JP2011037221A - Printing device and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printing device capable of suppressing deterioration of image quality. <P>SOLUTION: A first discharge operation, a first irradiation operation, a second discharge operation, and a second irradiation operation are performed in this order a plurality of times. In the first discharge operation, one of a plurality of heads discharges one of different electromagnetic wave hardening inks. In the first irradiation operation, one of a plurality of irradiation units corresponding to the one head irradiates one electromagnetic wave hardening ink with an electromagnetic wave. In the second discharge operation, the other head different from the one head discharges the other electromagnetic wave hardening ink different from the one electromagnetic wave hardening ink toward a pixel on a medium to which the one electromagnetic wave hardening ink has been discharged so as to overlap the one electromagnetic wave hardening ink. In the second irradiation operation, an irradiation unit corresponding to the other head irradiates the other electromagnetic hardening ink with an electromagnetic wave. Processing is executed so that a contact angle in the second processing performed after the first processing is larger than that of the other electromagnetic wave hardening ink with respect to the one electromagnetic wave hardening ink in the first processing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a printing apparatus and a printing method.

  A printing apparatus having a plurality of heads that eject different inks toward a medium is already well known. As such a printing apparatus, an ink jet printer that performs printing by discharging ink onto various media such as paper, cloth, and film is known. In addition, some of the printing apparatuses use electromagnetic wave curable ink that is cured when irradiated with electromagnetic waves such as ultraviolet rays. In the printing apparatus, different electromagnetic wave curable inks ejected by the plurality of heads are used. Are provided with a plurality of irradiation units.

JP 2004-1437 A

  In the printing apparatus, during printing, one head of the plurality of heads discharges one electromagnetic wave curable ink among the different electromagnetic wave curable inks; The first irradiation operation in which the irradiation unit corresponding to the head irradiates one electromagnetic wave curable ink with an electromagnetic wave, and the other electromagnetic wave curable ink so that the other head overlaps the other electromagnetic wave curable ink with the one electromagnetic wave curable ink. The second discharge operation for discharging toward the pixels on the medium on which the mold ink is discharged and the second irradiation operation in which the irradiation unit corresponding to the other head irradiates other electromagnetic wave curable ink with the electromagnetic wave are in this order. Executed. In such a case, another electromagnetic wave curable ink is superimposed on one electromagnetic wave curable ink. However, due to the manner in which the electromagnetic wave curable ink is overlapped, the image quality of the image may be deteriorated.

  The present invention has been made in view of such problems, and an object of the present invention is to suppress deterioration in image quality of an image.

The main present invention includes a plurality of heads that discharge different electromagnetic curing inks toward a medium,
A plurality of irradiation units corresponding to each of the plurality of heads for irradiating each of the different electromagnetic wave curable inks ejected by the plurality of heads;
A controller that controls the head and the irradiation unit,
When the controller performs printing,
A first ejection operation in which one head of the plurality of heads ejects one electromagnetic wave curable ink among the different electromagnetic curable inks;
A first irradiation operation in which an irradiation unit corresponding to the one head among the plurality of irradiation units irradiates the electromagnetic wave to the one electromagnetic wave curable ink;
The other electromagnetic wave curable ink is ejected by another head different from the one head so that the other electromagnetic wave curable ink different from the one electromagnetic wave curable ink overlaps the one electromagnetic wave curable ink. A second discharge operation for discharging toward the pixels on the medium,
A second irradiation operation in which an irradiation unit corresponding to the other head irradiates the electromagnetic wave to the other electromagnetic wave curable ink;
Are executed in this order a plurality of times while changing both the one head and the other head for each processing, and the other electromagnetic wave curable type in the first processing among the plurality of times the processing. The printing is characterized in that the treatment is performed such that the contact angle in the second treatment performed after the first treatment is larger than the contact angle of the ink with respect to the one electromagnetic wave curable ink. Device.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram of a printer 1 according to an embodiment. 1 is a schematic sectional view of a printer 1. FIG. 3A is a schematic diagram showing the shape of the ultraviolet curable ink on the paper S according to the comparative example, and FIG. 3B is a schematic diagram showing the shape of the ultraviolet curable ink on the paper S according to this example. is there. It is the schematic diagram showing the shape of the ultraviolet curable ink on the paper S concerning a reference example. FIG. 5A is a schematic diagram showing a contact angle by enlarging a circled portion indicated by C1 in FIGS. 3A and 3B. FIG. 5B is a schematic view showing the contact angle by enlarging the circled portion indicated by C2 in FIGS. 3A and 3B. It is the schematic diagram which showed the mode of the upper ink and lower ink when a contact angle is too large. It is a schematic diagram for demonstrating the merit of this example.

