JP7489657B2 - UV sterilization device and method for viruses - Google Patents

Description

This disclosure relates to an ultraviolet sterilization device and ultraviolet sterilization method for viruses.

Sterilization is essential not only in our daily lives but also in industry. Commonly known sterilization methods include chemical sterilization using chlorine and other substances, heat sterilization, ultraviolet sterilization, and ozone sterilization, but due to the harmful effects of chemicals and growing environmental awareness, there is a demand for higher quality sterilization techniques that do not alter the objects to be sterilized, do not leave unnecessary residues, and are environmentally friendly. Against this background, sterilization methods using ultraviolet (UV) light, i.e. ultraviolet sterilization, are becoming more widely used.

UV light inactivates viruses without leaving any residue like chemicals, making it extremely safe. UV light is also said to destroy the DNA or RNA of viruses, and has the advantage of not creating resistant bacteria, unlike chemical sterilization. The following is a general explanation for the sterilization mechanism by UV light: Inside the cells of living organisms, including bacteria, there is nucleic acid (DNA or RNA) that controls genetic information, and when irradiated with UV light, the nucleic acid absorbs the light, causing damage to some of the nucleic acid, disrupting transcriptional control from genes and interfering with metabolism, resulting in inactivation.

Figure 48 shows the wavelength characteristics of ultraviolet sterilization action that are currently recognized as the international standard (see Non-Patent Document 1). As is clear from Figure 48, the wavelength that shows the maximum sterilization action is around 260 nm, and lamps that efficiently emit UV of 253.7 nm (called sterilizing rays or sterilizing radiation) close to this wavelength are commonly used as germicidal lamps.

However, germicidal lamps are made from special glass tubes that allow germicidal rays to pass through, which makes them difficult to make small and lightweight, and there are restrictions on their shape, as well as problems such as higher power consumption compared to LEDs. In addition, the tubes contain argon gas and mercury, an environmental pollutant, which means special restrictions are placed on disposal and it is complicated. Furthermore, due to the recent increase in environmental awareness and environmental measures such as ROHS regulations, mercury lamps, which are germicidal lamps that use mercury, are tending to be disliked.

In recent years, ultraviolet sterilization devices that use LEDs (UV-LEDs) capable of emitting ultraviolet light have been proposed to replace germicidal lamps that have these problems. The inventors of the present application have been researching sterilization devices that use UV-LEDs for many years, and have also filed patent applications (see Patent Documents 1 to 3).

LEDs are generally considered to have a longer operating time and lower power consumption than mercury lamps. However, UV-LEDs, which can emit ultraviolet light (UVC) with a short wavelength such as 253.7 nm like mercury lamps, are technically difficult to develop and have not yet been put to practical use. They are also extremely expensive compared to other LEDs. For this reason, UV-LEDs, which can emit near-ultraviolet light of longer wavelengths such as UVA and UVB, are used instead.

However, UV-LEDs capable of emitting UVA and UVB rays have been considered to have inferior sterilization capabilities because their wavelengths are longer than UVC.

Meanwhile, the recent global spread of COVID-19, the so-called novel coronavirus, has created a worldwide need for virus prevention measures. Under these circumstances, as consumable items such as masks and disinfectants are difficult to obtain around the world, ultraviolet sterilization devices are attracting attention as a permanent and easy virus prevention measure that does not rely on consumable items.

However, as mentioned above, there were concerns that sterilization devices using UV-LEDs capable of emitting UVA had inferior virus removal performance and could not exert sufficient sterilizing power.

JP 2008-161095 A JP 2004-275335 A Patent No. 4067496

Applications of Germicidal, Erythemal and Infrared Energy 1st ed. 1946, 111 pages, Author: Matthew Luckiesh, Publisher: D. Van Nostrand Company, Inc.

The present invention was made in light of this background, and one of its objectives is to provide an ultraviolet sterilization device and ultraviolet sterilization method for viruses that significantly improves the sterilization ability that has been a drawback even when using UV-LEDs.

Means for solving the problem and effects of the invention

According to a first aspect of the present invention, the ultraviolet sterilization device for viruses inactivates specific viruses with ultraviolet light, and includes a first UV-LED that emits ultraviolet light having a first main emission peak wavelength, a second UV-LED that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED, and a current control unit that supplies drive currents to the first UV-LED and the second UV-LED to cause them to emit light so that the combined emission spectrum of the first UV-LED and the second UV-LED emitted simultaneously is similar to the absorption spectrum of the specific virus. With the above configuration, by combining multiple UV-LEDs with different wavelengths, it is possible to effectively exert sterilization performance against the viruses to be sterilized, without using a low-pressure mercury lamp.

Furthermore, according to the ultraviolet sterilization device for viruses according to the second aspect of the present invention, in addition to the above configuration, the correlation R o, defined by the following formula, of a synthetic emission spectrum S(λ) obtained by simultaneously emitting light by supplying a driving current to each of the first UV-LED and the second UV- _LED by the current control unit with an absorption spectrum A(λ) of the specific virus is set to be 0.7000 or more.

In the above formula, N is the number of measured wavelengths, λ ₁ , ... λ _N are measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1. With the above configuration, it is possible to achieve excellent sterilization performance by combining multiple UV-LEDs with different wavelengths.

Furthermore, according to the ultraviolet sterilization device for viruses related to the third aspect of the present invention, in addition to the above configuration, the correlation R, defined by the following formula, of a synthetic emission spectrum S(λ) obtained by simultaneously emitting light by supplying a driving current to each of the first UV-LED and the second UV-LED by the current control unit with an absorption spectrum A(λ) of the specific virus is set to be 0.7000 or more.

In the above equation, cov represents the covariance of the absorption spectrum A(λ) and the composite emission spectrum S(λ), σ _A represents the standard deviation of the absorption spectrum A(λ), and σ _S represents the standard deviation of the composite emission spectrum S(λ).

Furthermore, in the ultraviolet sterilization device for viruses according to the fourth aspect of the present invention, the correlation R AE, defined by the following formula, of a synthetic emission spectrum S(λ) produced by simultaneously emitting light by supplying a driving current to each of the first UV-LED and the second UV- _LED by the current control unit with an absorption spectrum A(λ) of the specific virus is 0.7000 or more.

In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.

Furthermore, in the ultraviolet sterilization device for viruses according to the fifth aspect of the present invention, the cosine similarity cos θ, defined by the following equation as the degree of correlation between the composite emission spectrum S(λ) produced by simultaneously emitting light when a driving current is supplied to each of the first UV-LED and the second UV-LED by the current control unit, and the absorption spectrum A(λ) of the specific virus, is set to be 0.7000 or more.

In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.

Furthermore, according to the ultraviolet sterilization device for viruses relating to the sixth aspect of the present invention, in addition to any one of the above configurations, the first main emission peak is 280 nm or less, and the second main emission peak is 280 nm or less.

Furthermore, according to an ultraviolet sterilization device for viruses relating to a seventh aspect of the present invention, in addition to any of the above configurations, the first main emission peak wavelength is included in the range of 245 nm to 257 nm, and the second main emission peak wavelength is included in the range of 257 nm to 270 nm.

Furthermore, according to the eighth aspect of the present invention, in addition to any of the above configurations, the ultraviolet sterilization device for viruses further includes a third UV-LED that emits ultraviolet light having a third main emission peak wavelength different from the first main emission peak wavelength and the second main emission peak wavelength, and the current control unit supplies a drive current to each of the first UV-LED, the second UV-LED, and the third UV-LED to emit light, and the correlation degree of the synthetic emission spectrum S(λ) of the combination of the ultraviolet light of the first UV-LED, the second UV-LED, and the third UV-LED with respect to the absorption spectrum A(λ) of the specific virus can be set to 0.7000 or more. With the above configuration, it is possible to achieve even better sterilization performance by combining three or more types of UV-LEDs with different wavelengths.

Furthermore, according to a ninth aspect of the present invention, in addition to any of the configurations described above, the ultraviolet sterilization device for viruses can be configured so that the third main emission peak wavelength is included in the range of 270 nm to 380 nm.

Furthermore, according to the ultraviolet sterilization device for viruses relating to the tenth aspect of the present invention, in addition to any of the configurations described above, the current control unit can vary the value of the drive current supplied to the first UV-LED and the second UV-LED.

Furthermore, according to the ultraviolet sterilization device for viruses of the eleventh aspect of the present invention, in addition to any of the configurations described above, the current control unit can set the ratio of the drive currents supplied to the first UV-LED and the second UV-LED to be from 1:0 to 0:1.

Furthermore, according to the ultraviolet sterilization device for viruses relating to the twelfth aspect of the present invention, in addition to any of the above configurations, the current control unit can pre-set drive current values at which the correlation with the synthetic emission spectrum is 0.7000 or more, corresponding to the absorption spectra of a plurality of different viruses, and can switch between these plurality of drive current values.

