Thermal printing apparatus comprising a cooler

Abstract

Thermal transfer printing apparatus comprising: a frame; an endless carbon ribbon for transporting ink on its outer surface; an application device for applying ink to the endless carbon ribbon; a print head for printing by thermal transfer to a substrate using part of the ink applied to the endless carbon ribbon; a plurality of first rollers along a path from the application device to the print head and from the print head to the application device, the plurality of first rollers supporting and transporting the endless carbon ribbon by its inner surface in a circulating manner; at least one first conveyor arranged to support the inner surface of the endless carbon ribbon between two adjacent first rollers along the path from the application device to the print head; the first conveyor comprising a plate fixed in translation and rotation with the frame and having a first convexity supporting the inner surface of the carbon ribbon; a heat exchanger arranged to cool the first convexity of the plate at a first predetermined temperature.

Description

TECHNICAL FIELD

[0001] The present invention relates to a printing device system, in particular to a printing device comprising a carbon ribbon able to hold ink thereon. BACKGROUND

[0002] Current solutions involving thermal transfer printing devices use disposable already coated carbon ribbons. One limitation of these solutions is that the carbon ribbon needs to be regularly replaced when the end of the carbon ribbon has been reached. This replacement requires stopping the printer for a period of time, which is very inconvenient for some applications, for example when the printer is a labeller on a production line.

[0003] To deal with this used carbon ribbon and the remaining untransferred ink, an alternative type of thermal transfer printing device has been developed, which uses a looped carbon ribbon instead of a roll of disposable carbon ribbon.

[0004] EP3055135B1 teaches such a printing device, in which the looped carbon ribbon is transported on a roller. The printing device comprises an application device to coat the carbon ribbon with hot melt ink.

[0005] The ink layer applied to this looped carbon ribbon is renewed to ensure multiple printing: thus only one ink ribbon is continuously used and the remaining ink can be reused, thus reducing the waste of material.

[0006] The looped carbon ribbon is transported with a roller, while in the process a portion of the carbon ribbon is continuously exposed to the thermal print head and the re-inking unit, therefore, it will be able to withstand a high number of cycles, for example, through the million cycles of the system. Between the re-inking unit and the thermal print head, the ink will recover its solid state, which is possible in a cooling phase. The cooling phase is essential to provide a suitable ink layer and affects the quality of the printed data on the substrate.

[0007] US4764776 or EP0412179 disclose the ink applied on the carbon ribbon to solidify after the application. However, the cooling occurs without thermal control, therefore it is affected by environmental conditions during use, for example humidity and room temperature.

[0008] CH553662 discloses a printing system provided with a cooling unit that uses a fan to accelerate the solidification of the ink, which is placed in the vicinity of the carbon ribbon.

[0009] A first limitation of these systems is that the printing speed can be limited. Indeed, above a limited speed, the applied hot-melt ink cannot solidify or can not solidify sufficiently before reaching the print head, which can have a negative impact on the printing quality. Moreover, cooling can be reached over time, while increasing the carbon ribbon path between the applicator and the print head, thus increasing the volume of such printing device. Therefore, such printing device has a large volume in order to travel a long distance between the re-inking station and the print head to ensure the solidification of the ink, thus guaranteeing a proper printing performance.

[0010] A second limitation is that the printing process is not standardized. Depending on the environmental temperature, humidity and thermal properties of the ink, the print head should be calibrated to ensure a high quality printing. Indeed, the ink is usually sensitive to humidity and temperature: therefore, the range of inks that can be used for such system can be limited, whereby the cooling phase cannot be controlled.

[0011] A third limitation is the potential or unavoidable misalignment between the transport rollers, leading to an unequal tension on the carbon ribbon width, such unequal tension causing a potential lateral movement of the film and potential wrinkles, creases or folds.

[0012] US2004 / 135870 describes a cooling roller transversally mounted to rotate in contact with the back face of the thermal transfer film. Likewise, EP0029313 describes a cooling roller or electric refrigeration element that uses the Peltier effect to solidify the ink layer.

[0013] However, such solution cannot avoid the above-mentioned drawbacks. In particular, the solution does not provide an optimal heat transfer between the ink and the cooling roller and the solution inevitably leads to an increase of the printing device volume, since the cooling relies on the contact surface between the carbon ribbon and the roller, i.e. the solidification of the ink relies on the diameter of the cooling roller.

[0014] The present invention aims at providing a compact thermal transfer printing device overcoming the above-mentioned limitations. SUMMARY

[0015] According to a first aspect, the present invention relates to a thermal transfer printing device comprising:

[0016] - an applicator for coating an endless carbon ribbon with an ink,

[0017] - a print head for printing by thermal transfer on a substrate using a portion of the ink coated on the endless carbon ribbon,

[0018] - a transport system supporting and conveying the endless carbon ribbon containing the ink in a looped manner along a first path from the applicator to the print head and a second path from the print head to the applicator,

[0019] - at least one cooler configured to cool the applied ink on the endless carbon belt at a first predetermined temperature along a first portion of the first path of the endless carbon belt.

[0020] The cooler advantageously improves the solidification of the hot melt ink applied on the carbon belt. Another advantage is to allow the use of a shorter carbon belt and / or a higher printing speed while keeping the printing device compact. Another advantage is to ensure a fast solidification of the ink, regardless of the ambient temperature and humidity.

[0021] In an embodiment, the printing device further comprises at least one heater to heat the ink on the endless carbon belt at a second predetermined temperature along a second portion of the second path. The heater advantageously melts the ink left on the carbon belt after printing or brings it close to its melting point. The heater advantageously improves the application of the applicator on the carbon belt and the ink replacement.

[0022] In an embodiment, the printing device further comprises at least one heater to heat the ink on the endless carbon belt at a third predetermined temperature along a third portion, the third portion being located at least between the applicator and the first portion of the first path. One advantage is to improve the uniformity of the ink thickness on the band before the ink cools. One advantage is to heat the ink on the carbon belt before, during and after the application to improve the application and the thickness uniformity along the width and the length of the carbon belt.

[0023] In an embodiment, the transport system comprises a first guide element to support the carbon belt, the first guide element being connected to the cooler so as to cool the applied ink on the carbon belt supported by the first guide element. One advantage of the first guide element is to cool the ink on the carbon belt with the contact surface between the first guide element and the carbon belt, the ink passing through the carbon belt being cooled by the first guide element.

[0024] In an embodiment, the first guide element comprises a core having a cavity in which a coolant circulates so as to cool the outer surface of the core, the outer surface being arranged to support the carbon belt.

[0025] In an embodiment, the transport system comprises a first conveyor comprising a first conveyor belt to fix and convey the endless carbon belt on at least a portion of the first portion. The first conveyor belt is guided by the first guide element so that one face of the first guide element faces the conveyor belt, the first conveyor belt acting as a heat conductor when conveying the carbon belt.

[0026] In an embodiment, the printing device further comprises at least two rollers to hold and support the first conveyor belt. In an embodiment, the at least two rollers are connected to the cooler to cool the ink passing through the rollers, through the carbon belt and through the first conveyor belt.

[0027] In an embodiment, the transport system comprises a second guide element for supporting the carbon ribbon, the second guide element being connected to a heater for heating the applied ink on the carbon ribbon supported by the second guide element on the second portion. In an embodiment, the heater comprises an electrical resistance for heating the second guide element by Joule heating.

[0028] In an embodiment, the transport system comprises a second conveyor comprising a second conveyor belt for fixing and transporting the endless carbon ribbon on the second portion and / or the third portion, the conveyor belt being guided by the second guide element such that an outer surface of the second guide element faces the second conveyor belt, the second conveyor belt acting as a heat conductor when conveying the carbon ribbon.

[0029] In an embodiment, the printing device comprises at least two rollers for holding and supporting the second conveyor belt, the rollers being connected to a heater for heating the ink passing through the carbon ribbon and the second conveyor belt.

[0030] In an embodiment, the cooler comprises a heat exchanger. In an embodiment, the cooler comprises a Peltier heat pump. In an embodiment, the heat exchanger comprises a heat pipe.

