JPH1178024A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet recorder combining the electrostatic system with the piezoelectric system or the thermal system in which the adverse effect of charges in an ink image formed on a recording sheet is prevented. SOLUTION: An ink jet head 1 carried on a carriage 2 for ink jet head reciprocates while being guided by a carriage shaft 3 and a neutralization brush 4 held by a carriage 6 for neutralization brush also reciprocates in same direction together with the ink jet head 1. A high voltage of about -2kV is applied from a power supply 8 between a counter electrode 7 and the ink jet head 1 and the neutralization brush 4 is set at same potential as the counter electrode 7. According to the arrangement, charges of an ink image recorded on a recording sheet 5 can be removed by means of the neutralization brush 4.

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 used for a printer for drawing characters or figures by discharging a liquid such as ink from minute nozzles and forming a liquid pattern on recording paper or a sheet. It is.

[0002]

2. Description of the Related Art In recent years, printers using an ink jet recording apparatus as a printing apparatus such as a personal computer have been widely used because of their easy handling, good printing performance, and low cost. This ink jet recording apparatus includes a thermal method in which bubbles are generated in ink by thermal energy and ink droplets are ejected by pressure waves generated by the bubbles, an electrostatic method in which ink droplets are sucked and ejected by electrostatic force, and a piezoelectric element. There are various systems such as a piezoelectric system using a pressure wave generated by such a vibrator.

[0003] Further, a system combining a thermal system and an electrostatic system and a system combining the piezoelectric system and the electrostatic system have been proposed. For example, a system in which the piezoelectric system and the electrostatic system are combined has been proposed in Japanese Patent Application Laid-Open No. Hei 5-278212. This proposal will be described with reference to FIG. FIG.
In the figure, 114 is a discharge port for discharging ink, and 115 is a pressure chamber which communicates with the discharge port 114 and stores ink. Reference numeral 118 denotes a piezoelectric element for applying pressure to the pressure chamber 115, and reference numeral 140 denotes an ink meniscus formed at the tip of the discharge port 114. Reference numeral 112 denotes a charging electrode for charging the ink portion forming the ink meniscus 140, and reference numeral 117 denotes a counter electrode that is arranged to face the charging electrode 112 via a recording paper. Then, the charging electrode 11
A high voltage is applied between the second electrode 117 and the counter electrode 117 by the high voltage power supply 108.

In this configuration, first, the piezoelectric element 118
, The volume of the pressure chamber 115 is reduced by the force generated by the piezoelectric element 118, and an ink meniscus 140 is formed at the ejection port 114. Next, the ink meniscus 1
When the charging electrode 112 is charged by the charging electrode 112, the ink meniscus 140
The liquid is ejected toward the counter electrode 117 by the electric field formed by the first and second electrodes 17. At this time, since the recording paper 105 is arranged between the recording paper 105 and the counter electrode 117, an ink image is formed on the recording paper 105.

Here, it is only necessary to form an ink meniscus 140 on the piezoelectric element 118, and the output of the piezoelectric element 118 may be small.

In FIG. 14, the ink meniscus 140 is formed by the piezoelectric element 118. However, the ink meniscus 140 may eject ink droplets. Also in this case, the ejection speed of the ink droplets may be low, and the output generated by the piezoelectric element 118 may be small. In other words, by combining the electrostatic method with the piezoelectric method, even if the discharge speed of the ink droplet is low, the ink droplet is accelerated by the electrostatic force and can be accurately landed at a desired position on the recording paper. It is possible. Therefore, the output of the piezoelectric element 118 can be small, and the density of the nozzle can be increased and the speed can be increased.

Similarly, when the thermal method and the electrostatic method are combined, the output of the heating element can be reduced as compared with the case where only the thermal method is used.
High-speed driving can be realized.

[0008]

However, FIG.
In the method of (1), the output of the piezoelectric element 118 can be small, and the density of the nozzles can be increased and the nozzle can be driven at high speed. However, since the ink droplets are charged, adverse effects due to the charges of the ink droplets occur Would. When an ink image is formed on the recording paper 105, the electric field of the charging electrode 112 and the counter electrode 117 weakens due to the electric charge of the ink image, thereby weakening the acceleration of the next ink droplet. The manner in which the electric field is weakened depends on the strength of the electric field, the physical properties of the ink, the recorded image, and the like. However, if the electric field is weakened, ink droplets cannot be recorded at desired positions on the recording paper 105. Since then
This phenomenon is called landing position deviation. If the landing position shift is large, the image quality is deteriorated.

SUMMARY OF THE INVENTION In view of the above problems, according to the present invention, even when an ink image is formed on a recording paper by charged ink droplets, the variation in the electric field intensity formed between the inkjet head and the counter electrode is small, and the landing position shifts. It is an object to provide an ink jet recording apparatus which is difficult.

[0010]

According to the present invention, there is provided an ink jet head for projecting ink droplets from a nozzle, a counter electrode arranged to face the ink jet head, and an ink jet head. A voltage is applied between the head and the opposing electrode, and the ink droplet protruding from the ink jet head is accelerated and flies to the opposing electrode side by electrostatic attraction. And a static eliminator for reducing or removing the charge caused by the charged ink on the recording paper.

According to a second aspect of the present invention, there is provided an ink jet recording apparatus, comprising: an ink jet head; an ink jet head scanning means for reciprocating the ink jet head; a counter electrode disposed at a position opposing the ink jet head; Voltage applying means for applying a voltage between the head and the counter electrode while the ink jet head is grounded, and a portion set at the same potential as the counter electrode and having the counter electrode on its back surface on recording paper Charge removing means for removing the electric charge of the ink jet head, and a charge removing means scanning means for causing the charge eliminating means to reciprocate in the same direction as the reciprocating operation of the ink jet head.

