JP3668032B2 - Inkjet printer head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet printer head that is used in an ink jet printer that prints by discharging ink, and particularly relates to an ink jet printer head that is small and has excellent gradation.
[0002]
[Prior art]
In recent years, with the spread of digital processing of image and character information, an inkjet printer that can easily obtain a color image at a low running cost has attracted attention as a device that outputs such information.
[0003]
The head used for such ink jet printing is a thermal jet method in which the pressure in the pressurizing chamber is increased by heating and boiling the ink with a heater provided in the pressurizing chamber to generate bubbles, thereby discharging the ink. In addition, a piezoelectric method is known in which the pressure in the pressurizing chamber is increased by bending or displacing the wall surface constituting the pressurizing chamber directly or indirectly by the piezoelectric / electrostrictive effect to discharge ink.
[0004]
Among these, piezoelectric heads are widely used because they are excellent in durability and responsiveness, and since the ink is not directly heated, the type thereof is not limited.
[0005]
As such a piezoelectric head, a plurality of partition walls 23 as shown in FIG. 4 are arranged side by side at equal intervals, and a concave member 22 having a pressure chamber 24 between the partition walls 23 and the partition wall 23 are formed. A pressurizing member 25 is composed of a thin diaphragm 26 joined to the top and covering each pressurizing chamber 24, and a piezoelectric element 27 is placed on the diaphragm 26 at a position facing each pressurizing chamber 24 on the lower electrode. A piezoelectric actuator 30 sandwiched between the upper electrode 29 and the upper electrode 29 is mounted, and the piezoelectric actuator 30 is driven to bend and displace the vibration plate 26 that forms the wall of the pressure chamber 24. A bend mode type head 21 (Japanese Patent Laid-Open Nos. 6-40030 and 6-218929) in which the pressure inside the pressure chamber 24 is changed and ink is ejected from the ink ejection holes 31 drilled in the bottom surface of the pressurizing chamber 24. (See publication) 5, a plurality of partition walls 43 made of piezoelectric ceramics as shown in FIG. 5 are arranged side by side at equal intervals, and the space between the partition walls 43 is bonded to a concave member 42 serving as a pressure chamber 44 and the top of the partition wall 43. A pressurizing member 45 is constituted by a top plate 46 covering each pressurizing chamber 44, and a nozzle plate 48 having an ink ejection hole 47 communicating with each pressurizing chamber 44 is provided on one end side of the pressurizing chamber 44. At the same time, drive electrodes 49 are provided on both side surfaces of each partition wall 43 along the longitudinal direction thereof, and the shear mode deformation of the piezoelectric ceramic is utilized by energizing the drive electrodes 49 formed on both side surfaces. A shear mode type head 41 (see Japanese Patent Application Laid-Open No. 9-164672) in which the partition wall 43 is bent and displaced to change the pressure in the pressurizing chamber 44 to discharge ink from the ink ejection holes 47. Proposed There. Reference numeral 50 denotes an ink introduction hole for supplying ink to the other end side of the pressurizing chamber 44.
[0006]
[Problems to be solved by the invention]
However, in the bend mode type head 21 shown in FIG. 4, since the diaphragm 26 and the piezoelectric actuator 30 constituting the flexible portion are thick and rigid, the displacement width of the diaphragm 26 is small. There is a problem that the gradation of the image is poor because the width of the ink volume that can be ejected from the hole 31 is narrow.
[0007]
On the other hand, the shear mode type head 41 shown in FIG. 5 has a structure in which the partition wall 43 is displaced. Therefore, when the partition wall 43 is bent and displaced in order to increase the pressure in one pressurizing chamber 44, the pressurization on both sides is performed. Since the pressure in the chamber 44 works in a direction to reduce the pressure, the ink cannot be ejected simultaneously from the ink ejection holes 47 communicating with all the pressurizing chambers 44 formed in the head 41. There is a problem that the time required for printing becomes long, and conversely, if the number of ink ejection holes 47 that can be ejected at one time is increased, the head 41 is increased in size and cannot cope with space saving. There was a problem.
[0008]
OBJECT OF THE INVENTION
SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet printer head that has the advantages of a bend mode head and a shear mode head and has a small size and excellent gradation.
