JP6550944B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image forming method.

  There is known an image forming method (three-dimensional object forming method) in which a three-dimensional image or a three-dimensional object is formed by discharging an ink using an inkjet method, drying or curing to form a layer, and laminating the layers. . Hereinafter, “image” includes a three-dimensional image and a three-dimensional object.

  In this method, for example, a photocurable ink (for example, UV ink) which is cured by irradiating light such as ultraviolet light (UV) onto a medium (image forming object) from a nozzle is discharged, and the medium is formed. The UV ink dots are fixed on the medium by irradiating the UV ink dots with light and curing them.

  In a serial type inkjet recording apparatus (image forming apparatus), an image is recorded by combining a main scan by scanning of a recording head and a sub-scan by conveyance of a medium. In the image formation of such an ink jet recording apparatus, band-like gloss unevenness called gloss banding may occur due to the difference in the printing surface shape for each line feed width. 22A and 22B are explanatory diagrams of gloss banding, in which FIG. 22A shows an example in which gloss banding occurs in a black solid image, and FIG. 22B shows the relationship between the pixel position and glossiness in FIG. .

  For this gloss banding, a method is known in which a colorless and transparent clear ink is coated on a color ink ejected to form an image.

  In the case of recording an image by a multi-pass method, according to Patent Document 1, the color ink is coated with the clear ink when the clear ink is dropped on the color ink deposited on the recording medium. As described above, ink jet recording can be applied to clear ink with a droplet ejection size larger than the color ink droplet ejection size, to smoothen the unevenness of the image caused by the color ink droplet ejection, and to prevent the occurrence of glossy banding. An apparatus is disclosed.

  In the technique described in Patent Document 1, the gloss banding is reduced by using a clear ink to make the printing surface uniform.

  However, in the case of bidirectional printing in which an image is formed both when scanning the recording head in the forward direction in the main scanning direction and when scanning in the backward direction, the light irradiation timing differs between the forward path and the backward path, There was a problem that glossy banding would remain.

  The gloss banding in the case of bidirectional printing will be described. The photocurable ink uses non-penetrable media (film, resin, etc.) as a medium to form an image while maintaining a three-dimensional shape, but the time from landing on the medium to irradiation of light is Due to the difference in the shape of the landed dots. Further, as a head for discharging the photocurable ink, a structure in which light irradiation parts (UV lamps) are mounted on both ends of the carriage of the head is often used. For this reason, as long as the head mounting position is not in the middle of the irradiation sections at both ends, the irradiation timing of light is different between the forward path and the return path.

  According to the technique described in Patent Document 1 described above, gloss banding can not be eliminated because the difference in printing surface height that occurs during bidirectional printing can not be filled in.

  Therefore, an object of the present invention is to provide an image forming apparatus capable of forming an image in which the occurrence of gloss banding is suppressed in bidirectional printing.

In order to achieve such an object, an image forming apparatus according to the present invention ejects ink that is cured by light irradiation, and forms an image on an image forming object by irradiating light to cure the ink. The ink is ejected both when the recording head is scanned in the forward direction in the main scanning direction and when the recording head is scanned in the backward direction, and at least a plurality of times are scanned in the image forming area where the image is formed. A multi-scan printing unit for forming an image in the image, a color image control unit for controlling image formation from the color ink head for discharging the color ink included in the recording head, and a clear ink head for discharging the clear ink included in the recording head Clear image control means for controlling the formation of an image from the A color image formed by the image forming unit, and a height adjusting clear image control unit that controls image formation with the clear ink so that the image height after formation is substantially uniform; and a color image formed by the color image control unit The surface shape adjusting clear image control means for controlling the image formation by the clear ink so that the image surface shape after the formation becomes substantially uniform after the clear image is formed by the height adjusting clear image control means, The clear ink head is disposed on the leading side in the forward direction of the recording head, and in the forward pass printing, a clear image is formed by the height adjusting clear image control means, and in the return pass printing, the surface shape adjustment is performed. A clear image is formed by the clear image control means .

  According to the present invention, it is possible to form an image in which the occurrence of gloss banding is suppressed in bidirectional printing.

It is a schematic block diagram of an image processing system. It is a functional block diagram of an image processing system. It is a figure showing an example of the hardware constitutions of an image processing device. 3 is a schematic diagram illustrating an example of a recording unit of the image forming apparatus. FIG. It is explanatory drawing of nozzle distribution in the case of 2 scan printing. It is explanatory drawing of nozzle distribution in the case of 5 scan printing. FIG. 4 is a schematic diagram illustrating a state in which ink is ejected from a head of a recording unit provided with UV lamps at both ends and UV irradiation is performed. It is explanatory drawing which shows the change of the ink after an ink lands on a support body. It is a schematic diagram which shows the example of generation | occurrence | production of gloss banding. It is a schematic diagram which shows the other example in which glossy banding generate | occur | produces. It is explanatory drawing which shows the example which formed the clear ink image on the color ink image. FIG. 2 is a schematic view showing an example of image formation by the image forming apparatus according to the present embodiment. 3 is a flowchart of an image forming method according to the present embodiment. 3 is an example of a recording unit provided in the image forming apparatus. 7 is another example of a recording unit provided in the image forming apparatus. 5 is another example of a recording unit provided in the image forming apparatus. 7 is another example of a recording unit provided in the image forming apparatus. It is an explanatory view showing a nozzle side of a head which discharges clear ink. It is an example of a glossiness evaluation chart. 7 is a flowchart of clear ink ejection amount determination processing using a gloss evaluation chart. It is a graph which shows the relationship between color ink placement amount and glossiness. It is explanatory drawing of glossy banding.