  At least the following will be made clear by the description of the present specification and the accompanying drawings.

A plurality of heads that discharge different electromagnetic curing inks toward the medium;
A plurality of irradiation units corresponding to each of the plurality of heads for irradiating each of the different electromagnetic wave curable inks ejected by the plurality of heads;
A controller that controls the head and the irradiation unit,
When the controller performs printing,
A first ejection operation in which one head of the plurality of heads ejects one electromagnetic wave curable ink among the different electromagnetic curable inks;
A first irradiation operation in which an irradiation unit corresponding to the one head among the plurality of irradiation units irradiates the electromagnetic wave to the one electromagnetic wave curable ink;
The other electromagnetic wave curable ink is ejected by another head different from the one head so that the other electromagnetic wave curable ink different from the one electromagnetic wave curable ink overlaps the one electromagnetic wave curable ink. A second discharge operation for discharging toward the pixels on the medium,
A second irradiation operation in which an irradiation unit corresponding to the other head irradiates the electromagnetic wave to the other electromagnetic wave curable ink;
Are executed in this order a plurality of times while changing both the one head and the other head for each processing, and the other electromagnetic wave curable type in the first processing among the plurality of times the processing. The printing is characterized in that the treatment is performed such that the contact angle in the second treatment performed after the first treatment is larger than the contact angle of the ink with respect to the one electromagnetic wave curable ink. apparatus.
According to such a printing apparatus, it is possible to suppress the deterioration of the image quality of the image.

The plurality of irradiation units are preliminary irradiation units for irradiating the electromagnetic wave curable ink with the electromagnetic wave to temporarily cure the electromagnetic wave curable ink,
Separately from the plurality of irradiation units, the electromagnetic wave curable ink is irradiated with the electromagnetic wave to provide a main irradiation unit for main curing the electromagnetic wave curable ink,
When the controller performs printing,
After performing the process a plurality of times, the main irradiating unit may be controlled to perform a main curing process for main curing the electromagnetic wave curable ink.

A moving mechanism for moving the medium;
When the controller performs printing,
After performing the process multiple times,
It is good also as performing the movement process which controls the said moving mechanism and moves the said medium, and performs the said main curing process after that.
In such a case, for example, the effectiveness of the present invention is enhanced as compared with a case where the medium does not move.

Next, a plurality of heads that discharge different electromagnetic curing inks toward the medium;
A plurality of irradiation units corresponding to each of the plurality of heads for irradiating each of the different electromagnetic wave curable inks ejected by the plurality of heads;
Preparing a printing apparatus having a controller for controlling the head and the irradiation unit;
A first ejection operation in which one head of the plurality of heads ejects one electromagnetic wave curable ink among the different electromagnetic curable inks;
A first irradiation operation in which an irradiation unit corresponding to the one head among the plurality of irradiation units irradiates the electromagnetic wave to the one electromagnetic wave curable ink;
The other electromagnetic wave curable ink is ejected by another head different from the one head so that the other electromagnetic wave curable ink different from the one electromagnetic wave curable ink overlaps the one electromagnetic wave curable ink. A second discharge operation for discharging toward the pixels on the medium,
A second irradiation operation in which an irradiation unit corresponding to the other head irradiates the electromagnetic wave to the other electromagnetic wave curable ink;
Are executed in this order a plurality of times while changing both the one head and the other head for each processing, and the other electromagnetic wave curable type in the first processing among the plurality of times the processing. Performing the treatment such that the contact angle in the second treatment performed after the first treatment is larger than the contact angle of the ink with respect to the one electromagnetic wave curable ink;
A printing method characterized by comprising:
According to such a printing method, it is possible to suppress deterioration in image quality.

=== Overview of Printer 1 ===
<<< Configuration of Printer 1 >>>
As an example of the printing apparatus, an ink jet printer (hereinafter referred to as printer 1) is taken as an example, and an embodiment will be described using a printing system in which the printer 1 and the computer 60 are connected.

  FIG. 1 is a block diagram of the overall configuration of the printer 1 according to the present embodiment. FIG. 2 is a schematic sectional view of the printer 1. The printer 1 that has received a print command (print data) from the computer 60, which is an external device, controls each unit (conveyance unit 20, head unit 30, ultraviolet irradiation unit 40) by the controller 10 to form an image on the paper S. To do. Further, the detector group 50 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

  The controller 10 is a control unit for controlling the printer 1. The interface unit 11 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 a unit control circuit 14 according to a program stored in the memory 13.

