JP2001105800A - Forgery preventing method for image receiving sheet, image receiving sheet provided with forgery prevention function and image display body using the image receiving sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forgery preventing method for an image receiving sheet on which the judgement of whether a latent image is genuine or not can be carried out a plurality of times, the durability and minuteness of the image are not restricted, a specified sensing device is not required and the judgement of whether the latent image is genuine or not can be easily carried out, and also provide an image receiving sheet provided with the forgery prevention function and an image display body using the image receiving sheet. SOLUTION: In a forgery preventing method for an image receiving sheet on which a latent image is added, the image sheet with the latent image formed by utilizing the orientation is used for forming a latent forming layer of the image receiving sheet 1 provided with a latent forming layer 13 and an image layer 12 laminated together on a substrate 11 so that the latent image is visible when visualizing the same through a polarization film 14 and invisible when visualizing the same not through the polarization film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing forgery using a latent image for displaying a hidden character or a hidden pattern, a sheet, and an image display using the same. The present invention relates to a method for preventing forgery of an image receiving sheet, which can easily determine whether the image is true or false, an image receiving sheet on which forgery prevention is performed, and an image display using the same.

[0002]

2. Description of the Related Art As a method of forming an image pattern based on image data, a laser printing method, an ink jet method, a sublimation (thermal diffusion) transfer method and a fusion heat transfer method are known. As an example of a method of forming an image pattern by a thermal transfer means such as a sublimation (thermal diffusion) transfer method or a melt heat transfer method, a heat transfer layer of each color containing a dye or pigment such as yellow, magenta, cyan, and black on a belt-like sheet. There is a method of forming an image pattern on a base material such as a card by using a transfer ribbon provided with an adhesive layer, a protective layer and the like, and appropriately generating heat from a group of heating elements of a thermal head based on image data. In this case, for example, the transfer ribbon is always transported in the forward direction, and the base material is pulled back every time the transfer of one color is completed, transported again in the forward direction, and the transfer of the second and subsequent colors is performed, and the color image pattern is placed on the substrate. To form.

If it is difficult to form an image directly on a final recording medium (final product) to which an image pattern is to be applied using these image forming means, an image pattern is formed on an intermediate transfer sheet for the time being. A method of re-transferring the image pattern to a final product by a heat roller or a hot press plate after that is adopted (for example, Japanese Patent Application Laid-Open No. 63-81093). For an image display containing personal identification data such as an ID card such as a credit card or a membership card or a passport, a method of forming an image pattern by such a thermal transfer unit is often used.

[0004] In order to prevent the falsification and forgery of such cards which are now widely used, various forgery prevention methods are used. For example, an OVD (optical) such as a hologram or a diffraction grating, or a multilayer thin film that changes color (color shift) depending on a viewing angle, which can express a stereoscopic image or a special decoration image using light interference.
Variable Device).

Since these OVDs give a unique impression such as a stereoscopic image and a color shift, they have an excellent decorative effect, and are used for general printed materials such as various packaging materials, picture books and catalogs. In addition, since the production of these OVDs requires advanced technology, as an effective means of preventing forgery, the OVD is attached to a part of a credit card, securities, certificates, or the like, or is formed on the entire surface to prevent forgery. Used as a media.

OVDs such as holograms and diffraction gratings
It has a diffractive structure such as a fine concavo-convex pattern or a striped pattern with a different refractive index. Depending on the angle viewed by light interference and diffraction (that is, the angle supporting the hologram), a unique image and color can be obtained. (Color shift). An OVD such as a multilayer thin film has a structure in which ceramics and metals having different optical characteristics are stacked in multiple layers. This multilayer thin film utilizes the interference effect of light obtained by the optical characteristics and film thickness of the constituent materials, and has reflection and transmission characteristics in a specific wavelength range. Is what happens. Hereinafter, a hologram, a diffraction grating, a multilayer thin film, and the like utilizing the interference of these lights will be collectively referred to as OVD.

In general, a hologram is prepared by forming a relief-type master hologram having a fine concavo-convex pattern by an optical photographing method, and then replicating the concavo-convex pattern from the master hologram by electroplating. And a press plate is heated and pressed on a layer for forming a hologram to perform mass replication. This type of hologram is called a relief hologram.

A reflection type hologram is called a volume hologram, in which a recording material such as a photosensitive resin is used to change the refractive index of the photosensitive resin in the volume direction and record interference fringes in the volume direction. is there. This type of hologram is called a Lippmann hologram.

Further, the hologram using a diffraction grating is different from a hologram capable of reproducing such a three-dimensional image, in which a plurality of types of simple diffraction gratings are arranged in a minute area to form pixels, and a grating image, a pixelgram, and the like. It represents an image called. An image using such a diffraction grating is copied in a large amount by a method similar to that of a relief hologram.

On the other hand, a latent image has been conventionally used for forgery prevention. For example, 1) Hidden characters etc. are inserted using the gap of the line pitch,
A line drawing in which hidden characters appear by hiding the lines, 2) Print a transparent ink medium with a filler, and rub the part with a pencil. Pencil powder adheres to the printed part and the hidden characters There is a pencil out print (deco mat) that appears. However, since these latent images are deciphered when viewed closely, they are used for play rather than forgery prevention methods using full-scale latent images.

3) A method of forming a latent image using a white or colorless and transparent irreversible thermosensitive coloring ink which develops color by applying heat requires a heat source device to display the latent image. Since an image displayed once cannot be erased, its use is limited. 4) A method of displaying a latent image by printing a white ink containing a filler harder than a metal such as titanium oxide on a white paper and rubbing it with a coin or the like is a visual method by providing a mat-like varnish. Although this is eliminated, the use of the latent image is limited because it can be displayed only once. That is, the above methods 3) and 4) are limited to one-time use.

