JPH08216518A - Reversible data recording medium - Google Patents

Abstract

PURPOSE: To obtain a reversible data recording medium enabling the recording/ reproduction/erasure in an invisible wavelength region and capable of holding invisible and variable data by laminating a concealing layer at least absorbing light of a visible region and permitting the near infrared region of the recording wavelength and reading wavelength of a thermal recording layer to transmit. CONSTITUTION: A reversible data recording medium 1 is constituted by providing a thermal recording layer 3, a light and heat absorbing layer 4 on the single surface of a base material 2. The concealing layer 5 permits infrared rays capable of being read by an infrared sensor to transmit and absorbs visible light impossible to discriminate a recording image by visual observation. The concealing layer 5 may be one wherein the transmissibility of infrared rays is larger than that of visible light or one excellent in the sensitivity of an infrared sensor or one wherein the discrimination of a recording image is difficult by visual observation but possible by an infrared sensor even if the transmissivity of infrared rays is smaller than that of visible light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible information recording medium which is invisible and is capable of recording, reproducing and erasing information in the infrared region, and particularly invisible information in a non-contact state by a laser or the like. The present invention relates to a reversible information recording medium capable of recording.

[0002]

2. Description of the Related Art In recent years, securities fields such as stock certificates, bonds, checks, gift certificates, lottery tickets, admission tickets, boarding tickets, coupon tickets, commuter tickets, ID cards, credit cards, cash cards,
With the widespread use of card fields such as prepaid cards, there is a demand for security technology that can effectively prevent these from the possibility of forgery, falsification, and alteration, and that can easily discriminate their authenticity. There is.

That is, the magnetic recording technology that is currently the mainstream of information recording means is characterized in that reversible recording and mechanical recording and reproduction are possible.
Although it is difficult to read by visual observation due to its physical properties, it is possible to intentionally erase or rewrite information due to the widespread use of magnetic recording / reproducing devices (magnetic readers / writers) in the general public. Many fraud prevention technologies that make it difficult have been proposed.

For example, as described in Japanese Utility Model Application Laid-Open No. 63-153317, a low coercive force layer is provided between a base material and a high coercive force layer, which makes it difficult to perform reproduction / recording by ordinary magnetic recording / reproducing means. In some cases, fixed information as described in Japanese Patent Laid-Open No. 61-136188 is recorded on a card and the fixed information is used to encrypt information by a specific algorithm. Or the special table Sho 63-50125
No. 0, Japanese Patent Laid-Open No. 6-32091, etc., means for identifying the existence by magnetism or high frequency is arranged on an information recording medium, and collation information is obtained from information unique to the information recording medium itself. There is a method in which the authenticity is determined from the comparison with the comparison information which is calculated and recorded in advance.

Optically, a copy prevention technique corresponding to the copy technique which has undergone remarkable technological innovation in recent years has been studied. One of them is a hologram or a diffraction grating (Japanese Patent Laid-Open No.
No. 233,684), and setting of the size of halftone dots (Japanese Patent Laid-Open No. Sho 5
Although there are some that make complete copying difficult according to Japanese Patent Laid-Open No. 3-145577), these are fixed information and cannot display variable information. Further, as a reversible information recording means, a thermal recording technique mainly using a thermal head, an optical recording technique utilizing light, etc. are widely used. Especially, the former is disclosed in JP-A-55-119377 and JP-A-55-
Although it is a visible information recording technology capable of reversible recording and erasing as described in 1454198, etc., it has a problem that a scanning trace of a heating printing means such as a thermal head remains on the recording surface. Japanese Patent Application No. 5-2292 filed by the applicant
As described in No. 11, by absorbing light, converting it to heat and indirectly performing thermal recording, the problem of causing a scanning trace of the heating printing means such as the thermal head is solved, but the information is Since it is visible, there is a problem of confidentiality of information.

[0006]

However, although each of the above fraud prevention means has a useful aspect, variable information unique to each medium can be recorded as invisible, and a complicated recording / reproducing means is required. However, there is a problem that it is difficult to use as an information recording medium that can surely repeat recording / reproducing / erasing without requiring the recording.

Therefore, the present invention has been made in order to solve the above problems, and provides an information recording medium capable of recording / reproducing / erasing in an invisible wavelength region and capable of holding invisible and variable information. The purpose is to provide.

[0008]

In order to achieve the above-mentioned object, the invention described in claim 1 is such that, on a base material, a colored portion by heating exhibits infrared absorption and exhibits absorption of an uncolored portion. A heat-sensitive recording layer capable of reversibly developing and erasing a recording image by a difference, a photothermal conversion layer which absorbs in at least a part of the infrared region and transmits in other infrared regions, at least visible The reversible information recording medium is characterized in that a concealing layer which absorbs light in a region and transmits in the near infrared region of the recording wavelength and the reading wavelength of the thermosensitive recording layer is laminated.

