JPS6218625A - Thermosensitive magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent resistance even when the titled medium is used under customers' severe use conditions by providing a leuco dye thermosensitive color forming layer contg. a sulfonate-contg. polyester resin as a binder on one surface of a substrate and providing a protective layer essentially consisting of a polyurethane resin via a barrier layer thereon. CONSTITUTION:A magnetic recording layer is formed by uniformly dispersing a ferromagnetic material such as gamma-Fe2O3, barium ferrite or strontium ferrite and the binder such as polyester resin, vinyl chloride resin or polyurethane resin in a solvent such as toluene or methyl ethyl ketone, coating such soln. on the substrate consisting of a plastic film or paper, etc. and drying the coating. On the other hand, the thermosensitive recording layer to be formed on another surface of the substrate is the leuco dye thermosensitive color forming layer contg. the sulfonate-contg. polyurethane resin as the binder and the protective layer essentially consisting of the polyurethane resin is further provided via the barrier layer on such leuco dye thermosensitive color forming layer.

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, and the like.

<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. . Possible means for performing such recording include leuco dye-based thermal recording, electrophotographic recording, electrostatic recording, chelate color recording, and diazo copying that utilizes a chemical reaction between two components. Among these methods, the thermal recording method is attracting a lot of attention as a recording layer that forms the back side of a magnetic card because a clear recorded image can be obtained simply by heating.

However, as is clear from its use, the heat-sensitive recording layer applied to a magnetic card is required to have extremely harsh practical characteristics in terms of ease of handling, frequency of use, etc. of the card, compared to that for ordinary facsimile. 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 card that is exposed to harsh usage conditions as in the present invention, there will be serious problems in storage stability, water resistance, chemical resistance, etc. , which poses a major problem in practice.

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

Means for Solving the Problems〉 The magnetic recording M constituting the thermosensitive magnetic recording medium of the present invention has γ
- A ferromagnetic material such as F e 203, barium ferrite, strontium ferrite, etc. and a binder such as polyester resin, vinyl chloride resin, polyurethane resin, etc. are uniformly dispersed in a solvent such as toluene or methyl ethyl ketone, and this is applied to a plastic film, paper, etc. It is formed by coating on a support consisting of and drying it.

In this case, in order to prevent the information recorded on the magnetic recording medium from being erased or attenuated by coming into contact with products using permanent magnets such as handbag clasps, toys, and magnetic necklaces, the present invention is used. As the ferromagnetic material, it is preferable to use a material having a high coercive force, such as barium ferrite or strontium ferrite, which has a coercive force of 1,500 to 5,000 oersteds.

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 carrying out 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 m 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. under a vacuum of mHg.

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;
In the present invention, acidic substances such as β-naphthol, bisphenol A1 benzoic acid, and salicylic acid are incorporated into the leuco dye-based heat-sensitive coloring layer. 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.

<Examples> The present invention will be explained in detail below using examples. Note that all parts in each recipe table are expressed in parts by weight.

Example 1 A high coercive force magnetic coating composition having the following composition was coated on a support made of a milky white polyester film having a thickness of 188 μm to a coating thickness of 13 μm and dried to provide a magnetic recording layer.

"Barium ferrite 100 parts 1 (
coercive force 30,000 e1 average particle size 0.6 μm) On the other hand, a leuco dye-based coloring layer, a barrier layer,
A thermosensitive magnetic recording medium of the present invention was prepared by sequentially coating and laminating protective layers according to the following formulation.

[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 116.3 g, adipic acid 21.9 g in a 500-inch flask equipped with a stirrer, thermometer, nitrogen blowing device, and packed tower.
g, 44.4 g of 5-sodium sulfoisophthalic acid dimethyl ester, 55.5 g of ethylene glycol, 75.0 g of neopentyl glycol, 27.0 g of 11'lyethylene glycol, 0.4 g of zinc acetate 0.2 g% Antimony trioxide 190 ~ After carrying out the esterification reaction at 220°C for 4 hours, the condensation reaction was carried out at 230-250°C under 1+nmHg. Melt viscosity 2000 boise (190
℃, measured with a Koka type flow tester), a sulfonic acid group-containing polyester resin was obtained. A 20% sulfonic acid group-containing polyester aqueous solution was prepared from this resin with 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: 25 parts of water, Solution B: 15 parts of bis(4-hydroxyphenyl), methyl acetate. A heat-sensitive recording paint was obtained by mixing 46 parts of water.

The paint was applied to the other side of the support having the magnetic recording layer in an amount of 6 g/n after drying. It was coated and dried to form a leuco dye-based heat-sensitive 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 a barrier layer, and dried to form a protective layer to produce a thermosensitive magnetic recording medium of the present invention.

Images were recorded on the thermosensitive magnetic recording medium obtained above using a line-tod type thin film thermal head at an energy of 0.45 W (1 mJ/dat), and the solid black portion was measured with a Macbeth densitometer. Eighteen 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 Macbeth densitometer, and the result was 1.14, confirming sufficient water resistance. In addition, in order to check the temperature and humidity storage stability, the temperature was 40℃.
When the color development properties were observed after being left in a constant temperature bath at 90% relative humidity for one week, a Macbeth densitometer reading of 1.16 was obtained, confirming excellent storage stability. Furthermore, by overlapping the color recording surface with a plasticizer-containing plastic eraser,
After crimping with a pressure of g/c+J and leaving for 24 hours, 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 recording medium 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 was no problem with implementation. It was done.

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

<Effects of the Invention> Since the present invention has the above-mentioned configuration, even when used under severe usage conditions by customers in applications such as cash coupons and commuter passes, it has excellent water resistance, temperature/humidity dependence, plasticizer resistance, etc. Extremely excellent durability was confirmed in terms of practical properties. In addition, since a magnetic material with high coercive force is used for the magnetic recording layer, the written magnetic information is not easily demagnetized by contact with daily necessities using permanent magnets, making it possible to obtain a highly practical thermosensitive magnetic recording medium. was completed.

Claims (1)

[Claims] 1. A magnetic recording layer mainly composed of a ferromagnetic material and a binder is provided on one side of a support, and a sulfonic acid group-containing polyester resin is provided on the other side of the support. 1. A thermosensitive magnetic recording medium comprising a thermosensitive coloring layer based on a leuco dye as a binder, 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 1,500 to 5,000 oersteds. 3. The thermosensitive magnetic recording medium according to claim 1, wherein the barrier layer has a sulfonic acid group-containing polyester resin as a main component.