JPS60259457A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To reduce the consumption of electrodes to a practically negligible extent by a method in which plural air outlets and plural ink outlets are arranged, and the surface of each peripheral electrode at the ink outlets is made up of a rhodium metal electrode. CONSTITUTION:The layer 10 filled with ink uses an oily ink on the market, having a specific resistivity of 10<6>OMEGAcm. Electrodes A1-An as the peripheral electrodes of each ink outlet are formed by the deposition of rhodium on the chromium base of the surface of a base plate 3, and the thickness of rhodium film is 200Angstrom -3mum. In the deposition of rhodium vapor, a 20% wider mask than the mask for the vapor deposition of chromium is used, and the base plate 3 is turned in relation to the vapor source. For taking out the electrodes so formed by vapor deposition on the base plate 3, the electrode is partly exposed to the outside and an ink chamber is provided. By covering the surface of the electrode formed on the periphery of the ink outlet with rhodium, the consumption of the electrodes can be suppressed to the minimum possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an inkjet recording head that uses electrostatic force to eject ink liquid from minute openings to form an image such as a single figure on a recording material. .

Conventional Structure and Problems The present applicant previously proposed an inkjet recording head that uses air flow and electrostatic force. FIG. 1 shows one example of this, which is shown in Japanese Patent Application Laid-Open No. 57-120462. To briefly describe the principle of ejecting ink liquid, in FIG. 1, an insulating air nozzle plate 2 is provided with air ejection ports 1, and the insulating ink nozzle plate is inserted approximately parallel to the air nozzle plate 2. 3 are arranged, and the ink nozzle plate 3 is provided with air discharge ports 4.

Air flows into the air supply path 8 from the air supply source 2o, is made uniform in the annular air chamber 9, and forms an air layer 70 created by the air nozzle plate 2 and the ink nozzle plate 3.
Air flows in from the periphery and flows out from the air outlet 1.

On the other hand, the ink chamber 1° adjacent to the ink discharge port 4 communicates with an ink reservoir 11 via an ink supply path 6, and the ink in the ink reservoir 11 is kept at a constant pressure by air from an air supply source 2o. is being applied. This constant pressure is adjusted by the pressure adjustment mechanism 21 as the case requires. This is because when the inkjet recording head is not driven, the air pressure near the ink ejection port 4 and the ink pressure in the ink ejection port 4 or the ink chamber 1o are approximately equal, and the meniscus of ink in the ink ejection port 4 is kept stationary. This is to make adjustments so that the

The signal source 5 includes an electrode 12 provided around the front surface of the air outlet 1 and an electrode 16 provided around the back surface of the ink outlet 4.
is connected to create a potential difference between electrode 12 and electrode 16. Due to the electrostatic force caused by this potential difference, the meniscus of the ink liquid generated at the ink ejection port 4 is
is stretched in the direction of Furthermore, since a constant air flow flows out from the air outlet 1 through the air layer 7, when the meniscus mentioned above is stretched beyond a certain length, it is accelerated by the air flow and the air outlet Fly from 1.

In order to increase the recording speed of an inkjet recording head with such a configuration, air discharge ports 1 and ink discharge ports 4 must be
It is sufficient to have a multi-structure in which a plurality of are arranged. This configuration is shown in Japanese Patent Application Laid-Open No. 58-220768, so a description thereof will be omitted.

Since the operating method of these ink jet recording heads uses electrostatic force, it is necessary to create a potential difference of about 900 to 1200 V between the air discharge port 1 and the ink discharge port 4. As an example, the electrode 12 of a plurality of air ejection ports 1 may be shared, and the electrode potential around the ink ejection ports 4 may be individually changed to perform the necessary ejection operation. For these electrode materials, materials such as Cu and Cjr, which are inexpensive and easy to use, have been used, made by etching or vapor deposition. In the multiple electrodes around the exit, potential differences occur between these individual electrodes, and as a result, these electrodes tend to wear out, and when the potential difference between the electrodes is actually changed, it takes about 3 to 40 hours to reach a practical level. The occurrence of electrode wear, which was a problem, was observed.

