Printing device

Abstract

To provide a printer that can remedy image quality defects such as streaks and uneven brightness.SOLUTION: A printer includes a carriage and a control unit. The control unit makes a discharge head discharge ink droplets, and imparts energy to the ink droplets impacted on a printed medium using energy imparting means, while moving the carriage in a main scanning direction, in order to form a dot connection part in which a plurality of impacted ink droplets is connected and extend to harden in the main scanning direction. Further, the control unit controls the discharge head and the energy imparting means while moving the carriage in the main scanning direction, in order to form a fragmented dot composed of a single ink droplet having hardened at a position adjacent to or overlapping with the dot connection part in the main scanning direction, or to form a fragmented dot connection part which is adjacent to or overlapping with the dot connection part in the main scanning direction and in which a plurality of ink droplets is connected and extend to harden in a sub scanning direction orthogonal to the main scanning direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a printing apparatus including a discharge head that discharges ink droplets onto a printing medium and an energy applying means for fixing the ink droplets.

Background Art

[0002] As an example of a printing apparatus that applies energy to fix ink on a printing medium, an inkjet module including a discharge head that discharges ultraviolet curable ink droplets onto the printing medium and a light source unit that cures the ink droplets is known (see Patent Document 1). The light source unit irradiates ultraviolet rays toward the ink droplets landed on the printing medium to cure the ink droplets and fix them on the printing medium.

[0003] In the inkjet module of Patent Document 1, interlace printing is performed in which the printing medium is not conveyed between one continuous discharge process and the other discharge process. In such interlace printing or the like, a method called singling printing is used to eliminate streaks at the joints between passes. Singling printing forms overlapping printed portions between passes and prints so as to reduce the discharge amount of ink droplets per pass in the overlapping printed portions. Such singling printing suppresses or prevents the occurrence of streaks at the joints between passes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when performing printing that requires fixing the ink to the printing medium, that is, printing using an ultraviolet-curing ink as in the above-described conventional method, the ink droplets landing on the printing medium remain uncured (i.e., in a liquid state) until irradiated with ultraviolet light. Therefore, when uncured ink droplets come into contact with each other, they are connected. In particular, when performing single-pass printing, ink droplet connection frequently occurs in areas where the ejection amount of ink droplets is large, while it is difficult for ink droplets to connect in areas where the ejection amount of ink droplets is small. As a result, streaks and gloss unevenness in the main scanning direction occur. This phenomenon is likely to occur especially when performing white printing that serves as a base for color printing and ejecting a large amount of ink droplets to ensure a high hiding power.

[0006] Therefore, an object of the present invention is to provide a printing apparatus capable of improving image quality defects such as streaks and gloss unevenness.

Means for Solving the Problems

[0007] The printing apparatus of the present invention includes an ejection head that ejects ultraviolet-curing ink droplets onto a printing medium, an energy applying means that applies energy for curing the ink droplets, a carriage that mounts the ejection head and the energy applying means and moves in the main scanning direction, and a control unit. The control unit moves the carriage in the main scanning direction, causes the ejection head to eject the ink droplets, and causes the energy applying means to apply energy to the ink droplets landing on the printing medium, so that a plurality of the landed ink droplets are connected to form a dot connection portion that extends in the main scanning direction and cures. While moving the carriage in the main scanning direction, the ejection head and the energy applying means are controlled to form a divided dot formed by curing a single one of the ink droplets at a position adjacent to or overlapping the dot connection portion in the main scanning direction, or to form a divided dot connection portion that is adjacent to or overlaps the dot connection portion in the main scanning direction and in which a plurality of the ink droplets are connected and extend in a sub-scanning direction intersecting the main scanning direction and cures.

[0008] According to the present invention, a divided dot adjacent to or overlapping a dot connection portion extending in the main scanning direction, or a divided dot connection portion adjacent to or overlapping the dot connection portion and extending in the sub-scanning direction is formed. In this case, for example, printing is performed by scanning the ejection head three times. Specifically, for the dot connection portion, it is formed by ejecting ink droplets and curing the ink droplets during the first scan of the ejection head. Then, during the second scan of the ejection head, ink droplets corresponding to the divided dots and ink droplets corresponding to a part of the divided dot connection portion are arranged on the printing medium. In this case, the ink droplets corresponding to the divided dots and the ink droplets corresponding to the above-mentioned part of the divided dot connection portion are not cured by the energy applying means. As a result, the ink droplets ejected during the third scan of the ejection head (that is, the ink droplets corresponding to the remaining part of the divided dot connection portion) are attracted to the uncured ink droplets ejected during the second scan (that is, the ink droplets corresponding to a part of the divided dot connection portion) and are connected to each other. That is, the post-printed ink droplets are connected so as to be pulled by the pre-printed ink droplets. As a result, the ink droplets ejected during the second scan and the ink droplets ejected during the third scan can be easily connected in the sub-scanning direction, and therefore, as described above, a divided dot connection portion extending in the sub-scanning direction can be formed. Thereby, it is possible to suppress or prevent the connection of ink droplets in the main scanning direction. On the other hand, since the divided dots are formed so as to be adjacent to or overlap the dot connection portion, the dot connection portion can be divided in the main scanning direction. Thereby, the continuity of the dot connection portion in the main scanning direction can be interrupted. As described above, it is possible to suppress or prevent the occurrence of streaks and gloss unevenness in the main scanning direction, and therefore it is possible to improve image quality defects.

Effect of the Invention

[0009] According to the present invention, it is possible to provide a printing apparatus capable of improving image quality defects such as streaks and gloss unevenness.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0011] Hereinafter, a printing apparatus according to an embodiment of the present invention will be described with reference to the drawings. The printing apparatus described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the following embodiments, and additions, deletions, and changes are possible without departing from the spirit of the present invention.

