Print data generating device, print data generating method, and image processing program for printing

Abstract

To suppress variation in ink discharge amounts in nozzle arrays communicating with each other through a common liquid chamber in a case in which printing is performed using a printing head having the nozzle arrays, and suppress deterioration in image quality of a printing image.SOLUTION: There is provided a printing data generating device 10, in which a printing head has a first nozzle array NC1 having a plurality of nozzles N1 to N5, and a second nozzle array NC2 having a plurality of nozzles N6 to N10, when each of the nozzle arrays NC1 and NC2 is arranged at an interval in a first direction and the nozzle arrays communicate each other through a common liquid chamber 200, generates printing data when an image is printed on a medium using the printing head, and has an image quality deterioration determination part 66 for determining whether ink discharge amounts of each of the nozzle arrays vary and image quality deteriorates, on ends 350R and 350L in the first direction in an image region of the image, and an image rotation processing part 68 for rotating the image data, for example, by a predetermined angle, and tilting the image data, when the image quality has deteriorated.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a print data generating device, a print data generating method, and a printing image processing program. [Background technology]

[0002] Patent Document 1 discloses a droplet ejection head including a plurality of nozzles that eject droplets, at least two nozzle rows formed by the plurality of nozzles, a plurality of pressure chambers each communicating with the plurality of nozzles, one or two common liquid chambers that supply liquid to the plurality of pressure chambers, and a damper that is provided in each of the common liquid chambers and forms at least one of a plurality of inner surfaces that define the common liquid chamber (

[0003] ,

[0044] ~

[0047] , Figure 5, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-273193 A Summary of the Invention [Problem to be solved by the invention]

[0004] As a result of investigations by the present inventors, the following points have become clear. In the following explanation, we will assume a print head equipped with first and second nozzle rows, which are arranged at a predetermined interval in a first direction (main scanning direction) and communicate with each other via a common liquid chamber, and each of the first and second nozzle rows is equipped with a plurality of nozzles (ink ejection orifices or liquid ejection orifices) arranged at intervals in a second direction (sub-scanning direction) that intersects with the first direction.

[0005] When printing begins, the print head is moved in a first direction (main scanning direction) and the first nozzle row enters the end of the image area closer to the scanning start end of the ink head and ink is ejected from the nozzles, and then the second nozzle row also enters that end and ink is ejected from the nozzles.

[0006] When the first nozzle row enters the edge of the image area, the first nozzle row suddenly changes from a state in which it does not eject ink to a state in which it ejects ink. For example, if the edge of the image area includes an area where ink is applied without gaps (solid image area), a large amount of ink is suddenly ejected, and this effect is propagated to the second nozzle row via the common liquid chamber.

[0007] Next, the second nozzle row enters the edge of the image area, and the second nozzle row also suddenly changes from a state in which it does not eject ink to a state in which it does eject ink. When a large amount of ink is suddenly ejected from the nozzles of the second nozzle row, ink tug-of-warping occurs in the common liquid chamber, the amount of ink supplied to the second nozzle row becomes insufficient, and the nozzles of the second nozzle row cannot eject the desired amount of ink, which may result in vertical streaks (which may also be called density unevenness that occurs in the arrangement direction of the nozzles in the nozzle row (in other words, the sub-scanning direction), and in which the desired density is not obtained).

[0008] When the print head reaches the center of the image area, the amount of ink ejected from the first and second nozzle rows stabilizes, reducing the likelihood of vertical streaks (uneven density).

[0009] As the print head moves further and approaches the end of the scan opposite the start of the scan, the first nozzle row leaves the image area, so ink ejection from the nozzles must be stopped just before that happens. As a result, the amount of ink ejected at the end of the image area closer to the end of the scan is suddenly reduced, which also affects the ink ejection from the second nozzle row. In other words, the amount of ink ejected from the second nozzle row becomes excessive, and vertical streaks (uneven density) may occur as in the above case.

[0010] In this way, a phenomenon in which the ink ejection amount of each nozzle row varies greatly is likely to occur at the end of the image area close to the start end of the print head scan in the first direction (main scanning direction) and at the end close to the end of the print head scan.

[0011] One possible solution to this problem is to appropriately adjust the density profile of the image to be printed (especially the density profile near the edges where fluctuations in the ink ejection amount are likely to occur) so as to prevent sudden changes in the amount of ink ejected. However, in this case, it is undeniable that the amount of ink ejected will be limited, and certain limitations on printing may occur.

[0012] The above-mentioned Patent Document 1 does not mention such a problem, nor does it mention any countermeasures against it.

[0013] One object of the present invention is to suppress fluctuations in the amount of ink ejected from nozzle rows in a print head that communicate with each other via a common liquid chamber, thereby suppressing deterioration in the quality of printed images.

[0014] Other objects of the present invention will become apparent to those skilled in the art by referring to the following exemplary aspects and best modes, as well as the accompanying drawings. [Means for solving the problem]

[0015] In order to facilitate an understanding of the outline of the present invention, embodiments according to the present invention will be exemplified below.

[0016] In an aspect according to the present invention, a print data generation device is a print head having a first nozzle row with a plurality of nozzles arranged side by side in a second direction intersecting a first direction, and a second nozzle row with a plurality of nozzles arranged side by side in the second direction, wherein the first and second nozzle rows are arranged at intervals in the first direction and communicate with each other via a common liquid chamber, the print data generation device generates print data for printing an image on a medium using the print head, the print data generation device having an image quality degradation determination unit that determines whether or not image quality degradation will occur due to fluctuations in the amount of ink ejection from the nozzles of the first and second nozzle rows at the ends of an image area of ​​the image in the first direction, and an image rotation processing unit that rotates and tilts the image data of the image to be printed by a predetermined angle or a calculated angle if it is determined that image quality degradation will occur.

