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A disinfection lighting device

FIELD OF THE INVENTION

The invention relates to a disinfection lighting device comprising at least one first UV light source comprising one or more solid-state light sources configured to, in operation, emit first UV light having a first dominant wavelength peak, XI, and a first spatial light distribution, SI, in a first main direction, DI, at least one second UV light source comprising one or more solid-state light sources configured to, in operation, emit second UV light having a second dominant wavelength peak, X2, and a second spatial light distribution, S2, in a second main direction, D2, and a photocatalytic layer.

BACKGROUND OF THE INVENTION

It is desired to protect yourself and others from the spread of bacteria and viruses such as influenza or against the outbreak of novel viruses like the recent COVID- 19. UV (Ultra-Violet) light can be used for disinfection. Therefore, UV light for disinfection has become a topic of renewed interest as the demand for disinfection and sterilization increases.

UV light has been used for disinfection for over 100 years. Wavelengths between about 190 nm and 300 nm may be strongly absorbed by nucleic acids, which may result in defects in an organism’s genome. This may be desired for inactivating (killing), bacteria and viruses, but may also have undesired side effects for humans. Therefore, the selection of wavelength of radiation, intensity of radiation and duration of irradiation may be limited in environments where people may reside such as offices, public transport, cinema’s, restaurants, shops, etc., thus limiting the disinfection capacity. Especially in such environments, additional measures of disinfection may be advantageous to prevent the spread of bacteria and viruses such as influenza or novel (corona) viruses like COVID-19, SARS and MERS.

The ultraviolet wavelength range is defined as light in a wavelength range from 100 to 380 nm. UV light suitable for disinfection purposes may in general terms be divided into three main types, namely UVA light with a wavelength in the range of 315 to 400 nm, UVB light with a wavelength in the range of 280 to 315 nm and UVC light with a wavelength in the range of 100 to 280 nm. UVC light inactivates both bacteria and viruses but may also be harmful to human beings and other living creatures. UVA light can only be used for killing viruses. Also, the germicidal effect of UV light varies within the spectrum of UV light. Furthermore, different bacteria and viruses may be vulnerable to different wavelengths of UV light. The ultraviolet wavelength range can in more details be divided into different types of UV light / UV wavelength ranges (Table 1). Different UV wavelengths of radiation may have different properties and thus may have different compatibility with human presence and may have different effects when used for disinfection (Table 1). Table 1: Properties of different types of UV, violet, and NIR wavelength light

Each UV type / wavelength range may have different benefits and/or drawbacks. Relevant aspects may be (relative) sterilization effectiveness, safety (regarding radiation), and ozone production (as result of its radiation). Depending on an application a specific type of UV light or a specific combination of UV light types may be selected and provides superior performance over other types of UV light. UV-A may be (relatively) safe and may inactivate (kill) bacteria, but may be less effective in inactivating (killing) viruses. UV-B may be (relatively) safe when a low dose (i.e. low exposure time and/or low intensity) is used, may inactivate (kill) bacteria, and may be moderately effective in inactivating (killing) viruses. UV-B may also have the additional benefit that it can be used effectively in the production of vitamin D in a skin of a person or animal. Near UV-C may be relatively unsafe, but may effectively inactivating, especially kill bacteria and viruses. Far UV may also be effective in inactivating (killing) bacteria and viruses, but may be (relatively to other UV- C wavelength ranges) (rather) safe. Far-UV light may generate some ozone which may be harmful for human beings and animals. Extreme UV-C may also be effective in inactivating (killing) bacteria and viruses, but may be relatively unsafe. Extreme UV-C may generate ozone which may be undesired when exposed to human beings or animals. In some application ozone may be desired and may contribute to disinfection, but then its shielding from humans and animals may be desired. Hence, in the table “+” for ozone production especially implies that ozone is produced which may be useful for disinfection applications, but may be harmful for humans / animals when they are exposed to it. Hence, in many applications this “+” may actually be undesired while in others, it may be desired. The types of light indicated in above table may in embodiments be used to sanitize air and/or surfaces.

The terms “inactivating” and “killing” with respect to a virus may herein especially refer to damaging the virus in such a way that the virus can no longer infect and/or reproduce in a host cell, i.e., the virus may be (essentially) harmless after inactivation or killing.

The disinfecting light, i.e. the first and second UV light, may therefore comprise a wavelength selected from the ultraviolet wavelength range (and/or optionally the violet wavelength range). However, other wavelengths are herein not excluded.