According to a third aspect of the present invention, there is provided an ink jet recording apparatus according to the second aspect, further comprising a voltage application intermittent means for intermittently applying a voltage by the voltage applying means, and at least the charge eliminating means is opposed to the voltage applying intermittent means. When moving to a place where the counter electrode does not exist,
A voltage is not applied between the ink jet head and the counter electrode by the pre-pressure application intermittent means.

According to a fourth aspect of the present invention, there is provided an ink jet recording apparatus, wherein the electric charge on the recording paper is removed by the charge eliminating means when the voltage is not applied by the voltage applying / interrupting means.

According to a fifth aspect of the present invention, there is provided an ink jet recording apparatus according to the fourth aspect, wherein the static elimination means removes charges on the recording paper by contacting the recording paper. Scanning means for reciprocating the scanning means; and discharging and separating means for separating and connecting the discharging means to and from the recording paper. At least when the voltage is applied by the voltage applying and interrupting means, the discharging means is separated. The contact removing means causes the discharging means to be separated from the recording paper.

According to a sixth aspect of the present invention, there is provided the ink jet recording apparatus according to the fourth aspect, further comprising a state switching unit for switching the charge removing unit between an electric ground state and a floating state, and at least applying a voltage. When a voltage is applied by the intermittent means, the static elimination means is switched to an electrically floating state by the state switching means.

According to a seventh aspect of the present invention, there is provided the ink jet recording apparatus according to the sixth aspect, wherein the voltage application intermittent means is connected to a power supply to a grounded switch means, and the power supply is connected to a counter electrode. They are connected in series, and the voltage application intermittent means also serves as the state switching means.

According to an eighth aspect of the present invention, in the ink jet recording apparatus according to any one of the second to seventh aspects, the recording paper is conveyed in a direction perpendicular to a reciprocating operation direction of the ink jet head. A recording paper transport unit is provided, and after the ink ejection operation by the ink jet head, the charge on the recording paper is removed by the discharging unit, and then the recording paper is transported by the recording paper transport unit.

According to a ninth aspect of the present invention, in the ink jet recording apparatus according to any one of the third to eighth aspects, when the ink jet head is moved forward by the ink jet head scanning means, the ink is applied to the recording paper. A device that performs a discharge operation and removes the charge on the recording paper during the return operation, or removes the charge on the recording paper during the forward operation and performs an ink discharge operation on the recording paper during the return operation. It is.

According to a tenth aspect of the present invention, there is provided an ink jet recording apparatus, comprising: an ink jet head; a counter electrode disposed at a position facing the ink jet head; And a voltage applying means for applying a voltage in the opposite direction, the counter electrode is a rectangular plate-like body, and a surface facing the ink jet head is in a recording range of the ink jet head with respect to a conveying direction of the recording paper. The shape is at least 6 mm or larger.

The ink jet recording apparatus according to the eleventh aspect of the present invention is the ink jet recording apparatus according to the tenth aspect, further comprising a charge eliminating means which is set to the same potential as the counter electrode and removes electric charges on the recording paper. The charge on the recording paper is removed from the portion where the counter electrode exists outside the recording range of the head, on the recording paper transport direction side, and on the back surface.

According to a twelfth aspect of the present invention, there is provided an ink jet recording apparatus, comprising: an ink jet head; an ink jet head scanning means for reciprocating the ink jet head; and a position facing the ink jet head.
At least the side in contact with the recording paper is an insulator, the opposite side is a counter electrode having a laminated structure of a conductor, and a voltage application unit that applies a voltage between the inkjet head and the opposite electrode while the inkjet head side is grounded. Charge removing means for removing charges on the counter electrode.

According to a thirteenth aspect of the present invention, in the ink jet recording apparatus according to the twelfth aspect, the electric charge on the counter electrode is removed when no recording paper is interposed between the counter electrode and the charge removing means. It is something to do.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a schematic configuration diagram of an ink jet recording apparatus according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an ink jet head, which is mounted on a carriage 2 for the ink jet head and is configured to reciprocate by driving means (not shown) while being guided by a carriage shaft 3. The inkjet head carriage 2 and the carriage shaft 3 constitute inkjet head scanning means in the claims. Reference numeral 4 denotes a discharging brush, which is a discharging means, and is held by a discharging brush carriage 6 such that the tip of the brush contacts the surface of the recording paper 5.
Further, the charge removing brush 4 is configured to be reciprocated by driving means (not shown) while being held by the charge removing brush carriage 6 and guided by the carriage shaft 3. The charge removal brush carriage 6 is configured to move in the same direction and at the same speed together with the inkjet head carriage 2. Reference numeral 7 denotes a counter electrode made of metal, whose distance from the inkjet head is set to about 1 mm. Further, the opposing electrode 7 and the inkjet head 1 are connected to each other by the power supply 8 while the inkjet head 1 is grounded.
A high voltage of about 2 KV is applied. The power supply 8 constitutes a voltage application unit. The discharging brush 4 is also configured to have the same potential as the counter electrode 7. Also,
Reference numeral 9 denotes a switch of a voltage application intermittent means in the claims, and the switch 9 turns on / off the application of a high voltage to the counter electrode 7 and the neutralization brush 4. Reference numeral 10 denotes a recording paper transport unit that transports the recording paper 5 in a direction perpendicular to the carriage shaft 3. Further, reference numeral 11 denotes an ink jet head cleaning means, which comprises a rubber blade member, a forced discharge member and the like.

