JP2023019616A - Color development structure - Google Patents

Abstract

To provide a color development structure capable of acquiring clear color development with a small number of layers independent of increase in the thickness of a thin film.SOLUTION: A color development structure 10 includes an optical functional layer 24 including a metal layer 22 and a dielectric layer 23, the optical functional layer 24 for emitting reflected light strengthened by interference. A refractive index in a visible area of the metal layer 22 is different from a refractive index in a visible area of the dielectric layer 23. The metal layer 22 has a wavelength range with 5% or more transmittance in the visible area. The film thickness of the metal layer 22 is 5 nm or more and 40 nm or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a coloring structure that exhibits structural color.

A coloring structure that exhibits structural color due to multilayer interference is known. Structural colors are colors that are visually recognized due to the action of optical phenomena caused by the fine structure of an object, such as diffraction, interference, and scattering of light. Structural color due to multilayer interference is caused by reflection of light at the interfaces of mutually adjacent thin films in the multilayer film and interference of the reflected light.

Since the exit angle of the reflected light that is strengthened by the interference in the multilayer film layer is determined depending on the angle of the incident light, in the color-developing structure in which the multilayer film layers are laminated on a plane, the visible color varies greatly depending on the viewing angle. change (see, for example, Patent Document 1). On the other hand, in a color-developing structure in which multiple layers are laminated on a fine uneven structure, the reflected light, which is strengthened by interference, is emitted in a multi-directional spread due to the unevenness, so that the color changes gradually depending on the viewing angle ( For example, see Patent Document 2). The degree of color change with viewing angle is selected according to the application of the coloring structure.

JP 2011-189519 A JP-A-2005-153192

By the way, in the manufacturing process of a multilayer film layer, it is necessary to sequentially laminate a plurality of thin films with precise film thickness so that thin films made of different materials are adjacent to each other. When the errors in the film thickness of each thin film accumulate, it becomes difficult to obtain desired color development, and there is concern about a decrease in yield. Therefore, the load required to manufacture a color-developing structure having multiple layers is large.

On the other hand, as a structure that produces structural color with a small number of layers while utilizing light interference, there is a structure that utilizes thin-film interference in a single layer. A conventionally known coloring structure utilizing thin film interference includes a reflective film made of metal or the like and a single-layer dielectric film laminated on the reflective film. Structural colors are visible due to the interference of the light reflected on the front and back of the dielectric film and the increase in the intensity of the reflected light by the reflective film.

However, in such a color-developing structure, the interface from which the reflected light that causes interference is emitted is limited to the front and back surfaces of the dielectric film. Therefore, the wavelength selectivity of the reflected light is low. That is, the monochromaticity of visually recognized light is reduced, and it is difficult to obtain a clear color development of a specific color.

By increasing the film thickness of the dielectric film to about several μm, it is possible to increase the intensity of the reflected light on the surface opposite to the surface in contact with the reflective film, thereby strengthening the interference. If the film thickness is too large, it becomes difficult to control the wavelength region intensified by interference, making it difficult to obtain desired color development. Further, when the thickness of the dielectric film is large, stress tends to cause warping of the coloring structure and peeling of the dielectric film. Furthermore, when the reflective film and the dielectric film are stacked on the uneven structure, it is difficult for the dielectric film to conform to the uneven structure, so that it is difficult to obtain the effect of scattering the reflected light.

Therefore, there is a demand for a structure capable of obtaining clear color development with a small number of layers without relying on an increase in the thickness of the thin film.

A coloring structure for solving the above problems is an optical function layer comprising a metal layer and a dielectric layer, the optical function layer emitting reflected light intensified by interference, and The refractive index in the region is different from the refractive index in the visible region of the dielectric layer, and the film thickness of the metal layer is 5 nm or more and 40 nm or less.

According to the above configuration, part of the light transmitted through the dielectric layer is transmitted through the metal layer. As a result, reflected light is emitted from the interface of the metal layer on the opposite side of the dielectric layer, causing interference. is strengthened.

Furthermore, since the metal layer has reflectivity, the intensity of reflected light from the optical function layer is increased compared to the case where a layer made of a dielectric with low reflectivity is arranged instead of the metal layer. On the other hand, compared to the case where the metal layer does not have transparency and has high reflectivity in the entire visible region, it is possible to suppress the reflection of light other than the specific wavelength region, which is intensified by interference, from increasing.

Therefore, even if the number of thin films laminated in the optical function layer is at least, the wavelength selectivity of the reflected light from the color-developing structure is enhanced, so that the color corresponding to the specific wavelength region can be clearly visually recognized.

The said structure WHEREIN: The said metal layer may have a wavelength range which has a transmittance|permeability of 5% or more in a visible region.
According to the above configuration, the transparency of the metal layer can be suitably obtained.

The said structure WHEREIN: The said metal layer may have a wavelength range which has a reflectance of 30% or more in a visible region.
According to the above configuration, the reflectivity of the metal layer can be suitably obtained.

In the above configuration, the visible range may include a wavelength range in which the difference between the refractive index of the metal layer and the refractive index of the dielectric layer is 0.3 or more.
According to the above configuration, since reflection occurs favorably at the interface between the dielectric layer and the metal layer, interference is strengthened, and it is easy to obtain reflected light with high intensity.

In the above structure, the film thickness of the dielectric layer may be 10 nm or more and 300 nm or less.
According to the above configuration, since the film thickness of the dielectric layer is kept small, it becomes difficult to control the wavelength region intensified by interference, and warping of the coloring structure and peeling of the dielectric film occur due to stress. Problems such as those caused by an increase in the thickness of the dielectric layer can be suppressed.

In the above configuration, the refractive index of the dielectric layer in the visible region may be greater than 1.5 and less than or equal to 3.0.
According to the above configuration, it is easy to ensure a large difference in refractive index between the dielectric layer and the layer adjacent to the dielectric layer, so reflected light with high intensity can be easily obtained.

The above structure further comprises an uneven structure layer that has an uneven structure composed of a plurality of uneven elements that are convex portions or concave portions on the surface and supports the optical function layer, wherein the optical function layer is attached to the uneven structure. In a plan view of the uneven structure viewed from the direction along the thickness direction of the uneven structure layer, each of the width in the short side direction and the width in the long side direction of the uneven element is It is 10 μm or more and 100 μm or less, and the dimension of the uneven element along the thickness direction increases from the end portion to the central portion of the uneven element in plan view, and the width in the short side direction A ratio of maximum values of dimensions along the thickness direction in the concave-convex element may be 0.1 or more and 1.0 or less.

According to the above configuration, the reflected light is scattered by the concave-convex structure. Therefore, the light in the specific wavelength range intensified by the interference is emitted in various directions, and the color corresponding to the specific wavelength range can be visually recognized at a wide viewing angle. In addition, it is possible to design the concave-convex structure so that reflected light is scattered isotropically. Moreover, since the size of the protrusions is micro-sized, it is easier to form the uneven structure than when the size of the protrusions is nano-sized.

The above configuration further includes an uneven structure layer that has an uneven structure on its surface and supports the optical function layer, and the optical function layer has a surface shape along the uneven structure and constitutes the uneven structure. The convex portion has a step shape of one or more steps from the plane on which the base portion of the convex portion is located, and when viewed from the viewpoint facing the surface of the uneven structure layer, the pattern formed by the plurality of convex portions is the following: A set of a plurality of graphic elements whose length along one direction is sub-wavelength or less and whose length along a second direction orthogonal to the first direction is greater than or equal to the length along the first direction wherein the plurality of graphic elements have a standard deviation of length along the second direction greater than a standard deviation of length along the first direction.

According to the above configuration, the reflected light is scattered by the concave-convex structure. Therefore, the light in the specific wavelength range intensified by the interference is emitted in various directions, and the color corresponding to the specific wavelength range can be visually recognized at a wide viewing angle. In addition, anisotropy is obtained in scattering of reflected light.

In the above configuration, when the rugged structure is viewed from a viewpoint facing the surface of the rugged structure layer, the pattern formed by the plurality of convex portions includes a first pattern formed by a set of the graphic elements and a pattern formed in the second direction. and a second pattern consisting of a plurality of band-shaped regions arranged along the first direction, wherein the second pattern includes an arrangement interval of the band-shaped regions along the first direction is not constant in the plurality of band-shaped regions, and the average value of the arrangement intervals in the plurality of band-shaped regions is 1/2 or more of the minimum wavelength in the wavelength range included in the incident light to the optical function layer, The projections are elements that constitute the first pattern when projected in the thickness direction of the uneven structure layer, and have a predetermined height. It may have a multi-stage shape in which convex elements having a predetermined height, which are elements constituting the second pattern, are stacked in the height direction.

According to the above configuration, the concave-convex structure provides a diffusion effect and a diffraction effect of reflected light. As a result, the reflected light intensified by the interference can be observed at a wide viewing angle, and the intensity of this reflected light is increased.

The above configuration further includes an uneven structure layer that has an uneven structure on its surface and supports the optical function layer, the optical function layer has a surface shape along the uneven structure, and the surface of the uneven structure layer , the pattern formed by the plurality of convex portions forming the concave-convex structure has a side along the first direction having a length equal to or less than the sub-wavelength and a second side perpendicular to the first direction. a pattern consisting of a set of a plurality of graphic elements each inscribed in a virtual rectangle having sides along a direction, and in each of a plurality of unit areas included in the uneven structure layer, the rectangle extends in the first direction The angle θ may be greater than 0° and less than 90°, or greater than 90° and less than 180° in at least one of the unit areas.

According to the above configuration, the reflected light is scattered by the concave-convex structure. Therefore, the light in the specific wavelength range intensified by the interference is emitted in various directions, and the color corresponding to the specific wavelength range can be visually recognized at a wide viewing angle. Also, by controlling the angle θ, the anisotropy of scattering of reflected light can be easily controlled.

In the above configuration, an absorption layer that absorbs at least part of light in the visible region may be provided on the opposite side of the uneven structure layer to the optical function layer.
In the above configuration, an absorption layer that absorbs at least part of light in the visible region may be provided on the side opposite to the uneven structure and the like with respect to the optical function layer.

According to each of the above configurations, at least part of the light transmitted through the optical function layer is absorbed by the absorption layer. Therefore, light in a wavelength range different from the wavelength range intensified by interference in the optical function layer is reflected at the interface between each layer inside the coloring structure and at the interface between the coloring structure and its exterior, and is emitted toward the observer. be suppressed. Therefore, the vividness of the colors visually recognized by the coloring structure is enhanced.

According to the present invention, clear color development can be obtained with a small number of layers without depending on the increase in the thickness of the thin film.

