JP5866849B2 - Liquid ejection apparatus and image forming method - Google Patents

Description

  The present invention relates to a liquid ejection apparatus and an image forming method.

  For example, an ink jet printer is known as a liquid ejecting apparatus that ejects liquid to form an image on a medium. Further, as such a printer, after forming an auxiliary image (for example, a white background image) on the medium, a main image is formed on the medium with color ink (hereinafter also referred to as a surface printing mode), and on the medium. It is known to perform a mode for forming an auxiliary image on a main image after forming the main image (hereinafter also referred to as a reverse printing mode). For example, in the printer of Patent Document 1, a plurality of nozzle rows are divided into halves, and a front printing mode and a back printing mode are switched by changing a used portion of each nozzle row during printing.

International Publication WO2005 / 105452 Pamphlet

In the reverse printing mode, a printed matter in which an image is viewed from the back side (medium side) of the printing surface is formed. Thus, when an image is viewed from the medium side, there is a characteristic that banding (band-like density unevenness) and graininess are not noticeable (that is, deterioration in image quality is difficult to visually recognize). For this reason, in the reverse printing mode, the printing speed may be required rather than the image quality. However, the above-described printer has a problem that it is difficult to increase the printing speed in the back printing mode because the front printing mode and the back printing mode are performed at the same printing speed.
In the above-described printer, half of each nozzle row is used, so that the dot formation of the auxiliary image and the dot formation of the main image are simultaneously performed in one dot formation operation. In this case, it becomes impossible to perform printing suitable for each of the auxiliary image and the main image. For this reason, it has been difficult to optimize printing quality and printing speed.
Accordingly, an object of the present invention is to optimize printing quality and printing speed.

The main invention for achieving the above object is:
A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in the medium transport direction, and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image are A plurality of second nozzle rows arranged in the transport direction, the second nozzle row provided so as to be aligned with the first nozzle row in a moving direction intersecting the transport direction, the first nozzle row, and the second nozzle Control to form an image on the medium by performing a dot forming operation for forming a dot on the medium by discharging liquid from each nozzle while moving the row in the moving direction, and a transport operation for transporting the medium in the transport direction A liquid ejection apparatus comprising: a surface printing mode in which the main image is formed on the auxiliary image after the auxiliary image is formed on the medium; and the main image is formed on the medium, On the main image A reverse printing mode for forming an image, and in the front printing mode, the control unit includes a nozzle in the first nozzle row that discharges the first liquid when performing each dot forming operation. In the reverse printing mode, the first nozzle row and the second nozzle row are partially used so that they are located downstream of the nozzles of the second nozzle row for discharging the second liquid in the transport direction. When performing each dot forming operation, all the nozzles of the first nozzle row or the second nozzle row are used, and the carrying amount of one carrying operation in the back printing mode is 1 in the front printing mode. The liquid ejection apparatus is characterized in that it is larger than the transport amount of the transport operation of the first time .
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

FIG. 2 is a block diagram illustrating a configuration of a printer. FIG. 2 is a schematic view around a printer head. 3A and 3B are cross-sectional views of the printer. It is explanatory drawing of a structure of a head. It is explanatory drawing of the image formed in front printing mode, and the image formed in back printing mode. FIG. 6A to FIG. 6F are schematic explanatory views of the state of image formation in the front printing mode. 7A to 7E are schematic explanatory views of the state of image formation in the reverse printing mode. It is the schematic of the head periphery in 2nd Embodiment.

At least the following matters will become clear from the description of the present specification and the accompanying drawings.
A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in the medium transport direction, and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image are A plurality of second nozzle rows arranged in the transport direction, the second nozzle row provided so as to be aligned with the first nozzle row in a moving direction intersecting the transport direction, the first nozzle row, and the second nozzle Control to form an image on the medium by performing a dot forming operation for forming a dot on the medium by discharging liquid from each nozzle while moving the row in the moving direction, and a transport operation for transporting the medium in the transport direction A liquid ejection apparatus comprising: a surface printing mode in which the main image is formed on the auxiliary image after the auxiliary image is formed on the medium; and the main image is formed on the medium, On the main image A reverse printing mode for forming an image, and in the front printing mode, the control unit includes a nozzle in the first nozzle row that discharges the first liquid when performing each dot forming operation. In the reverse printing mode, the first nozzle row and the second nozzle row are partially used so that they are located downstream of the nozzles of the second nozzle row for discharging the second liquid in the transport direction. When performing each dot forming operation, the liquid ejecting apparatus is characterized by using all the nozzles of the first nozzle row or the second nozzle row.
According to such a liquid ejecting apparatus, in the reverse printing mode, printing can be performed with a printing resolution and a dot size suitable for each of the main image and the auxiliary image, and the printing speed can be improved. Can do. Further, by partially using each nozzle row in the front printing mode, it is possible to perform printing with higher image quality than in the back printing mode. Therefore, it is possible to optimize printing quality and printing speed.