Furthermore, according to the ultraviolet sterilization device for viruses according to the thirteenth aspect of the present invention, in addition to any of the configurations described above, the correlation degree can be made 0.8000 or more.

Furthermore, according to a fourteenth aspect of the present invention, the ultraviolet sterilization method for viruses inactivates a specific virus with ultraviolet light, and includes the steps of preparing a first UV-LED that emits ultraviolet light having a first main emission peak wavelength and a second UV-LED that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED, and supplying a drive current to each of the first UV-LED and the second UV-LED by a current control unit so that the first UV-LED and the second UV-LED emit light simultaneously and the combined emission spectrum is approximated to the absorption spectrum of the specific virus. This makes it possible to effectively exert sterilization performance against the target virus by combining multiple UV-LEDs with different wavelengths without using a low-pressure mercury lamp.

FIG. 1 is a block diagram showing an ultraviolet sterilization device for viruses according to a first embodiment of the present invention. FIG. 4 is a block diagram showing an ultraviolet sterilization device for viruses according to a second embodiment of the present invention. 1 is a graph showing the inactivation effect of UV irradiation on H1N1 subtypes over time. 1 is a graph with an enlarged view of a main part showing the inactivation effect of each UV irradiation fluence against H1N1 subtypes. 1 is a graph showing the degree of inactivation by UV-LED in Reference Examples 7, 5, and 3. 1 is a graph showing the degree of RNA damage caused by UV-LED in Reference Examples 7, 5, and 3. FIG. 1 is a schematic diagram showing the mechanism of virus inactivation by UVC. FIG. 1 is a schematic diagram showing the mechanism of virus inactivation by UVA and UVB. 1 is a graph showing the amount of vRNA in host cells after UV irradiation for H1N1 subtypes. 1 is a graph showing the amount of cRNA in host cells after UV irradiation for H1N1 subtypes. 1 is a graph showing the amount of mRNA in host cells after UV irradiation for H1N1 subtypes. 1 is a graph showing the variation of vRNA in host cells after UV irradiation against H1N1 subtypes. 1 is a graph showing the variation of cRNA in host cells after UV irradiation against H1N1 subtypes. 1 is a graph showing the change in mRNA levels in host cells after UV irradiation for H1N1 subtypes. 1 is a graph showing the results of measuring the virus inactivation ratio when virus subspecies are irradiated with UVA, UVB, and UVC. FIG. 1 is a schematic diagram showing how UV irradiation represses vRNP replication and transcription. 1 is a graph showing the inactivation effect of UVC radiation of different peak wavelengths against H1N1 subtypes. 1 is a graph showing the infectivity ratio when H1N1 is exposed to UV light from different light sources. 1 is a graph showing infection ratios when embryonated chicken eggs are irradiated with UV light from different light sources. 1 is a graph showing the virus inactivation ratio for each wavelength when H1N1 is irradiated with UV light. 1 is a graph showing the virus inactivation ratio for each wavelength when embryonated chicken eggs are irradiated with UV light. 1 shows microscopic photographs taken after a HA titer experiment. 1 is a graph showing viral vRNA segment 6 by wavelength. 1 is a graph showing the relationship between viral vRNA segment 6 and viral inactivation ratio. 1 is a graph showing the RNA damage ratio for each wavelength. 1 is a graph showing the absorption curve of viral RNA. 27A is a graph showing the emission spectrum of a 254 nm low pressure mercury lamp, FIG. 27B is a graph showing the emission spectrum of a 260 nm UV-LED, FIG. 27C is a graph showing the emission spectrum of a 270 nm UV-LED, FIG. 27D is a graph showing the emission spectrum of a 280 nm UV-LED, FIG. 27E is a graph showing the emission spectrum of a 290 nm UV-LED, and FIG. 27F is a graph showing the emission spectrum of a 310 nm UV-LED. 1 is a graph showing an overlay of a composite emission spectrum and an absorption spectrum of viral RNA. 1 is a graph in which the composite emission spectrum of Example 1 is superimposed on the emission spectra of the UV-LEDs of Reference Examples 1, 2, and 3, and the low-pressure mercury lamp of Comparative Example 1. 1 is a graph showing the inactivation effects of Example 1, Reference Examples 1 to 3, and Comparative Example 1 against H1N1. 1 is a graph showing the inactivation effects of Example 1, Reference Examples 1 to 3, and Comparative Example 1 against H6N2. 1 is a graph showing the inactivation effect when H1N1 virus is applied to embryonated chicken eggs. 1 is a graph showing the inactivation effect when H6N2 virus is applied to embryonated chicken eggs. 1 is a graph showing the relationship between correlation and inactivation with respect to MDCK. 1 is a graph showing the relationship between correlation and inactivation for embryonated chicken eggs. 1 is a table summarizing the correlation between the inactivation ratio and wavelength, and the correlation degree R _AE between inactivation and MDCK and embryonated chicken eggs as hosts. 1 is a graph showing the virus inactivation effect by UV irradiation. 1 is a graph showing the virus inactivation effect by UVA irradiation. 1 is a graph showing the virus inactivation effect by UVB irradiation. Graph showing correlation of RT-qPCR products and FCV after UV irradiation. 10 is a flowchart showing the procedure for determining a combination of UV-LEDs in an ultraviolet virus sterilization device according to Example 2. 1 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 2. 1 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 3. 10 is a flowchart showing the procedure for determining a combination of UV-LEDs for an ultraviolet virus sterilization device according to Example 4. 13 is a graph showing an actually measured LED emission spectrum and an estimated LED emission spectrum according to Example 4. 1 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 4. 13 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 5. 1 is a graph showing the wavelength characteristics of ultraviolet sterilization action. 1 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 6. 13 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 7. 13 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 8. 13 is a graph showing a composite emission spectrum and a virus absorption spectrum according to Example 9.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as necessary. However, the embodiment shown below is an example for embodying the technical idea of the present invention, and the present invention is not limited to the following. In addition, this specification never specifies the members shown in the claims to the members of the embodiment. In particular, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiment are not intended to limit the scope of the present invention to those, and are merely explanatory examples, unless otherwise specified. Note that the size and positional relationship of the components shown in each drawing may be exaggerated to clarify the explanation. Furthermore, in the following explanation, the same name and symbol indicate the same or similar components, and detailed explanations will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured as a form in which multiple elements are composed of the same member, and one member serves multiple elements, or conversely, the function of one member can be shared and realized by multiple members. In addition, the contents described in some examples and embodiments may be applicable to other examples, embodiments, etc.
[Embodiment 1]

The block diagram of FIG. 1 shows an ultraviolet sterilization device 100 for viruses according to embodiment 1 of the present invention. The ultraviolet sterilization device 100 for viruses shown in this figure comprises a first UV-LED1, a second UV-LED2, and a current control unit 5. In this ultraviolet sterilization device for viruses 100, the current control unit 5 supplies drive current to each of the first UV-LED1 and the second UV-LED2, turning on the first UV-LED1 and the second UV-LED2 to irradiate ultraviolet light. With this ultraviolet sterilization device for viruses 100, for example, ultraviolet light is irradiated onto the sterilization target WK to sterilize viruses attached to the sterilization target WK. In this specification, sterilization of viruses is used to mean the inactivation or deactivation of viruses.

The first UV-LED1 is a light-emitting diode that emits ultraviolet light having a first main emission peak wavelength. The first main emission peak wavelength is 280 nm or less, preferably in the range of 245 nm to 260 nm, and more preferably in the range of 245 nm to 257 nm. The preferred first main emission peak is 250.3 nm, 256 nm, or 247.4 nm.

The second UV-LED2 is a light-emitting diode that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED1. The second main emission peak wavelength is 280 nm or less, preferably in the range of 256.5 nm to 270 nm, more preferably 257 nm to 270 nm, and even more preferably 260 nm to 270 nm. A suitable second main emission peak is 262.7 nm, or 270 nm, or 257.6 nm.

Preferably, the maximum amplitude of the emission spectrum of the first UV-LED1 is set to 0.95 to 0.99 when the peak of the virus absorption spectrum is normalized to 1. The maximum amplitude of the emission spectrum of the second UV-LED2 is set to 0.92 to 0.95.

The first UV-LED1 and second UV-LED2 may each be one, or multiple first UV-LEDs and second UV-LEDs2 may each be connected in series or parallel. By increasing the number of UV-LEDs, the amount of ultraviolet light irradiation can be increased. Furthermore, the first UV-LED1 and second UV-LED2 may be configured as physically separate packages, or, for example, may be configured with two LED chips included in a common package.

