JP2012088598A - Display body and labeled article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display body having an anti-counterfeit effect.SOLUTION: A display body includes at least a base material, a relief structure formation layer provided on one surface of the base material, and a reflecting layer covering the relief structure formation layer. Top surfaces of convex portions and bottom surfaces of concave portions of a relief structure of the relief structure formation layer are substantially parallel with the surface of the base material, and the convex portions and concave portions are arranged at random intervals so that an average interval between adjacent convex portions and concave portions is within a range of 1 to 3 μm. The relief structure formation layer includes linear and curved relief structure regions, and the curved relief structure region has a gradient angle, and differences in height between top surfaces of convex portions and bottom surfaces of concave portions which constitute the curved relief structure region, are uniform throughout the region and are within a range of 0.1 to 0.5 μm, whereby an observed image is colored in soft tones of light obtained by removing light of a partial spectral region from white light when the white light is made to impinge on the curved relief structure region.

Description

  The present invention relates to an image display body whose appearance changes depending on observation conditions used for prevention of counterfeiting, and in particular, an image display body whose image brightness or intention changes depending on the angle of illumination light, the observation direction, etc. The purpose is to provide.

  In recent years, it has a visual effect different from ordinary printed materials for the purpose of preventing counterfeiting of securities such as gift certificates and checks, cards such as credit cards, cash cards, ID cards, and certificates such as passports and licenses. A display body is provided in the form of a transfer foil, a sticker, or the like, which is attached to a surface of a certificate such as the securities or a card, and is bonded. Also, the distribution of counterfeit goods has become a social problem for articles other than securities and certificates, and there are increasing opportunities to apply similar anti-counterfeiting techniques to such articles.

  Examples of anti-counterfeiting technologies include micro characters, special light-emitting ink, watermarks, diffraction gratings, and holograms. This forgery prevention technology can be roughly divided into two. One is anti-counterfeiting measures that determine authenticity using a simple device or measuring device. The other is anti-counterfeiting that can be easily determined by the naked eye.

  In recent years, a security device has been developed in which various fine structures can be produced by an electron beam drawing apparatus (EB apparatus) and visually differentiated from similar techniques. As a most general security device, there is a surface relief type rainbow hologram (for example, Patent Document 1). Rainbow holograms have a more complex structure than ordinary printed materials, and are difficult to manufacture unless they are a specific vendor with high microfabrication technology. A large-scale replication device is required for replication. This makes it difficult to replicate easily. For this reason, it is difficult to produce a counterfeit product.

  Also, when illuminated with illumination light, it is reproduced with light close to a single wavelength, so it can be observed in bright and vivid colors corresponding to the seven colors of the rainbow, and the color and image pattern change when the observation conditions change To look like. For this reason, the difference from other members can be easily discriminated visually.

For these reasons, the rainbow hologram is excellent for visual security applications and has been widely used as an image display for preventing counterfeiting.
However, in the rainbow hologram, the color of the reproduced image changes greatly even if the observation condition changes slightly, so it is difficult to identify the difference in the color of the image.
For this reason, even a rainbow hologram in which different images are recorded, it is easy to give an impression similar to an observer, and it is difficult to distinguish between recorded images between holograms.

Patent Publication 2-72320

“Principles of Holography”, Optronics, p. By Hari Haran

As described above, the image display body for preventing counterfeiting of the rainbow hologram has a drawback that it is difficult to determine the difference between recorded images because the color change of the image is large.
The present invention has been made to solve such problems, and the color and pattern change depending on the observation conditions as in the hologram, but the color change is gentler than that of the rainbow hologram, and the normal observation conditions. Then, it aims at providing the forgery prevention medium which can distinguish the difference of an image easily by providing the image display body which looks almost the same color compared with a rainbow hologram.

