JPH11291503A - Ink-jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording apparatus which enhances aggregation efficiency of color material particles thereby solving density insufficiency and enables high-speed recording. SOLUTION: An ink 8 in which charged color material particles are dispersed in an insulating liquid is collected from an ink collection passage 7 while being supplied to an injection point P via an ink feed passage 6. An electric field of the same polarity as that of the charged color material particles is applied, whereby the color material particles are flown to a recording medium 4 from the injection point P. In an ink-jet recording apparatus of this constitution, a main electrode 20 is set at one side of the ink collection passage 7 for applying an electric field to flow the color material particles, and an auxiliary electrode 21 is set at the other side of the ink collection passage 7 to confront the main electrode 20 for applying the electric field of the same polarity as that of the color material particles. The electric field from the auxiliary electrode 21 enhances aggregation efficiency of color material particles, thereby solving density insufficiency and enabling high-speed recording.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for printing a character or an image on a recording medium by flying an ink obtained by dispersing charged colorant particles in an insulating liquid by electrostatic force.

[0002]

2. Description of the Related Art In recent years, as an output device of a personal computer, an ink jet recording type printer which forms a character or an image on a recording paper by ejecting ink particles toward a recording medium such as a recording paper opposed thereto has been widely used. ing. Among them, an electrostatic ink jet recording apparatus that uses an ink in which charged colorant particles are dispersed in an insulating liquid and ejects the colorant particles onto recording paper by electrostatic force to perform recording has attracted attention. ing. The reason for this is that a bubble jet recording apparatus that ejects ink from a nozzle by thermal expansion of a bubble or a bubble jet recording apparatus that ejects ink from a nozzle using a piezo pump uses a nozzle that causes liquid clogging. In addition to the fact that a large number of nozzles with different inner diameters must be prepared in order to give the density (gradation) of the recording, an electrostatic recording device requires only nozzles. This is because shading can be easily realized only by changing the voltage pulse width and the pulse height.

This electrostatic recording apparatus is disclosed in, for example,
JP-A-11475, JP-A-8-207303 and JP-A-8-149253 disclose charged colorant particles in an insulating liquid at an emission point of a sharp electrode. The resulting ink is supplied, a voltage having the same polarity as that of the charged colorant particles is applied to the electrode, and the colorant particles are ejected by the Coulomb force generated at that time to record. In order to form an image, a bias voltage for aggregating the charged colorant particles at the ejection point is applied to the electrodes, and recording is performed by applying a pulsed ejection voltage to the electrodes in accordance with an image input signal.

[0004]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open No.
In the recording apparatus disclosed in Japanese Patent No. 11475, a recording electrode and an auxiliary electrode are provided to increase the aggregation of colorant particles at an emission point. However, in this case, the electrode structure is such that an electric field of the same polarity is generated at a location where the ink is about to flow into the ejection point, so that the colorant particles are likely to stay near the entrance. On the other hand, the colorant particles carried by the viscosity of the insulating liquid have an electric field of the same polarity as that of the colorant particles applied to the recording electrode. Gather near the middle of. As a result, the colorant particles flow out of the discharge tube without being aggregated at the emission point, which is the tip of the recording electrode, and the aggregation efficiency is reduced. As a result, the agglomeration speed becomes slow and the density becomes insufficient, resulting in poor image quality or poor high-speed recording. here,
Even if the electric field is increased to increase the coagulation speed, most of the flying from the tip of the recording electrode becomes an insulating liquid.

In the recording apparatus disclosed in Japanese Patent Application Laid-Open No. 8-207307, a main electrode for applying an emission signal and an auxiliary electrode for applying a bias voltage are provided so as to face each other. Since both electrodes are provided in the flow path on the ink supply side with respect to the ejection point, aggregation of the colorant particles at the ejection point is hindered, and the same disadvantages as in the device disclosed in Japanese Patent Application Laid-Open No. 9-11475. Will occur. Further, in the recording apparatus disclosed in JP-A-8-149253, since the conductive member on the supply path side extends to the base of the electrode substrate on the upstream side of the emission point, an electric field of the same polarity flows. There is a problem that the colorant particles act on the colorant particles and easily stay in front of the electrode.

