JPS59165662A - Ink jet injector - Google Patents

Abstract

PURPOSE:To inject ink rapidly and stably without being limited by recording colors by electrolyzing the water contained in the ink components in a nozzle to generate gas and dividing ink into small drops by said gas while injecting ink in a jet shape by pressure on the expansion of the gas. CONSTITUTION:Water as the principal ingredient of ink 18 is electrolyzed by mounting electrodes 14, 15 in a nozzle 12 and applying voltage, H2 is generated from the electrode 14 and O2 from the electrode 15 respectively to form bubbles 21, 22, and an ink section 18A existing in the vicinity of an opening section is cut by the expansion of the bubbles 21, 22 while being injected in the external direction from the nozzle 12 as an ink drop 23. EFFECT:An ink jet injector need not be preheated, and the purpose can be attained economically by the simple device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet ejection device used in an inkjet printer.

[Technical Background of the Invention] Inkjet printers can record on plain paper, and
It has the advantage of not requiring development or fixing and low noise. The recording methods used in this printer can be roughly divided into two types: ■ A method in which inkjet is continuously ejected and selectively adheres to the paper, and ■ A method in which ink is ejected only when printing. can. In the former method, it is necessary to control the path of the ink by charging and deflecting the ink. For this reason, these control mechanisms not only become complicated, but also require space for arranging an ink circulation system, etc., making it impossible to make the printer sufficiently compact.

On the other hand, the latter method can be subdivided into several types depending on the ejection principle of the inkjet ejection device.Among these, inkjet ejection devices that perform recording using a method called magnetofluidography use magnetic ink and use it for control recording. A bump is placed on the needle, which is attracted by an electric field and ejected. For this reason, when attempting to perform color recording using this device, not only are the recorded colors limited by the color of the magnetic material itself, but there is also a risk that the ink may change color due to oxidation of the magnetic material. In addition, in an inkjet ejecting device that performs recording using a method called a bubble jet, ink is heated and agitated to create air bubbles, and the pressure generated at this time causes jet ejection. For this reason, a thermally stable ink is required, but there is a problem in that it is difficult to adjust the ink.

[Objective of the Invention] In view of the above circumstances, an object of the present invention is to provide an inkjet ejecting device that is not limited in recorded colors and can perform stable ejection [Means for achieving the object] The present invention includes a gas generating means that electrolyzes water, which is the main component of ink, to generate gas, and a nozzle that divides the ink into small droplets using the generated gas and jets them using the pressure when the gas expands. The above-mentioned object is achieved by equipping an inkjet jetting device with the following.

The present invention will be described in detail below with reference to Examples.

[Example] FIG. 1 shows the appearance of the print head.

The print head 10 includes an ink ejection surface 11 whose negative side has a length approximately equal to the width of a sheet of paper (not shown) on which recording is performed. On the ink ejection surface 11, a large number of ink jet ejection devices are arranged in a row at equal intervals in the length direction of the ink ejection surface 11.

In a printer that records A4 size at a recording density of 8 nozzles/mm, for example, each side of the opening of each nozzle 12 of the inkjet jetting device is set to approximately 60 μm, and in this case, a total of 1728 nozzles 12 are the same. <60 μm apart.

FIG. 2 shows the main parts of the inkjet jetting device. The nozzle 12 is composed of a columnar insulating cavity, and an upper electrode 14 and a lower electrode 15 are disposed at vertically opposing positions on an inner wall slightly recessed from the opening. A DC power supply 17 is connected between the upper electrode 14 and the lower electrode 15 via a switch 16. When the switch 16 is turned on, the ink (not shown) in the nozzle 12 is electrolyzed, resulting in jet spraying. The lower electrode 14 and the lower electrode 15 are made of metal such as nickel, iron, nickel-plated iron plate, gold or silver-plated iron plate, and are provided on the inner surface of the nozzle by vacuum deposition or a known method.

FIG. 3 shows the principle of jet jetting by this inkjet jetting device. Of these figures, (A) shows a standby state. Ink 18 is inside the nozzle 12.
is filled. These inks 18 are drawn up from an ink tank (not shown) by capillary action.

Ink 18 is made by dissolving pigments and conductive substances in approximately 80% water, and has a conductivity of 10-1 to 10-2 [Ω-1・C
It has been adjusted to "1".

FIG. 2B shows an initial state in which a recording voltage is applied to both electrodes 14 and 15.

Several volts to several tens of volts are applied to both electrodes 14 and 15.

