Coating module with flexible film, coating system, thermal transfer printing apparatus, system, and method

Abstract

To provide a coating module with a flexible film to cope with the emergence of ribs, hence improving the homogeneity and quality of a coated layer.SOLUTION: The invention relates to a coating module (1) to coat a substrate (4) with a coating composition (6), comprising: a coating device (2) to apply a layer of the coating composition on the outer surface of the substrate (4), and a flexible film (5) comprising a distal portion (54) designed to be in contact with the coated substrate (4).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a coating module for coating a substrate with improved coating quality and to an associated method, and further to a thermal transfer printing device comprising such a coating module. [Background technology]

[0002] 2. Background of the Invention Many coating techniques using free surface coating flow are well known to the skilled artisan, in which the substrate is coated with the coating composition using rollers, sprays, slot dies, screen printing, extrusion, knives, blades, bars, etc. Summary of the Invention [Problem to be solved by the invention]

[0003] However, in single / multilayer processes (i.e., dip coating, rod coating, knife coating, blade coating, air knife coating, gravure coating, forward / reverse roll coating, slot / extrusion coating, slide coating, curtain coating, etc.), the coating composition applied to the substrate is likely to experience flow instabilities that affect the uniformity of the coating layer, and periodic, wavy coating thickness variations, called ribbing, are commonly observed on the coating surface, regardless of the coating technique or nature of the coating composition. Therefore, limiting the appearance of ribbing and its associated defects is a constant challenge.

[0004] Fluid instabilities are complex in nature and small fluctuations can propagate into large defects. The origin of ribs can be diverse, as they can be the result of small disturbances occurring during the coating process in the coating composition. Their occurrence can depend on several factors, such as the characteristics of the coating composition, such as surface tension, viscosity, coating process parameters, such as coating speed, pressure, viscoelastic forces, or locally applied shear rate, and the material of the coating equipment.

[0005] Typically, it is measured in grams per square meter (e.g., weight basis 30 g / m 2 Limitations arise when coating thin layers (less than 200 μm) or when reaching a final coating layer thickness of less than 200 μm at high coating speeds, which may accentuate the protruding ribbing profile. The ribbing phenomenon may also be accentuated or relieved during downstream steps of curing, drying or cooling, whereby processing conditions such as temperature and relative humidity may also affect the final profile of the coated article.

[0006] In general, ribbing phenomenon refers to a non-uniform coating that results in a wavy thickness profile through the width and is more or less uniform in the coating direction. The occurrence of ribbing is a flow instability that causes the coating thickness to vary sinusoidally across the width, which can be detrimental or even lead to permanent defects that are unacceptable. The stripes or ribs appear on the surface along the machine direction (also called the transport direction or coating direction). This defect is sometimes called corduroy, rake lines, or phonography. In practice, ribbing mitigation involves modification of the coating speed, coating viscosity, wet coating thickness, or the addition of surfactants to the coating composition. These limitations are at odds with economic drivers.

[0007] The present invention aims to provide a new coating module to address the appearance of ribs, thereby improving the uniformity and quality of the coating layer. [Means for solving the problem]

[0008] overview The present invention relates to a coating module for coating a substrate with a coating composition comprising a coating device for applying a layer of the coating composition to the outer surface of the substrate, and a flexible film comprising a distal portion (terminal portion) designed to contact the coated substrate.

[0009] The present invention relates to a coating module for coating a substrate with a coating composition, comprising a coating device for applying a layer of the coating composition to a first surface of the substrate, and a flexible film (5) having at least one proximal end mechanically connected to a holding element and a free distal portion configured to contact the layer of the coating composition on the first surface of the substrate.

[0010] One advantage is that the free distal portion of the flexible film smooths the coating surface of the substrate after application of the coating. It has also been observed that the present invention improves the overall quality of the coating layer by mitigating and reducing other defects caused by streaks.

[0011] According to one embodiment, the coating module comprises a conveyor system for supporting and transporting the substrate by its inner surface or a second surface of the substrate opposite its outer surface.

[0012] According to one embodiment, the conveyor system comprises support rollers.

[0013] According to one embodiment, the conveyor system includes a temperature regulator configured to heat or cool a portion of the substrate.

[0014] According to one embodiment, the flexible film further comprises openings, grooves or fibers.

[0015] According to one embodiment, the coating module further comprises means for applying pressure to a distal portion of the flexible film.

[0016] According to one embodiment, the coating module comprises a holding element, to which the flexible film is fixed and which is mechanically connected by one or two side edges to the frame. One advantage is that it maintains the position of the proximal end or ends of the flexible film while the distal free part is in contact with the coated substrate.

[0017] According to one embodiment, the holding element is connected to the frame with at least one angle or degree of freedom. One advantage is to adjust the position of the flexible film. Another advantage is to eliminate streaks between the flexible film and the coated substrate.

[0018] According to one embodiment, the retaining element is removable from the frame.

[0019] According to one embodiment, the coating module comprises a source of electromagnetic radiation arranged to irradiate a distal portion of the flexible film, the flexible film being transparent to such radiation. One advantage is that it allows the transmission of electromagnetic waves of any desired wavelength or orientation to reach the reactive molecules and orient or polarize the components of the coating composition.

[0020] The invention further relates to a coating system comprising a coating module according to the invention and a substrate. The coating device is arranged to coat a surface of the substrate. The flexible film is arranged in planar contact with the coated substrate. According to one embodiment, the flexible film is arranged in planar contact with the coated substrate at its distal portion.

[0021] The invention further relates to a thermal transfer printing apparatus comprising a coating system according to the invention, in which the substrate is an endless ribbon, the thermal transfer printing apparatus comprising a conveyor system comprising a set of rollers for transporting the substrate along a path, a print roller for transporting a print substrate in contact with an outer surface of at least a portion of the substrate, and a print head arranged to thermally transfer a portion of the coated ink from the outer surface of the substrate to the print substrate in contact with the substrate.

[0022] The invention further relates to a system for producing an endless ribbon comprising the coating system according to the invention, where the substrate comprises a coating drum. One advantage is to form an endless ribbon or band of uniform thickness on the coating drum, for example using a dip coating method. The system also advantageously comprises a cylinder and a means, such as a motor or rotor / stator pair, for rotating the coating drum around the longitudinal axis of the cylinder.

[0023] The present invention further relates to a method of coating a substrate.

[0024] In one embodiment, the method comprises coating an exterior surface of a substrate with a coating composition, the method further comprising suspending a flexible film on a holding element and transporting the substrate by its interior surface along a predetermined path such that a free portion of the flexible film lies over the coated exterior surface of the substrate before it solidifies (sets), dries, or fully cures.

[0025] In one embodiment, the coating step comprises coating the outer surface of the substrate with at least two bands in parallel, separated from one another, and the coating module comprises at least two flexible films, each flexible film being positioned to overlap one of the bands of coating.

