Registers – Records – Magnetic
Patent
1989-10-09
1991-01-01
Pitts, Harold I.
Registers
Records
Magnetic
235449, G06K 1906
Patent
active
049820761
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic recording medium, and more particularly to improvement of security.
The invention can be applied to a magnetic recording medium requiring illegal use preventing function and forgery and altering preventing function, for example, a magnetic card or the like.
2. Description of the Prior Art
In the prior art, such method is adopted that codes for discriminating truth or falsehood are formed on a part of a magnetic card, and read by a magnetic head so as to discriminate truth or falsehood thereby the security of the card is improved.
In the magnetic card of the prior art, such codes for discriminating truth or falsehood are formed by magnetic print patterns and non-magnetic dummy print patterns so that the codes cannot be easily deciphered. Material of high coercive force, such as magnetite (Fe.sub.3 O.sub.4) or maghemite (.gamma.-Fe.sub.2 O.sub.3), is used as material for the magnetic print pattern.
In the magnetic recording medium in the prior art, however, if external magnetic field is applied to read the codes for discriminating truth or falsehood, residual magnetization is produced in the magnetic print patterns thereby the codes for discriminating truth or falsehood can be visualized using a magnetic viewer or the like on the market.
In order to solve the problem, after the external magnetic field is applied for the reading or the like, it must be demagnetized every time resulting in complication of the system.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problem in the prior art, an object of the invention is to provide a magnetic recording medium which has high security in a simple constitution.
A magnetic recording medium according to the invention is characterized in that three sorts or more of patterns being different in the coercive force are combined corresponding to information.
Since three sorts of the patterns being different in the coercive force are combined, the information for discriminating truth or falsehood is complicated thereby the security can be improved.
Also, when the external field is applied to read the information, the residual magnetization is produced only at a part of the pattern with high coercive force. Thereby, for example, even if the information of the codes for discriminating truth or falsehood is to be deciphered using a magnetic viewer or the like, the pattern with low coercive force cannot be detected. Consequently, without using the demagnetization being a special processing, the security can be improved in quite a simple constituion.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a typical sectional view of a magnetic recording medium as an embodiment of the invention;
FIG. 2 is a diagram illustrating reading method in the embodiment; and
FIG. 3 is a typical sectional view of the embodiment after external magnetic field is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the invention will now be described in detail referring to the accompanying drawings.
FIG. 1 is a typical sectional view of a magnetic recording medium as an embodiment of the invention.
In FIG. 1, on a substrate 1 on a card, a print pattern 2 of material with high coercive force, a print pattern 3 of material with low coercive force, a dummy print pattern 4 of non-magnetic material and a print pattern 5 of material with medium coercive force are arranged in combination corresponding to the recording content. In this case, the pattern 2 with high coercive force is previously magnetized in reverse direction to that of the detecting magnetic field.
The material with high coercive force is exemplified by BaFe.sub.12 O.sub.19, SrFe.sub.12 O.sub.19 or the like. The material with medium coercive force is exemplified by CrO.sub.2, .gamma.-Fe.sub.2 O.sub.3, Co-.gamma.-Fe.sub.2 O.sub.3, Fe.sub.3 O.sub.4 or the like. The material with low coercive force is exemplified by Fe powder, Sendust alloy powder, Mo-permalloy powder, Mn-Zn ferrite, Ni-Zn ferrite, Cu-Zn ferrite or t
REFERENCES:
patent: 4104513 (1978-08-01), Pearce
Kyodo Printing Co., Ltd.
Pitts Harold I.
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