_Gallium nitride semiconductor light emitting diodes can be suitably used for such ultraviolet light emitting diodes. For example, a semiconductor light emitting element using a nitride semiconductor with a composition represented by _{InXAlYGa1 -XYN} (0≦X, 0≦Y, X+Y≦1) can be used. This provides a stable ultraviolet sterilization device 100 that is highly efficient, has high linearity of output relative to input, and is resistant to mechanical shock.
(Current control unit 5)

The current control unit 5 is connected to a DC power supply 6. The DC power supply 6 can be, for example, a current converter that rectifies a commercial AC power supply of 50 Hz or 60 Hz and converts it to DC, or a DC stabilized power supply. The current control unit 5 may also be provided with such a current conversion function. In this case, the current control unit 5 can be used by connecting it directly to a commercial power supply.

The current control unit 5 supplies a drive current to each of the first UV-LED 1 and the second UV-LED 2 to cause them to emit light simultaneously, and irradiates light MS with a composite emission spectrum S(λ) that is a combination of these emitted lights. Note that in this specification, light does not mean visible light, but typically means light such as ultraviolet light or electromagnetic waves.

Here, the absorption spectrum A (λ) of the specific virus to be sterilized by the ultraviolet virus sterilization device 100 is acquired in advance. Then, the current control unit emits light so that the combined emission spectrum produced when the first UV-LED 1 and the second UV-LED 2 are simultaneously emitted in response to this absorption spectrum A (λ) is approximated to the absorption spectrum of the virus. This makes it possible to effectively exert sterilization performance against the target virus by combining multiple UV-LEDs with different wavelengths without using a low-pressure mercury lamp.

Specifically, the correlation R _o of the combined emission spectrum S(λ) obtained by combining the ultraviolet rays of the first UV-LED 1 and the second UV-LED 2 with respect to the absorption spectrum A(λ) is calculated based on the following formula 1.

In the above formula, N is the number of measured wavelengths, λ ₁ ,... λ _N are measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1. The current control unit 5 adjusts the drive currents of the first UV-LED 1 and the second UV-LED 2 so that the correlation degree R _o is 0.7000 or more. This makes it possible to achieve excellent sterilization performance by combining multiple UV-LEDs with different wavelengths.

In addition, formulas other than the above can be used to calculate the degree of correlation between the virus absorption spectrum A(λ) and the composite emission spectrum S(λ). For example, the following formula (2) can be used.

In the above equation, cov represents the covariance of the absorption spectrum A(λ) and the composite emission spectrum S(λ), σ _A represents the standard deviation of the absorption spectrum A(λ), and σ _S represents the standard deviation of the composite emission spectrum S(λ).

The correlation degree R can be normalized by dividing it by the energy value of the virus absorption spectrum. As an example of this, the following formula 3, which is a modification of the formula 1 for calculating the correlation degree between the virus absorption spectrum A(λ) and the composite emission spectrum S(λ), may be used.

In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.

Alternatively, the cosine similarity cosθ defined in the following formula 4 can be used to calculate the degree of correlation between the virus absorption spectrum A(λ) and the composite emission spectrum S(λ).

In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.

The higher the correlation between these, the better. The current control unit 5 controls the drive current so that the correlation is preferably 0.8000 or higher.

The current control unit may vary the value of the drive current supplied to the first UV-LED 1 and the second UV-LED 2. Furthermore, the current control unit can change the ratio of the drive current supplied to the first UV-LED 1 and the second UV-LED 2 from 1:0 to 0:1.

Furthermore, the ultraviolet sterilization device 100 for viruses may be configured to effectively sterilize multiple different viruses, in addition to being limited to one specific type of virus to be sterilized. In this case, it is preferable to adjust the drive current of multiple UV-LEDs so that the correlation R between the absorption spectrum of the virus to be sterilized and the composite emission spectrum is high. For example, the drive current values that correspond to the absorption spectra of multiple different viruses and the composite emission spectrum of 0.7000 or more are preset in the current control unit. Then, the values of these multiple drive currents may be switched depending on the virus to be sterilized. In addition, such switching of the drive current may be performed automatically. For example, the number of viruses to be sterilized is set to four, and the combination of drive currents corresponding to the absorption spectrum of each virus is periodically changed. For example, by supplying drive currents that correspond to the absorption spectrum of each virus and have a correlation R of 0.7000 or more for 30 seconds each, and switching automatically in sequence, it becomes possible to sterilize four types of viruses simultaneously.
(UV sterilization method for viruses)

A method for sterilizing viruses with ultraviolet light, in which a specific virus is inactivated with ultraviolet light using the above ultraviolet light sterilization device 100 for viruses, will be described. First, a first UV-LED 1 that emits ultraviolet light having a first main emission peak wavelength and a second UV-LED 2 that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED 1 are prepared. Next, a drive current is supplied to each of the first UV-LED 1 and the second UV-LED 2 by the current control unit 5 to cause them to emit light, and the correlation R, defined by the following formula, of the combined emission spectrum S(λ) of the ultraviolet light from the first UV-LED 1 and the second UV-LED 2 combined with the absorption spectrum A(λ) of the specific virus is set to 0.7000 or more. This makes it possible to achieve excellent sterilization performance by combining multiple UV-LEDs with different wavelengths.
[Embodiment 2]

In the above example, two types of UV-LEDs, a first UV-LED and a second UV-LED, with different main emission peak wavelengths, are used, but UV-LEDs with different main emission peak wavelengths may also be combined. As such an example, an ultraviolet sterilization device 200 for viruses according to embodiment 2 is shown in the block diagram of Figure 2. In this figure, components similar to those in Figure 1 described above are given the same reference numerals and detailed descriptions are omitted as appropriate.

The ultraviolet sterilization device 200 for viruses in Figure 2 comprises a first UV-LED 1, a second UV-LED 2, a third UV-LED 3, and a current control unit 5. The third UV-LED 3 emits ultraviolet light having a third main emission peak wavelength different from the first main emission peak wavelength and the second main emission peak wavelength. The third main emission peak wavelength is in the range of 270 nm to 380 nm, preferably 272 nm to 290 nm.

The current control unit 5 supplies a drive current to each of the first UV-LED 1, the second UV-LED 2, and the third UV-LED 3 to cause them to emit light. The correlation R defined by the formula 1 between the synthetic emission spectrum S(λ) obtained by combining the ultraviolet rays from the first UV-LED 1, the second UV-LED 2, and the third UV-LED 3 and the absorption spectrum A(λ) of the virus is set to 0.7000 or more.
(certain viruses)

The recent global pandemic of COVID-19, the so-called novel coronavirus, has highlighted the importance of sterilizing harmful viruses, including the novel coronavirus.

Conventional sterilization methods include sterilization using chemicals such as chlorine, ozone sterilization, heat sterilization, and ultraviolet sterilization. Of these, chemical sterilization using chlorine and other chemicals has the problem that the chlorine remaining after sterilization is harmful to the human body. There are also concerns about the emergence of drug-resistant bacteria. On the other hand, ozone sterilization has the problem that it is difficult to maintain the sterilization effect and is also harmful to the human body. Furthermore, heat sterilization has the problem that it requires a large amount of energy for heating and is inconvenient because the heating process is time-consuming.

In contrast, sterilization using ultraviolet light-emitting diodes does not leave any residual substances, unlike chemical sterilization, and unlike the widely used low-pressure mercury lamps, does not produce any mercury waste. Furthermore, it has the advantages of being able to be used continuously, consuming relatively low power, and allowing the device to be made compact.

However, it is difficult to achieve ultraviolet light with a wavelength of 253.7 nm (approximately 254 nm), which is used in low-pressure mercury lamps, in a light-emitting diode, and it has not yet been put to practical use. In particular, gallium nitride (GaN) absorbs wavelengths of 360 nm or less, so while AlGaN is used in the active layer of a light-emitting diode, there is a problem in that AlGaN has poor light-emitting efficiency in the short-wavelength region.

Therefore, the inventors of the present application have intensively studied a method for realizing effective virus sterilization using currently available ultraviolet light-emitting diodes, and have come to the present invention. Here, the inactivation effect of irradiation of ultraviolet light-emitting diodes on viruses was studied, and an attempt was made to clarify the inactivation mechanism. Specifically, using avian influenza virus as the virus, the inactivation effect due to differences in the main emission peak wavelengths of UVA-LED, UVB-LED, and UVC-LED, which are in practical use as ultraviolet light-emitting diodes, was compared. In addition, the UV irradiation inactivation mechanism using a virus subtype was studied. Furthermore, the inactivation effect due to differences in virus subtypes was compared. Here, the following two types of influenza A virus subtypes were used.
・H1N1 (A/Puerto Rico/8/1934): A seasonal influenza virus isolated from humans ・H5N1 (A/Duck/Hong Kong/960/1980): Highly pathogenic avian influenza virus (HPAI). It has occurred in Southeast Asia and other countries around the world. When it infects humans, it has a high mortality rate of over 50%.
(1: Inactivation effect due to differences in the main emission peak wavelength of UV-LED)

First, a UVA LED, a UVB LED, and a UVC LED were each turned on and irradiated onto a virus to compare their inactivation effects. Here, the H1N1 virus was placed in a stainless steel container and irradiated from above with a UV LED. The container was cylindrical, 15 mm high, 10 mm deep, and 10 mm in diameter, with an open top. 0.3 mL of virus solution was placed in each stainless steel container, and ultraviolet light was irradiated from the top of the container.

