Optical filter, sterilization device, and ultraviolet detection device

Abstract

The invention provides an optical filter capable of effectively transmitting ultraviolet rays in a wide wavelength range and improving the transmittance of the ultraviolet rays. The optical filter (1) has a transparent substrate (2) which is made of glass and has a thickness of 1.0 mm or less, and dielectric multilayer films (3A, 3B) which are provided on at least one main surface (2a, 2b) of the transparent substrate (2) and contain hafnium oxide, the optical filter (1) having a minimum value of spectral transmittance of 92% or more at a wavelength of 240-300 nm, and a wavelength [lambda] 60 at which the spectral transmittance is 60% is 230 nm or less.

Description

Technical Field

[0001] The present invention relates to an optical filter that can transmit light in a specific wavelength range, a sterilization device using the optical filter, and an ultraviolet detection device. Background Art

[0002] At present, optical filters that can transmit light in a specific wavelength range have been widely used in various applications. For example, ultraviolet transmission filters have been used in water sterilization devices, curing devices for curing ultraviolet curable resins, ultraviolet sensors, and other applications.

[0003] In Patent Document 1 described below, an ultraviolet transmission filter is disclosed, which includes: a glass plate having a transmittance of 70% or more at a medium wavelength of 254 nm in the spectral transmittance when the thickness is 0.5 mm; and a protective film disposed on the main surface of the glass plate. Patent Document 1 also describes that the average transmittance of the ultraviolet transmission filter in the wavelength range of 200 nm to 300 nm is 60% or less.

[0004] In Patent Document 2 described below, a microorganism inactivation treatment device is disclosed that inactivates microorganisms to be treated by irradiating emitted light from a light source through an optical filter. Patent Document 2 describes that the optical filter can transmit at least a part of ultraviolet rays having a wavelength of 190 nm or more and 230 nm or less and at least a part of ultraviolet rays having a wavelength greater than 230 nm and 237 nm or less when the emitted light from the light source is incident at an incident angle of 0°, and blocks ultraviolet rays outside the wavelength range of 190 nm or more and 237 nm or less.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: WO 2018 / 100991

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2019-115525 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] However, since the optical filters of Patent Document 1 or Patent Document 2 selectively transmit ultraviolet rays in a specific wavelength range, there are problems such as the types of objects to be treated, such as viruses, being limited. In addition, in the optical filters of Patent Document 1 or Patent Document 2, the transmittance of ultraviolet rays is not sufficient, sometimes the sterilization effect cannot be sufficiently improved, and there are also problems such as the inactivation treatment of the object to be treated taking a long time. Due to such a background, an optical filter that can effectively transmit ultraviolet rays in a wide wavelength range and can improve its transmittance is required.

[0011] An object of the present invention is to provide an optical filter that can effectively transmit ultraviolet light in a wide wavelength range and can increase its transmittance, a sterilization device using the optical filter, and an ultraviolet detection device.

[0012] Technical solutions for solving the problems

[0013] Each embodiment of an optical filter capable of solving the above technical problems, a sterilization device using the optical filter, and an ultraviolet detection device will be described.

[0014] The optical filter according to Embodiment 1 of the present invention is characterized in that it has a transparent substrate made of glass and having a thickness of 1.0 mm or less, and a dielectric multilayer film containing hafnium oxide provided on at least one main surface of the transparent substrate. The minimum value of the spectral transmittance of the optical filter at a wavelength of 240 nm to 300 nm is 92% or more, and the wavelength λ at which the spectral transmittance becomes 60% 60 is 230 nm or less.

[0015] In the optical filter according to Embodiment 2, in Embodiment 1, it is preferable that the dielectric multilayer film has a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index, and the high refractive index film contains hafnium oxide.

[0016] In the optical filter according to Embodiment 3, in Embodiment 2, it is preferable that among the plurality of high refractive index films, the thickness of the outermost high refractive index film farthest from the transparent substrate is thicker than the thickness of the innermost high refractive index film closest to the transparent substrate.

[0017] In the optical filter according to Embodiment 4, in Embodiment 3, it is preferable that the ratio (outermost layer / innermost layer) of the thickness of the outermost high refractive index film to the thickness of the innermost high refractive index film is 2 or more.

[0018] In the optical filter according to Embodiment 5, in any one of Embodiments 1 to 4, it is preferable that the number of stacked layers of the dielectric multilayer film provided on one main surface of the transparent substrate is 10 layers or less.

[0019] In the optical filter according to Embodiment 6, in any one of Embodiments 2 to 5, it is preferable that the total thickness of the high refractive index films constituting the dielectric multilayer film is 500 nm or less.

[0020] In the optical filter according to Embodiment 7, in any one of Embodiments 1 to 6, it is preferable that the dielectric multilayer film is provided on the main surfaces on both sides of the transparent substrate.

[0021] In the optical filter according to Mode 8, in any one of Modes 1 to 7, it is preferable that the transparent substrate has a dome shape.

[0022] In the optical filter according to Mode 9, in any one of Modes 1 to 8, it is preferable that the ratio of the height of the dome shape to the interval of the opening (height / interval of the opening) is 0.1 or more.

[0023] The sterilization device according to Mode 10 of the present invention is a sterilization device for inactivating a treatment object, and is characterized in that it has: a light source whose emitted light wavelength is in the ultraviolet wavelength range; and an optical filter according to any one of Modes 1 to 9, and the light source and the optical filter are arranged in such a manner that the treatment object is inactivated by irradiating the emitted light from the light source through the optical filter.

[0024] The ultraviolet detection device according to Mode 11 of the present invention is an ultraviolet detection device for detecting ultraviolet rays, and is characterized in that it has an optical filter according to any one of Modes 1 to 9 and an ultraviolet light receiving element.