In the liquid ejection apparatus, the control unit performs the transport operation between the dot forming operations in the front printing mode, and uses all the nozzles of the first nozzle row in the back printing mode. It is preferable that the carrying operation is performed after the dot forming operation and the dot forming operation using all the nozzles of the second nozzle row are performed.
According to such a liquid ejecting apparatus, the printing speed in the reverse printing mode can be increased.

In this liquid ejection apparatus, it is preferable that the transport amount of the transport operation in the front printing mode is shorter than the transport amount of the transport operation in the back printing mode.
According to such a liquid ejecting apparatus, it is possible to improve the image quality in the surface printing mode.

In this liquid ejection apparatus, in each dot forming operation in the front printing mode, the length of the used portion of the first nozzle row in the carrying direction is the length of the used portion of the second nozzle row in the carrying direction. Or less.
According to such a liquid ejecting apparatus, the auxiliary image can be formed thicker than the main image, and the main image can be easily seen by increasing the thickness of the auxiliary image.

In this liquid ejection apparatus, the first liquid and the second liquid are liquids that are cured by light irradiation, and the carriage is provided with the first nozzle row and the second nozzle row, A carriage that moves in a moving direction, and an irradiation unit that radiates the light, arranged at a position aligned with the first nozzle row and the second nozzle row in the moving direction in the carriage,
It is desirable to have
According to such a liquid ejecting apparatus, it is possible to cure the dots immediately after forming the dots with the first liquid and the second liquid.

In this liquid discharge apparatus, the irradiation unit is provided at both ends of the carriage in the movement direction, and the control unit is configured to irradiate the light according to the movement direction of the carriage. It is desirable to switch.
According to such a liquid ejecting apparatus, the number of dot forming operations can be reduced, and the printing speed can be increased.

Also, a first nozzle row in which a plurality of nozzles for discharging the first liquid for forming the main image are arranged in the medium transport direction, and a nozzle for discharging the second liquid for forming the auxiliary image for assisting the main image A plurality of second nozzle rows arranged in the transport direction, and a second nozzle row provided so as to be aligned with the first nozzle row in a moving direction that intersects the transport direction. A dot forming operation for forming a dot on a medium by discharging liquid from each nozzle while moving the first nozzle row and the second nozzle row in the moving direction; and a transport operation for transporting the medium in the transport direction; An image forming method for forming an image on a medium,
In each dot forming operation, the nozzles of the first nozzle row that discharges the first liquid are arranged downstream of the nozzles of the second nozzle row that discharges the second liquid in the transport direction. A first printing mode in which the first nozzle row and the second nozzle row are partially used to form the auxiliary image on a medium and then form the main image on the auxiliary image;
During a certain dot forming operation, the main image is formed on the medium using all the nozzles of the first nozzle row, and during the dot forming operation after the certain dot forming operation, the second image is formed. An image forming method comprising: a reverse printing mode for forming the auxiliary image on the main image formed by the certain dot forming operation using all the nozzles of the nozzle row. .

  In the following embodiments, an ink jet printer (hereinafter also referred to as a printer 1) will be described as an example of the liquid ejection device.

=== First Embodiment ===
<About printer configuration>
Hereinafter, the printer 1 of the present embodiment will be described with reference to FIGS. 1, 2, 3 </ b> A, and 3 </ b> B. FIG. 1 is a block diagram illustrating a configuration of the printer 1. FIG. 2 is a schematic view around the head of the printer 1. 3A and 3B are cross-sectional views of the printer 1. 3A corresponds to the AA cross section of FIG. 2, and FIG. 3B corresponds to the BB cross section of FIG.

  The printer 1 of the present embodiment is an ultraviolet curable ink (hereinafter referred to as UV) that is cured by irradiation with ultraviolet rays (hereinafter referred to as UV), which is a type of light, as an example of a liquid toward a medium such as paper, cloth, or film sheet. This is a device that prints an image on a medium by ejecting ink. The UV ink is an ink containing an ultraviolet curable resin, and is cured by undergoing a photopolymerization reaction in the ultraviolet curable resin when irradiated with UV. Note that the printer 1 of the present embodiment performs printing using four colors of CMYK ink (color ink) and each UV ink of white ink for background as described later.

  The printer 1 includes a transport unit 10, a carriage unit 20, a head unit 30, an irradiation unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 that is an external device controls each unit (the transport unit 10, the carriage unit 20, the head unit 30, and the irradiation unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on a medium. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 10 is for transporting a medium (for example, paper) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 10 includes a paper feed roller 11, a transport motor (not shown), a transport roller 13, a platen 14, and a paper discharge roller 15. The paper feed roller 11 is a roller for feeding the medium inserted into the paper insertion slot into the printer. The transport roller 13 is a roller that transports the medium fed by the paper feed roller 11 to a printable area, and is driven by a transport motor. The platen 14 supports the medium being printed. The paper discharge roller 15 is a roller for discharging the medium to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

  The carriage unit 20 is for moving (also referred to as “scanning”) the head in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 20 includes a carriage 21 and a carriage motor (not shown). The carriage 21 detachably holds an ink cartridge that stores UV ink. The carriage 21 is reciprocated along the guide shaft 24 by a carriage motor while being supported by a guide shaft 24 that intersects a conveyance direction described later.

