JP2004163562A - Optical diffraction structure having latent image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical diffraction structure having a latent image which can be discriminated by means of a discrimination tool although the discrimination of the latent image incorporated in an optical diffraction structure by means of visual observation is extremely difficult. <P>SOLUTION: The optical diffraction structure having the latent image is constituted as follow. The whole region containing the optical diffraction structure is divided into a discriminable partial region and a partial zone containing the latent image, the partial region at least containing the latent image is composed of fine stripes arranged in parallel, the fine stripes are composed of a pair of belts on which the diffraction grating is formed and a pixel based on the diffraction grating is partially formed on the one side belt of a pair of the belts. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light diffraction structure having a latent image that is difficult to distinguish in a normal viewing state.
[0002]
[Prior art]
2. Description of the Related Art In recent years, cases of counterfeiting of high-value bills and gift certificates with a color copier have frequently occurred.
For this reason, high-value bills and gift certificates incorporate small dots and fine lines, which cannot be read by a sensor of a color copier, in a pattern designed with the same reflection density in a part of the design.
As a result, when trying to copy these high-value banknotes and gift certificates with a color copier, the scanner of the copier reads small dots and thin lines, and the portions are white and discriminated as copy products. .
In addition, a method of discriminating a copy product by providing a shining metal portion in a part of the design of a printed material has been implemented.
Such a metal part reflects the incident light 100% specularly, so that the copier reproduces this part in black. As an embodiment, for example, a gold thread is sewn on a surface layer of paper to perform a copy check.
[0003]
In addition, the metal diffraction treatment is applied to the minute uneven surface of the light diffraction structure duplicated with a transparent resin, and it is thermally transferred to a part of the printing area, preventing fraud by copying, while preventing the light diffraction structure itself from forgery We use as.
Although the light diffraction structure has an extremely high anti-counterfeiting effect, analysis techniques have recently been advanced, and counterfeit products similar to the light diffraction structure have appeared.
For such counterfeiting, a method has been proposed in which a plurality of diffraction gratings are formed and a moire pattern is generated using a line-shaped determination pattern to determine a hidden pattern (see Patent Document 1).
These techniques have a problem that the hidden pattern is slightly distinguished depending on the viewing angle.
[0004]
[Patent Document 1]
JP-A-6-40190
[Problems to be solved by the invention]
The present invention has been made in view of such a problem, and it is extremely difficult to visually distinguish a latent image incorporated in a light diffraction structure, and a light diffraction structure having a latent image that can be clearly distinguished by a distinguishing tool is provided. provide.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the light diffraction structure having a latent image according to the present invention is characterized in that the entire region including the light diffraction structure has a discriminable partial region and a portion including the latent image. At least a partial region including the latent image is divided into fine regions arranged in parallel, and the fine stripes are formed of a pair of bands on which a diffraction grating is formed. In one of the bands, pixels formed by a diffraction grating are partially formed.
[0007]
According to a second aspect of the present invention, in the first aspect of the present invention, in the band in which the pixels formed by the diffraction grating are partially formed, the pixels formed by the diffraction grating are regularly formed in a portion of 40 to 60%. It is characterized by having been done.
[0008]
According to a third aspect of the present invention, in the invention according to the first or second aspect, the diffraction grating formed in one of the pair of bands is different from the diffraction grating formed in the other band by a pitch. , At least one of the diffraction angles is different.
[0009]
According to a fourth aspect of the present invention, in the third aspect of the invention, the density of the stripes is 5 stripes / mm or more.
[0010]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the latent image is bordered by stripes having a period shifted by a half period with respect to the period of the stripes forming the pattern. Is what you do.
[0011]
According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the partial region including the latent image includes at least a latent image and a background pattern. With the image incorporated, the stripes forming the latent image and the stripes forming the background pattern form an angle of 90 degrees.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an optical diffraction structure having a latent image according to the present invention will be described with reference to the drawings.
