) having a vibratable part for each pressure chamber (405), and a plurality of side walls (411) in contact with the first and the second walls (403), each said pressure chamber (405) receiving ink supplied through an ink supply port;

a first piezoelectric element (408) disposed for each of the pressure chambers (405) and having a first end disposed on the vibratable part, and a second end; and

a second piezoelectric element (409) disposed for each of the pressure chambers (405) and having a first end fixed to the side wall (411), and a second end;

characterized in that
the second ends of the first and the second piezoelectric elements (408, 409) for the pressure chambers (405) are coupled, and each piezoelectric element (408, 409) is polarized and electrically isolated.
An ink-jet recording head characterized by comprising:

a plurality of pressure chambers (405) including an opening covered with an elastic vibration plate (403), a supply port for supplying ink into the pressure chamber (405) and a nozzle (404) for ejecting the ink existing inside of the chamber (405):

a plurality of driving columns (408) which expand and contract based on a voltage applied between a pair of external electrodes (414, 415) for deforming the vibration plate (403), thereby driving the driving column (408) under an expanded state;

a plurality of fixing columns (409) which is polarized, electrically isolated and connected to a position between the pressure chambers (405); and

a single base section to which the fixing columns (409) and the other and of the driving column (408) are bonded.
The ink-jet recording head as defined in claim 29, wherein the single base section is a piezoelectric element which is polarized and electrically isolated.
The ink-jet recording head as defined in claim 30, wherein the driving column (408) and the fixing column (409) include internal electrodes (412a to 412d) disposed parallel to one another at a specified interval, and
the base section includes an internal electrode for depolarizing the base section parallel to the internal electrodes (412a to 412d) of the driving column (408) and the fixing column (409), and an external electrode for depolarizing the base section formed on a surface opposed to the internal electrode for depolarizing the base section.
An ink-jet recording head comprising:

a plurality of pressure chambers (405) including an opening covered with an elastic vibration plate (403), a supply port for supplying ink into the pressure chamber (405) and a nozzle (404) for ejecting the ink existing inside of the chamber (405):

a plurality of driving columns (408) which expand and contract based on a voltage applied between a pair of external electrodes (414, 415) for driving the pressure chamber (405) by deforming the vibration plate (403), thereby driving the driving column (408) under an expanded state; and

a plurality of fixing sections for fixing the other end of the driving columns (408) to a periphery of the opening:

characterized in that:
the fixing sections includes a plurality of fixing columns (409) bonded to the periphery of the opening of the pressure chamber (405) in a direction of the adjacent pressure chambers (405) and in a direction perpendicular thereto, and a base section is polarized and electrically isolated to which the plurality of the fixing columns (409) and the other ends of the driving columns (408) are bonded.
The ink-jet recording head as defined in claim 32, wherein each of the fixing columns (409) is polarized and electrically isolated.
The ink-jet recording head as defined in claim 33, wherein each of the fixing columns (409) includes electrodes for polarizing the fixing column on the inner surface of a gap for separating the driving column (408) and the fixing column (409), and on a side surface opposed to the inner surface of the gap.
The ink-jet recording head as defined in any of claims 32 to 34, wherein the driving column (408) includes internal electrodes (412a to 412d) disposed in parallel to each other at a specified interval, and the base section includes an internal electrode for polarizing the base section parallel to the internal electrodes (412a to 412d) of the driving column (408) and the fixing column (409), a surface opposed to the internal electrode for polarizing the base section, and an external electrode for polarizing the base section formed on the surface opposed to the internal electrode.
A method for fabricating an ink-jet recording head characterized by comprising the steps of:

forming a stacked piezoelectric material having a central portion of a specified width where electrodes (412a to 412d) are overlapped, by way of one layer of a piezoelectric material sheet, and both side portions thereof where the electrodes are overlapped, by way of two layers of the piezoelectric material sheets, by means of stacking the piezoelectric material sheets;

forming a base section (410) by forming a trench (419) in the stacked piezoelectric material such that a driving column (408) having the stacked portion of the piezoelectric material sheets inside thereof bonded to a vibration plate (403), a plurality of fixing columns (409) bonded to the vibration plate (403) at a peripheral portion of the opening of the pressure chamber (405), and at least one fixing column (409) bonded to an end piezoelectric element of the driving column (408) opposite to the pressure chamber (405) and a peripheral portion of the pressure chamber (405) are bonded to the base section (410);

forming a pair of driving electrodes alternately connected to the plurality of the electrodes inside each of the driving column (408);

forming at least a pair of polarization electrodes for polarizing the fixing column (409) or the base section (410) upon application of a voltage; and

polarizing the driving column (408) and the fixing column (409) by applying a voltage between the external electrodes (414, 415).
A method for fabricating an ink-jet recording head characterized by comprising the steps of:

forming a stacked member of piezoelectric materials by stacking piezoelectric material sheets having an electrode thereon such that the electrodes (412a to 412d) are overlapped by way of one layer of the piezoelectric material sheet on a central portion between a pair of side surfaces, the electrodes are overlapped by way of two layers of the piezoelectric material sheets on an outer portion thereof, and at least one of the both end surfaces of the electrodes is exposed to the side surfaces;

