JP2757833B2 - On-demand type inkjet head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head using a piezoelectric element. 2. Description of the Related Art On-demand jets have been developed as low-cost printing apparatuses because of their simple configuration.
Ink ejection is performed by deformation of a piezoelectric element. Conventionally, deformation perpendicular to polarization, that is, deformation caused by a piezoelectric distortion constant d31 has been used. For example, a head using a conventional unimorph shown in FIG. 4 has a piezoelectric element 102 laminated on a vibration plate 101.
Is polarized in the direction of (3 axes) in the figure, and (1) is applied by applying a voltage between the electrodes 103 and 104 provided above and below.
The piezoelectric element is contracted in the (axial) direction, and the diaphragm 101 and the piezoelectric element 102 cause bending deformation like a bimetal, thereby changing the volume of the pressurizing chamber 105. Since the deformation of the piezoelectric element 102 is proportional to the electric field and proportional to the length in the deformation direction, the electric field is increased by applying a voltage in a thin (three-axis) direction to increase the length of the long element (one axis). Utilizing deformation. On the other hand, in the case of using the deformation of the piezoelectric strain constant d31 perpendicular to the polarization direction, as shown in FIG. 5, the (one axis) direction of the piezoelectric element is arranged perpendicular to the diaphragm 101, and (1)
The diaphragm 101 is bent by deformation in the (axial) direction. In this example, as in the prior art shown in FIG. 4, a voltage is applied in the thin direction of the piezoelectric element, and deformation is generated in the long direction, thereby suppressing the driving voltage. [0005] Although it is possible to eject ink droplets at a relatively low drive voltage, a head capable of high-density printing by increasing the number of nozzles is provided. Was difficult. That is, 10 wires / mm
When the pressure chambers are integrated to such an extent, in the one shown in FIG. 4, the length of the piezoelectric element in the (uniaxial) direction becomes short, and a sufficient displacement cannot be obtained. When the voltage is increased, a circuit component having a large withstand voltage is required for the drive circuit, and it is difficult to integrate the drive circuit. On the other hand, in the case of FIG. 5, a large number of piezoelectric elements must be arranged side by side,
Adjacent electrodes are short-circuited, and it is impossible to arrange them at a high density of 10 wires / mm. The present invention has been made in view of such a problem, and an object thereof is to arrange a piezoelectric element at a high density corresponding to a nozzle or a pressure chamber provided at a high density. It is an object of the present invention to provide an on-demand type ink jet head which can be used. In order to solve such a problem, according to the present invention, there are provided a plurality of pressurizing chambers, a nozzle communicating with each of the pressurizing chambers, and a plurality of pressurizing chambers. A head body comprising a vibrating plate for sealing one surface, a piezoelectric material and a plurality of electrodes laminated so as to be polarized in the same direction as the direction of the electric field and have a piezoelectric strain constant d33, and serve as one pole. Electrode
On one side in a direction orthogonal to the arrangement direction of the pressurizing chambers ,
Further, the electrode serving as the other pole is arranged in the direction in which the pressure chambers are arranged.
A plurality of piezoelectric elements each formed by forming a plate connected in parallel by an electrode on the other side surface in the orthogonal direction into a comb shape, and one end of each of the plurality of piezoelectric elements faces the pressurizing chamber. A rigid member abutting on the diaphragm to support the other end of the piezoelectric element and the head body .
Caught. A large displacement due to the piezoelectric distortion constant d33 can be obtained and transmitted to the pressurizing chamber by the rigid member without fail.
Even if the piezoelectric element is made compact, sufficient pressure is generated,
Surface for easy connection with electrodes for connection to external drive circuits
Formed. 1 and 2 show one embodiment of the present invention. In the drawings, reference numeral 1 denotes a base slope of volisulfon, and an ink flow path is formed as a groove on the surface. . The width Wc of the pressurizing chamber 2 is about 80 μm, the width Wd of the wall defining the pressurizing chamber 2 is 20 μm, and the depth Dc of the pressurizing chamber 2 is 3 μm.
