JP2002254546A - Latent image recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a latent image recording medium such as a lottery ticket, passbooks, a show ticket, a membership certificate, a passport, a picture book, a game, a cash card, a telephone card or an IC card, of such a construction that a latent image in a latent image forming structural layer can be visually determined when viewed through a dedicated verifying medium, contrary to a normal state that an image such as a hologram image or a diffraction grating image played back through the mutual interference of a reflected and a diffracted light is only viewed. SOLUTION: At least the latent image forming structural layer and a diffraction forming structural layer with light transmission properties are laminated in that order on a base material. Further, the latent image forming structural layer is at least a reflective layer and a polymer material layer showing thermotropic properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for observing an image such as a hologram image or a diffraction grating image which is reproduced by interference of reflected and diffracted light under normal conditions. The latent image in the latent image forming structure layer can be recognized when observed through a device, such as a lottery ticket, passbook, appreciation ticket, membership card, passport, picture book, game, cash card, telephone card, IC card, etc. An image recording medium.

[0002]

2. Description of the Related Art There are various types of latent image recording media in which a latent image is provided at a desired portion. For example, a latent image (hidden characters, etc.) is inserted by using a line pitch of a line, and a line drawing or a filler is used in which a latent image is displayed by concealing the line portion with a verification member. Prints the latent image with transparent ink
A pencil-out printed matter (deco mat) or the like in which a pencil pattern adheres to a printed part when a latent image portion is rubbed with a pencil to display a hidden pattern or the like. These latent image recording media are used for play rather than full-scale latent image recording media because hidden latent images can be seen by observing them well.

Image recording materials for recording various latent images including these include irreversible thermosensitive coloring ink, filler-containing white ink, reversible thermosensitive coloring ink, photochromic ink, fluorescent ink, magnetic ink, and infrared ink. There are absorption inks and the like, which are used in various forms.

An irreversible thermosensitive ink is an ink which irreversibly develops color when heated, and forms a latent image on a substrate by using a white or colorless and transparent type of this ink to form a latent image recording medium. . However, the image recording medium having such a configuration requires a heat source device to display a latent image, and furthermore, an image displayed once by color cannot be erased, so that its use is limited.

[0005] The filler-containing white ink is a white ink containing a filler harder than a metal such as titanium oxide. A latent image is printed on white paper by using this ink. The latent image recording medium is overcoated with varnish. The latent image recording medium having such a configuration can display the intended image by rubbing the latent image portion with a coin or the like, but the display can be performed only once and the use is limited.

Further, a reversible thermosensitive coloring ink (thermochromic ink) is an ink which reversibly develops or decolors by applying heat, and utilizes the property of returning to the original state when the heating is stopped and left for a while. However, it is used as a material for forming a concealing layer or the like for temporarily concealing a latent image or image of a latent image recording medium to form a latent image. However, this ink and a latent image recording medium on which a latent image has been recorded with this ink have low durability, especially low heat resistance, and their applications are limited.

Furthermore, photochromic inks are
Ink that develops color when irradiated with light and is white or colorless and transparent is used as a material for forming a latent image on a latent image recording medium. However, this ink and a latent image recording medium on which a latent image is recorded with this ink are:
Poor resistance, especially light resistance, limits its use.

Further, a fluorescent ink is an ink which emits fluorescence when irradiated with actinic rays such as ultraviolet rays, and may form a latent image of a white or colorless transparent type. There are two types of fluorescent inks: organic and inorganic types. The organic type can be confirmed to emit light only by containing a very small amount of organic fluorescent substance in the ink. Limited. In addition, the inorganic type requires a large amount of an inorganic fluorescent substance to be contained in the ink (about 10 to 20%), and the latent image formed thereby can be visually recognized by itself. is necessary.

Further, the magnetic ink is obtained by dispersing magnetic fine particles in the ink. In order to form a latent image using the magnetic ink, first, a coercive force (about 300 Oe) capable of magnetic recording is used.
Above), a portion of this magnetic layer may be magnetized in a pattern thereafter. The latent image can be visualized by sprinkling iron powder on the magnetic layer and selectively adsorbing only the magnetized latent image portion. However, in this method, the process of displaying the latent image is complicated, and the image can be rewritten, and the application is limited.

