JP2011213033A - Printing apparatus and printing density adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing apparatus and a printing density adjusting method configured to secure a color reproduction range, simultaneously, suppress a granular feeling by appropriately adjusting printing density of each of a base color liquid and a dilution color liquid.SOLUTION: Color inks C, M, Y, and K having hues of cyan, magenta, yellow, and black, respectively, and diluted inks C50%, M50%, Y50%, K50%, and K25% obtained by diluting the respective color inks with the dilution liquid are ejected from a print head to a sheet. By applying a correction voltage V1max as a supply voltage to a drive signal generation circuit, the printing density of each of the color inks C, M, Y, and K is shifted close to the reference density d0 for each color. With application of the correction voltage V1max, the printing density of the diluted ink is shifted together (black square marks in Fig.). A dilution ratio is corrected so that the printing density of the diluted ink for each color becomes closer to the reference density d0 when the correction voltage V1max is applied (white triangle marks in the Fig.).

Description

  The present invention relates to a printing apparatus that performs printing using a basic color liquid and a diluted color liquid obtained by diluting the basic color liquid, and more particularly to a printing apparatus and a printing density adjustment method that optimize the printing density of each color.

  2. Description of the Related Art There is known a printing apparatus that prints an image (including characters and graphics) on a jetting target by jetting a liquid (eg, ink) from a print head onto the jetting target (eg, paper). In such a printing apparatus, a plurality of basic color liquids having different hues (for example, inks of four colors of cyan, magenta, yellow, and black) are ejected to mix the basic color dots formed on the paper. Thus, the hue, brightness, and saturation corresponding to the image are expressed. In this case, the dots themselves formed on the ejection target may be visually recognized, resulting in a grainy image.

  For example, Patent Documents 1 to 3 disclose printing apparatuses that perform printing by ejecting C, M, Y, and K basic color inks (basic color liquids) and diluted ink obtained by diluting basic color inks with a diluent. ing. Mixing undiluted basic ink dots with diluted ink dots reduces the density of each color dot compared to forming an image with only basic ink dots. Can be suppressed. That is, the graininess can be suppressed by reducing the dot area or the number of dots of the basic color inks of C, M, Y, and K, and supplementing the reduced color with the diluted ink dots.

  Further, even if the ink jet type printer is the same model, the ejection amount of ink droplets may be different for each machine. For example, even if ink droplets of the same size are to be ejected, ink droplets of slightly different sizes are ejected between the airframes. As a result, the colors expressed on the paper are different, making it difficult to ensure the necessary color reproduction range. Therefore, it is necessary to adjust the ejection amount of ink droplets for each machine even in the same model. Further, when a single machine body has a plurality of nozzle rows that eject ink droplets, it is necessary to adjust the ejection amount of the ink droplets for each nozzle row.

  For example, Patent Document 4 discloses a printing apparatus that can correct a deviation in the ejection amount of ink droplets between this type of machine. Specifically, a correction ID (error information) indicating a difference between the color measurement result of the patch printed by the reference printer and the color measurement result of the patch printed by the printer to be corrected is acquired, and the value of the correction ID is obtained. Correct the print data accordingly. Specifically, a patch for each color is printed, and the printed patch for each color is measured by a colorimeter. Then, the command value is corrected so that each density of each ink color (for each nozzle row) obtained by the color measurement approaches the target density (reference density), and the command value is output to the drive signal generation circuit. The drive signal generation circuit changes the amplitude of the drive pulse in the drive signal output to the piezoelectric element (piezo element), and adjusts the size of the ink droplet ejected from the nozzle by driving the piezoelectric element. Thereby, since each color is printed with an appropriate dot size, a necessary color reproduction range is ensured.

Japanese Patent Laid-Open No. 2002-248783 JP-A-11-10859 JP 2006-15559 A JP 2009-214479 A

  However, in a printing apparatus using diluted ink as in Patent Documents 1 to 3, when a technique for optimizing the print density by adjusting the ejection amount of ink droplets as in Patent Document 4 is applied, ink ejection It is not configured to individually adjust the amount for each color (nozzle row). For this reason, when adjusting the ink ejection amount, it is preferable to adjust the amplitude of the drive pulse in the drive signal common to all nozzle rows of the print head, for example, according to the appropriate ejection amount of the basic color ink. In this case, even if the ejection amount of the diluted ink is appropriate, it shifts together, so that the graininess is adversely affected, or conversely the diluted ink dots are smaller than expected and the color is blurred. There are problems such as becoming. Since the amplitude of the drive pulse also depends on the supply voltage to the drive signal generation circuit, the ink droplet ejection amount can be adjusted by correcting the supply voltage instead of the command value.

  The present invention has been made to solve the above-mentioned problems, and one of its purposes is to appropriately adjust the printing densities of the basic color liquid and the diluted color liquid together to ensure a color reproduction range and a graininess. It is an object of the present invention to provide a printing apparatus and a printing density adjustment method capable of achieving both suppression of printing.

  In order to achieve the above object, a printing apparatus according to the present invention includes a basic color liquid serving as a basic color for expressing a color, and at least one color obtained by diluting at least one of the basic color liquids with a diluent. A printing apparatus that performs printing by ejecting a diluted color liquid from an ejection unit onto an ejection target, the ejection unit ejecting the basic color liquid and the diluted color liquid based on image data, and the ejection unit Drive signal generating means for generating a drive signal to be output, defining means for defining the magnitude of the drive signal output from the drive signal generating means, and the magnitude defined by the first defining condition by the defining means A density acquisition unit that acquires, for each color, a print density of each color printed by the ejection unit based on the drive signal, and at least one print density of the basic color liquid acquired by the density acquisition unit is set to a target density. And determining means for determining the second prescribed condition by applying correction, and correcting for the print density of the diluted color liquid to be close to the target density in anticipation of a change in the print density of the diluted color liquid due to the correction. And a dilution ratio determining means for determining a corrected dilution ratio of the diluted color liquid.

  According to the present invention, since the specified condition by the specifying means is corrected from the first specified condition to the second specified condition so that the print density of at least one basic color liquid approaches the target density, color reproduction by the ejecting means is performed. A range is secured. In addition, the correction dilution ratio is determined by correcting the dilution ratio so that the print density of the diluted color liquid is close to the target density in anticipation of the correction to the second specified condition. Can be suppressed.

  In the printing apparatus according to the aspect of the invention, the specifying unit is a voltage supply unit that supplies a supply voltage that defines the magnitude of the drive signal to the drive signal generation unit, and provides the specified voltage as the first defining condition, Preferably, the determining unit is a voltage determining unit that determines a correction voltage by performing correction on the specified voltage so that at least one print density of the basic color liquid acquired by the density acquisition unit approaches a target density.

  According to the present invention, since the supply voltage applied from the voltage supply unit to the drive signal generation unit that outputs the drive signal is corrected, the printing densities of the basic color liquid and the diluted color liquid can be optimized relatively easily.

  In the printing apparatus of the present invention, the density acquisition unit also acquires a print density based on a printing result performed by supplying a second supply voltage different from the specified voltage, and the print density at the specified voltage, Computation means for computing first information indicating the relationship between the supply voltage and the print density based on the print density at the second supply voltage is further provided, and the voltage determination means is based on the first information. It is preferable that a voltage correction amount for making the print density at the specified voltage close to the target density is obtained, and the correction voltage is determined by adding the voltage correction amount to the specified voltage. According to this invention, the voltage correction amount for setting the print density at the specified voltage to the target density based on the first information is obtained, and the correction voltage is determined by adding the voltage correction amount to the specified voltage. Can do. Therefore, the correction voltage can be determined using the print density acquisition result.