[0026] In another alternative embodiment, a method comprises coating an exterior surface of a substrate with a coating composition using a coating device, and transporting the coating device and flexible film along a predetermined path such that a portion of the flexible film overlies a layer of the coating composition before it solidifies, dries, or fully cures. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic cross-sectional view of a coating module according to a first embodiment of the invention using a slot die coating device. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a coating module according to a second embodiment of the invention, in which the coating device comprises an ink roller. [Diagram 3] FIG. 3 is a schematic cross-sectional view of a flexible film of a coating system according to one embodiment of the present invention. [Figure 4] FIG. 4 is a perspective view of a flexible film of a coating system according to another embodiment of the invention, wherein the flexible film has an opening and the coating module has a means for maintaining a distal portion of the flexible film in contact with a coating layer of the coating composition. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a flexible film of a coating system according to another embodiment of the invention, in which two longitudinal ends of the flexible film are mechanically connected to holding elements. [Figure 6a] FIG. 6a is a diagram of a coating layer showing the rib phenomenon captured by a microscope. [Figure 6b] FIG. 6b is a microscopic image of a coating layer applied by a coating module according to an embodiment of the present invention, where the flexible film is 12 μm thick and made of polyester. [Figure 6c]FIG. 6c is a microscopic view of a coating layer coated with a coating module without a flexible film, where the coating device includes an ink roller with surface defects. [Figure 6d] FIG. 6d is a photometric image of a coating layer coated with a coating module according to FIG. 6c, further comprising a flexible film according to one embodiment of the present invention. [Figure 7] FIG. 7 is a schematic cross-sectional view of a flexible film and a holding element according to an embodiment of the present invention, where the coating module comprises a winding element for storing at least one portion of the flexible film. [Figure 8] FIG. 8 is a schematic diagram of a thermal transfer printing apparatus according to one embodiment of the present invention. [Figure 9] FIG. 9 is a schematic diagram of a coating module according to one embodiment of the present invention, where the substrate to be coated comprises a coating drum. [Figure 10] FIG. 10 is a schematic diagram of a coating module according to one embodiment of the invention, where the substrate to be coated comprises a coating drum and further the coating device comprises a knife coating device. [Figure 11] FIG. 11 is a schematic diagram of a coating module according to one embodiment of the present invention, where the coating device and flexible film are portable. [Figure 12A] FIG. 12A is a schematic diagram of a flexible film and a cleaning means for cleaning the flexible film. [Figure 12B] FIG. 12B is a schematic illustration of a flexible film attached to a holding element, according to one embodiment, where the flexible film is an endless film and the coating module further comprises a means for cleaning a spare portion of the flexible film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Detailed explanation In this application, the term "inner surface" is to be understood as the surface of the substrate that is in contact with an optional conveyor system, whereas the term "outer surface" is to be understood as the surface of the substrate that receives the coating composition.

[0029] As used herein, "substrate", "coated substrate", "coating layer" or "coated layer" are used interchangeably to refer to any surface that is in contact with a flexible film and receives a coating composition. Such surfaces include free-flowing coating compositions designed to produce any type of coating or laminate, such as a precoat, skin coat, topcoat, backcoat, covering, varnishing, finish, film laminating adhesive, etc.

[0030] FIG. 1 shows a first example of a coating module 1 according to one embodiment of the invention.

[0031] The coating module 1 comprises a coating device 2 for applying a coating composition 6 to an outer surface of a substrate 4 while it is transported along a predetermined path by a conveyor system 3. The coating module 1 further comprises a flexible film 5.

[0032] The coating module 1 can include any kind of coating device and the flexible film is made to comply with any coating technique available to the skilled person for direct or transfer (indirect) coating such as flexography, free-flow and curtain coating, dip coating, brushing, roll coating (forward roll coating, reverse roll coating, etc.), spraying, painting, brushing / wiping, extrusion coating, etc.

[0033] The use of flexible film in this coating module could be embedded in any continuous coating process. The present invention is especially adapted for free-flow coating where the final coating surface must be uniform and smooth.

[0034] The coating device is used to distribute the coating composition on the upper surface of the substrate. The coating composition flows to cover the entire or partial area. Thus, the flexible film can be designed to completely or partially improve the uniformity of the coating layer applied on the substrate, for example for strip coating or intermittent coating.

[0035] The coating process can consist of a single coating step or multiple step coating, whereby a series of coating compositions can be applied over previous coating layers, such as precoats, whether tack-free or not.

[0036] The coating module can also combine several different coating techniques in multi-method coating. Coating could be operated horizontally, vertically or at an oblique angle. In double-sided coating, the inner and outer surfaces may be switched during the process. The flexible film is placed to ensure contact with the coating composition, regardless of its viscosity, while said coating composition is still free-flowing, i.e. liquid, viscous or molten. It is therefore advantageous to place it between the coating device and the cooling, curing or drying equipment.

[0037] Flexible Film During coating, the flexible film is intended to contact the substrate to be coated. The coating layer is applied to the outer surface of the substrate. The flexible film operates when the coating remains levelable, i.e. before the surface becomes tack-free, and before the coating composition has cured, dried, or cooled. The flexible film can address all kinds of coating product imperfections and defects, avoiding ripples, wrinkles, wobble, and / or abandonment.

[0038] At least one end of the flexible film is attached to a holding element for holding it on the substrate. The bending ability of the film allows the distal portion (end portion) to cover a portion of the coating layer freshly applied to the substrate, while the coating composition can exhibit suitable thermo-mechanical behavior to be leveled or otherwise smoothed. The coating planarization, leveling, or leveling operation is performed in a process window positioned to accommodate the ribs and remove thickness irregularities.

[0039] In one embodiment, due to the movement of the substrate in the coating direction and the flexibility of the flexible film, the distal portion of the flexible film is dragged by the substrate, and thus the coating layer slides under or along the distal portion of the flexible film.

[0040] The flexible film is positioned and designed so that the face of the distal portion of the flexible film is in contact with the coating layer of the substrate, preferably in planar contact.

[0041] By "planar contact," it should be understood that the distal portion of the flexible film overlies, overlaps, or is juxtaposed with the upper coating layer of the substrate. The face of the distal portion 54 of the flexible film refers to the surface that contacts the coating layer of the substrate.

[0042] The length of the flexible film is designed to be long enough to ensure planar contact of the distal portion with the coating layer. The length of the distal portion of the flexible film may be longer than 0.5 mm, preferably 1 cm or more depending on the coating direction.

[0043] In one embodiment, the coating module can simultaneously coat at least two portions of the width of the substrate to form at least two bands or stripes of coating. According to one example, the coating module comprises a shim having at least two openings and positioned to guide the coating composition through the openings to form at least two separate bands or stripes of coating on the surface of the substrate.

[0044] In one embodiment, the coating module comprises at least two flexible films. Preferably, the at least two flexible films are arranged in the same plane fixed to the holding element, each flexible film being arranged to overlap a portion of the width of the substrate. Preferably, each flexible film is arranged on one band of coating, on the outer coating layer or on the substrate.

