A lighting device

Abstract

A lighting device (1) comprising at least one solid-state light source, SSLS, (2) configured to, in operation, emit SSLS light having a peak wavelength in a violet-blue wavelength range of 380 nm to 490 nm, a substrate (3) comprising at least a first surface (4), a plurality of layers (5, 6) comprising an electrically insulating layer (5) and an electrically conducting layer (6), and a wavelength-converting layer (7) comprising a luminescent material configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm. The wavelength-converting layer (7) is arranged in relation to the plurality of layers (5, 6) and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer (5).

Description

[0001] A lighting device

[0002] TECHNICAL FIELD

[0003] The present invention relates to a lighting device.

[0004] BACKGROUND

[0005] Lighting devices or luminaires may include one or more light-emitting diodes (LEDs). In a lighting device or luminaire, LEDs may be arranged on a mechanical and / or electrical support such as a printed circuit board (PCB). LED light sources which may be used in lighting devices or luminaires and which are capable of emitting light having a relatively high brightness may suffer from reliability issues and thermal limitations. As known in the art, in addition to conductive layers, for example comprising or being constituted by electrical tracks or traces, a PCB may have insulating layers and / or reflective layers. Prolonged exposure of such a reflective layer to light having a relatively high brightness may cause browning of the reflective layer. Thus, any reflective layer located close to the LED(s) may be browned as a result of prolonged exposure of the light emitted by the LED if it has a relatively high brightness. Further, prolonged exposure of such a conductive layer or insulating layer to light having a relatively high brightness may cause deterioration of the conductive layer or the insulating layer. Thus, any portion of any conductive layer and insulating layer located relatively close to the LED(s) may deteriorate as a result of prolonged exposure of the light emitted by the LED if it has a relatively high brightness. This may, in turn, lead to a short circuit.

[0006] US2017 / 186921A discloses a light emitting diode (LED) package includes a package body and an LED chip above the package body. The LED package further has a first wavelength conversion layer containing a first wavelength conversion material, having an upper surface portion covering a part of an upper surface of the LED chip and a lateral portion covering side surfaces of the LED chip. The LED package further has a second wavelength conversion layer containing a second wavelength conversion material different from the first wavelength conversion material, covering the first wavelength conversion layer and a remaining part of the upper surface of the LED chip. US2012 / 248488A discloses an LED package. The LED package comprises a metal plate, circuit patterns, and an LED. The metal plate comprises grooves. The insulating layer is formed on the metal plate. The circuit patterns are formed on the insulating layer. The LED is electrically connected with the circuit pattern on the insulating layer.

[0007] SUMMARY

[0008] In view of the above, a concern of the present invention is to provide a lighting device comprising at least one solid-state light source (SSLS) and a plurality of layers comprising an electrically conducting layer to which the at least one SSLS is electrically connected, which lighting device is capable of reducing or even avoiding the risk of any undesired or harmful effects on the plurality of layers if the light emitted by the at least one SSLS would have a relatively high brightness.

[0009] According to a first aspect of the present invention, a lighting device is provided. The lighting device is configured to, in operation, emit device light. The lighting device comprises at least one SSLS configured to, in operation, emit SSLS light having a peak wavelength in a violet-blue wavelength range of 380 nm to 490 nm. The lighting device comprises a substrate, which may comprise at least one metal layer (e.g., the substrate may be a metal layer such as a metal core of a metal core printed circuit board (PCB)). The substrate comprises at least a first surface. The lighting device comprises a plurality of layers, comprising an electrically insulating layer and an electrically conducting layer. The electrically insulating layer is arranged at at least a portion of the first surface of the substrate and between the substrate and the electrically conducting layer. The electrically conducting layer is arranged at at least a portion of a surface of the electrically insulating layer. The at least one SSLS may be electrically connected to the electrically conducting layer. The electrically conducting layer may comprise one or more electrically conductive tracks or traces. Thus, the electrically conducting layer may comprise one or more electrically conductive tracks or traces to which the at least one SSLS is electrically connected. The lighting device comprises a wavelength-converting layer, which comprises a luminescent material configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm. The wavelength-converting layer is arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer. The device light comprises at least the luminescent material light. The said luminescent material is of a type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, wherein X comprises a monovalent anion, at least comprising fluorine.

