JPH04303678A - Thermal information recording medium - Google Patents

Abstract

PURPOSE:To enable two kinds of information to be recorded by using a second thermal color-forming material differing from a first thermal color-forming material in color forming temp. and having no light-absorbing characteristics in an infrared wavelength range at the time of color forming. CONSTITUTION:A thermal recording layer 3 is made of a mixture mainly composed of a first thermal color-forming material having light-absorbing characteristics in an infrared wavelength range at the time of color forming and a second thermal color-forming material differing from the first thermal color-forming material in color forming temp. and having no light-absorbing characteristics in an infrared wavelength range at the time of color forming. In this manner, two kinds of information 5, 6 can be recorded by changing a heating temp. The information can be read by a visible light or an infrared light.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a thermal information recording medium made of a plurality of thermosensitive coloring materials capable of recording information by thermosensitive coloring, and in particular, the present invention relates to a thermal information recording medium comprising a plurality of thermosensitive coloring materials capable of recording information by thermosensitive coloring, and in particular, a thermally colored portion of at least one thermosensitive coloring material is capable of absorbing infrared rays. The present invention relates to a thermal information recording medium having a reading prevention function and a forgery/tampering prevention function.

0002

[Prior Art] Conventionally, letters, numbers, and marks can be easily printed using a thermal head on a thermal recording medium that is formed by coating a thermal coloring material, such as a leuco dye or a diazo dye, on a base material such as paper or a plastic sheet. Because they can record information such as patterns and can be visually read, they were used to record information of low confidentiality or value, such as shopping stamps. That is, it is extremely easy to falsify or forge, and the amount of information that can be recorded is small, so its uses are limited.

[0003] In recent years, magnetic recording media, optical recording media,
Information recording media such as electronic recording media take the form of cards, such as credit cards, cash cards, and ID cards, because they can store a large amount of recorded information and can be written and read by machines. It is used in many fields as prepaid cards, train tickets, coupon tickets, commuter passes, etc. In particular, magnetic recording media are rapidly becoming popular due to their economic efficiency and stability.

By the way, although the above-mentioned information recording medium can be written and read by a machine, it is impossible for the owner of the information recording medium to read the information visually, and in order to confirm the recorded information, It was necessary to make the reading device read the information recording medium. Therefore, for the convenience of the cardholder, in order to make at least a part of the written information visible, printing means using ink on the surface of the information recording medium, or thermosensitive coloring recording using thermosensitive coloring materials such as leuco dyes and diazo dyes is used. A heat-sensitive recording layer is formed by heat-melting recording using a low-melting point metal material such as , Sn, Pb, or Cd, and information is recorded by a heating printing means. Currently, prepaid cards with a heat-sensitive recording layer formed on a magnetic recording medium are in practical use. Fixed information, identification information, balance information, etc. are recorded on the magnetic recording layer, and the heat-sensitive recording layer corresponds to the information on the magnetic recording layer. For example, a method is adopted in which the latest balance information is added.

[0005]

[Problems to be Solved by the Invention] However, although thermosensitive color recording is easy to record and is highly economical, it is also susceptible to counterfeiting, such as erasing recorded information with alcohol or organic solvents, or writing or rewriting false information with a thermal head. It has the disadvantage that it can be easily altered or tampered with. Further, although heating and melting recording is easy to record, has high weather resistance, and is highly stable, it is possible to easily falsify a part of the recorded information by deleting or adding. Furthermore, when combining a thermosensitive recording layer with a magnetic recording medium, the magnetic recording itself has become easily available due to the spread of magnetic card readers/writers, and reading, erasing, and rewriting of recorded information requires knowledge in the field. It is obvious that forgery, alteration, and falsification can be easily done if it is a genuine product. To prevent counterfeiting, a method of determining the authenticity of the information recording medium itself is to form a hologram on its surface or attach a sticker with a hologram formed on it, but it is not possible to read the hologram by a machine. There was no way to determine the authenticity of the visible information displayed on the heat-sensitive recording layer.

