Thermal printing equipment with high sensitive printing speed

Abstract

The present invention relates to a thermal transfer printing device (1), comprising: a coater (3) for coating an endless carbon ribbon (5) with ink in a coating area; a print head (6) for thermally transferring a substrate (20) to print on a printing area using a portion of the ink coated on the endless carbon ribbon (5); a conveying system (10, 11) supporting and conveying the endless carbon ribbon (5) containing ink along a first path from the coater (3) to the print head (6) and along a second path from the print head (6) to the coater (3); a pre-printing buffer (8) for controlling the length of a first path of the carbon ribbon in the coating area; and a post-printing buffer (7) for controlling the length of a second path of the carbon ribbon in the printing area.

Description

Technical Field

[0001] The present invention relates to a thermal transfer printing device, in particular to a thermal transfer printing device comprising an endless carbon ribbon. Background Art

[0002] Current solutions involving thermal transfer printing devices use disposable, pre-coated ribbons. A limitation of these solutions is that the ribbon must be periodically replaced when the end of the ribbon is reached. This replacement requires stopping the printer for a period of time, which is inconvenient for some applications, such as when the printer is a labeling machine on a production line.

[0003] To overcome this shortcoming, EP3055135B1 teaches a printing device that uses an endless ribbon that is fed by rollers, with a portion of the ribbon exposed to a thermal print head and another portion of the ribbon exposed to a coater to re-coat the ribbon to replace the printed ink. The goal is to use a ribbon that can withstand a large number of cycles, such as millions of cycles, through the system, which limits the robustness and reliability of the ribbon composition and system structure.

[0004] The main disadvantage of this system is that it is difficult to meet the requirements of coating and printing at the same time.

[0005] In fact, coating requires a relatively constant speed, or at least avoid sudden changes in speed to achieve uniform coating. In addition, the lower the coating speed, the longer the carbon ribbon life and the higher the re-coating energy required.

[0006] However, printing requires flexibility because it needs to slow down between prints and quickly speed up to reach the print speed. In addition, the speed of the carbon ribbon should be as fast as possible to increase the print speed or the number of labels printed.

[0007] Therefore, because EP3055135B1 teaches a carbon ribbon whose speed cannot meet both requirements, such a printer cannot simultaneously achieve optimal coating and optimal printing, both of which require high flexibility to control the speed difference.

[0008] EP228866A1 describes a printer that includes a buffer mechanism for buffering the movement of a ribbon. However, a disadvantage of this solution is that it increases the size of the printer. Furthermore, due to the high tension applied to the ribbon, this solution can damage the ribbon. Summary of the Invention

[0009] The present invention aims to provide a thermal transfer printing device and related methods to overcome the above-mentioned shortcomings.

[0010] According to a first aspect, the present invention relates to a thermal transfer printing device comprising:

[0011] a coater for coating the endless carbon ribbon with ink in a coating area;

[0012] a print head for printing by thermally transferring a portion of the ink coated on the endless carbon ribbon to a substrate in a printing area;

[0013] a conveyor system that supports and transports an endless ribbon containing ink in a loop along a first path from the coater to the printhead and along a second path from the printhead to the coater;

[0014] a pre-printing buffer for controlling the length of a first path of the carbon ribbon; and

[0015] The post-printing buffer is used to control the length of the second path of the carbon ribbon.

[0016] Two buffers (one on each side of the printhead) advantageously allow for variations in ribbon speed relative to the coating zone between the two buffers. By adjusting the lengths of the first and second paths simultaneously, the ribbon speed in the printing zone can be varied and temporally independent of the ribbon speed in the coating zone.

[0017] Therefore, during printing, when the ribbon speed in the print area stops or increases, the ribbon speed can be maintained at a constant low speed.

[0018] According to another aspect, the thermal transfer printing device comprises:

[0019] an annular carbon ribbon, the annular carbon ribbon comprising an inner surface and an outer surface;

[0020] a coating device for coating the endless carbon ribbon with ink in the coating area;

[0021] a print head for printing by thermally transferring a portion of the ink coated on the endless carbon ribbon to a substrate in a printing area;

[0022] a conveying system for supporting and conveying the endless ribbon along a path from the coating device to the print head and from the print head to the coating device;

[0023] a pre-printing buffer comprising at least two moving rollers to support the coated carbon ribbon during its transfer from the coating device to the print head: a first moving roller arranged to support an inner surface of the endless carbon ribbon, and a second moving roller arranged to support an outer surface of the endless carbon ribbon;

[0024] A post-printing buffer includes at least two moving rollers to support the carbon ribbon during its transfer from the print head to the coating device: a third moving roller is arranged to support the inner surface of the endless carbon ribbon, and a fourth moving roller is arranged to support the outer surface of the endless carbon ribbon.

[0025] In one embodiment, each moving roller is movable along a predetermined trajectory, preferably in a plane substantially perpendicular to the axis of rotation of the moving roller.

[0026] In one embodiment, the printing device further includes a first controller configured to:

[0027] Controlling the movement of the first moving roller and the second moving roller along their predetermined tracks to increase or decrease the length of the coated carbon ribbon from the coating device to the print head; and

[0028] The third moving roller and the fourth moving roller are controlled to move along their predetermined tracks to increase or decrease the length of the carbon ribbon from the print head to the coating device after printing.

[0029] In one embodiment, the first moving roller and the second moving roller of the same buffer can both move along a circular trajectory around the same axis.

[0030] One advantage is that a unique motor controls the rotation of the frame to control the amount or length of ribbon in the buffer. Another advantage is that the volume of the buffer is reduced, thereby reducing the size of the printer.

[0031] In one embodiment, the printing apparatus further comprises a drive, optionally including a drive roller, to drive the ribbon at a first speed over the coating area.

[0032] In one embodiment, the printing apparatus further comprises a first controller configured to control the movement of each moving roller along its predetermined trajectory to:

[0033] driving the ribbon on the print area at a speed lower than the first speed by driving the pre-print buffer to reduce the length of the ribbon along the first path and simultaneously driving the post-print buffer to increase the length of the ribbon along the second path, and

[0034] The carbon ribbon on the printing area is driven at a speed higher than the first speed by driving the pre-printing buffer to increase the length of the carbon ribbon along the first path and simultaneously driving the post-printing buffer to reduce the length along the second path.

[0035] The first controller advantageously automatically applies a speed differential between the ribbon speed over the print zone and the ribbon speed in the coating zone.

[0036] In one embodiment, the printing device further comprises a print roller for holding and conveying the substrate and ribbon along the print zone, wherein the print roller and / or conveyor system is movable between two configurations: a printing configuration in which printing is enabled and the ribbon is supported by contact with the substrate, and a disengaged configuration. Preferably, in the printing configuration, the ribbon is sandwiched between the print head and the substrate. In the disengaged configuration, the ribbon is disengaged from the substrate and preferably from the print head.

[0037] In one embodiment, the printing device further comprises a second controller operable to command the print roller or transport system to change configuration between the printing configuration and the disengagement configuration.

[0038] In one embodiment, the printing device further comprises a speed sensor to measure the speed of the carbon ribbon in the printing area.

[0039] The second controller may be configured to automatically command a configuration change when the first controller secures the ribbon to the print zone, or may be configured to control the print roller to automatically switch the configuration of the drive roller when a measured speed of the ribbon in the print zone reaches zero. In an alternative embodiment, the first controller is configured to automatically stop the ribbon from being in the print zone when the second controller changes the configuration.

