Patent Publication Number: US-9415587-B1

Title: Printing control apparatus and printing control method

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a printing control apparatus and a printing control method. 
     2. Related Art 
     An ink jet printer is known which performs printing by discharging ink to a printing medium using a printing head which includes nozzle rows in which a plurality of nozzles capable of discharging the ink are arranged in a nozzle row direction. In the ink jet printer, a platen gap (hereinafter, PG) which is a distance from a platen supporting the printing medium on which the ink is discharged to the printing head is varied according to differences of the printing medium being used, or the like. 
     In addition, in the ink jet printer, when discharging the ink from the nozzles, together with discharged ink droplets (the main droplets), droplets which are so-called satellites, or the like, which are fine compared to the main droplets are discharged. The satellites are referred to as sub-droplets. In addition, a part of the main droplets which are discharged and flown is scattered and becomes the sub-droplets. 
     Also, a recording operation is known in which one ink droplet is ejected from the nozzle when a distance from a nozzle formed surface of a recording head to a recording medium is relatively short (for example, 1 mm or less), two ink droplets are continuously ejected from the nozzle (two ink droplets are combined and flown before reaching recording medium) when the distance is relatively long (for example, 2 mm or more), four ink droplets are continuously ejected from the nozzle (four ink droplets are combined and flown before reaching recording medium) when the distance is longer (for example, 3 mm or more) (refer to JP-A-2014-148110). 
     When the sub-droplets are combined with the main droplets in the air until being landed onto the printing medium, or a landed position thereof is within a range in which the main droplets are landed and formed, the sub-droplets are not actually seen in a printing result. Meanwhile, when the sub-droplets are deviated from the main droplets and landed onto the printing medium, the sub-droplets are preset in the printing result so that the image quality is deteriorated. Particularly, when the sub-droplets are generated at the time of printing letters or ruled lines, the letters or ruled lines are blurred such as giving an observer the impression of seeing double. Moreover, hereinafter, “generation” of the sub-droplets means a state in which the sub-droplets are present on the printing medium deviated from the main droplets. 
     The PG is correlated with the generation of the sub-droplets. An orbital of the sub-droplets, which are smaller and lighter than the main droplets, is likely to be scattered during flying, due to air resistance or the influence of air current. Accordingly, the sub-droplets are capable of being deviated from the main droplets to be followed, as much as flying time is long. As much as the PG is wide, the flying time of the ink discharged is likely to be long. For this reason, as much as the PG is wide, the sub-droplets are likely to be generated. Accordingly, measures for suppressing the deterioration of the image quality due to the sub-droplets, which are likely to be generated according to the PG, are required. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a printing control apparatus and a printing control method capable of suppressing deterioration of an image quality due to the influence of PG. 
     According to an aspect of the invention, there is provided a printing control apparatus which realizes printing by controlling a printing head including nozzle rows in which a plurality of nozzles are arranged in a predetermined nozzle row direction, the apparatus includes a control section that controls the printing head in which the plurality of nozzle rows discharging same types of ink are disposed to be deviated from the nozzle row direction, in which the control section is capable of selecting and performing any one of a first printing mode in which the printing is performed by setting a platen gap which is a distance from a platen supporting the printing medium on which the ink is discharged to the printing head as a first platen gap, and a second printing mode in which the printing is performed by setting the platen gap as a second platen gap which is narrower than the first platen gap, and the number of the nozzle rows used for discharging the ink in the first printing mode is smaller than the number of the nozzle rows used for discharging the ink in the second printing mode. 
     In this case, the number of the nozzle rows which are used in the first printing mode in which printing is performed with a relatively wide first PG is smaller than the number of the nozzle rows which are used in the second printing mode in which printing is performed with a relatively narrow second PG. Accordingly, in the first printing mode, compared to the second printing mode, the printing resolution in the nozzle row direction can be deteriorated. By deteriorating the printing resolution, since landed times of the ink per unit area of the printing medium (the number of dots per unit area) is reduced, the number of the generated sub-droplets is also reduced, as a result, the deterioration of the image quality (blurring of letters, ruled lines, or the like) due to generating of the sub-droplets can be suppressed. 
     In the printing control apparatus, the control section may allow a size of the ink discharged in the first printing mode to be greater than a size of the ink discharged in the second printing mode. 
     In this case, when the size of ink is increased in the first printing mode in which printing is performed with the relatively wide first PG, the deviation of the landed position of the ink on the printing medium is reduced, and thus, image quality can be improved. 
     In the printing control apparatus, the control section may allow a printing resolution in a direction intersecting with the nozzle row direction in the first printing mode to be smaller than a printing resolution in the second printing mode. 
     In this case, when the printing resolution of a direction intersecting with the nozzle row direction is deteriorated in the first printing mode in which printing is performed with the relatively wide first PG, the number of dots per unit area of the printing medium is relatively reduced, and thus, the number of the generated sub-droplets can be reduced. 
