JP2013103339A - Liquid ejection device and liquid ejection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejection device or the like including a head part for ejecting liquid to a medium to be processed, which can improve processing quality by uniformizing liquid ejection by an adjustment method of a driving signal given to the head part.SOLUTION: The liquid ejection device which forms dots by ejecting the liquid to the medium to be conveyed includes: a control unit supplying an electric signal based on a driving waveform that is stored in advance in accordance with the existence of an inputted dot; and the head part including a plurality of head units for ejecting the liquid from nozzles based on the supplied electric signal. The driving waveform is determined for the respective head units based on liquid ejection states in respective regions formed by dividing the region in the head unit in a plurality of regions.

Description

  The present invention relates to a liquid ejection apparatus including a head unit that ejects liquid onto a target medium, and in particular, liquid ejection can be made uniform by adjusting a driving signal applied to the head unit, thereby improving processing quality. The present invention relates to a liquid ejection device capable of performing

  Conventionally, a liquid ejection apparatus such as an ink jet printer has been used. Ink jet printers are usually equipped with a head having a plurality of nozzles for ejecting ink that is liquid, and a drive signal (electrical signal) is given to the operating portion of the head, and ink ejection according to the signal is performed. Is made.

  In an apparatus equipped with a plurality of heads, the liquid ejection characteristics differ from head to head, so if the same drive signal is used for all the heads, the liquid ejection amount varies and the ink density on the print medium becomes uneven. There is a problem that it ends up.

  The following Patent Document 1 describes an invention for correcting a difference in density generated for each head, and shows that a test pattern is formed to measure a density and a parameter of a driving pulse as a driving signal is corrected. Yes.

JP 2010-184380 A

  Further, in the prior art described in the above-described Patent Document 1 or the like, when determining the drive signal given to each head, the average print density in the entire area of each head is used as a criterion.

  However, the characteristics of the nozzles provided in each head are not uniform, and the print density may vary greatly depending on the area within the head. Therefore, the drive signal correction (adjustment) method using the average print density of the head as a criterion may cause insufficient print density.

  Accordingly, an object of the present invention is a liquid ejection apparatus including a head unit that ejects liquid onto a medium to be processed, in which liquid ejection is uniformed by a method of adjusting a drive signal given to the head unit, and processing quality is improved. It is an object to provide a liquid ejection device that can be improved.

  In order to achieve the above object, according to one aspect of the present invention, a liquid ejecting apparatus that ejects liquid onto a transported medium and forms dots is stored in advance according to information on whether or not the dots are formed. A control unit that supplies an electric signal based on a driving waveform; and a head unit that includes a plurality of head units that discharge the liquid from the nozzles based on the supplied electric signal, and the driving waveform is included in the head unit. This area is determined for each head unit based on the liquid ejection state of each area obtained by dividing the area.

Furthermore, in the above invention, a preferable aspect is that the liquid discharge state of each of the divided areas is an average value of color density on the medium of the liquid discharged from the nozzle provided in the area. And

  Further, in the above invention, according to one aspect, the drive waveform for each head unit is determined by determining an average value of the color density of each divided area and the liquid ejected from the nozzles provided in all the head units. The difference from the average value of the color density on the medium falls within a first predetermined range.

  Furthermore, in the above-described invention, one aspect is that the drive waveform for each head unit is determined such that an average value of color densities of the divided areas falls within a second predetermined range. It is characterized by.

  Furthermore, in the above-mentioned invention, one aspect is characterized in that an average value of color densities in a range located at an end of the head unit is used as an average value of color densities of the divided areas.

  Furthermore, in the above invention, one aspect is characterized in that a region where a predetermined number of the nozzles are located from the nozzles at the end of the head unit is excluded from the divided regions.

  Furthermore, in the above invention, when there is an overlap portion in which the position of the nozzle overlaps in a direction intersecting the conveyance of the medium between the head units, the determination of the driving waveform for each head unit is The difference between the average values of the color densities in the two divided areas adjacent to each other including the overlap portion is set to fall within a third predetermined range.

