Thermal printing device with cooler

Abstract

The thermal printing device (1) equipped with a cooler includes a frame, an endless ribbon (5) for transporting ink to an outer surface (51), a coating device (3) for coating the endless ribbon (5) with ink (4), a print head (6) for thermally transferring a portion of the ink (4) coated on the endless ribbon (5) to a substrate (20) for printing, a plurality of first rollers (9) for supporting and transporting the endless ribbon (5) on their inner surfaces (52) along a path from the coating device (3) to the print head (6) and from the print head (6) to the coating device (3), and two adjacent first rollers (9) along the path from the coating device (3) to the print head (6). (9), at least one first conveyor (7) including a plate (75) arranged to support an inner surface (52) of the endless ribbon (5) and fixed to a frame (75) in translation and rotation, and having a first convex surface that supports the inner surface (52) of the ribbon (5), and a heat exchanger (72) designed to cool a first surface of the plate (75) at a first predetermined temperature.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to printing device systems, and more particularly to printing devices having ribbons capable of carrying ink. [Background technology]

[0002] Current solutions involving thermal transfer printing equipment use disposable, pre-coated ribbons. One limitation of these solutions is the need to periodically replace the ribbon when it reaches its end. Such replacement requires the printer to be shut down for a period of time, which can be very inconvenient in some applications (for example, when the printer is a labeling machine on a production line). To address this waste of used ribbon and residual untransferred ink, alternative cooler thermal transfer printing devices have been developed that use endless ribbon instead of disposable ribbon spools. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] EP3055135B1 [Patent Document 2] US4764776 [Patent Document 3] EP0412179 [Patent Document 4] CH553662 [Patent Document 5] US2004 / 135870 Summary of the Invention [Problem to be solved by the invention]

[0004] EP 3055135 B1 suggests such a printing apparatus in which an endless ribbon is transported on rollers, and the printing apparatus described therein includes a coating device for coating the ribbon with hot melt ink.

[0005] The ink layer applied to such an endless ribbon must be allowed to recover to ensure multiple prints, so that only one ribbon is continuously used and the remaining ink can be reused, reducing material waste.

[0006] The endless ribbon is transported by rollers, during which parts of the ribbon are successively exposed to the thermal print head and the re-inking unit. This allows it to withstand a large number of cycles, for example, one million cycles. Between the re-inking unit and the thermal print head, the ink regains its solid state, which is possible during a cooling phase. This cooling phase is essential to provide a proper ink layer and affect the quality of the printed data on the substrate.

[0007] US4764776 or EP0412179 disclose that the ink coated on the ribbon solidifies after coating, but the cooling occurs without thermal control and is therefore exposed to environmental conditions during use, such as humidity and room temperature.

[0008] CH553662 discloses a printing system with a cooling unit that uses a fan positioned near the ribbon to promote solidification of the ink.

[0009] The first limitation of these systems is that they can be limited in printing speed. In fact, if the speed exceeds this limit, the coated hot molten ink may not solidify or may solidify insufficiently before reaching the printhead, which can adversely affect print quality. Also, increasing the ribbon path between the coater and the printhead allows it to cool over time, increasing the volume of the printing device. Therefore, such printing devices require a large capacity to travel long distances between the re-inking station and the printhead to ensure ink solidification and therefore proper printing performance.

[0010] A second limitation is the lack of standardization of the printing process: the printhead must be calibrated depending on the ambient temperature, humidity, and the thermal properties of the ink to ensure high-quality printing. In fact, inks are generally sensitive to humidity and temperature, which may limit the range of inks that can be used in such a system where the cooling phase cannot be controlled.

[0011] A third limitation is the potential or inevitable misalignment between the transport rollers, which induces uneven tension across the width of the ribbon. This uneven tension creates potential lateral movement of portions of the film and potential wrinkles, creases, or folds.

[0012] US2004 / 135870 describes a cooling roller mounted laterally to rotate in contact with the backside of the thermal transfer film. Similarly, EP0029313 describes a cooling roller or electric freezing element that employs the Peltier effect to solidify the ink layer.

[0013] However, this solution does not avoid the aforementioned drawbacks. In particular, this solution does not provide optimal heat transfer between the ink and the roller. This solution necessarily increases the volume of the printing device, since the cooling depends on the contact area between the ribbon and the roller. In other words, the ink solidification depends on the diameter of the roller.

[0014] SUMMARY OF THE INVENTION The present invention aims to provide a compact thermal transfer printing device that overcomes the aforementioned limitations. [Means for solving the problem]

[0015] According to a first aspect, the present invention provides a method for manufacturing a semiconductor device comprising: a coater for coating the endless ribbon with ink; a print head for thermally transferring a portion of the ink coated on the endless ribbon onto a substrate; a transport system for cyclically supporting and transporting an endless ribbon containing ink along a first path from the coater to the printhead and along a second path from the printhead to the coater; at least one cooler configured to cool the coated ink on the endless ribbon at a first predetermined temperature along a first portion of the endless first path; The present invention relates to a thermal transfer printing device including:

[0016] This cooler advantageously improves the solidification of the hot melt ink coated on the ribbon. Another advantage is that it allows for the use of shorter ribbons and / or faster printing while keeping the printing equipment compact. Another advantage is that it ensures rapid solidification of the ink, regardless of the rate of ambient temperature and humidity.

[0017] In one embodiment, the printing apparatus further includes at least one heater for heating the ink on the endless ribbon to a second predetermined temperature along a second portion of the second path. The heater is advantageous for melting ink remaining after printing or for bringing the ink on the ribbon closer to its melting point. The heater improves coating and facilitates replacement of the ink on the ribbon by the coater.

[0018] In one embodiment, the printing apparatus further includes at least one heater for heating the ink on the endless ribbon at a third predetermined temperature along a third portion located between the coater and the first portion of the first path. One advantage is improving the thickness uniformity of the ink on the band before the ink cools. One advantage is heating the ink on the ribbon before, during, and after coating to improve the coating and thickness uniformity along the width and length of the ribbon.

[0019] In one embodiment, the transport system includes a first guide element for supporting the ribbon, the first guide element being coupled to a cooler for cooling the ink coated on the ribbon supported by the first guide element. One advantage of the first guide element is that it utilizes the contact surface between the first guide element and the ribbon to cool the ink on the ribbon. The ink is cooled by the first guide element through the ribbon.

[0020] In one embodiment, the first guide element includes a core having a cavity through which a coolant circulates for cooling an outer surface of the core, the outer surface of the core being arranged to support the ribbon.

[0021] In one embodiment, the transport system includes a first transporter including a first transport belt that holds and transports an endless ribbon at at least a portion of a first portion, the first transport belt acting as a heat conductor while transporting the ribbon being guided by a first guide element such that a surface of the first guide element faces the transport belt.

[0022] In one embodiment, the printing apparatus further includes at least two rollers for holding and supporting the first transport belt, hi one embodiment, the at least two rollers are coupled to a cooler for cooling the ink through the rollers, the ribbon, and the first transport belt.

[0023] In one embodiment, the transport system includes a second guide element for supporting the ribbon. The second guide element is coupled to a heater for heating ink coated on the ribbon supported by the second guide element at a second portion. In one embodiment, the heater includes an electrical resistor for heating the second guide element by Joule heating.

[0024] In one embodiment, the conveying system includes a second conveyor. The second conveyor includes a second conveyor belt that holds and conveys the endless ribbon on the second portion and / or the third portion. The second conveyor belt is guided by a second guide element such that an outer surface of the second guide element faces the second conveyor belt. The second conveyor belt functions as a heat conductor while conveying the ribbon.

