Ink jet recording device, ink jet recording method, and program

Abstract

To provide an ink jet recording device, an ink jet recording method, and a program, which can reduce density unevenness which can be generated when printing is continuously performed on the same recording medium a plurality of times using active energy ray-curable ink.SOLUTION: An ink jet recording device performs printing on a first surface and printing on a second surface continuously after the printing on the first surface on the same recording medium using active energy ray-curable ink. The first surface and the second surface share a plurality of divided regions where a planar region of the recording medium is arbitrarily divided and fixed. The ink jet recording device includes a control section for controlling ink discharge amount for each divided region of the second surface according to ink discharge amount for each divided region of the first surface and time from the printing on the first surface up to the printing on the second surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus, an inkjet recording method, and a program.

Background Art

[0002] Conventionally, one of the factors that degrades the image quality of inkjet printing is ink bleeding to the back side of the paper. Patent Document 1 discloses a technique for reducing bleeding by changing the ink ejection amount according to the type of image and the degree of bleeding.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when continuously printing on the same recording medium a plurality of times using an active energy ray-curable ink, there is a phenomenon in which heat generation occurs at the ink adhesion portion due to ink curing after active energy ray irradiation during the first printing. As a result, the temperature distribution of the recording medium becomes non-uniform. Since the ink dot diameter after landing changes depending on the temperature even with the same ink ejection amount, there is a problem that an image cannot be formed at the assumed density in the second printing. The method of Patent Document 1 cannot reduce density unevenness caused by non-uniform temperature distribution in the second and subsequent printings.

[0005] The present invention has been made in view of the above circumstances. The problem to be solved by the present invention is to provide an inkjet recording apparatus, an inkjet recording method, and a program capable of reducing density unevenness that may occur when continuously printing on the same recording medium a plurality of times using an active energy ray-curable ink.

Means for Solving the Problem

[0006] The above problems can be solved by the following means.

[0007] 1. An inkjet recording apparatus that performs printing on a first surface and printing on a second surface that is consecutive to the printing on the first surface with respect to the same recording medium, using an active energy ray-curable ink, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing a planar region of the recording medium, and the inkjet recording apparatus includes a control unit that controls the ink ejection amount for each divided region of the second surface according to the ink ejection amount for each divided region of the first surface and the time from the printing on the first surface to the printing on the second surface.

[0008] 2. The inkjet recording apparatus according to item 1, wherein the control unit controls the ink ejection amount for each divided region of the second surface based on a correction value set according to the ink ejection amount for each divided region of the first surface and the time from the printing on the first surface to the printing on the second surface.

[0009] 3. The inkjet recording apparatus according to item 2, wherein the correction value is set according to the type of the recording medium.

[0010] 4. The inkjet recording apparatus according to item 2, wherein the correction value is set according to the basis weight and / or thickness of the recording medium.

[0011] 5. The inkjet recording apparatus according to item 2, wherein the correction value is set according to the type of the ink.

[0012] 6. The inkjet recording apparatus according to item 2, wherein the correction value is set according to the temperature inside the inkjet recording apparatus.

[0013] 7. The inkjet recording apparatus according to item 1, wherein the time from the printing on the first surface to the printing on the second surface is set according to the printing speed.

[0014] 8. The ink is ultraviolet curable, The inkjet recording apparatus according to claim 1, wherein the control unit controls the ink ejection amount for each of the divided regions on the second surface according to the irradiation amount of ultraviolet light.

[0015] 9. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in the main scanning direction.

[0016] 10. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in the sub-scanning direction.

[0017] 11. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in both the main scanning direction and the sub-scanning direction.

[0018] 12. The inkjet recording apparatus according to claim 1, wherein the divided region is a region that is variably divided in both the main scanning direction and the sub-scanning direction according to the ink ejection amount on the first surface.

[0019] 13. The inkjet recording apparatus according to claim 2, wherein the control unit controls the ink ejection amount for each of the divided regions on the second surface by correcting the head drive voltage in the printing on the second surface based on the correction value.

[0020] 14. The inkjet recording apparatus according to claim 2, wherein the control unit controls the ink ejection amount for each of the divided regions on the second surface by correcting the print image data in the printing on the second surface based on the correction value.

[0021] 15. The inkjet recording apparatus according to claim 2, wherein the control unit controls the ink ejection amount for each of the divided regions on the second surface by correcting the ink dot diameter in the printing on the second surface based on the correction value.

[0022] 16. An inkjet recording method in which, using an active energy ray-curable ink, printing on a first surface and printing on a second surface that is consecutive to the printing on the first surface are performed on the same recording medium by an inkjet recording apparatus, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing the planar region of the recording medium, and an inkjet recording method for controlling the ink ejection amount for each of the divided regions of the second surface according to the ink ejection amount for each of the divided regions of the first surface and the time from the printing on the first surface to the printing on the second surface.

[0023] 17. A program for causing a computer of an inkjet recording apparatus that performs printing on a first surface and printing on a second surface that is consecutive to the printing on the first surface on the same recording medium using an active energy ray-curable ink to function as a control unit, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing the planar region of the recording medium, and the control unit controls the ink ejection amount for each of the divided regions of the second surface according to the ink ejection amount for each of the divided regions of the first surface and the time from the printing on the first surface to the printing on the second surface.

Advantages of the Invention

[0024] By the above means of the present invention, it is possible to provide an inkjet recording apparatus, an inkjet recording method, and a program that can reduce density unevenness that may occur when continuously printing a plurality of times on the same recording medium using an active energy ray-curable ink.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0026] Hereinafter, with reference to the drawings, some embodiments of the present invention will be described. The features and technical effects of the embodiments will be understood from the following detailed description and the drawings. However, the scope of the present invention is not limited to the embodiments disclosed below. Since the drawings are provided for illustrative purposes only, the scope of the present invention is not limited to the illustrations in the drawings.

