JPH0995054A - Information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an unfair practice by providing a thermal recording layer consisting of a specific layer laminated on a substrate, on one of the surfaces of a core sheet, laminating a transparent oversheet on the thermal recording layer, and removing the part of the laminated specific layer a heat generated by an infrared beam emitted through the transparent oversheet to record information. SOLUTION: An information recording medium 1 is composed of a thermal recording layer 4 as an information display part provided between a core sheet and a transparent oversheet allowing permeation of lights in a visible ray region, a near-infrared region and an infrared region and least absorbing these lights. In addition, this thermal recording layer 4 is welded by thermal fusion to the core sheet 2 and the oversheet 3, then the entire laminate is formed into a sheet, and is punched out in the shape of a card. The thermal recording layer 4 consists of a colored layer 6, a vapor deposition anchor layer 7, a metal thin film layer with a thickness of 500-1200nm and an infrared absorptive layer 9 without light absorption in the visible ray region. If an infrared ray or a near infrared ray is emitted to the information recording medium 1, a metal thin film layer 9 to be absorbed into the infrared ray absorptive layer 9 of the thermal recording layer 4 is balled up without thermally affecting the oversheet 3, and an image is formed on the foundation colored layer 6.

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 capable of recording information by absorbing / heating near-infrared light or infrared light, and more specifically, a heat-sensitive recording layer utilizing heat generated by photothermal conversion for information recording. The present invention relates to an information recording medium which is provided inside a medium and allows additional recording of visual information by means of a non-contact means such as a laser beam after the medium is manufactured.

[0002]

2. Description of the Related Art At present, as a means for recording visible information on an information recording medium having a vinyl chloride resin, a polyethylene terephthalate (PET) resin, paper, etc. as a base material, an ink jet method, a sublimation transfer ribbon or a thermal fusion transfer ribbon is used for thermal transfer. There are various methods such as a method and an electrophotographic method using an electrophotographic toner. According to these methods, arbitrary visible information or an image is formed on the surface of the information recording medium. In particular, it is suitable for recording individual information that is different for each information recording medium. The visible information formed by these methods, or the upper surface of the image is several μm in order to protect them from external factors such as rubbing, rubbing, artificial peeling, penetration of water and chemicals, and ultraviolet rays. Overlay (transparent coating layer) is applied. A laminate such as a plastic sheet or a resin coating is used for this overlay, which can improve the durability of the image.

However, when the information is newly recorded after the information recording medium becomes a completed product, the overlay becomes a recording obstacle. In particular, when information or an image is additionally recorded on the information recording medium at any time or arbitrarily, it is substantially impossible to form an overlay on the recording surface every time the information is additionally recorded. Further, these overlays can be peeled off with a file or the like, and there is a risk that unauthorized information may be rewritten or additionally recorded on the peeled information recording surface.

Further, the sign panel for carrying a signature, which is a means for confirming the owner of a credit card, cash card, ID card, etc., is also handwritten, but there is a risk of alteration or tampering such as erasing the recording surface or replacing the sign panel. And were vulnerable to fraud.

There is also a method in which the information recording medium is completely laminated on the information recording medium by laminating and enclosing the information recording medium with a transparent plastic film. However, since the encapsulation process is performed after the information recording, a large amount of the information recording medium is processed. When it is carried out, it has a problem that it is complicated and it is not suitable for an information recording medium for additional recording as described above, and especially when a laminated transparent plastic film is peeled off. They were vulnerable to fraudulent acts because they could be altered or tampered with.

There are other optical recording methods, one of which is one in which information is recorded inside a medium such as an optical disk or an optical card. However, since recording is performed in pit units of 1 μmφ and 3 μmφ, It cannot be used for visual information recording mainly for visual inspection. Further, in JP-A-55-146795, the information recording medium is irradiated with laser light while controlling the position and output of the laser light, and the core sheet is exposed to the laser light through a transparent cover sheet laminated on the core sheet. Although the recording of information by heat is disclosed, depending on the fact that high-energy laser light is required and the control of high-energy laser light, the cover sheet laminated due to the heat generated may deform, position and output. There is a problem in that the recording apparatus becomes expensive because it is necessary to precisely control the above.