FIG. 2 is a diagram showing a cross-sectional structure of a coloring structure according to the first embodiment; FIG. 4 is a diagram showing wavelength distributions of reflectance and transmittance of metal layers having different film thicknesses; FIG. 4 is a diagram showing a wavelength distribution of transmittance of an optical function layer including metal layers with different film thicknesses; FIG. 4 is a diagram showing a wavelength distribution of transmittance of an optical function layer including metal layers made of different materials; FIG. 4 is a diagram showing a wavelength distribution of transmittance of an optical function layer including a metal layer and a dielectric layer having a large refractive index difference; FIG. 4 is a diagram showing a wavelength distribution of transmittance of an optical function layer including a metal layer and a dielectric layer having a large refractive index difference; FIG. 4 is a diagram showing a wavelength distribution of transmittance of an optical function layer including a metal layer and a dielectric layer with a small refractive index difference; FIG. 4 is a diagram showing the wavelength distribution of the transmittance of the optical function layer when it is assumed that the metal layer and the dielectric layer have the same refractive index. FIG. 4 is a diagram showing a perspective structure of a concavo-convex structure layer included in the coloring structure of the first embodiment; 4A and 4B are diagrams showing a planar structure and a cross-sectional structure of a concavo-convex structure layer included in the coloring structure of the first embodiment; FIG. The figure which shows the cross-section of the coloring structure of 2nd Embodiment. FIG. 8A is a diagram showing the planar structure of the concave-convex structure, and FIG. The figure which shows the cross-section of the coloring structure of 3rd Embodiment. Regarding the coloring structure of the third embodiment, (a) is a diagram showing the planar structure of the concave-convex structure consisting only of the second convex elements, and (b) is a sectional structure of the concave-convex structure consisting only of the second convex elements. illustration. 8A and 8B are diagrams showing the planar structure of the concave-convex structure, and FIG. The figure which shows the cross-section of the coloring structure of 4th Embodiment. FIG. 8A is a diagram showing a planar structure of a concave-convex structure, and FIG. 8B is a diagram showing a cross-sectional structure of the concave-convex structure of a coloring structure according to a fourth embodiment; The figure which expands and shows a part of planar structure of uneven|corrugated structure about the coloring structure of 4th Embodiment. The figure which shows the planar structure of the modification of the coloring structure of 4th Embodiment. The figure which shows the planar structure of the other modification of the coloring structure of 4th Embodiment. The figure which shows the planar structure of the other modification of the coloring structure of 4th Embodiment. The figure which shows the cross-section of the coloring structure of a modification. The figure which shows the cross-section of the coloring structure of another modification. The figure which shows the cross-section of the coloring structure of another modification.

(First embodiment)
A first embodiment of the coloring structure will be described with reference to FIGS. 1 to 10. FIG. Incident light and reflected light targeted by the color-developing structure are light in the visible region. In the following description, light in the visible region refers to light in the wavelength range of 360 nm or more and 830 nm or less.

[Overall configuration of coloring structure]
As shown in FIG. 1, the coloring structure 10 includes a substrate 20, an uneven structure layer 21, and an optical function layer 24 composed of a metal layer 22 and a dielectric layer .

The substrate 20 is a flat layer and supports the uneven structure layer 21 . The substrate 20 transmits light in the entire visible range, ie, is transparent to light in the visible range. The substrate 20 is, for example, a synthetic quartz substrate or a film made of resin such as polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), polymethyl methacrylate (PMMA). From the viewpoint of enhancing the flexibility of the coloring structure 10, the substrate 20 is preferably a resin film. The film thickness of the base material 20 is, for example, 10 μm or more and 100 μm or less.

The uneven structure layer 21 is located on the substrate 20 . The concave-convex structure layer 21 has a concave-convex structure on the surface opposite to the surface facing the substrate 20 . The uneven structure is composed of a plurality of protrusions 21a. The convex portion 21 a is an example of a concave-convex element, and protrudes toward the optical function layer 24 .

The concavo-convex structure layer 21 transmits light in the entire visible range, that is, is transparent to light in the visible range. The material of the concavo-convex structure layer 21 is, for example, a photocurable resin, a thermosetting resin, or a thermoplastic resin.

The optical function layer 24 covers the surface of the uneven structure layer 21 and has a surface shape that follows the uneven structure of the uneven structure layer 21 . The stacking order of the metal layer 22 and the dielectric layer 23 in the optical function layer 24 is not limited. Of the optical function layers 24 , the layer closer to the viewer, in other words, the layer closer to the exit space of the incident light with respect to the coloring structure 10 is preferably the dielectric layer 23 .

For example, when the coloring structure 10 is observed from the side where the optical function layer 24 is positioned with respect to the uneven structure layer 21, the metal layer 22 is in contact with the uneven structure layer 21, and the uneven structure layer is in contact with the metal layer 22. A dielectric layer 23 preferably contacts the metal layer 22 on the side opposite 21 . On the contrary, when the coloring structure 10 is observed from the side where the uneven structure layer 21 is located with respect to the optical function layer 24 , the dielectric layer 23 is in contact with the uneven structure layer 21 and the dielectric layer 23 is in contact with the dielectric layer 23 . The metal layer 22 is preferably in contact with the dielectric layer 23 on the side opposite to the uneven structure layer 21 . FIG. 1 shows a configuration in which these layers are laminated in the order of a metal layer 22 and a dielectric layer 23 from a position close to the uneven structure layer 21 .

The metal layer 22 is a single-layer thin film layer made of metal. The metal layer 22 has transparency and reflectivity for light in the visible region. Based on its transmittance, the metal layer 22 transmits part of the incident light and emits reflected light that acts on interference from the front and back interfaces of the metal layer 22, thereby enhancing light interference in the optical function layer 24. have a function. Moreover, the metal layer 22 has a function of enhancing the visibility of the reflected light by increasing the intensity of the reflected light of the optical function layer 24 based on its reflectivity.

The dielectric layer 23 is a single layer thin film made of a dielectric. The dielectric layer 23 transmits light in the entire visible range, ie, is transparent to light in the visible range. The dielectric layer 23 emits reflected light that acts on interference from the front and back interfaces of the dielectric layer 23 .

When light enters the optical function layer 24 , reflected light is emitted from each interface of the optical function layer 24 because the metal layer 22 and the dielectric layer 23 have transparency in the visible region.
For example, when the uneven structure layer 21, the metal layer 22, and the dielectric layer 23 are arranged in this order and light is incident from the side where the dielectric layer 23 is located, part of the incident light reflect at the interface with Furthermore, part of the incident light that has passed through the dielectric layer 23 is reflected at the interface between the dielectric layer 23 and the metal layer 22 . Further, part of the incident light transmitted through the dielectric layer 23 and the metal layer 22 is reflected at the interface between the metal layer 22 and the uneven structure layer 21 .

Similarly, when the rugged structure layer 21, the dielectric layer 23, and the metal layer 22 are arranged in this order and light is incident from the side where the rugged structure layer 21 is located, the interface between the rugged structure layer 21 and the dielectric layer 23, Part of the incident light is reflected at each of the interface between the dielectric layer 23 and the metal layer 22 and the interface between the metal layer 22 and the air layer.

The light reflected at each interface of the optical function layer 24 interferes, and thereby the light in the specific wavelength region is emitted from the coloring structure 10 . According to the present embodiment, compared with the case where the metal layer 22 does not transmit light, reflected light is also emitted from the interface of the metal layer 22 on the opposite side of the dielectric layer 23 to cause interference. , the interference of light in the optical function layer 24 is enhanced.

Furthermore, since the metal layer 22 is reflective, the amount of light reflected from the optical function layer 24 is reduced compared to when a layer made of a dielectric with low reflectivity is arranged instead of the metal layer 22 . strength is increased. On the other hand, compared to the case where the metal layer 22 does not transmit light and has high reflectivity in the entire visible region, the reflection of light other than the specific wavelength region enhanced by interference may become stronger. suppressed.

As described above, the intensity of light in a specific wavelength range is increased by increasing the interference, and the intensity of light in a wavelength range other than the specific wavelength range is suppressed. be done. As a result, the color corresponding to the specific wavelength range can be clearly visually recognized.

Due to the uneven structure of the uneven structure layer 21, the angle of each interface of the optical function layer 24 with respect to the incident light changes within the color-developing structure 10, so reflected light is emitted in various directions. That is, reflected light is scattered. As a result, the light in the specific wavelength band enhanced by the interference is emitted in various directions, and the colors corresponding to the specific wavelength band are visible at wide viewing angles.

[Detailed configuration of optical function layer]
Detailed configurations of the metal layer 22 and the dielectric layer 23 will be described.
The metal layer 22 has a transmission wavelength range, which is a wavelength range having a transmittance of 5% or more, in the visible region. In addition, the metal layer 22 has a reflection wavelength range, which is a wavelength range having a reflectance of 30% or more, in the visible region. It is preferable that the transmission wavelength range and the reflection wavelength range overlap.

When the wavelength range intensified by interference in the optical function layer 24 is set as the target wavelength range, by setting the target wavelength range within the transmission wavelength range, the metal layer 22 is transmitted and at the interface between the metal layer 22 and other layers The intensity of the light reflected and affecting the interference is increased. Therefore, the wavelength selectivity of the reflected light in the coloring structure 10 is enhanced. In order to enhance such an effect, it is preferable that the target wavelength range be set near the peak wavelength at which the transmittance of the metal layer 22 is highest in the transmission wavelength range. Further, in order to further enhance the wavelength selectivity of the reflected light, the metal layer 22 has a wavelength range having a transmittance of 20% or more in the transmission wavelength range. It is preferable that the target wavelength range is set in the .

Further, by setting the target wavelength range within the reflection wavelength range, the intensity of the light that is reflected at the interface between the metal layer 22 and the dielectric layer 23 and acts on the interference is increased. This also enhances the wavelength selectivity of the reflected light in the coloring structure 10 . In order to enhance such an effect, the metal layer 22 has a wavelength range having a reflectance of 50% or more in the reflection wavelength range, and the target wavelength range is included in the wavelength range having a reflectance of 50% or more. is preferably set.

By setting the target wavelength range to a wavelength range that is both a transmission wavelength range and a reflection wavelength range, the wavelength selectivity of the reflected light is further enhanced.
The transmission wavelength range and the magnitude of transmittance in the wavelength range, the reflection wavelength range and the magnitude of reflectance in the wavelength range can be controlled by the material and film thickness of the metal layer 22 . Also, the target wavelength range can be controlled by the materials and film thicknesses of the metal layer 22 and the dielectric layer 23 . For example, if the film thickness of the dielectric layer 23 differs by 10 nm, the difference in the target wavelength range can be recognized as different colors.

In addition, the reflectance of the metal layer 22 may or may not have a peak that protrudes in a specific wavelength range and becomes high or low. If the reflectance of the metal layer 22 does not have a prominent peak, a high reflectance in the reflected wavelength band indicates a trend of high reflectance over the entire visible region. That is, the intensity of the entire reflected light from the coloring structure 10 tends to increase. When the monochromaticity of the coloring in the coloring structure 10 is more important, the metal layer 22 may be designed so as to suppress the reflectance in the reflection wavelength range. , the metal layer 22 should be designed so that the reflectance in the reflected wavelength range is high within the range in which the wavelength selectivity of the reflected light is sufficiently obtained.

