JP5786430B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejection apparatus.

  There is known a liquid ejecting apparatus that performs printing using a liquid (for example, UV ink) that is cured by being irradiated with light (for example, ultraviolet (UV)) (for example, see Patent Document 1). Such a liquid ejecting apparatus includes an irradiation unit that irradiates light. After ejecting a liquid from a nozzle onto a medium, the dot formed on the medium is irradiated with light from the irradiation unit. By doing so, the dots are cured and fixed on the medium. Further, as such a liquid ejecting apparatus, in a carriage having a nozzle row in which a plurality of nozzles are arranged in the conveyance direction of the medium and moving in a movement direction intersecting the conveyance direction, the nozzle row is arranged at a position aligned with the nozzle row. The thing which provided the irradiation part so that it may respond | correspond is proposed. In this case, when the carriage moves in the movement direction, it is possible to discharge liquid from the nozzles and irradiate light to the dots formed on the medium.

JP 2003-191594 A

  In the liquid ejection apparatus as described above, the amount of light emitted from the irradiation unit may vary depending on the position. For example, there may be a greater variation in the amount of light in the portion corresponding to the end portion of the nozzle row than in the portion corresponding to the central portion of the nozzle row. In this case, the size of dots (dots after light irradiation) formed by each nozzle in the nozzle row varies. For this reason, there is a possibility that the image quality is deteriorated.

  An object of the present invention is to improve image quality.

A main invention for achieving the above object includes a carriage that has a nozzle row in which a plurality of nozzles that discharge a liquid that is cured by light irradiation are arranged in a medium transport direction, and that moves in a moving direction that intersects the transport direction. An irradiation unit that irradiates light along the transport direction corresponding to the nozzle row, and moves the carriage in the movement direction, while moving each carriage in the movement direction in the movement direction. by discharging the liquid to pixels in a predetermined position, Rutotomoni intermittently to form dots at predetermined pixel intervals, a discharge irradiating operation for irradiating the light from the irradiation unit to the dots formed on the medium, the medium by performing the conveying operation and to convey at a predetermined transport amount in the transport direction alternately, the discharge irradiating operation of multiple dot rows which dots lined up in the movement direction Thus a controller to form, a liquid ejecting apparatus wherein the nozzle array includes an end portion in the transport direction, a said central portion of the inner conveying direction than the end of the discharge irradiation operation In this case, the variation in the amount of light emitted from the irradiation unit to the dots formed by the central nozzle is smaller than the variation in the amount of light emitted from the irradiation unit to the dots formed by the nozzle at the end. And the controller performs the ejection irradiation operation and the transport of the medium in the transport direction smaller than the predetermined transport amount in the upper end process for printing the upper end of the medium or the lower end process for printing the lower end. run the transport operation and for conveying an amount alternatively, the controller, the dot row by the upper printing region or the lower end processing said dot row is formed by the upper end treatment forms When printing on lower-end printing region that is, a nozzle of the central portion of the first discharge irradiation operation for a certain the pixel, the second ejection irradiation operation later than the first ejection irradiation operation In the case where the dot can be formed by the nozzle at the end in the above, the liquid is not discharged from the nozzle at the end, and the liquid is discharged from the nozzle at the center to form the dot on the pixel. The liquid ejection device is characterized by that.

  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. 5A to 5C are explanatory diagrams of the shape of the UV ink (dots) landed on the medium and the irradiation energy of the pre-curing UV. It is a conceptual diagram for demonstrating the relationship between UV illumination intensity distribution and a nozzle row. It is a conceptual diagram for demonstrating the illumination intensity distribution of the 1st irradiation part 42a. It is explanatory drawing of normal printing in 1st Embodiment. It is explanatory drawing of upper end printing in 1st Embodiment. It is explanatory drawing of the lower end printing in 1st Embodiment. It is explanatory drawing of normal printing in 2nd Embodiment. It is explanatory drawing of upper end printing in 2nd Embodiment. It is explanatory drawing of the lower end printing in 2nd Embodiment.

At least the following matters will become clear from the description of the present specification and the accompanying drawings.
A carriage that discharges a liquid that is cured by light irradiation has a plurality of nozzle rows arranged in a medium transport direction, a carriage that moves in a moving direction that intersects the transport direction, and a transport direction that corresponds to the nozzle row An irradiation unit that irradiates light along the carriage, and discharges the liquid from each nozzle of the nozzle row while moving the carriage in the movement direction, and the dots formed on the medium A liquid ejection apparatus comprising: a controller that alternately performs a discharge irradiation operation for irradiating light from an irradiation unit and a transport operation for transporting a medium in the transport direction, wherein the nozzle row is in the transport direction And the dot formed by the nozzle in the central portion during the discharge irradiation operation from the irradiation unit. The light amount variation has a central portion smaller than the light amount variation irradiated from the irradiation unit to the dots formed by the nozzles at the end portion, the controller, when performing the upper end printing or the lower end printing, The liquid ejection, wherein the central nozzle in the first ejection irradiation operation is used in preference to the end nozzle in the second ejection irradiation operation after the first ejection irradiation operation. apparatus.
According to such a liquid ejecting apparatus, it is possible to reduce variation in the size of dots formed in upper end printing and lower end printing. Therefore, the image quality can be improved.