[0010] By the wavelength-converting layer being arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer, the risk of any undesired or harmful effects on the plurality of layers, even if the at least one SSLS would emit light having a relatively high brightness, may be reduced or even avoided. This is because light in the said violet-blue wavelength range may be harmful to “sensitive” layers of the lighting device, such as electrically insulating and / or reflective layers. Light having a peak wavelength in a violet-blue wavelength range of, e.g., 380 nm to 490 nm, and which has a relatively high brightness may degrade the electrically insulating layer, e.g., a dielectric layer, which may be arranged between the electrically conducting layer and the substrate which may have a metal layer. Degrading of the electrically insulating layer may result in short circuiting between the (e.g., ‘metal’) substrate and the electrically conducting layer which may comprise or be constituted by electrically conductive tracks to which the at least one SSLS is electrically connected. The electrically conducting layer may comprise or be constituted by one or more electrodes, for example. Short circuiting may lead to unsafe situations and a lower lifetime / reliability of the lighting device. Inventors have also found that degradation of the electrically insulating layer, e.g., a dielectric layer, by exposure to (e.g., high intensity) light having a peak wavelength in a violet-blue wavelength range of, e.g., 380 nm to 490 nm, may also result in detrimental effects in the electrically conducting layer such as short circuiting between electrodes. Part or parts of the electrically insulating layer and / or electrically conducting layer may come loose from the substrate such that electrodes contact each other, and thus short circuiting between electrodes may happen. In case of the latter, the substrate does not need to comprise at least one metal layer, i.e., the substrate may be free from a metal layer.

[0011] As mentioned, the luminescent material of the wavelength-converting layer is configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm. In contrast to visible light having a peak wavelength in other wavelength ranges than the said red wavelength range, light in the said red wavelength range does in general not have any harmful effects on the plurality of layers, which is contemplated to be true even if the red light would have a relatively high brightness. Thus, by the luminescent material of the wavelength-converting layer being configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm, the risk of any undesired or harmful effects on the plurality of layers, even if the light emitted by the at least one SSLS has a relatively high brightness, may be reduced or even avoided.

[0012] The luminescent material may be configured to, upon absorption of light, only emit light in the said red wavelength range. Thereby, only a relatively small amount of light or substantially no light having a peak wavelength in wavelength ranges other than the said red wavelength range, e.g., in a green-yellow wavelength range of 510 nm to 570 nm in the said violet-blue wavelength range, may reach (e.g., a portion of) the electrically insulating layer. The electrically insulating layer may comprise at least one dielectric layer.

[0013] As indicated previously, the plurality of layers may comprise a reflective layer, or an electrically insulating and / or reflective layer. The wavelength-converting layer may be arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the reflective layer, or an electrically insulating and / or reflective layer.

[0014] Thus, by means of the configuration of the lighting device according to the first aspect of the present invention, browning of any reflective layer of the plurality of layers and deterioration of any electrically conducting layer and electrically insulating layer located relatively close to the at least one SSLS due to light emitted by the at least one SSLS having a relatively high brightness may be reduced or even avoided.

[0015] In an embodiment, the lighting device comprises a further luminescent element that comprises a second luminescent material. The luminescent element may comprise a polymer matrix comprising the second luminescent material. The second luminescent material may comprise one or more luminescent materials. The luminescent materials may be of the type AsBsO Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. The luminescent materials may comprise NfcSis Eu2, or MAlSiHvEu2or Ca2AlSi3O2Ns:Eu2+, etc., wherein M comprises one or more of Ba, Sr, and Ca, especially in embodiments at least Sr. Each layer of the plurality of layers may have a first major surface and a second major surface opposite to the first major surface, wherein at least some of the plurality of layers may be arranged in a succession such that at least one of the first major surface and a second major surface of each of the at least some of the plurality of layers is facing in a direction towards a first major surface and a second major surface of a successive one of the at least some of the plurality of layers. Possibly, there could be some intermediate elements between successive ones of the plurality of layers. The plurality of layers may be arranged in a stacked arrangement such that at least one of the first major surface and a second major surface of each of the at least some of the plurality of layers is coupled to a first major surface and a second major surface of a successive one of the at least some of the plurality of layers.

