Resin-made reflective film

Abstract

A resin-made reflecting film having two or more regions with different refractive indexes, wherein the film thickness is 20 μm to 5000 μm, the total reflectance for deep ultraviolet rays with a wavelength of 220 nm to 300 nm is 60% or more, and the diffuse reflectance is 60% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a resin-made reflective film. BACKGROUND

[0002] The bactericidal effect of ultraviolet rays has been studied. As a light source of ultraviolet rays, low-pressure mercury lamps, xenon lamps and the like have been mainstream so far, but in recent years, LEDs that can emit light of the wavelength of this region have been developed, and germicidal apparatuses equipped with LEDs or germicidal methods using LEDs have been developed. For example, a fluid sterilization assembly is described in Patent Literature 1, which irradiates ultraviolet rays to a fluid flowing in a flow path, and sterilizes the fluid. In order to effectively diffuse the ultraviolet rays irradiated from the light source to a certain region, it is effective to use a reflective material that can effectively and uniformly reflect ultraviolet rays. The fluid sterilization assembly described in Patent Literature 1 uses an ultraviolet reflective material for the inner cylinder that forms a cylindrical treatment flow path.

[0003] As an ultraviolet reflective material, metal materials, resin materials and the like are known. As such metal materials, for example, an ultraviolet reflective material aluminum foil that exhibits high reflectance of ultraviolet rays by controlling aluminum particles (Patent Literature 2), an aluminum reflective member having a reflective layer or a UV-transmissive resin layer on the surface of an aluminum material, and the like (Patent Literature 3) are known. In addition, as the above-mentioned resin materials, materials in which a fluorine-based resin or a silicone-based resin is made into a multilayer laminate are known, for example, a multilayer optical film having two kinds of fluoropolymer materials having different refractive indices, an ultraviolet reflective polymer film having two different polymer layers (Patent Literatures 4 and 5) are known. In addition, a sintered compression or porous molded body made of polytetrafluoroethylene (PTFE) is also known as an ultraviolet reflective material.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2019-187657

[0007] Patent Literature 2: International Publication No. 2017 / 158989

[0008] Patent Literature 3: Japanese Patent Application Laid-Open No. 2016-042183

[0009] Patent Literature 4: Japanese Patent Application Laid-Open No. H7-507152

[0010] Patent Literature 5: Japanese Patent Application Laid-Open No. 2015-165298 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] Metal materials generally perform specular reflection (regular reflection) of ultraviolet light. Therefore, for example, in the case of irradiating ultraviolet light in water or air to perform sterilization, if a metal material is used as a reflection material, even if the apparent reflectance is high, the reflection intensity (illuminance) of the ultraviolet light is weak depending on the angle, the ultraviolet light cannot be uniformly distributed in the water or air, and it is difficult to obtain sufficient sterilization efficiency.

[0013] In addition, in the case where a multilayer laminate of a fluorine-based resin or a silicone-based resin is used as a reflection plate, since the refractive index of the resin itself is limited, it is difficult to increase the interlayer refractive index difference to a level at which sufficient reflectance can be achieved. Therefore, for example, in the case of the polymer films described in Patent Documents 4 and 5, there is currently a situation in which the reflected illuminance of deep ultraviolet is insufficient.

[0014] Further, a sintered compression or porous molded body made of PTFE has a large number of grain boundaries or pores inside, and has excellent reflection performance of ultraviolet light. However, in order to cause the sintered compression porous molded body to exhibit sufficient reflection performance of ultraviolet light, it is necessary to ensure a thickness of a certain degree or more (for example, about 10 mm). As a result, the sintered compression porous molded body having such a thickness is poor in flexibility, has low freedom of processing, and is limited in the applicable site of the ultraviolet light reflection material, and the like.

[0015] In view of the above, an object of the present application is to provide a resin reflection film which has excellent diffuse reflection performance of ultraviolet light, particularly deep ultraviolet light, and which is excellent in flexibility and has high freedom of processing.

[0016] Means for solving the problem

[0017] The above object of the present application is solved by the following means. (1)

[0019] A resin reflection film is provided, which is a resin reflection film having two or more regions having different refractive indexes from each other, wherein the thickness of the resin reflection film is 20 μm to 5000 μm, the total reflectance with respect to deep ultraviolet light having a wavelength of 220 nm to 300 nm is 60% or more, and the diffuse reflectance is 60% or more. (2)

[0021] The resin reflection film described in (1) above, wherein the thickness of the resin reflection film is 50 μm to 1000 μm. (3)

[0023] The resin reflection film described in (1) or (2) above, wherein the two or more regions constituting the resin reflection film each have a light transmittance of 30% to 100% with respect to deep ultraviolet light having a wavelength of 220 nm to 300 nm. (4)

[0025] The resinous reflecting film according to any one of (1) to (3) described above, characterized in that at least one of the two or more regions constituting the resinous reflecting film is a bubble. (5)

[0027] The resinous reflecting film according to any one of (1) to (4) described above, wherein the resinous reflecting film has a repeating structure portion in which a resin portion (resin region) and a void portion (gas region) are repeated. (6)

[0029] The resinous reflecting film according to (5) described above, wherein the width of at least one resin portion and / or the width of at least one void portion constituting the repeating structure portion is 0.1λ to 20λ with respect to the wavelength λ of the incident ultraviolet rays. (7)

[0031] The resinous reflecting film according to any one of (1) to (6) described above, wherein the resin material constituting the resinous reflecting film is a fluorine-containing resin or a silicone resin, and the resinous reflecting film is formed by foaming an inert gas impregnated in a film of the fluorine-containing resin or the silicone resin. (8)

[0033] The resinous reflecting film according to any one of (1) to (6) described above, wherein the resin material constituting the resinous reflecting film is a fluorine-containing resin, and the resinous reflecting film is formed by stretching a film of the fluorine-containing resin to form bubbles and / or voids inside. (9)

[0035] The resinous reflecting film according to any one of (7) or (8) described above, wherein the density (Q) of the resinous reflecting film with respect to the density (P) of the resin material constituting the resinous reflecting film satisfies Q / P = 0.2 to 0.99. (10)

[0037] A sterilization device provided with an ultraviolet light source and the resinous reflecting film according to any one of (1) to (9) described above.