CN 214198329 U discloses a sterilizing panel lamp comprising an air suction and air outlet ports. The lamp comprises a combination of UVC LEDs and UVA LEDs and also comprises a photocatalytic material coating on a carrier for sterilization. The photocatalyst carrier is irradiated by the UVA LEDs.

Other disinfection systems may use one or more anti-microbial and/or antiviral means to disinfect a space or an object. Examples of such means may be chemical agents which may raise concerns. For instance, the chemical agents may also be harmful for people and pets. It appears desirable to produce systems, that provide alternative ways for air treatment, such as disinfection. Further, existing systems for disinfection may not easily be implemented in existing infrastructure, such as in existing buildings like offices, hospitality areas, etc. and/or may not easily be able to serve larger spaces. This may again increase the risk of contamination. Further, incorporation in HVAC systems may not lead to desirable effects and appears to be relatively complex. Further, existing systems may not be efficient, or may be relatively bulky, and may also not easily be incorporated in functional devices, such as e.g. luminaires.

It is in particular desired to provide a lighting device providing improved disinfection.

It is further desired to provide such an improved lighting device which better exploits the fact that the lifetime of UVA solid-state light sources, and in particular LEDs, is much longer than UVC solid-state light sources, and in particular LEDs, and the fact that UVA solid-state light sources are much cheaper than UVC solid-state light sources .

Also, as UV light for disinfection has become a topic of renewed interest new safety restrictions and legislation has emerged, and it is therefore further desired to provide such an improved lighting device which also fulfills the requirements of the new safety restrictions and legislation.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide a lighting device of the type mentioned by way of introduction which provides for improved disinfection.

It is a further object of the invention to provide such a lighting device which exploits the fact that the lifetime of UVA solid-state light sources is much longer than UVC solid-state light sources, and the fact that UVA solid-state light sources are much cheaper than UVC solid-state light sources such as to further be cheaper to produce and more durable in use, that is has a longer expected lifetime.

It is a still further object of the invention to provide such a lighting device which also fulfills the requirements of the new safety restrictions and legislation.

According to a first aspect of the invention, this and other objects are achieved by means of a disinfection lighting device comprising at least one first UV light source comprising one or more solid-state light sources configured to, in operation, emit first UV light having a first dominant wavelength peak, XI, and a first spatial light distribution, SI, in a first main direction, DI, at least one second UV light source comprising one or more solid- state light sources configured to, in operation, emit second UV light having a second dominant wavelength peak, X2, and a second spatial light distribution, S2, in a second main direction, D2, and at least one photocatalytic layer arranged such that at least a part of the first UV light in operation impinges on the photocatalytic layer and thus activate the photocatalytic layer, where the disinfection lighting device further comprises a controller configured to (individually) control the at least one first UV light source and the at least one second UV light source, where the wavelength of the first dominant wavelength peak XI is larger than the wavelength of the second dominant wavelength peak X2, where the first main direction DI is different from the second main direction D2 and/or the first spatial light distribution SI is different from the second spatial light distribution S2, and where the disinfection lighting device is configured to, in operation, provide a total amount of UV light being the sum of the first UV light and the second UV light, and the controller is configured to control the magnitude of the fraction of the total amount of UV light which in operation impinges on the photocatalytic layer.

It is to be noted, that following the general mathematical meaning of the word direction, two light sources can emit light in the same direction also when these light sources are on different positions, that is the light of the two light sources is emitted in parallel. Further, spatial light distribution is a characteristic of a light source. Evidently, this characteristic is independent on the position of the light source and therefore two light sources at different positions can have the same spatial light distribution.

The solid-state light sources may comprise one or more laser diodes, one or more LEDs, and/or one or more super-luminescent diodes. Due to safety restrictions and legislation, the total amount of UV light which a disinfection lighting device of the type mentioned by way of introduction may provide in operation is limited and is dependent on both the first dominant wavelength peak XI and the second dominant wavelength peak X2. For instance, while UVC light inactivates both bacteria and viruses, UVA light can only be used for killing viruses, or the UVA light needs to be combined with a photocatalytic layer. The photocatalytic performance depends on the surface area of the photocatalytic layer irradiated and the intensity of the light. The intensity of light with longer UV wavelengths, such as UVA light, allowed by safety restrictions and legislation is much higher than the allowable intensity of light with shorter UV wavelengths, such as UVC light. The lifetime of solid-state light sources, such as UVA LEDs, providing light with longer UV wavelengths is much longer than the lifetime of solid-state light sources, such as UVC LEDs, providing light with shorter UV wavelengths. Also, solid-state light sources, such as UVA LEDs, providing light with longer UV wavelengths are much cheaper than the lifetime of solid-state light sources, such as UVC LEDs, providing light with shorter UV wavelengths. Therefore, providing a disinfection lighting device with light sources providing a combination of light with different UV wavelengths, for instance UVC light and UVA light, in combination with a photocatalytic layer improves the disinfection performance.

