JP2003226015A - Electrostatic inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic inkjet recorder which can solve clogging of an ink head part by preventing precipitation of solid components in ink at an ink discharge part. <P>SOLUTION: The electrostatic inkjet recorder forms images onto a recording paper P by discharging from the ink head part 10, the ink charged by a Coulomb force of an electric field generated when a voltage is impressed to discharge electrodes 103. The ink head part 10 is set standing so that the ink discharge part 102 faces upward. Moreover, an ink channel 107 is set in the rear of the ink discharge part 102. Solid components included in the ink near the ink discharge part 102 are collected by the action of a gravity into the ink channel 107, whereby the precipitation of the solid components in the ink at the ink discharge part 102 is prevented. <P>COPYRIGHT: (C)2003,JPO

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 forming an image on a recording medium by ejecting charged ink by Coulomb force.

[0002]

2. Description of the Related Art In recent years, an electric field is formed between an ink head portion and a counter electrode arranged so as to face the ink head portion, and ink charged by the Coulomb force from the electric field is discharged from the ink head portion. 2. Description of the Related Art There is known an electrostatic ink jet recording apparatus that forms an image on a recording sheet by discharging the recording sheet conveyed between a head portion and a counter electrode toward the recording sheet. In such an electrostatic ink jet recording apparatus, it is necessary to concentrate the ink in order to fix the ink on the recording medium and to make the ink diameter of the ejected ink suitable. Therefore, before ejecting the ink, a bias voltage is generally applied to the ejection electrode to concentrate the charged solid components contained in the ink on the ink ejection portion (concentrate the ink). Further, the ink ejecting portion needs to be formed so as to project toward the front in the ink ejecting direction from the ink head portion in order to reduce the diameter of ejected ink and obtain a high-definition image.

[0003]

However, not all of the ink concentrated in the ink ejecting section is ejected, and some remains without being ejected. Since the residual ink is concentrated, it contains a high-density solid component, and the solid component precipitates after long-term use. Further, the solid component of the ink is more likely to settle because the ink ejection portion is formed so as to project. Such precipitation of the solid component of the ink hinders the smooth supply of the ink to the ink ejecting portion and causes clogging of the ink head portion.

The present invention has been made in order to solve such a problem, and prevents the solid component in the ink from settling in the ink ejecting section, thereby eliminating the clogging of the ink head section. An object is to provide an electrostatic ink jet recording device.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 is such that a plurality of ejection electrodes arranged at a predetermined pitch in the width direction of the recording paper, and projecting forward from each ejection electrode. And an ink head portion including an ink discharge portion formed on the ink discharge portion and an ink flow path disposed behind the ink discharge portion and circulating ink in a direction intersecting the ink discharge direction at a predetermined speed, and facing the ink head portion. A recording medium by ejecting the ink supplied from the ink flow path to the ink ejecting section by a Coulomb force from an electric field generated between the counter electrode and the ink head section. An electrostatic ink head recording device for forming an image thereon, comprising solid component recovery means for recovering solid components in ink remaining in the vicinity of the ink ejecting section into the ink flow path. It is electrostatic ink jet recording apparatus characterized.

According to this structure, the ink supplied from the ink flow path to the ink ejection portion by the capillary phenomenon is concentrated after receiving the Coulomb force from the electric field formed between the ejection electrode and the counter electrode and then concentrated. It is discharged from the discharge part,
The ink concentrated and remaining in the vicinity of the ink ejecting portion is collected by the solid component collecting means in the ink flow path arranged behind the ink ejecting portion, so that the ink precipitates due to the concentration of the ink in the ink ejecting portion. Is prevented, and clogging of the ink head unit is eliminated.

According to a second aspect of the present invention, in the ink jet recording apparatus according to the first aspect, as the solid component recovery means, the ink head portion is arranged so that the ink ejection direction is above the horizontal direction. Is characterized by.

According to this structure, since the ink head portion is arranged so that the ink ejection direction is above the horizontal direction, the solid component of the ink remaining in the ink ejection portion is removed by the action of gravity. The ink is collected in the ink passage arranged in the rear.

According to a third aspect of the present invention, in the ink jet recording apparatus according to the first aspect, the ink head portion is rotatably arranged to change the ink ejection direction, and the solid component recovery means is The ink head unit is rotated so that the ink ejection direction is above the horizontal during standby without ink ejection, and is below the ink ejection direction during the standby state during ink ejection. It is characterized in that the part is rotated.

