WO2009063382A1

WO2009063382A1 - A lighting panel

Info

Publication number: WO2009063382A1
Application number: PCT/IB2008/054690
Authority: WO
Inventors: Lingli Wang
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-11-13
Filing date: 2008-11-10
Publication date: 2009-05-22
Also published as: TW200936954A

Abstract

The present invention relates to alighting panel (1) comprising a layer (2) having an upper surface (3), a lower surface (5) and a plurality of lightsources (7). The lighting panel (1) further comprises a distribution of optical elements (10), each optical element forming a recess (12) extending from the upper surface (3) towards the lower surface (5) wherein eachopticalelement (10) comprises at least one of said light sources (7) arranged at a bottom portion (16) of the recess (12). The present invention also relates to a method for providing such lighting panel (1).

Description

A LIGHTING PANEL

FIELD OF THE INVENTION

The present invention relates to a lighting panel comprising a layer having an upper surface, a lower surface and a plurality of light sources. The lighting panel further comprises a distribution of optical elements, each optical element forming a recess extending from the upper surface towards the lower surface wherein each optical element comprises at least one of said light sources arranged at a bottom portion of the recess. The present invention also relates to a method for providing such lighting panel.

BACKGROUN OF THE INVENTION Light emitting diodes (LEDs) are widely used in a vast amount of applications.

During operation of a LED, a voltage is applied over a p/n-junction which enables electrons to be relaxed to a lower energy state, thus emitting light. By designing p/n-junctions of different materials it is possible to obtain light of a specific color, ranging from deep ultraviolet up to infrared. LEDs can be low power consuming (i.e. in the order of milliwatts), but LEDs are also designed to consume more power, up to several Watts. Such LEDs are generally denoted by the term "high power LEDs".

High power LEDs are not commonly used for direct illumination due to glare and light uniformity issues. Further, applications for indirect illumination suffer from low system efficiency. Also, it is difficult to design a thin lighting module because of the need for heat sinks.

US7072096B addresses the need for optical uniformity by describing an optical illumination system which has a LED light source array, of which each LED region is surrounded by reflecting sidewalls whose output is processed by elevating prism films and polarization converting films. The main purpose of the disclosed illumination system is to provide a compact and efficient system for direct illumination.

However, the number of films makes the system inexpedient for applications where system size and thickness are two major parameters. Also, such films are very expensive and the number of processing steps during manufacturing leads to high production costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improvement of the above techniques and prior art. More particularly, it is an object of the present invention to provide a thin and compact lighting panel.

The above objective is provided according to a first aspect of the invention by a lighting panel comprising a layer having an upper surface and a lower surface, the layer further comprising a plurality of light sources, and a distribution of optical elements, each optical element forming a recess extending from the upper surface towards the lower surface. Each recess comprises an opening which is arranged in the plane of the upper surface, and a bottom portion defining a rounded surface, and each optical element comprises at least one of said light sources arranged at the bottom portion of said recess. The lighting panel according to the first aspect of the invention is advantageous in that it provides a thin panel with high efficiency.

The opening of each recess may define a rounded surface, which allows simple manufacturing processes. The opening of each recess may define a rectangular surface, which is advantageous in that each optical component provides a rectangular beam shape. This is advantageous when illuminating rectangular scenes, thus reducing overfill.

The surface defined by the bottom portion of each recess may be smaller than the surface defined by the opening of each recess, thus providing a divergent illumination profile. The lighting panel may further comprise a second layer arranged adjacent to the upper surface of the layer thus covering the top area of the recesses. The second layer may be optically transparent which is advantageous in that the light sources are protected from outer damage without deteriorating from the high efficiency of the lighting panel. The recess of each optical element may extend through the layer from the upper surface to the lower surface, whereby the thickness of the layer is reduced.

The distance between the opening and the bottom portion of each recess may be smaller than the distance between the upper surface and the lower surface of the layer, thus forming a supporting portion between the lower surface of the layer and the bottom portion of each recess. This is advantageous in that the lighting panel is made more robust. The layer may be made in one piece, which allows for a reduced number of processing steps.

Each optical element may comprise an optically reflective coating, which is advantageous in that the efficiency of the lighting panel is increased. The layer may be made of metal or polymer material. Thus, inexpensive and conventional materials are used.

Each recess may comprise an encapsulation extending from the bottom portion towards the opening, thus covering the at least one light source. This is advantageous in that the optical performance of each optical element is enhanced. Each light source may be a high power LED. Thus, the lighting panel provides high luminance in an efficient way.

According to a second aspect of the invention, a luminaire for illuminating a room is provided, the luminaire comprising at least one lighting panel according to the first aspect of the invention. The advantages of the first aspect of the invention are also applicable for this second aspect of the invention.

