Color-developing structure

Abstract

To provide a coloring structure capable of obtaining clear coloring with a small number of layers.SOLUTION: A coloring structure 10 is a multilayer film layer 30 including three or more thin film layers and emitting reflected light intensified by interference. The multilayer film layer 30 including a dielectric layer 31 being a thin film layer consisting of a dielectric and a metal layer 32 being a thin film layer consisting of metal has a structure obtained by alternately laminating the metal layer 32 and the dielectric layer 31; and the metal layer 32 has the reflectivity and transmissivity of light in a visible region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a color-producing structure that exhibits structural color. [Background technology]

[0002] Structural color is a color that is visible due to optical phenomena caused by the fine structure of an object, such as diffraction, interference, and scattering of light. An example of a structure that exhibits structural color due to light interference is a color-producing structure with a multilayer film. The multilayer film has a structure in which high refractive index layers and low refractive index layers are alternately stacked. Each of the high refractive index and low refractive index layers is a thin film made of a dielectric such as an inorganic oxide. Light is reflected at each interface between the high refractive index and low refractive index layers, and the interference of this reflected light intensifies light in a specific wavelength range.

[0003] The emission angle of reflected light, which is amplified by interference in a multilayer film, depends on the angle of the incident light. Therefore, in a color-producing structure in which multilayer films are stacked on a plane, the observation angle in which the reflected light can be seen for incident light from one angle is narrow (see, for example, Patent Document 1). On the other hand, in a color-producing structure in which multilayer films are stacked on a fine uneven surface, the reflected light amplified by interference is emitted in multiple directions due to the unevenness, thus widening the observation angle in which the reflected light can be seen (see, for example, Patent Document 2). The range of such observation angles is selected according to the application of the color-producing structure. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2008-229997 [Patent Document 2] Japanese Patent Publication No. 2005-153192 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In a color - developing structure having a multilayer film layer, in order to obtain vivid color development, it is necessary to increase the number of stacked layers of the high - refractive - index layer and the low - refractive - index layer. Thereby, the intensity of the reflected light in a specific wavelength range enhanced by interference is increased, and the light other than the above - mentioned specific wavelength range is weakened by interference and its reflection is suppressed. Generally, in order to obtain distinct color development of a specific color, stacking of 10 or more dielectric thin films is required.

[0006] In such a manufacturing process of the multilayer film layer, it is required to alternately stack high - refractive - index layers and low - refractive - index layers made of different materials with precise film thicknesses. When the errors in the film thickness of each layer accumulate, it becomes difficult to obtain the desired color development, so there is concern about a decrease in yield. Therefore, as the number of stacked dielectric thin films increases, the load required for manufacturing the color - developing structure becomes larger.

[0007] Also, the thicker the multilayer film layer, the greater the optical path difference caused by the difference in the angles of incident light and reflected light. If the observation angle changes, the angle of the observable reflected light and the corresponding angle of the incident light change. As a result, the wavelength range enhanced by interference is more likely to change depending on the observation angle as the multilayer film layer is thicker. Therefore, when a color - developing structure is used for an article observed from a plurality of angles, the visible color becomes less stable. Therefore, a structure that can obtain distinct color development with a small number of stacked layers is desired.

Means for Solving the Problem

[0008] The color - developing structure for solving the above problems is a multilayer film layer including 3 or more thin - film layers, provided with the multilayer film layer that emits reflected light enhanced by interference. The multilayer film layer includes a dielectric layer which is the thin - film layer made of a dielectric and a metal layer which is the thin - film layer made of a metal, and has a structure in which the metal layer and the dielectric layer are alternately stacked. The metal layer has reflectivity and transmittance for light in the visible region.

[0009] According to the above configuration, because the metal layer is light-transmitting, the light reflected at each interface of the multilayer film layer interferes, and light in a specific wavelength range that is amplified is emitted from the color-emitting structure. Furthermore, because the metal layer is light-reflecting, the intensity of the reflected light from the multilayer film layer is increased compared to when the multilayer film layer is a laminate of only dielectric thin films. On the other hand, compared to when the metal layer is not light-transmitting but has high reflectivity over a wide range of the visible region, the reflection of light outside the specific wavelength range amplified by interference is suppressed.

[0010] Therefore, clear color development corresponding to the specific wavelength range mentioned above can be obtained with a small number of layers. As a result, the burden required for manufacturing the color-developing structure can be reduced. In addition, because the thickness of the multilayer film can be reduced, it is possible to suppress the change in the wavelength range intensified by interference depending on the observation angle, and the color visible in the color-developing structure becomes more stable.

[0011] In the above configuration, the metal layer may have light-absorbing properties in the visible region. With the above configuration, since the metal layer has light-absorbing properties, it is possible to suppress the inclusion of light outside the specific wavelength range mentioned above in the reflected light from the color-producing structure. As a result, clearer coloration can be obtained.

[0012] In the above configuration, the thickness of the metal layer may be 5 nm or more and 40 nm or less. According to the above configuration, suitable light transmittance in the metal layer can be obtained.

[0013] In the above configuration, the multilayer film includes one or more metal layers, and each metal layer may be a single thin metal film. With the above configuration, compared to the case where the metal layer is a laminate of multiple thin metal films, it is possible to reduce the number of thin film layers and thus reduce the burden required to manufacture the color-developing structure.

[0014] In the above configuration, the multilayer film includes one or more metal layers, and at least one of the metal layers may be a laminate of multiple metal thin films made of different metals.

[0015] With the above configuration, since multiple metal thin films absorb light in different wavelength ranges, the metal layer can absorb light in a wider wavelength range compared to when the metal layer consists of a single metal thin film. Therefore, in the multilayer film, light other than the specific wavelength range mentioned above is absorbed over a wider wavelength range, which can narrow the peak width and full width at half maximum in the spectrum of the reflected light. Consequently, a more monochromatic color can be obtained.

[0016] In the above configuration, the multilayer film includes two or more metal layers, and among the multilayer film, only the metal layer closest to the incident surface, which is the surface to which light is incident in the color-generating structure, is a laminate of the plurality of metal thin films, while the other metal layers may be single metal thin films.

[0017] With the above configuration, the metal layer where light absorption primarily occurs is composed of multiple thin metal films, enabling precise absorption of light across a wide wavelength range. Therefore, highly monochromatic coloration can be obtained while suppressing an increase in the number of thin film layers in the multilayer film.

[0018] In the above configuration, the thickness of the dielectric layer may be 10 nm or more and 300 nm or less. With the above configuration, the thickness of the dielectric layer is kept low, which suppresses problems caused by an increase in the thickness of the dielectric layer, such as difficulty in controlling the wavelength range that is amplified by interference, and warping of the color-generating structure due to stress and peeling of the dielectric thin film.

[0019] In the above configuration, the refractive index of the dielectric layer in the visible region may be 1.5 or more and 3.0 or less. With the above configuration, the high refractive index of the dielectric layer enhances the interference of light in the multilayer film, making it easier to obtain high-intensity reflected light.

[0020] In the above configuration, the multilayer film includes two or more dielectric layers, and among the multilayer film, the thin film layer closest to the incident surface, which is the surface to which light is incident in the color-generating structure, may be the dielectric layer.

[0021] With the above configuration, light outside the specific wavelength range is more easily attenuated by interference. Therefore, it is possible to suppress the inclusion of light outside the specific wavelength range in the reflected light from the color-producing structure, resulting in clearer coloration.

[0022] In the above configuration, the dielectric layer closest to the incident surface may be thinner than the other dielectric layers. According to the above configuration, it is possible to narrow the peak width in the spectrum of reflected light, that is, to improve the monochromaticity of the reflected light.

