JP5869314B2 - Inkjet recording apparatus and recording method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus and a recording method. In particular, the present invention relates to a recording apparatus provided with a charge removal device and a recording method for controlling and recording the charge removal device.

  2. Description of the Related Art Conventionally, ink jet recording apparatuses that perform recording on a recording medium by discharging ink droplets from nozzles provided in a recording head are known. As inkjet recording apparatuses, not only small-sized inkjet recording apparatuses for consumer use but also large-sized inkjet recording apparatuses for industrial use such as textile printing and outdoor advertising are widely used.

  In an ink jet recording apparatus, part of ink ejected from a recording head may become a fine mist and float inside the apparatus. This floating mist may land on an undesired location on the recording medium and cause image quality defects. The cause of noticeable image quality failure due to mist is that a part of the ejected ink mist and the recording medium are charged, and the ink mist is attracted to the charged portion of the recording medium due to the electrical interaction between them. It is thought that it will adhere.

  As a method for preventing contamination caused by this mist, Patent Document 1 discloses that a corona discharge device and a metal plate are attached to the nozzle portion of the recording head as a static elimination mechanism to remove the charge of the ejected ink. In the recording document 2, in a full-line type ink jet recording apparatus, a corona discharge device is attached to the side surface of the mounted recording head to remove the charged ink.

  In these prior arts, the static eliminator must be mounted on a small recording head, resulting in a complicated mechanism. Further, in an industrial inkjet recording apparatus that records on various recording media, the charge amount of the recording medium increases depending on the type of the recording medium and the method of transporting the recording medium, and thus the charging removal of the recording medium itself is required. .

  However, as a conventional technique for removing the charge of the recording medium, a method of providing a neutralization brush in the recording medium conveyance unit is known. However, in this method, the neutralization effect of the recording medium may be thin. Further, the recording medium may be recharged before reaching the recording position of the recording head.

JP 2006-27156 A JP 2007-144791 A

  In the above-described prior art, the ink mist is mainly removed by charging, and the method for removing the charge from the recording medium may be insufficient. Some of the recording media are highly charged. Industrial ink-jet recording that records on various recording media can result in poor image quality and contamination of the recording media due to the mist removal alone. In the apparatus, it is necessary to perform effective charge removal on a highly chargeable recording medium.

  The reason why the recording medium is charged is considered to be friction between the transport section and the recording medium when the recording medium is transported by a recording medium transport section such as a roller or a belt provided in the recording apparatus. Therefore, as a method of suppressing the charging of the recording medium, a method of removing the charging of the recording medium and a method of reducing the charge amount during conveyance of the recording medium are conceivable, and a method including both is the most effective.

Accordingly, an object of the present invention is to propose an ink jet recording method having a charging removal mechanism for a recording medium.
It is another object of the present invention to provide an ink jet recording apparatus capable of performing the above ink jet recording method.

In order to solve the above problems, the present invention comprises a recording data input means, a recording medium conveying means, and a recording head, and the recording head according to the recording data while conveying the recording medium by the conveying means. A recording method of an ink jet recording apparatus that performs recording by discharging ink from the recording medium to the recording medium, the recording data input step, the ink type, the type of the recording medium, the ink ejection frequency, and the ink jet recording apparatus In accordance with at least one recording condition in the humidity of the installation environment, a condition for removing the charge of the recording medium of the charge removing means provided on the upstream side of the recording head in the transport direction of the recording medium is set. and charge removing condition setting step, in accordance with the presence or absence of history of the recording medium is conveyed by more than a certain speed, by controlling the conveying means, said recording medium A conveyance condition setting step for setting at least one of a recording start position and a conveyance speed to the recording start position; a charge removal step for removing the charge of the recording medium under the conditions set in the charge removal setting condition step; It has a recording step of recording in the recording area from which the charge has been removed in the charge removing step, in accordance with the recording data under the transport condition set in the transport condition setting step.