[0031] In an embodiment, the first predetermined temperature is in the range of 25°C to 50°C. In an embodiment, the second predetermined temperature is in the range of 50°C to 130°C.

[0032] In an embodiment, the printing device comprises a carbon ribbon and an ink carried by the carbon ribbon arranged in its path, wherein the first predetermined temperature is lower than the melting point of the ink. In an embodiment, the second predetermined temperature is higher than the melting point of the ink. In an embodiment, the first guide element and / or the second guide element is a curved guide.

[0033] In an embodiment, the printing device further comprises a thermal controller for controlling the temperature of the ink in the carbon ribbon on a fourth portion of the carbon ribbon path, the fourth portion of the path being located between the first portion and the printhead. In an embodiment, the thermal controller heats and / or cools the ink at a third predetermined temperature.

[0034] According to a second aspect, the application relates to a method of thermally sensitive printing a substrate, comprising:

[0035] - conveying an endless carbon ribbon having ink contained thereon in a looped manner along a first path from an applicator to a printhead and a second path from the printhead to the applicator;

[0036] - applying the ink to the endless carbon ribbon by the applicator;

[0037] - thermally transferring by the printhead for printing the substrate with a portion of the ink applied on the endless carbon ribbon.

[0038] - activating a cooler to cool the coated ink on the endless carbon belt at a first predetermined temperature along a first portion of the first path of the endless carbon belt.

[0039] In one embodiment, the method comprises activating a heater to heat the carbon belt to melt the ink on the belt over a portion of the path of the endless carbon belt.

[0040] In one embodiment, the method is implemented by a printing device according to the first aspect of the application. In one embodiment, the method comprises recovering excess ink during the replacement of the portion of ink transferred onto the substrate.

[0041] According to one aspect, the application relates to a thermal transfer printing device comprising:

[0042] - a frame,

[0043] - an endless carbon belt for transporting an ink on its outer surface,

[0044] - an application device for applying the ink on the endless carbon belt,

[0045] - a print head for printing by thermal transfer of a portion of the ink applied on the endless carbon belt to a substrate,

[0046] - a plurality of first rollers along a path from the application device to the print head and from the print head to the application device, the plurality of first rollers preferably supporting and transporting the endless carbon belt by its inner surface in a looped manner,

[0047] - a plate for supporting the inner surface of the endless carbon belt between two adjacent first rollers along the path from the application device to the print head; said plate being fixed so as to not translate and rotate with the frame and optionally having a first convex surface supporting the inner surface of the carbon belt;

[0048] - a heat exchanger arranged to cool the first surface of the plate at a first predetermined temperature.

[0049] In one embodiment, the first convex surface of the plate (75) is arranged in direct contact with the endless carbon belt.

[0050] In one embodiment, the thermal transfer printing device further comprises at least two second rollers; and a conveyor belt supported by the at least two second rollers and the first surface of the plate and arranged to support and transport the endless carbon belt by its inner surface. The second rollers and the plate are arranged so that the first surface of the plate supports the endless carbon belt through the conveyor belt.

[0051] In one embodiment, the thermal transfer printing device further comprises at least one heater fixed so as to not translate with the frame and arranged to heat the first portion of the endless carbon ribbon at a second predetermined temperature.

[0052] In one embodiment, the first portion of the endless carbon ribbon comprises a coated region of the carbon ribbon, wherein the carbon ribbon is coated by or in contact with a coating device.

[0053] In one embodiment, the plate comprises a frame having a cavity in which a coolant circulates in order to cool an outer surface of the frame, the outer surface being arranged to support the carbon ribbon.

[0054] In one embodiment, the heater comprises a roller and means for heating a circumferential surface of the roller, the roller being arranged to support the inner surface of the carbon ribbon on its circumferential surface.

[0055] In one embodiment, the means for heating the circumferential surface of the roller comprise an electrical resistance or a thermal resistance to heat the second guide element by Joule heating.

[0056] According to one aspect, the application relates to a thermal transfer printing device comprising:

[0057] - a frame,

[0058] - an endless carbon ribbon for transporting ink on an outer surface thereof,

[0059] - a coating device for coating the endless carbon ribbon with ink,

[0060] - a print head for printing by thermal transfer of a substrate with a portion of ink coated on the endless carbon ribbon,

[0061] - a plurality of first rollers along a path from the coating device to the print head and from the print head to the coating device, the plurality of first rollers supporting and transporting the endless carbon ribbon by an inner surface thereof in a looped manner,

[0062] - at least one cooling roller arranged to support the inner surface of the endless carbon ribbon between two adjacent first rollers along the path from the coating device to the print head; the cooling roller comprising a shaft comprising a pipe extending through a volume of the shaft and filled with a coolant;

[0063] - a heat exchanger arranged to cool the coolant within the pipe of the cooling roller at a first predetermined temperature.

[0064] According to another aspect, the application relates to a method for thermal printing of a substrate, comprising the steps of:

[0065] - providing a thermal transfer printing device according to the application;

[0066] - preferably in a cyclic manner, conveying the endless carbon ribbon having the ink contained thereon from the coating device to the print head, and from the print head to the coating device;

[0067] - coating the outer surface of the endless carbon ribbon with the ink by the coating device;

[0068] - cooling the plate supporting the inner surface of the endless carbon ribbon to solidify the coated ink;

[0069] - thermally transferring by the print head to the substrate using the portion of the ink coated on the outer surface of the endless carbon ribbon.

[0070] In one embodiment, the method further comprises activating the heater to heat the ink on the carbon ribbon above its melting point or glass transition temperature on both sides of the coating device. BRIEF DESCRIPTION OF DRAWINGS

[0071] Figure 1 is a schematic view of a printing device according to an embodiment of the present application, the printing device comprising a cooler and a heater.

[0072] Figure 2 is a schematic view of a printing device according to an embodiment of the present application, wherein the cooler and the heater are integrated in a conveyor comprising a conveyor belt.

[0073] Figure 3 is a perspective view of a printing device according to an embodiment of the present application, wherein the frame of the printing device has been removed.

[0074] Figure 4 is Figure 3 is a cutaway plan view of the printing device of

[0075] Figure 5 is Figure 3 is another perspective view of the printing device of

[0076] Figure 6 is a schematic view of a portion of a printing device according to an embodiment of the present application, wherein the cooler comprises a curved static plate arranged in contact with the inner surface of the carbon ribbon, and further comprising a device for coating the inner surface of the carbon ribbon with a lubricant before the carbon ribbon slides along the plate.

[0077] Figure 7 is a schematic view of a printing device according to another embodiment of the present application, the printing device comprising a cooling roller.

[0078] Figure 8 is a cross-sectional view of a cooling roller according to an embodiment of the present application.

[0079] Figure 9 This is a schematic diagram of a cooling roller according to an embodiment of the present invention, the cooling roller being connected to a motor to drive the cooling roller to rotate.

[0080] Figure 10 This is a diagram illustrating the thermal cycle of ink on a ribbon along its delivery path in a thermal printing apparatus according to an embodiment of the present invention.

[0081] Figure 11 This is a perspective view of a printing apparatus according to an embodiment of the present invention, wherein the frame of the printing apparatus has been removed, and the printing apparatus includes a cooling plate in direct contact with the ribbon. Detailed Implementation

[0082] The device includes a conveying system, a printhead 6, and a coating machine 3. The device may also include a ring-shaped ribbon 5 or be configured to receive the ring-shaped ribbon 5. Figure 1 A schematic diagram of a thermal transfer printing apparatus according to an embodiment of the present invention is shown.

[0083] Painter

[0084] The printing device 1 includes a coater 3, which is set up and arranged to coat the outer surface 51 of the ribbon 5 with ink 4.

[0085] like Figure 1 As shown, the coating machine 3 is connected to the reservoir 2, which is configured to include solid ink for supplying the coating machine 3. In another embodiment, the reservoir may include liquid ink, and the reservoir may be connected to a mixing element to maintain the ink under predetermined physical conditions, such as temperature and / or viscosity.

[0086] The coating machine 3 can be positioned to contact or near the carbon ribbon 5 in order to coat the outer surface 51 of the carbon ribbon 5.