[0027] FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of an inkjet recording apparatus 1.

[0028] The inkjet recording apparatus 1 of the present embodiment includes a medium supply unit 10, a recording main body unit 20, a medium discharge unit 30, and a control unit 40. In the inkjet recording apparatus 1, based on the control by the control unit 40, the recording medium M stored in the medium supply unit 10 is conveyed to the recording main body unit 20. Thereafter, an image is recorded on the recording medium M in the recording main body unit 20. Thereafter, the recording medium M is discharged to the medium discharge unit 30.

[0029] The medium supply unit 10 conveys the recording media M stored therein one by one to the recording main body unit 20. The medium supply unit 10 includes a supply tray 11 and a feeder board 12.

[0030] The type of the recording medium M is not particularly limited, and can be, for example, plain paper, coated paper, art paper, inkjet special paper, inkjet glossy paper, cardboard, wood, plastic, glass, metal, etc. The basis weight and thickness of the recording medium M are not particularly limited. In the case of the embodiment shown in FIG. 1, as the recording medium M, various types that can be curved and supported on the outer peripheral surface of the image recording drum 21 are used.

[0031] The supply tray 11 is a plate-like member provided so as to be able to place one or a plurality of recording media M. The supply tray 11 stores the recording media M. The supply tray 11 is provided so as to move up and down according to the amount of the recording media M placed on the supply tray 11. The supply tray 11 is held at a position in the vertical direction where the uppermost recording medium M is conveyed by the feeder board 12.

[0032] The feeder board 12 has a supply unit (not shown) that delivers the uppermost recording medium M placed on the supply tray 11 onto the belt 123. The feeder board 12 drives the annular belt 123 to convey the recording medium M on the belt 123. The belt 123 is supported by two rollers 121 and 122. The feeder board 12 conveys the recording medium M delivered onto the belt 123 by the supply unit along the belt 123.

[0033] The recording main body 20 includes an image recording drum 21, a delivery unit 22, a head unit 24, an irradiation unit 25, an image reading unit 28, a delivery unit 26, and a reversing unit 27.

[0034] The image recording drum 21 has a cylindrical outer shape. The image recording drum 21 carries, for example, up to three recording media M on its outer peripheral surface. The image recording drum 21 conveys the recording media M in accordance with a rotational operation with respect to the central axis of the cylinder. Ink is ejected from each nozzle of the head unit 24 at a position on the recording media M carried on the image recording drum 21 that faces the head unit 24. As a result, an image before curing is formed on the surface of the recording media M opposite to the contact surface with the image recording drum 21. The image is an image formed on the recording media M by ink and includes, for example, characters, patterns, photographic images, etc.

[0035] The delivery unit 22 delivers the recording media M received from the media supply unit 10 to the image recording drum 21. The delivery unit 22 has a swing arm unit 221 and a cylindrical delivery drum 222. The swing arm unit 221 holds one end of the recording media M conveyed by the feeder board 12. The delivery drum 222 delivers the recording media M held by the swing arm unit 221 to the image recording drum 21. The delivery drum 222 may be provided with a heater inside or outside. Thereby, the delivery drum 222 can heat the recording media M before the ink is applied to adjust the temperature of the recording media M.

[0036] The head unit 24 includes one or more inkjet heads 240. In the embodiment shown in FIG. 1, four inkjet heads 240 are arranged at a predetermined interval in the conveyance direction of the recording media M. The four inkjet heads 240 correspond to the four colors of ink: C (cyan), M (magenta), Y (yellow), and K (black). The arrangement order of these inkjet heads 240 may be determined as appropriate.

[0037] FIG. 2 is a bottom view of the ink ejection surface side of the inkjet head 240. The inkjet head 240 shown in FIG. 2 is a line head capable of recording an image by a single-pass method. The head unit 24 has a plurality of, here eight, inkjet heads 240 each, and fixes and holds these inkjet heads 240 to a support member. In the head chip 241 located on the bottom surface of each inkjet head 240, openings of a plurality of nozzles N for ejecting ink are arranged side by side. The array range of the nozzles N in each inkjet head 240 extends over the entire recordable width on the recording medium M in the X direction orthogonal to the conveyance direction (Y direction). As shown in FIG. 2, the array range of the nozzles N in the X direction may have an overlapping portion between different inkjet heads 240. The nozzles N of each inkjet head 240 are located above four columns. The four columns are arranged in the Y direction and extend in the X direction. The positions of the nozzles N above each column are shifted from each other by 1 / 4 of the interval between the nozzles N in each column. Therefore, the nozzles N are arranged continuously in the X direction at a predetermined interval as a whole.

[0038] The head unit 24 is attached to a support portion (not shown). The head unit 24 ejects ink droplets from the nozzles N at an appropriate timing with respect to the recording medium M that moves in accordance with the rotation of the image recording drum 21.

[0039] The ink used in the inkjet recording apparatus of the present disclosure is an active energy ray curable type. The active energy ray curable type refers to a property of being cured by being irradiated with a predetermined active energy ray. For example, an ink that is an ultraviolet curable type is cured by being irradiated with ultraviolet rays. The ink that is an active energy ray curable type contains a coloring material, a curable monomer, a polymerization initiator, a gelling agent, a solvent, and the like.

