JP2001010199A - Copy forgery prevention sheet - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the difficulty in visually recognizing a latent image, and to reduce the overall halftone screen density in response to a copier with improved resolution, even in a copy, the latent image or the The portions other than the latent image are made black so that the latent image appears so as to be easily recognized visually. A forgery prevention sheet (1) has a background pattern (4) composed of a halftone screen having a predetermined screen density, a latent image pattern (3), and a disappearing image pattern (5) on a surface of a sheet substrate (2).
And the common pattern 6 are applied, and the background pattern 4 and the latent image pattern 3 are of the same color, and it is difficult to identify the latent image with the naked eye, and the common pattern 6 and the disappearing image pattern 5 are different from the aforementioned colors. The erased image can be discriminated by the naked eye with the same color, and the combined pattern 6 and the latent image pattern 3 can be identified.
Is composed of a set of halftone dots having a non-uniform size and a pointed portion. When copied, the latent image appears in black and can be identified by the naked eye.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copy forgery prevention sheet which enables a latent image to appear on a copy by a copying machine so as to determine whether the copy is a copy or not. Consisting of a halftone screen of a predetermined screen density,
A background pattern, a latent image pattern, a vanishing image pattern,
Four patterns of the combined pattern (three patterns without the combined pattern in some cases) are applied, and the disappeared image can be recognized by the naked eye due to the difference in color. When the image is copied by a copy machine, a latent image appears and is displayed. The present invention relates to a copy forgery prevention sheet that can be identified with the naked eye.

[0002]

2. Description of the Related Art Conventionally, when a sheet printed on a special screen plate is copied, a latent image (warning character) that cannot be seen on the actual sheet appears on the copy,
A hidden word method that enables discrimination as to whether or not a copy is known. In this hidden word method, two types of screen plates having the same density and different numbers of lines are used, one of which is a latent image and the other is a background image. Things.

[0003]

However, in the conventional hidden word method, a halftone screen having a screen density of about 20% is generally used, but it is copied by a recent copier having improved resolution. Then, at a screen density of about 20%, there arises a problem that the latent image and the background in the copy cannot be distinguished. In order to eliminate this inconvenience and allow only the latent image to appear but not the background, the screen density of the background may be reduced, and the screen density of the latent image may be reduced accordingly. However, when the copy density adjustment of the copying machine is set low, a new inconvenience arises in that the latent image does not appear in the copy.

At present, the most commonly used combination of the screen ruling of the background and the latent image is the background 15
The latent image is about 50 to 80 lines for 0 to 200 lines. Under such conditions, in order to cope with a high-resolution copier, it is necessary to make the dot screen density less than 15% as a whole, and even under these conditions, the copy adjustment density is the lowest. In order to make the latent image appear in a good condition, although there is a slight difference depending on the screen color, at least about 18% of halftone dots exist in the halftone screen of the latent image, and the existence ratio is as small as possible. Higher is better.

The present applicant has already proposed a copy forgery prevention sheet disclosed in Japanese Patent Application Laid-Open No. 9-295484 to solve the above-mentioned disadvantages. The principle of the present invention, which is disclosed in Japanese Patent Application Laid-Open No. 9-295484, is as follows. That is, for example, a halftone screen plate of a latent image is added to 65 lines of 20% halftone dots, and halftone screens having different dot sizes such as screen densities of 5, 10, 15% are dispersed with the same number of lines. In this case, the density of the halftone screen of the latent image can be reduced to about 10% as a whole, and even when the copy density is the lowest,
Since the halftone screen of 65 lines and 20% is also included in the halftone screen at a specific ratio, a latent image appears on the copy.

If a halftone screen plate of a latent image having such a configuration is adopted, for example, by lowering the density of the background 175-line halftone screen to about 10%, it is possible to cope with a high-resolution copier. Although the latent image cannot be distinguished by the naked eye on the actual sheet, only the latent image appears in the copy and it can be determined whether or not the copy is a copy.

[0007] However, it is not easy to create a plate by specifying the size of halftone dots unevenly. Therefore, for example, as shown in FIG.
% Positive plate B is superimposed at an arbitrary angle θ, each halftone dot in the negative plate A has a missing portion, and the area is reduced only by the missing portion. The halftone screen can easily and easily obtain a halftone screen in which the average screen density as a whole falls below 30% and the size of the halftone dots becomes non-uniform.

