JP2008080501A - Antifalsifying medium, antifalsifying label, printed material, transfer foil and judging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antifalsifying medium, with which higher antifalsifying effects than ever can be realized. <P>SOLUTION: In the antifalsifying medium 10 equipped with a light reflecting layer 22 and a phase contrasting layer 23, which is opposite to some part of the front of the light reflecting layer, a first light reflecting region 11 corresponding to a portion opposite to the phase contrasting layer 23 of the light reflecting layer 22 and a second light reflecting region 12 corresponding to a portion being not opposite to the phase contrasting layer 23 of the light reflecting layer 22 in the antifalsifying medium 10 respectively form visible images mutually discriminable from each other. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a forgery prevention technique that can be used to prevent forgery of securities such as stock certificates, bonds, checks, and gift certificates, lotteries, and ID cards.

  In recent years, copiers using electrophotographic technology have become widespread, and anyone can easily copy documents using this. In particular, according to a recent color digital copying machine, even a copy that is extremely difficult to determine whether it is a manuscript or a copy can be easily produced.

  A general color digital copying machine performs copying by the following method. First, the original is irradiated with light, and the reflected light is detected by a CCD line sensor. The CCD line sensor generates a digital signal corresponding to the intensity of the reflected light and transmits it to a memory in the copying machine. This reading is performed for three colors of red (R), green (G), and blue (B), and digital signals obtained for the respective colors are stored in the memory. Next, based on the stored digital signal, an electrostatic latent image is drawn on the photosensitive drum with a laser beam. Subsequently, a toner image corresponding to the electrostatic latent image is formed on the photosensitive drum using electrostatic force. Thereafter, the toner image is transferred to a sheet, and the transferred toner image is fixed on the sheet. For example, by performing this process for three colors, an elaborate color copy can be obtained.

  While such color copying is convenient, it facilitates the forgery of securities such as stock certificates, bonds, promissory notes, checks, and printed materials such as admission tickets and boarding passes. For this reason, various proposals have been made to take measures to prevent duplication of printed matter so that they cannot be easily copied.

  As one of such measures, there is a technique for making the color of a copy by color copying different from the color of an original. For example, a technique for coloring a document such as securities with a very light color has been proposed. It is difficult to accurately reproduce this light color by copying. In addition, a technique for forming halftone dots of different sizes has been proposed. In these copies, the reproducibility of small halftone dots tends to be insufficient. Further, a technique for printing in a color that is not found in toner of color copiers such as green, purple, orange, gold, and silver has been proposed. In addition, reflection and / or absorption characteristics are almost equal in the wavelength range of light that can be easily perceived by humans, and reflection and / or absorption in wavelength ranges of light that are difficult for humans to perceive, for example, wavelength ranges of 380 nm to 450 nm and 650 nm to 780 nm. Techniques using two types of inks having different characteristics have been proposed. The two areas formed using these inks are visually the same color, but can be reproduced in different colors when copied on a color copier.

  However, the color copying machine can correct the output color. Also, digital presses that correct digital data read by a color scanner with a computer and output the data with a color printer are becoming widespread. Therefore, if a little effort is required, it is possible to precisely reproduce the color of the document, and it is difficult to prevent forgery with the above-described technique.

  In addition, for example, a technique has been proposed in which securities are provided with special parts that cannot be reproduced by a color copying machine. Among these, the technique of providing an OVD (Optical Variable Device) such as a hologram foil described in Patent Documents 1 and 2 on the surface of securities or the like has already been put into practical use. According to this technique, since the silver surface of the hologram specularly reflects light, the reflected light does not enter the CCD line sensor, and the silver surface portion of the original is reproduced in black on the copy. Patent Document 3 describes a technique using an optical thin film in which ceramic layers having different refractive indexes are stacked and the color changes depending on the viewing angle. Since this color change cannot be obtained with a copy, it is possible to easily determine the authenticity. Furthermore, it has also been proposed to perform printing by crushing the thin film formed by this method and mixing fragments into ink.

  However, due to the development of embossing technology, the formation of a reflective layer including a relief-type diffractive structure is becoming more difficult than before. In addition, multilayer thin film has begun to be sold as a general packaging film. As a result, the effect of preventing forgery of holograms has been reduced.

  Patent Documents 4 to 7 describe the use of cholesteric liquid crystal in order to obtain an effect of changing the color of reflected light in accordance with the viewing angle, that is, a color shift effect, similarly to a hologram.

  The wavelength of circularly polarized light selectively reflected by the polymer cholesteric liquid crystal changes according to the angle formed by the line of sight and the helical axis. Patent Documents 4 to 7 disclose that this color shift effect is used in order to obtain an anti-counterfeit effect. Also disclosed are techniques for laminating a cholesteric liquid crystal layer and a hologram forming portion, and using an ink containing a cholesteric liquid crystal pigment and an ionizing radiation curable resin. Furthermore, there is a disclosure of a technique for controlling the rotation direction of polarized light as reflected light by combining a cholesteric liquid crystal layer and a phase difference layer using nematic liquid crystal.

However, nowadays cholesteric liquid crystals are easily available because of the frequent use of circularly polarizing plates in displays. Therefore, the anti-counterfeit effect by the cholesteric liquid crystal is decreasing.
JP-A-6-259013 Japanese Patent Laid-Open No. 7-089293 JP-T-2004-505158 JP-A-63-51193 International Publication No. 00/13065 Pamphlet JP 2002-114935 A JP 2002-255200 A

  An object of the present invention is to achieve a higher anti-counterfeit effect.

  A first invention for solving the above problem is a forgery prevention medium comprising a light reflection layer and a retardation layer facing a part of the front surface of the light reflection layer and including a liquid crystal material. Of the anti-counterfeit medium, a first light reflecting region corresponding to a portion of the light reflecting layer facing the retardation layer, and a second light corresponding to a portion of the light reflecting layer not facing the retardation layer. Each of the reflection areas is a forgery prevention medium characterized in that a visible image that can be distinguished from each other is formed.

  The second invention is the anti-counterfeit medium according to the first invention, further comprising a light-transmitting colored layer positioned in front of the light reflecting layer and facing the retardation layer. .

  According to a third aspect of the invention, the retardation layer includes a light-transmitting colored layer and a pair of liquid crystal layers sandwiching the light-transmitting colored layer. is there.

  The fourth invention is the forgery prevention medium according to any one of the first to third inventions, wherein the light reflection includes a reflection layer exhibiting an interference color.

  Further, the fifth invention is the forgery prevention medium according to any one of the first to fourth inventions, further comprising an alignment film interposed between the light reflection layer and the retardation layer. is there.

  According to a sixth aspect of the present invention, there is provided an anti-counterfeit label comprising the anti-counterfeit medium according to any one of the first to fifth aspects and an adhesive layer supported on the back surface thereof.

  A seventh invention is a printed matter comprising the forgery prevention medium of any one of the first to fifth inventions and a paper into which the forgery prevention medium is inserted.

  Further, an eighth invention is supported by any one of the anti-counterfeit media of the first to fourth inventions, a base material that releasably supports the front surface of the anti-counterfeit medium, and a back surface of the anti-counterfeit medium. The transfer foil is characterized by including an adhesive layer.

  A ninth invention is a method for discriminating between an authentic product and an unauthentic product whose authenticity is unknown, wherein the authentic product is one of the first to fifth inventions. 1st and 2nd light reflection area | regions which are the articles | supports which supported one forgery prevention medium, and each forms the visible image which can be distinguished from each other, and a contrast ratio changes by observing through a polarizer If the article is unknown whether or not it is authentic, the determination method includes determining that the authentic or unknown article is a non-authentic product. .

