JP2013116623A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the coloring property of printed matter.SOLUTION: An image forming apparatus includes a nozzle array group having a first nozzle array comprising a plurality of nozzles lined up in a first direction, the nozzles delivering a first liquid for forming a main image, and a second nozzle array comprising a plurality of nozzles lined up in the first direction, the nozzles delivering a second liquid for forming an auxiliary image, and a control unit that performs a dot forming action of moving the nozzle array group in the second direction and delivering the liquid from each nozzle to form dots on a printing material and a shift action of shifting at least either one of the printing material and the nozzle array group in the first direction. In a first mode, when performing the dot forming action, the image forming apparatus divides each of the first nozzle array and the second nozzle array into N(Ndenotes an integer equal to or larger than 3) nozzle groups, and thereby superposes the auxiliary image and the main image into Nlayers of images. In a second mode, when performing the dot forming action, the image forming apparatus divides each of the first nozzle array and the second nozzle array into N(Ndenotes an integer equal to or larger than 2 and smaller than N) nozzle groups, thereby superposing the auxiliary image and the main image into Nlayers of images.

Description

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

  As an image forming apparatus that discharges liquid to form an image on a printing material, for example, an ink jet printer is known. Such a printer is provided with a nozzle row in which a plurality of nozzles for discharging a liquid are formed side by side for each color of the liquid. Further, there is known a technique in which images are formed by overlapping each nozzle row partially. For example, in Patent Document 1, an auxiliary image (for example, a background image) and a main image are overlapped and formed on a printing material by using the nozzle row divided in half.

International Publication No. 2005/105452 Pamphlet

  As described above, when an image formed by superimposing a main image and an auxiliary image is viewed, color developability may be impaired depending on the state of light striking the printed matter. For example, when light is applied to the front surface (for example, the printing surface) of the printing material, the thicker the auxiliary image (background image), the better the color developability of the main image printed thereon. However, when the image is viewed on the front side of the printed material, such as printed materials for electric decorations, by shining light on the back side (for example, the surface opposite to the printed surface), the thicker the auxiliary image, the more the light is blocked. As a result, the color developability of the main image deteriorates.

  Accordingly, an object of the present invention is to improve the color developability of printed matter.

A main invention for achieving the above object is to form a first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in a first direction, and an auxiliary image for assisting the main image. And a plurality of nozzles for discharging the second liquid are arranged in the first direction so as to line up with the first nozzle row in a second direction intersecting the first direction. A second nozzle row, a nozzle row group, and a dot forming operation for forming a dot on a printing material by discharging liquid from each nozzle while moving the nozzle row group in the second direction; A control unit that forms an image on the printing material by performing a moving operation of moving at least one of the printing material and the nozzle array group in the first direction, the image forming apparatus comprising: In the first mode, the control unit By dividing the first nozzle row and the second nozzle row in performing the door forming operation to the nozzle group of _one N, respectively (N ₁ is an integer of 3 or more), the auxiliary image and the to be printed material The main images are combined and formed on the N ₁ layer, and in the second mode, when the dot forming operation is performed, the first nozzle row and the second nozzle row are each N ₂ (N ₂ is 2 or more). And the auxiliary image and the main image are combined and formed on the N ₂ layer by being divided into nozzle groups of an integer smaller than N _1. is there.

  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. FIG. 5A is a schematic diagram illustrating a case where an image is observed with front light, and FIG. 5B is a schematic diagram illustrating a case where an image is observed with a backlight. It is explanatory drawing about the setting of the nozzle group at the time of performing the printing process of the 1st mode in 1st Embodiment. FIG. 7A to FIG. 7C are schematic explanatory views sequentially showing how images are formed in the first mode. It is explanatory drawing about the setting of the nozzle group at the time of performing the printing process of the 2nd mode in 1st Embodiment. FIG. 9A and FIG. 9B are schematic explanatory views sequentially showing how images are formed in the second mode. FIG. 10A is an explanatory diagram of the printed material in the first mode of the first embodiment, and FIG. 10B is an explanatory diagram of the printed material in the second mode of the first embodiment. FIG. 11A is an explanatory diagram for setting the nozzle group in the first mode in the second embodiment, and FIG. 11B is an explanatory diagram for setting the nozzle group in the second mode in the second embodiment. FIG. 12A is an explanatory diagram of a printed matter printed in the first mode in the second embodiment, and FIG. 12B is an explanatory diagram of a printed matter printed in the second mode in the second embodiment. It is explanatory drawing of embodiment of this invention by the interlace recording printing system.

