JP2017132149A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which image quality is deteriorated because dots are not formed into the desired shape when recording is performed on dots at the same position or adjacent to each other before the dots are dried in a case where an image is recorded in a recording medium by using a recording head having a plurality of nozzles arranged in the row in an ink jet printer.SOLUTION: Each recording head corresponding to each color is divided into two groups and one nozzle array is fixed onto a carriage with displacement by half pitch in comparison to the other nozzle array. The recording heads which belong to different groups are paired and discharge by the recording heads of each pair is controlled to record an image without forming dots at adjacent positions in the same scanning.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inkjet printer.

  2. Description of the Related Art An ink jet printer that records an image by ejecting ink from an ink jet recording head onto a recording medium such as paper or a resin film is known. In an ink jet printer, a recording head is mounted on a carriage with an interval of several millimeters with respect to a recording medium, and ink is moved back and forth in a direction crossing the conveyance direction of the recording medium, for example, in a perpendicular direction. Is known to perform recording. During the switching between the forward path and the return path of carriage reciprocating scanning (scanning is also referred to as scanning), the recording medium is conveyed by the conveying means, and a desired image is completed by alternately performing recording and conveyance.

  Various inks have been proposed for use in inkjet printers, such as solvent inks in which organic solvents are used as the main solvent and pigments are dispersed in the solvent, and UV inks that are cured by irradiation with ultraviolet rays. Has been. Also, higher resolution of the image is desired, and the nozzle arrangement of the recording head is becoming finer. Attempts have also been made to narrow the nozzle pitch by arranging the recording head.

  For example, as an example of the arrangement of the nozzles of the recording head, Japanese Patent Application Laid-Open No. 2014-97650 discloses that the nozzles of the transparent ink head are arranged at a position shifted by a half pitch with respect to the color ink head. Have been disclosed.

JP 2014-97650 A

  If the nozzles of the recording head are made finer and narrower, it is possible to record fine images in terms of image quality, while the closer nozzle pitch results in poor image quality due to the behavior of ink that has landed on the recording medium. Occurs.

  FIG. 2 is a diagram illustrating the behavior of ink. The problem of poor image quality due to ink behavior will be described with reference to FIG. For example, ink is ejected onto a recording medium 28 such as a vinyl chloride sheet. When the dot 21 is recorded in the adjacent pixel after the dot 20 is recorded, the dot recording range is expanded to the extent that the mesh is almost filled, like the dot 22 and the dot 23. At this time, the heights of the dots 22 and 23 are substantially the same. In this way, when recording is performed adjacently, a desired image can be recorded if the dot spread is not affected and can be recorded.

  However, when the dot 24 is recorded after the dot 24 is recorded, or when the ink comes in contact with the ink before it dries, such as when it is overlapped without landing at the target position due to a flying curve, the dot is combined. May end up. As a result, the amount of ink deposited in the range of one pixel increases, resulting in a problem that the drying property is deteriorated. When the ink is in a fluid state without being dried, there arises a problem that the ink flows or becomes uneven. As described above, when recording is performed at the same pixel position or adjacent positions, if the ink is combined and the drying property is deteriorated, the dots to be recorded are adversely affected. That is, there arises a problem that a desired image cannot be recorded.

  The present invention is an invention that solves the above-mentioned problems, and an inkjet printer according to the present invention includes a recording head in which a plurality of nozzles are arranged and ejects ink from the nozzles to a recording medium; a platen that supports the recording medium; A transport unit for transporting the recording medium, a carriage mounted with the recording head and reciprocatingly scanned in a main scanning direction intersecting the transport direction of the recording medium, and ink ejection from the nozzles of the recording head. Control means for controlling, the nozzles of the recording head are arranged at equal intervals in a direction along the conveyance direction of the recording medium, and a plurality of nozzles are provided on the carriage according to the color of the ink. The recording head is mounted, and the recording head is divided into a plurality of blocks, and a predetermined number of passes according to the number of divisions of the blocks are performed in a predetermined area. In the ink jet printer that records an image by recording the image by changing the block for each scan, the recording head is divided into two groups, a first group and a second group, and is arranged on the carriage. The row of nozzles ejecting the ink of the recording head belonging to the first group is located between the nozzles upstream in the transport direction with respect to the row of nozzles ejecting the ink belonging to the second group. Between the lines to be recorded on the recording medium in one scan by the nozzles of the recording head belonging to the first group and the nozzles belonging to the second group, At least one dot is separated and the top of the recording head belonging to the first group in the transport direction The block on the side has one more nozzle than the number of nozzles included in the block on the downstream side, and the control means uses the recording heads belonging to the same group in one scan, Control is performed such that the ink is not ejected to the same dot position.