[0040] Stopping the ribbon when changing configurations advantageously avoids friction between the print head and the ribbon during configuration changes, thereby preventing the ribbon from tearing.

[0041] In one embodiment, the second controller automatically drives the print roller to drive the substrate at a speed equal to the ribbon speed across the print zone in the printing configuration, which advantageously reduces ribbon-to-substrate friction.

[0042] In one embodiment, the pre-printing buffer and / or the post-printing buffer include at least moving rollers that are arranged and configured to hold and convey the carbon ribbon along its path, and each moving roller can move along a predetermined track to change the length of the carbon ribbon path.

[0043] In one embodiment, the moving roller can move along a circular trajectory, which advantageously allows reducing the volume of the buffer or increasing the difference between the maximum and minimum lengths of the ribbon path.

[0044] In one embodiment, the first axis is parallel to the axis of rotation of each moving roller of the at least one buffer, which advantageously allows providing a compact buffer.

[0045] In one embodiment, the printing device further comprises an endless carbon ribbon supported by the conveying system along the first and second paths. The carbon ribbon is preferably made of a material with an elastic modulus lower than 3 GPa, which advantageously enables the carbon ribbon to be pulled by the buffer without plastic deformation.

[0046] In one embodiment, the first moving roller and the second moving roller of the same buffer are mounted in a frame which is rotatably movable about an axis substantially parallel to the axis of rotation of the first and second moving rollers.

[0047] In one embodiment, the first controller is configured to control the pre-print buffer and the post-print buffer independently of each other.

[0048] In one embodiment, the first controller controls the bumper by controlling the rotation and direction of rotation of a frame of the bumper, optionally by controlling a motor of the frame.

[0049] According to another aspect, the present invention relates to a method of printing a substrate using a thermal transfer printing device. Preferably, the thermal transfer printing device is a transfer printing device according to the first aspect of the present invention.

[0050] In one embodiment, the method includes driving the carbon ribbon on the coating area at a first predetermined speed, and simultaneously driving the carbon ribbon on the printing area at a second speed different from the first predetermined speed.

[0051] Driving the ribbon on the print zone at a second speed different from the first predetermined speed is achieved by the following steps:

[0052] driving the moving roller of the pre-printing buffer to reduce the length of the carbon ribbon from the coating device to the print head, and driving the moving roller of the post-printing buffer to increase the length of the carbon ribbon from the print head to the coating device, or

[0053] The moving roller of the pre-printing buffer is driven to increase the length of the carbon ribbon from the coating device to the print head, and the moving roller of the post-printing buffer is driven to reduce the length of the carbon ribbon from the print head to the coating device.

[0054] In one embodiment, when the second speed is lower than the first speed, the second speed is achieved by driving the pre-printing buffer to increase the length of the ribbon along the first path and simultaneously driving the post-printing buffer to decrease the length of the ribbon along the second path.

[0055] The method advantageously allows for a sudden increase or decrease in ribbon speed on the printing area, thereby maintaining a constant ribbon speed on the coating area. The method advantageously provides highly flexible printing, uniform coating, and improved ribbon life.

[0056] In one embodiment, the method further comprises printing by:

[0057] Drive the carbon ribbon on the coating area at a predetermined speed; and at the same time

[0058] reducing the ribbon speed across the print area by driving the pre-print buffer to increase the length of the ribbon along the first path and simultaneously driving the post-print buffer to decrease the length of the ribbon along the second path; and

[0059] When the ribbon speed decreases on the print area, the print roller moves to the print position;

[0060] In one embodiment, the method further comprises operating printing by driving the carbon ribbon at a printing speed over the printing area.

[0061] In one embodiment, operating printing also includes driving the ribbon speed on the printing area higher than the ribbon speed on the coating area by driving the pre-printing buffer to reduce the length of the ribbon along the first path, and simultaneously driving the post-printing buffer to increase the length of the ribbon along the second path.

[0062] In one embodiment, the method further comprises disengaging printing by:

[0063] Drive the carbon ribbon on the coating area at a predetermined speed; and at the same time

[0064] reducing the ribbon speed across the print zone by driving the pre-print buffer to reduce the length of the ribbon along the first path while driving the post-print buffer to increase the length of the ribbon along the second path; and

[0065] When the ribbon speed across the print area decreases, the platen roller moves to the disengaged position. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a schematic diagram of a thermal transfer printing device according to one embodiment, wherein the thermal transfer printing device includes an endless ribbon and two buffers, each buffer including a movable roller in a first configuration;

[0067] Figure 2 is based on Figure 1 A schematic diagram of a thermal transfer printing apparatus wherein the movable roller is in a second configuration;

[0068] Figure 3 yes Figure 1 and Figure 2 A schematic diagram of a substrate transport system of a printing device in a printing configuration, wherein the print roller is movable and positioned to allow printing;

[0069] Figure 4 yes Figure 1 and Figure 2 A schematic diagram of a substrate transport system of a printing device in a disengaged configuration, wherein the print roller is movable and positioned where the ribbon disengages the substrate and the print head;

[0070] Figure 5is a schematic diagram of a buffer in a first configuration according to another embodiment;

[0071] Figure 6 is based on Figure 5 A schematic diagram of the buffer in a second configuration;

[0072] Figure 7 is a schematic diagram of a printing device according to one embodiment;

[0073] Figure 8 is a graph showing the printing of several labels according to an embodiment of the present invention, the graph showing the speed of the carbon ribbon in the coating area and the printing area and the path length of the carbon ribbon through the pre-printing buffer and the post-printing buffer;

[0074] Figure 9 is a graph showing printing of a label according to an embodiment of the present invention, the graph showing the speed of the carbon ribbon in the coating area and the printing area and the path length of the carbon ribbon through the pre-printing buffer and the post-printing buffer;

[0075] Figure 10 is a schematic diagram of a substrate conveying system of a printing device according to another embodiment of the present invention, wherein the printing device further includes two additional buffers near the print head. DETAILED DESCRIPTION

[0076] The present invention will be better understood from the following description with reference to the accompanying drawings.

[0077] Now refer to Figure 1 and Figure 2 A preferred embodiment of the printing apparatus 1 according to the present invention is described.

[0078] Printing apparatus 1 includes a coater 3 for coating a ribbon with ink and a print head 6 for printing by thermally transferring the ink coated on the ribbon to a substrate. Printing apparatus 1 also includes a transport system arranged and configured to secure and support an endless ribbon 5 along a path from coater 3 to print head 6 and from print head 6 to coater 3. The path of the ribbon defines a loop.

[0079] coating machine

[0080] The coater 3 is configured and arranged to coat the outer surface of the carbon ribbon 5 with ink.

[0081] The coater 3 may be connected to a reservoir (not shown). The reservoir is configured to receive solid ink to supply the coater 3. In another embodiment, the reservoir may include liquid ink, and the reservoir may be connected to a mixing element to maintain the ink at predetermined physical conditions, such as temperature and / or viscosity.

[0082] The coater may include an ink roller including an outer surface that contacts the ribbon and is supplied with ink from a reservoir.

[0083] Alternatively, the coater 3 may comprise a slot-die coating device arranged to coat the ink onto the outer surface of the carbon ribbon.

[0084] The coater (also called “coating device”) can also include all coating systems known to the person skilled in the art and compatible with the present invention.