[0038] Generally, "ultraviolet rays" refer to electromagnetic waves having a shorter wavelength than visible light. Note that in the present invention, "deep ultraviolet rays" refer to electromagnetic waves having a wavelength region of 200 nm to 300 nm.

[0039] In addition, in the present invention, "total reflectance" refers to the sum of "specular reflectance" and "diffuse reflectance". In addition, "specular reflectance" refers to the proportion of the irradiation light that is specularly reflected, and "diffuse reflectance" refers to the proportion of the irradiation light that is diffusely reflected.

[0040] Effects of the Invention

[0041] The resin-made reflecting film of the present application is excellent in diffuse reflection performance for ultraviolet rays, especially deep ultraviolet rays, and is excellent in softness, and also has high freedom in processing. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a photograph of a cross section of the reflecting material manufactured in Example 1, which is photographed by a scanning electron microscope instead of a photograph of a cross section of the reflecting material manufactured in Example 1, which is photographed by a scanning electron microscope.

[0043] Figure 2 is a photograph of a cross section of the reflecting material manufactured in Example 1, which is photographed by a scanning electron microscope instead of a photograph of a cross section of the reflecting material manufactured in Example 1, which is photographed by a scanning electron microscope.

[0044] Figure 3 is a photograph of a cross section of the reflecting material manufactured in Example 6, which is photographed by a scanning electron microscope instead of a photograph of a cross section of the reflecting material manufactured in Example 6, which is photographed by a scanning electron microscope.

[0045] Figure 4 is a photograph of a cross section of the reflecting material manufactured in Example 6, which is photographed by a scanning electron microscope instead of a photograph of a cross section of the reflecting material manufactured in Example 6, which is photographed by a scanning electron microscope.

[0046] Figure 5 is a schematic view for explaining a method for measuring ultraviolet irradiance in Test Example 2.

[0047] Figure 6 is a schematic view for explaining a method for measuring ultraviolet irradiance in Test Example 2. DETAILED DESCRIPTION

[0048] A preferred embodiment of the resin-made reflecting film of the present application will be described.

[0049] The resin-made reflecting film of the present application (hereinafter also referred to as "the reflecting film of the present application") has two or more regions having different refractive indexes from each other. By having such a structure, deep ultraviolet rays can be efficiently and uniformly diffusely reflected in a plurality of directions. That is, the reflecting film of the present application has a total reflectance of 60% or more and a diffuse reflectance of 60% or more for deep ultraviolet rays having a wavelength of 220 nm to 300 nm. In addition, the reflecting film of the present application has a thickness (film thickness) of 20 μm to 5000 μm.

[0050] The reflective film of the present application exhibits desired sufficient reflective properties even if it is in a thin film form. From the viewpoint of improving the diffuse reflectance of deep ultraviolet light having a wavelength of 220 nm to 300 nm, the film thickness of the reflective film of the present application is preferably 30 μm or more, more preferably 40 μm or more, further preferably 50 μm or more, and also preferably 100 μm or more. In addition, from the viewpoint of improving the flexibility of the reflective film and improving the degree of freedom in processing, the film thickness is preferably 3000 μm or less, more preferably 2000 μm or less, and further preferably 1000 μm or less.

[0051] In addition, from the same viewpoint as described above, the film thickness of the reflective film of the present application is preferably 30 μm to 3000 μm, more preferably 40 μm to 2000 μm, further preferably 50 μm to 1000 μm, and more further preferably 100 μm to 1000 μm.

[0052] From the viewpoint of increasing the total reflectance and the diffuse reflectance of deep ultraviolet light having a wavelength of 220 nm to 300 nm to a desired level, the reflective film of the present application preferably has a structure in which regions having different refractive indices are alternately laminated. This lamination method also includes a structure in which another region exists in a dot-like or line-like form in a cross-sectional view in one region. In addition, the reflective film of the present application can have a form in which the entire reflective film has the above-described lamination structure, or a form in which a part of the reflective film has the above-described lamination structure.

[0053] In the present application, the regions having different refractive indices differ in the refractive index of deep ultraviolet light having a wavelength of 220 nm to 300 nm between the regions. At wavelengths that are generally measured, such as visible light, if the refractive indices differ between the regions, the refractive indices also differ for deep ultraviolet light having a wavelength of 220 nm to 300 nm. Note that, generally, the shorter the wavelength of the irradiation, the higher the refractive index, and thus "the refractive indices differ for deep ultraviolet light having a wavelength of 220 nm to 300 nm" means that the regions exhibit different refractive indices for the same wavelength. From the viewpoint of improving the diffuse reflectance of the reflective film, the difference in the refractive indices between the regions having different refractive indices is preferably 0.005 or more, more preferably 0.01 or more, further preferably 0.05 or more, further preferably 0.1 or more, further preferably 0.2 or more, and further preferably 0.3 or more. In addition, the actual difference in the refractive indices is 2.0 or less.

[0054] By increasing the difference in the refractive indices between the regions having different refractive indices, the reflection at the interface between the regions having different refractive indices increases, and as a result, the diffuse reflectance of the reflective film improves.

[0055] As the regions constituting the reflective film of the present application, the light transmittance of all regions for deep ultraviolet rays having a wavelength of 220 nm to 300 nm is preferably 30% or more, more preferably 50% or more, and further preferably 60% or more. In addition, the light transmittance is usually 100% or less, and can also be 95% or less. That is, the constituent elements of each region constituting the reflective film are preferably substances or gases having low absorption ability for deep ultraviolet rays. In addition, in the present application, the "light transmittance" refers to the light transmittance in a single region. That is, even in the case where another region is included in one region, the light transmittance in each single region is preferably 30% or more, more preferably 50% or more, and further preferably 60% or more. By being such constituent elements, the ultraviolet ray reflection efficiency of the obtained reflective film can be further improved. The light transmittance for deep ultraviolet rays having a wavelength of 220 nm to 300 nm can be measured using the method described in the Examples described later.

