JP3342056B2 - Anti-counterfeit hologram - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram, and more particularly, to a forgery prevention hologram which cannot be easily reproduced.

[0002]

2. Description of the Related Art Holography is a technique for recording both the amplitude and phase of a light wave on a surface, and a hologram created by this technique has a different angle than a normal photograph that captures only a single point of view. It is possible to reproduce a stereoscopic image viewed from the viewer. Furthermore, holograms are sophisticated in manufacturing technology and the manufacturing equipment is complex and expensive, so it is generally difficult to forge or alter the hologram itself. Attempts have been made to use it as a security measure.

[0003]

However, it is extremely important to prevent forgery that a hologram can be easily duplicated and that it does not hinder the observation of the hologram and makes duplication difficult.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a hologram which makes duplication of a hologram difficult and can prevent forgery.

[0005]

According to the present invention, as shown in FIG. 1, a polarization control layer made of a polarizer, a retarder, a birefringent material or the like is provided on an upper surface of a hologram 1 on which an arbitrary image is recorded. Since the polarization control layer 2 is transparent, it is possible to observe a hologram image with natural light, but it is necessary to use a laser beam in the replication, and usually,
Since the laser light is polarized in a specific direction, it is difficult to copy a hologram that can be used for observation under the restriction of the polarization control layer 2. Of course, the polarization control layer 2 may be provided on the lower surface of the hologram 1 or on both surfaces.

FIG. 2 is an explanatory diagram of a case where a linear polarizing plate 4 is used as the polarization control layer 2 to prevent the Lippmann hologram 1 from being duplicated. The Lippmann hologram is duplicated by bringing the original hologram 1 into close contact with the duplicate photosensitive material 3 and irradiating a laser beam from the photosensitive material 3 side. In FIG. And the duplicate photosensitive material 3 are shown separately.

[0007] Since the linear polarizing plate 4 is transparent, there is no particular problem in observation with natural light. On the other hand, if the polarization direction of the laser beam 5 irradiated to the duplicate photosensitive material is the direction of arrow A in the figure and the polarization direction of the linear polarizing plate 4 is perpendicular to the direction, the laser beam 5 cannot pass through the linear polarizing plate 4. Therefore, duplication is not possible. Further, if the polarization direction of the linear polarizing plate 4 is not perpendicular to the polarization direction of the laser beam but has a certain angle, the amount of transmitted light is reduced, so that a hologram image having a practically usable brightness cannot be copied. .

FIG. 3 shows a case where a quarter-wave plate 6 is used as the polarization control layer 2. When the laser light 7 irradiated from the duplication sensitive material 3 side passes through the quarter-wave plate 6, it becomes circularly polarized light, and when the circularly polarized light diffracted by the original hologram 1 passes through the quarter-wave plate 6 again, It becomes linearly polarized light. At this time, since the polarization direction of the irradiation laser light 7 and the polarization direction of the diffracted light 8 are orthogonal to each other, they do not interfere with each other, and no hologram image is recorded on the duplicate photosensitive material 3.

It should be noted that, even if the polarization is not circularly polarized by the quarter-wave plate 6, the polarization is controlled by a birefringent material.
For example, even with elliptically polarized light, a bright hologram image cannot be duplicated even if hologram duplication cannot be completely prevented. Therefore, it is possible to function as substantial hologram forgery prevention.

FIG. 4 shows the use of a brittle hologram as an original hologram. The brittle hologram 10 is, for example, provided with a hologram forming layer 10b and a brittle layer 10c on a support 10a as shown in FIG. 4C. It adheres to the adhesive layer 11 of (a) with sufficient strength, and causes delamination in the brittle layer upon peeling.

Various synthetic resins can be used as the synthetic resin constituting the brittle layer 10c.
Styrene resin such as methylstyrene and styrene copolymer, polymethyl methacrylate, polyethyl methacrylate, polymethyl acrylate, polyethyl acrylate, acrylic or methacrylic resin such as polybutyl acrylate, homo- or copolymer resin, Ethyl cellulose, nitrocellulose, ethylhydroxyethyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, cellulose derivatives such as cellulose acetate, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, polypropylene, polyethylene, polyether resin, etc. Mixtures or copolymers of two or more kinds, thermosetting resins such as phenolic resins, urea resins, and melamine resins can be used.

[0012] The above-mentioned synthetic resin may further contain, as a filler,
Charcoal, talc, china clay, kaolin, micro silica, TiO ₂ , glass flakes, asbestos, pyroxene powder, silica stone powder (stone powder), barium sulfate, sherbene, shamott, etc. 100 parts by weight of synthetic resin When 80 to 200 parts by weight is added, the resulting coating composed of the synthetic resin and the fine powder becomes more brittle than the coating composed of the synthetic resin to which the fine powder is not added. The brittle layer 1
The thickness of Oc is preferably about 4 to 40 μm.

The adhesive layer 11 is provided on the hologram as a polarization control layer 12.
Various types of adhesives can be used for forming this layer, for example, phenolic resin, furan resin, urea resin, melamine resin, polyester resin, polyurethane resin Resin, epoxy resin or other thermosetting resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinyl butyral resin, poly (meth) acrylic resin, nitrocellulose, polyamide or other thermoplastic resin, Butadiene-acrylonitrile rubber,
Neoprene rubber or other rubber, or glue,
An adhesive containing one or more of natural resin, casein, sodium silicate, dextrin, starch, gum arabic and the like as a main component can be used.

These adhesives may be of a solution type, an emulsion type, a powder type or a film type.
Further, any of a room temperature solidification type, a solvent volatilization type, and a fusion solidification type may be used.

