JPH09156110A - Electrostatic ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably emit toner particles to a recording medium, in an electrostatic ink jet recording apparatus electrostatically bonding toner particles in liquid ink to a recording medium to perform recording, by providing a destaticizing device of the recording medium on the upstream side of a counter electrode along a paper feed passage. SOLUTION: In an electrostatic ink jet recording apparatus, an ink chamber 10 holding liquid ink containing charged toner particles is provided in a head main body 1 and a recording electrode is provided in the emitting opening part 14 formed to one end part of the ink chamber 10 and a migration electrode 9 is provided in the other end part of the ink chamber 10. A counter electrode 2 is arranged in counter relation to the recording electrode through a paper feed passage H and a destaticizing means 3 of a recording medium 4 is arranged on the upstream side of the counter electrode. The destaticizing means 3 is composed of a destaticizing brush coming into contact with the whole of the width of the recording medium 4 at a time of the feed of the recording medium 4 and the charge of the recording medium 4 is removed during feed process by the destaticizing brush and, thereafter, stable printing can be performed.

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 and, more particularly, to an electrostatic ink jet recording apparatus of the type which performs recording by electrostatically attaching toner particles in liquid ink to a recording medium. .

[0002]

2. Description of the Related Art A non-impact recording method, in which noise during recording is extremely small so as to be negligible, has recently attracted attention. In particular, an ink-jet recording method capable of performing high-speed recording on plain paper with a simple mechanism is practical, and various improvements have been proposed. For example, using an ink in which charged toner particles are dispersed in a carrier liquid, a voltage is applied between a recording electrode and a counter electrode facing the recording electrode via a paper conveyance path, and an electric field generated by the application of a voltage is generated. The development of a system in which the toner particles in the ink are caused to fly by the electrostatic force of the above and adhere to paper to perform recording is being advanced.

An example of this type is shown in FIGS. 3 to 5, the head main body 101 has an ink chamber 113 surrounded by a lower plate 110, a side wall 111, and an upper plate 112.
The ink in the ink chamber 113 is always circulated through the ink circulation ports 114 and 115 by a pump (not shown). A small gap (slit opening 109) for forming an ink meniscus is formed in a part of the side wall 111. In the slit opening 109, the recording electrode 102 whose tip slightly protrudes outside is provided. The recording electrode 102 has its tip sharply pointed.
The surface is coated with an insulator to be insulated from the ink.

On the other hand, the recording electrode 1 of the ink chamber 113
The other three sides without 02 are surrounded by the migration electrode 105. A part of the migration electrode 105 is provided in the in-chamber 113 and is in electrical contact with the ink. The recording electrode 102 is connected to a driver (not shown), and a high-voltage pulse is applied to the recording electrode 102 during recording. On the extension of the recording electrode 102, a counter electrode grounded via a paper transport path is provided (not shown). The ink is obtained by dispersing toner particles in a petroleum organic solvent (isoparaffin), and the toner particles are apparently positively charged by zeta potential.

When a bias voltage having the same polarity as that of the toner particles is applied to the migrating electrode 105, the toner particles in the ink are electrophoresed on the slit opening 109 and concentrated. Subsequently, when a high voltage pulse having the same polarity as the toner particles is applied to the recording electrode 102, an electric field is formed between the recording electrode 102 and the counter electrode. Since the recording electrode 102 has a sharp tip, an electric field is concentrated on the tip of the recording electrode 102, and a strong electric field is formed toward the counter electrode. Since the toner particles are charged by the zeta potential, the toner particles concentrated on the ink meniscus are pulled in the direction of the counter electrode by the action of Coulomb force by the electric field, and when the Coulomb force overcomes the surface tension of the ink, a group The toner particles fly toward the counter electrode. At this time, the group of toner particles adheres to the recording paper disposed in front of the counter electrode. By controlling the high voltage pulse applied to the recording electrode 102 according to the print data, desired recording can be performed.

In this method, since only toner particles are mainly consumed for recording, the toner concentration becomes low near the recording electrode 102 immediately after the toner particles fly. But,
Since a high voltage is always applied to the migration electrode 105,
The toner particles in the ink chamber 113
5, electrophoresis is performed toward the recording electrode 102, and only the toner particles are supplied near the recording electrode 102. In particular, since the recording electrode 102 is insulated from the ink, charged toner particles migrate and when the potential distribution in the ink chamber 113 reaches equilibrium, no more toner particles are supplied and the initial state Return to.