[0056] In the two or more regions having different refractive indexes from each other, which the reflective film of the present application has, one region is a region constituted by a resin. The resin can be a matrix. The resin used in the reflective film of the present application is constituted by a resin material having low absorption ability for deep ultraviolet rays having a wavelength of 220 nm to 300 nm. By using such a resin material, the ultraviolet ray reflection efficiency of the obtained reflective film can be further improved. In addition, the two or more regions having different refractive indexes from each other can be regions constituted by resin materials each having a different refractive index.

[0057] As the above resin material, one or two or more resins selected from among fluorine-containing resins and silicone resins are preferred. Among them, from the aspect of reducing rigidity and the influence on electronic parts, a fluorine-containing resin is more preferred. As the fluorine-containing resin, one or two or more resins selected from among polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyvinylidene fluoride (PVDF), and tetrafluoroethylene / perfluoroalkyl vinyl ether / chlorotrifluoroethylene copolymer (CPT) are preferred, and from the aspect of being relatively easy to melt process and having good mechanical properties, one or two or more resins selected from among PCTFE, ETFE, PFA, and CPT are more preferred. The light transmittance for deep ultraviolet rays having a wavelength of 220 nm to 300 nm of the above exemplified fluorine-containing resins is 30% or more. Among them, a resin having a light transmittance for deep ultraviolet rays having a wavelength of 220 nm to 300 nm of preferably 50% or more, and more preferably 60% or more is preferably used.

[0058] These resin materials can be added with various additives, such as heat-resistant stabilizers, organic lubricants, organic or inorganic fine particles, and antistatic agents, and the like, within a range not impairing the effects of the present application.

[0059] Further, in the reflective film of the present application, at least one of the regions having different refractive indexes is preferably a region composed of a gas, an inorganic material, or a liquid. In order to further increase the difference in refractive index between the regions having different refractive indexes, at least one of the regions having different refractive indexes is preferably a region composed of a gas, i.e., at least one of the regions is a bubble and / or a void.

[0060] In the present application, "gas" refers to a gas present in a void formed as a bubble or a void in the interior of a resin or an inorganic material or at the interface thereof. Further, in the present application, "gas" is a concept including a noble gas or the like other than atmospheric air. That is, it is preferable that the reflective film of the present application have a bubble and / or a void in the interior thereof, and by incorporating the bubble or the void, the deep ultraviolet light can be diffusely reflected efficiently and uniformly in a plurality of directions. The shape of the bubble and / or the void is not particularly limited and can be appropriately designed within a range not impairing the effects of the present application. For example, in a plan view of a cross section, it can be a circular shape, an elliptical shape, an approximately elliptical shape such as an elongated elliptical shape, or a long elliptical shape having acute angles at both ends with approximately circular arcs facing each other.

[0061] When the reflective film of the present application has a region composed of an inorganic material, as the inorganic material, for example, alumina, boron nitride, silica, a fluoride of an alkaline earth metal, or the like can be given.

[0062] Further, when the reflective film of the present application has a region composed of a liquid, as the liquid, for example, water, an organosiloxane, a fluorine-based noble liquid, or the like can be given.

[0063] When the reflective film of the present application has a region composed of a resin and a region composed of a gas, in order to increase the total reflectance and the diffuse reflectance of the obtained film for deep ultraviolet light having a wavelength of 220 nm to 300 nm to a desired level, the film is formed in a form having a bubble or a void in the interior of the resin, i.e., in a form in which voids are dispersed in the resin material.

[0064] Further, when the reflective film of the present application has regions composed of resins having different refractive indexes, in order to increase the total reflectance and the diffuse reflectance of the obtained film for deep ultraviolet light having a wavelength of 220 nm to 300 nm to a desired level, the regions can be composed of resin materials having different refractive indexes and the resin materials having different refractive indexes can be stacked, or the regions can be in a form in which a region composed of one resin material has regions composed of another resin material dispersed therein. In addition, voids such as bubbles or voids can be formed in the regions composed of these resins or at the interface thereof.

[0065] In addition, when the reflective film of the present application has a region composed of a resin and a region composed of an inorganic material, a resin material and an inorganic material having a different refractive index from the resin material can be used to form a pattern in which regions composed of the inorganic material are dispersed in the region composed of the resin material, in order to increase the total reflectance and the diffuse reflectance of the resulting film for deep ultraviolet rays having a wavelength of 220 nm to 300 nm to a desired level. In addition, a pattern in which regions composed of a resin material having a different refractive index are further dispersed in the region composed of the resin material can be formed. Furthermore, voids such as bubbles or air holes can be further formed in the regions composed of the resin materials or the inorganic material or at the interface.

[0066] When the reflective film of the present application includes a region composed of a resin and a region composed of a gas, in order to cause the reflective film of the present application to exhibit a desired reflective performance for deep ultraviolet rays, it is preferable that the reflective film have a pattern in which, in cross-sectional observation (planar observation of the cross section), a repeating structure portion in which resin portions (resin regions) and void portions (gas regions) are repeated is present.

