JPH03193455A - Ink-jet head - Google Patents

Abstract

PURPOSE:To make elements forming ink drops dense by a method wherein the present device is constructed of members including a plate-like member made of a material liable to suffer mechanical strain in an electric field and interdigital electrodes provided on one side of the plate-like member, and ink is brought into contact with the surface of the other side of the plate-like member that is opposite to the side on which the interdigital electrodes are provided. CONSTITUTION:Interdigital electrodes 2 made of a material including gold as a principal ingredient are provided in a shape of concentrical circle on a plate-like member made of sliced mono-crystal lithium niobate, a material liable to suffer mechanical strain with an electric field, with polishing applied, and the above-mentioned interdigital electrodes are connected to an electric source for driving. Walls 4 are provided to the other side of the plate-like member 1 on which the interdigital electrodes are provided so that the walls come between the interdigital electrodes 2. Areas encircled with the walls 4 and the plate-like member 1 are filled with ink 5 that is supplied from an ink supplying member. With high-frequency or pulsating current applied to the interdigital electrodes 2 from the electric source for driving, elastic wave is induced to occur to the plate-like member 1. The elastic wave propagates to the ink 5, letting ink drops 6 make optional flying from the free surface of the ink 5. Thereby two-dimensional arrangement of the interdigital electrodes 2 becomes possible and elements of ink drops can be made highly dense.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet printer that selectively deposits ink droplets onto an image recording medium.

[Conventional technology]

As a conventional technology, there is an inkjet head technology that utilizes surface acoustic waves using concentric interdigital electrodes (US
P4697195).

Furthermore, in order to increase the recording speed of an inkjet head, there is a method in which a plurality of interdigital electrodes are provided and ink droplets are ejected simultaneously.

[Problem to be solved by the invention]

However, in the prior art, since the electrodes were provided on the surface in contact with the ink, there was a problem in that it was difficult to arrange the interdigital electrodes two-dimensionally. In addition, in the conventional technology, since the electrode is in contact with the ink, there are problems in that the electrode is corroded by the ink components, conductive ink cannot be used, and the ink components adhere to the electrode due to electrophoresis. Ta.

Therefore, the object of the present invention is to solve these problems.The purpose of the present invention is to be able to form elements that form ink droplets with high density, to have a wide selection range of usable inks, and to achieve stability. Our goal is to supply inkjet heads with excellent durability.

[Means to solve the problem]

The inkjet head of the present invention has a plate-like member made of a material that is mechanically strained by an electric field, and interdigital electrodes provided on one surface of the plate-like member, and the interdigital electrodes are arranged between the plate-like member and the interdigital electrodes. The ink is in contact with the surface of the plate member on the opposite side.

In addition, the interdigital electrode has a concentric curved portion.

The invention is also characterized by further comprising a slit plate having a slit-shaped opening or a nozzle plate having a nozzle-shaped opening, and supplying the ink between the slit plate or the nozzle plate and the plate-shaped member. shall be.

[Effect]

When interdigital electrodes are placed on the surface of a material that undergoes mechanical strain due to an electric field, such as a piezoelectric material or an electrostrictive material, and a voltage is applied between the crossed electrodes, tensile and compressive strains corresponding to the interdigital electrodes are applied near the material surface. induced. When the voltage applied between the electrodes is pulsed or periodic, the induced strain propagates as an elastic wave. The propagating elastic waves become surface waves when the thickness of the material is sufficiently thicker than the interdigital electrode spacing, but when the material thickness becomes about the same as the electrode spacing, it propagates in the thickness direction as well, and Distortion due to elastic waves is also induced on the opposite surface. At this time, if the ink is in contact with the surface opposite to the surface on which the electrodes are provided, leakage elastic waves propagate into the ink. When the elastic waves propagating through the ink reach the free surface of the ink, the ink is turned into fine droplets or atomized and ejected onto the recording paper.

When the interdigital electrode has concentric curved portions, the induced elastic waves have a component that converges toward the center of the arc, and the elastic waves leaking into the ink also converge at one point in the ink. Therefore, it is possible to form minute ink droplets, and at the same time, the energy density of the elastic waves in the ink is increased, making it possible to fly the ink with lower energy.

〔Example〕

Embodiments of the invention are described in detail below.

In the drawings used to explain the following embodiments, the drive power supply device and the wiring means connecting the drive power supply device and each electrode are not shown because they are not related to the gist of the present invention.

In the example shown in FIG. 1, a single crystal of lithium niobate, which is a material that causes mechanical strain due to an electric field, is sliced into a 100 μm thick plate-shaped member 1 and polished using ordinary photolithography. Interdigital electrodes 2 made of gold as a main component were formed in concentric circles with an electrode period of 200 μm.