[0012] FIG. 1 is a perspective view showing a printing apparatus 1 according to an embodiment of the present invention. In FIG. 1, the directions orthogonal to each other are defined as the vertical direction, the horizontal direction, and the front-rear direction. Note that the horizontal direction is the main scanning direction Ds described later, and the front-rear direction is the sub-scanning direction Df described later. This printing apparatus 1 can perform not only printing on a printing medium W such as printing paper but also goods printing on a printing medium W such as goods made of resin.

[0013] As shown in FIG. 1, the printing apparatus 1 of the present embodiment includes a housing 2, a carriage 3, operation keys 4, a display unit 5, a platen 6, and an upper cover 7. The printing apparatus 1 also includes a control unit 19 (FIG. 3). The platen 6 corresponds to a conveyance mechanism, and the control unit 19 corresponds to a control unit. The control unit 19 will be described in detail later.

[0014] The housing 2 is formed in a box shape. The housing 2 has an opening 2a on the front surface and an opening (not shown) on the back surface. The operation keys 4 are provided at a position in front of the right side of the housing 2. Also, the display unit 5 is provided at a position behind the operation keys 4. The operation keys 4 receive operation inputs from the user. The display unit 5 is configured by, for example, a touch panel and displays predetermined information. A part of the display unit 5 also functions as an operation key at a predetermined timing. The control unit 19 realizes a printing function based on an input from the operation keys 4 or an external input via a communication interface (not shown) and controls the display on the display unit 5.

[0015] As shown in FIG. 2, two ejection heads 10 (10A, 10B) and two light source units 40 (40A, 40B) are mounted on the carriage 3. The light source unit 40 corresponds to an energy applying means. The carriage 3 is configured to be reciprocally movable along the main scanning direction Ds. Thereby, the carriage 3 moves the ejection head 10 and the light source unit 40 in the main scanning direction Ds.

[0016] As the ejection head 10, for example, an inkjet head that ejects ultraviolet curable ink droplets 50 (Fig. 6 etc.) can be used. Further, the light source unit 40 has a plurality of light emitting diode chips DT (Fig. 4) that emit ultraviolet light as the energy applied to the ejected ink droplets 50. The ejection head 10A and the ejection head 10B are arranged side by side along the sub-scanning direction Df. The ejection head 10B is arranged in front of the ejection head 10A. Also, the light source unit 40A and the light source unit 40B are arranged side by side along the sub-scanning direction Df. The light source unit 40B is arranged in front of the light source unit 40A. Further, the ejection head 10A and the light source unit 40A are arranged side by side along the main scanning direction Ds. The light source unit 40A is arranged to the left of the ejection head 10A. Also, the ejection head 10B and the light source unit 40B are arranged side by side along the main scanning direction Ds. The light source unit 40B is arranged to the left of the ejection head 10B. Note that the above arrangement is an example and is not limited thereto.

[0017] Each light emitting diode chip DT of the light source unit 40A is arranged such that the ultraviolet light emission region by the light emitting diode chip DT is larger than the nozzle row NL (Fig. 2) in the sub-scanning direction Df. Thereby, the ink droplets 50 ejected from the nozzles located at one end (i.e., the front end) and the other end (i.e., the rear end) of the nozzle row NL in the sub-scanning direction Df can also be sufficiently irradiated with ultraviolet light.

[0018] In the first scan of the printing process, the carriage 3 moves to the right in the main scanning direction Ds. As a result, during the printing process, the ejection head 10 and the light source unit 40 move to the right. In this case, the ejection head 10 ejects ink droplets 50 onto the printing medium W while moving to the right in the main scanning direction Ds, and the light source unit 40 irradiates ultraviolet rays onto the ink droplets 50 that have landed on the printing medium W while moving to the right in the main scanning direction Ds. Since the light source unit 40 is positioned behind the ejection head 10 in the moving direction of the carriage 3 during the printing process, ultraviolet rays can be irradiated onto the ink droplets 50 immediately after they land on the printing medium W. Details of the scanning of the ejection head 10 in this embodiment will be described in detail later.

[0019] In this embodiment, the ejection head 10A ejects ink droplets 50 of each color of yellow (Y), magenta (M), cyan (C), and black (K), which may be collectively referred to as color ink. In FIG. 2, an ejection head 10A for ejecting color ink is shown as an example of the ejection head 10. In the ejection head 10A, nozzle rows NL for ejecting the respective ink droplets 50 are provided so as to extend along the sub-scanning direction Df. Each nozzle row NL is provided at regular intervals in the main scanning direction Ds. The arrangement order of the nozzle rows NL in the main scanning direction Ds may be, in order from the left, the nozzle row NL for ejecting yellow-colored ink droplets 50, the nozzle row NL for ejecting magenta-colored ink droplets 50, the nozzle row NL for ejecting cyan-colored ink droplets 50, and the nozzle row NL for ejecting black-colored ink droplets 50.

[0020] On one hand, the ejection head 10B ejects ink droplets 50 of white (W) ink and clear (Cr) ink. A nozzle row NL for ejecting each of these ink droplets 50 is provided in the ejection head 10B so as to extend along the sub-scanning direction Df. Each nozzle row NL is provided at regular intervals along the main scanning direction Ds. The interval in the main scanning direction Ds of each nozzle row NL in the ejection head 10B may be different from or the same as the interval in the main scanning direction Ds of each nozzle row NL in the ejection head 10A. The arrangement order of each nozzle row NL in the main scanning direction Ds may be, for example, the nozzle row NL for ejecting white ink droplets 50 and the nozzle row NL for ejecting clear ink droplets 50 in that order from the left side.

[0021] By ejecting the above six-color ink droplets onto the print medium W, a color image is printed on the print medium W. Specifically, when printing a color image on a fabric or the like as the print medium W, in order to reduce the influence on the color and material of the fabric, white ink droplets 50 are first ejected as the base ink, and ink droplets 50 of color ink are ejected onto the ink droplets 50 of the white ink that have landed on the print medium W. Also, the ink droplets 50 of the clear ink are ejected when imparting gloss or protecting the printed portion.