  In the printing apparatus according to the aspect of the invention, the density acquisition unit may print the density of each color liquid printed by the ejection unit using at least two color liquids having different dilution ratios for each color of the basic color liquid and the diluted color liquid. The calculation means is configured to calculate second information indicating a relationship between the dilution ratio and the print density based on the print densities of at least two color liquids having different dilution ratios, and the dilution ratio determination means Preferably, a dilution correction amount that brings the print density of the diluted color liquid closer to the target density based on the second information is obtained, and the correction dilution ratio is determined by adding the dilution correction amount to the dilution ratio. . According to the present invention, the second information indicating the relationship between the dilution ratio and the print density can be calculated based on the measurement result of the print density of at least two color liquids having different dilution ratios. Using the second information, A dilution correction amount that brings the printing density of the diluted color liquid closer to the target density can be obtained. Therefore, the correction dilution ratio can be determined using the print density acquisition result.

  In the printing apparatus according to the aspect of the invention, the voltage determination unit may further include a diluted color liquid generation unit that sets the determined correction voltage in the voltage supply unit and generates a diluted color liquid at the dilution ratio determined by the dilution ratio determination unit. It is preferable to provide. According to the present invention, the correction voltage can be set to be supplied from the voltage supply means, and even when the correction voltage is supplied, a diluted color liquid having a correction dilution ratio is generated so that a print density close to the target density can be obtained. Since it can do, the granular feeling in a printing result can be suppressed.

  According to the present invention, a jet liquid includes a basic color liquid serving as a basic color for expressing a color, and at least one diluted color liquid generated by diluting at least one of the basic color liquids with a diluent. Is a print density adjustment method for adjusting the print density in printing performed by jetting onto a jetting object, wherein the magnitude of the drive signal for determining the print dot size by the jetting means is defined by a first prescribed condition, A density measurement step for measuring the print density of each color printed by the ejection means for each color, and a correction for making at least one print density of the basic color liquid measured in the density measurement step close to the target density And determining the printing density when the diluted color liquid is printed under the second specified condition determined in the determining step. Degrees and is summarized in that provided with a dilution rate determining step of determining a dilution ratio of the dilution color liquid by performing a correction to approach the target concentration of the diluted color liquid. According to the present invention, it is possible to obtain the same operational effects as the invention relating to the printing apparatus.

1 is a schematic diagram illustrating a schematic configuration of a printing apparatus according to an embodiment. The schematic diagram which shows the structure of a dilution ink production | generation apparatus. FIG. 2 is a block diagram illustrating an electrical configuration of the printing apparatus. 6 is a flowchart showing print density adjustment processing. The schematic diagram which shows the test chart which printed the patch for colorimetry. The graph which shows the relationship between density variation and voltage variation. The graph which shows the relationship between a density | concentration variation | change_quantity and a dilution ratio variation | change_quantity. The graph which shows the relationship between a density | concentration and supply voltage. The graph which shows the relationship between a density | concentration and a dilution ratio. The graph which shows the density | concentration of each color at the time of applying the maximum correction voltage V1max. The graph which shows the density | concentration of each color at the time of applying the average correction voltage V1ave.

  Hereinafter, an embodiment in which the present invention is embodied in a printing apparatus that prints an image, a document, or the like on a sheet by ejecting ink, which is an example of a liquid, on a sheet, which is an example of an ejection target, will be described with reference to the drawings. explain. The injection target is not particularly limited to paper (paper), and may be a substrate, glass, or other material such as wood, metal, resin, or cloth.

  FIG. 1 is a schematic diagram illustrating a schematic configuration of a printing apparatus 100 according to the present embodiment. As shown in FIG. 1, the printing apparatus 100 includes a printing mechanism 10 and a control device 30. The control device 30 is configured to control the printing mechanism 10 based on the input image data Dg or print data PD, and to eject a predetermined image by ejecting ink onto the paper P.

  The printing mechanism 10 includes a carriage 14 having a print head 15, which is an example of an ejection unit, an endless belt 13 wound around a driving pulley 11 and a driven pulley 12, and a rotating shaft fixed to the driving pulley 11. Carriage motor M1.

  The carriage 14 is guided so as to be movable in the main scanning direction (left and right direction in the drawing) along a guide shaft (not shown) and is fixed to a part of the belt 13. When the carriage motor M1 is driven forward and backward, the carriage 14 reciprocates along the main scanning direction through the movement of the belt 13 accompanying the rotation of the driving pulley 11 interlocked therewith.

  Further, the printing mechanism 10 includes a conveyance mechanism 16 that uses a position facing the print head 15 (a lower position in FIG. 1) as a conveyance path of the paper P, and a conveyance motor M2 that drives the conveyance mechanism 16. In the transport mechanism 16 of this example, the transport roller 16a is rotated by driving the transport motor M2, so that the paper P is transported in the transport direction (sub-scanning direction) that intersects the moving direction (main scanning direction) of the carriage 14. It has become.

  The printing mechanism 10 also includes basic color ink C (cyan), basic color ink M (magenta), basic color ink Y (yellow), and basic color ink K (black) as examples of basic color liquids that are different hue liquids. ) Ink tanks 18c, 18m, 18y, and 18k containing the inks of the respective colors, and a diluent tank 18w containing the diluent CL. Here, the dilution liquid is a liquid used for diluting the ink, and a colorless and transparent liquid is used in this example. As the dilution liquid, for example, a cleaning liquid is used. Of course, the dilution liquid may be a colorless and transparent liquid, and may be water, alcohol, oil, or the like. The diluent is preferably a liquid that is compatible with the liquid used as the solvent for the dye if the basic color ink is a dye ink, and is used as a pigment dispersion medium if the basic color ink is a pigment ink. A liquid compatible with the liquid is preferred. Hereinafter, the basic color inks C, M, Y, and K are simply referred to as color inks C, M, Y, and K.

  The ink tanks 18c, 18m, 18y, and 18k and the dilution liquid tank 18w generate a diluted color liquid that generates a diluted ink that is an example of a diluted color liquid obtained by diluting the color inks C, M, Y, and K with the dilution liquid CL. It is provided in the diluted ink generating apparatus 20 as an example of the means. The respective color inks C, M, Y, and K are mixed with the diluting liquid CL at a predetermined liquid volume ratio in the diluting ink generating apparatus 20. The color inks C, M, Y, K and the diluted ink are supplied to the carriage 14 through the supply pipe 17. Each tank 18 is mounted in a detachable state or a fixed state in the diluted ink generating device 20.

  The color inks C, M, Y, K and the diluted ink supplied from the tanks 18 to the carriage 14 are guided to the print head 15 through flow paths (not shown) in the carriage 14, respectively. In the following description, when the color inks C, M, Y, and K are not distinguished from the diluted ink obtained by diluting them, they are simply referred to as “ink”.

  In the print head 15, nozzle rows N (see FIG. 2) in which a plurality (for example, 180) of nozzles n that eject ink are arranged are arranged in the same number (9 rows) as the ink color. Ink is ejected from the nozzles n of each nozzle row and adhered onto the paper P with respect to the paper P arranged opposite to the nozzle row formation surface. In this embodiment, one nozzle row N corresponds to each color ink and diluted ink, and the print head 15 has a total of nine nozzle rows N from A to I, which will be described later. (See FIG. 2).

  The control device 30 controls the print head 15, the carriage motor M <b> 1, the transport motor M <b> 2, and the diluted ink generation device 20. The control device 30 prints an image based on the image data Dg or the print data PD on the paper P by ejecting color ink and dilution ink from the nozzle n of the print head 15 based on the input image data Dg or the print data PD. Perform print control. The control device 30 includes a computer 31 (microcomputer) that performs various controls. The computer 31 includes a CPU (Central Processing Unit) 32, an ASIC (Integrated Circuit) 33, a ROM (Read Only Memory) 34, a RAM (Random Access Memory) 35, and the like.

  The computer 31 in the control device 30 performs various controls in the printing device 100 by the CPU 32 executing a program stored in the ROM 34. The ROM 34 also stores setting data used for various controls. The ASIC 33 performs predetermined processing including image processing for generating print control data to be supplied for causing the print head 15 to perform ink droplet ejection control from the image data Dg. The RAM 35 is used for temporarily storing a program read from the ROM 34 by the CPU 32 and temporarily storing data such as calculation results obtained in the course of the operation of the program.

