Non-linear power control of thermal print heads in plastic card printers

Abstract

In an identity document printing system, a multicolor image is printed on a non-vinyl plastic identity document. Pixel density data of the multicolor image to be printed is adjusted using a non-linear pixel density adjustment curve, thereby adjusting power applied to a thermal print head. Adjusting the pixel density data using the non-linear pixel density adjustment curve improves the quality of the resulting multicolor printed image, reduces bulk transfer of the dye donor layer, and reduces breakage of the print ribbon carrier film.

Description

Technical Field

[0001] This technology disclosure relates to printing multicolor images on identity documents, such as plastic cards, including but not limited to financial cards (e.g., credit cards or debit cards), access cards, driver's licenses, national identity cards, business identity cards, gift cards, and other plastic cards. Background Technology

[0002] As is well known, multicolor printing ribbons, which use thermal printheads and include repeating sequences of dye-based ink plates, are used to print multicolor images, such as portrait images, on plastic cards or other identification documents. A typical dye-based printing ribbon consists of a carrier film having panels with repeating sequences of dye donor layers of different colors applied to one side. In typical printing applications, the thermal printhead applies heat to the side of the carrier film opposite to the dye donor layers while one panel of the dye donor layers is in contact with the plastic card or other substrate to be printed. The heat causes dye to move from the dye donor layers of the panel into the substrate through a mechanism commonly known as dye diffusion printing.

[0003] When printing the dark pixels of a multicolor image, a total (i.e., complete) transfer of the dye donor layer occurs (often referred to as mass transfer). Since the printed image is much darker in the areas where mass transfer occurs, and mass transfer often leads to the breakdown of the carrier film, total transfer of the dye donor layer is undesirable.

[0004] Compared to other types of substrate materials, the overall transfer of dye donor layers is more problematic on certain types of substrate materials. For example, polyethylene terephthalate (PETG) or polycarbonate substrates do not accept dyes as readily as other plastic substrates. Therefore, for PETG or polycarbonate substrates, higher printhead power is required to obtain images with attractive color densities. However, higher printhead power increases the likelihood of overall dye donor layer transfer.

[0005] Figure 1 A standard linear curve 10 for printing multicolor images is shown, along with a standard linear adjustment curve 12 for adjusting pixel data and thus the power of the thermal printhead to reduce mass transfer and carrier film breakage. However, even with linear adjustment curve 12, mass transfer and carrier film breakage remain problematic at higher pixel density values. Furthermore, at lower pixel density values, typically used for printing skin tones in portrait images, the resulting image quality is generally poor. Summary of the Invention

[0006] This paper describes the printing of multicolor images on non-vinyl plastic ID documents in an ID document printing system. A non-linear pixel density adjustment curve is used to adjust the pixel density data of the multicolor image to be printed, thereby regulating the power applied to the thermal printhead. Adjusting the pixel density data using the non-linear pixel density adjustment curve improves the quality of the resulting multicolor printed image, reduces massive transfer of dye donor layers, and minimizes breakage of the printing ribbon carrier film.

[0007] Non-vinyl plastic identification documents can be PETG or polycarbonate plastic identification documents. However, plastic identification documents can be formed from any type of plastic that will benefit from the use of a non-linear pixel density adjustment curve as described herein. Identification documents can be plastic cards issued to cardholders. Examples of plastic cards include, but are not limited to, driver's licenses, national identity cards, business identity cards, debit cards (e.g., credit or debit cards), access cards, gift cards, and other plastic cards printed with multicolor images. Identification documents can also be passports or pages in passports where multicolor images are printed.

[0008] In one embodiment described herein, a method for printing a multicolor image on a non-vinyl plastic ID document in a print station of an ID document printing system may include inputting print data corresponding to the multicolor image to be printed into a printer controller that controls the operation of the print station. The print data includes pixel density data, and the print data is processed using a non-linear pixel density adjustment curve to adjust the pixel density data to create corrected pixel density data. The corrected pixel density data is then used to control the thermal printhead of the print station to print the multicolor image.