The invention described in claim 2 is characterized in that:
A recorded image is formed by the difference in absorption between the photothermal conversion layer that absorbs in at least a part of the infrared region and transmits in the other infrared region, and the color-developed part that is heated by infrared absorption and the uncolored part And a concealment layer that absorbs at least light in the visible region and transmits in the near-infrared region of the recording wavelength and the reading wavelength of the thermosensitive recording layer. It is a characteristic reversible information recording medium.

According to the invention described in claim 3, on a substrate,
The color-developed portion due to heating exhibits infrared absorption, and a reversible color-erasable thermosensitive recording member that constitutes a recorded image by a difference in absorption from an uncolored portion, and exhibits absorption in at least a part of the infrared region, And in the other region, a heat-sensitive recording layer containing a photothermal conversion member that transmits, and a concealing layer that absorbs at least light in the visible region and transmits in the near infrared region of the recording wavelength and the reading wavelength of the heat-sensitive recording layer. It is a reversible information recording medium characterized by being laminated.

The invention described in claim 4 is the invention according to claim 1,
In the reversible information recording mediums described in 2 and 3, a leuco compound in which the heat-sensitive recording layer exhibits absorption in the infrared region during color development,
Having at least one of a phenolic hydroxyl group and a carboxyl group in the color-developing agent, and containing an amphoteric compound having an amino group as a functional group or as a part of a salt compound,
It is characterized by being composed of a reversible thermosensitive recording material that develops and erases color depending on the difference in thermal energy.

The invention described in claim 5 is the same as claim 1,
The reversible information recording mediums described in 2 and 3 are characterized in that the absorption wavelength in the infrared region of the colored portion of the thermosensitive recording layer is different from the absorption wavelength in the infrared region of the photothermal conversion layer.

[0013]

According to the reversible information recording medium described in claims 1 and 2 of the present invention, the absorption wavelength region of the photothermal conversion layer is matched from the thermosensitive recording layer and the photothermal conversion layer according to the information pattern to be recorded. The amount of reflected light generated from the information recording in which the heat-sensitive recording layer develops color due to the heat generated by the light-heat converting layer and the contrast between the colored portion and the uncolored portion of the heat-sensitive recording layer that is irradiated with light having a different absorption wavelength. It is possible to reversibly repeat the information reproduction by the difference of the above and the information erasing by applying the heat energy different from that at the time of the information recording to the thermosensitive recording layer. Further, the hiding layer makes it difficult to visually recognize the information pattern generated in the heat-sensitive recording layer, and does not affect the recording / reproducing / erasing of information by transmitting only light in the infrared region.

According to the reversible information recording medium of the third aspect of the present invention, the light-heat converting member is absorbed according to the information pattern recorded in the heat-sensitive recording layer containing the light-heat converting member and the heat-sensitive recording member. Irradiating light that matches the wavelength region, information recording in which the thermosensitive recording member develops color due to heat generation of the photothermal conversion member layer, and irradiation of light having a different absorption wavelength of the photothermal conversion member,
Reproduction of information by the difference in the amount of reflected light caused by the contrast between the colored portion and the uncolored portion of the thermosensitive recording layer and the erasure of information by applying heat energy different from that during information recording to the thermosensitive recording member via the photothermal conversion member are reversible. Can be repeated repeatedly. Further, the hiding layer makes it difficult to visually recognize the information pattern generated in the heat-sensitive recording layer, and does not affect the recording / reproducing / erasing of information by transmitting only light in the infrared region.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a partially enlarged cross-sectional view showing the first constitution of the reversible raw information recording medium of the present invention, and FIG.
It is a partial expanded sectional view which shows the 2nd structure of the reversible raw information recording medium of this invention, and FIG. 3 is a partial expanded sectional view which shows the 3rd structure of the reversible raw information recording medium of this invention.

That is, as shown in FIG. 1, the reversible information recording medium 1 of this embodiment has a structure in which a heat sensitive recording layer 3, a light and heat absorbing layer 4 and a concealing layer 5 are provided on one side of a substrate 2. .

As the base material 2, a transparent or opaque polyethylene terephthalate (PET) film, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, synthetic resin such as polystyrene, natural resin,
Materials such as paper, synthetic paper and glass can be used alone or as a composite. It is preferable to reflect light having a wavelength in the infrared region which is transmitted.

Further, the photothermal absorption layer 4 absorbs light having a specific wavelength in the infrared region or near infrared region, and transmits light in other wavelength regions other than that. Is converted into heat and is used as a means for recording information on the heat-sensitive recording layer 3 by the generated heat. In this embodiment, the photothermal absorption layer 4 is formed of an ink containing a dye / pigment that absorbs light having a specific wavelength in the infrared region. The forming method is a known coating method such as an offset printing method, a screen printing method and a gravure printing method.