[0040] As long as the ink is of the active energy ray curable type, the types of the ink components, the content of each component, etc. are not particularly limited. The types of inks distinguished by the types of the ink components, the content of each component, etc. are usually the same for the printing on the first side and the printing on the second side, but they may not be the same.

[0041] The ink may be appropriately heated and maintained at a suitable temperature inside and / or outside the head unit 24 by a heater (not shown) or the like, if necessary.

[0042] The irradiation unit 25 irradiates the ink on the recording medium M with active energy rays. The irradiation unit 25 is provided between the head unit 24 and the image reading unit 28. The ink irradiated with the active energy rays is cured and fixed on the recording medium M. Thereby, one-time printing is completed. The irradiation unit 25 may be provided with a light shielding wall (not shown) or the like for blocking the leakage of active energy rays to the outside of a desired irradiation range, if necessary.

[0043] The active energy ray is a radiation that can impart energy capable of generating reaction initiation species such as polymerization reactions in the ink by its irradiation. The active energy rays are, for example, α-rays, γ-rays, X-rays, ultraviolet rays, electron beams, etc. As the active energy rays, ultraviolet rays and electron beams are preferable, and ultraviolet rays are more preferable. The irradiation unit 25 that irradiates ultraviolet rays has, for example, a light emitting diode (LED), a mercury lamp, etc.

[0044] The irradiation amount of the active energy rays is not particularly limited, and may be set according to, for example, the type of the ink, the discharge amount, etc. The irradiation amount of the active energy rays is usually the same for the printing on the first side and the printing on the second side, but they may not be the same.

[0045] The image reading unit 28 irradiates light from a light source onto the printing surface and reads the reflected image. The image reading unit 28 is composed of, for example, an in-line sensor in which a plurality of detection elements are arranged along a direction (width direction) orthogonal to the conveyance direction of the recording medium M. The data of the image read by the image reading unit 28 is sent to the control unit 40.

[0046] The delivery unit 26 includes a selection roller 261, a transfer roller 262, two rollers 263 and 264, and a belt 265. The belt 265 is annular and supported by the rollers 263 and 264 on its inner surface.

[0047] The selection roller 261, according to the printing conditions, either leaves the recording medium M placed on the image recording drum 21 or retrieves the recording medium M from the image recording drum 21.

[0048] When printing again on the same surface of the recording medium M following the previous printing, the selection roller 261 leaves the recording medium M placed on the image recording drum 21 without retrieving it. In this case, the recording medium M is conveyed to the supply side and proceeds to the printing process again.

[0049] When printing on the opposite surface of the recording medium M following the previous printing, or when no more printing is to be performed, the selection roller 261 retrieves the recording medium M from the image recording drum 21 and transfers it to the transfer roller 262.

[0050] When printing on the opposite surface of the recording medium M following the previous printing, the transfer roller 262 transfers the recording medium M received from the selection roller 261 to the reversing drum 271 of the reversing unit 27.

[0051] The reversing unit 27 includes a reversing drum 271 and a reversing swing device 272. The reversing swing device 272 is provided at a position equidistant from the outer peripheral surface of the reversing drum 271 and the outer peripheral surface of the image recording drum 21 respectively. When the trailing end of the recording medium M on the reversing drum 271 in the conveyance direction reaches the opposing position of the reversing swing device 272, the reversing swing device 272 grips the trailing end. Next, the reversing swing device 272 guides the recording medium M along the outer peripheral surface of the image recording drum 21. As a result, the recording medium M is reversed so that the previously printed surface contacts the outer peripheral surface of the image recording drum 21. The reversed recording medium M is conveyed by the image recording drum 21 from the upstream side in the conveyance direction than the head unit 24. At this time, the trailing end of the recording medium M in the previous printing becomes the leading end in the conveyance direction in the next printing. In this way, the reversing unit 27 reverses the front and back of the recording medium M and places the recording medium on the outer peripheral surface of the image recording drum 21.

[0052] When no more printing is performed, the delivery roller 262 delivers the recording medium M received from the selection roller 261 to the belt 265. The belt 265 moves circularly as the rollers 263 and 264 rotate, conveys the recording medium M received from the selection roller 261, and sends it out to the medium discharge unit 30.

[0053] The medium discharge unit 30 has a plate-shaped discharge tray 31. The recording medium M sent out from the recording main body unit 20 is placed on the discharge tray 31 and stored in the medium discharge unit 30 until it is taken out by the user.

[0054] The control unit 40 will be described later.

[0055] FIG. 3 is a block diagram showing the functional configuration of an embodiment of the inkjet recording apparatus 1.

[0056] The inkjet recording apparatus 1 of the present embodiment includes a control unit 40, a conveyance unit 41, a head unit 24, an irradiation unit 25, an image reading unit 28, a display unit 42, an operation reception unit 43, a communication unit 44, and a bus 45.

[0057] The control unit 40 controls the operations of the medium supply unit 10, the recording main body unit 20, and the medium discharge unit 30 according to the print image data and the print settings. The control unit 40 includes a CPU (Central Processing Unit) 401, a RAM (Random Access Memory) 402, a ROM (Read Only Memory) 403, and a storage unit 404. The CPU 401 executes various control programs to drive and control the inkjet recording apparatus 1 and performs various arithmetic processes. The RAM 402 provides a working memory space for the CPU 401 and stores temporary data. The RAM 402 may include a non-volatile memory. The ROM 403 stores various control programs, setting data, etc. to be executed by the CPU 401. A rewritable non-volatile memory such as a flash memory may be used instead of the ROM 403. The storage unit 404 stores programs executed by the CPU 401, various setting data, etc. As the storage unit 404, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) etc. may be used in combination.