[0009] In another embodiment, a method for printing a multicolor portrait image of a person on a polyethylene terephthalate (PET) plastic card in a printing station of a plastic card printing system may include inputting print data corresponding to the multicolor portrait image to be printed into a printer controller, which controls the operation of the printing station. The print data includes pixel density data, and the print data is processed using a non-linear pixel density adjustment curve to adjust the pixel density data, thereby creating corrected pixel density data. The corrected pixel density data is then used to control the thermal printhead of the printing station to print the multicolor portrait image onto the PET plastic card.

[0010] In another embodiment, a plastic card printing system may include: a card input unit configured to input plastic cards; a printing station having multi-color printing ribbons and thermal printheads, or having multiple monochrome printing ribbons and multiple thermal printheads; a card transport mechanism for transporting plastic cards from the card input unit to the printing station; and a printer controller connected to the thermal printheads and controlling their operation. The printer controller is programmed to include a non-linear pixel density adjustment curve to adjust the pixel density data of the multi-color image to be printed. Attached Figure Description

[0011] Figure 1 The standard linear density curve and the standard linear density adjustment curve are shown.

[0012] Figure 2 An example of a plastic ID card in the form of a plastic card is shown.

[0013] Figure 3 This is a schematic diagram of an embodiment of the ID card printing system described herein.

[0014] Figure 4 An example of a printing station for an ID card printing system is shown.

[0015] Figure 5 A pair of nonlinear quadratic pixel density adjustment curves are shown.

[0016] Figure 6 The nonlinear gamma pixel density adjustment curve is shown.

[0017] Figure 7 The nonlinear logarithmic pixel density adjustment curve is shown. Detailed Implementation

[0018] The following describes several examples of printing multicolor images on non-vinyl plastic ID documents in an ID document printing system. A non-linear pixel density adjustment curve is used to adjust the pixel density data of the multicolor image to be printed, thereby adjusting the power applied to the thermal printhead. The following describes a quadratic adjustment curve (…). Figure 5 ), Gamma adjustment curve ( Figure 6 ) and logarithmic adjustment curve ( Figure 7 However, other forms of adjustment curves can be used. In one embodiment, the nonlinear adjustment curve is a downward-opening (e.g., concave) adjustment curve.

[0019] Non-vinyl plastic identification documents can be PETG or polycarbonate plastic identification documents. However, plastic identification documents can be formed from any type of plastic that will benefit from the use of a non-linear pixel density adjustment curve as described herein. Identification documents can be plastic cards issued to cardholders. Examples of plastic cards include, but are not limited to, driver's licenses, national identity cards, business identity cards, debit cards (e.g., credit cards or debit cards), access cards, gift cards, and other plastic cards printed with multicolor images. Identification documents can also be passports or pages in passports where multicolor images are printed. Unless otherwise stated, the term "plastic card" as used throughout the specification and claims refers to cards whose card substrate can be formed entirely of plastic as well as cards formed from a combination of plastic and non-plastic materials. In one embodiment, the card size can conform to ISO / IEC 7810, having approximately 85.60 × approximately 53.98 mm (approximately... Inches x Approximately The dimensions (in inches) and radius are approximately 3.18 millimeters (approximately...) The rounded corners are (inches). For convenience, the following description of the identification document will be a PETG plastic card.

[0020] Reference Figure 2 An example of a PETG plastic card 20 is depicted. The plastic card 20 may include personal data specific to the intended cardholder, including a personal account number, cardholder name, intended cardholder photograph, address, expiry date, and other personal data known in the art. The plastic card 20 may also include non-personal data, such as the issuer's name and / or logo and graphic elements. The card 20 is shown as including a front surface 22 and a rear surface or back side 24 opposite to the front surface 22 (e.g., ...). Figure 4 (As shown). Card 10 may also include a multicolor portrait image 26 of the intended cardholder, other personal data 28 such as the intended cardholder's name, an optional programmable integrated circuit chip 30, and an optional magnetic stripe 32. The portrait image 26 or other multicolor images (e.g., background graphic images) on the card surfaces 22, 24 may be printed using the techniques described below.

[0021] Reference Figure 3 An example of an ID card printing system 40 is shown. When used for printing plastic cards, system 40 may also be referred to as a plastic card printing system. For convenience, system 40 will be referred to as a plastic card printing system for printing on plastic cards.

