JP2009262509A - Thermal transfer medium and diffractive structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal transfer medium and a diffractive structure which have a unique and appreciable optical change when seen from the front and oblique direction, not existing in the conventional diffractive structure, thereby, have an improved forgery prevention effect and permit simple authenticity judgement. <P>SOLUTION: The thermal transfer medium has a thermally melted transfer diffractive structure layer on a substrate, wherein the thermally melted transfer diffractive structure layer comprises a strippable protection layer, a fine diffraction structure formation layer, a reflective layer and an adhesive layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal transfer medium having a diffractive structure and a diffractive structure using the same. In particular, the present invention relates to a thermal transfer medium having a forgery preventing function for making forgery or alteration difficult and a diffraction structure using the same.

Conventionally, as a method for forming a character pattern or an image pattern on a transfer substrate made of plastic or paper on demand, a thermal transfer ribbon formed with a sublimation transfer layer made of ink containing a sublimation dye is used. A sublimation transfer method is generally used in which a thermal head is pressed from the opposite surface and the thermal head generates heat in accordance with the density of an image to be formed.
(See Patent Document 1)

Recently, this sublimation transfer method is also used for applications that require on-demand printing and image formation with ID cards and various certificates. In this case, as a means for preventing counterfeiting, the sublimation transfer method is used. After forming letters and images, the relief type diffractive structure was partially transferred by post-processing, or printing with ink having an OVD effect having a high anti-counterfeit effect was performed.
(See Patent Document 2)

However, as the generation of counterfeit products increases, diffraction structures are becoming increasingly finer as a counterfeit prevention measure. As a result, it is not easy to determine authenticity, and even if the OVD effect is incomplete. There are an increasing number of counterfeit products that are simply not forged.
In addition, it is often difficult to actually perform printing with ink having an OVD effect by post-processing due to the problem of manufacturing cost.

Therefore, a diffractive structure transfer layer with light transmission is provided in the reflective layer in parallel with or separately from the same thermal transfer ribbon as the sublimation transfer layer, and the thermal transfer is performed on the entire surface of the substrate to be transferred by the same thermal head as the sublimation transfer. Therefore, since the diffractive structure affixed to the outermost surface has optical transparency, the image of the diffracted light generated by the diffractive structure and the images and characters located in the lower layer of the diffractive structure can be viewed at the same time. Since it is a method that makes it extremely difficult, it has been adopted as a forgery prevention measure for passports and ID cards.
(See Patent Document 3)

  However, even if the anti-counterfeit medium has a light-transmitting diffractive structure attached to the entire surface as a forgery prevention measure as described above, the forgery of the diffractive structure cannot be easily determined at a glance. Recently, there is a problem that its anti-counterfeiting effect is fading.

JP 63-22893 Japanese Patent No. 32633760 JP-A-6-67592

Therefore, the present invention solves the problems of the related art, and a thermal transfer medium and a diffractive structure having a unique and remarkable optical change when viewed from the front and oblique directions, which are not found in a conventional diffractive structure. The issue is to provide.
Furthermore, it is an object to make it possible to easily determine the authenticity while improving the effect of preventing forgery.

  The invention of claim 1 is a thermal transfer medium having a heat-melt transfer diffractive structure layer on a support, and the heat-melt transfer diffractive structure layer has a peeling protective layer, a fine diffractive structure forming layer, a reflective layer, and an adhesive layer. This is a thermal transfer medium.

  A second aspect of the present invention is the thermal transfer medium according to the first aspect, wherein a print layer is provided between the reflective layer and the adhesive layer of the thermal melt transfer diffraction structure layer.

  According to a third aspect of the present invention, the fine diffractive structure forming layer has a concavo-convex shape, the height of the convex portion of the concavo-convex shape is 5 nm to 1000 nm, and the height of the convex portion / the width of the convex portion (aspect ratio) is 1. 3. The thermal transfer medium according to claim 1, wherein the pitch of the concavo-convex shape is 5 nm to 1000 nm.