The present invention has been made to solve the above-mentioned problems, and is intended to prevent counterfeiting, falsification, and tampering of the displayed content of recorded information in a heat-sensitive recording layer, especially a heat-sensitive color recording, and the information recording medium. It is an object of the present invention to provide a heat-sensitive information recording medium that allows easy and accurate discrimination.

[0007]

[Means for Solving the Problems] The present invention, which has been made to achieve the above object, provides a thermal information recording medium of the first invention, which includes:
A first heat-sensitive coloring material having light absorption characteristics in the infrared wavelength region at least when coloring is formed on a sheet-like or plate-like base material; It is characterized in that it is formed by laminating a heat-sensitive recording layer made of a mixture whose main component is a second heat-sensitive coloring material having no light absorption characteristics in the wavelength range.

[0008] The heat-sensitive information recording medium of the second invention has a first heat-sensitive material on a sheet-like or plate-like base material, the main component of which is a heat-sensitive color-forming material having light absorption characteristics in the infrared wavelength region at least when coloring. A recording layer and a second heat-sensitive recording layer, which has a different color development temperature from the first heat-sensitive recording layer and whose main component is a heat-sensitive color-forming material that does not have light absorption characteristics in the infrared wavelength region during color development, are sequentially laminated. It is characterized by

[0009]

[Function] According to the first aspect of the present invention, when coloring the heat-sensitive recording layer, the first heat-sensitive coloring material having light absorption characteristics in the infrared wavelength region has a different coloring temperature from the first heat-sensitive coloring material, It is formed by a mixture whose main component is a second heat-sensitive coloring material that does not have light absorption characteristics in the infrared wavelength region when coloring, and by changing the heating temperature, two types of information can be recorded. It can be read using light or infrared light. In particular, when the same information is recorded in the same pattern, the recording at the coloring temperature of the first thermosensitive coloring material and the recording at the coloring temperature of the second thermosensitive coloring material, which is different from that coloring temperature, are at approximately the same position on the same surface. However, by irradiating the reading light in the visible wavelength region, the recording made by the first thermosensitive coloring material and the recording by the second thermosensitive coloring material are read, and by the irradiation with the reading light in the infrared wavelength region, the recording by the first thermosensitive coloring material and the recording by the second thermosensitive coloring material are read. It becomes possible to read only records made with thermosensitive color-forming materials. It is also possible to make the recordings partially overlap at the same position.

According to the second aspect of the invention, the first heat-sensitive recording layer is composed mainly of a first heat-sensitive color-forming material having light absorption characteristics in the infrared wavelength region when coloring the heat-sensitive recording layer; The heat-sensitive recording layer is formed by laminating a heat-sensitive color-forming material and a second heat-sensitive recording layer whose main component is a heat-sensitive color-forming material that has a different coloring temperature and does not have light absorption characteristics in the infrared wavelength region when coloring, and is separately separated from the heat-sensitive recording layer. Information can be recorded and read using visible or infrared light. In particular, when the same information is recorded in the same pattern, recording is performed on each thermosensitive recording layer at the coloring temperature of the thermosensitive coloring material of the first thermosensitive recording layer and at a different coloring temperature, so that the information is almost the same. By irradiating the reading light in the visible wavelength range, the record in the second heat-sensitive recording layer on the surface of the heat-sensitive information recording medium is read, and by further irradiating the reading light in the infrared wavelength range, It becomes possible to read only the records on the heat-sensitive recording layer.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of the thermal information recording medium of the present invention, and FIG. 2 is a sectional view of the thermal information recording medium of the present invention taken along line XX' in FIG.

In the figure, 1 is a thermosensitive information recording medium of the present invention, 2 is a base material, and 3 is a first thermosensitive coloring material having light absorption characteristics in the infrared wavelength region when coloring; This is a heat-sensitive recording layer mainly composed of a mixture of a heat-sensitive color-forming material and a second heat-sensitive color-forming material that has a different coloring temperature and does not have light absorption characteristics in the infrared wavelength region when coloring. This is a protective layer that protects from scratches and scratches, and is provided as necessary. Although not shown, the base material 2 is used to make it easier to detect the reflected light from the information pattern of the reading light in the infrared wavelength region.
An infrared reflective layer may be provided between the recording layer and the heat-sensitive recording layer 3, if necessary.

