Laminated thin film powder, light shielding agent, fiber structure, and method for manufacturing laminated thin film powder

Abstract

The present invention provides a multilayer thin-film powder that can achieve a sharp change in the reflection spectrum at the boundary between the high-reflectivity band and the low-reflectivity band. [Solution] The laminated thin film powder (100) comprises a laminated portion (10) including a plurality of low refractive index layers (11) and a plurality of high refractive index layers (12) having a refractive index greater than that of the plurality of low refractive index layers, wherein in the laminated portion, the low refractive index layers and the high refractive index layers are alternately laminated so as to reinforce each other with respect to the wavelength of interest reflected at the interface, and the surface has a wrinkled shape.

Description

Technical Field

[0001] The present invention relates to a laminated thin film powder, a light shielding agent, a fiber structure, and a method for producing a laminated thin film powder.

Background Art

[0002] The development of ultraviolet (UV) protection powders has a great demand for use in "sunscreen agents" including sunscreens, and there has already been a long-term accumulation of technology. The efficacy of UV protection powders is to "prevent spots and freckles caused by sunburn", but the key is to "reduce the amount of UV reaching the skin".

[0003] In the prior art, UV cut technologies are roughly classified into those based on "absorption" and those based on "reflection" in principle. That is, UV protection agents are roughly classified into UV absorbers and UV reflectors. UV absorbers are disclosed in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is room for improvement in UV absorbers from the viewpoints of safety to the human body and environmental load. On the other hand, UV reflectors have almost no influence such as allergies, and no harmfulness to the environment has been confirmed. However, conventional UV reflectors have drawbacks such as losing the natural texture of the skin during use due to becoming white by multiple reflections. That is, conventional UV reflectors have a problem of reflecting light in the visible light region as well.

[0006] Furthermore, not only with UV protection agents, but with conventional light shielding agents based on "reflection," the challenge has been to reduce the reflectivity of light other than the wavelength of interest (the wavelength of light to be reflected). In other words, the challenge has been to make the spectral change at the boundary between the high-reflectivity band and the low-reflectivity band as steep as possible.

[0007] One aspect of the present invention has been made in view of the above-mentioned problems, and its object is to provide a laminated thin film powder that can achieve a sharp change in the reflection spectrum at the boundary between a high-reflection band and a low-reflection band. [Means for solving the problem]

[0008] To solve the above problems, the laminated thin film powder according to embodiment 1 of the present invention comprises a laminated portion including a plurality of first layers and a plurality of second layers having a refractive index greater than that of the plurality of first layers, wherein the first layers and the second layers are alternately laminated so as to reinforce each other with light of a first wavelength reflected at the interface, and the surface has a wrinkled shape.

[0009] In the laminated thin film powder according to embodiment 2 of the present invention, in embodiment 1, each of the plurality of first layers may have a thickness of 1 / 4 of the first wavelength in terms of optical distance, and each of the plurality of second layers may have a thickness of 1 / 4 of the first wavelength in terms of optical distance.

[0010] In the laminated thin film powder according to embodiment 3 of the present invention, in embodiment 1 or 2, a first anti-reflective layer may be provided on one side of the laminated portion to reduce the reflection of light of a second wavelength different from the first wavelength.

[0011] In the laminated thin film powder according to embodiment 4 of the present invention, in embodiment 3, a second anti-reflective layer that reduces the reflection of light of the second wavelength may be provided on the other side of the laminated portion.

[0012] The laminated thin film powder according to embodiment 5 of the present invention may include, in any of embodiments 1 to 4 above, a third layer adjacent to the laminated portion, having a thickness of less than 1 / 4 of the first wavelength in optical distance, and not satisfying the conditions for mutual reinforcement of the reflection of light of the first wavelength.

[0013] In the laminated thin film powder according to embodiment 6 of the present invention, in embodiment 5, the third layer may have a thickness of 1 / 8 of the first wavelength in terms of optical distance.

[0014] In the laminated thin film powder according to embodiment 7 of the present invention, in any of embodiments 1 to 6, the first wavelength may be 400 nm or less.

[0015] In the laminated thin film powder according to embodiment 8 of the present invention, in embodiment 3 or 4, the second wavelength may be 700 nm or greater.

[0016] In the laminated thin film powder according to embodiment 9 of the present invention, in any of embodiments 1 to 8 above, the layer structure of the laminated thin film powder may be symmetrical in the film thickness direction.

