JP2015104851A - Fluorescent light latent image medium, verifier and verification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent light latent image medium 10 using a comparatively well-known forgery preventive verification method of ultraviolet light irradiation, the fluorescent light latent image medium 10 having a novel effect that no conventional one has and difficult to recognize, and also to provide a verifier 901 and a verification method.SOLUTION: A fluorescent light latent image medium 10 is obtained by laminating a fluorescent layer 102 and an angle control layer 101 sequentially on a substrate 103. The angle control layer 101 is a multilayer film that changes transmittance thereof by an irradiation angle of collimated excitation light. The excitation wavelength of the fluorescent layer 102 is within a range of a transmittance bottom wavelength 301 of the angle control layer 101.

Description

  The present invention relates to an anti-counterfeit medium used for various articles, and more particularly to a fluorescent latent image medium that emits fluorescence when irradiated with ultraviolet rays, a verifier, and a verification method.

  Anti-counterfeiting technology is used for various articles. For example, a bank note, a bond, a gift certificate, a check such as a check, or a securities. It is also used for various certificates such as credit cards, ID cards, official documents, and important documents.

  In recent years, it has been applied to various products and their packaging materials to ensure that the products are authentic. Needless to say, if these articles are inspected and proper anti-counterfeiting measures are taken, they are judged as genuine articles, and if no anti-counterfeiting measures are taken or improper measures are not accepted. It is determined as an authentic article.

  Such anti-counterfeiting means can generally be divided into an overt technique that uses human five senses without using a tool that requires complicated operations, and a covert technique that requires a verifier.

  The overt technique is a technique that anyone can recognize as anti-counterfeiting technology and enable authenticity determination. For example, a hologram or the like whose color or pattern changes depending on the viewing angle.

  The covert technique is a technique in which the presence itself cannot be recognized unless there is a special detector or skill. For example, a technique using a fluorescent pigment can be cited (Patent Document 1).

  In this method, fluorescence obtained by irradiating ultraviolet rays onto a medium on which a paint containing a fluorescent pigment is printed or a ribbon containing a fluorescent pigment is printed is confirmed as a visible light image.

  In particular, if the fluorescent pigment is colorless and the pattern cannot be visually recognized, the presence of the fluorescent pigment cannot be recognized until it is irradiated with ultraviolet light, so that it is possible to deal with a counterfeit product with only an appearance by a malicious person.

  Anti-counterfeiting means using fluorescent pigments are often used because the cost of forming anti-counterfeit media is low, and the UV irradiator that is a verifier is also relatively inexpensive and easily available. Verification means for confirming a latent image is one of relatively well-known techniques for preventing forgery. However, there is a problem that it is easy to see that anti-counterfeiting is performed, and there is a high risk that counterfeit products are made.

JP 2000-141863 A

  Therefore, in the present invention, there is provided a fluorescent latent image medium, a verifier and a verification method that have a new effect that is not conventionally seen and that is difficult to be seen while using a relatively well-known anti-counterfeiting confirmation method of irradiating ultraviolet light. The purpose is to provide.

  As a means for solving the above-mentioned problems, the invention according to claim 1 includes a base material, a fluorescent layer, and a multilayer film, and is transmitted according to an incident angle of collimated excitation light for causing the fluorescent layer to emit light. The fluorescent latent image medium is characterized in that angle control layers with varying rates are sequentially stacked, and an excitation wavelength of the fluorescent layer overlaps a transmittance bottom wavelength of the angle control layer.

  The invention according to claim 2 is the fluorescent latent image medium according to claim 1, wherein the fluorescent layer is composed of two or more fluorescent layers having different fluorescent wavelengths.

  According to a third aspect of the present invention, in the fluorescent latent image medium according to the first or second aspect, the fluorescent layer is provided as a pattern having a size smaller than or equal to visual recognition.

  The invention according to claim 4 is the fluorescent latent image medium according to claim 1 or 2, wherein the fluorescent layer is provided in a line pattern.

Further, the invention according to claim 5 is provided with two or more fluorescent layers having different fluorescent wavelengths and an angle control layer that changes an irradiation angle of the excitation light,
The fluorescent latent image medium according to any one of claims 1 to 4, wherein fluorescence of three or more colors is obtained by changing an irradiation angle of excitation light.

The invention described in claim 6 is a verifier for verifying a fluorescent latent image medium in which a fluorescent layer and an angle control layer are sequentially laminated on a substrate,
The verification device includes a plurality of light sources that irradiate collimated excitation light, and a half width of a spectrum of the light source is equal to or less than a half width of a transmission spectrum of the angle control layer.

The invention according to claim 7 is a verifier in which a plurality of light sources for irradiating collimated excitation light are installed.
An installation angle of the plurality of light sources is provided to be different from the fluorescent latent image medium,
The verification device is characterized in that the light source is blinked at a period equal to or less than a time when a human perceives an afterimage.

  The invention according to claim 8 is the verification device according to claim 6 or 7, wherein the collimated excitation light uses an LED as a light source.

  The invention according to claim 9 is the color of the fluorescent latent image medium by shaking the fluorescent latent image medium according to any one of claims 1 to 5 when irradiating collimated excitation light. This is a verification method characterized by observing changes.