[0023] In the above configuration, the multilayer film layer may consist of four thin film layers, each comprising two metal layers and two dielectric layers. With the above configuration, clear color development can be accurately obtained with a small number of layers. [Effects of the Invention]

[0024] According to the present invention, clear color development can be obtained in a color-developing structure with a small number of layers. [Brief explanation of the drawing]

[0025] [Figure 1] A diagram showing an example of the cross-sectional structure of the color-developing structure of the first embodiment. [Figure 2] A diagram showing an example of the cross-sectional structure of the color-developing structure of the first embodiment. [Figure 3] A diagram showing an example of the cross-sectional structure of the color-developing structure of the first embodiment. [Figure 4] A diagram showing an example of the cross-sectional structure of the color-developing structure of the first embodiment. [Figure 5] A diagram showing the reflectance spectra for test examples 1A to 1E. [Figure 6]A figure showing the reflectance spectrum for test example 2A. [Figure 7] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on test example 3A, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 8] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on Test Example 3B, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 9] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on test example 3C, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 10] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on Test Example 3D, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 11] A diagram showing the ratio of reflection, transmission, and absorption of light with a wavelength of 500 nm for test examples 3A to 3D. [Figure 12] A diagram showing the ratio of reflection, transmission, and absorption of light with a wavelength of 780 nm for test examples 3A to 3D. [Figure 13] A diagram showing the reflectance, transmission, and absorption spectra for test example 4A. [Figure 14] A diagram showing the reflectance, transmission, and absorption spectra for test example 4B. [Figure 15] A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 500 nm for test examples 4A and 4B. [Figure 16] A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 780 nm for test examples 4A and 4B. [Figure 17] This figure shows the reflectance spectra for test example 5A when the observation angle is changed. [Figure 18]This figure shows the reflectance spectrum for test example 6A when the observation angle is changed. [Figure 19] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on Test Example 6A at 0°, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 20] This figure shows the results of an electromagnetic field simulation analysis of the behavior of light incident on test example 6A at a 30° angle, where (a) shows the case where the wavelength of the incident light is 500 nm, and (a) shows the case where the wavelength of the incident light is 780 nm. [Figure 21] A diagram showing an example of the cross-sectional structure of the color-developing structure of the second embodiment. [Figure 22] A diagram showing the reflectance spectra for test examples 7A to 7E. [Figure 23] This diagram shows the color of the reflected light from test examples 7A to 7E using an xy chromaticity diagram. [Figure 24] A figure showing the reflectance spectrum for test example 8A. [Figure 25] A diagram showing the color of the reflected light from test example 8A using an xy chromaticity diagram. [Figure 26] A diagram showing the reflectance, transmission, and absorption spectra for test example 9A. [Figure 27] A diagram showing the reflectance, transmission, and absorption spectra for test example 9B. [Figure 28] A diagram showing the reflectance, transmission, and absorption spectra for test example 9C. [Figure 29] This diagram shows the color of the reflected light from test examples 9A to 9C using an xy chromaticity diagram. [Figure 30] A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 525 nm for test examples 9A to 9C. [Figure 31] A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 580 nm for test examples 9A to 9C. [Figure 32] A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 600 nm for test examples 9A to 9C. [Figure 33]A diagram showing the ratios of reflection, transmission, and absorption of light with a wavelength of 780 nm for test examples 9A to 9C. [Figure 34] This figure shows the reflectance spectra for test example 10A when the observation angle is changed. [Figure 35] A diagram showing the color of the reflected light from test example 10A using an xy chromaticity diagram. [Figure 36] This figure shows the reflectance spectra for test example 11A when the observation angle is changed. [Figure 37] A diagram showing the color of the reflected light from test example 11A using an xy chromaticity diagram. [Modes for carrying out the invention]

[0026] (First Embodiment) A first embodiment of the color-generating structure will be described with reference to Figures 1 to 20. The incident and reflected light targeted by the color-generating structure are visible light. In the following description, visible light refers to light in the wavelength range of 360 nm to 830 nm.

[0027] [Structure of the color-developing structure] As shown in Figure 1, the color-developing structure 10 comprises a support layer 20 and a multilayer film layer 30. The multilayer film layer 30 comprises a plurality of thin film layers including a dielectric layer 31 and a metal layer 32. The dielectric layer 31 and the metal layer 32 are stacked alternately.

[0028] The support layer 20 supports the multilayer film layer 30. The support layer 20 transmits light across the entire visible region, that is, it is transparent to light in the visible region. The support layer 20 is, for example, a synthetic quartz substrate or a resin film. Examples of resin films include films made of polyethylene terephthalate, polycarbonate, polypropylene, polymethyl methacrylate, etc. Alternatively, the support layer 20 may be a resin molded layer, which is a layer formed from a resin such as a photocurable resin, thermosetting resin, or thermoplastic resin. Furthermore, the support layer 20 may comprise a substrate such as a synthetic quartz substrate or a resin film, and a resin molded layer laminated on the substrate.

[0029] The surface of the support layer 20 that is in contact with the multilayer film layer 30 may be flat or may have irregularities. The size of the irregular elements, which are recesses or protrusions included in the irregular structure, may be on the micro-order or the nano-order. Furthermore, the irregular elements may be arranged regularly or irregularly. For example, when viewed from a viewpoint facing the surface of the support layer 20, the irregular elements may have a strip shape extending in a predetermined direction with a width less than or equal to the wavelength of light in the visible region and an irregular length distributed with a predetermined standard deviation. Alternatively, when viewed from the above viewpoint, the irregular elements may have a width of 10 μm to 100 μm and a length of 10 μm or more and may be arranged in a two-dimensional grid.

[0030] The multilayer film layer 30 covers the surface of the support layer 20 and has a shape that follows the surface shape of the support layer 20. That is, when the surface of the support layer 20 is flat, both the front and back surfaces of the multilayer film layer 30 are flat. On the other hand, when the surface of the support layer 20 is uneven, each thin film layer in the multilayer film layer 30 has a shape that follows the unevenness of the support layer 20, and both the front and back surfaces of the multilayer film layer 30 have unevenness that follows the unevenness of the support layer 20.

[0031] The number of thin film layers in the multilayer film layer 30 is preferably 3 to 8, and most preferably 4. The thin film layer in contact with the support layer 20 may be a dielectric layer 31 or a metal layer 32.

[0032] Figure 1 shows an example in which a multilayer film layer 30 comprises three thin film layers and a dielectric layer 31 is in contact with a support layer 20. In this case, the multilayer film layer 30 comprises two dielectric layers 31 and one metal layer 32, with the metal layer 32 sandwiched between the two dielectric layers 31. As illustrated in Figure 1, when the number of thin film layers is odd and the dielectric layer 31 is in contact with the support layer 20, the outermost layer of the multilayer film layer 30 on the side opposite the support layer 20 is the dielectric layer 31.

[0033] Figure 2 shows an example in which the multilayer film layer 30 comprises three thin film layers and a metal layer 32 is in contact with the support layer 20. In this case, the multilayer film layer 30 comprises two metal layers 32 and one dielectric layer 31, with the dielectric layer 31 sandwiched between the two metal layers 32. As illustrated in Figure 2, when the number of thin film layers is odd and the metal layer 32 is in contact with the support layer 20, the outermost layer of the multilayer film layer 30 on the side opposite the support layer 20 is the metal layer 32.

[0034] Figure 3 shows an example in which the multilayer film layer 30 comprises four thin film layers and a metal layer 32 is in contact with the support layer 20. In this case, the multilayer film layer 30 comprises two dielectric layers 31 and two metal layers 32, and the metal layers 32 and dielectric layers 31 are arranged alternately in this order on the support layer 20. As illustrated in Figure 3, when the number of thin film layers is even and the metal layer 32 is in contact with the support layer 20, the outermost layer of the multilayer film layer 30 on the side opposite the support layer 20 is the dielectric layer 31.

[0035] Figure 4 shows an example in which the multilayer film layer 30 comprises four thin film layers and the dielectric layer 31 is in contact with the support layer 20. In this case, the multilayer film layer 30 comprises two dielectric layers 31 and two metal layers 32, and the dielectric layers 31 and metal layers 32 are arranged alternately in this order on the support layer 20. As illustrated in Figure 4, when the number of thin film layers is even and the dielectric layer 31 is in contact with the support layer 20, the outermost layer of the multilayer film layer 30 on the side opposite the support layer 20 is the metal layer 32.

[0036] The dielectric layer 31 is a single thin film made of a dielectric material. The dielectric layer 31 transmits light across the entire visible region, that is, it is transparent to light in the visible region. The material of the dielectric layer 31 is a material with lower conductivity than a metallic conductor, and specifically, it is an insulator or a semiconductor. In this embodiment, a conductor is a material without a band gap, an insulator is a material with a band gap large enough not to conduct electricity, and a semiconductor is a material with a band gap small enough to conduct electricity. Specific examples of materials for the dielectric layer 31 include inorganic insulating materials such as TiO2, ZnS, Nb2O5, Ta2O5, and ZrO2, and semiconductor materials such as indium tin oxide. The dielectric layer 31 is preferably 10 nm or more and 300 nm or less in thickness. The dielectric layer 31 is formed by known thin-film formation techniques such as sputtering or vacuum deposition.

[0037] A high refractive index of the dielectric layer 31 is preferable because it can enhance the interference of light in the multilayer film layer 30 and also allow for a reduction in the thickness of the dielectric layer 31. Specifically, the refractive index of the dielectric layer 31 is preferably 1.5 to 3.0 across the entire visible region.

[0038] The metal layer 32 is a single thin film made of metal. The metal layer 32 has both transmittance and reflectivity of visible light. Furthermore, it is preferable that the metal layer 32 also has light absorption properties in the visible region. The material of the metal layer 32 is, for example, aluminum, copper, iron, nickel, gold, silver, chromium, titanium, tantalum, silicon, etc. The thickness of the metal layer 32 is preferably 5 nm or more and 40 nm or less. The metal layer 32 is formed by known thin film formation techniques such as sputtering or vacuum deposition.

