METHODS FOR IMPROVING IMAGE ADHESION TO SUBSTRATE USING INKJET PRINTING

Abstract

Provided herein is a method for digitally printing an image on a substrate in the form of a film attached to the surface of the substrate, such that the film is characterized by improved adhesion and fastness properties also in regions of sparse printing, the method includes digitally printing the image using colored ink composition(s) that comprises a particulate colorant and a binder, and digitally printing selectively a transparent colorless ink composition that includes a binder on regions of impaired adhesion of the image due to sparse printing, such that all parts of the image receive sufficient binding reagents according to a pre-determined threshold.

Claims

1. A method for inkjet printing an image on a surface of a substrate, comprising digitally printing the image on at least a portion of the surface using at least one colored ink composition that comprises a particulate colorant and a binder, and digitally printing a transparent colorless ink composition on at least a portion of the image, wherein: said transparent colorless ink composition is essentially devoid of a colorant and comprises a binder; said digitally printing said transparent colorless ink composition is effected on at least one region of impaired adhesion of the image that comprises at least one region of sparse printing, said region of sparse printing is characterized by receiving a total amount of said at least one colored ink composition lower than a threshold; said threshold is a minimal or optimal amount of said at least one colored ink composition that is sufficient for passing a fastness test; and a total of said regions of impaired adhesion is equal or larger than a total of said regions of sparse printing, and overlap less than 100% of the image.

2. (canceled)

3. The method of claim 1, wherein said threshold is determined experimentally.

4. The method of claim 1, wherein a printing resolution of said at least one colored ink composition is equal to a printing resolution of said transparent colorless ink composition.

5. The method of claim 1, wherein a printing resolution of said at least one colored ink composition is different than a printing resolution of said transparent colorless ink composition.

6. The method of claim 5, wherein said printing resolution of said transparent colorless ink composition is lower than said printing resolution of said at least one colored ink composition.

7. The method of claim 1, wherein said at least one region of impaired adhesion and said at least one region of sparse printing are co-extensive.

8. The method of claim 1, wherein said at least one region of impaired adhesion is larger than said at least one region of sparse printing.

9. The method of claim 1, wherein said digitally printing said transparent colorless ink composition is effected while the surface is still wet with said at least one colored ink composition and/or said digitally printing said at least one colored ink composition is effected while the surface is still wet with said transparent colorless ink composition.

10. The method of claim 1, further comprising, subsequent to said digitally printing, curing said image.

11. The method of claim 1, further comprising, prior to inkjet printing the image, digitally analyzing a digital form of the image that comprises a position data and information of said total amount of said at least one colored ink composition per each pixel of the image, said analyzing is for identifying said at least one region of sparse printing and determining said regions of impaired adhesion and said minimal or optimal amount of said transparent colorless ink composition per pixel of the image, based on said threshold.

12. A method for identifying at least one region of sparse printing in an image, comprising analyzing a digital form of the image that comprises a position data and information of the total amount of at least one colored ink composition per each pixel of the image, and listing each of said pixels in which said total amount of said at least one colored ink composition is lower than a threshold.

13. The method of claim 12, wherein said threshold is determined experimentally by digitally printing said at least one colored ink composition on a substrate in a predetermined series of shapes, each shape in printed at a different percent ink coverage, curing said predetermined series of shapes on said substrate, subjecting said substrate to a fastness test, and identifying a minimal and/or optimal percent ink coverage, thereby determining said threshold.

14. A product produced by the method of claim 1, wherein the image is characterized by having at least one region of impaired adhesion, identified by a film afforded by curing said transparent colorless ink composition.

Description

EXAMPLES

[0095] Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non-limiting fashion.

Example 1

[0096] A proof of concept of some embodiments of the present invention was carried out by printing an image wherein the design uses a vintage effect. Typically the vintage effect is afforded by using a relatively low amount of white ink under-base such that the original colors seem a bit duller. A wash-fastness problem arises from the fact that the white under-base ink is not dense enough in some sections of the image, and the film in not attached well enough to the substrate and fails wash-fastness requirements.

[0097] This problem of low wash-fastness due to sparse printing is solved, according to some embodiments of the present invention, by an algorithm that alters the contents of the RIP (Raster Image Processor) information prior to printing. The goal of such algorithm is to ensure each pixel of the image receives enough binder to match or slightly exceed a threshold amount, defined as the minimal or optimal amount of binder needed to achieve a required wash-fastness.

[0098] Exemplary Algorithm:

[0099] For each printed pixel in the design (image), the exemplary algorithm, according to some embodiments of the present invention, calculates the amount of transparent and colorless ink composition (e.g., clear binder composition, also referred to herein as the n+1 ink) that needs to be added to each pixel of the image in order to comply with the threshold criteria as described hereinabove. The algorithm essentially adds to the RIP printing instructions for the n+1 ink and some margin pixel around the edges of the original image.

[0100] The algorithm includes:

[0101] a) using a digital form of the image that can be processed by a computer, such as the RIP information, calculating the total amount of ink (by weight or volume) for each pixel of the image, by adding together the amount of ink contributed by each of the colored inks that are to be used in the pixel, thereby obtaining value a.sub.p;

[0102] b) calculating the total amount of ink in a neighboring cluster (pixels surrounding the pixel in a matrix of a 33 or 55 or 77 etc., which may extend beyond the edge of the image), thereby obtaining value b (b=a.sub.m);

[0103] c) combining a.sub.p and b, thereby obtaining value c (a.sub.p+b=c);

[0104] d) multiplying t by the number of pixels in the matrix, thereby obtaining value T;

[0105] e) if c<T and a.sub.p<t, registering an amount of n+1 ink (hereinafter value i) to the pixel, such that ta.sub.p=i, updating a.sub.p to t (a.sub.p=t) in the RIP and refreshing (recalculating) b and c;

[0106] f) if c<T and a.sub.pt, registering i to the neighboring pixel in the matrix with the lowest a.sub.m that is not zero (a.sub.m>0), such that ta.sub.m=i, updating a.sub.m to t in the RIP and refreshing b and c;

[0107] g) if c<T and each of a.sub.mt, registering i to the neighboring pixel with a.sub.m=0 such that i=t, updating a.sub.m to tin the RIP and refreshing b and c; and

[0108] h) if cT stopping the algorithm and using the updated RIP to print the image.

[0109] The above exemplary algorithm, according to some embodiments of the present invention, practically adds a margin of a few pixels to the original image, depending on the size of the matrix, such that a pixel that was on the edge of the image now has at least one neighboring pixel, a margin pixel, which is printed colorless using only the n+1 ink.

[0110] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0111] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.