  The invention of claim 4 has a heat-melt transfer ink layer on a support, and the heat-melt transfer diffraction structure layer and the heat-melt transfer ink layer are formed in a pattern. 4. The thermal transfer medium according to any one of 3 above.

  5. The thermal transfer medium according to claim 1, wherein the heat-melt transfer ink layer is one or more colors selected from four colors of yellow, magenta, cyan, and black. It is.

  A sixth aspect of the present invention is a diffractive structure obtained by transferring the thermal transfer medium according to any one of the first to fourth aspects to a substrate to be transferred.

According to the present invention, since the fine diffractive structure forming layer is provided, when viewed from the front, incident light is absorbed by the fine diffractive structure forming layer having a fine uneven shape to generate reflected light and diffracted light. There is almost no anti-counterfeit image forming layer in which diffracted light from the fine diffractive structure forming layer is observed when viewed from a certain angle.
By forming finer unevenness than conventional relief type diffractive structures, forgery and alteration are extremely difficult, but the optical change of the transfer layer after thermal transfer is unique, making it easy to determine the authenticity can do.
In addition, by providing a conventional hot melt transfer ink layer of yellow, magenta, cyan, black, etc. and a hot melt transfer diffraction structure layer in a pattern, color can be changed without changing the conventional character / image forming apparatus having a thermal head. An anti-counterfeit effect can be given to the image.

  In addition, when the image is transferred to the transfer substrate using the thermal transfer medium of the present invention, the color to be observed from gray or black is diffracted by diffracted light. Therefore, it is possible to manufacture an anti-counterfeit medium that can easily determine authenticity.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode of the thermal transfer medium and anti-counterfeit structure of the present invention will be described in detail below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of the present invention, in which a hot melt transfer diffraction structure layer 2 is laminated on a support 1. This heat-melt transfer diffractive structure layer 2 is peeled off from the support 1 at the time of thermal transfer and at least a part of the heat-transfer transfer diffractive structure layer 2 remains after the peeling, and the peeling protective layer 11 that protects the fine diffractive structure forming layer 12 and diffracted by incident light It has a fine diffractive structure forming layer 12 for generating light, a reflective layer 13 for reflecting diffracted light, and an adhesive layer 14 for adhering to a substrate to be transferred. It is. The fine diffractive structure forming layer 12 has an uneven surface 21 that is a fine diffractive structure.

  FIG. 2 is a cross-sectional view showing an example of the present invention, in order to make it appear darker when observed at an angle at which no diffracted light is generated between the reflective layer 13 and the adhesive layer 14 in the configuration of FIG. Thus, it is possible to further improve the contrast of light and dark when diffracted light can be observed and when it cannot be observed.

On the other hand, FIG. 3 is an enlarged view showing the structure of the fine diffractive structure forming layer 12, the reflective layer 13, and the concavo-convex processed surface 21 in FIGS. 1 and 2, where H is the height of the convex portion and W is the convex portion. , D represents the film thickness of the reflective layer 21, and the aspect ratio of the diffractive structure shown in FIG. 3 is H / W. 4 is a cross-sectional view taken along the line AA in FIG. 3, and L represents the pitch of the concavo-convex shape.
The height H of the convex portion is preferably in the range of 5 nm to 1000 nm. The aspect ratio H / W is preferably 1 or more. Furthermore, it is preferable that the concavo-convex pitch L is in the range of 5 nm to 1000 nm.
For example, when it is in this range, it looks black to gray because it has the effect of confining light when viewed from the front, but diffracted light is visible when tilted by a certain angle or more.

  In addition, in FIG. 3, the convex-and-concave convex shape is a rectangular cross section, and the shape is shown as a vertically long shape, but the shape of the fine diffraction structure used in the present invention is not particularly limited to this. Alternatively, the uneven shape may be a circular shape such as a sin curve, or the concave portion may be square and only the convex portion may be circular. Also, the shape shown in FIG. 4 may be various shapes such as a vertically and horizontally cross shape as well as a vertically long shape.