In this liquid ejection apparatus, the end portion of the nozzle row includes a first nozzle having a predetermined distance from the central portion and a second nozzle having a predetermined distance greater than the predetermined value from the central portion. And the amount of light emitted from the irradiation unit to the dots formed by the second nozzle may be smaller than the amount of light emitted from the irradiation unit to the dots formed by the first nozzle.
According to such a liquid ejecting apparatus, even when the illuminance of the irradiation unit decreases at the end of the nozzle row, the center nozzle is preferentially used in the upper end printing or the lower end printing, so the dot size is reduced. There is no impact.

In this liquid ejection apparatus, it is preferable that the controller forms a predetermined dot row in which dots are arranged in the movement direction by a plurality of ejection irradiation operations.
According to such a liquid ejecting apparatus, even when there is a tendency for the size of the dot depending on the nozzle, it is possible to disperse the dots having different sizes. Therefore, deterioration of image quality can be prevented.

In this liquid ejection apparatus, the first nozzle is provided at one end of the nozzle row in the transport direction, and the second nozzle is provided at the other end of the nozzle row in the transport direction. In addition, it is preferable that the controller preferentially uses the first nozzle when the first nozzle or the second nozzle can be used when forming the predetermined dot row.
According to such a liquid ejecting apparatus, it is possible to reduce the variation in dot size as much as possible.

In this liquid ejection apparatus, the first nozzle is provided at one end of the nozzle row in the transport direction, and the second nozzle is provided at the other end of the nozzle row in the transport direction. The controller preferably forms the predetermined dot row using the first nozzle and the second nozzle.
According to such a liquid ejecting apparatus, it is possible to make the deterioration of the image quality due to the variation in the size of the dots inconspicuous.

  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.

  The printer 1 of the present embodiment is an apparatus that prints an image on a medium by ejecting a liquid toward the medium such as paper, cloth, or film sheet. In the present embodiment, an ultraviolet curable ink (hereinafter also referred to as UV ink) that is cured by being irradiated with ultraviolet light (hereinafter also referred to as UV), which is a kind of light, is used as the liquid. 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 this embodiment prints an image using four colors of CMYK UV ink.

  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 the head in the movement direction (also called “scanning”). The moving direction is a direction that intersects the transport 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, a dot row (raster line) in which dots are arranged in the moving direction is formed on the medium. In the present embodiment, the path moving from one end side to the other end side in the moving direction in FIG. 2 is defined as the forward path, and the path moving from the other end side to the one end side is defined as the return path. In the present embodiment, UV ink is ejected from the head 31 in the forward path, and no ink is ejected in the backward path. That is, the printer 1 of the present embodiment performs unidirectional 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 the present embodiment includes first irradiation units 42 a and 42 b and a second irradiation unit 44. Among these, the first irradiation parts 42 a and 42 b are provided on the carriage 21. For this reason, when the carriage 21 moves in the movement direction, the first irradiation units 42a and 42b also move in the movement direction.

  The first irradiation parts 42a and 42b are provided along the transport direction on one end side and the other end side in the moving direction of the head 31 on the carriage 21 so as to sandwich the head 31, respectively. In the present embodiment, the length of the first 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. Then, the first irradiation units 42a and 42b move with the head 31 to irradiate UV to a range where the nozzle row of the head 31 forms dots (temporary curing described later). The 1st irradiation parts 42a and 42b of this embodiment are equipped with the light emitting diode (LED: Light Emitting Diode) as a UV light source. The LED can easily change the irradiation energy of the UV by controlling the magnitude of the input current.

  As shown in the figure, the first irradiation units 42a and 42b are provided at both ends of the carriage 21 in the moving direction. Therefore, by switching the irradiation unit that irradiates UV according to the forward path and the return path, the head 31 performs the pass. It is possible to irradiate the dots immediately after being formed on the medium with UV. In the present embodiment, only one (the first irradiation unit 42a) of the first irradiation units 42a and 42b is used.

  The second irradiation unit 44 is provided downstream of the carriage 21 in the transport direction. That is, the 2nd irradiation part 44 is provided in the conveyance direction downstream rather than the nozzle row of the head 31, and the 1st irradiation parts 42a and 42b. Further, the length of the second irradiation unit 44 in the moving direction is longer than the maximum width of the medium to be printed. And the 2nd irradiation part 44 irradiates UV toward the medium conveyed under the 2nd irradiation part 44 by conveyance operation (main hardening mentioned later). The 2nd irradiation part 44 of this embodiment is provided with the lamp | ramp (metal halide lamp, a mercury lamp, etc.) as a light source which irradiates UV.

  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 is composed of a plurality of dots by alternately repeating a discharge operation for discharging UV ink from the head 31 moving in the moving direction and a transport operation for transporting the medium in the transport direction as will be described later. The image to be printed is printed on the medium. In the following description, the discharge operation is referred to as “pass”. The n-th pass is called a pass n. In the present embodiment, as will be described later, the controller 60 also causes the medium to be irradiated with UV from the first irradiation unit 42a during the pass. That is, the pass corresponds to a discharge irradiation operation.