[0025] Advantages of the Invention

[0026] By using the present invention, it is possible to provide an optical filter that can effectively transmit ultraviolet rays in a wide wavelength range and can improve its transmittance, as well as a sterilization device and an ultraviolet detection device using the optical filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a front view schematic diagram showing an optical filter according to an embodiment of the present invention.

[0028] Figure 2 It is a cross-sectional schematic diagram showing an optical filter according to an embodiment of the present invention.

[0029] Figure 3 (a) to (c) are cross-sectional schematic diagrams for explaining a film forming method of an optical filter according to an embodiment of the present invention.

[0030] Figure 4 It is a cross-sectional schematic diagram showing a sterilization device according to an embodiment of the present invention.

[0031] Figure 5 It is a cross-sectional schematic diagram showing an ultraviolet detection device according to an embodiment of the present invention.

[0032] Figure 6It is a diagram showing the transmission spectra of the optical filter obtained in Example 1 and the glass substrate of Comparative Example 1 at wavelengths from 200 nm to 400 nm.

[0033] Figure 7 It is a diagram showing an enlarged view of the transmission spectrum of Figure 6 at wavelengths from 200 nm to 300 nm.

[0034] Figure 8 It is a diagram showing the transmission spectra of the optical filters obtained in Examples 2 to 7 at wavelengths from 200 nm to 400 nm.

[0035] Figure 9 It is a diagram showing an enlarged view of the transmission spectrum of Figure 8 at wavelengths from 200 nm to 300 nm. Detailed implementation mode

[0036] Hereinafter, preferred implementation modes will be described. However, the following implementation modes are merely examples, and the present invention is not limited to the following implementation modes. In addition, in each figure, components having substantially the same function are sometimes referred to by the same reference numerals.

[0037] [Optical filter]

[0038] Figure 1 It is a front view schematic diagram showing an optical filter according to an embodiment of the present invention. In addition, Figure 2 It is a cross-sectional schematic diagram showing an optical filter according to an embodiment of the present invention. Among them, Figure 2 is a cross-sectional schematic diagram assuming that the Figure 1 optical filter is flat. In addition, in Figure 2 , for ease of explanation, the dielectric multilayer film is enlarged.

[0039] As Figure 1 shown, the optical filter 1 has a transparent substrate 2, a first dielectric multilayer film 3A, and a second dielectric multilayer film 3B.

[0040] The transparent substrate 2 is made of glass. The thickness of the transparent substrate 2 is 1.0 mm or less. In addition, the transparent substrate 2 has opposite first main surface 2a and second main surface 2b.

[0041] On the first main surface 2a of the transparent substrate 2, a first dielectric multilayer film 3A containing hafnium oxide is provided. In addition, on the second main surface 2b of the transparent substrate 2, a second dielectric multilayer film 3B containing hafnium oxide is provided. Among them, in the present embodiment, the first dielectric multilayer film 3A and the second dielectric multilayer film 3B (hereinafter also referred to as dielectric multilayer films 3A, 3B) are multilayer films having the same structure.

[0042] In the present embodiment, the dielectric multilayer films 3A and 3B include a high refractive index film having a relatively high refractive index and a low refractive index film having a relatively low refractive index. Further, the high refractive index film contains hafnium oxide.

[0043] The optical filter 1 is an antireflection filter designed to prevent the reflection of ultraviolet rays by using the interference of light with the dielectric multilayer films 3A and 3B. More specifically, the minimum value of the spectral transmittance of the optical filter 1 at wavelengths of 240 nm to 300 nm is 92% or more. Further, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 is 230 nm or less.

[0044] Herein, the spectral transmittance can be obtained, for example, by measuring the spectral transmittance of the entire optical filter 1 using a spectral transmittance meter. As the spectral transmittance meter, for example, a product with the product number "UH4150" manufactured by Hitachi High-Technologies Corporation can be used. Further, as the measurement conditions for the spectral transmittance, the incident angle can be set to 0° and the measurement wavelength can be set to 200 nm to 800 nm for measurement.

[0045] Since the optical filter 1 of the present embodiment has the above-described configuration, it can effectively transmit ultraviolet rays in a wide wavelength range and can increase its transmittance. Therefore, when the optical filter 1 is used in a sterilization device, for example, the types of treatable objects (such as microorganisms and viruses) can be increased, the inactivation treatment time of the treatable objects can be shortened, etc., and the sterilization effect can be improved. Further, when the optical filter 1 is used in an ultraviolet detection device, it can detect ultraviolet rays in a wide wavelength range with high sensitivity.

[0046] In the present embodiment, the minimum value of the spectral transmittance of the optical filter 1 at wavelengths of 240 nm to 300 nm is 92% or more, preferably 93% or more, more preferably 94% or more, further preferably 96% or more, and particularly preferably 97% or more. In this case, ultraviolet rays in a wide wavelength range can be transmitted more effectively. Herein, the upper limit value of the minimum value of the spectral transmittance at wavelengths of 240 nm to 300 nm is not particularly limited and can be, for example, 99.5%.

[0047] Further, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 is 230 nm or less, preferably 225 nm or less, and more preferably 220 nm or less. In this case, ultraviolet rays in a wide wavelength range can be transmitted more effectively. The lower limit value of the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 is not particularly limited and can be, for example, 200 nm.

[0048] In this embodiment, the optical filter 1 has a dome shape. In this case, the planar shape of the optical filter 1 can be approximately circular or approximately rectangular. When the optical filter 1 has a dome shape, the effective irradiation area of ultraviolet rays passing through the optical filter 1 can be made larger. Of course, the optical filter 1 can also have a rectangular plate shape or a circular plate shape, and its shape is not particularly limited.

[0049] Hereinafter, the details of each component constituting the optical filter 1 will be described.

[0050] (Transparent substrate)

[0051] The transparent substrate 2 has a dome shape. In this case, the planar shape of the transparent substrate 2 can be approximately circular or approximately rectangular. When the transparent substrate 2 has a dome shape, the effective irradiation area of ultraviolet rays passing through the optical filter 1 can be made larger. Of course, the transparent substrate 2 can also have a rectangular plate shape or a circular plate shape, and its shape is not particularly limited.

