JP2001301134A - Recorder and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the adverse effect of an electric field for holding recording material on the behavior of an ink drop ejected from a recording head. SOLUTION: Conduction of a heater for ejecting an ink drop from an ink jet head is started at the rising timing of an ejection reference signal. In order to generate an electric field for attracting recording material to a carrier, an attraction electric field control voltage having a high voltage level VHI for an interval Ton preceding to the rising timing of the ejection reference signal and a low voltage level VLO during other interval is applied to a drum in synchronism with the ejection reference signal. Since the strength of attraction electric field is lowered at the time of ejecting an ink drop, deterioration of image quality and contamination of the head due to charging of an ejected ink drop can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus and a recording method, and more particularly, to a recording method for recording an image or the like on a recording medium by discharging ink droplets from a discharge section of a recording head and attaching the ink droplets to the recording medium. The present invention relates to a recording device to which the recording method is applied.

[0002]

2. Description of the Related Art In an ink jet recording system, ink droplets ejected from nozzles of a recording head are attached to a recording medium to form an image (eg, a character image or a photographic image) on the recording medium.
On-demand type is conventionally known as a kind of recording method for recording the information. The on-demand type is a method in which ink droplets are intermittently ejected from nozzles in accordance with recording information, and typical examples include a piezoelectric element method and a thermal method.

[0003] In the piezoelectric element system, a pulse voltage is applied to a piezoelectric element provided in an ink chamber to deform the piezoelectric element, thereby changing the ink liquid pressure in the ink chamber. In the thermal method, the ink is heated by a heating element provided in the ink chamber, and the ink droplet is ejected from a nozzle by a bubble generated in the ink chamber by this heating.

As a method for holding a recording medium for recording an image, an electric field is generated on a carrier such as a drum or a belt, and the sheet-like recording medium is placed on the carrier by the action of electrostatic force generated by the electric field. A method of holding by suction is also known. In this holding method, as shown in FIGS. 10 and 11, for example, a drum having an insulator layer formed on the surface is used as a carrier, and a constant voltage is constantly applied to a drum body made of a conductor (FIG. 10B). And FIG. 11 (B)
Thus, an electric field is generated for adsorbing and holding the recording medium on the carrier. Thus, the sheet-shaped recording medium can be stably held on the carrier, so that high-speed image recording on the recording medium can be realized.

[0005] Incidentally, a recording head is provided with a large number of nozzles, and ink droplets (ink drops) ejected from adjacent nozzles are, for example, as shown in FIG. It is desirable to land at a position separated by a distance corresponding to the nozzle interval S (0). In the state where no adsorption electric field is generated, the ink droplets ejected from the nozzles are not charged, and even when the ink droplets are ejected from the adjacent nozzles at the same time, each ink droplet remains on the recording medium at the nozzle interval. Land at a position separated by a distance corresponding to S (0).

On the other hand, as shown in FIG.
When ink droplets are simultaneously ejected from adjacent nozzles while a voltage E is applied to the drum to generate an adsorption electric field, the ink is ejected from the adjacent nozzles by the adsorption electric field existing between the nozzle and the drum. The paired ink droplets are charged to have the same polarity (charge amount e), so that an electrostatic repulsion F is generated between the pair of ink droplets (repulsion of the same polarity), and the ink droplet lands on the recording medium. The position interval S (L) is the nozzle interval S (0)
Larger than. This shift in the landing position has caused a deterioration in the image quality of the recorded image, such as the occurrence of white streaks or density unevenness in a solid region (a region where the entire surface has a constant density) in the image recorded on the recording medium.

Further, since the repulsive force F is proportional to the strength of the attracting electric field, if the strength of the attracting electric field is increased in order to increase the force for attracting the recording medium to the carrier, the distance S between the landing positions is increased.
Since (L) (that is, the displacement amount of the landing position) further increases, the image quality deterioration due to the displacement of the landing position becomes more remarkable.

[0008] In addition, the ejection of the ink droplet from the nozzle is performed by applying a force for ejecting the ink from the nozzle to the ink. An ink liquid column is formed so as to protrude from the discharge port of the nozzle, and is formed by a part of the ink liquid column being separated as an ink droplet and flying toward the recording medium due to the inertial force generated by the flow of the ink. However, if at least the ink droplets are ejected by the thermal method, it is confirmed that at this time, in addition to the ink droplets called the main drops, minute ink droplets called the satellite drops also separate from the ink liquid column. Have been.

In a state where no attracting electric field is generated, as shown in FIG. 11A, for example, the inertial force generated by the flow of the ink also acts on the satellite drop, so that the recording medium is formed similarly to the main drop. Flies to the same side as the main drop on the recording medium.

On the other hand, when the voltage E is applied to the drum to generate an attracting electric field, the satellite drops return to the recording head side without flying to the recording medium side and adhere to the vicinity of the discharge port of the nozzle. It is confirmed that the recording head is stained. Further, the ink droplets are formed in the vicinity of the nozzle orifices due to the repeated attachment of the satellite drops. However, the ink droplets reduce the ink discharge performance of the recording head or cause the ink stored in the nozzles to drop. Has been confirmed to have an adverse effect, such as pumping, due to surface tension.

As described above, the phenomenon that the satellite drop returns to the recording head side is caused by the fact that the ink liquid column formed so as to protrude from the nozzle is polarized so as to cancel the adsorption electric field. As shown, a portion of the polarized ink column having a charge of the opposite polarity to the drum is separated as a main drop, and a portion of the polarized ink liquid having a charge of the same polarity as the drum is separated as a satellite drop. It is assumed that

As a technique for solving the above problem, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 1-245389, a large number of conductive patterns are provided inside the transport belt along the transport direction of the transport belt,
By connecting each conductive pattern to voltage applying means via a first charging brush provided on the side of the conveyor belt at the same pitch as the conductive pattern, an attracting electric field for attracting the recording material to the belt is generated, and There is disclosed a technique in which a second charging brush is provided at a position corresponding to immediately below a recording head, and a conductive pattern arriving immediately below the recording head has the same potential as the recording head via the second charging brush.

[0013]

However, according to the technique described in the above publication, the conductive pattern arriving immediately below the recording head is set to the same potential as the recording head, and the other conductive patterns are applied with a voltage. It is necessary to provide a large number of charging brushes corresponding to each conductive pattern.However, the charging brush slides on the transport belt when the transport belt is transported, so that the charging brush itself becomes dirty, worn, damaged, and has a conductive pattern side. There is a problem that it is difficult to stably apply a predetermined voltage for a long period of time due to abrasion or the like.

The present invention has been made in consideration of the above facts, and has a recording apparatus and a recording apparatus which can reduce the adverse effect of a holding electric field for holding a recording medium on the behavior of ink droplets ejected from a recording head. The purpose is to obtain a recording method.