Next, FIGS. 5 and 6 show an example of the present invention, in which a heat-melt transfer ink layer and a heat-melt transfer diffraction structure layer are formed on a support 1 in a pattern. Here, the hot melt transfer ink layer and the hot melt transfer diffraction structure layer can be formed side by side.
As the melt transfer ink layer, for example, one or more colors selected from four colors (Y, M, C, K) can be used. For example, as shown in FIGS. 5 and 6, four colors (Y, M, C, K) or three colors (Y, M, C) and the heat-melt transfer diffraction structure layers 2 and 3 are appropriately arranged along the longitudinal direction. It is the structure arranged in order and repeatedly provided.
The color used for the melt transfer ink layer is not limited to the above.
Here, when the three colors (Y, M, C) and the heat-melt transfer diffractive structure layer are used, the heat-melt transfer diffractive structure layer can be used instead of the black ink layer. In this case, the heat-melt transfer diffractive structure layer looks black when viewed from the front, but the diffracted light is visible when viewed from a nearly horizontal state.

  Next, FIG. 7 is a plan view showing an example of the present invention, which is a forgery prevention body produced by thermally transferring the thermal transfer medium of FIG. 5 or FIG. 6 onto a substrate to be transferred. In FIG. 7, after the face photograph is printed in full color by sublimation transfer, the hot melt transfer diffraction structure layer 2 or 3 is transferred to the characters of the “ID card” and the black portion of the hair in the face image, and the characters and An image is formed. 8 is a cross-sectional view taken along the line BB in FIG.

FIG. 9 is a schematic diagram showing the effect of the present invention, and shows how the light observed changes rapidly due to the change in the viewpoint position of the observer.
If the anti-counterfeit body to which the heat-melt transfer diffractive structure layer is transferred is within a range of 45 to 90 ° with respect to the horizontal direction (diffracted light invisible angle), the heat-melt transfer diffractive structure layer is gray or black. Looks like.
If the viewpoint is further moved in the horizontal direction as it is, and it reaches a certain range of 1 to 45 °, the heat melting transfer diffraction structure layer that was gray or black until then generates diffracted light, and the observer can see the diffracted light. it can.
For this reason, when the thermal transfer medium of the present invention is used for gray or black portions of characters or images, it looks like ordinary characters or images within the diffracted light invisible angle, but the observation viewpoint is moved in the horizontal direction to make the diffracted light invisible angle When the value exceeds diffracted light, the diffracted light can be observed, and since the change in luminance and color at this time is large, anyone can easily determine authenticity.

  Hereinafter, the material and forming method of each layer constituting the thermal transfer medium of the present invention will be described.

(Support)
First, a resin film can be used as the support 1. As the resin film, a polyethylene terephthalate resin film, a polyethylene naphthalate resin film, a polyimide resin film, a polyethylene resin film, a polypropylene resin film, a heat-resistant vinyl chloride film, or the like can be used. Among these resins, since the heat resistance is high and the thickness is stable, a polyethylene terephthalate resin film can be preferably used.
The thermal transfer medium of the present invention can be used as a thermal transfer ribbon by using a long resin film as a support.

  Moreover, the film which processed antistatic treatment, mat processing, embossing, printing of a character and a pattern, laser marking etc. can also be used for these resin films.

(Peeling protection layer)
As the peeling protection layer 11, a resin added with a lubricant can be used. As the resin, a thermoplastic resin, a thermosetting resin, a moisture curable resin, an ultraviolet curable resin, an electron beam curable resin, or the like can be used. For example, acrylic resin, polyester resin, and polyamideimide resin. As the lubricant, wax such as polyethylene powder or carnauba wax can be used, and it can be added up to 20 parts by weight. These are formed as the peeling protective layer 11 on the support 1 by a known coating method such as a gravure printing method or a micro gravure method.

(Fine diffractive structure forming layer)
The fine diffractive structure forming layer 12 is a diffractive structure made of a relief type diffraction grating, but its optical characteristics are different from those of a conventional diffractive structure, and it does not only generate diffracted light within a certain angle range. A diffractive structure having a characteristic that hardly reflects light is used.