Therefore, by in particular providing that the controller is configured to (individually) control the at least one first UV light source and the at least one second UV light source, and further to control the magnitude of the fraction of the total amount of UV light which in operation impinges on the photocatalytic layer and thus is used to activate the photocatalytic layer, the disinfection performance of the lighting device may be controlled such as to be further improved and also adapted to the circumstances prevailing at a given place and to a given time.

The fraction is defined as follows: let Li be the amount of first UV light and xi the portion of this light that impinges on the photocatalytic layer, and in the same way, let L2 be the amount of second UV light and X2 the portion of this light that impinges on the photocatalytic layer, then the fraction is (xi.Li + X2.L2)/(LI + L2), with 0<xi<l and 0<X2<l.

The controller is arranged to control the magnitude of this fraction, which requires that xi X2, preferably xi > X2. The absolute value of the difference between xi and X2 should be preferably at least 0.3, more preferably at least 0.6 and most preferably at least 0.9. Note, that in case xi = X2 the fraction will be constant and independent from Li and L2, therewith it will not be possible to control the magnitude of the fraction.

Also, such a control of the light sources provides the possibility of using the solid-state light sources providing light with longer UV wavelengths more and the solid-state light sources providing light with shorter UV wavelengths less. This in turn provides for an improved exploitation of the above-mentioned differences in lifetime and costs of the solid- state light sources. Thereby, a lighting device which is cheaper to produce, is more durable in use, and has a longer expected lifetime is provided for, and which further also fulfills the requirements of the new safety restrictions and legislation.

In an embodiment, the controller is further configured to individually control the at least one first UV light source and the at least one second UV light source.

In an embodiment, the first main direction DI is different from the second main direction D2 and the first spatial light distribution SI is different from the second spatial light distribution S2. Providing different main directions of emission provides for a lighting device with which disinfection in different directions, and thus of different parts of, e.g., a room in which the lighting device is mounted, may be obtained.

Providing different spatial light distributions provides for a lighting device with which the first UV light and the second UV light may be directed differently, for instance such that one of the first UV light and the second UV light may be used for a more generalized disinfection and the other may be used for localized disinfection, such as for instance of a particular object, such as a table or a chair.

In an embodiment, the controller is configured to control the magnitude of the fraction of the total amount of UV light which in operation impinges on the photocatalytic layer by controlling a ratio between the part of the first UV light which in operation impinges on the photocatalytic layer and the sum of the remaining part of the first UV light and the second UV light.

Thereby, control of the magnitude of the fraction of the total amount of UV light which in operation impinges on the photocatalytic layer is provided in a straightforward manner.

In an embodiment, the control of the ratio between the part of the first UV light which in operation impinges on the photocatalytic layer and the sum of the remaining part of the first UV light and the second UV light may be obtained by controlling the intensity of the part of the first UV light which in operation impinges on the photocatalytic layer and the sum of the intensities of the remaining part of the first UV light and the second UV light.

Thereby, control of the magnitude of the fraction of the total amount of UV light which in operation impinges on the photocatalytic layer is provided in a manner being particularly simple to invoke in or by use of a controller.

In an embodiment, the controller is further adapted for controlling the magnitude of a surface area of the photocatalytic layer irradiated by the part of the first UV light which in operation impinges on the photocatalytic layer.

Thereby, a further way of controlling the photocatalytic performance is provided.

In an embodiment, the wavelength of the first dominant wavelength peak XI is at least 30 nm, at least 40 nm, at least 50 nm or at least 60 nm larger than the wavelength of the second dominant wavelength peak X2. In other words, XI - X2 > 30 nm, XI - X2 > 40 nm, XI - X2 > 50 nm or XI - X2 > 60 nm. Thereby it is ensured that the lighting device emits UV light with a broader range of wavelengths, which in turn further improves the disinfection efficiency.

In an embodiment, the intensity of the first dominant wavelength peak XI is larger than the intensity of the second dominant wavelength peak X2.

Thereby, the fact that the intensity of light with longer UV wavelengths, such as UVA light, allowed by safety restrictions and legislation is much higher than the allowable intensity of light with shorter UV wavelengths, such as UVC light, may exploited more fully such as to enable providing a lighting device with optimal disinfection efficiency.