The base material 2 is in the form of a sheet or plate, and is made of polyvinyl chloride, polyethylene, polypropylene,
Plastics such as polyimide, polycarbonate, polyethylene terephthalate, polyester, polymethyl methacrylate, polystyrene, nylon, paper, mixed paper,
Papers such as synthetic paper, metals such as aluminum, copper, iron, etc. can be used alone or in combination to form a composite. The physical properties required for the base material, such as strength, rigidity, hiding property, and light transmittance, are appropriately selected from the above-mentioned materials depending on the intended use.

The heat-sensitive recording layer 3 is composed mainly of a heat-sensitive coloring material and a polymer binder. The thermosensitive coloring material has a first thermosensitive coloring material that has light absorption properties in the infrared wavelength region when coloring, and a second thermosensitive coloring material that has a different coloring temperature from the first thermosensitive coloring material and does not have light absorption properties in the infrared wavelength region when coloring. It is a mixture with a thermosensitive coloring material.

The second thermosensitive coloring material exhibits highly sensitive coloring characteristics having a coloring density-energy curve as shown in FIG. 3, and the first thermosensitive coloring material exhibits a coloring density-energy curve as shown in FIG.
It exhibits low-sensitivity color development characteristics with an energy curve, and develops color at higher energy (heating temperature) than the color development density-energy curve shown in FIG.

The heat-sensitive recording layer 3 of the present invention can be obtained by combining a heat-sensitive color-forming material comprising a heat-sensitive color-forming dye and a color developer described below. Furthermore, it is preferable that there is no difference in hue between the two thermosensitive coloring materials. Examples of heat-sensitive coloring dyes include organic metal salts, leuco dyes, and diazo dyes.Specifically, organic metal salts include nickel stearate, iron oleate, ferric stearate, and copper oleate; There are fluoran compounds, fluorene compounds, and phthalide derivatives.The fluoran compounds include 3-dimethylamino-6-methoxyfluoran, 7-acetamino-3-dimethylaminofluoran,
3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-5,7-dimethylfluorane, 3,
There is 6-bis-β-methoxyethoxyfluorane, fluorene-based compounds include 3-(p-aminophenyl)fluorene, and phthalide derivatives include 3,3-bis(p-
dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-nitrophthalide, 3,3
-Bis(p-dibutylaminophenyl)-phthalide. Further, color developers that develop color by acting with these agents include phenol, cresol, and hydroquinone. Examples of the polymer binder include acrylic resin, vinyl chloride resin, and polyester resin.

[0017] The first thermosensitive coloring material and the second thermosensitive coloring material can be prepared by appropriately combining dyes of the above compounds and color developers, for example, by encapsulating them in microcapsules.

In this example, a leuco dye was used. The second thermosensitive coloring material consists of a highly sensitive type coloring material with a relatively low melting point of a phthalide compound, a color developer, [3,3-bis(p-dimethylamino phenyl)-phthalide and benzyl p-hydroxybenzoate], the first thermosensitive coloring material has a melting point of a fluoran compound that exhibits a coloring density-energy curve as shown in FIG. 4, which does not overlap with the melting point of the second thermosensitive coloring material. We use an extremely low-sensitivity coloring material and developer, [3-(p-aminophenyl)fluorene and bisphenol S], each dispersed in an appropriate polymeric binder, such as polyester, and roll them. coat method, knife edge method,
The heat-sensitive recording layer 3 is formed to a thickness of about 4 to 10 μm using a coating or printing method such as a gravure printing method or a screen printing method.

The protective layer 4 has a protective effect against external scratches and scratches, and is made of acrylic resin, vinyl chloride resin,
A coating liquid made by dissolving resin such as polyester resin or nitrocellulose in a solvent such as toluene or xylene is applied to a thickness of 1 to 100 ml using a coating or printing method such as a roll coating method, knife edge method, gravure printing method, or screen printing method. It is formed to a thickness of about 3 μm. In addition, it is also possible to use known thermosetting resins and ultraviolet curable resins. Furthermore, a lubricant such as silicone acrylic, zinc stearate, wax, etc. may be added for the purpose of improving thermal head suitability during heat-sensitive recording.