[0085] The coater 3 can be positioned in contact with or near the ribbon 5 to facilitate coating of the outer surface of the ribbon 5. "Outer surface" should be understood as the surface of the ribbon that faces outward toward the ribbon loop, as opposed to the inner surface. The coater 3 is configured to deposit a layer of hot melt ink on the outer surface of the ribbon 5, with the liquid ink layer preferably being evenly distributed across the surface of the ribbon 5. Ink control components (not shown) can ensure that a sufficient amount of ink is distributed across the surface of the ribbon 5 based on the rotational / displacement speed of the ribbon 5 and / or the print mode. The ribbon 5 is coated with hot melt ink in a coating area by the coater 3. In one embodiment, the coating area is defined by the contact between the ribbon and the coater. Preferably, the coating area is defined by the portion of the path of the endless ribbon where the hot melt ink is applied to the ribbon 5. Therefore, the speed of the ribbon in the coating area can be defined by the distance the ribbon travels along its path during a time interval in the coating area, i.e., where melted ink is applied to the ribbon 5.

[0086] Preferably, the printing device 1 comprises a support 11 for holding the ribbon in which the ink is deposited, in order to ensure that the ribbon 5 has sufficient mechanical stability during coating. Figure 1 In the embodiment shown, the support is a roller. In one embodiment, in the coating area, the ribbon is sandwiched between the coater 3 and the support 11. In one embodiment, the coating area is defined by a portion of the ribbon path where the ribbon is supported by the support 11.

[0087] The support 11 may comprise a roller, preferably a driven roller.

[0088] The reservoir and / or coater 3 may comprise heating means to melt the ink in the reservoir and / or coater 3, respectively. The reservoir may be filled with solid ink, the contact of which with the reservoir or coater 3 will tend to melt the ink.

[0089] In one embodiment, the printing device 1 comprises means for periodically adding new solid ink to the reservoir.

[0090] Print head

[0091] The printing device 1 comprises a print head 6. In a preferred embodiment, the print head 6 is a thermal transfer print head 6.

[0092] The print roller 21 can be used to transport the substrate 2 to the vicinity of the carbon ribbon 5. The thermal transfer print head 6 is used to transfer hot melt ink from the carbon ribbon 5 to the substrate 2. The print roller 21 can be configured and arranged to hold and transport the carbon ribbon 5 and the substrate 2.

[0093] In one embodiment, the print area is defined by a portion of the ribbon path where the ribbon 5 is held and supported by the print roller 21. In one embodiment, the print area is defined by a portion of the ribbon path where the ribbon 5 is in contact with the substrate 2, and in particular, where its outer surface is in contact with the substrate 2. In one embodiment, the print area is defined by a portion of the ribbon path where the coating ink on the ribbon 5 is transferred to the substrate 2.

[0094] Thus, the speed of the ribbon in the print zone may be defined by the distance the ribbon travels along its path within the time interval in the print zone, ie, where coating ink on the ribbon is applied to the substrate 2 .

[0095] The print head 6 preferably includes a micro heater area that contacts the ribbon in the printing area, particularly the inner surface of the ribbon, and heats the ribbon and the ink on the ribbon passing through the ribbon, and then transfers the heated ink to the substrate. The surface of the micro heater area can be from 500 μm 2 to 100,000 μm 2 , preferably from 10 000 μm 2 to 20000μm 2 The width of the micro heater area can be from 40 μm to 300 μm, and the length of the micro heater area can be 1 to 2 times the width of the micro heater area. The print head 6 is preferably arranged so that the longitudinal axis of the micro heater area is substantially parallel to the conveying axis of the carbon ribbon in the printing area.

[0096] During printing, the print head 6 or micro heater area contacts the inner surface of the ribbon 5 to enable thermal transfer of ink on the outer surface of the ribbon 5 .

[0097] In one embodiment, the print head includes a protective layer on the surface of the micro-heater zone. In this embodiment, during printing, the inner surface of the ribbon 5 slides in contact with the protective layer. The micro-heater zone heats the ink on the ribbon through the protective layer and through the thickness of the ribbon 5.

[0098] The protective layer may comprise a sol-gel material, preferably a borosilicate. The protective layer advantageously protects the ribbon from friction. The thickness of the protective layer advantageously allows for heat conduction and may be in the range of 1 to 50 μm. The protective layer may comprise a sol-gel material, preferably a borosilicate, which advantageously prevents high friction between the ribbon and the print head when the ribbon slides over the print head during printing.

[0099] During the printing process, the outer surface of the carbon ribbon 5 contacts the substrate 2 to transfer a portion of the ink used to print the substrate.

[0100] The print roller 21 ensures that there is sufficient pressure on the substrate 2 to keep the substrate 2 in contact with the ribbon 5 during the printing process. Then, during the printing process, the ribbon 5 can be kept in a moving sandwich between the substrate 2 and the print head 6 (or micro-heater area), and the movement direction of the substrate 2 is the same as the movement direction of the ribbon 5 near the print head 6. This movement of the substrate 2 and the ribbon 5 near the print head 6 is preferably a linear movement.

[0101] In an alternative embodiment, the print head 6 comprises a laser to heat the ink through the thickness of the ribbon 5, thereby enabling the ink in the outer surface 51 of the ribbon 5 to be thermally transferred 6. Preferably, the wavelength of the laser is between 950nm and 1450nm.

[0102] The arrangement between the print head 6, the ribbon 5, and the substrate 2 can be ensured by mechanical components that are precisely set according to the desired printing accuracy. Guides and position control components can be implemented to ensure at least the predetermined arrangement between the print head 6 and the ribbon 5. For example, a deflector 23 can be used to at least partially support the substrate 2.

[0103] carbon ribbon

[0104] The carbon ribbon 5 is configured to be implemented in a printing device 1 according to the present invention. The carbon ribbon 5 allows ink to be transported from the coater 3 to the print head 6 on its outer surface. The carbon ribbon 5 is an endless carbon ribbon, which should be understood as a carbon ribbon that forms a loop or a strip-shaped carbon ribbon. This carbon ribbon then allows it to be coated and used for printing in a circular manner. The remaining ink that is not used during the printing process is transported to an ink recovery device (not shown) via the print head and re-coated. As a result, the same carbon ribbon 5 is continuously used to transport ink for printing and for transporting the remaining ink after printing. The printing process is implemented to form a continuous circulation process in which the remaining ink is automatically recovered. This configuration allows the retrieval of ink that has not yet been printed, which can advantageously be re-coated and reused in the next turn of the carbon ribbon 5.

[0105] One advantage of the present invention is that an autonomous printing device is provided, wherein at least a portion, preferably 100% or substantially 100% of the ink is used, ie no ink is lost.

[0106] The carbon ribbon 5 can be made of various materials. The carbon ribbon 5 is preferably made of a material with high temperature resistance (for example, resistance to temperatures up to 300°C) and high chemical resistance (for example, resistance to alcohol, ink or solvents, etc.). Preferably, the carbon ribbon 5 is made of polyimide film, which allows the carbon ribbon to be used in a temperature range of up to [340°-380°] without deformation. In a preferred embodiment, the carbon ribbon 5 can also be made of metal or metal alloy. The carbon ribbon 5 can be made of metal alloys, such as stainless steel, aluminum alloy, titanium alloy, copper alloy, beryllium alloy. In one embodiment, the carbon ribbon can include an alloy containing nickel, tin and copper, preferably, the nickel content is between 14.5%m and 15.5%m, the tin content is between 7.5%m and 8.5%m, and the copper content is between 75%m and 79%m.

