Patent Publication Number: US-2022227149-A1

Title: Printing device, print controlling method, and storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-005772 filed on Jan. 18, 2021, whose descriptions, claims, abstracts, and drawings are incorporated herein by reference in its entirety. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a printing device, a print controlling method, and a storage medium 
     Description of Related Art 
     Conventionally, there are known printing devices (nail printers) that print nail designs on fingernails, toenails, and the like (see, for example, JP 2003-534083 A). 
     Such printing devices may, for example, form a base layer in white ink or the like on the fingernail before printing the nail design in order that the color of the nail itself does not affect the finish of printing on the nail. 
     SUMMARY 
     According to an aspect of the present disclosure, there is provided a printing device including: 
     a printing head that has a plurality of nozzles; 
     a movement mechanism that moves the printing head; and 
     at least one processor that:
         controls the printing head to eject ink from each of the plurality of nozzles and to print on each position in a printing target area while causing the movement mechanism to move the printing head; and   upon superposing printings of a plurality of times in the printing target area based on a plurality of pieces of data that are different from each other, controls the printing head to eject ink from at least one of the plurality of nozzles in each printing onto a different position from a position in a previous printing based on a different piece of data among the plurality of pieces of data for each of the superposing printings, the plurality of pieces of data being used in specifying from which of the plurality of nozzles ink is ejected onto each position in a printable area of the printing device.       

    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure, wherein: 
         FIG. 1  is a diagram showing a schematic configuration of a printing device in the present embodiment; 
         FIG. 2  is a main part block diagram showing a control structure of the printing device in the present embodiment and a terminal device cooperating therewith; 
         FIG. 3  is a flowchart showing the flow of printing processing by the printing device in  FIG. 1 ; 
         FIG. 4  is a diagram schematically showing a configuration of a base head and a design head; 
         FIG. 5A  is a diagram showing an example of a mask pattern of 4 pixels by 4 pixels; 
         FIG. 5B  is a diagram showing an example of a mask pattern that is different from the mask pattern in  FIG. 5A ; 
         FIG. 5C  is a diagram showing an example of a mask pattern that is different from the mask pattern in  FIG. 5A ; 
         FIG. 6A  is a diagram showing an example of a mask pattern of 8 pixels by 8 pixels; 
         FIG. 6B  is a diagram showing an example of a mask pattern that is different from the mask pattern in  FIG. 6A ; 
         FIG. 6C  is a diagram showing an example of a mask pattern that is different from the mask pattern in  FIG. 6A ; 
         FIG. 7A  is a diagram schematically showing a printing result of a first printing using the mask pattern of  FIG. 6A ; 
         FIG. 7B  is a diagram schematically showing a printing result of a second printing using the same mask pattern as the first printing; 
         FIG. 7C  is a diagram schematically showing a printing result of a third printing using the same mask pattern as the first printing; 
         FIG. 7D  is a diagram schematically showing an example of a printing result of three superposing printings using the mask pattern of  FIG. 6A ; 
         FIG. 8  is a flowchart showing a flow of base printing processing performed in step S 5  in  FIG. 3  by the printing controller in  FIG. 2 ; 
         FIG. 9A  is a diagram schematically showing a printing result of a first printing using the mask pattern of  FIG. 6A ; 
         FIG. 9B  is a diagram schematically showing a printing result of a second printing using the mask pattern of  FIG. 6B ; 
         FIG. 9C  is a diagram schematically showing a printing result of a third printing using the mask pattern of  FIG. 6C ; and 
         FIG. 9D  is a diagram schematically showing an example of a printing result of three superposing printings using the mask patterns of  FIG. 6A  to  FIG. 6C . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1  to  FIG. 9D , an embodiment of a printing device, a print controlling method, and a storage medium storing a program according to the present disclosure will be described. 
     In the embodiment described below, various limitations technically preferable for carrying out the present disclosure are disclosed. However, the scope of the present disclosure is not limited to the embodiment below or illustrated examples. 
     The printing device of the present embodiment prints by ejecting ink onto a printing target area. For example, a nail of a finger is set to be a printing target, and, depending on the nail design, a predetermined area of the nail is set to be the printing target area where nail printing is to be performed. 
     The printing target of the printing device in the present disclosure may be other than those shown here, for example, the printing target may be a nail of a toe finger. Alternatively, the printing target may be a nail-like object other than a human nail, such as a nail chip or the surface of various accessories, or various sheets or stickers. 
       FIG. 1  is a perspective view showing a main external configuration of the printing device in the present embodiment.  FIG. 2  is a main part block diagram showing the main control configuration of the printing device in the present embodiment. 
     In the following embodiment, up and down, left and right, and front and back are defined as the directions shown in  FIG. 1 . An X direction and a Y direction are defined as the directions shown in  FIG. 1 . The X direction is the main scanning direction, and the Y direction is the sub-scanning direction. 
     As shown in  FIG. 2 , the printing device  1  of the present embodiment and an external terminal device (a terminal device  7  in  FIG. 2 ) are configured to be able to communicate and cooperate with each other. 