[0010] Furthermore, a latent image is formed by forming an image with an ink that absorbs infrared rays, on which an infrared ray is transmitted to conceal the image to form a latent image (to make it invisible). Although there is a recording medium, an infrared irradiation device, an infrared camera, and the like are required to display and display the hidden latent image, and the device becomes large. Further, there is an ink (IV ink) which is white or colorless in the visible light region, but absorbs in the infrared region, and there is also a latent image recording medium on which a latent image is formed by using this ink. An infrared camera or the like is required for visualization.

On the other hand, a latent image composed of halftone dots or lines in which the pitch or angle is partially changed may be formed with ordinary printing ink. Visualization of the latent image having such a configuration is performed by superimposing a transparent film provided with neatly arranged halftone dots or lines so as to generate moire on the latent image, or the line portion other than the latent image is formed by the above-described method. It was superimposed so as to be concealed by the lines of the transparent film. In this case, the construction of the latent image and the latent image recording medium is simple, and the appearance and erasure of the latent image can be repeated. However, there is a problem that a latent image pattern having a complicated shape cannot be formed.

On the other hand, holograms and diffraction grating images have conventionally been able to express stereoscopic images and special decorative images by using the light diffraction / interference effect, and their manufacturing methods require advanced manufacturing techniques. Is used for some or all of credit cards, securities, certificates, and the like.

Holograms are classified into relief holograms and volume holograms according to the manufacturing method. For the relief hologram, a relief-type master hologram consisting of a fine uneven pattern is produced by an optical photographing method, and then the uneven pattern is duplicated by an electroplating method to produce a nickel press plate. The plate is manufactured by heating and pressing the plate on the hologram forming layer. On the other hand, a volume hologram is obtained by recording interference fringes in a volume direction using a recording material such as a photosensitive resin. In this type of hologram, a so-called Lippmann hologram is generally used, and the refractive index of the photosensitive resin is changed in the volume direction to form a reflection hologram.

Further, the diffraction grating image is formed by arranging a plurality of micro cells made of a diffraction grating on the surface of the diffraction forming layer, and changing at least one of the spatial frequency of the diffraction grating, the direction of the diffraction grating, and the arrangement of the cells. Like the hologram described above, it is used in the field of cards and printed matter as an effective means for preventing forgery.

However, these holograms and diffraction grating images are effective as a means for preventing forgery as described above, but with the recent progress in duplication technology, image recording having holograms and diffraction grating images has been carried out. Reproductions that are close to authentic media can also be obtained.

[0016]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-described situation, and it is difficult to reflect and reflect light in a normal state.
Only images such as hologram images and diffraction grating images, which are reproduced by diffracted light interfering with each other, are observed, but a latent image whose contents can be confirmed only when observed through a dedicated verification medium. It is another object of the present invention to provide a latent image recording medium having a forgery prevention effect.

[0017]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention according to claim 1 has the following features.
On the substrate, at least a latent image forming structure layer and a diffraction forming structure layer having optical transparency are laminated in this order,
The latent image forming structure layer comprises at least a reflective layer and a thermotropic polymer material layer.

The invention described in claim 2 is the same as the invention described in claim 1.
In the latent image recording medium described in the above, the diffraction forming structure layer having optical transparency comprises at least an image reproduction effect layer and a diffraction forming layer, has a higher refractive index than the constituent material of the diffraction forming layer, and has a lower latent formation layer. It is characterized by being composed of a constituent material having at least transparency enough to recognize the existence of the image forming structure layer.

Further, according to a third aspect of the present invention, in the latent image recording medium according to the first or second aspect,
The reflection layer constituting the latent image forming structure layer is provided on the entire surface or a part of the latent image forming structure layer, and is made of a metal material.

According to a fourth aspect of the present invention, there is provided the latent image recording medium according to any one of the first to third aspects, wherein the polymer material layer exhibiting the thermotropic property has a desired portion. Are formed, and a latent image is formed by orienting the latent images.

According to a fifth aspect of the present invention, there is provided the latent image recording medium according to any one of the first to fourth aspects, wherein the latent image recording medium has a latent image forming structure layer of a substrate and a light transmitting property. An adhesive layer is formed on the side where the diffraction forming structure layer is not laminated.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 is a schematic sectional explanatory view of a latent image recording medium showing an example of an embodiment of the present invention.
The latent image recording medium 1 basically includes a substrate 2, a latent image forming structure layer 5, and a light-transmitting diffraction forming structure layer 8 laminated in this order. In the latent image recording medium 1 shown in FIG. 1, a protective layer 9 is further formed on a light-transmitting diffraction forming structure layer 8.