[0067] The reflective film of the present application can have a fine resin column, a thin-walled resin column, or a fine protruding portion of a resin portion in a bubble and / or an air hole. When a plurality of resin portions composed of the resin column, the thin-walled resin column, or the protruding portion of the resin portion are formed in the same direction, the resin portion constituting the repeating structure portion described above refers to the resin column, and the void portion constituting the repeating structure portion described above refers to the space between the resin columns. That is, in the bubble and / or the air hole, a plurality of resin columns are formed in the same direction, and as a result, a repeating structure portion in which resin portions and void portions are repeated is present. In the present application, the "same direction" refers to substantially the same direction, and is not limited to a pattern in which the direction is exactly the same, as long as the effect of the present application is not impaired. In the repeating structure portion, the width of at least one resin portion constituting the repeating structure portion or the width of at least one void portion constituting the repeating structure portion (nm) with respect to the wavelength λ (nm) of the incident ultraviolet rays in the direction in which the resin columns repeat is preferably 0.1 λ to 20 λ, more preferably 0.2 λ to 10 λ, and further preferably 0.5 λ to 2 λ. By causing the width (nm) with respect to the wavelength λ (nm) of the ultraviolet rays to be within the above range, the reflective performance in the reflective film can be improved.

[0068] In addition, the reflective film of the present application can have a plurality of bubbles and / or air holes having the repeating structure portion described above. In the thickness direction of the reflective film, two or more, and more preferably three or more, of the bubbles and / or the air holes described above are preferably present in the cross section.

[0069] Figure 1 is a scanning electron microscope photograph of a cross section in which one embodiment of the reflective film of the present application is cut in the thickness direction, Figure 2 is a scanning electron microscope photograph of a cross section in which one embodiment of the reflective film of the present application is cut in the thickness direction, Figure 1The repeating structure portion is further enlarged. Figure 1 The illustrated reflective film (10) is a reflective film composed of a resin (1) and has inside an approximately elliptical bubble (2) that is elongated in plan view, and, inside the bubble (2), as shown in Figure 2 A plurality of thin columns (4) composed of a resin are formed in the short axis direction. In Figure 2 In the illustrated reflective film, the entire inside of the approximately elliptical bubble (2) in plan view is a repeating structure portion (3) in which the resin portion (3-2) and the void portion (3-1) are repeated. Also, in the thickness direction (the longitudinal direction of the drawing) of the reflective film (10), a plurality of bubbles (2) having these repeating structure portions are present in register. Note that the form of the reflective film of the present application is not limited to Figure 1 The form of the present application is not limited to the above, and the target reflective film can also be obtained by other methods, as demonstrated by the examples described later.

[0070] Figure 1 and Figure 2 The reflective film of the present application illustrated above can also, for example, after impregnating a resin film with an inert gas, form fine voids or bubbles inside by performing heating or the like to obtain the target reflective film.

[0071] In addition, the reflective film of the present application has, in plan view of a cross section, an approximately circular or approximately elliptical bubble, and the bubbles and / or voids are stacked in the thickness direction, whereby a repeating structure portion in which a resin portion and a void portion are repeated can be obtained. The stacking can be random or can have regularity. In this case, the width of at least one of the resin portions and / or the width of at least one of the void portions (nm) that constitute the repeating structure portion, and preferably the width of at least one of the void portions (nm) that constitute the repeating structure portion, is preferably 0.1λ to 20λ, more preferably 0.2λ to 10λ, and further preferably 0.5λ to 2λ, with respect to the wavelength λ (nm) of the incident ultraviolet light. In this case, the width of the void portion refers to the size of the bubble and / or void, i.e., the diameter of the bubble and / or void, and the width of the resin portion refers to the interval between the bubbles and / or voids. Here, in the present application, the "diameter of the bubble and / or void" refers to the longest width in the perpendicular width with respect to the longest width inside the bubble and / or void, in plan view of a cross section of the film. By making the width (nm) with respect to the wavelength λ (nm) of the ultraviolet light within the above range, the reflectance in the reflective film of the present application can be improved.

[0072] In addition, in the plan view observation of the above cross section, the diameter of the bubble and / or void is preferably controlled to be 20 nm to 6000 nm, can also be controlled to be 40 nm to 3000 nm, and further can be controlled to be 100 nm to 1000 nm. By making the diameter of the bubble and / or void within the above range, the reflectance can be improved.

[0073] Further, a particle of a different substance from the resin as the matrix can exist inside the bubbles and / or the voids. The particle is preferably a material that absorbs little deep ultraviolet light. In addition, the particle can be difficult to be mechanically deformed, thermally deformed, as compared with the resin as the matrix. For example, fluorine-based resins such as PTFE, boron nitride, alumina, glass powder, silica (quartz), and the like can be given. The particle can be the same as the fine particles added at the time of formation of the voids (bubbles) by stretching described above and hereinafter.

[0074] Further, the reflective film of the present application has elongated approximately elliptical bubbles, and the elongated elliptical bubbles are stacked, whereby a repeating structure portion in which a resin portion and a void portion are repeated can be obtained. With respect to the repeating structure portion, at least one of the width (nm) of the resin portion or the void portion constituting the repeating structure portion can be in the above-described preferable range.

[0075] Figure 3 is a scanning electron microscope photograph of a cross section of one embodiment of the reflective film of the present application cut in the thickness direction, Figure 4 is a further enlarged view of the repeating structure portion of Figure 3 . Figure 3 The reflective film (10) shown in FIG. 1 is a reflective film composed of a resin (1) and has bubbles (2) approximately elliptical in plan view inside. In the reflective film (10), a void portion (3-1) composed of the bubbles (2) approximately elliptical in plan view and a resin portion (3-2) composed of the resin (1) are repeated. Further, in the thickness direction (vertical direction of the drawing) of the reflective film (10), a plurality of these repeating structure portions exist in register. Figure 4 In the reflective film shown in FIG. 1, a repeating structure portion (3) in which a void portion (3-1) composed of bubbles (2) approximately elliptical in plan view and a resin portion (3-2) composed of a resin (1) are repeated is present. Further, in the thickness direction (vertical direction of the drawing) of the reflective film (10), a plurality of these repeating structure portions exist in register. Note that, in the drawing, the repeating structure portion is shown in a state in which the bubbles (2) are not present in the resin portion (3-2) for the sake of easy understanding of the repeating structure. Figure 4 In FIG. 2, the lead line indicating the symbol 3-1 is led from a bubble different from the lead line of the symbol 2, in order to easily understand the repeating structure.