Further, as a material constituting the adhesive layer, a material called an adhesive, for example, an acrylic resin, an acrylate resin, or a copolymer thereof, a styrene-butadiene copolymer, a natural rubber, casein, gelatin, Rosin esters, terpene resins, phenolic resins, styrene resins, chromanindene resins, xylene, aliphatic hydrocarbons, polyvinyl alcohol, polyethylene oxide, polymethylene oxide, polyethylene sulfonic acid, etc. can be used, and adhesiveness can be obtained by heating. May be used (in other words, a heat sealant). As a material constituting the heat-sensitive adhesive, polyethylene, polyvinyl acetate, or a copolymer thereof, an acrylic resin or an ethylene-acrylic acid copolymer, polyvinyl butyral, polyamide, polyester, plasticized chloroprene, polypropylene, polyvinyl alcohol, Polycarbonate, polyvinyl ether, polyurethane, cellulosic resin, waxes, paraffins, rosins,
Examples include thermoplastic resins such as asphalts, and uncured thermosetting resins such as epoxy resins and phenolic resins. The thickness of the adhesive layer is preferably 4 to 20 μm.

When the polarization control layer 12 is bonded to the brittle hologram 10 with the bonding layer 11 as shown in FIG. 4A, the hologram cannot be copied as described above. If the user notices the existence of the polarization control layer 12 and tries to peel it off, as shown in FIG.
Is broken between layers in the brittle layer 10c, so that the peeled surface exposes an uneven surface, making it impossible to duplicate the hologram.

As shown in FIG. 5A, the adhesive layer 11 is buried in a brittle hologram 10 in a pattern, and the polarization control layer 12 is peeled off. As shown in FIG. Breakage may occur in the layer, and a pattern as shown in FIG. 5C may appear at the broken portion. In this case, the hologram can be further prevented from being copied.

[0018]

According to the present invention, the presence of the polarization control layer does not hinder the observation of the hologram. Duplication becomes difficult, and if a brittle hologram is used and the polarization control layer is adhered to it, at least a part of the brittle hologram is removed even if the user notices the existence of the polarization control layer and tries to peel it off. Since it is destroyed, it cannot be copied and is extremely effective in preventing forgery.

[0019]

【Example】

Example 1 Holographic recording film (Omnidex 352 manufactured by DuPont) using the optical system shown in FIG.
Is a photosensitive material 20, and an Ar laser beam (wavelength 51) is applied to the subject 21 through the photosensitive material at an exposure energy of 30 mJ / cm ^2.
4 nm) to record a Lippmann hologram.
After recording, heat treatment was performed at 120 ° C. for 2 hours, and the completed hologram was placed on a plastic card 2 as shown in FIG.
2 was bonded with an adhesive 23, and a quarter-wave plate 25 was bonded and laminated on the upper surface with an adhesive 24. The completed card can be observed with natural light without any problem, but even when illuminated with polarized laser light, the polarization direction was changed, and optical duplication was not possible.

[Embodiment 2] A hologram is produced in the same manner as in Embodiment 1, and a plastic card 2 is formed as shown in FIG.
2 and a biaxially stretched PET2
6 was adhered. When optical replication was attempted using laser light, as shown in FIG. 8B, due to the birefringence of the biaxially stretched PET 26, stripe-like unevenness occurred, and good replication could not be performed.

[0021]

As described above, according to the present invention, the provision of the polarization control layer does not hinder observation by natural light, but cannot be reproduced at all even if reproduction is attempted by irradiating laser light. Alternatively, a hologram that can be used is not obtained, and if a brittle hologram is used, the hologram surface will be destroyed if the polarization control layer is to be peeled off. Can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hologram of the present invention provided with a polarization control layer.

FIG. 2 is a diagram illustrating prevention of hologram duplication by a linear polarizing plate.

FIG. 3 is a diagram illustrating hologram duplication prevention by a λ / 4 plate.

FIG. 4 is a diagram showing an example of a hologram in which a polarization control layer is bonded to a brittle hologram.

FIG. 5 is a view showing an example in which an adhesive layer for adhering a brittle hologram and a polarization control layer is provided in a pattern.

FIG. 6 is a diagram showing a hologram production optical system.

FIG. 7 is a diagram showing a card provided with a hologram to which a λ / 4 plate is adhered.

FIG. 8 is a view showing a card provided with a hologram to which biaxially stretched PET is adhered.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hologram, 2 ... Polarization control layer, 3 ... Photosensitive material for duplication, 4
… Linear polarizing plate, 5 laser light, 6 λ / 4 plate, 7 irradiation laser light, 8 diffraction light, 10 brittle hologram, 11…
Adhesive layer, 12: polarization control layer, 13: pattern.

Continuation of the front page (56) References JP-A-5-307113 (JP, A) JP-A-3-223882 (JP, A) JP-A-63-262614 (JP, A) JP-A-63-106780 (JP) JP-A-3-118198 (JP, A) JP-A-58-5065 (JP, U) JP-A-2-58278 (JP, U) JP-A-62-170971 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) G03H 1/02 G03H 1/18 G02B 5/32 G02B 5/18

Claims (3)

(57) [Claims] An anti-counterfeit hologram comprising a hologram and an upper surface and / or lower surface provided with a polarization control layer made of a polarizer, a retarder, a birefringent material, or the like. 2. The hologram according to claim 1, wherein the hologram is formed of a brittle hologram having a brittle layer at least in part, and the polarization control layer is bonded to the brittle hologram with an adhesive layer. Anti-counterfeit hologram. 3. The hologram according to claim 2, wherein the adhesive layer is provided in a pattern.