PRINTING DEVICE AND PRINTING METHOD

A printing device includes a control unit, and the print head including a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row arrayed along a second direction. A test pattern is printed by a main scan and a sub-scan, and the control unit prints the test pattern so as to include a first line group, a second line group, a third line group, and a fourth line group, and prints the test pattern so that the first line group and the third line group and the second line group and the fourth line group are shifted from each other by a first distance shorter than the nozzle interval in the first direction, and the first line group and the third line group overlap and the second line group and the fourth line group overlap when viewed from the second direction.

The present application is based on, and claims priority from JP Application Serial Number 2023-042039, filed Mar. 16, 2023, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a printing device and a printing method for printing a test pattern.

2. Related Art

In an inkjet printer that performs printing using a print head having a nozzle row in which a plurality of nozzles configured to eject liquid are arranged, an ejection failure may occur for each nozzle. The ejection failure includes, in addition to dot omission in which the liquid dot is not ejected from the nozzle due to clogging of the nozzle, a landing position shift in which the landing position of the dot is not ideal, dot thickening or dot thinning in which the ejected dot is too large or too small, and the like.

In addition, a technique is disclosed in which a test pattern for identifying an ejection port in which an ejection failure has occurred is recorded by a recording head, and an image data obtained by reading the test pattern with a reading device is analyzed to specify the ejection port in which the ejection failure has occurred (see Japanese Patent Application Laid-Open No. 2016-221835). According to the test pattern of JP-A- 2016-221835, each linear image recorded by each of the plurality of nozzles in the nozzle row is recorded side by side at the nozzle interval in the conveyance direction of a recording medium.

At the time of reading a document on which a test pattern is recorded by a reading device, a conveyance error such as a variation in a conveyance speed of the document occurs, and a reading error may appear in a thickness or an interval of a line image in obtained image data. Therefore, when analyzing the image data, the ejection failure cannot be accurately detected unless the image data is subjected to correction for removing such a reading error and then analyzed.

However, in the known test pattern, no pattern is recorded between the nozzles. Therefore, even if image data obtained by reading a test pattern is obtained, the presence or absence of a reading error is unknown for such a region where nothing is recorded in correspondence with a space between the nozzles, and the correction described above is difficult to appropriately perform on the image data.

In addition, in the known test pattern, in a case where the document on which the test pattern is recorded is read in an inclined state, it is often difficult to evaluate the thickness of the line image in comparison with other line images, and thus, it is difficult to accurately detect the thickening and thinning of the dot.

In view of such a problem, it is necessary to print a test pattern that contributes to improvement of detection accuracy of ejection failure.

SUMMARY

A printing device includes a print head including a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row which are nozzle rows including a plurality of nozzles configured to eject liquid and arrayed in a first direction at a predetermined nozzle interval, and are arranged along a second direction intersecting the first direction, a carriage provided with the print head and configured to reciprocate along the second direction, a moving unit configured to perform relative movement between a medium and the print head in the first direction, and a control unit configured to cause the print head to eject liquid from the plurality of nozzles onto the medium to print a test pattern. The test pattern is printed by a main scan by the print head ejecting liquid from the plurality of nozzles along with the movement of the carriage along the second direction and a sub-scan that is the relative movement in the first direction, the control unit is configured to print the test pattern so as to include a first line group formed by the first nozzle row, a second line group formed by the second nozzle row, a third line group formed by the third nozzle row, and a fourth line group formed by the fourth nozzle row which are a line group including a plurality of lines formed by liquid ejection from each of the plurality of nozzles of the nozzle rows, and print the test pattern such that the first line group and the third line group and the second line group and the fourth line group are shifted from each other in the first direction by a first distance shorter than the nozzle interval, and the first line group and the third line group overlap and the second line group and the fourth line group overlap when viewed from the second direction.

In a printing method for printing a test pattern by causing a print head that includes nozzle rows including a plurality of nozzles configured to eject liquid and arrayed in a first direction at a predetermined nozzle interval, to eject liquid from the plurality of nozzles to a medium, the print head including a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row which are the nozzle rows and arranged along a second direction intersecting the first direction, the printing method includes a printing step of printing the test pattern by a main scan by the print head moving along the second direction and ejecting liquid from the plurality of nozzles and a sub-scan that is relative movement between the medium and the print head in the first direction. The printing step includes printing the test pattern so as to include a first line group formed by a first nozzle row, a second line group formed by a second nozzle row, a third line group formed by a third nozzle row, and a fourth line group formed by a fourth nozzle row which are a line group including a plurality of lines formed by liquid ejection from each of the plurality of nozzles of the nozzle rows, and printing the test pattern such that the first line group and the third line group and the second line group and the fourth line group are shifted from each other in the first direction by a first distance shorter than the nozzle interval, and the first line group and the third line group overlap and the second line group and the fourth line group overlap when viewed from the second direction.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the drawings. Note that each figure is merely illustrative for describing the present embodiment. Since the drawings are illustrative, proportions, shapes, and shading may not be precise, consistent, or may be partially omitted.