  In order to achieve the above object, according to another aspect of the present invention, there is provided a liquid ejection method in a liquid ejection apparatus that ejects liquid onto a transported medium to form dots. A step of supplying an electric signal based on a driving waveform stored in advance according to the presence / absence information, and a step of ejecting the liquid from a nozzle by a plurality of head units according to the supplied electric signal. Is determined for each head unit based on the liquid discharge state of each region obtained by dividing the region in the head unit into a plurality of regions.

  Further objects and features of the present invention will become apparent from the embodiments of the invention described below.

1 is a configuration diagram according to an embodiment of a liquid ejection apparatus to which the present invention is applied. It is the figure which showed an example of the drive waveform. 3 is a diagram illustrating a schematic arrangement of a head unit 23 of the printer 2. FIG. It is the flowchart which illustrated the procedure of the determination process of a drive signal. FIG. 5 is a diagram illustrating an area of each head unit 231. It is a figure for demonstrating the 1st determination method. It is a figure for demonstrating the 2nd determination method. It is a figure for demonstrating the 3rd determination method. It is a figure for demonstrating the 4th determination method. It is a figure for demonstrating the 5th determination method.

Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. In the drawings, the same or similar elements are denoted by the same reference numerals or reference symbols.

  FIG. 1 is a configuration diagram according to an embodiment of a liquid ejection apparatus to which the present invention is applied. A printer 2 shown in FIG. 1 is a liquid ejecting apparatus according to the present embodiment, and ink is ejected from a head unit 23 having a plurality of head units to execute printing on a paper 26. The supplied drive signal (electrical signal) is determined based on the print density for each range (area) obtained by dividing the area in the head unit into a plurality of areas, and the print density is made more uniform than in the conventional apparatus. be able to.

  A host computer 1 shown in FIG. 1 is a host device of the printer 2 that gives a print instruction to the printer 2, and is composed of, for example, a personal computer. Therefore, although not shown, the host computer 1 includes a CPU, RAM, ROM, HDD, display, operation device, and the like.

  The application 11 is a print request source, and there may be applications having various functions such as a text creation application and a graphic creation application. The application 11 includes a program that instructs processing contents, the CPU that executes processing according to the programs, the RAM, and the like, and outputs image data representing the printing contents when a print request is made.

  The driver 12 is a driver for the printer 2, performs image processing on the image data output from the application 11 to obtain image data (print data) for the printer 2, sends the print data to the printer 2, and This is a part that issues a print instruction for printing requested by the application 11. The print data to be transmitted to the printer 2 is expressed by a command for the printer 2, and here, as an example, is data after so-called halftone processing that represents dot on / off.

  The driver 12 includes a driver program stored in the HDD and the like, the CPU that executes processing according to the driver program, the RAM, and the like. The driver program is stored in the HDD of the host computer 1 by being copied from a storage medium such as a CD to the host computer 1 or downloaded to the host computer 1 via a network such as the Internet. The

  The printer 2 (liquid ejection device) is, for example, a line head type ink jet printer that executes a printing process in accordance with a printing instruction from the host computer 1. As an example, the printer 2 is a type of printer that performs printing on the roll paper 25.

  As shown in FIG. 1, the printer 2 includes a controller unit 21 and a print execution unit 22. The controller unit 21 (the control unit of the liquid ejection apparatus) is a part that receives print data according to the print instruction and causes the print execution unit 22 to execute print processing according to the print data. Specifically, control of the head unit 23 of the print execution unit 22, that is, control related to ink ejection, and control of the transport system of the print execution unit 22, that is, control related to transport of the paper 26 fed out from the roll paper. I do. In the control of the head unit 23, a drive signal (electric signal) for the head unit is supplied to each head unit provided in the head unit 23 according to the print data.

Specifically, the controller unit 21 includes a program in which processing contents are described, a CPU that executes processing according to the program, a RAM, a ROM that stores programs, and the like.
It consists of IC etc.