The above objective is provided according to a third aspect of the invention by a method for providing a lighting panel, comprising the step of producing a layer having a distribution of optical elements, each optical element forming a recess extending from an upper surface of the layer towards a lower surface of the layer, the optical element comprising an opening which is arranged in the plane of the upper surface, and a bottom portion defining a rounded surface. The method further comprises the step of arranging a plurality of light sources so that each optical element comprises at least one of said light sources. The advantages of the first aspect of the invention are also applicable for this second aspect of the invention. The step of producing the layer may comprise injection moulding or etching, which is advantageous in that manufacturing processes known per se is used.

Other objectives, features and advantages of the present invention will appear from the following detailed disclosure, from the attached dependent claims as well as from the drawings.

The term "rounded" hereby refers to the shape of any two dimensional closed curve being simple (i.e. not intersecting itself), differentiable (i.e. no sharp corners), and convex. A rounded shape does not necessarily need to be symmetrical. For example, a rectangle is not considered to be rounded. The surface defined by the opening of each recess is referring to the cross- section of the open end of each recess. Correspondingly, the surface defined by the bottom portion of each recess is referring to the cross-section of the bottom end of each recess.

It should be noted that the term "luminaire" means a device that is used for providing light in a room, for purpose of illuminating objects in the room.

A room is in this context typically an apartment room or an office room, a gym hall, a room in a public place or a part of an outdoor environment, such as a part of a street. Accordingly, a luminaire is not, for example, a video projector or a backlight for a TV or mobile phone.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which

Fig. 1 is a side view of a lighting panel according to one embodiment of the invention.

Fig. 2a is a perspective view of an optical element according to a first embodiment.

Fig 2b is a perspective view of an optical element according to a second embodiment. Fig. 3 is a side view of a lighting panel according to a further embodiment of the invention.

Fig. 4 is a side view of a lighting panel according to yet another embodiment of the invention.

Fig. 5 is a side view of a lighting panel according to a further embodiment of the invention.

Fig. 6 is a side view of a lighting panel according to another embodiment of the invention.

Fig. 7 is a perspective view of a luminaire according to one embodiment of the invention. Fig. 8 is a side view of a room illuminated by luminaires according to the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows a lighting panel 1, having a layer 2 with an upper surface 3 and a lower surface 5. The layer 2 has a plurality of optical elements 10, each optical element forming a recess 12 extending from the upper surface 3 towards the lower surface 5. Each recess 12 has an opening 14 in the plane of the upper surface 3, and a bottom portion 16. A LED 7 is mounted at the bottom portion 16 of each recess 12.

In fig. 2a and 2b, different embodiments of the optical element 10 are shown. The bottom portion 16 is defining a rounded surface which has means (not shown) for mounting a LED thereto. In fig. 2a, the opening 14 is defining a rounded surface, and in fig. 2b, the opening 14 is defining a rectangular surface. The optical element 10 has sidewalls 17 extending between the bottom portion 16 and the opening 14, thus defining the recess 12.

With reference to fig. 1, the lighting panel 1 is operating as follows. Each LED is connected to a power means (not shown) for driving the LEDs. When a voltage is applied over the LED, light will be emitted. The light distribution can be lambertian, bat-wing, Gaussian, etc. The light will be incident on the sidewalls 17 and reflected, so that light is emitted out from the opening 14. The optical element 10 is thus shaping the light distribution of the emitted light.

The layer 2 may be made of polymeric material, metal or semiconductor materials. The optical elements 10 may be recesses filled with air, a dielectric material block or a recess filled with an encapsulation. The optical elements 10 may be covered by a second layer 20. The sidewalls 17 may reflect light either by means of a reflective coating or by total internal reflection. In case of total internal reflection, the refractive index of the recess 12 and the refractive index of the layer 2 must be different.

In fig. 3, the second layer 20 is mounted on top of layer 2. The second layer 20 is optically transparent in order for the light emitted from the LEDs 7 to be transmitted through the second layer 20. The lighting panel 1 further comprises a back plate 30. The back plate 30 is a printed circuit board (PCB), but may also serve as a heat sink.

Now referring to fig. 4, the optical elements 10 are extending from the upper surface 3 of the layer 2 towards the lower surface 5, leaving a residual portion 9 of the layer 2 to act as a support. In this particular embodiment, the light sources 7 are indicated as LED packages, including a lens 8. The residual portion 9 may have structures (not shown) for guiding electrical connections between the LEDs and a power means (not shown).

In fig. 5, the sidewalls 17 of the optical elements 10 are coated with an optically reflecting coating, e.g. aluminium, in order to reduce reflection losses. Fig. 6 shows a lighting panel 1, having a second layer 20 covering the optical elements 10 of the layer 2. The second layer 20 is partially filling the recesses 12 down to a level up to which the recess 12 is filled with an encapsulation 40. The encapsulation 40 and the second layer 20 may have different refractive index in order to enhance the efficiency of the lighting panel 1. Further, the encapsulation 40 may comprise small particles (not shown) to scatter the emitted light in order to reduce so called hot spots when viewing the lighting panel 1 directly.

