JP6638319B2 - Transfer foil, anti-counterfeiting medium and method of manufacturing the same - Google Patents

Description

  The present invention relates to a transfer foil, a forgery prevention medium, and a method for producing the same, which provide a forgery prevention effect and excellent design properties.

  2. Description of the Related Art Conventionally, securities such as banknotes, gift certificates, passports, and authentication media have been attached to media that are difficult to forge as countermeasures against forgery. There, the authenticity is determined by visual judgment (so-called overt function) or judgment using a verifier (so-called covert function).

  A forgery prevention medium on which an arbitrary image is formed by OVD having an overt function can be visually recognized, and thus is easily forged. Therefore, in recent years, anti-counterfeit media has been proposed which combines anti-counterfeit technology using a high-molecular liquid crystal material that cannot be visually confirmed, reveals a latent image by shaking the filter, and can be authenticated. (Patent Document 1)

By the way, such a forgery prevention medium is used in the form of, for example, an adhesive label or a transfer foil.
These media can be thinner when used in the form of a transfer foil than when used in the form of an adhesive label. When the forgery prevention medium is made thinner, when the medium attached to the article is peeled off, the medium can be easily broken. In other words, reuse of the forgery prevention medium can be made impossible, which is more effective. Therefore, the medium is often in the form of a transfer foil, especially when used for the purpose of preventing forgery.

The transfer foil is generally transferred in the form of a stripe or a spot. In the case of an anti-counterfeit medium which is transferred at a spot and further combines an overt function and a covert function, if both the overt image and the covert image are fixed patterns, the anti-counterfeit effect and design are higher than those of the continuous pattern.
However, in order to align the overt image and the covert image, it is necessary to form an alignment mark in advance by printing or the like, and to use the mark to align the overt image and the covert image. However, when the alignment mark is formed by printing or the like, the number of steps increases by the number of steps. In addition, the positioning accuracy of the conventional positioning mark may not be sufficient.

Patent No. 4054071

  In view of the above problems, an object of the present invention is to provide a transfer foil, a forgery prevention medium, and a method of manufacturing the same, which can obtain a forgery prevention effect and a high design property with a small number of steps and high alignment accuracy.

According to a first aspect of the present invention, there is provided a transfer foil in which a retardation layer, an OVD functional layer, and an adhesive layer, which are arranged on at least two axes or more, are sequentially laminated on a base material. A first alignment mark is provided, a second alignment mark is provided on the OVD functional layer at a position overlapping the first alignment mark, and the second alignment mark has a spatial frequency of 2,000. The present invention provides a transfer foil characterized by being constituted by a diffraction grating having an aspect ratio of 0.5 to 2 at a ratio of from 0.5 / mm to 4000 lines / mm .

According to a second aspect of the present invention, there is provided the method for manufacturing a transfer foil according to claim 1 , wherein a displacement between the first alignment mark and the second alignment mark is detected via a polarizer. A method for producing a transfer foil is provided.

According to a third aspect of the present invention, there is provided an anti-counterfeit medium using the transfer foil according to claim 1 .

  According to the transfer foil of the present invention, when the first alignment mark provided on the retardation layer and the second alignment mark provided on the OVD functional layer are superimposed, the displacement thereof is sensed via the polarizer. , It is possible to perform positioning by feedback control, so that a desired transfer foil can be obtained with high positional accuracy. Further, since the alignment mark can be formed simultaneously with the step of forming the phase difference layer and the OVD functional layer, the number of steps can be reduced.

