JP2023074245A - Ink jet printer - Google Patents

Abstract

To suppress density unevenness due to irregular mist impact on the periphery of a main droplet by blurring a sheet blank in a main droplet gap without adding new hardware.SOLUTION: In an ink jet printer which includes an ink jet head which has a first nozzle array 101 and a second nozzle array 102 and in which the first nozzle array 101 and the second nozzle array 102 are arranged with a half-pitch shift, when performing low-resolution printing by discharging ink from only the first nozzle array 101 of the ink jet head, sub droplet discharge data for the second nozzle array 102 divided from printing data printed from the first nozzle array 101 are created, ink is discharged from the first nozzle array 101 and sub droplets smaller than ink droplets discharged from the first nozzle array 101 are discharged from the second nozzle array 102.SELECTED DRAWING: Figure 2

Description

The present invention relates to an inkjet printing apparatus, and more particularly to an inkjet printing apparatus that suppresses density unevenness.

A line-type inkjet printing apparatus performs printing by ejecting ink from an inkjet head based on image data onto a sheet conveyed by a belt conveying section provided below the inkjet head.

In Patent Document 1, print control data for high-resolution printing is generated based on predetermined ink drop data for a specific color, and the print control data for high-resolution printing is output to an inkjet head for a specific color. Print control data for low-resolution printing is generated based on the high-resolution control data generation unit and ink drop data for colors other than the specific color, and the print control data for low-resolution printing is used for ink jet printing in colors other than the specific color. An image control apparatus is disclosed that includes a low-resolution control data generation unit for outputting to the head, and switches between high-resolution and low-resolution inkjet heads according to the application for printing.

JP 2021-146561 A

However, in the case of a configuration in which high-resolution and low-resolution inkjet heads are switched according to the application, as in the image control apparatus described in Japanese Patent Laid-Open No. 2002-200011, the ejection at low resolution is more difficult than the ejection at high resolution. Overall mist is reduced because the droplet volume is increased.

On the other hand, when unstable mist lands around the main droplets, it is visually recognized as density unevenness, and print quality deteriorates. When ejecting at such a low resolution, it is effective to eject the sub-droplet next to the main droplet as a means of making the density unevenness of black in particular inconspicuous, but it is necessary to provide new hardware for ejection. is required, and there is a problem that the device configuration and control become complicated.

The present invention has been made in view of these problems, and is an inkjet printer that blurs the white background of the paper between the main droplets and suppresses density unevenness caused by irregular mist landing around the main droplets without adding new hardware. An object of the present invention is to provide a printing device.

In order to achieve the above object, the inkjet printing apparatus according to the present invention is characterized by:
An inkjet printing apparatus comprising an inkjet head having a first nozzle row and a second nozzle row, wherein the first nozzle row and the second nozzle row are arranged with a half-pitch shift,
Creating sub-droplet ejection data for the second nozzle row distributed from print data to be printed from the first nozzle row when performing low-resolution printing by ejecting ink only from the first nozzle row of the inkjet head. Ink is ejected from the first nozzle row, and sub-droplets smaller than ink droplets ejected from the first nozzle row are ejected from the second nozzle row.

According to the characteristics of the inkjet printing apparatus according to the present invention, density unevenness due to irregular mist landing around the main droplet can be suppressed without adding new hardware.

1 is a schematic configuration diagram of an inkjet printer according to an embodiment of the present invention; FIG. It is a figure explaining control of the inkjet printing apparatus which concerns on embodiment of this invention. It is the figure which showed the ink droplet which landed on the paper discharged from the inkjet head with which the inkjet printing apparatus which concerns on embodiment of this invention is equipped.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent reference numerals are attached to the same or equivalent parts and components throughout each drawing. However, it should be noted that the drawings are schematic and differ from reality. In addition, there are portions with different dimensional relationships and ratios between the drawings.

Further, the embodiments shown below are examples of apparatuses and the like for embodying the technical idea of the present invention. not specific to The technical idea of this invention can be modified in various ways within the scope of claims.

(Configuration of inkjet printer 1)
An embodiment of an inkjet printer 1 according to the present invention will be described in detail below with reference to the accompanying drawings.

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

In the following description, the front side of FIG. 1 where the user is positioned is the left direction, and the back side of the paper is the right direction. Also, in FIG. 1, the up and down direction is defined as the up and down direction as viewed from the user. Further, the path indicated by the dashed line in FIG. 1 is the transport path R along which the paper PA, which is the print medium, is transported. The transport direction of the sheet of paper PA is defined as the front-rear direction. Upstream in the following description means forward direction and downstream means backward direction.

As shown in FIG. 1 , the inkjet printing apparatus 1 includes a paper feeding section 2 , a suction transport section 3 , a printing section 4 and a paper discharging section 6 .

The paper feed unit 2 feeds paper PA, which is a print medium. The paper feed unit 2 includes a paper feed table 11 , paper feed rollers 12 , and registration rollers 13 .

Sheets of paper PA used for printing are stacked on the paper feed table 11 .