  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 a first direction; and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image. A plurality of second nozzle rows arranged in a first direction, and a second nozzle row provided so as to line up with the first nozzle rows in a second direction intersecting the first direction. A dot forming operation of forming a dot on a printing material by discharging liquid from each nozzle while moving the nozzle row group in the second direction, and at least one of the printing material and the nozzle row group A control unit that forms an image on a printing material by performing a moving operation that moves the dot in the first direction, and the control unit is configured to perform the dot operation in the first mode. The first nozzle row when performing the forming operation By dividing finely the second nozzle array into nozzle groups _one each N (N ₁ is an integer of 3 or more), to overlap the N ₁ layer combined the auxiliary image and the main image the to be printed material In the second mode, N ₂ nozzle groups (N ₂ is an integer greater than or equal to 2 and smaller than N ₁ ) are provided for each of the first nozzle row and the second nozzle row when performing the dot forming operation. By dividing into _two , the image forming apparatus is characterized in that the auxiliary image and the main image are combined and formed on the N ₂ layer on the printing material. According to such an image forming apparatus, since the number of layers (number of layers) of the auxiliary image and the main image is changed in each mode, it is possible to improve the color developability of the printed matter.

In this image forming apparatus, the first mode is a mode in which light is applied to one surface of the printing material to print a printed material for viewing an image on the one surface side. The mode is preferably a mode in which a printed material for viewing an image on the one surface side is printed by applying light to the other surface of the printing material.
According to such an image forming apparatus, good color developability can be obtained regardless of the state of light hitting the printed matter.

In this image forming apparatus, it is preferable that the number of auxiliary images in the N ₁ layer is larger than the number of auxiliary images in the N ₂ layer.
According to such an image forming apparatus, the auxiliary image can be formed thick in the first mode, and the auxiliary image can be formed thin in the second mode. Thereby, the coloring property of the printed matter formed in each mode can be improved.

  In this image forming apparatus, when the first liquid uses a dye as a colorant and the second liquid uses a pigment as a colorant, it is particularly effective for improving color development.

In this image forming apparatus, the first liquid and the second liquid are liquids that are cured by light irradiation, and dots formed on the printing material by the first nozzle row and the second nozzle row. It is desirable to have an irradiation part for irradiating the light.
According to such an image forming apparatus, an auxiliary image and a main image can be reliably overlapped and formed on a plurality of layers on a printing material.

Also, a first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in a first direction, and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image A plurality of second nozzle rows arranged in the first direction, the second nozzle rows being arranged to line up with the first nozzle rows in a second direction intersecting the first direction. An image forming method for forming an image on the printing material by an image forming apparatus having a nozzle row group, wherein in the first mode, each of the first nozzle row and the second nozzle row is N ₁ (N ₁ Is divided into an integer of 3 or more), and in the second mode, each of the first nozzle row and the second nozzle row is N ₂ (N ₂ is an integer greater than or equal to 2 and smaller than N ₁ ). A dividing step of dividing the nozzle group, and the nozzle row group is divided into the second group Between the dot forming process and the dot forming process, in which liquid is discharged from the nozzles of the nozzle groups of the first nozzle row and the second nozzle row while moving in the direction to form dots on the printing material. A moving step of moving at least one of the printing material and the nozzle array group in the first direction, and in the first mode, the auxiliary image and the main image are combined with the printing material. The image forming method is characterized in that it is formed so as to overlap with the N ₁ layer, and in the second mode, the auxiliary image and the main image are combined and formed on the N ₂ layer in the printing material. .

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

=== First Embodiment ===
<About printer configuration>
Hereinafter, the printer 1 according to the embodiment of the present invention 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 is an ultraviolet curable ink that is cured by irradiating ultraviolet rays (abbreviated as “UV”), which is a kind of light, as an example of a liquid toward a printing material such as paper, cloth, and film sheet. This is an apparatus for printing an image on a printing material by discharging (hereinafter referred to as UV 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. The printer 1 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 the printing material. 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 conveyance unit 10 is for conveying a printing material (for example, a vinyl chloride film) in a predetermined direction (hereinafter referred to as a conveyance 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 printing material inserted into the paper insertion slot into the printer 1. The transport roller 13 is a roller that transports the printing material fed by the paper feed roller 11 to a printable region, and is driven by a transport motor. The platen 14 supports a printing material being printed. The paper discharge roller 15 is a roller for discharging the printing material to the outside of the printer 1 and is provided on the downstream side in the transport direction with respect to the printable region.

  The carriage unit 20 is for moving (also referred to as “scanning”) the head in a direction crossing the conveyance direction (hereinafter referred to as a moving direction). The intersecting direction is generally an orthogonal 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 the embodiment of the present invention) onto the printing material. 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 printing material. 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 printer 1, UV ink is ejected from the head 31 during both the forward and return periods. That is, the printer 1 performs bidirectional printing.
The configuration of the head 31 will be described later.