[0017] According to an aspect of the present invention, prior to printing, it is determined whether or not a large fluctuation in the amount of ink ejected from the nozzles will occur at the edges of the image area of ​​the printed image, resulting in a degradation of the image quality of the printed image.If it is determined that a degradation of image quality will occur, the image data (e.g., the entire image data) is rotated to tilt the image by a predetermined angle (or an angle calculated each time taking into account the characteristics of the print head, the shape of the printed image, the ink used, etc.), thereby suppressing large fluctuations in the amount of ink ejected from the first and second nozzle rows at the edges. Therefore, even when using a print head (sub-ink head) equipped with first and second nozzle rows that communicate with each other, the occurrence of degradation in image quality such as vertical streaks (uneven density) can be effectively suppressed.

[0018] Those skilled in the art will easily understand that the exemplified embodiments according to the present invention can be further modified without departing from the spirit of the present invention. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing an example of the overall configuration of a printing system. [Diagram 2]FIG. 2 is a diagram showing an example of the internal configuration of a print data generating device (host computer) and a printing device (inkjet printer) in the printing system. [Diagram 3] FIG. 3(A) is a perspective plan view of the print head as viewed from above, and FIG. 3(B) is a perspective plan view of the first and second nozzle rows, which communicate via a common liquid chamber, as viewed from above. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the structure of the first and second nozzle arrays shown in FIG. [Diagram 5] FIG. 5 is a diagram showing the state in which the first nozzle row enters the edge of the image area of ​​the printed image (the first edge in the first direction that is close to the scanning start end of the print head) as the print head moves. [Figure 6] Figure 6 is a diagram showing the state in which, as the print head moves, the second nozzle row also enters the edge of the image area of ​​the printed image (the first edge in the first direction that is close to the scanning start end of the print head). [Figure 7] FIG. 7 is a diagram showing the effect of suppressing fluctuations in the ink ejection amount in the first nozzle row by rotating the entire image data (image area) of the print image. [Figure 8] FIG. 8 is a diagram showing the effect of suppressing fluctuations in the amount of ink ejected from the second nozzle row by rotating the entire image data (image area) of the print image. [Figure 9] 9A, 9B, and 9C are diagrams showing an example of an image area of ​​a print image on a medium. [Figure 10] FIG. 10 is a diagram showing nozzles that eject ink at the edge of the image area in each pass when multi-pass printing is performed on the image area shown in FIG. 9(A). [Figure 11] FIG. 11 is a diagram showing nozzles that eject ink at the edge of the image area in each pass when multi-pass printing is performed on the image area shown in FIG. 9(B). [Figure 12]FIG. 12 is a diagram showing nozzles that eject ink at the edge of the image area in each pass when multi-pass printing is performed on the image area shown in FIG. 9(C). [Figure 13] Figure 13 is a diagram showing nozzles that eject ink at the edge of an image area in each pass when multi-pass printing is performed on an image area obtained by rotating the image area shown in Figures 9(A) and 10 clockwise by a predetermined angle. [Figure 14] Figure 14 is a diagram showing nozzles that eject ink at the edge of an image area in each pass when multi-pass printing is performed on an image area obtained by rotating the image area shown in Figures 9(C) and 12 clockwise by a predetermined angle. [Figure 15] FIG. 15 is a flowchart showing the main processing steps in the print data generating method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The best mode described below is used to easily understand the present invention. Therefore, those skilled in the art should be aware that the present invention is not unduly limited by the mode described below.

[0021] In this specification, the term "inkjet printer" can include all printers that use printing methods using conventional inkjet technology, for example, continuous methods such as binary deflection methods or continuous deflection methods, thermal methods, or various on-demand methods such as piezoelectric methods.

[0022] In addition, "printer (inkjet printer)" can include 2D printers that print two-dimensional images and 3D printers (three-dimensional modeling devices) that create three-dimensional objects.

[0023] Furthermore, the term "ink" can be interpreted in a broad sense. For example, it can also be expressed as "liquid." For example, the term "inkjet printer" can also be expressed as "liquid ejection device."

[0024] (First embodiment) Please refer to Fig. 1. Fig. 1 is a diagram showing an example of the overall configuration of a printing system. The printing system 1 has first and second folders 37, 44, a print data generating device (host computer) 10 connected to each folder, a display unit 16 consisting of a liquid crystal display or the like connected to the print data generating device (host computer) 10, a keyboard 18 and a mouse 19 as an operation unit (input unit), and a printing device (printer) 50 connected to the print data generating device (host computer) 10 via a communication line L11. Here, an inkjet printer is used as the printing device 50.

[0025] The print data generating device (host computer) 10 is provided with a storage device (memory) 12. This storage device (memory) 12 holds a print image processing program 15 according to the present invention.

[0026] Furthermore, image data of a print image (print image data) 39 is held in the first folder 37. This image data is, for example, RGB data of a vector image.

[0027] The second folder 44 also holds an input profile 45 corresponding to the image data, and an output profile 47 corresponding to the printing device 50. Note that the output profile 47 may be specified by selecting one output profile that matches the printing conditions from among a plurality of output profiles.

[0028] Next, reference will be made to Fig. 2. Fig. 2 is a diagram showing an example of the internal configuration of a print data generating device (host computer) and a printing device (inkjet printer) in a printing system.

[0029] The print data generating device (host computer) 10 that constitutes the printing system 1 has an image data interface (I / F) 60 to which image data to be printed is input, an image data processing unit 62 that performs image processing on the input image data, and a print data output unit 78 that outputs the image data after image processing (in other words, the generated print data).

[0030] The image data processing unit 62 includes an ink ejection amount variation suppression unit 64 and a RIP (Raster Image Processor) 72 . The RIP 72 has a rasterization unit 71 (including an image data storage unit 73 that temporarily stores image data) that converts vector image data into raster image (pixel image) data, a color conversion unit 74 that has a color conversion function (for example, a function to convert RGB data into CMYK data), and an image correction unit 76 that has functions such as gradation correction. In this specification, the RIP 72 performs "RIP processing." "RIP processing" is interpreted in a broad sense, and in this specification, it is treated as including general image processing such as rasterization processing, color conversion processing, and gradation correction processing. When vector image data is input, the rasterizing unit 71 performs a rasterizing process to convert the vector image data into raster image data. The converted image data is temporarily stored (stored) in the image data storage unit 73. Furthermore, when a raster image (pixel image) is input, rasterization processing is not required, so the rasterization unit 71 only performs processing to temporarily accumulate (store) the input image data in the image data storage unit 73 (i.e., buffering processing of the image data).