<Printing procedure>
The controller 60 causes each unit of the printer 1 to perform the following processing when printing the print data received from the computer 110.
First, the controller 60 rotates the paper feed roller 11 to send the medium to be printed (here, the paper S) to the transport roller 13. Next, the controller 60 rotates the transport roller 13 by driving a transport motor (not shown). When the transport roller 13 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount.

  When the paper S is conveyed to the lower part of the head 31, the controller 60 rotates a carriage motor (not shown) in a predetermined direction. In accordance with the rotation of the carriage motor, the carriage 21 moves in the movement direction. Further, when the carriage 21 moves, the head 31 and the first irradiation units 42a and 42b provided on the carriage 21 also move in the moving direction at the same time. The controller 60 then intermittently ejects ink droplets from the head 31 during this time. When the ink droplets land on the paper S, a dot row (raster line) in which a plurality of dots are arranged in the moving direction is formed. Further, the controller 60 causes the first irradiation section 42a of the carriage 21 to perform UV irradiation while the head 31 is moving. By this UV irradiation, the spread of dots formed on the paper S and the bleeding between dots are suppressed.

  Next, the controller 60 drives the transport motor between passes. The transport motor generates a driving force in the rotation direction according to the commanded driving amount from the controller 60. The transport motor rotates the transport roller 13 using this driving force. When the transport roller 13 rotates with a predetermined rotation amount, the paper S is transported with a predetermined transport amount. That is, the transport amount of the paper S is determined according to the rotation amount of the transport roller 13. In this way, the pass and the transport operation are alternately repeated to form dots on each pixel of the paper S. Thus, an image is printed on the paper S.

Then, the controller 60 causes the second irradiation unit 44 to perform UV irradiation toward the sheet S when the sheet S passes under the second irradiation unit 44 by the transport operation. With this UV irradiation, the dots on the paper S are completely cured and fixed on the paper S.
The printed paper S is discharged by a paper discharge roller 15 that rotates in synchronization with the transport roller 13.

  In the present embodiment, upper-end printing that is printed on the upper end (end on the downstream side in the transport direction) of the paper S and lower-end printing that is printed on the lower end (end on the upstream side in the transport direction) are also performed. Details of the upper end printing and the lower end printing will be 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 nozzles of the head 31 seen from above. As shown in FIG. 4, a black ink nozzle row K, a cyan ink nozzle row C, a magenta ink nozzle row M, and a yellow ink nozzle row Y are formed on the lower surface of the head 31. Each nozzle row includes a plurality of nozzles (180 in the present embodiment) that are ejection openings for ejecting each color of UV ink.

  The plurality of nozzles in each nozzle row are aligned at a constant interval (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the medium). K is an integer of 1 or more. For example, when the nozzle pitch is 180 dpi (1/180 inch) and the dot pitch in the transport direction is 720 dpi (1/720 inch), k = 4.

  The nozzles in each nozzle row are assigned a lower number toward the downstream side in the transport direction. Each nozzle 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. The dots formed on the medium are cured by receiving UV irradiation from the irradiation unit 40. In this embodiment, in order to cure the UV ink, two stages of curing, temporary curing and main curing, are performed.

<About temporary curing and main curing>
Temporary curing is UV irradiation for suppressing the flow (spreading) of dots formed on a medium and bleeding between dots. For this reason, the dots after temporary curing are not completely cured, but the final dot shape is determined by this temporary curing.

  5A to 5C are explanatory diagrams of the shape of the UV ink (dots) landed on the medium and the irradiation energy of the pre-curing UV. The irradiation energy of UV in the temporary curing is lower in the order of FIGS. 5A, 5B, and 5C. In each figure, the timing of UV irradiation (the time from when dots are formed to when UV is irradiated) is the same.

  When the UV irradiation energy at the time of temporary curing is high, for example, as shown in FIG. 5A, the flow (spreading) of dots becomes small. That is, the dot diameter is reduced. In this case, since the unevenness of the surface becomes large, the image quality becomes low gloss with suppressed gloss. In this case, it is difficult for bleeding to occur between other inks.

  On the other hand, when the UV irradiation energy at the time of temporary curing is low, for example, as shown in FIG. 5C, the flow (spread) of dots increases. That is, the dot diameter increases. In this case, since the unevenness on the surface is reduced, high gloss image quality with improved glossiness is obtained. In this case, bleeding tends to occur between other inks.

  The main curing is UV irradiation for completely curing the ink. For this reason, as the light source of the second irradiation unit 44, a light source (for example, a lamp) that irradiates UV having a stronger energy than the first irradiation units 42a and 42b is used.

<Relationship between illuminance distribution and nozzle array>
Next, the relationship between the illuminance distribution of the first irradiation units 42a and 42b and the nozzle row of the head 31 will be described. In addition, the 1st irradiation part 42a and the 1st irradiation part 42b are the same structures. Therefore, only one of these will be described using the first irradiation unit 42a in the present embodiment. The head 31 has four nozzle rows. Here, only one of them (for example, a black nozzle row) will be described.

  FIG. 6 is a conceptual diagram for explaining the relationship between UV illuminance distribution and nozzle rows. In the drawing, the first irradiation unit 42a, the nozzle row of the head 31 (for example, a black nozzle row), and an image of dots formed by the nozzle row are shown.

