Anti-counterfeiting media and method for verifying the same

Abstract

To provide a forgery prevention medium at low cost which can easily determine authenticity with high accuracy.SOLUTION: According to an embodiment, a forgery prevention medium comprises: a base material; and an ink layer which is arranged on the base material and contains at least either of a dye or a pigment having a perylene framework, wherein the ink layer comprises: a first part containing a pigment in first concentration per unit area on the base material; and a second part containing a pigment in second concentration higher than the first concentration per unit area on the base material, the ink layer is observed in a first color when first observation light reflects on the ink layer, the first part is observed in a second color and the second part is observed in a third color which can be identified from the second color when second observation light passes through the ink layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an anti-counterfeiting medium and a method for verifying the same. [Background technology]

[0002] Various technologies for preventing counterfeiting have been disclosed in the past.

[0003] For example, Patent Document 1 discloses a technology for applying inks that change color depending on the viewing angle, such as OVI ink and color-shift ink, to prevent counterfeiting.

[0004] Furthermore, Patent Documents 2 and 3 disclose a technique for applying inks that appear to have different colors depending on the lighting used, such as metameric inks, to prevent counterfeiting.

[0005] Furthermore, technologies that apply multilayer vapor-deposited films, cholesteric liquid crystals, and instrument detection inks to prevent counterfeiting are also known. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4172199 [Patent Document 2] Japanese Patent Publication No. 2001-159094 [Patent Document 3] Japanese Unexamined Patent Publication No. 159004 / 1983 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, these conventional anti-counterfeiting technologies have the following problems:

[0008] OVI ink changes color when tilted, but the color change is not very distinct. Therefore, anti-counterfeiting methods using OVI ink cannot reliably determine authenticity.

[0009] On the other hand, metameric inks are more suitable for authenticity testing than OVI inks because the color they appear under normal light sources such as sunlight, fluorescent lights, and incandescent bulbs is distinctly different from the color they appear when viewed through a desired filter or under a light source with a desired spectral energy distribution. However, obtaining a clear color change requires a special light source. For this reason, anti-counterfeiting methods using metameric inks cannot be implemented inexpensively.

[0010] Furthermore, multilayer vapor-deposited films and cholesteric liquid crystals are expensive in terms of both material costs and manufacturing costs. Therefore, anti-counterfeiting methods using multilayer vapor-deposited films or cholesteric liquid crystals cannot be realized at a low cost.

[0011] Furthermore, anti-counterfeiting technology using instrument-detection ink requires a special detector. Therefore, due to the manufacturing cost of this detector, it cannot be implemented cheaply. Moreover, even if this detector is manufactured, it can only be used by people who can operate it, making it lacking in versatility.

[0012] Furthermore, it is conceivable to apply smartphone authentication (also known as "smartphone authentication"), which has evolved significantly in recent years, to counterfeit prevention. This involves taking an image of the subject using the smartphone's camera and determining authenticity based on the image. However, smartphone authentication requires users to download a specific application to their smartphone, which is inconvenient for them. Moreover, even if a user downloads the application to their smartphone, the camera orientation and angle will differ from user to user, making it impossible to determine authenticity with high reliability.

[0013] The present invention has been made in view of such circumstances, and an object thereof is to provide an anti-counterfeiting medium that is inexpensive, highly accurate, and enables easy authenticity determination, and a verification method thereof.

Means for Solving the Problems

[0014] In order to achieve the above object, the present invention takes the following means.

[0015] That is, a first aspect of the present invention has a substrate and an ink layer disposed on the substrate and containing at least one of a dye or a pigment having a perylene skeleton. The ink layer includes a first portion containing a pigment having a first concentration per unit area on the substrate and a second portion containing a pigment having a second concentration higher than the first concentration per unit area on the substrate. When the first observation light is reflected in the ink layer, the ink layer is observed in a first color. When the second observation light passes through the ink layer, the first portion is observed in a second color, and the second portion is observed in a third color distinguishable from the second color. It is an anti-counterfeiting medium.

[0016] A second aspect of the present invention is the anti-counterfeiting medium according to the first aspect, in which the first portion and the second portion have the same thickness in a direction perpendicular to the main surface of the substrate.

