JPS6179668A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To enable the stable emission and stoppage of ink, by constituting the title recording head so as to emit ink by electrostatic force acting on the ink held to an ink emitting port and the acceleration due to an air stream and forming the surface opposed to the ink emitting port from a member oil- repellent to the ink. CONSTITUTION:A thin film 10 comprising a material hardly wetted with ink is applied to the surface opposed to the ink emitting orifice 1 of a flat plate 10 having an air emitting orifice provided thereto by drilling. By coating this thin film 10, the ink is hardly adhered to the interior or vicinity of the air emitting orifice 2 and, even if adhered, said ink is carried by the flow of an air stream, which is supplied from an air layer 4 and flowed out from the air emitting orifice 2, and flows out to the outside of the air emitting orifice 2. Because the speed of the air stream in the air emitting orifice is high, it is almost prevented that a large amount of ink is adhered and the removal thereof becomes impossible. By this method, concentrated line of electric force can be generated always stably and capacity is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an inkjet recording apparatus that records characters, figures, etc. on a recording material by ejecting ink from minute openings.

Structure of a conventional example and its problems FIG. 1 shows an inkjet recording head described in Japanese Patent Laid-Open No. 57-120452, which utilizes air flow and electrostatic force. An air discharge port 2 from which air flows out at all times is installed opposite the ink discharge port 1, and a synergistic effect of the electrostatic force generated by the electrode 3 provided in front of the air discharge port 2 and the accelerating force caused by the air flow. This is to eject ink.

FIG. 2 is an enlarged sectional view of the nozzle portion of the inkjet recording head of FIG. 1. An ink discharge port 1 and an air discharge port 2, which are bored in a flat plate, are arranged concentrically, and an air flow is supplied from an air layer 4 formed by the two flat plates and flows out from the air discharge port 2. On the other hand, the ink discharge port 1 is filled with ink, and a meniscus 6 is formed at the exit portion.

The air discharge port 2 is formed by perforating an insulator having a specific resistance of approximately 1 d0Ωα or more, and an electrode 3 is provided around the outlet. When a potential difference is generated between the electrode 3 and the ink inside the ink discharge port 1, electric lines of force 6 as shown in FIG.
occurs, the ink meniscus is stretched in the direction of the air outlet 2, and the air outlet 2 is exposed to the accelerating force of the air flow.
pass through and fly outward.

The electric lines of force 6 take the form as shown in FIG. 2, and the air outlet 2
An electric field is generated in the air from the inside of the insulator to the ink ejection port 1 because the dielectric constant of the insulator constituting the air ejection port 2 is higher than 1. This concentration of electric lines of force has the effect of increasing the suction force of the meniscus, making it possible to eject and stop ink at a low voltage.

Now, in the inkjet recording head as described above, ink often adheres to the inside or around the air discharge ports 2. FIG. 3 shows how ink 7 adheres to the inside of the air outlet 2 or in the vicinity thereof. Such ink adhesion occurs, for example, when an impactful pressure wave is propagated to the ink ejection port 1 or when the balance between air pressure and ink pressure is disrupted. It was found that the state of the electric lines of force changes.

Inkjet recording heads that use electrostatic force to suck ink generally use ink with a specific resistance of about 105 to 109Ω, and similar inks are used in the inkjet recording head shown in Figure 1. . Therefore, the adhered ink 7 can be considered to be more conductive than the insulating material in which the air outlet 2 is perforated, and when the adhered ink 7 is in contact with the electrode 3, the adhered ink 7 itself is connected to the electrode. It has the same potential as 3. Therefore, as shown in FIG. 3, electric lines of force 8 are generated between the adhered ink 7 and the meniscus 5. Since such electric lines of force 8 lack symmetry and are unstable, the direction in which the meniscus 5 is attracted is not determined, resulting in an unstable ink ejection state.

OBJECTS OF THE INVENTION It is an object of the present invention to realize an inkjet recording head that can always stably eject and stop ink while preventing ink from adhering to the inside of or near the air ejection openings.

Structure of the Invention The present invention provides an air discharge port through which an air flow flows out and an ink discharge port in which ink is held, which are installed to face each other, and an electrostatic force acting on the ink held in the ink discharge port and the air discharge port. The inkjet recording head is configured to eject ink using acceleration force generated by a flow, and at least a surface of a member having an air ejection port that faces the ink ejection port is made of an oil-repellent member to the ink.

DESCRIPTION OF THE EMBODIMENT FIG. 4 shows an embodiment of the present invention. In FIG. 4, a thin film 10 made of a material that is difficult to wet with ink is coated on the surface of a flat plate 9 having air discharge ports 2 perforated therein, which faces the ink discharge ports 1. As shown in FIG.

The thin film 10 is made of an inert material such as Teflon. When such a thin film 1o is coated, ink is difficult to adhere to the inside or vicinity of the air discharge port 2, and
Moreover, even if it adheres, it is carried by the air flow supplied from the air layer 4 and flowing out of the air outlet 2, and is blown away from the air outlet 2.

Note that the thin film 1o in FIG. 4 is not formed inside the air outlet 2, but since the flow rate of the air flow is fast inside the air outlet 2, a large amount of ink adheres to it, making it impossible to remove it. Very rarely. However, it can be said that it is safer and more reliable to apply a material that is difficult to get wet with ink also inside the air outlet 2.

Another method is to mirror polish the surface of the member 9 having the air outlet 2 facing the ink outlet 1, which is also very effective. This is because, in general, wettability with respect to liquid changes depending on the roughness of the surface of the material, and wettability is often significantly degraded when the material becomes mirror-finished.

Furthermore, as another method, there is a method in which the member having the air outlet 2 itself is made of an inert material such as Teflon, and it is clear from the above that this method is effective.

Effects of the Invention As explained above, the present invention provides an inkjet recording head in which at least the ink ejection port side of a member having an air ejection port is combed to prevent it from getting wet with ink, so that ink does not adhere to the inside of the air ejection port or the vicinity thereof. Since it is possible to always generate stable and concentrated electric lines of force, an inkjet recording head with stable performance can be provided.

[Brief explanation of the drawing]

1 to 3 are sectional views showing conventional examples of an ink jet recording head, and FIG. 4 is a sectional view showing an embodiment of an ink jet recording head according to the present invention. 1... Ink discharge port, 2... Air discharge port, 3... Electrode, 7... Adhesive ink,
6, 8... Lines of electric force, 10... Thin film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (4)

[Claims] (1) An air outlet through which an air flow flows out and an ink outlet in which ink is held are installed facing each other, and the electrostatic force acting on the ink held in the ink outlet and the acceleration force due to the air flow An inkjet recording head configured to eject ink, wherein at least a surface of the member having the air ejection port facing the ink ejection port is an oil-repellent member to ink. (2) The inkjet recording head according to claim 1, wherein a thin film of an oil-repellent material is formed on the surface of the member having the air discharge port facing the ink discharge port. (3) The inkjet recording head according to claim 1, wherein the surface of the member having air discharge ports facing the ink discharge ports is mirror-polished. (4) The inkjet recording head according to claim 1, wherein the member having the air discharge ports is made of an inert material.