[0006] The present invention focuses on the above problems,
An object of the present invention is to provide an ink jet recording apparatus capable of improving the coagulation efficiency of colorant particles, eliminating insufficient density, and performing high-speed recording.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an ink in which charged colorant particles are dispersed in an insulating liquid, via an ink supply path to an ejection point. The ink jet recording apparatus is configured to collect the colorant particles from the ejection point toward a recording medium by applying an electric field having the same polarity as the colorant particles by collecting the ink from the ink collection path while supplying the colorant particles. A main electrode for providing an electric field for flying the colorant particles is provided on one side of the ink recovery path, and an auxiliary electric field having the same polarity as the colorant particles is provided on the other side of the ink recovery path in opposition to the main electrode. It is configured to provide electrodes.

Since the main electrode and the auxiliary electrode are provided on the ink recovery path downstream from the ejection point, the flow of the colorant particles into the ejection point is not hindered. Outflow of the colorant particles from the point is suppressed. As a result, the colorant particles are efficiently aggregated near the emission point, which is the tip of the main electrode. In this case, a bias voltage is also applied to the main electrode, and both electrodes extend from the vicinity of the ejection point along the ink recovery path.

Further, the ink supply path and the ink recovery path are connected in series over a plurality of stages, and the ink is supplied to a connection point between the preceding ink recovery path and the subsequent ink supply path. Is configured so that the supply of the colorant particles to the second and subsequent ejection points can be eliminated, and the insufficient density and the insufficient dot size in high-speed printing can be eliminated. It is possible to do.

[0010]

FIG. 1 is an enlarged sectional view showing an ink jet recording apparatus according to the present invention, and FIG. 2 is a partial sectional view taken along line AA in FIG. As shown in the figure, the ink jet recording apparatus 1 has a recording head 2, and is configured to fly an ink obtained by dispersing a charged colorant particle in an insulating liquid by Coulomb force. A recording paper 4 as a recording medium held on a grounded counter electrode 3 is provided in front of the recording head 2, and characters and images are recorded on the recording paper 4 by relatively scanning the two. Is printed.

The recording head 2 is provided with an ink supply path 6 for supplying ink 8 toward the opening 5 at the tip and an ink recovery path 7 for flowing the ink stored in the opening 5. . Specifically, the ink supply path 6 and the ink recovery path 7 are communicated with each other through the opening 5 and intersect at a predetermined acute angle α with the opening 5 as a vertex. The opening 5 is configured as an ejection point P from which the ink particles 8A are to be ejected. In practice, a large number of pairs of the ink supply path 6 and the ink recovery path 7 are formed at a predetermined pitch in the direction perpendicular to the drawing. The ink supply path 6 and the ink recovery path 7 each have a cross section formed in a rectangular shape with a side of, for example, about 40 to 50 μm, depending on the required number of dots. At the time of actual molding, the concave head body 2A and the convex head body 2B having fine grooves formed on the surface are manufactured by extrusion molding of a polymer compound such as plastic, for example, and they may be fitted together. .

The ink supply path 6 has an ink 8 at the other end.
An ink introduction passage 10 provided with an ink tank 9 for storing the ink is connected, and a small amount of the ink 8 is pressure-fed by a micropump 11 in the middle of the ink introduction passage 10. Further, an ink discharge passage 13 provided with an ink recovery tank 12 is connected to the ink recovery path 7 so that the ink flowing through the ejection point P and passing therethrough can be recovered. The ink tank 9 and the ink recovery tank 12 may be the same, and the ink may be circulated.

Then, on the inner wall of the ink recovery path 7,
A main electrode 20 and an auxiliary electrode 21 which are features of the present invention are provided. Specifically, the main electrode 20 is connected to the ink recovery path 7.
Is formed relatively long along the extending direction of the ink recovery path 7 from the vicinity of the ejection point P on one side, that is, on the side of the convex head main body 2B. The main electrode 20 has
A signal pulse source 23 for generating a signal pulse for flying ink and a main bias source 24 for applying a predetermined bias voltage are connected via a lead wire 22, and a bias voltage is always applied to the main electrode 20. To apply a signal pulse.