  According to the present invention, it is relatively well known that a verifier having a specific light source can change a fluorescent color by irradiating light from different angles and irradiate an ultraviolet irradiator. By using the anti-counterfeiting confirmation method, it is possible to provide a fluorescent latent image medium, a verifier, and a verification method that have an unprecedented new effect and are difficult to see.

It is sectional drawing which shows an example of the fundamental layer structure of the fluorescence latent image medium which concerns on one Embodiment of this invention. It is a reflection spectrum which shows an example of the multilayer film which has an absorption peak at 365 nm. It is sectional drawing which showed an example of the layer structure of the type of fluorescent latent image medium of the type which emits fluorescence by the illumination from diagonally. These are the intensity spectrum of the irradiation light and the transmittance spectrum for each irradiation angle of the angle control layer in a type of fluorescent latent image medium that emits fluorescence when irradiated obliquely. It is a schematic diagram explaining the characteristic of collimated light. It is sectional drawing which showed an example of the layer structure of the type of fluorescent latent image medium of the type which emits fluorescence by irradiation from the front. It is the intensity spectrum of the irradiated light and the transmittance spectrum for each irradiation angle of the angle control layer in the type of fluorescent latent image medium that emits fluorescence when irradiated from the front. It is sectional drawing which shows an example of the layer structure of the fluorescence latent image medium which has a write-once latent image effect. It is the top view which showed an example of the fluorescence pattern of a color mixing effect type | mold fluorescence latent image medium. 2 is a cross-sectional view showing an example of a layer configuration of a full-color fluorescent latent image medium 30. FIG. It is sectional drawing which showed a mode that the additional recording latent image effect type | mold fluorescence latent image medium is verified with a verification device. It is the light emission timing chart of the verification device which showed the relationship of the intensity | strength with respect to time of front irradiation excitation light and diagonal irradiation excitation light in Duty ratio 50%. It is the timing chart of the verifier which showed the relationship of the irradiation intensity with respect to time of front irradiation excitation light and duty irradiation excitation light in Duty ratio 25%. It is a timing chart of the verifier which showed the relationship of irradiation intensity with respect to time of front irradiation excitation light and oblique irradiation excitation light when adjusting the irradiation intensity of a light source at a duty ratio of 25%. It is the schematic diagram which showed the verification method which switches an excitation light irradiation angle at high speed, without using a verification device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

<Layer Configuration of Fluorescent Latent Image Medium 10>
FIG. 1 shows an example of a basic layer configuration of a fluorescent latent image medium according to the present invention, and shows a minimum configuration composed of essential components. The fluorescent latent image medium shown in FIG. 10 includes an angle control layer 101 and a fluorescent layer 102 that are laminated in this order from the observation viewpoint 100.

  The angle control layer 101 is formed of a multilayer film, and is designed so that light of a specific band wavelength is reflected, and at the same time, the transmittance of the corresponding band wavelength is lowered.

<Multilayer film>
A multilayer film refers to a film formed by overlapping two or more materials having different refractive indexes. This is because the irradiated light is partially reflected at the surface of the film or at the interface between layers, while the light that is not reflected is transmitted. The light reflected by each layer overlaps and interferes with each other. At this time, a path difference is generated due to a difference in thickness and refractive index of the layer through which each reflected light has passed. Therefore, it is possible to create a film that reflects or transmits only light of a specific band wavelength by appropriately setting the refractive index and thickness of the material forming each layer, the order of overlapping, and the like.

  On the other hand, the wavelength band in which the multilayer film is reflected or transmitted varies depending on the angle of the irradiated light. Specifically, since the apparent pitch is narrower in the oblique direction than in the direction perpendicular to the surface, the spectral peak wavelength of reflected or transmitted light is usually on the short wavelength side. shift.

The thickness of each layer of the multilayer film is required to be a very thin film in order to use the path difference of the wavelength of light. As the material, it is sufficient if there is a difference in refractive index between the layers. For example, a low-refractive index material and a high-refractive index material are utilized by utilizing a dry coating utilizing a vacuum process such as a vacuum evaporation machine, sputtering, or ion plating. It is conceivable to form these alternately. As the material to be formed, for example, magnesium fluoride, titanium oxide, zinc oxide or the like is preferably used. This method has the advantage that the thin film thickness can be controlled finely and that a thin film with high film thickness uniformity can be formed. Further, a metal may be included as a forming material.

  Further, as a method for forming a multilayer film, a method in which a solution in which resins having different refractive indexes are dissolved is applied using a printing method is also conceivable. By making the solid content of the solution remarkably low, it is possible to form a thin film at the same level as dry coating even in the printing method. As a coating apparatus used for applying the solution, a comma coater, a micro gravure coater, a die coater, a spin coater, an offset, or the like can be used. This method has an advantage that it can be formed at a lower cost than the dry coating described above.

  As the anti-counterfeit medium, a light source having a light emission spectrum peak at 365 nm is often used as a general light source for verifying a fluorescent latent image medium.

  Regarding the material of each layer forming the multilayer film, its thickness and the number of layers, for example, when a total of three layers are formed in the order of 43 nm of titanium oxide, 120 nm of magnesium fluoride, and 43 nm of titanium oxide, an angle having an absorption spectrum peak at 365 nm A control layer can be created. FIG. 2 is a reflection spectrum of a multilayer film having an absorption peak at 365 nm. The reflection spectrum at this time is as shown in the three-layer multilayer film reflectance 198 in FIG.