  As a specific example of the relief type diffraction grating, for example, the aspect ratio of a conventional relief type diffraction grating is about 1.0, but the aspect ratio is 1.5 without changing the grating pitch and the width of the convex portion. By increasing the value as described above, it is possible to obtain a characteristic of less reflected light even at an observation angle where diffracted light is not generated. However, in order to obtain a clearer optical change characteristic, the height of the convex and concave parts of the concave and convex pattern The difference is 50 nm to 500 nm, the ratio of the height of the unevenness divided by the width (aspect ratio) is 2 or more, and the pitch of the uneven pattern is 50 nm to 500 nm, each being as uniform as possible. Is desirable. More preferably, the pitch of the concavo-convex pattern is in the range of 50 nm to 400 nm.

  Then, by forming a metal film on the surface of the relief-type master plate having the uneven pattern formed in this way by electroplating, the uneven pattern of the relief-type master plate is duplicated and used as a press plate. Then, the press plate is thermocompression bonded to the resin layer laminated on the support 1, and the fine concavo-convex pattern is transferred to the surface of the resin layer, whereby the fine diffractive structure forming layer 12 can be obtained.

  As the resin applied to the fine diffraction structure forming layer 12 by the relief type diffraction grating, a thermoplastic resin, a thermosetting resin, an ultraviolet ray, an electron beam curable resin, or the like can be used. For example, acrylic resins include acrylic resins, epoxy resins, cellulose resins, vinyl resins, and the like. In addition, urethane resins, melamine resins, phenol resins, and the like obtained by adding polyisocyanate as a crosslinking agent to an acrylic polyol or polyester polyol having a reactive hydroxyl group and crosslinking can be used. Further, as the ultraviolet ray or electron beam curable resin, epoxy (meth) acryl, urethane (meth) acrylate, or the like can be used. In addition, because of the special shape that is fine and has a large aspect ratio, in order to prevent the fine diffractive structure forming layer 12 from collapsing due to sticking to the master plate, silicone oil or resin, or fluorine resin is used as a peeling aid. Etc. are preferably used.

(Reflective layer)
The reflective layer 21 is provided in direct contact with the fine diffractive structure forming layer 12. In this case, the light reflected by the reflective layer 21 becomes diffracted light.

  As the reflective layer 21, a metal thin film can be preferably used in terms of high reflection luminance. Examples of the metal include Al, Sn, Cr, Ni, Cu, Au, and brass. And this metal thin film can be formed using a vacuum film-forming method. As the vacuum film-forming method, a vacuum deposition method, a sputtering method, or the like can be applied, and the thickness may be controlled to about 10 to 1200 nm. When the thickness is 10 nm or less, reflection of light becomes difficult, and diffracted light is hardly generated.

  Moreover, it is good also as a thin film layer by printing the ink which has metallic luster, such as an ink containing metal powder. In this case, the powder preferably has a particle diameter of 500 nm or less. The thickness of the thin film layer is preferably 0.1 to 10 μm, and a known printing method such as a gravure printing method, a flexographic printing method, or a screen printing method can be used as a printing method.

(Adhesive layer)
Any adhesive layer 14 may be used as long as it adheres to the transfer substrate by heat, and a known heat-sensitive adhesive material can be used.

(Other layers)
As the other layers, an anchor layer can be provided in order to make the adhesion between the layers stronger, and in this case, a well-known adhesion improver or adhesive can be used.
Further, in order to further increase the contrast due to the presence or absence of diffracted light, a printing layer 15 can be added between the fine diffractive structure forming layer 12 and the adhesive layer 14, preferably black or a reflection density of 0.8 after coating. It is good to have the above density.
Any ink can use a known printing ink.