1. Device Configuration

FIG.1simply illustrates a configuration of a printing device10according to the present embodiment. The printing device10includes a control unit11, a display unit13, an operation accepting unit14, a communication IF15, a storage unit16, a conveying unit17, a carriage18, a print head19, and the like. IF is an abbreviation for interface. The control unit11is configured by including one or a plurality of ICs each having a CPU11aserving as a processor, a ROM11b, a RAM11c, and the like, other non-volatile memories, and the like.

In the control unit11, the processor, that is, the CPU11a, executes arithmetic processing according to one or more programs12stored in the ROM11b, other memories, or the like using the RAM11cor the like as a work area, thereby controlling the printing device10. Also, the processor is not limited to a single CPU, and a configuration in which the processing is performed by a hardware circuit such as a plurality of CPUs, an ASIC, or the like may be adopted, or a configuration in which a CPU and a hardware circuit cooperate to perform the processing may be adopted.

The display unit13is a means that displays visual information and is configured by, for example, a liquid crystal display, an organic EL display, or the like. The display unit13may have a configuration including a display and a drive circuit for driving the display. The operation accepting unit14is a means that accepts an operation performed by a user and is realized by, for example, a physical button, a touch panel, a mouse, a keyboard, or the like. Of course, the touch panel may be realized as one function of the display unit13.

The display unit13and the operation accepting unit14may be part of the configuration of the printing device10, or may be peripheral devices externally attached to the printing device10. The communication IF15is a general term for one or a plurality of IFs for connecting the printing device10to an external device in a wired or wireless manner in accordance with a predetermined communication protocol including known communication standards. The external device is, for example, various communication devices such as a personal computer, a server, a smartphone, and a tablet terminal.

The storage unit16is configured by, for example, a storage device such as a hard disk drive, or a solid state drive. The storage unit16may be part of the memory included in the control unit11. The storage unit16may be understood as part of the control unit11. The storage unit16stores various types of information required for controlling the printing device10.

The conveying unit17is a means that convey a medium in a predetermined “conveyance direction”, and includes a rotating roller and a motor for rotating the roller. Upstream and downstream in the conveyance direction are hereinafter simply referred to as upstream and downstream. The medium is typically paper, but in addition to paper, various materials that can be a target of printing with a liquid, such as fabric and film, can be adopted as the medium. The conveyance direction is also referred to as a “sub-scanning direction”. The conveying unit17may be a mechanism that conveys the medium on a belt or a pallet. The sub-scanning direction corresponds to a “first direction”, and the conveying unit17corresponds to a specific example of a “moving unit” that performs relative movement of the medium and the print head19in the first direction. This relative movement is also referred to as “sub-scan”.

The carriage18is a mechanism that can reciprocate in a predetermined “main scanning direction” upon receiving power from a carriage motor (not illustrated). The main scanning direction and the sub-scanning direction intersect each other. The intersection between the main scanning direction and the sub-scanning direction may be understood as being orthogonal or substantially orthogonal. The main scanning direction corresponds to a “second direction”. The print head19is mounted on the carriage18. Accordingly, the print head19reciprocates along the main scanning direction together with the carriage18. Movement of the print head19and movement of the carriage18are synonymous.

The print head19has a plurality of nozzles20for ejecting liquid dots. The dots are droplets. In the following description, the liquid is assumed to be ink, but the print head19can also eject liquid other than ink. The print head19performs ink ejection based on print data for printing an image. As is known, the control unit11controls application of drive signals to drive elements (not illustrated) included in each of the nozzles20in accordance with the print data to cause each of the nozzles20to eject or not to eject the dots, thereby printing the image on the medium. The print head19can eject each color ink such as cyan (C) ink, magenta (M) ink, yellow (Y) ink, and black (K) ink. Of course, the ink ejected by the print head19is not limited to CMYK.

FIG.2simply illustrates a relationship between a medium30and the print head19from above. The print head19mounted on the carriage18performs, together with the carriage18, a forward movement that is a movement from one end to the other end in a main scanning direction D2and a backward movement that is a movement from the other end to the one end.FIG.2illustrates an example of arrangement of the nozzles20on a nozzle surface23. The nozzle surface23is a lower surface of the print head19and is a surface facing the medium30. Individual small circles in the nozzle surface23represent individual nozzles20.