[0025] In one embodiment, the printing apparatus includes at least two rollers for holding and supporting the second transport belt, the rollers being coupled to a heater for heating the ink through the ribbon and the second transport belt.

[0026] In one embodiment, the cooler comprises a heat exchanger. In one embodiment, the cooler comprises a Peltier heat pump. In one embodiment, the heat exchanger comprises a heat pipe.

[0027] In one embodiment, the first predetermined temperature is in the range of 25°C to 50°C. In one embodiment, the second predetermined temperature is in the range of 50°C to 130°C.

[0028] In one embodiment, the printing device includes a ribbon disposed on a path of the printing device and ink carried by the ribbon, and the first predetermined temperature is below a melting point of the ink. In one embodiment, the second predetermined temperature is equal to or greater than a melting point of the ink. In one embodiment, the first guide element and / or the second guide element guide in a curved line.

[0029] In one embodiment, the printing apparatus further includes a thermal control device that controls a temperature of the ink in the ribbon at a fourth portion of the ribbon path, the fourth portion of the path being located between the first portion and the print head. In one embodiment, the thermal control device heats and / or cools the ink at a third predetermined temperature.

[0030] According to a second aspect, the present invention provides a method for manufacturing a semiconductor device comprising: conveying an endless ribbon carrying ink circulatingly along a first path from the coater to the printhead and along a second path from the printhead to the coater; Coating the endless ribbon with ink using a coater; Printing is performed by thermally transferring a portion of the ink coated on an endless ribbon onto a substrate using a print head. activating a cooler to cool the ink coated on the endless ribbon at a first predetermined temperature along a first portion of a first path of the endless ribbon; The present invention relates to a method of thermally printing a substrate comprising:

[0031] In one embodiment, the method includes activating a heater to heat the ribbon and melt ink on the bands along a portion of the path of the endless ribbon.

[0032] In one embodiment, the method is implemented by a printing apparatus according to the first aspect of the invention. In one embodiment, the method includes recovering a portion of the excess ink when replacing a portion of the ink transferred to the substrate.

[0033] According to one aspect, the present invention provides a method for manufacturing a semiconductor device comprising: The frame and an endless ribbon for carrying the ink to its outer surface; a coating device for coating the endless ribbon with ink; A print head that thermally transfers ink coated on an endless ribbon onto a substrate for printing; a plurality of first rollers for supporting and transporting an endless ribbon on their inner surfaces along a path from the coating device to the print head and from the print head to the coating device, preferably periodically; a plate for supporting an inner surface of the endless ribbon between two adjacent first rollers along a path from the coating device to the print head, the plate being fixed to the frame in translation and rotation, and optionally having a first convex surface for supporting the inner surface of the ribbon; a heat exchanger designed to cool a first surface of the plate at a first predetermined temperature; The present invention relates to a thermal transfer printing device including:

[0034] In one embodiment, the first convex surface of the plate is placed in direct contact with the endless ribbon.

[0035] In one embodiment, the thermal transfer printing apparatus further includes at least two second rollers. The transport belt is supported by the at least two second rollers and the first surface of the plate, and is arranged to support and transport the endless ribbon by its inner surface. The second rollers and the plate are arranged so that the first surface of the plate supports the endless ribbon through the transport belt.

[0036] In one embodiment, the thermal transfer printing apparatus further includes at least one heater secured to the frame in translational motion and positioned to heat a first portion of the endless ribbon at a second predetermined temperature.

[0037] In one embodiment, the first portion of the endless ribbon comprises a coating zone of the ribbon, where the ribbon is coated by or in contact with a coating device.

[0038] In one embodiment, the plate includes a frame having a cavity through which a coolant circulates for cooling an outer surface of the frame, the outer surface of the frame being arranged to support the ribbon.

[0039] In one embodiment, the heater includes a roller positioned to support the inner surface of the ribbon on its circumferential surface, and means for heating the circumferential surface of the roller.

[0040] In one embodiment, the means for heating said circumferential surface of the roller comprises an electrical or thermal resistor which heats the second guide element by Joule heating.

[0041] According to one aspect, the present invention provides a method for manufacturing a semiconductor device comprising: The frame and an endless ribbon for carrying ink to its outer surface; a coating device for coating the endless ribbon with ink; a print head for thermally transferring a portion of the ink coated on the endless ribbon onto a substrate; a plurality of first rollers for supporting and transporting an endless ribbon on their inner surfaces along a path from the coating device to the print head and from the print head to the coating device; at least one cooling roller arranged to support an inner surface of the endless ribbon between two adjacent first rollers along a path from the coating device to the print head, the cooling roller including a shaft including a pipe extending through a volume of the shaft and filled with a coolant; a heat exchanger designed to cool the refrigerant in the pipe of the cooling roller to a first predetermined temperature; The present invention relates to a thermal transfer printing device including:

[0042] According to another aspect, the present invention relates to a method of thermally printing a substrate, comprising the steps of: providing a thermal transfer printing device according to the present invention; conveying an endless ribbon carrying ink from the coating device to the print head and from the print head to the coating device, preferably in a circular manner; coating the outer surface of the endless ribbon with ink in a coating device; cooling the plate supporting the inner surface of the endless ribbon to solidify the coated ink; A print head thermally transfers a portion of the ink coated on the outer surface of the endless ribbon onto a substrate for printing; Includes.

[0043] In one embodiment, the method further includes activating heaters to heat the ink on the ribbons on both sides of the coating device above its melting point or glass transition temperature. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a schematic diagram of a printing apparatus including a cooler and a heater according to one embodiment of the present invention;

[0045] [Figure 2] 1 is a schematic diagram of a printing apparatus according to an embodiment of the present invention, in which a cooler and a heater are integrated into a conveyor that constitutes a conveyor belt.

[0046] [Figure 3] 1 is a perspective view of a printing device with the frame of the printing device removed, according to one embodiment of the present invention;

[0047] [Figure 4] 4 is a cutaway plan view of the printing apparatus of Figure 3, where the printing apparatus includes an isolation wall for isolating the heater and coater from the cooler.

[0048] [Figure 5] FIG. 4 is another perspective view of the printing apparatus of FIG. 3, where the cooler includes a heat exchanger consisting of a coil, a condenser, and a radiator that cools the condenser.

[0049] [Figure 6]1 is a schematic diagram of a portion of a printing apparatus according to one embodiment of the present invention, in which a cooler includes a curved static plate positioned to contact the inner surface of the ribbon, and further includes means for coating the inner surface of the ribbon with a lubricant before the ribbon slides along the plate.

[0050] [Figure 7] FIG. 4 is a schematic diagram of a printing apparatus according to another embodiment of the present invention including a cooling roller.

[0051] [Figure 8] FIG. 2 is a cross-sectional view of a cooling roller according to one embodiment of the present invention.

[0052] [Figure 9] 1 is a schematic diagram of a cooling roller coupled to a motor that drives the cooling roller in rotation, according to one embodiment of the present invention;

[0053] [Figure 10] 3 is a diagram of a thermal cycle along the transport of ink on a ribbon in a thermal printing device according to one embodiment of the present invention;

[0054] [Figure 11] 1 is a perspective view of a printing apparatus in accordance with one embodiment of the present invention, where the frame has been removed and the printing apparatus includes a cooling plate that directly contacts the ribbon. DETAILED DESCRIPTION OF THE INVENTION

[0055] The apparatus comprises a transport system, a printhead 6, and a coater 3. The apparatus also comprises or is designed to receive an endless ribbon 5. Figure 1 shows a schematic diagram of a thermal transfer printing apparatus according to one embodiment of the present invention.

