Inkjet printing method for decorative images
An inkjet printing method, performed by an industrial inkjet system to form a decoration layer, includes the steps of printing copies of a decorative image with a printing unit on a substrate by transmitting consecutive bitmap rows of the decorative image to a printing unit, measuring dimensional changes in the substrate while printing copies of the decorative image, and compensating the dimensional changes while printing copies of the decorative image by one of: skipping at least one bitmap row of the decorative image upon dimensional expansion, or reprinting at least one bitmap row of the decorative image on the substrate upon dimensional shrink.
1. A single pass inkjet printing method for forming a decoration layer, the method comprising the steps of:
printing copies of a decorative image with a printing unit on a web-shaped substrate by transmitting consecutive bitmap rows of the decorative image to the printing unit;
measuring dimensional changes in the web-shaped substrate while printing the copies of the decorative image; and
compensating for the dimensional changes while printing the copies of the decorative image by:
reprinting at least one of the bitmap rows of the decorative image on the web-shaped substrate.
2. The method according to claim 1 , wherein the dimensional changes are measured in a printed copy of the decorative image or in a printed control strip on the web-shaped substrate.
3. The method according to claim 2 , further comprising the steps of:
image analyzing at least one of the bitmap rows of the decorative image and determining if the at least one of the bitmap rows is reprintable; and
selecting at least one of the bitmap rows of the decorative image to compensate for the dimensional changes depending on a determination whether the at least one of the bitmap rows is reprintable.
4. The method according to claim 3 , wherein the dimensional changes are measured after the printing step and after:
drying the web-shaped substrate with a dryer;
cutting the web-shaped substrate with a cutter;
priming the web-shaped substrate with a liquid; or
impregnating the web-shaped substrate with a liquid.
5. The method according to claim 4 , wherein the web-shaped substrate is a paper substrate and the dimensional changes are measured after impregnating the paper substrate with a thermosetting resin.
6. The method according to claim 5 , wherein the thermosetting resin includes a melamine-formaldehyde based resin, ureum-formaldehyde based resin, and/or phenol-formaldehyde based resin.
7. The method according to claim 6 , wherein the decorative image represents a wood pattern, and wood grains in the wood pattern are oriented perpendicular or substantially perpendicular to the bitmap rows of the decorative image.
8. The method according to claim 7 , wherein a nominal row print distance between two consecutive transmitted bitmap rows is less than 45 μm.
9. The method according to claim 8 , wherein the printing of the copies of the decorative image is performed at a speed between 35 m/min and 450 m/min with a horizontal and vertical resolution between 300 dots-per-inch and 2400 dots-per-inch.
10. The method according to claim 3 , further comprising step of:
halftoning consecutive transmitted bitmap rows while printing; wherein
the halftoning includes dithering or an amplitude modulated halftoning method or a frequency modulated halftoning method.
11. The method according to claim 10 , further comprising, prior to the halftoning step, the step of:
compensating for ink volume differences between nozzles of the printing unit for the consecutive transmitted bitmap rows.