[0022] The platen 6 is configured to be able to mount the print medium W. The platen 6 has a predetermined thickness and is formed of, for example, a rectangular plate material having the sub-scanning direction Df as the longitudinal direction. The platen 6 is removably supported by a platen support base (not shown). The above platen support base is configured to be movable between a printing position for performing printing on the print medium W and a detaching position for detaching the print medium W from the platen 6. The printing position is the position where the platen 6 faces the ejection head 10, and the detaching position is the position where the above platen support base is disposed outside the housing 2 and the print medium W can be mounted on the platen 6. During printing, since the platen 6 moves in the sub-scanning direction Df, the print medium W mounted on the platen 6 is conveyed in the sub-scanning direction Df.

[0023] When the upper cover 7 is lifted at its front part, it is configured to rotate upward with the base end, which is configured to be rotatable, as a fulcrum. As a result, the inside of the housing 2 is exposed.

[0024] Next, the functions of each component of the printing apparatus 1 will be described with reference to the block diagrams. As shown in FIG. 3, in addition to the above-described components, the printing apparatus 1 of the present embodiment includes motor driver ICs 30 and 31, head driver ICs 32 and 36, a conveyance motor 33, a carriage motor 34, light source driver ICs 37 and 38, an internal power source 15, and a power receiving unit 16.

[0025] The control unit 19 includes a CPU 20 corresponding to a control section, a storage section (ROM 21, RAM 22, EEPROM 23, HDD 24), and an ASIC 25. The CPU 20 is a control section of the printing apparatus 1, is connected to the above storage section, and controls each of the driver ICs 30 to 32, 36 to 38, and the display section 5.

[0026] The CPU 20 executes various functions by executing a predetermined program stored in the ROM 21. The CPU 20 may be implemented as one processor in the control unit 19, or may be implemented as a plurality of processors that cooperate with each other.

[0027] The ROM 21 stores a print control program for causing the CPU 20 to execute printing processing. The RAM 22 stores the calculation results of the CPU 20. The EEPROM 23 stores various initial setting information input by the user. The HDD 24 stores specific information and the like. This specific information is highly confidential information for which external leakage is not preferable, and includes, for example, information about the user, job data including a user ID that the printing apparatus 1 receives from the outside and identifies the transmission source, user usage history information including the user ID in the job data, secure job data including a password and data related to a secure job, a print history, and cloud setting data and the like. The above information about the user includes, for example, address book information, e-mail address information, information about the administrator (security administrator) of the printing apparatus 1, and network setting information and the like. When the printing apparatus 1 receives job data, the CPU 20 stores the user usage history information including the user ID in the job data in the HDD 24.

[0028] The ASIC 25 has the motor driver ICs 30, 31, the head driver ICs 32, 36, and the light source driver ICs 37, 38 connected thereto. When the CPU 20 receives a print job from the user, it outputs a print command to the ASIC 25 based on the print control program. The ASIC 25 drives each of the driver ICs 30 to 32, 36 to 38 based on the print command. The CPU 20 drives the conveyance motor 33 by the motor driver IC 30, so that the platen 6 moves in the sub-scanning direction Df, and thus the printing medium W is conveyed in the sub-scanning direction Df. Further, the CPU 20 drives the carriage motor 34 by the motor driver IC 31 to move the carriage 3 in the main scanning direction Ds. Further, the CPU 20 causes the ejection heads 10 mounted on the carriage 3 that moves by the head driver ICs 32, 36 to eject ink droplets 50, and prints image data on the conveyed printing medium W. Further, the CPU 20 causes the light source driver ICs 37, 38 to irradiate ultraviolet rays for curing the ink droplets 50 that have landed on the printing medium W from the light source units 40A, 40B.

[0029] The internal power source 15 is provided at a predetermined position within the housing 2. The internal power source 15 enables the control unit 19 to operate when the main power source of the printing apparatus 1 is in the OFF state. The internal power source 15 is, for example, a secondary battery. Also, the power receiving unit 16 is provided so as to be exposed to the outside from the housing 2 and receives power supply from an external power source. When the main power source is in the ON state, power from the outside is supplied to each part of the printing apparatus 1 via the power receiving unit 16. Irrespective of the state of the main power source, power from the outside is supplied to the internal power source 15 via the power receiving unit 16, and the internal power source 15 is charged by this power.

[0030] Each light emitting diode chip DT in the light source unit 40 is a semiconductor element that generates ultraviolet rays. As shown in FIG. 4, the light source unit 40A includes a support substrate 41 formed, for example, in a rectangular shape in plan view. The support substrate 41 is, for example, an aluminum substrate. Each light emitting diode chip DT is arranged on the support substrate 41. Each light emitting diode chip DT is arranged in a matrix. Each light emitting diode chip DT forms dots by irradiating ultraviolet rays onto the ink droplets 50 that have landed on the printing medium W, thereby fixing the ink droplets 50 to the printing medium W. Hereinafter, the ink droplets 50 that have landed on the printing medium W and have been cured by ultraviolet rays are referred to as dots. Note that the configuration of the light source unit 40B may be the same as the configuration of the light source unit 40A.

[0031] Next, the scanning of the ejection head 10 in the present embodiment will be described in detail. Since the scanning of the ejection head 10B is the same as the scanning of the ejection head 10A, the operation of the ejection head 10A and the operation of the light source unit 40A will be typically described below.

[0032] In this embodiment, the ejection head 10A can perform bidirectional printing. Specifically, in bidirectional printing, the CPU 20 of the control unit 19 moves the ejection head 10A in both directions of one direction (i.e., the forward path) OP and the other direction (i.e., the return path) RP of the main scanning direction Ds by the carriage 3 and ejects ink droplets 50 from the ejection head 10A. Specifically, as shown in FIG. 5, the CPU 20 of the control unit 19 moves the ejection head 10A in one direction OP (i.e., to the right) of the main scanning direction Ds in the first scan of the carriage 3 and ejects ink droplets 50 from the ejection head 10A. At this time, the CPU 20 of the control unit 19 irradiates the ink droplets 50 landed on the printing medium W by the light source unit 40A with ultraviolet rays to cure the ink droplets 50. Thereby, the printed portion PR1 is formed.

