Printing apparatus and printing method

Abstract

A printing device and a printing method that reduce ejection failure caused by solidification of a liquid containing a color material in the vicinity of a nozzle due to light leaking from an irradiation section. The printing device includes: an ejection head having a first nozzle row that ejects a first liquid toward a recording medium, the first liquid containing a photopolymerization initiator that initiates a polymerization reaction of a polymerizable compound by irradiation of light, and a second nozzle row that ejects a second liquid toward the recording medium, the second liquid containing the polymerizable compound and a color material without containing the photopolymerization initiator; a driving section that changes a relative position of the ejection head to the recording medium; and an irradiation section that irradiates light toward the recording medium on which the first liquid and the second liquid are attached, the printing device ejecting the first liquid and the second liquid from the ejection head in a manner in which the second liquid overlaps the first liquid on a surface of the recording medium. A distance between the irradiation section and the first nozzle row is longer than a distance between the irradiation section and the second nozzle row.

Description

Technical Field

[0001] This invention relates to a technique for printing on recording media using a photocurable liquid containing colorants. Background Technology

[0002] Inkjet printers are known to eject ultraviolet-curable ink, known as UV ink, from nozzles in a printhead onto a recording medium. These printers have an irradiator next to the printhead that irradiates ultraviolet light onto the recording medium to which the UV ink is adhered. However, when ultraviolet light leaking from the irradiator enters the ejection surface of the printhead, which has multiple nozzles, the UV ink adhering to the ejection surface cures, sometimes causing nozzle clogging and other ejection defects. Therefore, maintenance is performed by wiping away the cured UV ink from the ejection surface. However, if the UV ink adhering to the ejection surface is over-cured, it becomes difficult to remove the cured UV ink from the ejection surface. The technology disclosed in Patent Document 1 simplifies maintenance by tilting the irradiator, located between the printheads in the recording medium transport direction, toward the printhead that ejects ink that is more difficult to cure.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent Application Publication No. 2014-195889.

[0006] If the curing of UV ink on the ejection surface can be further suppressed, ejection defects such as nozzle clogging can be reduced.

[0007] It should be noted that the aforementioned problems also exist in printing devices other than inkjet printers that spray UV inks, such as inkjet printers that spray inks that cure due to visible light. Summary of the Invention

[0008] The printing apparatus of the present invention comprises, in other words:

[0009] The ejector head has a first nozzle array and a second nozzle array. The first nozzle array ejects a first liquid toward a recording medium. The first liquid contains a photopolymerization initiator that initiates a polymerization reaction of a polymerizable compound by light irradiation. The second nozzle array ejects a second liquid toward the recording medium. The second liquid does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant.

[0010] A drive unit that changes the relative position of the ejector head and the recording medium; and

[0011] The irradiation unit irradiates the recording medium, to which the first liquid and the second liquid are attached, with light.

[0012] Furthermore, the printing apparatus ejects the first liquid and the second liquid from the ejector head in such a manner that the second liquid overlaps with the first liquid on the surface of the recording medium.

[0013] The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array.

[0014] Furthermore, the printing method of the present invention has the following characteristics:

[0015] The present invention pertains to a printing method in a printing apparatus comprising: an ejector head for ejecting a liquid that is cured by irradiation with light onto a recording medium; a drive unit for changing the relative position of the ejector head and the recording medium; and an irradiation unit for irradiating the recording medium with light, wherein the ejector head has a first nozzle array and a second nozzle array.

[0016] The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array.

[0017] The printing method includes: an ejection step, wherein a first liquid containing a photopolymerization initiator is ejected from a first nozzle array onto the recording medium, the photopolymerization initiator triggering a polymerization reaction of a polymerizable compound by irradiation with light; a second liquid, which does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant, is ejected from a second nozzle array onto the recording medium; and the second liquid is overlapped with the first liquid on the surface of the recording medium; and

[0018] The irradiation process involves irradiating the recording medium, which is coated with the first liquid and the second liquid, with light. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating an example of a printing system that includes a printing apparatus that uses a liquid that cures through light irradiation.

[0020] Figure 2 This is a top view used to schematically illustrate an example of the operation of a serial printing apparatus.

[0021] Figure 3 It is a bottom view schematically showing an example of the configuration of the nozzle and the irradiation section.

[0022] Figure 4 This is a schematic diagram illustrating the operation of a serial printing apparatus.

[0023] Figure 5 This is a top view used to schematically illustrate an example of the operation of a line printing apparatus.

[0024] Figure 6 It is a schematic diagram illustrating the operation of a linear printing apparatus.

[0025] Figure 7 This is a top view used to schematically illustrate examples of the operation of other serial printing devices.

[0026] Figure 8 This is a diagram that schematically illustrates the function of other serial printing devices.

[0027] Figure 9 This is a top view schematically illustrating an example of the components of a carriage mounted on another serial printing device.

[0028] Figure 10 This is a top view schematically showing an example of a serial printing apparatus having a first carriage for a first head and a second carriage for a second head.

[0029] Symbol Explanation

[0030] 1. Printing apparatus; 10. Controller; 20. Printhead; 20a. Nozzle face; 21. First head; 22. Second head; 33. Nozzle array; 34. 34a. 34b. Nozzle; 36. Ink; 36CL. Transparent ink; 36c. Cyan ink; 36m. Magenta ink; 36y. Yellow ink; 36k. Black ink; 37. Ink droplet; 41. First nozzle array; 42. Second nozzle array; 50. Drive unit; 51. Carriage drive unit; 51a. First carriage drive unit; 51b. Second carriage drive unit; 52. Carriage; 52a. First carriage; 52b. Second carriage. Carriage, 55, Roller drive unit, 60, Irradiation unit, 60a, First irradiation unit, 60b, Second irradiation unit, A1~A3, Area, D1, Main scanning direction, D2, Conveying direction, D3, Nozzle arrangement direction, D4, Relative movement direction, D11, Forward direction, D12, Return direction, DT0, Point, L1, L2, Distance, IMO, Output image, LQ1, First liquid, LQ2, Second liquid, ME1, Recording medium, ME1a, Surface, S1, Upstream side, S2, Downstream side, ST1, Ejection process, ST2, Irradiation process, SY1, Printing system. Detailed Implementation

[0031] The embodiments of the present invention will now be described. Of course, the embodiments described below are merely illustrative of the present invention, and not all features shown in the embodiments are necessarily necessary for the solutions provided by the invention.

[0032] (1) Summary of the technology included in this invention:

[0033] First, refer to Figures 1-10The examples shown illustrate a general overview of the technology included in this invention. It should be noted that the figures in this application are schematic illustrations of examples, and the magnification in different directions may vary, and the figures may sometimes not match. Of course, the elements of this technology are not limited to the specific examples shown by the symbols. In the "Summary of the Technology Included in this Invention," the parts in parentheses indicate supplementary explanations of the preceding terms.

[0034] Furthermore, in this application, the numerical range "Min~Max" means a minimum value above Min and a maximum value below Max. The composition ratios shown in the chemical formulas represent stoichiometric ratios, and the substances shown in the chemical formulas also include substances that deviate from stoichiometric ratios.

[0035] Method 1

[0036] One aspect of this technology relates to a printing apparatus 1 comprising an ejector head 20, a drive unit 50, and an irradiation unit 60. The ejector head 20 includes: a first nozzle array 41 for ejecting a first liquid LQ1 onto a recording medium ME1, the first liquid LQ1 containing a photopolymerization initiator that initiates a polymerization reaction of a polymerizable compound upon light irradiation; and a second nozzle array 42 for ejecting a second liquid LQ2 onto the recording medium ME1, which does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant. The drive unit 50 changes the relative position of the ejector head 20 and the recording medium ME1. The irradiation unit 60 irradiates the recording medium ME1, to which the first liquid LQ1 and the second liquid LQ2 are attached, with the light irradiating the medium. The printing apparatus 1 ejects the first liquid LQ1 and the second liquid LQ2 from the ejector head 20 such that the second liquid LQ2 overlaps with the first liquid LQ1 on the surface ME1a of the recording medium ME1. The distance L1 between the irradiation section 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation section 60 and the second nozzle array 42.