[0045] Single end fixed In a first embodiment shown in Fig. 3, the proximal end 52 of the flexible film 5 is mechanically connected to a holding element 53, which is preferably mechanically connected to a frame of the coating module. The proximal end of the flexible film is preferably mechanically connected to the holding element 53 with zero degrees of freedom.

[0046] In other words, the flexible film is fixed to and suspended by its proximal end on the holding element 53 above the coated substrate 4 which is transported by the conveyor system. Since the length of the flexible film 4 is longer than the distance between the holding element 53 and the coated substrate 4, the distal portion 54 of the flexible film overlaps a portion of the upper coating layer 6 and is bent over to lie on the coated substrate 4.

[0047] Both ends fixed In a second embodiment shown in FIG. 5, both ends of the flexible film 521, 522 are mechanically connected to a holding element 53. In this embodiment, the flexible film 5 forms a closed loop. The distal portion 54, remote from the holding element, is arranged to be in contact with the coating layer 6. The first advantage is to prevent defects of the flexible film due to a resultant miscut or sharp end 58. The second advantage is to reduce the risk of losing contact between the flexible film and the coated substrate, exerting a slight pressure when the film is deflected over the substrate. The third advantage is to reduce the risk of misalignment between the distal portion 54 of the flexible film 5 and the substrate.

[0048] In both the first and second embodiments, the flexible film could be positioned to contact the substrate as close as possible from the coating device.

[0049] Additional Embodiments Other embodiments will be described in conjunction with the above first or second embodiment.

[0050] In an embodiment shown in Fig. 7, the coating module comprises at least one unit 61 or 62 for winding up a portion of the flexible film. In an embodiment, the at least one winding unit is designed to store a certain amount of film.

[0051] In a further embodiment, the coating module comprises a first unit 62 and a second unit 61. The first and second units are preferably mechanically connected to the holding element 5. The flexible film is held between these first unit 61 and second unit 62, forming a storage unit for the flexible film such that the length of the flexible film from the first unit to the second unit is longer than the distance between the first unit and the second unit. One advantage is to adjust the distal portion 54 of the flexible film in contact with the newly coated layer 6.

[0052] In one embodiment, the first unit and / or the second unit comprises at least one winder, allowing a user to unwind the flexible film from the first unit 62, cut off the old portion of the flexible film and renew the distal portion of the flexible film intended to contact the coating layer. In one embodiment, the first unit and / or the second unit comprises at least one motor for controlling the winder and its rotation speed.

[0053] As the flexible film is unwound from the first unit and wound onto the second unit, its distal portion in contact with the coating layer can be renewed. A reserve of flexible film stored in the first unit is rolled out and spread over the coating layer. The unwound portion of flexible film becomes the new distal portion. One advantage is the continuous replacement of the distal portion of the flexible film.

[0054] In one embodiment, the coating module 1 further controls a degradation sensor designed to measure the degradation of the flexible film. The degradation sensor may comprise at least one optical sensor. In one embodiment, the coating module comprises means (such as a controller controlling the motors of the first and / or second unit) for automatically replacing the distal portion of the flexible film when the degradation measured by the degradation sensor reaches a predefined threshold. One advantage is the automatic replacement of the distal portion of the flexible film.

[0055] The holding element 53 is preferably mechanically connected to the frame of the coating module 1. The holding element 53 advantageously comprises fastening means for fastening the flexible film 5 at one or both ends.

[0056] In one embodiment, the coating module 1 comprises at least two flexible films 5, each of which is fixed to a holding element 53. For multiple coating steps, an array of multiple flexible films as described above could be connected to the same frame or operated independently. Each holding element 53 can be mechanically connected to the frame of the coating module 1 with at least one rotational or translational degree of freedom. This degree of freedom favors alignment of the flexible films as well as ease of exchange of the flexible films 5.

[0057] In one embodiment, at least one end of the flexible film is attached to the holding element with double sided tape. The flexible film may be glued, clamped, nailed, screwed, or riveted to the holding element 53.

[0058] In another embodiment, the coating module comprises means for easily changing or replacing the flexible film 5. In one example, the first unit 61 and / or the second unit 62 are removably connected to the holding element 53 or to the frame. In a second example, the flexible film is connected to the frame or holding element by removable fastening means such as screws, tongs, adhesive or magnetic fastening means. In one embodiment, the holding element may be coupled with a drying unit as described below.

[0059] In another alternative embodiment, the flexible film and holding element may be attached in accordance with the present invention to a portable support device intended to be placed on the ground and to suspend the flexible film above a substrate.

[0060] In another embodiment, the coating module further comprises a means for providing a lateral movement to the flexible film, which may induce a vibration means for providing vibration to the flexible film. The vibration of the flexible film may improve the reduction of the rib effect on the coating layer 6. Another advantage of the vibration is to improve the removal of defects caused by the presence of particles, dust, air bubbles, streaks caused by prematurely dried coating, small chips, lumps, or caused by nicks in the coating device. Thus, the quality of the coating layer could be improved by the mitigation of air pockets in the coating composition remaining after filtration or other operations performed before the actual coating.

[0061] In one embodiment, the vibration means may comprise a motor controlling a holding element or a piezoelectric element. In one embodiment, the coating module comprises a controller. The controller controls the vibration means. In one embodiment, the controller is configured to automatically activate the vibration means to provide vibration to the flexible film periodically and / or when a streak is detected between the flexible film and the substrate.

[0062] In one embodiment, the coating module comprises means for providing a translation or rotation of the holding element 54. The axis of rotation is preferably nominally parallel to the length of the flexible film.

[0063] In one embodiment, the holding element is mechanically fixed in a frame with at least one or two degrees of freedom in translation and / or rotation. One advantage is that the holding element can be moved to adjust the position of the flexible film to the orientation and position of the substrate.

[0064] In one example, the retaining element is free to translate in a first direction that is perpendicular or axially perpendicular to the surface of the substrate. One advantage is to adjust the length of the distal portion that contacts the substrate.

[0065] In one alternative or cumulative example, the retaining elements are free to translate in a second direction parallel or symmetrically parallel to the transport direction of the substrate. One advantage is that streaks are reduced or eliminated.

[0066] In one embodiment, the movement of the retaining element along the second direction is controlled by a controller, hi one embodiment, the controller is configured to automatically periodically provide movement of the retaining element along the second direction (such as a back and forth movement) to remove streaks.

[0067] In one embodiment, the coating module includes a sensor, such as an optical sensor, for detecting streaks between the flexible film and the substrate, the sensor being connected to a controller, the controller being configured to initiate movement of the holding element as a function of the sensor measurement.

[0068] Preferably, the flexible film is suspended from the holding element such that the direction of the film from its proximal end to its distal portion coincides intuitively with the direction of transport of the substrate.

[0069] In one embodiment, the film 5 and substrate 4 are aligned end to end, and optionally the film 5 is positioned such that the width of the substrate 4 is equal or approximately equal to the width of the flexible film. The flexible film 5 is necessarily curved on the coating surface, and is aligned or oriented depending on the direction of transport or coating induced by the conveyor system. Another advantage of the design is the ability to spread or level the coating on the outer surface of the substrate and precisely control its width edge.