[0052] When the transparent substrate 2 has a dome shape, Figure 1 The height H of the shown opening is preferably 0.5 mm or more, more preferably 0.6 mm or more, preferably 1.5 mm or less, more preferably 1.2 mm or less. In addition, the interval R between the openings is preferably 2.0 mm or more, more preferably 2.5 mm or more, preferably 6.0 mm or less, more preferably 5.5 mm or less. In addition, for example, when the planar shape of the transparent substrate 2 is approximately circular, the interval R between the openings corresponds to the diameter of the opening.

[0053] The ratio of the height H of the dome shape to the interval R between the openings (height H / interval R between the openings) is preferably 0.1 or more, more preferably 0.15 or more, further preferably 0.2 or more, preferably 0.6 or less, more preferably 0.5 or less, further preferably 0.4 or less. When the ratio (height H / interval R between the openings) is within the above range, the effective irradiation area of ultraviolet rays passing through the optical filter 1 can be made larger.

[0054] The transparent substrate 2 is made of glass. Among them, the transparent substrate 2 is preferably glass that is transparent in the wavelength range of use of the optical filter 1. More specifically, the transparent substrate 2 preferably has an average light transmittance of 80% or more in the ultraviolet wavelength range of 200 nm to 400 nm.

[0055] Examples of the glass constituting the transparent substrate 2 include quartz glass, borosilicate glass, etc. The quartz glass can be synthetic quartz glass or fused quartz glass. Regarding borosilicate glass, as the glass composition, it preferably contains 50% to 80% of SiO 2, 0% to 10% of Al 2 O 3 , 5% to 30% of B 2 O 3 , 0% to 5% of CaO, 0% to 5% of BaO, 0% to 15% of Li 2 O + Na 2 O + K 2 O, as a glass composition, more preferably contains 55% to 75% of SiO 2 , 1% to 10% of Al 2 O 3 , 10% to 30% of B 2 O 3 , 0% to 5% of CaO, 0% to 5% of BaO, 1.0% to 15% of Li 2 O + Na 2 O + K 2 O.

[0056] SiO 2 is a component that forms the glass network and is a component that significantly improves the light transmittance in the ultraviolet wavelength region to the visible light region. Especially in the case of high refractive index glass, it is easy to obtain the effect of improving the light transmittance. In addition, SiO 2 is a component that improves heat resistance and weather resistance. The content of SiO 2 is preferably 50% to 80%, more preferably 55% to 75%, and further preferably 58% to 70%. When the content of SiO 2 is too small, it is difficult to obtain the above effects. Moreover, when the film-coated transparent substrate after film formation is heat-treated, it is easy to soften and deform. On the other hand, when the content of SiO 2 is too large, the softening point becomes high and the molding of the transparent substrate 2 becomes difficult.

[0057] Al 2 O 3 is a component that forms the glass network and is a component that improves the light transmittance in the ultraviolet wavelength region to the visible light region. Especially in the case of high refractive index glass, it is easy to obtain the effect of improving the light transmittance. The content of Al 2 O 3 is preferably 0% to 10%, more preferably 1% to 10%, further preferably 3% to 10%, further more preferably 4% to 9.5%, and particularly preferably greater than 4% and 9% or less. When the content of Al 2 O 3 is too small, it is difficult to obtain the above effects. Moreover, when the film-coated transparent substrate after film formation is heat-treated, it is easy to soften and deform. On the other hand, when the content of Al 2 O 3When the content of is excessive, the softening point becomes high, and it becomes difficult to form the transparent substrate 2.

[0058] B 2 O 3 is a component that forms a glass network and is a component that improves the light transmittance in the ultraviolet wavelength region to the visible light region. Especially in the case of high refractive index glass, it is easy to obtain the effect of improving the light transmittance. B 2 O 3 The content of is preferably 5% to 30%, more preferably 10% to 30%, and further preferably 12% to 28%. When the content of B 2 O 3 is too small, it is difficult to obtain the above effect. On the other hand, when the content of B 2 O 3 is excessive, when the film-coated transparent substrate after film formation is heat-treated, it is easy to soften and deform.

[0059] As the glass composition, MgO, CaO, SrO, BaO, and ZnO may also be contained. MgO, CaO, SrO, BaO, and ZnO are components that act as fluxes. In addition, MgO, CaO, SrO, BaO, and ZnO are also components that inhibit devitrification or improve weather resistance. The content of MgO + CaO + SrO + BaO + ZnO is preferably 0% to 10%, more preferably 0.1% to 9%, further preferably 0.5% to 8%, further more preferably 1% to 7%, further more preferably 1.5% to 6%, and particularly preferably 2% to 5%. On the other hand, when the content of MgO, CaO, SrO, BaO, and ZnO is excessive, it is easy to devitrify during molding or sintering. Moreover, the light transmittance is likely to decrease.

[0060] The content of MgO, CaO, SrO, BaO, and ZnO is preferably 0% to 10%, more preferably 0.1% to 9%, further preferably 0.5% to 8%, further more preferably 1% to 7%, further more preferably 1.5% to 6%, and particularly preferably 2% to 5% respectively.

[0061] Li 2 O, Na 2 O, K 2 O are components that lower the softening point. Li 2 O + Na 2 O + K 2 O content is preferably 0.1% to 15%, more preferably 0.5% to 10%, and further preferably 1 to 5%. When the content of Li 2 O, Na 2 O, K 2 O is too small, it is difficult to obtain the above effect. On the other hand, in Li 2 O, Na2 O, K 2 When the content of O is excessive, the weather resistance and refractive index are likely to decrease, or the light transmittance is likely to decrease.

[0062] Moreover, in addition to containing the above components, the borosilicate glass preferably further contains 0% to 0.001% of TiO as a glass composition 2 , 0% to 0.001% of Fe 2 O 3 , 0.5% to 2.0% of F.