disposing a piezoelectric material block (401) on the stacked member of piezoelectric material to form a stacked piezoelectric material by means of sintering;

forming a plural pairs of external electrodes (414, 415) connected to the electrodes having the exposed end surface at a position corresponding to each pressure chamber (405) or at a position between the pressure chambers (405);

forming a trench (419) between the adjacent external electrodes (414, 415) to separate the stacked piezoelectric material sheets, thereby forming a driving column (408) bonded to the vibration plate (403) overlying the pressure chamber (405) and a fixing column (408) bonded to the vibration plate (403) between the pressure chambers (405);

contacting a probe (420) with the plural pairs of the external electrodes (414, 415); and

applying a voltage between the corresponding external electrodes (414, 415) for polarizing the driving column (408) and the fixing column (409).
The method as defined in claim 37, wherein the stacked member forming step further includes forming an internal electrode for depolarizing the base section (410) by further stacking the piezoelectric material sheets until a height thereof becomes higher than a depth of the trench (419), the external electrode forming step further includes forming an external electrode for depolarizing the base section (410) on a top surface of the piezoelectric material block; and the voltage applying step further includes applying a voltage between the external electrode for depolarizing the base section (410) and the internal electrode for depolarizing the base section depending on an interval therebetween for polarizing the piezoelectric material between the electrodes.
A method for fabricating an ink-jet recording head characterized by comprising the steps of:

forming a stacked member of piezoelectric materials by stacking piezoelectric material sheets having an electrode thereon such that the electrodes (412a to 412d) are overlapped by way of one layer of the piezoelectric material sheet on a central portion between a pair of side surfaces (413a, 413b), the electrodes are overlapped by way of two layers of the piezoelectric material sheets on an outer portion thereof, and at least one of the both end surfaces of the electrodes is exposed to the side surfaces;

disposing a piezoelectric material block (401) on the stacked member of piezoelectric material to form a stacked piezoelectric material by means of sintering;

forming gaps at a depth not to reach to the uppermost electrode in the both side surfaces where the electrodes are overlapped by way of one layer of the piezoelectric material sheet to separate a driving column (408) and a fixing column (409) in a direction from the one side surface to the other;

forming an electrode in an inner surface of the gap, and forming a plural pairs of external electrodes, connected to the above electrodes having the exposed surface, on positions on the both side surfaces corresponding to the pressure chambers (405);

forming an electrode on the top surface of the piezoelectric material block (401);

bonding the stacked piezoelectric material to the vibration plate (403) after position adjustment such that an intermediate portion of the gaps and an intermediate portion of the respective pairs of the external electrodes are positioned overlying the pressure chamber (405), and outer edges of the gaps are positioned on both sides of the pressure chamber (405);

dividing the stacked piezoelectric material to form piezoelectric elements having the driving column (408) and the fixing column (409) corresponding to each pressure chamber (405);

contacting a probe (420) with the plural pairs of the external electrodes (414, 415);

applying a voltage between the corresponding external electrodes (414, 415) for polarizing the driving column (408); and

applying a voltage between the electrode on the top surface of the block (401) and the uppermost electrode for depolarizing the piezoelectric material between the electrodes depending on an interval therebetween.
A method for fabricating an ink-jet recording head characterized by comprising the steps of:

forming a stacked member of piezoelectric materials by stacking piezoelectric material sheets having an electrode thereon such that the electrodes (412a to 412d) are overlapped by way of one layer of the piezoelectric material sheet on a central portion between a pair of side surfaces, the electrodes are overlapped by way of two layers of the piezoelectric material sheets on an outer portion thereof;

disposing a piezoelectric material block (401) having electrodes on both surfaces, a specified width and an exposed end surface on its top surface, on the stacked member of piezoelectric material to form a stacked piezoelectric material by means of sintering;

forming gaps at a depth to reach to electrodes in the both side surfaces of the piezoelectric material block (401) in both sides where the electrodes are overlapped by way of one layer of the piezoelectric material sheet to separate a driving column (408) and a fixing column (409) in a direction from the one side surface to the other;

forming an electrode in an inner surface of the gap, and forming a plural pairs of external electrodes (414, 415) connected to the above electrodes having the exposed surface, on positions corresponding to the pressure chamber (405) on the top surface of the piezoelectric material block (401);

forming electrodes between the plural pairs of the external electrodes,

bonding the stacked piezoelectric material to the vibration plate (403) after position adjustment such that an intermediate portion of the gaps and an intermediate portion of the respective pairs of the external electrodes are positioned overlying the pressure chamber (405), and outer edges of the gaps are positioned on both sides of the pressure chamber (405);

dividing the stacked piezoelectric material to form a piezoelectric element having the driving column (408) and the fixing column (409) corresponding to each pressure chamber (405);

contacting a probe (420) with the plural pairs of the external electrodes (414, 415);

applying a voltage between the electrode formed between the external electrodes and the uppermost electrode depending on an interval therebetween for polarizing the piezoelectric material between the electrodes.