  Next, the configuration of the diluted ink generator 20 will be described. FIG. 2 shows a dilution mechanism of each color ink C, M, Y, K supplied from each tank 18 in the diluted ink generating apparatus 20, and each color ink C, M, Y, K and diluted ink are supplied to the print head 15. It is explanatory drawing which showed a mode that it was supplied.

  As shown in FIG. 2, the diluted ink generating device 20 includes a diluted ink (C + CL) in which the color ink C and the diluent CL are mixed, a diluted ink (M + CL) in which the color ink M and the diluent CL are mixed, and the color ink. Dilution ink (Y + CL) in which Y and the dilution liquid CL are mixed is generated. Further, a diluted ink (B + CL) obtained by mixing the color ink K and the diluent CL is generated. In this embodiment, the dilution ink (C + CL), the dilution ink (M + CL), and the dilution ink (Y + CL) each have a mixing ratio of the color inks C, M, Y, K and the dilution liquid CL of 50:50, Dilution inks C50%, M50%, and Y50% with a dilution ratio of 50% are generated. Further, in the diluted ink generating apparatus 20, the color ink K and the diluted liquid CL are mixed at mixing ratios of 50:50 and 25:75, respectively, and the diluted ink K25 having a dilution ratio of 50% and the diluted ink K25 having a dilution ratio of 25%. % Is generated respectively. By diluting each color ink in this way, diluted ink having the same hue as the color ink is generated. The diluted ink generating device 20 is provided with piping for supplying each color ink and each generated diluted ink, and mixing tanks 21 to 25 for storing the diluted ink.

As an example of the specific mixing process (dilution process), a description will be given of a diluted ink C50% obtained by mixing the color ink C and the diluted liquid CL.
The color ink C is supplied from the ink tank 18c to the mixing tank 21 through a pipe provided with a valve VL1 in the middle of the path. The diluent CL is also supplied from the diluent tank 18w to the mixing tank 21 through a pipe provided with a valve VL2 in the middle of the path. As a result, diluted ink C50% is generated in the mixing tank 21 by controlling the opening and closing of the valves VL1 and VL6.

  Similarly, by controlling the opening and closing of the valves VL2 and VL7, the diluted ink M50% is generated in the mixing tank 22, and by controlling the opening and closing of the valves VL3 and VL8, the diluted ink Y50% is generated in the mixing tank 23. Generated. Further, by controlling the opening and closing of the valves VL4 and VL9, the diluted ink K50% is generated in the mixing tank 24, and by controlling the opening and closing of the valves VL5 and VL10, the diluted ink K25% is generated in the mixing tank 25. Is done. In this way, a total of five types of diluted ink are generated. Each of the mixing tanks 21 to 25 is provided with a stirring device (not shown) so that the generated diluted ink is sufficiently mixed.

  The valves VL1 to VL10 are controlled to be opened and closed by the control device 30. By controlling the opening and closing of the valves, the ink storage amount of the diluted ink in each of the mixing tanks 21 to 25 and the mixing ratio (dilution ratio) of each color ink C, M, Y, K and the diluent CL are controlled. . In other words, by controlling the opening and closing of the valves VL1 to VL10, it is possible to control the amount of diluted ink stored in each of the mixing tanks 21 to 25 and the hue (mainly brightness) exhibited by the diluted ink.

  Here, the diluted ink exhibits a hue close to the light color (light color) of the same hue as the color ink before dilution. That is, when the diluted ink C50% is printed on the paper P, the diluted ink C50% exhibits a hue close to light cyan due to the mixed color of the diluted cyan C and the white color of the paper P. Similarly, the diluted ink M50% exhibits a hue close to light magenta, and the diluted ink Y50% exhibits a hue close to light yellow. Further, the diluted ink K50% has a hue close to light black, and the diluted ink K25% has a lighter hue close to dark gray.

  Then, as shown in FIG. 2, a total of nine types of four types of color inks C, M, Y, and K and five types of diluted inks C50%, M50%, Y50%, K50%, and K25% generated. The ink is supplied to the print head 15 through the supply pipe 17 and the flow paths in the carriage 14, respectively. The print head 15 shown in FIG. 2 has a drive element 19 (see FIG. 2) such as an electrostrictive element (piezo element) or a heating element that can pressurize ink at a position corresponding to each nozzle n for each nozzle row N. Is provided. The print head 15 incorporates a head drive circuit 15 a that is common to all nozzle rows N that drive a plurality of drive elements 19.

  The nine types of ink supplied to the print head 15 are respectively introduced into ink chambers individually communicating with the respective nozzles n of the corresponding nozzle row N, and the head drive circuit 15a is driven by the drive elements 19 corresponding to the ink chambers. Apply a pulse (drive voltage). By applying the driving pulse, the driving element 19 is driven to apply pressure to the ink in the ink chamber, whereby an ink droplet is ejected from the nozzle n. The amount of ink droplets to be ejected is defined by the magnitude (amplitude, pulse period, etc.) of the drive pulse applied to the drive element 19. At this time, ink of a color corresponding to the nozzle row N is ejected from each nozzle n of the nozzle row N of 9 rows (A row to I row). Incidentally, the color ink C is ejected from the nozzle A row, the diluted ink C 50% is ejected from the nozzle E row, and the diluted ink K50% is ejected from the nozzle H row.

  Next, the electrical configuration of the printing apparatus 100 will be described. FIG. 3 is a block diagram illustrating an electrical configuration of the printing apparatus. In FIG. 3, in the computer 31, a functional part composed of software constructed by the CPU 32 executing a program stored in the ROM 34 and a functional part composed of hardware constructed by various circuits in the ASIC 33. Are shown in functional blocks for each function.

  As shown in FIG. 3, a colorimeter 80 (color colorimeter) is attached to the printing apparatus 100 via a communication interface (communication I / F 41). When performing color measurement using the colorimeter 80, the control device 30 inputs test pattern data Dt for color measurement as print data PD, and drives and controls the printing mechanism 10 based on the test pattern data Dt. Then, a test chart including patches of each color is printed on the paper P by the print head 15. The colorimeter 80 measures the color of the nine color patch groups (density patterns) in the test chart printed on the paper P.

  In addition, a host device 200 is connected to the printing apparatus 100. By transmitting the print data PD to the printing apparatus 100 by operating an input operation unit (for example, a keyboard or a mouse) of the host apparatus 200, it is possible to cause the printing apparatus 100 to print a desired image. The host device 200 is also connected to the colorimeter 80 and outputs a colorimetry command to the colorimeter 80. The printing apparatus 100 can also acquire a color measurement result (described later) measured by the colorimeter 80. The colorimeter 80 is attached to the printing apparatus 100 so that the portion corresponding to the paper P can be moved in the main scanning direction, and moves while measuring the color in the main scanning direction, whereby a test chart TC ( The color density of each color patch in FIG. 5) is measured.

  The control device 30 includes a computer 31, a drive circuit 42 for driving a motor, and a drive circuit 43 for driving a valve. The computer 31 drives the carriage motor M1 through the drive circuit 42 to cause the carriage 14 to travel in the main scanning direction, and during this travel, the drive head 15a in the print head 15 is driven to control the print head. The color ink and the diluted ink having a hue corresponding to the nozzle row N are ejected from 15 respectively. Further, the computer 31 drives and controls the carry motor M2 via the drive circuit 42 to carry the paper P in the carrying direction. Then, the printing operation performed by moving the print head 15 in the main scanning direction and the conveying operation for conveying the paper P to the printing position of the next line in the conveying direction (paper feeding) are performed approximately alternately, thereby P is printed.

  In addition, the computer 31 controls opening and closing of the first valve VL1 to the tenth valve VL10 via the drive circuit 43, thereby controlling the mixing ratio of the color ink and the diluted ink in the diluted ink generating apparatus 20, and a predetermined dilution ratio. Diluted ink C50%, M50%, Y50%, K50%, and K25%. However, this dilution ratio is an initial set value, and is appropriately adjusted as necessary by a correction process described later.

