Portable storage medium

Abstract: A portable storage medium having an electronic component therein includes a card-shape case for housing the electronic component (44,46,48). The card-shape case includes a metallic plate substantially surrounding the electronic component for withstanding substantial external forces. The card-shape case includes a cushion member which has a greater flexibility than that of the metallic plate. The cushion member is attached to the metallic plate for cushioning a portion of the card-shape case against external forces. A magnetic stripe (52) is flexibly supported on the card-shape case for deforming a limited amount under the application of external forces to the magnetic stripe in response to the flexibility of the cushion member.

Description: The present invention relates to a portable storage medium, such as a multifunctional IC card, with a magnetic stripe. A multifunctional IC card houses an IC chip comprising a CPU and a memory, a liquid crystal display (hereafter LCD) and a thin battery packaged on a wiring board in a portable-sized card body. The display unit of the LCD can be seen from outside through a suitably open window, and a keyboard is provided on the surface of the card body. Also, contacts are formed on the surface of the card body for sending/receiving required data to and from external systems, such as a reader/writer. According to ISO (International Organisation for Standardisation) standard, the thickness of a multifunctional IC card is defined as 0.76 mm, and the length and width dimensions are also defined A multifunctional IC card has not only a recording function for required information, but also various functions, such as key input, calculation, and character display. Therefore, in order to protect the housed electronic components against external impact and load, the multifunctional IC card is required to have high rigidity. As shown in Figures 1 and 2, a card body 10 of a multifunctional IC card is constructed as a metal case having a pair of stainless steel outer plates 12, 14 welded to a stainless steel frame 16. A contact section 18 comprising a plurality of contacts is formed on outer plate 12 and a wiring board 20 is located between the pair of stainless steel outer plates 12 and 14. From the viewpoint of combined use with the magnetic cards as, for example, cash cards for banks, the present multifunctional IC cards are constructed as hybrid multifunctional IC cards in which a magnetic strip 22 is bonded on to the surface of the card body 10 for magnetically recording information in a similar way to magnetic cards. In a conventional multifunctional IC card with a magnetic strip information data often cannot be written accurately on a magnetic stripe 22. As shown in Figure 3, when magnetic head MH makes contact with magnetic stripe 22, the information data is being written on magnetic stripe 22 formed on outer plate 12. The magnetic flux generated by magnetic head MH, as shown by dotted lines, not only passes through the layer of magnetic strip 22, but also passes into the outer plate 12, due to a leakage magnetic flux from magnetic strip 22. Therefore, since the magnetic flux passes through magnetic stripe 22, it is difficult to obtain good magnetic recording on magnetic stripe 22. As a result, an accurate reading of the information data from magnetic stripe 22 is very difficult due to small level of output of the magnetic flux from the stripe 22 in comparison to the plate 12. We have discovered that this problem may be overcome, according to the present invention, by a portable storage medium including an electronic component therein which comprises metal means having an outer surface, and a maximum permeability of about 1.005 for housing the electronic component and limiting influence on the applied external magnetic flux; and a magnetic recording region on the outer surface of the metal means for magnetically storing data thereon. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a plan view showing a portable storage medium of the prior art; Figure 2 is a sectional view of the portable storage medium of Figure 1 taken along the Line II -II of Figure 1; Figure 3 is a partial sectional view of the portable storage medium of Figure 1 along the longitudinal direction of a magnetic stripe showing the magnetic read/write operation with the magnetic head; Figure 4 is a partial sectional view showing a portable storage medium embodying the present invention; Figure 5 is a partial sectional view of the portable storage medium of Figure 4 along the longitudinal direction of a magnetic stripe showing the magnetic read/write operation with a magnetic head; Figure 6 is a graph showing the relationship between the permeability of the magnetic stripe used in the portable storage medium of Figure 4 and the output voltage; and Figure 7 is a graph showing the relationship between the hardness of the metal used as an outer plate and the permeability. An embodiment of the present invention will be described with reference to Figures 4 to 7. As shown in Figure 4, a card body 80 comprises an outer frame 82 and a pair of outer plates 84 and 86 made of metal which are bonded by welding to both faces of outer frame 82. In card body 80, a wiring board 88 on which electronic components 90 are mounted is housed. An under layer 92 is laminated on to outer plate 84 and a printed layer 94 is coated on under layer 92. As magnetic stripe 96 is mounted on printed layer 94. This magnetic stripe 96 comprises a magnetic layer 98, which forms the magnetic recording medium, and an overcoat layer 100 on magnetic layer 98. Outer plate 84 is designed to protect electronic components 90 mechanically, and is formed of metal with a permeability of 1.005 or less. By this means, the unfavourable effect on the magnetic stripe, as shown in Figure 3 in prior art, is reduced. That is, as shown in Figure 5, magnetic head MH makes contact with magnetic stripe 96 when the information data is being written on magnetic stripe 96. Magnetic flux generated by magnetic head MH, as shown by the dotted lines, almost passes through the layer of magnetic stripe 96. Therefore, since the magnetic flux passes sufficiently through magnetic stripe 96 a good magnetic recording and reading out operation can be performed. Figure 6 is a graph showing the output read out from magnetic stripe 96 when the permeability of the metal used as outer plate 84 is varied. A curve shown by the solid line shows the mean voltage when the output read out from magnetic stripe 96 is logic "O", and the dotted line is logic "1". The output voltages from magnetic stripe 96 fall as the permeability increases. Also, it can be seen that the voltage difference between the output voltages for logic "O" and logic "1" is comparatively small and hardly varies. Figure 7 is a graph showing the permeability against the hardness of the metal when four types of metals with different properties were used as the metal for outer plate 84. A curve A shows the properties when "SUS304" ( S teel Special U se S tainless is abbreviated "SUS" in Japanese Industrial Standard) was used as the metal, curve B shows the properties when "SUS316" was used, curve C shows the properties when "SUS316L" was used, and curve D shows the properties when "NAR-304G" made by Nippon Stainless Steel Co. was used. As shown in Figure 7, it can be seen that when the hardness increased, the permeability rapidly increased after it had exceeded a certain point. The point at which the hardness starts to increase in this way is in the region of a permeability of about 1.005. Therefore, from the curves shown in Figures 6 and 7, it is desirable to form outer plate 84 of a metal with a permeability of 1.005 or less. By setting the permeability at 1.005 or less in this way, as shown in Figure 7, the type of metal, that is to say the material, can be determined according to the required hardness. For instance, it can be seen from Figure 7 that when a metal with a hardness of 300-350 Hv is required, "NAR-304G" is a suitable example. Although an IC card is exemplified in the above description of the first to embodiments as the portable storage medium, the present invention is not limited to IC cards.

Claims: A portable storage medium including an electronic component therein, comprising metal means having an outer surface, and a maximum permeability of about 1.005 for housing the electronic component and limiting influence on the applied external magnetic flux; and a magnetic recording region on the outer surface of the metal means for magnetically storing data thereon. The portable storage medium of claim 1, characterised in that the metal means includes a metal outer plate, an under layer on the metal outer plate and a printed layer on the under layer.

Inventors: NAKAMURA KOICHIRO C O PATENT D, TANAKA YOSHINORI C O PATENT DI, NAKAMURA, KOICHIRO C/O PATENT DIVISION, TANAKA, YOSHINORI C/O PATENT DIVISION
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1988
Main classification: B42D15
IPC codes: G06K19