In an embodiment, the at least one first UV light source comprises a first optical power, Woptl, wherein the at least one second UV light source comprises a second optical power, Wopt2, and wherein Woptl > 2 * Wopt2, or Woptl > 5 * Wopt2, or Woptl > 8 * Wopt2, or even Woptl > 10 * Wopt2.

Thereby, the fact that the optical power of light with longer UV wavelengths, such as UVA light, allowed by safety restrictions and legislation is much higher than the allowable optical power of light with shorter UV wavelengths, such as UVC light, may exploited more fully such as to enable providing a lighting device with optimal disinfection efficiency.

In an embodiment, the first dominant wavelength peak I lies within the UVA spectrum and wherein the second dominant wavelength peak X2 lies within the UVC spectrum.

Thereby, a lighting device is provided with which it may be exploited that the above-described advantages relating to lifetime and costs of LEDs are particularly profound when it comes to UVA LEDs and UVC LEDs.

In an embodiment, the at least one first UV light source and the at least one second UV light source are both configured to be operated in a direct mode in which the first UV light and the second UV light does not impinge on the photocatalytic layer, or in which at least 95 % of the first UV light and the second UV light does not impinge on the photocatalytic layer.

Thereby, most or all light from the first and second UV light sources may be used for direct or photolytic disinfection. This may in turn provide for a faster disinfection of a surface which it is desired to disinfect.

In an embodiment, the at least one first UV light source is configured to be operated in an indirect mode, in which at least a part of the first UV light impinges on the photocatalytic layer, and the at least one second UV light source is configured to be operated in a direct mode in which the second UV light does not impinge on the photocatalytic layer.

Thereby, a part of, most or even all light from the first UV light source may be used for indirect or photocatalytic disinfection, while all light from the second UV light source may be used for direct or photolytic disinfection. Thereby air disinfection and surface disinfection may be performed simultaneously.

In an embodiment, the first spatial light distribution SI is larger than the second spatial light distribution S2. For instance, the full width at half maximum of the first UV light, FWHM1, is larger than or equal to the full width at half maximum of the second UV light FWHM2, or FWHM1 > FWHM2 + 10 degrees or FWHM1 > FWHM2 + 20 degrees or FWHM1 > FWHM2 + 30 degrees.

Thereby, a lighting device is provided with which the fact that the first UV light with longer UV wavelengths, which has the first spatial light distribution SI, may be provided with a higher intensity than the second UV light with shorter UV wavelengths, which has the second spatial light distribution S2, may be exploited to disinfect a larger area with the first UV light than with the second UV light. This in turn further improves the disinfection efficiency of the lighting device.

In an embodiment, the disinfection lighting device further comprises at least one third light source configured to, in operation, emit white light.

Thereby, a lighting device is provided which may work both as a disinfection lighting device and an ordinary lighting device for lighting up a room or area.

In an embodiment, the at least one first UV light source comprises a larger number of solid-state light sources than the at least one second UV light source. In an embodiment, the at least one first UV light source comprises more than five times, more than six times or more than eight times as many solid-state light sources than the at least one second UV light source.

Thereby, a lighting device is provided with which it may be exploited that the above-described advantages relating to lifetime and costs of solid-state light sources are exploited even further, as the number of solid-state light sources of the first UV light source is increased and the number of solid-state light sources of the second UV light source is decreased.

In an embodiment, the at least one first UV light source and the at least one second UV light source are provided on the same substrate, on the same heat sink element or both. Thereby, a lighting device with a particularly simple structure is provided.

In an embodiment, the first main direction DI and the second main direction D2 are perpendicular to one another. In other embodiments, the first main direction DI and the second main direction D2 extend in an angle being larger than 45 degrees, larger than 60 degrees or larger than 80 degrees. In alternative or additional embodiments, the first main direction DI and the second main direction D2 extend in an angle being smaller than 180 degrees, smaller than 150 degrees, smaller than 135 degrees or smaller than 90 degrees.

Thereby, a lighting device is provided with which both disinfection close to a surface on which the lighting device is mounted and disinfection farther away from the lighting device, such as disinfection of, e.g., objects in a room, may be provided.

Also, if the disinfection lighting device is placed in a space where people are present, potentially harmful UVC light may in this way be targeted in a first direction away from where people go about, e.g. towards a wall or a ceiling or close to and parallel with a ceiling, and the UVA and/or UVB light may be targeted in a direction where people are present. Consequently, the strong germicidal effect from the UVC light is still achieved, without posing a risk to any people. However, recent studies have shown that deep UVC light, 200 nm - 230 nm, may not be harmful to people, as a result of a low skin penetration depth, such deep UVC light may in some embodiments be targeted to where people are present.