Further, another invention for solving the above-described problems is as follows.
An inkjet recording apparatus that includes a recording medium conveying unit and a recording head, and performs recording by ejecting ink from the recording head to the recording medium while conveying the recording medium by the conveying unit,
Charging removal means provided upstream of the recording head in the transport direction of the recording medium;
Conditions for electrifying and removing the recording medium of the charge removing means according to at least one of the recording conditions of the ink type, the recording medium type, the ink ejection frequency, and the humidity of the installation environment of the ink jet recording apparatus Charge removal condition setting means for setting
Depending on the presence / absence of a history that the recording medium has been conveyed at a certain speed or higher, the conveying means is controlled to set at least one of the recording start position of the recording medium and the conveying speed to the recording start position. It has the conveyance condition setting means to perform.

  According to the present invention, the charge of the recording medium is removed before recording by charging the recording medium with the charge removing means provided upstream of the recording head in the transport direction of the recording medium. Moreover, static electricity generated in the recording medium is reduced by controlling the conveyance speed of the recording medium. For the first time by combining these, stains due to ink mist are effectively prevented.

1 is a front view schematically showing a schematic configuration of an ink jet recording apparatus according to a preferred embodiment of the present invention. FIG. 2 is an enlarged side view of a peripheral portion of a recording medium conveyance unit of the ink jet recording apparatus of FIG. 1. 1 is a block diagram schematically showing a schematic configuration of an ink jet recording apparatus according to a preferred embodiment of the present invention. It is a flowchart which shows preferable embodiment of the inkjet recording method of this invention.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a front view schematically showing a schematic configuration of an ink jet recording apparatus according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the ink jet recording apparatus 1 of the present embodiment arranges a recording medium 50 horizontally and conveys it in the depth direction of the paper surface of FIG. Record images and text.

  The inkjet recording apparatus 1 includes a recording medium holding unit 40 that holds the recording medium 50 and a recording unit 41 that records on the recording medium 50. The recording head 9 includes a recording head 9 that performs reciprocating scanning in a direction orthogonal to the conveyance direction of the recording medium 50, and a cleaning unit 10 that cleans the recording head 9. The inkjet recording apparatus 1 includes a control unit (not shown) that controls the entire apparatus including reception of recording data and control of recording operations.

  The recording medium holding unit 40 includes a plurality of pinch rollers 3 that are rotated about a horizontal axis along the paper surface by a motor 5 on the substantially flat platen 2 that extends in the depth direction of the paper surface of FIG. A plurality of grid rollers 4 supported by these pinch rollers 3 so as to be rotatable about a rotation axis parallel to the rotation axis of the pinch roller 3 are arranged in the depth direction of the drawing. These grid rollers 4 are aligned above the platen 2 in a horizontal plane extending in the depth direction in FIG. 1 to form a conveyance path for the recording medium 50.

  The recording unit 41 is provided above the recording medium holding unit 40 and the cleaning unit 10, and is provided so as to be movable along the carriage rail 7 that extends in a direction orthogonal to the conveyance direction of the recording medium 50. And a recording head unit 8. In addition, a motor 6 that reciprocates the recording head unit 8 on the carriage rail 7 so as to be capable of position control and speed control is provided. Furthermore, a detachable ink cartridge 17 that supplies recording ink to the recording head unit 8 is provided.

  In the present embodiment, the ink cartridge 17 is provided with a plurality of colors of ink for performing color recording, and can be supplied to the recording head unit 8 for each color via a plurality of ink tubes 16 as pipes. It has become. The ink cartridge 17 is provided with a plurality of ink tanks corresponding to each ink, and each ink is accommodated in a corresponding ink tank.

  The recording head unit 8 is provided with a plurality of recording heads 9 on the lower surface side in accordance with the ink color and recording range, and the ink supplied from the ink tube 16 is distributed to the recording heads 9 that perform recording of the same color. Supplied. Further, the recording head unit 8 is provided with a cooling fan 18 for keeping the temperature of each recording head 9 in an appropriate temperature range.