FIG. 1 is a view for explaining an example of a printed material on which a light diffraction structure having a latent image of the present invention is transferred, FIG. 2 is an enlarged view of a partial area in which the latent image is incorporated, and FIG. FIG. 4 is a diagram for explaining an aggregate of two bands, FIG. 4 is a diagram for explaining the density of bands constituting stripes, and FIG. 5 is a diagram for explaining an example of a diffraction grating formed in the bands. FIGS. 6 and 7 are explanatory diagrams of an example of a discriminating tool, FIG. 7 is an explanatory diagram of a method of discriminating a latent image, and FIG. 8 is an explanatory diagram of a cross section of a discriminating pattern forming body.
[0013]
In FIG. 1, in order to prevent counterfeiting or copying, the extremely thin resin of the light diffraction structure (5) having the latent image 1 is blown to a predetermined size by heat, and the heat-reactive adhesive is used to form paper or the like. Is formed on the substrate 6 of FIG.
In a state where the light diffraction structure is formed on the base film, the sheet is punched into a predetermined size, and may be formed on a printed material with an adhesive or an adhesive together with the base film.
[0014]
The printed matter on which the light diffractive structure is formed is often difficult to copy or copy. For example, bills, gift certificates, entrance tickets, gift certificates, bills, checks, and the like are targets.
These printed materials use special printing techniques and materials, and are double-protected against forgery and copying abuse.
[0015]
In FIG. 1, an entire region 5 of a pattern by an optical diffraction structure is formed at the lower right of a base 6 such as a gift certificate, an admission ticket, a gift certificate, a bill, a check, or the like.
The whole area 5 by the light diffraction structure is composed of a partial area 4 and other patterns 3, and the partial area 4 on which a latent image is formed is composed of a latent image 1 and a background pattern 2.
The partial region 4 is composed of a set of fine stripes composed of pixels having different diffraction angles and pitches for both the latent image 1 and the background pattern 2.
Further, the design area of the other pattern 3 is configured by a pattern such as a hologram or a diffraction grating or a design by printing.
The light diffraction structure includes a diffraction grating that displays a plurality of symbols by turning back, and a hologram that displays the symbols in a three-dimensional state. There are many light diffraction structures used for printed matter, such as a rainbow hologram that reflects light by fine irregularities and displays a design in a rainbow color, or a diffraction grating.
[0016]
In the case where the other pattern 3 is a hologram or a pattern formed by a diffraction grating, the presence of the latent image is difficult to be noticed because the pattern 3 is composed of the same quality as the latent image 1 formed by the diffraction grating formed in the partial area 4. There is an effect that the degree of discrimination in a visual state is low.
Conversely, if the other pattern 3 is a printed pattern, the latent image 1 formed in the partial area 4 and the background pattern 2 must have a complicated design and not be camouflaged. It is easy to find that a means is provided.
[0017]
In the embodiment shown in FIG. 1, a star pattern formed by a diffraction grating is incorporated as the latent image 1.
The latent image 1 by the diffraction grating is built in such a manner that it cannot be distinguished in a normal visual recognition state, and cannot be distinguished without a special distinguishing tool.
When a latent image by such a diffraction grating is used in a practical state, if only the latent image by the diffraction grating and a background pattern are formed on a printed material, it is understood that a partial area in the entire area is a forgery restraint means. Easily.
For this purpose, the periphery is designed with a hologram or the like having a property close to the diffraction grating that forms the latent image, and the latent image 1 is incorporated into the background pattern 2 in a state of being harmonized therein.
[0018]
With reference to FIG. 2, the partial region 4 in FIG. 1 will be described.
The latent image 1 forming the partial area 4 for generating the latent image and the background pattern 2 are constituted by a plurality of fine stripes which are a set of pixels formed by a diffraction grating.
In FIG. 1, the partial area 4 that generates the latent image 1 when the lower end of the base 6 of the printed matter is placed in a horizontal state is visually recognized in a state as shown in FIG.
That is, the angle formed by the stripes forming the latent image 1 with respect to a line parallel to the line connecting the left and right eyes of the discriminating means (hereinafter referred to as a horizontal line) is 45 degrees, and the angle of the background pattern 2 It is incorporated so that the angle formed by the stripes is 135 degrees.