The head unit 30 is for ejecting liquid (UV ink in this embodiment) onto a medium. The head unit 30 includes a head 31 having a plurality of nozzles. Since the head 31 is provided on the carriage 21, when the carriage 21 moves in the movement direction, the head 31 also moves in the movement direction. Then, when the head 31 is intermittently ejected while moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the medium. In the following description, a path moving from one end side to the other end side in the moving direction shown in FIG. 2 is called a forward path, and a path moving from the other end side to the one end side in the moving direction is called a return path. Call. In the present embodiment, UV ink is ejected from the head 31 in both the forward and return periods. That is, the printer 1 of this embodiment performs bidirectional printing.
The configuration of the head 31 will be described later.

  The irradiation unit 40 irradiates UV toward the UV ink that has landed on the medium. The dots formed on the medium are cured by receiving UV irradiation from the irradiation unit 40. The irradiation unit 40 of this embodiment includes irradiation units 42a and 42b. The irradiation units 42 a and 42 b are provided on the carriage 21. For this reason, when the carriage 21 moves in the movement direction, the irradiation units 42a and 42b also move in the movement direction.

  The irradiation units 42 a and 42 b are provided on one end side and the other end side in the moving direction on the carriage 21 so as to sandwich the head 31. Further, the length of the irradiation units 42 a and 42 b in the transport direction is substantially the same as the length of the nozzle row of the head 31. In other words, the irradiation units 42a and 42b are provided at positions aligned with the nozzle rows of the head 31 in the moving direction. The irradiation units 42a and 42b move together with the head 31 and irradiate UV to a range where the nozzle row of the head 31 forms dots. The irradiation units 42a and 42b of the present embodiment include a light emitting diode (LED) as a light source for UV irradiation. As described above, when the light source is an LED, it is possible to easily change the UV irradiation energy by controlling the magnitude of the input current. Although not shown, the irradiation units 42a and 42b according to the present embodiment include a plurality of LEDs along the transport direction. By controlling the lighting and extinction of each LED, the UV irradiation range (transport) Direction range) can be set. For example, in the case where only half of the nozzle rows of the head 31 on the downstream side in the transport direction are used, UV can be applied to a range where the half nozzles form dots. By so doing, it is possible to efficiently irradiate UV to the dots formed on the medium, and to reduce energy consumption.

  The detector group 50 includes a linear encoder (not shown), a rotary encoder (not shown), a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder detects the position of the carriage 21 in the moving direction. The rotary encoder detects the rotation amount of the transport roller 13. The paper detection sensor 53 detects the position of the leading edge of the medium being fed. The optical sensor 54 detects the presence or absence of a medium by a light emitting unit and a light receiving unit attached to the carriage 21. The optical sensor 54 can detect the position of the end of the medium while being moved by the carriage 21 to detect the width of the medium. The optical sensor 54 also detects the front end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can.

  The controller 60 is a control unit (control unit) for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  When performing printing, the controller 60 repeatedly performs a dot forming operation for discharging UV ink from the head 31 moving in the forward direction and the backward direction and a transport operation for transporting paper in the transport direction, as will be described later. An image composed of a plurality of dots is printed on paper. In the following description, the dot forming operation is referred to as “pass”. The n-th pass is called a pass n. In the pass, UV irradiation is also performed as described later.

<About the configuration of the head 31>
FIG. 4 is an explanatory diagram of an example of the configuration of the head 31. FIG. 4 is a view of the head 31 as viewed from below (that is, from the platen 14 side). As shown in FIG. 4, a cyan ink nozzle row C, a magenta ink nozzle row M, a yellow ink nozzle row Y, a black ink nozzle row K, and a white ink nozzle row W are formed on the lower surface of the head 31. ing. Each nozzle row includes a plurality of nozzles (180 in the present embodiment) that are ejection openings for ejecting each color of UV ink. Further, as shown in the figure, the nozzle rows are provided so as to be aligned in the moving direction. In the following description, cyan ink is also called C ink, magenta ink is called M ink, yellow ink is called Y ink, black ink is called K ink, and white (white) ink is also called W ink. Furthermore, C ink, M ink, Y ink, and K ink are collectively referred to as color ink (corresponding to the first liquid), and each nozzle row that discharges these color inks is designated as a color ink nozzle row (first nozzle). It is also called a column. An image formed with these color inks is also referred to as a color image (corresponding to a main image).

  The white ink nozzle row W that discharges W ink (corresponding to the second liquid) corresponds to the second nozzle row, and an image formed by the W ink is also referred to as a background image. This W ink is a white ink for printing the background color of a color image when printing on a medium, and contains inorganic material particles such as titanium oxide. Thus, by making the background white, it becomes easier to see the color image formed in an overlapping manner. That is, in the present embodiment, the white background image corresponds to an auxiliary image that assists the color image (main image). In the present embodiment, “white” is not limited to white in the strict sense that is the surface color of an object that reflects 100% of all wavelengths of visible light, but is a so-called “white”. It is common to include a color called white.

