JP2002067502A - Thermosensitive recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive recording medium capable of effectively preventing a forgery by copying, a falsification or an alteration of a thermosensitive recording part, facilitating a decision of a truth or a falsehood by using a visual observation or a polarizing plate without using a special equipment and being simply manufactured by not specially manufacturing steps. SOLUTION: The thermosensitive recording medium 1 comprises a thermosensitive recording layer 3 provided on a base 2, and a cholesteric liquid crystal layer 4 provided on at least a part of the layer 3 and having two characteristics of circular polarizing selectivity and selective reflectivity. Thus, a character or an image color developed and recorded in the layer 3 is covered with the cholesteric liquid crystal by heating a thermal head or the like to have the circular polarizing selectivity and the selective reflectivity as well as excellent expressability and design properties. Further, the forgery by copying, the falsification or the alternation can be effectively prevented, and the decision of the truth or the falsehood can be facilitated by using the visual observation or the polarizing plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium having a heat-sensitive recording layer provided on a base material, and particularly to a ticket, a lottery, a delivery slip, a display tag, a label, a ticket, an entrance passport, and a financial institution. The present invention relates to a heat-sensitive recording medium which can be used for a journal such as a transaction statement used in the above.

[0002]

2. Description of the Related Art Conventionally, several proposals have been made as countermeasures against forgery in a thermosensitive recording medium having a thermosensitive coloring layer. For example, JP-A-11-344930 describes a forgery-preventing thermosensitive recording medium in which a pattern to be used as a watermark is printed on the surface of a support and a milky white thermosensitive coloring layer is further formed thereon. However, similar counterfeit tickets can be relatively easily manufactured using color copiers and scanner printers. JP-A-11-314449 discloses a thermosensitive recording material in which a near-infrared fluorescent compound is contained in a base sheet or a heat-sensitive coating layer on the base sheet. Do not cause an early reaction. However, a special device such as a silicon photodiode or the like for a photon detector is required to determine whether the thermosensitive recording material is forged.

Japanese Patent Application Laid-Open No. 11-78326 describes anti-counterfeit paper in which a glittering thread such as a hologram, a magnetic recording layer, and a heat-sensitive recording layer are provided on a base paper. At the stage, special processing such as thread papermaking is involved, so the manufacturing process becomes special and complicated,
Manufacturing costs will increase. In addition, any of the above-described heat-sensitive recording media, even if it is effective to determine the authenticity of the heat-sensitive recording medium itself,
It has little effect on preventing the falsification of the recording portion of the thermosensitive coloring and the characters and picture patterns to be displayed.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, to effectively prevent forgery by copying, falsification and alteration of a heat-sensitive recording section, and to visually check the authenticity. It is an object of the present invention to provide a thermosensitive recording medium which can be easily manufactured by using a polarizing plate or a polarizing plate without using any special equipment, and has a special manufacturing process and can be easily manufactured.

[0005]

According to the present invention, in order to solve the above-mentioned problems, in a heat-sensitive recording medium having a heat-sensitive recording layer provided on a base material, at least a part of the heat-sensitive recording layer is provided with circularly polarized light. A cholesteric liquid crystal layer having two properties, that is, a property of selective reflection and a property of selective reflection, was provided. Thus, by heating the thermal head or the like, the characters and images color-recorded on the heat-sensitive recording layer are covered with cholesteric liquid crystal, have circular polarization selectivity and selective reflection, and have excellent expressiveness and design. Become.
In addition, forgery by copying, falsification and alteration of characters can be effectively prevented, and the authenticity can be easily determined visually or by using a polarizing plate.

[0006] A printing layer can be provided on the cholesteric liquid crystal layer, and a heat-sensitive recording medium having more excellent expression and design can be provided. It is also possible to provide a printing layer on the above-mentioned heat-sensitive recording layer, and a heat-sensitive recording medium having more excellent expressiveness and design can be obtained as described above. It is preferable to provide a protective layer on the outermost surface on the side where the heat-sensitive recording layer is provided in any one of the above-described heat-sensitive recording media, thereby preventing the cholesteric liquid crystal layer from peeling off from the heat-sensitive recording medium and preventing the heat-sensitive recording medium from being peeled off. Damage prevention,
Improved durability can be obtained.