[0063] When the content of Fe component as an impurity in the glass is relatively high (for example, 20 ppm or more), TiO 2 tends to significantly reduce the light transmittance and the softening point is likely to rise. Therefore, the content of TiO 2 is preferably 1% or less, more preferably 0.5% or less, further preferably 0.1% or less, still more preferably 0.01% or less, and particularly preferably 0.001% or less.

[0064] Fe 2 O 3 tends to significantly reduce the light transmittance and the softening point is likely to rise. Therefore, the content of Fe 2 O 3 is preferably 1% or less, more preferably 0.5% or less, further preferably 0.1% or less, still more preferably 0.01% or less, and particularly preferably 0.001% or less.

[0065] F is a component that reduces the softening point. In addition, F is a component that significantly improves the light transmittance in the ultraviolet region. The content of F is preferably 0% to 5%, more preferably 0.1% to 4.5%, further preferably 0.2% to 5%, still more preferably 0.3% to 4%, still more preferably 0.4% to 3%, and particularly preferably 0.5% to 2%. When the content of F is excessive, the weather resistance and devitrification resistance are likely to deteriorate.

[0066] The thickness of the transparent substrate 2 is preferably 0.5 mm or less, more preferably 0.3 mm or less, and further preferably 0.2 mm or less. In this case, it is possible to easily form a shape such as a dome shape. In addition, the lower limit value of the thickness of the transparent substrate 2 is not particularly limited, and from the viewpoint of more easily forming the dielectric multilayer films 3A and 3B on the transparent substrate 2, it is preferably 0.05 mm or more, more preferably 0.1 mm or more.

[0067] (Dielectric Multilayer Film)

[0068] The dielectric multilayer films 3A and 3B are dielectric multilayer films having the same configuration. Of course, the dielectric multilayer films 3A and 3B may also be composed of dielectric multilayer films having different configurations, and there is no particular limitation.

[0069] The dielectric multilayer films used for the dielectric multilayer films 3A and 3B are multilayer films having a high refractive index film 4 with a relatively high refractive index and a low refractive index film 5 with a relatively low refractive index. In the present embodiment, the multilayer film is formed by alternately laminating the high refractive index film 4 and the low refractive index film 5 on the main surfaces 2a and 2b on both sides of the transparent substrate 2 in sequence.

[0070] In the present embodiment, the high refractive index film 4 is composed of hafnium oxide and is a film mainly composed of hafnium oxide. Of course, as long as the effects of the present invention are not hindered, part of the high refractive index film 4 may also be a film mainly composed of alumina or the like.

[0071] In addition, the low refractive index film 5 is composed of silicon oxide and is a film mainly composed of silicon oxide. Of course, the low refractive index film 5 may also be a film mainly composed of alumina, zirconia, tin oxide, magnesium fluoride, or silicon nitride. These materials of the low refractive index film 5 may be used alone or in combination of multiple kinds.

[0072] In addition, in the present specification, a film as the main component means a film containing 50% by mass or more of the material in the film. In the film as the main component, it is preferably to contain 80% by mass or more of the material in the film, and more preferably to contain 90% by mass or more. Of course, the film as the main component may also be a film containing 100% of the material in the film.

[0073] In the present embodiment, there is no particular limitation on the total thickness of the dielectric multilayer films 3A and 3B. It is preferably 160 nm or more, more preferably 200 nm or more, preferably 700 nm or less, more preferably 600 nm or less, further preferably 500 nm or less, and particularly preferably 400 nm or less. When the total thickness of the dielectric multilayer films 3A and 3B is within the above range, ultraviolet rays in a wider wavelength range can be effectively transmitted, and the transmittance can be further improved. In particular, when the total thickness of the dielectric multilayer films 3A and 3B is below the above upper limit value, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 moves to the lower wavelength side.

[0074] The total thickness of the high refractive index film 4 (the sum of the thicknesses of the respective high refractive index films 4) is preferably 70 nm or more, more preferably 80 nm or more, still more preferably 90 nm or more, preferably 500 nm or less, more preferably 480 nm or less, still more preferably 350 nm or less, and particularly preferably 240 nm or less. When the total thickness of the high refractive index film 4 is within the above range, ultraviolet rays in a wider wavelength range can be effectively transmitted, and its transmittance can be further improved. In particular, when the total thickness of the high refractive index film 4 is below the above upper limit value, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0075] The thickness of each layer of the high refractive index film 4 is not particularly limited, and is preferably 1.0 nm or more, more preferably 2.0 nm or more, still more preferably 4.0 nm or more, preferably 220 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less.

[0076] In the present embodiment, it is preferable that in the high refractive index film 4, the thickness of the outermost high refractive index film 4B farthest from the transparent substrate 2 is thicker than the thickness of the innermost high refractive index film 4A closest to the transparent substrate 2. In this case, ultraviolet rays in a wider wavelength range can be effectively transmitted, and its transmittance can be further improved. In addition, in the high refractive index film 4, it is preferable to have a film thickness gradient structure in which the thickness increases from the innermost high refractive index film 4A to the outermost high refractive index film 4B. In this case, the minimum value of the spectral transmittance of the optical filter 1 at wavelengths of 240 nm to 300 nm can be further increased.

[0077] In the present embodiment, the ratio of the thickness of the outermost high refractive index film 4B to the thickness of the innermost high refractive index film 4A (outermost / innermost) is preferably 2 or more, more preferably 3 or more, still more preferably 5 or more, even more preferably 8 or more, even more preferably 10 or more, even more preferably 15 or more, preferably 120 or less, more preferably 100 or less, still more preferably 80 or less, even more preferably 60 or less, even more preferably 50 or less, even more preferably 30 or less, and particularly preferably 20 or less. In this case, ultraviolet rays in a wider wavelength range can be effectively transmitted, and its transmittance can be further improved. In particular, when the ratio of the thickness of the outermost high refractive index film 4B to the thickness of the innermost high refractive index film 4A (outermost / innermost) is above the above lower limit value, the minimum value of the spectral transmittance of the optical filter 1 at wavelengths of 240 nm to 300 nm can be further increased.