The auxiliary electrode 21 is provided on the other side of the ink recovery path 7, that is, on the concave head body 2A side, by a predetermined length along the extending direction of the ink recovery path 7 from near the ejection point P. Is formed. Therefore, this auxiliary electrode 2
Numeral 1 is opposed to the main electrode 20 and arranged in an insulated state. The auxiliary electrode 21 is connected to an auxiliary bias source 26 for applying a predetermined bias voltage via a lead wire 25, so that a bias voltage is always applied to the auxiliary electrode 21. This auxiliary bias source 26 is commonly connected to each auxiliary electrode 21. The electrodes 20 and 21 are formed of a conductive member such as a copper foil. Each of the bias sources 24 and 26 generates an electric field having the same polarity as the charge of the colorant particles in the ink 8, and acts to prevent the flow of the colorant particles. The voltages of the bias sources 24 and 26 vary depending on the viscosity of the ink 8 and the amount of charge of the colorant particles. In FIG. 2, each main electrode 2
However, the present invention is not limited thereto, and the main electrode 20 of the adjacent ink recovery path 7 may be supplied.
Two of them may be electrically connected in common. In this case, the emission point P at which the ink particles 8A actually scatter is an intermediate point between the adjacent openings 5.

Next, the operation of the apparatus of the present invention configured as described above will be described. First, the main electrode 20 is supplied from the main bias power supply 24, and the auxiliary electrode 21 is supplied from the auxiliary bias source 2.
6, and an electric field having the same polarity as that of the charged colorant particles is generated. Then, by driving the micropump 11 provided in the ink introduction passage 10, the ink 8 in the ink tank 9 is supplied little by little, and flows in the ink supply passage 6 in the direction of the arrow 30. At this time, since no electrodes are provided in the ink supply path 6, the charged colorant particles in the ink 8 are substantially uniformly dispersed in the insulating liquid. Then, the tip 20 of the main electrode 20
In the vicinity of A, the colorant particles in the ink 8 repel the main electrode 20 by an electric field of the same polarity generated by the bias voltage from the main bias source 24, and aggregate near the emission point P.

Further, when the ink 8 advances from the ejection point P in the direction of the arrow 31, the colorant particles are moved from the ejection point P by the influence of each electric field generated by the bias voltage applied to the main electrode 20 and the auxiliary electrode 21. Movement is suppressed, most of the ink is collected here, and part of the ink is collected in the center of the ink recovery path 7 by the viscosity of the insulating liquid against the electric field, and a small amount of colorant particles is recovered. Become. Therefore, many colorant particles stay and aggregate at the ejection point P. As described above, when the signal pulse voltage from the signal pulse source 23 is superimposed on the main electrode 20 in the state where the ink 8 is circulated, a large Coulomb force is generated, and the colorant particles aggregated at the ejection point P are insulative. The ink particles 8A are separated against the viscosity of the liquid, fly toward the recording paper 4 held on the counter electrode 3, and adhere to the recording paper 4. Thus, characters and images are formed on the recording paper 4 by sequentially flying the colorant particles.

As described above, in this embodiment, the main electrode and the auxiliary electrode for applying only the bias voltage are provided only on the ink recovery path 7 side, so that the colorant particles are efficiently aggregated at the ejection point P. As a result, the colorant particles are abundant, the lack of density is eliminated, and high-quality printing without image unevenness can be performed. In addition, since the colorant particles can be quickly and efficiently aggregated at the ejection point P, it is possible to perform high-speed recording by dramatically increasing the frequency of the signal pulse.