[0039] The refractive index of the metal layer 32 is preferably smaller than that of the dielectric layer 31. In order to enhance the interference of light in the multilayer film layer 30, the difference in refractive index between the dielectric layer 31 and the metal layer 32 is preferably 0.3 or more across the entire visible region. Furthermore, the multilayer film layer 30 is electrically insulated; in other words, each layer of the dielectric layer 31 and the metal layer 32 is electrically insulated. That is, no voltage is applied to these layers when the color-developing structure 10 develops color.

[0040] Since the dielectric layer 31 and the metal layer 32 are transparent to the visible region, when light is incident on the multilayer film layer 30, a portion of the light incident on the dielectric layer 31 passes through the dielectric layer 31 and is reflected at the interface between the dielectric layer 31 and the underlying metal layer 32, and a portion of the light incident on the metal layer 32 passes through the metal layer 32 and is reflected at the interface between the metal layer 32 and the underlying dielectric layer 31. In this way, the light reflected at each interface of the multilayer film layer 30 interferes, causing strengthened light in a specific wavelength range to be emitted from the color-emitting structure 10.

[0041] If the surface of the support layer 20 is uneven, the angle of each interface of the multilayer film layer 30 with respect to the incident light changes within the color-generating structure 10, causing reflected light to be emitted in various directions. In other words, the reflected light is scattered. As a result, light in a specific wavelength range, which is strengthened by interference, is emitted in various directions, and the color corresponding to the above specific wavelength range becomes visible over a wide observation angle.

[0042] Because the metal layer 32 is reflective, the intensity of reflected light from the multilayer film 30 can be increased even with fewer layers compared to the case where a layer made of a less reflective dielectric is placed in place of the metal layer 32, i.e., when the multilayer film is a laminate of only dielectric thin films. On the other hand, compared to the case where the metal layer 32 does not transmit light but has high reflectivity over a wide range of the visible region, the increase in reflection of light outside of specific wavelength ranges that are amplified by interference is suppressed.

[0043] Furthermore, it is preferable that the metal layer 32 has absorption properties in a wavelength range different from the specific wavelength range corresponding to the color to be produced by the color-producing structure 10. This makes it possible to suppress the inclusion of light outside the specific wavelength range in the reflected light from the color-producing structure 10.

[0044] By utilizing the light absorption properties of the metal layer 32, it is possible to produce vivid hues that were difficult to achieve with multilayer films consisting only of dielectric thin films. For example, when it is desired to produce red color, it is difficult to suppress the appearance of peaks in wavelength ranges other than the wavelength range corresponding to red in the reflected light spectrum of a multilayer film consisting only of dielectric thin films. In contrast, with the color-producing structure 10 of this embodiment, vivid red coloration is possible by using a metal layer 32 made of a metal that absorbs wavelength ranges other than red, such as copper.

[0045] Thus, it is preferable that the metal layer 32 has transmittance, reflectivity, and absorption properties for light in the visible region. Specifically, when the target wavelength range is defined as the specific wavelength range in which the multilayer film layer 30 is reinforced by interference within the visible region, and the wavelength range outside the target wavelength range is defined as the non-target wavelength range, it is preferable that the metal layer 32 has a transmittance of 5% or more in at least a portion of the target wavelength range, and more preferably a transmittance of 20% or more. Furthermore, it is preferable that the metal layer 32 has a reflectance of 30% or more in at least a portion of the target wavelength range, and more preferably a reflectance of 50% or more. In addition, it is preferable that the metal layer 32 has an absorptive rate of 20% or more in at least a portion of the non-target wavelength range. Furthermore, it is preferable that the metal layer 32 has a reflectance of 50% or less in at least a portion of the non-target wavelength range. In addition, it is preferable that the reflectance of the metal layer 32 over the entire non-target wavelength range is 60% or less.

[0046] The magnitudes of transmittance, reflectance, and absorptance in each wavelength range of the metal layer 32 can be controlled by the material and thickness of the metal layer 32. Preferably, the material of the metal layer 32 is a metal material with a large imaginary part of the complex dielectric constant in the non-symmetric wavelength range and a small real part of the complex dielectric constant in the symmetric wavelength range. The thickness of the metal layer 32 should be set so that the magnitudes of transmittance, reflectance, and absorptance in the symmetric and non-symmetric wavelength ranges are balanced as described above. Note that multiple metal layers 32 may include metal layers 32 made of different types of metals. This allows for adjustment of the wavelength range absorbed in the multilayer film layer 30.

[0047] Furthermore, the target wavelength range can be controlled by the material and thickness of the metal layer 32 and the dielectric layer 31. For example, if the thickness of the dielectric layer 31 differs by 10 nm, the difference in the target wavelength range can be recognized as a different color. Multiple dielectric layers 31 may include dielectric layers 31 made of different types of dielectrics.

[0048] Furthermore, by weakening the light in the asymmetric wavelength range through interference, the inclusion of light in the asymmetric wavelength range in the reflected light can also be suppressed. Since light in the asymmetric wavelength range is easily included in the reflected light from the metal layer 32, in order to effectively cause cancellation by interference, it is preferable that the dielectric layer 31 is the thin film layer closest to the observer among the multilayer film layers 30, in other words, the thin film layer closest to the incident surface, which is the surface on which light is incident in the color-generating structure 10.

[0049] For example, when the color-producing structure 10 is observed from the side opposite the support layer 20 relative to the multilayer film layer 30, it is preferable that the outermost layer of the multilayer film layer 30 opposite the support layer 20 is a dielectric layer 31. Furthermore, if the thickness of the outermost dielectric layer 31 is 70% or less of the thickness of the other dielectric layers 31, the peak width in the spectrum of reflected light becomes narrower, that is, the monochromaticity of the reflected light is enhanced.

[0050] As described above, with a multilayer film layer 30 in which dielectric layers 31 and metal layers 32 are alternately stacked, the intensity of reflected light is increased, and the inclusion of light outside the specific wavelength range that is amplified by interference in the reflected light is suppressed, thereby improving the wavelength selectivity of the reflected light. Therefore, compared to a multilayer film layer consisting only of dielectric thin films, a clear color corresponding to the above-mentioned specific wavelength range can be obtained with fewer layers.

[0051] As a result, the burden required for manufacturing the color-emitting structure 10 can be reduced. In addition, the thickness of the multilayer film layer 30 can be reduced, and the number of dielectric thin films can be reduced, thereby reducing the optical path difference caused by the difference in angle of incident and reflected light. This suppresses the change in the wavelength range that is strengthened by interference depending on the observation angle, making the color visible in the color-emitting structure 10 more stable.

[0052] Furthermore, it is possible to avoid excessively increasing the thickness of the dielectric layer 31 in order to strengthen the interference. As a result, problems caused by increasing the thickness of the dielectric layer 31, such as difficulty in controlling the wavelength range strengthened by interference, warping of the color-generating structure and peeling of the dielectric thin film due to stress, and difficulty in obtaining the scattering effect of reflected light because the dielectric thin film does not conform to the uneven structure, are suppressed.

[0053] [Optical effects of color-producing structures] The optical properties of the color-generating structure 10 will be explained in detail, in comparison with conventional structures equipped with multilayer films.

[0054] <Analysis of the number of layers of thin films> Figure 5 shows the reflection spectra obtained by simulation for test examples 1A to 1E, which consist of a multilayer film layer made only of dielectric thin films. The angle of incidence of light for each test example is 0°, and the reflection spectra shown in Figure 5 are the reflection spectra at a reflection angle of 0°.

[0055] Each test example consists of a support layer with a high-refractive-index layer and a low-refractive-index layer, the number of such layers differing from example to example. The support layer is made of polyethylene terephthalate, the high-refractive-index layer is made of TiO2, and the low-refractive-index layer is made of SiO2. The high-refractive-index layer has a thickness of 60 nm, the low-refractive-index layer has a thickness of 80 nm, and the layer in contact with the support layer is the high-refractive-index layer. Incident light enters the structure from the side opposite the support layer relative to the multilayer film layer.

[0056] Test Example 1A comprises one set of high-refractive-index layers and low-refractive-index layers. Test Example 1B comprises two sets of high-refractive-index layers and low-refractive-index layers. Test Example 1C comprises three sets of high-refractive-index layers and low-refractive-index layers. Test Example 1D comprises four sets of high-refractive-index layers and low-refractive-index layers. Test Example 1E comprises five sets of high-refractive-index layers and low-refractive-index layers. In other words, the number of thin film layers in each test example is 2 for Test Example 1A, 4 for Test Example 1B, 6 for Test Example 1C, 8 for Test Example 1D, and 10 for Test Example 1E.