  Further, the computer 31 includes a main control unit 51, a print control unit 52, an image processing unit 53, and a head control unit 54. The main control unit 51 comprehensively controls the printing apparatus 100. The main control unit 51 inputs image data from a memory card (none of which is shown) inserted in a card slot provided in the printing apparatus 100 or receives print data transferred from the host apparatus 200. Or The main control unit 51 generates a command necessary for print control based on the input image data Dg and outputs the command to the print control unit 52, or obtains a command obtained by interpreting the print language description command in the received print data PD Is output to the print control unit 52. The print control unit 52 controls the drive of the carriage motor M1 and the transport motor M2 via the drive circuit 42 according to the command.

  The image processing unit 53 performs predetermined image processing on the image data Dg to generate print data Dp. That is, the image data Dg is converted into print data Dp indicating the amount of liquid to be ejected from the print head 15 (nozzle A row to I row) for each of the color inks C, M, Y, K and the diluted ink. Here, the image data Dg is, for example, Jpeg image data or RGB image data. The Jpeg image data is decompressed to YUV image data by a decompression unit (not shown) and then converted to RGB image data. In the present embodiment, the RGB image data is 256 gradation data conforming to the sRGB standard represented by 8 bits each for R (red), G (green), and B (blue).

  The image processing unit 53 includes a color conversion processing unit 53a, a halftone processing unit 53b, and a rasterization processing unit 53c. The color conversion processing unit 53a converts the RGB image data into CMYK image data that is data corresponding to the ejection amounts of the color ink and the diluted ink with reference to a conversion table (lookup table). In this conversion table, each color ink C, M, Y, K and each diluted ink C50%, M50%, Y50%, for a combination of 256 colors (8 bits) of R, G, B A combination of values represented by 256 gradations of K50% and K25% is defined.

  The halftone processing unit 53b is a well-known process that converts 256 tone CMYK image data into low tone data such as binary or quaternary values according to the type (number) of dot sizes (that is, ink droplet sizes). is there. The rasterization processing unit 53c is a process of rearranging the pixel arrangement order in accordance with the ejection order of the print head 15, and includes vertical / horizontal conversion processing, interlace processing (including microweave processing), and the like.

  The head control unit 54 converts the print data Dp generated by the image processing unit 53 into head control data Dh in a format that can be handled by the head drive circuit 15a, and performs one scan (one pass) of the print head 15 to the head drive circuit 15a. Transfer sequentially.

  The drive signal generation circuit 55 generates a drive pulse (drive waveform signal) having a signal waveform corresponding to the dot size (ink droplet size) based on the supply voltage supplied from the voltage supply unit 56 for one dot ejection period (one ejection). Drive signal COM arranged within a period) is generated. The drive signal COM includes, for example, one type of drive pulse PS1 for each ejection cycle if the dot size is one type, and three types of drive pulses PS1 to PS3 for each ejection cycle if the dot size is three types. Including.

  The head drive circuit 15a includes a logic circuit that inputs the head control data Dh and the drive signal COM, and a drive circuit (both not shown) of the logic circuit for each nozzle row. The logic circuit selects output / non-output to the subsequent drive circuit of the drive pulse in the drive signal COM based on the head control data Dh. The head control data Dh is binary data that takes “0” (non-ejection) or “1” (ejection) per dot when the dot size is one type, and per dot when the dot size is three types. The four-value data is any one of “00” (non-injection), “01” (small dot), “10” (medium dot), and “11” (large dot). When the dot size is one type, the drive pulse PS1 is not output when the value of the head control data Dh is “0”, and the drive pulse PS1 is output when the value is “1”. Further, when the dot size is three types, none of the drive pulses PS1 to PS3 is output when the value of the head control data Dh is “00”, and when the value is “01”, the drive pulse PS1 is When the value is “10”, the drive pulse PS2 is output, and when the value is “11”, the drive pulse PS3 is output.

  The head drive circuit 15a does not apply a drive voltage to the drive element 19 unless the drive pulse PS1 is output to the internal drive circuit. In this case, ink droplets are not ejected from the nozzle n. On the other hand, the head drive circuit 15a applies a drive voltage to the drive element 19 when the drive pulse PS1 is output to the drive circuit. In this case, ink droplets are ejected from the nozzle n. At this time, ink droplets of large, medium, and small dot sizes are ejected according to the drive pulses PS1, PS2, and PS3 output to the drive circuit.

  Here, the magnitude of the drive signal COM generated by the drive signal generation circuit 55, that is, the magnitude of the drive pulse PS 1 or PS 1, PS 2, PS 3 depends on the magnitude of the supply voltage V input from the voltage supply unit 56. Further, since the drive signal COM is a signal common to the logic circuit and the drive circuit for each nozzle row (A row to I row), for example, the supply voltage V is changed for adjustment according to individual differences of the printing apparatus 100. And the configuration that affects the ejection dot size of all nozzle rows (A row to I row). The supply voltage is initially a standard voltage.

  The drive signal generation circuit 55 generates a drive signal COM to be applied to the drive element 19. This drive signal COM is used in common for all the nozzle rows N when ejecting ink droplets from the nozzles n of the nozzle rows N. The drive signal COM includes one or a plurality of drive pulses corresponding to the amount of ink droplets ejected from the nozzle n (the type of dot size).

  The drive signal generation circuit 55 generates a drive pulse according to a command value described later from the main control unit 51. Specifically, a DA converter (not shown) included in the drive signal generation circuit 55 generates a voltage signal corresponding to the command value. The voltage signal is amplified by a transistor (not shown) included in the drive signal generation circuit 55 to generate a drive signal COM including a drive pulse having a desired pulse waveform indicated by the command value.

  The valve control unit 57 generates diluted ink to be used by controlling the opening and closing of the valves VL1 to VL10 via the drive circuit 42. In addition, the valve control unit 57 includes a dilution rate acquisition unit 57a that acquires the dilution rate of the mixed color ink and the dilution liquid CL with respect to the diluted ink generated by opening and closing the valves VL1 to VL10. Specifically, the dilution ratio acquisition unit 57a measures, for each of the valves VL1 to VL10, the opening time of the valve that supplies the color ink to each of the mixing tanks 21 to 25 and the opening time of the valve that supplies the dilution liquid CL. Thus, the ratio (%) of the color ink in the generated diluted ink is acquired. Then, the valve control unit 57 controls the opening times of the valves VL1 to VL10 so that the ratio (%) acquired by the dilution ratio acquisition unit 57a matches the target dilution rate of the diluted ink to be generated.

  In the present embodiment, the printing apparatus 100 receives test pattern data Dt, which is color measurement image data for causing the colorimeter 80 to perform color measurement as image data Dg, from the host apparatus 200, and performs a test based on the test pattern data Dt. The chart TC is printed (patch printing). In the patch printing at this time, the initial voltage (standard voltage) V0 is output as the supply voltage V from the voltage supply unit 56, and the dilution ratio of the diluted ink is the initial dilution ratio C50%, M50%, Y50%, K50%, K25. % Is done. Colorimetric data including colorimetric values obtained by measuring colors of the colorimeter 80 is input to a calculation unit 58 as an example of calculation means in the computer 31 via the communication I / F 41. The calculation unit 58 is based on the colorimetric values of each color in the colorimetric data, the coefficient in the relational expression indicating the relationship between the print density and the supply voltage for each color, and the relationship indicating the relationship between the print density and the dilution ratio for each color. Calculate the coefficients in the equation. In this embodiment, the communication I / F 41 for acquiring the print density from the colorimeter 80 and the calculation unit 58 for acquiring the print density for calculation constitute an example of a density acquisition unit.