[0037] The second liquid LQ2 ejected from the second nozzle array 42, which is closer to the irradiation unit 60, contains a polymerizable compound and a colorant, but does not contain a photopolymerization initiator. Therefore, even if light leaking from the irradiation unit 60 enters the vicinity of the second nozzle array 42, the curing of the second liquid LQ2 near the second nozzle array 42 can be suppressed. The first liquid LQ1 ejected from the first nozzle array 41, which is farther from the irradiation unit 60, contains a photopolymerization initiator. When the second liquid LQ2 overlaps with the first liquid LQ1 on the surface ME1a of the recording medium ME1, the photopolymerization initiator initiates a polymerization reaction of the polymerizable compound by the light irradiated from the irradiation unit 60, and the second liquid LQ2 containing the polymerizable compound and the colorant quickly cures. The first nozzle array 41, which ejects the first liquid LQ1 containing the photopolymerization initiator, is farther from the irradiation unit 60; therefore, light leaking from the irradiation unit 60 has difficulty entering the vicinity of the first nozzle array 41. Therefore, the curing of the first liquid LQ1 near the first nozzle array 41 is suppressed. Therefore, the above-described method 1 can provide a printing apparatus that reduces poor ejection caused by the curing of liquid containing pigment near the nozzle due to light leaking from the irradiation section.

[0038] Here, the nozzle head may also include two or more separate heads. The first nozzle row and the second nozzle row may be set in separate heads.

[0039] The drive unit can move the ejector head without moving the recording medium, move the recording medium without moving the ejector head, move both the ejector head and the recording medium, move the ejector head without moving the recording medium in a first direction, and move the recording medium without moving the ejector head in a second direction intersecting the first direction. In any case, it includes the case where the relative position of the ejector head and the recording medium changes.

[0040] Light includes ultraviolet light, often simply referred to as UV, and visible light.

[0041] The overlap of the second liquid with the first liquid on the surface of the recording medium includes both the second liquid overlapping the first liquid adhering to the recording medium and the first liquid overlapping the second liquid adhering to the recording medium. Within the first liquid adhering to the recording medium, there may also be portions that do not overlap with the second liquid.

[0042] The distance between the irradiation unit and the first nozzle array is the distance between the nozzle with the shortest distance from the irradiation unit among the multiple nozzles included in the first nozzle array. The distance between the irradiation unit and the second nozzle array is the distance between the nozzle with the shortest distance from the irradiation unit among the multiple nozzles included in the second nozzle array.

[0043] In this application, "first," "second," ... are terms used to identify the constituent elements contained in a plurality of similar constituent elements and do not imply any order.

[0044] It should be noted that the above supplementary explanations also apply in the following ways.

[0045] Method 2

[0046] The first liquid LQ1 may also contain the polymerizable compound. The first nozzle array 41 may also eject the first liquid LQ1 containing the photopolymerization initiator and the polymerizable compound. In this case, if the polymerization reaction of the polymerizable compound in the first liquid LQ1 is initiated by light irradiated from the irradiation unit 60, the polymerization reaction of the polymerizable compound in the first liquid LQ1 promotes the polymerization reaction of the polymerizable compound in the second liquid LQ2. Therefore, this method enables the liquid adhering to the recording medium to solidify rapidly.

[0047] It should be noted that although it is not included in Method 2 above, it is also included in this technology when the first liquid does not contain a polymerizable compound, because the photopolymerization initiator of the first liquid initiates the polymerization reaction of the polymerizable compound of the second liquid, and the liquid solidifies on the surface of the recording medium.

[0048] Method 3

[0049] The first liquid LQ1 may also contain a second colorant. The first nozzle array 41 may also eject the first liquid LQ1 containing the photopolymerization initiator and the second colorant. For example, in the case where the liquid contains resin components, the cured resin sometimes yellows due to changes over time. In this case, it is possible to make the yellowing less noticeable by adding a blue colorant to the liquid beforehand. Thus, this method can add a base color to the image formed on the recording medium ME1, thereby providing a preferred printing apparatus.

[0050] Method 4

[0051] like Figure 2As illustrated, the drive unit 50 can change the relative position of the ejector head 20 with respect to the recording medium ME1 in the main scanning direction D1, and can also change the relative position of the recording medium ME1 with respect to the ejector head 20 in the transport direction D2, which intersects the main scanning direction D1, without ejecting the first liquid LQ1 and the second liquid LQ2 from the ejector head 20 to the recording medium ME1. Here, the transport direction D2 is set to be from the upstream side S1 to the downstream side S2. The irradiation unit 60 can be disposed on the downstream side S2 compared to the first nozzle array 41, at a position where it can irradiate the second liquid LQ2 attached to the recording medium ME1. By disposing the irradiation unit 60 on the downstream side S2 of the transport direction D2 compared to the first nozzle array 41, it is easy to irradiate the first liquid LQ1 attached to the recording medium ME1, and it is easy to make the distance L1 between the irradiation unit 60 and the first nozzle array 41 longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42. Therefore, this method can provide a preferred serial printing apparatus.

[0052] Here, "not spraying liquid from the nozzle toward the recording medium" is not limited to not spraying liquid from the nozzle at all, but also includes spraying liquid from the nozzle without toward the recording medium, as in rinsing. This supplementary explanation also applies in the following situations.

[0053] Method 5

[0054] like Figure 2 , 3 As illustrated, the second nozzle array 42 can be positioned downstream of the first nozzle array 41 on the S2 side. During a single main scan of the ejector head 20, which moves relative to the main scanning direction D1, the area irradiated by the irradiation unit 60 in the recording medium ME1 may include an area from which the second liquid LQ2 can be ejected from the second nozzle array 42, but does not include an area from which the first liquid LQ1 can be ejected from the first nozzle array 41. During a single main scan, the second liquid LQ2 is ejected into the area irradiated by the irradiation unit 60, and light is applied, thus curing the second liquid LQ2 while the shape of the dots containing the colorant is sufficiently maintained. Therefore, this method provides a serial printing apparatus that improves the image quality of images formed on a recording medium.

[0055] Method 6

[0056] like Figure 5 , 7As illustrated, the drive unit 50 can change the relative position of the recording medium ME1 with respect to the ejector head 20 in the relative movement direction D4. Here, the relative movement direction D4 is set to the direction from the upstream side S1 toward the downstream side S2. The second nozzle array 42 can be arranged on the downstream side S2 compared to the first nozzle array 41. The irradiation unit 60 can be arranged on the downstream side S2 compared to the second nozzle array 42. For example, in the case of a line printing apparatus in which the recording medium ME1 moves in the transport direction D2 without moving the ejector head 20, the relative movement direction D4 is the transport direction D2 of the recording medium ME1. By arranging the first nozzle array 41, the second nozzle array 42, and the irradiation unit 60 in the order of transport direction D2, light can be irradiated onto the recording medium ME1 to which the first liquid LQ1 and the second liquid LQ2 are attached, and it is easy to make the distance L1 between the irradiation unit 60 and the first nozzle array 41 longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42. Furthermore, even in the case of a serial printing apparatus where the printhead 20 moves along the main scanning direction D1, the relative movement direction D4 can be applied to the main scanning direction D1. In this case, by arranging the first nozzle array 41, the second nozzle array 42, and the irradiation unit 60 in sequence according to the main scanning direction D1, light can be irradiated onto the recording medium ME1 to which the first liquid LQ1 and the second liquid LQ2 are attached, and it is easy to make the distance L1 between the irradiation unit 60 and the first nozzle array 41 longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42. Therefore, this method can provide a preferred printing apparatus.

[0057] Method 7

[0058] like Figure 7 As illustrated, the drive unit 50 can change the relative position of the ejector head 20 with respect to the recording medium ME1 in the main scanning direction D1, and can also change the relative position of the recording medium ME1 with respect to the ejector head 20 in the transport direction D2, which intersects the main scanning direction D1, without ejecting the first liquid LQ1 and the second liquid LQ2 from the ejector head 20 to the recording medium ME1. The irradiation unit 60, the second nozzle array 42, the first nozzle array 41, the second nozzle array 42, and the irradiation unit 60 can be sequentially arranged in the main scanning direction D1. This configuration enables image formation on the recording medium ME1 during both the forward and return main scans, thus providing a preferred serial printing apparatus.

[0059] Method 8

[0060] like Figure 10As illustrated, the ejector head 20 may include a first head 21 having the first nozzle array 41 and a second head 22 having the second nozzle array 42. The drive unit 50 may include: a first main scanning unit (e.g., a first carriage drive unit 51a) having a first carriage 52a mounted on the first head 21, and changing the relative position of the first carriage 52a with respect to the recording medium ME1 in the main scanning direction D1; and a second main scanning unit (e.g., a second carriage drive unit 51b) having a second carriage 52b mounted on the second head 22 and separate from the first carriage 52a, and changing the relative position of the second carriage 52b with respect to the recording medium ME1 in the main scanning direction D1. This configuration provides a preferred serial printing apparatus.

