Patent Description:
There is a color developing phenomenon created by periodic structures having a wavelength comparable to or smaller than the wavelength of light. In this color developing phenomenon, colors are developed by exclusively reflecting or transmitting light having a specific wavelength, through diffraction, interference and diffusion ascribed to the periodic structures, although the substances in the structures have no light absorbability. This color developing phenomenon is different from the one created by pigments, through electron transition ascribed to light absorption. Hereinafter, in the present specification, this color developing phenomenon using periodic structures is referred to as structural color development.

When periodic structures are formed, for example, of inorganic dielectric materials that are not deteriorated by ultraviolet light, the structural color development will not be impaired, as long as the structures are retained, even if the structures are left exposed to ultraviolet light.

Further, structural color development through diffraction and interference is characterized in that the recognized wavelength of light changes, depending on the observation angle, and therefore expressions with high designability can be accomplished.

As a color developing member for such structural color development, a color developing structure utilizing multilayer film interference is being proposed (Patent Literature <NUM>). This color developing structure includes a multilayer structure made of polymer materials having different refractive indices.

The color developing structure proposed in Patent Literature <NUM> has a multilayer structure made of polymer materials, and therefore there is only a small difference in refractive index of the materials forming the adjoining layers. Therefore, it is necessary to laminate a number of layers to accomplish intense reflection and thus the production cost increases. In addition, in the proposed structure, the influence of the multilayer film interference becomes dominant, and the color change depending on the observation angle becomes abrupt. Therefore, it is difficult to express specific colors.

As measures against these problems, another type of color developing member is being proposed (Patent Literature <NUM>). This color developing member provides intense reflection, and exhibits a moderate color change depending on the observation angle, as do Morpho butterflies inhabiting a natural environment.

Also, <CIT> discusses that it is desirable to provide a display device for which small size and space saving are attained. It proposes a display device which has a display unit, having an arrangement of a first structural color developing body developing red, a second structural color developing body developing green, and a third structural color developing body developing blue. The first structural color developing body, the second structural color developing body and the third structural color developing body comprise a substrate produced by arranging in XY directions, a great number of projections or recesses being square on a plan view with a width of <NUM> or smaller in X-direction which is more uniform as compared with that in Y direction, an indefinite length in the Y direction, and a height or depth of <NUM> or larger in Z direction; and a layered body formed by alternately depositing in the Z direction, high refractive index layers, having a high refractive index and low refractive index layers that have a low refractive index so as to follow the projections or recesses of the substrate.

<CIT> aims at providing a light reflecting functional body based on a color developing mechanism, which does not take on gray at a wide angle of view (blind angles) and develops a color depth function originating in the steepness of a prism at the wavelength of the objective developed color. It proposes using at least two materials different from each other in refractive index and light reflecting structures obtained by arranging a plurality of fine structures comprising the second material in the first material having light transmittance with regularity sufficient to develop a light reflecting function based on diffraction-scattering action disposed in at least two layers in a fibrous or film-like body.

However, it is difficult for the color developing member proposed in Patent Literature <NUM> to accomplish multi-hued color through a simple process.

Accordingly, the present invention has an object of providing a color developing structure capable of accomplishing multi-hued color through a simple process, and a method of producing the same.

The subject matter of the invention is claimed with the independent claims. Further, some preferred embodiments are claimed in the dependent claims.

In an example useful for understanding the background of the present invention, there is provided a color developing structure formed on a surface of a base material, characterized in that the color developing structure has a rectangular shape in plan view and is formed of a concavo-convex structure having a plurality of convexities with different heights and a laminated film including a plurality of layers laminated on the concavo-convex structure; the plurality of layers adjoining in a lamination direction are made of materials that transmit light of the same wavelength band and have different refractive indices with respect to light of the wavelength band; and each of the plurality of layers has a uniform film thickness.

Further, in another example useful for understanding the background of the present invention, there is provided a method of producing a color developing structure including a base material, a concavo-convex structure formed in a surface of the base material or on the base material, and a laminated film laminated on the concavo-convex structure, characterized in that the method includes: a step of preparing an imprinting mold having a predetermined structure formed on a surface of the mold; a step of forming the concavo-convex structure by transferring the structure formed on the mold to the base material by photo imprinting or thermal imprinting; and a step of forming the laminated film on the concavo-convex structure transferred to the base material by laminating materials that transmit light of the same wavelength band and have different refractive indices with respect to light of the wavelength band. In the method, the laminated film is formed of a plurality of layers and the film thickness of each of the plurality of layers is uniform.

The present invention provides a color developing structure that can accomplish multi-hued color through a simple process, and a method of producing the same.

In the invention, a wavelength band, which a color developing structure acts on, is determined by the line width and array pitches of convexities (concavities) forming a concavo-convex structure, and the refractive index and film thickness of the laminated film formed on the concavo-convex structure. The wavelength band which the color developing structure acts on as a target is not limited. However, the description is focused on a color developing structure targeting light of a visible region, in particular, referring to the figures. The visible region refers to light in a wavelength band in the range of <NUM> to <NUM>.

<FIG> are schematic diagrams each illustrating a concavo-convex structure A provided to induce a light dispersion effect in the color developing structure of the first embodiment. <FIG> is a schematic plan view, and <FIG> is a schematic cross-sectional view taken along the line α-α' of <FIG>. For the sake of convenience, in <FIG>, the direction in which the convexities forming the concavo-convex structure are arrayed in parallel is taken to be an x-direction, and the direction perpendicular to the x-direction and parallel to the direction in which the convexities extend is taken to be a y-direction. These directions are specified using the x-axis and the y-axis.

The concavo-convex structure A shown in <FIG> has flat convexities (protrusions) <NUM> made up of rectangles each having a line width of d1 in the x-direction and a line length of d1 or more in the y-direction. The rectangles are arrayed so as to overlap with one another neither in the x-direction nor in the y-direction. The line lengths in the y-direction of the rectangles forming the flat convexities <NUM> are selected from a population having a predetermined standard deviation. In the case of a color developing structure in the visible region, d1 is preferably <NUM> or less. For example, in the case of a blue color developing structure, d1 is preferably in the order of <NUM>. In the example of <FIG>, the rectangles configuring the convexities <NUM> are arrayed such that the rectangles do not overlap with one another in the x-direction. Therefore, in the example of <FIG>, the width in the x-direction of one convexity <NUM> is an integral multiple of d1.

It should be noted that the rectangles configuring the convexities <NUM> may be arrayed such that the rectangles overlap with one another in the x-direction to form the flat convexities <NUM>, and the width of one convexity <NUM> does not necessarily have to be an integral multiple of d1. Even when the width of one convexity <NUM> is not an integral multiple of d1, a light dispersion effect can be induced.

