JP2017104996A - Liquid discharge unit, liquid discharge device, and liquid discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge unit which is capable of reducing the size of a carriage in a sub-scanning direction as compared with a conventional size in the liquid discharge unit which has the carriage provided with a discharge head for color ink and a discharge head for background ink.SOLUTION: A liquid discharge unit includes: a first head which is movable in a first direction and has a first nozzle array for discharging first liquid; a second head which is arranged at a position deviated from the first head in a second direction, has a second nozzle array for discharging second liquid different from the first liquid, has a first overlapped region where the first nozzle array is overlapped with the second nozzle array in the first direction, and is movable together with the first head; and a control section which controls the discharge of the first liquid and the second liquid so that the first liquid and the second liquid are adhered to different positions on an article to be discharged when the first nozzle array in the first overlapped region and the second nozzle array in the first overlapped region discharge liquid.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a liquid discharge unit, a liquid discharge apparatus, and a liquid discharge method.

  In recent years, ink jet printers are used not only for penetrating media such as paper but also for printing on non-penetrating media such as films. Among non-penetrating media, background inks such as white and silver are used for permeable media.

  A carriage of a conventional ink jet printer includes a color ink discharge head having a nozzle row for discharging color ink, and a background ink discharge head having a nozzle row for discharging background ink. A plurality of nozzles of the color ink ejection head and the background ink ejection head are arranged in the sub-scanning direction, which is the media transport direction. The background ink ejection head is disposed at a position that does not overlap the color ink ejection head in the main scanning direction orthogonal to the sub-scanning direction.

  In actual image formation, heads at different positions in the main scanning direction are used. Therefore, there is a problem that the carriage is increased in size in the sub-scanning direction by the amount of the background ink ejection head that is shifted in the sub-scanning direction.

  The present invention has been made in view of the above, and in a liquid discharge unit having a carriage provided with a color ink discharge head and a background ink discharge head, the size of the carriage in the sub-scanning direction is compared with the conventional size. Another object is to provide a liquid discharge unit, a liquid discharge apparatus, and a liquid discharge method that can be reduced in size.

  In order to solve the above-described problems and achieve the object, the present invention provides a first head that has a first nozzle row that is movable in a first direction and that discharges a first liquid, A second nozzle array that is disposed at a position shifted in a second direction orthogonal to the first direction with respect to one head and that discharges a second liquid different from the first liquid; and A second head having a first overlapping region in which the first nozzle row and the second nozzle row overlap in the first direction and movable with the first head; When the first nozzle row in one overlapping region and the second nozzle row in the first overlapping region discharge liquid, the first liquid and the second liquid are on the discharge target. A control unit that controls ejection of the first liquid and the second liquid so as to adhere to different positions; A liquid ejecting unit, characterized in that it comprises.

  According to the present invention, since the second head is disposed so as to partially overlap the first head in the first direction, the first head and the second head are disposed in the region where the first head and the second head are disposed. There is an effect that the size in the second direction can be reduced as compared with the conventional size.

FIG. 1 is a side view showing an example of the configuration of the liquid ejection apparatus according to the first embodiment. FIG. 2 is a top view schematically showing an example of the configuration of the carriage according to the first embodiment. FIG. 3 is a plan view illustrating an example of an arrangement of nozzles in the recording head according to the first embodiment. FIG. 4 is a block diagram illustrating an example of a hardware configuration mainly of a control unit of the liquid ejection apparatus according to the first embodiment. FIG. 5 is a diagram illustrating an example of the state of the head used in the printing mode of the liquid ejection unit according to the first embodiment. FIG. 6 is a cross-sectional view schematically showing the difference in the laminated state of the ink layer depending on the printing mode. FIG. 7 is a diagram illustrating an example of an ejection block for each scan of the recording head in front-surface printing according to the first embodiment. FIG. 8 is a diagram illustrating an example of the dot arrangement order in each scan at the time of surface printing according to the first embodiment. FIG. 9 is a diagram for explaining a printing state in front printing when the arrangement of the recording heads is not a natural number multiple of the media conveyance amount. FIG. 10 is a diagram schematically illustrating an example of the structure of the carriage according to the second embodiment. FIG. 11 is a diagram schematically showing an example of the structure of the carriage according to the third embodiment. FIG. 12 is a diagram schematically illustrating another example of the carriage structure according to the third embodiment.

  Hereinafter, embodiments of a liquid discharge unit, a liquid discharge apparatus, and a liquid discharge method will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

(First embodiment)
FIG. 1 is a side view showing an example of the configuration of the liquid ejection apparatus according to the first embodiment, and FIG. 2 is a top view schematically showing an example of the configuration of the carriage according to the first embodiment. . FIG. 3 is a plan view showing an example of nozzle arrangement in the recording head according to the first embodiment. In this example, a serial ink jet recording apparatus is taken as an example of the liquid ejection apparatus. The ink jet recording apparatus 10 includes a platen 11, a roll media storage unit 12, a take-up roll 13, a transport unit 14, and an image forming unit 20 inside the main body.