In order to suppress reflection of light outside the target wavelength range, the reflectance of the metal layer 22 is preferably 80% or less in the wavelength range other than the target wavelength range. When the reflectance of the metal layer 22 does not have a protruding peak, the reflectance of the metal layer 22 should be 80% or less in the entire visible region including the target wavelength range. Moreover, when the monochromaticity of color development is more important as described above, the reflectance of the metal layer 22 is preferably 60% or less in the entire visible region including the target wavelength range.

Moreover, the metal layer 22 may have an absorptivity for part of the wavelengths in the visible region. In this case, the target wavelength range is preferably set to a wavelength range different from the absorptive wavelength range. When the metal layer 22 has light absorption properties, light in the wavelength range absorbed by the metal layer 22 is suppressed from being included in the reflected light of the optical function layer 24 . This also enhances the wavelength selectivity of the reflected light in the coloring structure 10 .

Materials for the metal layer 22 are, for example, aluminum, copper, iron, nickel, gold, silver, chromium, titanium, tantalum, and silicon. The film thickness of the metal layer 22 is 5 nm or more and 40 nm or less. If the thickness of the metal layer 22 is 40 nm or less, part of the light incident on the optical function layer 24 is transmitted through the metal layer 22 and reflected at the interface between the metal layer 22 and other layers, thereby acting on interference. .

The material of the dielectric layer ₂₃ is, for example, an inorganic material such as _TiO2 , _ZnS , _Nb2O5 , _Ta2O5 , _ZrO2 . The film thickness of the dielectric layer 23 is preferably 10 nm or more and 300 nm or less. According to the present embodiment, since the metal layer 22 has the above-described light transmittance and reflectivity, even when the film thickness of the dielectric layer 23 is suppressed to 300 nm or less, the light reflected by the coloring structure 10 Sufficient wavelength selectivity is obtained. Therefore, it becomes difficult to control the wavelength range intensified by interference, warping of the coloring structure and peeling of the dielectric film due to stress, and scattering of reflected light due to difficulty in conforming the dielectric film to the uneven structure. It is possible to suppress the occurrence of problems due to an increase in the film thickness of the dielectric layer 23, such as difficulty in obtaining .

An example of the relationship between the specific material and film thickness of the metal layer 22 and the reflectance and transmittance will be described with reference to FIGS. 2 to 6. FIG.
FIG. 2 shows wavelength distributions of reflectance and transmittance in the metal layer 22 formed on the substrate 20 by vacuum deposition. The material of the metal layer 22 is aluminum. Curve A1 indicates the reflectance when the thickness of the metal layer 22 is 10 nm, and curve A2 indicates the transmittance when the thickness of the metal layer 22 is 10 nm. Curve B1 indicates the reflectance when the thickness of the metal layer 22 is 20 nm, and curve B2 indicates the transmittance when the thickness of the metal layer 22 is 20 nm.

From FIG. 2, it is suggested that the smaller the film thickness of the metal layer 22, the higher the overall transmittance and the lower the overall reflectance.
Specifically, as indicated by the curves A1 and A2, when the film thickness of the metal layer 22 is 10 nm, a transmittance of 20% or more is obtained at wavelengths in the vicinity of 350 nm to 600 nm. At this time, the reflectance is about 40% to 60% at wavelengths around 350 nm to 600 nm. For example, at a wavelength of 500 nm the transmittance is about 25% and the reflectance is about 55%.

On the other hand, as shown by the curves B1 and B2, when the film thickness of the metal layer 22 is 20 nm, a transmittance of 5% or more is obtained at wavelengths in the vicinity of 350 nm to 600 nm. At this time, the reflectance is about 70% to 80% at wavelengths around 350 nm to 600 nm. For example, at a wavelength of 500 nm the transmittance is about 5% and the reflectance is about 80%.

FIG. 3 shows the reflection of the optical function layer 24 when the material of the dielectric layer 23 is TiO ₂ , the film thickness of the dielectric layer 23 is 50 nm, and the material of the metal layer 22 is aluminum, and the film thickness of the metal layer 22 is changed. 1 shows the wavelength distribution of light. Curve C1 shows the case where the thickness of the metal layer 22 is 10 nm, curve C2 shows the case where the thickness of the metal layer 22 is 20 nm, and curve C3 shows the case where the thickness of the metal layer 22 is 50 nm. Curve C4 shows the case where the film thickness of the metal layer 22 is 100 nm.

As shown by the curves C1 and C2, when the film thickness of the metal layer 22 is 20 nm or less, a reflectance peak is confirmed near about 350 nm. A blue color is visually recognized in the coloring structure 10 having such an optical function layer 24 .

On the other hand, as shown by the curves C3 and C4, when the film thickness of the metal layer 22 is 50 nm or more, the intensity of reflected light is generally high and the peak of reflectance is low. That is, the wavelength selectivity of reflected light is lower than when the thickness of the metal layer 22 is 20 nm or less. In the coloring structure 10 having such an optical function layer 24, a silver color close to the color of the aluminum thin film itself is visually recognized.

As described with reference to FIG. 2, the larger the film thickness of the metal layer 22, the smaller the transmittance of the metal layer 22 as a whole and the larger the reflectance of the metal layer 22 as a whole. The interference at 24 becomes weaker, and the reflection outside the wavelength range enhanced by the interference becomes greater. As a result, as shown in FIG. 3, if the thickness of the metal layer 22 is large, the wavelength selectivity of the light reflected by the optical function layer 24 cannot be sufficiently obtained.

FIG. 4 shows the reflection of the optical function layer 24 when the material of the dielectric layer 23 is TiO ₂ , the thickness of the dielectric layer 23 is 50 nm, the thickness of the metal layer 22 is 20 nm, and the material of the metal layer 22 is changed. 1 shows the wavelength distribution of light. Curve D1 indicates that the material of the metal layer 22 is aluminum, curve D2 indicates that the material of the metal layer 22 is copper, and curve D3 indicates that the material of the metal layer 22 is nickel. .

When the material of the metal layer 22 is aluminum or silver, the reflectance of the metal layer 22 tends to be high throughout the visible region without having a prominent peak. On the other hand, when the material of the metal layer 22 is copper or gold, the reflectance of the metal layer 22 is high in the long wavelength region, and the metal layer 22 absorbs part of the short wavelength region to the middle wavelength region. have sex. In addition, when the material of the metal layer 22 is a magnetic material such as nickel or iron, the reflectance of the metal layer 22 tends to be low in the entire visible range because the absorption in the visible range is large.

From the above, as shown in FIG. 4, the material of the metal layer 22 causes a difference in the wavelength range in which the intensity of the reflected light from the optical function layer 24 increases and in the overall magnitude of the reflected light. The material of the metal layer 22 may be selected according to the desired color and brightness of the coloring structure 10 . For example, when it is desired to develop a color including yellow to red, bright colors are easily obtained by using copper or gold. Further, when aluminum or silver is used, bright color development is likely to be obtained, and when nickel or iron is used, dark color development is likely to be obtained.

Next, the difference in refractive index between the metal layer 22 and the dielectric layer 23 will be described.
The metal layer 22 and the dielectric layer 23 have different refractive indices in the visible region. As a result, reflection occurs at the interface between the metal layer 22 and the dielectric layer 23 , and interference occurs due to reflected light at each interface of the optical function layer 24 .

Either of the refractive index of the metal layer 22 and the refractive index of the dielectric layer 23 may be large. Preferably, there is a wavelength band in which the difference is 0.3 or more. The refractive index of each of the metal layer 22 and the dielectric layer 23 in the visible region is not particularly limited. It is preferable because it is easy to secure a large difference in refractive index between the air layer or the metal layer 22 .

5 to 8 show wavelength distributions of reflected light from the optical function layer 24 when the difference in refractive index between the metal layer 22 and the dielectric layer 23 is changed. The material of the dielectric layer 23 is TiO ₂ , the thickness of the dielectric layer 23 is 50 nm, and the thickness of the metal layer 22 is 20 nm.

FIG. 5 shows the case where the refractive index of the metal layer 22 is smaller than the refractive index of the dielectric layer 23 by 0.3 or more. Curve E1 indicates that the material of the metal layer 22 is aluminum, curve E2 indicates that the material of the metal layer 22 is silver, and curve E3 indicates that the material of the metal layer 22 is gold. , curve E4 show the case where the material of the metal layer 22 is copper.

FIG. 6 shows the case where the refractive index of the metal layer 22 is greater than that of the dielectric layer 23 by 0.3 or more. Curve F1 shows the case where the material of the metal layer 22 is silicon and curve F2 shows the case where the material of the metal layer 22 is chromium.

FIG. 7 shows the case where the difference in refractive index between the metal layer 22 and the dielectric layer 23 is less than 0.3 over the entire visible region. Curve G1 shows the case where the material of the metal layer 22 is nickel, curve G2 shows the case where the material of the metal layer 22 is titanium, and curve G3 shows the case where the material of the metal layer 22 is tantalum. .

FIG. 8 shows simulation results of the wavelength distribution of reflected light when it is assumed that the metal layer 22 and the dielectric layer 23 have the same refractive index. In this case, since no reflection occurs at the interface between the metal layer 22 and the dielectric layer 23, no wavelength selectivity due to interference occurs in the reflected light, as indicated by the curve H1.

5 to 8, if there is a difference in refractive index between the metal layer 22 and the dielectric layer 23, wavelength selectivity occurs due to interference in the reflected light, and the difference in refractive index between the metal layer 22 and the dielectric layer 23 is 0.3 or more, it is suggested that the intensity of the reflected light enhanced by interference is likely to be high.

[Construction of concave-convex structure]
The concave-convex structure of the concave-convex structure layer 21 will be described in detail with reference to FIGS. 9 and 10. FIG. 9 shows a perspective structure of the uneven structure layer 21, and FIG. 10 shows a planar structure and a cross-sectional structure of the uneven structure layer 21. As shown in FIG.

As shown in FIG. 9, the uneven structure has a structure in which a plurality of protrusions 21a are arranged without gaps. For example, the convex portions 21a constitute microlenses, and the concavo-convex structure layer 21 constitutes a microlens array.

As shown in FIG. 10 , in a planar view of the uneven structure from the direction along the thickness direction of the uneven structure layer 21, that is, in a planar view from a viewpoint facing the surface of the uneven structure layer 21, the convex portions 21a preferably has a quadrangular shape, particularly preferably a square shape. It is preferable that the plurality of protrusions 21a have the same square shape, and that the plurality of protrusions 21a be arranged in a square lattice along the direction in which the sides of the square extend. Since the plurality of protrusions 21a are arranged in a two-dimensional grid pattern, that is, arranged along each of two intersecting directions, scattering of reflected light tends to be isotropic.