Here, the constituent materials of the substrate 2 include synthetic resin such as polyethylene terephthalate, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polystyrene, etc., films such as natural resin, synthetic paper, paper, and thin film glass. Alternatively, a composite or the like in which one selected from these materials is appropriately combined can be used.

On the other hand, the latent image forming structure layer 5 formed on the substrate 2 can record and form a latent image thereon, and the latent image is formed only when observed through a dedicated verification medium. This is a layer that allows the latent image to be recognized, and includes at least a reflective layer 3 and a polymer layer 4 having thermotropic properties thereon.

The reflecting layer 3 only needs to have reflectivity.
The constituent materials are not particularly limited. For example, A
l, various metals such as Cr, Ni, Cu, Ag, or P
An appropriate alloy may be selected from various alloys such as t-Rh and Ni-Cr, and may be provided by vapor deposition or sputtering.

On the other hand, the polymer material layer 4 having a thermotropic property has a melting point of about 80 to 200 ° C. and has a thermotropic property, and is, for example, a polyester copolymer, a polyether, a polycarbonate, a polyisocyanate, or a polyglutamic acid. It is made of a thermotropic polymer material such as an ester, and may be formed by a known layer forming means such as a printing means such as a gravure printing method or a screen printing method or a coating means such as a nozzle coater method.

When the polymer material layer 4 having the thermotropic property is formed normally, the polymer material layer 4 has a random molecular arrangement state having no specific crystal structure. When heat is partially applied to the thermotropic polymer material layer 4 formed in such a molecular arrangement state by a thermal head, a laser beam, a hot stamper or the like, and the portion is melted, the portion is melted. Is oriented in a certain direction, and a latent image corresponding to the heated portion is formed. Although the existence of this latent image is not confirmed as it is, it is recognized when observed through a verification medium such as a polarizing film or a polarizing filter.

The situation at this time is shown in FIG. The latent image recording medium 1 shown in FIG. 2A cannot be recognized simply by visual observation, but can be seen only as a mere image forming body in which a reproduced image 22 such as a hologram image or a diffraction grating image is recognized. . However, as shown in FIG. 2B, when the polarizing film 23 is superimposed on the latent image recording medium 1 having the latent image and observed, an image 24 that has been turned into a latent image appears. The latent image is a portion where a part of the polymer material layer 4 exhibiting thermotropic property is selectively oriented by heat, electricity, magnetic energy, or the like.

The verification medium used for visualizing the latent image is, specifically, a polarizing film or a polarizing filter. For types of polarizing film and polarizing filter, PV
There are various types such as PVA-iodine type, iodine-absorbed PVA-iodine type, dichroic dye type, metal or metal compound-containing type, polyene type and other high molecular polycrystalline types. What is necessary is just to select one and use it by superimposing it on the latent image recording medium 1 as shown in FIG. In the polarizing film, there is also a circular polarizing film in which a quarter-wave film is superimposed on the polarizing film, but by using the circular polarizing film, a latent image can be easily made to appear without depending on an observation angle. It becomes possible.

On the other hand, the diffraction forming structure layer 8 is formed above the latent image forming structure layer 5 described above. The diffraction-forming structure layer 5 is a structure layer in which an image reproduced and irradiated with reflected or diffracted light interferes with each other, that is, a hologram image or a diffraction grating image is observed.

Here, the diffraction grating image is constituted by arranging a plurality of minute cells each composed of a diffraction grating, and changing at least one of the spatial frequency of the diffraction grating, the direction of the diffraction grating, and the arrangement of each cell. This is an image reproduced when reflected and diffracted light when the image constituent part is irradiated with light interferes with each other.

As described above, the diffraction forming layer 7 is a layer for reproducing these diffraction grating images and hologram images. The interference fringes and minute unevenness for reproducing the hologram images and diffraction grating images are stably formed. Any material that can be molded can be used, and it is made of a material that has good moldability by hot pressing, hardly causes press unevenness, and can provide a bright reproduced image. For example, thermoplastic resins such as polycarbonate resin, polystyrene resin and polyvinyl chloride resin, thermosetting resins such as unsaturated polyester resin, melamine resin and epoxy resin, or ultraviolet or electron beam curable having radical polymerizable unsaturated groups What is necessary is just to form with resin alone or these composite materials.