[0009]
[Means for Solving the Problems]
Therefore, in view of the above problems, the present invention has a pressurizing member in which a plurality of pressurizing chambers are arranged in parallel, and each pressurizing chamber other than the above partitioning walls has a pressurizing member having a partition wall as a partition wall. A part of the wall portion is formed as a diaphragm, and the diaphragm and the partition are integrally formed of piezoelectric ceramics, and a common electrode is formed on the surface of the diaphragm on the inside of the pressurizing chamber along the longitudinal direction thereof. In addition, on the outer surface of the pressurizing chamber, two independent driving electrodes are provided along the longitudinal direction to form an ink jet printer head, and a voltage is applied between the driving electrode and the common electrode. Thus, ink is ejected.
[0010]
[Action]
According to the present invention, a part of the wall constituting the pressurizing chamber excluding the partition wall of the pressurizing member is formed as a diaphragm, and the diaphragm is formed of piezoelectric ceramics and is common to the surface on the pressurizing chamber side. Since the electrodes are provided as driving actuators on the outer surface of the pressurizing chamber to form a piezoelectric actuator, and the piezoelectric actuator is driven to directly bend and displace the walls constituting the pressurizing chamber, the bend Since the ink can be ejected simultaneously from the ink ejection holes communicating with all the pressure chambers formed in the head as in the mode type head, the head can be downsized and the printing time can be shortened. Moreover, since the thickness of the common electrode, the diaphragm, and the driving electrode constituting the flexible portion can be reduced as compared with the bend mode type head, the displacement width capable of instantaneously bending and displacing the diaphragm is increased. can do.
[0011]
Furthermore, according to the present invention, since two independent driving electrodes are provided along the longitudinal direction on the outer surface of the pressure chamber of the diaphragm, a voltage is applied to the common electrode and one of the driving electrodes. The diaphragm can be bent and displaced convexly, and the diaphragm can be bent and displaced concavely by applying voltages having different polarities to the common electrode and the other drive electrode. The displacement width can be finely adjusted, and printing with high gradation and gradation can be realized.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0013]
FIG. 1 is a partially cutaway perspective view showing an example of an ink jet printer head according to the present invention, which has a plurality of partition walls 3 aligned in parallel, and a concave portion made of piezoelectric ceramics that forms a pressurizing chamber 4 between the partition walls 3. A pressurizing member 5 is constituted by the member 2 and a conductive nozzle plate 8 having an ink ejection hole 7 joined to the top of each partition wall 3 of the recess member 2 and communicating with each pressurizing chamber 4. Thus, the wall portion forming the bottom surface of the pressurizing chamber 4 is formed as the diaphragm 6, and the common electrode 9 is provided on the surface of the diaphragm 6 on the pressurizing chamber 4 side and the side surface of the partition wall 3 along the longitudinal direction thereof. And two independent driving electrodes 10a and 10b are formed on the surface corresponding to each pressurizing chamber 4 opposite to the pressurizing chamber 4 along the longitudinal direction thereof. The electrode 9, the diaphragm 5, and the two drive electrodes 10a and 10b It has configured Yueta 11.
[0014]
The dimensions of the partition wall 3 forming the pressure member 2 may be 50 to 80 μm in width, 1.2 to 3.6 mm in length, and 60 to 150 μm in depth, and the partition wall 3 may be 127 to 169. The head 1 of 150 to 200 dpi can be obtained by standing up to 45 to 60 with a pitch of 3 μm.
[0015]
The diaphragm 6 is provided with ink introduction holes (not shown) for supplying ink to the pressure chambers 4, and the common electrode 9 formed on each pressure chamber 4 side is electrically conductive. The nozzle plate 8 having a ground is grounded (not shown), and voltages having different polarities are applied to the two driving electrodes 10a and 10b facing the pressurizing chambers 4 from a driving circuit (not shown). It is. Further, the diaphragm 6 is previously polarized in the direction of the arrow.