[0107] In a preferred embodiment, the carbon ribbon 5 is made of a material having an elastic modulus (also called Young's modulus) lower than or equal to 3 GPa, which advantageously allows the carbon ribbon 5 to support the tension provided by the transport system without damaging the carbon ribbon.

[0108] The carbon ribbon 5 is preferably made of a material with a heat transfer rate greater than 0.120 W / mK.

[0109] The thickness and composition of the ribbon material are configured to produce heat transfer through the ribbon, thereby enabling printing.

[0110] Preferably, the thickness of the carbon ribbon 5 is less than 50 μm or 20 μm. This thickness advantageously allows for low resistance to heat transfer between its inner and outer surfaces, thereby improving print quality. The thickness of the carbon ribbon 5 can generally be between 0.5 μm and 50 μm, and most preferably between 0.5 μm and 20 μm. In one embodiment, the thickness of the carbon ribbon 5 is selected within the range of [3-25 μm] or [5-10 μm].

[0111] In one embodiment, the print head 6 comprises a laser, the wavelength of which the carbon ribbon 5 is transparent. In this embodiment, the thickness of the carbon ribbon 5 is selected within the range of [3-200 μm].

[0112] Conveying system

[0113] The carbon ribbon 5 is held and transported using a conveyor system that supports and transports the carbon ribbon 5 along its path.

[0114] The conveying system may include at least one roller 10 to hold and convey the endless carbon ribbon 5. The conveying system may include a plurality of rollers 10, 11 to hold and convey the endless carbon ribbon 5 along its path.

[0115] At least one of the rollers may be a drive roller 11 connected to a motor for rotating the drive roller 11. At least one battery or electrical supply may be provided in the printing device to provide power to the motor. Rotation of the drive roller 11 causes displacement of the endless carbon ribbon 5 along its path, which also causes rotation of the other rollers 10.

[0116] The rollers 10, 11 are mounted to the frame of the printing apparatus to rotate themselves so as to convey the carbon ribbon along their circumferential surfaces. The rollers 10, 11 have a cylindrical shape and are mounted to the frame of the printing apparatus to rotate about their longitudinal axes.

[0117] In an embodiment not shown, the conveying system includes at least one conveyor belt that is configured and arranged to hold and convey the carbon ribbon 5 along a portion of the carbon ribbon path through the inner surface of the carbon ribbon. The conveyor belt performs the same function as a continuous track that drives the carbon ribbon 5 in one rotational direction. In one embodiment, the conveyor belt includes a thin sheet in the form of a parallelogram, which is wound into a loop to form a carbon ribbon support. The conveyor belt can be supported by at least two rollers. In another example, the conveyor belt is supported by three rollers to form a triangle. One advantage of the conveyor belt is that the carbon ribbon 5 is transported along the distance between the two rollers without undergoing mechanical deformation, and the conveyor belt advantageously minimizes the stress on the carbon ribbon 5, which increases the life of the carbon ribbon 5. In addition, minimizing the stress on the carbon ribbon 5 allows avoiding the generation of a corrugated profile on the carbon ribbon 5. In addition, the use of a conveyor belt reduces the risk of wrinkling and misalignment of the carbon ribbon 5.

[0118] separation wall

[0119] In one embodiment, the printing apparatus 1 may include a frame that includes the coater 3, the print head 6, the transport system, and the path for the ribbon 5. The frame includes at least one aperture for exiting the printed substrate 2. In one embodiment, the printing apparatus 1 also includes a partition wall 4 that is arranged to isolate the area including the coater 3 from the rest of the apparatus. The partition wall 14 may include an aperture for passage of the ribbon 5. One advantage is that the heat provided by the coater 3 is contained. During the period when the ribbon is transported from the coater to the printing area, the applied ink is more easily cured on the ribbon.

[0120] Double buffer

[0121] Printing device 1 includes buffers 7 and 8. These buffers define an area within which a portion of the ribbon path is controlled by the buffers. The buffers can control the ribbon path by increasing or decreasing the length of the ribbon path within or through the area defined by the buffers. Thus, the buffers are configured and arranged to shorten or lengthen a portion of the ribbon path.

[0122] The carbon ribbon 5 is transported along a path including a first path (from the coating area to the printing area) and a second path (from the printing area to the coating area).

[0123] The first path of the ribbon includes the portion of the ribbon that has been re-inked (also known as the "re-inked" ribbon) that is conveyed from the coater 3 (or coating area) to the print head 6 (or printing area). The second path of the ribbon includes another portion of the ribbon that has been printed (also known as the "printed ribbon"), or includes the remaining ink that is conveyed from the print head (or printing area) to the coater 3 (or coating area) after printing.

[0124] The printing device 1 according to the present invention comprises a pre-printing buffer 8 in the first path of the carbon ribbon and a post-printing buffer 7 in the second path of the carbon ribbon. Thus, the pre-printing buffer 8 controls the length of the first path of the carbon ribbon, and the post-printing buffer 7 controls the length of the second path of the carbon ribbon.

[0125] In other words, the pre-printing buffer 8 is configured to buffer a predetermined portion of the heavy ink ribbon, and the post-printing buffer 7 is configured to buffer a predetermined portion of the print ribbon.

[0126] “Arranged to buffer” should be understood as meaning that each buffer is arranged to store a variable amount or length of ribbon thereon, the length of the ribbon being defined between the inlet and outlet of the pre-printing buffer 8 or the post-printing buffer 7 .

[0127] In a preferred embodiment, the driver 11 is positioned to drive the carbon ribbon 5 at a first speed on the coating area. Preferably, the driver 11 is located between the pre-printing buffer 8 and the post-printing buffer 7, on one side of the coating area.

[0128] The two buffers 7 , 8 on each side of the printing zone advantageously allow driving the ribbon 5 on the printing zone at a second speed that is different from the first speed of the ribbon in the coating zone driven by the drive 11 .

[0129] In fact, when the length of the first path is reduced by the pre-printing buffer 8 and at the same time the length of the second path is increased by the post-printing buffer 7, the speed of the ribbon 5 on the printing area is superior to that in the coating area.

[0130] In another way, when the length of the first path is increased by the pre-printing buffer 8 and simultaneously the length of the second path is decreased by the post-printing buffer 7 , the speed of the ribbon on the printing area is lower than that in the coating area.

[0131] buffer

[0132] Preferably, the buffers 7 and 8 include moving rollers 71 and 81 that are positioned and arranged to hold and convey the ribbon 5. The positions of the rollers 71 and 81 define the path of the ribbon 5 through the buffers 7 and 8. In one embodiment, each buffer 7 and 8 includes at least one moving roller that is configured to support the ribbon by its inner ribbon surface, and the buffers 7 and 8 include at least one moving roller that is configured to support the ribbon by its outer ribbon surface. Each moving roller 71, 83, 73, 81 is mounted to the frame of the printing device to rotate itself, thereby conveying the ribbon along its circumferential surface. Each moving roller 71, 83, 73, 81 has a cylindrical shape and is mounted to the frame of the printing device to rotate around its longitudinal axis.

[0133] In addition, each moving roller can also move freely along the predetermined track 72 , 82 , 92 .

[0134] Movement of the moving rollers 72 , 82 , 92 along their predetermined trajectories 72 , 82 , 92 increases or decreases the amount of ribbon stored in the buffer or the length of ribbon stored between the buffer entrance and exit.