  The voltage determination unit 59 as an example of voltage determination means determines a correction voltage V1 that brings the print density d1 closer to the reference density d0 by using a coefficient in the relational expression between the print density and the supply voltage, and sets the correction voltage V1 to the initial voltage V0. Instead, the correction voltage V <b> 1 is set in the voltage supply unit 56. In the present embodiment, the initial voltage V0 (specified voltage) supplied by the voltage supply unit 56, which is an example of the specifying means, corresponds to the first specified condition, and the correction voltage V1 corresponds to the second specified condition.

  Further, the dilution ratio determination unit 60 as an example of the dilution ratio determination means uses the coefficient in the relational expression between the print density and the dilution ratio to set the correction dilution ratio S1 that makes the print density d11 close to the reference density d0 as the diluted ink. The corrected dilution ratio S1 is set in the valve controller 57 instead of the initial dilution ratio S0.

  When the correction voltage V1 determined by the voltage determination unit 59 and the correction dilution rate S1 determined by the dilution rate determination unit 60 are values that are not preferable in terms of graininess in the printed image, the halftone correction unit 61 performs the image processing unit 53. A correction is instructed to the halftone processing unit 53b of the inside together with the set value for correction. Then, the halftone processing unit 53b performs halftone processing under the condition that the number of dots per unit area (dot density) is reduced below the standard value based on the correction setting value.

  FIG. 4 is a flowchart showing correction processing (print density adjustment processing) of supply voltage and dilution ratio. Hereinafter, this correction process will be described. In this correction processing, the printing apparatus 100 corrects the supply voltage V of the voltage supply unit 56 and the dilution ratio of diluted ink.

First, in step S10, an initial voltage V0 is applied. That is, the supply voltage V is set to the initial voltage (standard voltage V0).
In step S20, patch printing of each color of basic ink (C, M, Y, K) and diluted ink C50%, M50%, Y50%, K50%, K25% is performed. At this time, after patch printing is performed with the initial voltage V0, in order to calculate the coefficients α and β used in the subsequent calculations, the supply voltage (V0− Patch printing is also performed at Δv) and supply voltage (V0 + Δv). At this time, test pattern data Dt for the test chart TC is sent from the host apparatus 200 to the printing apparatus 100, so that the test chart TC is printed on a sheet.

  FIG. 5 shows a test chart used for color measurement for correction processing. The test chart includes first to third patch groups 71 to 73. In the figure, the symbol shown above each patch represents the ink color. Further, on the left side of the figure, the supply voltage V when printing patches arranged on the right side is shown. As shown in FIG. 5, when the first patch group 71 is formed, (V0−Δv) is set as the supply voltage V commonly used in each nozzle row. When the second patch group 72 is formed, (V0 + Δv) is set as the supply voltage V that is commonly used in each nozzle row. When the third patch group 73 is formed, the standard voltage V0 is set as the supply voltage V commonly used in each nozzle row.

  In the next step S30, the correction voltage V1 is determined from the density d1 of each patch of the color inks C, M, Y, and K that have been measured. First, the colorimeter 80 measures the density d of each patch of the test chart TC. In this case, L * value, a * value, and b * value are obtained as colorimetric values for each patch. Then, by obtaining the density of each patch based on these colorimetric values, the density of each ink color with respect to the supply voltage V can be obtained. Here, as the density d, a color space distance is adopted as an example. In this case, the density is the distance between the colorimetric values in the L * a * b * color space. When the colorimetric values are Lm *, am *, and bm *, the density d = [(Lm *) 2+ ( am *) 2+ (bm *) 2] 1/2.

  At this time, the patch density d1 when the supply voltage V is the initial voltage V0, the patch density d2 when the supply voltage is (V0−Δv), and the patch when the supply voltage V is (V0 + Δv). The concentration d3 of each is measured. Then, using the relationship between the supply voltages (V0−Δv) and (V0 + Δv) and the concentrations d2 and d3, a linear function expression ΔV = α × Δd + β indicating the relationship between the voltage change amount ΔV and the concentration change amount Δd of the supply voltage V. The coefficients α and β at are obtained.

  FIG. 6 is a graph showing a linear function indicating the relationship between the voltage change amount ΔV and the concentration change amount Δd. In the present embodiment, the relationship between the voltage change amount ΔV and the concentration change amount Δd is approximated by a linear function. In the figure, the horizontal axis indicates the voltage change ΔV, and the vertical axis indicates the density change Δd. A linear function ΔV = α · Δd + β indicating the relationship between the density change amount Δd and the voltage change amount Δ is shown. The calculation unit 58 calculates coefficients α and β that define the linear function. The coefficients α and β are calculated for the color inks C, M, Y, and K, which are examples of the basic color liquid. In this example, since four color inks C, M, Y, and K are used, a total of four sets of coefficients α and β are obtained. The second and third patch groups 72 and 73 are used for calculating the coefficients α and β, and once the coefficients α and β are stored in the volatile memory, the test is performed during the subsequent correction processing. The chart TC can be a patch print of only the first patch group 71.

  As shown in FIG. 8, in this embodiment, the relationship between the supply voltage V and the concentration d is approximated by a linear function. When the density d1 when the supply voltage V is the initial voltage V0 deviates from the reference density d0, the correction is made to the correction voltage V1 that can ensure the reference density d0. However, in this embodiment, since there are four color inks, the correction voltage V1 is calculated for each color.

  FIG. 10 illustrates a voltage correction process for correcting the supply voltage V in a direction in which the density d1 of each patch of the color inks C, M, Y, and K approaches the reference density d0, and diluted ink even if the supply voltage V is corrected. 5 is a graph for explaining a dilution ratio correction process for correcting the dilution ratio of diluted ink so that the density of the ink can ensure the reference density. FIG. 10 shows an example in which the maximum correction voltage V1max is adopted as the correction voltage V1.

  As shown in FIG. 10, at the initial voltage V0 before voltage correction (when there is no correction), the densities d1 of the nine ink colors take values as indicated by black rhombus plot points in the graph. Among these, the correction voltage V1 is determined so that the reference density d0 is secured even for the ink color having the lowest density d1min (magenta M in the example of FIG. 10) among the densities d1 of the color inks C, M, Y, and K. That is, correction voltages V1 (C), V1 (M), and V1 (Y) for the color inks C, M, Y, and K for setting the densities d1 of the color inks C, M, Y, and K to the reference density d0. , V1 (K) are calculated, and the maximum correction voltage V1max (V1 (M) in the example of FIG. 10) is determined as the correction voltage V1 (V1 = V1max). The correction voltage V1 is determined by the voltage determination unit 59, and the voltage determination unit 59 sets the determined correction voltage V1 as the supply voltage V to be output to the voltage supply unit 56 thereafter.

  When the correction voltage V1 is corrected, the amplitude of the drive pulse PS constituting the drive signal COM changes according to the voltage correction amount ΔV1, and as a result, the ink droplet size (that is, the dot size) changes. Changes. For example, in the example of FIG. 10, the correction voltage V1 is determined by correcting the initial voltage V0 by the voltage correction amount ΔV1 (= V0−V1min) in the direction of increasing the density d. In this case, since the initial voltage V0 is changed to the correction voltage V1 in common for all ink colors (all nozzle rows), diluted inks C50%, M50%, Y50%, K50 other than the color inks C, M, Y, K are used. % And K25% also increase the density d (see the black square plot points in FIG. 10).

  In FIG. 10, when the correction voltage V1 is set in this way, the density d11 of the diluted ink is separated from the reference density d0. Therefore, the density d11 of the diluted ink when the correction voltage V1 is set is estimated by calculation, and the dilution ratio S is corrected so that the estimated density d11 approaches the reference density d0.

