JPH01204750A - Electrostatic type ink jet recording apparatus - Google Patents

Abstract

PURPOSE:To obtain a stable jet characteristic, by providing a nozzle plate formed in such a structure that nozzles are separated in the lateral direction of recording paper corresponding to recording electrodes and a means for cyclically changing the volume of the liquid chamber in a head to form a definite meniscus to the outlet of each of the nozzles and applying definite bias voltage between the recording electrodes and an opposed electrode. CONSTITUTION:Pulse voltage VA for operating a volume varying mechanism is driven at constant frequency and a semicircular meniscus a' is formed at the outlet of each of nozzles 4a on the basis of the volumetric variation of a liquid chamber 1. Next, after a time t1 from the start of the driving of pulse voltage VA, bias voltage VB is applied between each terminal 2 and an opposed electrode 6 to form an electrostatic field. By this method, the meniscus is changed from the semicircular shape a' to a triangular shape b'. Subsequently, recording voltage VP is superposed on the pulse voltage VA in synchronous relationship after a time t2 from the start of the driving of the pulse voltage VA and the meniscus becomes a triangular shape c' and can not withstand surface tension to fly in a stringing shape. By this method, the force for overcoming initial static friction force or inertial force becomes unnecessary and fast response can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic inkjet recording device, and more particularly, to a head portion of an electrostatic inkjet recording device.

Conventionally, in electrostatic inkjet recording devices, a vibrator is provided in the slit-shaped opening of the head section to create unevenness on the ink liquid surface, which promotes the formation of an ink meniscus due to electrostatic force, or There is a method that aims to shorten the formation process (see Japanese Patent Application Laid-Open No. 179663/1983), but this is difficult because it is difficult to tune the standing waves, and the printing position changes due to changes in the physical properties of the ink. The drawback was that it was difficult to maintain image quality. In addition, there are also devices that are equipped with a pressure adjustment section that lowers the ink pressure after the high voltage is cut off than when the high voltage is applied, or that apply pressure pulses to the ink that are synchronized with the recording high voltage applied to the electrodes (Japanese Patent Application Laid-Open No. 59
(see Japanese Patent Publication No. 202859 and Japanese Patent Publication No. 60-59871), the orifice has a slit shape, so the fluid mass is large and selective high-speed injection is difficult even when high pressure is applied.

Purpose The present invention was made in view of the above-mentioned circumstances.
In particular, this was done with the aim of lowering the switching voltage of recording signals, reducing costs, and increasing printing speed.

In order to achieve the above object, the present invention provides an electrostatic inkjet recording device that uses electrostatic attraction to eject ink from an ink jetting port and adheres to recording paper. Correspondingly, a nozzle plate is formed with nozzles separated in the width direction of the recording paper, and the volume of the liquid chamber in the head is changed periodically to apply pressure pulses to the ink in the liquid chamber periodically. means for forming a constant meniscus at the exit of said nozzle; means for applying a constant bias voltage between said recording electrode and a counter electrode; and means for applying a recording signal to a recording electrode corresponding to each nozzle in synchronization with said pressure pulse. The invention is characterized in that it has a means for applying the voltage at a constant rate. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a main part configuration diagram for explaining an embodiment of an electrostatic inkjet recording apparatus according to the present invention. In the figure, 1 is a head liquid chamber, and 2 is a large number of recording electrodes arranged; 3 a recording voltage (Vp); 4 a nozzle plate integrally formed with a plurality of nozzles 4a in the longitudinal direction and joined to the slit-shaped opening of the head liquid chamber 1;
Each nozzle 4a corresponds to each recording electrode 2.

Reference numeral 5 denotes a pulse voltage source (V^), which is driven at a constant frequency regardless of other signals, operates a volume variation mechanism (not shown) that changes the volume of the head liquid chamber 1, and changes the ink in the head. Generate pressure pulses periodically. 6 is a counter electrode, 7 is a bias voltage source (VR), and 8 is a recording paper provided in front of the counter electrode 6.

