JP2007144896A - Recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium which does not lose a variation effect of cast or color in a selective reflection layer, and has very high forgery-proofness with a capability of recording information whose genuineness can be judged using a tool. <P>SOLUTION: This recording medium 1 has at least a light-selective reflection layer 3 which is a cholesteric liquid crystal layer and a black layer 4 laminated over each other, and is preferably in such a condition that the medium 1 has information recorded by breaking the black layer 4 by a heating means. In this recording medium 1, the black layer 4, as a ground, of an information recording part 5 disappears because the black layer 4 partially breaks down to be removed, so that the light selective reflection layer 3 is inconspicuous. On the other hand, since a non-recording part 6 has a remnant black layer 4, the former has the light selective reflection layer 3 with the black layer 4 as a ground, and therefore, its variation effect of the cast or color possessed by the light selective reflection layer 3 conspicuously appears. Consequently, the recorded information is legible by virtue of a contrast between the non-recording part and the recording part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording medium having a very high anti-counterfeiting property and capable of recording information that can be checked for authenticity using a tool.

  Conventionally, authenticity is determined for expensive products with high economic value, credit cards, traveler's checks, or vouchers that produce high value when used as ID (Identification) means. A hologram (label) suitable for the above is given to prevent forgery and prove as a genuine product. However, recently, holograms that are indistinguishable from the real thing are manufactured, and new ones that prove authenticity are required.

  As an anti-counterfeiting measure, for example, as disclosed in Patent Document 1, as an identification medium provided on an object to identify the authenticity of the object, either left-handed polarized light or right-handed polarized light among incident light is used. As a light selective reflection layer that reflects only the light, it is described that the light selective reflection layer is formed by printing with cholesteric liquid crystal ink. Although it has been improved by the above method as a countermeasure against forgery, it is not impossible to forge if a polymer cholesteric liquid crystal material is obtained, and it is still satisfactory as a method for preventing forgery. I can't say that.

Further, in the card for recording the unique information by providing the visible information recording unit, the visible information recording unit is an irreversibly recorded thermal recording unit, and the card provided with an information recording unit such as a magnetic recording unit is provided. Patent Document 2 proposes. This is because at least a part of the card is provided with a visible information recording part for irreversibly recording information unique to the card, and the visible information recording part is a thermal recording part of the thermal coloring layer or a thermal destruction recording. A layer in which a hologram forming layer or a diffraction grating forming layer is provided above or below the visible information recording portion is shown. This card is difficult to forge or alter, but because the visible information recording part is laminated, the color and color changing effect of the light selective reflection layer of the hologram or diffraction grating forming layer is lost. There is.
JP 2000-25373 A JP-A-8-80680

  Therefore, in order to solve the above-described problems, the present invention has a very high anti-counterfeiting property without losing the color and color changing effect of the light selective reflection layer, and authenticity using a tool. An object of the present invention is to provide a recording medium capable of recording information that can be determined.

  In view of the above situation, earnest research and development has been proceeded, and the present invention is a recording medium characterized in that at least a light selective reflection layer which is a cholesteric liquid crystal layer and a black layer are laminated. . According to a second aspect of the present invention, there is provided a recording medium in which the black layer is destroyed by a heating means to record information. In this recording medium, since the black layer of the information recording part is partially destroyed and removed, the underlying black layer is lost, and thus the light selective reflection layer is not conspicuous. On the other hand, since the black layer remains in the non-recording part, it has a light selective reflection layer with the black layer as a base, and the color and color changing effect of the light selective reflection layer is noticeable, and the non-recording part The recording of information is easy to read due to the contrast between the recording section and the recording section.

  According to a third aspect of the present invention, there is provided a recording medium comprising two or more light selective reflection layers. The invention of claim 4 is a recording medium characterized in that a retardation layer is interposed between the light selective reflection layers. A retardation layer is provided between the light selective reflection layers, which are cholesteric liquid crystal layers, and information by reflected light from different liquid crystal layers can be observed depending on the angle at which the recording medium is viewed.