  In addition, when a total of 5 layers are formed in the order of 120 nm of magnesium fluoride, 45 nm of titanium oxide, 120 nm of magnesium fluoride, 45 nm of titanium oxide, and 120 nm of magnesium fluoride, an angle control layer having an absorption spectrum peak at 365 nm is also created. Illustrate what can be done. The reflection spectrum at this time is as shown in FIG.

<Fluorescent layer>
The fluorescent layer 102 is excited by light of a specific wavelength and emits light of a different wavelength, and generally corresponds to printed matter or printed matter using ink or ribbon using a fluorescent pigment. It may be excited by ultraviolet light to emit visible light, excited by visible light to emit visible light, or excited by ultraviolet light or visible light to emit infrared light. Further, a material that emits visible light when excited by infrared light, a so-called up-conversion type material may be used.

  Specific examples of fluorescent pigments include rare earth elements such as europium and terbium, transition metals, calcium halophosphate used in fluorescent lamps, silicon nitride, aluminum nitride, europium oxide, and iridium complexes. Materials can be used. In addition, materials in which vanadate, molybdate, tungstate, phosphate, etc. are doped with rare earth elements such as neodymium and ytterbium as active agents, or materials in which part of neodymium or ytterbium is replaced with yttrium or lanthanum It is also possible to use a material that emits infrared light, represented by the above.

<Effect and principle of fluorescent latent image medium 10>
The basic effect of the fluorescent latent image medium 10 is that the angle control layer 101 specifies that the transmittance when the light of a specific wavelength is irradiated from the direction perpendicular to the surface is different from that when the light is irradiated from an oblique direction. The light of the wavelength makes the excitation energy of the fluorescent layer 102 different, and as a result, the fluorescence intensity changes.

  There are two specific effects in this configuration. In the first type, as shown in FIG. 3, light 202 irradiated from a direction perpendicular to the surface does not pass, but light 204 irradiated from an oblique direction to the surface passes.

  FIG. 3 is a cross-sectional view showing an example of the layer structure of a fluorescent latent image medium of a type that emits fluorescence by oblique light. For the sake of explanation, a gap is provided between the angle control layer 101 and the fluorescent layer 102.

  4A to 4C show the light intensity spectrum of the irradiated light and the transmittance spectrum fluorescent layer for each irradiation angle of the angle control layer 101 in a fluorescent latent image medium of a type that emits fluorescence by oblique light. Excitation spectrum and fluorescence spectrum.

  Here, the transmittance bottom wavelength 301 having the lowest transmission spectrum of the angle control layer 101 is the irradiation peak wavelength of the light 202 emitted from the light source 201 from the direction perpendicular to the surface and irradiated from the direction perpendicular to the surface. 302, the transmittance in the angle control layer 101 is lowered, and the fluorescent layer 102 is not excited, so it does not emit fluorescence or emits fluorescence very weakly, whereas the light source 203 from an oblique direction with respect to the surface emits light. The irradiation peak wavelength 302 of the emitted light 204 that is emitted obliquely with respect to the surface does not coincide with the oblique bottom wavelength 303 in which the transmittance bottom wavelength in the angle control layer 101 is shifted to the short wavelength side. The transmittance at 101 does not decrease, and the fluorescent layer 102 is excited to emit fluorescence.

  Here, the irradiation light spectrum half width 304 at the irradiation peak wavelength 302 of the light intensity spectrum of the irradiation light in FIG. 4 is the same as the transmission spectrum half width 305 at the transmittance bottom wavelength 301 of the transmission spectrum of the angle control layer 101, or It needs to be narrower. If the emission spectrum half-width 304 emits broader light than the transmission spectrum half-width 305, a wavelength in a band where the transmittance does not decrease is transmitted, contributing to excitation and emission of the fluorescent layer 102. Because.

  In order to satisfy this condition, either a light source with a narrow emission spectrum half width 304 or a selected angle control layer 101 with a wide transmission spectrum half width 305 may be selected.

  One method of selecting a light source having a narrow emission spectrum half width 304 is to use an LED. In particular, an ultraviolet LED that is often used to excite a fluorescent pigment has a very narrow and steep spectrum with an irradiation light spectrum half width 304 of about 15 to 50 nm.

  As another method, even if a light source having a broader spectrum than that of an LED is used, the spectral half-value width of light that is finally emitted is narrowed by using a low-pass filter and a high-pass filter or a band-pass filter. be able to. Alternatively, there is a method of using a laser light source that emits a single wavelength. In the case of using a laser light source, it is preferable to widen the beam diameter of light using a lens or the like as appropriate.

  Furthermore, the light source needs to have a feature that it emits collimated light in addition to the wavelength and the half width. Collimated light is parallel light. FIG. 5 is a schematic diagram for explaining the collimated light. As illustrated in FIG. 5A, collimated light refers to light emitted from a light source that travels straight through a space with high directivity. This is because in the present invention the effect is manifested by the irradiation angle of the irradiation light on the medium, so that the omnidirectional diffused light from the point light source as shown in FIG. This is because the medium is irradiated with light simultaneously from various angles.