  The present invention can provide an ink jet printer that can suppress the mutual influence of adjacent dots stored in a recording medium even when the nozzle pitch of the recording head is narrowly arranged.

FIG. 1 is a diagram illustrating the arrangement of recording heads. FIG. 2 is a diagram illustrating the behavior of ink. FIG. 3 is a block diagram of the ink jet printer. FIG. 4 is a diagram for explaining an image recording operation. FIG. 5 is an external view of the ink jet printer.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating the arrangement of recording heads. In order to perform color recording on a recording medium, a C head 1 that ejects cyan ink, an M head 2 that ejects magenta ink, a Y head 3 that ejects yellow ink, and a black ink are ejected. Four recording heads of the K head 4 are fixed to a carriage described later. In these recording heads, the C head 1 and the Y head 3 are arranged such that the nozzles overlap in the traveling direction of the carriage. The M head 2 and the K head 4 are arranged so that the nozzles overlap in the carriage traveling direction. Further, the nozzles of the C head 1 and the M head 2 are arranged so as to be shifted by a half pitch. The carriage movement direction is called a main scanning direction, and the recording medium conveyance direction is called a sub-scanning direction.

  For example, the nozzles of each recording head are arranged with 180 nozzles per inch. As a result, 180 dpi recording can be performed. Adjacent recording heads can record at this half interval. The nozzle pitch of adjacent recording heads is fixed to the carriage so as to be shifted by a half pitch in the recording medium conveyance direction.

  The nozzle 7 of the M head 2 and the nozzle 9 of the K head 4 can record dots on the same line by scanning the same carriage. The nozzle 5 of the C head 1 and the nozzle 8 of the Y head 3 can record dots on the same line by scanning the same carriage. If a group of two recording heads whose nozzle positions are shifted in the sub-scanning direction can be formed, they need not be adjacent to each other.

  For example, the dots 10 and 11 can be recorded by the M head 2, and the dots 12 can be recorded by the K head 4. However, when dots 11 and 12 are recorded in the same scan, the next recorded dot is attracted to the first recorded dot, causing an image defect. Therefore, it is necessary to control the recording order. . Further, even if the nozzle 5 and the nozzle 6 of the C head 1 are discharged at the same time, they are separated from each other, so that dots do not overlap. When the nozzle 5 of the C head 1 and the nozzle 7 of the M head 2 are ejected at the same time, the dot does not overlap because there is a gap of one dot between the dot 10 and the dot 13. If there is a gap of one dot between the dots 10 and 11, the dots do not overlap. Although an example has been described in which one recording head includes three dots between dots recorded in one scan, the resolution can be further increased in the transport direction.

  FIG. 3 is a block diagram of the printer. The control means 30 is a control circuit including a CPU that executes processing operations such as calculation, control, determination, and setting. The control means 30 operates according to a control program stored in the ROM 31. The RAM 32 is used as a buffer for recording data, a work area for processing by the control means 30, and a memory for temporarily storing data. The operation panel 33 operates under the control of the control means 30. The operation panel 33 includes an LCD panel, can perform various displays, and includes a keyboard for input. Various setting values can be input by the user, the status of the device can be displayed, and warnings can be issued.

  The carriage movement motor drive circuit 34 operates under the control of the control means 30 and drives a motor that moves the carriage. The carriage position detection sensor 35 is a sensor that detects the position of the carriage. The control means 30 acquires the output of the carriage position detection sensor 35, calculates it, and uses it for various controls. For example, the carriage position detection sensor 35 is configured to detect a scale of a linear scale arranged along a rail on which the carriage is movably fixed by a linear sensor. The position of the carriage can be calculated and acquired based on the sensor output. Based on this position, the control means 30 can control the movement of the carriage.