[0056] Coater The printing apparatus 1 includes a coater 3 designed and arranged to coat the outer surface 51 of the ribbon 5 with ink 4.

[0057] As shown in Figure 1, the coater 3 is connected to a reservoir 2. The reservoir is designed to contain solid ink that is supplied to the coater 3. In another embodiment, the reservoir contains liquid ink, which may be coupled with a mixing element to maintain the ink at predefined physical conditions, such as temperature and viscosity.

[0058] Coater 3 may be positioned in contact with or near ribbon 5 to facilitate coating of outer surface 51 of ribbon 5 .

[0059] The coater 3 is designed to coat the outer surface of the ribbon 5 with a layer of liquid ink 4. The layer of liquid ink 4 is preferably homogeneously distributed on the surface of the ribbon 5. Ink control components (not shown) may ensure sufficient ink distribution on the surface of the ribbon 5 as a function of the speed of rotation / displacement of the ribbon 5 and / or the print mode.

[0060] One purpose of the ink control component is to ensure a substantially constant coating thickness on the ribbon 5 regardless of the displacement speed of the ribbon 5. In one embodiment, the ink control component includes an electrical input for reading the displacement speed of the ribbon 5. In this manner, the ink control component can ensure a constant coating and even distribution over time laps at variable speeds. In such a configuration, the printing and coating sequences are synchronized.

[0061] In a first example (not shown), the coater 3 includes a conduit containing liquid ink, such as a slot die coating apparatus. A first end of the conduit is connected to the reservoir 2. A second end of the conduit forms the coater head. The coater head outlet is adjacent to the outer surface of the ribbon 5, most preferably perpendicular to the outer surface of the ribbon 5. The conduit may also include tapered or parallel slits. Gravity and capillary action transport the liquid ink to the second end of the conduit, where it is coated onto the outer surface of the ribbon 5. In this example, the axis of the coating head may be parallel to the axis along which the ink is projected from the coater 3. This axis is preferably perpendicular to the major axis of the adjacent portion of the ribbon 5 or the surface of the ribbon 5.

[0062] In a second example, not shown, coater 3 includes a device for transporting liquid ink from reservoir 2 to ribbon 5. The device may include an ink roller that is at least partially within reservoir 2 and adjacent to or in contact with the outer surface of ribbon 5. The ink roller transports liquid ink from reservoir 2 to the outer surface of ribbon 5 by rotation. The device may also include a material that is at least partially within reservoir 2, adjacent to or in contact with ribbon 5, and capable of transporting ink to ribbon 5 by capillary action. The material may include a foam, a sponge material, or a material that can improve such capillary action.

[0063] The coater 3 may be selected from a list of conventional coating techniques. In some other, not shown, examples, the coater 3 is designed to coat an endless ribbon with ink using any technique available to the skilled artisan, such as knife coating, curtain coating, extrusion coating, slot die, transfer coating, flexo coating, screen printing, or a combination of such techniques.

[0064] The coater 3 can be selected from a traditional list of printing techniques: roll-to-roll, sheet-to-sheet, or roll-to-sheet. Printing techniques include heliogranulation, serigraphy, flexography, inkjet, or offset, resulting in a thin, uniform, and controlled thickness of ink applied to an endless ribbon. The amount of ink applied to the ribbon varies depending on the technique used, the temperature of the ink during coating, and its characteristics.

[0065] In both examples, the reservoir 2 and / or coater 3 are equipped with a heating device to melt the ink in the reservoir 2 and / or coater 3, respectively. The reservoir 2 can be filled with solid ink, which readily melts when it comes into contact with the reservoir 2 or coater 3.

[0066] In one embodiment, printing apparatus 1 includes a device for periodically adding new solid ink to reservoir 2 .

[0067] ink The ink used is preferably a thermoplastic composition that melts at a temperature above its melting point. Thermoplastic means meltable or heat-fusible and is understood to include any material characterized by its melting point or melting point. As used herein, the term hot melt ink or ink refers to any thermoplastic ink composition used in thermal printing devices and characterized by its melting point. During the process described herein, the ink is melted to the appropriate consistency or viscosity and applied to an endless ribbon. The ink can also be a material that is very viscous at room temperature and does not tack upon cooling.

[0068] The coating device may include means for melting the ink using any technique available to the skilled artisan, such as, but not limited to, direct or indirect heating, inductive heating, or conductive heating, etc. In one example, the coating device includes a heat resistor for melting the ink.

[0069] In a preferred embodiment, the ink composition includes at least a colorant or pigment, and optionally includes a natural wax, a synthetic resin, or a combination of the two. The ink composition optionally includes a surfactant, and optionally includes organic and / or inorganic fillers and a solvent. Various other surfactants and other flow aids can also be used.

[0070] Ink is characterized by being solid at room temperature and liquid above room temperature. During printing, the ink is usually heated until it becomes liquid. Therefore, the transfer of ink from the ribbon to the printed circuit board is ensured by the ink's ability to rapidly change phase from solid to liquid when it coats the substrate near the printhead during printing, allowing it to form an image. Ink can begin to solidify at room temperature.

[0071] The melting point of the ink is preferably between 50°C and 100°C.

[0072] print head The printing device 1 comprises a printhead 6. In a preferred embodiment, the printhead 6 is a thermal transfer printhead 6.

[0073] In one embodiment, the printhead has two configurations.

[0074] In the first configuration, the printhead 6 contacts the inner surface of the ribbon 5 to allow thermal transfer of the ink on the outer surface 51 of the ribbon 5. During this printing process, the outer surface 51 of the ribbon 5 contacts the substrate 20 to transfer a portion of the ink intended for printing on the substrate.

[0075] In the second configuration, the printhead 6 is not in contact with the ribbon 5. This mode may be activated when the printing device is switched off or during two consecutive printing sequences. The switching between the first and second modes may be configured by the print mode.

[0076] Print rollers 21 can be used to transport substrate 20 near ribbon 5. A thermal transfer print head 6 is preferably located near substrate 20 and is used to transfer hot melt ink 4 from ribbon 5 to substrate 20. Alignment between print head 6, ribbon 5, and substrate 20 is ensured by mechanical components that are precisely set depending on the desired printing accuracy. Several guidance and position control components may be implemented to ensure a predetermined alignment between at least print head 6 and ribbon 5.

[0077] The print roller 21 ensures sufficient pressure on the substrate 20 to keep it in contact with the ribbon 5 as the printing process occurs. 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 movement of the substrate is in the same direction as the displacement of the ribbon 5 near the print head. This movement near the print head is preferably linear.

[0078] In another embodiment, the printhead includes a laser that heats the ink through the thickness of the ribbon 5 to enable heat transfer of the ink located on the outer surface 51 of the ribbon 5. The wavelength of the laser is preferably between 950 nm and 1450 nm.

[0079] ribbon The ribbon 5 of the printing device 1 can transport the ink 4 from the coater 3 to the printhead 6 on the outer surface 51. The ribbon 5 preferably forms a loop. In such a configuration, residual ink not used during the printing process is transported past the printhead to an ink recovery device (not shown). As a result, the same ribbon 5 is continuously used, preferably in a cyclical manner, to transport the ink for printing and the residual ink after printing. The printing process is implemented to form a continuous loop process in which the residual ink is automatically removed. This configuration allows the removal of unused ink, which can be advantageously reused in the next turn of the ribbon 5.