     As shown in  FIG. 1 , the printing device  1  has a housing  2  that is formed in an almost box shape. 
     The housing  2  has an opening  21  formed in the lower part of the front surface (the front surface side of the printing device  1 , the front side in  FIG. 1 ) almost entirely in the left-right direction (in the lateral direction of the printing device  1 , left-right direction or X direction in  FIG. 1 ). Also, a cut-out  22  that is continuous with the upper side of the opening  21  is formed almost at the middle of the left-right direction of the housing  2 . The cut-out  22  functions as an entrance and exit when a printing head  41  is attached to and detached from the device, which will be described later. 
     On the upper surface (top panel) of the housing  2 , there is an operation unit  12  of the printing device  1 . The operation unit  12  is, for example, an operation button (a power switch button) that turns the power of the printing device  1  on and off. When the operation unit  12  is operated, an operation signal is output to the control device  30 , and the control device  30  controls and operates each part of the printing device  1  depending on the operation signal. For example, when the operation unit  12  is a power switch button, the power of the printing device  1  is turned on and off depending on the button operation. 
     Alternatively, each part of the printing device  1  may be operated depending on the operation signal input from the operation unit  71  of the terminal device  7  described later, instead of the operation unit  12 . 
     An external configuration of the printing device  1 , the shape of each part of the housing  2 , the arrangement of each part, and the like are not limited to the illustrated example, and can be set as needed. For example, the operation unit  12  may be provided not on the upper surface of the housing  2  but on the side surface or the back surface. In addition, various operation buttons may be further provided as the operation unit  12  on the housing  2 , and various displays, indicators, and the like may also be provided. 
     The housing  2  contains a device body  10 . 
     The device body  10  includes a base  11 , a finger holder  6  attached to the base  11 , a printing unit  40 , and the like. 
     The finger holder  6  is arranged almost in the middle in the left-right direction (X direction) on the front surface side of the device in the base  11 , and holds a finger with a nail (both not shown in the drawings), which is the printing target in the present embodiment, at a position suitable for printing. 
     As shown in  FIG. 1 , the finger holder  6  has an opening  61  on the front surface side of the device. The finger holder  6  has a finger fixing member  62  in it. When a finger is inserted through the opening  61 , the finger fixing member  62  pushes up and supports the finger from below. The finger fixing member  62  is made of a flexible resin, for example. 
     On the upper surface of the back side (rear side of the device) of the finger holder  6 , a window  63  is formed so as to expose the nail of the finger inserted through the opening  61  and held by the finger fixing member  62 . In addition, in the finger holder  6 , there is a nail placing unit (not shown in the drawings) where the tip of the nail is placed. An upper surface of the finger holder  6  in front of (on the front side of the device of) the window  63  functions as a finger press (not shown in the drawings) that specifies an upper surface position of the finger. 
     The tip of the nail is placed on the nail placing unit, and the upper surface position of the finger is specified by the finger press, such that the finger inserted into the finger holder  6  is held at a proper position suitable for printing by the printing head  41 . 
     The printing unit  40  prints on the printing target area (nail) according to printing data that is generated by a print data generator  814  described later (a controller  81  of the terminal device  7  described later, see  FIG. 2 ). 
     The printing unit  40  includes a head that performs printing operations (hereinafter referred to as the “printing head  41 ”), a carriage  42  on which the printing head  41  is mounted and held, and the head movement mechanism (see  FIG. 2 ) that moves the printing head  41  and the carriage  42 . 
     As shown in  FIG. 1 , the printing head  41  is mounted on the carriage  42 . 
     The printing device  1  has a plurality of heads that print on the printing target area (nail) in different colors from each other. In the present embodiment, a base head  41   a  and a design head  41   b  are mounted as the printing heads  41 . In the following, when the term “printing head  41 ” is used simply, it refers to both the base head  41   a  and the design head  41   b . The arrangement of the base head  41   a  and the design head  41   b  is not limited to the example illustrated in the drawings. 
     Before a design is printed, the base head  41   a  prints a base on the printing target area where a design is to be printed. A liquid (hereinafter referred to as a “base ink”) used for printing the base is preferably a white or near-white colored fluid so that ink has a good coloring property when the design is printed. 
     The design head  41   b  prints a design on the printing target area where the base has been printed by the base head  41   a , and is capable of ejecting ink(s) of respective color(s) (hereinafter referred to as “colored ink(s)”), such as cyan (C), magenta (M), yellow (Y), and the like. The color inks that can be ejected by the design head  41   b  are not limited to these, and inks of other colors may also be ejected. 
     In the present embodiment, the base head  41   a  and the design head  41   b  have respective ink ejection surfaces (not shown in the drawings) that face the nail surface and have a plurality of nozzles (for example, nozzles  1  to  8  in  FIG. 4 ) from each of which ink is ejected. Both the base head  41   a  and the design head  41   b  are inkjet heads for the inkjet method where fine droplets of ink are made and sprayed directly from the ink ejection surface to a nail surface (a surface to be printed) of the printing target (nail). 
