JP5807544B2 - 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 a photocurable ink that is cured by irradiation with light such as ultraviolet rays (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 2009-208286 A

  Some printers that use photo-curable inks, for example, eject clear ink on an image printed with color ink in order to adjust the glossiness of the image. However, if clear ink is ejected on a color image that has been completely cured, the clear ink droplets flow on the color image, and the adjacent clear ink droplets are connected or separated. If it does so, the image surface will become uneven | corrugated shape and it will become impossible to print the image which has desired glossiness. On the other hand, by discharging a large amount of clear ink that covers the entire surface of the color image, the surface of the image can be smoothed and an image having a desired glossiness can be printed, but the consumption of clear ink increases. End up.

  Accordingly, an object of the present invention is to print an image having a desired glossiness while suppressing consumption of clear ink.

The main invention for solving the above-mentioned problems is: (A) a main ink for printing a main image, and a first head for discharging a main ink that is cured by light irradiation; and (B) curing by the light irradiation. A second head that ejects clear ink, (C) an irradiation unit that irradiates the light, and (D) the main image is printed on the medium by the first head, and the main image is printed on the main image by the irradiation unit. A control unit that discharges the clear ink onto the main image by the second head after irradiating light, and irradiates the light to the clear ink by the irradiating unit, wherein the first mode is set If it is, control is performed so that light of the first energy is emitted per unit area of the main image before the clear ink is ejected, and gloss is higher than that of the image printed in the first mode. The degree image is marked When the second mode is set, control is performed so that light having a second energy lower than the first energy is emitted per unit area of the main image before the clear ink is ejected. And (E) a printing device.
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 and 3B are diagrams illustrating a printing method in a glossy mode in a comparative example. It is a figure explaining the printing method of the glossy mode in this embodiment. 3 is a flowchart illustrating a printing method according to the first exemplary embodiment. It is a table | surface which shows the evaluation result which changed the ratio of the irradiation energy at the time of the glossy tone mode with respect to the time of the matte tone mode. 10 is a flowchart illustrating a printing method according to the second exemplary embodiment.

=== 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 main ink for printing a main image, and a first head that discharges a main ink that is cured by light irradiation; and (B) a second head that discharges a clear ink that is cured by light irradiation. (C) an irradiation unit that irradiates the light; and (D) after the main image is printed on a medium by the first head and the main image is irradiated by the irradiation unit, A control unit that ejects the clear ink onto the main image by two heads and irradiates the light to the clear ink by the irradiation unit, and when the first mode is set, the clear ink Control is performed so that light of the first energy is emitted per unit area of the main image before being discharged, and a second glossy image is printed than an image printed in the first mode. Mode is set A control unit that controls so that light of a second energy lower than the first energy is irradiated per unit area of the main image before the clear ink is ejected, and (E) A printing apparatus is provided.
According to such a printing apparatus, it is possible to print an image having a desired glossiness while suppressing consumption of the clear ink.

In this printing apparatus, the control unit may irradiate the main image in the second mode than the irradiation intensity of the light that the irradiation unit irradiates the main image in the first mode. Decreasing the irradiation intensity of the light.
According to such a printing apparatus, the amount of light irradiated per unit area of the main image in the second mode is higher than the energy (first energy) of light irradiated per unit area of the main image in the first mode. Energy (second energy) can be lowered.

In this printing apparatus, the irradiating unit irradiates the main image with the light while relatively moving in a predetermined direction with respect to the medium on which the main image is printed, and the control unit is configured to operate in the first mode. The relative movement speed between the irradiation unit and the medium in the second mode is made faster than the relative movement speed between the irradiation unit and the medium.
According to such a printing apparatus, the amount of light irradiated per unit area of the main image in the second mode is higher than the energy (first energy) of light irradiated per unit area of the main image in the first mode. Energy (second energy) can be lowered.

In this printing apparatus, the second energy is 45% or more and 55% or less of the first energy.
According to such a printing apparatus, it is possible to ensure the peelability of the main image while printing an image having a desired glossiness.