[0015]

According to another aspect of the present invention, there is provided a recording apparatus, comprising: a holding unit for generating a holding electric field for holding a recording medium on a holding surface of a holding member; A print head having an ejection unit for ejecting ink droplets toward the carrying surface, and a drive for ejecting ink droplets for attaching to a recording medium held on the carrying surface from the ejection unit of the recording head. Means for controlling the intensity of the holding electric field when an ink droplet is ejected from the ejection unit.

According to the first aspect of the present invention, the holding means generates a holding electric field for holding the recording medium on the holding surface of the holding member. As the carrier, for example, a drum-shaped member or a belt-shaped member can be used. Further, the recording head includes an ejection unit that ejects ink droplets toward the carrying surface of the carrier, and the driving unit applies ink droplets for attaching to the recording medium held on the carrying surface of the recording head. Discharge from the discharge unit. Then, an image or the like is recorded on the recording medium by landing and attaching the ink droplets discharged from the discharge unit to the recording medium. In addition, as a driving method by the driving means, a known arbitrary method such as a thermal method or a piezoelectric element method can be applied.

Here, the ink droplets ejected from the ejection portion of the recording head are charged by the holding electric field generated by the holding means, so that, for example, the landing position on the recording medium shifts or the ejection portion ejects from the ejection portion. Inconveniences such as the minute ink droplets (so-called satellite drops) returned to the recording head side to form ink pools occur.

For this reason, the control means according to the first aspect of the present invention reduces the strength of the holding electric field when the ink droplet is ejected from the ejection portion of the recording head (for example, when the ink droplet is ejected from the ejection portion of the recording head). Lower than the maximum strength of the holding electric field during the period in which no ejection is performed). As a result, the amount of charge of the ink droplets discharged from the discharge unit due to the holding electric field can be reduced, so that the displacement amount of the landing position of the ink droplet on the recording medium is reduced, and the minute amount discharged from the discharge unit is reduced. It is possible to suppress the formation of an ink liquid pool due to an unnecessary ink droplet returning to the recording head side.

Therefore, according to the first aspect of the present invention, it is possible to reduce the adverse effect of the holding electric field for holding the recording medium on the behavior of ink droplets ejected from the recording head. Further, by reducing the strength of the holding electric field, the holding force for holding the recording medium on the holding surface of the holding member also temporarily decreases.
Since the intensity of the holding electric field is reduced when the ink droplets are ejected from the ejection portion of the recording head, the holding medium is reliably held by the action of the holding electric field generated by the holding means during other periods. Can be.

According to a second aspect of the present invention, there is provided a recording apparatus, comprising: holding means for generating a holding electric field for holding a recording material on a holding surface of a support; and discharging means for discharging ink droplets toward the holding surface. A recording head having a unit, and a driving unit that ejects ink droplets for attaching to a recording material held on the support surface from an ejection unit of the recording head,
And control means for reducing the intensity of the holding electric field generated by the holding means during a period when the ink droplets are ejected from the ejection section.

According to a second aspect of the present invention, there are provided the same holding means, recording head and driving means as those of the first aspect. Further, the control means according to the second aspect of the present invention reduces the intensity of the holding electric field generated by the holding means during a period when the ink droplet is ejected from the ejection section. This allows
Similarly to the first aspect, it is possible to reduce the adverse effect of the holding electric field on the behavior of the ink droplets ejected from the recording head, and to surely hold the recording medium on the supporting surface.

According to the second aspect of the present invention, the intensity of the holding electric field generated by the holding means is reduced during a period in which ink droplets are ejected from the ejection section, so that the holding electric field for holding the recording material is reduced. Since it is possible to reduce adverse effects on the behavior of ink droplets ejected from the recording head, a large number of charging brushes are provided in order to reduce the strength of the holding electric field only in the space near the recording head, as in the related art. This eliminates the necessity and has an effect that the holding electric field can be generated stably for a long period of time.

More specifically, the charging of the ink droplet is performed in such a manner that a force for discharging the ink from the discharge portion is applied to the ink, and the ink liquid column formed so as to protrude from the nozzle is polarized so as to cancel the holding electric field. This occurs when a portion of the ink column having a certain polarity of charge is separated as an ink droplet. For this reason, the control unit may be configured to perform the first operation from when at least a force for ejecting the ink from the ejection unit is applied to the ink to when a part of the ink is separated from the ejection unit as an ink droplet. It is preferable to control the intensity of the holding electric field to decrease during the period.

This makes it possible to surely reduce the intensity of polarization generated in the ink liquid column (the amount of charge in a portion of the ink liquid column having a charge of a certain polarity), and to reduce the ink liquid column (discharge unit). ) Can reliably reduce the charge amount of the ink droplets ejected separately from the ink droplets. Also, if the holding electric field in the first period can be made 0,
It is possible to prevent the ink droplets discharged from the discharge unit from being charged.

According to the third aspect of the present invention, it is not possible to completely prevent the ink droplets discharged from the discharge unit from being charged, and the ink droplets discharged from the discharge unit are slightly charged. According to another aspect of the present invention, the control means controls the intensity of the holding electric field to be reduced even in the second period until the ink droplet separated from the ejection unit adheres to the recording medium. Is preferred. As a result, the strength of the holding electric field acting on the ink droplets separated (discharged) from the discharge unit is reduced. Therefore, when the ink droplets discharged from the discharge unit are charged, the ink discharged from the recording head is charged. The adverse effect of the holding electric field on the behavior of the droplet can be reliably reduced.

The generation of the holding electric field by the holding means is as follows.
For example, it can be performed by applying a voltage to a carrier or the like, but the intensity of the holding electric field generated with the application of the voltage gradually increases when the voltage is started due to the influence of the capacitance, and the voltage of the voltage increases. When the application is stopped, the change often decreases gradually.

In the case where the strength of the holding electric field changes as described above with respect to the application of the voltage for generating the holding electric field, the strength of the holding electric field is reduced, for example, as described in claim 5. In addition, it can be performed by switching the voltage applied by the holding means to generate a holding electric field to a predetermined low voltage or by stopping the application of the voltage. As a result, the intensity of the holding electric field can be reduced by a very simple control, as compared with a mode in which the magnitude of the voltage applied to generate the holding electric field is adjusted.

In the case where the driving means is configured to discharge the ink droplets from the discharge portion of the recording head at a timing synchronized with the drive timing signal, the intensity of the holding electric field is reduced when the ink droplets are discharged from the discharge portion. For example, as described in claim 6, the voltage applied by the holding unit for generating the holding electric field is reduced by n times (n is an integer of 1 or more) the period of the drive timing signal. This can be realized by setting a predetermined high voltage only during a period in which ink droplets are not ejected from the ejection unit.