     In the printing control apparatus, when the number of the nozzle rows used in the first printing mode is set to N, the control section may use nozzle rows as N rows in vicinity of one end side of a direction intersecting with the nozzle row direction in the first printing mode. 
     In this case, when N nozzle rows used in the first printing mode is set to N rows inclined in one end side of a direction intersecting with the nozzle row direction, variation of nozzle intervals (intervals within group of used nozzle rows) at the time of generating a tilt in the printing head can be reduced as much as possible. 
     Technical ideas of the invention are also realized an apparatus other than the printing control apparatus. For example, the invention may be realized by a method including processes executed by the printing control apparatus (printing control method), a computer program causing the method to executed by a computer, or various categories of recording mediums which can be read by the computer storing the program. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a block diagram exemplifying a configuration of an apparatus according to an embodiment. 
         FIG. 2  is a flow chart illustrating a printing control process. 
         FIG. 3  is a diagram exemplifying a configuration of a printing head. 
         FIG. 4  is a diagram illustrating an example of a table which assumes a corresponding relationship of a printing mode and a printing resolution, or the like. 
         FIG. 5  is a diagram simply illustrating a configuration of a part of a range of a printing section when seen from a side. 
         FIG. 6  is a flow chart illustrating a process of a generation of printing data. 
         FIGS. 7A and 7B  are diagrams exemplifying a case in which a nozzle row direction is not tilted and a case in which the nozzle row direction is tilted. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to each of drawings. Each of the drawings only is exemplified for describing the embodiments, and may be not matched with the other. 
     1. Schematic Description of Apparatus 
       FIG. 1  exemplifies functions of a printing control apparatus  10  according to the embodiment as a block diagram. The printing control apparatus  10  is recognized as a product, for example, a printer, or a multifunction machine including a function of the printer. When the printing control apparatus  10  is configured to have a printing section  30  which actually performs printing on a printing medium, and a configuration of a part for controlling a behavior of the printing section  30  (for example, control section  11  described later), the configuration of a part may be referred to as the printing control apparatus  10 . In addition, the printing control apparatus  10  may be referred to as a printing apparatus, an image processing apparatus, or the like. Each of configurations illustrated in  FIG. 1  is not limited to a case in which components are aggregated in one position or one case, and may be a system in which the components are present at a position by being separated from each other respectively and in a state of being capable of communication. For example, the printing control apparatus  10  may be configured to have a printer which actually performs printing on the printing medium and an apparatus (personal computer, or the like) in which a computer program (printer driver) for controlling a behavior of the printer is mounted so as to control the printer. 
       FIG. 1  exemplifies the printing control apparatus  10  which is configured to have the control section  11 , an operation input section  16 , a display section  17 , a communication interface (I/F)  18 , a slot section  19 , a printing section  30 , and the like. The control section  11  is configured to have, for example, an IC including a CPU, a ROM, a RAM, and the like, or the other recording medium, and the like. In the control section  11 , the CPU realizes various processing (for example, printing control process to be described later) by executing arithmetic processing according to a program which is stored in the ROM, or the like by using the RAM, or the like as a work area. 
     The operation input section  16  includes various buttons, keys, or the like for receiving an operation performed by a user. The display section  17  is a portion for displaying various information relating to the printing control apparatus  10 , and is formed of, for example, a liquid crystal display (LCD). A part of the operation input section  16  may be realized as a touch panel displayed on the display section  17 . 
     The printing section  30  is a mechanism for printing an image on the printing medium. When a printing method is an ink jet method which is applied to the printing section  30 , the printing section  30  is configured to have a printing head  31  (refer to  FIG. 3 ), a carriage  35  which moves (main scanning) the printing head  31  in a predetermined main scanning direction, a transportation section  36  which transports the printing medium in a transportation direction intersecting with the main scanning direction, and the like. The printing section  30  may be a device which is capable of performing color printing, and may be a device which is capable of performing black-and-white printing without performing color printing. 
     The printing head  31  receives the ink supplied from an ink cartridge which is not illustrated. In a case in which the printing section  30  is a device which is capable of performing color printing as described above, the printing head  31  receives the ink from the ink cartridge of each of various ink (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, and the like). Meanwhile, In a case in which the printing section  30  is a device which is capable of performing black-and-white printing as described above, the printing head  31  receives the K ink from the ink cartridge of the K ink. The printing head  31  is capable of discharging (ejecting) the ink (ink droplets) from a plurality of nozzles  34  (refer to  FIG. 3 ). Printing is realized when the discharged ink is landed onto the printing medium so as to form dots on the printing medium. The term “dots” basically means ink droplets which are landed onto the printing medium; however, even in a description relating to a process before the ink droplets are landed on the printing medium, an expression of “dots” can be appropriately used. Specific types or numbers of liquid used for the printing section  30  are not illustrated, and for example, various inks or liquid such as light cyan, light magenta, orange, green, gray, light gray, white, metallic, and the like can be used. 
     The transportation section  36  includes rollers for supporting and transporting the printing medium or motors for rotating the rollers (neither is illustrated). The printing medium is typical paper. However, in the embodiment, when the printing medium is made of a material which is capable of performing recording with liquid and being transported by the transportation section  36 , a material other than paper is also included in a concept of the printing medium. 