[0033] Next, the CPU 20 of the control unit 19 moves the ejection head 10A in the other direction RP (i.e., to the left) of the main scanning direction Ds in the second scan of the carriage 3 without conveying the printing medium W in the sub-scanning direction Df and ejects ink droplets 50 from the ejection head 10A. Thereby, a printed portion PR2 overlapping the printed portion PR1 is formed. That is, interlace printing for forming printed portions overlapping between passes is performed. At this time, the CPU 20 of the control unit 19 does not emit light from the light source unit 40A in the second scan. Thereby, the ink droplets 50 ejected in the second scan and landed on the printing medium W remain uncured.

[0034] Then, after the CPU 20 of the control unit 19 conveys the printing medium W in the sub-scanning direction Df by a predetermined amount, the CPU 20 of the control unit 19 moves the ejection head 10A in one direction OP (i.e., to the right) of the main scanning direction Ds in the third scan of the carriage 3 and ejects ink droplets 50 from the ejection head 10A. At this time, the CPU 20 of the control unit 19 irradiates the ink droplets 50 landed on the printing medium W by the light source unit 40A with ultraviolet rays to cure the ink droplets 50. Thereby, the printed portion PR3 is formed. In this case, singling printing may be performed in which a part of the previously formed printed portion PR2 and a part of the printed portion PR3 overlap in the sub-scanning direction Df.

[0035] Here, in the case of forming dots on the printing medium W by discharging the ink droplets 50 from the discharge head 10A in order to improve image quality defects such as streaks and gloss unevenness, it will be described in detail with reference to the drawings. FIG. 6 is a schematic diagram showing an example of the arrangement of each ink droplet and the landing state of the ink droplets 50 in the first to third scans of the carriage 3. Note that the ink droplet arrangements in FIG. 6, FIG. 8, and FIGS. 10 to 12 described later are the same as those showing dot data (discharge data) two-dimensionally, and show the arrangement of the discharged ink droplets 50. Further, in FIG. 6 and FIGS. 8 to 12 described later, as an example, the ink droplet arrangement in 25 (= 5 × 5) pixels will be described, and the position of each ink droplet 50 will be specified by rows and columns.

[0036] As shown in FIG. 6, as an example of the ink droplet arrangement in the first scan of the carriage 3, each ink droplet 50 is arranged continuously in the main scanning direction Ds or arranged singly and independently. Specifically, the groups of ink droplets 50 arranged continuously in the main scanning direction Ds are positioned in the first row, the third row, and the fifth row. Further, the adjacent ink droplets 50 in the sub-scanning direction Df are arranged at a distance of one pixel or more. In order to realize such an ink droplet arrangement, the CPU 20 of the control unit 19 moves the carriage 3 to the right in the main scanning direction Ds while discharging the ink droplets 50 from the discharge head 10A and irradiating the ink droplets 50 landed on the printing medium W with ultraviolet rays by the light source unit 40A. As a result, dot connection portions 51 in which a plurality of ink droplets 50 are connected and extended in the main scanning direction Ds and cured are formed on the printing medium W.

[0037] Next, as an example of the ink droplet arrangement in the second scan of the carriage 3, each ink droplet 50 is arranged singly and independently. Specifically, each ink droplet 50 in the second scan is arranged at a position adjacent to one or two ink droplets 50 in the first scan in the main scanning direction Ds. That is, each ink droplet 50 is positioned in the first row, the third row, and the fifth row in the same manner as in the first scan. However, each ink droplet 50 in the second scan is arranged so as to be separated from each other by at least one pixel in the main scanning direction Ds and the sub-scanning direction Df, respectively. To realize such an ink droplet arrangement, the CPU 20 of the control unit 19 moves the carriage 3 to the left in the main scanning direction Ds without conveying the printing medium W by the platen 6, and causes the ejection head 10A to eject ink droplets 50 while not irradiating the light source unit 40A with ultraviolet rays. Thereby, uncured ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 are arranged on the printing medium W. Note that the divided dot connection portion 53 described later is formed by the connection and curing of the ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 and the ink droplets 50 corresponding to the remaining portion 53b arranged in the next process.

[0038] Next, as an example of the ink droplet arrangement in the third scan of the carriage 3, each ink droplet 50 is arranged continuously in the main scanning direction Ds or singly and independently. Specifically, a group of ink droplets 50 arranged continuously in the main scanning direction Ds is positioned in the second row and the fourth row. That is, each ink droplet 50 in the third scan is positioned at a pixel in the blank row in the first scan. Also, a part of all the ink droplets 50 in the third scan is arranged at a position adjacent to the ink droplets 50 in the second scan in the sub-scanning direction Df. To realize such an ink droplet arrangement, the CPU 20 of the control unit 19 conveys the printing medium W by the platen 6 by a predetermined amount in the sub-scanning direction Df, and then moves the carriage 3 to the right in the main scanning direction Ds, while causing the ejection head 10A to eject ink droplets 50 and the light source unit 40A to irradiate the ink droplets 50 landing on the printing medium W with ultraviolet rays. Thereby, the ink droplets 50 corresponding to the remaining portion 53b of the divided dot connection portion 53 are arranged, and the divided dot connection portion 53 is formed by the connection and curing of the ink droplets 50 corresponding to the part 53a and the ink droplets 50 corresponding to the remaining portion 53b.

[0039] Thus, the divided dot connection portion 53 is formed adjacent to or overlapping the dot connection portion 51 and extending in the sub-scanning direction Df. A part 53a and the remaining part 53b of the divided dot connection portion 53 are adjacent to each other in the sub-scanning direction Df. Also, in FIG. 6, each of the plurality of divided dot connection portions 53 is positioned shifted from each other in the main scanning direction Ds.