Further, as a method for preventing forgery by a latent image which can be repeatedly displayed, 5) a reversible thermosensitive coloring ink (thermochromic ink)
There is a method using. The thermochromic ink reversibly develops or decolors when heated, and returns to its original state after being left for a while. This ink is used as a latent image or for concealing an image, but its use is limited because of its low resistance, especially heat resistance. 6) Photochromic ink is an ink that develops color when irradiated with light, particularly ultraviolet light, and is used as a latent image by using it as a white or colorless and transparent ink. Limited. 7) The fluorescent ink is an ink that emits light when irradiated with ultraviolet light, and is used as a latent image by being used as a white or colorless transparent ink. The fluorescent ink includes an organic type and an inorganic type. The organic type emits light only when it is contained in a very small amount in the printing ink, but its use is limited due to its low light resistance. Further, the inorganic type needs to be contained in a large amount in the printing ink (about 10 to 20%), and is easily visible as a latent image by visual observation. That is, the methods 5), 6) and 7) are restricted in terms of durability.

As another method of preventing forgery using a latent image which can be repeatedly displayed, there is a method of 8) forming a latent image by using moire (interference fringes) of halftone dots or lines. In this method, a latent image is formed by partially changing the pitch or angle of a halftone dot or a line, and an image appears by overlaying an orderly arranged halftone dot or a line of transparent film on this latent image. is there. In this method, the display can be easily repeated with the transparent film, and there is no limitation in terms of durability, but there is a problem that a complicated image cannot be formed.

Another method for preventing forgery using a latent image that can be repeatedly displayed is 9) a method using a latent image using magnetic ink. This is to form a latent image by magnetizing a magnetic layer having a coercive force (about 300 Oe or more) capable of magnetic recording in a pattern.
This is a method in which a magnetized portion is displayed as an image by sprinkling iron powder on the magnetic layer. However, in this method, the latent image can be easily rewritten and forged, and the process of displaying the latent image is complicated, and a specific detection device is required. 10) There is a method in which a latent image is formed with ink that absorbs infrared light, and a layer that transmits infrared light without transmitting visible light is provided on the latent image. However, in order to display this latent image, an infrared camera or the like is required, and the apparatus becomes large. In addition, there is a method using an ink (IV ink) which is white or colorless in the visible region but absorbs in the infrared region. An infrared camera or the like is also required.

That is, the above methods 9) and 10) are methods capable of repeated display and are not restricted in terms of durability and image definition, but a specific detection device is required for displaying a latent image. It is what becomes.

[0016]

As described above, the methods using the latent image for preventing forgery have different problems. The present invention has been made to solve the above problems, and when using a latent image to prevent forgery of an image receiving sheet that records visual information such as a card, it is possible to make a genuineness determination a large number of times, endurance, image quality Is not constrained in terms of definition and does not require a particular detection device for its interpretation,
An object of the present invention is to provide a method for preventing forgery of an image receiving sheet, which can easily determine the authenticity of forgery. It is another object of the present invention to provide an image receiving sheet having such a forgery prevention and an image display using the image receiving sheet.

[0017]

According to the present invention, there is provided a method for preventing forgery of an image receiving sheet in which a latent image is added to forgery prevention. The method comprises laminating a latent image forming layer and an image receiving layer for recording visual information on a support. The latent image forming layer of the image receiving sheet was provided with a latent image formed by using an orientation such that the latent image was visually recognizable through a polarizing film and invisible or difficult to visually recognize without a polarizing film. A method for preventing forgery of an image receiving sheet, characterized by using an image receiving sheet.

The present invention also relates to an image receiving sheet provided with a latent image for preventing forgery, wherein the latent image forming layer and the image receiving layer for recording visual information are laminated on a support. To prevent forgery, characterized by providing a latent image formed by using an orientation so as to be visually invisible through a polarizing film and invisible or difficult to visually recognize through a polarizing film. It is an image receiving sheet applied.

According to the present invention, in the forgery-prevented image-receiving sheet according to the second aspect, the image-receiving layer has an adhesive property, and the support is peelable. This is an image receiving sheet that has been prevented.

The present invention also provides a forgery-prevented image receiving sheet according to the above invention, wherein a light reflection layer is provided above or below the latent image forming layer. It is.

The present invention also provides a forgery-prevented image receiving sheet according to the above invention, wherein the light reflection layer is an OVD layer also serving as a light reflection layer. .

According to the present invention, there is provided an image receiving sheet provided with the forgery prevention device according to the above invention, wherein the material of the latent image forming layer is provided with a latent image which can be formed by being oriented by an external force. A forgery-prevented image receiving sheet characterized by being a material.

The present invention also provides a forgery-prevented image receiving sheet according to the above invention, wherein the material of the latent image forming layer is a polymer liquid crystal material. .

Further, the present invention provides an image receiving sheet provided with the forgery prevention according to the above invention, wherein the polymer liquid crystal material is
An image receiving sheet, which is a polymer liquid crystal material having a thermotropic property, wherein the latent image is provided by orienting the latent image by heating and pressurizing, and wherein forgery prevention is performed.

According to the present invention, there is provided an image receiving sheet provided with the forgery prevention according to the above invention, wherein the latent image is a latent image having a pattern shape having information such as characters and pictures. This is an image receiving sheet.

The present invention also provides a forgery-prevented image receiving sheet according to the above invention, wherein the polarizing film is a circularly polarizing film.

Further, the present invention is an image display using the image receiving sheet provided with the forgery prevention according to the above invention.

[0028]

Embodiments of the present invention will be described below. FIG. 1 is a plan view showing an embodiment of an image receiving sheet provided with a forgery prevention according to the present invention. FIG. 2 is a cross-sectional view showing one embodiment along the line XX ′ in FIG. As shown in FIGS. 1 and 2, an image receiving sheet (1) on which forgery protection has been performed is formed by laminating a latent image forming layer (13) and an image receiving layer (12) for recording visual information on a support (11). It was formed.