  Hereinafter, a configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

  The image forming apparatus (image forming apparatus 30) according to the present embodiment discharges the ink (droplet 32) that is cured by the irradiation of light, and irradiates the light to cure the ink to form an image forming object (support P) An image forming apparatus for forming an image (image 17), which ejects ink both when scanning the recording head (recording unit 14) in the forward direction in the main scanning direction and when scanning in the backward direction And a multi-scan printing unit (multi-scan control unit 28A) that forms an image by scanning at least a plurality of times in an image forming area in which an image is formed, and a color ink head Color image control means (color ink image control unit 28B) for controlling image formation from the heads 18K, 18C, 18M, 18Y, 18W) and recording Clear image control means for controlling image formation from a clear ink head (head 18T) that ejects clear ink included in the image forming apparatus, the clear image control means forming along with formation of a color image by the color image control means Clear image control unit for height adjustment (clear ink control unit for height adjustment 28C) for controlling image formation by clear ink so that the image height afterward becomes substantially uniform, and color image by color image control unit And a clear image control means for controlling the surface shape for controlling the image formation by the clear ink so that the image surface shape after formation becomes substantially uniform after the clear image for height adjustment is formed by the clear image control means (surface shape An adjustment clear ink image control unit 28D). In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

<Image processing system>
FIG. 1 is a schematic configuration diagram illustrating an example of an image processing system 10. The image processing system 10 includes an image processing device 12 and an image forming device 30. The image processing apparatus 12 and the image forming apparatus 30 are connected to be communicable.

  The image forming apparatus 30 is a serial inkjet recording apparatus that includes a recording unit 14, an operation stage 16, and a driving unit 25. The recording unit 14 is an inkjet carriage including a plurality of heads 18 (recording heads) provided with a plurality of nozzles, and discharges droplets from the nozzles of the head 18 to record dots. The nozzles are provided on the surface of the recording unit 14 that faces the operation stage 16.

  The droplets are ink droplets and additional droplets. The ink droplet is a droplet (color ink) of an ink containing a coloring material used for image formation.

  The additional droplet is a color droplet that does not affect the image. The additional droplets are, for example, transparent (referred to as clear ink). Further, the additional liquid droplets may have the same color as the support P that is the image forming object. The support P is an image forming object of an image with ink droplets. The support P is, for example, a non-penetrable medium such as a film or a resin. Alternatively, the support P itself may be formed on the operation stage 16 by discharging droplets using an inkjet method or the like.

  The ink droplets and additional droplets are stimulus curable. The stimulation is, for example, light (ultraviolet light, infrared light, etc.), heat, electricity, etc. In the present embodiment, the case where the ink droplet and the additional droplet have ultraviolet curable properties will be described as an example. The ink droplets and the additional droplets are not limited to the form having ultraviolet curability.

  The irradiation units 22 are provided on both sides of the recording unit 14 in the main scanning direction X. The irradiation units 22 are opposed to the operation stage 16 in the recording unit 14. The irradiation unit 22 irradiates the support P with light having a wavelength that cures the ink droplets and additional droplets ejected from the nozzles. The irradiation unit 22 irradiates ultraviolet rays, for example. Further, in the case of a UV lamp, there are metal halide type and LED type lamps, and an appropriate lamp is selected according to the curing property of the photocurable ink.

  The operation stage 16 holds the support P. The drive unit 25 moves the recording unit 14 and the operation stage 16 in the vertical direction (the arrow Z direction in FIG. 1), the main scanning direction X perpendicular to the vertical direction Z, and the sub-direction perpendicular to the vertical direction Z and the main scanning direction X. It is moved relatively in the scanning direction Y. In the present embodiment, the plane formed by the main scanning direction X and the sub scanning direction Y corresponds to an XY plane along the surface of the operation stage 16 facing the recording unit 14.

  The drive unit 25 includes a first drive unit 23 and a second drive unit 24. The first drive unit 23 moves the recording unit 14 in the vertical direction Z, the main scanning direction X, and the sub-scanning direction Y. The second drive unit 24 moves the operation stage 16 in the vertical direction Z, the main scanning direction X, and the sub-scanning direction Y. The recording unit 14 and the operation stage 16 may be relatively movable in the vertical direction Z, the main scanning direction X, and the sub scanning direction Y, and the image forming apparatus 30 includes the first driving unit 23 and the second driving unit 23. The structure provided with either one of the drive parts 24 may be sufficient.

  FIG. 2 is a functional block diagram of the image processing system 10.

  The image processing device 12 includes a main control unit 13. The main control unit 13 is a computer that includes a CPU (Central Processing Unit) and the like, and controls the entire image processing apparatus 12. The main control unit 13 may be configured other than a general-purpose CPU. For example, the main control unit 13 may be configured by a circuit or the like.

  The main control unit 13 includes a data reception unit 12A, a data creation unit 12B, and a data output unit 12C. For example, part or all of the data receiving unit 12A, the data creating unit 12B, and the data output unit 12C may be realized by causing a processing device such as a CPU to execute a program, that is, realized by software or IC (Integrated Circuit) Circuit) or other hardware, or a combination of software and hardware.