[0007]

However, in the above-described conventional example, the recording medium itself may be charged due to friction between the media and friction with the feed roller in the process of transporting the recording medium. Therefore, the recording medium weakens the electric field formed between the recording electrode and the counter electrode, and therefore, a sufficient electrostatic force for discharging toner particles cannot be obtained, and stable toner discharge, that is, stable There is a disadvantage that the printing operation cannot be performed.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art and, in particular, to stabilize the ejection of toner particles onto a recording medium.

[0009]

In order to achieve the above object, the present invention provides an ink chamber for holding liquid ink containing charged toner particles, and a discharge opening provided at one end of the ink chamber. An electrophoretic electrode provided at the other end of the ink chamber, a recording electrode provided at the ejection opening, and a counter electrode facing the recording electrode via a paper transport path. Then, a configuration is employed in which a charge eliminator for the recording medium is provided on the upstream side of the counter electrode along the paper transport path.

According to this, before the recording medium is conveyed between the recording electrode and the counter electrode, static elimination is performed in advance by the static elimination means. Here, as the charge removing means, a charge removing brush, a charge removing brush roller, a conductive rubber blade, or the like can be used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG.
It will be described with reference to FIG.

In the electrostatic ink jet recording apparatus shown in FIGS. 1 and 2, a head main body 1 includes an ink chamber 10 for holding a liquid ink 11 containing charged toner particles,
An ejection opening 14 provided at one end of the ink chamber 10
And an electrophoresis electrode 9 provided at the other end of the ink chamber 10;
And the recording electrode 12 provided in the ejection opening 14. Among them, the recording electrode 12 is provided with the opposing electrode 2 opposed thereto via the paper transport path H. Also, the paper transport path H
A discharge means 3 for the recording medium 4 is provided upstream of the counter electrode 2 along.

More specifically, in this embodiment, the head main body 1 reciprocates in the direction (the direction of arrow E in FIG. 1) perpendicular to the direction of conveyance of the recording medium 4 (the direction of arrow D in FIG. 1). The carriage 5 is mounted on the carriage 5. The head main body 1 is a serial print head, and its outer shell is mainly made of a dielectric member. The carriage 5 reciprocates along the guide shaft 5A. As shown in FIG. 2, an ink chamber 10 is provided in the head body 1 and holds ink 11. This ink 11
Fine particles of a thermoplastic resin colored in a petroleum organic solvent (isoparaffin) together with a charge control agent, so-called toner, is dispersed. The toner is positively charged to a positive polarity by a zeta potential. Ink 1 in this ink chamber 10
1 is constantly circulated through an ink supply port 6 and an ink discharge port 7 by an external power such as a pump.

As shown in FIG. 2B, a plurality of strip-shaped recording electrodes 12 are formed in the ejection opening 14 in parallel at intervals corresponding to a desired number of dots. Each recording electrode 12 is made of an electroformed product of a conductive material such as Cu or Ni having a width of about 50 μm, and a portion in contact with the ink 11 is coated with an insulating resin. This insulating resin is preferably hydrophilic in order to improve the affinity between the surface of the recording electrode 12 and the ink 11. The tip of the recording electrode 12 is set at a position projecting from the ejection opening 14 by about 80 to 100 μm. On each of the recording electrodes 12, a flow path wall 13 is provided, and a plurality of minute slit-shaped flow paths for supplying the ink 11 and generating a capillary force are formed. Each of the flow path walls 13 and the recording electrode 1
An ink meniscus is formed between the first and second end portions.

On the other hand, the migrating electrode 9 is made of a conductive material such as a metal material, is provided on the opposite side of the discharge opening 14 in the ink chamber 10, and is in direct contact with the ink 11. The recording electrode 12 and the migration electrode 9 are connected to a voltage driver (not shown) via a cable 8. The voltage driving unit has a function of applying a high voltage bias having the same polarity as the toner particles in the ink 11 to the migration electrode 9 and a high voltage having the same polarity as the toner particles to the predetermined recording electrode 12 in accordance with the timing of dot recording. It has the function of applying a pulse. Here, the cable 8 is a flexible printed cable (FPC).

The counter electrode 2 is grounded via a predetermined resistor so that a large current does not flow between the counter electrode 2 and the recording electrode 12.
Further, the counter electrode 2 is formed corresponding to the width of the recording medium 4 and also functions as a platen for the recording medium 4. Reference symbol R indicates a transport roller for transporting the recording medium 4.

The static eliminator 3 is disposed upstream of the counter electrode 2 with respect to the direction in which the recording medium 4 is conveyed, and always contacts the entire width of the recording medium 4 when the recording medium 4 is conveyed. ing. In the present embodiment, the charge removing means 3 is a charge removing brush extending in the width direction of the recording medium 4, but the charge removing means 3 may be a charge removing brush roller, a conductive rubber blade, or the like.