In an embodiment, the disinfection lighting device is configured to be operated in an intermittent way such that over time a switching between a second light, and particularly UVC, disinfection mode and a first light, and in particular UVA, and photocatalytic oxidation mode is obtained. This may for example be obtained by configuring the controller to operate the disinfection lighting device correspondingly.

Thereby, a lighting device is provided which may be controlled to adapt to varying conditions, such as people coming and going, in a particularly simple manner.

In an embodiment, the at least one second UV light source comprises a plurality of solid-state light sources being a combination of UCV solid-state light sources and UVB solid-state light sources.

In embodiments, the light may comprise a wavelength in the UV-A range. In further embodiments, the light may comprise a wavelength in the UV-B range. In further embodiments, the light may comprise a wavelength in the Near UV-C range. In further embodiments, the light may comprise a wavelength in the Far UV range. In further embodiments, the light may comprise a wavelength in the extreme UV-C range. The Near UV-C, the Far UV and the extreme UV-C ranges may herein also collectively be referred to as the UV-C range. Hence, in embodiments, the light may comprise a wavelength in the UV- C range. In other embodiments, the light may comprise violet radiation.

Thereby, a light emitting device is provided with which advantageous germicidal effects related to UVB light may also be obtained.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Fig. 1 shows a cross sectional side view of a disinfection lighting device according to an embodiment of the invention and comprising a first UV light source comprising LEDs configured to, in operation, emit first UV light and a second UV light source comprising an LED configured to, in operation, emit second UV light in a mode in which only the first UV light source emits light.

Fig. 2 shows a cross sectional side view of the disinfection lighting device according to Fig. 1 in a mode in which only the second UV light source emits light.

Fig. 3 shows a cross sectional side view of a disinfection lighting device according to another embodiment of the invention in a mode in which only the first UV light source emits light.

Fig. 4 shows a cross sectional side view of the disinfection lighting device according to Fig. 3 in a mode in which only the second UV light source emits light.

Fig. 5 shows a cross sectional side view of a disinfection lighting device according to another embodiment of the invention in a mode in which both the first UV light source and the second UV light source emits light.

Fig. 6 shows a logarithmic plot of the maximum allowable relative spectral disinfection effectiveness of UV light as a function of wavelength and further illustrating an exemplary first dominant peak wavelength XI of first light emitted by a first UV light source and a second dominant peak wavelength Z2 of second light emitted by a second UV light source, respectively, of a disinfection lighting device according to the invention. The dotted line illustrates the maximum allowable relative spectral disinfection effectiveness for skin, while the solid line illustrates the maximum allowable relative spectral disinfection effectiveness for eyes, as a function of wavelength. As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

Figs. 1 and 2 show cross sectional side views of a disinfection lighting device 1 according to an embodiment of the invention. The lighting device 1 generally and irrespective of the embodiment comprises a first UV light source 2 comprising one or more solid-state light sources 21, 22 configured to, in operation, emit first UV light 3 and a second UV light source 4 comprising one or more solid-state light sources 41 configured to, in operation, emit second UV light 5. Fig. 1 shows the lighting device 1 in a mode in which only the solid-state light sources 21, 22 of the first UV light source 2 emits UV light 3. Fig. 2 shows the lighting device 1 in a mode in which only the solid-state light source 41 of the second UV light source 4 emits UV light 5. The lighting device 1 generally and irrespective of the embodiment further comprises a photocatalytic layer 6 and a controller 7.

In the embodiment shown, the first UV light source 2 comprises a larger number of solid-state light sources 21, 22 than the at least one second UV light source 4. More particularly, the first UV light source 2 comprises five solid-state light sources 21, 22 configured to, in operation, emit first UV light 3 and the second UV light source 4 comprises one solid-state light source 41 configured to, in operation, emit second UV light 5. Other numbers of solid-state light sources 21, 22 and LEDs 41 are also feasible.

The first UV light 3 emitted by the solid-state light sources 21, 22 of the first light source 2 is generally and irrespective of the embodiment emitted in a first main direction, DI. In the first main direction DI the first UV light 3 comprises a first dominant wavelength peak, XI, and a first spatial light distribution, SI. The second UV light 5 emitted by the solid-state light source 41 of the second light source 4 is generally and irrespective of the embodiment emitted in a second main direction, D2. In the second main direction D2 the second UV light 5 comprises a second dominant wavelength peak, X2, and a second spatial light distribution, S2. The first UV light 3 may be UVA light. Thus, the first dominant wavelength peak I may he within the UVA spectrum. The second UV light 5 may be UVC light or a combination of UVC light and UVB light. The second dominant wavelength peak X2 may he within the UVC spectrum. Consequently, the second spectral distribution S2 may comprise one or more wavelengths within the UVC spectrum, 100 nm - 280 nm and/or one or more wavelengths with the UVB spectrum, 280 nm - 320 nm, and the first spectral distribution SI may comprise one or more wavelengths within the UVA spectrum, 320 nm - 400 nm. Therefore, the wavelength of the first dominant wavelength peak I is generally larger than the wavelength of the second dominant wavelength peak X2. For instance, the wavelength of the first dominant wavelength peak XI may be more than 30 nm, or even more than 40 nm, larger than the wavelength of the second dominant wavelength peak X2. Further, the intensity of the first dominant wavelength peak XI may be larger than the intensity of the second dominant wavelength peak X2.

