JPH05270174A - Information recording medium - Google Patents

Abstract

PURPOSE:To provide an information recording medium optically stably reading a recorded image information and making the information recorded on a thermal recording layer invisible. CONSTITUTION:An information recording medium has a metal membrane layer 4 generating at least mirror surface reflection, a thermal recording layer 5 containing hollow microcapsules and low in infrared transmissivity at room temp. and increasing infrared transmissivity at predetermined temp. or higher and a visible light blocking layer pervious to infrared rays but absorbing visible light. When information recording due to magnetism is performed, a magnetic recording layer and an anchor layer 3 may be provided and a protective layer 7 may be provided in order to impart scratch resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium in which information recorded on a thermosensitive recording layer is invisible.

[0002]

2. Description of the Related Art In recent years, magnetic recording means, recording means using a semiconductor integrated circuit, optical recording means, etc. have been used as means for recording information on media such as cards, securities, gift certificates, tickets, and slips. Taking a card as an example, a magnetic recording means is a cashless card, a magnetic card such as a credit card or a prepaid card, a recording means using a semiconductor integrated circuit is an IC card, an IC memory card, an optical recording means is an optical card, a red card. Infrared reading cards and the like that utilize reflection or absorption of external light have been developed, and various types of cards have been provided.

In recent years, information is recorded (a color-developing portion is provided) by a thermal head on a thermosensitive recording layer formed by coating and curing an infrared absorption leucothermal, and the recorded information is irradiated with infrared rays. An information recording medium has been proposed in which mechanical reading is performed by reading the difference in reflectance with a detector.

However, the difference between the color-developed portion (black or dark color) and the non-color-developed portion can be visually observed as it is in the thermosensitive recording layer. Therefore, in order to make the information printed and recorded on the heat-sensitive recording layer invisible, a concealing layer that transmits infrared rays and absorbs visible light is mixed with yellow, magenta, and cyan process inks in an appropriate ratio, such as gray ink. (See, for example, JP-A-64-87395). However, these inks have a lower hiding power than ordinary black inks, and a film thickness of 3 μm or more is necessary for hiding the thermal recording information of the lower layer by the hiding layer. When the hiding layer becomes thicker, the difference in reflectance (hereinafter referred to as contrast) between the recording image formed by the printing portion and the non-printing portion of the heat-sensitive recording layer becomes smaller as the sensitivity decreases, so that the recording image cannot be read stably. Have difficulty.

Further, in the case of an information recording medium having a magnetic recording layer between the substrate and the thermosensitive recording layer, the film thickness on the magnetic recording layer (for example, the thickness of the thermosensitive recording layer and the concealing layer) depends on that of the magnetic material or the magnetic head. It is limited by the characteristics. That is, providing a thick hiding layer means that a thin thermosensitive recording layer must be provided. And as the thermal recording layer becomes thinner, the contrast tends to decrease,
It is difficult to stably read a recorded image.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and it is possible to optically and stably read a recorded image (information) recorded, and It is an object of the present invention to provide an information recording medium that makes information recorded on the thermosensitive recording layer invisible.

[0007]

Means for Solving the Problems The present invention, which has been made to achieve the above-mentioned object, includes a metal thin film layer that causes at least specular reflection and hollow microcapsules on a substrate, and has a low infrared transmittance at room temperature, It has been found to be achieved by providing an information recording medium having a thermosensitive recording layer whose infrared transmittance increases above a predetermined temperature and a visible light blocking layer which transmits infrared light but absorbs visible light. ..

The particle size of the hollow microcapsules is 0.
It also includes that the magnetic recording layer is provided between the substrate and the metal thin film layer.

The present invention will be described in detail below. The information recording medium of the present invention has a magnetic recording layer on the substrate as necessary,
A metal thin film layer that causes specular reflection is provided on the magnetic recording layer. When the surface of the magnetic recording layer is rough, an anchor layer or the like may be provided to improve smoothness and then the metal thin film layer may be provided.

