The present invention relates to a method of protecting printed data, and a printer implementing such a method.
A thermal transfer printer, and more particularly a plastic card printer thermal transfer includes:
- a supply system that supplies power to the printer with a virgin plastic card, this supply system may be a supply board to board system or a reservoir of multiple cards with a card separation system ,
- an ejection system that ejects each printer plastic card after printing, and

- between the supply system and the ejection system, a printing module for printing on the plastic card.

The print module includes:

- a supply roll on which is wound a transfer film having an ink layer to be deposited,

- a recovery roller on which rolls the transfer film after the ink layer was applied on the plastic card,

- a print head between the supply roller and roller recovery, and

- against a roller disposed against the print head.

The transfer film is positioned between the plastic card and the print head. When a plastic card is to be printed, the transfer film and the plastic card to be printed is synchronized with respect to the printing head so that said plastic card and a blank area of ​​the transfer film are present at the same time of the printhead. Synchronization occurs for example by using position detectors which detect other between the front edge of the plastic card when the plastic card to advance the print head.

When printing, the print head heats the transfer film according to the characters to be printed, resulting in the transfer of the ink of the transfer film on the plastic card. As and when printing, the plastic card and the transfer film simultaneously advancing under the print head to print the plastic card and the transfer film is wound progressively on the recovery roller.

The characters that were printed on the plastic card find themselves in negative on the transfer film. By recovering the coiled transfer film on the roll of recovery, it is possible to recover data that have been printed, which is unsatisfactory from the point of view of confidentiality.

An object of the present invention is to provide a protection method which protects data that are on the transfer film after printing.

For this purpose there is provided a method of protecting data printed on a transfer film by a thermal transfer printer to a plastic card having a print head, the protection method comprising:

- a first printing step during which the transfer film and the plastic card simultaneously advance on a printing length Lo in the print head and in which the print head is heated according to the text to be printed ,

- a rewinding step in which the transfer film is rewound on a rewind length Lo +/- different from the print length L, and in which the plastic card is returned upstream of the head impression,

- a subsequent printing step during which the transfer film and the plastic card simultaneously advance on another printing length under the print head and in which the print head is heated according to the text to be printed and

- an ejection step in which the plastic card is discharged from the printer.

Advantageously, the protection method comprises a looping step in which the printing step higher loop on the rewinding step.

Advantageously, the protection method comprises, between the step of rewinding and subsequent printing step, a format step in which, if the rewinding length is less than the previous print length, the part of the text original extending to the end of the text on a length equal to the difference between the print length and the rewinding length is suppressed, and if the rewinding length is greater than the print length, the portion the original text that extends to the text of a length equal to the difference between the length of rewinding and printing length is suppressed.

Advantageously, the first printing step is accompanied by a counting substep in which No number of pulses generated from the first print is recorded, and in which a number of pulses corresponding to the rewinding length is calculated, and the rewinding step is accompanied by a counting substep in which the number of pulses generated during the rewinding is recorded and in which the rewinding stops when said number of pulses has reached the number of pulses corresponding to the rewinding length calculated above.

The invention also provides a thermal transfer printer comprising:

- a supply system for supplying the printer with a plastic card,

- a supply roll on which is wound a transfer film having an ink layer to be deposited,

- a recovery roller on which rolls the transfer film after the ink layer was applied on a plastic card,

- a print head between the supply roller and roller recovery

- an ejection system for ejecting the plastic card printer after printing and

- a processor arranged to:

- controlling the advance simultaneously on a print length L 0 , the transfer film and the plastic card under the print head and the heating of the printhead according to the text to be printed,

- controlling the rewinding of the transfer film on a rewind length Lo +/- different from the print length L 0 , and the return of the plastic card upstream of the printhead,

- controlling the advance simultaneously on another printing length, the transfer film and the plastic card under the print head and the heating of the printhead according to the text to be printed, and

- controlling the advance of the plastic card to the ejection system.