[0135] like Figure 1 and Figure 2 As shown, the pre-printing buffer includes a first moving roller 81 that supports the inner surface of the carbon ribbon 5 and a second moving roller 83 that supports the outer surface of the carbon ribbon 5. Similarly, the pre-printing buffer 7 includes a third moving roller 71 that supports the inner surface of the carbon ribbon 5 and a second moving roller 73 that supports the outer surface of the carbon ribbon 5. Because each buffer includes a roller on both sides of the carbon ribbon, the length of the carbon ribbon can be advantageously increased or decreased by moving the roller.

[0136] In one embodiment, the rollers 71, 81, 73, 83 are movable along the predetermined trajectory 72, 82. By "movable", it should be understood that the rotation axis of the roller B is free to translate or rotate along the predetermined trajectory, preferably in a plane substantially perpendicular to the rotation axis B, which corresponds to the longitudinal axis of the roller.

[0137] The movement of the roller causes a change in the ribbon path, thereby shortening or lengthening the ribbon path.

[0138] In other words, the movement of the roller changes the amount of ribbon stored between the buffer inlet and outlet.

[0139] Thus, in one example, as the amount of ribbon stored between the inlet and outlet of the pre-print buffer increases or decreases, the length of the heavy ink ribbon also increases or decreases, respectively.

[0140] In the second example, when the amount of the ribbon stored between the inlet and the outlet of the post-printing buffer increases or decreases, the length of the printing ribbon also increases or decreases, respectively.

[0141] In one embodiment, when the length of the heavy ink ribbon increases or decreases, the length of the print ribbon automatically decreases or increases, respectively.

[0142] exist Figure 1 and Figure 2 In the first embodiment shown, the buffer 7, 8 comprises two rollers 71, 81. The two rollers 71, 81 of the same buffer are movable along predetermined trajectories (shown in dashed lines) 72, 82. The movement of the rollers of the same buffer may be synchronized or performed simultaneously.

[0143] like Figure 1 As shown, the pre-printing buffer 8 is in a long configuration, wherein the length of the first path is the largest. Figure 2 As shown, the roller 81 of the pre-printing buffer 8 can be shifted to achieve a short configuration in which the length of the first path is minimal. In one embodiment, the ratio of the maximum length to the minimum length of the ribbon path between the buffer inlet and outlet is greater than 1.3, preferably between 1.3 and 3.

[0144] Figure 1 and Figure 2 An embodiment is shown in which the rollers 71, 81 of the buffers 7, 8 are movable along circular trajectories 72, 82, the two rollers rotating about the same axis to allow the ribbon 5 to be "wound" or "unwound" in the buffer and thereby increase or decrease the length of the ribbon of the first or second path, respectively. This embodiment of the buffer advantageously provides a compact buffer in both long and short configurations. A "buffer" can be defined between an inlet and an outlet of the buffer. The inlet and outlet of the buffer, or the boundaries of the buffer, can be defined by two adjacent rollers 10 on either side of the buffer 7, 8, 9. For example, the inlet of the buffer is defined by the contact between the ribbon and the preceding roller of the buffer and the outlet of the buffer is defined by the contact between the ribbon and the following roller of the buffer.

[0145] The terms “previous roller” and “next roller” are understood here to mean the closest rollers of the transport system 2 that support the ribbon 20 before and after the buffer system, respectively, according to the transport direction of the ribbon 20 .

[0146] In another embodiment, the inlet of the pre-print buffer is the coating zone, and the outlet of the pre-print buffer is the print zone. Therefore, the outlet of the post-print buffer is the coating zone, and the inlet of the post-print buffer is the print zone.

[0147] Figure 8An embodiment of such a buffer is shown comprising a frame 84 mounted on the printing apparatus with one degree of freedom of rotation about an axis A. The frame 84 may comprise a pivot 85 about which the frame is rotatable.

[0148] The roller 81 is mounted on a frame 84. The roller 81 can be mounted on the frame 81 with one degree of freedom to rotate about an axis B to convey the carbon ribbon on its outer surface. In one embodiment, the axis of rotation A of the frame 84 is parallel to the axis of rotation B of the roller 81.

[0149] Thus, frame 84 rotates about its axis A, allowing both rollers 81 to move simultaneously along a curved path 82. Depending on the direction of rotation of frame 84, this path causes the ribbon 5 to wind or unwind, respectively increasing or decreasing the ribbon's path. This embodiment advantageously provides a buffer 8 in which only one motor is required to move both rollers 81 of the same buffer 8 along their predetermined path 82. The number of motors can be advantageously reduced, and the printing apparatus 1 advantageously becomes simpler and more compact.

[0150] Figure 5 and Figure 6 An alternative embodiment of the buffer 9 is shown in FIG. 1 , in which each roller 91 is movable along a linear trajectory 92 and all rollers 91 are movable along the trajectory 92 between a first and a second position. Figure 5 In the first position shown, the buffer 9 is in the long configuration and the length of the ribbon path through the buffer is maximum. Figure 6 In the second position shown, the buffer is in a short configuration and the length of the ribbon path through the buffer is minimized.

[0151] In one embodiment, the buffer comprises a track that guides the rollers 71 , 81 , 91 along a predetermined trajectory.

[0152] Because each moving roller is arranged to support an opposite side of the carbon ribbon, the simultaneous movement of the two moving rollers 71, 81 causes the amount or length of the carbon ribbon in the buffer zone to increase or decrease. In addition, the two moving rollers move in the same direction along a circular trajectory around the same axis A, so that the buffer zone will become compact with respect to the difference in the amount or length of the carbon ribbon stored in the buffer zone.

[0153] First controller

[0154] In one embodiment, the printing apparatus 1 comprises a first controller CALC which controls the pre-printing buffer 8 and the post-printing buffer 7. In one embodiment, the control of the buffer is operated by operating the movement of first and second moving rollers of the buffer along their predetermined trajectories.

[0155] In one embodiment, the first controller is configured to move the moving rollers 71, 81, 91 along a predetermined trajectory 71, 83, 93 of the moving rollers 71, 81, 91. In one embodiment, each buffer includes at least one motor to move its roller 71, 81, 91 along the predetermined trajectory of the rollers 71, 81, 91, and the first controller controls the motor.

[0156] exist Figure 1 and Figure 2 In one embodiment shown, a first controller for controlling the length of the heavy ink ribbon or the printing ribbon rotates the frame 84 of the pre-printing buffer 8 or the post-printing buffer 7, respectively. The direction of rotation of the frame 84 determines whether the amount of ribbon stored in the buffer increases or decreases.

[0157] Preferably, each buffer comprises a motor MT connected to a frame 84 for rotating the frame about its pivot 85. The motor MT is controlled by a first controller CALC in such a way that the first controller CALC is configured to control the motor MT. Thus, the first controller is configured to control the rotation of the frame 84 and to control the direction of rotation of the frame 84.

[0158] The first controller CALC is configured to control the two buffers to increase the length of the carbon ribbon along the first path by driving the pre-printing buffer 8, and at the same time reduce the length of the carbon ribbon along the second path by driving the post-printing buffer 7, thereby driving the carbon ribbon at a speed lower than the first speed of the carbon ribbon in the coating area.

[0159] The first controller CALC is configured to control the two buffers to reduce the length of the carbon ribbon along the first path by driving the pre-printing buffer 8, and at the same time increase the length of the carbon ribbon along the second path by driving the post-printing buffer 7, thereby driving the carbon ribbon at a speed higher than the first speed of the carbon ribbon on the coating area.