The concavo-convex structure A may have a structural height h1 designed to take an optimal value depending on the wavelength of light reflected at the surface of the color developing structure. A diffraction effect can be obtained as long as the structural height h1 is larger than the surface roughness of the laminated film described later. However, when the structural height h1 is excessively large, the diffusion effect of light is intensified and the chroma of the light reflected at the surface of the laminated film is impaired. Therefore, in the case of a color developing structure where a target wavelength band is in the visible region, it is preferable that h1 is generally in the range <NUM> to <NUM>. For example, in a blue color developing structure, it is preferable that h1 be in the order of <NUM> to <NUM> to achieve an effective diffusion of light. To reduce the diffusion effect, the structural height h1 is preferably <NUM> or less in a blue color developing structure.

<FIG> are schematic diagrams illustrating a concavo-convex structure B provided to induce diffraction in the color developing structure of the invention. <FIG>is a schematic plan view, and <FIG> is a schematic cross-sectional view taken along the line β-β' of <FIG>.

The concavo-convex structure B shown in <FIG> is formed being overlapped with the concavo-convex structure A shown in <FIG>, and is configured by convex linear structures <NUM>, also described as 'linear structures <NUM>' or'protruding strips <NUM>'. The x- and y-directions shown in <FIG> denote the same directions as the x- and y-directions shown in <FIG>, respectively. The linear structures <NUM> are designed such that at least part of the reflection is observed as first order diffracted light (diffraction order m = ±<NUM>). Therefore, when the incident angle, reflection angle and wavelength of diffracted light are designated as θ, φ and λ, respectively, then an array pitch d of the linear structures <NUM> in the x-direction needs to fulfill an inequality d ≥ λ/(sin θ + sin φ). For example, when visible light of λ = <NUM> is targeted, the array pitches of the linear structures <NUM> only need to be <NUM> or more.

The linear structure <NUM> has a line width d2 in the x-direction which may be equal to or different from the line width d1 of the concavo-convex structure A shown in <FIG>.

The array pitches of the linear structures <NUM> are reflected on the periodicity of the concavo-convex structure of the outermost surface of a laminated film described latter. Therefore, when the array pitches of the linear structures <NUM> are constant, light having a specific wavelength is reflected at a specific angle due to the diffraction phenomenon at the surface of the color developing structure. The reflection intensity of light reflected due to the diffraction phenomenon is extremely high compared to the reflection intensity of light obtained due to the light dispersion effect of the concavo-convex structure A shown in <FIG>. Therefore, intense light resembling a metallic luster can be visually recognized; however, the light is dispersed in relation to a change in observation angle. Specifically, the concavo-convex structure A shown in <FIG> may be designed to serve as a color developing structure exhibiting a blue color, for example. In this case, however, if the array pitches of the linear structures <NUM> are designed to be constant in the order of <NUM> to <NUM>, surface reflection of intense green to red colors will be generated by diffraction, depending on the observation angle. If the array pitches of the linear structures <NUM> are designed to be larger in the order of <NUM>, for example, the angular range of light diffracted in the visible region is narrowed, and therefore colors having a specific wavelength are unlikely to be visually recognized, but only a glitter like metallic luster is exhibited at a specific observation angle.

In the case where the linear structures <NUM> are formed by overlapping a plurality of periodic structures having different periodicity, wavelengths of light reflected by a diffraction phenomenon are intermingled, and therefore dispersed light of high monochromaticity is unlikely to be visually recognized. However, as the standard deviation of periodicity becomes larger, the diffusion effect becomes more dominant, and intense reflection produced by a diffraction phenomenon is not obtained.

In this regard, the periodicity of the linear structures <NUM> can be determined based on a diffusion angle which depends on the light dispersion effect exerted by the concavo-convex structure A shown in <FIG>. For example, blue light may be diffused in an angular range of ±<NUM>° with respect to the incident angle. In this case, if the array pitches of the linear structure <NUM> are in the order of <NUM> to <NUM> with a standard deviation being in the order of <NUM>, reflection due to the diffraction phenomenon is generated in an angular range commensurate with the diffusion angle due to the light dispersion effect of the concavo-convex structure A.

To produce a diffraction phenomenon of longer periodicity, the linear structures <NUM> may be formed with an average array pitch being in the order of <NUM> to <NUM> and with a standard deviation being in the order of <NUM>, for location in a rectangular region having sides of <NUM> to <NUM>, and such rectangular regions may be arrayed without overlapping the adjacent regions.

Further, the linear structures <NUM> having a given periodicity may be formed in the rectangular region having sides of <NUM> to <NUM>, with the structural period being selected from a range <NUM> to <NUM>. In this case as well, an equivalent effect can be anticipated with the resolution of the human eyes, as long as the periodicity of the linear structures of either of adjoining rectangular regions differs from the other within a range of variation that is comparable to a standard deviation of <NUM>.

The linear structures <NUM> of <FIG> are arrayed only in the x-direction. However, the light dispersion effect exerted by the concavo-convex structure A shown in <FIG> partially has an influence in the y-direction as well. Therefore, the linear structures <NUM> of <FIG> may also have periodicity in the y-direction. In this case, the average of array pitches of the linear structures <NUM> in the x- and y-directions may be <NUM> or more and <NUM> or less. Further, the periodicity of the linear structures <NUM> may be designed such that the average value and/or standard deviation of the array pitches differ, depending on the influence of the light dispersion effect, in the x- and y-directions, of the concavo-convex structure A shown in <FIG>.

The linear structure <NUM> has a structural height h2 larger than the surface roughness of a laminated film described later, similarly to the structural height h1 of the convexity <NUM> of the concavo-convex structure A. However, as the value of h2 increases, the diffraction effect of the linear structures <NUM> becomes more dominant. In addition to the diffraction efficiency becoming excessively high due to the linear structures <NUM>, the diffusion effect of the concavo-convex structure is enhanced by the multilevel structure. Therefore, there is a concern that the light dispersion effect of the concavo-convex structure A shown in <FIG> cannot be sufficiently obtained. Therefore, h2 may preferably be comparable with or equal to h1. For example, in a blue color developing structure, h2 is preferably in the order of <NUM> to <NUM>.

<FIG> are schematic diagrams illustrating a concavo-convex structure obtained by overlapping the concavo-convex structure A shown in <FIG> with the concavo-convex structure B shown in <FIG>. <FIG> is a schematic plan view, and <FIG> is a schematic cross-sectional view taken along the line γ-γ' of <FIG>. The x- and y-directions shown in <FIG> denote the same directions as the x- and y-directions shown in <FIG> and <FIG>, respectively.