(A) printing a main image on the medium by discharging main ink that is cured by light irradiation onto the medium; and (B) printing on the medium when the first mode is set. When the second mode in which an image having a higher gloss than the image printed in the first mode is set by irradiating light of the first energy per unit area of the main image is set, Irradiating light of a second energy lower than the first energy per unit area of the main image printed on a medium; and (C) on the main image irradiated with the light, Printing comprising: discharging a clear ink that is cured by light irradiation; (D) irradiating the clear ink discharged on the main image with the light; and (E). Is the method.
According to such a printing method, it is possible to print an image having a desired glossiness while suppressing consumption of the clear ink.

=== 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 viewed from a direction that intersects the conveyance direction of the medium S.
The printer 1 of the present embodiment prints an image on a medium S (for example, paper, cloth, plastic film, etc.) using ultraviolet curable ink (photo curable ink) that is cured by irradiating ultraviolet (light). To do. The ultraviolet curable ink (UV ink) is an ink containing an ultraviolet curable resin, and is cured by a photopolymerization reaction occurring in the ultraviolet curable resin when irradiated with ultraviolet rays.

  The computer 60 is communicably connected to the printer 1 and outputs print data for causing the printer 1 to print an image to the printer 1 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 irradiation units 41 and 42 when being transported on the transport belt 21.

  The head unit 30 is for ejecting UV ink onto the medium S, and has a plurality of heads 31. In the printer 1 of the present embodiment, as shown in FIG. 2, a head 31 that ejects black ink (K), a head 31 that ejects cyan ink (C), a head 31 that ejects magenta ink (M), and yellow ink A head 31 for discharging (Y) and a head 31 for discharging colorless and transparent clear ink (Cl) are arranged in order from the upstream side in the transport direction. Therefore, in the printer 1 of the present embodiment, clear ink is ejected on a main image (monochrome image or color image) printed with four colored inks (YMCK, corresponding to the main ink). Here, the clear ink is a colorless and transparent ink that does not include a color material, but is not limited thereto. For example, the clear ink may include a small amount of a color material, but may have transparency. Any ink can be used as long as the main image can be visually recognized.

  On the lower surface of the head 31, a large number of nozzle openings, which are ejection openings for UV ink, are provided side by side at a predetermined interval in the width direction intersecting the transport direction of the medium S (not shown). The length of the row of nozzle openings along the width direction is equal to or longer than the maximum width of the medium S. Accordingly, 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 (corresponding to the irradiation unit) is for irradiating the UV ink on the medium S with ultraviolet rays to cure the UV ink, and includes a first irradiation unit 41 and a second irradiation unit 42. Have. The first irradiation unit 41 and the second irradiation unit 42 irradiate the medium S moving in the transport direction (corresponding to a predetermined direction) with ultraviolet rays. Examples of the light source (ultraviolet irradiation source) include a light emitting diode (LED), a metal halide lamp, and a mercury lamp.

The first irradiation unit 41 is located downstream in the transport direction from the head 31 that ejects four colored inks (YMCK), and is located upstream in the transport direction from the head 31 that ejects clear ink (Cl). Placed in position. Therefore, the first irradiation unit 41 cures the main image printed with the four colored inks.
The second irradiation unit 42 is disposed at a position downstream of the head 31 that discharges clear ink (Cl) in the transport direction. For this reason, the second irradiation unit 42 mainly cures the clear ink ejected on the main image.

The controller 10 adjusts the irradiation intensity (mW / cm ² ) of the ultraviolet rays that the irradiation units 41 and 42 irradiate per unit area by changing the current value input to the light sources of the irradiation units 41 and 42. . In addition, the irradiation energy (mJ / cm ² ) of the ultraviolet rays irradiated to the UV ink per unit area on the medium S is determined by the product of the irradiation intensity (mW / cm ² ) of the ultraviolet rays and the irradiation time (s). Although not illustrated in FIG. 2, an irradiation unit that irradiates weak ultraviolet rays is arranged between the heads 31 that discharge each colored ink (YMCK), and the ink of each color is temporarily cured to the extent that it does not flow. Good. By doing so, it is possible to prevent color mixing and bleeding between different color inks.

  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 on which dots are formed” in the “number of pixels corresponding to the unit area of the medium S”) is expressed as “ The ink duty is high when the ink discharge amount per unit area is large, and the ink duty is low when the ink discharge amount per unit area is small.

=== Print mode ===
The printer 1 according to the present embodiment has a “matte tone mode” and a “glossy tone mode” so that printing with different glossiness (texture) of an image can be performed according to a user's application.
When the matte tone mode is set, the printer 1 prints a matte tone image having relatively large unevenness on the image surface and lower gloss than an image printed in the glossy tone mode. 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.

