DE102021131754A1 - Process and device for printing containers - Google Patents

Abstract

Method for printing containers, wherein several layers are applied to an area of the container to be printed, with the steps: - pretreatment of the area to be printed, - application of a color print, in particular a color print layer, - application of a further layer of lacquer, characterized in that as a further Varnish layer a vacuum varnish (pre varnish) is applied.

Description

The present invention relates to a method for printing containers and in particular for printing containers with a color print (or a greyscale print or a black and white print or a solid print). It has long been known from the prior art to design containers, for example, with labels. Recently, there has also been a move towards printing containers directly. For this purpose it is common for several layers, including a colored printing layer, to be applied to the containers, which can be, for example, glass bottles, plastic bottles or cans.

These prints have to withstand different requirements. After printing, the containers are usually processed further, for example filled or provided with an outer packaging or also mechanically and/or chemically treated (e.g. pasteurized). Furthermore, such prints should also withstand subsequent transport of the containers. In some cases, there is the additional problem of printing on containers that are themselves transparent. In these cases, an additional layer of a uniform and, in particular, white color is often applied.

The WO 2008/064248 A2 describes plastic containers that are digitally printed. From the WO 2017/174262 A1 a method and a device for printing containers are known.

Another special print has elevations and/or recesses, which overall convey an overall haptic impression. From the US 10,752,538 B1 a three-dimensional imprint on a glass container is known.

The object of the present invention is therefore to improve the printing of containers. According to the invention, this is achieved by the subject matter of the independent patent claims. Advantageous embodiments and developments are the subject of the dependent claims.

In a method according to the invention for printing containers, a plurality of layers are applied and/or printed onto a region of the container to be printed. In this case, the container to be printed and in particular the area to be printed is preferably first pretreated. In a further and in particular subsequent process step, a color print (and/or a greyscale print and/or a full-tone print) and in particular at least one color print layer (or a grayscale print layer and/or a full-tone print) is applied at least to the pretreated area. In a further process step, at least one further lacquer layer is applied to the color print or applied outside of the color print layer.

According to the invention, a sub-printing varnish (pre-varnish) is applied as a further varnish layer.

The loading or the application of the layers of the container preferably takes place from the inside to the outside. The area of the surface of the container is particularly preferably an area of the outer surface. In particular, the surface is an area of a base body of the container, with this base body serving to receive at least a significant portion of a liquid to be filled.

The area to which the layers are applied is particularly preferably a curved surface and in particular a peripheral surface of the plastic container or the glass container. This surface preferably has a substantially constant curvature (however, it would also be conceivable for the curvature to vary over the circumference of the container).

In a preferred embodiment, the underprint varnish comprises a substance selected from a group of substances containing binders, monomers, photoinitiators, fillers and additives. The additives can be, for example, defoamers, leveling additives, thickeners, dispersing additives, matting agents and the like. Additives can also be used to prevent pigment leaching in pigmented paints. In addition or in addition, the underprint varnish can have a substance which is selected from a group of substances which contains inks, in particular UV inks, water-based inks and solvent-based inks and the like.

The properties of the underprint varnish are preferably similar to the properties of other system inks and varnishes. The underprint varnishes used are preferably optimized for optimum crosslinking behavior and/or overprintability. The paints used (such as varnish, protective paint) and inks are preferably designed according to the respective requirements such as pigmentation, physical resilience (scratch resistance, elasticity) or spreading behavior.

Depending on which printhead is used, the inks used can be somewhat thinner or thicker. The viscosity of the inks is preferably up to 40 mPas at 20° C. (the high-viscosity range begins from 40 to 400 mPas).

Jetting temperatures between 35 and 55 degrees are preferred for the prints. The underprint varnish is particularly preferably transparent.

The underprint varnish is preferably printed in black-and-white printing and/or full-tone printing. In some cases, however, grayscale printing is also possible.

