NL2016697B1

NL2016697B1 - Digital printing apparatus and process using liquid toner.

Info

Publication number: NL2016697B1
Application number: NL2016697A
Authority: NL
Inventors: Erik Dries Deprez Lode
Original assignee: Xeikon Mfg Nv
Priority date: 2016-04-29
Filing date: 2016-04-29
Publication date: 2017-11-20
Also published as: NL2016697A

Abstract

A digital printing process for xerography printing with liquid toner, said liquid toner comprising a curable carrier liquid and imaging particles suspended in the carrier liquid, wherein said process comprises: forming a latent image as a pattern of electric charge on a surface of a rotating imaging member; transferring the liquid toner onto a rotating development member; developing the latent image by transferring liquid toner from the development member onto the imaging member in accordance with the pattern; transferring the liquid toner from the imaging member to a substrate absorbing carrier liquid of the transferred liquid toner; and heating the liquid toner to at least a temperature at which the imaging particles form a polymer melt; and irradiating the substrate with particle beams to cure the carrier liquid of the transferred liquid toner.

Description

Digital printing apparatus and process using liquid toner

Field of Invention

The field of the invention relates to digital printing apparatus and processes using liquid toner comprising carrier liquid and imaging particles, and in particular to digital printing apparatus and processes for printing on substrates capable of absorbing carrier liquid.

Background

Prior art digital printing apparatus using liquid toner typically comprise an image forming unit with an imaging member adapted to sustain a pattern of electric charge forming a latent image on its surface, a development member arranged to receive liquid toner, and to develop said latent image by transferring a portion of said liquid toner onto the imaging member in accordance with said pattern. The liquid toner is then applied from the imaging member on the substrate, optionally via an intermediate member.

It is known to apply coatings on printed toner images to reduce the sensitivity to rubbing and/or to improve the gloss. However, such embodiments have the disadvantage that a separate coating unit is needed resulting in an increase of the cost of the printing process. US 8,931,412 discloses to fix an image film to the substrate by cross-linking the carrier liquid on the substrate using radiation. The toner particles are not melted, and the carrier liquid on top of the toner particles fixes the toner particles to the substrate. This process is meant for substrates that do not absorb carrier liquid. Further, using actinic radiation it will only be possible to cure a thin layer of carrier liquid on the surface of the substrate, and the process will not work well when the layer of carrier liquid is too thick or when the UV light absorption of the ink particles is too high.

Summary

The object of embodiments of the invention is to provide a digital printing process and apparatus with improved printing results for substrates which absorb carrier liquid, such as paper, paperboard, fibreboard, etc. used in the food packaging industry.

According to a first aspect there is provided a digital printing process for xerography printing with liquid toner. The liquid toner comprises a curable carrier liquid and imaging particles suspended in the carrier liquid. The process comprises the following steps: forming a latent image as a pattern of electric charge on a surface of a rotating imaging member; transferring the liquid toner onto a rotating development member; developing the latent image by transferring liquid toner from the development member onto the imaging member in accordance with the pattern; transferring the liquid toner from the imaging member to a substrate absorbing carrier liquid of the transferred liquid toner, and heating the transferred liquid toner to at least a temperature at which the imaging particles form a polymer melt toner; and irradiating the substrate with particle beams to cure or crosslink the carrier liquid of the transferred liquid toner.

By first heating the imaging particles of the transferred liquid toner, the imaging particles can form films on the substrate whilst additional carrier liquid (which was present between the imaging particles) is liberated during the heating and is absorbed into the substrate, in addition to the carrier liquid which was already absorbed immediately after the transfer of the liquid toner onto the substrate. The advantage of using particle beams is that the particle beams can penetrate over a certain depth in the substrate material, and hence can cure or crosslink the carrier liquid absorbed into the substrate. Further, using particle beams has the advantage that it is not necessary to include a photo-initiator in the carrier liquid, such that migration problems due to the presence of a photoinitiator or photo initiator fragments can be avoided.

Further, exemplary embodiments have the advantage that the resulting substrate, i.e. the substrate obtained after the curing or crosslinking step, only contains traces of single carrier liquid molecules. Especially for substrates used in the food packing industry this is beneficial in order to avoid food contamination with non crosslinked carrier liquid. Also, for recycling of the paper and/or packaging materials it is beneficial that the substrate material does not contain non crosslinked carrier liquid which could end up in recycled material (paper, paperboard, cardboard).