  The platen 11 supports the medium 100 from the non-recording surface side when the liquid is discharged. The roll media storage unit 12 is a paper feeding unit, and a wound medium (a discharge target) 100 is set therein. In the roll media storage unit 12, media 100 having different sizes in the width direction can be set. The take-up roll 13 is a paper discharge unit, and takes up and collects the image-formed medium 100. The platen 11, the roll media storage unit 12, and the winding roll 13 are arranged so that the medium 100 reaches the winding roll 13 from the roll media storage unit 12 through the platen 11.

  The transport unit 14 is a member having a function of transporting the medium 100 in the transport direction. In this example, the conveyance unit 14 is configured by a feed roller 141 disposed below the platen 11 and a pressing roller 142 disposed above the platen 11. The medium 100 is sandwiched between the feed roller 141 and the presser roller 142. By rotating the feed roller 141 forward (in the direction of the arrow in FIG. 1), the medium 100 carried on the platen 11 can be conveyed forward on the platen 11.

  The image forming unit 20 is disposed in a region facing the platen 11. The image forming unit 20 includes a carriage 21. A recording head 22 is provided on the surface of the carriage 21 on the platen 11 side. The recording head 22 is a liquid ejection head having a nozzle row in which nozzle holes, which are a plurality of ejection openings for ejecting liquid, are arranged. In the first embodiment, the recording head 22 includes a color ink ejection head 221 (first head) having a first nozzle array for ejecting color ink (first liquid), and a background ink (second head). A background ink discharge head 222 (second head) having a second nozzle row for discharging the liquid).

  As shown in FIG. 2, in the inkjet recording apparatus 10 according to the first embodiment, the background ink ejection head 222 with respect to the arrangement position of the color ink ejection head 221 in the main scanning direction which is the first direction. Are arranged so that a part of them overlap. In other words, the background ink ejection head 222 is shifted from the arrangement position of the color ink ejection head 221 in the sub-scanning direction, which is the second direction, on the upstream side in the conveyance direction of the medium 100. Here, the main scanning direction is a direction in which the carriage 21 is moved, and is a direction perpendicular to the conveyance direction of the medium 100. The sub-scanning direction is a direction perpendicular to the main scanning direction and parallel to the conveyance direction of the medium 100. Further, with the platen 11 as a reference, the side on which the roll media storage unit 12 is disposed is the upstream side, and the side on which the winding roll 13 is disposed is the downstream side. That is, the arrangement of the ejection heads shown in FIG. 2 is an arrangement for surface printing. As will be described later, when the background ink discharge head 222 is shifted from the arrangement position of the color ink discharge head 221 in the sub-scanning direction to the downstream side in the conveyance direction of the medium 100, Become.

  The carriage 21 is slidably held by a guide shaft 23 extending in the scanning direction. The carriage 21 is moved (main scanning) along the guide shaft 23 by a main scanning motor. A sensor for optically detecting the end of the medium 100 is attached to the carriage 21. By detecting the end of the medium 100 as the carriage 21 moves, the position of the end of the medium 100 in the main scanning direction and the width of the medium 100 are calculated. In the recording area where printing is performed in the main scanning area of the carriage 21, the medium 100 is intermittently conveyed in the sub-scanning direction.

  The carriage 21 is equipped with a sub-tank, and is configured to replenish and supply ink as liquid to each ejection head from the main tank to the sub-tank. Instead of this configuration, an ink cartridge that supplies liquid to each ejection head on the carriage 21 may be detachably mounted.

  In the example of FIG. 2, four liquid discharge heads that discharge ink droplets of yellow (Y), magenta (M), cyan (C), and black (K) are provided as the color ink discharge heads 221. . The background ink ejection head 222 is provided with one liquid ejection head that ejects ink droplets of a background color such as white or silver.

  As shown in FIG. 3, the color ink discharge head 221 and the background ink discharge head 222 include a plurality of nozzles 221a and 222a for discharging ink. In each ejection head, the nozzles 221a and 222a are arranged along the sub-scanning direction. Further, in the overlapping region Ro where the color ink ejection head 221 and the background ink ejection head 222 overlap, the color ink ejection so that the positions of the nozzles 221a and 222a of the respective ejection heads in the sub-scanning direction coincide with each other. The head 221 and the background ink discharge head 222 are disposed. That is, in the overlapping region Ro, the nozzles 221a and 222a of the color ink ejection head 221 and the background ink ejection head 222 are arranged to overlap in the main scanning direction.