The concavo-convex structure includes overlapped portions <NUM> in each of which the convexity <NUM> of the concavo-convex structure A shown in <FIG> overlaps the linear structure <NUM> of the concavo-convex structure B shown in <FIG>. Each overlapped portion <NUM> has a height that is a sum of h1 and h2. This color developing structure is designed such that the concavo-convex structure A for inducing the light dispersion effect and the concavo-convex structure B for inducing the diffraction phenomenon are overlapped with each other. However, the effect of the present invention can also be obtained if the color developing structure is designed such that the concavo-convex structures are not overlapped with each other. However, in this case, the concavo-convex structure for inducing the light dispersion effect cannot be formed in the region where the linear structures <NUM> are formed, and the region for forming the concavo-convex structure for inducing the light diffusion effect becomes small. Therefore, the structure is preferably a multilevel structure as shown in <FIG>.

To create the concavo-convex structure shown in <FIG> on a base material, a well-known technique, such as electron beam or optical lithography and dry etching, may be used.

<FIG> are schematic cross-sectional views illustrating an example of a color developing structure according to the invention. The color developing structure shown in <FIG> includes a base material <NUM> and a laminated film <NUM> formed on the base material <NUM>. The base material <NUM> is made of synthetic quartz, with its surface being formed with the concavo-convex structure shown in <FIG>. The laminated film <NUM> includes <NUM> layers made of two materials that are transparent and have different refractive indices with respect to light in the visible region. The laminated film <NUM> is configured by alternately laminating high refractive index layers <NUM> and low refractive index layers <NUM>. A high refractive index layer <NUM> is formed on the surface of the base material <NUM>, and a low refractive index layer <NUM> is formed at the outermost surface of the color developing structure. The wavelength of light reflected at the surface of the laminated film <NUM> is determined by the refractive indices and film thicknesses of the materials forming the high refractive index layers <NUM> and the low refractive index layers <NUM> and the refractive index of the base material <NUM>. Therefore, the laminated film <NUM> may be designed using a transfer matrix method or the like so that light with a desired wavelength is reflected. Further, as the difference in refractive index becomes larger between the material forming the high refractive index layers <NUM> and the material forming the low refractive index layers <NUM>, a higher refractive index can be obtained with fewer laminated layers. For example, when inorganic materials are used, it is preferable to use titanium dioxide (TiO<NUM>) for the high refractive index layers <NUM> and silicon dioxide (SiO<NUM>) for the low refractive index layers <NUM>. For example, in the case of a blue color developing structure, it is preferable that the thickness of TiO<NUM> be in the order of <NUM>, and the thickness of SiO<NUM> be in the order of <NUM>. However, as long as there is a difference in refractive index between the materials forming adjoining layers, reflection occurs at the interface. Therefore, the combination of materials is not limited to the one mentioned above. Further, in the case of forming the laminated film <NUM> with the inorganic materials mentioned above, a well-known technique can be used, such as sputtering, atomic layer deposition, or vacuum vapor deposition. The materials forming the laminated film <NUM> may be organic materials. In the case of forming the laminated film <NUM> with organic materials, a well-known technique, such as self-organization, can be used.

The materials forming the color developing structure <NUM> shown in <FIG> are all transparent to light in the visible region. Accordingly, the color developing structure transmits light other than the light in a reflecting wavelength band. Therefore, when the rear surface of the base material <NUM> is, for example, white paper, the light in the wavelength band transmitted by the color developing structure <NUM> is unavoidably visually recognized as a color. Therefore, as shown in <FIG>, an absorption layer <NUM> made of a material, such as carbon, may be formed on the rear surface of the base material to absorb light in the visible region. The absorption layer <NUM> absorbs light that has been transmitted through the color developing structure <NUM> and improves the contrast of light reflected by the color developing structure.

To form the concavo-convex structure shown in <FIG>, thermal or optical nanoimprinting can be applied using an original plate that has been prepared by a well-known technique, such as a combination of electron beam or optical lithography with dry etching.

<FIG> are schematic cross-sectional views illustrating another example of the color developing structure of the first embodiment. The color developing structure shown in <FIG> includes the concavo-convex structure shown in <FIG> formed through optical nanoimprinting. More specifically, this concavo-convex structure is formed by applying a photo-curable resin <NUM> onto a surface of a base material <NUM>, and forming the concavo-convex structure shown in <FIG> in the photo-curable resin through optical nanoimprinting, followed by forming the laminated film <NUM> and the absorption layer <NUM>. The absorption layer <NUM> may be formed in advance on the rear surface of the base material <NUM> before application of the photo-curable resin <NUM>. However, in this case, the light used for curing the photo-curable resin <NUM> needs to be irradiated not from the rear surface side of the base material <NUM>, but from the front surface side of the base, that is, from the original plate side. When this method is used, the base material <NUM> does not need to have the transmissivity of the wavelength of the light irradiated at the time of optical nanoimprinting. As shown in <FIG>, the absorption layer <NUM> may be formed on the surface of the base material <NUM>, and the photo-curable resin <NUM> may be applied onto the surface of the absorption layer <NUM>, followed by optical nanoimprinting. As shown in <FIG>, the color developing structure may include a base material <NUM> made of a material that absorbs light in the visible region. For example, a carbon nanotube-dispersed polymer film may be used as the material for forming the base material <NUM>.

In a conventional concavo-convex structure, when the height of the structure is increased to enhance the light dispersion effect, color change due to the change in observation angle becomes moderate due to the increased light diffusion effect. However, the increase of height may impair color contrast, in addition to causing shifting of the reflection wavelength to the long wavelength side. Further, glossiness may be lost due to the diffusion effect. When a metallic thin film is inserted between the multilayer film and the base material to add glossiness, light in the visible region transmitted through the multilayer film is reflected by the metallic thin film and impairs color contrast. On the other hand, when the height of the concavo-convex structure is decreased to reduce the diffusion effect, light cannot be sufficiently diffused and color change due to the change in observation angle becomes abrupt.

According to the color developing structure and the method of producing the same of the first embodiment, multi-hued color can be accomplished through a simple process. The color developing structure of the first embodiment includes a concavo-convex structure in which the concavo-convex structure A for inducing a light dispersion effect is overlapped with the concavo-convex structure B for inducing a diffraction phenomenon. Accordingly, chroma or glossiness is prevented from being deteriorated in color development, while moderating color change due to the change in observation angle.

The elements and items described in relation to <FIG> are not a part of the invention.

<FIG> is a plan view illustrating a configuration of a display member <NUM>. This is not a part of the invention.

Specifically, the display member <NUM> shown in <FIG> includes a base material <NUM> whose surface is formed with a plurality of pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>). In <FIG>, for the sake of clarity, only two pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>) are illustrated. However, the display member <NUM> of the present embodiment may include three or more pixel regions <NUM>. In <FIG>, the two pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>) are illustrated as having the same size. However, the plurality of pixel regions <NUM> may have different sizes. There are four alignment marks <NUM> arrayed on the surface of the base material <NUM>. The pixel regions <NUM> are arrayed according to the alignment marks <NUM> such that the x- and y-directions of the pixel regions <NUM> agree with the x- and y-directions of the base material <NUM>, respectively. As described later, the alignment marks <NUM> are formed and arrayed at the time when the pixel region <NUM> is initially formed on the base material <NUM>.