  Although details of the recording head 9 are not shown, an ink chamber for supplying ink to each nozzle and an ejection mechanism using a piezoelectric element are provided. The recording head 9 is configured to be able to perform an idle driving operation in which the ink is ejected and the ink meniscus of the nozzle is finely oscillated by an ejection mechanism using the piezoelectric element. By finely vibrating the ink meniscus, ink thickening in the vicinity of the nozzles is suppressed, and poor image quality is avoided. Since there is a case where the influence of this ink thickening cannot be eliminated only by the fine vibration, a preliminary ejection mechanism for ejecting ink outside the image forming range and discharging the thickened ink in the vicinity of the nozzle is provided. Further, the nozzles can be provided with an appropriate number and arrangement pitch according to the configuration of the ejection mechanism, the recording pixel pitch, and the like. For example, a large number of nozzles such as 256 can be arranged. The recording head 9 of this embodiment uses a piezoelectric element as the recording element, but may be a recording head using a heater as the recording element.

  Position control and speed control of the motor 6 are performed according to control signals from the control unit. During the recording operation, the motor 6 is controlled so that the recording head reciprocates on the recording medium 50 at a predetermined speed. Further, the motor 6 can move the recording head unit 8 to a predetermined cleaning position in the cleaning unit 10 during the cleaning operation.

  In this embodiment, the cleaning unit 10 includes a suction cleaning unit 14A that cleans the recording head 9 by sucking the ink in the recording head 9 from the nozzles to the outside, and the recording head 9 by wiping the recording head surface. It consists of a wipe part 14B to be cleaned. The cleaning unit 10 is arranged on the moving path of the recording head unit 8 on the side of the recording medium holding unit 40 and below the recording unit 41 in the order of the wiping unit 14B and the suction cleaning unit 14A from the recording medium holding unit 40 side. Yes. In the present embodiment, the upper positions of the suction cleaning unit 14A and the wipe unit 14B are predetermined cleaning positions.

  The schematic configuration of the suction cleaning unit 14A includes a cap 11, a cap drive unit (not shown), a suction pump 12, a pump drive unit (not shown), an air release valve (not shown), and an air release valve drive unit (not shown). Become.

  Among these, at least the cap 11 is provided for each recording head 9. However, the cap drive unit, the suction pump 12, the air release valve, and the air release valve drive unit may be configured to be provided for each of the plurality of caps 11 when each operation can be made common for each recording head 9. .

  The cap drive unit moves up and down to selectively switch the position of the cap 11 in the vertical direction, and includes, for example, appropriate mechanical, electromagnetic, and fluid lifting means. Therefore, the cap drive unit moves the cap 11 up and down with respect to the recording head unit 8 which is moved above the carriage rail 7 by the motor 6 and positioned above the suction cleaning unit 14A. The state where the head surface is sealed and the state where the sealing is released can be switched.

  The suction pump 12 is for sucking contents such as air and ink in the suction space and discharging them to the outside of the suction space, and an appropriately configured fluid pump such as a rotary pump can be adopted. A liquid passing means for passing ink from the ink cartridge 17 to the recording head 9 and a suction pump 12 are used here. The suction pump 12 has a suction port connected to the suction pipe and a discharge port connected to the discharge pipe. The other end of the discharge pipe is connected to the waste liquid bottle 15.

The wipe unit 14B may have any configuration as long as it performs a known wiping process. For example, it is possible to employ a configuration in which the recording head surface is wiped by relatively moving a wiping blade containing a wiping liquid on the recording head surface of the recording head 9 moved above the wiping portion 14B.

