JP6035786B2 - Printing apparatus and printing method - Google Patents

Description

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

  Examples of the printing apparatus include an ink jet printer (hereinafter referred to as a printer) that prints an image on a medium by ejecting ink droplets from a nozzle provided in a head toward a medium such as paper. Some printers use ultraviolet curable inks that are cured by irradiation with ultraviolet rays, and those using LED elements as ultraviolet irradiation light sources have been proposed (see, for example, Patent Document 1). With such a printer, it is possible to print an image on a medium made of plastic or metal that does not have an ink receiving layer.

JP 2005-254560 A

  When a color image is printed with a high ink duty, that is, by increasing the ink discharge amount per unit area, the surface of the image is smoothed, so that a matte tone image with low glossiness cannot be printed. On the other hand, even for a color image printed with high ink duty, the surface of the image can be made uneven by sparsely ejecting clear ink droplets thereon, and a matte tone image can be printed. However, the clear ink droplets are easily peeled off from the color image, and the rub resistance cannot be ensured.

  Accordingly, an object of the present invention is to print a matte tone image having abrasion resistance.

The main invention for solving the above problems is that (A) a head unit that discharges yellow ultraviolet curable ink onto a medium, (B) an LED irradiation unit that irradiates ultraviolet light, and (C) a first mode are set. When the ultraviolet curable ink ejected per unit area of the medium is irradiated with the first energy ultraviolet light, the second energy ultraviolet light stronger than the first energy is irradiated. The UV curable ink ejected per unit area of the medium when the second mode in which an image having a higher glossiness than the image printed in the first mode is set is set. On the other hand, a printing apparatus comprising: (D) a control unit that controls to irradiate ultraviolet rays having energy stronger than the first energy.
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 an overall configuration of a printer. It is a schematic sectional drawing of a printer. 3A to 3C are diagrams illustrating a printing method of a comparative example. It is a figure explaining the printing method of this embodiment. 3 is a flowchart illustrating a printing method according to the first exemplary embodiment. 6A and 6B are diagrams illustrating the LED irradiation unit in Example 1, and FIG. 6C is a diagram illustrating a case where both adjacent LEDs are lit. FIG. 7A is a diagram showing the LED irradiation unit in the glossy tone mode in the second embodiment, and FIG. 7B is a diagram showing the LED irradiation unit in the matte tone mode in the second embodiment. FIG. 8A is a diagram illustrating the LED irradiation unit in the glossy tone mode in Example 3, and FIG. 8B is a diagram illustrating the LED irradiation unit in the matte mode in Example 3. 9A and 9B are diagrams for explaining the LED irradiation unit for the matte mode.

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

That is, (A) a head unit that discharges yellow ultraviolet curable ink onto a medium, (B) an LED irradiation unit that irradiates ultraviolet light, and (C) a unit area of the medium when the first mode is set. The first mode is controlled such that after the ultraviolet curable ink ejected per hit is irradiated with ultraviolet rays of the first energy, the ultraviolet rays of the second energy stronger than the first energy are irradiated. When the second mode in which an image having a glossiness higher than that of the image printed at is set is set, the first energy is applied to the ultraviolet curable ink ejected per unit area of the medium. A printing apparatus comprising: a control unit that controls so as to irradiate ultraviolet rays having higher energy; and (D).
According to such a printing apparatus, it is possible to print an image having a glossiness corresponding to the print mode, and it is possible to print a matte image having abrasion resistance.

In this printing apparatus, the medium is transported downstream in the transport direction with respect to the LED irradiation unit, and the LED irradiation unit includes a plurality of LEDs, and the transport in the LED irradiation unit in the first mode is performed. Per unit area of the downstream part of the direction and the upstream part of the transport direction in the LED irradiation part in the first mode than the LED irradiation part in the second mode The number of lighting of the LED is small.
According to such a printing apparatus, it is possible to irradiate ultraviolet curable ink with weak energy ultraviolet light in the first mode, and then to irradiate strong energy ultraviolet light in the second mode. It can be irradiated with ultraviolet rays.

In this printing apparatus, in the LED irradiation unit, a plurality of LED rows in which the plurality of LEDs are arranged in a direction intersecting the conveyance direction are arranged in the conveyance direction, and the LED irradiation unit in the first mode is in the first mode. In the upstream portion of the transport direction, the positions of the LEDs that are lit in the LED rows adjacent to each other in the transport direction are shifted in the intersecting direction.
According to such a printing apparatus, it is possible to further weaken the energy of ultraviolet rays that are first irradiated in the first mode.

In this printing apparatus, the medium is transported to the downstream side in the transport direction with respect to the LED irradiation unit, and the LED irradiation unit includes an LED array in which a plurality of LEDs are arranged in a direction intersecting the transport direction. A plurality of LEDs arranged in the transport direction, and the positions of the LEDs belonging to the LED rows adjacent to the transport direction in the intersecting direction are located at the upstream side of the transport direction in the LED irradiation unit in the first mode. In the LED irradiation unit in the first mode, the downstream part of the transport direction in the LED irradiation unit, and the LED irradiation unit in the second mode in the LED row adjacent to the transport direction, respectively. The positions of the LEDs to which they belong are aligned.
According to such a printing apparatus, it is possible to irradiate ultraviolet curable ink with weak energy ultraviolet light in the first mode, and then to irradiate strong energy ultraviolet light in the second mode. It can be irradiated with ultraviolet rays.