The pressure chambers 2 are arranged in a pitch of 100 μm at 0 μm. Reference numeral 3 denotes a diaphragm made of polysulfone having a thickness of 10 μm and laminated on the substrate 1. Reference numeral 4 denotes a piezoelectric element provided opposite to all the pressurizing chambers 2 and has electrodes 5 and 6 on the upper and lower sides, and a part of an upper part is left by a groove 7 so as to correspond to each pressurizing chamber. It is divided into a comb shape. Diaphragm 3
The piezoelectric element 4 is bonded to an electrode 8 provided on the surface of the diaphragm 3. The width Wp of the portion corresponding to each processing chamber 2 of the piezoelectric element 4 is 50 μm, the length Lp is 300 μm, and the distance L between the electrodes is L.
e is 350 μm. Reference numeral 9 denotes an electrode 5 of the piezoelectric element 4 via an electrode 10.
A rigid member laminated on the diaphragm 3 has a thickness Lg sufficiently larger than the thickness of the diaphragm 3, for example, 1 mm, is formed in a substantially “U” shape, and both ends are adhered to the diaphragm 3. In such a head, the base 1 is made by injection molding, and the nozzle 1
1. The ink passages such as the supply path 12 and the supply pipe 13 are
It is formed with. Thereafter, the diaphragm 3 is adhered to the surface by solvent-type adhesion to form a head body. A metal thin film is sputtered on the surface of the diaphragm 3, and the electrode 3 as shown in the figure is formed by etching. On the other hand, the rigid member 9 is made by injection molding of polysulfone, and an electrode 10 is formed on the lower surface by sputtering. After bonding the piezoelectric element 4 having the electrodes 5 and 6 on the upper and lower surfaces to the rigid member 9, the groove 7 is formed with a diamond saw. Further, the rigid member 9 and the piezoelectric element 4 are adhered to the vibration plate 3, and a cable for supplying a drive signal from a control circuit (not shown) is connected to the rear portion 8-1 of the electrode 10 and the electrode 8. 1 and 2, the number of nozzles is four.
Although two heads are shown, it is actually possible to make heads with 24 to 2000 nozzles. Next, the operation of the above embodiment will be described. When the flow path is filled with ink and a drive signal from a control circuit (not shown) is applied between the electrode 8 and the electrode 10, an electric field is applied to the piezoelectric element 4 via the electrodes 5 and 6. Assuming that the voltage at this time is V, a distortion of ε = d33 V / Le occurs in the piezoelectric element 4, thereby flexing the diaphragm 3 to pressurize the ink in the pressurizing chamber 2, and Since ink droplets can be ejected, recording is performed on a recording medium. The thickness Lg of the rigid member 9 is 100
Since it is about twice, the bending rigidity becomes 100 times the power of three,
Almost all the displacement of the piezoelectric element 4 is transmitted to the diaphragm 3. In order to eject ink droplets, it is desirable that the rigidity of the rigid member 9 be 100 times or more that of the diaphragm. As can be seen from the above embodiment, by utilizing the deformation of the piezoelectric element in the direction of polarization, the piezoelectric element can be easily arranged in each of a large number of pressurizing chambers, so that a multi-nose head can be easily formed. It becomes possible. Also, the value of the piezoelectric strain constant d33, which is the same as the polarization direction, is two to three times the piezoelectric strain constant d31 in the direction perpendicular to the polarization direction, so that the distance between the electrodes 5, 6 is relatively long. Large piezoelectric strain can be obtained. In the above embodiment, the electrodes 5, 6, 8, 1
0, but the electrodes 5 and 10 and the electrodes 6 and 8
Can be used as the same member to reduce the number of electrodes. When the rigid member 9 is made of metal, it can be used instead of the electrode 10. Further, since the groove 7 is formed halfway of the piezoelectric element 4 and the bonding surface is the same, the bonding area is large and the bonding strength with the rigid member 9 can be increased. If an adhesive having a larger bonding strength can be used, the groove 7
Is extended to the other end to make each piezoelectric element independent, thereby reducing the mutual influence of the piezoelectric elements and reducing the voltage loss. FIG. 3 shows another embodiment of the present invention in a cross-sectional structure cut along a flow path. In this embodiment, unlike the embodiment shown in FIGS. The element 20 is a stack of nine 50 μm elements, and the electrode 2
