EP3960462A1 - Matting by means of a tranfer process - Google Patents

Abstract

Method for applying a matting fluid layer (9) to a printing substrate (6) via a printing form (3), the matting fluid layer (9) being dried on the printing form (3) before application to the printing substrate (6), which is characterized is that the degree of dullness of the applied fluid layer (9) is modified via parameters of the drying process and the nature of the surface of the printing form (3).

Description

The present invention discloses a method for applying a thin matting fluid layer to a printing substrate via a printing form with targeted mattness control.

The invention lies in the technical field of printing, in particular packaging and commercial printing.

When printing using the film transfer process, certain phenomena occur, in particular matting of gloss coatings that occurs during film transfer. The matting of the gloss coatings is independent of the substrate used and, depending on the process parameters, can be different and vary in intensity.

In the prior art, matt lacquer coating with water-based lacquers, in particular in packaging and commercial printing, is carried out using two approaches. One variant is the addition of matting agents, i.e. additives that roughen the surface, for example, whereby on the one hand the printability, in the form of the viscosity of the coating, is changed and therefore has to be readjusted in each case, and on the other hand the volume addition of matting agent is limited and thus also the degree of matting.

A further variant is the use of printing forms, which achieve a matting of the varnish due to their surface structure/screening. In this case, the matting that can be achieved is dependent on the form and is partly subordinate to the manufacturing process of the printing form, so that the matting effect can only be set to a limited extent. However, particularly good matt coatings are subject to certain optical requirements, which can be achieved primarily through a defined surface roughness/matting.

However, mixing in fillers/additives, i.e. matting agents, changes the viscosity of the coating composition so that it has to be adjusted again for printing. Depending on the printing process, additional measures are also required such as the selection of a suitable anilox roller in terms of cell volume, cell type and size, or constant agitation of the coating to prevent the matting agent from settling.

The object of the present invention is therefore to find a method for specifically modifying the matting effect in various printing methods.

This object is achieved by a method for applying a matting fluid layer to a printing substrate via a printing form, the matting fluid layer being dried on the printing form before it is applied to the printing substrate, which is characterized in that the degree of mattness of the applied fluid layer has parameters of the drying process and the nature of the surface of the printing form is modified. Through the targeted combination of the two modification options of the drying parameters and the surface of the printing form, the desired degree of mattness can be set much more precisely than with previous methods.

Advantageous and therefore preferred developments of the method according to the invention result from the associated subclaims and from the description with the associated drawings.

In a preferred embodiment, the matting fluid layer is a lacquer or paint layer. In a particularly preferred embodiment, the matting fluid layer is a layer of dispersion paint. In a very particularly preferred embodiment, the matting fluid layer is a dispersion paint layer of a gloss paint.

A further preferred development of the method according to the invention is that the parameters of the drying process include the drying performance by supplying hot air. The drying performance is the most important parameter. This is preferably realized and quantified by supplying hot air.

A further preferred development of the method according to the invention is that the applied fluid layer is dried on the printing form by applying heat and a final drying of the fluid film after the transfer to the printing substrate without further heat input takes place. Due to the partial drying already carried out before transfer to the print substrate, no further active heat source is necessary for the remaining final drying after transfer.

A further preferred development of the method according to the invention is that the nature of the surface of the printing form is modified by a variable roughness and/or a full-area or spot-like shape of the surface and/or the selection of the material of the printing form. Which variant is chosen depends on the desired texture. A combination of the three variants increases the accuracy of the desired degree of mattness.

A further preferred development of the method according to the invention is that, in order to control the parameters of the drying process and the nature of the surface of the printing form, a control strip made of different microstructures, which in printed form provide information about the current process and the print quality that can be achieved, is integrated into the printing form . This control strip then also releases a “printed image” of fluid onto the print substrate and can be evaluated analogously to a color control strip.

A further preferred development of the method according to the invention is that the matting fluid layer is applied to the printing form by a paint metering unit, in particular an anilox roller, or a digital printing system, in particular an inkjet print head. The distinction is not synonymous with the use of a corresponding printing press. It is entirely possible, although not always advantageous, to use an inkjet metering unit for applying the fluid in an offset printing machine and vice versa to use a lacquer metering unit with anilox roller in an inkjet printing machine.

The invention as such and constructively and/or functionally advantageous developments of the invention are described in more detail below with reference to the associated drawings using at least one preferred exemplary embodiment. In the drawings, corresponding elements are given the same reference numbers.