  The transport unit 20 (corresponding to a moving mechanism) is for transporting a sheet S as an example of a medium in a predetermined direction (hereinafter referred to as a transport direction). As shown in FIG. 2, the transport unit 20 includes an upstream transport roller 23 a, a downstream transport roller 23 b, and a belt 24. When a transport motor (not shown) rotates, the upstream transport roller 23a and the downstream transport roller 23b rotate, and the belt 24 rotates. The paper S fed by a paper feed roller (not shown) is conveyed by the belt 24 to a printable area (area facing the head). When the belt 24 transports the paper S, the paper S moves in the transport direction with respect to the head unit 30. The paper S that has passed through the printable area is discharged to the outside by the belt 24. The sheet S being conveyed is electrostatically attracted or vacuum attracted to the belt 24.

  The head unit 30 has a head 31 for ejecting ink onto paper. In the printer 1 shown in FIG. 2, a plurality of heads 31 that eject different inks toward the paper S are provided. A plurality of nozzles that are ink discharge portions are provided on the lower surface of each head 31. Each nozzle is provided with a pressure chamber (not shown) containing ink, and a driving element (for example, a piezo element) for discharging ink by changing the capacity of the pressure chamber. When the drive signal is applied to the drive element, the drive element is deformed, and the pressure chamber expands / contracts along with the deformation, and ink is ejected.

  In the present embodiment, an ultraviolet curable ink as an example of an electromagnetic wave curable ink that is cured by being irradiated with ultraviolet rays as an example of electromagnetic waves is used as the ink. Here, the ultraviolet curable ink (hereinafter also simply referred to as ink) is prepared by adding an auxiliary agent such as an antifoaming agent or a polymerization inhibitor to a mixture of a vehicle, a photopolymerization initiator and a pigment. The vehicle is prepared by adjusting the viscosity of a photopolymerization-curing oligomer, monomer or the like with a reactive diluent. The ink includes both water-based ink and oil-based ink.

  The printer 1 can eject nine colored inks. A head 31 (W) that discharges white ink W, a head 31 (K) that discharges black ink K, and a head 31 (C) that discharges cyan ink C in order from the upstream side to the downstream side in the transport direction. A head 31 (M) that ejects magenta ink M, a head 31 (Y) that ejects yellow ink Y, a head 31 (Lm) that ejects light magenta ink Lm, and a head 31 that ejects light cyan ink Lc. (Lc), a head 31 (O) that ejects orange ink O, and a head 31 (G) that ejects green ink G are provided.

The ultraviolet irradiation unit 40 is for irradiating the ink discharged by the head 31 toward the paper S with ultraviolet rays to cure the ink. The ultraviolet irradiation unit 40 includes a preliminary irradiation unit 41 (corresponding to a plurality of irradiation units) for irradiating the ink with ultraviolet rays to temporarily cure the ink and a main irradiation for irradiating the ink with ultraviolet rays to fully cure the ink. Part 42. The preliminary irradiation unit 41 and the main irradiation unit 42 include a lamp (for example, a metal halide lamp or an LED) that cures by irradiating the ultraviolet curable ink with ultraviolet rays.
The preliminary irradiation unit 41 irradiates ultraviolet rays having a lower irradiation intensity than the main irradiation unit 42. As a result, the ultraviolet curable ink ejected from the head 31 is not completely cured by the ultraviolet rays irradiated by the preliminary irradiation unit 41 (preliminary curing), and the ultraviolet rays irradiated by the main irradiation unit 42. Is completely cured (main curing).