  According to the present invention, a higher forgery prevention effect can be achieved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is a plan view schematically showing a forgery prevention medium according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the forgery prevention medium shown in FIG.

  The anti-counterfeit medium 10 includes a base material 21 shown in FIG. The base material 21 is a biaxially stretched film made of, for example, polyethylene terephthalate.

  A light reflection layer 22 is formed on the substrate 21. Typically, the light reflecting layer 22 is a specular reflector. The light reflecting layer 22 can be formed by evaporating aluminum, for example.

The front surface of the light reflecting layer 22 is partially covered with a λ / 8 retardation layer 23. The λ / 8 retardation layer 23 is made of, for example, nematic liquid crystal. The λ / 8 retardation layer 23 includes a _fast axis along the direction indicated by an arrow n _A23 in FIG. 1 and a slow axis n _B23 (not shown in FIG. 1) perpendicular to the _fast axis n _A23 . Have. The λ / 8 phase difference layer 23 has a wavelength of λ and a polarization plane (oscillation plane of an electric field vector) that is obliquely incident on the fast axis n _A23 is incident on the plane of polarization n _B23. And a second linearly polarized light whose plane of polarization is parallel to the fast axis n _A23 and whose phase is advanced by λ / 8 from the first linearly polarized light.

  The wavelength λ is a design wavelength. The design wavelength λ is typically a wavelength of green light in which natural human light cells have high sensitivity, for example, about 550 nm. The retardation of the λ / 8 retardation layer 23 at the design wavelength λ may not be as designed due to variations in the thickness thereof. Even in such a case, if the deviation of the retardation from the design value is about 10% or less of the design value, the verification described later is not greatly affected.

  Typically, an alignment film is interposed between the light reflection layer 22 and the retardation layer 23. The alignment film is made of, for example, polyvinyl alcohol (PVA). The alignment film has a function of controlling the alignment direction of mesogenic groups of liquid crystal molecules included in the liquid crystal layer formed thereon.

  The λ / 8 retardation layer 23 is covered with a light-transmitting colored layer 24. The colored layer 24 transmits light having a wavelength of λ. The colored layer 24 contains a dye such as a direct dye, a disperse dye, and a dichroic dye, or a pigment. The colored layer 24 can further contain a transparent resin.

  Hereinafter, a region corresponding to a portion of the anti-counterfeit medium 10 or the front surface thereof facing the λ / 8 retardation layer 23 of the light reflection layer 22 is referred to as a first light reflection region 11, and λ / A region corresponding to a portion not facing the eight retardation layer 23 is referred to as a second light reflection region 12.

  Next, an image that is seen when natural light is irradiated onto the anti-counterfeit medium 10 and observed with the naked eye will be described.

  Since the colored layer 24 absorbs part of the incident natural light, the first light reflecting region 11 emits light having a lower intensity than the incident light. On the other hand, the second light reflecting region 12 emits light having substantially the same intensity as the incident light. Therefore, the first light reflection region 11 looks darker than the second light reflection region 12. Further, the hue of the colored layer 24 can be seen in the first light reflection region 11. That is, each of the first light reflection region 11 and the second light reflection region 12 forms a visible image that can be distinguished from each other when viewed with the naked eye.

  Next, a verification tool used for confirming that the article supporting the forgery prevention medium 10 is a genuine product will be described.

  FIG. 3 is an exploded view schematically showing an example of the verification tool. A verification tool 50 shown in FIG. 3 includes a linearly polarizing film 51 and a λ / 4 retardation layer 52.

  The linearly polarizing film 51 is, for example, an absorptive polarizing film. In this case, the linearly polarizing film 51 transmits linearly polarized light having a polarization plane parallel to the transmission axis OP, and absorbs linearly polarized light having a polarization plane orthogonal to the transmission axis OP.

  As the absorption-type polarizing film 51, for example, a PVA-iodine type film or a dichroic dye type film in which iodine is absorbed in a stretched film made of PVA can be used. Since these polarizing films have low physical strength, they may be used by being sandwiched between films made of triacetylrose (TAC).

The λ / 4 retardation layer 52 faces one main surface of the linearly polarizing film 51. The _fast axis n _A52 of the λ / 4 retardation layer 52 is oblique to the transmission axis OP of the linearly polarizing film 51. As an example, when the λ / 4 retardation layer 52 is viewed from the linearly polarizing film 51 side, the direction of the _fast axis n _A52 of the λ / 4 retardation layer 52 is counterclockwise from the direction parallel to the transmission axis OP. It is assumed that the direction is rotated by 45 °. In this case, the verification tool 50 functions as a left circular polarizer.

  The retardation of the λ / 4 retardation layer 52 at the design wavelength λ may not be as designed due to variations in the thickness thereof. Even in such a case, if the deviation of the retardation from the design value is about 10% or less of the design value, the verification described later is not greatly affected.

  Next, a method for verifying that the article supporting the forgery prevention medium 10 is an authentic product using the verification tool 50 will be described.

  4A is a plan view schematically showing an example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped.

In FIG. 4A, the forgery prevention medium 10 and the verification tool 50 are arranged such that the λ / 4 retardation layer 52 faces both the light reflection regions 11 and 12. Furthermore, the light transmission axis OP of the linearly polarizing film 51 is orthogonal to the _fast axis n _A23 of the λ / 8 retardation layer 23. In this case, as shown in FIG. 4A, the second light reflection region 12 appears as a dark portion, and the first light reflection region 11 appears brighter than the second light reflection region 12. The reason for this will be described below. Here, for simplicity, only light having a wavelength equal to the design wavelength λ is considered.

First, light reflection by the first light reflection region 11 will be described.
The left circularly polarized light emitted from the verification tool 50 enters the λ / 8 phase difference layer 23 shown in FIG. The λ / 8 retardation layer 23 converts the incident left circularly polarized light into left elliptically polarized light. The locus of the end of the electric field vector of the left elliptical polarization forms an ellipse whose major axis is inclined 45 ° clockwise with respect to the _fast axis n _A23 when viewed from the light reflecting layer 22 side.

The left elliptical polarized light emitted from the λ / 8 retardation layer 23 is specularly reflected by the light reflecting layer 22 and converted into right elliptical polarized light. The end locus of the electric field vector of right elliptically polarized light forms an ellipse whose major axis is inclined 45 ° counterclockwise with respect to the _fast axis n _A23 when viewed from the observer side.

The right elliptically polarized light is incident on the λ / 8 retardation layer 23. The λ / 8 retardation layer 23 converts the right elliptically polarized light into linearly polarized light. When viewed from the observer side, the plane of polarization of this linearly polarized light is inclined 45 ° counterclockwise with respect to the _fast axis n _A23 .

  This linearly polarized light is incident on the λ / 4 retardation layer 52 of the verification tool 50. The λ / phase difference layer 52 converts this linearly polarized light into left circularly polarized light.

  This left circularly polarized light enters the linearly polarizing film 51. Of the left circularly polarized light, the linearly polarizing film 51 transmits linearly polarized light whose polarization plane is parallel to the transmission axis OP, and absorbs linearly polarized light whose polarization plane is perpendicular to the transmission axis OP. That is, the verification tool 50 ideally transmits half of the reflected light from the first light reflection region 11 and absorbs the remaining half.

Next, light reflection by the second light reflection region 12 will be described.
The second light reflection region 12 converts the left circularly polarized light emitted from the verification tool 50 into right circularly polarized light. That is, the reflected light from the second light reflection region 12 incident on the λ / 4 retardation layer 52 is right circularly polarized light. This right circularly polarized light cannot pass through the verification tool 50.

