MEMORY CARD AND METHOD OF PRODUCING SAME

Abstract: The invention relates to a memory card and its method of manufacture. The memory card has a flexible substrate, a first conductive ink composition which is adhered thereto, and a second conductive ink composition which is printed over at least a portion of the first conductive ink composition to form at least one site on the memory card which is readable by an external reader device. A protective layer is provided to overlie and protect at least the one site of the memory card.

Description: MEMORY CARD AND METHOD OF PRODUCING SAME Field of the Invention This invention relates to memory cards of the type used as prepaid cards for dispensing goods and/or services, and to an improved method for producing such cards. Background of the Invention Prepaid memory cards which enable their owner to perform purchases without the use of cash or tokens have become very popular. Such cards have been used to obtain a variety of goods and/or services, as for example, in vending machines for beverages or food, in prepayment of public transportation such as buses, trains or subways, or for use with public telephones or photocopy machines. Typically, a memory card is purchased for a predetermined monetary value which is stored in the card and the monetary value is decremented as and when the card is used. Such memory cards are intended to be used until the prepaid monetary value of the card has been exhausted. Once the monetary amount on the card has been spent by the user, the card is either recycled or thrown away. The memory cards presently available may be categorized into three general types: magnetically readable cards, microcircuit cards, and contactless cards. Magnetically readable cards have a magnetic stripe located on the outer surface where information, such as the remaining value of the card, is stored. They have the advantage of being relatively inexpensive, and have been used successfully, for example, as fare cards for transit systems. However, this type of card is of limited usefulness as a prepaid card for security reasons. The magnetically encoded information stored on the cards is capable of being accidentally erased or intentionally altered by unauthorized persons to increase the units originally contained on the memory card. Microcircuit cards have a memory device, such as an integrated circuit or printed circuit, embedded into the card which, through suitable electrical contacts, can be connected to an external reader for determining the remaining value of the card. Examples of such microcircuit cards may be seen in U.S. Patent Nos. 4,737,620 to Mollet et al . and 4,719,140 to Hara et al .. Although much more resistant to tampering than magnetically readable cards, microcircuit cards have the disadvantage of being relatively expensive to produce. Therefore, they are not well suited to be used for denominations of relatively small monetary value. Contactless cards do not have any contacts for physically making connection to an external reader device. Instead, contactless cards utilize means such as inductive and/or capacitive coupling for providing an external reader device with signals indicative of the monetary value of the card. Examples of contactless cards may be seen in U.S. Patent No. 5,272,596 to Honore et al. and Brazilian Patent Specifications PI 9105585 and PI 9201380. Regardless of the type of prepaid memory card, a limiting factor in determining practical uses or applications of the card is its associated cost. Typically, the use of prepaid memory cards is practical only where the total monetary value represented by the card exceeds the cost of the card itself. Thus, if the cost of the card can be reduced, this opens the possibility for issuing smaller denomination (i.e., a lower total monetary value) cards in the many existing applications where prepaid cards are presently used, and also expands the number of potential applications or uses for prepaid memory cards. However, manufacturers are faced with a very significant challenge in reducing manufacturing costs without sacrificing the overall quality, reliability, and durability of the memory card. In addition, the nature of the materials and manufacturing techniques currently being used can result in stiff or brittle memory cards. Consequently, bending of the memory card during typical use may cause damage to or destruction of portions of the memory card. As a result, the memory card is prematurely decremented or rendered unusable. Summary of the Invention With the foregoing in mind, it is an object of the present invention to produce a memory card at reduced overall cost . It is a further object of the present invention to provide an improved, reduced cost memory card having good reliability and durability. These and other objects, features, and advantages are obtained in accordance with the present invention by forming conductive sites or cells on a memory card by printing with conductive ink compositions. Memory cards in accordance with the present invention have a flexible substrate and at least one site provided on the card forming a closed loop conductive path in the card for electrical current inductively induced by an external reader device. Each site comprises a first ink composition in predetermined areas of the site so as to form a first portion of the closed loop conductive path and a second ink layer composition on the substrate forming a second portion of the closed loop conductive path which defines a fusible link which interrupts a closed loop conductive path. A protective layer preferably overlays and protects the ink layers. Printed indicia is preferably provided on the front and/or back of the memory card to