  In the printer 1 of this embodiment, a plurality of preliminary irradiation units 41 corresponding to each of the plurality of heads 31 for irradiating each of the different inks ejected by the plurality of heads 31 are provided. More specifically, the white ink W that corresponds to the head 31 (W) that discharges the white ink W in order from the upstream side to the downstream side in the transport direction and that is located downstream from the head 31 (W). Corresponding to the preliminary irradiation unit 41 (W) for irradiating the black ink K and the head 31 (K) for discharging the black ink K, and for irradiating the black ink K positioned downstream from the head 31 (K). The preliminary irradiation unit 41 (K) corresponds to the head 31 (C) that discharges the cyan ink C, and the preliminary irradiation unit 41 (irradiates the cyan ink C located downstream from the head 31 (C). C), a pre-irradiation unit 41 (M) for irradiating magenta ink M, which corresponds to the head 31 (M) that discharges the magenta ink M and is located downstream from the head 31 (M), and yellow Head that ejects ink Y 1 (Y), a pre-irradiation unit 41 (Y) for irradiating yellow ink Y located on the downstream side when viewed from the head 31 (Y), and a head 31 (Lm) that ejects light magenta ink Lm. Corresponding to the preliminary irradiation section 41 (Lm) for irradiating the light magenta ink Lm located downstream from the head 31 (Lm), and the head 31 (Lc) for discharging the light cyan ink Lc, The head 31 (O) corresponds to the preliminary irradiation unit 41 (Lc) for irradiating the light cyan ink Lc located on the downstream side when viewed from the head 31 (Lc) and the head 31 (O) that discharges the orange ink O. Corresponding to the preliminary irradiation unit 41 (O) for irradiating the orange ink O located on the downstream side as viewed from the head 31 and the head 31 (G) for discharging the green ink G, the head 31 (G A pre-irradiation section 41 for irradiating the green ink G located downstream (G) as viewed from, are provided. In addition, only one main irradiation unit 42 is provided on the most downstream side in the transport direction.

<<< Operation of Printer 1 >>>
By the way, the printer 1 according to the present embodiment has a large number of print modes. For example, cyan, magenta, and yellow inks are used to print a color image using a cyan, magenta, and yellow ink (hereinafter referred to as the first printing mode), and white (ink) background images using cyan, magenta, and yellow inks. A printing mode for printing a color image (hereinafter referred to as a second printing mode), a printing mode for printing a color image using all inks other than white ink (hereinafter referred to as a third printing mode), and the like. All of the nine heads 31 and the nine preliminary irradiation units 41 described above are not always used, and which head 31 and the preliminary irradiation unit 41 are used depends on the printing mode. It will be. That is, when printing is performed in the first printing mode, the three heads 31 and the three preliminary irradiation units 41 corresponding to cyan, magenta, and yellow ink are operated, and printing is performed in the second printing mode. In this case, four heads 31 and four preliminary irradiation units 41 corresponding to white, cyan, magenta, and yellow inks operate, and when printing is performed in the third print mode, ink other than white is used. The corresponding eight heads 31 and eight preliminary irradiation units 41 are operated.

  Hereinafter, the printing operation of the printer 1 will be described by taking the operation when printing in the first printing mode is performed as an example. Various operations of the printer 1 when printing is performed are mainly realized by the controller 10. In particular, this embodiment is realized by the CPU 12 processing a program stored in the memory 13. And this program is comprised from the code | cord | chord for performing the various operation | movement demonstrated below.

  When receiving the print data, the controller 10 feeds the paper S onto the belt 24. The sheet S is conveyed by the belt 24 without stopping at a constant speed, and eventually faces the head 31 (C). At this time, the controller 10 controls the head 31 (C) and performs a cyan ink ejection operation in which the head 31 (C) ejects cyan ink. Next, the controller 10 controls the preliminary irradiation unit 41 (C) so that the preliminary irradiation unit 41 (C) irradiates the cyan ink ejected onto the paper S with ultraviolet rays (cyan ink is temporarily cured). (Preliminary curing process) is performed (while the sheet S is being conveyed). Thereafter, the controller 10 sequentially controls the head 31 (M), the pre-irradiation unit 41 (M), the head 31 (Y), and the pre-irradiation unit 41 (Y) to perform a magenta ink ejection operation and a magenta ink irradiation operation ( A magenta ink temporary curing process), a yellow ink ejection operation, and a yellow ink irradiation operation (yellow ink temporary curing process) are executed (here, ink ejection and preliminary irradiation are completed). After the preliminary irradiation is completed, the controller 10 executes a main curing process for controlling the main irradiation unit 42 to cure the ink. As a result, the printing of the image on the paper S is completed, and the paper S is discharged to the outside.

=== About the shape of the ink on the paper S ===
Here, the shape of the ultraviolet curable inks that are superimposed on each other on the paper S after the above-described printing operation (printing in the first printing mode) is performed will be considered with reference to the drawings while comparing this example with a comparative example. To do. FIG. 3A is a schematic diagram showing the shape of the ultraviolet curable ink on the paper S according to the comparative example, and FIG. 3B is a schematic diagram showing the shape of the ultraviolet curable ink on the paper S according to this example. is there. FIG. 4 is a schematic diagram showing the shape of the ultraviolet curable ink on the paper S according to the reference example. FIG. 5A is a schematic diagram showing a contact angle by enlarging a circled portion indicated by C1 in FIGS. 3A and 3B. FIG. 5B is a schematic view showing the contact angle by enlarging the circled portion indicated by C2 in FIGS. 3A and 3B. FIG. 6 is a schematic diagram showing the state of the upper ink and the lower ink when the contact angle is too large. FIG. 7 is a schematic diagram for explaining the merit of this example.

