METHOD FOR MANUFACTURING PRINTED PRODUCTS

Abstract

A method for manufacturing printed products contains the steps of applying at least one colored and water-containing ink to image regions on a printing material in a drop-on-demand process. An essentially colorless and water-containing liquid is applied a) to non-image regions and/or b) to image regions that have only little ink in the drop-on-demand process. The printing material is dried. The printing material has a coating that contains at least one acid. After the application of ink and the application of a liquid, a water-containing further liquid, for instance a varnish, is applied both to image regions and to non-image regions of the printing material, and that the liquid and/or the further liquid contains at least one substance that at least partly neutralizes the acid. The undesired formation of waves and glossiness fluctuations between varnished image regions and varnished non-image regions may thus advantageously be avoided.

Claims

1. A method for manufacturing printed products, which comprises the steps of: applying at least one colored and water-containing ink to image regions on a printing material in a drop-on-demand process; applying a generally colorless and water-containing liquid to at least one of a) non-image regions or b) the image regions that have little of said ink in the drop-on-demand process; drying the printing material, the printing material having a coating containing at least one acid; and applying a water-containing further liquid both to the image regions and to the non-image regions of the printing material after performing the applying of the ink and the applying of the liquid, wherein at least one of the liquid or the further liquid containing at least one neutralizing substance for at least partly neutralizing the acid, the neutralizing substance being a salt of a further acid that is weaker than the acid of the coating.

2. The method according to claim 1, which further comprises using the salt of a carboxylic acid as the neutralizing substance.

3. The method according to claim 1, which further comprises using an alkali carbonate as the neutralizing substance.

4. The method according to claim 1, which further comprises creating the neutralizing substance in a form of a solution of an acidic polymer, the solution being at least partly neutralized.

5. The method according to claim 1, which further comprises providing the neutralizing substance in a form of a solution of an acidic, the solution at least being partly neutralized.

6. The method according to claim 1, wherein the liquid is a colorless and the ink is generally without any binding agent.

7. The method according to claim 1, wherein a concentration of the neutralizing substance corresponds to a defined concentration value and the defined concentration value is in dependence on a concentration of the acid in the coating.

8. The method according to claim 7, which further comprises selecting the defined concentration value in a way to achieve a complete neutralization of the acid.

9. The method according to claim 1, which further comprises performing the drying step by applying infrared (IR) radiation to the printing material and wherein the liquid contains an IR absorber as a second substance.

10. The method according to claim 1, wherein the liquid contains an optical whitener as a third substance.

11. The method according to claim 1, wherein in the case a) an average of an amount of the liquid applied per unit area calculated for the printing material corresponds to an average amount of the ink applied per unit area calculated for the printing material.

12. The method according to claim 1, wherein the further liquid is colorless.

13. The method according to claim 1, which further comprises creating the neutralizing substance in a form of a solution of an acidic polymer on a basis of acrylic aid or methacrylic acid, the solution at least being partly neutralized with NaOH or KOH.

14. The method according to claim 1, which further comprises providing the neutralizing substance in a form of a solution of an acidic being a polymeric dispersing agent contained in the ink, the solution at least partly neutralized with NaOH or KOH.

15. The method according to claim 1, wherein the liquid is a colorless, non-pigmented or colorant-free and the ink is without any binding agent.

16. The method according to claim 1, wherein the further liquid is a colorless and water-based varnish.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0030] The single FIGURE of the drawing is a flow chart of a preferred exemplary embodiment of a method of the invention as well as an illustration of device-related measures for implementing the method.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring now to the single FIGURE of the drawing in detail, there is schematically illustrated steps A to E and E′, respectively, of a preferred embodiment of the method of the invention in a flow chart. Next to every step, the FIGURE also schematically shows the respective device-related measures that may be taken and how the printed product may successively be produced.

[0032] Step A is to provide a printing material 10 having a surface 10′. The printing material may be a sheet or a web. The printing material may be made of paper, cardboard, or plastic. A coating 11 containing an acid 11a is applied to the printing material. The coating may for instance be applied by means of a roller 13. As an alternative to the illustrated step A, it may be envisaged that a printing material that already has an acidic coating is provided.

[0033] In step B, a water-based ink 21 is printed onto the printing material 10 or rather the surface 10′ thereof, i.e. an ink layer 21 is created. The image region may for instance represent a pattern, image, or text. To create the ink layer 21, ink drops 22 are transferred to the printing material, i.e. the surface thereof, in a contact-free way by means of a print head 23. In this process, the print head is controlled in a known way, making use of the print data required for the image. In general, this process requires a relative movement between the print head and the printing material to be generated. It is possible to apply more than one ink, e.g. four (CMYK) or more than four (CMYK plus spot color/s) inks. The ink may contain pigments or colorants to give it color.

[0034] In step C, a liquid 31 is applied to a non-image region 31 and/or a liquid layer 31 is created. The liquid contains at least one substance 31a for neutralizing the acid 11a. In addition, the liquid may contain a second substance 31b, preferably an IR absorber. In addition, the liquid may contain a third substance 31c, preferably an optical whitener. In the non-image regions of the surface 10′ of the printing material 10, the application of the liquid 31 and the neutralizing substance 31a contained therein neutralizes the acid 11a. The application of the liquid 31 is achieved by transferring liquid drops 32 to the surface of the printing material in a contact-free way by a further print head 33. The use of a print head makes it easy to control the amount of liquid that is applied.

[0035] In step D, a further liquid 41 is applied to the printing material 10, i.e. the surface 10′ thereof, and/or a further liquid layer 41 is created. The application may for instance be achieved by a roller 43. The further liquid may be a colorless or transparent water-based varnish. Such a layer of varnish may essentially cover the entire surface of the printing material, i.e. both the image regions 20 and the non-image regions 30. In accordance with the invention, the neutralized acid has no (chemical) effect or only a minor (chemical) effect on the varnish layer, which thus globally (over the entire printing material, i.e. in image regions and non-image regions) exhibits an essentially homogeneous glossiness.

[0036] In step E, the printing material 10 or rather the surface 10′ thereof and in particular the ink 21 and liquids 31 and 41 applied thereto are dried, preferably thermally. For this purpose, an IR radiation 52 may be generated and directed towards the printing material surface by an IR drier 53, e.g. an LED drier or an LED laser drier. This process may likewise require a relative movement between the drier and the printing material to be carried out. The intensity of the radiation may be controlled.

[0037] An alternative to step E is to carry out a drying step E′, which preferably occurs after step C and before step D. Another alternative is to carry out both drying steps E and E′.

[0038] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0039] 1 printed product [0040] 10 printing material [0041] 10′ surface [0042] 11 coating [0043] 11a acid [0044] 13 roller [0045] 20 image region [0046] 21 ink/ink layer [0047] 22 ink drops [0048] 23 print head [0049] 30 non-image region [0050] 31 liquid/liquid layer [0051] 31a neutralizing substance [0052] 31b second substance/IR absorber [0053] 31c third substance/optical whitener [0054] 32 drops of liquid [0055] 33 further print head [0056] 41 further liquids/further liquid layer/varnish layer [0057] 43 roller [0058] 52 IR radiation [0059] 53 IR drier [0060] A providing printing material with coating [0061] B applying ink [0062] C applying liquid [0063] C applying further liquid/varnish [0064] E, E′ IR drying