  For the above reasons, the second light reflection region 12 appears as a dark portion, and the first light reflection region 11 appears brighter than the second light reflection region 12.

  FIGS. 4B to 4D are planes schematically showing other examples of images that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. FIG. 4 (b) to 4 (d) respectively show a state in which only the verification tool 50 is rotated 45 °, 90 ° and 135 ° clockwise as viewed from the observer side from the state shown in FIG. 4 (a). Is drawn.

  As shown in FIGS. 4A to 4D, the brightness of the first light reflection area 11 and the brightness of the second light reflection area 12 are determined by rotating the verification tool 50 around the normal line. Will not change. This is because the verification tool 50 is a circular polarizer, and the light emitted from the first light reflection region 11 and the second light reflection region 12 toward the verification tool 50 is circularly polarized light and linearly polarized light, respectively.

  As described above, when the anti-counterfeit medium 10 is observed without using the verification tool 50, the colored layer 24 causes a difference in brightness between the first light reflection region 11 and the second light reflection region 12. Specifically, when the anti-counterfeit medium 10 is observed without using the verification tool 50, the first light reflection region 11 looks darker than the second light reflection region 12. Then, the verification tool 50 and the anti-counterfeit medium 10 are arranged so that the λ / 4 phase difference layer 52 and the anti-counterfeit medium 10 face each other, and the anti-counterfeit medium 10 is observed through the verification tool 50 in this state. The two-light reflection area 12 appears as a dark part, and the first light reflection area 11 appears brighter than the second light reflection area 12. That is, by using the verification tool 50, the bright portion and the dark portion are switched between the first light reflection region 11 and the second light reflection region 12.

  Next, an image that is seen when the verification tool 50 is turned over and superimposed on the forgery prevention medium 10 will be described.

FIG. 5A is a plan view schematically showing another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. In FIG. 5A, the verification tool 50 is turned over, and the transmission axis OP of the linearly polarizing film 51 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 are orthogonal to each other.

  When the verification tool 50 is turned upside down, the verification tool 50 functions as a linear polarizer having a transmission axis OP. In other words, when the verification tool 50 is irradiated with natural light from the λ / 4 phase difference layer 52 side, the verification tool 50 has a linearly polarized light having a polarization plane parallel to the transmission axis OP of the linear polarization film 51 toward the forgery prevention medium 10. Release.

  When the anti-counterfeit medium 10 and the verification tool 50 are arranged as shown in FIG. 5A, the first light reflection region 11 is placed on the anti-counterfeit medium 10 and the verification tool 50 as shown in FIGS. It looks brighter than when using the arrangement shown in. On the other hand, the second light reflection region 12 appears as a bright portion. Hereinafter, the reason why both the first light reflection region 11 and the second light reflection region 12 of the anti-counterfeit medium 10 appear bright will be described.

First, light reflection by the first light reflection region 11 will be described.
The linearly polarized light emitted from the verification tool 50 enters the λ / 8 phase difference layer 23 in the first light reflection region 11. This linearly polarized light has a plane of polarization orthogonal to the fast axis n _A23 of the λ / 8 retardation layer 23. Therefore, this linearly polarized light is transmitted through the λ / 8 phase difference layer 23 as linearly polarized light having a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51. The linearly polarized light emitted from the λ / 8 retardation layer 23 is specularly reflected by the light reflecting layer 22. The reflected linearly polarized light is incident on the λ / 8 retardation layer 23 again, and is transmitted through the λ / 8 retardation layer 23 with the linearly polarized light having a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51. The linearly polarized light is transmitted through the linearly polarizing film 51 without being absorbed ideally. The linearly polarized light transmitted through the linearly polarizing film 51 enters the λ / 4 retardation layer 52 and is converted into left circularly polarized light. Thus, the verification tool 50 ideally transmits all of the reflected light from the first light reflection region 11.

Next, light reflection by the second light reflection region 12 will be described.
The linearly polarized light emitted from the verification tool 50 enters the light reflecting layer 22 in the second light reflecting region 12. The light reflecting layer 22 specularly reflects this linearly polarized light. Since the reflected linearly polarized light has a plane of polarization parallel to the transmission axis OP of the linearly polarizing film 51, it is ideally transmitted without passing through the linearly polarizing film 51. The linearly polarized light transmitted through the linearly polarizing film 51 enters the λ / 4 retardation layer 52 and is converted into left circularly polarized light. Thus, the verification tool 50 ideally transmits all of the reflected light from the second light reflection region 12.

  For the above reasons, when the arrangement shown in FIG. 5A is adopted, both the first light reflection region 11 and the second light reflection region 12 appear bright. Unlike the second light reflecting region 12, the first light reflecting region 11 includes a colored layer 24. Therefore, when the arrangement shown in FIG. 5A is adopted, the second light reflection region 12 looks brighter than the first light reflection region 11.

FIG. 5B is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 5B illustrates a state in which only the verification tool 50 is rotated 45 ° clockwise as viewed from the observer side from the state illustrated in FIG. That is, in the arrangement of FIG. 5B, the optical axis OP of the linearly polarizing film 51 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 form an angle of 45 °. Further, the _fast axis n _{A52 of} the λ / 4 retardation layer 52 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 are parallel to each other.

  When the anti-counterfeit medium 10 and the verification tool 50 are arranged as shown in FIG. 5B, the first light reflection region 11 looks darker than the case where the arrangement of FIG. 5A is adopted. Further, the second light reflection region 12 appears to have the same brightness as when the arrangement of FIG. Here, the reason for causing such a difference in brightness will be described.

When the arrangement of FIG. 5B is adopted, the vibration direction of the electric field vector of linearly polarized light incident on the λ / 8 phase difference layer 23 of the first light reflection region 11 is λ // when viewed from the anti-counterfeit medium 10 side. This is a direction rotated clockwise by 45 ° from a direction parallel to the _fast axis n _A23 of the eight retardation layer 23. Therefore, this linearly polarized light is converted into right elliptically polarized light by the λ / 8 retardation layer 23. The locus of the end of the electric field vector of the right elliptically polarized light forms an ellipse whose major axis is inclined 45 ° clockwise with respect to the _fast axis n _A23 when viewed from the light reflecting layer 22 side.
The right elliptically polarized light is reflected by the light reflecting layer 22 and converted into left elliptically polarized light. The end locus of the electric field vector of the left elliptical polarization forms an ellipse whose major axis is inclined 45 ° counterclockwise with respect to the _fast axis n _A23 when viewed from the observer side.
This left elliptical polarized light is incident on the λ / 8 retardation layer 23. The λ / 8 retardation layer 23 converts the left elliptical polarized light into left circularly polarized light.
This left circularly polarized light enters the linearly polarizing film 51. The linearly polarizing film 51 transmits linearly polarized light having a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51 out of the left circularly polarized light incident thereon, and linearly polarized light having a polarization plane perpendicular to the transmission axis OP. Absorb. The linearly polarized light transmitted through the linearly polarizing film 51 is incident on the λ / 4 retardation layer 52. The λ / 4 retardation layer 52 converts this linearly polarized light into left circularly polarized light. That is, the verification tool 50 ideally transmits half of the reflected light from the first light reflection region 11 and absorbs the remaining half.

  On the other hand, the light reflection by the second light reflection region 12 is the same as when the arrangement of FIG.

  As described above, when the arrangement of FIG. 5B is adopted, the verification tool 50 absorbs about half of the reflected light from the first light reflecting region 11 and almost reflects the reflected light from the second light reflecting region 12. Make everything transparent. Therefore, when the arrangement shown in FIG. 5B is adopted, the first light reflection region 11 looks darker than the case where the arrangement shown in FIG. 5A is adopted, and the second light reflection region 12 is shown in FIG. It looks the same brightness as when the arrangement of a) is adopted.