In the above description, the angle formed by the stripes forming the latent image 1 is 45 degrees and the angle formed by the background pattern 2 is 135 degrees with respect to the horizontal line. The angle formed by the stripes forming the image 1 may be 135 degrees, and the angle formed by the background pattern 2 may be 45 degrees.
Further, the angles of 45 degrees and 135 degrees can be slightly increased or decreased as long as the latent image effect does not change.
[0019]
In the above description, it can be seen that the latent image 1 and the background pattern 2 are incorporated so that the stripes constituting each become 90 degrees, but when the allowable angle is included, the range of 90 degrees plus or minus 10 degrees In this case, the latent image and the background pattern may be combined.
When combining the two patterns, the reason why the angles are set to 45 degrees and 135 degrees is that, in many cases, the observation environment is indoors, and the position of the light source is often in front of or above the printed matter, and the angle described above is hidden. This is because it is preferable in terms of the image effect and the observation effect.
[0020]
Next, the configuration of the stripe will be described with reference to FIG.
The stripe 100 is composed of two bands (a band 110 and a band 111) on which a diffraction grating is formed. The band 110 is composed of pixels formed by a diffraction grating different from the band 111 in at least one of the diffraction angle and the pitch.
For example, in FIG. 3, the band 110 is formed such that the diffraction angle of the diffraction grating is lowered to the right, and the band 111 is formed such that the diffraction angle of the diffraction grating is raised to the right.
Thus, two bands of the diffraction grating formed at different diffraction angles or pitches form a pair to form a fringe, form a latent image or background pattern, and form a partial area. ing.
Further, as described with reference to FIG. 5, the number of pixels of the diffraction grating in the band 111 is 40% to 60% of that of the band 110, so that the effect of discriminating the latent image is enhanced.
[0021]
As shown in FIG. 4, it has been found by experiments of the inventor that it is preferable to set the density of stripes to 5 or more in 1 mm in order to enhance the latent image effect.
One of the reasons for setting the number of stripes to 5 lines / mm or more is to make the width of the stripes narrow to make it difficult to distinguish a latent image. The second reason is that the size of the pixels formed by the diffraction grating forming the stripe band and the balance between the pixels and the space of the band 111 described later.
[0022]
With reference to FIG. 5, a band and a fringe constituted by a diffraction grating will be described.
When the stripe 100 is enlarged, it is as shown in FIG. 5. A pair of bands 110 and 111 are connected to form one stripe 100.
Further, each band is constituted by pixels 1100 and 1110 and a space 1111 by a plurality of diffraction gratings. These pixels are regularly arranged at the same diffraction angle and the same pitch for one band, and each band is formed at an angle of α in this embodiment. The angle α is 45 degrees or 135 degrees.
[0023]
As described above, for the bands 110 and 111, there are a method of changing the diffraction angle of the pixel and a method of changing the pitch.
For example, when the pixels forming the band 110 are formed at a diffraction angle of 135 degrees, the pixels forming the band 111 are formed at a diffraction angle of 45 degrees.
The band 110 is filled with pixels 1100 at the same pitch and at the aforementioned diffraction angle.
In the band 111, the pixels 1110 formed by the above-described diffraction angles and the pixels (spaces) 1111 where no diffraction grating is formed are regularly arranged, and the number or the area ratio of the pixels 1110 and the pixels 1111 is, for example, 50:50. It is formed to become.
[0024]
In this way, a stripe is formed by a band that is a set of pixels by a diffraction grating, and a latent image formed by the set of stripes and a background pattern are combined so that the stripes intersect at right angles, and a color reflected from each stripe is differentiated. Thus, the latent image formed by the diffraction grating is regarded as a latent image that is difficult to be distinguished by ordinary visual means, and a clearer distinction can be made when the latent image is distinguished by the distinguishing pattern.
[0025]
One embodiment of the discriminator will be described with reference to FIG.
The discrimination tool 2 is obtained by cutting a transparent film on which a discrimination pattern is formed into a predetermined size and reinforcing it with a strong frame.
A handle is provided so as to be easily distinguished and to prevent fingerprints and the like from adhering to the surface of the film on which the determination pattern is formed.