Next, FIG. 2 is a partial sectional view showing the ejection port of the ink jet head 1 and the actuator.

In FIG. 2, reference numeral 12 denotes a nozzle plate made of stainless steel, and the nozzle plate 12 is provided with a discharge port 14 for discharging ink 13. An aqueous ink is used as the ink 13. Reference numeral 15 denotes a pressure chamber which communicates with the ejection port 14 and stores ink. Reference numeral 16 denotes a pressure chamber structure made of resin.
2 form a pressure chamber 15. Pressure chamber structure 16
Is provided with an ink supply port 17 for supplying the ink 13 to the pressure chamber 15. 18 is a 0.02 mm thick PZ
The piezoelectric element 18 is a piezoelectric element, and the piezoelectric element 18 vibrates a diaphragm 19 made of stainless steel having a thickness of 0.01 mm. Reference numeral 20 denotes an ink droplet ejected from the ejection port 14. Although FIG. 2 is a sectional view, one pressure chamber 15 is provided with one discharge port 14 in actuality. However, in practice, each of the plurality of pressure chambers 15 is provided with one discharge port 13.

The operation of the thus configured ink jet recording apparatus will be described below with reference to FIGS.

First, the discharge operation of the ink droplet 20 for causing the ink 13 to fly from the discharge port 14 will be described with reference to FIG. A voltage is applied to the piezoelectric element 18. Then, the diaphragm 19 bends in the direction of reducing the volume of the pressure chamber 15 together with the piezoelectric element 18. As a result, the pressure in the pressure chamber 15 increases, and the ink 13 becomes
The ink is further discharged toward the recording paper 5. At this time, the nozzle plate 1
Since an electrostatic field is applied between the counter electrode 2 and the counter electrode 7, a positive charge is induced before the ink 13 becomes the ink droplet 20, and the ink 13 becomes the positively charged ink droplet 20 and becomes the discharge port 14.
Discharge more. Also, due to the force of the electrostatic field, the ink droplet 2
0 flies toward the recording paper 5 while being accelerated.

At this time, even if the ejection speed of the ink droplet 20 is low, the ink droplet 20 is accelerated by the electrostatic force,
That is, the recording paper 5 can be accurately landed at a desired position. Accordingly, the output of the piezoelectric element 18 can be small, and the density of the nozzle can be increased and the high-speed driving can be performed. This is the effect of applying the electrostatic field.

Next, the operation of the ink jet recording apparatus will be described with reference to FIGS. 1, 3 and 4. In FIG. 1, a recording paper 5 is transported to a desired position by a recording paper transporting means 10. In this state, the switch 9 is closed and the counter electrode 7 is closed.
And the neutralizing brush 4 with respect to the inkjet head 1 at -2K
V. The ink droplets 20 are ejected from the ejection ports 14 while the inkjet head carriage 2 is moved from the position A to the position B by means not shown. Thereby, a recording image for one scan of the inkjet head 1 can be recorded on the recording paper 5. Next, while returning the inkjet head carriage 2 from the position B to the position A, the recording paper transport means 10 transports the recording paper 5 by a desired amount. Further, the ink droplets 20 are ejected from the ejection ports 14 while the inkjet head carriage 2 is moved from the position A to the position B again. Thus, a recording image for one scan of the inkjet head 1 is recorded on the recording paper 5. Image formation on the recording paper 5 can be realized by repeating this operation. The charge removing brush 4 moves in the same direction and at the same speed together with the inkjet head carriage 2 in a state where the leading end of the brush 4 contacts the recording paper 5. Accordingly, the charges of the ink droplets 20 recorded on the recording paper 5 can be eliminated, and stable recording can be performed without any displacement of the landing position.

The inkjet head 1 needs to be cleaned to prevent clogging. At the time of cleaning, the inkjet head 1 is moved to the position of the cleaning means 11 in FIG. 1, and cleaning is performed by wiping, forced ejection, or the like. At this time, the switch 9 is opened, and the application of the voltage to the counter electrode 7 and the neutralizing brush 4 is stopped.
It is not always necessary to stop the voltage application to the counter electrode 7 and the neutralizing brush 4, but in that case, it is necessary to completely insulate the cleaning means 11 from the ink jet recording apparatus, which is not practical. In addition, when the inkjet head 1 is at the position of the cleaning unit 11, the counter electrode 7 is easily touched by humans. Therefore, it is preferable that the counter electrode 7 simultaneously stops applying the voltage. Therefore, the configuration is such that one switch 9 simultaneously opens and closes the voltage application to the counter electrode 7 and the neutralization brush 4.

Next, a problem in the case where the static elimination brush 4 is not provided will be described. The ink droplet 20 is charged, and when an image is formed on the recording paper 5, an electrostatic field between the counter electrode 7 and the inkjet head 1 is generated by the charge of the ink droplet 20 on the recording paper 5. Will change.

The change in the static electric field includes the change in the intensity of the static electric field,
This is a change in the direction of the electrostatic field, and also the amount of charge in the charged state of the ink droplet 20 is changed, and these changes cause a landing position shift. The state of the landing position shift will be described with reference to FIGS. 3A, 3B, 4A, and 4B.