According to this structure, since the ink head portion is rotated so that the ink ejection direction is above the horizontal during standby, the solid components of the ink remaining in the ink ejection portion are affected by the action of gravity. Collected in the ink flow path.
Further, when ejecting ink, the ink head portion is rotated so as to be lower than the ink ejection direction during standby, so that the action of gravity on the solid components of the ink in the ink ejection portion is reduced, and ink concentration is promoted. .

According to a fourth aspect of the present invention, in the electrostatic ink jet recording apparatus according to any one of the first to third aspects, the solid component recovery means is configured such that the Coulomb force is equal to the ink in a standby state in which the ink is not ejected. It is characterized in that a voltage is applied to the ejection electrode or a voltage is not applied to the ejection electrode so as to be opposite to the ejection direction. According to this configuration, since voltage is applied to the ejection electrodes so that the ink ejection direction is opposite to the ink ejection direction during standby, the solid components of the ink remaining in the ink ejection portion are in the direction opposite to the ejection direction (ink flow path side). To the ink flow path.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment) FIG. 1 is a perspective view showing an entire ink head portion of an ink jet recording apparatus according to a first embodiment of the present invention. In addition, FIG.
FIG. 2 is a sectional view of the ink jet recording apparatus according to the embodiment, taken along the line AA in FIG. 1. The inkjet recording apparatus according to the first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In this ink jet recording apparatus, as shown in FIG. 2, an ink head portion 10 is erected so that the ink ejection direction is an upward direction, and a counter electrode is disposed opposite to the ink head portion 10. 20 and an intermediate electrode 30 disposed between the ink head portion 10 and the ink head portion.

The ink head portion 10 is formed at a predetermined pitch in the width direction orthogonal to the conveying direction of the recording paper P (the direction of the arrow in FIG. 2) so as to project to the front of the base 101 made of, for example, ceramic. Ink ejector 10
2. Ejection electrodes 103 arranged on the upper surface side of the base 101 at the same pitch as the ink ejection portion 102 in the width direction, electric field separation electrodes 104 arranged at intermediate positions in the width direction of the ejection electrodes 103, and the upper surface of the base 101. And an ink containing portion 105 for covering.

The ink ejecting portion 102 is formed in a plate shape having an isosceles triangle whose tip is a top portion by cutting the end surface of the base 101 or the like. Therefore, the solid component in the ink is concentrated at the top and the ink is easily concentrated, and the diameter of the ejected ink is reduced, and a high-definition image layer can be obtained.

The pitch interval of the ink ejecting portion 102 is 40 μm when the resolution of the printer is 600 dpi, for example.
Is.

The ejection electrode 103 is made of a metal member having a high electric conductivity, such as gold, and has a base 10.
1 is stacked on top. A bias voltage source E1 and a pulse voltage source E2 are connected to each ejection electrode 103, a predetermined electric field is applied to the ejection electrode, and each ejection electrode 1
03 An electric field is formed between the ink head unit 10 and the counter electrode 20. The negative electrode of the pulse voltage source E2 is the intermediate electrode 30.
It is connected to the positive electrode of a voltage source E4 that applies a predetermined voltage to. The bias voltage source E1 applies a voltage of 1500 V to the ejection electrode 103. The pulse voltage source E2 is a voltage capable of obtaining a sufficient Coulomb force for ejecting the ink of the ink ejecting unit 102, for example, 5
00V is applied to the ejection electrode 103. The ejection electrode 1
In order to prevent the ejection electrode 103 from being peeled off, a groove is formed in the width direction at a predetermined pitch, and a metal member having high conductivity is formed inside the groove instead of stacking 03 on the base 101. The ejection electrode 103 may be formed by stacking layers.

The electric field separation electrodes 104 are arranged to electrically shield (screen) each of the ejection electrodes 103, and the electric field generated by the ejection electrodes 103 affects the adjacent ejection electrodes 103, so that the ink is It has a function of preventing the ink from being ejected in an oblique direction and a function of preventing the ink from being erroneously ejected by the electric field from the adjacent ejection electrode 103 during the standby time when the ink is not ejected.
The electric field separation electrode 104 is made of a metal member having high electric conductivity, such as gold. Electric field separation electrode 104
A voltage source E3 is connected to each of the. The negative electrode of the voltage source E3 is connected to the positive electrode of the voltage source E4. The voltage source E3 provides the electric field separation electrode 104 with a voltage sufficient to electrically shield the ejection electrodes 103, for example, a voltage of 1000V.