The invention of claim 1 includes at least (a) a base material, (b) an uneven structure forming layer having an uneven structure provided on one surface side of the base material, and (c) at least of the uneven structure forming layer. A reflective layer covering a part of the display body, wherein an upper surface of the convex portion and a lower surface of the concave portion constituting the concave-convex structure are substantially parallel to the substrate surface, and the concave-convex structure is adjacent thereto Concavities and convexities are arranged at random intervals within a range where the average arrangement interval between the convex portions or the concave portions is 1 to 3 μm, and the concave-convex structure forming layer includes a linear concave-convex structure region and a curved concave-convex structure region The curved concavo-convex structure has a gradient angle so as to correspond to the brightness of the pixels of the image prepared in advance, and the upper surface of the convex part and the concave part constituting the curved concavo-convex structure region. The difference in height of the lower surface is constant over the entire area, and 0.1 μm By being in the range of not less than m and not more than 0.5 μm, light in a part of the spectral region of visible light is not emitted, so that an image observed when white light is incident on the curved uneven structure region Is a display body characterized by being colored with a gentle color obtained by removing light from a part of the spectral region from white light.
According to a second aspect of the present invention, the height difference between the upper surface of the convex portion and the lower surface of the concave portion of the curved concavo-convex structure region, and the height of the upper surface of the convex portion and the lower surface of the concave portion of the linear concavo-convex structure region. The display body according to claim 1, wherein the difference is substantially the same.
According to a third aspect of the present invention, the height difference between the upper surface of the convex portion and the lower surface of the concave portion of the curved concavo-convex structure region, and the height of the upper surface of the convex portion and the lower surface of the concave portion of the linear concavo-convex structure region. The display body according to claim 1, wherein the difference is different.
The invention according to claim 4 is characterized in that the height or depth of the convex portion or the concave portion of the region having the gradient angle is different for each image region of the image prepared in advance. It is a display object given in one paragraph.
The invention according to claim 5 is the display body according to any one of claims 1 to 4, wherein the luminance and the gradient angle are in a trade-off correspondence relationship.
The invention according to claim 6 is the display body according to any one of claims 1 to 5, wherein the area occupied by the plurality of convex portions or concave portions in the region is 20% or more and 80% or less. .
Invention of Claim 7 is provided with the printed material base material and the display body as described in any one of Claims 1-6 provided in the at least one part area | region of the surface of the said printed material base material, Printed information.

According to the first to third aspects of the invention, the diffracted light observed from the image display body has a wide range of wavelength distribution because the structure is a random structure. Therefore, compared with a rainbow hologram, an image colored in a gentle color can be observed, in which the color change of the reproduced image due to a change in observation conditions is not abrupt. In addition, when the incident angle of the illumination light changes, the wavelength distribution of the diffracted light changes, so that the color appears to change.
Further, the height or depth of the convex portion or concave portion having a gradient angle is constant so that an image colored with a gentle color can be observed. It is possible to provide an image display body in which the color is reproduced with a gentle color and the color of the image changes depending on the observation conditions, a color with high contrast can be expressed, and visibility can be improved. . Furthermore, even when different images are recorded, it is easy to distinguish the recorded images without giving an impression similar to the observer.
Further, since the shape is curved, the viewing area in the horizontal or vertical direction can be expanded, and visibility can be improved.
According to the invention of claim 4, it is possible to express different colors in one display body by changing the height of the convex portion (or the depth of the concave portion) for each image region. That is, a display body capable of displaying a plurality of colors can be realized.
According to the invention of claim 5, it is possible to adjust the brightness and the viewing zone by controlling the gradient of the curve, and the expressiveness of the design is increased.
According to the invention of claim 6, when the width of the convex portion or the concave portion (corresponding to the lattice line width L in the formula (2)) is half of the pitch d from the formula (2) described later (L = d / 2), the diffraction efficiency is highest. Therefore, the remarkable effect that the brightest display image can be obtained when the area occupied by the convex portion or the concave portion is about 50% can be obtained. According to the invention of claim 7, it is possible to give a high anti-counterfeiting effect to a conventional article by pasting or combining the display body of the present invention on a printed matter, a card, or other article.

Schematic of the display body of the present invention. The figure which showed the cross section of the display body shown in FIG. The A area enlarged view of FIG. Explanatory drawing of a curvilinear uneven structure. The figure which showed the diffraction direction when light injects into the uneven structure of FIG. The figure which showed the cross section of the conventional display body.