[0022] System 40 is shown to include at least one printing station 42. System 40 may also include a card input unit 44, an optional magnetic stripe station 46, an optional integrated circuit chip station 48 for testing and programming integrated circuit chips, a card flipper 50 (or card redirection mechanism), a card output unit 52, and one or more optional additional card processing stations 54.

[0023] Print station 42 is configured to personalize plastic card 20 by printing on one or more surfaces of plastic card 20 (e.g., printing portrait image 26 on surface 22). See reference. Figure 4 Print station 42 is configured to perform direct-to-card thermal printing on plastic card 20. However, the techniques described herein can be used for other types of thermal printing, including but not limited to re-transfer (e.g., dye re-transfer). Print station 42 includes a print ribbon supply unit 60, a print ribbon tensioner 62, a multi-color print ribbon 64, a thermal printhead 66, a paper pressure spool 68 located opposite the thermal printhead 66, and a printer controller 69.

[0024] The printing ribbon 64 may be a multicolor printing ribbon known in the art. The printing ribbon 64 is supplied by the printing ribbon supply unit 60 and tightened on the printing ribbon tightener 62 after use. The printing ribbon 64 includes a plurality of color panels arranged in a repeating sequence. For example, as is known in the art, the printing ribbon 64 may be a YMCK ribbon with a plurality of sequences of yellow (Y), magenta (M), cyan (C), and black (K) panels. The YMC panels are typically dye materials, while the K panels are pigment materials. In some embodiments, the printing ribbon 64 may include one or more additional panels associated with each color sequence, including but not limited to a topcoat material panel (typically designated as a YMCKT ribbon) and / or a cover material panel (typically designated as a YMCKO ribbon).

[0025] The thermal printhead 66 can be any thermal printhead known in the field of plastic card printing technology. As is well known to those skilled in the art, the thermal printhead 66 includes a plurality of individually energized heating elements (not shown), each of which can be selectively energized by an electronic gating pulse that heats the corresponding heating element to transfer colored material from one panel of the printing ribbon 64 to the plastic card 20. Figure 4 As shown, the thermal printhead 66 can move toward the paper roll 68 during printing to position the printhead 66 during printing, and move away from the paper roll 68 when not printing to reposition the card 20 for the next printing.

[0026] In another embodiment, print station 42 may include multiple individual monochrome print ribbons (not shown), such as Y print ribbon, M print ribbon, C print ribbon, K print ribbon, etc. Furthermore, print station 42 may include corresponding multiple thermal printheads, with each monochrome print ribbon associated with one thermal printhead. Card 20 is conveyed through each monochrome print ribbon / thermal printhead combination, which prints the respective colors on card 20 to produce the final multicolor image.

[0027] One or more mechanical card transport mechanisms (e.g., one or more pairs of transport rollers 70) transport cards 20 in the printing station 42 and throughout the system 40. The card transport mechanism is preferably reversible to allow forward and reverse transport of cards 20, thereby allowing multiple prints through the print head 66. Mechanical card transport mechanisms for transporting plastic cards in a plastic card printing system are well known in the art. Other examples of card transport mechanisms that can be used are known in the art and include, but are not limited to, conveyor belts (with and / or without tabs), vacuum transport mechanisms, transport carriages, and combinations thereof. Card transport mechanisms are well known in the art, including those disclosed in U.S. Patents 6,902,107, 5,837,991, 6,131,817, and 4,995,501 and U.S. Publication No. 2,007 / 0187870, all of which are incorporated herein by reference in their entirety. Those skilled in the art will readily understand the types of card transport mechanisms that can be used, as well as their construction and operation.