In this printing apparatus, the medium is transported to the downstream side in the transport direction with respect to the LED irradiation unit, and the LED irradiation unit includes an LED array in which a plurality of LEDs are arranged in a direction intersecting the transport direction. A plurality of LEDs arranged in the conveyance direction, the portion in the conveyance direction downstream of the LED irradiation unit in the first mode, and the LED in the first mode than the LED irradiation unit in the second mode. The space | interval of the said conveyance direction of the said LED row is wider in the upstream part of the said conveyance direction in an irradiation part.
According to such a printing apparatus, it is possible to irradiate ultraviolet curable ink with weak energy ultraviolet light in the first mode, and then to irradiate strong energy ultraviolet light in the second mode. It can be irradiated with ultraviolet rays.

In this printing apparatus, the head unit discharges at least one ultraviolet curable ink of cyan and magenta onto the medium, and the ultraviolet curable ink of at least one of cyan and magenta is the LED. Containing an auxiliary agent that absorbs light at the peak wavelength of the irradiated part.
According to such a printing apparatus, a matte tone image can be printed more reliably.

In this printing apparatus, the head unit ejects black ultraviolet curable ink onto the medium.
According to such a printing apparatus, it is possible to print a matte image having abrasion resistance.

Further, (A) a printing method in which yellow ultraviolet curable ink is discharged onto a medium, and (B) when the first mode is set, an LED irradiation unit that irradiates ultraviolet rays causes a unit area of the medium Irradiating the ultraviolet curable ink discharged to the first energy ultraviolet light, and then irradiating the second energy ultraviolet light stronger than the first energy; and (C) printing in the first mode. When the second mode in which an image having a gloss level higher than that of the image to be printed is set, the LED irradiating unit applies the ultraviolet curable ink ejected per unit area of the medium. A printing method comprising irradiating ultraviolet rays having energy stronger than the first energy and (D).
According to such a printing method, it is possible to print an image having a glossiness corresponding to the print mode, and it is possible to print a matte image having abrasion resistance.

=== Printing system ===
The embodiment will be described with reference to an example of a printing system in which a “printing 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 the overall configuration of the printer 1, and FIG. 2 is a schematic cross-sectional view of the printer 1 as viewed in the width direction intersecting the conveyance direction of the medium S.
The printer 1 of the present embodiment prints an image on a medium S (paper, cloth, plastic film, etc.) using ultraviolet curable ink (hereinafter referred to as UV ink) that is cured when irradiated with ultraviolet rays. The UV ink contains a photopolymerization initiator, an ultraviolet curable resin (monomer or oligomer), a colorant, and the like. When the UV ink is irradiated with ultraviolet rays, the photopolymerization initiator absorbs light to generate active species such as radicals, whereby a polymerization reaction occurs in the ultraviolet curable resin, and the UV ink is cured.

  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 by a printer driver installed therein. The printer driver is recorded on a recording medium such as a CD-ROM or can be downloaded to the computer 60 via the Internet.

  The controller 10 is a control unit for controlling the printer 1, and includes an interface unit 11, a CPU 12, a memory 13, and a unit control circuit 14. The interface unit 11 transmits and receives data between the computer 60 that is an external device and the printer 1. The CPU 12 is an arithmetic processing device for performing overall control of the 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 via the unit control circuit 14 in accordance with a program stored in the memory 13. 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 transport unit 20 is for transporting the medium S in the transport direction, and includes a transport belt 21 and transport rollers 22a and 22b. As the motor (not shown) rotates, the transport rollers 22a and 22b rotate and the transport belt 21 rotates, whereby the medium S on the transport belt 21 is transported downstream in the transport direction. The medium S faces the head 31 and the LED irradiation unit 41 when being conveyed on the conveyance belt 21.

  The head unit 30 is for ejecting UV ink onto the medium S, and has a plurality of heads 31. The printer 1 of the present embodiment is capable of ejecting four colors of UV ink (KCMY). As shown in FIG. 2, the head 31 ejecting black UV ink K, the head 31 ejecting cyan UV ink C, and magenta. The head 31 for discharging the UV ink M and the head 31 for discharging the yellow UV ink Y are arranged in order from the upstream side in the transport direction.

  On the lower surface of each head 31, a large number of nozzle openings, which are ejection openings for UV ink, are provided side by side at predetermined intervals in the width direction that intersects the transport direction of the medium S. The length of the row of nozzle openings along the width direction is equal to or greater than the maximum width of the medium S. When the medium S passes under the head 31, the head 31 ejects UV ink toward the medium S, whereby a two-dimensional image is printed on the medium S.

  The ink discharge method from the nozzle opening may be a piezo method in which ink is discharged from the nozzle opening by applying a voltage to the drive element (piezo element) to expand and contract the ink chamber, or a nozzle using a heating element. A thermal method may be employed in which bubbles are generated inside and ink is ejected from the nozzle openings by the bubbles.

  The irradiation unit 40 is for irradiating the UV ink on the medium S with ultraviolet rays (light) to cure the UV ink, and includes an LED irradiation unit 41. In the present embodiment, a light emitting diode (LED) is used as an ultraviolet light irradiation light source, and a plurality of LEDs (surfaces facing the medium S) on the lower surface of the LED irradiation unit 41 (a surface facing the medium S) as shown in FIG. LED package having LED elements) is disposed. Further, the irradiation unit 40 includes the same number of four LED irradiation units 41 as the heads 31, and one LED irradiation unit 41 is provided on the downstream side in the transport direction of each head 31. Therefore, the UV ink ejected from a certain head 31 onto the medium S is cured by ultraviolet rays from the LED irradiation unit 41 located immediately downstream of the head 31.