     The communication I/F  18  is a general term of an interface for connecting the printing control apparatus  10  to an external device  100  by wired or wireless communication. As the external device  100 , for example, there are various devices such as smart phones, tablet type terminals, digital steel cameras, and personal computers (PC), which become an input source of image data to the printing control apparatus  10 . The printing control apparatus  10  can be connected to the external device  100  through the communication I/F  18 , and for example, through various units such as a USB cable, a wired network, a wireless LAN, or an electronic mail communication or communication standard. 
     The slot section  19  is a portion for introducing an external recording medium such as a memory card. That is, the printing control apparatus  10  is also capable of inputting image data stored in a recording medium, from the external recording medium such as a memory card which is inserted into the slot section  19 . 
       FIG. 2  illustrates a printing control process which is performed by the control section  11  using a flow chart. When inputting the image data (Step S 100 ) expressing an image of a printing object, the control section  11  performs an image process for generating printing data from the image data (Step S 200 ). A format of the image data is considered as various types, and for example, is data in which gradation is expressed using RGB (red, green, and blue) in each pixel. The control section  11  appropriately performs an image process such as a resolution conversion process, a color (color model) conversion process, and a halftone process with respect to the image data, so as to generate printing data in which the image of the printing object is expressed as a pattern of dots using a plurality of pixels. 
     The pattern of dots (dot pattern) is an arrangement of ON of the dots (formation of dots, that is, ink discharging) • OFF of the dots (non-formation of dots, that is, ink non-discharging), and it can be said that the pattern specifies ON or OFF of the dots in each pixel. When the printing section  30  corresponds to the color printing and the printing head  31  discharges, for example, the CMYK ink, the printing data includes data in which ON or OFF of the dots in each pixel is specified in each of the CMYK. Meanwhile, when the printing section  30  corresponds to the black-and-white printing and the printing head  31  discharges, for example, the K ink, the printing data is data in which ON or OFF of the dots of the K ink in each pixel. Moreover, Step S 200  will be described later in detail. 
     Regarding each pixel constituting such a printing data, the control section  11  determines a nozzle  34  of an allocated address, and performs an output process in which, according to a determined result, the resultant is transmitted to the printing head  31  by rearranging a predetermined arrangement for being transmitted to the printing head  31  (Step S 300 ). By allocating each of pixels to the nozzle  34 , it is confirmed that the dot of each of pixels constituting the printing data is discharged according to colors of the ink and the pixel position, by any nozzle  34  of the printing head  31 . 
     The printing head  31  drives each nozzle  34  based on the transmitted printing data. For example, a driving signal (type of pulse) for driving each nozzle  34  is applied to the printing head  31  by the control section  11 . A detailed description will not be repeated; however, in the printing head  31 , applying the driving signal provided in each nozzle  34  to a driving element is switched, according to information relating to ON or OFF of the dots in each pixel specified by the printing data. Accordingly, each nozzle  34  realizes discharging and non-discharging of the ink according to information relating to the pixel allocated thereto. As a result, the image of the printing object is printed on the printing medium. 
       FIG. 3  simply exemplifies a configuration, or the like of the printing head  31 . In  FIG. 3 , an arrangement of the nozzles  34  in an ink discharging surface  31   a  of the printing head  31  is exemplified from a point of view when seen from the top of the printing head  31 . In  FIG. 3 , each of the nozzles  34  is expressed by a circle. The ink discharging surface  31   a  is a surface in which the nozzles  34  are open, and is a surface facing the printing medium S transported by the transportation section  36  in a transportation direction. In  FIG. 3 , a direction D 1  corresponds to a main scanning direction, and a direction D 2  corresponds to a transportation direction. Basically, the main scanning direction D 1  and the transportation direction D 2  are orthogonal to each other. 
     Hereinafter, unless otherwise specified, a case in which the printing section  30  corresponds to the black-and-white printing is assumed and described. In an example of  FIG. 3 , the printing head  31  includes nozzle rows  33   a ,  33   b ,  33   c , and  33   d  corresponding to discharging of the K ink. The nozzle rows  33   a ,  33   b ,  33   c , and  33   d  are respectively nozzle rows in which the plurality of nozzles  34  for discharging the K ink are arranged at predetermined intervals (constant nozzle pitch NP) in a predetermined nozzle row direction D 3 . 
     The nozzle row direction D 3  where the nozzle row is toward intersects with the main scanning direction D 1 . It depends on a design of the printing section  30 ; however, the nozzle row direction D 3  is orthogonal to the main scanning direction D 1 , or intersects with the main scanning direction at an oblique angle which is not orthogonal thereto (90 degrees). Hereinafter, for convenience of description, the nozzle row direction D 3  is orthogonal to the main scanning direction D 1 . Accordingly, the nozzle row direction D 3  and the transportation direction D 2  are parallel to each other. Also, in this specification, even when expressions which is strictly interpreted, such as “orthogonal”, “parallel”, and “constant” are used, it does not mean “orthogonal”, “parallel”, and “constant”, and meaning of an error allowable within a product performance or an error generated at the time of manufacturing the product also included. 