  Therefore, in step S40 in FIG. 4, the density d11 at the correction voltage V1 is calculated for each color (nozzle row) of diluted ink. In the present embodiment, as for diluted ink, as shown in FIG. 6, the relationship between the voltage change amount ΔV and the density change amount Δd is approximated by a linear function. For the diluted ink, the calculation unit 58 calculates coefficients α and β that define a linear function expression ΔV = α × Δd + β indicating the relationship between the density change amount Δd and the voltage change amount Δ. The coefficients α and β are calculated for each of the diluted inks C50%, M50%, Y50%, K50%, and K25%. Here, since five diluted inks are used, a total of five sets of coefficients α and β are required. The five sets of coefficients α and β for each diluted ink may be calculated together when calculating the four sets of coefficients α and β for the color inks C, M, Y, and K in step S30.

  Using a linear function expression ΔV = α · Δd + β defined by using the coefficients α and β of each of these diluted inks, a density change amount Δd (= (ΔV1-β) when correction for the voltage correction amount ΔV1 is performed. ) / Α) is calculated individually for each diluted ink. Then, the density change amount Δd is added to the ink color density d of the diluted ink at the initial voltage V0 to calculate the density d11 of each diluted ink when the correction voltage V1 is set (d11 = d + Δd). For example, the density d11 (C50) of the ink color printed with the diluted ink C50% when the correction voltage V1 is set is the density change amount Δd corresponding to the voltage correction amount ΔV1 to the density d (C50) at the initial voltage V0. (C50) is added and it is calculated as d11 (C50) = d (C50) + Δd (C50). Thus, in FIG. 10, the density d11 (black square in FIG. 10) at the correction voltage of the diluted inks C50%, M50%, Y50%, K50%, and K25% is calculated.

  Further, in the next step S50 shown in FIG. 4, a correction dilution ratio S1 is determined for each color of the diluted ink. In the test chart TC shown in FIG. 5, the density d of each color patch of diluted ink C50%, M50%, Y50%, K50%, K25% is measured. At this time, combinations (C100%, C50%), (M100%, M50%), (Y100%, Y100%) of the basic color inks C, M, Y, K having a dilution ratio of 100% Y50%) and combinations of diluted inks with different dilution ratios (K50%, K25%), the densities d12 and d13 of two patches with different dilution ratios are obtained. Then, using the relationship between the dilution ratios (S0−Δs), (S0 + Δs) and the concentrations d12 and d13, the coefficient γ in the linear function equation ΔS = γ × Δd + δ showing the relationship between the dilution ratio change amount ΔS and the concentration change amount Δd. , Δ.

  FIG. 7 is a graph showing a linear function showing the relationship between the dilution ratio change amount ΔS and the concentration change amount Δd. In the present embodiment, the relationship between the dilution ratio change amount ΔS and the concentration change amount Δd is approximated by a linear function. In the figure, the horizontal axis represents the dilution ratio change amount ΔS, and the vertical axis represents the concentration change amount Δd. A linear function ΔS = γ × Δd + δ indicating the relationship between the dilution ratio change amount ΔS and the concentration change amount Δd is shown. The calculation unit 58 calculates coefficients γ and δ that define the linear function. The coefficients γ and δ are calculated for diluted ink C50%, M50%, Y50%, K50%, and K25% (however, the coefficients γ and δ are common for K50% and K25%). Here, since five colors of diluted ink are used, a total of five sets of coefficients γ and δ are required. Of course, for each diluted ink, a diluted ink is generated by changing the dilution ratio up and down by Δs (for example, a value in the range of 1% to 10%), and three types of patches are used with the diluted ink with different dilution ratios by Δs. Can be used to calculate coefficients γ and δ with higher accuracy for each diluted ink using the density d of three types of patches. The initial dilution ratio S0 for each of the diluted inks C50%, M50%, Y50%, K50%, and K25% is “50%” for each of the diluted inks C50%, M50%, Y50%, and K50% (S0 = 50%). ), The diluted ink K25% is “25%” (S0 = 25%).

  As shown in FIG. 9, in this embodiment, the relationship between the dilution ratio S and the concentration d is approximated by a linear function. When the density d11 at the initial dilution ratio S0 when the supply voltage V is the correction voltage V1 deviates from the reference density d0, the dilution ratio S is corrected to the correction dilution ratio S1 that can ensure the reference density d0. That is, the dilution ratio determining unit 60 performs the dilution corresponding to the density difference Δd11 (= d0−d11) until the density d11 at the correction voltage V1 and the initial dilution ratio S0 is matched with the reference density d0 for each diluted ink. The correction dilution ratio S1 is determined by adding the correction amount ΔS1 to the initial dilution ratio S0. However, in this embodiment, since there are five diluted inks, the corrected dilution ratio S1 is calculated for each color.

  FIG. 10 shows that the density d11 of the patch of diluted ink C50%, M50%, Y50%, K50%, K25% is diluted in a direction in which the density can be brought closer to the reference density d0 under the assumption that the correction voltage V1 is supplied. A dilution ratio correction process for correcting S will also be described.

  As shown in FIG. 10, when the voltage determining unit 59 determines the maximum correction voltage V1max as the correction voltage V1, the amplitudes of the drive pulses PS1 to PS3 constituting the drive signal COM change according to the voltage correction amount ΔV1. As a result, the ink droplet size (that is, the dot size) changes, and the density d also increases for diluted inks C50%, M50%, Y50%, K50%, and K25% (black square plot points in FIG. 10). See).

  For each diluted ink, a corrected dilution ratio S1 that can correct each density d11 (black square plot point in FIG. 10) of the diluted ink C50%, M50%, Y50%, K50%, and K25% toward the reference density d0. Determine individually. Thus, by determining the correction dilution ratio S1 for each diluted ink, the respective densities of the diluted ink C50%, M50%, Y50%, K50%, and K25% when the correction voltage V1 is applied are shown in FIG. Corrections are made as plotted points indicated by white triangles. The determination of the correction dilution ratio S1 is performed by the dilution ratio determination unit 60. Then, the dilution ratio determination unit 60 sets the determined correction dilution ratio S1 for each diluted ink in the valve control unit 57. As a result, in the subsequent control, the valve control unit 57 performs opening / closing control of the color ink supply valve and the dilution liquid supply valve so that the ratio of the color ink to the diluted ink becomes the corrected dilution ratio S1.

  As the voltage supply unit 56 outputs the correction voltage V1 determined by the voltage determination unit 59 in this way, the density of each ink color of the color inks C, M, Y, and K is ensured as close to the reference density d0 as possible. At this time, the valve control unit 57 controls the opening / closing of the valve so that the diluted ink having the correction dilution rate S1 determined by the dilution rate determination unit 60 can be generated. For this reason, diluted ink C50%, M50%, Y50%, K50%, and K25% of the respective corrected dilution ratios S1 are supplied from the diluted ink generator 20 to the print head 15, respectively. For this reason, the density of dots printed with diluted ink C50%, M50%, Y50%, K50%, and K25% is as close as possible to the reference density d0 for each diluted ink. Note that the halftone correction unit 61 has a function of suppressing graininess by adjusting the number of dots. When the correction voltage V1 determined by the voltage determination unit 59 and the correction dilution rate S1 determined by the dilution rate determination unit 60 are values that are not preferable in terms of graininess, the halftone correction unit 61 performs a half adjustment in the image processing unit 53. A correction setting value is instructed to the tone processing unit 53b. Then, the halftone processing unit 53b suppresses the graininess by reducing the number of dots per unit area (dot density) from the standard value based on the correction setting value.

According to the embodiment described above, the following effects can be obtained.
(1) The color inks C, M, and Y are determined by determining the correction voltage V1 based on the density d of each color patch printed at the initial voltage V0 so that at least the print density d of the color ink can be close to the reference density d0. , K can be as close as possible to the reference density d0. For this reason, the printing density of the color inks C, M, Y, and K is optimized and a necessary color reproduction range can be ensured. On the other hand, setting the correction voltage V1 may change the print density d of the diluted ink, but for the diluted ink, the density d11 that is expected when the correction voltage V1 is supplied is made closer to the reference density d0 of each color. A correct dilution ratio S1 is determined. Therefore, compared to the case where the dilution ratio is not corrected, the density of the color inks C, M, Y, and K can be ensured as close to the reference density d0 as the target density, so that the graininess in the printed image can be suppressed. Therefore, it is possible to provide a printed image in which the granularity is suppressed while ensuring the necessary color reproduction range. In addition, it is possible to suppress variations in print quality due to individual differences among the printing apparatuses 100, variations in print quality between pages during repeated printing in the same printing apparatus 100, and the like.