The ink accommodating portion 105 includes the ink ejecting portion 10.
It has a substantially rectangular parallelepiped shape with a taper formed on the second side, and has a cavity 105a inside. Ink storage unit 105
Ink supply pipes 106 are connected to both side surfaces 105c of the cartridge so that ink is supplied from an unillustrated ink tank. A pump for circulating ink at a predetermined speed between the ink supply pipe 106 and the ink tank.
(Not shown) is connected, and by the driving force of this pump,
The ink is always circulated in the cavity 105a in a direction intersecting with the ink ejection direction (direction shown by an arrow in FIG. 1), and an ink flow path 107 is formed. An elongated slit 105b is formed in the width direction of the recording paper P on the ink ejection portion 102 side of the ink storage portion 105, and a part of the ink circulating in the ink flow path 107 is provided through this slit 105b. Due to the capillary phenomenon.
Flows to.

Since the ink constantly circulates in the ink flow path 107, a negative pressure is applied to the ink in the vicinity of the ink ejection portion 102 from the ink circulating in the ink flow path 107 in the direction of collecting the ink in the ink flow path 107. . As a result, the solid component in the ink remaining in the ink ejection unit 102 is collected in the ink flow path 107, and the ink is prevented from settling.

The counter electrode 20 is grounded and functions as an electrode facing the ejection electrode 103. The counter electrode 20 has a flat plate shape and is made of a conductor such as copper.
The recording paper P is slidable on the counter electrode 20.
A transport mechanism that transports the recording paper P in the sub-scanning direction at a constant speed is connected to the counter electrode 20.
The recording paper P set on is conveyed at a constant speed.
The counter electrode 20 may be a drum-shaped one that rotates, instead of the flat-plate-shaped one.

A voltage source E4 is connected to the intermediate electrode 30, and a predetermined voltage, for example, a voltage of 500 V is applied to increase the potential gradient between the ink head portion 10 and the intermediate electrode 30, and the ink ejecting portion. The electric field near 102 is strengthened. The intermediate electrode 30 is made of a conductive metal such as copper and has a flat plate shape, and a slit 31 for passing ink ejected from the ink ejecting unit 102 is formed in a substantially central portion.

FIG. 3 is an explanatory diagram showing the voltage applied to the ejection electrode 103, where the vertical axis represents voltage and the horizontal axis represents time. In this embodiment, PWM control is performed, and for example, the pulse width of the voltage applied to the ejection electrode 103 is changed in 256 steps to express 256 steps of gradation. That is, the higher the gradation, the larger the pulse width of the pulse voltage source E2 and the longer the ink ejection time, thereby increasing the amount of ink ejected from the ink ejecting unit 102 and increasing the pixel density.

Next, the operation of ejecting ink will be described with reference to FIG. First, in a standby state in which ink is not ejected, a bias voltage is applied to each ejection electrode 103 by the bias voltage source E1. As the ink, a pigment-based ink having a positive charge and a density of 3 to 10% is used. By the bias voltage, the ink ejection unit 1
In the vicinity of 02, an electric field is generated in the ink ejection direction,
The ink in the ink ejection unit 102 is concentrated to a concentration of about 20%. In this case, the discharge electrode 103 is applied with a voltage of 2000 V by the bias voltage source E1 and the voltage source E4.

Next, when a pulse voltage is applied to the ejection electrode 103, the electric field in the vicinity of the ink ejection section 102 becomes larger, and the ink concentrated in the ink ejection section 102 due to the Coulomb force from this electric field is Towards recording paper P
It is ejected (in the ink ejection direction). In this case, the ejection electrode 1
A voltage of 2500 V is applied to 03 from the bias voltage source E1, the pulse voltage source E2, and the voltage source E4. In this inkjet recording apparatus, the width dimension of the ink head portion 10 is larger than the width dimension of the recording paper P.
One line of image is printed at the same time. Therefore, the ink head unit 10 performs the printing operation in a fixed state without moving in the width direction (main scanning direction).

The ejected ink is accelerated by the Coulomb force from the electric field formed between the intermediate electrode 30 and the ejection electrode 103, and passes through the slit 31. The ink that has passed through the slit 31 advances further forward by the Coulomb force of the electric field formed between the counter electrode 20 and the intermediate electrode 30, and eventually reaches the recording paper P. This completes the printing of one line of the image. Next, the recording paper P is conveyed by the paper conveyance mechanism, and printing of the next line is started. In this way, the image is printed on the recording paper P.