[0078] The thickness of the innermost high refractive index film 4A is preferably 1.0 nm or more, more preferably 2.0 nm or more, still more preferably 4.0 nm or more, preferably 20 nm or less, and more preferably 10 nm or less. Further, the thickness of the outermost high refractive index film 4B is preferably 20 nm or more, more preferably 30 nm or more, preferably 220 nm or less, and more preferably 110 nm or less.

[0079] The total thickness of the low refractive index films 5 (the sum of the thicknesses of the respective low refractive index films 5) is preferably 60 nm or more, more preferably 80 nm or more, still more preferably 100 nm or more, preferably 500 nm or less, more preferably 450 nm or less, and still more preferably 320 nm or less.

[0080] The thickness of each low refractive index film 5 is not particularly limited, and is preferably 1.0 nm or more, more preferably 2.0 nm or more, still more preferably 3.0 nm or more, preferably 130 nm or less, and more preferably 100 nm or less.

[0081] Further, the total thickness of the dielectric multilayer films 3A and 3B, the high refractive index films 4, and the low refractive index films 5 is the total thickness of the films provided on one main surface (the first main surface 2a or the second main surface 2b) of the transparent substrate 2.

[0082] In the present embodiment, the number of layers of the films constituting the dielectric multilayer films 3A and 3B is preferably 4 or more, preferably 14 or less, more preferably 10 or less, and still more preferably 4 or less. When the number of layers of the films constituting the dielectric multilayer films 3A and 3B is within the above range, ultraviolet rays in a wider wavelength range can be effectively transmitted, and the transmittance can be further improved. In particular, when the number of layers of the films constituting the dielectric multilayer films 3A and 3B is equal to or less than the above upper limit value, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0083] The number of layers of the films constituting the high refractive index films 4 is preferably 1 or more, preferably 7 or less, and more preferably 2 or less. Further, the number of layers of the films constituting the low refractive index films 5 is preferably 1 or more, preferably 7 or less, and more preferably 2 or less.

[0084] Here, the number of layers of the films constituting the dielectric multilayer films 3A and 3B, the high refractive index films 4, and the low refractive index films 5 is the number of layers of the films provided on one main surface (the first main surface 2a or the second main surface 2b) of the transparent substrate 2.

[0085] In the present embodiment, the dielectric multilayer films 3A and 3B preferably contain hafnium oxide crystals. More specifically, the high refractive index films 4 constituting the dielectric multilayer films 3A and 3B preferably contain hafnium oxide crystals, and more preferably contain one or more selected from cubic hafnium oxide crystals and tetragonal hafnium oxide crystals. In this case, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0086] Herein, in this specification, whether cubic hafnium oxide crystals are contained can be confirmed by whether a diffraction peak generated from the (1,1,1) crystal plane of cubic hafnium oxide crystals or tetragonal hafnium oxide crystals is observed in X-ray diffraction measurement.

[0087] In addition, in this specification, X-ray diffraction measurement can be performed using wide-angle X-ray diffraction method. As the X-ray diffraction apparatus, for example, a product with the product number "SmartLab" manufactured by Rigaku Corporation can be used. In addition, as the radiation source, CuKα rays can be used. Among them, in X-ray diffraction measurement, the entire optical filter 1 is supplied for measurement from the main surface side of the dielectric multilayer films 3A and 3B.

[0088] In the present invention, in X-ray diffraction measurement, the diffraction peak generated from the (1,1,1) crystal plane of cubic hafnium oxide crystals or tetragonal hafnium oxide crystals is preferably larger than the diffraction peak generated from the (-1,1,1) crystal plane of monoclinic hafnium oxide crystals. In this case, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0089] In the present invention, the ratio Ic / Im of the peak area intensity Ic of the diffraction peak generated from the (1,1,1) crystal plane of cubic hafnium oxide crystals or tetragonal hafnium oxide crystals to the peak area intensity Im of the diffraction peak generated from the (-1,1,1) crystal plane of monoclinic hafnium oxide crystals is preferably 0.1 or more, more preferably 1 or more, further preferably 2 or more, particularly preferably 2.5 or more, and most preferably 3 or more. When the ratio Ic / Im is at the above lower limit value or more, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side. In addition, the upper limit value of the ratio Ic / Im is not particularly limited, and can be, for example, 10000.

[0090] In the present embodiment, dielectric multilayer films 3A and 3B are provided on the main surfaces 2a and 2b on both sides of the transparent substrate 2. Thus, in the present invention, it is preferable to provide dielectric multilayer films 3A and 3B on the main surfaces 2a and 2b on both sides of the transparent substrate 2, but it is sufficient to provide dielectric multilayer films 3A and 3B on one of the first main surface 2a and the second main surface 2b of the transparent substrate 2.

[0091] In addition, as long as the effects of the present invention are not hindered, other films such as an antifouling film may be laminated on the main surfaces 2a and 2b of the transparent substrate 2.

[0092] Hereinafter, an example of a method for manufacturing the optical filter 1 will be described in detail.

[0093] (Method for manufacturing an optical filter)

[0094] Film-bearing transparent substrate forming step:

[0095] First, as shown in (a) of Figure 3 , a base material 22 of the transparent substrate is prepared, and the base material 22 of the transparent substrate is fixed to a film-forming jig 26 using a fixing member 27. As the base material 22 of the transparent substrate, a base material in which a plurality of dome-shaped portions 22A are arranged can be used. In addition, although not shown in the drawings, in the present embodiment, the base material 22 of the transparent substrate has a flat plate shape, and the dome-shaped portions 22A are arranged in the length direction and the width direction, respectively, in a plan view. In addition, as the fixing member 27, for example, a tape such as a polyimide tape can be used.