<FIG> and7B are cross-sectional views showing configuration examples of the pixel region <NUM>. <FIG>is a vertical cross-sectional view in the x-direction of the pixel region <NUM> (#<NUM>) shown in <FIG>. <FIG> is a vertical cross-sectional view in the x-direction of the pixel region <NUM> (#<NUM>) shown in <FIG>.

Specifically, as shown in <FIG>, the pixel region <NUM> (#<NUM>) includes a concavo-convex structure <NUM> (#<NUM>), and a laminated film <NUM> (#<NUM>) laminated on the concavo-convex structure <NUM> (#<NUM>). The laminated film <NUM> (#<NUM>) is made up of a plurality of layers <NUM> (#<NUM>-<NUM>) to <NUM> (#<NUM>-<NUM>) (ten layers herein as an example). Further, convexities <NUM> (#<NUM>) and concavities <NUM> (#<NUM>) are formed conforming to the unevenness of the concavo-convex structure <NUM> (#<NUM>).

Similarly, as shown in <FIG>, the pixel region <NUM> (#<NUM>) includes a concavo-convex structure <NUM> (#<NUM>), and a laminated film <NUM> (#<NUM>) laminated on the concavo-convex structure <NUM> (#<NUM>). The laminated film <NUM> (#<NUM>) is made up of a plurality of layers <NUM> (#<NUM>-<NUM>) to <NUM> (#<NUM>-<NUM>) (ten layers herein as an example). Similarly, convexities <NUM> (#<NUM>) and concavities <NUM> (#<NUM>) are formed conforming to the unevenness of the concavo-convex structure <NUM> (#<NUM>).

Such a concavo-convex structure <NUM> is formed, for example, by using a well-known technique, such as lithography using irradiation of light or charged particle beams, or dry etching.

In the display member <NUM>, among the plurality of pixel regions <NUM> formed on the surface of the base material <NUM>, at least two are different in the height of the convexities (hereinafter referred to as "structural height") in the concavo-convex structure <NUM>. Specifically, in the example shown in <FIG> and <FIG>, the pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>) are different in the structural height dz of the concavo-convex structures <NUM>. More specifically, the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) is different from the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>).

In the method of production, lithography using irradiation of light or charged particle beams, or dry etching is performed n times (n=<NUM> in the example of <FIG>) to thereby form pixel regions <NUM> (the pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>) in the example of <FIG>) in n locations with different structural heights dz in the concavo-convex structures <NUM>.

When using lithography that uses irradiation of charged particle beams, and when the base material <NUM> is made of an insulating material, such as synthetic quartz, it is preferable that an electrically conductive film made of chromium (Cr) and the like is formed on the base material <NUM> prior to each lithography process. If the Cr film is formed as an electrically conductive film, Cr needs to be dry-etched before etching the synthetic quartz, using a resist formed in the lithography process as a mask. To form a resist pattern, optical or thermal imprinting may be used.

In the method of production, structural heights dz (#<NUM>) and dz (#<NUM>) of the pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>), respectively, are controlled by, for example, adjusting the etching time in each dry etching process. The etching time in each dry etching process may be adjusted such that, for example, when the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) is larger than the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>), the etching time of the pixel region <NUM> (#<NUM>) may be made longer than the etching time of the pixel region <NUM> (#<NUM>).

In the case of forming the pixel region <NUM> (#<NUM>) after forming the pixel region <NUM> (#<NUM>), alignment marks <NUM> are formed on the surface of the base material <NUM> at the time of forming a resist pattern of the pixel region <NUM> (#<NUM>) thereon. Then, in the lithography process of forming the pixel region <NUM> (#<NUM>), the pixel region <NUM> (#<NUM>) is ensured to be accurately formed at a desired position without overlapping the pixel region <NUM> (#<NUM>), by correcting the position with reference to the coordinates of the alignment marks <NUM>.

The thickness of each of the layers <NUM> (<NUM> (#<NUM>-<NUM>) to <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) to <NUM> (#<NUM>-<NUM>) is uniform, irrespective of the pixel region <NUM>.

Further, two vertically adjoining layers (for example, layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>)) are made of different materials that transmit light of the same wavelength region and have different refractive indices in this wavelength region. The types of materials of the layers <NUM> and the number of layers <NUM> may be designed as appropriate depending on desired requirements.

<FIG> and <FIG> show, as an example, a laminated film including a total of ten layers, that is, alternate lamination often layers made of two types of materials. Specifically, of the layers <NUM>, the layers <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), and <NUM> (#<NUM>-<NUM>) are made of a first material. Further, the layers <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), <NUM> (#<NUM>-<NUM>), and <NUM> (#<NUM>-<NUM>) are made of a second material. Further, a third material may be used for the layers <NUM>. Specifically, the number of types of materials for forming the laminated film is not limited to two, as long as the materials have different refractive indices.

The laminated film <NUM> of the pixel region <NUM> is laminated through one laminating process under the same film forming conditions. Therefore, the thickness of each layer <NUM> forming the laminated film <NUM> will be the uniform under ideal conditions where deformation or the like is not considered. This thickness may be designed to be a desired thickness using a transfer matrix method or the like.

In the method production, among the layers <NUM> forming the laminated film <NUM>, the layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of high refractive index are formed first on the surface of the base material <NUM>. Then, the layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of low refractive index are formed on the layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of high refractive index, respectively. Thereafter, the layers of high refractive index and the layers of low refractive index are alternately formed, e.g., layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of high refractive index, and then, layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of low refractive index, respectively, and so on. Finally, the layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>) of low refractive index are formed at the very top surface. However, the order of laminating layers of high refractive index and layers of low refractive index is not limited to the order mentioned above.

As the difference in refractive index becomes larger between the material of the layers <NUM> (for example, layer <NUM> (#<NUM>-<NUM>)) of high refractive index and the material of the layers <NUM> (for example, layer <NUM> (#<NUM>-<NUM>)) of low refractive index, a higher reflectance can be accomplished with fewer laminated layers.

For example, when using inorganic materials, it is preferable to use titanium dioxide (TiO<NUM>) for the layers <NUM> (for example, layer <NUM> (#<NUM>-<NUM>)) of high refractive index, and silicon dioxide (SiO<NUM>) for the layers <NUM> (for example, layer <NUM> (#<NUM>-<NUM>)) of low refractive index. However, reflection of light at the interface occurs due to the difference in refractive index of the materials forming the vertically adjoining layers <NUM> (for example, layers <NUM> (#<NUM>-<NUM>) and <NUM> (#<NUM>-<NUM>)), and therefore the material combination is not limited to the one mentioned above. As will be described later, organic materials can also be used for the layers <NUM>.