The first UV light source 2 further comprises a first optical power, Woptl, and the second UV light source 4 comprises a second optical power, Wopt2. The first optical power Woptl may be more than two times larger than the second optical power Wopt2.

Furthermore, in the embodiment shown in Figs. 1 and 2, the first spatial light distribution SI is different from the second spatial light distribution S2, while the first main direction DI is the same as the second main direction D2. For instance, the first spatial light distribution SI may be larger than the second spatial light distribution S2. In other embodiments, the first spatial light distribution SI may be the same as the second spatial light distribution S2, while the first main direction DI is different from the second main direction D2.

Generally, and irrespective of the embodiment, the controller 7 is configured to (individually) control the first and second UV light sources 2 and 4, and in particular the solid-state light sources 21, 22 and 41, respectively, of the first and second UV light sources 2 and 4. The controller 7 may configured to control at least a part of the first UV light 3 which impinges on the photocatalytic layer 6 such that the first UV light source 2 is used to activate the photocatalytic layer 6. Especially, the controller 7 may be configured to control a ratio between at least the part of the first UV light 3 which impinges on the photocatalytic layer 6 and the second UV light 5. The ratio may for instance be expressed in terms of the ratio of the intensity of the part of the first UV light 3 which impinges on the photocatalytic layer 6 to the sum of the intensities of the remaining part of the first UV light 3 and of the second UV light 5.

The controller 7 may further be configured to operate the lighting device 1 in an intermittent way such that over time a switching between a UVC disinfection mode, i.e. the second light source 4 emitting second UV light 5 (Fig. 2), and a UVA and photocatalytic oxidation mode, i.e. the first light source 2 emitting first UV light 3 (Fig. 1), is obtained. The controller 7 may further be configured to control the magnitude of a surface area of the photocatalytic layer 6 irradiated by the part of the first UV light 3 which in operation impinges on the photocatalytic layer 6.

As shown in Figs. 1-4, the controller 7 is mainly for the sake of clarity arranged on a surface of a heat sink element 11 to be described further below. It is also feasible to integrate the controller 7 into the heat sink element for a more compact and aesthetically more pleasing construction. The controller 7 may be any feasible type of controller.

The photocatalytic layer 6 is arranged such that when the first UV light source is in operation, the first UV light 3, or at least a part of the first UV light 3, emitted by the first light source 2 impinges on and activates the photocatalytic layer 6. In the embodiment shown in Figs. 1 and 2, the photocatalytic layer 6 is arranged at a light exit surface 12 of the lighting device 1. More particularly, the photocatalytic layer 6 may be arranged at a part of the light exit surface 12 extending over the first light source 2. The photocatalytic layer 6 may be or comprise any suitable type of photocatalyst materials suitable for decomposing detrimental substances, such as in particular bacteria or virus but also bad smells, stains and nitrogen oxides (N0 _x ), under light containing UV rays. A commonly used example of a suitable such photocatalyst is titanium dioxide (TiCh). Another example of a photocatalyst being efficient in the UV range is sodium tantalite (NaTaOs). optionally doped with lanthanum and loaded with a cocatalyst nickel oxide (NiO). The photocatalytic layer may be provided as a separate element or as a coating or a layer provided on a substrate.

When first UV light 3 emitted by the first light source 2 impinges on and activates the photocatalytic layer 6, the result is that electron hole pairs are generated and emitted from the photocatalytic layer in a direction (arrow 17) away from the first light source 2, in a direction (arrow 19) back towards the first light source 2 or both. The electron hole pairs react with molecules in the air creating free radicals, e.g. OH' or 02', which in turn react with and degrade bacteria and virus in the air. The second UV light source 4 is configured to be operated, for instance by the controller 7, in a direct mode in which the second UV light 5 does not impinge on the photocatalytic layer 6. The first UV light source 2 is configured to be operated, for instance by the controller 7, in either a direct mode in which the first UV light 3 does not impinge on the photocatalytic layer 6, or in an indirect mode, in which at least a part of the first UV light 3 impinges on the photocatalytic layer 6.