Figur 1:

den schematischen Aufbau bei Auftragung des Fluids mittels einer Rasterwalze

Figur 2:

den schematischen Aufbau bei Auftragung des Fluids mittels einer Inkjet-Einheit

Figur 3:

den Ablauf des erfindungsgemäßen Verfahrens

The drawings show:

Figure 1:

the schematic structure when the fluid is applied by means of an anilox roller

Figure 2:

the schematic structure when applying the fluid using an inkjet unit

Figure 3:

the course of the method according to the invention

figure 3 shows the sequence of the method according to the invention schematically. In a first step, the fluid 9, usually varnish or paint, is metered onto a printing form 3, which can be implemented over the entire surface or in spots, with the metering being able to take place conventionally or digitally. The fluid 9 applied to the printing form 3 is dried before it is transferred to the substrate 6 by applying heat. The resulting fluid film 9 is then transferred to the substrate 6 in an already solidified state.

The achievable mattness of the applied layer of varnish can be influenced or adjusted in the printing process using two parameters. On the one hand, the achievable mattness can be adjusted by the degree of drying before film transfer, i.e. by the selection of the drying parameters. On the other hand, the dullness of the lacquer layer can be further influenced by using a printing form 3, which is designed either over the entire surface or in a spot-like manner, with a rough surface. Due to the rough surface, the fluid film 9 is conditioned during drying in such a way that a matting effect occurs on the printed product 10. The manipulated variables mentioned can also be combined in any way.

A control strip, similar to the print control strip, is integrated on the printing form 3 in order to continuously check the process with regard to the achievable quality of the matt effect and to coordinate the process parameters. This is composed of different microstructures that provide information about the current process and the achievable print quality in printed form. The production of a printing form 3 with microstructures, which serve as a control element in the matting process, can be carried out on printing forms 3 known from the prior art, such as those in DE 10 2014 222 677 A1 described printing form 3, are based.

• Phase 1: Fluid 9 wird auf eine Druckform 3 dosiert, z.B. mittels einer Rasterwalze 1 wie im Flexodruck
• Phase 2: Das aufgetragene Fluid 9 wird auf der Druckform 3 durch einen Wärmeeintrag, bevorzugt Heißluftzufuhr über eine Trocknungsdüse, angetrocknet.
• Phase 3: Der angetrocknete Fluidfilm 9 wird auf das Substrat 6 übertragen

The process steps described can also be divided into three phases:

• Phase 1: Fluid 9 is metered onto a printing forme 3, for example by means of an anilox roller 1 as in flexographic printing
• Phase 2: The applied fluid 9 is dried on the printing forme 3 by applying heat, preferably supplying hot air via a drying nozzle.
• Phase 3: The dried fluid film 9 is transferred to the substrate 6

The final drying of the fluid film 9 on the substrate 6 preferably takes place without any further supply of energy. The printing form 3 consists of a suitable material, for example a silicone, and has a rough surface that has a direct influence on the degree of matting. In addition, a control element is integrated on the printing form 3, which is used for quality assurance. figure 1 shows schematically the structure of the system when the fluid 9 is applied by means of an anilox roller 1. Other components of the system include the inking unit 2, the drying unit 4, the drive for the web transport 5 of the printing substrate 6 and a cleaning unit 7.

The preferred application is graphic use as a finishing process in packaging and commercial printing, e.g. matt-gloss, frost effect, etc.

An alternative procedure relates to the use of another paint metering unit 11 instead of the anilox roller 1. In particular, the use of a digital printing system 11 such as an inkjet print head 11 for applying the fluid 9 is one possibility. That is, a transparent ink is used as a coating, which is transferred in its mattness to a carrier material, such as a graphic printing material 6 or a technical surface, via the transfer process described above with a textured transfer mold in conjunction with an intermediate thermal treatment. figure 2 shows the application of the fluid 9 using an inkjet unit 11.

• Die Erzeugung einer porösen Schicht, um die poröse Schicht z.B. als einen Absorber zu nutzen, der Feuchtigkeit in den Poren oberflächennah aufnehmen kann. Bei höherem Wärmeeintrag bilden sich hier im Lack z.T. Bläschen, die dadurch eine Porosität erzeugen.
• Auftrag einer mattierenden oder porösen Schicht auf ein Foliensubstrat, wobei die aufgetragene Schicht in Kombination mit einer transparenten Folie die Funktion eines optischen Diffusors ("Mattscheibe") realisieren kann.
• Technische Anwendung der mattierten Schicht auf transparente Substrate (z.B. Folien) für das sogenannte Light-Harvesting (Auftrag einer funktionalen Schicht) im Bereich der Optik, insbesondere der Fotovoltaik.