  The recording medium of the present invention has a structure in which at least a light selective reflection layer, which is a cholesteric liquid crystal layer, and a black layer are laminated, and it is preferable to record information by destroying the black layer with a heating means. At the time of information recording, since the black layer of the information recording part is partially removed, the light-selective reflection layer is not conspicuous because the underlying black layer is eliminated. On the other hand, since the black layer remains in the non-recording part, it has a light selective reflection layer with the black layer as a base, and the color and color changing effect of the light selective reflection layer is noticeable, and the non-recording part The recording of information can be read by the contrast between the recording section and the recording section. Therefore, the recording medium of the present invention has a very high anti-counterfeit property without losing the tint and color variable effect of the light selective reflection layer, which is a cholesteric liquid crystal layer, and can also determine authenticity using a tool. Yes, information can be recorded freely.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of a recording medium 1 of the present invention, in which a light selective reflection layer 3 of a cholesteric liquid crystal layer and a black layer 4 are laminated on a substrate 2 of a film. . In FIG. 1, the light selective reflection layer 3 and the black layer 4 of the cholesteric liquid crystal layer are laminated on the base material 2, but not limited to this, for example, the black layer is manufactured by a melt extrusion method or the like. As a form of the plastic film, it is possible to provide the function of a substrate and to provide a light selective reflection layer on the film. FIG. 2 is a schematic cross-sectional view showing a state after recording the information by breaking the black layer with a heating means on the recording medium shown in FIG. For example, from the base material 2 side, the laser beam is irradiated with a pattern according to information, and the material contained in the black layer 4 absorbs the laser, generates heat, melts, or decomposes, and the irradiation unit Becomes the recording unit 5. In this recording medium 1, since the black layer of the information recording portion 5 is partially removed, the underlying black layer is eliminated, and thus the light selective reflection layer is inconspicuous. On the other hand, since the black layer 4 remains in the non-recording portion 6, the light selective reflection layer 3 is provided with the black layer 4 as a base, and the color and color change effects of the light selective reflection layer 3 are remarkably exhibited. Due to the contrast between the non-recording part 6 and the recording part 5, the recording of information is easy to read.

  FIG. 3 is a schematic cross-sectional view showing another embodiment of the recording medium 1 of the present invention. A light selective reflection layer 3, a black layer 4 and an adhesive layer 7 of a cholesteric liquid crystal layer are formed on a substrate 2 of a film. It is a laminated structure. This recording medium can be used by adhering the recording medium to an arbitrary object via an adhesive layer by pressure alone or by heating and pressing depending on the type of the adhesive layer. Also in the recording medium of FIG. 3, it is possible to record information as shown in FIG. FIG. 4 is a schematic sectional view showing another embodiment of the recording medium 1 of the present invention. The adhesive layer 7, the black layer 4, and the light selective reflection layer 3 of the cholesteric liquid crystal layer are provided on one surface of the substrate 2. It is the structure which laminated | stacked and laminated | stacked the adhesion layer 8 and the peeling sheet 9 on the other surface of the base material 2. FIG. The recording medium 1 shown in FIG. 4 can be used by peeling off the release sheet and attaching it to an arbitrary object with an adhesive layer. This type of recording medium is a so-called (adhesive) label type. In the recording medium shown in FIG. 4, each layer is provided on a base material by a coating method, or a light selective reflection layer 3, a black layer 4 and an adhesive layer of a cholesteric liquid crystal layer that can be peeled off in advance on another base material. A transfer foil formed by laminating 7 is prepared, and the above-mentioned transfer foil is formed on the base material 2 on which the adhesive layer 8 and the release sheet 9 are previously formed. It is also possible to transfer and provide a laminate of the light selective reflection layer 3, the black layer 4 and the adhesive layer 7 of the cholesteric liquid crystal layer.

  FIG. 5 is a schematic cross-sectional view showing an embodiment in which the recording medium 1 of the present invention is attached to an adherend (arbitrary object) 10. A light selective reflection layer is provided on the adherend 10. 3, a recording medium 1 on which a black layer 4 and an adhesive layer 7 are laminated is in close contact with the adhesive layer. In this case, using a transfer foil formed by laminating the light selective reflection layer 3, the black layer 4 and the adhesive layer 7 of the cholesteric liquid crystal layer so as to be peelable on the substrate, the light selection is performed on the adherend 10. The reflective layer 3, the black layer 4, and the adhesive layer 7 are provided by transfer, or the film is provided with a light selective reflection layer in the form of a plastic film produced by a melt extrusion method or the like. The recording medium 1 provided with the adhesive layer 7 made of a pressure-sensitive adhesive on the surface can be pressed and pasted onto the adherend 10.

  FIG. 6 is a schematic plan view showing an embodiment of the medium 1 in which information is recorded by destroying the black layer of the recording medium of the present invention with a heating means. The light of the cholesteric liquid crystal layer is formed on the entire surface of the recording medium 1. A selective reflection layer and a black layer are laminated, and as the recording unit 5, a number “12345” indicating a date and the like and a “name” such as a name are recorded as individual data, that is, as variable information. The other part excluding the recording part 5 is a non-recording part 6, and the non-recording part 6 has a black selective layer 3 with a black layer 4 as a base, and a light selective part 6. The color and color changing effects of the reflective layer are prominent. On the other hand, in the information recording unit 5, the black layer is partially removed and there is no underlying black layer, so the light selective reflection layer becomes inconspicuous, and the contrast between the non-recording unit 6 and the recording unit 5 causes the information The records are easy to read.

