JPH0954940A - Magnetic recording medium and it production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent malfunction and to obtain stable reproduced signals by magnetizing a magnetic layer so as to be balanced with noise at the time of reading while applying a DC bias magnetic field, thereby diminishing the output of the noise from the card edge. SOLUTION: This medium 1 has a magnetic layer 3 having 1500 to 5000Oe coercive force on a nonmagnetic substrate 2. the layer 3 is magnetized by a CD magnetic field after completely demagnetized by an AC magnetic field. The intensity of magnetization is controlled to be balanced with the pulse noise produced on the edge at the time of reading while a DC bias magnetic field is applied. The intensity may be changeda little according to the reading rate, the DC bias magnetic field to be applied, and kinds of a reading device, and is preferably 1-30% of the saturation magnetization of the layer 3. For example, when information is read out at 1000m/sec while 100G bias magnetic field is applied, the layer is magnetized by a DC magnetic field of about 1.5kG. The noise from the card edge is thereby diminished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces noise generated during reading in a commuter pass, a ticket, a coupon ticket, a prepaid card, a shopping card, a savings card, a credit card, a cash card, a point card, an identification card, etc. And a method for manufacturing the same.

[0002]

2. Description of the Related Art Recently, magnetically recorded cards have been widely used in the above-mentioned fields of application, and due to their simplicity,
Its uses are increasing more and more. The basic structure is such that a magnetic recording layer containing a magnetic material is provided on a base body made of a non-magnetic material, and magnetic recording is performed on the magnetic recording layer. The magnetic recording layer is generally formed by coating a nonmagnetic substrate with a magnetic coating material in which magnetic fine particles, a polymer resin, and various additives are dispersed in an organic or aqueous medium, and drying. Preferably, after applying the magnetic paint, before drying, a magnetic field is applied by a permanent magnet or an electromagnet to perform a magnetic field orientation treatment, and then dried in a drying device to be fixed as a magnetic layer. By this magnetic field orientation treatment, the easy axis of magnetization of the magnetic fine particles contained in the magnetic layer is aligned with the orientation direction, the magnetic recording characteristics in this direction are improved, and the magnetic particles are uniformly magnetized (magnetized) in the same direction. The magnetic recording medium manufactured in this way becomes one plate magnet when it is formed into a magnetic sheet or a magnetic card, for example.

Usually, such a magnetic recording medium is magnetically recorded or
When reading is performed using the reproducing device, a pulse output due to the magnetization due to the magnetic field orientation processing is generated at the card end of the magnetic card, for example. In recent magnetic cards, a magnetic bar code made of a magnetic material having a low coercive force of 100 Oersted or less or a soft magnetic material may be formed from the viewpoint of forgery prevention. In order to take out a signal from the magnetic bar code portion, reading is performed while applying a DC bias magnetic field with a permanent magnet or electromagnet when reading with the magnetic head. At this time, the aforementioned pulse output is observed in addition to the signal based on the magnetic bar code.

In the magnetic card having the bar code formed in this way, the magnetic card as a whole or the track portion including the magnetic bar code may be degaussed with an alternating current to be used without generating a pulse at the card end. But,
When reading is performed without applying a DC bias magnetic field, no pulse is generated at the card edge, but a signal based on a magnetic bar code cannot be obtained. Therefore, in order to extract the output from the magnetic bar code, a low magnetic substance having a low coercive force is magnetized, but the magnetic layer is not magnetically reversed, for example, 100.
When reproducing while applying a DC bias magnetic field (of the order of Gauss), the output from the bar code is obtained, but the pulse at the card edge is generated again. This pulse output is considered to be due to the characteristics of the magnetic material itself (for example, magnetic fine particles having a coercive force of 1500 to 5000 Oersteds) in the magnetic layer itself, or a low coercive force component or a soft magnetic component contained therein.

The output level at the card edge depends on the absolute content of the magnetic material components contained in the magnetic layer, the strength of the applied bias magnetic field, the card transport speed, and the like. For example, as shown in Table 1. When a magnetic card with various configurations and magnetic characteristics is read while applying a bias magnetic field of 100 Gauss, the pulse output generated at the card edge is the pulse output observed with a magnetic card that is not degaussed by AC. It is about 1/20.

