JP7191312B2 - Identification tag, its interference waveform detection method, and its authenticity judgment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an identification tag suitable for use as a tag for various products, an interference waveform detection method therefor, and an authenticity determination method therefor.

There are various types of product tags, but tags that simply record information such as product names, product numbers, prices, etc. are easily counterfeited. For this reason, conventionally, in order to identify product tags, tags with complex patterns such as bar codes and QR codes (registered trademark), or RF tags with memory, control circuits and A tag equipped with an anti-counterfeiting structure has been developed that enables product identification by incorporating an antenna and reading it with electromagnetic waves.

The identification tag in the present invention refers to a structure having anti-counterfeiting effect by imparting identification power to a product or object, like the product tag described above. The objects of identification tags that have distinctiveness and anti-counterfeiting effects are interpreted in a broad sense and include those for identifying products distributed in manufacturing, mining, agriculture, fisheries and transportation, finance, commerce, service industries, etc. be In addition, it is not limited to those for identifying commodities that are mass-distributed to general consumers, such as clothing and food, but also includes those for identifying works of art and crafts that are not mass-distributed. Furthermore, the target is not limited to identifying finished products distributed to general consumers, and may be, for example, identifying semi-finished products in the manufacturing process in the manufacturing industry. Also, the shape of the identification tag can be considered in many forms, such as a shape that is directly affixed to the product, a shape that is attached to the product via a tag holder or the like.

For example, in Patent Document 1, an information code is formed by combining a large number of concave portions having different depths from a reference plane, a laser beam is irradiated onto the surface of the information code, reflected light is received, and the distance from the reference plane is measured. An anti-counterfeit structure is described which reads an information code by means of an anti-counterfeiting structure. However, since the laser rangefinder is a common device, it is relatively easy to read the information code and possibly forge it.

Therefore, as shown in Patent Document 2, a technique has been developed in which a tag is irradiated with terahertz waves and the waveform data obtained by the interference is used to determine authenticity. A terahertz wave generator is disclosed in Patent Document 3, etc., but it is not as common as a laser range finder, so it is difficult to read the information code.

However, PET resin and polyethylene resin, which are used as the base material of the tag in Patent Document 2, have the advantage that they are easy to surface-process and can easily form various patterns. Since the ratio is low, the amplitude of the waveform data is small. On the contrary, the Si material has a high refractive index, but there is a problem that the surface processing is not easy.

There is also an RF tag as a tag that can be read through a shield, but this requires an antenna to receive radio waves or magnetic fields inside the tag material. If the distance between the antennas in the tag is short, problems such as reading and writing becoming impossible due to interference between the antennas in the tag occur.

Japanese Patent No. 4967778 Japanese Patent No. 5119566 JP-A-2002-72269

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described conventional problems, to provide an identification tag which can be easily surface-processed, can easily form various patterns, and can obtain waveform data with a large amplitude when irradiated with terahertz waves, and an identification tag therefor. It is to provide a manufacturing method, its interference waveform detection method, and its authenticity determination method.

In order to solve the above problems, the present invention employs the following means (1) to (4) .
(1) It is made of a material that can reflect and transmit terahertz waves and interferes with terahertz waves inside, has a flat plate structure combining multiple regions with different thicknesses, and contains metal powder on one or both sides An identification tag characterized by applying a metallic paint to amplify an interference waveform .
(2) The identification tag according to (1) , wherein the material is a thermoplastic material, and the thickness of the plurality of regions is adjusted by thermal processing .
(3) The identification tag of (1) or (2) above is irradiated with terahertz waves having different frequencies, and the terahertz waves that are reflected or transmitted by the front and rear surfaces of the identification tag and interfere with each other due to the optical path difference are emitted from the identification tag. A method for detecting an interference waveform of an identification tag, characterized by detecting from the irradiation side or the back side of the terahertz wave, and converting the detected terahertz wave into waveform data representing reflectance or transmittance for each frequency.
(4) A method for determining authenticity of an identification tag, characterized in that the waveform data obtained by the waveform detection method of (3) above is compared with pre-stored reference waveform data to determine the authenticity of the identification tag. .

The anti-counterfeiting structure of the present invention is a material that can reflect and transmit terahertz waves and is made by applying a paint containing metal powder to one or both sides of a material in which terahertz waves interfere . waveform data with large amplitude can be obtained. Therefore, the accuracy of thickness detection is enhanced, and the accuracy of authenticity determination can be enhanced. Moreover, according to the present invention, an identification tag in which a large number of regions with different thicknesses are combined in a complicated manner can be economically manufactured by thermal processing.

In addition, since terahertz waves can pass through various materials such as paper, plastic, vinyl, fiber, semiconductors, and powders, they can be read through obstacles. It is possible to arrange it and perform product identification and counterfeit prevention. Furthermore, the identification tag of the present invention does not have an antenna for receiving radio waves or magnetic fields inside the identification tag, and there is no interference between the antennas due to radio waves or magnetic fields. It is possible to perform product identification and forgery prevention even in a state where the product is worn.

