JP7524642B2 - Method for manufacturing a secret information forming body - Google Patents

Description

The present invention relates to a method for manufacturing a secret information forming body that has a latent image that is difficult to recognize as it is, and that becomes visible when the surface is rubbed with a coin or the like.

Such secret information forming bodies have been known for a long time and are used, for example, in scratch-off lottery tickets or scratch-off postcards.

A typical example of such a secret information forming body is described in Patent Document 1. This secret information forming body is formed by covering a latent image portion printed on a substrate with a concealing layer. The concealing layer is formed by screen printing an opaque ink containing metal powder, and as it is covered with such an opaque ink, the latent image portion cannot be recognized as it is. The latent image portion becomes visible when the concealing layer is removed by rubbing with a coin or the like.

However, this secret information forming body has a problem in that when rubbed with a coin or the like, the concealing layer turns into fine debris and contaminates the surrounding area. For this reason, secret information forming bodies have been devised that do not produce debris from the concealing layer when the latent image portion is visualized.

For example, there is a secret information forming body in which the latent image and its background are formed using printing inks of the same color system that are difficult to distinguish from each other, and further, the latent image is formed using ink containing a material that is harder than the metal used in coins (Patent Document 2). With this secret information forming body, the latent image cannot be distinguished from the background as it is. On the other hand, by rubbing the body with a coin or the like, the coin is scraped off by the latent image and the color of the latent image changes, so that the latent image can be distinguished from the background and made visible. In this way, the concealing layer is not removed when making the latent image visible, so no residue is generated from the concealing layer. However, with this secret information forming body, there is a problem in that when rubbed with a coin or the like, a small amount of the coin is scraped off.

A secret information forming body that uses ink that is erased by heat or pressure is also known (Patent Document 3). In this secret information forming body, a concealing layer and an erasing layer are laminated to cover the latent image portion. The concealing layer is an opaque layer that is printed by encapsulating a decolorizing composition that becomes transparent when it comes into contact with the components of the erasing layer in microcapsules and turning it into ink. The erasing layer is printed with an ink containing a component that erases the color-changing composition. In this secret information forming body, the latent image portion is also covered with an opaque concealing layer, so it cannot be recognized as it is. On the other hand, when the secret information forming body is pressurized to break the microcapsules in the concealing layer, the decolorizing composition in the microcapsules comes into contact with the erasing layer and becomes transparent due to this destruction, and as a result, the latent image portion can be made visible. In this secret information forming body, the latent image portion can be made visible without generating any residue or damaging the coin.

Japanese Utility Model Publication No. 44-12094 Patent No. 5262961 JP 2002-103864 A

However, in the confidential information forming body described in Patent Document 3, it is necessary to use microcapsules with a diameter of 10 to 50 μm. Because the latent image portion is covered with a concealing layer using microcapsules with a large diameter, there is a problem in that the latent image portion may be visible when viewed from the side, which is approximately parallel to the paper surface.

The present invention aims to provide a method for manufacturing a secret information forming body that can visualize a latent image without producing waste or damaging the coin, and in which the latent image cannot be recognized even when viewed from the side, which is approximately parallel to the paper surface.

That is, the invention described in claim 1 is a method for producing a secret information forming body formed by laminating a secret information forming layer and a concealing layer in this order on a base material,
The secret information forming layer is composed of a latent image portion and a background portion thereof arranged in parallel,
The latent image portion and the background portion are both made of printing inks of the same color system that are difficult to distinguish from each other, and the latent image portion and the concealing layer are both made of printing inks that change color due to frictional heat generated when the surfaces of the latent image portion and the concealing layer are rubbed,
the latent image portion, the background portion and the concealing layer are all formed of a set of halftone dots of the printing ink,
The background portion is printed using a printing plate having halftone dots of a substantially circular or substantially elliptical shape;
On the other hand, there is a method for manufacturing a confidential information forming body, characterized in that the latent image portion and the concealing layer are printed with a printing plate having approximately rectangular dots, and the dots are transformed by bleeding into approximately circular or elliptical dots.

The invention described in claim 2 is the method for manufacturing the confidential information forming body described in claim 1, characterized in that the background portion is made of ink that does not discolor even when its surface is rubbed.

The invention described in claim 3 is the method for manufacturing the confidential information forming body described in claim 1 or 2, characterized in that the concealing layer is made of ink that becomes transparent when frictional heat is applied when the surface of the concealing layer is rubbed.

The invention described in claim 4 is a method for manufacturing a confidential information forming body described in any one of claims 1 to 3, characterized in that the concealing layer is made of a printing ink of the same color system that is difficult to distinguish from the latent image portion and its background portion.