(Embodiment 1)
Hereinafter, the display body of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of the display body of the present invention.
FIG. 2 is a cross-sectional view taken along line II of the display body shown in FIG. The display body 10 has a structure in which the reflective layer 3 is formed adjacent to the concavo-convex structure regions 11 and 12 and the region 15 having no concavo-convex structure made of UV curable resin, and the transparent layer 2 is filled therewith. It has become. The material of the reflective layer laminated on the concavo-convex structure is not particularly limited, but it is preferable to use a metal material such as aluminum that exhibits a high reflectance with respect to visible light. The thickness of the metal film layer is preferably about 20 to 50 nm from the viewpoint of optical characteristics. As a method for laminating the reflective layer, metal vapor deposition or the like may be used.
In the concavo-convex structure regions 17a and 17b, the concavo-convex structure is linearly formed in a plane parallel to the resin layer, and the depth is 0.3 μm. Further, the concavo-convex structure regions 11 and 12 in FIG. 2 are formed in a curved shape in a plane parallel to the resin layer, and the depth D1 is 0.3 μm and D2 is 0.2 μm, respectively. That is, the depths of the linear uneven structure region 17a and the curved uneven structure region 11 are the same, and the depths of the linear uneven structure region 17b and the curved uneven structure region 12 are different. Moreover, the uneven | corrugated structure area | regions 11 and 12 differ in the arrangement | positioning space | interval of unevenness | corrugation, and it is a random thing which does not have periodicity. FIG. 3 shows an enlarged view of region A in FIG. FIG. 3 shows that the concavo-convex structure of the concavo-convex structure region 17a is linear and the cycle is random, and the concavo-convex structure of the concavo-convex structure region 11 is curvilinear and the interval between the concavo-convex has no periodicity.
When such an image display is observed, the light diffracted by the reflective layer 3 in the concavo-convex structure regions 11 and 12 enters the eyes, but since this diffracted light is colored, a colored image is observed. Will be.
The concavo-convex structure as described above should be formed on the resist material by pinpoint drawing with a charged particle beam such as an electron beam laser so that the concavo-convex structure is not affected by the scattering of energy when a laser or the like is emitted. Is desirable. It is desirable to produce a metal plate by electroforming the drawn resist material, and the plate is pressed against a resin and molded. Also, it is preferable to apply a UV curable resin to the metal plate and press and mold the plate against the resin because a more accurate uneven structure can be obtained. Although a UV curable resin is used here, a photocurable resin or the like may be used. In this way, it is possible to accurately shape the concavo-convex structure, whereby light in a part of the spectral region of visible light is not emitted in the line-of-sight direction, and thus white light is emitted from the curved concavo-convex structure. When incident on a region, the observed image is colored with a gentle color that excludes light in some spectral regions from white light, so the display color changes to rainbow as in the past. The effect of suppressing the phenomenon can be obtained.

The principle that the light diffracted by such an image display body is colored will be described.
When there is a concavo-convex structure, incident light is diffracted by the concavo-convex structure, and part of the light travels in the regular reflection direction, and another part becomes diffracted light.
With respect to the concavo-convex structure on the surface, when the refractive index is n, the depth is d, and the wavelength is λ, the optical path difference of the light reflected at the crest and trough of the illumination light incident at the internal angle θ is 2 d cos θ. The phase difference between these lights is 4πnd cos θ / λ multiplied by 2πn / λ.
At this time, if the phase difference is an integral multiple of 2π, the phases of the light in the regular reflection direction are aligned, so that the regular reflection light becomes strong due to the interference of light from the convex and concave portions, and the intensity of the diffracted light becomes weak.
If the phase difference is an integral multiple of 2π + π, the phase of the light in the regular reflection direction is reversed, so that the light in the regular reflection direction is weakened by interference, and the intensity of the diffracted light is increased.
By the way, the wavelength of visible light is distributed over a relatively wide range of 380 to 780 nm.
In the case of a depth of about 0.1 μm (optical path difference of about half of the wavelength) or less as used in a normal diffraction image display body, the difference depending on the wavelength is small and no significant difference.
However, when the depth of the unevenness becomes deep to some extent, the diffracted light becomes strong at a certain wavelength and the phase difference becomes an integral multiple of 2π + π, and the diffracted light becomes weak at a certain wavelength and the phase difference becomes an integral multiple of 2π. Become.
For this reason, the intensity of diffracted light varies greatly depending on the wavelength.
Moreover, in the image display body of this invention, the uneven structure is random and does not have periodicity.
Therefore, unlike the hologram and diffraction grating, the direction of the diffracted light is not greatly changed depending on the wavelength, and is emitted in substantially the same direction.
That is, the diffracted light with respect to each wavelength is observed in an overlapping manner, and a color due to the difference in the intensity of the diffracted light is obtained. When the angle of illumination light incident on the image display body is 30 degrees from the normal to the surface of the concavo-convex structure of the display body and the observation position is the normal direction, the color change is yellow when the depth D1 is 0.3 μm and the depth The color of magenta is confirmed when D2 is 0.2 um.

