WO2017114692A1

WO2017114692A1 - Lighting device

Info

Publication number: WO2017114692A1
Application number: PCT/EP2016/081923
Authority: WO
Inventors: Robertus Johannes Maria Mathilde SNIJKERS; Vincent Johannes Jacobus Van Montfort; Wouter Lambertus Petrus WILLAERT; Johannes Maria THIJSSEN; Rudolf VAN DER HOORN; Adrianus Johannes Stephanus Maria De Vaan; Menno Van Baardwijk
Original assignee: Philips Lighting Holding B.V.
Priority date: 2015-12-28
Filing date: 2016-12-20
Publication date: 2017-07-06

Abstract

The present invention relates to a lighting device (10; 110), comprising: a substrate (12; 112); at least one solid state light source (14; 114) mounted to the substrate; a moisture protection (28; 120); and a shielding arrangement (18; 18a; 18b; 18c; 116) covering the at least one solid state light source, said shielding arrangement creating a void (22; 118) to prevent mechanical contact between the at least one solid state light source and the moisture protection. The present invention also relates to a method of manufacturing a lighting device (10).

Description

Lighting device

FIELD OF THE INVENTION

The present invention relates to a lighting device comprising a substrate, at least one solid state light source mounted to the substrate, and a moisture protection. The present invention also relates to a method of manufacturing a lighting device.

BACKGROUND OF THE INVENTION

Usually LEDs (light emitting diodes) are inserted and soldered on a printed circuit board (PCB) or flexible printed circuit (FPC). Applications of such lighting devices in the open require a protection against moisture. This can be done by capsulation with an elastomeric transparent substance e.g. Poly-Urethane (PUR), silicone, epoxy, etc. However, direct capsulation of warm white and cool white LEDs with PUR leads to unwanted and unpredictable colour shifts.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide an improved lighting device.

According to a first aspect of the invention, this and other objects are achieved by a lighting device, comprising: a substrate; at least one solid state light source mounted to the substrate; a moisture protection; and a shielding arrangement covering the at least one solid state light source, said shielding arrangement creating a void to prevent mechanical contact between the at least one solid state light source and the moisture protection.

The present invention is based on the understanding that the colour performance of the lighting device may be improved by adding a shielding arrangement that covers the solid state light source(s) and creates a void to prevent mechanical contact between the solid state light source(s) and the moisture protection. In particular, unwanted and unpredictable colour shifts may be avoided. The void may for example be an air layer or air gap.

In one embodiment, the at least one solid state light source is one or more phosphor-converted white light emitting diodes, each phosphor-converted white light emitting diode having a phosphor(ic) layer; the moisture protection is an encapsulation for protecting the phosphor-converted white light emitting diode(s) against moisture; and the shielding arrangement is arranged between the phosphor-converted white light emitting diode(s) and the encapsulation, and adapted to prevent mechanical contact between said phosphor(ic) layer(s) and the encapsulation.

The phosphor(ic) layer may the optical surface (light exit window) of the white LED(s). The colourpoint of the white light is tuned by the phosphor(ic) layer and defined by the difference in refraction between the phosphor(ic) layer and air. Due to the aforementioned void, there is no optical contact between the phosphor(ic) layer and the encapsulation. In this way, the tuning of the phosphor(ic) layer is maintained, as the ratio in refraction between phosphor(ic) layer and adjoining material (air) is preserved, even when the encapsulation for protecting the phosphor-converted white light emitting diode(s) against moisture is applied, which encapsulation has a different refractive index than air.

The shielding arrangement may be at least one foil. In this way, the shielding arrangement does not add so much to the thickness or height of the lighting device.

The at least one foil may be transparent, pre-formed and elastic. The at least one foil may for example be made of Poly-Ethylene-Terephthalate (PET).

The at least one foil may be provided with one or more cups covering the one or more of phosphor-converted white light emitting diodes, typically one cup per LED. The at least one foil may for example be pre-formed and provided with the cup(s) by a blister vacuum forming technique, which technique is known per se.

At least one other portion of the at least one foil apart from the cup(s) may contact the substrate, wherein said at least one other portion of the at least one foil comprises at least one through hole. The at least one through hole may increase the flexibility of the foil. The at least one through hole may also be used to capture the at least one foil to the substrate by means of the encapsulation (e.g. PUR). The at least one through hole may be punched where there are no components that need protection.