FIG. 1 is a conceptual cross-sectional view illustrating an example of an embodiment of a transfer foil according to the present invention. (A) In an example of an embodiment of the present invention, a conceptual diagram showing a pattern of a phase difference layer. (B) A conceptual diagram showing a pattern of an OVD functional layer in an example of an embodiment of the present invention. FIG. 4 is a conceptual diagram showing a part of an image in which patterns of a retardation layer and an OVD functional layer overlap in an example of an embodiment of the present invention. FIG. 3 is a conceptual diagram showing a case where a first alignment mark and a second alignment mark are superimposed and observed from a substrate side in an example of an embodiment of the present invention. FIG. 5 is a conceptual diagram showing a case where the alignment marks overlap in the example of FIG. 4 when observed through a polarizer. FIG. 9 is a conceptual diagram showing a case where a first alignment mark and a second alignment mark are superimposed and observed from the base material side in another example of the embodiment of the present invention. FIG. 7 is a conceptual diagram showing a case where the alignment marks overlap in the example of FIG. 6 when observed through a polarizer. FIG. 9 is a conceptual diagram showing a case where a first alignment mark and a second alignment mark are superimposed and observed from the base material side in another example of the embodiment of the present invention. FIG. 9 is a conceptual diagram showing a case where the alignment marks overlap in the example of FIG. 8 when observed through a polarizer.

  Hereinafter, embodiments of a transfer foil, a forgery prevention medium, and a method of manufacturing the same according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to only these embodiments.

  FIG. 1 is a conceptual sectional view showing an example of an embodiment of a transfer foil according to the present invention. The transfer foil 10 has a configuration in which a retardation layer 12, an OVD functional layer 13, and an adhesive layer 14 are sequentially laminated on a base material 11.

FIG. 2 shows the retardation layer 12 and the OVD functional layer 13 including the alignment mark. FIG. 2A shows the retardation layer 12 including the retarders 15 and 16 arranged in a pattern. The retardation layer 12 has a first alignment mark 17. The phase difference layer 12 is a layer in which light passing through this layer causes a predetermined phase difference as compared with light passing through the air. The phase difference elements 15 and 16 are both transparent but different from each other. A phase difference can be generated. By utilizing this, for example, the optical axis can be set to 0 ° and 45 °.
FIG. 2B is a plan view showing the OVD functional layer 13 of FIG. 1 and includes an OVD 18 and a second alignment mark 19 arranged in a pattern. The OVD pattern 18 can have, for example, a diffraction grating structure, and the second alignment mark 19 can have polarization characteristics by providing a plurality of grooves at a pitch equal to or less than the wavelength of visible light.
2A and 2B are provided so that the pattern of the retardation layer and the pattern of the OVD functional layer, and the first alignment mark and the second alignment mark are overlapped at the same position. It shows the situation.

FIG. 3 shows an observation image of the anti-counterfeit medium after spot transfer of the transfer foil shown in FIG. In the figure, a circular cedar tree-shaped pattern is OVD 18, a star pattern is a retarder 16, and the background is a retarder 15. Observation is made by visual observation, after transfer, from the retarder side.
FIG. 3A is an image diagram when the retarders 15 and 16 and the OVD 18 are combined.
FIG. 3B is an image diagram when the forgery prevention medium is visually observed. Since the retarders 15 and 16 cannot be visually observed, only the OVD 18 is observed.
FIG. 3C is an image diagram when the polarizer (not shown) is observed with the polarizer held up. The pattern of the retarder 16 is visualized by passing through the polarizer.
Further, FIG. 3D is an image diagram observed when the polarizer is rotated, and the pattern formed by the retarder 16 is negative-positive inverted by the polarization effect. Further, since the pattern of the retarder layer 12 and the pattern of the OVD functional layer 13 are aligned at the time of manufacturing the transfer foil 10, stars on the tree which are not visually observed as shown in FIG. It became possible to observe by holding the polarizer.

FIGS. 4, 6, and 8 show an example of a state of the superposition of the first alignment mark 17 and the second alignment mark 19 in the superposition of the phase difference layer 12 and the OVD functional layer 13, and FIG. (A) is when the positions match, (b) is when the position is shifted in the printing flow direction, (c) is when the position is shifted in the width direction of the transfer foil, (d) is when the position is shifted in the printing direction. FIG. 3 shows an image diagram when the position is shifted in both width directions.
FIGS. 5, 7, and 9 show images observed when detection is performed via the polarizer 20 with respect to the respective positional shifts in FIGS. 4, 6, and 8. As an example, the case where the position of the pattern of the second alignment mark 19 is changed has been illustrated. However, the present invention is not limited to this. For example, even if the pattern of the first alignment mark 17 is changed, the first and second alignment marks may be changed. Both may be changed.