The identification tag of the present invention is suitable for use as a product tag or the like. Since very slight differences in thickness can be accurately detected by using terahertz waves, it is possible to make the difference in thickness of each region very small. is extremely difficult to decipher and decipher the pattern. In addition, as described above, terahertz waves can pass through various substances, so there is the advantage that even when the identification tag of the present invention is sealed inside, it can be used.

FIG. 4 is an explanatory diagram showing reflection and transmission of terahertz waves; It is a graph of an interference waveform obtained by frequency analysis of a transmitted wave. It is a schematic diagram of the anti-counterfeit body of the present invention. Fig. 4 is a graph of interference waveforms corresponding to different frequencies; FIG. 10 is a graph showing interference waveforms with and without spraying of metallic paint; FIG. 1 is a cross-sectional view of an identification tag of the present invention; FIG. 1 is a cross-sectional view of an identification tag of the present invention; FIG. 1 is a cross-sectional view of an identification tag of the present invention; FIG.

Embodiments of the present invention are described below.
The identification tag of the present invention is a flat plate made of a material capable of reflecting and transmitting terahertz waves. The terahertz wave in the present invention is an electromagnetic wave with a wavelength of 100 μm to 3 mm (frequency of 100 GHz to 3 THz), and has the property of penetrating various substances such as paper, plastic, vinyl, fiber, semiconductor, and powder like radio waves. Like light, it also has the property of being able to be reflected and focused by mirrors and lenses.

As shown in FIG. 1, when the surface of a substrate 10 having a certain thickness is irradiated with a terahertz wave from an irradiation source 1, part of the irradiation wave 11 is reflected by the substrate surface and becomes a reflected wave 12, and part of the Although it becomes a transmitted wave 13, the remainder is multiple-reflected on the back and front surfaces of the substrate 10 to become a reflected wave 14 and a transmitted wave 15 as shown in the drawing. Since the reflected wave 14 from the back surface of the base material 10 reciprocates inside the base material 10, the optical path is longer than the reflected wave 12 from the front surface of the base material 10 by an amount corresponding to the thickness, and this optical path difference makes the reflected wave A phase difference occurs between 12 and the reflected wave 14 . Two types of terahertz waves having a phase difference interfere with each other, and the interference waveform changes depending on the thickness of the substrate 10 and the frequency of the terahertz waves. The same is true for the transmitted waves 13 and 15, and an interference waveform that varies depending on the thickness of the substrate 10 is obtained.

This principle has been conventionally used in interferometric film thickness gauges, and usually a sensor is installed on the irradiation side to use the reflected wave. It is also possible to install the sensor 2 on the side opposite to the irradiation side where the irradiation source 1 is located and detect the transmitted wave. FIG. 2 is a graph of an interference waveform obtained by frequency analysis of detected transmitted waves, where the vertical axis represents transmittance and the horizontal axis represents frequency. The frequency interval X changes according to the thickness of the substrate 10. FIG. The wave height Y represents the strength of interference due to the phase difference.

In the present invention, this interference waveform is used to determine the authenticity of an identification tag. The principle is as follows.
FIG. 3 is a schematic diagram of the identification tag of the present invention. To simplify the explanation, the identification tag is shown divided into four areas (1), (2), (3), and (4). These four regions have different thicknesses, for example, two thicknesses of 1 mm and 1.5 mm. Note that these thicknesses are for the convenience of the following description.

In the identification tag shown in FIG. 3, the thickness of the upper left (1) and lower left (3) regions is 1.5 mm, and the thickness of the upper right (2) and lower right (4) regions is 1 mm. ing. This identification tag is irradiated with terahertz waves of frequencies A, B, C, and D that have the maximum transmittance when the film thickness is 1.5 mm. Then, waveform 1 data peculiar to the regions (1) and (3) where the transmittance is maximum at the frequencies A, B, C, and D are obtained. Next, when terahertz waves with frequencies A, B, C, and D are irradiated to regions (2) and (4) with a film thickness of 1 mm, the transmittance is maximized at frequencies A and C, as shown by the broken lines in FIG. Waveform data 2 peculiar to the regions (2) and (4) are obtained. In this explanation, the difference in thickness of each region is 0.5 mm, but in reality, the difference in thickness may be further reduced, or three or more types of thickness may be provided to enhance the anti-counterfeiting effect. is preferred.

As described above, according to the present invention, an identification tag that combines a plurality of regions with different thicknesses is irradiated with terahertz waves of different frequencies, and the detected terahertz waves are converted into waveform data representing transmittance for each frequency. Note that the waveform data in the present invention is nothing more than a graph obtained by connecting discrete data obtained by plotting transmittance with respect to an arbitrary frequency, and the waveform data itself includes this discrete data itself. By comparing the detected waveform with pre-stored reference waveform data, the authenticity of the identification tag can be determined.