[0096] Next, a dielectric multilayer film 3A is formed on the first main surface 22a on the vertex side of the dome shape on the base material 22 of the transparent substrate ( Figure 3 The illustration is omitted in (a) to (c) of ). The dielectric multilayer film 3A can be formed by alternately laminating a high refractive index film 4 and a low refractive index film 5 on the first main surface 22a of the base material 22 of the transparent substrate. The high refractive index film 4 and the low refractive index film 5 can be formed by a vapor deposition method, a sputtering method, a CVD method, or the like, respectively. Among them, from the viewpoint of more precisely controlling the thickness of each layer and forming a denser film, the high refractive index film 4 and the low refractive index film 5 are preferably formed by a sputtering method using the RAS (Radical Assisted Sputtering) method.

[0097] The temperature of the base material 22 of the transparent substrate when forming the high refractive index film 4 is preferably 300 °C or lower, and more preferably 150 °C or lower. Among them, the lower limit value of the temperature of the base material 22 of the transparent substrate when forming the high refractive index film 4 can be, for example, 20 °C (room temperature).

[0098] For example, when forming the high refractive index film 4, a target of the material constituting the high refractive index film 4 can be used, and the flow rate of an inert gas such as argon as a carrier gas can be set to 50 sccm to 500 sccm, and the applied power can be set to 0.5 kW to 40 kW for the film formation.

[0099] When forming the low refractive index film 5, the temperature of the base material 22 of the transparent substrate is preferably 300°C or lower, and more preferably 270°C or lower. Here, the lower limit value of the temperature of the base material 22 of the transparent substrate when forming the low refractive index film 5 can be, for example, 20°C (room temperature).

[0100] For example, when forming the low refractive index film 5, a target of the material constituting the low refractive index film 5 can be used, and the flow rate of an inert gas such as argon as a carrier gas can be set to 50 sccm to 500 sccm, and the applied power can be set to 0.5 kW to 40 kW for the film formation.

[0101] Next, as Figure 3 shown in (b) of , the concave surface forming jig 28 is adhered to the film forming jig 26, and the film forming jig 29 having openings arranged in the same arrangement as the dome-shaped portion 22A is prepared.

[0102] Next, as Figure 3 shown in (c) of , on the base material 22 of the transparent substrate, the base material 22 of the transparent substrate is placed in such a manner that the first main surface 22a on the vertex side of the dome shape is disposed on the hole portion side of the film forming jig 29, and the base material 22 of the transparent substrate is fixed to the film forming jig 29 using the fixing material 27.

[0103] Next, on the base material 22 of the transparent substrate, a dielectric multilayer film 3B ( Figure 3 the illustration is omitted in (a) to (c) of ) is formed on the second main surface 22b on the side opposite to the vertex of the dome shape, and the base material of the film-bearing transparent substrate is formed. The dielectric multilayer film 3B can be formed by the same method as the dielectric multilayer film 3A. Next, by singulating the base material 22 of the film-bearing transparent substrate, a film-bearing transparent substrate can be obtained.

[0104] Heat treatment process:

[0105] Next, the obtained film-bearing transparent substrate is heat-treated. Thereby, the optical filter 1 can be obtained. The temperature of the heat treatment can be set to 450°C or higher, for example. In particular, when the film-bearing transparent substrate is heated at a temperature of 450°C or higher, the content of cubic hafnium oxide crystals can be relatively increased. Therefore, in the obtained optical filter 1, the wavelength λ at which the spectral transmittance is 60% 60 can be shifted to a lower wavelength side.

[0106] The temperature of the heat treatment of the transparent substrate with a film is preferably 450 °C or higher, more preferably 500 °C or higher, further preferably 550 °C or higher, preferably 800 °C or lower, and more preferably 750 °C or lower. When the temperature of the heat treatment is within the above range, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0107] The time of the heat treatment of the transparent substrate with a film is not particularly limited, and can be set, for example, to be 10 minutes or more and 120 minutes or less.

[0108] In the obtained optical filter 1, the minimum value of the spectral transmittance at wavelengths of 240 nm to 300 nm is 92% or more. In addition, in the obtained optical filter 1, the wavelength λ at which the spectral transmittance becomes 60% 60 is 230 nm or less.

[0109] Among them, the minimum value of the spectral transmittance of the optical filter 1 at wavelengths of 240 nm to 300 nm can be increased, for example, by increasing the ratio of the thickness of the outermost high-refractive-index film 4B to the thickness of the innermost high-refractive-index film 4A.

[0110] In addition, for example, by reducing the number of stacked layers of the films constituting the dielectric multilayer films 3A and 3B, or reducing the total thickness of the dielectric multilayer films 3A and 3B, or reducing the total thickness of the high-refractive-index film 4, the wavelength λ at which the spectral transmittance of the optical filter 1 becomes 60% 60 shifts to a lower wavelength side.

[0111] In addition, after the step of forming the transparent substrate with a film, a heat treatment step can be carried out, and then the mother substrate of the transparent substrate with a film can be made into individual pieces, thereby obtaining the transparent substrate with a film.

[0112] In addition, after making the mother substrate of the transparent substrate with a film into individual pieces, an optical filter can be obtained without performing heat treatment.

[0113] [Sterilization device]

[0114] Figure 4 is a schematic cross-sectional view showing a sterilization device according to an embodiment of the present invention.

[0115] Figure 4 The shown sterilization device 30 is a sterilization device for inactivating treatment objects (such as microorganisms and viruses) contained in a sterilization target object P due to adhesion or the like. The sterilization device 30 includes a light source 32, a reflector 33, a housing 34, and an optical filter 1.

[0116] In the sterilization device 30, there is the optical filter 1 having the above-described dome shape. The optical filter 1 is provided on the housing 34 in such a manner that the first main surface 2a on the vertex side of the dome shape is disposed on the outer side (the side of the object to be sterilized P). In the sterilization device 30, the emitted light emitted from the light source 32 is irradiated on the object to be sterilized P via the optical filter 1.