In the embodiment shown in Figs. 1 and 2, the lighting device 1 further comprises an optional third light source 8 configured to, in operation, emit white light 9 (Fig. 1). The third light source 8 may for instance comprise a white solid-state light source 81. Where a third light source 8 is provided, the controller 7 may further be configured to operate the third light source 8, for instance to switch between the third light source 8 being on (Fig. 1) and off (Fig. 2). The third light source 8 may also be configured to, in operation, emit visible light of another color than white. Thus, the third light source 8 may also comprise one or more solid-state light sources 81 of another color than white, such as red, green or blue.

The at least one first UV light source 2, and thus the first solid-state light sources 21, 22, and the at least one second UV light source 4, and thus the second solid-state light source 41, are provided on the same substrate 10. It is also feasible to provide at least one first UV light source 2, and thus the first solid-state light sources 21, 22, on one substrate, and to provide the at least one second UV light source 4, and thus the second solid- state light source 41, on another substrate. The substrate 10 may for instance be a printed circuit board (PCB). Further, in the embodiment shown in Figs. 1 and 2 the third light source 8 is arranged on a substrate 18 being different from the substrate 10. Alternatively, the third light source 8 may be arranged on the same substrate as the first light source or on the same substrate as the second light source, or the first, second and third light source may all be arranged on one and the same substrate.

The first solid-state light sources 2, the second solid-state light sources 4 and third solid-state light sources 8, respectively, may comprise one or more laser diodes, one or more LEDs, and/or one or more super-luminescent diodes.

In the embodiment shown in Figs. 1 and 2, the lighting device 1 further comprises an optional heat sink element 11. The substrates 10 and 18 are attached to the heat sink element 11. Thus, the substrates 10 and 18 are arranged between the respective solid- state light sources 21, 22, 41, 81 and the heat sink element 11. The heat sink element 11 serves to lead heat generated by the solid-state light sources 21, 22, 41, 81, away from the solid-state light sources 21, 22, 41, 81 and the substrates 10, 18. The heat sink element 11 is made of a material having a good thermal conductivity, such as a suitable metal or alloy.

The solid-state light sources 21, 22, 41, 81 may further optionally be provided with a respective cover or covering layer 13, 14, 15. The cover or covering layer 13, 14, 15 is transparent and may serve to protect the solid-state light sources 21, 22, 41, 81 from external influences such as dust and moisture, thereby extending the lifetime of the solid-state light sources 21, 22, 41, 81. The cover or covering layer 13, 14, 15 may further optionally comprise diffusing elements, light outcoupling elements, light conversion elements or a combination thereof.

Figs. 3 and 4 show cross-sectional side views of a lighting device 100 according to another embodiment of the invention. Fig. 3 shows the lighting device 100 in a mode in which only the solid-state light sources 21, 21’ of the first UV light source 2 emits light. Fig. 4 shows the lighting device 100 in a mode in which only the solid-state light sources 41 of the second UV light source 4 emits light. The lighting device 100 differs from the lighting device 1 described above in relation to Figs. 1 and 2 in virtue of the following.

The substrate 10, on which the solid-state light sources 21, 21’ and 41 are arranged, is in this embodiment substantially though-shaped and comprises two side sections 110 and 111 tapering towards one another and connected by a bottom section 112 extending between the ends of the two side sections 110 and 111 being closest to one another. The heat sink element 11 is arranged in the cavity formed by the sections 110, 111, 112 of the substrate 10. The heat sink element 11 is therefore substantially trapezoid in cross section.

The lighting device 100 comprises two first light sources 2, 2’, each with two LEDs 21, respectively 21’. The solid-state light sources 21 are arranged on the side section 110 of the substrate 10, and the solid-state light sources 21 ’ are arranged on the opposite side section 111 of the substrate 10. In operation, the solid-state light sources 21 emit light 3 in a first direction of emission DI and the solid-state light sources 21’ emit light 3’ in a first direction of emission DI’. The lighting device 100 further comprises a second light source 4 with two LEDs 41. The solid-state light sources 41 are arranged on the bottom section 112 of the substrate 10. In operation, the solid-state light sources 41 emit light 5 in a second direction of emission D2. The first directions DI and DI’ are mutually opposite and extend in the same angle with the second direction D2.

