JP4334855B2 - Optical diffraction structure with latent image - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical diffraction structure having a latent image that is difficult to distinguish in a normal visual state.
[0002]
[Prior art]
In recent years, forgery cases of high-value banknotes and gift certificates using color copiers have frequently occurred.
For this reason, high-value banknotes and gift certificates have a small halftone dot or fine line that cannot be read by a color copier sensor in a part of the design, and is incorporated in a pattern designed with the same reflection density.
As a result, when trying to copy these high-value banknotes and gift certificates with a color copier, the copier scanner reads out small dots and fine lines, and those parts are identified as white and are identified as copies. .
In addition, a method of discriminating a copy product by providing a brilliant metal part in a part of the design of the printed material is also implemented.
Since such a metal part reflects the incident light 100% regularly, the copier reproduces this part in black. As an example, for example, a gold thread is sewed on the surface layer of paper, and copy check is performed.
[0003]
In addition, a metal vapor deposition process is applied to the fine uneven surface of the light diffraction structure replicated with a transparent resin, which is then thermally transferred to a part of the printing area to prevent fraud caused by copying, while the light diffraction structure itself is prevented from being counterfeited. It is used as.
Although the optical diffraction structure has a very high anti-counterfeit effect as described above, in recent years, analysis techniques have advanced and counterfeit products similar to the optical diffraction structure have appeared.
For such counterfeiting, a method has been proposed in which a hidden pattern is discriminated by forming a plurality of diffraction gratings and generating a moire pattern from a line-like discrimination pattern (see Patent Document 1).
These techniques have a problem that the hidden pattern is slightly discriminated depending on the viewing angle.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 6-40190
[Problems to be solved by the invention]
The present invention has been made in view of such problems, and an optical diffraction structure having a latent image that is extremely difficult to visually distinguish a latent image incorporated in the optical diffraction structure and can be clearly determined by a determination tool. provide.
[0006]
[Means for Solving the Problems]
In order to achieve the object, the invention according to claim 1 of the light diffractive structure having a latent image of the present invention is characterized in that the entire region including the light diffractive structure is a partial region that can be distinguished in a normal visual state. , Divided into partial areas including a latent image incorporated so as to be indistinguishable in a normal visual state , at least the partial area including the latent image is configured by fine stripes arranged in parallel, The stripes are composed of a pair of bands on which diffraction gratings are formed, and pixels of the diffraction grating are partially formed on one band of the pair of bands.
[0007]
Further, in the invention described in claim 2, in the invention described in claim 1, in the band in which pixels by the diffraction grating are partially formed, pixels by the diffraction grating are regularly formed in a portion of 40 to 60%. It is characterized by being.
[0008]
Further, in the invention described in claim 3, the diffraction grating formed in one band of the pair of bands in the invention described in claim 1 or 2 is different from the diffraction grating formed in the other band in pitch. , At least one of the diffraction angles is different.
[0009]
The invention according to claim 4 is the invention according to claim 3, wherein the density of the stripes is 5 stripes / mm or more.
[0011]
The invention according to claim 5 is the invention according to any one of claims 1 to 4 , wherein the partial region including the latent image is composed of at least a latent image and a background pattern, and the latent pattern is included in the background pattern. In the state in which the image is incorporated, the stripes forming the latent image and the stripes forming the background pattern form an angle of 90 degrees.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An optical diffraction structure having a latent image according to the present invention will be described below with reference to the drawings.
FIG. 1 is a view for explaining an example of a printed material to which a light diffraction structure having a latent image of the present invention is transferred, FIG. 2 is an enlarged view of a partial region in which the latent image is incorporated, and FIG. FIG. 4 is a diagram for explaining the aggregate of two bands, FIG. 4 is a diagram for explaining the density of the bands constituting the stripe, and FIG. 5 is a diagram for explaining an example of a diffraction grating formed in the band FIGS. 6 and 6 are explanatory diagrams of an example of a discriminating tool, FIG. 7 is an explanatory diagram of a latent image discrimination method, and FIG. 8 is an explanatory diagram of a cross section of a discrimination pattern forming body.
[0013]
In FIG. 1, in order to check forgery or copying, a very thin resin of the light diffraction structure (5) having the latent image 1 is melted to a predetermined size by heat, and paper or the like is applied by a heat-reactive adhesive. Formed on the substrate 6.
In some cases, a light diffraction structure is formed on the base film and punched out to a predetermined size, and may be formed on the printed material together with the base film using an adhesive or an adhesive.