FIG. 5C is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 5C illustrates a state in which only the verification tool 50 is rotated 90 ° clockwise as viewed from the observer side from the state illustrated in FIG. That is, in the arrangement of FIG. 5C, the transmission axis OP of the linearly polarizing film 51 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 are parallel.

  When the arrangement shown in FIG. 5C is adopted, the first light reflection region 11 looks the same brightness as when the arrangement shown in FIG. 5A is adopted. Further, when the arrangement shown in FIG. 5C is adopted, the second light reflection region 12 looks the same brightness as when the arrangement shown in FIG. 5A is adopted.

FIG. 5D is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 5D illustrates a state in which only the verification tool 50 is rotated 135 ° clockwise as viewed from the observer side from the state illustrated in FIG. That is, in the arrangement of FIG. 5D, the optical axis OP of the linearly polarizing film 51 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 form an angle of 45 °. Further, the _fast axis n _A52 of the λ / 4 retardation layer 52 of the verification tool 50 and the _fast axis n _{A23 of the} λ / 8 retardation layer 23 are orthogonal to each other.

  When the arrangement shown in FIG. 5D is adopted, the first light reflection region 11 looks the same brightness as when the arrangement shown in FIG. 5B is adopted. Further, when the arrangement shown in FIG. 5D is adopted, the second light reflection region 12 looks the same brightness as when the arrangement shown in FIG. 5B is adopted.

  As is clear from the above description, the anti-counterfeit medium 10 and the verification tool 50 are overlapped so that the linearly polarizing film 51 and the anti-counterfeit medium 10 face each other, and the anti-counterfeit medium 10 is passed through the verification tool 50 in this state. When observed, the brightness of the first light reflection region 11 changes according to the orientation of the transmission axis OP of the linearly polarizing film 51. On the other hand, the brightness of the second light reflection region 12 does not change even if the orientation of the transmission axis OP of the linearly polarizing film 51 is changed.

  5A and 5C, when the anti-counterfeit medium 10 and the verification tool 50 are arranged so that the first light reflection area 11 looks brightest, the colored layer 24 absorbs light. As a result, the first light reflection region 11 appears darker than the second light reflection region 12. When the anti-counterfeit medium 10 and the verification tool 50 are arranged so that the first light reflection region 11 looks darkest as shown in FIGS. 5B and 5D, the second light reflection region 12 is It looks brighter than the first light reflection region 11.

  The anti-counterfeit medium 10 is supported on an article to be confirmed to be authentic. Even in the case where it is not possible to discriminate between such an article with anti-counterfeit measures and a non-authentic product such as a counterfeit product with the naked eye, they can be discriminated by using a polarizer such as the verification tool 50. For example, the first light reflection region 11 and the second light reflection region 12 that each form a visible image that can be distinguished from each other and whose contrast ratio changes when observed through the verification tool 50 are genuine. When an article whose existence is unknown is not included, it can be determined that the article is non-genuine. Also, the first and second contrast ratios change when the articles whose authenticity is unknown or not form a visible image that can be distinguished from each other and are observed through the verification tool 50. Even if the light reflection areas are included, the light reflection areas change the contrast ratio according to the arrangement of the forgery prevention medium 10 and the verification tool 50 described with reference to FIGS. If it does not occur, it can be determined that the article is non-genuine.

  As described above, the contrast ratio between the first light reflection region 11 and the second light reflection region 12 is changed by observing through the verification tool 50. In the anti-counterfeit medium 10, the λ / 8 retardation layer 23 and the colored layer 24 that cause the change in the contrast ratio are overlaid. Therefore, there is a possibility that a person who does not know that the change in the contrast ratio described above is used for the authenticity determination and that the λ / 8 retardation layer 23 is formed in the forgery prevention medium 10. Is low. In addition, the change in the contrast ratio cannot be reproduced with a copy of the anti-counterfeit medium 10 and the anti-counterfeit medium 10 uses a liquid crystal layer as the λ / 8 retardation layer 23. , Its replication is difficult. Therefore, when this anti-counterfeit medium 10 is used, a higher anti-counterfeit effect can be achieved.

Next, another embodiment of the present invention will be described.
FIG. 6 is a plan view schematically showing a forgery prevention medium according to the second embodiment of the present invention. 7 is a cross-sectional view of the forgery prevention medium shown in FIG. 6 taken along line VII-VII.

  The forgery prevention medium 10 is the same as the forgery prevention medium 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, the forgery prevention medium 10 shown in FIGS. 6 and 7 includes a λ / 4 retardation layer 26 instead of the λ / 8 retardation layer 23 shown in FIG. The λ / 4 retardation layer 26 partially covers the front surface of the light reflecting layer 22. In the anti-counterfeit medium 10 shown in FIGS. 6 and 7, the colored layer 24 is interposed between the λ / 4 retardation layer 26 and the light reflecting layer 22.

  In FIG. 7, the member indicated by reference numeral 25 is the alignment film described in the first embodiment. The alignment film 25 is interposed between the colored layer 24 and the λ / 4 retardation layer 26. The alignment film 25 may cover the entire front surface of the light reflecting layer 22 as shown in FIG. 7, may exist only between the colored layer 24 and the λ / 4 retardation layer 26, or , May be omitted.

The λ / 4 retardation layer 26 is made of, for example, nematic liquid crystal. The λ / 4 retardation layer 26 includes a _fast axis along a direction indicated by an arrow n _A26 in FIG. 6 and a slow axis n _B26 (not shown in FIG. 6) perpendicular to the _fast axis n _A26 . Have. The λ / 4 retardation layer 26 has a wavelength of λ and a plane of polarization (oscillation plane of the electric field vector) is incident on linearly polarized light oblique to the fast axis n _{A26, so} that the plane of polarization is the slow axis n _B26. And a second linearly polarized light whose plane of polarization is parallel to the fast axis n _A26 and whose phase is advanced by λ / 4 from the first linearly polarized light.

Note that the retardation of the λ / 4 retardation layer 26 at the design wavelength λ may not be as designed due to variations in the thickness thereof. Even in such a case, if the deviation of the retardation from the design value is about 10% or less of the design value, the verification described later is not greatly affected.

  Hereinafter, a region corresponding to the portion of the light reflection layer 22 facing the λ / 4 retardation layer 26 of the anti-counterfeit medium 10 or the front surface thereof is referred to as a first light reflection region 11, and λ / A region corresponding to a portion not facing the four retardation layer 26 is referred to as a second light reflection region 12.

  Next, an image that is seen when natural light is irradiated onto the anti-counterfeit medium 10 and observed with the naked eye will be described.

  As described in the first embodiment, the second light reflection region 12 emits light having substantially the same intensity as the incident light. Furthermore, as in the first light reflecting region 11 of the first embodiment, the first light reflecting region 11 absorbs a part of the incident natural light by the colored layer 24, so that light having a lower intensity than the incident light is emitted. discharge. Therefore, when the forgery prevention medium 10 is irradiated with natural light and observed with the naked eye, the first light reflection region 11 looks darker than the second light reflection region 12. Further, the hue of the colored layer 24 can be seen in the first light reflection region 11. That is, each of the first light reflection region 11 and the second light reflection region 12 forms a visible image that can be distinguished from each other when viewed with the naked eye.

  Next, an image displayed when the anti-counterfeit medium 10 is observed using the verification tool 50 shown in FIG. 3 will be described.

  FIG. 8A is a plan view schematically showing an example of an image that can be observed when the anti-counterfeit medium shown in FIGS. 6 and 7 and the verification tool shown in FIG. 3 are overlapped.