[0016]
Thus, the head 1 of the present invention can reduce the thickness of the common electrode 9, the diaphragm 6, and the driving electrodes 10 a and 10 b that constitute the flexible portion, so that the conventional bend mode type head 21 shown in FIG. In comparison, the displacement width in which the wall portion (diaphragm 6) constituting the pressurizing chamber 4 can be instantaneously bent and displaced can be increased.
[0017]
In order to drive the head 1, for example, when a positive voltage V is applied to the driving electrode 10a from the state shown in FIG. 2 (a), shear mode deformation occurs as shown in FIG. 2 (b). Since the diaphragm 6 is curved convexly, the pressure in the pressurizing chamber 4 is reduced. As a result, ink can be introduced into the pressurizing chamber 4 from an ink introduction hole (not shown). When the energization to 10a is interrupted, as shown in FIG. 2 (c), the diaphragm 6 is elastically recovered to increase the pressure in the pressurizing chamber 4, so that ink can be ejected from the ink ejection holes 7.
[0018]
Therefore, characters and images can be printed by repeating the operations shown in FIGS. 2A to 2C. However, according to the present invention, the driving electrode 10b is further increased from the state shown in FIG. By applying the negative electrode voltage V to the diaphragm 6, as shown in FIG. 2 (d), the diaphragm 6 can be deformed in a shearing mode to bend into a concave shape. 2 (a) to 2 (c), in which ink is ejected separately from the ejection holes 7 and combined with the ink ejected from the state of FIG. 2 (c), so that a large volume of ink can be ejected. By combining the operation with the operations shown in FIGS. 2A to 2D, the width of the ink volume discharged from the ink ejection hole 7 can be finely adjusted, and the voltage applied to each of the driving electrodes 10a and 10b. Change the value of diaphragm 6 By controlling the amount, it is possible to adjust the width of the ink volume ejected from the ink ejection hole 7 in more detailed, it is possible to realize an excellent gradation.
[0019]
In addition, according to the present invention, since the wall portion constituting the pressurizing chamber 4 other than the partition wall 3 is bent and displaced, similarly to the conventional bend mode type head 21 shown in FIG. Since ink can be ejected simultaneously from the ink ejection holes 7 communicating with all the pressurizing chambers 4 formed, the head 1 can be reduced in size and compared with the conventional shear mode type head 41 shown in FIG. Printing time can be reduced.
[0020]
By the way, as the piezoelectric ceramics for forming the recess material 2, piezoelectric ceramics mainly composed of lead zirconate titanate (PZT), piezoelectric ceramics mainly composed of lead magnesium niobate (PMN), nickel niobate Piezoelectric ceramics based on lead, piezoelectric ceramics based on lead antimony stannate, piezoelectric ceramics based on lead titanate, piezoelectric ceramics based on barium titanate, and composites of these main components Piezoelectric ceramics, preferably piezoelectric ceramics mainly composed of lead magnesium niobate, lead zirconate and lead titanate, or lead nickel niobate, lead magnesium niobate, lead zirconate and lead titanate are preferred. It is good to form with piezoelectric ceramics as a component.
[0021]
The common electrode 9 and the driving electrodes 10a and 10b may be made of metals such as platinum (Pt), gold (Au), palladium (Pd), rhodium (Rh), nickel (Ni), aluminum (Al), etc. An alloy mainly composed of Pt—Au, Pb—Ag, Pt—Pb, or the like can be used.
[0022]
Further, the material for forming the nozzle plate 8 may be any material as long as it has conductivity, such as a metal such as aluminum or stainless steel, a resin having conductivity, or a ceramic such as alumina containing a cermet material or a conductivity-imparting agent. Can be used.
[0023]
Next, the manufacturing method of the inkjet printer head 1 of this invention is demonstrated.
[0024]
First, as shown in FIG. 3A, a block body made of the piezoelectric ceramic is prepared, and a plurality of grooves are arranged in parallel by cutting or blasting with a dicing saw, and the grooves are used as a pressure chamber 4. At the same time, the concave member 2 is manufactured in which the wall partitioning the pressurizing chamber 4 is used as the partition wall 3.