Next, the invention described in claim 5 is a method for manufacturing a secret information forming body described in any of claims 1 to 4, characterized in that a second concealing layer is laminated on the concealing layer, and this second concealing layer is made of ink that changes color due to frictional heat when its surface is rubbed.

According to the secret information forming body of the present invention, the latent image portion and the concealing layer are made of ink that changes color due to frictional heat when the surface is rubbed. For example, by rubbing the surface of the secret information forming body with an eraser or a coin, the latent image portion changes color, increasing the contrast with the background portion. At the same time, the concealing layer also changes color. This makes it possible to observe and recognize the latent image portion with the naked eye.

In the present invention, the background portion is printed with a printing plate having dots of approximately circular or elliptical shape, while the latent image portion and the concealing layer are printed with a printing plate having dots of approximately square shape. However, since the latent image portion and the concealing layer are made of inks that change color due to frictional heat when the surface is rubbed, the approximately square dots printed in this way bleed on the substrate and change to approximately circular or elliptical dots. As a result, the dots of the latent image portion and the dots of the concealing layer are both approximately circular or elliptical like the dots of the background portion, and the latent image portion and its background portion are made of printing inks of the same color system that are difficult to distinguish from each other, and the concealing layer is laminated on the latent image portion and its background portion (secret information forming layer), so it is virtually impossible to distinguish the latent image portion from the background portion. In this way, even though the latent image portion and the concealing layer are printed with a printing plate having dots of approximately square shape, the latent image portion cannot be distinguished from the background portion.

FIG. 1 is a cross-sectional view of a secret information forming device according to a first embodiment of the present invention. FIG. 2 is a plan view of a secret information forming device according to a first embodiment of the present invention. 3A and 3B relate to a first embodiment of the present invention, and FIG. 3A is an enlarged view of a part of a printing plate for printing a latent image portion, and FIG. 3B is an enlarged view of the said part where the printed dots have smudged. FIG. 4 relates to a first embodiment of the present invention and is an enlarged view of a partial area of a printing plate for printing a background portion. FIG. 5 is a cross-sectional view showing a state in which a latent image portion is visualized according to a first embodiment of the present invention. 6A and 6B relate to a second embodiment of the present invention, and FIG. 6A is an enlarged view of a part of a printing plate for printing a latent image portion, and FIG. 6B is an enlarged view of the said area where the printed dots have smudged. FIG. 7 relates to a second embodiment of the present invention and is an enlarged view of a partial area of a printing plate for printing a background portion. 8A and 8B relate to a third embodiment of the present invention, and FIG. 8A is an enlarged view of a part of a printing plate for printing a latent image portion, and FIG. 8B is an enlarged view of the said area where the printed dots have smudged. FIG. 9 is an enlarged view of a partial area of a printing plate for printing a background portion according to a third embodiment of the present invention. FIG. 10 is an enlarged view of a partial area of a latent image portion according to a fourth embodiment of the present invention. FIG. 11 is an enlarged view of a partial region of the background according to a fourth embodiment of the present invention. 12A and 12B relate to a fifth embodiment of the present invention, and FIG. 12A is an enlarged view of a part of a printing plate for printing a latent image portion, and FIG. 12B is an enlarged view of the said part where the printed dots have smudged. 13A and 13B relate to a fifth embodiment of the present invention, and FIG. 13A is an enlarged view of a portion of a printing plate for printing a background portion, and FIG. 13B is an enlarged view of the aforementioned portion where the printed dots have smudged. FIG. 14 is a cross-sectional view of a secret information forming device according to a sixth embodiment of the present invention.

Specific examples of the present disclosure will be described below with reference to the attached drawings. FIG. 1 is a cross-sectional view of a secret information forming body according to a first specific example of the present invention, and FIG. 2 is a plan view thereof. Note that in order to explain the shape of the dots on the printing plate that prints the latent image portion 21 and the shape of the dots that have smudged after printing, FIG. 3 shows an enlarged view of a partial area A of the latent image portion 21. FIG. 3(a) is an enlarged view of the area A on the printing plate that prints the latent image portion 21, and FIG. 3(b) is an enlarged view of the area A where the printed dots have smudged. Similarly, in order to explain the shape of the dots on the printing plate that prints the background portion 22, FIG. 4 shows an enlarged view of a partial area B of the printing plate that prints the background portion 22.

As can be seen from FIG. 1, this secret information forming body 100 is constructed by laminating a secret information forming layer 20 and a concealing layer 30 in this order on a substrate 10. The secret information forming layer 20 is constructed by arranging a latent image portion 21 and its background portion 22 in parallel.