[0028] Continue to refer to Figure 4 The printer controller 69 communicates directly or indirectly with the thermal printhead 66. The printer controller 69 may be part of the print station 42 and may be located within the housing of the print station 42 (shown by dashed lines), or the printer controller 69 may be located remotely from the print station 42 (i.e., physically separate from the print station 42) and situated in... Figure 4 Outside the housing shown by the dashed line. The printer controller 69 processes print data and generates data in the form of strobe pulses to control the energization of the individually energized heating element of the thermal printhead 66, thereby printing on the card 20. The printer controller 69 can also control the drive of the ribbon supply unit 60 and / or the print ribbon tensioner 62 during printing, control the movement of the thermal printhead 66 during printing, and / or control the operation of the transport roller 70 during printing. Alternatively, the drive of the ribbon supply unit 60 and / or the print ribbon tensioner 62, the movement of the thermal printhead 66, and / or the operation of the transport roller 70 can be controlled by a separate control mechanism located within or outside the print station 42. For example, in some embodiments, when the printer controller is remote from the print station 42, only the portion of the printer controller that processes print data and generates strobe pulses to control the energization of the individually energized heating element of the thermal printhead 66 can be remote from or outside the print station. Other functions of the printer controller 69 (e.g., control of the card delivery mechanism, control of the movement of the printing ribbon 64, and control of the movement of the thermal printhead 66) can be performed on or within the print station.

[0029] The printer controller 69 also includes a non-linear pixel density adjustment curve, which will be further described below, for adjusting the pixel density data of the print data to create corrected pixel density data. The corrected pixel density data is used to print images such as portrait images 26 (…). Figure 2 (Multicolor image)

[0030] Back Figure 3 The card input section 44 may be a card input reservoir designed to hold multiple plastic cards awaiting individual feeding into the system 40 for processing. An example of a card input reservoir is described in U.S. Patent 6,902,107, which is incorporated herein by reference in its entirety. Alternatively, the card input section 44 may be an input slot through which individual cards are fed into the system 40 one by one. The card input section 44 may be located anywhere in the system 40 relative to other elements in the system 40 suitable for inputting plastic cards.

[0031] Magnetic stripe station 46 is optional. If present, magnetic stripe station 46 can verify the operation of the magnetic stripe on the plastic card and / or encode data on the magnetic stripe. An example of a magnetic stripe station is described in U.S. Patent 6,902,107, which is incorporated herein by reference in its entirety.

[0032] Integrated circuit chip station 48 is also optional, and if present, it is designed to verify the operation of the chip on the plastic card and / or program the chip with data. Chip station 48 may include a single chip programming station for programming one card at a time within chip station 48, or chip station 48 may be configured to program multiple cards simultaneously. Chip stations capable of simultaneous multi-card programming are described in U.S. Patent 6,695,205 (Linear Cylinder Construction) and U.S. Patent 5,943,238 (Cylinder Construction), both of which are incorporated herein by reference in their entirety.

[0033] Card flipper 50 is also optional, and if present, it is configured to flip the card 180 degrees such that the surface of the card that previously faced one direction (e.g., upward) now faces the opposite direction after the flip. Card flippers are well known in the art. Examples of suitable card flippers are described in U.S. Patent 2013 / 0220984 and U.S. Patent 7398972, both of which are incorporated herein by reference in their entirety.

[0034] Card output section 52 may be a card output reservoir designed to accommodate multiple processed plastic cards that are processed and output one by one within system 40. An example of a card output reservoir is described in U.S. Patent 6,902,107, which is incorporated herein by reference in its entirety. Alternatively, card output section 52 may be an output slot through which individual cards are output one by one. Card output section 52 may be located anywhere within system 40 that is suitable for card output section 52.

[0035] Additional processing station 54 may be another card processing mechanism configured to perform other card processing operations. Examples of additional processing station 54 include one or more of a laminator, an embossing mechanism, a marking mechanism, a printing mechanism different from the printing mechanism in print station 42, and a vision / quality assurance mechanism.

[0036] In one embodiment, system 40 may be configured as a plastic card printing system, referred to as a desktop card printer or desktop card printing system, which is typically designed for printing individual plastic cards on a smaller scale. In a desktop card printer, individual plastic cards to be printed are fed into the system for printing and then output. These systems are often called desktop machines or desktop printers because they have a small footprint, allowing the machine to reside on a desktop. Many examples of desktop machines are known, such as the SD or CD series desktop card printers manufactured by Enturus Ltd. in Shacopi, Minnesota. Other examples of desktop card machines are disclosed in U.S. Patents 7,434,728, 7,398,972, and 9,904,876, all of which are incorporated herein by reference in their entirety.