Then, as disclosed in Japanese Patent Application Laid-Open No. 9-295484, the background halftone screen is displayed with a line number of 150 to 20.
0 lines, especially 175 lines, the screen density is 7 to 15%, especially 14%, while the halftone screen of the latent image is a negative 50 to 80 lines, especially 65 lines, the density is 15 to 25%, especially 20 %, The positive plate is 25 to 35 lines, especially 30 lines, and the density is 30 to 50%, especially 40%. It is preferable to apply the two plates on a halftone screen plate obtained by superimposing them at an angle of 30 degrees. In this case, the average density of the halftone screen of the latent image can be reduced to about 14%, and the density of the halftone screen is 1%.
The existence ratio of the halftone dots of 8% or more is also 75% or more, and it has been confirmed that the latent image can be favorably displayed.

By the way, in the copy forgery prevention sheet proposed in Japanese Patent Application Laid-Open No. 9-295484, even when the copy density adjustment of the copying machine is set low, only the latent image appears on the copy and the background appears. However, there is a problem that the visibility of the latent image on the actual sheet is inferior and that the latent image can be visually recognized when observed very carefully.

Further, the applicant of the present invention discloses that a halftone screen constituted by a set of halftone dots having a non-uniform size and having sharp points can be copied by a copier, even if it is a color copier. Experiments have confirmed that even in the case of color, it is copied to black.

The present invention further improves the copy forgery prevention sheet proposed in Japanese Patent Application Laid-Open No. 9-295484,
In order to solve the above problem and increase the visibility of the latent image on the actual sheet, and to copy the image with a copier, the latent image or a portion excluding the latent image is blackened to make it easier to recognize whether the image is a copy. An object of the present invention is to provide a copy forgery prevention sheet which is facilitated.

[0012]

In order to achieve this object, a copy forgery prevention sheet according to claim 1 of the present invention comprises a halftone screen having a predetermined screen density on a sheet substrate surface. A background pattern that forms the background, a latent image pattern that forms a part of the latent image, a vanishing image pattern that forms a part of the vanishing image, and a part where the latent image and the vanishing image partially overlap The background pattern and the latent image pattern are of the same color, and it is difficult to identify the latent image with the naked eye, and the combined pattern and the disappearing image pattern are applied with the same color, which is different from the aforementioned color, and are erased by the naked eye. An image can be identified, and a halftone screen of a combined pattern and a latent image pattern, or a halftone screen of a background pattern and a vanishing image pattern is formed by a set of halftone dots having a nonuniform size and a sharp portion. Configure it, is a portion other than the latent image or the latent image with black when copying, in which it is possible to identify the latent image with the naked eye.

Also, in order to achieve the above object,
The copy forgery prevention sheet according to claim 2 of the present invention has a background pattern that forms a background and a latent image pattern that forms a latent image, which is formed of a halftone screen having a predetermined screen density on the sheet substrate surface. The three patterns of the disappearing image pattern forming the disappearing image are applied, the background pattern and the latent image pattern are the same color, and it is difficult to identify the latent image with the naked eye, and the disappearing image pattern has a different color from the aforementioned color. It is possible to identify the disappeared image by the naked eye by applying the halftone screen of the latent image pattern or the halftone screen of the background pattern and the disappeared image pattern with a set of halftone dots having a non-uniform size and a pointed part. When constructed and copied, the latent image or a portion other than the latent image turns black, and the latent image can be identified by the naked eye.

Further, in order to achieve the above-mentioned object, a copy forgery prevention sheet according to a third aspect of the present invention has a nonuniform size in the configuration according to the first or second aspect. A halftone screen constituted by a set of halftone dots having a sharp portion has a screen number of 50 to 80.
A halftone screen obtained by superimposing a negative plate selected from the range of lines and density of 15 to 20% and a positive plate selected from the range of 25 to 35 lines and density of 30 to 50% at a predetermined overlapping angle. It consists of

[0015]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Here, FIGS.
4 shows a first embodiment, FIG. 1 is a schematic plan view of each pattern state of the forgery prevention sheet, FIG. 2 is an enlarged explanatory view of the X portion thereof, and FIG. 3 is a forgery state visually recognized by the naked eye. FIG. 4 is a schematic plan view showing a state in which the forgery prevention sheet after copying is visually recognized with the naked eye. FIG. 5 is a schematic plan view of each pattern state of the forgery prevention sheet according to the second embodiment.