The print head19includes nozzle rows26for each ink color in a configuration in which the print head19receives supply of ink of each color from a liquid holding means (not illustrated) referred to as ink cartridges, ink tanks, or the like and ejects them through the nozzles20.FIG.2is an example of the print head19that ejects CMYK inks. The nozzle row26including the nozzles20that eject C ink is a nozzle row26C. Similarly, the nozzle row26including the nozzles20that eject M ink is a nozzle row26M, the nozzle row26including the nozzles20that eject Y ink is a nozzle row26Y, and the nozzle row26including the nozzles20that eject K ink is a nozzle row26K.

In the example ofFIG.2, the nozzle rows26C,26M,26Y, and26K are arranged along the main scanning direction D2. Also, the plurality of nozzle rows26for each color are arranged at the same position in a sub-scanning direction D1. One nozzle row26includes a plurality of nozzles20in which a “nozzle interval”, which is an interval between the nozzles20in the sub-scanning direction D1, is constant or substantially constant.

The direction in which the plurality of nozzles20forming the nozzle row26are arranged is also referred to as a “nozzle arranging direction”. In the example ofFIG.2, the nozzle arranging direction is parallel to the sub-scanning direction D1. Accordingly, it can be said that the plurality of nozzles20forming the nozzle row26are arranged in the sub-scanning direction D1. In such a configuration, the nozzle arranging direction is orthogonal to the main scanning direction D2. However, the nozzle arranging direction may be oblique with respect to the sub-scanning direction D1instead of parallel thereto. Regardless of whether or not the nozzle arranging direction is parallel to the sub-scanning direction D1, it can be said that the nozzle arranging direction intersects the main scanning direction D2, and it can be said that the plurality of nozzles20forming the nozzle row26are arranged at a predetermined nozzle interval in the sub-scanning direction D1. Accordingly, in the present embodiment, even if the nozzle arranging direction is oblique to the sub-scanning direction D1, the plurality of nozzles20forming the nozzle row26may be interpreted as also being arranged in the sub-scanning direction D1.

The operation in which the print head19ejects the ink together with the movement of the carriage18along the main scanning direction D2is referred to as “main scan” or “pass”. In addition, an operation in which the conveying unit17conveys the medium30downstream by a predetermined distance between passes is referred to as “paper feeding”. The paper feeding is a kind of sub-scan. By controlling the print head19, the carriage18, and the conveying unit17in this manner, the control unit11executes passing and paper feeding to print a two-dimensional image on the medium30. In the present embodiment, the control unit11causes the print head19to eject liquid from the nozzle20to the medium30to print a test pattern. The test pattern is a type of image printed in this manner.

The print head19has at least four nozzle rows26. In order to identify certain four nozzle rows26included in the print head19, they are also referred to as a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row, respectively. For example, the nozzle row26C may be referred to as a first nozzle row, the nozzle row26M may be referred to as a second nozzle row, the nozzle row26Y may be referred to as a third nozzle row, and the nozzle row26K may be referred to as a fourth nozzle row. The first nozzle row, the second nozzle row, the third nozzle row, and the fourth nozzle row may not be arranged in this order in the main scanning direction D2. Thus, for example, the nozzle row26M may be referred to as a first nozzle row, the nozzle row26Y may be referred to as a second nozzle row, the nozzle row26C may be referred to as a third nozzle row, and the nozzle row26K may be referred to as a fourth nozzle row. That is, any correspondence relationship may be adopted as the correspondence relationship among the first nozzle row, the second nozzle row, the third nozzle row, and the fourth nozzle row and the nozzle rows26C,26M,26Y, and26K.

The sub-scan may not be performed by the conveying unit17conveying the medium30, but instead may be performed by the print head19moving upstream in parallel with the sub-scanning direction D1. That is, the printing device10may have a mechanism that supports the carriage18on which the print head19is mounted so as to be able to reciprocate not only in the main scanning direction D2but also in the sub-scanning direction D1, and may execute printing on the medium30by the print head19two-dimensionally moving on the stationary medium30. In this case, a mechanism that moves the carriage18along the sub-scanning direction D1corresponds to a moving unit that performs relative movement between the media30and the print head19in the first direction.

The configuration of the printing device10illustrated inFIG.1may be realized by one printer, or may be realized by a plurality of devices communicably connected to each other. That is, the printing device10may be a printing system10in actuality. The printing system10includes, for example, a printing control device that functions as the control unit11and the storage unit16, and a printer that includes the conveying unit17, the carriage18, the print head19, and the like. A printing method according to the present embodiment is realized by such a printing device10or printing system10.