In FIG. 2, (23) is a part of the latent image forming layer (13) so that it is visually observable through a polarizing film and not visible or difficult to visually recognize without a polarizing film. , A latent image formed using orientation. (22) is the image receiving layer (1).
This is an image pattern recorded in 2), which can be visually recognized without using a polarizing film. (15)
This is a light reflection plate used when observing the image receiving sheet.

The latent image portion (23) is formed on the latent image forming layer (1).
Part of 3) is a portion oriented by external force such as heat, pressure, scratching, friction, light, electricity, magnetism and the like. In FIG. 1, the forgery-prevented image receiving sheet (1) is such that the latent image (23) cannot be confirmed by visual observation without a polarizing film and only a simple image pattern can be seen.

FIG. 3 is a plan view showing a state of reading the latent image (23) of the embodiment of the image receiving sheet provided with the forgery prevention shown in FIG. FIG. 4 is a cross-sectional view of FIG.
It is sectional drawing which shows the state at the time of reading the latent image (23) shown by X 'cross section. As shown in FIG. 3 and FIG. 4, an image receiving sheet (1) provided with anti-counterfeiting is disposed above the light reflection plate (15), and a polarizing film (14) is overlaid thereon and visually observed through the polarizing film. By doing so, the latent image (23) becomes a visible image (23 ').

FIG. 5 is an explanatory view conceptually showing a state of an optical path when reading an image receiving sheet on which forgery prevention is performed according to the present invention. As shown in FIG. 5, the white light (56) from the light source (58) passes through the polarizing film (14) and becomes linearly polarized light, and the oriented latent image (23) part which is a part of the latent image forming layer is formed. The transmitted light changes to elliptically polarized light.
The light is reflected by 5), passes through the polarizing film (14) again, and becomes reflected light (57).

Since the intensity of the reflected light (57) varies depending on the wavelength, images having various hues can be obtained. Further, the hue that can be seen differs depending on the angle between the orientation direction of the polarizing film and the orientation direction of the latent image. The linearly polarized light that has passed through the other part (not shown), which is the other part of the latent image forming layer (13), is reflected by the light reflector (15) without being changed to the elliptically polarized light, and again the polarizing film (14).
Through which the image pattern is observed.

FIGS. 6 (a) and 6 (b) are explanatory views showing a state in which the latent image (23) of the image receiving sheet (1) protected from forgery according to the present invention is read. One of them is FIG.
As shown in (a), the support (11) surface of the image receiving sheet (1) is disposed above the light reflecting plate (15), and the polarizing film (14) is overlaid thereon to form a polarizing film. The latent image (23) is visually recognizable by visual observation through the. The other one, as shown in FIG. 6B, arranges the image receiving layer (12) surface of the image receiving sheet (1) upward above the light reflecting plate (15), and places the polarizing film above the light receiving plate (12). The latent image (23) can be visually recognized by superimposing (14) and visually observing through the polarizing film.

The invention according to claim 3 is an image receiving sheet in which the image receiving layer (12) in FIG. 2 has adhesiveness and the support (11) is peelable. In this image receiving sheet, the image receiving layer (12) of the image receiving sheet (1) is adhered to the transfer object, and the support (11) is peeled off. This is a transferred object.

FIG. 7A is an explanatory view showing an example of the invention according to claim 4. FIG. 7B is an explanatory diagram showing a state when the latent image (23) on the image receiving sheet (7) is read. As shown in FIG. 7A, the image receiving sheet (7)
Has a light reflection layer (25) provided on the latent image forming layer (13) on the support (11). When reading such a latent image (23) on the image receiving sheet (7), FIG.
As shown in (b), the support (1) of the image receiving sheet (7) is used.
1) With the surface facing upward, a light reflecting plate (1) as shown in FIG.
Without using 5), the latent image (23) can be visually recognized by superimposing the polarizing film (14) on the image receiving sheet (7) and visually observing through the polarizing film.

FIG. 8 (a) is an explanatory view showing another example of the invention according to claim 4. FIG. 8B is an explanatory diagram showing a state when the latent image (23) of the image receiving sheet (8) is read. As shown in FIG. 8A, the image receiving sheet (8) has a light reflecting layer (25) provided below the latent image forming layer (13) on the support (11). When reading such a latent image (23) of the image receiving sheet (8),
As shown in FIG. 8B, the image receiving layer (12) of the image receiving sheet (8) faces upward, and the image receiving sheet (8) is used without using the light reflecting plate (15) as shown in FIG. The latent image (23) can be visually recognized by superimposing the polarizing film (14) on the upper side and visually checking through the polarizing film.

FIGS. 9 and 10 are explanatory diagrams showing an example of the invention according to claim 5. FIG. As shown in FIG. 9, the image receiving sheet (9) has a latent image forming layer (1) on a support (11).
3), an OVD layer (35) also serving as a light reflection layer, and an image receiving layer (1).
2) is provided. That is, in the image receiving sheet (9), the light reflection layer (25) in FIG. 7A is the OVD layer (35) which also functions as the light reflection layer. This OVD
The layer (35) is made of an OVD (36) such as a relief hologram or a diffraction grating, and an OVD made of a high refractive material thin film or a metal thin film in order to diffract interference light from the OVD (36) with more effective intensity. It is composed of an effect layer (37). In FIG. 9, a circularly polarizing film (94) is used as the polarizing film.
4) is obtained by superimposing a quarter-wave retardation film (93) on a polarizing film (92).

As shown in FIG. 10, an image receiving sheet (10) is provided with a latent image forming layer (13) on a support (11).
An OVD layer (45) also serving as a light reflection layer and an image receiving layer (12) are provided. That is, the image receiving sheet (10)
In FIG. 7A, the light reflection layer (25) in FIG. 7A is the OVD layer (45) also serving as the light reflection layer. This OVD layer (4
5) has a multilayer structure of thin films 46, 47 and 48 having different optical characteristics. In FIG. 10, a circularly polarizing film (94) is used as the polarizing film.
The circularly polarizing film (94) is 1 /
A four-wavelength retardation film (93) is superposed. As described above, the OVD layer has a configuration in which a plurality of materials are stacked, and the configuration differs depending on the OVD.

