JPS6157343A - Ink jet recording equipment - Google Patents

Abstract

PURPOSE:To make the titled device into a static acceleration type which can be turned into a multinozzle, by a method wherein insulated ink is made to charge by making use of drift charge and the ink is made to fly from the tip of a nozzle through electrophoretic force. CONSTITUTION:Insulated ink introduced into an ink chamber 1 flows within a porous material 3 as per an arrow 14 through mechanical vibration of a bimorph vibrator 6 to be driven through voltage V13 from a driving circuit 13. Then the ink possesses electric charge by receiving drift charge. The ink having the electric charge moves in the direction of a nozzle 8, swelling 15 is built up from the tip of the nozzle 8 according to a vibration of the vibrator 6. When, therefore, a signal voltage VN is applied to a space between a signal electrode 9 and a back electrode 10, irregular electric field is formed in the vicinity of the swelling 15 part. In consequence of the above, even when the nozzle is turned into a multinozzle state, a strong electric field is generated only on the swollen tip part, static attraction is acted upon a space between the ink and the back electrode 10 and ink particles fly to a recording material 11, discrimination can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an inkjet recording device, and more particularly to an inkjet recording device in which insulating ink is charged with flow charging and the ink is controlled by electrostatic attraction. .

[Technical background of the invention and its problems]

As inkjet recording methods capable of recording on plain paper, the electrostatic acceleration method, pressure pulse method, and pressurized vibration method are conventionally known, and recently, the bubble jet method has also been developed. Of these various methods, the latter three all use mechanical pressure to make the ink fly, which has the disadvantage of causing print stains due to the generation of satellite ink accompanying the ejection of ink particles. . Furthermore, there is instability in flight due to contamination of the nozzle due to the atomization phenomenon of ink at the tip of the nozzle, which impairs the stability of the device. On the other hand, the electrostatic acceleration type has the advantage of stable ink flight, but has the disadvantage of slow recording speed. For this reason, although it is desired to use multiple nozzles, this is currently not possible and only single nozzles have been commercialized. The reason why nozzles cannot be multiplied will be explained in detail.

Ink includes water-based ink and oil-based ink.

Water-based ink has a higher surface tension than oil-based ink, and the particle size of the ink formed is larger. Therefore, when applied to an electrostatic acceleration type inkjet recording device with a single nozzle, the recording speed is 1/1 that of oil-based ink. It becomes 2 or less. For this reason, the use of oil-based ink is being considered in electrostatic acceleration type inkjet recording devices.

Furthermore, when considering multi-nozzle design, water-based ink has a low resistivity, making it impossible to electrically isolate each nozzle.

On the other hand, in the case of oil-based ink, electrical isolation between nozzles is possible. However, in general, in the case of electrostatic acceleration type inkjet that uses an electric field, the electric field strength between each nozzle and the back electrode on the back of the recording medium becomes uniform due to multi-nozzle design, and the ink in the desired nozzle is It is not possible to selectively apply force due to dielectric polarization only to the ink, and even if oil-based ink is used, it is still impossible to make the ink fly.

Although electrostatic acceleration inkjet recording devices have many advantages over other types of devices, they also have the problem of being unsuitable for high-speed recording because it is extremely difficult to use multiple nozzles with the conventional configuration. Ta.

[Purpose of the invention]

An object of the present invention is to provide an electrostatic acceleration type inkjet recording device that can be configured with multiple nozzles.

[Summary of the invention]

This invention uses so-called flow charging, a phenomenon in which an insulating liquid is charged at its interface with a solid when it flows, to charge the insulating ink, and the ink is ejected from the nozzle tip by electrophoretic force. It is.

That is, the inkjet recording device according to the present invention has the following features:
an ink chamber into which insulating ink is introduced; a porous body provided within the ink chamber; a pump means for flowing the ink into the porous body; a nozzle connected to the ink chamber; The signal electrode provided in
A back electrode is provided to face the electrode with a recording body in between, and by applying a signal voltage between the signal electrode and the back N pole, the pumping means can increase the flow in the porous body. The invention is characterized in that the charged ink is ejected from the tip of the nozzle, an asymmetric electric field is generated at the tip of the ink, and the ink is caused to fly onto the recording medium. Further, in the present invention, preferably, an auxiliary electrode is provided on the inner wall of the ink, and after the ink is ejected from the nozzle tip,
By applying a voltage of a predetermined polarity between the auxiliary electrode and the signal electrode, ink is forcibly replenished into the nozzle.

〔Effect of the invention〕

According to this invention, since insulating ink can be used, it is advantageous in terms of recording speed compared to the case where aqueous ink is used, and even if nozzles are multiplied, it is possible to electrically separate the nozzles. Furthermore, since the ink itself is charged by flow charging before reaching the nozzle tip, the ink can be drawn out from the nozzle tip and flown toward the recording medium by electrostatic attraction due to the application of a voltage. Nozzle.

In the case of multiple nozzles, the ink in the nozzle to which the signal voltage is applied will be given a sufficiently larger electrostatic attraction force than the ink in other nozzles.

Therefore, ink can be ejected from each nozzle in a pattern according to the image signal to be printed, and good printing results can be obtained. That is, while maximizing the advantages of the electrostatic acceleration method, it is possible to dramatically improve the recording speed by using multiple nozzles.

[Embodiments of the invention]

FIG. 1 shows a schematic configuration of an inkjet recording apparatus according to an embodiment of the present invention.

In the figure, an ink chamber 1 is made of an insulator, and insulating ink is introduced through an ink introduction port 2 provided at the left end in the figure. A porous body 3 is provided within the ink 1 to allow the ink to flow and be charged. A bimorph oscillator 6 is installed above the porous body 3 in the ink chamber 1 and is made up of a piezoelectric body 4 in the form of a plate or film and an electrode film 5 bonded to the piezoelectric body 4 .

This bimorph vibrator 6 constitutes a pump means for causing ink to flow into the porous body 3 and for making the ink swell.

The amount of flow charge of the ink on the porous body 3 is proportional to the flow rate. However, its value is determined by a complex combination of the material of the ink, the electrolyte contained, the material and surface condition of the porous body 3, and electrochemical factors at the interface between the porous body 3 and the ink. In particular, when an insulating liquid flows through a porous body, it is known that 10 to 200 times more charge is generated than when it flows inside a pipe. Kar
el and A.

L. Ludwina: Broc, A1. Pe
t, Inst,.

1961.26). This is thought to be because the porous body has a much larger contact area with the liquid than a pipe. This charging phenomenon is due to the formation of an electric double layer at the interface between the solid and the liquid, and when the charge in the liquid of the electric double layer is carried away, the remaining charge is neutralized through the solid. For this reason, the porous body 3 is preferably made of metal. This is because in the case of an insulating material, the remaining charges are accumulated without being neutralized, affecting the next charge, and changing the amount of charge.

An auxiliary electrode 7 is provided on the bottom wall of the ink chamber 1 . This auxiliary electrode 7 is provided for forcibly replenishing ink to the nozzle, as will be described later. A nozzle 8 is integrally formed at the right end of the ink chamber 1 in the figure. A signal electrode 9 is formed on the inner wall of the nozzle 8 .

Auxiliary electrode7. The signal electrode 9 may be formed by a film forming technique such as vapor deposition, or may be coated with metal foil. Moreover, when the nozzle 8 is made of a conductive material, the nozzle 8 can also serve as the signal electrode 9.

On the other hand, a back electrode 10 made of a conductive roller is arranged facing the nozzle 8, and a recording medium 1 is placed in front of the back electrode 10.
1 are movably in contact with each other in the direction of arrow 12. Recording body 11
Plain paper can be used.

The operation of the inkjet recording apparatus based on the present invention configured as described above will be explained with reference to FIGS. 2 to 4.

The insulating ink introduced into the ink chamber 1 from the ink introduction port 2 is moved through the porous body 3 as shown by the arrow 14 by the mechanical vibration of the bimorph vibrator 6 driven by the voltage Vs from the drive circuit 13. Flow. As a result, the ink is subjected to flow charging according to the above-described principle and is charged. The charged ink moves in the direction of the nozzle 8 and swells up from the tip of the nozzle 8 as shown in 15 in response to the vibration of the bimorph oscillator 6. Due to this ink bulge 15, when a signal voltage VN is applied from the recording circuit 17 between the signal electrode 7 and the back electrode 10, this ink bulge 15
An asymmetric electric field is formed in the vicinity of the part. As a result, a stronger electric field is generated by the tip of the raised ink, a strong electrostatic attraction moves between the ink and the back electrode 10, and the ink particles 16 fly toward the recording medium 11.

The nozzles 8 are multi-shaped, for example, as shown in FIG. 2(a) or FIG. 3(a). FIG. 2(a) shows a case where each nozzle is separated, and FIG. 3(a) shows a case where each nozzle communicates and forms a slit. However, in either case, the signal electrode 9 is provided for each nozzle. The ink rises from the tip of each nozzle due to the vibration of the bimorph oscillator 6, but the ink in the nozzles to which the signal voltage is applied to the signal electrode 9 rises as shown in FIG. 2(b), respectively.
As shown in Fig. 3(b), the electric charge generated by the flowing electrification and the electric charge @electric lf! The ink particles are attracted toward the rear surface type ff 110 by the electric field between 9 and the back surface electrode 10, become ink particles, reach the recording medium 11, and form an image. Thereafter, the ink replenishment voltage VH is applied from the 111 circuit 17 to the auxiliary electrode 7, so that ink is forcibly replenished into the nozzle B.

Figure 4 shows bimorph oscillator 6. It shows the voltages applied to the signal conductor 9 and the auxiliary electrode 7, and shows the case where the ink is positively charged by flow charging. The voltage Va applied to the bimorph vibrator 6 is set during a period Tl during which ink swells from the tip of the nozzle 8, as shown in FIG. 4(a).
The period T2 has different widths and periods.

That is, during the period T1, the voltage Va is applied to the bimorph vibrator 6 for a relatively long time so that the ink is sufficiently swelled from the tip of the nozzle 8. On the other hand, in the temporary work 2, the voltage is repeatedly applied to the bimorph vibrator 6 at short intervals so that the ink is efficiently charged in a flowing manner through the porous body 3.

Ink is ejected from the tip of the nozzle 8 by applying the signal voltage VN to the signal electrode 9 in synchronization with the application of the voltage Ve during the period Tl. After this ink is ejected, an appropriate ink replenishment voltage Vo of positive polarity is applied to the auxiliary electrode 7, and the auxiliary electrode 7 and the signal electrode 8 due to the application of this voltage VH.
(The voltage VN is not applied to the signal electrode 8 at this time, and the potential is zero.) Due to the potential gradient between Then, ink is replenished. By repeating such operations, an image is recorded on the recording medium 11 according to the pattern of the signal voltage applied to the signal electrode 9.

FIG. 5 shows another embodiment of the present invention, which is an example in which flow charging of ink can be carried out more efficiently.

Flow charging occurs significantly at the entrance of the porous body. Therefore, in order to charge efficiently, it is effective to pass the ink through a large number of porous bodies without reducing the flow rate of the ink.

The embodiment shown in FIG. 5 focuses on this point, so an ink flow path 19 with a small ink flow path diameter is provided in the rear part of the nozzle 8 for ink to 1, and a plurality of porous holes are provided in one ink flow path. Mass bodies 3a to 3d are arranged in series. In this way, the insulating ink introduced from the ink introduction port 2 after ink ejection is guided to the ink flow path 19 and the flow rate is increased, and the vibration of the bimorph oscillator 6 causes the insulating ink to be introduced into the porous body 3a.
By flowing through ~3d, it is sufficiently charged and guided to the nozzle 8.

Note that the present invention is not limited to the above-mentioned embodiments; for example, in the embodiment, an auxiliary electrode 7 is provided to replenish the ink, but the pump means is powerful and replenishing the ink is unnecessary. The auxiliary electrode 7 may be omitted if this is done, or if the signal voltage application interval is long. Furthermore, although a bimorph vibrator is illustrated as the pump means, other devices may also be used. In addition, various modifications can be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an inkjet recording apparatus according to an embodiment of the present invention, and FIGS. 2(a) and 2(b) show a front view of an example of a multi-nozzle and the state of ink ejection from the nozzle tip. 3(a) and 3(b) are front views of another example of multi-nozzles and diagrams showing the state of ink ejection from the nozzle tip, and FIG. 4 is for explaining the operation of the same embodiment. FIG. 5 is a time chart showing voltage waveforms applied to each part of the inkjet recording apparatus according to another embodiment of the present invention. 1... Ink chamber, 2... Ink introduction port, 3, 3a ~
3d... Porous body, 6... Bimorph oscillator, 7.
...Auxiliary electrode, 8...Nozzle, 9...Signal electrode, 1
0... Rear snow scraper, 11... Recording body, 19... Ink channel. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (7)

[Claims] (1) an ink chamber into which insulating ink is introduced, a porous body provided within the ink chamber, a pump means for flowing the ink into the porous body, and a nozzle connected to the ink chamber; The nozzle includes a signal electrode provided in the nozzle, and a back electrode provided opposite to the signal electrode via the recording medium, and by applying a signal voltage between the signal electrode and the back electrode, An inkjet recording apparatus characterized in that charged ink is ejected from the tip of the nozzle by flowing in the porous body by the pump means, and is caused to fly onto the recording medium. (2) The ink jet recording apparatus according to claim 1, wherein the pump means causes the ink to flow into the porous body by performing mechanical vibration. (3) A signal voltage is applied between the signal electrode and the back electrode in synchronization with the flow of ink in the porous body by the pump means. Inkjet recording device. (4) Claim 1 or 2 characterized in that the pump means is driven at a higher speed during a period in which no signal voltage is applied between the signal electrode and the back electrode than during other periods. The inkjet recording device described in Section 1. (5) The inkjet recording apparatus according to claim 1, wherein a plurality of porous bodies are provided in series in the ink flow path. (6) Inkjet recording according to claim 1 or 5, characterized in that the ink flow path diameter when flowing into the porous body is smaller than the ink flow path diameter immediately before the porous body. Device. (7) an ink chamber into which insulating ink is introduced, a porous body provided within the ink chamber, a pump means for flowing the ink into the porous body, and a nozzle connected to the ink chamber; The nozzle includes a signal electrode provided in the nozzle, a back electrode provided opposite to the signal electrode with a recording medium in between, and an auxiliary electrode provided on the wall of the ink chamber, and the signal electrode and the back electrode are provided. By applying a signal voltage between the pump means, charged ink is ejected from the tip of the nozzle by flowing in the porous body, and is caused to fly onto the recording medium, and then the auxiliary electrode An inkjet recording apparatus characterized in that ink is replenished into the nozzle by applying a voltage of a predetermined polarity between the nozzle and the signal electrode.