JP2006026934A - Inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording device that can stably perform high quality drawing and does not require frequent replacement of an ink and is less costly drawing when continuously performing recording for many hours. <P>SOLUTION: The inkjet recording device has communication piping to connect at least one of one or more ink tanks and at least one capping means and an inkjet head. The communication piping has a communication opening to make air of the capping means and at least one ink tank formed in the capping surface of the inkjet head communicate with the outside air. The capping means is mounted to the inkjet head to cut off communication with outside air by the communication piping, and the capping means is separated from the inkjet head to ensure communication with outside air by the communication piping. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus that performs recording by ejecting ink toward a recording medium, and more specifically to an ink jet recording apparatus that performs recording by circulating ink using hydrostatic pressure.

  An electrostatic drive system, a thermal jet system, an electromechanical transducer (piezo) system, or the like is used for a recording apparatus (inkjet recording apparatus) using an inkjet recording system. As a recording material (ink) used in the ink jet recording apparatus, generally, a recording material in which colored particles are dispersed in a solvent is used. Recording (printing) is performed by using the recording method described above and causing ink to fly onto a recording medium such as recording paper.

In an electrostatic ink jet recording apparatus, normally, ink is circulated between a main ink tank (main tank) that stores ink and an ejection head, and a certain amount of ink is supplied to the ejection head. Drawing is performed by discharging ink onto a recording medium.
As a method of circulating ink between an ink tank and an ejection head, a method of circulating ink using a height difference between the ejection head and the ink tank is known. For example, Patent Document 1 discloses an ink jet recording apparatus that performs ink supply and recovery with a difference in height of ink chamber arrangement positions.

FIG. 11 shows a schematic configuration of an ink circulation device of the ink jet recording apparatus disclosed in Patent Document 1.
The ink circulation device 220 includes an ink recovery container 214, an ink flow rate adjustment chamber 216, pipes 223a to 223d connecting them, a filter 225, electromagnetic valves 226a and 226b, and a pump 224. The ink flow rate adjustment chamber 216 is an ink chamber for adjusting the flow rate of ink supplied to the ink ejection unit 212, and the ink recovery container 216 is an ink chamber for storing the circulating ink. The filter 225 is provided to remove contaminants in the ink, and the electromagnetic valves 226a and 226b are provided to control the flow of ink. In the ink circulation device 220, the ink stored in the ink recovery container 214 is sucked up by the pump 224, passes through the filter 225, and is sent to the ink flow rate adjustment chamber 216. The ink stored in the ink flow rate adjusting chamber 216 naturally flows toward the ink ejecting portion 212 by the pressure based on the position energy determined by the height difference between the ink liquid level in the ink liquid amount adjusting chamber 216 and the ink ejecting portion 212.

The ink that has passed through the ink discharge unit 212 naturally flows toward the ink recovery container 214 due to the height difference between the ink discharge unit 212 and the ink recovery container 214. In this ink circulation device, a stable amount of ink is supplied to the ink ejection unit 212 due to the difference in height between the ink flow rate adjustment chambers 216 provided above and below the ink ejection unit 212 and the ink collection container 214, and the ink collection container 214 is supplied. The ink is collected stably.
When the ink amount in the ink collection container is insufficient, ink is supplied from the replenishment ink tank 222 to the ink collection container 214 through the pipes 229 and 231 by the pump 228.

JP 2001-219580 A

  However, in the ink jet recording apparatus disclosed in Patent Document 1, since the ink circulation path of the ink circulation device 220 is sealed, the ink ejected when ink is ejected continuously from the ink ejection unit 212. The internal pressure of the ink collection container 214 or the ink flow rate adjustment chamber 216 is reduced by the amount. For this reason, a pressure difference is generated between the atmospheric pressure and the internal pressure of the ink recovery container 214 or between the atmospheric pressure and the internal pressure of the ink flow rate adjusting chamber 216, and ink is ejected from the ink ejection unit 212 due to this differential pressure. There is a problem that it becomes difficult to be done.

  Further, when the driving of the pump 224 is stopped and the supply of ink to the ink flow rate adjustment chamber 216 is stopped in a state where such a differential pressure is generated, the internal pressure of the ink recovery container 214 or the ink flow rate adjustment chamber is There is also a possibility that air may enter from the ink discharge portion 212 of the recording head due to the pressure difference from the atmospheric pressure.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and can stably perform high-quality drawing even when recording is performed continuously for a long time, and does not require frequent ink replacement. Another object of the present invention is to provide a low-cost ink jet recording apparatus.

In order to solve the above problems, the present invention provides an inkjet head having an ejection port for ejecting ink on a recording medium based on an image signal, and a capping unit attached to the inkjet head and covering the ejection port. And one or more ink tanks that supply ink to the inkjet head by a static pressure method, and a communication pipe that connects at least one of the one or more ink tanks and at least one of the capping means and the inkjet head. The communication pipe includes a communication port formed on the capping surface of the capping unit and the inkjet head for communicating the air of the at least one ink tank with the outside air, and the capping unit is attached to the inkjet head. To the outside air by the communication pipe Disconnect passing, said capping means is detached from the inkjet head, an inkjet recording apparatus and performs communication to the outside air by the communicating pipe.
Here, at least one ink tank connected to the communication pipe includes a supply ink tank that supplies ink to the inkjet head, and the supply ink tank is disposed at a position higher than the inkjet head, and overflows. Thus, it is preferable to supply ink to the inkjet head while keeping the height of the ink liquid surface constant.
Further, at least one ink tank connected to the communication pipe includes the recovery ink tank that recovers ink from the inkjet head, and the recovery ink tank is disposed at a position lower than the inkjet head, and overflows Therefore, it is preferable to collect ink from the inkjet head while keeping the height of the ink liquid level constant.
The at least one ink tank connected to the communication pipe further includes a storage tank for storing ink to be supplied to the supply ink tank and / or ink recovered from the recovery ink tank, and the storage tank. It is preferable to include at least one of a replenishing tank for replenishing the tank with ink.

Further, it is preferable that the communication port is formed only on the surface of the inkjet head on the capping unit side.
The communication port is preferably formed only on the surface of the capping unit on the ink jet head side.
Further, it is preferable that the capping unit is attached to the inkjet head in a non-contact manner with the discharge port.
Further, it is preferable that the capping unit disconnects the discharge port of the inkjet head from outside air by pressing the cap unit against the inkjet head by an urging unit that does not require power in a non-operating state.
The ink is an ink formed by dispersing charged fine particles including at least a coloring material in an insulating dispersion medium. The ink jet head discharges the ink from the discharge port onto the recording medium. An inkjet head is preferred.

  According to the present invention, the communication pipe communicates with the outside air, so that the inside of the ink tank communicates with the outside air, the pressure in the ink tank becomes constant, and even in the case of a static pressure type ink jet recording apparatus, the ink tank continues for a long time. Thus, stable recording can be performed. Furthermore, the capping means is attached to the ink jet head and cuts off the communication with the outside air of the communication pipe, so that when the capping means is attached, the ink tank is blocked from communicating with the outside air, and the ink is evaporated. It is suppressed, and it is possible to prevent the ink from adhering to the dry state and increasing the density of the ink. Furthermore, since the state in the ink tank can be switched by the capping unit, the apparatus can be simply configured.

  Hereinafter, the ink jet recording apparatus of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 conceptually shows an example of the ink jet recording apparatus of the present invention.
An ink jet recording apparatus (hereinafter referred to as a recording apparatus 10) 10 shown in FIG. 1 is obtained by dispersing charged fine particles containing a color material (hereinafter referred to as color material particles) in an insulating carrier liquid (dispersion medium). This is an electrostatic ink jet recording apparatus that uses ink Q and discharges ink droplets by applying an electrostatic force to the ink. As shown in FIG. 1, the recording apparatus 10 basically includes an ejection head (inkjet head) 12, a capping member 14, a main tank 16, a supply sub tank 18, a collection sub tank 20, a replenishment tank 22, An ink circulation path 24 and a communication pipe 40 are provided.

  The ink circulation path 24 of the recording apparatus 10 mainly includes an ink supply system that supplies the ink Q in the main tank 16 to the ejection head 12 and an ink collection system that collects the ink Q that has not been ejected from the ejection head 12. Is done. The ink supply system includes an ink circulation pump 26, a supply subtank 18, a first supply channel 30 that connects the ink circulation pump 26 and the supply subtank 18, and a second supply channel 32 that connects the supply subtank 18 and the ejection head 12. And a third recovery flow path 38 for recovering the ink Q overflowed from the overflow pipe 18a in the supply sub tank 18. The ink collection system includes a collection subtank 20, a first collection channel 34 that connects the ejection head 12 and the collection subtank 20, and a second collection channel 36 that collects the overflowed ink from the overflow pipe 20a in the collection subtank 20. Consists mainly of. The supply flow path and the recovery flow path can be configured from, for example, a pipe or a flexible tube.

  FIG. 1 mainly shows the characteristic portions of the present invention. However, the recording apparatus 10 of the present invention is not limited to the ink circulation system shown in FIG. A driver that discharges droplets, a scanning conveyance unit that conveys (scans and conveys) the recording medium P in a direction orthogonal to a nozzle row direction (row direction), which will be described later, on a predetermined path facing the ejection head 12, and the ejection head 12. Prior to image recording, charging means for charging a predetermined bias voltage to the recording medium P (or an opposite electrode to the control electrode of the ejection head 12), discharging means for discharging the charged recording medium P, and the recording medium P by a predetermined path. Each of the known electrostatic ink jet recording apparatuses includes a transporting means for transporting, a sensor for detecting the transported recording medium P, a solvent discharging means for discharging the carrier liquid staying in the apparatus, and the like. It is What has components, is of course.

In addition, the inkjet recording apparatus of the present invention may be a monochrome recording apparatus that records an image of one color such as K (black) alone, and Y (yellow), M (magenta), C (cyan). And a recording apparatus that draws a full-color image on a recording medium using four colors of inks K and K.
The ejection head is not limited to an electrostatic inkjet head, and various inkjet heads such as a thermal inkjet head, an inkjet head that ejects ink by vibrating a diaphragm of an ink chamber by a piezo element, a micromachine, or the like can be used. It can be suitably used.