  In order to radiate collimated light, a method of using a reflecting mirror or a lens designed by a combination of Galileo type, Kepler type, etc. can be considered. Even if it is not perfect collimated light, it has a certain degree of directivity, and if it is close to the medium, it cannot be sufficiently diffused until it is irradiated to the medium. Conversely, even a light source that emits diffused light in all directions, such as a bare light bulb, if the distance from the medium is sufficiently large, as a result, a part of the diffused light is irradiated to the medium as collimated light. Therefore, it is not necessarily based on the radiation method of the light source, but considering problems such as spatial propagation loss due to distance, the package also serves as a part of the lens, and a bullet-type LED having a certain degree of directivity is used. Is preferred. Collimated light refers to collimated light produced using such a method.

  In addition, although the light source has an effect of reducing the transmittance at a specific angle by the angle control layer 101, if the light is irradiated with an output higher than that, a sufficient amount of excitation light reaches the fluorescent layer. become. In particular, when the excitation wavelength is outside visible light, even if it is strong light, humans cannot perceive it. When using strong visible light excitation light, it is possible to visually recognize fluorescence emission at an unintended angle. There is. Therefore, it is also necessary to adjust the output of the light source so that it looks appropriate in a realistic observation space.

  In the second type, as shown in FIG. 6, light 404 irradiated from an oblique direction to the surface is not transmitted, but light 402 irradiated from a direction perpendicular to the surface is transmitted.

  FIG. 6 is a cross-sectional view showing an example of a layer structure of a fluorescent latent image medium of a type that emits fluorescence with light irradiated from the front. For the sake of explanation, a gap is provided between the angle control layer 101 and the fluorescent layer 102.

  FIGS. 7A and 7B show the emission intensity spectrum of the irradiation light and the transmittance spectrum for each irradiation angle of the angle control layer 101 in the type of fluorescent latent image medium that emits fluorescence with the irradiation light from the front. is there.

  Here, the transmittance bottom wavelength 501 having the lowest transmission spectrum of the angle control layer 101 is irradiated from the light source 401 from the direction perpendicular to the surface, and the irradiation light peak wavelength of the light 402 irradiated from the direction perpendicular to the surface. 502 does not match 502, the transmittance in the angle control layer 101 does not decrease, the fluorescent layer 102 is excited and emits fluorescence, whereas the surface irradiated from the light source 403 obliquely with respect to the surface Since the irradiation light peak wavelength 502 of the light 404 irradiated from the oblique direction coincides with the oblique bottom wavelength 503 in which the transmittance bottom wavelength in the angle control layer 101 is shifted to the short wavelength side, the transmittance in the angle control layer 101 decreases. Since the fluorescent layer 102 is not excited, it does not emit fluorescence or emits fluorescence very weakly. The point is that the angle control layer 101 designed to have the lowest transmittance when irradiated from an oblique direction with a specific angle is used.

  Here, the irradiation light spectrum half width 504 at the irradiation peak wavelength 502 of the light intensity spectrum of the irradiation light in FIG. 7 is the same as or narrower than the transmission spectrum half width 505 at the oblique bottom wavelength 503 of the transmission spectrum of the angle control layer 101. It is necessary to be the same as the first type, and even if an irradiation light source with a narrow emission spectrum half width 304 is selected to satisfy this condition, an angle control layer 101 with a wide transmission spectrum half width 305 is selected. The same is true either way.

When the excitation light is irradiated to the fluorescent latent image medium of the present invention, surface reflection at the outermost surface and reflection due to a difference in refractive index at the boundary between layers occur, and the amount of light reaching the fluorescent layer 102 is lost. The reflectance of these reflections varies depending on the irradiation angle, and in principle, the light irradiated from an angle rather than the front is
Since the reflectivity increases, the fluorescence latent image can be seen by irradiating the excitation light from an oblique angle, which is a factor that inhibits the fluorescence of the latent image, but the influence is slight except when the excitation light is too weak. Because it is a thing, the effect is not lost.

  The specific effect of the fluorescent latent image medium 10 provided in this way is that, when excitation light is irradiated from the front or obliquely, a fluorescent latent image cannot be seen in one irradiation direction, but in the other irradiation direction. This is the effect of the presence or absence of a fluorescent latent image depending on the irradiation direction, in which a fluorescent latent image is visible.

  As shown in FIG. 4, the excitation wavelength of the fluorescent layer 102 overlaps the transmittance bottom wavelength 301 of the angle control layer 101. At this time, the excitation peak wavelength 308 that is the peak wavelength among the excitation wavelengths does not necessarily match the transmittance bottom wavelength 301 of the angle control layer 101.

  The excitation wavelength spectrum half-value width 308 is preferably wider than the transmission spectrum half-value width 305 because excitation is easier. The excitation wavelength of the fluorescent layer 102 mentioned here refers to a wavelength that causes a light emission phenomenon when light of the corresponding wavelength is absorbed by the fluorescent layer 102. The peak wavelength is the excitation peak wavelength 308, and the half width is the excitation spectrum half. The value range is 306.

  The peak wavelength of light emitted by the light emission phenomenon is the fluorescence emission peak wavelength 309, and the half width is the fluorescence emission spectrum half width 307. This includes not only a normal excitation process excited by light having a wavelength shorter than the fluorescence emission wavelength but also an up-conversion type fluorescence emission phenomenon excited by light having a wavelength longer than the fluorescence emission wavelength. FIG. 4 illustrates this up-conversion type fluorescence emission phenomenon.