[0017] A light shielding agent according to embodiment 10 of the present invention comprises a laminated thin film powder described in any of embodiments 1 to 9 above, and a base, wherein the laminated thin film powder is dispersed in the base.

[0018] A fibrous structure according to aspect 11 of the present invention comprises a laminated thin film powder as described in any of aspects 1 to 9 above, and a plurality of fibers, wherein the laminated thin film powder is mixed in with the plurality of fibers.

[0019] To solve the above problems, a method for manufacturing a laminated thin film powder according to embodiment 12 of the present invention includes a base layer formation step of forming a base layer on a substrate, a laminated thin film formation step of forming a laminated thin film on the base layer, which includes a laminated portion in which a first layer and a second layer having a higher refractive index than the first layer are alternately laminated so as to reinforce the first wavelength of light reflected at the interface, a removal step of removing the base layer, and a grinding step of grinding the laminated thin film into a powder.

[0020] In the method for producing a laminated thin film powder according to Aspect 13 of the present invention, in the above Aspect 12, the coefficient of thermal expansion of the base layer is larger than that of the laminated thin film, and a cooling step of cooling the base layer and the laminated thin film may be included between the laminated thin film forming step and the removing step.

Advantages of the Invention

[0021] According to one aspect of the present invention, a sharp change in the reflection spectrum at the boundary between the high reflection band and the low reflection band can be realized.

Brief Description of the Drawings

[0022] [Figure 1] It is a graph showing the reflection and transmission spectra of an ideal UV reflector. [Figure 2] It is a schematic cross-sectional view showing the configuration of the laminated thin film powder according to Embodiment 1. [Figure 3] It is a process diagram showing an example of the method for producing the laminated thin film powder. [Figure 4] It is a diagram showing a microscopic image of the laminated thin film powder. [Figure 5] It is a graph showing the reflection spectrum of the laminated thin film in the examples. [Figure 6] It is a graph showing the transmission spectrum of the laminated thin film in the examples. [Figure 7] It is a schematic cross-sectional view showing the configuration of the laminated thin film powder according to Embodiment 2. [Figure 8] It is a schematic cross-sectional view showing the configuration of the laminated thin film powder according to Embodiment 3.

Modes for Carrying Out the Invention

[0023] (Regarding the characteristic points according to one aspect of the present invention) Although UV absorbers have advantages such as being colorless and transparent and being able to shield UV while maintaining a natural texture, they have disadvantages such as the molecular structure being damaged when absorbing UV energy and the protective performance deteriorating over time. There is also room for improvement from the viewpoints of safety for the human body and environmental load.

[0024] Furthermore, while UV reflectors have advantages such as causing virtually no allergic reactions and no known environmental harm, they also have the disadvantage of causing a whitening effect due to multiple reflections, which can diminish the natural texture of the skin during use.

[0025] In other words, in conventional UV protection agents, both UV absorbers and UV reflectors currently have their own advantages and disadvantages. Therefore, the inventors of this invention investigated methods to improve the transparency of UV reflectors.

[0026] Figure 1 is a graph showing the reflectance and transmission spectra of an ideal UV reflector designed based on the technical concept described above. To achieve a highly transparent UV reflector, it is necessary to achieve optical properties such as extremely low transmittance (i.e., extremely high reflectance) in the UV region and extremely low reflectance (i.e., extremely high transmittance) in the visible light region, as shown in Figure 1. In other words, it is necessary to achieve a steep change in the transmittance and reflectance spectra at the boundary wavelength between the UV and visible light regions.

[0027] The inventors focused on the fact that a laminated structure in which low refractive index layers and high refractive index layers are alternately stacked causes a sharp change in the spectrum near the wavelength of interest, and conceived the idea of ​​applying this laminated structure to a UV reflector. Specifically, the inventors found that by constructing a UV reflector using a laminated thin film powder having the above-mentioned laminated structure with the wavelength of interest being the wavelength of UV light (340 nm), it is possible to realize a UV reflector that strongly reflects UV light while almost not reflecting visible light. The detailed structure of such a laminated thin film powder will be described below.