The interdigital electrode 2 is provided with contacts 3 for wiring,
It is connected to a drive power supply unit (not shown). Although four interdigital electrode elements are formed in FIG. 1, the number of interdigital electrode elements is not limited. FIG. 2 is a diagram showing the configuration of an inkjet head using the plate-like member 1 shown in FIG. It is formed to be located in the middle of the electrode 2. Ink 5 is supplied to the area surrounded by the wall 4 and the plate member 1 from an ink supply section (not shown). IMHz is supplied to the interdigital electrode 2 from a drive power supply unit (not shown).
By applying high frequency waves or pulses of 100 MHz to 100 MHz, elastic waves are induced in the lithium niobate plate member 1. The induced elastic waves propagate to the ink 5 from the contact area between the lithium niobate plate member 1 and the ink 5,
Ink droplets 6 are selectively ejected from the free surface of ink 5.

In FIG. 3, which is another embodiment of the present invention, the material of the plate member 1 is lead zirconate titanate, which has a high electromechanical coupling coefficient, and the interdigital electrodes 2 have a concentric ring structure to increase the integration density. It has a structure in which both sides are trimmed. FIG. 4 is a diagram showing the configuration of an inkjet head using the plate-like member 1 shown in FIG. The aperture 10 and interdigital electrode 2 are combined so that their central axes coincide. The space between the plate member 1 and the slit plate 11 is filled with ink 5. When a high frequency or pulse voltage is applied to the interdigital electrodes 2 from a drive power source (not shown) through the contacts 3, the elastic waves induced in the plate-shaped member 1 are transmitted to the surface on which the interdigital electrodes 2 are provided. The ink is propagated into the ink 5 from the opposite surface, converges on the slit-shaped opening 10 , and ejects ink droplets from the slit-shaped opening 10 .

FIG. 5 shows the slit-shaped opening 10 of the embodiment shown in FIG.
FIG. 4 is a diagram showing an example in which the opening portion 12 is changed to a single slit-like opening portion 12.

FIG. 6 is a diagram showing another embodiment of the present invention, in which lead zirconate titanate, which has a high electromechanical coupling coefficient, is used as the material of the plate member 1, and the interdigital electrodes 2 have a concentric ring structure to increase the integration density. It has a staggered structure. FIG. 7 is a diagram showing the configuration of an inkjet head using the plate-like member 1 shown in FIG. The opening 13 and the interdigital electrodes 2 are combined so that their central axes coincide. The space between the plate member 1 and the nozzle plate 14 is filled with ink 5. When a high frequency or pulse voltage is applied to the interdigital electrodes 2 from a drive power source (not shown) through the contacts 3, the elastic waves induced in the plate-shaped member 1 are transmitted to the surface on which the interdigital electrodes 2 are provided. The ink is propagated into the ink 5 from the opposite surface, converges on the nozzle-shaped opening 13 , and ink droplets are ejected from the nozzle-shaped opening 13 .

Although the embodiments of the present invention have been described above, other materials such as zinc oxide and lead titanate can be used as the material for the plate member, and the present invention is not limited to these materials.

〔Effect of the invention〕

As described above, according to the present invention, an interdigital electrode is provided on one side of a plate-shaped member made of a material that causes mechanical distortion due to an electric field, and a high frequency or pulse voltage is applied to the interdigital electrode. Ink can be made to fly by propagating elastic waves from the surface of the plate member opposite to the surface on which the interdigital electrodes are provided into the ink that is in contact with this surface. 2 interdigital electrodes
It becomes possible to arrange the elements dimensionally, and the effect of increasing the density of the elements can be obtained. Further, since the electrode portion and the ink are not in contact with each other, it is possible to use conductive ink or ink that aggregates due to an electric field, and the effect of widening the selection range of ink can be obtained. Further, since the structure is simple, an effect can be obtained in that an inkjet head with excellent stability and durability can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of interdigital electrodes used in the inkjet head of the present invention. FIG. 2 is a diagram showing an embodiment of the inkjet head of the present invention using the interdigital electrodes shown in FIG. 1. FIG. 3 is a diagram showing one embodiment of interdigital electrodes used in the inkjet head of the present invention. Fourth
This figure shows an embodiment of the inkjet head of the present invention using the interdigital electrodes shown in FIG. 3. FIG. 5 is a diagram showing an embodiment of the inkjet head of the present invention using the interdigital electrodes shown in FIG. 3. FIG. 6 is a diagram showing one embodiment of interdigital electrodes used in the inkjet head of the present invention. FIG. 7 is a diagram showing an embodiment of the inkjet head of the present invention using the interdigital electrodes shown in FIG. 6. 100. Plate member, 200. interdigital electrode, 501. Ink, 11. ,,slit plate,14,, nozzle plate or more

Claims (4)

[Claims] (1) A plate-shaped member made of a material that causes mechanical distortion due to an electric field, and an interdigital electrode provided on one surface of the plate-shaped member, and an interdigital electrode on the opposite side of the interdigital electrode with the plate-shaped member in between. An inkjet head characterized in that ink is in contact with the surface of the plate-like member. (2) The inkjet head according to claim 1, wherein the interdigital electrodes have concentric curved portions. (3) having a slit plate having a slit-shaped opening;
3. The inkjet head according to claim 1, wherein the ink is supplied between the slit plate and the plate-like member. (4) The inkjet head according to claim 1 or 2, characterized in that it has a nozzle plate having a nozzle-shaped opening, and supplies the ink between the nozzle plate and the plate-like member. .