  In addition, the LED irradiation part 41 which irradiates the light of the wavelength which the photoinitiator in UV ink absorbs so that UV ink may harden | cure with the light from LED irradiation part 41 is used. In the present embodiment, the LED irradiation unit 41 having a peak wavelength of 395 nm is used, but the present invention is not limited to this. The LED irradiation unit 41 having a peak wavelength in the range of 355 nm to 420 nm may be used so that a general UV ink is cured.

In addition, as shown in FIG. 2, not only the LED irradiation unit 41 is provided for each head 31, but only one LED irradiation unit 41 may be arranged at the most downstream position in the transport direction, for example. Further, the irradiation energy (mJ / cm ² ) of the ultraviolet light applied to the UV ink ejected per unit area of the medium S is the product of the irradiation intensity (mW / cm ² ) of the ultraviolet light and the irradiation time (s). Determined by

  In the following description, the ink discharge amount per unit area of the medium S (in other words, the ratio of “the number of pixels in which dots are formed” in the “number of pixels corresponding to the unit area of the medium S”) is expressed as follows: This is called “ink duty”. The ink duty is high when the amount of ink ejected per unit area of the medium S is large, and conversely, the ink duty is low when the amount of ink ejected per unit area of the medium S is small. . Further, an image (including a monochrome image) printed by appropriately using four colors of UV ink (KCMY) is referred to as a color image.

=== Print mode ===
The printer 1 of the present embodiment has a “matte tone mode” and a “glossy tone mode” so that printing can be performed while changing the glossiness of the image according to the user's application.
When the matte tone mode is set, the printer 1 has a mat having a relatively large unevenness on the surface of the image so that the light applied to the image is irregularly reflected and has a lower gloss than an image printed in the glossy tone mode. Print a tone image.
On the other hand, when the glossy mode is set, the printer 1 prints a glossy image having a smooth image surface and higher gloss than an image printed in the matte mode.

=== Printing Method of Comparative Example ===
3A to 3C are diagrams illustrating a printing method of a comparative example. FIG. 3A shows a color image of low ink duty, and FIG. 3B shows a color image of high ink duty. In the printing method of the comparative example shown in FIG. 3A and FIG. 3B, when the matte tone mode is set, the color image is irradiated with strong energy light (ultraviolet rays) from the beginning, and from the surface layer portion of the color image. Hardens all the way to the inside.

  Since the UV ink has a relatively high viscosity, the UV ink droplet immediately after landing on the medium S is raised in a granular shape. Therefore, when printing a color image with a low ink duty, each UV ink droplet lands on a distant position on the medium S as shown in FIG. 3A. After that, by irradiating light of strong energy, the granular UV ink droplets are cured at a stretch in an independent state. Therefore, the image surface has a concavo-convex shape, and a matte image with a low glossiness is printed.

  On the other hand, when a color image of high ink duty is printed, most of the medium S is covered with UV ink droplets, and the UV ink droplets that have landed on the medium S are connected to each other. The surface is flattened. Thereafter, the light from the surface layer to the inside of the image is cured at a stretch by irradiating with light of strong energy. In this case, the image surface is cured in a smooth state, and the glossiness of the image is increased. That is, a glossy image is printed instead of a matte image.

  In other words, when printing a color image of low ink duty, a matte tone image can be printed even when UV ink is cured at once with strong energy light (ultraviolet rays), but a color image of high ink duty is printed. In the case of printing, if the UV ink is cured at once with strong energy light (ultraviolet rays), a matte tone image cannot be printed.

  FIG. 3C is a diagram illustrating a state where clear ink droplets are ejected onto a color image. Even in the case of a color image of a high ink duty with a smooth surface as shown in FIG. 3B, the surface of the image can be made uneven by sparsely ejecting clear ink droplets on the color image. Can be printed. However, since the convex portion is formed with a clear ink different from the ink constituting the color image, the clear ink is easily peeled off from the color image, and the abrasion resistance is poor. Further, since clear ink is used in addition to ink for printing a color image, the cost increases.

  Therefore, an object of the present embodiment is to print a matte tone image having abrasion resistance without using clear ink even when printing a color image of high ink duty.

=== Printing Method of the Present Embodiment ===
FIG. 4 is a diagram illustrating the manner in which the printing method of the present embodiment is described. In the printing method according to the present embodiment, when the matte tone mode is set, for example, a yellow image of high ink duty with yellow UV ink is first irradiated with light (ultraviolet light) having low energy. After curing only the surface layer portion, the entire image is cured to the inside of the image by irradiating light (ultraviolet light) with high energy. By doing so, as shown in FIG. 4, the image surface can be wrinkled to make the image surface uneven. That is, a matte tone image can be printed.

  In this way, the phenomenon of wrinkles on the image surface is caused by first irradiating light of weak energy and curing only the surface layer portion of the image, so that the volume shrinkage due to curing is larger in the surface layer portion of the image than in the interior. This is considered to be caused by the volume balance being lost between the surface layer portion and the inside of the image.

  Further, the phenomenon of wrinkles on the surface of the image appears more conspicuously in the image using yellow UV ink than in the image using magenta or cyan UV ink. This is considered to be caused by the fact that the wavelength region of light contributing to the curing of the UV ink, that is, the wavelength region of light absorbed by the photopolymerization initiator is included in or close to the wavelength region of blue light. It is done. Therefore, in yellow inks that have an absorption region in the blue light wavelength region to absorb blue light, light with a wavelength that contributes to curing is more easily absorbed by the colorant than in magenta and cyan inks, and light reaches the inside of the image. Is difficult to reach. That is, the yellow ink has a lower light transmittance for wavelengths that contribute to curing than the magenta and cyan inks. Therefore, when light of low energy is first irradiated as in the printing method of the present embodiment, light does not reach the photopolymerization initiator inside the yellow image, and only the surface layer portion of the image is cured. Therefore, according to the printing method of the present embodiment, the surface of the yellow image can be wrinkled to make the image surface uneven, and a matte yellow image can be printed.

  Similarly, in the black UV ink, light having a wavelength contributing to curing is easily absorbed by the colorant as compared with the magenta or cyan UV ink, and the light does not easily reach the photopolymerization initiator in the image. Therefore, only the surface layer portion of the image can be cured by irradiating light of low energy first with respect to the image using black UV ink. As a result, the surface of the black image can be wrinkled to make the image surface uneven, and a matte black image can be printed.

  Also, the higher the ink duty and the thicker the image, the more likely the phenomenon of wrinkles on the surface occurs, and the easier it is to have a matte image. This is because the thicker the image is, the more difficult it is for light to reach the photopolymerization initiator inside the image, and the harder the inside of the image is to cure. Therefore, in the printing method of the comparative example shown in FIG. 3B, the glossiness becomes higher as the image of the high ink duty increases. However, according to the printing method of the present embodiment, the surface of the high ink duty tends to be wrinkled. It tends to be a matte image.

  Conversely, when the glossy mode is set, if the surface of the image is cured by irradiating light (ultraviolet light) with low energy first, the image surface becomes uneven. End up. Therefore, a glossy image with high glossiness cannot be printed.

  Therefore, in the printer 1 of the present embodiment, when the matte tone mode (corresponding to the first mode) is set, weak energy (to the first energy) with respect to the UV ink ejected per unit area of the medium S. The controller 10 performs control so that ultraviolet light having a higher energy (corresponding to the second energy) is irradiated after the ultraviolet light is irradiated. On the other hand, when the glossy mode (corresponding to the second mode) is set, the UV ink ejected per unit area of the medium S is more than the first irradiation energy (first energy) in the matte mode. The controller 10 performs control so that ultraviolet rays having higher energy are irradiated from the beginning.

  By doing so, in the matte tone mode, only the surface layer portion of the image using yellow or black ink is cured first, so that the image surface can be wrinkled and the image surface can be made uneven. Therefore, even when printing an image with a high ink duty, it is possible to print a matte image with a low glossiness without using clear ink. In addition, since light with high energy (ultraviolet rays) is irradiated after light with low energy (ultraviolet rays), the entire image is cured and the image can be fixed on the medium S. Further, since the surface of the image has an uneven shape without using clear ink, it is possible to print a matte tone image having abrasion resistance. In addition, since clear ink is not used, the cost can be reduced.

  When printing an image with a low ink duty, even if the low-energy ultraviolet rays are not irradiated first, that is, even if the high-energy ultraviolet rays are irradiated from the beginning, the matte tone as shown in FIG. Images can be printed. However, in the present embodiment, when the matte tone mode is set, irradiation with strong energy ultraviolet rays is performed after irradiation with weak energy ultraviolet rays regardless of the ink duty. By doing so, control of the controller 10 can be made easy.

  On the other hand, in the gross tone mode, the entire image can be cured at once, and the image surface can be cured in a smooth state. Therefore, as shown in FIG. 3B, when printing an image of high ink duty, the image surface can be smoothed and a glossy image with high glossiness can be printed. When printing an image with a low ink duty, it is preferable to smooth the surface of the image by ejecting the rear ink from the top of the image and print a glossy image with high glossiness.

  In addition, as described above, even if light (ultraviolet light) is first irradiated, the image with magenta or cyan ink is harder to the inside than the image with yellow or black ink, and the image surface It is hard to get wrinkles. That is, it is difficult to obtain a matte image. However, magenta and cyan inks are generally used in an overlapping manner with yellow and black inks. Therefore, even if the image surface of magenta or cyan ink is difficult to be uneven, the image surface of yellow or black ink is uneven, so the entire surface of the image can be uneven, and a matte image can be printed. can do.

  In addition, yellow ink is more likely to be used in combination with magenta or cyan ink than black ink. Therefore, as shown in FIG. 2, the head 31 that discharges yellow ink is disposed on the most downstream side in the transport direction. By doing so, it is possible to superimpose a yellow ink image whose surface tends to be uneven on a magenta or cyan ink image. Therefore, the image surface of yellow ink can be made the surface of the entire image, and the surface of the entire image is more likely to be uneven. Therefore, a matte tone image can be printed more reliably. However, the present invention is not limited to this. For example, the head 31 that discharges black ink may be disposed on the most downstream side in the transport direction. Thus, a matte image can be printed more reliably.

=== Printing Method: Example 1 ===
FIG. 5 is a flowchart illustrating a printing method according to the first embodiment. FIGS. 6A and 6B are diagrams illustrating LEDs arranged on the lower surface of the LED irradiation unit 41 according to the first embodiment. 6A is a diagram illustrating the LED irradiation unit 41 in the glossy mode, and FIG. 6B is a diagram illustrating the LED irradiation unit 41 in the matte mode. As shown in FIG. 2, the LED irradiation unit 41 arranged on the downstream side in the transport direction of each head 31 corresponds to the LED irradiation unit 41 shown in FIGS. 6A and 6B.

  On the lower surface of each LED irradiation section 41, ten “LED rows” are formed in which ten LEDs (n1 to n10) are arranged at predetermined intervals along the width direction intersecting the conveyance direction of the medium S. And ten LED row | line | columns (L1-L10) are located in a line at predetermined intervals along the conveyance direction. For the following explanation, a small number is assigned in order from the LED row located on the upstream side in the transport direction (L1, L2...), And a small number is given in order from the LED located on the upper side in the width direction (n1, n2...). .

  In Example 1, the portion of the LED irradiation unit 41 (FIG. 6B) in the mat-tone mode upstream in the conveyance direction (hereinafter, upstream portion) is conveyed in the LED irradiation unit 41 (FIG. 6B) in the mat-tone mode. Control is performed so that the number of LEDs to be lit per unit area is smaller than that of the portion on the downstream side in the direction (hereinafter, downstream portion) and the LED irradiation unit 41 in the glossy mode (FIG. 6A). By doing so, in the matte tone mode, the UV ink on the medium S can be irradiated with weak energy ultraviolet rays (light), and then in the glossy mode, the medium S can be irradiated. The upper UV ink can be irradiated with ultraviolet rays of strong energy from the beginning.

  Here, in the LED irradiation unit 41, an area including four LED rows (L1 to L4) from the upstream side in the transport direction is referred to as an “upstream portion”, and six LED rows (L5 to L5) from the downstream side in the transport direction. A region including L10) is defined as a “downstream portion”. However, the present invention is not limited to this, and the number of LED rows belonging to the upstream portion may be increased or decreased.

  Hereinafter, the flow of a specific printing method will be described according to the flow of FIG. First, when receiving a print job (S01), the controller 10 checks whether the print mode is set to the glossy mode or the matte mode (S02). For example, when the user sets the print mode in the computer 60 in which the printer driver is installed, the controller 10 acquires information about the print mode from the printer driver and confirms the print mode.

  When the print mode is set to “gross tone mode” (S02 → Y), the controller 10 turns on all the LEDs of the LED irradiation unit 41 as shown in FIG. 6A. Therefore, the number of LED lighting per unit area is constant regardless of the position in the transport direction. Therefore, in the gross tone mode, the irradiation intensity Ic of the LED irradiation unit 41 can be made strong and constant regardless of the position in the transport direction.

  On the other hand, when the print mode is set to “matte mode” (S02 → N), the controller 10 applies the LED rows (L1 to L4) included in the upstream portion of the LED irradiation unit 41 as illustrated in FIG. 6B. Every other LED that belongs is turned on, and all the LEDs that belong to the LED rows (L5 to L10) in the downstream portion are turned on. Therefore, the number of LED lighting per unit area is smaller in the upstream portion than in the downstream portion. Therefore, the irradiation intensity Iu in the upstream part of the LED irradiation part 41 can be made weaker than the irradiation intensity Il in the downstream part (Iu <Il). Further, the number of LED lighting per unit area is smaller in the upstream part of the LED irradiation unit 41 (FIG. 6B) in the matte mode than in the LED irradiation unit 41 (FIG. 6A) in the glossy mode. . Therefore, the upstream irradiation intensity Iu in the LED irradiation unit 41 in the matte mode can be made weaker than the irradiation intensity Ic in the LED irradiation unit 41 in the glossy mode (Iu <Il, Ic).

  FIG. 6C is a diagram illustrating a case where both LEDs adjacent in the transport direction and the width direction are turned on. Since the light emitted from the LED gradually spreads, when both the LEDs adjacent in the transport direction and the width direction are turned on, a part of the irradiation range overlaps. In the region where the irradiation range overlaps, the irradiation intensity increases, and the energy of the light (ultraviolet rays) irradiated to the UV ink passing through the region increases.

  Therefore, in the upstream part of the LED irradiation unit 41 (FIG. 6B) in the matte mode, the positions in the width direction of the LEDs that are lit in the LED rows (for example, L1 and L2) adjacent in the transport direction are shifted. More specifically, the odd-numbered LED rows (L1, L3) light up the odd-numbered LEDs (n1, n3, n5...), And the even-numbered LED rows (L2, L4) turn on the even-numbered LEDs (n2). , N4, n6... By doing so, the area | region where the irradiation range of LED overlaps in the upstream part of the LED irradiation part 41 can be eliminated or reduced, and the irradiation intensity Iu of an upstream part can be made weaker. Accordingly, in the matte tone mode, only the surface layer portion of the image can be cured first, and the image surface can be wrinkled.

  Conversely, in the LED irradiation unit 41 (FIG. 6B) in the matte mode and the LED irradiation unit 41 (FIG. 6A) in the glossy mode, the LEDs adjacent to each other in the transport direction and the width direction are lit. Irradiation intensities Il and Ic can be increased. Therefore, in the matte tone mode, the inside of the image that has not been cured at the upstream portion of the LED irradiation unit 41 can be cured by the downstream portion. In the glossy mode, the entire image can be cured at once, and the image surface can be cured in a smooth state.

  After controlling the number of lighting of LEDs in this way, the controller 10 executes a printing process (S05). As a result, as shown in FIG. 2, ink is ejected from the head 31 for each color of ink onto the medium S conveyed on the conveyor belt 21, and the ink on the medium S is cured by the LED irradiation unit 41. The It is assumed that the conveyance speed of the medium S passing under the LED irradiation unit 41 is constant.

  As a result, in the glossy mode (FIG. 6A), the medium S passes under the LED irradiation unit 41 having a constant irradiation intensity Ic and a strong irradiation intensity Ic regardless of the position in the transport direction. For this reason, the UV ink on the medium S is irradiated with light (ultraviolet rays) with high energy from the beginning, and the entire image is cured from the surface layer portion to the inside of the image at once. Therefore, the image is cured with a smooth surface, and a glossy image with high glossiness can be printed.

  On the other hand, in the matte mode (FIG. 6B), the medium S passes under the LED irradiation unit 41 where the irradiation intensity Iu in the upstream part is weak and the irradiation intensity Il in the downstream part is strong. Therefore, the UV ink on the medium S is first irradiated with light (ultraviolet light) having a weak energy from the upstream portion, and then the light (ultraviolet light) having a strong energy is irradiated to the downstream portion. Therefore, in an image using yellow ink or black ink, only the surface layer portion of the image is cured first, so that the image surface is wrinkled and the image surface becomes uneven. Therefore, in an image using at least one of yellow ink and black ink, the entire surface of the image has an uneven shape, and a matte tone image with low glossiness can be printed. As described above, according to the printing method of the first embodiment, it is possible to print a matte tone image having abrasion resistance without using the clear ink.

  In the matte mode, some LEDs belonging to the upstream portion of the LED irradiation unit 41 are turned off, but the present invention is not limited to this. For example, instead of turning off the LED, the LED may be covered with a filter that cuts light (ultraviolet rays) that contributes to curing of the UV ink. Also in this case, the upstream irradiation intensity Iu in the LED irradiation unit 41 in the matte mode can be made lower than the downstream irradiation intensity Il.

=== Printing Method: Example 2 ===
7A is a diagram illustrating the LED irradiation unit 41 in the glossy tone mode in the second embodiment, and FIG. 7B is a diagram illustrating the LED irradiation unit 41 in the matte tone mode in the second embodiment. In the second embodiment, the controller 10 adjusts “the position in the width direction of the LED array” according to the print mode. Therefore, in the LED irradiation part 41 used in Example 2, the 2nd and 4th LED row | line | column (L2, L4) from the conveyance direction upstream becomes a structure which can move to the width direction. However, for simplicity of explanation, the LED row moving mechanism is omitted in FIG.

  More specifically, when the print mode is set to “gross tone mode”, the controller 10, as shown in FIG. 7A, the LEDs belonging to the LED rows (for example, L1 and L2) adjacent to each other in the transport direction. Align the positions in the width direction and turn on all LEDs. By doing so, as shown to FIG. 6C, the irradiation range of LED adjacent to a conveyance direction and the width direction overlaps, and the irradiation intensity | strength Ic of the LED irradiation part 41 can be strengthened. In addition, since the positions in the width direction of the LEDs belonging to all the LED rows (L1 to L10) are aligned, the irradiation intensity Ic of the LED irradiation unit 41 is constant regardless of the position in the transport direction.

  Therefore, in the glossy mode, the UV ink on the medium S is irradiated with light of high energy (ultraviolet rays) from the beginning, and the entire image is hardened at once from the surface layer portion to the inside of the image. Therefore, the image is cured with a smooth surface, and a glossy image with high glossiness can be printed.

  On the other hand, when the print mode is set to “matte mode”, the controller 10, as shown in FIG. 7B, in the upstream portion of the LED irradiation unit 41, the LED rows (for example, L1 and L2) adjacent in the transport direction. In the downstream portion, the positions in the width direction of the LEDs belonging to the LED rows (for example, L5 and L6) adjacent in the transport direction are aligned. Moreover, the controller 10 lights up all the LEDs.

  For this purpose, the controller 10 shifts the second and fourth LED rows (L2, L4) from the upstream side in the transport direction to the lower side in the width direction among the LED rows (L1 to L4) included in the upstream portion. The shift amount of the LED rows (L2, L4) is half the interval between the LEDs arranged in the width direction. As a result, for example, in the center of the first and second LEDs (n1, n2) from the top in the width direction belonging to the first LED row (L1), the top in the width direction belonging to the second LED row (L2). To the first LED (n1) can be arranged. It should be noted that the shift amount of the LED rows (L2, L4) is not limited to half the interval between the LEDs arranged in the width direction, but may be shorter or longer.

  In this way, in the upstream portion of the LED irradiation unit 41, by shifting the position in the width direction of the LEDs belonging to the LED rows adjacent to each other in the transport direction, an area where the irradiation ranges of the LEDs adjacent in the transport direction overlap can be eliminated. It is possible to reduce the irradiation intensity Iu in the upstream portion. On the other hand, in the downstream part of the LED irradiation part 41, in order to align the positions in the width direction of the LEDs belonging to the LED rows adjacent in the transport direction, the irradiation ranges of the LEDs adjacent in the transport direction and the width direction overlap, Irradiation intensity Il can be increased.

  That is, the upstream irradiation intensity Iu in the LED irradiation section 41 in the matte mode can be made weaker than the downstream irradiation intensity Il. Further, the irradiation intensity Iu in the upstream portion of the LED irradiation unit 41 in the matte tone mode can be made weaker than the irradiation intensity Ic of the LED irradiation unit 41 in the glossy tone mode (Iu <Il, Ic).

  For this reason, in the matte tone mode, the UV ink on the medium S is first irradiated with light (ultraviolet light) with low energy from the upstream portion, and then is irradiated with light (ultraviolet light) with strong energy in the downstream portion. Therefore, in an image using yellow or black ink, only the surface layer portion of the image is first cured to cause wrinkles on the image surface, and the image surface becomes uneven. Therefore, in an image using at least one of yellow ink and black ink, the entire surface of the image is uneven, and a matte tone image can be printed. As described above, according to the printing method of Example 2, it is possible to print a matte tone image having abrasion resistance without using clear ink.

=== Printing Method: Example 3 ===
8A is a diagram illustrating the LED irradiation unit 41 in the glossy tone mode in the third embodiment, and FIG. 8B is a diagram illustrating the LED irradiation unit 41 in the matte tone mode in the third embodiment. In the third embodiment, the controller 10 adjusts the “interval in the LED row conveyance direction” according to the print mode. Therefore, in the LED irradiation part 41 used in Example 3, three LED rows (L1 to L3) are movable in the transport direction from the upstream side in the transport direction. However, for simplicity of explanation, the LED row moving mechanism is omitted in FIG.

  More specifically, when the print mode is set to “gross tone mode”, the controller 10 relatively narrows the interval D1 in the transport direction of the LED rows, as shown in FIG. Turn on the LED. By doing so, as shown to FIG. 6C, the irradiation range of LED adjacent to a conveyance direction and the width direction overlaps, and the irradiation intensity | strength Ic of the LED irradiation part 41 can be strengthened. Further, the controller 10 makes the interval D1 in the transport direction of all the LED rows (L1 to L10) constant. By doing so, the irradiation intensity Ic of the LED irradiation unit 41 can be made constant regardless of the position in the transport direction.

  Therefore, in the glossy mode, the UV ink on the medium S is irradiated with light of high energy (ultraviolet rays) from the beginning, and the entire image is hardened at once from the surface layer portion to the inside of the image. Therefore, the image is cured with a smooth surface, and a glossy image with high glossiness can be printed.

  On the other hand, when the print mode is set to the “matte mode”, the controller 10 increases the distance D2 in the transport direction of the LED rows in the upstream part of the LED irradiation unit 41 as shown in FIG. The space | interval D1 of the conveyance direction of the LED row which a part has is narrowed. Therefore, the controller 10 widens the interval D2 in the transport direction of the LED rows (L1 to L4) while shifting the three LED rows (L1 to L3) from the upstream side in the transport direction to the upstream side in the transport direction. By widening the distance D2 in the transport direction of the LED rows, it is possible to eliminate or reduce a region where the irradiation ranges of the LEDs adjacent in the transport direction overlap, and to weaken the irradiation intensity Iu in the upstream portion.

  Thus, in Example 3, the LED irradiation unit 41 in the glossy mode (FIG. 8A) and the LED irradiation unit 41 in the matte mode (FIG. 8B) are more downstream than the LED in the matte mode. The upstream portion of the irradiation unit 41 (FIG. 8B) is set to have a wider interval in the transport direction of the LED rows. Thus, the upstream of the LED irradiation unit 41 in the matte mode is higher than the irradiation intensity Ic of the LED irradiation unit 41 in the glossy mode and the irradiation intensity Il of the downstream part of the LED irradiation unit 41 in the matte mode. The irradiation intensity Iu of the part is weakened (Iu <Il, Ic).

  By doing so, in the matte tone mode, the UV ink on the medium S is first irradiated with light (ultraviolet light) of weak energy from the upstream portion, and then irradiated with light (ultraviolet light) of strong energy to the downstream portion. Is done. Therefore, in an image using yellow or black ink, only the surface layer portion of the image is first cured to cause wrinkles on the image surface, and the image surface becomes uneven. Therefore, in an image using at least one of yellow ink and black ink, the entire surface of the image is uneven, and a matte tone image can be printed. As described above, according to the printing method of Example 3, it is possible to print a matte tone image having abrasion resistance without using the clear ink.

=== Printing Method: Example 4 ===
As described above, the LED irradiation unit 41 that irradiates light having a wavelength that is absorbed by the photopolymerization initiator in the UV ink is used so that the UV ink is cured by the light from the LED irradiation unit 41. Therefore, the peak wavelength of the LED irradiation unit 41 is included in the wavelength region of light absorbed by the photopolymerization initiator.

  Further, the colorant for magenta or cyan ink is less likely to absorb light having a wavelength that contributes to curing of the UV ink, that is, light having a wavelength that is absorbed by the photopolymerization initiator, than the colorant for yellow or black ink. Therefore, even when light of low energy is first irradiated to an image of magenta or cyan ink, the light reaches the photopolymerization initiator inside the image and is easily cured to the inside of the image. For this reason, in an image using magenta or cyan ink, the surface of the image is not easily wrinkled, and it is difficult to obtain a matte image.

  Therefore, in Example 4, an auxiliary agent that absorbs light of the peak wavelength of the LED irradiation unit 41 is included in cyan and magenta UV ink. By doing so, when light (ultraviolet rays) is irradiated onto an image of cyan or magenta ink, the auxiliary agent absorbs light having a wavelength that is absorbed by the photopolymerization initiator, so that the light transmittance is deteriorated.

  Therefore, by irradiating light (ultraviolet rays) with weak energy to the cyan or magenta ink image first in the matte tone mode, it becomes difficult for light to reach the photopolymerization initiator inside the image, and the inside of the image is not cured. Only the surface layer portion can be cured. As a result, the image surface can be wrinkled to make the image surface uneven, and a matte tone image can be printed.

  As described above, in Example 4, since the image surface can be made uneven not only in the image using yellow or black ink but also in the image using cyan or magenta ink, the surface unevenness of the entire image can be made larger. The matte tone image can be printed more reliably. Further, even when yellow or black ink is not used, a matte tone image can be printed. Further, an auxiliary agent may be contained only in the UV ink of one color of cyan and magenta.

  In addition, the thing of the following compositions is mentioned as an adjuvant which absorbs the light of the peak wavelength (395 nm) of the LED irradiation part 41. FIG. For example, 1- (phenyl) ethanone, di (4-methoxyphenyl) diketone, 1,2-bis (phenyl) ethanedione, α-hydroxy-α-phenylacetophenone, 1,2-diphenyl-2-ethoxyethanone, , 2-Diphenyl-2- (isobutoxy) ethanone, 1,2-diphenyl-2- (isopropyloxy) ethane-1-one, 1-[(diphenylphosphinyl) carbonyl] -2,4,6-trimethylbenzene 2- (methoxycarbonyl) benzophenone.