[0028] [Embodiment 1] (Composition of the laminated thin-film powder 100) Figure 2 is a schematic cross-sectional view showing the configuration of the laminated thin film powder 100 according to Embodiment 1. As shown in Figure 2, the laminated thin film powder 100 comprises a laminated portion 10, a first surface layer 20a (third layer), a second surface layer 20b (third layer), a first anti-reflective layer 30a, and a second anti-reflective layer 30b. The laminated thin film powder 100 is a piece (powder) of a laminate in which a large number of thin films are laminated. The laminated thin film powder 100 is configured to selectively reflect light in a specific wavelength band. The laminated thin film powder 100 is used as a light shielding agent. In this embodiment, the laminated thin film powder 100 selectively reflects light in a wavelength band lower than a specific wavelength (i.e., it functions like an edge filter). The laminated thin film powder 100 may also transmit light in a specific wavelength band and reflect other light (i.e., it may function like a bandpass filter).

[0029] The laminated portion 10 includes a plurality of low refractive index layers 11 (first layer) and a plurality of high refractive index layers 12 (second layer) with a refractive index greater than that of the plurality of low refractive index layers 11. In the laminated portion 10, the low refractive index layers 11 and the high refractive index layers 12 are stacked alternately such that they reinforce each other when light of the target wavelength λ (first wavelength) is incident at an incident angle of 0° and reflected at the interface. Specifically, the low refractive index layers 11 and the high refractive index layers 12 have a thickness of (2m+1)λ / 4 in optical distance with respect to the target wavelength λ (m=0,1,...). As a result, the reflectance spectrum of the laminated portion 10 (of light incident at an incident angle of 0° on the surface of the laminated portion 10) produces a high reflectance band near the target wavelength λ. Therefore, the laminated thin film powder 100 can selectively reflect light near the target wavelength λ and keep the reflectance of other light extremely low. Therefore, the laminated thin-film powder 100 can achieve a sharp change in the spectrum at the boundary between the high-reflectance band and the low-reflectance band.

[0030] In this embodiment, the wavelength of interest λ is 400 nm or less. The wavelength of interest λ is the wavelength of UV light. As a result, the multilayer thin film powder 100 can achieve high reflectivity in the UV region. Therefore, the multilayer thin film powder 100 can be used as a UV reflector that reflects UV light. The wavelength of interest λ is, for example, 340 nm. In this case, the multilayer thin film powder 100 achieves high reflectivity in the UV region, and as a result, the transmittance at λ < 380 nm can be suppressed to almost 0%. Note that the wavelength of interest λ is not limited to this, and may be set to reflect only light in a specific visible light region, for example.

[0031] Preferably, each of the multiple low refractive index layers 11 has a thickness of 1 / 4 of the wavelength of interest λ in optical distance, and each of the multiple high refractive index layers 12 has a thickness of 1 / 4 of the wavelength of interest λ in optical distance. That is, m=0 is preferable. This leads to cost reduction by making the film thickness as small as possible. It also prevents wavelengths longer than the wavelength of the reflection band near the wavelength of interest λ from satisfying the condition for constructive interference of reflected light. Therefore, the laminated thin film powder 100 can selectively reflect UV light. If the film thickness is (3 / 4)λ (when m=1), the condition for constructive interference of reflected light near the wavelength of 3λ (1120nm: infrared region) is also satisfied. That is, the laminated thin film powder 100 reflects not only UV light but also infrared light. If the film thickness is further increased (m=2,3,...), the wavelength that satisfies the condition for constructive interference approaches the wavelength of interest λ. Therefore, for the purpose of reflecting UV light and transmitting visible light, m=0 is preferable. Furthermore, if the application also needs to reflect IR light (λ=1120nm), then m=1 may be used.

[0032] The materials for the low refractive index layer 11 and the high refractive index layer 12 are inorganic materials, and any material with a large refractive index ratio between the low refractive index layer 11 and the high refractive index layer 12 is acceptable. Hereafter, the materials for the low refractive index layer 11 and the high refractive index layer 12 will be denoted as low refractive index material X and high refractive index material Y, respectively. Low refractive index material X may be, for example, SiO2, and high refractive index material Y may be, for example, TiO2. In this case, for a wavelength of interest λ = 340 nm, the film thickness of the low refractive index layer 11 should be approximately 57 nm, and the film thickness of the high refractive index layer 12 should be approximately 28 nm. The following explanation assumes that the low refractive index material X is SiO2 and the high refractive index material Y is TiO2. Note that low refractive index material X may also be Al2O3. Also, high refractive index material Y may be CeO2 or ZnO.