[0061] Method 9

[0062] Furthermore, one aspect of this technology relates to a printing method in a printing apparatus 1 described below. The printing apparatus 1 includes: an ejector head 20 that ejects a liquid that is cured by light irradiation onto a recording medium ME1; a drive unit 50 that changes the relative position of the ejector head 20 and the recording medium ME1; and an irradiation unit 60 that irradiates the recording medium ME1 with light. The ejector head 20 has a first nozzle array 41 and a second nozzle array 42. Here, the distance L1 between the irradiation unit 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42. This printing method includes the following steps (A) and (B):

[0063] (A) Ejection process ST1: A first liquid LQ1 is ejected from the first nozzle array 41 onto the recording medium ME1. The first liquid LQ1 contains a photopolymerization initiator that initiates the polymerization reaction of a polymerizable compound by irradiation with light. A second liquid LQ2 is ejected from the second nozzle array 42 onto the recording medium ME1. The second liquid LQ2 does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant. The second liquid LQ2 overlaps with the first liquid LQ1 on the surface ME1a of the recording medium ME1.

[0064] (B) Irradiation step ST2, irradiating the recording medium ME1 with the first liquid LQ1 and the second liquid LQ2 attached with light.

[0065] This method provides a printing method that reduces poor ejection caused by the curing of liquid containing pigment near the nozzle due to light leaking from the irradiation section.

[0066] Furthermore, this technology can also be applied to printing systems including the aforementioned printing apparatus, printing methods for such printing systems, etc. The printing apparatus can be composed of multiple discrete parts.

[0067] (2) Specific examples of printing systems that include printing apparatus:

[0068] Figure 1 A printing system including a printing apparatus is illustrated schematically, which uses UV ink, which is a liquid that cures upon exposure to light. Here, ultraviolet light, simply referred to as UV, is an example of light. The ink contains a liquid that does not contain colorants. Figure 1 The printing system SY1 shown includes a main unit HO1 and a printing unit 1. It should be noted that the printing system SY1 may include... Figure 1 Additional elements not shown in the figure may also be included in the printing apparatus 1. Figure 1 Additional elements not shown in the text.

[0069] exist Figure 1 The printing apparatus 1 shown is a serial printer, a type of UV inkjet printer. The printing apparatus 1 includes a controller 10, a non-volatile memory 15, a RAM 16, a communication I / F 17, a printhead 20, a drive unit 50, and an irradiation unit 60. Here, RAM is short for Random Access Memory, and I / F is short for Interface. The controller 10, non-volatile memory 15, RAM 16, and communication I / F 17 are connected to a bus and can input and output information to each other.

[0070] Non-volatile memory 15 is a rewritable, high-capacity memory such as firmware, storing information required for the operation of the printing apparatus 1. Non-volatile memory 15 can be a non-volatile semiconductor memory such as flash memory, a magnetic storage device such as a hard disk, etc. RAM 16 is a high-capacity, volatile semiconductor memory that stores input images and other data received from the host device HO1, external memory (not shown), etc. Communication I / F 17 connects to the host device HO1 via wired or wireless connection, inputting and outputting information to the host device HO1. The host device HO1 includes computers such as personal computers and tablet terminals, mobile phones such as smartphones, digital cameras, digital camcorders, etc.

[0071] The controller 10 includes a CPU 11, a memory 12 such as a ROM, and implements a resolution conversion unit 13a, a color conversion unit 13b, a halftone processing unit 13c, a nozzle distribution unit 13d, and a drive signal transmission unit 13e. Here, CPU is short for Central Processing Unit, and ROM is short for Read Only Memory. The controller 10 is based on... Figure 2 The output image IM0 shown is used to control the main and sub-scans of the drive unit 50, the ejection of ink droplets 37 from the ejector head 20, and the UV irradiation of the irradiation unit 60. The main scan refers to the relative movement of the ejector head 20 and the recording medium ME1 in the main scan direction, while the sub-scan refers to the relative movement of the ejector head 20 and the recording medium ME1 in the transport direction D2. The controller 10 can be configured as a SoC (System on a Chip).

[0072] CPU11 is a device that focuses on information processing and control in the printing apparatus 1.

[0073] The resolution conversion unit 13a converts the resolution of the input image from the host device HO1, etc., to a set resolution. The input image is, for example, represented by original RGB data with multiple grayscale integer values ​​(R, G, and B) in each pixel. Here, R represents red, G represents green, and B represents blue. The resolution conversion unit 13a converts the original RGB data into input color grayscale data DA1 at the set resolution. The input color grayscale data DA1 is, for example, represented by RGB data with multiple grayscale integer values ​​(R, G, and B) in each pixel. The grayscale levels of this RGB data and the original RGB data have 2... 8 2 16 wait.

[0074] The color conversion unit 13b refers to a color conversion lookup table that specifies, for example, the correspondence between the grayscale values ​​of R, G, and B and the grayscale values ​​of C, M, Y, and K, and converts the input grayscale data DA1 into output grayscale data DA2, which has multiple grayscale integer values ​​of C, M, Y, and K in each pixel. Here, C represents cyan, M represents magenta, Y represents yellow, and K represents black. The output grayscale data DA2 has 2 grayscale levels. 8 2 16 The output grayscale data DA2 represents the amount of ink used per pixel (36).

[0075] The halftone processing unit 13c reduces the grayscale value of each pixel constituting the output color grayscale data DA2 by performing predefined halftone processing, such as dithering, error diffusion, or density patterning, thereby generating halftone data DA3. Halftone data DA3 represents the formation state of a point. Halftone data DA3 can be binary data indicating whether a point has formed, or multi-valued data with 3 or more grayscale values ​​corresponding to points of different sizes, such as small, medium, and large points. Binary data can be configured such that 1 corresponds to a point formation and 0 corresponds to no point. Quadratic data can represent small, medium, and large points using two bits.

[0076] The nozzle allocation unit 13d performs nozzle allocation processing to rearrange the halftone data DA3 according to the order of the points formed by the drive unit 50, thereby generating nozzle data DA4. The nozzle allocation processing in a serial printer is also known as rasterization processing.

[0077] The drive signal transmitting unit 13e generates a drive signal SG corresponding to the voltage signal applied to the drive element 32 of the print head 20 based on the nozzle data DA4 and outputs it to the drive circuit 31. For example, if the nozzle data DA4 is "dot formation", the drive signal transmitting unit 13e outputs the drive signal SG to eject ink droplets 37 for dot formation. In addition, if the nozzle data DA4 is four-value data, the drive signal SG is output to eject ink droplets 37 corresponding to small, medium and large dots.

[0078] The aforementioned parts 13a to 13e can be constructed using an ASIC, or the data to be processed can be directly read from RAM 16 or the processed data can be directly written to RAM 16. Here, ASIC is short for Application Specific Integrated Circuit. Furthermore, the printing apparatus 1 can receive any one of the input grayscale data DA1, output grayscale data DA2, halftone data DA3, and nozzle data DA4 from the host device HO1 to generate a drive signal SG.

[0079] The drive unit 50, controlled by the controller 10, includes a carriage drive unit 51, a carriage 52, a roller drive unit 55, a conveying roller pair 56, a discharge roller pair 57, and a pressure plate 58. An ejector head 20 and an irradiation unit 60 are mounted on the carriage 52. The drive unit 50 drives the carriage 52 to reciprocate via the carriage drive unit 51, and drives the recording medium ME1 along the conveying path 59 in the conveying direction D2 via the roller drive unit 55. Here, the conveying direction D2 is set to be from the upstream side S1 towards the downstream side S2. Figure 1 In the middle, the conveying direction D2 is to the right, the upstream side S1 is to the left, and the downstream side S2 is to the right. The carriage drive unit 51, under the control of the controller 10, moves the carriage 52 towards... Figure 2 The main scan moves in the main scan direction D1 as shown. For example... Figure 2 As shown, the main scanning direction D1 is the collective name for the forward direction D11 and the return direction D12, which is opposite to the forward direction D11. The roller drive unit 55, under the control of the controller 10, rotates the rollers 56a and 57a of roller pairs 56 and 57, thereby performing a sub-scan to transport the recording medium ME1 in the transport direction D2. There are no particular limitations on the material of the recording medium ME1; various materials such as resin, metal, and paper can be considered. There are also no particular limitations on the shape of the recording medium ME1; various shapes such as rectangular, rolled, or three-dimensional can be considered.

[0080] Alternatively, an ink cartridge 35 can be mounted on the carriage 52, which is equipped with the printhead 20 and the irradiation section 60, and the ink cartridge 35 supplies ink 36, which is ejected as ink droplets 37, to the printhead 20. Of course, ink 36 can also be supplied to the printhead 20 from the ink cartridge 35, which is located outside the carriage 52, via a tube. The carriage 52 is fixed to an annular belt (not shown) and can move along the guide 53... Figure 2 The carriage 52 moves in the main scanning direction D1 as shown. The guide member 53 is a long strip member with its long side facing the main scanning direction D1. The carriage drive unit 51 is composed of a servo motor, which moves the carriage 52 in the forward direction D11 and the return direction D12 according to the instructions from the controller 10.