(Diffraction structure layered body)
After the thermal transfer medium according to the present invention is stacked on the transfer substrate 6 and bonded by thermal melting, the support 1 is peeled and removed, whereby the thermal melt transfer diffractive structure layer 2 or 3 is transferred and the diffractive structure 7 is transferred. Can be manufactured. In the case of a card substrate, as the substrate 6 to be transferred, for example, a resin film substrate such as polyvinyl chloride resin, polyester resin, polylactic acid resin, polyethylene terephthalate resin, resin card substrate, certificate, gift certificate, etc. If so, for example, paper, synthetic paper and the like can be mentioned.

  Since the thermal transfer medium of the present invention and the diffractive structure using the same have unique and remarkable optical changes when viewed from the front and oblique directions, they can be suitably used for anti-counterfeiting applications. It can also be used for decorative purposes.

  Next, the present invention will be described by way of examples.

<Example 1>
As the support 1, a transparent polyethylene terephthalate (commonly known as PET) film having a thickness of 25 μm was used.
On one side of the support 1, an ink composed of the following composition was applied and dried to form a release protective layer 11 having a thickness of 1.5 μm.

Next, an ink comprising the following composition is applied and dried to form a layer having a thickness of 1.0 μm, and then a press plate for forming a diffraction grating is hot-pressed by a roll embossing method to generate a diffraction grating on the surface. The emboss 21 for forming the fine diffractive structure forming layer 12 was formed.
The height of the concavo-convex convex portion of this fine diffractive structure forming layer was 250 μm.
Further, the height of the convex portion / the width of the convex portion was 0.8. The pitch of the concavo-convex shape was 300 μm.

  Next, an aluminum vapor deposition film was uniformly formed with a film thickness of 60 nm on the entire surface of the diffraction structure forming layer 12 by a vacuum vapor deposition method, and a thin film of the reflective layer 13 was formed.

Finally, an ink composed of the following composition is applied and dried to form an adhesive layer 14 having a thickness of 3 μm.
A thermal transfer medium was produced.

"Peeling protective layer ink composition"
Acrylic resin 30.0 parts by weight Polyethylene powder 1.0 part by weight Toluene 40.0 parts by weight Methyl ethyl ketone 40.0 parts by weight Methyl isobutyl ketone 20.0 parts by weight

"Diffraction structure forming layer ink composition"
Urethane resin 20.0 parts by weight Silicone oil 1.0 part by weight Methyl ethyl ketone 50.0 parts by weight Ethyl acetate 30.0 parts by weight

"Adhesive layer ink composition"
Vinyl chloride vinyl acetate copolymer resin 15.0 parts by weight Acrylic resin (Tg. 20 ° C.) 10.0 parts by weight Silica 1.0 part by weight Methyl ethyl ketone 44.0 parts by weight Toluene 30.0 parts by weight

  Next, this thermal transfer medium was set in a transfer apparatus equipped with a thermal head, and a diffractive structure was manufactured by performing thermal transfer as a character pattern using a plastic card made of polyvinyl chloride as a transfer target substrate.

  When this diffractive structure is observed from the front, it is observed as a general character pattern of gray or black single color, but when the viewpoint is moved in the horizontal direction, it is within a range of 0 to 45 ° with respect to the horizontal direction. It was confirmed that the color changed suddenly by the diffracted light.

<Example 2>
As the support 1, a transparent polyethylene terephthalate (commonly known as PET) film having a thickness of 25 μm was used.
A hot melt transfer ink layer 4 of Y, M, C ink composed of the following composition is applied and dried on one side of the support 1 alternately in the longitudinal direction of the film, and each hot melt transfer ink layer 4 is coated. A thermal transfer medium formed with a thickness of 1 μm and including a thermal melt transfer ink layer was obtained.

  Next, the thermal transfer medium having the diffractive structure obtained in Example 1 is used by physical means between each C and Y of the thermal melt transfer ink layer 4 of the thermal transfer medium including the thermal melt transfer ink layer. They were joined together to produce a thermal transfer medium.

