JPH04292948A - Liquid drop jetting device - Google Patents

Abstract

PURPOSE:To eliminate the need for a process for forming a metal electrode and a process for making the electrode passive to lower the cost by a method wherein in a device in which a volume of an ink flow path is changed by a piezoelectric transducer for jetting ink, conductive ink is used for the ink in the ink flow paths. CONSTITUTION:In an ink jet printer, a liquid drop jetting device is disposed opposingly to a platen which supports paper. The liquid drop jetting device is loaded on a carriage together with an ink supply device. An array 1 used for the liquid drop jetting device is polarized in the arrow directions 26, 28. The array 1 is formed by bonding upper and lower ceramics plates 2, 3 having a plurality of vertically-open parallel grooves formed by side walls 60a, 60c, 60e, 60g; 60b, 60d, 60f, 60h through an adhesive 12. In this manner, ink flow paths 4a-4e of a rectangular cross section are formed. As ink to be charged in the ink flow paths, conductive ink, e.g. water-soluble ink, is used for eliminating the need for a process for forming a metal electrode and a process for making the electrode passive.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a droplet jetting device.
More specifically, the present invention relates to a droplet ejecting device that utilizes the deformation of a piezoelectric transducer.

0002

2. Description of the Related Art Conventionally, printer heads using piezoelectric inkjet have been proposed in recent years. this is,
By changing the volume of the ink flow path by dimensional displacement of the piezoelectric actuator, ink in the ink flow path is ejected from the orifice when the volume decreases, and ink is introduced into the ink flow path from the other valve when the volume increases. This is called the drop-on-demand method. By arranging a large number of such ejecting devices close to each other and ejecting ink from the ejecting devices at predetermined positions, desired characters and images are formed.

[0003] As this type of droplet ejecting device, there is one shown in FIG. 7, for example. Hereinafter, a conventional example will be specifically explained with reference to FIG. 7 showing a cross-sectional view of a part of the array. Ceramic plate 2 and a plurality of side walls 60b, 60d, 60f, 60h
and the lower piezoelectric ceramic plate 3 which has been polarized in the direction of the arrow 28 and is bonded to the lower piezoelectric ceramic plate 3 via the adhesive layer 12, a large number of parallel ink channels 4a, 4b are formed with a space between each other in the lateral direction. , 4c, and 4d are constructed. The ink flow path 4 is long and narrow with a rectangular cross section, and the side wall 60 extends over the entire length of the flow path and is deformable perpendicular to the flow path axis to vary the ink pressure within the flow path. A metal electrode 6 for applying a driving electric field is formed on the surface of the side wall 60.
The surface has been treated to prevent corrosion by ink.

When, for example, the injection device 34b is selected in accordance with predetermined print data in this array, the metal electrode 6
A driving electric field is applied between each of the metal electrodes 6d and 6e and the metal electrodes 6d and 6e. At this time, since the driving electric field direction and the polarization direction are perpendicular to each other, the side walls 60c, 60d and the side walls 60e, 60
f deforms into a dogleg shape toward the inside of the ink flow path 4b due to the piezoelectric thickness sliding effect. This deformation increases the ink pressure within the ink flow path 4b, and ink droplets are ejected from an orifice (not shown).

[0005]

[Problems to be Solved by the Invention] However, in the manufacturing process of the conventional droplet ejecting device described above, a metal electrode for driving is formed on the inner wall of the groove of a piezoelectric ceramic plate having a groove for forming an ink flow path. This required a process of decontamination, and a passivation treatment to prevent corrosion of this electrode. For this reason, there was a problem in that the manufacturing cost was high.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a droplet injection device that requires fewer manufacturing steps and is inexpensive to manufacture.

[0007]

[Means for Solving the Problem] In order to achieve this object, the droplet ejecting device of the present invention is an ejecting device that ejects ink in an ink flow path by changing the volume of the ink flow path using a piezoelectric transducer. The ink in the ink flow path is conductive ink.

[0008]

[Operation] According to the droplet ejecting device of the present invention having the above configuration, when a driving electric field is applied to the conductive ink in the ink flow path, the piezoelectric material in contact with the ink flow path undergoes a piezoelectric effect deformation. Then, the flow path volume is changed and ink is jetted from the jetting device.

[0009]

[Example] Hereinafter, an example embodying the present invention will be shown in Figure 1.
This will be explained in detail with reference to FIGS. For convenience, the same parts as in the conventional example will be described with the same reference numerals.

FIG. 6 is a diagram showing the main parts of an inkjet printer equipped with a droplet ejecting device according to an embodiment of the present invention, in which a platen 36 supporting paper 58 is rotatably connected to a frame 40 by a shaft 38. and is driven by a motor 42. A droplet ejecting device 44 is provided opposite the platen 36. The droplet ejecting device 44 is mounted on a carriage 48 together with an ink supply device 46 . The carriage 48 is slidably supported by two guide rods 50 arranged parallel to the axis of the platen 36, and is coupled to a timing belt 56 wound around a pair of pulleys 52. Then, one pulley 52 is rotated by the motor 54, and the timing belt 56 is fed, thereby moving the carriage 48 along the platen 36.

FIG. 1 is a cross-sectional view of the array 1 used in the droplet ejecting device 44. The array 1 is polarized in the direction of the arrow 26, and has side walls 60a, 60c, 60e.
, 60g and having a plurality of downwardly opening parallel grooves, and side walls 60b, 60d, 60f, which are polarized in the direction of arrow 28.
, 60h and a lower piezoelectric ceramic plate 3 having a plurality of upwardly opening parallel grooves formed in the side wall 60.
The ink flow channels 4a, 4b, 4c, 4d, and 4e having rectangular cross sections are formed by bonding through the adhesive layer 12 at some portions. The ink flow path 4 is filled with conductive ink, for example, water-soluble ink.