[0080] That is, the ribbon 5 is transported in a continuous loop process, i.e., cyclically, along a path consisting of a first path from the coater 3 to the printhead 6 and a second path from the printhead 6 to the coater 3. On its first path, the ribbon 5 carries the newly coated ink. On its second path, the ribbon 5 carries and transports the portion of the ink that has not been printed by the printhead 6.

[0081] One advantage of the present invention is that it provides an autonomous printing device in which at least a portion, preferably 100% or substantially 100% of the ink is used, i.e., there is no ink loss.

[0082] The ribbon 5 can be made from a variety of materials. Preferably, the ribbon 5 is made from a material with high heat resistance, such as resistance to temperatures up to 300°C, and high chemical resistance, such as resistance to alcohol, ink, and solvents. Preferably, the ribbon 5 is made from polyimide. Polyimide allows for use in temperatures ranging from 340°C to 380°C without deformation of the ribbon. In a preferred embodiment, the ribbon 5 can be made from a metal or metal alloy. The ribbon can be made from a metal alloy, such as stainless steel, aluminum alloy, titanium alloy, copper alloy, or beryllium alloy. In one embodiment, the ribbon can be comprised of an alloy containing nickel, tin, and copper, preferably with nickel between 14.5% and 15.5% of the metal, tin between 7.5% and 8.5% of the metal, and copper between 75% and 79% of the metal.

[0083] The ribbon 5 is preferably made of a material having a thermal conductivity greater than 0.120 watts per meter Kelvin.

[0084] The thickness and composition of the ribbon material is designed to create heat transfer through the ribbon that enables printing.

[0085] The ribbon thickness is preferably less than 50 μm or 20 μm. This thickness is advantageous for reducing the heat transfer resistance between the inner and outer surfaces and improving printing quality. The ribbon thickness can be substantially between 0.5 μm and 50 μm, and most preferably between 0.5 μm and 20 μm. In one example, the ribbon thickness is selected from the range of 3-25 μm or 5-10 μm.

[0086] In one embodiment where printhead 6 includes a laser, ribbon 5 is transparent at the wavelength of the laser. In this embodiment, the thickness of ribbon 5 is selected in the range [3-200 μm].

[0087] cooler According to the present invention, the printing apparatus 1 includes at least one cooler 72 configured to cool the coating ink 4 on the endless ribbon 5 in a first portion of the ribbon's 5 path, preferably along a portion of the ribbon's 5 first path from the coater 3 to the printhead 6. The cooler 72 advantageously improves the solidification of the molten ink 4 after coating. The ink 4 near the printhead 6 advantageously regains its solid state thanks to the cooler 72, improving the quality of the thermal transfer print. Indeed, since the printhead 6 melts a portion of the ink 4 before printing it on the substrate 20, cooling the ink 4 to a predetermined temperature before it arrives near the printhead improves the accuracy of the print.

[0088] The cooler 72 is preferably configured to cool the ink 4 to a predetermined temperature. The cooler is preferably designed to cool the ink on the ribbon to a temperature below the melting temperature of the ink.

[0089] The cooler 72 may be an active cooler. An active cooler includes a means for providing nutrients to generate cooling. An active cooler does not include a conventional fan used to extract heat from the system. Such fans simply transport heat by convection and do not generate a low temperature, which is the desired effect of cooling the ink to a predetermined temperature. The cooler 72 may be positioned to cool the ink 4 through the ribbon 5.

[0090] In a first embodiment, the cooler 72 includes at least one thermoelectric material, preferably one that exhibits the Peltier effect. A thermoelectric material that exhibits the Peltier effect generates heat flow from an electric current. When an electric current is passed through a junction between two conductors, heat is removed at one junction. The cooler 72 can include a Peltier heat pump. A Peltier heat pump consists of multiple junctions in series and is driven by an electric current. Some junctions lose heat through the Peltier effect, while others gain heat. The Peltier heat pump is designed to be positioned, preferably through the ribbon, so that the junctions that lose heat cool the ink in the ribbon.

[0091] In a second embodiment, the cooler 72 includes a heat exchanger, preferably positioned through the ribbon, to cool the ink in the ribbon. The heat exchanger consists of a circulating fluid (also called a coolant) passing through a radiator coil and air flowing through the coil, which cools the coolant and heats the incoming air. The coolant, cooled by the radiator, is then driven to cool the ink, preferably through the ribbon. The heat exchanger may include a fan to improve airflow over the radiator to cool the coolant.

[0092] The first and second embodiments can be combined to cool the ink 4 on the ribbon 5, preferably through the ribbon 5.

[0093] heater According to one embodiment, the printing apparatus includes at least one first heater 82. The first heater 82 is configured to heat the ink on the ribbon 5 along a second portion of the ribbon's path, the second portion extending at least part of the ribbon's path. The heater 82 is advantageous for melting the ink 4 remaining after printing or for bringing the ink 4 close to the melting point of the ribbon 5. The first heater 82 is advantageous for improving the coating and replacing the ink 4 on the ribbon by the coater 3. The first heater 82 is preferably configured to heat the ink on the ribbon in the second portion above a second predetermined temperature.

[0094] In one embodiment, the first heater 82 is also configured to heat the ink on the ribbon along a third portion of the path of the ribbon 5. In another embodiment, the printing apparatus includes 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 includes a coating zone where the ribbon 5 is coated with ink by the coater 3.

[0095] In one embodiment, the third portion extends along at least 2 cm of each portion of the coating zone. Preferably, the third portion extends along a length of less than 10 cm.

[0096] Preferably, the first heater 82 and / or the second heater 84 are configured to heat the ink on the third portion of the ribbon to a third predetermined temperature or above. In one embodiment, the second and third predetermined temperatures are equal. Preferably, the third predetermined temperature is higher than the second predetermined temperature. Preferably, the third predetermined temperature is higher than the melting point of the ink.

[0097] In this embodiment, heating this third portion advantageously causes the ink 4 to flow and improves ink thickness uniformity on the band before the ink cools. In one embodiment shown in Figures 1 and 2, the first or second heater is positioned to heat the ink on the ribbon in portions extending from both sides of the coater. One advantage is that the ink 4 on the ribbon can be heated before, during, and after coating to improve coating and thickness uniformity along the width and length of the ribbon 5. The heater 82 can include several means, each configured to heat the ink in the second or third portion.

[0098] The heaters 82, 84 may comprise resistors that heat the ink 4 through the ribbon 5 by Joule heating. In another embodiment, the heaters comprise radiation heating means that heat the ink on the ribbon 5.

[0099] In this embodiment, the ink on the ribbon 5 is first heated before arriving at the coater (optionally after the coater) and then cooled by a cooler before the printing stage, providing solid ink and improving print quality.

[0100] In one embodiment, the second portion and the third portion are adjacent.

[0101] Transport System The ribbon 5 is held and transported using a transport system that supports and transports the ribbon 5 in a circular manner along a path from the coater to the print head. The transport system supports and transports the endless ribbon along a first path from the coater to the print head and along a second path from the print head to the coater.

[0102] 1, the transport system can include at least one roller 9 for holding and transporting the endless ribbon 5. The transport system can include multiple rollers 9 for holding and transporting the endless ribbon 5 along its path.