enhance the attractiveness of the memory card and provide instructions for its use. The substrate may be made from a flexible thermoplastic polymer such as acrylonitrile-butadiene- styrene, polyethylene terephthalate or polyvinylchloride. An alternative material for making the substrate is a silk-screenable nonporous paper. The preferred substrate provides a memory card with excellent durability and reliability. Moreover, the card has good flexibility, enabling the memory card to be bent almost 180° in each direction during use and/or storage by the owner, without damaging or destroying the memory. As a result, the memory card can withstand extensive abuse and still perform its intended function until its monetary value has been exhausted. In one embodiment of the invention, the first and second ink compositions of the memory card are designed to provide for storing a predetermined number of "units" of some preassigned value, and for incrementally and permanently decrementing the number of units as the memory card is used and the units of value are "spent." Preferably, the memory card has a plurality of spaced apart sites or cells which are adapted to be read by an external reader device. Each site on the memory card is capable of being irreversibly converted from a first readable state to a second readable state. This ability to irreversibly coπvert each site enables the memory card to be decremented as and when it is used in a secure, tamper- proof manner. The above described memory card is preferably manufactured by an efficient low cost method which enables the memory card to be used in a wide variety of applications while maintaining its high quality. More particularly, the preferred method involves printing a first magnetic conductive ink composition in predetermined areas on a surface of a flexible substrate so as to form a first portion of a closed loop conductive path. The first magnetic conductive ink composition is dried to eliminate the solvent contained therein and ensure that it permanently adheres to the substrate. Then a second electrically conductive ink composition is printed in conductive contact with the first electrically conductive ink composition. The second conductive ink composition forms a thermally fusible link to complete the closed loop conductive path, which in cooperation with the first portion of the closed loop conductive path, forms a site on the card readable by an external reader device. Once the second ink has sufficiently dried, a protective sealant layer is applied thereto to overlay and protect the site. The first magnetic conductive ink composition comprises a polymer binder which has a conductive magnetic filler therein. A suitable conductive magnetic filler is silver-nickel alloy flakes. The second conductive ink composition also comprises a polymer binder containing an electrically conductive filler. The filler contains a lower melting electrically conductive metallic component which gives the ink composition a relatively lower thermal stability or melting point than the first electrically conductive ink composition. As a result, the second electrically conductive ink composition, upon heating to an elevated temperature, will soften and retract. Therefore the second electrically conductive ink is used to form a fusible link of the site, which enables the site to be irreversibly converted from the first readable state to the second readable state by an external reader device as the memory card is used. The conductive filler in the second ink composition may, for example, include nickel-silver alloy flakes or particles as well as flakes or particles of a lower melting metal composition, such as a solder formed of a tin-lead alloy or other alloys or eutectic compositions. Brief Description of the Drawings FIG. 1 is a front perspective view of a memory card in accordance with the present invention; FIG. 2A is a cross-sectional view of the card taken along line 2-2 of FIG. 1, showing a flexible thermoplastic polymer substrate; FIG. 2B is a cross-sectional view of the card taken along line 2-2 of FIG. 1, showing a nonporous paper substrate; FIG. 3 is a front perspective view of the card during its manufacture, showing the first conductive ink printed on the surface of the substrate in a predetermined pattern; FIG. 4 is a view similar to FIG. 3 showing the second ink printed on the first conductive ink in a predetermined pattern; FIG. 5 is a top plan view of one cell on the memory card showing the cell in its first readable state; and FIG. 6 is a top plan view of the cell shown in Fig. 5, in its second unreadable state after it has been decremented by an external reader device. Detailed Description of the Preferred Embodiments The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art . Like numbers refer to like elements throughout. According to the illustrated embodiment, a flexible contactless memory card 10 is provided for use with a card reader device similar to that disclosed in Brazilian Patent Specification No. PI 9201380, which is incorporated herein by reference. The memory card has a plurality of readable sites, as explained more fully below, and the card reader device is designed to sense the status or state the readable sites and to determine therefrom the monetary value remaining on the card. As shown in Fig. 1 of the drawings, the memory card 10 has a generally rectangular configuration with rounded corners. The memory card 10 has an overall dimension of approximately 8.55 cm (3.36 inches) by 5.39 cm (2.12 inches) and a thickness of approximately 12 to 14 mils. The front and/or back surface of the memory card 10 may bear printed indicia in the form of text and/or designs as indicated at 11. As shown