JPH11105292A - Electrostatic ink jet head and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure stabilized printing by eliminating deficiency of charged particles. SOLUTION: A jet electrode 13 is provided, at the forward end thereof, with a jet port having a pointed jet point (e) which is provided with a passage (h) for supplying a toner liquid dispersed with charged color particles and a passage (i) for collecting the toner liquid not consumed at the jet point (e). Furthermore, an auxiliary electrode 14 is disposed in the vicinity of the jet port in order to stabilize printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet recording apparatus for performing recording by discharging a colored particle onto recording paper by electrostatic force using a toner liquid in which charged colored particles are dispersed, and an image forming apparatus using the same. The present invention relates to an electrostatic inkjet head used.

[0002]

2. Description of the Related Art In recent years, as an output device of a personal computer, an ink jet recording system in which characters and images are formed on a recording medium (recording paper) by discharging ink particles from an ink jet head toward a recording medium mounted thereon. Printers are widespread.

[0003] Among them, an electrostatic ink jet recording apparatus that performs recording by discharging a colored particle onto a recording paper by electrostatic force using a toner liquid in which charged colored particles are dispersed has attracted attention.

In these methods, a liquid toner in which charged colored particles are dispersed in an insulating liquid is supplied to a discharge point of a recording electrode having a sharp tip, and a voltage having the same polarity as the charged colored particles is supplied to the recording electrode. The liquid toner is ejected by the applied Coulomb force and recorded.

In order to form an image, a bias voltage for aggregating the charged colored particles at the discharge point is applied to the recording electrode, and recording is performed by applying a discharge voltage to the recording electrode in accordance with an image input signal.

In this method, high-density printing can be performed by discharging agglomerated charged colored particles. In addition, since the inkjet head has a simple structure, recording electrodes are arranged in a line to form a multi-discharge port, thereby facilitating high-speed printing. Has features that can be.

[0007] In order to stabilize the printing quality, for example, as described in JP-A-8-258270, charged colored particles are applied to a recording electrode of a selected discharge port to be printed. A bias voltage for coagulation is applied, and thereafter, an ejection voltage is applied for printing, and printing is performed.

Further, as described in JP-A-9-85954, a migration electrode is provided behind the recording electrode, and a high voltage having the same polarity as that of the charged colored particles is applied to the electrode, and the electrophoresis is performed by electrophoresis. There has also been proposed one in which the charged colored particles are easily aggregated at a discharge point of a discharge port.

[0009]

By the way, in the above case, the amount of the charged colored particles to be discharged (the density to be printed)
In the method, the amount of the ejected particles changes depending on the height of the voltage applied to the ejection electrode or the length of the application time. Therefore,
By controlling them, halftone printing with gradation can be realized. However, immediately after the high-density printing is performed, particularly when the high-density printing is continuously performed, the supply of the charged colored particles becomes insufficient and the printing density changes (sag in the printed image).
There is a problem. Accordingly, an object of the present invention is to provide an electrostatic inkjet head capable of promoting aggregation and preventing printing density from becoming unstable, and capable of performing stable and high-speed printing, and an image forming apparatus using this head.

[0010]

The present invention, in order to solve the above problems, comprises the following means (1) and (2). That is, (1) a supply port for supplying a toner liquid in which charged colored particles are dispersed is provided at the tip of the discharge electrode, the discharge port having a sharpened tip to form a discharge point. And a recovery path for recovering the toner liquid not consumed at the discharge point, and an auxiliary electrode is provided near the discharge port.

(2) means for applying a first voltage to the discharge electrode for aggregating charged colored particles at a discharge port, comprising: the electrostatic ink jet head according to claim 1; Means for applying a second voltage higher than the voltage of (a) to discharge the agglomerated colored particles from the ejection port to a recording medium mounted opposite to the ejection port, wherein the auxiliary electrode comprises: An image forming apparatus for applying a third voltage between the second voltage and the second voltage.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to preferred embodiments. FIG. 1 is a schematic configuration diagram of an electrostatic inkjet head according to an embodiment of the present invention. FIG. 1A is a plan view, and e is a discharge point. FIG. 1B is a left side view thereof, as viewed from the ejection point side. FIG. 1C is a cross-sectional view taken along a plane AA.

In the electrostatic ink jet head He (hereinafter simply referred to as a head) shown in FIG. 1, a head housing 10 made of an insulator has a discharge electrode base 12 inside.
The tip is sharpened on the discharge point e side of the tip. On the ejection electrode base 12, the ejection electrode 1 is provided.
3 is formed from a position slightly retreated from the discharge point e, and the rear end (the side opposite to the discharge point e) is bonded to a conductor and is drawn out as a discharge electrode terminal f.

The head housing 10 has a configuration in which the inside is divided into two by an ejection electrode base 12. The discharge electrode side of the divided gap becomes a supply path h for supplying a toner liquid in which charged colored particles are dispersed, and the rear end thereof is connected to a toner liquid tank (not shown). This supply path h
An auxiliary electrode 14 is formed on the surface facing the discharge electrode 13 in the inside, the discharge point side is formed to almost the same position as the discharge electrode 13, and a conductor is bonded at the rear end (opposite the discharge point e). Then, it is drawn out as an auxiliary electrode terminal g.

The other of the two halves of the head housing 10 passes through a recovery path i for recovering the toner liquid 17, passes through a suction pump (not shown), and passes through the toner liquid tank (not shown). )It is connected to the.