In the above embodiment, the main electrode 20 is formed on a part of the inner wall surface of the ink recovery path. However, the present invention is not limited to this. For example, as shown in FIG.
May be enlarged to the inside of the convex head main body 2B so as to reach about half in the illustrated example. In this case, the main electrode 2
1, the upper end portion 20B on the left side in the figure is preferably located a small distance on the ink supply path 6 side in the same manner as in the case shown in FIG. 1 so as to enhance the aggregation efficiency of the colorant particles. Also,
In the above embodiment, a large number of pairs of the ink supply path 6 and the ink recovery path 7 are provided in parallel in the horizontal direction (see FIG. 2). As shown in the figure, it may be provided in multiple stages in the vertical direction in the figure. In the illustrated example, the case of two stages is described, but the number of stages may be further increased.

In this case, the former ink recovery path 7 and the latter ink supply path 6 are connected, and at this connection point X, an ink supply path 33 for replenishing the colorant particles consumed in the previous step.
Connect. Even when three or more stages are provided, the ink supply path 33 is connected to each connection point X other than the ink recovery path at the bottom.
The other end of the ink supply path 33 is connected to the discharge side of the micro pump 11 in the uppermost ink introduction path 10. According to this, in addition to the above-described functions and effects, the colorant particles consumed in the upper stage can be sequentially replenished, so that higher-speed printing can be performed without causing the concentration of the colorant particles to be insufficient.

[0020]

As described above, according to the ink jet recording apparatus of the present invention, the following excellent functions and effects can be exhibited. A main electrode and an auxiliary electrode are provided only on the ink recovery path side, and a bias voltage is applied to the main electrode and the auxiliary electrode to suppress the flow of the colorant particles from the ejection point to the downstream side. Colorant particles can be quickly and efficiently aggregated and maintained. Therefore, since there is no shortage of colorant particles during recording, image quality does not occur and high image quality can be obtained. In addition, since the colorant particles can be efficiently aggregated at the ejection point, high-speed recording at a high frequency can be performed without causing a concentration shortage of the colorant particles. Further, by providing an ink supply path and an ink recovery path in multiple stages and providing an ink supply path at a connection point, it is possible to perform higher-speed printing without causing insufficient colorant particle concentration or insufficient dot size. .

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing an ink jet recording apparatus according to the present invention.

FIG. 2 is a partial sectional view taken along line AA in FIG.

FIG. 3 is an enlarged sectional view showing a modification of the recording head.

FIG. 4 is an enlarged sectional view showing another embodiment of the ink jet recording apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ink jet recording apparatus, 2 ... Recording head, 3 ... Counter electrode, 4 ... Recording paper (recording medium), 6 ... Ink supply path,
7 ... ink recovery path, 8 ... ink, 9 ... ink tank, 10 ...
Ink introduction passage, 12: ink recovery tank, 20: main electrode,
Reference numeral 21: auxiliary electrode, 23: signal pulse source, 24: main bias source, 26: auxiliary bias source, 33: ink supply path, P
... the injection point.

Claims (4)

[Claims] An ink in which charged colorant particles are dispersed in an insulating liquid is recovered from an ink recovery path while being supplied to an ejection point via an ink supply path, and the same as the colorant particles. In an ink jet recording apparatus in which the colorant particles fly from the ejection point toward the recording medium by applying a polar electric field, an electric field for flying the colorant particles is provided to one side of the ink recovery path. An ink-jet recording apparatus, wherein a main electrode is provided, and an auxiliary electrode for providing an electric field having the same polarity as the colorant particles is provided on the other side of the ink recovery path so as to face the main electrode. 2. The ink jet recording apparatus according to claim 1, wherein a bias voltage for applying an electric field having the same polarity as that of the colorant particles is applied to the main electrode. 3. The ink jet recording apparatus according to claim 1, wherein the main electrode and the auxiliary electrode are provided so as to extend from the vicinity of the ejection point along the ink recovery path. 4. The ink supply path and the ink recovery path are connected in series over a plurality of stages, and the ink is supplied to a connection point between the preceding ink recovery path and the subsequent ink supply path. 4. An ink jet recording apparatus according to claim 1, wherein an ink supply path is connected.