[0081] The transport roller pair 56 located upstream of the ejector head 20 includes a drive transport roller 56a that contacts one side of the recording medium ME1 and a driven transport roller 56b that contacts the other side of the recording medium ME1. During sub-scanning, the transport roller pair 56 transports the clamped recording medium ME1 toward the ejector head 20 and the irradiation section 60 by rotating the drive transport roller 56a.

[0082] The discharge roller pair 57 located downstream of the ejector head 20 includes a drive discharge roller 57a that contacts one side of the recording medium ME1 and a driven discharge roller 57b that contacts the other side of the recording medium ME1. During sub-scanning, the discharge roller pair 57 conveys the clamped recording medium ME1 toward a discharge tray (not shown) by rotating the drive discharge roller 57a.

[0083] The roller drive unit 55 is composed of a servo motor, which rotates the rollers 56a and 57a according to the instructions from the controller 10. The rollers 56a and 57a transport the recording medium ME1 in the transport direction D2 by rotating.

[0084] A pressure plate 58 supports a recording medium ME1 located on a transport path 59. An ejector head 20, controlled by a controller 10, ejects ink droplets 37 onto the recording medium ME1 supported by the pressure plate 58, causing ink 36 to adhere to the recording medium ME1. An irradiation unit 60, controlled by the controller 10, cures the ink 36 adhered to the recording medium ME1 by irradiating it with UV light.

[0085] like Figure 2As illustrated, the printhead 20 includes a first head 21 having a first nozzle array 41 and a second head 22 having a second nozzle array 42. Details of the first head 21 and the second head 22 will be described later. The printhead 20 has a nozzle array 33 containing a plurality of nozzles 34 on a nozzle surface 20a, and includes a drive circuit 31, a drive element 32, etc. The nozzle surface 20a is the ejection surface for ink droplets 37, which are liquid droplets. The drive circuit 31 applies a voltage signal to the drive element 32 according to the drive signal SG input from the drive signal transmission unit 13e. The drive element 32 can be a piezoelectric element that applies pressure to the ink 36 in a pressure chamber connected to the nozzle 34, or a drive element that generates bubbles in the pressure chamber by heat to eject ink droplets 37 from the nozzle 34, etc. A nozzle is a small hole for ejecting ink droplets 37. Ink 36 is supplied from the ink cartridge 35 to the pressure chamber of the printhead 20. The combination of the ink cartridge 35 and the nozzle array 33 is, for example, configured as CL, C, M, Y, and K. Here, CL means transparent, and CL ink means transparent ink as the first liquid LQ1. The ink 36 in the pressure chamber is ejected as ink droplets 37 from the nozzle 34 onto the recording medium ME1 by the drive element 32. Thus, ink droplets 37 are formed at the point on the recording medium ME1.

[0086] Figure 2 This is a top view schematically illustrating the operation of the serial printing apparatus 1. Figure 3 This is a bottom view schematically illustrating the configuration of the nozzle 20 and the irradiation section 60.

[0087] exist Figure 2 , Figure 3 The carriage 52 shown is equipped with a first head 21, a second head 22, and a plurality of irradiation units 60. The second head 22 and the plurality of irradiation units 60 are disposed on the downstream side S2 compared to the first head 21. The plurality of irradiation units 60 include: a first irradiation unit 60a, located at a position from the second head 22 toward the forward direction D11; and a second irradiation unit 60b, located at a position from the second head 22 toward the return direction D12.

[0088] The first head 21 has a first nozzle array 41 on the nozzle surface 20a, which includes a plurality of nozzles 34a arranged at intervals of nozzle pitch Np along the nozzle arrangement direction D3. The nozzles 34a eject transparent ink 36CL, which is a first liquid LQ1, as ink droplets 37. The transparent ink 36CL contains a polymerizable compound and a photopolymerization initiator that initiates the polymerization reaction of the polymerizable compound by UV irradiation as a UV ink component, but does not contain colorant. Thus, the transparent ink 36CL is a substantially colorless and transparent liquid.

[0089] The second head 22 has a plurality of second nozzle rows 42 on the nozzle surface 20a, which includes a plurality of nozzles 34b arranged at intervals of nozzle pitch Np along the nozzle arrangement direction D3. The nozzles 34b eject a second liquid LQ2 containing pigment as a colorant as ink droplets 37. The second liquid LQ2 includes cyan ink 36c containing cyan pigment, magenta ink 36m containing magenta pigment, yellow ink 36y containing yellow pigment, and black ink 36k containing black pigment. It should be noted that these inks are sometimes referred to as colored inks 36c, 36m, 36y, and 36k. Although the second liquid LQ2 contains polymerizable compounds as UV ink components, it does not contain photopolymerization initiators. The second head 22 has the following nozzle array as the second nozzle array 42: a magenta nozzle array including a plurality of nozzles 34b that spray magenta ink 36m, a cyan nozzle array including a plurality of nozzles 34b that spray cyan ink 36c, a yellow nozzle array including a plurality of nozzles 34b that spray yellow ink 36y, and a black nozzle array including a plurality of nozzles 34b that spray black ink 36k.

[0090] It should be noted that the nozzle 20 is the collective name for the first nozzle 21 and the second nozzle 22, the nozzle row 33 is the collective name for the first nozzle row 41 and the second nozzle row 42, and the nozzle 34 is the collective name for nozzles 34a and 34b.

[0091] The nozzle arrangement direction D3 can be as follows Figure 3 As shown, the nozzle arrangement direction D3 can be perpendicular to the main scanning direction D1, or it can be obliquely intersecting D1 instead of being perpendicular to it. In other words, the nozzle arrangement direction D3 can be as shown... Figure 3 As shown, it can be aligned with the conveying direction D2, or it can deviate from the conveying direction D2 within a range of less than 90°. The multiple nozzles 34 included in the nozzle array 33 can be arranged as follows: Figure 3 The arrangement shown can be in a single column, or it can be arranged in a staggered pattern.

[0092] Each irradiation unit 60 includes: a housing 61 having an opening opposite to the recording medium ME1; and a light source 62 disposed within the interior space of the housing 61 facing opposite to the recording medium ME1. The light source 62 emits UV light with a peak wavelength in the range of 360–420 nm, for example, around 395 nm. The UV light emitted from the light source 62 irradiates the recording medium ME1 through the opening in the housing 61. The light source 62 is preferably an LED, i.e., a light-emitting diode, but a metal halide lamp or the like can also be used.

[0093] A first irradiation section 60a and a second irradiation section 60b are respectively arranged at a position from the second nozzle line 42 toward the forward direction D11 and the return direction D12 at a position S2 downstream of the first nozzle line 41. Thus, the irradiation section 60 is located at a position that can irradiate the second liquid LQ2 attached to the recording medium ME1.

[0094] like Figure 2 , 3 As shown, the distance L1 between the irradiation unit 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42. Here, distance L1 is the distance when the irradiation unit 60 and the first nozzle array 41 are projected onto a plane along the main scanning direction D1 and the transport direction D2; it is the distance between the irradiation unit 60 and the nozzle among the plurality of nozzles 34a included in the first nozzle array 41 that has the shortest distance to the irradiation unit 60. Distance L2 is the distance when the irradiation unit 60 and the second nozzle array 42 are projected onto a plane along the main scanning direction D1 and the transport direction D2; it is set to the distance between the irradiation unit 60 and the nozzle among the plurality of nozzles 34b included in the second nozzle array 42 that has the shortest distance to the irradiation unit 60.

[0095] Figure 2 The printing apparatus 1 shown performs bidirectional printing by ejecting ink droplets 37 from the ejector head 20 as the carriage 52 moves in both the forward direction D11 and the return direction D12. The carriage 52 and the recording medium ME1 operate as follows, for example.

[0096] During the first main scan, the carriage 52 moves in the forward direction D11 driven by the carriage drive unit 51. The ejector head 20 ejects ink droplets 37 onto the recording medium ME1 while moving in the return direction D11. Figure 2 In the example shown, the first nozzle 21 ejects transparent ink 36CL from the first nozzle array 41 into the downstream region A1 of the surface ME1a of the recording medium ME1. Although the transparent ink 36CL is ejected from each nozzle 34a in the form of ink droplets 37, the transparent ink 36CL is coated on the entire surface of region A1 in a manner that avoids gaps in region A1. After the ejection of ink droplets 37 is completed in the first main scan, in the sub-scan, the recording medium ME1 is moved by a belt amount in the transport direction D2 by the drive of the roller drive unit 55.

[0097] During the second main scan, the carriage 52 moves in the return direction D12, driven by the carriage drive unit 51. The ejector head 20 ejects ink droplets 37 onto the recording medium ME1 while moving in the return direction D12. Figure 2 In the example shown, the first nozzle 21 ejects transparent ink 36CL from region A1 to region A2 immediately following upstream on side S1 from the first nozzle array 41. Here, transparent ink 36CL is also coated on the entire surface of region A2. After the ejection of ink droplets 37 is completed in the second main scan, in the sub-scan, the recording medium ME1 is moved by a belt amount in the transport direction D2 by the drive of the roller drive unit 55.