[0103] The rollers 9 are cylindrical. They are joined to the frame 12 with at least one rotational degree of freedom along an axis that is the longitudinal axis of the roller's cylinder. Preferably, the rollers 9 are mechanically connected to the frame such that the longitudinal axis of the roller is acutely perpendicular to the surface of the frame that contacts the roller 9. In one embodiment, at least one roller 9 is coupled to the frame with at least one translational degree of freedom. Preferably, at least one roller 9 is free to translate relative to the frame along a plane that is acutely perpendicular to the longitudinal axis of the roller's cylinder.

[0104] At least one of the rollers 9 may be a drive roller. The drive roller is connected to a motor to rotate the drive roller. At least one battery or electrical circuit may be implemented in the printing apparatus to power the motor. Rotation of the drive roller generates displacement of the endless ribbon 5 along its path, which also causes rotation of the other rollers.

[0105] First embodiment: cooling roller In a first embodiment shown in FIGS. 7, 8, and 9, the cooler 82 is positioned to cool at least one roller 100, preferably the roller 100 positioned in the first portion. For example, a thermoelectric material can be integrated into or in contact with one roller 100 supporting the ribbon 5 in the first portion of the ribbon 5's path. The roller 100 is then cooled, and the ink 4 is cooled through the ribbon 5 in the first portion of its path. In another example, the heat exchanger is designed so that a coolant is induced to cool the roller 100. The roller 100 is preferably made of a material with high thermal conductivity. The roller 100 may be made of a metal such as aluminum or copper, or an alloy of such a metal. One advantage is improved heat transfer from the coolant to the roller and from the roller to the ribbon.

[0106] The cooling roller 100 is positioned to contact and support the inner surface 52 of the ribbon 5. In one embodiment, the cooling roller is designed and positioned to support the ribbon 5 with its inner surface 52 along an angle A greater than 100°, preferably greater than 120°. This angle can be adjusted by changing the position and / or diameter of two adjacent rollers 9 on either side of the cooling roller. In one embodiment, the diameter of the cooling roller section is greater than 50 mm, preferably greater than 70 mm.

[0107] This angle A in combination with the diameter of the cooling roller 100 allows for a longer contact area between the cooling roller 100 and the ribbon 5, which is advantageous for improving the cooling and solidification of the coating layer of ink 4 on the ribbon.

[0108] One advantage of using a chill roller 100 rather than a static plate 75 as previously described is that the ribbon does not slide along the roller. The roller may be driven to rotate by a motor or by the ribbon itself by gripping the circumferential surface of the chill roller and ribbon.

[0109] The cooling roller 100 is preferably connected to a cooler 72 which includes a heat exchanger as described below for the guide elements.

[0110] Next, one embodiment of such a cooling roller will be described with reference to FIGS.

[0111] The cooling roller 100 comprises a shaft 101. The shaft is made of a highly heat-conductive material such as a metal (for example, an aluminum alloy).

[0112] The shaft 101 includes at least one pipe 103. The pipe 103 extends along the volume of the shaft and is fluidly connected to the heat exchanger coil 73. The coolant is then cooled by the radiator 76 and re-injected into the pipe 103 of the shaft 101 to cool the shaft 101. In one embodiment, the diameter of the pipe 103 ranges from 5 to 20 mm. In one embodiment, the length of the pipe 103 ranges from 150 to 400 mm.

[0113] The cooling roller 100 also includes a rotor 102 that is free to rotate about a shaft 101. The outer surface of the rotor supports the ribbon 5.

[0114] The cavity between the shaft 101 and the rotor 102 is preferably filled with a lubricant such as silicone oil. One advantage is to reduce friction between the shaft 101 and the rotor 102. Another advantage is to improve heat transfer between the shaft 101 and the rotor 102.

[0115] In one embodiment, the cooling roller 100 includes a seal ring 104 between the shaft 101 and the rotor 102 to avoid leakage of lubricating oil in the cavity during rotation of the rotor 102 .

[0116] In one embodiment, the printing apparatus further comprises a motor 110. The motor 110 is positioned and designed to drive the rotation of the rotor 102 of the cooling roller 100.

[0117] The motor may be connected to a controller, which in one embodiment is configured to control the rotational speed of the motor 110 depending on the rotational speed of the drive roller.

[0118] 9 , the motor 110 includes a drive pulley 114, and the rotor 102 of the cooler 100 includes a drive pulley 112. The printing device further includes a belt 111 for transmitting the rotation of the drive pulley 114 to the drive pulley 112, and thus to the rotor 102 of the cooler. In one embodiment, the system further includes a tensioner 113 arranged to ensure belt tension and increase the contact angle between the belt 111 and the drive pulley 114 and / or the drive pulley 112.

[0119] Second embodiment: cooling plate In a second embodiment shown in Figures 1 and 11, the conveyor includes a first guide element. The first guide element may comprise a static support element preferably arranged between two adjacent rollers 9. The static support element is preferably a plate, such as a metal plate or sheet. The ribbon 5 slides along its length on the first guide element 75 (e.g., a metal plate). In the following description, the term "plate" is used to designate the first guide element 75. The plate preferably comprises an element having a volume whose third dimension is at least five times smaller than either the second or first dimension.

[0120] A portion of the plate is placed in contact with the inside of the ribbon 5, cooling the ink through the ribbon. The metal plate is preferably made of aluminum or an aluminum alloy to improve heat conduction.

[0121] The plate is preferably a static support element with respect to the frame 12. The plate is preferably mechanically connected to the frame with zero degrees of freedom. The plate and frame are fully coupled. This connection is sometimes referred to as an interlocking connection; that is, the frame 12 and the plate cannot move relative to one another. This connection between the frame 12 and the plate 75 can be direct (e.g., by direct contact) or indirect (e.g., both the plate 75 and the frame are fully coupled to intermediate or auxiliary elements).

[0122] In one embodiment, the first guide element includes a lubricant between the plate 75 and the ribbon 5 to improve sliding of the ribbon over the plate. In one embodiment, the lubricant can include liquid oil, which advantageously allows for lubrication and electrostatic discharge from the ribbon or plate to the frame for grounding.

[0123] In one embodiment shown in FIG. 6, the cooler includes an absorbent material 63. The absorbent material 63 is designed to retain or absorb oil or other lubricant thereon. The absorbent material 63 is positioned to contact the inner surface 52 of the ribbon 5, preferably between the coater and the plate 75. The absorbent material 63 is adapted to be saturated with the lubricant. To this end, the printing apparatus further includes a reservoir 61 for filling with the lubricant (e.g., liquid oil) and a means for conveying the lubricant from the reservoir 61 to the absorbent material 63. The means may include a pipe 62 fluidly connecting the reservoir 61 to the absorbent material 63. The absorbent material 63 is preferably fixed to the frame for translational movement. In one example, the absorbent material is made of a sponge-like material, fabric, or cotton. Thus, the absorbent material can supply lubricant to the inner surface of the ribbon before it slides over the plate. One advantage is that it reduces damage to the ribbon during sliding due to friction between the ribbon and the plate, thereby improving the ribbon's lifespan.

[0124] The first guide element 75 is arranged to guide the moving ribbon 5 along a predetermined path, for example a curved path. The first guide element 75 is a rounded guide that supports the ribbon 5.

[0125] The first advantage of the rounded or curved shape of the plate 75 is that it reduces the frictional forces that occur on the ribbons 5 at their contact points 65 with the plate 75. In fact, this shape ensures that the ribbons do not rub against the edges of the plate. The second advantage is that the curved shape further ensures contact between the ribbons and the plate, reducing the risk of air bubbles being inserted between the ribbons and the plate. This advantageously improves the heat transfer between the ribbons and the plate.

[0126] For this purpose, the plate 75 has an outer surface intended to support the inner surface of the ribbon, which is convex.