Advantageously, the processor is arranged to, if the rewinding length is less than the previous print length, remove the part of the original text that extends to the end of the text on a length equal to the difference between the length printing and rewinding length, and, if the rewinding length is greater than the printing length, remove the part of the original text that extends to the top of the text on a length equal to the difference between the length of rewinding and the print length.

The characteristics of the invention mentioned above, as well as others, will emerge more clearly on reading the following description of an exemplary embodiment, said description being given in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic representation of a printer according to the invention, Fig. 2 shows an architecture of a printer control unit according to the invention,

Fig. 3 is a representation of printed elements when printing to a plastic card, and

Fig. 4 shows an algorithm of a protection method according to the invention.

Fig. 1 shows a printer that prints 100 by thermal transfer on a plastic card 10. The printer 100 comprises:

- a supply system 102 that supplies power to the printer 100 with a plastic card 10 blank there supply system 102 may be a provisioning system board to board or a reservoir of multiple cards provided with a system separation cards

- an ejection system 104 which ejects each plastic card 10 of the printer 100 after printing, and

- between the provisioning system 102 and the ejector system 104, a printing module 106 for printing the plastic card 10.

The supply system 102 and the ejection system 104 are not described further, for all types of known systems using motorized drive rollers can be used.

The print module 106 includes:

- a feed roll 108 on which is wound a transfer film 12 bearing an ink layer to be deposited,

- a recovery roller 110 which rolls the transfer film 12 after the ink layer has been applied to the plastic card 10,

- a printhead 112 between the supply roller 108 and the roller 110 of recovery, and

- against a roller 114 disposed against the print head 112 for pressurizing the plastic card 10 against the print head 112.

The transfer film 12 is positioned between the plastic card 10 and the print head 112.

The general principle of operation of the printer 100 is identical to the principle of operation of a printer of the state of the art. A plastic card 10 is received by the provisioning system 102 and driven to the print head 112, which heats the transfer film 12 according to the print data, and then when the data is printed on the plastic card 10, the card plastic 10 is supported by the ejecting system 104 that ejects the printer of the plastic card 100. the plastic card 10 and the transfer film 12 move both in one direction printing 250.

Conventionally, when the plastic card 10 to be printed, it is synchronized with respect to the print head 112, with an area of ​​the transfer film 12 which is blank, that is to say not yet passed under the print head 112.

The drive of the transfer film 12 when printing is performed by a motor which is equipped with the recovery roller 110 and which drives said recovery roller 110 in a winding direction 14 of the transfer film 10 on the roller recovery 110.

In the context of the invention, the printer 100 also includes a rewind motor 150 which is provided for driving the feed roll 108 in a winding direction 16 of the transfer film 10 on the feed roll 108. the transfer film 12 is then driven in the reverse direction to the printing direction 250. the rewind motor 150 is here by means of a belt 154 installed between the rewind motor shaft 150 and the shaft the supply roll 108.

The printer 100 also includes an angular encoder 152 mounted on the supply roller 108 and which is used to count the number of degrees that rotates the feed roll 108 during printing. This angular encoder 152 may take various forms such as a set of fixed teeth or holes on the feed roll 108 and disposed on the periphery of a circle coaxial with the axis of rotation of feed roll 108, and an optical sensor which counts the number of teeth or holes passing in front of him when printing. This angular encoder 152 may also be a magnetic encoder. The angular encoder 152 typically delivers information on the number of pulses generated during rotation, the pulses are generated by magnetic or optical elements as described above.

The printer 100 also comprises moving means 160 for moving the plastic card 10 with respect to the print head 112, from upstream to downstream (printing direction 250) and vice versa. The movement means 160 here take the form of rollers which rest against the upper face and the lower face of the plastic card 10 and which comprise a motor provided for driving the rollers in one direction or the other. Thus, depending on the direction of rotation of the rollers, the plastic card 10 moves in the supply system 102 to the ejection system 104 (printing direction 250) or vice versa. These or some of these rollers may be part of the supply system 102 and the ejector system 104 depending on their positions relative to the print head 112.