  When the above-described printing operation (printing in the first printing mode) is performed, as shown in FIGS. 3A and 3B, cyan, magenta, and yellow inks are sequentially overlaid (the color color is expressed by this overlapping). Here, unlike a normal water-based ink, the ultraviolet curable ink does not cause a phenomenon of solvent evaporation, and thus a state in which each of cyan, magenta, and yellow ink overlaps clearly appears. Here, paying attention to the manner in which the upper ink (that is, the magenta ink for the cyan ink and the yellow ink for the magenta ink) overlaps with the lower ink, in both the comparative example and the present example, The upper ink overlaps the lower ink so that the portion (indicated by reference characters e2 and f2 in FIG. 3A and indicated by reference characters e1 and f1 in FIG. 3B) enters inside. And the following merit arises by having overlapped in this way. That is, if the upper ink is overlapped with the lower ink so that the end portion of the upper ink spreads outward as opposed to the overlapping method (see the reference example in FIG. 4), There is a high possibility that the end portions e3 and f3 will drop downward due to the fact that the end portions (indicated by reference symbols e3 and f3) are spread outward (for example, some vibration (for example, a sheet of paper) The dropout is particularly likely to occur when vibration (when S is transported) is applied, and if such dropout occurs, the image quality of the image will be degraded). On the other hand, in the comparative example and the present example, since the end portions e1, f1, e2, and f2 enter the inside, the end portions e1, f1, e2, and f2 are difficult to drop down. .

  As described above, in the comparative example and the present example, the end portions e1, f1, e2, and f2 enter the inside, but whether the end portions enter the inside or spread outward is determined by the upper ink. Can be cut by using the contact angle for the ink below. That is, in the comparative example and the present example in which the end portions e1, f1, e2, and f2 enter the inside, the contact angles α1 and α2 are larger than 90 degrees (FIGS. 3A, 3B, 5A, and On the other hand, in the reference example in which the end portions e3 and f3 spread outward, the contact angle is smaller than 90 degrees (see FIG. 4), and the end portion is outside. It can be understood from FIG. 3A to FIG. 5B that the boundary between whether the contact is spread out or inside is contact angle = 90 degrees. The contact angle α1 (α2) of the upper ink with the lower ink is the tangent line P1 (P2) with respect to the upper ink and the tangent line Q1 (Q2) with respect to the lower ink at the extreme end x1 (x2) of the upper ink. ) Is the angle formed by P1 and Q1 (P2 and Q2). For the contact angle, the lower ink ejection operation, the lower ink irradiation operation (temporary curing process), the upper ink ejection operation, and the upper ink irradiation operation (preliminary curing process) are all performed. When the shape of the upper ink and the lower ink is determined, the angle clearly appears (in addition, after all the above four processes are performed and the contact angle appears clearly, There is almost no change in the contact angle due to the above).

  As described above, the comparative example and the present example are common in that the contact angle is larger than 90 degrees and the end portions e1, f1, e2, and f2 enter inside. However, both differ in the following points.

  That is, as is apparent from FIGS. 3A, 3B, 5A, and 5B, in the comparative example, the contact angle α2 of magenta ink with respect to cyan ink (in other words, in the previous process (corresponding to the first process)). The upper ink contact angle α1 for the magenta ink than the lower ink contact angle α2 (the lower ink in the post-processing (corresponding to the second processing) performed after the previous processing). In this example, the contact angle α1 of magenta ink with respect to cyan ink (the contact angle α1 of the upper ink with respect to the lower ink in the pre-processing) is yellow in this example. The ink contact angle α2 (the upper ink contact angle α2 with respect to the lower ink in post-processing) is larger.

  Note that the value at which the contact angle is set can be controlled (a specific control method will be described later). Therefore, the above can be paraphrased as follows.

