Method for printing on a body by using inkjet printing

Abstract

A method for printing tracks on bodies by using inkjet printing provides printed images with a homogeneous appearance on the bodies, in particular when printing large single-color areas. The homogeneous appearance is obtained by reducing the intensity of the UV radiation from at least one inkjet print head when pinning in track connection regions.

Claims

1. A method for printing on a body by using inkjet printing, the method comprising the following steps: i) using at least one inkjet print head to print an image composed of at least two tracks on a body, each of the tracks having an inner core region and two outer edge regions, and the outer edge regions of adjacent tracks adjoining or partly overlapping one another; and ii) using a UV radiation source to irradiate the tracks produced in step i) with UV radiation, and reducing an intensity of the UV radiation from the inner core region to outer edges of the outer edge regions of the tracks produced in step i) during the irradiating.

2. The method according to claim 1, which further comprises using an ink to be cured by UV radiation when printing on the body by inkjet printing.

3. The method according to claim 1, which further comprises moving the body along a path under the at least one inkjet print head when using the at least one inkjet print head to produce the at least two tracks, and moving the UV radiation source to follow the path.

4. The method according to claim 1, which further comprises: only partially curing the tracks produced in step i) with the irradiation carried out in step ii); and iii) fully curing the partly cured tracks by irradiation with UV radiation following step ii).

5. The method according to claim 1, which further comprises carrying out the step of reducing the intensity of the UV radiation in step ii) by reducing the intensity of the UV radiation down to an intensity of zero from the inner core regions to the outer edges of the outer edge regions of the tracks produced in step i).

6. The method according to claim 1, which further comprises using an intensity of the UV radiation in a range between 0 and 5000 mW/cm.sup.2 over an entire width of the track when irradiating in step ii).

7. The method according to claim 1, which further comprises placing the at least two tracks produced in step i) parallel to one another.

8. The method according to claim 1, which further comprises providing a width of a track produced in step i) in a range between 0.5 and 10 cm.

9. The method according to claim 1, which further comprises providing a ratio of a width of the inner core region to a width of an outer edge region of a track in a range between 1:500 and 500:1.

10. The method according to claim 1, which further comprises obtaining the reduction in the intensity of the UV radiation from the inner core region to the outer edges of the outer edge regions of the irradiated tracks by at least one of: a) partially shielding the UV radiation source; b) partially shielding the body; c) changing a position of the body and the UV radiation source relative to one another; or d) controlling a local power of the UV radiation source.

11. The method according to claim 10, which further comprises partially shielding the UV radiation source by using a stop, partially shielding the body by using a stop, and changing the position of the body and the UV radiation source relative to one another by changing an angle of the body and the UV radiation source relative to one another.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIGS. 1-3 are top-plan views of paths, webs or tracks of an image printed on a body and having a core region and outer regions and being irradiated with UV radiation according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) Referring now in detail to the figures of the drawings and first, particularly, to FIG. 1 thereof, there is seen a diagrammatic illustration of two paths, webs or tracks 1, 2 of an image printed on a body and lying in parallel next to one another, directly adjoin one another and each have an inner core region 3 and two outer edge regions 4. A UV radiation source 5, which may have non-illustrated UV LEDs disposed next to one another, for example, is also illustrated. The first track 1 is produced by virtue of the body 8 being displaced from top to bottom (along the y-axis) under a stationary inkjet print head 7 in a first step and the track produced in this manner then being cured (pinning) with UV radiation by using the UV radiation source 5 in a second step. In this case, the UV radiation source 5 follows the trajectory of the track and therefore, i.e., it is likewise displaced from top to bottom (along the y-axis, as symbolized by the arrow on the UV radiation source). Subsequently, the second track 2 is produced in the same way and cured by irradiation with the UV radiation source 5.

(3) FIG. 2 shows the two tracks 1, 2 of FIG. 1, lying in parallel next to one another, with the spatial directions x and y and, additionally in schematic fashion, a local distribution of the applied UV radiation intensity, which can also be referred to as UV power, on both tracks 1, 2 (shown by lines with dots having an increasing UV radiation intensity in the y-direction). In the inner core regions 3 of the tracks 1, 2, the UV radiation intensity is virtually constant and at a maximum level over the entire width of the respective inner core region. In the outer edge regions 4, the UV radiation intensity reduces from the high level of the inner core region 3 down to a UV radiation intensity of zero at the outer edges of the outer edge regions 4. The drop in the UV radiation intensity from the inner core region 3 to an outer edge of an outer edge region 4 is also referred to as a flank 6.

(4) FIG. 3 shows a principle similar to that shown in FIG. 2, with the two tracks 1, 2 lying in parallel next to one another having a partly overlapping outer edge region 4a of their respective outer edge regions 4. Accordingly, there is also irradiation with the non-illustrated UV radiation source in such a way that the areas irradiated by UV radiation in the outer edge regions of the tracks partly overlap (as indicated by lines with dots).

LIST OF REFERENCE SIGNS

(5) 1 First track

(6) 2 Second track

(7) 3 Inner core region

(8) 4 Outer edge region

(9) 4a Overlapping outer edge regions

(10) 5 UV radiation source

(11) 6 Drop in the curve of the UV radiation intensity (flank)

(12) 7 Inkjet print head

(13) 8 Body

(14) x Spatial direction x

(15) y Spatial direction y