When reading the latent image of the image receiving sheet provided with no light reflecting layer, as shown in FIGS. 3 and 4, an image receiving sheet provided with anti-counterfeiting is disposed above the light reflecting plate. A polarizing film is superposed thereon and visually observed through the polarizing film. Therefore, it is necessary that the support of the image receiving sheet at this time has transparency. In addition, when the image receiving sheet is attached to another transparent substrate and the support is peeled off, the support does not have to have transparency.

Examples of the support of the image receiving sheet which has been subjected to forgery prevention in the present invention include synthetic resins such as polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate and polystyrene, natural resins, paper, and the like. Composites such as synthetic papers alone or in combination can be used. Also,
On the support, a peelable protective layer provided as needed,
Latent image forming layer, light reflecting layer, OVD layer, image receiving layer are laminated,
Further, thereafter, for example, an image is formed by, for example, a thermal transfer method, and therefore, strength, heat resistance, and durability depending on a use are required. Therefore, the material of the support is selected in consideration of these. On the other hand, the thickness of the support can be used in a range of 2 to 1000 μm in consideration of handling properties.
A thickness of 300 μm is desirable. In addition, in the case of an image receiving sheet using a light reflection plate outside, the support used must have transparency.

If necessary, a peelable protective layer can be provided on the support. As the releasable protective layer, any of a thermoplastic resin, a thermosetting resin, an ultraviolet ray or an electron beam curable resin may be used as long as the material can be easily separated from the support. For example, polyacrylate resin,
Chlorinated rubber resin, vinyl chloride-vinyl acetate copolymer resin,
Thermosetting resins such as cellulose resins, chlorinated polypropylene resins, epoxy resins, polyester resins, nitrocellulose resins, styrene acrylate resins, polyether resins, polycarbonate resins, and thermosetting resins such as melamine and epoxy Or an ultraviolet or electron beam curable resin having a radically polymerizable unsaturated group, or a combination thereof.

In consideration of the foil breaking property and the abrasion resistance, various waxes such as petroleum wax and vegetable wax, fatty acids such as stearic acid and metal salts thereof, lubricants such as silicone oil, Teflon powder, polyethylene powder, Organic fillers such as silicone-based fine particles and acrylonitrile-based fine particles and inorganic fillers such as silica fine particles can also be added. These materials are applied to a support by a known application means such as a gravure printing method, a screen printing method, and a nozzle coater method.

As the latent image forming layer, a material having the same orientation over the entire surface and exhibiting the same polarization property over the entire surface, a material having a partially different orientation, or a partially changed orientation due to an external force. For example, a material that can provide a latent image that imparts different polarization to the image is used. For example, a polymer material such as polypropylene, polyethylene, polystyrene, or polyester can be used.

When a high-molecular liquid crystal material is used for the latent image forming layer, a high-molecular liquid crystal material such as polyester copolymer, polyether, polycarbonate, polyisocyanate, and polyglutamate can be used. Further, it is preferable that the polymer liquid crystal material has a thermotropic property that can be easily oriented by heating and pressing. Then, as a method of aligning, a simple method such as hot stamping, thermal head, heating by laser, or the like can be used, and by these methods, a fine latent image can be easily formed.

Further, it is also possible to form a latent image forming layer by preliminarily aligning a polymer material having a polarizing property into fine pieces, dispersing the polymer material in a polymer resin such as polyester or acrylic, and applying the dispersion. In this case, it is difficult to form an arbitrary image as a latent image, but since the latent image is observed as a random pattern, it is possible to add a verification function.

The material to be used is not limited to the above, but may be a material having the same orientation over the entire surface and exhibiting the same polarization over the entire surface, a material having a partially different orientation, or a partial external force. Any material can be used as long as it can change the orientation and provide a latent image imparting partially different polarization. The latent image forming layer is formed by using these materials by a known coating means such as a gravure printing method, a screen printing method, and a nozzle coater method. Or,
It is also possible to bond and form a film obtained by a fill molding technique such as an extrusion molding method or a biaxial stretching method.

As the image receiving layer, a laser printing method,
It is necessary to have a performance capable of forming an image by a known image forming method such as an ink jet method, a sublimation (thermal diffusion) transfer method, a melt transfer method, and the like. Is further required. But,
When it is difficult to coexist with the image receiving aptitude and the adhesiveness, the adhesiveness can be imparted to the substrate side. After an image is formed on the image receiving layer, an adhesive layer may be separately provided by using a method such as a thermal transfer method, a coating method, or lamination of an adhesive.

The material is preferably a thermoplastic resin, but may be cured if the heat during image formation causes a problem such as sticking of the transfer ribbon and the image receiving aptitude is not obtained. Usually, a single or a copolymer of 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, but is not limited thereto.

In consideration of prevention of blocking, prevention of sticking of the ribbon, and cut-off of the foil, various waxes such as petroleum wax and vegetable wax, fatty acids such as stearic acid and metal salts thereof, lubricants such as silicone oil and the like can be used. , Teflon powder, polyethylene powder, organic fillers such as silicone-based fine particles and acrylonitrile-based fine particles, and
An inorganic filler such as silica fine particles can also be added. Further, an ultraviolet absorber can be added for the purpose of protecting the image. These materials for the image receiving layer are applied by a known application means such as a gravure printing method, a screen printing method, and a nozzle coater method.

