JPS6233325A - Heat sensitive magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent forgery by successively laminating a magnetic layer of high coercive force, high magnetic permeability layer and magnetic layer of low coercive force on one surface of a base and providing a leuco dye heat sensitive color forming layer consisting of a sulfonate-contg. polyester resin as a binder, barrier layer and protective layer essentially consisting of a polyurethane resin on the other surface. CONSTITUTION:Normal data is recorded to the high coercive force of a magnetic recording medium constituted by successively laminating the high coercive force magnetic layer, the high magnetic permeability layer 13 and the low coercive force magnetic layer 14 on one surface of the base 11 consisting of a nonmagnetic sheet and a dummy signal is recorded to the low coercive force layer. The heat sensitive recording layer to be formed on another surface of the base is the leuco dye heat sensitive color forming layer consisting of the sulfonate-contg. polyester resin as the binder and further the protective layer essentially consisting of the polyurethane resin is provided via the barrier layer thereon. The magnetic permeability layer 3 is magnetically saturated when a card for reproduction is brought into tight contact with the magnetic surface and a magnetic field for transfer is applied thereto. The magnetic permeability is then decreased and the magnetic shielding effect is lost. The normal data recorded to the high coercive force layer 12 and the dummy signal recorded to the low coercive force layer 4 are thereby mixedly reproduced on the card for reproduction. The forgery is thus prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a heat-sensitive magnetic recording medium used for cashless coupon tickets, commuter passes, etc. for purchasing train tickets or for telephone use. The present invention relates to a thermosensitive magnetic recording medium that is highly resistant to counterfeiting and in which a predetermined recorded signal cannot be read unless a predetermined operation is performed.

<Prior Art> In recent years, magnetic cards have become rapidly popular in cashless coupons, magnetic coupons, road passes, commuter passes, and the like. In this case, it is necessary to record visible information on the other side of the support with a magnetic recording layer, such as a balance display that changes each time a customer uses the card, or the card's validity period, date of issue, etc. . As a means for performing such recording, thermal recording, which can obtain clear images simply by heating, has attracted much attention as a recording layer constituting the back surface of a magnetic card.

With the expansion of the use of thermosensitive magnetic recording media, it has become possible to easily read and rewrite signals recorded on magnetic media using commercially available playback devices, making it possible for conventional magnetic recording media to It is not possible to effectively prevent counterfeiting.

-As is clear from its use, the heat-sensitive recording layer applied to force-sensitive thermomagnetic recording media is required to have extremely harsh practical characteristics in terms of ease of handling and frequency of use for customers' cards, compared to those for ordinary facsimile machines. There is. Therefore, if the leuco dye-based heat-sensitive material in the prior art is applied as it is to the recording layer of a magnetic recording medium that is exposed to harsh usage conditions as in the present invention, there will be serious problems in terms of storage stability, water resistance, chemical resistance, etc. This caused problems and caused major practical problems.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and is effective in preventing forgery of magnetic signals, and has the severe storage stability and water resistance required of a strong heat-sensitive recording layer. , provides a thermosensitive magnetic recording medium having chemical resistance.

Means for Solving the Problems> The present invention provides a high coercive force magnetic layer, a high permeability magnetic layer and a low coercive force magnetic layer on one side of a support made of a non-magnetic sheet such as a polyester film. The purpose of preventing counterfeiting can be achieved by recording regular data on the high coercive force layer and recording dummy signals on the resistive magnetic layer of the magnetic recording medium, which are sequentially laminated as shown in FIG. In this case, the high coercive force magnetic layer is made of barium ferrite or strontium ferrite with a coercive force of 1500 to 5000 oersted, and the high permeability magnetic layer is made of materials such as sendust or permalloy, and the resistive magnetic layer is made of materials such as sendust or permalloy. is like iron oxide magnetic powder 200~10
00 millstones are preferably used in the present invention, and these are coated on a support together with a binder such as polyester resin or vinyl chloride resin, and dried to form three magnetic layers.