[0037] In another embodiment, system 40 may be configured as a plastic card printing system known as a central card issuance processing system, which is typically designed for high-volume processing of plastic cards and typically employs multiple processing stations or modules to process multiple plastic cards simultaneously to reduce the overall processing time per card. Examples of central card issuance processing systems include the MX and MPR series of central issuance systems offered by Enturus Ltd., Shacopi, Minnesota. Other examples of central issuance systems are disclosed in U.S. Patents 4,825,054, 5,266,781, 6,783,067, and 6,902,107, all of which are incorporated herein by reference in their entirety.

[0038] Now refer to Figure 4 Describes printing multicolor images on plastic card 20 (e.g., Figure 2 Example of a portrait image 26. Assuming the image to be printed is portrait image 26, the print data corresponding to the portrait image is input or provided to the printer controller 69 in any suitable manner. The print data includes pixel density data indicating the color density of each pixel of the portrait image to be printed. The printer controller 69 processes the print data to adjust the pixel density data using a non-linear pixel density adjustment curve (or only a non-linear density curve), thereby creating corrected pixel density data. The corrected pixel density data is then used to control the power supplied to the individually energized heating elements of the thermal printhead to print the portrait image.

[0039] The non-linear pixel density adjustment curve can be stored in the printer controller 69 or in another location accessible to the printer controller 69. Figures 5-7 Examples of possible nonlinear pixel density adjustment curves are shown. However, other nonlinear pixel density adjustment curves can be used. In one embodiment, the nonlinear adjustment curve can be a parametric curve. One form of a parametric curve is a quadratic curve. However, other forms of parametric curves can also be used.

[0040] Figure 5 An example of a quadratic density curve 80 is shown. Density curve 80 is derived from the following quadratic equation:

[0041] ax 2 +bx+c= 0

[0042] The three points of the defined density curve 80 include:

[0043] x1,y1 – This point defines the density of the brightest pixels (white).

[0044] x2,y2 – This point is set to separate the darkest density from the bright and medium pixel densities.

[0045] x3,y3 – This point sets the darkest pixel density (black).

[0046] Use these three points to determine a, b, and c:

[0047] m = x1 - x2

[0048] n = x3 - x2

[0049] a = (n(y1-y2) + m(y3-y2)) / (n(x1 2 - x2 2 ) + m(x3 2 - x2 2 ))

[0050] b = ((y3-y2) - a(x3 2 - x2 2 )) / (x3-x2)

[0051] c = y1 - ax1 2 - bx1

[0052] For each x (image pixel value, x-axis) in density curve 80, the values ​​of a, b, and c, along with a quadratic equation, are used to determine y (printed pixel value, y-axis):

[0053] y = ax 2 + bx + c.

[0054] Continue to refer to Figure 5 The diagram illustrates another example of a quadratic density curve 82, a variation of quadratic density curve 80. In density curve 82, the portion of curve 82 at the brightest pixel density is adjusted such that the printed pixel value (y-axis) is set to zero or approximately zero for the input or image pixel value (x-axis) until the input or image pixel value reaches approximately pixel value 10, at which point the quadratic non-linear portion of curve 82 begins. Setting the printed pixel value to zero in this manner helps improve the print quality of the bright pixel density portions of a portrait image (e.g., the quality of skin tones in a portrait image).

[0055] Figure 6 A non-linear gamma pixel density adjustment curve 90 derived using known gamma correction is shown. Gamma correction can be implemented using many formulas. For example, in one embodiment, gamma correction can be implemented using the following formula:

[0056] .

[0057] Figure 7 This demonstrates the use of the known logarithmic function y = log a x-derived nonlinear logarithmic pixel density adjustment curve 100.

[0058] The examples disclosed in this application should be considered illustrative rather than limiting in all respects. The scope of the invention is indicated by the appended claims rather than the foregoing description; and all variations in the meaning and scope of equivalents of the claims are intended to be included therein.