An image reproducing effect layer 6 is provided below the diffraction forming layer 7 as required. This image reproduction effect layer 6
Is provided to increase the diffraction efficiency during reproduction of a hologram image or diffraction grating image, and to reproduce a clearer image and obtain a change in color.

This image reproducing effect layer 6 has a higher refractive index and a higher reflection effect than the constituent material of the diffraction forming layer 7 in which interference fringes for reproducing a hologram image or a diffraction grating image or the like are formed. It is made of a material having at least transparency enough to recognize the existence of the lower latent image forming structure layer 5.

Specifically, TiO ₂ , S having different refractive indexes
High refractive index materials such as i ₂ O ₃ , SiO, Fe ₂ O ₃ , ZnS, and Al, Sn, Cr, Ni, Cu, A
and metal materials such as u, and these materials can be used alone or in a laminated form. This layer is formed by a known thin film forming technique such as a vacuum evaporation method and sputtering, and its thickness varies depending on the application, but may be about 5 to 1000 nm. In addition to the above, as a material constituting the image reproduction effect layer, a material whose refractive index is higher than the polymer material (refractive index n = 1.3 to 1.5) used in the diffraction forming layer 7 is used. , An organic material other than the above inorganic materials, an organic-inorganic composite,
Even a material in which an inorganic filler is dispersed in an organic material can be used. Gravure coat,
It may be formed with a layer thickness of about 0.1 μm to 10 μm by a known coating method such as die coating or screen printing, or a printing method. Further, any material other than the above may be used as long as the material has reflectivity and transparency to the extent that it does not hinder the confirmation of the latent image in the latent image forming structure layer. is there.

On the other hand, the protective layer 9 formed on the diffraction forming structure layer 8 protects the latent image recording medium 1 from external damage, and visually recognizes the latent image by the latent image forming trace from the heat pressure at the time of forming the latent image. The resin used has the role of preventing, for example, acrylic resin, urethane resin, vinyl chloride resin-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin, polystyrene resin A conventionally known thermoplastic resin such as a polyimide resin, a thermosetting resin, an ultraviolet or electron beam curable resin is used alone or in combination.

This layer is further provided with a curing agent for cross-linking the resin, polyethylene washes, carnauba wax, silicone, in order to further enhance the effect of not leaving a print mark when a latent image is formed by a thermal head or the like. Waxes such as waxes, extenders such as calcium carbonate, zinc stearate, silica, alumina and talc;
Fats and oils such as oils and fats can be added within a range that does not impair transparency. The protective layer 9 is formed by a known coating means such as a gravure printing method, a screen printing method, a nozzle coater method, or a printing means such as an offset printing method or a flexographic printing method.

FIG. 3 is an explanatory view showing a latent image recording medium 30 according to another embodiment of the present invention and an example of its use.
The latent image recording medium 30 has a latent image forming structure layer 5, a light-transmitting diffraction forming structure layer 8 and a protective layer 9 formed on a base material 2 in the same manner as the latent image recording medium 1 shown in FIG. They are stacked in order. The difference between the two is that the reflective layer 3 constituting the latent image forming structure layer 5 and the polymer material layer 4 exhibiting thermotropic property, and further, the latent image forming structure layer 5 and the diffractive forming structure having optical transparency. Anchor layer 3 between layer 8
2 and 33 are formed, and the adhesive layer 35 is formed on the base material surface on which the above-described layers are not formed.

The anchor layers 32 and 33 are necessary for firmly adhering the reflective layer 3, the polymer layer 4 exhibiting thermotropic property, the latent image forming structural layer 5 and the diffraction forming structural layer 8 having light transmittance. Are provided according to the conditions. As a constituent material thereof, a thermoplastic resin is preferable, and an acrylic resin, a urethane resin, an epoxy resin, a polyester resin, a vinyl resin or the like can be used alone or in combination. It is not necessarily limited to this. These anchor materials are applied by a known application means such as a gravure printing method, a screen printing method, and a nozzle coater method.

