JP2616195B2 - Thermal magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] In recent years, magnetic recording media such as so-called prepaid cards, such as telephone cards, orange cards, and other private railway cards, which are prepaid, have become widespread. The present invention relates to a thermosensitive magnetic recording medium capable of recording visible information by a heating recording method using a thermal head, a thermal printing plate, a laser beam or the like among these magnetic recording media.

[Prior Art] Printing on a thermosensitive magnetic recording medium having a thermosensitive recording layer made of a low-melting metal utilizes the fact that the metal is melted by heating and becomes spherical by surface tension.

However, simply providing the low-melting-point metal thin-film layer has a glossy surface and poor print visibility, so that the particle size of a few μm below the low-melting-point metal thin-film layer (hereinafter referred to as an anchor layer). A method has been proposed in which fine particles are mixed and the surface of the low melting point metal thin film layer is roughened to reduce gloss and improve visibility.

In order to further improve the visibility, a method of adding a black pigment such as carbon black to the anchor layer has been proposed.

[Problems to be Solved by the Invention] However, if fine particles are mixed in the anchor layer,
Obviously, the print density decreases. That is, since the transparency of the anchor layer is reduced by the incorporation of the fine particles, the blackness inherent in the magnetic recording layer is reduced and the print density is reduced.

Similarly, when a resin having poor transparency is used for the anchor layer, the blackness decreases and the print density decreases.

As a measure to solve this problem, a method of adding a black pigment such as carbon black to the anchor layer as described above has been proposed. However, when these black pigments are added to the anchor layer, a low melting point metal thin film is used. Since the lower layer of the layer becomes unnecessarily black due to the synergistic effect of the magnetic recording layer and the anchor layer, it is necessary to increase the thickness of the low-melting-point metal deposition layer by a considerable amount in order to hide this hue. As a result, the print recording sensitivity is reduced and the load on the print head is increased, and a solution has been desired.

In view of such circumstances, an object of the present invention is to improve the visibility of visible information by increasing the print density without increasing the thickness of the low-melting-point metal deposition layer.

[Means for Solving the Problems] In order to achieve the above object, the thermosensitive magnetic recording medium of the present invention comprises at least a magnetic recording layer, an anchor layer, a metal thin film layer, and a protective layer provided in this order on a support. The recording medium is characterized by using a hot-melt transferable dye dissolved or dispersed in the anchor layer to increase the black print density without lowering the sensitivity.

That is, as a result of melting the low-melting metal vapor-deposited layer by instantaneous heating printing of the thermal head, the magnetic recording layer via the anchor layer is conventionally recognized as character information.
That is, the user does not directly see the black color of the magnetic recording layer, but sees the magnetic recording layer whose concentration has been reduced by the anchor layer.

This problem is certainly solved by blackening the anchor layer itself. However, as described above, when the anchor layer is blackened with a black pigment such as carbon black, the thickness of the low-melting-point metal deposition layer must be increased more than necessary to cover the black.

On the other hand, in the present invention, by using a hot-melt transferable dye of a dark color such as black as a colorant for concealment, high contrast without increasing the thickness of the low-melting metal layer,
A thermosensitive magnetic recording medium with good visibility can be obtained.

The hot-melt transferable dye described in the present invention is generally referred to as a sublimable dye or a dye for sublimation-type thermal transfer recording, and is mainly a disperse dye, an oil-soluble dye, or a part of a basic dye. More specifically, JP-B-39-18739 and "Dyeing Industry" (Vol. 19, p. 127, issued by Shisensha Co., Ltd., 1971) and "Color Material Association" (Vol. 61, p. 234, It is described in detail in the Japan Color Material Association (1988).

A common feature of these dyes is that when they are used alone or simply dispersed or dissolved in a binder resin and dried, the color density is extremely low and the hue lacks sharpness. Heating under the above temperature conditions improves the color density and the sharpness. That is, the dye adsorbs or chemically bonds to the binder resin by heating, and the color density and the sharpness are improved.

This phenomenon is that the dye does not develop in the state where the dye is simply printed on the polyester fiber, and the hue and concentration are unclear and low density, but when the heating process is applied by the thermosol method, the color becomes high and clear. Can be easily explained.

In other words, in a state where the hot-melt transfer dye is simply mixed with the anchor layer, such an anchor layer does not bring about the effect of improving the blackness of the magnetic recording layer, and thus the low melting point metal thin film layer for hiding the magnetic recording layer. Can be kept to the minimum necessary. That is, the printing sensitivity can be kept extremely high.

On the other hand, considering the state after printing, the heat-melt transfer dye mixed in the anchor layer is chemically bonded to the binder resin by the principle of thermosol dyeing due to the heat from the thermal head during printing, resulting in high concentration. , Giving a vivid color. Therefore, if the hue is black, the printed portion functions to promote the black color of the magnetic recording layer, and the density is not reduced by the anchor layer as in the conventional case, and the high contrast of the printed portion can be maintained. it can.

[Operation] Therefore, according to the present invention, it is possible to provide a thermosensitive recording medium having excellent visibility that exceeds conventional ones without lowering the printing sensitivity.

Examples Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a prepaid card which is an example of the thermosensitive magnetic recording medium of the present invention. Reference numeral 1 denotes a prepaid card, which is composed of a base material 2, a magnetic recording layer 3, an anchor layer 4, a low melting point metal thin film layer 5, and a protective layer 6 in this order.