[0033] The more layers there are in the laminated section 10, the steeper the change in the spectrum near the wavelength λ of interest becomes, and therefore the higher the transmittance in the visible light region adjacent to the ultraviolet region. From the viewpoint of achieving a steep change in the spectrum, it is preferable that the number of layers in the laminated section 10 be 10 or more. For example, the number of layers in the laminated section 10 may be 19. Also, in order to reduce costs, it is preferable to reduce the number of layers in the laminated section 10 as much as possible.

[0034] In this embodiment, the laminated portion 10 is constructed by alternately laminating low refractive index layers 11 and high refractive index layers 12 so as to be symmetrical in the film thickness direction. The laminated portion 10 has low refractive index layers 11 at one end and the other end.

[0035] The first surface layer 20a is a layer adjacent to one side of the laminated portion 10. The second surface layer 20b is a layer adjacent to the other side of the laminated portion 10. Hereinafter, unless otherwise distinguished, the first surface layer 20a and the second surface layer 20b will simply be referred to as the surface layer 20. The surface layer 20 has a thickness of less than 1 / 4 of the wavelength of interest λ in optical distance and is configured not to satisfy the condition of reinforcing the reflection of light of interest wavelength λ. This reduces ripple (interference fringes) in wavelength bands longer than the wavelength of the reflection band near the wavelength of interest λ (i.e., the visible light region). Furthermore, the thickness of the surface layer 20 does not satisfy the condition of reinforcing the reflection of visible light longer than the wavelength of interest λ.

[0036] The thickness of the surface layer 20 should, for example, be 1 / 8 of the wavelength λ in terms of optical distance. This effectively reduces ripple in the visible light region.

[0037] If the layer of the laminated portion 10 adjacent to the surface layer 20 is a low refractive index layer 11, the material of the surface layer 20 is a high refractive index material Y. If the layer of the laminated portion 10 adjacent to the surface layer 20 is a high refractive index layer 12, the material of the surface layer 20 is a low refractive index material X. In this embodiment, the material of both the first surface layer 20a and the second surface layer 20b is a high refractive index material Y, and more specifically, TiO2.

[0038] If the material of the surface layer 20 is TiO2, the thickness of the surface layer 20 should be approximately 14 nm for a wavelength of interest λ = 340 nm.

[0039] The first anti-reflective layer 30a is provided on one side of the laminated portion 10. The first anti-reflective layer 30a is a layer adjacent to one side of the first surface layer 20a. The second anti-reflective layer 30b is provided on the other side of the laminated portion 10. The second anti-reflective layer 30b is a layer adjacent to the other side of the second surface layer 20b. Hereinafter, unless otherwise distinguished, the first anti-reflective layer 30a and the second anti-reflective layer 30b will simply be referred to as the anti-reflective layer 30. The anti-reflective layer 30 is a layer exposed to the outside, provided at the edge in the film thickness direction of the laminated thin film powder 100. The anti-reflective layer 30 is configured to reduce the reflection of light at a second wavelength λ', which is different from the wavelength λ of interest. Here, the second wavelength λ' is longer than the wavelength λ of interest, and if the anti-reflective layer 30 were not present, the reflectivity would increase due to optical interference. Such an anti-reflective layer 30 can reduce the reflection of light at a second wavelength λ', which is different from the wavelength λ of interest.

[0040] In this embodiment, the second wavelength λ' is 700 nm or greater. The second wavelength λ' is a wavelength in the visible light range (380 nm to 830 nm). Therefore, if the anti-reflective layer 30 is not present, the laminated thin film powder 100 will reflect light of the second wavelength λ', which is visible light, resulting in reduced transparency. On the other hand, by providing the anti-reflective layer 30, the reflection of such light of the second wavelength λ' can be reduced, thereby further improving the transparency of the UV reflector using the laminated thin film powder 100. In this embodiment, if the wavelength of interest λ is 340 nm, the second wavelength λ' is 800 nm.

[0041] If the material of the surface layer 20 adjacent to the anti-reflective layer 30 is a low refractive index material X, then the material of the anti-reflective layer 30 is a high refractive index material Y. If the material of the surface layer 20 adjacent to the anti-reflective layer 30 is a high refractive index material Y, then the material of the anti-reflective layer 30 is a low refractive index material X. In this embodiment, the materials of both the first anti-reflective layer 30a and the second anti-reflective layer 30b are low refractive index material X, and more specifically, SiO2.