The cup(s) and one or more areas of the at least one foil adjacent the cup(s) may be frosted. The frosting provides for scattering inside and through the foil while spreading the light over the complete frosted area. This may enlarge the window of radiation of the one or more phosphor-converted white light emitting diodes.

The one or more cups may be dome-shaped. In this way, the foil and the encapsulation (flat or locally bulb-shaped) may together form a lens shape which can be used to steer the light form the LED(s), whereby low cost optical lenses may be provided. The lens shape may be convex or concave.

The at least one foil may be a single foil covering the complete substrate and the phosphor-converted white light emitting diode(s). Alternatively, the at least one foil is at least one foil strip or patch covering only the area(s) of the substrate where the one or more phosphor-converted white light emitting diodes are mounted. For example, the strip may be an elongate foil, whereas the patch may be a separate, single or dual cup foil. Using a smaller/less foil may improve the flexibility of the lighting device.

Instead of a foil, the shielding arrangement may be a plastic layer which is thicker than the phosphor-converted white light emitting diode(s) and which comprises one or more pockets where one or more phosphor-converted white light emitting diode(s) are placed. Such a plastic layer may protect against substantial mechanical pressures and forces.

The encapsulation may be made by an elastomeric transparent substance, such as Poly-Urethane (PUR), silicone, epoxy, etc.

The substrate may be a printed circuit board (PCB) or a flexible printed circuit

(FPC), for example.

In another embodiment, the shielding arrangement comprises a lens for each of said at least one solid state light source; and the moisture protection is an IP rated coating on the substrate around the lens(es). In this way, most light emitted by the solid state light source(s) is not obstructed by the coating. This is particularly important when the coating is not transparent. 'IP rated', or Ingress Protection rating, classifies the degrees of protection provided against the intrusion of solid objects, dust, accidental contact, and water in (electrical) enclosures. The coating may for example have the rating IP66, IP67, or IP45.

According to a second aspect of the invention, where is provided a method of manufacturing a lighting device, which method comprises: providing a substrate; mounting one or more phosphor-converted white light emitting diodes to the substrate, wherein each phosphor-converted white light emitting diode has a phosphor(ic) layer; arranging a shielding arrangement over the phosphor-converted white light emitting diode(s); and providing an encapsulation over the shielding arrangement for protecting the phosphor-converted white light emitting diode(s) against moisture, wherein the shielding arrangement prevents mechanical or physical contact between said phosphor(ic) layer(s) and the encapsulation. This aspect may exhibit the same or similar features and/or technical effects as the first aspect. 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 is a cross-sectional side view of a lighting device according to an embodiment of the present invention.

Fig. 2 is a top view of the lighting device of fig. 1.

Figs. 3a-3c show various variants of the lighting device of fig. 1.

Fig. 4 is a flowchart over a method of manufacturing a lighting device according to an embodiment of the present invention.

Fig. 5 is a cross-sectional side view of lighting device according to another embodiment of the present invention.

Fig. 6 is a top view of the lighting device of fig. 5.

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.

Figures 1-2 illustrate a lighting device 10 according to an embodiment of the present invention.

The lighting device 10 comprises a substrate 12. The substrate 12 may for example be a printed circuit board (PCB) or a flexible printed circuit (FPC). The substrate 12 may be rigid or flexible.

The lighting device 10 further comprises a plurality of solid state light sources in the form of phosphor-converted white light emitting diodes (LEDs) 14. The phosphor- converted white light emitting diodes 14 may for example be warm white or cool white LEDs. The LEDs 14 are mounted to the substrate 12. The LEDs 14 may for example be soldered on the substrate 12. The LEDs 14 can for example be arranged in one or more rows on the substrate 12. Each LED 14 has a phosphor(ic) layer 16. The phosphor(ic) layer 16 may be a top-layer, as in fig. 1. The phosphor(ic) layer 16 can be a layer made of phosphor or a phosphoric substance.