The width d1 of the convex portion 21a is the length of one side of the square, and the width d1 is constant in the plurality of convex portions 21a. The width d1 is 10 μm or more and 100 μm or less. When the width d1 is 10 μm or more, light diffraction due to the regular arrangement of the protrusions 21a is suppressed. Therefore, the visibility of the rainbow color as diffracted light is suppressed, so that the visibility of the color corresponding to the reflected light intensified by the interference in the optical function layer 24 is enhanced. Further, when the width d1 is 10 μm or more, the projections 21a do not become too fine, which facilitates the formation of the projections and depressions structure, thereby enhancing the production efficiency of the coloring structure 10. FIG. On the other hand, when the width d1 is 100 μm or less, it is suppressed that the convex portion 21a is recognized as one structure by human eyes. The width d1 is preferably 40 μm or more and 50 μm or less from the viewpoint of obtaining these effects in a balanced manner.

The maximum height h1 of the protrusions 21 a is the maximum dimension of the protrusions 21 a along the thickness direction of the uneven structure layer 21 . In other words, the maximum height h1 is the length between the proximal end and the distal end of the peripheral surface of the projection 21a in the thickness direction. The maximum height h1 is constant among the plurality of protrusions 21a. The maximum height h1 is preferably 10 μm or less, for example.

The aspect ratio of the convex portion 21a, that is, the ratio of the maximum height h1 to the width d1 is 0.1 or more and 1.0 or less. If the aspect ratio is 0.1 or more, a concavo-convex structure having sufficient undulations compared to a plane is formed, so that a high scattering effect can be obtained by the concavo-convex structure.

On the other hand, if the aspect ratio is 1.0 or less, reflection of light within the convex portion 21a is suppressed. If the reflection in the convex portion 21a is large, the light in the wavelength range different from the wavelength band intensified by the optical function layer 24 among the incident light is reflected in the convex portion 21a and emitted from the coloring structure 10. things can happen. On the other hand, as described above, if the aspect ratio is 1.0 or less, the reflection of light within the convex portion 21a is suppressed, so the reduction in the clarity of the color of the reflected light that is visually recognized is suppressed. be done. In addition, it is preferable that the convex portion 21a is designed to have a shape that hardly reflects light in a wavelength range different from the wavelength range intensified by the optical function layer 24 .

The height of the projections 21a continuously changes and gradually increases from the ends of the projections 21a toward the center in the direction in which the uneven structure layer 21 spreads, that is, the direction perpendicular to the thickness direction. . The height of the convex portion 21a becomes maximum at the central portion of the convex portion 21a in the direction in which the concave-convex structure layer 21 spreads. In other words, the height of the convex portion 21a is continuous from the portion corresponding to the end portion of the convex portion 21a in plan view toward the portion corresponding to the central portion of the convex portion 21a in plan view. growing. The height of the convex portion 21a is maximized at the portion where the center C of the convex portion 21a, which is the center of gravity of the square in plan view, is located.

In a cross section along the thickness direction passing through the center C, the surface, which is the peripheral surface of the convex portion 21 a , forms a curve that curves so as to protrude toward the optical function layer 24 . The curvature of this curve may or may not be constant. For example, the curvature of the curve formed by the surface may be different between the ends and the central portion of the convex portion 21a.

When the curvature of the curve is constant, it is easier to suppress the reflection of light within the convex portion 21a, compared to the case where the curvature is large at the central portion of the convex portion 21a. On the other hand, if the curvature of the curve is not constant, the convex portion 21a can be configured so that the angle of the peripheral surface of the convex portion 21a with respect to the incident light becomes more uneven within the peripheral surface. The shape of the convex portion 21a can also be designed so as to enhance the scattering effect of the reflected light.

The pitch P of the arrangement of the projections 21a matches the width d1 in both of the arrangement directions of the projections 21a, that is, the two directions along the sides forming the square. In such a configuration, the surface of the uneven structure layer 21 does not have flat portions.

In addition, the plurality of convex portions 21a may be arranged side by side with a gap between adjacent convex portions 21a. In other words, the surface of the concavo-convex structure layer 21 may have flat portions between adjacent convex portions 21a. However, it is preferable that the ratio of the flat portion per unit area on the surface of the uneven structure layer 21 is 10% or less in the above plan view. In the region where the optical function layer 24 is laminated on the flat part, the scattering of the reflected light is small. Therefore, the color change due to the change in viewing angle can be suppressed appropriately. Further, if the ratio of the flat portion is 10% or less, the ratio of specular reflection components in the reflected light from the optical function layer 24 can be kept small, so that the strain on the eyes of the observer is reduced. In order to enhance such an effect, it is preferable that the ratio of the flat portion is as small as possible.

A modification of the concave-convex structure will be described. The shape of the convex portion 21a in plan view is not limited to a square, and may be a polygon such as a triangle, rectangle, or hexagon, or a circle. Further, the shape of the protrusions 21a in plan view may not be uniform among the plurality of protrusions 21a. Further, the maximum height h1 of the plurality of protrusions 21a may not be constant.

Here, in order to enhance the scattering effect of the reflected light and emit the reflected light in more directions, it is preferable that the angle of the peripheral surface of the convex portion 21a with respect to the incident light is non-uniform within the peripheral surface. For example, when the shape of the convex portion 21a in plan view is a quadrangle, the change in the inclination of the peripheral surface from the vertex of the quadrangle toward the center of the quadrangle and the is different from the change in the slope of Therefore, there is a large variation in inclination depending on the portion within the peripheral surface of the convex portion 21a. Therefore, if the shape of the convex portion 21a is a quadrangle, the shape of the convex portion 21a is simple and the formation of the convex portion 21a is easy, and the scattering effect of the reflected light is enhanced.

When the width in the short-side direction and the width in the long-side direction of the convex portion 21a are different from each other in the plan view, both the width in the short-side direction and the width in the long-side direction are set to 10 μm or more and 100 μm or less. . The width in the direction of the short side is the length of the short side of a virtually arranged minimum rectangle in which the convex portion 21a is inscribed in the plan view. The width in the long side direction is the length of the long side of the smallest rectangle. Further, the maximum height h1 of the projections 21a may be set based on the width in the short side direction. If it is The form in which the convex portion 21a has a square shape in plan view is a form in which the width in the short side direction and the width in the long side direction are the same.

Moreover, the plurality of protrusions 21a are not limited to being arranged in a square lattice, but may be arranged in another two-dimensional lattice such as a hexagonal lattice, or may be arranged irregularly. Moreover, the period of arrangement of the plurality of convex portions 21a may not be constant.

The higher the irregularity of the shape and the irregularity of the arrangement of the plurality of projections 21a, the greater the scattering effect of the reflected light. For example, when the projections 21a have a rectangular shape in plan view and at least one of the widths in the short-side direction and the width in the long-side direction of the adjacent projections 21a is different from each other, a plurality of projections can be obtained. Compared with the form in which the shape of 21a is constant, the scattering effect of reflected light is enhanced.

Further, if the height of the convex portion 21a gradually increases from the end portion of the convex portion 21a in plan view toward the center, which is the center of gravity, the height of the convex portion 21a in the cross section along the thickness direction may constitute a straight line connecting the base end and the tip end of the peripheral surface. However, if the peripheral surface of the convex portion 21a forms a curved line in the cross section, the angle of the peripheral surface of the convex portion 21a with respect to the incident light becomes uneven within the peripheral surface, so that the scattering effect of the reflected light is enhanced. be done.

Note that the coloring structure 10 does not have to include the substrate 20 . When the coloring structure 10 does not include the substrate 20, the uneven structure layer 21 may be made of a material different from resin, such as synthetic quartz.

[Manufacturing method of coloring structure]
A method for manufacturing the coloring structure 10 will be described. As a method for forming the concave-convex structure of the concave-convex structure layer 21, transfer molding using heat or light, injection molding, machining such as cutting, etching, and the like are used. Intaglio plates used in transfer molding and injection molding are formed by machining or etching.

For example, a coating liquid made of a photocurable resin, which is the material of the uneven structure layer 21, is applied to an intaglio plate having unevenness in which the unevenness to be formed is reversed, and the base material 20 is overlaid on the surface of the layer made of the coating liquid. be done. After the substrate 20 and the intaglio are pressed against each other and irradiated with light such as ultraviolet rays, the layer made of the cured resin and the substrate 20 are released from the intaglio. As a result, the unevenness of the intaglio is transferred to the resin, the uneven structure layer 21 having the uneven structure on the surface is formed, and the laminate composed of the substrate 20 and the uneven structure layer 21 is formed.

Subsequently, an optical function layer 24 is formed on the uneven surface of the uneven structure layer 21 . The metal layer 22 and the dielectric layer 23 are formed by a known thin film forming technique such as sputtering or vacuum deposition depending on the material. Thereby, the coloring structure 10 is formed.

Since the color-developing structure 10 of the present embodiment includes the optical function layer 24 composed of two layers, the metal layer 22 and the dielectric layer 23, as the layer that causes interference, it includes a multilayer film layer as the layer that causes interference. Compared with the structure, its configuration is simple, and the number of necessary thin films to be formed is small. In addition, compared to a structure having multiple layers, manufacturing errors in the film thickness of the thin films are less likely to accumulate and affect the coloring of the coloring structure 10 . Therefore, the load required for manufacturing the coloring structure 10 can be reduced, and desired coloring can be easily obtained. In addition, since the heat load applied to the base material 20 and the uneven structure layer 21 during lamination of the thin films is reduced, the degree of freedom in selecting materials for the base material 20 and the uneven structure layer 21 is also increased.

In addition, in the above embodiment, the uneven structure of the uneven structure layer 21 may be composed of a plurality of recesses that are recessed with respect to the optical function layer 24 . That is, the concave-convex structure may be composed of a plurality of concave-convex elements that are convex portions or concave portions. When the concave-convex element is a concave portion, the configuration similar to the shape of the convex portion 21a is applied to the shape of the concave portion in plan view. That is, each of the width in the short-side direction and the width in the long-side direction of the concave portion in plan view should be 10 μm or more and 100 μm or less. Moreover, the same configuration as that for the height of the convex portion 21a is applied to the configuration relating to the depth of the concave portion. That is, the depth, which is the dimension of the concave portion along the thickness direction of the concave-convex structure layer 21, continuously increases from the end portion of the concave portion toward the central portion in plan view, and the width in the short side direction The ratio of the maximum depths in the recess may be 0.1 or more and 1.0 or less.

As described above, according to the first embodiment, the following effects can be obtained.
(1) Since the metal layer 22 is transparent to light in the visible region, reflected light is emitted from each interface of the optical function layer 24 and interference occurs. Therefore, the interference of light in the optical function layer 24 is enhanced. Furthermore, since the metal layer 22 is reflective, the intensity of the reflected light is enhanced. On the other hand, compared to the case where the metal layer 22 does not have transparency and has high reflectivity in the entire visible region, it is possible to suppress the reflection of light other than the specific wavelength region intensified by interference from becoming stronger. .