  FIG. 7 is a schematic plan view showing an embodiment in which a medium 1 on which information is recorded by breaking a black layer of a recording medium of the present invention by a heating means is provided on a part of a substrate 11 (of an arbitrary object). is there. On a base material 11 of an arbitrary object such as a card, a medium 1 on which information is recorded by destroying a black layer of a recording medium by a heating means is affixed. This recording medium 1 is formed by laminating a light selective reflection layer of a cholesteric liquid crystal layer and a black layer. As the recording unit 5, a number “12345” indicating a date and the like and a “name” such as a name as individual data. That is, it is recorded as variable information. The other part of the recording medium 1 excluding the recording part 5 is a non-recording part 6, and the non-recording part 6 has a black layer, so that the light selective reflection layer 3 is provided with the black layer 4 as a base. In addition, the color and color variable effects of the light selective reflection layer are conspicuous. On the other hand, in the information recording unit 5, the black layer is partially removed and there is no underlying black layer, so the light selective reflection layer becomes inconspicuous, and the contrast between the non-recording unit 6 and the recording unit 5 causes the information The records are easy to read.

  The recording media shown in FIGS. 1 to 5 are not limited to the illustrated shapes, and can be changed as appropriate. For example, the cholesteric liquid crystal layer can have a laminated structure of two or more layers. However, in the case of laminating, it is possible to interpose a retardation layer between the light selective reflection layers without directly laminating them between the cholesteric liquid crystal layers. By providing this retardation layer, information by reflected light from different liquid crystal layers can be observed depending on the viewing angle of the recording medium, and the forgery prevention property is further enhanced. Hereinafter, each layer and components constituting the recording medium of the present invention will be described in detail.

(Base material)
The recording medium in the present invention can have a structure in which a light selective reflection layer of a cholesteric liquid crystal layer and a black layer are laminated on a substrate 2. The substrate in this recording medium is made of a sheet-like, film-like or plate-like material, and the material is not particularly limited. Polyethylene terephthalate (PET), nylon, cellulose diacetate, polystyrene, polyethylene, polypropylene In addition, plastics such as polyester, polyimide, polyvinyl chloride, and polycarbonate, metals such as copper and aluminum, paper, impregnated paper, and the like can be used alone or in combination and laminated. The thickness of the substrate is suitably about 0.005 to 5 mm.

(Light selective reflection layer)
As an element constituting the recording medium of the present invention, there is a light selective reflection layer 3, which is a cholesteric liquid crystal layer. The cholesteric liquid crystal layer can be formed on the above-mentioned base material by converting the cholesteric liquid crystal into an ink and using intaglio printing such as gravure printing, lithographic printing such as an offset method, letterpress printing, and screen printing. If necessary, an alignment film may be provided on the side of the substrate on which the cholesteric liquid crystal layer is laminated. The alignment film may be used as an alignment film in general, such as polyvinyl alcohol resin (PVA) or polyimide resin. Any of them may be used. The alignment film can be formed by applying a solvent solution of these resins to the surface of a substrate such as a plastic film by an appropriate application method and drying, followed by rubbing with a cloth, a brush, or the like. it can.

The thickness of the cholesteric liquid crystal layer thus formed is desirably about 1 μm to 20 μm. The mass per unit area is about 1 to 20 g / m ² when dried. If the thickness is too small, the two characteristics of circularly polarized light selectivity and selective reflection characteristic peculiar to cholesteric liquid crystals cannot be fully exhibited. If the thickness is too thick, the orientation of the liquid crystal is lowered, which is also disadvantageous in terms of cost. . The cholesteric liquid crystal layer can be provided not only as a single layer but also as a laminate of two or more layers. For example, a cholesteric liquid crystal “HELICONE (registered trademark)” manufactured by Wacker Chemie, Inc. can be used as the cholesteric liquid crystal material.

  The cholesteric liquid crystal used in the present invention has a regular twist so that the alignment structure of liquid crystal molecules draws a spiral in the film thickness direction. A cholesteric liquid crystal has two optical properties of selective reflectivity and circular polarization selectivity when the pitch P (the film thickness necessary for the liquid crystal molecules to rotate 360 °) and the wavelength λ of incident light are substantially equal. It is known to exhibit properties. (Reference: Basics of liquid crystal and display applications, Corona, etc.)