First, FIG. 3A shows a recorded image when the recording paper 5 is conveyed by the recording paper conveying means 10 by one scanning recording width of the ink jet head 1. 2
Reference numeral 1 denotes a pre-scanning recording image, and reference numeral 22 denotes a next scanning recording image. The state at the time of the next scanning recording in this case is shown in FIG. FIG. 3-b is enlarged with respect to FIG. 3-a. The solid line shows the trajectory that actually flies, and the wavy line shows the trajectory that should be landed. As can be seen from FIG. 3B, the landing position shifts due to a change in the electrostatic field due to the pre-scanning recording image 21. In this figure, the landing position shift in the sub-scanning direction is shown, but the landing position shift in the vertical direction (main scanning direction) as shown in FIG. That is, the electrostatic field is weakened in the vicinity of the ejection port 14 above the inkjet head 1 in the state shown in FIG. 3B, and the charge amount of the ink droplet 20 is also reduced. Therefore, the acceleration force of the ink droplet 20 in the direction of the recording paper 5 is weakened, and a landing position shift occurs.

FIG. 4A shows a pre-scan recording image 21 in the case of performing a so-called minute feed in which the recording paper conveying means 10 conveys the recording paper 5 by an amount smaller than one scanning recording width of the ink jet head 1. And the next scan recording image 22. The state at the time of the next scan recording in this case is shown in FIG.
Shown in FIG. 4-b is enlarged with respect to FIG. 4-a. The solid line shows the trajectory that actually flies, and the wavy line shows the trajectory that should be landed. The change in the electrostatic field due to the pre-scanning recording image 21 causes the landing position to shift. In this figure, the landing position shift in the sub-scanning direction is shown. However, the landing position shift in the vertical direction (main scanning direction) as shown in FIG. That is, in the state shown in FIG. 4B, the electrostatic field is weaker in the next scan printing than in the previous scan printing, and the charge amount of the ink droplet 20 is also reduced. Therefore, the acceleration force of the ink droplet 20 in the direction of the recording paper 5 is weakened, and a landing position shift occurs.

However, in the first embodiment, since the discharging brush 4 is provided, the ink droplets 20 on the recording paper 5 are removed.
Can be removed, and the electrostatic field can always be kept constant. In addition, the recording paper 5 moves in the same direction and at the same speed together with the carriage 2 for the inkjet head while the leading end portion thereof is in contact with the recording paper 5. As a result, the charge of the ink droplet 20 due to the pre-scan recording can be reliably removed.
It is possible to perform printing that is not affected at all by pre-scan printing.

Usually, the discharging brush 4 is often grounded, but in the first embodiment, it is set to -2 KV. This is because the opposing electrode 7 is set at -2 KV. If the opposing electrode 7 is set at -2 KV and the neutralizing brush 4 is grounded, the charge of the ink droplet 20 can be removed. As a result, the ink droplet 20 and the recording paper 5 are positively charged. In addition, it is not impossible to adopt a configuration in which the inkjet head 1 is set to a high voltage and the counter electrode 7 is grounded.
This is not practical because of the severe restrictions imposed on the insulation in the configuration described above. Therefore, a configuration in which the inkjet head 1 side is grounded and the charge removing brush 4 is set to the same potential as the counter electrode 7 is essential.

As described above, in the first embodiment, by removing the charges of the ink droplets recorded on the recording paper 5, stable recording without any displacement of the landing position can be performed. An inkjet recording device can be provided.

In addition, it is possible to provide an ink jet recording apparatus having a simple apparatus configuration in which the cleaning means need not be completely insulated from the ink jet recording apparatus.

In the first embodiment, the discharging brush 4
Is provided on the front side of the inkjet head 1 with respect to the scanning direction at the time of recording by the inkjet head 1, but it may be provided on the rear side, or may be provided on both front and rear sides.

Further, in the first embodiment, the charge elimination brush 4 is used as the charge elimination means. However, as long as the charge elimination is possible, the charge elimination brush 4 may be made of, for example, a thin metal plate and provided with a jagged end. .

Further, in the first embodiment, recording was performed by the ink jet head 1 when moving from A to B.
In this case, recording may be performed when moving from B to A, or recording may be performed during both reciprocating operations.

Further, in the first embodiment, the carriage 6 for the neutralizing brush is provided, and the reciprocating operation of the neutralizing brush 4 is performed by the carriage 6 for the neutralizing brush, but the neutralizing brush 4 is moved to the inkjet head 1 or the carriage 2 for the inkjet head. A configuration in which the carriage for the static elimination brush is omitted and the carriage for the neutralization brush is omitted is also preferably used.

Further, in the first embodiment, the piezoelectric element 18 and the vibration plate 19 are used as pressure generating means for ink ejection. However, as the pressure generating means, means for generating bubbles in ink by thermal energy, A device using high-frequency energy means by an element or a device in which solid ink is melted and the melted ink is ejected by a piezoelectric element may be used.

(Embodiment 2) FIG. 5 is a schematic structural view of an ink jet recording apparatus according to a second embodiment of the present invention. 23 is a rotation shaft, and 24 is an eccentric cam.
The rotating shaft 23 and the eccentric cam 24 constitute a charge removing / separating / contacting means in the claims. 1 is different from FIG. 1 in that the brush 4 is grounded instead of applying a voltage, and that the brush 4 is configured to be rotatable around a rotating shaft 23 with respect to the carriage 6 for the brush. is there. In addition, the illustration of the cleaning unit 11 and the recording paper conveying unit 10 is omitted for easy understanding of the drawing. Also,
FIG. 6 is a detailed view showing a state in which the charge removing brush 4 is separated.