[0016] The substrate and / or the plurality of layers may be implemented or realized by means of at least one printed circuit board (PCB), e.g., a metal core PCB.

[0017] The at least one SSLS may for example comprise or be constituted by at least one light-emitting diode (LED). The at least one LED may comprise at least one sideemitting LED. The at least one LED may comprise a Chip Scale Package (CSP) LED. The CSP LED may comprise a LED die directly attached to the electrically conducting layer to which the at least one SSLS (e.g., LED) is electrically connected, and not via a sub-mount.

[0018] As seen from above the lighting device, in a direction towards the first surface of the substrate, the wavelength-converting layer may extend around the at least one SSLS, and a shape of a periphery (or circumference) of the wavelength-converting layer as seen from above the lighting device may be spaced from a periphery (or circumference) of the at least one SSLS as seen from above the lighting device by at least 1 mm, preferably by at least 2 mm or by at least 3 mm.

[0019] The luminescent material may comprise a potassium fluorosilicate-based phosphor. The luminescent material may comprise or be constituted by K2SiFe:Mn4+. Thus, the luminescent material may comprise a K2SiFe:Mn4+-based phosphor.

[0020] The wavelength-converting layer may be configured to, by conversion of light, provide wavelength-converting layer light, and at least 80% or at least 90% of the wavelength-converting layer light, e.g., all of the wavelength-converting layer light, may be the luminescent material light. In alternative or in addition, the luminescent material may comprise luminescent particles, and at least 80% or at least 90% of the luminescent particles, e.g., all of the luminescent particles, of the luminescent material may be potassium fluorosilicate-based phosphor particles. The wavelength-converting layer may be arranged to overlie, or cover, the portion of the electrically insulating layer such that the wavelength-converting layer is arranged between the at least one SSLS and the portion of the electrically insulating layer.

[0021] The wavelength-converting layer may comprise a (e.g., polymeric) binder material. The luminescent material may be dispersed in the (e.g., polymeric) binder material. The (polymeric) binder material may be a polymeric binder material, such as, for example, silicone. For example, the polymeric binder material may comprise (e.g., cross-linked) polydimethylsiloxane.

[0022] The wavelength-converting layer may be configured so as to prevent at least a portion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of said electrically conducting layer.

[0023] The wavelength-converting layer may be arranged to overlie, or cover, the portion of said electrically conducting layer such that the wavelength-converting layer is arranged between the at least one SSLS and the portion of said electrically conducting layer.

[0024] The at least one SSLS may be electrically connected to the one or more electrically conductive tracks of the electrically conducting layer via one or more electrically conducting elements. The wavelength-converting layer may be configured so as to prevent at least a portion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of the said one or more electrically conducting elements. The said one or more electrically conducting elements may for example comprise one or more bond pads, solder and / or one or more (sub-)mounts.

[0025] The wavelength-converting layer may be arranged to overlie, or cover, the at least a portion of the said one or more electrically conducting elements such that the wavelength-converting layer is arranged between the at least one SSLS and the at least a portion of the said one or more electrically conducting elements.

[0026] The at least one SSLS may have a first side facing the first surface of the substrate and a second side opposite to the first side of the at least one SSLS, wherein the wavelength-converting layer may be arranged between the first side of the at least one SSLS and the first surface of the substrate. For example, the wavelength-converting layer may be arranged underneath the at least one SSLS.

[0027] A portion of the electrically insulating layer may be between the first side of the at least one SSLS and the first surface of the substrate. The wavelength-converting layer may be arranged to overlie, or cover, at least a portion of the portion of the electrically insulating layer between the first side of the at least one SSLS and the first surface of the substrate.