[0117] Inside the housing 34, a light source 32 and a reflector 33 are disposed. The light source 32 is a light source whose emitted light wavelength exists in the wavelength range of ultraviolet rays (for example, the wavelength range of 200 nm to 400 nm). The reflector 33 can diffusely spread the light emitted from the light source over a wide range. The light source 32 is disposed opposite to the concave surface of the optical filter 1.

[0118] As the light source 32, for example, an excimer lamp can be used. As the excimer lamp, an excimer lamp that emits ultraviolet rays in the range of a wavelength of 220 nm to 300 nm is preferably used. As such an excimer lamp, for example, a KrCl excimer lamp can be used. The excimer lamp can also be a KrF excimer lamp. A plurality of UV-LEDs having different peak wavelengths in the range of 250 nm to 320 nm can also be used.

[0119] By using the sterilization device 30, it is possible to inactivate the treatment objects (such as microorganisms and viruses) contained on the object to be sterilized P due to adhesion or the like. In the sterilization device 30, since ultraviolet rays useful for the sterilization treatment can be efficiently transmitted, it is possible to efficiently perform ultraviolet sterilization on the object to be sterilized P. For example, by ultraviolet sterilization, it is possible to make ultraviolet rays act on the DNA inside the cells of microorganisms such as bacteria to selectively inactivate the microorganisms, or to make ultraviolet rays act on viruses to selectively inactivate them.

[0120] Since the sterilization device 30 of the present embodiment has the optical filter 1, it can effectively transmit ultraviolet rays in a wide wavelength range and can increase its transmittance. Therefore, when the optical filter 1 is used for a sterilization device, it can expand the types of applicable treatment objects (such as microorganisms and viruses), shorten the inactivation treatment time, etc., and improve the sterilization effect.

[0121] In addition, in the sterilization device 30 of the present embodiment, there is the optical filter 1 having a dome shape. Therefore, not only near the center of the optical filter 1 above the light source 32, but also in the portion obliquely above the light source 32 and far from the center of the optical filter 1, it is possible to make the emitted light with a small incident angle incident. Therefore, by using the sterilization device 30, even when the effective irradiation area of the emitted light from the light source 32 is increased, it is possible to efficiently transmit ultraviolet rays useful for the sterilization treatment.

[0122] In the sterilization device 30 of the present embodiment, as Figure 4As shown, the optical filter 1 is preferably arranged in a concentric circle with the light source 32 as the center in a cross-sectional view along the thickness direction. In this case, ultraviolet rays useful for the sterilization treatment can be transmitted more efficiently, and the effective irradiation area of the emitted light can be increased.

[0123] In addition, one light source 32 is used in the sterilization device 30 of the present embodiment. However, for example, a plurality of light sources 32 having different wavelength ranges of the irradiated light can also be used. In this case, for a plurality of processing objects having different wavelength ranges that can improve the sterilization effect, the light source 32 capable of irradiating the light corresponding to each wavelength range is used, so that the sterilization treatment can be performed on a plurality of processing objects simultaneously. Among them, the plurality of light sources 32 can be arranged in the same housing 34, or can be separately arranged in a plurality of housings 34.

[0124] [Ultraviolet detection device]

[0125] Figure 5 It is a schematic cross-sectional view showing an ultraviolet detection device according to an embodiment of the present invention.

[0126] Figure 5 The ultraviolet detection device 40 shown has a substrate 42, an ultraviolet light receiving element 41, and an optical filter 1. In the ultraviolet detection device 40, ultraviolet rays from the outside enter the substrate 42 through the optical filter 1. And the ultraviolet light receiving element 41 can detect the ultraviolet rays incident on the substrate 42.

[0127] Since the ultraviolet detection device 40 of the present embodiment has the optical filter 1, it can transmit ultraviolet rays in a wide wavelength range and can improve its transmittance. Therefore, the ultraviolet detection device 40 can detect ultraviolet rays in a wide wavelength range with high sensitivity.

[0128] Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is not limited by any of the following examples, and can be appropriately modified and implemented within the scope without changing its gist.

[0129] (Example 1)

[0130] First, a borosilicate glass substrate with a thickness of 0.2 mm (manufactured by Nippon Electric Glass Co., Ltd., product number "BU-41", size: 100 mm × 100 mm × 0.2 mm) is prepared. Then, the prepared glass substrate is processed into a dome shape by press molding to prepare a transparent substrate (spacing of the opening: 4.0 mm, height: 1.0 mm). Among them, the processing of the dome shape of the glass substrate can also be formed by heating it to cause thermal deformation.

[0131] Next, a dielectric multilayer film is formed on one main surface of a transparent substrate processed into a dome shape by a sputtering method using the RAS method. Specifically, first, a hafnium target is sputtered using argon and oxygen as carrier gases to form a hafnium oxide film (HfO 2 film) on one main surface of the transparent substrate. At this time, the flow rate of argon is set to 500 sccm, the flow rate of oxygen is set to 156 sccm, and the power applied to the target (film formation power) is set to 4.5 kW. Next, a silicon target is sputtered using argon and oxygen as carrier gases to form a silicon oxide film (SiO 2 film) on the HfO 2 film. At this time, the flow rate of argon is set to 600 sccm, the flow rate of oxygen is set to 240 sccm, and the power applied to the target (film formation power) is set to 5.0 kW. By repeating this operation, a dielectric multilayer film having a total of 4 layers, in which HfO 2 films and SiO 2 films are alternately laminated layer by layer, is formed on one main surface of the transparent substrate. By the same operation, a dielectric multilayer film having a total of 4 layers, in which HfO 2 films and SiO 2 films are alternately laminated layer by layer, is formed on the other main surface of the transparent substrate, and a film-coated transparent substrate is obtained. In addition, during film formation, the atmosphere temperature is set to room temperature (20 °C) without external heating. Next, the film-coated transparent substrate is heat-treated at a temperature of 600 °C for 60 minutes in an atmospheric atmosphere to obtain an optical filter.