In order to solve the above-mentioned problems, a heat-sensitive recording layer and a photothermal conversion layer which absorbs energy light such as laser light to generate heat are laminated, and an oversheet is laminated on the outermost layer. There is an information recording medium that
There is known a method of indirectly recording information by using the heat generated by the absorption and heat generation of the laser light of the photothermal conversion layer as the heat source of the thermal recording layer. According to this, when information is directly recorded on the heat-sensitive recording layer from the outside, it is possible to record the information through the oversheet, so that a thermal print recording means such as a thermal head is provided for the heat-sensitive recording layer in the information recording medium. When a fraudulent act such as alteration or tampering is used, a scanning trace of the thermal head remains on the oversheet located in the outermost layer, and the fact of the fraudulent act can be clarified. Therefore, in order to perform recording on the heat-sensitive recording layer, it is necessary to increase the heat load applied from the outside, and if the heat load is large, the information recording medium is physically damaged such as deformed. Some have the effect of deterring misconduct or being able to easily know the fact.

Further, by narrowing the beam diameter, the beam power per unit area can be increased, and by expanding the beam diameter, the beam power per unit area becomes low and recording becomes difficult. In order to record visible character / image information on an information recording medium, it is necessary to record the irradiated beam diameter at 60 to 100 μmφ and the character / image at a line width of 100 to 150 μmφ.

[0009]

However, in the above configuration, if the character / image is 1 μmφ to 3 μmφ,
When the laser light to be radiated is narrowed down and radiated, the temperature does not rise until the oversheet on the surface is deformed, even if the laser-radiated portion is heated to the melting point or the coloring temperature of the thermosensitive recording material composed of a metal thin film or the like Character / image has a line width of 10
When recording at 0 to 150 μmφ, the thickness of the oversheet is 100 μm, which is almost the same as the line width, so that the oversheet is deformed by the heat generated by the laser beam and at the same time, it is generated from the thermal recording material. The generated gas may cause swelling of the sheet in the portion located above the thermal recording section.

Therefore, according to the present invention, it is possible to record information inside the information recording medium without causing deformation or swelling of the surface of the oversheet due to the irradiation of the laser beam, and to the colored layer of the information recording medium. By stacking multi-layer interference thin film layers,
An object of the present invention is to provide an information recording medium in which recorded characters / images appear to change in color (color shift) depending on the viewing angle, and the recorded characters / images are difficult to copy by a color copier or color printer. And

[0011]

The present invention, which has been made to achieve the above object, provides a coloring layer, a vapor deposition anchor layer, and a metal thin film layer having a thickness of 500 to 1200 nm on a substrate. The thermosensitive recording layer formed by laminating an infrared absorption layer having no absorption in the visible region is provided on one side or both sides of the core sheet,
A transparent oversheet is laminated on the core sheet, and the infrared absorption layer generates information by partially removing the metal thin film layer from heat generated by absorption of near infrared light or infrared light radiated through the transparent oversheet. The information recording medium is characterized by recording.

According to a second aspect of the invention, in the information recording medium of the first aspect, a heat-sensitive adhesive layer is provided on the back surface of the base material.

According to a third aspect of the present invention, in the information recording medium according to the first aspect, a multilayer interference thin film is laminated on the colored layer.

According to a fourth aspect of the present invention, in the information recording medium of the first aspect, the metal thin film layer is tin, indium,
It is characterized by being bismuth or its alloy.

The invention described in claim 5 is the information recording medium according to claim 1, wherein the infrared absorbing layer contains an infrared light absorbing dye represented by the following general formula (1).