The head is driven by supplying the toner liquid 17 to the supply path h by static pressure or by a capillary method. The charged colored particles aggregated at the discharge point e are subjected to Coulomb force by a high voltage pulse applied to the discharge electrode 13. Thus, printing is performed by causing charged colored particles to fly onto a recording medium (recording paper, not shown) mounted at a predetermined position with a minute gap (0.2-1 mm) from the discharge point e. .

FIG. 2 is an enlarged view of the vicinity of the discharge point.
FIG. 2A shows a state in which no voltage is applied to the electrodes. The charged colored particles are substantially uniformly dispersed in the toner liquid 17. The toner liquid 17 forms a meniscus as shown at the discharge point e. In this state, as shown in FIG. 2B, by applying a high voltage pulse to the discharge electrode 13, the charged colored particles can fly from the discharge point e. However, when the high voltage pulse is applied,
The charged colored particles in the toner liquid supply path h are repelled from the ejection electrode 3 and are unevenly distributed on the opposite side (the auxiliary electrode side). Therefore, during the aggregation period in which the ejection is stopped, there are few charged colored particles that aggregate at the ejection point e, so that high-density printing or high-speed printing cannot be performed, and flying particles decrease immediately after high-density printing.

Therefore, a voltage is applied to the auxiliary electrode 14 formed with the supply path h interposed therebetween to move the unevenly charged charged particles to the discharge point e side, thereby solving the problem by increasing the amount of aggregation of the charged colored particles. doing. As the voltage applied to the auxiliary electrode 14, a voltage having the same polarity as that of the charged colored particles is applied.

In the present embodiment, the discharge electrode 13 and the auxiliary electrode 14 are used. However, the same applies if the auxiliary electrode is formed so as to sandwich the discharge electrode, or if the discharge electrode is configured to surround the discharge electrode. The effect is obtained.

Next, an image forming apparatus employing the above-mentioned electrostatic ink jet head He will be described with reference to FIGS. The above-described electrostatic ink jet head He is not shown with its internal structure omitted.

The recording medium 16 is mounted at a predetermined position with a small gap (0.2-1.0 mm) from the discharge point e at the tip of the head. The toner liquid tank 18 contains the toner liquid 17 in which charged colored particles are dispersed in an insulating liquid. This toner liquid 17 is guided to the toner supply path h of the head He. Although the static pressure supply method is used to supply the toner liquid 17 in this figure, a supply method utilizing a capillary phenomenon or a method of forcibly supplying a liquid pump may be used. (In the pulsating flow supply, the amount of aggregation of the charged particles fluctuates, and the discharge amount also fluctuates, so that the print density fluctuates).

In the supplied toner liquid 17, the overflowed toner liquid 17 is guided to the recovery path i via the toner discharge point e at the formed meniscus or in the vicinity thereof. Then, the toner liquid tank 18 is forcibly forced by the pump 19.
Is returned to.

To perform printing, a voltage is applied to the auxiliary electrode 14 and the ejection electrode 13. FIG. 4 shows a supply voltage waveform applied at that time. In this example, for example, DC12 is connected to the auxiliary electrode g.
A voltage of 50 V is applied, a bias of 900 V is applied to the discharge electrode 13, and sufficient charged particles are aggregated at the discharge point e. In order to discharge charged particles, 1600
A high voltage pulse of V is applied. At this time, the size (density) of a dot (not shown) to be printed can be changed by changing the application time of the 1600 V ejection voltage pulse.

The voltage applied to the auxiliary electrode 14 is set to a level at which the discharge is not performed by itself. That is, since the value is set to a value close to the voltage applied to the ejection electrode 13 (between the ejection voltage applied to the ejection electrode and the aggregation voltage), insulation between the electrodes is easy.

[0025]

As described above, according to the electrostatic ink jet head and the image forming apparatus of the present invention, the auxiliary electrode is provided in the vicinity of the discharge electrode, and the voltage higher than the discharge electrode is applied during the aggregation period of the charged particles. When applied, the charged particles are moved to the discharge point side, so that the aggregation of the charged particles is sufficient,
Even when high-density printing or high-speed printing is performed, stable printing can be performed without causing shortage of charged particles.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrostatic inkjet head according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a discharge point portion.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing voltage waveforms applied to an ejection electrode and an auxiliary electrode.

[Explanation of symbols]

 Reference Signs List 10 head housing 12 discharge electrode base 13 discharge electrode 14 auxiliary electrode 16 recording medium He electrostatic inkjet head e discharge point f discharge electrode terminal g common auxiliary electrode h supply path i recovery path

Claims (2)

[Claims] A discharge path having a discharge point formed by sharpening the end of the discharge electrode at a distal end of the discharge electrode, and supplying a toner liquid in which charged colored particles are dispersed to the discharge point. And a recovery path for recovering the toner liquid not consumed at the discharge point, and an auxiliary electrode is provided near the discharge port. 2. A means for applying a first voltage for aggregating charged colored particles to an ejection port to said ejection electrode, comprising: the electrostatic ink jet head according to claim 1; Means for applying a second voltage higher than the voltage to discharge the aggregated colored particles from the discharge port to a recording medium mounted opposite to the discharge port, wherein the auxiliary electrode comprises: The third between the second
An image forming apparatus characterized by applying a voltage of: