Printing method and printing device

1. A printing method that carries out an inkjet printing operation for a print surface of a medium as a print target, the printing method comprising use of:

a colored ink head as an inkjet head that discharges ink droplets of a colored ink of ultraviolet curing type;

a clear ink head as an inkjet head that discharges ink droplets of a UV clear ink of ultraviolet curing type having a clear color; and

an ultraviolet irradiator that emits ultraviolet light,

the printing method further comprising:

a color printing step of having the colored ink head discharge the ink droplets to at least a partial region on the print surface of the medium based on a print image as an image to be printed and having the ultraviolet irradiator emit ultraviolet light to the partial region to print the print image using the colored ink;

a non-colored region clear printing step of having the clear ink head discharge the ink droplets and having the ultraviolet irradiator emit ultraviolet light to apply the UV clear ink to a region at least including a non-colored region on the print surface of the medium, the non-colored region being a region in which the ink droplets are not discharged in the color printing step; and

an overcoat layer forming step that follows the non-colored region clear printing step, the overcoat layer forming step being a step of having the clear ink head discharge the ink droplets to a region covering at least the print image printed in the color printing step and having the ultraviolet irradiator emit ultraviolet light to the region to form an overcoat layer that covers the print image using the UV clear ink,

wherein in the non-colored region clear printing step, the ink droplets are discharged from the clear ink head based on a gray-scaled and gradation-inverted image of the print image.

2. The printing method as set forth in claim 1 , wherein

in the overcoat layer forming step, a region preconfigured to cover at least the print image is painted out with the UV clear ink.

3. The printing method as set forth in claim 1 , wherein the UV clear ink is cured matte in the non-colored region clear printing step, and the UV clear ink is cured glossy in the overcoat layer forming step.

4. The printing method as set forth in claim 1 , wherein the colored ink head and the clear ink head perform a main scan and a sub scan for the inkjet printing operation for the medium, the main scan being a scan in which the colored ink head and the clear ink head, while moving in a predetermined main scanning direction, discharge the ink droplets, the sub scan being a scan in which the colored ink head and the clear ink head move relative to the medium in a sub scanning direction orthogonal to the main scanning direction,

the main scan by the colored ink head in the color printing step and the main scan by the clear ink head in the non-colored region clear printing step proceed in parallel.

5. The printing method as set forth in claim 1 , wherein the medium is a plastic card.

6. A printing device that performs an inkjet printing operation using the printing method as set forth in claim 1 .

7. A printing method that carries out an inkjet printing operation for a print surface of a medium as a print target, the printing method comprising use of:

a colored ink head as an inkjet head that discharges ink droplets of a colored ink of ultraviolet curing type;

a clear ink head as an inkjet head that discharges ink droplets of a UV clear ink of ultraviolet curing type having a clear color; and

an ultraviolet irradiator that emits ultraviolet light,

the printing method further comprising:

a color printing step of having the colored ink head discharge the ink droplets to at least a partial region on the print surface of the medium based on a print image as an image to be printed and having the ultraviolet irradiator emit ultraviolet light to the partial region to print the print image using the colored ink;

a non-colored region clear printing step of having the clear ink head discharge the ink droplets and having the ultraviolet irradiator emit ultraviolet light to apply the UV clear ink to a region at least including a non-colored region on the print surface of the medium, the non-colored region being a region in which the ink droplets are not discharged in the color printing step; and

an overcoat layer forming step that follows the non-colored region clear printing step, the overcoat layer forming step being a step of having the clear ink head discharge the ink droplets to a region covering at least the print image printed in the color printing step and having the ultraviolet irradiator emit ultraviolet light to the region to form an overcoat layer that covers the print image using the UV clear ink;

the printing method further comprising a matte clear printing step subsequent to the non-colored region clear printing step, wherein

in the matte clear printing step, a region covering at least the print image printed in the color printing step is painted out with the UV clear ink, and the UV clear is cured matte, and

in the overcoat layer forming step, the overcoat layer is formed on the UV clear ink cured matte in the matte clear printing step.

8. The printing method as set forth in claim 7 , wherein

in the matte clear printing step, a first region that covers at least the print mage is painted out with the UV clear ink, and

in the overcoat layer forming step, a second region narrower than the first region and having an edge part located within the first region is painted out with the UV clear ink.

9. A printing method that carries out an inkjet printing operation for a print surface of a medium as a print target, the printing method comprising use of:

a colored ink head as an inkjet head that discharges ink droplets of a colored ink of ultraviolet curing type;

a clear ink head as an inkjet head that discharges ink droplets of a UV clear ink of ultraviolet curing type having a clear color;

a predetermined color ink head as an inkjet head that discharges ink droplets of a predetermined color ink of ultraviolet curing type having a predetermined color; and

an ultraviolet irradiator that emits ultraviolet light,

the printing method further comprising:

a predetermined color printing step of having the predetermined color ink head discharge the ink droplets to at least a partial region on the print surface of the medium and having the ultraviolet irradiator emit ultraviolet light to the partial region;

a color printing step of having the colored ink head discharge the ink droplets to at least a partial region on the print surface of the medium based on a print image as an image to be printed and having the ultraviolet irradiator emit ultraviolet light to the partial region to print the print image using the colored ink; and

an overcoat layer forming step of having the clear ink head discharge the ink droplets to a region covering at least the print image printed in the color printing step and having the ultraviolet irradiator emit ultraviolet light to the region to form an overcoat layer that covers the print image using the UV clear ink,

the predetermined color printing step further being a step of applying the predetermined color ink to a region at least including a non-colored region on the print surface of the medium, the non-colored region being a region in which the ink droplets are not discharged in the color printing step; wherein in the predetermined color printing step, the ink droplets are discharged from the predetermined color ink head based on a gray-scaled and gradation-inverted image of the print image.

10. The printing method as set forth in claim 9 , wherein the predetermined color ink is applied in the predetermined color printing step prior to the color printing step.

11. A printing device that performs an inkjet printing operation using the printing method as set forth in claim 9 .

12. The printing method as set forth in claim 10 , wherein the predetermined color ink is a white ink.