For these reasons, even if the number of thin films laminated in the optical function layer 24 is at least, the wavelength selectivity of the light reflected by the color-developing structure 10 is enhanced, so that the color corresponding to the specific wavelength range can be clearly visually recognized.

(2) Compared to the case of providing a multilayer film layer as a layer that causes light interference, the number of laminated thin films is small, so the load required for manufacturing the coloring structure 10 can be reduced, and the desired coloring can be achieved. easy to obtain. In addition, since the heat load applied to the base material 20 and the uneven structure layer 21 during lamination of the thin films is reduced, the degree of freedom in selecting materials for the base material 20 and the uneven structure layer 21 is also increased.

(3) Since the metal layer 22 has a wavelength band with a transmittance of 5% or more in the visible region, the light transmittance of the metal layer 22 is preferably obtained.
(4) Since the film thickness of the metal layer is 5 nm or more and 40 nm or less, the light transmittance of the metal layer 22 is preferably obtained.

(5) Since the metal layer 22 has a wavelength band with a reflectance of 30% or more in the visible region, the reflectivity of the metal layer 22 is preferably obtained.
(6) The visible region includes a wavelength region in which the difference between the refractive index of the metal layer 22 and the refractive index of the dielectric layer 23 is 0.3 or more. As a result, reflection occurs favorably at the interface between the dielectric layer 23 and the metal layer 22, so interference is strengthened, and reflected light with high intensity can be easily obtained.

(7) Since the film thickness of the dielectric layer 23 is 10 nm or more and 300 nm or less, the film thickness of the dielectric layer 23 is kept small. occurrence is suppressed.

(8) The refractive index of the dielectric layer 23 in the visible region is greater than 1.5 and less than or equal to 3.0, so that the difference in refractive index between the dielectric layer 23 and a layer adjacent to the dielectric layer 23 large and easy to secure. Therefore, it is easy to obtain reflected light with high intensity.

(9) Reflected light is scattered by the concave-convex structure, so that the color corresponding to the specific wavelength region intensified by the interference can be visually recognized at a wide viewing angle.
(10) Since the projections 25a can be arranged in a two-dimensional lattice, it is easy to design the arrangement of the projections 25a so that the reflected light is scattered isotropically. Therefore, it is possible to obtain the coloring structure 10 that is suitable for applications in which a small change in brightness depending on the viewing direction is desired. Moreover, since the size of the protrusions 25a is micro-sized, it is easier to form the uneven structure than when the size of the protrusions 25a is nano-sized.

(Second embodiment)
A second embodiment of the coloring structure will be described with reference to FIGS. 11 and 12. FIG. In the second embodiment, the concave-convex structure is different from that in the first embodiment. In the following, the differences between the second embodiment and the first embodiment will be mainly described, and the same reference numerals will be given to the same configurations as in the first embodiment, and the description thereof will be omitted.

As shown in FIG. 11, the coloring structure 11 of the second embodiment includes an uneven structure layer 25 instead of the uneven structure layer 21 of the first embodiment. The configurations of the substrate 20 and the optical function layer 24 composed of the metal layer 22 and the dielectric layer 23 are the same as in the first embodiment.

The concave-convex structure layer 25 has a concave-convex structure on the surface opposite to the surface facing the substrate 20 . The uneven structure includes a plurality of irregularly arranged protrusions 25a and recesses 25b positioned between the plurality of protrusions 25a. The material of the uneven structure layer 25 is the same as that of the uneven structure layer 21 of the first embodiment.

Also in the second embodiment, since the metal layer 22 has transmissivity and reflectivity, the wavelength selectivity of the light reflected by the coloring structure 11 is enhanced. Then, since the reflected light intensified by the interference in the optical function layer 24 is scattered due to the uneven structure of the uneven structure layer 25, the color corresponding to the specific wavelength range intensified by the interference can be widely observed. Clearly visible at any angle.

Details of the uneven structure of the uneven structure layer 25 will be described with reference to FIG. 12 . FIG. 12(a) is a plan view of the uneven structure layer 25 viewed from a viewpoint facing the surface thereof, and FIG. 12(b) shows the uneven structure layer 25 along the line II-II in FIG. is a cross-sectional view of. In FIG. 12(a), the convex portions 25a forming the concave-convex structure are indicated by dots.

As shown in FIG. 12A, the first direction Dx and the second direction Dy are directions included in a plane along the direction in which the uneven structure layer 25 spreads. are orthogonal. The plane is a plane orthogonal to the thickness direction of the uneven structure layer 25 .

When the uneven structure layer 25 is viewed from a viewpoint facing the surface thereof, the pattern formed by the convex portions 25a is a pattern consisting of a set of a plurality of rectangles R1 indicated by broken lines. Rectangle R1 is an example of a graphic element. The rectangle R1 has a shape extending in the second direction Dy, and in the rectangle R1, the length d3 in the second direction Dy is greater than or equal to the length d2 in the first direction Dx. The multiple rectangles R1 are arranged so as not to overlap in either the first direction Dx or the second direction Dy.

The length d2 in the first direction Dx is constant in the plurality of rectangles R1. The arrangement interval of the plurality of rectangles R1 in the first direction Dx is d2, that is, the plurality of rectangles R1 are arranged in the first direction Dx with a period of d2.

On the other hand, in the plurality of rectangles R1, the length d3 in the second direction Dy is irregular, and the length d3 in each rectangle R1 is a value selected from a population having a predetermined standard deviation. This population preferably follows a normal distribution. A pattern consisting of a plurality of rectangles R1 is obtained by, for example, temporarily arranging a plurality of rectangles R1 having a length d3 distributed with a predetermined standard deviation in a predetermined area, and determining whether or not each rectangle R1 is actually arranged according to a certain probability. By determining, it is formed by setting an area where the rectangle R1 is arranged and an area where the rectangle R1 is not arranged. In order to efficiently scatter the reflected light, the length d3 preferably has a distribution with an average value of 4.15 μm or less and a standard deviation of 1 μm or less.

When the area where the rectangles R1 are arranged is the area where the convex portion 25a is arranged and the adjacent rectangles R1 are in contact with each other, 1 area is formed by combining the areas where the rectangles R1 are arranged. One convex portion 25a is arranged. In such a configuration, the length of the convex portion 25a in the first direction Dx is an integral multiple of the length d2 of the rectangle R1.

The length d2 of the first direction Dx in the rectangle R1 is set equal to or less than the wavelength of light in the visible region in order to suppress the occurrence of rainbow-colored spectrum due to unevenness. In other words, the length d2 has a length below the sub-wavelength, ie below the wavelength band of the incident light. That is, the length d2 is preferably 830 nm or less, more preferably 700 nm or less. Furthermore, the length d2 is preferably smaller than the wavelength range of reflected light enhanced by the optical function layer 24 . For example, the length d2 is preferably about 300 nm when the color-developing structure 11 is used to develop a blue color, and the length d2 is preferably about 400 nm when the color-developing structure 11 is used to develop a green color. Preferably, the length d2 is about 460 nm when the coloring structure 11 is to develop a red color.

In order to enhance the scattering effect of reflected light, it is preferable that the concave-convex structure has many undulations, and when viewed from the viewpoint facing the surface of the concave-convex structure layer 25, the ratio of the area occupied by the convex portions 25a per unit area is 40%. It is preferable that it is more than 60%. For example, when viewed from the viewpoint facing the surface of the uneven structure layer 25, the ratio of the areas of the convex portions 25a and the concave portions 25b per unit area is preferably 1:1.

As shown in FIG. 12(b), the height h2 of the convex portion 25a is constant within the convex portion 25a and is also constant among the plurality of convex portions 25a. The convex portion 25a has a stepped shape that is one step from the plane on which the base portion of the convex portion 25a is located. The height h2 of the convex portion 25a may be set according to the desired color to be developed by the coloring structure 11 . If the height h2 of the projections 25a is larger than the surface roughness of the optical function layer 24 on the projections 25a and the recesses 25b, the effect of scattering the reflected light can be obtained.

However, in order to suppress interference of light caused by reflection on irregularities, the height h2 is preferably 1/2 or less of the wavelength of light in the visible region, that is, 415 nm or less. Furthermore, in order to suppress the interference of light, the height h2 is more preferably 1/2 or less of the wavelength range of the reflected light that is enhanced by the optical function layer 24 .

Moreover, if the height h2 is excessively large, the scattering effect of the reflected light due to the unevenness becomes too high, and the intensity of the reflected light tends to decrease. For example, in the coloring structure 11 exhibiting blue, the height h2 is preferably about 40 nm or more and 150 nm or less in order to obtain an effective spread of light, and in order to suppress the scattering effect from becoming too high. is preferably 100 nm or less.

Note that the rectangles R1 may form the pattern of the convex portion 25a by arranging two rectangles R1 arranged along the first direction Dx such that parts of the rectangles R1 overlap each other. That is, the plurality of rectangles R1 may be arranged in the first direction Dx at an arrangement interval smaller than the length d2, and the arrangement interval of the rectangles R1 may not be constant. In the portion where the rectangles R1 overlap, one convex portion 25a is positioned in one area where the areas in which the rectangles R1 are arranged are combined. In this case, the length of the convex portion 25a in the first direction Dx is different from the integral multiple of the length d2 of the rectangle R1. In addition, the length d2 of the rectangle R1 may not be constant. should be greater than the standard deviation. Even with such a configuration, the effect of scattering the reflected light can be obtained.

According to the concave-convex structure of the second embodiment, since the plurality of convex portions 25a extend along the second direction Dy, the light scattering effect of the concave-convex structure is mainly the first It acts on the reflected light in the direction along the direction Dx. That is, anisotropy occurs in scattering of reflected light.

The coloring structure 11 of the second embodiment is manufactured by a manufacturing method similar to that of the coloring structure 10 of the first embodiment. However, it is preferable to use a nanoimprint method such as a photo-nanoimprint method as a method for forming the uneven structure of the uneven structure layer 25 . The intaglio plate used in the nanoimprint method is made of, for example, synthetic quartz or silicon, and is formed using known microfabrication techniques such as lithography or dry etching that irradiates light or charged particle beams.

Note that the coloring structure 11 does not have to include the substrate 20 . When the color-developing structure does not include the base material 20, the uneven structure layer 25 may be formed of a material different from resin, such as synthetic quartz. It should be used.

Also, the figure forming the pattern of the convex portion 25a is not limited to a rectangle. The figure forming the pattern may be an oval or the like, and in short, any figure element having a shape whose length along the second direction Dy is equal to or greater than the length along the first direction Dx. good. It is sufficient that the length d2 in the first direction Dx and the length d3 in the second direction Dy of the graphic element satisfy the various conditions described above.

According to the second embodiment, the following effects are obtained in addition to the effects (1) to (9) of the first embodiment.
(10) Anisotropic scattering of reflected light can be obtained, so that the coloring structure 11 suitable for applications in which it is desired that the brightness of the visually recognized color changes depending on the viewing direction can be obtained.