The paper feed rollers 12 pick up the paper sheets PA stacked on the paper feed table 11 one by one and convey them toward the registration rollers 13 . The paper feed roller 12 is arranged above the paper feed table 11 . The paper feed roller 12 is rotationally driven by a motor (not shown).

The registration rollers 13 temporarily stop the paper PA transported by the paper feed rollers 12 and then transport the paper toward the suction transport unit 3 . The registration rollers 13 are arranged downstream of the paper feed rollers 12 . The registration rollers 13 are rotationally driven by a motor (not shown).

The suction transport unit 3 transports the paper PA transported from the registration rollers 13 toward the printing unit 4 and the paper discharge unit 6 . The suction conveying section 3 includes a conveying belt 21 , a drive roller 22 , driven rollers 23 to 25 , a belt drive motor 26 , a platen plate 27 and a suction fan 28 .

The conveying belt 21 is an annular endless belt stretched over a driving roller 22 and driven rollers 23-25. In the transport belt 21, suction holes, which are through holes for sucking and holding the paper PA, are formed at predetermined intervals along the transport direction of the transport belt 21. As shown in FIG. The conveying belt 21 sucks and holds the sheet of paper PA on the conveying belt 21 by means of negative pressure (adsorption force) generated in the suction holes by driving the suction fan 28 .

The conveying belt 21 rotates clockwise in FIG. As a result, the conveying belt 21 conveys the sheet of paper PA to the right by endlessly moving.

The driving roller 22 and the driven rollers 23 to 25 are over which the conveying belt 21 is stretched. The driving roller 22 is rotationally driven by a belt driving motor 26 to rotate the conveying belt 21 . The driven rollers 23 to 25 are driven by the driving roller 22 via the conveying belt 21 . The driven roller 23 has substantially the same height as the drive roller 22 and is spaced apart from the drive roller 22 in the left-right direction by a predetermined distance. The driven rollers 24 and 25 are arranged below the driving roller 22 and the driven roller 23 at substantially the same height, separated from each other by a predetermined distance in the horizontal direction.

A belt drive motor 26 rotates the drive roller 22 .

The platen template 27 is arranged below the conveying belt 21 between the driving roller 22 and the driven roller 23 and supports the lower surface of the conveying belt 21 so as to be slidable.

The suction fan 28 is arranged below the platen plate 27 to generate a downward airflow.

The printing unit 4 prints on the paper PA conveyed by the suction conveying unit 3 . The printing unit 4 is provided above the suction transport unit 3 . The printing unit 4 is fixed inside a housing (not shown) of the inkjet printer 1 . The printing unit 4 includes a black (K) inkjet head 31 K, a cyan (C) and magenta (M) inkjet head 31 CM, a yellow (Y) and gray (G) inkjet head 31 YG, and a head holder 32 . Prepare.

Inkjet heads 31K, 31CM, and 31YG have two rows of nozzles arranged in a straight line at the bottom, and ink is applied from the nozzles to paper PA conveyed while being sucked by suction conveying unit 3. Print by ejecting.

Black (K) ink is ejected from both of the two nozzle rows arranged in the inkjet head 31K. During low-resolution printing, ink is ejected from only one nozzle row, and during high-resolution printing, ink is ejected from both nozzle rows.

The inkjet head 31CM ejects cyan (C) ink from one of the two nozzle rows, and magenta (M) ink from the other nozzle row. The inkjet head 31YG ejects yellow (Y) ink from one of the two nozzle rows, and gray (G) ink from the other nozzle row.

The head holder 32 holds the inkjet head 31 above the suction/conveyance unit 3 . The head holder 32 is formed in a hollow, substantially rectangular parallelepiped shape.

The paper PA printed by the printing unit 4 is discharged to the paper discharge unit 6 .

FIG. 2 is a diagram explaining control of the inkjet printing apparatus 1 according to the embodiment of the present invention.

The inkjet head 31K includes a first nozzle row 101 and a second nozzle row 102, respectively.

The first nozzle row 101 and the second nozzle row 102 each have nozzles arranged in a row in the horizontal direction (main scanning direction). The positions of the nozzles of the first nozzle row 101 and the nozzles of the second nozzle row 102 are shifted by half a pitch in the horizontal direction (main scanning direction).

The inkjet printing apparatus 1 includes an image processing section 41 , an image control section 42 , a control section 43 and a head control section 44 .

The image processing unit 41 obtains image data to be printed output from a computer or the like or image data to be printed output by reading a document image with a document reading device (not shown), and performs various operations on the image data. process. Specifically, the image processing unit 41 converts, for example, input RGB format image data into C (cyan), M (magenta), Y (yellow), K (black), and G (gray) image data. Convert. This color conversion is performed using a table in which correspondence between RGB values and CMYKG values is recorded in advance.

The image processing unit 41 also applies halftone processing to the image data of each color of C, M, Y, K, and G to generate ink drop data of each color. Error diffusion processing and dither mask processing are used as halftone processing. The ink drop data is data indicating the number of ink drops for each print dot (print pixel) of each color.

The image control unit 42 generates print data for controlling the inkjet heads 31K, 31CM, and 31YG based on the ink drop data for each color.