On the other hand, the adhesive layer 35 is formed so as to be attached to and integrated with a medium such as a lottery ticket, passbooks, appreciation ticket, membership card, passport, picture book, game, cash card, telephone card, IC card and the like. Layer. FIG. 3 shows medium 3
FIG. 4 shows a state when the adhesive layer 35 is bonded and integrated. By doing so, the forgery prevention effect, the copy prevention effect, and the like, of the attached medium 34 can be further improved. 4A shows a plan view of the medium 34 to which the latent image recording medium 30 of the present invention shown in FIG. 3 is attached, and FIG. 4B shows the medium 34 observed through the polarizing filter 38. The state at the time is shown. Polarizing filter 38
Observed through the CPU, the latent image appears in the latent image recording medium 30.

FIG. 5 shows the polarizing film 43 and the transparent polymer material layer when the polarizing film 43 is superimposed on the latent image recording medium of the present invention and the latent image in the latent image forming structure layer is observed. FIG. 4 is a diagram conceptually illustrating an optical path state between three layers 41 and a reflection layer 42. When the white irradiation light 44 emitted from the light source 46 passes through the polarizing film 43 to become linearly polarized light, and further passes through the partially transparent polymer material layer 41 having anisotropy in molecular orientation. The light changes to elliptically polarized light and is reflected by the deposition layer 42. The reflected elliptically polarized light passes through the polarizing film 43 again, and is transmitted and reflected light 45.
Come back as. Since the transmitted and reflected light 45 has different light intensity depending on the wavelength, an image having various hues can be obtained. Further, the visible hue varies depending on the angle between the orientation direction of the polarizing film and the polymer material layer having the molecular orientation.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to specific embodiments. <Example 1> An Al film having a thickness of about 60 nm was formed on one surface of a polyethylene terephthalate (PET) substrate having a thickness of 50 µm by a vacuum evaporation method to form a metal reflection layer.
A thermotropic polymer material ink composed of the following [composition of the polymer material layer] is applied thereon by a gravure printing method under the conditions of a drying temperature of 60 ° C. and a coating thickness of 0.5 μm. A molecular material layer was formed. Also,
On the other surface of the base material, an adhesive material ink composed of the following [composition of the adhesive layer 1] was dried at a drying temperature of 80 by a gravure printing method.
An adhesive layer was formed by coating at a temperature of 2.0 ° C. and a thickness of 2.0 μm to obtain a polymer material medium.

On the other hand, on a support made of a transparent PET film having a thickness of 25 μm, a protective layer material ink comprising the following [protective layer composition] was applied by gravure printing at a drying temperature of 60 ° C. and a film thickness of 0.4 μm. It was applied to form a protective layer. Next, on the protective layer, a diffraction forming layer material ink consisting of the following [composition of the diffraction forming layer] is dried at a drying temperature of 80 by a gravure printing method.
The resultant was applied under the conditions of a temperature of 1.0 ° C. and a film thickness of 1.0 μm to form a diffraction-forming layer, thereby obtaining an original transfer foil of a diffraction-forming structure layer.

Next, a nickel image mold having a hologram relief pattern was heated to 100 ° C. and pressed onto the diffraction layer by a known roll embossing method to form a relief pattern on the hologram layer. . On the diffraction forming layer on which the relief pattern was formed by the above method, a 0.05 μm-thick deposited thin film layer made of ZnS was formed by a vacuum deposition method to provide a diffraction effect layer. Next, an adhesive layer material ink composed of the following [composition of the adhesive layer 2] is applied onto the diffraction effect layer by a gravure printing method at a drying temperature of 80 ° C. and a coating thickness of 2.0 μm to form an adhesive layer. Thus, a transfer foil for a diffraction-formed structure layer was obtained.

Further, the polymer liquid crystal medium obtained in each of the above steps and the diffraction-forming structure layer transfer foil are overlapped so that the polymer layer exhibiting thermotropic property and the adhesive layer are in contact with each other. The latent image recording medium of the present invention was obtained by peeling off the support of the transfer foil for the diffraction forming structure layer.

The polymer layer exhibiting thermotropic property of the latent image recording medium is partially oriented by applying a heat pressure with a hot stamper at 120 ° C. for 0.2 seconds.
A latent image recording medium of the present invention having a latent image was obtained.