Next, the pitch condition is examined from the spread of diffracted light.
The diffracted light needs to spread from the specular reflection direction to a sufficiently distant direction so that the diffracted light and the light in the specular reflection direction can be observed separately.
The above expansion is
a = mλ / (sin α−sin β) Equation (1)
Can be expressed as a is the size of the grating, m is the diffraction order, λ is the incident light and the wavelength of the diffracted light, α is the incident angle, and β is the emission angle.

  In general, the illumination light and the observation angle are generally different by about 30 °. Therefore, the diffracted light needs to spread at an angle of about 30 ° from the display body. The refractive index of the transparent resin layer is assumed to be around 1.5, and the refractive index in air is assumed to be 1.0. In order to set the diffraction angle from the display body to 30 °, the diffraction angle β in the transparent resin needs to be about 20 degrees or more according to Snell's law. Assuming that the wavelength of the illumination light is 500 nm, the size a of the grating is 1.5 μm or less. That is, in order for the diffracted light to have a sufficient spread, the size of the grating needs to be 1.5 μm or less, and the pitch of the grating peaks and valleys needs to be 3 μm or less. By doing so, diffracted light having a sufficient angular spread can be obtained from the display body.

ここで、ηは回折効率（０〜１の値をとる）、ｒは回折格子の高さ、Ｌは回折格子線幅、ｄは格子線のピッチ、θは照明光の角度、λは入射光及び回折光の波長である。この式は、凹凸構造からなる浅い矩形回折格子に成り立つものである。 From Equation 1, illumination light incident on the grating at an incident angle of α emits diffracted light in the direction of angle β. At this time, the emission intensity of the light having the wavelength λ, that is, the diffraction efficiency, varies depending on the size and height of the grating and is derived from Equation 2.

Here, η is diffraction efficiency (having a value of 0 to 1), r is the height of the diffraction grating, L is the diffraction grating line width, d is the pitch of the grating line, θ is the angle of the illumination light, and λ is the incident light. And the wavelength of the diffracted light. This equation holds for a shallow rectangular diffraction grating having a concavo-convex structure.

  As is clear from Equation 2, the diffraction efficiency varies depending on the height r of the diffraction grating, the pitch d of the grating lines, the incident angle θ of incident light, and the wavelength λ. In practice, the diffraction efficiency tends to gradually decrease as the diffraction order m becomes higher.

The occupation area of the convex portion or the concave portion is preferably 20% or more and 80% or less. From Equation 2, the diffraction efficiency is highest when the width of the convex portion or the concave portion (corresponding to the lattice line width L of Equation 2) is half of the pitch d. Therefore, the brightest display image can be obtained when the area occupied by the protrusions or recesses is about 50%, and it is most desirable. If the area is 20% or more and 80% or less, the diffraction efficiency decreases as the distance from 50% increases. Although the image becomes darker, it is possible to visually recognize a display image composed of light having a plurality of wavelengths. Note that the diffraction efficiency when the occupied area is 20% and 80% is about 30% of the brightness of 50% from Equation 2.
When the area occupied by the convex portion or the concave portion is smaller than 20% or larger than 80%, sufficient brightness cannot be obtained, and it becomes difficult to obtain a sufficient eye-catching effect.