According to the sixth aspect of the present invention, the fact that the ink droplets are ejected from the ejection section of the recording head at a timing synchronized with the drive timing signal is used, and the ink droplets are actually ejected from the ejection section of the recording head. The voltage applied by the holding means is set to a predetermined high voltage only during a period in which it can be determined that ink droplets are not ejected from the ejection unit based on the drive timing signal without detecting whether or not the ink is ejected. Is periodically performed, it is not necessary to detect whether or not an ink droplet is actually ejected from the ejection unit of the recording head, and the control of the control unit can be simplified.

The length of the period in which the voltage applied by the holding means is set to a predetermined high voltage may be constant, for example, or may be a magnitude required as a holding force for holding the recording medium. May be changed as appropriate in accordance with the change of Also, the period (value of n) in which the voltage for generating the holding electric field is set to a predetermined high voltage may be constant, or may be appropriately changed according to a change in magnitude required as the holding force. It may be. Further, during a period in which the voltage applied by the holding unit is not set to the predetermined high voltage, the applied voltage may be set to the predetermined low voltage, or the applied voltage may be set to 0 (that is, the application of the voltage is stopped). Good.

In the case where the driving means is configured to discharge ink droplets from a discharge portion of a recording head at a timing corresponding to an image signal for recording an image to be recorded on a recording medium, Decreasing the intensity of the holding electric field when is ejected, as described in claim 7, detects a period during which ink droplets are ejected from the ejection unit based on the image signal, and at least during the detected period, This can be realized by switching the voltage applied by the holding means to generate a holding electric field to a predetermined low voltage, or by stopping the application of the voltage.

According to the seventh aspect of the present invention, the period during which the ink droplets are actually ejected from the ejection section is detected based on the image signal. Although there is a possibility that the voltage may be complicated, the voltage applied by the holding unit may be set in a period in which the ink droplets are not ejected from the ejection unit based on the result of the detection of the period, that is, a period in which the intensity of the holding electric field does not need to be reduced. Is maintained at a predetermined high voltage, it is also possible to perform control so as not to decrease the strength of the holding electric field, so that the decrease in the holding power of the recording medium due to the decrease in the strength of the holding electric field is minimized. It becomes possible.

According to the recording method of the present invention, a holding electric field for holding the recording medium on the supporting surface of the carrier is generated, and the recording medium is held on the supporting surface. In performing printing by discharging ink droplets to be attached to the recording medium from a discharge unit of a print head, when the ink droplets are discharged from the discharge unit, the strength of the holding electric field is reduced. Therefore, similarly to the first aspect, it is possible to reduce the adverse effect of the holding electric field for holding the recording medium on the behavior of the ink droplets ejected from the recording head.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. In the following, description will be made using numerical values that do not hinder the present invention, but the present invention is not limited to the numerical values described below.

[First Embodiment] FIG. 1 shows an ink jet printer 10 to which a recording method according to the present invention can be applied. The ink jet printer 10 corresponds to the recording device according to the present invention.

The ink jet printer 10 includes a bottomed cylindrical drum 12 as a carrier according to the present invention. As schematically shown in FIG. 3, the drum 12 has a main body made of a conductive material (for example, aluminum), and has an insulator layer formed on the peripheral surface by resin coating or the like. When the main body of the drum 12 is formed of aluminum, the insulator layer can be formed by subjecting the surface of the drum 12 to alumite treatment (the alumite treatment layer formed on the surface layer by the alumite treatment is used as the insulator layer). Can be used).

The drum 12 is rotatable about an axis, and is rotated by transmitting a driving force of a drum rotation driving means (not shown) (counterclockwise direction in FIG. 1). Further, the peripheral surface of the drum 12 is a support surface for holding a recording medium.
Is used as an electrode for generating an adsorption electric field (holding electric field according to the present invention) for adsorbing and holding the recording medium on the peripheral surface.

In FIG. 1, a paper tray 14 capable of storing a large number of sheet-shaped recording media is arranged at the lower left side of the drum 12. Inkjet printer 10
Is capable of using sheet materials of various materials (for example, plain paper and OHP sheets), sizes and thicknesses as recording media. The paper tray 14 is used for the inkjet printer 10.
And a plurality of types are prepared corresponding to various sizes of sheet materials usable as a recording medium, and a paper tray 14 corresponding to a sheet material used as a recording medium is selectively provided. Is set on the main body of the inkjet printer 10.

A draw-out conveyance roller 16 is arranged near the position where the paper tray 14 is set when the paper tray 14 is set in the main body of the ink jet printer 10. When an image (for example, a character image or a photographic image) is recorded on a recording medium, the pull-out transport roller 16 is rotated by transmitting a driving force of a pull-out transport roller rotation driving unit (not shown), and is stored in the paper tray 14. The recording medium that is present is pulled out of the paper tray 14 and is conveyed below the drum 12.

On the outer periphery of the drum 12, the recording medium pulled out from the paper tray 14 by the pull-out transport roller 16 is brought into contact with the peripheral surface of the drum 12 (a position corresponding to a position vertically below the axis of the drum 12). A pressing roller 18 is provided. The paper holding roller 18 is, for example, an EPDM
(Ethylene propylene diene rubber), silicon rubber, urethane rubber, or the like. More specifically, in order to improve the adhesion between the recording medium and the peripheral surface (supporting surface) of the drum 12, It is desirable to select a material having a small rubber hardness (a rubber hardness of about 30 to 50 degrees) such that the width (nip width) of a region where the peripheral surface of the drum 12 and the peripheral surface of the drum 12 are in contact is widened.

The paper holding roller 18 has an outer peripheral surface of the drum 1
2 (a retracted position shown by imaginary lines in FIG. 1), and the driving force of a pressing roller driving means (not shown) is transmitted from the nip position shown by a solid line in FIG. It is moved to the retreat position or from the retreat position to the nip position. The pressing roller driving means is a drawer conveying roller 1
After the recording medium conveyed by the drum 6 arrives at the position where the drum 12 is disposed, the paper holding roller 18 is maintained between the time when the recording medium is attracted to the peripheral surface of the drum 12 by the generation of the attracting electric field. The recording medium is held at the nip position by nipping the recording medium by the drum 12 and the sheet pressing roller 18. Further, after the recording medium is attracted to the peripheral surface of the drum 12 by the attracting electric field, the paper holding roller 18 is moved to the retracted position (a position where the rotation of the drum 12 does not become a resistance).

On the outer periphery of the drum 12, an ink jet head 20 (corresponding to a recording head according to the present invention) is disposed downstream of the paper holding roller 18 in the rotation direction of the drum 12. The ink jet head 20 is movable along a rail (not shown) provided in parallel with the axis of the drum 12, and is moved along the rail by a driving force of a head moving means (not shown). Main body of the inkjet head 20 (carriage 32: see FIG. 2)
Has a built-in ink storage unit (not shown), in which ink to be ejected from the inkjet head 20 and adhered to a recording medium is stored.