Further, a white protective layer may be formed on the three-layer magnetic layer, if necessary.

Next, the present invention will be explained in detail based on the accompanying drawings. 1st
The figure is a sectional view showing an embodiment of the thermosensitive magnetic recording medium according to the present invention. A support 11, a high coercive force layer 12, a high permeability layer 13, a low coercive force layer 14, a protective printing layer 15, and a protective layer 18 is formed on a leuco dye-based thermosensitive coloring layer 16 via a barrier layer 17. It is provided.

Regular data is recorded on the high coercive force layer 12 of this thermosensitive magnetic recording medium by a magnetic head, and dummy signals are first recorded on the resistive magnetic layer 14. At this time, if an appropriate recording current is applied to the magnetic head, the normal data on the high coercive force layer 12 will not be affected. When the magnetic card recorded in this way is reproduced, the high magnetic permeability layer 13 The normal data of the high coercive force layer 12 is magnetically shielded and is hardly sensed as an output. What is sensed is only the dummy signal of the low coercive force layer, which is observed as if it were regular data.

Suppose that an attempt is made to copy this thermosensitive magnetic recording medium by the contact transfer method. When a copying card is brought into close contact with a magnetic surface and a transfer magnetic field is applied, the high magnetic permeability layer 3 is magnetically saturated by the transfer magnetic field, the permeability decreases, and the magnetic shielding effect disappears. Therefore, the normal data recorded on the high coercive force layer 12 and the dummy signal recorded on the low coercive force layer 14 are mixed and duplicated on the copy card.

Furthermore, if this magnetism is attempted to be copied by a thermal transfer method, only the dummy signal of the low coercive force layer 14 will be copied, making it possible to prevent easy counterfeiting.

Actually, there are 4 reading methods when using this magnetic card.
This is done using a reading device with a magnetic head. As shown in FIG. 2, the first magnetic head 21 reads the dummy signal recorded on the low coercive force layer 14, confirms that the card is a legitimate card, and then sends this signal to the second magnetic head 22. Demagnetize.

Next, the third magnetic head 23 reads the regular data, and the fourth magnetic head 24 records new data and demagnetizes the previous data. Next, move on to the return process, check the new data as it passes through the third magnetic head again, record a dummy signal in the low coercive force layer with the second magnetic head, and record the dummy signal with the first magnetic head. The feature is that the card is checked, taken out of the device, and returned to a magnetic card that can be prevented from being duplicated in the same way as before it was inserted into the device.

On the other hand, the heat-sensitive recording layer formed on the other side of the support is
This is a leuco dye-based heat-sensitive coloring layer using a sulfonic acid group-containing polyester resin as a binder, and the sulfonic acid group-containing polyester resin is synthesized, for example, as follows.

That is, the synthesis of the sulfonic acid group-containing polyester resin involves the synthesis of a dicarboxylic acid such as oxalic acid, malonic acid, or succinic acid, an alkylene glycol such as ethylene glycol or propylene glycol, and a sulfonic acid group-containing dicarboxylic acid group such as sulfonadium phthalate or sulfokalium phthalate. acid and
After an esterification reaction at a temperature of 170 to 280°C in the presence of an esterification catalyst such as dibutyltin oxide or antimony trioxide, 0.5 to 1.0+ in the presence of a polycondensation catalyst.
It can be obtained by polycondensation reaction at a temperature of 240 to 280'C under a vacuum of imHg.

Leuco dyes dispersed in such binders are usually colorless or light-colored triphenylmethane-based, fluoran-based,
Leuco bodies such as phenothiozine type, auramine type, spiropyran type, etc. are applied, and α-naphthol, which causes a thermochromic reaction with the leuco body and causes the leuco body to develop color;
Acidic substances such as β-naphthol, bisphenol A1 benzoic acid, and salicylic acid are blended into the leuco dye-based heat-sensitive coloring layer in the present invention. A heat-sensitive coloring coating liquid consisting of a binder resin, a leuco dye, and an acidic substance as described above is applied to the other side of the support having a magnetic recording layer on one side, and dried to form a leuco dye-based heat-sensitive coloring layer. .