[0087] The coating machine 3 is configured to apply a liquid ink layer 4 to the outer surface of the ribbon 5, the liquid ink layer 4 preferably being uniformly distributed on the surface of the ribbon 5. An ink control unit (not shown) can ensure that a sufficient amount of ink is distributed on the surface of the ribbon 5 according to the rotation / displacement speed of the ribbon 5 and / or the printing mode.

[0088] One purpose of the ink control component is to ensure that the coating thickness on the ribbon 5 is quasi-constant, regardless of the ribbon 5's travel speed. In one embodiment, the ink control component includes an electrical input for reading the displacement speed of the ribbon 5. In this way, the ink control component can ensure a constant and uniform coating distribution over a period of time at variable speeds. In this configuration, the printing and coating sequences are synchronized.

[0089] In a first example, not shown, the coater 3 comprises a pipe containing the liquid ink, for example a slot-die coating device. The first end of the pipe is connected to the reservoir 2 and the second end of the pipe forms a coater head, the output of which is adjacent to the outer surface of the carbon tape 5, most preferably perpendicular to the outer surface of the carbon tape 5. The conduit can also comprise a tapered or parallel slit. By gravity and capillarity, the liquid ink is transported to the second end of the pipe and is coated on the outer surface of the carbon tape 5. In this example, the axis of the coating head can be parallel to the axis through which the ink is ejected from the coater 3. This axis is preferably perpendicular to the main axis of the adjacent portion of the carbon tape 5, or to the surface of the carbon tape 5.

[0090] In a second example, not shown, the coater 3 comprises a device for transporting the liquid ink from the reservoir 2 to the carbon tape 5, which can comprise an ink roller, at least partially located inside the reservoir 2 and adjacent to or in contact with the outer surface of the carbon tape 5. The ink roller transports the liquid ink from the reservoir 2 to the outer surface of the carbon tape 5 by rotation. The device can also comprise a material, at least partially located in the reservoir 2 and adjacent to or in contact with the carbon tape 5, which is capable of transporting the ink by capillarity to the carbon tape 5, which can comprise a foam or sponge material or any material capable of improving this capillarity.

[0091] The coater 3 can also be chosen from conventional coating techniques. In some other examples, not shown, the coater 3 is arranged to use any technique available to the person skilled in the art to apply the ink to the endless carbon tape, for example but not limited to blade coating, curtain coating, extrusion coating, slot die, transfer coating, aniline coating, screen printing or a combination of these techniques.

[0092] The coater 3 can be chosen in conventional printing techniques, roll-to-roll or sheet-to-sheet or roll-to-sheet. The printing technique can comprise a method using heliogravure, serigraphy, flexography, inkjet or offset, so as to apply a thin, uniform and controlled thickness of ink to the endless carbon tape. The amount of ink applied to the carbon tape depends on the technique used, the temperature of the ink during the coating process and its properties.

[0093] In both examples, the reservoir 2 and / or the coater 3 comprise heating means to melt the ink in the reservoir 2 and / or the coater 3, respectively. The reservoir 2 can be filled with solid ink, the contact of which with the reservoir 2 or the coater 3 will easily melt the ink.

[0094] In one embodiment, the printing apparatus 1 comprises means to periodically add new solid ink in the reservoir 2.

[0095] Ink

[0096] The ink used is preferably a thermoplastic composition that will melt at a temperature above its melting point. It should be understood that thermoplastic material refers to a material that can melt or hot melt and includes any material characterized by a melting point or melting temperature. Here, the term hot melt ink or ink refers to any component of a thermoplastic ink used in a thermal printer characterized by its melting point. In the process described here, the ink is melted to the right consistency or viscosity to be applied to the endless carbon ribbon. This ink can also be used with a material that is very viscous at room temperature and not adhesive when cooled.

[0097] The coating means can comprise means to melt the ink using any technique available to the person skilled in the art, such as but not limited to direct or indirect convection heating, induction heating or conduction heating. In one example, the coating means comprise a thermal resistor to melt the ink.

[0098] In a preferred embodiment, the ink composition comprises at least a colorant or pigment, optionally a natural wax, optionally a synthetic resin or a combination of the two. The ink composition optionally comprises a surfactant, optionally an organic and / or inorganic filler, and optionally a solvent. Other various surfactants and other flow aids can also be used.

[0099] This ink is characterized in that it is solid at ambient temperature and liquid at a temperature above ambient temperature. During printing, the ink is generally subjected to heating until it becomes liquid. Thus, since during printing the ink is able to quickly change from a solid state to a liquid state near the print head and the ink is able to change from a liquid state to a solid state once the ink is applied to the substrate, the transfer of the ink from the carbon ribbon to the printing substrate is ensured, whereby an image can be formed. The ink can start to solidify at room temperature.

[0100] Preferably, the melting point of the ink ranges from 50°C to 100°C

[0101] Print head

[0102] The printing apparatus 1 comprises a print head 6. In one preferred embodiment, the print head 6 is a thermal transfer print head 6.

[0103] In one embodiment, the print head has two configurations.

[0104] In a first configuration, the print head 6 is in contact with the inner surface of the ribbon 5, so as to enable thermal transfer printing of the ink located in the outer surface 51 of the ribbon 5. During this printing process, the outer surface 51 of the ribbon 5 is in contact with the substrate 20, so as to transfer part of the ink for printing the substrate.

[0105] In a second configuration, the print head 6 is not in contact with the ribbon 5. This mode can be used when the printing device is turned off or during two successive printing sequences. The alternation of the first and second modes can be configured according to the printing mode.

[0106] The printing roller 21 can be used to convey the substrate 20 in the vicinity of the ribbon 5. The thermal transfer print head 6 is preferably located in the vicinity of the substrate 20 and is used to transfer the hot melt ink 4 from the ribbon 5 to the substrate 20. The arrangement between the print head 6, the ribbon 5 and the substrate 20 can be guaranteed by mechanical parts set with precision according to the desired printing accuracy. Some guiding means and position control parts can be implemented in order to ensure a predetermined arrangement between at least the print head 6 and the ribbon 5.

[0107] The printing roller 21 ensures that there is sufficient pressure on the substrate 20 so as to maintain the substrate 20 in contact with the ribbon 5 when the printing process is performed. In this configuration, the ribbon 5 is maintained in a moving sandwich between the substrate 20 and the print head 6 during the printing process. The direction of movement of the substrate is the same as the direction of movement of the ribbon 5 in the vicinity of the print head, this movement in the vicinity of the print head being preferably a rectilinear movement.

[0108] In an alternative embodiment, the print head comprises a laser for heating the ink to pass through the thickness of the ribbon 5, so as to enable thermal transfer printing of the ink located on the outer surface 51 of the ribbon 5. Preferably, the wavelength of the laser is between 950 nanometers and 1450 nanometers.

[0109] The ribbon

[0110] The ribbon 5 of the printing device 1 allows the ink 4 to be conveyed from the coater 3 to the print head 6 on its outer surface 51. The ribbon 5 preferably forms a loop, in this configuration, the remaining ink not used during the printing process passes through the print head and is conveyed to an ink recovery device (not shown). Thus, preferably in a cyclic manner, the same ribbon 5 is successively used to convey the ink for printing and to convey the remaining ink after printing. The printing process is implemented to form a continuous cycle in which the remaining ink is automatically recovered, this configuration allows to recover the ink that has not been printed, this ink can advantageously be reused on the next turn of the ribbon 5.

[0111] In other words, in a continuous cycle, i.e. in a loop, the carbon tape 5 is transported along a path comprising a first path from the coater 3 to the print head 6 and a second path from the print head 6 to the coater 3. On its first path, the carbon tape 5 supports freshly applied ink. On its second path, the carbon tape 5 supports and transports the portion of ink that has not been printed by the print head 6.

[0112] One advantage of the present invention is to provide an autonomous printing device in which at least a portion of the ink is used, preferably 100% or substantially 100% of the ink is used, i.e. there is no ink loss.

