Patent Description:
Securities, such as gift vouchers or checks, cards, such as credit cards, cash cards, or ID cards, and certificates, such as passports or driver's licenses, typically have a display adhered thereto that has visual effects different from those of normal printed matter to prevent counterfeiting of these articles. In recent years, the circulation of counterfeits is also a social problem for articles other than those mentioned above, and similar anti-counterfeiting techniques are increasingly applied to these articles.

A known display having visual effects different from those of normal printed matter includes a diffraction grating with aligned grooves. This display, for example, displays an image that changes according to the observation conditions, or displays a stereoscopic image. In addition, iridescent colors produced by a diffraction grating cannot be produced by normal printing techniques. Therefore, a display including a diffraction grating is widely used for an article that requires anti-counterfeiting measures.

PTL1, for example, discloses a technique for displaying a picture by arranging plural diffraction gratings in which grooves have different longitudinal directions or lattice constants (i.e., groove pitches). As the position of the observer or light source relative to the diffraction gratings changes, the wavelength of the diffracted light reaching the observer's eyes changes. Therefore, the abovementioned technique enables the representation of an image that changes to show iridescent colors.

In a display that employs a diffraction grating, a relief diffraction grating (grating lines) formed of plural grooves is typically used. The relief diffraction grating is usually reproduced from an original plate made by photolithography.

PTL <NUM> discloses a method for manufacturing an original plate of a relief diffraction grating. This method involves placing a plate-like substrate having one main surface coated with a photosensitive resist on an XY stage, and pattern-exposing the photosensitive resist by irradiating it with an electron beam while moving the stage under computer control. The original plate of the diffraction grating can also be formed using two-beam interference of laser light.

In the manufacture of a relief diffraction grating, an original plate is usually formed using such a method, and a metal stamper is produced therefrom by electroforming or the like. This metal stamper is then used as a matrix to replicate a relief diffraction grating. That is, for example, a thermoplastic resin or a photocurable resin is first applied onto a thin, film or sheet-like transparent substrate made of polyethylene terephthalate (PET) or polycarbonate (PC). Then the coating is brought into close contact with the metal stamper, and the resin layer is applied with heat or light in this state. After the resin is cured, a replica of the relief diffraction grating is obtained by releasing the metal stamper from the cured resin.

Typically, the relief diffraction grating is transparent. Usually, therefore, a reflective layer is formed on the resin layer provided with a relief structure by depositing a metal such as aluminum or a dielectric in a single layer or multiple layers by vapor deposition.

The display thus obtained is then adhered via an adhesive layer or pressure-sensitive adhesive layer to a support substrate made of, for example, paper or plastic film. An anti-counterfeiting display is thus obtained.

The original plate used for manufacturing the display including the relief diffraction grating is difficult to manufacture. Furthermore, the relief structure needs to be transferred from the metal stamper to the resin layer with high accuracy. That is, advanced technology is required for manufacturing a display including a relief diffraction grating.

However, as many articles requiring anti-counterfeiting measures employ displays including relief diffraction gratings, this technique has come to be widely known, and the numbers of counterfeits has been increasing. Therefore, it has become increasingly difficult to achieve a sufficient anti-counterfeiting effect with a display that is characterized only by exhibiting iridescence due to diffracted light.

Displays have been disclosed that have visual effects different from changes in iridescent colors due to a conventional diffraction grating. In a technique disclosed in PTL <NUM>, for example, pixels including diffraction gratings are formed with different lattice constants, and the tones thereof are modulated by amplituide modulation to express a full-color image.

However, the manufacturing method for such a display has the following problems.

First, since the colors emitted from the diffraction grating vary depending on the angle at which the colors intersect with the normal of the main surface of the display, different colors are provided depending on the elevation angle for observation and the distance between the display and the observer. Depending on these observation conditions, color expression may be different from that intended by a designer(s).

In addition, since the diffraction grating emits diffracted light in a direction perpendicular to the direction in which the grating extends, an intended image or even no image will be perceived by an observer from an azimuth angle different from that intended by the designer.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a display that exhibits a high anti-counterfeiting effect by expressing an image as intended, and an article including the display.

To achieve the above object, the present invention takes the means as described in the claims.

According to the display of the present invention, since each color of the emitted light is not expressed by a diffraction grating, the color can be expressed as expected at a wide viewing angle with little change due to the reflection angle, that is, the elevation angle or the azimuth angle during observation. In addition, the hue and saturation can be changed by appropriately increasing or decreasing the area ratio of the concavo-convex region in the sub-pixel and the height or depth of protrusions and recesses. Thus, a clear full-color image can be expressed.

Furthermore, bonding together or combining such displays allows articles such as printed matter and cards to have a high anti-counterfeiting effect.

The embodiments of the present invention will be described in detail with reference to the drawings. Components that exhibit identical or similar functions are denoted by the same reference signs throughout the drawings, and redundant description thereof is omitted.

<FIG> is a schematic plan view of a display and a pixel according to a first embodiment of the present invention.

<FIG> is a cross-sectional view of an example sub-pixel.