[0098] During the third main scan, the carriage 52 moves in the forward direction D11, driven by the carriage drive unit 51. The ejector head 20 ejects ink droplets 37 onto the recording medium ME1 while moving in the forward direction D11. Figure 2 In the example shown, the first nozzle 21 ejects transparent ink 36CL from region A2 towards region A3 immediately following upstream on the S1 side from the first nozzle array 41, and the second nozzle 22 ejects a second liquid LQ2 from the second nozzle array 42 towards the downstream region A1. The ejection of the second liquid LQ2 is based on... Figure 1 The nozzle data DA4 shown is used. If cyan ink 36c is ejected from nozzle 34b, point C DT0 is formed in region A1; if magenta ink 36m is ejected from nozzle 34b, point M DT0 is formed in region A1; if yellow ink 36y is ejected from nozzle 34b, point Y DT0 is formed in region A1; and if black ink 36k is ejected from nozzle 34b, point K DT0 is formed in region A1. Therefore, the first liquid LQ1 and the second liquid LQ2 are ejected from the ejector head 20 in such a way that the second liquid LQ2 overlaps with the first liquid LQ1 on the surface ME1a of the recording medium ME1. In addition, during the third main scan, the controller 10 turns off the light source 62 of the first irradiation unit 60a and turns on the light source 62 of the second irradiation unit 60b, thereby irradiating region A1 with UV light from the second irradiation unit 60b. The UV light from the second irradiation unit 60b does not irradiate region A3. Therefore, in the third main scan, the area that the irradiation unit 60 in the recording medium ME1 can irradiate includes the area A1 where the second liquid LQ2 can be ejected from the second nozzle array 42, but does not include the area A3 where the first liquid LQ1 can be ejected from the first nozzle array 41.

[0099] After the ink droplets 37 are ejected in the third main scan, in the sub-scan, the recording medium ME1 moves by a belt length in the transport direction D2 by the drive of the roller drive unit 55.

[0100] During the fourth main scan, the carriage 52 moves in the return direction D12, driven by the carriage drive unit 51. The ejector head 20 ejects ink droplets 37 onto the recording medium ME1 while moving in the return direction D12. Figure 2In the example shown, the first head 21 ejects transparent ink 36CL from region A3 to an unshown region immediately adjacent to upstream side S1 from the first nozzle array 41, and the second head 22 ejects the second liquid LQ2 from the second nozzle array 42 to region A2. Furthermore, during the fourth main scan, the controller 10 turns off the light source 62 of the second irradiation unit 60b and illuminates the light source 62 of the first irradiation unit 60a, thereby irradiating region A2 with UV light from the first irradiation unit 60a. Therefore, during the fourth main scan, the region irradiated by the irradiation unit 60 in the recording medium ME1 includes region A2, where the second liquid LQ2 can be ejected from the second nozzle array 42, but does not include the region where the first liquid LQ1 can be ejected from the first nozzle array 41.

[0101] After the ink droplet 37 is ejected in the fourth main scan, in the sub-scan, the recording medium ME1 moves by a belt length in the transport direction D2 by the drive of the roller drive unit 55.

[0102] The following steps involve repeatedly performing main and secondary scans of the carriage 52 moving in the forward direction D11 and the carriage 52 moving in the return direction D12.

[0103] In summary, the carriage drive unit 51 changes the relative position of the ejector head 20 with respect to the recording medium ME1 in the main scanning direction D1. When the first liquid LQ1 and the second liquid LQ2 are not ejected from the ejector head 20 to the recording medium ME1, the roller drive unit 55 changes the relative position of the recording medium ME1 with respect to the ejector head 20 in the transport direction D2. The ejector head 20 ejects the first liquid LQ1 and the second liquid LQ2 during the main scan.

[0104] Next, examples of the composition of the first liquid LQ1 and the second liquid LQ2 will be explained.

[0105] The first liquid LQ1 contains a photopolymerization initiator. The first liquid LQ1 may contain a polymerizable compound, like the aforementioned transparent ink 36CL, or it may not contain a polymerizable compound. Furthermore, the first liquid LQ1 may not contain a colorant, like the transparent ink 36CL, or it may contain a colorant. For example, when the first liquid LQ1 contains a resin component, the cured resin may sometimes yellow over time. In this case, by pre-adding a blue colorant to the first liquid LQ1, the yellowing can be made less noticeable. In this example, the blue colorant is an example of a second colorant. On the other hand, the second liquid LQ2 does not contain a photopolymerization initiator, but contains a polymerizable compound and a colorant.

[0106] The polymerizable compound is polymerized by a photopolymerization initiator, which cures the ink containing the first liquid LQ1 and the second liquid LQ2. The polymerizable compound can be various (meth)acrylate monomers, various (meth)acrylate oligomers, various vinyl monomers, various vinyl ether monomers, etc., and can be a (meth)acrylate containing a vinyl ether group as shown in the following general formula (1) (let's call it monomer A).

[0107] CH2=CR 1 -COOR 2 -O-CH=CH-R 3 ……(1)

[0108] Among them, R 1 It is a hydrogen atom or a methyl group, R 2 It is a divalent organic residue with 2 to 20 carbon atoms, R 3 It is a monovalent organic residue with 1 to 11 hydrogen or carbon atoms. Monomer A can be any monomer disclosed in Japanese Patent Application Publication No. 2014-195889. The content of the polymerizable compound in the first liquid LQ1 and the second liquid LQ2 can be set to, for example, about 60 to 95% by mass.

[0109] Photopolymerization initiators initiate the polymerization reaction of polymerizable compounds through UV irradiation. Photopolymerization initiators can include alkylphenyl ketone-based, acylphosphine-based, titanoceramsite-based, and thioxanthone-based photopolymerization initiators, among others. The content of the photopolymerization initiator in the first liquid LQ1 can be set to, for example, approximately 9–14% by mass.

[0110] Colorants can be inorganic or organic pigments. Inorganic pigments can be metal oxides such as carbon black, iron oxide, or titanium oxide. Organic pigments can be azo pigments such as monoazo and diazo azo pigments; condensed polycyclic pigments such as phthalocyanine, perylene, violet ketone, and anthraquinone pigments; lake pigments such as dyeing lake pigments; and fluorescent pigments. The average particle size of the pigments based on dynamic light scattering can be set to, for example, approximately 30–2000 nm. The colorant added to the first liquid LQ1 and the second liquid LQ2 can be one or more types. The content of the colorant in the colored inks 36c, 36m, 36y, and 36k can be set to, for example, approximately 1.5–6% by mass.

[0111] It should be noted that the first liquid LQ1 and the second liquid LQ2 may also contain additives such as dispersants, surfactants (also known as leveling agents), polymerization inhibitors, polymerization accelerators, penetration accelerators, and wetting agents, as needed.

[0112] However, when a UV irradiation section exists next to the nozzle of a UV ink containing photopolymerization initiator and polymerizable compound, UV ink can solidify on the nozzle surface due to UV leakage from the irradiation section, sometimes causing nozzle clogging and other ejection defects. If the UV ink adhering to the nozzle surface is too solidified, it can become difficult to remove from the nozzle surface even after wiping it off during maintenance.

[0113] This specific example has the following features: a second nozzle array 42 is provided in the nozzle head 20, the second nozzle array 42 sprays a second liquid LQ2 containing a polymerizable compound and a colorant but not a photopolymerization initiator, and the first nozzle array 41 sprays a first liquid LQ1 containing a photopolymerization initiator further away from the irradiation section 60 than the second nozzle array 42. Figure 2 , Figure 3 As shown, the distance L1 between the irradiation section 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation section 60 and the second nozzle array 42. Therefore, spray defects caused by the curing of the colorant-containing liquid near the nozzle due to UV leakage from the irradiation section 60 are reduced.

[0114] (3) The function and effect of the serial printing device involved in the specific example:

[0115] Figure 4 It is an illustrative example. Figure 1 , 2 The function of the serial printing apparatus 1 shown is illustrated. Figure 4 The upper part shows the main scan SC1 and Figure 2 The first main scan is shown. Figure 4 The lower part shows the main scan SC2 and Figure 2 The third main scan is shown. Figure 4 The case of region A1 in the surface ME1a of the recording medium ME1 is shown.