[0007]

Next, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a schematic cross-sectional view showing one embodiment of a heat-sensitive recording medium 1 of the present invention, in which a heat-sensitive recording layer 3 is provided on the entire surface of a base material 2.
The cholesteric liquid crystal layer 4 is provided on the entire surface of the cholesteric liquid crystal layer 4, and the printing layer 5 is provided partially on the cholesteric liquid crystal layer 4. In this case, a character and an image pattern can be displayed and recorded as the coloring portion 7 in an area m between the printing layers 5. All of the coloring portions 7 are covered with the cholesteric liquid crystal layer 4.

FIG. 2 is a schematic sectional view showing another embodiment of the heat-sensitive recording medium 1 according to the present invention, in which a heat-sensitive recording layer 3 is provided on the entire surface of a substrate 2 and the heat-sensitive recording layer 3 The cholesteric liquid crystal layer 4 is provided on a part of the printing layer 5 and on a part of the thermosensitive recording layer 3 as shown in FIG. Recording medium 1
The protective layer 6 is provided on the entire outermost surface on the side where the heat-sensitive recording layer 3 is provided. In this case, a character and an image pattern can be displayed and recorded in the area m between the print layers 5 as the coloring part 7, and the coloring part 7 is covered with the cholesteric liquid crystal layer 4 and uncoated. And the part directly in contact with the protective layer is mixed.

Hereinafter, the material of each layer constituting the thermal recording medium of the present invention and a method of laminating each layer using the material will be described. (Substrate) As the substrate 2 used for the heat-sensitive recording medium of the present invention, a conventionally known material can be used. For example, paper, a plastic sheet, a metal foil or a metal plate, or the like can be used. They can be used alone or in combination, and can be selected according to the application. Usually, paper and plastic sheets are often used.

As the above-mentioned plastic sheet, those made of various synthetic resins as exemplified below can be used. Various synthetic resins are polyethylene resins,
Polypropylene resin, polymethylene resin, polymethylpentene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, vinyl chloride-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl alcohol copolymer resin, Polyethylene terephthalate resin, polybutylene terephthalate resin,
Polyethylene naphthalate-isophthalate copolymer resin, polymethyl methacrylate resin, polyethyl methacrylate resin, polybutyl acrylate resin, polyamide resin represented by nylon 6 or nylon 66, cellulose triacetate resin, cellophane, polystyrene resin , Polycarbonate resin, polyarylate resin, or polyimide resin. The thickness of such a substrate is not particularly limited and can be appropriately selected depending on the application. For example, about 0.05 to 2 mm is considered in consideration of the substrate strength and the like.

(Thermal Recording Layer) On the thermal recording medium of the present invention
The heat-sensitive recording layer 3 provided on the base material described above
The combination of the basic dye and developer used
As the main component, and if necessary,
The coating solution containing the additive is applied to the blade coater
Fu coater, roll coater, rod coater, courtesy
It can be formed by coating with a coating means such as a coater.
You. The coating amount of the heat-sensitive recording layer is not limited,
Usually 3 to 15 g / m in solid ^Two, Preferably 4 to 10 g /
m^TwoRange.

The basic dye is a colorless or light-colored dye which develops a color with an acid, and may be used alone or as a mixture of two or more kinds as necessary. What is applied to the material is arbitrarily applied, for example, trianylmethane-based, fluoran-based, thiazine-based, spiropyran-based, lactam-based leuco compounds are preferably used, particularly fluoran-based leuco dyes are widely used. Commonly used.

The following are specific examples of the basic dye. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3
-Bis (p-dimethylaminophenyl) phthalide, 3-
(P-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole-
3-yl), 5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
Triallylmethane dyes such as (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 6 '-[ethyl (3-methylbutyl) amino] -3'-methyl-2'
-(Phenylamino) -spiro [isobenzylfuran-
1,9'-xanthen] -3-one, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-
Methyl-N-propylamino) -6-methyl-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluoran,
-Dimethylamino-6-methyl-7-chlorofluorane, 3-dimethylamino-7-methyl-7-chlorofluorane, 3-dimethylamino-6-methyl-7-anilinofluoran, 3,3-bis Fluorane dyes such as (4-dimethylaminophenyl) 6-diethylaminophthalide, 3-diethylamino-7 (2-chloroanilino) fluoran, 3-dibutylamino-7 (2-chloroanilino) fluoran, benzoylleucomethylene blue, p
-Thiazine dyes such as nitribenzoyl leuconnetylene blue, 3-methyl-spiro-dinaphthopyran, 3-phenylspirodinaphthopyran, 3-benzyl-spirodinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) ) Spiropyran, 3-propyl-spiro-
Examples include spiropyran-based dyes such as dibenzopyran, and lactam-based dyes such as rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam. The above various basic dyes are reacted with a developer,
Depending on the type of the dye, the color is developed in a hue such as black, red, blue, or green. In the present invention, the color hue can be arbitrarily selected.

