JPH06119504A - Magnetic bar code and it reading method and reader - Google Patents

Abstract

PURPOSE:To provide a magnetic bar code and its reading method and reader capable of improving the secrecy of magnetic bar code information. CONSTITUTION:A magnetic bar code is constituted of combining plural magnetic bars containing plural magnetic powder components selected from a spinel type ferrite power group and having respectively different curie temperatures Tc. A difference between the curie temperatures of magnetic powder components constituting the ferrite power group is at least 50 deg.C. In the case of reading out the bar code by a magnetic head, a difference ¦TC-TH¦ between the curie temperature Tc of the magnetic power and the temperature TH of the head is set up at least to 120 deg.C. A reader for the magnetic bar code is provided with a heating means for heating the magnetic head so that the temperature difference ¦TC-TH¦ becomes 120 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic powder used for a magnetic bar code, a magnetic bar code reading method using the magnetic powder, and a reading apparatus for the magnetic bar code.

[0002]

2. Description of the Related Art Conventionally, a magnetic bar code of this kind is inexpensive, has high stability, and has a relatively high magnetization amount (4πI) and a relatively low coercive force ( _I H _C ). Series ferrite (general formula MFe ₂ O ₄ , where M is 2
A metal that has a value) is used.

In general, a magnetic bar code using this powder employs a method of combining a magnetic bar and a non-magnetic bar in order to improve the confidentiality of information, and the part of the bar having magnetism can be visually identified. It will not be easy.

Here, the high magnetization amount of the magnetic powder in this bar code corresponds to an increase in read output. On the other hand, low _I
H _C makes it difficult to detect the magnetic bar by a magnetic viewer and is a countermeasure against forgery.

[0005]

However, the magnetic bar code formed by the combination of the magnetic bar and the non-magnetic bar as described above is closely related to the composition of the spinel powder. For example, magnetite (Fe with a high value of 4πI)
₃ O ₄ ) powder and Mn-Zn-based ferrite powder are black, Ni-Zn-based ferrite powder is brown, and non-magnetic ZnFe ₂ O ₃ powder is yellowish brown.
Therefore, by carefully observing the magnetic bar code formed using these magnetic and non-magnetic powders, it is possible to visually distinguish the magnetic bar from the non-magnetic bar, and the confidentiality of information using this Can be said to be in a state of being significantly reduced.

Therefore, a technical object of the present invention is to form magnetic bars by using ferrite powders having different Curie temperatures, arbitrarily change the temperature of a magnetic head for reading the magnetic bars, and process magnetic data corresponding thereto. By doing so, the confidentiality of the magnetic barcode information is improved.

[0007]

According to the present invention, a magnetic bar containing magnetic powders selected from a plurality of spinel-type ferrite powders having different Curie temperatures T _C is combined. A magnetic barcode is obtained.

In the present invention, a non-magnetic bar may be added to this magnetic bar to form a magnetic bar code, and essentially the same effect as obtained by only the magnetic bar can be obtained.

Further, according to the present invention, there is provided a magnetic bar code reading method for reading any one of the above magnetic bar codes by using a magnetic head, wherein the Curie temperature T _{C of the} magnetic powder and the temperature of the magnetic head are used. Difference from T _H | T _C −
A method of reading a magnetic bar code is obtained in which T _H | is set to at least 120 ° C.

According to the present invention, there is provided an apparatus for reading any one of the above magnetic bar codes by using a magnetic head, wherein the difference between the Curie temperature T _{C of the} magnetic powder and the temperature T _{H of the} magnetic head. | T _C -T _H | of at least 12
A magnetic bar code reader is provided which is equipped with heating means for heating the reading surface of the magnetic head or the magnetic bar code to be read so as to reach 0 ° C.

In the present invention, the difference in Curie temperature between the ferrite powders used for the magnetic bar code is 5
The reason why the temperature is set to 0 ° C. or higher is that the determination of reading by the magnetic head becomes uncertain below that, and the reliability of information remarkably decreases.

Further, in the present invention, the temperature difference between the ferrite powder used for the magnetic bar code and the reading magnetic head is set to 120 ° C. or more. Below that, the determination of reading by the magnetic head becomes uncertain, and the information This is because the reliability is significantly reduced. Furthermore, in the present invention,
Since the difference in T _C of the ferrite powder that constitutes the magnetic barcode is used, powders with similar shades can be used if they have similar composition systems, and powders with different shades can be used if they have different composition systems. You can also do it. Therefore, the degree of freedom in selecting the shade of the powder to be used is expanded. It can also be combined with a bar made of non-magnetic powder.

Further, in the present invention, the heating means may use a method of self-heating by energizing the magnetic head. However, the heating surface of the magnetic head can be heated or a magnetic bar code to be read is read. The method is not limited to these methods as long as it uses light, electricity or the like that can be heated immediately before or during reading.