FIG. 2 is an enlarged side view of the periphery of the recording medium conveyance unit of the ink jet recording apparatus of FIG.
The recording medium 50 is fixed by a pinch roller 3 and a grid roller 4 as conveying means, and is conveyed onto the platen 2 on the right side of FIG. 2 by the rotational movement of these rollers. The recording head unit 8 equipped with the recording head 9 reciprocates on the platen 2 to form an image on the conveyed recording medium 50.

  An ionizer 20 having a charge removing function is installed between the conveying means and the recording head unit 8, and the recording medium 50 is generated by friction between the pinch roller 3 and the grid roller 4 and the recording medium 50 during conveyance. Remove the static electricity. In this embodiment, the ionizer 20 is installed between the conveying means and the recording head unit 8, but an apparatus configuration in which the ionizer 20 is mounted on the recording head unit 8 may be used. Further, although the ionizer is used as the charge removing device, the device is not limited to the ionizer, and other devices having a charge removing function may be used.

FIG. 3 is a block diagram schematically showing a schematic configuration of the ink jet recording apparatus according to the preferred embodiment of the present invention.
In FIG. 3, reference numeral 30 denotes a control unit. The control unit 30 includes a CPU 31 that executes processing operations such as calculation, control, determination, and setting, a ROM 32 that stores a control program to be executed by the CPU 31, and a recording data A RAM 33 or the like used as a buffer or a work area for processing by the CPU 31 is provided. The input unit 34 outputs recording data and the like input from a host computer (not shown) to the control unit 30.

  In the inkjet recording apparatus 1 of the present embodiment, the control unit 30 operates the recording head 9 via the recording head drive unit 37. When a plurality of recording heads 9 are mounted, the control unit 30 and the recording head driving unit 37 can drive each recording head 9 individually.

Further, the control unit 30 rotates the pinch roller 3 through the transport equipment driving unit 38 and transports the recording medium 50. Further, the conveyance speed can be changed, and a history of the conveyance speed can be temporarily stored in the RAM 33.
Further, the control unit 30 can operate the ionizer 20 via the ionizer driving unit 39.

  The recording head drive unit 37 generates ink ejection timing or non-ejection timing of each recording head 9 based on information input from the control unit 30 and drives the recording head 9. When ink ejection is performed, an ON waveform is generated. When ink ejection is not performed, an OFF waveform is generated and transferred to each recording head 9.

  The operation panel 35 includes a switch for performing startup, maintenance, paper feed (recording medium supply), paper discharge (discharge of the recording medium), and other operations of the inkjet recording apparatus 1, and a display screen (for example, a liquid crystal screen). Prepare. The user can execute the above operation by operating the switch while looking at the display screen.

  Further, it is possible to set the ink type mounted on the ink jet recording apparatus 1 and the type of recording medium attached to the ink jet recording apparatus 1 on the operation panel 35 and transmit the information to the control unit 30. When the ink type and the recording medium type to be mounted are registered in advance via the operation panel 35 and the ink type and the recording medium type in which the stain due to the ink mist becomes conspicuous are set, the information of the recording medium is set based on the information. The control unit 30 can set the recording start position and the conveyance speed to the recording start position. In addition, based on the information, it is possible to take stronger charging measures such as increasing the output of the ionizer 20.

  The humidity measuring unit 36 measures the environmental condition of the humidity where the inkjet recording apparatus 1 is placed, and transmits it to the control unit 30. For example, when it is detected that the environment in which the inkjet recording apparatus 1 is placed is low humidity of 30% or less where static electricity is likely to occur, the recording start position of the recording medium and the conveyance speed to the recording start position based on that information Can be set. In addition, based on the information, it is possible to take stronger charging measures such as increasing the output of the ionizer 20.