  The ROM of the controller unit 21 stores drive waveforms of the drive signals (electric signals) for the head units described above. FIG. 2 is a diagram showing an example of the drive waveform. In the waveform shown in FIG. 2, Vh indicating the peak voltage (hereinafter referred to as drive voltage) is one of the parameters that determine the waveform of the drive signal. It is driven greatly and a lot of ink (liquid) is ejected. This value is adjusted in the drive signal determination process in the present embodiment described later.

  Next, the print execution unit 22 includes an ink discharge system mechanism and a paper transport system mechanism (transport unit) as described above. The paper transport system mechanism includes a paper feed roller 27 for supplying the paper 26 from the roll paper 25 to the transport path, a transport roller 28 for transporting the supplied paper 26 to the printing position, and a paper 26 after printing. A paper discharge roller 29 and the like are provided for discharging to the outside, and the paper 26 is conveyed at a constant speed during the printing process. Although not shown, the paper transport system mechanism includes a driving device for each roller, a position detection device, and the like in addition to these.

  The ink ejection system mechanism includes a platen 24 and a head portion 23 positioned thereon. The head unit 23 is a line head that includes a plurality of nozzles that eject ink (liquid) that is a color material onto a sheet 26 (processing medium). Here, as an example, CMYK (cyan, magenta, yellow, black) four-color ink is used. Further, the line head is divided into a plurality of head units (231a-c, see FIG. 3), and these are alternately arranged in a so-called zigzag pattern. The head unit 23 performs a printing process by ejecting ink onto the paper 26 that is transported at a fixed speed by the paper transport system mechanism at a fixed position.

  FIG. 3 is a diagram illustrating a schematic arrangement of the head unit 23 of the printer 2. Here, as an example, the head unit 23 is divided into three head units 231a, 231b, and 231c, and is shown in FIG. 3 with respect to the conveyance direction (arrow a in the figure) of the paper 26 that is the processing target medium. As shown, they are arranged in a staggered pattern. In FIG. 3, the right direction means the transport direction, the left direction means the direction opposite to the transport direction, and the upward direction means the direction of the left hand toward the transport direction orthogonal to the transport direction. The downward direction means the direction of the right hand toward the transport direction orthogonal to the transport direction.

  Each head unit 231 includes four nozzle rows 232, and each nozzle row 232 includes a plurality of nozzles (here, 360 nozzles as an example). The nozzle rows 232 are configured to eject KCMY inks in the order of the transport direction of the paper 26 in each nozzle unit. That is, in the nozzle row 232 located at the rear end in the transport direction of the paper 26, Y-color ink is ejected from the nozzle, and in the next nozzle row 232, M-color ink is ejected from the nozzle, and the next nozzle row 232 is further ejected. In FIG. 2, C color ink is ejected from the nozzles, and K color ink is ejected from the nozzles in the nozzle row 232 at the head end.

  Therefore, in this example, the head unit 23 is provided with 1080 nozzles for each color. The nozzle numbers in these nozzle rows 232 are 0-1079. Further, as shown in FIG. 3, the adjacent head units are arranged so as to partially overlap in the width direction of the paper 26, and in the overlap portion indicated by b in FIG. Two nozzles are arranged at the same position (can eject ink with two nozzles).

At the time of printing, ink of each color is ejected from each nozzle of such an arrangement provided in the fixed head unit with respect to the paper 26 moving in the transport direction. Specifically, the drive signal described above is applied to the operation portion (for example, a piezo element and an elastic plate) for each nozzle, and ink is ejected from the nozzle by driving the operation portion.

  In the host computer 1 and printer 2 having the configuration described above, the printing process is executed as follows. First, when the application 11 issues a print request in the host computer 1, the image data is received by the driver 12. Thereafter, the driver 12 performs various types of image processing on the received image data. Specifically, first, rasterization processing is performed on image data expressed in units of objects, and the received image data is converted into bitmap data having a density gradation value of each color for each pixel. Next, color conversion processing for converting the color representation of the bitmap data into the color representation of the color material used in the printer 2 is executed. Specifically, for example, data expressed in RGB (red, green, blue) is converted into data expressed in CMYK. Next, correction processing depending on the apparatus of the printer 2 (specifically, each nozzle of the head unit 23) is performed on the bitmap data, and then image data indicating dot on / off by halftone processing is performed. To do.