[0057] Table 1 shows the color of the reflected light for test examples 1A to 1E. *a * b * Indicates the values of each coordinate when represented in color space. The larger the value of L * , the greater the brightness, and the farther the values of a * and b * 0

[0058]

Table 1

[0059] As shown in FIG. 5 and Table 1, as the number of stacked thin film layers increases, the intensity of the reflected light in the wavelength range near 500 nm increases, and a vivid blue color development can be obtained. As shown in Test Example 1A and Test Example 1B, when the number of stacked thin film layers is 4 or less, the wavelength selectivity of the reflected light is low, and blue color development could not be confirmed. <o000348> FIG. 6 shows the measured reflection spectrum for Test Example 2A corresponding to the color development structure 10 of the first embodiment. The color development structure 10 of Test Example 2A includes a multilayer film layer 30 composed of 4 thin film layers. From the position close to the support layer 20, the first metal layer 32, the first dielectric layer 31, the second metal layer 32, and the second dielectric layer 31 are arranged in this order. The reflection spectrum was measured by irradiating light from the side opposite to the support layer 20 with respect to the multilayer film layer 30.

[0061] The material of the support layer is polyethylene terephthalate, the material of each dielectric layer 31 is TiO2, and the material of each metal layer 32 is copper. The thickness of the first dielectric layer 31 is 50 nm, and the thickness of the second dielectric layer 31 is 35 nm. The thicknesses of the two metal layers 32 are both 20 nm. Each dielectric layer 31 and each metal layer 32 were formed by vacuum evaporation.

[0062] Table 2 shows the values of each coordinate when the color of the reflected light in Test Example 2A is represented in the L * a * b * color space.

[0063]

Table 2

[0064] As shown in Figure 6 and Table 2, high intensity of reflected light was obtained in the wavelength range around 800 nm, resulting in a vivid red color. Thus, in Test Example 2A, sufficient color development was obtained even with only four layers of thin film stacking, confirming that clear color development can be obtained with fewer layers compared to cases where the multilayer film consists only of dielectric thin films, as in Test Examples 1A to 1E.

[0065] Next, for test examples 3A to 3D, which consist of 1 to 4 thin film layers, the behavior of light in each layer was analyzed by electromagnetic field simulation. Figures 7 to 10 show the simulation results of the energy absorbed by the structures and the distribution of electromagnetic field energy when light of wavelengths 500 nm and 780 nm was incident on the structures of test examples 3A to 3D, respectively. The angle of incidence of the light is 0°.

[0066] The materials and thicknesses of each thin film layer in Test Examples 3A to 3D are the same as in Test Example 2A. As shown in Figure 6, in Test Example 2A, 500 nm is the wavelength in the region of lowest reflectivity and is included in the non-symmetric wavelength range. On the other hand, 780 nm is the wavelength in the region of highest reflectivity and is included in the symmetric wavelength range. Figures 7 to 10 show the layer configuration and energy distribution of the test examples for each wavelength of incident light. In the energy distribution, the left side shows the energy distribution of absorption, and the right side shows the energy distribution of the electromagnetic field.

[0067] Figures 7(a) and 7(b) show the simulation results for Test Example 3A. Test Example 3A consists only of a 20 nm first metal layer 32 made of copper on a support layer 20 made of polyethylene terephthalate. The target wavelength for Figure 7(a) is 500 nm, and the target wavelength for Figure 7(b) is 780 nm.

[0068] As shown in Figure 7(a), at a wavelength of 500 nm, both the absorption energy and the electromagnetic field energy are high in the first metal layer 32. Therefore, it can be seen that light absorption is occurring in the first metal layer 32. In addition, the electromagnetic field energy is also slightly high both above and below the first metal layer 32, indicating that light reflection and transmission are also occurring. As shown in Figure 7(b), at a wavelength of 780 nm, the absorption energy in the first metal layer 32 is relatively high, but its value is significantly smaller compared to the case at 500 nm, and the electromagnetic field energy is high above the first metal layer 32. Therefore, it can be concluded that the dominant behavior of light is reflection at the interface between the first metal layer 32 and the air layer above it.

[0069] Figures 8(a) and 8(b) show the simulation results for Test Example 3B. Test Example 3B includes a first dielectric layer 31 made of TiO2 with a thickness of 50 nm, on top of the same support layer 20 and first metal layer 32 as Test Example 3A. The target wavelength for Figure 8(a) is 500 nm, and the target wavelength for Figure 8(b) is 780 nm.

[0070] As shown in Figures 8(a) and 8(b), at both wavelengths of 500 nm and 780 nm, the absorption energy is high in the first metal layer 32 and low in the first dielectric layer 31. Furthermore, the electromagnetic field energy is high in both the first metal layer 32 and the first dielectric layer 31, with the energy below the first metal layer 32 being higher than the energy above the first dielectric layer 31. Therefore, it can be concluded that light absorption occurs in the first metal layer 32, while no light absorption occurs in the first dielectric layer 31, indicating that transmission is dominant over reflection of light.

[0071] Furthermore, comparing the magnitude of absorption energy and the energy distribution of the electromagnetic field at wavelengths of 500 nm and 780 nm, it can be determined that absorption is smaller and reflection and transmission are greater at the 780 nm wavelength.

[0072] Figures 9(a) and 9(b) show the simulation results for Test Example 3C. Test Example 3C includes a 20 nm second metal layer 32 made of copper on top of the same support layer 20, first metal layer 32, and first dielectric layer 31 as Test Example 3B. The target wavelength for Figure 9(a) is 500 nm, and the target wavelength for Figure 9(b) is 780 nm.

[0073] As shown in Figure 9(a), at a wavelength of 500 nm, both the absorption energy and the electromagnetic field energy are high in the second metal layer 32, and the absorption energy is also slightly high in the first metal layer 32. Therefore, it can be seen that light is largely absorbed in the second metal layer 32, and that slight light absorption is also occurring in the first metal layer 32. In addition, the electromagnetic field energy is also slightly high above the second metal layer 32, indicating that light reflection is also occurring.

[0074] As shown in Figure 9(b), at a wavelength of 780 nm, the absorption energy in the second metal layer 32 is relatively large, but this value is significantly smaller compared to the case at 500 nm, and the electromagnetic field energy is larger above the second metal layer 32. Therefore, it can be concluded that reflection in the first and second metal layers 32 is dominant in the behavior of light.

[0075] Figures 10(a) and (b) show the simulation results for Test Example 3D. Test Example 3D has the same support layer 20, first metal layer 32, first dielectric layer 31, and second metal layer 32 as Test Example 3C, with a second dielectric layer 31 made of TiO2 and a thickness of 35 nm. The target wavelength for Figure 10(a) is 500 nm, and the target wavelength for Figure 10(b) is 780 nm.

[0076] As shown in Figure 10(a), at a wavelength of 500 nm, the absorption energy is high in the second metal layer 32 and also slightly high in the first metal layer 32. On the other hand, the electromagnetic field energy is high in the second dielectric layer 31 and low above the second dielectric layer 31. Therefore, light at a wavelength of 500 nm is largely absorbed in the second metal layer 32 and slightly absorbed in the first metal layer 32. Furthermore, the components reflected by each metal layer 32 are weakened by interference in the second dielectric layer 31, and it can be concluded that there is almost no component emitted as reflected light from the multilayer film layer 30.

[0077] As shown in Figure 10(b), at a wavelength of 780 nm, the absorption energy in the second metal layer 32 is relatively large, but this value is significantly smaller than that at 500 nm, and the electromagnetic field energy is larger above the second dielectric layer 31. Therefore, it can be concluded that reflection in the multilayer layer 30 is dominant in the behavior of light at a wavelength of 780 nm.

[0078] As described above, in the color-producing structure 10, which has a multilayer film layer 30 consisting of four thin film layers, reflection is high at a wavelength of 780 nm corresponding to the color to be produced, and reflection is accurately suppressed at a wavelength of 500 nm, which is different from the color to be produced. Therefore, vivid color is obtained.

[0079] Furthermore, referring to Figures 7 to 10, at all wavelengths, as the number of stacked thin film layers increases, and more specifically as the number of stacked metal layers 32 increases, the energy of the electromagnetic field in the bottommost first metal layer 32 decreases. In test example 3D, which consists of four thin film layers, the energy of the first metal layer 32 is less than 30% of the maximum. Therefore, even if more than four thin film layers are stacked, the influence of the bottommost layer and the thin film layers near it on the behavior of light is small.

[0080] Therefore, for example, in the cases where the thin film layer consists of 4, 6, or 8 layers, the intensity of the reflected light from the color-producing structure 10 does not change significantly, and the color visible to the color-producing structure 10 does not change significantly. Consequently, from the viewpoint of reducing the number of thin film layers, it is most preferable that the multilayer film layer 30 consists of 4 thin film layers.

[0081] Furthermore, the ratios of reflection, transmission, and absorption of light at each wavelength were calculated for test examples 3A to 3D. Table 3 shows the refractive index n, extinction coefficient k, and the real part ε' and imaginary part ε'' of the complex dielectric constant calculated from these values ​​at wavelengths of 500 nm and 780 nm for the thin film layer materials of test examples 3A to 3D. Table 4 and Figure 11 show the ratios of reflection, transmission, and absorption of light at a wavelength of 500 nm for test examples 3A to 3D, and Table 5 and Figure 12 show the ratios of reflection, transmission, and absorption of light at a wavelength of 780 nm for test examples 3A to 3D.