2. Test Pattern Printing

FIG.3is a flowchart illustrating a printing step of a test pattern executed by the control unit11according to the program12. Although not illustrated in the flowchart, the control unit11acquires print data for printing the test pattern prior to the printing step of the test pattern. A test pattern image data that is image data expressing a test pattern is stored in advance, for example, in the storage unit16. Of course, the control unit11may acquire the test pattern image data from an external device through the communication IF15.

The control unit11appropriately performs various types of image processing such as resolution conversion process, color conversion process, and halftone process on the test pattern image data to generate print data. The print data here is assumed to be data in which ejection or non-ejection of dots is defined for each pixel and for each CMYK ink color. The ejection of dots is also referred to as dot-on, and non-ejection of dots is also referred to as dot-off.

In the printing step of a test pattern, the control unit11prints the test pattern on the medium30based on the print data for printing the test pattern. The control unit11schematically prints the test pattern such that the test pattern includes a first line group formed by a first nozzle row, a second line group formed by a second nozzle row, a third line group formed by a third nozzle row, and a fourth line group formed by a fourth nozzle row, which are line groups having a plurality of lines formed by liquid ejection from each nozzle20of the nozzle row26, the first line group and the third line group are shifted from the second line group and the fourth line group by a first distance shorter than the nozzle interval in the sub-scanning direction D1, and the first line group and the third line group overlap and the second line group and the fourth line group overlap when viewed from the main scanning direction D2.

In step S100, the control unit11controls the carriage18and the print head19to execute the first pass. In the present embodiment, a pass executed first of the two passes for printing a test pattern is referred to as a first pass, and a pass executed later is referred to as a second pass. In the first pass, control unit11causes ink to be ejected from the first nozzle row and the third nozzle row to form the first line group and the third line group on the medium30.

In step S110, the control unit11controls the moving unit, here, the conveying unit17to execute the sub-scan by the “first distance” shorter than the nozzle interval, that is, the paper feeding of the medium30.

In step S120, the control unit11controls the carriage18and the print head19to execute the second pass. For example, if the first pass is ink ejection accompanied by forward movement, the second pass is ink ejection accompanied by backward movement in a direction opposite to the first pass. Alternatively, in order to prevent the deviation between the printing by the forward movement and the printing by the backward movement of the carriage18from appearing in the test pattern, the first pass and the second pass may be unified to one of the forward movement and the backward movement.

In the second pass, the control unit11causes ink to be ejected from the second nozzle row and the fourth nozzle row to form the second line group and the fourth line group on the medium30. As described above, in the printing step of the test pattern, the test pattern is printed by two main scans and one sub-scan executed between the two main scans.

FIG.4shows an example of the test pattern40printed on the medium30as a result of steps S100to S120.FIG.4also shows how the positional relationship between the print head19and the medium30changes in the sub-scanning direction D1. Reference numeral NP indicates a nozzle interval NP between the nozzles20adjacent to each other in the sub-scanning direction D1, and reference numeral L indicates a predetermined first distance L shorter than the nozzle interval NP. As an example, the control unit11executes step S110with the first distance L as a distance of half of the nozzle interval NP.

“P1” shown in parentheses next to reference numeral19means the first pass P1of step S100, and “P2” means the second pass P2of step S120. That is,FIG.4illustrates that the positional relationship between the print head19and the medium30at the time of executing the first pass P1and the positional relationship between the print head19and the medium30at the time of executing the second pass P2are changed by the first distance L by the sub-scan of step S110.

InFIG.4, as an example, it is assumed that the nozzle row26C is a first nozzle row, the nozzle row26M is a second nozzle row, the nozzle row26Y is a third nozzle row, and the nozzle row26K is a fourth nozzle row. In the first pass P1, the first line group41is formed on the medium30by the nozzle row26C ejecting the C ink from each nozzle20, and the third line group43is formed on the medium30by the nozzle row26Y ejecting the Y ink from each nozzle20. The first line group41is a set of a plurality of lines41aformed by the C ink ejected by each nozzle20of the nozzle row26C. The third line group43is a set of a plurality of lines43aformed by the Y ink ejected by each nozzle20of the nozzle row26Y.

The lines41aand43aand lines42aand44ato be described later are line images each having a length component in the main scanning direction D2formed by one nozzle20. Such a line is suitably a solid line, but may be, for example, a broken line. The line may be referred to as a ruled line. Each line in the same line group is arranged in the sub-scanning direction D1at an interval corresponding to the nozzle interval NP, similarly to each nozzle20of the nozzle row26forming the line group. The first line group41and the third line group43are separated in the main scanning direction D2, and are formed at the same position in the sub-scanning direction D1. That is, the first line group41and the third line group43overlap when viewed from the main scanning direction D2. The term “overlapped” as used herein may include not only a state in which they are completely overlapped but also a state in which they are partially overlapped.