  The data receiving unit 12A receives image data. The image data is information such as the shape and color of the image to be formed. The data receiving unit 12A may obtain image data from an external device via the communication unit, or may obtain image data from storage means provided in the image processing device 12.

  The data creating unit 12B performs predetermined data processing such as mask processing on the image data received by the data receiving unit 12A. In this embodiment, color ink image data, height adjustment clear ink image data, and surface shape adjustment clear ink image data based on image data (for example, JPEG image data) and desired glossiness. Create Details of each image will be described later.

  The data output unit 12C outputs the image data created by the data creation unit 12B to the image forming apparatus 30.

  The image forming apparatus 30 includes a recording unit 14, a recording control unit 28, a driving unit 25, and an irradiation unit 22.

  The recording control unit 28 receives print data from the image processing apparatus 12. The recording control unit 28 controls the recording unit 14, the driving unit 25, and the irradiation unit 22 so as to discharge the droplet 32 corresponding to each pixel from the head 18 according to the received print data.

  For example, the recording control unit 28 calculates the time from the discharge of the ink to the irradiation of light, the calculation of the glossiness of the image formed on the support P from the discharge amount of the ink and the time to the irradiation of light, In order to make the degree uniform, calculations etc. are performed to determine the discharge amount of the clear ink.

  The recording control unit 28 includes a multiscan control unit 28A (multiscan printing unit), a color ink image control unit 28B (color image control unit), and a height adjustment clear ink image control unit 28C (height adjustment clear image). A control unit), a clear ink image control unit 28D for surface shape adjustment (clear image control unit for surface shape adjustment), and a gloss evaluation chart formation unit 28E (gloss evaluation chart formation unit) are provided.

  In the image forming area where an image is formed, the multi-scan control unit 28A forms an image both when scanning the recording unit 14 in the forward direction in the main scanning direction and when scanning in the backward direction (bidirectional Printing), and in the same image forming region, control is performed to form an image by scanning at least a plurality of times.

  The color ink image control unit 28B controls image formation of a color ink image based on the color ink image data. That is, the order of formation for each ink color, the amount of each ink shot, and the shot position (dot placement position) are controlled.

  The height adjusting clear ink image control unit 28C controls image formation of the height adjusting clear ink image based on the height adjusting clear ink image data. The order of forming the height adjustment clear ink image, the amount of clear ink applied, and the position of the ink are controlled.

  The surface shape adjustment clear ink image control unit 28D controls image formation of the surface shape adjustment clear ink image based on the surface shape adjustment clear ink image data. The control unit controls the order of forming the surface shape adjusting clear ink image, the amount of clear ink applied, and the position of the ink.

  The gloss evaluation chart forming unit 28E forms a gloss evaluation chart (described later, FIG. 19).

  Next, the hardware configuration of the image processing apparatus 12 will be described. FIG. 3 shows an example of a block diagram showing the hardware configuration of the image processing apparatus 12. The image processing apparatus 12 includes an input unit 130 for inputting data, a display unit 131 such as a display, a communication unit 132 for performing data communication, a CPU 133 as control means for controlling the entire apparatus, and a CPU 133 And a recording unit 135 storing various programs for operating the CPU 133 and the like.

  The input unit 130 includes a keyboard having cursor keys, numeric input keys, various function keys and the like, a mouse for selecting a key on the display screen of the display unit 131, and a slice pad. This is a user interface for a user to give an operation instruction to the CPU 133 or to input data.

  Examples of the display unit 131 include a CRT and an LCD, and display is performed according to display data input from the CPU 133. The communication unit 132 is for data communication with the outside, and is for data communication with the image forming apparatus 30 through a predetermined communication interface.

  The CPU 133 is a central control unit that controls the entire apparatus according to a program stored in the recording unit 135, and the input unit 130, the display unit 131, the communication unit 132, the RAM 134, and the recording unit 135 are connected to the CPU 133. It controls data communication, reading of application programs by accessing the memory, reading / writing of various data, data / command input, display, and the like.

  The CPU 133 also sends out image data for forming an image to the image forming apparatus 30 via the communication unit 132 based on the image data input from the input unit 130 and the image data stored in the recording unit 135. Do.

  The RAM 134 includes a work memory for storing a designated program, an input instruction, input data, a processing result, and the like, and a display memory for temporarily storing display data to be displayed on the display screen of the display unit 131.

  The recording unit 135 stores various programs and data such as an OS program (for example, an operating system Windows (registered trademark) of Microsoft Corporation) executable by the CPU 133 and a printer driver corresponding to the image forming apparatus 30. As the recording unit 135, for example, an optical, magnetic, or electrical recording medium such as a hard disk, a CD-ROM, or a DVD-ROM can be used.

  Various programs are stored in the recording unit 135 in the form of data readable by the CPU 133. Also, various programs may be recorded in advance in the recording unit 135 or may be downloaded via a communication line such as the Internet and stored in the recording unit 135.

<Image forming apparatus>
Next, details of the image forming apparatus 30 will be described. The image forming apparatus 30 forms an image by an optical modeling method that discharges ink (photocurable ink) of a photocurable resin and irradiates light to cure the photocurable resin.

(Recording department)
As shown in FIG. 4, the recording unit 14 in the image forming apparatus 30 is a carriage in which a plurality of nozzles 19 are arranged in a predetermined direction. Each nozzle 19 discharges an ink droplet, an additional droplet, or a mixture of an ink droplet and an additional droplet as a droplet 32. The configuration for discharging the nozzle 19 and droplets is the same as that of a known ink jet system.