[0028] The wavelength-converting layer may be arranged in relation to the electrically conducting layer and the electrically insulation layer such that the wavelengthconverting layer overlies, or covers, at most 40% or at most 30% of the electrically conducting layer and / or at most 40% or at most 30% of the electrically insulating layer. For calculation of these percentages, the total surface area of the electrically insulating layer is taken into account, as well as the total surface area of the electrically conducting layer(s).

[0029] The lighting device may comprise a plurality of SSLSs and a plurality of wavelength-converting layers. Each of the plurality of wavelength-converting layers may correspond to one or more SSLSs spaced apart from the other SSLSs and may be arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the light emitted by the corresponding one or more SSLSs in the said violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer. The plurality of wavelength-converting layers may be arranged such that for each pair of adjacent SSLSs, at least one surface area of the electrically conducting layer and / or the electrically insulating layer between the SSLSs of the pair of adjacent SSLSs is not covered by a wavelengthconverting layer as seen from above the lighting device, in a direction towards the first surface of the substrate.

[0030] The wavelength-converting layer may comprise a solder resist layer (e.g., an insulating ink that covers the surface of a PCB and protects a circuit pattern). One of the main roles of solder resist may be to prevent solder from adhering to unnecessary or unintended parts when components are mounted on a substrate such as a PCB.

[0031] As seen from above the lighting device, in a direction towards the first surface of the substrate, the wavelength-converting layer may extend around the at least one SSLS, and a periphery (or circumference) of the at least one SSLS as seen from above the lighting device may have a shape that is different from a shape of a periphery (or circumference) of the wavelength-converting layer as seen from above the lighting device.

[0032] A portion of the wavelength-converting layer may be arranged to overlie, or cover, a portion of the plurality of layers, wherein the said portion of the wavelengthconverting layer may be arranged to form a selected shape or pattern as seen from above the lighting device, in a direction towards the first surface of the substrate.

[0033] According to a second aspect of the present invention, a lamp or luminaire, comprising a lighting device according to the first aspect of the present invention, is provided. The lamp may comprise a connector, e.g., a cap, for electrically and mechanically connecting the lamp to a socket of a luminaire. The lamp may comprise an envelope which at least partly encloses the lighting device. The luminaire may comprise a light exit (e.g., a light exit window) for exiting or outputting luminaire light from the luminaire.

[0034] As mentioned, the luminescent material is of a type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, wherein X comprises a monovalent anion, at least comprising fluorine.

[0035] Relevant alkaline cations (M) are sodium (Na), potassium (K) and rubidium (Rb). Optionally, also lithium and / or cesium may be applied. In a preferred embodiment of the present invention, M comprises at least potassium. In yet another embodiment of the present invention, M comprises at least rubidium. The phrase “wherein M comprises at least potassium” indicates for instance that of all M cations in a mole M’xM2-2xAX6, a fraction comprises K+and an optionally remaining fraction comprises one or more other monovalent (alkaline) cations (see also below). In another preferred embodiment of the present invention, M comprises at least potassium and rubidium. Optionally, the M’xM2-2xAX6 luminescent material has the hexagonal phase. In yet another embodiment of the present invention, the M’XM2-2XAX6 luminescent material has the cubic phase. For x=0, the composition is M2AX6.

[0036] Relevant alkaline earth cations (M’) are magnesium (Mg), strontium (Sr), calcium (Ca) and barium (Ba), especially one or more of Sr and Ba.

[0037] The term “tetravalent manganese” refers to Mn4+. This is a well-known luminescent ion. In the formula as indicated above, part of the tetravalent cation A (such as Si) is being replaced by manganese. Hence, M’xM2-2xAX6 doped with tetravalent manganese may also be indicated as M’xM2-2xAi-mMnmX6. The mole percentage of manganese, i.e., the percentage it replaces the tetravalent cation A will in general be in the range of 0.1-15 %, especially 1-12 %, i.e., m is in the range of 0.001-0.15, especially in the range of 0.01-0.12.

[0038] As indicated above, X relates to a monovalent anion, but comprises at least fluorine. Other monovalent anions that may optionally be present may be selected from the group consisting of chlorine (Cl), bromine (Br), and iodine (I).