Fig. 2 shows a control unit 200 of the printer 100. The control unit 200 has, connected by a communication bus 202: a 204 or CPU ( "Central Processing Unit"), a RAM 206 ( "Random Access memory" in English), a ROM 208 ( "Read Only memory" in English), at least one communication interface 210 of the type Input / Output, allowing the control unit 200 to communicate with the different engines, the print head 112 and the various sensors of the printer 100, and optionally a storage unit 212 such as a hard disk or a storage medium drive such as a SD card reader ( "Secure Digital "in English).

The processor 204 is capable of executing instructions loaded into the RAM 206 from the ROM 208, an external memory (not shown), a storage medium (such as an SD card), or a communication network. When the printer 100 is turned on, the processor 204 is capable of reading the RAM 206 instructions and execute them. These instructions form a computer program causing the implementation, by the processor 204, all or part of the algorithms and steps described below.

All or part of algorithms and steps described below can be implemented in software by executing a set of instructions for a programmable machine, such as a DSP ( "Digital Signal Processor" in English) or microcontroller, or be implemented in hardware by a machine or a dedicated component, such as an FPGA ( "Field-Programmable Gate Array" in English) or an ASIC ( "application-specific integrated circuit" in English).

Fig. 3 shows examples of prints that are performed during the printing of a plastic card 10 by the printer 100.

The elements bearing the reference numbers 302a-c represent the plastic card 10 on which is printed the text to be printed at different printing stages.

The elements bearing the reference numbers 304a-c represent the transfer film 12 with the portion of ink which disappeared after printing.

The elements bearing the reference numbers 306b-c show the transfer film 12 on which a printing has been notionally offset transversely to the printing direction 250 to facilitate understanding of the invention.

When the plastic card 10 passes under the print head 112, it is printed (302) a first time with the data transmitted by the processor 204 to the printhead 112. In the example, the data is the text " 1234 5678 9012 3456 ". At the same time, the ink corresponding to the text is removed from the transfer film 12 and the text appears in negative (304a). Following this first impression, the text appears clearly on the transfer film 12 on the line 308a.

Following the first printing, the plastic board 10 is repositioned in front of the print head 112 by the moving means 160 by moving in a reverse direction 350 to the printing direction 250. Similarly, the film transfer 12 is rewound in the reverse direction 350 of the feed roll 108 by the rewind motor 150. the rewinding is carried out with a di shift in one direction or the other with respect to the reverse direction 350 (here offset is in the direction of the printing-direction 250, that is to say, the transfer film 12 has been rewound less than what was needed to perform the first printing). The same plastic card 10 is then synchronized to the print head 112 to a new printing the same text or part of the same text.

The printing in the printing direction 250, the new line of text is performed on the plastic card 10, and the new line of text is superimposed on the previously printed line of text on the plastic card 10 (302b) .

The line 308b represents the print line that has disappeared from the transfer film 12 when printing, it appears negative.

Without the dummy offset applied between the lines 308a and 308b, the lines 308a-b are superposed in a line 310b which represents what actually appears on the transfer film 12 which is then unreadable.

According to a particular embodiment, to avoid consuming the portion of the transfer film 12 at the end of text characters (here 5 and 6) which are offset are deleted by the processor 204, here over a length corresponding to the di shift . Furthermore, such a withdrawal strengthens F illegibility of the text, especially the end of the text.

Following the second printing, the plastic board 10 is repositioned in front of the print head 112 by the moving means 160 by moving in a reverse direction 350 to the printing direction 250. Similarly, the film transfer 12 is rewound in the reverse direction 350 of the feed roll 108 by the rewind motor 150. the rewinding is carried out with an offset d 2 in one direction or the other with respect to the reverse direction 350 (here the offset is in the direction of the reverse direction 350, that is to say, the transfer film 12 has been rewound more than what was needed to perform the second printing). The same plastic card 10 is then synchronized to the print head 112 to a new printing the same text or part of the same text.