The step of heating the liquid toner to at least a temperature at which the imaging particles start to coalesce and form a polymer melt, is a so-called fusing step which is such that the imaging particles of the liquid toner form films on the substrate. At the glass transition temperature Tg, the solid imaging particles undergo a glass transition and change from an amorphous hard and rigid structure to a flexible structure in which the internal molecules of the imaging particles can move relative to each other. If the solid is continued to be heated above its glass transition temperature Tg, the imaging particles will eventually form a disordered polymer melt. As well as having imaging particles with an entirely amorphous structure, the imaging particles may have a semicrystalline structure comprising amorphous portions. If the imaging particles comprise such a semi-crystalline material, the glass transition temperature Tg will correspond to the point at which these amorphous portions undergo the glass transition.

In embodiments of the invention, the step of heating may be performed after or before the transferring of the liquid toner to the substrate.

In an exemplary embodiment the substrate and carrier liquid are selected such that more than 60% , more preferably 80% and even more preferably 95% of the transferred carrier liquid is absorbed in the substrate prior to the crosslinking action. The amount of carrier liquid that will be absorbed into the substrate will depend on the chemical nature of the carrier liquid and the type of substrate. The absorbing properties of the substrate will not only depend on the thickness and weight of the paper but also for example on the type and thickness of the coating, composition of the paper (for example type of sizing agents, paper fibres, etc.), production method of the paper , the speed of printing, the printing engine architecture, the amount of carrier removal means before the final transfer to the substrate, etc.

In an exemplary embodiment the substrate is provided as a continuous web during printing; and, during printing, the development member and the imaging member rotate continuously.

In an exemplary embodiment the curable carrier liquid is an electron beam-curable carrier liquid, and the irradiating step comprises irradiating the liquid toner with electron beams. The addition or use of nitrogen gas to increase the efficiency of the crosslinking can be provided.

In an exemplary embodiment the substrate comprises any one of the following: paper, paperboard (single- or multi-ply), fibreboard, and combinations thereof. The substrate may have a multilayer structure. Examples of applications comprise: food cartons or lids, chocolate and pastry boxes, pharmaceutical cartons, health and beauty cartons, etc. Preferably the substrate has a grammage (as defined in ISO standard 536) between 40-600 g/m2. Preferably, the substrate has a thickness between 40 micron and 1 mm. Embodiments of the invention are particularly useful for paperboard with a grammage above 200 g/m2 and a thickness above 0.1 mm.

In an exemplary embodiment the imaging particles are any one of the following: colour pigments, coated colour pigments, dyes and preferably toner particles with colour pigments.

In an exemplary embodiment the liquid toner is transferred from the imaging member to the substrate either directly or via an intermediate rotating member.

In an exemplary embodiment the carrier liquid comprises a curable dispersing agent, such that the curable dispersing agent is also cured during the irradiating step.

In an exemplary embodiment an amount of curable liquid is applied on the substrate after the heating and before curing to create a layer of curable liquid on top of the substrate in which carrier liquid is absorbed. The additional curable liquid is preferably such that it is not absorbed in the substrate or only to a limited extent absorbed in the substrate. The addition can be done for example by an anilox roller or by an inkjet head. An electrical bias can be applied during the addition of the curable liquid to avoid image disturbance. Indeed, by applying an electrical bias the imaging particles may remain fixed in their position on the substrate.

In an exemplary embodiment the step of heating may be preceded by a step consisting of modifying the dispersing agent in the transferred liquid toner transferred to reduce the dispersion capacity of the dispersing agent. Preferably, the imaging particles are below their glass transition temperature during this modification step. The concept of dispersion capacity modification is explained in more detail in European patent application EP14723901.6 in the name of the Applicant, which is included herein by reference.

According to a second aspect there is provided a digital printing apparatus for xerography printing with liquid toner. The liquid toner used in said printing apparatus comprises a curable carrier liquid and imaging particles suspended in the carrier liquid. The digital printing apparatus comprises an image forming unit, a second substrate application unit, a melting device and a curing unit. The image forming unit comprises a rotatable imaging member adapted to sustain a pattern of electric charge forming a latent image on its surface, and a rotatable development member arranged to receive liquid toner, and to develop said latent image by transferring said liquid toner onto said imaging member in accordance with said pattern. The image forming unit is further configured to transfer the liquid toner from the imaging member to a substrate. The melting device is configured to heat the liquid toner to at least a temperature at which the imaging particles form a polymer melt. The curing unit is configured to irradiate the transferred liquid toner with particle beams to cure the carrier liquid in the substrate, wherein the curing unit is arranged downstream of the image forming unit and the melting device such that the transferring and heating are performed before the curing.

