JP2012051252A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in quality of an image.SOLUTION: The image forming apparatus includes: a first head discharging a first electromagnetic wave curable ink; a first irradiation part irradiating a first electromagnetic wave in a first irradiation amount; a second head discharging a second electromagnetic curable ink; and a second irradiation part irradiating a second electromagnetic wave in a second irradiation amount. When the first electromagnetic curable ink is irradiated with the first electromagnetic wave, predetermined glossiness can be obtained, however when it is irradiated with the second electromagnetic wave, the predetermined glossiness cannot be obtained. When the second electromagnetic curable ink is irradiated with the second electromagnetic wave, the predetermined glossiness can be obtained. The second head is disposed more upstream side in a predetermined direction than the first head.

Description

  The present invention relates to an image forming apparatus.

  Some printers that are image forming apparatuses use an electromagnetic wave curable ink that is cured when irradiated with an electromagnetic wave such as ultraviolet rays. In a printer using electromagnetic curable inks of a plurality of colors, a printer has been proposed in which a provisional irradiator that irradiates ultraviolet rays to the extent that the ink is not completely cured is provided between heads that eject different color inks (for example, , See Patent Document 1). By doing so, it is possible to prevent bleeding due to a mixture of different color inks.

JP-A-2005-280346

  In the case of the above-described printer, the ink ejected from the head on the upstream side in the medium transport direction is also affected by the provisional irradiator for semi-curing the ink ejected from the head on the downstream side in the medium transport direction. In the electromagnetic wave curable ink, the provisional irradiation conditions (the number of irradiations and the irradiation energy) for obtaining glossiness differ depending on the composition of each ink. Therefore, if the heads are randomly arranged, an image with no glossiness is printed, and the image quality of the image may be deteriorated.

  Therefore, an object of the present invention is to suppress image quality deterioration of an image.

  The main invention for solving the above problems is that the first electromagnetic wave curable ink is ejected onto the medium, the first head, and the first electromagnetic wave whose irradiation amount per unit area is the first irradiation amount, A first irradiation unit capable of irradiating the first electromagnetic wave curable ink on the medium; a second head capable of ejecting the second electromagnetic wave curable ink to the medium; and an irradiation amount per unit area. A second irradiation unit capable of irradiating the second electromagnetic wave curable ink on the medium with a second electromagnetic wave having a second irradiation amount, and the first head and the second head with respect to the second head. A control unit that forms an image on the medium while moving the relative position of the medium to the downstream side in a predetermined direction, and the first electromagnetic wave curable ink is predetermined when irradiated with the first electromagnetic wave. Is obtained, but the second electromagnetic wave is irradiated. Then, the predetermined glossiness cannot be obtained, and when the second electromagnetic wave curable ink is irradiated with the second electromagnetic wave after landing on the medium, the predetermined glossiness is obtained, The image forming apparatus is characterized in that the second head and the second irradiation unit are arranged upstream of the first head and the first irradiation unit in the predetermined direction.

    Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

1 is a block diagram illustrating a configuration of a printing system. 2A is a schematic sectional view of the printer, and FIG. 2B is a schematic top view of the head unit and the irradiation unit. It is a flow which shows the determination method of arrangement | positioning of UV ink. It is a graph which shows the glossiness and the filling degree with respect to provisional irradiation energy amount. It is a table | surface which shows the result of having evaluated glossiness by changing temporary irradiation energy amount and temporary irradiation frequency | count. It is a figure which shows arrangement | positioning of the determined ink AD.

=== Summary of disclosure ===
At least the following will become apparent from the description of the present specification and the accompanying drawings.

That is, a first head capable of ejecting a first electromagnetic wave curable ink onto a medium, and a first electromagnetic wave whose irradiation amount per unit area is the first irradiation amount are referred to as the first electromagnetic wave on the medium. A first irradiation unit capable of irradiating the curable ink; a second head capable of ejecting the second electromagnetic wave curable ink to the medium; and a second irradiation amount per unit area. A second irradiation unit capable of irradiating the second electromagnetic wave curable ink on the medium with the second electromagnetic wave, and a relative position of the medium with respect to the first head and the second head in a predetermined direction downstream. A control unit that forms an image on the medium while moving to the side, and the first electromagnetic wave curable ink has a predetermined gloss when irradiated with the first electromagnetic wave. When the second electromagnetic wave is irradiated, the predetermined glossiness is obtained. When the second electromagnetic wave curable ink is irradiated with the second electromagnetic wave after landing on the medium, the predetermined glossiness is obtained, and the second head and the second irradiation unit are The image forming apparatus is disposed upstream of the first head and the first irradiation unit in the predetermined direction.
According to such an image forming apparatus, it is possible to obtain a predetermined gloss level for an image portion formed by the first electromagnetic wave curable ink and the second electromagnetic wave curable ink, and to suppress deterioration in image quality of the image. Can do.

In this image forming apparatus, a third head capable of ejecting the third electromagnetic wave curable ink to the medium, and the third electromagnetic wave curable ink on the medium can be irradiated with the first electromagnetic wave. A third irradiating section, and the third electromagnetic wave curable ink can obtain the predetermined glossiness even when the first electromagnetic wave is irradiated a plurality of times, but is irradiated with the second electromagnetic wave. Then, the predetermined glossiness is not obtained, and the third head and the first irradiation unit and the second head and the second irradiation unit in the predetermined direction are arranged between the third head and the second irradiation unit. A head and the third irradiation unit are disposed.
According to such an image forming apparatus, it is possible to obtain a predetermined gloss level for an image portion formed with the third electromagnetic wave curable ink, and to suppress image quality deterioration of the image.

In this image forming apparatus, a fourth head capable of ejecting a fourth electromagnetic wave curable ink onto the medium, and a fourth irradiation capable of irradiating the fourth electromagnetic wave curable ink on the medium with an electromagnetic wave. And the fourth electromagnetic wave curable ink can obtain the predetermined glossiness regardless of whether it is irradiated with the first electromagnetic wave or the second electromagnetic wave. The maximum total irradiation amount of electromagnetic waves per unit area for obtaining glossiness is smaller in the third electromagnetic wave curable ink than in the fourth electromagnetic wave curable ink, and the third head and the third irradiation. The unit is disposed on the downstream side in the predetermined direction with respect to the fourth head and the fourth irradiation unit.
According to such an image forming apparatus, even if an error occurs in the irradiation amount of electromagnetic waves, a predetermined glossiness can be obtained for an image portion formed with the third electromagnetic wave curable ink.

In this image forming apparatus, a fourth head capable of ejecting a fourth electromagnetic wave curable ink onto the medium, and a fourth irradiation capable of irradiating the fourth electromagnetic wave curable ink on the medium with an electromagnetic wave. And the fourth electromagnetic wave curable ink can obtain the predetermined glossiness regardless of whether it is irradiated with the first electromagnetic wave or the second electromagnetic wave. The second electromagnetic wave curable ink is larger in the minimum total irradiation amount of electromagnetic waves per unit area at which glossiness can be obtained than the fourth electromagnetic wave curable ink. The irradiation unit is disposed on the upstream side in the predetermined direction with respect to the fourth head and the fourth irradiation unit.
According to such an image forming apparatus, even when an error occurs in the irradiation amount of the electromagnetic wave, a predetermined glossiness can be obtained for the image portion formed with the second electromagnetic wave curable ink.