[0026]
In FIG. 7, a light diffraction structure 5 is formed on the surface of a medium substrate (hereinafter referred to as a printed material) 6 via an adhesive 9.
When the latent image incorporated in the light diffraction structure is brought closer to the printed material 6 by a predetermined angle with respect to the printed matter 6 when the latent image is incorporated in the light diffraction structure, the latent image incorporated in the light diffraction structure is obtained. It is displayed on the discriminator 2 in a moiré state.
Since the light applied to the latent image portion formed on the printed matter must pass through the discriminating tool 2 and reach the discriminating means (eye) 8 of the observer, the discriminating tool has a transparent base. Substrates are used.
[0027]
In the determination of the latent image, the determination is made by bringing the determination tool 2 close to the degree of contact with the printed matter 6.
Although the latent image can be distinguished from a state in which the distance between the discriminator and the printed matter is close to a certain distance from the state of close contact, the light diffraction structure 5 on which the latent image is formed because the moiré phenomenon is used. If the distance of the discrimination tool 2 is too empty, it becomes difficult to discriminate. Further, the light which causes the discrimination tool 2 to generate moiré of the latent image becomes light incident from the direction of the discrimination means 8, and is therefore preferably a base material having high transparency.
[0028]
With reference to FIG. 8, an example of a cross section of the discrimination pattern forming body on which the discrimination pattern of the discrimination tool 2 is formed will be described.
The discriminator fixes the discrimination pattern forming body 70 on which the discrimination pattern is formed as described above with a frame made of synthetic resin or the like.
On one surface of the transparent substrate 71, a colored material layer 73 is formed via a transparent adhesive layer 72. Although not shown, a protective layer is provided on the surface of the colored material layer 23 as necessary.
[0029]
The discrimination pattern is formed by a method such as photolithography, etching, printing, and transfer. When it is desired to increase the line width accuracy between the colored straight line portion and the transparent straight line portion, a photoengraving method and an etching method are selected. If the required accuracy is relatively low, a printing and transfer method is selected. Etching is performed by coating a photosensitive resin on a thin metal film formed on the entire surface of the transparent substrate, then performing close contact exposure with a plate making film having a discrimination pattern baked, and washing away the unexposed portions to expose the exposed metal portions. Is melted by corrosion to form a transparent linear portion.
[0030]
(Example)
A thin metal-deposited glass plate was irradiated with an electron beam having a diameter of 4 μm to form a pixel having a size of 18 μ × 18 μ at a 45 ° angle with respect to one cut surface of the glass.
The pixels were formed at a density of 4 rows / band in the horizontal direction, and were formed at one pixel pitch in the vertical direction of the band.
The pixels formed in the connected bands were formed by changing the diffraction angle.
Further, the density of the stripes was set to 7 stripes / mm.
A latent image and a background pattern were produced by a masking pattern, and incorporated as a part in a design pattern by a designed diffraction grating to produce an original.
A duplicate plate was prepared from this master plate, and the surface of the transparent acrylic resin applied on the base film was reproduced with irregularities to prepare an optical diffraction structure. A yellow colorant was applied to the transparent resin on the base film on which the optical diffraction structure was duplicated, a thin aluminum curtain was formed thereon by a vacuum evaporation method, and a heat-sensitive adhesive was applied thereon.
The light diffraction structure formed on the base film was thermally transferred to a high-quality paper having a line drawing printed on the surface by using a metal plate heated to 160 degrees Celsius.
As a result of observing the latent image portion at a position where the printed design can be seen correctly, the latent image could not be discriminated by visual observation means.
[0031]
【The invention's effect】
With the light diffraction structure having a latent image according to the present invention, the following effects can be obtained.
1) As in the first aspect, the entire area including the light diffraction structure is divided into a identifiable partial area and a partial area including a latent image, and at least the partial areas including the latent image are arranged in parallel. The fine stripes are composed of a pair of bands on which a diffraction grating is formed, and a pixel by the diffraction grating is partially formed on one of the pair of bands. This makes it more difficult to determine the presence of a latent image. Further, by designing a partial area for forming a latent image with a diffraction grating, it is easy to combine with a forgery restraining means formed by a hologram or the like.