  The irradiation unit 40 irradiates UV toward the UV ink landed on the printing material. The dots formed on the printing material are cured by receiving UV irradiation from the irradiation unit 40. The irradiation unit 40 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 42a and 42b in the transport direction is substantially the same as or longer than 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. Note that a metal halide lamp, a light emitting diode (LED), or the like is used as a light source for UV irradiation of the irradiation units 42a and 42b. 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 are provided with a plurality of LEDs along the transport direction, and the irradiation range of UV (range in the transport direction) is controlled by controlling the turning on and off of each LED. 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 doing so, it is possible to efficiently irradiate UV to dots formed on the printing material, 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 tip of the printing material being fed. The optical sensor 54 detects the presence or absence of a printing material 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 printing material while being moved by the carriage 21, and can detect the width of the printing material. Further, the optical sensor 54 has a front end (an end on the downstream side in the transport direction, also referred to as an upper end) and a rear end (an end on the upstream side in the transport direction, also referred to as a lower end) of the printing material depending on the situation. Can also be detected.

  The controller 60 is a control unit (control unit) for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU (Central Processing Unit) 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 (Random Access Memory) and an EEPROM (Electrically Erasable Programmable Read-Only Memory). 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 by the irradiation units 42a and 42b in the pass.

<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 Nc, a magenta ink nozzle row Nm, a yellow ink nozzle row Ny, a black ink nozzle row Nk, and a white ink nozzle row Nw are formed on the lower surface of the head 31. ing. Each nozzle row includes a plurality of nozzles (for example, 180 nozzles) 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 color ink uses a dye as a colorant.

  The white ink nozzle row Nw 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 printing material, and a pigment such as titanium oxide is used as a colorant. In general, pigment-based inks have lower light transmittance than dye-based inks. That is, the W ink has lower light transmittance than the color ink.

  By using W ink and making the background white, it is easy to see the color image formed in an overlapping manner. That is, the white background image corresponds to an auxiliary image that assists the color image (main image). Note that “white” is not limited to white in the strict sense of being the surface color of an object that reflects 100% of all wavelengths of visible light. It shall include the called color.

  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 printing material and forms dots.

≪About front light and backlight≫
As printed matter, light is applied to one side of the printing material (for example, printing surface: hereinafter referred to as the front side) and the image is viewed on the front side, and the other side of the printing material (for example, the back side of the printing surface). There is a thing (for example, printed matter for an electric decoration advertisement etc.) which shines light and sees an image on the front side. In the following description, light applied to the front is referred to as front light, and light applied to the back is referred to as backlight.

FIG. 5A is a schematic diagram illustrating a case where an image is observed with front light, and FIG. 5B is a schematic diagram illustrating a case where an image is observed with a backlight.
In the drawing, a white background image W is formed on a printing material S (for example, a transparent film), and a color image C is formed thereon. The printer 1 uses UV ink, and as will be described later, UV irradiation is performed immediately after dot formation to cure the dots. Since dots can be cured instantaneously by UV irradiation in this way, a thick image can often be formed without depending on the ink absorbability of the printing material S. That is, the background image W and the color image C can be formed on the printing material S so as to overlap each other.

In FIG. 5A, a light source is provided on the printing surface side, and light (front light) is applied from the light source toward the printing material S. In this way, the image (color image C and background image W) on the printing material S is visually recognized by the observer on the printing surface side.
On the other hand, in FIG. 5B, a light source is provided on the back side of the printing surface, and light (backlight) is applied from the light source toward the marking material S. The light passes through the printing material S and the image (color image C and background image W), so that the image on the printing material S is visually recognized by the observer on the printing surface side.

≪About overprinting≫
5A and 5B, the background image W and the color image C are each formed as one layer. However, by increasing the number of overlapping images (number of layers), the color of the printed matter (more specifically, the color image C) is developed. Can be improved. For example, when the background image W is printed in two layers and the color image C is formed thereon, when the image is viewed with front light, the color of the color image C is good due to the thick white background. become. However, when the image is viewed with the backlight as shown in FIG. 5B, the light from the backlight is blocked by the two-layer background image W (W ink with low light transmittance), and the amount of light transmitted (the amount of light) decreases. As a result, the color developability of the color image C is deteriorated. In particular, since a pigment having low light transmittance is used for the W ink, when the background image W becomes thick, the color developability of the color image C is significantly deteriorated.
In this way, when the color image C and the background image W are formed in an overlapping manner, the color developability may be impaired in the state of light hitting the printed matter.

  Therefore, as shown below, the printer 1 performs two printing modes, a first mode for printing an image viewed with front light and a second mode for printing an image viewed with a backlight. And in the 1st mode and the 2nd mode, the color development nature of the printed matter of each mode is aimed at by changing the number of layers (number of layers) of color image C and background image W.