[0031] The ink discharge amount variation suppression unit 64 has an image quality degradation determination unit 66 that determines whether or not image quality degradation will occur at the edge of the image area, and an image rotation processing unit 68 that rotates and tilts the image data, for example, as a whole, in order to suppress the image quality degradation when it is determined that image quality degradation will occur. The image rotation processing unit 68 may also include a rotation amount calculation unit 70 that calculates the amount of rotation as appropriate, taking into account the print head used, the shape and density of the printed image, the ink used, etc.

[0032] As described above, image data input from the image data interface (image data I / F) 60 is rasterized by the rasterization unit 71 as necessary, and temporarily stored in the image data storage unit 73. The stored image data (which is assumed to be copied image data here, with the original image data remaining in the image data storage unit 73) is supplied to the image quality degradation determination unit 66.

[0033] The image quality degradation determination unit 66 determines whether image quality degradation will occur, and if it is determined that image quality degradation will not occur, transmits the determination result to the RIP 72. In this case, the RIP 72 supplies the image data stored in the image data storage unit 73 to the color conversion unit 74.

[0034] On the other hand, when the image quality degradation determination unit 66 determines that image quality degradation will occur, image rotation processing unit 68 performs image rotation processing to suppress image quality degradation. In this case, the image rotation processing unit 68 acquires image data again from the image data interface (image data I / F) 60, performs rotation processing on the image data by a predetermined angle or a calculated angle, and supplies the image data after rotation processing to a rasterization unit 71.

[0035] The rasterizing unit 71 rasterizes the image data after the rotation process as necessary, and stores (in this case, overwrites and saves) it in the image data storage unit 73. Thereafter, the image data stored in the image data storage unit 73 is supplied to a color conversion unit 74.

[0036] Inkjet printer (printing device) 50 has a communications interface (I / F) 80, a control unit 82, a scanning system configuration 20 that scans (in other words, moves) a carriage 22 (mounting a print head 42) in a first direction (main scanning direction), a transport system configuration 30 that transports the medium in a second direction (sub-scanning direction) that intersects (e.g., perpendicular to) the first direction, and an ink ejection system configuration 40 that controls the ejection of ink (broadly speaking, liquid) from nozzles in a nozzle row mounted on the print head 42. The above configuration is merely an example, and the present invention is not limited to this configuration. For example, a configuration in which the carriage 22 moves in the main scanning direction and the sub-scanning direction may be adopted. Furthermore, a configuration in which the medium is moved in the main scanning direction and the sub-scanning direction may be adopted. Also, a configuration (line method) may be employed in which the carriage 22 does not move and the medium is transported in a direction intersecting (for example, perpendicular to) the direction in which the nozzles are arranged.

[0037] The control unit 82 has a scanning control unit 84 that controls the scanning (movement) of the carriage 22 in a first direction, a transport control unit 85 that controls the transport of the media in a second direction, and an ink ejection control unit 87 that controls the ejection of ink from the nozzles of the print head 42.

[0038] The scanning system 20 includes a carriage motor 21, a carriage 22, and a position detector 23 that detects the position of the carriage 22 in a first direction.

[0039] The transport system configuration 30 includes a transport motor 31, a transport roller 32, and a transport detector 33 that detects the transport amount of the medium in the second direction.

[0040] The ink ejection system 40 includes a print head drive unit 41 , a print head 42 , and an ink amount detection unit 43 .

[0041] The print head 42 ejects ink onto the medium based on print data supplied from a print data generating device (host computer) 10. The print head 42 is mounted on the carriage 22.

[0042] The carriage motor 21, the transport motor 31, and the print head drive unit 41 make up a drive unit 86. The position detection unit 23, the transport detection unit 33, and the ink amount detection unit 43 make up a detection unit 88. The detection result (detection signal) of the detection unit 88 is fed back to the control unit 82.

[0043] Next, reference is made to Figure 3. Figure 3(A) is a perspective plan view of the print head as viewed from above, and Figure 3(B) is a perspective plan view of the first and second nozzle rows, which communicate via a common liquid chamber, as viewed from above.

[0044] In the following description, the first direction (main scanning direction) is defined as the X direction, the second direction (sub-scanning direction) that intersects with (for example, is perpendicular to) the first direction is defined as the Y direction, and the direction perpendicular to each of the X and Y directions (the up-down direction) is defined as the Z direction.

[0045] Furthermore, if it is assumed that the media is moved (transported) along the second direction, the direction from which the media is transported can be referred to as “upstream,” and the direction to which the media is transported can be referred to as “downstream.” In other words, when the media is moved relative to the print head along the second direction, the “source” direction of the media can be referred to as the “upstream side (+Y),” and the “destination” direction can be referred to as the “downstream side (-Y).”

[0046] In FIG. 3A, print head (ink head) 42 has sub-ink heads 102, 104, 106, and 108 that eject color inks of C (cyan), M (magenta), Y (yellow), and K (black).

[0047] The arrangement of nozzles (ink ejection ports) in each sub-ink head is the same. In the following explanation, the sub-ink head 102 will be used as an example.

[0048] The sub-ink head 102 has first and second nozzle rows NC1 and NC2 that are arranged at an interval in a first direction (X direction).

[0049] Each of the nozzle arrays NC1, NC2 actually has a large number of nozzles, but for ease of explanation, in FIG. 3, each nozzle array is simply depicted as having five nozzles.

[0050] Each of the first and second nozzle rows NC1 and NC2 includes a plurality of nozzles N1 to N5 and N6 to N10 that eject ink and are arranged in a second direction (Y direction) that intersects with the first direction (X direction).