The image forming apparatus includes a fourth head capable of ejecting a fourth electromagnetic wave curable ink onto the medium, and the fourth electromagnetic wave curable ink is irradiated with the first electromagnetic wave, Even when the second electromagnetic wave is irradiated, the predetermined glossiness is obtained, and the fourth head is more than a head capable of discharging an electromagnetic wave curable ink having a lightness lower than that of the fourth electromagnetic wave curable ink. Is also disposed on the downstream side in the predetermined direction.
According to such an image forming apparatus, color reproducibility can be improved and image quality deterioration of an image can be suppressed.

=== About the printing system ===
Hereinafter, an embodiment will be described by taking an example of a printing system in which an image forming apparatus is an inkjet printer (hereinafter referred to as a printer) and a printer and a computer are connected.

  FIG. 1 is a block diagram illustrating a configuration of a printing system, FIG. 2A is a schematic cross-sectional view of the printer 1, and FIG. 2B is a schematic top view of a head unit 30 and an irradiation unit 40. The printer 1 of the present embodiment discharges an ultraviolet curable ink (corresponding to “electromagnetic wave curable ink”) that is cured by irradiation of ultraviolet rays toward a medium S such as paper, cloth, or film, thereby causing an image on the medium. Is a device for printing. The ultraviolet curable ink (hereinafter referred to as UV ink) is an ink containing an ultraviolet curable resin, and is cured by a photopolymerization reaction occurring in the ultraviolet curable resin when irradiated with ultraviolet rays.

  The computer 60 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1. The computer 60 is installed with a printer driver for converting image data output from the application program into print data.

  The printer 1 that has received the print data from the computer 60 controls each unit by the controller 10 and prints an image on the medium S. The detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result. The interface unit 11 in the controller 10 is for transmitting and receiving data between the computer 60 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by the unit control circuit 14.

  As shown in FIG. 2A, the transport unit 20 includes transport rollers 21A and 21B and a transport belt 22, and transports the medium S from the upstream side to the downstream side in the transport direction at a constant transport speed. The medium S is transported at a constant transport speed without stopping on the transport belt 22 while facing the head group 31 that ejects UV ink and the irradiation units 41 and 42 that irradiate ultraviolet rays. Note that the medium S on the conveyor belt 22 is attracted by suction or electrostatically attracted, and the displacement of the medium S is prevented.

  The head unit 30 ejects UV ink onto the medium S. The printer 1 according to this embodiment ejects four types of UV inks (details will be described later) having different colors, and the head unit 30 includes four head groups 31 that eject UV inks of the respective colors. The first head group 31 (1), the second head group 31 (2), the third head group 31 (3), and the fourth head group 31 (4) are sequentially referred to from the head group 31 on the upstream side in the transport direction.

  As shown in FIG. 2B, each head group 31 has a plurality of short heads 32 arranged in the width direction intersecting the transport direction. In the short head 32, two nozzle rows are formed in which a plurality of nozzles that discharge UV ink are arranged at intervals of 360 dpi in the width direction. The two nozzle rows are formed so as to be shifted by 720 dpi in the width direction. Further, the ends of the short heads 32 arranged in the width direction overlap. Therefore, in each head group 31, a large number of nozzles are arranged at intervals of 720 dpi in the width direction. The ink discharge method from the nozzle may be a piezo method in which a voltage is applied to the drive element to expand and contract the pressure chamber filled with the ink, or a heating element is used in the nozzle. A thermal method in which bubbles are generated and ink is ejected by the bubbles may be used.

  The irradiation unit 40 is for irradiating the UV ink landed on the medium S with ultraviolet rays and curing the UV ink. The irradiation unit 40 includes a plurality of provisional irradiation units 41 and a main irradiation unit 42. Therefore, the UV ink is cured in two stages by the provisional irradiation unit 41 and the main irradiation unit 42.

In the printer 1 of the present embodiment, the number of provisional irradiation units 41 is four, which is the same as the number of head groups 31, and the provisional irradiation units 41 are provided on the downstream side in the transport direction of each head group 31. The first provisional irradiation section 41 (1), the second provisional irradiation section 41 (2), the third provisional irradiation section 41 (3), and the fourth provisional irradiation section 41 (4) in order from the provisional irradiation section 41 on the upstream side in the transport direction. ). The provisional irradiation unit 41 includes a number of light emitting diodes (LEDs) as a light source for ultraviolet irradiation. The LED can change the irradiation intensity (mW / cm ² ) of ultraviolet rays by controlling the magnitude of the input current.

  Further, the provisional irradiation unit 41 temporarily irradiates the UV ink ejected from the head group 31 with ultraviolet rays, and temporarily cures the UV ink. Temporary curing means that the UV ink is not completely cured. By temporary curing, it is possible to suppress the flow (spreading of dots) of the UV ink that has landed on the medium S. Further, in the printer 1 of the present embodiment, the provisional irradiation unit 41 is provided between the head groups 31 that discharge UV inks of different colors. Therefore, the UV ink ejected from a certain head group 31 is temporarily cured by the provisional irradiation unit 41 before the UV ink is ejected from the head group 31 downstream of the head group 31 in the transport direction. As a result, bleeding between different color UV inks can be prevented.

  As shown in FIG. 2, the main irradiation unit 42 is provided downstream of the head group 31 and the provisional irradiation unit 41 in the transport direction, and the main ultraviolet irradiation is performed on the UV ink ejected from the four head groups 31. Then, the UV ink is fully cured. The main curing means that the UV ink is completely cured. The main irradiation unit 42 includes a lamp (for example, a metal halide lamp or a mercury lamp) as a light source for ultraviolet irradiation.

The provisional irradiation unit 41 does not completely cure the UV ink, and the main irradiation unit 42 completely cures the UV ink. Therefore, the main irradiation unit 42 has a higher irradiation energy amount (mJ / cm ² ) of ultraviolet rays per unit area than the provisional irradiation unit 41. The amount of irradiation energy per unit area (mJ / cm ² ) is determined by the product of ultraviolet irradiation intensity (mW / cm ² ) and irradiation time (s). Further, as shown in FIG. 2B, the width in the width direction of the provisional irradiation unit 41 and the main irradiation unit 42 is approximately the same as the length in the width direction of the head group 31. By doing so, the UV ink that has landed on the medium S can be irradiated with ultraviolet rays over the entire region in the width direction.

  In summary, in the printer 1 of the present embodiment, the head group 31 ejects UV ink to the medium S that is transported on the transport belt 22 at a constant speed, and the provisional irradiation unit 41 is on the medium S. The landing UV ink is temporarily cured. Finally, the main irradiation unit 42 performs the main curing of the UV ink, and the printing of the image on the medium S is completed.

=== Regarding UV Ink Arrangement ===
<About ink composition>
The printer 1 of this embodiment ejects four types of UV ink (ink A, ink B, ink C, and ink D). The composition of each ink A to D is shown below. Inks A to D have viscosities of 27 to 33 mPa · s at 20 ° C. and 10 to 13 mPa · s at 40 ° C.