  When the excitation wavelength of the fluorescent layer 102 does not overlap the transmittance bottom wavelength 301 of the angle control layer 101, that is, when the excitation wavelength of the fluorescent layer 102 does not exist at the light peak wavelength 302 of the irradiation light, the angle of the irradiation light is In any state, the fluorescent light emission phenomenon does not occur in the fluorescent layer 102, and the effect of the present invention cannot be exhibited.

  On the other hand, when the excitation wavelength of the fluorescent layer 102 overlaps the transmittance bottom wavelength 301 of the angle control layer 101, that is, when the excitation wavelength of the fluorescent layer 102 exists at the light peak wavelength 302 of the irradiation light. It is possible to confirm the effect of the present invention that the fluorescence of the fluorescent layer 102 is generated except at a specific angle.

  Further, the transmittance bottom wavelength is not limited to the transmittance bottom wavelength 301 in FIG. 4, but can also be said to be similar to the oblique bottom wavelength 303, the transmittance bottom wavelength 501, and the oblique bottom wavelength 503 in FIG. 7. The transmission spectrum half-value width 305 can be said to be similar to the transmission spectrum half-value width 505 in FIG.

  Furthermore, when the fluorescence wavelength of the fluorescent layer 102 and the transmittance bottom wavelength of the angle control layer overlap, the change in the fluorescence intensity of the fluorescent layer 102 can be confirmed not only by the angle of the irradiation light but also by the observation angle of the observer. An effect is added.

<Layer structure and effect of write-once latent image effect type fluorescent latent image medium 20>
On the other hand, the fluorescence latent image medium shown in FIG. 8 is irradiated with excitation light from the front or obliquely, so that one fluorescent latent image can be seen in one irradiation direction, and in the other irradiation direction, additional recording is made. This shows the effect of changing the fluorescence latent image depending on the irradiation direction so that the fluorescence latent image can be seen.

  FIG. 8 is a sectional view showing an example of a layer structure of a fluorescent latent image medium having a write-once latent image effect in the present invention. The additional-recording latent image effect type fluorescent latent image medium 20 described above is formed by laminating a first fluorescent layer 601, an angle control layer 101, and a second fluorescent layer 602 in this order from the observation viewpoint 100.

  The fluorescent latent image medium 10 shown in FIG. The angle control layer 101 is the same in FIGS. 1 and 8, and the fluorescent layer 102 in FIG. 1 is the same as the second fluorescent layer 602 in FIG. Accordingly, the recordable latent image effect type fluorescent latent image medium 20 is obtained by laminating the first fluorescent layer 601 on the fluorescent latent image medium 10 of FIG.

  That is, since the first fluorescent layer 601 is on the outermost surface when viewed from the observation viewpoint 100, there is nothing to block the excitation light, and the first fluorescent layer 601 emits fluorescence uniformly regardless of the direction from which the excitation light is irradiated. This is the first fluorescent latent image in the recordable latent image effect type fluorescent latent image medium 20.

  On the other hand, the second fluorescent layer 602 is irradiated with excitation light from the front or obliquely by the angle control layer 101 and the second fluorescent layer 602, so that the second fluorescent latent image of the second fluorescent layer in one irradiation direction. However, since the second fluorescent latent image can be seen in the other irradiation direction, the effect of the presence or absence of the second fluorescent latent image depending on the irradiation direction, in other words, the additional recording effect of the fluorescent latent image can be obtained.

<Color mixing effect type fluorescent latent image medium>
FIG. 9 shows an example of the fluorescence pattern of the color mixing effect type fluorescent latent image medium that uses the recordable latent image effect type fluorescent latent image medium 20 and produces a special effect by the pattern of the first fluorescent layer 601 and the second fluorescent layer 602. FIG.

  The effect of the mixed-color-type fluorescent latent image medium is that, when excitation light is irradiated from the front or obliquely, a single-color fluorescent latent image pattern can be seen in one irradiation direction, and two-color fluorescence is further displayed in the other irradiation direction. By viewing the latent image pattern, it is possible to visually recognize the three-color fluorescent latent image pattern.

  A first fluorescent pattern R701 illustrated in FIG. 9 is a part of the pattern of the first fluorescent layer 601, and is a fluorescent layer that emits red light and has a letter “R” as a pattern. The first fluorescent pattern Y702 is also a part of the pattern of the first fluorescent layer 601, and is a fluorescent layer that fluoresces red, and the letter “Y” is a dot-like pattern.

  On the other hand, the second fluorescent pattern Y703 is a part of the pattern of the second fluorescent layer 602, and is a fluorescent layer that emits green fluorescence, and the letter “Y” is a dot-like pattern. Here, the positional relationship between the first fluorescent pattern Y702 and the second fluorescent pattern Y703 is such that the halftone dots are staggered and do not overlap.

  The second fluorescent pattern G704 is a part of the pattern of the second fluorescent layer 602. The second fluorescent pattern G704 is a fluorescent layer that emits green light and has a letter “G” as a pattern. The third fluorescent pattern Y705 shows both the first fluorescent pattern Y702 and the second fluorescent pattern Y703 that are arranged alternately.

  In the color mixture effect type fluorescent latent image medium shown in FIG. 9, the first fluorescent pattern R701 and the first fluorescent pattern Y702 emit red light in one irradiation direction when the excitation light is irradiated from either the front side or the oblique direction. You can see how they are doing. Since the first fluorescent pattern Y702 is a halftone dot than the first fluorescent pattern R701, the fluorescence emission intensity per unit area appears weaker.