     The head movement mechanism  49  moves the printing head  41 , and includes an X-direction movement mechanism (not shown in the drawings) and a Y-direction movement mechanism (not shown in the drawings). The X-direction movement mechanism moves the printing head  41  in the left-right direction (X-direction) of the device, which is the main scanning direction, and the Y-direction movement mechanism moves the printing head  41  in the front-back direction (Y-direction) of the device, which is the sub-scanning direction. 
     The X-direction movement mechanism includes an X-direction movement motor  46  and moves the printing head  41  in the left-right direction (X-direction) of the device when the X-direction movement motor  46  is driven. The Y-direction movement mechanism includes a Y-direction movement motor  48  and moves the printing head  41  in the front-back direction (Y-direction) of the device when the Y-direction movement motor  48  is driven. 
     The operations of the X-direction movement motor  46  and the Y-direction movement motor  48  of the head movement mechanism  49 , and the printing head  41  are controlled by a printing controller  313  (see  FIG. 2 ) of the control device  30 . 
     At an inner side of the upper surface (top plate) of the housing  2  and above the window  63  of the finger holder  6 , there is an photographing unit  50  that photographs a nail (a finger including the nail) exposed through the window and acquires an image of the nail (an image of the finger including the nail, hereinafter referred to as a “nail image”). 
     The photographing unit  50  includes a photographing device  51 , which is a camera, for example, and a lighting device  52  constituted by white LEDs, etc., which illuminates the nail to be photographed (see  FIG. 2 ). 
     This photographing unit  50  is connected to a photographing controller  312  (see  FIG. 2 ) of the control device  30  described later, and is controlled by the photographing controller  312 . 
     The nail image photographed by the photographing device  51  is acquired by the photographing controller  312  and sent to the cooperating terminal device  7  as appropriate. 
     Image data of the image photographed by the photographing unit  50  may be stored in a storage  32  described later. 
     In the example of the present embodiment, the photographing device  51  and the lighting device  52  are inside of the top surface of the housing  2  and are fixedly arranged so as to face the nail (the surface of the nail) of the finger placed on the finger holder  6 . However, the specific arrangement of the photographing unit  50  is not particularly limited, as long as it is in a position where the nail of the finger placed on the finger holder  6  can be photographed. 
     For example, the photographing unit  50  may be configured to be movable in the X direction and in the Y direction by the head movement mechanism  49  that moves the printing head  41 . 
     The control device  30  mounted in the printing device  1  is a computer that includes a controller  31  (see  FIG. 2 ) configured with at least one processor such as a CPU (Central Processing Unit) (not shown in the drawings), and a storage (see  FIG. 2 ) configured with at least one memory such as ROM (Read Only Memory) and RAM (Random Access Memory) (both not shown in the drawings). 
     The storage  32  has a program storage area  321  in which various programs and the like for operating the printing device  1  are stored. In the program storage area  321 , various programs such as a printing program for printing processing are stored. The controller  31  expands these programs in the working area of RAM, for example, and executes the programs to totally control various parts of the printing device  1 . 
     The controller  31 , when viewed functionally, includes a communication controller  311 , the photographing controller  312 , the printing controller  313 , and the like. The functions as the communication controller  311 , the photographing controller  312 , the printing controller  313 , and the like are realized through cooperation between the controller  31  and the programs stored in the program storage area  321  of the storage  32 . 
     The communication controller  311  controls operations of a communication unit  13 . 
     The communication unit  13  includes a wireless communication module and the like that can communicate with the communication unit  73  of the terminal device  7 . The communication controller  311  controls the operation of the communication unit  13  when sending and receiving various kinds of data and the like between the printing device  1  and the terminal device  7 . 
     The printing device  1  of the present embodiment prints a nail design (hereinafter also simply referred to as a “design”) in cooperation with the terminal device  7  described later. For example, data of the design to be printed on the nail is stored in the terminal device  7 , and the communication controller  311  controls the communication by the communication unit  13  as appropriate, and acquires the data of the design from the terminal device  7  via the communication unit  13 . 
     Also, as described later, the image acquired by the photographing unit  50  of the printing device  1  is appropriately sent to the terminal device  7 , and the controller  81  (a nail information detector  813  described later) of the terminal device  7  detects various kinds of nail information based on the acquired image. Furthermore, in the present embodiment, the controller  81  (a print data generator  814  described later) of the terminal device  7  generates printing data based on the nail information. The various kinds of information and printing data that are detected and generated in the terminal device  7  are sent from the terminal device  7  to the printing device  1  via the communication units  13 ,  73 . 
     The communication between the printing device  1  and the terminal device  7  may be one that uses a network line such as the Internet, or wireless communication based on a short-distance wireless communication standard such as Bluetooth (registered trademark), Wi-Fi, or the like. In a communication via a network, any network line may be used for the communication. The communication between the printing device  1  and the terminal device  7  is not limited to wireless communication, but various kinds of data may be configured to be sent and received between them through a wired connection. 
     The communication unit  13  needs only to be communicable with the terminal device  7 . The applicable communication unit  13  uses a communication standard consistent with that of the communication unit  73  of the terminal device  7 . 
     The photographing controller  312  controls the photographing device  51  and the lighting device  52  of the photographing unit  50  and causes the photographing device  51  to photograph an image of a finger including an image of a nail of the finger (the nail image) placed on the finger holder  6 . 
     The image of the nail (nail image) acquired by the photographing unit  50  is sent to the photographing controller  312 . The photographing controller  312  acquires data of the nail image. The photographing controller  312  may store the nail image in the storage  32 . 
     The printing controller  313  controls the printing unit  40  to print on the printing target area corresponding to the nail (the printing target) according to the printing data generated in the printing data generator  814  described later. 
     Specifically, the printing controller  313  outputs a control signal to the printing unit  40  based on the printing data to cause the printing head  41  to eject ink from any of the plurality of nozzles  1  to  8  onto each position in the printing target area corresponding to the nail (the printing target) while moving the printing head  41  with the X direction movement motor  46  and the Y direction movement motor  48  with respect to the printing target area that has been fixed, so as to control the printing unit  40  to print on the printing target area. 
     In addition, as mentioned above, the printing device  1  of the present embodiment prints on a nail in cooperation with the terminal device  7 . 
     The terminal device  7  is a portable terminal device such as a smart phone. The terminal device  7  is not limited to a smart phone. The terminal device  7  may be, for example, a tablet-type personal computer (hereinafter referred to as a “PC”), a notebook PC, a stationary PC, or a terminal device for games. As shown in  FIG. 2 , the terminal device  7  includes an operation unit  71 , a display  72 , a communication unit  73 , and a control device  80 . 
     The operation unit  71  is, for example, a touch panel integrally provided on the surface of the display  72  and is capable of performing various inputs, settings, and the like in response to user operations. When the operation unit  71  is operated, the input signal corresponding to the operation is sent to the controller  81 . 
     Various operation screens are displayed on the touch panel configured on the display  72  according to the control by the display controller  812  described later, and allows the user to perform various input and setting operations by touching the touch panel. 
     The operation unit  71  for the various input and setting operations is not limited to the touch panel. For example, various operation buttons, a keyboard, a pointing device, and the like may be provided as the operation unit  71 . 
     In the present embodiment, when the user operates the operation unit  71 , the terminal device  7  outputs various instructions such as a printing start instruction to the printing device  1 , and the terminal device  7  also functions as the operation unit of the printing device  1 . 
     Also, by operating the operation unit  71 , the user can select the nail design (design) to be printed on the nail. 
     The display  72  is configured, for example, with a liquid crystal display (LCD), an organic electroluminescent display, or other flat display. 
     As described above, a touch panel for various inputs may be integrally configured on the surface of the display  72 . In this case, the touch panel functions as the operation unit  71 . 
     In the present embodiment, nail designs that are input and selected by the user via the operation unit  71 , various guidance screens, warning display screens, and the like can be displayed on the display  72 . 
     The communication unit  73  is configured to be able to communicate with the communication unit  13  of the printing device  1 . 
     The specific method of communication between the printing device  1  and the terminal device  7  is not limited, and may be either a wireless connection method or a wired connection method, as described above. The communication unit  73  is not limited as long as it is communicable with the printing device  1 . The applicable communication unit  73  uses a communication standard consistent with that of the communication unit  13  of the printing device  1 . 
     The communication unit  73  is connected to the communication controller  811  (see  FIG. 2 ) of the control device  80  (described later), and is controlled by the communication controller  811 . 
     As shown in  FIG. 2 , the control device  80  of the terminal device  7  of the present embodiment is a computer having the controller  81  composed of a processor such as a CPU (Central Processing Unit) not shown in the drawings, and a storage  82  composed of ROM (Read Only Memory) and RAM (Random Access Memory) not shown in the drawings. 
     Various programs, various kinds of data, and the like are stored in the storage  82  for operating each part of the terminal device  7 . 
     Specifically, in the ROM and the like of the present embodiment, in addition to an operation program  821   a  that totally control various parts of the terminal device  7 , a nail print application program  821   b  for nail printing using the printing device  1  (hereinafter referred to as a “nail print AP”) is stored. The controller  81  expands these programs in the working area of RAM, for example, and executes the programs to totally control the various parts of the terminal device  7 . 
     In addition, the storage  82  of the present embodiment has a design storage area  822  for storing nail design (design) data, a nail information storage area  823 , and the like. In the nail information storage area  823 , various kinds of information on nails detected by the nail information detector  813  (described later) are stored. 
     The nail design (design) stored in the design storage area  822  may be an existing design prepared in advance or a design created by the user. In addition, when the terminal device  7  can be connected to various networks, it may be possible to import nail designs (designs) stored in a server device or the like (not shown in the drawings) that is connectable to the network. 
     The controller  81  of the terminal device  7 , when viewed functionally, has a communication controller  811 , a display controller  812 , a nail information detector  813 , a print data generator  814 , and the like. The functions as the communication controller  811 , the display controller  812 , the nail information detector  813 , the print data generator  814 , and the like are realized through cooperation between the CPU of the controller  81  and the program stored in the ROM of the storage  82 . 
     The communication controller  811  controls the operation of the communication unit  73 . 