  Ink A (yellow ink) is 19.0 parts by mass of a pigment dispersion (described later) and 100 parts by mass of tripropylene glycol diacrylate (trade name: NK ester APG-200, as a photopolymerizable monomer). 16.1 parts by mass of Shin-Nakamura Chemical Co., Ltd., 15.5 parts by mass of dipropylene glycol diacrylate (trade name: NK Ester APG-100, manufactured by Shin-Nakamura Chemical Co., Ltd.), phenoxyethyl acrylate (trade name: Biscote #) 192, manufactured by Osaka Organic Chemical Industry Co., Ltd.), 27.1 parts by mass, and dimethylol tricyclodecane diacrylate (trade name: NK Ester A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.), 5.5 parts by mass, and amino acrylate (Product name: EBECRYL7100, manufactured by Daicel Cytec Co., Ltd.) 3.5 parts by mass, p-Met as a polymerization inhibitor BYK UV-3500 (product) with 0.2 parts by weight of siphenol (trade name, manufactured by Kanto Chemical Co., Ltd.) and 0.1 part by weight of UV-10 (trade name, manufactured by Ciba Specialty Chemicals) and a surfactant. Name, manufactured by Big Chemie Japan) 0.2 parts by mass, and photoinitiator, IRGACURE 819 (trade name, manufactured by Ciba Specialty Chemicals) 5.5 parts by mass, DAROCURE TPO (trade name, manufactured by Ciba Specialty Chemicals) 4.5 parts by mass and 2.8 parts by mass of KAYACURE DETX-S (trade name, manufactured by Nippon Kayaku Co., Ltd.) are mixed. The ink A is produced by sufficiently stirring and dissolving the mixture.

  The pigment dispersion of ink A is prepared as follows. As a colorant with respect to 100 parts by mass, C.I. I. 15 parts by weight of Pigment Yellow 180, 5 parts by weight of Discol N-509 (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.) and phenoxyethyl acrylate (trade name: Biscote # 192, Osaka Organic Chemical Industry) 80 parts by mass of the product (manufactured) is sufficiently mixed, and dispersion treatment is performed for 10 hours with zirconia beads (diameter 1.5 mm) using a sand mill (manufactured by Yaskawa Seisakusho). Thereafter, the zirconia beads are separated with a separator.

  Ink B (black ink) is 14.0 parts by weight of pigment dispersion, 19.6 parts by weight of tripropylene glycol diacrylate, 19.1 parts by weight of dipropylene glycol diacrylate, and 100 parts by weight of phenoxy. 23.0 parts by mass of ethyl acrylate, 7.5 parts by mass of dimethylol tricyclodecane diacrylate, 3.5 parts by mass of amino acrylate, 0.2 parts by mass of p-methoxyphenol, 0.1% of UV-10 0.2 parts by mass of BYK UV-3500, 5.5 parts by mass of IRGACURE 819, 4.5 parts by mass of DAROCURE TPO, and 2.8 parts by mass of KAYACURE DETX-S are mixed. The ink B is produced by sufficiently stirring and dissolving the mixture.

  The composition of the pigment dispersion of ink B is C.I. I. The pigment black 7 is 15 parts by mass, the disc N-509 is 5 parts by mass, and the phenoxyethyl acrylate is 80 parts by mass.

  Ink C (magenta ink) is 26.5 parts by mass of the pigment dispersion, 10.5 parts by mass of tripropylene glycol diacrylate, 10.6 parts by mass of dipropylene glycol diacrylate, and 100 parts by mass of phenoxy. 32.0 parts by mass of ethyl acrylate, 4.5 parts by mass of dimethylol tricyclodecane diacrylate, 3.5 parts by mass of amino acrylate, 0.2 parts by mass of p-methoxyphenol, 0.1% of UV-10 0.2 parts by mass of BYK UV-3500, 5.0 parts by mass of IRGACURE 819, 4.5 parts by mass of DAROCURE TPO, and 2.4 parts by mass of KAYACURE DETX-S are mixed. The ink C is produced by sufficiently stirring and dissolving the mixture.

  The composition of the pigment dispersion of ink B is C.I. I. The pigment red 122 is 15 parts by mass, the disc N-509 is 5 parts by mass, and the phenoxyethyl acrylate is 80 parts by mass.

  Ink D (green ink) is 17.5 parts by mass of pigment dispersion, 17.5 parts by mass of tripropylene glycol diacrylate, 17.0 parts by mass of dipropylene glycol diacrylate, and 100 parts by mass of phenoxy. 26.6 parts by mass of ethyl acrylate, 5.5 parts by mass of dimethylol tricyclodecane diacrylate, 3.5 parts by mass of amino acrylate, 0.2 parts by mass of p-methoxyphenol, 0.1% of UV-10 0.2 parts by mass of BYK UV-3500, 5.0 parts by mass of IRGACURE 819, 4.5 parts by mass of DAROCURE TPO, and 2.4 parts by mass of KAYACURE DETX-S are mixed. The ink D is produced by sufficiently stirring and dissolving the mixture.

  The composition of the pigment dispersion of ink D is 100 parts by mass with respect to C.I. I. The pigment green 36 is 15 parts by mass, Discol N-509 is 5 parts by mass, and phenoxyethyl acrylate is 80 parts by mass.

  Usually, in color printing, four colors of ink (yellow, magenta, cyan, black) are used as basic inks. In order to improve color reproducibility, green ink or orange ink is used. However, in this embodiment, for the sake of simplicity, an example in which the printer 1 uses four types of ink (yellow, black, magenta, and green) having different characteristics will be described.

<Method for determining UV ink arrangement>
FIG. 3 is a flow showing a method for determining the arrangement of UV ink, FIG. 4 is a graph showing the glossiness and the degree of filling with respect to the provisional irradiation energy amount, and FIG. 5 shows the provisional irradiation energy amount and the number of provisional irradiations. It is a table | surface which shows the result of having changed and evaluated the glossiness. “Determining the arrangement of UV ink” means determining from which head group 31 of the four head groups 31 (1) to 31 (4) the four types of inks A to D are ejected. Say. Hereinafter, the irradiation energy amount (mJ / cm ² ) per unit area in the temporary irradiation unit 41 is referred to as “temporary irradiation energy amount”.

  In the printer 1 of the present embodiment, provisional irradiation units 41 (1) to 41 (4) are provided on the downstream sides of the four head groups 31 (1) to 31 (4). Therefore, the ink ejected from the first head group 31 (1) is provisionally irradiated four times by the first provisional irradiation unit 41 (1) to the fourth provisional irradiation unit 41 (4). On the other hand, the ink ejected from the second head group 31 (2) is provisionally irradiated three times by the second provisional irradiation unit 41 (2) to the fourth provisional irradiation unit 41 (4), and the third head group 31 (3). The ink ejected from the head is temporarily irradiated twice by the third provisional irradiation unit 41 (3) and the fourth provisional irradiation unit 41 (4), and the ink ejected from the fourth head group 31 (4) is the fourth provisional irradiation. Preliminary irradiation is performed only once by the unit 41 (4). In other words, the number of provisional irradiations with respect to the inks A to D varies depending on which of the head groups 31 (1) to 31 (4) ejects which inks A to D.