[0070] The width of the flexible film is preferably between 100% and 50% of the width of the substrate.

[0071] In another embodiment, the coating composition is applied to a central portion of the substrate, In such an embodiment, the width of the flexible film can be adjusted to control the spread of the coating composition beyond the initial width, thereby controlling the subsequent width and thickness.

[0072] The chemical composition of the flexible film can be selected, but is not limited to any of the following materials or combinations thereof: The flexible film may be based on thermoplastic, thermosetting or elastomeric polymers and may comprise at least one polymer selected from polyesters, polyamides, polycarbonates, polyolefins, polysulfones, polyurethanes, vinyl or cellulose derivatives, fluorinated or chlorinated derivatives, polyaryletherketones, polybenzimidazoles, polyethylene glycols, polyimides, polyurethanes, acrylic styrenes, acrylic copolymers, and mixtures thereof. The flexible film may advantageously be made of materials based on polyethylene terephthalate (PET) or its derivatives, polyimides, PTFE ("polytetrafluoroethylene") or PEEK ("polyetheretherketone").

[0073] In another embodiment, the flexible film is a foil or sheet of metal, such as aluminum. In another embodiment, the flexible film is comprised of a combination of a polymer layer and a metal layer. In another embodiment, the flexible film includes at least one filler selected from powders, fibers, whiskers, particles, nanosheets, etc. The filler can be selected from carbon, carbon black, graphite, graphene, carbon nanotubes, activated carbon nanotubes, activated carbon fibers, non-activated carbon nanofibers, metal flakes, metal powders, metal fibers.

[0074] The material and thickness of the flexible film allows the flexible film to contact the substrate along a distal portion, which is supported by the moving substrate.

[0075] In one embodiment, the film is adjusted to be transparent or opaque to electromagnetic fields. The flexible film may be transparent to ultraviolet (UV) radiation to trigger a photochemical reaction when a UV-curable composition is used. This embodiment is particularly advantageous for thick coatings. In fact, the reaction of solidification (coagulation) can advantageously be triggered deep inside (deep penetration cure). Therefore, the reaction can be initiated in the bulk coating while the surface remains liquid, which allows the flexible film to improve the quality of the top coating layer. Conversely, the film can block such electromagnetic waves to prevent premature curing near the coating device, for example in a luminous environment.

[0076] In another embodiment, the flexible film can be transparent, transmissive, or porous to other types of radiation such as electron beam, laser, plasma, corona, etc. The flexible film can also be transparent to and transmit electromagnetic waves such as linear, circular, or elliptical waves used to polarize the coating composition in situ.

[0077] In one embodiment, the Young's modulus of the flexible film is less than 10 GPa, preferably less than 5 GPa. The thickness of the flexible film is greater than 1 μm. The thickness of the flexible film is preferably in the range of 3 μm to 50 μm, preferably in the range of 3 μm to 15 μm. This thickness of the flexible film is advantageously adapted for coating in thin layers (e.g., layers thinner than 100 μm).

[0078] In another embodiment, the flexible film has a thickness of greater than 50 μm, or desirably greater than 100 μm, which has the advantage that the flexible film can be more easily manually handled and helps maintain contact between the flexible film and the coated substrate.

[0079] If desired, the basis weight of the flexible film can be lower than the basis weight of the wet coating. One advantage is that the thickness uniformity of the coating layer can be better controlled. In one embodiment, the basis weight of the flexible film is 30 g / m 2 Lighter than 20 g / m 2 The combination of mechanical properties and chemical / physical characteristics of the flexible film can be selected or tailored to ensure the formation of a free-floating curvature of the flexible film between the retaining element and the distal portion that is in planar contact with the coating.

[0080] In one embodiment, at least one surface of the flexible film 5 is textured.

[0081] In one embodiment, the flexible film is provided with a texture on a limited area. Preferably, the grooves are distributed over the area closest to the retaining element, allowing the last part of the distal portion to contact the substrate. One advantage is the progressive effect that makes the flexible film smooth on the coating layer.

[0082] In one embodiment, the flexible film is configured with grooves that are patterned or randomly decorated.

[0083] The grooves are preferably produced by laser ablation. Preferably the grooves comprise a plurality of grooves extending in a direction non-parallel to the transport direction of the substrate.

[0084] One advantage is that the angled grooves can create perturbations of the coating layer 6 on the substrate 4, thus advantageously reducing ribbing in cases where leveling of complex coating compositions is otherwise difficult to achieve.

[0085] In one embodiment, the grooves extend along the surface of the flexible film 5 along a direction that presents an angle of 10° to 30° with the transport direction of the substrate. Surprisingly, it has been discovered by the inventors that the particular orientation of the grooves further improves the quality of the coating. Indeed, such an arrangement induces additional shear in the upper coating layer, leading to a significant reduction of the rib effect.

[0086] In one embodiment, the depth of the groove ranges from 1 to 10 μm.In one embodiment, the width of the groove ranges from 0.5 to 10 μm.

[0087] 4, the flexible film 5 includes at least one opening 56 or a plurality of openings 56. The openings are desirably located on the flexible film 5 in portions between the distal portions 54. More preferably, the openings 56 are located near the distal portions 54 of the flexible film 5 that contact the coating layer 6.

[0088] The opening 56 is advantageous for maintaining contact between the distal portion 54 and a coating layer on a substrate.

[0089] Indeed, increasing the speed of the substrate 4 may cause the flexible film 5 to peel off from the coating layer 6 due to air resistance against the flexible film 5, thus reducing the quality of the coating. Furthermore, the openings may also provide holes, or holes in the flexible film, for radiation to pass through to reach the coating composition, as discussed above.

[0090] The opening 56 is preferably a through hole along two sides of the flexible film. The surface of this opening is 1 μm 2 to 10μm 2 It is desirable that the range is.

[0091] In one embodiment, the flexible film 5 presents two faces with different surface energies. Optionally, the surface of the flexible film in contact with the coating layer 6 is more oleophilic or hydrophilic than the outer surface of the substrate 4 in contact with the coating layer, or vice versa. Preferably, the flexible film 5 is made of an oleophilic material and the outer surface of the substrate is made of an oleophilic material. The contact with the distal portion is enhanced by adjusting the surface tension of the flexible film depending on the coating composition. In one embodiment, the surface energy of the film is precisely 50 mN / m on both sides. Thus, the effective contact of the distal portion of the film with the coating layer is enhanced by capillary forces and a homogenizing effect is created by shear in the fluid.

[0092] In one embodiment, the flexible film is designed to regulate the spread and control the distribution of the coating composition across its width.

[0093] In one embodiment, the flexible film comprises a fibrous structure. In one embodiment, the fibrous structure is disposed on a fabric. The fabric may comprise a woven, nonwoven, knitted, braided, or any other type of open or closed structure.