[0016]

Embedded image

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view of the information recording medium of the present invention, FIG. 2 is a sectional view of the information recording medium taken along line XX of FIG. 1, and FIG. 3 is a sectional view of the heat-sensitive recording layer in FIG. 4 is a cross-sectional view of the heat-sensitive recording layer of another embodiment of FIG.

The information recording medium 1 of the present invention shown in FIGS. 1 and 2.
From the thermosensitive recording layer 4 composed of the colored layer 6, the vapor deposition anchor layer 7, the metal thin film layer 8 having a thickness of 500 to 1200 nm, and the infrared absorbing layer 9 having no absorption in the visible region on the core sheet 2 on the base material 5. The information display section 20 is provided, and an oversheet 3 that is transparent, that is, that transmits light in the visible region, the near infrared region, and the infrared region and that absorbs little light is laminated on the upper surface of the information display unit 20. . After providing the thermosensitive recording layer 4, the core sheet 2 and the oversheet 3 are formed into a sheet by heat fusion and then punched into a card shape to form the information recording medium 1.

The information recording medium 1 is displayed on the information display section 20.
The unique information, related information, and the like are recorded as an image 21 on the information recording medium 1 from the outside by irradiation with laser light in the near infrared region and the infrared region. The thermal recording layer 4 constituting the information display section 20 is provided between the core sheet 2 and the oversheet 3 as shown in FIG. The size of the heat-sensitive recording layer 4 can be arbitrary and is appropriately determined as needed.

Further, the structure of the thermosensitive recording layer 4 will be described in detail with reference to the sectional view of FIG. First, the base material 5, that is, the plastic base material, may be any material that can be used for a card, and is not particularly limited, and examples thereof include vinyl chloride, polyethylene terephthalate (PET), acrylonitrile-butadiene-. Styrene copolymer (AB
S), thermoplastic resins such as polystyrene and polycarbonate, thermosetting resins, or microbial-produced polyesters,
Examples include so-called biodegradable resins such as polylactic acid. The thickness of the base material 5 varies depending on its application, but is generally 0.4 to 0.8 m.

Next, as the colored layer 6, an ink containing an optional color material such as black, blue, green, red, etc. can be used. However, if gas is generated by heating, the heat-sensitive recording layer print portion swells. Therefore, it is necessary to avoid an excessive temperature rise, and it is desirable to use one that does not have absorption in the infrared region.Printing means such as screen printing, offset printing, gravure printing, coating means such as gravure coat, roll coat, bar coat, etc. The colored layer 6 is formed by printing or coating on a necessary portion of the substrate 5 by various known forming methods such as the above, and then drying.

Further, the vapor deposition anchor layer 7 improves the adhesiveness of the metal thin film layer 8 and assists the ball-up by melting of the metal thin film layer 8 by the irradiation of the laser beam, such as acrylic, acrylic polyol, polyester, A resin such as a vinyl chloride-vinyl acetate copolymer is provided by a coating means such as gravure coating, roll coating or bar coating.

The metal thin film material used for the metal thin film layer 8 includes bismuth (melting point 271 ° C.), tin (melting point 23).
2 ° C.), indium (melting point 156 ° C.), and Sb, Sn, Bi-based Rose alloy (Bi: 50)
%, Pb: 28%, Sn: 22%, melting point 100 ° C.), Newton alloy (Bi: 50%, Pb: 31%, Sn: 1)
9%, 95 ° C) and Bi, Pb, Sn, Cd-based wood alloys (Bi: 50%, Pb: 24%, Sn: 14%, C
d: 12%, approx. 70 ° C), Lipovitz alloy (Bi: 50
%, Pb: 27%, Sn: 13%, Cd: 10%, 70
° C) is effective. A known method can be used as a forming method, and it is sufficient that the film thickness and the like can be controlled. The film thickness is preferably 500 to 1200 nm, and the forming method is a physical method such as an ordinary vacuum evaporation method or a sputtering method. A chemical vapor deposition method such as a vapor deposition method or a CVD method can be used.

