Method for producing printed products and printing machine for implementing the method

Abstract

A method for producing a printed product includes coating a preferably paper or cardboard substrate with a precoat or supplying a substrate that has been coated with a precoat, in which the precoat contains at least one acid, applying a water-based ink to image areas on the coated substrate by using at least one ink print head, and drying the printed substrate and/or the ink, preferably using IR radiation and/or heated air. The precoat includes a photobase generator or a photobase generator is applied at least locally to non-image areas on the substrate, the substrate is irradiated at least locally in non-image areas, preferably using UV radiation, to locally generate a base, and the printed substrate is varnished with a water-based varnish.

Claims

1. A method for producing printed products, the method comprising the following steps: coating a substrate with a precoat containing at least one acid or supplying a substrate having been coated with a precoat containing at least one acid; using at least one ink print head to apply a water-based ink to image areas on the coated substrate; drying at least one of the printed substrate or the ink; providing a photobase generator in the precoat or applying a photobase generator at least locally to non-image areas on the substrate; irradiating the substrate at least locally in non-image areas to generate a base; and varnishing the printed substrate with a water-based varnish.

2. The method according to claim 1, which further comprises supplying the precoat already containing the photobase generator or separately supplying and mixing the precoat and the photobase generator.

3. The method according to claim 1, which further comprises selecting the photobase generator from the group of photobase generators consisting of: quaternary ammonium salts of organic acids or phenylglyoxylic acid, or oxo xanthan propionic acid, or O-acyloximes, amine-substituted ketones or 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and quaternary ammonium salts of dithiocarbamate.

4. The method according to claim 1, which further comprises carrying out the irradiation step at least one of: in an ultraviolet wavelength range, by using at least one LED to create the radiation, or in a wavelength range below 400 nanometers.

5. The method according to claim 1, which further comprises carrying out the irradiation step before or immediately before the ink applying step.

6. The method according to claim 1, which further comprises carrying out the irradiation step before or immediately before the drying step.

7. The method according to claim 1, which further comprises carrying out the irradiation step before or immediately before the varnishing step.

8. The method according to claim 1, which further comprises carrying out the drying step as a thermal process by applying at least one of electromagnetic irradiation or heated air.

9. A printing machine for producing printed products, the printing machine comprising: a substrate feeder for supplying a substrate; a precoat application device disposed downstream of said substrate feeder for coating the substrate with a precoat containing at least one acid and for coating the substrate with a photobase generator at least locally in non-image areas of the substrate; at least one ink print head disposed downstream of said precoat application device for applying a water-based ink to image areas on the coated substrate; an emitter disposed downstream of said precoat application device for irradiating the substrate at least locally in non-image areas to generate a base; a drier disposed downstream of said precoat application device or downstream of said emitter for drying at least one of the printed substrate or the ink; and a varnishing unit disposed downstream of said emitter for varnishing the printed substrate with a water-based varnish.

10. A printing machine for producing printed products, the printing machine comprising: a substrate feeder for supplying a substrate; at least one application device disposed downstream of said substrate feeder for applying a precoat containing al least one acid and for separately applying a photobase generator at least locally to non-image areas on the substrate; at least one ink print head disposed downstream of said at least one application device for applying a water-based ink to image areas on the coated substrate; an emitter disposed downstream of said at least one application device for irradiating the substrate at least locally in non-image areas to generate a base; a drier disposed downstream of said at least one application device or downstream of said emitter for drying at least one of the printed substrate or the ink; and a varnishing unit disposed downstream of said emitter for varnishing the printed substrate with a water-based varnish.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a flow chart of a preferred exemplary embodiment of a method of the invention;

(2) FIG. 2 is a diagrammatic, longitudinal-sectional view of a preferred exemplary embodiment of a printing machine of the invention implementing the method of the invention; and

(3) FIG. 3 is a plan view of a printed product that has been created in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) Referring now in detail to the figures of the drawings, in which identical reference symbols identify mutually corresponding elements and merely repetitive symbols have partly been omitted for clarity, and first, particularly, to FIG. 1 thereof, there is seen a flow chart which represents a preferred embodiment of the method of the invention for producing a high-quality printed product, in particular a printed product that has been finished, i.e. varnished. The individual steps of the method will be listed and explained in more detail below. When reference is made to the printing machine of the invention for implementing the method or the components thereof used to carry out the steps, the reference symbols refer to FIG. 2.

(5) Step 10 (supplying the substrate): the substrate 1, which is preferably a sheet or web of paper or cardboard, is supplied for further steps. The sheet may be supplied in a sheet-feeder 21 (substrate feeder). Alternatively, there may be a web feeder.

(6) Step 11 (supplying the precoat containing an acid): a precoat 2 including at least one acid 3, i.e. an acid-containing precoat, is supplied for the further steps. The precoat may be supplied in an application device 26, e.g. by using a trough and a dipping roller.

(7) Step 12 (supplying a photobase generator): a photobase generator 4 is supplied for the further steps. The photobase generator may be supplied in a reservoir inside or outside the printing machine 20. It may be connected to the aforementioned precoat trough by a generator supply line. The dashed arrows are intended to imply that the generator may either be added to the precoat 2 and/or may be applied to the substrate 1. In a preferred process, the generator is added to the precoat, e.g. the precoat contains a photobase generator and the two are jointly applied by using a common application device. The generator may be applied to the substrate before, during, or after the application of the precoat. The photobase generator is applied at least locally to non-image areas on the substrate (see step 15 for a definition of non-image areas).