In FIG. 8A, the anti-counterfeit medium 10 and the verification tool 50 are arranged such that the λ / 4 retardation layer 52 faces the first light reflection region 11 and the second light reflection region 12. Further, the light transmission axis OP of the linearly polarizing film 51 is orthogonal to the _fast axis n _A26 of the λ / 4 retardation layer 26. In this case, the second light reflection region 12 appears as a dark part as described with reference to FIG.

Here, light reflection by the first light reflection region 11 will be described.
The left circularly polarized light emitted from the verification tool 50 enters the λ / 4 retardation layer 26 shown in FIG. The λ / 4 retardation layer 26 converts the incident left circularly polarized light into linearly polarized light. The plane of polarization of this linearly polarized light is inclined 45 ° clockwise with respect to the _fast axis n _A26 of the λ / 4 retardation layer 26 when viewed from the light reflection layer 22 side. The light reflecting layer 22 specularly reflects this linearly polarized light. The λ / 4 retardation layer 26 converts this linearly polarized light into left circularly polarized light. This left circularly polarized light is incident on the λ / 4 retardation layer 52 of the verification tool 50. The λ / 4 retardation layer 52 converts the left circularly polarized light into linearly polarized light having a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51. This linearly polarized light is transmitted through the linearly polarizing film 51.

  For the above reasons, the first light reflection region 11 appears as a bright portion, and the second light reflection region 12 appears as a dark portion.

  FIGS. 8B to 8D are planes schematically showing other examples of images that can be observed when the anti-counterfeit medium 10 shown in FIGS. 6 and 7 and the verification tool 50 shown in FIG. 3 are overlapped. FIG. FIGS. 8B to 8D show states in which only the verification tool 50 is rotated 45 °, 90 ° and 135 ° clockwise as viewed from the observer side from the state shown in FIG. 8A. Is drawn.

  As shown in FIGS. 8A to 8D, the brightness of the first light reflection region 11 and the brightness of the second light reflection region 12 are determined by rotating the verification tool 50 around the normal line. Will not change. This is because the verification tool 50 is a circular polarizer, and the light emitted from the first light reflection region 11 and the second light reflection region 12 toward the verification tool 50 is circularly polarized light.

  As described above, when the anti-counterfeit medium 10 is observed without using the verification tool 50, the colored layer 24 causes a difference in brightness between the first light reflection region 11 and the second light reflection region 12. Specifically, when the anti-counterfeit medium 10 is observed without using the verification tool 50, the first light reflection region 11 looks darker than the second light reflection region 12. Then, the verification tool 50 and the anti-counterfeit medium 10 are arranged so that the λ / 4 phase difference layer 52 and the anti-counterfeit medium 10 face each other, and the anti-counterfeit medium 10 is observed through the verification tool 50 in this state. The one light reflection area looks brighter than the second light reflection area 12, and the second light reflection area 12 appears as a dark part. That is, by using the verification tool 50, the bright portion and the dark portion are switched between the first light reflection region 11 and the second light reflection region.

  Next, an image that is seen when the verification tool 50 is turned over and superimposed on the forgery prevention medium 10 will be described.

FIG. 9A is a plan view schematically showing another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 6 and 7 and the verification tool 50 shown in FIG. 3 are overlapped. In FIG. 9A, the verification tool 50 is turned upside down, and the transmission axis OP of the linearly polarizing film 51 and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 are orthogonal to each other.
In this case, the second light reflection region 12 appears with the same brightness as described with reference to FIG.

Next, light reflection by the first light reflection region 11 will be described.
The linearly polarized light incident on the λ / 4 retardation layer 26 of the first light reflection region 11 has a polarization plane orthogonal to the fast axis n _A26 of the λ / 4 retardation layer 26. Therefore, this linearly polarized light is transmitted through the λ / 4 retardation layer 26 as linearly polarized light having a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51. The linearly polarized light emitted from the λ / 4 retardation layer 26 is specularly reflected by the light reflecting layer 22. The reflected linearly polarized light is incident on the λ / 4 retardation layer 26 again, and for the same reason as described above, the λ / 4 retardation layer 26 remains linearly polarized light having a polarization plane parallel to the transmission axis OP of the polarizing film 51. Transparent. The linearly polarized light is transmitted through the linearly polarizing film 51 without being absorbed ideally. The linearly polarized light transmitted through the linearly polarizing film 51 enters the λ / 4 retardation layer 52 and is converted into left circularly polarized light. Thus, the verification tool 50 ideally transmits all of the reflected light from the first light reflection region 11.

  For the above reasons, when the arrangement shown in FIG. 9A is adopted, both the first light reflection region 11 and the second light reflection region 12 appear bright. Unlike the second light reflecting region 12, the first light reflecting region 11 includes a colored layer 24. Therefore, when the arrangement shown in FIG. 9A is adopted, the second light reflection region 12 looks brighter than the first light reflection region 11.

FIG. 9B is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 9B illustrates a state in which only the verification tool 50 is rotated 45 ° clockwise as viewed from the observer side from the state illustrated in FIG. That is, in the arrangement of FIG. 9B, the optical axis OP of the linearly polarizing film 51 and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 form an angle of 45 °. Further, the _fast axis n _A52 of the λ / 4 retardation layer ₅₂ and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 are parallel.

  When the anti-counterfeit medium 10 and the verification tool 50 are arranged as shown in FIG. 9B, the first light reflection region 11 looks darker than when the arrangement of FIG. 9A is adopted. Moreover, the 2nd light reflection area | region 12 looks the same brightness as the case where the arrangement | positioning of Fig.9 (a) is employ | adopted. Here, the reason for causing such a difference in brightness will be described.

When the arrangement of FIG. 9B is adopted, the vibration direction of the electric field vector of the linearly polarized light emitted from the verification tool 50 toward the forgery prevention medium 10 is λ / 4 retardation layer as viewed from the forgery prevention medium 10 side. 26, which is a direction rotated 45 ° clockwise from a direction parallel to the _fast axis n _A26 . Therefore, this linearly polarized light is converted into right circularly polarized light by the λ / 4 retardation layer 26.

This right circularly polarized light is reflected by the light reflecting layer 22 and converted into left circularly polarized light.
This left circularly polarized light is incident on the λ / 4 retardation layer 26. The λ / 4 retardation layer 26 converts the left circularly polarized light into linearly polarized light. Since this linearly polarized light has a polarization plane orthogonal to the transmission axis OP of the linearly polarizing film 51, it cannot be transmitted through the linearly polarizing film 51.

  On the other hand, the light reflection by the second light reflection region 12 is the same as the case where the arrangement of FIG.

  As described above, when the arrangement of FIG. 9B is adopted, the verification tool 50 absorbs almost all of the reflected light from the first light reflecting region 11 and almost reflects the reflected light from the second light reflecting region 12. Make everything transparent. Therefore, when the arrangement of FIG. 9B is adopted, the first light reflection area 11 looks darker than the arrangement of FIG. 9A, and the second light reflection area 12 is shown in FIG. It looks the same brightness as when the arrangement of a) is adopted.

FIG. 9C is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 6 and 7 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 9C illustrates a state in which only the verification tool 50 is rotated 90 ° clockwise as viewed from the observer side from the state illustrated in FIG. That is, in the arrangement of FIG. 9C, the transmission axis OP of the linearly polarizing film 51 and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 are parallel.

  When the arrangement shown in FIG. 9C is adopted, the first light reflection region 11 looks the same brightness as when the arrangement shown in FIG. 9A is adopted. Further, when the arrangement shown in FIG. 9C is adopted, the second light reflection region 12 looks the same brightness as when the arrangement shown in FIG. 9A is adopted.