In the present invention, an emulsion obtained by emulsifying hollow microcapsules having a particle size of about 0.05 to 1 μm on a metal thin film layer which causes specular reflection, and has a low infrared transmittance at room temperature. A heat-sensitive recording layer (hereinafter, referred to as a heat-sensitive recording layer of the present invention) that increases the infrared transmittance above a predetermined temperature and forms a recorded image by the difference in the infrared transmittance is provided. That is, the heat-sensitive recording layer of the present invention is composed of a hollow microcapsule emulsion having a particle size of 0.05 to 1 μm prepared by an emulsion polymerization method or the like. The heat-sensitive recording layer in which such hollow microcapsules are emulsified and dispersed has a change in the refractive index of light due to the presence of air in the hollow microcapsules with respect to the incidence of infrared light at room temperature, and as a result, light scattering occurs and infrared rays are generated. The transmittance decreases. On the other hand, by heating above a predetermined temperature, that is, above the glass transition point of the resin forming the hollow microcapsules, the microcapsules are destroyed and fused, the particle-air interface is reduced, and light scattering is suppressed. It becomes transparent and the transmittance of infrared light increases.

In the present invention, the visible light shielding layer means a layer which transmits infrared rays that can be read by an infrared sensor and blocks visible rays to the extent that a recorded image cannot be discriminated by the naked eye. Not only the infrared transmittance is higher than the visible light transmittance, but also the infrared sensor has excellent sensitivity, so even if the infrared transmittance is lower than the visible light transmittance, the recorded image will be visible to the naked eye. Cannot be identified,
Anything that can be identified by an infrared sensor may be used.

Further, in order to prevent the recorded image from being discernible with the naked eye due to the change in gloss due to the deformation of the visible light blocking layer due to the heat generation of the thermal head, on the visible light blocking layer, Furthermore, a heat-resistant protective layer which is transparent to infrared rays may be provided.

As the substrate for use in the present invention, various types can be used depending on the application, for example, paper, PET,
A plastic such as PVC is used. As described above, the information recording medium according to the present invention records information by causing the heating elements of the thermal head to selectively generate heat while running to form a recorded image on the thermal recording layer.
When the thermal recording layer is in a state where the infrared transmittance is small, by heating it to the glass transition temperature of the hollow microcapsules by the thermal head, the infrared transmittance of the heated portion becomes large, and the infrared transmittance of the portion becomes large. Configure a recorded image.

Since the recorded image is covered with the visible light blocking layer, it cannot be discerned by the naked eye, and the confidentiality of information is maintained. When reading a recorded image, it is sufficient to irradiate an infrared laser with a wavelength of 700 nm or more and detect the reflected light from the recorded image with an infrared sensor.

[0015]

The heat-sensitive recording layer comprising hollow microcapsules according to the present invention, when irradiated with infrared rays, changes the refractive index of light due to the presence of air in the hollow microcapsules in the non-printed portion, that is, at room temperature. As a result, light scattering occurs. Therefore, the infrared sensor detects a part of the scattered light. On the other hand, the printed portion, that is, the microcapsules are destroyed and fused by heating at a temperature higher than a predetermined temperature (the glass transition temperature of the hollow microcapsules or higher), and
The air interface decreases, the scattering of light is suppressed, the material becomes transparent, and the transmittance of infrared light increases. At that time, the infrared light incident on the heat-sensitive recording layer causes specular reflection on the metal thin film layer below the heat-sensitive recording layer, and thus the reflected infrared light is not detected by the infrared sensor. Therefore, the presence or absence of a recorded image can be identified by the intensity of the reflected light detected by the infrared sensor.

The recorded image recorded on the heat-sensitive recording layer is invisible due to the presence of the visible ray blocking layer.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of the information recording medium of the present invention. In FIG. 1, a magnetic recording layer (2) is provided on the surface of a substrate (1), and an anchor layer (3) for smoothing the roughness of the magnetic layer surface is further provided thereon. Further, a metal thin film layer (4) is provided thereon, and a thermal recording layer (5) having a low infrared transmittance at room temperature and having an increased infrared transmittance by heating above a predetermined temperature is provided thereon. On the heat-sensitive recording layer (5), a visible light-blocking layer (which absorbs light in the visible range and transmits infrared light at a high efficiency) makes the information printed on the heat-sensitive recording layer (5) invisible. 6) is provided, and a protective layer (7) having heat resistance to the extent that surface properties are not deformed by thermal energy during recording or erasing of information on the thermosensitive recording layer is further provided thereon.