That is, the display <NUM> according to this embodiment includes plural pixels <NUM>. As illustrated in <FIG>, the plural pixels <NUM> may be arranged in a grid pattern on a two-dimensional plane. As illustrated in <FIG>, each pixel <NUM> includes a sub-pixel <NUM>, a sub-pixel <NUM>, and a sub-pixel <NUM>. As illustrated in <FIG>, which is a cross-sectional view of the sub-pixel <NUM>, the sub-pixel <NUM> is a laminate in which a light-transmitting layer <NUM> and a reflective layer <NUM> are laminated. The light-transmitting layer <NUM> is formed by layering a transparent substrate <NUM> and a relief structure forming layer <NUM>.

The pixels <NUM> may be arranged differently from the grid pattern illustrated in <FIG>. The size (the length of the long side and the short side) of the pixel <NUM> is preferably <NUM> or more and <NUM> or less. The size (the length of the long side and the short side) of the sub-pixels <NUM>, <NUM>, and <NUM> is preferably <NUM> or more and <NUM> or less.

The transparent substrate <NUM> is a film or sheet that can be handled by itself, and, for example, polyethylene terephthalate (PET), polycarbonate (PC), or the like is suitable. The transparent base material <NUM> can have a thickness of, for example, <NUM> or more and <NUM> or less.

The relief structure forming layer <NUM> is a layer formed on a surface of the transparent substrate <NUM>. As the relief structure forming layer <NUM>, for example, a resin having light transparency, such as the thermoplastic resin, the thermosetting resin, or the photocurable resin, is suitable. By applying the thermoplastic resin or photocurable resin as the material of the relief structure forming layer <NUM>, this makes it possible to form a light-transmitting layer <NUM> which has protrusions or recesses transferred onto one main surface from, for example, protrusions or recesses formed on a metal stamper.

As the thermoplastic resin, for example, a plastic such as the polyethylene resin or the polypropylene can be applied. As the thermosetting resin, the urethane resin, epoxy resin, or the like can be applied. As the photocurable resin, the acrylic resin, the urethane acrylic resin, or the like can be applied.

The relief structure forming layer <NUM> can have a thickness of <NUM> or more and <NUM> or less.

As the reflective layer <NUM>, a metal layer of metal material is preferably applied. As the metal material, for example, aluminum, silver, gold, alloys thereof, or the like can be applied. Alternatively, the reflective layer <NUM> may be a dielectric layer having a refractive index different from that of the relief structure forming layer <NUM>. Alternatively, the reflective layer <NUM> may be a laminate of dielectric layers having refractive indices different between adjacent ones thereof, that is, a dielectric multilayer film. Preferably, of the dielectric layers in the dielectric multilayer film, the one in contact with the relief structure forming layer <NUM> has a refractive index different from that of the relief structure forming layer <NUM>. The reflective layer <NUM> can be formed by vapor deposition. Examples of the vapor deposition include, for example, vacuum deposition and sputtering. The reflective layer <NUM> can have a thickness of <NUM> or more and <NUM> or less.

The sub-pixels <NUM> and <NUM> also have a configuration similar to that of the sub-pixel <NUM>, and thus illustration and description thereof are omitted.

As shown in <FIG>, the incident light I enters the pixel <NUM> including such sub-pixels <NUM>, <NUM>, and <NUM> from above in <FIG>. The incident light I is reflected by the reflective layer <NUM>, and is emitted as reflected light R.

The sub-pixel <NUM> includes a concavo-convex region <NUM> that emits red reflected light R. As shown in <FIG>, the concavo-convex region <NUM> includes an upper surface (a surface on the light-transmitting layer <NUM> side) provided with plural protrusions 111a having a surface substantially parallel to the main surface of the display <NUM>. The protrusions 111a are irregularly arranged in the concavo-convex region <NUM>, and the region excluding the protrusions 111a is a flat portion 111b. The region around the concavo-convex region <NUM> on the upper surface (a surface on the light-transmitting layer <NUM> side) is a flat portion 111c substantially parallel to the main surface of the display <NUM>, and there are no protrusions 111a in the flat portion <NUM> c. The upper surface of the protrusions 111a and the main surface of the display <NUM> may be substantially parallel such that there is no optical problem with visible light.

The sub-pixel <NUM> includes a concavo-convex region <NUM> that emits green reflected light R. The sub-pixel <NUM> includes a concavo-convex region <NUM> that emits blue reflected light R. Although not illustrated, the concavo-convex region <NUM> and the concavo-convex region <NUM> also include plural protrusions 111a, which have a plane substantially parallel to the main surface of the display <NUM>, on the upper surface (a surface on the light-transmitting layer <NUM> side), similarly to the concavo-convex region <NUM>. The concavo-convex region <NUM> and the concavo-convex region <NUM> of the concavo-convex region <NUM> also have irregularly arranged protrusions 111a, where the region excluding the protrusions 111a is the flat portion 111b.

The region around the concavo-convex regions <NUM> and <NUM> on the upper surface (a surface on the light-transmitting layer <NUM> side) is a flat portion 111c substantially parallel to the main surface of the display <NUM>, and there are no protrusions 111a on the flat portion 111c.

The display <NUM> thus includes plural pixels <NUM> formed of a red sub-pixel <NUM>, a green sub-pixel <NUM>, and a blue sub-pixel <NUM>, and this configuration allows the display <NUM> to display a color image by reflected light R. Therefore, the upper side in <FIG> corresponds to the front side (observer side), and the lower side in <FIG> corresponds to the back side.