As shown in FIG. 1, in the ejection head 12 of the present embodiment, a communication port 41 is formed on a surface where a discharge port is formed (a surface on the side of a capping member described later). The communication port 41 is connected to a communication pipe 40, and the communication pipe 40 communicates with air portions of the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishment tank 22. By this communication pipe 40, the inside of the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishing tank 22 is vented to the outside air, so that the atmosphere is the same as the outside air. The communication pipe 40 passes through the inside of the discharge head 12 and is connected to the communication port 41.
Here, it is preferable that the communication port 41 is provided above the portion in which the discharge port is formed in the gravity direction. As a result, the communication port 41 is prevented from being blocked by ink overflowing from the ejection port. It is also preferable that the communication port 41 has a shape protruding from the surface on which the discharge port is formed, and it is also preferable to perform an ink repellent treatment around the communication port 41. With this configuration, it is possible to more reliably prevent the communication port 41 from being blocked by the ink overflowing from the ejection port.

The capping member 14 is attached to the discharge port side of the discharge head 12 when the ink circulation is stopped or when drawing is not performed for a long time, so that all the discharge ports of the discharge head 12 are disconnected from the outside air. In this way, dry fixation due to evaporation of the ink Q remaining in the ejection port is prevented. As shown in FIG. 1, a communication port 42 is formed on the surface of the capping member 14 on the discharge head 12 side. The communication port 42 is connected to the communication pipe 40. The communication pipe 40 will be described in detail later.
Such a capping member 14 is not limited to an electrostatic ink jet recording apparatus, and various kinds of capping members that are normally used in various ink jet recording apparatuses can be used.
The configuration of the capping member 14 will also be described in detail later.

  Further, the recording apparatus 10 shown in the figure has an ink circulation system composed of a main tank 16, a supply sub tank 18, a recovery sub tank 20, and respective flow paths connecting them. This is a static pressure ink jet recording apparatus that supplies ink to the ejection head 12 by circulating Q.

The main tank 16 is a sealed ink tank for mainly storing ink that circulates in the ink circulation system of the recording apparatus 10. The main tank 16 preferably has a stirring means for preventing the sedimentation / deposition of the color material particles and a temperature adjusting means for improving the stability of ink ejection. Further, an opening 16 a is formed on the upper surface of the main tank 16, and the opening 16 a is connected to the communication pipe 40.
An ink circulation pump 26 for sending the ink Q from the main tank 16 to the supply sub tank 18 is disposed on the first supply flow path 30. The amount of liquid fed by the ink circulation pump 26 is set to be larger than the amount of ink Q supplied from the supply sub tank 18 to the ejection head 12.

The supply sub tank 18 is a sealed ink tank to which the first supply flow path 30 and the second supply flow path 32 are connected, and is disposed above the discharge head 12 in the vertical direction. The other end of the second supply flow path 32 connected to the supply sub tank 18 is connected to the ejection head 12. Further, as shown in FIG. 1, an opening 18b is formed above the side surface of the supply sub tank 18, and the opening 18b is connected to a communication pipe 40 to be described later. The communication pipe 40 will be described in detail later.
The supply sub-tank 18 stores the ink Q supplied from the main tank 16 through the first supply flow path 30, and the stored ink Q is supplied to the ejection head 12 through the second supply flow path 32.

  In addition, an overflow pipe 18a connected to the third recovery flow path 38 is disposed in the supply sub tank 18, and the second supply flow path 32 is connected below the upper end of the overflow pipe 18a. In the illustrated example, a connection portion with the second supply channel 32 is provided on the bottom surface of the supply sub tank 18.

The ink stored in the supply sub tank 18 is supplied from the second supply flow path 32 to the discharge head 12 by gravity drop at a pressure corresponding to the height difference (drop) between the supply sub tank 18 and the discharge head 12 (or the recovery sub tank 20). Is done.
Further, in the supply sub-tank 18, even if the ink supplied by the ink circulation pump 26 exceeds the height of the overflow pipe 18a, it overflows and is discharged from the overflow pipe 18a, so the liquid level in the tank is constant. To be kept. As a result, the supply amount and supply pressure (pressure head) of the ink Q from the supply sub tank 18 to the ejection head 12 are kept constant, and ink supply is performed in a so-called static pressure system.
The ink Q discharged from the overflow pipe 18a is returned to the main tank 16 from the third recovery flow path 38, and is again used for circulation.

The collection sub tank 20 is a sealed ink tank connected to the first collection flow path 34 and the second collection flow path 36 and is disposed below the ejection head 12 in the vertical direction. As described above, the other end of the first recovery flow path 34 is connected to the ejection head 12 and the other end of the second recovery flow path 36 is connected to the main tank 16. Further, as shown in the drawing, an opening 20b is formed on the upper surface of the collection sub tank 20, and the opening 20b is connected to a communication pipe 40 described later. The communication pipe 40 will be described in detail later.
The recovery sub tank 20 stores the ink Q that has not been discharged from the discharge head 12 through the first recovery flow path 34. The ink Q stored in the recovery sub tank 20 is returned from the second recovery flow path 36 to the main tank 16.

The ink Q discharged from the ink discharge port 12b of the discharge head 12 without being discharged from the discharge head 12 has a pressure corresponding to the height difference (drop) between the discharge head 12 (or the supply sub tank 18) and the recovery sub tank 20. It is supplied to the recovery sub tank 20 from the first recovery flow path 34 by gravity drop. In the recovery sub-tank 20, the ink Q that has exceeded the overflow pipe 20a is returned to the main tank 16 through the second recovery flow path 36 and is circulated again.
Further, the ink liquid level in the collection sub tank 20 is kept constant by the overflow pipe 20a. As a result, a certain amount of pressure (pressure head) corresponding to the liquid level of the recovery sub-tank 20 is also applied to the inflow of ink from the ejection head 12. That is, a constant static pressure can be applied to the ejection head 12.

  In the recording apparatus 10, ink is supplied from the supply subtank 18 to the discharge head 12 by a constant pressure head of ink stored in the supply subtank 18 as described above, and ink is supplied from the discharge head 12 to the recovery subtank 20. Also apply a certain pressure. As a result, the pressure relating to the ink flow path formed inside the ejection head 12, that is, the ink supply and ejection to the ejection head 12, can be made completely static and formed at the ejection port of the ejection head 12, which will be described later. The meniscus or the like of the ink Q to be used can be stabilized.

The ink replenishment tank 22 is a sealed tank that replenishes the consumed ink Q to the main tank 16, and is connected to the main tank 16 by an ink flow path 39. As shown in the figure, an opening 22a is formed on the upper surface of the ink replenishing tank 22, and the opening 22a is connected to a communication pipe 40 described later. The communication pipe 40 will be described in detail later.
The ink replenishment tank 22 replenishes the main tank 16 with ink so that the ink Q in the main tank 16 has a predetermined concentration and a predetermined amount. The configuration of the ink replenishing tank 22 is not particularly limited. For example, the ink replenishing tank 22 has a concent tank that stores conch ink (high-concentration ink) and a dilution liquid tank that stores ink dilution liquid, and has a predetermined concentration and a predetermined amount. The ink tank may be replenished with a determined amount of concentrated ink and diluent. As the diluent, for example, a carrier liquid of ink Q described later may be used.

In the recording apparatus 10, the replenishment timing of the ink Q is not particularly limited. For example, it may be performed automatically every time a predetermined number of images are drawn, or may be automatically performed by detecting the amount of ink Q in the ink tank 16, and input based on the judgment of an operator who observes the drawn image. It may be performed in response to an instruction, or may be performed selectively with a plurality of timing determination means.
Also, there is no particular limitation on the method for determining the replenishment amount of the concentrate and the diluent. For example, in addition to the expected ink evaporation amount, the total number of ink ejections found from the image data, the density measurement result of the circulating ink, the ink amount in the main tank 16 and the like are used to predict the ink Q consumption. The ink replenishment amount may be determined so that the ink Q in the main tank 16 has a predetermined concentration and a predetermined amount.

In the recording apparatus 10 of the present invention, the height of the meniscus of the ink Q formed at the discharge port of the discharge head can be set high by setting the height of the supply sub tank 18 and / or the recovery sub tank 20 as appropriate. It is also possible to select in degrees. Therefore, it is preferable to have a height adjusting means for adjusting the height of the supply sub tank 18 and / or the recovery sub tank 20 in order to control the state and height of the meniscus.
As the height adjusting means, various methods capable of adjusting the height in the vertical direction, such as a method using a screw shaft and a nut that are screwed together, a method using a cylinder or an actuator, and a method using a cam can be used.

Here, the communication pipe 40 will be described. As described above, the communication pipe 40 communicates with the opening 16a of the main tank 16, the opening 18b of the supply sub tank 18, the opening 20b of the recovery sub tank 20, and the opening 22a of the ink replenishing tank 22. The communication pipe 40 allows the air portions of the tanks to vent each other, so that the air portions of the main tank 16, the supply sub-tank 18, the recovery sub-tank 20, and the ink replenishment tank 22 are in the same atmosphere.
Furthermore, the communication pipe 40 is also connected to a communication port 41 formed in the ejection head 12 and a communication port 42 formed in the capping member 14. Here, since the discharge head 12 and the capping member 14 are disposed in an outside air environment, the communication pipe 40 is communicated with the outside air through the communication ports 41 and 42. As a result, the inside of the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishment tank 22 has the same pressure as the outside air.
Here, as described above, the capping member 14 is attached to the ejection head 12 during a pause, thereby disconnecting communication with the outside air at the ejection port. When the capping member 14 is attached to the ejection head 12, the communication ports 41 and 42 formed in the capping member 14 and the ejection head 12 are blocked, and communication with the outside air of the communication ports 41 and 42 is cut off. . As a result, the inside of the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishing tank 22 is also disconnected from the outside air.