The lighting device 10 further comprises a shielding arrangement in the form of a foil 18. The foil 18 is generally provided over the substrate 12 and the LEDs 14. The foil 18 may cover the complete (top-side of the) substrate 12 and the LEDs 14. The foil 18 may be transparent. The foil 18 may be pre-formed. The foil 18 may be elastic. The foil 18 can for example be made of Poly-Ethylene-Terephthalate (PET). The foil 18 can for example be 0.2 mm thick. The foil 18 is provided with pre-formed cups 20 which cover the LEDs 14, such that the LEDs 14 fit into the cups 20. The foil 18 here has one cup 20 per LED 14. The cups 20 may be pre-formed using a blister vacuum forming technique. The cups 20 may for example have a flat ("bottom") portion facing the phosphor(ic) layer 16, rounded corners, and perpendicular or sloping side walls. The cups 20 may also be dome shaped, e.g.

hemispherical, as will be elaborated more below. Furthermore, each cup 20 of the foil 18 is designed such that a void, for example an air layer or air gap 22, is created between the phosphor(ic) layer 16 and the inside of the cup 20. The air layer or air gap 22 may be thin. The air layer or air gap 22 can for example be at least thicker than the wavelength of the emitted light or only few molecules of air thick. Other portions 24 of the foil 18 apart from the cups 20 contact the substrate 12. These other portions 24 of the foil 18 may be flexible, whereas the cups 20 are more rigid in shape. The other portions 24 may comprise through holes 26, as shown in figures 1 and 2. The through holes 26 may i.a. increase the flexibility of the foil 18. The through holes 26 may be formed by punching the foil 18. The cups 20 and areas of the foil 18 adjacent the cups 20 may be frosted (not shown), in order to enlarge the window of radiation of the LEDs 14. The foil 18 could also have diffusing properties.

The lighting device 10 further comprises a moisture protection in the form of an encapsulation 28. The encapsulation 28 protects the LEDs 14 against moisture. The encapsulation 28 is generally provided over the foil 18, whereby the foil 18 is arranged between the LEDs 14 and the encapsulation 28. The foil 18 thus prevents mechanical contact between the phosphor(ic) layers 16 and the encapsulation 28. The encapsulation 28 may be made by an elastomeric transparent substance, such as Poly-Urethane (PUR), silicone, epoxy, etc. Furthermore, adding the encapsulation 28 may capture (attach) the foil 18 to the substrate 12 by means of the through holes 26, as the encapsulation 28 runs down through the holes 26 and contacts the substrate 12. Furthermore, dome-shaped cups 20 and the encapsulation 28 may together form a lens shape which can be used to steer the light from the LEDs 14.

During operation of the lighting device 10, light emitted by the LEDs 14 travels through the transparent foil 18 and the encapsulation 28. However, as the air layer or air gap 22 prevents direct optical contact between the encapsulation 28 and the optical surfaces, i.e. the phosphor(ic) layers 16, of the LEDs 14, unwanted and unpredictable colour shifts during operation may be avoided.

Fig. 3a is a top view of a variant of the lighting device of figures 1-2, wherein the foil 18 is replaced by an elongate foil strip 18a which does not cover the complete substrate 12 but only areas of the substrate 12 where the LEDs 14 are mounted.

Fig. 3b is a top view of another variant of the lighting device of figures 1-2, wherein the foil 18 is replaced by several separate foil patches 18b which do not cover the complete substrate 12 but only areas of the substrate 12 where the LEDs 14 are mounted. Each foil patch 18b in fig. 3b has dual cups 20.

Fig. 3c is a cross-sectional side view of yet another variant of the lighting device of figures 1-2, wherein the foil 18 is replaced by a plastic layer 18c. The plastic layer 18c is generally thicker than the LEDs 14. The plastic layer 18c comprises pockets 20' where the LEDs 14 are placed, whereby a thin transparent layer portion 30 covers each LED 14.

Fig. 4 is a flowchart of a method of manufacturing a lighting device, e.g. the light device 10 according to any of figures 1-2 or 3a-3c. The method comprises the steps of:

51) providing a substrate 12;

52) mounting phosphor-converted white light emitting diodes 14 on the substrate 12, wherein each LED 14 has a phosphor(ic) layer 16;

53) arranging a shielding arrangement, e.g. the foil 18, the strip 18a, the patches 18b or the plastic layer 18c, over the LEDs 14; and

54) providing an encapsulation 28 over the shielding arrangement for protecting the phosphor-converted white light emitting diode(s) against moisture, wherein the shielding arrangement prevents mechanical or physical contact between the phosphor(ic) layers 16 and the encapsulation 28.