(Third embodiment)
A third embodiment of the coloring structure will be described with reference to FIGS. 13-15. In the third embodiment, the concave-convex structure is different from that in the first embodiment. The following description will focus on the differences between the third embodiment and the first and second embodiments, and the same reference numerals will be assigned to the same configurations as in the first and second embodiments. omitted.

As shown in FIG. 13, the coloring structure 12 of the third embodiment includes an uneven structure layer 26 instead of the uneven structure layer 21 of the first embodiment. The configurations of the substrate 20 and the optical function layer 24 composed of the metal layer 22 and the dielectric layer 23 are the same as in the first embodiment.

The concave-convex structure layer 26 has a concave-convex structure on the surface opposite to the surface facing the substrate 20 . The uneven structure includes a plurality of irregularly arranged protrusions 26a and recesses 26b positioned between the plurality of protrusions 26a. The material of the uneven structure layer 26 is the same as that of the uneven structure layer 21 of the first embodiment.

Also in the third embodiment, since the metal layer 22 has transmissivity and reflectivity, the wavelength selectivity of the light reflected by the coloring structure 12 is enhanced. Since the reflected light intensified by the interference in the optical function layer 24 is scattered due to the uneven structure of the uneven structure layer 26, the color corresponding to the specific wavelength region intensified by the interference can be broadly observed. Clearly visible at any angle.

The protrusions 26a that constitute the uneven structure of the third embodiment are composed of first protrusion elements having the same configuration as the protrusions 25a of the second embodiment and second protrusion elements that extend in a band shape. It has 26 thickness superimposed structures.

The second convex elements are arranged so that the incident light is strongly diffracted in various directions. In the third embodiment, the light scattering effect based on the first convex elements and the Due to the diffraction effect of light, brighter colors can be observed than in the second embodiment.

Details of the uneven structure of the uneven structure layer 26 will be described with reference to FIGS. 14 and 15 . FIG. 14(a) is a plan view of a concave-convex structure composed only of second convex elements, and FIG. 14(b) is a cross-sectional view taken along line IV--IV in FIG. 14(a). In FIG. 14(a), the second convex elements are indicated by dots. The first direction Dx and the second direction Dy are defined similarly to the second embodiment.

As shown in FIG. 14(a), in plan view, the second convex element 26Eb has a belt-like shape extending with a constant width along the second direction Dy, and the plurality of second convex elements 26Eb has a They are arranged at intervals along one direction Dx. In other words, the pattern formed by the second convex elements 26Eb is a pattern consisting of a plurality of belt-like regions extending along the second direction Dy and arranged along the first direction Dx. The length d4 of the second convex element 26Eb in the first direction Dx may be the same as or different from the length d2 of the rectangle R1 that determines the pattern of the first convex element.

The arrangement interval de of the second convex elements 26Eb in the first direction Dx, that is, the arrangement interval of the band-shaped regions in the first direction Dx is at least part of the light reflected on the surface of the uneven structure formed by the second convex elements 26Eb part is set so as to be observed as first-order diffracted light. The first-order diffracted light is, in other words, diffracted light whose diffraction order m is 1 or -1. That is, when the incident angle of incident light is θ, the reflection angle of reflected light is φ, and the wavelength of diffracted light is λ, the arrangement interval de satisfies de≧λ/(sin θ+sin φ). For example, when targeting visible light with λ=360 nm, the arrangement interval de of the second convex elements 26Eb should be 180 nm or more. 1/2 or more. The arrangement interval de is the distance along the first direction Dx between the ends of two adjacent second convex elements 26Eb, and is the same for the second convex elements 26Eb in the first direction Dx. is the distance between the ends located on the sides of the

The periodicity of the pattern formed by the second convex elements 26Eb is reflected in the periodicity of the uneven structure of the uneven structure layer 26 . When the arrangement interval de of the plurality of second convex elements 26Eb is constant, a diffraction phenomenon on the outermost surface of the optical function layer 24 causes reflected light of a specific wavelength to be emitted from the optical function layer 24 at a specific angle. be. Since the reflection intensity of the light due to this diffraction is much stronger than the reflection intensity of the reflected light caused by the light scattering effect based on the first convex element, the light having metallic luster is visually recognized. On the other hand, a spectrum is generated by diffraction, and the visually recognized color changes according to the change in the viewing angle.

Therefore, for example, even if the structure of the optical function layer 24 and the first convex elements is designed so as to obtain the coloring structure 12 exhibiting blue, the arrangement interval de of the second convex elements 26Eb is about 400 nm to 5 μm. , a strong green to red light due to diffraction is observed depending on the viewing angle. On the other hand, for example, if the arrangement interval de of the second convex elements 26Eb is increased to about 50 μm, the range of angles at which light in the visible region is diffracted becomes narrower, so that the color change caused by diffraction is less visible. However, light with metallic luster can only be observed at a specific viewing angle.

Therefore, if the pattern of the second convex elements 26Eb is a pattern in which a plurality of periodic structures with different periods are superimposed instead of setting the array interval de to a constant value, light of a plurality of wavelengths will be mixed in the reflected light due to diffraction. Therefore, highly monochromatic light that has been spectrally separated becomes less visible. Therefore, bright and glossy colors can be observed at a wide viewing angle. In this case, the array spacing de is selected, for example, from a range of 360 nm or more and 5 μm or less, and the average value of the array spacing de of the plurality of second convex elements 26Eb is 1/ of the minimum wavelength in the wavelength range included in the incident light. 2 or more is sufficient.

However, as the standard deviation of the arrangement interval de increases, the arrangement of the second convex elements 26Eb becomes irregular and the scattering effect becomes dominant, making it difficult to obtain strong reflection by diffraction. Therefore, the arrangement interval de of the second convex elements 26Eb is determined according to the angle at which the light spreads due to the scattering effect of the light based on the first convex elements. It is preferable to decide to be emitted. For example, when the reflected blue light is emitted in a range of ±40° with respect to the incident angle, in the pattern of the second convex elements 26Eb, the arrangement interval de is set to an average value of 1 μm or more and 5 μm or less. It is set so that the standard deviation is about 1 μm. As a result, reflected light due to diffraction occurs at an angle that is approximately the same as the angle at which the light spreads due to the light scattering effect based on the first convex element.

That is, unlike a structure for diffracting and extracting light in a specific wavelength band, the uneven structure based on the plurality of second convex elements 26Eb uses diffraction to obtain a predetermined angular range by dispersing the arrangement interval de. It is a structure for emitting light of various wavelength ranges to the .

Furthermore, in order to generate a longer-period diffraction phenomenon, a square area with a side of 10 μm or more and 100 μm or less is used as a unit area, and in the pattern of the second convex elements 26Eb for each unit area, the arrangement interval de is It may be about 1 μm or more and 5 μm or less, and the standard deviation may be about 1 μm. Note that the plurality of unit regions may include a region having a constant array interval de within a range of 1 μm to 5 μm. Even if there is a unit area with a constant array interval de, if the array interval de varies with a standard deviation of about 1 μm in any of the unit areas adjacent to this unit area, the resolution of the human eye is reduced. can be expected to have the same effect as the configuration in which the arrangement interval de varies in all the unit regions.

The second convex elements 26Eb shown in FIG. 14A have periodicity only in the first direction Dx due to the arrangement interval de. The light scattering effect based on the first convex element mainly acts on the reflected light in the direction along the first direction Dx in plan view of the coloring structure 12, but the light reflected in the direction along the second direction Dy It can also partially affect the reflected light to the Therefore, the second convex elements 26Eb may also have periodicity in the second direction Dy. That is, the pattern of the second convex element 26Eb may be a pattern in which a plurality of band-like regions extending in the second direction Dy are arranged along each of the first direction Dx and the second direction Dy.

In such a pattern of the second convex elements 26Eb, for example, each of the arrangement intervals along the first direction Dx and the arrangement interval along the second direction Dy of the band-like regions has an average value of 1 μm or more and 100 μm or less. It suffices if there is some variation. Further, according to the difference between the influence of the light scattering effect based on the first convex element on the first direction Dx and the influence on the second direction Dy, the average value of the arrangement intervals along the first direction Dx, The average value of the array spacing along the second direction Dy may be different from each other, and the standard deviation of the array spacing along the first direction Dx and the standard deviation of the array spacing along the second direction Dy are different from each other. can be different.

As shown in FIG. 14B, the height h3 of the second convex elements 26Eb should be larger than the surface roughness of the optical function layer 24 on the convex portions 26a and concave portions 26b. However, as the height h3 increases, the diffraction effect based on the second convex elements 26Eb becomes more dominant in the effect of the concave-convex structure on the reflected light, and the light scattering effect based on the first convex elements is less likely to be obtained. Therefore, the height h3 is preferably approximately the same as the height h2 of the first projection element, and the height h3 may match the height h2. For example, the height h2 of the first convex element and the height h3 of the second convex element 26Eb are preferably within a range of 10 nm or more and 200 nm or less. The height h2 of the first convex element and the height h3 of the second convex element 26Eb are preferably within the range of 10 nm or more and 150 nm or less.

FIG. 15(a) is a plan view of the uneven structure layer 26 viewed from a viewpoint facing the surface thereof, and FIG. is a cross-sectional view of. In FIG. 15(a), the pattern formed by the first convex elements and the pattern formed by the second convex elements are shown with dots having different densities.

As shown in FIG. 15A, when the uneven structure layer 26 is viewed from a viewpoint facing the surface thereof, the pattern formed by the convex portions 26a is the first pattern formed by the first convex elements 26Ea. , and a second pattern formed by the second convex element 26Eb. That is, the region where the convex portion 26a is located includes a region S1 composed only of the first convex element 26Ea, a region S2 where the first convex element 26Ea and the second convex element 26Eb overlap, and a second convex element 26Eb. A region S3 composed only of two convex elements 26Eb is included. In FIG. 15(a), the first convex element 26Ea and the second convex element 26Eb are overlapped so that their ends are aligned in the first direction Dx. The end of the first projection element 26Ea and the end of the second projection element 26Eb may be displaced.

As shown in FIG. 15(b), in the region S1, the height of the projection 26a is the height h2 of the first projection element 26Ea. In the region S2, the height of the convex portion 26a is the sum of the height h2 of the first convex element 26Ea and the height h3 of the second convex element 26Eb. Also, in the region S3, the height of the convex portion 26a is the height h3 of the second convex portion element 26Eb. In this way, the projected portion 26a of the uneven structure layer 26 forms the first pattern in the projection image in the thickness direction, and the first projected portion element 26Ea having a predetermined height h2 and the projection image in the thickness direction The projected image constitutes the second pattern, and has a multi-stage shape in which the second convex elements 26Eb having a predetermined height h3 are stacked in the height direction. By the way, the convex portion 26a can be regarded as having the second convex element 26Eb stacked on the first convex element 26Ea from the base of the convex portion 26a, or the first convex element 26Eb is laminated on the second convex element 26Eb. It can also be considered that the elements 26Ea are laminated.