[0058] The conveyance unit 41 is a motor that drives each part that operates to move the recording medium M. The conveyance unit 41 operates each part that operates to move the recording medium M at an appropriate timing based on a control signal sent from the control unit 40.

[0059] The head unit 24 includes the above-described head chip etc. Piezoelectric elements (electromechanical conversion elements) are provided along the ink flow paths communicating with the respective nozzles in the head chip. Based on a control signal sent from the control unit 40, the waveform of the voltage signal applied to the piezoelectric element is controlled. According to this waveform, the piezoelectric element deforms and the pressure on the ink fluctuates. Due to this pressure fluctuation, the ink is ejected from the nozzle.

[0060] The irradiation unit 25 irradiates active energy rays based on a control signal sent from the control unit 40. In the irradiation unit 25, the irradiation timing, irradiation time, irradiation intensity, etc. of the active energy rays can be controlled.

[0061] The image reading unit 28 reads the image data of the printing surface and sends this image data to the control unit 40. The control unit 40 can create a correction table based on the image data sent from the image reading unit 28, for example, in the process of creating the correction table.

[0062] The display unit 42 displays various statuses, menus, etc. on the display screen based on a control signal sent from the control unit 40. The display unit 42 has, for example, a display screen, an LED lamp, etc. The display screen is not particularly limited, but is, for example, an LCD (Liquid Crystal Display). In the LED lamp, for example, lamps of positions and colors corresponding to each situation are lit according to the power supply situation, the occurrence situation of an abnormality, etc.

[0063] The operation reception unit 43 receives an input operation by a user or the like from the outside and outputs this as an input signal to the control unit 40. The operation reception unit 43 has, for example, a touch panel, a push button switch, etc. The touch panel may be positioned overlapping the display screen of the display unit 42. The operation reception unit 43 may also have various other operation switches, etc.

[0064] The communication unit 44 controls the transmission and reception of data (signals) with external devices, etc. according to a predetermined communication standard. The communication unit 44 controls communication, for example, according to the standard of a LAN (Local Area Network). The communication unit 44 may also be connectable to peripheral devices according to a standard such as USB (Universal Serial Bus).

[0065] The bus 45 is a path for transmitting and receiving signals between the control unit 40 and other functional configurations.

[0066] Each functional component may operate based on a control signal transmitted from a processor (such as a CPU) separate from the control unit 40 respectively.

[0067] Next, a method for controlling the ink ejection amount in the inkjet recording apparatus 1 of the present disclosure will be described.

[0068] The inkjet recording apparatus 1 of the present disclosure performs printing on the first surface and printing on the second surface that is consecutive after the printing on the first surface on the same recording medium M. The inkjet recording apparatus 1 uses an active energy ray curable ink. Specifically, the inkjet recording apparatus 1 uses an active energy ray curable ink at least in the printing on the first surface. The printing on the first surface includes active energy ray irradiation. It is preferable that the same active energy ray curable ink is used in the printing on the second surface as in the printing on the first surface, and the printing on the second surface includes active energy ray irradiation.

[0069] The relationship between the printing on the first surface and the printing on the second surface may be double-sided printing where the first surface and the second surface are opposite surfaces of the recording medium M. The relationship between the printing on the first surface and the printing on the second surface may be overprinting where the first surface and the second surface are the same surface of the recording medium M.

[0070] Figures 4A to 4C are diagrams illustrating the printing on the first surface and the printing on the second surface. Here, the character "A" is printed in white on the first surface, and the character "B" is printed in black on the second surface. Figure 4A is a view of the first surface of the recording medium M when only the printing on the first surface is performed, viewed from above. Figure 4B is a view of the second surface of the recording medium M when the printing on the first surface and the printing on the second surface are performed by double-sided printing, viewed from above. Figure 4C is a view of the first surface and the second surface of the recording medium M when the printing on the first surface and the printing on the second surface are performed by overprinting, viewed from above.

[0071] The inkjet recording apparatus 1 may perform printing other than the printing on the first surface and the printing on the second surface on the same recording medium M. In this case, any two consecutive printings among the multiple printings are defined as "printing on the first surface" and "printing on the second surface".

[0072] The first surface and the second surface according to the present disclosure share a plurality of divided regions defined by arbitrarily dividing the planar region of the recording medium M. Each divided region exists on both the front and back sides of the recording medium M. It can be said that the divided regions at the same position on the front and back surfaces of the recording medium M are the same divided region.

[0073] The method of defining the divided regions is not particularly limited. The divided regions are defined, for example, as follows.

[0074] FIG. 5 is an example of the print image data of the first surface. In the print image data, there are portions with a large ink ejection amount such as the photo portion 51 and the decorative frame portion 52, portions with a small ink ejection amount such as the character portion 53, and portions where no ink is ejected. FIGS. 6 to 9 are examples of dividing the planar region of the recording medium M on which the first surface shown in FIG. 5 is printed. The broken lines in FIGS. 6 to 9 represent the boundaries of the respective divided regions.

[0075] As shown in FIG. 6, the divided region may be a region divided in the main scanning direction X. The division can be made in any number and width. At this time, as shown in FIG. 6, the planar region of the recording medium M may be divided so as to correspond to the print ranges of the respective inkjet heads 240 arranged in the main scanning direction X, and the divided regions a1 to a8 may be defined.

[0076] As shown in FIG. 7, the divided region may be a region divided in the sub-scanning direction Y. The division can be made in any number and width.

[0077] As shown in FIG. 8, the divided region may be a region divided in both the main scanning direction X and the sub-scanning direction Y. The division can be made in any number and width.