When forming the laminated film <NUM> (layers <NUM>) with inorganic materials such as those mentioned above, a well-known technique may be used, such as sputtering, atomic layer deposition, or vacuum vapor deposition. When forming the laminated film <NUM> (layers <NUM>) with organic materials, a well-known technique, such as self-organization, may be used.

<FIG> shows an example of an XY plan view of the pixel region <NUM> as seen from above in <FIG> and <FIG>. This figure corresponds to the planar distribution in the concavo-convex structure <NUM>. In the figure, the regions of rectangles <NUM> shown in black correspond to the convexities <NUM>, and all other portions <NUM> shown in white correspond to the concavities <NUM>.

<FIG> is a cross-sectional view taken along the line A-A of <FIG>. The protruded portions are the convexities <NUM>, and the recessed portions are the concavities <NUM>. It should be noted that <FIG> and <FIG> correspond to specific cross-sectional views taken along the line B-B of <FIG>.

As is clear from the above, the two-dimensional distribution of the protrusions and recesses illustrated in <FIG> corresponds to the two-dimensional distribution in the concavo-convex structure <NUM>.

Such a two-dimensional distribution is so accomplished that the plurality of rectangles <NUM> are arrayed without being overlapped with each other on the XY plane. The x- and y-directions of these rectangles <NUM> agree with the x- and y-directions of the pixel region <NUM>. In each pixel region <NUM>, the plurality of rectangles <NUM> have a given length dx in the x-direction.

In each pixel region <NUM>, the plurality of rectangles <NUM> each have a length dy in the y-direction which is not less than the length dx of the plurality of rectangles <NUM> in the x-direction, and not more than a length Ly of the pixel region <NUM> in the y-direction.

In each pixel region <NUM>, the length dy of the plurality of rectangles <NUM> in the y-direction conforms to a normal distribution.

In each pixel region <NUM>, whether the rectangles <NUM> are arrayed or not is determined according to a fixed probability. Alternatively, in each pixel region <NUM>, the array of the rectangles <NUM> may be determined such that the ratio of the area for arraying the rectangles <NUM>, to the area not containing the rectangles <NUM> takes a predetermined value. <FIG> shows an example where the ratio of the area for arraying the rectangles <NUM>, to the area not containing the rectangles <NUM> is <NUM>: <NUM>. Specifically, in the example of <FIG>, the total area of regions occupied by the black rectangles <NUM> is equal to the total area of other white portions <NUM>.

In the display member <NUM> configured in this way, the wavelength region of the light used as incident light is not particularly limited. The following description is provided by way of an example of using a visible light wavelength region as incident light. The visible light wavelength region as mentioned in the present invention refers to a wavelength band of <NUM> to <NUM>.

Specifically, when visible light is used as incident light, the materials forming the display member <NUM> that is produced by the method of production of the present embodiment all transmit light in the visible light wavelength region. For example, the base material <NUM> may be made of a material transmitting light in the visible light wavelength region as synthetic quartz does. Further, for example, titanium dioxide (TiO<NUM>) may be applied to the layers <NUM> (for example, the layer <NUM> (#<NUM>-<NUM>)) of high refractive index, and silicon dioxide (SiO<NUM>) to the layers <NUM> (for example, the layer <NUM> (#<NUM>-<NUM>)) of low refractive index, in the laminated film <NUM>. Other examples of the material having high transmissivity with respect to the visible light wavelength region include inorganic dielectric materials, such as Nb<NUM>O<NUM>, Ta<NUM>O<NUM>, Al<NUM>O<NUM>, Fe<NUM>O<NUM>, HfO<NUM>, MgO, ZrO, SnO<NUM>, Sb<NUM>O<NUM>, CeO<NUM>, WO<NUM>, PbO, In<NUM>O<NUM>, CdO, BaTiO<NUM>, ITO, LiF, BaF<NUM>, CaF<NUM>, MgF<NUM>, AlF<NUM>, CeF<NUM>, ZnS, and PbCl<NUM>; and organic resin materials, such as an acrylic resin, a phenolic resin, and an epoxy resin. These materials may be used as appropriate.

In this way, the display member <NUM> transmits all types of light in the visible light wavelength region. Therefore, when using color development ascribed to reflection in the display member <NUM>, the base material <NUM> or the rear surface thereof is preferably formed of a material absorbing light in the visible light wavelength region. Alternatively, a light absorbent may be applied onto the front surface of the base material <NUM> to obtain color development ascribed to reflection from the rear surface.

The size of the pixel region <NUM> may be determined based on the resolution of the image to be displayed. In order to display a higher precision image, each side of the pixel region <NUM> is preferably <NUM> or more. Specifically, it is preferable that the length Lx in the x-direction and the length Ly in the y-direction are <NUM> or more in the pixel region <NUM> shown in <FIG>.

To develop a sharper color in the pixel region <NUM>, the light diffusion effect exerted by the concavo-convex structure <NUM> is preferably made larger. To accomplish this, the concavo-convex structure <NUM> in the pixel region <NUM> preferably has the area ratio of <NUM>: <NUM>, as an example, between the concavities and the convexities as mentioned above.

Further, to more enhance the light dispersion effect of the display member in the pixel region <NUM>, the length dx of the rectangles <NUM> in the x-direction in <FIG> needs to be adjusted for each desired color. For example, when using visible light as incident light, it is preferable that the length dx of each rectangle <NUM> in the x-direction is <NUM> or less. When using the pixel region <NUM> as a blue pixel among various colors of visible light, the length dx of each rectangle <NUM> in the x-direction is preferably in the order of <NUM>. However, even if the length dx is not adjusted for each color, the light dispersion effect of the display member can be exerted.

The structural height dz in the pixel region <NUM> is determined, depending on the desired color. Specifically, the optimal values of the structural height dz (#<NUM>) of the concavo-convex structure <NUM> (#<NUM>) and the structural height dz (#<NUM>) of the concavo-convex structure <NUM> (#<NUM>) shown in <FIG> and <FIG>, respectively, are determined based on the wavelength of light which is color-developed in the pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>), taking account of the length dx of the rectangles <NUM> in the x-direction shown in <FIG>.

Let us take an example, herein, where the wavelength of reflection in the laminated film <NUM> is <NUM>. In this case, when green is desired to be produced, the length dx of each rectangle <NUM> in the x-direction is preferably in the order of <NUM>, and the structural heights dz (#<NUM>) and dz (#<NUM>) are each preferably in the order of <NUM>. Also, when red is desired to be produced, the length dx of each rectangle <NUM> in the x-direction is preferably in the order of <NUM>, and the structural heights dz (#<NUM>) and dz (#<NUM>) are each preferably in the order of <NUM>.

The pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>) are designed to develop different colors by setting the structural heights dz to different values. Specifically, as the difference becomes larger between the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) and the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>), the difference in color becomes more prominent, and the difference in color comes to be perceptible even to the human eye. In this regard, as an example, the difference between the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) and the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) is designed to be <NUM> or more. When the wavelength of reflection in the laminated film <NUM> is <NUM>, <NUM> corresponds to <NUM>% thereof. In this way, it is preferable that the difference between the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) and the structural height dz (#<NUM>) of the pixel region <NUM> (#<NUM>) is <NUM>% or more of the wavelength of light reflected by the laminated film <NUM>.