  After the image processing is performed in this way, the driver 12 generates print data for a print instruction including the processed image data. The print data is expressed by a command for the printer 2 and includes various information related to printing such as the type of paper to be used.

  The print data is transmitted from the driver 12 to the printer 2 and received by the controller unit 21. The controller unit 21 interprets the received print data, and sequentially instructs the print execution unit 22 to execute print processing according to the result.

  In accordance with the instruction, the paper conveyance system of the print execution unit 22 moves the paper 26 to a predetermined position and then conveys the paper 26 at the constant speed described above until the printing process is completed. Further, the head unit 23 of the print execution unit 22 discharges ink from each nozzle in the nozzle row 232 of each head unit 231 in accordance with the above instruction. Specifically, based on the data indicating ON / OFF of the dot, the ink discharge is executed from the nozzle at the position where the dot is formed.

  Thereafter, when the instructed print processing is completed, the printed portion 22 is cut and discharged from the printer 2 by the print execution unit 22 according to an instruction from the controller unit 21.

  Next, processing for determining the drive signal (drive waveform) of each head unit 231 described above will be described. This process is performed before use of the printer 2 (before shipment), and the generated drive waveform is stored in the ROM of the controller unit 21 as described above.

  FIG. 4 is a flowchart illustrating the procedure of the drive signal determination process. The processing for one color will be described based on FIG.

  First, a printing process (output) of a test pattern (density measurement pattern) is executed in the printer 2 (step S1). The printing process is performed for all the nozzles (in this case, nozzles) of each color for a plurality of density gradation values (for example, five levels obtained by dividing 0 to 255 equally) from low density to high density. Number 0-1079). In printing with each gradation value, each nozzle ejects ink a plurality of times. In the printing, a common standard drive signal (drive waveform) is used for each head unit 231.

  Next, the density of the generated test pattern is measured (step S2). Specifically, the print density of the test pattern is measured at a predetermined pitch (for example, at the same pitch as the nozzle pitch) using a scanner.

  Thereafter, the concentration measurement value is input to a computer having a function of determining a drive signal, and the drive signal is determined by the computer as follows. In addition, in the said determination process, it can also be set as the method in which a person intervenes.

  First, an average value for each area of the input density measurement value is calculated (step S3). Here, the area means an area obtained by dividing the area in each head unit 231 into a plurality of areas. Here, as an example, the area in the head unit 231 is divided into three areas. Each has three areas.

  FIG. 5 is a diagram illustrating the area. As shown in FIG. 5, the area is an area obtained by dividing the area of the head unit 231 in a direction orthogonal to the conveyance direction of the paper 26, and here, there are area (1) -area (9).

  The average value for each area is the average value of the density measurement values obtained from the portion printed by the nozzles included (located) in the area in each gradation of the printed test pattern. .

  Therefore, for the area (1), the average print density of the pattern printed by the nozzles included in the area (1) in the nozzle row 232 of the head unit 231a is calculated for each gradation. That is, here, the average value of the print density is obtained for five gradation levels from low density to high density. Similarly, an average value of each gradation is obtained for area (2) -area (9).

  When the average value for each area is obtained in this way, it is determined (determined) whether or not it is necessary to switch the drive signal for each head unit 231 using the average print density (liquid ejection state) for each area (step S4). ). That is, it is determined whether or not it is necessary to switch the standard drive signal used at the time of test pattern printing, in other words, whether or not the standard drive signal can be determined as a drive signal to be used as it is.

  The determination is performed for each density gradation range of the printed test pattern, and when it is determined that switching is necessary for any density gradation, it is determined that switching is necessary. . Hereinafter, a determination method for one density gradation will be described.

  Although there are several methods as the specific method of the determination, in any case, the determination is performed using the average print density of the area obtained by dividing the area in each head unit 231 into a plurality of features. To do.