FIG. 4 is a flowchart showing a preferred embodiment of the control method.
First, in step S100, when recording data is input, it is determined whether or not a predetermined charge removal method needs to be performed based on information about information conditions input to the control unit 30. The recording conditions in this embodiment are ink type, recording medium type to be used, ink ejection frequency based on input image data, and environmental humidity in which the inkjet recording apparatus 1 is placed. If it is determined that the charge removal method of the present invention is necessary under any one of the above recording conditions, the process proceeds to step S110. If it is determined that the charging removal method is not necessary, the process proceeds to step S160, and image formation is started by a normal recording method. In other words, the control unit 30 sets a charge removal condition for the recording medium according to the recording condition.

  For the ink type that is one of the determination items, an ink type in which mist easily scatters is set in advance, and if it is determined that the set ink type is mounted, the process proceeds to step S110. For example, an ink type having an AC impedance value of 50 kΩ or less at an ink frequency of 1 kHz tends to be easily charged, and it is necessary to remove the charge of the recording medium 50 to suppress recording medium contamination due to ink mist.

  Some recording media are easily charged and others are not. In general, a recording medium made of polyethylene terephthalate is known as an easily charged recording medium. However, since the charging property of the recording medium varies depending on the surface treatment of the recording medium, it is difficult to determine whether the recording medium is easily charged. For this reason, information about a recording medium that is empirically charged can be stored in an EEPROM (not shown) provided in the inkjet recording apparatus 1 through the operation panel 35. When a recording medium that is easily charged is used, the control unit 30 determines to take a charge removing method.

  Depending on the environmental humidity where the inkjet recording apparatus 1 is placed, mist may be easily scattered. Specifically, the mist tends to be scattered as the humidity decreases. In the present embodiment, the control unit 30 sets the charging removal method to be performed when the measured value measured by the humidity measuring unit 36 is equal to or lower than a predetermined humidity stored in the ROM 32.

  Further, it is determined whether or not it is necessary to carry out the charge removal method based on the ink ejection frequency based on the input recording data. When an image with a large amount of ink ejected from the recording head 9 is output, the amount of ink mist scattered also increases, so it is necessary to carry out a charge removal method. Therefore, the control unit 30 detects whether or not the ink discharge amount is larger than a preset value, and determines whether or not to implement the charge removal method.

  If it is determined by the above determination that the charge removal method needs to be performed, the process proceeds to step S110, and the control unit 30 reads the conveyance speed history information and proceeds to step S120.

  In step S120, the control unit 30 determines whether there is a history that the recording medium 50 is conveyed at a certain speed or more and the charge amount of the recording medium 50 is high. If it is determined that there is a history that the recording medium 50 has been transported at high speed, the process proceeds to step S130. If there is no history that the recording medium 50 has been transported at high speed, the process proceeds to step S140. In other words, the control unit 30 sets the conveyance condition of the recording medium according to whether or not there is a history that the recording medium 50 has been conveyed at a certain speed or higher.

In step S130, since there is a possibility that the charge amount at the scheduled recording start position on the recording medium 50 may be high, an operation of changing the image formation (recording) start position and the conveyance speed to the recording start position is performed. The control unit 30 rotates the pinch roller 3 at a low speed via the transport equipment drive unit 38, and moves the recording medium 50 to a position where the charging amount of the recording medium 50 decreases to a position where the recording medium 50 is reduced. Transport. By the above process, recording from a position where the charge amount of the recording medium 50 is small becomes possible. In the present embodiment, both the recording start position and the conveyance speed up to the recording start position are changed. However, the present invention includes a case where either one is changed.
In step S140, since the charge amount of the recording medium 50 is already small, no special conveyance control is performed, and the recording medium 50 is conveyed at a normal conveyance speed to a normal recording start position.

After step S130 or step S140, the process proceeds to step S150 to start image formation. At this time, in order to remove the charge on the recording medium 50, the control unit 30 performs image formation while operating the ionizer 20 with a predetermined output via the ionizer driving unit 39. By the above process, image formation can be performed in parallel with the charge removing process on the recording medium 50. In the present invention, the output condition of the ionizer 20 may be changed according to the recording condition.
The recording method of the present embodiment is completed when step S150 or step S160 ends.

