JPH0848031A - On-demand inkjet head - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To arrange piezoelectric elements with high density corresponding to nozzles and pressurizing chambers provided with high density. A head body including a plurality of pressurizing chambers 2, a nozzle 13 communicating with each pressurizing chamber 2, and a vibrating plate 3 that seals one surface of each pressurizing chamber, and has the same electric field direction. The piezoelectric material 23 and a plurality of electrodes 21 and 22 are laminated so that the piezoelectric material 23 is polarized in the direction and has a piezoelectric strain constant d33.
A plurality of piezoelectric elements 20 in which 1 is exposed on one side surface and an electrode 22 serving as the other pole is exposed on the other side surface, are connected in parallel by the electrodes 24 and 25 and are drawn to the outside,
A rigid member 9 is provided which supports one end of the plurality of piezoelectric elements 20 against the vibration plate 3 and supports the other end of the piezoelectric elements 20 and the head body. It is possible to obtain a large displacement due to the piezoelectric strain constant d33 and reliably transmit this to the pressurizing chamber to sufficiently eject ink droplets even if the piezoelectric element 20 is downsized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head using a piezoelectric element.

[0002]

2. Description of the Related Art On-demand jets are being developed as low-priced printing devices because of their simple structure.
The ink is ejected by the deformation of the piezoelectric element, and conventionally, the deformation in the direction perpendicular to the polarization, that is, the deformation based on the piezoelectric strain constant d31 has been used.

For example, a conventional head using a 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 by applying a voltage between the electrodes 103 and 104 provided above and below (1
The piezoelectric element is contracted in the (axial) direction, and the diaphragm 101 and the piezoelectric element 102 are bent and deformed like a bimetal to change 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 the thin (three-axis) direction to increase the electric field in the longitudinal direction (one-axis) of the long element. Utilized the transformation.

On the other hand, in the case of utilizing the deformation of the piezoelectric strain constant d31 perpendicular to the polarization direction, as shown in FIG. 5, the (uniaxial) direction of the piezoelectric element is arranged perpendicular to the diaphragm 101, and (1
The diaphragm 101 is bent by the deformation in the (axial) direction. Also in this example, similarly to the conventional one shown in FIG. 4, a voltage is applied in the thin direction of the piezoelectric element, deformation is generated in the long direction, and the drive voltage is kept low.

[0005]

Although it is possible to eject ink droplets with a relatively low driving voltage as described above, it is difficult to construct a head capable of high-density printing by increasing the number of nozzles. there were. That is, 10 / mm
When the pressurizing chamber is integrated to some extent, the piezoelectric element shown in FIG. 4 has a short length in the (uniaxial) direction, and a sufficient displacement cannot be obtained. When the voltage is increased, it is difficult to form an integrated circuit because a driving circuit requires a circuit component having a high withstand voltage. On the other hand, in the case of FIG. 5, it is necessary to arrange many piezoelectric elements adjacent to each other,
It is impossible to arrange the electrodes at a high density of 10 electrodes / mm because adjacent electrodes are short-circuited. The present invention has been made in view of such a problem, and an object thereof is to arrange piezoelectric elements in high density corresponding to nozzles and pressurizing chambers provided in high density. An object of the present invention is to provide an on-demand type inkjet head that can be used.

[0006]

In order to solve such a problem, in the present invention, a plurality of pressurizing chambers, a nozzle communicating with each of the pressurizing chambers, and one surface of each of the pressurizing chambers are provided. A head body composed of a vibrating plate that seals the piezoelectric material, a piezoelectric material and a plurality of electrodes that are polarized in the same direction as the electric field and have a piezoelectric strain constant d33, and one of the electrodes that serves as one pole is A plurality of piezoelectric elements in which the electrodes serving as the other pole on the other side are connected in parallel by electrodes on the other side, and the vibration is performed so that one ends of the plurality of piezoelectric elements face the pressurizing chamber. A rigid member that abuts on the plate and supports the other end of the piezoelectric element and the head body is provided.

[0007]

[Function] Since a large displacement due to the piezoelectric strain constant d33 is obtained and this can be reliably transmitted to the pressurizing chamber by the rigid member,
Ink droplets can be sufficiently ejected even if the piezoelectric element is made small.

[0008]

1 and 2 each show an embodiment of the present invention. In the drawings, reference numeral 1 is a base hill of bolisulfon, in which ink channels are formed as grooves. 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.
At 0 μm, the pressurizing chambers 2 are arranged in pitches of 100 μm.

A diaphragm 3 made of polysulfone has a thickness of 10 μm and is laminated on the substrate 1. Reference numeral 4 denotes a piezoelectric element provided so as to face all the pressurizing chambers 2, which has electrodes 5 and 6 on the upper and lower sides, and a part of the upper part is left so as to correspond to each pressurizing chamber by a groove 7. It is divided like a comb. Diaphragm 3
The piezoelectric element 4 and the piezoelectric element 4 are bonded to the electrode 8 provided on the surface of the diaphragm 3.