As described above, in the present ink jet recording apparatus, the ink flow path 107 is formed behind the ink ejection portion 102 in the direction intersecting the ink ejection direction, and the solid component in the ink remaining in the ink ejection portion 102 is formed. The ink flow path 1
07, the solid component in the ink is prevented from settling, and the ink head portion 10 is erected to further enhance the effect of preventing the solid component in the ink from settling. That is, since the ink head unit 10 is erected, the ink in the ink ejecting unit 102 is in the downward direction, that is, in the ink ejecting direction in addition to the negative pressure in the direction opposite to the ink ejecting direction by the ink circulating in the ink flow path 107. Since gravity is applied in the opposite direction, gravity is applied in the opposite direction to the ink ejection direction. As a result, the ink ejection unit 102
The solid component in the ink remaining in step (3) is reliably collected in the ink flow path 107, and the clogging of the ink head is eliminated.

(Second Embodiment) Next, a second embodiment of the ink jet recording apparatus according to the present invention will be described. In the ink jet recording apparatus according to the second embodiment, in the standby state where ink is not ejected, the direction of the electric field near the ink ejection unit 102 is opposite to the ink ejection direction, that is, the ink flow path 1
A voltage is applied to the ejection electrode 103 so as to be directed in the 07 direction to prevent ink precipitation.

FIG. 4 is a graph showing the voltage applied to the ejection electrode 103, where the vertical axis represents voltage and the horizontal axis represents time. First, when the inkjet recording apparatus is turned on (T0 in FIG. 4), a bias voltage is applied to the ejection electrode 103, and the ink in the vicinity of the ink ejection portion 102 is concentrated. Next, a signal voltage is applied to the ejection electrode 103 (T1 in FIG. 4), a larger electric field is applied to the ink ejection unit 102, and ink is ejected from the ink ejection unit 102. Then, when printing is completed, a reverse bias voltage is applied to the ejection electrode 103 (T2 in FIG. 4). Here, the timing of applying the reverse bias voltage may be set, for example, each time printing of one image is completed, or when printing a plurality of images in succession, each time continuous printing is completed. You can also do this. Also, even while printing one image,
A reverse bias voltage may be applied to each ejection electrode 103 from which ink is not ejected.

Next, when printing is restarted, a bias voltage is applied to the ejection electrode 103 (T3 in FIG. 4), the ink in the vicinity of the ink ejection portion 102 is condensed, and a signal is sent to the ejection electrode 103 after a lapse of a predetermined time. Voltage is applied (T in FIG.
4) Ink is ejected from the ink ejecting unit 102.

The present invention can take the following forms.

(1) In the ink jet recording apparatus according to the first embodiment, the ink in the ink ejecting section 102 is supplied to the ink flow path 10.
The ink head unit 10 is erected in order to collect the ink in No. 7, but the present invention is not limited to this, and the ink head unit 10 is rotatably attached so that the ink ejection direction is horizontal when ejecting ink. Rotate the ink head unit 10
(See FIG. 5A) In the standby state, the ink ejection unit 1
The ink head unit 10 may be rotated so that 02 is in the upward direction (see FIG. 5B). That is, when the ink is ejected, since the ink head unit 10 is in the horizontal direction, the action of gravity to collect the ink in the ink ejection unit 102 into the ink flow path 107 is weakened, and the ink in the ink ejection unit 102 is quickly concentrated. To be done. On the other hand, in the standby state where it is not necessary to concentrate the ink, the ink ejection unit 102
Since the ink head unit 10 is rotated so that the ink is directed upward, the solid component in the ink near the ink ejection unit 102 is collected in the ink flow path 107 by the action of gravity.
Precipitation of solid components in the ink is prevented. To rotate the ink head unit 10, a motor may be attached to the ink head unit, and the ink head unit 10 may be rotated by appropriately outputting a control signal to the motor.

(2) In the ink jet recording apparatus of the second embodiment, the reverse bias voltage is applied to the ejection electrode 103 in the standby state, but the invention is not limited to this, and the voltage applied to the ejection electrode 103 is 0V. Good. Discharge electrode 1
Even if the reverse bias voltage is not applied to 03, even if the voltage applied to the ejection electrode 103 is 0 V, the ink ejection unit 1
The solid component in the ink around 02 weakens the Coulomb force in the ink ejection direction, and is thus collected in the ink flow path 107 by the negative pressure from the ink flowing in the ink flow path 107. As described above, by setting the voltage applied to the ejection electrode 103 to 0 V in the ink standby state, it is possible to reduce the power consumption.

(3) In the above description, the first and second embodiments have been shown individually, but the present invention is not limited to this.
A combination of the first embodiment and the second embodiment, that is, an ink jet recording apparatus in which the ink head unit 10 is erected and a reverse bias voltage is applied to the ejection electrode 103 during standby may be adopted.