[0160] Control of the buffer is achieved by controlling the movement of the moving rollers along their predetermined trajectories 72,82.

[0161] The simultaneous actuation of the two buffers allows the path length of the ribbon to be increased on one side of the print zone, while simultaneously reducing the path length of the ribbon on the other side of the print zone. In other words, one of the two buffers is used to control the speed of the ribbon on the print zone, while the other buffer is used to compensate for the length of the ribbon path in order to avoid an increase in tension along the ribbon on one side of the print zone.

[0162] In other words, by reducing the amount or length of the carbon ribbon stored between the inlet and outlet of the pre-printing buffer 8 and simultaneously increasing the amount of the carbon ribbon stored between the inlet and outlet of the post-printing buffer 7, the speed of the carbon ribbon in the printing area is faster than the speed of the carbon ribbon in the coating area. Alternatively, by increasing the amount of the carbon ribbon stored between the inlet and outlet of the pre-printing buffer 8 and simultaneously reducing the amount of the carbon ribbon stored between the inlet and outlet of the post-printing buffer 7, the speed of the carbon ribbon in the printing area is slower than the speed of the carbon ribbon in the coating area.

[0163] In one embodiment, the first controller further controls the speed of the carbon ribbon in the coating area by controlling a drive of the conveying system (eg, the rotation of the drive roller 11 ).

[0164] In one embodiment, the first controller CALC is configured to control the pre-print buffer and the post-print buffer independently of each other. During printing, the ribbon is sandwiched between the print head 6 and the substrate 2, and between the drive roller 11 and the coater 3. Therefore, the tension applied to the ribbon on either side of the print head may differ. One advantage of independently controlling the buffers 7 and 8 is that it prevents excessive tension on one side of the ribbon during printing.

[0165] Print configuration and escape configuration

[0166] like Figures 1 to 4 As shown, the printing device 1 includes a substrate 2 that is in contact with a ribbon and is conveyed along a print zone to allow ink to be thermally transferred from the ribbon to the substrate. The printing device may also include substrate rollers 22 and 23 to hold and support the substrate. The printing device may also include a print roller 21 as previously described to hold and convey the substrate in contact with the ribbon along the print zone.

[0167] In one embodiment, the printing device is arranged to provide two configurations: a printing configuration and a disengagement configuration.

[0168] exist Figure 3 In the illustrated printing configuration, the ribbon 5 is supported by contact with the substrate 2. The ribbon 5 is supported by the print roller 21 via the substrate 2. "Supported by the print roller via the roller" should be understood to mean that the print roller 21 supports the ribbon 5, and the substrate 2 is positioned between the ribbon 5 and the print roller 21. In the printing configuration, the print roller 21 ensures sufficient pressure on the substrate 2 to maintain contact between the substrate 2 and the ribbon 5 during printing, which advantageously allows ink to be transferred from the ribbon 5 to the substrate 2.

[0169] In one embodiment, in a printing configuration, the print roller 21 maintains the ribbon 5 in contact with the substrate 2 and optionally maintains the ribbon 5 in contact with the print head 6 or micro heater areas of the print head 6 .

[0170] Preferably, in the printing configuration, the ribbon travels in contact with the protective layer of the print head. This protective layer is capable of conducting heat from the micro-heater region and advantageously prevents the ribbon from tearing, which advantageously allows the ink passing through the ribbon to be heated to melt the ink and transfer it from the ribbon 5 to the substrate 2. Therefore, the speed of the ribbon in the printing zone can be defined by the distance the ribbon travels along its path during the time interval in the printing zone, i.e., the time during which the coating ink on the ribbon is applied to the substrate 2 by thermal transfer.

[0171] In an alternative embodiment, where the print head 6 includes a laser for heating the ink, the ribbon 5 is not in contact with the print head 6 in the printing configuration.

[0172] In one embodiment, the printing device 1 includes a drive for driving the substrate 2. "Driving the substrate" should be understood as controlling the movement of the substrate and the speed of the substrate along its path. The drive may be a print roller 21. The printing device 1 may include a motor connected to the print roller 21 to rotate the roller and transport the substrate 2 along its path. The drive may be used to transport the substrate 2 to the vicinity of the ribbon 5.

[0173] exist Figure 4 In the disengaged configuration shown, the ribbon 5 is disengaged from the substrate 2. In this configuration, it is not possible to print or thermally transfer ink from the ribbon 5 to the substrate 2. In the disengaged configuration, the ribbon 5 is not in contact with the print head 6. Therefore, in both configurations, the ribbon speed in the print zone can be defined by the distance the ribbon travels along its path during the time interval that the ribbon is between the substrate 2 and the print head 6.

[0174] In one embodiment, an element of the printing device is movable to switch the printing device from the printing configuration to the disengaged configuration, or vice versa. The element may be a roller 10 of the conveying system, which is movable. Figure 3 and Figure 4 As shown, the element may be a print roller 21 , which is movable between two positions, a first position corresponding to a printing configuration and a second position corresponding to a disengaged configuration.

[0175] Second controller

[0176] The printing device 1 may comprise a second controller COMP configured to control the movable element to switch between the printing configuration and the disengaging configuration.

[0177] exist Figure 3 and Figure 4 In the embodiment, the element is the printing roller 21, and the second controller controls the printing roller 21 to move between two positions.

[0178] In one embodiment, the second controller COMP is configured to automatically switch the configuration of the printing device 1 when the speed of the ribbon 5 in the printing area is zero and the speed of the ribbon 5 in the coating area is non-zero. This allows the ribbon 5 to stop on the printing area when the printing device 1 switches configurations.

[0179] Therefore, when the carbon ribbon 5 contacts the micro-heater area of ​​the print head, or when the carbon ribbon leaves the micro-heater area, the speed of the carbon ribbon 5 is zero, and there is no friction between the carbon ribbon and the print head, thus advantageously reducing the risk of tearing.

[0180] Preferably, in the printing configuration, the print roller 21 is controlled to automatically transport the substrate at the same speed as the ribbon in the print zone.

[0181] In one embodiment, the first and second controllers are a unique computer or are connected to a unique user interface. In one embodiment, the first and / or second controllers also control the print head 6.

[0182] The first controller CALC is connected to the drive roller 11 of the conveying system or to the motor connected to the drive roller to drive the drive roller 11 to rotate and thus drive the speed of the carbon ribbon in the coating area. The first controller CALC is also connected to the buffers 7 and 8 or the moving rollers 71, 81, 73, 83 connected to the buffers to control the speed difference between the carbon ribbon speed in the coating area and the carbon ribbon speed in the printing area.

[0183] The first controller CALC and / or the second controller COMP may comprise a memory or any computer-readable medium including a computer program comprising instructions for causing the printing device to perform the steps of the method according to the present invention. The first controller may comprise a processor or a computer configured to cause the printing device to perform the steps of the method according to the present invention.

[0184] The first controller CALC and the second controller COMP can control the moving roller and / or the driving roller 11 and / or the printing roller 21 according to the instructions received by the communication device. The instructions may include values ​​measured by a sensor (e.g., a speed sensor) configured to measure the speed of the substrate 2, and / or the speed of the carbon ribbon in the coating area, and / or the speed of the carbon ribbon in the printing area.

[0185] Additional buffer device

[0186] exist Figure 10 In one embodiment shown, the thermal transfer printing device includes two additional buffers 101 , 110 .