Selective reflectivity refers to the property of strongly reflecting light within a specific wavelength band of incident light. Since the selective reflectivity is limited and expressed within a specific wavelength band, the reflected light becomes a chromatic color with high color purity by appropriately selecting the pitch P of the polymer cholesteric liquid crystal. If the center wavelength of the band lambda _S, the bandwidth [Delta] [lambda], these optical media pitch P (= λ / nm) and average refractive index _{n m (= √ ((ne} 2 + no 2) / 2)) Is determined by the following equations (1) and (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 (Δn = n e -n} o).
λ _S = n _m · P (1)
Δλ = Δn · P / n _m (2)

The center wavelength λs and the wavelength bandwidth Δλ shown in the above equations (1) and (2) are defined when the incident light to the cholesteric liquid crystal layer is vertically incident (0 ° incidence, on-axis incidence). When the incident light is obliquely incident (off-axis incident), the pitch P apparently decreases, so that the center wavelength λ _S shifts to the short wavelength side, and the wavelength bandwidth Δλ decreases. This phenomenon is called blue shift because λ _S shifts to the short wavelength side, and the shift amount depends on the incident angle, but can be easily identified by visual observation. For example, the reflected color of a cholesteric liquid crystal that is colored red when viewed from the vertical (0 ° incidence position) changes in order of orange, yellow, green, blue-green, and blue as the viewing angle increases. Observed. In this way, the cholesteric liquid crystal layer shifts to the short wavelength side depending on the viewing angle, and shows (changes) a special color that cannot be reproduced by color copying. It is a thing.

  Since the cholesteric liquid crystal layer shows a unique reflection color, it is possible to easily determine whether the recording medium using the liquid crystal layer is true or false, and also has circular polarization selectivity. , Selectively reflects either left circularly polarized light or right circularly polarized light. The circularly polarized light selectivity means a property of transmitting only circularly polarized light in a specific rotation direction and reflecting circularly polarized light having the opposite rotation direction. Of the incident light, the circularly polarized light component in the same direction as the twist direction of the alignment structure of the cholesteric liquid crystal is reflected, and the rotational direction of the reflected light is also the same direction, while the circularly polarized light component rotating in the opposite direction is transmitted. Is a unique property unique to cholesteric liquid crystals. In the case of a cholesteric liquid crystal having a left twisted structure, the left circularly polarized light is reflected, the reflected light remains as the left circularly polarized light, and the right circularly polarized light is transmitted. In the case of a cholesteric liquid crystal having a right twist structure, right circularly polarized light is reflected, reflected light remains right circularly polarized light, and left circularly polarized light is transmitted.

  The liquid crystal material used for the cholesteric liquid crystal layer in the recording medium of the present invention is, for example, a side chain polymer such as polyacrylate, polymethacrylate, polysiloxane, polymalonate having a liquid crystal forming group in the side chain, and a liquid crystal forming group in the main chain. Main chain polymers such as polyester, polyesteramide, polycarbonate, polyamide, polyimide, etc. can be mentioned.

  The polymer cholesteric liquid crystal layer in the aligned state has a property of reflecting either left circularly polarized light or right circularly polarized light in incident light. Also, it has an effect that the hue looks different depending on the viewing angle. Therefore, this polymer cholesteric liquid crystal layer is a layer that selectively reflects light, in other words, a light selective reflection layer. This light selective reflection layer can be formed by applying a solvent solution of cholesteric liquid crystal by various printing methods and drying, or at this time, preparing an ultraviolet polymerizable composition using polymerizable cholesteric liquid crystal In addition, the obtained ultraviolet polymerizable composition can be applied by various printing methods, dried, and then irradiated with ultraviolet rays to be polymerized. The light selective reflection layer made of a cholesteric liquid crystal layer has transparency, except that the hue looks different depending on the viewing angle, and in that sense, has transparency.

  In order to realize the alignment state, an ultraviolet polymerizable composition prepared using a solvent solution of cholesteric liquid crystal or polymerizable cholesteric liquid crystal is applied to the surface of the stretched plastic sheet, or an alignment film is formed on the surface of the object. After the formation, an ultraviolet polymerizable composition prepared by using a cholesteric liquid crystal solvent solution or a polymerizable cholesteric liquid crystal may be applied. When two or more light selective reflection layers are provided, the thickness of the layers, the helical pitch of the material, and the like can be configured differently to give more complicated optical characteristics. Alternatively, since the light selective reflection layer can be formed in a pattern, one may be formed as a uniform layer and the other may be formed in a pattern.

Examples of the polymerizable cholesteric liquid crystal material include compounds represented by the following general formula (1) and compounds represented by the formulas (2) to (10). These examples are monomers, but may be oligomers or polymers. Two or more kinds selected from the compounds represented by the general formula (1) and the compounds represented by the formulas (2) to (10) are used in combination of two or more compounds represented by the general formula (1) You may use together.