[0020] The infrared reflective layer uses a material with high infrared reflective efficiency, such as aluminum, chromium,
Metal thin films made by vacuum deposition, sputtering, and plating of nickel, sendust, tin, etc., calcium carbonate, titanium oxide, barium oxide, zinc oxide, talc, etc. as main ingredients, acrylic resin, vinyl chloride resin, polyester resin,
An infrared reflective layer is formed using coating and printing techniques such as the well-known roll coating method, knife edge method, gravure printing method, and screen printing method with a white ink or paint obtained by mixing and dispersing it in a binder such as nitrocellulose. It is something to do. Moreover, it is also possible to make the base material 2 serve as an infrared reflective layer, and white or milky white polyvinyl chloride or polyethylene terephthalate is preferable.

In this embodiment, in the heat-sensitive information recording medium constructed as described above, recording and reading on the heat-sensitive recording layer 3 are performed as follows.

The second heat-sensitive coloring material exhibiting the coloring density-energy curve as shown in FIG. The information (pattern information) 5 is developed as visible information in black color and thermally recorded. Furthermore, the color density-energy curve as shown in FIG. 4 is shown,
The first heat-sensitive color forming material, which develops color at a higher temperature than the second heat-sensitive color forming material, is similarly coated with a pattern, such as letters, using a heat printing means such as a conventionally known thermal head.
Information such as numbers, marks, barcodes (pattern information) 6
It is colored green and thermally recorded so that it can be read in both the visible and infrared wavelength regions.

Since the recording on the first thermosensitive coloring material overlaps with the recording on the second thermosensitive coloring material, the green coloring of the first thermosensitive coloring material is masked by the black coloring of the second thermosensitive coloring material. , Since only the ink color of the second heat-sensitive coloring material is visible, when determining the authenticity of a heat-sensitive information recording medium, it is necessary to determine whether or not there is a recording on the first heat-sensitive coloring material that is to be masked. This can be easily determined. In other words, since the second thermosensitive coloring material can develop color at a temperature at which the first thermosensitive coloring material does not develop color, it is possible to record only the coloring of the first thermosensitive coloring material and use these records as dummy information. In addition, the true information can be recorded on the second thermosensitive coloring material, and the colors of the first and second thermosensitive coloring materials are on the same plane and there is no difference in hue. Therefore, it becomes difficult to detect the coloring of the first thermosensitive coloring material. In particular, the recording pattern for the second thermosensitive coloring material may be the same as or different from the recording pattern for the first thermosensitive coloring material. When the coloring temperature of the first thermosensitive coloring material is higher than the coloring temperature of the second thermosensitive coloring material, information for both thermosensitive coloring materials can be recorded simultaneously.

Although the method for reading the information recorded on the thermosensitive recording layer 3 is not shown, it can be read by a detection device that irradiates infrared rays of a specific wavelength and detects the infrared rays reflected from the recording surface of the thermosensitive information recording medium. can. The dummy information portion colored by the second thermosensitive coloring material and the uncolored portions of the first and second thermosensitive coloring materials have spectral reflection characteristics as shown in FIGS. 5 and 6, respectively, and as shown in FIG. like 700
In the infrared wavelength region of nm or more, the true information portion colored by the first thermosensitive coloring material hardly reflects infrared rays, so information can be read from the difference in reflectance. If information is formed into a pattern such as a bar code, an output signal corresponding to the pattern can be obtained, and the output signal can be used to determine authenticity and recognize the data content. It is also possible to directly view letters, numbers, marks, and patterns using an IR scope.

FIG. 8 is a plan view of a thermal information recording medium according to the second aspect of the present invention, and FIG. 9 is a sectional view of the thermal information recording medium taken along the line YY' in FIG.