  That is, in this example, when the controller 10 performs printing, the first ejection operation in which one head 31 ejects one electromagnetic wave curable ink and the preliminary irradiation unit 41 corresponding to one head are one. The first irradiation operation of irradiating the electromagnetic wave curable ink with ultraviolet rays, and the sheet S on which the other electromagnetic wave curable ink is discharged so that the other head 31 overlaps the other electromagnetic wave curable ink with the electromagnetic wave curable ink. A process of executing in this order the second ejection operation for ejecting toward the upper pixel and the second irradiation operation in which the preliminary irradiation unit 41 corresponding to the other head 31 irradiates the other electromagnetic wave curing type with ultraviolet rays. Execute multiple times while changing both the one head and the other head for each process (in this embodiment, the first process and the second process are executed twice. Head The head 31 (C) and the head 31 (M), and one head and the other head in the post-processing are the head 31 (M) and the head 31 (Y)), and a plurality of times of the processing The contact angle α1 with respect to one electromagnetic wave curable ink (cyan ink in this embodiment) of the other electromagnetic wave curable ink (magenta ink in the present embodiment) in the first treatment (pretreatment) of , One electromagnetic wave curable ink (in this embodiment, yellow ink) in another electromagnetic wave curable ink (in this embodiment) in the second process (post process) performed after the first process (in this embodiment, The above process is performed so that the contact angle α2 with respect to magenta ink becomes larger.

  On the other hand, in the comparative example, when the controller 10 performs printing, one head 31 discharges one electromagnetic wave curable ink, and the preliminary irradiation unit 41 corresponding to one head has one. The first irradiation operation of irradiating the electromagnetic wave curable ink with ultraviolet rays, and the sheet S on which the other electromagnetic wave curable ink is discharged so that the other head 31 overlaps the other electromagnetic wave curable ink with the electromagnetic wave curable ink. A process of executing in this order the second ejection operation for ejecting toward the upper pixel and the second irradiation operation in which the preliminary irradiation unit 41 corresponding to the other head 31 irradiates the other electromagnetic wave curing type with ultraviolet rays. Execute multiple times while changing both the one head and the other head for each process (in this embodiment, the first process and the second process are executed twice. The head of The head 31 (C) and the head 31 (M), and one head and the other head in the post-processing are the head 31 (M) and the head 31 (Y)), The contact angle α2 with respect to one electromagnetic wave curable ink (cyan ink in this embodiment) of the other electromagnetic wave curable ink (magenta ink in the present embodiment) in the first treatment (pretreatment) of , One electromagnetic wave curable ink (in this embodiment, yellow ink) in another electromagnetic wave curable ink (in this embodiment) in the second process (post process) performed after the first process (in this embodiment, The above processing is performed so that the contact angle α1 with respect to magenta ink becomes smaller.

  Due to such differences, the comparative example has a demerit and the present example has a merit. That is, as described above, in both the comparative example and the present example, the contact angle is larger than 90 degrees and the end portions e1, f1, e2, and f2 enter the inside, so the end portions e1, f1, e2 and f2 are difficult to drop downward. However, there is no possibility that the end portions e1, f1, e2, and f2 drop out, and a situation in which the drop occurs may occur. As a matter of course, the smaller the contact angle, the higher the possibility of dropout.

  On the other hand, too large a contact angle is not preferable in the following points. That is, the upper ink is repelled by the lower ink, and the upper ink is contracted, and the overall size of the upper ink becomes smaller (see FIG. 6).

  And in such a situation (a situation where a larger contact angle is better from the viewpoint of “dropping out” and a smaller contact angle is better from the viewpoint of “shrinkage”), in this example, for the following reasons, The contact angle α2 of the upper ink with respect to the lower ink in the post-processing is made larger than the contact angle α1 of the upper ink with respect to the lower ink in the processing. That is, as shown in FIG. 7, the end portion f1 of the upper ink in the post-processing is positioned higher than the end portion e1 of the upper ink in the pre-processing, so that the end portion f1 is In the case of dropping, compared to the case where the end portion e1 is dropped, the dropped ink tends to fall to a position far away from the overlapping ink (in other words, the pixel on which the ink is overlapped). For this reason, the degree of the adverse effect on the image quality is greater when the end portion f1 is dropped than when the end portion e1 is dropped. Therefore, in this example, the contact angle α1 in the post-processing is increased with a greater emphasis on the viewpoint of “dropout” (so that no dropout occurs), and the contact angle α2 in the previous process is set to “dropout”. The point of view is slightly disregarded, and the point of view of “shrinkage” is emphasized and made smaller. And in this case, in this example, the viewpoint of “dropping” and the viewpoint of “shrinkage” are considered in a well-balanced manner, and there is a merit that image quality deterioration is appropriately suppressed (in the comparative example, Since the magnitude relationship between the contact angles in the pre-processing and post-processing is opposite to that in the present example, the balance is lacking. Needless to say, the image quality of the image is more significantly deteriorated than in this example. ).