  In the above general formula (1), R1 and R2 each represent hydrogen or a methyl group, and X is preferably a chlorine or methyl group. Moreover, it is preferable when a and b which show the chain length of the alkylene group which is a spacer of the compound represented by General formula (1) are the range of 2-9 to express liquid crystallinity.

You may mix | blend the chiral agent represented by following formula (11)-formula (13) with said liquid crystalline compound.

In the above formula (11), R3 represents hydrogen or a methyl group. In the above formulas (11) and (12), Y is any one of formulas (i) to (xxiv) represented by the following formulas (14) and (15). In the above formulas (11) to (13), c, d, and e, which indicate the chain length of the alkylene group, are preferably in the range of 2 to 9 in terms of exhibiting liquid crystallinity.

  The above-mentioned cholesteric liquid crystal material and chiral agent include, as an example, an ultraviolet polymerization initiator, a solvent and a diluent, as an example. It is preferable to prepare a coating solution having a concentration of about 30% by mass by mixing at a blending ratio of 2 and dissolving the powder obtained by mixing using a solvent such as toluene. The blending ratio can be appropriately determined depending on the type of cholesteric liquid crystal material, chiral agent, or ultraviolet polymerization initiator to be used, the coating method or coating machine, or the desired coating amount.

  The cholesteric liquid crystal layer may be of a type that reflects either left-handed polarized light or right-handed polarized light, and may use a liquid crystal material that exhibits a plurality of different reflected colors in the same direction. Further, as a method of forming a cholesteric liquid crystal layer on a substrate, for example, a liquid crystal pigment obtained by aligning the liquid crystal material described above with, for example, molecular orientation, then irradiating with ultraviolet rays, crosslinking, and then pulverizing and pigmenting the vehicle is used. A known printing method as described above may be used by dispersing in, that is, converting the liquid crystal material into an ink.

  Further, as the light selective reflection layer, not only the above cholesteric liquid crystal layer but also various materials can be used. For example, a pigment whose color changes depending on the viewing angle, a vapor deposition thin film, or two colors are used. It can comprise by using a sex pigment. Examples of pigments whose color changes depending on the viewing angle include pearl pigments in which layers of high refractive index silicon oxide, titanium oxide, iron oxide, and the like, and layers of low refractive index mica, etc. are laminated. Are available from Shiseido Co., Ltd. under the trade name; Infinite Color and Merck (Germany) trade name; Iriodin. The deposited thin film is formed by forming a metal such as aluminum or other material as a thin film by a vapor phase method, and exhibits a so-called interference color like an oil thin film floating on the water surface. A dichroic dye is composed of long-chain dye molecules that have different light absorption depending on the direction of the molecular axis. For example, the light component in the normal direction relative to the direction of the molecular axis of the dye molecule has almost no absorption. The light component in the direction parallel to the direction of the molecular axis has an absorptive property and does not transmit light, and examples include anthraquinone, azo, or bisazo dyes. can do. Among the above, pigments or dichroic dyes that change color depending on the viewing angle are dispersed in an appropriate binder resin, diluted with a solvent to form a coating composition, silk screen printing, gravure printing, or a known one What is necessary is just to apply to a target surface by the coating method.

(Black layer)
The black layer 4 which is a component of the recording medium of the present invention is a recording medium for recording information by heating or melting the material contained in the black layer by heating means such as a laser beam or a thermal head. As a part, it is partially destroyed and removed. In this recording portion, since the underlying black layer is lost, the light selective reflection layer is inconspicuous. On the other hand, since the black layer remains in the non-recording portion of the recording medium, the light selective reflection layer is provided with the black layer as a base, and the color and color variable effects of the light selective reflection layer are noticeable. The recording of information becomes easy to read due to the contrast between the non-recording portion and the recording portion. The laser (light) that is the above recording means is a well-known solid laser such as ruby laser, YAG laser, glass laser, He-Ne laser, He-Xe laser, ion laser, nitrogen laser, carbon dioxide gas laser. A gas laser such as a carbon monoxide laser, other discharge-excited molecular laser, or an excimer laser, a chemical laser, a dye laser, or a semiconductor laser can be used. In particular, when used in the present invention, those that oscillate infrared rays having a wavelength in the range of about 0.7 to 30 μm are preferable.