The pattern formed by the first convex element 26Ea and the pattern formed by the second convex element 26Eb may be arranged so that the first convex element 26Ea and the second convex element 26Eb do not overlap. good. Even with such a structure, the light scattering effect based on the first convex element 26Ea and the light diffraction effect based on the second convex element 26Eb can be obtained. However, if the first convex element 26Ea and the second convex element 26Eb are arranged so as not to overlap each other, the first convex element 26Ea can be arranged per unit area compared to the second embodiment. area becomes smaller, and the light scattering effect is reduced. Therefore, in order to enhance the light scattering effect and diffraction effect based on the convex elements 26Ea and 26Eb, the first convex element 26Ea and the second convex element 26Eb are arranged as shown in FIG. It is preferable to stack the convex portion 26a into a multi-stage shape.

The coloring structure 12 of the third embodiment can be manufactured by the same manufacturing method as that of the coloring structure 11 of the second embodiment. Also, the coloring structure 12 may not include the substrate 20 .
Also, the figure forming the pattern formed by the first convex element 26Ea is not limited to a rectangle. The figure forming the pattern may be an oval or the like, and in short, any figure element having a shape whose length along the second direction Dy is equal to or greater than the length along the first direction Dx. good. The length d2 in the first direction Dx and the length d3 in the second direction Dy of the graphic element only need to satisfy the various conditions described in the second embodiment.

According to the third embodiment, in addition to the effects (1) to (9) of the first embodiment and the effect (10) of the second embodiment, the following effects are obtained.
(11) The concave-convex structure provides a diffusion effect and a diffraction effect of reflected light. As a result, the reflected light intensified by the interference can be observed at a wide viewing angle, and the intensity of this reflected light is increased.

(Fourth embodiment)
A fourth embodiment of the coloring structure will be described with reference to FIGS. 16 to 21. FIG. In the fourth embodiment, the concave-convex structure is different from that in the first embodiment. In the following description, the differences between the fourth embodiment and the first to third embodiments will be mainly described, and the same reference numerals will be assigned to the same configurations as in the first to third embodiments, and the description thereof will be omitted.

As shown in FIG. 16, the coloring structure 13 of the fourth embodiment includes an uneven structure layer 27 instead of the uneven structure layer 21 of the first embodiment. The configurations of the substrate 20 and the optical function layer 24 composed of the metal layer 22 and the dielectric layer 23 are the same as in the first embodiment.

The concave-convex structure layer 27 has a concave-convex structure on the surface opposite to the surface facing the substrate 20 . The uneven structure includes a plurality of irregularly arranged protrusions 27a and recesses 27b positioned between the plurality of protrusions 27a. The material of the uneven structure layer 27 is the same as that of the uneven structure layer 21 of the first embodiment.

Also in the fourth embodiment, since the metal layer 22 has transmissivity and reflectivity, the wavelength selectivity of the light reflected by the coloring structure 13 is enhanced. Since the reflected light intensified by the interference in the optical function layer 24 is scattered due to the uneven structure of the uneven structure layer 27, the color corresponding to the specific wavelength region intensified by the interference can be broadly observed. Clearly visible at any angle.

Details of the concave-convex structure of the concave-convex structure layer 27 will be described with reference to FIGS. 17 and 18 . FIG. 17(a) is a plan view of the uneven structure layer 27 viewed from a viewpoint facing the surface thereof, and FIG. 17(b) shows the uneven structure layer 27 along line VII-VII in FIG. is a cross-sectional view of. In FIG. 17(a), the convex portions 27a forming the concave-convex structure are indicated by dots.

The first direction Dx and the second direction Dy are directions included in a plane along the direction in which the concavo-convex structure layer 27 spreads, and the first direction Dx and the second direction Dy are orthogonal to each other. The plane is a plane perpendicular to the thickness direction of the uneven structure layer 27 .

When the rugged structure layer 27 is viewed from a viewpoint facing the surface thereof, the pattern formed by the plurality of protrusions 27a is a pattern formed of a plurality of rectangles R2, which are formed of a plurality of rectangles R2 that are continuously arranged. It contains a plurality of rectangle groups RG. The sides of the rectangle R2 extend along each of the first direction Dx and the second direction Dy. One convex portion 27a is positioned in a region where one rectangular group RG is positioned.

Each rectangle group RG includes two or more rectangles R2 arranged in a row. In each rectangle group RG, a plurality of rectangles R2 are arranged along a predetermined direction, and adjacent rectangles R2 are in contact with each other. The number of rectangles R2 included in one rectangle group RG is not limited, and the number of rectangles R2 may not be constant in a plurality of rectangle groups RG.

FIG. 18 shows an enlarged view of the group of rectangles RG. The plurality of rectangles R2 are arranged along a virtual straight line V1 passing through the upper left vertices of the rectangles R2. The angle θ is the angle formed between the direction in which the plurality of rectangles R2 are arranged, that is, the direction in which the straight line V1 extends, and the first direction Dx.

The concavo-convex structure layer 27 includes a plurality of unit areas having a predetermined area in plan view, and the angle θ is constant for each unit area. The plurality of unit areas may include unit areas having different angles θ.

The length d5 in the first direction Dx is constant in the plurality of rectangles R2. The length d5 of the first direction Dx in the rectangle R2 is set equal to or less than the wavelength of light in the visible region in order to suppress the occurrence of rainbow-colored spectrum due to unevenness. That is, the length d5 is preferably 830 nm or less. For example, when the color-developing structure 13 is used to develop a blue color, the length d5 is preferably about 300 nm.

On the other hand, in the plurality of rectangles R2, the length d6 in the second direction Dy satisfies tan θ=d6/L when the angle θ is greater than 0° and less than 90° or greater than 90° and less than 180°. set. The length L satisfies αcos θ=L, where α is the length between the upper left vertices of two rectangles R2 adjacent to each other in the rectangle group RG. The length L may satisfy the above formula with the precision required in the manufacturing process, and for example, the decimal point in the above formula may be rounded down. That is, the length d5 and the length L do not have to match.

In order to efficiently scatter the reflected light, half the sum of the lengths d6 of the plurality of rectangles R2 in the second direction Dy in each rectangle group RG must have an average value of 4.15 μm or less and a standard deviation of It is preferable to have a distribution of 1 μm or less.

Further, in order to enhance the scattering effect of reflected light, it is preferable that the uneven structure has many undulations. It is preferably 40% or more and 60% or less.

As shown in FIG. 17(b), the height h4 of the convex portion 27a is constant within the convex portion 27a and is also constant among the plurality of convex portions 27a. The convex portion 27a has a stepped shape that is one step from the plane on which the base of the convex portion 27a is located. The height h4 of the convex portion 27a may be set according to the desired color to be developed by the coloring structure 13. FIG. If the height h4 of the convex portion 27a is larger than the surface roughness of the optical function layer 24 on the convex portion 27a and the concave portion 27b, the scattering effect of the reflected light can be obtained.

However, in order to suppress interference of light caused by reflection on irregularities, the height h4 is preferably 1/2 or less of the wavelength of light in the visible region, that is, 415 nm or less. Furthermore, in order to suppress the interference of light, the height h4 is more preferably 1/2 or less of the wavelength range of the reflected light that is enhanced by the optical function layer 24 .

Moreover, if the height h4 is excessively large, the scattering effect of the reflected light due to the unevenness becomes too high, and the intensity of the reflected light tends to decrease. For example, in the color-developing structure 13 exhibiting blue, the height h4 is preferably about 40 nm or more and 150 nm or less in order to obtain an effective spread of light. is preferably 100 nm or less.

Note that the height h4 of the convex portion 27a may be different for each unit region. When there is a difference in the height h4 of the convex portion 27a in a plurality of unit regions, the difference is preferably 5 nm or more and 200 nm or less.

FIG. 19 shows the arrangement of the convex portions 27a when θ=0° or θ=180°. In this case, length L is equal to length α. Also, FIG. 20 shows the arrangement of the convex portions 27a when θ=90°. In this case, the length L is 0 and the length α matches the length d6.

In the fourth embodiment, the light scattering effect of the projections 27a mainly acts on the reflected light in the direction orthogonal to the direction in which the rectangles R2 are arranged when the coloring structure 13 is viewed from above. Therefore, by controlling the angle θ, it is possible to control the direction in which the reflected light is scattered, that is, to control the anisotropy in the scattering of the reflected light. Further, the color-developing structure 13 can be configured such that the area where a bright color is visually recognized changes according to the viewing direction by controlling the angle θ in a plurality of unit areas. According to such a configuration, the color-developing structure 13 can be manufactured more easily than, for example, when the protrusions are band-shaped and the directions in which the protrusions extend are changed for each unit region.

Note that the length d5 of the rectangle R2 may not be constant. The standard deviation of 1/2 of the sum of the lengths d6 of the plurality of rectangles R2 in the second direction Dy in each rectangle group RG is preferably larger than the standard deviation of the lengths d5 of the rectangles R2 in the first direction Dx. A large variation in the length d5 enhances the scattering effect of the reflected light.

Further, the shape of the convex portion 27a in plan view may be a circle or a polygon such as a pentagon as long as the shape is inscribed in the rectangle R2. FIG. 21 shows an example in which the convex portion 27a is circular and inscribed in the rectangle R2.

In other words, the shape of the protrusions 27a in plan view may be a figure inscribed in a virtual rectangle having sides along the first direction Dx and the second direction Dy. The pattern to be constructed may be a pattern consisting of a set of a plurality of graphic elements that are such figures. The configuration of the virtual rectangle may be the same as the configuration of the rectangle R2 described above.

The coloring structure 13 of the fourth embodiment can be manufactured by the same manufacturing method as that of the coloring structure 11 of the second embodiment. When the shape of the convex portion 27a in a plan view is a rectangle R2 inscribed in the virtual rectangle, that is, a shape matching the virtual rectangle, the convex portion 27a is formed or an intaglio for forming the convex portion 27a is used. When fabricating , the pattern can be drawn at high speed by using the electron beam lithography of the variable shaping system. Also, the coloring structure 13 may not include the substrate 20 .

According to the fourth embodiment, the following effects are obtained in addition to the effects (1) to (9) of the first embodiment.
(12) Since anisotropy can be obtained in the scattering of reflected light, the coloring structure 13 suitable for applications in which it is desired that the brightness of the visually recognized color changes depending on the viewing direction can be obtained. By controlling the angle θ, the anisotropy of scattering of reflected light can be easily controlled.

[Modification]
Each of the above embodiments can be modified and implemented as follows.
- As shown in FIG. 22, the coloring structure may include an absorption layer 28 that absorbs light in the visible region on the opposite side of the uneven structure layer to the optical function layer 24 . In this case, the rugged structure layer, the metal layer 22, and the dielectric layer 23 are arranged in this order, and the coloring structure is observed from the side where the optical function layer 24 is positioned with respect to the rugged structure layer. The absorption layer 28 is, for example, in contact with the surface of the substrate 20 opposite to the uneven structure layer.