[0039] In an embodiment of the present invention, M’xM2-2xAX6 comprises K^SiFe (which may be referred to herein also as KSiF system). As indicated above, in another preferred embodiment of the present invention, M’xM2-2xAX6 comprises KRbSiFe (which may be referred to herein also as K,Rb system). As indicated above, part of silicon is replaced by manganese (i.e., the formula may also be described as K2Sii-mMnmF6 or KRbSii-mMnmF6, with m as indicated above, or as KRbSiFe:Mn and K2SiFe:Mn, respectively). As manganese replaces part of a host lattice ion and has a specific function, it is also indicated as “dopant” or “activator”. Hence, the hexafluorosilicate is doped or activated with manganese (Mn4+).

[0040] In specific embodiments of the present invention, the luminescent material may comprise (K,Rb)2SiFe:Mn4+. Alternatively or additionally, in embodiments of the present invention, the luminescent material may comprise K2SiFe:Mn4+. Alternatively or additionally, in embodiments of the present invention, the luminescent material may comprise K2TiFe:Mn4+. In embodiments of the present invention, the luminescent material may comprise K2(Si,Ti)Fe:Mn4+. As can be derived from the above, “Si,Ti” may indicate one or more of Si and Ti.

[0041] As mentioned, the lighting device comprises at least one solid-state light source (SSLS). The at least one SSLS may for example comprise at least one light-emitting diode (LED), and / or a solid-state laser. Solid state light emitters are relatively cost-efficient light sources since they in general are relatively inexpensive and have a relatively high optical efficiency and a relatively long lifetime.

[0042] In embodiments, the at least one LED provides LED light and may be covered by an encapsulant comprising an encapsulant luminescent material. The encapsulant luminescent material may be configured to at least partially convert the LED light into encapsulant luminescent material light. The device light may comprise the LED light, the encapsulant luminescent material light and luminescent material light. The encapsulant luminescent material may comprise a green-yellow phosphor and a red phosphor, which may, e.g., be different from the luminescent material.

[0043] In embodiments, the device (and lamp and / or luminaire) light may be white light having a correlated color temperature in a range from 1700 K to 6500 K and preferably a color rendering index (CRI) of at least 80 or at least 85.

[0044] Each or any one of the at least one LED may for example include or be constituted by an inorganic LED and / or an organic LED (OLED). Examples of LEDs include semiconductor, organic, or polymer / polymeric LEDs, optically pumped phosphor coated LEDs, optically pumped nano-crystal LEDs or any other similar devices as would be readily understood by a person skilled in the art. For example, the term LED can encompass a bare LED die arranged in a housing, which may be referred to as a LED package. According to another example, the term LED can encompass a Chip Scale Package (CSP) LED, which may comprise a LED die directly attached to a substrate, and not via a sub-mount. The term LED can for example encompass a laser diode, because a laser diode is a diode which emits light.

[0045] Further objects and advantages of the present invention are described in the following by means of exemplifying embodiments. It is noted that the present invention relates to all possible combinations of features recited in the claims. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the description herein. Those skilled in the art realize that different features of the present invention can be combined to create embodiments other than those described herein.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Exemplifying embodiments of the invention will be described below with reference to the accompanying drawings.

[0048] Each of Figures 1, 2 and 3 is a schematic sectional side view of a lighting device according to an embodiment of the present invention.

[0049] Figure 4 is a schematic view from the above of a lighting device according to an embodiment of the present invention.

[0050] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate embodiments of the present invention, wherein other parts may be omitted or merely suggested.

[0051] DESCRIPTION WITH REFERENCE TO THE DRAWINGS

[0052] The present invention will now be described hereinafter with reference to the accompanying drawings, in which exemplifying embodiments of the present invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments of the present invention set forth herein; rather, these embodiments of the present invention are provided by way of example so that this disclosure will convey the scope of the invention to those skilled in the art. In the drawings, identical reference numerals denote the same or similar components having a same or similar function, unless specifically stated otherwise.