By the way, in the UV ink, the conditions of provisional irradiation for obtaining a glossy feeling differ depending on the composition. The provisional irradiation conditions are the number of provisional irradiations and the provisional irradiation energy amount (mJ / cm ² ). For this reason, for example, if ink that does not provide glossiness is ejected from the first head group 31 (1) on the upstream side in the transport direction when the number of provisional irradiations is large, the ink is provisionally irradiated four times. As a result, the glossiness of the ink cannot be obtained, and the image quality of the printed image is deteriorated. Also, ink that does not give a glossy feeling when irradiated with ultraviolet rays having a high provisional irradiation energy amount is ejected from the head group 31 located upstream in the transport direction from the provisional irradiation unit 41 having a high provisional irradiation energy amount. Then, the ink is irradiated with ultraviolet rays having a high provisional irradiation energy amount. As a result, the glossiness of the ink cannot be obtained, and the image quality of the printed image is deteriorated.

That is, if the arrangement of the UV ink is randomly determined without considering the provisional irradiation condition for obtaining a glossy feeling, the image quality of the printed image may be deteriorated.
Therefore, when determining the arrangement of the UV ink in the design process of the printer 1 or re-deciding the arrangement of the UV ink in order to change the type of UV ink to be used, the arrangement of the UV ink is determined according to the flow shown in FIG. Good.

First, regarding the inks A to D to be used, the glossiness with respect to the provisional irradiation energy amount and the filling degree are acquired (S01). For this purpose, the graph shown in FIG. 4 is created. In the graph of FIG. 4, the horizontal axis indicates a temporary irradiation energy amount (mJ / cm ² ) for one time, the temporary irradiation energy amount is higher on the right side of the horizontal axis, and the temporary irradiation energy amount is lower on the left side. The vertical axis indicates the glossiness, the glossiness is better as the upper side of the vertical axis is lower, and the glossiness is lower as the lower side of the vertical axis. The pre-irradiation unit 41 changes the energy amount of ultraviolet rays irradiated to each of the inks A to D once to evaluate the glossiness, and creates the graph shown in FIG. More specifically, a pattern is printed for each of the inks A to D, and the amount of ultraviolet energy that is irradiated once to the pattern is changed. The glossiness of the pattern thus obtained is evaluated.

From the graph of FIG. 4, the following can be seen for ink A to ink D used in the present embodiment.
The glossiness of the ink A is indicated by a thick dashed line in the graph of FIG. The ink A has good glossiness in a region where the provisional irradiation energy amount is low (low energy region in the figure), but the glossiness deteriorates in a region where the provisional irradiation energy amount is intermediate (intermediate energy region in the drawing). However, the glossiness is improved again in a region where the provisional irradiation energy amount is high (high energy region in the figure).
The glossiness of the ink B is indicated by a thick dotted line in the graph of FIG. Like ink A, ink B has good gloss in the low energy region and high energy region, but poor gloss in the intermediate energy region. However, the ink B has a higher provisional irradiation energy amount than the ink A, starting to deteriorate in glossiness from the low energy region to the intermediate energy region.
The glossiness of the ink C is indicated by a two-dot chain thick line in the graph of FIG. Ink C always has good gloss regardless of the amount of provisional irradiation energy.
The glossiness of the ink D is indicated by a solid thick line in the graph of FIG. The ink D has a low glossiness in the low energy region, but the glossiness improves as the temporary irradiation energy amount increases, and the glossiness improves in the intermediate energy region and the high energy region.

  In the graph of FIG. 4, not only the glossiness of each of the inks A to D but also the filling degree is shown. The degree of filling indicates the degree to which the medium fills the ink (degree of covering the medium with ink). The degree of filling is better as the upper side of the vertical axis in FIG. 4 (a wide range of media is filled with ink), and the degree of filling is lower as the lower side of the vertical axis (only a narrow range of media is filled with ink). Since the degree of filling does not change greatly according to the composition of the ink, the degree of filling of all the inks A to D is collectively shown by solid thin lines in the graph of FIG.

  From the graph of FIG. 4, it can be seen that the degree of filling worsens as the amount of provisional irradiation energy increases. This is because, as the UV ink is irradiated with a higher energy amount of ultraviolet light, the degree of cure of the UV ink increases and the spread of the UV ink is suppressed. That is, as the provisional irradiation energy amount increases, the dot diameter of the UV ink decreases and the filling of the medium worsens.

  Further, the UV ink has a property that, when the degree of curing is increased, the ink droplets ejected thereon are easily repelled. Therefore, when dots of UV inks of different colors are formed in an overlapping manner, if the degree of cure of the lower layer dots increases, ink droplets ejected thereon are likely to be repelled. Also from this point, it can be said that as the provisional irradiation energy amount becomes higher, the filling of the medium becomes worse. In addition, when the degree of cure of the lower layer dots is high and the upper layer dots are likely to be repelled, the fixing of the lower layer dots and the upper layer dots is poor, and the upper layer dots are easily peeled off.

After the graph of FIG. 4 is created in this way, a table (FIG. 5) showing the result of evaluating the glossiness by changing the provisional irradiation energy amount and the number of provisional irradiations is created (S02 in FIG. 3). In the printer 1 of the present embodiment, the number of provisional irradiations with respect to the UV ink ejected from the head group 31 on the upstream side in the transport direction is a plurality of times. Further, in the UV ink, even when the total amount of provisional irradiation energy to be irradiated is the same, the case of irradiating a high amount of provisional irradiation energy at one time and the case of irradiating a low amount of provisional irradiation energy in multiple times. In some cases, the effect on glossiness is different. For example, in the case of irradiating ultraviolet rays of 20 mJ / cm ² at a time, in the case of irradiation in four ultraviolet rays 5 mJ / cm ^2, the glossiness of the UV ink is different. Therefore, in addition to the graph of FIG. 4 which is the result of evaluating the glossiness when ultraviolet rays are temporarily irradiated once, a table showing the results of evaluating the glossiness by changing the amount of temporary irradiation energy and the number of temporary irradiations (FIG. 4) 5) is also created.

  In the graph of FIG. 4, the glossiness of all inks A to D is improved in the high energy region, but the filling degree is deteriorated. Therefore, the provisional irradiation energy amount in the provisional irradiation unit 41 is determined within the low energy region in order to improve the degree of filling while obtaining a glossy feeling.

In the present embodiment, the range of the low energy region in the graph of FIG. 4 and ^{5mJ / cm 2 ~15mJ / cm 2} , the candidate values of the provisional irradiation energy amount in preliminary radiating unit ^{41, 5mJ / cm 2 · 10mJ} / cm 2 - and 15mJ / cm ^2. In addition, since the printer 1 of the present embodiment includes the four provisional irradiation units 41, the number of times that the inks A to D may be provisionally irradiated is 1 to 4 times. Therefore, the glossiness of inks A to D is evaluated by changing the provisional irradiation energy amount to 5 · 10 · 15 mJ / cm ² and changing the provisional irradiation frequency from 1 to 4 times.

More specifically, first, a pattern is printed for each of the inks A to D. Then, the glossiness in each case where the pattern is temporarily irradiated once to four times with a temporary irradiation energy amount of 5 mJ / cm ² is evaluated. Similarly, the glossiness in each case where the pattern was temporarily irradiated once to four times with a temporary irradiation energy amount of 10 mJ / cm ² was evaluated, and the pattern was subjected to a temporary irradiation energy amount of 15 mJ / cm ^2. The glossiness in each case of preliminary irradiation from 1 to 4 times is evaluated. That is, the glossiness is evaluated 12 times for each of the inks A to D.