  (2) Since the print density can be acquired for each color based on the colorimetric values obtained by measuring the patches of the respective colors with the colorimeter 80, the accuracy of the colorimetric density is high and the supply voltage V can be accurately corrected. Therefore, the color reproduction range can be secured and the graininess can be suppressed by correcting the dilution ratio of the diluted color liquid.

  (3) A voltage correction amount ΔV1 for obtaining the printing density at the initial voltage V0 (specified voltage) close to the reference density d0 (target density) based on the coefficients α and β as an example of the first information is obtained. The correction voltage V1 can be determined by adding the voltage correction amount ΔV1 to the initial voltage V0. Therefore, the correction voltage V1 can be determined using the print density measurement result.

  (4) A dilution correction amount ΔS1 for obtaining the print density at the initial dilution ratio S0 (specified dilution ratio) as the reference density d0 (target density) is obtained based on the coefficients γ and δ as an example of the second information. The correction dilution ratio S1 can be determined by adding the dilution correction amount ΔS1 to the initial dilution ratio S0. Therefore, the correction dilution ratio S1 can be determined using the print density measurement result.

(5) Since the dilution ratio S in the diluted ink generating apparatus 20 is corrected, it is possible to generate a diluted ink having a dilution ratio capable of printing an image with a graininess suppressed.
(6) Since the halftone correction unit 61 sets a correction setting value in the halftone processing unit 53b and adjusts the number of dots per unit area (dot density), graininess can also be suppressed by this adjustment.

In addition, you may implement in the following aspects, without being limited to embodiment.
The correction voltage V1 is not limited to the maximum correction voltage V1max, and an average correction voltage V1ave as shown in FIG. 11 can also be adopted. That is, as shown in FIG. 11, the average density d1ave, which is the average of the densities d1 of the color inks C, M, Y, and K, is calculated, and the voltage correction amount ΔV1 is obtained so that the average density d1ave becomes the reference density d0. The average correction voltage V1ave is determined by adding the voltage correction amount ΔV1 to the initial voltage V0.

  In the above embodiment, a correction method is adopted in which the minimum value or average value of the respective densities d1 of the basic color liquids (C, M, Y, K) is brought close to the reference density d0, but the basic color liquids (C, M, Y) are used. , K), a correction method for bringing the density of a specific color close to the reference density d0 can also be adopted. Thus, the basic color liquid to be corrected may be at least one color. Further, a method of correcting the maximum value of the density d1 to the reference density d0 may be used. In short, it is only necessary that the printing density of the basic color liquid can be brought close to the reference density (target density). In addition, when using an average value, the average value including a diluted color liquid is also employable.

  The defining means is not limited to the voltage supply unit 56 that supplies the drive signal generation circuit 55 with the supply voltage V that defines the magnitude (amplitude, etc.) of the drive signal. For example, the main controller 51 that provides the drive signal generation circuit 55 with a command value that defines the pulse waveform in order to generate the drive pulse PS that constitutes the drive signal COM may be used as the defining means. That is, the command value to be output to the AD converter in the drive signal generation circuit 55 is set to the initial command value (standard command value), patch printing of each color is performed, and correction is performed so that the printing density of each color approaches the reference density d0. Determine the correction command value. Also with this configuration, by outputting the correction command value, the amplitude of the drive pulse in the drive signal COM generated by the drive signal generation circuit 55 can be changed and adjusted to an appropriate ink droplet ejection amount. The command value includes the condition values necessary for constructing the pulse waveform such as the rising angle (rising slope), height, holding time, and falling angle (falling slope) of the pulse waveform (eg trapezoidal wave). The value defines the drive pulse waveform to be generated.

  The second information (for example, coefficients γ and δ) indicating the relationship between the density change amount Δd and the dilution rate change amount ΔS of each diluted ink is stored in a memory in the printing apparatus 100 in advance as a result of experiments and the like. You may keep it. With this configuration, the processing necessary for obtaining the second information can be relatively simplified, and the density d11 at the correction voltage V1 can be set with a relatively high accuracy using the relatively accurate second information. Since it can be calculated, the correction dilution ratio S1 with relatively high accuracy can be acquired. For the first information (for example, coefficients α and β) indicating the relationship between the density change amount Δd and the voltage change amount ΔV of each color ink, values measured in advance through experiments or the like are stored in the memory in the printing apparatus 100. You may keep it.

  -In the case of a printing device without a colorimeter, the manufacturer measures the color before the shipment or during maintenance after shipment, and sets the correction voltage V1 and the correction dilution ratio S1 determined according to the obtained print density. You may employ | adopt the method set to a printing apparatus. With this method, even in a printing apparatus that does not include a colorimeter, it is possible to set an appropriate correction voltage V1 and correction dilution ratio S1, and provide a print image quality in which graininess is suppressed while ensuring a necessary color reproduction range. it can. In addition, it is possible to suppress variations in print quality due to individual differences among printing apparatuses and variations in print quality between pages during repeated printing in the same printing apparatus.

  -The diluted liquid of the diluted color liquid is not limited to a transparent liquid. For example, a light color ink similar to each of the basic color inks of CMYK may be used as the diluent. For example, a configuration may be used in which diluted ink is generated by diluting cyan ink with light cyan ink, diluting magenta ink with light magenta ink, and further diluting yellow ink with light yellow ink. Also in this case, when the correction voltage is determined so that the printing density of the basic color ink is as close to the target density as possible, the dilution ratio of the diluted ink is determined accordingly, and printing is performed while ensuring the color reproduction range. The graininess of the image can be improved.

  A configuration in which the user can change the reference density d0 by key operation can be adopted. In addition, a configuration in which the user can select a correction method for bringing the printing density of the basic color liquid closer to the reference density d0 from a plurality of methods (minimum value, average value, etc.) can be employed.

  In the embodiment, the density acquisition unit is configured by the communication I / F 41 and the calculation unit 58 for acquiring the color measurement data from the colorimeter 80. However, in the printing apparatus with the colorimeter, the color measurement is performed. It is also possible to use a density acquisition means including a color meter (color measurement means).

  The basic color liquid that is a basic color for expressing the color is not limited to four colors of C, M, Y, and K, and may be three colors of C, M, and Y. Further, at least one of basic color inks such as green, orange, and gray may be added to these basic color liquids. In this case, there may be provided a nozzle row that generates diluted ink for each of the orange, green, and gray inks and ejects the diluted ink. In addition, it is not necessary to generate each diluted ink for all colors of the basic color ink, and a configuration in which the diluted ink is generated for at least one of the plurality of basic color inks may be employed.

  For the basic color inks of C, M, and Y, a plurality of types of dilution inks (for example, 50% and 25%) may be prepared. Further, the dilution ratio is not limited to these values, and other dilution ratios (for example, 10%, 75%, etc.) can be appropriately set.

  -The measurement of printing density is not limited to the method using a colorimeter. For example, the size (volume or weight) of the ejected ink droplets of each color is measured and the print density of each color is obtained from the size, or the dot area of each color is measured and the print density of each color is obtained from the dot area. May be.

  -On the test chart TC, a patch formed by ejecting only small dots continuously, a patch formed by ejecting only medium dots continuously, or a patch formed by ejecting only large dots continuously is printed. Then, coefficient determination processing is performed for each dot size, and a correction voltage is obtained for each dot size. The average value of the correction voltages V1 (l), V1 (m), and V1 (s) for each dot size may be adopted as the correction voltage V1.