[0006]

[Table 1]

[0007]

However, even if the output level is small, such a pulse generated at the card edge is not the output that should be originally and depending on the data processing method of the magnetic card recording / reproducing apparatus, This output may cause noise in the reading process and may cause malfunction. Therefore, an object of the present invention is to eliminate the output from the card end and prevent malfunctions when reproducing while applying a DC bias magnetic field, and a magnetic recording medium and a method of manufacturing the same which can obtain a stable reproduced signal. To provide.

[0008]

In order to achieve the above object, a magnetic recording medium of the present invention is a magnetic recording medium having a magnetic layer having a coercive force of 1500 Oersted to 5000 Oersted on a substrate made of a non-magnetic material. In the recording medium,
It is characterized in that the magnetic layer has magnetization of a size commensurate with noise when reading while applying a DC bias magnetic field, and reduces noise at the end of the recording medium at the time of reading. Further, according to the present invention, a magnetic layer having a coercive force of 1500 Oersted to 5000 Oersted is formed on a substrate made of a non-magnetic material, the magnetic layer is completely degaussed by alternating current, and then the magnetic layer is magnetized by direct current. And a method for manufacturing the above-mentioned magnetic recording medium, which comprises magnetizing the magnetic recording medium by a magnitude commensurate with noise when reading while applying a DC bias magnetic field.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic recording medium of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an example of a magnetic recording medium of the present invention, in which 1 denotes a magnetic recording medium (magnetic card). In this magnetic recording medium, a magnetic layer 3 having a coercive force of 1500 Oersted to 5000 Oersted is formed on a non-magnetic substrate 2. If necessary, a further coating layer (not shown) may be laminated on the magnetic layer. As this non-magnetic substrate 2,
A sheet-shaped non-magnetic material such as a polyester film, a vinyl chloride film, a synthetic paper, a wood pulp paper, and a laminated paper having a thickness of about 150 μm to 1 mm is preferably used.

The magnetic material forming the magnetic layer 3 is γ
-Iron oxide, cobalt-doped gamma-iron oxide, chromium oxide,
Barium ferrite, strontium ferrite, etc. are applied, and fine particles of these magnetic materials are used as vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane resin, polyester resin,
For binders such as epoxy resin and polyisocyanate resin,
The magnetic layer 3 can be formed by applying a coating material, which is dispersed together with other additives such as a pigment, if necessary, onto the substrate 2 and drying the coating material.

The magnetic layer 3 has a coercive force of 1500 to 5000 Oersted. In addition, this magnetic layer 3
Is completely demagnetized by alternating current and then magnetized by direct current magnetization. The magnitude of this magnetization is set to a magnitude that is commensurate with the magnitude of pulse-like noise generated at the end when the magnetic storage medium is read while applying a DC bias magnetic field. The magnitude thereof varies to some extent depending on the reading speed, the magnitude of the applied DC bias magnetic field, the type of reader, etc., but is preferably 1 to 30% with respect to the saturation magnetization of the magnetic layer 3. More specifically, for example, when reading at a speed of 1000 mm / sec while applying a bias magnetic field of 100 gauss, it is preferable to perform direct current magnetization at about 1.5 K gauss.

As a reader for reading such a magnetic recording medium of the present invention while applying a DC bias magnetic field, a conventionally used magnetic recording reader is used. For example, as shown in FIG. A reading device having various configurations is used. FIG. 4A shows a reader equipped with a permanent magnet 41 for generating a DC bias magnetic field,
When the magnetic recording medium 1 of the present invention is scanned, for example, from right to left in the figure, a magnetic change corresponding to the magnetic information recorded on the magnetic recording medium 1 causes a magnetic change between both terminals of the reading coil 43 via the reading head 42. It is output as a voltage change that occurs in the.

FIG. 4B shows another example of the reading device, which is provided with a DC bias generating electromagnet 44, and supplies a current to a coil 45 of the electromagnet 44 to generate a DC bias magnetic field. Similarly, the reading head 46
Output via. FIG. 4C shows still another example of the reading device, which has a DC bias magnetic field generating coil 50. A current is supplied to the coil 50 to generate a DC bias magnetic field, which is characterized in that the coil 50 is integrated with the read head 48. The magnetic recording medium of the present invention is designed so that noise is not generated at the card edge regardless of which type of reading device is used.