[0017] A third aspect of the present invention is the anti-counterfeiting medium according to the first aspect, in which the first portion and the second portion have different thicknesses in a direction perpendicular to the main surface of the substrate.

[0018] A fourth aspect of the present invention is the anti-counterfeiting medium according to the first or second aspect, in which the first color is black, the second color is green, and the third color is red.

[0019] A fifth aspect of the present invention is the anti-counterfeiting medium according to the first or second aspect, in which the higher the second concentration, the more the third color shifts to the higher wavelength side.

[0020] A sixth aspect of the present invention is the anti-counterfeiting medium according to the first aspect, in which the first observation light is light from a fluorescent lamp or sunlight, and the second observation light is light from a white light source.

[0021] The seventh aspect of the present invention is a forgery prevention medium according to the first aspect, wherein the ink layer is a pigment having a perylene skeleton that appears black in reflection, and the transmittance at the first concentration is 0.2% or more and less than 10% near 540 nm and 60% or more and less than 100% near 780 nm, and the transmittance at the second concentration is less than 0.2% near 540 nm and 40% or more and less than 100% near 780 nm.

[0022] The eighth aspect of the present invention is a verification method for the forgery prevention medium according to the first aspect, wherein when the first observation light is reflected by the ink layer, the ink layer is observed in the first color, and when the second observation light is transmitted through the ink layer, if the first part is observed in the second color and the second part is observed in the third color, the forgery prevention medium is determined to be genuine, and in other cases, the forgery prevention medium is determined not to be genuine.

[0023] The ninth aspect of the present invention is the verification method according to the eighth aspect, wherein the first observation light is light from a fluorescent lamp or sunlight, and the second observation light is white light from a white light source.

[0024] The tenth aspect of the present invention is the verification method according to the ninth aspect, wherein the white light source is a white LED mounted on a smartphone.

Advantages of the Invention

[0025] According to the present invention, it is possible to provide a forgery prevention medium and a verification method thereof that are inexpensive, highly accurate, and can easily perform authenticity determination.

Brief Description of the Drawings

[0026] [Figure 1] FIG. 1 is a plan view showing an example of a forgery prevention medium according to the first embodiment of the present invention. [Figure 2] FIG. 2 is a side cross-sectional view of the forgery prevention medium along the line X-X' of FIG. 1. [Figure 3]Figure 3 is a side cross-sectional view corresponding to Figure 2, showing the case where observation light is irradiated from a reflected light source and the observation light is reflected by the ink layer. [Figure 4] Figure 4 is a plan view corresponding to Figure 1, showing the state observed by the observer when the observation light from the reflected light source is reflected by the ink layer. [Figure 5] Figure 5 is a side cross-sectional view corresponding to Figure 2, showing the case where observation light is irradiated from a transmitted light source and the observation light passes through the ink layer. [Figure 6] Figure 6 is a plan view corresponding to Figure 1, showing the state as observed by the observer when observation light is irradiated from a transmitted light source and the observation light passes through the ink layer. [Figure 7] Figure 7 shows the light emission intensity characteristics of the LEDs emitted from a smartphone. [Figure 8] Figure 8 shows the light transmission properties of a pigment having a perylene skeleton. [Figure 9] Figure 9 is a detailed light transmission characteristic diagram of the pigment having a perylene skeleton in the wavelength range of 380 nm to 630 nm shown in Figure 8. [Figure 10] Figure 10 shows a typical luminous efficiency curve. [Figure 11] Figure 11 is a side cross-sectional view showing an example of an anti-counterfeiting medium according to a second embodiment of the present invention. [Figure 12] Figure 12 is a table showing the correlation between the number of layers and the L*a*b* value obtained from the characterization of the sample in Example 4. [Figure 13] Figure 13 shows the correlation between the number of layers and the a* value obtained from Figure 12. [Figure 14] Figure 14 is a typical L*a*b* color space chromaticity diagram. [Modes for carrying out the invention]

[0027] Embodiments of the present invention will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes of the parts, etc., are not necessarily the same as those of reality. Furthermore, even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In this specification and each drawing, the same reference numerals are used for elements that are the same as those described above with respect to previously shown drawings, and detailed explanations are omitted as appropriate.