[0042] When the materials of the surface layer 20 and the anti-reflective layer 30 are a high refractive index material Y and a low refractive index material X, respectively, the anti-reflective layer 30 only needs to have a thickness of (2m'+1)λ' / 4 in optical distance (m'=0,1,...). This allows the anti-reflective layer 30 to reduce the reflection of light at the second wavelength λ'. From the viewpoint of cost reduction, it is preferable that the anti-reflective layer 30 has a thickness of 1 / 4 of the second wavelength λ' in optical distance. When the material of the anti-reflective layer 30 is SiO2, the film thickness of the anti-reflective layer 30 should be approximately 135 nm for a second wavelength λ' = 800 nm.

[0043] As shown in Figure 2, the layer structure of the laminated thin film powder 100 (including the laminated portion 10, the surface layer 20, and the anti-reflective layer 30) is symmetrical in the film thickness direction. This makes it possible to make the optical properties of the laminated thin film powder 100 with respect to light rays incident from the surface and the optical properties with respect to light rays incident from the back surface identical. Therefore, even in situations where the front and back sides of the laminated thin film powder 100 cannot be controlled (for example, when the laminated thin film powder 100 is dispersed in the base material 111 as shown in Figure 4), the light shielding agent can be implemented without reducing its ability to selectively reflect light near the wavelength λ of interest.

[0044] Furthermore, the multilayer thin film powder 100 has a wrinkled shape on its surface (see Figure 4). The wrinkles are several micrometers in size. The wrinkles are formed randomly in two dimensions on the surface of the multilayer thin film powder 100. In other words, the cross-section of the multilayer thin film powder 100 shows a wavy layer structure as shown in Figure 2. This reduces the dependence of the optical properties (viewing angle dependence) on the angle of incidence of light rays incident on the surface (or back surface) of the multilayer thin film powder 100. Therefore, the performance as a UV reflector can be improved.

[0045] Furthermore, the layer structure of the laminated thin film powder 100 does not contain any unnecessary layers (for example, hollow sections or core layers during film formation) that do not contribute to improving optical properties. Each layer in the laminated thin film powder 100 is densely stacked. This increases the proportion of the laminated section 10 per unit volume in the UV reflector, thereby improving its performance as a UV reflector. In addition, since the laminated thin film powder 100 does not have the hollow sections described above, it is possible to prevent an increase in ripple in the visible light region and also improve its strength.

[0046] (Method for manufacturing laminated thin film powder 100) Figure 3 is a process diagram showing an example of a method for manufacturing the laminated thin film powder 100. Reference numerals 1031 to 1035 in Figure 3 schematically indicate cross-sectional views of the base layer 52 and / or laminated thin film 53, etc., at each step of the manufacturing method. The method for manufacturing the laminated thin film powder 100 will now be described with reference to Figure 3.

[0047] First, as shown in reference numeral 1031, a base layer 52 is formed on the substrate 51 (base layer formation step). Specifically, the base layer 52 is coated onto the substrate 51 by spin coating. The substrate 51 is, for example, a glass substrate. The base layer 52 is, for example, an acetone-soluble resist (e.g., OFR resist (manufactured by Tokyo Ohka Kogyo Co., Ltd.), SML resist (manufactured by EM Resist), PMMA resist (manufactured by EM Resist)). The thickness of the base layer 52 coated on the substrate 51 is about 5 μm.

[0048] Next, as shown in reference numeral 1032, a laminated thin film 53 having the layered structure of the laminated thin film powder 100 is formed on the base layer 52 (laminated thin film formation step). The laminated thin film 53 includes at least a laminated portion in which a low refractive index layer and a high refractive index layer with a refractive index greater than that of the low refractive index layer are alternately stacked so as to reinforce the light of the wavelength of interest λ reflected at the interface. Specifically, the laminated thin film 53 is deposited on the base layer 52 by vacuum deposition. As shown in reference numeral 1032, the laminated thin film 53 is deposited on the base layer 52 which has expanded due to thermal expansion during vacuum deposition.

[0049] Next, as shown by reference numeral 1033, the base layer 52 and the multilayer thin film 53 are cooled (cooling step). Here, the thermal expansion coefficient of the base layer 52 is greater than that of each layer of the multilayer thin film 53. Therefore, the base layer 52 shrinks significantly relative to the multilayer thin film 53 due to cooling. As a result, μm-sized wrinkles are randomly formed in two dimensions on the surface of the multilayer thin film 53.

[0050] Next, as shown in reference numeral 1034, the base layer 52 is removed from the multilayer thin film 53 (removal step). Specifically, the base layer 52 and the multilayer thin film 53 are immersed in a solution (acetone) that dissolves the base layer 52 and heated. This dissolves the base layer 52 and peels the multilayer thin film 53 from the substrate 51.