The printing in the printing direction 250, the new line of text is performed on the plastic card 10, the new line of text is superimposed on the line of text already printed on the plastic card 10 (302c).

The 308c line represents the line of ink that disappeared from the transfer film 12 when printing, it appears negative.

Without the dummy offset applied between the lines 310b and 308c, the lines 310b and

308c 310c overlap in a line that represents what actually appears on the transfer film 12 which is then even more unreadable.

In this case, too, the characters (here 1 and 2) which are shifted below the beginning of the text may be deleted by the processor 204, here over a length

corresponding to the offset of 2 to strengthen Pillisibilité text, in particular the beginning of the text.

In the embodiment presented here, there are two di shifts and 2 , but there could be more, although at least an offset printing is sufficient, more makes the text unreadable.

Similarly, here there is a di shift in one direction followed by a shift of 2 in the other direction, but they are all in the same direction.

The value of each difference di, d 2 must be small enough to prevent too much of the text remains readable. For example, in the case of the line 310b, di offset is of the order of two characters which preserves legibility of the first two characters. Each shift is preferably comprised between the width of 0.5 characters and width of 2.5 characters, which substantially corresponds to a width between 1.5 and 7.5 mm for characters of a height of 3 mm and 3 mm spacing such as OCR a font size Extended 14. of course depending on the character size, a different offset may be used.

Similarly, each shift di, d 2 may be a predefined value to the construction, or a value generated by the processor 204 in each printing depending on the height of the characters or other variables.

In general, each length is obtained after a number of motor pulses that achieve this length. The displacement length due to a pulse of an engine is known by construction, and also depends on the motor, gears between the motor and the roller, and the diameter of the roll that allows to cause the plastic card 10 or the film transfer 12.

To best position the transfer film 12, it is best to consider the transfer film of the diameter 12 of the feed roll 108. Thus, when different impressions of the text, the processor 204 receives angular encoder information 152, this information, which typically correspond to a number of pulses, represent the number of degrees qu'effectue the feed roll 108 during printing. The processor 204 may then calculate the ratio between the number of impulses No and the transfer film length Lo 12 having been unwound for printing the text the first time, the ratio takes into account the transfer film of the diameter 12 of the supply roller 108 as the number of pulses for a length varies in accordance with said diameter. The length L is preferably greater than or equal to the length of the text to be printed, particularly the length L is sufficient to put at least the entire plastic card 10 under the print head 112.

The processor 204 may then determine the pulse numbers corresponding to lengths of di offsets and 2 which are respectively the * - and

)

N

L 0

The processor 204 then controls the rewind motor 150 so as to rewind the transfer film 12 while counting the number of pulses generated by the shaft encoder 152 and stops the rewind motor 150 when the number of pulses thus counted is equal as applicable to N ,, - ^ * - or

) N 0 + d 2 * ^ -.

Preferably, to facilitate rewinding the transfer film 12, the printhead 112 is raised and therefore spaced from the plastic card 10 before rewinding and is lowered at the end of rewinding. To do this, the printer 100 has a fork 170 to which the print head 112 is fixed and which is arranged to raise and lower the print head 112. The elevator 170 controlled by the processor 204 may take various forms such as for example a motor with a cam, a solenoid ....

To prevent rotation of the supply roller 108 during printing generates forces on the rewind motor 150, it is best to implement a disengagement between the rewind motor 150 and the supply roller 108. This clutch is arranged to transmit a force of the rewind motor 150 to the feed roll 108 and preventing the transmission of forces of the feed roll 108 to the rewinding motor 150. This clutch may be electrical and controlled by the processor 204 or be mechanical spring-type clutch.