  The ejection mode of ink droplets ejected from the color ink ejection head 221 and the background ink ejection head 222 is controlled by drive pulses applied to the drive elements provided corresponding to the nozzles 221a and 222a of the ejection heads. Is done. For example, a piezoelectric element such as PZT is used as the drive element.

  The ink jet recording apparatus 10 includes a media heating unit 30 and a warm air fan 34. The media heating unit 30 includes a print heater 31, a preheater 32, and a post heater 33. The print heater 31 is provided in an image forming area where the image forming unit 20 is provided, and heats the medium 100 on which ink droplets ejected from the nozzles of the recording head 22 are landed. The preheater 32 is provided upstream of the print heater 31 in the transport direction of the medium 100 and preheats the medium 100. The post-heater 33 is provided on the downstream side of the print heater 31 in the conveyance direction of the medium 100 and continuously heats the medium 100 to promote drying of the landed ink droplets. As the print heater 31, the preheater 32, and the post heater 33, an electric heater using a ceramic or nichrome wire is used.

  The hot air fan 34 is provided on the downstream side of the post heater 33 in the conveyance direction of the medium 100, and blows hot air on the recording surface on which the ink of the medium 100 has landed. Warm air directly hits the ink on the recording surface by the hot air fan 34. As a result, the humidity of the atmosphere around the recording surface is lowered, and the ink is completely dried before the medium 100 is taken up by the take-up roll 13.

  As described above, the ink jet recording apparatus 10 is equipped with a drying mechanism, and can also print on non-penetrating media in which ink such as vinyl chloride, PET (PolyEthylene Terephthalate), and acrylic does not soak. For non-penetrating media, solvent-based inks or aqueous resin inks with many resin components are good.

  The inkjet recording apparatus 10 that forms an image by ejecting ink while the carriage 21 reciprocates in the width direction of the medium 100 can perform one-way printing and two-way printing. One-way printing is a method of forming an image by ejecting ink only when the carriage 21 is in the forward path. Bidirectional printing is a method of forming an image by ejecting ink in both the forward and backward operations of the carriage 21. Since the bidirectional printing is faster than the unidirectional printing, it is desirable to perform the printing by the bidirectional printing.

  FIG. 4 is a block diagram illustrating an example of a hardware configuration mainly of a control unit of the liquid ejection apparatus according to the first embodiment. The control unit 50 includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an ASIC (Application Specific Integrated Circuits) 54, and an I / O 55.

  The CPU 51 controls the entire inkjet recording apparatus 10. The ROM 52 is a rewritable nonvolatile memory for holding data even when the power of the inkjet recording apparatus 10 is shut off, and stores a program executed by the CPU 51 and other fixed data. The RAM 53 temporarily stores image data or print data. The ASIC 54 processes various signal processing for image data or print data, image processing for performing rearrangement, or other input / output signals for controlling the entire inkjet recording apparatus 10. The I / O 55 inputs detection pulses from the encoder 71 and the wheel encoder 72, and detection signals from the temperature sensor 73, the ink temperature sensor 74, and other various sensors. The temperature sensor 73 measures the temperatures of the print heater 31, preheater 32, and postheater 33. The ink temperature sensor 74 is installed in the vicinity of the recording head 22 and detects the temperature of the ink ejected by the recording head 22.

  The control unit 50 includes a host I / F 56, a head drive control unit 61, a main scanning motor drive unit 62, a carry motor control unit 63, a heater control unit 64, and a hot air fan control unit 65. The host I / F 56 exchanges data and signals with the host 150 side. Examples of the host 150 include an information processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera.

  The head drive control unit 61 includes data transfer means for driving and controlling the recording head 22. The recording head 22 and the head drive control unit 61 constitute a liquid discharge unit. The head drive control unit 61 transfers image data (processed data and ejection data) to the drive circuit inside the recording head 22 as serial data. At this time, the head drive controller 61 generates a transfer clock and a latch signal necessary for transferring the image data and confirming the transfer, and a drive waveform used when ejecting ink (liquid) from the recording head 22. Input to the drive circuit inside the recording head 22. Here, since the viscosity of the ink varies depending on the temperature, the head drive control unit 61 changes the drive waveform generated according to the ink temperature detected by the ink temperature sensor 74. By generating a drive waveform corresponding to the ink viscosity by the head drive control unit 61, variation in ejection associated with a change in ink viscosity is suppressed. The drive circuit selectively inputs a drive waveform corresponding to the input image data to the piezoelectric element (actuator) of each nozzle of the recording head 22.