Next, materials of each layer constituting the transfer foil 10 will be described.
(Base material)
As the substrate 11, a non-stretched film produced by extrusion or casting, a stretched film produced by stretching, or the like can be used. The stretched film includes a uniaxially stretched film and a biaxially stretched film depending on how it is stretched, and both can be used.

  Materials for these unstretched films and stretched films include cellophane, polycarbonate (PC), polyethylene (PE), polypropylene (PP), polyolefin (PO), ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVA), and polychlorinated Examples include vinyl, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), nylon, acrylic resin, and triacetyl cellulose (TAC) film.

(Retardation layer)
For the retardation layer 12 included in the transfer foil of the present invention, a birefringent material can be used. Birefringence refers to the fact that the refractive index of a substance differs depending on the direction of the optical axis, and therefore, the speed of light passing through the substance differs. Therefore, a phase difference is generated in the light after passing through the substance by an amount corresponding to the difference in the passing speed. As such a material, for example, a liquid crystal material can be used.

  Further, the retardation layer 12 is arranged on two axes or more. As a method of arranging the optical axis of the retardation layer in two or more axes, a multiaxially oriented liquid crystal can be obtained by performing an orientation treatment on the orientation film in a multiaxial direction and applying a liquid crystal thereon. . For the alignment treatment of the alignment film for aligning the liquid crystal material, for example, a rubbing alignment method or a photo alignment method can be used. The retardation value can be determined by the birefringence and the film thickness of the liquid crystal.

  The photo-alignment method is a method of irradiating the alignment film with light having anisotropy such as polarization or irradiating non-polarized light obliquely to induce the rearrangement of molecules in the alignment film and the anisotropic chemical reaction. The method utilizes the fact that anisotropy is imparted to the alignment film, whereby the liquid crystal molecules are aligned. Examples of the mechanism of photo-alignment include photo-anisotropy of azobenzene derivatives, photo-dimerization and cross-linking of derivatives such as cinnamate, coumarin, chalcone and benzophenone, and photo-decomposition of polyimide and the like.

  Specifically, pattern exposure is performed using polarized light in an appropriate wavelength band or unpolarized light obliquely. For example, when biaxially orienting, pattern exposure is performed by covering a portion where the orientation direction is to be changed with a photomask, and then exposure is performed by changing the direction to process an unexposed portion covered by the photomask. good. Alternatively, after the entire surface is once subjected to pattern exposure, it may be partially covered with a photomask, changed in direction, and exposed again.

  The rubbing alignment method is a method of rubbing an alignment film created by applying a polymer solution onto a substrate with a cloth, and utilizes the property that the properties of the alignment film surface change in the rubbing direction and the liquid crystal molecules are aligned in this direction. It was done. Polyimide, PVA, or the like is used for the alignment film.

  To orient the optical axis in two directions, cover the portion where the orientation direction is desired to be changed with a mask and rub with a cloth, remove the mask, then cover the rubbed portion with the mask and change the direction again. After changing and rubbing with a cloth, the mask is removed. Alternatively, the mask may be removed after the entire surface is rubbed with a cloth, partially covered with a mask, changed in direction, and rubbed with a cloth.

  As a method for forming these alignment films, a known method such as a gravure coating method or a microgravure coating method can be used.

  A retardation layer can be obtained by providing a liquid crystal material on the alignment film that has been subjected to the alignment treatment. Examples of such a liquid crystal material include a photocurable liquid crystal monomer having acrylates at both ends of a mesogen group, a polymer liquid crystal cured by EB or UV, a polymer liquid crystal having a mesogen group in the polymer main chain, and the molecular main chain itself. Can be used. After application, these liquid crystals can be subjected to a heat treatment at a temperature slightly lower than the NI point at which a phase transition occurs to promote the orientation.