  As described above, in the ink jet recording apparatus of the present invention, the capping member 14 is provided with the communication heads 41 and 42 serving as ventilation portions for the outside air of the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishment tank 22. It is arranged on the part (capping surface) where communication with the outside air is cut off when it is attached. Thereby, when the capping member 14 is detached from the ejection head 12, that is, during operation, the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishment tank 22 are communicated with the outside air. On the other hand, when the capping member 14 is attached to the ejection head 12, that is, during a pause, communication with the outside air of the main tank 16, the supply subtank 18, the recovery subtank 20, and the ink replenishment tank 22 is cut off.

  When the capping member 14 is detached from the ejection head 12, since the same pressure as the outside air is always applied to the liquid level of each ink tank, it is possible to stably supply ink from the supply sub tank 18 to the ejection head 12. Thus, it is possible to stably eject ink from the ejection head 12. In addition, when the capping member 14 is attached to the ejection head 12, communication with the outside air of each ink tank is interrupted, so that ink evaporation is suppressed, and ink adhesion due to ink evaporation and An increase in ink density can be prevented. Thereby, even when recording is not performed for a long time, maintenance can be made unnecessary or light, and stable ink density management can be performed.

Further, according to the present invention, the communication ports 42 and 41 are provided in the capping member 14 and the ejection head 12, respectively, so that the ink tank communicates with the outside air only by the attaching / detaching operation of the capping member 14 to the ejection head 12. It is possible to switch to a state where communication with is interrupted. As described above, the atmosphere in the tank in which the ink is stored can be controlled with a simple apparatus configuration without installing a special apparatus.
Further, while the capping member 14 is attached to the ejection head 12, the atmosphere of the space formed between the ejection head 12 and the capping member 14 is the same as the ink tank and is filled with ink vapor. Therefore, drying of the discharge port of the discharge head 12 can be further prevented.

In the present embodiment, the communication pipe 40 is connected to the main tank 16, the supply sub tank 18, the recovery sub tank 20, and the ink replenishment tank 22. However, the present invention is not limited to this, and at least one of these ink tanks is used. It is only necessary that the ink tank and the communication pipe 40 be connected. It is preferable that a plurality of ink tanks 16 including the supply sub tank 18 and the communication pipe 40 are connected. By connecting the supply sub tank 16 and the communication pipe, ink is stably supplied to the ejection head, and stable recording can be performed.
Here, in the ink jet recording apparatus of the present invention, the communication pipe and at least one ink tank (air circulation system formed by) are formed in a communication space sealed from the outside air at the time of capping.

  Next, as another embodiment of the recording apparatus according to the present invention, a configuration example in the case where the communication port is formed only in the ejection head will be described. FIG. 2 shows an example of a recording apparatus in which the communication port 45 is formed only in the ejection head 12.

The recording apparatus in the present embodiment has basically the same configuration as the recording apparatus shown in FIG. 1 except for the communication pipe 44 and the communication port 45. Therefore, the same reference numerals are given to the same components in both, and detailed description thereof will be omitted. Hereinafter, the points peculiar to the recording apparatus of the present embodiment will be mainly described.
The communication pipe 44 of the recording apparatus according to the present embodiment includes a communication pipe 44 a that connects the discharge head 12 and the supply sub tank 18, and a communication pipe 44 b that connects the discharge head 12 and the collection sub tank 20.
The communication port 45a and the communication port 45b are formed on the surface of the ejection head 12 on the capping member 14, the communication port 45a is connected to the communication pipe 44a, and the communication port 45b is connected to the communication pipe 45b. The communication pipes 44a and 44b penetrate the ejection head 12 and are connected to the communication ports 41 and 42, respectively.
The supply tank 18 communicates with the outside air through the communication pipe 44a and the communication port 45a, and the recovery sub-tank 20 communicates with the outside air through the communication pipe 44b and the communication port 45b. Here, also in the present embodiment, the communication ports 45a and 45b communicating with the outside air are formed on the surface of the ejection head 12 on the capping member 14 side, so that the communication port is provided by attaching the capping member 14 to the ejection head 12. By closing 45a and 45b, the supply sub-tank 18 and the recovery sub-tank 20 can be brought into a state where communication with the outside air is interrupted.

Thus, in the present invention, a plurality of communication pipes communicating with each ink tank can be provided, and each communication pipe can be individually connected to a communication port communicating with the outside air. Each communication tank connected to each ink tank communicates with the outside air, whereby each ink tank can have the same atmosphere as the outside air.
Further, the communication port is not limited to being provided in both the ejection head and the capping member, and the communication port may be provided only in the ejection head as in this embodiment.

Next, a configuration example further different from the above-described recording apparatus will be described with reference to FIG. In the recording apparatus shown in FIG. 3, the communication port 41 is not formed in the ejection head 12 in FIG. 1, but the communication port 47 is formed only in the cap member 14, and the communication pipe 46 is connected to the communication port 47, the supply sub tank 18, and the recovery sub tank. Except for being connected to 20, the recording apparatus basically has the same configuration as that shown in FIG. Therefore, the same reference numerals are given to the same components in both, and detailed description thereof will be omitted. Hereinafter, the points peculiar to the recording apparatus of the present embodiment will be mainly described.
The communication pipe 46 of this embodiment is in communication with the supply sub tank 18 and the recovery sub tank 20. The communication port 47 is formed on the side facing the side wall surface of the ejection head 12 when the capping member 14 is attached to the ejection head 12, and is connected to the communication pipe 46. As shown in FIG. 3, the communication pipe 46 penetrates the side wall surface of the capping member 14 and is connected to the communication port 47.
Even in such a configuration, when the capping member 14 is detached from the ejection head 12 as described above, the supply sub tank 18 and the recovery sub tank 20 are in communication with the outside air, and the capping member 14 is attached to the ejection head 12. When this is done, the supply sub-tank 18 and the recovery sub-tank 20 can be disconnected from the outside air.

Next, the structure of the capping member 14 will be described in detail with reference to FIGS. 4 and 5. Here, FIG. 4 is a perspective view showing a schematic configuration of the capping member of the ink jet recording apparatus shown in FIG. 1, and FIG. 5 is a trihedral view of the capping member 14 shown in FIG.
As described above, the capping member 14 is used as a discharge port by setting all the discharge ports of the discharge head 12 to be disconnected from the outside air when the circulation of ink is stopped or drawing is not performed for a long time. This prevents dry adhesion due to evaporation of the remaining ink Q.
The capping member 14 has a communication port 42 and a capping rubber member 54 that contacts the ejection head 12, a rubber holding member 52 that supports the capping rubber member 54, and a pressing pressure that adjusts the pressing pressure against the ejection head 12. The adjustment spring 56, the case 50, and a communication tube 58 that connects the communication port 42 and the communication tube 44 are provided.

The capping rubber member 54 is a lid member having a rectangular surface wider than the discharge port disposition surface of the discharge head 12, and the outer peripheral portion of the rectangular surface facing the discharge head 12 is convex toward the discharge head 12 side. It has a structure. When the capping member 12 is mounted on the ejection head 12, only the outer peripheral portion of the capping rubber member 54 is in contact with the ejection port arrangement surface of the ejection head. Thereby, it can contact the discharge port arrangement | positioning surface of the discharge head 12, and can disconnect a communication with a discharge port and external air. As described above, the discharge port is configured to be able to cut off the communication with the outside air without directly contacting the discharge port of the discharge head 12, so that the discharge port has a complicated shape or includes an ink guide. In this case, the ejection head can also be used in the ink jet recording apparatus of the present invention.
The capping rubber member 54 preferably has adhesiveness to the discharge port arrangement surface and ink resistance. For example, the capping rubber member 54 is formed of a flexible rubber or foam member, and specifically has a hardness of 60 degrees or less. Examples thereof include NMR rubber and fluorine rubber.
A communication port 42 is formed on the surface of the capping member 54. In the illustrated example, two communication ports are formed, but the number of communication ports is not particularly limited, and any number may be provided.

  The rubber holding member 52 is provided on the surface of the capping rubber member 54 opposite to the contact surface with the ejection head 12 and holds the capping rubber member 54. The rubber holding member 52 is formed of a material having rigidity and ink resistance. Specifically, the rubber holding member 52 is made of metal such as slurless or aluminum, or is hard such as polyetheretherketone (PEEK), polycarbonate (PC), or hard vinyl chloride. Plastic is exemplified.

  The pressing pressure adjusting spring 56 is disposed between the rubber holding member 52 and the case 50 and adjusts the pressing pressure of the capping rubber member 54 against the discharge head 12. Here, as shown in FIG. 5, it is preferable to provide a plurality of pressing pressure adjusting springs 56 at predetermined intervals so that the pressing pressure to the ejection head 12 is constant.

The case 50 is a case for accommodating and holding the rubber holding member 52 movably in the direction of the arrow in FIG. The rubber holding member 52 housed in the case 50 and holding the capping rubber member 54 is pressed against the discharge port arrangement surface of the discharge head 12 with an appropriate pressure by the pressing pressure adjusting spring 56. In addition, since the rubber holding member 52 is held by the plurality of pressing pressure adjusting springs 56, the case 50 is attached to the discharge head 12 even when the capping rubber member 54 and the discharge port arrangement surface of the discharge head 12 are arranged obliquely. When the capping rubber member 54 is brought into contact with the discharge port arrangement surface of the discharge head 12 by being advanced toward the discharge port arrangement surface, the capping rubber member 54 is inclined and the discharge port arrangement surface of the discharge head 12 Contact in parallel. Thereby, the discharge port arrangement surface of the discharge head 12 is firmly sealed with the capping rubber member 54. The entire case 50 may be configured to be moved toward the discharge head 12 by, for example, a motor mechanism or a pressure mechanism. When performing capping, the case 50 moves so as to contact the discharge port arrangement surface of the discharge head 12. Be made.
Here, the case 50 is preferably formed of a material having rigidity and ink resistance. Specifically, the case 50 is made of a metal such as stainless steel or aluminum, polyether ether ketone (PEEK), polycarbonate (PC), or hard. Rigid plastics such as vinyl chloride are preferred.