  In the present embodiment, the ink condition, the recording medium type to be used, the ink ejection frequency based on the input image data, and the environment in which the inkjet recording apparatus 1 is placed are used as the recording conditions when setting the charge removal condition of the recording medium. Humidity was used. Further, the presence / absence of a history of the recording medium 50 being conveyed at a certain speed or higher was used as a recording condition when setting the conveying condition of the recording medium. However, the present invention may include the presence / absence of a history in which the recording medium 50 is conveyed at a certain speed or more as the recording condition when setting the charging removal condition of the recording medium. In addition, the present invention includes the ink type, the recording medium type to be used, the ink ejection frequency based on the input image data, and the environmental humidity in which the inkjet recording apparatus 1 is placed as the recording conditions when setting the conveyance conditions of the recording medium. May be. In the case of forming an image on a recording medium having high chargeability, such as polyvinyl chloride, polyethylene terephthalate, and paper, the present invention is particularly effective in the conventional ink jet recording method because stains due to ink mist are remarkable. .

  The ink jet recording method and the ink jet recording apparatus of the present invention can be used for a general ink jet recording apparatus.

DESCRIPTION OF SYMBOLS 1 Recording device 2 Platen 3 Pinch roller 4 Grid roller 8 Recording head unit 9 Recording head 20 Ionizer 35 Operation panel 36 Humidity measurement part 50 Recording medium

Claims (7)

A recording data input unit, a recording medium conveying unit, and a recording head are provided. While the recording medium is conveyed by the conveying unit, ink is ejected from the recording head to the recording medium according to the recording data, and recording is performed. A recording method of an ink jet recording apparatus for performing
An input step of the recording data;
According to at least one of the recording conditions of the ink type, the recording medium type, the ink ejection frequency, and the humidity of the installation environment of the inkjet recording apparatus, the recording medium is transported upstream of the recording medium. A charge removal condition setting step for setting conditions for charge removal of the recording medium of the charge removal means provided;
Depending on the presence / absence of a history that the recording medium has been conveyed at a certain speed or higher, the conveying means is controlled to set at least one of the recording start position of the recording medium and the conveying speed to the recording start position. Carrying condition setting process to
A charge removal step of removing the charge of the recording medium under the conditions set in the charge removal condition setting step;
A recording method comprising: a recording step of recording in the recording area decharged in the charge removal step, according to the recording data, under the conveyance condition set in the conveyance condition setting step. The inkjet recording apparatus includes a storage unit that stores a history of a conveyance speed of the recording medium,
The conveyance condition setting step sets a conveyance speed slower than a predetermined threshold when there is a conveyance speed faster than a predetermined threshold among the conveyance speeds stored in the storage unit. 2. The recording method according to 1. The recording method according to claim 1, wherein the recording medium is made of any one of polyvinyl chloride, polyethylene terephthalate, and paper. The recording method according to any one of claims 1 to 3, wherein the ink has an AC impedance value of 50 kΩ or less at a frequency of 1 kHz. The recording method according to claim 1, wherein the charge removal is performed by an ion generator. The recording method according to claim 5, wherein the ion generator is an ionizer. An inkjet recording apparatus that includes a recording medium conveying unit and a recording head, and performs recording by ejecting ink from the recording head to the recording medium while conveying the recording medium by the conveying unit,
Charging removal means provided upstream of the recording head in the transport direction of the recording medium;
Conditions for electrifying and removing the recording medium of the charge removing means according to at least one of the recording conditions of the ink type, the recording medium type, the ink ejection frequency, and the humidity of the installation environment of the ink jet recording apparatus Charge removal condition setting means for setting
Depending on the presence / absence of a history that the recording medium has been conveyed at a certain speed or higher, the conveying means is controlled to set at least one of the recording start position of the recording medium and the conveying speed to the recording start position. An ink jet recording apparatus comprising transport condition setting means.