On the other hand, since the second fluorescence pattern Y703 and the second fluorescence pattern G704 emit additional fluorescence in the other irradiation direction, particularly the third fluorescence pattern Y705 emits red fluorescence with the first fluorescence pattern Y702 that emits red fluorescence. Since the second fluorescent pattern Y702 appears to be mixed, it appears that yellow fluorescence is emitted by additive color mixing.

  Further, the third fluorescent pattern Y705 is more orange near red or closer green by causing the area occupancy of each of the first fluorescent pattern Y702 and second fluorescent pattern Y703 to be biased. It can be yellowish green or create slightly different colors and gradations.

  The first fluorescent pattern Y702, the second fluorescent pattern Y703, and the third fluorescent pattern Y705 need to be provided in a pattern having a size that is smaller than or equal to the visual recognition. The size below the visual recognition is a size in which the observer cannot recognize the pattern as a shape and recognizes the pattern as a uniform solid. Generally speaking, the size is 42 μ (600 dpi) to 85 μm ( 300 dpi).

  Therefore, the distance varies depending on the distance between the observer and the medium, the visual acuity of the observer, the observation instrument used, and the like. For example, in the case of a medium on the assumption that a general adult holds it in his / her hand, it is preferable that one pattern shape is provided with a size of several hundred micrometers or less. On the other hand, if it is a huge poster posted on the outer wall of the building, the distance to the observer will be several tens of meters, so even if one pattern shape is several tens of centimeters, the size may be smaller than the visual recognition. it can.

  As described above, the color mixing effect type fluorescent latent image medium has an effect that three or more different colors can be expressed only by using two types of fluorescent layers of red fluorescent emission and green fluorescent emission.

<Line latent image fluorescent latent image medium>
On the other hand, instead of two layers and two types of fluorescent layers, two layers and one type of fluorescent layer can be used to produce another effect by devising the pattern while fluorescing the same color. That is, the pattern of one layer is a line pattern, and the other pattern is a pattern that creates a latent image by overlapping with the line pattern.

  Specifically, the line pattern of the area to be a latent image looks like a solid line pattern at a glance by shifting the pitch compared to other areas, but it is a uniform regular line pattern. Is a known prior art that appears as a latent image by overlapping.

  This is not originally a fluorescent latent image, but is usually formed by a visually observable printed pattern, but the present invention, which can be confirmed while always aligning the positions of each other, is capable of irradiating light by forming a line pattern. With this angle, the effect of emitting light from the line latent image pattern as a fluorescent latent image is obtained.

<Full-color fluorescent latent image medium>
The medium using the single angle control layer 101 has been described so far, but when viewed from the observation viewpoint 100 in FIG. 10, the outermost surface fluorescent layer 801, the first angle control layer 802, the first fluorescent layer 803, By increasing the number of combinations of the angle control layer and the fluorescent layer as shown in the cross-sectional view showing an example of the layer structure of the full-color fluorescent latent image medium 30 provided in the order of the two-angle control layer 804 and the second fluorescent layer 805 , Increase the color and pattern of light emission, you will be able to express complex. In this case, the number of combinations of expressions is increased by individually setting the transmittance bottom wavelength of the angle control layer or by using a plurality of types of light sources having different irradiation light wavelengths.

<Verifier>
FIG. 11 is a cross-sectional view showing a state in which the write-once latent image effect type fluorescent latent image medium 20 is verified by the verifier 901. The verifier 901 has two or more light sources 902 and is installed at different angles. As shown by the arrows in the figure, the verifier 901 is installed to irradiate light from a different angle to a specific part of the medium when the distance to the medium is specific, and each light source is at an arbitrary timing. Lighting / extinguishing can be controlled.

  Note that the medium to be used is not necessarily the write-once latent image effect type fluorescent latent image medium 20, and may be the fluorescent latent image medium 10 or the full-color fluorescent latent image medium 30. In particular, since the recordable latent image effect type fluorescent latent image medium 20 exhibits a more characteristic effect, the following description will be given with reference to the recordable latent image effect type fluorescent latent image medium 20.

  The write-once latent image effect type fluorescent latent image medium 20 controls the light emission of the two fluorescent layers according to the irradiation angle of the excitation light. In particular, three colors can be obtained by devising a pattern using two types of fluorescent layers. Although the above colors can be expressed, the emission color can be dynamically changed by controlling the emission time of two types of excitation light having different irradiation angles.

  That is, the third fluorescent pattern Y705 in FIG. 9 emits a weak red color when irradiation with excitation light from the front is continued, and yellow when irradiation with excitation light from an oblique direction is continued. However, when the excitation light from the front and the excitation light from the diagonal blink at a time division ratio of 1: 1, with a period less than the time for humans to perceive afterimages, the orange color between red and yellow is changed. Looks like it's emitting light.

  FIGS. 12A and 12B show the state of time division. FIGS. 12A and 12B show the time of front irradiation light and oblique irradiation light at a duty ratio of 50% with respect to time. It is the light emission timing chart of the verification device which showed the relationship of light emission intensity.

  This is because light remaining as an afterimage in human eyes appears to be mixed in color by additive color mixing. The time for a human to perceive an afterimage, which is a blinking cycle, is the temporal resolution of the human eye, and is approximately 50 ms to 100 ms, although it varies depending on gender and age. Light blinking shorter than this is perceived as being continuously lit.