in Figs. 3 and 4, the memory card 10 has a flexible substrate 12 and at least one, preferably a plurality, of readable sites or cells generally indicated as 14. Each readable site 14 forms a closed loop conductive path (represented in Fig. 5 by the arrow) in the card surface 12 for electrical current induced by an external pulse generator or reader device. The site 14 is formed from a first ink composition having good magnetic properties and electrical conductivity, applied on the substrate in a predetermined area, generally indicated as 16, and a second ink composition applied to the substrate and overlying a portion of the predetermined area 16 to form a fusible link, generally indicated as 18. The second ink composition has good electrical conductivity properties. A protective layer 20 (Figs. 1 and 2) overlies and protects the first and second ink compositions, and provides an abrasion resistant front surface for the card 10. The protective layer 20 may also bear either offset or litho printed indicia 11, shown in Fig. 1, to enhance the attractiveness of the memory card 10 and provide necessary instructions for use of the card. In one embodiment of the invention, as shown in Fig. 2A, the substrate 12 is made from a durable, flexible thermoplastic polymer such as acrylonitrile- butadiene-styrene, polyethylene terephthalate or polyvinylchloride. Alternatively, as shown in Fig. 2B, the substrate 12 may be formed of paper of suitable weight and surface finish. Preferably, the paper substrate has a calendered, relatively nonporous surface finish suitable for printing by silk-screening. The substrate 12 of this embodiment preferably may have a thickness of approximately 0.3 mm +/- 0.02mm. The first and second ink compositions each comprise a polymer binder having an electrically conductive filler dispersed therein and a suitable diluent or solvent to maintain the ink composition at the appropriate viscosity for printing and to provide for rapid drying after printing. Preferably, the polymer binder is a thermoplastic resin material, such as an acrylic resin. Any of a number of filler materials which are known in the art for use in conductive ink compositions could be employed in the ink composition. The filler material used in the first conductive ink composition has both magnetic properties and good electrical conductivity. The ink composition preferably is a relatively high melting material so that after the ink composition has dried, the predetermined area 16 formed by the ink composition has a relatively high thermal stability. Nickel-silver flake pigments have been suitably employed for this purpose as the magnetic conductive filler material . A lower-melting filler material is used in the second ink composition so that the fusible link 18 formed from the ink composition has a lower thermal stability and will soften and retract when heated to thereby interrupt the conductive path formed by the fusible link 18. A mixture of silver flake and a solder powder of a low melting metal such as a tin/lead eutectic composition has been suitably employed for this purpose. By way of illustration, the first ink composition may employ nickel-silver flake of approximately 81% pure silver dispersed in an acrylic thermoplastic resin binder. Butylglycolacetate may be used as a diluent or solvent as necessary to give the ink composition a suitable consistency for printing. For silk screen printing, the ink composition preferably has a Brooksfield viscosity of about 15000 mPaS. After printing, the ink composition is oven dried. The predetermined area 16 of conductive ink formed by the first ink composition preferably has a sheet resistance of 0.010 ohms/sq with 25 microns of thickness. By way of illustration, the second electrically conductive ink composition may suitably have a solids content of approximately 77%, of which silver flake is approximately 60%, tin is approximately 10% and lead is approximately 7%. The remaining percentage of the second ink is made up of a thermoplastic resin binder, such as an acrylic resin, and a butylglycolacetate diluent or solvent . For application by screen printing, the second ink composition preferably has a lower viscosity than tl" t of the first ink composition and is applied over a smaller area of the surface of the substrate and at less thickness than the first ink composition. A suitable viscosity for the second ink composition is about 22000 mPaS Brooksfield viscosity. The fusible link 18 formed by the second ink composition preferably has a sheet resistance of 0.060 ohms per square of 25 microns of thickness. The lower-melting tin and lead components gives the fusible link 18 a lower melting point or thermal stability than the predetermined area 16 formed of the first electrically conductive ink composition. When the fusible link 18 is heated, for example by passage of an inductive current of sufficient magnitude, the link 18 will soften and melt. Capillary forces and/or the wetting characteristics of the second ink composition are such that fusible link 18 retracts or pulls apart upon melting so as to interrupt the closed loop conductive path formed by fusible link 18, thereby irreversibly converting the cell 14 from a first readable state, shown in Fig. 5, to a second readable state shown in Fig. 6. Figs. 3 through 5 illustrate one suitable method for manufacturing the card 10. As shown in Fig. 3, the first ink composition is applied on the surface of the substrate 12 in predetermined areas 16 by means of silk-screening. The silk screen equipment used to manufacture the card 10 has a metal mesh screen of at least #120. The rubber squeegee or blade (not shown) used therewith preferably has at least 65 shore D to ensure