[0076] The form of the reflective film of the present application is not limited to Figure 3 the form of FIG. 1 at all, and the target reflective film can be obtained by other methods, as is demonstrated in the examples described hereinafter.

[0077] As the reflective film of the present application, for example, Figure 3 and Figure 4As the method for forming the reflective film of the present application, for example, the following method can be mentioned: a resin material is added with organic or inorganic fine particles or the like, or a resin which is not compatible with the resin material and organic or inorganic particles are added to the resin material, and after melt-extrusion, at least in one direction, stretching is performed, and fine voids are formed inside. Alternatively, the resin material can be molded into a film shape, and then physical force can be applied to the film to produce fine cracks, and the desired reflective properties can be exhibited. Alternatively, foaming particles can be added to the resin material and melt-extrusion can be performed, or an inert gas such as carbon dioxide or nitrogen can be injected into the resin material or the film-shaped molded product thereof and extrusion foaming can be performed, and the target reflective film can be obtained.

[0078] In the reflective film of the present application, the thickness (width) of the resin portion (resin wall) constituting the bubbles and the bubbles can be uniform or non-uniform, and can be different in the plane direction of the film and the thickness direction of the film. In addition, the thickness of the resin wall in the plane direction of the film can be thicker than the thickness of the resin wall in the thickness direction of the film. By making the thickness of the resin wall in the plane direction of the film thicker than the thickness of the resin wall in the thickness direction of the film, high reflectivity, easy bendability of the film, and mechanical strength (tensile strength) of the film can be simultaneously achieved. That is, by making the thickness of the resin wall in the thickness direction of the film thin, the repeating structure of the resin portion and the void portion can be imparted in a large amount, which can improve the reflectivity of ultraviolet rays, and when the film is bent, the thin resin wall in the thickness direction of the film is deformed, whereby the film can be bent more easily, and the film can be further imparted with softness; on the other hand, by making the resin wall in the plane direction of the film thick, the mechanical strength (tensile strength) can be improved. For example, it is also preferable that the thickness of the resin wall in the plane direction of the film be 1 μm or more, and the thickness of the resin wall in the thickness direction of the film be less than 1 μm.

[0079] The above cross-sectional observation can be performed using a scanning electron microscope.

[0080] As described above, the total reflectivity of the reflective film of the present application for deep ultraviolet rays of 220 nm to 300 nm is 60% or more, preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. In the present application, the "total reflectivity for deep ultraviolet rays of 220 nm to 300 nm" means the average value of the total reflectivity at each wavelength (1 nm unit, that is, every 1 nm) in the wavelength region of deep ultraviolet rays of 220 nm to 300 nm. The total reflectivity for deep ultraviolet rays can be measured by the method described in the Examples described later.

[0081] In addition, as described above, the reflective film of the present application has a diffuse reflectance of 60% or more for deep ultraviolet rays of 220 nm to 300 nm. The diffuse reflectance is preferably 70% or more, more preferably 80% or more, and further preferably 89% or more. In the present application, the "diffuse reflectance for deep ultraviolet rays of 220 nm to 300 nm" means the average value of the diffuse reflectance at each wavelength (1 nm unit, i.e., every 1 nm) in the wavelength region of deep ultraviolet rays of 220 nm to 300 nm. The diffuse reflectance in the deep ultraviolet region of 220 nm to 300 nm can be measured by the method described in the Examples below.

[0082] In the reflective film of the present application, the density of the film (bulk density, Q) with respect to the density (P) of the resin material itself constituting the film (film having a bubble or a void) is preferably Q / P = 0.1 to 0.99, more preferably Q / P = 0.3 to 0.99, and further preferably Q / P = 0.5 to 0.99. Note that the units of the densities P and Q are the same. The density (bulk density) of the reflective film of the present application can be measured by the water displacement method (JIS K 7112).

[0083] The production method of the reflective film of the present application will be described below.

[0084] <Production of Reflective Film Based on Foaming of Fluorine-Containing Resin Film>

[0085] Figure 1 The structure shown is a film in which a PCTFE film is impregnated with carbon dioxide and then foamed by heating. By using a fluorine-containing resin as the resin material constituting the reflective film, as shown in Figure 1 A reflective film in which a large number of fine columnar structures are formed inside the bubbles can be obtained. An example of a method for obtaining a reflective film having such a unique bubble structure will be described.

[0086] The production method exemplified here has the following steps: a gas sealing step in which a fluorine-containing resin film is impregnated with an inactive gas (carbon dioxide, nitrogen, etc.) under high pressure; and a heating foaming step in which bubbles are generated inside the resin after the pressure is released and heating is performed.

[0087] In the gas sealing step, the fluorine-containing resin film is preferably exposed to the inactive gas under a pressure of 1 MPa to 20 MPa, more preferably 5 MPa to 10 MPa, for preferably 1 hour to 100 hours, more preferably 2 hours to 24 hours, to seal the inactive gas in the resin film. This gas sealing step can be suitably performed using, for example, an autoclave or a pressure cooker, etc.

[0088] In the heating and foaming process, the fluorine-containing resin film after the gas sealing process is preferably heated at a temperature of 120°C to 200°C, more preferably 130°C to 170°C, for preferably 0.5 minutes to 3 minutes, more preferably 0.5 minutes to 1 minute. By going through this process, a reflective film having bubbles or voids in the interior of the resin film can be obtained.

[0089] Further, before the above gas sealing process, the fluorine-containing resin film is preferably subjected to a heat treatment (annealing treatment). By moving to the gas sealing process after the annealing process, the interior of the bubbles generated in the subsequent heating and foaming process can be made Figure 1 The more fine column structure shown in FIG. 6 can introduce a repeating structure part in which the resin part and the air part are densely repeated to the interior of the film. Therefore, the reflective efficiency of the deep ultraviolet light can be effectively improved, and the total reflectance and the diffuse reflectance for the deep ultraviolet light having a wavelength of 220 nm to 300 nm can be more reliably guided to be 60% or more.