As the developer used in the heat-sensitive recording layer of the heat-sensitive recording medium of the present invention, an electron-accepting substance generally used for heat-sensitive recording paper is used.
Aromatic carboxylic acid derivatives or metal compounds thereof,
N'-diarylthiourea derivatives and the like are used. Of these, particularly preferred are phenol derivatives. The above basic dye and the developer react with each other by a heating means such as a thermal head or laser light irradiation to form a color. These basic dyes and the color developing agent may be mixed in one heat-sensitive recording layer, and the basic dye and / or the color developing agent may be mixed with a shell material which is broken by heat to improve the stability. Each of the agents may be microencapsulated.

Other thermosensitive recording layers include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin and the like as pigments. , As an additive to further improve the sensitivity,
Waxes such as N-hydroxymethyl stearamide, stearamide, and palmitamide;
Naphthol derivatives such as benzyloxynaphthalene, p-
Biphenyl derivatives such as benzylbiphenyl and 4-allyloxybiphenyl, 1,2-bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl)
Polyether compounds such as ethers, diphenyl carbonate, dibenzyl oxalate, di (p-fluorobenzyl) oxalate
Carbonic acid or oxalic acid diester derivatives such as esters can be added. In addition, for the purpose of head abrasion prevention, sticking prevention, etc., zinc stearate, higher fatty acid metal salts such as calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearic acid amide, wax such as caster wax, A dispersant such as sodium dioctylsulfosuccinate, an ultraviolet absorber such as a benzophenone type or a benzotriazole type, a surfactant, and a fluorescent dye are added as necessary.

As the binder used for the heat-sensitive recording layer, various kinds of adhesives which are usually used can be used. For example, starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol sodium polyacrylate, acrylamide / acrylate copolymer acrylamide / acrylate / methacrylic acid ternary Copolymer,
Water-soluble adhesives such as alkali acid of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylate, styrene / butadiene copolymer, acrylonitrile / Latexes such as butadiene copolymer and methyl acrylate / butadiene copolymer ethylene / vinyl acetate copolymer are exemplified.

(Cholesteric Liquid Crystal Layer) The cholesteric liquid crystal layer provided in the heat-sensitive recording medium of the present invention is an optically selective reflective film such as a polymer film having cholesteric liquid crystal alignment fixed or a film in which cholesteric liquid crystal particles are dispersed in a carrier. Any material can be used as long as the material exhibits circular polarization selectivity. First, the cholesteric liquid crystal has a regular twist such that the alignment structure of the liquid crystal molecules draws a spiral in the film thickness direction. Further, when the pitch P (the film thickness required for liquid crystal molecules to rotate 360 °) and the wavelength λ of incident light are almost equal, the cholesteric liquid crystal has two optical properties of selective reflection and circular polarization selectivity. It is known to exhibit properties. (References: Basics of liquid crystal and display applications, Corona, etc.)

The term "selective reflection" refers to the property of strongly reflecting light within a specific wavelength band among incident light. Since this selective reflectivity is expressed only within a specific wavelength band,
By appropriately selecting the pitch P of the cholesteric liquid crystal, the reflected light becomes a chromatic color with high color purity. If the center wavelength of the band is λ _S and the bandwidth is Δλ, these are the pitch P (= λ / _nm ) of the optical medium and the average refractive index _nm (= √).
^{_{((N e 2 + n o}} 2) / 2)) by the following formula (1),
Determined as in (2). Here, [Delta] n is the extraordinary ray refraction index n _e in the plane of the optical medium, the difference between the ordinary refractive index n _o ([Delta] n =
n _e -n _o) to. λ _s = n _m · P (1) Δλ = Δn · P / _nm (2)

The center wavelength λ shown in the above equations (1) and (2)
_{The s} and the wavelength bandwidth Δλ are defined when the incident light on the cholesteric liquid crystal layer is vertically incident (0 ° incident, on-axis incident), but the incident light is obliquely incident (off).
If a -axis incidence), the apparent pitch P, since the decrease, the central wavelength lambda _s shifts to the shorter wavelength side, the wavelength bandwidth Δλ decreases. This phenomenon is called blue shift because λ _s shifts to the shorter wavelength side, and the shift amount depends on the incident angle, but can be easily identified by visual observation. For example, the reflection color of a cholesteric liquid crystal that exhibits a red color when observed from a vertical direction (0 ° incident position) is orange, yellow, green,
Observed to change sequentially to blue-green and blue. Thus, the cholesteric liquid crystal layer depends on the viewing angle
Since the color shifts to the short wavelength side and shows (changes) a special color that cannot be reproduced by color copying or the like, it is very effective in preventing forgery.