[0078] As shown in FIG. 9, the divided area may be an area that is variably divided in both the main scanning direction X and the sub-scanning direction Y according to the ink ejection amount on the first surface. Thereby, the inkjet recording apparatus 1 can, for example, divide a portion with a large ink ejection amount and a portion with a small ink ejection amount on the first surface into different divided areas while reducing the number of divided areas. Thereby, the inkjet recording apparatus 1 can more accurately control the ink ejection amount for each divided area on the second surface while suppressing the number of control operations in some cases.

[0079] The inkjet recording apparatus 1 of the present disclosure controls the ink ejection amount for each divided area on the second surface according to the factors that affect the temperature for each divided area during printing on the second surface.

[0080] The temperature of the ink landing position affects the degree of spread of the ink that has landed at that position. For example, when the temperature of the landing position is high, the ink tends to spread widely. Therefore, when the temperature for each divided area is different during printing on the second surface, the degree of spread of the ink will be different for each divided area. In this case, for example, even with the same ejection amount, problems such as non-uniform ink dot diameters in each divided area will occur. Thus, when the temperature for each divided area is different during printing on the second surface, an image with the assumed density cannot be formed on the second surface by the conventional method, and density unevenness will occur. In contrast, in the inkjet recording apparatus 1 of the present disclosure, the control unit 40 controls the ink ejection amount for each divided area on the second surface according to the factors that affect the temperature for each divided area during printing on the second surface. Thereby, the inkjet recording apparatus 1 of the present disclosure can easily control the ink dot diameter in printing on the second surface to the assumed size, and can reduce density unevenness in printing on the second surface.

[0081] Examples of the factors that affect the temperature for each divided area during printing on the second surface include the following. · The ink ejection amount for each divided area on the first surface · The time from printing on the first surface to printing on the second surface · The irradiation amount of the active energy ray in printing on the first surface · The type of the recording medium · The basis weight of the recording medium · The thickness of the recording medium · Type of ink in the printing of the first side · Internal temperature of the inkjet recording device

[0082] [Ink ejection amount for each divided area of the first side] Figure 10 is a graph illustrating the temperature transition of the ink after landing in the printing of the first side. The vertical axis of the graph is the temperature of the ink after landing. The horizontal axis of the graph is the elapsed time since landing. First, the temperature of the landed ink decreases as the heat of the ink is taken away by the recording medium, air, the atmosphere inside the device, etc. While the temperature of the ink is decreasing or after it has decreased, the ink is cured by irradiation with active energy rays. Due to the heat (curing heat) associated with this curing reaction, the temperature of the ink during the curing reaction rises. The larger the ink dot diameter, the greater the curing heat. When the curing reaction ends, the temperature of the ink decreases again as the heat of the ink is taken away by the recording medium, air, the atmosphere inside the device, etc. The rates of these temperature changes differ depending on the dot diameter of the ink, as shown in the graph. The larger the dot diameter, the slower the temperature change of the ink contained in that dot tends to be. The larger the dot diameter becomes in the divided area with a larger ink ejection amount. The temperature of each divided area in the printing of the second side becomes higher as the temperature of the ink on the first side in that divided area is higher. In this way, the ink ejection amount for each divided area of the first side affects the temperature for each divided area during the printing of the second side. For example, when the printing of the second side starts at a timing when the temperature of the ink with a large dot diameter, like the graph in Figure 10, has not completely dropped, the temperature for each divided area during the printing of the second side will be different.

[0083] The inkjet recording device 1 of the present disclosure can reduce density unevenness, for example, in a divided area with a large ink ejection amount on the first side, by reducing the ink ejection amount on the second side compared to a divided area with a small ink ejection amount on the first side.

[0084] [Time from the printing of the first side to the printing of the second side] As can be seen from the graph shown in FIG. 10, the temperature difference due to the difference in the ink dot diameter on the first surface changes depending on the elapsed time since the printing of the first surface. Therefore, the time from the printing of the first surface to the printing of the second surface affects the temperature of each divided area at the time of printing the second surface. The "time from the printing of the first surface to the printing of the second surface" refers to the time from the end of the active energy ray irradiation in the printing of the first surface to the start of the ink ejection in the printing of the second surface. The time from the printing of the first surface to the printing of the second surface is set according to, for example, the printing speed. In the case of the embodiment shown in FIG. 1, the time from the printing of the first surface to the printing of the second surface is set according to the printing speed determined by the rotation speed of the image recording drum 21 or the like, for example.

[0085] For example, when the time from the printing of the first surface to the printing of the second surface is short, the ink ejection amount for each control area on the second surface is controlled so that the correction width becomes larger than when the time is long.

[0086] [Irradiation amount of active energy rays in the printing of the first surface] The overall temperature of the ink on the first surface and the temperature difference due to the difference in the ink dot diameter on the first surface change depending on the irradiation amount of the active energy rays in the printing of the first surface. Therefore, the irradiation amount of the active energy rays in the printing of the first surface affects the temperature of each divided area at the time of printing the second surface. For example, when the ink is ultraviolet curable and ultraviolet rays are irradiated in the printing of the first surface, the overall temperature of the ink on the first surface and the temperature difference due to the difference in the ink dot diameter on the first surface change depending on the irradiation amount of the ultraviolet rays in the printing of the first surface.

[0087] For example, when the irradiation amount of the active energy rays in the printing of the first surface is large, the ink ejection amount for each control area on the second surface is controlled so that the correction width becomes larger than when the irradiation amount is small.