Further, in order to prevent forgery, as shown in FIG. 4, the multilayer interference thin film 12 is formed on the coloring layer 6 of the thermal recording layer 11.
By providing the above, it is possible to provide effectiveness even against forgery by color copying. The multilayer interference thin film 12 has a structure in which high refractive index ceramic thin film layers 22 and low refractive index ceramic thin film layers 23 are alternately arranged. In particular, it has the property of reflecting or transmitting light rays in a specific wavelength region by alternately combining ceramic thin film layers with different refractive indices, and because the film thickness of the multilayer interference thin film changes by changing the viewing angle, The wavelength range shifts and the colors look different. The multilayer interference thin film 12 is appropriately selected according to optical properties such as refractive index, reflectance and transmittance, weather resistance, chemical resistance, interlayer adhesion, etc., and is laminated as a thin film to form the multilayer interference thin film 12. A known method can be used as the forming method, and the film thickness, the film forming speed, the number of stacked layers,
Alternatively, it is possible to control the optical film thickness (= n · d, n: refractive index, d: film thickness) and the like, and a chemical vapor deposition method such as an ordinary vacuum vapor deposition method or a sputtering method or a chemical method such as a CVD method. Vapor deposition can be used. Although the present invention discloses ceramics, metals have the same function as ceramics, and include metals such as chromium, nickel, aluminum, iron, titanium, silver, gold, copper, silicon and nickel. The selected single substance or a mixture thereof,
Examples include alloys. The thin film made of a metal may have different optical characteristics such as a refractive index depending on the state of the constituent material and the forming conditions. Further, other than these ceramics and metals, any one having similar refractive index and reflectance can be used.

As the multilayer interference thin film having such different optical characteristics, the above-mentioned metal thin film, ceramics thin film, or a composite thin film formed by combining them is laminated and formed. For example, when laminating thin films having different refractive indexes. The high refractive index thin film and the low refractive index thin film may be combined, or a specific combination may be alternately laminated.
A desired multilayer film can be obtained by a combination thereof.

Specific examples of high refractive index ceramic materials include titanium dioxide (n = 2.4), zirconium dioxide (n = 2.0), zinc sulfide (n = 2.3) and cerium dioxide (n). = 2.3) indium oxide (n =
2.0), tantalum oxide (n = 2.1) zinc oxide (n =
2.1) etc. can be mentioned.

As the low refractive index ceramic material,
Magnesium oxide (n = 1.6), silicon dioxide (n =
1.5), magnesium fluoride (n = 1.4), calcium fluoride (n = 1.3 to 1.4), cerium fluoride (n = 1.3), aluminum fluoride (1.3) , Aluminum oxide (1.6), and the like.

The total thickness of the multilayer interference thin film 12 is preferably 1 μm or less, and if it exceeds 1 μm, the flexibility becomes poor.
This is because cracks occur in the multilayer interference thin film 12.

Further, the infrared absorption layer 8 having no absorption in the visible region used in the present invention has absorption from the near infrared region of 700 nm to 1100 nm to the infrared region, and its heat generation temperature can melt the metal thin film layer 7. It is necessary to be able to raise the temperature to a proper temperature, to be colorless, to have little influence on the visual reading of the thermosensitive recording layer 3 , and to obtain a sufficient contrast.

A metal thin film, which is a heat-sensitive recording material, does not cause a thermal change at 120 ° C. to 150 ° C., which is the heat-sealing temperature of the core sheet 2 and the transparent oversheet 3, and does not generate gas during character / image formation. In order to prevent heat from being raised to the deformation temperature of the transparent oversheet 3 by conduction even when the temperature of the layer 7 generated by the irradiation of the laser light is 200 ° C. or higher, the heat-sensitive recording layer can be formed with a small irradiation energy amount. The infrared light absorbing material (infrared absorbing layer that does not absorb light in the visible region) that performs photothermal conversion in order to raise the temperature is provided on the surface of the metal thin film layer 7. Since the information recording medium of the present invention visually judges recorded information,
A material that does not absorb in the visible region is required for the infrared absorption layer.