  For simplification of explanation, the number of nozzles in the nozzle row of the head 31 is 12 (# 1 to # 12). For this reason, the 1st irradiation part 42a is shown by the length corresponding to 12 nozzle rows of the head 31. FIG.

  The first irradiation unit 42 a is provided at a position corresponding to the nozzle row of the head 31 in the carriage 21 (that is, a position aligned in the movement direction). The first irradiation unit 42a applies UV for pre-curing to the dots formed by the nozzle row of the head 31 when the carriage 21 moves in the forward direction (from one end side to the other end side in the moving direction). Irradiate. Here, UV ink is ejected from each nozzle in the nozzle row in the figure under the same conditions (ink ejection amount, etc.). That is, the size of the dot immediately after being formed on the medium (dot before receiving UV irradiation) is the same. These dots are temporarily cured by receiving UV irradiation from the first irradiation unit 42a located downstream of the nozzle row in the movement direction during the pass.

  In the figure, the curve shown below the first irradiation unit 42a indicates the illuminance distribution of the first irradiation unit 42a. This illuminance distribution conceptually shows the irradiation amount (light quantity) of UV from the first irradiation unit 42a, and is lower on the upper side and higher on the lower side in the figure. As can be seen from the figure, the illuminance is high and stable in the vicinity of the center of the first irradiation unit 42a, but the illuminance decreases as it approaches the end of the first irradiation unit 42a. That is, the variation in illuminance is greater at the end than at the center.

Hereinafter, the reason why the illuminance distribution is as shown in FIG. 6 will be described with reference to FIG.
FIG. 7 is a conceptual diagram for explaining the illuminance distribution of the first irradiation unit 42a. The first irradiating section 42a is provided with a plurality of LEDs 421 as light sources for irradiating UV as shown in the left side of FIG. In the figure, a plurality of LEDs 421 are provided in each of the vertical direction (conveyance direction) and the horizontal direction (movement direction). However, it is only necessary that a plurality of LEDs 421 be provided along at least the vertical direction (conveyance direction). By doing so, each dot formed by the nozzle row of the head 31 can be irradiated with UV.

  The diagram on the right side of FIG. 7 shows the illuminance distribution of the first irradiation unit 42a. In the figure, the solid line indicates the illuminance distribution of the LEDs 421 arranged in the transport direction, and the broken line indicates the illuminance distribution of the first irradiation unit 42a.

  As indicated by the solid line in the figure, the illuminance of each LED 421 is maximum (peak) at the center, and the illuminance decreases in a curve as the distance from the center increases. When the UV illuminance distributions of these LEDs 421 are superimposed, the illuminance distribution becomes as shown by the broken line in the figure. That is, the illuminance is high near the center in the transport direction and the variation is small, but the illuminance decreases as the end in the transport direction is approached, thereby increasing the variation. Therefore, the UV irradiation distribution of the first irradiation unit 42a has a distribution shape as shown in FIG.

  FIG. 6 shows the dot shape of the dots formed by each nozzle (dot shape after receiving UV irradiation from the first irradiation unit 42a). Since the illuminance of the first irradiation unit 42a is a distribution shape as described above, when dots are formed under the same conditions by each nozzle of the nozzle row of the head 31, the size is the same immediately after dot formation (before UV irradiation). Even if there is, the size of the dots after UV irradiation varies as shown in the figure. Specifically, the dots formed by the nozzles in the center of the nozzle row in the carrying direction have substantially the same dot size, but the dots formed by the nozzles at the end of the nozzle row in the carrying direction are in the carrying direction. The dot size increases as it approaches the edge. For this reason, if an image is printed using all the nozzles in the same manner, the image quality may be deteriorated. Therefore, in this embodiment, image quality is improved by providing a priority order for the nozzles used during printing. In the following description, the central portion of the nozzle row is also referred to as a region Nc. Further, the nozzle end on the downstream side in the transport direction is referred to as a region Nt, and the nozzle end on the upstream side in the transport direction is also referred to as a region Nb. As shown in the figure, the nozzles in the area Nc are nozzles # 3 to # 10, the nozzles in the area Nt are nozzles # 1 and # 2, and the nozzles in the area Nb are nozzles # 11 and # 12.

=== Printing Method of First Embodiment ===
<Normal printing (full overlap printing)>
In the printer 1 of the present embodiment, an image is formed by full overlap printing. “Full overlap printing” means a printing method in which a raster line is formed by a plurality of nozzles. The following printing operation is executed by the controller 60.

  FIG. 8 is an explanatory diagram of normal printing in the first embodiment. In full overlap printing, each time a medium (paper) is transported at a constant transport amount F in the transport direction, each nozzle intermittently forms dots every few dots. In another pass, by forming dots so that the intermittent dots already formed by other nozzles are complemented (filling between the dots), one raster line is formed by a plurality of nozzles. It is formed. When one raster line is formed in M passes in this way, it is defined as “overlap number M”. For example, when one raster line is formed in two passes, the overlap number M = 2. In the printing method of the present embodiment, one raster line is sandwiched between the raster lines formed by the nozzles of the nozzle row. That is, the nozzle pitch is twice the dot pitch (D) (k = 2).