In an exemplary embodiment the melting device is arranged between the image forming unit and the curing unit. However, in other embodiments the melting device may be integrated in the image forming unit such that the liquid toner is heated before transferring it to the substrate.

In an exemplary embodiment the apparatus further comprises a substrate feeding means configured to feed the substrate as a continuous web during printing, and a winding means configured for winding the resulting substrate with the cured liquid toner. Also, the development member and the imaging member are preferably configured to rotate continuously during printing. The substrate feeding means may comprise a spool reel with a substrate comprising any one of the following: paper, paperboard, fibreboard, and combinations thereof.

In a preferred embodiment the curing unit is an electron beam curing unit.

In an exemplary embodiment the apparatus further comprises a coating station for applying a curable liquid, e.g. a curable lacquer, on the substrate between the melting device and the curing unit to combine two actions in one: preventing migration of the carrier liquid and applying a very good crosslinkable curable liquid, e.g. a lacquer, on top of the substrate to protect the image against mechanical damage and increase the gloss and gamut of the printed material. The coating station may comprise for example an anilox roller and/or one or more inkjet heads. The applied curable liquid is preferably such that it is not absorbed in the substrate or only to a limited extent absorbed in the substrate.

In an exemplary embodiment the image forming unit is configured to transfer the liquid toner from the imaging member to the substrate either directly or via an intermediate member.

Brief description of the figures

The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present invention. The above and other advantages of the features and objects of the invention will become more apparent and the invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

Figure 1 is block diagram of an exemplary embodiment of a digital printing apparatus;

Figure 2 is block diagram of another exemplary embodiment of a digital printing apparatus;

Figures 3A and 3B illustrate schematically a cross section of a printed image before and after heating (fusing), respectively; and

Figure 4 is block diagram of another exemplary embodiment of a digital printing apparatus. Description of embodiments

In electrophotographic processes operating with liquid toner (also called liquid toner dispersion), imaging particles (also called marking particles) are supplied as solid particles suspended in a carrier liquid. In embodiments of the invention a curable carrier liquid is used. The imaging particles may be colour pigments, coated colour pigments, toner particles with colour pigments, dyes. Toner particles comprise pigment grains, typically embedded in a small bead of resin. A dispersing agent, also called dispersant is added to the mix to avoid clustering of the imaging particles. Dispersants deflocculate the imaging particles and reduce the viscosity of the liquid toner dispersion.

The curable carrier liquid in a liquid toner according to the present invention can be any suitable liquid having the desired conductivity and viscosity characteristics and capable of becoming cured to form a solid. The curable carrier liquid has typically a conductivity lower than 50 pS/cm, more preferably lower than 20 pS/cm and even more preferable lower than 5pS/cm. Further, the liquid carrier must be capable of permitting the imaging particles of the liquid toner to migrate through the carrier liquid to develop electrostatic latent images.

Typical carrier liquids suitable as the curable liquid vehicle include ethylenically unsaturated compounds, including monomers, dimers, or oligomers having one or more ethylenically unsaturated groups such as vinyl or allyl groups, and polymers having terminal or pendant ethylenic unsaturation. Examples of suitable curable liquids include, but are not limited to, acrylate and methacrylate monomers or polymers containing acrylic or methacrylic group(s). Also suitable are epoxy monomers or epoxy containing polymers having one or a plurality of epoxy functional groups. Further examples of suitable curable materials include vinyl ether monomers, oligomers, or polymers containing vinyl ether groups. Also suitable are internal or terminal alkenes and polyenes , fatty acid mono-, di-, tri- and polyesters based on unsaturated fatty acids and/or unsaturated alcohols and alkyl carbonates based on unsaturated alcohols. Depending on the functionality of the curable carrier liquid (number of double bounds) the bonding strength and flexibility of the print with cured carrier liquid can be adjusted.

Examples of curable carrier liquids are Ebecryl® and UceCoat® from Allnex, Radia®, Radiasolve®, Radiasurf® and Radiamuls® from Oleon and Alpha Olefins from Ineos Oligomers.