  The glossiness is evaluated as a three-level evaluation, with “◯” when the glossiness is good, “Δ” when the glossiness is not very good, and “X” when the glossiness is bad. In the present embodiment, the condition that the glossiness evaluation result is “◯” is set as a condition for obtaining a predetermined glossiness, and the condition that the glossiness evaluation result is “Δ” or “×” is set as a predetermined glossiness. It is assumed that the degree cannot be obtained. The glossiness evaluation method is not limited to this. For example, when the glossiness is digitized, a threshold value is set, a condition where the glossiness is equal to or higher than the threshold value is set as a condition for obtaining the predetermined glossiness, and a condition where the glossiness is lower than the threshold value is obtained for the predetermined glossiness. It may be a condition that is not possible.

The following can be understood from the table of FIG.
When the ink A is temporarily irradiated once or twice with a temporary irradiation energy amount of 5 mJ / cm ² , a predetermined glossiness is obtained (evaluation of the glossiness becomes “good”). However, a predetermined glossiness cannot be obtained when the amount of provisional irradiation energy or the number of provisional irradiations is more than that (evaluation of glossiness is Δ or x).
When the ink B is preliminarily irradiated from 1 to 4 times with a temporary irradiation energy amount of 5 mJ / cm ² , a predetermined glossiness is obtained. However, a predetermined glossiness cannot be obtained with a temporary irradiation energy amount of 10 mJ / cm ² or more.

Ink C has a predetermined gloss level under all provisional irradiation conditions.
When the ink D is temporarily irradiated from 1 to 4 times with a temporary irradiation energy amount of 15 mJ / cm ² , a predetermined glossiness is obtained. However, a predetermined glossiness cannot be obtained with a temporary irradiation energy amount of 10 mJ / cm ² or less.

  Finally, the arrangement of the UV ink (inks A to D) is determined based on the graph of FIG. 4 and the table of FIG. 5 (S03 in FIG. 3). That is, it is determined which ink A to D is ejected from which head group 31 (1) to 31 (4). Moreover, the temporary irradiation energy amount in each temporary irradiation part 41 (1) -41 (4) is determined.

First, the temporary irradiation energy amount in each temporary irradiation part 41 (1) -41 (4) is determined. Therefore, in each of the inks A to D, a range of provisional irradiation energy in which a predetermined glossiness is obtained (that is, a range of provisional irradiation energy amount in which the glossiness evaluation is “◯”. Focus on the range of energy). Ink A and ink B have only a temporary irradiation energy amount of “5 mJ / cm ² ” for obtaining a predetermined glossiness. The ink C has a provisional irradiation energy amount of “5 mJ / cm ² or more and 15 mJ / cm ² or less” for obtaining a predetermined glossiness. The ink D has only a temporary irradiation energy amount of “15 mJ / cm ² ” for obtaining a predetermined glossiness.

As shown in the graph of FIG. 4, the higher the provisional irradiation energy amount, the worse the degree of filling. Therefore, the provisional irradiation energy amount of the provisional irradiation unit 41 is preferably set as low as possible. Therefore, the temporary irradiation energy amount of ink A to ink C is set to “5 mJ / cm ² ”, and the temporary irradiation energy amount of ink D is set to “15 mJ / cm ² ”. That is, the provisional irradiation energy amount of the provisional irradiation unit 41 located immediately downstream of the head group 31 that ejects ink A to ink C is set to “5 mJ / cm ² ”, and the head group 31 that ejects ink D is set. The temporary irradiation energy amount of the temporary irradiation part 41 located immediately downstream is set to “15 mJ / cm ² ”.

  Thus, the provisional irradiation energy amount in the provisional irradiation unit 41 may be set to the lowest provisional irradiation energy amount in the range of the provisional irradiation energy amount in which a predetermined glossiness is obtained. By doing so, it is possible to improve the filling of the medium while obtaining a predetermined glossiness. In other words, the ink dot diameter can be prevented from becoming too small, and a desired color can be reproduced. Moreover, by setting the provisional irradiation energy amount in the provisional irradiation unit 41 to be low, the number of LEDs provided in the provisional irradiation unit 41 can be reduced, the cost can be reduced, and the power consumption can be suppressed.

  Next, the arrangement is determined from the ink having a narrow provisional irradiation condition for obtaining a predetermined glossiness. Since the ink C has a predetermined glossiness under all provisional irradiation conditions, first, the arrangement of the ink A, the ink B, and the ink D is determined.

By the way, the UV ink is most affected by the provisional irradiation energy amount that is first irradiated after the UV ink has landed on the medium. For example, ink D is, 15 mJ / cm but ² of ultraviolet is improved glossiness if temporarily irradiated once, the degree of gloss is deteriorated only ultraviolet 5 mJ / cm ² is temporarily irradiated one or more times . In such a case, if the temporary irradiation energy amount irradiated to the ink D for the first time is set to 15 mJ / cm ² , the ink D is glossy even if the temporary irradiation energy amount irradiated for the second time or later is lower than 15 mJ / cm ^2. The degree improves.

However, when the temporary irradiation energy amount irradiated after the second time is higher than the temporary irradiation energy amount irradiated the first time, the UV ink is affected by the higher temporary irradiation energy amount. For example, the ink A and ink B, 5 mJ / cm but ² of ultraviolet is improved glossiness if temporarily irradiated once, the glossiness is deteriorated with ultraviolet 15 mJ / cm ² are temporarily irradiated once. In such a case, even if the temporary irradiation energy amount that is first irradiated to the inks A and B is set to 5 mJ / cm ² , the inks A and B are irradiated with ultraviolet rays of 15 mJ / cm ^{2 from} the second time onward. , Glossiness will deteriorate.

That is, the ink A · Ink B is the provisional irradiation energy amount is irradiated with ultraviolet rays is 5 mJ / cm ² given gloss is obtained, ultraviolet provisional irradiation energy amount is 10 mJ / cm ² and, When irradiated with ultraviolet rays of 15 mJ / cm ² , a predetermined glossiness cannot be obtained. On the other hand, when the ink D is first irradiated with ultraviolet rays having a temporary irradiation energy amount of 15 mJ / cm ² after landing on the medium, a predetermined glossiness is obtained.

As described above, the ink ejected from the head group 31 on the upstream side in the transport direction temporarily irradiates the ink ejected from the head group 31 on the downstream side in the transport direction as well as the provisional irradiation unit 41 located immediately downstream. Therefore, ultraviolet rays are also emitted from the provisional irradiation unit 41. Therefore, if the ink A and the ink B are ejected from the head group 31 on the upstream side of the transport direction with respect to the ink D, the ultraviolet rays of 15 mJ / cm ² for temporarily curing the ink D are applied to the ink A and the ink B. Will be irradiated. As a result, the ink A and the ink B cannot obtain a predetermined glossiness. Therefore, the ink D is ejected from the head group 31 upstream of the inks A and B in the transport direction. In other words, the ink D having a higher provisional irradiation energy amount is ejected from the head group 31 on the upstream side in the transport direction than the inks A and B having a lower provisional irradiation energy amount.