As shown in FIG. 2, a recording head 34 is provided on a side surface of the carriage 32 facing the peripheral surface of the drum 12. The recording head 34 is formed with a plurality of circular holes (nozzles) 36 as ejection portions according to the present invention at a constant pitch along a direction B shown in FIG. 2 (a direction orthogonal to the rail). Head surface 34A (drum 1
The ink discharge ports 38 of the respective nozzles 36 are formed on a surface (surface facing the peripheral surface of the second 2).

In this embodiment, as the recording head 34,
A recording head that ejects ink droplets by a thermal method is used. A heater is provided in an ink chamber provided for each nozzle 36 (both are not shown). The ink is supplied from the unit via an ink supply path (not shown).

The ink droplets are ejected from the nozzles 36 when the heater in the ink chamber corresponding to the nozzles 36 is energized, and the heat generated by the heater heats the ink in the ink chambers to generate bubbles. After the ink flows toward the ink discharge port 38 of the nozzle 36 due to the bubble, the ink liquid column is formed so as to protrude from the ink discharge port 38 due to the surface tension of the ink, and the inertia force generated by the flow of the ink causes A part of the ink liquid column is separated as an ink droplet and flies (discharges) toward the peripheral surface of the drum 12 (recording medium side).

On the outer periphery of the drum 12, a peeling claw 22 is provided downstream of the ink jet head 20 in the rotation direction of the drum 12. The peeling claw 22 is rotatably supported at one end (base) as shown by an arrow A in FIG. 1, and receives the driving force of a peeling claw driving unit (not shown) to thereby rotate the other end (the distal end). ) Is moved to a peeling position (a position shown by a solid line in FIG. 1) in contact with the peripheral surface of the drum 12 or a position retracted from the peeling position (a position shown by an imaginary line in FIG. 1).

When the peeling claw 22 is located at the peeling position, its leading end enters between the peripheral surface of the drum 12 and the recording medium held on the peripheral surface as the drum 12 rotates. Thus, the recording medium can be peeled off from the peripheral surface of the drum 12, and the recording medium peeled off from the peripheral surface of the drum 12 is guided in a certain direction by the peeling claw 22.

A guide roller 24, a pair of transport rollers 26, and a tray 2
8 are arranged in order. Drum 1 by peeling claw 22
The recording medium peeled off from the peripheral surface of the tray 2 is guided and conveyed by the guide roller 24 and the conveying roller pair 26, and
8.

Next, the electrical configuration of the ink jet printer 10 will be described with reference to FIG. The ejection reference signal generation circuit 42 generates an ejection reference signal (corresponding to a drive timing signal according to claim 6) that defines the ejection timing of ink droplets from the inkjet head 20. The ejection reference signal is a signal having a constant cycle (discharge basic cycle T ₀ ) as shown in FIG. 4 and having a high level for a certain time at the beginning of the basic discharge cycle T ₀ . Discharge reference signal generation circuit 4
The ejection reference signal generated in step 2 is output to the image signal generation circuit 44.
, And are input to the attracting electric field control circuit 52, respectively.

An image information generating circuit 46 is connected to the image signal generating circuit 44, and from the image information generating circuit 46, image information representing an image to be recorded on a recording medium is input. The image signal generation circuit 44 drives the respective nozzles 36 of the inkjet head 20 based on the input ejection reference signal and the image information so that the image represented by the image information is recorded on the recording medium in units of dots. More specifically, an image signal is generated that indicates the timing of energization of the heater provided for each nozzle 36.

The generated image signal is input to an ink jet head driving circuit 48 connected to the image signal generating circuit 44. In the inkjet head drive circuit 48,
Power for driving the inkjet head 20 is supplied from an inkjet head drive power supply 50. The ink jet head drive circuit 48 selectively energizes heaters provided corresponding to the respective nozzles 36 at a timing according to the input image signal, and selectively ejects ink droplets from the respective nozzles 36. to move the inkjet head 20 along the rail at a moving speed corresponding to the discharge fundamental period T _0.

As a result, the main scanning is performed by the movement of the inkjet head 20 and the sub-scanning is performed by the rotation of the drum 12, and the inkjet head 20 is provided on the recording medium held on the peripheral surface of the drum 12. The image is recorded in units of the same number of dot rows as the number of nozzles 36 that are present. The energization of the heater by the inkjet head drive circuit 48 starts at the timing when the ejection reference signal rises (switches from low level to high level). It is discharged from the nozzle 36.

The ink jet head driving circuit 48
Corresponds to the driving means of the present invention (specifically, the driving means described in claims 6 and 7).

On the other hand, the attracting electric field control circuit 52
Is electrically connected to the main body (conductor) of the drum 1
In the first embodiment, as shown in FIG. 4, at a timing synchronized with the ejection reference signal input from the ejection reference signal generation circuit 42 in order to generate an adsorption electric field for adsorbing the recording medium on the peripheral surface of the recording medium 2. , High voltage V _HI (eg, V _HI = + 300
[V]) or low voltage V _LO (eg, V _LO = + 100 [V] or V
_An adsorption electric field control voltage that periodically switches to ( _LO = 0 [V]) is applied to the drum 12.

More specifically, the adsorption electric field control voltage according to the first embodiment has the same cycle as the ejection reference signal (period _Tv =
At T ₀ ), the waveform is a high voltage V _HI during a period from a time before the discharge reference signal rises by a predetermined time T _on to a rise of the discharge reference signal, and a low voltage V _LO during other periods. In the same cycle as the reference signal, the high voltage V _HI is applied to the drum 12 only during a period from a predetermined time T _on before the rising timing of the ejection reference signal to the rising of the ejection reference signal. 12, the application of the low voltage V _LO is repeated.

The attracting electric field control circuit 52 is, for example,
Voltage V_HIAnd low voltage V_LOPower supply circuit that generates
_LO= 0 [V] if V_LOIs unnecessary) and the drum 12
At the timing synchronized with the ejection reference signal
High voltage V_HIOr low voltage V_LOSwitching circuit to switch to
And can be configured. The power supply circuit is constant
Voltage may be output, but the power supply circuit
Output voltage can be changed by using switching power supply circuit
(For example, the range of 0 [V] to +2.0 [kV] or 0 [V] to -2.0 [kV]
Box), the type and size of the recording medium, thickness,
Frequency (period T ₀), Depending on the peripheral speed of the drum 12, etc.
Voltage V_HIAnd low voltage V_LOAdopt configuration to adjust the size of
May be.

As a switching circuit, for example,
Timing adjustment (phase adjustment) for the ejection reference signal
By performing the inversion and amplification, at the timing shown in FIG.
A configuration for switching the voltage applied to the drum 12 should be adopted.
Can be. Note that the high voltage V _HIFrom low voltage V_LOOr that
Slew rate so that the reverse voltage change of
Power circuit or signal with high (for example, about several tens [V / μs])
It is desirable to use an amplifier.