[0053] Figure l is a schematic sectional side view of a lighting device 1 according to an embodiment of the present invention. The lighting device 1 is configured to, in operation, emit device light, which device light is schematically indicated by the arrow at 10.

[0054] The lighting device 1 comprises at least one solid-state light source (SSLS) 2. The at least one SSLS 2 is configured to, in operation, emit SSLS light having a peak wavelength in a violet-blue wavelength range of 380 nm to 490 nm. The at least one SSLS 2 may for example comprise at least one light-emitting diode (LED).

[0055] The lighting device 1 comprises a substrate 3, which may comprise at least one metal layer 3’. In accordance with the embodiment of the present invention illustrated in Figure 1, the substrate 3 may be constituted by the at least one metal layer 3’. The substrate 3 comprises at least a first surface 4.

[0056] The lighting device 1 comprises a plurality of layers 5, 6. The plurality of layers 5, 6 comprises an electrically insulating layer 5 and an electrically conducting layer 6. The electrically insulating layer 5 is arranged at at least a portion of the first surface 4 of the substrate 3 and between the substrate 4 and the electrically conducting layer 6. The electrically conducting layer 6 is arranged at at least a portion of a surface of the electrically insulating layer 5. The electrically conducting layer 6 comprises one or more electrically conductive tracks (not shown in Figure 1) to which the at least one SSLS 2 is electrically connected. It is to be understood that the lighting device 1 may comprise one or more further layers in addition to the electrically insulating layer 5 and the electrically conducting layer 6 illustrated in Figure 1, such as, for example, a reflective layer, or an electrically insulating and / or reflective layer.

[0057] The lighting device 1 comprises a wavelength-converting layer 7. The wavelength-converting layer 7 comprises a luminescent material configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm. The wavelength-converting layer 7 is arranged in relation to the plurality of layers 5, 6 and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer 5. The device light 10 comprises at least the luminescent material light.

[0058] The said luminescent material is of a type M’xM2-2xAX6 doped with tetraval ent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, wherein X comprises a monovalent anion, at least comprising fluorine.

[0059] In accordance with the embodiment of the present invention illustrated in Figure 1, the wavelength-converting layer 7 may be arranged to overlie the portion of the electrically insulating layer 5 such that the wavelength-converting layer 7 is arranged between the at least one SSLS 2 and the portion of the electrically insulating layer 5. Further in accordance with the embodiment of the present invention illustrated in Figure 1, the at least one SSLS 2 may be electrically connected to the said one or more electrically conductive tracks of the electrically conducting layer 6 via, or by means of, one or more electrically conducting elements 8, 9, In accordance with the embodiment of the present invention illustrated in Figure 1, the electrically conducting elements 8, 9 comprise solder 8 and bond pads 9.

[0060] Figure 2 is a schematic sectional side view of a lighting device 1 according to an embodiment of the present invention. The lighting device 1 illustrated in Figure 2 is similar to the lighting device 1 illustrated in Figure 1, and the same reference numerals in Figures 1 and 2 denote the same or similar components or elements, having the same or similar function. In accordance with the embodiment of the present invention illustrated in Figure 2, the wavelength-converting layer 7 is further configured so as to prevent at least a portion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of said electrically conducting layer 6. To that end, the wavelength-converting layer 7 may be arranged to overlie the portion of said electrically conducting layer 6 such that the wavelength-converting layer 7 is arranged between the at least one SSLS 2 and the portion of said electrically conducting layer 6, such as illustrated in Figure 2.

[0061] Further in accordance with the embodiment of the present invention illustrated in Figure 2, the at least one SSLS 2 may have a first side facing the first surface 4 of the substrate 3 and a second side opposite to the first side of the at least one SSLS 2, with the wavelength-converting layer 7 being arranged between the first side of the at least one SSLS 2 and the first surface 4 of the substrate 3. Thus, as illustrated in Figure 2, the wavelengthconverting layer 7 may be arranged underneath the at least one SSLS 2.