[0028] (First Embodiment) Figure 1 is a plan view showing an example of a counterfeit prevention medium according to the first embodiment of the present invention.

[0029] Figure 2 is a side cross-sectional view of the anti-counterfeiting medium along the line X-X' in Figure 1.

[0030] In other words, the anti-counterfeiting medium 1 is constructed by placing an ink layer 3 on a substrate 2.

[0031] The base material 2 can be paper, plastic, wood, glass, or resin that is transparent to white light from an LED or the like, and an appropriate material will be selected from these depending on the application of the anti-counterfeiting medium 1.

[0032] The ink layer 3 includes a first portion 3a containing a pigment at a first concentration per unit area on the substrate 2, and a second portion 3b containing a pigment at a second concentration higher than the first concentration per unit area on the substrate 2.

[0033] The ink layer 3 is formed by a printing method such as offset printing, gravure printing, screen printing, and flexographic printing.

[0034] In the examples shown in Figures 1 and 2, the ink layer 3 is composed of a first ink layer 3' having a circular planar shape and a second ink layer 3'' having a star-shaped planar shape that is laminated on a portion of the first ink layer 3'.

[0035] In the examples shown in Figures 1 and 2, the first area 3a is formed by a single layer of the first ink layer 3', and the second area 3b is formed by a multilayer structure consisting of the first ink layer 3' and the second ink layer 3''. Therefore, in the second area 3b, the pigment concentration per unit area on the substrate 2 is higher than in the first area 3a.

[0036] Figure 3 is a side cross-sectional view corresponding to Figure 2, showing the case where observation light is irradiated from a reflected light source and the observation light is reflected by the ink layer.

[0037] Figure 4 is a plan view corresponding to Figure 1, showing the state observed by the observer when the observation light from the reflected light source is reflected by the ink layer.

[0038] The reflected light source 4' can be any light source, such as a fluorescent lamp or the sun. Therefore, white light from a fluorescent lamp or sunlight can be used as the observation light R.

[0039] As shown in Figure 3, when observation light R is shone onto the anti-counterfeiting medium 1 from a reflective light source 4', and the observation light R is reflected by the ink layer 3, the ink layer 3 is observed by observer K in a first color, as shown in Figure 4. The first color is, for example, black.

[0040] Figure 5 is a side cross-sectional view corresponding to Figure 2, showing the case where observation light is irradiated from a transmitted light source and the observation light passes through the ink layer.

[0041] Figure 6 is a plan view corresponding to Figure 1, showing the state as observed by the observer when observation light is irradiated from a transmitted light source and the observation light passes through the ink layer.

[0042] The transmitted light source 4'' can be a white light source, such as a white LED installed in a smartphone. Therefore, the observation light T from the transmitted light source 4'' can be white light.

[0043] Figure 7 shows the light emission intensity characteristics of the LEDs emitted from a smartphone.

[0044] Methods for emitting white light include creating white light by combining the blue light of an LED with a phosphor that emits yellow light, which is the complementary color of the LED, or creating white light by combining LEDs of the three primary colors: red, green, and blue.

[0045] As shown in Figure 5, when observation light T is irradiated onto the anti-counterfeiting medium 1 from a transmitted light source 4'', and the observation light T passes through the anti-counterfeiting ink layer 3, as shown in Figure 6, in the ink layer 3, the first area 3a is observed in a second color different from the first color, and the second area 3b is observed in a third color different from the first color but distinguishable from the second color. The second color is, for example, green, and the third color is, for example, red.

[0046] Figures 2, 3, and 5 show examples where the second area 3b is formed from two layers: the first ink layer 3' and the second ink layer 3''. However, the second area 3b can also be formed from three or more layers, and the more layers there are, the more the third color shifts to a higher wavelength. In other words, if the third color is red, the more layers there are, the redder it becomes.

[0047] Suitable materials for the ink layer 3 having such characteristics include a pigment having a perylene skeleton that exhibits black color in reflection, has a transmittance of 0.2% to less than 10% around 540 nm and 60% to less than 100% around 780 nm when it is a single layer, and has a transmittance of less than 0.2% around 540 nm and 40% to less than 100% around 780 nm when it is a multi-layered material. Pigments having a perylene skeleton have the characteristic of exhibiting high transmittance in the near-infrared region while being black in reflection. Furthermore, the transmission wavelength can be controlled by changing the substituents.