Next, with regard to the ink A and the ink B, attention is focused on the maximum number of irradiation times of 5 mJ / cm ² ultraviolet rays that can be irradiated to obtain a predetermined glossiness. From the table of FIG. 5, it can be seen that the maximum number of times of irradiation of ink A is two and the maximum number of times of irradiation of ink B is four. As described above, the ink A and the ink B can obtain a predetermined glossiness even when the ultraviolet ray of 5 mJ / cm ² is irradiated a plurality of times. Therefore, the ink B may be ejected from the head group 31 between the head group 31 that ejects the ink D and the head group 31 that ejects the ink A, or the head group 31 that ejects the ink D and the ink B are ejected. Ink A may be ejected from the head group 31 between the head groups 31.

  However, it is preferable to discharge the ink having the smaller maximum number of irradiations, that is, the ink A, from the head group 31 on the downstream side in the transport direction. The fact that the maximum number of times of irradiation is small means that the maximum value of the total amount of provisional irradiation energy for obtaining a predetermined glossiness is small. That is, it is preferable that the smaller the maximum value of the provisional irradiation energy total amount that provides a predetermined glossiness, the more the ink is ejected from the head group 31 on the downstream side in the transport direction.

  The provisional irradiation energy amount may be higher than the design value due to an error in irradiation intensity of the provisional irradiation unit 41 or an error in irradiation time due to uneven conveyance of the medium. When ink A having a small maximum value of the total amount of provisional irradiation energy that provides a predetermined glossiness is ejected from the head group 31 on the upstream side in the transport direction, the margin for errors in the amount of provisional irradiation energy becomes small. Therefore, if the provisional irradiation energy amount is higher than the design value, the ink A may not obtain a predetermined glossiness.

Specifically, in ink A, a predetermined glossiness is obtained until the total amount of provisional irradiation energy is “10 mJ / cm ² (= 5 mJ / cm ² × 2 times)”, and in ink B, provisional irradiation energy is obtained. A predetermined glossiness is obtained until the total amount is “20 mJ / cm ² (= 5 mJ / cm ² × 4 times)”. If the ink A is ejected from the head group 31 on the upstream side in the transport direction with respect to the ink B, the total design amount of the provisional irradiation energy applied to the ink A is 10 mJ / cm ² . Therefore, if an error occurs in the temporary irradiation energy amount, the total amount of temporary irradiation energy irradiated to the ink A becomes larger than 10 mJ / cm ² , and the ink A cannot obtain a predetermined glossiness. On the other hand, if the ink B is ejected from the head group 31 on the upstream side in the transport direction from the ink A, an error occurs in the temporary irradiation energy amount, and the total amount of the temporary irradiation energy amount irradiated to the ink B is 10 mJ / cm ^2. Even if it becomes larger than this, the ink B can obtain a predetermined glossiness.

  In other words, the smaller the maximum value of the total amount of provisional irradiation energy that can obtain the predetermined glossiness, the more the predetermined glossiness can be obtained more reliably by ejecting it from the head group 31 on the downstream side in the transport direction. Therefore, in this embodiment, ink D, ink B, and ink A are ejected in this order from the upstream side in the transport direction.

Note that if the ink A cannot obtain a predetermined glossiness when it is irradiated with ultraviolet rays of 5 mJ / cm ² a plurality of times, the ink A will naturally be in the fourth head group 31 located on the most downstream side in the transport direction. It is determined that the liquid is discharged from (4).

Next, the order in which the ink C is ejected with respect to the ink A, the ink B, and the ink D is determined. First, the order of ink C and ink D is determined. In order to obtain a predetermined glossiness, the ink C can be irradiated with ultraviolet rays of 15 mJ / cm ² or less up to four times, and the ink D can be irradiated with ultraviolet rays of 15 mJ / cm ² up to four times (from the second time onward) The ultraviolet ray may be 15 mJ / cm ² or less). Therefore, ink C, ink D, ink B, and ink A may be ejected in this order from the upstream side in the transport direction, or ink D, ink C, ink B, and ink A may be ejected in this order.

  As described above, the provisional irradiation energy amount may be higher than the design value due to an error in the provisional irradiation unit 41 or a medium conveyance error. For this reason, it is preferable that ink having a small maximum value of the total provisional irradiation energy that can obtain a predetermined glossiness be ejected from the head group 31 on the downstream side in the transport direction. On the contrary, the provisional irradiation energy amount may be lower than the design value due to an error of the provisional irradiation unit 41 or a medium conveyance error. For this reason, it is preferable that ink having a large minimum value of the total provisional irradiation energy that provides a predetermined glossiness is ejected from the head group 31 on the upstream side in the transport direction. By doing so, even if the provisional irradiation energy amount becomes lower than the design value, since a larger number of provisional irradiation units 41 are irradiated with ultraviolet rays, the total provisional irradiation energy amount can be increased as much as possible. As a result, a predetermined glossiness can be obtained more reliably.

Therefore, in order to determine the order of the ink C and the ink D, attention is paid to the range of the total amount of provisional irradiation energy in which a predetermined glossiness is obtained. In the ink C, and to obtain a predetermined gloss to the ultraviolet rays of 5 mJ / cm ² may be applied once, or may be irradiated up to four times the ultraviolet 15 mJ / cm ^2. Therefore, in ink C, the range of the total amount of provisional irradiation energy for obtaining a predetermined glossiness is “5 mJ / cm ² or more and 60 mJ / cm ² or less”. On the other hand, in order to obtain a predetermined gloss level, the ink D may be irradiated with ultraviolet rays of 15 mJ / cm ² up to four times. Therefore, in the ink D, the range of the total amount of provisional irradiation energy for obtaining a predetermined glossiness is “15 mJ / cm ² or more and 60 mJ / cm ² or less”.

Ink C and Ink D have the same maximum value (60 mJ / cm ² ) of the total amount of provisional irradiation energy for obtaining a predetermined glossiness. Therefore, the minimum value of the total provisional irradiation energy amount for obtaining the predetermined glossiness is compared between the ink C and the ink D. As a result, the minimum value of the total amount of provisional irradiation energy with which the predetermined glossiness can be obtained for ink D is larger than that for ink C. In this case, the ink D is ejected from the head group 31 upstream of the ink C in the transport direction. By doing so, since the total amount of provisional irradiation energy irradiated to the ink D becomes large, even if an error occurs in the amount of provisional irradiation energy, a predetermined glossiness can be obtained.

Similarly, the order of inks A and B and ink C is also determined. In order to obtain a predetermined glossiness, the ink A can be irradiated with ultraviolet rays of 5 mJ / cm ² up to two times, and the ink B and the ink C can be irradiated with ultraviolet rays of 5 mJ / cm ² up to four times. Therefore, ink D, ink C, ink B, and ink A may be ejected in this order from the upstream side in the transport direction, ink D, ink B, ink C, and ink A may be ejected in this order, or ink D Ink B, ink A, and ink C may be ejected in this order.