the best transfer of the low solvent first ink composition and the second ink composition and to assist in obtaining a uniform layer of each of the first and second inks. It is to be understood that the size of the mesh and the blade are dependent upon and may vary depending on the relative viscosity of the first and second inks being used and other factors. As shown, the predetermined areas 16 define an open central area 22 having a generally keyhole shape and opposing spaced apart leg portions, which extend along opposed sides of the keyhole shaped open central area. This open central area 22 is not electrically conductive. An elongate open area 23 extends between each cell 14 to thereby avoid material contact therebetween. The predetermined areas 16 thus form a first portion of the closed loop conductive path represented by the arrow in Fig. 5. As seen in the drawings, a plurality of individual sites 14 is provided arranged in columns and rows to create a magnetic interaction between the card and correspondingly located reader sites on the external reading device. The number of sites and their organization on the card are predetermined based on the intended use of the card. After the first electrically conductive ink composition has been applied to the substrate 12 in the desired pattern, the first ink is dried. One acceptable method of drying the first electrically conductive ink composition set forth above is by being exposing it to an oven (not shown) for 15 minutes at a temperature of between 90° C and 120° C. This heating causes the solvent existing in the first conductive ink composition to be evaporated. Once dried, the resultant predetermined area 16 is magnetic and has a sheet resistance of less than 0.01 ohms per square. It is also possible to cure the first conductive ink composition by allowing it to air dry over a prolonged period of time and still achieve the same desired results . The process for applying the second conductive ink composition is shown best in Figs. 4 and 5 of the drawings. The second ink composition is printed onto the formation in the predetermined areas 16 by means of silk-screening. The second ink composition forms the fusible link 18, which conductively overlies a portion of the first ink composition such that the fusible link spans transversely across a narrow elongated slot portion of the open central area 24. Once applied, the second electrically conductive ink composition may be dried in a manner similar to that described above with reference to the first ink composition. The fusible link 18 forms the remaining portion of the closed loop conductive path. As shown by the arrow in Fig. 5, the current induced by the external reader device is directed around the generally circular closed loop magnetic conductive path of the site 14. When the site 14 is subjected to an electromagnetic field pulse, a current is generated causing the temperature at the site to increase. As the site 14 is heated to a sufficiently high elevated temperature, the fusible link 18 softens and retracts thereby interrupting the closed loop conductive path of the induced current. As a result of this interruption in the closed loop conductive path, the site 14 is irreversibly converted from the first readable state shown in Fig. 5 to the second readable state shown in Fig. 6. Although only one site 14 on the surface of the card has been described, it will be understood that the memory card 10 will have a plurality of such sites, typically arranged in columns and rows. A protective layer 20 is then applied so as to overlie and seal the plurality of sites 14. The protective layer 20 may, or example, comprise a preformed film layer laminated to the substrate 12 by a suitable adhesive. Alternatively, the protective layer may comprise a coating layer of a suitable hardenaule composition, such as an epoxy composition, overlying the printed surface of the substrate. Printed indicia may then be added to the front and/or the back of the memory card 10 by offset or litho printing to enhance the attractiveness of the card and/or provide instructions for its use. The memory card 10, manufactured by the above-described method, is inserted into an external inductive reader device, such as that described in Brazilian Patent Specification No. PI 9210380, which locates the respective sites 14 in the card. As illustrated in Figs. 4 and 5, the sites are initially in a first, non-decremented state in which the fusible link 18 is intact. In order to decrement the card by one unit of value, the fusible link 18 can be fused and broken. The external reader device accomplishes this by inducing a current into the site 14, which concentrates at the fusible link 18, causing the link to soften and retract, thereby interrupting the closed loop conductive path. The site 14, as shown in Fig. 6, is thus irreversibly converted to the second readable state. The external reader device can detect the difference between a site 14 in the first readable state and one in the second readable state. In this manner, the reader device can determine the number of sites in the first readable state, to thus ascertain the number of monetary units of value remaining on the card. When a monetary unit of value is "spent", the reader device causes a site to be converted to the second readable state by fusing i.e., softening and retracting the fusible link 18. The memory card 10 is usable until all its sites have been decremented in the above-described fashion. Many modifications and other embodiments of the invention will come to mind in one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, and that modifications and embodiments are intended to be included within the scope of the claims.