  In the present embodiment, the heads 18 K, 18 C, 18 M, 18 Y, 18 W, 18 T (in the case of no distinction, the heads 18) are arranged in a predetermined direction. The head 18T is also called a clear ink head, and the heads 18K, 18C, 18M, 18Y, and 18W are also called color ink heads.

  Each head 18 has nozzles 19 K, 19 C, 19 M, 19 Y, 19 W, 19 T (in the case of no distinction, the nozzles 19) for discharging ink droplets. Nozzle 19K is black ink droplet, nozzle 19C is cyan ink droplet, nozzle 19M is magenta ink droplet, nozzle 19Y is yellow ink droplet, nozzle 19W is white ink droplet, nozzle 19T is transparent additional droplet (clear Discharge ink).

  Here, the head 18 </ b> T that discharges the clear ink is on the most end side of the recording unit 14. With this arrangement, the clear ink can be formed below or above the color ink by controlling the printing direction (the details will be described later).

  By ejecting the droplet 32 from the nozzle 19, dots 34 corresponding to the droplet 32 are formed on the support P, and the image 17 is formed. In addition, the droplets 32 are stacked and discharged, so that the dots 34 are stacked and the three-dimensional image 17 is formed.

  In the present embodiment, the irradiation units 22 are provided at both ends of the heads 18 K, 18 C, 18 M, 18 Y, 18 W, and 18 T in the arrangement direction. By irradiating light from the irradiation unit 22 to the droplets 32 discharged from each nozzle 19, the droplets 32 are cured.

  The irradiation unit 22 is provided on both ends in the main scanning direction. The irradiation unit 22 is preferably disposed in the vicinity of the nozzle 19. By arranging the irradiation unit 22 in the vicinity of the nozzle 19, it is possible to shorten the curing time from the deposition of the droplet 32 discharged from the nozzle 19 on the support P side to the curing. For this reason, a higher definition image can be formed.

  Although FIG. 4 shows the case where each of the heads 18 discharges droplets 32 of one color (one type), the invention is not limited thereto. For example, each head 18 has two or more nozzles. 19 may be provided. Further, the nozzle 19 may discharge mixed droplets of a plurality of types of droplets 32. Further, the color of the ink ejected from the recording unit 14 is not limited to black, cyan, magenta, yellow, and white. Further, the types of the droplets 32 ejected from the recording unit 14 are not limited to six types (black, cyan, magenta, yellow, white, transparent).

  Further, as shown in FIG. 1, in the image forming apparatus 30, while discharging the droplets 32 from the nozzles 19 of the recording unit 14, the recording unit 14 and the support P are relatively moved, whereby the support P is obtained. It is possible to form dots 34 by the droplets 32 or to stack the dots 34 thereon. The support P may be planar or may be a three-dimensional shape with irregularities.

(Multi scan method)
Next, image formation by the multi-scan method will be described. As an image forming method of an ink jet image forming apparatus, an image is formed by performing multiple times of main scanning (scanning) with the same or different nozzle groups on the same region (image forming region) of the support P. Multi-scan printing (multi-pass printing) is known. By performing a plurality of main scans on the same area of the support P, it is possible to form an image with high resolution. Hereinafter, printing by n times of main scanning on the same area of the support P is referred to as n-scan printing. In the multi-scan printing of this embodiment, image formation is performed by ejecting ink during both forward scanning and backward scanning in the main scanning direction of the recording unit 14 (bidirectional printing).

  In multi-scan printing, mask processing is performed to equally distribute the nozzles 19 for the number of scans. 5 and 6 are schematic views of the head 18 having 12 nozzles. The number of nozzles is, for example, generally 1,000 nozzles or more, such as 1280 nozzles, but an example in which the number of nozzles is 12 will be described here in order to simplify the description.

  As shown in FIG. 5, when an image is formed by two-scan printing using a head 18 having twelve nozzles 19, six nozzles are required for one scan based on the number of nozzles 12 / number of scans = 2 = 6. It will be used. Therefore, for example, in the first scan, mask processing is performed so that an image is formed using the six nozzles 19 of the nozzle group 20a and the six nozzles 19 of the nozzle group 20b at the second scan.

  If the number of nozzles is not divisible by the number of scans, an unused nozzle may be provided and a divisible number of nozzles may be used. At this time, the number of unused nozzles should be minimized. Therefore, for example, as shown in FIG. 6, when forming an image by 5-scan printing using a head 18 having 12 nozzles 19, the number of nozzles 12 / number of scans 5 = 2 more than once. In this scan, 2 nozzles are used, and 2 nozzles become unused nozzles 19n. For example, in the first scan, the two nozzles 19 in the nozzle group 20a, in the second scan, the two nozzles 19 in the nozzle group 20b, in the third scan, the two nozzles 19 in the nozzle group 20c, in the fourth scan, the nozzles In the second nozzle 19 and the fifth scan of the group 20d, an image is formed using the two nozzles 19 of the nozzle group 20e.

(Glossy banding)
Next, gloss banding will be described. FIG. 7 shows the recording unit 14 provided with UV lamps 22a and 22b at both ends in the main scanning direction as the irradiation unit 22. The ink (droplet 32) is ejected from the head 18K, and from the UV lamps 22a and 22b. It is a schematic diagram which shows a mode that UV irradiation is performed.

  The glossy banding is caused by the difference in UV irradiation timing between the forward path and the return path. Note that printing during forward scanning is referred to as forward printing, and printing during backward scanning is referred to as backward printing.