FIG. 2 shows another example of the magnetic recording medium of the present invention. The magnetic recording medium (magnetic card) of this example shown by 11 in the figure has a non-magnetic substrate 12 similar to that of the above example 1500.
A magnetic layer 13 having a coercive force of up to 5000 Oersted is formed, and a magnetic bar code 15 having a low coercive force of about 100 Oersted or less is further provided thereon. The magnetic bar code 15 is formed only on the track portion 5 for performing magnetic recording and reading. Further, a concealing layer 14 is provided so as to cover the entire surface of the magnetic layer 13 including the barcode 15, and a protective layer 16 made of an ultraviolet resin or the like is provided thereon.

The magnetic bar code 15 in the magnetic recording medium of this example preferably has a low coercive force of about 100 Oersted or less. For example, forgery prevention information may be recorded on this magnetic bar code. . The magnetic bar code 15 may be provided only on the track portion as described above, but may be provided over the entire surface of the magnetic recording medium, and is preferably formed by, for example, a screen printing method. The concealing layer 14 is a coloring layer containing silver powder, aluminum powder, white pigment, or the like, and conceals the coloring of the magnetic layer (including the bar code) provided thereunder. Therefore, the shape of the bar code cannot be read from the outside, which makes counterfeiting difficult. Further, a print recording layer (not shown) such as a leuco dye type thermal recording layer or a recording layer formed of a metal vapor deposition film of tin, aluminum or the like may be provided between the hiding layer 14 and the protective layer 16.

The magnetic recording medium 11 thus formed
Is completely demagnetized by alternating current as in the above example, and then magnetized by direct current magnetization. Similarly, the magnitude of the magnetization is set to a magnitude commensurate with the magnitude of pulse-like noise generated at the end when the magnetic storage medium is read while applying a DC bias magnetic field.

FIG. 3 is a diagram showing still another example of the magnetic recording medium of the present invention. The magnetic layer 22 having a coercive force of 1500 Oersted to 5000 Oersted is provided only on the track portion of the non-magnetic substrate 21. This magnetic layer 2
Like No. 2 above, No. 2 is completely demagnetized by alternating current and then magnetized by direct current magnetization. Similarly, the magnitude of the magnetization is set to a magnitude commensurate with the magnitude of pulse-like noise generated at the end when the magnetic storage medium is read while applying a DC bias magnetic field.

Next, a method of manufacturing the magnetic recording medium of the present invention will be described. For example, FIG. 6 is a diagram showing an example of a system suitable for carrying out the manufacturing method of the present invention.
For example, 188 sent out from the roll 60 of the non-magnetic substrate
A base sheet 61 made of a white polyester film having a thickness of μm is guided to a coating device 62 having a coating head, and a coating material in which magnetic fine particles are dispersed is applied. Next, the base sheet coated with this magnetic coating material is introduced into the magnetic field aligner 63 via the roll 65, and magnetic field orientation is performed using, for example, a 5000 Gauss permanent magnet. Further, the magnetic material oriented magnetic sheet 71 is obtained by drying the base sheet having a magnetic layer having a magnetic layer orientation of, for example, 12 μm in a drying device 64, and winding the roll 66 through a winding roll.

Next, as shown in FIG.
1 is cut into an appropriate size to form a magnetic raw sheet 72,
Further, the magnetic original sheet 72 is punched out in a size conforming to, for example, the JIS standard to obtain a magnetic recording medium (magnetic card) 73. After the magnetic card 73 is completely demagnetized with alternating current, when the magnetic recording medium is read while applying a direct current bias magnetic field, magnetization of a size commensurate with the magnitude of pulse-like noise generated at the end remains. Thus, the magnetic recording medium of the present invention is obtained by direct-current magnetization.

[0020]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 A coating material for the magnetic layer was prepared with the following composition. Barium ferrite BaO ・ 6Fe ₂ O ₃ (MC127 manufactured by Toda Kogyo Co., Ltd.) (coercive force 2750 Oersted specific surface area 5 m ² / g) 100 parts by weight carbon black 3 parts by weight lecithin 1 part by weight Vinyl chloride / vinyl acetate / vinyl alcohol co-weight Combined 20 parts by weight Polyurethane resin 20 parts by weight Toluene 60 parts by weight Methyl ethyl ketone 60 parts by weight Methyl isobutyl ketone 60 parts by weight