[0088] [Type, basis weight, and thickness of the recording medium] Depending on the type, basis weight, and thickness of the recording medium M, the rate of temperature change of the ink on the first surface varies. When the type of the recording medium M has a relatively low thermal conductivity, such as coated paper for example, the rate of temperature change of the ink on the first surface tends to be slow. Also, the greater the basis weight of the recording medium M, or the greater the thickness of the recording medium M, the more the rate of temperature change of the ink on the first surface tends to be slow. Therefore, the type, basis weight, and thickness of the recording medium M each affect the temperature for each divided area during printing on the second surface.

[0089] For example, when using a recording medium M with a low thermal conductivity due to its type, basis weight, and thickness, the ink ejection amount for each control area on the second surface is controlled so that the correction width becomes larger compared to the case of using a recording medium M with a high thermal conductivity.

[0090] [Type of Ink in Printing on the First Surface] The type of ink in printing on the first surface can be distinguished, for example, by the type of ink components, the content of each component, etc. Due to the type of these ink components, the content of each component, etc., the amount of curing heat differs. Therefore, the type of ink in printing on the first surface affects the temperature for each divided area during printing on the second surface.

[0091] For example, when using an ink with a large amount of curing heat in printing on the first surface, the ink ejection amount for each control area on the second surface is controlled so that the correction width becomes larger compared to the case of using an ink with a small amount of curing heat.

[0092] [Internal Temperature of the Inkjet Recording Apparatus] Depending on the internal temperature of the inkjet recording apparatus 1, the rate of temperature change of the ink on the first surface varies. Therefore, the internal temperature of the inkjet recording apparatus 1 affects the temperature for each divided area during printing on the second surface.

[0093] For example, when the internal temperature of the inkjet recording apparatus 1 is high, the ink ejection amount for each control area on the second surface is controlled so that the correction width becomes larger compared to the case when the internal temperature is low.

[0094] In the control of the ink ejection amount for each divided area during printing on the second side, among the above elements, the ink ejection amount for each divided area on the first side and the time from printing on the first side to printing on the second side are particularly important. The control unit 40 in the inkjet recording apparatus 1 of the present disclosure controls the ink ejection amount for each divided area on the second side according to at least these two elements. Thereby, the inkjet recording apparatus 1 of the present disclosure can easily control the size assuming the ink dot diameter in printing on the second side, and can reduce density unevenness in printing on the second side.

[0095] In addition to the ink ejection amount for each divided area on the first side and the time from printing on the first side to printing on the second side, the control unit 40 may control the ink ejection amount for each divided area on the second side according to the above elements other than these. Thereby, the inkjet recording apparatus 1 of the present disclosure can be more easily controlled to the size assuming the ink dot diameter in printing on the second side, and can further reduce density unevenness in printing on the second side.

[0096] The control of the ink ejection amount for each divided area on the second side is preferably based on a correction value set according to elements that affect the temperature for each divided area during printing on the second side. For example, it is preferable that the control is based on a correction value set according to the ink ejection amount for each divided area on the first side and the time from printing on the first side to printing on the second side. The correction value may be set according to the above elements other than the ink ejection amount for each divided area on the first side and the time from printing on the first side to printing on the second side.

[0097] The correction value is a value for correcting setting data for controlling the ink ejection amount for each divided area on the second side. The setting data for controlling the ink ejection amount for each divided area on the second side is, for example, the head drive voltage, print image data, ink dot diameter, etc. in printing on the second side. By correcting these setting data based on the correction value, the ink ejection amount for each divided area on the second side is controlled more accurately.

[0098] As an example, the case of correcting the head driving voltage in the printing of the second surface based on a correction value will be described with reference to FIG. 6. Among the divided regions a1 to a8 in FIG. 6, the divided regions a5 to a7 have a larger ink ejection amount on the first surface than the other divided regions. In the divided regions a1 to a8 where the ink ejection amount on the first surface is large, the curing heat is large and the temperature change is slow. Therefore, when printing the second surface, the temperature of the divided regions a1 to a8 becomes higher than the temperature of the other divided regions. Since the dot diameter of the ink expands and becomes larger as the temperature of the landing position is higher, the dot diameter of the ink landing on the divided regions a1 to a8 becomes relatively large. In order to suppress such a relative change in the ink dot diameter on the second surface depending on the landing position, the inkjet recording apparatus 1 of the present disclosure sets, for example, a correction value of the head driving voltage. The temperature for each divided region during the printing of the second surface also varies greatly depending on the time from the printing of the first surface to the printing of the second surface. Therefore, the correction value is set according to at least the ink ejection amount for each divided region of the first surface and the time from the printing of the first surface to the printing of the second surface. In this case, the correction value is, for example, to make the head driving voltage for printing the divided regions a5 to a7 lower than the head driving voltage for printing the other divided regions. Thereby, the ink ejection amount of the divided regions a5 to a7 on the second surface is controlled to be relatively small. As a result, the ink dot diameter in the printing of the second surface is controlled to the assumed size, and the density unevenness in the printing of the second surface is reduced.

[0099] The correction value can be obtained, for example, from a correction table created in advance. FIG. 11 is a flowchart showing an example of the flow of creating the correction table.

[0100] In step S11, the control unit 40 acquires data necessary for creating a correction table, which is input to the inkjet recording apparatus 1. The data necessary for creating the correction table is selected, for example, from elements that affect the temperature for each divided area during printing of the second side as described above. In the present disclosure, at least the ink ejection amount for each divided area of the first side and the time from printing of the first side to printing of the second side are required. In addition to the ink ejection amount for each divided area of the first side and the time from printing of the first side to printing of the second side, if necessary, the irradiation amount of the active energy ray during printing of the first side, the type of the recording medium M, the basis weight of the recording medium M, the thickness of the recording medium M, the type of ink during printing of the first side, the internal temperature of the inkjet recording apparatus, etc. are input to the inkjet recording apparatus 1.