No absorption in the visible region, 700 nm to
Examples of the infrared light absorbing material having absorption in the near infrared region of 1100 nm include infrared absorption ability among phthalocyanine-based materials, naphthalocyanine-based materials, squalium-based, naphthoquinone-based, carbocyanine-based, aminium salt-based materials,
Although a dye having a color in the visible region and various resistances can be used, an aminium salt-based dye represented by the following chemical formula (1) is particularly effective.

[0033]

Embedded image

This, a binder, a solvent, and other defoaming agent,
The infrared absorbing layer 8 is a layer coated with an infrared absorbing ink formed by mixing various additives such as a lubricant into an ink. The binder may be one that is commonly used unless it alters or damages the infrared absorbing material, such as vinyl acetate, vinyl chloride-vinyl acetate copolymer, polyurethane, ethylene vinyl acetate, polyamide, By using polyester or ATACTEC polypropylene resin, a transparent oversheet made of transparent plastic and necessary adhesive strength can be obtained in the heat fusion step. The binder is 20 in the infrared absorbing ink composition excluding the solvent.
It is preferably contained in an amount of not more than wt%.

Further, as the solvent used for the infrared absorbing ink, toluene, methyl isobutyl ketone, xylene, cyclohexanol, isobutyl acetate, cyclohexanone, methyl cyclohexanone, glycol derivatives such as ethylene glycol monobutyl ether, etc., or a mixed solvent thereof is used. Can be mentioned.

This infrared absorbing ink is applied to necessary portions of the substrate 4 by various known forming methods such as printing means such as screen printing, offset printing and gravure printing, coating means such as gravure coat, roll coat and bar coat. After printing or coating, the infrared absorption layer 3 is formed by drying.

Next, the core sheet 2 may be made of any material normally used for information recording media such as cards, and is not particularly limited. For example, vinyl chloride, polyethylene terephthalate (PET), acrylonitrile-butadiene. -Styrene copolymer (ABS), polystyrene,
Thermoplastic resin such as polycarbonate or thermosetting resin,
Alternatively, so-called biodegradable resins such as microorganism-produced polyester and polylactic acid may be used. The thickness of the core base material 2 varies depending on its use, but is generally 300 to 800 μm for use as a card.

The oversheet 3 used as the transparent coating layer has sufficient transparency, that is, the oversheet 3 transmits light in the visible region, the near infrared region and the infrared region and has a small absorption. Is required, and it is sufficient if it has a certain degree of rigidity and surface smoothness, and is not particularly limited. Examples thereof include polymer films such as polyester film, polyolefin film, vinyl chloride film, polylactic acid film and the like. The thickness of the oversheet 3 varies depending on its application, but in consideration of the relationship with the core sheet 2, it is 50 to 150 μm for general card applications. It is also possible to color the oversheet 3 with a coloring agent within a range that does not affect the color.

A printing layer (not shown) such as a picture or a character may be provided on the area surface of the core sheet 2 other than the heat-sensitive recording layer 4 as long as it does not interfere, and it may be provided on one side or both sides. The oversheet 3 may be provided only on the surface of the core sheet 2 on which the thermosensitive recording layer 4 is formed, or may be laminated on the surface on which the thermosensitive recording layer 4 is not formed. When the heat-sensitive recording layer 4 is not formed, the heat-sensitive recording layer 4 may not be transparent, and a print layer (not shown) such as a picture or letters may be provided on the upper surface thereof. Further, a protective layer (not shown) can be provided as necessary to protect it.