(Phase difference value)
As a retardation value, for example, when a polarizer is used for a verifier (not shown) and a reflection layer is incorporated in a transfer foil, the retardation value is preferably λλ. When a transparent substrate is used, a polarizer is arranged on the back surface of the medium to be transferred, and a polarizer is used as a verifier, 1 / 2λ is effective.
Further, for example, when a circular polarizer is disposed on the back surface of the medium to be transferred and a circular polarizer is used as a verifier, ８λ is effective, but in each case, λλ, 1λ is effective. The phase difference value may be any of / 2λ and よ い λ.

(OVD functional layer)
As shown in FIG. 1, the OVD functional layer 13 is provided by applying an emboss 13b to an OVD forming layer 13a and forming an OVD 18. An OVD (Optical Variable Device) is an image display that utilizes light interference, and is a display that produces a color shift in which the color changes depending on the representation of a stereoscopic image and the viewing angle. Media.
In particular, as an OVD having a structure such as a hologram or a diffraction grating, there are a relief type in which light interference fringes are recorded as a fine uneven pattern on a plane, and a volume type in which interference fringes are recorded in a volume direction.

  Although the method is different from that of the OVD functional layer 13 in the present invention, a material which changes color (color shift) depending on a viewing angle, such as a multilayer film in which thin films of ceramics and metal materials having different optical characteristics are laminated is also an example. is there. These OVDs give unique impressions such as stereoscopic images and color shifts, and require advanced manufacturing techniques, and thus can be said to be effective means for preventing forgery.

  As a method for producing a relief hologram or a relief diffraction grating, mass production can be performed using a relief press plate having a fine uneven pattern forming a hologram or a diffraction grating, respectively. That is, the OVD forming layer 13a can be heated and pressed with a press plate to replicate a fine concavo-convex pattern.

As a material of the OVD forming layer 13a, for example, a thermoplastic resin such as an acrylic resin, an epoxy resin, a cellulose resin, a vinyl resin, or an acrylic polyol or a polyester polyol having a reactive hydroxyl group, and a polyisocyanate as a crosslinking agent Thermosetting resins such as added and crosslinked urethane resins, melamine resins, epoxy resins, and phenolic resins can be used alone or in combination. In addition, any material other than the above may be appropriately used as long as it is a material capable of forming the concavo-convex pattern. Further, the transferability may be further improved by adding a filler or the like to the extent that the effect of OVD is not impaired.
The OVD forming layer 13a is provided in a pattern by a known printing method.

In order to increase the diffraction efficiency of the OVD 18 in which the OVD forming layer 13a is formed by embossing, a material constituting the relief surface is a high refractive index material such as TiO ₂ , Si ₂ O ₃ , SiO, Fe ₂ O ₃ , and ZnS. Further, metal materials such as Al, Sn, Cr, Ni, Cu, and Au having a higher reflection effect may be used, and these materials may be used alone or in a laminate. These materials are formed by a known thin film forming technique such as a vacuum evaporation method and sputtering. These materials can also be used as a reflective layer.

  As the adhesive layer 14, for example, a heat-sensitive adhesive that exhibits tackiness when heated can be used. The adhesive layer 14 is provided by applying a resin satisfying its performance to a base material using a gravure coater, a microgravure coater, a roll coater, or the like. As a material that can be used, an acrylic resin, a vinyl chloride-vinyl acetate copolymer, epoxy, or a thermoplastic resin such as EVA can be used.

(First alignment mark)
The first alignment mark 17 is provided in the retardation layer 12 at the same time as the retarders 15 and 16 as shown in FIG. As an example, FIG. 2 shows a case where the retarders 15 and 16 are arranged in a pattern on two axes. In this case, the first alignment mark 17 may be arranged in a different direction from the retarders 15 and 16, but may be arranged in the same direction as the retarder 16 to reduce the number of steps. Although FIG. 2 shows an example in which the first alignment mark 17 is uniaxially oriented, the inside of the first alignment mark 17 may be further divided and multiaxially oriented.

  The first alignment mark 17 is used for alignment when forming the OVD 18 shown in FIG. At this time, the first alignment mark 17 may be read by a sensor with the polarizer interposed therebetween. Then, since the alignment axes of the first alignment mark 17 and the periphery thereof (corresponding to the phase difference unit 15) are different, image contrast can be obtained. The OVD 18 may be formed by embossing while reading it with a sensor and aligning the position.