When reading the latent image portion of the image receiving sheet not provided with the light reflecting layer, as shown in FIGS. 3 and 4, the image receiving sheet provided with the forgery prevention is disposed above the light reflecting plate. Then, a polarizing film is superposed thereon and visually observed through the polarizing film. That is, the light reflecting plate is provided outside the image receiving sheet. Further, as shown in FIG. 7A, when a light reflection layer is provided on the latent image forming layer on the support, it is not necessary to provide the light reflection plate outside the image receiving sheet. Furthermore, as shown in FIGS. 9 and 10,
This light reflection layer may be an OVD layer also serving as the light reflection layer.

As the light reflecting layer, TiO ₂ , Si
High refractive index materials such as ₂ O ₃ , SiO, Fe ₂ O ₃ , ZnS, and Al, Sn, Cr, Ni, C
Metal materials such as u, Au and the like can be mentioned, and these materials can be used alone or in a laminate. These materials are formed by a known thin film forming technique such as a vacuum evaporation method and a sputtering method.
It is formed at about 0 °. In addition to the inorganic materials described above, the light-reflecting layer may be made of any organic or organic material as long as its refractive index is higher than that of the upper layer, which usually has a refractive index n of about 1.3 to 1.5. An inorganic composite, an organic material in which an inorganic filler is dispersed, and the like can be used.

These materials are formed to a thickness of about 0.1 μm to 10 μm by a known coating method or printing method such as gravure coating, die coating, screen printing and the like. Further, any material other than the above can be used as long as it has a reflective property. The light reflecting layer does not need to be adjacent to the latent image forming layer, and may be located in the order of the latent image forming layer and the light reflecting layer when viewed from the observation surface side. However, it is not possible to dispose a light-shielding member between the light reflection layer and the latent image forming layer, except in a case where the light reflection layer is partially formed.

The OVD layer is a layer on which a hologram, a diffraction grating, a multilayer thin film and the like utilizing light interference are formed, and an OVD such as a hologram or a diffraction grating converts light interference fringes into a fine uneven pattern. There are a relief type for recording on a flat surface and a volume type for recording interference fringes in the volume direction. Also,
As an OVD such as a multilayer thin film which causes a color change (color shift) depending on a viewing angle, there is a laminate of ceramic or metal thin films having different optical characteristics. In addition,
However, the present invention is not limited thereto as long as it causes a unique image or color change using light interference. These OVDs
Among them, in consideration of mass productivity and cost, a relief hologram (diffraction grating) or a multilayer thin film is preferable.

For the relief hologram (diffraction grating), a relief master hologram composed of a fine concavo-convex pattern is produced by an optical photographing method, and then a nickel concavo-convex pattern is reproduced from this master hologram by electroplating. Press plates are manufactured and mass-produced. That is, the press plate is heated and pressed against the OVD forming layer to copy the concavo-convex pattern. Therefore, the OVD-forming layer needs to be a material that has good moldability due to heat, hardly causes press unevenness, and can provide a bright reproduced image. A thermosetting resin such as a plastic resin, an unsaturated polyester resin, a melamine resin, an epoxy resin, or an ultraviolet or electron beam curable resin having a radically polymerizable unsaturated group can be used alone or in combination. In addition, any material other than the above can be used as long as it is a stable material capable of forming a concavo-convex pattern as the OVD formation layer.

As shown in FIG. 9, the OVD (36)
When a relief hologram (diffraction grating) is used, it is preferable to provide an OVD effect layer (reflection layer) having a different refractive index from the polymer material forming the relief surface in order to increase the diffraction efficiency. By providing the OVD effect layer (37), the diffraction efficiency is improved, and a clearer image and color change can be obtained. The OVD layer and the OVD effect layer must be adjacent to each other. OVD is OV
The OVD effect layer may be formed in the same shape along the OVD, or may be formed smoothly so as to fill the pattern, since the D effect layer can be provided and then formed using the press plate. There is no problem if done.

As materials for the OVD effect layer, TiO ₂ , Si ₂ O ₃ , SiO, Fe ₂ O ₃ , Zn having different refractive indices are used.
High refractive index material such as S, Al with higher reflection effect,
Metal materials such as Sn, Cr, Ni, Cu, and Au are exemplified. These materials can be used alone or in a laminated form. These materials are formed by a known thin-film forming technique such as a vacuum evaporation method and sputtering, and the thickness thereof varies depending on the application. It is formed.

In addition to the above, as a material constituting the OVD effect layer, a material whose refractive index is higher than the polymer material (refractive index n = 1.3 to 1.5) used in the OVD forming layer is used. If so, an organic material other than the above-mentioned inorganic material, an organic-inorganic composite, a material obtained by dispersing an inorganic filler in an organic material, or the like can be used. These materials are known coating methods such as gravure coating, die coating, screen printing,
Or an OVD effect layer of about 0.1 μm to 10 μm by a printing method. In addition, any material other than the above can be used as long as it has a reflective property.

On the other hand, as shown in FIG.
The OVD layer (45) on which the VD is formed is composed of multilayer thin film layers 46, 47 and 48 having different optical aptitudes, and is formed by laminating a metal thin film, a ceramic thin film, or a composite thin film formed by combining them. For example, when thin films having different refractive indices are stacked, a thin film having a high refractive index and a thin film having a low refractive index may be combined, or a specific combination may be alternately stacked. By their combination,
A desired multilayer thin film can be obtained.

This multilayer thin film includes ceramics and metals.
Which material is used and the refractive index is approximately 2.0 or higher
Predetermined refractive index material and low refractive index material with a refractive index of about 1.5
Are laminated with a film thickness of Of the materials used below
Take an example. First, as ceramics, for example,
Sb_TwoO_Three(3.0 = refractive index: the same applies hereinafter), Fe_TwoO_Three
(2.7), TiO_Two(2.6), CdS (2.6),
CeO _Two(2.3), ZnS (2.3), PbCl
_Two(2.3), CdO (2.2), Sb_TwoO_Three(2.
0), WO_Three(2.0), SiO (2.0), Si_TwoO
_Three(2.5), In_TwoO_Three(2.0), PbO (2.
6), Ta_TwoO_Three(2.4), ZnO (2.1), Zr
O_Two(2.0), MgO (1.6), SiO_Two(1.
5), MgF_Two(1.4), CeF_Three(1.6), Ca
F_Two(1.3-1.4), AlF_Three(1.6), Al_Two
9O_Three(1.6), GaO (1.7) and the like.