After the core sheet 2, the thermosensitive recording layer 4, and the oversheet 3 are laminated, they are heated and pressed (for example, 80 to 160 ° C., 30 to 150 Kg) in a heat fusion (thermal lamination) step.
/ Cm ² , for 1 to 5 minutes), and the layers are integrated by heat fusion to form an information recording medium. The thickness at this time is not particularly limited, but is 500 to 1000 μm for general card applications. As described above, the information recording medium 1 is formed by forming a sheet by heat fusion and then punching it into a card shape.

If the thermal recording layer 4 is not sufficiently adhered to the plastic overcoat and the core sheet, the mechanical strength of the information recording medium 1 itself becomes insufficient. An adhesive layer 14 may be provided on the back surface of the base material 5, that is, on the core sheet 2 side in order to strengthen the adhesion with the layer 4. As the adhesive layer 14, there are ethylene vinyl acetate, polyamide, polyester, ATACTEC polypropylene, etc., and if necessary, as a tackifier, rosin resin, petroleum resin, waxes, antioxidants, inorganic fillers, plasticizers, etc. Agents and the like can be added.
The adhesive layer 14 can also be formed by various similar known forming methods.

The heat-sensitive recording layer 4 of the information recording medium of the present invention is provided with an infrared absorbing layer on the metal thin film layer in order to efficiently absorb the irradiated laser beam. The vapor-deposited layer can be raised, and if the temperature rises for a long time, the transparent plastic will deform the oversheet due to heat conduction, so the temperature can be raised in a short time with the minimum required energy.

According to the information recording medium of the present invention, a heat-sensitive recording layer capable of recording by irradiation of infrared rays or near infrared rays and having high sensitivity and withstanding the heat fusion temperature of the core sheet 2 and the transparent oversheet 3 is used. By providing the information inside the recording medium, it is possible to additionally write the individual information of a visible size without deforming the oversheet positioned in the outer layer by heat or the like when the information is recorded in the thermosensitive recording layer. Moreover, since the thermosensitive recording layer has high sensitivity, recording can be performed with a simple device and with low energy laser light. Furthermore, by providing a multi-layer interference thin film between the base material 5 and the metal thin film layer 8, color shift (color change) occurs depending on the angle at which the recorded image is viewed, and thus it is possible to prevent duplication by a color copier or color printer. Is.

[0044]

Embodiments will be described below with reference to the drawings. (Example 1) A polyester sheet having a thickness of 25 μm was used as a base material between a core sheet made of a vinyl chloride resin having a thickness of 540 μm and an oversheet made of a transparent vinyl chloride resin having a thickness of 100 μm as an base material of an acrylic recording medium. MEK of resin (Paraloid A21 Rohm & Haas)
A 4 μm thick colored layer made by adding phthalocyanine blue to a toluene solution, and a thickness of 1000 n by a resistance heating method.
m tin-deposited thin film layer, paraloid A21 with MEK-toluene-γ-butyrolactone bis (P-dibutylaminophenyl) [N, N, -bis (P-dibutylaminophenyl) -P-aminophenyl] aminium hexafluoride antimony An 8% solution of acid salt is applied to form a colorless infrared absorbing layer having a dry film thickness of 2 μm, and a polyamide resin is coated on the back surface of the polyester sheet, and a thermosensitive recording layer formed into a tape by cutting is arranged, After heat-sealing by heating and pressurizing at 140 ° C., it was punched into a card shape to prepare an information recording medium. The core sheet is printed if necessary.

The prepared information recording medium has a wavelength of 830 nm,
Using a semiconductor laser with a beam diameter of 60 μm and an output of 3 W,
Recording was performed at a scanning speed of 20 mm / sec. The irradiated laser light is absorbed by the colorless infrared absorption layer without thermally affecting the oversheet made of transparent vinyl chloride resin, and the tin vapor deposition thin film is balled up by heating up, and the underlying colored layer appears. It was The line width at this time is 140μ
It was about m and was a sufficiently visible image. Further, each layer had sufficient mechanical strength, and peeling did not occur even when the information recording medium was externally deformed.