  The plurality of nozzles in each nozzle row are aligned at regular intervals (nozzle pitch: D) along the transport direction. The nozzles in each nozzle row are assigned a lower number toward the downstream side in the transport direction. Each of these nozzles is provided with a piezo element (not shown) as a drive element for discharging UV ink from each nozzle. By driving this piezo element with a drive signal, droplet-like UV ink is ejected from each nozzle. The discharged UV ink lands on the medium and forms dots.

<About print mode>
The printer 1 of the present embodiment has a mode for printing a printed material for viewing an image from the printing surface side (front printing mode) and a mode for printing a printed material for viewing an image from the medium side (back side of the printing surface) using a transparent medium. Two printing modes (back printing mode) are performed.
FIG. 5 is an explanatory diagram of an image formed in the front printing mode and an image formed in the back printing mode.
In the front printing mode, a background image is first formed with W ink on the medium. Then, a color image with color ink is formed so as to overlap the background image. Thereby, a printed matter in which an image is viewed from the printing surface side is formed.
On the other hand, in the reverse printing mode, first, a color image by color ink is formed on the medium. Then, a background image with W ink is formed so as to overlap the color image. As a result, a printed material in which an image is viewed from the medium side is formed.

In the following description, an image in which a color image and a background image are superimposed on a medium is also referred to as a completed image, and an image in which only one of them is formed is also referred to as an incomplete image.
Comparing the printed material formed in the front printing mode with the printed material formed in the reverse printing mode, the printed material formed in the reverse printing mode has a lower image quality (for example, banding and graininess) than the printed material formed in the front printing mode. Etc.) are not noticeable. This is because, for example, in a printed material formed in the reverse printing mode, since the surface on which the image is viewed (that is, the medium surface) is flat, scattering of light when viewing the image looks at the image formed in the surface printing mode. This is probably because it is smaller than the case. Therefore, in this embodiment, as will be described later, different printing operations are performed in the front printing mode and the back printing mode, and when an image is formed in the back printing mode, the printing speed is given priority over the image quality. I have to.

<Print operation in front printing mode>
First, the printing operation in the front printing mode in this embodiment will be described.
FIG. 6A to FIG. 6F are schematic explanatory views of the state of image formation in the front printing mode in the present embodiment.
In these drawings, a dot formation operation (pass) and a transport operation in the front printing mode are shown in order. In each figure, the hatched portion (shaded portion) of the head 31 indicates the range of nozzles that eject ink, and the non-hatched portion indicates the range of nozzles that do not eject ink. Moreover, the hatching part (gray part) of each irradiation part shows the area | region which turns on LED (area | region which irradiates UV), and the unhatched part shows the area | region which light-extinguishes LED (area | region which does not irradiate UV).

  First, as shown in FIG. 6A, in the first pass (forward path), the controller 60 moves the carriage 21 in the movement direction (forward path direction) while upstream of the white ink nozzle row W of the head 31 in the transport direction. W ink is ejected from half of the nozzles (the side with the larger nozzle number). In this way, dots are formed in the first pass (pass 1) using half of the nozzles on the upstream side of the nozzle row of the head 31. Thereby, a dot row in which dots of W ink are arranged in the transport direction is formed along the movement direction.

  Further, in this pass, the controller 60 irradiates UV from the irradiation unit 42 a on the upstream side in the moving direction of the head 31. At this time, the controller 60 illuminates the UV by turning on the LED of the portion (gray portion in the figure) corresponding to the range where the nozzles of the white ink nozzle row W form dots in the irradiation unit 42a. Thus, in pass 1, UV irradiation is performed using a half region on the upstream side of the irradiation unit. In pass 1, the irradiation unit 42b is not used (UV irradiation is not performed). Since the irradiation part 42a is provided in the carriage 21 at a position aligned with each nozzle row of the head 31 in the movement direction, it is possible to perform UV irradiation at the timing immediately after the dot formation.

By this pass 1, a white background image is printed in the area R1 of the medium as shown in FIG. 6B. Also, here, the print image in the region R1 is an incomplete image (image of only the background).
After pass 1, the controller 60 transports the medium by a transport amount that is half the nozzle row length (transport operation). By this transport operation, as shown in FIG. 6C, the print image (background image) in the region R1 in FIG. 6B moves to the downstream portion of the print region in the transport direction.

After the carrying operation, the controller 60 causes pass 2 (return pass). As shown in FIG. 6C, the controller 60 discharges UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (return path direction).
At this time, similarly to the case of pass 1, the controller 60 discharges W ink from half of the white ink nozzle row W of the head 31 on the upstream side in the transport direction (side with the larger nozzle number). In pass 2, color ink is ejected from half of the color ink nozzle rows (C, M, Y, K) of the head 31 on the downstream side in the transport direction (side with the smaller nozzle number).