A protective layer containing a polyurethane resin as a main component is further provided on the leuco dye-based heat-sensitive coloring layer with a barrier layer interposed therebetween.

In this case, the barrier layer is for separating the protective layer made of a solvent-based paint from the heat-sensitive coloring layer, and its material is generally known water-soluble resin. In view of solvent resistance and compatibility with the leuco dye-based heat-sensitive coloring layer, it is preferable to use the above-mentioned sulfonic acid group-containing polyester resin as the main component. In addition, additives such as a resin curing agent and a coating property modifier may be added to the barrier layer in the present invention, if necessary.

Further, the polyurethane resin which forms the main component of the protective layer can be obtained, for example, by the following synthesis method. That is, add 128 parts by weight of toluene, 85 parts by weight of methyl isobutyl ketone, 100 parts by weight of polyester polyol, 15 parts by weight of diphenylmethane diisocyanate, and 0.1 parts by weight of dibutyltin silaurylate into a reaction vessel, and react at 70 to 90°C for 4 hours. In this manner, a polyurethane resin that can be applied to the protective layer of the present invention having an isocyanate group at the terminal can be obtained.

The protective layer in the present invention may contain various additives such as acrylic resin and lubricant in order to control physical properties such as hardness of the coating film.

<Example> Next, specific examples according to the present invention will be described.

Magnetic paints 1, II, and (2) having the composition shown below were coated with a roll coater in order to a coating thickness of 5μ, 10μ, and 10μ on a 250μ titanium oxide-mixed polyester film as a support and laminated to prepare a magnetic card.

Coating Formulation Example (2) On the other hand, a leuco dye-based coloring layer, a barrier layer, and a protective layer were sequentially coated and laminated on the other side of the support according to the following formulation to prepare a thermosensitive magnetic recording medium of the present invention.

[Leuco dye-based thermosensitive coloring layer]

First, a sulfonic acid group-containing polyester resin to be used as a binder was synthesized as follows.

Terephthalic acid 116.3g, adipic acid 21.9g in a 500Ω flask equipped with a stirrer, thermometer, nitrogen blowing device, and packed tower.
g, 5-sodium sulfoisophthalic acid dimethyl ester 44.4 g, ethylene glycol 55.5 g % Neopentyl glycol 75.0 g, triethylene glycol 27,0 g N Zinc acetate 0.2 g 1 antimony trioxide 0.4 g 190 After carrying out an esterification reaction at ~220°C for 4 hours, a condensation reaction was carried out at 230 - 250°C under LaaHg, resulting in a melt viscosity of 2000 voids (190°C).
A sulfonic acid group-containing polyester resin was obtained. This resin was prepared into a 20% sulfonic acid group-containing polyester aqueous solution using hot water at 90°C.

Next, in order to obtain a heat-sensitive paint, each mixture consisting of the following formulations was ground and dispersed in a ball mill for one day to prepare solutions A to C.

Solution A Solution B Solution C 10 parts of Solution A, 33.3 parts of Solution B, 49 parts of Solution C, 15 parts of an aqueous sulfonic acid group-containing polyester solution, and 46 parts of water were mixed to obtain a heat-sensitive recording paint.

The coating material was coated on the other side of the support having the magnetic recording layer so that the coated amount after drying was 6 g/nf, and dried to provide a leuco dye-based thermosensitive coloring layer.

[Barrier layer]

A barrier layer coating solution having the following formulation was prepared using the polyester resin used in the heat-sensitive color forming layer, and was applied onto the heat-sensitive color forming layer and dried to form a barrier layer.

[Protective layer]

A protective layer coating solution having the following formulation was prepared, coated on the barrier layer, and dried to form a protective layer to produce a heat-sensitive magnetic card of the present invention.