FIG. 9D is a plan view schematically showing still another example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 6 and 7 and the verification tool 50 shown in FIG. 3 are overlapped. . FIG. 9D shows a state in which only the verification tool 50 is rotated 135 ° clockwise as viewed from the observer side from the state shown in FIG. 9C. That is, in the arrangement of FIG. 9D, the optical axis OP of the linearly polarizing film 51 and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 form an angle of 45 °. Further, the _fast axis n _A52 of the λ / 4 retardation layer 52 of the verification tool 50 and the _fast axis n _{A26 of the} λ / 4 retardation layer 26 are orthogonal to each other.

  When the arrangement shown in FIG. 9D is adopted, the first light reflection region 11 looks the same brightness as when the arrangement shown in FIG. 9B is adopted. Further, when the arrangement shown in FIG. 9D is adopted, the second light reflection region 12 looks the same brightness as when the arrangement shown in FIG. 9B is adopted.

  As is clear from the above description, the anti-counterfeit medium 10 and the verification tool 50 are overlapped so that the linearly polarizing film 51 and the anti-counterfeit medium 10 face each other, and the anti-counterfeit medium 10 is passed through the verification tool 50 in this state. When observed, the brightness of the first light reflection region 11 changes according to the orientation of the transmission axis OP of the linearly polarizing film 51. On the other hand, the brightness of the second light reflection region 12 does not change even if the orientation of the transmission axis OP of the linearly polarizing film 51 is changed.

  9A and 9C, when the anti-counterfeit medium 10 and the verification tool 50 are arranged so that the first light reflection region 11 looks brightest, the colored layer 24 absorbs light. As a result, the first light reflection region 11 appears darker than the second light reflection region 12. When the anti-counterfeit medium 10 and the verification tool 50 are arranged so that the first light reflection area 11 looks darkest as shown in FIGS. 9B and 9D, the first light reflection area 11 is In addition, it looks darker than the second light reflection region 12, and the difference in brightness between these regions is larger than that in the case where they are arranged as shown in FIGS. 9 (a) and 9 (c).

  The anti-counterfeit medium 10 is supported on an article to be confirmed to be authentic. Even if it is not possible to discriminate between such an article with anti-counterfeit measures and a non-authentic product such as a counterfeit product with the naked eye, they can be discriminated by the same method as described in the first embodiment. it can.

  Further, as in the first embodiment, the contrast ratio between the first light reflection region 11 and the second light reflection region 12 is changed by observation through the verification tool 50. In the anti-counterfeit medium 10, the λ / 4 retardation layer 26 and the colored layer 24 that cause the change in the contrast ratio are overlaid. Therefore, there is a possibility that a person who does not know that the change in the contrast ratio described above is used for authenticity determination and that the λ / 4 retardation layer 26 is formed in the forgery prevention medium 10. Is low. Moreover, the change in contrast ratio cannot be reproduced with a copy of the anti-counterfeit medium 10, and the anti-counterfeit medium 10 uses a liquid crystal layer as the λ / 4 retardation layer 26. , Its replication is difficult. Therefore, when this anti-counterfeit medium 10 is used, a higher anti-counterfeit effect can be achieved.

  Various modifications can be made to the forgery prevention medium 10 described above. For example, although the colored layer 24 covers the λ / 8 retardation layer 23 in FIG. 2, the colored layer 24 may be disposed between the λ / 8 retardation layer 23 and the reflective layer 22. Alternatively, the λ / 8 retardation layer 23 may be composed of the colored layer 24 and a pair of liquid crystal layers sandwiching it. In FIG. 7, the colored layer 24 is disposed between the λ / 4 retardation layer 26 and the light reflecting layer 22, but the colored layer 24 covers the front surface of the λ / 4 retardation layer 26. Also good. Alternatively, the λ / 4 retardation layer 26 may be composed of the colored layer 24 and a pair of liquid crystal layers sandwiching it.

  The colored layer 24 may be installed in the second light reflection region 12 instead of being installed in the first light reflection region 11. Alternatively, in addition to providing the colored layer 24 in the first light reflecting region 11, a colored layer having a hue different from that of the colored layer 24 may be provided in the second light reflecting region 12.

  When a plurality of colored layers 24 having different hues are arranged, these colored layers 24 may be formed on the same substrate or on different substrates. For example, a portion of the front surface of the reflective layer 22 corresponding to the second light reflecting region 12 is covered with the colored layer 24, and the λ / 8 phase difference layer 23 or the λ / 4 phase difference layer 26 has the hue of the color layer 24. Alternatively, a structure in which colored layers having different sizes are sandwiched between a pair of liquid crystal layers may be employed.

  In the forgery prevention medium 10 described above, the colored layer 26 is used to form a visible image, but the visible image may be formed by other methods. For example, instead of using the colored layer 24, a convex pattern and / or a concave pattern is formed on the front surface of the light reflecting layer 22 corresponding to the first light reflecting region 11 or the second light reflecting region 12 by using embossing or the like. A pattern may be formed. For example, when the convex pattern and / or the concave pattern impart light scattering properties to the light reflecting layer 22, each of the first light reflecting region 11 and the second light reflecting region 12 is a visible image that can be distinguished from each other. Form.

  The light reflecting layer 22 may include a diffractive structure. For example, the light reflection layer 22 may be a metal reflection layer having a relief structure.

  The light reflection layer 22 may include a reflection layer exhibiting an interference color. In this case, as the light reflection layer 22, a reflection layer exhibiting an interference color may be used alone, or a laminate of a reflection layer exhibiting an interference color and a metal reflection layer may be used. As the reflective layer exhibiting an interference color, for example, a layer formed using a cholesteric liquid crystal layer and a pearl pigment can be used.

  A protective layer may be provided on the front surface of the anti-counterfeit medium 10 for the purpose of protection from ultraviolet rays and physical impact.

  Instead of the verification tool 50 that functions as a left circular polarizer, a verification tool 50 that functions as a right circular polarizer may be used. Further, instead of stacking the verification tool 50 upside down and stacking on the forgery prevention medium 10, a separately prepared linear polarizing film may be stacked on the forgery prevention medium 10.

  The back surface of the anti-counterfeit medium 10, here, the surface on which the reflective layer 22 is not formed, of the two main surfaces of the base material 21 may be subjected to adhesion or adhesion processing. That is, an adhesive label that can be used as an anti-counterfeit label may be formed using the anti-counterfeit medium 10.

  The anti-counterfeit medium 10 can be applied to printed matter by various methods. For example, you may affix said adhesive label on printed matter. In this case, the base material 21 may be provided with cuts or perforations. In other words, a structure may be employed in which the base material 21 is broken from the notch or at the position of the perforation when the label is to be peeled off. Of course, the forgery prevention medium 10 can also be affixed to articles other than printed matter.

  A transfer foil containing the anti-counterfeit medium 10 may be formed and used to attach the anti-counterfeit medium 10 to the article.

  FIG. 10 is a cross-sectional view schematically showing an example of a transfer foil. A transfer foil 90 shown in FIG. 10 includes a base material 91. On the base material 91, a peeling layer 92, an anti-counterfeit medium 10, and an adhesive layer 93 are sequentially laminated.

  The front surface of the anti-counterfeit medium 10 faces the base material 91. The forgery prevention medium 10 may not include the base material 21 described with reference to FIG.

  When the anti-counterfeit medium 10 is applied to a printed matter, it may be cut into paper in a form called a thread (also called a strip, a filament, a thread, a safety strip, or the like).