=== Modification ===
<Modification 1>
FIG. 9A and FIG. 9B are diagrams illustrating the LED irradiation unit for the matte mode. In the above-described embodiment, the same LED irradiation unit 41 is used in the matte tone mode and the glossy tone mode. However, the present invention is not limited thereto, and the LED irradiation unit 41 for the matte tone mode and the LED irradiation unit for the glossy tone mode are used. 41 may be provided separately. In that case, it is not necessary to control the on / off of the LED or to move the LED row included in the upstream portion of the LED irradiation unit 41 in the width direction or the transport direction according to the printing mode.

  For example, when changing the number of LEDs to be lit per unit area according to the printing mode, the matte tone mode LED irradiation unit 41 shown in FIG. 9A may be used. In the upstream portion of the LED irradiation unit 41 shown in FIG. 9A, every other LED is thinned out and disposed as compared with the downstream portion. Specifically, in the upstream portion, even-numbered LEDs (n2, n4...) Belonging to odd-numbered LED rows (L1, L3) are thinned out, and odd-numbered LEDs belonging to even-numbered LED rows (L2, L4). Numbered LEDs (n1, n3...) Are thinned out.

  Also, for example, when the interval in the LED row conveyance direction is changed according to the printing mode, the matte tone mode LED irradiation unit 41 shown in FIG. 9B may be used. In the upstream part of the LED irradiation part 41 shown to FIG. 9B, compared with the downstream part, the LED row | line | column is thinned and arrange | positioned. More specifically, in the upstream portion, even-numbered LED rows (L2, L4) are thinned out.

  Even in such an LED irradiation unit 41 (FIGS. 9A and 9B), the irradiation intensity Iu in the upstream part can be made weaker than the irradiation intensity Il in the downstream part. Therefore, in the matte tone mode, the UV ink on the medium S can be first irradiated with light (ultraviolet rays) having a weak energy, and a matte tone image can be printed.

<Modification 2>
In the above embodiment, in the matte mode, the irradiation intensity Iu in the upstream part of the LED irradiation part 41 is made weaker than the irradiation intensity Il in the downstream part, but this is not restrictive. For example, when the two LED irradiation units 41 are used to irradiate the UV ink on the medium S with ultraviolet rays, the time when the first LED irradiation unit 41 is opposed to the medium S and the second LED irradiation unit 41 is the medium S. It may be shorter than the time of facing. That is, the relative movement speed of the first LED irradiation unit 41 and the medium S may be faster than the relative movement speed of the second LED irradiation unit 41 and the medium S. Also in this case, the UV ink on the medium S is first irradiated with light with low energy and then with light with high energy, so that a matte tone image is printed.

=== Other Embodiments ===
The above-described embodiments are for facilitating the 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 embodiment, when the medium passes under the fixed head extending over the width of the medium, the head ejects ink onto the medium, thereby generating a two-dimensional image on the medium. Although a printer for printing is taken as an example, the present invention is not limited to this. For example, the operation of ejecting ink to the medium while the head moves in the movement direction and the operation of conveying the medium to the downstream side of the conveyance direction with respect to the head are alternately repeated, and further to the downstream side of the conveyance direction than the head. It may be a printer that cures the photocurable ink on the medium by the arranged LED irradiation unit.

1 Printer, 10 Controller, 11 Interface section,
12 CPU, 13 memory, 14 unit control circuit,
20 transport unit, 21 transport belt, 22a transport roller,
22b Transport roller, 30 head unit, 31 head,
40 irradiation unit, 41 LED irradiation unit,
50 detector groups, 60 computers

Claims (4)

(A) a head unit that discharges yellow UV-curable ink to a medium;
(B) an LED irradiation unit that irradiates ultraviolet rays;
(C) When the first mode is set, the ultraviolet curable ink ejected per unit area of the medium is stronger than the first energy after being irradiated with ultraviolet rays of the first energy. Control to irradiate the second energy of ultraviolet rays,
When the second mode in which an image having a higher gloss than the image printed in the first mode is set is set, the ultraviolet curable ink ejected per unit area of the medium A control unit that controls the irradiation with ultraviolet rays having energy stronger than the first energy;
With
(D) The medium is transported downstream in the transport direction with respect to the LED irradiation unit,
In the LED irradiation unit, a plurality of LED rows in which a plurality of LEDs are arranged in a direction intersecting the transport direction are arranged in the transport direction,
In the upstream portion of the LED irradiation section in the first mode in the transport direction, the positions of the LEDs that belong to the LED rows adjacent to the transport direction are shifted,
In the portion on the downstream side in the transport direction in the LED irradiation unit in the first mode and in the LED irradiation unit in the second mode, each of the LEDs belonging to the LED rows adjacent in the transport direction. The positions in the intersecting direction are aligned,
A printing apparatus characterized by that. The printing apparatus according to claim 1 ,
The medium is transported downstream in the transport direction with respect to the LED irradiation unit,
In the LED irradiation unit, a plurality of LED rows in which a plurality of LEDs are arranged in a direction intersecting the transport direction are arranged in the transport direction,
The transport direction in the LED irradiation section in the first mode than the downstream portion of the transport direction in the LED irradiation section in the first mode and the LED irradiation section in the second mode The upstream side of the LED row has a wider interval in the transport direction of the LED row,
Printing device. The printing apparatus according to claim 1 or 2 , wherein
The head unit ejects ultraviolet curable ink of at least one of cyan and magenta onto the medium,
The ultraviolet curable ink of at least one of the cyan and magenta contains an auxiliary agent that absorbs light having a peak wavelength of the LED irradiation portion.
Printing device. The printing apparatus according to any one of claims 1 to 3 , wherein
The head unit discharges black ultraviolet curable ink to the medium.
Printing device.

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