[0113] The carbon tape 5 can be made of various materials. The carbon tape 5 is preferably made of a material having high temperature resistance (e.g. resistant to temperatures up to 300°C) and high chemical resistance (e.g. resistant to alcohol, ink or solvents, etc.). Preferably, the carbon tape 5 is made of polyimide which allows the carbon tape to be used at temperatures up to [340°-380°] without deforming. In a preferred embodiment, the carbon tape 5 can also be made of a metal or a metal alloy. The carbon tape can be made of a metal alloy, for example stainless steel, aluminum alloy, titanium alloy, copper alloy, beryllium alloy. In one embodiment, the carbon tape can comprise an alloy containing nickel, tin and copper, preferably the content of nickel is between 14.5% m and 15.5% m, the content of tin is between 7.5% m and 8.5% m, the content of copper is between 75% m and 79% m.

[0114] The carbon tape 5 is preferably made of a material having a heat transfer rate greater than 0.120 W / mK.

[0115] The thickness and composition of the carbon tape material are set to produce heat transfer through the carbon tape, thereby enabling printing.

[0116] Preferably, the thickness of the carbon tape is less than 50 pm or 20 pm. This thickness advantageously allows the thermal resistance between the inner and outer surfaces thereof to be at a low level, thereby improving the quality of printing. The thickness of the carbon tape 5 can be substantially between 0.5 pm and 50 pm, most preferably between 0.5 pm and 20 pm. In one example, the thickness of the carbon tape 5 is selected in the range [3-25 pm] or [5-10 pm].

[0117] In one embodiment, the print head 6 comprises a laser, the carbon tape 5 being transparent at the wavelength of the laser. In this embodiment, the thickness of the carbon tape 5 is selected in the range [3-200 pm].

[0118] Cooler

[0119] According to the application, the printing device 1 comprises at least one cooler 72 configured to cool the applied ink 4 on the endless carbon ribbon 5 in a first portion of the path of the carbon ribbon 5. The first portion is preferably set along a portion of the first path of the carbon ribbon 5 from the applicator 3 to the print head 6. The cooler 72 advantageously improves the solidification of the ink 4 after application. Thanks to the cooler 72, the ink 4 in the vicinity of the print head 6 advantageously recovers its solid state, thus improving the print quality by thermal transfer. Indeed, the print head 6 melts a portion of the ink 4 to be printed on the substrate 20, cooling the ink 4 at a predetermined temperature before reaching the vicinity of the print head improves the print precision.

[0120] The cooler 72 is preferably configured to cool the ink 4 at a predetermined temperature. Preferably, the cooler is set to cool the ink on the carbon ribbon at a temperature lower than the melting temperature of the ink.

[0121] The cooler 72 can be an active cooler. An active cooler comprises a device supplied by an alimentation to generate cooling. An active cooler does not comprise a common fan for extracting heat outside the system, such a fan only transports heat by convection, without generating cold and without generating the expected effect of cooling the ink at a predetermined temperature. The cooler 72 can be arranged to cool the ink 4 passing through the carbon ribbon 5.

[0122] In a first embodiment, the cooler 72 comprises at least one thermoelectric material, preferably a thermoelectric material exhibiting the Peltier effect. A thermoelectric material exhibiting the Peltier effect generates a heat flow from an electric current, removing heat at one junction when the electric current flows through the junction between two conductors. The cooler 72 can comprise a Peltier heat pump. A Peltier heat pump comprises a plurality of junctions in series through which the electric current is driven. Due to the Peltier effect, some junctions lose heat while others gain heat. The Peltier heat pump is arranged in such a way that the junctions losing heat are arranged to cool the ink in the carbon ribbon, preferably the ink passing through the carbon ribbon.

[0123] In a second embodiment, the cooler 72 comprises a heat exchanger arranged to cool the ink in the carbon ribbon, preferably the ink passing through the carbon ribbon. The heat exchanger can comprise a circulating fluid (also called coolant) through a radiator coil and air flowing through the coil, thus cooling the coolant and heating the incoming air. The coolant cooled by the radiator is driven to cool the ink, preferably the ink passing through the carbon ribbon. The heat exchanger can comprise a fan to improve the air flow in contact with the radiator, thus cooling the coolant.

[0124] The first and second embodiments can be combined to cool the ink 4 on the carbon ribbon 5, preferably the ink passing through the carbon ribbon 5.

[0125] Heater

[0126] According to one embodiment, the printing apparatus comprises at least one first heater 82 configured to heat the ink on the ribbon along a second portion of the path of the ribbon 5. The second portion extends over at least a portion of the second path of the ribbon. The heater 82 advantageously melts or brings the residual ink 4 after printing on the ribbon 5 to its melting point. The first heater 82 advantageously improves the coating and replacement of the ink 4 on the ribbon by the applicator 3. Preferably, the first heater 82 is configured to heat the ink on the ribbon over the second portion at or above a second predetermined temperature.

[0127] In one embodiment, the first heater 82 is further configured to heat the ink on the ribbon along a third portion of the path of the ribbon 5. In an alternative embodiment, the printing apparatus comprises a second heater 84 configured to heat the ink on the ribbon along a third portion of the path of the ribbon 5. The third portion preferably comprises the coating area in which the ribbon 5 is coated with ink by the applicator 3.

[0128] In one embodiment, the third portion extends over at least 2 cm of each portion of the coating area. Preferably, the third portion extends along a length of less than 10 cm.

[0129] Preferably, the first heater 82 and / or the second heater 84 are configured to heat the ink on the ribbon over the third portion above a third predetermined temperature. In one embodiment, the second predetermined temperature and the third predetermined temperature are equal. Preferably, the third predetermined temperature is higher than the second predetermined temperature. The third predetermined temperature is preferably higher than the melting point of the ink.

[0130] In this embodiment, heating the third portion advantageously causes the ink 4 to flow to improve the uniformity of the thickness of the ink on the ribbon before the ink cools. In Figure 1 and Figure 2 In one embodiment as shown, the first heater or the second heater is arranged to heat the ink on the ribbon over the portion extending from both sides of the applicator. One advantage is to heat the ink 4 on the ribbon before, during and after coating to improve the coating and the uniformity of the thickness along the width and the length of the ribbon 5. The heater 82 can comprise several devices each configured to heat the ink over the second portion or the third portion.

[0131] The heater 82, 84 can comprise an electrical resistance to heat the ink 4 passing through the ribbon 5 by Joule heating. In another embodiment, the heater comprises a heating device to heat the ink on the ribbon 5 by radiation.

[0132] In this embodiment, first, the ink on the carbon tape 5 is heated before reaching the coater (and optionally after reaching the coater) and, second, the ink on the carbon tape 5 is cooled by a cooler before the printing step to provide solid ink and improve the printing quality.

[0133] In one embodiment, the second portion and the third portion are adjacent.

[0134] Conveying system

[0135] A conveying system is used to hold and transport the carbon tape 5. The conveying system supports and transports the carbon tape 5 in a loop along the path from the coater to the print head. The conveying system supports and transports the endless carbon tape along a first path from the coater to the print head and a second path from the print head to the coater.

[0136] As Figure 1 illustrated, the conveying system can comprise at least one roller 9 to hold and transport the endless carbon tape 5. The conveying system can comprise a plurality of rollers 9 to hold and transport the endless carbon tape 5 along its path.

[0137] The roller 9 has a cylindrical shape. The roller is connected to the frame 12 and has at least one rotational degree of freedom along the longitudinal axis of the cylinder of the roller. Preferably, the longitudinal axis of the roller is substantially perpendicular to the surface of the frame in contact with the roller 9, so that the roller 9 is mechanically connected to the frame. In one embodiment, the at least one roller 9 is connected to the frame with at least one translational degree of freedom. Preferably, the at least one roller 9 is free to translate with respect to the frame along a plane substantially perpendicular to the longitudinal axis of the cylinder of the roller.

[0138] The at least one roller 9 can be a drive roller connected to a motor to rotate the drive roller. At least one battery or electrical alimentation can be implemented in the printing device to power the motor. The rotation of the drive roller generates the displacement of the endless carbon tape 5 along its path, which also causes the rotation of the other rollers.