[Composition of polymer liquid crystal layer] Polymer liquid crystal (Kiracol PLC-7003: manufactured by Asahi Denka Kogyo KK) 20 parts by weight Methyl ethyl ketone 80 parts by weight [Composition of adhesive layer 1] Polyester resin 10 parts by weight Acrylic resin 10 Parts by weight methyl ethyl ketone 40 parts by weight toluene 40 parts by weight [composition of protective layer] acrylic resin 10 parts by weight methyl ethyl ketone 45 parts by weight toluene 45 parts by weight [composition of diffraction forming layer] vinyl chloride-vinyl acetate copolymer 15 parts by weight urethane resin 10 Parts by weight methyl ethyl ketone 50 parts by weight toluene 25 parts by weight [composition of adhesive layer 2] acrylic resin 10 parts by weight polyester resin 10 parts by weight methyl ethyl ketone 30 parts by weight toluene 50 parts by weight

Although the latent image recording medium having the obtained latent image could not be visually recognized at all and the hologram image could be observed as a mere hologram film, the latent image was formed by superimposing a polarizing film. Pattern appeared clearly.

Example 2 An Al film having a thickness of about 60 nm was formed on one surface of a PET base material having a thickness of 50 μm by a vacuum evaporation method to form a metal reflection layer. An anchor layer material ink consisting of the following [composition of anchor layer] was applied thereon by a gravure printing method at a drying temperature of 80 ° C. and a coating thickness of 1.0 μm to form an anchor layer. Next, a thermotropic polymer material ink composed of the following [composition of the polymer material layer] is applied onto the anchor layer by a gravure printing method at a drying temperature of 60 ° C. and a coating thickness of 0.5 μm. A polymer material layer exhibiting tropic properties was formed. On the other surface of the base material, an adhesive material ink composed of the following [composition of the adhesive layer 3] was dried at a drying temperature of 80 by a gravure printing method.
C, applied under the condition of a film thickness of 2.0 μm to form an adhesive layer,
A polymer material medium was obtained.

On the other hand, on a support made of a transparent PET film having a thickness of 25 μm, a protective layer material ink consisting of the following [protective layer composition] was applied by gravure printing at a drying temperature of 80 ° C. and a thickness of 1.0 μm. It was applied to form a protective layer. Next, on the protective layer, a diffraction forming layer material ink composed of the following [Diffraction forming layer composition] is applied by a gravure printing method at a drying temperature of 80 ° C. and a thickness of 2.0 μm to form a diffraction forming layer. Thus, an original transfer foil of the diffraction forming structure layer was obtained.

Next, a nickel image mold having a hologram relief pattern is heated to 100 ° C. and pressed by a known roll embossing method on the diffraction forming layer of the transfer foil of the diffraction forming structure layer, thereby forming a diffraction pattern. A relief pattern was formed on the layer. On the diffraction forming layer on which the relief pattern has been formed by the above method, a film thickness of 0.
It provided a diffraction effect layer (reproduced image effect layer) to form a vapor deposited thin film layer made of Si ₂ O ₃ of 05Myuemu. Next, on the hologram effect layer, an adhesive layer material ink composed of the following [composition of the adhesive layer 4] is applied by a gravure printing method at a drying temperature of 80 ° C. and a coating thickness of 2.0 μm to form an adhesive layer. A diffraction forming structure layer transfer foil was obtained.

The polymer liquid crystal medium obtained in each of the above steps and the transfer foil for the diffraction-forming structure layer are overlapped with each other so that the polymer material layer having thermotropic property and the adhesive layer are in contact with each other, and they are fused by a roll transfer method. Thereafter, the support of the transfer foil for the diffraction-forming structure layer was peeled off to obtain a latent image recording medium of the present invention.

The latent image recording medium is partially orientated by applying heat and pressure with a hot stamper at 120 ° C. for 0.2 seconds on the polymer material layer showing the thermotropic property to have a latent image. A latent image recording medium of the present invention was obtained.

[Composition of Polymer Liquid Crystal Layer] Polymer liquid crystal (Kiracol PLC-7003: manufactured by Asahi Denka Kogyo KK) 20 parts by weight Methyl ethyl ketone 80 parts by weight [Composition of adhesive layer 3] Polyester resin 5 parts by weight Acrylic resin 15 Parts by weight methyl ethyl ketone 40 parts by weight toluene 40 parts by weight [composition of protective layer] acrylic resin 10 parts by weight methyl ethyl ketone 45 parts by weight toluene 45 parts by weight [composition of diffraction forming layer] acrylic polyol resin 20 parts by weight hexamethylene diisocyanate 3 parts by weight methyl ethyl ketone 50 Parts by weight toluene 27 parts by weight [Composition of adhesive layer 4] acrylic resin 10 parts by weight polyester resin 10 parts by weight methyl ethyl ketone 30 parts by weight toluene 50 parts by weight

Although the latent image recording medium having the obtained latent image was visually invisible, the latent image contained therein could not be visually recognized at all, and it looked like a mere diffraction-formed structure film in which only a hologram image was observed. By overlapping the polarizing films, a desired image could be clearly displayed without depending on the angle. Also, no trace at the time of recording the latent image could be recognized.