[0082] [Table 3]

[0083] [Table 4]

[0084] [Table 5]

[0085] As shown in Tables 4 and 5 and Figures 11 and 12, in Test Example 3A, which has a single thin film layer, the reflectance is high at a wavelength of 780 nm, exceeding 70%, and also relatively high at a wavelength of nearly 40% at 500 nm. Therefore, in Test Example 3A, the reflectance in the visible wavelength range is generally high, resulting in metallic coloration with a glossy appearance.

[0086] In Test Example 3B, which features two thin film layers, at a wavelength of 500 nm, the reflectance is significantly reduced to less than 10% compared to Test Example 3A, while transmission and absorption are increased. On the other hand, at a wavelength of 780 nm, the reflectance is reduced to less than 40%, while transmission and absorption are increased. In particular, transmission is increased to nearly 50%. Therefore, even in Test Example 3B, highly wavelength-selective color development cannot be obtained.

[0087] In test example 3C, which features three thin film layers, the reflectivity increases to nearly 90% at a wavelength of 780nm. Even at a wavelength of 500nm, the reflectivity increases to 25%, but the red coloration can still be observed.

[0088] In Test Example 3D, which features four thin film layers, the reflection at a wavelength of 780 nm is still quite high at nearly 80%, although it is about 10% lower compared to Test Example 3C. On the other hand, at a wavelength of 500 nm, absorption increases to about 80%, while reflection becomes 0%. Therefore, in Test Example 3D, the reflection of light in wavelength ranges other than the desired color is effectively suppressed, resulting in highly wavelength-selective color development, i.e., a clear red color.

[0089] Next, for test examples 4A and 4B, which have metal layers 32 of different thicknesses, the spectra of reflection, transmission, and absorption were obtained by simulation, and the ratios of reflection, transmission, and absorption of light at each wavelength were calculated.

[0090] Test Example 4A has the same layer configuration as Test Example 2A. Specifically, Test Example 4A comprises a multilayer film layer 30 in which metal layers 32 made of copper and dielectric layers 31 made of TiO2 are alternately stacked, and Test Example 4A has four thin film layers. The thickness of the first dielectric layer 31 is 50 nm, the thickness of the second dielectric layer 31 is 35 nm, and the thickness of both metal layers 32 is 20 nm. Test Example 4B differs from Test Example 4A only in the thickness of the first metal layer 32. The thickness of the first metal layer 32 in Test Example 4B is 100 nm.

[0091] Figure 13 shows the reflectance spectrum, transmission spectrum, and absorption spectrum for test example 4A. Figure 14 shows the reflectance spectrum, transmission spectrum, and absorption spectrum for test example 4B. Figure 15 shows the ratio of reflection, transmission, and absorption of light at a wavelength of 500 nm in test examples 4A and 4B, and Figure 16 shows the ratio of reflection, transmission, and absorption of light at a wavelength of 780 nm in test examples 4A and 4B.

[0092] As shown in Figures 13, 15, and 16, in Test Example 4A, at a wavelength of 500 nm, the reflection was 0%, the transmission was 19%, and the absorption was 81%, while at a wavelength of 780 nm, the reflection was 77%, the transmission was 7%, and the absorption was 16%. On the other hand, as shown in Figures 14, 15, and 16, in Test Example 4B, at a wavelength of 500 nm, the reflection was 3%, the transmission was 0%, and the absorption was 97%, while at a wavelength of 780 nm, the reflection was 85%, the transmission was 0%, and the absorption was 15%.

[0093] In Test Example 4A, the first metal layer 32 has transmittance of visible light, whereas in Test Example 4B, the first metal layer 32 does not have transmittance of visible light due to its greater thickness. Therefore, the first metal layer 32 in Test Example 4B tends to have a higher reflectance than the first metal layer 32 in Test Example 4A.

[0094] As a result, at a wavelength of 500 nm, test example 4A showed 0% reflection, while test example 4B showed 3% reflection. On the other hand, at a wavelength of 780 nm, reflection was dominant in both test examples 4A and 4B, and absorption was similar in both test examples 4A and 4B. Therefore, by using a transmissive metal layer 32, the reflection of light in wavelength ranges other than the color to be produced is accurately suppressed, resulting in clear color development.

[0095] <Analysis regarding observation angles> Figure 17 shows the corresponding reflection spectra for Test Example 5A, which has a multilayer film layer consisting only of dielectric thin films, when the observation angle is changed. Specifically, Figure 17 shows the reflection spectra obtained by simulation when the angle of incidence and reflection of light are 0°, 30°, and 40°, respectively. The reflection angle corresponds to the observation angle.

[0096] Test Example 5A has the same layer structure as Test Example 1E. Specifically, Test Example 5A has a multilayer film layer in which a 60 nm thick high refractive index layer made of TiO2 and an 80 nm thick low refractive index layer made of SiO2 are alternately stacked, and the number of thin film layers in Test Example 5A is 10.

[0097] Table 6 shows the color of the reflected light at each observation angle for test example 5A. * a * b * The values ​​of each coordinate when represented in color space are shown. Furthermore, Table 6 shows the difference in each coordinate and the color difference (ΔE) for observation angles of 30° and 40° compared to the case where the observation angle is 0°. * This shows ΔE * A smaller value means that the difference in color from the reflected light at 0° is smaller.

[0098] [Table 6]

[0099] As shown in Figure 17, it can be seen that the wavelength range of the reflected light changes when the observation angle changes. Also, ΔE * A value of 6.5 or higher indicates a color difference greater than or equal to the Class C tolerance, which corresponds to a one-step difference in standard color charts or Munsell color charts according to JIS standards. Therefore, as shown in Table 6, the colors at each observation angle of 0°, 30°, and 40° are distinct from each other.

[0100] Figure 18 shows the corresponding reflection spectra for test example 6A, which corresponds to the color-developing structure 10 of the first embodiment, when the observation angle is changed. Specifically, Figure 18 shows the reflection spectra obtained by simulation when the angle of incidence and reflection of light are 0°, 30°, and 40°, respectively.

[0101] Test example 6A has the same layer configuration as test example 2A. Specifically, test example 6A has a multilayer film layer 30 in which metal layers 32 made of copper and dielectric layers 31 made of TiO2 are alternately stacked, and the number of thin film layers in test example 6A is four. The thickness of the first dielectric layer 31 is 50 nm, the thickness of the second dielectric layer 31 is 35 nm, and the thickness of both metal layers 32 is 20 nm.

[0102] Table 7 shows the color of the reflected light at each observation angle for test example 6A. * a * b * The values ​​of each coordinate when represented in color space, the difference between each coordinate and the reference point when the observation angle is 0°, and the ΔE color difference. * This indicates that.

[0103] [Table 7]

[0104] As shown in Figure 18, in test example 6A, the change in the wavelength range of reflected light is small even when the observation angle changes. Also, as shown in Table 7, ΔE * Since the value is less than 6.5 in all cases, it can be said that the colors at each observation angle of 0°, 30°, and 40° do not differ enough to be perceived as different colors.

[0105] Next, for Test Example 6A, the behavior of light when the angle of incidence of light was changed was analyzed using electromagnetic field simulation. Figures 19 and 20 show the simulation results of the energy absorbed by the structure and the distribution of electromagnetic field energy when light of wavelengths of 500 nm and 780 nm were incident on the structure of Test Example 6A, respectively.

[0106] Figure 19 shows the case where the angle of incidence of light is 0°, and Figure 20 shows the case where the angle of incidence of light is 30°. The target wavelength for Figures 19(a) and 20(a) is 500 nm, and the target wavelength for Figures 19(b) and 20(b) is 780 nm. Each figure shows the layer configuration and energy distribution of the test example for each wavelength of incident light. In the energy distribution, the left side shows the energy distribution of absorption, and the right side shows the energy distribution of the electromagnetic field.

[0107] As shown in Figures 19 and 20, no difference in the behavior of light due to the difference in the angle of incidence can be observed for either the 500 nm or 780 nm wavelengths. From this, it can be said that in Test Example 6A, there is almost no change in color due to the observation angle.

[0108] As described above, the following effects can be obtained according to the first embodiment. (1) The color-generating structure 10 comprises a multilayer film layer 30 in which dielectric layers 31 and metal layers 32 that transmit light in the visible region are alternately stacked. As a result, light reflected at each interface of the multilayer film layer 30 interferes, and light in a specific wavelength range that is amplified is emitted from the color-generating structure 10. Because the metal layers 32 are reflective, the intensity of the reflected light from the multilayer film layer 30 is increased compared to the case where the multilayer film layer is a stack of dielectric thin films only. On the other hand, compared to the case where the metal layers 32 do not transmit light but have high reflectivity over a wide range of the visible region, the reflection of light outside the specific wavelength range amplified by interference is suppressed.

[0109] Therefore, clear color development corresponding to the specific wavelength range mentioned above can be obtained with a small number of layers. As a result, the burden required for manufacturing the color-developing structure 10 can be reduced. In addition, since the thickness of the multilayer film layer 30 can be reduced, it is possible to suppress the change in the wavelength range intensified by interference depending on the observation angle, and the color visible in the color-developing structure 10 becomes more stable.