[0094] In one embodiment, shown in FIG. 4, the coating module 1 further comprises means for applying pressure to the distal portion of the flexible film to maintain contact with the coating layer.

[0095] In one embodiment, these means comprise a plate 55 intended for planar contact with the outer surface or flexible film 5, and may further comprise an arm 57 for exerting a force on said plate 55 towards the substrate 4 from above the distal portion 54 of said flexible film 5. This plate 55 therefore advantageously presses the flexible film 5 in order to maintain contact between it and the coating layer 6. The arm 57 may be moved translationally and / or rotationally with respect to the frame of the coating module 1 in order to exert a force by the plate 55 towards the substrate 4.

[0096] In another embodiment, the means for applying pressure to the distal portion of the flexible film comprises a fan arranged to generate an air flow towards the distal portion of the flexible film, in which case the pressure is applied by air, In another embodiment, the means for applying pressure comprises any kind of pressing element, such as a roller.

[0097] In one embodiment, the plate 55 comprises means for fastening to the flexible film. The plate 55 may comprise means for bonding, connecting, attaching or adhering to the flexible film.

[0098] For example, the plate 55 can be equipped with an adhesive or a suction system. These means advantageously enable the plate 55 to detach the flexible film when the arm 57 detaches the plate 55.

[0099] One advantage is a better control of the coating distribution in width while the coating composition slides along the flexible film. As a matter of fact, given that the flexible film exhibits wetting properties associated with the coating composition, a narrower portion of the substrate can be coated and the coating layer spread in the width direction. This setup could be advantageously used in combination with pressure applied to maintain or press the flexible film to the coating layer. The coating width is expanded and the thickness can be reduced to perfection in order to reduce the amount of coating poured or applied onto the substrate, opening new process windows and allowing the management of coating stripes or intermittent coatings.

[0100] Plate 55 also conducts electricity and can be connected to system ground. One advantage is that it improves static electricity distribution, reducing the risk of sparks and fire. In one embodiment, plate 55 is made of metal or conductive plastic.

[0101] In another refinement, the flexible film is made of an electrically conductive material and the coating module comprises means for passing an electric current through the flexible film.

[0102] The advantage is that the passage of electric current orients the polar molecules of the coating composition or conductive filler. The coating module preferably comprises a generator connected to the flexible film for transmitting an electromagnetic field through said flexible film.

[0103] In one embodiment, the coating module 1 further comprises means for removing the flexible film 5 from the substrate or coating layer. In another embodiment, the flexible film can be optionally removed for replacement, for example as part of a maintenance operation.

[0104] Conveyor Systems The coating module may comprise a conveyor system 3. The conveyor system is designed to support and transport the substrate 4 along a predetermined path. Preferably, the conveyor system is designed to drive the substrate from the coating device to a flexible film.

[0105] The conveyor system is preferably designed to drive the relative speed of the substrates in a controlled manner during coating.

[0106] In one embodiment, the conveyor system 3 is designed to hold and transport the substrate 4 by its inner surface along a predetermined path.

[0107] The conveyor system 3 may comprise at least one roller 30. In one embodiment, the conveyor system 3 comprises at least one drive roller. The drive roller is connected to a motor to rotate the drive roller. The rotation of the drive roller advantageously drives the substrate.

[0108] The coating module 1 may further comprise a motor for rotating a drive roller of the conveyor system and a speed controller coupled to the motor for generating the rotation of the drive roller, the speed of the substrate along its path then being related to the rotational speed of the drive roller of the conveyor system and controlled by the speed controller.

[0109] In one embodiment, at least one battery or electrical armature may be implemented in the conveyor system to provide power to the motor.

[0110] In another non-illustrated embodiment, the support roller 30 can be replaced by a guide for guiding and supporting the substrate 4 by its inner surface. The guide is preferably a curved guide or a partially rounded guide. The guide is static with respect to the frame of the coating module. This guide can be flat or curved to guide the movement of the substrate 4.

[0111] Coating Composition The coating composition can be a solution, slurry, dispersion, emulsion, paste, ink, slurry, or any liquid, fluid, solvent-based, molten, or viscous composition, or any type of chemical composition. The coating composition is intended to solidify, dry, harden, or cool after being applied to the exterior surface of the substrate and passing under a flexible film. The coating composition can comprise a sol-gel composition, or any transitional composition between a fluid and a solid, or a polymeric composition.

[0112] The coating composition may comprise one or more polymers selected from thermoplastic polymers, thermoset polymers, elastomers, and mixtures thereof.

[0113] Examples of thermoplastic polymers include, but are not limited to, polymers derived from the polymerization of aliphatic or cycloaliphatic vinyl monomers, such as polyolefins (including polyethylene or polypropylene), polymers derived from the polymerization of aromatic vinyl monomers, such as polystyrene, polymers derived from the polymerization of acrylic and / or (meth)acrylic monomers, polyamides, polyether ketones, polyimides.

[0114] Examples of thermosetting polymers include thermosetting resins (epoxy resins, polyester resins, etc.), optionally mixed with polyurethane or polyether polyols.

[0115] Examples of elastomeric polymers include, but are not limited to, natural rubber, synthetic rubber, styrene-butadiene copolymers, ethylene-propylene copolymers, and silicones.

[0116] The coating composition can comprise one or more fillers.

[0117] Examples of fillers include, but are not limited to, carbon, graphite, graphene, metals, oxides, and ceramics.

[0118] The filler may be in the form of, but is not limited to, particles of any size range, flakes, powders, fibers, nanofibers, nanotubes, whiskers, aggregates, sheets.

[0119] The coating composition may also be any combination of all of the above.

[0120] In one embodiment, the coating composition comprises a solvent, and evaporation of the solvent results in drying or solidification of the coating composition. In such an embodiment, the coating module can comprise a means for facilitating evaporation of the solvent, such as a heat source or an air blower. The heat source or airflow is desirably directed toward the coated exterior surface of the substrate after the substrate has passed along the flexible film.

[0121] In an alternative embodiment, the coating composition comprises a molten ink, which is intended to be cooled and solidified after coating. In one embodiment, the coating module comprises a means for promoting the solidification of the coating layer, such as a cooler. In one embodiment, the cooler may comprise a cooling roller 201, as shown in FIG. 8, which is arranged to support the inner surface of the substrate and cools the coated composition through the substrate. Preferably, a flexible film is arranged to slide over the coated substrate between the coating device and the cooler or cooling roller.

[0122] In another alternative embodiment, the coating composition comprises chemical compounds that react with an electromagnetic field, such as polarizable molecules or photoinitiators. In the example of photoinitiators, these compounds can UV cure the coating composition upon UV radiation. In this embodiment, the coating module comprises a curing unit that exposes the coating layer to radiation. In one example, the curing unit is arranged to expose the coating layer to UV radiation through the flexible film to initiate the photoreaction as described above. In this embodiment, the flexible film is transparent or transmissive to such radiation, as previously described.