Moreover, it is preferable that the optimal value of the height of a convex part or the depth of a recessed part is the range of 0.1 to 0.5 um. Assuming that the pitch d and the grating line width L are constant in Equation 2, the diffraction efficiency is highest when light having a wavelength in the visible light range is incident at an incident angle θ (greater than 0 degree and less than 90 degrees). The value of the height of the convex portion or the depth of the concave portion is in the range of 0.1 μm or more and 0.5 μm or less. Note that, from Equation 2, the conditions for the highest diffraction efficiency are repeated even when the value is larger than that. However, in terms of manufacturing, it is easier to fabricate when the height of the convex portion or the depth of the concave portion is as shallow as possible. Therefore, it is preferable that the high diffraction efficiency can be obtained at a shallower value under the condition of 0.1 μm or more and 0.5 μm or less.
In the conventional display body, the concavo-convex structure does not have a cross-sectional shape as shown in FIG. 2, but has a cross-sectional shape such as a so-called corrugated shape as shown in FIG. Since the depths of the recesses are also different, the effect of changing the diffraction efficiency in accordance with the height of the concavo-convex structure, such as Equation 2 described above, is less likely to occur. With such a conventional concavo-convex structure, although diffraction of light occurs, only a rainbow hologram can be created. Moreover, it has not been known that a hologram colored with a gentle color as in the present invention is created by accurately arranging the concavo-convex structure as shown in FIG. However, in the present invention, since the height of the convex portion or the depth of the concave portion is substantially the same and is substantially parallel to the base material surface, a colored image can be displayed. In other words, in the present invention, light in a part of the spectral region of visible light is not emitted in the line-of-sight direction, so that when white light is incident on the curved concavo-convex structure region, the observed image is derived from white light. Since it is colored with a gentle color excluding light in a part of the spectral region, it is possible to suppress the phenomenon that the display color changes to a rainbow color as in the past.

  If the height of the convex part or the depth of the concave part is shallower than 0.1 um, the quality is stable and stable due to external factors during manufacturing (variation in machine and environmental conditions, slight changes in material composition, etc.) It is difficult to manufacture a rugged structure, and when forming a concavo-convex structure deeper than 0.5 μm, it becomes difficult to precisely transfer and mold a fine and deep structure.

  Further, the pitch, the height of the convex portion, or the height of the concave portion need not be considered only by a single element, but also the aspect ratio (ratio of the depth to the pitch) needs to be considered. As the concavo-convex structure has a higher aspect ratio, it becomes more difficult to transfer. In addition, when the aspect ratio is high, that is, when the ratio of the depth to the pitch is high, it is difficult for light to reach the bottom of the unevenness, so that it may be difficult to produce a color or the image may become dark. When the aspect ratio is 1 or more, these problems become prominent. Considering the use of a depth of about 0.5 μm, it is better to set the size of each lattice to 0.5 μm or more. It is considered that the pitch is particularly preferably 1 μm or more.

Next, the spread of diffracted light in the YZ and XZ planes due to the concavo-convex structure will be described.
FIG. 5 shows the case of incident light having an optical axis parallel to the YZ plane. In this case, the diffraction angles βx and βy of the + 1st order diffracted light in the figure follow the following equation.
λ = dx (sin βx) Equation (3)
λ = dy (sin βy−sin θy) Equation (4)
Where λ is the wavelength of light, dx and dy are the X component and Y component of the lattice spacing, θx and θy are diffraction angles in the XZ plane and YZ plane, and βy is in the YZ plane. The diffraction angle is shown. Note that the gradient of the diffraction grating in the XY plane is Ω = arctan (dy / dx).

  From Equations 3 and 4, it can be seen in which range the light is emitted from the concavo-convex structure. In other words, the concavo-convex structure has a curved shape in a plane parallel to the resin layer, so that the spread of diffracted light in the XZ plane can be increased compared to a linear shape, and the display body can be viewed from a wide range. It becomes possible.

In the present invention, the slope angle of the curve is desirably 90 degrees or less or -90 degrees or more. When the value of dx is reduced as in Expression 3, the diffraction angle is increased and the diffracted light of the display body can be confirmed from a wide range, but the brightness is lowered because the diffracted light is emitted over a wide range. When the slope angle of the curve is 90 degrees or -90 degrees, the luminance is about 50% of that in which the concavo-convex structure is linear in a plane parallel to the resin layer. By providing the gradient in this way, the brightness is lowered and the display image becomes dark, but a display image with sufficient brightness can be visually recognized from a wide range. When the slope of the curve is 90 degrees or more, the brightness is less than 50%, so that sufficient brightness cannot be obtained and it is difficult to obtain the eye catching effect.
The gradient angle range is a range from the minimum value to the maximum value of the gradient indicated by each divided line segment obtained by dividing the curve into line segments. The gradient angle range is −90 degrees to 90 degrees, and the X axis of the XY graph is the reference (0 degree), and the counterclockwise direction is positive.
There is a trade-off relationship between the gradient angle range and the luminance. For example, the brightness of the area where the image is divided into pixels is divided into 0 to 255 levels, and when the brightness is 0, the gradient angle range is set to -90 degrees to 90 degrees. When the luminance is 255, the gradient angle range is set to -1 degree to 1 degree. By setting in this way, the display body can have a gradation effect.