  The communication tube 58 passes through the capping rubber member 54, the rubber holding member 52, and the case 50. An end portion of the communication tube 58 on the capping rubber member 54 side forms a communication port 42, and an end portion on the case 50 side is connected to a communication tube 40 (not shown).

  Here, in the present invention, the attachment and detachment of the capping member 14 may be controlled in any manner. For example, the capping member 14 is attached except during recording (operation) by the ejection head 12. Alternatively, the capping member may be attached when recording has not been performed for a predetermined time.

Here, in the present invention, the capping member 14 is a biasing member such as a spring or an elastic member that does not require power, as in the present embodiment, when the cap moving unit is not in operation (power-off state). It is preferable that the discharge port is configured to be disconnected from the outside air by pressing the cap member.
By having the above configuration, even if a power failure occurs while communication with the outside air at the discharge port is interrupted, the discharge port can be maintained in a state where communication with the outside air is interrupted, and ink circulation can be prevented. It is possible to reliably maintain a state in which the communication between the ejection head and the outside air of each ink tank is stopped at the time of stopping.

FIG. 6 shows a conceptual diagram of the ejection head 12. 6A is a partially sectional perspective view, and FIG. 6B is a sectional view.
In the recording apparatus 10, a recording image, that is, a supplied image is supplied while scanning and conveying the recording medium P charged to a negative high voltage (charging a bias voltage) in a direction perpendicular to the arrangement direction (row direction described later) of the ejection units. In accordance with the image data, each ejection unit of the ejection head 12 is modulated and driven to turn ejection on / off, thereby ejecting ink droplets R on demand and recording a target image on the recording medium P. .

  As described above, the ejection head 12 is a line head having a row of ejection openings corresponding to the width of the recording medium P. As conceptually shown in FIG. FIG. 6 shows only a part of the ejection unit in order to clearly show the structure.

The discharge head 12 discharges ink material droplets R by applying an electrostatic force to the ink Q formed by dispersing color material particles (including the color material and charged fine particles as described above) in a carrier liquid. The electrostatic inkjet head includes a head substrate 72, an ejection substrate 74, and an ink guide 76.
In the ejection head 12, the head substrate 72 and the ejection substrate 74 face each other and are spaced apart from each other by a predetermined distance, and an ink flow path 78 for supplying the ink Q to each ejection port 96 is formed therebetween. . The ink Q is circulated through a predetermined path including the ink flow path 78 by the ink circulation system. At the time of recording, the ink Q is circulated through the ink flow path 78 in a predetermined direction at a predetermined speed (for example, an ink flow of 200 mm / s), for example. , In the direction of the arrow in the figure.

The head substrate 72 is a sheet-like insulative substrate common to all ejection units, and a floating conductive plate 80 that is in an electrically floating state is provided on the surface thereof.
The floating conductive plate 80 generates an induced voltage that is induced in accordance with a drive voltage applied to a first control electrode 82 and a second control electrode 84 described later during image recording. In addition, the voltage value of the induced voltage automatically changes according to the number of operating channels. By this induced voltage, the color material particles contained in the ink Q in the ink flow path 78 are energized and migrate to the discharge substrate 74 side, that is, the concentration of the ink Q at the discharge port 96 described later is more preferably performed. Is called.

  The floating conductive plate 80 is not an essential component and is preferably provided as necessary. The floating conductive plate 80 may be disposed on the head substrate 72 side with respect to the ink flow path 78, and may be disposed, for example, inside the head substrate 72. The floating conductive plate 80 is preferably arranged on the upstream side of the ink flow path 78 from the position where the ejection unit is arranged. Further, a predetermined voltage may be applied to the floating conductive plate 80.

On the other hand, the ejection substrate 74 is a sheet-like insulating substrate that is common to all ejection sections, like the head substrate 72, and includes an insulating substrate 86, a first control electrode 82, a second control electrode 84, and a guard. An electrode 88 and insulating layers 90, 92, and 94 are provided. In addition, ink discharge ports 96 are opened through the discharge substrate 74 at positions corresponding to the respective ink guides 76, and the leading end portion 98 of the ink guide protrudes from the surface of the discharge substrate 74 to form the ink guide 76. Is inserted. As described above, the head substrate 72 and the discharge substrate 74 are arranged apart from each other, and the ink flow path 78 is formed therebetween.
In the ejection head 12, the first control electrode 82, the second control electrode 84, the ejection port 96, the ink guide 76, and the like that correspond to each other constitute one ink ejection unit.

The first control electrode 82 and the second control electrode 84 are circular electrodes provided in a ring shape on the surfaces of the upper surface and the lower surface of the insulating substrate 86, respectively, so as to surround the periphery of the corresponding discharge ports 96. Yes (see FIG. 7 and FIG. 8). The surfaces of the insulating substrate 86 and the first control electrode 82 are covered with an insulating layer 92 that protects and planarizes the surface, and similarly, the surfaces of the insulating substrate 86 and the second control electrode 84 are covered with the insulating layer 92. An insulating layer 90 for planarizing the surface is covered. Further, a guard electrode 88 is formed on the insulating layer 92, and an insulating layer 94 for planarizing the surface is formed on the guard electrode 88 and the insulating layer 92.
Note that the first control electrode 82 and the second control electrode 84 are not limited to ring-shaped circular electrodes, and may be substantially circular electrodes, divided circular electrodes, parallel electrodes, for example, as long as the electrodes are disposed so as to face the ink guide 76. Any shape such as a substantially parallel electrode may be used.

As shown in FIGS. 7 and 8, in the ejection head 12, each ejection unit including the ink guide 76, the first control electrode 82 and the second control electrode 84, the ejection port 96, and the like is two-dimensionally arranged in a matrix. Is arranged.
Here, FIG. 7A is a plan view in the case of cutting along a plane parallel to the insulating substrate 86 including the guard electrode 88 in FIG. FIG. 7B is a plan view when the first control electrode 82 in FIG. 6A is cut along a plane parallel to the insulating substrate 86. FIG. 7C is a plan view in the case of cutting along a plane parallel to the insulating substrate 86 including the second control electrode 84 in FIG.

Specifically, as shown in FIGS. 7B and 7C, the ejection head 12 is arranged in a row direction (scanning conveyance direction (FIG. 7)) in a row of ejection units arranged in the row direction (lateral direction in FIG. 7). 7 vertical directions)) and 3 rows (A row, B row, C row). FIG. 7 shows a total of 15 ejection units arranged in a matrix of 5 (1 column, 2 columns, 3 columns, 4 columns, 5 columns) in the row direction.
The ejection head 12 is a line head, and has a row of ejection portions (nozzle row) corresponding to the entire size of the recording medium P in the row direction. Therefore, in the recording apparatus 10, the recording medium P is drawn by electrostatic ink jet while being scanned and conveyed in the column direction orthogonal to the row direction (arrangement direction of the discharge units (discharge ports 96) = nozzle column direction).
The ejection units in each row are arranged at a predetermined interval in the column direction. In addition, each row is arranged so that the ejection units are shifted from each other by 1/3 pitch in the row direction so that their ejection units are located between the ejection units of other rows (between the row directions).

As shown in FIG. 7A, the guard electrode 88 is a sheet-like electrode in which regions corresponding to the discharge port 96 and the control electrode open in a circular shape. That is, the guard electrode 88 is formed between the control electrodes.
Further, as shown in FIG. 7B, the first control electrodes 82 of the discharge units arranged in the same column are connected to each other and arranged in the same row as shown in FIG. 7C. The second control electrodes 84 of the discharge unit are connected to each other.
Further, although not shown, the first control electrode 82 and the second control electrode 84 are each applied with a drive voltage (pulse voltage), and each electrode is modulated to drive ejection of the ink droplet R. It is connected to a pulse power supply for turning off.

At the time of image recording, the first control electrodes 82 arranged in the same column are simultaneously applied (on) with a driving voltage of the same voltage level. Similarly, the drive voltages are applied (on) to the second control electrodes 84 arranged in the same row simultaneously and at the same voltage level.
In addition, one row recorded on the recording medium P is divided into three groups corresponding to the number of rows of the second control electrodes 84 in the column direction, and each row of A row, B row, and C row It is recorded sequentially by dividing.
For example, in the example shown in FIG. 6, the A line, the B line, and the C line of the second control electrode 84 are sequentially turned on at a predetermined timing. Corresponding to this driving, the first control electrode 82 is modulated and driven (on / off) according to image data (recorded image), so that one line on the recording medium P is recorded by three times of time-divided recording. Is drawn. As described above, since the recording medium P is conveyed in the column direction, it is possible to perform drawing with a recording density three times the recording density (discharge portion density) of each row in the row direction (sub-scanning direction). .

  The control electrode is not limited to the two-layer electrode structure of the first control electrode 82 and the second control electrode 84, and may be a single-layer electrode structure or an electrode structure having three or more layers.

As described above, as shown in FIG. 7A, the guard electrode 88 has a ring-shaped portion corresponding to the first control electrode 82 and the second control electrode 84 formed around each discharge port 96. It is a sheet-like electrode common to all the discharge parts. That is, the guard electrode 88 is an electrode disposed between the control electrodes. The surfaces of the insulating layer 92 and the guard electrode 88 are covered with an insulating layer 94 that protects and flattens the surfaces.
A predetermined voltage is applied to the guard electrode 88 and plays a role of suppressing electric field interference generated between the ink guides 76 of the adjacent ejection portions.
The guard electrode 88 is not an essential component. Further, in order to shield the repulsive electric field from the first control electrode 82 or the second control electrode 84 toward the ink flow path 78, the discharge substrate 74 has a shield electrode on the ink flow path 78 side from the second control electrode 84. May be provided.