[0048] The basis for the transmittance of the ink layer 3, which consists of pigments having such a perylene skeleton, is as follows.

[0049] Specifically, focusing on the transmittance around 540nm, if the transmittance of ink layer 3 is less than 0.2% when it is a single layer, the transmitted light will appear red. Conversely, if the transmittance of the single layer is 10% or more, the green color will be too strongly visible, and the reflected light will also appear greenish. In addition, if the transmittance of the single layer is 10% or more, when it is made into a multi-layered system, the transmittance will not easily fall below 0.2%, making the red color difficult to see. Furthermore, if the transmittance of the multi-layered system is 0.2% or more, the transmitted light will appear green.

[0050] Focusing on the transmittance around 780nm, if the ink layer 3 is a single layer, a transmittance of less than 60% may make the red color more visible due to the lower overall transmittance. On the other hand, if the transmittance is less than 40%, the transmitted light will appear dark, making the red color difficult to see.

[0051] Figures 8 and 9 show the light transmission properties of pigments having a perylene skeleton.

[0052] In particular, Figure 9 is a detailed light transmission characteristic diagram of a pigment having a perylene skeleton in the wavelength range of 380 nm to 630 nm shown in Figure 8.

[0053] Figure 10 shows a typical luminous efficiency curve.

[0054] In the case of single layer a, as shown in Figure 8, the transmittance in the visible region is generally low, but as shown in Figure 9, it shows a maximum value around 540 nm. Also, from the luminous efficiency curve shown in Figure 10, humans perceive green light around 555 nm most strongly in bright light. Therefore, when observation light T is transmitted through single layer a, it becomes easily visible as green.

[0055] In the case of multilayer b, the overall transmittance is lower compared to the case of singlelayer a, and in particular, as shown in Figure 9, the transmittance around 540 nm decreases to almost 0%. Therefore, when observation light T is transmitted through multilayer b, it becomes difficult to see in green and easier to see in red around 780 nm.

[0056] Therefore, when observation light T is shone from a transmitted light source 4'' onto the ink layer 3 formed by coating with such pigment, the first part 3a, which is a single layer a, appears green due to the transmission of observation light T, while the second part 3b, which is a multilayer b, appears red.

[0057] In the ink layer 3 formed with a pigment having a perylene skeleton with these characteristics, a clearer color change between green and red can be observed compared to the ink layer formed with OVI ink.

[0058] Next, we will explain the method for verifying the authenticity of the anti-counterfeiting medium 1 configured as described above.

[0059] In this verification method, first, the anti-counterfeiting medium 1, which is the test subject, is made to reflect observation light R obtained from the sun or fluorescent lamp, as illustrated in Figure 3.

[0060] As a result, when observer K observes that the ink layer 3 turns black, as illustrated in Figure 4, observer K then places a smartphone, for example, as a light source 4'' behind the subject, as illustrated in Figure 5, and shines observation light T from the smartphone's LED towards the subject, causing the ink layer 3 to pass through.

[0061] As a result, when observer K observes that the ink layer 3, which was displayed in black as exemplified in Figure 4, now displays a predetermined design in the shape of a star, in two distinguishable colors such as green and red, as exemplified in Figure 6, observer K determines that this subject is genuine.

[0062] On the other hand, if the ink layer 3 does not appear black even when reflected by observation light R, or if the ink layer 3 appears black when reflected by observation light R, but does not appear in a predetermined design with two distinguishable colors such as green and red when transmitted by observation light T, then observer K will determine that this subject is not genuine.

[0063] As described above, this verification method utilizes the color shift effect caused by light reflection and transmission, making it inexpensive and easy to implement without the need for special verification equipment. This verification method requires both reflected and transmitted light, but sunlight can be used as the reflected light, and the LEDs installed in smartphones can be used as the transmitted light, so there is no need to equip special light sources. Furthermore, since the authenticity can be determined by the visual confirmation of observer K, anyone can easily and inexpensively perform highly accurate authenticity determination without using any special applications.

[0064] (Second embodiment) Figure 11 is a side cross-sectional view showing an example of an anti-counterfeiting medium according to a second embodiment of the present invention.

