METHOD OF PRINTING WITH GLOSS CONTROL
A method of printing a color surface of an object by printing dots of curable ink in several superposed layers includes defining a micro-texture, the micro-texture being a repetitive pattern of elevated parts and depressed parts; establishing a gloss function that indicates a gloss value of a surface having the micro-texture, as a function of a height difference between a maximum height of the elevated parts and a minimum height of the depressed parts of the micro-texture; assigning a target gloss value to at least a part of a surface area of the object; determining, on the basis of the gloss function, a required local height difference corresponding to the target gloss value; and forming, on the at least a part of a surface area of the object, the micro-texture with a height profile scaled to the required local height difference.
1 . A method of printing a color surface of an object by printing dots of curable ink in several superposed layers, the method comprising the steps of:
defining a micro-texture, the micro-texture being a repetitive pattern of elevated parts and depressed parts;
establishing a gloss function that indicates a gloss value of a surface having said micro-texture, as a function of a height difference between a maximum height of the elevated parts and a minimum height of the depressed parts of the micro-texture;
assigning a target gloss value to at least a part of a surface area of the object;
determining, on the basis of the gloss function, a required local height difference corresponding to the target gloss value; and
forming, on said at least a part of the surface area of the object, the micro-texture with a height profile scaled to the required local height difference.
2 . The method according to claim 1 , wherein the elevated parts take the form of pillars that have a uniform height and a uniform cross-sectional shape over an entire height of the pillars thereof, and the depressed parts take the form of gaps between the pillars.
3 . The method according to claim 1 , wherein the elevated parts have a size in a range from p to 350 μm, when p is a size of a single pixel that is printable in a print process in which the object is formed.
4 . The method according to claim 2 , wherein the elevated parts take the form of square pillars with a size of 2×2 pixels.
5 . The method according to claim 1 , wherein the gloss function is established based on a gloss measurement of the micro-texture with various height differences.
6 . The method according to claim 1 , wherein a continuous color layer is formed on top of the micro-texture.
7 . The method according to claim 6 , wherein a composition of colorants constituting a color appearance of the color layer is incorporated in the gloss function.
8 . The method according to claim 7 , wherein a quadratic relation between a gloss value and colorant composition for a fixed height difference is applied in a multidimensional gloss function.
9 . The method according to claim 6 , wherein the height difference is modulated across the color surface to enhance a uniformity of a gloss appearance of a full color surface.
10 . A software product comprising program code on a machine-readable non-transitory medium, the program code, when loaded into a controller of a printer, causing the controller to perform the method according to claim 1 .