Dyes / pigments which absorb light in this infrared region or a specific wavelength in the near infrared region, for example, in the vicinity of 780 to 830 nm, include cyanine type, pyrylium type, thiopyrylium type, squarylium type, croconium type. , Azurenium-based polymethine dyes, phthalocyanine dyes, naphthalocyanine dyes, dithiol metal complex dyes, naphthoquinone dyes, anthraquinone dyes, triphenylmethane dyes, aminium dyes, organic dyes such as diimmonium dyes Other than the above, it is possible to use an inorganic pigment such as a metal oxide, a metal hydroxide, or a powder of heat ray absorbing glass. The substance is appropriately selected from these depending on the application, but substances other than the above are not particularly limited as long as they have the above characteristics.

In the case of the offset printing method, the ink may be a transparent medium which does not absorb in the near-infrared / infrared region other than the absorption wavelength region of the above-mentioned dyes / pigments as a binder, alkyd resin, acrylate resin, etc. An ink appropriately selected from the above dyes and pigments is put therein, and kneaded, dissolved or dispersed using a three-roll or the like to obtain an ink.

In the case of screen printing, the ink is a polyester-based, acrylic polyol-based, urethane-based, etc. which does not absorb in the near infrared / infrared region other than the absorption wavelength region of the above dyes / pigments as a binder. -Combine appropriately selected pigments, knead using a three-roll, etc.,
Dissolve or disperse into ink.

In the case of the gravure printing method, the ink is a vinyl chloride-vinyl acetate copolymer resin, saturated polyester resin, polyurethane having no absorption in the near infrared / infrared region other than the absorption wavelength region of the above dye / pigment as a binder. An elastomer resin or the like is used, and those appropriately selected from the above dyes and pigments are combined and kneaded, dissolved or dispersed using a three-roll roll or the like to obtain an ink. The printing methods are not limited to the above. Further, a defoaming agent or the like can be added as an additive.

The solvent used for diluting the above ink to an appropriate viscosity suitable for each printing method is toluene, methyl isobutyl ketone, xylene, cyclohexanol, isobutyl acetate, cyclohexanone, methylcyclohexanone,
Examples thereof include glycol derivatives such as ethylene glycol monobutyl ether, and mixed solutions thereof.

Next, the heat-sensitive recording layer 3 is formed by coating a reversible heat-sensitive recording material containing at least a leuco compound, an amphoteric compound as a color-developing and color-reducing agent, and a binder, which exhibits absorption in the infrared region during color development. In addition, reversible thermosensitive recording materials other than the above may be used as long as they exhibit absorption in the infrared region during recording (color development). Examples of the leuco compound include fluorene compounds, fluoran compounds, and phthalide derivatives. Specific examples include crystal violet lactone, 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluorane, 2- (2-fluorophenylamino) -6-diethylamino. Fluoran,
2- (2-fluorophenylamino) -6-di-n-butylaminofluorane, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5
-Methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6 -Chlorofluorane, 2-anilino-3-methyl-6- (N-ethyl-
p-toluidino) -fluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-pyrrolidino-7
-Cyclohexylaminofluorane, 3-N-methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-N-ethylpentylamino-6-methyl-7
Anilino fluoran etc. can be mentioned.

The amphoteric compound acting as a color-developing agent for the leuco compound has at least one of a phenolic hydroxyl group and a carboxyl group, and has an amino group as a functional group or as a part of a salt compound. is there. The amphoteric compound has at least one of a phenolic hydroxyl group and a carboxyl group and an amino group, and is a compound represented by the following general formula (1), or a compound having at least one phenolic hydroxyl group and / or a carboxyl group. And a complex salt of an aliphatic amine.

[0026]

Embedded image (In the formula, X represents a hydroxyl group or a carboxyl group, and R represents a hydrogen atom or a hydroxyl group.)

Furthermore, as an amphoteric compound having at least one of a phenolic hydroxyl group and a carboxyl group and an amino group and represented by the above general formula (1), an aminophenol or aminobenzoate represented by the following general formula (2) Examples thereof include acids or hydroxyaminobenzoic acid represented by the following general formula (3).

[0028]

Embedded image (In the formula, X represents a hydroxyl group or a carboxyl group.)

[0029]

Embedded image

Specific examples of the aminophenol or aminobenzoic acid represented by the above general formula (2) are 2-
Examples thereof include aminophenols, aminophenols such as 3-aminophenol and 4-aminophenol, and aminobenzoic acids such as 2-aminobenzoic acid, 3-aminobenzoic acid and 4-aminobenzoic acid. Examples of the hydroxyaminobenzoic acid represented by the general formula (3) include 2
-Hydroxy-3-aminobenzoic acid, 2-amino-3-
Hydroxybenzoic acid, 2-amino-4-hydroxybenzoic acid, 2-hydroxy-4-aminobenzoic acid, 2-hydroxy-6-aminobenzoic acid, 3-amino-4-hydroxybenzoic acid, 3-hydroxy-5- Aminobenzoic acid etc. can be mentioned.