[0062] Figure 3 is a schematic sectional side view of a lighting device 1 according to an embodiment of the present invention. The lighting device 1 illustrated in Figure 3 is similar to the lighting devices 1 illustrated in Figures 1 and 2, and the same reference numerals in Figure 3 and Figures 1 and 2 denote the same or similar components or elements, having the same or similar function. In accordance with the embodiment of the present invention illustrated in Figure 3, the wavelength-converting layer 7 is further configured so as to prevent at least a portion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of said one or more electrically conducting elements 8, 9. To that end, the wavelength-converting layer 7 may be arranged to overlie the at least a portion of said one or more electrically conducting elements - e.g., lateral portions of the electrically conducting elements 8, 9 as illustrated in Figure 3 - such that the wavelength-converting layer 7 is arranged between the at least one SSLS and the at least a portion of said one or more electrically conducting elements 8, 9.

[0063] Figure 4 is a schematic view from the above of a lighting device 1 according to an embodiment of the present invention. The same reference numerals in Figure 4 and Figures 1 to 3 denote the same or similar components or elements, having the same or similar function. The lighting device 1 illustrated in Figure 4 comprises a plurality of SSLSs 2 and a plurality of wavelength-converting layers 7. Each of the plurality of wavelength-converting layers 7 corresponds to one or more SSLSs 2 spaced apart from the other SSLSs 2 and is arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the light emitted by the corresponding one or more SSLSs 2 in the said violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer 5. It is to be understood that the number of SSLSs 2 and the number of wavelength-converting layers 7 illustrated in Figure 4 is exemplifying, and that there could be provided fewer or more SSLSs 2 and / or wavelength-converting layers 7 than illustrated in Figure 4. There may, in principle, be provided any number of SSLSs 2 and wavelength-converting layers 7 in the lighting device. In accordance with the embodiment of the present invention illustrated in Figure 4, the plurality of wavelength-converting layers 7 are arranged such that for each pair of adjacent SSLSs 2, at least one surface area of the electrically conducting layer and / or the electrically insulating layer 5 between the SSLSs 2 of the pair of adjacent SSLSs 2 is not covered by a wavelength-converting layer 7 as seen from above the lighting device 1, in a direction towards the first surface of the substrate.

[0064] In conclusion, a lighting device is disclosed, comprising at least one SSLS configured to, in operation, emit SSLS light having a peak wavelength in a violet-blue wavelength range of 380 nm to 490 nm. The lighting device comprises a substrate which comprises at least a first surface. The lighting device comprises a plurality of layers comprising an electrically insulating layer and an electrically conducting layer. The lighting device comprises a wavelength-converting layer comprising a luminescent material configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm. The wavelength-converting layer is arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer.

[0065] While the present invention has been illustrated in the appended drawings and the foregoing description, such illustration is to be considered illustrative or exemplifying and not restrictive; the present invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the appended 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 measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lighting device (1) configured to, in operation, emit device light (10), the lighting device comprising: at least one solid-state light source, SSLS, (2) configured to, in operation, emit SSLS light having a peak wavelength in a violet-blue wavelength range of 380 nm to 490 nm; a substrate (3) comprising at least one metal layer (3’), the substrate comprising at least a first surface (4); a plurality of layers (5, 6) comprising an electrically insulating layer (5) and an electrically conducting layer (6), the electrically insulating layer being arranged at at least a portion of the first surface of the substrate and between the substrate and the electrically conducting layer, the electrically conducting layer being arranged at at least a portion of a surface of the electrically insulating layer, the electrically conducting layer comprising one or more electrically conductive tracks to which the at least one SSLS is electrically connected; and a wavelength-converting layer (7) comprising a luminescent material configured to convert at least part of the SSLS light in the violet-blue wavelength range into luminescent material light having a peak wavelength in a red wavelength range of 600 nm to 660 nm, the wavelength-converting layer being arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the SSLS light in the violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer, wherein the wavelength-converting layer is configured to, by conversion of SSLS light, provide wavelength-converting layer light, and at least 90% of the wavelength-converting layer light is the luminescent material light; wherein the device light comprises at least the luminescent material light; wherein said luminescent material is of a type M’xM2-2xAX6 doped with tetravalent manganese, wherein M’ comprises an alkaline earth cation, M comprises an alkaline cation, and x is in the range of 0-1, wherein A comprises a tetravalent cation, wherein X comprises a monovalent anion, at least comprising fluorine.