The lighting panel 1 may be manufactured by providing the layer 2, having a plurality of optical elements 10. Secondly, LEDs 7 are arranged in each optical element 10, and connected to electrical connections. As an optional step, encapsulations 40 and/or further layers 20 may be arranged. The step of providing the layer 2 can be performed by conventional manufacturing processes. In case of a layer 2 made by polymeric material, the layer 2 may be provided by means of injection moulding. Thus, the layer 2 having optical elements 10 is provided in a single step. The sidewalls 17 may then be coated with a reflective material, or the recesses 12 may be filled with an encapsulation 40. If metals or semiconductor materials are preferred, the step of providing the layer 2 may be performed by means of etching. In case of a silicon layer 2, the etching may be performed using KOH, which is an isotropic process. After etching, the recesses 12 may be coated with a reflective material, or filled with an encapsulation 40. With reference made to all previously described embodiments, the size of the optical elements 10 depend on the use of LED dies or LED packages as light sources 7. In case of LED dies, the bottom portion 16 of each recess 12 may be 2 mm in diameter, the opening 14 may be 3.3 mm in diameter, and the height of the optical element 10, i.e. the shortest distance between the bottom portion 16 and the opening 14, may be 1.7 mm. In case of LED packages, the bottom portion 16 of each recess 12 may be 6 mm in diameter, the opening 14 may be 10 mm in diameter, and the height of the optical element 10 may be 4,75 mm. Other sizes may however also be possible.

A number of lighting panels 1 may be combined in order to provide a large surface luminaire 100, as shown in fig. 7. In such luminaire 100, the optical elements 110 are arranged in a two-dimensional distribution.

In fig. 8, four luminaires 100 are mounted in a ceiling 200 in order to provide a general lighting in a room. By changing the shape of the optical elements 10, the output beam angle of the luminaires could be controlled. The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

Claims

CLAIMS:

1. A lighting panel comprising a layer (2) having an upper surface (3) and a lower surface (5), the layer (2) further comprising: a plurality of light sources (7), and a distribution of optical elements (10), each optical element (10) forming a recess (12) extending from the upper surface (3) towards the lower surface (5), wherein each recess (12) comprises an opening (14) which is arranged in the plane of the upper surface (3), and a bottom portion (16) defining a rounded surface, and each optical element (10) comprises at least one of said light sources (7) arranged at the bottom portion ( 16) of said recess (12).

2. A lighting panel according to claim 1, wherein the opening (14) of each recess (12) is defining a rounded surface.

3. A lighting panel according to claim 1, wherein the opening (14) of each recess (12) is defining a rectangular surface.

4. A lighting panel according to any one of claims 1-3, wherein the surface defined by the bottom portion (16) of each recess (12) is smaller than the surface defined by the opening (14) of each recess (12).

5. A lighting panel according to any one of claims 1-4 further comprising a second layer (20) arranged adjacent to the upper surface (3) of the layer (2).

6. A lighting panel according to any one of claims 5, wherein the second layer (20) is optically transparent.

7. A lighting panel according to any one of claims 1-6, wherein each recess (12) is extending through the layer (2) from the upper surface (3) to the lower surface (5).

8. A lighting panel according to any one of claims 1-6, wherein the distance between the opening (14) and the bottom portion (16) of each recess (12) is smaller than the distance between the upper surface (3) and the lower surface (5) of the layer (2).

9. A lighting panel according to claim 8, wherein the layer (2) is made in one piece.

10. A lighting panel according to any one of claims 1-9, wherein each optical element (10) comprises an optically reflective coating.

11. A lighting panel according to any one of claims 1-10, wherein the layer (2) is made of metal.

12. A lighting panel according to any one of claims 1-10, wherein the layer (2) is made of polymer material.

13. A lighting panel according to any one of claims 1-12, wherein each recess (12) comprises an encapsulation (40) extending from the bottom portion (16) towards the opening (14), thus covering the at least one light source (7).

14. A lighting panel according to any one of claims 1-13, wherein each light source (7) comprises a high power light emitting diode.

15. A luminaire for illuminating a room, the luminaire (100) comprising at least one lighting panel (1) according to any one of claims 1-14.

16. A method for providing a lighting panel, comprising the steps of producing a layer having a distribution of optical elements, each optical element forming a recess extending from an upper surface of the layer towards a lower surface of the layer, the optical element comprising an opening which is arranged in the plane of the upper surface, and a bottom portion defining a rounded surface, and arranging a plurality of light sources so that each optical element comprises at least one of said light sources.

17. A method according to claim 16, wherein the step of producing the first layer comprises injection moulding.

18. A method according to claim 16, wherein the step of producing the first layer comprises etching.