The guide shaft 5A, the counter electrode 2, and the charge removing means 3 of the carriage 5 are fixed to a part of the apparatus body.

Next, the overall operation of the above embodiment will be described.

When a voltage having the same polarity as that of the toner particles in the ink 11 is applied to the migrating electrode 9 in contact with the ink 11, the recording electrode 1 set to a lower potential than the migrating electrode 9
2 and a potential difference is generated. Under this potential difference, ink 1
The toner particles in 1 function as apparent charges, and toner particles whose potential in the ink 11 is equal to the potential of the migrating electrode 9 is supplied to the surface of the insulating resin covering the recording electrode 12. Thereby, the ink 11 on the recording electrode 12 is
Is set to be equal to the potential of the migration electrode 9.

On the other hand, the recording medium 4 is conveyed from the bottom to the top in FIG. At this time, the brush of the static elimination means 3 comes into contact with the back surface of the recording medium 4, and the electric charges carried on the recording medium 4 during the transport process are removed before the recording medium 4 is transported between the counter electrode 2 and the recording electrode 12. Is done.

Subsequently, when a high-voltage pulse having the same polarity as that of the toner particles is applied to an arbitrary recording electrode 12, an electric field is generated between the recording electrode 12 and the counter electrode 2. When the Coulomb force acting on the toner particles in the ink meniscus overcomes the surface tension of the meniscus, the ejection opening 14
, An ink droplet 15 is ejected toward the counter electrode 2.
The ejected group of toner particles adheres to the recording medium 4 conveyed before the opposing electrode 2, and dot recording is performed.

On the other hand, if the toner particles are insufficient in the vicinity of the recording electrode 12 due to the discharge, the migration electrode 9 and the recording electrode 1
2, and a toner particle sufficient to compensate for the insufficient charge is supplied to the surface of the insulating resin covering the recording electrode 12. Then, desired recording is performed by repeating the above-described recording operation.

As described above, according to the present embodiment, even if the recording medium 4 is charged in the course of conveyance, it is possible to eliminate the charge carried on the recording medium 4 before being conveyed onto the counter electrode 2. It is possible to stabilize the electric field formed between the recording electrode 12 and the counter electrode 2 during recording,
The stable ejection of the ink droplet 15 can be always performed.

Here, the head body of this embodiment is a serial type print head, but may be a line type print head.

[0026]

Since the present invention is constructed and functions as described above, according to the present invention, since the discharging means for the recording medium is provided on the upstream side of the counter electrode along the paper transporting path, the recording medium is transported. Even when the recording medium is charged, it is possible to eliminate the electric charge carried on the recording medium before being conveyed onto the counter electrode, and to stabilize the electric field formed between the recording electrode and the counter electrode during recording. Thus, it is possible to provide an unprecedented excellent electrostatic ink jet recording apparatus capable of always performing stable ejection of ink droplets.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of the present invention.

2 is a configuration diagram in which a part viewed from the direction of arrow B in FIG. 1 is a cross section, FIG. 2 (a) shows an arrangement of each component, and FIG. 2 (b) is a configuration diagram of FIG. 2 (a). The enlarged view of the code A part is shown.

FIG. 3 is a front view showing a configuration of a conventional example.

FIG. 4 is a sectional view taken along line CC in FIG. 3;

FIG. 5 is a right side view of the conventional example shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head main body 2 Counter electrode 3 Static elimination means 4 Recording medium 5 Carriage 6 Ink supply port 7 Ink discharge port 8 Cable 9 Electrophoresis electrode 10 Ink chamber 11 Ink 12 Recording electrode 13 Flow path wall 14 Discharge opening 15 Ink droplet

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Minemoto 5-7-1, Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Yoshihiro Hagiwara 5-7-1, Shiba, Minato-ku, Tokyo Inside NEC Corporation

Claims (4)

[Claims] 1. An ink chamber for holding liquid ink containing charged toner particles, a discharge opening provided at one end of the ink chamber, and a migration electrode provided at the other end of the ink chamber. A recording electrode provided in the discharge opening,
In the electrostatic ink jet recording apparatus including the recording electrode and an opposing electrode opposed to the recording electrode via a paper transport path, a static eliminator for a recording medium is provided on the upstream side of the counter electrode along the paper transport path. An electrostatic ink jet recording apparatus characterized by the above-mentioned. 2. An electrostatic ink jet recording apparatus according to claim 1, wherein said discharging means is a discharging brush. 3. An electrostatic ink jet recording apparatus according to claim 1, wherein said discharging means is a discharging brush roller. 4. The electrostatic ink jet recording apparatus according to claim 1, wherein the charge removing unit is a conductive rubber blade.