JP2003260797A - Electrostatic inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent instability of an ink discharge amount and clogging of an ink head because of excess concentration of a solid component in ink in an electrostatic inkjet recorder which forms images on a recording paper by discharging ink drops from the ink head with the use of the ink containing the solid component charged to + or -. <P>SOLUTION: An ink supply tube 106a and a discharge tube 106b are set in a cavity 105a in the rear of an ink discharge part 102 to circulate the ink in a direction orthogonal to an ink projection direction. Discharge electrodes 103 having a predetermined angle to an ink flow direction are arranged in parallel to each other in the vicinity of each ink discharge part 102. An ink circulation velocity by a pump 108 is made variable, and an ink flow velocity at a non printing time in the vicinity of a main channel inside the cavity 105a is made faster than a flow velocity at a printing time. The solid component stored in the vicinity of the ink discharge part 102 is sucked by a negative pressure towards the main channel to ride on the circulating ink flow and collected in an ink tank 107. <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 ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus which forms an electric field and ejects ink charged by Coulomb force.

[0002]

2. Description of the Related Art In an electrostatic ink jet recording apparatus, a plurality of ejection electrodes for ejecting ink droplets are arranged in parallel with the width direction of recording paper to form an ink head, and the ejection electrodes and the ejection electrodes are arranged. An electric field is formed between the discharge electrode and a counter electrode disposed so as to face the discharge electrode, and the Coulomb force of the electric field causes the charged ink to be discharged from the ink discharge portion formed in front of each discharge electrode. An image is formed on the recording paper. Each ink ejecting portion is provided so as to correspond to one pixel of the image, and by controlling the amount of ink ejected from the ink ejecting portion,
The gradation of each pixel can be changed.

The ink used in such an electrostatic ink jet recording apparatus contains a solid component charged to + or-in a proportion of, for example, 3 to 10%, and the ink is well fixed on the recording paper. In order to do so, the solid component in the ink is concentrated to about 20% and ejected.

For example, in the conventional apparatus described in Japanese Patent Laid-Open No. 9-11475, the ink is circulated in the cavity formed behind the ink ejection portion in a direction parallel to the ejection direction of the ink, and the ink is circulated in the cavity. A predetermined voltage is applied to the provided ink concentrating electrode, and the charged solid component is sucked in the vicinity of the electrode to concentrate the solid component in the ink.

[0005]

However, not all of the concentrated ink is ejected in the vicinity of the ink ejection portion of the ink head, and some of the solid components in the ink remain in the vicinity of the ink ejection portion. To do. As a result of using the electrostatic ink jet recording device for a long time, the solid component in the ink is excessively concentrated and the ink ejection amount becomes unstable, or the solid component is solidified in the ink ejection part and the ink head is clogged. Had a problem of causing.

Further, the above-mentioned conventional apparatus has a problem that only the solid component in the ink is concentrated, and the excessively concentrated solid component cannot be diluted or controlled within a certain concentration range. It was

The present invention has been made in order to solve the above-mentioned problems of the conventional example, and enables the dilution of the solid component in the excessively concentrated ink in the electrostatic ink jet recording apparatus, and While stabilizing the discharge amount,
The purpose is to prevent clogging of the ink head.

[0008]

In order to achieve the above object, an electrostatic ink jet recording apparatus according to the present invention comprises a plurality of ink ejecting portions arranged at a predetermined pitch in a direction orthogonal to a protruding direction of ink. A cavity for storing a certain amount of ink, the cavity being formed behind the ink ejecting portion, and an ink supply provided in the cavity so that the ink flows in a direction orthogonal to a protruding direction of the ink. A discharge pipe and a discharge pipe, and discharge electrodes provided in the vicinity of the respective ink discharge portions in the cavity, and by changing the flow velocity of the ink in the cavity, It is characterized by controlling the concentration of the solid component in the ink.