Here, the substrate (1) is made of paper, plastic, or the like, and may have any strength as long as it can be used as an information recording medium.

The magnetic recording layer (2) is composed of γ-Fe ₂ O ₃ and Co deposited γ
-Fe ₂ O ₃ , Fe ₃ O ₄ , CrO ₂ , Fe, Fe-Cr, Fe-Co, Co-Cr, C
A magnetic binder such as o-Ni, MnAl, Ba ferrite, or Sr ferrite is dispersed in an ink vehicle or a binder solution consisting of a suitable polymer binder and a solvent. A coating solution is gravure method, roll coating method, bar coater method. Alternatively, it is formed by coating and drying by a known coating method such as a screen printing method.

The anchor layer (3) is provided for adhering the magnetic recording layer (2) and the metal thin film layer (4) together and for improving the specularity of the metal thin film layer. Resins such as vinyl chloride resin, vinyl chloride-butyl acetate copolymer, polyvinyl butyral resin, polymethylmethacrylate (PMMA), polyurethane resin, and epoxy resin are used as main components.

The metal thin film layer (4) is made of Sn, Te, In,
A simple metal such as Al, Bi, Zn, or Pb, or an alloy or compound of these metals is formed by a method such as vacuum thin film, sputtering, plating, transfer, or laminating. The thickness of this metal thin film layer is 0.01 μm or more and 0.5 μm
The following may be provided.

The heat-sensitive recording layer (5) is an emulsion obtained by emulsifying and dispersing hollow microcapsules having a particle diameter of 0.05 to 1 μm, and has a low infrared transmittance at room temperature and an increased infrared transmittance at a predetermined temperature or higher. Then, a heat-sensitive recording layer that forms a recorded image by the difference in the infrared transmittance is provided. As a wall material for forming such a microcapsule,
Those having a glass transition temperature of about 50 ° C. to 150 ° C. are preferable, and polyurea, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, gelatin, polyvinylpyrrolidone, polyvinyl alcohol and the like are preferable. It may be selected according to the clearing temperature of. The heat-sensitive recording layer is an emulsion obtained by emulsifying and dispersing these, and is formed on the metal thin film layer (4) by coating and drying by a known coating means such as a gravure printing method.

The visible light blocking layer (6) is a thermal recording layer (5).
It is a layer provided for hiding the information printed on the surface invisible to the naked eye. As an optical property, it is a process ink that transmits infrared rays but does not transmit visible light (yellow,
It is formed by coating and drying a gray ink containing a mixture of magenta and cyan at an appropriate ratio by a known coating means such as offset or screen printing.

For the protective layer (7), it is desirable to use a resin having heat resistance to the extent that thermal deformation of surface properties does not occur in recording information on the heat-sensitive recording layer (3). Examples of such a resin include a polymer binder, and examples of the polymer binder include hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, styrene-maleic acid copolymer, polyester resin, ABS resin, nitrocellulose and the like. Be done. A coating solution prepared by dissolving this in a solvent is applied by the above-mentioned coating method and dried to form the protective layer (7). In addition, a thermosetting resin or an ultraviolet curable resin may be used. Further, a lubricant or the like may be added for the purpose of improving suitability for the thermal head.

Information is recorded on the information recording medium having the above-mentioned structure by applying thermal energy to the heat-sensitive recording layer with a thermal head.

The configuration of the present invention will be described using a specific example. In addition, "part" in a text shows a weight part.