More specifically, the present invention uses two types of ferromagnetic Mn-Zn-based ferrite powders having different Curie temperatures and ZnFe ₂ O ₄ powder which is non-ferromagnetic, and is composed of the respective powders. In the case of forming a magnetic bar code in 1), 1) the Mn-Zn ferrite powder is black, but since it has a similar composition, there is no significant color difference. ZnFe ₂
The O ₄ powder is yellowish brown. Therefore, it is possible to distinguish between the magnetic bar and the non-magnetic bar by color.

2) By reading at a temperature at which the magnetism of one of the Mn-Zn-based ferrite powders is significantly reduced, it is possible to distinguish magnetic bars that cannot be visually identified.

Therefore, by arbitrarily changing the reading conditions of the magnetic bar code, the discrimination based only on the color becomes uncertain, and the discrimination by the magnetic viewer or the like becomes uncertain, and if the bar arrangement is also combined. ， This magnetic bar code is extremely confidential.

4π used in the following examples of the invention
I _1kOe is the amount of magnetization measured by applying a magnetic field of 1 _kOe, and _I H _c represents the coercive force of the powder magnetized under this condition.

[0018]

EXAMPLES Examples of the present invention will be described below.

Example 1 The chemical composition ratio is MnFe ₂ O ₄
And Mn _0.5 Zn _0.5 Fe ₂ O ₄ so that iron oxide (α-Fe ₂ O ₃ ) and trimanganese tetraoxide (Mn ₃ O ₄ )
And zinc oxide were used as raw materials and wet-mixed in a ball mill for 20 hours.

Next, these raw material mixed powders were fired at 1100 ° C. for 2 hours in a nitrogen atmosphere with rapid heating and rapid cooling to obtain spinel ferrite.

Next, this powder was wet-milled for 3 hours with a ball mill to obtain a ferrite powder for coating. The specific surface area of this powder by the BET method was about 2 m ² / g. When the magnetic characteristics of this powder were measured by a vibrating magnetometer, it was found that MnFe ₂ O ₄ powder had 4πI _1kOe 5100G, _I H
_C 15 Oe, T _C 300 ° C., Mn _0.5 Zn _0.5 F
e ₂ O ₄ powder is 4πI _1kOe 3000G, _I H _C 8Oe,
It was T _C 130 ° C. Using these powders and a commercially available ZnFe ₂ O ₄ powder (this is a non-ferromagnetic spinel ferrite), magnetic inks made of urethane resin of 30 wt% were prepared. Use this magnetic ink,
Silk screen printing was performed alternately in a bar code shape having a length of 4 mm, a width of 0.2 mm and a thickness of about 10 μm.

Next, using this magnetic bar code, a magnetic ink character reader (MICR) designed to generate a magnetic field of about 1 kOe in the magnetic head was used to set the critical output for reading the magnetic signal to 300 mV. Then, the presence or absence of bar code signal recording was detected. Further, the magnetic head used here is a so-called thermal head of a type capable of simultaneously heating by energization. The magnetic signal was read at room temperature (about 20 ° C) and 150 ° C. The presence / absence determination based on the result is shown in Table 1 below. The head temperature in Table 1 indicates the temperature of the portion that comes into contact with the magnetic bar code.

[0023]

[Table 1]

As is clear from Table 1, the security of a card or the like using this magnetic bar code can be remarkably improved by arbitrarily changing the setting of the reading temperature.

Example 2 The chemical composition ratio is Ni _0.7 Zn
Iron oxide, nickel oxide (NiO), and zinc oxide were used as raw materials so as to obtain _0.3 Fe ₂ O ₄ and Ni _0.3 Zn _0.7 Fe ₂ O _4, and mixed in the same manner as in Example 1, and then in air for 2 hours. It was baked into spinel type ferrite and pulverized to obtain ferrite powder for coating.

The specific surface area of this powder is about 3 m ² / g, and Ni _0.7 Zn _0.3 Fe ₂ O ₄ is 4πI _1kOe 4900.
G, _I H _c 25 Oe, T _C 410 ° C., Ni _0.3 Zn _0.7
Fe ₂ O ₄ is _{4πI 1kOe 3800G, I H C 10Oe} ,
Was T _C 170 ° C..

In the same manner as in Example 1, three types of magnetic bar codes were printed and the presence or absence of bar code signal recording was determined. The results are shown in Table 2 below. The head temperature in Table 2 indicates the temperature of the portion of the magnetic head that contacts the bar code.

[0028]

[Table 2]

As is clear from Table 2, the confidentiality of a card or the like using this bar code can be remarkably improved by arbitrarily changing the setting of the reading temperature.

Example 3 The chemical composition ratio is Li _0.4 Zn
Iron oxide, lithium carbonate (Li ₂ CO ₃ ) and zinc oxide were used so as to obtain _0.2 Fe _2.4 O ₄ and Li _0.15 Zn _0.7 Fe _2.15 O _4, and calcined at 1000 ° C. in the same manner as in Example 2, A spinel ferrite powder for coating was obtained.