OBJECTS OF THE INVENTION The present invention is intended to solve the above-mentioned problem of electrode wear, and aims to reduce the wear of the electrodes to a level that does not pose a problem in practical use.

Structure of the Invention The present invention is an inkjet recording device in which a plurality of air discharge ports and ink discharge ports are arranged, and each peripheral electrode of each ink discharge port is constituted by an electrode having at least an electrode surface made of rhodium metal.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 schematically shows the cross-sectional structure of the electrode, excluding the air outlet. The other parts are the same as those in FIG. 1, so their illustration is omitted. 10 in the figure is a layer filled with ink, and in this example, commercially available oil-based ink is used, and specific resistance f
A material with f10 ΩG was used. Also electrode person 1~mu nid
These are electrodes around each ink ejection port. In this embodiment, a chromium layer is formed as a base layer on the surface of the substrate 3 by vapor deposition, and rhodium is redeposited thereon. The thickness of rhodium is 2
008 to 3μ. In vapor deposition of rhodium, a mask 20% wider than the underlying chromium vapor deposition mask was used, and the substrate 30 was rotated with respect to the vapor deposition source. In order to take out the deposited substrate 3o, an ink chamber is provided in such a manner that a part of the electrode is completely exposed outside. In this configuration, Table 1 shows the time required for each electrode to withstand actual use when a potential difference of eoov is generated between adjacent electrodes with respect to the electrodes ˜An in the figure.

(Left below) Table 1 As can be seen from Table 1, rhodium metal greatly improves the life of the electrode, and if it is 500% or more, there will be no problem in actual use. In this case, the thickness of the rhodium vapor deposition film is 3 μm.
If the rhodium thickness exceeds m, the effect will not be so great, so for practical purposes, the rhodium film thickness is preferably in the range of 5,008 to 3 μm.

It should be noted that almost the same results were obtained even if the rhodium film was directly deposited by sputtering without providing a chromium layer.Table 2 shows the rhodium film formed by plating. In this example, after etching the copper on the substrate, nickel was plated as an underlayer, and rhodium was deposited on top of it by plating. The ink used and the test method are the same as in the case of vapor deposition described above.

Table 2 The plating film thickness is the average value of several points.

From the results in Table 2, the film formed by plating needs to be somewhat thicker than that formed by I vapor deposition. The reason for this seems to be the pinhole. In any case, if it is 5000A or more, there will be no practical problem.

The above explanation has been made using the head shown in Figure 1, but any inkjet head can be used as long as it has electrodes arranged in the ink and discharges the ink by fully controlling the potential of the electrodes. It is clear that it can be applied to

Effects of the Invention As described above, the present invention covers the surface of the electrode formed around the ink ejection opening of an inkjet recording head that controls the ejection of oil-based ink using electrostatic force, thereby minimizing electrode wear and reducing the holding length. This makes it possible to extend the lifespan.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an inkjet recording apparatus using electrostatic force to which the present invention is applied, and FIG. 2 is a sectional view of a main part of an inkjet wiring head according to the present invention. 1... Air discharge port, 2... Air nozzle plate, 3... Ink nozzle plate, 4... Ink discharge port, 6... - Signal source, 6... Ink supply path, 7... Air layer, 8... Air supply path, 9... Air chamber, 1o... ...Ink chamber, 11...Ink reservoir, 12...
Electrode, 13...Head body, 15, A,
~5... Back electrode of ink ejection port, 20...
...Air supply source, 21...Pressure adjustment mechanism.

Claims (1)

Scope of Claims: (1) In an ink chamber having an opening through which ink is discharged, a plurality of first electrodes coated with rhodium metal are arranged near the opening, and the first electrode and the ink chamber An inkjet recording head characterized in that ink is ejected by creating a potential difference between the inkjet recording head and a second electrode provided outside the inkjet recording head. @) Claim 1 consisting of a configuration in which the thickness of the rhodium metal in the first electrode is in the range of 5008 to 7μ.
The inkjet recording head described in . (3) The ink jet recording head according to claim 1, wherein the first electrode is formed of rhodium metal on a base metal other than rhodium.