Each array 1 is provided with an electrical circuit as shown in FIG. Ink channels 4a, 4b
, 4c, 4d, and 4e are separately connected to the driving LSI chip 16 via the driving line 17,
Clock line 18, data line 20, voltage line 2
2 and a ground line 24 are also connected to the driving LSI chip 16. The ink flow path 4 has first and second ink channels that are not adjacent to each other.
The first and second groups are successively driven by successive clock pulses supplied from the clock line 18. The data in the form of a multi-bit word appearing on the data line 20 determines which ink flow path 4 in each group is to be activated, and the driving L
The voltage V of the voltage line 22 is applied to the ink in the ink flow path 4 of the group selected by the circuit of the SI chip 16. Side walls 6 on both sides of the ink flow path 4 selected by this voltage
0 undergoes deformation due to the piezoelectric effect, and therefore all ink flow paths 4 in each group become operable. Ink in the ink flow path 4 of the same group that is not activated at this time,
Ink in all ink channels 4 belonging to other groups is grounded.

FIG. 2 shows a case where the ejecting device 34c is selected according to predetermined print data, and the ink flow path 4
The voltage V of the voltage line 22 is applied to the ink in the channel c, and the ink in the other ink channels 4a, 4b, 4d, and 4e is grounded. Since an electric field perpendicular to the polarization direction is applied to the side walls 60c, 60d, 60e, and 60f, the side walls 60c, 60d and the side wall 60 are deformed by the piezoelectric thickness shear effect.
e and 60f are deformed into a dogleg shape toward the ink flow path 4c between them. Therefore, the volume of the ink flow path 4c decreases, and the ink within the flow path is ejected from an orifice (not shown). Note that, for example, when another ejecting device 34b is selected, the side walls 60a, 60b, 60c, and 60d are deformed and the ink in the ink flow path 4b is ejected.

The array 1 is easily manufactured by the following manufacturing method.

As shown in FIG. 3(a), first, a two-stage step-shaped ceramic material made of lead zirconate titanate (PZT), which has ferroelectric properties, is polarized in the direction of arrow 28. Prepare a plate, thin piezoelectric ceramic 3b
The lower ceramic plate 3 is manufactured by cutting a plurality of parallel grooves from the piezoelectric ceramic plate 3a toward the thick piezoelectric ceramic plate 3a using a rotating diamond cutting disk, a laser, or the like to form an ink flow path 4. At this time, as shown in FIG. 3(b), the ink flow path 4 is stopped at a place slightly cut into the thick piezoelectric ceramic 3a. As shown in FIG. 3(c), a drive line 17 and a driving LSI chip 16 are arranged in the thick piezoelectric ceramic 3a portion of the lower piezoelectric ceramic plate 3, and the thin piezoelectric ceramic of the lower piezoelectric ceramic plate 3 is The upper piezoelectric ceramic plate 2, which has been polarized in the direction of the arrow 26, is bonded to the ceramic portion 3b at the side wall 60 portion, with the piezoelectric ceramic portion 3b turned upside down.

The part where the ink flow path 4 is slightly cut into the thick piezoelectric ceramic 3a is the ink supply port 1.
form 4. An array 1 is obtained by joining an orifice plate 8 having orifices 10 for ejecting droplets corresponding to the ink channels 4 in front of the ink channels 4. Each ink flow path 4 has a vertical cross-sectional shape as shown in FIG. 4 and is connected to an ink supply port 14 that opens upward. The ink supply port 14 is not connected to the ink supply device 46, and ink droplets are dropped from the ink supply device 46 as necessary. This prevents the inks in each ink flow path 4 from being electrically short-circuited. Also,
The ink in the ink flow path 4 at both left and right ends of the ink flow path 4 that is ejected serves only as a driving electrode, and therefore is not ejected.

As described above, in the droplet injection device of this embodiment,
Manufacturing costs are reduced because the process of forming metal electrodes and the passivation process for preventing corrosion of the electrodes, which were conventionally necessary, are no longer necessary.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be modified in many ways without departing from the spirit thereof. For example, the ink need not be limited to water-soluble ink, and any ink may be used as long as it has conductivity. Furthermore, the displacement mode of piezoelectric ceramics is not limited to the piezoelectric thickness shear effect, and may be any mode. For example, FIG. 5 shows a configuration example in the case of displacement mode of piezoelectric longitudinal effect. Although a metal electrode 6 is provided as a common ground electrode, there is no need to form divided electrodes corresponding to the ink channels 4.

[0019]

As is clear from the above explanation, the droplet ejecting device of the present invention makes the ink in the ink flow path conductive and uses it as the drive electrode, so the process of forming the metal electrode,
This eliminates the need for the passivation process and reduces manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an array forming part of a droplet ejection device.

FIG. 2 is a diagram showing a state in which the array is provided with an electric circuit.

FIG. 3 is a perspective view showing the manufacturing process of the array.

FIG. 4 is a longitudinal cross-sectional view of the array.

FIG. 5 is a cross-sectional view of an array forming part of a droplet ejecting device in another embodiment.

FIG. 6 is a perspective view showing the main parts of an inkjet printer equipped with a droplet ejecting device.

FIG. 7 is a cross-sectional view of an array forming part of a conventional droplet ejecting device.

[Explanation of symbols]

2 Piezoelectric ceramics (upper piezoelectric ceramics plate) 3
Piezoelectric ceramics (lower piezoelectric ceramics plate) 4
Ink flow path 34 Ejection device 44 Droplet ejection device

Claims (1)

[Claims] 1. A droplet ejecting device including a plurality of ejecting devices that eject ink in an ink flow path by changing the volume of the ink flow path using a piezoelectric transducer. A droplet ejecting device characterized in that is a conductive ink.