  The ink guide 76 is a ceramic flat plate having a convex end portion 98 having a predetermined thickness. In the illustrated example, the ink guides 76 of the ejection units in the same row are disposed on the same support 47 disposed on the floating conductive plate 80 on the head substrate 72 at a predetermined interval. The ink guide 76 passes through the ejection port 96 opened in the ejection substrate 74, and the tip end portion 98 is above the outermost surface of the ejection substrate 74 on the recording medium P side (the upper surface in the drawing of the insulating layer 94). It protrudes.

The leading end portion 98 of the ink guide 76 is formed in a substantially triangular shape (or trapezoidal shape) that gradually becomes thinner toward the holding means 17 of the recording medium P.
In addition, it is preferable that the tip portion 98 (the most advanced portion) is deposited with metal. Although metal deposition of the tip portion 98 is not an essential element, this has an effect that the dielectric constant of the tip portion 98 is substantially increased and a strong electric field can be easily generated.

  The shape of the ink guide 76 is not particularly limited as long as the colorant particles in the ink Q can be migrated toward the tip portion 98 (that is, the ink Q is concentrated). For example, the tip portion 98 is convex. You may change freely, such as not having to. Further, in order to promote the concentration of ink, a notch serving as an ink guide groove for collecting the ink Q in the tip end portion 98 by capillary action may be formed in the central portion of the ink guide 76 along the vertical direction in the drawing. .

  As described above, the second control electrodes 84 are sequentially turned on (driven (high voltage level (for example, 400 to 600 V) or high impedance state)) one row at a time at a predetermined timing, and all the remaining second electrodes are driven. The control electrode 84 is turned off (non-driven (ground level (ground state)). Further, the first control electrode 82 is turned on (on a column basis) in accordance with image data (recorded image) in all columns at the same time. By setting the high voltage level or the ground level, ink ejection / non-ejection (ink ejection on / off) in each ejection unit is controlled.

That is, when the second control electrode 84 is on and the first control electrode 82 is on, the ink Q is ejected (ejection on) as the ink droplet R, and the first control electrode 82 and the second control electrode 84 are When at least one is off, ink is not ejected (ejection off).
Then, the ink droplets R ejected from each ejection unit are attracted to the recording medium P charged with a negative bias voltage, and adhere to a predetermined position of the recording medium P to form an image.

  As described above, when the row of the second lower control electrode 84 is sequentially turned on and the upper first control electrode 82 is turned on / off according to the image data, the first control electrode 82 is turned on according to the image data. Therefore, the first control electrode 82 frequently changes to the high voltage level or the ground level at the discharge portions on both sides of each discharge portion in the column direction. In this case, by biasing the guard electrode 88 to a predetermined guard potential, for example, the ground level, at the time of image recording, it is possible to eliminate the influence of the electric field of the adjacent ejection unit.

  In the ejection head 12, whether the on / off control of ink ejection is performed by one or both of the first control electrode 82 and the second control electrode 84 is not limited. That is, ink is ejected when the difference between the voltage value at the time of ink on / off on the control electrode side and the voltage value on the recording medium P side is larger than a predetermined value, and ink is discharged when the difference is smaller than the predetermined value. What is necessary is just to set the voltage of the control electrode side and the recording medium P side suitably so that it may not discharge.

Accordingly, in the ejection head 12, the first control electrode 82 is sequentially turned on for each column and the second control electrode 84 is turned on in accordance with the image data. It is also possible to turn off / off.
In this case, the column direction is turned on for each column of the first control electrodes 82, and the first control electrodes 82 of the discharge units in the columns on both sides thereof are always at the ground level with the respective discharge units in the column direction as the center. The first control electrodes 26 of the ejection portions in the rows on both sides serve as the guard electrode 88. As described above, when each column is sequentially turned on by the upper first control electrode 82 and the lower second control electrode 84 is driven in accordance with the image data, the adjacent ejection can be performed without providing the guard electrode 88. It is possible to improve the recording quality by eliminating the influence of the part.

  In this embodiment, the color material particles in the ink Q are positively charged and the recording medium side is charged to a negative high voltage. However, the present invention is not limited to this, and conversely, the color material particles in the ink are negatively charged. The recording medium P side may be charged to a positive high voltage. As described above, when the polarity of the color material particles is reversed from that of the present embodiment, the applied voltage to the counter electrode, the charging unit of the recording medium P, and the first control electrode 82 and the second control electrode 84 of each discharge unit. What is necessary is just to make polarity etc. reverse to said example.

In the electrostatic ink jet using the ink Q containing the colorant particles as described above, the force is applied to the entire ink to cause the ink to fly toward the recording medium as in the conventional ink jet system. Instead, a force is applied to the colorant particles, which are solid components dispersed in the carrier liquid, to cause the ink to fly. Hereinafter, the operation of discharging the ink droplet R in the discharge head 12 will be described.
In the following example, the color material particles are positively charged. Therefore, when ejection is on, a positive drive voltage is applied to the first control electrode 82 and the second control electrode 84, and the recording medium P has A negative high voltage (bias voltage) is charged.

At the time of recording an image, the ink Q is circulated by the above-described ink circulation system, and flows in the ink flow path 78 from the right side to the left side (in the direction of the arrow in FIG. 6B) at a predetermined speed.
Further, as described above, the recording medium P is charged to a negative high voltage, and is scanned and conveyed facing the ejection head 12.
The negative high voltage charged on the recording medium P acts as a bias voltage in electrostatic ink jet, and the charged recording medium P having this bias voltage acts as a counter electrode for the control electrode of the ejection head 12. This is as described above.

  When the recording medium P is transported to a predetermined position, a drive signal is supplied to the ejection head 12 according to the transport timing of the recording medium P and the image data, and each ejection head 12 responds accordingly to each row. The second control electrodes 84 are sequentially driven, the first control electrodes 82 in each column are modulated and driven according to the image data, and the ink ejection is modulated and turned on / off according to the image data.

Here, when at least one of the first control electrode 82 and the second control electrode 84 is off, that is, in a state where only the bias voltage is applied, the ink Q has the bias voltage and the color material particles (charge) of the ink Q. Particle) and the Coulomb repulsive force between the coloring material particles, the coulomb repulsive force between the coloring material particles, the viscosity of the carrier liquid, the surface tension, the dielectric polarization force, etc., which are coupled to move the coloring material particles and the carrier liquid. As conceptually shown in FIG. 6 (B), a meniscus shape slightly raised from the discharge port 96 is balanced.
In addition, the colorant particles move toward the recording medium P charged with a bias voltage by so-called electrophoresis due to the Coulomb attractive force or the like. That is, the ink Q is concentrated in the meniscus of the discharge port 96.

  From this state, a driving voltage (pulse voltage) for ejecting the ink droplet R is applied. That is, in the illustrated example, when both the first control electrode 82 and the second control electrode 84 are turned on, the drive voltage is superimposed on the bias voltage, and the previous coupling is further performed by the superposition of the drive voltage. The formed movement occurs, the colorant particles and the carrier liquid are pulled by the electrostatic force to the bias voltage (counter electrode) side, that is, the recording medium P side, the meniscus grows, and a so-called conical ink liquid column is so-called from the upper part. A tailor cone is formed. Similarly to the above, the color material particles are moved to the meniscus by electrophoresis, and the ink Q of the meniscus is concentrated and is in a substantially uniform high density state having a large number of color material particles.

When a finite time has passed after the start of the application of the drive voltage, the balance between the color material particles and the surface tension of the carrier liquid mainly breaks at the tip of the meniscus with high electric field strength due to the movement of the color material particles, The meniscus grows abruptly to form an elongated ink liquid column having a diameter of about several to several tens of μm, which is called a kite string.
Further, when a finite time elapses, the silk thread grows, and the growth of the silk thread, vibration caused by Rayleigh / Weber instability, uneven distribution of colorant particles in the meniscus, uneven distribution of electrostatic field on the meniscus, etc. As a result of this interaction, the kite string is divided, ejected / flyed as ink droplets R, and pulled by the bias voltage to land on the recording medium P.
The growth and splitting of the kite string, and further the movement of the color material particles to the meniscus (punch kite) occur continuously during the application of the drive voltage. When the application of the drive voltage is finished (at least one of the first control electrode 82 and the second control electrode 84 is turned off), the state returns to the meniscus state in FIG. 6B where only the bias voltage is applied.
One dot of ink on the recording medium P is usually obtained by applying the drive voltage once (one pulse). Therefore, one dot is separated from the string by applying the drive voltage once. Formed by a plurality of ink droplets R ejected in this manner.

Here, the ink used in the recording apparatus of the present invention will be described.
Ink Q is obtained by dispersing colorant particles in a carrier liquid. The carrier liquid is preferably a dielectric liquid (nonaqueous solvent) having a high electric resistivity (10 ⁹ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more). If the electric resistance of the carrier liquid is low, the carrier liquid itself is charged by charge injection due to the drive voltage applied to the control electrode, and the colorant particles do not concentrate. In addition, a carrier liquid having a low electrical resistance is not suitable because there is a concern of causing electrical conduction between adjacent control electrodes.

The relative dielectric constant of the dielectric liquid used as the carrier liquid is preferably 5 or less, more preferably 4 or less, and still more preferably 3.5 or less. By setting the relative dielectric constant in such a range, an electric field effectively acts on the colorant particles in the carrier liquid, and migration easily occurs.
The upper limit value of the specific electric resistance of such a carrier liquid is preferably about 10 ¹⁶ Ωcm, and the lower limit value of the relative dielectric constant is preferably about 1.9. The reason why it is desirable that the electric resistance of the carrier liquid is in the above range is that if the electric resistance is low, ink ejection under a low electric field is deteriorated, and the reason why the relative dielectric constant is preferably in the above range is the reason. This is because, when the dielectric constant increases, the electric field is relaxed by the polarization of the solvent, and the color of the dots formed thereby becomes thin or causes blurring.