  The main scanning motor driving unit 62 controls the movement of the carriage 21 in the main scanning direction by controlling the driving of the main scanning motor under the control of the CPU 51. The main scanning motor 75 rotates and moves the carriage 21 in the main scanning direction via the timing belt. The encoder 71 detects the rotation of the main scanning motor 75 and outputs the detection result to the CPU 51 via the I / O 55.

  The transport motor control unit 63 drives the media transport motor 76. The media transport motor 76 is a motor that rotates, for example, the feed roller 141 of FIG. The conveyance motor control unit 63 calculates a control value based on the target value given from the CPU 51 side and the actual conveyance speed value obtained by sampling the detection pulse from the wheel encoder 72. Then, the transport motor control unit 63 drives the media transport motor 76 through an internal motor drive circuit based on the control value.

  The heater control unit 64 controls the print heater 31, preheater 32, and postheater 33. The heater control unit 64 monitors the temperatures of the print heater 31, the preheater 32, and the postheater 33 using each temperature sensor 73 provided in the vicinity thereof. Further, the heater control unit 64 controls the print heater 31, the preheater 32, and the postheater 33 based on the temperature data acquired from each temperature sensor 73. The heaters provided on the head tank and the ink path are similarly controlled. The hot air fan control unit 65 controls the hot air fan 34 so that the air is blown at a predetermined temperature and at a predetermined air volume.

  The control unit 50 is connected to an operation panel 160 for inputting and displaying information necessary for the ink jet recording apparatus 10. The operation panel 160 is configured by a touch panel, for example.

  An outline of the operation of the liquid ejection apparatus having such a configuration will be described. The control unit 50 receives print data and the like from the host 150 side via the host I / F 56 via a cable or a network. Then, the CPU 51 reads and analyzes the print data in the reception buffer included in the host I / F 56. Subsequently, the ASIC 54 performs necessary image processing, data rearrangement processing, and the like, and transfers the processed data (image data) to the recording head 22 via the head drive control unit 61. The generation of dot pattern data for outputting an image may be performed by storing font data in the ROM 52, for example, or the image data is developed into bitmap data by a printer driver on the host side, and the inkjet recording apparatus You may make it transfer to 10 side.

  Next, a liquid ejection method in the inkjet recording apparatus 10 according to the first embodiment will be described. In the following, the print mode will be described first, and then the print sequence will be described.

<Print mode>
The print modes include surface printing, back printing, and whiteless printing. FIG. 5 is a diagram illustrating an example of the state of the head used in the printing mode of the liquid ejection unit according to the first embodiment, and FIG. 6 schematically illustrates the difference in the ink layer lamination state depending on the printing mode. It is sectional drawing shown. In each figure, (a) shows the case of the front printing mode, (b) shows the case of the back printing mode, and (c) shows the case of the whiteless printing mode. In FIG. 5, the ejection head used for printing is hatched.

  In front printing, as shown in FIG. 5A, the color ink ejection head 221 and the background ink ejection head 222 disposed on the upstream side in the transport direction of the medium 100 with respect to the color ink ejection head 221. Are used. First, background ink is dropped onto the medium 100 from the background ink ejection head 222 on the upstream side in the transport direction of the medium 100. The background ink is dried to form the background ink layer 101. Thereafter, color ink is dropped onto the background ink layer 101 from the color ink ejection head 221. The color ink is dried to form the color ink layer 102. As a result, the cross section of the image formed by surface printing is as shown in FIG.

  In reverse printing, as shown in FIG. 5B, the color ink discharge head 221 and the background ink discharge head 222 arranged on the downstream side in the transport direction of the medium 100 with respect to the color ink discharge head 221. Are used. First, color ink is dropped onto the medium 100 from the color ink ejection head 221 on the upstream side in the transport direction of the medium 100. The color ink is dried to form the color ink layer 102. Thereafter, the background ink is dropped onto the color ink layer 102 from the background ink ejection head 222. The background ink is dried to form the background ink layer 101. As a result, the background of the cross section of the image formed by reverse printing is formed so as to cover the color image on the medium 100 as shown in FIG.

  In whiteless printing, as shown in FIG. 5C, only the color ink ejection head 221 is used, and the background ink ejection head 222 is not used. In other words, whiteless printing can be performed by either the recording head 22 for surface printing or the recording head 22 for back printing. First, color ink is dropped onto the medium 100 from the color ink ejection head 221. Then, the color ink is dried to form the color ink layer 102. As a result, a cross section of an image formed by whiteless printing is as shown in FIG. Thus, since the background ink layer 101 is not provided, it is mainly used for non-transparent media.