  For convenience of explanation, FIG. 8 shows only one nozzle row among a plurality of nozzle rows, and the number of nozzles in the nozzle row is the same as that in FIG. 6 (12). In the nozzle row in the figure, the nozzles indicated by squares are nozzles at the end portions (regions Nt and Nb) of the nozzle row, and the nozzles indicated by circles are nozzles at the center portion (region Nc) of the nozzle row.

  In the figure, the position of the head 31 (that is, the nozzle row) for each pass is shown. For convenience of explanation, the nozzle row is depicted as moving in the transport direction (vertical direction in the figure) for each pass, but this figure shows the relative position of the nozzle row with respect to the medium, Actually, the medium is transported (moved) in the transport direction. Further, in the figure, for convenience of explanation, only the nozzle row is shown, but when this nozzle row moves in the movement direction (left and right direction in the figure), ink droplets are intermittently ejected from the nozzle. A large number of dots are arranged along the direction.

  In the figure, the feed amount is a relative movement amount (that is, a medium conveyance amount) between the medium and the nozzle row in the conveyance operation between passes. The unit of the feed amount is the dot pitch D. In FIG. 8, the medium is conveyed 5D in the conveyance direction for each pass. Thereby, the relative position in the conveyance direction of the nozzle row and the medium is shifted by 5D. For example, nozzle # 1 in pass 2 has a dot row (dot row in the moving direction) formed by nozzle # 3 and a dot row (moving direction in the moving direction) formed by nozzle # 3 in the previous pass (pass 1) in the transport direction. Dots are formed between the dot rows).

  In the figure, the nozzle whose horizontal position is “1” forms dots at odd-numbered pixels (hereinafter also referred to as odd-numbered pixels) among the pixels lined up in the moving direction of the medium. In addition, the nozzle whose horizontal position is “2” forms dots in even-numbered pixels (hereinafter also referred to as even-numbered pixels) among the pixels arranged in the moving direction of the medium. That is, each nozzle shown in the figure forms dots at a rate of one pixel for every two pixels during the pass. For example, in pass 1, since the horizontal position is “1”, ink is ejected from each nozzle to odd-numbered pixels while the nozzle row moves in the movement direction. Thereby, dots are formed on the medium every other pixel (odd pixel) in the moving direction.

  As can be seen, the controller 60 forms a raster line in a plurality of passes by the nozzles that are shown side by side in the movement direction. For example, nozzle # 8 in pass 1 and nozzle # 3 in pass 3 are shown side by side in the movement direction (positions in the transport direction are the same). In this case, since the horizontal position is “1” in pass 1, nozzle # 8 forms dots in odd pixels, and in pass 3, the horizontal position is “2”, so nozzle # 3 forms dots in even pixels. That is, nozzle # 3 in pass 3 forms dots between the dots formed by nozzle # 8 in pass 1 (that is, even pixels). In this way, a dot row (raster line) in which dots are arranged in the movement direction in two passes is formed.

  Also, among the nozzles shown side by side in the moving direction of each pass, nozzles with the same horizontal position number form dots alternately for even pixels or odd pixels. For example, the horizontal position of nozzle # 11 in pass 1 and nozzle # 1 in pass 5 are both “1”. In this case, nozzle # 11 and nozzle # 1 alternately form dots for odd-numbered pixels. That is, nozzle # 11 in pass 1 and nozzle # 1 in pass 5 form dots at a rate of 1 pixel per 4 pixels. Such a nozzle is called a “POL nozzle”. When the POL nozzle is used in this way, a raster line is formed in three passes (overlap number M = 3).

  In addition, as shown in FIG. 6, there is a tendency that the dots become larger toward the end of the nozzle row. For this reason, when the end of the nozzle row (region Nt, region Nb) is used as the POL nozzle, when the POL is combined with the endmost nozzles (for example, nozzle # 1 and nozzle # 12) of the nozzle row, the raster line becomes The number of dots larger than the dots formed by the nozzles in the region Nc increases, and image quality degradation is conspicuous. On the other hand, in the present embodiment, when the end of the nozzle row (region Nt, region Nb) is used as the POL nozzle, the nozzle near the end of the nozzle row and the nozzle near the center (region Nc) are combined. To use. For example, in the case of the nozzle # 11 in pass 1 and the nozzle # 1 in pass 5, the nozzle # 11 is a nozzle close to the region Nc, and the nozzle # 1 is a nozzle close to the end of the nozzle row. By doing so, a raster line is formed by a combination of the dot having the largest dot diameter among the dots shown in FIG. 6, the next largest dot, and the small dot at the center, and viewed macroscopically. In this case, the variation in dot size is less noticeable. The same applies to nozzle # 12 in pass 1, nozzle # 2 in pass 5, and the like.

<About top-end printing and bottom-end printing>
When printing as described above (FIG. 8) is performed from the beginning, some raster lines may not be continuously formed. For example, in FIG. 8, the first raster line formed by nozzle # 1 and the second raster line formed by nozzle # 2 are not formed as raster lines continuous in the transport direction.
Therefore, the controller 60 forms a raster line continuous in the transport direction by performing “upper end printing” as described below.
Also, when the above printing is finished last, some raster lines may not be formed continuously. For example, in FIG. 8, the raster line on the upstream side in the transport direction is not formed as a raster line continuous in the transport direction. Therefore, the controller 60 forms a raster line continuous in the transport direction by performing “bottom edge printing” as described below.