[0101] In step S12, the recording main body unit 20 is driven and controlled by the control unit 40 to print a correction chart. The correction chart is a chart for confirming the ink dot diameter when actually printed under each condition. In step S12, double-sided printing or overprinting is performed as necessary.

[0102] In step S13, the control unit 40 creates a correction table based on the correction chart. Specifically, the control unit 40 obtains the ink dot diameter from the image density of the correction chart, and based on this ink dot diameter, obtains a correction value for controlling the ink ejection amount of the second side. Next, the control unit 40 arranges this correction value to create a correction table.

[0103] FIG. 12 is a flowchart showing an example of the flow of the inkjet recording method using the inkjet recording apparatus 1.

[0104] In step S21, the control unit 40 acquires the data necessary for inkjet recording that has been input to the inkjet recording apparatus 1. The data necessary for inkjet recording includes the print image data for the first side, the print image data for the second side, print conditions, correction tables, and the like. The print conditions include the print speed, the irradiation amount of the active energy ray, the type of the recording medium M, the basis weight of the recording medium M, the thickness of the recording medium M, the type of ink, the internal temperature of the inkjet recording apparatus 1, and the like. These data may be received and input from an external device. According to these data, the ink ejection amount for each divided area of the first side is set.

[0105] In step S22, the control unit 40 acquires the measured value of the actual print speed measured by operating the conveyance unit 41 of the inkjet recording apparatus 1. According to the acquired print speed, the time from the printing of the first side to the printing of the second side is set.

[0106] In step S23, the control unit 40 acquires correction values necessary for controlling the ink ejection amount for each divided area of the second side, for example, from a correction table created in advance.

[0107] In step S24, the control unit 40 corrects the setting data for controlling the ink ejection amount for each divided area of the second side. The setting data is corrected based on the various data input or set in steps S21 and S22 and the correction values acquired in step S23. The setting data to be corrected is, for example, the head drive voltage in the printing of the second side, the print image data, the ink dot diameter, and the like.

[0108] In step S25, the recording main body unit 20 is driven and controlled by the control unit 40, and the first side is printed based on the print image data of the first side input in step S21. Step S25 includes a step of ejecting ink onto the recording medium M and a step of curing the ink landed on the recording medium M by irradiation with an active energy ray.

[0109] In step S26, the recording main body 20 is driven and controlled by the control unit 40 to print the second side based on the print image data of the second side input in step S21. Step S26 includes a step of discharging ink onto the recording medium M and a step of curing the ink landed on the recording medium M by irradiation with active energy rays. In the step of discharging ink onto the recording medium M, the ink discharge amount for each divided area of the second side is controlled based on the set data corrected in step 24.

[0110] The flowchart shown in FIG. 12 is an example, and the flow of the inkjet recording method is not limited thereto. For example, the correction of the set data in step 24 may be performed in parallel with the printing of the first side in step 25, or may be performed after the printing of the first side in step 25.

[0111] As described above, the inkjet recording apparatus of the present disclosure performs printing on the first side and printing on the second side that is continuous after the printing on the first side with respect to the same recording medium. The inkjet recording apparatus uses an active energy ray curable ink. The first side and the second side share a plurality of divided areas defined by arbitrarily dividing the planar area of the recording medium. The inkjet recording apparatus of the present disclosure includes a control unit that controls the ink discharge amount for each divided area of the second side according to the ink discharge amount for each divided area of the first side and the time from the printing of the first side to the printing of the second side. Thereby, density unevenness on the second side is reduced.

[0112] The control unit may control the ink discharge amount for each divided area of the second side based on a correction value set according to the ink discharge amount for each divided area of the first side and the time from the printing of the first side to the printing of the second side. Thereby, the ink discharge amount for each divided area of the second side is controlled more accurately.

[0113] The correction value may be set according to the type of the recording medium. Thereby, the ink discharge amount for each divided area of the second side is controlled more accurately.

[0114] The correction value may be set according to the basis weight and / or thickness of the recording medium. Thereby, the ink ejection amount for each divided area on the second surface is controlled more accurately.

[0115] The correction value may be set according to the type of ink. Thereby, the ink ejection amount for each divided area on the second surface is controlled more accurately.

[0116] The correction value may be set according to the internal temperature of the inkjet recording apparatus. Thereby, the ink ejection amount for each divided area on the second surface is controlled more accurately.

[0117] The time from printing on the first surface to printing on the second surface may be set according to the printing speed. Thereby, the ink ejection amount for each divided area on the second surface is controlled more accurately.

[0118] The ink may be ultraviolet curable. At this time, the control unit may control the ink ejection amount for each divided area on the second surface according to the irradiation amount of ultraviolet light. Thereby, the ink ejection amount for each divided area on the second surface is controlled more accurately.

[0119] The divided area may be an area divided in the main scanning direction.

[0120] The divided area may be an area divided in the sub-scanning direction.

[0121] The divided area may be an area divided in both the main scanning direction and the sub-scanning direction.

[0122] The divided area may be an area that is variably divided in both the main scanning direction and the sub-scanning direction according to the ink ejection amount on the first surface. Thereby, the control unit can, for example, divide a portion with a large ink ejection amount and a portion with a small ink ejection amount on the first surface into different divided areas while reducing the number of divided areas. Thereby, the control unit can more accurately control the ink ejection amount for each divided area on the second surface while suppressing the number of control operation times in some cases.