[0110] (2) Because the metal layer 32 has the ability to absorb light in the visible region, it is possible to suppress the inclusion of light outside the specific wavelength range mentioned above in the reflected light from the color-producing structure 10. As a result, clearer color development can be obtained.

[0111] (3) By having a thickness of 5 nm or more and 40 nm or less in the metal layer 32, suitable light transmittance in the metal layer 32 can be obtained. (4) Since each metal layer 32 is a single thin metal film, it is possible to reduce the number of layers of thin films and thus reduce the burden required to manufacture the color-developing structure 10, compared to the case where the metal layer 32 is a laminate of multiple thin metal films.

[0112] (5) Because the thickness of the dielectric layer 31 is between 10 nm and 300 nm, the thickness of the dielectric layer 31 is kept small, which suppresses problems caused by an increase in the thickness of the dielectric layer 31, such as difficulty in controlling the wavelength range that is strengthened by interference, and warping of the color-producing structure due to stress and peeling of the dielectric thin film.

[0113] (6) By having a dielectric layer 31 with a refractive index of 1.5 or more and 3.0 or less in the visible region, a dielectric layer 31 with a high refractive index is realized, which strengthens the interference of light in the multilayer film layer 30 and makes it easier to obtain reflected light of high intensity.

[0114] (7) Among the multilayer film layers 30, the dielectric layer 31 is the thin film layer closest to the incident surface of light in the color-producing structure 10, which makes it easier for light outside the specific wavelength range to be weakened by interference. Therefore, it is possible to suppress the inclusion of light outside the specific wavelength range in the reflected light from the color-producing structure 10, resulting in clearer coloration.

[0115] (8) The dielectric layer 31 closest to the incident surface is thinner than the other dielectric layers 31, which makes it possible to narrow the peak width in the spectrum of the reflected light, that is, to improve the monochromaticity of the reflected light. (9) If the multilayer film layer 30 has a structure consisting of four thin film layers including two metal layers 32 and two dielectric layers 31, then clear color development can be accurately obtained with a small number of layers.

[0116] (Second Embodiment) A second embodiment of the color-developing structure will be described with reference to Figures 21 to 37. In the following description, the differences between the second embodiment and the first embodiment will be the main focus, and components similar to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted.

[0117] To enhance the vividness, or in other words, the monochromaticity, of the color exhibited by a color-producing structure, it is preferable to have a narrow wavelength range of visible reflected light. For example, if the color to be produced corresponds to a wavelength range at the edge of the visible region, such as red or blue, it is possible to narrow the wavelength range of visible reflected light by designing the multilayer film so that the peak position of the reflection spectrum is near the boundary between the visible region and the near-infrared or ultraviolet region, thereby making some of the wavelength range included in the peak an invisible wavelength range. On the other hand, if the color to be produced corresponds to a wavelength range near the center of the visible region, such as green or yellow, the method of narrowing the visible wavelength range by adjusting the peak position, as with red and blue, cannot be applied. Therefore, in order to enhance monochromaticity, it is necessary to narrow the peak width or full width at half maximum of the reflection spectrum.

[0118] Generally, in multilayer films, increasing the number of high-refractive-index and low-refractive-index layers can narrow the peak width of the reflection spectrum. However, as mentioned above, increasing the number of layers increases the burden on manufacturing, and increasing the thickness of the multilayer film leads to problems such as the color changing more easily depending on the observation angle due to the increased optical path difference. The objective of the second embodiment is to improve the monochromaticity of reflected light while minimizing the increase in the number of thin film layers and the thickness of the multilayer film layers.

[0119] [Structure of the color-developing structure] As shown in Figure 21, the color-developing structure 11 of the second embodiment comprises a support layer 20 and a multilayer film layer 30 in which dielectric layers 31 and metal layers 32 are alternately stacked, similar to the first embodiment. However, in the second embodiment, at least one metal layer 32 is a laminate of two or more metal thin films made of different materials. That is, the multilayer film layer 30 has a portion in which metal thin films are continuously stacked.

[0120] In the example shown in Figure 21, the first metal layer 32, the first dielectric layer 31, the second metal layer 32, and the second dielectric layer 31 are arranged alternately on the support layer 20 in this order. The second metal layer 32 comprises two metal thin films, the first metal thin film 33a and the second metal thin film 33b. The materials of the first metal thin film 33a and the second metal thin film 33b are different from each other. Furthermore, the material of the first metal layer 32 may be the same as the material of either the first metal thin film 33a or the second metal thin film 33b, or it may be different from both of them. The same configuration as that of the color-developing structure 10 in the first embodiment can be applied to the number of dielectric layers 31 and metal layers 32 and the stacking order.

[0121] The materials for the metal thin films 33a and 33b are, for example, aluminum, copper, iron, nickel, gold, silver, chromium, titanium, tantalum, silicon, etc. The refractive index of the metal thin films 33a and 33b is preferably smaller than that of the dielectric layer 31, and the difference in refractive index between the dielectric layer 31 and the metal thin films 33a and 33b is preferably 0.3 or more in the entire visible region.

[0122] The thickness of the metal layer 32, which consists of multiple metal thin films 33a and 33b, is preferably 5 nm to 40 nm. It is preferable that the thickness of the metal layer 32, which consists of multiple metal thin films 33a and 33b, is controlled so that it has light transmittance, reflectivity, and absorption properties in the visible region, similar to the first embodiment. The configuration of the support layer 20 and the dielectric layer 31 is the same as in the first embodiment.

[0123] In the second embodiment, since the materials of the first metal thin film 33a and the second metal thin film 33b are different, the wavelength ranges of light absorbed by the first metal thin film 33a and the second metal thin film 33b are different. Therefore, compared to the case where the metal layer 32 consists of a single metal thin film, the metal layer 32 can absorb light over a wider wavelength range. Consequently, in the multilayer film layer 30, light other than the wavelength range strengthened by interference is absorbed over a wider wavelength range, making it possible to narrow the peak width and full width at half maximum in the spectrum of the reflected light. Therefore, a more monochromatic color can be obtained.

[0124] For example, if the first metal thin film 33a and the second metal thin film 33b are each made into a single metal layer 32, and a dielectric layer 31 is sandwiched between them, the number of layers of thin films in the multilayer film layer 30 increases. Furthermore, in order to adjust the wavelength range that is strengthened by interference, the thickness of each metal thin film must be larger than when the laminate of the first metal thin film 33a and the second metal thin film 33b is made into a single metal layer 32. Consequently, the thickness of the multilayer film layer 30 increases. In contrast, the color-generating structure 11 of the second embodiment can enhance the monochromaticity of reflected light while suppressing an increase in the number and thickness of thin films in the multilayer film layer 30.

[0125] From the viewpoint of suppressing an increase in the number of stacked thin films in the multilayer film layer 30, it is preferable that the number of metal layers 32 in the multilayer film layer 30 that consist of multiple metal thin films is one. Furthermore, as described in the first embodiment, even if more than four layers of dielectric layers 31 and metal layers 32 are stacked, the influence of the thin film layers near the bottom layer on the behavior of light is small, and light absorption mainly occurs in the metal layer 32 closest to the outermost layer. Therefore, it is preferable that the multilayer film layer 30 comprises two dielectric layers 31 and two metal layers 32, and that the metal layer 32 closer to the incident surface of light is composed of multiple metal thin films 33a, 33b.

[0126] Specifically, as shown in Figure 21, the color-generating structure 11 comprises a first metal layer 32, a first dielectric layer 31, a second metal layer 32, and a second dielectric layer 31 on the support layer 20 in this order. When light is incident on the multilayer film layer 30 from the side opposite the support layer 20, it is preferable that the second metal layer 32 is composed of multiple metal thin films 33a and 33b. Furthermore, it is preferable that the first metal layer 32 consists of a single metal thin film.

[0127] [Optical effects of color-producing structures] The optical properties of the color-generating structure 11 will be explained in detail, in comparison with conventional structures equipped with multilayer films.

[0128] <Analysis of the number of layers of thin films> Figure 22 shows the reflection spectra obtained by simulation for test examples 7A to 7E, which consist of a multilayer film layer made only of dielectric thin films. The angle of incidence of light for each test example is 0°, and the reflection spectra shown in Figure 22 are the reflection spectra at a reflection angle of 0°.

[0129] Each test example consists of a support layer with a high-refractive-index layer and a low-refractive-index layer, the number of such layers differing from example to example. The support layer is made of polyethylene terephthalate, the high-refractive-index layer is made of TiO2, and the low-refractive-index layer is made of SiO2. The high-refractive-index layer has a thickness of 85 nm, the low-refractive-index layer has a thickness of 50 nm, and the layer in contact with the support layer is the high-refractive-index layer. Incident light enters the structure from the side opposite the support layer relative to the multilayer film layer.