(4) In the first embodiment, the ink head portion 10 is erected so that the ink ejecting portion 102 faces upward. However, the present invention is not limited to this, and the ink ejecting portion 102 lies obliquely upward. The ink head unit 10 may be provided. In this case, the effect of gravity on the solid components in the ink in the vicinity of the ink ejecting portion 102 is weakened, but the ink can be rapidly concentrated accordingly. In short, from the balance between the concentration of the ink in the ink ejection unit 102 and the gravity acting to collect the ink in the ink flow path 107,
The inclination of the ink head unit 10 may be set.

(5) In the first and second embodiments, the intermediate electrode 30 is arranged between the ink head portion 10 and the counter electrode 20, but the invention is not limited to this, and the intermediate electrode 30 may be omitted. By omitting the intermediate electrode 30, the structure can be simplified.

(6) In the first and second embodiments, the ink head portion 10 having an isosceles triangle whose plane is parallel to the width direction is adopted, but the invention is not limited to this, and the ink ejection portion 102 is
As shown in FIG. 6, the ink ejection unit 102 may be formed so that the plane of the ink ejection unit 102 is perpendicular to the width direction of the ink head unit 10. In this case, each ink ejection unit 1
By forming the convex portion 120 protruding from the ink ejection portion 102 with a short dimension in the ink ejection portion 102, a meniscus of ink is formed between the ink ejection portion 102 and the convex portion.

(7) In the first and second embodiments, the plane of the ink ejection portion 102 on the isosceles triangle is arranged so as to be parallel to the width direction, but the invention is not limited to this, and is shown in FIG. Thus, the plane may be arranged so as to be perpendicular to the width direction. In this case, the slits 13 are provided between the ink ejection units.
A part of the ink that circulates in the ink flow path 107 through this slit is supplied to the ink ejection portion by the capillary phenomenon.

[0039]

As described above, according to the present invention, since the ink recovery means for recovering the solid component in the ink is provided, it is possible to prevent the solid component in the ink from being deposited in the vicinity of the ink ejecting portion, and the ink head. It is possible to eliminate clogging of parts.

[Brief description of drawings]

FIG. 1 is a perspective view showing an overall configuration of an ink head unit of an inkjet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of the inkjet recording apparatus according to the first embodiment of the present invention.

FIG. 3 is a graph showing a voltage applied to the ejection electrode with the intermediate electrode as a reference in the first embodiment.

FIG. 4 is a graph showing a voltage applied to a discharge electrode of an inkjet recording device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a modified example of the present invention, in which the ink head portion rotates.

FIG. 6 is a view showing a convex ink ejecting portion, which is a modified example of the invention.

FIG. 7 is a modification of the present invention, showing a perspective view of an ink head portion when the ink ejection portions are arranged such that the planes are perpendicular to the width direction.

[Explanation of symbols]

10 Ink head part 20 Counter electrode 30 intermediate electrode 31 slits 101 base 102 ink ejector 103 each discharge electrode 103 ejection electrode 104 electric field separation electrode 105 ink container 105a cavity 105b slit 106 ink supply pipe 107 ink flow path

Claims (4)

[Claims] 1. A plurality of ejection electrodes arranged at a predetermined pitch in the width direction of a recording sheet, an ink ejection section formed so as to project forward from each ejection electrode, and an ink disposed behind the ink ejection section. An ink head portion including an ink flow path that circulates the ink in a direction intersecting the ink discharge direction at a predetermined speed, and a counter electrode that is disposed so as to face the ink head portion, and discharges the ink from the ink flow path. An electrostatic ink head recording apparatus for forming an image on a recording medium by ejecting ink supplied to a recording section by a Coulomb force from an electric field generated between the counter electrode and the ink head section, An electrostatic ink jet recording apparatus comprising solid component recovery means for recovering a solid component in ink remaining in the vicinity of an ejection portion into the ink flow path. 2. The electrostatic ink jet recording apparatus according to claim 1, wherein, as the solid component recovery means, the ink head portion is arranged such that an ink ejection direction is above a horizontal direction. 3. The ink head section is rotatably arranged to change the ink ejection direction, and the solid component recovery means has an ink ejection direction higher than horizontal when in a standby state in which ink is not ejected. 2. The static ink according to claim 1, wherein the ink head section is rotated so that the ink head section is rotated below the ink discharge direction in the standby state during ink discharge. Electric inkjet recording device. 4. The solid component recovery means applies a voltage to the ejection electrode or applies a voltage to the ejection electrode so that the Coulomb force is in a direction opposite to an ink ejection direction in a standby state in which ink is not ejected. The electrostatic ink jet recording apparatus according to claim 1, wherein no voltage is applied.