≪About print processing≫
<Printing process in the first mode>
First, the printing process in the first mode will be described.
FIG. 6 is an explanatory diagram illustrating the setting of the nozzle group when performing the printing process in the first mode in the first embodiment. In the figure, for convenience of explanation, each nozzle row is indicated by a straight line. When printing in the first mode, the controller 60 uses each nozzle row of the head 31 equally divided into three (ie, equally divided into three) as shown in the figure. The group of nozzles divided into three is referred to as a nozzle group X ₁ , a nozzle group X ₂ , and a nozzle group X _{3 in} order from the upstream side in the transport direction. For example, if the number of nozzles of each nozzle row is 180, the nozzle groups X ₁ are the nozzle numbers # 121 to # 180, the nozzle groups X ₂ are nozzle numbers # 61 to # 120, the nozzle group X ₃ is nozzle numbers # 1 # 60.

Further, in FIG. 6, nozzle groups used in the first mode printing in each nozzle row are circled. For example, the nozzle group X ₁ and the nozzle group X ₂ are used in the white ink nozzle row Nw. Further, in a color ink nozzle array using the nozzle group X _3.

FIG. 7A to FIG. 7C are schematic explanatory views sequentially showing how images are formed in the first mode. Note that the printing area of the printer 1 already printing material S is conveyed, and that the target for printing S at a position opposing the nozzle group X ₁ is not yet the image is formed.

First, the controller 60 causes ink to be ejected from each nozzle of the head 31 while moving the carriage 21 in the movement direction (forward path direction) in the path n (for example, the forward path). At this time, as shown in FIG. 6, the controller 60 discharges W ink from the nozzles X ₁ and X ₂ of the white ink nozzle row Nw of the head 31. Further, the color ink is ejected from the nozzle group X ₃ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31. Thus, the target for printing on S at a position opposing the nozzle group X _1, and W ink is ejected from the white ink nozzle row Nw, background image W is formed as shown in Figure 7A. Moreover, the controller 60 irradiates UV from the irradiation part 42a on the upstream side in the movement direction. As a result, the background image W formed on the printing material S is immediately cured.

After pass n, the controller 60 transports the printing material S downstream in the transport direction by a transport amount that is 1/3 of the nozzle row length (that is, the length of the nozzle group) (transport operation). Because the printing material S is 1/3 movement of the nozzle row length in the conveyance direction downstream side, the background image W in FIG. 7A is conveyed to a position opposite to the nozzle group X ₂ by the conveying operation. Further, this conveying operation, the position facing the nozzle group X _1, the printing material S is not formed yet the image is conveyed.

  After the transport operation, the controller 60 performs a pass (n + 1). Since the printer 1 performs bidirectional printing, when the path n is a forward path, the path (n + 1) is a backward path.

The controller 60 ejects UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (return path direction). At this time, the controller 60 causes the W ink to be ejected from the nozzle group X ₁ and the nozzle group X ₂ of the white ink nozzle row Nw of the head 31 as in the case of pass n. Further, the color ink is ejected from the nozzle group X ₃ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31. Thus, on the background image W which has been conveyed to a position opposing the nozzle group X _2, and W ink is ejected from the nozzle group X ₂ of the white ink nozzle row Nw, overlapping the background image W as shown in FIG. 7B Formed. That is, a two-layer background image W is formed.

  Further, the controller 60 causes the irradiation unit 42b on the upstream side in the moving direction of the head 31 to emit UV in the path (n + 1). As described above, in the path (n + 1), the moving direction is opposite to that in the path n, so that the irradiation unit used for UV irradiation is different from that in the path n.

After pass (n + 1), the controller 60 transports the printing material S downstream in the transport direction by a transport amount that is 1/3 of the nozzle row length (that is, the length of the nozzle group) (transport operation). Because the printing material S is 1/3 movement of the nozzle row length in the conveyance direction downstream side, the background image W of two layers of Fig. 7B is conveyed to the position facing the nozzle group X ₃ by the conveying operation.

Thereafter, the controller 60 performs a pass (n + 2). In pass (n + 2), the controller 60 ejects ink from each nozzle of the head 31 while moving the carriage 21 in the movement direction (forward direction). Also in this pass, the controller 60 ejects W ink from the nozzle group X ₁ and the nozzle group X ₂ of the white ink nozzle row Nw of the head 31. Further, the color ink is ejected from the nozzle group X ₃ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31. Thus, on the background image W of two layers which are conveyed to a position opposing the nozzle group X _3, the color ink is ejected from the nozzle group X ₃ color ink nozzle row. In this way, as shown in FIG. 7C, the two-layer background image W and the one-layer color image C are formed to overlap each other.

  In the path (n + 2), the controller 60 irradiates UV from the irradiation unit 42a on the upstream side in the moving direction of the head 31.

  After the pass (n + 2), the controller 60 transports the printing material S downstream in the transport direction by a transport amount that is 1/3 of the nozzle row length (that is, the length of each nozzle group) (transport operation). By this transport operation, the image of FIG. 7C is transported outside the print region (downstream in the transport direction from the head 31). Further, the printing material S on which an image is not yet formed is transported upstream of the printing area in the transport direction.

  Thereafter, similarly, the controller 60 repeatedly executes the pass and the transport operation alternately. As a result, images (two layers of the background image W and one layer of the color image C) are sequentially printed on the printing material S.