The black layer can be a layer containing carbon black having laser absorptivity in a binder. In this case, as the binder, polyamide resin, phenol resin, alkyd resin, vinyl resin, acrylic resin, nitrocellulose, or a mixture thereof can be used. The content is preferably in the range of 5 to 15% by mass. When the carbon black content is less than 5% by mass, the laser absorption in the black layer is insufficient, and the black layer as the recording portion cannot be removed satisfactorily. On the other hand, if the content of carbon black exceeds 15% by mass, heat generation / destruction due to laser absorption in the black layer becomes excessive, and the recorded portion becomes unclear. The black layer can be formed using a coating liquid in which a binder resin and carbon black are dissolved or dispersed in a solvent. Coating is performed by a general method such as a roll coater method, a reverse coater method, a knife coater method, a comma coater method, or a gravure coater method. The coating amount is preferably 0.1 to 10 g / m ² (dry state).

  In addition, a black metal oxide such as titanium oxide, chromium oxide, nickel oxide, iron oxide or the like is formed by a vacuum evaporation method, a sputtering method, a plating method, etc., and the black layer is a light selective reflection layer that is a cholesteric liquid crystal layer. And can be laminated. In addition, the black layer can be formed by laminating the following metal vapor deposition layer and black printing layer. The metal vapor deposition layer is made of, for example, a metal or alloy such as Te, Sn, In, Al, Bi, Pb, Zn, Cu, Fe, Co, Ni, Cr, Ti, a mixture thereof, or other elements such as Te-carbide. And can be formed by vacuum deposition, sputtering, plating, or the like. The film thickness of the black layer and metal vapor deposition layer made of the above metal oxide is 100 to 1 μm, preferably about 400 to 1000 μm. The black layer is not only formed by the above-described coating method and vapor deposition method, but is also produced by forming a raw material containing the binder and carbon black described in the coating method into a film shape by a melt extrusion method. It is also possible.

(Middle layer)
When the recording medium of the present invention has a structure in which two or more cholesteric liquid crystal layers are laminated, it is preferable that the cholesteric liquid crystal layers are laminated via an intermediate layer without being directly laminated. This intermediate layer can prevent adverse effects such as coloring troubles due to the interaction between the polymer cholesteric liquid crystal layers.

As the resin constituting the intermediate layer, starches, celluloses, gelatin, casein, polyvinyl alcohols, maleic anhydride copolymers, acrylics, styrene-butadiene copolymer emulsions, urea resins, melamine resins, amide resins, A polyurethane resin etc. are mentioned. The resin as described above and various auxiliary agents as necessary can be added to adjust the ink, and can be formed by known coating methods such as offset printing, letterpress printing, and gravure coating. The intermediate layer is formed so as not to impair the transparency in order to make it easy to distinguish a cholesteric liquid crystal layer located below the intermediate layer as viewed from the viewer. The thickness of the intermediate layer is about 0.1 μm or more, preferably 1 to 10 μm. In this case, the coating amount at the time of drying is about 0.1 to 10 g / m ² . If the thickness is too small, the function as an intermediate layer is insufficient, and if it is too thick, the adhesion to the cholesteric liquid crystal layer is lowered, which is disadvantageous in terms of cost.

(Retardation layer)
In the recording medium label of the present invention, the retardation layer can be used in combination with the cholesteric liquid crystal layer. In particular, it is possible to laminate two or more cholesteric liquid crystal layers. When two or more layers are laminated, a retardation layer is provided between the liquid crystal layers, and information by reflected light from different liquid crystal layers can be observed depending on the viewing angle of the recording medium. The phase difference layer is not limited as long as it is a material that generates a phase difference, and examples thereof include a liquid crystal material and a stretched film that can form a nematic phase. Examples of the liquid crystal material capable of forming a nematic phase include a polymerizable liquid crystal material and a non-polymerizable polymer liquid crystal material. As the polymerizable liquid crystal material, any of a polymerizable liquid crystal monomer, a polymerizable liquid crystal oligomer, and a polymerizable liquid crystal polymer can be used.

  The stretched film is a plastic film produced by a stretching process. Stretching is a method for producing a film by stretching a plastic at an appropriate temperature not higher than the melting point and not lower than the glass transition point, and includes uniaxial stretching and biaxial stretching depending on the stretching direction. In the present invention, since it is sufficient that the refractive index anisotropy exists, a film produced by any method of uniaxial stretching and biaxial stretching can be used. Specifically, the retardation layer is made of cellophane, cellulose, polyester, polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), or polyvinylidene chloride (PVDC). , Stretched films made of polymethyl methacrylate (PMMA), polystyrene (PS), polyethylene terephthalate (PET), nylon or the like can be used.