Specific Example (a) Composition of coating liquid for magnetic recording layer 40 parts of BaO-6Fe ₂ O ₃ 2 parts of carbon 10 parts of vinyl chloride-based resin 10 parts (Sekisui Chemical Co., Ltd., trade name “ESREC A”) Saturated polyester resin 5 parts (product name "Byron 103" manufactured by Toyobo Co., Ltd.) Polyurethane elastomer 7 parts (product name "N-230 manufactured by Nippon Polyurethane Co., Ltd."
4 ") Oleic acid 5 parts Toluene 30 parts Isocyanate curing agent 3 parts (Nippon Polyurethane Co., Ltd. trade name" Coronate H "
L ”) 0.5 parts of triethylenediamine

(B) Composition of coating liquid for anchor layer 100 parts vinyl chloride resin (solid content 20%) Polyurethane resin (40% solid content) 50 parts Diluting solvent 70 parts

(C) Composition of coating liquid for thermosensitive recording layer Acrylic hollow microcapsule resin emulsion (average particle size 0.5 μm, solid content ratio 33.6%)

(D) Composition of coating liquid for visible light blocking layer: Black-red indigo process ink mixed color ink UV curable yellow ink 4 parts UV curable magenta ink 3 parts UV curable cyan ink 3 parts

(E) Composition of coating liquid for protective layer UV curable hard coat

Among the materials of the magnetic recording layer coating liquid of the above (a), a material containing no isocyanate curing agent is uniformly dispersed in advance by a sand mill for 2 hours, and the coating liquid added with the isocyanate curing agent at the time of coating has a thickness of 188 μm. It is formed by coating and drying using a roll coater having an orienter attached so that the dry film thickness is about 15 μm on the white polyester. On this magnetic layer, an anchor layer coating solution having the composition of (b) is applied and dried to a thickness of about 3 μm in order to improve the specularity of the metal thin film layer (4). On the anchor layer, Al was formed as a metal thin film layer (4) with a film thickness of 0.1 μm by a vacuum deposition method. A thermosensitive recording layer (5) composed of the composition (c) is formed on the metal thin film layer by a gravure printing method so that the dry film thickness is about 5 μm.

Further, a visible light blocking layer (6) having the composition (d) is formed on the heat-sensitive recording layer by a UV offset method so that the dry film thickness becomes about 2 μm. Finally, the heat resistant protective layer (e) was formed by a UV offset method to a dry film thickness of about 2 μm to obtain a sheet for an information recording medium according to the present invention. When thermal energy was applied to this information recording medium sheet by a thermal head to record information, the recorded pattern could not be recognized with the naked eye, but the reader could recognize the print pattern. It was

Further, a thermal tilt plate tester (manufactured by Toyo Seiki Co., Ltd.)
The difference in the reflectance (contrast) of the recorded image formed by the printed part and the non-printed part was measured under the conditions of 120 ° C., 2 seconds and 1 Kgf / cm ² , and it was confirmed that the printed part was printed on the thermal recording layer of 5 μm. The infrared reflectances (810 nm) of the non-printed portions were 10% and 67.5% (PCS value 0.85), which were good.

[0036]

EFFECT OF THE INVENTION The information recording medium according to the present invention has a large contrast between the reflected light from the heat-sensitive recording layer composed of hollow microcapsules and the reflected light having strong specular reflection at the metal thin film layer below the heat-sensitive recording layer ( Information) can be read. The recorded image recorded on the heat-sensitive recording layer is
It is invisible due to the presence of the visible light blocking layer.

Therefore, even if a thick visible light blocking layer (concealing layer) is provided, the recorded image (information) recorded on the thermosensitive recording layer can be optically read stably.

[0038]

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an information recording medium according to the present invention.

[Explanation of symbols]

 1 Base 2 Magnetic Recording Layer 3 Anchor Layer 4 Metal Thin Film Layer 5 Thermosensitive Recording Layer 6 Visible Light Blocking Layer 7 Protective Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G11B 11/00 9075-5D 13/00 9075-5D

Claims (3)

[Claims] 1. A heat-sensitive recording layer containing at least a metal thin film layer that causes specular reflection and hollow microcapsules on a substrate and having a low infrared transmittance at room temperature and an increased infrared transmittance at a predetermined temperature or higher. An information recording medium having a laminated visible light blocking layer that transmits light but absorbs visible light. 2. The particle size of the hollow microcapsules is 0.05 to 1.
The information recording medium according to claim 1, wherein the information recording medium is μm. 3. An information recording medium according to claim 1, wherein a magnetic recording layer is provided between the substrate and the metal thin film layer.