<FIG> is a perspective view showing an example configuration of the concavo-convex region <NUM> on the reflective surface of the reflective layer <NUM>. The configuration of the concavo-convex regions <NUM> and <NUM> will be similarly described with reference to <FIG>. In this example, the observer side is the top side and corresponds to the light-transmitting layer <NUM> side in <FIG>. For the sake of description, the light-transmitting layer <NUM> is omitted in the drawing.

As illustrated in <FIG>, in the display <NUM> according to the first embodiment, the protrusions 111a are irregularly arranged in the concavo-convex regions <NUM>, <NUM>, and <NUM> on the upper surface of the reflective layer <NUM>. Alternatively, instead of the protrusions 111a, recesses (not shown) may be irregularly arranged. The height T of the protrusions 111a (or the depth of the recesses) is set according to the color displayed by each of the sub-pixels <NUM>, <NUM>, and <NUM>. For example, in the concavo-convex region <NUM> of the sub-pixel <NUM> for providing a red color, the height T is increased (or the depth of recesses is increased); in the concavo-convex region <NUM> of the sub-pixel <NUM> for providing a blue color, the height T is reduced (or the depth of recesses is reduced); and in the concavo-convex region <NUM> for providing a green color, the height T is in the middle range (or the depth of recesses is in the middle range).

Furthermore, in each of the sub-pixels <NUM>, <NUM>, and <NUM>, the ratio of the area occupied by the concavo-convex regions <NUM>, <NUM>, and <NUM> is set corresponding to the hue and saturation of the pixel <NUM>. For example, as shown in <FIG>, if the area ratio of the concavo-convex region <NUM> in the sub-pixel <NUM> is increased, the saturation of red can be increased. Similarly, if the area ratio of the concavo-convex region <NUM> in the sub-region <NUM> is increased, the saturation of blue can be increased. In addition, if the area ratio of the concavo-convex region <NUM> in the sub-region <NUM> is reduced, the saturation of green can be reduced. Thus, by increasing the saturation in the sub-pixels <NUM> and <NUM> and decreasing the saturation in the sub-pixel <NUM>, the pixel <NUM> can emit a purple hue.

In addition, as shown in <FIG>, the pixel <NUM> can emit cyan hue when the red saturation is lowered by reducing the area ratio of the concavo-convex region <NUM> in the sub-pixel <NUM>, the blue saturation is increased by increasing the area ratio of the concavo-convex region <NUM> in the sub-pixel <NUM>, and the green saturation is made medium by making the area ratio of the concavo-convex region <NUM> in the sub-pixel <NUM> medium.

The area ratio of the sub-pixels <NUM>, <NUM>, and <NUM> can be changed by changing both the long side and the short side of the sub-pixels <NUM>, <NUM>, and <NUM>. Furthermore, the sub-pixels <NUM>, <NUM>, and <NUM> having a large area ratio can be produced by changing only the long sides of the sub-pixels <NUM>, <NUM>, and <NUM>, and the sub-pixels <NUM>, <NUM>, and <NUM> having a small area ratio can be produced by changing both the long sides and the short sides of the sub-pixels <NUM>, <NUM>, and <NUM>. In particular, with each of the sub-pixels <NUM>, <NUM>, and <NUM> having a certain area ratio or larger, the luminance and saturation may be modulated by dither diffusion for dark pixels.

Furthermore, as shown in <FIG>, by providing the concavo-convex regions <NUM>, <NUM>, and <NUM> having a constant area ratio as adjusters in each of the sub-pixels <NUM>, <NUM>, and <NUM>, the color shifting can be easily adjusted. Each of the sub-pixels <NUM>, <NUM>, and <NUM> may have the same area.

The sub-pixels <NUM>, <NUM>, and <NUM> may have a size that is not recognizable by the human eye. If the sub-pixels <NUM>, <NUM>, and <NUM> are of a size that cannot be recognized by the human eye, the location of the concavo-convex regions <NUM>, <NUM>, and <NUM> in the sub-pixels <NUM>, <NUM>, and <NUM> is less limited.

In addition, although a square is shown in <FIG> as a planar shape of a protrusion 111a or a recess (not shown), the planar shape thereof may be a rectangle, a polygon, a circle, or any other shape. Furthermore, the size and the planar shape of protrusions 111a or recesses (not shown) may be different in each of the concavo-convex region <NUM>, <NUM>, <NUM>. With any planar shape, if the length Lx of one side (the length of the long side and the short side in the case of a rectangle) or the diameter in the case of a circle (the long diameter and the short diameter in the case of an elliptical shape) is smaller than <NUM> or larger than <NUM>, scattering necessary for distributing the reflected light R is less likely to be generated. Preferably, therefore, regardless of the planar shape of protrusions 111a or recesses (not shown), the outer diameter is typically about <NUM>.

At the area ratio of the protrusions 111a or recesses (not shown) in the concavo-convex regions <NUM>, <NUM>, and <NUM> of <NUM>%, the intensity of color provided by the reflected light R is the strongest, and when the area ratio is <NUM>% or less and <NUM>% or more, sufficient color cannot be provided. Preferably, the center-to-center distance P between adjacent protrusions 111a or recesses (not shown) in each of the concavo-convex regions <NUM>, <NUM>, and <NUM> is <NUM> or more and <NUM> or less on average, depending on the intensity of the color, the size of the concavo-convex regions, and the size of the sub-pixels.