<Printing process in the second mode>
Next, the printing process in the second mode will be described.
FIG. 8 is an explanatory diagram regarding the setting of the nozzle group when performing the printing process in the second mode in the first embodiment. When printing in the second mode, the controller 60 divides each nozzle row of the head 31 into two nozzle groups as shown in the figure. Of these two nozzle groups, the nozzle group on the upstream side in the transport direction is referred to as nozzle group X ₁ ′, and the nozzle group on the downstream side in the transport direction is referred to as nozzle group X ₂ ′. Thus, in the second mode, the number of nozzle row divisions (that is, the number of nozzle groups) is smaller than in the first mode. When the printing process in the second mode is performed, the nozzle group X ₁ ′ is used in the white ink nozzle row Nw. In the color ink nozzle row, the nozzle group X ₂ ′ is used.

FIG. 9A and FIG. 9B are schematic explanatory views sequentially showing how images are formed in the second mode. It is assumed that the printing material S has already been transported to the printing area of the printer 1 and no image has yet been formed on the printing material S at a position facing the nozzle group X ₁ ′.

First, the controller 60 causes ink to be ejected from each nozzle of the head 31 while moving the carriage 21 in the movement direction (forward path direction) in the path n (for example, the forward path). At this time, the controller 60 discharges W ink from the nozzles of the nozzle group X ₁ ′ of the white ink nozzle row W of the head 31, as shown in FIG. Further, the color ink is ejected from the nozzles of the nozzle group X ₂ ′ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31. As a result, W ink is ejected from the white ink nozzle row Nw on the printing material S at a position facing the nozzle group X ₁ ′, and a background image W is formed as shown in FIG. 9A. Moreover, the controller 60 irradiates UV from the irradiation part 42a on the upstream side in the movement direction. As a result, the background image W formed on the printing material S is immediately cured.

After pass n, the controller 60 transports the printing material S downstream in the transport direction by a transport amount that is ½ of the nozzle row length (that is, the length of the nozzle group) (transport operation). Since the printing material S moves 1/2 of the nozzle row length downstream in the transport direction, the background image W in FIG. 9A is transported to a position facing the nozzle group X ₂ ′ by this transport operation. In addition, by this transport operation, the printing material S on which an image has not yet been formed is transported to the upstream side of the print region in the transport direction.

  After the transport operation, the controller 60 performs a pass (n + 1). Since the printer 1 performs bidirectional printing, when the path n is a forward path, the path (n + 1) is a backward path.

The controller 60 ejects UV ink from the nozzles of the head 31 while moving the carriage 21 in the movement direction (return path direction). At this time, the controller 60 causes W ink to be ejected from the nozzles of the nozzle group X ₁ ′ of the white ink nozzle row Nw of the head 31 as in the case of pass n. Further, the color ink is ejected from the nozzle group X ₂ ′ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31. As a result, color ink is ejected from each nozzle group X ₂ ′ of the color ink nozzle row on the background image W in FIG. 9A, and the color image C is formed on the background image W as shown in FIG. 9B. Is done.

  Further, the controller 60 causes the irradiation unit 42b on the upstream side in the moving direction of the head 31 to emit UV in the path (n + 1). As described above, in the path (n + 1), the moving direction is opposite to that in the path n, so that the irradiation unit used for UV irradiation is different from that in the path n.

  After the pass (n + 1), the controller 60 transports the printing material S downstream in the transport direction by a transport amount that is ½ of the nozzle row length (that is, the length of each nozzle group) (transport operation). Since the printing material S moves 1/2 of the nozzle row length to the downstream side in the transport direction, the background image w and the color image c in FIG. 9B are out of the print region by this transport operation (downstream in the transport direction from the head 31). ).

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

≪About printed matter≫
FIG. 10A is an explanatory diagram of the printed material in the first mode of the first embodiment, and FIG. 10B is an explanatory diagram of the printed material in the second mode of the first embodiment.

  The printed matter printed by the printing process in the first mode is formed by superimposing two layers of the background image W and one layer of the color image C on the printing material S. When front light is applied to the printed matter, the background image W is printed thick, so that the color developability of the color image C is improved and the color image C is easy to see.

  On the other hand, the printed matter printed by the printing process in the second mode is formed by superimposing a single layer background image W and a single layer color image C on the printing material S. That is, the number of overlapping layers is smaller than that of the printed material in the first mode. In particular, in this case, the background image W is thinner than that in the first mode. Therefore, when the backlight is applied, light is more easily transmitted than the printed material in the first mode. Therefore, the color image C has better color development when the second mode printed material is viewed with the backlight than when the first mode printed material is viewed with the backlight.