     The display controller  812  controls the display  72  and displays various display screens on the display  72 . 
     The nail information detector  813  detects nail information regarding a nail based on an image of the nail (a nail image) acquired by the photographing controller  312  of the printing device  1 . In the present embodiment, the nail information detected by the nail information detector  813  is nail outline information that delineate an area of the nail. 
     The nail information detected by the nail information detector  813  is not limited to this. 
     The nail information detected by the nail information detector  813  may include, for example, an angle of inclination of the surface of the nail with respect to an XY plane (an inclination angle of the nail, nail curvature). In addition, when the height of the nail (vertical position of the nail) can be acquired from the image or the like photographed by the photographing device  51 , the nail information may also include the height of the nail. 
     The various kinds of information detected by the nail information detector  813  are stored in the nail information storage area  823 . In the present embodiment, the various kinds of information detected by the nail information detector  813  may be sent to the printing device  1 . The various processes based on the nail information may be performed by the printing device  1 . 
     The print data generator  814  generates printing data by matching the desired design to the nail area detected by the nail information detector  813 . 
     For example, the print data generator  814  cuts out image data of the nail design (design) selected by the user, fits it to the nail area detected from the nail image by appropriately scaling the image data up and down, adjusting the layout, and the like, and generates design printing data. 
     Next, the operation of the printing device  1  will be described. 
       FIG. 3  is a flowchart showing the flow of the printing processing executed by the printing device  1 . The printing processing shown in  FIG. 3  is executed, for example, when the power of the printing device  1  is turned on, in cooperation with the controller  31  shown in  FIG. 2  and a program stored in the program storage area  321  of the storage  32 . 
     First, the controller  31  causes the user to select the nail design to be printed on the nail (the printing target) using the terminal device  7  (Step S 1 ). 
     For example, the controller  31  as the communication controller  311  controls, via the communication unit  13 , to instruct the terminal device  7  to display a selection screen of nail design. When the terminal device  7  receives the instruction on nail design selection from the printing device  1  via the communication unit  73 , the display controller  812  causes the display  72  to display a selection screen of nail designs stored in the design storage area  822 . When the user operates the operation unit  71  to select a nail design, the image data of the selected nail design in the design storage area  822  is read by the RAM. 
     Next, the controller  31  prompts the finger corresponding to the nail (the printing target) to be placed on the finger holder  6 , and the photographing controller  312  causes the photographing unit  50  to photograph and acquire the nail image (Step S 2 ). 
     For example, the controller  31  as the communication controller  311  instructs, via the communication unit  13 , the terminal device  7  to display a notification screen that prompts the user to set the finger corresponding to the nail (the printing target) on the finger holder  6 . When the terminal device  7  receives an instruction from the printing device  1  via the communication unit  73 , the display controller  812  causes the display  72  to display a notification screen that prompts the user to set the finger corresponding to the nail (the printing target) on the finger holder  6  and instructs the printing device  1  to start printing. Upon instruction to start printing via the operation unit  71 , the controller  81  as the communication controller  811  sends the printing start instruction to the printing device  1  via the communication unit  73 . 
     In the printing device  1 , when the finger to be printed is placed on the finger holder  6  and the communication unit  13  receives the printing start instruction, the controller as the photographing controller  312  causes the photographing unit  50  to photograph and acquire the nail image. 
     Next, the controller  31  as the communication controller  311  causes the communication unit  13  to send the image data of the nail image acquired by the photographing unit  50  to the terminal device  7 , causes the terminal device  7  to acquire nail information from the nail image (Step S 3 ), and instructs the terminal device  7  to generate printing data (Step S 4 ). 
     When the terminal device  7  receives the nail image from the printing device  1  via the communication unit  73 , the nail information detector  813  of the controller  81  detects the nail outline shape (nail area) from the nail image and acquires the nail outline information (nail area information). Then, based on the acquired nail outline information, the print data generator  814  generates printing data, and the communication controller  811  sends the printing data to the printing device  1  via the communication unit  73 . 
     Here, the print data generator  814  cuts the image data of the nail design depending on the outline shape of the nail (the printing target), scales it up or down as appropriate, identifies the printing target area corresponding to the nail (the printing target), and generates printing data for the design that indicates the color to be ejected at each position (each pixel position) of the printing target area. The nail design may be one for which printing is performed on the entire nail, and in such a case, the printing target area is the same as the outline shape of the nail. Alternatively, the nail design may be one for which printing is performed on a part of the nail, such as a French nail. In this case, the printing target area is the nail design area corresponding to the nail. The print data generator  814  generates base printing data for instructions on printing with the base ink in the entire printing target area. 
     In the printing device  1 , when the communication unit receives the printing data, the controller  31  as the printing controller  313  controls the X direction movement motor  46 , the Y direction movement motor  46 , and the base head  41   a  based on the base printing data to perform the base printing in the printing target area of the nail (printing target) placed on the finger holder  6  (step S 5 ). 
     Next, the controller  31  as the printing controller  313  controls the X direction movement motor  46 , the Y direction movement motor  46 , and the design head  41   b  based on the design printing data to print the design in the printing target area of the nail (printing target) placed on the finger holder  6  (step S 6 ) and finishes the printing processing. 
     Here, the base printing in step S 5  is performed using a multi-pass method. Hereinafter, an example of the base printing of the present embodiment will be explained when the base head  41   a  has eight nozzles (nozzles  1  to  8 ) as shown in  FIG. 4 . 
     In multi-pass printing, it is determined in advance from which of the plurality of nozzles (nozzles  1  to  8  in  FIG. 4  in the present embodiment) of the printing head  41  the ink is ejected onto each position where ink is to land (each pixel position), and several scans are made in the main scanning direction (X direction in  FIG. 1 ). This prevents ejection of ink from a single nozzle onto consecutive pixels, thus reducing the influence of error nozzles (nozzles having defects) on image quality. 
     The multi-pass printing is controlled by using a mask pattern. The mask pattern is a table (data) that specifies from which of the nozzles  1  to  8  of the printing head  41  the ink is to be ejected onto each position (each pixel position) in the printable area by the printing device  1 . 
       FIG. 5A  to  FIG. 5C  show examples of mask patterns for printing in an area of 4 pixels by 4 pixels. For example, it is shown that ink is ejected from the nozzle  1  onto the pixel at position “1” of the mask pattern, and from the nozzle  4  onto the pixel at position “4”. In the mask pattern, the same nozzle number is not arranged successively in neighboring pixels. This makes it possible to control the printing head not to eject ink successively from a single nozzle. 
     For example, when a mask pattern of 4 pixels by 4 pixels is used for printing in an area larger than the mask pattern, the mask pattern can be used by tiling it to the size of the printing target area. For example, in order to print in an area of 8 pixels by 8 pixels, tiling of four mask patterns of 4 pixels by 4 pixels can be used as shown in  FIG. 6A  to  FIG. 6C . 
     In the base printing by the multi-pass method, the printing controller  313  arranges the nozzle  8  of the base head  41   a  shown in  FIG. 4  so as to be positioned at the first line (line  1 ) in the Y direction in the printing target area, and, while causing the base head  41   a  to move in the main scanning direction (X direction), causes the base head  41   a  to eject ink (print) from the nozzle  8  onto the position “8” in the first line of the mask pattern. Next, the printing controller  313  shifts the base head  41   a  by one line in the sub-scanning direction (Y direction), and while causing the base head  41   a  to move in the main scanning direction (X direction), causes the base head  41   a  to eject ink from the nozzle  8  onto the position “8” in the second line of the mask pattern and from the nozzle  7  onto the position “7” in the first line of the mask pattern. Next, the printing controller  313  further shifts the base head  41   a  by one line in the sub-scanning direction (Y direction), and while causing the base head  41   a  to move in the main scanning direction (X direction), causes the base head  41   a  to eject ink from the nozzle  8  onto the position “8” in the third line of the mask pattern, from the nozzle  7  onto the position “7” in the second line of the mask pattern, and from the nozzle  6  onto the position “6” in the first line of the mask pattern. Such operations are repeated until the nozzle  1  reaches the last line and the ink ejection at the position “1” of the mask pattern in the main scanning direction is completed. Thus, in the multi-pass printing, scanning in the main direction is repeated each time the base head  41   a  is shifted in the sub-scanning direction (Y direction), and printing is performed on the printing target area by multiple scans. 
     In the base printing processing, superposing printings are sometimes performed in order to ensure a concealing property. In the superposing printings, after printing once, multiple printings are superposed on the first printing. In the conventional superposing printings, the same printing as the first one is repeated multiple times. 
     For example, assuming that the nozzle  1  of the base head  41   a  is a clogged error nozzle and printing is performed in an area of 8 pixels by 8 pixels using the mask pattern shown in  FIG. 6A , for example, as a result of the first printing, ink does not land on a position (pixel position) where ink is to be ejected from the error nozzle (the nozzle  1 ), and the surface of the printing target at the position is visible as shown in  FIG. 7A . Here, the hatched portions in  FIG. 7A  to  FIG. 7C  are the positions where no ink lands. Also, the density of the base is not sufficient with printing only once. As a result, concealing property is not ensured, and the coloring property of the ink for design printing is poor due to the color of the printing target itself (ground color), resulting in poor finish quality. 
     Therefore, in order to apply a thick base, superposing printings are performed using a conventional method. However, as the second printing is performed in the same way as the first printing in the conventional superposing printing method, ink does not land on the position where ink is to be ejected from the nozzle  1  in the second printing as well, as shown in  FIG. 7B . Even after the third printing in the same manner, ink does not land on the position where ink is to be ejected from the nozzle  1  in the second printing, as shown in  FIG. 7C . Thus, when superposing printings are performed three times repeatedly by the conventional method, ink lands all three times on the position(s) where ink can land, while ink remains unlanded on the position(s) where ink cannot land. Therefore, as shown in  FIG. 7D , the difference in color becomes large between the positions where ink can land and the positions where ink cannot land. 
     Therefore, in the present embodiment, control in the superposing printings for the base printing is performed such that ink from at least one of the nozzles  1  to  8  is ejected onto different positions for each of the printings. 