(Embodiment 2) In the structure of Embodiment 1, the colored layer is made of an acrylic resin (Paraloid A21 Rohm &
After forming using an ink prepared by dissolving Sudan the deep black MEK- toluene solution manufactured by Haas Company), silicon dioxide as the low refractive index _{layer, ZnS / SiO 2 / ZnS /} SiO using zinc sulfide as a high refractive index layer A multilayer interference thin film having a 2-layer structure of ₂ / ZnS having a total film thickness of 1 μm and a vapor deposition anchor layer made of an acrylic resin (Paraloid A21 Rohm & Haas Co., Ltd.) having a thickness of 2 μm were provided. The subsequent 1000 nm tin vapor-deposited thin film layer, infrared absorption layer, etc. were prepared in the same manner as in Example 1 to prepare an information recording medium.

Recording was performed on the produced card at a scanning speed of 40 mm / sec using a YAG laser having a wavelength of 1067 nm, a beam diameter of 100 μm and an output of 6 W. The irradiated laser light is absorbed by the colorless infrared absorption layer without thermally affecting the oversheet made of transparent vinyl chloride resin, and the tin vapor deposition thin film is balled up by heating up, and the underlying colored layer appears. It was The line width at this time is 140μ
m is a sufficiently visible image, this image has a vertical central wavelength of visible light absorption of 550 nm, and when visible light is incident at an angle of 45 °, the central wavelength is on the low wavelength side. To produce a color shift. Even if this is illegally copied by a color copying machine, the color of the image to be copied is one of the color shifts (color change), and the forged one does not cause color shift (color change). It was easy to determine if it was illegally copied.

(Example 3) Thickness of information recording medium 540 μ
m core sheet made of vinyl chloride resin and thickness 100μ
The thickness obtained by adding phthalocyanine blue to a MEK-toluene solution of acrylic resin (Paraloid A21 Rohm & Haas) on a polyester sheet having a thickness of 25 μm as a base material between oversheets made of transparent vinyl chloride resin of m. is 4μm colored layer, the silicon dioxide as the low refractive index layer, TiO ₂ using zinc sulfide as a high refractive index layer
/ SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ multi-layer interference thin film having a total film thickness of 1 μm with a 5-layer structure, and a thickness of 2
μm acrylic resin (Paraloid A21 ROHM &
A vapor deposition anchor layer made of Haas Co. was provided.

Thickness of 1000 nm by resistance heating method
Of Bismuth vapor-deposited thin film layer, Paraloid A21, of bis (P-dibutylaminophenyl) [N, N, -bis (P-dibutylaminophenyl) -P-aminophenyl] aminium perchlorate of MEK-toluene-γ-butyrolactone. An 8% solution was applied to form a colorless infrared absorbing layer having a dry film thickness of 2 μm, a polyamide resin was coated on the back surface of a polyester sheet, and a thermosensitive recording layer formed by cutting into a tape was arranged and heated at 130 ° C. After heat-sealing by pressurizing, it was punched out into a card shape to prepare an information recording medium. The core sheet is printed if necessary.

Recording was carried out at a scanning speed of 20 mm / sec on the manufactured card using a semiconductor laser having a wavelength of 830 nm, a beam diameter of 60 μm and an output of 3 W. Irradiated laser light is absorbed by the colorless infrared absorption layer without thermally affecting the oversheet made of transparent vinyl chloride resin, and the bismuth vapor deposition thin film is balled up by heating up,
The underlying colored layer appeared. The line width at this time is about 80 μm, and it is a sufficiently visible image. This image has a vertical central wavelength of absorption of visible light of 550 nm, and when visible light is incident at an angle of 45 °. The center wavelength was shifted to the lower wavelength side, and a color shift (color change) occurred. Even if this is illegally copied by a color copying machine, the color of the image to be copied is one of the color shifts (color change), and the forged one does not cause color shift (color change). It was easy to determine if it was illegally copied. Further, each layer had sufficient mechanical strength, and peeling did not occur even when the information recording medium was externally deformed.