In a further preferred method, the underprint varnish is not overly sensitive to UV light and/or pinning with LED lamps and is significantly softer in comparison to the varnish/protective varnish.

If the underprint varnish should be harder (for better resistance), it loses the property of being insensitive to pinning.

In a preferred method, a printing speed comprised between 200 and 1500 mm/s is used. In another preferred method, a print resolution of between 75 and 1440 dpi is used. The prints are particularly preferably applied using an inkjet method.

In a preferred method, the underprinting varnish is applied or printed on in several layers. In a preferred method, the underprinting varnish is applied in a total thickness (i.e. thickness of the at least one layer or total thickness in the case of a composite of several layers) which is greater than 0.1 μm, preferably greater than 0.5 μm and particularly preferably greater than 1.0 μm . In a further preferred method, the underprinting lacquer is applied with a total thickness of less than 20 mm, preferably less than 15 mm and particularly preferably less than 10 mm.

In a preferred method, the color print and/or the color print layer contains chromatic colors and/or CMYK colors and/or spot colors and/or white color. UV printing and/or digital printing is particularly preferred. In this case, the printing lacquer or the printing ink can have components which are selected from a group of components which contains pigments, binders, monomers, photoinitiators, fillers and/or additives.

In a further preferred method, the color print is applied or printed in several layers. The color print preferably has a thickness of between 0.5 μm and 200 μm.

In a further preferred method, the container is selected from a group of containers containing glass bottles, plastic bottles, in particular PET bottles, and cans. As mentioned above, these containers preferably have curved outer surfaces.

In a preferred method, a protective varnish is applied in addition to the underprint varnish, with this protective varnish preferably being applied on and/or over the underprint varnish. So it is possible that this protective paint is the outermost paint layer. It is possible that a protective lacquer layer is applied, but it would also be conceivable that several protective lacquer layers are applied. The protective lacquer layer is particularly preferably applied directly to the underprint lacquer layer. An underprint varnish is preferably applied where the protective varnish is normally applied (at the end, in the protective layer or during embossing). In a preferred method, the protective varnish is applied on top (and/or above the varnish layer and/or print layer) and the underprint varnish is applied below (and/or below the varnish layer and/or print layer).

The protective lacquer preferably has a thickness of between 1 μm and 500 μm. If an embossing protective lacquer is used, it can have a thickness that ranges up to 10 mm and is in particular between 1 mm and 10 mm.

The protective lacquer preferably has a substance which is selected from a group of substances which contains binders, monomers, photoinitiators, fillers and additives. The additives can be, for example, defoamers, leveling additives, thickeners, dispersing additives, matting agents and the like. Additives can also be used to prevent pigment leaching in pigmented paints.

Furthermore, the protective coating can have different degrees of hardness depending on the application.

The underprinting varnish is particularly preferably transparent to light in the visible range. The protective lacquer is particularly preferably essentially transparent to light in the visible range. However, it would also be conceivable for the underprint varnish to have a color cast, for example a yellowish or bluish color cast. In addition, the underprint varnish can also have coloring.

In a further preferred method, the pretreatment is a plasma treatment and/or a corona treatment and/or a flame treatment, with the flame treatment preferably being a flame treatment with silane. Due to the surface properties, the corresponding substrates, such as the surfaces or containers here, are preferably pretreated before printing. In the case of plastics, for example, plasma, corona or flame treatments can be used as pretreatment methods. Glass is preferably silanized and flamed, which means that the substrate can also be cleaned and/or pre-coatings from glass production can be removed. If the containers are cans, they can be pretreated with plasma or flame.

In a further preferred method, the containers are cleaned before the print is applied to their outer surface and in particular to the area to be printed.

In a further preferred method, a primer or adhesion promoter is applied to the container after the pretreatment. In order to achieve sufficient durability of the printed layers in an industrial process, such an adhesion promoter, also referred to as a primer, is applied to glass, for example.