The substrate 10 may be any sheet, but in order to prevent the latent image portion 21 from being read by looking through the substrate 10, it is desirable that the substrate 10 be opaque enough that the latent image portion 21 cannot be seen through. As such a substrate 10, ordinary printing paper, card paper, paperboard, etc. can be used, but it may also be an opaque plastic sheet whose main material is vinyl chloride, polyester, etc.

Next, the secret information forming layer 20 makes the contents of the latent image portion 21 secret information, and the background portion 22 arranged in parallel with it makes the contents of the latent image portion 21 unrecognizable. For this reason, the latent image portion 21 is a character or symbol indicating the result of winning or losing, such as "winner" or "first prize." In the figure, the letter "T" is used as the latent image portion 21.

In addition, in order to make the contents of the latent image portion 21 unrecognizable by the background portion 22, it is necessary to print the latent image portion 21 and the background portion 22 with printing inks of the same color system that are difficult to distinguish from each other.

In order to make the latent image portion 21 visible when the surface of the confidential information forming body 100 is rubbed with an eraser or a coin, the latent image portion 21 must be made of printing ink that changes color due to frictional heat generated when the surface is rubbed. On the other hand, it is desirable that the background portion 22 be made of ink that does not change color even when rubbed in this manner.

Printing inks that change color due to frictional heat when the surface is rubbed are described, for example, in JP-B-4-17154 and JP-A-7-179777. For example, they are inks made of an electron-donating color-forming organic compound, a compound having a phenolic hydroxyl group, and a carboxylic acid ester having a substituted aromatic ring in the molecule and a melting point and cloud point difference of 5 to 50°C. Examples of electron-donating color-forming organic compounds include crystal violet lactone and malachite green lactone. Examples of compounds having a phenolic hydroxyl group include tertiary butylphenol and nonylphenol. Examples of carboxylic acid esters having a substituted aromatic ring in the molecule and a melting point and cloud point difference of 5 to 50°C include stearyl 2-methylbenzoate and cetyl 4-tert-butylbenzoate.

General-purpose printing inks can be used as inks that do not discolor when rubbed.

Both the latent image portion 21 and the background portion 22 are composed of a collection of dots of the printing ink. The latent image portion 21 is printed using a printing plate having approximately square dots 21a' (see FIG. 3(a)). As described above, this printing ink changes color due to frictional heat when the surface is rubbed. Therefore, when printed using a printing plate having approximately square dots 21a', the ink bleeds on the substrate 10 and changes into approximately circular or elliptical dots 21a (see FIG. 3(b)). On the other hand, the background portion 22 is printed on the substrate 10 using a printing plate having approximately circular or elliptical dots 22a (see FIG. 4), and the shape of the dots 22a is reproduced on the substrate 10 as is. As a result, the latent image portion 21 and the background portion 22 are both composed of approximately circular or approximately elliptical dots 21a, 22a, and because they are made of printing inks of the same color that are difficult to distinguish from each other as described above, it is virtually impossible to distinguish the latent image portion 21 from the surrounding background portion 22.

As will be described later as a second specific example, the numerous halftone dots that make up these latent image portions 21 can be composed of two or more types of halftone dots that differ from one another in density. Similarly, it is desirable that the numerous halftone dots that make up the background portion 22 are also composed of two or more types of halftone dots that differ from one another in density. In this way, when both the latent image portion 21 and the background portion 22 are composed of two or more types of halftone dots that differ from one another in density, the contrast between the latent image portion 21 and the background portion 22 can be reduced, making it even more difficult to recognize the latent image portion 21.

The density of the dots can be adjusted by their diameter. The diameter of the dots 21a that make up the latent image portion 21 and the dots 22a that make up the background portion 22 may be 0.03 to 0.3 mm. Of the numerous dots 21a that make up the latent image portion 21, it is desirable that the high density dots be present in 10 to 80% of the cases compared to the low density dots. Similarly, of the numerous dots 22a that make up the background portion 22, it is desirable that the high density dots be present in 10 to 80% of the cases compared to the low density dots.

As a third specific example described later, a blank area can be provided in part of the numerous dots 21a that make up the latent image portion 21, and a blank area can also be provided in part of the numerous dots 22a that make up the background portion 22. By providing blank areas in the numerous dots that make up the latent image portion 21 and the background portion 22 in this way, the contrast between the latent image portion 21 and the background portion 22 can be reduced, making it even more difficult to recognize the latent image portion 21.

Alternatively, low-density halftone dots may be randomly scattered over the entire surface including the latent image portion 21 and the background portion 22 (fourth specific example).