[0051] Fig. 3(B) shows a specific example of the configuration of the first and second nozzle rows NC1 and NC2 in the sub-ink head 102 of Fig. 3(A). Note that in Fig. 3(B), only the nozzles N1 and N6 included in the area Z1 indicated by the dashed ellipse are labeled, and the other nozzles are not labeled.

[0052] As shown in the figure, the first and second nozzle rows NC1 and NC2 communicate with each other via a common liquid chamber 200 and flow paths 204, 206, 208, 210, 212, 214, 216, 218, 220, 222, and 224 through which ink flows. Note that ink is supplied to the common liquid chamber 200 via an ink supply port 202. Also, each of the flow paths may be included as a component of the common liquid chamber.

[0053] Next, reference is made to Fig. 4. Fig. 4 is a cross-sectional view showing an example of the structure of the first and second nozzle rows shown in Fig. 3(B). In Fig. 4, parts common to Fig. 3 are given the same reference numerals.

[0054] 4 shows a simplified schematic cross-sectional structure of region Z1 shown by the dashed ellipse in FIG. 3(B). The arrows in the figure show a typical example of the flow of ink inside the sub-ink head 102.

[0055] The sub-ink head 102 has a nozzle plate 240a for nozzle N1, a nozzle plate 240b for nozzle N6, flow path partitions 250a, 250b that form ink flow paths, actuators 270a, 270b formed of piezoelectric elements, vibration plates 260a, 260b that are driven to vibrate by the actuators 270a, 270b, and container walls 280a, 280b that form the container of the sub-ink head 102. Ink is ejected from each of the nozzles N1, N6 by pressure caused by the vibration of each of the vibration plates 260a, 260b.

[0056] As described above, the sub-ink head 102 has an ink supply port 202 , a common liquid chamber 200 , and flow paths 204 , 206 , and 208 .

[0057] Next, reference is made to Fig. 5. Fig. 5 is a diagram showing a state in which the first nozzle row enters the edge of the image area of ​​the printed image (the first edge in the first direction that is close to the scanning start edge of the print head) as the print head moves.

[0058] In A-1 of FIG. 5, a rectangular image area (area where an image is to be printed) 302 is shown on a medium 300.

[0059] Furthermore, end portions (end portions) 350R and 350L in the first direction (X direction) are set in the image region 302. A sand pattern is applied to each of the end portions 350R and 350L.

[0060] It should be noted that end 350R may be referred to as a first end, and end 350L may be referred to as a second end.

[0061] Furthermore, the ends 350R, 350L are appropriately set by the image quality degradation determination unit 66 shown in FIG. 2, taking into consideration the shape of the printed image, the nozzle arrangement in the print head, and the like.

[0062] Furthermore, as shown in A-1 of Figure 5, it is preferable to set the width L2 in the first direction (main scanning direction) of the first end 350R to be greater than or equal to the width L1 in the first direction (main scanning direction) of the first and second nozzle rows NC1 and NC2 in the sub-ink head 102 (the same applies to the second end).

[0063] Also, in the example of Figure 5, the image area 302 is an area (solid image area) where a solid image (particularly a dark solid image) is formed in which ink of the same color is applied without any gaps, at least at the first and second ends (end areas) 350R, 350L.

[0064] When printing starts, the print head 42 moves from the scanning start end P1 along the first direction (+X direction) toward the scanning end end P2. Accordingly, the sub-ink head 102 mounted on the print head 42 also moves in the same manner. In the following explanation, it is assumed that the sub-ink head 102 ejects ink.

[0065] In A-2 of FIG. 5, first, all of the nozzles N1 to N5 in the first nozzle row NC1 enter the first end 350R of the image area 302, and therefore ink is ejected from each of these nozzles N1 to N5 simultaneously.

[0066] Next, reference is made to Fig. 6. Fig. 6 is a diagram showing a state in which, as the print head moves, the second nozzle row also enters the end of the image area of ​​the print image (the first end in the first direction that is close to the scanning start end of the print head).

[0067] A-1 in FIG. 6 is a reprint of A-2 in FIG. 5. In A-2 in FIG. 6, as the print head 42 moves, the second nozzle row NC2 also enters the first end 350R. Therefore, ink is ejected simultaneously from all of the nozzles N6 to N10 in the second nozzle row NC2. That is, the ink ejection amount varies greatly in each of the first and second nozzle rows NC1 and NC2, and therefore, ink tug-of-war occurs in the first and second nozzle rows NC1 and NC2 that communicate via the common liquid chamber 200, causing ink shortage in the second nozzle row NC2, which may result in vertical streaks or the like.

[0068] In other words, at the first end 350R, the proportion of the number of nozzles (N1 to N10) from which ink is ejected to the total number of nozzles (10) in the first and second nozzle rows NC1 and NC2 (N1 to N5, N6 to N10) is 100%.

[0069] Here, if the first threshold is 80%, the calculated (detected) ratio is equal to or greater than the first threshold, and the image quality degradation determination unit 66 shown in FIG. 2 determines that image quality degradation will occur (in other words, there is a high possibility that image quality degradation will occur) at the first end 350R.

[0070] The same is true for the second end (end on the scanning end side) 350L (this example is not shown).

[0071] That is, when the sub-ink head 102 is within the second end 350L, in other words, immediately before the end of ink ejection, the amount of ink supplied to each nozzle N1 to N10 in the first nozzle row NC1 decreases rapidly. As a result, excessive ink supply occurs in each nozzle N6 to N10 in the second nozzle row NC2, and it can be determined that uneven density such as vertical streaks occurs (in other words, there is a high possibility that they will occur).

[0072] In the above case, the ratio of the number of nozzles (N1-N10) where ink ejection has been completed (in other words, where ink ejection is scheduled to be completed) to the total number of nozzles (10) obtained by adding up the numbers of nozzles (N1-N5, N6-N10) in the first and second nozzle rows NC1 and NC2 is 100%. Here, when the calculated (detected) ratio is compared with the above-mentioned first threshold value (80%), the calculated (detected) ratio is equal to or greater than the first threshold value. Therefore, the image quality degradation determination unit 66 shown previously in FIG. 2 determines that image quality degradation will occur (in other words, there is a high possibility that it will occur) at the second end portion 350L.