Then, with respect to ink A, ink B, and ink C, attention is focused on the range of the total amount of provisional irradiation energy that provides a predetermined glossiness. In the ink A, the scope of the provisional irradiation energy total amount of predetermined glossiness is obtained "5 mJ / cm ² or more 10 mJ / cm ² or less", and the ink B, of the preliminary radiating energy total amount of predetermined glossiness is obtained range is "5 mJ / cm ² or more 20 mJ / cm ² or less", and the ink C, the range of the provisional irradiation energy total amount of predetermined glossiness is obtained "5 mJ / cm ² or more 60 mJ / cm ² or less."

Ink A, ink B, and ink C have the same minimum value (5 mJ / cm ² ) of the total amount of provisional irradiation energy that provides a predetermined glossiness. Therefore, in ink A, ink B, and ink C, the maximum values of the total provisional irradiation energy amounts that can obtain a predetermined glossiness are compared. As a result, the maximum value of the total amount of provisional irradiation energy with which the predetermined glossiness is obtained is smaller for ink A and ink B than for ink C. In this case, ink A and ink B are ejected from the head group 31 downstream of the ink C in the transport direction. That is, ink D, ink C, ink B, and ink A are ejected in this order from the upstream side in the transport direction. By doing so, even if an error occurs in the provisional irradiation energy amount, the ultraviolet rays are temporarily irradiated to the ink A and the ink B exceeding the maximum value of the total provisional irradiation energy amount that provides a predetermined glossiness. And a predetermined glossiness can be obtained.

  Thus, the provisional irradiation energy amount that is first irradiated after the ink A to the ink D land on the medium and the arrangement of the ink A to the ink D are determined.

FIG. 6 is a diagram showing the determined arrangement of inks A to D. As shown in FIG. In the present embodiment, as described above, it is determined that ink D, ink C, ink B, and ink A are ejected in this order from the upstream side in the transport direction. That is, the ink D is ejected from the first head group 31 (1), the ink C is ejected from the second head group 31 (2), the ink B is ejected from the third head group 31 (3), and the fourth head Ink A is ejected from the group 31 (4). Further, the first preliminary irradiation unit 41 (1) is irradiated with ultraviolet rays of 15 mJ / cm ² (ultraviolet rays having an irradiation amount per unit area of 15 mJ), and the second preliminary irradiation unit 41 (2) and the third preliminary irradiation. The unit 41 (3) and the fourth provisional irradiation unit 41 (4) irradiate with 5 mJ / cm ² of ultraviolet rays (ultraviolet rays having an irradiation amount per unit area of 5 mJ).

In summary, in the printer 1 of the present embodiment, the ink A to be used (corresponding to the first electromagnetic wave curable ink) is predetermined when irradiated with ultraviolet rays (corresponding to the first electromagnetic wave) of 5 mJ / cm ^2. However, when irradiated with ultraviolet rays (corresponding to the second electromagnetic wave) of 15 mJ / cm ² , the predetermined glossiness cannot be obtained, and ink D (corresponding to the second electromagnetic wave curable ink) is obtained. ) Is the first head group 31 (1) (corresponding to the second head) that discharges the ink D when the first ultraviolet ray of 15 mJ / cm ² is irradiated after the landing on the medium. ) And a fourth head group 31 (4) that ejects ink A by a first irradiation unit 41 (1) (corresponding to a second irradiation unit) that irradiates the ink D on the medium with ultraviolet rays of 15 mJ / cm ^2. ) (Equivalent to the first head) and ink A on the medium It is arranged upstream of the fourth irradiation section 41 (4) (corresponding to the first irradiation section) that irradiates 5 mJ / cm ² of ultraviolet rays. Note that if the ink D is irradiated with 15 mJ / cm ² of ultraviolet light for the first time, a predetermined glossiness can be obtained even when irradiated with 5 mJ / cm ² of ultraviolet light for the second time and thereafter.

By doing so, the ink D is irradiated with ultraviolet rays of 15 mJ / cm ^2, a predetermined glossiness is obtained for the image portion formed with the ink D, and the ink A is irradiated with ultraviolet rays of 5 mJ / cm ² , Further, since it is possible to prevent the ink A from being irradiated with ultraviolet rays of 15 mJ / cm ^2, a predetermined glossiness can be obtained for the image portion formed with the ink A. As a result, it is possible to suppress image quality deterioration of the printed image.

Further, in the printer 1 of the present embodiment, the ink B (corresponding to the third electromagnetic wave curable ink) to be used can obtain a predetermined glossiness even when irradiated with ultraviolet rays of 5 mJ / cm ² a plurality of times, but 15 mJ When the ultraviolet ray of / cm ² is irradiated, a predetermined glossiness cannot be obtained, and the fourth head group 31 (4) and the fourth provisional irradiation unit 41 (4) in the transport direction, and the first head group 31 (1) And a third head group 31 (3) (corresponding to the third head) that ejects ink B between the first preliminary irradiation section 41 (1) and the ink B on the medium of 5 mJ / cm ² . A third provisional irradiation unit 41 (3) (corresponding to a third irradiation unit) that irradiates ultraviolet rays is arranged.

By doing so, the ink B can be prevented from being irradiated with 15 mJ / cm ² of ultraviolet light, and the ink B can be irradiated with 5 mJ / cm ² of ultraviolet light multiple times. A predetermined gloss level is obtained for the image portion. As a result, it is possible to suppress image quality deterioration of the printed image.

Further, in the printer 1 of the embodiment, (corresponding to a fourth electromagnetic wave curable ink) Ink C to be used, it is irradiated with ultraviolet light of 5 mJ / cm ^2, even if irradiated with ultraviolet rays of 15 mJ / cm ² The maximum value of the total amount of provisional irradiation energy at which the predetermined glossiness is obtained and the predetermined glossiness is obtained (the maximum total irradiation amount of electromagnetic waves per unit area at which the predetermined glossiness is obtained) is greater than that of the ink C. The third head group 31 (3) and the third provisional irradiation unit 41 (3) that eject ink B are smaller than the ink B, and the second head group 31 (2) (fourth head) that ejects ink C. And the second preliminary radiating unit 41 (2) (corresponding to the fourth irradiating unit) that irradiates the ink C with ultraviolet rays.

  By doing so, even if an error occurs in the provisional irradiation energy amount of the provisional irradiation unit 41, it is difficult to irradiate the ink B with ultraviolet rays exceeding the maximum value of the total provisional irradiation energy amount that provides a predetermined glossiness. The predetermined glossiness can be obtained more reliably for the image portion formed with the ink B.

  Further, in the printer 1 of the present embodiment, the minimum value of the provisional irradiation energy total amount at which a predetermined glossiness is obtained (the minimum total irradiation amount of electromagnetic waves per unit area at which the predetermined glossiness is obtained) is from the ink C. Ink D is larger, and the first head group 31 (1) and the first provisional irradiation unit 41 (1) that eject ink D are the second head group 31 (2) and the second provisional irradiation section that eject ink C. It arrange | positions rather than the irradiation part 41 (2) in the conveyance direction upstream.

  By doing so, even if an error occurs in the amount of provisional irradiation energy of the provisional irradiation unit 41, the ink D is irradiated with ultraviolet rays having an energy amount higher than the minimum value of the total amount of provisional irradiation energy that provides a predetermined glossiness. Therefore, the predetermined glossiness can be obtained more reliably for the image portion formed with the ink D.