       FIG. 8  is a flowchart showing a flow of the base printing processing performed by the printing controller  313  in step S 5  in  FIG. 3 . Hereinafter, the base printing processing performed by the printing controller  313  is explained. 
     First, the printing controller  313  prepares a mask pattern to be used in multi-pass printing (Step S 51 ). For example, a mask pattern is stored in the storage  32  in advance, and the printing controller  313  reads the mask pattern from the storage  32  in step S 51 . Alternatively, a mask pattern may be generated in step S 51 . The mask pattern may be a dedicated mask pattern for multi-pass printing, or a blue noise mask for halftone processing may be used as a mask pattern for multi-pass printing. 
     Next, the printing controller  313  controls the X direction movement motor  46 , the Y direction movement motor  46 , and the base head  41   a  based on the base printing data and the prepared mask pattern, to perform the base printing by the multi-pass printing in the printing target area of the nail placed on the finger holder  6  (step S 52 ). 
     Next, the printing controller  313  determines whether or not the predetermined number of times (e.g., three times) of superposing printings have been completed (Step S 53 ). 
     For example, a predetermined numerical value is set in a counter, and 1 is subtracted from the predetermined numerical value each time multi-pass printing is completed. When the numerical value in the counter becomes 0, it is determined that superposing printings of the predetermined number of times have been completed. Alternatively, a numerical value of 0 is set in the counter, and 1 is added to the counter each time multi-pass printing is completed. When the numerical value in the counter becomes a predetermined value, it is determined that superposing printings of the predetermined number of times have been completed. 
     If it is determined that the superposing printings of the predetermined number of times have not been completed (step S 53 ; NO), the printing controller  313  prepares another mask pattern (Step S 54 ), returns to Step S 52 , and performs multi-pass printing using the prepared mask pattern. 
     In step S 54 , the printing controller  313  may rotate (for example, rotate by 90 degrees), flip (for example, left-right flip), replace the numbers of, and the like, the mask pattern used in step S 52  to generate another mask pattern different from the one used so far. Alternatively, multiple different mask patterns may be prepared and stored in storage  32  in advance, and then the mask pattern different from the mask pattern used so far may be read out. 
     The printing controller  313  repeatedly performs the processes of steps S 52  to S 54  until determining that the superposing printings of the predetermined number of times have been completed. When it is determined that the superposing printings of the predetermined number of times have been completed (step S 53 ; YES), the printing controller  313  ends the base printing processing. 
     With reference to  FIG. 9A  to  FIG. 9D , the printing results of the above base printing processing will be explained, for example, when three superposing printings are performed in an area of 8 pixels by 8 pixels using the base head  41   a  having eight nozzles as shown in  FIG. 4 . The gray portions in  FIG. 9A  to  FIG. 9C  are the positions where ink does not land. In the following explanation, nozzle  1  is an error nozzle, the mask pattern shown in  FIG. 6A  is used for the first printing, the mask pattern shown in  FIG. 6B  is used for the second printing, and the mask pattern shown in  FIG. 6C  is used for the third printing. 
     In the first printing, ink does not land on positions (pixel positions) where ink is to be ejected from nozzle  1  as shown in  FIG. 9A . In the second printing, the mask pattern is changed to the one shown in  FIG. 6B , so the positions where ink is to be ejected from each nozzle are different from those in the first printing, as shown in  FIG. 9B . In the third printing, the mask pattern is changed to the one shown in  FIG. 6C , so the positions where ink is to be ejected from each nozzle are different from those in the first printing or in the second printing, and the positions where ink does not land are different from those in the first printing or in the second printing, as shown in  FIG. 9C . 
       FIG. 9D  shows the result of superposing printings of three times by the above base printing processing. As shown in  FIG. 9D , there are no pixels where no ink has landed at all, that is, lacking of ink application, have been eliminated, and the concealing property has been improved. Therefore, the ground color of the printing target has less influence on the design printing, and the coloring property of ink can be improved. Also, it is possible to reduce roughness caused by the coexistence of areas where no ink is ejected and areas where ink is ejected. 
     Preferably, all the positions where ink is to be ejected from each of the nozzles (that is, the positions where ink is supposed to be ejected) for the first, second, and third times (that is, in each printing) are different from each other. However, even if some of the positions are the same, the concealing effects can be exhibited when many of the positions are different from each other. Therefore, for example, a different mask pattern is used for each printing in the base printing processing such that ink from at least one of the plurality of nozzles in the base head  41   a  is ejected at different positions in the superposing printings of a plurality of times. 
     As described above, according to the printing device  1 , the printing controller  313  performs control in the superposing printings of a plurality of times in the printing target area such that ink from at least one of the nozzles of the base head  41   a  is ejected at different positions for each of the printings. 
     Therefore, lacking of ink application due to nozzle failure can be reduced. As a result, the concealing property and the ink coloring property can be improved because the ground color of the printing target less affects the design printing. Also, it is possible to reduce the roughness due to coexistence of areas where no ink is ejected and areas where ink is ejected. 