Generally, near-ultraviolet rays are divided into UVA (400-315 nm), UVB (315-280 nm), and UVC (less than 280 nm). Here, Nichia Corporation's NVSU233A (main emission peak wavelength 365 nm, power 106 mW/cm ² ) was used as the UVA-LED, Nichia Corporation's NCSU234A (310 nm, 4.4 mW/cm ² ) was used as the UVB-LED, and NCISU234A (280 nm, 5.5 mW/cm ² ) was used as the UVC-LED. Each UV-LED was irradiated with its rated maximum forward current. The 365 nm UVA-LED is Reference Example 7, the 310 nm UVB-LED is Reference Example 6, and the 280 nm UVC-LED is Reference Example 3.

The virus titer was 10 ⁶ PFU/mL. The inactivation ratio of the H1N1 subtype was then evaluated by plaque assay (PFU). The results are shown in the graphs of Figures 3 and 4. In these figures, Figure 3 shows the inactivation effect of UV irradiation versus irradiation time. Figure 4 shows the inactivation effect of UV irradiation versus fluence (the time integral value of the radiant flux passing through a unit area). A partially enlarged graph is also shown in Figure 4. As shown in these figures, the inactivation effect of UV-LED irradiation was observed against the H1N1 subtype. The inactivation effect was proportional to the shorter the wavelength, with 280 nm showing the highest inactivation efficiency.

Next, to investigate the mechanism of virus inactivation, the UVA-LED of Reference Example 7, the UVB-LED of Reference Example 6, and the UVC-LED of Reference Example 3 were irradiated with ultraviolet light at an irradiation dose that inactivates the virus to the same extent, that is, to a virus inactivation ratio [log 10 ratio] of about -1 to -1.5 as shown in FIG. 5. In this state, RNA damage was investigated. Here, the amount of Segment 6 vRNA was examined by processing with RT-qPCR. The results are shown in the graph of FIG. 6. As shown in this figure, RNA damage was observed only with UVC irradiation. This revealed that UVC and UVA have different bactericidal effects. That is, with UVC, as shown in FIG. 7, the physical force acting on the chinidine of the nucleic acid cuts the double helix, impairing the ability of the RNA. In contrast, with UVA and UVB, as shown in FIG. 8, it is presumed that the virus inactivation mechanism is due to oxidation.

Furthermore, the amounts of vRNA, cRNA, and mRNA in host cells at the early stage of infection after UV irradiation of the H1N1 subtype were examined. The results are shown in the graphs of Figures 9, 10, and 11, respectively. In these figures, Figure 9 shows the amount of vRNA in host cells 2 hours after irradiation for the H1N1 subtype in the cases of no UV-LED irradiation, irradiation with UVA-LED according to Reference Example 7, irradiation with UVB-LED according to Reference Example 6, and irradiation with UVC-LED according to Reference Example 3, Figure 10 shows the amount of cRNA, and Figure 11 shows the amount of mRNA, respectively. Note that in these figures, it has been confirmed that vRNA, cRNA, and mRNA are specifically increased. From these figures, it was found that UV-LED irradiation does not affect vRNA. From this, it is inferred that UV irradiation does not affect the adhesion and invasion of the H1N1 subtype into cells.

Furthermore, the changes in vRNA, cRNA, and mRNA in host cells after UV irradiation of the H1N1 subtype were measured. The results are shown in the graphs of Figures 12, 13, and 14, respectively. In these figures, Figure 12 shows the time variation in the amount of vRNA in host cells after UV irradiation for each of the cases of not irradiating the H1N1 subtype with UV-LED, irradiating with the UVA-LED of Reference Example 7, irradiating with the UVB-LED of Reference Example 6, and irradiating with the UVC-LED of Reference Example 3, Figure 13 shows the time variation in the amount of cRNA, and Figure 14 shows the time variation in the amount of mRNA. Furthermore, vRNA in Figure 12 and cRNA in Figure 13 represent the effect of suppressing replication in host cells, and mRNA in Figure 14 represents the effect of suppressing transcription. From these figures, it was found that UV irradiation, as shown in Figure 16, with UVA, UVB, and UVC, suppresses both the replication and transcription of vRNP.

From the above, it was found that (1) the efficiency of virus inactivation by UV irradiation differs depending on the wavelength. Specifically, the main emission peak wavelength was 280 nm>310 nm>365 nm, and the shorter the wavelength, the higher the inactivation efficiency. It was also found that (2) the mechanism of virus inactivation by UV irradiation differs depending on the wavelength. Specifically, it was confirmed that UVA and UVB show transcription and replication inhibition in host cells, and UVC shows viral RNA damage and transcription and replication inhibition effect in host cells. Furthermore, (3) the inactivation effect by UV irradiation differed depending on the virus subtype. Specifically, the inactivation effect of UV irradiation on H5N1 was greater than that of H1N1 when irradiated with UVB and UVC. Here, the results of measuring the virus inactivation ratio by irradiating each virus subtype with UVA, UVB, and UVC are shown in FIG. 15. In this figure, UVA was irradiated for 5 minutes using a UVA-LED (main emission peak wavelength 365 nm, Reference Example 7) and UVB was irradiated for 5 minutes using a UVB-LED (310 nm, Reference Example 6). The former had an energy density of 31.8 J/ ^cm2 and the latter 1.32 J/ ^cm2 . UVC was irradiated for 10 seconds using a UVC-LED (280 nm, Reference Example 3) with an energy density of 0.055 J/ ^cm2 . The virus subspecies H1N1 and H5N1 were used, and the virus inactivation ratio [log 10 ratio] was measured and shown on the vertical axis. These will be discussed in detail below.
(1: Differences in inactivation efficiency depending on wavelength)

First, regarding the difference in inactivation efficiency depending on wavelength, the inactivation efficiency by UV irradiation differs depending on the wavelength. Here, when considering mercury lamps with a main emission peak wavelength of 253.7 nm, which is currently widely used for sterilization purposes, the results are 254 nm < 270 nm > 280 nm > 310 nm > 365 nm, and 270 nm had the highest inactivation efficiency. From this, it is inferred that there is a wavelength range or peak wavelength with high inactivation efficiency, not just a short wavelength. In a report on the bacterial sterilization effect by Kim SJ et al. (Kim SJ et al. Appl. Environ. Microbiol. 2015, 18;82(1):11-7), it is said that the inactivation efficiency of UV-LED at 266 nm is higher than that of mercury lamp at 254 nm. The reason for this is thought to be that the maximum DNA absorption wavelength is different inside the cell, or that longer wavelengths are more easily absorbed. The wavelength of around 260 nm is the maximum absorption wavelength of DNA (outside the cell). The above suggests that the more effective wavelength for killing bacteria and inactivating viruses may be around 260 nm to 270 nm. This finding is different from the conventional belief that shorter wavelengths are more effective at inactivating viruses, or that the 254 nm wavelength of a mercury lamp is suitable for sterilization.
(2: Differences in inactivation mechanism depending on wavelength)

The inactivation mechanism by UV irradiation differed depending on the wavelength. Specifically, as mentioned above, UVA and UVB are thought to suppress transcription and replication in host cells, while UVC is thought to damage viral RNA and suppress transcription and replication in host cells. In particular, since no damage to nucleic acids was observed in the inactivation mechanism by UVA and UVB irradiation, it is speculated that the inhibition of transcription and replication by damage to polymerase activity is involved.
(3: Differences in inactivation effect depending on virus species)

Furthermore, it has been reported that the inactivation effect differs depending on the virus species, and that the sensitivity differs depending on the virus species. For example, Kim D.K. et al., Food. Res. Int. 2017, 91:115-123, reported that UVC-LED irradiation with a main emission peak wavelength of 280 nm inactivated coliphage. From this, it is considered that the sensitivity of coliphage to UVC-LED is higher than that of H1N1. Also, according to Beck S.E. et al., Water. Res. 2016, 109:207-216, it was reported that a greater amount of irradiation energy was required to inactivate the UV-resistant human adenovirus serotype 2 (HAdV2) by UVC-LED irradiation with a main emission peak wavelength of 280 nm than that of IAV. From these, it is assumed that the sensitivity to UV irradiation differs depending on the virus species.