Since the cholesteric liquid crystal layer exhibits a specific reflection color, it is possible to easily determine whether the thermosensitive recording medium using the liquid crystal layer is true or false by visual inspection, and further has its circular polarization selectivity. Therefore, either the left circularly polarized light or the right circularly polarized light is selectively reflected. The circular polarization selectivity refers to a property of transmitting only circularly polarized light in a specific rotation direction and reflecting circularly polarized light having the opposite rotation direction. The incident light reflects circularly polarized light components in the same direction as the twisting direction of the cholesteric liquid crystal alignment structure, and the direction of rotation of the reflected light is also in the same direction, while the circularly polarized light components rotating in the opposite direction are transmitted. Is a unique property unique to cholesteric liquid crystals. In the case of a cholesteric liquid crystal having a left-handed structure, left circularly polarized light is reflected, the reflected light is left circularly polarized light, and right circularly polarized light is transmitted.

In order to selectively reflect either left-handed circularly polarized light or right-handed circularly polarized light due to the circularly polarized light selectivity of the cholesteric liquid crystal, a left-handed circularly polarizing plate capable of changing left-handed circularly polarized light into linearly polarized light and transmitting the same. If right circularly polarized light that can be transmitted by changing right circularly polarized light into linearly polarized light is used as a discriminating device, final true / false judgment can be made accurately. The above truth judgment will be described in detail below. FIG. 3 is a diagram for explaining the authenticity judgment of the thermosensitive recording medium which is the authenticity judging body. Note that, here, the authenticity determination body is described by laminating the cholesteric liquid crystal layer 4 on the base material 2. However, it is needless to say that the thermosensitive recording medium of the present invention has a thermosensitive recording layer provided on the base material. Further, a cholesteric liquid crystal layer is provided on the heat-sensitive recording layer, and the heat-sensitive recording layer is omitted from the description. The authenticity determination body will be described with reference to a case where the authenticity determination body is colored including cholesteric liquid crystal molecules that reflect the counterclockwise polarized light 12. The authenticity determination body is authenticated by the authenticity determining tools 8a and 8b. The first authenticity determination tool 8a includes a phase plate 9 and a polarizer 10a. The second authenticity determination tool 8b includes a phase plate 9 and a polarizer 10b.

The phase plate 9 is an optical plate for giving a phase difference to incident light. In this example, a so-called quarter-wave plate is used. A quarter-wave plate is an optical plate having the property of converting circularly polarized light into linearly polarized light and converting linearly polarized light into circularly polarized light. The phase plate 9 transmits the counterclockwise polarized light 12 reflected by the cholesteric liquid crystal layer 4 and converts it into linearly polarized light 14 having a vertical polarization plane. Also, the phase plate 9
The light passes through the cholesteric liquid crystal layer 4 and transmits the clockwise polarized light 13 reflected by the substrate 2 to be converted into linearly polarized light 15 having a plane of polarization in the left and right directions.

The polarizers 10a and 10b are usually elements for converting natural light into linearly polarized light, and when linearly polarized light is transmitted, only light having a specific polarization plane is transmitted. The polarizer 10 a is a polarizer that transmits linearly polarized light having a vertical polarization plane, and transmits linearly polarized light 14 but does not transmit linearly polarized light 15. The polarizer 10b is a polarizer that transmits linearly polarized light having a plane of polarization in the left-right direction, and transmits linearly polarized light 15 but does not transmit linearly polarized light 14.