The width Wp of the portion of the piezoelectric element 4 corresponding to each processing chamber 2 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 is an electrode 5 of the piezoelectric element 4 via an electrode 10.
Is a rigid member laminated to the diaphragm 3, and has a thickness Lg sufficiently thicker than the thickness of the diaphragm 3, for example, 1 mm, and is formed in a substantially U shape, and both ends are bonded to the diaphragm 3. In such a head, the base 1 is manufactured by injection molding, and the nozzle 1
1, the ink passages such as the supply passage 12 and the supply pipe 13 are the pressure chambers 2.
Formed with. Then, the vibration plate 3 is bonded to the surface by solvent-type bonding 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 the 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 diaphragm 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. In the embodiment of FIGS. 1 and 2, the number of nozzles is 4
Although only two heads are shown, it is possible to make heads with 24 to 2000 nozzles in practice.

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 electrodes 8 and 10, an electric field is applied to the piezoelectric element 4 via the electrodes 5 and 6. If the voltage at this time is set to V, a strain of ε = d33V / Le is generated in the piezoelectric element 4, which causes the vibrating plate 3 to bend and pressurize the ink in the pressurizing chamber 2 to eject it from the nozzle 11. Since ink droplets can be ejected, recording is performed on the recording medium.

The thickness Lg of the rigid member 9 is 100 of the vibration plate 3.
Since it is about double, the bending rigidity becomes 100 times the cube,
Almost all the displacement of the piezoelectric element 4 is transmitted to the diaphragm 3. In order to eject the ink droplets, it is necessary that the bending rigidity of the rigid member 9 is 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 polarization direction, the piezoelectric element can be easily arranged in each of the plurality of pressurizing chambers, and the multinosed head can be easily constructed. It becomes possible. Further, the value of the piezoelectric strain constant d33, which is the same as the polarization direction, is 2 to 3 times the piezoelectric strain constant d31 in the direction perpendicular to the polarization direction, so that the distance between the electrodes 5 and 6 is relatively long. A large piezoelectric strain can be obtained.

In the above embodiment, the electrodes 5, 6, 8, 1
0 is provided, but electrode 5 and electrode 10, electrode 6 and electrode 8
It is possible to reduce the number of electrodes by using the same member. Further, if the rigid member 9 is made of metal, it can be used instead of the electrode 10.

Further, since the groove 7 is formed in the middle of the piezoelectric element 4 and the joint surface is the same surface, the joint area is large and the joint strength with the rigid member 9 can be increased. If an adhesive with greater bonding strength can be used, the groove 7
Can be extended to the other end and each piezoelectric element can be made independent, so that the mutual influence of the piezoelectric elements can be reduced and the loss of voltage can be reduced.

FIG. 3 shows another embodiment of the present invention in a sectional structure cut along a flow path. In this embodiment, unlike the embodiment shown in FIGS. Element 20 is a laminate of 9 layers of 50 μm elements,
Piezoelectric material 23 is laminated between 1 and 22 so that only one end of electrodes 21, 21 ... serving as one pole is located on one side and electrodes 22, 22 ,. Only one end is extended to the other side and exposed, and these exposed parts are formed with electrodes 24 and 25 on the side surface to connect electrodes 21, 21 ... And 22, 22 ... Of the same pole in parallel. In addition, the electrodes 24 and 25 are connected to the electrode 8 provided on the surface of the diaphragm 3 and the electrode 10 provided on the surface of the rigid member 9.

Piezoelectric element 2 having such a laminated structure
At 0, the electric field acting on each piezoelectric material 23 is 9 times as large as that in the above-described embodiment of FIG. 1, so that the embodiment of FIG. 1 requires a voltage of 80 V as a drive signal. 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, the drive circuit can be integrated.

[0020]

As described above, in the present invention, a plurality of pressurizing chambers, a nozzle communicating with each pressurizing chamber, and a vibration plate for sealing one surface of each pressurizing chamber are provided. A head body, 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 electrode serves as one side and the other pole. A plurality of piezoelectric elements whose electrodes are connected in parallel to each other on the other side surface, and one end of the plurality of piezoelectric elements are brought into contact with the vibrating plate so as to face the pressurizing chamber, and the other end of the piezoelectric element and the head body. Since a rigid member for supporting and is provided, a large displacement due to the piezoelectric strain constant d33 can be obtained and this displacement can be reliably transmitted to the pressurizing chamber, so that the piezoelectric element can be downsized. Easy placement of multiple piezoelectric elements in a densely arranged pressure chamber You can

Further, since the plurality of electrodes forming the piezoelectric element can be drawn out from the side portions, the electrical connection between the piezoelectric element and the external device can be simplified.

[Brief description of drawings]

FIG. 1 is a sectional view showing an 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 sectional view showing an example of a conventional inkjet head.

FIG. 5 is a cross-sectional view showing an example of a conventional inkjet head.

[Explanation of symbols]

 1 Substrate 2 Pressurizing Chamber 3 Vibration 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)

[Claims] 1. 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 the same direction as the electric field direction. A piezoelectric material and a plurality of electrodes are laminated so as to have a piezoelectric strain constant d33 and are polarized on one side, the electrode that is one pole is on one side surface, and the electrode that is the other pole is on the other side surface, respectively. A plurality of piezoelectric elements connected in parallel by electrodes, and the other end of the piezoelectric element and the head body are brought into contact with the vibration plate so that one end of the plurality of piezoelectric elements faces the pressure chamber. An on-demand inkjet head consisting of a supporting rigid member.