  As described above, in the mode (first mode) in which an image viewed with front light is printed (first mode), each nozzle row is divided into three nozzle groups, two background images W on the printing material S, and 1 The color image C of the layers is formed so as to overlap. In the mode (second mode) for printing an image viewed by the backlight, each nozzle row is divided into two nozzle groups, and one layer of the background image W and one layer of the color image C are formed on the printing material S. Overlaid. Thus, by increasing the number of divisions of the nozzle row in the first mode to be larger than the number of divisions of the nozzle row in the second mode, the number of overlying layers of the printed material in the first mode becomes the overlying layer of the printed material in the second mode. More than the number. Thereby, for example, in the first mode, the background image W can be formed thick, and the color developability of the color image C can be improved. Conversely, in the second mode, the number of overlapping layers is smaller than in the first mode, so that light is easily transmitted. Thereby, the color developability of the color image C can be improved when viewed with a backlight. In the first embodiment, the number of divisions of the nozzle row in the second mode is a minimum value of 2. In this case, the number of divisions of the nozzle row in the first mode may be three or more. Therefore, in the first mode, the number of nozzle row divisions may be four or more, and the color image C and the background image W may be combined and formed in four or more layers.

=== Second Embodiment ===
In the second embodiment, the division number of each nozzle in the second mode is different from that in the first embodiment. Note that the configuration of the printer 1 is the same as in the first embodiment, and a description thereof will be omitted.

  FIG. 11A is an explanatory diagram for setting the nozzle group in the first mode in the second embodiment, and FIG. 11B is an explanatory diagram for setting the nozzle group in the second mode in the second embodiment.

In the first mode of the second embodiment, each nozzle row of the head 31 is divided into _four nozzle groups (Y _{1 to} Y ₄ ) as shown in FIG. 11A. In addition, the conveyance amount by the conveyance operation between passes is determined according to the division number of the nozzle row. For example, when the nozzle row is divided into n, the carrying amount of the carrying operation is 1 / n of the nozzle row length. Here, since the nozzle row is divided into four (n = 4), the carrying amount of the carrying operation is 1/4 of the nozzle row length. In addition, the nozzle group used in each printing mode is circled. For example, in the white ink nozzle row Nw, the nozzle group Y ₁ and the nozzle group Y ₂ are used. In the color ink nozzle row, the nozzle group Y ₃ and the nozzle group Y ₄ are used.

In the second mode of the second embodiment, as shown in FIG. 11B, each nozzle row of the head 31 is divided into _three nozzle groups (Y ₁ ′ to Y ₃ ′) (divided into three equal parts). In the figure, the nozzle group used in each printing mode is circled. For example, in the white ink nozzle row Nw, the nozzle group Y ₁ ′ is used. In the color ink nozzle row, the nozzle group Y ₂ ′ and the nozzle group Y ₃ ′ are used.

Thus, also in the case of the second embodiment, the number of divisions of the nozzle rows in the first mode (4) is larger than the number of divisions of the nozzle rows in the second mode (3).
Also in the second embodiment, similarly to the first embodiment, the pass and the conveying operation are repeated, and an image is formed on the printing material S. As described above, the transport amount in the transport operation between passes is determined according to the number of divisions of the nozzle row.

  FIG. 12A is an explanatory diagram of a printed matter printed in the first mode in the second embodiment, and FIG. 12B is an explanatory diagram of a printed matter printed in the second mode in the second embodiment.

  As shown in FIG. 12A, the printed matter printed in the first mode printing process is formed by superimposing a two-layer background image W and a two-layer color image C on the printing material S. When the image is viewed by applying front light to the printed matter, since the background image W is printed thick (two layers), the color developability of the color image C becomes good and the color image C becomes easy to see.

  On the other hand, as shown in FIG. 12B, the printed matter printed in the second mode printing process is formed by superimposing a single layer of the background image W and two layers of the color image C on the printing material S. In this case, since the background image W is thinner than the printed material in the first mode, light (backlight) is more easily transmitted than the printed material in the first mode, and the color image C is formed in two layers. The color developability of the color image C can be improved.

In the first mode, for example, the white ink nozzle row Nw uses the nozzle group Y ₁ , and the color ink nozzle row uses the nozzle groups Y _{2 to} Y _4, thereby forming a single-layer color image. C and the three-layer background image W may be formed to overlap each other.

  Further, in the first mode, the nozzle row may be divided into five or more, and the background image W and the color image C may be formed in five or more layers. For example, in the case of five layers, a two-layer color image C and a three-layer background image W may be overlapped, or a one-layer color image C and a four-layer background image W may be overlapped. Good.

  As described above, by increasing the number of overlapping layers in the first mode as compared with the number of overlapping layers in the second mode, in the first mode, for example, the background image W can be formed thick, and when viewing with front light, a color image is formed. The color developability of C can be improved. In the second mode, since the number of overlapping layers is small, light (backlight) is not easily blocked by the background image W or the like when viewed with a backlight. Thereby, the color developability of the color image C can be improved.

=== 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, a printer has been described as an example of an 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 You may apply the technique similar to embodiment mentioned above to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus.