[0073] In this case, image processing is performed to rotate and tilt the image data in order to prevent deterioration in the image quality of the printed image. This point will be described below.

[0074] Next, reference is made to Fig. 7. Fig. 7 is a diagram showing the effect of suppressing fluctuations in the amount of ink ejected from the first nozzle row by rotating the entire image data (image area) of the print image.

[0075] A-1 and A-2 in Fig. 7 correspond to A-1 and A-2 in Fig. 5 described above. In A-1 in Fig. 7, the image area 302 is rotated by a predetermined angle (approximately 15° clockwise here) due to the rotation of the image data of the print image. In other words, the image area 302 is tilted by approximately 15° with respect to the Y direction (sub-scanning direction).

[0076] As a result, the shape of the first end 350R (the sandblasted area) is modified and its area is reduced compared to A-1 in FIG.

[0077] Therefore, as shown in A-2 of FIG. 7, when the first nozzle row NC1 enters the first end portion 350R, there are two nozzles, N2 and N3, from which ink is ejected. In A-2 of FIG. 7, the fluctuation in the ink ejection amount in the first nozzle row NC1 is sufficiently suppressed compared to A-2 of FIG.

[0078] Next, reference is made to Fig. 8. Fig. 8 is a diagram showing the effect of suppressing fluctuations in the amount of ink ejected from the second nozzle row by rotating the entire image data (image area) of the print image.

[0079] A-1 and A-2 in Fig. 8 correspond to A-1 and A-2 in Fig. 6 described above. A-1 in Fig. 8 is a reprint of A-2 in Fig. 7.

[0080] In A-2 of Fig. 8, when the second nozzle row NC2 enters the first end 350R, there are two nozzles, N6 and N7, from which ink is ejected. Compared to A-2 of Fig. 6, the fluctuation in the amount of ink ejected from the second nozzle row NC2 is sufficiently suppressed.

[0081] 8, at the first end 350R, the ratio of the number of nozzles from which ink is ejected (N2, N3, N6, N7: a total of four) to the total number of nozzles (10) obtained by combining the nozzles (N1-N5, N6-N10) of the first and second nozzle rows NC1 and NC2 is 40%, which is less than the first threshold value (80%). This prevents degradation of image quality.

[0082] The effect of suppressing the degradation of image quality can be obtained similarly at the second end 350L.

[0083] Second embodiment In this embodiment, a case where a print image is printed on a medium by multi-pass printing will be described by taking three types of print images as examples.

[0084] Next, reference is made to Fig. 9. Figs. 9(A), (B) and (C) are diagrams showing an example of an image area of ​​a print image on a medium.

[0085] FIG. 9A shows a quadrangular (rectangular) image area 302 (which is assumed to be the same as that shown in FIG. 5 and FIG. 6).

[0086] In FIG. 9B, a relatively large star-shaped image area 306 is set in the center of the media 300.

[0087] In FIG. 9(C), a rectangular image area 308 is set on the upstream side of media 300 in the second direction (Y direction), and a relatively small star-shaped image area 309 is set in the center of the downstream side of media 300.

[0088] Here, it is assumed that at least the end portion in the first direction (X direction) of each of the image regions 302, 306, 308, and 309 is a solid image (particularly a dark solid image). The end portions of each image will be described later with reference to Figs. 10 to 14.

[0089] Please refer to Fig. 10. Fig. 10 is a diagram showing nozzles that eject ink at the edge of an image area in each pass when performing multi-pass printing on the image area shown in Fig. 9(A). In Fig. 10, parts that are common to the previous drawings are given the same reference numerals.

[0090] In the example of Figure 10, one pass is defined as the operation of the print head 42 (in other words, the sub-ink head 102) moving in one direction along the first direction (X direction), and for each pass, the relative positional relationship between the print head 42 (sub-ink head 102) and the medium 300 in the second direction (Y direction) is updated by, for example, a distance ST equivalent to a predetermined number of pixels, and printing is performed, and it is assumed that the entire rectangular image area 302 is printed in m passes (m is an integer of 2 or more, but for ease of explanation, m=4 in the example of Figure 10). When bidirectional printing is performed, the print head 42 is controlled so that it moves in one direction on the outbound path (outbound pass), then transports the medium, then moves in one direction on the return path (return pass), then transports the medium. In bidirectional printing, the above-mentioned "one pass" may be either a pass on the outbound path or a pass on the return path. In other words, one pass is defined as the movement of the print head along the first direction at least once.

[0091] In FIG. 10, an area 311 corresponding to one pass is shaded. 10, in the sub-ink heads 102 corresponding to the first to fourth passes, the nozzles N1 to N5 and N6 to N10 in the first and second nozzle rows NC1 and NC2 that eject ink at the end 350R or 350L of the image area 302 are depicted solid in black, and the nozzles that do not eject ink are depicted blank. This is the same in FIGS. 11 to 14.

[0092] As previously described with reference to Figures 5 and 6, in the first pass, at the first end 350R, the proportion of the number of nozzles (N1 to N10) from which ink is ejected out of the total number of nozzles (10) obtained by adding up the numbers of nozzles (N1 to N5, N6 to N10) in the first and second nozzle rows NC1 and NC2 is 100%. Here, when the calculated (detected) proportion is compared with the above-mentioned first threshold value (80%), the calculated (detected) proportion is equal to or greater than the first threshold value. The same is true for the second to fourth passes.

[0093] Here, the ratio of the number of paths (all of the first to fourth paths) determined to be equal to or greater than the first threshold to the total number of paths (m paths: m=4 here) is 100%. If the second threshold is 50%, the calculated (detected) ratio (100%) is equal to or greater than the second threshold (50%).