[0116] In the first main scan SC1, the first head 21 mounted on the carriage 52 moves in the forward direction D11, during which ink droplets 37 of transparent ink 36CL, which is the first liquid LQ1, are ejected from the nozzles 34a of the first nozzle array 41 into region A1. The transparent ink 36CL contains a photopolymerization initiator and a polymerizable compound, and may also contain a second colorant. In the first main scan SC1, the transparent ink 36CL is coated on the entire surface of region A1. After the ejection of the transparent ink 36CL is completed, a sub-scan, a main scan in the return direction D12, and a sub-scan are performed.

[0117] In the second main scan SC2, the second head 22 mounted on the carriage 52 and the irradiation unit 60 move in the forward direction D11. During this movement, ink droplets 37 of the second liquid LQ2 are ejected from the nozzle 34b of the second nozzle array 42 into region A1. The second liquid LQ2 does not contain a photopolymerization initiator but contains a polymerizable compound and a colorant, including at least a portion of colored inks 36c, 36m, 36y, and 36k in this specific example. The point DT0 of the second liquid LQ2 overlaps with the transparent ink 36CL on the surface ME1a of the recording medium ME1. Therefore, the first liquid LQ1 and the second liquid LQ2 are ejected from the ejector head 20 into the surface ME1a of the recording medium ME1 in such a way that the second liquid LQ2 overlaps with the first liquid LQ1. It should be noted that in the region where the main scan is performed in the return direction D12 as in region A2, only the moving directions of the first head 21 and the second head 22 are different, and the second liquid LQ2 is similarly overlapped with the first liquid LQ1 on the surface ME1a of the recording medium ME1.

[0118] Through the above process, the ejection step ST1 is performed. In the ejection step ST1, the first liquid LQ1 is ejected from the first nozzle array 41 to the recording medium ME1, and the second liquid LQ2 is ejected from the second nozzle array 42 to the recording medium ME1, so that the second liquid LQ2 overlaps with the first liquid LQ1 on the surface ME1a of the recording medium ME1.

[0119] Here, in the second primary scan SC2... Figure 1 The controller 10 shown turns off the first irradiation unit 60a, which is positioned from the second head 22 toward the forward direction D11, and turns on the second irradiation unit 60b, which is positioned from the second head 22 toward the return direction D12. As a result, UV light is irradiated from the second irradiation unit 60b onto region A1, on which transparent ink 36CL and colored inks 36c, 36m, 36y, and 36k are adhered to the recording medium ME1. The transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k are cured, forming an output image IM0 on the recording medium ME1. It should be noted that in regions like region A2, where the main scan is performed in the return direction D12, the second irradiation unit 60b is turned off, and the first irradiation unit 60a is turned on, thereby irradiating with UV light.

[0120] Through the above process, irradiation step ST2 is carried out, in which UV is irradiated onto the recording medium ME1 to which the first liquid LQ1 and the second liquid LQ2 are attached.

[0121] It should be noted that the time from the ejection of colored inks 36c, 36m, 36y, and 36k to UV irradiation is shorter than the time from the ejection of transparent ink 36CL to UV irradiation, thus forming a high-quality output image IM0.

[0122] The colored inks 36c, 36m, 36y, and 36k ejected from the second nozzle array 42, which is closer to the irradiation unit 60, contain polymerizable compounds and colorants, but do not contain photopolymerization initiators. Therefore, even if UV light leaking from the irradiation unit 60 enters the vicinity of the second nozzle array 42, the curing of the colored inks 36c, 36m, 36y, and 36k in the vicinity of the second nozzle array 42 can be suppressed.

[0123] The transparent ink 36CL ejected from the first nozzle array 41, which is relatively far from the irradiation unit 60, contains a photopolymerization initiator. When the colored inks 36c, 36m, 36y, and 36k overlap with the transparent ink 36CL on the surface ME1a of the recording medium ME1, the UV radiation from the irradiation unit 60 initiates a polymerization reaction of the polymerizable compounds in the transparent ink 36CL through the photopolymerization initiator. This polymerization reaction in the transparent ink 36CL promotes the polymerization reaction of the polymerizable compounds in the colored inks 36c, 36m, 36y, and 36k. As a result, the transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k cure rapidly. Because the first nozzle array 41 from which the transparent ink 36CL is ejected is relatively far from the irradiation unit 60, the UV radiation leaking from the irradiation unit 60 is unlikely to penetrate into the vicinity of the first nozzle array 41. Therefore, the curing of the transparent ink 36CL in the vicinity of the first nozzle array 41 can be suppressed. Therefore, this specific example can reduce poor ejection caused by UV ink curing near the nozzle due to UV leakage from the irradiation section 60.

[0124] As a result, this embodiment can reduce the maintenance cost of wiping cured UV ink from the nozzle surface. In addition, this embodiment can increase the amount of UV light irradiating the recording medium ME1, thereby improving printing efficiency and reducing printing operating costs.

[0125] (4) Examples of applications for linear printing apparatus:

[0126] Figure 5 This is a top view schematically illustrating the operation of the printing apparatus 1A. The printing apparatus 1A is included in the concept of the printing apparatus 1.

[0127] Reference Figure 1 , Figure 5 To explain, a line printer such as the 1A does not have a carriage 52. While moving the recording medium ME1 in the transport direction D2 without moving the printhead 20, ink droplets 37 are ejected from the nozzle array 33 onto the recording medium ME1. For convenience, in Figure 5The diagram shows the main scanning direction D1, which corresponds to the width direction of the recording medium ME1 orthogonal to the transport direction D2. The ejector head 20 has a nozzle array 33 with nozzles 34 arranged substantially throughout the recording medium ME1 in the aforementioned width direction. The roller drive unit 55, which serves as the drive unit 50, moves the recording medium ME1 in the transport direction D2. In this case, the transport direction D2 is an example of the relative movement direction D4, and the roller drive unit 55 changes the relative position of the recording medium ME1 with respect to the ejector head 20 in the relative movement direction D4.

[0128] Here, the conveying direction D2 is set to be from the upstream side S1 toward the downstream side S2. Figure 5 The printing apparatus 1A shown is arranged in sequence in the transport direction D2 as follows: a first head 21 having a first nozzle array 41 for ejecting transparent ink 36CL; a second head 22 having a second nozzle array 42 for ejecting colored inks 36c, 36m, 36y, and 36k; and an irradiation unit 60. In other words, the second nozzle array 42 is located downstream of the first nozzle array 41 on the S2 side, and the irradiation unit 60 is located downstream of the second nozzle array 42 on the S2 side. Therefore, the distance L1 between the irradiation unit 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42.

[0129] Figure 6 illustrative example Figure 5 The function of the line printing device 1 shown.

[0130] The recording medium ME1 moves in the transport direction D2. During this movement, droplets 37 of transparent ink 36CL are ejected from nozzles 34a of the first nozzle array 41 onto the recording medium ME1, thereby coating almost the entire surface of ME1a with transparent ink 36CL. Transparent ink 36CL contains a photopolymerization initiator and a polymerizable compound. Additionally, during the movement of the recording medium ME1, droplets 37 of colored inks 36c, 36m, 36y, and 36k are ejected from nozzles 34b of the second nozzle array 42 onto the recording medium ME1, causing dots DT0 of the colored inks 36c, 36m, 36y, and 36k to overlap with the transparent ink 36CL on the surface ME1a. The colored inks 36c, 36m, 36y, and 36k do not contain a photopolymerization initiator but contain a polymerizable compound and a colorant.

[0131] Through the above process, the spraying process ST1 is carried out.

[0132] Furthermore, during the movement of the recording medium ME1, UV light is irradiated from the irradiation unit 60 onto the surface ME1a of the recording medium ME1, to which the transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k are attached. As a result, the transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k are cured, forming the output image IMO on the recording medium ME1.

[0133] Through the above process, the irradiation procedure ST2 is carried out.

[0134] It should be noted that, since colored inks 36c, 36m, 36y, and 36k are sprayed after the transparent ink 36CL is sprayed, a high-quality output image IM0 is formed.

[0135] Since the colored inks 36c, 36m, 36y, and 36k ejected from the second nozzle array 42, which is relatively close to the irradiation unit 60, do not contain photopolymerization initiators, the curing of the colored inks 36c, 36m, 36y, and 36k near the second nozzle array 42 is suppressed. Furthermore, by overlapping the colored inks 36c, 36m, 36y, and 36k onto the transparent ink 36CL, which contains a photopolymerization initiator and a polymerizable compound, the photopolymerization initiator initiates a polymerization reaction of the polymerizable compound, causing the transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k to cure. Therefore, the line printing apparatus 1A can also reduce ejection defects caused by UV ink curing near the nozzles due to UV leakage from the irradiation unit 60.

[0136] (5) Examples of application to other serial printing devices:

[0137] Figure 7 This is a top view schematically illustrating the operation of another serial printing apparatus 1B. The printing apparatus 1B is also included in the concept of printing apparatus 1.