<Modification>
In the above-described embodiment, in order to prevent the ink B from being irradiated with ultraviolet rays exceeding the maximum value of the total amount of provisional irradiation energy that provides a predetermined glossiness, the ink C is more upstream than the ink B in the transport direction. However, the present invention is not limited to this. For example, since the ink B (black) has lower brightness than the ink C (magenta) (because the density is higher), the ink C may be ejected from the head group 31 on the downstream side in the transport direction than the ink B.

  This is because, if UV ink with high brightness (light UV ink with low density) is ejected upstream in the transport direction, UV ink with low brightness (UV ink with high density) ejected on the ink will have high brightness. This is because the color of the UV ink may be canceled out. As a result, the color reproducibility is lowered and the image quality of the printed image is deteriorated.

  In particular, when the amount of provisional irradiation energy applied to the lower UV ink is high, the degree of curing of the lower UV ink increases. Then, the UV ink ejected above is repelled by the lower UV ink and the dot diameter becomes smaller, the brightness of the dots of the UV ink ejected above becomes lower (the density becomes higher), and the lower UV ink Will cancel the color.

Therefore, when the conditions of provisional irradiation for obtaining a predetermined gloss level are wide like ink C (for example, a predetermined gloss level is applied regardless of whether 5 mJ / cm ² ultraviolet rays or 15 mJ / cm ² ultraviolet rays are irradiated). In other words, the head group 31 that ejects the ink C may be arranged on the downstream side in the transport direction with respect to the head group 31 that ejects ink having a lower brightness than the ink C. By doing so, color reproducibility can be improved and image quality degradation of the printed image can be suppressed.

=== Other Embodiments ===
Although the above embodiment is described mainly for a printing system having an ink jet printer, disclosure of the arrangement of heads and the like is included. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About the printer>
In the above-described embodiment, the printer 1 in which the medium is conveyed under the fixed head group 31 and the provisional irradiation unit 41 is provided between the head groups 31 that discharge different color inks is taken as an example. Not limited to. For example, a printer having a head in which nozzle rows that discharge UV inks of different colors are arranged in a moving direction intersecting the nozzle row direction and a provisional irradiation unit is provided between the nozzle rows may be used. In this printer, an operation of forming an image while moving the head in the movement direction with respect to the medium and an operation of conveying the medium in the nozzle row direction with respect to the head are repeated. Even in such a printer, for example, to move the head to the right side of the moving direction, the nozzle rows of the ink D to ultraviolet 15 mJ / cm ² is irradiated, ultraviolet 15 mJ / cm ² is irradiated to the medium It is better to dispose the nozzles on the right side in the movement direction than the nozzle rows of ink A for which a predetermined glossiness cannot be obtained.

<About ink>
In the above-described embodiment, the ultraviolet curable ink (UV ink) is taken as an example of the ink ejected from the head group 31, but the present invention is not limited to this. For example, ink that cures when irradiated with electromagnetic waves such as electron beams, X-rays, and visible light from the head group 31 may be ejected. In this case, the provisional irradiation unit 41 and the main irradiation unit 42 irradiate an electromagnetic wave that cures the ink.

1 Printer, 10 Controller, 11 Interface section,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 21A transport roller, 21B transport roller, 22 transport belt, 30 head unit,
31 (1) first head group, 31 (2) second head group,
31 (3) third head group, 31 (4) fourth head group,
32 short head, 40 irradiation unit,
41 (1) first preliminary irradiation unit, 41 (2) second preliminary irradiation unit,
41 (3) third preliminary irradiation unit, 41 (4) fourth preliminary irradiation unit,
42 irradiation units, 50 detector groups, 60 computers

Claims (5)

A first head capable of discharging a first electromagnetic wave curable ink onto a medium;
A first irradiation unit capable of irradiating the first electromagnetic wave curable ink on the medium with a first electromagnetic wave having a first irradiation amount per unit area;
A second head capable of discharging the second electromagnetic wave curable ink to the medium;
A second irradiation unit capable of irradiating the second electromagnetic wave curable ink on the medium with a second electromagnetic wave having a second irradiation amount per unit area;
A control unit that forms an image on the medium while moving the relative position of the medium with respect to the first head and the second head to the downstream side in a predetermined direction;
With
When the first electromagnetic wave curable ink is irradiated with the first electromagnetic wave, a predetermined gloss is obtained, but when the second electromagnetic wave is irradiated, the predetermined gloss is not obtained.
When the second electromagnetic wave curable ink is irradiated with the second electromagnetic wave after landing on the medium, the predetermined glossiness is obtained,
The second head and the second irradiation unit are disposed on the upstream side in the predetermined direction with respect to the first head and the first irradiation unit.
An image forming apparatus. The image forming apparatus according to claim 1,
A third head capable of ejecting a third electromagnetic wave curable ink onto the medium; and a third irradiation unit capable of irradiating the third electromagnetic wave curable ink on the medium with the first electromagnetic wave. Prepared,
The third electromagnetic wave curable ink can obtain the predetermined glossiness even when irradiated with the first electromagnetic wave a plurality of times, but can obtain the predetermined glossiness when irradiated with the second electromagnetic wave. Without
The third head and the third irradiation unit are arranged between the first head and the first irradiation unit and the second head and the second irradiation unit in the predetermined direction. Yes,
Image forming apparatus. The image forming apparatus according to claim 2,
A fourth head capable of ejecting a fourth electromagnetic wave curable ink onto the medium; and a fourth irradiation unit capable of irradiating the fourth electromagnetic wave curable ink on the medium with an electromagnetic wave.
Even if the fourth electromagnetic wave curable ink is irradiated with the first electromagnetic wave or the second electromagnetic wave, the predetermined glossiness is obtained.
The maximum total irradiation amount of electromagnetic waves per unit area for obtaining the predetermined glossiness is smaller in the third electromagnetic wave curable ink than in the fourth electromagnetic wave curable ink,
The third head and the third irradiation unit are arranged on the downstream side in the predetermined direction with respect to the fourth head and the fourth irradiation unit.
Image forming apparatus. The image forming apparatus according to any one of claims 1 to 3, wherein
A fourth head capable of ejecting a fourth electromagnetic wave curable ink onto the medium; and a fourth irradiation unit capable of irradiating the fourth electromagnetic wave curable ink on the medium with an electromagnetic wave.
Even if the fourth electromagnetic wave curable ink is irradiated with the first electromagnetic wave or the second electromagnetic wave, the predetermined glossiness is obtained.
The minimum total irradiation amount of electromagnetic waves per unit area for obtaining the predetermined glossiness is larger in the second electromagnetic wave curable ink than in the fourth electromagnetic wave curable ink,
The second head and the second irradiation unit are disposed on the upstream side in the predetermined direction with respect to the fourth head and the fourth irradiation unit.
Image forming apparatus. The image forming apparatus according to any one of claims 1 to 4, wherein:
A fourth head capable of discharging a fourth electromagnetic wave curable ink to the medium;
Even if the fourth electromagnetic wave curable ink is irradiated with the first electromagnetic wave or the second electromagnetic wave, the predetermined glossiness is obtained.
The fourth head is disposed on the downstream side in the predetermined direction with respect to the head capable of discharging the electromagnetic wave curable ink having a lightness lower than that of the fourth electromagnetic wave curable ink.
Image forming apparatus.

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