FIG. 9 is an explanatory diagram of upper end printing in the first embodiment.
In FIG. 9, pass 1 to pass 4 are upper end processing, and pass 5 and subsequent are normal printing processing. In the upper end process, the feed amount (transport amount) in the transport process between the passes is set to 1 (that is, the dot pitch D). In the drawing, the nozzles shown in black are nozzles that are set to be undischargeable during the pass (nozzles that do not discharge ink).
Note that the “upper end print area” in the drawing refers to an area from the raster line downstream in the transport direction formed on the medium to the raster line upstream in the transport direction among the raster lines formed by upper end printing. . Here, the upper end printing is printing for forming a raster line in the upper end printing area. In the case of this example, pass 1 to pass 7 are included in the upper end printing, and the upper end print area is an area of 17 raster lines.
In addition, the “normal area” in the figure indicates an area of a raster line formed after the upper end print area. The normal area in FIG. 9 is an area after the 18th raster line.

FIG. 10 is an explanatory diagram of lower-end printing in the first embodiment. In the figure, the notation method of the nozzle rows and the like is the same as in FIG. In the figure, for convenience of explanation, printing is started from normal printing (pass 1).
In FIG. 10, pass 7 to pass 10 are the lower end processing, and the feed amount is smaller than the feed amount in the normal region. Pass 1 to pass 6 are normal printing processes. The lower end printing is printing that forms a raster line in the lower end printing area. In this example, pass 3 to pass 10 are included in the lower end printing, and the upper end print area is an area of 20 raster lines.

<About non-ejection nozzles>
For example, in FIG. 9, nozzle # 5 in pass 1 and nozzle # 1 in pass 5 can form odd-numbered pixels on the third raster line from the downstream side in the transport direction of the upper-end printing region. Therefore, there are a method in which nozzle # 5 in pass 1 and nozzle # 1 in pass 5 are POL nozzles, or a method in which nozzle # 5 in pass 1 is a non-ejection nozzle. However, in this embodiment, nozzle # 1 in pass 5 is a non-ejection nozzle. If nozzle # 1 in pass 5 is used, the size of dots formed in the raster line 3 in the upper end processing area becomes larger than the size of dots formed in the nozzle in the area Nc, so that the image quality deteriorates. There is a risk (see FIG. 6). Therefore, as shown in the figure, in the present embodiment, in the upper end printing, the nozzles in the area Nc in the previous pass are given priority, and the nozzles in the area Nt in the subsequent pass are set as non-ejection nozzles. In the case of nozzle # 7 in pass 2 and nozzle # 1 in pass 6 and nozzle # 9 in pass 3 and nozzle # 1 in pass 7 as well, nozzle # 1 is set as a non-ejection nozzle. By doing so, the size of the dots formed in the upper end processing area can be made uniform, and the image quality can be improved.

  The same applies to the lower end printing in FIG. For example, nozzle # 10 in pass 3 and nozzle # 1 in pass 7 can form dots on even pixels in the same raster line (the raster line on the most downstream side of the transport high school in the bottom print area). Also in this case, priority is given to the nozzle (nozzle # 10) in the region Nc in the previous pass (pass 3), and the nozzle (nozzle # 1) in the region Nt in the subsequent pass (pass 7) is a non-ejection nozzle. It is said. In this way, the image quality can be improved. As can be seen from FIG. 6, when forming a raster line, if a nozzle in the region Nc cannot be used, it is desirable to use a nozzle closer to the region Nc.

  As described above, the printer 1 according to the present embodiment has a nozzle row in which a plurality of nozzles that eject ink that is cured by UV irradiation are arranged in the carrying direction, the carriage 21 that moves in the moving direction, and the nozzle row. Correspondingly, a first irradiation unit 42a is provided on the carriage 21 along the conveyance direction and irradiates UV. In addition, while moving the carriage 21 in the movement direction, ink is ejected from each nozzle of the nozzle row, and a path for irradiating light from the first irradiation unit 42a to the dots formed on the medium, and the medium in the conveyance direction A controller 60 that alternately performs a transport operation for transport is provided. The nozzle row of the carriage 21 has end regions Nt and Nb in the transport direction, and a central region Nc, and dots formed by the nozzles in the region Nc during the pass from the first irradiation unit 42a. The variation in the amount of UV light to be irradiated is smaller than the variation in the amount of UV light emitted from the first irradiation unit 42a to the dots formed by the nozzles in the regions Nt and Nb.

  In such a configuration, the controller 60 preferentially uses the nozzles in the area Nc in the previous pass over the nozzles in the areas Nt and Nb in the subsequent pass when performing the upper end printing or the lower end printing. By doing so, it is possible to reduce the variation in the size of dots (dots after UV irradiation) formed in the upper end print region and the lower end print region. Therefore, the image quality can be improved.