Further, another electrostatic ink jet recording apparatus of the present invention is formed with a plurality of ink ejection portions arranged at a predetermined pitch in a direction orthogonal to the ink ejection direction, and behind the ink ejection portion. And a cavity for storing a fixed amount of ink, an ink supply pipe and a discharge pipe provided in the cavity so that the ink flows in a direction orthogonal to the direction of protrusion of the ink, and the inside of the cavity. And a discharge electrode provided in the vicinity of each of the ink discharge portions, and a structure that provides resistance to the flow of ink in the cavity is provided.
It is characterized in that the concentration of the solid component in the ink in the vicinity of the ink ejecting portion is controlled by switching the circulation direction of the ink in the cavity.

In the above structure, the structure is preferably an electrode formed so as to be convex or concave with respect to the inner wall of the cavity.

Further, it is preferable that the structure is a film which is provided so as to be able to be taken in and out from the cavity and has unevenness at an end portion or a flat portion corresponding to a pitch of the ink ejection portion.

Further, the structure may be a thin plate which is provided so as to be able to be taken in and out of the cavity and which is formed in a predetermined shape so as to provide resistance to a circulating ink flow in the vicinity of an end thereof. preferable.

[0013]

DETAILED DESCRIPTION OF THE INVENTION (First Embodiment) An electrostatic ink jet recording apparatus according to a first embodiment of the present invention will be described. FIG. 1 shows the configuration of the ink head in the electrostatic ink jet recording apparatus of the first embodiment. Further, FIG. 2 shows a schematic configuration of an ink ejection mechanism in the electrostatic ink jet recording apparatus.

As shown in FIG. 2, in the electrostatic ink jet recording apparatus of the first embodiment, the recording paper P is in the direction shown by the arrow in FIG. 2 (for example, vertical direction, hereinafter referred to as "sub-scanning direction"). It shall be transported at a constant speed. The ink head 10 is in a direction orthogonal to the recording surface of the recording paper P (eg, horizontal direction, hereinafter referred to as “main scanning direction”).
It is arranged so that the ink is ejected to. The counter electrode 20 is provided so as to face the ink head 10 with the recording paper P in between. A secondary electrode 30 is provided between the ink head 10 and the counter electrode 20.
It is provided so as to face 0. The counter electrode 20 and the secondary electrode 30 are substantially parallel to the recording surface of the recording paper P.

The ink head 10 is fixed and has a printing width longer than the width of the recording paper P in the main scanning direction. As an example, in the case of printing a high-quality print of a photographic quality with the electrostatic ink jet recording apparatus of the present embodiment, if the width of the recording paper P in the main scanning direction is 3.5 inches (about 89 mm), the ink The print width of the head 10 is 90 mm or more so as to be longer than that. The ink is ejected onto the recording paper P all at once from the ink ejection unit 102, which will be described later.
Is ejected toward and is printed in line units of the image.
Since only a predetermined color (1 color) of ink can be ejected from the ink head 10, it is assumed that the ink heads 10 corresponding to the respective color inks are arranged in the sub-scanning direction in the case of color printing. The basic structure of the electrostatic ink jet recording apparatus is the same in the other embodiments, and therefore its description is omitted.

As shown in FIG. 1, the ink head 10 includes
For example, the base member 101 and the cover member 105 are made of a ceramic material. At the end of the base member 101 on the ink ejection side, a plurality of ink ejection portions 102 are formed at a predetermined pitch so as to eject in the ink ejection direction. In addition, the upper surface 101 of the base member 101
In a, a plurality of ejection electrodes 103 and electric field separation electrodes 104 are formed at the above-mentioned predetermined pitch corresponding to each ink ejection portion 102.

The ink ejecting portion 102 is formed into an isosceles triangle whose tip is the apex, for example, by cutting the end face of the base member 101, and the solid component in the ink is the apex of the ink ejecting portion 102. The solid component in the ink is concentrated by concentrating on the ink.
The resolution of this electrostatic ink jet recording device is 600d.
Assuming pi, the pitch of the ink ejection unit 102 is about 40 μm.
m.