Claims: THAT WHICH IS CLAIMED: 1. A memory card comprising: a substrate; at least one site provided on said substrate forming a closed loop conductive path in said card for electrical current inductively induced by an external reader device, said site comprising; a first conductive ink composition in predetermined areas of said site forming a first portion of said closed loop conductive path, and a second conductive ink composition forming a second portion of said closed loop conductive path and defining a fusible link which interrupts said closed loop conductive path when fused. 2. A memory card as set forth in Claim 1 wherein said second conductive ink composition comprises a heat retractive thermoplastic composition which, upon heating to an elevated temperature, will soften and retract to interrupt said closed loop conductive path. 3. A memory card as set forth in Claim 2 wherein said second conductive ink composition comprises a polymer binder having an electrically conductive filler therein. 4. A memory card as set forth in Claim 4 wherein said electrically conductive filler comprises silver, tin, and lead. 5. A memory card as set forth in Claim 3 wherein said first conductive ink composition also comprises a polymer binder having a conductive filler therein, and has a higher thermal stability than said second electrically conductive ink composition. 6. A memory card as set forth in Claim 5 wherein said conductive filler in said first ink composition comprises a nickel-silver alloy. 7. A memory card as set forth in Claim 1 wherein said substrate comprises a flexible thermoplastic polymer sheet. 8. A memory card as set forth in Claim 1 wherein said substrate comprises a nonporous paper. 9. A memory card as set forth in Claim 1 additionally including a film laminated to said substrate to form a protective layer overlying and protecting said site. 10. A memory card as set forth in Claim 1 additionally including an epoxy layer on said substrate forming a protective layer overlying and protecting said site. 11. A memory card as set forth in Claim 1 wherein said substrate and said first and second electrically conductive ink compositions have a combined thickness of between 12 mils and 14 mils. 12. A memory card comprising: a flexible substrate; a plurality of sites on said substrate, each site being readable by an external reader device, and each of said sites comprising; a first magnetic conductive ink composition applied in a predetermined area on said substrate; a second electrically conductive ink composition in conductive contact with said first conductive ink composition and forming a fusible link which can be fused and broken by current from an external reader device so as to thereby convert the site from a first readable state to a second readable state; and a protective layer overlying and protecting said first and second electrically conductive ink compositions. 13. A memory card as set forth in Claim 12 wherein said second electrically conductive ink composition comprises a heat retractive thermoplastic composition which, upon heating to an elevated temperature, will soften and retract. 14. A memory card as set forth in Claim 13 wherein said second electrically conductive ink composition comprises a polymer binder having an electrically conductive filler therein. 15. A memory card as set forth in Claim 14 wherein said electrically conductive filler comprises silver, tin, and lead. 16. A memory card as set forth in Claim 12 wherein said first magnetic conductive ink composition also comprises a polymer binder having an electrically conductive filler therein, and has a higher thermal stability than said second electrically conductive ink composition. 17. A memory card as set forth in Claim 16 wherein said electrically conductive filler in said first ink composition comprises a nickel-silver alloy. 18. A memory card as set forth in Claim 12 wherein said substrate comprises a flexible thermoplastic polymer sheet. 19. A memory card as set forth in Claim 12 wherein said substrate comprises a nonporous paper. 20. A memory card as set forth in Claim 12 wherein said protective layer comprises a film laminated to said substrate to overlay and protect said site. 21. A memory card as set forth in Claim 12 wherein said protective layer comprises an epoxy layer. 