=== Glossiness of image ===
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 the ink duty is low (that is, the ink discharge amount per unit area of the medium S is small) and each UV ink droplet lands on a distant position on the medium S, the granular UV ink droplet is in an independent state. Cured. For this reason, the image surface has an uneven shape, and the light irradiated to the image is irregularly reflected, so that the glossiness of the image is lowered. On the other hand, when the ink duty is high (that is, when the ink discharge amount per unit area of the medium S is large), most of the medium S is covered with the UV ink droplets, so that the image surface is smoothed and the image The glossiness of the becomes higher.

  However, the relationship between the ink duty and the glossiness is not always as described above. For example, when the surface-treated medium S such as glossy paper is used, when the ink duty is extremely low, the glossiness of the image is high due to the influence of the glossiness of the exposed part of the medium S, and the medium S increases as the ink duty increases. The exposed part of the image is reduced and the glossiness of the image is lowered. However, when the ink duty exceeds a predetermined value, the ink duty changes and the glossiness of the image increases as the ink duty increases. As described above, the glossiness of an image changes depending on the difference in ink duty, and the relationship between the ink duty and the glossiness is complicated.

  In addition, the main image printed with four color inks (YMCK) is determined by the ink duty according to the image desired by the user. Furthermore, in one image (in one page), there are many cases where a high ink duty portion and a low ink duty portion are mixed. Therefore, if only the main image is printed on the medium S, the glossiness of the image is determined by the ink duty of the main image, and an image having a glossiness according to the matte tone mode or the glossy tone mode is printed. I can't. In addition, a high-gloss part and a low-gloss part are mixed in one image, and uneven glossiness occurs in the image.

Therefore, in the printer 1 of the present embodiment, the controller 10 (corresponding to the control unit) prints the main image on the medium S by the head 31 (corresponding to the first head) that discharges colored ink (YMCK), and then The main image is cured by irradiating the main image with ultraviolet rays by the one irradiation unit 41. Thereafter, the controller 10 ejects the clear ink onto the main image by the head 31 (corresponding to the second head) that ejects the clear ink (Cl), and then causes the second irradiation unit 42 to irradiate the clear ink with ultraviolet rays. Cure the clear ink.
By doing so, the glossiness of the image can be adjusted regardless of the ink duty of the main image, and an image with a glossiness corresponding to the print mode can be printed or gloss unevenness can be suppressed.

=== Printing Method of Comparative Example ===
3A and 3B are diagrams illustrating a printing method in a glossy mode in a comparative example. In the comparative example, when the glossy tone mode is set, the first irradiation unit 41 irradiates the main image before the clear ink is ejected with a strong irradiation intensity to completely cure the main image. . Then, clear ink is ejected onto the main image in a completely cured state.

  FIG. 3A shows an image printed when the ink duty of the clear ink is relatively low, for example, when the ink duty is 50%. When the ink duty is 50%, clear ink droplets are ejected to 50% of the pixels defined on the medium S or the main image, that is, every other pixel. Therefore, as shown in the left diagram of FIG. 3A, the clear ink droplet immediately after landing on the main image is in an independent state without coming into contact with the nearby clear ink droplet.

  However, the clear ink droplets that have landed on the main image are not immediately irradiated with ultraviolet rays, but are irradiated with ultraviolet rays after the medium S is conveyed from the head 31 that discharges the clear ink to the second irradiation unit 42. Further, as the degree of curing of the lower layer image is higher, the UV ink droplets landed thereon do not penetrate into the lower layer image and are repelled on the lower layer image, so that the lower image is more likely to flow on the lower layer image. Therefore, as shown in this comparative example, if the clear ink droplet is ejected onto the fully cured main image, the clear ink droplet will not be The clear ink droplets in the vicinity are connected or separated from each other. As a result, as shown in the right diagram of FIG. 3A, a plurality of clear ink droplets are connected, and the clear ink droplets are cured in a separated state. Therefore, the unevenness of the image surface becomes large, and the glossiness of the main image is lowered. Accordingly, the printing method of the comparative example in FIG. 3A cannot print a glossy image.

  FIG. 3B shows an image printed when the ink duty of the clear ink is high, for example, when the ink duty is 100%. When the ink duty is 100%, clear ink droplets are ejected to all pixels defined on the medium S or the main image. For this reason, the clear ink droplet immediately after landing on the main image is in contact with the adjacent clear ink droplet as shown in the left diagram of FIG. 3B.

  In this case, even if the degree of cure of the main image is high and the clear ink droplets easily flow on the main image, all the clear ink droplets are connected, and as shown in the right diagram of FIG. Can be covered. Accordingly, the surface of the image is smoothed, the glossiness of the main image is increased, and a glossy image can be printed.

  However, as shown in FIG. 3B, if the ink duty of the clear ink is increased and printing is performed, the consumption of the clear ink is large and the cost is increased. In addition, since a large amount of clear ink is ejected onto the main image, a feeling of thickness is generated in the image, resulting in poor appearance.

  Accordingly, the printer 1 of the present embodiment is intended to print an image having a desired gloss level (an image with a high gloss level) while suppressing consumption of clear ink when the glossy tone mode is set. To do.

=== Printing Method of this Embodiment (Overview) ===
FIG. 4 is a diagram illustrating a printing method in the glossy mode according to the present embodiment. In the present embodiment, when the glossy mode is set, the main image before the clear ink is ejected is irradiated with ultraviolet rays having relatively weak energy. Then, clear ink is ejected onto the semi-cured main image that is not completely cured. In this embodiment, the ink duty of clear ink is set lower than that of the comparative example (ie, ink duty 100%) in FIG. 3B. Here, similarly to the comparative example of FIG. 3A, it is assumed that the clear ink ink duty is 50%, and clear ink droplets are ejected every other pixel.

  Compared to the case where it is ejected onto the completely cured lower layer image, the UV ink droplets ejected onto the semi-cured lower layer image penetrates the lower layer image and spreads on the lower layer image. It is difficult to flow on the lower layer image. Therefore, as in this embodiment, when clear ink droplets are ejected onto a semi-cured main image, the clear ink droplets flow on the main image during the period from landing until irradiation with ultraviolet rays. Instead, it spreads wet on the spot. That is, unlike the comparative example (FIG. 3A), adjacent clear ink droplets are not connected or separated, and the main image can be thinly covered with clear ink as shown in the right diagram of FIG. can do. Therefore, according to the printing method of the present embodiment, it is possible to print a glossy image with high glossiness even if the ink duty of the clear ink is lowered.

  Therefore, conversely, when the matte mode is set, if clear ink droplets are ejected onto the semi-cured main image, the image surface is smoothed and the glossiness of the image is increased. The matte tone image cannot be printed. Therefore, when the matte mode is set, printing is performed as in the comparative example of FIG. 3A so that the unevenness of the image surface becomes large and the glossiness of the image is suppressed.

  That is, when the matte tone mode is set, the main image before the clear ink is ejected is irradiated with relatively strong energy ultraviolet rays, and the main image is completely cured. Clear ink is ejected. By doing so, as shown in FIG. 3A, the clear ink droplets flow on the main image, and the adjacent clear ink droplets are connected to or separated from each other, so that the image surface can be formed into an uneven shape. Accordingly, it is possible to print a matte tone image with reduced glossiness.

  In summary, the controller 10 of the printer 1 of the present embodiment is configured so that the gloss per unit area of the main image before the clear ink is ejected when the matte tone mode (corresponding to the first mode) is set. Control is performed so that ultraviolet rays having higher energy (corresponding to the first energy) than in the adjustment mode are irradiated. In addition, when the glossy tone mode (corresponding to the second mode) in which an image having a higher glossiness than that of the image printed in the matte tone mode is set, the controller 10 is set before the clear ink is ejected. Control is performed so that ultraviolet light having a weaker energy (corresponding to the second energy) is irradiated per unit area of the main image than in the matte tone mode.

That is, the controller 10 changes the irradiation energy (mJ / cm ² ) of the ultraviolet light applied to the lower layer main image according to the print mode, and the energy that is strong enough to completely cure the main image in the matte mode. In the gross tone mode, the main image is irradiated with ultraviolet light having a weak energy that does not completely cure the main image.

  By doing so, in the matte tone mode, the image surface can be made uneven, and a matte tone image with reduced gloss can be printed. Further, in the glossy mode, the flow of the clear ink droplet on the main image is suppressed, and the clear ink droplet spreads on the main image, so that a large amount of clear ink is not discharged as in the comparative example (FIG. 3B). However, the image surface can be smoothed and a glossy image with high glossiness can be printed. That is, it is possible to print an image with high glossiness while suppressing consumption of the clear ink. In the present embodiment, the clear ink can be made thinner (t1> t2) in order to lower the ink duty of the clear ink than in the comparative example (FIG. 3B). Therefore, it is possible to suppress the thick feeling of the clear ink and improve the image quality.

=== Example 1: Printing Method ===
FIG. 5 is a flowchart illustrating the printing method according to the first embodiment. In the first embodiment, in order to change the irradiation energy (mJ / cm ² ) of the ultraviolet rays that irradiate the main image according to the printing mode, the controller 10 applies the irradiation intensity of the ultraviolet rays that the first irradiation unit 41 irradiates the main image. (MW / cm ² ) is controlled.

Hereinafter, a specific flow of the printing method will be described with reference to FIG.
First, when receiving a print job (S001), the controller 10 checks whether the print mode is set to the glossy mode or the matte mode (S002). 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 printing mode is set to “matte mode” (S002 → N), the controller 10 determines the irradiation intensity of the first irradiation unit 41 that irradiates the main image before the clear ink is discharged with ultraviolet rays. Set to “I (mW / cm ² )”. On the other hand, when the printing mode is set to “glossy mode” (S002 → Y), the controller 10 sets the irradiation intensity of the first irradiation unit 41 to the irradiation intensity I (mW / cm ² ) in the matte mode. The irradiation intensity is set to “I / 2 (mW / cm ² )”.

  Further, in the first embodiment, regardless of the print mode, the clear ink ink duty is set to a constant 50% and the matte tone mode is set or the glossy tone mode is set. The same amount of clear ink is ejected per unit area of the image. For ease of explanation, here, the ink duty of the clear ink is set to a constant 50% regardless of the ink duty of the main image. However, the present invention is not limited to this. For example, the ink duty of the clear ink may be changed for each unit area according to the ink duty for each unit area of the main image. In addition, similarly to the print data related to other colored inks (YMCK), the print data related to the clear ink is also created by the printer driver.

  In the first embodiment, the controller 10 controls the transport unit 20 so that the transport speed of the medium S becomes a constant speed “V (cm / s)” regardless of the print mode. That is, regardless of the print mode, the time during which the unit area of the main image and the first irradiation unit 41 face each other is constant, and the time during which the first irradiation unit 41 irradiates the unit area of the main image with ultraviolet rays is constant. To do.

  The irradiation intensity of the second irradiation unit 42 that cures the clear ink is constant regardless of the printing mode. That is, even when the matte tone mode is set and when the glossy tone mode is set, the irradiation energy of the ultraviolet rays that the second irradiation unit 42 irradiates per unit area of the clear ink is made constant.

  As described above, the controller 10 executes the printing process while controlling each unit (S005). That is, the controller 10 prints the main image on the medium S with four colored inks (YMCK), and irradiates the main image with ultraviolet rays having energy corresponding to the print mode, and then cures the main image. The clear ink is discharged onto the surface, and the clear ink is irradiated with ultraviolet rays and cured.

Therefore, when the matte tone mode is set, the medium S on which the main image is printed is conveyed under the first irradiation unit 41 whose ultraviolet irradiation intensity per unit area is I (mW / cm ² ). It is conveyed at a speed V (cm / s). That is, each unit area (cm ² ) of the first irradiation unit 41 and the main image faces each other during the time “1 / V (s)”, and the first irradiation unit 41 has a unit area (cm ² ) is irradiated with ultraviolet rays for a time 1 / V (s). Therefore, for each unit area of the first irradiation unit 41, the irradiation energy of the ultraviolet rays irradiated per unit area of the main image is “irradiation intensity × irradiation time = I (mW / cm ² ) × 1 / V (s)”. = I / V (mJ / cm ² ) ”.

On the other hand, when the gross tone mode is set, the medium S on which the main image is printed is below the first irradiation unit 41 whose ultraviolet irradiation intensity per unit area is I / 2 (mW / cm ² ). , And conveyed at a conveyance speed V (cm / s). That is, the first irradiation unit 41 and each unit area (cm ² ) of the main image face each other over time 1 / V (s). Therefore, for each unit area of the first irradiation unit 41, the irradiation energy of the ultraviolet rays irradiated per unit area of the main image is “irradiation intensity × irradiation time = I / 2 (mW / cm ² ) × 1 / V ( s) = I / 2V (mJ / cm ² ) ”.

As described above, the controller 10 is configured so that the first irradiation unit 41 is mainly used in the glossy mode than the irradiation intensity (I (mW / cm ² )) of the ultraviolet rays that the first irradiation unit 41 irradiates the main image in the matte mode. The irradiation intensity (I / 2 (mW / cm ² )) of the ultraviolet rays that irradiate the image is reduced (in this case, half). By doing so, the irradiation energy of the ultraviolet ray irradiated per unit area of the main image in the glossy mode can be made lower than the irradiation energy of the ultraviolet ray irradiated per unit area of the main image in the matte tone mode. (Here it is half).

  Note that the irradiation intensity of the first irradiation unit 41 and the conveyance speed of the medium S are set so that the irradiation energy of the ultraviolet light irradiated to the main image in the matte tone mode becomes the irradiation energy recommended by the type of ink. . In other words, in the gross tone mode, the irradiation intensity of the first irradiation unit 41 and the conveyance speed of the medium S are set so that half of the recommended irradiation energy is irradiated to the main image.

  Accordingly, in the matte tone mode, the clear ink is ejected onto the fully cured main image. As a result, as shown in FIG. 3A, since the clear ink droplet flows on the main image, the image surface has an uneven shape, and a matte tone image with reduced glossiness can be printed. On the other hand, in the glossy mode, clear ink is ejected onto a semi-cured main image that is not completely cured. As a result, as shown in FIG. 4, the flow of the clear ink droplet on the main image is suppressed, and the clear ink can be spread thinly and wetly. Can be printed.

  In the present embodiment, the irradiation energy of the ultraviolet rays irradiated per unit area of the main image in the glossy mode is set to half (50%) in the matte mode. If the irradiation energy of the ultraviolet rays applied to the UV ink is lowered in this way, the degree of cure of the UV ink is lowered and the UV ink is easily peeled off from the medium S. Therefore, the irradiation energy of the ultraviolet rays in the glossy mode is set so that the problem of the peelability of the main image with respect to the medium S does not occur while lowering the curing degree of the main image so that a glossy image with high glossiness is printed. It is good to decide.

  FIG. 6 is a table showing evaluation results obtained by changing the ratio of irradiation energy in the glossy tone mode to that in the matte tone mode. The irradiation energy of the ultraviolet rays applied to the main image in the matte tone mode is set to the irradiation energy recommended for the UV ink for printing the main image. Then, in order to determine the appropriate irradiation energy in the glossy mode, the main image is cured with irradiation energy that is changed from 35%, 45%, 55%, and 65% to the recommended irradiation energy. To do. Thereafter, the clear ink is discharged onto the main image with the ink duty of the clear ink being 50%, and the clear ink is cured. Note that the irradiation energy for curing the clear ink is constant and the irradiation energy recommended for the clear ink. Glossiness and peelability were evaluated for images printed under the above conditions.

As a result, as shown in FIG. 6, when the main image was cured with an irradiation energy of 65% in the matte tone mode (recommended irradiation energy), there was no problem of peelability (◎), but the glossiness of the image. Has become lower than the desired glossiness (×).
When the main image was cured at an irradiation energy of 45% and 55% in the matte tone mode, the glossiness of the image became a desired glossiness (◎). Moreover, although the peelability was lower than that at the irradiation energy of 65%, the peelability to the extent that no problem occurred was obtained (◯).
When the main image was cured with an irradiation energy of 35% in the matte tone mode, the glossiness of the image became the desired glossiness (◎). However, the peelability deteriorated to the extent that a problem occurred (x).

  As a result, the irradiation energy (corresponding to the second energy) of the ultraviolet light irradiated per unit area of the main image in the glossy mode is changed to the irradiation energy (first energy) irradiated per unit area of the main image in the matte mode. Of 45% to 55% of the energy). By doing so, when the glossy mode is set, the peelability of the main image can be ensured so as not to cause a problem while printing a glossy image having a high glossiness.

=== Example 2: Printing Method ===
FIG. 7 is a flowchart illustrating the printing method according to the second embodiment. In Example 2, in order to change the irradiation energy (mJ / cm ² ) of ultraviolet rays that irradiate the main image according to the printing mode, the controller 10 transports the medium S that passes under the first irradiation unit 41. (Cm / s) is controlled. That is, according to the printing mode, the time when the unit area of the main image and the first irradiation unit 41 face each other is controlled, and the time when the first irradiation unit 41 irradiates the unit area of the main image with ultraviolet rays is controlled. .

Hereinafter, a specific description will be given according to the flow of FIG. First, when receiving a print job (S101), the controller 10 confirms the set print mode (S102). When the matte tone mode is set (S102 → N), the controller 10 sets the conveyance speed of the medium S passing under the first irradiation unit 41 to “V (cm / s)” (S103). ). On the other hand, when the glossy mode is set (S102 → Y), the controller 10 transports the transport speed of the medium S that passes under the first irradiation unit 41 at twice the speed in the matte mode. The speed is set to “2 V (cm / s)” (S104). Regardless of the printing mode, the irradiation intensity of the first irradiation unit 41 is set to a constant “I (mW / cm ² )”, and the ink duty of the clear ink is set to a fixed 50%.

By doing so, when the matte tone mode is set, the medium S on which the main image is printed is below the first irradiation unit 41 whose ultraviolet irradiation intensity per unit area is I (mW / cm ² ). Is conveyed at a conveyance speed V (cm / s). Accordingly, the first irradiation unit 41 and each unit area (cm ² ) of the main image face each other over time 1 / V (s). Therefore, for each unit area of the first irradiation unit 41, the irradiation energy of the ultraviolet rays irradiated per unit area of the main image is “irradiation intensity × irradiation time = I (mW / cm ² ) × 1 / V (s)”. = I / V (mJ / cm ² ) ”.

On the other hand, when the glossy mode is set, the medium S on which the main image is printed is matted under the first irradiation unit 41 whose ultraviolet irradiation intensity per unit area is I (mW / cm ² ). It is transported at a transport speed 2V (cm / s) which is twice that in the adjustment mode. Accordingly, the first irradiation unit 41 and each unit area (cm ² ) of the main image face each other during a time ½ V (s) which is half of the matte mode. Therefore, for each unit area of the first irradiation unit 41, the irradiation energy of the ultraviolet rays irradiated per unit area of the main image is “irradiation intensity × irradiation time = I (mW / cm ² ) × 1/2 V (s)”. = I / 2V (mJ / cm ² ) ”.

  As described above, the controller 10 increases the conveyance speed 2V of the medium S in the glossy mode (in this case, doubled) than the conveyance speed V (corresponding to the relative movement speed) of the medium S in the matte mode. ). By doing so, the irradiation energy of the ultraviolet ray irradiated per unit area of the main image in the glossy mode can be made lower than the irradiation energy of the ultraviolet ray irradiated per unit area of the main image in the matte tone mode. (Here it is half).

  Accordingly, in the matte tone mode, the clear ink is ejected onto the fully cured main image. As a result, since the clear ink droplet flows on the main image, the image surface has an uneven shape, and a matte tone image with a suppressed glossiness can be printed. On the other hand, in the glossy mode, clear ink is ejected onto a semi-cured main image that is not completely cured. As a result, the flow of clear ink droplets on the main image can be suppressed, and the clear ink can be thinly spread. Therefore, the image surface can be smoothed and a glossy image with high glossiness can be printed.

  As shown in FIG. 2, generally, a part of the medium S faces the first irradiation unit 41, and at the same time, another part of the medium S faces the head 31 that discharges colored ink (YMCK). Or opposed to the second irradiation unit 42. That is, the ultraviolet irradiation by the first irradiation unit 41 and the printing by the head 31 and the ultraviolet irradiation by the second irradiation unit 42 are performed simultaneously. For this reason, in the second embodiment in which the conveyance speed of the medium S in the glossy tone mode is doubled in the matte tone mode, the ink discharge interval from the nozzles is also different between the glossy tone mode and the matte tone mode. Further, the irradiation intensity of the second irradiation unit 42 may be set to be twice the irradiation intensity of the first irradiation unit 41 so that the clear ink is completely cured even in the glossy mode in which the conveyance speed of the medium S is doubled. .