[0123] In either case, the physical, chemical, or mechanical characteristics of the flexible film are selected by the coating composition.

[0124] Base material The substrate 4 can be any surface for coating. If desired, it can be a flat surface such as metal, glass, paper, fabric, plastic, etc. In one embodiment, the substrate is a sheet or foil. In one embodiment, the substrate comprises a ribbon, such as a polyimide ribbon. The ribbon can be a band or an endless ribbon. In one embodiment, shown in FIG. 9, the substrate is a coating drum 37, as described in the following description.

[0125] Coating Device The coating device 2 may be any type of coating device capable of coating a layer of fluid onto a substrate. The coating device is designed and arranged to apply a layer of a coating composition onto the outer surface of a substrate, preferably with a wet coating weight of 30 g / m 2 It is smaller and / or preferably a layer less than 100 μm in thickness.

[0126] The coating device is preferably mechanically connected to the frame of the coating module.

[0127] The coating device is intended to apply a layer of a coating composition to the outer surface of a substrate. The coating device is positioned to apply said coating composition to the substrate in a so-called "coating zone". The "coating zone" is defined by the portion of the substrate that is in contact with a portion of the coating device or to which the coating composition is applied. This "coating zone" may correspond to the length of the substrate that receives fresh ink from the coating device.

[0128] In one embodiment, the coating device is designed to coat both sides of a substrate. The coating composition can exhibit very low viscosities, similar to those of water, as well as viscosities up to several thousand centipoise. The coating composition is cured or solidified using conventional techniques, such as drying a solvent-based or water-based composition, inducing a polymerization or crosslinking reaction, triggering a radiation-curable composition, or cooling a molten coating composition.

[0129] The flexible film is desirably positioned so that a distal portion of the flexible film is in contact with the upper coating layer.

[0130] As shown in Figure 6b, the quality of the coating layer obtained using the coating module according to the invention with a flexible film is more homogeneous than that obtained without a flexible film as shown in Figure 6a. In fact, the surface appearance of the coating layer in Figure 6b was obtained with a flexible film with a thickness of 12 μm and a length of 22 mm, made of polyester.

[0131] In Figures 6a and 6b, white pixels indicate surfaces with a low coating thickness, and black pixels indicate surfaces with a high coating thickness.

[0132] The present invention has been found to advantageously improve coating uniformity on a substrate, which is particularly advantageous for coating ink donor ribbons for thermal transfer printing applications, for example.

[0133] Another advantage of the flexible film is that it eliminates imperfections from the coating layer induced by imperfections on the exterior surface of the ink roller.

[0134] The inventors have further surprisingly discovered that such flexible films are highly effective at limiting the effect of imperfections on the exterior surface of the ink roller.

[0135] An example is shown by comparing Figures 6c and 6d. In both cases, the coating layer is applied by a coating device with an ink roller 24, as shown in Figure 2. To check the quality of the top coat layer, the same coating part is recorded using a microscope or a backlit telecentric camera system.

[0136] As a matter of fact, when the ink roller 24 shows some defects on the outer surface, subsequent scratches appear on the coating layer. Such scratches are caused on the coating layer by the abnormal presence of indentations on the ink roller, as shown in FIG. 6c. When using a flexible film according to the invention, the inventors have observed that the impact of such defects 65 disappears, as shown in FIG. 6d. The defects on the ink roller cause scratches on the coating layer on the same part of the coated substrate, but disappear when using said flexible film. So, not only the ribbing of the coating is mitigated, but also the scratches due to defects on the outer surface of the ink roller are mitigated.

[0137] Therefore, the use of flexible film can limit the replacement of damaged ink rollers while maintaining the high quality of the coating layer. Therefore, the present invention has the advantage of limiting the replacement of ink rollers, increasing the use of the coating module, and improving the throughput and yield of the entire process.

[0138] According to one embodiment, if the coating composition needs to be softened or melted, the coating module 1 comprises additional heating means which ensure that the temperature of the coating layer 6 is above the melting point or above the glass transition temperature of the coating composition until it reaches the distal portion 54 of the flexible film 5.

[0139] This additional heating means advantageously ensures that the coating composition remains liquid or viscous enough to distort upon contact with the distal portion 54 of the flexible film. The additional heating means advantageously keeps the coating composition at a low enough viscosity so that capillary forces can allow for interaction between the film and the substrate. Thus, the flexible film is desirably designed to reach a level of flexibility such that capillary forces can manage the interaction between the flexible film and the substrate.

[0140] 3, a distal portion 54 of the flexible film 5 is in contact with the coating layer 6, which is supported by a support element 30, such as a support roller. The distal portion 54 of the flexible film 5 is in contact with the coating layer 6 and is preferably supported by the conveyor system 3 or the support roller 30. In one embodiment, the support roller 30 is provided with a heating means, such as an electrical resistance, for heating the substrate 4 in contact with the surface of the support roller 30.

[0141] The support roller 30 is preferably positioned to support the substrate 4 from at least the coating zone to the distal portion 54 of the flexible film 5 and is designed to heat the coating layer 6 from at least the coating zone to the distal portion 54 of the flexible film 5.

[0142] In one embodiment, the coating module 1 comprises means for heating the coating layer 6 by radiation.

[0143] The means may comprise an infrared source or other thermal radiation source arranged to heat the flexible film 5. In such an embodiment, the flexible film 5 is made of a material that converts the radiation emitted by the thermal radiation source into heat. For this purpose, the flexible film 5 may be made of a metal sheet, such as a gold or titanium sheet.

[0144] In another embodiment, the thermal radiation source may be replaced with a radiation source, such as a UV source, capable of initiating polymerization or reticulation deep within the coating layer.

[0145] In such an embodiment, the flexible film 5 is made of a material that is transparent to the radiation emitted by the radiation source or thermal radiation source.

[0146] Example 1: Slot die coating device Figure 1 shows one embodiment of a coating module according to the invention. The coating device 2 comprises a slot die coating device 21 designed to melt and dispense a coating composition 6 onto a substrate 4. The slot die coating device 21 may also comprise a fluid reservoir for storing a primary supply of the coating composition and a pump for driving the coating composition through an inlet 23 of the slot die head 21. The slot die further comprises a slot 22 formed for applying the coating composition to the substrate 4 designed to measure an amount of the coating composition, e.g., a coating composition having a basis weight of 10 g / m 2 The wet coating is applied to a 2μm foil substrate with a thickness of around 1.5μm.

[0147] While the coating composition is being extruded through the slot die, a meniscus forms between the slot die tip and the substrate where flow instabilities can occur. The presence of the flexible film 5 prevents ribbing caused by such flow instabilities and levels the thin coating layer.

[0148] Additionally, slot die coating is often chosen to produce stripes along the coating direction. Using several sections of flexible film 5 arranged across the width of the substrate allows for leveling of the coating composition and sharpness of the edges of each coated stripe. Therefore, the risk of overlapping stripes is greatly reduced and the coating cleanliness is improved.