<<< Contact angle control method >>>
Here, a method for controlling the contact angle will be described. The magnitude of the contact angle depends on the degree of temporary curing of the upper and lower inks when the upper and lower inks are pre-cured (that is, what percentage of the monomer in the UV curable ink has changed to polymer). ). Therefore, if the irradiation intensity of the preliminary irradiation unit 41 is adjusted, the contact angle can be set to a desired value. In particular, since the degree of temporary curing of the lower ink has a large effect on the contact angle (the higher the degree of temporary curing of the lower ink, the larger the contact angle tends to increase), preliminary irradiation for irradiating the lower ink with ultraviolet rays It is preferable to adjust the irradiation intensity of the part 41 as the center.

  The adjustment is performed as follows, for example, before shipment of the printer 1. That is, the four operations described above (that is, the lower ink ejection operation, the lower ink irradiation operation (preliminary curing process), the upper ink ejection operation, and the upper ink irradiation operation (preliminary curing process)). After that, the contact angle with respect to the ink under the ink on the paper S is actually measured. If the measured value of the contact angle is not a desired value, the irradiation intensity of the preliminary irradiation unit 41 is changed, and the measurement is repeated until the measured value becomes a desired value. Then, the irradiation intensity when the measured value becomes a desired value is set in the preliminary irradiation unit 41.

  Note that the measurement of the contact angle can be performed without any difficulty by a known method. However, when the contact angle is difficult to measure, a so-called solid image may be formed by the lower ink ejection operation. . When the solid image is formed, the surface formed by the lower ink is a flat surface similar to the surface of the paper S. Therefore, the contact angle of the upper ink with the lower ink is above the paper S. It can be easily measured as the contact angle of the upper ink. Note that the contact angle of the upper ink with respect to the lower ink that forms the solid image and the contact angle of the upper ink with respect to the lower ink that does not form the solid image are the same as long as the irradiation intensity is the same.

=== Other Embodiments ===
Although the above embodiments are mainly described with respect to a printing apparatus, disclosure of a printing method and the like is also 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. In particular, the embodiments described below are also included in the present invention.

  Moreover, in the said embodiment, although the printing apparatus was actualized to the inkjet printer, it is not restricted to this, The present invention can also be applied to other printing apparatuses.

  In the above embodiment, the ultraviolet curable ink is exemplified as the electromagnetic wave curable ink. However, the present invention is not limited to this. For example, an ink that is cured by an electromagnetic wave such as an electron beam, an X-ray, visible light, or infrared light may be used.

Moreover, in the said embodiment, these irradiation parts are the preliminary irradiation parts 41 for irradiating electromagnetic waves to electromagnetic wave curable ink, and preliminarily hardening this electromagnetic wave curable ink, What are these irradiation parts? In addition, the controller 10 includes a main irradiation unit 42 for irradiating the electromagnetic wave curable ink with an electromagnetic wave to perform main curing of the electromagnetic wave curable ink, and the controller 10 performs the first ejection operation and the first irradiation when performing printing. After performing the process of performing the operation, the second discharge operation, and the second irradiation operation in this order a plurality of times, the main curing unit 42 is controlled to perform the main curing process for main curing of the electromagnetic wave curable ink. However, the present invention is not limited to this.
For example, the plurality of irradiation units are main irradiation units 42, and the first irradiation operation and the second irradiation operation are irradiation operations by the main irradiation unit 42 (the book after the processing is performed a plurality of times). There is no curing treatment).

  In addition, the printer 1 according to the above-described embodiment includes the transport unit 20 that moves the paper S, and the controller 10 controls the transport unit 20 after performing the above process a plurality of times when performing printing. Although the moving process for moving the paper S is executed and then the main curing process is executed, the present invention is not limited to this.

For example, the paper S may be a printer 1 in which printing is performed by moving the head 31, the preliminary irradiation unit 41, and the main irradiation unit 42 without moving, and the present invention can also be applied to the printer 1.
However, when the controller 10 performs printing, the printer 1 performs the moving process of moving the paper S by controlling the transport unit 20 after performing the process a plurality of times, and then executes the main curing process. In this movement process, the possibility that the above-mentioned end portion of the ink drops off in the movement process is larger than that in the case where the sheet S does not move. For this reason, when the controller 10 performs printing, the controller 1 executes the process a plurality of times, then executes a moving process for controlling the transport unit 20 to move the paper S, and then executes the main curing process. The application of the present invention to the above is more desirable in that the effectiveness of the present invention can be improved to suppress the drop of the end portion f1 of the upper ink in post-processing.