  The dielectric liquid used as the carrier liquid is preferably a linear or branched aliphatic hydrocarbon, alicyclic hydrocarbon, or aromatic hydrocarbon, and halogen-substituted products of these hydrocarbons. For example, hexane, heptane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, Isopar M (isopar: trade name of Exxon), Shellsol 70, Shellsol 71 (shellsol: trade name of Shell Oil), Amsco OMS, Amsco 460 Solvent (trade name of Amsco: Spirits), Silicone oil (for example, KF-96L manufactured by Shin-Etsu Silicone) or the like can be used alone or in combination.

  The colorant particles dispersed in such a carrier liquid may be dispersed in the carrier liquid as the colorant itself as colorant particles, but preferably contain dispersed resin particles for improving fixability. When the dispersed resin particles are included, the pigment is generally coated with the resin material of the dispersed resin particles to form resin-coated particles, and the dye is colored with the dispersed resin particles to form colored particles. Is common.

As the coloring material, any of conventional pigments and dyes used in a flow channel kujet ink composition, a printing (oil-based) ink composition, or an electrophotographic liquid developer can be used.
As the pigment used as the color material, regardless of inorganic pigments or organic pigments, those generally used in the technical field of printing can be used. Specifically, for example, carbon black, cadmium red, molybdenum red, chrome yellow, cadmium yellow, titanium yellow, chromium oxide, viridian, cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment Conventionally known pigments such as quinacridone pigments, isoindolinone pigments, dioxazine pigments, selenium pigments, perylene pigments, perinone pigments, thioindigo pigments, quinophthalone pigments and metal complex pigments are used without particular limitation. be able to.
As dyes used as coloring materials, azo dyes, metal complex dyes, naphthol dyes, anthraquinone dyes, indigo dyes, carbonium dyes, quinoneimine dyes, xanthene dyes, aniline dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes And oil-soluble dyes such as phthalocyanine dyes and metal phthalocyanine dyes.

Further, as dispersed resin particles, for example, rosins, rosin-modified phenol resins, alkyd resins, (meth) acrylic polymers, polyurethane, polyester, polyamide, polyethylene, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl alcohol, acetal-modified Products, polycarbonate and the like.
Among these, from the viewpoint of ease of particle formation, the weight average molecular weight is in the range of 2,000 to 1,000,000 and the polydispersity (weight average molecular weight / number average molecular weight) is 1.0 to 5 Polymers in the range of 0.0 are preferred. Furthermore, from the viewpoint of ease of fixing, a polymer having any one of a softening point, a glass transition point, and a melting point within a range of 40 ° C. to 120 ° C. is preferable.

  In the ink Q, the content of the color material particles (the total content of the color material particles or further dispersed resin particles) is preferably contained in the range of 0.5 to 30% by weight with respect to the whole ink, and more preferably. Is preferably contained in the range of 1.5 to 25% by weight, more preferably 3 to 20% by weight. If the content of the colorant particles is reduced, problems such as insufficient printed image density or difficulty in obtaining a strong image due to difficulty in obtaining the affinity between the ink Q and the surface of the recording medium P are likely to occur. On the other hand, when the content is increased, it becomes difficult to obtain a uniform dispersion liquid, or the ink Q is easily clogged with an inkjet head or the like, and it is difficult to obtain stable ink discharge. is there.

  The average particle diameter of the colorant particles dispersed in the carrier liquid is preferably 0.1 to 5 μm, more preferably 0.2 to 1.5 μm, and still more preferably 0.4 to 1.0 μm. . This particle size is determined by CAPA-500 (trade name, manufactured by Horiba, Ltd.).

After the colorant particles are dispersed in the carrier liquid (a dispersant may be used if necessary), the chargeant is added to the carrier liquid to charge the colorant particles, and the charged colorant The ink Q is obtained by dispersing particles in a carrier liquid. When dispersing the colorant particles, a dispersion medium may be added as necessary.
As an example of the charge control agent, various materials used in electrophotographic liquid developers can be used. Also, “Recent development and commercialization of electrophotographic development systems and toner materials”, pages 139 to 148, “The Basics and Applications of Electrophotographic Technology” edited by Electrophotographic Society, pages 497 to 505 (Corona Inc., published in 1988), Yuji Harasaki Various charge control agents described in “Electrophotography” 16 (No. 2), p. 44 (1977) can also be used.

The color material particles may be positively charged or negatively charged as long as they have the same polarity as the drive voltage applied to the control electrode.
The charge amount of the color material particles is preferably in the range of 5 to 200 μC / g, more preferably 10 to 150 μC / g, and still more preferably 15 to 100 μC / g.

In addition, since the electric resistance of the dielectric solvent may change due to the addition of the charge control agent, the distribution ratio P defined below is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. And
P = 100 × (σ1−σ2) / σ1
Here, σ1 is the electrical conductivity of the ink Q, and σ2 is the electrical conductivity of the supernatant obtained by applying the ink Q to the centrifuge. The electrical conductivity was measured using an LCR meter (AG-4311 manufactured by Ando Electric Co., Ltd.) and an electrode for liquid (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) under the conditions of an applied voltage of 5 V and a frequency of 1 kHz. This is the measured value. Centrifugation was performed for 30 minutes using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) under conditions of a rotational speed of 14500 rpm and a temperature of 23 ° C.
By using the ink Q as described above, migration of charged particles is likely to occur, and concentration is facilitated.

The electrical conductivity of the ink Q is preferably 100 to 3000 pS / cm, more preferably 150 to 2500 pS / cm, and still more preferably 200 to 2000 pS / cm. By setting the electric conductivity in the above range, the voltage applied to the control electrode does not become extremely high, and there is no fear of causing electrical continuity between adjacent recording electrodes.
The surface tension of the ink Q is preferably in the range of 15 to 50 mN / m, more preferably 15.5 to 45 mN / m, and still more preferably 16 to 40 mN / m. By setting the surface tension within this range, the voltage applied to the control electrode does not become extremely high, and the ink does not leak around the head to be contaminated.
Furthermore, the viscosity of the ink Q is preferably 0.5 to 5 mPa · sec, more preferably 0.6 to 3.0 mPa · sec, and still more preferably 0.7 to 2.0 mPa · sec.

As an example, such an ink Q can be prepared by dispersing color material particles in a carrier liquid to form particles, and adding a charge adjusting agent to the dispersion medium to cause the color material particles to be charged. Specific methods include the following methods.
(1) A method in which a color material or further dispersed resin particles are mixed (kneaded) in advance, and then dispersed in a carrier liquid using a dispersant as required, and a charge adjusting agent is added.
(2) A method in which a coloring material, or further dispersed resin particles and a dispersing agent are simultaneously added to a carrier liquid, dispersed, and a charge adjusting agent is added.
(3) A method in which a coloring material and a charge adjusting agent, or further dispersed resin particles and a dispersing agent are simultaneously added to a carrier liquid and dispersed.

Next, a specific example of the ink jet recording apparatus of the present invention will be described with reference to FIGS.
FIG. 9 is a schematic configuration diagram of an embodiment of the ink jet recording apparatus of the present invention. An ink jet recording apparatus 10 shown in FIG. 1 controls discharge of ink containing charged fine particles by electrostatic force, and performs monochrome printing on a recording medium (recording paper) P to record a monochrome image. P holding means 112, conveying means 114, recording means 116, ink circulation means 118, solvent recovery means 120, and housing 122 are provided. Hereinafter, the holding unit 112, the transport unit 114, the recording unit 116, the ink circulation unit 118, and the solvent recovery unit 120 will be described in order.

First, the holding means 112 for the recording medium P will be described with reference to FIG.
The holding means 112 for the recording medium P includes a paper feed tray 124 that holds the recording medium P before recording, a feed roller 126, and a discharge tray 128 that holds the recording medium P after recording.

  The front end of the paper feed tray 124 is inserted into the mounting portion of the paper feed tray 124 (the lower left portion of the housing 122 in the figure), and is detachable at a predetermined position of the mounting portion. In a state where the paper feed tray 124 is completely attached to the attachment portion, the leading end in the insertion direction contacts the back end portion of the attachment portion, and the rear end portion of the paper feed tray 124 protrudes outside the housing 122. Mounted in a state. Further, the feed roller 126 is disposed in the vicinity of the back of the mounting portion of the paper feed tray 124.

  In the paper feed tray 124, a plurality of recording media P before recording are stacked and stocked. At the time of recording an image, the recording medium P is taken out from the paper feed tray 124 one by one by the feed roller 126 and supplied to the conveying means 114 for the recording medium P.

  The discharge tray 128 is provided in the vicinity of the discharge portion of the recording medium P (the central portion on the left surface of the housing 122 in the drawing). The front end portion side (the conveyance direction side of the recording medium P) of the discharge tray 128 is located outside the housing 122, and the rear end portion side is located inside the housing 122. Further, the discharge tray 128 is disposed at a predetermined inclination angle such that the front end portion is lower than the rear end portion.

  The recording medium P after recording is transported by the transport means 114, then discharged from the discharge unit, and stacked and stocked sequentially in the discharge tray 128.

Next, the conveying unit 114 for the recording medium P will be described.
The transport unit 114 electrostatically attracts the recording medium P and transports the recording medium P along a predetermined path from the paper feed tray 124 to the discharge tray 128. The transport roller pair 130, the transport belt 132, the belt roller 134a, 134b and 134c, a conductive platen 136, a charging device 138 and a charge eliminating device 140 for the recording medium P, a separation claw 142, a guide 144, and a fixing roller pair 146.

  The conveyance roller pair 130 is provided at a position between the feed roller 126 and the conveyance belt 132 on the conveyance path of the recording medium P.

  The recording medium P taken out from the paper feed tray 124 by the feed roller 126 is nipped and conveyed by the conveying roller pair 130 and is supplied to a predetermined position on the conveying belt 132.

  The charging device 138 for the recording medium P includes a scorotron charger 138a and a negative high-voltage power supply 38b. The scorotron charger 138 a is located on the conveyance path of the recording medium P between the conveyance roller pair 130 and the recording unit 116, and the surface of the conveyance belt 132 where the recording medium P is supplied by the conveyance roller pair 130. It is arrange | positioned in the position facing. The negative terminal of the negative high-voltage power supply 138b is connected to the scorotron charger 138a, and the positive terminal is grounded.