(Second alignment mark)
The second alignment mark 19 is provided at the same time as the OVD 18 is formed by embossing the OVD forming layer 13a. This is for detecting a positional deviation from the degree of overlap with the first alignment mark 17 and performing alignment between the pattern of the retardation layer 12 and the OVD 18. The second alignment mark 19 may be provided in the same structure as that of the OVD. For example, the second alignment mark 19 can be provided by a relief type diffraction grating having a plurality of grooves arranged, and the spatial frequency is from 2,000 to 4,000. / mm, and the value of the height / width ratio (aspect ratio) of the groove of the diffraction grating is preferably in the range of 0.5 to 2.
It is further preferable that the spatial frequency of the diffraction grating is in the range of 2500 lines / mm to 3500 lines / mm as a more optimal range.

  A diffraction grating having such a structure has a very special visual effect. This structure is different from a commonly used diffraction grating in that diffracted light returns in a direction close to the direction of incident light, and the diffracted light has polarization characteristics. Further, the reflected light also has polarization characteristics. For example, if the arrangement of the diffraction grating is inclined by 90 °, the polarization characteristic of reflection changes by 90 °. However, the present invention is not limited to this, and a fine concavo-convex pattern or color shift can also be used as in OVD.

  When the above-mentioned diffraction grating is used as the second alignment mark 19, the polarization characteristics change depending on the optical axes of the phase difference elements 15 and 16 of the first alignment mark 17 by combining with the first alignment mark 17. When observed through a polarizer, a contrast can be generated in the second alignment mark 19. Thereby, when manufacturing the transfer foil of the present invention, it is possible to read with higher accuracy a positional shift when the first alignment mark 17 and the second alignment mark 19 are superimposed.

(Alignment)
When the OVD 18 is formed by embossing, the first alignment mark 17 is read by a laser sensor or the like with the polarizer interposed therebetween, and embossing is performed while performing alignment.

(Detection of displacement)
After the OVD 18 is formed by embossing, the positional deviation is confirmed by detecting the degree of overlap between the first alignment mark 17 and the second alignment mark 19 with a sensor. Hereinafter, the displacement will be described with reference to FIGS. 4 and 5 as an example.

After the OVD 18 is formed, the degree of overlap between the first alignment mark 17 and the second alignment mark 19 is read by an image sensor via a polarizer and feedback-controlled. FIG. 4A shows a case where the first alignment mark 17 and the second alignment mark 19 match, that is, it means that the image of the phase difference layer 12 and the image of the OVD 18 match. ing.
In this case, the image read by the sensor via the polarizer is as shown in FIG.
Since the positions of the second alignment mark 19 and the first alignment mark 17 match, a dark gray square is detected. In order to achieve this state where there is no displacement, feedback control is performed when a displacement has occurred.

  FIG. 4B shows a case where the image of the phase difference layer 12 and the image of the OVD 18 are displaced in the flow direction. In this case, the image read through the polarizer is as shown in FIG. 5B, and the portion of the second alignment mark 19 overlapping the first alignment mark 17 is observed in dark gray, The portion of the second alignment mark 19 that does not overlap with the one alignment mark 17 is observed in light gray, and in the example of FIG. 4B, a dark gray square on the lower side and a light gray square on the upper side are detected. Become.

  FIG. 4 (c) shows an example of displacement in the width direction, and FIG. 4 (d) shows an example of displacement in the flow direction and the width direction. The portions where the marks 19 overlap are observed in dark gray, and the portions where the first alignment mark 17 and the second alignment mark 19 do not overlap are observed in light gray. As described above, a partially gray square is detected. The amount of displacement is sensed from these images, and based on the information, feedback control is performed so that the alignment state is as shown in FIG.

  Also, as shown in FIGS. 6 and 7, the second alignment mark 19 may be arranged in a multi-axis arrangement instead of a simple uni-axis arrangement. In this case, as in the above example, the feedback control is performed so that the alignment state is as shown in FIG.