Figures 5-6 illustrate a lighting device 110 according to another embodiment of the present invention.

The lighting device 110 comprises a substrate 112. The lighting device 10 further comprises a plurality of solid state light sources 114 mounted to the substrate 112. The solid state light sources 114 may for example be LEDs. The light sources 114 may be adapted to emit white light or coloured light. The substrate 112 with the solid state light sources 114 and optionally other components mounted on the substrate 112 may be an L2 board.

The lighting device 110 further comprises a shielding arrangement in the form of a plurality of lenses 116; one lens 116 over each solid state light source 114. Each lens 116 is designed such that there is a (small) air gap ('void') 118 between the solid state light source 114 and the (inside of) the lens 116.

The lighting device 110 further comprises a moisture protection in the form of an IP rated coating 120 on the substrate 112 around the lenses 116. The coating 120 may for example have the rating IP66, IP67 or IP45. The coating 120 may for example be made of Poly-Urethane (PUR), silicone, epoxy, etc. The coating 120 may for example be transparent or non-transparent. The coating 120 is thinner than the height of the lenses 116, such that the lenses 116 protrude above the coating 120.

During operation of the lighting device 110, most light emitted by the solid state light sources 114 is not obstructed by the surrounding coating 120. Furthermore, the lighting device 110 may be used in moist or humid conditions.

The lighting devices 10, 100 may for example be used in luminaires, light fixtures, LED strips, outdoor applications, etc.

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.

Claims

CLAIMS:

1. A lighting device (10; 110), comprising:

a substrate (12; 112);

at least one solid state light source (14; 114) mounted to the substrate;

a moisture protection (28; 120); and

a shielding arrangement (18; 18a; 18b; 18c; 116) covering the at least one solid state light source, said shielding arrangement creating a void (22; 118) to prevent mechanical contact between the at least one solid state light source and the moisture protection,

wherein:

the at least one solid state light source is one or more phosphor-converted white light emitting diodes (14), each phosphor-converted white light emitting diode having a phosphor(ic) layer (16);

the moisture protection is an encapsulation (28) for protecting the phosphor- converted white light emitting diode(s) against moisture; and

the shielding arrangement is arranged between the phosphor-converted white light emitting diode(s) and the encapsulation, and adapted to prevent mechanical contact between said phosphor(ic) layer(s) and the encapsulation, and

wherein the shielding arrangement is at least one foil (18; 18a; 18b).

2. A lighting device according to claim 1, wherein the at least one foil is transparent, pre-formed and elastic.

3. A lighting device according to claim 1 or 2, wherein the at least one foil is provided with one or more cups (20) covering the one or more of phosphor-converted white light emitting diodes.

4. A lighting device according to claim 3, wherein at least one other portion (24) of the at least one foil apart from the cup(s) contacts the substrate, and wherein said at least one other portion of the at least one foil comprises at least one through hole (26).

5. A lighting device according to any preceding claim 3-4, wherein the cup(s) and one or more areas of the at least one foil adjacent the cup(s) are frosted.

6. A lighting device according to any preceding claim 3-5, wherein the one or more cups are dome-shaped.

7. A lighting device according to any preceding claim 1-6, wherein the at least one foil is a single foil (18) covering the complete substrate and the phosphor-converted white light emitting diode(s).

8. A lighting device according to any preceding claim 1-6, wherein the at least one foil is at least one foil strip (18a) or patch (18b) covering only the area(s) of the substrate where the one or more phosphor-converted white light emitting diodes are mounted.

9. A lighting device according to claim 1, wherein the shielding arrangement is a plastic layer (18c) which is thicker than the phosphor-converted white light emitting diode(s) and which comprises one or more pockets where one or more phosphor-converted white light emitting diode(s) are placed.

10. A lighting device according to any preceding claim 1-9, wherein the encapsulation is made by an elastomeric transparent substance.

11. A lighting device according to any preceding claim 1-10, wherein said substrate is a printed circuit board or a flexible printed circuit.