The discharge electrode 103 is made of a highly conductive material such as gold, and is laminated on the upper surface 101a of the base member 101. As shown in FIG. 2, a bias voltage source E1 for applying a bias voltage, a pulse voltage source E2 for applying a pulse voltage at the time of ink ejection, and a solid component in ink are applied to each ejection electrode 103. A reverse bias voltage source E3 for applying a reverse bias voltage for dilution is connected. The positive electrode of the pulse voltage source E2 and the negative electrode of the reverse bias voltage source E3 are switchably connected by a switch S1. The negative electrode of the bias voltage source E1 and the positive electrode of the reverse bias voltage source E3 are connected to the positive electrode of a voltage source E5 for applying a predetermined voltage (for example, 500 V) to the secondary electrode 30. The bias voltage source E1 applies a bias voltage of, for example, 1500 V to the ejection electrode 103. The pulse voltage source E2 is
A voltage (eg, 500 V) sufficient to eject ink from the ink ejecting unit 102 is applied to the ejection electrode 103. Therefore, the voltage applied to the ink ejection unit 102 when ejecting ink is 2500V. The discharge electrode 10
The upper surface 1 of the base member 101 to prevent peeling
A plurality of grooves may be formed in the groove 01a at the above-described predetermined pitch, and a highly conductive material may be laminated inside each groove to form the ejection electrode 103.

The electric field separation electrode 104 is the discharge electrode 103.
Like the above, it is formed of a material having high conductivity, and is laminated on the upper surface 101a of the base member 101. A voltage source E4 is connected to each electric field separation electrode 104, and a predetermined voltage (for example, 10000 V) is applied. The electric field separation electrode 104 is located approximately in the middle of two adjacent ejection electrodes 103 and has a function of electrically shielding (screening) each ejection electrode 103. That is, assuming that the electric field separation electrode 104 does not exist, an electric field is generated due to the potential difference between the adjacent ejection electrodes 103, and the electric field may affect the ink to be ejected obliquely to the original ejection direction. . Further, in a standby state in which ink is not ejected, the electric field generated by the potential difference between the adjacent ejection electrodes 103 may cause the ink to be ejected by mistake. On the other hand, the electric field separation electrode 104
Are arranged between the adjacent ejection electrodes 103, the influence of the electric field generated between the adjacent ejection electrodes 103 is reduced, and the ink is prevented from being obliquely ejected or erroneously ejected. can do.

Discharge electrode 103 and electric field separation electrode 104
Are arranged in a direction substantially orthogonal to the ink flowing direction shown by arrow A in FIG. 1, but the arrangement is not necessarily limited to this, and the solid component in the ink is near the ink ejecting portion 102. In order to make it easier to collect in the
You may form so that it may make about 10 degrees.

An elongated single slit 105b parallel to the main scanning direction, that is, the arrangement direction of the ink ejection portions 102 is formed at the end of the cover member 105 on the ink ejection side. Behind the slit 105b and the cover member 10
A cavity 105a that functions as an ink storage portion is formed inside the ink container 5. In addition, an ink supply pipe 106a and an ink discharge pipe 106b are provided on both sides 105c of the cover member 105, and the ink flows in the direction indicated by arrow A in FIG. 1 (ink circulation direction).

Ink supply pipe 106a and ink discharge pipe 1
Reference numeral 06b is connected to an ink tank 107 and a pump 108, which are schematically shown, and is configured to circulate ink between the ink tank 107 and the cavity 105a at a predetermined flow rate. In the first embodiment, the flow rate of ink circulating in the pump 108 can be changed by, for example, changing the rotation speed of a motor for rotating the impeller of the pump 108.

Since the cross-sectional area of the cavity 105a is larger than the cross-sectional area of the ink supply pipe 106a, the ink tank 1
Even if the flow velocity of the ink circulating between 07 and the cavity 105a is constant, the flow velocity in the vicinity of the main flow path connecting the ink supply pipe 106a and the ink discharge pipe 106b is the highest inside the cavity 105a, and the ink ejection unit A phenomenon occurs in which the flow velocity in the vicinity of 102 and the vicinity on the opposite side to the main flow path becomes slow. In this way, when a difference in the flow rate of the ink occurs inside the cavity 105a, a negative pressure is generated so that the ink and the solid component therein are sucked from the portion having the slow flow velocity to the portion having the fast flow velocity. This negative pressure increases as the flow velocity difference inside the cavity 105a increases.

