Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1999-02-04
2001-03-20
Le, Thien M. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S494000, C235S380000, C235S454000, C503S217000, C503S216000
Reexamination Certificate
active
06202926
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method of using magnetic recording media, typically magnetic cards.
BACKGROUND ART
In recent years, magnetic cards have enjoyed widespread use in a variety of fields. In particular, magnetic cards find an expanding application as rewritable or prepaid cards in which monetary information is recorded as magnetic bits of information so that the amount of money may be reduced on every use.
In this application, the safety of the card system is fatally lost if magnetic cards are not fully protected against forgery by the alteration of recorded data or counterfeit cards can be easily produced. There is a strong demand for magnetic cards having a protective function of preventing the alteration of the recorded data. To meet the demand, a variety of magnetic cards have been proposed and used in practice. For example, if magnetic cards are locally provided with a region of a special material, they are difficult to counterfeit and whether they are false or true can be judged by detecting the special region. Magnetic cards with a complex layer arrangement are also known.
These magnetic cards having the protective function incorporated therein are difficult to forge or to duplicate in numbers. However, there is still a possibility that the monetary information in an exhausted card be restored to the initial information by false alteration, for example, by rewriting the monetary information. One countermeasure is to punch holes in the card in accordance with the number of uses although this raises several problems, such as punched chips left behind, and repair by refilling the holes being possible. Another possible countermeasure is to record visible data corresponding to the number of uses by thermographic recording. These cards carrying visible data, however, are weak against staining because the visible data must be optically read. The falsification of the record is easy on account of visible data. Another problem is that optical readers are generally expensive.
In view of the above problems, JP-A 77622/1996 proposes a magnetic recording medium comprising an irreversible recording layer using as a magnetic recording material an alloy whose ratio of the saturation magnetization in a crystalline state to the magnetization in an amorphous state is at least 5. This magnetic recording medium has an irreversible recording layer composed of a recording material which undergoes an irreversible change of saturation magnetization upon heating. Although this recording material changes its saturation magnetization upon heating, rewriting is substantially impossible because in order to restore the saturation magnetization to the value prior to heating, the magnetic recording medium must be heated to such an extent that the medium may be deformed or melted. The medium insures high safety.
However, the only method for effecting information recording in such an irreversible recording layer disclosed therein is a method of heating the layer in a pattern corresponding to the record information using a thermal head. A method taking advantage of an irreversible recording material has not been proposed.
SUMMARY OF THE INVENTION
A first object of the invention is to hinder the false alteration of record information in a magnetic recording medium such as a magnetic card and to facilitate recording of substantially unalterable information.
A second object of the invention is to suppress an output variation of the magnetic recording medium in addition to the attainment of the first object.
A third object of the invention is to improve the secrecy of recorded information in addition to the attainment of the first object.
A fourth object of the invention is to enable to easily detect the false alteration of record information in addition to the attainment of the first object.
A fifth object of the invention is to make it more difficult to forge or counterfeit the medium in addition to the attainment of the first object.
The first to fifth objects are attained by the following first to fifth embodiments, respectively.
First embodiment
(1) to (5) below
Second embodiment
(6) below
Third embodiment
(7) to (9) below
Fourth embodiment
(10) to (15) below
Fifth embodiment
(16) below
(1) A method of using a magnetic recording medium comprising on at least a portion of a substrate an irreversible recording layer which contains an irreversible recording material undergoing an irreversible change of saturation magnetization upon heating, said method comprising the steps of:
previously heating said irreversible recording layer to form an initial heated region in which a plurality of heated bars whose saturation magnetization has been irreversibly changed are arrayed in a bar code pattern, and
converting unheated bars disposed between the heated bars into a heated state for changing the array pattern of heated bars, thereby effecting information recording.
(2) A method of using a magnetic recording medium as set forth in (1) wherein said magnetic recording medium is a magnetic card, said information recording is recording of the fixed information of the magnetic card, and said information recording is effected at the issue of the magnetic card.
(3) A method of using a magnetic recording medium as set forth in (1) or (2) wherein said information recording is recording of the use history of the magnetic recording medium.
(4) A method of using a magnetic recording medium as set forth in any one of (1) to (3) wherein the step of converting unheated bars into a heated state changes the array pattern of heated bars into an encoded array pattern.
(5) A method of using a magnetic recording medium as set forth in any one of (1) to (4) wherein said initial heated region includes a region where the heated bars of equal width are arrayed in an equi-spacing pattern.
(6) A method of using a magnetic recording medium as set forth in any one of (1) to (5) wherein said irreversible recording layer is scanned with a heating means for heating for effecting recording, and
the scanning direction of said heating means is substantially perpendicular to the direction in which the layer is scanned with a read head during reading operation.
(7) A method of using a magnetic recording medium as set forth in any one of (1) to (6) wherein said magnetic recording medium has a magnetic recording layer between said irreversible recording layer and said substrate wherein said irreversible recording layer functions as a magnetic shield layer.
(8) A method of using a magnetic recording medium as set forth in (7) wherein said irreversible recording layer contains a soft magnetic material in addition to the irreversible recording material.
(9) A method of using a magnetic recording medium as set forth in (7) wherein said irreversible recording layer is comprised of a soft magnetic material layer containing said soft magnetic material and an irreversible recording material layer containing said irreversible recording material.
(10) A method of using a magnetic recording medium as set forth in any one of (1) to (9) wherein said irreversible recording layer contains a hard magnetic material whose saturation magnetization does not substantially change upon heating and which has a higher coercivity than said irreversible recording material.
(11) A method of using a magnetic recording medium as set forth in (10) wherein said irreversible recording layer is comprised of an irreversible recording material layer containing said irreversible recording material and a hard magnetic material layer containing said hard magnetic material.
(12) A method of using a magnetic recording medium as set forth in (10) or (11) wherein said hard magnetic material has a coercivity of at least 300 Oe.
(13) A method of using a magnetic recording medium as set forth in any one of (10) to (12) wherein
recording is effected by heating said irreversible recording layer for causing said irreversible recording material to undergo a change of saturation magnetization, and
reading is effected by detecting a magnetization change of said irreversible recordin
Chou Tsutomu
Ito Masahiro
Mimura Shohei
Shigeta Masao
Felten Daniel S.
Le Thien M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Magnetic Printing Co. Ltd.
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