The operation of the ink jet recording apparatus configured as described above will be described. In the first embodiment, the charge removing brush 4 is set to have the same potential as the counter electrode 7. The neutralization brush 4 needs to be electrically conductive for the purpose of neutralization, and therefore, there is a possibility that the neutralization brush 4 may be touched by a human hand to cause an electric shock. There is no particular problem in forming an image on the recording paper 5, but it is not preferable in terms of security. Although it is sufficiently possible to avoid touching human hands, considerable measures must be taken to completely prevent electric shock. Further, the discharging brush 4 is configured to reciprocate, and when applying a high voltage to the operating brush, a measure against electrical noise to the device circuit becomes a problem. As a countermeasure, it is usual to shield the circuit portion and the wiring portion, but this is not preferable because it increases the cost of the device.

Therefore, in Embodiment 2, the static elimination brush 4 is grounded. Thereby, the static elimination brush 4
A device that does not cause an electric shock even when a person touches the device.

First, the recording paper 5 is transported to a desired position by the recording paper transporting means 10. In this state, the switch 9 is closed, and the counter electrode 7
V. The carriage 2 for the ink jet head and the carriage 6 for the discharging brush are moved to A by means not shown.
The ink droplet 20 is ejected from the ejection port 14 while moving from the position to the position B. Thereby, a recording image for one scan of the inkjet head 1 can be recorded on the recording paper 5. At this time, the charge removing brush 4 is kept separated as shown in FIG.

Next, the switch 9 is opened to bring the charge removing brush 4 into a contact state. In this state, the carriage 2 for the ink jet head and the carriage 6 for the discharging brush are moved from the position B to the position A.
Return to position. At this time, ink is not ejected from the inkjet head 1. Thereby, the recording paper 5
The electric charge of the upper ink droplet 20 can be removed.

Next, the recording paper 5 is conveyed by a desired amount. Further, the ink droplets 20 are ejected from the ejection ports 14 while the inkjet head carriage 2 is moved from the position A to the position B again. Thus, a recording image for one scan of the inkjet head 1 is recorded on the recording paper 5. As described above, the recording operation is performed by repeating the operation of recording the ink image on the recording paper 5 during the forward operation and the operation of removing the charge of the recording paper 5 during the returning operation.
Image formation can be realized.

When returning from the position B to the position A, the switch 9 is opened. When the neutralizing brush 4 is brought into contact with the switch 9 closed, the ink droplet 20
Will have the same polarity as the charge of

It is also conceivable to employ a configuration without the charge removing / separating means. In this case, while the switch 9 is closed,
It is necessary to move the neutralizing brush 4 by the neutralizing brush carriage 6 to a place not affected by the electric field from the counter electrode 7, and a moving time and a moving place are required. The size is increased. Therefore, this is not a preferable method.

In the second embodiment, attention is also paid to the timing at which the recording paper 5 is conveyed by the recording paper conveying means 10. Ink droplets 2
After recording 0, the charge of the ink droplets 20 on the recording paper 5 is discharged by a discharging brush, and then the recording paper 5 is transported by a desired amount. If the recording paper 5 is transported without removing the electric charge of the ink droplet 20, the electric charge of the counter electrode 7 and the electric charge of the ink droplet 20 on the recording paper 5 attract each other, and a large force is applied to the conveyance of the recording paper 5. Is required. There is no problem if the conveyance force of the recording paper conveyance means 10 is increased, but it is not preferable because it leads to an increase in energy and an increase in size of the apparatus.
However, in the second embodiment, since the recording paper 5 is transported after removing the charge of the ink droplet 20, the recording paper 5 can be transported stably.

As described above, in the second embodiment, since the recording paper 5 can be neutralized with the static elimination brush 4 grounded, the ink jet recording is highly safe and hardly generates electric noise. An apparatus can be provided.

Further, by providing the static elimination means separating / contacting means, it is possible to provide an ink jet recording apparatus capable of quickly performing the static elimination and non-static elimination operations in conjunction with the opening and closing of the switch 9 and without increasing the size of the apparatus.

Further, since the recording paper 5 is conveyed after the charge of the ink droplets 20 on the recording paper 5 is removed, the apparatus which does not increase the energy required for conveying the recording paper 5 is also large. In other words, it is possible to provide an ink jet recording apparatus that can stably convey the recording paper 5.

In the second embodiment, the recording is performed during the forward operation and the charge is removed during the return operation. This is because the switch 9 is closed and the charge removing brush 4 is in the separated state. Alternatively, the recording may be performed, and the static elimination operation may be performed occasionally.

(Embodiment 3) FIG. 7 is a schematic structural view of an ink jet recording apparatus according to a third embodiment of the present invention. A switch 25 switches the neutralizing brush 4 between a ground state and a floating state. The switch 25 constitutes a state switching means in the claims. What is different from FIG. 5 is that a state switching unit is provided instead of the static elimination unit separation / contact unit.

The operation of the ink jet recording apparatus configured as described above will be described. The operation is also substantially the same as the operation of the second embodiment, and the difference is the operation of neutralization by the neutralization brush 4. In Embodiment 2, while the switch 9 is closed, the charge removing brush 4 is set to the separated state. In Embodiment 3, while the switch 9 is closed, the switch 25 is opened. I did it. Accordingly, an operation of performing recording during the forward operation and performing static elimination during the return operation can be realized with a very simple configuration including the switch 25.

As described above, the third embodiment has a very simple configuration in which only the switch 25 is added.
The same effect as in the second embodiment can be obtained.

(Embodiment 4) FIG. 8 is a schematic structural view of an ink jet recording apparatus according to a fourth embodiment of the present invention. The difference from FIG. 7 is that switch 9 is switch 25
That is, the configuration is also used.