After the mixture having the above composition was dispersed by a ball mill for 8 hours, 5 parts by weight of polyisocyanate resin was added and further dispersed for 1 hour to obtain a coating material for magnetic layer. The coating may be performed according to a usual method for manufacturing a magnetic recording medium. That is, as shown in FIG. 6, the coating material for the magnetic layer having the above composition was applied onto a substrate made of a white polyester film having a thickness of 188 μm by a coating head, and 50
A magnetic field orientation treatment was performed in a coating direction with a 00 Gauss permanent magnet, followed by drying in a drying device to form a magnetic layer having a thickness of 12 μm, which was wound as a magnetic original sheet. The magnetic original sheet thus obtained was cut into a sheet to obtain a magnetic original sheet.

Next, a magnetic layer coating material for a magnetic bar code was prepared with the following composition. Carbonyl iron powder (coercive force 40 oersted, specific surface area 1 m ² / g) 100 parts by weight lecithin 1 part by weight vinyl chloride / vinyl acetate / vinyl alcohol copolymer 20 parts by weight polyurethane resin 20 parts by weight xylene 60 parts by weight methyl isobutyl ketone 60 parts by weight Part Isophorone 60 parts by weight

After the above mixture was dispersed by a ball mill for 8 hours, 5 parts by weight of a polyisocyanate resin was added and further dispersed for 1 hour to obtain a magnetic coating material magnetic layer for magnetic bar code. The coating was carried out in the form of a bar code using a screen printing method in the form of being laminated on the magnetic layer of the magnetic raw sheet having the magnetic layer formed thereon, and dried.

Further, a coating material having the following composition was applied to the entire surface of this magnetic raw sheet by a screen printing method and dried to form a silver colored layer to obtain a card original sheet. Aluminum paste 5 parts by weight Polyester resin 15 parts by weight Methyl isobutyl ketone 40 parts by weight Isophorone 40 parts by weight

Further, a leuco heat-sensitive ink was printed on the silver colored layer by a screen printing method, and the caution statement printing and the protective layer printing were performed by a UV offset printing method. Also, four-color full-color printing and protective layer printing were performed on the opposite side of the polyester film using a UV offset printing method. From the magnetic raw sheet thus obtained,
A JIS size magnetic card was punched out.

This magnetic card has a maximum magnetic field of 6K gauss,
The entire card was degaussed using a 50 Hz AC degausser. Then, the entire card was DC magnetized at 1.5 K gauss to obtain a magnetic card of this example.

Next, this magnetic card was read using a reader of the type shown in FIG. 4 while applying a DC bias magnetic field. For comparison, the same reading was performed on a magnetic card manufactured in the same manner as this example and not subjected to AC demagnetization and DC magnetization, and a magnetic card subjected to AC demagnetization and not DC magnetization. Results are shown in FIG. However, the card transport speed is 1000 mm / se
c and the magnitude of the DC bias magnetic field was 100 gauss.

First, in the magnetic card which was not subjected to AC degaussing or DC magnetization, when read without applying a DC bias magnetic field, only noise pulses appeared at the card edge as shown in FIG. Also, when a similar magnetic card is read by applying a DC bias magnetic field, FIG.
As shown in (b), although magnetic information based on the bar code can be read, noise pulses at the card edge were also observed.

Next, in a magnetic card that was completely demagnetized by AC and not magnetized by DC, the noise pulse at the card edge disappeared as shown in FIG. 5C when reading without applying a DC bias magnetic field. , I could not read the magnetic information of the bar code. Further, when a DC bias magnetic field is applied, as shown in FIG. 5D, the magnetic information of the bar code can be read, but
A noise pulse in the opposite direction to that in FIGS. 5A and 5B appeared. However, the height of this pulse was considerably lower than the height of the pulse shown in FIG.

Finally, in the magnetic card of this embodiment according to the present invention, when no DC bias magnetic field was applied, a small pulse appeared at the card edge as shown in FIG.
This pulse has a size that balances with the pulse at the card edge in FIG. 5D, and can be almost canceled.
However, when a DC bias magnetic field is applied, as shown in FIG.
As in (f), no noise pulse was observed at the card edge, and only an output based on the magnetic information of the magnetic barcode could be obtained.