In order to improve the accuracy of the authenticity determination described above, it is desirable that the amplitude of the interference waveform shown in FIG. 2, that is, the height Y of the wave is large. For this reason, in the present invention, the interference due to the etalon effect can be strengthened by applying a metallic paint containing metallic powder to one or both surfaces of the substrate. FIG. 5 is a transmission spectrum diagram showing a specific example thereof. The waveform obtained by irradiating a polyethylene substrate with terahertz waves is shown by the dashed line. A large clear waveform was obtained. As the zinc spray, a commercially available spray containing 55 parts by weight of zinc powder, 5 parts by weight of epoxy ester resin, and 40 parts by weight of an organic solvent was used. When dried, the organic solvent evaporates to form a coating of 92 parts by weight of zinc powder and 8 parts by weight of epoxy ester resin.

However, in the present invention, the type of metal powder is not limited to zinc powder, and other metal powders such as gold, silver, aluminum, copper, tin, indium, iron and magnesium can also be used. However, when used as a tag, it is left in contact with air for a long period of time, so it is preferable that the metal be stable in the air. From an economical point of view, it is preferable to use zinc, tin, or the like rather than expensive gold or silver.

The application method is not necessarily limited to spraying, and other means such as dipping and screen printing can also be employed. However, since it is preferable to form a uniform and thin metal powder layer, the spray method is most suitable. The film thickness is preferably 5 μm to 200 μm. This is because if the film thickness is thinner than this range, the metal particles are easily peeled off, and if it exceeds this range, the metal particles are not arranged on the surface of the responsive material in an orderly manner, and the terahertz wave is not properly transmitted. Also, the particle size of the metal powder is preferably 2 μm to 20 μm.

The layer 20 of metal paint containing metal powder may be formed on the uneven surface of the substrate 10 as shown in FIG. 6 or may be formed on the flat surface of the substrate 10 as shown in FIG. As in 8, it may be formed on both the uneven surface and the flat surface. In the case of FIG. 6, it can be manufactured by forming a plurality of regions with different thicknesses on the base material 10 by the method described below and then spraying the metal paint. In the case of FIG. 7, after forming the layer 20 of metallic paint on one side of the substrate 10 in advance, it can be manufactured by forming a plurality of regions with different thicknesses on the opposite side.

The identification tag described above can increase the difficulty of counterfeiting by increasing the number of regions formed on the substrate. However, as described above, it is difficult to economically manufacture an identification tag with an increased number of regions by the method of adhering blocks or the method of using a mold. On the other hand, according to the present invention, as will be described below, identification tags can be manufactured economically by applying the technique of stamp manufacturing.

That is, in the manufacturing method of the present invention, first, a block copy of a pattern in which a plurality of areas are combined in a complicated manner is created. Then, thermal processing is performed by pressing a thermal head against the plate-shaped base material 10 made of a thermoplastic material capable of reflecting or transmitting terahertz waves, in accordance with the block copy. A thermal head has a large number of heating elements arranged in a straight line, and the position, pressing pressure, time, amount of heat, etc. are controlled by a computer. The heat control data of the heating element is created according to the image data created by the typesetting software, and based on the data, a plurality of regions with different thicknesses can be formed on the substrate 10 by thermal processing. Incidentally, the technique of forming a stamp surface using a thermal head is described in Japanese Patent No. 6205731 of the present applicant.

Using the manufacturing method described above, identification tags with multiple regions of different thicknesses can be economically manufactured. A thermoplastic material that is easily thermally processed is used as the material 10 . Specific examples include polyethylene, polypropylene, polybutylene, polyvinyl chloride, and polyester. From the viewpoint of workability with a thermal head, it is more preferable to use a porous material.

As described above, the identification tag of the present invention can obtain waveform data with a large amplitude when irradiated with terahertz waves by applying a metal paint containing metal powder. Therefore, the accuracy of thickness detection is enhanced, and the accuracy of authenticity determination can be enhanced.

1 irradiation source 2 sensor 10 substrate 11 irradiation wave 12 reflected wave 13 transmitted wave 14 reflected wave 15 transmitted wave 20 layer of metallic paint

Claims (4)

It is made of a material that can reflect and transmit terahertz waves and interferes with terahertz waves inside. It has a flat plate structure that combines multiple regions with different thicknesses, and has a metal paint containing metal powder on one or both sides. An identification tag characterized by amplifying an interference waveform by applying it . 2. The identification tag according to claim 1, wherein the material is a thermoplastic material, and the plurality of areas are adjusted in thickness by thermal processing . irradiating the identification tag according to claim 1 or 2 with terahertz waves having different frequencies,
Detecting terahertz waves reflected and transmitted by the front and back surfaces of the identification tag and interfering due to an optical path difference from the irradiation side or the back side of the identification tag,
A method for detecting an interference waveform of an identification tag, characterized in that the detected terahertz wave is converted into waveform data representing reflectance or transmittance for each frequency. 4. A method for determining the authenticity of an identification tag, wherein the waveform data obtained by the waveform detection method according to claim 3 is compared with pre-stored reference waveform data to determine the authenticity of the identification tag.

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