  In the above embodiment, the case where three color inks are superimposed (that is, the case where printing is performed in the first printing mode) is described as an example. However, the present invention is not limited to this. A case where inks of colors or more are superposed is also conceivable, and the present invention can be applied to such a case.

  For example, when printing is performed in the second printing mode described above, four colors of ink of white, cyan, magenta, and yellow ink are overlaid in this order. In such a case, a contact angle β1 of cyan ink with respect to white ink, a contact angle β2 of magenta ink with respect to cyan ink, and a contact angle β3 of magenta ink with respect to magenta ink are defined. Is preferably β1 <β2 <β3 (however, the present invention is not limited to this, and the case of β1 <β2 (> β3) and the case of (β1>) β2 <β3 are also included in the present invention. )

1 Printer, 10 Controller, 11 Interface section, 12 CPU, 13 Memory, 14 Unit control circuit, 20 Transport unit, 23a Upstream transport roller, 23b Downstream transport roller, 24 belt, 30 head unit, 31 head, 40 UV irradiation Unit, 41 Preliminary irradiation unit, 42 main irradiation unit, 50 detector group

Claims (4)

A plurality of heads that discharge different electromagnetic curing inks toward the medium;
A plurality of irradiation units corresponding to each of the plurality of heads for irradiating each of the different electromagnetic wave curable inks ejected by the plurality of heads;
A controller that controls the head and the irradiation unit,
When the controller performs printing,
A first ejection operation in which one head of the plurality of heads ejects one electromagnetic wave curable ink among the different electromagnetic curable inks;
A first irradiation operation in which an irradiation unit corresponding to the one head among the plurality of irradiation units irradiates the electromagnetic wave to the one electromagnetic wave curable ink;
The other electromagnetic wave curable ink is ejected by another head different from the one head so that the other electromagnetic wave curable ink different from the one electromagnetic wave curable ink overlaps the one electromagnetic wave curable ink. A second discharge operation for discharging toward the pixels on the medium,
A second irradiation operation in which an irradiation unit corresponding to the other head irradiates the electromagnetic wave to the other electromagnetic wave curable ink;
Are executed in this order a plurality of times while changing both the one head and the other head for each processing, and the other electromagnetic wave curable type in the first processing among the plurality of times the processing. The printing is characterized in that the treatment is performed such that the contact angle in the second treatment performed after the first treatment is larger than the contact angle of the ink with respect to the one electromagnetic wave curable ink. apparatus. The printing apparatus according to claim 1,
The plurality of irradiation units are preliminary irradiation units for irradiating the electromagnetic wave curable ink with the electromagnetic wave to temporarily cure the electromagnetic wave curable ink,
Separately from the plurality of irradiation units, the electromagnetic wave curable ink is irradiated with the electromagnetic wave to provide a main irradiation unit for main curing the electromagnetic wave curable ink,
When the controller performs printing,
After performing the said process in multiple times, the printing apparatus characterized by performing the main hardening process which controls the said main irradiation part and carries out the main hardening of the said electromagnetic wave curable ink. The printing apparatus according to claim 2,
A moving mechanism for moving the medium;
When the controller performs printing,
After performing the process multiple times,
A printing apparatus that performs a moving process of moving the medium by controlling the moving mechanism, and then executes the main curing process. A plurality of heads that discharge different electromagnetic curing inks toward the medium;
A plurality of irradiation units corresponding to each of the plurality of heads for irradiating each of the different electromagnetic wave curable inks ejected by the plurality of heads;
Preparing a printing apparatus having a controller for controlling the head and the irradiation unit;
A first ejection operation in which one head of the plurality of heads ejects one electromagnetic wave curable ink among the different electromagnetic curable inks;
A first irradiation operation in which an irradiation unit corresponding to the one head among the plurality of irradiation units irradiates the electromagnetic wave to the one electromagnetic wave curable ink;
The other electromagnetic wave curable ink is ejected by another head different from the one head so that the other electromagnetic wave curable ink different from the one electromagnetic wave curable ink overlaps the one electromagnetic wave curable ink. A second discharge operation for discharging toward the pixels on the medium,
A second irradiation operation in which an irradiation unit corresponding to the other head irradiates the electromagnetic wave to the other electromagnetic wave curable ink;
Are executed in this order a plurality of times while changing both the one head and the other head for each processing, and the other electromagnetic wave curable type in the first processing among the plurality of times the processing. Performing the treatment such that the contact angle in the second treatment performed after the first treatment is larger than the contact angle of the ink with respect to the one electromagnetic wave curable ink;
A printing method characterized by comprising:

Images