[0127] In one embodiment, the radius of curvature of the convex surface is greater than 2 cm.

[0128] In one embodiment, the length of the first surface of plate 75 ranges from 2 cm to 20 cm.

[0129] In one embodiment, the first guide element 75 (e.g., a plate) is coupled to a cooler 72 to cool the coating ink 4 on the ribbon 5 supported by the first guide element 75. As previously described, the first guide element 75 may be cooled by a thermoelectric material. The heat-dissipating junction of the thermoelectric material may be in contact with one side of the guide, preferably the side opposite the side in contact with the ribbon 5. In another embodiment, a coolant from a heat exchanger is driven through the first guide element 75 to provide cooling. In one embodiment, the first guide element includes a core having a cavity through which a coolant circulates to cool the outer surface of the core, the outer surface being positioned to support the ribbon 5. The first guide element 75 is preferably positioned to cool the portion of the ribbon 5 supported by the first guide element 75 along a first portion of the ribbon 5's path. The cooler 72 may include a Peltier element.

[0130] One advantage of the first guiding element 75 is that it utilizes the contact surface between the first guiding element 75 and the ribbon 5 to cool the ink on the ribbon 5. The ink 4 is cooled by the first conductor 75 through the ribbon.

[0131] In one embodiment shown in FIG. 1 , the transport system can include a second conductor 85 positioned to guide the moving ribbon along a predetermined path in the same manner as described for the first conductor 75. The second conductor 85 can be coupled to the first heater 82 and / or the second heater 84 to heat the ink 4 on the ribbon 5 supported by the second conductor 85. The second conductor 85 is positioned to hold and support the ribbon 5 along a second portion of the ribbon 5's path and / or a third portion of the ribbon's path. Preferably, as shown in FIG. 1 , the second conductor 85 is positioned to contact the ribbon 5 at portions extending from both sides of the coater 3. An electrical resistance can be incorporated within the second conductor to heat the ink 4 through the ribbon 5 and through the walls of the second conductor 85.

[0132] One advantage of a chill plate in direct contact with the ribbon is that such a configuration reduces the volume of the printing device compared to a chill roller. In fact, a chill roller requires a significant diameter to cool the same amount of ink as a plate, which increases the overall volume of the printing device. Even if the ribbon path length is shortened by using a chill roller instead of a chill plate, the obstruction of the roller is greater than that of a plate.

[0133] In one embodiment, plate 75 is removable from frame 12. Plate 75 may also be partially disassembled from frame 12, for example, to facilitate placement of the ribbon along its path. Third embodiment: Cooling conveyor belt In an alternative embodiment shown in FIG. 2, the transport system includes at least one first transport 7 comprising a transport belt 71 .

[0134] The transport belt 71 is designed and arranged to hold the ribbon 5 and transport it by its inner surface along at least a first portion of the ribbon's path. The first transport belt 71 performs the same function as a continuous track that rotates the ribbon 5 in one direction. In one embodiment, the transport belt 71 is configured as a parallelogram that is looped to form a ribbon support.

[0135] The inner surface of the ribbon 5 is held against the outer surface of the conveyor belt 71. In the example of Figure 2, 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.

[0136] The transport belt 71 supports a portion of the ribbon 5 during its movement, reducing tension along the ribbon 5. This support function of the transport belt 71 is intended to better distribute the tension on the ribbon 5.

[0137] By "part of the ribbon" it is to be understood a part of the ribbon that is in part of the path of the ribbon.

[0138] One advantage of the transport belt 71 is that the ribbon 5 is conveyed along the distance between the two rollers 11 without being subjected to mechanical deformation.

[0139] In a preferred embodiment, the ribbon 5 is conveyed along its distance on a rounded surface of the conveyor belt 71. Indeed, a rounded surface with a maximum radius of curvature can reduce friction between the belt and the ribbon, further reducing the normal force applied to the ribbon. In such a configuration, the rounded surface of the conveyor can be designed to maximize the radius of curvature of the ribbon 5.

[0140] The conveyor 7 advantageously minimizes stress on the ribbon 5, improving the lifespan of the ribbon 5. Furthermore, minimizing stress on the ribbon 5 avoids creating a ripple profile in the ribbon 5. Furthermore, the use of the conveyor belt 71 reduces the risk of wrinkling or shifting of the ribbon 5.

[0141] The conveyor belt 71 may consist of a plastic band placed around at least two rollers 11. In other embodiments, the conveyor belt 71 may be made of any flexible material such as an elastomer, a thermosetting plastic such as a thermosetting resin or polyimide, a cork band or a metal plate such as stainless steel.

[0142] These rollers 11 carry the transport belt 71 around a path that includes a portion where the transport belt 71 carries the ribbon 5 along a portion of the path of the ribbon 5 .

[0143] In one embodiment, a first transport 7 including a first conveyor belt 71 is coupled to a cooler 72. The first conveyor belt 71 holds and supports the ribbon in a first portion of the ribbon's path. In one embodiment, rollers 11 of the first transport 7 are coupled to the cooler 72.

[0144] In another embodiment, the first transporter 7 includes a first guide element 75. The first guide element 75 guides the transport belt 71 moving along a predetermined path, similar to how the first guide element in FIG. 1 guides the ribbon 5. In particular, the portion of the first transport belt 71 carrying the ribbon 5 is supported by the first guide element 75. The first guide element 75 may be a guide element having a partially rounded shape.

[0145] The first inductive element may constitute a plate, as described in the first embodiment, the convex surface of which indirectly supports the ribbon 5 entrained by the conveyor belt 71 .

[0146] The first guide element 75 is preferably coupled to a cooler 72 for cooling the ink 4 coated through the first transport belt 71 and ribbon 5. In this embodiment, the first transport belt 1 is preferably made of a material with high thermal conductivity, such as metal, preferably aluminum or copper, or an alloy of such metals. The first guide element 75 can be coupled to the cooler in a similar manner as previously described in the description of the first guide element of FIG. 1.

[0147] Similarly, the transport system can include a second transporter 8 including a second transport belt 81. The second transport belt 81 holds and transports the ribbon 5 along at least a second portion of the ribbon 5's path and / or a third portion of the ribbon 5's path. The second transport belt 81 can include a second guide element 85 coupled to a heater 82. The second guide element 85 can be configured to heat the ink 4 on the ribbon 5 along the second portion of the ribbon 5's path. Similar to how the rollers 11 of the first transporter 7 are coupled to the cooler 72, the rollers of the second transporter 8 can also be coupled to the heater 82. The heater 82 can include at least one resistor configured to heat the transport belt 81 by Joule heating. The at least one resistor can be disposed within or in contact with the rollers of the second transporter 8 or the second guide element 85.

[0148] In one embodiment, the second and third portions are adjacent and heaters 82, 84 are configured to heat the ink on the ribbon along a portion that includes the point where the ribbon is coated by coater 3.

[0149] In one embodiment, the first heater 82 and / or the second heater 84 are coupled to the rollers 9 of the transport system and / or the rollers 11 supporting the transport belt 71 .

[0150] A preferred embodiment of the printing device is shown in FIGS.

[0151] The printing device 1 comprises a coater 3 and a printhead 6. The coater 3 coats an endless ribbon 5, forming a layer of ink on one side of the ribbon 5.

[0152] The coater 3 is designed to coat the ribbon 5 with a layer of ink having a thickness of 1 to 8 micrometers. Preferably, the coater is designed so that the thickness of the coated ink layer is perceptibly uniform along the width and length of the ribbon 5.