When a voltage printing pulse is applied, hydrogen flows from the upper electrode 14, which is a cathode electrode, and from the lower electrode 15, which is an anode electrode.
Oxygen is generated from each gas, forming gas bubbles 21,22. These bubbles 21 and 22 grow rapidly, as shown in the same figure (C).
Combine as shown. As a result, the ink portion 18A that was present near the opening is separated. ink part 1
8A is given outward kinetic energy as the bubbles 21 and 22 grow, and is finally ejected as an ink droplet 23 as shown in FIG. 8D.

The above operation is performed by applying a printing pulse of 1 to several hundred microns.
Finishes in seconds. The ink droplet 23 collides with a recording paper placed at a short distance in front of the inkjet ejection device 10, and one dot is printed. In reality, a large number of inkjet ejecting devices of the print head 10 shown in FIG. 1 are selectively driven in accordance with image signals, and one line of printing is performed at one time. When recording for one line is completed, the paper or the inkjet jetting device 10 is moved by one line in the sub-scanning direction, and the next printing operation is started. At this time, the ink 18 in the nozzle 12 has been restored to the state shown in FIG. 3(A) due to capillary action.

In this inkjet ejecting device, by appropriately setting the voltage of the printing pulse and the size of the ink droplets, the IKI
It is possible to perform recording at a frequency of Iz culm, and a sufficient recording speed can be achieved. Moreover, since the ink does not need to contain a magnetic substance and can be used at room temperature, it can be used stably for a long period of time.

[Modification 1 FIG. 4 shows another example of the nozzle portion of the inkjet spraying device. Only the lower electrode 15 is arranged in the nozzle 25, and the other inner wall portions are made of an insulator. A metal plate or metal rod made of nickel or the like is disposed in an ink path (not shown) leading to the ink tank, and this constitutes the other electrode.

5(A) to (D) correspond to FIG. 3(Δ) to (D>) and represent the principle of jet injection in this modification.The same parts as in FIG. The same reference numerals are used, and detailed explanations are omitted.In this modification of the inkjet jetting device, the distance between the lower electrode 15 and the other electrodes is large, and only the bubbles 22 generated by the lower electrode 15 are separated. is directly used as the energy for jet injection. Therefore, in order to ensure the same recording speed under the same conditions as in the previous embodiment, it is necessary to set the voltage of the printing pulse to be somewhat higher. However, the voltage of the nozzle 25 Since it is only necessary to arrange the lower electrode 15 on the inner wall, there is an advantage that manufacturing of the inkjet spraying device is simplified and costs can be reduced.

In this example, the inkjet jetting devices were arranged across the entire width of the paper so that recording of one line could be completed at once, but if high-speed recording is not required, one to several dozen inkjet jetting devices could be installed. It may also be arranged in a print head and recorded while being moved in the main scanning direction by a carriage. Also, it goes without saying that the cross section of the nozzle need not be square or rectangular.

[Effects of the Invention] 1/- As explained above, according to the present invention, bubbles are generated by electrolysis, so there is no need to preheat the inkjet ejecting device, and the recording operation can be started quickly. Furthermore, the configuration is simpler than other devices that eject ink using pressure waves generated from electromechanical transducers, etc., and the device can be manufactured at low cost and with high reliability.

[Brief explanation of the drawing]

Fig. 1 is an external view of a print head using an inkjet ejection device according to an embodiment of the present invention, Fig. 2 is a perspective view showing the main parts of the inkjet ejection device, and Fig. 3 (A
) to (D) are diagrams for explaining the principle of jet jetting by this inkjet jetting device, FIG. 4 is a perspective view showing essential parts of an inkjet jetting device in a modification of the present invention, and FIG. 5(A) -(D) are diagrams for explaining the principle of jet injection by the device of this modification. 12.25... Nozzle, 14... Upper electrode, 15... Lower electrode, 8- 18... Ink, 23... Ink drop. Applicant Fuji Xerox Co., Ltd. Representative Patent Attorney Umeo Yamauchi

Claims (1)

[Scope of Claims] 1. Gas generating means that electrolyzes water, which is the main component of ink, to generate gas, and the generated gas divides the ink into small droplets, and the pressure when the gas expands is used to split the ink into small droplets. An inkjet ejection device comprising: a nozzle for ejecting a jet. 2. The inkjet spraying device according to claim 1, wherein one or both of the electrodes for electrolysis are disposed near the opening of the nozzle.