The operation of the ink jet recording apparatus configured as described above will be described. The operation is almost the same as the operation of the third embodiment. In the third embodiment, the switch 25 is always open when the switch 9 is closed. On the other hand, the same can be realized when only the switch 9 is used. In the case where only the switch 9 is used, in the third embodiment, the switch 25 is always closed when the switch 9 is open, but this is not a problem.

As described above, in the fourth embodiment, the same effect as in the third embodiment can be obtained with one switch, so that an ink jet recording apparatus having a simpler configuration can be provided.

(Embodiment 5) FIG. 9 is a schematic structural view of an ink jet recording apparatus according to a fifth embodiment of the present invention. The difference from FIG. 1 is that the switch 9, the neutralizing brush 4, and the neutralizing brush carriage 6 are omitted, and the shape of the counter electrode 7 is devised. FIG.
FIG. 10 is a partial detailed view of the inkjet head 1 and the opposing electrode 7 as viewed from a lateral direction with respect to FIG. 9. Reference numeral 26 denotes an ink image recorded on the recording paper 5. In order to make the drawing easier to understand, the carriage 2 for the inkjet head
The description of the carriage shaft 3 is omitted. In FIG. 10, A
The portion indicates the portion where the nozzle of the inkjet head 1 is located, and the width of the counter electrode 7 is increased so that the length of L is 6 mm or more, preferably 10 mm or more with respect to the A portion.

The operation of the ink jet recording apparatus configured as described above will be described. FIG. 11 is a partial detailed view when a normal counter electrode is used. In this case, when the recording paper is transported in the direction of the arrow while recording is performed by the inkjet head 1, the charges of the ink image 26 are collected at a portion corresponding to the end of the counter electrode. This is because charges can easily move in the ink image 26 because the ink 13 is a water-based ink. When electric charges are collected, the electric field formed by the inkjet head 1 and the counter electrode 7 is weakened, or the direction of the electric field is bent.
As a result, a landing position shift occurs.

On the other hand, in FIG. 10, since the width of the opposing electrode 7 is increased in the direction of transport of the recording paper 5, the electric field formed between the ink jet head 1 and the opposing electrode 7 is weakened even if charges are collected. In addition, the direction of the electric field is less likely to bend. Through intensive studies, it was obtained from experiments that if the length of L is 6 mm or more, landing position deviation hardly occurs.

As described above, in the fifth embodiment, the width of the counter electrode 7 is increased in the transport direction of the recording paper 5, so that the negative effect of the charge of the ink image 26 can be obtained without providing any special discharging means. No inkjet recording device can be provided.

The ink jet head 1 is connected to the recording paper 5
A line head having a length corresponding to the entire width of the line head may be used.

(Embodiment 6) FIG. 12 is a partial detailed view of an inkjet head 1 and a counter electrode 7 of an inkjet recording apparatus according to a sixth embodiment of the present invention. The difference from the fifth embodiment is that a neutralization brush 4 set to have the same potential as the counter electrode 7 is provided.

The operation of the ink jet recording apparatus configured as described above will be described. In the fifth embodiment, the static elimination brush 4 is not provided. In this case, the recording paper 5
There is no problem when so-called ink-only paper is used, but when the recording paper 5 into which the ink 13 is very easy to penetrate is used, the electric charge collected at the portion corresponding to the end of the counter electrode 7 and the counter electrode 7 may occur. Therefore, in the present embodiment, the charge removing brush 4 is provided.

Accordingly, since the static elimination can be performed while the recording paper 5 is being conveyed, it is possible to provide a stable ink jet recording apparatus in which no discharge occurs.

The ink jet head 1 is the same as that shown in FIG.
Or a line head having a length corresponding to the front width of the recording paper 5 may be used.

Also, even if the static elimination brush 4 is in a serial form reciprocating in the direction perpendicular to the paper surface of FIG. 12 similarly to the ink jet head 1, it has a length corresponding to the front width of the recording paper 5. Even if it is in the form of a line, it does not matter.

(Embodiment 7) An ink jet recording apparatus according to a seventh embodiment of the present invention is substantially the same as that of the first embodiment shown in FIG. FIG. 13 shows a counter electrode 7 of an ink jet recording apparatus according to a seventh embodiment of the present invention.
It is sectional drawing of a part. 7a is a metal plate.
a, an insulating film 7b on the side facing the inkjet head 1;
Is formed. The metal plate 7a and the insulating film 7b constitute the counter electrode 7. The thickness of the insulating film 7b is 0.0
It is preferably from 0.05 mm to 0.2 mm, more preferably from 0.
01 mm to 0.05 mm. The difference from the first embodiment is that the counter electrode 7 has a two-layer structure.

The operation of the ink jet recording apparatus configured as described above will be described. The operation different from that of the first embodiment is that not only the charge on the recording paper 5 is removed by the charge removing brush 4 but also the charge on the counter electrode 7 is removed.
There is no problem when so-called inkjet paper is used as the recording paper 5, but when the recording paper 5 is very easy to penetrate the ink 13, the electric charge collected at the portion corresponding to the end of the counter electrode 7 is used. In some cases, discharge may occur between the electrode and the counter electrode 7. In the present embodiment, since the insulator 7b is provided on the counter electrode 7, no discharge occurs. In addition, since the insulator 7b is provided even when the counter electrode 7 is touched by hand, electric shock can be prevented and a highly safe device can be provided.

However, in the case where the insulator 7b is provided on the counter electrode 7, if the recording is performed on about one sheet of the recording paper 5, there is not much problem.
Electric charges are accumulated more and more on the opposing electrode 7, and the electric field formed by the inkjet head 1 and the opposing electrode 7 is weakened, or the direction of the electric field is bent, so that a landing position shift occurs. In the present embodiment, after recording is performed on one sheet of recording paper 5, the discharging brush 4 is moved in the same direction and at the same speed together with the carriage 2 for the ink jet head in a state where the tip of the brush 4 is in contact with the counter electrode 7. . This makes it possible to remove charges accumulated on the counter electrode 7.

Accordingly, by providing a structure for removing the electric charge stored in the counter electrode 7, there is provided a highly safe ink jet recording apparatus which does not discharge due to the electric charge of the ink droplet 20 and which does not cause an electric shock or the like. it can.

In the seventh embodiment, the charge on the counter electrode 7 is also removed by the charge elimination brush 4 for removing the charge on the recording paper 5. However, this is a special means for removing the charge on the counter electrode 7. You may be prepared.

The two-layered counter electrode 7 can be preferably used in the first, second, third, and fourth embodiments.

[0081]

As described above, according to the present invention, an ink-jet head for projecting ink droplets from a nozzle, a counter electrode arranged to face the ink-jet head, and a voltage between the ink-jet head and the counter electrode. Is applied, and the ink droplet protruding from the inkjet head is accelerated and flies to the counter electrode side by electrostatic attraction,
By providing a voltage application unit that lands on the recording paper inserted between the inkjet head and the counter electrode, and a charge elimination unit that reduces or removes the charge due to the charged ink on the recording paper, the charged ink liquid Even if an ink image is formed on the recording paper by the droplet, the fluctuation of the electric field intensity formed between the inkjet head and the counter electrode is small, and it is possible to make the landing position shift hard to occur.

Further, the ink jet head was grounded between the ink jet head, the ink jet head scanning means for reciprocating the ink jet head, a counter electrode arranged at a position facing the ink jet head, and the ink jet recording and the counter electrode. Voltage applying means for applying a voltage in a state, static elimination means for removing electric charges in a portion of the recording paper which is set to the same potential as the opposite electrode and having the opposite electrode on its back surface, and static elimination means scanning means for reciprocating the static elimination means When the ink image is formed on the recording paper by the charged ink droplets in a state where the ink jet head is grounded, the fluctuation of the electric field intensity formed between the ink jet head and the counter electrode is small, It is possible to make the displacement less likely to occur.

Further, there is provided a voltage application intermittent means for intermittently applying the voltage by the voltage application means, and at least when the static elimination means is moved to a position where the opposing electrode does not exist at the position facing the voltage application intermittent means, By not applying a voltage between the inkjet head and the counter electrode, a highly safe device can be provided.

Further, a voltage application intermittent means for intermittently applying the voltage by the voltage applying means is provided, and the charge on the recording paper is removed by the charge eliminating means when no voltage is applied by the voltage application intermittent means. It is possible to provide an ink jet recording apparatus which is high in cost and hardly generates electric noise.

Further, by providing the static elimination means separating / contacting means, it is possible to provide an ink jet recording apparatus which can quickly perform static elimination and non-static elimination operations in conjunction with opening and closing of the switch and does not increase the size of the apparatus.

Further, the provision of the state switching means for switching the neutralizing means between the electrical ground state and the floating state is provided, so that the neutralizing means has a very simple structure in which only a switch is added. Similar effects can be obtained.

Further, since the voltage application intermittent means is also used as the state switching means, the same effect as when the state switching means is provided can be obtained without any special means.

Further, after the ink discharge operation by the ink jet head, the charge on the recording paper is removed by the discharging means and then the recording paper is transported by the recording paper transporting means, so that the recording paper can be transported stably. Can be.

The counter electrode is a rectangular plate-like body, and the surface facing the ink jet head has a shape that is at least 6 mm larger than the recording range of the ink jet head in the direction of transport of the recording paper. By doing so, it is possible to provide an ink jet recording apparatus which does not have any special charge removing means or the like and which has no adverse effect of the charge of the ink droplets.

Further, there is provided a charge eliminating means which is set to the same potential as the counter electrode and removes electric charges on the recording paper. Since the charge on the recording paper in the existing portion is removed, a stable ink jet recording apparatus free from discharge can be provided.

Further, an insulating electrode is provided on the side in contact with the recording paper, and a counter electrode having a laminated structure of a conductor on the opposite side, and a charge removing means for removing charges on the counter electrode are provided. It is possible to provide a highly safe ink jet recording apparatus that does not discharge due to electric charge and does not cause an electric shock or the like.

[Brief description of the drawings]

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

FIG. 2 is a partial sectional view showing an ejection port and an actuator of the inkjet head according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a recorded image when a recording sheet is conveyed by one scan recording width of an inkjet head according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating a recorded image when the recording paper is conveyed by an amount smaller than one scanning recording width of the inkjet head according to the first embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of an inkjet recording apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a detailed view showing a state where the static elimination brush according to the second embodiment of the present invention is separated.

FIG. 7 is a schematic configuration diagram of an inkjet recording apparatus according to Embodiment 3 of the present invention.

FIG. 8 is a schematic configuration diagram of an inkjet recording apparatus according to Embodiment 4 of the present invention.

FIG. 9 is a schematic configuration diagram of an inkjet recording apparatus according to Embodiment 5 of the present invention.

FIG. 10 is a partial detailed view of an inkjet head and a counter electrode according to a fifth embodiment of the present invention.

FIG. 11 is a partial detailed view of an inkjet head and a counter electrode when a normal counter electrode according to Embodiment 5 of the present invention is used.

FIG. 12 is a partial detailed view of an inkjet head and a counter electrode according to a sixth embodiment of the present invention.