11 in the figure is a thermal information recording medium;
2 is a base material, 13 is a first heat-sensitive recording layer whose main component is a heat-sensitive color-forming material that has light absorption characteristics in the infrared wavelength region during color development, and 14 is a material whose color development temperature is the same as that of the first heat-sensitive recording layer. 15 is a protective layer that protects the heat-sensitive recording layer from scratches and abrasions; provided accordingly. Although not shown in the drawings, an infrared reflective layer may be provided between the base material 12 and the first heat-sensitive recording layer 13 as necessary in order to facilitate the detection of the reflected light for the information pattern of the reading light in the infrared wavelength region. Good too.

The materials constituting each component and their combinations are the same as those described above, and will therefore be omitted here.

In this embodiment, in the heat-sensitive information recording medium constructed as described above, recording and reading on the heat-sensitive recording layer 3 are performed as follows.

The second heat-sensitive recording layer 14 is mainly composed of a heat-sensitive coloring material that develops color at a temperature lower than the coloring temperature of the first heat-sensitive recording layer, transmits infrared rays, and has no light absorption characteristics in the infrared wavelength region. In addition, the first heat-sensitive recording layer 13, which is mainly composed of a heat-sensitive color-forming material that has light absorption properties in the infrared wavelength region during color development, is required to exhibit spectral reflection properties for infrared rays in the uncolored portions. For example, the heat-sensitive color forming material of the first heat-sensitive recording layer is a mixture of 3,3-bis(p-dimethylaminophenyl)-phthalide and benzyl p-hydroxybenzoate, and the heat-sensitive color forming material of the second heat-sensitive recording layer is 3-(
It is a mixture of p-aminophenyl)fluorene and bisphenol S. The respective color development density-energy curves are shown in FIGS. 10 and 11.

Patterns such as letters, numbers, marks, bar codes, etc. are printed on the second heat-sensitive recording layer exhibiting a coloring density-energy curve as shown in FIG. 11 using a conventional heating printing means such as a thermal head. The information (pattern information) 16 is colored as visible information and thermally recorded. Furthermore, with respect to the first heat-sensitive recording layer which shows a color development density-energy curve as shown in FIG. Information in a pattern, such as letters, numbers, marks, barcodes, etc. (pattern information) 17
The information is thermally recorded in a green color, for example, so that it can be read in the infrared wavelength region along with visible information.

In particular, the color development temperature of the second heat-sensitive recording layer is higher than that of the first heat-sensitive recording layer.
Since the coloring temperature is lower than the coloring temperature of the heat-sensitive recording layer, for example, dummy information, which is different from the information recorded on the first heat-sensitive recording layer, is recorded, and furthermore, the coloring temperature of the second heat-sensitive recording layer is lower than the coloring temperature of the first heat-sensitive recording layer.
Real information can be simultaneously recorded on the second heat-sensitive recording layer, and only the second heat-sensitive recording layer containing dummy information is visible, while the true information recorded on the first heat-sensitive recording layer is visible. Difficult to detect. Furthermore, if the true information is not recorded in the first heat-sensitive recording layer at the coloring temperature of the second heat-sensitive recording layer, and the information in the second heat-sensitive recording layer can be read,
The heat-sensitive information recording medium is proven to be genuine and has not been tampered with, falsified, or counterfeited.

[0032] The information recorded on the first and second heat-sensitive recording layers is in the form of patterns, characters, numbers, marks, bar codes, etc.

Although not shown, the method of reading the information recorded on the heat-sensitive recording layer 13 is by irradiating infrared rays of a specific wavelength,
It can be read by a detection device that detects infrared rays reflected from the recording surface of the thermosensitive information recording medium. The dummy information part colored by the heat-sensitive coloring material of the second heat-sensitive recording layer and the uncolored part of the heat-sensitive coloring material of the first and second heat-sensitive recording layers have spectral reflection characteristics as shown in FIGS. 12 and 13, respectively. As shown in FIG. 14, in the infrared wavelength region of 700 nm or more, the true information portion hardly reflects infrared rays, so information can be read from the difference in reflectance. If information is formed into a pattern like a barcode, it is possible to obtain an output signal according to the pattern.
Authenticity is determined from the output signal and data content is recognized. It is also possible to directly view patterns, letters, numbers, and marks using an IR scope.