Further, the controller 60 causes the irradiation unit 42 b on the upstream side in the moving direction of the head 31 to irradiate UV in pass 2. Thus, in FIG. 6C, since the moving direction is opposite to that in FIG. 6A, the irradiation unit used for UV irradiation is different from that in FIG. 6A (pass 1).
Since the irradiation unit 42b is provided in the carriage 21 at a position aligned with each nozzle row of the head 31 in the movement direction, it is possible to perform UV irradiation at a timing immediately after dot formation.
By this pass 2, as shown in FIG. 6D, a color image is printed in the region R1 so as to overlap the background image formed by the pass 1. A white background image is printed in the region R2 upstream of the region R1 in the transport direction. At this time, the print image in the region R2 is an incomplete image (background only image), and the print image in the region R1 is a complete image (background image + color image).

  After pass 2, the controller 60 transports the medium by a transport amount that is half the nozzle row length (transport operation). By this transport operation, as shown in FIG. 6E, the region R2 moves to the downstream portion of the print region in the transport direction, and the region R1 moves to the downstream side of the print region in the transport direction.

In pass 3 (outward pass), the controller 60 discharges UV ink from each nozzle of the head 31 while moving the carriage 21 in the movement direction (outward direction), as shown in FIG. 6E. At this time, the controller 60 causes the W ink to be ejected from half of the white ink nozzle row W of the head 31 on the upstream side in the transport direction (the side with the larger nozzle number) in the same manner as in pass 2. In addition, color ink is ejected from half of the nozzles on the downstream side in the transport direction of the color ink nozzle rows (C, M, Y, K) of the head 31 (on the side where the nozzle number is small).
Further, the controller 60 irradiates the UV from the first temporary curing irradiation section 42a on the upstream side in the moving direction of the head 31 in the pass 3 (outward path). In FIG. 6E, since the moving direction is reverse to that in FIG. 6C, the irradiation unit that performs UV irradiation is reverse to that in FIG. 6C.

  With this pass 3, as shown in FIG. 6F, a color image is printed on the background image formed in pass 2 in the region R2. In addition, a white image (background image) is printed in the region R3 upstream of the region R2 in the transport direction. At this time, the print image in the region R3 is an incomplete image (image of only the background).

  Thereafter, similarly, the controller 60 repeatedly executes the pass and the transport operation alternately. As a result, images are sequentially printed on the medium.

<Printing operation in reverse printing mode>
In the reverse printing mode, a printed material viewed from the medium side (the back side of the printing surface) is formed using a transparent medium. As described above, banding and graininess are less noticeable in the reverse printing mode than in the front printing mode (that is, deterioration in image quality is less noticeable). For this reason, in the reverse printing mode, the printing speed may be required rather than the image quality. Even in the reverse printing mode, if printing is performed by dividing the nozzle row in the same manner as in the front printing mode described above, the medium must be transported by a transport amount that is half the nozzle row length between each pass. It will not be. For this reason, it is difficult to improve the printing speed.

  In the front printing mode, the color ink nozzle row for forming a color image and the white ink nozzle row W for forming a background image are used in half, not using all the nozzles. In this way, in one pass, the formation of the color image dots and the background image dots are simultaneously performed. In this case, printing suitable for each of the background image and the color image cannot be performed.

  Therefore, the printer 1 according to the present embodiment performs a printing operation (specifically, band printing using all nozzles) different from the front printing mode in the reverse printing mode. Note that, as described above, in the reverse printing mode, a printed material in which an image is viewed from the medium side is formed. Therefore, a transparent medium is used as the medium here.

Hereinafter, the printing operation in the reverse printing mode in the present embodiment will be described with reference to the drawings.
7A to 7E are schematic explanatory views of the state of image formation in the reverse printing mode.
In these drawings, a dot forming operation (pass) and a transport operation in the reverse printing mode are shown in order. As in the front printing mode, the hatched portion (shaded portion) of the head 31 indicates the range of nozzles that eject ink, and the non-hatched portion indicates the range of nozzles that do not eject ink. Moreover, the hatching part (gray part) of each irradiation part shows the area | region which turns on LED (area | region which irradiates UV), and the unhatched part shows the area | region which light-extinguishes LED (area | region which does not irradiate UV).

First, as shown in FIG. 7A, in the first pass (outward path), the controller 60 moves the carriage 21 in the movement direction (outward direction), while moving the color ink nozzle rows (C, M, Y, K) of the head 31. ) Color ink is discharged from all nozzles. Thus, a dot row in which color ink dots are arranged in the transport direction is formed along the movement direction.
Further, in this pass, the controller 60 irradiates UV from the irradiation unit 42 a on the upstream side in the moving direction of the head 31. At this time, the controller 60 turns on the LEDs in the entire range (gray portion in the drawing) of the irradiation unit 42a corresponding to the nozzle row length to irradiate UV.

  In the present embodiment, the irradiation unit 42a is provided on the carriage 21 at a position aligned with the nozzle row of the head 31 in the moving direction, so that UV irradiation can be performed immediately after the dots are formed during the pass. .

  By this pass 1, as shown in FIG. 7B, an image (color image) formed with color ink is printed in the region R1 ′ of the medium. Here, the print image in the region R1 ′ is an incomplete image (only a color image). In the front printing mode (FIG. 6), the length in the transport direction of the region R1 is half the nozzle row length, whereas in the reverse printing mode, the length in the transport direction of the region R1 ′ is the same as the nozzle row length ( In other words, it is twice the length of the region R1 in the transport direction).