[0065] The anti-counterfeiting medium 1A according to the second embodiment is a modified example of the anti-counterfeiting medium 1 according to the first embodiment.

[0066] In the anti-counterfeiting medium 1A, an ink layer 3 is arranged on the substrate 2, and the ink layer 3 includes a first portion 3a containing a first concentration of pigment per unit area on the substrate 2, and a second portion 3b containing a second concentration of pigment higher than the first concentration per unit area on the substrate 2. The first portion 3a is formed by the first ink layer 3', as in the case of the anti-counterfeiting medium 1.

[0067] On the other hand, while the second part 3b was realized in anti-counterfeiting medium 1 by a multilayer structure consisting of a first ink layer 3' and a second ink layer 3'', in anti-counterfeiting medium 1A it is realized by a single layer of the third ink layer 3''''. However, the third ink layer 3'''' contains pigment at a higher concentration than the first ink layer 3'.

[0068] This configuration also makes it possible to realize an ink layer 3 that includes a first portion 3a containing a first concentration of pigment per unit area on the substrate 2, and a second portion 3b containing a second concentration of pigment higher than the first concentration per unit area on the substrate 2.

[0069] Furthermore, with this configuration, unlike the anti-counterfeiting medium 1, the heights of the first portion 3a and the second portion 3b can be made equal, and a flat ink layer 3 can be realized. For example, as shown in the plan view in Figure 1, if the ink layer 3 includes a second portion 3b having a star-shaped planar shape, it can be formed by first printing the second portion 3b (third ink layer 3'') having a star-shaped planar shape onto the substrate 2, and then printing the first portion 3a (first ink layer 3') around it so that the planar shape of the ink layer 3 becomes circular.

[0070] Even with this configuration, as described in the first embodiment, the ink layer 3 is displayed in black due to the reflection of observation light R, and the first part 3a is displayed in green and the second part 3b in red due to the transmission of observation light T, so it can be used well for the verification method described in the first embodiment.

[0071] Next, we will describe Examples 1 to 4, in which we actually created samples of the anti-counterfeiting medium 1 and evaluated the characteristics of the samples. [Examples]

[0072] In Example 1, an ink layer 3 was formed using an ink containing a perylene-based material as a pigment under the following conditions. Base material: Transparent PET film Pigments: Perylene-based materials Ink: UV-curing flexographic ink Pigment concentration: 20% Printing method: An ink layer 3 was formed by printing a 5 μm area in a single layer to create the first area 3a, and then printing a 10 μm area in a second pass to create the second area b. Characterization (in the case of a genuine product): The ink layer 3 appeared black due to the reflection of observation light R, and the first part 3a appeared green and the second part 3b appeared red due to the transmission of observation light T. Therefore, the anti-counterfeiting medium 1 having the ink layer 3 formed in Example 1 can be determined to be a genuine product. Characterization (in the case of counterfeit products): On the other hand, the anti-counterfeiting medium 1 having the ink layer 3 formed in Example 1 was copied using a copier. The copied material is formed not by the specified ink, but by the inkjet ink or toner of the copier, so it appears black due to reflection, but the transmitted color is white, and therefore it can be determined to be a counterfeit product. [Examples]

[0073] In Example 2, the ink layer 3 was formed under the following conditions. Base material: Transparent PET film Pigments: Perylene-based materials Ink: UV-curing flexographic ink Pigment concentration: 20% and 40% Printing method: An ink layer 3 was formed by applying a single layer with a thickness of 5 μm, with areas having a pigment concentration of 20% and areas with a pigment concentration of 40%. Characteristic evaluation: Ink layer 3 appears black in reflection, appears green in areas with a pigment concentration of 20%, and appears red in areas with a pigment concentration of 40%, thus it can be determined to be a genuine product. [Examples]

[0074] In Example 3, the ink layer 3 was formed using a pigment-free ink under the following conditions. Base material: Transparent PET film Pigment: None Ink: UV-curing flexographic ink Printing method: Similar to Example 1, the ink layer 3 was formed by printing a 5 μm area in a single layer to form the first area 3a, and then printing a 10 μm area in a second pass to form the second area b. Characterization: The ink layer 3 appeared black due to the reflection of observation light R, but appeared white due to the transmission of observation light T. Therefore, the anti-counterfeiting medium 1 having the ink layer 3 formed in Example 3 can be determined to be a counterfeit product. [Examples]

