JPH0664729B2 - Thermal magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a thermosensitive magnetic recording medium used for cashless coupons, commuter passes, etc. for ticket purchase or telephone use.

<Prior Art> In recent years, magnetic cards have been remarkably popularized in cashless coupons, magnetic coupons, road tickets, commuter passes, and the like. In this case, it is necessary to record visible information such as the balance display that changes every time the customer uses the card, or the validity period and the issue date of the card on the other surface of the support provided with the magnetic recording layer. . As means for performing such recording, there are considered a leuco dye-based thermosensitive recording, other electrophotographic method, electrostatic recording, chelate color recording, diazo copying method utilizing a chemical reaction by two components, and the like. Among them, the heat-sensitive recording method is particularly attracting much attention as a recording layer constituting the back surface of a magnetic card because a clear recording image can be obtained by simply heating it.

However, the heat-sensitive recording layer applied to a magnetic card is required to have extremely harsh practical characteristics in handling, usage frequency, etc. for a customer's card, as is clear from its application, as compared with that for an ordinary facsimile. Therefore,
If the conventional leuco dye-based heat-sensitive material is directly applied to the recording layer of the magnetic card exposed to the severe operating conditions as in the present invention, serious problems will occur in storage stability, water resistance, chemical resistance, etc. , Was a big problem in practice.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and has severe storage stability and water resistance and chemical resistance required for a recording layer on a magnetic card such as a cashless card. Provided is a thermosensitive magnetic recording medium having properties.

<Means for Solving Problems> The magnetic recording layer constituting the thermosensitive magnetic recording medium of the present invention has a γ
-Fe _{2 O 3,} barium ferrite, ferromagnetic and polyester resins such as strontium ferrite, vinyl chloride resin, and a binder such as a polyurethane resin, homogeneously dispersed plastic film or paper to which a solvent of toluene or methyl ethyl ketone It is formed by coating and drying on a support composed of the like.

In this case, the information recorded on the magnetic recording medium is used in the present invention in order to prevent troubles such that information recorded on the magnetic recording medium is erased or attenuated by contact with a product using a permanent magnet such as a handbag clasp, a toy, and a magnetic necklace. As the ferromagnetic material, it is preferable to apply a material having a high coercive force of 1500 to 5000 Oersted such as barium ferrite or strontium ferrite.

On the other hand, the magnetic recording layer formed on the other surface of the support is
A leuco dye-based thermosensitive coloring layer using a sulfonate group-containing polyester resin as a binder, and the sulfonate group-containing polyester resin is synthesized, for example, as follows.

That is, the synthesis of the sulfonate group-containing polyester resin is carried out by dicarboxylic acid such as acid, malonic acid, succinic acid and alkylene glycol such as ethylene glycol and propylene glycol and sulfosodium phthalic acid such as sulfosodium phthalic acid and sulfopotassium phthalic acid. Acid and
After an esterification reaction at a temperature of 170 to 280 ℃ in the presence of an esterification catalyst such as dibutyltin oxide, antimony trioxide, etc., in a vacuum of 0.5 to 1.0 mmHg in the presence of a polycondensation catalyst.
It can be obtained by carrying out a polycondensation reaction at a temperature of 240 to 280 ° C.

The leuco dye dispersed in such a binder is usually colorless or light-colored triphenylmethane type, fluorane type,
Phenothiazine-based, auramine-based, and spiropyran-based leuco bodies are applied, and α-naphthol that causes a color reaction with the leuco body at the time of heat generation to cause the leuco body to develop color,
An acidic substance such as β-naphthol, bisphenol A, benzoic acid and salicylic acid is blended in the leuco dye-based thermosensitive coloring layer in the present invention. A heat-sensitive color-forming coating liquid comprising a binder resin, a leuco dye and an acidic substance as described above is applied to the other surface of a support having a magnetic recording layer on one surface and dried to form a leuco dye-based heat-sensitive color developing layer. .

On the above leuco dye-based thermosensitive coloring layer, a protective layer containing a polyurethane resin as a main component is further provided via a barrier layer.
In this case, the barrier layer is for separating the protective layer made of a solvent-based paint from the thermosensitive coloring layer, and a generally known water-soluble resin is used as the material thereof, but in the present invention, water resistance, From the viewpoint of solvent resistance and compatibility with the leuco dye-based thermosensitive coloring layer, it is preferable to use the above-mentioned sulfonate group-containing polyester resin as a main component. Incidentally, the barrier layer in the present invention is used by adding additives such as a resin curing agent and a coatability adjusting agent, if necessary.
The polyurethane resin which is the main component of the protective layer can be obtained, for example, by the following synthetic method. That is, toluene 128 parts by weight in the reaction vessel, methyl isobutyl ketone 85 parts by weight, polyester polyol 100 parts by weight, diphenylmethane diisocyanate 15 parts by weight, dibutyltin dilaurylate 0.
By adding 1 part by weight and reacting at 70 to 90 ° C. for 4 hours, a polyurethane resin applicable to the protective layer of the present invention having an isocyanate group at its end can be obtained.

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

<Examples> The present invention will be described in detail below with reference to Examples. In addition, all the parts in each recipe are parts by weight.