First, a first embodiment will be described with reference to FIGS. As shown in FIG. 1, forgery prevention sheet 1
Is a background pattern 4 for forming a background on the sheet base 2
, A latent image pattern 3 that forms a part of the latent image 8 “A” (see FIG. 4), and an “O” that is the disappearance image 7 (see FIG. 3).
And a combined pattern 6 forming a portion where the latent image and the disappeared image overlap each other. Although it is not clear in FIG. 1, the background pattern 4 and the latent image pattern 3 have the same color, for example, magenta printing color, and are hardly distinguished from each other with the naked eye.

On the other hand, the disappearing image pattern 5 and the combined pattern 6
Is applied in a color different from the background pattern 4 and the latent image pattern 3, for example, a cyan printing color. Therefore, when the forgery prevention sheet 1 is viewed with the naked eye, as shown in FIG.
Only "O" which is the disappeared image 7 can be identified.

The background pattern 4 and the erased image pattern 5 are composed of 175 halftone screen lines and 14% density. Further, the halftone screen of the latent image pattern 3 and the dual-purpose pattern 6 is composed of a negative plate 65 lines 20% and a positive plate 30 lines 40%.
It is printed on a halftone screen stencil composed of a set of halftone dots having non-uniform size and pointed portions obtained by superimposing at a superimposition angle of 0 degrees. As shown in the enlarged view of FIG. 2, the halftone screen constituting the latent image pattern 3 and the dual purpose pattern 6 has an average density of about 14%, and has a halftone dot P having an uneven size and a sharp portion. It consists of a set, and the halftone screen of 65 lines and 18% has about 75% in the halftone screen.

According to the forgery prevention sheet 1 configured as described above, in the actual forgery prevention sheet 1, "O", which is the vanishing image 7 that is visually recognizable due to different colors, partially overlaps. This increases the difficulty in visually recognizing the latent image pattern 3 and makes it difficult to visually recognize the latent image 8 “A” (see FIGS. 1 and 3).

On the other hand, a copy of the forgery prevention sheet 1 is made up of a halftone screen constituted by a set of halftone dots having a non-uniform size and having sharp points even when a color copier is used. The latent image pattern 3 and the combined pattern 6 become black, and the latent image 8 “A” can be visually recognized. When a copy is obtained by changing the copy density adjustment of the forgery prevention sheet 1 in a commercially available color copying machine in a stepwise manner, the blackened latent image 8 appears in the entire range of the copy density. Make sure you do.

Next, a second embodiment will be described with reference to FIG. The forgery prevention sheet 11 of the present embodiment includes a background pattern 14 that forms a background on the surface of the sheet substrate 12,
The latent image pattern 13 forming the latent image “A” and the disappearing image pattern 15 forming the disappearing image “O” are provided. Although it is not clear in FIG. 5, the background pattern 14 and the latent image pattern 13 are of the same color, for example, magenta printing color, and are difficult to distinguish from each other with the naked eye.

On the other hand, the disappearing image pattern 15 is provided in a different color from the background pattern 14 and the latent image pattern 13, for example, in a cyan printing color. Therefore, when the forgery prevention sheet 11 is viewed with the naked eye, only the disappeared image “O” can be identified (see FIG. 3).

Background pattern 14 and vanishing image pattern 15
Consists of 175 halftone screen lines and 14% density. Further, the halftone screen of the latent image pattern 13 has a non-uniform pointed portion obtained by superimposing a negative printing line of 65 lines 20% and a positive printing plate 30 lines of 40% at an overlapping angle of 30 degrees. It is printed on a halftone screen composed of a set of halftone dots. As shown in the enlarged view of FIG. 2, the halftone screen constituting the latent image pattern 13 has an average density of about 14%, and is composed of a set of halftone dots P having a non-uniform size and a pointed portion. , 6 in the halftone screen
There are also about 75% halftone dots of 5 lines and 18%.

According to the anti-counterfeit sheet 11 configured as described above, in the real anti-counterfeit sheet 11, the disappearing image pattern 15 having a different color can be visually recognized. The difficulty in visually recognizing the pattern 13 is increased, so that the latent image pattern 13 is difficult to visually recognize.

On the other hand, in a copy of the forgery prevention sheet 11, even when a color copier is used, the latent image pattern 13 becomes black, and the latent image "A" can be visually recognized. it can. When a copy is obtained from the forgery prevention sheet 11 by changing the copy density step by step by using a commercially available color copying machine, the latent image pattern 13 is blackened over the entire range of the copy density, and the copy is well displayed. I confirmed that it would come out.