[0025]
Next, as shown in FIG. 3 (b), after the polarization treatment is performed on the concave portion 2 in the direction of the arrow, film formation such as vapor deposition, sputtering, plating, etc. is performed on the inner wall surface of the groove of the concave portion 2. The common electrode 9 made of the metal material is formed by each means, and the surface corresponding to each pressurizing chamber 4 on the opposite side to the pressurizing chamber 4 of the concave member 2 is formed by film forming means such as vapor deposition, sputtering, plating, etc. Two independent drive electrodes 10a and 10b made of the metal material are formed.
[0026]
Thereafter, a conductive nozzle plate 8 having ink ejection holes 7 communicating with the respective pressure chambers 4 is joined to the top of the partition wall 3 with a conductive adhesive, whereby the ink jet printer head shown in FIG. 1 can be obtained.
[0027]
Thus, the concave member 2 in which the diaphragm 6 and the partition wall 3 are joined and integrated is formed, the common electrode 9 is formed on the inner wall surface of the groove of the concave member 2, and the nozzle plate 8 is made of a conductive material. By forming them and joining them together with a conductive adhesive, it is possible to simplify the routing of the wiring to the common electrode 9 and increase the productivity of the head 1.
[0028]
【The invention's effect】
As described above, according to the present invention, a plurality of pressurizing chambers are arranged in a row, and the pressurizing member having the walls that partition the pressurizing chambers as partition walls is provided. A part of the wall portion constituting the diaphragm is formed as a diaphragm, and the diaphragm is formed of piezoelectric ceramics, and a common electrode is provided on the surface of the diaphragm on the inside of the pressurizing chamber along the longitudinal direction thereof. An ink jet printer head is formed by providing two independent drive electrodes along the longitudinal direction on the outer surface of the pressure chamber, and ink is ejected by applying a voltage between the drive electrode and the common electrode. As a result, unlike the bend mode type head, the wall portion (vibration plate) constituting the pressurizing chamber can be directly bent and displaced, so the displacement width that can be instantaneously bent and displaced is increased. As well as two Since the displacement width of the wall (diaphragm) can be finely adjusted by the voltage value applied to the moving electrode, images with excellent gradation can be printed by changing the pulse voltage value applied continuously. can do.
[0029]
In addition, according to the present invention, since the wall portion constituting the pressurizing chamber other than the partition wall is bent and displaced, all the pressurizing chambers formed in the head are formed like the conventional bend mode type head. Since the ink can be ejected simultaneously from the ink ejection holes communicating with the head, the head can be downsized and the printing time can be shortened as compared with a conventional shear mode head.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing an example of an inkjet printer head of the present invention.
2A to 2D are cross-sectional views for explaining the driving principle of the ink jet printer head shown in FIG.
FIGS. 3A to 3C are diagrams for explaining a manufacturing process of the ink jet printer head shown in FIG.
FIG. 4 is a partially cutaway perspective view showing an example of a conventional inkjet printer head of a bend mode type.
FIG. 5 is a partially cutaway perspective view showing an example of a conventional ink jet printer head of a shear mode type.
[Explanation of symbols]
1, 21, 41: Inkjet printer heads 2, 22, 42: Recess members 3, 23, 43: Partition walls 4, 24, 44: Pressurizing chambers 5, 25, 45: Pressurizing members 6, 26: Diaphragm 7, 31, 47: Ink ejection holes 8, 48: Nozzle plate 9: Common electrodes 10a, 10b, 49: Driving electrodes 11, 30: Piezoelectric actuator 27: Piezoelectric element 28: Lower electrode 29: Upper electrode 46: Top plate 50: Ink introduction hole

Claims (1)

A plurality of pressurizing chambers are provided in a row, each of the pressurizing chambers includes a pressurizing member having walls that partition the pressurizing chambers as partition walls, and a part of the wall constituting each pressurizing chamber other than the partition walls is a diaphragm. None, the diaphragm and the partition are integrally formed of piezoelectric ceramics, and a common electrode is provided on the surface of the diaphragm on the inside of the pressurizing chamber along the longitudinal direction thereof, and on the surface on the outer side of the pressurizing chamber. An ink jet printer head characterized in that two independent drive electrodes are provided along the longitudinal direction, and ink is ejected by applying a voltage between the drive electrode and the common electrode. .

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