"Hot-melt transfer ink layer-Y ink composition"
Yellow dye 10.0 parts by weight Butyral resin 10.0 parts by weight Silicon modified polyester resin 0.1 part by weight Methyl ethyl ketone 90.0 parts by weight Toluene 90.0 parts by weight

"Thermal transfer ink layer-M ink composition"
Red dye 10.0 parts by weight Butyral resin 10.0 parts by weight Silicon modified polyester resin 0.1 part by weight Methyl ethyl ketone 90.0 parts by weight Toluene 90.0 parts by weight

"Hot-melt transfer ink layer-C ink composition"
Blue dye 10.0 parts by weight Butyral resin 10.0 parts by weight Silicon modified polyester resin 0.1 part by weight Methyl ethyl ketone 90.0 parts by weight Toluene 90.0 parts by weight

  Next, this thermal transfer medium is set in a transfer device equipped with a thermal head, and first, Y, M, and C hot melt transfer ink layers are thermally transferred using a plastic card made of polyvinyl chloride as a transfer target substrate. Then, the image pattern was formed in full color, and then the heat-melt transfer diffractive structure layer was transferred to the portion where the previously transferred character or the gray or black portion of the image pattern was formed, thereby producing a diffractive structure.

  When the obtained diffractive structure is observed, it can be recognized as a normal full-color image in a certain angle range from the front, and when the viewpoint is moved in the horizontal direction, it is gray in the range of 0 to 45 ° with respect to the horizontal direction. Or we could observe a sudden color change due to diffracted light in the black part.

In both the first and second embodiments, the obtained diffractive structure generates diffracted light when the observation angle is moved in the horizontal direction, and the color of the gray or black portion changes abruptly. It has a diffractive structure with unique optical characteristics.
This diffractive structure is easy to determine authenticity when the diffractive structure is observed in a certain angle range from the front, since it does not reduce the visibility of other images and character patterns. Since the optical characteristics cannot be manifested in a diffractive structure, a diffractive structure having a high anti-counterfeiting effect could be obtained.

Sectional drawing which shows an example of the thermal transfer medium of this invention Sectional drawing which shows an example of the thermal transfer medium of this invention Sectional drawing which shows an example of the thermal transfer medium of this invention AA plan view in FIG. Sectional drawing which shows an example of the thermal transfer medium of this invention Sectional drawing which shows an example of the thermal transfer medium of this invention Sectional drawing which shows an example of the diffraction structure of this invention BB sectional view of FIG. Schematic showing the optical effect of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Support body 2 ... Thermal melting transfer diffraction structure layer (4 layer structure)
3 ··· Heat-melt transfer diffraction structure layer (5 layers)
4... Three-color hot-melt transfer ink layers 5 of Y, M, and C... Four-color hot-melt transfer ink layers 6 of Y, M, C, and K. ··· Diffraction structure 11 ··· Peeling protective layer 12 ··· Fine diffraction structure forming layer 13 ··· Reflection layer 14 ··· Adhesive layer 15 ··· Print layer 21 ···・ Rough surface

Claims (6)

A thermal transfer medium having a thermal melt transfer diffractive structure layer on a support,
A thermal transfer medium, wherein the heat-melt transfer diffractive structure layer has a peeling protective layer, a fine diffractive structure forming layer, a reflective layer, and an adhesive layer.   The thermal transfer medium according to claim 1, further comprising a printing layer between the reflective layer and the adhesive layer of the thermal melt transfer diffraction structure layer.   The fine diffractive structure forming layer has a concavo-convex shape, the height of the convex portion of the concavo-convex shape is 5 nm to 1000 nm, the height of the convex portion / the width of the convex portion (aspect ratio) is 1 or more, and the pitch of the concave and convex shape is 3. The thermal transfer medium according to claim 1, wherein the thermal transfer medium is 5 nm to 1000 nm.   The heat-melting transfer ink layer is provided on a support, and the heat-melting transfer diffraction structure layer and the heat-melting transfer ink layer are formed in a pattern. Thermal transfer medium.   5. The thermal transfer medium according to claim 1, wherein the heat-melt transfer ink layer is one or more colors selected from four colors of yellow, magenta, cyan, and black.   A diffraction structure obtained by transferring the thermal transfer medium according to any one of claims 1 to 4 to a substrate to be transferred.