The absorption layer 28 absorbs at least part of the light that has passed through the optical function layer 24 in the visible region. The absorption layer 28 is a black layer containing a black pigment or the like, and may absorb light in the entire visible range. Since the absorption layer 28 is provided, light in a wavelength range different from the wavelength range intensified by interference in the optical function layer 24 is absorbed at the interface between each layer inside the color-developing structure and the interface between the color-developing structure and its exterior. It is suppressed that the light is reflected by and emitted toward the observer. Therefore, the vividness of the color seen in the coloring structure is enhanced.

Further, instead of providing the absorption layer 28, the substrate 20 may have a property of absorbing light in the visible region and function as an absorption layer.
In FIG. 22, the coloring structure includes the uneven structure layer 21 of the first embodiment, but the coloring structure may include the uneven structure layer of the second to fourth embodiments. .

- As shown in FIG. 23, the color-developing structure may include an absorption layer 28 that absorbs light in the visible region on the opposite side of the optical function layer 24 to the concave-convex structure layer. In this case, the concave-convex structure layer, the dielectric layer 23 and the metal layer 22 are arranged in this order, and the coloring structure is observed from the side where the concave-convex structure layer is positioned with respect to the optical function layer 24 . Absorbing layer 28 contacts metal layer 22 .

The absorption layer 28 absorbs at least part of the light that has passed through the optical function layer 24 in the visible region. The absorption layer 28 is a black layer containing a black pigment or the like, and may absorb light in the entire visible range. Since the absorption layer 28 is provided, light in a wavelength range different from the wavelength range intensified by interference in the optical function layer 24 is absorbed at the interface between each layer inside the color-developing structure and the interface between the color-developing structure and its exterior. It is suppressed that the light is reflected by and emitted toward the observer. Therefore, the vividness of the color seen in the coloring structure is enhanced.

In FIG. 23, the coloring structure includes the uneven structure layer 21 of the first embodiment, but the coloring structure may include the uneven structure layer of the second to fourth embodiments. .
- As shown in FIG. 24, the coloring structure 14 may be provided with the optical function layer 24 on the support layer 29, which is a flat layer, without the uneven structure layer. According to such a configuration, at a specific viewing angle, a color corresponding to a specific wavelength region intensified by interference in the optical function layer 24 can be clearly visually recognized.

- The dielectric layer 23 may have absorptivity in a partial wavelength range of light in the visible region. With such a configuration, it is possible to prevent the light in the wavelength range having absorption properties from being included in the reflected light from the color-developing structure. Therefore, the vividness of the color seen in the coloring structure is enhanced. Such a dielectric layer 23 is made of, for example, a metal compound such as a metal oxide, a metal nitride, or a metal oxynitride. have.

[Example]
The coloring structure described above and the method for manufacturing the same will be described using specific examples.

(Example 1)
As Example 1, a coloring structure corresponding to the first embodiment was formed.
First, a mold for forming an uneven structure was formed by transfer molding using light. Since light with a wavelength of 365 nm is used as light to be irradiated, synthetic quartz, which transmits light with this wavelength, was used as the material of the mold. A mold was formed by forming on a synthetic quartz substrate the unevenness which was the reverse of the unevenness to be formed on the uneven layer, using electron beam writing and dry etching. Specifically, a square region with a side of 45 μm in plan view was recessed from the end to the center while continuously changing the depth so as to draw an arc. . The central depth of the square area is 7 μm. OPTOOL HD-1100 (manufactured by Daikin Industries, Ltd.) was applied as a release agent to the surface of the mold.

Next, a photocurable resin is applied to a PET film that has been subjected to an easy-adhesion treatment on one side. was cured. After that, the cured resin and PET film were separated from the mold. As a result, a laminate of the concave-convex structure layer having the concave-convex structure and the PET film as the substrate was obtained.

Subsequently, a one-layer aluminum film having a thickness of 10 nm was formed as a metal layer on the uneven surface of the obtained laminate of the uneven structure layer and the base material by a vacuum deposition method. Furthermore, a one-layer titanium oxide film having a film thickness of 50 nm was formed as a dielectric layer on the upper surface of the metal layer by vacuum deposition.
Thus, a coloring structure of Example 1 was obtained.

(Example 2)
As Example 2, a coloring structure corresponding to the second embodiment was formed.

First, a mold for forming a concavo-convex structure was formed using an optical imprint method. Since light with a wavelength of 365 nm is used as light for irradiation in the photo-nanoimprinting method, synthetic quartz, which transmits light with this wavelength, was used as a material for the mold. A mold was formed by forming, on a synthetic quartz substrate, unevenness obtained by reversing the unevenness to be formed on the uneven structure layer using electron beam writing and dry etching. The concave-convex structure to be formed is the concave-convex structure of the second embodiment. OPTOOL HD-1100 (manufactured by Daikin Industries, Ltd.) was applied as a release agent to the surface of the mold.

Next, a photocurable resin is applied to a PET film that has been subjected to an easy-adhesion treatment on one side. was cured. After that, the cured resin and PET film were separated from the mold. As a result, a laminate of the concave-convex structure layer having the concave-convex structure and the PET film as the substrate was obtained.

Subsequently, a one-layer aluminum film having a thickness of 10 nm was formed as a metal layer on the uneven surface of the obtained laminate of the uneven structure layer and the base material by a vacuum deposition method. Furthermore, a one-layer titanium oxide film having a film thickness of 50 nm was formed as a dielectric layer on the upper surface of the metal layer by vacuum deposition.
Thus, a coloring structure of Example 2 was obtained.

(observation result)
The coloring structures of Examples 1 and 2 were observed from the side where the optical function layer is positioned with respect to the uneven structure layer. As a result of observation from a direction inclined at 30° with respect to the direction perpendicular to the surface of the base material, in both Examples 1 and 2, a glossy blue color was confirmed with good visibility.

Furthermore, the angular dependence of the reflected light of the coloring structure was measured. As a result of incident white light on the color-developing structure at an incident angle of 30°, in both Examples 1 and 2, scattered light was observed within a range of ±30° with respect to specularly reflected light.

Dx... First direction Dy... Second direction 10, 11, 12, 13, 14... Color development structure 20... Base material 21, 25, 26, 27... Concavo-convex structure layer 22... Metal layer 23... Dielectric layer 24... Optics Functional layer 21a, 25a, 26a, 27a... Protrusions 25b, 26b, 27b... Recesses 28... Absorption layer.

Claims (12)

An optical functional layer comprising a metal layer and a dielectric layer, the optical functional layer emitting reflected light enhanced by interference,
The refractive index of the metal layer in the visible region is different from the refractive index of the dielectric layer in the visible region,
The coloring structure, wherein the thickness of the metal layer is 5 nm or more and 40 nm or less. 2. The coloring structure according to claim 1, wherein the metal layer has a wavelength band with a transmittance of 5% or more in the visible region. 3. The coloring structure according to claim 1, wherein the metal layer has a wavelength band with a reflectance of 30% or more in the visible region. The coloring structure according to any one of claims 1 to 3, wherein the visible region includes a wavelength region in which the difference between the refractive index of the metal layer and the refractive index of the dielectric layer is 0.3 or more. The coloring structure according to any one of claims 1 to 4, wherein the dielectric layer has a thickness of 10 nm or more and 300 nm or less. The coloring structure according to any one of claims 1 to 5, wherein the dielectric layer has a refractive index of more than 1.5 and not more than 3.0 in the visible region. further comprising an uneven structure layer that has an uneven structure composed of a plurality of uneven elements that are convex parts or concave parts on the surface and supports the optical function layer;
The optical function layer has a surface shape along the uneven structure,
In a plan view of the uneven structure viewed from the direction along the thickness direction of the uneven structure layer, each of the width in the short side direction and the width in the long side direction of the uneven element is 10 μm or more and 100 μm or less, and The dimension of the concave-convex element along the thickness direction increases from the end to the center of the concave-convex element in plan view, and the thickness direction in the concave-convex element with respect to the width in the short side direction. 7. The coloring structure according to any one of claims 1 to 6, wherein the ratio of the maximum values of the dimensions along is 0.1 or more and 1.0 or less. further comprising an uneven structure layer that has an uneven structure on its surface and supports the optical function layer;
The optical function layer has a surface shape along the uneven structure,
The protrusions forming the uneven structure have a step shape of one or more steps from the plane on which the base of the protrusion is located, and when viewed from the viewpoint facing the surface of the uneven structure layer, the plurality of protrusions are A plurality of patterns having a length along a first direction equal to or less than a sub-wavelength and a length along a second direction perpendicular to the first direction equal to or greater than the length along the first direction wherein the standard deviation of the length along the second direction is greater than the standard deviation of the length along the first direction in the plurality of graphic elements 7. The coloring structure according to any one of 1 to 6. When the rugged structure is viewed from a viewpoint facing the surface of the rugged structure layer, the pattern formed by the plurality of convex portions includes a first pattern formed by a set of the graphic elements and a pattern extending along the second direction. , and a second pattern made up of a plurality of band-shaped regions arranged along the first direction are superimposed on each other,
In the second pattern, the arrangement interval of the strip-shaped regions along the first direction is not constant among the plurality of strip-shaped regions, and the average value of the arrangement spacing of the plurality of strip-shaped regions is the same as the optical function layer. 1/2 or more of the minimum wavelength in the wavelength range included in the incident light of
The projections are elements that constitute the first pattern when projected in the thickness direction of the uneven structure layer, and have a predetermined height. 9. The coloring structure according to claim 8, wherein the elements constituting the second pattern and having a predetermined height have a multi-stage shape in which the convex elements are stacked in the height direction. further comprising an uneven structure layer that has an uneven structure on its surface and supports the optical function layer;
The optical function layer has a surface shape along the uneven structure,
Seen from a viewpoint facing the surface of the uneven structure layer,
The pattern formed by the plurality of protrusions forming the uneven structure has a side along a first direction having a length equal to or less than the sub-wavelength and a side along a second direction perpendicular to the first direction. A pattern consisting of a set of multiple graphic elements each inscribed in a virtual rectangle,
In each of a plurality of unit regions included in the uneven structure layer, the rectangles are arranged along a direction forming an angle of θ with respect to the first direction, and in at least one of the unit regions, the angle θ is 0°. The coloring structure according to any one of claims 1 to 6, which is greater than 90° or greater than 90° and less than 180°. 11. The color-developing structure according to any one of claims 7 to 10, further comprising an absorption layer that absorbs at least part of light in the visible region on the side opposite to the optical function layer with respect to the uneven structure layer. 11. The color-developing structure according to any one of claims 7 to 10, further comprising an absorption layer that absorbs at least part of light in the visible region on the side opposite to the uneven structure layer with respect to the optical function layer.

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