In the first embodiment, at the time of printing, the flow velocity of the ink circulating between the ink tank 107 and the cavity 105a is set to the first flow velocity which is slowed down to reduce the negative pressure due to the flow velocity difference in the cavity 105a. At the same time, a bias voltage is applied to the ejection electrode 103 to forcibly collect the solid component charged with, for example, + in the vicinity of the ink ejection portion 102, and after concentrating it to a predetermined concentration (for example, about 20%). Further, a pulse voltage is applied to the ejection electrode 103 to eject ink.

On the other hand, when the solid component in the ink is excessively concentrated, or when it is necessary to adjust the concentration of the solid component in the other ink, the amount of the ink circulating between the ink tank 107 and the cavity 105a is reduced. The flow velocity is set to a second flow velocity that is faster than the first flow velocity, the negative pressure due to the flow velocity difference in the cavity 105a is increased, and the discharge voltage 10
By turning off the bias voltage applied to No. 3, the solid component in the ink accumulated in the vicinity of the ink ejecting unit 102 is sucked to the main flow path side, the solid component in the ink is collected in the ink tank 107, and the ink is ejected. The concentration of the solid component in the ink near the portion 102 is lowered (diluted).

The counter electrode 20 is grounded and functions as an electrode facing the discharge electrode 103. Counter electrode 20
Is formed in a flat plate shape by a conductor such as copper, and the recording paper P slides on it. The secondary electrode 30 is
It is provided to strengthen the electric field in the vicinity of the ink ejecting unit 102, and a predetermined voltage (500 V) is applied by the voltage source E5 in order to increase the potential gradient between the ink head 10 and the secondary electrode 30. It The secondary electrode 30 is also formed in a flat plate shape with a conductor such as copper. In addition, in the vicinity of the center of the secondary electrode 30, the ink head 1
A slit 31 is formed in parallel with the width direction (main scanning direction) of the recording paper P for allowing the ink ejected from the zero ink ejecting unit 102 to pass therethrough.

The ink ejection control section 40 switches the switch S1 to the pulse voltage source E2 side when the main switch of the apparatus is turned on or when a print start signal is received, and the ejection electrode 10 is discharged.
A bias voltage is applied to 3 to concentrate the solid component in the ink in the vicinity of the ink ejection portion 102. Further, when the printing of one image of the apparatus is completed, the switch S1 is switched to the reverse bias voltage source E3 side, and the reverse bias voltage is applied to the ejection electrode 103 so that the solid component in the ink in the vicinity of the ink ejection section 102 is changed. Dilute. Also, during printing, for example, 2
Based on the image signal of 56 gradations, the pulse voltage source E2
Are controlled to apply a signal having a pulse width corresponding to the gradation of each pixel signal to the corresponding ejection electrode 103.

Next, the operation of the electrostatic ink jet recording apparatus of the first embodiment will be described with reference to FIG. First, as ink, the solid component charged to + is 3
A pigment-based ink containing about 10% is used.

When the main switch of the apparatus is turned on or the print start signal is received, the flow velocity of the ink by the pump 108 is switched to the slower first flow velocity. In parallel with this, the switch S1 is switched to the pulse voltage source E2 side, and a predetermined bias voltage is applied to each ejection electrode 103 by the bias voltage source E1. As a result, an electric field is generated near the ink ejection portion 102 in the ink ejection direction, and the concentration of the solid component in the ink is concentrated to about 20% near the ink ejection portion 102.

Next, when a predetermined signal voltage is applied to each ejection electrode 103 by the pulse voltage source E2, the electric field in the vicinity of the ink ejection section 102 becomes stronger, and the Coulomb force due to this electric field is received to concentrate the electric field. The ejected ink droplets are ejected from the ink ejection unit 102 toward the recording paper P.

The ejected ink droplet is accelerated by the Coulomb force due to the electric field formed between the secondary electrode 30 and the ejection electrode 103, and passes through the slit 31 of the secondary electrode 30. The ink droplets that have passed through the slits 31 are the secondary electrodes 3
0, the Coulomb force is generated by the electric field formed between the counter electrode 20 and the counter electrode 20, and further advances forward, and eventually reaches the recording paper P. As a result, printing for one line in the sub-scanning direction is completed. Next, the recording paper P is conveyed by one line in the sub-scanning direction, and the next line is printed. An image is formed on the recording sheet P by repeating these operations.