In this way, the wavelength band of light to be used is used as a basis for determining the length Lx in the x-direction and the length Ly in the y-direction of each side of the pixel region <NUM>, the difference in the structural height dz between the plurality of pixel regions <NUM>, and the length dx of each rectangle <NUM> in the x-direction.

As described above, a display member <NUM> capable of expressing hues with a single multi-layer laminated film can be produced through a simple production process without having to perform a complicated production process.

In particular, since a uniform laminated film <NUM> including a plurality of (for example, ten) layers <NUM> is formed on all the pixel regions <NUM> (for example, pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>)), masking and lamination do not have to be repeated by the number of times corresponding to the desired number of colors. Thus the display member <NUM> expressing multi-colors can be produced through a single laminating process.

In this way, the simplified production process can curb the reduction of productivity of the display member <NUM>.

With the display member <NUM> produced through such a method of production, physical thickness of the laminated film <NUM> becomes uniform between different pixel regions <NUM> (for example, pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>)), and therefore color mixing between adjoining pixel regions (for example, pixel regions <NUM> (#<NUM>) and <NUM> (#<NUM>)) will not occur. Further, the color for each pixel region <NUM> can be easily controlled by adjusting the structural height dz and the length dx in the x-direction of the pixel region <NUM>. Accordingly, the fine pixel regions <NUM> can be sharply expressed, and thus high designability is accomplished.

<FIG> is a cross-sectional view illustrating a configuration example of a pixel region of a display member, which is not a part of the invention. This configuration corresponds to the one shown in <FIG>.

In <FIG>, like reference signs are assigned to like portions to avoid duplicate description. The following description is focused on differences with the above description.

Specifically, as shown in the cross-sectional view of <FIG>, the display member is different in that a concavo-convex structure is formed in a resin layer <NUM> formed between the laminated film <NUM> and the base material <NUM>.

The resin layer <NUM> is made of a photo-curable resin which is applied onto the surface of the base material <NUM> when, for example, forming the concavo-convex structure <NUM> through optical nanoimprinting.

In the method, the concavo-convex structure <NUM> is formed on the photo-curable resin <NUM>. In this case, it is necessary to prepare a photo imprinting mold which is designed to have desired structural heights dz for respective pixel regions <NUM>.

To prepare an imprinting mold with different structural heights dz for respective pixel regions <NUM>, lithography and dry etching may be repeated, as described in the second embodiment, every time a pixel region <NUM> is formed. Alternatively, an imprinting mold can be prepared more simply. To this end, for example, a method of preparing an imprinting mold made of Ni may be used. In this method, the dose of charged particle beams irradiated to a resist in charged particle beam lithography is changed for each pixel region <NUM>, and the developing time is adjusted such that a desired structural height dz is obtained in each pixel region <NUM>, followed by forming a metal film such as of Ni on the formed resist pattern, which is further followed by electroforming to dissolve the resist, thereby obtaining the Ni imprinting mold.

With this method of production as well, the display member <NUM> can be produced.

According to the display member and the method of producing the same, multi-hued color can be provided through a simple process. Further, a uniform laminated film is formed on all the pixel regions, and therefore masking and lamination need not be performed a number of times corresponding to the desired number of colors. Thus, a display member expressing multi-colors can be produced through a single laminating process. In this way, the simplified production process can curb the reduction of productivity of the display member. Further, the laminated film will have a uniform physical thickness between different pixel regions, and therefore color mixing between adjoining pixel regions does not occur. Accordingly, the fine pixel regions can be sharply expressed, and thus high designability is accomplished.

In the foregoing a display member which is not a part of the invention has been described, in which a plurality of pixel regions each include a concavo-convex structure and a laminated film laminated on the concavo-convex structure. However, the configuration is not limited to this. For example, it may be so configured that a color developing structure made up of a concavo-convex structure and a laminated film laminated on the concavo-convex structure is formed in a plurality of pixel regions.

Referring to the drawings, the following description addresses Example <NUM> for preparing the color developing structure according to the invention.

<FIG> are schematic diagrams each illustrating a concavo-convex structure provided to the color developing structure of Example <NUM>. <FIG> is a schematic plan view illustrating part of a region of the concavo-convex structure A for inducing the light dispersion effect. <FIG> is a schematic plan view illustrating part of a region of the concavo-convex structure B formed of linear structures for inducing a diffraction phenomenon. <FIG> is a schematic plan view illustrating a concavo-convex structure where the concavo-convex structure A shown in <FIG> and the concavo-convex structure B shown in <FIG> are overlapped with each other. Further, <FIG> is a schematic cross-sectional view taken along the line δ-δ' of <FIG>. The schematic plan views of <FIG>, <FIG>, and <FIG> each illustrate an enlarged microscopic region of about <NUM> on each side, on the surface of the color developing structure. The color developing structure was prepared through optical nanoimprinting. However, a thermal nanoimprint method may be used for the preparation.

Convexities <NUM> shown in <FIG> are made up of rectangles each having a line width d3 of <NUM> in the x-direction and a line length selected from integral multiples of not less than twice of d3 in the y-direction, with the average being <NUM> and standard deviation being <NUM>. The rectangles were so designed as to be arrayed in the x- and y-directions, at a pitch of <NUM> in the x-direction, allowing the rectangles to be overlapped with each other in the x-direction, but not allowing them to be overlapped with each other in the y-direction. Regions where the rectangles were overlapped with each other in the x-direction to form a plurality of layered structures were approximated to a single-layer structure.

Linear structures <NUM> shown in <FIG> include rectangles each having a line width d4 of <NUM> in the x-direction and a line length of <NUM> in the y-direction. These rectangles were arrayed at an average pitch of <NUM> in the x-direction and a standard deviation of <NUM>, in a rectangular region having a length of <NUM> in the x-direction and a length of <NUM> in the y-direction. Such linear structures were so designed as to be arrayed at an average pitch of <NUM> in the x-direction and a standard deviation of <NUM>, and at an average pitch of <NUM> in the y-direction and a standard deviation of <NUM>. Regions where the rectangles were overlapped with each other in the x-direction or the y-direction to form a plurality of layered structures were approximated to a single-layer structure.