=== Modification ===
<Modification 1>
In the above-described embodiment, the ink duty of the clear ink is fixed (50%) regardless of whether the glossy tone mode is set or the matte tone mode is set. However, the present invention is not limited to this. . For example, the clear ink ink duty in the glossy mode may be set higher (eg, 80%) than the clear ink ink duty in the matte mode (eg, 50%).

  Further, the glossiness of the image increases as the ink duty of the clear ink ejected on the main image is increased. Therefore, even if the glossy mode is the same, if you want to print an image with a higher glossiness than the normal case where the ink duty of the clear ink is set to 50%, for example, the ink duty of the clear ink is set to 80%, for example. May be raised.

<Modification 2>
In the above-described embodiment, either the irradiation intensity of the first irradiation unit 41 or the conveyance speed of the medium S is adjusted in order to change the irradiation energy of the ultraviolet rays irradiated to the main image according to the printing mode. However, the present invention is not limited to this, and both may be adjusted. That is, in the glossy mode, the irradiation intensity of the first irradiation unit 41 may be weakened and the conveyance speed of the medium S may be increased as compared with the matte mode.

<Modification 3>
When the second irradiation unit 42 irradiates the clear ink with ultraviolet rays, part of the ultraviolet rays may pass through the clear ink and contribute to the curing of the main image which is the lower layer. Further, in the glossy mode, the curing energy of the main image is low in order to lower the irradiation energy of the ultraviolet rays that irradiate the main image compared to the matte mode. Therefore, in the glossy mode, the irradiation intensity of the second irradiation unit 42 may be increased as compared with the matte mode so that the main image is cured even when the clear ink is cured. By doing so, even when the main image before the clear ink is ejected is set to a semi-cured state in the glossy mode, the degree of cure of the main image can be increased by the second irradiation unit 42.

=== 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. The following embodiments may be used.

<About ink>
In the above embodiment, the case of using an ultraviolet curable ink (UV ink) is taken as an example, but the present invention is not limited to this. For example, the present invention can also be applied when using ink that is cured by irradiation with light such as visible light.

<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 photocurable ink onto the medium while the head moves in the moving direction and the operation of the transport unit transporting the medium in the transport direction are alternately repeated and arranged downstream of the head in the transport direction. A printer that cures the photocurable ink on the medium by the irradiated unit may be used.

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 1st irradiation part, 42 2nd irradiation part,
50 detector groups, 60 computers

Claims (5)

(A) a first ink for printing a main image, the first head discharging a main ink that is cured by light irradiation;
(B) a second head that ejects clear ink that is cured by the light irradiation;
(C) an irradiation unit for irradiating the light;
(D) After the main image is printed on the medium by the first head and the main image is irradiated with the light by the irradiation unit, the clear ink is ejected onto the main image by the second head. A controller that irradiates the clear ink with the light by the irradiator;
When the first mode is set, control is performed so that light of the first energy is emitted per unit area of the main image before the clear ink is ejected,
When the second mode in which an image having a higher gloss level than the image printed in the first mode is set is set, the unit area of the main image before the clear ink is ejected is A control unit that controls to emit light of second energy lower than the first energy;
A printing apparatus comprising (E). The printing apparatus according to claim 1,
The control unit weakens the irradiation intensity of the light that the irradiation unit irradiates the main image in the second mode, rather than the irradiation intensity of the light that the irradiation unit irradiates the main image in the first mode. To
Printing device. The printing apparatus according to claim 1 or 2, wherein
The irradiation unit irradiates the main image with the light while relatively moving in a predetermined direction with the medium on which the main image is printed,
The control unit increases the relative movement speed of the irradiation unit and the medium in the second mode than the relative movement speed of the irradiation unit and the medium in the first mode.
Printing device. The printing apparatus according to any one of claims 1 to 3, wherein
The second energy is 45% or more and 55% or less of the first energy.
Printing device. (A) printing a main image on the medium by discharging a main ink that is cured by light irradiation onto the medium;
(B) When the first mode is set, light of the first energy is irradiated per unit area of the main image printed on the medium;
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 first energy per unit area of the main image printed on the medium is set. Irradiating light of lower second energy,
(C) discharging a clear ink that is cured by the light irradiation on the main image irradiated with the light;
(D) irradiating the clear ink ejected on the main image with the light;
A printing method comprising (E).

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