<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 that is cured by receiving ultraviolet (UV) irradiation (UV ink) is ejected from the nozzle. 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 W 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 printing material may be formed using a metallic ink having a color different from that of the printing material (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 effectively produce a visually metallic texture, the aforementioned metal pigment is preferably a plate-like particle. 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, it is only necessary to set a nozzle group and eject ink as in the case of 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, as in the above-described embodiment, if the irradiation units 42 a and 42 b are provided on the carriage 21 and the irradiation unit to be used is changed according to the movement direction of the carriage 21, the number of passes can be reduced and the printing speed can be increased. 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.

<Division of nozzle row>
Each nozzle row may be divided in addition to the embodiment described above. At this time, at least the number of nozzle row divisions in the first mode may be larger than the number of nozzle row divisions in the second mode. In this case, the number of overlapping layers of the background image W and the color image W can be increased in the first mode, thereby improving the color developability of the color image C. In the first mode, it is desirable to make the background image W thick, and in the second mode, it is desirable to make the background image W thin.

<About the recording method>
In the above-described embodiment, the bandwidth print recording method corresponding to the number of divisions of the nozzle row has been described. However, other print recording methods may be used. For example, an interlace printing method using nozzles within the divided range may be used. Interlaced printing means that the dot interval (d) to be formed is at least twice the nozzle pitch D (D = k · d where k is 2 or more), and the raster lines recorded in one pass are printed. It means a printing method in which raster lines that are not recorded are sandwiched between them. That is, in interlaced printing, a color image and a background image can be formed with a resolution finer than the nozzle pitch D. In the example shown below, k is 4, and three raster lines are sandwiched between raster lines formed in one pass. The raster line is a dot line (dot row) arranged in the moving direction formed by intermittently ejecting ink droplets from the nozzle moving in the moving direction during the pass as described above. .

  In interlace printing, each time a printing material is transported in the transport direction by a constant transport amount F, each nozzle records a raster line immediately above the raster line recorded in the immediately preceding pass. In order to perform recording with a constant carry amount in this way, (1) the number N (integer) of nozzles that can eject ink is relatively prime to k, and (2) the carry amount F is N · The condition is that it is set to d.

  In the case of interlace printing, k passes are required to complete a raster line having a continuous nozzle pitch width. For example, in order to complete four raster lines that are continuous at a dot interval of 720 dpi using a nozzle row having a nozzle pitch of 180 dpi, four passes are required.

  FIG. 13 is an explanatory diagram of an embodiment of the present invention using an interlaced printing recording method. In this example, a case will be described in which interlace printing is performed by dividing the nozzle row into three. In the drawing, for simplification of description, a color nozzle row of color ink (cyan, magenta, yellow, black) is shown as one nozzle row. Further, the nozzles of the color nozzle row are indicated by circles, and the nozzles of the white (white) nozzle row are indicated by triangles. Further, the nozzles shown in black in the figure are nozzles that can eject ink, and the nozzles shown in white are nozzles that cannot eject ink. Further, for convenience of explanation, the head (nozzle row) is depicted as moving relative to the printing material, but this figure shows the relative positions of the head and the printing material. Actually, the printing material is conveyed in the conveying direction.

In this embodiment, the number of nozzles in each nozzle row is set to 18 for simplification of description. Each nozzle row is divided into three nozzle groups (Z ₁ , Z ₂ , Z ₃ ).

For example, when the color image C is formed after the two-layer background image W is formed, the nozzle group Z ₁ (nozzles # 1 to 6) of the color nozzle row and the nozzle group Z ₂ (white nozzle row Z ₂ ( nozzle # 7-12) and the nozzle group Z ₃ (nozzles # 13 to 18) is used. The interlace printing conditions already described ((1) The number of nozzles N (integer) that can eject ink is coprime to k, and (2) the carry amount F is set to N · d). In order to satisfy this condition, when interlace printing is performed with six nozzles, ink is ejected from the five nozzles and the medium is transported by a transport amount of 5 · d.

By forming dots in this way, white dots (white dots) are formed twice on the printing material by the nozzles of the white nozzle row, and then color dots can be formed by the nozzles of the color nozzle row. For example, in the raster line at the position indicated by the dotted line in the figure, white dots are formed in pass 1 and white dots are formed in pass 5. Color dots are formed in pass 9. Therefore, one color image can be formed on the two background images. When printing is similarly performed using the nozzle groups Z ₁ and Z _{2 of} the color nozzle row and the row Z _{3 of the} white nozzle, two color images can be formed on one background image.