The natural light 11 includes left-handed polarized light 12 and right-handed polarized light 13. When the natural light 11 is incident on the authenticity determination body, the following occurs. (1) Of the natural light 11 incident on the authenticity determination body, the counterclockwise polarized light 12 is reflected by the cholesteric liquid crystal layer 4. On the other hand, the clockwise polarized light 13 passes through the cholesteric liquid crystal layer 4 and is reflected by the substrate 2. (2) In (1), the counterclockwise polarized light 12 reflected by the cholesteric liquid crystal layer 4 can pass through the first authenticity judgment tool 8a but cannot pass through the second authenticity judgment tool 8b. Here, in the cholesteric liquid crystal layer 4, the left-handed polarized light reflected by the determination unit and the left-handed polarized light reflected by a part other than the determination unit are:
Because the direction of travel is different, there is a difference in brightness,
The judgment information becomes visible. (3) In (1), the clockwise polarized light 1 reflected by the substrate 2
3 can be transmitted through the second authenticity judgment tool 8b, but cannot be transmitted through the first authenticity judgment tool 8a. Therefore, it can be confirmed as the color of the authenticity determination body. In this manner, by changing the authenticity determination tool, the appearance of the authenticity determination body changes.

The cholesteric liquid crystal layer reflects only one of the left and right circularly polarized light components of a specific wavelength depending on the helical pitch of the molecule, and transmits all other light. Strongly influenced by the groundwork. When a liquid crystal layer is formed on the heat-sensitive recording layer side of the heat-sensitive paper, the white part without printing is mixed with the complementary color of the liquid crystal reflection color and the irregularly reflected light of the transmitted light to give a human-like color close to white with a unique gloss. However, if the color of the pattern (black color of the recording layer) is black, the transmitted light is well absorbed, and only the reflected color of the liquid crystal layer is captured. Are observed, and that portion shows the luminance and the viewing angle characteristic peculiar to the liquid crystal. If a part of the pattern formed in this way is cut off for the purpose of falsification, the part loses its unique white glossiness, and it is difficult to add a colored part with a unique reflected color by adding it. This has a great effect on preventing the falsification of the thermal recording medium.

The heat-sensitive recording medium of the present invention has at least one cholesteric liquid crystal layer provided on at least a part of the heat-sensitive recording layer on the substrate. The liquid crystal material used for the cholesteric liquid crystal layer is, for example, polyacrylate having a liquid crystal forming group in a side chain, polymethacrylate,
Side-chain polymers such as polysiloxane and polymalonate;
Main chain polymers such as polyester, polyester amide, polycarbonate, polyamide, and polyimide having a liquid crystal forming group in the main chain can be used. As the cholesteric liquid crystal layer, a polymer film in which the cholesteric liquid crystal alignment is fixed can be suitably used.After the side chain type or main chain type thermotropic polymer liquid crystal is cholesterically aligned in a liquid crystal state, the liquid crystal transition point is changed. A polymer film produced by cooling to the following temperature and fixing the orientation state can be given. Furthermore, a polymer film produced by cholesterically aligning a side-chain type or main-chain type lyotropic polymer liquid crystal in a solution and then gradually removing the solvent to fix the alignment state can be used. Further, as an example of the polymer film, a polymer film in which a low-molecular liquid crystal is cholesterically aligned, and then the low-molecular liquid crystal is cross-linked by a photoreaction or a heat reaction to fix the orientation thereof is used.

The cholesteric liquid crystal layer may be of a type that reflects either left-handed or right-handed polarized light, and may use a plurality of liquid crystal materials exhibiting different reflected colors in the same direction. Further, as a method of forming the cholesteric liquid crystal layer on at least a part of the heat-sensitive recording layer, after forming the polymer film described above, it is performed by a method of bonding or transferring using an adhesive. Can be. Examples of the adhesive include thermosetting resins (for example, phenolic resins, furan resins, urea resins, melamine resins, polyester resins, polyurethane resins, epoxy resins, and other resins), thermoplastic resins (For example, polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride resin,
Polyvinyl butyral resin, poly (meth) acrylic resin, nitrocellulose, polyamide, other resins),
Rubber (eg, butadiene-acrylonitrile rubber, neoprene rubber, other rubbers), glue, natural resin, casein, sodium silicate, dextrin, starch,
Among the gum arabic and the like, an adhesive mainly containing one or more kinds can be used. These adhesives may be any of a solution type, an emulsion type, a powder type and a film type. Further, these adhesives may be any of a room temperature solidification type, a solvent volatilization type, and a fusion solidification type.