[0090] Note that, in the above production method, the production of the reflective film based on the foaming of the fluorine-containing resin film is described, but in the case where another resin having a low deep ultraviolet light absorbing ability such as a silicone resin is used, the same foaming is performed, whereby a reflective film of the present application that exhibits the target reflective performance can be obtained.

[0091] In the reflective film obtained by the above foaming, the size of the bubbles formed in the interior of the film (the size of the bubbles in the cross-sectional observation) Figure 1 is 0.1 μm to 50 μm, more preferably 0.5 to 30 μm, and also preferably 1 μm to 20 μm in the thickness direction.

[0092] <Production of a reflective film by stretching treatment of a fluorine-containing resin>

[0093] Figure 3 The structure shown in FIG. 5 is a film in which PTFE particles are added to a PCTFE film, and then the film is stretched to generate voids. By using a fluorine-containing resin as the resin material constituting the reflective film, and adding a material having a low deep ultraviolet light absorbing ability as the particles and stretching the film, a reflective film having a large number of fine void structures (porous structures) can be obtained as shown in FIG. 6. Figure 3 An example of a method for obtaining a reflective film having such porous structures will be described.

[0094] In the production method exemplified here, a stretching process of stretching the fluorine-containing resin film is included.

[0095] In the stretching process, under a heated atmosphere (e.g., 50°C to 120°C), the resin film is stretched slowly at a speed of approximately 0.05 m / min to 1.5 m / min until the stress reaches the yield point. After necking occurs at the yield point, the speed is increased to approximately 2.0 m / min to 4.0 m / min for further stretching. This stretching can be unidirectional or bidirectional; bidirectional stretching is preferred from the perspective of increasing the number of bubbles or pores obtained.

[0096] Furthermore, when stretching the resin film, it is preferable to add microparticles or other materials that are different from the resin beforehand, and then mix them using a melt-blending method or the like. By including microparticles in the resin, an interface is created between the resin film (which serves as the base material) and the microparticles. Starting from this interface, fine bubbles or pores can be generated during stretching.

[0097] Examples of added microparticles include polytetrafluoroethylene (PTFE), boron nitride, alumina, and glass powder. Furthermore, the amount of microparticles added is preferably 1% to 50% by mass, more preferably 1% to 30% by mass, and even more preferably 5% to 20% by mass.

[0098] In the reflective film obtained by the above stretching, the size of the bubbles formed inside the film ( Figure 3 The approximately elliptical bubble (in the cross-section) has a thickness dimension relative to the wavelength λ (nm) of the incident ultraviolet light, which is preferably 0.1λ to 20λ, more preferably 0.2λ to 10λ, and even more preferably 0.5λ to 2λ. For example, the size of the bubble in the thickness direction in the cross-section can be 20nm to 6000nm, preferably 40nm to 3000nm, and even more preferably 100nm to 2000nm.

[0099] It should be noted that the resin-based reflective film of the present invention is practically difficult to accurately and unambiguously represent its tiny and complex structure. Therefore, in this invention, structural features are specified as inventive specificities, while its properties and the required manufacturing method are also specified as inventive specificities, clearly indicating the differences from those based on the prior art to clarify the invention.

[0100] The reflective film of the present invention, with its excellent total reflectance and diffuse reflectance, can be used, for example, as a reflective film for a deep ultraviolet light source, thereby efficiently reflecting deep ultraviolet light emitted from the light source. Therefore, for example, for deep ultraviolet light emitted from mercury lamps or metal halide lamps, barrier discharge lamps, deep ultraviolet LEDs, etc., it can reflect light deviating from the irradiated object, enabling the use of all deep ultraviolet light. Units combining such light sources with reflective films are suitable for use in water sterilization equipment, space sterilization equipment, and equipment (sterilization devices) for sterilizing the surfaces of medical supplies or household goods, various processed products or foods, etc.

[0101] In addition, the reflective film of the present application prevents transmission by highly reflecting deep ultraviolet rays, and thus can be used as a shielding film for protecting a substance exposed to deep ultraviolet rays, for example.

[0102] Examples

[0103] The present application will be explained in more detail based on the following examples and comparative examples, but the present application is not limited to these.

[0104] [Preparation of reflective film]

[0105] The reflective films of Examples 1 to 6 and Comparative Examples 1 to 3 were prepared by the following method. Note that the reflective films of Examples 1 to 6 and Comparative Examples 1 to 3 were each 100 mm long, 33 mm wide, and had the thicknesses shown in the following table.

[0106] (Example 1)

[0107] A polytrifluorochloroethylene (PCTFE) resin film (trade name: Neoflon PCTFE, manufactured by Daikin Industries, Ltd.) was heat-treated at 180°C for 10 minutes in an atmosphere. The heat-treated resin film was put in an autoclave, and treated at 17°C under a pressure of 5.2 MPa for 24 hours to enclose carbon dioxide in the resin film. Thereafter, the resin film was taken out of the autoclave and heated at 150°C for 1 minute to foam the carbon dioxide in the resin film, thereby preparing a reflective film having a thickness of 0.2 mm.

[0108] (Example 2)

[0109] A reflective film was prepared in the same manner as in Example 1, except that the thickness of the obtained reflective film was 0.4 mm.

[0110] (Example 3)

[0111] A reflective film was prepared in the same manner as in Example 1, except that the thickness of the obtained reflective film was 0.8 mm.

[0112] (Example 4)

[0113] A reflective film was prepared in the same manner as in Example 1, except that the resin film used in the preparation of the reflective film was replaced with a film of tetrafluoroethylene-ethylene (ETFE) copolymer (trade name: Neoflon ETFE, manufactured by Daikin Industries, Ltd.).

[0114] (Example 5)

[0115] A resin film used in the production of the reflective film was replaced with a film of tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) copolymer (trade name: Neoflon PFA, manufactured by Daikin Industries, Ltd.), and the reflective film was produced in the same manner as in Example 1, except for this.