FIG. 2 shows the pulse voltage (V^) applied to operate the electrostatic inkjet recording apparatus according to the present invention;
A time chart of the bias voltage (VB) and the recording voltage (Vp), and a diagram for explaining the ejection state of ink droplets in the inkjet head of the inkjet recording apparatus, in which the pulse voltage (V ^) is driven at a constant frequency regardless of other signals, as shown in figure (a), and a semicircular meniscus a' is created at the outlet of the nozzle 4a due to the volume variation of the liquid chamber 1.
form. Next, as shown in Figure (b), a bias voltage (VFI) is applied between the recording electrode 2 and the counter electrode 6 to form an electrostatic field t1 hours after the start of driving the pulse voltage (V^).

Due to this V^+VR, the meniscus changes from the semicircular shape a' to the triangular shape b'. This is naturally a pulse voltage (V^)
The triangular meniscus is formed periodically. Next, as shown in figure (c), t2 hours after the start of driving the pulse voltage (V^), the recording voltage (Vp) is superimposed in synchronization with the pulse voltage (V^), and the meniscus becomes C'. As shown in the figure, the apex of the triangle is further stretched, and the object is unable to resist the surface tension and flies in the form of a thread. The recording voltage (Vp) is cut off by cutting off the pulse voltage (V^) at t4 hours after the recording voltage (Vp) is cut off, and then cutting off the bias voltage (V B) at t3 hours, contrary to the start-up time. do. By sequentially shutting off the valves in this manner, air is prevented from being drawn in when the valves are shut off.

FIG. 3 is a block diagram of main parts for explaining another embodiment of the present invention, in which a volume variation mechanism 9 that is not integrated with the head liquid chamber 1 is provided. In this case, a plurality of heads can be driven by one volume variation mechanism, which is effective for color printing.

FIG. 4 is a diagram showing changes in the inter-electrode distance (Gp) and gap margin due to application or non-application of the pulse voltage (■^). When the pulse voltage (V^) is applied, the inter-electrode distance (Gp) changes. It can be made large. Also, if the distance at which ink starts flying just by applying a bias voltage (VR) is a p /, then the gap margin is ap - G
It can be determined by the equation p', and as shown by hatching in the figure, the gap margin region is expanded when the pulse voltage (V^) is applied. Thereby, the value of the recording voltage (Vp) that requires switching can be reduced, and the number of drive circuits can be reduced. Furthermore, the widening of the gap margin leads to the expansion of the permissible value for assembling one mechanical component, and furthermore, the margin against fluctuations in various environmental conditions is increased, and reliability can be improved.

Effects As is clear from the above explanation, according to the present invention, a meniscus is always formed at a constant frequency, so stable jetting characteristics can be obtained from constant surface characteristics regardless of the wettability around the nozzle. . Furthermore, since the pressure pulse and bias voltage are applied prior to the recording signal, there is no need for a force to overcome the initial static friction force or inertial force, and high-speed response is possible.

[Brief explanation of the drawing]

FIG. 1 is a main part configuration diagram for explaining an embodiment of an electrostatic inkjet recording device according to the present invention, and FIG. 2 is a time chart of each voltage applied to operate the device and an inkjet recording device. FIG. 3 is a diagram for explaining the droplet ejection state, FIG. 3 is a main part configuration diagram for explaining another embodiment of the present invention, and FIG. 4 is a diagram showing the application or non-application of pulse voltage in the apparatus of the present invention. FIG. 3 is a diagram showing changes in inter-electrode distance and gap margin due to the change in the inter-electrode distance and gap margin. 1... Head liquid chamber, 2... Recording electrode, 3... Recording voltage. 4... Nozzle plate, 4a... Nozzle, 5...
Pulsed voltage source for volume variation, 6... counter electrode, 7...
Bias voltage source, 8... Recording paper, 9... Volume variation mechanism. Figure 1 et al Figure 2 Figure 3 Figure 4 a V

Claims (1)

[Claims] 1. In an electrostatic inkjet recording device that uses electrostatic attraction to eject ink from an ink ejection port and adhere it to recording paper, the nozzle is separated in the width direction of the recording paper in correspondence with the recording electrode. a nozzle plate formed of a nozzle plate, and means for periodically changing the volume of the liquid chamber in the head to apply periodic pressure pulses to the ink in the liquid chamber to form a constant meniscus at the outlet of the nozzle. and means for applying a constant bias voltage between the recording electrode and a counter electrode, and means for applying a recording signal to the recording electrode corresponding to each nozzle in synchronization with the pressure pulse. type inkjet recording device.