The application of the attraction electric field control voltage to the drum 12 can be performed, for example, through power supply means such as a charging brush. In the present embodiment, the magnitude of the attraction electric field control voltage is determined by the ink jet head 20. By changing the timing in synchronization with the ejection of the ink droplets from the ink jet head, it is possible to reduce the adverse effect of the attraction electric field generated by the application of the attraction electric field control voltage on the behavior of the ink droplets ejected from the inkjet head 20 (for details) Therefore, even when a charging brush is used as the power supply means, the attraction electric field control voltage can be applied by a very small number of charging brushes. Therefore, the adsorption electric field control voltage can be stably applied over a long period of time, and the adsorption electric field can be stably generated over a long period of time.

The attracting electric field control circuit 52 is connected to the drum 1
2 corresponds to the holding means according to the present invention together with the main body and the insulator layer, and the control means according to the present invention (specifically, claim 3)
To the control means according to claim 6).

In the above configuration, when an instruction to record an image on a recording medium is issued, the recording medium is pulled out of the paper tray 14 by the rotationally driven draw-out conveyance roller 16 and is conveyed below the drum 12. The sheet is nipped (nipped) by the drum 12 and the sheet pressing roller 18. The ejection reference signal generation circuit 42 generates an ejection reference signal, and the attraction electric field control circuit 52 controls the ejection reference signal generation circuit 4.
A suction electric field control voltage (see FIG. 4), which periodically switches to a high voltage V _HI or a low voltage V _LO at a timing synchronized with the ejection reference signal inputted from 2, is applied to the drum 12, and is adsorbed on the peripheral surface of the drum 12. Generate an electric field. Due to the attracting electric field, the recording medium nipped by the drum 12 and the sheet pressing roller 18 can be attracted and held on the peripheral surface of the drum 12 with an attracting force corresponding to the intensity of the attracting electric field. The recording medium sucked and held in the drum 12
Is transported to the position where the ink jet head 20 is disposed in accordance with the rotational driving of. In addition, the adsorption electric field control circuit 5
The application of the attraction electric field control voltage by the second step 2 is performed independently of the recording of the image on the recording medium while the recording medium is held at least on the peripheral surface of the drum 12 (the recording medium is not peeled off from the peripheral surface of the drum 12). Until it is started).

When the recording medium reaches the position where the head 20 is disposed, the image signal generation circuit 44 outputs the ejection reference signal inputted from the ejection reference signal generation circuit 42 and the image signal inputted from the image information generation circuit 46. An image signal is generated based on the information, and the inkjet head drive circuit 48 selectively energizes a heater provided corresponding to each nozzle 36 at a timing according to the input image signal, so that each nozzle 36 And selectively eject ink droplets from
At a moving speed corresponding to the discharge fundamental period T ₀ to move the inkjet head 20 along the rail. Thus, an image is recorded on the recording medium held on the peripheral surface of the drum 12.

Here, when ink droplets are ejected from the nozzles 36 of the ink jet head 20, an attracting electric field is generated. For example, ink droplets ejected simultaneously from the adjacent nozzles 36 are charged to the same polarity. The impact position (attachment position) on the recording medium is remarkably shifted, and the image quality of the recorded image is degraded (for example, a white streak or density unevenness occurs in a solid area), or the ink droplet is separated from the ink ejection port 38. When the minute ink droplets (satellite drops) generated at the time are charged, the satellite drops return to the inkjet head 20 side without flying to the recording medium side,
There is a possibility that inconveniences such as attaching to the head surface 34A of the recording head 34 and soiling the recording head 34 may occur.

On the other hand, in the first embodiment, as is apparent from the electric field strength curve (shown by imaginary lines) shown in FIG. When the voltage is switched from the low voltage V _LO to the high voltage V _HI , the intensity gradually increases due to the influence of the capacitance. When the adsorption electric field control voltage switches from the high voltage V _HI to the low voltage V _LO , the intensity also increases due to the capacitance. Indicates a gradually decreasing change. On the other hand, the energization of the heater by the inkjet head drive circuit 48 starts at the timing when the ejection reference signal rises (switches from the low level to the high level). It is discharged from the nozzle 36.

Therefore, in the first embodiment, the ink is formed so as to protrude from the ink ejection port 38 after the force for flowing the ink is applied to the ink by the bubble generated by energizing the heater of the ink jet head 20. The period until a part of the ink column is separated as an ink droplet (corresponding to the first period of the third aspect), and after the ink droplet is separated from the ink ejection port 38, the ink droplet is recorded. In a period (corresponding to the second period according to the fourth aspect) until the recording medium flies to the recording medium and lands (adheres), the attraction electric field control voltage is a low voltage V _LO for a certain time or more. As apparent from FIG. 4, the intensity of the attracting electric field is lower than the peak value (when the attracting electric field control voltage is switched from V _HI to V _LO ) by a predetermined value or more.

As a result, the amount of charge of the ink drop (main drop) separated from the ink ejection port 38 and the satellite drop generated when the ink drop is separated is reduced, and the ink drop separated from the ink ejection port 38 is used as a recording medium. Since the intensity of the attracting electric field acting on the ink droplets before landing on the recording medium is also reduced, the landing positions of the ink droplets simultaneously discharged from the adjacent nozzles 36 on the recording medium are shifted, and the image quality of the recorded image is degraded. It is possible to prevent the recording head 34 from being contaminated and adhered to the head surface 34A or the like of the recording head 34, thereby making the recording head 34 dirty.

When the strength of the attraction electric field decreases, the attraction force for adsorbing the recording medium on the peripheral surface of the drum 12 also decreases, but the attraction electric field control voltage is periodically changed (the ink is not ejected from the ink jet head 20). During this period, the high voltage V _HI is maintained for a predetermined time T _on , and the strength of the attracting electric field and the attracting force to the recording medium are also restored. Accordingly, the recording medium is attracted and held on the peripheral surface of the drum 12. And stabilized.

The suction force required to stably hold and hold the recording medium on the peripheral surface of the drum 12 varies depending on various conditions such as the type of the recording medium and the moving speed of the carrier (drum 12). I do. Therefore, based on the various conditions, it may be set changing a high voltage V _HI in size even consideration to time T _on.

[Second Embodiment] Next, a second embodiment of the present invention will be described. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Only parts different from those in the first embodiment will be described.

FIG. 5 shows an ink jet printer 60 according to the second embodiment. The inkjet printer 60 includes an endless belt 64 wound around a pair of pulleys 62 instead of the drum 12 described in the first embodiment.
It has. As shown in FIG.
Is formed on the outer peripheral surface of the belt base material 64A by the electrostatic attraction film 6
6 are adhered and formed in a seamless shape.