As a fifth specific example described later, the latent image portion 21 can also be dotted with halftone dots using the same printing ink as the printing ink that forms the background portion 22. In this case, it is desirable to also dot the background portion 22 with halftone dots using the same printing ink as the printing ink that forms the latent image portion 21.

It is desirable that the halftone dots 21a constituting the latent image portion 21 and the halftone dots 22a constituting the background portion 22 partially overlap at the boundary between the latent image portion 21 and the background portion 22. By partially overlapping the two halftone dots at the boundary in this way, the boundary can be blurred, making it even more difficult to recognize the latent image portion 21.

Next, the concealment layer 30 is provided to cover the secret information forming layer 20 (latent image portion 21 and background portion 22) in order to make the contents of the latent image portion 21 unrecognizable.

It is desirable that this concealing layer 30 be made of printing ink of the same color system that makes it difficult to distinguish between the latent image portion 21 and its background portion 22.

The concealing layer 30 must be transparent when the latent image portion 21 is visualized. For this reason, the concealing layer 30 must be made of an ink that changes color due to frictional heat generated when the surface is rubbed. Preferably, the ink becomes transparent due to the frictional heat. As such an ink, the inks described above as the ink constituting the latent image portion 21 can be used. That is, inks made of electron-donating color-forming organic compounds, compounds having phenolic hydroxyl groups, and carboxylic acid esters having a difference between the melting point and the cloud point of 5 to 50°C and containing substituted aromatic rings in the molecule, etc.

When this concealing layer 30 is printed using a printing plate having approximately square dots 21a', like the latent image portion 21, it bleeds onto the substrate 10 and deforms into approximately circular or approximately elliptical dots 21a. As a result, the latent image portion 21, the background portion 22, and the concealing layer 30 are all composed of approximately circular or approximately elliptical dots, making it difficult to distinguish between the latent image portion 21 and the background portion 22.

With this confidential information forming body 100, the latent image portion 21 cannot be distinguished from the background portion 22 as it is. Even if the confidential information forming body 100 is tilted and viewed from the side, which is approximately parallel to the paper surface, it is impossible to recognize the contents of the latent image portion 21.

On the other hand, when this surface is rubbed with a rubber band or a coin, the frictional heat causes the latent image portion 21 and the concealing layer 30 to discolor (see Figure 5). The discolored latent image portion 21 and concealing layer 30 maintain their discolored state even after they are returned to room temperature. Therefore, even after rubbing with a rubber band or a coin has stopped, the latent image portion 21 and the concealing layer 30 remain discolored. This increases the contrast between the latent image portion 21 and the background portion 22, and the contents of the latent image portion 21 can be recognized through the concealing layer 30.

Next, a second specific example of the present invention will be described with reference to Figures 6 to 7. Figures 6 and 7 relate to a second specific example of the present invention, with Figure 6(a) being an enlarged view of a partial area A of the printing plate on which the latent image portion 21 is printed, and Figure 6(b) being an enlarged view of said area A where the printed dots have smudged. Also, Figure 7 is an enlarged view of a partial area B of the printing plate on which the background portion 22 is printed.

In this example, the latent image portion 21 is printed using a printing plate having two types of roughly rectangular dots 21a', 21b' with different densities (see FIG. 6(a)). The dots 21a', 21b' printed in this way both bleed onto the substrate 10 and transform into roughly circular or roughly elliptical dots 21a, 21b (see FIG. 6(b)).

The background portion 22 is also printed using a printing plate having two types of halftone dots 22a and 22b with different densities (see Figure 7). The shape of the halftone dots 22a is reproduced as is on the substrate 10.

Figures 8 and 9 relate to a third specific example of the present invention, where Figure 8(a) is an enlarged view of a partial area A of the printing plate on which the latent image portion 21 is printed, and Figure 8(b) is an enlarged view of the area A where the printed dots have smudged. Figure 9 is an enlarged view of a partial area B of the printing plate on which the background portion 22 is printed.

In this example, blank areas 21c, 22c are provided in parts of the latent image portion 21 and the background portion 22, respectively, and the rest is the same as the first specific example. Note that in FIG. 8(a), the blank area 21c' in the printing plate is drawn as a roughly rectangular shape, and in FIG. 8(b), the blank area 21c in the confidential information forming body is drawn as a roughly circular or roughly elliptical shape, but of course the blank area 21c does not have a shape.

Next, Figures 10 and 11 relate to a fourth specific example of the present invention, with Figure 10 being an enlarged view of a partial area A of the latent image portion 21. Also, Figure 11 being an enlarged view of a partial area B of the background portion 22.