[0116] (Example 6)

[0117] A PCTFE resin was added with 10 mass% of PTFE particles (trade name: POLYFLON PTFE, type: M-12, particle diameter 0.1 μm, manufactured by Daikin Industries, Ltd.), and the composite material was molded into a film shape having a thickness of 0.5 mm and then installed to a tensile machine (trade name: Tensilon universal testing machine, type: RTA-2.5T, manufactured by ORIENTEC Co., Ltd.), and stretching was performed at 120°C in an atmosphere. With respect to the stretching speed, stretching was performed at a speed of 0.5 m / minute until the yield point of the resin film was exceeded, and after necking started, stretching was performed at a speed of 3.0 m / minute without interruption, and a reflective material having a thickness of 0.25 mm was obtained.

[0118] The reflective films of Examples 1 to 6 each had a repeating structure portion in which a resin portion and a void portion were repeated, and the width of at least one resin portion and / or the width of at least one void portion (nm) constituting the repeating structure portion was 0.1λ to 20λ with respect to the wavelength λ (256 nm) of the incident ultraviolet rays.

[0119] Note that the widths of the resin portion and the void portion were confirmed as follows: each film was frozen and fractured in a high vacuum, and the cross section thereof was observed using a scanning electron microscope (type: JSM-6390LV, manufactured by JEOL Ltd.), and the widths were determined from the obtained data, whereby confirmation was possible.

[0120] [Comparative Example]

[0121] (Comparative Example 1)

[0122] A polyethylene terephthalate (PET) resin film (raw material trade name: UNIPET RT553C, manufactured by Japan UNIPET Co., Ltd.) was heat-treated at 180°C in an atmosphere for 10 minutes. The resin film after heat treatment was installed in an autoclave, and treated at 17°C under a pressure of 5.2 MPa for 24 hours, and carbon dioxide was enclosed in the resin film. Thereafter, the resin film was taken out of the autoclave and heated at 220°C for 1 minute, and the carbon dioxide in the resin film was foamed, and a reflective film having a thickness of 0.5 mm was produced.

[0123] (Comparative Example 2)

[0124] As the reflecting film, an aluminum foil for ultraviolet reflection (trade name: MIRO-UV, manufactured by Material House) having a thickness of 0.5 mm was used.

[0125] (Comparative Example 3)

[0126] As the reflecting film, a polytetrafluoroethylene plate (trade name: POLYFLON PTFE, model number: M-18, manufactured by Daikin Industries, Ltd., sintered compression molded body) having a thickness of 9.8 mm was used.

[0127] <Measurement of Deep Ultraviolet Transmittance of Resin Material>

[0128] Using a spectrophotometer (trade name: U-4100, manufactured by Hitachi High-Technologies Corporation), the amount of light captured by a detector when the amount of irradiated light was set to 100% was measured as the transmittance in the deep ultraviolet region of wavelengths of 220 nm to 300 nm, by irradiating light of each wavelength from the front surface of each film before heat treatment (before foaming) or before stretching (before formation of voids). The transmittance of each wavelength per 1 nm was read from the obtained graph (measurement results), and the arithmetic mean of the transmittance of all wavelengths (81 measurement values (%)) in the above deep ultraviolet region was calculated as the transmittance of the above deep ultraviolet light. Note that the thickness of each film measured was 100 μm.

[0129] <Test Example 1>

[0130] The thickness of each of the obtained reflecting films (Examples 1 to 6, Comparative Examples 1 to 3) was measured using a micrometer (trade name: Coolant Proof Micrometer, model number: MDC-25MX, manufactured by Mitutoyo Corporation). A Φ60 standard integrating sphere was attached to a spectrophotometer (trade name: U-4100, manufactured by Hitachi High-Technologies Corporation), and the total reflectance of each reflecting film when the total reflectance of a Spectralon standard reflectance plate (manufactured by Labsphere, white, model number: USRS-99-010) was set to 100% and the diffuse reflectance of the above Spectralon standard reflectance plate was set to 100% was measured in the deep ultraviolet region of wavelengths of 220 nm to 300 nm. The reflectance of each wavelength per 1 nm was read from the obtained graph (measurement results), and the arithmetic mean of the total reflectance (81 measurement values (%)) and the arithmetic mean of the diffuse reflectance (81 measurement values (%)) in the above deep ultraviolet region were calculated as the "deep ultraviolet total reflectance" and the "deep ultraviolet diffuse reflectance", respectively. The results are shown in Table 1 below.

[0131] <Test Example 2>

[0132] For the obtained reflective films (Examples 1-6, Comparative Examples 1-3), ultraviolet LEDs (emission wavelength 256nm, model: 265-FL-02-G01, manufactured by DOWA Electronics Co., Ltd.) and ultraviolet irradiance meters (trade name: ultraviolet irradiance meter UVR-300, model: UD-250, manufactured by Topcon Technohouse Co., Ltd.) were used to measure the ultraviolet irradiance at each reflection angle as follows.

[0133] like Figure 5 As shown, the ultraviolet LED light source is positioned at a 30° angle relative to the center (centroid) of each reflective film surface (the angle between the straight line connecting the ultraviolet LED light source and the center of the film surface and the perpendicular line extending from the center of the film surface is 30°). Furthermore, an ultraviolet illuminance meter is positioned linearly symmetrically with respect to the ultraviolet LED light source, using the perpendicular line extending from the center of the film surface as its axis. That is, the plane connecting the center of the film surface, the ultraviolet LED light source, and the ultraviolet illuminance meter intersects the film surface perpendicularly, and the angle between the straight line connecting the ultraviolet illuminance meter and the center of the film surface and the perpendicular line is 30°. It should be noted that the distance from both the ultraviolet LED and the ultraviolet illuminance meter to the center of the film surface is 40 mm.