The imprint is preferably carried out in a spraying process, it also being conceivable to imprint this primer using an inkjet print head. When using plastics, the use of a primer is rather unusual. The use of a primer is also conceivable for cans. This primer is particularly preferably an alcohol-based primer and in particular a primer that can be dried out by air and in particular by warm air.

The primer is preferably adapted to the substrate material and/or the ink used (ie, for example, to glass and an acrylic UV ink). With certain substrate qualities, however, it would also be possible to dispense with the primer.

In a preferred method, a further layer of underprinting lacquer is applied to the primer or the primer layer. This underprint lacquer layer is particularly preferably applied directly to the primer. In this preferred method, therefore, at least two layers of underprinting lacquer are used, and in particular at least two layers of underprinting lacquer, which are separated from one another by at least one further layer and preferably by a plurality of further layers.

The above-mentioned color layer is preferably arranged between the at least two layers of underprinting lacquer.

In a further preferred method, at least one layer is hardened and/or pinned after it has been applied. It is thus possible for initial curing to take place after each printing step or the application of a further layer, with UV light in particular being used for this purpose. Final curing is particularly preferably carried out after the last or outermost layer has been applied. More preferably, multiple layers and most preferably all layers are hardened and/or pinned after they have been applied.

After the outermost layer has been applied, the layered composite is preferably cured by irradiation, with a radiation source preferably being used which is selected from a group of radiation sources which contains light-emitting diodes (LED), UV lamps and mercury vapor lamps.

A haptically perceptible layer is particularly preferably applied and this haptically perceptible layer is preferably applied after the application of the color print layer and/or outside of the color print layer. It would also be conceivable to print the haptically perceptible layer or 3D structures in general without colors and/or without white color. However, a combination of an underprint varnish and a protective varnish is advantageously used.

In a further preferred method, the haptically perceptible layer contains at least one layer of an underprinting lacquer and preferably at least one protective lacquer layer arranged on this at least one layer of the underprinting lacquer.

If the product or the container is to have not only optical but also haptic features, these are preferably applied in one or more layers. A Xaar High Laydown Technology can be used for this purpose and/or a high-viscosity lacquer.

It is possible for several such layers to be applied one on top of the other. Thus, for example, between 2 and 100, preferably between 2 and 40 and particularly preferably between 4 and 16 thicker layers lying one on top of the other can be applied.

In a preferred method, such layers can be applied with a protective lacquer or varnish already present in the system. This protective lacquer preferably contains a substance which is selected from a group of substances containing binders, monomers, photoinitiators, fillers and additives.

This haptically perceptible layer (also referred to as embossing or 2.5D printing or 3D printing) preferably has 1-2 sublayers.

An inkjet printing system is preferably used to print the container.

A combination of at least two lacquers or at least two lacquer layers is preferably used for printing, with one of these lacquer layers preferably being an underprinting lacquer layer and the other lacquer layer preferably being a protective lacquer layer.

In addition, it is also possible to apply the haptic properties using colors (white, CMYK and special colors), in particular up to a certain layer thickness that depends on curing.

The protective lacquer mentioned above can be used to enable a special protection of the printed layers, for example during passage in a production line, during pasteurization or in use. This protective lacquer, also known as varnish, is particularly preferably digitally printed over all layers, at least in a last step. Such a protective lacquer is preferably used on rigid substrates. In the case of flexible substrates such as plastics, however, it is also possible and preferable to use a special flexible and/or softer protective lacquer.

The term digital printing refers to a group of printing processes in which the print image is transferred directly from a file or a data stream from a computer to a printing machine without using a static printing form. The most common methods are electrophotography, e.g. B. laser printing, and inkjet printing.

In a further preferred method, to produce the haptically perceptible layer, a plurality of underprinting lacquer layers and a plurality of protective layers are applied, which are preferably printed alternately on top of one another.