In summary, UV-LED irradiation inactivated influenza A viruses, including avian influenza viruses. Furthermore, because the inactivation efficiency differed depending on the virus subtype and UV wavelength, it was found that it was necessary to explore the optimal combination of subtype and wavelength for inactivation.
(Differences in sensitivity depending on wavelength)

Next, we will examine the differences in sensitivity of virus species depending on the wavelength. First, we compared the inactivation effect of UVC irradiation with different peak wavelengths on the H1N1 subtype. Here, two types of UV-LEDs were used: one with a conventional main emission peak wavelength of 280 nm and one with a shorter wavelength of 270 nm. As a comparison example, a mercury lamp with a wavelength of 254 nm was used. The results are shown in the graph in Figure 17. The horizontal axis of the graph shows the amount of irradiation energy, and the vertical axis shows the inactivation effect. This graph shows that while an inactivation effect was observed when irradiating the H1N1 subtype with UV-LED and a mercury lamp, the inactivation efficiency was not proportional to the shorter wavelength, and 270 nm was shown to have the highest inactivation efficiency.

Here, the difference in the inactivation effect on influenza viruses between commonly used low-pressure mercury lamps and UV-LEDs is unclear. The inactivation effect on influenza viruses in each wavelength range is also unknown. Therefore, we investigated the inactivation effect of avian influenza viruses by irradiation with ultraviolet light-emitting diodes (UV-LEDs) in various wavelength ranges. Specifically,
(1) We compared low-pressure mercury lamps and UV-LEDs, (2) determined which wavelength of UV-LED is effective, and (3) examined the irradiation conditions that can be expected to achieve high inactivation.

First, a comparison is made between low-pressure mercury lamps and UV-LEDs. Here, the virus was irradiated to the above-mentioned H1N1 subtype, and MDCK cells and embryonated chicken eggs were used as hosts. These were irradiated with ultraviolet light using a low-pressure mercury lamp with a main emission peak wavelength of 254 nm (Comparative Example 1), a UV-LED with a main emission peak wavelength of 260 nm (Reference Example 1), and UV-LEDs with main emission peak wavelengths of 270 nm (Reference Example 2), 280 nm (Reference Example 3), 290 nm (Reference Example 4), 300 nm (Reference Example 5), 310 nm (Reference Example 6), and 365 nm (Reference Example 7). These results are shown in Figures 18 to 21. In these figures, Figures 18 and 19 show graphs showing the infection ratio [log] for each ultraviolet light source, and Figures 20 and 21 show graphs showing the infection ratio [log] for each wavelength [nm], respectively. Figures 18 and 20 show the results of infection of MDCK cells, and Figures 19 and 21 show the results of infection of developing chicken eggs. These figures confirm that a 260 nm UV-LED is superior in inactivating viruses compared to other wavelengths.

The photograph in Figure 22 shows the results of an HA titer experiment performed on each virus. As a result of the HA titer experiment, none of the light sources changed the HA titer. In other words, no changes were observed in the viral HA. This suggests that UV irradiation does not affect the cell invasion activity.

Next, we consider what causes the inactivation. Here, we used RT-qPCR to confirm the toxicity of viral vRNA segment 6. The results are shown in FIG. 23, which is a graph plotting Segment 6vRNA [log 10 ratio] for each main emission peak wavelength. FIG. 24 shows a graph with Segment 6vRNA [log 10 ratio] on the horizontal axis and infection ratio [log] on the vertical axis. In FIG. 24, embryonated chicken eggs (R = 0.91027; P = 1.69 × 10 ^-3 , ● in FIG. 24) and MDCK cells (R = 0.9524; P = 2.6 × 10 ^-4 , □ in FIG. 24)) were used as hosts. Furthermore, FIG. 25 shows a graph with viral RNA toxicity by UV-LED on the horizontal axis and RNA damage ratio [log] on the vertical axis. The energy density of each UV-LED was 4.8 mJ/cm ² . These figures confirm that dominant damage was obtained at 260 nm, where damage was observed in viral vRNA. As such, a strong correlation was confirmed between damage and inactivation ratio, suggesting that viral inactivation is due to damage to viral RNA.

From the above, in the comparison between the low pressure mercury lamp and the UV-LED, it was confirmed that the virus inactivation effect was the same as that of the UV-LED with the main emission peak wavelength of 270 nm and 280 nm, and that the most effective inactivation was especially at 260 nm. In addition, as described above, it was found that the 260 nm UV-LED was the most effective wavelength for inactivation, and that the shorter the peak wavelength, the more effective it was. Furthermore, as a factor in inactivating the virus, no effect was observed on the HA constituting the virus, while when the damage to RNA was confirmed, it was found that the proliferation in cells after infection may have been suppressed. From this, it is considered that the cause of the inactivation of the virus is not the HA but the damage to the viral RNA. Therefore, it was thought that it may be important that the waveform is closer to the absorption curve than the maximum absorption wavelength, and then the RNA absorption curve and the emission spectrum were compared.
(Relationship between viral RNA absorption curve and LED)

The viral RNA absorption curve is shown in Figure 26, and the emission spectra of each UV light source are shown in Figures 27A to 27F. Here, Figure 27A shows the emission spectrum of a low-pressure mercury lamp with a main emission peak wavelength of 254 nm, Figure 27B shows the emission spectrum of a UV-LED with a main emission peak wavelength of 260 nm, Figure 27C shows the emission spectrum of 270 nm, Figure 27D shows the emission spectrum of 280 nm, Figure 27E shows the emission spectrum of 290 nm, and Figure 27F shows the emission spectrum of 310 nm.

Here, as an index showing the relationship between the two, the correlation degree R _o is defined by the following equation (5).

In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.

When the correlation degree R _A of RNA in FIG. 26 was set to 100, the correlation degrees R _AE of FIG. 27A to FIG. 27F were calculated to be 11.1, 68.6, 42.2, 21.4, 8.8, and 0.3, respectively. From the above, it was confirmed that the wavelength with the highest correlation with the absorption wavelength spectrum of influenza virus RNA is 260 nm with a correlation degree R _AE = 68.6. And, from the above test results, since the virus inactivation effect of the 260 nm UV-LED is the highest, it is considered that this correlation degree can be an index showing the inactivation of the virus. Next, the creation of a UV-LED with an R _AE higher than this 260 nm was considered.
[Example 1: Three-wavelength combined LED (HYBRID-LED)]

Here, we considered a hybrid LED that combines multiple UV-LEDs. Specifically, since a correlation degree R _AE = 68.6 was achieved with a single UV-LED, we aimed for a higher correlation degree R _AE = 70 or more. First, as shown in Figure 2, we created an ultraviolet sterilization device for viruses as Example 1, using three UV-LEDs with main emission peak wavelengths of 256 nm, 260 nm, and 270 nm, respectively. Here, each UV-LED was irradiated with a wavelength of 0.8 mW/cm ² (total 2.4 mW/cm ² ). Each light source had an irradiance of 2.4 mW/cm ^2. Figure 28 shows a graph of the combined emission spectrum of this ultraviolet sterilization device superimposed on the absorption spectrum of viral RNA. In addition to the composite emission spectrum of Example 1 (R _AE = 86.3), Figure 29 shows a graph in which the emission spectra of the above-mentioned 260 nm UV-LED as Reference Example 1 (R _AE = 68.6), the 270 nm UV-LED as Reference Example 2 (R _AE = 42.2), the 280 nm UV-LED as Reference Example 3 (R _AE = 21.4), and the low-pressure mercury lamp as Comparative Example 1 (R _AE = 11.1) are superimposed.

In FIG. 28, the degree of correlation R _AE with the absorption spectrum of viral RNA was 86.3, which was higher than that of the above-mentioned 260 nm UV-LED.
(Inactivation effect of 3-wavelength combined LED (HYBRID-LED))

Next, the inactivation effect against multiple viruses was confirmed by the ultraviolet sterilization device of Example 1. Here, H1N1 and H6N2 were used as viruses. H1N1 is a seasonal influenza, and the Spanish type (1918) and the Soviet type (1977) are known. On the other hand, H6N2 is a low pathogenic avian influenza virus (LPAI), and there have been no cases of human infection. The results of using these viruses are shown in Figures 30 to 33. In these figures, Figure 30 shows the infection ratio [log] when MDCK cells are infected with H1N1 using the ultraviolet light sources of Example 1, Reference Examples 1 to 3, and Comparative Example 1 at 4.8 mJ/cm ² , and Figure 31 shows the inactivation ratio against H6N2. Also, Figure 32 shows the inactivation ratio when the H1N1 virus is applied to the host embryonated chicken egg, and Figure 33 shows the inactivation ratio when the H6N2 virus is applied to the embryonated chicken egg. As shown in these figures, it was confirmed that the ultraviolet sterilization device of Example 1, which has a high correlation with the absorption spectrum of RNA, can effectively inactivate viruses.
(RNA toxicity of Example 1)

Furthermore, the RNA damage of the ultraviolet sterilization device for viruses according to Example 1 was examined. Here, the log survival ratio indicating inactivation was plotted on the vertical axis, and the correlation degree R _AE indicating the correlation with RNA was plotted on the horizontal axis in a scatter diagram. The results are shown in Figures 34 to 35. In these figures, Figure 34 shows an example of a host being MDCK, and Figure 35 shows an example of an embryonated chicken egg. In this way, it was confirmed that effective inactivation can be achieved by irradiating ultraviolet light of a wavelength that is highly correlated with the absorption spectrum of the viral RNA. That is, a strong correlation was confirmed between the viral RNA absorption spectrum and the ultraviolet emission spectrum. Furthermore, the results of summarizing the correlation between the inactivation ratio and the wavelength, and the correlation degree R _AE between inactivation and the correlation degree R AE for the hosts being MDCK and embryonated chicken eggs are shown in Figure 36. As shown in this figure, it was confirmed that there is a high correlation between inactivation and the correlation degree R _AE . It was also confirmed that for the inactivation of viruses, it is important that the emission spectrum has a waveform that fits the RNA absorption curve, rather than the wavelength.