[0094] Therefore, the image quality degradation determining unit 66 determines that image quality degradation occurs at the first end 350R. The same is true for the second end 350L.

[0095] Next, reference is made to Fig. 11. Fig. 11 is a diagram showing nozzles that eject ink at the edge of the image area in each pass when multi-pass printing is performed on the image area shown in Fig. 9(B).

[0096] 11, four ends 350RU, 350RD, 350LU, and 350LD in a first direction (X direction) are shown in a star-shaped image region 306. Here, RU means upper right, RD means lower right, LU means upper left, and LD means lower left.

[0097] These four ends 350RU, 350RD, 350LU, and 350LD are appropriately set by the ink discharge amount variation suppression unit 64 as locations where image quality degradation is likely to occur, taking into consideration the shape of the image area, the nozzle configuration of the print head, etc. This point is also the same in the example of FIG. 12 described later.

[0098] Moreover, ends 350RU, 350RD are ends closer to the scanning start end of print head 42, and therefore correspond to the "first end" in the example of Figures 5 and 6. Moreover, ends 350LU, 350LD are ends closer to the scanning end end of print head 42, and therefore correspond to the "second end" in the example of Figures 5 and 6.

[0099] In the example of Figure 11, at end portion 350RU, the number of nozzles that eject ink in the first pass (here, 2) accounts for 20% of the total number of nozzles (10), and the number of nozzles that eject ink in the second pass (here, 2) accounts for 20% of the total number of nozzles (10).

[0100] Furthermore, at the end 350RD, the number of nozzles that eject ink in the third pass (here, two) accounts for 20% of the total number of nozzles (10).

[0101] In each of the first, second, and third passes, the determined (detected) proportion (20%) is equal to or less than the first threshold (80%).

[0102] Therefore, the number of paths that are equal to or greater than the first threshold is zero, and the ratio of the number of paths that are equal to or greater than the first threshold to the number of m paths (m=3) is 0%.

[0103] Therefore, image quality degradation determining section 66 determines that no degradation in image quality occurs at first ends 350RU and 350RD. The same is true for second ends 350LU and 350LD.

[0104] Next, reference is made to Fig. 12. Fig. 12 is a diagram showing nozzles that eject ink at the edge of the image area in each pass when multi-pass printing is performed on the image area shown in Fig. 9(C).

[0105] In FIG. 12, a rectangular image area 308 is set on the upstream side (+Y direction) of the media 300 in the second direction (Y direction), and an end 350R on the scanning start end side of the print head 42 and an end 350L on the scanning end end side are set.

[0106] Furthermore, in star-shaped image area 309, which is set in the center and downstream of square image area 308 on medium 300, end portion 350RU on the scanning start end side of print head 42 and end portion 350LU on the scanning end end side are set.

[0107] The ends 350R, 350RU correspond to the "first end" in the example of FIGS. 5 and 6, and the ends 350L, 350LU correspond to the "second end" in the example of FIGS.

[0108] In the example of Figure 11, at the end 350R of the rectangular image area 308, the number of nozzles ejecting ink in the first pass (here, 10) accounts for 100% of the total number of nozzles (10), and the number of nozzles ejecting ink in the second pass (here, 8) accounts for 80% of the total number of nozzles (10).

[0109] Furthermore, at end 350RU in star-shaped image area 309, the number of nozzles ejecting ink in the third pass (here, four) accounts for 40% of the total number of nozzles (10), and the number of nozzles ejecting ink in the fourth pass (here, two) accounts for 20% of the total number of nozzles (10).

[0110] In the first and second passes, the obtained (detected) proportions (100%, 80%) are equal to or greater than the first threshold (80%).

[0111] On the other hand, in the third and fourth passes, the obtained (detected) proportions (40%, 20%) are equal to or less than the first threshold (80%).

[0112] Therefore, the proportion of the number of paths that are equal to or greater than the first threshold among the m paths (m=4) is 50%, which is equal to or greater than the second threshold (50%).

[0113] Therefore, the image quality degradation determining unit 66 determines that image quality degradation will occur at the first ends 350R and 350RU, and similarly at the second ends 350L and 350LU.

[0114] Next, reference is made to Fig. 13. Fig. 13 is a diagram showing nozzles that eject ink at the edge of an image area in each pass when multi-pass printing is performed on an image area obtained by rotating the image area shown in Fig. 9(A) and Fig. 10 clockwise by a predetermined angle.

[0115] 13, the rectangular image area 302 is rotated clockwise, for example, by about 15° to 20°, and as a result, the rectangular image area 302 is disposed at an angle. A first end 350R1 and a second end 350L1 are set in the rectangular image area 302. Ink ejection at the first end 350R1 will be described below.

[0116] In each of the first to sixth passes, there are two nozzles ejecting ink at the first end 350R1, which is 20% of the total number of nozzles (10), which is less than the first threshold (80%). In other words, there are no passes that are greater than or equal to the first threshold.

[0117] Therefore, the ratio of the number of paths equal to or greater than the first threshold to the number of m paths (here, m=6) is 0% (i.e., equal to or less than 50% of the second threshold), and degradation of image quality is suppressed. The same is true for the second end 350L1.

[0118] Next, reference is made to Fig. 14. Fig. 14 is a diagram showing nozzles that eject ink at the edge of an image area in each pass when multi-pass printing is performed on an image area obtained by rotating the image area shown in Fig. 9(C) and Fig. 12 clockwise by a predetermined angle.

[0119] In the example of FIG. 14, the square image area 308 and the star-shaped image area 309 are rotated clockwise, for example, by 15°, so that the square image area 308 and the star-shaped image area 309 are arranged at an angle.

[0120] Ends 350R2 and 350R3 are set as first ends in the rectangular image region 309, and end 350L2 is set as a second end in the rectangular image region 309. Note that no ends are set in the star-shaped image region 309.

[0121] Ink ejection at the first ends 350R2 and 350R3 in the rectangular image area 308 will be described below.

[0122] In each of the first to fourth passes, there are two nozzles ejecting ink at end 350R2 constituting the first end, which accounts for 20% of the total number of nozzles (10), which is less than the first threshold (80%).

[0123] Also, in the fifth pass, there are three nozzles ejecting ink at end 350R3 constituting the first end, which accounts for 30% of the total number of nozzles (10), which is less than the first threshold (80%).

[0124] Therefore, there is no pass that is equal to or greater than the first threshold value in any of the first to fifth passes.

[0125] In other words, the ratio of the number of paths equal to or greater than the first threshold to the number of m paths (here, m=5) is 0% (i.e., equal to or less than the second threshold (50%)), and degradation of image quality is suppressed. The same is true for the second end 350L2.

[0126] Next, reference is made to Fig. 15. Fig. 15 is a flowchart showing the main processing steps in the print data generating method.

[0127] In step S1, image data of an input image (image data of an image to be printed) is obtained. Then, in step S2, the image data of the input image is subjected to RIP processing and converted into print data.

[0128] In step S3, it is determined whether or not a large fluctuation in the ink ejection amount occurs at the edge of the image area, causing a deterioration in the image quality of the printed image.

[0129] If the answer is N in step S3, the process proceeds to step S6, where the print data is output. If the answer is Y in step S3, the process proceeds to step S4.

[0130] In step S4, a rotation process is performed on the image data of the input image.

[0131] In step S5, the rotated image data is subjected to RIP processing and converted into print data.

[0132] Then, in step S6, the generated print data is output.

[0133] As described above, in the first aspect of the present invention, the print data generation device 10 has a print head including a first nozzle row NC1 having a plurality of nozzles N1 to N5 arranged side by side in a second direction intersecting the first direction, and a second nozzle row NC2 having a plurality of nozzles N6 to N10 arranged side by side in the second direction, and the first and second nozzle rows NC1, NC2 are arranged at intervals in the first direction and communicate with each other via a common liquid chamber 200. In this case, the print data generation device generates print data for printing an image on a medium using the print head, and has an image quality degradation determination unit 66 that determines whether or not image quality degradation will occur due to fluctuations in the amount of ink discharged from the nozzles of the first and second nozzle rows at ends 350R, 350L in the first direction of an image area of ​​the image, and an image rotation processing unit 68 that rotates and tilts the image data of the image to be printed by a predetermined angle or a calculated angle when it is determined that image quality degradation will occur.

[0134] According to the first aspect, prior to printing, it is determined (estimated) whether or not a large fluctuation in the amount of ink ejected from the nozzles will occur at the edge of the image area of ​​the print image, resulting in a degradation in the image quality of the print image, and if it is determined (estimated) that a degradation in image quality will occur, the image data (e.g., the entire image data) is rotated to tilt the image by a predetermined angle (or an angle calculated each time taking into consideration the characteristics of the print head, the shape of the print image, the ink used, etc.), thereby suppressing large fluctuations in the amount of ink ejected from the first and second nozzle rows at the edge. Therefore, even when printing on a medium using a print head (sub-ink head) equipped with first and second nozzle rows that communicate with each other, it is possible to effectively suppress the occurrence of degradation in image quality such as vertical streaks (uneven density).

[0135] In a second aspect dependent on the first aspect, the image quality degradation determination unit may determine that image quality degradation will occur when the proportion of the number of nozzles that eject ink at the ends, or the number of nozzles that terminate ink ejection at the ends, to the total number of nozzles obtained by adding up the numbers of nozzles in the first and second nozzle rows is equal to or greater than a first threshold value.

[0136] According to the second aspect, it is possible to efficiently and accurately determine whether or not degradation of image quality occurs at the edge of an image area using an objective criterion.

[0137] In a third aspect that is dependent on the first aspect, an operation in which the print head moves at least once along a first direction is defined as one pass, and printing is performed by updating the relative positional relationship between the print head and the medium in the second direction for each pass, and the image area is printed in m passes (m is an integer of 2 or greater), the image quality degradation determination unit determines for each pass whether the proportion of the number of nozzles that eject ink at the ends or the number of nozzles that stop ejecting ink at the ends to the total number of nozzles obtained by adding up the numbers of nozzles in the first and second nozzle rows is equal to or greater than a first threshold, and may determine that image quality degradation will occur if the proportion of the number of passes that were equal to or greater than the first threshold to m passes is equal to or greater than a second threshold.

[0138] According to the third aspect, the degree of image quality degradation occurring throughout the entire printed image can be objectively, efficiently, and accurately determined by using the proportion of the number of passes determined to cause image quality degradation to the total number of passes required to print the entire image area.

[0139] In a fourth aspect dependent on the first aspect, the determination by the image quality degradation determining section may be made when at least an edge of the image area is a solid image area where ink is applied without any gaps.

[0140] According to the fourth aspect, density unevenness can be effectively suppressed in solid image areas (especially solid image areas of high density) at the edges of an image area, where density unevenness such as vertical streaks is likely to occur, and the image quality of printed images including solid images can be improved.

[0141] In a fifth aspect of the present invention, a print data generation method is a method for generating print data when a print head has a first nozzle row having a plurality of nozzles arranged side by side in a second direction intersecting a first direction, and a second nozzle row having a plurality of nozzles arranged side by side in the second direction, and the first and second nozzle rows are arranged at intervals in the first direction and communicate with each other via a common liquid chamber, the method comprising: a first step of determining whether or not a degradation in image quality will occur due to fluctuations in the amount of ink ejected from nozzles of the first and second nozzle rows at ends of an image area of ​​the image in the first direction; a second step of rotating and tilting image data of the image to be printed by a predetermined angle or a calculated angle if it is determined that a degradation in image quality will occur; and a third step of performing RIP (Raster Image Processor) processing on the image data after the second step to generate print data.

[0142] According to the fifth aspect, even if there is a high possibility that unevenness such as vertical streaks will occur at the edges of the image area of ​​the printed image, degradation of image quality can be sufficiently suppressed by image processing.

[0143] In a sixth aspect of the present invention, an image processing program for printing causes a computer to function as the image quality degradation determination section and image rotation processing section in any one of the first to fourth aspects.

[0144] According to the sixth aspect, the print data generating method of the fifth aspect can be easily realized by installing the print image processing program in a computer.

[0145] As described above, according to the present invention, it is possible to suppress fluctuations in the amount of ink ejected from nozzle rows in a print head that communicate via a common liquid chamber, and to effectively suppress deterioration in the image quality of printed images.

[0146] For example, for image data with a solid background such as a poster, the entire image data is rotated, for example, in the range of about 15° to 25° to suppress the occurrence of vertical streaks, while for image data without a background such as a sticker, the image data is used as print data to print the image without performing image rotation processing. This achieves high functionality in the printing system. In addition, it becomes possible to print dark solid images, which have been considered to be prone to uneven density in the past, with higher resolution.

[0147] It should be noted that if the image data is rotated and cutting of the media becomes necessary later, no particular problem will arise if the cutting area is also rotated in accordance with the amount of rotation of the image data.

[0148] The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. For example, when rotating image data, if the image data contains multiple images that can be distinguished from one another, it is possible to rotate each of the multiple images by a different amount rather than rotating the entire image data uniformly, or to rotate only some of the images, thereby improving the degree of freedom in image processing.

[0149] The present invention is not limited to the above-described exemplary embodiments, and those skilled in the art could easily modify the above-described exemplary embodiments to the extent that they fall within the scope of the claims. [Explanation of symbols]

[0150] 1 printing system, 10 print data generating device (host computer), 12 storage device (memory), 15 print image processing program, 16 display unit, 18 keyboard, 19 mouse, 20 scanning system configuration, 21 carriage motor, 22 carriage, 23 position detection unit, 30 transport system configuration, 31 transport motor, 32 transport rollers, 33 transport detection unit, 40 ink ejection system configuration, 41 printing Print head drive section, 42...print head, 43...ink amount detection section, 37, 44...first and second folders, 39...image data of a print image (print image data), 45...input profile, 47...output profile, 50...printing device (inkjet printer, etc.), 60...image data interface (I / F), 62...image data processing section, 64...ink ejection amount fluctuation suppression section, 66...image quality degradation determination section, 68...image rotation processing section, 70...rotation amount calculation section output unit, 72...RIP, 73...image data storage unit, 74...color conversion unit, 76...image correction unit, 78...print data output unit, 80...communication interface (I / F), 82...control unit, 84...scan control unit, 85...transport control unit, 86...drive unit, 87...ink ejection control unit, 88...detection unit, 102, 104, 106, 108...sub-ink head, 200...common liquid chamber, 204, 206, 208, 210, 212, 214, 216, 218, 220 , 222, 224...flow path, 202...ink supply port, 240a, 240b...nozzle plate, 250a, 250b...flow path partition, 260a, 260b...vibration plate, 270a, 270b...actuator (piezoelectric element), 280a, 280b...container wall, 300...media, 302...rectangular image area, 306, 309...star-shaped image area, 350R...first end (first end area), 350L...second end (second end area), L11...communication line.

Claims

1. A print data generation device that generates print data for printing an image on a medium using a print head, the print head having a first nozzle row having a plurality of nozzles arranged side by side in a second direction intersecting a first direction, and a second nozzle row having a plurality of nozzles arranged side by side in the second direction, the first and second nozzle rows being spaced apart in the first direction and communicating with each other via a common liquid chamber, comprising: an image quality degradation determination unit that determines whether or not image quality degradation occurs due to fluctuations in the ink ejection amounts from the nozzles of the first and second nozzle rows at ends of an image area of ​​the image in the first direction; an image rotation processing unit that rotates and tilts image data of an image to be printed by a predetermined angle or a calculated angle when it is determined that image quality degradation will occur; A print data generating device comprising:

2. The image quality degradation determination unit determining that image quality will deteriorate when a ratio of the number of nozzles that eject ink at the end portion or the number of nozzles that terminate ink ejection at the end portion to a total number of nozzles obtained by adding up the numbers of nozzles in the first and second nozzle rows is equal to or greater than a first threshold value; The print data generating device according to claim 1 .

3. An operation in which the print head moves at least once along the first direction is defined as one pass, and printing is performed by updating the relative positional relationship between the print head and the medium in the second direction for each pass, and the image area is printed in m passes (m is an integer of 2 or more); The image quality degradation determination unit determining, for each pass, whether or not a ratio of the number of nozzles that eject ink at the end portion or the number of nozzles that terminate ink ejection at the end portion to a total number of nozzles obtained by adding up the numbers of nozzles in the first and second nozzle rows is equal to or greater than a first threshold value; determining that image quality degradation will occur when a ratio of the number of paths that are equal to or greater than the first threshold to the m paths is equal to or greater than a second threshold; The print data generating device according to claim 1 .

4. the determination by the image quality degradation determination unit is performed when at least the edge of the image area is a solid image area in which ink is applied without any gaps; The print data generating device according to claim 1 .

5. A print data generation method for generating print data for printing an image on a medium by moving the print head and a medium relatively along the first direction, the method comprising: a print head having a first nozzle row having a plurality of nozzles arranged side by side in a second direction intersecting a first direction; and a second nozzle row having a plurality of nozzles arranged side by side in the second direction, the first and second nozzle rows being arranged at intervals in the first direction and communicating with each other via a common liquid chamber, the method comprising: a first step of determining whether or not a deterioration in image quality occurs due to a fluctuation in the amount of ink ejected from nozzles of the first and second nozzle rows at an end portion in the first direction of an image area of ​​the image; a second step of rotating and tilting the image data of the image to be printed by a predetermined angle or a calculated angle when it is determined that image quality degradation will occur; a third step of generating print data by RIP (Raster Image Processor) processing the image data after the second step; A print data generating method comprising:

6. A printing image processing program that causes a computer to function as the image quality degradation determination unit and the image rotation processing unit according to any one of claims 1 to 4.

Images