Although the typical configuration of the display <NUM> according to the present embodiment has been described, the display <NUM> of the present embodiment may be further provided with another layer such as an adhesive layer or a resin layer (not shown). Hereinafter, a configuration example in the case where the adhesive layer and the resin layer are provided will be described.

The adhesive layer is provided, for example, so as to cover the reflective layer <NUM>. When the display <NUM> includes both the light-transmitting layer <NUM> and the reflective layer <NUM>, the surface shape of the reflective layer <NUM> is substantially identical to the interface shape between the light-transmitting layer <NUM> and the reflective layer <NUM>. The adhesive layer prevents exposure of the surface of the reflective layer <NUM>, making it difficult for the concavo-convex regions <NUM>, <NUM>, <NUM> at the interface between the light-transmitting layer <NUM> and the reflective layer <NUM> to be copied for counterfeiting. When the light-transmitting layer <NUM> side is the back side and the reflective layer <NUM> side is the front side, such an adhesive layer is formed on the light-transmitting layer <NUM>. As the material of the adhesive layer, the acrylic resin, the urethane resin, or the like can be applied. The adhesive layer can have a thickness of <NUM> or more and <NUM> or less.

The resin layer is, for example, provided as a hard coat layer for preventing the surface of the display <NUM> from being scratched during use, or provided as a print layer made of resin ink curable by light or heat and provided on a part of the display <NUM>. Such a resin layer is provided on the front surface side of the laminate of the light-transmitting layer <NUM> and the reflective layer <NUM>. For example, when the light-transmitting layer <NUM> side is the back side and the reflective layer <NUM> side is the front side, covering the reflective layer <NUM> with the resin layer prevents damage to the reflective layer <NUM> and makes it difficult to copy the concavo-convex regions <NUM>, <NUM>, <NUM> on the surface thereof for counterfeiting.

Next, a description will now be given of the principle that a wide viewing-angle full-color image can be displayed by the display <NUM> according to the present embodiment configured as described above. In the following description, "image" means something that can be observed as a spatial distribution of hue and/or saturation. In addition, it is understood that "image" includes photographs, figures, pictures, letters, symbols, and the like.

According to the display <NUM> of the present embodiment, as illustrated in <FIG>, the protrusions 111a are irregularly arranged in the concavo-convex regions <NUM>, <NUM>, and <NUM>. When natural light or illumination light having plural wavelengths is incident as the incident light I on the concavo-convex regions <NUM>, <NUM>, and <NUM> formed by such irregular arrangement of the protrusions 111a as described above, the reflected light R is scattered at any wavelength, so that the spatial distribution of each wavelength becomes substantially uniform in the direction of elevation angle and azimuth angle. In other words, the distribution of a particular wavelength will not vary with a particular angle (elevation angle and azimuth angle), as with the reflection of light on a known diffraction grating.

In addition, in the reflected light R on the upper surfaces of the concavo-convex regions <NUM>, <NUM>, and <NUM> as shown in <FIG>, a phase difference occurs according to the height T of the protrusions 111a or the depth of protrusions (not shown). Therefore, these reflected lights R interfere with each other to provide a particular color at a certain height T or a depth of protrusions (not shown). In this case, for example, when the refractive index of the light-transmitting layer <NUM> is <NUM>, which is the refractive index of a typical resin, and the viewing angle is <NUM> degrees, the angle of light inside the light-transmitting layer <NUM> is approximately <NUM> degrees according to Snell's law. The cosine of this angle gives a ratio of <NUM> between the height T of the protrusions 111a or the depth of the protrusions (not shown), in other words, the optical path length as viewed from the front, and the optical path length as viewed from an oblique direction at <NUM> degrees, and thus the shift amount is only <NUM>% therebetween. The refractive index of the light-transmitting layer <NUM> can be <NUM> or more and <NUM> or less.

As described above, since the degree of interference due to the phase difference is close between a front view of the display <NUM> and a perspective view of the display <NUM>, the provided colors are substantially the same across a wide angle, unlike the case where the diffraction grating color.

Furthermore, the spatial distribution of the reflective light in the protrusions 111a on the upper surface of the reflective layer <NUM> in the concavo-convex region <NUM> and the spatial distribution of the light reflected from the flat portion 111b except for the protrusions 111a are equal due to the Babinet's principle. Thus, since light and other light interfering with each other have the same spatial distribution, the intensity (efficiency) of interference is independent of the spatial direction, and the intensity of the mutual light is substantially the same across a wide angle, unlike the case of light from a diffraction grating.

As described above, with the display <NUM> according to the embodiment of the present invention, the provided color in a wide elevation angle and azimuth angle is substantially the same and has substantially the same intensity, and thus a full-color image having a wide viewing angle is displayed. As described above, the display <NUM> according to the embodiment of the present invention allows the display of a color image having a wide viewing angle, which does not depend on the elevation angle or the azimuth angle.

Furthermore, in the display <NUM> according to the embodiment of the present invention, in particular, the area ratio of the concavo-convex regions <NUM>, <NUM>, and <NUM> in each of the sub-pixels <NUM>, <NUM>, and <NUM> can be set corresponding to the hue and saturation of the color of the pixel <NUM>. As a result, the following functions and effects can be achieved.