[0123] The control unit may control the ink ejection amount for each divided area on the second surface by correcting the head drive voltage in the printing of the second surface based on the correction value.

[0124] The control unit may control the ink ejection amount for each divided area on the second surface by correcting the print image data in the printing of the second surface based on the correction value.

[0125] The control unit may control the ink ejection amount for each divided area on the second surface by correcting the ink dot diameter in the printing of the second surface based on the correction value.

[0126] The inkjet recording method of the present disclosure performs printing on a first surface and printing on a second surface consecutive to the printing on the first surface on the same recording medium by an inkjet recording apparatus. The inkjet recording method uses an active energy ray curable ink. The first surface and the second surface share a plurality of divided areas defined by arbitrarily dividing the planar area of the recording medium. The inkjet recording method controls the ink ejection amount for each divided area on the second surface according to the ink ejection amount for each divided area on the first surface and the time from the printing on the first surface to the printing on the second surface. Thereby, density unevenness on the second surface is reduced.

[0127] The program of the present disclosure causes a computer of an inkjet recording apparatus to function as a control unit. The inkjet recording apparatus performs printing on a first surface and printing on a second surface consecutive to the printing on the first surface on the same recording medium using an active energy ray curable ink. The first surface and the second surface share a plurality of divided areas defined by arbitrarily dividing the planar area of the recording medium. The control unit controls the ink ejection amount for each divided area on the second surface according to the ink ejection amount for each divided area on the first surface and the time from the printing on the first surface to the printing on the second surface.

Description of Reference Numerals

[0128] 1 Inkjet recording apparatus 10 Medium supply unit 11 Supply tray 12 Feeder board 121 and 122 Rollers 123 Belt 20 Recording main body part 21 Image recording drum 22 Delivery unit 221 Swing arm part 222 Delivery drum 24 Head unit 240 Inkjet head 241 Head chip 25 Irradiation part 26 Delivery part 261 Selection roller 262 Delivery roller 263 and 264 Rollers 265 Belt 27 Reversal part 271 Reversal drum 272 Reversal swing device 28 Image reading part 30 Media discharge part 31 Discharge tray 40 Control part 401 CPU 402 RAM 403 ROM 404 Memory part 41 Conveying part 42 Display part 43 Operation reception part 44 Communication part 45 Bus M Recording medium

Claims

1. An inkjet recording apparatus that performs printing on a first surface and printing on a second surface that is consecutive to the printing on the first surface on the same recording medium using an active energy ray-curable ink, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing a planar region of the recording medium, and the inkjet recording apparatus includes a control unit that controls the ink ejection amount for each divided region of the second surface according to the ink ejection amount for each divided region of the first surface and the time from the printing on the first surface to the printing on the second surface.

2. The inkjet recording apparatus according to claim 1, wherein the control unit controls the ink ejection amount for each divided region of the second surface based on a correction value set according to the ink ejection amount for each divided region of the first surface and the time from the printing on the first surface to the printing on the second surface.

3. The inkjet recording apparatus according to claim 2, wherein the correction value is set according to the type of the recording medium.

4. The inkjet recording apparatus according to claim 2, wherein the correction value is set according to the basis weight and / or thickness of the recording medium.

5. The inkjet recording apparatus according to claim 2, wherein the correction value is set according to the type of the ink.

6. The inkjet recording apparatus according to claim 2, wherein the correction value is set according to the temperature inside the inkjet recording apparatus.

7. The inkjet recording apparatus according to claim 1, wherein the time from the printing on the first surface to the printing on the second surface is set according to the printing speed.

8. The ink is ultraviolet curable, and the control unit controls the ink ejection amount for each divided region of the second surface according to the amount of ultraviolet irradiation. The inkjet recording apparatus according to claim 1.

9. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in the main scanning direction.

10. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in the sub-scanning direction.

11. The inkjet recording apparatus according to claim 1, wherein the divided region is a region divided in both the main scanning direction and the sub-scanning direction.

12. The inkjet recording apparatus according to claim 1, wherein the divided region is a region that is variably divided in both the main scanning direction and the sub-scanning direction according to the ink ejection amount on the first surface.

13. The inkjet recording apparatus according to claim 2, wherein the control unit corrects the head driving voltage in printing on the second surface based on the correction value, thereby controlling the ink ejection amount for each divided region on the second surface.

14. The inkjet recording apparatus according to claim 2, wherein the control unit corrects the print image data in printing on the second surface based on the correction value, thereby controlling the ink ejection amount for each divided region on the second surface.

15. The inkjet recording apparatus according to claim 2, wherein the control unit corrects the ink dot diameter in printing on the second surface based on the correction value, thereby controlling the ink ejection amount for each divided region on the second surface.

16. An inkjet recording method of performing printing on a first surface and printing on a second surface consecutive to the printing on the first surface on the same recording medium by an inkjet recording apparatus using an active energy ray curable ink, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing the planar region of the recording medium, and an inkjet recording method of controlling the ink ejection amount for each divided region on the second surface according to the ink ejection amount for each divided region on the first surface and the time from the printing on the first surface to the printing on the second surface.

17. A program for causing a computer of an inkjet recording apparatus that performs printing on a first surface and printing on a second surface consecutive to the printing on the first surface on the same recording medium using an active energy ray curable ink to function as a control unit, wherein the first surface and the second surface share a plurality of divided regions defined by arbitrarily dividing the planar region of the recording medium, and the control unit controls the ink ejection amount for each divided region on the second surface according to the ink ejection amount for each divided region on the first surface and the time from the printing on the first surface to the printing on the second surface.

Images