In a further preferred method, a monochromatic layer and in particular a white layer is applied in particular below the color printing layer. The layer preferably serves to prevent light from shining through the layers. In the case of containers that are transparent, semi-transparent or coloured, white is printed over the entire surface or partially and in particular as a base layer in this process in order to prevent the colors from showing through and at the same time to increase the contrast. Something else may apply if the colors should show through for design reasons. Attempts are made not to use this white color on white and/or light-colored containers, unless penetration resistance without white color is not guaranteed.

In a preferred method, the undercoat layer is used to even out uneven surfaces of substrates such as glass bottles. It is thus possible to apply this underprinted layer, for example, after the primer has been applied. This is particularly preferably a transparent and/or glossy underprint varnish.

A surface tension of the underprint layer particularly preferably remains unchanged, regardless of how often and to what extent the underprint lacquer layer is cured by means of UV. For example, the white or a white layer can be printed very homogeneously over it. Further process colors can also be applied to the underprint layer without any disadvantages due to the intermediate curing of the other colors.

The advantage of an underprint varnish layer or an underprint varnish compared to the protective varnish is that it is optimized for the printing underneath and its surface tension preferably does not change, regardless of the number and strength of the UV intermediate curings. This is usually not the case with a protective coating. Its application cannot guarantee homogeneous printing of other colors, for example a white layer on it.

With strong or frequent pinning, subsequent colors can sometimes only be printed in stripes, i.e. inhomogeneously. However, the underprint varnish cannot guarantee the required resistance of the color layers underneath, for which the protective varnish layer is optimized. For this reason, a protective lacquer layer is preferably applied in a last step.

In the context of the invention, it is therefore proposed, in order to optimize the process, the number of system components and/or the system performance, to use the underprinting varnish or an underprinting varnish layer not only after a primer application as a base layer, but also when applying the protective varnish layer and with a if necessary, embossing is carried out, especially if this is preferably applied in several layers. This is explained in more detail with reference to the figures.

In a further preferred method, the containers are transported along a predetermined transport path during the printing. In a further advantageous method, the containers are rotated with respect to their longitudinal axis during printing.

The present invention is further directed to a container which is provided with a multi-layer print, wherein an area to be printed on the outer surface of the container is pre-treated and a color printing layer (and/or a greyscale layer and/or a solid layer or the like) is attached to this pre-treated area. and at least one protective varnish layer is provided, the protective varnish layer being arranged outside the color printing layer.

According to the invention, a sub-printing layer is provided between the colored printing layer and the protective lacquer layer.

A layer applied outside of another layer is understood to mean that this layer is further to the outside in relation to the surface of the container to be printed.

The use of a negative pressure layer is therefore also proposed on the device side. The coating preferably has at least two vacuum layers, which are particularly preferably separated from one another by further layers.

In addition, there is also the option of printing two layers of underprinting varnish (in particular directly) one after the other if one underprinting varnish layer is not sufficient. After that, white and CMYK colors could be printed. A varnish could then be arranged as an embossing and protective varnish in combination with pre-varnish, whereby it is preferred here to print individual layers alternately.

In a preferred embodiment, the multilayer print has a primer layer arranged below the color print layer, a particularly monochromatic layer arranged below the color print layer and/or a haptically perceptible layer or layer composition arranged above the color print layer.

Since the protective varnish or a protective varnish layer is often applied in more than one layer and/or relatively thickly for better protection of the underlying print layers and/or for better flow on the underlying print layers, its application is particularly preferably combined with preferably one layer of the underprint varnish (however, two, three or more layers of underprint varnish could also be used). This combination brings about trouble-free flow and/or homogeneous application of the protective lacquer and thus preferably improves both the print quality and the durability of the print layers.

If the embossing is preferably made up of more than one layer, it is also advantageous to combine the two lacquers (protective lacquer layer and underprinting lacquer layer). Each layer of the underprint varnish preferably ensures a gap-free and homogeneous application of the subsequent protective varnish layer, which in turn ensures perfect durability of the entire structure. In this way, the desired thickness of the embossing can preferably be gradually built up.