<About printed matter>
In the above-described embodiment, the case of forming a printed material in which an image is viewed from the printing surface side has been described. For example, an image is formed on a transparent printing material and a printed material in which the image is viewed from the opposite side of the printing surface is formed. You may do it. For example, in the first mode of the first embodiment, the color ink is ejected from the nozzle group X ₁ of the color ink nozzle row (Nc, Nm, Ny, Nk) of the head 31, and the white ink nozzle row of the head 31. When the W ink is ejected from the Nw nozzle groups X ₂ and X ₃ , a one-layer color image C is formed on the printing material S, and a two-layer background image W is formed thereon. In the case of this printed matter, the color image C with the background image W of the two layers as the background is viewed from the opposite surface (non-printing surface) side of the printing surface through the transparent printing material S. In such printed matter, the front light is applied to the non-printing surface of the printing material, and the backlight is applied to the printing surface of the printing material.
Also in this case, the color developability of the color image C can be improved by forming the color image C and the background image W so as to overlap each other as in the above-described embodiment.

  In the above-described embodiment, the configuration in which the printing material is transported in the transport direction is adopted, but the present invention is not limited to this. For example, printing may be performed by moving the head 31 in the moving direction and in a direction crossing the moving direction with the printing material fixed at a predetermined position. Furthermore, printing may be performed by moving both the printing material and the head 31 in a direction crossing the moving direction. In other words, any configuration may be used as long as at least one of the head 31 and the printing material moves and the head 31 moves relative to the printing material.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 10 ... Conveyance unit, 11 ... Feed roller, 13 ... Conveyance roller, 14 ... Platen, 15 ... Discharge roller, 20 ... Carriage unit, 21 ... Carriage, 30 ... Head unit, 31 ... Head, 40 ... Irradiation unit 42a, 42b ... irradiation unit 50 ... detector group 53 ... paper detection sensor 54 ... optical sensor 60 ... controller 61 ... interface unit 62 ... CPU 63 ... memory 64 ... unit control circuit 110: Computer.

Claims (6)

A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in a first direction; and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image. A plurality of second nozzle rows arranged in a first direction, and a second nozzle row provided so as to line up with the first nozzle rows in a second direction intersecting the first direction. Group,
A dot forming operation for forming a dot on a printing material by discharging liquid from each nozzle while moving the nozzle row group in the second direction; and at least one of the printing material and the nozzle row group A control unit that forms an image on the printing material by performing a moving operation of moving in the direction of 1;
An image forming apparatus comprising:
The controller is
In the first mode, when the dot forming operation is performed, the first nozzle row and the second nozzle row are divided into N ₁ nozzle groups (N ₁ is an integer of 3 or more), respectively, thereby performing the printing. the auxiliary image and combined the main image is formed to overlap the N ₁ layer in wood,
In the second mode, when the dot forming operation is performed, each of the first nozzle row and the second nozzle row is divided into N ₂ nozzle groups (N ₂ is an integer greater than or equal to 2 and smaller than N ₁ ). Thus, the auxiliary image and the main image are combined and formed on the N ₂ layer on the printing material.
An image forming apparatus. The image forming apparatus according to claim 1,
The first mode is a mode in which light is applied to one surface of the printing material to print a printed material for viewing an image on the one surface side,
The second mode is a mode in which light is applied to the other surface of the printing material to print a printed material for viewing an image on the one surface side.
An image forming apparatus. The image forming apparatus according to claim 1, wherein
The number of layers of the auxiliary image in the N ₁ layer is greater than the number of layers of the auxiliary image in the N ₂ layer.
An image forming apparatus. The image forming apparatus according to claim 1,
The first liquid uses a dye as a colorant,
The second liquid uses a pigment as a colorant,
An image forming apparatus. The image forming apparatus according to claim 1,
The first liquid and the second liquid are liquids that are cured by light irradiation,
An irradiation unit configured to irradiate the light to the dots formed on the printing material by the first nozzle row and the second nozzle row;
An image forming apparatus. A first nozzle row in which a plurality of nozzles for discharging a first liquid for forming a main image are arranged in a first direction; and a nozzle for discharging a second liquid for forming an auxiliary image for assisting the main image. A plurality of second nozzle rows arranged in a first direction, and a second nozzle row provided so as to line up with the first nozzle rows in a second direction intersecting the first direction. An image forming method for forming an image on the printing material by an image forming apparatus including a group,
In the first mode, the first nozzle array and _one N, respectively the second nozzle row (N ₁ is an integer of 3 or more) is divided into nozzle groups, in the second mode, the first nozzle row and the first 2 nozzle rows _two N, respectively (N ₂ is 2 or more, and, N ₁ is smaller than an integer) and dividing step of dividing the nozzle groups,
A dot formation step of forming dots on the printing material by discharging liquid from nozzles of the nozzle groups of the first nozzle row and the second nozzle row while moving the nozzle row group in the second direction. When,
A moving step of moving at least one of the printing material and the nozzle row group in the first direction between the dot forming steps,
In the first mode, the auxiliary image and the main image are combined and formed on the N ₁ layer on the printing material,
In the second mode, the auxiliary image and the main image are combined and formed on the N ₂ layer on the printing material.

Images