  The surface of the recording medium P is uniformly charged to a predetermined negative high potential by a scorotron charger 138a connected to a negative high voltage power source 138b, and a constant DC bias voltage (for example, about -1.5 kV) is always applied. It will be in the state. As a result, the recording medium P is electrostatically adsorbed on the insulating surface of the transport belt 132.

  The conveyor belt 132 is a ring-shaped endless belt, and is stretched in a triangular shape by three belt rollers 134a, 134b, and 134c. Further, a flat plate-like conductive platen 136 is disposed inside the conveyance belt 132 at a position facing the recording unit 116.

  In the conveyance belt 132, the surface (front surface) on the side where the recording medium P is electrostatically attracted exhibits insulation, and the surface (back surface) on the side in contact with the belt rollers 134a, 134b, and 134c exhibits conductivity. The belt roller 134b is grounded. Therefore, the belt rollers 134a and 134c and the conductive platen 136 are also grounded via the back surface of the conveying belt 132. Thereby, the conveyance belt 132 at a position facing the recording unit 116 functions as a counter electrode of the inkjet head.

  At least one of the belt rollers 134a, 134b, and 134c is connected to a drive source (not shown), and is driven to rotate at a predetermined speed during recording. Due to the rotation of the belt rollers 134a, 134b, and 134c, the conveyor belt 132 moves in the direction of the arrow in the drawing during recording. Accordingly, the recording medium P is moved along with the movement of the conveying belt 132 and is conveyed in front of the recording unit 116.

  The static elimination device 140 for the recording medium P includes a corotron static eliminator 140a and a high voltage power source 140b. The corotron static eliminator 140a is located on the conveyance path of the recording medium P between the recording means 116 and the separation claw 142 and is opposed to the surface of the conveying belt 132 where the recording medium P after recording is conveyed. Is arranged. One end of the high-voltage power supply 140b is connected to the corotron static eliminator 140a, and the other end is grounded.

  The recording medium P after recording is discharged by the corotron charger 140a connected to the high voltage power supply 140b. Thereby, the recording medium P is easily separated from the transport belt 132.

  Further, the separation claw 142, the guide 144, and the fixing roller pair 146 are arranged in this order on the downstream side of the static eliminator 140 on the conveyance path of the recording medium P.

  The recording medium P that has been neutralized by the neutralization device 140 is separated from the conveying belt 132 by the separation claw 142 and is supplied to the fixing roller pair 146 along the guide 144. The fixing roller pair 146 is a roller pair including a heat roller. The recording medium P is nipped and conveyed by the fixing roller pair 146, and the image recorded thereon is contact-heated and fixed. The recording medium P after fixing is discharged from the discharge unit, and is sequentially stacked in the discharge tray 128 and stocked.

Next, the recording unit 116 of the recording medium P of the inkjet recording apparatus 100 shown in FIG. 9 will be described.
The recording means 116 performs monochrome printing on the recording medium P by electrostatic force to record a monochrome image, and includes a head unit 148, a head driver 150, and a position detection device 152 for the recording medium P. Yes.
The head unit 148 includes the discharge head 12 shown in FIGS. 6 to 8, the supply sub-tank and the recovery sub-tank shown in FIG. 10, the sub-tank position adjusting mechanism for adjusting the height of these tanks, and the like. In the present embodiment, the head unit 148 can eject ink while main-scanning the ejection head 12 in a direction orthogonal to the conveyance direction of the recording medium P. Recording is performed on the recording medium P by performing a serial scan in which the recording medium P is transported by a predetermined amount by the transport unit 114 described above. The structure of such a head unit 148 will be described in detail later.

  The position detection device 152 of the recording medium P is position detection means such as a photosensor, and as shown in FIG. 9, at a position between the charging device 138 and the head unit 148 on the conveyance path of the recording medium P. The recording medium P is disposed at a position facing the surface of the conveying belt 132 on which the recording medium P is conveyed. The position of the recording medium P is detected by the position detection device 152, and the position information is supplied to the head driver 158.

  The head driver 150 is attached to the right side of the housing 122 in the drawing and is connected to the ejection head 12 of the head unit 148. Image data is input to the head driver 150 from an external device, and position information of the recording medium P is input from the position detection device 152. Under the control of the head driver 150, the ejection timing of the ejection head provided in the head unit 148 is controlled according to the position information of the recording medium P, and the ink is ejected from the ejection head according to the image data. The image corresponding to the image data is recorded.

Here, the head unit 148 will be described with reference to FIG. FIG. 10 is an enlarged perspective view showing the configuration of the head unit 148, and the arrow X direction in the drawing is the conveyance direction of the conveyance belt 132.
The head unit 148 includes a discharge head 12, a supply sub tank 18, a recovery sub tank 20, a sub tank position adjustment mechanism (supply sub tank side 176, recovery sub tank side 178), driving means 182, guide rail 184 a, guide rail 184 b, and support member 186. ing.

  The ejection head 12 is arranged in the head unit 148 so that the ejection portion thereof is substantially parallel to the conveyance direction of the recording medium P. Further, the ejection unit of the ejection head 12 is a recording medium that is electrostatically adsorbed and conveyed on the conveyance belt 132 at a position facing the surface of the conveyance belt 32 where the conductive platen 136 shown in FIG. 9 is disposed. It arrange | positions so that it may become a predetermined fixed space | interval with the surface of P.

The guide rail 184a and the guide rail 184b are arranged in parallel at a predetermined interval in a direction orthogonal to the conveyance direction (arrow X direction) of the conveyance belt 132.
The driving means 182 is a ball screw or the like driven by a motor (not shown), and is disposed between the guide rail 184a and the guide rail 184b.

The support member 186 is supported by the guide rail 184a, the guide rail 184b, and the driving unit 182 and is moved by the driving unit 182 along the guide rails 184a and 184b in a direction perpendicular to the conveying direction of the conveying belt (arrow X direction). . Further, the support member 186 has a plate shape, on which the ejection head 12, the supply sub tank 18, the recovery sub tank 20, and the sub tank position adjustment mechanism (supply sub tank side 176, recovery sub tank side 178) are arranged. .
Sub-tank position adjusting mechanisms (supply sub-tank side 176 and recovery sub-tank side 178) disposed on the support member support the supply sub-tank 18 and the recovery sub-tank 20, respectively. The sub tank position adjusting mechanism (supply sub tank side 176 and recovery sub tank side 178) includes motors 176a and 178a, respectively. By driving these motors, the supply sub tank 18 and the recovery sub tank 20 are moved vertically (arrow X). Direction).

  Here, as the sub tank position adjusting mechanisms 176 and 178, a system in which the ball screws 176b and 178b are driven by the motors 176a and 178a can be used, but the present invention is not limited to this, and various types of position adjusting mechanisms by other systems can be used. Available. Since the positions of the supply sub tank 18 and the collection sub tank 20 are not frequently changed basically, the position adjustment mechanism may be configured to be manually adjusted.

Next, the ink circulation means 118 of the inkjet recording apparatus 100 shown in FIG. 9 will be described with reference to FIGS.
The ink circulation means 118 includes a main tank 16, an ink replenishment tank 22, a supply subtank 18, a recovery subtank 20, a pump (not shown), a first supply channel 30, and an ink recovery channel 160. The supply sub tank 18 and the recovery sub tank 20 are provided in the head unit 148 as described above. The main tank 16 is connected to the supply sub tank 18 and the recovery sub tank 20 provided in the head unit 148 via the first supply flow path 30 and the ink recovery flow path 160.

In the main tank 64, ink containing charged fine particles (coloring material particles) and a dispersion solvent for dispersing them is held. The ink in the main tank 64 is supplied to the supply sub tank 18 through the first supply flow path 30 by a pump (not shown).
Further, ink that has not been used by the ejection head 12 (ink containing colorant particles that has not been ejected by the ejection head 12) is collected in the main tank 16 via the ink collection channel 160. In this way, the ink circulates between the ejection head 12 and the main tank 16.

  The ink replenishment tank 22 is provided for replenishing the main tank 16 with ink. The ink replenishing tank 22 is preferably a replaceable cartridge type.

  As the ink is discharged from the discharge head 12, the density of the ink circulating in the ink circulating means 118 decreases, so the ink circulating means 118 detects and detects the ink density with an ink density detector (not shown). It is preferable to appropriately replenish ink from the ink replenishment tank 22 to the main tank 16 in accordance with the ink concentration so as to keep the ink concentration within a predetermined range.

  Further, the main tank 16 is preferably provided with a stirring device for suppressing precipitation / concentration of the solid component of the ink and an ink temperature adjusting unit for suppressing temperature change of the ink. The reason for this is that if the temperature is not controlled, the ink temperature changes due to changes in the environmental temperature, etc., the ink physical properties change, the ink droplet dot diameter changes, and high-quality images can be stably formed. This is because it may disappear. On the other hand, a rotating blade, an ultrasonic vibrator, a circulation pump, or the like can be used as the stirring device.

  The ink temperature adjustment unit includes a heating element such as a heater, a heating means and / or a heating / absorption element such as a Peltier element, and / or a cooling means such as a cooler, and a controller and temperature thereof. A temperature control element and temperature control means are controlled by a controller in accordance with the ink density detected by the temperature sensor, and the temperature control element and temperature control means are integrated with the temperature sensor and the controller, for example, A known temperature control unit such as one controlled by a thermostat can be used. Further, the arrangement position of the temperature adjustment unit is not limited to the main tank 16 as long as the temperature of the ink discharged as ink droplets can be controlled, and may be anywhere, for example, in the head unit 148, the ink piping system, or the like. You may arrange.