[0051]

According to the information recording medium of the present invention, it is possible to record any visible information for each information recording medium, and the information is recorded inside the information recording medium. In order to carry out illegal acts such as tampering, it is necessary to perform an operation such as peeling off an oversheet laminated on the surface, for example, a 100 μm transparent plastic sheet,
Since the trace of the act remains, the fact of the misconduct becomes clear.

The heat-sensitive recording layer disposed by integrating the core sheet and the oversheet by the heat-fusion method is a leuco-based, diazo-based or low-molecular / polymer-based conventional heat-sensitive recording material. No change in heat was observed, and no deterioration in recording performance was observed even after heat fusion. In addition, since the image is formed by thin-film boiling, there is no large volume change when forming characters and images, so even if it is formed while the core sheet and the transparent oversheet are integrated by the heat fusion method, recording is performed. Does not reduce sensitivity. Furthermore, the infrared absorption layer has no absorption in the visible region, and is 700 nm to 1
Lasers such as semiconductor lasers and YAG lasers can be used because they have absorption in the near-infrared region up to 100 nm, and because the irradiated laser light can be absorbed efficiently, it is possible to record with a low energy output laser. Therefore, it is possible to record on the metal thin film layer without thermally deforming the transparent plastic sheet on the surface of the information recording medium by the irradiation of the laser beam.

In addition, the heat-sensitive recording layer formed between the core sheet and the oversheet and integrated by the heat-sealing step can be used for dipping in hot water at 80 ° C. or by repeated bending tests. No peeling occurred.

Further, since the recorded characters / images are formed by the multilayer interference thin film, the characters / images are color-shifted (color change) depending on the viewing angle, and even if an illegal copy is attempted by a color copying machine, the texture is Not only,
It is possible to easily detect a fraudulent activity depending on the presence or absence of color shift (color change).

[Brief description of drawings]

FIG. 1 is a plan view of an information recording medium of the present invention.

FIG. 2 is a cross-sectional view of the information recording medium taken along line XX of FIG.

FIG. 3 is a cross-sectional view of the thermosensitive recording layer in FIG.

FIG. 4 is a sectional view of a heat-sensitive recording layer of another example of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Information recording medium 2 Core sheet 3 Over sheet 4, 11 Thermal recording layer 5 Base material 6 Coloring layer 7 Deposition anchor layer 8 Metal thin film layer 9 Infrared absorbing layer 12 Multilayer interference thin film 22 High refractive index ceramic thin film layer 23 Low refractive index ceramic Thin film layer 14 Adhesive layer 20 Information display area 21 Image

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G11B 7/24 511 G06K 19/00 C

Claims (5)

[Claims] 1. A colored layer, a vapor deposition anchor layer, and a film thickness 5 on a substrate.
A heat-sensitive recording layer formed by laminating a metal thin film layer having a thickness of 00 to 1200 nm and an infrared absorbing layer having no absorption in the visible region is provided on one side or both sides of a core sheet, and a transparent oversheet is laminated on the core sheet, and An information recording medium, wherein the infrared absorption layer records information by partially removing the metal thin film layer from heat generated by absorption of near infrared light or infrared light irradiated through the transparent oversheet. 2. The information recording medium according to claim 1, wherein a heat-sensitive adhesive layer is provided on the back surface of the base material. 3. The information recording medium according to claim 1, wherein a multilayer interference thin film layer is laminated on the colored layer. 4. The metal thin film layer is made of tin, indium, bismuth or an alloy thereof.
Information recording medium as described. 5. The information recording medium according to claim 1, wherein the infrared absorption layer contains an infrared light absorption dye represented by the following general formula (1). Embedded image