The protective lacquer layer is preferably always applied last, since only this layer brings about the sufficient durability of the printed layers.

The present invention offers a number of advantages. In this way, a homogeneous and trouble-free application of color is possible after each layer of the underprint varnish and, in particular, independently of the previous pinning processes. Reliable protection by the protective coating at the end of the printing process is also advantageous.

Furthermore, an increase in performance can be achieved since the last protective layers and the embossing can be printed not only with one print head, but also with two in one direction of rotation (of the container). Four or six printheads could also be used.

In addition, it is preferable to use up the underprint varnish more quickly, since otherwise its properties can change in the system.

With the invention, the underprint varnish can be used up at least twice as fast or generally much faster. Typically, such paints only have a shelf life of 9 months and can break down/change/lose their properties due to constant heating in an ink supply system.

Furthermore, better crosslinking is preferably achieved through the independence of the pinning performance, since the underprinting varnish has better wetting properties and deviations in the surface tension are less critical. It can with higher pinning powers are pinned. In this way, the degree of crosslinking is increased.

Especially with the first layers, excellent crosslinking to the base substrate can be achieved, which improves adhesion and thus reduces the requirements for the pretreatment processes. As a result, simplification of the processes is possible. In addition, greater robustness can also be achieved and thus also increased industrial suitability of the system. Furthermore, an improvement in the print quality can be achieved, in particular through sharper edges and a more homogeneous application of ink.

In another method, a similar process flow is also possible for plastics with an embossing print with special, flexible lacquers. Corresponding processes can also be considered for cans with adapted paints and coatings. Flat substrates can also be treated in this way.

If another special high-viscosity varnish is to be used for embossing, it can also be combined with the protective varnish and underprint varnish. Its leveling can improve the underprint varnish. In addition, its protection can also be guaranteed by subsequent layers of a protective varnish.

• Darin zeigen:
  • 1 eine Darstellung eines Schichtaufbaus auf einem Behältnis gemäß dem Stand der Technik;
  • 2 einen weiteren Schichtaufbau nach dem Stand der Technik;
  • 3 einen erfindungsgemäßen Schichtaufbau.

Further advantages and embodiments result from the attached drawings:

• Show in it:
  • 1 a representation of a layer structure on a container according to the prior art;
  • 2 another layer structure according to the prior art;
  • 3 a layer structure according to the invention.

1 shows a prior art print coating. First of all, a substrate 10 is provided, which is in particular an area of a container that is to be coated. The reference number 12 denotes a flame treatment with silane or a silanization or generally a pretreatment. Reference number 14 designates a primer layer which is first applied to the pretreated substrate.

In a further process step, a white layer is applied here, which is intended to prevent transparency, particularly in the case of transparent containers. This white layer can in turn be composed of several layers arranged one on top of the other.

The color printing layer 20 is or is applied to this monochromatic or white layer. This color printing layer can also be composed of several layers arranged one on top of the other. A protective lacquer 22 (which can also be multi-layered) is or is applied to this color print layer and, if necessary, a so-called embossing, which can ensure a haptic surface.

2 shows a further illustration of a print coating according to the invention on containers. In addition to the layers mentioned above, an underprint lacquer layer is provided here, which is arranged below the white layer and preferably above the primer coating. In this embodiment, a protective lacquer layer 22 is arranged above the chromatic color layer, as well as an embossing or an embossing layer, which also consists of protective lacquer and in particular a multiplicity of protective lacquer layers.

3 illustrates a layer composition according to the invention. Here, too, an underprint lacquer layer is preferably provided between the primer 14 and the white coating 18 . In this configuration, a multiplicity of underprinting lacquer layers can be provided at this point.

The protective lacquer layer is also replaced in this embodiment according to the invention. At this point, for example, 2-3 layers of a protective lacquer can be replaced by (at least) one layer of an underprinting lacquer and (at least) one layer of a protective lacquer. However, it would also be conceivable to use multiple layers of underprinting lacquer and multiple layers of protective lacquer.