In this example, low-density halftone dots x are randomly scattered over the entire surface including the latent image portion 21 and the background portion 22. The halftone dots x can be printed using a printing plate separate from the printing plate used to print the latent image portion 21 and the printing plate used to print the background portion 22, so that the halftone dots x are uniformly scattered over the entire surface of the substrate 10. The printing ink can be an ink that does not discolor when the surface is rubbed, similar to the ink used for the background portion 22. The halftone dots on the printing plate can be approximately circular or approximately elliptical.

Next, Figures 12 and 13 relate to a fifth specific example of the present invention, with Figure 12 being an enlarged view of a partial area A of the latent image portion. Figure 13 is an enlarged view of a partial area B of the background portion 22.

In this example, the latent image portion 21 is printed using a printing plate having roughly rectangular dots 21a' made of printing ink that changes color due to frictional heat, and another printing plate is used to print dots 21d made of the same printing ink as the printing ink that constitutes the background portion 22, so that these dots are scattered within the latent image portion 21. The roughly rectangular dots 21a' bleed onto the substrate 10 and transform into roughly circular or roughly elliptical dots 21a (see FIG. 12).

In this example, the background portion 22 is printed using a printing plate having approximately circular or approximately elliptical dots 22a made of a printing ink that does not discolor due to frictional heat, and is printed using another printing plate so that approximately rectangular dots are scattered within the background portion 22 using the same printing ink as the printing ink that constitutes the latent image portion 21. The approximately rectangular dots bleed onto the substrate 10 and deform into approximately circular or approximately elliptical dots 22d (see FIG. 13).

14 is a cross-sectional view of a secret information forming body 200 according to a sixth embodiment of the present invention, which is configured by laminating a second concealing layer 40 on a concealing layer 30, and is otherwise similar to the secret information forming body 100 according to the first embodiment. By laminating the second concealing layer 40 on the concealing layer 30 in this manner, it becomes even more difficult to recognize the latent image portion 21 before it is visualized.

The second concealing layer 40, like the concealing layer 30, is desirably made of a printing ink of the same color system that is difficult to distinguish from the latent image portion 21 and its background portion 22. In order to make the latent image portion 21 visible by rubbing the surface of the confidential information forming body 300, the second concealing layer 40, like the concealing layer 30, must also be made of an ink that changes color with frictional heat generated when the surface is rubbed. Desirably, the ink is one that becomes transparent with the frictional heat. As such an ink, the inks described above as the inks that constitute the latent image portion 21 and the concealing layer 30 can be used. The second concealing layer 40 can also be made of a collection of many halftone dots of printing ink. The halftone dots may be approximately square, approximately circular, or approximately elliptical, but it is preferable that they are approximately square.

100, 200: Confidential information forming body 10: Substrate 20: Confidential information forming layer 21: Latent image portion 21a: Approximately circular or elliptical halftone dots of the latent image portion 21a': Approximately rectangular halftone dots of a printing plate for printing the latent image portion 22: Background portion 22a: Halftone dots of the background portion 30: Concealing layer 40: Second concealing layer

Claims (5)

A method for producing a secret information forming body formed by laminating a secret information forming layer and a concealing layer in this order on a base material, comprising the steps of:
The secret information forming layer is composed of a latent image portion and a background portion thereof arranged in parallel,
The latent image portion and the background portion are both made of printing inks of the same color system that are difficult to distinguish from each other, and the latent image portion and the concealing layer are both made of printing inks that change color due to frictional heat generated when the surfaces of the latent image portion and the concealing layer are rubbed,
the latent image portion, the background portion and the concealing layer are all formed of a set of halftone dots of the printing ink,
The background portion is printed using a printing plate having halftone dots of a substantially circular or substantially elliptical shape;
On the other hand, a method for manufacturing a confidential information forming body is characterized in that the latent image portion and the concealing layer are printed with a printing plate having approximately rectangular dots, and the dots are transformed into approximately circular or elliptical dots by bleeding. The method for manufacturing the confidential information forming body according to claim 1, characterized in that the background portion is made of ink that does not discolor even when its surface is rubbed. The method for manufacturing a confidential information forming body according to claim 1 or 2, characterized in that the concealing layer is made of ink that becomes transparent when frictional heat is applied to the surface of the concealing layer. The method for manufacturing a confidential information forming body according to any one of claims 1 to 3, characterized in that the concealing layer is made of a printing ink of the same color system that is difficult to distinguish from the latent image portion and its background portion. A method for manufacturing a secret information forming body as described in any one of claims 1 to 4, characterized in that a second concealing layer is laminated on the concealing layer, and this second concealing layer is composed of an ink that changes color due to frictional heat when its surface is rubbed.

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