A piezoelectric material 23 is laminated in a sandwich shape between the first and second electrodes 22 and 22. One end of each of the electrodes 21 and 21 # serving as one pole is provided on one side and the other of the electrodes 22 and 22 # serving as the other pole is provided. Only one end is extended to the other side to be exposed, and these exposed portions are formed on the side surface with electrodes 24 and 25 to connect electrodes 21, 21 'and 22, 22' of the same polarity in parallel. In addition, the electrodes 24 and 25 connect the electrode 8 provided on the surface of the diaphragm 3 and the electrode 10 provided on the surface of the rigid member 9. The piezoelectric element 2 having such a laminated structure
At 0, the electric field acting on each piezoelectric material 23 is nine times as large as that of the embodiment of FIG. 1 described above, so that the embodiment of FIG. In this embodiment, ink droplets can be ejected at 10 V or less. In particular, when a large number of nozzles such as 2000 nozzles are driven, an integrated drive circuit can be formed. As described above, according to the present invention, a plurality of pressurizing chambers, a nozzle communicating with each pressurizing chamber, and a diaphragm for sealing one surface of each pressurizing chamber are provided. And a piezoelectric material and a plurality of electrodes are laminated so as to be polarized in the same direction as the electric field direction and have a piezoelectric strain constant d33, and one of the electrodes is orthogonal to the direction in which the pressure chambers are arranged. distribution in the side one <br/> lateral direction, also said electrode is the other electrode of the pressure chamber to
A plurality of piezoelectric elements each formed by forming a plate connected in parallel by an electrode on the other side surface in a direction orthogonal to the column direction into a comb shape, and one end of each of the plurality of piezoelectric elements are added. because a rigid member for supporting the other end and the head of the piezoelectric element is brought into contact with the vibrating plate so as to face the pressure chamber, and be Rukoto obtain a large displacement by the piezoelectric strain constant d33, the plate Pickpocket on the body
A very small piezoelectric element with the simple task of inserting
Not only can be easily formed, but also a large number of piezoelectric elements can be easily arranged in the pressurized chambers arranged at a high density. A plurality of electrodes constituting the piezoelectric element can be formed on a surface orthogonal to the direction in which the pressure chambers are arranged.
When the poles are built, the electrical connection between the piezoelectric element and the external device is
Work can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is a perspective view showing one embodiment of the present invention. FIG. 3 is a sectional view showing another embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating an example of a conventional inkjet head. FIG. 5 is a cross-sectional view illustrating an example of a conventional inkjet head. [Description of Signs] 1 Substrate 2 Pressurizing chamber 3 Vibrating plate 4, 20 Piezoelectric element 5, 6, 8, 10, 21, 22 Electrode 7 Groove 9 Rigid member 11 Nozzle 12 Supply path 23 Piezoelectric material

Claims (1)

(57) [Claims] A head body comprising a plurality of pressurizing chambers, a nozzle communicating with each of the pressurizing chambers, and a vibration plate sealing one surface of each of the pressurizing chambers; and a piezoelectric body polarized in the same direction as the electric field direction. A piezoelectric material and a plurality of electrodes are stacked so as to have a strain constant d33, and the electrode serving as one of the electrodes is in a direction orthogonal to the arrangement direction of the pressure chambers.
In one aspect, also said electrode is the other electrode the pressure
On the other side surface in the direction orthogonal to the direction in which the pressure chambers are arranged, the plate bodies connected in parallel by electrodes are formed into a comb shape.
A plurality of formed piezoelectric elements, and a rigid member that supports the other end of the piezoelectric elements and the head body by bringing one end of the plurality of piezoelectric elements into contact with the vibration plate so as to face the pressurizing chamber. On-demand type inkjet head consisting of and.