  That is, by knowing the position of the carriage, the position of the recording head fixed to the carriage is also known, and it is possible to control the ejection of ink from the recording head in accordance with the position of the carriage.

  The head drive circuit 36 is controlled by the control means 30. The recording head is operated via the head driving circuit 36. When a plurality of recording heads are mounted, the control unit 30 and the head drive circuit 36 can individually drive each recording head. The head drive circuit 36 generates ink ejection or non-ejection data and ejection timing signal for each recording head based on the information input from the control means 30, and outputs the data to the recording head to drive the recording head. This timing is calculated based on the carriage position acquired by the carriage position detection sensor 35. Ink ejection and non-ejection can be controlled corresponding to each nozzle. When ink is ejected, an ON waveform is generated, and when ink is not ejected, an OFF waveform is generated and transferred to each recording head. The ejection timing is calculated according to the position of the carriage, and gives a signal to the recording head.

  From the carriage movement time and the position information obtained from the carriage position detection sensor 35, the carriage movement speed can be calculated. Normally, ink is ejected while the carriage moving speed is controlled to be constant. By setting the ink ejection timing to a constant period, the interval between dots to be recorded can be made constant. According to this ejection timing, printing can be performed for each dot in the carriage movement direction. Further, the discharge timing can be calculated more finely and used. The ejection timing is determined in advance so as to be optimal depending on the distance between the recording medium and the nozzle surface of the recording head. The relationship between the distance and the discharge timing is stored in the ROM 31 in advance, and the control unit 30 acquires the distance as necessary, and uses the relationship stored in the ROM 31 according to the acquired distance to discharge timing. To decide. A distance sensor (not shown) connected to the control means 30 is used. In the ROM 31, stepwise distances and discharge timing data corresponding to the distances are stored in association with each other.

  The recording medium transport unit 37 operates under the control of the control unit 30. The recording medium transport unit 37 includes a transport roller and a motor that drives the transport roller. The recording medium is conveyed by operating the conveying roller. The recording medium can be transported in the transport direction with a feed accuracy of at least one dot unit. Further fine control may be performed. Depending on the type of the recording medium, the paper is deformed while being sandwiched between the transport rollers, and transported in a deformed state, thereby causing a transport error and requiring correction. The recording medium can be transported preferably at a distance of 0.01 to 0.1 dots.

  FIG. 4 is a diagram for explaining an image recording operation. The control unit 30 controls elements such as the recording medium transport unit 37, the carriage detection sensor 35, and the head drive circuit 36, and records an image on the recording medium. The recording head 40 is disposed upstream of the recording head 41 in the conveyance direction of the recording medium. In order to simplify the description, 13 nozzles of each recording head 40 and 41 will be described. Further, a case where it is divided into four blocks will be described. This difference in nozzle arrangement is a distance half the pitch between nozzles. That is, each nozzle of the recording head 41 is arranged between each nozzle of the recording head 40 in the recording medium conveyance direction. Thereby, it is possible to record at a double resolution by two recording heads in one scan. That is, 180 dpi for one head, but 360 dpi for two heads.

  Here, a description will be given using an example in which four scans, that is, four-pass printing, are performed to complete an image with a resolution of 720 dpi. The recording head 40 will be described as a recording head belonging to the first group, and the recording head 41 will be described as a recording head belonging to the second group. For example, the first group can be divided into cyan and yellow, and the second group can be divided into magenta and black. It is preferable because a suitable image quality can be obtained by separating dark and warm colors.

  Among the blocks of the recording head 40, the first block 44 on the most upstream side in the conveyance direction of the recording medium includes the nozzle 42 on the most upstream side, and other blocks such as the second block 45, the third block 46, and the fourth block. One nozzle more than the block 47 is arranged. Further, the recording head 41 includes the nozzles 43 of the most downstream block, and one more nozzle is arranged than the other blocks.

  An operation for completing an image of an area corresponding to the width of one block in four scans will be described. By explaining the operations from the first scan to the sixth scan, an operation for completing an image of three regions of the region corresponding to the width of one block will be explained. By repeating the same operation, the entire image can be recorded. In the example shown in the figure, one area is 12 lines continuous in the sub-scanning direction because the number of nozzles included in one block to which nozzles are not added is three.