22. A memory card comprising: a substrate; a plurality of sites provided on said substrate, each site forming a closed loop conductive path in said card for electrical current inductively induced by an external reader device, each said site comprising; a first magnetic conductive ink composition on a surface of said substrate defining a formation with an open central area and opposing spaced apart leg portions, said formation forming a portion of said closed loop conductive path; a second electrically conductive ink composition in conductive contact with said first magnetic conductive ink composition and spanning said leg portions of said formation to form the remaining portion of said closed loop conductive path, said second electrically conductive ink composition defining a fusible link which can be fused and broken by current from an external reader device so as to thereby convert said site from a first readable state to a second readable state; and a protective layer overlying and protecting said first and second electrically conductive ink compositions. 23. A memory card as set forth in Claim 22 wherein said formation defines a generally keyhole shaped open nonconductive central area. 24. A memory card as set forth in Claim 23 wherein said second conductive ink composition which defines said fusible link overlies a portion of said first electrically conductive ink composition and spans said nonconductive area. 25. A memory card as set forth in Claim 24 wherein said second conductive ink composition which defines said fusible link is in the form of a band of said conductive ink composition located overlying and in conductive contact with said leg portions of said formation and spanning across the space between said leg portions. 26. A memory card as set forth in Claim 22 wherein said second electrically conductive ink composition comprises a heat retractive thermoplastic composition which, upon heating to an elevated temperature, will soften and retract to interrupt said closed loop conductive path. 27. A memory card as set forth in Claim 26 wherein said second electrically conductive ink composition comprises a polymer binder having an electrically conductive filler therein. 28. A memory card as set forth in Claim 27 wherein said electrically conductive filler comprises silver, tin, and lead. 29. A memory card as set forth in Claim 22 wherein said first magnetic conductive ink composition also comprises a polymer binder having an electrically conductive filler therein, and has a higher thermal stability than said second electrically conductive ink composition. 30. A memory card as set forth in Claim 29 wherein said electrically conductive filler in said first ink composition comprises a nickel-silver alloy. 31. A memory card as set forth in Claim 22 wherein said substrate comprises a flexible thermoplastic polymer sheet. 32. A memory card as set forth in Claim 22 wherein said substrate comprises a nonporous paper. 33. A memory card as set forth in Claim 22 wherein said protective layer comprises a film laminated to said substrate to overlay and protect said site. 34. A memory card as set forth in Claim 22 wherein said protective layer comprises an epoxy layer. 35. A method of forming a memory card comprising: printing a first conductive ink composition on a predetermined area of a substrate and forming a portion of a closed loop conductive path; and printing a second conductive ink composition on the substrate in conductive contact with said first electrically conductive ink composition and forming a thermally fusible link to complete said closed loop conductive path and thereby form a site on the card readable by an external reader device. 36. A method of forming memory card comprising: printing a first magnetic conductive ink composition onto a substrate to define a formation with an open central area and opposing spaced apart leg portions, said formation forming a portion of a closed loop conductive path; printing a second electrically conductive ink composition in conductive contact with said first electrically conductive ink composition to form a thermally fusible link spanning said leg portions of said formation to complete said closed loop conductive path and thereby form a site on the card readable by an external reader device, the fusible link being capable of being fused and broken so as to thereby convert said site from a first readable state to a second readable state; and applying a protective layer to said substrate overlying and protecting the first and second electrically conductive ink compositions.

Inventors: MEDLEY PETER, ORTIZ FERNANDO JR, MEDLEY, PETER, ORTIZ, FERNANDO, JR.
Applicants: INTERPRINT FORMULARIOS LTD, MEDLEY PETER, ORTIZ FERNANDO JR, INTERPRINT FORMULARIOS LTDA., MEDLEY, PETER, ORTIZ, FERNANDO, JR.
Application year: 1995
Main classification: G06K19
IPC codes: G06K1, G06K19