  Hereinafter, materials that can be used for the anti-spoofing medium 10 will be described.

  Examples of the base material 21 include a synthetic resin film made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polystyrene, and the like. Resin film, synthetic paper, paper, glass plate, aluminum foil, and the like can be used alone or in combination as a composite. The thickness may be appropriately selected according to the purpose of use of the forgery prevention medium 10.

  The material used for the light reflecting layer 22 is not particularly limited as long as light reflectivity is obtained. For example, a metal or an alloy such as aluminum, gold, silver, or copper can be used. These materials can be used alone or laminated. The light reflecting layer 22 can be formed using a method such as vacuum deposition or sputtering, for example. The thickness of the light reflection layer 22 is, for example, in the range of 50 to 1000 mm.

  As a material for the alignment film 25, for example, a resin such as polyvinyl alcohol (PVA) or polyimide can be used. A resin solution in which these resins are appropriately dissolved is applied onto the light reflecting layer 22 by using a coating method such as wire bar, gravure, or micro gravure, and this coating film is dried. After drying, a rubbing process is performed by rubbing the alignment film surface with a rubbing cloth to obtain an alignment film 25. Materials such as cotton and velvet can be used for the rubbing cloth.

  The λ / 8 retardation layer 23 and the λ / 4 retardation layer 26 formed on the alignment film 25 are, for example, a smectic liquid crystal or a nematic liquid crystal. In this case, the λ / 8 retardation layer 23 and the λ / 4 retardation layer 26 are made of, for example, a thermotropic liquid crystal material or a polymer liquid crystal material.

  For example, when a retardation layer made of a thermotropic liquid crystal material is formed, a printing pattern is formed using ink containing the retardation layer. For this printing, for example, a method such as a gravure printing method can be used. Moreover, the previous ink may further contain, for example, a solvent and / or an additive. Next, heat and / or pressure are applied to the printed pattern as necessary. Thereby, the retardation layers 23 and 26 are obtained. In the case where a thermotropic liquid crystal material is used, the alignment film 25 may be omitted.

  In the case of forming a retardation layer made of a polymer liquid crystal material, for example, a printing pattern is formed on the alignment film 25 using an ink containing a polymerizable liquid crystal material. For this printing, for example, a method such as a gravure printing method can be used. Moreover, the previous ink may further contain, for example, a solvent and / or an additive. Next, the polymerizable liquid crystal material is polymerized by heating or energy beam irradiation. Thereby, the retardation layers 23 and 26 are obtained.

  As the polymerizable liquid crystal material, for example, an energy ray curable compound having a polymerizable group, a polycondensable group, or a group effective for polyaddition can be used. In this case, the polymerizable liquid crystal material preferably contains a monomer or oligomer having two or more energy ray-curable groups in the molecule. Those in which a functional group such as an acryl group is introduced into the terminal of the liquid crystal are more preferable because the physical strength is improved by crosslinking by irradiation with activated energy rays after the alignment of the liquid crystal is completed.

  The polymerizable liquid crystal material is typically used by adding a polymerization initiator or the like. For example, polymerization initiators such as α-hydroxyacetophenone-based, α-aminoacetophenone-based acetophenone-based, benzoin ether-based, benzyl ketal-based, α-dicarbonyl-based, α-acyloxime ester-based are added to the polymerizable liquid crystal material. May be.

  The retardation layers 24 and 26 may contain dyes such as direct dyes, disperse dyes and dichroic dyes, or pigments. In this case, the content of the colorant is adjusted so that the lightness L * in the ULCS (uniform lightness chromaticness scale) color system of the retardation layer is preferably 25 or more, more preferably 35 or more.

  Between the reflective layer 22 and the λ / 8 retardation layer 23 or λ / 4 retardation layer 26, a layer containing a powder obtained by pulverizing a dielectric multilayer film and a resin may be provided. The color of the dielectric multilayer film changes depending on the viewing angle. Therefore, a new optical characteristic can be given to the anti-counterfeit medium 10 by using a layer containing a powder obtained by pulverizing this. Furthermore, infrared absorbers and fluorescent pigments can be used as appropriate.

  A general material can be used as the adhesive for applying the forgery prevention medium 10 to a printed matter or the like. For example, an adhesive such as vinyl chloride-vinyl acetate copolymer, polyester polyamide, acrylic, butyl rubber, natural rubber, silicon, polyisobutyl, etc. can be used alone, or these adhesives can be used. Aggregating components such as alkyl methacrylates, vinyl esters, acrylonitrile, styrene, vinyl monomers, unsaturated carboxylic acids, hydroxy group-containing monomers, modifying components such as acrylonitrile, polymerization initiators, plasticizers, curing agents, curing What added additives, such as an accelerator and antioxidant, as needed can also be used. For the formation of the adhesive layer, for example, a printing method such as a gravure printing method, an offset printing method, a screen printing method, or a coating method such as a bar coating method, a gravure method, or a roll coating method can be used. Or you may use the separator which formed the adhesion layer in one main surface. That is, the adhesive layer may be attached to the anti-counterfeit medium 10 together with the separator, and then only the separator may be peeled off from the anti-counterfeit medium 10. You may affix the release paper and release film which performed the release process to the adhesion layer. Thereby, handling of the forgery prevention medium 10 which gave the adhesive process becomes easy.

Examples of the present invention will be described below.
(Example 1)
A single-sided aluminum vapor-deposited polyethylene terephthalate film having a thickness of 25 μm was prepared, and a liquid crystal layer ink was applied to a part of the aluminum vapor-deposited surface by a gravure printing method. This coating film was formed so that the cured film thickness was about 0.5 μm. The composition of the ink for the liquid crystal layer is shown below.

Liquid crystal (trade name: Paliocolor LC242 manufactured by BASF Corp.) 30% by weight
Polymerization initiator (trade name: Doluca 184, Ciba Kaigie Co., Ltd.) 1.5% by weight
Solvent (mixture of 50 parts by weight toluene and 50 parts by weight methyl ethyl ketone) 68.5% by weight
After this coating film was dried at 100 ° C. for 1 minute, it was irradiated with light of 500 mJ / cm ^{2 with} a high-pressure mercury lamp to cure the coating film. Thereby, a λ / 8 retardation layer was obtained.

  Next, in order to form a colored layer, gravure printing was performed on the λ / 8 retardation layer using a flat table calibrator so that the dried film thickness was 1 μm.

Polyester resin (trade name: Byron 200, manufactured by Toyobo Co., Ltd.) 20% by weight
Dye (trade name: Kayaset Flavine FG Nippon Kayaku Co., Ltd.) 1% by weight
Solvent (mixture of 50 parts by weight toluene and 50 parts by weight methyl ethyl ketone) 79% by weight
Next, this coating film was subjected to drying at 80 ° C. for 30 seconds. Thereby, a colored layer was obtained.

  The anti-counterfeit medium was manufactured as described above.

  When this anti-counterfeit medium was observed with the naked eye while irradiating white light, the hue of the colored layer was confirmed in the region corresponding to the colored layer. Further, the area around the colored layer appeared white.

  Next, a false image is obtained under the same conditions as described above except that the anti-counterfeit medium and the verification tool 50 described with reference to FIG. 3 are overlapped so that the retardation layer 52 faces the anti-counterfeit medium. The prevention medium was observed. As a result, in the anti-counterfeit medium, the region where the retardation layer is not formed appears as a dark portion, and the region where the λ / 8 retardation layer is formed appears brighter than the region where the retardation layer is not formed. It was.