=== Second Embodiment ===
In the second embodiment, the number of nozzles in the nozzle row and the nozzles used in the pass are different from those in the first embodiment.
FIG. 11 is an explanatory diagram of normal printing in the second embodiment. Also in the second embodiment, printing is performed by full overlap printing. However, as shown in the drawing, in the second embodiment, the number of nozzles in the nozzle row is 14 (# 1 to # 14). As in the first embodiment, the nozzles indicated by squares in the drawing are nozzles at the end portions (regions Nt and Nb) of the nozzle row, and the nozzles indicated by circles are the central portions (region Nc) of the nozzle rows. Nozzle. In the second embodiment, the region Nt is nozzles # 1 to # 4, the region Nc is nozzles # 5 to # 10, and the region Nb is nozzles # 11 to # 14. Also in the second embodiment, in the region Nt and the region Nb, the illuminance of UV decreases as it approaches the end of the nozzle row. That is, the dot diameter after UV irradiation increases as it approaches the end of the nozzle row. On the other hand, in the region Nc, the dot diameter after UV irradiation is almost uniform.

  In FIG. 11, the notation method of the nozzle rows and the like is the same as that in the first embodiment, and thus description thereof is omitted. Also in the second embodiment, when the POL nozzle is configured by the nozzles of the region Nt and the region Nb, the controller 60 uses a combination of a nozzle near the center of the nozzle row and a nozzle near the end of the nozzle row. ing. For example, nozzle # 11 in pass 1 (nozzle near the center of the nozzle row in region Nb) and nozzle # 1 in pass 5 (nozzle near the end of the nozzle row in region Nt) are used as POL nozzles. The same applies to nozzle # 12 in pass 1, nozzle # 2 in pass 5, and the like. If the POL nozzle is configured by the nozzle at the end of the region Nt and the nozzle at the end of the region Nb, the dot having a large dot diameter increases in the raster line formed by the POL nozzle, so that the deterioration of the image quality is conspicuous. It becomes easy. Therefore, when the POL nozzle is configured by the region Nt and the region Nb as described above, the deterioration of the image quality can be suppressed by combining the nozzle near the center of the nozzle row and the nozzle near the end of the nozzle row.

FIG. 12 is an explanatory diagram of upper end printing in the second embodiment.
In FIG. 12, pass 1 to pass 4 are upper end processing, and pass 5 and subsequent are normal printing processing. In the upper end process, the feed amount (transport amount) in the transport process between the passes is set to 1 (that is, the dot pitch D). In the drawing, the nozzles shown in black are nozzles that are set to be undischargeable during the pass (nozzles that do not discharge ink).

In the second embodiment, upper end printing for forming raster lines in the upper end print area in the drawing includes pass 1 to pass 7, and the upper end print area is an area of 13 raster lines. Normal printing is an area after the 14th raster line.
Also in the second embodiment, the controller 60 preferentially uses the nozzles in the area Nc in the previous pass over the nozzles in the areas Nt and Nb in the subsequent pass during upper end printing. For example, the nozzle # 6 in pass 1 and the nozzle # 2 in pass 5 can form odd-numbered pixels on the raster line on the most downstream side in the transport direction of the upper end print area. In this case, priority is given to the nozzle (nozzle # 6) in the area Nc in the previous pass (pass 1), and the nozzle (nozzle # 2) in the area Nt in the subsequent pass (pass 5) is set as a non-ejection nozzle. . The same applies to other cases. By doing so, it is possible to reduce the variation in the size of the dots formed in the upper end print area, and to improve the image quality.

  Furthermore, if the controller 60 cannot use the nozzles in the area Nc when forming the raster line, the controller 60 selects the nozzle closer to the area Nc (that is, the lower gradient of the illuminance distribution) from among the nozzles in the area Nt or the area Nb. Use with priority. For example, nozzle # 11 (region Nb) in pass 3 and nozzle # 3 (region Nt) in pass 7 can form even-numbered pixels in the raster line on the most upstream side in the transport direction of the upper end print region. In this case, the controller 60 preferentially uses the nozzle close to the region Nc. As can be seen from the figure, with nozzle # 11 and nozzle # 3, nozzle # 11 is closer to region Nc. Therefore, the controller 60 gives priority to the nozzle # 11 in pass 3, and sets the nozzle # 3 in pass 7 as a non-ejection nozzle.

The controller 60 performs the same processing not only in the upper end print area but also in the normal area. For example, nozzle # 11 (region Nb) in pass 4 and nozzle # 1 (region Nt) in pass 8 can form odd-numbered pixels in the raster line on the most downstream side in the transport direction of the normal region. Even in this case, the controller 60 preferentially uses the nozzle close to the region Nc. As can be seen from the figure, with nozzle # 11 and nozzle # 1, nozzle # 11 is closer to region Nc. Therefore, the controller 60 gives priority to the nozzle # 11 in pass 4 and sets the nozzle # 1 in pass 8 as a non-ejection nozzle.
FIG. 13 is an explanatory diagram of lower-end printing in the second embodiment. In the figure, for convenience of explanation, printing is started from normal printing (pass 1).

In FIG. 13, pass 6 to pass 9 are the lower end processing, and the feed amount is smaller than the feed amount in the normal region. Pass 1 to pass 5 are normal printing processes.
Also in this case, the controller 60 preferentially uses the nozzles in the previous pass area Nc over the nozzles in the subsequent pass areas Nt and Nb in the lower end printing, as in the case described above. If the nozzles in the region Nc cannot be used to form a raster line, the nozzles in the region Nt or the region Nb that are closer to the region Nc (that is, the one having the lower illuminance distribution gradient) are used with priority. . By doing so, the image quality can be improved also in the second embodiment.