The carrier liquid may further contain variable amounts of charge control agent (CCA), wax, plasticizers, and other additives, although they also can be incorporated into the imaging particle itself. The carrier liquid may be volatile or non-volatile. Typically, the toner liquid may have a solid concentration between 5% and 60 wt%. The high-shear viscosity , as measured at a shear rate of 3000 s-1 at 25°C with a cone plate geometry of C60/10 and a gap of 52 pm, is preferably in the range of 5-500 mPa»s.

Figure 1 illustrates schematically an exemplary embodiment of a digital printing apparatus using liquid toner. The apparatus comprises a first image forming unit 100a for applying liquid toner Ta having a first colour, e.g. black, onto a substrate S, a second image forming unit 100b for applying liquid toner Tb having a second colour, e.g. cyan, onto the substrate S, a third image forming unit 100c for applying liquid toner Tc having a third colour, e.g. magenta, onto the substrate S, and a fourth image forming unit lOOd for applying liquid toner Td having a fourth colour, e.g. yellow, onto the substrate S.

The first image forming unit 100a comprises a toner reservoir 110a, a feed member 120a, a first development member 130a, a first imaging member 140a, and an optional intermediate member 150a. The first imaging member 140a is adapted to sustain a first pattern of electric charge forming a first latent image on its surface. The first development member 130a is arranged to receive first liquid toner Ta from the feed member 120a, and to develop said first latent image by transferring a portion of said first liquid toner Ta onto first imaging member 140a in accordance with said first pattern. Similarly, the second image forming unit 100b comprises a toner reservoir 110b, a feed member 120b, a second development member 130b, a second imaging member 140b, and an optional intermediate member 150b. The second imaging member 140b is adapted to sustain a second pattern of electric charge forming a second latent image on its surface. The second development member 130b is arranged to receive second liquid toner Tb from the feed member 120b, and to develop said second latent image by transferring a portion of said second liquid toner Tb onto second imaging member 140b in accordance with said second pattern. The third and fourth imaging member 100c, lOOd may be implemented in a similar manner.

The substrate S is supported on a substrate support assembly which comprises in the illustrated embodiment first, second, third and fourth support members 200a, 200b, 200c, 200d for supporting the substrate S during the subsequent transfer of first, second, third and fourth liquid toner Ta, Tb, Tc, Td from the first, second, third and fourth image forming unit 100a, 100b, 100c, lOOd, respectively, whilst the substrate S moves in a movement direction M from the first image forming unit 100a to the fourth image forming unit lOOd.

In the development stage, imaging particles travel from a development member 130a supplied with a thin, film-like layer of liquid toner Ta, onto the imaging member 140a that carries the first latent image. In a subsequent step, the developed first latent image is transferred from the imaging member 140a onto the intermediate member 150a. In the final transfer step, the developed image is transferred from the intermediate roller 150a onto the substrate S, which is supported by the support roller 200a that may be kept at a suitable potential. Similar development stages apply for the second, third and fourth image forming units 100b, 100c, lOOd.

Throughout the application, the various stages of the image forming units 100a, 100b, 100c, lOOd and of the support assembly 200a, 200b, 200c, 200d have been described as members. These members may be rotating rollers, but the skilled person will appreciate that the same principles may be applied with other members, e.g. comprising a suitably designed rotating belt with a roll and/or a belt tracking shoe.

This process results in imaging particles P being applied to the substrate S, whilst carrier liquid CL is absorbed in the substrate, see figure 3A. However, before heating, also some carrier liquid CL’ will remain present in-between the imaging particles.

The digital printing apparatus further comprises a melting device 300 configured to fuse the imaging particles of the transferred liquid toner on the substrate S by heating the liquid toner to at least a temperature at which the imaging particles form a polymer melt, and a curing unit 400 configured to irradiate the carrier liquid absorbed in the substrate S with particle beams to cure the carrier liquid in the substrate S. The melting device 300 is arranged downstream of the the image forming units 100a, 100b, 100c, lOOd. Figure 3A shows the substrate S in which a layer of carrier liquid CL has been absorbed whilst imaging particles P are present on the surface of the substrate S. Figure 3B shows the substrate S downstream of the melting device 300, with films F of imaging particles present on the surface of the substrate S. During heating carrier liquid CL’ remaining between the imaging particles P is liberated and the imaging particles form films F. The liberated carrier liquid CL’ is absorbed in the substrate. Both the carrier liquid CL absorbed during the transfer stage and the carrier liquid CL’ liberated during heating will be cured in the curing unit. In other words, preferably the resulting substrate S’ (i.e. the substrate S with the printed image) does not contain any uncured carrier liquid.