Further, in the salt or complex salt of the compound having at least one phenolic hydroxyl group and / or carboxyl group and the aliphatic amine, as the compound having at least one phenolic hydroxyl group and / or carboxyl group, the following general formula ( The compounds represented by 4) or (5) and ester compounds of these compounds can be mentioned.

[0032]

[Chemical 4] (In the formula, n represents an integer of 1 to 3, preferably 2 or 3.)

[0033]

Embedded image (In the formula, R ₁ represents a hydrogen atom or a methyl group, and n ₁ is 0.
Represents an integer of 6; )

Specific examples of the compound represented by the above general formula (4) include the following. n = 1: 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, etc. n = 2: 3,4-dihydroxybenzoic acid 3,5-dihydroxybenzoic acid 2,3-dihydroxybenzoic acid 2,4 -Dihydroxybenzoic acid 2,5-dihydroxybenzoic acid 2,6-dihydroxybenzoic acid 3,6-dihydroxybenzoic acid 4,5-dihydroxybenzoic acid 4,6-dihydroxybenzoic acid 3,5-dihydroxybenzoic acid 4-hydroxysalicylic acid 5-hydroxysalicylic acid n = 3: gallic acid

Specific examples of the ester compound of the compound represented by the above general formula (4) include the following. Hexyl gallate, heptyl gallate, octyl gallate, nonyl gallate, decyl gallate, undecyl gallate, lauryl gallate, tridecyl gallate, tetradecyl gallate, pentadecyl gallate, cetyl gallate, gallic acid heptadecyl, gallic acid Stearyl and the like can be mentioned.

Specific examples of the compound represented by the above general formula (5) include the following. 2,2-bis (4-hydroxyphenyl) ethanoic acid 2,2-bis (4-hydroxyphenyl) propionic acid 3,3-bis (4-hydroxyphenyl) propionic acid 4,4-bis (4-hydroxyphenyl) Butanoic acid 4,4-bis (4-hydroxyphenyl) heptanoic acid 5,5-bis (4-hydroxyphenyl) pentanoic acid 5,5-bis (4-hydroxyphenyl) hexanoic acid 6,6-bis (4-hydroxy) Phenyl) heptanoic acid 7,7-bis (4-hydroxyphenyl) heptanoic acid 8,8-bis (4-hydroxyphenyl) octanoic acid 7,7-bis (4-hydroxyphenyl) octanoic acid 8,8-bis (4 -Hydroxyphenyl) nonanoic acid

In the salt or complex salt of the compound having at least one phenolic hydroxyl group and / or carboxyl group with the aliphatic amine, the aliphatic amine is
Examples thereof include compounds represented by the following general formula (6) or (7).

[0038]

[Chemical 6] (In the formula, R ₂ represents an alkyl group having 8 or more carbon atoms.)

[0039]

[Chemical 7] (In the formula, R ₃ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, and n ₂ represents an integer of 1 to 18.)

Specific examples of the aliphatic amine represented by the above general formula (6) include octylamine, nonylamine,
Examples thereof include decylamine, undecylamine, laurylamine, tridecylamine, tetradecylamine, pentadecylamine, heptadecylamine, heptadecylamine, cetylamine, stearylamine, hexylamine and heptylamine.

Specific examples of the aliphatic amine represented by the above general formula (7) include benzylamine 2-phenylethylamine, 3-phenylpropylamine, 4-phenylbutylamine, 5-phenylpentylamine and 6-phenylhexyl. Amine, 7-phenylheptylamine, 8
-Phenyloctylamine, 9-phenylnonylamine, 10-phenyldecylamine, 11-phenylundecylamine, 12-phenyldodecylamine, 13-
Phenyltridecylamine, 14-phenyltetradecylamine, 15-phenylpentadecylamine, 16-
Phenylhexadecylamine, 17-phenylheptadecylamine, 18-phenyloctadecylamine, methylbenzylamine, 2-triethylamine, 3-tolylpropylamine, 4-tolylbutylamine, 5-tolylpentylamine, 6-hexylamine, 7- Trilylheptylamine, 8-tolyloctylamine, 9-tolylnonylamine, 10-tolyldecylamine, 11-tolylundecylamine, 12-tolyldecylamine, 13
-Tolyltridecylamine, 14-tolyltetradecylamine, 15-tolylpentadecylamine, 16-tolylhexadecylamine, 17-tolylheptadecylamine, 18-tolyloctadecylamine, chlorobenzylamine, 2-chlorophenylethylamine, bromo Examples thereof include benzylamine, 2-bromophenylethylamine, methoxybenzylamine, ethoxybenzylamine and the like. The number of carbon atoms of R _{2 in} the general formula (7) is 7
In the following cases, the melting point may be high and it may be difficult to erase the color,
Not preferred.

The following are preferable salts or complex salts of the above-mentioned compound having at least one phenolic hydroxyl group and / or carboxyl group with an aliphatic amine. For example, a salt of dihydroxybenzoic acid represented by the following general formula (8) and a higher aliphatic amine having an alkyl group having 8 or more carbon atoms, gallic acid and a higher aliphatic amine represented by the following general formula (9) Salt with the following general formula (1
0) a salt of hydroxybenzoic acid or dihydroxybenzoic acid with an aliphatic amine, a salt of gallic acid represented by the following general formula (11) with an aliphatic amine, represented by the following general formula (12) Salt of bis (hydroxyphenyl) acetic acid or bis (hydroxyphenyl) butyric acid with a higher aliphatic amine, a salt of an aliphatic amine having two hydroxyphenyl groups represented by the following general formula (13), or There is a complex salt of a gallic acid ester represented by the general formula (14) and a higher aliphatic amine.

[0043]

Embedded image (In the formula, R ₄ represents an alkyl group having 8 or more carbon atoms.)

[0044]

[Chemical 9] (In the formula, R ₅ represents an alkyl group having 8 or more carbon atoms.)

[0045]

[Chemical 10] (In the formula, R ₆ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, n ₂ is 1 or 2, and n ₃ is 1 to 2.
Represents an integer of 18. )

[0046]

[Chemical 11] (In the formula, R ₇ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, and n ₄ represents an integer of 1 to 18.)

[0047]

[Chemical 12] (In the formula, R ₈ represents a hydrogen atom or a methyl group, and R ₉ represents an alkyl group having 8 or more carbon atoms.)

[0048]

[Chemical 13] (In the formula, R ₁₀ represents a hydrogen atom or a methyl group, R ₁₁ represents a hydrogen atom, an alkyl group, a halogen atom or an alkoxy group, n ₅ represents an integer of 0 to 6, and n ₆ represents an integer of 1 to 18. )

[0049]

Embedded image (In the formula, R ₁₂ and R ₁₃ each represent an alkyl group having 8 or more carbon atoms.)

Further, as the binder, a generally used polymer material which is soluble in water or an organic solvent can be used. As such a polymer material, specifically, polyvinyl alcohol, methyl cellulose, ethyl cellulose, cellulose acetate, polystyrene, polyvinyl chloride, linear saturated polyester, polymethyl methacrylate,
There are homopolymers or copolymers of methacrylic resins such as polyethylmethacrylate, and thermoplastic resins such as polyurethane, polybutyral and nitrocellulose.

The binder is dissolved in a coating liquid in which the above leuco compound or amphoteric compound is uniformly dispersed or dissolved in water or an organic solvent, and if necessary, a liquid property of a dispersant, a defoaming agent, a thickener and the like. The heat-sensitive recording layer 3 is formed by applying a coating solution containing an improving agent by a known coating method such as bar coating, blade coating, air knife coating, gravure coating, or roll coating and drying. Color development of this system
The color-developing / reducing agent in the erasing mechanism exhibits alkalinity by itself. However, the reaction rate at which the acidic component opens the lactone ring of the leuco compound is faster than the reaction rate at which the basic component closes the ring. Therefore, the chromophore is melted by heating and the lactone ring is preferentially cleaved by the acidic component (for example, a hydrogen ion is released from the phenolic hydroxyl group or the carboxyl group of the chromophore and reacts with the leuco compound to give a leuco compound. Is open). Next, ring closure occurs due to the basic component, but the heat rapidly spreads due to high-speed point heating and is rapidly cooled, so it is fixed in a colored state. In the case of gradual cooling, it is considered that after the ring is once opened, the basic component closes the ring and tilts to decolorize the leuco body (for example, hydrogen ions are deprived by the action of the amino group of the color-developing / reducing agent and leuco compound is removed). The compound is closed). That is, the color develops when heated and rapidly cooled, and the color disappears when heated and gradually cooled. This coloring / decoloring occurs reversibly and can be repeated. That is, the reversible color development / decolorization has an action of causing infrared absorption ability in a wavelength region other than the absorption wavelength of the photothermal conversion layer 4 due to color development and losing the infrared absorption ability due to color disappearance.

The concealing layer 4 is a layer for visually concealing changes in layers below this layer, and absorbs a large amount at least in the visible region, and is optically in the infrared region, particularly in the recording wavelength and the reading wavelength. It is necessary that the material has a spectrum that can be regarded as transparent or almost transparent.

That is, the concealing layer 4 transmits infrared rays that can be read by an infrared sensor and absorbs visible rays to the extent that a recorded image cannot be visually identified. If the transmittance of visible light is higher or the sensitivity of the infrared sensor is excellent, even if the transmittance of infrared light is lower than the transmittance of visible light, it is difficult to visually identify the recorded image. Anything can be used as long as it can be identified by an infrared sensor.