[0187] The additional buffer comprises a roller 104 on an arm 103. The additional buffer is arranged to support the carbon ribbon with the roller 104 of the additional buffer.

[0188] The arm 103 of the additional buffer is pivotally movable about an axis 102 , which pivoting motion drives the roller 104 between at least a first position N and a second position M.

[0189] In the first position N, the roller defines a path for the ribbon that is shorter than the path of the ribbon when the roller is in the second position M.

[0190] Preferably, the additional buffers 101 , 110 are arranged between the pre-printing buffer 8 and the print head 6 or between the post-printing buffer 7 and the print head 6 .

[0191] Each additional buffer controls the length of the carbon ribbon in the same manner as the pre-printing buffer 8 and the post-printing buffer 7. The first additional buffer 101 is arranged between the pre-printing buffer 8 and the print head 6 to control the length of the carbon ribbon between the pre-printing buffer 8 and the print head 6. The second additional buffer 110 is arranged between the post-printing buffer 7 and the print head 6 to control the length of the carbon ribbon 5 between the post-printing buffer 7 and the print head 6.

[0192] In one embodiment, the path length difference of the carbon ribbon from the first position N to the second position M is smaller than the path length difference of the carbon ribbon achievable by the post-printing buffer 7 or the pre-printing buffer 8 .

[0193] In the first configuration, the first additional buffer 101 is in the first position N, and the second additional buffer 110 is in the second position M ( Figure 10 In the second configuration, the first additional buffer 101 is in the second position M, and the second additional buffer 110 is in the first position N.

[0194] By simultaneously switching the additional buffer, i.e., the first additional buffer 101, from the first configuration to the second configuration, the system is able to temporarily stop the speed of the carbon ribbon in the printing area, which advantageously allows the print roller 21 to be moved to the printing configuration or out of the configuration when the carbon ribbon is stationary, thereby reducing damage to the carbon ribbon and increasing its service life.

[0195] In one embodiment, the pivoting 102 of the arm 103 comprises a torsion spring. One advantage of a torsion spring is that it can very quickly switch the roller 104 between the first position and the second position.

[0196] Methods for printing substrates

[0197] According to a second aspect, the present invention also relates to a method of printing a substrate. Preferably, the method of printing a substrate comprises providing a printing device according to the present invention.

[0198] Now refer to Figure 9 and Figure 8 An example of a method of printing a substrate according to the present invention is described.

[0199] Figure 9 and Figure 8 A graph is shown including the ribbon speed in the coating area SC and the ribbon speed in the printing area SP, as well as the path length of the ribbon through the pre-printing buffer PRB and the path length of the ribbon through the post-printing buffer POB.

[0200] In phase A, the printing device is in a disengaged configuration, with the ribbon conveyed along its path and coated with ink as it passes through the coating zone. During phase A, speed SC increases until it reaches a first predetermined speed S1. At the end of phase A, speed SC and speed SP are preferably equal, meaning that no buffer increases or decreases the length of the ribbon's path through the buffer, which advantageously allows for uniform coating of the ribbon prior to printing.

[0201] In stage B, the printing device moves to the printing configuration. As before, the print roller 21 can move to press the carbon ribbon thereon to support the substrate.

[0202] In one embodiment, in a printing configuration, the print roller 21 holds the carbon ribbon 5 in contact with the print head 6 or with the micro heater area of ​​the print head or with the protective layer of the print head 6 .

[0203] During the transition to the printing configuration, the print roller 21 exerts a force between the ribbon and the print head. This force increases the friction applied by the print head to the ribbon, which increases the risk of the ribbon tearing. To avoid this, stage B may include stopping the ribbon on the print area. Figure 9 As shown, the speed SP is reduced to zero while the speed SC is maintained at the first predetermined speed S1. Figure 9 As can be seen in FIG, the speed difference between SC and SP is achieved by driving the pre-print buffer 8 to increase the length of the ribbon along the first path PRB and simultaneously driving the post-print buffer 7 to decrease the length of the ribbon along the second path POB. Preferably, as a function of the speed SC, the length PRB increases and the length POB decreases to ensure that the speed SP is equal to zero.

[0204] "Driving the buffer" can be understood as controlling the movement of the moving roller of the buffer to reduce or increase the length of the carbon ribbon path.

[0205] This phase B allows the ribbon to be stopped while maintaining contact with the printhead. Therefore, stopping the ribbon during this configuration change advantageously prevents the ribbon from tearing while in contact with the printhead. Indeed, when the print roller exerts force on the ribbon, if the ribbon is stopped, there is no friction between the ribbon and the printhead.

[0206] In one embodiment, the substrate is transported at the same speed as the speed SP during phase B. This allows for reduced friction when operating the contact between the ribbon and the substrate, thereby advantageously reducing the risk of tearing and damaging the ribbon.

[0207] The method and the printing apparatus advantageously allow stopping the ribbon and the printing zone without changing the speed of the ribbon in the coating zone.

[0208] Preferably, during phase A, the pre-printing buffer 8 is controlled to increase the length of the first path of the ribbon or the length of the path of the ribbon through the pre-printing buffer 8, and the post-printing buffer 7 is controlled to decrease the length of the second path of the ribbon or the length of the path of the ribbon through the post-printing buffer 7. This advantageously prepares the buffers for the subsequent phase B.

[0209] Phase C corresponds to the printing step. During printing, the speed SP can be higher than the speed SC by driving the pre-print buffer 8 to reduce the length of the ribbon along the first path PRB and simultaneously driving the post-print buffer 7 to increase the length of the ribbon along the second path POB. During printing, the speed SP can be maintained constant at a second predetermined speed S2.

[0210] This advantageously allows providing high printing speeds without changing the speed SC in the coating area.

[0211] In the first embodiment, the printing time is very short, such as Figure 9 For example, phase C includes printing a unique label. In this embodiment, the speed SC can be maintained at a first predetermined speed S1 during printing, which is lower than a second predetermined speed S2.

[0212] exist Figure 8 In the second alternative embodiment shown, the printing time is longer. For example, phase C includes printing several labels in succession. In this second embodiment, during printing in phase C, the speed SC in the coating zone is gradually increased until the printing speed S2 is reached. Preferably, during the increase in speed SC, the buffer is controlled to maintain the speed SP in the printing zone at a constant speed.

[0213] During stage D, the printing device moves to the disengaged configuration. As previously described, the print roller 21 can be moved in such a manner that the ribbon does not contact either the print head or the substrate. During stage D, the speed of the ribbon can be reduced, preferably to zero, as described in stage B. This allows friction between the ribbon and the substrate and the print head to be avoided when the ribbon is disengaged from the print head.

[0214] In phase E, the printing device is in the disengaged configuration. In this phase, the speed SP and the speed SC are equal, thereby driving the buffer. Figure 8 In one embodiment shown, the speed SC of the coating zone is gradually reduced to reach a first predetermined speed S1.

[0215] During printing (phase C), the ribbon can be held at two locations along the ribbon path by its two sides: the coating zone (between the coater and the support) and the printing zone (between the print head or micro-heater zone and the print roller 21). These zones divide the ribbon path into two parts, a first path from the coating zone to the printing zone, where the ribbon transports coated ink, and a second path from the printing zone to the coating zone, where the ribbon transports unprinted ink.

[0216] Therefore, the tension of the carbon ribbon in the first path can be different from the tension of the carbon ribbon along the second path. Therefore, the torque applied to the moving roller of one buffer can be different from the torque applied to the moving roller of another buffer at the same time.