  First, in the first scan, the first recording of the first area is performed by the most upstream block of the recording head 40 and the most upstream block of the recording head 41. At that time, recording is performed without using the nozzle 42. In addition, recording is always performed with at least one dot interval without controlling to continuously record dots in the main scanning direction. In FIG. 4, dots recorded by the recording head 40 are indicated by white circles, dots recorded by the recording head 41 are indicated by black circles, and dots recorded by the previous scan or previous scan are indicated by gray circles.

  In addition, dots formed on the same line can be formed by using other recording heads in the same group between the dots formed at a distance. Dots between recording heads in the same group are preferable because dots can be prevented from being formed at the same pixel position in the same scan. When two dots are formed at the same pixel position in the same scan, the bulk of the ink increases and the drying property deteriorates. Therefore, control is performed so that dots are formed at the same pixel position not in the same scan but in different scans.

  Next, the recording medium is conveyed until the carriage passes through the recording area, turns back, and reaches the recording area again, that is, when switching between the forward scanning and the backward scanning. At this time, a distance of 1 dot is added to the reference carry amount and carried. Accordingly, dots are formed on the line adjacent to the upstream side of the previously recorded dots by the head nozzle of the second block from the upstream side of the recording head 41. The reference transport amount is a distance between the head nozzles of each block. For example, in FIG. 4, the conveyance amount corresponds to 12 dots. When transporting for the reference transport amount, dots overlap on the previously recorded line.

  Next, when switching between forward scanning and backward scanning, the recording medium is conveyed. At this time, the transport is performed by subtracting the distance of 2 dots from the reference transport amount. Thus, dots are formed on the lines recorded along the main scanning direction of the previously recorded dots by the head nozzle of the third block from the upstream of the recording head 41. At this time, the first scan in the third area is performed, and dots are formed by the nozzles 42.

  Next, when switching between forward scanning and backward scanning, the recording medium is conveyed. At this time, the distance for one dot is subtracted from the reference transport amount. Thus, dots are formed on the line adjacent to the downstream side of the previously recorded dots by the head nozzle of the fourth block from the upstream side of the recording head 41.

  Next, when switching between forward scanning and backward scanning, the recording medium is conveyed. At this time, the distance is conveyed by adding a distance of 2 dots to the reference conveyance amount. As a result, the image in the second region is completed by the most downstream block of the recording heads 40 and 41.

  Next, when switching between forward scanning and backward scanning, the recording medium is conveyed. At this time, a distance of 1 dot is added to the reference carry amount and carried. As a result, the image in the third region is completed by the most downstream block of the recording heads 40 and 41.

  Since at least one dot is separated between the nozzles in the transport direction of the two recording heads, dots cannot be formed at the adjacent positions of the dots in the sub-scanning direction in the same scanning. The control means performs the control not to record adjacent dots in the main scanning direction for each pass, that is, the control to record with a gap of one dot or more between the dots, so that the adjacent dots in the same scan are recorded. You can prevent recording. In addition, by placing a block with one nozzle on the most upstream side, it is possible to continuously record without forming dots at adjacent positions in the same scan. Further, since there is a gap of 3 dots between the nozzles, it is necessary to carry out the conveyance control to compensate for this, and it is necessary to carry the necessary amount in units of one dot.

  In addition, the print heads belonging to the same group use a print mask so that the two colors do not overlap. For example, if one side is ejected, data that is not ejected from one side is used in a print mask, and ink ejection processing is performed accordingly to prevent dot overlap.

  In one scan, it is possible to prevent dots from being combined in a state where the ink is not dry and has fluidity. As a result, poor drying due to an increase in the volume of ink in an area of 1 dot can be suppressed as much as possible, and a high-quality image can be obtained by arranging dots at a desired position, that is, an ideal position. it can. In addition, since each dot is interspersed and can be made uniform as described above, variation in the amount of energy applied to one dot can be suppressed, and waste can be avoided. The time for drying or curing the dots can be expected to be smaller than the conventional time even if the energy is the same. High-speed printing is possible while maintaining high image quality.