  The fluorescence wavelength of the third fluorescence pattern Y705 can be dynamically controlled by controlling the duty ratio between the emission time of the excitation light irradiated from the front and the emission time of the excitation light irradiated obliquely. In other words, if the occupancy of the emission time of excitation light irradiated from the front is large within a period of time that humans perceive an afterimage, the color close to red emits fluorescence, and the emission time of excitation light emitted obliquely If the occupation ratio is large, it emits fluorescence of a color close to yellow.

  FIGS. 13A and 13B are light emission timing charts of the verifier showing the relationship of the fluorescence intensity with respect to time between the front irradiation excitation light and the oblique irradiation excitation light at a duty ratio of 25%. Here, the oblique irradiation excitation light is shown. Since the fluorescence emission time of is longer, it emits fluorescence of a light orange color close to yellow.

  Further, when the duty ratio approaches 0% or 100% and the occupancy ratio of the fluorescence emission time is biased, the ratio of the fluorescence pattern is determined from the ratio of the area occupied by the first fluorescence pattern Y702 and the second fluorescence pattern Y703 in the third fluorescence pattern Y705. Since the fluorescence intensity becomes weak, it is possible to maintain the fluorescence intensity of a certain fluorescence pattern by adding control for adjusting the irradiation intensity of the light source according to the change in the duty ratio.

  As a method of blinking while controlling the irradiation time, a timing signal for blinking is created using a relaxation oscillation circuit, a timer IC, a pulse width modulation function of a microcomputer, etc., and via a drive circuit as necessary. There are a method of blinking the light source and a method of blocking the path of the light source that continues to be turned on at a specific timing using various shutters such as mechanical shutters and liquid crystal shutters, but considering the cost, failure rate, simplicity, etc. A method using generation of a timing signal is preferable. At this time, it is preferable to use a light source having a high response speed, which is the time from application of voltage to irradiation, and especially the response speed of the LED is very high, tens to hundreds of nanoseconds. Is preferred.

  In addition, as a method of adjusting the irradiation intensity of the light source, a method of adjusting the output by increasing / decreasing the voltage applied to the light source or a method of reducing the output by applying a high frequency signal and utilizing the afterimage time can be considered. Since it is necessary to perform adjustment corresponding to the duty ratio change of the irradiation time, it is preferable to use a method linked to the irradiation time control method. Therefore, it is preferable to follow the method of generating the timing signal by the electronic circuit as in the irradiation time control.

  FIGS. 14A and 14B show the relationship between the irradiation light intensity with respect to time of the front irradiation excitation light and the oblique irradiation excitation light when adjusting the light source emission intensity utilizing the afterimage time at a duty ratio of 25%. It is the irradiation light timing chart of the verification device. Basically, the irradiation time of vertical light and oblique light should be the same in total.

  The verifiers described so far have exemplified the case of controlling the irradiation light from two irradiation angles, but the number of light sources is not limited to two, and a large number of light sources are arranged to increase the resolution of the irradiation angle, and more complicated control is performed. It is also possible to do.

<Verification method>
Even if the verifier is not used, as shown in FIG. 15, the center of the write-behind latent image effect type fluorescent latent image medium 20 is held and shaken at high speed using a finger or a wrist. The incident angle of the excitation light can be switched at a high speed, and the fluorescence emission effect by additive color mixture can be obtained.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the spirit of the present invention.

  First, after depositing 43 nm of titanium oxide on one side of a polyethylene terephthalate film having a thickness of 25 μm serving as a base material, using a vacuum vapor deposition machine, magnesium fluoride is then vapor deposited to 120 nm. Subsequently, 43 nm of titanium oxide was again deposited. This corresponds to the angle control layer 101 in FIG.

  Subsequently, on the surface of the angle control layer 101, the following red fluorescent ink was used, and printing was performed with a screen printer in a pattern such as the first fluorescent pattern R701 and the first fluorescent pattern Y702 shown in FIG. Thereafter, it was dried at 80 ° C. for 2 minutes. This corresponds to the first fluorescent layer 601 in FIG.

<Red fluorescent ink>
Red fluorescent pigment (YS-A, manufactured by Nemoto Special Chemical) 2% by weight
Medium for screen printing (SS8 WAC varnish, manufactured by Toyo Ink Co., Ltd.) 8% by weight
It is.

  Similarly, the green fluorescent ink shown below is used on the surface of the polyethylene terephthalate film where the angle control layer 101 is not provided, and the second fluorescent pattern Y703 and the second fluorescent pattern G704 shown in FIG. 9 are used. After printing with a screen printer so that the first fluorescent pattern Y702 and the second fluorescent pattern Y703 are staggered with each other, the pattern of the first fluorescent layer is registered with the pattern of the first fluorescent layer, and then dried at 80 ° C. for 2 minutes. did. Since the red fluorescent ink and the green fluorescent ink are normally white when visually observed, registration is easy. By irradiating with ultraviolet rays as necessary, visibility is further improved and registration is further facilitated. This corresponds to the second fluorescent layer 602 in FIG.