The control unit 43 controls the paper feed unit 2, the suction/conveyance unit 3, the paper discharge unit 6, and the like provided in the inkjet printing apparatus 1. FIG. The controller 43 supplies the coefficients to the head controller 44 .

Based on the print data, the head control unit 44 creates main droplet ejection data for each of C (cyan), M (magenta), Y (yellow), and G (gray), and also creates main droplet ejection data for each of the ink jet heads 31CM and 31YG. Ink is ejected from each corresponding nozzle row based on the main droplet ejection data.

In addition, the head control unit 44 can perform low-resolution printing in which ink is ejected only from the first nozzle row 101 of the inkjet head 31K, and resolution printing in which ink is ejected from both the first nozzle row 101 and the second nozzle row 102. Can be run selectively.

The head control unit 44 is composed of a simple arithmetic circuit such as an integer part and a decimal part.

When the head control unit 44 performs low-resolution printing, the head control unit 44 selects the print data for the first nozzle row 101 based on the print data supplied from the image control unit 42 and the coefficients supplied from the control unit 43 . , and sub-droplet ejection data for the second nozzle row 102 distributed from the main droplet ejection data printed from the first nozzle row 101 is created.

Then, the head control unit 44 causes the first nozzle rows 101 of the inkjet head 31K to eject ink based on the main droplet ejection data, and the ink liquid ejected from the first nozzle rows 101 based on the sub-droplet ejection data. A sub-droplet smaller than the droplet is ejected from the second nozzle row 102 .

FIG. 3 is a diagram showing ink droplets ejected from the inkjet head 31K and landed on the paper.

As shown in FIG. 3A, ink droplets 201 ejected from the first nozzle row 101 based on the main droplet ejection data and ink droplets 201 ejected from the second nozzle row 102 based on the sub-droplet ejection data are formed on the paper. The ejected ink droplets 202 are alternately formed in the horizontal direction.

The ink droplets 201 and 202 are arranged at the same position in the front-rear direction, that is, on the imaginary line L1 in the left-right direction.

In this way, when the inkjet head 31K performs low-resolution printing, sub-droplet ejection data for the second nozzle row 102 distributed from the print data printed from the first nozzle row 101 is used to eject the droplets from the first nozzle row 101. By ejecting sub-droplets that are smaller than the main droplets, it is possible to blur the white background of the paper between the main droplets and suppress density unevenness due to irregular mist landing around the main droplets without adding new hardware. .

Here, the ink droplets 201 and the ink droplets 202 are ejected so as to be arranged at the same position in the front-rear direction, that is, on the imaginary line L1 in the left-right direction, but the present invention is not limited to this.

For example, as shown in FIG. 3B, the ink droplets 203 ejected from the first nozzle row 101 are ejected so as to be arranged on the virtual line L1 based on the main droplet ejection data, and the sub droplet ejection data , the ink droplets 204 ejected from the second nozzle row 102 may be ejected so as to be arranged on the virtual line L2 shifted backward from the virtual line L1.

Further, as shown in FIG. 3C, the ink droplets 203 ejected from the first nozzle row 101 are ejected so as to be arranged on the virtual line L1 based on the main droplet ejection data, and the sub droplet ejection data , the ink droplets 204 ejected from the second nozzle row 102 may be ejected so as to be randomly arranged.

(Appendix)
This application discloses the following inventions.

(Appendix 1)
An inkjet printing apparatus comprising an inkjet head having a first nozzle row and a second nozzle row, wherein the first nozzle row and the second nozzle row are arranged with a half-pitch shift,
Creating sub-droplet ejection data for the second nozzle row distributed from print data to be printed from the first nozzle row when performing low-resolution printing by ejecting ink only from the first nozzle row of the inkjet head. and ink is ejected from the first nozzle row, and sub-droplets smaller than ink droplets ejected from the first nozzle row are ejected from the second nozzle row.

As a result, when performing low-resolution printing, the sub-droplet ejection data for the second nozzle row distributed from the print data for printing from the first nozzle row is used to eject sub-droplets that are smaller than the main droplets ejected from the first nozzle row. By ejecting, it is possible to blur the white background of the paper between the main droplets and suppress density unevenness due to irregular mist landing around the main droplets without adding new hardware.

1 Inkjet printer 2 Paper feed unit 3 Suction transport unit 4 Print unit 6 Paper discharge unit 31, 31CM, 31K, 31YG Inkjet head 32 Head holder 41 Image processing unit 42 Image control unit 43 Control unit 44 Head control unit

Claims (1)

An inkjet printing apparatus comprising an inkjet head having a first nozzle row and a second nozzle row, wherein the first nozzle row and the second nozzle row are arranged with a half-pitch shift,
Creating sub-droplet ejection data for the second nozzle row distributed from print data to be printed from the first nozzle row when performing low-resolution printing by ejecting ink only from the first nozzle row of the inkjet head. and ink is ejected from the first nozzle row, and sub-droplets smaller than ink droplets ejected from the first nozzle row are ejected from the second nozzle row.

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