The present invention as described above can be combined with a magnetic recording medium as another recording medium to form a heat-sensitive magnetic recording medium 21 as shown in the sectional view of FIG. The thermosensitive magnetic recording medium 21 includes a base material 22 , a magnetic recording layer 23 , a hiding layer 24 , a thermosensitive recording layer 25 , and a protective layer 26 . The magnetic recording layer 23 is made of γ-Fe2 Co3, Co-coated γ-Fe
2Co3, Fe3O4, Ba ferrite, Fe
A coating liquid in which magnetic powder such as the following is dispersed in a suitable resin or ink vehicle is applied using a coating or printing method such as a roll coating method, a knife edge method, a gravure printing method, a screen printing method, etc., and then dried and formed. It is something. The concealing layer 24 is formed by applying a coating liquid in which scale-shaped nonmagnetic metal powder such as Ag, Cr, Al, or Sn is dispersed in a binder solution such as polyvinyl alcohol or polymethacrylic acid resin using a roll coating method, a knife edge method, or a gravure printing method. It is formed by coating and drying using a coating or printing method such as a screen printing method. The base material 22, the heat-sensitive recording layer 25, and the protective layer 26 can have the configurations described above. That is, for the heat-sensitive recording layer 25, either the heat-sensitive recording layer of the first invention or the heat-sensitive recording layer of the second invention can be used. In this example, as shown in FIG. 15, the heat-sensitive recording layer of the first invention is used as the heat-sensitive recording layer 25, and 27 in the figure is an information pattern recorded on the first heat-sensitive coloring material, and 28 is an information pattern recorded on the first heat-sensitive coloring material. This is an information pattern recorded on the first thermosensitive coloring material. These information patterns have the same effects as described above.

According to this, the information recorded on the magnetic recording layer and the optically recorded information on the thermosensitive recording layer can be recorded on the information recording medium, and if both are related information, it is possible to read the information. The content can be confirmed from the information recorded on the heat-sensitive recording layer even without a device, and the authenticity of that information can be confirmed from other information recorded on the heat-sensitive recording layer, preventing forgery, falsification, and falsification. can be discovered.

[0036]

Effects of the Invention As described above, according to the present invention, the first thermosensitive coloring material which has light absorption characteristics in the infrared wavelength region when coloring is different from the first thermosensitive coloring material in coloring temperature, and Since the heat-sensitive recording layer is formed of a mixture whose main component is a second heat-sensitive color-forming material that does not have light absorption characteristics in the infrared wavelength region, two types of information can be recorded. In particular, when the same information is recorded in the same pattern, the recording at the coloring temperature of the first thermosensitive coloring material and the recording at the coloring temperature of the second thermosensitive coloring material, which is different from that coloring temperature, are at approximately the same position on the same surface. The information read in the visible wavelength region on the surface of the thermal information recording medium can be easily read because it appears to overlap with the surface of the thermal information recording medium. By making it difficult to know the existence of such information, it can be used as a means of determining authenticity. Further, only the color development of the second thermosensitive coloring material is recorded, and these records are used as dummy information, and the recording of true information on the first thermosensitive coloring material is formed so as to partially overlap with the recording of the dummy information. For example, since there is no difference in hue between these, it is difficult to detect the color development of the first thermosensitive color forming material, which is true information.