<Print sequence>
FIG. 7 is a diagram illustrating an example of an ejection block for each scan of the recording head in front-surface printing according to the first embodiment. The area from the upstream end of the background ink discharge head 222 to the downstream end of the color ink discharge head 221 is divided into seven equal parts along the transport direction (sub-scanning direction) of the medium 100 to form seven regions. It is separated. Then, a first block, a second block,..., A seventh block are formed from the upstream area in the conveyance direction of the medium 100 toward the downstream area.

  FIG. 8 is a diagram illustrating an example of the dot arrangement order in each scan at the time of surface printing according to the first embodiment. In this figure, a circle indicates a background ink dot, and a square indicates a color ink dot. In addition, the ◯ mark or □ mark that is hatched indicates dots formed by the corresponding scan. Furthermore, the numbers described in the circles or squares indicate the number of scans (which block of the recording head 22 was used).

  The following description is an example in which the image is completed by four scans (dot formation) for both the color ink and the background ink. The background ink dots formed in the first scan are dried in the fourth scan. Assuming that That is, it is assumed that the dots are dried after the time of two scans after the dot formation.

  First, as shown in FIG. 8A, in the first scan, the first dots 301 of the background ink are formed on the medium 100 using the nozzles belonging to the first block of the background ink ejection head 222. To do. Since the carriage 21 is scanned in the main scanning direction, for example, the first dots 301 of the background ink are dropped from the left side to the right side in the drawing. A distance between adjacent first dots 301 in the main scanning direction is defined as a first pitch.

  Further, when the carriage 21 exists at a certain position in the main scanning direction, a plurality of first dots 301 of background ink are dropped from the nozzles existing in the first block in the sub scanning direction. In this example, three first dots 301 are dropped. A distance between adjacent first dots 301 in the sub-scanning direction is defined as a second pitch. As a result, nine first dots 301 are formed on the medium 100 in the first scan.

  As shown in FIG. 8B, in the second scan, the second dots 302 of the background ink are formed on the medium 100 using the nozzles belonging to the second block of the background ink ejection head 222. The second dots 302 are arranged at positions shifted from the first dots 301 by half of the first pitch in the main scanning direction and further shifted by half of the second pitch on the downstream side in the transport direction of the medium 100. Even when the second dots are formed, nine second dots 302 are formed as the carriage 21 moves in the main scanning direction. In the second scan, the carriage 21 is scanned from the right side to the left side in the drawing. Hereinafter, in the odd-numbered scan, the carriage 21 is scanned from the left side to the right side in the drawing, and in the even-numbered scan, the carriage 21 is scanned from the right side to the left side in the drawing.

  As shown in FIG. 8C, in the third scan, the third dots 303 of the background ink are formed on the medium 100 using the nozzles belonging to the third block of the background ink ejection head 222. The third dots 303 are arranged at positions shifted from the second dots 302 by half the first pitch in the main scanning direction. Even when the third dots 303 are formed, nine dots are formed as the carriage 21 moves in the main scanning direction.

  As shown in FIG. 8D, in the fourth scan, the nozzles belonging to the fourth block of the background ink ejection head 222 and the color ink ejection head 221 are used. Background ink 4a dots 304a are dropped onto the medium 100 from nozzles belonging to the fourth block of the background ink ejection head 222. Also, the 4b dots 304b of color ink are dropped onto the first dots 301 of the background ink from the nozzles belonging to the fourth block of the color ink ejection head 221. Since the ink is presumed to be dried at the fourth scan, the 4b dot 304b is dropped onto the dried first dot 301. As described above, in the fourth scan, the head drive control unit 61 controls the background ink and the color ink to be dropped simultaneously at different positions. When the 4a dot 304a and the 4b dot 304b are formed, 18 dots are formed as the carriage 21 moves in the main scanning direction.

  As shown in FIG. 8E, in the fifth scan, the fifth dot 305 of the color ink is changed to the second dot that has been dried using the nozzle belonging to the fifth block of the color ink ejection head 221. 302 is formed. When the fifth dot 305 is formed, nine dots are formed as the carriage 21 moves in the main scanning direction.

  As shown in FIG. 8F, in the sixth scan, the sixth dot 306 of the color ink is changed to the third dot which is dried using the nozzle belonging to the sixth block of the color ink ejection head 221. 303 is formed. Even when the sixth dot 306 is formed, nine dots are formed as the carriage 21 moves in the main scanning direction.

  Then, as shown in FIG. 8G, in the seventh scan, the seventh dot 307 of the color ink is dried by using the nozzle belonging to the seventh block of the color ink discharge head 221. Formed on the dots 304a. Even when the seventh dot 307 is formed, nine dots are formed as the carriage 21 moves in the main scanning direction.

  Thereafter, the medium 100 is transported by the third pitch of the second pitch downstream in the transport direction, and the above-described processes of FIGS. 8A to 8G are repeatedly performed.