Similarly, in the second pass P2, the second line group42is formed on the medium30by the nozzle row26M ejecting the M ink from each nozzle20, and the fourth line group44is formed on the medium30by the nozzle row26K ejecting the K ink from each nozzle20. The second line group42is a set of a plurality of lines42aformed by the M ink ejected by each nozzle20of the nozzle row26M. The fourth line group44is a set of a plurality of lines44aformed by the K ink ejected by each nozzle20of the nozzle row26K. The second line group42and the fourth line group44are separated in the main scanning direction D2, and are formed at the same position in the sub-scanning direction D1. That is, the second line group42and the fourth line group44overlap when viewed from the main scanning direction D2.

As described above, the test pattern40includes the first line group41, the third line group43, the second line group42, and the fourth line group44. As is apparent fromFIG.4, the first line group41and the third line group43, and the second line group42and the fourth line group44are formed at positions shifted by the first distance L in the sub-scanning direction D1due to the sub-scan in step S110. Therefore, in the present embodiment, when the entire test pattern40is viewed, the line image is printed at a density twice the density of the nozzle20in the sub-scanning direction D1.

The first line group41, the third line group43, the second line group42, and the fourth line group44are arranged along the main scanning direction D2. In the example ofFIG.4, the first line group41, the second line group42, the third line group43, and the fourth line group44are arranged in this order from one end side to the other end side in the main scanning direction D2, but the arrangement order of the plurality of line groups in the main scanning direction D2is not necessarily as illustrated.

As can be seen fromFIG.4, the lines adjacent in the sub-scanning direction D1in the same line group are formed shifted in the main scanning direction D2. That is, in step S100and step S120, the control unit11controls the print head19to form the lines formed by the nozzles20adjacent to each other in the sub-scanning direction D1within the nozzle row26to be shifted in the main scanning direction D2. This makes it easy to grasp each line.

Although not illustrated inFIG.4, depending on the condition of each nozzle20when the test pattern40is printed, the ejection failure as described above appears in some of the lines41a,42a,43a, and44aon the medium30.

3. Description and Effect after Test Pattern Printing

FIG.5Aillustrates scan data50of a medium30on which a test pattern40has been printed. The user sets the medium30on which the test pattern40has been printed by the printing device10as a document in a scanner (not illustrated), and causes the medium30to be read. As a result, the scanner generates image data serving as a reading result of the test pattern40. The image data serving as the reading result is the scan data50.

A device that acquires the scan data50and processes or analyzes the scan data50is referred to as an image processing device for convenience. The entity of the image processing device may be a scanner, the printing device10, or the external device described above. The image processing device can detect ejection failure of each nozzle20by analyzing the scan data50. The analysis and evaluation of the scan data50may be visually performed by a user.

Also inFIG.5A, the same reference numerals as those inFIG.4are used for the test pattern40. The direction D3is a direction D3in which the document is conveyed when the scanner reads the document. Here, the scanner is assumed to be a so-called seed feed type product that reads a document by an image sensor while conveying the document. However, the scanner may be a so-called flatbed type product that reads a document held still on a document table. In this case, a moving direction of a reading means such as a sensor that moves with respect to the document in order to read the document may be regarded as the direction D3. In the following, the conveyance error of the document by the scanner may be read as such a movement error of the reading means. As can be understood fromFIGS.4and5A, the direction D3corresponds to the sub-scanning direction D1. The conveyance error and the movement error in the scanner are also collectively referred to as a reading error.

According toFIG.5A, when the scan data50is viewed along the direction D3, a plurality of lines exist at any position. As a specific example, all of the image regions51,52, and53at different positions in the direction D3indicated by a chain line in the scan data50include a plurality of lines having a common position in the sub-scanning direction D1at the time of printing. The image region51includes a certain line41aof the first line group41and a certain line43aof the third line group43. Similarly, the image region52includes one line42aof the second line group42and one line44aof the fourth line group44. The image region53includes one line41aof the first line group41and one line43aof the third line group43.

When the lines41aand43aincluded in the image region51are compared, it can be seen that both have the same thickness and are thick. The thickness of the line is a width in a direction intersecting the longitudinal direction of the line. Since the thickness of each line forming the test pattern40is known in design, the standard value of the thickness of each line forming the test pattern40is known in advance in the scan data50as well. Since the lines41aand43aincluded in the image region51are both thicker than the standard value, the image processing device determines that a conveyance error at the time of reading by the scanner appears in the image region51, and corrects the image region51. The correction on the image region51is a process of reducing in the direction D3so that the thicknesses of the lines41aand43abecome standard values. As a result, it is possible to avoid erroneous detection that the lines41aand43aincluded in the image region51are dot thickening.