[0132] In addition, the thickness of each layer of the dielectric multilayer film is as shown in Table 1 below.

[0133] [Table 1]

[0134]

[0135] (Examples 2 to 7)

[0136] A dielectric multilayer film is formed according to the composition and film thickness shown in Table 1 above, and no heat treatment is performed after film formation. Except for this, the same operations as in Example 1 are performed to obtain an optical filter.

[0137] (Comparative Example 1)

[0138] A borosilicate glass substrate having a thickness of 0.2 mm (manufactured by Nippon Electric Glass Co., Ltd., product number "BU-41", size: 100 mm × 100 mm × 0.2 mm) is prepared. Next, the prepared glass substrate is processed into a dome shape (spacing of the opening part: 4.0 mm, height: 1.0 mm) by press molding, and a transparent substrate is prepared and used directly without forming a dielectric multilayer film.

[0139] [Evaluation]

[0140] (Spectral transmittance)

[0141] For the optical filter of Example 1 and the transparent substrate of Comparative Example 1, the spectral transmittance was measured using a spectral transmittance meter (manufactured by Hitachi High-Technologies Corporation, product number “UH4150”). Specifically, the angle of incidence (AOI) was set to 0°, and the measurement wavelength was set to 200 nm to 400 nm.

[0142] Figure 6 It is a graph showing the transmission spectra of the optical filter obtained in Example 1 and the glass substrate of Comparative Example 1 at wavelengths from 200 nm to 400 nm. In addition, Figure 7 is a graph showing Figure 6 the transmission spectrum at wavelengths from 200 nm to 300 nm magnified. In addition, in Figure 6 and Figure 7 , the transmission spectrum of the optical filter obtained in Example 1 (after firing) is represented by a solid line, and the transmission spectrum of the optical filter obtained in Example 1 before firing is represented by a dotted line. In addition, the transmission spectrum of the glass substrate of Comparative Example 1 is represented by a dashed line.

[0143] As shown in Figure 6 and Figure 7 , it can be seen that in Example 1, the transmittance of ultraviolet rays in a wide wavelength range has increased, and in particular, the spectral transmittance at wavelengths from 240 nm to 300 nm is higher than that of the transparent substrate of Comparative Example 1 itself.

[0144] In addition, Figure 8 is a graph showing the transmission spectra of the optical filters obtained in Examples 2 to 7 at wavelengths from 200 nm to 400 nm. In addition, Figure 9 is a graph showing Figure 8 the transmission spectrum at wavelengths from 200 nm to 300 nm magnified.

[0145] As shown in Figure 8 and Figure 9 , it can be seen that in Examples 2 to 7, the transmittance of ultraviolet rays in a wide wavelength range has increased.

[0146] Symbol Explanation

[0147] 1: Optical filter; 2: Transparent substrate; 2a, 22a: First main surface; 2b, 22b: Second main surface; 3A, 3B: First dielectric multilayer film, second dielectric multilayer film; 4: High refractive index film; 4A: Innermost high refractive index film; 4B: Outermost high refractive index film; 5: Low refractive index film; 22: Base material of the transparent substrate; 22A: Dome-shaped portion; 26, 29: Film-forming jig; 27: Fixing member; 28: Concave surface forming jig; 30: Sterilization device; 32: Light source; 33: Reflector; 34: Housing; 40: Ultraviolet detection device; 41: Ultraviolet light receiving element; 42: Substrate; P: Object to be sterilized.

Claims

1. An optical filter, characterized in that, it has: a transparent substrate made of glass with a thickness of 1.0 mm or less; and a dielectric multilayer film containing hafnium oxide provided on at least one main surface of the transparent substrate, the minimum value of the spectral transmittance of the optical filter at a wavelength of 240 nm to 300 nm is 92% or more, The wavelength λ at which the spectral transmittance becomes 60% 60 is 230 nm or less.

2. The optical filter according to claim 1, characterized in that: the dielectric multilayer film has a high refractive index film with a relatively high refractive index and a low refractive index film with a relatively low refractive index, the high refractive index film contains hafnium oxide.

3. The optical filter according to claim 2, characterized in that: among the plurality of high refractive index films, the outermost high refractive index film farthest from the transparent substrate is thicker than the innermost high refractive index film closest to the transparent substrate.

4. The optical filter according to claim 3, characterized in that: the ratio of the thickness of the outermost high refractive index film to the thickness of the innermost high refractive index film is 2 or more in terms of outermost layer / innermost layer.

5. The optical filter according to any one of claims 1 to 4, characterized in that: the number of stacked layers of the dielectric multilayer film provided on one main surface of the transparent substrate is 10 layers or less.

6. The optical filter according to any one of claims 2 to 4, characterized in that: the total thickness of the high refractive index films constituting the dielectric multilayer film is 500 nm or less.

7. The optical filter according to any one of claims 1 to 4, characterized in that: the dielectric multilayer film is provided on both main surfaces of the transparent substrate.

8. The optical filter according to any one of claims 1 to 4, characterized in that: the transparent substrate has a dome shape.

9. The optical filter according to claim 8, characterized in that: the ratio of the height of the dome shape to the interval of the opening is 0.1 or more in terms of height / interval of the opening.

10. A sterilization device for inactivating a treatment object, the sterilization device is characterized in that it has: a light source that emits light in the ultraviolet wavelength range; and the optical filter according to any one of claims 1 to 4, the light source and the optical filter are arranged in such a way that the treatment object is inactivated by irradiating the emitted light from the light source through the optical filter.

11. An ultraviolet detection device for detecting ultraviolet rays, the ultraviolet detection device is characterized in that it has: the optical filter according to any one of claims 1 to 4; and an ultraviolet light receiving element.

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