As shown in FIG. 6B, an electrode 6 extending along the width direction of the belt 64 is provided on the electrostatic attraction film 66.
8 are buried at a constant pitch along the circumferential direction of the belt 64. On the outer peripheral surface of the belt 64, conductive patterns 70A and 70B are formed at both ends in the width direction of the belt 64 with the electrostatic attraction film 66 interposed therebetween, and the large number of electrodes 68 embedded in the electrostatic attraction film 66 Are connected to every other conductive pattern 70A along the circumferential direction of the belt 64, and the conductive pattern 70A and the conductive pattern 70A are connected to each other.
The electrode 68 connected to A (in FIG. 6A, for convenience, "6
8A ") to form a comb-like electrode 72. The comb-shaped electrode 72 is grounded.

The electrodes 68 which are not connected to the conductive pattern 70A among the many electrodes 68 are the conductive patterns 70A.
B, and a comb-shaped electrode 74 is formed by the conductive pattern 70B and the electrode 68 connected to the conductive pattern 70B (in FIG. 6A, the reference numeral “68B” is used for convenience). Have been. The comb-tooth electrode 74 is connected to the attraction electric field control circuit 52, and an attraction electric field control voltage is applied to the comb-tooth electrode 74 by the attraction electric field control circuit 52. When a voltage is applied to the comb-shaped electrode 74, the belt 64
An electric field is generated on the outer peripheral surface of the belt 64. At this time, if a recording medium is placed on the outer peripheral surface of the belt 64, a current path is formed through the recording medium, and the outer periphery of the belt 64 is formed by the Johnsen-Rahbek effect. The recording medium is adsorbed on the surface. As described above, in the second embodiment, the outer peripheral surface of the belt 64 corresponds to the carrying surface according to the present invention.

The application of the attraction electric field control voltage in the second embodiment can be performed, for example, through power supply means such as a charging brush. In the second embodiment, the same as in the first embodiment. In addition, even when a charging brush is used as the power supply means, the attracting electric field control voltage can be applied by a very small number of charging brushes, so that the attracting electric field control voltage can be stably applied over a long period of time,
An adsorption electric field can be stably generated over a long period of time.

Above the belt 64, inks of different colors are ejected toward the outer peripheral surface of the belt 64.
The plurality of inkjet heads 20 are provided. The image signal generation circuit 44 includes a single ejection reference signal output from the ejection reference signal generation circuit 42 and an image information generation circuit 46.
Generating four types of image signals corresponding to the respective inkjet heads 20 based on the image information input from
The generated image signal is supplied to the inkjet head drive circuit 48.
Enter each.

Further, as shown in FIG. 7, the attracting electric field control circuit 52 according to the second embodiment controls the ejection reference signal 3 at a timing synchronized with the ejection reference signal input from the ejection reference signal generation circuit 42. in multiple of the period (the period T _v = 3T _0),
A predetermined time T from the timing when the ejection reference signal rises
_The high voltage V
_HI , and in the other periods, an attraction electric field control voltage having a waveform of a low voltage V _LO is applied to the belt 64 (specifically, the comb-like electrode 74).

Thus, the attracting electric field generated on the outer peripheral surface of the belt 64 is changed until the attracting electric field control voltage is switched to the high voltage V _HI , as is apparent from the electric field strength curve (shown by the imaginary line) shown in FIG. (The period corresponding to a cycle approximately three times as long as the ejection reference signal), the intensity gradually decreases, and the intensity gradually increases while the attraction electric field control voltage is switched to the high voltage V _HI . As described above, when the cycle of applying the high voltage V _HI is set to n times (n ≧ 2, n = 3 in the second embodiment) the ejection reference signal, a power supply circuit or a signal amplifier having low frequency response is used. The electric field control circuit 52 can be configured by the
Cost can be reduced.

If the cycle of applying the high voltage V _HI is set to n times (n ≧ 2) of the ejection reference signal, as is clear from the comparison of the transition of the intensity of the adsorption electric field between FIGS. Compared with the first embodiment (in the case of n = 1), the average strength of the attracting electric field may be reduced and the attracting force to the recording medium may be reduced. Time T _on for applying high voltage V _HI so as to obtain an appropriate suction force
And the magnitudes of the high voltage V _HI and the low voltage V _LO are adjusted to compensate for the decrease in the attraction force to the recording medium, and the recording medium is adsorbed and held on the outer peripheral surface of the belt 64. It is stable in the state that it is.

On the other hand, the energization of the heater of each ink jet head 20 is started at the timing when the ejection reference signal rises in synchronism with the single ejection reference signal as in the first embodiment. A period (a first period) from the time when the force for flowing the ink is applied to the ink until the ink droplet is separated from the ink ejection port 38, and the time when the ink droplet is separated from the ink ejection port 38, During the period (the second period) before landing on the recording medium, as in the first embodiment, the intensity of the attracted electric field is lower than the peak value by a predetermined value or more.

Therefore, also in the second embodiment, the first
In the same manner as in the embodiment, the landing positions of the ink droplets simultaneously ejected from the adjacent nozzles 36 on the recording medium are shifted to cause deterioration in the image quality of the recorded image, or the satellite drops adhere to the head surface 34A of the recording head 34 or the like. Recording head 3
4 can be suppressed.

In the above description, an example is described in which the magnitude of the attraction electric field control voltage is periodically switched at a timing synchronized with the ejection reference signal to control the attraction electric field. However, the present invention is not limited to this. As shown in FIG. 8, an image signal is input to the attraction electric field control circuit 52 instead of the ejection reference signal, and the attraction electric field control circuit 52 ejects ink droplets from the inkjet head 20 based on the input image signal. For example, the application of the voltage may be stopped at the timing shown in FIG. 9 so that the period is detected and the intensity of the attracted electric field is reduced during the period in which the ink droplet is ejected.

In this example, when the image signal shown in FIG. 9 (corresponding to the image signal of claim 7) is at a high level, ink droplets are ejected from the ink jet head 20. In the attraction electric field control circuit 52, the attraction electric field control voltage is set to the high voltage V _HI during a period from a time before the ejection reference signal rises by a predetermined time T _on until the ejection reference signal rises.
In addition, when the ejection reference signal rises, the image signal level is referred to. If the image signal is switched to the high level, it is determined that the ink droplet is ejected, and the attraction electric field control voltage is switched to the low voltage V _LO . If the image signal is not switched to the high level, it is determined that the ink droplet is not ejected, and the attraction electric field control voltage is maintained at the high voltage _VHI .

In this embodiment, although the operation of the attracting electric field control circuit 52 is slightly complicated, the attracting electric field control voltage is switched to the low voltage _VLO only when the ink droplet is ejected, and the ink droplet is ejected. In the absence period, since the attraction electric field control voltage is maintained at the high voltage V _HI even during the period after the ejection reference signal rises, the attraction force to the recording medium is maintained at a predetermined value or more. It is possible to minimize a decrease in the adsorbing force of the medium and to suppress the displacement of the landing position of the ink droplet and the stain on the recording head 34 due to the adsorbing electric field. It should be noted that the attraction electric field control circuit 52 in this embodiment corresponds to the control means described in claim 7 in detail.