That is, according to such a configuration, it is possible to appropriately vary the area ratio of the color providing region included in the pixel <NUM>, that is, the concavo-convex region <NUM>, which emits red, to the sub-pixel <NUM>, the area ratio of the concavo-convex region <NUM>, which emits green, to the sub-pixel <NUM>, and the area ratio of the concavo-convex region <NUM>, which emits blue, to the sub-pixel <NUM>. In other words, it is possible to adjust the color emission amount of red, green, and blue in the pixel <NUM>. Thus, adjusting the mixing ratio of red, green, and blue allows other perceivable colors to be provided for each pixel <NUM> by color mixing, and allows the saturation to be adjusted for each pixel <NUM> based on the total amount of each color.

As described above, with the display <NUM> according to the first embodiment, the hue and saturation obtained can be adjusted, which makes it possible to more easily achieve a wide viewing-angle full-color image. Examples of such full-color images include historical sites or portraits. Historical sites and portraits are suitable as pictures when applied to articles. In addition, with the display <NUM> according to the embodiment of the present invention, a symbolic image can be formed as a full-color image, thus providing an impressive article. In the above description, as shown in <FIG>, the protrusions 111a are disposed on the upper surface of the reflective layer <NUM>. However, a person skilled in the art would appreciate that the display <NUM> according to the present embodiment can achieve similar functions and effects even if recesses (not shown) are disposed on the upper surface of the reflective layer <NUM> instead of the protrusions 111a.

Details of a method for manufacturing a display as described above and characteristics of the display produced by the manufacturing method will now be described as Examples.

<FIG> illustrates the relationship between the dosage of irradiated electron beam and the height T of the protrusions 111a in the concavo-convex regions <NUM>, <NUM>, and <NUM> in the case where a commercially available electron beam resist (ZEP7000, manufactured by Nippon ZEON) is irradiated with an electron beam and immersed for development in diethyl malonate for <NUM> minutes.

<FIG> shows that the height T of the protrusions 111a can be adjusted by controlling the dosage of irradiated electron beams. The concavo-convex surface of the electron beam resist, which has protrusions and recesses formed by this adjustment, was subjected to nickel electroforming, to produce a nickel stamper having a thickness of <NUM>. The nickel stamper was pressure-bonded to a PET film coated with a photo-curable resin, and the photo-curable resin was cured by ultraviolet light, to form a light-transmitting layer <NUM>. Lastly, a layer of aluminum was formed on the concavo-convex surface of the light-transmitting layer <NUM> to have a thickness of <NUM> using a vacuum deposition apparatus, to form a reflective layer <NUM>.

<FIG> illustrates measured hues with respect to the height T of the protrusions 111a in the sub-pixels <NUM>, <NUM>, and <NUM> having the reflective layer <NUM> formed as described above. In each of the sub-pixels <NUM>, <NUM>, and <NUM>, rectangular protrusions 111a, each having a side of <NUM>, are irregularly arranged in the concavo-convex regions <NUM>, <NUM>, and <NUM> at an area ratio of <NUM>%. Therefore, the concavo-convex height T, which is indicated on the horizontal axis in <FIG>, corresponds to the height of the protrusions 111a in this case, but corresponds to the depth of recesses if these recesses are provided instead of the protrusions 111a on the surface of the reflective layer <NUM> on the light-transmitting layer <NUM> side.

The vertical axis in <FIG> represents the hue (H) in the HSV color system. In hue (H), red is <NUM> degrees or <NUM> degrees, green is <NUM> degrees, and blue is <NUM> degrees. In the present Example, the same hue appears repeatedly in circulation according to the height of the protrusions 111a. <FIG> shows that in the example configuration, red is obtained with the height of the protrusions 111a being approximately <NUM> or <NUM>. Similarly, green is obtained when the height of the protrusions 111a is approximately <NUM>, and blue is obtained when the height of the protrusions 111a is approximately <NUM>.

As described above, red is obtained with the height of the protrusions 111a being approximately <NUM> or <NUM>. As shown in <FIG>, at hues of red obtained with the height of the protrusions 111a of <NUM> corresponding to the hue of <NUM> degrees, variations in color with respect to the variation in the concavo-convex height (processing error) are smaller, which can produce stable color.

Likewise, green and blue can also be obtained with the protrusions 111a having a greater height than the height of the protrusions 111a mentioned above. However, excessively tall protrusions 111a make transfer formation difficult. For this reason, the height of the protrusions 111a is preferably up to <NUM>, and thus <NUM> and <NUM> are adopted for green and blue, respectively.

The height of the protrusions 111a is set according to each color, and the range of the height can be provided within a range in which color shifting is tolerable. The allowable range of the color shifting may be based on a class D tolerance defined by JIS Z <NUM> or a class C tolerance defined by JIS D <NUM>. In this case, the height of the protrusions 111a can be ±<NUM>, more preferably ±<NUM>, with respect to the abovementioned height.

When the height of the protrusions 111a is less than <NUM>, the phase difference to provide color (or to suppress non-target hues) is insufficient for any wavelength, so that a white screen will be displayed. Therefore, the minimum height of the protrusions 111a is preferably <NUM>.