[0014]
The printed matter on which the light diffractive structure is formed is often difficult to forge or be copied, for example, banknotes, gift certificates, admission tickets, gift certificates, bills, checks, and the like.
These printed materials use special printing techniques and materials, and are double protected against forgery and abuse by copying.
[0015]
In FIG. 1, the entire region 5 of the pattern by the light diffraction structure is formed on the lower right side of the base 6 such as the gift certificate, admission ticket, gift certificate, bill, check or the like.
The entire region 5 by the light diffraction structure is composed of a partial region 4 and another pattern 3, and the partial region 4 on which the latent image is formed is composed of a latent image 1 and a background pattern 2.
The partial area 4 is composed of a set of fine stripes composed of pixels having different diffraction angles and pitches in both the latent image 1 and the background pattern 2.
The design area of the other pattern 3 is composed of a pattern such as a hologram or a diffraction grating, or a printed pattern.
Examples of the optical diffraction structure include a diffraction grating that displays a plurality of designs by cutting back, a hologram that displays a design in a three-dimensional state, and the like. In many cases, the light diffraction structure used for printed matter is a rainbow hologram that reflects light by fine unevenness and displays a design in rainbow colors, or a diffraction grating.
[0016]
When the other pattern 3 is a hologram or a pattern by a diffraction grating, it is difficult to notice the presence of the latent image because it is composed of the same quality as the latent image 1 by the diffraction grating formed in the partial region 4. There is an effect that the degree of discrimination in the visual state is low.
On the other hand, if the other pattern 3 is a printed pattern, the latent image 1 formed in the partial area 4 and the background pattern 2 have a complicated configuration and are not camouflaged so that the partial area 4 can be prevented from being copied and counterfeited. It is easy to discover that means are provided.
[0017]
In the embodiment shown in FIG. 1, a star pattern by a diffraction grating is incorporated as the latent image 1.
The latent image 1 by the diffraction grating is incorporated so as not to be discriminated in a normal visual state, and cannot be discriminated unless using a special discriminating tool.
When such a latent image by a diffraction grating is used in a practical state, if only a latent image by a diffraction grating and a background pattern are formed on a printed matter, it is understood that a partial area in the entire area is a counterfeit check means. It is easy to be done.
For this purpose, the periphery is designed with a hologram or the like having properties close to the diffraction grating constituting the latent image, and the latent image 1 is incorporated into the background pattern 2 in a state of being harmonized therein.
[0018]
The partial region 4 in FIG. 1 will be described with reference to FIG.
The latent image 1 and the background pattern 2 that form the partial region 4 for generating the latent image are composed of a plurality of fine stripes that are a set of pixels formed by a diffraction grating.
In FIG. 1, the partial region 4 that generates the latent image 1 when the lower end of the substrate 6 of the printed material is placed in a horizontal state is visually recognized in the state shown in FIG. 2.
That is, the angle formed by the stripes forming the latent image 1 with respect to a line parallel to a line connecting the left and right eyes of the discrimination means (hereinafter referred to as a horizontal line) is 45 degrees, and the background pattern 2 It is incorporated so that the angle formed by the stripes is 135 degrees.
In the above, the angle formed by the stripes forming the latent image 1 with respect to the horizontal line is 45 degrees, and the angle formed by the background pattern 2 is 135 degrees. The angle formed by the stripes constituting the image 1 may be 135 degrees, and the angle formed by the background pattern 2 may be 45 degrees.
The angles of 45 degrees and 135 degrees can be slightly increased or decreased within a range where 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 the latent image 1 and the background pattern 2 are 90 degrees. However, when the allowable angle is included, the range is 90 degrees plus or minus 10 degrees. The latent image and the background pattern may be combined within.
The reason for setting the two patterns to 45 degrees and 135 degrees is that the observation environment in many cases is indoors, and the position of the light source is often in front of or above the printed material. This is because it is preferable in terms of image effect and observation effect.
[0020]
Next, the stripe configuration will be described with reference to FIG.
The stripe 100 is composed of two bands (band 110 and band 111) in which a diffraction grating is formed. The band 110 is composed of pixels of diffraction gratings that differ 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 with the diffraction angle of the diffraction grating falling to the right, and the band 111 is formed with the diffraction angle of the diffraction grating rising to the right.
In this way, two bands of diffraction gratings formed at different diffraction angles or pitches form a pair to form a stripe, form a latent image or background pattern, and form a partial region. ing.