[0139] First embodiment: cooling roller

[0140] In Figure 7 , Figure 8 and Figure 9In the first embodiment shown, the cooler 82 is arranged to cool at least one roller 100, preferably the roller 100 arranged on the first portion. For example, a thermoelectric material can be integrated in or in contact with a roller 100 that supports the carbon ribbon 5 in the first portion of the path of the carbon ribbon 5. Then, the roller 100 is cooled so that the ink 4 passing through the carbon ribbon 5 on the first portion of its path is cooled. In another example, a heat exchanger is arranged to direct a coolant to cool the roller 100. The roller 100 is preferably made of a material comprising a high thermal conductivity. The roller 100 can be made of a metal, for example aluminum or copper or an alloy of these metals. One advantage is that the thermal transfer from the coolant to the roller and from the roller to the carbon ribbon is improved.

[0141] The cooling roller 100 is arranged to contact and support the inner surface 52 of the carbon ribbon 5. In one embodiment, the cooling roller is arranged and disposed to support the carbon ribbon 5 through the inner surface 52 along an angle A greater than 100°, preferably greater than 120°, which can be adjusted by changing the position and / or diameter of the two adjacent rollers 9 on either side of the cooling roller. In one embodiment, the diameter of the cooling roller portion is greater than 50 mm, preferably greater than 70 mm

[0142] The angle A, in combination with the diameter of the cooling roller 100, advantageously allows a longer contact area between the cooling roller 100 and the carbon ribbon 5, improving the cooling and solidification of the ink 4 coating on the carbon ribbon.

[0143] One advantage of using a cooling roller 100 instead of a static plate 75 as previously described is that the carbon ribbon does not slide along the roller. The roller can be driven in rotation by a motor or by the carbon ribbon itself by clamping the circumferential surface of the cooling roller and the carbon ribbon.

[0144] The cooling roller 100 is preferably connected to the cooler 72 comprising a heat exchanger for the guide element as described below.

[0145] Reference is now made to Figure 8 and Figure 9 Embodiments of such a cooling roller are described.

[0146] The cooling roller 100 comprises a shaft 101 made of a high thermal conductivity material, for example a metal (e.g. an aluminum alloy).

[0147] The shaft 101 comprises at least one duct 103. The duct 103 extends along the volume of the shaft and is fluidically connected to the coil 73 of the heat exchanger. Then, the coolant is cooled by the radiator 76 and reinjected into the duct 103 of the shaft 101 to cool the shaft 101. In one embodiment, the diameter of the duct 103 ranges from 5 to 20 mm. In one embodiment, the length of the duct 103 ranges from 150 to 400 mm.

[0148] The cooling roller 100 further comprises a rotor 102, which is free to rotate around the shaft 101. The outer surface of the rotor supports the carbon tape 5.

[0149] The cavity between the shaft 101 and the rotor 102 is preferably filled with a lubricant, for example silicon oil. One advantage is to reduce the friction between the shaft 101 and the rotor 102. Another advantage is to improve the heat conduction between the shaft 101 and the rotor 102.

[0150] In one embodiment, the cooling roller 100 comprises a sealing ring 104 between the shaft 101 and the rotor 102, to avoid the leakage of the lubricant in the cavity during the rotation of the rotor 102.

[0151] In one embodiment, the printer further comprises a motor 110, which is arranged and configured to drive the rotation of the rotor 102 of the cooling roller 100.

[0152] The motor can be connected to a controller. In one embodiment, the controller is configured to control the rotation speed of the motor 110 as a function of the rotation speed of the drive roller.

[0153] In Figure 9 In the embodiment shown, the motor 110 comprises a driving pulley 114 and the rotor 102 of the cooling roller 100 comprises a driven pulley 112. The printer further comprises a belt 111 to transmit the rotation of the driving pulley 114 to the driven pulley 112 and thus to the rotor 102 of the cooling roller. In one embodiment, the system further comprises a tensioner 113, which is arranged to ensure the tension of the belt and to increase the contact angle between the belt 111 and the driving and / or driven pulleys 114, 112.

[0154] Second embodiment: cooling plate

[0155] In Figure 1 and Figure 11 In the second embodiment shown, the conveyor comprises a first guiding element, which can comprise a static support element, which is preferably arranged between two adjacent rollers 9. This static support element is preferably a plate, for example a metal plate or sheet. The carbon tape 5 slides along its length on the first guiding element 75, for example a metal plate. In the following description, the term "plate" will be used to design the first guiding element 75. The plate preferably comprises an element comprising a volume which is at least 5 times smaller than the second dimension or the first dimension. The plate can also comprise a segment.

[0156] A part of the plate is arranged in contact with the inner side of the carbon tape 5 to cool the ink passing through this carbon tape. The metal plate is preferably made of aluminum or an aluminum alloy to improve the heat conduction.

[0157] Preferably, the plate is a static support element with respect to the frame 12. Preferably, the plate is mechanically connected to the frame with 0 degrees of freedom, the plate and the frame being fully connected together, such a connection being sometimes called an interlocking connection. In other words, the frame 12 and the plate cannot move with respect to each other. This connection between the frame 12 and the plate 75 can be direct (for example, by direct contact) or can be indirect (for example, the plate 75 and the frame are both fully connected to an intermediate or auxiliary element).

[0158] In one embodiment, the first guiding element comprises a lubricant between the plate 75 and the carbon ribbon 5 to improve the sliding of the carbon ribbon on the plate. In one embodiment, the lubricant can comprise a liquid oil, which advantageously allows lubrication and electrostatic discharge from the carbon ribbon towards the ground frame or from the plate towards the ground frame.

[0159] In Figure 6 In the illustrated embodiment, the cooler comprises an absorbent material 63 arranged to retain or absorb oil or other lubricant thereon. The absorbent material 63 is arranged in contact with the inner surface 52 of the carbon ribbon 5, preferably between the applicator and the plate 75. The absorbent material 63 is intended to be soaked with lubricant. To this end, the printer further comprises a reservoir 61 for filling with lubricant, for example liquid oil, and means for delivering this lubricant from the reservoir 61 to the absorbent material 63. The means can comprise a duct 62 fluidically connecting the reservoir 61 to the absorbent material 63, the absorbent material 63 being preferably fixed so as to translate with the frame.

[0160] In one example, the absorbent material comprises a sponge-like material, a fabric or cotton. Thus, the absorbent material is able to supply lubricant on the inner surface of the carbon ribbon before the carbon ribbon slides on the plate. One advantage is to reduce the damage to the carbon ribbon due to friction between the carbon ribbon and the plate during the sliding. Thus, the life of the carbon ribbon is improved.

[0161] The first guiding element 75 is arranged for guiding the moving carbon ribbon 5 along a predetermined path, for example a curved path. The first guiding element 75 is a circular guide supporting the carbon ribbon 5.

[0162] A first advantage of the circular or curved shape of the plate 75 is to reduce the friction force generated on the carbon ribbon 5 at the contact point 65 between the carbon ribbon 5 and the plate 75, indeed, such a shape ensures that the carbon ribbon does not rub against the edges of the plate. A second advantage is that this curved shape further ensures the contact between the carbon ribbon and the plate and reduces the risk of air bubbles being inserted between the carbon ribbon and the plate. Thus, the thermal conduction between the carbon ribbon and the plate is advantageously improved.

[0163] To this end, the plate 75 has an outer surface, for supporting the inner surface of the carbon ribbon, which is convex.

[0164] In one embodiment, the radius of curvature of the convexity is greater than 2 cm.

[0165] In one embodiment, the length of the first surface of the plate 75 is between 2 cm and 20 cm.

[0166] In one embodiment, the first guide element 75, for example the plate, is connected to a cooler 72 in order to cool the coating ink 4 on the carbon ribbon 5 supported by the first guide element 75. As mentioned above, the first guide element 75 can be cooled by a thermoelectric material, the point of which the thermoelectric material dissipates heat can be in contact with one face of the guide, preferably the face opposite the face in contact with the carbon ribbon 5. In another embodiment, a coolant of a heat exchanger is driven through the first guide element 75 in order to cool it. In one embodiment, the first guide element comprises a core having a cavity in which a coolant circulates in order to cool the outer surface of the core, which is arranged to support the carbon ribbon 5. The first guide element 75 is then arranged to cool the portion of the carbon ribbon 5 supported by the first guide element 75, preferably along a first portion of the path of the carbon ribbon 5. The cooler 72 can comprise a Peltier element.

[0167] One advantage of the first guide element 75 is to cool the ink on the carbon ribbon using the contact surface between the first guide element 75 and the carbon ribbon 5. The ink 4 passing through the carbon ribbon is cooled by the first guide element 75.

[0168] In Figure 1 In one embodiment as illustrated, the transport system can comprise a second guide element 85 arranged to guide the mobile carbon ribbon along the predetermined path in the same way as the first guide element 75. The second guide element 85 can be connected to the first heater 82 and / or to the second heater 84 in order to heat the ink 4 on the carbon ribbon 5 supported by the second guide element 85. The second guide element 85 is arranged to fix and support the carbon ribbon along a second portion of the path of the carbon ribbon 5 and / or along a third portion of the path of the carbon ribbon. Preferably, as illustrated, the second guide element 85 is arranged to be in contact with the carbon ribbon 5 on portions extending from both sides of the coater 3. Resistances can be integrated inside the second guide in order to heat the ink 4 by the carbon ribbon 5 and by the walls of the second guide element 85. Figure 1

[0169] One advantage of the cooling plate being in direct contact with the carbon ribbon is that this configuration allows to reduce the volume of the printing device compared to a cooling roller. Indeed, in order to cool as much ink as the plate, a cooling roller would need to have a large diameter, resulting in an increase of the volume of the entire printing device. Even if a cooling roller is used instead of a cooling plate to shorten the path length of the carbon ribbon, the burden of the roller would be greater than the burden of the plate.

[0170] ​In one embodiment, the plate 75 is removable from the frame 12. The plate 75 can also be partially detached from the frame 12, for example, to facilitate the positioning of the carbon ribbon along its path.

[0171] Third embodiment: cooling the conveyor belt

[0172] In Figure 2 In the alternative embodiment illustrated, the transport system comprises at least one first conveyor 7 comprising a conveyor belt 71.

[0173] The conveyor belt 71 is arranged and designed to fix and transport the carbon ribbon 5 by its inner surface at least along a first portion of the path of the carbon ribbon. The first conveyor belt 71 implements the same function as the continuous track, which drives the carbon ribbon 5 in one rotation direction. In one embodiment, the conveyor belt 71 comprises a parallelogram form, which is annular so as to form a carbon ribbon support.

[0174] The inner surface of the carbon ribbon 5 is fixed on the outer surface of the conveyor belt 71. In the example illustrated, the inner surface of the carbon ribbon 5 is fixed on the outer surface of the conveyor belt 71 by means of an adhesive. Figure 2 In one example, the conveyor belt 71 is supported by at least two rollers 11. In another example, the conveyor belt 71 is supported by three rollers 11, for example to form a triangle or a prism.

[0175] The conveyor belt 71 supports a portion of the carbon ribbon 5 during its movement, reducing the tension along the carbon ribbon 5. This support function of the conveyor belt 71 aims to better distribute the tension exerted on the carbon ribbon 5.

[0176] By "a portion of the carbon ribbon" is meant a portion of the carbon ribbon over a portion of the path of the carbon ribbon.

[0177] One advantage of the conveyor belt 71 is that the carbon ribbon 5 is transported along the distance between the two rollers 11 without undergoing mechanical deformations.

[0178] In the preferred embodiment, the carbon ribbon 5 is transported along this distance on a circular surface of the conveyor belt 71. Indeed, a circular surface comprising a maximum radius of curvature allows to reduce the friction between the belt and the carbon ribbon and also allows to reduce the vertical force exerted on the carbon ribbon. In this configuration, the circular surface of the conveyor can be arranged so as to maximize the radius of curvature of the carbon ribbon 5.

[0179] The conveyor 7 advantageously minimizes the stresses on the carbon ribbon 5, which improves the lifetime of this carbon ribbon 5. Moreover, minimizing the stresses on the carbon ribbon 5 allows to avoid the creation of a corrugated profile on the carbon ribbon 5. Furthermore, the use of a conveyor belt 71 reduces the risk of wrinkling and mispositioning of the carbon ribbon 5.

[0180] The conveyor belt 71 may include a plastic belt arranged around at least two rollers 11. In other embodiments, the conveyor belt 71 may be made of any flexible material, such as an elastomer, thermosetting resin or thermosetting plastic (e.g., polyimide), cork belt or metal sheet (e.g., stainless steel).

[0181] These rollers 11 transport conveyor belt 71 around a path that includes a portion in which conveyor belt 71 transports carbon belt 5 along a portion of the path of carbon belt 5.

[0182] In one embodiment, a first conveyor 7, including a first conveyor belt 71, is connected to a cooler 72, the first conveyor belt 71 fixing and supporting the carbon ribbon on a first portion of the carbon ribbon path. In another embodiment, rollers 11 of the first conveyor 7 are connected to the cooler 72.

[0183] In another embodiment, the first conveyor 7 includes a first guide element 75, the first guide element 75 being coupled with... Figure 1 The first guide element guides the carbon ribbon 5 along a predetermined path in the same way as the first guide element 75. In particular, the portion of the first conveyor belt 71 carrying the carbon ribbon 5 is supported by the first guide element 75. The first guide element 75 may be a partially circular guide element.

[0184] The first guiding element may include a plate as described in the first embodiment, wherein the convex surface of the plate indirectly supports the carbon belt 5 dragged by the conveyor belt 71.

[0185] The first guide element 75 may preferably be connected to a cooler 72 to cool the coating ink 4 passing through the first conveyor belt 71 and the carbon ribbon 5. In this embodiment, the first conveyor belt 1 is preferably made of a material with high thermal conductivity, such as a metal, preferably aluminum or copper or an alloy of these metals. The first guide element 75 may be in a similar manner to... Figure 1 The first guide element is connected to the cooler in the manner described in the description.

[0186] Similarly, the conveying system may include a second conveyor 8, which includes a second conveyor belt 81 that secures and conveys the ribbon 5 at least on a second portion and / or a third portion of the path of the ribbon 5. The second conveyor belt 81 may include a second guide element 85 connected to a heater 82. The second guide element 85 may be arranged to heat the ink 4 on the ribbon 5 on the second portion of the path of the ribbon 5. The rollers of the second conveyor 8 may also be connected to the heater 82 in the same manner as the rollers 11 and cooler 72 of the first conveyor 7. The heater 82 may include at least one resistor configured to heat the conveyor belt 81 by Joule heating. The at least one resistor may be disposed inside or in contact with the rollers of the second conveyor 8 or disposed inside or in contact with the second guide element 85.

[0187] In one embodiment, the second and third portions are adjacent and the heaters 82, 84 are configured to heat the ink on the carbon ribbon along the portion of the point at which the carbon ribbon is coated by the coater 3.

[0188] In one embodiment, the first heater 82 and / or the second heater 84 are connected to the rollers 9 of the transport system and / or the rollers 11 supporting the conveyor belt 71.

[0189] Reference is now made to Figures 3 to 5 A preferred embodiment of a printing apparatus is described.

[0190] The printing apparatus 1 comprises a coater 3 and a print head 6, the coater 3 coating an endless carbon ribbon 5 to produce a layer of ink on one side of the carbon ribbon 5.

[0191] The coater 3 can be arranged to apply a layer of ink on the carbon ribbon 5 having a thickness of 1 to 8 microns. Preferably, the coater is arranged such that the thickness of the applied layer of ink is substantially uniform along the width and length of the carbon ribbon 5.

[0192] The print head 6 is arranged to transfer at least a portion of the ink 4 on the carbon ribbon 5 to a substrate 20 by thermal transfer printing.

[0193] The transport system ensures that the ribbon 5 moves along a path, thereby carrying the ink 4 from the coater 3 to the print head 6 in a first path and from the print head 6 to the coater 3 in a second path in a looped manner. The transport system comprises a plurality of rollers 9 to hold and convey the carbon ribbon 5. The transport system can further comprise a spring-loaded tension roller 10. The spring-loaded tension roller 10 can be connected to a linear slide. The spring-loaded tension roller 10 comprises a spring element loaded and arranged to push or pull the roller 10 along the linear slide to maintain a mechanical tension on the carbon ribbon. In one embodiment, the spring-loaded tension roller 10 is a drive roller.

[0194] The transport system can further comprise a first conveyor 7 comprising a conveyor belt 71, the conveyor belt 71 of the first conveyor 7 being arranged to hold and convey the carbon ribbon 5 at least along a first portion of the path of the carbon ribbon 5. The first portion of the path of the carbon ribbon is in the first path of the carbon ribbon 5 from the coater 3 to the print head 6, at which the carbon ribbon carries fresh ink to the print head 6. The first conveyor 7 comprises three rollers to hold and convey the conveyor belt 71.

[0195] The first conveyor 7 comprises a first guide element 75 to hold and convey the portion of the conveyor belt 71 holding and conveying the carbon ribbon 5. The first guide element 75 indirectly holds and conveys the carbon ribbon 5 at least along the first portion of the path of the carbon ribbon 5 through the conveyor belt 71.

[0196] Cooler examples

[0197] As shown, the first guide element 75 is connected to a cooler 72. In this example, the cooler 72 comprises a heat exchanger arranged to cool the first guide element 75. The cooler 72 comprises a heat sink 76 to cool the coolant of the heat exchanger. The heat exchanger can also comprise a condenser 74, the heat sink 76 being arranged to cool the condenser 74.

[0198] In one embodiment, the coolant is an alcohol solvent, which has the advantage of having a low boiling point. In this embodiment, the coolant boils in contact with the first guide element 75, resulting in a large heat loss from the first guide element 75. In the condenser, the coolant is returned to a liquid form.

[0199] In Figure 5 In the example shown, the heat exchanger comprises a coil 73 to direct the coolant between the first guide element 75 and the condenser 74. In one embodiment, the rollers 11 of the first transport system are also connected to the cooler 72 to improve cooling of the ink 4.

[0200] In one embodiment, the coil 73 is a heat pipe.

[0201] The heat pipe comprises an evaporator portion contained in the first guide element 75 and a condenser portion contained in the condenser 74.

[0202] Heat applied from the outside to the evaporator portion is conducted through the walls of the heat pipe and the wick structure, which causes the coolant to evaporate. The resulting vapour pressure drives the vapour through the pipe via an adiabatic section to the condenser 74, where the vapour condenses against the latent heat of its evaporation to the heat sink provided. The capillary pressure generated by the menisci in the heat pipe pumps the condensed coolant back to the evaporator portion. Thus, the heat pipe can continuously transport the latent heat of vaporization from the first guide element 75 to the condenser 74 without any mechanical pumping device, as long as there is sufficient capillary pressure to drive the condensed coolant back to the evaporator, the process continues. The operating conditions of the orientation and structure of such heat pipes are well known to the person skilled in the art.

[0203] The heat pipe advantageously allows the volume of the heat exchanger to be reduced. The condenser 74 can be cooled to continue condensing the coolant using the heat sink 76 and / or a Peltier heat pump. The heat pipe also advantageously allows any mechanical pumping device for transporting the coolant to be avoided.

[0204] The cooler 72 can also be used to cool the plate 75 described in the second embodiment of the application or the cooling roller 100 described in the first embodiment of the application.

[0205] The cooler 72 is configured to cool the ink 4 at a predetermined temperature by the conveyor belt 71 and the carbon ribbon 5. The advantage is to cool the ink 4 at least below its melting temperature, in this way, the ink 4 reaching the carbon ribbon 5 under the printhead 6 will be in solid state, regardless of the ambient temperature of the printing device used.

[0206] Preferably, the conveyor belt 71 comprises a metal sheet to advantageously increase the thermal conductivity between the ink 4 and the first guiding element 75. Preferably, the carbon ribbon 5 has a thickness less than 30 pm or 25 pm to advantageously increase the thermal conductivity between the ink 4 and the first guiding element 75.

[0207] In one embodiment, when the thickness of the ink layer on the carbon ribbon is in the range of 2 to 7 pm and the thickness of the carbon ribbon composed of polyimide is in the range of 5 to 25 pm, the power applied to cool the ink can be between 1500 and 6000 Watt / m at a carbon ribbon speed of 1 m / s.

[0208] Additional transport system to heat the ink

[0209] In one embodiment, the transport system further comprises a second conveyor 8 comprising a second conveyor belt 81. The second conveyor belt 81 fixes and transports the carbon ribbon 5 on a second portion of the carbon ribbon 5 path. Preferably, the second portion of the carbon ribbon path comprises at least a portion of the second path of the carbon ribbon, in other words, the second conveyor belt 81 fixes and transports the carbon ribbon 5 at least on a portion of the path from the printhead 6 to the applicator 3. The second conveyor belt 81 can also fix and transport the carbon ribbon 5 on a third portion of the carbon ribbon 5 path. Preferably, the third portion of the carbon ribbon path comprises at least a portion of the second path of the carbon ribbon, in other words, the second conveyor belt 81 fixes and transports the carbon ribbon 5 at least on a portion of the path from the applicator 3 to the first portion cooled by the cooler.

[0210] The second conveyor 8 comprises at least one second guiding element 85 and / or a roller holding and transporting the second conveyor belt 81 connected to a heater 82. The heater 82 is configured to heat the ink 4 at a second predetermined temperature. Preferably, the second predetermined temperature is higher than the melting point of the ink 4. Melting the ink flow before reaching the applicator 3 advantageously allows the ink on the carbon ribbon 5 to melt and flow to improve the uniformity of the ink layer on the carbon ribbon after coating. This heating further improves the recovery of the remaining ink before coating (not shown).

[0211] The heater is configured to heat the carbon ribbon on the second and / or third portion of the carbon ribbon path. The second portion can also comprise the portion of the carbon ribbon 5 coated by the coater, which advantageously allows heating the ink 4 on the carbon ribbon 5 during the coating process to improve the uniformity of the ink layer on the carbon ribbon 5. Indeed, said heating avoids the rapid solidification of the ink 4 in contact with the carbon ribbon 5 and reduces the viscosity of the ink 4, thereby allowing the ink to spread uniformly on the surface of the carbon ribbon. In one embodiment, the third portion comprises a portion of the first path of the carbon ribbon extending from the coater, which advantageously allows heating the ink immediately after the coating process to further improve the uniformity of the ink thickness on the carbon ribbon. In other words, as Figure 3 shown, the heating device can be arranged to heat the ink on the carbon ribbon in a portion of the carbon ribbon path located before and after the coater 3 and before the portion cooled by the cooler 72.

[0212] In one embodiment, the printing device 1 can comprise a frame 12 comprising the coater 3, the printhead 6 and the path of the carbon ribbon 5. The frame 12 comprises at least one aperture 15 serving as an outlet for the printed substrate 20. In one embodiment, the printing device 1 further comprises a partition wall 14 arranged to separate the first portion of the cooled carbon ribbon path and the second and / or third portion of the heated carbon ribbon path. The partition wall 14 can comprise an aperture for the passage of the carbon ribbon 5. As Figure 4 shown, the partition wall 14 can extend from the frame 12 of the printing device 1. The partition wall 14 isolates the coater 3 and the heater 82 from the first portion of the carbon ribbon path in which the ink is cooled by the cooler 72. One advantage is to contain the heat provided by the heater 82 and the coater 3, in such a way that the power applied to the cooler 72 to cool the ink 4 to the first predetermined temperature can be reduced. The partition wall 14 can be made of an insulating material. In one embodiment, the partition wall 14 comprises mineral wool.

[0213] In one embodiment, the printing device 1 comprises two printing rollers 21 to guide the substrate 20 to the printhead 6. As shown, the printing device 1 further comprises a third guide element 22 to secure and transport the substrate 20 and the carbon ribbon 6 and to transport the substrate 20 and the carbon ribbon 6 along a predetermined length to the printhead 6.

[0214] In one embodiment, the printing roller 21 and / or the third guide element 22 are connected to a heater and / or a cooler to control the temperature of the ink 4 on the fourth portion of the first path, the fourth portion being located on the first path of the ribbon, preferably between the first portion and the print head. In one embodiment, the fourth path extends from the print head along a predetermined length of the first path of the ribbon 5, which allows to provide an ink at an optimal temperature to ensure a high quality printing by thermal transfer. In a preferred embodiment, the cooler and / or the heater controlling the temperature are intended to control the temperature of the ink 4 at a third predetermined temperature determined to be a few degrees below the melting point of the ink, which advantageously allows to reduce the energy to be transferred to ensure thermal transfer and to increase the printing speed without loss of printing quality.

[0215] Cooling parameters

[0216] In one embodiment, the length of contact between the cooling plate 75, the conveyor belt 71 or the length between the cooling roller 100 and the ribbon 5 is greater than 15% of the first path of the ribbon 5 from the coating device 3 to the print head 6. In one embodiment, the length of contact between the ribbon 5 and the cooling plate 75, the conveyor belt 71 or the cooling roller 100 is in the range of 5 to 30 centimeters. Preferably, the circumference of the cooling roller or the length of the conveyor belt is in the range of 10 to 60 centimeters.

[0217] Figure 10 The graph shown in Figure 2 illustrates the temperature level of the coated ink on the ribbon along the ribbon transport (the graph is not drawn to scale).

[0218] In a first step E, the ink on the ribbon is heated on both sides of the coating device B along a distance corresponding to the third portion of the path of the ribbon. In this portion, the ink is heated at a second predetermined temperature T2 higher than the melting point TF of the ink. In one embodiment, the second predetermined temperature T2 is higher than the glass transition temperature of the ink.

[0219] In one embodiment, the printing device comprises a support roller arranged and disposed to support the ribbon along a portion of the path comprising the coating area. Preferably, the roller comprises a heating device to heat the ribbon in contact therewith.

[0220] In a second step, the ink on the ribbon reaches a portion of the path of the ribbon where the ink is cooled. The portion C corresponds to the portion of the ribbon in contact with the plate 75, the conveyor belt 71 or the cooling roller 100. At the end of this portion C, the temperature of the ink drops to a first predetermined temperature T1 lower than the melting point TF of the ink, preferably 20°C lower than the melting point TF of the ink.

[0221] In a third step, the ink is locally heated in a zone D in the vicinity of the print head to thermally transfer the ink from the ribbon 5 onto the substrate 20. Thus, the ink in this zone D is heated above its fusion point TF to perform the thermal transfer. In this zone D, the ink can be heated above or below the second predetermined temperature T2.

[0222] Then, the remaining ink on the ribbon is transported from the print head to the coating device B to perform a recoating as described in the first step.

[0223] One advantage of the cooling plate being in direct contact with the ribbon is that the temperature of the ink is more easily controlled.

[0224] Another advantage of the application is to better control the solidification of the coated ink. The application advantageously allows to reduce the length of the ribbon between the coating device and the print head, thus the application allows to reduce the volume of the printing device. Preferably, the length of the endless ribbon 5 is less than 150 cm, more preferably between 40 cm and 110 cm.

[0225] Preferably, the length of the first path of the ribbon, i.e. the length of the coated ribbon, is in the range of 20 cm to 80 cm, preferably in the range of 30 cm to 50 cm.

[0226] The application further provides a more controlled cooling of the ink and advantageously allows to sufficiently cool the coated ink to prevent the ink from sticking to the substrate, thus achieving a complete solidification of the ink and the ink layer remains tack-free during the printing process.

[0227] In one embodiment, the printing device is set and configured so that the temperature of the ink in contact with the substrate is lower than 60°C or 20°C below its fusion point to cool the coated ink on the ribbon.

[0228] The application advantageously provides a cooling process of the ink on the ribbon allowing the ink to reach such a temperature

[0229] Moreover, the application allows to use the printing device in a large range of environmental or climatic conditions. Indeed, the temperature of the first convex surface is controlled by the cooler 72, the power used by the cooler can depend on the environmental conditions (temperature, humidity, pressure). Thus, the application allows to standardize the printing process worldwide.

[0230] Indeed, the application ensures that the temperature of the ink reaching the printing zone, in which the print head is in contact with the ribbon, is equal to or lower than the first predetermined temperature.

Claims

1. A thermal transfer printing device (1), comprising: Frame (12); A ring-shaped carbon ribbon (5) is used to transfer ink on its outer surface (51); A coating device (3) is used to coat the annular carbon ribbon (5) with ink (4); A printhead (6) is used to thermally transfer ink (4) onto a substrate (20) by means of a portion of the ink (4) coated on an annular ribbon (5) for printing. Multiple first rollers (9) support and transport the annular ribbon (5) along the path from the coating device (3) to the print head (6) and from the print head (6) to the coating device (3) via their inner surfaces (52); A plate (75) is used to support the inner surface (52) of the annular ribbon (5) between two adjacent first rollers (9) along the path from the coating device (3) to the print head (6); the plate (75) is fixed so as not to translate or rotate with the frame (12) and has a first convex surface supporting the inner surface (52) of the ribbon (5); A heat exchanger (72) is configured to cool the first convex surface of the plate (75) at a first predetermined temperature (T1).

2. The thermal transfer printing apparatus (1) according to claim 1, wherein, The first convex surface of the plate (75) is arranged to be in direct contact with the annular carbon ribbon.

3. The thermal transfer printing apparatus (1) according to claim 1, further comprising: At least two second rollers (11); A conveyor belt (71) is supported by the first surfaces of the at least two second rollers (11) and the plate (75) and is arranged to support and convey the annular carbon belt (5) through its inner surface (52). The second roller (11) and the plate (75) are arranged such that the first surface of the plate (75) supports the annular carbon belt (5) via the conveyor belt (71).

4. The thermal transfer printing apparatus (1) according to claim 2 further includes an absorbent material (63) configured to absorb lubricant thereon and arranged to contact the inner surface (52) of the ribbon (5) between the coating device (3) and the plate (75), the thermal transfer printing apparatus (1) further includes a lubricant container (61) for storing lubricant and means for conveying lubricant from the lubricant container (61) to the absorbent material (63).

5. The thermal transfer printing apparatus (1) according to any one of claims 1 to 3 further includes at least one heater (82), said at least one heater (82) being fixed to not translate from said frame (12) and arranged to heat a first portion of said annular ribbon (5), said first portion of said annular ribbon (5) including a coating area of ​​said ribbon (5), said ribbon (5) being coated by said coating device (3) or in contact with said coating device.

6. The thermal transfer printing apparatus (1) according to claim 5, wherein, The plate (75) includes a core with a cavity in which a coolant circulates to cool the outer surface of the core, the outer surface being arranged to support the carbon ribbon (5).

7. The thermal transfer printing apparatus (1) according to claim 5, wherein, The heater (82) includes a roller and means for heating the circumferential surface of the roller, the roller being arranged to support the inner surface (52) of the carbon ribbon on its circumferential surface.

8. The thermal transfer printing apparatus (1) according to claim 7, wherein, The means for heating the circumferential surface of the roller includes a resistor for heating the second guide element (85) by Joule heating.

9. The thermal transfer printing apparatus (1) according to claim 1, wherein, The length of the annular carbon ribbon (5) is less than 150 cm.

10. A method for use on a thermal printing substrate (20), comprising: Provide a thermal transfer printing apparatus according to any one of claims 1 to 9; The annular carbon ribbon (5) containing ink (4) is conveyed from the coating device (3) to the print head (6) in a circulating manner, and from the print head (6) to the coating device (3); The outer surface (51) of the annular carbon ribbon (5) is coated with ink using the coating device (3); The plate (75) supporting the inner surface (52) of the annular carbon ribbon (5) is cooled to cure the coated ink; The printhead (6) uses a portion of the ink coated on the outer surface of the annular ribbon (5) to thermally transfer ink onto the substrate (20) for printing.

11. The method according to claim 10, further comprising activating a heater (82) to heat the ink (4) on the carbon ribbon to above its melting point or its glass transition temperature on both sides of the coating apparatus (3).

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