  In addition, although a method in which dots are not continuously formed in the main scanning direction is preferable, a method of forming dots by forming a plurality of dots and separating a plurality of dots can be considered. For example, there is a method in which three dots are formed continuously, three dots are formed, and dots are formed by another recording head in the same group at the positions. Since dots are formed continuously, the time interval for forming dots is short, so dots are formed in the adjacent pixels without the dots being dried. Therefore, there is a possibility that the possibility of dot combination is slightly increased.

  Ink that contains 50% by weight or more of water in the main solvent, that is, water containing 50% by weight or more of the main solvent, is highly likely to be combined when dots are adjacent in the same scan, and control is not performed to form dots at adjacent positions. Is preferred.

  FIG. 5 is a diagram illustrating an overview of the entire printer. The ink jet printer 50 records an image by ejecting ink onto a recording medium adsorbed on the platen 54 while reciprocating the carriage 53 over the platen 54. The platen 54 is a flat plate, pores are formed in the plate, a suction chamber is arranged on the back side, air is drawn in, and the recording medium is adsorbed by the force and supported flat. A heater is disposed on the back surface of the platen 54. The recording medium on the platen 54 is heated by this heater. The drying of the ink is promoted by this heating. A paper guide 55 is disposed on the downstream side of the platen 54 in the sub-scanning direction, and heats the discharged recording medium to promote ink fixing. In addition, a fan heater 51 is provided at a position facing the paper guide 55 and promotes fixing of ink by heating or blowing.

  A plurality of conveying rollers 52 are arranged along the longitudinal direction of the platen 54 to convey the recording medium. The recording medium is conveyed in the direction of the platen 54 by the conveyance roller 52, and an image is recorded by ejecting ink from a recording head mounted thereon while the carriage 53 scans above the recording medium supported by the platen 54. .

  The present invention can be applied to an ink jet printer.

1 C head 2 M head 3 Y head 4 K head 5 Nozzle 10 Dot 30 Control means 31 ROM
32 RAM
33 Operation Panel 34 Carriage Movement Motor Drive Circuit 35 Carriage Position Detection Sensor 36 Head Drive Circuit 37 Recording Medium Conveying Means 40 Recording Head 41 Recording Head 42 Nozzle 50 Inkjet Printer 52 Conveying Roller 53 Carriage 54 Platen

Claims (4)

A plurality of nozzles, and a recording head that discharges ink from the nozzles to a recording medium;
A platen that supports the recording medium;
Conveying means for conveying the recording medium;
A carriage mounted with the recording head and reciprocatingly scanned in a main scanning direction intersecting a conveyance direction of the recording medium;
Control means for controlling the ejection of ink from the nozzles of the recording head,
The nozzles of the recording head are arranged at equal intervals in a direction along the conveyance direction of the recording medium,
A plurality of the recording heads are mounted on the carriage according to the color of the ink,
The recording head is divided into a plurality of blocks, and an image is recorded in a predetermined area by recording by scanning a number of passes corresponding to the number of divisions of the block while changing the block for each scanning. In an inkjet printer,
The recording head is divided into two groups, a first group and a second group, arranged on the carriage, and the row of nozzles that eject the ink of the recording head belonging to the first group is the second group. Is arranged with a deviation of half the pitch between the nozzles in the upstream direction of the transport direction with respect to the row of nozzles that eject the ink belonging to
At least one dot is separated between lines to be recorded on the recording medium in one scan by the nozzles of the recording head belonging to the first group and the nozzles belonging to the second group;
The most upstream block in the transport direction of the recording heads belonging to the first group has one more nozzle than the number of nozzles included in the downstream block,
The ink jet printer according to claim 1, wherein the control unit performs control so that the recording heads belonging to the same group do not discharge the ink to the same dot position in one scan.   2. The control unit according to claim 1, wherein each of the recording heads controls the ejection of the ink with an interval of one dot between the dots in the main scanning direction in one scan. The inkjet printer as described in.   The recording heads included in the first group are controlled by a print mask whether or not the ink is ejected from the nozzles, and the print mask is different at the same position in the same scan. The inkjet printer according to claim 1, wherein non-ejection data is arranged for the ink from a head.   4. The ink jet printer according to claim 1, wherein the main solvent of the ink is water, and the solvent of the ink contains 50% by weight or more of the water. 5.

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