Next, the operation of the ink circulating means 118 will be described in detail with reference to FIG.
As shown in FIG. 10, the ejection head 12, the supply sub-tank 18, and the recovery sub-tank 20 are disposed on the plate-like support member 186 of the head unit 148. The supply sub tank 18 and the recovery sub tank 20 can be moved vertically up and down on the support member 186 by the supply sub tank position adjustment mechanism 176 and the recovery sub tank position adjustment mechanism 178. Thereby, the fluid pressure of the ink supplied to the ejection head 12 can be adjusted.

  The supply sub tank 18 is connected to the main tank 16 shown in FIG. 9 via the first supply flow path 30, and is connected to the discharge head 12 via the discharge head 12 and the second supply flow path 32. The recovery sub tank 20 is connected to the ejection head 12 via the first recovery flow path 34. The third recovery flow path 38 indicates the drain piping from the supply sub tank 18 to the main tank 16, and the second recovery flow path 36 indicates the drain piping from the recovery sub tank 20 to the main tank 16. The third recovery channel 38 and the second recovery channel 36 are connected to the ink recovery channel 160 shown in FIG.

  The supply sub-tank 18 supplies the ink supplied from the main tank 16 via the first supply channel 30 to the ejection head 12 via the second supply channel 32. Here, the ink excessively supplied to the supply sub tank 18 is recovered from the overflow pipe arranged in the supply sub tank 18 to the ink tank 54 shown in FIG. As a result, the ink amount in the supply sub tank 72 is kept constant.

A communication pipe 44 a is connected to the supply sub tank 18. The communication pipe 44a communicates with a communication port 45a formed in the discharge head 12, and the supply sub tank 18 communicates with the outside air through the communication port 45a. In addition, a communication pipe 44 b is connected to the collection sub tank 20. The communication pipe 44b communicates with a communication port 45b formed in the ejection head 12, and the supply sub tank 18 communicates with the outside air through the communication port 45b. As a result, the atmosphere in the supply sub-tank 18 and the recovery sub-tank 20 becomes the same atmosphere as the outside air, the pressure applied to the liquid level is constant, and the pressure supplied to the ejection head is stabilized.
Further, although not shown, in the recording apparatus 100 of the present embodiment, a capping member is disposed at a predetermined position facing the ejection head, similarly to the recording apparatus shown in FIG. By attaching this capping member to the ejection head, the communication ports 45a and 45b are disconnected from the outside air, and the supply sub tank 18 and the recovery sub tank 20 are disconnected from the outside air, and the ink is evaporated. It is the same as that of the said embodiment that is suppressed.

  A part of the ink supplied from the discharge head 12 is discharged from the discharge port, and the ink not used by the discharge head 12 is supplied to the recovery sub tank 20 through the first recovery flow path 34. The ink supplied from the ejection head 12 to the collection sub tank 20 is collected in the ink tank 14 shown in FIG. 9 via the second collection channel 36 and the ink collection channel 160. The ink collected in the ink tank 16 shown in FIG. 9 is circulated and supplied again to the ejection head 12 from the second supply channel 32.

Next, the solvent recovery means 120 of the inkjet recording apparatus will be described with reference to FIG.
The solvent recovery means 120 recovers the dispersion solvent that evaporates from the ink ejected from the ejection head 12 onto the recording medium P, the dispersion solvent that evaporates from the ink when the image is fixed, and the like. 166. The activated carbon filter 166 is attached to the back surface of the upper surface (upper side in the figure) of the housing 122, and the exhaust fan 164 is attached below the activated carbon filter 166.

  The air containing the dispersed solvent component inside the housing 122 is exhausted to the outside of the housing 122 through the activated carbon filter 166 by the exhaust fan 164. At that time, the dispersed solvent component contained in the air inside the housing 122 is adsorbed and removed by the activated carbon filter 166.

  The configuration of the inkjet recording apparatus 100 of the present invention has been specifically described above.

  In the above-described example, the ink jet recording apparatus has been described in which the colorant particles in the ink are positively charged, the recording electrode or the counter electrode on the back of the recording medium is set to a negative high voltage, and image recording is performed by the ejected ink jet. However, the present invention is not limited to this, and conversely, the colorant particles in the ink may be negatively charged and the recording medium or the counter electrode may be set to a positive high voltage to perform image recording by inkjet. Thus, when the polarity of the colorant particles is reversed from the above example, the applied voltage to the parallel electrode of the particle size distribution removing unit, the electrostatic adsorption unit, the counter electrode, and the discharge electrode of the electrostatic inkjet head What is necessary is just to make polarity etc. reverse to said example.

Although a monochrome image is recorded, the present invention is not limited to this. For example, full-color printing of four colors of cyan (C), magenta (M), yellow (Y), and black (B) may be performed. . In this case, a head unit may be provided for each color, or an inkjet head for each color may be provided for one ejection head.
In this embodiment, the head unit is a serial head type. However, the head unit is not limited to this, and may be any type such as a line head type head unit.

  Although the ink jet recording apparatus of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various improvements and modifications may be made without departing from the gist of the present invention. Of course.

  For example, in the above example, the ink jet recording apparatus of the present invention is used for a concentration type electrostatic ink jet recording apparatus that uses ink in which color material particles (charged particles including a color material) are dispersed in a carrier liquid. However, the present invention is not limited to this, and can be suitably used for a non-concentrated electrostatic ink jet recording apparatus that does not use ink containing charged particles.

It is a conceptual diagram of an example of the inkjet recording device of this invention. It is a conceptual diagram of another example of the ink jet recording apparatus of the present invention. It is a conceptual diagram of another example of the ink jet recording apparatus of the present invention. It is a perspective view which shows schematic structure of the capping member of the inkjet recording device shown in FIG. FIG. 5 is a three-side view of the capping member shown in FIG. 4. FIG. 2 is a conceptual diagram of an ink jet head of the ink jet recording apparatus shown in FIG. 1, (A) is a perspective view, and (B) is a cross-sectional view. (A), (B), and (C) are the schematic diagrams for demonstrating the inkjet head shown in FIG. It is a schematic perspective view for demonstrating the recording head shown in FIG. It is a conceptual diagram of a specific example of the ink jet recording apparatus of the present invention. FIG. 10 is a conceptual diagram of the head unit shown in FIG. 9. It is a conceptual diagram which shows an example of the conventional inkjet recording device.

Explanation of symbols

10 Inkjet recording device 12 Discharge head (inkjet head)
14 Capping member 16 Main tank 18 Supply sub tank 18a, 20a Overflow pipe 20 Recovery sub tank 22 Ink replenishment tank 24 Ink circulation path 26 Ink circulation pump 30 First supply path 32 Second supply path 34 First recovery path 36 Second Recovery channel 38 Third recovery channel 39 Ink channel 40, 44, 46 Communication piping 41, 42, 45, 47 Communication port 50 Case 52 Rubber holding member 54 Capping rubber member 56 Pressing pressure adjustment spring 58 Communication tube 72 Head Substrate 74 Discharge port substrate 76 Ink guide 78 Ink flow path 80 Floating conductive plate 82 Control electrode 86 Second control electrode 86 Insulating substrate 88 Guard electrode 90, 92, 94 Insulating layer 96 Discharge port 98 Tip portion 112 Holding means 114 Conveying means 116 Recording means 118 A Link circulation means 120 Solvent recovery means 122 Case 124 Paper feed tray 126 Feed roller 128 Discharge tray 130 Conveying roller pair 132 Conveying belt 134 Belt roller 136 Conductive platen 138 Charging device 140 Neutralizing device 142 Separation claw 144 Guide 146 Fixing roller pair 148 Head unit 150 Head driver 152 Position detection means 160 Common recovery flow path 164 Activated carbon filter 166 Exhaust fan 176, 178 Sub tank position adjustment mechanism 180 Ink flow path 182 Drive means 184a, 184b Guide rail 186 Support member

Claims (9)

An inkjet head having an ejection port for ejecting ink on a recording medium based on an image signal;
Capping means mounted on the inkjet head and covering the discharge port;
One or more ink tanks for supplying ink to the inkjet head by a static pressure method;
A communication pipe connecting at least one of the one or more ink tanks and at least one of the capping means and the inkjet head;
The communication pipe includes a communication port formed on the capping surface of the capping unit and the inkjet head for communicating air of the at least one ink tank with outside air,
The capping unit is attached to the ink jet head, the communication to the outside air through the communication pipe is cut off, and the capping unit is detached from the ink jet head to communicate with the outside air through the communication pipe. Inkjet recording device. At least one ink tank connected to the communication pipe includes a supply ink tank for supplying ink to the inkjet head;
2. The ink jet recording apparatus according to claim 1, wherein the supply ink tank is disposed at a position higher than the ink jet head, and supplies ink to the ink jet head while maintaining a constant ink liquid level by overflow. 3. . At least one ink tank connected to the communication pipe includes a recovery ink tank that recovers ink from the inkjet head;
3. The inkjet according to claim 1, wherein the recovery ink tank is disposed at a position lower than the inkjet head, and recovers ink from the inkjet head while maintaining a constant ink liquid level by overflow. Recording device.   The at least one ink tank connected to the communication pipe further includes a storage tank for storing ink to be supplied to the supply ink tank and / or ink recovered from the recovery ink tank and the storage tank. The ink jet recording apparatus according to claim 2 or 3, comprising at least one of a replenishing tank for replenishing ink.   The inkjet recording apparatus according to claim 1, wherein the communication port is formed only on a surface of the inkjet head on the capping unit side.   The ink jet recording apparatus according to claim 1, wherein the communication port is formed only on a surface of the capping unit on the ink jet head side.   The inkjet recording apparatus according to claim 1, wherein the capping unit is attached to the inkjet head in a non-contact manner with the ejection port.   8. The capping unit disconnects communication between the discharge port of the inkjet head and outside air by pressing the cap unit against the inkjet head by an urging unit that does not require power in a non-operating state. An ink jet recording apparatus according to any one of the above. The ink is an ink obtained by dispersing charged fine particles containing at least a coloring material in an insulating dispersion medium,
The ink jet recording apparatus according to claim 1, wherein the ink jet head is an electrostatic ink jet head that discharges the ink from the discharge port onto the recording medium.

Images