[0138] exist Figure 7 On the carriage 52 shown, in the main scanning direction D1, a first irradiation unit 60a, a second nozzle array 42, a first nozzle array 41, a second nozzle array 42, and a second irradiation unit 60b are arranged sequentially.

[0139] During the main scan, in which the carriage drive unit 51 moves the carriage 52 in the forward direction D11, the controller 10 does not use the second head 22, which is located from the first head 21 toward the forward direction D11, thus turning off the first irradiation unit 60a and illuminating the second irradiation unit 60b. In the main scan in the forward direction D11, the first head 21 ejects transparent ink 36CL from the first nozzle array 41 to a certain area of ​​the recording medium ME1, and the second head 22 ejects colored inks 36c, 36m, 36y, and 36k from the second nozzle array 42 to the same area. Figure 7In the example shown, transparent ink 36CL and colored inks 36c, 36m, 36y, and 36k are ejected into region A1 in the first main scan and into region A3 in the third main scan. During the main scan in the forward direction D11, the return direction D12 is the relative movement direction D4, where the relative position of the recording medium ME1 relative to the ejector head 20 changes. On the carriage 52, arranged in order of relative movement direction D4 are a first nozzle array 41 for ejecting the first liquid LQ1, a second nozzle array 42 for ejecting the second liquid LQ2, and a second irradiation section 60b.

[0140] During the main scan, in which the carriage drive unit 51 moves the carriage 52 in the return direction D12, the controller 10 does not use the second head 22 located from the first head 21 toward the return direction D12, thus turning off the second irradiation unit 60b and illuminating the first irradiation unit 60a. In the main scan toward the return direction D12, the first head 21 ejects transparent ink 36CL from the first nozzle array 41 to a certain area of ​​the recording medium ME1, and the second head 22 ejects colored inks 36c, 36m, 36y, and 36k from the second nozzle array 42 to the same area. Figure 7 In the example shown, transparent ink 36CL and colored inks 36c, 36m, 36y, and 36k are ejected into region A2 during the second main scan. During the main scan in the return direction D12, the forward direction D11 is the relative movement direction D4 in which the relative position of the recording medium ME1 relative to the ejector head 20 changes. On the carriage 52, a first nozzle array 41 for ejecting the first liquid LQ1, a second nozzle array 42 for ejecting the second liquid LQ2, and a first irradiation section 60a are arranged in order of relative movement direction D4.

[0141] Figure 8 illustrative example Figure 7 The function of the serial printing apparatus 1B shown is explained. Figure 8 The diagram shows the main scan in the forward direction D11. However, as described above, the relative movement direction D4 is the return direction D12 during the main scan in the forward direction D11, and the forward direction D11 during the main scan in the return direction D12. Here, the relative movement direction D4 is set as the direction from the upstream side S1 to the downstream side S2.

[0142] During the main scan, as the carriage 52 moves, droplets 37 of transparent ink 36CL are ejected from nozzles 34a of the first nozzle array 41 onto the recording medium ME1, thereby coating almost the entire surface of the ME1a with transparent ink 36CL. Additionally, as the carriage 52 moves, droplets 37 of colored inks 36c, 36m, 36y, and 36k are ejected from nozzles 34b of the second nozzle array 42 onto the recording medium ME1, thereby overlapping the dots DT0 of the colored inks 36c, 36m, 36y, and 36k onto the surface ME1a with the transparent ink 36CL.

[0143] Through the above process, the spraying process ST1 is carried out.

[0144] Furthermore, during the movement of the carriage 52, UV light is irradiated from the irradiation unit 60 onto the surface ME1a of the recording medium ME1, which is coated with transparent ink 36CL and colored inks 36c, 36m, 36y, and 36k. As a result, the transparent ink 36CL and the colored inks 36c, 36m, 36y, and 36k are cured, forming an output image IMO on the recording medium ME1.

[0145] Through the above process, the irradiation procedure ST2 is carried out.

[0146] By performing the same function as the line printing apparatus 1A, the serial printing apparatus 1B can also reduce poor ejection caused by UV ink curing near the nozzle due to UV leakage from the irradiation section 60.

[0147] It should be noted that in the case of unidirectional printing in which the printing apparatus 1B performs printing only during the main scan in the forward direction D11, the second head 22 and the first irradiation section 60a located from the first head 21 toward the forward direction D11 may not exist in the carriage 52.

[0148] In addition, such as Figure 9 As illustrated, a nozzle 20 may have both a first nozzle array 41 and a second nozzle array 42. Figure 9 This is a top view schematically illustrating the components mounted on the carriage 52 in another serial printing apparatus 1C. The printing apparatus 1C is also included in the concept of printing apparatus 1.

[0149] exist Figure 9 In the nozzle head 20 shown, a second nozzle array 42 is arranged on the downstream side S2 of the first nozzle array 41 in the conveying direction D2. A plurality of irradiation sections 60 are arranged on the downstream side S2 compared to the first nozzle array 41, and include: a first irradiation section 60a, located at a position from the second nozzle array 42 toward the forward direction D11; and a second irradiation section 60b, located at a position from the second nozzle array 42 toward the return direction D12.

[0150] The movement of carriage 52 and recording medium ME1 and Figure 2 The actions shown are the same. For example, in the third main scan, the carriage 52 moves in the forward direction D11. During this movement, the nozzle 20 ejects transparent ink 36CL from the first nozzle array 41 to region A3, and colored inks 36c, 36m, 36y, and 36k from the second nozzle array 42 to region A1. The controller 10 irradiates region A1 with UV light from the second irradiation unit 60b. In the fourth main scan, the carriage 52 moves in the return direction D12. During this movement, the nozzle 20 ejects transparent ink 36CL from the first nozzle array 41 to a region (not shown), and colored inks 36c, 36m, 36y, and 36k from the second nozzle array 42 to region A2. The controller 10 irradiates region A2 with UV light from the first irradiation unit 60a.

[0151] Through with Figure 2 The same as the printing apparatus 1 shown, the serial printing apparatus 1C can also reduce poor ejection caused by UV ink curing near the nozzle due to UV leakage from the irradiation section 60.

[0152] On the other hand, such as Figure 10 As illustrated, the first head 21 and the second head 22 can also be mounted on different carriages. Figure 10 This is a schematic top view illustrating another serial printing apparatus 1D. The printing apparatus 1D is also included in the concept of printing apparatus 1.

[0153] The drive unit 50, which changes the relative position of the ejector head 20 and the recording medium ME1, includes a first carriage drive unit 51a with a first carriage 52a, a second carriage drive unit 51b with a second carriage 52b, and a roller drive unit 55. The second carriage 52b is separate from the first carriage 52a and is located downstream of the first carriage 52a on the S2 side. The first carriage 52a and the second carriage 52b can move independently along the main scanning direction D1. The first carriage drive unit 51a is an example of a first main scanning unit, and the second carriage drive unit 51b is an example of a second main scanning unit.

[0154] A first head 21 with a first nozzle array 41 that ejects transparent ink 36CL is mounted on a first carriage 52a. A first carriage drive unit 51a moves the first carriage 52a along the main scanning direction D1. A second head 22 with a second nozzle array 42 that ejects colored inks 36c, 36m, 36y, and 36k, a first irradiation unit 60a, and a second irradiation unit 60b are mounted on a second carriage 52b. A second carriage drive unit 51b moves the second carriage 52b along the main scanning direction D1. Even when the first nozzle array 41 mounted on the first head 21 of the first carriage 52a is closest to the irradiation unit 60, the distance L1 between the irradiation unit 60 and the first nozzle array 41 is longer than the distance L2 between the irradiation unit 60 and the second nozzle array 42.

[0155] In summary, the first carriage drive unit 51a moves the first carriage 52a upstream of the second carriage 52b along the main scanning direction D1 at a position S1 upstream of the second carriage 52b, and the first head 21 first sprays transparent ink 36CL into regions A1, A2, A3... The second carriage drive unit 51b moves the second carriage 52b downstream of the first carriage 52a along the main scanning direction D1, and the second head 22 delays spraying colored inks 36c, 36m, 36y, 36k into regions A1, A2, A3... Here, when the second carriage 52b is moving in the forward direction D11, the controller 10 turns off the first irradiation unit 60a, and UV light is irradiated from the second irradiation unit 60b into the regions where the colored inks 36c, 36m, 36y, 36k are sprayed. When the second carriage 52b is moving in the return direction D12, the controller 10 turns off the second irradiation unit 60b and irradiates the area where the colored inks 36c, 36m, 36y, and 36k are sprayed from the first irradiation unit 60a with UV light.

[0156] Through with Figure 2 The same as the printing apparatus 1 shown, the serial printing apparatus 1D can also reduce poor ejection caused by UV ink curing near the nozzle due to UV leakage from the irradiation section 60.

[0157] (6) Variation example:

[0158] Various modifications of this invention are possible.