  Next, the anti-counterfeit medium was observed under the same conditions as described above except that the anti-counterfeit medium and the verification tool 50 were overlapped so that the linearly polarizing film 51 faced the anti-counterfeit medium. The region where the λ / 8 retardation layer of the anti-counterfeit medium is formed when the orientation direction of the mesogen group included in the λ / 8 retardation layer of the anti-counterfeit medium is parallel or orthogonal to the transmission axis OP of the linear polarizing film 51 The reflected light from the can was observed. However, if the angle formed by the orientation direction of the mesogen group contained in the λ / 8 retardation layer of the anti-counterfeit medium and the transmission axis OP of the polarizing film 51 is 45 °, the λ / 8 retardation layer is formed in the anti-counterfeit medium. The applied area has changed to dark.

  Next, this anti-counterfeit medium was color copied and verified by the same method as described above using a verification tool. As a result, no change in brightness could be confirmed.

(Example 2)
A single-sided aluminum vapor-deposited polyethylene terephthalate film similar to that used in Example 1 was prepared, and a colored layer ink was applied to a part of the aluminum vapor-deposited surface by a screen printing method. The composition of this coloring ink is shown below.

Color-shifting pigment (trade name: CYCASTAR 9Z7P041 manufactured by SICPA)
This coating film was subjected to drying at 80 ° C. for 1 minute. Thereby, a colored layer having a color shift effect was obtained.

  Next, the ink for alignment films was apply | coated to the colored layer and the aluminum vapor deposition surface using the bar-coat method. This coating film was formed so as to have a dry film thickness of 3 μm. The composition of this alignment film ink is shown below.

Polyvinyl alcohol resin (trade name: Poval 117 Kuraray Co., Ltd.) 10% by weight
Solvent (mixture of 95 parts by weight of water and 5 parts by weight of isopropyl alcohol) 90% by weight
After the coating film was dried at 100 ° C. for 2 minutes, the coating film was rubbed. As the rubbing cloth, FINE PUFF YA-20-R manufactured by Yoshikawa Chemical Co., Ltd. was used. Thereby, an alignment film was obtained.

Next, gravure printing was performed on the portion of the alignment film corresponding to the colored layer using the same retardation layer ink as used in Example 1 so that the cured film thickness was 1 μm. After this coating film was dried at 100 ° C. for 1 minute, it was irradiated with light of 500 mJ / cm ^{2 with} a high-pressure mercury lamp to cure the coating film. Thereby, a λ / 4 retardation layer was obtained.

  Thereafter, a double-faced tape was attached to the resin surface of the single-sided aluminum vapor-deposited polyethylene terephthalate film to obtain a forgery prevention label. As the double-sided tape, product name No. manufactured by Nitto Denko Corporation. 531 was used.

  When this anti-counterfeit label was observed with the naked eye while irradiating white light, the color shift effect attributable to the colored layer was confirmed in the region corresponding to the colored layer. Further, the area around the colored layer appeared white.

  Next, a false image is obtained under the same conditions as described above except that the forgery prevention label and the verification tool 50 described with reference to FIG. 3 are overlapped so that the phase difference layer 52 faces the forgery prevention label. The prevention label was observed. As a result, in the anti-counterfeit label, the region where the retardation layer is not formed appears as a dark portion, and the region where the λ / 4 retardation layer is formed appears brighter than the region where the retardation layer is not formed. It was.

  Next, the anti-counterfeit label was observed under the same conditions as described above except that the anti-counterfeit label and the verification tool 50 were overlapped so that the linearly polarizing film 51 faced the anti-counterfeit label. Region in which λ / 4 retardation layer of anti-counterfeit label is formed when orientation direction of mesogen group included in λ / 4 retardation layer of anti-counterfeit label is parallel or orthogonal to transmission axis OP of linear polarizing film 51 The reflected light from the can was observed. However, if the angle formed by the orientation direction of the mesogen group contained in the λ / 4 retardation layer of the anti-counterfeit label and the transmission axis OP of the polarizing film 51 is 45 °, the λ / 4 retardation layer is formed in the anti-counterfeit label. The applied area has changed to dark.

  Next, this anti-counterfeit medium was color copied and verified by the same method as described above using a verification tool. As a result, no change in brightness could be confirmed.

The top view which shows roughly the forgery prevention medium of 1st Embodiment of this invention. Sectional drawing along the II-II line of the forgery prevention medium shown in FIG. The exploded view which shows an example of a verification tool roughly. (A)-(d) is a top view which shows roughly the example of the image which can be observed when the forgery prevention medium shown in FIG.1 and FIG.2 and the verification tool shown in FIG.3 are piled up. (A)-(d) is a top view which shows roughly the other example of the image which can be observed when the forgery prevention medium shown in FIG. 1 and FIG. 2 and the verification tool shown in FIG. 3 are piled up. The top view which shows roughly the forgery prevention medium of 2nd Embodiment of this invention. Sectional drawing along the VII-VII line of the forgery prevention medium shown in FIG. (A)-(d) is a top view which shows roughly the example of the image which can be observed when the forgery prevention medium shown in FIG.6 and FIG.7 and the verification tool shown in FIG.3 are piled up. (A)-(d) is a top view which shows roughly the other example of the image which can be observed when the forgery prevention medium shown in FIG.6 and FIG.7 and the verification tool shown in FIG.3 are piled up. The top view which shows an example of transfer foil roughly.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Anti-counterfeit medium, 11 ... 1st light reflection area | region, 12 ... 2nd light reflection area | region, 21 ... Base material, 22 ... Light reflection layer, 23 ... (lambda) / 8 phase difference layer, 24 ... Colored layer, 25 ... Orientation Membrane, 26 ... λ / 4 retardation layer, 50 ... verification tool, 51 ... linearly polarizing film, 52 ... λ / 4 retardation layer, 90 ... transfer foil, 91 ... substrate, 92 ... release layer, 93 ... adhesive layer .

Claims (9)

  An anti-counterfeit medium comprising a light reflection layer and a phase difference layer facing a part of the front surface of the light reflection layer and including a liquid crystal material, wherein the position of the light reflection layer of the anti-counterfeit medium is Each of the first light reflection region corresponding to the portion facing the phase difference layer and the second light reflection region corresponding to the portion of the light reflection layer not facing the phase difference layer can be distinguished from each other. An anti-counterfeit medium characterized by forming a visible image.   The forgery prevention medium according to claim 1, further comprising a light-transmitting colored layer positioned in front of the light reflection layer and facing the retardation layer.   The anti-counterfeit medium according to claim 1, wherein the retardation layer includes a light-transmitting colored layer and a pair of liquid crystal layers sandwiching the colored layer.   The forgery prevention medium according to any one of claims 1 to 3, wherein the light reflection includes a reflection layer exhibiting an interference color.   The forgery prevention medium according to claim 1, further comprising an alignment film interposed between the light reflection layer and the retardation layer.   An anti-counterfeit label comprising the anti-counterfeit medium according to any one of claims 1 to 5, and an adhesive layer supported on the back surface thereof.   A printed matter comprising the anti-counterfeit medium according to any one of claims 1 to 5 and paper into which the medium is inserted. An anti-counterfeit medium according to any one of claims 1 to 4,
A base material that releasably supports the front surface of the anti-counterfeit medium,
A transfer foil comprising an adhesive layer supported on the back surface of the anti-counterfeit medium. It is a method for discriminating between an authentic product and an unauthentic product for an article whose authenticity is unknown,
The genuine product is an article that supports the anti-counterfeit medium according to any one of claims 1 to 5,
Articles in which each of the first and second light reflection regions, each of which forms a visible image distinguishable from each other and whose contrast ratio changes by observing through a polarizer, is not genuine Is included, it is determined that the genuine or unknown article is a non-genuine product.

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