First, an optical nanoimprinting mold was prepared. Specifically, since the wavelength of the light irradiated during optical nanoimprinting was <NUM>, synthetic quartz that transmits light of this wavelength was used as a material for the mold. A film of Cr was formed by sputtering on a surface of a synthetic quartz base plate, followed by electron beam lithography to thereby form an electron beam resist pattern. The electron beam resist used was of a positive type, and had a thickness of <NUM>. Electron beam irradiating regions were the regions corresponding to the rectangular structures <NUM> shown in <FIG>. High frequency waves were applied to a mixed gas of chlorine and oxygen, and the generated plasma was used for etching to remove Cr in the regions where the surfaces were exposed. Then, high frequency waves were applied to a hexafluoroethane gas, and the generated plasma was used for etching quartz in the regions where the surfaces were exposed. The depth of the quartz resulting from the etching was <NUM>. The residual resist and the Cr film were removed, thereby obtaining a synthetic quartz base plate where concavities for forming the convexities <NUM> shown in <FIG> were formed.

Then, a film of Cr was formed by sputtering on the surface of the synthetic quartz base plate where concavities for forming the convexities <NUM> were formed, followed by electron beam lithography to form an electron beam resist pattern. The electron beam resist used was of a positive type, and had a thickness of <NUM>. Electron beam irradiating regions were the regions corresponding to the linear structures <NUM> shown in <FIG>. High frequency waves were applied to a mixed gas of chlorine and oxygen, and the generated plasma was used for etching to remove Cr in the regions where the surfaces were exposed. Then, high frequency waves were applied to a hexafluoroethane gas, and the generated plasma was used for etching quartz in the regions where the surfaces were exposed. The depth of the quartz resulting from the etching was <NUM>. The residual resist and Cr film were removed, thereby obtaining a synthetic quartz base plate formed with concavities for forming the concavo-convex structure shown in <FIG> where the convexities <NUM> were overlapped with the linear structures <NUM>.

Then, OPTOOL HD-<NUM> (product of Daikin Industries, Ltd. ) was applied, as a mold release agent, onto the surface of the synthetic quartz base plate, thereby obtaining an optical nanoimprinting mold, the mold being formed with concavities for forming a concavo-convex structure where the concavo-convex structure for inducing the light dispersion effect was overlapped with the concavo-convex structure formed of the linear structures for inducing a diffraction phenomenon.

Then, photo-curable resin PAK-<NUM> (product of Toyo Gosei Co. ) was applied onto an easily adherent surface of a polyester film COSMOSHINE A4100 (product of Toyobo Co. ), the surface being applied with easy adhesion treatment. Then, the optical nanoimprinting mold was pressed against the resin-applied surface of the polyester film, followed by irradiating light of <NUM> from the rear surface of the mold to cure the photo-curable resin. Then, the polyester film was peeled off from the mold to thereby obtain a polyester film formed with the concavo-convex structure shown in <FIG>.

Then, the surface of the obtained polyester film was subjected to vacuum vapor deposition to form a laminate of ten layers in which a TiO<NUM> layer with a thickness of <NUM> and a SiO<NUM> layer with a thickness of <NUM> were alternately laminated in this order five times, thereby obtaining a color developing structure of Example <NUM>.

Similarly to Example <NUM>, the concavities for forming the convexities <NUM> shown in <FIG> were formed in a synthetic quartz base plate, followed by applying a mold release agent, without forming and overlapping the concavities for forming the linear structures <NUM> shown in <FIG>, thereby obtaining an optical nanoimprinting mold of Comparative Example <NUM>. Similarly to Example <NUM>, a color developing structure of Comparative Example <NUM> was obtained using the optical nanoimprinting mold.

Then, as shown in the schematic diagram of <FIG>, the surfaces of the color developing structures of Example <NUM> and Comparative Example <NUM> were irradiated with light emitted from a xenon lamp light source at incident angles of <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> degrees, followed by measuring spectral characteristic changes at a reflection angle of <NUM> degrees, using a spectroradiometer SR-UL2 (product of Topcon Co. The incident angle or the reflection angle refers to an angle between a line normal to the surface of the polyester film and the incidence direction or the reflection direction of the light source, respectively.

<FIG> shows measurements of a reflection spectrum of the color developing structure of Comparative Example <NUM>, and <FIG> shows measurements of a reflection spectrum of the color developing structure of Example <NUM>. The value range ranges on the vertical axis are the same between these spectra. Comparisons between these spectra showed that, formation of the linear structures for inducing a diffraction phenomenon can accomplish relatively intense reflection in a broad incident angle range with no great change in the peak positions of the spectra.

The following description addresses, as Comparative example <NUM>, characteristics of a method of production and the display member (color developing structure, which is not according to the invention, and which is produced by the method.

The display member <NUM> will be described as a specific example. The display member <NUM> is configured by forming the pixel regions <NUM> by providing fine concavo-convex structures by dry etching on a surface of a synthetic quartz wafer, and performing vacuum vapor deposition to thereby deposit the laminated film <NUM> including TiO<NUM> layers that is the layers <NUM> of high refractive index and SiO<NUM> layers that is the layers <NUM> of low refractive index.

First, an optical nanoimprinting mold was prepared. Since the wavelength of light irradiated in optical nanoimprinting is <NUM>, synthetic quartz that transmits light of this wavelength was used as a material for the mold. Further, a film of chromium (Cr) was formed by sputtering on a surface of the synthetic quartz, followed by electron beam lithography to thereby form an electron beam resist pattern.

The formed pattern had a concavo-convex structure that was an inversion of the concavo-convex structure having a two-dimensional distribution as illustrated in <FIG>, with a single pixel being in a square shape having a side length of <NUM>. The length dx in the x-direction shown in <FIG> was <NUM>, and the length dy in the y-direction was selected from a normal distribution where an average was <NUM> and a standard deviation was <NUM>. A plurality of rectangles having a length dx in the x-direction and a length dy in the y-direction were arrayed such that the rectangles were not overlapped with each other in the x-direction.

Then, alignment marks as references for positioning were formed on the mold. The electron beam resist used was of a positive type, and had a thickness of <NUM>. Further, high frequency waves were applied to a mixed gas of chlorine (Cl<NUM>) and oxygen (O<NUM>), and the generated plasma was used for etching to remove Cr in the regions where the surfaces were exposed.

Then, high frequency waves were applied to a hexafluoroethane gas, and the generated plasma was used for etching quartz in the regions where the surfaces were exposed. The depth of the quartz resulting from the etching was <NUM>.

Then, residual resist and the Cr film were removed, thereby obtaining an optical nanoimprinting mold made of synthetic quartz in which a pixel region configured by a concavo-convex structure was formed. Then, OPTOOL HD-<NUM> (product of Daikin Industries, Ltd. ) was applied, as a mold release agent, onto the surface of the optical nanoimprinting mold.

Then, a synthetic quartz wafer was prepared. The synthetic quartz wafer was used as a base material <NUM> as illustrated in <FIG>. A photo-curable resin was applied onto a surface of the synthetic quartz wafer. Then, the optical nanoimprinting mold was pressed against the resin-applied surface of the wafer, followed by irradiating light of <NUM> from the rear surface of the mold to cure the photo-curable resin. Then, the synthetic quartz wafer was peeled off from the mold. Thus, a synthetic quartz wafer was obtained, in which a concavo-convex structure having a two-dimensional distribution as illustrated in <FIG> was formed in the photo-curable resin.