When the lines41aand43aincluded in the image region53are compared, it can be seen that both have the same thickness and are thin. Since the lines41aand43aincluded in the image region53are both thinner than the standard value, the image processing device determines that a conveyance error at the time of reading by the scanner appears in the image region53, and corrects the image region53. The correction on the image region53is a process of enlarging in the direction D3so that the thicknesses of the lines41aand43abecome standard values. As a result, it is possible to avoid erroneous detection that the lines41aand43aincluded in the image region53are dot thinning.

Comparing the lines42aand44aincluded in the image region52, the line42ahas a standard thickness, but the line44ais thin. As described above, in a case where only some lines are thinner or thicker than the standard value when comparing the lines having substantially the same position in the direction D3, the ejection failure of the nozzle20is recognized. That is, the image processing device can determine that the cause of the thin line44aincluded in the image region52is not the conveyance error at the time of reading but is the defect of the nozzle20used to form the line44a, and thus, does not perform correction on the image region52.

The image processing device can accurately detect the ejection failure of the nozzle20by analyzing and evaluating the scan data50after performing the necessary correction on the scan data50to remove the reading error.

FIG.6Aillustrates scan data6of a medium on which a known test pattern5is printed. The view ofFIG.6Ais the same as that ofFIG.5A. Typically, the test pattern5is printed on the medium by ejecting ink from each nozzle20of each nozzle row26by one pass of the print head19as illustrated inFIG.2. In the test pattern5, as can be seen from the scan data6, the plurality of line groups1,2,3, and4corresponding to the plurality of nozzle rows26are arranged in correspondence with the main scanning direction D2, and the plurality of line groups1,2,3, and4are not shifted from each other in the sub-scanning direction D1. Each of the line groups1,2,3,4is configured by a plurality of lines1a,2a,3a, and4a. The plurality of lines1aforming the line group1, the plurality of lines2aforming the line group2, the plurality of lines3aforming the line group3, and the plurality of lines4aforming the line group4are arranged at intervals corresponding to the nozzle intervals NP in the sub-scanning direction D1. Therefore, in the test pattern5, a region where nothing is printed is generated in the sub-scanning direction D1.

The region7in the scan data6is one of the reading results corresponding to a region where nothing is printed in the sub-scanning direction D1. The width of the region7in the direction D3is thicker than the width of the region between the other lines of the scan data6in the direction D3. However, since no pattern is formed in the region7, evaluation is impossible. That is, it is not possible to determine whether the width of the region7is increased due to a conveyance error at the time of reading of the test pattern5by the scanner or the width of the region7is increased due to an ejection failure of the nozzle20such as a dot landing position shift or dot thinning. Therefore, correct correction cannot be performed on the scan data6including the region7, and it is difficult to improve the accuracy of detecting the ejection failure of the nozzle20from the scan data6.

To solve such a problem, according to the present embodiment, as illustrated inFIGS.4and5A, a region where nothing is printed is not generated in the sub-scanning direction D1in the test pattern40, or is hardly generated as compared with the related art. Therefore, the necessity of correction of the scan data50can be determined based on the comparison between the lines belonging to different line groups as described above, and the scan data50can be appropriately corrected.

FIG.6Billustrates scan data6of a medium on which a known test pattern5is printed. However,FIG.6Billustrates an example of the scan data6obtained when the document is conveyed in an inclined state at the time of reading by the scanner. Since the test pattern5has a low line forming frequency in the sub-scanning direction D1, when the document is inclined during conveyance at the time of reading, a state in which lines having a common position in the direction D3cannot be compared easily occurs in the scan data6. For example, the region8in the scan data6only includes one line4aforming the line group4. Therefore, there is no comparison target for the line4ain the region8, and it is not possible to determine whether ejection failure such as dot thickening has occurred or the influence of the conveyance error has appeared in the region8by viewing the line4a.

On the other hand,FIG.5Billustrates an example of the scan data50of the medium30on which the test pattern40is printed, which is the scan data50obtained when the document is conveyed in an inclined state at the time of reading by the scanner. In the test pattern40of the present embodiment, since the line forming frequency in the sub-scanning direction D1is higher than in the related art, even if the document is inclined during conveyance at the time of reading, a state in which lines having a common position in the direction D3cannot be compared with each other is less likely to occur in the scan data50. For example, the image region54at a certain position in the direction D3substantially includes one line41aforming the first line group41and one line44aforming the fourth line group44. Therefore, by comparing these two lines41aand44a, it is possible to determine whether ejection failure such as dot thickening or dot thinning has occurred in one of the lines or whether the influence of the conveyance error has appeared in the region54. As described above, it can be said that the test pattern40improves the detection accuracy of the ejection failure of the nozzle20as compared with the related art even when the document is inclined during conveyance at the time of reading.