The photocatalytic layer 6 of the lighting device 100 comprises two mutually opposite parts 6’ and 6”. The part 6” of the photocatalytic layer 6 extends perpendicular to and away from the side section 110 of the substrate 10. The part 6’ of the photocatalytic layer 6 extends perpendicular to and away from the side section 111 of the substrate 10. The parts 6’ and 6” of the photocatalytic layer 6 may be arranged on a respective substrate or element 16 and 16’, respectively. The substrates 16 and 16’ may for instance be a reflector. The light exit surface 12 of the lighting device 100 extends between free ends of the respective parts 6’ and 6” of the photocatalytic layer 6 opposite to the substrate 10.

When light 3 and 3’ is emitted by the solid-state light sources 21 and 21’ of the first light sources 2 and 2’ in the first directions DI and DI’, the light 3 and 3’ impinges on and activates the respective parts 6’ and 6” of the photocatalytic layer 6 as is shown in Fig. 3. At least a part 17, 17’ of the light 3, 3’ is then reflected towards the light exit surface 12. When light 5 is emitted by the solid-state light sources 41 of the second light source 4, the light 5 is emitted directly towards the light exit surface 12 without impinging on the photocatalytic layer 6 as is shown in Fig. 4.

In a variant embodiment of the lighting device 100 shown in Figs. 3 and 4, the substrate 10 may be provided with side sections 110, 111 being mutually parallel and a bottom section 112 extending perpendicular to and between ends of the two side sections 110 and 111. The heat sink element 11 would in such an embodiment be substantially box-shaped in cross section. It is also feasible to omit one of the two mutually opposite and parallel side sections 110 and 111 of the substrate 10.

Fig. 5 shows a cross-sectional side view of a lighting device 101 according to yet another embodiment of the invention. Fig. 5 shows that the solid-state light sources 21, 22 of the first UV light source 2 emits light 3 and that the solid-state light sources 41 of the second UV light source 4 emits light 5. The lighting device 101 differs from the lighting devices 1 and 100 described above in relation to Figs. 1 to 4 in virtue of the following.

The substrate 10 is substantially L-shaped with a first section 110 and a second section 111 extending perpendicular to the first section 110. The solid-state light sources 21, 22, which are arranged on the first section 110 of the substrate 10, will, in operation, emit light 3 in a first direction of emission DI. The solid-state light sources 41, which are arranged on the second section 111 of the substrate 10, will, in operation emit light 5 in a second direction of emission D2. The first direction DI is perpendicular to the second direction D2. In this way, when the lighting device 101 is mounted on for instance a ceiling 23, the light 3 emitted by the solid-state light sources 21, 22 and thus by the first light source 2 will be emitted in a direction DI substantially perpendicular to and away from the ceiling 23, and thus in a direction suitable for disinfection of objects in a room in which the lighting device 101 is mounted. The light 5 emitted by the solid-state light sources 41 and thus by the second light source 4 will be emitted in a direction substantially parallel to the ceiling 23, and thus in a direction suitable for upper air disinfection.

As shown on Fig. 5, the heat sink element 11 is also substantially L-shaped, such that both sections 110 and 111 of the substrate 10 are in direct contact with the heat sink element 11 for optimal heat dissipation. The controller 7 is furthermore integrated into the heat sink element 11 for a more compact construction of the lighting device 101.

Turning finally to Fig. 6, a logarithmic plot of the relative spectral disinfection effectiveness of UV light as a function of wavelength is shown. The plot further illustrates an exemplary first dominant peak wavelength XI of first light 3 emitted by a first UV light source and an exemplary second dominant peak wavelength X2 of second light 5 emitted by a second UV light source, respectively, of a disinfection lighting device according to the invention. The dotted line illustrates the maximum allowable relative spectral disinfection effectiveness for skin, while the solid line illustrates the maximum allowable relative spectral disinfection effectiveness for eyes, as a function of wavelength.

As may be seen from Fig. 6, the first dominant peak wavelength XI is larger than the second dominant peak wavelength X2 in terms of intensity. Furthermore, the reflective spectral effectiveness at the second dominant peak wavelength X2 is provided to be well below the allowable maximum at the relevant wavelength as indicated by the dotted and solid lines such as to avoid damaging exposure of individuals passing though the light. This is necessary due to the light 5 with the second dominant peak wavelength X2 being emitted directly from the lighting device. The reflective spectral effectiveness at the first dominant peak wavelength XI is, on the other hand, provided to be well above the allowable maximum at the relevant wavelength as indicated by the dotted and solid lines. This is possible due to the fact that at least a part of the light 3 with first dominant peak wavelength XI is used to activate the photocatalytic layer 6 and is thus not emitted directly, but rather only indirectly, from the lighting device.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.