From the results of <FIG> and <FIG>, the sub-pixel <NUM>, which emits red light, was irradiated with an electron beam of <NUM>µC per square centimeter to form a concavo-convex region <NUM> with protrusions 111a having a height of approximately <NUM>; the sub-pixel <NUM>, which emits green light, was irradiated with an electron beam of <NUM>µC per square centimeter to form a concavo-convex region <NUM> with protrusions 111a having a height of approximately <NUM>; and the sub-pixel <NUM>, which emits blue light, was irradiated with an electron beam of <NUM>µC per square centimeter to form a concavo-convex region <NUM> with protrusions 111a having a height of approximately <NUM>.

<FIG> illustrates the relationship of the brightness (V of the HSV color system) to the hue of <FIG>. In <FIG>, the brightness is a little over <NUM>% at the hue of <NUM> degrees, which provides green, and at the hue of <NUM> degrees, which provides blue. As described above, red is obtained when the hue is <NUM> degrees or <NUM> degrees. <FIG> shows that the brightness of red is a little over <NUM>% similarly to the brightness when the hue is <NUM> degrees, whereas the brightness is approximately <NUM>% when the hue is <NUM> degrees, thus deviating from the brightness of the other colors to become dark. Therefore, <NUM> degrees of hue is preferably adopted for red from the viewpoint of not only the stability of the hue described above but also the uniformity of the brightness.

A method for achieving a full-color image will now be described. First, an original image to be displayed is decomposed into pixels, and an average color for each pixel is obtained. In this case, the size of the pixel is set to <NUM> in length × <NUM> in width, although a resolution of about <NUM> is sufficient at the maximum because the resolution of an image only needs to allow an observer to recognize that a set of pixels constitutes the image. The size of of the sub-pixel <NUM> for providing red, the sub-pixel <NUM> for providing green, and the sub-pixel <NUM> for providing blue, included in each of the pixels, was <NUM> in length × <NUM> in width, that is, <NUM> square millimeters.

The colors of the obtained pixels were then decomposed into <NUM> tones of red, green, and blue. For example, for the color light orange, red = <NUM>, green = <NUM>, and blue = <NUM>.

Next, the areas of the concavo-convex region <NUM> for providing red, concavo-convex region <NUM> for providing green, and concavo-convex region <NUM> for providing blue, which are respectively included in the sub-pixel <NUM> for providing red, sub-pixel <NUM> for providing green, and sub-pixel <NUM> for providing blue, corresponded to the tones mentioned above. As a result, the area of the concavo-convex region <NUM> for emitting red was <NUM>/<NUM> × <NUM>, that is, <NUM> square millimeters. The area of the concavo-convex region <NUM> for emitting green was <NUM>/<NUM> × <NUM>, that is, approximately <NUM> square millimeters. The area of the concavo-convex region <NUM> for emitting blue was <NUM>/<NUM> × <NUM>, that is, approximately <NUM> square millimeters.

All the pixels <NUM> were produced as above to enable the display <NUM> to display a full-color image of the original image.

An article including a display <NUM> as described above will now be described.

The above-described display <NUM> can be adhered to printed matter or any other article via an adhesive or the like to, for example, prevent counterfeiting. As described above, the display <NUM> itself is difficult to counterfeit or fake. Therefore, when the display <NUM> is supported by an article, this article, which is authentic, is itself difficult to counterfeit or fake. Examples of an article include banknotes, cards, booklets, tags, seals, and the like.

<FIG> is a schematic plan view of an example article with a display.

<FIG> is a cross-sectional view of the article with a display, taken along the line X-X of <FIG>.

In <FIG>, printed matter <NUM> is depicted as an example of the article with a display. The printed matter <NUM> is an integrated circuit (IC) card and includes a support substrate <NUM>. The support substrate <NUM> is made of, for example, plastic. One main surface of the support substrate <NUM> has a recess in which an IC chip <NUM> is fitted. The IC chip <NUM> has its surface provided with electrodes through which information is written in or read from an IC. A print layer <NUM> is formed on the support substrate <NUM>. The display <NUM> described above is secured to a surface of the support substrate <NUM> on which the print layer <NUM> is formed via, for example, an adhesive layer. The display <NUM> is, for example, prepared as an adhesive sticker or a transfer foil, and is adhered to the print layer <NUM> so as to be secured to the support substrate <NUM>.

Thus, the printed matter <NUM> includes the display <NUM>, and is therefore difficult to counterfeit or fake. Furthermore, since the printed matter <NUM> includes the IC chip <NUM> and the print layer <NUM> in addition to the display <NUM>, anti-counterfeiting measures using these components can be taken.

In <FIG>, an IC card is illustrated as an example of printed matter including the display <NUM>, but this is not limiting. For example, the printed matter including the display <NUM> may be a magnetic card, a wireless card, or an identification (ID) card. Alternatively, the printed matter including the display <NUM> may be securities such as gift vouchers and stock certificates. Still alternatively, the printed matter including the display <NUM> may be a tag to be attached to an article that should be verified as authentic. Still alternatively, the printed matter including the display <NUM> may be a package or a part thereof for containing an article that should be verified as authentic.

In the printed matter <NUM> shown in <FIG>, the display1 is adhered to the support substrate <NUM>, but the display <NUM> may be supported by the support substrate <NUM> using other methods. For example, when paper is used as the support substrate <NUM>, the display <NUM> may be embedded in the paper, and the paper may have an opening at a position corresponding to the display <NUM>. Alternatively, if a light-transmitting material is used as the support substrate <NUM>, the display <NUM> may be embedded therein, and the display <NUM> may be secured to the back surface of the support substrate <NUM>, that is, a surface opposite to a display surface.