[0051] Next, as shown in reference numeral 1035, the laminated thin film 53 is pulverized into powder (pulverization step). Specifically, the laminated thin film 53 is pulverized into powder by ultrasonic pulverization to form flakes. The pulverized laminated thin film 53 becomes the laminated thin film powder 100. The laminated thin film 53 is pulverized until the length is at least 1 mm or less. Preferably, the laminated thin film 53 is pulverized to a size of 50 μm. By pulverizing the laminated thin film 53 to a size of 50 μm, the optical properties of the laminated thin film powder 100 are not impaired, and the roughness when the light shielding agent containing the laminated thin film powder 100 is applied to the skin can be reduced.

[0052] Furthermore, the method for forming the multilayer thin film 53 on the base layer 52 in the multilayer thin film formation step is not limited to vacuum deposition. For example, the multilayer thin film 53 may be deposited on the base layer 52 by a wet method (specifically, the sol-gel method, etc.).

[0053] Furthermore, the combination of the base layer 52 and the solution for dissolving the base layer 52 is not limited to those described above. The solution may be any solution that does not affect the laminated thin film 53, and the thermal expansion coefficient of the base layer 52 may be greater than that of the laminated thin film 53. For example, the base layer 52 may be a resist containing novolac resin, and the solution may be an alkaline aqueous solution. Alternatively, the base layer 52 may be a photoresist, and the solution may be a developer. Alternatively, the material of the base layer 52 may be methylcellulose, and the solution may be cold water.

[0054] (Examples of application) The laminated thin film powder 100 according to this embodiment is used in the light shielding agent 110 described below. The light shielding agent 110 includes the laminated thin film powder 100 and a base 111 (see Figure 4). The laminated thin film powder 100 is dispersed in the base 111. The base 111 can be any material that can disperse the flake-shaped laminated thin film powder 100, such as a liquid, emulsion, cream, solid, paste, gel, powder, foam, or sprayable liquid. This makes it possible to construct a light shielding agent 110 that selectively reflects light in a specific wavelength band. In particular, by designing the laminated thin film powder 100 with a wavelength of interest λ of 400 nm or less, the light shielding agent 110 can be used as a UV reflector that strongly reflects UV light while almost not reflecting visible light.

[0055] Such a light-shielding agent 110 can be applied to cosmetics or paints. In particular, when applied to cosmetics, the light-shielding agent 110 reflects almost no visible light, thus overcoming the drawback of conventional UV reflectors, which is the loss of the natural texture of the skin. In other words, it is possible to provide cosmetics that have high transparency and a natural texture. Furthermore, since the laminated thin film powder 100 contained in the light-shielding agent 110 has a wrinkled shape, the dependence on the viewing angle can be reduced even when applied to the skin. Therefore, the performance as a UV reflector can be improved. Also, when applied to paints, since the light-shielding agent 110 reflects UV light, the deterioration of the protective performance over time can be suppressed.

[0056] Furthermore, the laminated thin film powder 100 according to this embodiment can also be used in the fiber structure 120 described below. The fiber structure 120 includes the laminated thin film powder 100 and a plurality of fibers 121. The laminated thin film powder 100 is mixed in with the plurality of fibers 121. The plurality of fibers 121 are thin fibers that constitute a thread. The shape of the fiber structure 120 may be a thread, a cloth woven from threads, or a nonwoven fabric. Such a fiber structure 120 can be applied to parasols, clothing, etc.

[0057] (Examples) The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0058] In this example, the optical properties of the multilayer thin film powder 100 corresponding to the design conditions described later were determined by measurement and simulation. Figure 4 shows a microscopic image of the multilayer thin film powder 100 prepared based on the design conditions described later. Figure 5 is a graph showing the reflection spectrum of the multilayer thin film 53 in the example. Figure 6 is a graph showing the transmission spectrum of the multilayer thin film 53 in the example. In Figures 5 and 6, the spectra determined by measurement and simulation are labeled as "measured value" and "set value," respectively.

[0059] The above design conditions were as follows: "X" and "Y" in Figure 2 were SiO2 and TiO2, respectively, and the wavelength of interest was set to λ = 340 nm. At this time, the film thicknesses of the low refractive index layer 11, high refractive index layer 12, surface layer 20, and anti-reflective layer 30 were 57 nm, 28 nm, 14 nm, and 135 nm, respectively. For the preparation of the sample for measurement, a multilayer thin film 53 was deposited on the base layer 52 by vacuum deposition based on the above design conditions. OFR-5 BE 6-189cP (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as the base layer 52, and the multilayer thin film 53 was peeled off from the substrate 51 by immersion in acetone.