The synthetic quartz wafer was subjected to plasma etching using O<NUM> gas to remove the photo-curable resin remaining in the concavities of the concavo-convex structure. Further, <NUM> (sccm) of O<NUM> gas was introduced and plasma was discharged. It should be noted that <NUM> (sccm) is equivalent to <NUM> (ml/min).

Then, plasma etching was performed using a mixed gas of octafluorocyclobutane (C<NUM>F<NUM>) and argon (Ar) for the transfer of the concavo-convex structure. <NUM> sccm of C<NUM>F<NUM> and <NUM> sccm of Ar were introduced, and after setting the pressure in a plasma chamber to <NUM> mTorr, plasma was discharged with an application of <NUM> W of RIE power and <NUM> W of ICP power. The structural height dz was adjusted by changing the etching time. The structural height dz of the concavo-convex structure in the pixel region <NUM> was set to <NUM>. It should be noted that <NUM> (Torr) is equivalent to <NUM> (mmHg). Namely, <NUM> (Torr) is equivalent to about <NUM> (Pa).

Then, organic cleaning was performed using ST-<NUM> (solution of dimethyl sulfoxide and monoethanolamine mixed at a ratio of <NUM>: <NUM>, product of Kanto Chemical Co. ) and acid cleaning was performed using SH-<NUM> (solution of sulfuric acid and hydrogen peroxide solution mixed as basic components, product of Kanto Chemical Co. ), thereby obtaining a pixel region <NUM> having a concavo-convex structure <NUM> with the structural height dz.

Then, a photo-curable resin was again applied onto the surface of the synthetic quartz wafer. Then, the optical nanoimprinting mold was pressed against the resin-applied surface of the wafer, being displaced, so that the mold would not overlap the already formed pixel region <NUM> (for example, pixel region <NUM> (#<NUM>)), followed by irradiating light of <NUM> from the rear surface of the mold to cure the photo-curable resin. Then, the synthetic quartz was peeled off from the mold to thereby form the concavo-convex structure <NUM> (#<NUM>) of the next pixel region <NUM> (for example, pixel region <NUM> (#<NUM>)) in the photo-curable resin. Positioning was performed using the alignment marks <NUM> formed on the synthetic quartz wafer, and the pixel region <NUM> (#<NUM>) was formed at a position not overlapping the first formed pixel region <NUM> (#<NUM>).

Then, the synthetic quartz wafer was subjected to plasma etching using O<NUM> gas to remove the photo-curable resin remaining in the concavities of the concavo-convex structure. Further, <NUM> sccm of O<NUM> was introduced and plasma was discharged.

Then, plasma etching was performed using a mixed gas of C<NUM>F<NUM> and Ar for the transfer of the concavo-convex structure <NUM>. <NUM> sccm of C<NUM>F<NUM> and <NUM> sccm of Ar were introduced, and after setting the pressure in a plasma chamber to <NUM> mTorr, plasma was discharged with an application of <NUM> W of RIE power and <NUM> W of ICP power. The structural height dz was adjusted, by changing the etching time, to <NUM>.

Then, acid cleaning was performed using SH-<NUM>, that is, organic cleaning was performed using ST-<NUM>, thereby forming a pixel region <NUM> (#<NUM>) having a concavo-convex structure <NUM> with the structural height dz. Then, the surface of the synthetic quartz wafer was subjected to vacuum vapor deposition to form a laminated film <NUM> of ten layers in which a TiO<NUM> layer <NUM> with a thickness of <NUM> and a SiO<NUM> layer <NUM> with a thickness of <NUM> were alternately laminated five times, thereby obtaining a display member <NUM> including the pixel regions <NUM> (#<NUM> and #<NUM>) in each of which the laminated film <NUM> was formed on the concavo-convex structure <NUM>.

<FIG> shows a relationship between wavelength and reflection intensity observed at <NUM>° in the x-direction in the case where light is incident at an angle of <NUM>° with respect to the pixel regions <NUM> (#<NUM> and #<NUM>) of the display member <NUM>.

Specifically, in the case of structural height dz = <NUM>, green light having a wavelength of <NUM> was reflected with glossiness as shown by the curve α, and in the case of structural height dz = <NUM>, orange light having a wavelength of <NUM> was reflected as shown by the curve β.

As described, to produce the display member <NUM>, an imprinting mold is prepared first, whose surface is formed with an array of a plurality of regions having respective concavo-convex structures. Each concavo-convex structure has a structure, as shown in <FIG>, that is an inversion of the concavo-convex structure <NUM> of each pixel region <NUM> of the display member <NUM>.

Then, the plurality of regions formed in the mold are sequentially transferred to the base material <NUM> through optical or thermal imprinting. Thus, a desired concavo-convex structure <NUM>, such as the one shown in <FIG>, is transferred onto the base material <NUM>.

Then, a plurality of layers <NUM> are laminated on each concavo-convex structure <NUM> transferred to the base material <NUM> to form the laminated film <NUM>. Consequently, a display member <NUM> is produced with the pixel regions <NUM> being formed therein.

As described above referring to <FIG>, the display member <NUM> produced in this way exhibited that the color of reflection can be controlled by adjusting the structural height dz.

Claim 1:
A color developing structure formed on a surface of a base material (<NUM>, <NUM>, <NUM>), wherein:
the color developing structure has a rectangular shape in plan view, and is formed of a concavo-convex structure having a plurality of convexities with different heights and a laminated film (<NUM>) including a plurality of layers (<NUM>, <NUM>) laminated on the concavo-convex structure;
the plurality of layers (<NUM>, <NUM>), adjoining in a lamination direction are made of materials that transmit light of the same wavelength band and have different refractive indices with respect to light of the wavelength band; wherein
each layer of the plurality of layers has a uniform thickness,
the concavo-convex structure includes a concavo-convex structure A and a concavo-convex structure B overlapped (<NUM>) with each other to form a multilevel structure of at least two levels or more;
the concavo-convex structure A has flat convexities (<NUM>, <NUM>) configured by arraying rectangles in a first direction and a second direction, each rectangle having a line width (d1, d3) in the first direction (X), the line width being not more than a minimum wavelength of the wavelength band, and a line length in the second direction (Y), the line length being perpendicular to the first direction and greater than the line width in the first direction, the line length in the second direction having a standard deviation of greater than a standard deviation of the line width in the first direction; and
the concavo-convex structure B includes a plurality of linear structures (<NUM>, <NUM>) extending in the second direction and arrayed in the first direction at pitches of not less than a half of the minimum wavelength of the wavelength band,
the concavo-convex structure B has periodicity in both the first direction and the second direction, and
at least one of an average and a standard deviation of pitches of the linear structures forming the concavo-convex structure B is different between the first direction and the second direction.