[0075] In Example 4, similar to Example 1, ink layers 3 with different numbers of layers were formed using an ink containing a perylene-based material as a pigment. Substrate: Transparent PET film Pigment: Perylene-based material Ink: UV-curable flexographic ink Pigment concentration: 20% Printing method: Samples of the first to fifth layers were created with a single layer being 3 μm. Characteristic evaluation: The ink layer 3 was displayed as black by the reflection of observation light R, and by the transmission of observation light T, the first to second layers were displayed as yellowish green and the third to fifth layers were displayed as yellowish red.

[0076] Figure 12 is a table showing the correlation between the number of layers obtained from the characteristic evaluation of the sample of Example 4 and the L * a * b * value.

[0077] Figure 13 is a diagram showing the correlation between the number of layers obtained from Figure 12 and the a * value.

[0078] Figure 14 is a chromaticity diagram of a general L * a * b * color space.

[0079] As shown in Figures 12 and 13, it was found that as the number of layers increased (i.e., the pigment concentration per unit area increased), the a * value shifted in the + direction. This corresponds to a shift from green to red in the L * a * b * color system.

[0080] [[ID=�3]] Thus, according to Example 4, it was confirmed that the higher the concentration of the pigment contained in the second part 3b of the ink layer 3, the more the red color observed in the second part 3b by the transmission of observation light T shifted to the higher wavelength side.

[0081] The best mode for carrying out the present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to this configuration. Within the scope of the invented technical idea of ​​the claims, a person skilled in the art can conceive of various modifications and alterations, and it is understood that such modifications and alterations also fall within the technical scope of the present invention. [Explanation of Symbols]

[0082] 1, 1A... Anti-counterfeiting medium, 2... Substrate, 3... Ink layer, 3'... First ink layer, 3''... Second ink layer, 3'''... Third ink layer, 3a... First part, 3b... Second part, 4'... Reflected light source, 4''... Transmitted light source, a... Single layer, b... Multiple layers, K... Observer, R... Observation light, T... Observation light

Claims

1. Substrate and The substrate is disposed on the aforementioned substrate and comprises an ink layer containing a pigment having a perylene skeleton, The ink layer comprises a first portion containing the pigment at a first concentration per unit area on the substrate, and a second portion containing the pigment at a second concentration higher than the first concentration per unit area on the substrate. When the first observation light is reflected by the ink layer, the ink layer is observed as black. When the second observation light passes through the ink layer, the first portion is observed in green, and the second portion is observed in red. The transmittance at the first concentration is 0.2% or more and less than 10% around 540 nm, and 60% or more and less than 100% around 780 nm. An anti-counterfeiting medium in which the transmittance at the second concentration is less than 0.2% around 540 nm and 40% or more but less than 100% around 780 nm.

2. The anti-counterfeiting medium according to claim 1, wherein the first portion and the second portion have equal thickness in a direction perpendicular to the main surface of the substrate.

3. The anti-counterfeiting medium according to claim 1, wherein the first portion and the second portion have different thicknesses in a direction perpendicular to the main surface of the substrate.

4. The anti-counterfeiting medium according to claim 1 or 2, wherein the higher the second concentration, the more the red color shifts to a higher wavelength side.

5. The anti-counterfeiting medium according to claim 1, wherein the first observation light is light from a fluorescent lamp or sunlight, and the second observation light is light from a white light source.

6. A method for verifying an anti-counterfeiting medium according to claim 1, A verification method comprising: determining that the anti-counterfeiting medium is genuine if, when the first observation light is reflected by the ink layer, the ink layer is observed as black, and when the second observation light is transmitted through the ink layer, the first portion is observed as green and the second portion is observed as red; otherwise, determining that the anti-counterfeiting medium is not genuine.

7. The verification method according to claim 6, wherein the first observation light is light from a fluorescent lamp or sunlight, and the second observation light is white light from a white light source.

8. The verification method according to claim 7, wherein the white light source is a white LED installed in a smartphone.

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