     A pair of the nozzle row  33   a  and the nozzle row  33   b  adjacent to each other among the nozzle rows  33   a ,  33   b ,  33   c , and  33   d , is disposed in a state in which positions thereof are deviated from each other in the nozzle row direction D 3  as a distance of half of the nozzle pitch NP. A pair of the nozzle row  33   c  and the nozzle row  33   d  is also disposed in a state in which positions thereof are deviated from each other in the nozzle row direction D 3  as a distance of half of the nozzle pitch NP. Further, the pair of the nozzle rows  33   a  and  33   b , and the pair of the nozzle rows  33   c  and  33   d  are disposed in a state in which positions thereof are deviated from each other in the nozzle row direction D 3  as a distance of ¼ of the nozzle pitch NP. 
     Accordingly, the nozzle resolution (the number of nozzles per 1 inch, npi) in the transportation direction D 2  by the pair of the nozzle rows  33   a  and  33   b , and the nozzle resolution in the transportation direction D 2  by the pair of the nozzle rows  33   c  and  33   d , are respectively twice of the nozzle resolution (equal to 1/NP inch) in the transportation direction D 2  by one nozzle row. In addition, the nozzle resolution in the transportation direction D 2  by all of the nozzle rows  33   a ,  33   b ,  33   c , and  33   d , is four times of the nozzle resolution in the transportation direction D 2  by one nozzle row. As an example, when the nozzle resolution in the transportation direction D 2  by the one nozzle row is set to 300 npi, the nozzle resolution in the transportation direction D 2  by the pair of nozzle rows  33   a  and  33   b , and the nozzle resolution in the transportation direction D 2  by the pair of nozzle rows  33   c  and  33   d  are respectively 600 npi, and the nozzle resolution in the transportation direction D 2  by all of the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  is 1200 npi. 
     The carriage  35  on which the printing head  31  is mounted receives a motivity of a carriage motor (not illustrated), and is moved parallel to the main scanning direction D 1 . The printing head  31  is moved together with the carriage  35  and discharges the ink onto the printing medium S so as to realize printing. A process, in which the printing head  31  discharges the ink according to a movement from one end side of the main scanning direction D 1  to the other end side thereof, or a movement from the other side of the main scanning direction D 1  to one end side thereof, is referred to as “main scanning” or “pass” at one time. According to such a configuration, it can be said that the printing control apparatus  10  realizes printing by controlling the printing head  31  which includes the nozzle row (for example, nozzle rows  33   a ,  33   b ,  33   c , and  33   d ) in which the plurality of nozzles  34  are arranged in the nozzle row direction D 3 . In addition, it can be said that the control section  11  controls the printing head  31  in which a plurality of nozzle rows discharging the same type of ink (for example, nozzle rows  33   a ,  33   b ,  33   c , and  33   d ) are disposed by being deviated from the nozzle row direction D 3 . 
     2. Description Relating to Printing Mode and PG 
     Next, the printing mode set by a user and the PG according to the printing mode will be described. The user can arbitrary set the printing mode, for example, by operating the operation input section  16  while seeing a user interface (UI) screen displayed on the display section  17  before starting the printing control process ( FIG. 2 ) in the printing control apparatus  10 . The user can simply set the printing mode by selecting a predetermined printing condition out of menus in the UI screen (for example, menu “normal paper”, “envelope”, and the like relating to selecting printing medium, menu for selecting “single-surface printing” or “double-surface printing”, menu for selecting “enabling” or “disabling” of rubbing reducing mode, or the like). The rubbing reducing mode is an option of enabling for a case in which contacting of the printing head  31  and the printing medium S is reliably avoid. 
       FIG. 4  exemplifies Table T which assumes a corresponding relationship of the printing mode, and the printing resolution and the size of ink. The control section  11  stores such a Table T in a predetermined memory in advance so that Table T can be used for reference. In Table T, the PG determined according to a printing condition selected by the user is specified. 
     For example, with respect to a combination of the printing conditions of normal paper, single-surface printing, and the rubbing reducing mode OFF (disabling), the PG is specified to 0.9 mm. 
     In addition, with respect to a combination of the printing conditions of normal paper, single-surface printing, and the rubbing reducing mode ON (enabling), the PG is specified to 2.5 mm. 
     In addition, with respect to a combination of the printing conditions of normal paper, double-surface printing, and the rubbing reducing mode OFF, the PG is specified to 2.0 mm. 
     In addition, with respect to a combination of the printing conditions of normal paper, double-surface printing, and the rubbing reducing mode ON, the PG is specified to 2.5 mm. 
     In addition, with respect to a combination of the printing conditions of the envelope and single-surface printing, regardless ON and OFF of the rubbing reducing mode, the PG is specified to 4.4 mm. Also, when printing is performed on the envelope, double-surface printing cannot be selected. 