[0037] Furthermore, the first heat-sensitive recording layer is composed mainly of a first heat-sensitive color-forming material having light absorption characteristics in the infrared wavelength region when coloring, and the heat-sensitive color-forming material of the first heat-sensitive recording layer. Since it is formed by lamination with a second heat-sensitive recording layer whose main component is a heat-sensitive color-forming material that has a different color development temperature and has no light absorption characteristics in the infrared wavelength region during color development, it is possible to record two types of information. . In particular, when the same information is recorded in the same pattern, recording at the coloring temperature of the thermosensitive coloring material of the first thermosensitive recording layer and recording at a different coloring temperature from that coloring temperature are performed on each thermosensitive recording layer, and the information is recorded at approximately the same position. Because they appear to overlap, the information read in the visible wavelength range on the surface of the thermal information recording medium can be easily read, but because they overlap, the information read in the infrared wavelength range, which is difficult to distinguish with the naked eye, can be read easily. making it difficult to know about its existence,
This can be used as a means of determining authenticity. Furthermore, the second
If recording is performed only on the first heat-sensitive recording layer and these records are used as dummy information, and the recording of true information on the first heat-sensitive recording layer is formed so as to partially overlap with the recording of dummy information, the true information can be recorded. This has the effect of making it difficult to detect the color development of the first heat-sensitive recording layer.

[Brief explanation of drawings]

FIG. 1 is a plan view of a heat-sensitive information recording medium according to a first aspect of the present invention.

FIG. 2 is a sectional view taken along line X-X' in FIG. 1;

FIG. 3 is a graph showing a coloring density-energy curve of the first thermosensitive coloring material.

FIG. 4 is a graph showing a coloring density-energy curve of a second thermosensitive coloring material.

FIG. 5 is a graph showing the spectral reflection characteristics of a colored portion of the second thermosensitive coloring material.

FIG. 6 is a graph showing the spectral reflection characteristics of uncolored portions of the first and second thermosensitive coloring materials.

FIG. 7 is a graph showing the spectral reflection characteristics of a portion colored by the first thermosensitive coloring material.

FIG. 8 is a plan view of a thermal information recording medium according to the first aspect of the present invention.

9 is a sectional view taken along the line Y-Y' in FIG. 8. FIG.

FIG. 10 is a graph showing a color density-energy curve of the first thermosensitive recording layer.

FIG. 11 is a graph showing a color density-energy curve of the second thermosensitive recording layer.

FIG. 12 is a graph showing the spectral reflection characteristics of a colored portion of the second thermosensitive recording layer.

FIG. 13 is a graph showing the spectral reflection characteristics of uncolored portions of the first and second heat-sensitive recording layers.

FIG. 14 is a graph showing the spectral reflection characteristics of a colored portion of the first thermosensitive coloring material.

FIG. 15 is a sectional view of a thermosensitive magnetic recording medium according to another embodiment of the present invention.

[Explanation of symbols]

1, 11, 21 Heat-sensitive information recording medium 2, 12, 2
2 Base material 3, 25 Thermosensitive recording layer 4, 15, 2
6 Protective layer 5, 16, 27 Information readable with visible light (
Pattern information) 13 First thermosensitive recording layer 14 Second thermosensitive recording layer 6, 17, 28 Information readable in the infrared wavelength region (pattern information)

Claims (4)

[Claims] 1. A first thermosensitive coloring material having light absorption characteristics in an infrared wavelength region at least when coloring is disposed on a sheet-like or plate-like base material, and a coloring temperature different from that of the first thermosensitive coloring material, And when coloring, the second layer has no light absorption characteristics in the infrared wavelength region.
1. A heat-sensitive information recording medium comprising a heat-sensitive recording layer laminated with a mixture mainly composed of a heat-sensitive coloring material and a heat-sensitive coloring material. 2. A first heat-sensitive recording layer comprising, as a main component, a heat-sensitive color-forming material having light absorption characteristics in an infrared wavelength region at least when coloring is formed, on a sheet-like or plate-like base material; A heat-sensitive information recording medium comprising a second heat-sensitive recording layer which has a different coloring temperature from that of the recording layer and is mainly composed of a heat-sensitive color-forming material having no light absorption characteristics in the infrared wavelength region during coloring. 3. The heat-sensitive information recording medium according to claim 2, wherein the second heat-sensitive recording layer transmits light in an infrared wavelength region. 4. The heat-sensitive information recording medium according to claim 1, wherein a magnetic recording layer and a hiding layer are laminated between the sheet-like or plate-like base material and the heat-sensitive recording layer.