After pass 1, as shown in FIG. 7C, the controller 60 causes pass 2 (return pass) to be performed without transporting the medium. At this time, the controller 60 discharges W ink from all the nozzles of the white ink nozzle row W of the head 31. Further, the controller 60 causes the irradiation unit 42 b on the upstream side in the moving direction of the head 31 to irradiate UV in pass 2. Thus, in FIG. 7C, since the moving direction is opposite to that in FIG. 7A, the irradiation unit used for UV irradiation is different from that in FIG. 7A (pass 1).
With this pass 2, as shown in FIG. 6D, a white background image is printed on the color image formed in pass 1 in the region R1 ′. The print image in the area R1 ′ after pass 2 is a completed image (color image + background image).

After pass 2, the controller 60 transports the medium by a transport amount corresponding to the nozzle row length (transport operation). By this transport operation, as shown in FIG. 7E, the region R1 ′ moves downstream in the transport direction from the print region.
After this transport operation, the controller 60 causes the pass 3 to be executed. In pass 3, as in pass 1, color ink is ejected from all the nozzles of the color ink nozzle rows (C, M, Y, K) of the head 31 while moving the carriage 21 in the movement direction (forward direction). . Further, the controller 60 irradiates UV from the irradiation unit 42 a on the upstream side in the moving direction of the head 31.
Although not shown, this pass 3 prints an image (color image) formed with color ink in a region downstream of the medium region R1 ′ in the transport direction, as in pass 1.

  Similarly, the controller 60 repeatedly executes a reciprocating path (odd path and even path) and a transport operation.

  As described above, in the present embodiment, in the reverse printing mode, an image is formed using all the nozzles of the color ink nozzle row or the white ink nozzle row W during each pass. In addition, after the pass for forming the color image, the pass for forming the background image is performed without performing the transport operation. As described above, the conveying operation is not performed until the completed image is formed in the region corresponding to the nozzle row length. That is, the number of times of carrying operation is smaller than that in the front printing mode. Therefore, in the present embodiment, the printing speed in the reverse printing mode can be made faster than the printing speed in the front printing mode. In the reverse printing mode, only one of the color image and the background image is formed in each pass (outward pass and return pass). That is, the dot formation process in each pass can be controlled separately. For example, the drive waveform of the piezo element can be changed between a pass for forming a background image (even pass) and a pass for printing a color image (odd pass) according to the viscosity of the ink. In addition, the print resolution and dot size can be changed between the even pass and the odd pass. Furthermore, the moving speed of the carriage 21 can be changed between the even-numbered path and the odd-numbered path. As a result, it is possible to increase the printing speed of only the background image or to form only the color image with high resolution. Thus, printing suitable for each of the background image and the color image can be performed.

  As described above, the printer 1 according to the present embodiment performs printing by using half of each color ink nozzle row and each white ink nozzle row W during the pass in the front printing mode, and in the back printing mode, During the pass, all the nozzles of each color ink nozzle row or white ink nozzle row W are used. By doing so, in the reverse printing mode, printing suitable for each image (color image, background image) can be performed, and printing can be performed at a higher printing speed than in the front printing mode. In the front printing mode, a higher quality image can be printed than in the back printing mode. Therefore, it is possible to optimize the printing quality and the printing speed.

  In the present embodiment, in the front printing mode, each nozzle row is divided and used in half in the transport direction. However, the nozzle row is not limited to half as long as it is divided into a plurality. For example, each nozzle row may be divided into three in the transport direction. In this case, in the transport operation between the passes, the medium may be transported by a transport amount that is 1/3 of the nozzle row length.

  For example, as in the above-described embodiment, a portion divided into three so that the lengths of the nozzle rows used in the color ink nozzle row and the white ink nozzle row W may be the same may be selected and used. Specifically, the white ink nozzle row W uses the most upstream portion in the carrying direction among the three divided portions, and the color ink nozzle row uses the most downstream portion in the carrying direction among the three divided portions. It may be. In this case, it is possible to earn time from the formation of the background image to the formation of the color image thereon.

  Further, for example, the length of the used portion of the color ink nozzle row may be equal to or shorter than the length of the used portion of the white ink nozzle row W. Specifically, in each pass, the white ink nozzle row W uses two of the three divided upstream sides in the carrying direction, and the color ink nozzle row divided into three divided ones on the downstream side in the carrying direction. May be used. By doing so, the printed matter in which the color image is formed on the two-layer background image is sequentially printed. Thereby, the background image can be formed darker than the above-described embodiment, and the color image can be made easier to see. In the reverse printing mode corresponding to this case, the color image, the background image, and the pass for forming the background image are performed three times in succession, and then the medium is transported by the transport amount of the nozzle row length.