Furthermore, an article with a display is not limited to printed matter. That is, the display <NUM> may be supported by an article that does not include a print layer. For example, the display <NUM> may be supported by a luxury article such as an artwork.

The display <NUM> according to the first embodiment may be appropriately modified and implemented as follows.

The sub-pixels for providing colors may or may not include colors other than red, green, and blue. For example, in the case of a display composed of only red pixels, appropriately changing the saturation with the above-described method allows a red monotone image to be displayed.

It is known that a larger color gamut is obtained by adding a sub-pixel for providing yellow, cyan, or the like as a sub-pixel for providing a fourth color other than red, green, and blue. Since hues of yellow are <NUM> degrees, it can be understood from <FIG> that yellow can be provided by setting the height of protrusions 111a to approximately <NUM>. Since hues of cyan are <NUM> degrees, it can be understood from <FIG> that cyan can be provided by setting the height of protrusions 111a to approximately <NUM>.

By adding a sub-pixel for providing white as a sub-pixel that provides a fourth color other than red, green, and blue, it is possible to display an image with a bright impression by increasing the brightness. The color white can be provided by, for example, forming a shallow concavo-convex region or a concavo-convex region having uneven heights.

In addition, by making the flat portion 111c non-reflective or low reflective, a so-called black matrix can be formed to increase the contrast. Non-reflection or low reflection can be achieved by forming a so-called moth-eye structure on the flat portion 111c, or by printing or patterning black ink or black resist on the flat portion 111c after transfer formation.

A second embodiment will be described with reference to <FIG>. A display according to the second embodiment differs from the display according to the first embodiment described above in the shape of protrusions and recesses that form a concavo-convex surface. Such a difference will now be described in detail; the same reference signs as those in the first embodiment are assigned to the same configurations as those in the first embodiment, and detailed description thereof is omitted.

As illustrated in <FIG>, in the display <NUM> according to the second embodiment, the protrusions 111a are extended in the Y direction and are arranged irregularly in the X direction in the concavo-convex region <NUM>, the concavo-convex region <NUM>, and the concavo-convex region <NUM> on the upper surface of the reflective layer <NUM>. Each of the protrusions 111a may have a different length of the long side LL or a different length of the short side LS. In <FIG>, recesses (not shown) may be disposed instead of the protrusions 111a. The height T of the protrusions 111a (or the depth of the recesses) is set according to the colors displayed by the sub-pixel <NUM>, sub-pixel <NUM>, and sub-pixel <NUM>.

As shown in <FIG>, when an observer observes the display <NUM> from the direction OB1 parallel to the XZ plane, the reflected light R is scattered by the protrusions 111a, which are irregularly arranged in the X direction, at a wide elevation angle in the direction parallel to the XZ plane, so that the interference light is emitted. As described in the first embodiment, the interference color provided in this manner is substantially the same at a wide elevation angle.

In cases where an image of the display <NUM> is constituted by the sub-pixel <NUM> for providing red, sub-pixel <NUM> for providing green, and sub-pixel <NUM> for providing blue, each including such protrusions 111a, a full-color image of high visibility can be visually recognized from the direction OB1 at a wide elevation angle, similarly to the case described in the first embodiment.

In contrast, when the observer observes the display <NUM> from the direction OB2 parallel to the YZ plane as shown in <FIG>, the reflected light R is not scattered by the protrusions 111a, so that light other than the specular reflected light is not emitted in the direction OB <NUM>, and thus the image is generally concealed.

As described above, according to the display of the second embodiment, a full-color image can be visually recognized at a wide elevation angle in the direction OB1, while the image is concealed in the direction OB2. Therefore, the visual effect of the display <NUM> on the observer is further enhanced and counterfeiting of the display <NUM> is more difficult than in the case of displaying an image in all directions.

"Extended" as used herein means that the long side LL of the protrusions 111a is extended to <NUM> or more. When the length in the Y direction is <NUM> or more, scattering is less likely to occur in the Y direction, and interference light is less likely to be emitted in the direction OB2, thus ensuring concealment of the image. In the first embodiment, the length Lx of one side is set to <NUM> or less. In the second embodiment, the length of the short side Ls is preferably <NUM> or less. In this case, a greater amount of light is distributed in the direction OB than in the direction OB2, thereby increasing the directivity (directional dependency) and improving the visibility of the image.

A third embodiment will be described with reference to <FIG>. In the display of the second embodiment, only a single extension direction is considered for the protrusions or recesses constituting the concavo-convex surface, whereas in a display of the third embodiment, plural extension directions are considered for the protrusions or recesses constituting the concavo-convex surface. Such a difference will now be described in detail; the same reference signs as those in the first and second embodiments are assigned to the same configurations as those in the first and second embodiments, and detailed description thereof is omitted.

<FIG> is a partial plan view showing an example of the configuration of a concavo-convex region <NUM> in the display according to the third embodiment. The configuration of concavo-convex regions <NUM> and <NUM> will be similarly described with reference to <FIG>.