Typical materials include, for example, a gelatin film, a paint containing an infrared-transmissive dye such as Orazole Black BV, Orazole 2RG, yellow ink, and red ink,
It is possible to use a black or gray ink made by mixing printing inks that do not absorb in the infrared region, such as indigo ink. These can be provided by a known coating method such as a gravure printing method, a screen printing method and an offset printing method.

Although not shown, a protective layer that protects the lower layer can be provided. For example, acrylic resin, urethane resin, vinyl chloride-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin,
Based on conventionally known synthetic resins such as polystyrene resins or natural resins, as a material for improving the resistance, isocyanate-based curing agents, waxes such as polyethylene wax and carnauba wax, calcium carbonate, silica, alumina It is possible to add and use extender pigments such as and the like, oils and fats of silicone oils and fats, etc. within a range not impairing transparency. A barrier layer may be provided between the heat-sensitive recording layer 3 and the light-heat converting layer 4 in order to suppress color development of the heat-sensitive recording layer due to the solvent contained in the ink forming the light-heat converting layer. For example, any material such as a water-based urethane resin that prevents the elution of the solvent may be used.

For recording information on the reversible information recording medium 1, a light source that oscillates infrared light, for example, a semiconductor laser is used as a light source, or the light source is set so as to match the absorption characteristics of the photothermal conversion layer 4, or It is desirable to set the material of the photothermal conversion layer 4 so as to match the absorption characteristics of infrared light. When heat energy (h1) generated by the heat generation of the photothermal conversion layer 4 is applied to the heat-sensitive recording layer 3 at a high temperature for a short time (several millimeters to several hundreds of milliseconds), a color is formed and a recorded image is formed. When heat energy (h2) different from that at the time of recording is applied to this recorded image, for example, at a low temperature (around the melting point of the color-developing / reducing agent or higher) for a long time (1 second or more), the heat-sensitive recording layer 3 is applied. , The colored portion is erased and the recorded image is erased. Further, when heat energy (h1) is applied to the erased heat-sensitive recording layer 3 in the same manner, it is possible to repeatedly perform formation / erasure of a recorded image so that a recorded image is formed, and the thermal energy is reduced. The recording image forming state or the recording image erasing state is maintained unless it is acted upon. Therefore, the recording image formation and the recording image erasing are performed by controlling the thermal energy.

Further, since the absorption characteristics of the photothermal conversion layer 4 are transmitted except for the specific wavelength, when reproducing the information, when a wavelength different from the wavelength at the time of recording the information is irradiated, it is incident on the uncolored portion of the thermosensitive recording layer 3. The reflected infrared light is reflected and scattered, but the incident infrared light is not absorbed and reflected at the colored area.Therefore, the contrast between the colored area that absorbs the infrared light and the uncolored area that does not absorb the infrared light The recorded information is reproduced due to the difference in the amount of reflected light that occurs. The reflected infrared light can be detected by an infrared sensor.

In the reversible information recording medium 11 of the second structure of the present invention shown in FIG. 2, a light and heat absorbing layer 14, a heat sensitive recording layer 13, and a concealing layer 15 are sequentially provided on one surface of a base material 12. In addition, it has a configuration in which the arrangement of the light-heat absorbing layer and the heat-sensitive recording layer is changed from the first configuration. That is, since infrared light emitted from the outside passes through the hiding layer 15 and the heat-sensitive recording layer 13 and enters, the hiding layer 15 and the heat-sensitive recording layer 13 are transparent to the infrared light. It is a thing. The heat-sensitive recording layer 13 may be any one as long as it transmits the infrared wavelengths absorbed in the light-heat absorbing layer 14, and the same composition and forming method as the above-mentioned first structure can be used. For the light-heat absorbing layer 14 and the concealing layer 15, the same composition and forming method as the first structure can be used.

Further, in the reversible information recording medium 21 of the third constitution of the present invention shown in FIG. 3, the heat sensitive recording layer 23 also serving as the light and heat absorbing layer and the concealing layer 24 are sequentially provided on one surface of the base material 22. It has a specific configuration. The heat-sensitive recording layer 23 also serving as the light-heat absorbing layer is prepared by dispersing or dissolving a dye / pigment that absorbs light at a specific wavelength in the infrared region in the reversible heat-sensitive recording material used in the first structure. Although it can be used as a heat-sensitive recording layer that also has a function as a light-to-heat conversion layer, it is required to use a dye / pigment that does not cause color development of the reversible heat-sensitive recording material at times other than recording such as storage. .