The curing unit 400 is preferably an electron beam (EB) curing unit. EB penetration depends amongst others upon the mass density and thickness of the material. EB curing has the advantage that electrons are substantially “color blind” and that penetration is not affected by pigments and opaque substrates. This has also the advantage that EB curing can take place through the substrate. An EB curing unit typically comprises electrically operated filaments and grids contained within a vacuum chamber. The electrons are accelerated through a window/foil structure to reach the area to be cured at atmospheric pressure. In an embodiment of the invention low-voltage EB equipment operating from about 70 to 125 kV may be used for most applications. EB penetration may be controlled by varying the accelerating potential (voltage) of the EB curing unit. The effect of the electron beams on the substrate S may in certain embodiments be beneficial. E.g. EB-induced ionization of the substrate surface may result in enhanced adhesion. Electron beams can also potentially be used for simultaneous curing of the carrier liquid and surface sterilization of the substrate S. Such embodiments may be useful for food packaging materials.

During the heating step the substrate is heated up to a temperature which is higher than the melting temperature of the imaging particles. In the embodiment shown in figure 1, the melting device 300 comprises a heat source configured to melt the imaging particles. As the melting device 300 is melting the imaging particles, it will heat the imaging particles above their melting temperature. In some embodiments, the melting device 300 may use heat and compression between rollers to melt the curable imaging particles. Alternatively, the melting device 300 may use a non-contact method such as infrared radiation to heat and melt the imaging particles.

Particular embodiments of the invention relate to the field of digital printing apparatus and processes for so-called “continuous” webs, i.e. printing systems where a continuous roll of substrate is run through the printer, in particular to print large numbers of copies of the same image(s), or alternatively, series of images, or even large sets of individually varying images.

The digital printing apparatus comprises to that end a substrate feeding means 500 configured to feed the substrate S as a continuous web during printing. The resulting substrate S’ may then be wound on a roll 600. In another embodiment the resulting substrate S’ may be immediately cut and stacked.

Figure 2 illustrates another exemplary embodiment of a digital printing apparatus of the invention in which components similar to the components of the embodiment of figure 1 have been indicated with the same reference numerals. The digital printing apparatus comprises a substrate feeding means 500 for feeding a substrate S, an image forming unit 100 for forming a printed image by transferring liquid toner on the substrate S, a melting device 300, and a curing unit 400. The digital printing apparatus of figure 2 further comprises a coating station 700 configured for applying additional curable liquid, e.g. a lacquer. The coating station 700 can be configured to add the curable liquid non-image-wise, e.g. as an even layer. The coating station 700 may comprise for example an anilox roller and/or one or more inkjet heads.

Another embodiment of a digital printing process and apparatus according to the present invention will now be described in connection with Figure 4 in which components similar to the components of the embodiment of figure 1 have been indicated with the same reference numerals. The printing apparatus comprises a development roller 130a, an imaging roller 140a, an intermediate member 150a, a melting device 300, a curing unit 400, a pressure roller 200a, and an optional dispersing capacity modification unit 350.

In Figure 4, downstream of the imaging roller 140a, there is provided an intermediate member in the form of a belt 150a. The melting device 300 takes the form of a fuse roller arranged along the intermediate belt 150a, upstream of the pressure roller 200a, and downstream of the imaging roller 140a. The fuse roller 300 is configured to fuse imaging particles of a transferred part of liquid toner using heat. The fuse roller 300 is brought at a temperature suitable for melting the imaging particles of the liquid toner. The roller 300 can also be at the outside of the intermediate belt 150a or opposite to pressure roller 200a to form a nip and assist the transfer to the substrate S.

Optionally there may be provided a dispersing capacity modifying unit 350 between the imaging roller 140a and pressure roller 200a, upstream of the melting device 300, in order to change the dispersing capacity of the dispersing agent in the liquid toner that is going to be heated by the melting device 300. As in the embodiment of figure 2, optionally, there may be provided a coating station (not shown) immediately upstream of the curing unit 400.

In the embodiment of figure 4 only one development roller 130a and imaging roller 140a are shown. However, the skilled person understands that multiple development rollers and imaging rollers may be provided for printing in different colours. In that case, multiple imaging rollers may be provided along belt 150a.