On the other hand, when the main switch of the apparatus is turned off or the printing is completed, the flow velocity of the ink by the pump 108 is switched to the faster second flow velocity. In parallel with this, all the voltages applied to the respective electrodes are turned off. As the ink flow velocity increases, the difference between the ink flow velocity in the vicinity of the ink ejection portion 102 and the ink flow velocity in the vicinity of the main flow path in the cavity 105a increases, and the solid component is sucked from the slow flow velocity portion to the fast flow velocity portion. Because of this, the negative pressure increases. Further, at that time, since the bias voltage is not applied to the ejection electrode 103, the force for attracting the solid component in the ink to the vicinity of the ink ejection portion 102 does not act. Therefore, the solid component accumulated in the vicinity of the ink ejecting unit 102 is sucked into the main flow path side, rides on the circulating ink flow, and is collected in the ink tank 107. As a result, the concentration of the solid component in the ink in the vicinity of the ink ejecting unit 102 decreases, the solid component does not settle or solidify in the slit 105b portion of the cover member 105, and the clogging of the ink head 10 is prevented. You can

(Second Embodiment) Next, an electrostatic ink jet recording apparatus according to a second embodiment of the present invention will be described. FIG. 3 shows the configuration of the ink head in the electrostatic ink jet recording apparatus of the second embodiment.

In the first embodiment, the ink tank 10
7 is configured to concentrate and dilute the solid component in the ink in the vicinity of the ink ejecting portion 102 by changing the flow rate of the ink circulating between the cavity 105a and the cavity 105a. By providing a structure that provides resistance to the flow of ink inside and switching the circulation direction of the ink in the cavity 105a, the solid matter in the ink in the vicinity of the ink ejection unit 102 is concentrated and diluted.

In FIG. 3, the ejection electrode 103 and the electric field separation electrode 104 are respectively formed in the vicinity of the main ink flow path in the cavity 105a so as to form a predetermined angle other than 90 degrees with respect to the ink circulation direction. Moreover, the inner wall of the cavity 105a, for example, the upper surface 10 of the base member 101.
They are formed parallel to each other so as to be concave or convex with respect to 1a.

When the solid components of the ink in the vicinity of the ink ejection portion 102 are concentrated in response to the main switch on of the apparatus or the reception of the print start signal, the ejection electrode 103 and the electric field separation electrode 104 resist the flow of ink. The circulation direction of the ink is switched so that the solid component in the ink is easily collected near the ink ejection unit 102. Specifically, the ink circulation direction is the direction indicated by the arrow A in FIG. 3, and the ejection electrode 103 and the electric field separation electrode 104.
9 is a clockwise view of the angle α formed by the
0 degree or more (obtuse angle).

With this structure, the ink flow in the vicinity of the main flow path, which has a high flow velocity, inside the cavity 105a causes the ejection electrode 103 and the electric field separation electrode 104 to flow.
The flow is disturbed by and the flow velocity becomes slow. at the same time,
The flow of ink is the ejection electrode 103 and the electric field separation electrode 10.
4 is blocked by the route 4, and tries to flow toward the ink ejection portion 102 side along the ejection electrode 103 and the electric field separation electrode 104. As a result, the concentration of the solid component in the ink in the vicinity of the ink ejection unit 102 becomes high (concentrated).

On the other hand, when the solid component of the ink in the vicinity of the ink ejection portion 102 is diluted in response to the main switch-off of the apparatus or the completion of printing, the ink circulation direction is indicated by an arrow A in FIG.
The direction is opposite to the direction indicated by. When the circulation direction of the ink is switched in this way, contrary to the above case, the ink flow tends to flow to the side opposite to the ink ejection direction in the cavity 105a. Then, the ink ejecting unit 102
The flow of ink in the vicinity of is further slowed down, and the difference from the flow velocity of ink in the vicinity of the main flow path becomes large. As a result, a negative pressure is generated in the cavity 105a, and the ink ejection unit 102 is
The solid component in the ink in the vicinity of the ink is sucked toward the main flow path of the ink, and the concentration of the solid component in the ink in the vicinity of the ink ejection unit 102 becomes low (diluted).