Further, as a method of forming a cholesteric liquid crystal layer on at least a part of the heat-sensitive recording layer, a liquid crystal material is converted to ink, intaglio printing such as gravure printing, lithographic printing such as offset method, letterpress printing, screen printing. printing,
Or may be printed directly on the heat-sensitive recording medium, such as by inkjet printing, in this case, reacts with the heat-sensitive recording medium,
Care must be taken, such as by limiting the type of ink solvent, so that the heat-sensitive recording layer does not develop color. The thickness of the cholesteric liquid crystal layer as described above is 1 μm to 20 μm.
A degree is desirable.

The place where the cholesteric liquid crystal layer is formed is as follows:
As shown in FIG. 1, it is provided on the entire surface of the heat-sensitive recording layer 3 or
Alternatively, as shown in FIG. 2, it can be provided partially on the heat-sensitive recording layer 3 or partially provided on at least the print layer 5. As shown in FIGS. 1 and 2, the cholesteric liquid crystal layer can be printed so as to cover (cover) a color-developed portion that is thermally recorded, regardless of whether the layer is solid or patterned. It is more effective in preventing tampering.

(Printing Layer) A heat-sensitive recording layer on the substrate of the present invention,
In the thermosensitive recording medium provided with the cholesteric liquid crystal layer in order, the printing layer 5 can be provided on the thermosensitive recording layer or on the cholesteric liquid crystal layer.
It can be excellent in design and anti-counterfeiting. The printing layer is formed by directly printing an arbitrary character or image such as a tint block or a pattern on a thermosensitive recording medium by intaglio printing such as gravure printing, lithographic printing such as offset printing, letterpress printing, screen printing, or inkjet printing. be able to.

FIG. 4 shows a case where the thermosensitive recording medium 1 shown in FIG. 1 is shaved at the position (a). In this case, (a)
In the position (b), the glossy feeling is lost, and in the position (b) shown (unshaved portion), even if a pattern is formed with the same color ink as the color of the heat-sensitive recording layer, the reflection color peculiar to the heat-sensitive recording medium is lost. Since it is difficult to reproduce a color of the same hue having a viewing angle dependency, it is determined at a glance that the color is not real (forgery). The falsification of the display pattern (color recording section) often occurs when there are a lot of "missing tickets with different numbers" such as lottery (Japan Lottery Association; Numbers). Applying a thermal recording medium is effective in preventing tampering and forgery.

(Protective Layer) In the present invention, in order to improve sticking when a thermal head is used as a heating means at the time of recording on the heat-sensitive recording layer, and to improve chemical resistance and scratch resistance in handling the heat-sensitive recording medium. In order to prevent the cholesteric liquid crystal layer from peeling off from the thermosensitive recording medium, a protective layer 6 can be provided on the outermost surface on the side where the thermosensitive recording layer is provided. The protective layer is made of various water-soluble resins, latex,
An ionizing radiation-curable resin or the like by ultraviolet rays or electron beams is used, and, if necessary, a pigment, a water-resistant agent, a water-repellent agent,
An antifoaming agent, an ultraviolet absorber and the like can be added.

Examples of the resin constituting the protective layer include acrylic resin, urethane resin, epoxy resin, silicone resin, ethylene-vinyl acetate copolymer resin, polyimide resin, polyester resin, polystyrene resin, cellulose resin, polyvinyl alcohol resin and the like. Or a mixture thereof. However, it is not limited to these constituent resins, and may be appropriately selected according to the required physical properties such as light resistance, smoothness, hard coat property, and abrasion resistance required for the surface of the thermal recording medium according to the application. Can be.

The protective layer used in the heat-sensitive recording medium of the present invention can be provided as one or more layers on the outermost surface of the heat-sensitive recording medium. The protective layer is transparent so as not to impair the characteristics of the underlying cholesteric liquid crystal. It is made of a material that has properties and does not contain a polarization component. Cholesteric liquid crystal layer used in the thermosensitive recording medium of the present invention, because of generally low scratch resistance,
As a thermal recording means, besides recording with a thermal head,
It is preferable to use a printer of the type using laser light.In this case, the layer to which an infrared absorbent corresponding to the wavelength of laser light used for the protective layer or cholesteric liquid crystal layer of the thermal recording medium to be used is added. And 1-5
% (% By mass), the thermal sensitivity at the time of recording is further improved, which is effective.