[0060] As shown in Figure 4, it was confirmed that wrinkles were formed on the surface of the laminated thin-film powder 100 manufactured based on the above design conditions.

[0061] Furthermore, as shown in Figures 5 and 6, a sharp change in the transmittance and reflectance spectra was obtained at the boundary wavelength between the UV and visible light regions. Such a sharp change indicates that it is possible to realize a UV reflector that strongly reflects UV light while almost not reflecting visible light, demonstrating a remarkable effect compared to conventional UV reflectors.

[0062] In detail, as shown in Figure 5, the reflectance was suppressed to an average of about 5.5% in the visible light range, and as shown in Figure 6, the transmittance was suppressed to almost 0% in the UV range below 380 nm. Furthermore, shielding was achieved not only in the UVB region (280-320 nm) but also in the UVA region (320-400 nm). These optical properties were largely preserved even in the flake-like laminated thin film powder 100 obtained by crushing the laminated thin film 53.

[0063] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0064] Figure 7 is a schematic cross-sectional view showing the configuration of the laminated thin film powder 100A according to Embodiment 2. The laminated thin film powder 100A comprises a laminated portion 10A, a surface layer 20A, and an anti-reflective layer 30A. The surface layer 20A includes a first surface layer 20Aa (third layer) and a second surface layer 20Ab (third layer). The anti-reflective layer 30A includes a first anti-reflective layer 30Aa and a second anti-reflective layer 30Ab. The laminated thin film powder 100A according to Embodiment 2 differs from the laminated thin film powder 100 according to Embodiment 1 in that the layer containing the low refractive index material X and the layer containing the high refractive index material Y are swapped.

[0065] In other words, in this embodiment, the laminated portion 10A has high refractive index layers 12 at both ends. The materials of the first surface layer 20Aa and the second surface layer 20Ab are both low refractive index material X. The materials of the first anti-reflective layer 30Aa and the second anti-reflective layer 30Ab are both high refractive index material Y. Here, the anti-reflective layer 30 may have a thickness of m'λ' / 2 in optical distance to reduce the reflection of light at the second wavelength λ' (m'=1,...). From the viewpoint of cost reduction, it is preferable that the anti-reflective layer 30 has a thickness of 1 / 2 of the second wavelength λ' in optical distance.

[0066] As described above, even if the layer containing the low refractive index material X and the layer containing the high refractive index material Y are swapped compared to the laminated thin film powder 100 according to Embodiment 1, the laminated portion 10A generates a high reflectivity band near the wavelength λ of interest. Therefore, the laminated thin film powder 100A functions as a UV reflector that strongly reflects UV light while almost not reflecting visible light, similar to the laminated thin film powder 100 according to Embodiment 1.

[0067] Furthermore, the layer structure of the laminated thin film powder 100A is symmetrical in the film thickness direction, similar to that of the laminated thin film powder 100. Therefore, even in situations where the front and back sides of the laminated thin film powder 100A cannot be controlled, it is possible to selectively reflect light near the wavelength λ of interest.

[0068] [Embodiment 3] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0069] Figure 8 is a schematic cross-sectional view showing the configuration of the laminated thin film powder 100B according to Embodiment 3. The laminated thin film powder 100B comprises a laminated portion 10B, a surface layer 20B, and an anti-reflective layer 30B. The surface layer 20B includes a first surface layer 20Aa (third layer) and a second surface layer 20b (third layer). The anti-reflective layer 30B includes a first anti-reflective layer 30Aa and a second anti-reflective layer 30b. The laminated thin film powder 100B according to Embodiment 3 differs from the laminated thin film powder 100 according to Embodiment 1 in that it is not symmetrical in the film thickness direction.

[0070] In other words, in this embodiment, the laminated portion 10B has a high refractive index layer 12 at one end and a low refractive index layer 11 at the other end. The number of layers in the laminated portion 10B is even.

[0071] As described above, compared to the laminated thin film powder 100 according to Embodiment 1, even when it is not symmetrical in the film thickness direction, it can selectively reflect UV light incident from the front and back surfaces of the laminated thin film powder 100. That is, the laminated thin film powder 100B functions as a UV reflector that strongly reflects UV light while almost not reflecting visible light, similar to the laminated thin film powder 100 according to Embodiment 1.