The ink flow velocity in the second embodiment is not particularly limited, and the ink flow velocity may be the same when the solid component in the ink near the ink ejection portion 102 is concentrated and when it is diluted. Alternatively, the flow rate in the case of diluting as in the case of the first embodiment may be increased.

In the description of the second embodiment,
As a structure for giving resistance to the flow of ink, the ejection electrode 103 and the electric field separation electrode 104 are formed on the inner wall of the cavity 105a, for example, the upper surface 1 of the base member 101.
Although it is formed to be concave or convex with respect to 01a, on the surface of the cover member 105 facing the base member 101,
The protrusions may be formed so as to form a predetermined angle other than 90 degrees with respect to the ink flow direction A.

As a method of switching the ink flow direction A, the ink supply direction by the pump 108 is made constant, and a plurality of valves are provided between the ink tank 107 and the pump 108 and the ink supply pipe 106a and the discharge pipe 106b. The circulation direction of the ink may be switched by providing and switching the valve, or the rotation direction of the impeller of the pump 108 may be simply switched.

(Third Embodiment) Next, an electrostatic ink jet recording apparatus according to a third embodiment of the present invention will be described. The structure of the ink head in the electrostatic ink jet recording apparatus of the third embodiment is shown in FIGS. 4 and 5.

In the second embodiment, the cavity 105
A structure for providing resistance to the flow of ink is provided in a, and by changing the circulation direction of the ink in the cavity 105a, the solid matter in the ink in the vicinity of the ink ejection unit 102 is concentrated and diluted. However,
In the third embodiment, a structure that can be taken in and out (inserted and pulled out) from the cavity 105a is provided, and the structure is inserted into the cavity 105a to give a resistance to the ink flow in the cavity 105a, and the flow velocity of the ink. Is slowed down to concentrate the solid component in the ink, the structure is drawn out from the cavity 105a, and the flow velocity of the ink in the cavity 105a is increased to dilute the solid component in the ink. The direction of ink flow is not changed.

As shown in FIGS. 4 and 5, for example, a structure (hereinafter referred to as “film”) 110 in which projections 111 are formed on the surface of a resin film is prepared, and an actuator such as a piezoelectric element is used. The film 110 is driven in a direction orthogonal to the ink flow direction A so that it can be taken in and out of the cavity 105a. In addition, the longitudinal direction of the protrusion 111 is set to a predetermined angle (obtuse angle) of 90 degrees or more with respect to the ink flowing direction A so that the protrusion 111 functions as a structure that gives resistance to the ink flow.
Is set.

When the solid component of the ink in the vicinity of the ink ejecting portion 102 is concentrated in response to the main switch on of the apparatus or the reception of the print start signal, as shown in FIG. 5, the actuator is driven to move the film 110 into the cavity 105a. Insert inside. At this time, the film 110 is stopped so that the position of the protrusion 111 is near the main flow path of the ink in the cavity 105a. By doing so, the protrusion 111 functions as a structure for giving resistance to the flow of ink, slows the flow velocity of ink, and facilitates the solid component in the ink to collect near the ink ejection unit 102. As a result, inside the cavity 105a, the ink flow in the vicinity of the main flow path with a high flow velocity is disturbed by the protrusion 111, the flow velocity becomes slow, and the flow of the ink is blocked by the protrusion 111, so that the ink is ejected. It tries to flow to the part 102 side. As a result, the concentration of the solid component in the ink in the vicinity of the ink ejection unit 102 becomes high (concentrated).

On the other hand, when diluting the solid component of the ink in the vicinity of the ink ejecting portion 102 in response to the main switch-off of the apparatus or the completion of printing, as shown in FIG. 4, the actuator is driven to move the film 110 into the cavity 105a. Pull out from inside. Then, there is no obstacle to the flow of ink in the vicinity of the main flow path in the cavity 105a, so that the flow velocity of ink in the vicinity of the main flow passage becomes faster, and the flow velocity of ink in the vicinity of the ink ejection unit 102 and the ink in the vicinity of the main flow passage are increased. The difference with the flow velocity of is large. As a result, cavity 1
A negative pressure is generated in 05a, the solid component in the ink in the vicinity of the ink ejection unit 102 is sucked toward the main flow path of the ink, and the concentration of the solid component in the ink in the vicinity of the ink ejection unit 102 becomes low (dilution). Be done).