When the display body 10 is observed, the letter “T” and the concavo-convex structure region 17a can be visually recognized in yellow. The portion where “T” overlaps with the uneven structure region 17a cannot be determined by color, but since the diffracted light spreads differently, the yellow color can be confirmed over a wide range in the “T” portion. In 17a, colors cannot be confirmed over a wide range. That is, there is a position where only the “T” portion can confirm the color at a position where the color of the concavo-convex structure region 17a cannot be observed by changing the observation position. Therefore, it is possible to express different visual effects between the “T” portion and the uneven structure region 17a.
Further, since the depth of the letter “P” and the uneven structure region 17b is different from 0.3 μm and 0.2 μm, the angle of the illumination light incident on the display body is 30 degrees from the perpendicular to the surface of the uneven structure of the display body. When the observation position is a perpendicular direction, “P” is visually recognized in yellow, and the uneven structure region 17b is visually recognized in magenta. Of course, in the present embodiment, a display body is described in which the depth of the concavo-convex structure region is the same as the depth of the background and a combination of the depth different from the background is described. It is not necessary to adopt such a form, and the depth of each uneven structure region may be set as appropriate.

  Further, since the color of the display body is generated due to the difference in the optical path difference between the concave portion and the convex portion, the color can be controlled by controlling the depth for each region. By controlling the color, it is possible to express colors such as orange, blue, and cyan, and it is possible to improve the design.

DESCRIPTION OF SYMBOLS 10 ... Display body, 11, 12 ... Uneven structure area (curve), 17a, b ... Uneven structure area (straight line), 15 ... Area without uneven structure

Claims (7)

At least (a) a substrate and (b) a concavo-convex structure forming layer having a concavo-convex structure provided on one surface side of the substrate;
(C) a reflective layer that covers at least a part of the concavo-convex structure forming layer,
The upper surface of the convex portion and the lower surface of the concave portion constituting the concave-convex structure are substantially parallel to the base material surface,
In the concavo-convex structure, the concavo-convex portions are arranged at random intervals within a range in which the average arrangement interval between adjacent convex portions or concave portions is 1 to 3 μm.
The concavo-convex structure forming layer includes a linear concavo-convex structure region and a curved concavo-convex structure region,
The curved concavo-convex structure has a gradient angle so as to correspond to the luminance of pixels of an image prepared in advance,
The difference in height between the upper surface of the convex portion and the lower surface of the concave portion constituting the curved concavo-convex structure region is constant over the entire region and is in the range of 0.1 μm or more and 0.5 μm or less. Light in a part of the spectral region is not emitted, so when white light is incident on the curved uneven structure region, the observed image excludes part of the spectral region from white light. A display body characterized by being colored gently.   The difference in height between the upper surface of the convex portion and the lower surface of the concave portion in the curved concavo-convex structure region is substantially the same as the difference in height between the upper surface of the convex portion and the lower surface of the concave portion in the linear concavo-convex structure region. The display body according to claim 1.   The difference in height between the upper surface of the convex portion and the lower surface of the concave portion in the curved concavo-convex structure region is different from the height difference between the upper surface of the convex portion and the lower surface of the concave portion in the linear concavo-convex structure region. The display body according to claim 1.   The display body according to any one of claims 1 to 3, wherein a height or a depth of a convex portion or a concave portion of the region having the gradient angle is different for each image region of the image prepared in advance. .   The display body according to claim 1, wherein the luminance and the gradient angle are in a trade-off correspondence relationship.   The display body according to any one of claims 1 to 5, wherein the area occupied by the plurality of convex portions or concave portions in the region is 20% or more and 80% or less.   An information printed matter comprising: a printed matter base material; and a display body according to any one of claims 1 to 6 provided in at least a partial region of the surface of the printed matter base material.

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