Example 1 A magnetic coating material having a high coercive force having the following composition was applied onto a support made of a milky white polyester film having a thickness of 188 μm.
A magnetic recording layer was provided by coating and drying so as to have a thickness of μm.

On the other hand, a leuco dye color-developing layer, a barrier layer and a protective layer were sequentially coated and laminated on the other surface 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 sulfonate group-containing polyester resin as a binder was synthesized as follows.

Stirrer, thermometer, nitrogen blowing device, terephthalic acid 116.3 g, adipic acid 21.9 g, 5-sodium sulfoisophthalic acid dimethyl ester 44.4 g, ethylene glycol 55.5 g, neopentyl glycol 75.0 in a 500 cc flask with a packed tower
g, triethylene glycol 27.0 g, zinc acetate 0.2 g, and antimony trioxide 0.4 g were charged to carry out an esterification reaction at 190 to 220 ° C. for 4 hours and then a condensation reaction at 230 to 250 ° C. under mmHg. A sulfonate group-containing polyester resin having a melt viscosity of 2000 boys (190 ° C., measured by a Koka type flow tester) was obtained. A 20% aqueous solution of a sulfonate group-containing polyester resin was prepared from this resin by hot water at 90 ° C.

Next, in order to obtain a heat-sensitive paint, a mixture having the following formulation was pulverized and dispersed by a ball mill for 1 day to prepare liquids A to C.

A heat-sensitive recording coating material was obtained by mixing 10 parts of solution A, 33.3 parts of solution B, 49 parts of solution C, 15 parts of an aqueous polyester solution containing a sulfonate group, and 46 parts of water. The coating material was applied to the other surface of the support having the magnetic recording layer so that the coating amount after drying was 6 g / m ² , and dried to form a leuco dye-based thermosensitive coloring layer.

[Barrier layer]

A barrier layer coating solution having the following composition was prepared by using the polyester resin used for the thermosensitive color forming layer, and applied on the thermosensitive color developing layer and dried to form a barrier layer.

[Protective Layer] A protective layer coating solution having the following composition was prepared, coated on the barrier layer and dried to form a protective layer, to prepare a thermosensitive magnetic recording medium of the present invention.

The thermosensitive magnetic recording medium obtained above was recorded with an image of 0.45 W (1 mJ / dot) using a line dot type thin film thermal head, and the solid black portion was measured with a Macbeth densitometer, and a clear image of 1.18 was obtained. An excellent color image was obtained. Next, as a water resistance test, when the sample immediately after color development was immersed in water at 20 ° C. for 3 days and the decrease in density was observed by a Macbeth densitometer, it was 1.14, and sufficient water resistance was confirmed. In addition, in order to check the storage stability of temperature and humidity, the color development characteristics after being left for 1 week in a thermostatic chamber at a temperature of 40 ° C and a relative humidity of 90% were confirmed to be 1.16 with a Macbeth densitometer, confirming excellent storage stability. Was done.
Furthermore, the color-recorded recording surface was overlaid with a plasticizer-containing plastic eraser, pressure-bonded at a pressure of ² kg / cm ² and left for 24 hours, then the eraser was peeled off and the recording surface was examined and no change was observed. Excellent plastic resistance. The drug substance was confirmed.

Furthermore, when this heat-sensitive magnetic recording medium was applied to a vending machine for cash vouchers having a heat-sensitive recording mechanism, and the specified magnetic information was written, read, and the balance display amount was applied to the heat-sensitive recording surface, it was confirmed that there was no problem in mounting. Was done.

Example 2 All the examples except that benzyl-4-hydroxybenzoate was used in place of the acidic substance in the heat-sensitive recording layer, that is, the bis (4-hydroxyphenyl) acetic acid methyl ester of the heat-sensitive coating liquid B in Example 1. The thermosensitive magnetic recording medium of the present invention was produced based on 1. As a result, the practical properties such as thermosensitive coloring property, water resistance, storage stability, and plasticizer resistance were excellent as in Example 1.

<Effects of the Invention> Since the present invention is configured as described above, even when used in the severe usage conditions of customers in applications such as cash vouchers and commuter passes, water resistance, temperature / humidity dependency, plasticizer resistance, etc. Very good durability was confirmed in practical characteristics. In addition, since a magnetic material having a high coercive force is used for the magnetic recording layer, the written magnetic information is not easily demagnetized by contact with daily commodities using permanent magnets, and a highly practical thermosensitive magnetic recording medium is obtained. I was able to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisato Hamata 3-1, Somune-cho, Shizuoka-shi, Shizuoka Pref. Hidemi Kobayashi (56) JP, A) JP 61-180927 (JP, A) Actually developed 56-170534 (JP, U)

Claims (3)

[Claims] 1. A magnetic recording layer containing a ferromagnetic material and a binder as main components is provided on one surface of a support, and a sulfonate group-containing polyester resin is bound on the other surface of the support. A heat-sensitive magnetic recording medium, comprising a leuco dye-based thermosensitive coloring layer as an agent, and a protective layer containing a polyurethane resin as a main component provided thereon via a barrier layer. 2. The thermosensitive magnetic recording medium according to claim 1, wherein the ferromagnetic material has a coercive force of 1500 to 5000 Oersted. 3. The thermosensitive magnetic recording medium according to claim 1, wherein the barrier layer is mainly composed of a sulfonate group-containing polyester resin.