[0040] Here, as described above, the ink droplets 50 of the second pass are adjacent to the ink droplets 50 of the third pass in the sub-scanning direction Df. Therefore, in FIG. 6, with respect to a part 53a of the divided dot connection portion 53 formed by landing in the second pass, the remaining part 53b of the divided dot connection portion 53 formed by landing in the third pass is adjacent to the part 53a in the sub-scanning direction Df. At this time, when the subsequent ink droplets 50 (ink droplets 50 of the third pass) land so as to be adjacent to and contact the previously landed uncured ink droplets 50 (ink droplets 50 of the second pass), a phenomenon occurs in which the subsequent ink droplets 50 are attracted to the previous ink droplets 50 and connected to the previous ink droplets 50. This will be described in detail below.

[0041] As shown in FIG. 7, in the first stage, after the ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 are previously arranged on the printing medium W, subsequent ink droplets 50 are ejected so as to be adjacent to and contact the part 53a in the sub-scanning direction Df. At this time, since ultraviolet rays are not irradiated to the part 53a of the divided dot connection portion 53, the part 53a is in a state of spreading wet on the printing medium W. In this state, in the second stage, before the ink droplets 50 land, they contact the ink droplets 50 corresponding to the part 53a of the divided dot connection portion 53. At this time, due to surface tension, the ink droplets 50 corresponding to the part 53a of the divided dot connection portion 53 and the subsequent ink droplets 50 tend to be connected.

[0042] Next, in the third stage, since the ink droplet 50 corresponding to a part 53a of the divided dot connection part 53 is in contact with the printing medium W, it is considered that the subsequent ink droplet 50 which exists in the air and is easy to move is attracted to the ink droplet 50 corresponding to the part 53a. Then, in the fourth stage, the subsequent ink droplet 50 (the ink droplet 50 corresponding to the remaining part 53b) and the preceding ink droplet 50 (the ink droplet 50 corresponding to the part 53a) are connected and cured, so that the divided dot connection part 53 is formed on the printing medium W.

[0043] As described above, the ink droplet 50 ejected during the second scan and the ink droplet 50 ejected during the third scan can be easily connected in the sub-scanning direction Df. Therefore, the divided dot connection part 53 extending in the sub-scanning direction Df can be formed.

[0044] Specifically, taking an example in FIG. 6 for explanation, by arranging in advance a part 53a of the divided dot connection part 53 with the ink droplet 50 of the second scan (the ink droplet 50 in the first column of the third row), the remaining part 53b of the divided dot connection part 53 formed by the ink droplet 50 of the third scan (the ink droplet 50 in the first column of the second row) can be attracted in the sub-scanning direction Df. By this, it is possible to avoid the ink droplet 50 in the first column of the second row of the third scan from connecting to its adjacent ink droplet 50 (the ink droplet 50 in the second column of the second row). Also, by arranging in advance a part 53a of the above-mentioned divided dot connection part 53, the remaining part 53b of the divided dot connection part 53 formed by the ink droplet 50 of the third scan (the ink droplet 50 in the first column of the fourth row) can be attracted in the sub-scanning direction Df. By this, it is possible to avoid the ink droplet 50 in the first column of the fourth row of the third scan from connecting to its adjacent ink droplet 50 (the ink droplet 50 in the second column of the fourth row). As a result, it is possible to prevent some of the ink droplets 50 of the third scan from connecting in the main scanning direction Ds.

[0045] As another example of FIG. 6, the ink droplet arrangement may be set as follows. FIG. 8 is a schematic diagram showing an example of each ink droplet arrangement and the landing state of the ink droplet 50 in the first to third scans of the carriage 3.

[0046] As shown in FIG. 8, the ink droplet arrangement of the first scan of carriage 3 is the same as the ink droplet arrangement of the first scan of FIG. 6. The dot connection portion 51 in FIG. 8 is formed in the same manner as in FIG. 6.

[0047] An example of the ink droplet arrangement of the second scan of carriage 3 will be described. The ink droplets 50 of the second scan are partially different from the positions of the ink droplets 50 of the second scan in FIG. 6, but are basically positioned in the same manner as the method described above with respect to FIG. 6. However, in FIG. 8, the ink droplets 50 at the 1st row and 4th column and the 3rd row and 3rd column of the second scan are respectively arranged at positions overlapping the ink droplets 50 of the first scan. Further, in FIG. 8, each of the divided dots 52 formed by curing a plurality of ink droplets 50 is positioned shifted from each other in the main scanning direction Ds. In order to realize such an ink droplet arrangement, the CPU 20 of the control unit 19 moves the carriage 3 to the left in the main scanning direction Ds without transporting the printing medium W by the platen 6, and while causing the ejection head 10A to eject the ink droplets 50, does not irradiate the light source unit 40A with ultraviolet rays. As a result, the uncured ink droplets 50 corresponding to the divided dots 52 and the uncured ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 are arranged on the printing medium W.

[0048] The ink droplet arrangement of the third scan of carriage 3 is the same as the ink droplet arrangement of the third scan of FIG. 6. Here, also in FIG. 8, a part of all the ink droplets 50 of the third scan is arranged at a position adjacent to the ink droplets 50 of the second scan in the sub-scanning direction Df. It should be noted that the ink droplets 50 ejected in the third scan do not include those adjacent to the ink droplets 50 at the 1st row and 4th column of the second scan in the sub-scanning direction Df. This is because, unlike the above-mentioned purpose of attracting the subsequent ink droplets 50 to the preceding ink droplets 50 in the sub-scanning direction Df, the ink droplets 50 at the 1st row and 4th column of the second scan are based on the purpose of dividing the dot connection portion 51 formed in the first scan in the main scanning direction Ds.