The specific surface area of this powder is about 2.5 m ² / g, and Li _0.4 Zn _0.2 Fe _2.4 O ₄ is 4πI _1kOe 42
_{00G, I H C 30Oe, T} C 490 ℃, Li 0.15 Zn
_0.7 Fe _2.15 O ₄ is 4πI _1kOe 2900G, _I H _C 10
Oe, it was T _C 180 ° C..

In the same manner as in Example 1, three kinds of magnetic bar codes were printed and the presence or absence of bar code signal recording was determined. The results are shown in Table 3 below. The head temperature in Table 3 indicates the temperature of the portion of the magnetic head that contacts the magnetic bar code.

[0033]

[Table 3]

As is clear from Table 3, the security of a card or the like using this bar code is significantly improved by arbitrarily changing the setting of the reading temperature.

Example 4 The chemical composition ratio is (Ni _0.7 Cu
_{0.3) (1-x) ·} Zn X · Fe 2 O 4 with x = 0.2, 0.
3, 0.4, 0.5, 0.6, 0.7, 0.
In the same manner as in Example 2, iron oxide, nickel oxide, cupric oxide (CuO), and zinc oxide were used to obtain No. 8, and firing was performed at 900 ° C. to obtain spinel ferrite powder for coating.

The specific surface area of these powders is about 2.5 m ² / g
Table 4 below shows the measurement results of the magnetic properties.

[0037]

[Table 4]

Next, using these powders, a magnetic bar code was printed in the same manner as in Example 1, and the MICR read critical output was set to 200 mV to determine the presence or absence of the bar code and the temperature of the thermal head. At room temperature (20 ° C), 50
The temperature was set to 100 ° C, 150 ° C, and 200 ° C. The results are shown in Table 5 below. In the table, ○ mark Yes, × represents the free, () numbers in the [Delta] T = (T _C of ferrite powder) - (temperature of the thermal head) shows a ° C..

[0039]

[Table 5]

From the results shown in Table 5, the T of ferrite powder was
_It can be seen that when the temperature difference between _C and the thermal head is 110 ° C or less, the discrimination is impossible, and when 120 ° C or more, the discrimination is possible.

Further, Table 6 below shows the critical region in which the judgment based on the difference in T _C between the ferrite powders is possible.

[0042]

[Table 6]

From the results shown in Table 6, it can be seen that if the difference in T _C between the ferrite powders is 50 ° C. or more, the discrimination becomes possible.

As can be seen from the above examples, magnetic bar codes are formed by combining magnetic bars having a Curie temperature difference of 50 ° C. or more between spinel ferrite powders constituting the magnetic bar code to form a magnetic bar code. T _C -T _H | | difference between the temperature T _H of the powder Curie temperature T _C and read magnetic head by using a reading device which was 120 ° C. or more, it can be seen that significantly improved the sensitivity of the magnetic bar code .

The spinel ferrites shown in the examples of the present invention are Mn-Zn ferrites, Ni-Zn ferrites, Li-Zn ferrites, Ni-Cu-Zn.
System ferrite only, and the formed magnetic bar codes are of the same system, but the present invention utilizes the temperature change of the magnetization of spinel system ferrites having different T _C , so only this range The present invention is not limited to the above, but spinel type ferrites of different compositions may be combined, and as the ferrite type, spinel type ferrite containing various elements including Fe ₃ O ₄ etc. may be used. The range can be easily understood by those skilled in the art.

In the embodiment of the present invention, the raw material powder is mixed and fired as a method for producing the spinel ferrite powder. However, if the ferrite powder for coating is spinel ferrite, the production method is spray roasting. Method, coprecipitation method, hydrothermal synthesis method, etc. may be used.

In the embodiment of the present invention, only the screen printing is shown as the method of forming the bar code, but the bar code may be formed by another method such as offset printing. .

[0048]

As described above, according to the present invention, it is possible to provide the magnetic bar code which improves the confidentiality of the magnetic bar code information, the reading method thereof, and the reading apparatus thereof.

Claims (4)

[Claims] 1. A magnetic bar code comprising a combination of magnetic bars each containing a magnetic powder selected from a plurality of spinel-type ferrite powder groups having different Curie temperatures T _C. 2. The magnetic barcode according to claim 1, wherein a difference in Curie temperature T _C between the magnetic powders constituting the spinel type ferrite powder group is at least 50 ° C. 3. A method of reading a magnetic bar code according to claim 1 or 2 by using a magnetic head, comprising a Curie temperature T _{C of the} magnetic powder and a temperature T _{H of the} magnetic head. difference | T _C -T _H | a reading method of a magnetic bar code, characterized in that it has at least 120 ° C.. 4. A device for reading the magnetic bar code according to claim 1 or 2 by using a magnetic head, wherein a difference | T _C − between the Curie temperature T _{C of the} magnetic powder and the temperature T _{H of the} magnetic head. A magnetic bar code reader comprising heating means for heating the reading surface of the magnetic head or the magnetic bar code to be read such that T _H | is at least 120 ° C.