  The first method determines whether or not the difference between the obtained average print density of each area and the average print density of all the head units 231a-c is within a predetermined range (first range). To do. If the average print density of any area is not within the range, it is determined that switching is necessary. The average print density of all the head units is the average value of the density measurement values at the density gradation of the printed test pattern, that is, the average print density of all the nozzles included in the nozzle row 232 of the color. Value.

  The predetermined range is determined in advance as a range that can be dealt with by the correction processing in the image processing by the driver 12 described above.

  FIG. 6 is a diagram for explaining the first determination method. FIG. 6 is a graph showing the average print density in the order of nozzle numbers. FIG. 6A illustrates the average print density for each area. In FIG. 6A, the average print density of area (1) -area (9) shown in FIG. 5 is plotted with black circles. The average print density of all the head units is indicated by a solid line as an average of all nozzles, and the predetermined first range is a range from an upper limit value to a lower limit value indicated by a broken line in the drawing.

  In the example shown in FIG. 6A, the average print density of the area (7) of the head unit 231c is not within the predetermined range, and it is determined that the drive signal needs to be switched. That is, for example, as indicated by an arrow in the figure, it is determined that the drive signal for the head unit 231c needs to be switched from the standard drive signal so that the average density value falls within the above range.

  FIG. 6B shows the case of the conventional method described above. When the same test pattern as in FIG. 6A is obtained, in the conventional method, the average print density for each head unit (black circle in FIG. 6B) is used as a criterion for determination, so the head units 231a-c Any of these average print densities falls within the predetermined range. Therefore, with this conventional method, it is determined that switching of the drive signal is not necessary. However, in practice, high density exceeding the predetermined range is printed in the area (7), resulting in insufficient density uniformity.

  Next, in the second method, the determination is made based on whether or not the difference between the maximum value and the minimum value of the average print density in each area obtained above falls within a predetermined range (second range). If it is not within the range, it is determined that switching is necessary. The second range is determined in advance as a range that can be handled by the correction processing in the image processing by the driver 12 described above.

  FIG. 7 is a diagram for explaining the second determination method. FIG. 7 is a graph showing the average print density (black circles in the figure) in the order of nozzle numbers, as in FIG. 6, and FIG. 7A illustrates the average print density for each area. A broken line range shown as a tolerance in FIG. 7A represents the predetermined second range when the minimum average print density for each area is set as a lower limit.

  In the example shown in FIG. 7A, the average print density of the area (7) of the head unit 231c is the maximum value and does not fall within the second range, and the drive signal needs to be switched. To be judged. That is, for example, as indicated by an arrow in the figure, it is determined that the drive signal for the head unit 231c needs to be switched from the standard drive signal so that the average density value falls within the above range.

  FIG. 7B shows the case of the conventional method. When the same test pattern as that shown in FIG. 7A is obtained, in the conventional method, the average print density for each head unit (black circle in FIG. 7B) is used as a criterion for determination. The average print density of the unit 231a and the average print density of the head unit 231c, which is the maximum value, fall within the second range. Therefore, with this conventional method, it is determined that switching of the drive signal is not necessary. However, in practice, a high density exceeding the second range is printed in the area (7), resulting in insufficient density uniformity.

Next, the third method is a method that uses the average print density of the end area of each head unit 231. Similar to the first method, the average print density of each end area and all the head units 2 are used.
Depending on whether or not the difference from the average print density of 31a-c is within the first range or similar to the second method, the maximum and minimum values of the average print density in each end area Is determined by whether or not the difference is within the second range. In any case, if it is not within the above range, it is determined that switching is necessary.

  Here, the end area is an area including an end (see FIGS. 3 and 5) in a direction orthogonal to the conveyance direction of the paper 26 in each head unit 231, and has the same range as the area shown in FIG. 5. It may be used or may be a range of different sizes. For example, in the head unit 231a, the area (1) and the area (3) may be the end area, or a narrower range may be the end area. Further, the average print density of the end area is obtained in the same manner as in step S3 described above, and in this method, the average print density of the area other than the end area need not be obtained.