[0056]

As described above, according to the present invention, a latent image can be formed by partially orienting the polymer material layer exhibiting the thermotropic property, and its location can be obtained by directly looking at the latent image. The image whose content is not known at all and which has been turned into a latent image can be easily displayed by using a polarizing film or the like. Further, the latent image can be easily formed by a thermal head or a laser beam without leaving any trace at the time of recording.

[Brief description of the drawings]

FIG. 1 is a schematic sectional explanatory view showing an embodiment of a latent image recording medium of the present invention.

FIG. 2 is an explanatory diagram of a state in which a latent image is displayed by superposing a polarizing film on the latent image recording medium shown in FIG. 1 and the medium;

FIG. 3 is a schematic sectional explanatory view showing a latent image recording medium according to another embodiment of the present invention and a use state thereof.

4 is an explanatory plan view showing a medium 34 to which the latent image recording medium of the present invention shown in FIG. 3 is attached, and a state when the medium is observed through a polarizing filter.

FIG. 5 shows a state in which a polarizing film is superimposed on the latent image recording medium of the present invention and a latent image in the latent image forming structure layer is observed.
FIG. 3 is an explanatory view conceptually illustrating an optical path state between three layers of a polarizing film, a polymer material layer having transparency, and a reflective layer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 30 Latent image recording medium 2 Substrate 3, 42 Reflective layer 4 Polymer material layer showing thermotropic property 5 Latent image forming structure layer 6 Image reproducing effect layer 7 Diffraction forming layer 8 Diffraction forming structure layer 9 Protective layer 22 Reproduction Image 23 Polarizing film 24 Image 32, 33 Anchor layer 34 Medium 35 Adhesive layer 38 Polarizing filter 43 Polarizing film 31 Circular polarizing film 44 White irradiation light 45 Transmitted reflected light 46 Light source

Of the front page Continued (51) Int.Cl. ⁷ identification mark FI theme Court Bu (Reference) G02B 5/30 G02B 5/30 G03H 1/18 G03H 1/18 G06K 19/06 G06K 19/00 D 19/077 K F Terms (reference) 2C005 HB02 HB05 HB09 HB12 JB08 JB09 KA37 KA48 LA20 LA30 LB22 2H049 AA02 AA03 AA06 AA12 AA13 AA40 AA43 AA60 AA64 AA66 AA68 BA02 BA03 BA07 BC22 2K008 AA13 H03 H01A01 CCH AK42 AL01C AR00B AR00C AR00D AT00A BA03 BA04 BA07 BA10C BA10D BA44C CB00D EC04 EH46 EH66 GB71 GB90 HB08 HB31 JJ10C JL00B JL00C JL11D JN01B JN06C JN18B 5B035 BA03 BB03 BB05 BB05

Claims (5)

[Claims] 1. A latent image forming structure layer and a light-transmitting diffraction forming structure layer are laminated on a substrate in this order, and the latent image forming structure layer has at least a thermotropic property with a reflective layer. A latent image recording medium comprising a polymer material layer as shown in the following. 2. The light-transmitting diffraction-forming structure layer comprises at least an image reproduction effect layer and a diffraction-forming layer, has a higher refractive index than the constituent material of the diffraction-forming layer, and has a lower latent image-forming structure layer. 2. A material comprising at least a material having at least transparency enough to recognize the presence of the material.
2. The latent image recording material according to item 1. 3. The latent image forming structure according to claim 1, wherein the reflective layer constituting the latent image forming structure layer is provided on the entire surface or a part of the latent image forming structure layer, and is made of a metal material. Image recording medium. 4. The method according to claim 1, wherein a latent image formed by orienting a desired portion is formed on the polymer material layer exhibiting thermotropic property.
Item. The latent image forming material according to item 1. 5. An adhesive layer is formed on the side of the substrate on which the latent image forming structure layer and the light transmitting diffraction forming structure layer are not laminated. The latent image forming body according to any one of the above.