Hereinafter, specific examples of the present invention will be described in detail. <Example 1> As shown in FIG. 1, a heat-sensitive recording layer 3 having the following composition was provided on a white base material 2 made of polyethylene terephthalate (PET) to a thickness of 6 μm by a gravure printing method, and the heat-sensitive recording layer 3 was placed in an oven at 50 ° C. After being dried, a photothermal conversion layer 4 having the following composition was provided to a thickness of 2 μm by a gravure printing method, dried in an oven at 50 ° C. and cured for 48 hours. Further, a concealing layer 5 having the following composition was provided to a thickness of 2 μm by an offset printing method, and the coating film was cured by irradiating with ultraviolet rays to prepare a reversible information recording medium 1 of the present invention. Composition of heat-sensitive recording layer Leuco compound [tri (p-aminophenyl) fluorene] 4 parts Color-developing agent (amphoteric compound) [4,4-bis (4-hydroxyphenyl) heptanoic acid 8 parts Salt of aminoethylbenzene]

[0061]

[Chemical 15]

Binder [thermoplastic acrylic resin] 8 parts Solvent [toluene] 80 parts ○ Composition of photothermal conversion layer Infrared absorber [cyanine dye CY-20 manufactured by Nippon Kayaku Co., Ltd.] 2 parts Binder [acrylic resin BR-56 Mitsubishi Rayon Co., Ltd.] 18 parts Hardener [Isocyanate hardener D24A100 manufactured by Asahi Kasei] 2 parts Solvent [Toluene] 78 parts ○ Composition of hiding layer Gray ink by mixing three process inks below Yellow ink [RT-7 Yellow Dai Nippon Ink Co., Ltd.] 40 parts Beni Ink [RT-7 Beni Dai Nippon Ink Co., Ltd.] 30 parts Indigo ink [RT-7 Indigo Dai Nippon Ink Co., Ltd.] 30 parts

Information was recorded by irradiating the above reversible information recording medium 1 with laser light having a wavelength of 780 nm and an output of 150 mW from a semiconductor laser according to a pattern such as letters, numbers and marks. This information recording was not visible, but when the information was reproduced with an IR scope (made by Ikegami Tsushinki Co., Ltd.) through a visible light cut filter that transmits only light of 850 nm or more, the recorded pattern was recognized. Was done. Furthermore, the entire surface of the reversible information recording medium 1,
At least the surface of the heat-sensitive recording layer is heated and pressed with a hot stamp plate heated to 120 ° C. for 1 second to erase information.
When information was reproduced with an IR scope (made by Ikegami Communication Equipment Co., Ltd.) through a visible light cut filter that transmits only light of m or more, the recorded pattern was not recognized. When this recording / erasing operation was repeated 50 times, it was confirmed that recording / erasing could be performed reliably.

Example 2 As shown in FIG. 2, a white base material 12 made of polyethylene terephthalate (PET) 12 is used.
Then, the photothermal conversion layer 4 having the composition of Example 1 was provided to a thickness of 2 μm by a gravure printing method, and the coating film was cured for 48 hours after drying in an oven at 50 ° C. Next, the heat-sensitive recording layer 14 having the composition of Example 1 was formed to a thickness of 6 μm by the gravure printing method, and dried in an oven at 50 ° C. atmosphere. Further, the concealing layer 5 having the composition of Example 1 was provided to a thickness of 2 μm by the offset printing method, and the coating film was cured by irradiation with ultraviolet rays to prepare the reversible information recording medium 11 of the present invention.

Information was recorded by irradiating the reversible information recording medium 11 with laser light having a wavelength of 780 nm and an output of 150 mW according to a pattern such as letters, numbers and marks. This information recording was not visible, but when the information was reproduced with an IR scope (made by Ikegami Tsushinki Co., Ltd.) through a visible light cut filter that transmits only light of 850 nm or more, the recorded pattern was recognized. Was done. Further, the entire surface of the reversible information recording medium 11, at least the surface of the heat-sensitive recording layer, is heated and pressed with a hot stamp plate heated to 120 ° C. for 1 second to erase information.
When information was reproduced with an IR scope (manufactured by Ikegami Tsushinki Co., Ltd.) through a visible light cut filter that transmits only light of 0 nm or more, the recorded pattern was not recognized.
When this recording / erasing operation was repeated 50 times, it was confirmed that recording / erasing could be performed reliably.

Example 3 As shown in FIG. 3, a white base material 22 made of polyethylene terephthalate (PET) 22.
A heat-sensitive recording layer 23 having the following composition was provided by a gravure printing method to a thickness of 6 μm, and dried in an oven at 50 ° C. Further, a concealing layer 5 having the composition of Example 1 was provided to a thickness of 2 μm by an offset printing method, and the coating film was cured by irradiation with ultraviolet rays, and then the reversible information recording medium 2 of the present invention.
1 was produced. Composition of heat-sensitive recording layer Leuco compound [tri (p-aminophenyl) fluorane] 4 parts Color-developing agent [4,4-bis (4-hydroxyphenyl) heptanoic acid 10 parts Salt of aminoethylbenzene]