The resulting magnetic card has a gap of 30μ and a track width of 4m.
A normal signal is recorded using a magnetic head of 700 mA at a recording current of FM system at a recording density of 2108 PI. Furthermore, a dummy signal is recorded using the above head at a recording current of 70 mA and at the same <FM recording density of 210 BPI.

As a result of reproducing this recorded magnetic card using the above-mentioned reading device, only the data of the 2108P■ dummy signal could be read by the first magnetic head.

This is because the signal recorded in the high coercive force magnetic layer is magnetically shielded by the high permeability magnetic layer, and its output is below the slice level of the reader. When this signal was demagnetized by the second magnetic head and read by the third magnetic head,
I was able to read the data of the 2108PI regular signal.

This requires a special DC auxiliary magnetic field.

Next, in order to duplicate this recorded magnetic card, a coercive force of 3000e and a residual magnetic flux of 1.4 M are used as a duplicate card.
Using the contact method using a stickerless commuter pass from x/are,
The magnetic surfaces of both cards were brought into close contact with each other, and a 50 Hz alternating current attenuation magnetic field of 1000 e was applied. As a result of reproducing the duplicated magnetic card with the above-mentioned reader, the first magnetic head reads 2108 pages.
The output waveform of the I dummy signal was modulated by the 210 BPI regular signal and could not be read.

When this signal was demagnetized by the second magnetic head and read by the third magnetic head, all the signals were erased and duplication was prevented.

On the other hand, a line-tod type thin film thermal head was used for the thermosensitive recording layer of the thermosensitive magnetic recording medium of the present invention, and a 0.45W (
1mJ/dat) was recorded, and the solid black part was measured with a Macbeth densitometer, and it was found to be 1.1
8 clear colored images were obtained. Next, as a water resistance test, the sample immediately after color development was immersed in water at 20° C. for 3 days, and the decrease in density was measured using a Maches densitometer, and the result was 1.14, confirming sufficient water resistance. In addition, in order to check the storage stability of temperature and humidity, 1.
When the color development characteristics were examined after being left for a week, a value of 1.16 was obtained using a Macbeth densitometer, confirming poor storage stability. Furthermore, the colored recording surface was overlapped with a plasticizer-containing plastic eraser and pressed at a pressure of 2 kg/cnt.
After standing for a period of time, the eraser was removed and the recording surface was examined, and no change was observed, confirming excellent plasticizer resistance.

Furthermore, when this heat-sensitive magnetic card was applied to a ticket vending machine with a heat-sensitive recording mechanism, and predetermined magnetic information was written and read, and the remaining amount was displayed on the heat-sensitive recording surface, it was confirmed that there were no problems with implementation. Ta.

<Effects of the Invention> Since the present invention has the above-described configuration, it becomes impossible to easily detect a regular magnetic signal recorded on a thermosensitive magnetic recording medium, and counterfeiting by thermal transfer or contact transfer methods can be prevented.

In addition, even when the heat-sensitive recording layer is used under severe customer conditions, it has been confirmed that it has excellent durability in terms of practical properties such as water resistance, temperature/humidity dependence, and plasticizer resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged cross-sectional view in the width direction of a thermosensitive magnetic recording medium of the present invention, and FIG. 2 is a schematic diagram of a recording layer reading mechanism of the present invention.

Claims (1)

[Claims] 1. A high coercive force magnetic layer is provided on one side of a support, a high permeability magnetic layer and a low coercive force magnetic layer are sequentially laminated thereon, and a high coercive force magnetic layer is provided on the other side of the support. A heat-sensitive magnet, comprising: a leuco dye-based heat-sensitive coloring layer using a sulfonic acid group-containing polyester resin as a binder; and a protective layer containing a polyurethane resin as a main component on top of the layer through a barrier layer. recoding media. 2. The thermosensitive magnetic recording medium according to claim 1, wherein the barrier layer contains a sulfonic acid group-containing polyester resin as a main component.