(Example 2) A magnetic recording medium (magnetic card) was produced in the same manner as in Example 1, and only the track portion including the magnetic bar code was degaussed by alternating current using a magnetic head for alternating current degaussing. Next, only the track portion was DC magnetized using the magnetic head in the same manner as in Example 1 to obtain the magnetic card of this example. When this magnetic card was read while applying a DC bias magnetic field, no noise at the card edge was observed as in Example 1, and only the magnetic information of the bar code could be read.

[0032]

As described above, the magnetic recording medium of the present invention has a magnetic layer having a coercive force of 1500 to 5000 Oersted on a non-magnetic substrate, and after demagnetizing the same with an alternating current, it is applied to the card edge. The direct current magnetization leaves 1 to 30% of the saturation magnetization so as to have a magnitude corresponding to the generated noise pulse. Therefore, particularly when reading is performed by the magnetic head while applying the DC bias magnetic field, the noise output from the card edge can be significantly reduced or eliminated, and the magnetic information recorded on the medium can be accurately read. Further, it is possible to apply to the prevention of forgery by a system in which such noise output information is input in advance.

[Brief description of drawings]

FIG. 1 is an example of a magnetic recording medium of the present invention (magnetic card).
FIG. 4 is a top view (a) and a side sectional view (b) showing FIG.

FIG. 2 is a top view (a) and a side sectional view (b) showing another example (magnetic card) of the magnetic recording medium of the present invention.

FIG. 3 is a top view showing still another example (magnetic card) of the magnetic recording medium of the present invention.

FIG. 4 is an example of an apparatus for reading while applying a DC bias magnetic field, showing an apparatus including a permanent magnet (a), an electromagnet (b), or a coil (c) for generating a DC bias magnetic field. is there.

FIG. 5 is a diagram showing a result of reading a magnetic card of Example 1, including (a) output when a magnetic card without AC demagnetization and DC magnetization is read without a DC bias magnetic field;
(B) Output when a magnetic card without AC demagnetization and DC magnetization is read by applying a DC bias magnetic field. (C) Output when a magnetic card with AC demagnetization and no DC magnetization is read without a DC bias magnetic field. (D) Output when a magnetic card with alternating current demagnetization and no direct current magnetization is read by applying a direct current bias magnetic field. (E) The magnetic card of the present invention with alternating current demagnetization and direct current magnetization is read without a direct current bias magnetic field. FIG. 4 is a diagram showing an output when the magnetic card of the present invention having (f) AC demagnetization and DC magnetization is read by applying a DC bias magnetic field.

FIG. 6 is a diagram showing an example of a system suitable for carrying out a part of the method for manufacturing a magnetic recording medium of the present invention.

FIG. 7 shows a method for manufacturing a magnetic recording medium of the present invention,
It is a figure explaining the process of following the process implemented in the system shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic recording medium (magnetic card), 2 ... Base | substrate, 3 ... Magnetic layer, 5 ... Track part, 14 ... Concealment layer, 15 ... Magnetic barcode, 16 ... Protective layer

Claims (5)

[Claims] 1. A magnetic recording medium comprising a magnetic layer having a coercive force of 1500 Oersted to 5000 Oersted on a substrate made of a non-magnetic material, wherein the magnetic layer causes noise when reading while applying a DC bias magnetic field. A magnetic recording medium characterized in that it has magnetization of a size commensurate with that of the magnetic recording medium and has reduced noise during reading. 2. A magnetic layer having a coercive force of 1500 Oersted to 5000 Oersted is formed on a substrate made of a non-magnetic material, the magnetic layer is completely demagnetized by AC, and then the magnetic layer is DC-magnetized. A magnetic recording medium, characterized in that it is magnetized by a size commensurate with noise when reading while applying a DC bias magnetic field. 3. The magnetic recording medium according to claim 1, wherein the magnitude of the magnetization is 1 to 30% of the saturation magnetization of the magnetic layer. 4. A magnetic layer having a coercive force of 1500 Oersteds to 5000 Oersteds is formed on a substrate made of a non-magnetic material, the magnetic layers are completely demagnetized by AC, and then the magnetic layers are DC magnetized. A method for manufacturing a magnetic recording medium, characterized in that the magnetic recording medium is magnetized by a magnitude commensurate with noise when reading while applying a DC bias magnetic field. 5. The method of manufacturing a magnetic recording medium according to claim 4, wherein the magnitude of the magnetization for direct-current magnetization is 1 to 30% of the saturation magnetization of the magnetic layer.