FIG. 9 shows a case in which the attraction electric field is controlled based on a single image signal. When there are a plurality of image signals (for example, the image signal In the case where each of them is present or in the case where a plurality of inkjet heads 20 are provided), a signal corresponding to a logical product (: AND, if negative logic, negative logical product: NAND) of all image signals is generated, The generated electric signal may be used as the image signal shown in FIG. 9 to control the attraction electric field.

In the above description, as the means for generating the attracting electric field, an example in which an insulator layer is formed on the peripheral surface of the drum 12 in the first embodiment, and an electrostatic charge is applied to the outer peripheral surface of the belt 64 in the second embodiment. Although the example in which the suction film 66 is bonded has been described, the present invention is not limited to this, and an electrostatic suction film may be bonded to the peripheral surface of the drum 12, or a conductor layer and an insulating layer may be formed on the outer peripheral surface of the belt 64. May be formed to generate an adsorption electric field.

In the above description, the recording head according to the present invention has been described by taking the ink jet head 20 for ejecting ink droplets by a thermal method as an example. However, the present invention is not limited to this. A recording head that ejects ink droplets according to the above may be used.

[0085]

Next, an experiment conducted by the present inventor to confirm the effect of the present invention will be described.

[First Example] The present inventor manufactured the ink jet printer 10 described in the first embodiment under the following conditions.

"Drum 12": made of aluminum having a diameter of 120 [mm], surface hard anodized (Vickers hardness 40)
0 degree, film thickness 20 [μm]), rotation speed 100 [rpm] (≒ 630 [mm /
s]) “Inkjet head 20”: Thermal inkjet method, resolution 400 [dpi] of nozzle 36 (nozzle 36
Inkjet heads arranged at a pitch equivalent to 400 [dpi]), ejection frequency 7 [kHz] "Paper holding roller 18": Silicon rubber roll (rubber hardness 30 degrees, JIS A scale), diameter 40 [mm] And production Using the inkjet printer 10
First, as a comparative example, the voltage applied to the drum 12 was +500
[V] is maintained at a constant value (however, it is switched to 0 [V] when the recording medium is peeled off from the drum 12), and a character image is continuously recorded (printed) on 50 sheets of A4 paper at a print coverage of 20% at 20%. The printing test was performed under the printing test condition of performing the printing test.

As a result, it was confirmed that white streaks and density unevenness due to displacement of landing positions of ink droplets occurred in a solid portion (solid portion) in a character image from the first sheet of printing. After the printing test, the head surface 34A of the recording head 34 was observed, and it was confirmed that dirt due to satellite drops had occurred in some places.

Next, the same ink jet printer 10
The high voltage V _HI = + 500 [V], the low voltage V _LO = 0 [V], the same cycle as the ejection reference signal (ejection frequency 7 [kHz]), and the predetermined time T at the timing shown in FIG. _A printing test was performed under the same printing test conditions as in the comparative example, by applying an attraction electric field control voltage for applying a high voltage V _HI only to _on = 50 [μs] to the drum 12.

As a result, no white streaks were generated in the solid portion (solid portion) in the character image due to the displacement of the landing position of the ink droplet. After the printing test, the head surface 34A of the recording head 34 was observed. As a result, there was almost no ink drop due to satellite drop or ink mist.

According to the above experiment, assuming that the voltage applied to the drum 12 is constant and the intensity of the attracting electric field is constant as in the comparative example, ink droplets ejected from the ink jet head 20 are charged and landed by homopolar repulsion. While the recording head 34 is contaminated due to misregistration and satellite drop, the ink jet head 20 discharges the ink from the drum 12 while the ink droplets are ejected from the inkjet head 20 as in the first embodiment.
It was confirmed that, when the voltage applied to the _substrate was set to a low voltage V _{LO and} the intensity of the attracting electric field was reduced, the ejection of ink droplets was stabilized, and high-quality recording could be achieved.

[Second Embodiment] The present inventor manufactured the ink jet printer 60 described in the second embodiment under the following conditions.

"Belt 64": chloroprene rubber and EPDM
A belt base material 64A is formed from a material obtained by blending carbon black with an acrylic resin and carbon black is dispersed in an acrylic resin. An electrostatic attraction film 66 in which electrodes having a width of 10 [mm] are arranged at a pitch of 5 [mm] is used as a belt base. A seamless belt is created by bonding on the outer surface of the material 64A. The diameter of the pulley 62 is 10
At 0 [mm], the movement speed of the belt 64 is 1000 [mm / s].

"Inkjet head 20": Thermal ink jet system, resolution of nozzle 36: 600 [dpi],
Discharge frequency 10 [kHz] “Paper holding roller 18”: Silicon rubber roll (rubber hardness 30 degrees, JIS A scale), diameter 40 [mm]
First, as a comparative example, the voltage applied to the belt 64 was +300
[V] is maintained constant (however, it is switched to 0 [V] when the recording medium is peeled off from the belt 64), and character images are continuously recorded (printed) on 50 sheets of A4 paper with a print coverage of 20%. The printing test was performed under the printing test condition of performing the printing test.

As a result, it was confirmed that white streaks and density unevenness due to displacement of landing positions of ink droplets occurred in a solid portion (solid portion) in a character image from the first sheet of printing. After the printing test, the head surface 34A of the recording head 34 was observed, and it was confirmed that dirt due to satellite drops had occurred in some places.

Next, the same ink jet printer 60
The high voltage V _HI = + 300 [V], the low voltage V _LO = 0 [V], and a cycle three times as long as the ejection reference signal (ejection frequency 10 [kHz]) at a timing shown in FIG. A printing test was performed under the same printing test conditions as in the comparative example by applying an attraction electric field control voltage for applying a high voltage V _HI for only T _on = 30 [μs] to the drum 12.

As a result, no white streaks were generated in the solid portion (solid portion) in the character image due to the displacement of the landing position of the ink droplet. After the printing test, the head surface 34A of the recording head 34 was observed. As a result, there was almost no ink drop due to satellite drop or ink mist.

According to the above experiment, assuming that the voltage applied to the belt 64 is constant and the intensity of the attracting electric field is constant as in the comparative example, ink droplets ejected from the ink jet head 20 are charged and landed by homopolar repulsion. While the recording head 34 is contaminated due to misalignment and satellite drops, the ink jet head 20 ejects ink droplets during the period in which ink droplets are ejected, as in the second embodiment.
It was confirmed that, when the voltage applied to the _substrate was set to a low voltage V _{LO and} the intensity of the attracting electric field was reduced, the ejection of ink droplets was stabilized, and high-quality recording could be achieved.

[0099]

As described above, according to the first and eighth aspects of the present invention, when the ink droplets are ejected from the ejection portion of the recording head which ejects the ink droplets toward the holding surface, the recording medium is ejected. Since the intensity of the holding electric field for holding on the holding surface of the holding body is reduced, the holding electric field for holding the recording medium can reduce the adverse effect on the behavior of ink droplets ejected from the print head. It has an excellent effect.

According to a second aspect of the present invention, there is provided a method for holding a recording medium on a supporting surface of a carrier during a period in which ink droplets are ejected from a discharge portion of a recording head which ejects ink droplets toward the carrying surface. Since the intensity of the holding electric field is reduced, the holding electric field for holding the recording medium can be prevented from adversely affecting the behavior of the ink droplets ejected from the recording head, and the holding electric field can be stably maintained for a long period of time. It has an excellent effect that it can be generated.

According to a third aspect of the present invention, in the first or second aspect of the invention, at least a part of the ink is formed as an ink droplet from the discharge part after the force for discharging the ink from the discharge part is applied to the ink. Since the intensity of the holding electric field is reduced during the first period until the separation, the above-described effect is obtained.
This has the effect that the charge amount of the ink droplet ejected from the ejection unit can be reliably reduced.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the intensity of the holding electric field is also reduced during the second period until the ink droplet separated from the discharge section adheres to the recording medium. In addition to the effect, when the ink droplet ejected from the ejection unit is charged, the effect that the holding electric field adversely affects the behavior of the ink droplet ejected from the recording head can be reliably reduced. Have.

According to a fifth aspect of the present invention, in the first or the second aspect of the present invention, the voltage applied to generate the holding electric field when the ink droplet is ejected from the ejection portion is a predetermined low voltage. Since the intensity of the holding electric field is reduced by switching to or stopping the application of the voltage, the effect of reducing the intensity of the holding electric field can be realized by extremely simple control in addition to the above effects. .

According to a sixth aspect of the present invention, in the first or second aspect, the voltage applied to generate the holding electric field is set to n times (n times the period of the drive timing signal).
Is an integer of 1 or more) and the predetermined high voltage is set only during a period in which the ink droplets are not ejected from the ejection unit.
In addition to the above effects, there is an effect that control by the control means can be simplified.

According to a seventh aspect of the present invention, in the first or the second aspect of the present invention, a period during which ink droplets are ejected from the ejection unit is detected based on an image signal, and at least during the detected period, the holding period is maintained. Since the voltage applied to generate the electric field is switched to a predetermined low voltage or the application of the voltage is stopped, in addition to the above-described effects, the reduction in the holding power of the recording medium due to the reduction in the strength of the holding electric field is minimized. This has the effect that it can be suppressed to a minimum.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an inkjet printer according to a first embodiment.

FIG. 2 is a perspective view showing the vicinity of a discharge unit of the inkjet head.

FIG. 3 is a schematic block diagram of an electric signal system of the ink jet printer.

FIG. 4 is a timing chart of an ejection reference signal and an attraction electric field control voltage in the first embodiment.

FIG. 5 is a schematic configuration diagram of an inkjet printer according to a second embodiment.

FIG. 6A is a cross-sectional view of the belt according to the second embodiment, and FIG. 6B is a plan view showing electrodes seen through.

FIG. 7 is a timing chart of an ejection reference signal and an attraction electric field control voltage in a second embodiment.

FIG. 8 is a schematic block diagram showing another configuration of the electric signal system of the ink jet printer.

9 is a timing chart of an ejection reference signal, an image signal, and an attraction electric field control voltage in the configuration of FIG. 8;

10A shows a flying state of an ink drop when an attracting electric field = 0, and FIG. 10B shows a flying state of an ink drop when an attracting electric field = E when ink droplets are simultaneously ejected from adjacent nozzles. FIG.

11A is a conceptual diagram showing the behavior of a satellite drop when the adsorption electric field = 0, and FIG. 11B is a conceptual diagram showing the behavior of the satellite drop when the adsorption electric field = E.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ink-jet printer 12 Drum 20 Ink-jet head 36 Nozzle 38 Ink ejection opening 42 Ejection reference signal generation circuit 48 Ink-jet head drive circuit 52 Adsorption electric field control circuit 60 Ink-jet printer 64 Belt 72 Comb-like electrode 74 Comb-like electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuji Suemitsu 430 Green Tech Nakai, Nakai-cho, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Co., Ltd. F-term (reference) 2C056 EA04 EC06 EC37 EC38 FA10 HA27

Claims (8)

[Claims] 1. A holding unit for generating a holding electric field for holding a recording medium on a holding surface of a holding member, a printing head having a discharge unit for discharging ink droplets toward the holding surface, A driving unit for ejecting ink droplets from the ejection unit of the recording head for causing the ink droplets to adhere to the recording medium held on the surface, and reducing the strength of the holding electric field when the ink droplets are ejected from the ejection unit. Control means; and a recording device. 2. A printing head comprising: a holding unit for generating a holding electric field for holding a recording material on a holding surface of a holding member; a printing head having a discharge unit for discharging ink droplets toward the holding surface; Driving means for ejecting ink droplets from the ejection portion of the recording head for causing the ink droplets to adhere to the recording material held on the surface; and holding generated by the holding means during a period in which the ink droplets are ejected from the ejection portion. Control means for reducing the intensity of the electric field; 3. The method according to claim 1, wherein the control unit is configured to perform the first period from when a force for discharging the ink from the discharge unit is applied to the ink to when a part of the ink is separated from the discharge unit as an ink droplet. 3. The recording apparatus according to claim 1, wherein the control is performed such that the intensity of the holding electric field is reduced. 4. The control device according to claim 1, wherein the control unit controls the intensity of the holding electric field to decrease even in a second period until the ink droplet separated from the discharge unit adheres to the recording medium. The recording apparatus according to claim 3, wherein 5. The control unit switches the voltage applied by the holding unit to a predetermined low voltage to generate the holding electric field when the ink droplet is ejected from the ejection unit, or The intensity of the holding electric field is reduced by stopping the application of the electric field.
Or the recording device according to claim 2. 6. The driving unit discharges ink droplets from a discharge unit of the recording head at a timing synchronized with a driving timing signal, and the control unit applies the holding electric field to generate the holding electric field. The voltage is set to a predetermined high voltage in a cycle of n times (n is an integer of 1 or more) of a cycle of the drive timing signal and only during a period in which ink droplets are not ejected from the ejection unit. 3. The recording apparatus according to claim 1, wherein: 7. The driving unit discharges ink droplets from a discharge unit of the recording head at a timing according to an image signal for recording an image to be recorded on a recording medium. A period during which ink droplets are ejected is detected based on the image signal, and at least during the detected period, the voltage applied by the holding unit for generating the holding electric field is switched to a predetermined low voltage, 3. The recording apparatus according to claim 1, wherein the application of the voltage is stopped. 8. An ink droplet for generating a holding electric field for holding a recording medium on a holding surface of a carrier and attaching the recording medium to the recording medium while holding the recording medium on the holding surface. A recording method in which the intensity of the holding electric field is reduced when ink droplets are ejected from the ejection unit when ejecting the ink from the ejection unit of the recording head.