=== 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 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.

<About the head>
In the above-described embodiment, one head 31 is provided on the carriage 21, but the present invention is not limited to this, and a plurality of heads 31 may be provided on the carriage 21. In this case, the first irradiation portions 42a and 42b may be provided in the dot formation range of each nozzle row of the plurality of heads 31 so that UV can be irradiated. Further, although unidirectional printing is used in the present embodiment, bidirectional printing may be performed. In this case, the first irradiation unit 42b may be used during the return path.

<About nozzle>
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.

<About the irradiation unit>
In the above-described embodiment, unidirectional printing is performed. However, bidirectional printing may be performed. In this case, what is necessary is just to switch the irradiation part (the 1st irradiation part 42a or the 1st irradiation part 42b) to be used according to the moving direction of the carriage 21 (head 31).

  In the above-described embodiment, the first irradiation unit 42 a and the first irradiation unit 42 b are provided at both ends of the carriage 21 in the moving direction, respectively, but either one may be provided. In this case, if the first irradiation unit is provided on the downstream side in the moving direction of the head 31, it is possible to perform temporary curing UV irradiation immediately after dot formation.

  In the above-described embodiment, the second irradiation unit 44 is provided and the UV after the main curing is performed on the temporarily cured dots. However, the main curing may be performed by the first irradiation units 42a and 42b. For example, when the carriage 21 reciprocates in the moving direction, the dots may be completely cured by irradiating UV from the first irradiating units 42a and 42b (that is, performing temporary curing UV irradiation twice). . Alternatively, the UV irradiation energy of the first irradiation units 42a and 42b may be increased so that the dots are completely cured by one UV irradiation. In addition, when the dots are completely cured by the first irradiation units 42a and 42b as described above, the second irradiation unit 44 may not be provided.

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,
40 irradiation unit, 42a, 42b 1st irradiation part, 44 2nd irradiation part,
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 (5)

A carriage that has a plurality of nozzle rows in which a plurality of nozzles that discharge a liquid that is cured by light irradiation are arranged in the conveyance direction of the medium, and moves in a movement direction that intersects the conveyance direction;
An irradiation unit that is provided in the carriage along the transport direction in correspondence with the nozzle row, and irradiates light;
While moving the carriage in the moving direction, said each nozzle of the nozzle array by ejecting the liquid to pixels in a predetermined position in the movement direction, Rutotomoni intermittently to form dots at predetermined pixel intervals, the medium a discharge irradiating operation for irradiating the light from the irradiation portion formed the dot, by performing alternately and conveying operation for conveying a predetermined transport amount of the medium in the transport direction, dots in the direction of movement A controller that forms a line of aligned dots by a plurality of ejection irradiation operations ;
A liquid ejection device comprising:
The nozzle row includes an end portion in the transport direction and a center portion on the inner side in the transport direction from the end portion, and a dot formed on the nozzle in the center portion at the time of discharge irradiation operation. The light amount variation emitted from the center portion is smaller than the light amount variation emitted from the irradiation unit to the dots formed by the nozzles of the end portion,
The controller causes the ejection irradiation operation and the medium to be transported in the transport direction by a transport amount smaller than the predetermined transport amount in an upper end process for printing the upper end of the medium or a lower end process for printing the lower end. Alternately with the transfer operation,
The controller prints a first pixel on a certain pixel when performing printing in a top end printing area where the dot row is formed by the top end processing or a bottom end printing region where the dot row is formed by the bottom end processing . When the dots can be formed by the central nozzle in the discharge irradiation operation and the end nozzle in the second discharge irradiation operation after the first discharge irradiation operation, from the end nozzle The liquid ejecting apparatus, wherein the liquid is ejected without ejecting the liquid, and the liquid is ejected from the central nozzle to form the dot on the pixel . The liquid ejection device according to claim 1,
The end of the nozzle row includes a first nozzle having a predetermined value from the center and a second nozzle having a distance from the center larger than the predetermined value.
The liquid ejecting apparatus according to claim 1, wherein a light amount applied to the dots formed by the second nozzle from the irradiation unit is smaller than a light amount applied to the dots formed by the first nozzle from the irradiation unit. The liquid ejection device according to claim 2,
The liquid ejecting apparatus according to claim 1, wherein the controller forms a predetermined dot row in which dots are arranged in the moving direction by a plurality of ejection irradiation operations. The liquid ejection device according to claim 3,
The first nozzle is provided at one end of the nozzle row in the transport direction, and the second nozzle is provided at the other end of the nozzle row in the transport direction,
When the controller is capable of using the first nozzle or the second nozzle when forming the predetermined dot row, the controller does not eject the liquid from the second nozzle. The liquid ejecting apparatus, wherein the liquid is ejected to form the dots of the predetermined dot row . The liquid ejection device according to claim 3,
The first nozzle is provided at one end of the nozzle row in the transport direction, and the second nozzle is provided at the other end of the nozzle row in the transport direction,
The liquid ejection apparatus, wherein the controller forms the predetermined dot row using the first nozzle and the second nozzle.

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