Preferably the substrate S comprises any one of the following: paper, paperboard (single- or multiply), fibreboard, and combinations thereof. The substrate S may also have a multilayer structure. Examples of commercially available substrates suitable for use with the invention are: Galerie Fine from Sappi, Digi Color Laser from UPM, W50422 Inspire from Felix Schoeller, Incada Excel from Iggesund, Tambrite, Ensocard, Chromocard and Aurocard from Stora Enso, Carta Solida GC1, Carta Allura GC1 and Carta Integra GC1 from Metsaboard, Tango C2S and Crescendo C2S from Meadwestvaco, MM Digi, Kromopak GC2 and Multicolor Mirabell GD2 from Mayr Meinhof and Alaska CIS from International Paper.

While the invention has been described hereinabove with reference to specific embodiments and examples, this is done to illustrate and not to limit the invention. The skilled person will appreciate that other ways of implementing the inventive concept described herein are within the scope of the invention, as defined by the accompanying claims.

Claims

A digital printing process for xerographic printing with liquid toner, which liquid toner comprises a curable carrier liquid and image-forming particles in suspension in the carrier liquid, the process comprising: - forming a latent image as a pattern of electric charge on a surface of a rotating imaging element; - transferring the liquid toner to a rotating developing element; - developing the latent image by transferring the liquid toner from the developing element to the imaging element in accordance with the pattern; - transferring the liquid toner from the imaging element to a substrate that absorbs carrier fluid from the transferred liquid toner; and heating the liquid toner to at least a temperature for which the imaging particles form a polymer melt; and - irradiating the substrate with particle bundles for curing the carrier liquid of the transferred liquid toner.

The process of claim 1, wherein the substrate and the carrier fluid are selected such that more than 60% of the transferred carrier fluid is absorbed into the substrate.

The process according to any of the preceding claims, wherein the curable carrier liquid is an electron beam curable carrier liquid, and the irradiating step comprises irradiating the liquid toner with electron beams.

The process according to any of the preceding claims, wherein the irradiation is performed under a nitrogen gas atmosphere.

The process of any one of the preceding claims, wherein the substrate is applied as a continuous web during printing.

The process of any one of the preceding claims, wherein the substrate comprises one of the following: paper, cardboard, fiber board, and combinations thereof.

The process according to any one of the preceding claims, wherein the imaging particles are one of the following: color pigments, coated color pigments, toner particles with color pigments, colorants.

The process of any one of the preceding claims, wherein the liquid toner is transferred from the imaging element to the substrate, either directly or via an intermediate rotating element.

The process according to any of the preceding claims, wherein the carrier liquid comprises radiation-curable dispersants.

The process according to any one of the preceding claims, wherein an amount of curable liquid is applied to the substrate after heating and before curing, to create a layer of the curable liquid on top of the substrate in which the carrier liquid is absorbed.

A digital printing device for xerographic printing with liquid toner, wherein the liquid toner used in the printing device comprises a curable carrier liquid and image-forming particles in suspension in the carrier liquid, and wherein the device comprises: - an image-forming unit comprising a rotatable image-forming element arranged to carry a pattern of electric charge that forms a latent image on its surface, a rotatable developing element disposed for receiving liquid toner, and to develop the latent image by transferring the liquid toner to the imaging element in agreement with the pattern, wherein the imaging unit is further adapted to transfer the liquid toner from the imaging element to a substrate; - a melting device adapted to heat the liquid toner to at least a temperature for which the imaging particles form a polymer melt; - a curing unit adapted to irradiate the transferred liquid toner with particle bundles for curing the carrier liquid in the substrate; wherein the curing unit is arranged downstream of the imaging unit and the melting device is such that transferring and heating are performed prior to curing.

The device of the preceding claim, further comprising a substrate supply means adapted to add the substrate as a continuous web during printing; and a roll-up means adapted to roll up the resulting substrate with the cured liquid toner.

The device of the preceding claim, wherein the substrate feed means comprises a reel with a substrate, which substrate is one of the following: paper, cardboard, fiber board, and combinations thereof.

The device of any one of claims 11-13, wherein the curing unit is an electron beam curing unit.

The device of any one of claims 11-14, wherein the imaging unit is adapted to transfer liquid toner from the imaging element to the substrate, either directly or via an intermediate element.

The device of any one of claims 11-15, wherein the curing unit is adapted to perform curing under a nitrogen atmosphere.

The device according to any of claims 11-16, wherein the device further comprises a coating station adapted to apply a quantity of curable liquid to the substrate, after heating by the melting device and before curing by the curing unit, for creating a layer of curable liquid on top of the substrate in which carrier liquid is absorbed.