[0130] Test example 7A comprises one set of high-refractive-index layers and low-refractive-index layers. Test example 7B comprises two sets of high-refractive-index layers and low-refractive-index layers. Test example 7C comprises three sets of high-refractive-index layers and low-refractive-index layers. Test example 7D comprises four sets of high-refractive-index layers and low-refractive-index layers. Test example 7E comprises five sets of high-refractive-index layers and low-refractive-index layers. In other words, the number of thin film layers in each test example is 2 layers for test example 7A, 4 layers for test example 7B, 6 layers for test example 7C, 8 layers for test example 7D, and 10 layers for test example 7E.

[0131] Table 8 shows the color of the reflected light for test examples 7A to 7E, expressed in the CIE 1931 XYZ color space, and L * a * b * The values ​​of each coordinate when represented in color space are shown. Figure 23 also shows the reflected light colors of test examples 7A to 7E in the xy chromaticity diagram of the CIE1931 XYZ color space. In Figure 23, the approximate positions of the colors red (R), yellow (Y), green (G), cyan (C), and blue (B) in the xy chromaticity diagram are indicated by the corresponding symbols for each color.

[0132] [Table 8]

[0133] As shown in Figure 22, the more layers of dielectric thin films there are, the narrower the peak width in the reflection spectrum becomes, and the higher the reflectance. As a result, as shown in Figure 23, the more layers of dielectric thin films there are, the closer the color of the reflected light becomes to green, rather than a mixture of green, yellow, and red.

[0134] L * a * b * When represented in a color space, a * The smaller the value, the closer the hue is to green, b * The larger the value, the closer the hue approaches yellow. As shown in Table 8, even in test example 7E, which has the largest number of dielectric thin film layers, a * While b is small * The value is large. Therefore, even in test example 7E, where the reflected light is closest to green among test examples 7A to 7E, the color of the reflected light can be said to be a yellowish-green, that is, yellowish-green.

[0135] Figure 24 shows the measured reflection spectrum for test example 8A, which corresponds to the color-developing structure 11 of the second embodiment. The color-developing structure 11 of test example 8A has the structure shown in Figure 21, and comprises a first metal layer 32, a first dielectric layer 31, a second metal layer 32, and a second dielectric layer 31 in that order, starting from a position close to the support layer 20. The second metal layer 32 consists of a first metal thin film 33a and a second metal thin film 33b. The first metal thin film 33a is in contact with the first dielectric layer 31, and the second metal thin film 33b is in contact with the second dielectric layer 31. The reflection spectrum was measured by irradiating the multilayer film layer 30 from the side opposite to the support layer 20.

[0136] The material of the support layer 20 is polyethylene terephthalate, and the material of each dielectric layer 31 is TiO2. The material of the first metal layer 32 is aluminum, the material of the first metal thin film 33a in the second metal layer 32 is nickel, and the material of the second metal thin film 33b is copper. The thickness of the first dielectric layer 31 is 100 nm, and the thickness of the second dielectric layer 31 is 25 nm. The thickness of the first metal layer 32 is 20 nm, and the thickness of the first metal thin film 33a and the second metal thin film 33b in the second metal layer 32 is 10 nm each. That is, the thickness of the second metal layer 32 is 20 nm. The dielectric layer 31 and the metal layer 32 were deposited by vacuum deposition.

[0137] Table 9 shows the color of the reflected light from test example 8A when expressed in the CIE 1931 XYZ color space, and L * a * b * The values ​​of each coordinate when represented in color space are shown. Figure 25 shows the color of the reflected light from test example 8A in the xy chromaticity diagram of the CIE1931 XYZ color space. In Figure 25, the approximate positions of the colors red (R), yellow (Y), green (G), cyan (C), and blue (B) in the xy chromaticity diagram are indicated by the corresponding symbols for each color.

[0138] [Table 9]

[0139] As shown in Figure 24, in Test Example 8A, the peak width and full width at half maximum, especially the full width at half maximum, in the reflection spectrum are narrower than in Test Example 7E, which has 10 layers of dielectric thin films stacked as shown in Figure 22. Furthermore, as shown in Figure 25, the color of the reflected light in Test Example 8A is closer to green than the color of the reflected light in Test Example 7E, shown in Figure 23. As shown in Table 9, in Test Example 8A, a * In addition to being small, b * The size has also decreased, and it can be said that a highly monochromatic green reflected light is being obtained.

[0140] In Test Example 7E, the thickness of the multilayer film layer is 675 nm, while in Test Example 8A, the thickness of the multilayer film layer 30 is 165 nm. Thus, according to the color-developing structure 11 of this embodiment, compared to conventional structures having a multilayer film layer in which dielectric thin films are stacked, the number of stacked thin films and the thickness of the multilayer film layer 30 are significantly reduced, while still achieving highly monochromatic color development.

[0141] Next, the reflectance, transmission, and absorption spectra were obtained by simulation for test examples 9A and 9B corresponding to the color-developing structure 10 of the first embodiment, and for test example 9C corresponding to the color-developing structure 11 of the second embodiment.

[0142] Test Examples 9A to 9C consist of a support layer 20 made of polyethylene terephthalate, on which a first metal layer 32, a first dielectric layer 31, a second metal layer 32, and a second dielectric layer 31 are arranged in this order. The materials and thicknesses of the layers other than the second metal layer 32 are common to Test Examples 9A to 9C. The material of the first metal layer 32 is aluminum, and its thickness is 20 nm. The material of the first dielectric layer 31 is TiO2, and its thickness is 100 nm. The material of the second dielectric layer 31 is TiO2, and its thickness is 25 nm.

[0143] The second metal layer 32 in Test Example 9A is a single thin metal film made of copper with a thickness of 20 nm. The second metal layer 32 in Test Example 9B is a single thin metal film made of nickel with a thickness of 20 nm. The second metal layer 32 in Test Example 9C is a laminate of a first thin metal film 33a and a second thin metal film 33b. The first thin metal film 33a is made of nickel with a thickness of 10 nm. The second thin metal film 33b is made of copper with a thickness of 10 nm. In other words, the configuration of Test Example 9C is the same as the configuration of Test Example 8A.

[0144] Figure 26 shows the reflectance spectrum, transmission spectrum, and absorption spectrum for test example 9A. Similarly, Figure 27 shows the spectra for test example 9B, and Figure 28 shows the spectra for test example 9C.

[0145] Table 10 shows the reflected light colors of test examples 9A to 9C expressed in the CIE 1931 XYZ color space, and L * a * b * The values ​​of each coordinate when represented in color space are shown. Figure 29 shows the reflected light colors of test examples 9A to 9C in the xy chromaticity diagram of the CIE1931 XYZ color space. In Figure 29, the approximate positions of the colors red (R), yellow (Y), green (G), cyan (C), and blue (B) in the xy chromaticity diagram are indicated by the corresponding symbols for each color. Furthermore, the discrepancy between the measured values ​​in Test Example 8A and the simulation results in Test Example 9C regarding the spectrum and reflected light color is thought to be due to the influence of metal oxidation in the measured values, which occurs when a region is formed near the interface between the dielectric layer 31 and the metal layer 32 where the materials of these layers are mixed.

[0146] [Table 10]

[0147] As shown in Figures 26 to 28, a comparison of the reflectance spectra of test examples 9A to 9C reveals that the peak width is narrowest in test example 9C. In particular, in test example 9C, compared with test examples 9A and 9B, absorption is greater in the high-wavelength region and across a wide wavelength range, which reduces reflectance.

[0148] Furthermore, as shown in Figure 29, regarding the color of reflected light, test example 9C is the furthest from yellow and red and closest to green. In Table 10, test example 9C is also a * and b * Both are smaller. Therefore, among test examples 9A to 9C, test example 9C can be said to have obtained the most monochromatic green reflected light with the lowest yellow component.

[0149] Figures 30 to 33 show the ratios of reflection, transmission, and absorption when light of typical wavelengths in the visible region is incident on test examples 9A to 9C. The target wavelength in Figure 30 is 525 nm, the dominant wavelength of green light; the target wavelength in Figure 31 is 580 nm, the dominant wavelength of yellow light; the target wavelength in Figure 32 is 600 nm, the dominant wavelength of orange light; and the target wavelength in Figure 33 is 780 nm, the dominant wavelength of red light. When trying to produce a highly monochromatic green color, it is important to suppress the yellow component of the reflected light, as shown in each analysis above, so representative wavelengths from the longer wavelength region than green are used.

[0150] As shown in Figure 30, at the 525nm wavelength corresponding to green, there are no significant differences in reflection, transmission, and absorption between Test Examples 9A and 9C. On the other hand, as shown in Figures 31 and 32, at the 580nm wavelength corresponding to yellow and the 600nm wavelength corresponding to orange, Test Example 9C exhibits the lowest reflection and highest absorption. Furthermore, as shown in Figure 33, at the 780nm wavelength corresponding to red, Test Examples 9B and 9C exhibit low reflection and high absorption.