Further, as described in FIG. 5, the band 111 has 40% to 60% of the number of pixels of the diffraction grating as described in FIG.
[0021]
As shown in FIG. 4, the inventors' experiments have shown that it is preferable to set the density of the 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 narrow the width of the stripes and make it difficult to distinguish the latent image. The second reason is due to the balance between the size of the pixel by the diffraction grating constituting the striped band and the pixel and space of the band 111 described later.
[0022]
With reference to FIG. 5, a band and a stripe formed of a diffraction grating will be described.
When the stripe 100 is enlarged, it is as shown in FIG. 5, and a pair of bands 110 and 111 are connected to form one stripe 100.
Further, each band includes pixels 1100 and 1110 and spaces 1111 formed of 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 α in this embodiment. The angle α may be 45 degrees or 135 degrees.
[0023]
As described above, for the band 110 and the band 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 with a diffraction angle of 135 degrees, the pixels forming the band 111 are formed with a diffraction angle of 45 degrees.
The band 110 is filled with the pixels 1100 having the same pitch and the aforementioned diffraction angles.
In the band 111, the pixels 1110 having the above-described diffraction angles and the pixels (spaces) 1111 where the diffraction grating is not formed are regularly arranged, and the number of pixels 1110 and the pixels 1111 or the area ratio 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 the latent image by the set of stripes and the background pattern are combined so that the stripes intersect at right angles, and the colors reflected from each stripe are differentiated. As a result, the latent image formed of the diffraction grating is made a latent image that is difficult to discriminate with ordinary visual means, and a clearer discrimination becomes possible when discriminating the latent image by the discrimination pattern.
[0025]
An embodiment of the discriminator will be described with reference to FIG.
The discriminator 7 is obtained by cutting a transparent film on which a discriminating pattern is formed into a predetermined size and reinforcing it with a tough frame.
A handle is provided so that fingerprints or the like are not attached to the surface of the film on which the discrimination pattern is formed so that the discrimination is easy.
[0026]
In FIG. 7, the light diffraction structure 5 is formed on the surface of a medium substrate (hereinafter referred to as a printed product) 6 with an adhesive 9.
When a latent image is incorporated in the light diffractive structure, when the discriminator 7 for discriminating the latent image by the light diffractive structure is brought close to the printed material 6 at a predetermined angle, the latent image incorporated in the light diffractive structure is It is displayed on the discriminator 7 in a moire state.
Since the light applied to the latent image portion formed on the printed material must pass through the discriminator 7 and reach the discriminating means (eyes) 8 of the observer, the discrimination pattern of the discriminator has a transparent base. A substrate is used.
[0027]
When determining the latent image, the determination is made so that the determination tool 7 is brought into close contact with the printed matter 6.
Although the latent image can be discriminated when the distance between the discriminator and the printed material is close to a certain distance, since the moire phenomenon is used, the light diffraction structure 5 on which the latent image is formed If the distance of the discriminating tool 7 is too large, discrimination becomes difficult. Further, since the light that causes the moire of the latent image in the discriminator 7 becomes light incident from the direction of the discriminating means 8, it is preferable that the base material has 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 7 is formed will be described.
The discriminating tool fixes the discriminating pattern forming body 70 on which the discriminating pattern is formed as described above with a frame made of synthetic resin or the like.
One surface of the transparent substrate 71, colored material layer 73 via the transparent adhesive layer 72 is formed. 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, or transfer. When it is desired to increase the formation accuracy of the line width between the colored straight line portion and the transparent straight line portion, the photoengraving method and the etching method are selected. If the required accuracy is relatively low, the printing and transfer methods are selected. Etching is performed by coating and exposing a photosensitive resin on a thin metal film formed on the entire surface of the transparent substrate, and then exposing the contact pattern with a plate-making film on which the discrimination pattern is baked, washing away the unexposed areas and exposing the metal parts. Is melted by corrosion to form a transparent straight portion.
[0030]
(Example)
A thin metal-deposited glass plate was irradiated with an electron beam having a diameter of 4 microns to form a pixel having a diffraction grating of 18 μ × 18 μ at an angle of 45 degrees with respect to one cut surface of the glass.
The formation density of the pixels was 4 rows / band in the horizontal direction, and was formed at a pitch of 1 pixel in the vertical direction of the band.
Pixels formed in the connected bands were formed with different diffraction angles.
The stripe density was set to 7 stripes / mm.