[0159] For example, the color of the second liquid colorant that does not contain a photopolymerization initiator is not limited to C, M, Y, and K, and may also include white, orange, green, light cyan with a concentration lower than C, light magenta with a concentration lower than M, deep yellow with a concentration higher than Y, and light black with a concentration lower than K. Furthermore, this technology can also be applied when the color of the second liquid colorant does not include a portion of C, M, Y, and K. In addition, the color of the second colorant in the first liquid containing a photopolymerization initiator is not limited to blue, and various base colors such as white, C, M, and Y can be used.

[0160] In addition to belt printing, serial printing apparatuses can also perform overlapping printing that partially overlaps between areas, pseudo-belt printing that performs two or more main scans of each area, and interlaced printing that leaves gaps between grids and fills the gaps between grids in subsequent main scans.

[0161] In addition, during sub-scanning, the serial printing apparatus can move the recording medium ME1 in the transport direction D2 and the carriage 52 in the opposite direction to the transport direction D2.

[0162] The printing apparatus can first attach a second liquid, which does not contain a photopolymerization initiator, to the recording medium, and then attach a first liquid to the recording medium. For example, on the carriage 52, a first head 21 can be positioned at a position from the second head 22 with a second nozzle array 42 towards the forward direction D11 and towards the return direction D12, respectively, and an irradiation section 60 can be positioned downstream of the second head 22 at a position S2 such that L1>L2. For example, in the main scan towards the forward direction D11, the second liquid LQ2 is ejected from the second nozzle array 42 of the second head 22, and the first liquid LQ1 is ejected from the first nozzle array 41 of the first head 21 located from the second head 22 towards the return direction D12, so that the first liquid LQ1 overlaps the second liquid LQ2. Even in this case, the photopolymerization initiator of the first liquid LQ1 initiates a polymerization reaction of the polymerizable compound, and the first liquid LQ1 and the second liquid LQ2 solidify.

[0163] It should be noted that when the first liquid LQ1 does not contain a polymerizable compound, the first liquid LQ1 and the second liquid LQ2 will also solidify in an integrated state on the surface ME1a of the recording medium ME1 because the photopolymerization initiator of the first liquid LQ1 initiates the polymerization reaction of the polymerizable compound of the second liquid LQ2.

[0164] (7) Summary:

[0165] As explained above, according to the present invention, by various means, it is possible to provide a technique, etc., to reduce poor spraying caused by the solidification of liquid containing colorant near the nozzle due to light leakage from the irradiation section. Of course, even a technique consisting only of the constituent elements covered by the independent claims can achieve the above-mentioned basic functions and effects.

[0166] Alternatively, configurations can be implemented by substituting or changing the components disclosed in the above examples, or by substituting or changing the components disclosed in the above examples using known technologies. This invention also includes these configurations.

Claims

1. A printing apparatus, characterized in that, have: The ejector head has a first nozzle array and a second nozzle array. The first nozzle array ejects a first liquid toward a recording medium. The first liquid contains a photopolymerization initiator that initiates the polymerization reaction of a polymerizable compound by light irradiation. The second nozzle array ejects a second liquid toward the recording medium. The second liquid does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant. The driving unit causes the relative position of the ejector head and the recording medium to change; as well as The irradiation unit irradiates the recording medium, to which the first liquid and the second liquid are attached, with light. The first liquid and the second liquid are ejected from the nozzle in such a manner that the second liquid overlaps with the first liquid on the surface of the recording medium. The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array. The drive unit changes the relative position of the ejector head with respect to the recording medium in the main scanning direction, and when the first liquid and the second liquid are not ejected from the ejector head onto the recording medium, changes the relative position of the recording medium with respect to the ejector head in a transport direction that intersects the main scanning direction. The conveying direction is set from the upstream side to the downstream side. The irradiation section is disposed on the downstream side compared to the first nozzle array, and is located at a position capable of irradiating the second liquid adhering to the recording medium. The second nozzle array is positioned on the downstream side compared to the first nozzle array. In a single main scan of the ejector head that moves relative to the main scanning direction, the area that the irradiation portion in the recording medium can irradiate includes the area that can eject the second liquid from the second nozzle array, but does not include the area that can eject the first liquid from the first nozzle array.

2. A printing apparatus, characterized in that, have: The ejector head has a first nozzle array and a second nozzle array. The first nozzle array ejects a first liquid toward a recording medium. The first liquid contains a photopolymerization initiator that initiates the polymerization reaction of a polymerizable compound by light irradiation. The second nozzle array ejects a second liquid toward the recording medium. The second liquid does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant. The driving unit causes the relative position of the ejector head and the recording medium to change; as well as The irradiation unit irradiates the recording medium, to which the first liquid and the second liquid are attached, with light. The first liquid and the second liquid are ejected from the nozzle in such a manner that the second liquid overlaps with the first liquid on the surface of the recording medium. The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array. The nozzle includes: a first head having the first nozzle array; and a second head having the second nozzle array. The drive unit includes: a first main scanning unit having a first carriage on which the first head is mounted, and changing the relative position of the first carriage with respect to the recording medium in the main scanning direction; and a second main scanning unit having a second carriage on which the second head is mounted and separate from the first carriage, and changing the relative position of the second carriage with respect to the recording medium in the main scanning direction.

3. The printing apparatus according to claim 1 or 2, wherein, The first liquid contains the polymeric compound. The first nozzle array sprays out the first liquid containing the photopolymerization initiator and the polymerizable compound.

4. The printing apparatus according to claim 1 or 2, wherein, The first liquid contains a second colorant. The first nozzle array sprays out the first liquid containing the photopolymerization initiator and the second colorant.

5. The printing apparatus according to claim 3, wherein, The first liquid contains a second colorant. The first nozzle array sprays out the first liquid containing the photopolymerization initiator and the second colorant.

6. A printing method, characterized in that, This is a printing method in a printing apparatus, the printing apparatus comprising: an ejector head for ejecting a liquid that solidifies upon exposure to light onto a recording medium; a drive unit for changing the relative position of the ejector head and the recording medium; and an irradiation unit for irradiating the recording medium with light, wherein the ejector head has a first nozzle array and a second nozzle array. The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array. The printing method includes: In the ejection process, a first liquid containing a photopolymerization initiator is ejected from the first nozzle array toward the recording medium. The photopolymerization initiator initiates a polymerization reaction of the polymerizable compound by irradiation with light. A second liquid, which does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant, is ejected from the second nozzle array toward the recording medium. The second liquid overlaps with the first liquid on the surface of the recording medium. The irradiation process involves irradiating the recording medium, to which the first liquid and the second liquid are attached, with light. The drive unit changes the relative position of the ejector head with respect to the recording medium in the main scanning direction, and when the first liquid and the second liquid are not ejected from the ejector head onto the recording medium, changes the relative position of the recording medium with respect to the ejector head in a transport direction that intersects the main scanning direction. The conveying direction is set from the upstream side to the downstream side. The irradiation section is disposed on the downstream side compared to the first nozzle array, and is located at a position capable of irradiating the second liquid adhering to the recording medium. The second nozzle array is positioned on the downstream side compared to the first nozzle array. In a single main scan of the ejector head that moves relative to the main scanning direction, the area that the irradiation portion in the recording medium can irradiate includes the area that can eject the second liquid from the second nozzle array, but does not include the area that can eject the first liquid from the first nozzle array.

7. A printing method, characterized in that, This is a printing method in a printing apparatus, the printing apparatus comprising: an ejector head for ejecting a liquid that solidifies upon exposure to light onto a recording medium; a drive unit for changing the relative position of the ejector head and the recording medium; and an irradiation unit for irradiating the recording medium with light, wherein the ejector head has a first nozzle array and a second nozzle array. The distance between the irradiation section and the first nozzle array is longer than the distance between the irradiation section and the second nozzle array. The nozzle includes: a first head having the first nozzle array; and a second head having the second nozzle array. The drive unit includes: a first main scanning unit having a first carriage on which the first head is mounted, and the relative position of the first carriage relative to the recording medium is changed in the main scanning direction; and a second main scanning unit having a second carriage on which the second head is mounted and is separate from the first carriage, and the relative position of the second carriage relative to the recording medium is changed in the main scanning direction. The printing method includes: In the ejection process, a first liquid containing a photopolymerization initiator is ejected from the first nozzle array toward the recording medium. The photopolymerization initiator initiates a polymerization reaction of the polymerizable compound by irradiation with light. A second liquid, which does not contain the photopolymerization initiator but contains the polymerizable compound and a colorant, is ejected from the second nozzle array toward the recording medium. The second liquid overlaps with the first liquid on the surface of the recording medium. The irradiation process involves irradiating the recording medium, to which the first liquid and the second liquid are attached, with light.

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