[0072] (Effects and Benefits) With the above configuration, a steep change in the reflectance spectrum at the boundary between the visible light and UV regions can be achieved. Such effects contribute to achieving, for example, Goal 3 of the United Nations' Sustainable Development Goals (SDGs), "Ensure healthy lives and promote well-being for all."

[0073] In the laminated thin film powder 100 according to Embodiment 1, the low refractive index layer 11 is arranged on both outer sides of the laminated portion 10. Therefore, the laminated thin film powder 100 according to Embodiment 1 has smaller ripple in the visible light region compared to the laminated thin film powders 100A and 100B according to other embodiments. As a result, a more colorless and transparent UV reflector can be realized. Furthermore, in the laminated thin film powder 100 according to Embodiment 1, the material of the anti-reflective layer 30 exposed to the outside is formed from a low refractive index material X, rather than a high refractive index material Y, which is generally considered brittle (in the case of TiO2, it also has photocatalytic activity). This improves the stability of the laminated thin film powder 100.

[0074] (Additional notes) The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0075] 10, 10A, 10B laminated section 11. Low refractive index layer (first layer) 12. High refractive index layer (second layer) 20, 20A, 20B surface layer 20a, 20Aa 1st surface layer (3rd layer) 20b, 20Ab 2nd surface layer (3rd layer) 30, 30A, 30B Anti-reflection layer 30a, 30Aa 1st anti-reflection layer 30b, 30Ab 2nd anti-reflection layer 51 circuit boards 52 Base Layer 53 Multilayer Thin Films 100, 100A, 100B Multilayer Thin Film Powder 110 Light-shielding agent 111 Base 120 Fiber Structures 121 Fibers

Claims

1. The laminate comprises a plurality of first layers and a plurality of second layers having a refractive index greater than that of the plurality of first layers, In the laminated portion, the first layer and the second layer are stacked alternately such that they reinforce each other with light of the first wavelength reflected at the interface. A laminated thin-film powder having a wrinkled surface.

2. Each of the plurality of first layers has a thickness of 1 / 4 of the first wavelength in optical distance, The laminated thin film powder according to claim 1, wherein each of the plurality of second layers has a thickness of 1 / 4 of the first wavelength in terms of optical distance.

3. The laminated thin film powder according to claim 1, wherein one side of the laminated portion is provided with a first anti-reflective layer that reduces the reflection of light of a second wavelength different from the first wavelength.

4. The laminated thin film powder according to claim 3, further comprising a second anti-reflective layer on the other side of the laminated portion for reducing the reflection of light of the second wavelength.

5. The laminated thin film powder according to claim 1, further comprising a third layer adjacent to the laminated portion, having a thickness of less than 1 / 4 of the first wavelength in optical distance, and not satisfying the conditions for mutual reinforcement of the reflection of light of the first wavelength.

6. The laminated thin film powder according to claim 5, wherein the third layer has a thickness of 1 / 8 of the first wavelength in terms of optical distance.

7. The laminated thin film powder according to claim 1, wherein the first wavelength is 400 nm or less.

8. The laminated thin film powder according to claim 3, wherein the second wavelength is 700 nm or greater.

9. The laminated thin film powder according to claim 1, wherein the layer structure of the laminated thin film powder is symmetrical in the film thickness direction.

10. A laminated thin film powder according to any one of claims 1 to 9, Includes a base, The aforementioned laminated thin film powder is a light-shielding agent dispersed in the aforementioned base.

11. A laminated thin film powder according to any one of claims 1 to 9, It contains multiple fibers, The laminated thin film powder is a fibrous structure in which the powder is mixed with the plurality of fibers.

12. A base layer formation step in which a base layer is formed on a substrate, A laminated thin film formation step of forming a laminated thin film on the base layer, which includes a laminated portion in which a first layer and a second layer having a higher refractive index than the first layer are alternately stacked so as to reinforce the first wavelength of light reflected at the interface, A removal step of removing the base layer, A method for producing a laminated thin film powder, comprising a grinding step of grinding the laminated thin film into a powder.

13. The thermal expansion coefficient of the base layer is greater than that of the laminated thin film. A method for producing a laminated thin film powder according to claim 12, comprising a cooling step of cooling the base layer and the laminated thin film between the laminated thin film formation step and the removal step.

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