[0153] The printhead 6 is positioned to transfer at least a portion of the ink 4 on the ribbon 5 onto the substrate 20 by thermal transfer.

[0154] The transport system ensures the displacement of the ribbon 5 along a path that cyclically carries the ink 4 from the coater 3 to the print head 6 on a first path, and from the print head 6 to the coater 3 on a second path. The transport system comprises a plurality of rollers 9 for holding and transporting the ribbon 5. The transport system may also comprise a spring-loaded tension roller 10. The spring-loaded tension roller 10 may be attached to a linear slide. The spring-loaded tension roller 10 comprises a spring element that is loaded and arranged to push or pull the roller 10 along the linear slide to maintain mechanical tension on the ribbon. In one embodiment, the spring-loaded tension roller 10 is a drive roller.

[0155] The transport system may also include a first transport 7 including a transport belt 71. The transport belt 71 of the first transport 7 is positioned to hold the ribbon 5 and transport it along at least a first portion of its path. The first portion of the ribbon's path is located in the first path of the ribbon 5 from the coater 3 to the print head 6. In the first portion of the ribbon's path, the ribbon carries fresh ink to the print head 6. The first transport 7 is composed of three rollers for holding and transporting the transport belt 71.

[0156] The first conveyor 7 comprises a first guide element 75 for holding and conveying a portion of the conveyor belt 71 that holds and conveys the ribbon 5. The first guide element 75 holds and conveys the ribbon 5 indirectly via the conveyor belt 71 along at least a first portion of the path of the ribbon 5.

[0157] Cooler example As shown in the figure, the first guide element 75 is coupled 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 radiator 76 for cooling the coolant of the heat exchanger. The heat exchanger may comprise a condenser 74. The radiator 76 is arranged to cool the condenser 74.

[0158] In one embodiment, the coolant is an alcohol solvent. The advantage of such a coolant is its low boiling point. In this embodiment, the coolant boils in contact with the first guide element 75, resulting in a high heat loss through the first guide element 75. In the condenser, the refrigerant returns to a liquid state.

[0159] 5, the heat exchanger consists of a coil 73 that guides the refrigerant between a first guiding element 75 and a condenser 74. In one embodiment, the rollers 11 of the first transport system are also coupled to a cooler 72 in order to improve the cooling of the ink 4.

[0160] In one embodiment, the coil 73 is a heat pipe.

[0161] The heat pipe consists of an evaporator section and a condenser section. The evaporator section is contained in the first guide element 75. The condenser section is contained in the condenser 74.

[0162] Externally applied heat to the evaporator section is conducted through the heat pipe wall and wick structure, vaporizing the refrigerant. The resulting vapor pressure drives the vapor through the pipe through the thermal insulation and into the condenser 74, where the vapor condenses, compared to the latent heat of evaporation to a given heat sink. Capillary pressure generated by the meniscus within the heat pipe pumps the condensed refrigerant back to the evaporator section. This allows the heat pipe to continuously transport the latent heat of evaporation from the first guide element 75 to the condenser 74 without the use of mechanical pumping means. This process continues as long as there is sufficient capillary pressure to return the condensed refrigerant to the evaporator. The orientation and construction requirements for a heat pipe to operate in this manner are well known to those skilled in the art.

[0163] Heat pipes are advantageous for reducing the volume of the heat exchanger. The cooler 74 can be cooled to continue condensing the coolant in a radiator 76 and / or a Peltier heat pump. Heat pipes allow avoiding mechanical pumping means for transporting the coolant.

[0164] The described cooler 72 can also be used to cool the plate 75 described in the second embodiment of the present invention or the cooling roller 100 described in the first embodiment of the present invention.

[0165] The cooler 72 is configured to cool the ink 4 at a predetermined temperature via the transport belt 71 and ribbon 5. The advantage is that it cools the ink 4 at least below its melting temperature. In this way, the ink 4 on the ribbon 5 that arrives under the printhead 6 is in a solid state, regardless of the ambient temperature at which the printing device is used.

[0166] Preferably, the transport belt 71 is made of a metal sheet to advantageously improve the thermal conductivity between the ink 4 and the first guide element 75. Preferably, the thickness of the ribbon 5 is less than 30 μm or 25 μm to advantageously improve the thermal conductivity between the ink 4 and the first guide element 75.

[0167] In one embodiment, the power applied to cool the ink can be between 1500 and 6000 watts / m of ribbon at a ribbon speed of 1 m / s when the ink layer thickness on the ribbon is in the range of 2 to 7 μm and the ribbon comprised of polyimide is in the range of 5 to 25 μm. The power applied to cool the ink can be proportional to the ribbon speed, the ink layer thickness, or the polyimide ribbon thickness.

[0168] Additional delivery system for heating the ink In one embodiment, the conveying system further includes a second conveyor 8 including a second conveyor belt 81. The second conveyor belt 81 holds and conveys the ribbon 5 in a second portion of the ribbon's path. The second portion of the ribbon's path preferably constitutes at least a portion of the ribbon's second path. That is, the second conveyor belt 81 holds and conveys the ribbon 5 in at least a portion of the path from the print head 6 to the coater 3. The second conveyor belt 81 can also hold and convey the ribbon 5 in a third portion of the ribbon's path. The third portion of the ribbon's path preferably includes at least a portion of the ribbon's second path. That is, the second conveyor belt 81 holds and conveys the ribbon 5 in at least a portion of the path from the coater 3 to the first portion cooled by the cooler.

[0169] The second transport belt 8 includes at least one second guide element 85 and / or roller that holds and transports the second transport belt 81 coupled to a heater 82. The heater 82 is configured to heat the ink 4 to a second predetermined temperature, which is preferably equal to or greater than the melting point of the ink 4. Melting the ink before it reaches the coater 3 is advantageous for melting and flowing the ink on the ribbon 5 and improving the uniformity of the ink layer on the ribbon after coating. Such heating further improves the recovery of the remaining ink before coating (not shown).

[0170] The heater is configured to heat the ribbon in the second and / or third portions of the ribbon's path. The second portion can also include the portion where the coater coats the ribbon 5. This is advantageous for heating the ink 4 on the ribbon 5 during the coating process to improve the uniformity of the ink layer on the ribbon 5. Indeed, heating can prevent rapid solidification of the ink 4 in contact with the ribbon 5, reduce the viscosity of the ink 4, and allow the ink to spread evenly over the ribbon's surface. In one embodiment, the third portion constitutes part of the ribbon's first path extending from the coater. This is advantageous for heating the ink immediately after the coating process to further improve the uniformity of the ink thickness on the ribbon. That is, as shown in FIG. 3, heating devices can be positioned to heat the ink on the ribbon before and after the coater 3 and in portions of the path before the portion cooled by the cooler 72.

[0171] In one embodiment, the printing apparatus 1 may include a frame 12. The frame 12 includes the coater 3, the printhead 6, and the ribbon 5 path. The frame 12 includes at least one opening 15 for the exit of the printed substrate 20. In one embodiment, the printing apparatus 1 further includes an isolation wall 14. The isolation wall 14 is positioned to separate a first portion of the cooled ribbon path from a second and / or third portion of the heated ribbon path. The isolation wall 14 may include an opening for the passage of the ribbon 5. As shown in FIG. 4, the isolation wall 14 may extend from the frame 12 of the printing apparatus 1. The isolation wall 14 isolates the coater 3 and the heater 82 from the first portion of the ribbon path where the ink is cooled by the cooler 72. One advantage is that the isolation wall 14 contains the heat provided by the heater 82 and the coater 3. In this way, the power required to cool the ink 4 to the first predetermined temperature can be reduced. The isolation wall 14 may be made of an insulating material. In one embodiment, the separator 14 comprises mineral wool.