The ink flow velocity in the third embodiment is not particularly limited, and the ink flow velocity is the same when the solid component in the ink in the vicinity of the ink ejection portion 102 is concentrated and when it is diluted. Good, first
The flow rate when diluting as in the embodiment may be increased.

As the structure to be put in and taken out from the cavity 105a, in addition to the film 110 having the projections 111 as described above, a thin plate having comb teeth or saw teeth at the ends is used. Is also good. Alternatively, the base member 101 and the cover member 105 that form the ink head 10
Is made of piezoelectric ceramics, the ejection electrode 103 and the electric field separation electrode 104 are formed so as to form a predetermined angle with respect to the ink circulation direction as in the second embodiment, and a predetermined voltage is applied to these electrodes. The application of the voltage may make the inner wall of the cavity 105a uneven.

(Other Embodiments) In each of the above-described embodiments, the shape of the ink ejecting portion 102 is formed into an isosceles triangle projecting from the end face of the base member 101 to the recording paper P side. For example, as shown in FIG. 6, it may be formed in a comb shape protruding from the end surface of the base member 101 toward the recording paper P side. In that case, by forming a convex portion 120 shorter than the ink ejecting portion 102 between two adjacent ink ejecting portions 102, the ink causes meniscus between the ink ejecting portion 102 and the convex portion 120 due to surface tension. Become a state.

Further, in each of the above-described embodiments, the isosceles triangular portion of the ink ejection portion 102 is configured to be parallel (same surface) to the upper surface 101a of the base member 101.
The present invention is not limited to this, and may be configured to be perpendicular to the upper surface 101a of the base member 101 as shown in FIG. 7, for example. In that case, a slit 130 may be provided for each ink ejection unit 102, and the ink may be supplied to the ink ejection unit 102 through the slit 130 by utilizing a capillary phenomenon.

Further, in each of the above embodiments, the case where the solid component in the ink is positively charged has been described.
When the solid component is negatively charged, the discharge electrode 103
The solid component in the ink may be diluted by applying a voltage higher than the voltage applied to the secondary electrode 30 to the ink.

[0052]

As described above, in the electrostatic ink jet recording apparatus of the present invention, a plurality of ink ejection portions arranged at a predetermined pitch in the direction orthogonal to the ink ejection direction, and the ink ejection portion. A cavity for storing a fixed amount of ink, and an ink supply pipe and a discharge pipe provided in the cavity so that the ink flows in a direction orthogonal to the protruding direction of the ink. A solid component in the ink in the vicinity of the ink ejecting portion by changing the flow velocity of the ink in the cavity. Since the density of the ink is controlled, the ink circulation speed during non-printing is made faster than that during printing, so that The solid component that remains in the vicinity of the click discharge portion is sucked into the main flow path side by the negative pressure, can be recovered to the ink tank placed in the ink flow to circulate. As a result, during non-printing, it is possible to dilute the solid component in the ink that is excessively concentrated in the vicinity of the ink ejection portion, stabilize the ejection amount of ink, and prevent clogging of the ink head.

In another electrostatic ink jet recording apparatus of the present invention, a plurality of ink ejecting portions arranged at a predetermined pitch in a direction orthogonal to the ink protruding direction, and formed behind the ink ejecting portion. And a cavity for storing a fixed amount of ink, an ink supply pipe and a discharge pipe provided in the cavity so that the ink flows in a direction orthogonal to the direction of protrusion of the ink, and the inside of the cavity. And a discharge electrode provided in the vicinity of each of the ink discharge portions, and a structure that provides resistance to the flow of ink in the cavity is provided.
Since the concentration of the solid component in the ink in the vicinity of the ink ejecting portion is controlled by switching the direction in which the ink flows in the cavity, the solid component accumulated in the vicinity of the ink ejecting portion during the non-printing is removed by the ink ejecting portion. Can be sucked in the direction away from, for example, the main flow path side,
Similar to the above case, it is possible to dilute the solid component in the ink that is excessively concentrated in the vicinity of the ink ejection portion, stabilize the ejection amount of the ink, and prevent clogging of the ink head.