As a thin film of a simple metal or an alloy, for example, Al, Fe, Mg, Zn, Au, Ag, Cr, N
i, Cu, Si and the like. Further, as the low refractive index organic polymer, for example, polyethylene (1.5
1), polypropylene (1.49), polytetrafluoroethylene (1.35), polymethyl methacrylate (1.49), polystyrene (1.60) and the like. These high-refractive-index materials or transmittances of 30% to 6
By selecting at least one kind from a 0% metal thin film and at least one kind from a low refractive index material and alternately laminating them at a predetermined thickness, a multilayer thin film showing absorption or reflection for visible light of a specific wavelength is obtained.

From the above materials, the refractive index, the reflectance,
Materials are appropriately selected based on optical properties such as transmittance, weather resistance, chemical resistance, interlayer adhesion, and the like, and are laminated as thin films to form a multilayer thin film. A known method can be used for the formation method, and the film thickness, the film formation rate, the number of layers, or the optical film thickness (= n
Use of a physical vapor deposition method such as a normal vacuum deposition method or a sputtering method or a chemical vapor deposition method such as a CVD method, which can control d, n: refractive index, d: film thickness, etc. Can be. In addition, as a method for forming a low-refractive-index organic polymer, a known printing method such as a gravure printing method, an offset printing method, a screen printing method, or a coating method such as a bar coating method, a gravure method, or a roll coating method is used. be able to. In the present invention, only ceramics and metals are shown, but any material having a refractive index and a reflectance similar or similar to those of ceramics and metals can be used.

The thickness of this multilayer thin film layer is specifically 50
20,000 °, and the layer structure of the thin film is a thin film made of the above-mentioned high refractive index material or metal material, for example, ZnS, TiO ₂ , ZrO ₂ , In ₂ O ₃ , Sn
O, ITO, CeO ₂ , ZnO, Ta ₂ O ₃ , Al, F
e, Mg, Zn, Au, Ag, Cr, Ni, Cu, Si
And a thin film made of the material having a low refractive index, for example, M
It is a combination with gF ₂ , SiO ₂ , CaF ₂ , MgO, Al ₂ O _3, etc., which are alternately laminated, and the number of laminated layers is 2 or more, preferably 2 to 9 layers. The spectral characteristics change according to the number of layers. The optical characteristics of the multilayer film vary depending on the materials and combinations used, and the present invention is not limited to this. When the latent image forming layer on the OVD layer is made of an organic polymer having a low refractive index, the first thin film layer in contact with the latent image forming layer preferably has a high refractive index.

In the image receiving sheet which has been subjected to forgery prevention in the present invention, by providing a colored layer of colored transparent ink or the like so as to be located on the latent image forming layer or the OVD layer, the observed color change of OVD can be observed. Are more versatile and easier to see, and their confirmation is easier, and the forgery prevention effect can be further improved.

Examples of the polarizing film include a polymer polycrystalline type such as a PVA-iodine type, a dichroic dye type, a metal or metal compound containing type, and a polyene type in which iodine is absorbed in a PVA stretched film. In particular, PVA-iodine type,
The dichroic dye type is preferred. The circularly polarizing film is a film in which a quarter-wave retardation film is overlaid on a polarizing film.

[0066]

The present invention will be described in detail with reference to the following examples.
In the present invention, a method for forming an image pattern is a method capable of forming an image such as a sublimation (thermal diffusion) transfer method, a resin-type melt transfer method, a wax-type melt transfer method, a laser print method, an ink jet method, and a printing method. Although any method can be used as long as it is suitable, in this example, an image pattern was formed using a composite ribbon of a sublimation transfer method and a resin-type melt transfer method.

Example 1 (Production of Thermal Transfer Ribbon) Three sublimable dyes (yellow,
(Cyan, magenta) are each dispersed in polyvinyl butyral resin to prepare a dye ink and a coating solution in which carbon black is dispersed in a vinyl chloride-vinyl acetate copolymer resin, each having a thickness of 3. using a gravure coater. 5μ
m on a polyethylene terephthalate film, and apply and dry so that each color is alternately arranged.
A thermal transfer ribbon having a colored resin layer was manufactured.

(Production of Image Receiving Sheet) First, a 25 μm-thick transparent polyethylene terephthalate (P
ET) A polymer liquid crystal coating composed of a thermotropic liquid crystal, and an image receiving layer coating on a film using a gravure method.
Coating was performed sequentially at a drying temperature of 80 ° C. with a coating thickness of 1.0 μm to obtain an image receiving sheet.

Hereinafter, the used paint will be described. (Coating for polymer liquid crystal layer) Polymer liquid crystal (Kiracol PLC7003: manufactured by Asahi Denka Kogyo KK) 20 parts Tetrahydrofuran 40 parts Toluene 40 parts (Coating for image receiving layer) Vinyl chloride / vinyl acetate copolymer resin 15 Part Polyester resin ... 5 parts Methyl ethyl ketone ... 30 parts Toluene ... 50 parts

(Formation of Image Pattern on Image Receiving Sheet) An image pattern was formed on the image receiving sheet thus obtained by using a thermal transfer ribbon and a known thermal printer.