  A configuration in which the diluted ink generating device 20 of the above embodiment is not provided and a tank (including an ink cartridge) in which diluted ink is stored in advance is mounted on the holder of the printing apparatus may be employed. In this case, it is only necessary to have a dilution ratio adjustment function for at least the diluted ink to be set as the correction dilution ratio. With this configuration, it is possible to adjust the correction dilution ratio by simply mixing a small amount of basic ink or diluent with the diluted ink from the tank, so that color unevenness in the diluted ink can be easily suppressed.

  In the above embodiment, the present invention is embodied in the printing apparatus 100 that ejects ink as a liquid. However, a printing apparatus that ejects or discharges liquid other than ink may be employed. Note that the droplets ejected by the ejecting means of the printing device refer to the state of the liquid ejected from the printing device, and include those that have tails in the form of particles, tears, and threads. The liquid here may be any material that can be ejected by the printing apparatus. For example, it may be in a state in which the substance is in a liquid phase, such as a liquid with high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals (metal melts ) And a liquid as one state of a substance, as well as a material in which particles of a functional material made of a solid such as a pigment or metal particles are dissolved, dispersed or mixed in a solvent. When the liquid is an ink, the ink includes various liquid compositions such as general water-based ink and oil-based ink, gel ink, and hot melt ink. Specific examples of printing apparatuses that eject liquids other than ink include, for example, materials such as liquid crystal displays, EL (electroluminescence) displays, surface-emitting displays, and color materials used in the manufacture of color filters in the form of dispersion or dissolution. There is a printing device that ejects a liquid that contains it. In this case, the basic color liquid serving as a basic color for expressing the color may be an R (red), G (green), or B (blue) liquid. Furthermore, the printing apparatus may be a textile printing apparatus, a micro dispenser, or the like. The present invention can be applied to any one of these printing apparatuses.

Hereinafter, the technical idea grasped from the embodiment and each modification will be described below.
(A) The density acquisition means supplies, from the voltage supply means, a supply voltage for determining the magnitude of the drive signal as a specified voltage to a drive signal generation means for generating a drive signal for determining the dot size to be ejected by the ejection means. 2. The configuration according to claim 1, wherein each color patch is printed, and the print density is acquired for each color based on a color measurement result obtained by measuring the color patch by a color measurement unit. Printing device. According to the present invention, since the print density can be acquired for each color based on the color measurement result obtained by measuring the color patches by the color measuring unit, the accuracy of the color measurement density is high, and the voltage can be corrected with high accuracy. Therefore, the color reproduction range can be secured and the graininess can be suppressed by correcting the dilution ratio of the diluted color liquid.

  DESCRIPTION OF SYMBOLS 10 ... Printing mechanism, 14 ... Carriage, 15 ... Print head as an example of an ejection means, 15a ... Head drive circuit, 18, 18c, 18m, 18y, 18k, 18w ... Tank, 20 ... As an example of a diluted color liquid production | generation means Dilution ink generating device, 21-25 ... mixing tank, 30 ... control device, 31 ... computer, 32 ... CPU, 33 ... ASIC, 34 ... ROM, 35 ... RAM, 41 ... communication I constituting an example of density acquisition means / F, 42, 43 ... drive circuit, 51 ... main control unit, 52 ... print control unit, 53 ... image processing unit, 54 ... head control unit, 55 ... drive signal generation circuit as an example of drive signal generation means, 56 ... Voltage supply unit as an example of voltage supply means, 57 ... Valve control unit, 57a ... Dilution ratio acquisition unit, 58 ... Calculation as an example of concentration acquisition means and calculation means 59 ... Voltage determination unit as an example of voltage determination unit, 60 ... Dilution ratio determination unit, 61 ... Halftone correction unit, 80 ... Colorimeter as an example of color measurement unit, 100 ... Printing device, 200 ... Host device , P: paper as an example of an injection target, n: nozzle, N: nozzle row, M1: carriage motor, M2: transport motor, C, M, Y, K ... colored ink, C50%, M50%, Y50% , K50%, K25% ... dilution ink, CL ... dilution liquid, VL1 to VL10 ... valve, Dg ... image data, Dp ... print data, COM ... drive signal, P1-P3 ... drive pulse, [alpha], [beta] ... first Coefficient that is an example of information, γ, δ, coefficient that is an example of second information, V, supply voltage, V0, initial voltage (standard voltage) that is an example of the first specified condition and specified voltage, V0−Δv , V0 + Δv ... second power supply , ΔV 1, voltage correction amount, V 1, V 1 max, V 1 ave, correction voltage as an example of the second prescribed condition, d, d 1, d 11, density (print density), d 0, reference density as an example of target density, S Dilution ratio, ΔS1... Dilution correction amount, S1... Correction dilution ratio.

Claims (6)

A basic color liquid serving as a basic color for developing a color and at least one diluted color liquid obtained by diluting at least one of the basic color liquids with a diluent are ejected from an ejection unit onto an ejection target. A printing device that performs printing,
Injecting means for injecting the basic color liquid and the diluted color liquid based on image data;
Drive signal generation means for generating a drive signal to be output to the ejection means;
Defining means for defining the magnitude of the drive signal output from the drive signal generating means;
A density acquisition unit that acquires, for each color, a print density of each color printed by the ejection unit based on a drive signal having a magnitude defined by the first regulation condition by the regulation unit;
Determining means for determining a second prescribed condition by performing correction to bring at least one print density of the basic color liquid acquired by the density acquisition means close to a target density;
A dilution ratio determining unit that estimates a change in the print density of the diluted color liquid due to the correction and corrects the print density of the diluted color liquid to a target density to determine a corrected dilution ratio of the diluted color liquid;
A printing apparatus comprising: The defining means is a voltage supply means for supplying the drive signal generating means with a supply voltage that defines the magnitude of the drive signal, and provides the specified voltage as the first defining condition,
The determination unit is a voltage determination unit that determines a correction voltage by performing correction on the specified voltage so that at least one print density of the basic color liquid acquired by the density acquisition unit approaches a target density. The printing apparatus according to claim 1. The density acquisition means also acquires a print density based on a printing result performed by supplying a second supply voltage different from the specified voltage;
A calculation means for calculating first information indicating a relationship between the supply voltage and the print density based on the print density at the specified voltage and the print density at the second supply voltage;
The voltage determining means obtains a voltage correction amount for bringing the print density at the specified voltage close to the target density based on the first information, and adds the voltage correction amount to the specified voltage to perform the correction. The printing apparatus according to claim 2, wherein the voltage is determined. The density acquisition means acquires the print density of each color liquid printed by the ejection means with at least two color liquids having different dilution ratios for each color of the basic color liquid and the diluted color liquid,
The calculation means is configured to calculate second information indicating a relationship between a dilution ratio and a print density based on print densities of at least two color liquids having different dilution ratios,
The dilution ratio determining means obtains a dilution correction amount for bringing the print density of the diluted color liquid closer to the target density based on the second information, and adds the dilution correction amount to the dilution ratio to correct dilution. The printing apparatus according to claim 3, wherein the ratio is determined. The voltage determination means sets the determined correction voltage in the voltage supply means,
5. The printing apparatus according to claim 2, further comprising a diluted color liquid generating unit configured to generate a diluted color liquid at a dilution ratio determined by the dilution ratio determining unit. An ejecting means includes a basic color liquid serving as a basic color for expressing a color and at least one diluted color liquid generated by diluting at least one of the basic color liquids with a diluent. A print density adjustment method for adjusting a print density in printing performed by spraying on
A density measuring step for measuring, for each color, the print density of each color printed by the ejecting means by defining the size of a drive signal for determining the print dot size by the ejecting means under a first defining condition;
A determination step of determining a second prescribed condition by performing correction to bring at least one print density of the basic color liquid measured in the density measurement step close to a target density;
The print density when the diluted color liquid is printed under the second specified condition determined in the determining step is estimated, and the estimated print density is corrected so as to be close to the target density of the diluted color liquid. A dilution ratio determining step for determining a dilution ratio of the diluted color liquid;
A printing density adjustment method comprising:

Images