[0049] In order to achieve such an ink droplet arrangement, the CPU 20 of the control unit 19 causes the platen 6 to convey the printing medium W in the sub-scanning direction Df by a predetermined amount, and then while moving the carriage 3 to the right in the main scanning direction Ds, discharges ink droplets 50 from the discharge head 10A and irradiates the ink droplets 50 with ultraviolet rays by the light source unit 40A. As a result, the ink droplets 50 corresponding to the remaining portion 53b of the divided dot connection portion 53 are arranged, and the divided dot connection portion 53 is formed by the connection and curing of the ink droplets 50 corresponding to a part and the ink droplets 50 corresponding to the remaining portion 53b. Also, in the example of FIG. 8, by forming the divided dots 52, the dot connection portion 51 can be divided in the main scanning direction Ds. Thereby, the continuity of the dot connection portion 51 in the main scanning direction Ds can be interrupted.

[0050] Here, the conditions for the ink droplet arrangement in the second scan and the third scan in the present embodiment are summarized as follows. First, in order to prevent the connection of the ink droplets 50 in the second scan, each ink droplet 50 discharged in the second scan is positioned at a distance of one pixel or more (condition 1). Also, in order to promote the connection in the sub-scanning direction Df for an ink droplet group that is likely to connect in the main scanning direction Ds, each ink droplet 50 in the second scan is positioned at a position where the number of adjacent droplets to the ink droplets 50 in the third scan is large (condition 2). The above-mentioned number of adjacent droplets is the total number of the ink droplets 50 in the second scan that are adjacent to the ink droplets 50 in the third scan without leaving blank pixels in the left-right direction, front-back direction, and diagonal direction. This will be specifically described below.

[0051] In FIG. 9, the ink droplets 50 (50s1, 50s2) in the second scan are indicated by a wavy line, and the ink droplets 50 in the third scan are indicated by a solid line. According to the above definition of the number of adjacent droplets, the number of adjacent droplets of the ink droplet 50s1 is 6, and the number of adjacent droplets of the ink droplet 50s2 is 4. In this case, a threshold value of the required number of adjacent droplets (for example, 4) can be set in advance, and the ink droplets 50 in the second scan can be positioned at positions where the number of adjacent droplets is 4 or more.

[0052] Also, on the premise that the above conditions 1 and 2 are satisfied, the following condition may be further added. That is, the ink droplets 50 in the second scan are arranged at positions overlapping the ink droplets 50 in the first scan and at positions with a relatively large number of adjacent droplets with respect to the ink droplets 50 in the first scan (Condition 3). This is based on the intention of dividing the connection in the main scanning direction Ds by each ink droplet 50 in the first scan. Condition 3 will be specifically described. In FIG. 10, the ink droplet 50s3 indicated by the wavy line is positioned at the 3rd row and 3rd column. The ink droplet 50s3 overlaps the ink droplet at the 3rd row and 3rd column in the first scan, and the number of adjacent droplets with respect to the ink droplet 50 in the first scan is also 2, which is relatively large. Note that a threshold value may be set in advance for the number of adjacent ink droplets 50s3 in the second scan with respect to the ink droplets 50 in the first scan.

[0053] The dot connection portion 51, the divided dots 52, and the divided dot connection portion 53 described above may be formed when the discharge amount of the ink droplets is equal to or greater than a threshold value. Note that the discharge amount of the ink droplets can be the duty for one sheet of the printing medium W or the duty for one pass.

[0054] As described above, according to the printing apparatus 1 of the present embodiment, the divided dots 52 adjacent to or overlapping the dot connection portion 51 extending in the main scanning direction Ds, and the divided dot connection portion 53 adjacent to or overlapping the dot connection portion 51 and extending in the sub-scanning direction Df are formed. For the dot connection portion 51, it is formed by discharging the ink droplets 50 and curing the ink droplets 50 during the first scan of the carriage 3. Then, during the second scan of the carriage 3, the ink droplets 50 corresponding to the divided dots 52 and the ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 are arranged on the printing medium W. In this case, the ink droplets 50 corresponding to the divided dots 52 and the ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53 are not cured by ultraviolet irradiation. As a result, the ink droplets 50 discharged during the third scan of the carriage 3 (that is, the ink droplets 50 corresponding to the remaining portion 53b of the divided dot connection portion 53) are attracted to the uncured ink droplets 50 discharged during the second scan (that is, the ink droplets 50 corresponding to a part 53a of the divided dot connection portion 53) and are connected to each other. Thereby, the uncured ink droplets 50 discharged during the second scan and the ink droplets 50 discharged during the third scan can be easily connected in the sub-scanning direction Df, and therefore the divided dot connection portion 53 extending in the sub-scanning direction Df can be formed. As a result, it is possible to suppress or prevent the ink droplets 50 from being connected to each other in the main scanning direction Ds. On the other hand, since the divided dots 52 are formed so as to be adjacent to or overlap the dot connection portion 51, the dot connection portion 51 can be divided in the main scanning direction Ds. Thereby, the continuity of the dot connection portion 51 in the main scanning direction Ds can be interrupted. As described above, it is possible to suppress or prevent the occurrence of streaks and gloss unevenness in the main scanning direction Ds, and therefore it is possible to improve the image quality defect.

[0055] In addition, in the present embodiment, since bidirectional printing is performed by the discharge head 10A, high-duty printing can be realized.

[0056] In addition, in the present embodiment, a part 53a and the remaining portion 53b of the divided dot connection portion 53 are adjacent to each other in the sub-scanning direction Df. Thereby, the divided dot connection portion 53 extending in the sub-scanning direction Df can be formed.

[0057] Also, in the present embodiment, each of the plurality of divided dot connection portions 53 is positioned so as to be shifted from each other in the main scanning direction Ds. That is, each of the divided dot connection portions 53 is positioned without overlapping in the main scanning direction Ds. Further, as shown in FIG. 8, each of the plurality of divided dots 52 is positioned so as to be shifted from each other in the main scanning direction Ds. Thereby, it is possible to avoid the occurrence of continuity in the main scanning direction Ds due to the overlap of the divided dot connection portions 53 and the continuity in the main scanning direction Ds due to the overlap of the divided dots 52.