  In the above description, the case of surface printing is described. However, in the case of back printing, the same is true except that the order of forming the color ink dots and the background ink dots is reversed. In other words, in the case of reverse printing, in FIG. 8, the ◯ marks indicate the color ink dots, and the □ marks indicate the background ink dots.

Here, the relationship between the length of the overlapping area between the color ink discharge head 221 and the background ink discharge head 222 (hereinafter referred to as the overlap nozzle length) and the print length per scan will be described. When the overlapping nozzle length is L as shown in FIG. 3 and the print length (medium transport amount) per scan is a as shown in FIG. 7, the relationship shown in the following equation (1) is established.
L = n · a (where n is a natural number) (1)

  In the example of FIG. 8, the case where n = 1 is shown. n is the same as the number of times that the printing scans of the background ink ejection head 222 and the color ink ejection head 221 are made common. That is, by increasing n, the nozzles can be used efficiently, so that the number of scans can be reduced and the printing speed can be increased.

  FIGS. 9A and 9B are diagrams for explaining a printing state in surface printing when the arrangement of the recording head is not a natural number multiple of the medium conveyance amount. FIG. 9A is a case where n = 0, and FIG. This is the case of <1, and (c) is the case of n> 1, which is not a natural number multiple. In this case, it is also assumed that the ink is dried at the fourth scan, that is, the dots are dried after the time of two scans after the dot formation.

  FIG. 9A shows a case where n = 0, that is, a conventional example in which the overlapping nozzle length L is zero. In this case, as is apparent from the figure, 8 scans are required.

  As shown in FIG. 9B, in the case of n <1, that is, when the overlapping nozzle length L is less than the media conveyance amount a, the background ink ejection head 222 belonging to the fourth block and the color in the fourth scan A nozzle with the ink ejection head 221 is used. However, the ink ejected from the nozzles of the color ink ejection head 221 is ejected only in the region b shorter than the media transport amount a. For this reason, the color ink has to be dropped again on the area that was obtained in the fourth scan at the eighth scan. Therefore, as in the conventional example, 8 scans are required, and the printing speed is the same.

  As shown in FIG. 9C, when n> 1, that is, when the overlapping nozzle length L is longer than the medium transport amount a, the upstream end of the color ink ejection head 221 in the transport direction of the medium 100 is the first end. 3 blocks. That is, the color ink can be ejected from the color ink ejection head 221 in the third scan. However, since it is assumed that the ink is dried in the fourth scan, the color ink cannot be ejected from the color ink ejection head 221 in the third scan. Therefore, the usable nozzle length of the color ink ejection head 221 is shortened. That is, in the figure, the nozzle length that can be used by the nozzle belonging to the region c is set. As a result, the printing speed becomes slower than that in the first embodiment. In the seventh scan, ejection is performed only in a region d shorter than the media transport amount a. For this reason, it is necessary to drop the color ink again on the area that was obtained at the seventh scan in the eighth scan.

  If the background ink is dried at the third scan, the printing speed is faster than the conventional example. However, as in the case of n <1, it is necessary to print in the seventh scan for the area e that was not printed in the third scan. Therefore, the effect of overlapping the background ink ejection head 222 and the color ink ejection head 221 cannot be sufficiently obtained. Specifically, the number of scans is increased by one as compared with the case where n = 2. For the above reasons, it is desirable to set the overlapping nozzle length L so as to satisfy the expression (1).

  In the first embodiment, the background ink ejection head 222 is disposed so as to partially overlap the color ink ejection head 221 in the main scanning direction. As a result, the size of the carriage 21 including the color ink discharge head 221 and the background ink discharge head 222 in the sub-scanning direction can be reduced as compared with the related art.

  In the overlapping region where the color ink ejection head 221 and the background ink ejection head 222 overlap in the main scanning direction, the color ink is ejected from the color ink ejection head 221 and the background ink is ejected from the background ink ejection head 222. The ink was discharged simultaneously at a position different from the discharge position of the color ink. As a result, the number of scans during printing can be reduced as compared with the conventional case, and the printing speed can be increased.

(Second Embodiment)
In the first embodiment, the background ink ejection head is shifted from the color ink ejection head in the sub-scanning direction so as to partially overlap in the main scanning direction. For this reason, the liquid discharge unit can cope with only one of front surface printing and back surface printing. In the second embodiment, a liquid discharge unit that can cope with both front printing and back printing will be described.