[0149] The conveyor system 3 is designed to drive the relative velocity of the substrate 4 to the slot die coating device 21 .

[0150] In the embodiment shown in FIG. 1, the conveyor system 3 comprises at least two rollers 30 shown supporting the substrate 4 on either side of the slot die coating device 21 .

[0151] Example 2: Ink roller coating device Figure 2 shows another embodiment of a coating module 1 according to the invention. In this embodiment, the coating device 2 comprises an inking roller 24, which is mounted to rotate on its own and delivers ink on its circumferential surface. Coating occurs while the circumferential surface of the inking roller is in contact with the substrate, transferring the coating composition at a predetermined thickness.

[0152] In one embodiment, the circumferential surface of the ink roller 24 is imprinted and consists of regularly arranged depressions forming a series of grooves, cavities or patterns, the depth of the depressions being comprised between 5 μm and 50 μm, the depressions being advantageous for transporting the coating composition until the ink roller 24 comes into contact with the substrate 4.

[0153] The inking roller may be an anilox roller or a flexographic roller.

[0154] Example 3: Thermal transfer printing device In another aspect, the present invention relates to a thermal transfer printing device 200 with an endless ribbon. Such a thermal transfer printing device 200 will be described with reference to FIG.

[0155] The thermal transfer printing apparatus comprises a coating module 1, which can be any kind of coating device. In this example, the coating device is an ink roller designed to press molten ink onto the coating substrate. The substrate is an endless ribbon, such as a polyimide-based ribbon, driven by a conveyor system along a path defined by the arrangement of rollers, on its inner side.

[0156] The thermal transfer printing apparatus 200 comprises a print head 101 for thermally transferring a portion of a coating layer 6 from a ribbon to a print support 202. The endless ribbon 4 is then transported from the print head 101 to a coating device 1 for recoating.

[0157] The thermal transfer printing apparatus 200 further includes a plurality of rollers 201 and 204 for holding and transporting the endless ribbon 4 .

[0158] In one embodiment, the thermal transfer printing apparatus further comprises a cooling element, which is designed to actively cool the coating layer 6 on the ribbon between the print head 101 and the coating device 1. Preferably, the flexible film 5 is arranged in contact with the substrate 4 between the coating device 1 and the cooling element 201.

[0159] As previously mentioned, the cooling element may comprise a cooling roller in contact with the inner surface of the substrate 4 .

[0160] The printing device 200 includes a print head 101. In a preferred embodiment, the print head 101 is a thermal transfer print head.

[0161] In a first mode, the print head 101 contacts the inner surface of the ribbon 4 and enables thermal transfer of ink located on the outer surface of the ribbon 4. During this printing process, the outer surface of the ribbon 4 contacts (preferably under pressure) a substrate 202, such as a sheet of paper (herein referred to as the "print substrate"), to transfer portions of the ink for printing onto the print substrate 202.

[0162] In the second mode, the print head 101 is not in contact with the endless ribbon 4. This mode may be activated when the printing device is switched off or during two consecutive printing sequences. The alternation between the first and second modes can be set by the print mode.

[0163] At least one print roller 203 or print plate may be used to transport the print substrate 202 in contact with the ribbon 4 while the thermal transfer occurs. The thermal transfer print head 101 is designed to transfer the hot melt ink from the ribbon 4 to the print substrate 202. The alignment between the print head 101, the ribbon 4 and the print substrate 202 may be ensured by precisely set mechanical parts depending on the required printing accuracy. Several guides and position control components may be implemented to ensure a predetermined alignment at least between the print head 101 and the ribbon 4.

[0164] The print roller 203 ensures sufficient pressure on the print support 202 to keep it in contact with the ribbon 4 as the printing process takes place. In this configuration, the ribbon 4 is maintained in a moving sandwich layer between the print support 202 and the print head 101 during the printing process. The movement of the print support 202 is in the same direction as the displacement direction of the ribbon 4 near the print head 101. This movement near the print head is preferably a linear movement.

[0165] The ribbon 4 of the printing device 200 makes it possible, on its outer surface, to transport the ink from the coating module 1 to the print head 101 .

[0166] The printing process is implemented to form a continuous loop process. During printing, the print head 101 contacts the inner surface of the ribbon 4 and allows the ink on the outer surface of the ribbon 4 to be thermally transferred to the print support 202. After printing, the endless ribbon 4 is transported from the print head 101 to the coating device 1 for recoating. Residual ink is then collected and the coating layer is replenished by the coating device. This arrangement allows recovery and rejuvenation of the partially depleted ink layer that has not been printed. The ink can be advantageously reused on the next turn of the ribbon 4.

[0167] Example 4: Coating onto a coating drum In one embodiment, shown in Figure 9, the substrate is a coating drum 37. The coating drum 37 comprises a cylinder, such as a rotating cylinder. The conveyor system comprises means for rotating the coating drum 37 about the longitudinal axis A of the cylinder.

[0168] The conveyor system may include a drive shaft 38 that rotatably drives a coating drum 37. The coating drum 37 is rotatably driven by a motor connected to the drive shaft 38.

[0169] The coating device 2 is positioned to coat the exterior surface of a coating drum 37 while the coating drum is rotating. A flexible film 5, as described herein, is positioned in contact with the coating layer.

[0170] The coating drum is used to support one or more coating layers designed to produce a band or endless ribbon using one or more coating layers. Such a substrate advantageously allows for the creation of seamless bands or endless ribbons with coating compositions having improved surface aspects. This band could be used as a substrate for coating with the aforementioned thermal printer.

[0171] Example 5: Knife coating FIG. 10 shows another embodiment of a coating drum 37 according to one embodiment of the present invention.

[0172] In this illustrated embodiment, the coating drum is partially immersed in a tank 28 filled with the coating composition. A stationary knife coating device 2 is provided to control the thickness of the coating layer within the coating drum.

[0173] The rotation of the coating drum in the coating composition continuously supplies a meniscus standing between the substrate and the knife. The movement of the substrate ensures the deposition of the layer as it passes the knife. The thickness of the coating layer is related to the gap size between the knife and the substrate and to some extent also to the substrate speed. Knife coating is suitable for the deposition of uniform layers over large areas and can be carried out at high speeds (>10 m / s).

[0174] A flexible film is also provided and positioned so that a distal portion of the flexible film contacts the coating surface of the coating drum 37 .

[0175] Example 6: Movable coating module In one embodiment, shown in Figure 11, the coating device 2 and the flexible film 5 are mechanically connected by an arm 29. The arm 28 is connected to a movable base 18. The movable base is movable on the ground. In one embodiment, the movable base 18 comprises one or more wheels for translational movement on the ground.

[0176] In this embodiment, the substrate 4 is fixed. In one example, the substrate is disposed on a fixed support 17.

[0177] During coating, the base 18 moves along a track such that both the coating device and the flexible film move along or across the substrate 4. In this embodiment, the "transport direction of the substrate" should be understood as the orientation of the substrate relative to the coating device 2.

[0178] Example 7: Cleaning means In one embodiment, shown in Figures 12A and 12B, the coating module comprises a cleaning means 591 for cleaning the portion 59 of the flexible film 5. In one embodiment, the cleaning means 591 comprises a foam or sponge arranged to contact the surface of the flexible film 5. One advantage is that it cleans the surface that was in contact with the coating layer of the substrate. Thus, the flexible film 5 can be reused, advantageously improving the lifetime of the coating module.

[0179] In another embodiment, the cleaning means 591 comprises a tank filled with a cleaning fluid arranged so that the flexible film passes through the cleaning fluid. Preferably, the composition of the cleaning fluid is designed to remove ink from the flexible film.

[0180] As shown in Fig. 12A, the cleaning means 591 is arranged between the distal portion 54 and the first unit 61 to wind up the flexible film. When the flexible film 5 is wound into the first unit 61, the cleaning means 591 cleans the flexible film 5. When the flexible film 5 is unwound from the first unit 61 and wound into the second unit 62, after two passes through the cleaning means, a new distal portion of the flexible film 5 is cleaned. Preferably, the coating module comprises a roller 63 for guiding the endless ribbon between the cleaning means 591 and the first unit 61.

[0181] In another embodiment, shown in Fig. 12B, the flexible film 5 is an endless flexible film forming a loop, the path of which is predetermined by the positions of several support elements 531, 532, and the cleaning means is arranged to clean a portion of the flexible film.

[0182] Preferably, the cleaning means 591 contacts a portion of said endless flexible film between the distal portion 54 and the support element 532 supporting said flexible film 5. One advantage is that cleaning the flexible film before contacting the support element is advantageous to reduce the risk of such a support element becoming soiled with ink or coating composition residues.

[0183] In one embodiment, the cleaning means 591 is embedded or fixed to the holding element 53 .

[0184] The coating module preferably comprises an additional conveyor system for driving the flexible film along a predetermined path past the cleaning means 591. The conveyor system may comprise rollers 531 and / or drive rollers 532 for driving the flexible film.

[0185] In one embodiment, the coating module comprises a controller for controlling the first and / or second unit or an additional conveyor system for controlling the passage of the flexible film 5 through the cleaning means 591 .

[0186] The process carried out According to another aspect, the invention refers to a process for coating a substrate. According to this description, the process is preferably carried out in a coating module and / or in a flexible film.

[0187] The process comprises a first step of coating an outer surface of a substrate with a coating composition, which is applied by a coating device while driving the substrate at a relative speed with respect to the coating device and / or holding element 53.

[0188] As previously discussed, coating can be done with any coating device, such as a slot die coating device, a knife coating device, an ink roller, or the like.

[0189] In a second step, the wet coating layer within the substrate is driven along a predetermined path into contact with the distal portion 54 of the flexible film 5 .

[0190] Preferably, the coating layer slides along the distal portion of the flexible film a distance of more than 5 mm, preferably a distance of more than 1 cm.

[0191] The process may further comprise a downstream step of drying, cooling, or hardening the coating layer after passing under the flexible film. Drying or solidification of the coating composition may occur after the step of sliding along the distal portion of the flexible film. This solidification is accomplished by evaporation of a solvent present in the coating composition or by cooling the coating composition below its glass transition temperature.

[0192] In one alternative embodiment, the coating device 2 and the distal portion 54 of the flexible film are driven along a predetermined path that contacts the outer surface of the substrate, in either case the substrate is moving relative to the holding elements of the coating device and / or the flexible film.

[0193] Cooling of the coating composition can be accomplished by contact of the substrate with chilled rollers or other cooling devices as previously described, including fans.

[0194] The process may further comprise a means for switching the substrate surface, with the inner surface becoming the outer surface and the outer surface becoming the inner surface with respect to the coating device, so as to coat the substrate on both sides. In this implementation, at least one flexible film may be used to smooth the relative top coating layers.

Claims

1. A coating module for coating a substrate with a coating composition, A coating device for applying a layer of coating composition to the first surface of the substrate, A flexible film comprising at least one proximal end mechanically connected to a retaining element, and a free distal portion configured to contact the layer of the coating composition on the first surface of the substrate, A coating module equipped with the following features.

2. The coating module according to claim 1, further comprising a conveyor system for supporting and transporting the substrate by a second surface of the substrate opposite to the first surface.

3. The coating module according to claim 2, wherein the conveyor system comprises support rollers.

4. The coating module according to claim 2 or 3, wherein the conveyor system comprises a temperature controller configured to heat or cool a portion of the substrate.

5. The coating module according to claim 1 or 2, wherein the flexible film further comprises openings, grooves, or fibers.

6. The coating module according to claim 1 or 2, further comprising means for applying pressure to the free distal portion of the flexible film.

7. The coating module according to claim 1 or 2, further comprising a retaining element and a frame, wherein the flexible film is fixed to the retaining element, and the retaining element is mechanically connected to the frame by one or two side ends.

8. The coating module according to claim 7, wherein the retaining element is removable from the frame.

9. The coating module according to claim 1 or 2, further comprising a source of electromagnetic radiation positioned to irradiate the coating composition beneath the free distal portion of the flexible film, wherein the flexible film is transparent to such electromagnetic radiation emitted by the source.

10. A coating system comprising a coating module according to claim 1 or 2 and a substrate, wherein the coating device is arranged to coat the surface of the substrate, and the flexible film is arranged so that its free distal portion is in contact with the coated substrate.

11. A coating system according to claim 10, wherein the substrate is an endless ribbon, A conveyor system comprising a set of rollers for transporting the substrate along a route, A printing roller for transporting a printing support in contact with at least a portion of the first surface of the substrate, A print head is positioned to thermally transfer a portion of the coating composition from the first surface of the substrate to the print support in contact with the substrate, A thermal transfer printing apparatus equipped with the following features.

12. A system for manufacturing an endless ribbon, comprising the coating system according to claim 10, wherein the substrate comprises a coating drum having a cylinder, and means for rotating the coating drum about the vertical axis of the cylinder.

13. A method for coating a substrate, To provide a coating module according to claim 1 or 2, In order to form a layer of the coating composition with the coating device, the first surface of the substrate is coated with the coating composition, and Transporting the substrate along a predetermined route such that a portion of the flexible film lies on the layer of the coating composition before it solidifies, dries, or fully hardens. A method for coating a substrate, comprising the following:

14. A method for coating a substrate according to claim 13, wherein the coating step comprises coating a first surface of the substrate with at least two parallel coating compositions separated from each other, and the coating module comprises at least two flexible films, each flexible film being arranged to overlap one layer of coating composition.

15. A method for coating a substrate, To provide a coating module according to claim 1 or 2, The coating device coats the first surface of the substrate with the coating composition, and forms a layer of the coating composition with the coating device, Transporting the coating device and the flexible film along a predetermined route such that a portion of the flexible film lies on the layer of the coating composition before it solidifies, dries, or fully hardens. A method for coating a substrate, comprising the following:

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