Fig. 4 shows an algorithm of a protection method 400 of the data printed by the printer 100, the protection method 400 comprises:

- a first printing step 402 in which processor 204 controls the advanced simultaneously over a printing length Lo, the transfer film 12 and the plastic card 10 in the print head 112 and Heating the print head 112 according to the text to be printed,

- a rewinding step 404 in which processor 204 controls the rewinding of the transfer film 12 on a rewind length Lo +/- different from the print length L 0 , and the return of the plastic card 10 upstream of the print head 112, and

- printing a higher step 408 in which processor 204 controls the advanced simultaneously on another printing length, the transfer film 12 and the plastic card 10 in the print head 112 and Heating the print head 112 according to the text to be printed.

The progress of the transfer film 12 in the first printing step 402 and the subsequent step of printing 408 is performed by the motor 110 associated with the retrieving roll is controlled by the processor 204. Similarly , advanced simultaneous plastic card 10 in the first printing step 402 and the subsequent printing step 408 is performed by the motor of the moving means 160 which is controlled by processor 204.

Rewinding the transfer film 12 is produced by the rewind motor

150 which is controlled by the processor 204. Similarly, the return of the plastic card 10 during the rewinding step 404 is performed by the motor of the moving means 160 which is controlled by processor 204.

Such a method allows shifting to each printing the text that is negative on the transfer film 12, so that the same text is superimposed at least twice in a manner offset according to the printing direction 250.

Following the subsequent printing step 408, the process may continue with an ejection step 410 in which processor 204 controls the advance of the plastic card 10 to the ejection system 104 where the card plastic 10 is discharged from the printer 100.

As described above, following the subsequent printing step 408, the process may loop (412) on the rewind step 404 to perform a subsequent step of printing 408 with a different offset. The number of loops 412 can be set in the processor 204, for example based on a degree of confidentiality to achieve.

In the case of the board 302b, the rewinding length is equal to Lo-di and the other print length is at least equal to Lo-di. This length will vary in particular according to the last two characters are retained or deleted, and another subsequent printing is carried out or that the plastic card 10 is ejected.

Generally, the further printing length varies depending on the offset applied, since the plastic card 10 is ejected or not. As Lo, the other print length is preferably sufficient to put at least the entire plastic card 10 in the head 12 impressionl.

The rewinding length will be determined by the processor 204 so that there is a superposition of the impressions of the transfer film 12. In the case 302c of the card, the transfer film 12 has been rewound by a length L relative to its previous position (302b). The further printing length is also dependent on this new length rewind and ejection or not of the plastic card 10.

As described above, it is possible to amend the text in two impressions. In general, when the di offset is in the direction of the printing-direction 250, the processor 204 removes the portion of text that extends to the end of the text on a length equal to di offset, and when the offset d 2 is in the opposite direction to the printing direction 250, the processor 204 deletes the part of the text that extends to the top of the text on a length equal to the offset d 2 .

The protection method 400 then comprises between the rewinding step 404 and the subsequent printing step 408, a formatting step 406 during which, if the rewinding length is less than the previous printing length, processor 204 deletes the part of the original text that extends to the end of the text on a length equal to the difference between the print length and the length of rewinding, and if the rewinding of a length greater than the length of printing, the processor 204 deletes the part of the original text that extends to the top of the text on a length equal to the difference between the length of rewinding and the print length, the modified text provides the subsequently printed text . This formatting step is applied before every printing according to the offset applied and previously applied different offsets.

As described above in order to take into account the diameter of the transfer film 12 on the feed roll 108, the first printing step 402 is accompanied by a counting substep during which the processor 204 :

- No records number of pulses generated by the shaft encoder 152 at the first impression,

- calculates the number of pulses corresponding to the length of rewinding, that is to say, the print length with the offset (N 0 - d s * -, N 0 + d 2 * -).

) A)

The rewinding step 404 is then accompanied by a counting sub-step during which the processor 204 counts the number of pulses generated by the shaft encoder 152 when rewinding and stops the rewinding when said number of pulses has reached the number of pulses corresponding to the rewinding length calculated above.

Similarly, for the other stages, the processor 204 takes into account these values ​​to calculate the number of pulses to count to obtain the desired length.