FIG. 13 is a partial detailed view of a counter electrode according to a seventh embodiment of the present invention.

FIG. 14 is a schematic sectional view of a conventional ink jet recording apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ink-jet head 2 Ink-jet head carriage 3 Carriage shaft 4 Static elimination brush 5 Recording paper 6 Static elimination brush carriage 7 Counter electrode 7a Metal plate 7b Insulator 8 Power supply 9 Switch 10 Recording paper conveying means 11 Ink jet head cleaning means 12 Nozzle plate 13 Ink 14 Discharge Port 15 Pressure Chamber 16 Pressure Chamber Structure 17 Ink Supply Port 18 Piezoelectric Element 19 Vibration Plate 20 Ink Droplet 21 Prescanning Recorded Image 22 Next Scanning Recorded Image 23 Rotating Axis 24 Eccentric Cam 25 Switch 26 Ink Image

Claims (13)

[Claims] An ink jet head for projecting ink droplets from a nozzle; a counter electrode arranged to face the ink jet head; and a voltage applied between the ink jet head and the counter electrode, whereby a voltage is applied from the ink jet head to the ink jet head. Voltage applying means for causing the ejected ink droplet to accelerate and fly toward the counter electrode side by electrostatic attraction and land on a recording paper inserted between the inkjet head and the counter electrode; and a charged ink on the recording paper. And an electricity removing means for reducing or removing the electric charges caused by the ink. 2. An inkjet head, an inkjet head scanning means for reciprocating the inkjet head, a counter electrode disposed at a position facing the inkjet head, and the inkjet between the inkjet head and the counter electrode. Voltage applying means for applying a voltage while the head side is grounded, static elimination means set to the same potential as the counter electrode, and eliminating charge on a portion of the recording paper where the counter electrode is present on its back surface; An ink jet recording apparatus comprising: a charge removing means scanning means for causing the means to reciprocate in the same direction as the reciprocating operation of the ink jet head. And a voltage application intermittent means for intermittently applying the voltage by the voltage applying means. 3. An ink jet recording apparatus according to claim 2, wherein no voltage is applied between said ink jet head and said counter electrode by means. 4. An inkjet head, an inkjet head scanning means for reciprocating the inkjet head, a counter electrode disposed at a position facing the inkjet head, and the inkjet between the inkjet head and the counter electrode. Voltage applying means for applying a voltage with the head side grounded, voltage applying and interrupting means for interrupting the voltage application by the voltage applying means, and removing the charge on the portion of the recording paper where the counter electrode is present on its back surface. An ink jet recording apparatus, comprising: a charge eliminator; wherein the voltage application intermittent means removes charges on the recording paper by the charge eliminator when no voltage is applied. 5. The charge removing device according to claim 1, wherein the charge removing device is configured to remove the charge on the recording paper by contacting the recording paper, and further includes a charge removing device scanning device for reciprocating the charge removing device, and a separation of the charge removing device from the recording paper. And static elimination means separating and contacting means for making contact
5. At least when the voltage is applied by the voltage application intermittent means, the static elimination means is separated from the recording paper by the static elimination means separating / contacting means.
The inkjet recording apparatus according to any one of the preceding claims. 6. A state switching means for switching the charge eliminating means between an electrical ground state and a floating state, and at least by the voltage applying / disconnecting means when the voltage is being applied, the state switching means makes the charge eliminating means 5. The ink jet recording apparatus according to claim 4, wherein the device is switched to an electrically floating state. 7. The voltage application intermittent means is one in which a power supply is connected to a grounded switch means, and an opposite electrode is connected in series to the power supply, and the voltage application intermittent means also serves as a state switching means. The ink jet recording apparatus according to claim 6, wherein 8. A recording paper conveying means for conveying a recording paper in a direction perpendicular to a reciprocating operation direction of the ink jet head, and after the ink discharging operation by the ink jet head, the electric charge on the recording paper is removed by the discharging means. The ink jet recording apparatus according to claim 1, wherein the recording paper is transported by the recording paper transport unit after a lapse of time. 9. The ink jet head scan means performs an ink discharge operation on the recording paper during the forward operation of the ink jet head, and removes the charge on the recording paper during the return operation, or removes the charge on the recording paper during the forward operation. The ink jet recording apparatus according to any one of claims 3 to 8, wherein the electric charge is removed, and an ink ejection operation to the recording paper is performed during the return operation. 10. An inkjet head, a counter electrode disposed at a position facing the inkjet head,
A voltage applying unit that applies a voltage between the inkjet head and the counter electrode while the inkjet head side is grounded, wherein the counter electrode is a rectangular plate, and An ink jet recording apparatus, wherein the opposing surface has a shape that is at least 6 mm larger than a recording range of the ink jet head in a conveying direction of the recording paper. 11. An electric discharger which is set at the same potential as the counter electrode and removes electric charge on the recording paper, wherein the electric discharger is provided outside the recording range of the ink jet head, on the recording paper transport direction side, and on the back surface. 11. The ink jet recording apparatus according to claim 10, wherein the electric charge on the recording paper in a portion where is present is removed. 12. An ink-jet head, an ink-jet head scanning means for reciprocating the ink-jet head, and an ink-jet head arranged at a position facing the ink-jet head. A counter electrode having a configuration, voltage applying means for applying a voltage between the ink jet head and the counter electrode while the ink jet head side is grounded, and charge removing means for removing charges on the counter electrode. An ink jet recording apparatus characterized in that: 13. The ink jet recording apparatus according to claim 12, wherein the electric charge on the counter electrode is removed when no recording paper is interposed between the counter electrode and the charge removing means.