2. A lighting device according claim 1, wherein as seen from above the lighting device, in a direction towards the first surface of the substrate, the wavelength-converting layer extends around the at least one SSLS, and wherein a shape of a periphery of the wavelength-converting layer as seen from above the lighting device is spaced from a periphery of the at least one SSLS as seen from above the lighting device by at least 1 mm.

3. A lighting device according to claim 1 or 2, wherein the luminescent material comprises luminescent particles, and wherein at least 90% of the luminescent particles of the luminescent material are potassium fluorosilicate-based phosphor particles.

4. A lighting device according to any one of claims 1-3, wherein the wavelengthconverting layer is arranged to overlie the portion of the electrically insulating layer such that the wavelength-converting layer is arranged between the at least one SSLS and the portion of the electrically insulating layer.

5. A lighting device according to any one of the preceding claims, wherein the wavelength-converting layer comprises a binder material, wherein the luminescent material is dispersed in the binder material.

6. A lighting device according to any one of the preceding claims, wherein the wavelength-converting layer is further configured so as to prevent at least a portion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of said electrically conducting layer.

7. A lighting device according to claim 6, wherein the wavelength-converting layer is arranged to overlie the portion of said electrically conducting layer such that the wavelength-converting layer is arranged between the at least one SSLS and the portion of said electrically conducting layer.

8. A lighting device according to any one of the preceding claims, wherein the at least one SSLS is electrically connected to said one or more electrically conductive tracks of the electrically conducting layer via one or more electrically conducting elements (8, 9), wherein the wavelength-converting layer is further configured so as to prevent at least aportion of the SSLS light in the said violet-blue wavelength range from impinging on at least a portion of said one or more electrically conducting elements.

9. A lighting device according to claim 8, wherein the wavelength-converting layer is arranged to overlie the at least a portion of said one or more electrically conducting elements such that the wavelength-converting layer is arranged between the at least one SSLS and the at least a portion of said one or more electrically conducting elements.

10. A lighting device according to any one of the preceding claims, wherein the at least one SSLS has a first side facing the first surface of the substrate and a second side opposite to the first side of the at least one SSLS, wherein the wavelength-converting layer is arranged between the first side of the at least one SSLS and the first surface of the substrate.

11. A lighting device according to claim 10, wherein a portion of the electrically insulating layer is between the first side of the at least one SSLS and the first surface of the substrate, and wherein the wavelength-converting layer is arranged to overlie at least a portion of the portion of the electrically insulating layer between the first side of the at least one SSLS and the first surface of the substrate.

12. A lighting device according to any one of preceding claims, wherein the wavelength-converting layer is arranged in relation to the electrically conducting layer and the electrically insulation layer such that the wavelength-converting layer covers at most 40% of the electrically conducting layer and / or at most 40% of the electrically insulating layer.

13. A lighting device according to any one of the preceding claims, comprising a plurality of SSLSs and a plurality of wavelength-converting layers, wherein each of the plurality of wavelength-converting layers corresponds to one or more SSLSs spaced apart from the other SSLSs and is arranged in relation to the plurality of layers and configured so as to prevent at least a portion of the light emitted by the corresponding one or more SSLSs in the said violet-blue wavelength range from impinging on at least a portion of the electrically insulating layer, and wherein the plurality of wavelength-converting layers are arranged such that for each pair of adjacent SSLSs, at least one surface area of the electrically conducting layer and / or the electrically insulating layer between the SSLSs of the pair ofadjacent SSLSs is not covered by a wavelength-converting layer as seen from above the lighting device, in a direction towards the first surface of the substrate.

14. A lighting device according to any one of the preceding claims, wherein the wavelength-converting layer comprises a solder resist layer.

15. A lamp or luminaire comprising a lighting device (1) according to any one of the preceding claims.

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