The concavo-convex region <NUM> includes both a sub-concavo-convex region 111v in which protrusions 111a are extended in the Y direction and are arranged irregularly in the X direction, and a sub-concavo-convex region <NUM> in which protrusions 111a are extended in the X direction and are arranged irregularly in the Y direction. As described in the second embodiment, the sub-concavo-convex region 111v having the protrusions 111a extending in the Y direction and arranged irregularly in the X direction emit interference light scattered in the direction OB1 parallel to the XZ plane.

Similarly, the sub-concavo-convex region <NUM> having the protrusions 111a extending in the X direction and arranged irregularly in the Y direction emit interference light scattered in the direction OB2 parallel to the YZ plane.

As described in the first embodiment, the interference color thus provided is substantially the same at a wide elevation angle. Here, the height T of the protrusions 111a (or the depth of recesses) in the sub-concavo-convex region 111v and the sub-concavo-convex region <NUM> is set according to the color displayed by the sub-pixel <NUM>.

Similarly, the height T of protrusions 111a (or the depth of recesses) in the sub-concavo-convex region 121v and the sub-concavo-convex region <NUM> is set according to the color displayed by the sub-pixel <NUM>, and the height T of protrusions 111a (or the depth of recesses) in the sub-concavo-convex region 131v and the sub-concavo-convex region <NUM> is set according to the color displayed by the sub-pixel <NUM>.

<FIG> illustrate the operation of the display <NUM> according to the third embodiment. <FIG> illustrates an example where an image showing the alphabet "A" is displayed in the direction OB1, while <FIG> illustrates an example where an image showing the alphabet "B" is displayed in the direction OB2. The reason why these different images can be displayed in different directions will be described below.

<FIG> illustrates a case where the observer observes the display <NUM> from the direction OB1. When an image showing the alphabet "A" is constituted by the sub-pixel <NUM> for providing red, sub-pixel <NUM> for providing green, sub-pixel <NUM> for providing blue, which respectively include the sub-concavo-convex region 111v, sub-concavo-convex region 121v, and sub-concavo-convex region 131v, the display <NUM> emits interference colors due to scattering of reflected light in the direction OB1 at a wide elevation angle, so that the observer can visually recognize the full-color image. In this case, the sub concavo-convex region <NUM>, sub concavo-convex region <NUM>, and sub concavo-convex region <NUM> do not emit light other than specular reflection light, and thus do not contribute to the configuration of an image.

<FIG> illustrates a case where the observer observes the display <NUM> from the direction OB2. When an image showing the alphabet "B" is constituted by the sub-pixel <NUM> for providing red, sub-pixel <NUM> for providing green, sub-pixel <NUM> for providing blue, which respectively include the sub-concavo-convex region <NUM>, sub-concavo-convex region <NUM>, and sub-concavo-convex region <NUM>, the display <NUM> emits interference colors due to scattering of reflected light in the direction OB2 at a wide elevation angle, so that the observer can visually recognize the full-color image. In this case, the sub concavo-convex region 111v, sub concavo-convex region 121v, and sub concavo-convex region 131v do not emit light other than specular reflection light, and thus do not contribute to the configuration of an image.

As described above, the display of the third embodiment can display a full-color image showing the alphabet "A" in the direction OB1, and display a full-color image showing the alphabet "B" in the direction OB2. As described above, since different full-color images can be visually recognized in different directions, the display of the third embodiment can further enhance the visual effect on the observer as compared with the case of displaying the same image in all directions or the case of displaying an image in only one direction, thus making it more difficult to counterfeit the display <NUM>.

While the best mode for carrying out the present invention has been described with reference to the accompanying drawings, the present invention is not limited to such a configuration. It is understood that various changes and modifications can be made by those skilled in the art within the scope of the appended claims, and these changes and modifications also belong to the technical scope of the present invention.

Claim 1:
A display (<NUM>) comprising plural pixels (<NUM>),
each of the pixels includes a first sub-pixel (<NUM>), a second sub-pixel (<NUM>), and a third sub-pixel (<NUM>),
each of the sub-pixels (<NUM>, <NUM>, <NUM>) includes a concavo-convex region (<NUM>, <NUM>, <NUM>) on a reflective surface on which incident light is reflected, wherein plural protrusions (111a) or recesses are arranged irregularly in the concavo-convex region,
in the first sub-pixel, the plural protrusions or recesses arranged in the concavo-convex region each have a first height (T) or depth configured to display a first color, the first height or depth is <NUM> ± <NUM>, wherein the saturation of the first color is adjustable by an area ratio of the concavo-convex region in the first sub-pixel, wherein the first color is red,
in the second sub-pixel, the plural protrusions or recesses arranged in the concavo-convex region each have a second height (T) or depth configured to display a second color, the second height or depth is <NUM> ± <NUM>, wherein the saturation of the second color is adjustable by an area ratio of the concavo-convex region in the second sub-pixel, wherein the second color is green, and
in the third sub-pixel, the plural protrusions or recesses arranged in the concavo-convex region each have a third height (T) or depth configured to display a third color, the third height or depth is <NUM> ± <NUM>, wherein the saturation of the third color is adjustable by an area ratio of the concavo-convex region in the third sub-pixel, wherein the third color is blue,
wherein the plural protrusions or recesses are extended in one direction and have a long side formed by this extension to have a length of <NUM> or more so as to provide an interference color in a specific direction.