Claims

1. A method for printing a multicolor image on a non-vinyl plastic identity card having an integrated circuit chip in a printing station of an identity document printing system, the method comprising: Printing data corresponding to the multicolor image to be printed is input into the printer controller, which controls the operation of the thermal printhead of the printing station. The printing data includes pixel density data. The printed data is processed to generate corrected pixel density data by adjusting the pixel density data of the printed data corresponding to the multicolor image using a non-linear pixel density adjustment curve. as well as The multicolor image is printed on the non-vinyl plastic identity card using the multicolor printing ribbon and the thermal printhead of the printing station by controlling the thermal printhead with modified pixel density data.

2. The method according to claim 1, wherein, The non-vinyl plastic identity card includes polyethylene terephthalate.

3. The method according to claim 1, wherein the method includes printing the multicolor image directly onto the non-vinyl plastic identity card.

4. The method according to claim 1, wherein, The nonlinear pixel density adjustment curve is an adjustment curve with its opening facing downwards, and the nonlinear pixel density adjustment curve includes a parameter curve.

5. The method according to claim 4, wherein, The parameter curves include quadratic curves.

6. The method according to claim 1, wherein, The multicolor image includes portrait images of people or background graphic images.

7. The method according to claim 1, further comprising: At least one of the following steps before or after printing the multicolor image: Data is encoded on the magnetic stripe on the non-vinyl plastic identity card; Data is programmed on the integrated circuit chip on the non-vinyl plastic identity card; Print data on the non-vinyl plastic identity card; Data is marked on the non-vinyl plastic identity card using a laser.

8. A method for printing a multicolor background graphic image on a polyethylene terephthalate plastic card having an integrated circuit chip in a printing station of a plastic card printing system, the method comprising: Printing data corresponding to the multi-color background graphic image to be printed is input into the printer controller, which controls the operation of the thermal printhead of the printing station. The printing data includes pixel density data. The printed data is processed to generate corrected pixel density data by adjusting the pixel density data of the printed data corresponding to the multicolor background graphic image using a non-linear pixel density adjustment curve. as well as The multicolor background graphic image is printed onto the polyethylene terephthalate plastic card by using the multicolor printing ribbon and the thermal printhead of the printing station to control the thermal printhead of the printing station using modified pixel density data.

9. The method according to claim 8, wherein, The nonlinear pixel density adjustment curve is an adjustment curve with its opening facing downwards, and the nonlinear pixel density adjustment curve includes a parameter curve.

10. The method according to claim 9, wherein, The parameter curves include quadratic curves.

11. The method according to claim 8, further comprising: At least one of the following steps before or after printing the multicolor background graphic image: Data is encoded on the magnetic stripe of the polyethylene terephthalate plastic card; Data is programmed onto the integrated circuit chip on the polyethylene terephthalate plastic card; Print data on the polyethylene terephthalate plastic card; Data was marked on the polyethylene terephthalate plastic card using a laser.

12. A non-vinyl plastic identity card printing system, the plastic identity card printing system comprising: A card input section configured to input a non-vinyl plastic identity card having an integrated circuit chip; A printing station having a multi-color printing ribbon and a thermal printhead; A card delivery mechanism for delivering the non-vinyl plastic identity card from the card input section to the printing station; A printer controller, connected to and controlling the operation of the thermal printhead, is programmed to include a non-linear pixel density adjustment curve to adjust the pixel density data of the multicolor image to be printed onto the non-vinyl plastic identity card.

13. The non-vinyl plastic identity card printing system according to claim 12, wherein, The plastic identity card comprises polyethylene terephthalate.

14. The non-vinyl plastic identity card printing system according to claim 12, wherein, The nonlinear pixel density adjustment curve is an adjustment curve with its opening facing downwards, and the nonlinear pixel density adjustment curve includes a parameter curve.

15. The non-vinyl plastic identity card printing system according to claim 14, wherein, The parameter curves include quadratic curves.

16. The non-vinyl plastic identity card printing system of claim 12, wherein the plastic identity card printing system further comprises at least one of the following: An encoder configured to encode data on a magnetic stripe on the non-vinyl plastic identity card; A chip programmer configured to program data on an integrated circuit chip on the non-vinyl plastic identity card; An additional printer, configured to print data on the non-vinyl plastic identity card; A laser, configured to mark data on the non-vinyl plastic identity card.

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