A latent image and a background pattern were created using a masking pattern and incorporated as part of a design pattern with a designed diffraction grating to produce an original.
A duplicate was produced from this original plate, and irregularities were reproduced on the surface of a transparent acrylic resin coated on the base film to produce a light diffraction structure. A yellow colorant was applied to the transparent resin on the base film on which the light diffractive structure was replicated, and an aluminum thin film was formed thereon by vacuum deposition, 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 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 correctly viewed, the latent image cannot be determined by the visual means.
[0031]
【The invention's effect】
The light diffraction structure having a latent image of the present invention can provide the following effects.
1) As in the first aspect of the invention, the entire area including the light diffraction structure is divided into a distinguishable partial area and a partial area including the 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 formed with diffraction gratings, and pixels of the diffraction grating are partially formed on one band of the pair of bands. Therefore, it is possible to make it difficult to determine the presence of the latent image. In addition, by designing the partial area for forming the latent image with a diffraction grating, it becomes easy to combine with the counterfeit checking means formed by a hologram or the like, and the security can be further improved by using a collective design.
2) As in the invention described in claim 2, in the invention described in claim 1, in the band in which the pixels by the diffraction grating are partially formed, the pixels by the diffraction grating are regularly formed in a portion of 40 to 60%. By being formed, the moire generation pattern at the time of discrimination can be clarified.
3) As in the invention described in claim 3, in the invention described in claim 1 or 2, the diffraction grating formed in one band of the pair of bands is a diffraction grating formed in the other band; By at least one of the pitch and diffraction angle being different, the color of the two bands is differentiated, and the effect of making it difficult to distinguish the latent image in a normal visual state is exhibited.
4) As in the invention described in claim 4, in the invention described in claim 3, if the number of stripes in which two bands are connected is set to 5 / mm or more, the band by the diffraction grating constituting the stripes The thickness of the image is 100 μm or less, and since the thickness of the band and stripe per line is fine, the presence of the latent image can be made more difficult to distinguish.
5 ) As in the invention according to claim 5 , in the invention according to any one of claims 1 to 4 , the partial region including the latent image is configured by at least a latent image and a background pattern, and the background pattern includes the In the state in which the latent image is incorporated, the stripes constituting the latent image and the stripes constituting the background pattern form an angle of 90 degrees to enhance the latent image effect and facilitate discrimination by the discrimination pattern.
[Brief description of the drawings]
FIG. 1 is a diagram 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 region in which the latent image is incorporated. FIG. 4 is a diagram for explaining the density of the bands constituting the stripes. FIG. 5 is a diagram for explaining an example of the diffraction grating formed on the bands. [Fig. 7] An explanatory diagram of an example of a discriminator [Fig. 7] An explanatory diagram of a method for discriminating a latent image [Fig. 8] An explanatory diagram of a cross section of the discriminating pattern forming body [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Latent image 2 Background pattern 3 Other pattern 4 Partial area | region 5 Whole area | region 6 Base | substrate 7 Discriminating tool 8 Observer discriminating means 9 Adhesive 70 Discriminating pattern formation body 71 Transparent base material 72 Adhesive 73 Discriminating pattern 100 Stripes 110, 111 Band 1100, 1110 pixel 1111 space

Claims (5)

Entire area including the optical diffraction structure includes a partial area that can be determined in a normal observation state, in a normal observation state is divided into partial areas containing embedded so as to be unreadable latent image, at least the latent image The partial region including a plurality of stripes arranged in parallel is constituted by a pair of bands on which diffraction gratings are formed, and one of the pair of bands is diffracted. An optical diffractive structure having a latent image, wherein a pixel by a grating is partially formed. 2. The light having a latent image according to claim 1, wherein the band in which the pixels formed by the diffraction grating are partially formed has pixels formed by the diffraction grating regularly in a portion of 40 to 60%. Diffraction structure. The diffraction grating formed in one band of the pair of bands is different from the diffraction grating formed in the other band in at least one of pitch and diffraction angle. A light diffraction structure having the latent image described in 1. 4. The optical diffraction structure having a latent image according to claim 3, wherein the fringe density is 5 stripes / mm or more. The partial area including the latent image is composed of at least a latent image and a background pattern, and the stripes constituting the latent image and the stripes constituting the background pattern are 90 degrees with the latent image incorporated in the background pattern. optical diffraction structure having a latent image according to any one of claims 1-4, characterized in that an angle of.

Images