[0134] With the ultraviolet LED fixed in place, place the ultraviolet illuminometer as follows: Figure 6 The diagram shows the movement from the 0° position to the 30° and 60° positions. It should be noted that... Figure 6 Observing from X to Y Figure 5 The diagram showing the reflective film, ultraviolet LED light source, and ultraviolet illuminance meter illustrates the state of the ultraviolet illuminance meter at a 60° position. The ultraviolet illuminance detected by the ultraviolet illuminance meter was measured at these 0°, 30°, and 60° positions. The measurement results are shown in Table 1 below.

[0135] In addition, the retention rate of ultraviolet illuminance when the illuminance meter angle is moved from 0° to 30° and 60° is recorded as "illuminance retention rate (%)" in Table 1 below. The illuminance retention rate (%) is calculated by the following (Equation 2). When the illuminance retention rate is 50% or more at both angles of 30° and 60°, the "reflection" criterion is marked as "0", and otherwise (less than 50%), the "reflection" criterion is marked as "×".

[0136] Illuminance retention rate (%) = [UV illuminance at 30° or 60°] / [UV illuminance at 0°] (Equation 2)

[0137] Note that in Test Example 1 and Test Example 2, the thickness, the total deep ultraviolet reflectance, the diffuse deep ultraviolet reflectance, the ultraviolet illuminance, and the illuminance retention rate were measured at three points (except for points within 5 mm from the end) in each reflective film surface at random. The values described in Table 1 below are average values of the three points.

[0138] < Test Example 3 >

[0139] The bending processability of the obtained reflective materials (Examples 1 to 6, Comparative Examples 1 to 3) was determined by the following evaluation method.

[0140] It was verified whether each reflective material could be bent and disposed along the inside of a resin tube having an inner diameter of 40 mm. In a case where the bending processability could be disposed by human power, the determination was recorded as "O", and in a case where the bending processability could not be disposed by human power, the determination was recorded as "X". The results are shown in Table 1 below.

[0141]

[0142] According to Table 1, in the case of the reflective film of Comparative Example 1 which is a PET foamed film, the PET absorbs deep ultraviolet light, and as a result, the total deep ultraviolet reflectance and the diffuse deep ultraviolet reflectance are significantly low. In addition, in the case of the reflective film of Comparative Example 2 which is an aluminum foil, the total deep ultraviolet reflectance and the diffuse deep ultraviolet reflectance are also low, and the illuminance retention rate is also poor. In addition, in the case of the reflective film of Comparative Example 3 which is a sintered compression-molded body of PTFE, the total deep ultraviolet reflectance and the diffuse deep ultraviolet reflectance are good. However, the diffuse reflection has angle dependence, and as a result, the performance of uniformly diffusing the incident deep ultraviolet light in multiple directions is slightly poor. In addition, the thickness of the reflective film of Comparative Example 3 is as thick as 9.8 mm, and the bending processability is also poor.

[0143] On the other hand, the reflective films of Examples 1 to 6 achieved a film in which both the total deep ultraviolet reflectance and the diffuse deep ultraviolet reflectance were 80% or more by causing a bubble or a void in the inside of the resin film, although it was a thin film. For the reflective film of the resin which exhibits such a reflection characteristic, the angle dependence of the diffuse reflection of the deep ultraviolet light is also low, and the performance of uniformly diffusing the incident deep ultraviolet light in multiple directions is excellent. In addition, it was also found that the film could be thinned, and sufficient bending processability could be achieved.

[0144] Although the present application has been described together with embodiments thereof, the present applicant believes that, unless specifically specified, the present application is not intended to be limited to any detail of the description, and should be interpreted broadly without departing from the spirit and scope of the application disclosed in the appended claims.

[0145] This application claims priority based on Japanese Patent Application No. 2020-158811 filed on September 23, 2020 in Japan, the contents of which are incorporated herein by reference in its entirety as part of the disclosure of the present specification.

[0146] Symbol explanation

[0147] 1 Resin

[0148] 2 Bubble

[0149] 3 Repeating structure portion

[0150] 3-1 Void portion

[0151] 3-2 Resin portion

[0152] 4 Column

[0153] 10 Reflective film

[0154] 11 Ultraviolet LED light source

[0155] 12 Ultraviolet illuminometer

Claims

1. A resinous reflecting film which is a resinous reflecting film having two or more regions different from each other in refractive index, wherein The resin-made reflecting film has a thickness of 20 μm to 5000 μm, a total reflectance of 60% or more, and a diffuse reflectance of 60% or more with respect to deep ultraviolet rays having a wavelength of 220 nm to 300 nm, The resin material constituting the resin-made reflecting film is a fluorine-containing resin selected from one or two or more of polytrifluorochloroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene / perfluoroalkyl vinyl ether / trifluorochloroethylene copolymer (CPT), The resin-made reflecting film is foamed by an inert gas impregnated in the fluorine-containing resin film.

2. The resinous reflective film of claim 1, wherein, The resin-made reflecting film has a thickness of 50 μm to 1000 μm.

3. The resinous reflective film of claim 1 or 2, wherein, The two or more regions constituting the resin-made reflecting film each have a light transmittance of 30% to 100% with respect to deep ultraviolet rays having a wavelength of 220 nm to 300 nm.

4. The resinous reflective film according to claim 1 or 2, wherein At least one of the two or more regions constituting the resin-made reflecting film is a bubble.

5. The resinous reflective film of claim 1 or 2, wherein, The resin-made reflecting film has a repeating structure in which a resin portion, i.e., a resin region, and a void portion, i.e., a gas region, are repeated.

6. The resinous reflective film of claim 5, wherein, The width of at least one resin portion and / or the width of at least one void portion constituting the repeating structure portion is 0.1λ to 20λ with respect to the wavelength λ of incident ultraviolet rays.

7. The resinous reflective film of claim 1, wherein, The density Q of the resin-made reflecting film satisfies Q / P = 0.2 to 0.99 with respect to the density P of the resin material constituting the resin-made reflecting film.

8. A sterilization device provided with an ultraviolet light source and the resin-made reflecting film according to any one of claims 1 to 7.

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