=== Second Embodiment ===
In the second embodiment, the configuration of the head is different from that of the first embodiment. FIG. 8 is a schematic view of the periphery of the head in the second embodiment. In FIG. 8, the same components as those in FIG.
As shown in FIG. 8, in the second embodiment, the carriage 21 is provided with a first head 31a and a second head 31b.
The first head 31a is provided at one end side in the moving direction from the center of the carriage 21 and at an upstream side in the transport direction.
The second head 31b is provided on the other end side in the movement direction from the center of the carriage 21 and on the downstream side in the transport direction.

  The configuration of each head (the first head 31a and the second head 31b) is the same as the configuration of the head 31 of the first embodiment. However, the length in the transport direction is half that of the head 31. Further, the number of nozzles in the nozzle row of each head is also half the number of nozzles in the nozzle row of the head 31 (for example, 90 (= 180/2)). Thus, when ink is ejected from the same color nozzle rows of the first head 31a and the second head 31b, an image is formed in the same range as when ink is ejected from all the nozzle rows of the head 31 of the first embodiment. It will be. That is, in the second embodiment, the length of each color nozzle row corresponds to the combined length of the nozzle row of the first head 31a and the nozzle row of the second head 31b.

In the second embodiment, ink ejected in units of heads during the pass is controlled.
For example, in the front printing mode, ink is ejected from the white ink nozzle row W of the first head 31a, and ink is ejected from the color ink nozzle row of the second head 31b. Further, UV is irradiated from the irradiation units 42a and 42b corresponding to the nozzles that ejected the ink.

In the reverse printing mode, ink is ejected from each color ink nozzle row of the first head 31a and the second head 31b or all the nozzles of the white ink nozzle row W during the pass.
Note that the image forming operation according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

  Also in the second embodiment, similarly to the first embodiment, it is possible to optimize the printing quality and the printing speed. In the second embodiment, it is only necessary to select a nozzle row for ejecting ink for each head (the first head 31a and the second head 31b), and therefore, the portion of each nozzle row that ejects ink is easily controlled. be able to.

=== Other Embodiments ===
Although a printer or the like as one embodiment has been described, the above embodiment is for facilitating the understanding of the present invention, and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<About the printer>
In the above-described embodiment, the printer has been described as an example of the liquid ejection apparatus, but the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied.

<Discharge method>
In the above-described embodiment, ink is ejected using a piezoelectric element (piezo element). However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<About ink>
In the above-described embodiment, ink (UV ink) that is cured by being irradiated with ultraviolet rays (UV) is ejected from the nozzles. However, the liquid ejected from the nozzle is not limited to such ink, and a liquid that is cured by irradiation with light other than UV (for example, visible light) may be ejected from the nozzle. In this case, light (such as visible light) for curing the liquid may be irradiated from each irradiation unit.

Moreover, you may use ink other than such a photocurable ink. For example, the ink may be dried by forming dots using resin ink and heating with a heater or the like. In this case, the UV irradiation unit may not be provided.
In the above-described embodiment, the color inks are four colors of CMYK. However, inks of other colors (for example, light cyan and light magenta) may be used.

  In the above-described embodiment, the white background image is formed using W ink, but ink other than W ink may be used. For example, a background image having a color different from that of the medium may be formed using a metallic ink having a color different from that of the medium (such as silver). The metallic ink is an ink in which a printed material exhibits a metallic feeling. As such a metallic ink, for example, an oil-based ink composition containing a metal pigment, an organic solvent, and a resin can be used. In order to produce a visually metallic texture effectively, the above-mentioned metal pigment is preferably tabular grains, the major axis on the plane of the tabular grains is X, the minor axis is Y, When the thickness is Z, the 50% average particle diameter R50 of the equivalent circle diameter determined from the area of the XY plane of the tabular grains is 0.5 to 3 μm, and the condition of R50 / Z> 5 is satisfied. It is preferable. Such a metal pigment can be formed of, for example, aluminum or an aluminum alloy, or can be formed by crushing a metal vapor-deposited film. The concentration of the metal pigment contained in the metallic ink can be set to 0.1 to 10.0% by weight, for example. Of course, the metallic ink is not limited to such a composition, and any other composition can be adopted as long as it is a composition that produces a metallic feeling. Even when metallic in is used in this way, control may be performed so that ink is ejected in the same manner as the W ink of the above-described embodiment.

  Also, clear ink may be used. The clear ink is a colorless and transparent ink, and is used for surface coating (surface coating) and for improving the adhesion of the color ink to the medium (anchor coating). Since clear ink contains no pigment, it adheres to the medium more easily than color ink. For this reason, it is better to form a color image after forming a layer of clear ink on the medium than to directly form a color image on a medium to which ink does not easily adhere. Such clear ink may be used like the W ink of the above-described embodiment.

<About the irradiation unit>
In the above-described embodiment, the UV irradiation portions (42a, 42b) are provided at both ends of the carriage 21 in the moving direction. And although the irradiation part to be used was switched according to the moving direction (moving direction) of the carriage 21 in bidirectional printing, it is not limited to this. For example, an irradiating unit may be provided at one end of the carriage 21 to perform unidirectional printing. In this case, the irradiation unit may be provided so as to be positioned upstream of the head in the movement direction during a pass for forming dots. In this way, UV irradiation can be performed immediately after dot formation. However, the number of passes can be reduced and the printing speed can be increased by providing the irradiation units 42 a and 42 b on the carriage 21 and switching the irradiation unit to be used according to the moving direction of the carriage 21 as in the above-described embodiment. can do.