Next, in order to form a latent image on the latent image forming layer of the image receiving sheet on which the image pattern has been formed, an engraving plate having a letter "TOP" formed in a convex shape is used at 140.degree.
Orientation was performed by applying heat and pressure with a hot stamp from the support side for 2 seconds to provide a latent image. The anti-counterfeit image-receiving sheet obtained in this way could not be visually recognized at all by visual observation without a circular polarizing film, and appeared as a mere image display. The latent image was clearly visible by visual observation through the circularly polarizing film, and the latent image could be confirmed.

Example 2 A 25 μm thick transparent polyethylene terephthalate (PET) film support was coated with a coating for a peelable protective layer at a drying temperature of 80 ° C. to a coating thickness of 1.0 μm using a gravure method. Thereafter, a polymer liquid crystal coating composed of a thermotropic liquid crystal was formed to a thickness of 0.5 μm in the letters “TOP” by a gravure printing method. Here, the drying temperature was set to 150 ° C., the film was pressed by passing through a Rami roll, and the liquid crystal polymer was aligned at the same time. Next, the coating for the image receiving layer was applied by a gravure method at a drying temperature of 80 ° C. with a coating thickness of 2 μm. The paint used in Example 2 is the same as in Example 1.

On the image receiving sheet obtained as described above,
An image was formed using a commercially available thermal printer in the same manner as in Example 1. The resulting image-receiving sheet was a visual image without a circularly polarizing film, in which the latent image was not visible at all, and appeared as a mere image display. The letters "TOP" appeared clearly, and the latent image could be confirmed.

<Example 3> A coating for a latent image forming layer, in which small pieces obtained by stretching a polyethylene film formed into fine pieces were dispersed, was applied to a support made of a transparent polyethylene terephthalate (PET) film having a thickness of 25 µm to a thickness of 10 µm. Thus, a latent image forming layer was formed. Further, an image receiving layer was provided with a coating of 2.0 μm in a gravure method to obtain an image receiving sheet.

The coating materials used are shown below. Except for the latent image forming layer coating material, it is the same as Example 1. (Coating for latent image forming layer) Stretched polypropylene small piece ... 5 parts Urethane resin ... 20 parts Methyl ethyl ketone ... 50 parts Toluene ... 25 parts

The formation of the image pattern and the verification method were performed in the same manner as in Example 2. In the image receiving sheet obtained here, no latent image can be visually recognized at all without visual observation through a circularly polarizing film,
Although it looked like a mere image display, a pattern of random polypropylene small pieces was observed by visual observation through the circularly polarizing film with the circularly polarizing film overlaid.

<Example 4> The image receiving sheets prepared in Examples 1 to 3 were coated with a coating for a releasable protective layer having the following composition between the support and the latent image forming layer. A peelable protective layer was formed so as to have a thickness of 1 μm. In this embodiment, the image receiving layer serves as an image receiving / adhesive layer.

(Coating for Removable Protective Layer) Acrylic resin ... 15 parts Polyester resin ... 2 parts Polyethylene wax ... 3 parts Methyl ethyl ketone ... 50 parts Toluene ... 30 parts

Next, after forming an image pattern in the same manner as in Examples 1 to 3, a transparent vinyl chloride sheet substrate having a thickness of 0.78 μm, and aluminum provided on the substrate by a vacuum deposition method Using a thin-film (800 ° thick) substrate with a light reflecting layer, the image forming surface of the image receiving sheet is brought into contact with the above substrate, and heated and pressed by a transfer roller made of silicon rubber heated to 100 ° C. Thereafter, the support was peeled off from the peelable protective layer to obtain an image display.

With respect to the image display prepared using the base material, a latent image was confirmed from both sides by the same verification method as in Examples 1 to 3. For the image display body made with the base material,
Without using a light reflection plate, the latent image could be easily confirmed by visual observation through the circularly polarizing film with the circularly polarizing film laminated on the peelable protective layer side as the upper surface.

<Example 5> Light of titanium oxide (refractive index 2.1: film thickness 400 °) provided by the EB method between the latent image forming layer and the image receiving (and bonding) layer of the image receiving sheet manufactured in Example 4 A reflective layer was provided. Next, after forming an image pattern in the same manner as in Examples 1 to 3, a white vinyl chloride sheet base material having a thickness of 0.78 μm was used, and the image pattern forming surface of the image receiving sheet was brought into contact with the base material. After heating and pressing with a transfer roller made of silicone rubber heated to 100 ° C., the support was peeled off from the peelable protective layer to obtain an image display.

With respect to the image display body produced in this embodiment, a latent image can be easily confirmed by visual observation through a circularly polarizing film without using a light reflector. did it.

<Embodiment 6> In this embodiment, the embodiment 5
The image receiving sheet was manufactured using an OVD image which also functions as a light reflecting layer as the light reflecting layer. First, a coating for a peelable protective layer is formed on a substrate made of a foamed PET (having a white or milky white) film having a thickness of 50 μm by a gravure method at a drying temperature of 80 ° C. to a coating thickness of 1.0 μm. A 0.5 μm thick polymer liquid crystal coating composed of a tropic liquid crystal was formed on the letters “TOP” by a gravure printing method. Next, an OVD forming layer coating material was applied by a gravure method at 2 μm.
Then, an OVD relief pattern was formed on the OVD formation layer by pressing a nickel press plate having an OVD relief pattern onto the OVD formation layer.

In this embodiment, the alignment of the polymer liquid crystal was performed simultaneously with the OVD formation by the thermal processing. Next, the same light reflection layer as the light reflection layer provided in Example 5 was formed as an OVD effect layer on the OVD surface on the OVD formation layer on which the OVD relief pattern was formed by the above method. After forming titanium oxide to a thickness of 400 mm, the image-receiving layer paint is applied by gravure method.
μm was applied.

The composition of the coating for the OVD forming layer is shown below (Coating for the OVD forming layer) Vinyl chloride / vinyl acetate copolymer resin: 5 parts Urethane resin: 15 parts Methyl ethyl ketone: 50 parts Toluene: 30 parts

The formation of the image pattern and the transfer to the substrate were performed in the same manner as in Example 5 to obtain an image display. In the image display body prepared in this example, a latent image could be easily confirmed by visual observation through the circularly polarizing film without using a light reflecting plate. In addition, since the image display has an OVD image also serving as a light reflection layer, the forgery prevention property is further improved.