It should be noted that the present invention is not limited to the embodiments described above.
And a halftone screen plate for applying the combined pattern 6
In addition to obtaining a negative plate and a positive plate by superimposing them at a predetermined angle, a plate composed of halftone dots having a non-uniform size and having sharp points may be newly created. Further, the latent image 8 is not limited to the warning character “A”, and the disappeared image 7 is not limited to the character “O”. Further, the latent image patterns 3 and 13 and the shared pattern 6
And the halftone screens of the background patterns 4 and 14 and the disappearing image patterns 5 and 15 are reversed, and when copied, the background patterns 4 and 14 and the disappearing image patterns 5 and 15 become black and the latent image 8 emerges. May appear.

[0027]

As described above, according to the forgery prevention sheet of claim 1 of the present invention, in the actual sheet,
By making the background pattern and the latent image pattern the same color, and applying the combined pattern and the disappearing image pattern so as to be visually recognizable in the same color different from the above-mentioned color, the latent image and the disappearing image partially overlap with each other, and identification by color is performed. In addition, the latent image or the portions other than the latent image can be improved even if the overall halftone screen density is reduced in response to a copier with improved resolution while increasing the visibility of the latent image. The latent image can be made black and the latent image can be made to appear, and it is easy to visually recognize the latent image.

According to the forgery prevention sheet of the second aspect of the present invention, in the actual sheet, the background pattern and the latent image pattern are made the same color, and the disappearing image pattern is made visible in different colors. This makes it possible to increase the difficulty in visually recognizing a latent image by color identification, but in response to a copier with an improved resolution, even if the overall halftone screen density is reduced, the latent image or The portion other than the latent image becomes black, so that the latent image can be made to appear, and there is an effect that the visual recognition of the latent image is easy.

Further, according to the forgery prevention sheet of claim 3 of the present invention, in addition to the above-described effects, a halftone screen constituted by a set of halftone dots having a non-uniform size and having sharp points is provided. There is an effect that it can be obtained simply and easily.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing each pattern state of a forgery prevention sheet of a first embodiment.

FIG. 2 is an enlarged explanatory view of a portion X in FIG. 1;

FIG. 3 is a schematic plan view of the forgery prevention sheet visually recognized by the naked eye.

FIG. 4 is a schematic plan view showing a state in which the forgery prevention sheet after copying is visually recognized with the naked eye.

FIG. 5 is a schematic plan view showing each pattern state of the forgery prevention sheet of the second embodiment.

FIG. 6 is a schematic plan view showing a state where a negative plate and a positive plate of a halftone screen are overlapped at a predetermined angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,11 Forgery prevention sheet 2,12 Sheet base material 3,13 Latent image pattern 4,14 Background pattern 5,15 Disappearing image pattern 6 Combined pattern 7 Disappearing image 8 Latent image P Halftone dot A Negative plate B Positive plate

Claims (3)

[Claims] 1. A background pattern forming a background, a latent image pattern forming a part of a latent image, and a part of a disappearing image are formed on a sheet substrate surface, which is formed by a halftone screen having a predetermined screen density. And the latent image pattern are of the same color, and it is difficult to identify the latent image with the naked eye by applying a combined pattern that forms a part where the latent image and the disappeared image partially overlap each other. The combined pattern and the disappearing image pattern are applied in the same color different from the above-mentioned color, and the disappearing image can be identified by the naked eye, and the combined pattern and the latent image pattern have a halftone screen, or the background pattern and the disappearing image pattern have a halftone screen. A copy forgery prevention sheet, wherein the dot screen is constituted by a set of halftone dots having a nonuniform size and a pointed portion. 2. A background pattern forming a background, a latent image pattern forming a latent image, and a vanishing image pattern forming a vanishing image, comprising a halftone screen having a predetermined screen density on a sheet substrate surface. It is difficult to identify the latent image with the naked eye in the same color as the background pattern and the latent image pattern, and the vanishing image pattern is given in a color different from the above-mentioned color, and the vanishing image can be identified by the naked eye. There is a halftone screen of a latent image pattern, or a halftone screen of a background pattern and a vanishing image pattern, which is constituted by a set of halftone dots having a nonuniform size and a pointed portion. Sheet. 3. A halftone screen constituted by a set of halftone dots having a nonuniform size and a pointed portion has a screen number of 50.
A mesh obtained by superposing a negative plate selected from a range of ~ 80 lines and a density of 15 to 20% and a positive plate selected from a range of 25 to 35 lines and a density of 30 to 50% at a predetermined overlapping angle. 3. The copy forgery prevention sheet according to claim 1, wherein the sheet comprises a dot screen.