[0058] Furthermore, in the present embodiment, the dot connection portion 51, the divided dots 52, and the divided dot connection portion 53 can be formed when the discharge amount of the ink droplets is equal to or greater than a threshold value. Thereby, when the discharge amount of the ink droplets is less than the threshold value, that is, when streaks and gloss unevenness in the main scanning direction Ds hardly occur, it is possible to avoid unnecessarily forming the dot connection portion 51, the divided dots 52, and the divided dot connection portion 53.

[0059] (Modification example) The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention. For example, as follows.

[0060] The arrangement of the ink droplets in the first to third scans described with reference to FIG. 8 may be changed in the order of the arrangement of the ink droplets in the second scan, the arrangement of the ink droplets in the third scan, and the arrangement of the ink droplets in the first scan. Similarly, the order of the aspect of FIG. 6 may also be changed.

[0061] As shown in FIG. 11, the ink droplet arrangement in the first scan is the same as the ink droplet arrangement in the second scan of FIG. 8. While moving the carriage 3 to the right in the main scanning direction Ds, the CPU 20 of the control unit 19 causes the ejection head 10A to eject ink droplets 50, and does not cause the light source unit 40A to irradiate ultraviolet rays. Thereby, the ink droplets 50 in the fourth column of the first row can be arranged in association with the divided dots 52, and the ink droplets 50 in the third column of the third row and the ink droplets 50 in the second column of the fifth row can be arranged in association with a part 53a of the divided dot connecting portion 53.

[0062] The ink droplet arrangement in the second scan is the same as the ink droplet arrangement in the third scan of FIG. 8. The CPU 20 of the control unit 19 causes the platen 6 to convey the printing medium W in the sub-scanning direction Df, and then while moving the carriage 3 to the left in the main scanning direction Ds, causes the ejection head 10A to eject ink droplets 50 and causes the light source unit 40A to irradiate ultraviolet rays. Thereby, the divided dots 52 are formed by curing the ink droplets 50 corresponding to the divided dots 52, and the divided dot connecting portion 53 extending in the sub-scanning direction Df can be formed by curing the ink droplets 50 corresponding to the remaining portion 53b of the divided dot connecting portion 53 and the ink droplets 50 corresponding to the above-mentioned part 53a. Regarding the point that the ink droplets 50 corresponding to the remaining portion 53b of the divided dot connecting portion 53 are attracted and connected to the ink droplets 50 corresponding to the part 53a in the sub-scanning direction Df, it is as described above.

[0063] The ink droplet arrangement in the third scan is the same as the ink droplet arrangement in the first scan of FIG. 8. The CPU 20 of the control unit 19 causes the ejection head 10A to eject ink droplets 50 and causes the light source unit 40A to irradiate ultraviolet rays while moving the carriage 3 to the right in the main scanning direction Ds without causing the platen 6 to convey the printing medium W. Thereby, the cured dot connecting portion 51 is formed. Also by the above order, it is possible to prevent a part of the plurality of ink droplets 50 in the second scan from being connected in the main scanning direction Ds.

[0064] Alternatively, the ink droplet arrangements for the first to third scans in FIG. 8 may be changed in the order of the ink droplet arrangement for the third scan, the ink droplet arrangement for the second scan, and the ink droplet arrangement for the first scan. Similarly, the order of the aspect in FIG. 6 may also be changed.

[0065] As shown in FIG. 12, the ink droplet arrangement for the first scan is the same as the ink droplet arrangement for the third scan in FIG. 8. While moving the carriage 3 to the right in the main scanning direction Ds, the CPU 20 of the control unit 19 causes the ejection head 10A to eject ink droplets 50, and does not cause the light source unit 40A to irradiate ultraviolet rays. Thereby, each ink droplet 50 in the second row and third column and each ink droplet 50 in the fourth row and third column can be arranged in association with a part 53c of the divided dot connection part 53.

[0066] The ink droplet arrangement for the second scan is the same as the ink droplet arrangement for the second scan in FIG. 8. The CPU 20 of the control unit 19 causes the platen 6 to convey the printing medium W in the sub-scanning direction Df, and then moves the carriage 3 to the left in the main scanning direction Ds while causing the ejection head 10A to eject ink droplets 50. In this case, the uncured ink droplets 50 (the ink droplets 50 corresponding to a part 53c of the divided dot connection part 53) formed in the first scan are partially attracted to the ink droplets 50 corresponding to the remaining part 53d of the divided dot connection part 53. Thereby, it is possible to suppress each ink droplet 50 in the fourth row and first to fourth columns arranged in the first scan from being connected to each other in the main scanning direction Ds. In this state, the CPU 20 of the control unit 19 causes the light source unit 40A to irradiate ultraviolet rays. As a result, the divided dots 52 are formed, and the divided dot connection part 53 extending in the sub-scanning direction Df is formed by the connection of the part 53c and the remaining part 53d.

[0067] The ink droplet arrangement for the third scan is the same as the ink droplet arrangement for the first scan in FIG. 8. Without conveying the printing medium W by the platen 6, the CPU 20 of the control unit 19 moves the carriage 3 to the right in the main scanning direction Ds, while causing the ejection head 10A to eject ink droplets 50 and the light source unit 40A to irradiate ultraviolet rays. Thereby, the cured dot connection portions 51 are formed. Also by the above sequence, it is possible to suppress the connection of some of the plurality of ink droplets 50 in the first scan in the main scanning direction Ds.

[0068] In the above embodiment, the light source unit 40 that irradiates the ink droplets 50 with ultraviolet rays is adopted as the energy applying means for applying energy to the ejected ink droplets 50, but it is not limited thereto. For example, other energy applying means that apply other energy such as heat or microwaves to the ink droplets 50 to cure the ink droplets 50 may be used.

[0069] Furthermore, in the above embodiment, two ejection heads 10 (10A, 10B) and two light source units 40 (40A, 40B) are mounted on the carriage 3, but it is not limited thereto, and only the ejection head 10A and the light source unit 40A may be mounted.