<Green fluorescent ink>
Green fluorescent pigment: HG-A (manufactured by Nemoto Special Chemical Co., Ltd.) 2% by weight Screen printing medium: SS8 WAC varnish (manufactured by Toyo Ink Co., Ltd.) 8% by weight.
Next, on the surface of the second fluorescent layer 602, a pressure-sensitive adhesive having the following formulation was adjusted using a wire bar so that the film thickness after drying and curing was 3 μm, and the coating was applied at 80 ° C. for 1 minute. The adhesive layer was obtained by making it dry.

<Adhesive>
Acrylic adhesive: SK Dyne 1501B (manufactured by Soken Chemical Co., Ltd.) 50% by weight Solvent: methyl ethyl ketone 50% by weight.

  The following white-type high-quality paper was laminated and adhered so as to be in contact with the adhesive layer, thereby obtaining a write-once latent image effect type fluorescent latent image medium. Appearance is a white medium.

<Quality paper>
White fine paper: Shiraoi (manufactured by Nippon Paper Industries Co., Ltd.) The basis weight is 81.4 grams square meter.

  When the obtained recordable latent image effect type fluorescent latent image medium is irradiated from the direction perpendicular to the surface using an ultraviolet LED emitting light with an irradiation wavelength of 365 nm, a red “R” and a slightly light red “Y” are visually recognized. did it. Subsequently, when irradiated from an oblique direction, red “R”, yellow “Y”, and green “G” were visually recognized.

  The fluorescent latent image medium thus obtained is not only used for certificates such as credit cards, passports and official documents, important documents, and various stickers used for authenticity of goods. It can be used as wallpaper, posters, advertisements, etc. for amusement facilities because of the design and unique effects that can be freely designed, and it can also be used as a huge medium for building advertisements and contemporary art.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying constituent elements without departing from the spirit of the invention in the implementation stage.

DESCRIPTION OF SYMBOLS 10 ... Fluorescent latent image medium 20 ... Write-once latent image effect type fluorescent latent image medium 30 ... Full-color fluorescent latent image medium 100 ... Observation viewpoint 101 ... Angle control layer 102 ... Fluorescent layer 103 ... Substrate 198 ... Three-layer multilayer film reflectance 199 ... Five-layer multilayer film reflectance 201 ... Light source from a direction perpendicular to the surface 202 ... Irradiation from a direction perpendicular to the surface Light 203... Light source 204 obliquely with respect to the surface light... Light 301 obliquely illuminated with respect to the surface 301... Transmittance bottom wavelength 302. Bottom wavelength 304 ... Irradiation light spectrum half width 305 ... Transmission spectrum half width 306 ... Excitation spectrum half width 307 ... Fluorescence emission spectrum half width 308 ... Excitation wavelength spectrum half width 309 ... Fluorescence Luminous pea Wavelength 401... Light source 402 perpendicular to the surface 402. Light irradiating from the direction perpendicular to the surface 403... Light source 404 oblique to the surface 404. Light 501 irradiating from direction 501 transmittance bottom wavelength 502 irradiating light peak wavelength 503 ... oblique bottom wavelength 504 irradiating light spectrum half width 505 ... transmission spectrum half width 601 ... first One fluorescent layer 602 ... second fluorescent layer 701 ... first fluorescent pattern R
702: First fluorescent pattern Y
703 ... Second fluorescent pattern Y
704 ... Second fluorescent pattern G
705 ... Third fluorescence pattern Y
801: outermost fluorescent layer 802 ... first angle control layer 803 ... first fluorescent layer 804 ... second angle control layer 805 ... second fluorescent layer 901 ... verifier 902 ..Light source 998 ... fluorescent latent image 999 ... irradiation light source

Claims (9)

  An angle control layer comprising a base material, a fluorescent layer, and a multilayer film, the transmittance of which varies depending on the incident angle of collimated excitation light for causing the fluorescent layer to emit light, is sequentially laminated, and the excitation wavelength of the fluorescent layer is A fluorescent latent image medium characterized by overlapping the transmittance bottom wavelength of an angle control layer.   The fluorescent latent image medium according to claim 1, wherein the fluorescent layer is composed of two or more fluorescent layers having different fluorescent wavelengths.   The fluorescent latent image medium according to claim 1, wherein the fluorescent layer is provided as a pattern having a size smaller than or equal to visual recognition.   The fluorescent latent image medium according to claim 1, wherein the fluorescent layer is provided in a line pattern. Provide two or more fluorescent layers with different fluorescent wavelengths and an angle control layer that changes the irradiation angle of the excitation light,
The fluorescent latent image medium according to any one of claims 1 to 4, wherein fluorescence of three or more colors is obtained by changing an irradiation angle of light to be excited. A verification device for verifying a fluorescent latent image medium in which a fluorescent layer and an angle control layer are sequentially laminated on a substrate,
A verifier having a plurality of light sources for irradiating collimated excitation light, wherein a half width of a spectrum of the light source is equal to or less than a half width of a transmission spectrum of the angle control layer. A verifier having a plurality of light sources for irradiating collimated excitation light,
An installation angle of the plurality of light sources is set differently with respect to the fluorescent latent image medium,
A verifier which blinks the light source at a period equal to or shorter than a time when a human perceives an afterimage.   The verifier according to claim 6 or 7, wherein the collimated excitation light uses an LED as a light source.   6. A verification method characterized by observing a color change of a fluorescent latent image medium by shaking the fluorescent latent image medium according to claim 1 when irradiating collimated excitation light. .

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