Further, as the structure, a film which is provided so as to be able to be taken in and out of the cavity and has unevenness at the end portion or the flat surface portion corresponding to the pitch of the ink discharge portion, or the film of the end portion By using a thin plate formed in a predetermined shape so as to provide resistance to the circulating ink flow in the vicinity, at the time of non-printing, the above-mentioned structure is pulled out from the cavity so that non-printing in the vicinity of the main flow path in the cavity is performed. The flow velocity of the ink during printing can be made faster than the flow velocity during printing, and as in the above case, it is possible to dilute the solid component in the ink that is excessively concentrated in the vicinity of the ink ejection portion, and the ink ejection It is possible to stabilize the amount and prevent clogging of the ink head.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration example of an ink head in an electrostatic ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of an ink ejection mechanism in the electrostatic ink jet recording apparatus.

FIG. 3 is a perspective view showing a configuration example of an ink head in an electrostatic ink jet recording apparatus according to a second embodiment of the invention.

FIG. 4 is a perspective view showing a configuration example of an ink head in an electrostatic ink jet recording apparatus according to a third embodiment of the invention.

FIG. 5 is a perspective view showing a state of the film after the operation in the third embodiment.

FIG. 6 is a perspective view showing a modified example of the ink ejection portion of the ink head that can be applied to each of the above embodiments.

FIG. 7 is a perspective view showing another modified example of the ink ejection unit of the ink head that can be applied to each of the above embodiments.

[Explanation of symbols]

K: Ink drop P: Recording paper S1: Switch E1: Bias voltage source E2: Pulse voltage source E3: Reverse bias voltage source E4: Voltage source (for electric field separation electrode) E5: (for secondary electrode) voltage source 10: Ink head 20: Counter electrode 30: Secondary electrode 40: Ink ejection control unit 101: Base member 102: Ink ejection section 103: discharge electrode 104: electric field separation electrode 105: cover member 105a: cavity 105b: slit 106a: Ink supply pipe 106b: ink discharge tube 107: Ink tank 108: Pump 110: Film 111: Protrusion

Claims (5)

[Claims] 1. A plurality of ink ejecting portions arranged at a predetermined pitch in a direction orthogonal to a protruding direction of ink, and a cavity formed behind the ink ejecting portion for storing a constant amount of ink. , In the cavity,
The ink supply pipe and the discharge pipe are provided so that the ink flows in a direction orthogonal to the ink ejection direction, and the ejection electrodes are provided in the cavity in the vicinity of the respective ink ejection portions. Then, the electrostatic ink jet recording apparatus is characterized in that the concentration of the solid component in the ink in the vicinity of the ink ejecting portion is controlled by changing the flow velocity of the ink in the cavity. 2. A plurality of ink ejecting portions arranged at a predetermined pitch in a direction orthogonal to a protruding direction of ink, and a cavity formed behind the ink ejecting portion for storing a fixed amount of ink. , In the cavity,
The ink supply pipe and the discharge pipe are provided so that the ink flows in a direction orthogonal to the ink ejection direction, and the ejection electrodes are provided in the cavity in the vicinity of the respective ink ejection portions. Then, by providing a structure that gives resistance to the ink flow in the cavity and switching the direction of the ink flow in the cavity, the concentration of the solid component in the ink in the vicinity of the ink ejection portion is controlled. An electrostatic ink jet recording apparatus characterized by the above. 3. The electrostatic ink jet recording apparatus according to claim 2, wherein the structure is an electrode formed to be convex or concave with respect to the inner wall of the cavity. 4. The structure is a film that is provided so as to be able to be taken in and out of the cavity and has an unevenness at an end portion or a flat portion corresponding to a pitch of the ink ejection portion. The electrostatic ink jet recording apparatus according to claim 2. 5. The structure is a thin plate that is provided so as to be able to be taken in and out of the cavity and has a predetermined shape so as to provide resistance to a circulating ink flow in the vicinity of an end thereof. The electrostatic ink jet recording apparatus according to claim 2, which is characterized in that.