As the substrate 2, a non-magnetic material such as plastic, paper, or glass which has been conventionally used can be applied. The above magnetic recording layer is obtained by applying, drying and curing a magnetic coating material in which a conventionally known ferromagnetic powder such as Ba-ferrite, γ-iron oxide or magnetite is dispersed in a resin. . In the present invention, an anchor layer 4 is provided on the magnetic recording layer 3.

The anchor layer 4 is obtained by applying a varnish obtained by mixing a hot-melt transferable dye in a resin.

As the hot-melt transferable dye, those described in the above-mentioned patent publications and literatures can also be used. Specifically, for a yellow dye, a color index number (hereinafter abbreviated as CI), Disperse Yellow 54, Disperse Yellow 8, Disperse Yellow 3, Disperse Yellow 7, Disperse Yellow 16, Solvent Yellow 77, Solvent Yellow 16, Red dye CI. Disperse Red 4, Disperse Red 11, Disperse・ Red 60, Disperse Violet 26, Solvent Violet 26, Solvent Red 19, and blue dyes such as CI Solvent Blue 36 and Solvent Blue 63 can be used. , Hindrin azo, styryl, 5-
Nitrothiazole azo, 3-alkylthio 1,2,4-
It can be classified into thiazole / azo type, naphthoquinone type, heterocyclic / azo type and indoaniline type dyes,
It is most effective to use a black color by blending these dyes.

As the resin, for example, a resin such as a polyester resin, a urethane resin, an acrylic resin, an acrylic polyol resin, a polyolefin resin, and a vinyl chloride-vinyl acetate copolymer resin can be used alone or as a mixture.

The dye is well dyed on these resins by heating under a certain condition, and exhibits a sharp high density hue from a dull low density hue after dyeing.

As the low melting point metal thin film layer 5, it is appropriate to use metals such as Sn, Bi, In, Cd and Pb or alloys thereof in consideration of toxicity and the like.

The protective layer 6 may be selected from resins having excellent heat resistance and friction resistance of the coating film.

 Hereinafter, examples will be described.

Example: Using a 188 μm-thick polyester film as the base material 2, a magnetic paint MGP-2751 (Toyo Ink Mfg. Co., Ltd.) was applied on the base material 2 by a gravure coating method to a thickness of 15 μm to form a magnetic recording layer. 3 was obtained.

Next, the raw materials of CI. Disperse Yellow 8, Disperse Red 60 and Solvent Blue 36 were mixed in a one-to-one equivalent amount with a polyester resin chemit K-588 (Toray Industries, Inc.). The material was added to the magnetic recording layer 3 by a gravure coating method at a thickness of 2 μm by using a material dispersed in a sand mill and added as a material for forming an anchor layer, thereby obtaining an anchor layer 4.

The low melting point metal thin film layer 5 on the anchor layer is made of Sn (purity 99.9%).
9%) by vapor deposition to a thickness of 40 nm, and a protective layer 6 thereon is coated with an acrylic resin TR-15 (Dainippon Ink Chemical Co., Ltd.) to a thickness of 1.5 μm by a gravure method. As a result, the thermosensitive magnetic recording medium 1 of the present invention was completed.

Next, for comparison, carbon black R was added to the anchor layer 4 and Chemit K-588 (described above) of the thermosensitive magnetic recording medium 1.
AVEN1250 (Columbia Carbon Co., Ltd.) was added at 10% by weight solids ratio, dispersed in a sand mill in the same manner, and replaced with an anchor layer obtained by coating to a thickness of 2 μm by a gravure coating method. A thermosensitive magnetic recording medium having the same configuration for the magnetic recording layer 3, the low melting point metal thin film layer 5, and the protective layer 6 was prepared.

The above items were punched out in a card shape, printing was performed under the same conditions, and the reflection density on the surface of the protective layer 6 in the printed portion and the non-printed portion was measured.

Table 1 shows the results. As can be seen from the results, the reflection density of the printed portion is almost the same, while the reflection density of the non-printed portion is lower when the heat-melt transferable dye is mixed as the anchor layer 4. That is, the concentration of the black layer below the low melting point metal thin film layer 5 before printing was lower in the anchor layer to which the hot-melt transferable dye of the present invention was added as a black auxiliary than in the carbon layer using carbon black. Therefore, considering that the black layer is concealed by the low-melting metal vapor-deposited film layer having the same thickness, the reflection density of the non-printed portion is low.

That is, according to the present invention, since the density of the printing portion is high and the density of the non-printing portion is low, it is possible to obtain a printing quality with extremely good contrast.

Further, Table 2 also shows the results when the thickness of the low melting point metal layer was increased in order to make the contrast when using carbon black the same as when using the hot melt transferable dye. In this case, as much as the thickness of the low melting point metal layer was increased, higher energy was required for printing, resulting in a decrease in sensitivity.

[Effects of the Invention] As described above in detail, according to the present invention, it is possible to provide a thermosensitive magnetic recording medium having good visibility without lowering sensitivity in printing as compared with the related art.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view showing the structure of the present invention. DESCRIPTION OF SYMBOLS 1 ... Prepaid card 2 ... Base material 3 ... Magnetic recording layer 4 ... Anchor layer 5 ... Low melting point metal thin film layer 6 ... Protective layer 7 ... Heat melting transfer dye in anchor layer

Claims (2)

(57) [Claims] 1. A thermosensitive magnetic recording medium comprising at least a magnetic recording layer, an anchor layer, a metal thin film layer, and a protective layer provided in this order on a support, wherein a thermofusible dye is mixed in the anchor layer. A thermosensitive magnetic recording medium characterized by the following. 2. The thermosensitive magnetic recording medium according to claim 1, wherein the color of the heat-melt transferable dye is black.