(8) Step 13 (coating the substrate or supplying a coated substrate): the supplied substrate 1 is preferably coated with the supplied precoat 2. The precoat is preferably applied as a liquid, in particular as an aqueous liquid. The application is preferably achieved by using an applicator roller (or a spraying device) of the application device 26, or alternatively by using a drop-on-demand device comparable to a print head. Alternatively, a substrate 1 that has previously been coated with a precoat 2 may be provided, that is to say that steps 10, 11 and 13 may be combined. In any case, a substrate including the precoat, preferably in the form of a coating on the substrate side to be printed on, is available for the subsequent steps. Optionally, the precoat and/or the substrate are dried, preferably in a drier 25a, in particular a thermal drier such as an IR drier and/or a hot-air drier.

(9) Steps 14a, 14b and 14c (irradiating and generating a base): afterwards the substrate 1 is locally irradiated at least in non-image locations 6 shown in FIG. 3. Thus, a base 4 is generated by using the photobase generator 4 in a photochemical or photolytical process. Global irradiation, i.e. an irradiation of the entire surface, is possible, but not preferred. The base acts to neutralize the acid 3 in the precoat 2. This advantageously prevents non-neutralized acid from having any undesirable effects on the glossiness of a printed product 8. The irradiation is preferably achieved by using an emitter 27, in particular an emitter including LEDs or alternatively a blower 27, and its radiation or alternatively heated air 27. The irradiation may be implemented in accordance with step 14a, step 14b, or step 14c. In accordance with step 14a, the irradiation may occur before a printing operation (15) (see below), in particular immediately before the printing operation. In accordance with step 14b, the irradiation may occur before a drying operation 16 (see below), in particular immediately before the drying operation. In accordance with step 14c, the irradiation may occur before a varnishing operation, in particular immediately before the varnishing operation. In accordance with a particularly preferred aspect, the irradiation occurs after the drying operation 16 and before the varnishing operation 17. In addition, two or three irradiation steps are possible, i.e. in accordance with steps 14a, 14b and 14c. The irradiation preferably occurs in a UV wavelength range, in particular with radiation that is created by at least one LED 27, and/or in a wavelength range below 400 nanometers.

(10) Step 15 (printing on the substrate): a water-based ink 23 is now applied to image areas 5 on the precoated substrate 2 by using at least one ink print head 23 (see FIG. 3). Image data are supplied to the print head for this purpose. Areas on the substrate that do not receive any ink are referred to as non-image areas. The precoat 2 is covered with ink in image areas 5. The precoat 2 is not covered by ink in non-image areas 6, i.e. the precoat (and any photobase generator 4 contained therein) is exposed.

(11) Step 16 (drying the substrate and/or the ink): the printed substrate 2 and/or the ink 23 on the substrate are dried. The drying operation preferably takes place in a drier 25b and/or 25c, in particular a thermal drier such as an IR drier and/or a hot-air drier. In the drying process, water is evaporated from the ink and/or from the substrate and, if necessary, actively removed, e.g. by suction.

(12) Step 17 (varnishing the substrate and/or the ink): the printed substrate 1 is now varnished with a water-based varnish 7. The application of varnish is preferably carried out in a varnishing unit 28, in particular using an applicator roller or a spraying device or, alternatively, a drop-on-demand device comparable to a print head. The varnish may be applied in accordance with a varnish image or across the entire surface. In accordance with a preferred process, at least the image areas are varnished.

(13) Step 18 (drying the substrate and/or the ink and/or the varnish): the varnish 7 and/or the printed substrate 1 are now dried. The drying process preferably takes place in a drier 25d, in particular a thermal drier such as an IR drier and/or a hot-air drier. The dried printed products 8 may finally be delivered to a stack in a sheet delivery 24 and/or subjected to further processing steps such as cutting or folding. A web-shaped substrate may then be wound up or cut in a transverse direction and deposited.

(14) FIG. 2 illustrates a preferred exemplary embodiment of a printing machine 20 of the invention for carrying out the method illustrated in FIG. 1. The machine and thus the method of the invention carried out thereon are controlled by a computer 30 or rather a program running thereon.

(15) The printing machine 20 includes the substrate feeder 21, preferably a sheet feeder 21, the at least one ink print head 23, and the at least one drier 25a, 25b, 25c and/or 25d, in particular a thermal drier, e.g. an IR drier and/or a hot-air drier. The print head (preferably seven print heads or print head rows for the colors K, CMY and OGV) may be disposed in a printing unit 22.

(16) The printing machine 20 further includes the application device 26 for the precoat 2, the at least one emitter 27 for generating the base 4 in a photolytic process, and the varnishing unit 28.

(17) The photobase generator 4 may be supplied in accordance with an option A shown in FIG. 2. In accordance with this option, the generator has previously been added to the precoat 2 and applied to the substrate 1 together with the latter. Alternatively (in accordance with an illustrated option B), the generator and the precoat may be mixed in a mixer 29 before being applied to the substrate. In accordance with a further alternative (as illustrated in option C), the generator and the precoat may be separately applied to the substrate, e.g. sprayed on.

(18) FIG. 3 is a diagrammatic view of the printed product 8 that has been created in accordance with the invention, including a precoat 2 applied to a substrate, with the precoat 2 containing an acid 3, as well as image areas 5 and non-image areas 6 located on the substrate. Both image areas and non-image areas have been varnished, i.e. covered with a water-based varnish 7. In the illustrated example, the photobase generator 4 has been applied together with the precoat, i.e. it is present in the same location. Depending on the irradiation, the base 4 is present at least in the non-image areas.