As described above, it was confirmed that the ultraviolet sterilization device of Example 1 can effectively inactivate viruses that are highly correlated with viral RNA. In other words, it was confirmed that viruses can be effectively inactivated by approximating the combined emission spectrum of a combination of multiple UV-LEDs with different wavelengths to an absorption curve.

In addition, regarding the relationship between the virus subtype and the host, although differences in susceptibility were confirmed between the two virus subtypes, the inactivation tendency did not change. Furthermore, when the host was changed, the infectivity changed. However, even in this case, the inactivation tendency was not changed.

Furthermore, it was found that the key to inactivation is to irradiate the virus with a wavelength that fits the entire absorption curve, rather than the maximum absorption wavelength. In particular, it was confirmed that the correlation R _AE can be an index for effective inactivation.
(Differences in subtypes and hosts)

As shown in Figures 30 to 33, the susceptibility to UV differed depending on the virus subtype. Specifically, when comparing H1N1 and H6N2, H1N1 was inactivated by approximately log(-0.5) to log(-1). It has been reported that the characteristics of influenza infection differ depending on the subtype (Park J.E., et al., Infect. Genet. Evol.65:288-292.). Thus, the result that H1N1 was inactivated more is consistent with reports that the characteristics of infection differ depending on the subtype.

The infectivity of the virus also differed depending on the host. Specifically, when comparing MDCK and developing chicken eggs as hosts, MDCK was less susceptible to infection for both subtypes than developing chicken eggs. There are also reports that differences in hosts affect the infection status (Kash J.C., et. al., Am. J. Pathol. 2015, 185(6):1528-36). Therefore, when comparing the two host cells, MDCK and developing chicken eggs, developing chicken eggs are more susceptible to infection, which is consistent with reports that differences in hosts affect the infection status.

However, the tendency that the virus was most inactivated using the ultraviolet sterilization device of Example 1 was the same for all viruses. From these findings, it is believed that UV irradiation is similarly effective for other virus subtypes not examined in the above examples.
(effective wavelength range)

Furthermore, the inactivation effect of UV-LEDs and low-pressure mercury lamps differed depending on the wavelength. As mentioned above, the UV-LEDs with a main emission peak wavelength of 260 nm were the most effective. The 254 nm low-pressure mercury lamp of Comparative Example 1 showed the same level of inactivation as UV-LEDs with main emission peak wavelengths of 270 nm and 280 nm. Furthermore, for UV-LEDs with longer wavelengths, the inactivation efficiency decreased as the wavelength increased. For the UV-LEDs of the Reference Example, the order was 290 nm > 300 nm > 310 nm > 365 nm.

No change was observed in the viral HA, but toxic effects were observed in the viral vRNA. This suggests that the RNA that constitutes the virus was damaged, preventing it from replicating within the host cell.

In addition, when comparing the ultraviolet sterilization device for viruses according to Example 1 with the other six types of light sources, the 260 nm UV-LED according to Example 1 was the most effective in inactivating viruses compared to the other light sources. It was also more effective than the widely used low-pressure mercury lamp, which is thought to be due to the damage it caused to the viral RNA. In particular, according to Example 1, the effect of combining UV-LEDs of three different wavelengths and irradiating them with a total of 4.8 mW/cm ² was log(-3) in FFU (focus forming unit) as shown in FIG. 30. There is also a report that a combination of multiple wavelengths is more effective for sterilization, although not for influenza viruses (Nyangaresi PO, et al. Water. Res. 2018, 147:331-341.). According to this, it is said that the same effect was obtained with about half the energy compared to other reports that combined 267 nm and 275 nm, and the results were in line with the report. As far as the inventors of this application know, there are no reports of irradiation using a combination of three or more types of wavelengths. It has also been confirmed that ultraviolet light with a highly correlated wavelength is highly damaging to viral RNA.Furthermore, there are reports that a combination of UVC/UVB and UVA can effectively inactivate Escherichia coli (Song K., et al. Sci. Total. Environ. 2019, 665:1103-1110.), and that a combination of UVA-LED and low-pressure mercury lamps has a synergistic bactericidal effect on Vibrio parahaemolyticus (Nakahashi M., et al. Photochem. Photobiol. 2014, 90(6):1397-1403.).

From these, in order to effectively inactivate the virus, it was verified whether it is important to match the peak wavelength (260 nm) to the maximum absorption wavelength of the viral RNA, or to match the entire emission spectrum waveform of the light source to the absorption curve of the viral RNA. It was found that it is important to fit the emission wavelength to the viral RNA, which is believed to be the most effective way to inactivate the virus. In addition, the correlation degree R _AE defined as above allows an effective irradiation curve to be obtained, which can be used as a new index for inactivating influenza viruses.

As described above, 260 nm is the most effective UV-LED for inactivating influenza viruses, and by combining three UV-LEDs, 256 nm and 270 nm in addition to 260 nm, we succeeded in further improving the inactivation efficiency. In addition, the optimal wavelength for inactivation from viral RNA can be derived using the correlation degree R _AE as an index.
(Other viruses)

Next, we will consider other viruses. Viruses are classified as follows according to the classification system of the International Committee on Taxonomy of Viruses:
Group I - double-stranded DNA
Group II - single stranded DNA
Group VII - double-stranded DNA reverse transcription Group III - double-stranded RNA
Group IV - single stranded RNA + strand (acts as mRNA)
Group V - single-stranded RNA negative strand Group VI - single-stranded RNA positive strand reverse transcription

Here, three types of viruses were used: Feline calci virus, HSV-1, and Adenovirus. The results of inactivation of these viruses when irradiated with UV are shown in the graph of FIG. 37. Here, ultraviolet light was irradiated at 4.8 J/cm 2 using a low-pressure mercury lamp according to Comparative Example 1, a UV-LED with a main emission peak wavelength of 260 nm according to Reference Example 1, a UV-LED with a main emission peak wavelength of 270 nm according to Reference Example ² , a UV-LED with a main emission peak wavelength of 280 nm according to Reference Example 3, a UV-LED with a main emission peak wavelength of 310 nm according to Reference Example 6, and a UV-LED with a main emission peak wavelength of 365 nm according to Reference Example 7.

For reference, the results of inactivation by UV irradiation using a UVA-LED and a UVB-LED are shown in the graphs of Figures 38 and 39, respectively. In these figures, the horizontal axis represents UV-LED energy [J/ ^cm2 ], and the vertical axis represents cytopathic units (Log TCID50 (Tissue Culture Infectious Dose 50)). The viruses used were FCV, Herpes simplex virus-1 (HSV-1), Adenovirus, and H1N1.

Figure 40 shows the correlation between RT-qPCR products and FCV infection ratio after UV irradiation at 4.8 mJ/ ^cm2 . This graph shows Log CFU on the horizontal axis and RT-qPCR (reverse transcription qPCR) on the vertical axis. These figures show that there is a high correlation between the reduction in RT-qPCR products (damage to viral RNA) and the inactivation effect due to UV irradiation.

These findings confirm that viruses differ in their sensitivity to UV light, and that there is a good correlation between damage to the viral genome and inactivation.

In the above embodiment 1, an example of ultraviolet sterilization of viruses was described using three types of UV-LEDs with different main emission peak wavelengths, namely, those with main emission peak wavelengths of 256 nm, 260 nm, and 270 nm, but it goes without saying that the main emission peak wavelength of each UV-LED is not limited to the above. For example, the first main emission peak of the first UV-LED can be set to 245 nm to 260 nm, the second main emission peak of the second UV-LED can be set to 260 nm to 270 nm, and the third main emission peak of the third UV-LED can be set to 270 nm to 290 nm.
[Example 2]

In addition, in Example 1, an example was described in which the correlation degree R of the composite emission spectrum S(λ) of ultraviolet light emitted by a preselected first UV-LED, second UV-LED, and third UV-LED was calculated. Conversely, it is also possible to obtain an optimal combination of the first UV-LED, second UV-LED, and third UV-LED from the correlation degree R by simulation. Such an example is described below as an ultraviolet sterilization device for viruses according to Example 2.

In Example 2, three LEDs are used to study the optimal combination of LEDs for virus inactivation. Here, a computer simulation is performed according to the procedure shown in the flowchart in Figure 41.