  In the case of FIG. 7, in the forward printing, the distance from the head 18K to the UV lamp 22b used for irradiation in the forward printing is the distance B, and in the backward printing, the UV lamp 22a used for irradiation in the backward printing from the head 18K. Is the distance A, and the distances A and B are greatly different.

  The difference between the distance A and the distance B means the difference in the distance from the ink landing position to the irradiation position by the UV lamp. In the example of FIG. 7, the time from the ink landing to the UV irradiation is in the forward printing. This is longer than the return pass printing, and in the return pass printing, the time from ink landing to UV irradiation is shorter than the forward pass printing.

  8A to 8C are explanatory diagrams showing changes in ink after the ink (dot 34) has landed on the support P. FIG. (A) shows the appearance of the ink at the time of landing, (B) shows the appearance of the ink after a predetermined time from the landing, and (C) shows the appearance of the ink when time has further elapsed from the state shown in (B) .

  As shown in FIG. 8, the ink spreads and becomes smooth (leveling) as time passes. The glossiness is affected by the height and shape of the print surface, and generally the glossiness is higher if the surface shape is smooth.

  Therefore, as shown in FIG. 7, when the time from the landing of the ink to the UV irradiation is different, the ink landed on the support P is irradiated in a different state. Specifically, as the irradiation timing is delayed, the dot diameter is larger and the dot height is lower (in a state as shown in FIG. 8C).

  For this reason, for example, as shown in FIG. 9, in the case of bi-directional printing, the image 17 is formed with two types of print surface shapes according to the line feed width, and both the print surface height and shape are different, resulting in glossy banding. It will be done. As shown in FIG. 10A, the gloss is also different when the surface shape is different but the surface height is uniform, or when the surface shape is uniform but the surface height is different as shown in FIG. Banding occurs.

  Therefore, in order to eliminate gloss banding, it is necessary to make the print surface height and the print surface shape uniform.

  At this time, for example, as shown in FIG. 11, the color ink is dropped so that the color ink is covered with the clear ink on the color ink image 17c having both the print surface height and the shape shown in FIG. 9 different. Even if the clear ink image 17t is formed by ejecting clear ink having a droplet ejection size larger than the size, the surface shape is fixed to some extent, but the print surface height cannot be made uniform, and gloss banding is eliminated. It is not possible.

(Clear ink control)
Therefore, in the image forming apparatus 30 according to the present embodiment, both the printing surface height and the printing surface shape are made substantially uniform by the height adjusting clear ink image and the surface shape adjusting clear ink image. .

  FIG. 12 is a schematic diagram illustrating an example of image formation by the image forming apparatus 30 according to the present embodiment. Similar to FIG. 9, the color ink image 17 c is in a state in which both the printing surface height and the shape are different, but when the color ink image 17 c is formed, the height of the clear ink for height adjustment is reduced to a low printing surface height. The height adjustment clear ink image 17 h is formed by driving in a density area, a leveling area, etc., and the print surface heights are aligned.

  Then, the surface shape adjusting clear ink is further applied over the color ink (color ink image 17c) and the clear ink (height adjusting clear ink image 17h), and the surface shape adjusting clear ink image 17s. To form a uniform surface shape.

  That is, in the image forming method according to the present embodiment, a clear image is formed so that the image height after formation is substantially uniform in parallel with the color image forming process for forming a color image and the color image forming process. For surface shape adjustment to form a clear image so that the image surface shape after formation is substantially uniform after forming height adjustment clear image forming processing, color image forming processing and height adjustment clear image forming processing The clear image forming process is performed.

  FIG. 13 is a flowchart illustrating an overview of image forming processing executed by the image forming apparatus 30 according to the present embodiment.

  In the image forming process, first, the color ink image control unit 28B forms the color ink image 17c, and the height adjustment clear ink image control unit 28C simultaneously forms the height adjustment clear ink image 17h (S101). ).

  After formation of the color ink image 17c and the height adjustment clear ink image 17h for a certain image formation area, the surface shape adjustment clear ink image control unit 28D forms the surface shape adjustment clear ink image 17s (S102). ).

  For example, in the case of forming an image in one image forming area by one bidirectional printing (two scan printing), the formation of the color ink image 17c and the height adjusting clear ink image 17h (S101) is forwarded. At the time of scanning, formation (S102) of the clear ink image 17s for surface shape adjustment is performed at the time of backward scanning.

  The forward pass printing and the return pass printing do not necessarily have to be started from the forward pass printing, and may be started from the backward pass printing. Also, for example, in the case of 8 scan printing, the color ink image 17c and the height adjustment clear ink image 17h are formed in the 1st to 7th scans, and the surface shape adjustment clear ink image 17s is formed in the 8th scan. Just do it. Further, it goes without saying that the surface shape adjusting clear ink image 17s may be formed by a plurality of scans.

  Further, in the present embodiment, in order to simplify the description, in the image forming process, first, the color ink image 17 c and the height adjustment clear ink image 17 h are formed (S 101), and then the surface shape adjustment clear The formation of the ink image 17s (S102) has been described, but this does not exclude the form in which color ink is ejected during the formation of the surface shape adjusting clear ink image 17s. For example, a small amount of color ink is ejected. It may be done.

  Next, a printing method and an image allocation method for the height adjusting clear ink image 17h and the surface shape adjusting clear ink image 17s will be described.

(First Clear Ink Image Forming Method)
First, an image forming method for switching a clear ink image to be printed in forward pass printing and return pass printing will be described.

  FIG. 14 is an example of the recording unit 14 provided in the image forming apparatus 30. The recording unit 14 illustrated in FIG. 14 includes a head 18T that discharges clear ink on the leading side in the traveling direction during forward printing. In this configuration, since the clear ink is discharged first during the forward pass printing, the height adjustment clear ink image is formed in the forward pass printing. Then, a clear ink image for surface shape adjustment is formed at the time of the return pass printing.

  In principle, the color ink image is formed by the same scan as the formation of the height adjusting clear ink image. Since the head 18T that discharges the clear ink is provided on the leading side in the traveling direction, the clear ink (forward pass printing), the color ink (forward pass printing), and the clear ink (return pass printing) are landed on the support P in this order. The same applies to the other cases described below.

  FIG. 15 is another example of the recording unit 14 provided in the image forming apparatus 30. The recording unit 14 illustrated in FIG. 15 includes a head 18T that discharges clear ink on the trailing side in the traveling direction during forward path printing. In this configuration, the clear ink is first ejected during the return pass printing, and thus the height adjustment clear ink image is formed in the return pass printing. Then, a clear ink image for surface shape adjustment is formed at the time of forward pass printing. In the case of the configuration in FIG. 15, clear ink is not ejected in the forward printing of the first scan. For this reason, it is preferable to start printing from return pass printing.

(Second Clear Ink Image Forming Method)
Next, an image forming method in which two clear ink heads that discharge clear ink are provided and a height adjusting clear ink image and a surface shape adjusting clear ink image are assigned to each head will be described.

FIG. 16 is another example of the recording unit 14 included in the image forming apparatus 30. The recording unit 14 shown in FIG. 16 includes two heads 18T ₁ and 18T ₂ that discharge clear ink on the leading side in the traveling direction during forward printing.

The height adjusting clear ink image and the surface shape adjusting clear ink image are assigned to the two heads 18T ₁ and 18T ₂ that discharge the clear ink, and one of the heads (for example, the head 18T ₁ ) has a height. The head for forming the adjustment clear ink image and the other head (for example, the head 18T ₂ ) are the heads for forming the surface shape adjustment clear ink image. There is no limitation on the positional relationship between the head for forming the height adjusting clear ink image and the head for forming the surface shape adjusting clear ink image.

In this configuration, when the forward printing, the clear ink from being discharged at the beginning, in the forward path printing forming a height adjustment for the clear ink image by driving the head 18T _1. Then, when the return printing form surface shape adjusting clear ink image by driving the head 18T _2.

  In the configuration provided with two clear ink heads, it is not necessary to switch between images printed in forward pass printing and return pass printing on the same head, and control becomes easy.

FIG. 17 is another example of the recording unit 14 included in the image forming apparatus 30. The recording unit 14 shown in FIG. 17 includes two heads 18T ₁ and 18T ₂ that discharge clear ink on the trailing side in the traveling direction during forward printing.

Similar to FIG. 16, a head for one of the head 18T ₁ to form a height adjustment for the clear ink image, the other of the head 18T ₂ is a head for forming a surface shape adjusted for the clear ink image.

In this configuration, when the backward printing, the clear ink from being discharged at the beginning, in the backward path printing forming a height adjustment for the clear ink image by driving the head 18T _1. Then, when the forward printing, it is sufficient to form a surface shape adjusted for the clear ink image by driving the head 18T _2. In the case of the configuration of FIG. 17, the clear ink is not discharged in the forward pass printing of the first scan. For this reason, it is preferable to start printing from the return pass printing.

(Third clear ink image forming method)
Next, in a configuration in which each head 18 of the recording unit 14 has two nozzle rows, image formation in which a height adjustment clear ink image and a surface shape adjustment clear ink image are assigned to each nozzle row of the clear ink head 18T. The method will be described. In this configuration, there is one head 18T (FIGS. 14, 15, etc.).

  Here, an example having two nozzle rows will be described, but it is sufficient if there are a plurality of nozzle rows and the height adjustment clear ink image and the surface shape adjustment clear ink image are assigned in units of nozzles. . The number of assigned nozzle rows may be different.

FIG. 18 is a diagram illustrating a nozzle surface of a head 18T that discharges clear ink. The head 18T has two nozzle rows 19T ₁ and 19T ₂ . In the example of FIG. 18, the nozzle row 19T ₁ is a height adjustment for the clear ink images, the nozzle row 19T ₂ is allocated for the surface shape adjusting clear ink image.

  In the case of the configuration shown in FIG. 18, each clear ink is printed with half the number of nozzles compared to other color inks, so the nozzle pitch is doubled. Therefore, it is preferable to adjust the image resolution as half of the color image. In this configuration, the image resolution is defined as 1/2 of the color ink also for the gloss evaluation chart described later.

(Gloss uniformity control)
Hereinafter, using the image processing system 10 according to the present embodiment to perform image formation with a glossiness desired by the user will be described.

  The image forming apparatus 30 according to the present embodiment includes a gloss evaluation chart forming unit 28E (FIG. 2). FIG. 19 is an example of a gloss evaluation chart.

  The gloss evaluation chart forming unit 28E is a test chart in which a plurality of patches formed while changing the combination of the color ink injection amount per unit area and the clear ink injection amount per unit area for each color of color ink ( A gloss evaluation chart, FIG. 19) is printed. At this time, since the time from landing of ink to UV irradiation is different between forward pass printing and return pass printing, a gloss imparting chart is prepared for each of forward pass printing and return pass printing.

  The process of determining the clear ink ejection amount using the gloss evaluation chart will be described below. FIG. 20 is a flowchart of clear ink impact amount determination processing using the gloss evaluation chart.

  First, the gloss evaluation chart forming unit 28E forms the gloss evaluation chart shown in FIG. 19 for each ink color and for each print direction (S201).

  Next, the degree of gloss of each patch is measured for each patch of the created gloss evaluation chart (S202). The glossiness is, for example, 60 ° glossiness and is measured by a gloss meter. The measurement result of each patch is stored, for example, in the recording unit 135 of the image processing apparatus 12, and processed as follows by the data generation unit 12B.

  FIG. 21 is a graph showing the relationship between the color ink placement amount per unit area and the glossiness. As shown in FIG. 21, there is a correlation between the color ink injection amount per unit area and the degree of gloss, and this is grasped (S203).

  Further, since the time from the landing of the ink to the UV irradiation is different for each printing direction, the change of the glossiness for each printing direction is grasped (S204).

  Next, regardless of the color ink injection amount and the printing direction, a combination of the color ink ejection amount per unit area and the clear ink ejection amount per unit area that minimizes the difference in glossiness is selected the most, and the combination is high The amount of clear ink to be ejected is adjusted (S205).

  In the process of S205, for example, among the patches in FIG. 19, the difference in glossiness is the minimum on the basis of the glossiness of an image in which the ratio of clear ink is 0 and color ink is 100 (patch A enclosed by solid line in FIG. 19). The image to be is selected for each row (nine patches B1 to B9 surrounded by a dotted line in FIG. 19), and the clear ink ejection amount for height adjustment is determined based on the clear ink ejection amount of the selected patch.

  At this time, if there are two patches with uniform gloss, select the one with a smaller absolute value of the difference between the amount of ink applied to patch A (the amount of ink applied to color A) and the amount applied to clear ink. Just do it. If the absolute value of the difference between the ink hit amount and the ink shot is the same, the smaller ink hit amount may be selected.

  In the present embodiment, an example is shown in which the gloss application chart has patches of 10 × 10 squares, but the number of patches is not limited to this, and the color ink injection amount per unit area and the unit area The accuracy of gloss uniformity control can be increased by forming patches while changing the combination with the clear ink placement amount more finely and increasing the number of patches (the grid of the glossing chart).

  After determining the clear ink driving amount, a height adjusting clear ink image and a surface shape adjusting clear ink image are formed (S206, S207).

  The height of the print surface is determined by the amount of color ink and the timing of UV irradiation. For example, the less the color ink and the later the timing of UV irradiation, the lower the printing surface height. Therefore, it is necessary to discharge a large amount of height-adjusting clear ink in order to adjust the height. The height-adjusting clear ink image is formed at other locations in accordance with, for example, the location where the color ink image is high.

  Also, as described above, since the print surface shape does not become uniform only with the clear ink for height adjustment, the gloss banding does not disappear, so that the surface shape adjustment clear in order to make the print surface shape uniform. The amount of ink is also determined.

  It should be noted that the glossing chart may be formed when the support P is changed or when the printing conditions are changed, such as a change in temperature and humidity.

  With the above processing, it is possible to select the color ink amount and the clear ink amount in accordance with the glossiness desired by the user, and an image without gloss banding can be formed with the glossiness desired by the user.

  According to the image forming apparatus according to the embodiment described above, the difference in height and shape of the printing surface generated due to the difference in the timing of the light irradiation of the forward pass printing and the backward pass printing in the bidirectional printing is performed using the clear ink. It is possible to make the image uniform without gloss banding and uniformizing the glossiness.

  That is, first, a color ink image and a clear ink image for height adjustment are formed to make the image heights at the time of forming the two images uniform, and then a color ink image and a clear ink image for height adjustment A clear ink image for surface shape adjustment is formed on the surface to make the surface shape uniform.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

  For example, the irradiation part 22 is not limited to the form shown in FIG. For example, the irradiation unit 22 may be provided only on the rear side in the forward traveling direction of the main scanning direction of the recording unit 14. In this case, since the image printed by the backward scan is irradiated by the next forward scan, the time difference from ink landing to irradiation in the forward scan and the backward scan becomes large. Even in the configuration in which the irradiation unit 22 is provided only at one end, gloss banding in bidirectional printing can be prevented.

DESCRIPTION OF SYMBOLS 10 Image processing system 12 Image processing apparatus 12A Data receiving part 12B Data preparation part 12C Data output part 13 Main control part 14 Recording part 16 Operation | movement stage 17 Image 17c Color ink image 17t Clear ink image 17h Clear ink image 17s for height adjustment Surface shape adjusting clear ink images 18K, 18C, 18M, 18Y, 18W, 18T, 18T 1, 18T 2 heads 19K, 19C, 19M, 19Y, 19W, 19T nozzle 20 nozzle group 22 irradiation unit 22a, 22b UV lamp 23 first Drive unit 24 Second drive unit 25 Drive unit 28 Recording control unit 28A Multi-scan control unit 28B Color ink image control unit 28C Height adjustment clear ink image control unit 28D Surface shape adjustment clear ink image control unit 28E Gloss evaluation chart formation Part 30 Image forming equipment 32 droplets 34 dot

JP, 2014-37086, A

Claims (9)

An image forming apparatus that discharges ink that is cured by irradiation of light and cures the ink by irradiating light to form an image on an image forming object,
Ink is ejected both when the recording head is scanned in the forward direction of the main scanning direction and when it is scanned in the backward direction, and an image is formed by scanning at least a plurality of times in the image forming area where the image is formed. A multi-scan printing means,
Color image control means for controlling image formation from a color ink head which ejects color ink included in the recording head;
And clear image control means for controlling image formation from a clear ink head which ejects clear ink included in the recording head,
The clear image control means
A height-adjusting clear image control means for controlling image formation with clear ink so that the image height after formation is substantially uniform along with the formation of a color image by the color image control means,
Surface shape for controlling image formation with clear ink so that the image surface shape after formation is substantially uniform after formation of the color image by the color image control unit and the clear image by the height adjusting clear image control unit Clear image control means for adjustment,
Equipped with a,
The clear ink head is disposed on the leading side in the forward direction of the recording head,
In forward printing, a clear image is formed by the height adjusting clear image control means,
An image forming apparatus characterized in that a clear image is formed by the clear image control means for surface shape adjustment in the return pass printing . An image forming apparatus that discharges ink that is cured by irradiation of light and cures the ink by irradiating light to form an image on an image forming object,
Ink is ejected both when the recording head is scanned in the forward direction of the main scanning direction and when it is scanned in the backward direction, and an image is formed by scanning at least a plurality of times in the image forming area where the image is formed. A multi-scan printing means,
Color image control means for controlling image formation from a color ink head for discharging the color ink provided in the recording head;
And clear image control means for controlling image formation from a clear ink head which ejects clear ink included in the recording head,
The clear image control means
A height-adjusting clear image control means for controlling image formation with clear ink so that the image height after formation is substantially uniform along with the formation of a color image by the color image control means,
Surface shape for controlling image formation with clear ink so that the image surface shape after formation is substantially uniform after formation of the color image by the color image control unit and the clear image by the height adjusting clear image control unit Clear image control means for adjustment,
Equipped with a,
The clear ink head is disposed on the rear side in the forward direction of the recording head,
In the forward printing, a clear image is formed by the surface shape adjusting clear image control means,
An image forming apparatus characterized in that a clear image is formed by the height adjustment clear image control means in the return pass printing . The recording head is
A first clear ink head for discharging clear ink for forming a clear image by the height adjustment clear image control means;
A second clear ink head for discharging clear ink for forming a clear image by the clear image control means for adjusting the surface shape;
The image forming apparatus according to claim 1 or 2, characterized in that it comprises a. The clear ink head has two or more nozzle rows,
In nozzle row unit,
A nozzle array that discharges a clear ink for forming a clear image by the height adjustment clear image control unit;
The image forming apparatus according to claim 1 or 2, characterized in that assigned a nozzle array for discharging clear ink for forming a clear image by the surface shape adjusting clear image control means, a. Claim 4, characterized in that the clear image by the height adjusting clear image control means, and a clear image by the surface shape adjusting clear image control means, a low resolution than the color image by the color image control means The image forming apparatus according to claim 1. Gloss evaluation chart in which multiple patches are formed for each color ink color while changing the combination of the color ink placement amount per unit area and the clear ink placement amount per unit area for each of the forward printing and the backward printing The image forming apparatus according to any one of claims 1 to 5, further comprising a gloss evaluation chart forming unit that forms the image forming unit. The image forming apparatus according to claim 1, characterized in that it comprises an irradiation unit that irradiates the light at both ends in the main scanning direction of the recording head to 6. An image forming method of discharging an ink that is cured by light irradiation and curing the ink by irradiating light to form an image on an image forming object,
Ink is ejected both when the recording head is scanned in the forward direction of the main scanning direction and when it is scanned in the backward direction, and an image is formed by scanning at least a plurality of times in the image forming area where the image is formed. In the process
A color image forming process for forming a color image;
In parallel with the color image forming process, a height adjusting clear image forming process for forming a clear image so that the image height after formation is substantially uniform;
After the color image forming process and the height adjustment for the clear image forming process, so that the image surface shape after forming becomes substantially uniform, it has rows and the surface shape adjusting clear image forming process for forming a clear image, and
The clear image forming process for height adjustment forms a clear image in the forward pass printing by the clear ink head that is disposed on the leading side in the forward pass direction of the recording head, and the front surface in the forward pass printing. An image forming method, wherein the clear image forming process for shape adjustment forms a clear image . An image forming method of discharging an ink that is cured by light irradiation and curing the ink by irradiating light to form an image on an image forming object,
Ink is ejected both when the recording head is scanned in the forward direction of the main scanning direction and when it is scanned in the backward direction, and an image is formed by scanning at least a plurality of times in the image forming area where the image is formed. In the process
A color image forming process for forming a color image;
In parallel with the color image forming process, a height adjusting clear image forming process for forming a clear image so that the image height after formation is substantially uniform;
After the color image forming process and the height adjustment for the clear image forming process, so that the image surface shape after forming becomes substantially uniform, it has rows and the surface shape adjusting clear image forming process for forming a clear image, and
With the clear ink head that is disposed on the rear side in the forward direction of the recording head and discharges clear ink, the clear image forming process for surface shape adjustment forms a clear image in the forward pass printing, and the high- An image forming method, wherein the clear image forming process for adjusting the depth forms a clear image .