Further alternative embodiments relate in particular to alternative applications of such lacquer layers, such as:

• The creation of a porous layer in order to use the porous layer, for example, as an absorber that can absorb moisture in the pores near the surface. at When the heat input is higher, bubbles sometimes form in the paint, which creates porosity.
• Application of a matting or porous layer to a foil substrate, whereby the applied layer can realize the function of an optical diffuser ("matt screen") in combination with a transparent foil.
• Technical application of the matted layer on transparent substrates (e.g. foils) for so-called light harvesting (application of a functional layer) in the field of optics, in particular photovoltaics.

• Hybrid-Ansatz: Verwendung von Hybridlacken, um in einem ersten Schritt die Mattierung durch Verdunsten des wässrigen Anteils zu erzeugen und anschließend im UV-Härtungsprozess zu fixieren und einen Matt-Glanzeffekt einzustellen.

Alternative fluid/lacquer systems:

• Hybrid approach: Use of hybrid coatings to produce the matting in a first step by evaporating the aqueous component and then fix it in the UV curing process and set a matt-gloss effect.

• Bogendruckmaschinen
• Rollendruckmaschinen
• Beschichtungsmaschinen

Options for use in a machine primarily concern:

• sheetfed presses
• web presses
• coating machines

The method according to the invention for applying a thin matting fluid layer 9 to a substrate 6, wherein the transfer of fluid in the context of the method means the transfer of an already solidified fluid to the substrate 6, has various advantages. It is particularly stable when applying thin layers, as less drying power is required. It is even no longer necessary to introduce any additional energy within the printing press if a combination with printing forms 3 is used for the matting effect.

The invention makes it possible to apply particularly thin layers, over the entire surface or as a spot surface, and to achieve targeted matting without the addition of matting additives or fillers. The process is implemented by metering a fluid film 9 onto a printing forme 3, drying it in a second step on the printing forme 3 by a drying unit 4 using a defined heat input, and transferring it to a substrate 6 in a third step. The degree of matting is determined by two independent process parameters, the drying performance and the design of the printing form. adjustable. If the matting 10 is primarily implemented via the printing form 3, it is also possible to implement different matting effects 10, possibly executed spotwise, over the sheet surface.

Opposite of DE 10 2014 222 677 it is not a classic/exclusive molding process of the surface of the printing form 3, but a more general transfer printing with modification, in particular by the (thermal) parameters of the drying process, which lead to a matting effect on the paint change. Of course, the rough surface texture of the printing form 3 also affects the matting 10, but the surface texture affects it only indirectly.

Reference sign

1

dosing unit

2

inking unit

3

printing form

4

drying unit

5

Drive for rail transport

6

print substrate

7

cleaning unit

8th

anilox roller

9

Fluid

10

Matted print product

11

digital dosing unit (Inkj et)

Claims (9)

Method for applying a matting fluid layer (9) to a printing substrate (6) via a printing form (3), the matting fluid layer (9) being dried on the printing form (3) before being applied to the printing substrate (6),
characterized,
that the degree of dullness of the applied fluid layer (9) is modified via parameters of the drying process and the nature of the surface of the printing form (3). Method according to claim 1,
characterized,
that the matting fluid layer (9) is a varnish or paint layer. Method according to one of the preceding claims,
characterized,
that the matting fluid layer (9) is a dispersion paint layer. Method according to one of the preceding claims,
characterized,
that the matting fluid layer (9) is a dispersion paint layer of a gloss paint. Method according to one of the preceding claims,
characterized,
that the parameters of the drying process include the drying performance by supplying hot air. Method according to one of the preceding claims,
characterized,
that the applied fluid layer (9) on the printing form (3) is dried by applying heat and final drying of the fluid film (9) after transfer to the printing substrate (6) takes place without further heat input. Method according to one of the preceding claims,
characterized,
that the nature of the surface of the printing form (3) is modified by a variable roughness and/or a full-area or spot-like shape of the surface and/or the selection of the material of the printing form (3). Method according to one of the preceding claims,
characterized,
that in order to control the parameters of the drying process and the nature of the surface of the printing form (3), a control strip made of different microstructures is integrated into the printing form (3), which in printed form provides information about the current process and the achievable print quality. Method according to one of the preceding claims,
characterized,
that the matting fluid layer (9) is applied to the print substrate (6) by a paint metering unit (1, 11), in particular an anilox roller (1), or a digital printing system (11), in particular an inkjet print head (11).

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