[0067]

Embedded image

Infrared absorber [cyanine dye CY-20 manufactured by Nippon Kayaku Co., Ltd.] 1 part Binder [thermoplastic acrylic resin] 10 parts Solvent [toluene] 100 parts

Information was recorded by irradiating the reversible information recording medium 21 with a laser beam having a wavelength of 780 nm and an output of 150 mW from a semiconductor laser according to a pattern such as letters, numbers and marks. This information recording was not visible, but when the information was reproduced with an IR scope (made by Ikegami Tsushinki Co., Ltd.) through a visible light cut filter that transmits only light of 850 nm or more, the recorded pattern was recognized. Was done. Further, the entire surface of the reversible information recording medium 21, at least the surface of the heat-sensitive recording layer, is heated and pressed for 1 second by a hot stamp plate heated to 120 ° C. to erase information.
When information was reproduced with an IR scope (manufactured by Ikegami Tsushinki Co., Ltd.) through a visible light cut filter that transmits only light of 0 nm or more, the recorded pattern was not recognized.
When this recording / erasing operation was repeated 50 times, it was confirmed that recording / erasing could be performed reliably.

[0070]

As described above, according to the reversible information recording medium of the present invention, by combining the heat-sensitive recording layer, the light-heat conversion layer and the concealing layer, the coloring region of which absorbs light in the infrared region, By combining the thermal recording layer also as the conversion layer with the concealing layer, it is possible to record variable information peculiar to each medium in which it is difficult to detect the information pattern generated in the thermal recording layer and only the light in the infrared region is recorded. In the invisible state, the recording is performed indirectly by coloring the thermosensitive recording layer according to the information pattern to be recorded, and light with a wavelength different from the absorption wavelength of the photothermal conversion layer is irradiated, and the colored and uncolored portions of the thermosensitive recording layer are irradiated. Reversible repetition of the reproduction of information from the difference in the amount of reflected light caused by the contrast in, and the erasing by applying heat energy different from that at the time of information recording to the thermosensitive recording layer. Can order, forgery, alteration, forgery becomes difficult, it is possible to prevent the fraud.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view showing a first configuration of a reversible raw information recording medium of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a second configuration of the reversible raw information recording medium of the present invention.

FIG. 3 is a partially enlarged sectional view showing a third configuration of the reversible raw information recording medium of the present invention.

[Explanation of symbols]

1, 11, 21 Reversible raw information recording medium 2, 12, 22 Base material 3, 14 Thermosensitive recording layer 4, 13 Photothermal conversion layer 5, 15, 24 Concealing layer 23 Thermal recording layer also serving as photothermal absorption layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G06K 19/00 R

Claims (5)

[Claims] 1. A heat-sensitive recording layer capable of reversibly developing and erasing a color image on a base material, wherein a color-developed portion by heating exhibits infrared absorption and a recorded image is formed by a difference in absorption from an uncolored portion. A photothermal conversion layer that absorbs in at least a part of the region and transmits in the other infrared region, and absorbs at least light in the visible region and transmits in the near infrared region of the recording wavelength and reading wavelength of the thermosensitive recording layer. A reversible information recording medium, comprising a concealing layer that is laminated. 2. A photothermal conversion layer which exhibits absorption in at least a part of the infrared region and transmits it in the other infrared region, and a color-developed portion by heating exhibits infrared absorptivity and an uncolored portion. The heat-sensitive recording layer capable of reversibly developing and erasing the recorded image due to the difference in absorption with and absorbs at least light in the visible region and transmits the near-infrared region of the recording wavelength and the reading wavelength of the heat-sensitive recording layer. A reversible information recording medium, comprising a concealing layer that is laminated. 3. A heat-sensitive recording member capable of reversibly developing and erasing a color image on a base material, wherein a color-developed portion by heating exhibits infrared absorption and a recorded image is formed by a difference in absorption from an uncolored portion. A heat-sensitive recording layer containing a photothermal conversion member that exhibits absorption in at least a part of the region, and a concealment that absorbs at least light in the visible region and transmits in the near-infrared region of the recording wavelength and reading wavelength of the heat-sensitive recording layer. A reversible information recording medium comprising a stack of layers. 4. A leuco compound, wherein the heat-sensitive recording layer exhibits absorption in the infrared region during color development, and a color-developing / reducing agent having at least one of a phenolic hydroxyl group and a carboxyl group, and an amino group as a functional group. The reversible thermosensitive recording material according to claim 1, 2, or 3, which comprises a reversible thermosensitive recording material containing an amphoteric compound as a part of a salt compound and capable of coloring and decoloring due to a difference in thermal energy. Information recording medium. 5. The absorption wavelength in the infrared region of the color-developed portion of the heat-sensitive recording layer and the absorption wavelength in the infrared region of the photothermal conversion layer are different from each other. Reversible information recording medium.