     In addition, according to Table T of  FIG. 4 , with respect to the PG less than 2.5 mm, horizontal and vertical printing resolutions (dpi) are respectively specified to 1200 dpi (however, in a case of normal paper, double-surface printing, and rubbing reducing mode OFF, horizontal printing resolution is specified to 900 dpi), and a weight of the ink droplets is specified to 8 nanograms (ng). Meanwhile, with respect to the PG equal to or more than 2.5 mm, the horizontal and vertical printing resolutions are respectively specified to 600 dpi, and the weight of the ink droplets is specified to 16 ng. The horizontal printing resolution is the printing resolution of the main scanning direction D 1 , and the vertical printing resolution indicates the printing resolution of the transportation direction D 2 . 
     In the embodiment, the nozzles  34  are capable of discharging various size ink. At least two sizes ink can be discharged because of various sizes. Two different sizes out of such various sizes are respectively referred to as a first size and a second size. Also, the first size is greater than the second size. The ink droplets having 16 ng weight per one droplet described above corresponds to an example of the ink of the first size. In addition, the ink droplets having 8 ng weight per one droplet corresponds to an example of the ink of the second size. Both of the first size and the second size indicate a size (weight) of the main droplets described above. That is, the printing section  30  is designed so as to discharge the ink (main droplets) of a size which is set to the first size, the second size, or the like in advance. Of course, since there is an error included in an actual size of the ink (main droplets) discharged from the nozzles  34 , the size thereof is not strictly matched with the preset size such as the first size or the second size. In addition, as already said, sub droplets, which are fine droplets separated from the main droplets, can be generated. 
     The control section  11  is capable of performing one process out of at least the first printing mode in which printing is performed with the PG as a first PG and the second printing mode in which printing is performed with the PG as a second PG narrower than the first PG. When referring to Table T of  FIG. 4 , the 2.5 mm or more PG is referred to as the first PG, and the PG less than 2.5 mm is referred to as the second PG. That is, the control section  11  determines that the first printing mode is set in a case in which the user sets a combination of the printing conditions (for example, combination of printing conditions of normal paper, single-surface printing, and rubbing reducing mode ON) when the PG is the first PG, and the control section  11  determines that the second printing mode is set in a case in which the user sets a combination of the printing conditions (for example, combination of printing conditions of normal paper, single-surface printing, and rubbing reducing mode OFF) when the PG is the second PG. 
       FIG. 5  simply illustrates a configuration of a part of a range of the printing section  30  when seen from a side. In the printing section  30 , the platen  32  is provided to correspond to the ink discharging surface  31   a  of the printing head  31 . The printing medium S is transported onto the platen  32  in the transportation direction D 2  by the transportation section  36 . In  FIG. 5 , the main scanning direction D 1  is a direction perpendicular to a surface of a paper of the drawing. As we known, the printing section  30  is capable of adjusting a height from the platen  32  to the printing head  31  (ink discharging surface  31   a ), that is, the PG, by adjusting a position of a height direction of the carriage  35 , or the like. 
     Accordingly, when the printing mode is set according to selecting of the printing condition by the user as described above, with reference to Table T, the control section  11  specifies the PG corresponding to the printing condition currently, and adjusts the PG in the printing section  30  so as to become the specified PG. As a result, for example, when a combination (one first printing mode) of the printing conditions of the normal paper, single-surface printing, and the rubbing reducing mode ON is set, the actual PG is adjusted to be 2.5 mm. In addition, for example, when a combination (one second printing mode) of the printing conditions of the normal paper, single-surface printing, and the rubbing reducing mode OFF is set, the actual PG is adjusted to be 0.9 mm. 
     As already said, the PG is correlated with the generation of the sub droplets. That is, as much as the PG is wide, the sub droplets are likely to be generated. An inventor experiments a relationship of the PG and generation of the sub droplets, as a result, the inventor obtains an opinion that the sub droplets are rapidly generated at peripheries of the PG in each of substantially 2.0 to 2.5 mm. It can be said that an aspect in which the 2.5 mm or more PG is set to the first PG and the less than 2.5 mm PG is set to the second PG, is based on the opinion described above. That is, it can be said that, the first printing mode in which printing is performed with the PG as the first PG is a printing mode in which the image quality is easily deteriorated due to generation of the sub droplets, compared to the second printing mode in which printing is performed with the PG as the second PG. 
     Of course, specific contents (types of printing conditions and various numbers) of Table T illustrated in  FIG. 4  are only an example. Technical ideas of the invention are not limited and described to the specific contents of such a Table T. 