(Adhesive layer)
The recording medium of the present invention can have a structure in which a light selective reflection layer of a cholesteric liquid crystal layer, a black layer, and an adhesive layer 7 are sequentially laminated. Depending on the type of the adhesive layer, the recording medium can be adhered to an arbitrary object only by pressure, or by heating and pressing. First, examples of the adhesive layer include a heat seal layer that melts and adheres by heating, and is formed from a heat-sensitive adhesive having a relatively low melting point and a large adhesive force. Examples of such heat-sensitive adhesives include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer (EEA), polyethylene, polystyrene, polyester, polypropylene, polybutene, petroleum resin, and vinyl chloride resin. , Vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose or polyacetal In particular, those having a relatively low softening point, for example, a softening point of 50 to 80 ° C., which has been conventionally used as a heat-sensitive adhesive are preferable. Prepare ink prepared by dissolving or dispersing these materials in a solvent, and can be formed by general coating methods such as roll coater method, reverse coater method, knife coater method, comma coater method, gravure coater method, and the thickness is Usually, it is preferably in the range of about 0.5 to 5 g / m ² at the time of drying.

(Adhesive layer)
A recording medium can be affixed to an arbitrary object using not the heat-seal type adhesive layer but the pressure-sensitive adhesive layer 8 that adheres only by pressure. Usually, since the surface of the adhesive layer has adhesiveness at room temperature (25 ° C.), the release layer is handled by laminating the adhesive layer on the adhesive layer. In this case, the release sheet is peeled off, and the recording medium can be attached to an arbitrary article by the adhesive layer. The pressure-sensitive adhesive layer can be formed using, for example, an aqueous type or solvent type coating solution made of an acrylic resin, a natural rubber resin, a synthetic rubber resin, a silicone resin, or the like. Coating is performed by a general method such as a roll coater method, a reverse coater method, a knife coater method, a comma coater method, or a gravure coater method. The coating amount is preferably 0.1 to 50 g / m ² (dry state).

The release sheet is laminated to protect the adhesive layer until the recording medium is attached to the article, and is peeled off during use. A general release sheet can be used and is not particularly limited. For example, high-quality paper, coated paper, cast coated paper, aluminum foil / paper, resin-impregnated paper, synthetic paper, and other paper base materials, polyester resin, polypropylene resin, vinyl chloride resin, foamed polyester resin, foamed polypropylene resin, etc. A material obtained by coating a silicone resin as a release agent on one surface of the molecular resin film base substrate can be used. In the case of a paper base, a paper having a basis weight of 30 to 300 g / m ² can be used, and in the case of a film base, a film having a thickness in the range of 10 to 300 μm can be used.

  Note that the recording medium of the present invention includes at least a light selective reflection layer that is a cholesteric liquid crystal layer without providing an adhesive layer or an adhesive layer, even if the adhesive layer or the adhesive layer / release sheet is laminated. Needless to say, the black layer can be used in a laminated form.

(Recording variable information)
In the present invention, in the recording medium described above, heating by a thermal head or laser light irradiation, the black layer is heated, melted or decomposed, and the black layer is destroyed and removed, so that information can be received. To be recorded. Examples of the recorded information include fixed information and variable information that is different information for each recording medium. In the present invention, it is preferable to record variable information in order to improve forgery prevention. This variable information includes the date of manufacture, product name, name, address, and other items to which the recording medium is given (high-priced products, identification cards, credit cards, savings cards, prepaid cards, commuter passes, traveler's checks Or individual data specifying the type of the recording medium itself.

  In the recording medium described above, information is recorded by heating with a thermal head or irradiating a laser beam to heat, melt or decompose the black layer to destroy and remove the black layer. However, depending on the information recording conditions, not only the black layer but also a part of the adjacent light selective reflection layer may be destroyed or removed. However, the light selective reflection layer is not completely destroyed or removed by the information recording, and the base black layer is lost in the recording portion, but the light selective reflection layer remains.

  Next, the present invention will be described more specifically with reference to examples. Hereinafter, unless otherwise specified, parts or% is based on mass.

Example 1
Using a transparent polyethylene terephthalate film with a thickness of 16 μm as a base material, printing is performed on one surface of the base material by screen printing using a cholesteric liquid crystal layer ink having the following composition, followed by irradiation with ultraviolet rays immediately after printing. The light selective reflection layer shown in FIG. 1 consisting of a cholesteric liquid crystal layer having a thickness of 10 g / m ² is sometimes formed, and a black layer ink having the following composition is further formed on the light selective reflection layer by a gravure coating method. A black layer having a thickness of 5 g / m ² was formed at the time of drying, and a recording medium of Example 1 having a structure as shown in FIG. 1 was produced.