     For example, the printing controller  313  controls ejection of ink from the plurality of nozzles based on a mask pattern that specifies from which of the nozzles ink is to be ejected onto each position in the printable area by the printing device  1 . In superposing printings of a plurality of times in the printing target area, a different mask pattern is used for each printing such that ink from at least one of the nozzles is controlled to be ejected onto a different position for each printing. Therefore, even when the position of the defective nozzle is not known, lacking of ink application due to nozzle defects can be easily reduced. 
     Also, in superposing printings of a plurality of times in the printing target area, the printing controller  313  generates a plurality of different mask patterns, for example, by rotating or reversing the mask pattern used in the first printing, and uses a different mask pattern for each printing. As a result, there is no need to store a plurality of mask patterns, and the storage capacity of the mask pattern can be reduced. Alternatively, in printings of a plurality of times, the printing controller  313  may generate different (a plurality of) mask patterns in the second or later printing by rotating or reversing the mask pattern used in the previous printing. 
     When a plurality of different mask patterns has been stored in the storage  32 , and the printing controller  313  reads different mask pattern for each printing from the storage  32  to use them in the superposing printings of a plurality of times in the printing target area, it is not necessary to generate different mask pattern for each printing. 
     The printing controller  313  controls the base head  41   a  to print on the fixed printing target area by ejecting ink from the nozzles while causing the base head  41   a  to move in the main scanning direction and in the sub-scanning direction. When the base head  41   a  ejects ink from the same nozzle onto the same pixel position in superposing printings of a plurality of times where pixel positions of the printing target area are the same, no printing is performed at the position where ink is to be ejected from a defective nozzle (error nozzle), resulting in lacking of ink application. However, by the control such that ink from at least one of the plurality of nozzles is ejected at a different position for each printing, lacking of ink application can be reduced. 
     The printing device  1  is a nail printing device that prints on a nail as the printing target, and the printing target area corresponds to the area of the nail detected based on a photographed image acquired by the photographing unit  50 . While moving the base head  41   a , the printing controller  313  controls the base head  41   a  to print on the printing target area by ejecting ink from one of a plurality of nozzles on each position of the printing target area. Then, in the superposing printings of a plurality of times in the printing target area, the printing controller  313  performs control such that base ink from at least one of the nozzles is ejected at a different position for each of the printings. Therefore, lacking of base application in the nail printing device can be reduced, the concealing property is improved, and ink coloring property in printing the design can be improved. Also, it is possible to reduce the roughness due to coexistence of areas where no ink is ejected and areas where ink is ejected. 
     Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments and that various modifications can be made without departing from the gist of the invention. 
     For example, in the present embodiment, the entire printing head  41  (both the base head  41   a  and the design head  41   b ) is mounted on a single carriage  42  and moved by the same head movement mechanism  49 , but the configuration of the printing head  41  is not limited thereto. For example, the base head  41   a  and the design head  41   b  may be configured to perform printing operations while being moved separately. 
     Further, the present embodiment has been described in a case where the printing device  1  and the terminal device cooperate to print, but the printing device  1  may be configured to perform all operations alone. 
     In such a case, the printing device  1  may have a display such that the user can check the image and design of the nail. 
     Further, for example, the storage  32  of the printing device  1  may have a design storage area that stores nail designs, and the designs stored in the storage  32  may be presented to the user so that the user can select one of the designs. 
     When the printing device  1  can be connected to various networks, the printing device  1  may be able to import nail designs (designs) stored in a server or other device (not shown in the drawings) that is connectable to the network. When designs acquired from external sources in this way can be presented to the user as potential nail design options, it is possible to print a wide variety of nail designs on the nail. 
     Further, in the present embodiment, processes such as detection of nail information and generation of printing data are described as being performed by the controller  81  of the terminal device  7 , but do not necessarily have to be performed entirely in the terminal device  7 . Some or all of these processes may be performed by the controller  31  of the printing device  1 . 
     In this way, when the various processes are configured to be performed separately on the printing device  1  and the terminal device  7 , the load on the control devices  30  and  80  (in terms of the processing ability of the controllers  31  and  81  and the memory capacity of the storage  32  and  82 ) can also be separated, reducing the burden on each part. 
     In the above embodiment, in the superposing printings of a plurality of times in the printing target area, a different mask pattern is used for each printing such that ink from at least one of the plurality of nozzles is controlled to be ejected onto different position for each printing. However, superposing printings may be performed using other methods. For example, when the position of an error nozzle (that is, a defective nozzle) has been already known, the printing controller  313  may perform control such that the position where ink is to be ejected from at least the error nozzle is different for each printing. Alternatively, for example, the printing controller  313  may identify the position of the error nozzle by photographing the printing target area after the first printing, analyze the photographed image, and then perform control such that the position where ink is to be ejected from at least the identified error nozzle is different for each printing. 
     In the above embodiment, the superposing printings are performed in the base printing such that ink from at least one of the plurality of nozzles is controlled to be ejected at a different position each printing, but such control may be also performed in nail design printing. 
     Although several embodiments of the present invention have been described above, the scope of the present invention is not limited to the embodiments described above, but includes the scope of the present invention described in the claims and the scope of their equivalents.