The embossing layer 24 is also replaced by a layer composition 34 within the scope of the invention. More specifically, two to n layers of a protective lacquer coating can be replaced by (at least) one layer of an underprinting lacquer (in the case of an odd number of protective lacquer layers and in addition to this underprinting lacquer layer (at least) a layer of conformal varnish (in the case of an even number of underprint varnish layers).

As reference number 36 illustrates, an alternating sequence of protective lacquer layers and underprinting lacquer layers can be provided here in the embossing.

The applicant reserves the right to claim all features disclosed in the application documents as essential to the invention, provided they are new compared to the prior art, either individually or in combination. It is also pointed out that the individual figures also describe features which can be advantageous in and of themselves. The person skilled in the art recognizes immediately that a specific feature described in a figure can also be advantageous without adopting further features from this figure. Furthermore, the person skilled in the art recognizes that advantages can also result from a combination of several features shown in individual figures or in different figures.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2008064248 A2 [0003]
• WO 2017174262 A1 [0003]
• US10752538B1 [0004]

Claims (15)

Method for printing containers (10), several layers being applied to an area of the container to be printed, with the steps: - pretreating the area to be printed, - applying a color print (12), in particular a color print layer (12), - applying a further lacquer layer (16), characterized in that a pre-varnish is applied as a further lacquer layer. procedure after claim 1 , characterized in that the underprint varnish has a substance which is selected from a group of substances which contains inks, in particular UV inks, water-based inks and solvent-based inks, binders, monomers, photoinitiators, fillers and additives and the like. procedure after claim 1 , characterized in that the container (10) is selected from a group of containers containing glass bottles, plastic bottles, glass bottles, cups and paper containers, in particular paper bottles and cans. Method according to at least one of the preceding claims, characterized in that a protective varnish (16) is applied in addition to the underprint varnish (14), this protective varnish preferably being applied to the underprint varnish. Method according to at least one of the preceding claims, characterized in that the pretreatment is a plasma treatment and/or a corona treatment and/or a flame treatment, the flame treatment preferably being a flame treatment with silane. Method according to at least one of the preceding claims, characterized in that a primer (22) is applied to the container after the pretreatment. Method according to the preceding claim, characterized in that a further layer of underprinting lacquer (24) is applied to the primer (22). Method according to at least one of the preceding claims, characterized in that at least one layer is hardened and/or pinned after it has been applied. Method according to at least one of the preceding claims, characterized in that after the attachment of the outermost layer of the layered composite is cured by irradiation, a radiation source preferably being used which is selected from a group of radiation sources which light-emitting diodes (LED), UV contains lamps and mercury lamps. Method according to at least one of the preceding claims, characterized in that after the application of the color print layer a haptically perceptible layer is applied (24). Method according to the preceding claim, characterized in that the haptically perceptible layer (24) contains at least one layer of an underprinting lacquer (34) and preferably at least one protective lacquer layer arranged on this layer of the underprinting lacquer. Method according to at least one of the preceding claims 9 - 10 , characterized in that the haptically perceptible layer has a plurality of underprinting lacquer layers and a plurality of protective layers, which are preferably alternately printed one on top of the other. Method according to at least one of the preceding claims 9 - 10 , characterized in that a monochromatic layer and in particular a white layer (18) is applied underneath the color printing layer. Container with a multi-layer print, wherein at least one area of the outer surface of the container (10) to be printed is pretreated and a color print layer (20) and at least one protective lacquer layer (22) are provided on this pretreated area, the protective lacquer layer outside the color print layer (20) is arranged, characterized in that at least one underprinting layer is provided between the color printing layer (20) and the protective lacquer layer (22). Container according to the preceding claim, characterized in that the multi-layer print comprises a primer layer (14) arranged below the color print layer (20), a single-color layer (18) arranged below the color print layer (20) and/or a layer above the color print layer (20). haptically perceptible layer or layer composition (24).

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