As described above, according to the present embodiment, the printing device10includes the print head19in which the first nozzle row, the second nozzle row, the third nozzle row, and the fourth nozzle row, which are the nozzle rows26in which the plurality of nozzles20that eject liquid are arranged in the first direction at the predetermined nozzle interval NP, are arranged along the second direction intersecting the first direction, the carriage18on which the print head19is mounted and configured to reciprocate along the second direction, the moving unit that performs relative movement between the medium30and the print head19in the first direction, and the control unit11that causes the print head19to eject liquid from the nozzle20to the medium30to print the test pattern40. The test pattern40is printed by main scan in which the print head19ejects liquid from the nozzle20along with the movement of the carriage18along the second direction, and sub-scan which is the relative movement in the first direction. The control unit11includes a first line group formed by a first nozzle row, a second line group formed by a second nozzle row, a third line group formed by a third nozzle row, and a fourth line group formed by a fourth nozzle row, which are line groups having a plurality of lines formed by liquid ejection from each of the nozzles20of the nozzle row26, and prints the test pattern40such that the first line group and the third line group, and the second line group and the fourth line group are shifted by a first distance L shorter than the nozzle interval NP in the first direction, and the first line group and the third line group overlap each other and the second line group and the fourth line group overlap each other when viewed from the second direction.

According to the above configuration, the test pattern40is printed such that the first line group and the third line group are shifted from the second line group and the fourth line group by the first distance L in the first direction, and the first line group and the third line group overlap each other and the second line group and the fourth line group overlap each other when viewed from the second direction. Therefore, as compared with the known test pattern, the forming frequency of the lines configuring the test pattern40in the first direction increases, and the lines can be compared at each position in the first direction. As a result, assuming that the printed test pattern40is read and the ejection failure of the nozzle20is detected based on the scan data, the test pattern40contributes to optimization of correction of the scan data and improvement of detection accuracy of the ejection failure.

According to the present embodiment, the control unit11may print the test pattern40with the first distance L as a distance of half of the nozzle interval NP.

According to the above configuration, the region where the line is not printed in the first direction can be minimized most efficiently.

However, the disclosure range of the present embodiment merely needs to be NP>L, and the disclosure range may not be narrowed to NP/2=L.

Furthermore, according to the present embodiment, the printing device10prints the test pattern40by two main scans and one sub-scan executed between the two main scans.

The test pattern40can be printed in four passes according to the number of line groups, for example, but according to the above configuration, the test pattern40is printed with the minimum pass number. As a result, it is possible to minimize the influence on the printing result due to the error at the time of printing such as the error of the printing position for each pass and the conveyance error of the medium30. Furthermore, the test pattern40can be printed in as short a time as possible.

Furthermore, according to the present embodiment, the control unit11may control the print head19to form the lines formed by the nozzles20adjacent to each other in the first direction within the nozzle row26to be shifted in the second direction.

According to the above configuration, since each line forming the test pattern40is formed to be shifted in each of the first direction and the second direction, it is easy to recognize each line.

However, the disclosure of the present embodiment also includes a mode in which the lines formed by the nozzles20belonging to the common nozzle row26and adjacent in the first direction are formed at the same position in the second direction.

Note that, in the scope of the claims, only some of the combinations of the claims are described. However, as a matter of course, the present embodiment includes various combinations of the plurality of dependent claims, as well as one-to-one combinations of the independent claims and the dependent claims.

In addition to the printing device10, the present embodiment discloses the printing method and the program12for executing the printing method in cooperation with a processor. That is, a printing method for printing a test pattern40by causing a print head19having a nozzle row26in which a plurality of nozzles20that eject liquid are arranged in a first direction at a predetermined nozzle interval NP to eject liquid from the nozzles20to a medium30, in which in the print head19, a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row, which are the nozzle rows26, are arranged along a second direction intersecting the first direction, the printing method includes a printing step of printing the test pattern40by main scan in which the print head19moving along the second direction ejects liquid from the nozzles20and sub-scan that is a relative movement between the medium30and the print head19in the first direction, and the printing step includes a first line group formed by a first nozzle row, a second line group formed by a second nozzle row, a third line group formed by a third nozzle row, and a fourth line group formed by a fourth nozzle row, which are line groups having a plurality of lines formed by liquid ejection from each nozzle of the nozzle row26, and print the test pattern40so that the first line group and the third line group are shifted from the second line group and the fourth line group by a first distance L shorter than the nozzle interval NP in the first direction, and the first line group and the third line group overlap each other and the second line group and the fourth line group overlap each other when viewed from the second direction.