As mentioned above, between each printing step and each step of rewinding, the protection method 400 includes a recovery step in which the processor 204 controls the lifting of the print head 112, and between each step rewind and each printing step, the protection method 400 comprises a lowering step in which processor 204 controls the lowering of the print head 112.

Before the first printing step 402, the protection method 400 conventionally comprises a supply step in which the processor 204 controls the supply system 102 for supplying the printing module 106 with a plastic card 10 and print .

Although the invention has been particularly shown in the case where the ink of the transfer film is completely transferred upon heating of the print head, it also applies in the case of a sublimation printing, where the amount of ink of the transfer film that is transferred depends on the temperature of the printhead.

CLAIMS
1) A method of protecting (400) the data printed on a transfer film (12) of a printer (100) by heat transfer to a plastic card (10) having a print head (1 12), the method of protection (400) comprising:

- a first printing step (402) during which the transfer film

(12) and the plastic board (10) advance simultaneously on a printing length Lo under the print head (1 12) and in which the print head (1 12) heater according to the text to be printed,

- a rewinding step (404) during which the transfer film (12) is rewound on a rewind length Lo +/- different from the print length L, and in which the plastic card (10) is returned upstream of the print head (1 12)

- a subsequent step of printing (408) in which the transfer film (12) and the plastic board (10) advance simultaneously on another printing length under the print head (1 12) and in which the print head (112) is heated according to the text to be printed, and

- an ejection stage (410) in which the plastic card (10) is expelled from the printer (100).

2) A method of protecting (400) according to claim 1, characterized in that it comprises a looping step (412) during which the subsequent printing step (408) on the loop rewinding step (404 ).

3) A method of protecting (400) according to one of claims 1 or 2, characterized in that it comprises between the rewinding step (404) and the subsequent step of printing (408), a step of formatting (406) during which, if the rewinding length is less than the previous print length, the part of the original text that extends to the end of the text on a length equal to the difference between the length d printing and rewinding length is suppressed, and if the rewinding length is greater than the print length, the part of the original text that extends to the top of the text on a length equal to the difference between the length rewind and the print length is suppressed.

4) A method of protecting (400) according to one of claims 1 to 3, characterized in that the first printing step (402) is accompanied by a counting substep in which the number No of pulse generated from the first print is recorded, and in which a number of pulses corresponding to the rewinding length is calculated, and in that rewinding step (404) is accompanied by a sub counting step in which the number of pulses generated during the rewinding is recorded and in which the winding stops when said number of pulses has reached the number of pulses corresponding to the rewinding length calculated above.

5) A printer (100) by heat transfer comprising:

- a supply system (102) for supplying the printer (100) with a plastic board (10),

- a supply roll (108) on which is wound a transfer film (12) carrying an ink layer to be deposited,

- a recovery roller (110) on which the transfer film is wound (12) after the ink layer was applied on a plastic card (10),

- a printhead (112) between the feed roll (108) and the recovery roll (110),

- an ejection system (104) for ejecting the plastic card (10) of the printer (100) after printing and

- a processor (204) arranged to:

- controlling the advance simultaneously on a print length L 0 , the transfer film (12) and the plastic board (10) under the printhead (112) and heating the printhead ( 112) according to the text to be printed,

- controlling the rewinding of the transfer film (12) on a rewind length Lo +/- different from the print length L 0 , and the return of the plastic card (10) upstream of the printing head (112 )

- controlling the advance simultaneously on another printing length, the transfer film (12) and the plastic board (10) under the printhead (112) and heating the printhead (112 ) according to the text to be printed, and

- controlling the advance of the plastic card (10) to the ejection system (104).

6) A printer (100) according to claim 5, characterized in that the processor (204) is arranged to, if the rewinding length is less than the previous print length, remove the part of the original text that s' extends to the end of the text on a length equal to the difference between the print length and the length of rewinding, and, if the rewinding length is greater than the printing length, remove the part of the original text which extends to the top of the text on a length equal to the difference between the length of rewinding and the print length.