[0151] As described above, in Test Example 9C, where the second metal layer 32 consists of two types of thin metal films, the absorption in the wavelength range adjacent to green is greater and the reflection in that wavelength range is suppressed compared to Test Examples 9A and 9B, where the second metal layer 32 consists of one type of thin metal film. As a result, it can be said that in Test Example 9C, a more monochromatic green reflected light is obtained.

[0152] <Analysis regarding observation angles> Figure 34 shows the corresponding reflection spectra for test example 10A, which has a multilayer film layer consisting only of dielectric thin films, when the observation angle is changed. Specifically, Figure 34 shows the reflection spectra obtained by simulation for cases where the angle of incidence and the angle of reflection of light are 0°, 10°, 20°, 30°, and 40°. The angle of reflection corresponds to the observation angle.

[0153] Test example 10A has the same layer structure as test example 7E. Specifically, test example 10A has a multilayer film in which a high refractive index layer made of TiO2 with a thickness of 85 nm and a low refractive index layer made of SiO2 with a thickness of 50 nm are alternately stacked, and the number of thin film layers in test example 10A is 10.

[0154] Table 11 shows the coordinate values ​​for each color of reflected light at each observation angle in the CIE 1931 XYZ color space for test example 10A. Figure 35 shows the color of reflected light at each observation angle in the xy chromaticity diagram of the CIE 1931 XYZ color space. In Figure 35, the approximate positions of the colors red (R), yellow (Y), green (G), cyan (C), and blue (B) in the xy chromaticity diagram are indicated by the corresponding symbols for each color.

[0155] Table 12 also shows the color of the reflected light at each observation angle for test example 10A. * a * b * The values ​​of each coordinate when represented in color space are shown. Furthermore, for each observation angle from 10° to 40°, the difference in coordinates and color difference (ΔE) relative to the observation angle of 0° are shown. * This indicates.

[0156] [Table 11]

[0157] [Table 12]

[0158] As shown in Figures 34 and 35 and Tables 11 and 12, when the observation angle changes, the wavelength range of the reflected light changes, and consequently, the color of the reflected light also changes. As shown in Table 12, in test example 10A, when the observation angle is 20° or more, ΔE is different from when the observation angle is 0°. * The value becomes 6.5 or higher. Therefore, it can be said that the color at each observation angle of 20° or higher is different from the color at the observation angle of 0°.

[0159] Figure 36 shows the corresponding reflection spectra for test example 11A, which corresponds to the color-developing structure 11 of the second embodiment, when the observation angle is changed. Specifically, Figure 36 shows the reflection spectra obtained by simulation for cases where the angle of incidence and reflection of light are 0°, 10°, 20°, 30°, and 40°, respectively.

[0160] Test example 11A has the same layer configuration as test example 8A. That is, test example 11A has a first metal layer 32, a first dielectric layer 31, a second metal layer 32, and a second dielectric layer 31 on a support layer 20 in this order. The material of the first metal layer 32 is aluminum and has a thickness of 20 nm. The material of the first dielectric layer 31 is TiO2 and has a thickness of 100 nm. The second metal layer 32 is a laminate of a first metal thin film 33a and a second metal thin film 33b. The material of the first metal thin film 33a is nickel and has a thickness of 10 nm. The material of the second metal thin film 33b is copper and has a thickness of 10 nm. The material of the second dielectric layer 31 is TiO2 and has a thickness of 25 nm.

[0161] Table 13 shows the coordinate values ​​for each color of reflected light at each observation angle in the CIE 1931 XYZ color space for test example 11A. Figure 37 shows the color of reflected light at each observation angle in the xy chromaticity diagram of the CIE 1931 XYZ color space. In Figure 37, the approximate positions of the colors red (R), yellow (Y), green (G), cyan (C), and blue (B) in the xy chromaticity diagram are indicated by the corresponding symbols for each color.

[0162] Table 13 also shows the color of the reflected light at each observation angle for test example 11A, L * a * b * The values ​​of each coordinate when represented in space are shown. Furthermore, for each observation angle from 10° to 40°, the difference in coordinates and color difference ΔE are shown relative to the observation angle of 0°. * This indicates.

[0163] [Table 13]

[0164] [Table 14]

[0165] As shown in Figures 36 and 37 and Tables 13 and 14, in Test Example 11A, the change in the wavelength range and color of reflected light is smaller even when the observation angle changes, compared to Test Example 10A shown in Figures 34 and 35 and Tables 11 and 12. Also, as shown in Table 14, in Test Example 11A, when the observation angle is 30° or more, the ΔE is smaller compared to when the observation angle is 0°. * The result is 6.5 or higher. In test example 10A shown in Table 12, ΔE * While the observation angle where ΔE was less than 6.5 was up to 10°, in test example 11A, ΔE was observed up to 20°. * It is less than 6.5. Also, for observation angles greater than 20°, ΔE in Test Example 11A is compared to Test Example 10A. *The change in the color of the reflected light due to the change in observation angle is small in Test Example 11A, where the multilayer film layer 30 has a metal layer 32, compared to Test Example 10A, where the multilayer film layer consists only of a dielectric thin film.

[0166] As described above, according to the second embodiment, in addition to the effects of (1) to (3) and (5) to (9) of the first embodiment, the following effects can be obtained. (10) At least one metal layer 32 is a laminate of multiple metal thin films 33a, 33b made of different metals. With the above configuration, since the wavelength ranges of light absorbed by the multiple metal thin films 33a, 33b are different, the metal layer 32 can absorb light over a wider wavelength range compared to the case where the metal layer 32 is made of a single metal thin film. Therefore, in the multilayer film layer 30, light other than the wavelength range that is strengthened by interference is absorbed over a wider wavelength range, so the peak width and full width at half maximum in the spectrum of reflected light can be narrowed. Thus, a more monochromatic color can be obtained.

[0167] (11) In the multilayer film layer 30, only the metal layer 32 closest to the incident surface of light in the color-producing structure 11 is a laminate of multiple metal thin films 33a and 33b, while the other metal layers 32 are single metal thin films. With the above configuration, since the metal layer 32 where light absorption mainly occurs is composed of multiple metal thin films 33a and 33b, accurate absorption of light over a wide wavelength range is possible. Therefore, highly monochromatic coloration can be obtained while suppressing an increase in the number of layers of thin films in the multilayer film layer 30.

[0168] (modified version) Each of the above embodiments can be implemented with the following modifications. The color-developing structures 10 and 11 may further comprise layers other than the support layer 20 and the multilayer film layer 30. For example, the color-developing structures 10 and 11 may have an absorption layer that absorbs transmitted light from the multilayer film layer 30, on the side opposite to the light incident surface relative to the multilayer film layer 30. The absorption layer is, for example, a black layer containing a black pigment. The presence of the absorption layer suppresses the reflection of light in wavelength ranges different from those strengthened by interference in the multilayer film layer 30 from the interfaces of each layer inside the color-developing structures 10 and 11, and from the interface between the color-developing structures 10 and 11 and the outside, and from being emitted towards the observer. In addition, the color-developing structures 10 and 11 may have an adhesive layer for attaching the color-developing structures 10 and 11 to an article, on the outermost side opposite to the light incident surface. [Explanation of Symbols]

[0169] 10,11…Color-developing structures 20…Support layer 30…Multilayer film layer 31…Dielectric layer 32...Metal layer 33a,33b…Metal thin film

Claims

1. A color-generating structure comprising a multilayer film layer containing three or more thin film layers, wherein the multilayer film layer emits reflected light that is enhanced by interference, The multilayer film includes a dielectric layer which is a thin film layer made of a dielectric and a metal layer which is a thin film layer made of a metal, and has a structure in which the metal layer and the dielectric layer are alternately stacked. The metal layer has reflectivity and transmittance of light in the visible region. The multilayer film includes two or more of the metal layers, Among the multilayer film layers, only the metal layer closest to the incident surface, which is the surface on which light enters the color-generating structure, is a laminate of multiple metal thin films made of different metals, while the other metal layers are single metal thin films. Color-producing structure.

2. The metal layer has light absorption properties in the visible region. The color-developing structure according to claim 1.

3. The thickness of the metal layer is 5 nm or more and 40 nm or less. The color-developing structure according to claim 1.

4. The thickness of the dielectric layer is 10 nm or more and 300 nm or less. The color-developing structure according to claim 1.

5. The refractive index of the dielectric layer in the visible region is 1.5 or more and 3.0 or less. The color-developing structure according to claim 1.

6. The multilayer film includes two or more dielectric layers, Among the multilayer film layers, the thin film layer closest to the incident surface, which is the surface on which light enters the color-generating structure, is the dielectric layer. The color-developing structure according to any one of claims 1, 4, or 5.

7. The dielectric layer closest to the incident surface is thinner than the other dielectric layers. The color-developing structure according to claim 6.

8. The multilayer film consists of four thin film layers, each containing two metal layers and two dielectric layers. The color-developing structure according to claim 1.

Images