  Further, if the second alignment mark 19 is formed in a diamond shape or the like so as to enter the inside of the first alignment mark 17 as shown in FIGS. Since the image is clearly different from the case where there is a shift in the direction and the width direction, it is easy to detect the positional shift.

(Transcription)
As the transfer method, the transfer foil is transferred to the transfer target by a spot transfer by an up-down method or a stripe transfer method by a roll transfer method. The base material of the transfer object is not particularly limited as long as it is a sheet-like material such as a resin film, a metal plate, and a glass plate in addition to paper.

  The anti-counterfeit medium to which the transfer foil according to the present invention has been transferred is as shown in FIG. 3A, and the retarders 15 and 16 cannot be visually observed. Therefore, as shown in FIG. , OVD18 only are observed. Here, when the polarizer is moved, an image in which the patterns of the retarders 15 and 16 are visualized as shown in FIGS. 3C and 3D is observed.

  Hereinafter, embodiments of the present invention will be described.

Using a mirror 11F60 as the base material 11, an alignment film solution in which an alignment film resin was dissolved was applied by a microgravure method to form a film. Thereafter, the substrate was covered with a mask provided with a star-shaped retarder 16 and a first alignment mark 17 which were continuously arranged, and rubbed with a rubbing cloth in the flow direction of the raw material.
Further, the portion rubbed in the flow direction was covered with a mask, and rubbed with a rubbing cloth at an angle of 45 ° with respect to the flow direction to prepare an alignment film.

  Thereafter, UV curable liquid crystal UCL-008 manufactured by DIC Co., Ltd. was applied by microgravure to a film thickness having a phase difference value of λ / 4, and UV curing was performed in an oxygen atmosphere. As a result, the flow direction and the retarders 15 and 16 inclined by 45 ° in the flow direction were obtained.

  Next, an OVD forming layer composed of an acrylic polyol and an isocyanate was provided on the entire surface by direct gravure printing. Thereafter, the first alignment mark 17 was sandwiched between polarizers, and while reading with a line sensor, heating embossing was applied to the OVD 18 and the plate provided with the second alignment mark 19 to form an OVD functional layer. Further, thereafter, the misalignment between the first alignment mark 17 and the second alignment mark 19 is read by an image sensor via a polarizer, and feedback control of the alignment is performed, and the star pattern of the phase difference layer 12 and the cedar of the OVD 18 are controlled. The wooden pattern was aligned.

Thereafter, an aluminum thin film was formed using a vacuum deposition method so as to have a thickness of 500 °.
Further, an acrylic resin was provided as a bonding layer 14 on the entire surface by microgravure to obtain a transfer foil of the present invention.

  The obtained transfer foil was transferred to a transfer object using a hot stamp. When the transferred forgery prevention medium was visually observed, only the OVD18 cedar tree pattern was observed. Next, when the observation was performed with the polarizer held up, a star pattern appeared exactly at the apex of the cedar tree, and the star pattern was inverted when the polarizer was rotated.

  From the above experimental results, it has been confirmed that a desired transfer foil can be obtained with high positional accuracy, and that the number of steps can be reduced because the alignment marks can be formed simultaneously with the steps of forming the retardation layer and the OVD functional layer.

REFERENCE SIGNS LIST 10 transfer foil 11 base material 12 retardation layer 13 OVD functional layer 13 a OVD formation layer 13 b emboss 14 adhesive layer 15, 16 retarder 17 first alignment mark 18 OVD
19 Second alignment mark 20 Polarizer

Claims (3)

A transfer foil in which a retardation layer, an OVD functional layer, and an adhesive layer, which are arranged at least biaxially, are sequentially laminated on a base material,
A first alignment mark is provided on the retardation layer,
The OVD functional layer is provided with a second alignment mark at a position overlapping the first alignment mark,
The second alignment mark has a spatial frequency of 2000 lines / mm to 4000 lines / mm,
A transfer foil comprising a diffraction grating having an aspect ratio of 0.5 to 2.   The method for manufacturing a transfer foil according to claim 1, wherein a displacement between the first alignment mark and the second alignment mark is detected via a polarizer. . A forgery prevention medium using the transfer foil according to claim 1 .