(Cholesteric liquid crystal layer ink)
Cholesteric liquid crystal pigment (Wacker Chemie, HELICONE (registered trademark) HCXL) 30 parts Medium ink (The Inktec Co., Ltd., UV card) 70 parts

(Black layer ink)
Carbon black 12 parts Polyamide resin 88 parts Methyl ethyl ketone 20 parts Toluene 20 parts

(Example 2)
On the black layer of the recording medium prepared in Example 1 above, an adhesive of ethylene-vinyl acetate copolymer having a glass transition temperature of 30 ° C. is used, and a thickness of 2 g / m when dried by a gravure coating method. ^Two heat-seal type adhesive layers were formed. The adhesive layer of this recording medium and the card substrate under the following conditions are superposed so that they are in contact with each other, and heated and pressurized at a heating temperature of 90 ° C. for 10 seconds to bond them together. After that, the recording medium (transfer foil) was peeled from the card base material, and an adhesive layer, a black layer, and a light selective reflection layer were sequentially laminated on the card base material.

(Card base material)
White polyethylene terephthalate film (thickness: 188 μm, E-24 manufactured by Toray Industries, Inc.)

  From the light selective reflection layer side of the card substrate to which the black layer or the like is transferred, the carbon dioxide laser is irradiated, and the black layer is destroyed and removed by a heating means using a laser as shown in FIG. A recording medium on which variable information was recorded was obtained.

(Example 3)
On the black layer of the recording medium prepared in Example 1 above, an adhesive of ethylene-vinyl acetate copolymer having a glass transition temperature of 30 ° C. is used, and a thickness of 2 g / m when dried by a gravure coating method. ^Two heat-seal type adhesive layers were formed. The adhesive layer of this recording medium and the transparent polyethylene terephthalate film (PET) substrate having a thickness of 25 μm are superposed so that they are in contact with each other by heating and pressing at a heating temperature of 90 ° C. for 10 seconds. After the temperature reached room temperature (25 ° C.), the recording medium (transfer foil) was peeled from the PET base material, and an adhesive layer, a black layer, and a light selective reflection layer were sequentially laminated on the PET base material. .

Further, on the opposite surface of the PET substrate to which the black layer or the like is transferred, by using a strong adhesive pressure sensitive adhesive made of an acrylic resin, by gravure printing so as to have a thickness of 30 g / m ² at the time of drying, An adhesive layer is formed on the entire back surface of the PET substrate, and a commercially available release paper having a basis weight of 90 g / m ² coated with a silicone resin on a high-quality paper base is used as a release sheet on the adhesive layer. The labels were produced by pasting and pasting. A carbon dioxide laser is irradiated from the light selective reflection layer side of the label, and the black layer is broken and removed by a laser heating means as shown in FIG. 6 to obtain a recording medium on which variable information is recorded. It was.

  The recording medium of Example 1 obtained as described above has a light selective reflection layer with the black layer as a base on the entire surface of the recording medium, and the color and color variable effects of the light selective reflection layer are remarkable. It was. The recording media obtained in Examples 2 and 3 were those in which the black layer was destroyed and removed by heating means to record information, and the black layer in the information recording part was partially destroyed. Since the black layer is removed, the light selective reflection layer is inconspicuous. On the other hand, the black layer remains in the non-recording area. In addition, the color and color variation effect of the light selective reflection layer is prominent, the contrast between the non-recording portion and the recording portion is high, and information recording is easy to read.

It is a schematic sectional drawing which shows one Embodiment of the recording medium of this invention. It is a schematic sectional drawing which shows the state after destroying a black layer with a heating means with respect to the recording medium shown in FIG. 1, and recording information. It is a schematic sectional drawing which shows other embodiment of the recording medium of this invention. It is a schematic sectional drawing which shows other embodiment of the recording medium 1 of this invention. It is a schematic sectional drawing which shows embodiment of the state in which the recording medium of this invention was affixed on the to-be-adhered body (arbitrary object). FIG. 3 is a schematic plan view showing an embodiment of a medium on which information is recorded by breaking a black layer of the recording medium of the present invention with a heating means. FIG. 3 is a schematic plan view showing an embodiment in which a medium on which information is recorded by breaking a black layer of a recording medium of the present invention with a heating means is provided on a part of a substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording medium 2 Base material 3 Light selective reflection layer 4 Black layer 5 Recording part 6 Non-recording part 7 Adhesive layer 8 Adhesive layer 9 Release sheet 10 Substrate 11 (Any object) Base material

Claims (4)

  A recording medium comprising at least a light selective reflection layer, which is a cholesteric liquid crystal layer, and a black layer.   The recording medium according to claim 1, wherein the black layer is destroyed by a heating unit to record information.   The recording medium according to claim 1, wherein two or more light selective reflection layers are provided. The recording medium according to claim 3, wherein a retardation layer is interposed between the light selective reflection layers.

Images