5. Additional Description

In the print head19, n nozzle rows26including a first nozzle row, a second nozzle row, a third nozzle row, and a fourth nozzle row are arranged along the second direction. In other words, n may be 4 or an integer greater than 4. For example, if the print head19is a head that ejects each ink of light cyan and light magenta in addition to CMYK, the print head19includes a total of six nozzle rows26corresponding to six colors. In addition, the print head19may include each nozzle row26for ejecting various types of ink, for example, matte black, gray, orange, green, violet, and the like. Of course, the print head19may include two or more nozzle rows26for ink of one color. In the configuration in which the number of nozzle rows26is larger than 4, the nozzle rows26as shown inFIGS.2and4are merely added along the main scanning direction D2in the print head19, and thus illustration will be omitted.

In the printing step of the test pattern, in a case where the test pattern40having n line groups is printed by causing each of the n nozzle rows26to form the line group, the control unit11prints the test pattern40such that if n is an even number, n/2 line groups of the n line groups and the remaining line groups are shifted by the first distance L in the first direction, and prints the test pattern40such that if n is an odd number, n/2±1 line groups of the n line groups and the remaining line groups are shifted by the first distance L in the first direction.

FIG.7illustrates an example that differs fromFIG.4in the test pattern40printed on the medium30as a result of steps S100to S120. With respect toFIG.7, it is assumed that n=6 and the print head19includes a fifth nozzle row and a sixth nozzle row in addition to the first to fourth nozzle rows as the plurality of nozzle rows26. The first to fourth line groups41,42,43, and44are as described above. However, inFIG.7, a difference in color between line groups is not represented.

In the first pass of step S100, the control unit11forms the first line group41, the third line group43, and the fifth line group45on the medium30by causing each of the first nozzle row, the third nozzle row, and the fifth nozzle row to eject ink from each nozzle20. The fifth line group45is a set of a plurality of lines45aformed by each nozzle20of the fifth nozzle row ejecting ink. In the second pass of step S120after step S110, the control unit11causes each of the second nozzle row, the fourth nozzle row, and the sixth nozzle row to eject ink from each nozzle20to form the second line group42, the fourth line group44, and the sixth line group46on the medium30. The sixth line group46is a set of a plurality of lines46aformed by each nozzle20of the sixth nozzle row ejecting ink. When viewed from the main scanning direction D2, the test pattern40is printed such that the first line group, the third line group, and the fifth line group overlap each other, and the second line group, the fourth line group, and the sixth line group overlap each other.

Furthermore, it is assumed that n=5, and the print head19includes a fifth nozzle row in addition to the first to fourth nozzle rows as the plurality of nozzle rows26. In this case, for example, the control unit11may form the second line group42and the fourth line group44on the medium30by executing the same process as in the case of n=6 in the first pass of step S100and causing each of the second nozzle row and the fourth nozzle row to eject ink from each nozzle20in the second pass of step S120. The test pattern40when n=5 is a content obtained by simply eliminating the sixth line group46from the test pattern40ofFIG.7, and thus illustration will be omitted. Of course, when n=5, the control unit11may cause two line groups to be formed by the two nozzle rows26in the first pass of step S100, and may cause three line groups to be formed by the three nozzle rows26in the second pass of step S120.

In this manner, the control unit11brings the number of line groups as close as possible between the plurality of line groups including the first line group41and the third line group43and the plurality of line groups including the second line group42and the fourth line group44formed to be shifted by the first distance L in the sub-scanning direction D1. As a result, in the printed test pattern40, the same number of lines can be compared at any position in the sub-scanning direction D1, and the detection accuracy of the ejection failure of the nozzle20can be improved.

However, the disclosure of the present embodiment also includes a configuration in which the number of line groups is biased to one of a plurality of line groups including the first line group41and the third line group43and a plurality of line groups including the second line group42and the fourth line group44formed to be shifted by the first distance L in the sub-scanning direction D1. For example, when n=6, four line groups may be formed by the four nozzle rows26in the first pass, and two line groups may be formed by the remaining two nozzle rows26in the second pass.

The inclination of the test pattern described inFIGS.5B and6Bmay be understood as not the inclination caused by the conveyance when the scanner reads the document but the inclination caused by the conveyance by the conveying unit17when the printing device10prints the test pattern. That is, when the printing device10prints a test pattern on the medium30inclined with respect to the sub-scanning direction D1, and the scanner reads the medium30on which the test pattern is printed as a document while conveying the same, scan data representing the test pattern in a state inclined within a frame of a non-inclined rectangular document may be obtained.