The pigments added to the protective layer include mica,
Talc, calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, kaolin, talc, fluorite, synthetic silicate, amorphous silica, urea formalin resin, and the like. Aluminum oxide, kaolin, silica, mica and talc are preferably used. And the coating liquid for the protective layer is a pigment or a solution of the above resin, depending on the purpose, zinc stearate, calcium stearate, paraffin wax, lubricant and dispersant such as polyethylene wax, fluorescent brightener,
A cross-linking agent, a sulfosuccinic acid-based alkali metal salt and a fluorine-containing surfactant, and various assistants such as a polyoxyethylene surfactant may be further added. The protective layer is a coating liquid containing the above-mentioned materials, and is provided by a conventionally known coating means in an amount of about 0.1 to 5 g / m ^{2 in} terms of a solid content.

[0036]

Next, the present invention will be described more specifically with reference to examples. A polymer liquid crystal film separately prepared by fixing a cholesteric liquid crystal orientation based on a transparent polyvinyl chloride resin film on a black coloring type heat sensitive paper (manufactured by Oji Paper) having a heat sensitive recording layer provided on a base material, The liquid crystal surface and the heat-sensitive recording layer were adhered to the entire surface including the pattern display portion (recording portion) using a vinyl chloride-vinyl acetate copolymer adhesive so that the heat-sensitive recording of the embodiment of the present invention was performed. A medium was prepared.

The thickness of the polyvinyl chloride resin film used is 15 μm, and the thickness of the cholesteric liquid crystal layer is 9 μm.
At a wavelength of 560 nm, the light having a wavelength of 560 nm shows a peak with a reflectivity of 9%. When observed from a vertical direction on a black background, it is a vivid green, and as the angle of observation increases, the incident light increases with respect to the vertical direction. (In the case of oblique incidence and approaching the horizontal direction), a shift to blue was observed. The thermal recording medium of the above embodiment was transferred to a thermal printer using a thermal printer at a transport speed of 1.54 m / sec and a printing energy of 1.00 mJ / dot.
When pattern printing was performed under the conditions described above, a color was well formed and a pattern having a reflected color could be observed.

Further, when a part of the above-mentioned color-developed portion of the heat-sensitive recording medium is shaved with a cutter knife, the portion clearly loses its luster, and a new black ink is applied on the polymer liquid crystal film of the heat-sensitive recording medium. The part where the pattern was formed appeared clearly different from the colored part having pearl luster.
Therefore, falsification and alteration of the heat-sensitive recording portion can be effectively prevented, and the authenticity determination can be easily performed visually.

[0039]

As described above, according to the present invention, in a heat-sensitive recording medium in which a heat-sensitive recording layer is provided on a substrate, at least a part of the heat-sensitive recording layer has a circular polarization selectivity and a selective reflection property.
A cholesteric liquid crystal layer having two characteristics was provided. Thus, by heating the thermal head or the like, the characters and images color-recorded on the heat-sensitive recording layer are covered with cholesteric liquid crystal, have circular polarization selectivity and selective reflection, and have excellent expressiveness and design. Become. In addition, forgery by copying, falsification and alteration of characters can be effectively prevented, and the authenticity can be easily determined visually or by using a polarizing plate.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a heat-sensitive recording medium of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment which is a heat-sensitive recording medium of the present invention.

FIG. 3 is a diagram illustrating the authenticity determination of the authenticity determination body.

FIG. 4 is a schematic sectional view showing a case where the thermosensitive recording medium shown in FIG. 1 is shaved at a position (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal recording medium 2 Base material 3 Thermal recording layer 4 Cholesteric liquid crystal layer 5 Printing layer 6 Protective layer 7 Coloring part 8a, 8b Authenticator 9 Phase plate 10a, 10b Polarizer 11 Natural light 12 Left-handed polarization 13 Right-handed polarization 14 , 15 linearly polarized light m region

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G02F 1/13 102 G09F 3/02 F G09F 3/02 B42D 11/00 E // B42D 11/00 B41M 5 / 18 E 101E

Claims (4)

[Claims] 1. A thermosensitive recording medium having a thermosensitive recording layer provided on a substrate, wherein a cholesteric liquid crystal layer having two characteristics of circular polarization selectivity and selective reflection is provided on at least a part of the thermosensitive recording layer. A heat-sensitive recording medium characterized in that: 2. The thermosensitive recording medium according to claim 1, wherein a printing layer is provided on the cholesteric liquid crystal layer. 3. The heat-sensitive recording medium according to claim 1, wherein a printing layer is provided on the heat-sensitive recording layer. 4. A heat-sensitive recording medium according to claim 1, wherein a protective layer is provided on the outermost surface of the heat-sensitive recording medium on the side where the heat-sensitive recording layer is provided.