  FIG. 8 is a diagram for explaining the third determination method. In FIG. 8, the average print density of the end areas (black circles in the figure) is shown in the order of nozzle numbers, the average print density of all the head units is shown as a solid line as the average of all nozzles, and the first range is It is shown as a range from an upper limit value to a lower limit value indicated by a broken line in the figure. For example, end portions A and B in the drawing represent the end portion area of the head unit 231a.

  In the example shown in FIG. 8, the average print density of the left end area of the head unit 231c is not within the first range, and it is determined that the drive signal needs to be switched. That is, for example, as indicated by an arrow in the figure, it is determined that the drive signal for the head unit 231c needs to be switched from the standard drive signal so that the average density value falls within the above range.

  Usually, the liquid ejection characteristics in the head unit 231 often change in the same tendency from one end to the other, and therefore the density is made uniform even if only the end area is used as a criterion for the above determination. It is thought that there is almost no obstacle in the above.

  Next, the fourth method is that, in the first to third methods, the print density in the endmost area of each head unit 231 is not used for determination. That is, the above-described determination is performed based on the average print density for a range obtained by removing the endmost area from the area or end area. Here, the endmost area is a range including the end of each head unit 231 described above, a range including the predetermined nozzle from the endmost nozzle or the endmost, and a range smaller than the end area described above. It is.

  Since the endmost area is different from other areas in terms of ink flow and electrical interference, the ink ejection characteristics from the nozzles are also special, and it is necessary to grasp the average characteristics of other areas. It is considered desirable to exclude them at

  FIG. 9 is a diagram for explaining a fourth determination method. FIG. 9 illustrates a graph having the same expression format as FIG. 6 and the like. In this example, each head unit 231 is divided into four areas except for the endmost area. The black circles in the figure represent the average print density of each area, and the bent portions at both ends thereof represent the endmost area (determination exclusion region in the figure). In this example, the case where the print density in the endmost area is considerably higher than the print density in other areas is shown. In this example, when the above-described first method is used except for the endmost area, the portion indicated by C is not used for the determination, so that the drive signal is not switched.

Next, in the fifth method, whether or not the difference in average print density between the adjacent areas in the end area including the overlap portion is within a predetermined range (third range). Determine by. If it is not within the predetermined third range, it is determined that the drive signal needs to be switched.

  FIG. 10 is a diagram for explaining the fifth determination method. In FIG. 10, the average print density of the same edge area as in FIG. 8 is plotted, but the determination method is different from the third method. The area indicated by the end OL in the figure is an end area adjacent to each other including the overlap portion. In the example shown here, the average print density between the right end area (the lower end area in FIG. 3) of the head unit 231a and the left end area (the upper end area in FIG. 3) of the head unit 231b. Although the difference D1 is small, the average print density between the right end area of the head unit 231b (lower end area in FIG. 3) and the left end area of the head unit 231c (upper end area in FIG. 3) The difference D2 is large. For example, if this D2 does not fall within the third range, it is determined that the drive signal is switched.

  In the fifth method, a drive signal is determined such that the density is uniform in an area including an overlap portion that prints the same range on the paper 26.

  As described above, whether or not switching is necessary is determined for one density gradation of the test pattern, but the same determination is made for other density gradations. Note that the test pattern may be determined in the same manner as only one density gradation having a high density.

  When the determination is made in this way, the drive signal (drive waveform) of each head unit 231 is determined according to the determination result (step S5). The drive signal is determined by the method used in the determination described above so that the difference relating to the average print density in each area falls within the first range, the second range, or the third range. Is done. Further, when the drive signal is switched from the standard one, the value of the drive voltage Vh is increased or decreased. For example, in the example shown in FIG. 6, it is determined that the standard drive signal is used for the head units 231a and 231b, and the drive signal whose drive voltage Vh is lower than the standard drive signal is used for the head unit 231c. To be determined. The drive voltage Vh at that time is determined using the relationship between the drive voltage and the print density obtained in advance by experiments or the like, or the value is lowered step by step until the measured value of the test pattern satisfies the condition. , And the like. Since the parameter for determining the drive signal (drive waveform) is not only the drive voltage Vh, an appropriate drive signal may be determined using other parameters.