     3. Generation of Printing Data and Printing Based on Printing Data 
       FIG. 6  illustrates Step S 200  (generation of printing data) in  FIG. 2  by a flow chart in detail. In Step S 210 , the control section  11  sets the printing resolution and the size of the ink according to the printing mode set currently. That is, the control section  11  sets the printing resolution and the size of the ink corresponding to the first printing mode when the printing mode set currently is the first printing mode, and sets the printing resolution and the size of the ink corresponding to the second printing mode when the printing mode set currently is the second printing mode. The setting is performed with reference to Table T. According to Table T exemplified in  FIG. 4 , when the printing mode is the first printing mode, the horizontal and vertical printing resolutions are respectively set to 600 dpi, and the size of ink is set to the first size (weight of ink droplets is 16 ng). Meanwhile, when the printing mode is the second printing mode, the horizontal and vertical printing resolutions are respectively set to 1200 dpi (however, in a case of normal paper, double-surface printing, and rubbing reducing mode OFF, horizontal printing resolution is set to 900 dpi), and the size of the ink is set to the second size (weight of ink droplets is 8 ng). 
     In Step S 220 , the control section  11  performs the resolution conversion process on the image data input in Step S 100  ( FIG. 2 ). That is, horizontal resolution and vertical resolution of the image data are converted (compensating or thinning of pixels) so as to respectively correspond to the horizontal printing resolution and the vertical printing resolution set in Step S 210  (horizontal printing resolution and vertical printing resolution adopted by the printing section  30 ). As a result, when current printing mode is the first printing mode, both of the horizontal resolution and the vertical resolution of the image data become 600 dpi, and when current printing mode is the second printing mode, both of the horizontal resolution and the vertical resolution of the image data become 1200 dpi (however, in a case of normal paper, double-surface printing, and the rubbing reducing mode OFF, horizontal printing resolution is 900 dpi). 
     Next, in Step S 230 , the control section  11  performs the color conversion process on image data after Step S 220 , and converts the image data to image data in which a density of the K ink in each pixel is expressed by gradation (for example, 256 gradation from 0 to 255). The color conversion process is performed with reference to a look up table, or the like in which a conversion relationship of RGB and K is specified and stored in a predetermined memory in advance. Otherwise, the control section  11  may specify a gradation value of K corresponding to a level of brightness of each pixel by calculating the brightness using a predetermined conversion equation from the RGB in each pixel. 
     In Step S 240 , the control section  11  generates the printing data in which the K ink is expressed by a dot pattern by performing the halftone process on the image data after Step S 230 . The halftone process is performed by, for example, a dither method or an error diffusion method. 
     Even a process in Step S 300  ( FIG. 2 ) is also restricted in contents of setting in Step S 210 . The control section  11  reduces the number of the nozzle rows (the number of used nozzle rows used for printing (the number of used nozzle rows)) which is an allocation address of the pixels constituting the printing data generated in Step S 200 , in a case in which the vertical printing resolution is set to 600 dpi (in a case of first printing mode), compared to a case in which the vertical printing resolution is set to 1200 dpi (in a case of second printing mode). Specifically, when the vertical printing resolution is set to 600 dpi, the number of the used nozzle rows is set to two, and when the vertical printing resolution is set to 1200 dpi, the number of the used nozzle rows is set to four. In Table T, the number of the used nozzle rows is also specified according to such vertical printing resolution (according to printing mode). 
     With reference to  FIG. 3 , in the embodiment, when the number of the used nozzle rows is 4, all of the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  are set to the used nozzle rows, and thus it is realized that the vertical printing resolution (printing resolution of transportation direction D 2 ) is 1200 dpi. Meanwhile, when the number of the used nozzle rows is 2, the nozzle rows  33   a  and  33   b  among the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  are set to the used nozzle row, and thus it is realized that the vertical printing resolution (printing resolution of transportation direction D 2 ) is 600 dpi. That is, the control section  11  determines the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  as a target when the nozzles  34  of an allocation address relating to each pixel constituting the printing data are set to the number of the used nozzle rows is 4, otherwise, when the number of the used nozzle rows is 2, the control section  11  determines by limiting to the nozzle rows  33   a  and  33   b.    
     In addition, in a case in which the size of ink is set to the first size (in a case of first printing mode) and a case in which the size of ink is set to the second size (in a case of second printing mode), the control section  11  controls the printing section  30  so as to make the driving signal applying to a driving element of the nozzle  34  different. Being difference of the driving signal applied to the driving element means that, for example, a waveform or the number of the driving signals (pulse) which are applied to the driving element for forming one dot on the printing medium is different. That is, when the size of ink is set to the first size, according to information relating to dots ON of the pixels, the driving signal for discharging the ink of the first size (weight of ink droplets is 16 ng) is applied to the driving element of the nozzle  34  which is allocated to the pixel. In addition, when the size of ink is set to the second size, according to information relating to dots ON of the pixels, the driving signal for discharging the ink of the second size (weight of ink droplets is 8 ng) is applied to the driving element of the nozzle  34  which is allocated to the pixel. 
     Moreover, “the size of ink discharged using the nozzle  34 ” is not evaluated as a size of ink at the time of being discharged from the nozzle  34 , and is evaluated as a size of dot formed by landing the discharged ink onto the printing medium. Because it is thought that the nozzle  34  continuously discharges various ink having substantially same size by corresponding to one pixel, and the continuously discharged various ink are combined with each other in the air so that ink becomes a large size and landed onto the printing medium. That is, the nozzle  34  may allow the first size or the second size ink to be landed onto the printing medium by discharging the ink having different size at the time of discharging according to the different driving signal, and may allow the first size or the second size ink to be landed onto the printing medium by making the number of the ink having substantially same size be different according to the different driving signal. 