Explanation of Reference Numerals

[0070] 1 Printing apparatus 3 Carriage 6 Platen 10, 10A, 10B Ejection head 20 CPU 40, 40A, 40B Light source unit 50 Ink droplet 51 Dot connection portion 52 Divided dot 53 Divided dot connection portion 53a, 53c Part of the divided dot connection portion 53b, 53d Remaining part of the divided dot connection portion Df Sub-scanning direction Ds Main scanning direction OP One direction in the main scanning direction Other direction than the RP main scanning direction W Printed medium

Claims

1. A discharge head that discharges ultraviolet curable ink droplets onto a printing medium, Energy applying means for applying energy to cure the ink droplets, A carriage that mounts the discharge head and the energy applying means and moves in the main scanning direction, A control unit, and The control unit While moving the carriage in the main scanning direction, discharges the ink droplets from the discharge head and applies energy to the ink droplets landed on the printing medium by the energy applying means, so that the landed ink droplets are connected in plurality to form a dot connection portion that extends in the main scanning direction and is cured, While moving the carriage in the main scanning direction, controls the discharge head and the energy applying means to form a divided dot formed by curing a single ink droplet at a position adjacent to or overlapping the dot connection portion in the main scanning direction, or a divided dot connection portion formed by connecting a plurality of the ink droplets adjacent to or overlapping the dot connection portion in the main scanning direction and extending in a sub-scanning direction intersecting the main scanning direction and being cured, a printing apparatus.

2. Further comprising a conveyance mechanism for conveying the printing medium, The control unit When forming the dot connection portion, While causing a first movement of moving the carriage in the main scanning direction, discharges the ink droplets from the discharge head and applies energy by the energy applying means to cure the ink droplets corresponding to the dot connection portion to form the dot connection portion, When forming the divided dot or the divided dot connection portion, After the first movement, without conveying the printing medium by the conveyance mechanism, while causing a second movement of moving the carriage in the main scanning direction, discharges the ink droplets from the discharge head and does not apply energy by the energy applying means, so as to dispose uncured ink droplets corresponding to the divided dot and uncured ink droplets corresponding to a part of the divided dot connection portion on the printing medium, After the second movement, the transport mechanism transports the printing medium in the sub-scanning direction, and then while causing the carriage to perform a third movement in the main scanning direction, ink droplets are ejected from the ejection head and energy is applied by the energy applying means, thereby curing the ink droplets corresponding to the divided dots to form the divided dots, and disposing the ink droplets corresponding to the remaining portion of the divided dot connection portion on the printing medium and curing the ink droplets corresponding to the part and the ink droplets corresponding to the remaining portion to form the divided dot connection portion. The printing apparatus according to claim 1.

3. The control unit causes the ejection head to eject the ink droplets while moving the carriage in one direction in the main scanning direction and in the other direction opposite to the one direction to perform bidirectional printing. In the first movement and the third movement, the carriage moves in the one direction, and in the second movement, the carriage moves in the other direction. The printing apparatus according to claim 2.

4. The printing apparatus further includes a transport mechanism for transporting the printing medium. The control unit When forming the divided dots or the divided dot connection portion, while causing the carriage to perform a first movement in the main scanning direction, the ejection head ejects the ink droplets, and by not applying energy from the energy applying means, the uncured ink droplets corresponding to the divided dots and the uncured ink droplets corresponding to a part of the divided dot connection portion are disposed on the printing medium. After the first movement, the transport mechanism transports the printing medium in the sub-scanning direction, and then while causing the carriage to perform a second movement in the main scanning direction, the ejection head ejects the ink droplets and energy is applied by the energy applying means, thereby curing the ink droplets corresponding to the divided dots to form the divided dots, and disposing the ink droplets corresponding to the remaining portion of the divided dot connection portion on the printing medium and curing the ink droplets corresponding to the part and the ink droplets corresponding to the remaining portion to form the divided dot connection portion. After the second movement, while causing the carriage to perform a third movement in the main scanning direction without causing the transport mechanism to transport the print medium, by causing ejection of the ink droplets from the ejection head and application of energy by the energy application means, the ink droplets corresponding to the dot connection portion are cured to form the dot connection portion, the printing apparatus according to claim 1.

5. further comprising a transport mechanism for transporting the print medium, the control unit, while causing the carriage to perform a first movement in the main scanning direction, causing ejection of the ink droplets from the ejection head and not causing application of energy from the energy application means, thereby disposing ink droplets corresponding to a part of the divided dot connection portion on the print medium, after the first movement, causing the transport mechanism to transport the print medium in the sub-scanning direction, and then while causing the carriage to perform a second movement in the main scanning direction, causing ejection of the ink droplets from the ejection head and application of energy by the energy application means, thereby curing the ink droplets corresponding to the divided dots to form the divided dots, and disposing the ink droplets corresponding to the remaining part of the divided dot connection portion on the print medium and curing the ink droplets corresponding to the part and the ink droplets corresponding to the remaining part to form the divided dot connection portion, after the second movement, while causing the carriage to perform a third movement in the main scanning direction without causing the transport mechanism to transport the print medium, by causing ejection of the ink from the ejection head and application of energy by the energy application means, the ink droplets corresponding to the dot connection portion are cured to form the dot connection portion, the printing apparatus according to claim 1.

6. the part of the divided dot connection portion and the remaining part of the divided dot connection portion are adjacent to each other in the sub-scanning direction, the printing apparatus according to any one of claims 2 to 5.

7. a plurality of the divided dots and the divided dot connection portions are respectively formed, each of the plurality of divided dots is positioned shifted from each other in the main scanning direction, and each of the plurality of divided dot connection portions is positioned shifted from each other in the main scanning direction, the printing apparatus according to any one of claims 2 to 6.

8. The printing apparatus according to any one of claims 1 to 7, wherein the control unit forms the dot connection portion and forms the divided dots or the divided dot connection portion when the discharge amount of the ink droplets discharged onto the printing medium is equal to or greater than a threshold value.

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