  As described above, the drive signal determination processing described with reference to FIG. 4 is performed for each color, and then the drive signals determined for each color for each head unit 231 are averaged, and the averaged drive signal is the final drive. Signal. The final drive signal (drive waveform) of each head unit is stored in the ROM and used for the printing process described above. Note that the final drive signal is determined by averaging the drive signals when the switching is performed by changing the value of the drive voltage Vh as described above, and the drive voltage of the drive signal determined for each color. The average value of Vh is set to the drive voltage Vh of the final drive signal.

  As described above, in the printer 2 according to the present embodiment, the drive signal for each head unit 231 is determined based on the print density execution value for each area obtained by dividing the area of the head unit 231 into a plurality of areas. Therefore, printing is performed with a drive signal that also takes into account variations in the ink ejection characteristics in the head unit 231, and density uniformity can be improved as compared with the prior art, thus improving print quality. it can.

  In addition, by using the above-described third method, only the edge area is processed in the calculation of the average print density and the switching determination process, and the processing efficiency can be improved.

  In addition, by using the fourth method described above, the influence of the endmost area of the head unit 231 having special characteristics is excluded, and accurate processing can be executed in the switching determination.

  Further, by using the fifth method described above, the uniformity of the density is improved for the overlap portion.

  In addition, the number of head units, the number of nozzles, and the number of areas shown in the present embodiment are examples, and other numbers may be used.

  Further, the present invention can be applied not only to a printer but also to a similar liquid ejection apparatus.

  The protection scope of the present invention is not limited to the above-described embodiment, but covers the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 Host computer, 2 Printer, 11 Application, 12 Driver, 21 Controller part, 22 Print execution part, 23 Head part, 24 Platen, 25 Roll paper, 26 Paper, 27 Paper feed roller, 28 Transport roller, 29 Paper discharge roller, 231a-c head unit, 232 nozzle array

Claims (8)

A liquid ejection apparatus that ejects liquid onto a medium to be transported to form dots,
A controller for supplying an electrical signal with a drive waveform stored in advance according to the information on the presence or absence of formation of the dots;
A head unit including a plurality of head units that discharge the liquid from a nozzle by the supplied electrical signal;
The liquid ejection apparatus according to claim 1, wherein the driving waveform is determined for each head unit based on a liquid ejection state of each region obtained by dividing the region in the head unit into a plurality of regions. In claim 1,
The liquid ejection state of each of the divided areas is an average value of color density on the medium of the liquid ejected from the nozzle provided in the area. In claim 2,
The drive waveform for each head unit is determined by calculating the average value of the color density of each divided area and the average value of the color density on the medium of the liquid ejected from the nozzles provided in all the head units. The liquid ejecting apparatus is characterized in that the difference falls within a first predetermined range. In claim 2,
The drive waveform for each head unit is determined such that an average value of color densities of the divided areas falls within a second predetermined range. In claim 3 or 4,
The liquid ejection apparatus according to claim 1, wherein an average value of color densities in a range located at an end of the head unit is used as an average value of color densities of the divided areas. In any of claims 3 to 5,
An area where a predetermined number of the nozzles are located from the nozzles at the end of the head unit is excluded from the divided areas. In claim 2,
When there is an overlap portion where the position of the nozzle overlaps in the direction intersecting the conveyance of the medium between the head units,
The determination of the drive waveform for each head unit is made such that the difference in the average value of the color densities in the two adjacent regions including the overlap portion falls within a third predetermined range. A liquid discharge apparatus characterized by that. A liquid ejection method in a liquid ejection apparatus that ejects liquid onto a conveyed medium to form dots,
A step of supplying an electric signal based on a driving waveform stored in advance according to information on whether or not the dot is formed,
A plurality of head units, the step of discharging the liquid from the nozzle by the supplied electric signal,
The liquid ejection method, wherein the drive waveform is determined for each head unit based on a liquid ejection state of each region obtained by dividing a region in the head unit into a plurality of regions.

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