  FIG. 10 is a diagram schematically illustrating an example of the structure of the carriage according to the second embodiment. In this figure, a background ink ejection head 222, which is a second head, is disposed upstream of the color ink ejection head 221, which is the first head, in the transport direction of the medium 100, and a third head is disposed downstream. A certain background ink discharge head 223 is disposed. The background ink discharge head 222 is disposed so as to partially overlap the color ink discharge head 221 in the main scanning direction, and the background ink discharge head 223 is mainly connected to the color ink discharge head 221. It arrange | positions so that a part may overlap in a scanning direction. Here, they are arranged so as to partially overlap, and all do not overlap.

  In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted. In addition, the printing method in the liquid ejection unit having the recording head having such a structure is the same as that described in the first embodiment, and thus the description thereof is omitted.

  In the second embodiment, the background ink ejection heads 222 and 223 are respectively arranged on the upstream side and the downstream side in the conveyance direction of the medium 100 with respect to the color ink ejection head 221, and each is in the main scanning direction. The color ink ejection head 221 partially overlaps. As a result, the effect that the single recording head 22 can cope with both front printing and back printing can be obtained in addition to the effect of the first embodiment.

(Third embodiment)
In the second embodiment, the background ink discharge heads are arranged on the upstream side and the downstream side in the media transport direction with respect to the color ink discharge heads to support both front printing and back printing. A liquid discharge unit that can be shown. In the third embodiment, a description will be given of a liquid ejection unit according to another aspect capable of dealing with both front printing and back printing.

  FIG. 11 is a diagram schematically showing an example of the structure of the carriage according to the third embodiment. In this figure, the color ink ejection head 221 is fixed to the vicinity of the central portion of the lower surface of the carriage 21 in the sub-scanning direction. The background ink ejection head 222 is provided at one end of the color ink ejection head 221 on the main scanning direction side. The carriage 21 has a switching unit configured to be able to move the background ink ejection head 222 in the sub-scanning direction.

  The switching unit includes, for example, a background ink guide 225 provided adjacent to the color ink ejection head 221 on the lower surface of the carriage 21, and a head holding unit movable along the background ink guide 225. The head holding unit holds the background ink ejection head 222. Note that the position of the end of the background ink guide 225 on the sub-scanning direction side is set so that the background ink ejection head 222 can be disposed at a position satisfying the expression (1).

  When surface printing is performed, the background ink discharge head 222 is arranged at the position shown in FIG. At this time, the position of the nozzle of the color ink ejection head 221 and the position of the nozzle of the background ink ejection head 222 in the overlapping region overlap in the main scanning direction.

  On the other hand, when performing reverse printing, the background ink discharge head 222 is arranged at a position 222A indicated by a broken line in FIG. At this time, the position of the nozzle of the color ink ejection head 221 and the position of the nozzle of the background ink ejection head 222 in the overlapping region overlap in the main scanning direction.

  Note that the switching by the switching unit is not limited to n = 1, but may be performed so that n ≧ 2. FIG. 11 illustrates a case where the background ink discharge head 222 is moved in the sub-scanning direction by providing a switching unit on the background ink discharge head 222. However, the color ink ejection head 221 may be provided with a switching unit to move the color ink ejection head 221 in the sub-scanning direction. The same components as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 12 is a diagram schematically illustrating another example of the carriage structure according to the third embodiment. In this figure, the color ink discharge head 221 and the background ink discharge head 222 are configured to be movable in the sub-scanning direction. The carriage 21 is provided with a switching unit configured to move the color ink discharge head 221 and the background ink discharge head 222 in the sub-scanning direction in opposite directions.

  The switching unit includes a color ink guide 226, a background ink guide 225, a color ink head holding unit, and a background ink head holding unit. The color ink guide 226 is provided in the arrangement area of the color ink ejection head 221. The background ink guide 225 is provided in the arrangement area of the background ink ejection head 222. The color ink head holding unit holds the color ink ejection head 221 in the color ink guide 226 and is configured to be movable along the color ink guide 226. The background ink head holding unit holds the background ink ejection head 222 in the background ink guide 225 and has a configuration capable of moving along the background ink guide 225.

  The color ink guide 226 and the background ink guide 225 are configured to move in different directions. For example, when the color ink guide 226 is moved upstream in the sub-scanning direction, the background ink guide 225 is moved downstream. In addition, it is desirable that the amount of movement in the sub-scanning direction at this time is the same.

  FIG. 12 shows an arrangement state of recording heads for surface printing. In the case of reverse printing, the color ink ejection head 221 is located on the upstream side in the conveyance direction of the medium 100, and the background ink ejection head 222 is located on the downstream side in the conveyance direction of the medium 100. In these cases, the color ink ejection head 221 and the background ink ejection head 222 partially overlap in the main scanning direction so as to satisfy the expression (1). Note that the switching by the switching unit is not limited to n = 1, but may be performed so that n ≧ 2.