[0217] In another embodiment, the speed at which the ribbon path length is increased in one buffer may not be exactly equal to the speed at which the ribbon path length is decreased in another buffer.

Claims

1. Thermal transfer printing equipment (1), comprising: An annular carbon belt (5), the annular carbon belt (5) comprising an inner surface and an outer surface; A coating device (3) for coating the endless carbon ribbon (5) with ink in a coating area; A print head (6) for printing on a substrate (2) by thermally transferring a portion of the ink coated on the endless carbon ribbon (5) in a printing area; a conveying system for supporting and conveying the endless carbon ribbon (5) 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 pre-printing buffer (8), the pre-printing buffer (8) comprising a first moving roller (81) and a second moving roller (83) for supporting the coated endless carbon ribbon (5) during the period when the coated endless carbon ribbon (5) is transferred from the coating device (3) to the print head (6): the first moving roller (81) is arranged to support the inner surface of the endless carbon ribbon (5), and the second moving roller (83) is arranged to support the outer surface of the endless carbon ribbon; a post-printing buffer (7), the post-printing buffer (7) comprising a third moving roller (71) and a fourth moving roller (73) for supporting the endless carbon ribbon (5) during the period when the endless carbon ribbon (5) is conveyed from the print head (6) to the coating device (3): the third moving roller (71) is arranged to support the inner surface of the endless carbon ribbon (5), and the fourth moving roller (73) is arranged to support the outer surface of the endless carbon ribbon (5); wherein in a plane perpendicular to the longitudinal axis of the movable rollers (71, 73, 81, 83), each movable roller (71, 73, 81, 83) is capable of moving along a predetermined trajectory (72, 82), wherein the predetermined trajectory (72, 82) includes a first predetermined trajectory (72) and a second predetermined trajectory (82); The first controller CALC is configured as follows: Controlling the movement of the first moving roller (81) and the second moving roller (83) along their second predetermined trajectory (82) to increase or decrease the length of the path of the coated endless carbon ribbon from the coating device (3) to the print head (6); and The movement of the third moving roller (71) and the fourth moving roller (73) along their first predetermined trajectory (72) is controlled to increase or decrease the length of the path of the endless carbon ribbon from the print head (6) to the coating device (3) after printing.

2. The thermal transfer printing device (1) according to claim 1, wherein: The first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) are both capable of moving around the same first axis (A) along a second predetermined trajectory (82), and / or the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) are both capable of moving around the same second axis along a first predetermined trajectory (72).

3. The thermal transfer printing device (1) according to claim 2, wherein: The first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) are both mounted in a frame (84), and the frame is capable of rotating and moving around a first axis (A) parallel to the rotation axis (B) of the first moving roller and the second moving roller, and / or the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) are mounted in a frame, and the frame is capable of rotating and moving around a first axis parallel to the rotation axis of the third moving roller and the fourth moving roller.

4. The thermal transfer printing device (1) according to any one of claims 1 to 3, further comprising a driving roller (11) for driving the endless carbon ribbon (5) at a first speed on the coating area; and wherein the first controller CALC is configured to control the movement of each moving roller (71, 73, 81, 83) along its predetermined trajectory (72, 82) to: by driving the pre-printing buffer (8) to reduce the length of the endless carbon ribbon from the coating device (3) to the print head (6), and simultaneously by driving the post-printing buffer (7) to increase the length of the endless carbon ribbon from the print head (6) to the coating device, thereby driving the endless carbon ribbon on the printing area at a speed lower than the first speed, and The annular carbon ribbon on the printing area is driven at a speed higher than the first speed by driving the pre-printing buffer (8) to increase the length of the annular carbon ribbon from the coating device (3) to the print head (6), and at the same time by driving the post-printing buffer (7) to reduce the length of the annular carbon ribbon from the print head (6) to the coating device (3).

5. The thermal transfer printing device (1) according to claim 4, further comprising a printing roller (21) for holding and conveying the substrate (2) and the endless carbon ribbon (5) along the printing area, wherein the printing roller (21) is movable relative to the print head (6) between the following two configurations: a printing arrangement capable of printing, wherein the endless carbon ribbon (5) is supported by the printing roller passing through the substrate (2); and A detachment configuration wherein the annular carbon ribbon (5) is detached from the substrate (2).

6. The thermal transfer printing device (1) according to claim 5 further comprises a speed sensor for measuring the speed of the endless carbon ribbon in the printing area, and the thermal transfer printing device (1) further comprises a second controller COMP, the second controller being configured to control the printing roller (21) to automatically switch the configuration of the driving roller when the measured speed of the endless carbon ribbon in the printing area is zero.

7. The thermal transfer printing device (1) according to claim 6, wherein: The second controller COMP is configured to automatically drive the printing roller (21) to transport the substrate (2) at the same speed as the endless carbon ribbon on the printing area in the printing configuration.

8. The thermal transfer printing device (1) according to claim 4, wherein: The first controller CALC is configured to control the movement of the first moving roller (81) and the second moving roller (83) independently of the control of the movement of the third moving roller (71) and the fourth moving roller (73).

9. The thermal transfer printing device (1) according to claim 1, wherein: The elastic modulus of the endless carbon ribbon is lower than 3 GPa.

10. The thermal transfer printing device (1) according to claim 4, wherein: The first controller CALC is configured to control the rotation of the driving roller (11) to control the first speed of the endless carbon ribbon (5) on the coating area.

11. A method for printing a substrate using the thermal transfer printing apparatus according to claim 5, wherein: The method comprises: driving the annular carbon belt (5) on the coating area at a first predetermined speed; and simultaneously The endless carbon belt (5) is driven on the printing area at a second speed different from the first predetermined speed by: driving the first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) to reduce the length of the endless carbon ribbon from the coating device (3) to the print head (6), and simultaneously driving the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) to increase the length of the endless carbon ribbon from the print head (6) to the coating device (3), or The first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) are driven to increase the length of the annular carbon ribbon from the coating device (3) to the print head (6), and the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) are driven simultaneously to reduce the length of the annular carbon ribbon (5) from the print head (6) to the coating device (3).

12. The method according to claim 11, wherein The method further comprises printing by: driving the annular carbon belt (5) on the coating area at a first predetermined speed; and simultaneously driving the endless carbon belt (5) on the printing area at a second speed lower than the first predetermined speed; The printing roller (21) is moved from the disengaging configuration to the printing configuration when the second speed is lower than the first predetermined speed.

13. The method according to claim 12 further includes a step of operating printing, the step including driving the first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) to reduce the length of the endless carbon ribbon from the coating device (3) to the print head (6), and simultaneously driving the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) to increase the length of the endless carbon ribbon from the print head (6) to the coating device (3), so as to drive the endless carbon ribbon speed on the printing area higher than the endless carbon ribbon speed on the coating area.

14. The method according to claim 12 or 13, wherein: The method further comprises disengaging from printing by: driving the endless carbon belt on the coating area at a first speed; and at the same time The speed of the circular carbon ribbon on the printing area is driven to be lower than the speed of the circular carbon ribbon on the coating area by driving the first moving roller (81) and the second moving roller (83) of the pre-printing buffer (8) to reduce the length of the circular carbon ribbon from the coating device (3) to the print head (6), and simultaneously driving the third moving roller (71) and the fourth moving roller (73) of the post-printing buffer (7) to increase the length of the circular carbon ribbon from the print head (6) to the coating device (3); and The print roller (21) is moved to the disengaged configuration.

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