[0172] In one embodiment, the printing apparatus 1 includes two print rollers 21 for guiding the substrate 20 to the print head 6. As shown, the printing apparatus 1 further includes a third guide element 22 for holding the substrate 20 and ribbon 6 along a predetermined length and transporting them to the print head 6.

[0173] In one embodiment, the print roller 21 and / or the third guide element 22 are coupled to a heater and / or cooler to control the temperature of the ink 4 in the fourth portion of the first path. The fourth portion is located in 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 defined length on the first path of the ribbon 5. This optimizes the ink temperature and ensures high-quality printing by thermal transfer. In a preferred embodiment, the cooler and / or heater for temperature control is intended to control the temperature of the ink 4 to a third predetermined temperature. The third predetermined temperature is determined to be a few degrees below the melting point of the ink. This reduces the energy transferred, ensuring heat transfer and increasing printing speed without compromising print quality.

[0174] Cooling Parameters In one embodiment, the contact length between the cooling plate 75, transport belt 71, or 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 contact length between the ribbon 5 and the cooling plate 75, transport belt 71, or cooling roller 100 is in the range of 5 to 30 cm. The circumference of the cooling roller or the length of the transport belt is preferably in the range of 10 to 60 cm.

[0175] The diagram shown in Figure 10 shows the temperature levels of the ink coated on the ribbon along its travel (not to scale).

[0176] 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 a third portion of the ribbon's path, where the ink is heated to a second predetermined temperature T2 above the ink's melting point TF. In one embodiment, the second predetermined temperature T2 is above the ink's glass transition temperature.

[0177] In one embodiment, the printing apparatus includes a support roller positioned and designed to support the ribbon along a portion of the path that constitutes the coating zone, and preferably the roller is provided with heating means for contacting and heating the ribbon.

[0178] In a second stage, the ink on the ribbon arrives at a portion of the ribbon's path where the ink is cooled. Portion C corresponds to the portion of the ribbon that contacts plate 75, transport belt 71, or cooling roller 100. At the end of this portion C, the temperature of the ink drops to a first predetermined temperature T1. The first predetermined temperature T1 is lower than the melting point TF of the ink, preferably 20° C. lower than the melting point TF of the ink.

[0179] In the third stage, the ink is locally heated in region D near the print head to effect thermal transfer of the ink from ribbon 5 to substrate 20. To achieve this, the ink in region D is heated above its melting point TF to effect this thermal transfer. In region D, the ink can be heated above or below a second predetermined temperature T2.

[0180] The remaining ink on the ribbon is then transported from the printhead to coating station B for recoating as described in the first step.

[0181] One advantage of a cooling plate that is in direct contact with the ribbon is that it is easier to control the temperature of the ink.

[0182] A further advantage of the present invention is that it allows for better control of solidification of the coated ink. The present invention also has the advantage of shortening the length of the ribbon between the coating device and the printhead. Therefore, the present invention allows for a reduction in 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.

[0183] The length of the first pass of the ribbon (ie the length of the coated ribbon) is preferably in the range of 20 cm to 80 cm, more preferably in the range of 30 cm to 50 cm.

[0184] The present invention further has the advantage of providing more controlled cooling of the ink, cooling the coated ink sufficiently to prevent the ink from adhering to the substrate, thus resulting in complete solidification of the ink and leaving the ink layer tack-free during printing.

[0185] In one embodiment, the printing apparatus is designed and configured to cool the coated ink on the ribbon so that the temperature of the ink that reaches the substrate in contact with it is less than 60°C or 20°C below its melting point.

[0186] The present invention advantageously provides a cooling process for the ink on the ribbon that allows the ink to reach such temperatures when the length of the coated ribbon (i.e., the length of the first path) is less than 80 cm and the ribbon speed is greater than 1 m / s.

[0187] Furthermore, the present invention allows the printing device to be used in a wide 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 may depend on the environmental conditions (temperature, humidity, pressure). Thus, the present invention allows for a globally standardized printing process.

[0188] In effect, the present invention ensures that the temperature of the ink arriving at the print zone, where the printhead is in contact with the ribbon, is equal to or lower than the initially defined temperature.

Claims

1. Frame (12) and an endless ribbon (5) for transporting ink to an outer surface (51); a coating device (3) for coating an endless ribbon (5) with ink (4); a print head (6) that performs printing by thermally transferring a portion of the ink (4) coated on the endless ribbon (5) onto a substrate (20); a plurality of first rollers (9) for supporting and transporting the endless ribbon (5) by their inner surfaces (52) along a path from the coating device (3) to the print head (6) and from the print head (6) to the coating device (3); a plate (75) for supporting an inner surface (52) of the endless ribbon (5) between two adjacent first rollers (9) along a path from the coating device (3) to the print head (6), the plate (75) being fixed to a frame (12) in translation and rotation and having a first convex surface for supporting the inner surface (52) of the ribbon (5); a heat exchanger (72) designed to cool the first convex surface of said plate (75) at a first predetermined temperature (T1); A thermal transfer printing device (1) comprising:

2. 2. The thermal transfer printing device (1) of claim 1, wherein the first convex surface of the plate (75) is disposed in direct contact with the endless ribbon.

3. at least two second rollers (11); a conveyor belt (71) supported by the at least two second rollers (11) and the first surface of the plate (75), and arranged to support and convey an endless ribbon (5) by its inner surface (51); Further provided with 2. The thermal transfer printing device (1) according to claim 1, wherein the second roller (11) and the plate (75) are arranged so that a first surface of the plate (75) supports the endless ribbon (5) via the conveyor belt (71).

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

5. further comprising at least one heater (82); the heater (82) is fixed to the frame (12) in translation and is positioned to heat a first portion of the endless ribbon (5); 4. A thermal transfer printing device (1) according to any one of claims 1 to 3, wherein a first portion of the endless ribbon (5) comprises a coating zone of the ribbon (5), the ribbon (5) being coated by the coating device (3) or in contact with the coating device.

6. The plate (75) includes a core having a cavity through which a coolant circulates to cool the outer surface of the core; 6. The thermal transfer printing device (1) according to claim 5, wherein the outer surface of the core is arranged to support the ribbon (5).

7. 7. The thermal transfer printing device (1) according to claim 5 or claim 6, wherein the heater (82) comprises a roller arranged to support the inner surface (52) of the ribbon on its circumferential surface, and means for heating the circumferential surface of the roller.

8. 8. A thermal transfer printing device (1) according to claim 7, wherein the means for heating the circumferential surface of the roller comprises an electrical resistor for heating the second guide element (85) by Joule heating.

9. 9. The thermal transfer printing device (1) according to any one of claims 1 to 8, wherein the endless ribbon (5) has a length of less than 150 cm.

10. A method of thermally printing a substrate (20), comprising: A thermal transfer printing device according to any one of claims 1 to 9 is provided, cyclically transporting the endless ribbon (5) carrying the ink (4) from the coating device (3) to the print head (6) and from the print head (6) to the coating device (3); The coating device (3) coats the outer surface (51) of the endless ribbon (5) with ink; cooling the plate (75) supporting the inner surface (52) of the endless ribbon (5) to solidify the coated ink; The method includes thermally transferring a portion of the ink coated on the outer surface of the endless ribbon (5) to the substrate (20) using the print head (6).

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

Images