[0087]

According to the present invention, there is provided a method for preventing forgery of an image receiving sheet in which a latent image is added to forgery prevention, wherein the image receiving sheet having a latent image forming layer and an image receiving layer for recording visual information is laminated on a support. In the latent image forming layer, an image receiving sheet provided with a latent image formed by using an orientation so that the latent image can be visually recognized through a polarizing film and is invisible or difficult to visually recognize through a polarizing film is used. As a result, it is possible to judge the authenticity a large number of times, and it is not restricted in terms of durability and image definition, and does not require a specific detection device for its interpretation. Is a method for preventing forgery of an image receiving sheet, which can be easily performed.

The present invention also relates to an image receiving sheet having a latent image added to prevent forgery, wherein the latent image forming layer and an image receiving layer for recording visual information are laminated on a support. In addition, a latent image formed by using the orientation is provided so that it is visually or visually invisible through a polarizing film and invisible or difficult to visually recognize through a polarizing film. Possible, resistant,
An image receiving sheet that is not restricted in terms of image definition, and does not require a specific detection device for its interpretation, and is further provided with a forgery-prevention sheet that can easily determine whether it is forgery or not. Become.

Further, since the present invention is an image display using an image receiving sheet subjected to the above-described forgery prevention, the authenticity can be determined many times, and there is no restriction in terms of durability and image definition. And does not require a specific detection device for its interpretation,
Furthermore, an image display using an image receiving sheet, which can easily determine whether the device is forged or not, is provided.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of an image receiving sheet provided with a forgery prevention according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment along a line XX ′ in FIG. 1;

FIG. 3 is a plan view showing a state in which a latent image of one embodiment of the image receiving sheet subjected to forgery prevention shown in FIG. 1 is read.

FIG. 4 is a cross-sectional view showing a state when the latent image shown by the XX ′ cross section in FIG. 3 is read.

FIG. 5 is a diagram conceptually illustrating a state of an optical path when reading a forgery-prevented image receiving sheet according to the present invention.

FIGS. 6A and 6B are explanatory diagrams showing a state when reading a latent image on an image receiving sheet on which forgery has been prevented according to the present invention.

FIG. 7A is an explanatory diagram illustrating an example of an image receiving sheet. FIG. 4B is an explanatory diagram showing a state when the latent image on the image receiving sheet is read.

FIG. 8A is an explanatory diagram illustrating another example of the image receiving sheet. FIG. 4B is an explanatory diagram showing a state when the latent image on the image receiving sheet is read.

FIG. 9 is an explanatory diagram showing another example of the image receiving sheet.

FIG. 10 is an explanatory diagram showing another example of the image receiving sheet.

[Explanation of symbols]

 1, 7, 8, 9, 10 {forgery-prevented image receiving sheet 11} support 12 {image receiving layer 13} latent image forming layer 14, 92} polarizing film 15} light reflector 22} {Visible image pattern 23} Latent image 23 '{Visible image 25} Light reflecting layer 35, 45 OVD layer 36 OVD 37 OVD effect layer 46 Thin film 47 having different optical characteristics ... Thin films with different optical characteristics 48 ... Thin films with different optical characteristics 56 White light 57 Reflected light 58 Light source 93 Quarter-wave retardation film 94 Circularly polarizing film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Atsushi Kijima 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd. F-term (reference) 2C005 HA02 HA04 HB02 HB09 JA18 JA19 JB01 JB25 JB27 JC02 JC03 KA08 KA26 KA40

Claims (11)

[Claims] 1. A method for preventing forgery of an image receiving sheet in which a latent image is added to forgery prevention, the latent image forming layer of the image receiving sheet having a latent image forming layer and an image receiving layer for recording visual information laminated on a support. Wherein an image receiving sheet provided with a latent image formed by using an orientation is used so that the image is visually or visually invisible through a polarizing film and invisible or difficult to visually recognize through a polarizing film. Forgery prevention method for an image receiving sheet. 2. A latent image forming sheet comprising a latent image forming layer and an image receiving layer for recording visual information laminated on a support, wherein the latent image forming layer is a polarizing film. An image receiving sheet provided with a latent image formed by using an orientation so as to be visually invisible or difficult to visually recognize through a polarizing film, and provided with an orientation. . 3. The forgery-prevented image receiving sheet according to claim 2, wherein said image receiving layer has an adhesive property and said support is peelable. . 4. A light reflecting layer is provided on an upper layer or a lower layer of the latent image forming layer.
An image receiving sheet provided with the forgery prevention described. 5. The image receiving sheet according to claim 4, wherein said light reflecting layer is an OVD layer also serving as a light reflecting layer. 6. A material according to claim 2, wherein the material of the latent image forming layer is a polymer material capable of providing a latent image which can be formed by being oriented by an external force. An image receiving sheet provided with the forgery prevention according to claim 4 or 5. 7. The image receiving sheet according to claim 2, wherein the material of the latent image forming layer is a polymer liquid crystal material. . 8. The forgery prevention device according to claim 7, wherein said polymer liquid crystal material is a polymer liquid crystal material having a thermotropic property, and said latent image is provided by being oriented by heating and pressing. Image receiving sheet. 9. The latent image of claim 2, wherein the latent image is a pattern-shaped latent image having information such as characters and pictures. An image receiving sheet provided with the forgery prevention according to claim 7 or 8. 10. The polarizing film as claimed in claim 2, wherein the polarizing film is a circular polarizing film. 9
An image receiving sheet provided with the forgery prevention described. 11. An image display using the image receiving sheet for which forgery prevention according to claim 2 is provided.