2) As in the second aspect of the present invention, in the first aspect of the present invention, the band in which the pixels by the diffraction grating are partially formed has a regular arrangement of the pixels by the diffraction grating in a portion of 40 to 60%. By being formed, it becomes possible to sharpen the moiré generation pattern at the time of discrimination.
3) As in the invention described in claim 3, in the invention described in claim 1 or 2, the diffraction grating formed in one of the pair of bands is the same as the diffraction grating formed in the other band; At least one of the pitch and the diffraction angle is different so that the colors of the two bands are different, and an effect of making it difficult to determine a latent image in a normal visual recognition state is exhibited.
4) As in the invention according to the fourth aspect, in the invention according to the third aspect, if the number of stripes in which the two stripes are connected is 5 stripes / mm or more, the stripes formed by the diffraction gratings that form the stripes. Has a thickness of 100 μm or less, and since the thickness of each band or stripe is fine, the existence of a latent image can be made more difficult to determine.
5) As in the invention described in claim 5, in the invention described in claim 4, the latent image is bordered by being fringed by a stripe having a period shifted by a half period with respect to the period of the stripe constituting the pattern. The sharpness at the time of image discrimination can be improved.
6) As in the invention according to claim 6, in the invention according to any one of claims 1 to 5, the partial region including the latent image includes at least a latent image and a background pattern. With the latent image incorporated, the stripes forming the latent image and the stripes forming the background pattern form an angle of 90 degrees, thereby enhancing the latent image effect and facilitating the discrimination by the discrimination pattern.
[Brief description of the drawings]
FIG. 1 is a view for explaining an example of a printed material on which a light diffraction structure having a latent image according to the present invention is transferred. FIG. 2 is an enlarged view of a partial area in which the latent image is incorporated. FIG. FIG. 4 is a diagram for explaining an aggregate of bands of FIG. 4. FIG. 4 is a diagram for explaining the density of bands constituting stripes. FIG. 5 is a diagram for explaining an example of a diffraction grating formed in the band. FIG. 7 is an explanatory diagram of an example of a discriminating tool. FIG. 7 is an explanatory diagram of a method of discriminating a latent image. FIG. 8 is an explanatory diagram of a cross section of a discriminating pattern forming body.
REFERENCE SIGNS LIST 1 latent image 2 background pattern 3 other pattern 4 partial area 5 whole area 6 base 7 discriminator 8 observer discriminating means 9 adhesive 70 discriminating pattern forming body 71 transparent base material 72 adhesive 73 discriminating pattern 100 stripes 110, 111 Obi 1100, 1110 Pixel 1111 Space

Claims (6)

The entire area including the light diffraction structure is divided into a identifiable partial area and a partial area including a latent image,
At least a partial region including the latent image is configured by fine stripes arranged in parallel,
The fine stripes are composed of a pair of bands on which a diffraction grating is formed,
A light diffraction structure having a latent image, wherein pixels by a diffraction grating are partially formed in one of the pair of bands. 2. The light having a latent image according to claim 1, wherein the band in which pixels by the diffraction grating are partially formed has pixels regularly formed by the diffraction grating in a portion of 40 to 60%. 3. Diffraction structure. The diffraction grating formed in one of the pair of bands is different from the diffraction grating formed in the other band in at least one of a pitch and a diffraction angle. An optical diffraction structure having the latent image according to 1. The light diffraction structure having a latent image according to claim 3, wherein the density of the stripes is 5 stripes / mm or more. 5. The light diffraction structure having a latent image according to claim 4, wherein the latent image is bordered by stripes having a period shifted by a half period with respect to the period of the stripes forming the pattern. The partial area including the latent image is composed of at least a latent image and a background pattern, and in a state where the latent image is incorporated in the background pattern, the stripes forming the latent image and the stripes forming the background pattern are 90 degrees. The light diffraction structure having a latent image according to any one of claims 1 to 5, wherein the light diffraction structure has an angle of?

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