<About the controller>
In the above-described embodiment, the printer 1 corresponds to a liquid ejecting apparatus, and the controller 60 (control unit) of the printer 1 controls the dot forming operation and the conveying operation when forming an image. Not limited. For example, the liquid ejection apparatus may be configured by an apparatus (system) including the printer 1 and the computer 110. In this case, the computer 110 may be a control unit. Alternatively, the controller 60 and the computer 110 of the printer 1 may constitute a control unit.

1 printer, 10 transport unit, 11 paper feed roller,
13 transport roller, 14 platen, 15 paper discharge roller,
20 carriage unit, 21 carriage,
30 head units, 31 heads,
31a 1st head, 31b 2nd head,
40 irradiation unit, 42a, 42b irradiation unit,
50 detector groups, 53 paper detection sensors, 54 optical sensors,
60 controller, 61 interface, 62 CPU,
63 memory, 64 unit control circuit,
110 computer

Claims (7)

A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in the medium transport direction;
A plurality of nozzles for discharging a second liquid for forming an auxiliary image for assisting the main image are arranged in the transport direction in a plurality of second nozzle rows, and the first nozzle row in a movement direction intersecting the transport direction. A second nozzle row arranged in a line;
A dot forming operation for forming a dot on a medium by discharging liquid from each nozzle while moving the first nozzle row and the second nozzle row in the moving direction, and a transport operation for transporting the medium in the transport direction. A controller that forms an image on the medium by performing,
A liquid ejection device comprising:
A surface printing mode for forming the main image on the auxiliary image after forming the auxiliary image on a medium;
After forming the main image on a medium, a reverse printing mode for forming the auxiliary image on the main image;
Have
The controller is
In the front printing mode, when each dot forming operation is performed, the nozzles of the first nozzle row that discharges the first liquid are more in the transport direction than the nozzles of the second nozzle row that discharges the second liquid. The first nozzle row and the second nozzle row are partially used so as to be on the downstream side of
In the back printing mode, when performing each dot forming operation, use all the nozzles of the first nozzle row or the second nozzle row ,
The conveyance amount of one conveyance operation in the reverse printing mode is larger than the conveyance amount of one conveyance operation in the front printing mode.
A liquid discharge apparatus characterized by that. The liquid ejection device according to claim 1,
The controller is
In the front printing mode, the carrying operation is performed between the dot forming operations,
In the reverse printing mode, after performing the dot forming operation using all nozzles of the first nozzle row and the dot forming operation using all nozzles of the second nozzle row, the transport operation is performed.
A liquid discharge apparatus characterized by that. The liquid ejection device according to claim 1 or 2 ,
The controller is configured to reduce the number of conveyance operations in the reverse printing mode to less than the number of conveyance operations in the front printing mode;
A liquid discharge apparatus characterized by that. The liquid ejection device according to any one of claims 1 to 3,
In each dot forming operation in the front printing mode, the length of the used portion of the first nozzle row in the transport direction is equal to or shorter than the length of the used portion of the second nozzle row in the transport direction.
A liquid discharge apparatus characterized by that. A liquid ejection apparatus according to any one of claims 1 to 4,
The first liquid and the second liquid are liquids that are cured by light irradiation,
A carriage provided with the first nozzle row and the second nozzle row, the carriage moving in the moving direction;
An irradiating unit that radiates the light, arranged at a position aligned with the first nozzle row and the second nozzle row in the movement direction in the carriage;
A liquid ejecting apparatus comprising: The liquid ejection device according to claim 5,
The irradiation section is provided at both ends of the carriage in the moving direction,
The control unit switches the irradiation unit that irradiates the light according to a direction in which the carriage moves.
A liquid discharge apparatus characterized by that. A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in the medium transport direction, and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image are A plurality of second nozzle rows arranged in the transport direction, and a second nozzle row provided so as to be aligned with the first nozzle row in a moving direction that intersects the transport direction. A dot forming operation for forming a dot on the medium by discharging liquid from each nozzle while moving the one nozzle row and the second nozzle row in the moving direction, and a carrying operation for carrying the medium in the carrying direction are performed. An image forming method for forming an image on a medium,
In each dot forming operation, the nozzles of the first nozzle row that discharges the first liquid are arranged downstream of the nozzles of the second nozzle row that discharges the second liquid in the transport direction. A first printing mode in which the first nozzle row and the second nozzle row are partially used to form the auxiliary image on a medium and then form the main image on the auxiliary image;
During a certain dot forming operation, the main image is formed on the medium using all the nozzles of the first nozzle row, and during the dot forming operation after the certain dot forming operation, the second image is formed. A reverse printing mode in which the auxiliary image is formed on the main image formed by the certain dot forming operation using all the nozzles of the nozzle row;
I have a,
The transport amount of the transport operation in the reverse printing mode is greater than the transport amount of the transport operation in the front printing mode.
An image forming method.