     Even intervals of driving each nozzle  34  constituting the used nozzle row are also restricted in contents of setting in Step S 210 . That is, when the horizontal printing resolution is set to 600 dpi (in a case of first printing mode), the control section  11  generates the driving signal at intervals which need for driving each nozzle  34  constituting the used nozzle row (nozzle rows  33   a  and  33   b ) by corresponding to 600 dpi during moving along the main scanning direction D 1  of the printing head  31 . Meanwhile, when the horizontal printing resolution is set to 900 dpi or 1200 dpi (in a case of second printing mode), the control section  11  generates the driving signal at intervals which need for driving each nozzle  34  constituting the used nozzle row (nozzle rows  33   a ,  33   b ,  33   c , and  33   d ) by corresponding to 900 dpi or 1200 dpi during moving along the main scanning direction D 1  of the printing head  31 . 
     According to the embodiment, in the printing control apparatus  10 , the number of the used nozzle rows used for discharging the same types of ink in the first printing mode in which printing is performed by applying the first PG widen to any degree, or more, is smaller than the number of the used nozzle rows used for discharging the same types of ink in the second printing mode in which printing is performed by applying the relatively narrow second PG. Accordingly, in the first printing mode, the printing resolution in the nozzle row direction D 3  (similar to transportation direction D 2 ) can be deteriorated compared to the second printing mode. By deteriorating the printing resolution, landed times (the number of dots per unit area) of the ink (main droplets) per unit area of the printing medium are reduced. When the number of the main droplets is reduced, of course, the number of generation of the sub droplets is also reduced. Accordingly, in the embodiment, in the first printing mode in which the image quality is basically easily deteriorated due to the generation of the sub droplets, by suppressing the deterioration of the image quality, a printing result of a vivid image quality having less blurring (particularly, blurring of letters, ruled lines, or the like) can be obtained. 
     In addition, in the embodiment, in the first printing mode, compared to the second printing mode, the printing resolution in the main scanning direction D 1  is also deteriorated. When the printing resolutions of the nozzle row direction D 3  (similar to transportation direction D 2 ) and the main scanning direction D 1  are deteriorated, the number of dots per unit area is further reduced, and the deterioration of the image quality can be reliably reduced in the first printing mode in which the image quality is basically easily deteriorated due to the generation of the sub droplets. However, being different of the printing resolution in the main scanning direction D 1  in the first printing mode and the second printing mode, is not a necessary configuration of the embodiment. For example, in Table T illustrated in  FIG. 4 , all of the horizontal printing resolutions may be unified as 1200 dpi. 
     Moreover, if the size of ink is maintained same as the size in a case in which the number of the used nozzle rows is not reduced when the number of the used nozzle rows is reduced and the printing resolution in the nozzle row direction D 3  (similar to transportation direction D 2 ) is deteriorated, there are concerns that a balance between the printing resolution and the size of ink is inappropriate and the image quality is deteriorated. For example, at the time of deteriorating the printing resolution, the size of ink is the same as that of in a case in which the number of the used nozzle rows is reduced, and thus there may be a case in which an amount of the discharged ink per unit area of the printing medium is insufficient so that the image quality is deteriorated. In consideration of such a situation, in the embodiment, the size of ink (first size) discharged in the first printing mode is increased more than the size of ink (second size) discharged in the second printing mode. Accordingly, a balance between the printing resolution and the size of ink is good, and thus the deterioration of the image quality is suppressed. 
     As already said, as much as the PG is wide, a flying time of the ink discharged is likely to be long. In addition, as much as the flying time of the ink is long, a deviation is generated in an orbital of the ink until being landed to the printing medium, as a result, a deviation of a landed position of the ink (deviation from ideal position to which the ink is landed basically) is likely to be generated. Such a deviation of the orbital is likely to be generated as an amount ink (light) which has a relatively small size to be landed. That is, when the PG is wide as the first PG, the deviation of the landed position of the ink is significantly generated if the size of ink is small, and for example, unnecessary backlashes, curves, or the like are likely to be generated in letters or ruled lines. In the embodiment, in the first printing mode described above, the size of ink is increased more than the size of ink in the second printing mode, the deviation of the landed position, which is likely to be generated when the PG is wide as the first PG, is reduced, backlashes, curves, or the like generated in letters or ruled lines can be suppressed. 
     In addition, in the embodiment, when the number of the used nozzle rows used in the first printing mode is set to N, the control section  11  uses the nozzle rows as N rows in vicinity of one end side of a direction (main scanning direction D 1 ) intersecting with the nozzle row direction D 3  in the first printing mode. N is two according to Table T in  FIG. 4 . One end side of the main scanning direction D 1  is the left side or the right side in  FIG. 3 . That is, in the first printing mode, when the number of the used nozzle rows is two, the nozzle rows  33   a ,  33   b  among the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  are set to the used nozzle rows (or the nozzle rows  33   c  and  33   d  are set to the used nozzle rows). Because a tilt of the printing head  31  with respect to the transportation direction D 2  (hereinafter, simply tilt of printing head  31 ) is considered. 