  In the third embodiment, at least one of the color ink ejection head 221 and the background ink ejection head 222 is configured to be movable in the sub-scanning direction with respect to the other. As a result, even if there is only one background ink ejection head 222, it is possible to obtain the effect of being able to cope with both front printing and back printing in addition to the effects of the first embodiment. it can.

  In the above embodiment, the ink jet recording apparatus 10 has been mainly described as the liquid ejecting apparatus. However, the present invention can also be applied to a copying apparatus, a facsimile apparatus, a plotter apparatus, etc., and a multifunction machine thereof, and the same effect is obtained. be able to.

DESCRIPTION OF SYMBOLS 10 Inkjet recording apparatus 11 Platen 12 Roll media accommodating part 13 Winding roll 14 Conveying part 20 Image forming part 21 Carriage 22 Recording head 23 Guide shaft 30 Media heating part 31 Print heater 32 Preheater 33 Post heater 34 Hot air fan 141 Feeding roller 142 Presser roller 221 Color ink ejection heads 222 and 223 Background ink ejection head 225 Background ink guide 226 Color ink guide

JP 2012-71559 A

Claims (7)

A first head that is movable in a first direction and has a first nozzle row that ejects a first liquid;
A second nozzle array that is disposed at a position shifted in a second direction orthogonal to the first direction with respect to the first head and that discharges a second liquid different from the first liquid; And a second head having a first overlapping region in which the first nozzle row and the second nozzle row overlap in the first direction, and movable with the first head,
When the first nozzle row in the first overlapping region and the second nozzle row in the first overlapping region discharge liquid, the first liquid and the second liquid are discharged objects. A control unit that controls ejection of the first liquid and the second liquid so as to adhere to different positions on the upper side;
A liquid discharge unit comprising:   2. The liquid according to claim 1, wherein a length of the first overlapping region in the second direction is equal to or longer than a printing length of one scan of the first head and the second head. Discharge unit.   3. The liquid ejection unit according to claim 2, wherein the length of the first overlapping region in the second direction is a natural number multiple of the print length per scan.   4. The liquid ejection unit according to claim 1, wherein at least one of the first head and the second head is configured to be movable in the second direction. 5. . A third nozzle row that is disposed at a position shifted in the second direction on the side where the second head is not disposed with respect to the first head, and that discharges the second liquid; In the first direction, the first nozzle row and the third nozzle row have a second overlapping region where the first nozzle row and the third nozzle row overlap, and the second head is movable together with the first head and the second head. 3 heads,
The controller is
In the first mode using the first head and the second head, the first nozzle row in the first overlapping region and the second nozzle row in the first overlapping region are liquid. When discharging the first liquid and the second liquid so that the first liquid and the second liquid adhere to different positions on the discharge target,
In the second mode using the first head and the third head, when used in the second mode, the first nozzle row in the second overlapping region and the second head are used. When the third nozzle row in two overlapping regions discharges the liquid, the first liquid and the second liquid are attached to different positions on the discharged object. The liquid discharge unit according to claim 1, wherein the discharge of the second liquid is controlled. A first head that is movable in a first direction and has a first nozzle row that ejects a first liquid;
A second nozzle array that is disposed at a position shifted in a second direction orthogonal to the first direction with respect to the first head and that discharges a second liquid different from the first liquid; And a second head having a first overlapping region in which the first nozzle row and the second nozzle row overlap in the first direction, and movable with the first head,
Conveying means for conveying an object to be discharged in the second direction;
A controller that scans the first head and the second head in the first direction and moves the discharge target in the second direction;
With
When the first nozzle row in the first overlap region and the second nozzle row in the first overlap region discharge liquid, the control unit is configured to discharge the first liquid and the second liquid. A liquid ejection apparatus that controls ejection of the first liquid and the second liquid so that the liquid adheres to different positions on the object to be ejected. A first head that is movable in a first direction and has a first nozzle row that ejects a first liquid;
A second nozzle array that is disposed at a position shifted in a second direction orthogonal to the first direction with respect to the first head and that discharges a second liquid different from the first liquid; And a second head having an overlapping region in which the first nozzle row and the second nozzle row overlap in the first direction, and movable with the first head,
A liquid discharge method using a liquid discharge unit comprising:
A step of discharging the first liquid to a predetermined position on an object to be discharged when the first nozzle row other than the overlapping region discharges the first liquid;
When the first nozzle row in the overlap region and the second nozzle row in the overlap region discharge liquid, the first liquid and the second liquid are at different positions on the discharge target. Discharging the first liquid and the second liquid to adhere;
A step of discharging the second liquid to a predetermined position on the discharged object when the second nozzle row other than the overlapping region discharges the second liquid;
A liquid discharge method comprising:

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