First, in step S1, the emission spectrum of the UV-LEDs that are candidates for combination is obtained. Here, candidate UV-LEDs that are candidates for combination are prepared, and the emission spectrum of each UV-LED is measured. Here, eight candidate UV-LEDs with main emission peak wavelengths of 256 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, and 365 nm are prepared. The LED emission spectrum is also interpolated as necessary. For example, spline interpolation is used to interpolate in the range from 245 nm to 400 nm at intervals of 0.1 nm.

Next, in step S2, the viral RNA absorption spectrum A(λ) is obtained. Here, the RNA of H1N1 is measured as the target virus. Here, as with the LED emission spectrum, interpolation is performed as necessary. For example, spline interpolation is used to interpolate in the range from 245 nm to 400 nm at intervals of 0.1 nm. Here, the viral RNA absorption spectrum is normalized to be in the range from 0 to 1.

Further, in step S3, three LED emission spectra are extracted from the LED emission spectrum to obtain a composite emission spectrum S(λ). Here, three LED emission spectra are selected from the eight LED emission spectra S _i (λ), i=1, 2,...,8 obtained in step S1. The number of combinations is ₈ C ₃ =56, and each combination is superimposed. For example, the first LED emission spectrum, the second LED emission spectrum, and the third LED emission spectrum are superimposed to generate a composite emission spectrum S(λ)=S ₁ (λ)+S ₂ (λ)+S ₃ (λ). The composite emission spectrum S(λ) of the mixed LED combining three LEDs is normalized to be in the range of 0 to 1, similar to the viral RNA absorption spectrum.

Finally, in step S4, a combination is calculated that maximizes the correlation R ₀ in the above-mentioned equation 1. Here, all 56 combinations of UV-LEDs are examined to derive the combination that maximizes the correlation R ₀ .

As a result of carrying out such a simulation, it was confirmed that the correlation R o was maximized when a mixed LED composite emission spectrum obtained by using UV-LEDs with main emission _peak wavelengths of 256 nm, 270 nm, and 280 nm was used as the three UV-LEDs. The graph in Figure 42 shows the composite emission spectrum and the absorption spectrum of the H1N1 virus to be sterilized when the main emission peak wavelengths of 256 nm for the first UV-LED, 270 nm for the second UV-LED, and 280 nm for the third UV-LED are used in the ultraviolet sterilization device for viruses according to Example 2. In this example, the correlation R _o showed a high value of 119.3948.
[Example 3]

In the above example, an ultraviolet sterilization device for viruses was constructed using three types of UV-LEDs with different main emission peak wavelengths. However, the present invention does not limit the number of LEDs used to three, but may use four or more, or conversely, may use two. In this way, the present invention requires only the use of multiple UV-LEDs.

Here, an example of an ultraviolet sterilization device for viruses according to Example 3, using two UV-LEDs as shown in FIG. 1, will be described. In Example 3, as in Example 2, two LEDs were extracted from eight UV-LEDs by simulation to study the optimal combination of LEDs for virus inactivation. As a result of the simulation, it was confirmed that the correlation ratio R _o was maximized when using a mixed LED composite emission spectrum obtained from two UV-LEDs of 256 nm and 270 nm. This composite emission spectrum and the absorption spectrum of the viral RNA are shown in the graph of FIG. 43. In this example, the correlation ratio R _o was 107.6404.

The above results suggest that the correlation R _o of Equation 1 is greater when three UV-LEDs are combined than when two UV-LEDs are combined.
[Example 4]

In the above embodiments 2 and 3, examples were described in which an optimal combination of a first UV-LED, a second UV-LED, and optionally a third UV-LED was determined by simulation based on the correlation degree R. However, in the present invention, the targets selected based on the correlation degree R are not limited to candidate UV-LEDs, and combinations of their main emission peak wavelengths can also be calculated by simulation. Such an example will be described below as an ultraviolet sterilization device and method for viruses according to embodiment 4, based on the flowchart in FIG. 44. Here, since it is considered that the emission spectrum of the LEDs differs depending on the product and individual differences, the spectral half-width is estimated and a combination of UV-LEDs with the maximum correlation degree R _o is searched for.

First, two UV-LEDs are used to study the optimum combination of UV-LEDs that maximizes the correlation R _o . Here, a Monte Carlo simulation is performed according to the following procedure.

In step S1', the emission spectrum of the UV-LED is acquired. Specifically, the UV-LED emission spectrum is estimated based on a normal distribution f(m, σ). Here, m is the central wavelength of the LED emission spectrum, and σ is the half-width of the spectrum. σ can be estimated from the measured LED emission spectrum. The measured LED emission spectrum (central wavelength: 310 nm) and the estimated LED emission spectrum (normal distribution f(650, 50)) are shown in FIG. 45. In Example 4, fitting processing was performed as shown in FIG. 45, and σ was estimated to be 50. Also, as in Examples 2 and 3 described above, spline interpolation was used to interpolate in the range from 245 nm to 400 nm at intervals of 0.1 nm. Furthermore, the amplitude was normalized to be in the range from 0 to 1.

Next, in step S2', a composite emission spectrum is obtained. Here, two LED emission spectra are estimated based on a normal distribution f(m, 50). m can be selected randomly in the range of 245 nm to 310 nm. Similarly, the amplitude of the composite emission spectrum S(λ) can be selected randomly in the range of 0 to 1 using α and β. For example, it can be expressed as S(λ) = αS ₁ (λ) + βS ₂ (λ).

After selecting m and the spectral amplitudes α and β in this way, the two LED emission spectra are superimposed. This composite emission spectrum S(λ) = αS ₁ (λ) + βS ₂ (λ) is also normalized to be in the range of 0 to 1, similar to the viral RNA absorption spectrum.

Finally, in step S3', the combination with the maximum correlation R _o is calculated. Here, the number of trials is set to N, and m and the spectral amplitudes α and β are randomly selected to derive the combination with the maximum correlation R _o . As a result, a Monte Carlo simulation was performed N=1000 times, and it was confirmed that the correlation R _o is maximum when two estimated LED emission spectra are used, and when a synthetic emission spectrum obtained from 250.3 nm and 262.7 nm is used. Such a synthetic emission spectrum is shown in FIG. 46. Here, the correlation R _o was 152.6380. In addition, the maximum amplitudes of the emission spectra of the first UV-LED and the second UV-LED at this time were 0.9812 and 0.9353, respectively, in a state normalized so that the peak of the virus absorption spectrum was 1.
[Example 5]

In the above embodiment 4, an example was described in which a combination of main emission peak wavelengths with a maximum correlation R _o was calculated by simulation from a composite emission spectrum when two UV-LEDs are used. Similarly, an example in which a combination of main emission peak wavelengths with a maximum correlation R _o was calculated by simulation from a composite emission spectrum when three UV-LEDs are used will be described below as an ultraviolet sterilization device for viruses according to embodiment 5.

Here, the Monte Carlo simulation was performed N=1000 times using the three estimated LED emission spectra in the same procedure as in FIG. 41. As a result, when a composite emission spectrum obtained from the first UV-LED, the second UV-LED, and the third UV-LED, each having a first main emission peak wavelength of 247.4 nm, a second main emission peak wavelength of 257.6 nm, and a third emission peak wavelength of 268.1 nm, was used, the correlation degree R _o was maximized. This composite emission spectrum and the absorption spectrum of the virus RNA are shown in the graph of FIG. 47. The correlation degree R _o at this time was 181.9675. In addition, the maximum amplitudes of the emission spectra of the first UV-LED, the second UV-LED, and the third UV-LED at this time were 0.9814, 0.7312, and 0.9293, respectively, in a state normalized so that the peak of the virus absorption spectrum was 1.
[Example 6]

In the above Examples 2 to 5, the correlation between the absorption spectrum of the virus and the composite emission spectrum was calculated using Equation 1. However, the present invention does not limit the calculation of the correlation to Equation 1, and other equations, for example, Equation 2 to Equation 4, may be used. Here, in the example of Example 2 using three UV-LEDs, a case where the correlation R is calculated using Equation 2 instead of Equation 1 will be described as Example 6. Here, a computer simulation was performed according to the procedure shown in the flowchart of FIG. 41. As candidate UV-LEDs for combination, eight LEDs with main emission peak wavelengths of 256 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, and 365 nm were prepared and calculations were performed. As shown in the graph of FIG. 49, it was confirmed that when a composite emission spectrum obtained from three UV-LEDs, i.e., main emission peak wavelengths of 256 nm, 260 nm, and 270 nm, was used, R in Equation 2 was maximized (R = 0.8266). At this time, the ratio of the drive currents of the first UV-LED with a main emission peak wavelength of 256 nm, the second UV-LED with a main emission peak wavelength of 260 nm, and the third UV-LED with a main emission peak wavelength of 270 nm was 0.1:1:0.68.
[Example 7]

Similarly, in the example of Example 3 using two UV-LEDs, the case where the correlation degree R is calculated using Equation 2 instead of Equation 1 will be described as Example 7. Here again, when performing a computer simulation using the procedure shown in the flowchart of FIG. 41, eight candidate UV-LEDs with main emission peak wavelengths of 256 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, and 365 nm were prepared as combination candidates, and calculations were performed. As shown in the graph of FIG. 50, it was confirmed that when using two UV-LEDs, that is, a composite emission spectrum obtained from main emission peak wavelengths of 256 nm and 270 nm, R in Equation 2 was maximized (R = 0.8287). In this case, the ratio of the drive current of each UV-LED was 0.9:1 for the first UV-LED with a main emission peak wavelength of 256 nm and the second UV-LED with a main emission peak wavelength of 270 nm.