     The tilt of the printing head  31  is a tilt of the nozzle row direction D 3  with respect to the transportation direction D 2 . When the transportation direction D 2  and the nozzle row direction D 3  are parallel, the printing head  31  is mounted on the carriage  35  in a state of not being tilted (type of ideal state). However, regarding an actual product, since there is variation of manufacturing in each solid, the nozzle row direction D 3  is slightly tilted with respect to the transportation direction D 2 . The transportation direction D 2  and the nozzle row direction D 3  are parallel, as exemplified in  FIG. 7A , intervals P of the nozzles  34  in the transportation direction D 2  by a group of the plurality of used nozzle rows (two used nozzle rows  33  and  33 ) are constant. However, when the nozzle row direction D 3  is tilted with respect to the transportation direction D 2 , as exemplified in  FIG. 7B , the intervals P of the nozzles  34  in the transportation direction D 2  by the group of the plurality of used nozzle rows (two used nozzle rows  33  and  33 ) is not constant. 
     Such a variation of the intervals P (difference between narrow interval P and wide interval P) causes variation of the landed position of the ink in the transportation direction D 2  to be generated. In addition, the variation of the intervals P becomes great as much as each distance between the used nozzle rows  33  and  33  in the main scanning direction D 1  is away from each other. Here, in the embodiment, even if the variation of the intervals P is present, in the first printing mode, the nozzle rows (for example, nozzle rows  33   a  and  33   b ) which are close to each other in the main scanning direction D 1  are set to the used nozzle rows so as to make the variation be small as possible. Accordingly, even if the tilt of the printing head  31  is present, in the first printing mode, the variation of the landed position of the ink caused by such a tilt can be as an invisible degree. 
     In addition, in the first printing mode, when the number of the used nozzle rows is set to two, among the nozzle rows  33   a ,  33   b ,  33   c , and  33   d , two nozzle rows (nozzle rows  33   a  and  33   b ) in a vicinity side of a tilt adjusting member  40  of the printing head  31  are set to the used nozzle rows. For example, as illustrated in  FIG. 3 , the tilt adjusting member  40  is a member provided on one of four corners of the printing head  31  (ink discharging surface  31   a ). An examiner or the user can adjust the tile of the printing head  31  by operating the tilt adjusting member  40 . That is, at the center of the tilt adjusting member  40 , the printing head  31  is rotated. In this case, as the nozzle row present at a position nearer than the tilt adjusting member  40 , adjusting is easily performed because a changed amount of a position with respect to an adjustment amount is small, in addition, it is likely to avoid that the position is excessively changed due to adjusting. Here, from this point of view, in the first printing mode, when the number of the used nozzle rows is set to two, not the group of the nozzle rows  33   c  and  33   d , but the group of the nozzle rows  33   a  and  33   b  near the tilt adjusting member  40  is set to the used nozzle row. 
     4. Modification Example 
     The invention is not limited to the above described embodiment, and can be performed in accordance with aspects within a range which does not depart from a gist thereof, for example, modification examples to be described below can be adopted. A configuration in which the embodiment described above and modification examples are appropriately combined is included in a disclosure range of the invention. In description of the modification examples hereinbelow, description of common issues same as the above described embodiment will not be repeated. 
     When the printing section  30  corresponds to color printing, a description same as a description relating to the data and the configurations of the K ink, is applied to data and configurations of the other color of ink. That is, in the same manner as that of the nozzle rows  33   a ,  33   b ,  33   c , and  33   d  discharging the K ink, a plurality of the nozzle rows discharging the same types of ink are provided in the printing head  31  corresponding to each ink of the CMY ink, or the like. Of course, in a process of generating the printing data, the color conversion process are performed from the RGB to the CMYK, or the like. 
     In addition, the number of the nozzle rows included in the printing head  31  as the plurality of nozzle rows discharging the same type of the ink may be the other numbers in addition to four rows as illustrated in  FIG. 3 . 
     Hitherto, it is premised that the printing head  31  discharges the ink while being moved by the carriage  35 ; however, the printing head may be a line head mounted in a so called line printer. The printing head  31  as the line head, is fixed at a predetermined position in the printing section  30  without moving. In this case, the carriage  35  is unnecessary. When the printing head  31  illustrated in  FIG. 3  is assumed as the line head, the printing medium S is transported by the transportation section  36  in the direction D 1 , not a direction D 2 . Even in this case, the line head (printing head  31 ) has the PG which is adjusted according to the printing mode, and the control section  11  changes the printing resolution or the size of the ink according to the printing mode (PG). 
     The entire disclosure of Japanese Patent Application No. 2015-053258, filed Mar. 17, 2015 is expressly incorporated by reference herein.