Thus, based on the correlation degree of Equation 2, when considering a combination of LEDs from eight candidate UV-LEDs, it is suggested that the correlation degree R of Equation 2 will be slightly greater when two candidate UV-LEDs are combined than when three candidate UV-LEDs are combined.
[Example 8]

In the above-mentioned Examples 6 and 7, as in Examples 2 and 3, an example was described in which an optimal combination of the first UV-LED and the second UV-LED, and optionally the third UV-LED, was found from the correlation degree R by simulation. However, as described above, in the present invention, the target to be selected from the correlation degree R _o is not limited to the candidate UV-LEDs, and a combination of main emission peak wavelengths can be calculated by simulation as in Example 4. In this case, the correlation degree is not limited to Equation 1, and other correlation degrees may be used. Here, an example is described as Example 8 in which the spectrum half width is estimated based on the flowchart of FIG. 44, and a combination of UV-LEDs with the maximum correlation degree R of Equation 2 is searched for. In this Example 8, as a result of performing Monte Carlo simulation N=5000 times, it was confirmed that when two estimated LED emission spectra were used, and when a mixed type LED emission spectrum obtained from 254.1 nm and 268.5 nm was used, R was maximum. As a result, the correlation degree R was 0.9184 as shown in FIG. 51. Furthermore, the maximum amplitudes of the spectra at this time were 0.8066 and 0.6711, respectively.
[Example 9]

In the above Example 8, an example was described in which a combination of main emission peak wavelengths with a maximum correlation R was calculated by simulation from a composite emission spectrum when two UV-LEDs are used. Similarly, an example is described below as Example 9 in which a combination of main emission peak wavelengths with a maximum correlation R defined by Equation 2 was calculated by simulation from a composite emission spectrum when three UV-LEDs are used.

Again, using the three estimated LED emission spectra, a Monte Carlo simulation was performed N=5000 times in the same manner as in FIG. 41. As a result, it was confirmed that the correlation degree R was maximum when using a mixed LED emission spectrum obtained from 249.7 nm, 261.4 nm, and 274.2 nm. The correlation degree R in this case was R=0.9694, as shown in FIG. 52. The maximum amplitudes of the spectra in this case were 0.8542, 0.8687, and 0.8822, respectively.

As described above, by combining multiple UV-LEDs with different main emission peak wavelengths, it is possible to obtain an ultraviolet sterilization device for viruses with improved inactivation effect by increasing the correlation with the absorption spectrum of the viral RNA to be sterilized.

The ultraviolet sterilization device and ultraviolet sterilization method for viruses disclosed herein can be suitably used as germicidal lamps installed at factory entrances or on ceilings, in toilets, in cars or trains, and in places used by an unspecified number of people, such as doors and counters.

100, 200...Ultraviolet sterilization device 1...First UV-LED
2...Second UV-LED
3...Third UV-LED
5... Current control unit 6... DC power supply WK... Sterilization object MS... Light of composite emission spectrum

Claims (14)

A virus ultraviolet sterilization device that inactivates specific viruses with ultraviolet light,
A first UV-LED emitting ultraviolet light having a first main emission peak wavelength;
A second UV-LED that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED;
a current control unit for supplying a drive current to each of the first UV-LED and the second UV-LED so that a composite emission spectrum obtained by simultaneously emitting light from the first UV-LED and the second UV-LED approximates an absorption spectrum of the specific virus; and
An ultraviolet sterilization device for viruses. The ultraviolet sterilization device for viruses according to claim 1,
The ultraviolet sterilization device for viruses has a correlation R o, defined by the following formula, of 0.7000 or more for a synthetic emission spectrum S(λ) produced by simultaneously emitting light from the first UV-LED and the second UV-LED when a driving current is supplied to each of the first UV-LED and the second UV- _LED by the current control unit, with an absorption spectrum A(λ) of the specific virus.

(In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.) The ultraviolet sterilization device for viruses according to claim 1,
The ultraviolet sterilization device for viruses has a correlation R, defined by the following formula, of 0.7000 or more for a synthetic emission spectrum S(λ) produced by simultaneously emitting light from the first UV-LED and the second UV-LED when a driving current is supplied to each of the first UV-LED and the second UV-LED by the current control unit, and an absorption spectrum A(λ) of the specific virus.

(In the above formula, cov represents the covariance of the absorption spectrum A(λ) and the composite emission spectrum S(λ), σ _A represents the standard deviation of the absorption spectrum A(λ), and σ _S represents the standard deviation of the composite emission spectrum S(λ).) The ultraviolet sterilization device for viruses according to claim 1,
The ultraviolet sterilization device for viruses has a correlation R AE, defined by the following formula, of 0.7000 or more for a synthetic emission spectrum S(λ) produced by simultaneously emitting light from the first UV-LED and the second UV-LED when a driving current is supplied to each of the first UV- _LED and the second UV-LED by the current control unit, with an absorption spectrum A(λ) of the specific virus.

(In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.) The ultraviolet sterilization device for viruses according to claim 1,
The ultraviolet sterilization device for viruses has a cosine similarity cos θ, defined by the following formula as the correlation between a synthetic emission spectrum S(λ) produced by simultaneously emitting light by supplying a driving current to each of the first UV-LED and the second UV-LED via the current control unit and an absorption spectrum A(λ) of the specific virus, of 0.7000 or more.

(In the above equation, N is the number of measured wavelengths, λ ₁ , . . . λ _N are the measured wavelengths, and the values of A(λ _i ) and S(λ _i ) are normalized from 0 to 1.) The ultraviolet sterilization device according to any one of claims 1 to 5,
The first main emission peak wavelength is 280 nm or less,
An ultraviolet sterilization device for viruses, wherein the second main emission peak wavelength is 280 nm or less. The ultraviolet sterilization device according to any one of claims 1 to 6,
The first main emission peak wavelength is included in the range of 245 nm to 257 nm;
The ultraviolet sterilization device for viruses, wherein the second main emission peak wavelength is included in the range of 257 nm to 270 nm. The ultraviolet sterilization device according to any one of claims 2 to 5 , further comprising:
a third UV-LED that emits ultraviolet light having a third main emission peak wavelength different from the first main emission peak wavelength and the second main emission peak wavelength;
The current control unit supplies a drive current to each of the first UV-LED, the second UV-LED, and the third UV-LED to emit light, and the correlation degree of a synthetic emission spectrum S(λ) obtained by combining the ultraviolet rays of the first UV-LED, the second UV-LED, and the third UV-LED with an absorption spectrum A(λ) of the specific virus is 0.7000 or more. The ultraviolet sterilization device for viruses according to claim 8,
The third main emission peak wavelength is included in 270 nm to 380 nm. The ultraviolet sterilization device according to any one of claims 1 to 9,
The ultraviolet sterilization device, wherein the current control unit varies the value of the driving current supplied to the first UV-LED and the second UV-LED. The ultraviolet sterilization device according to any one of claims 1 to 10,
The ultraviolet sterilization device, wherein the current control unit sets the ratio of the driving current supplied to the first UV-LED and the second UV-LED to be from 1:0 to 0:1. The ultraviolet sterilization device according to any one of claims 2 to 5 ,
The current control unit pre -sets drive current values at which the correlation with the synthetic emission spectrum is 0.7000 or more, corresponding to the absorption spectra of a plurality of different viruses, and is capable of switching between these plurality of drive current values. The ultraviolet sterilization device according to any one of claims 2 to 5 ,
An ultraviolet sterilization device for viruses, wherein the correlation degree is 0.8000 or more. A method for sterilizing a virus by ultraviolet light, which inactivates a specific virus with ultraviolet light,
Preparing a first UV-LED that emits ultraviolet light having a first main emission peak wavelength and a second UV-LED that emits ultraviolet light having a second main emission peak wavelength different from that of the first UV-LED;
a step of simultaneously emitting light from the first UV-LED and the second UV-LED, and supplying a drive current to each of the first UV-LED and the second UV-LED by a current control unit so that the combined emission spectrum is approximated to the absorption spectrum of the specific virus;
A method for sterilizing a virus with ultraviolet light, comprising: