WO2009101579A1

WO2009101579A1 - Lighting device with variable beam characteristics

Info

Publication number: WO2009101579A1
Application number: PCT/IB2009/050546
Authority: WO
Inventors: Hans-Peter Stormberg
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2008-02-13
Filing date: 2009-02-10
Publication date: 2009-08-20
Also published as: TW200949146A

Abstract

The invention relates to a lighting device (100) comprising at least two OLED zones (Z, Z') with corresponding light out-coupling elements (110, 110'), wherein said OLED zones can individually be supplied with power (i, i') to adjust the overall output light beam. The OLED zones can particularly be established by separate OLEDs or by a continuous OLED layer in contact with separate electrodes.

Description

LIGHTING DEVICE WITH VARIABLE BEAM CHARACTERISTICS

FIELD OF THE INVENTION

The invention relates to a lighting device having adjustable beam characteristics.

BACKGROUND OF THE INVENTION

The GB 2 437 162 A discloses a lighting fixture for passenger cabins in an aircraft that comprises an array of light emitting diodes behind a lens. By selectively powering or switching-off different sub-sections of the array, different light beams can be generated that are for example directed two neighboring passenger seats.

SUMMARY OF THE INVENTION

Based on this situation it was an object of the present invention to provide a lighting device with a high flexibility regarding the adjustment of its overall output light beam. This object is achieved by a lighting device according to claim 1.

Preferred embodiments are disclosed in the dependent claims.

The lighting device according to the present invention comprises the following components: a) At least two individually controllable "OLED zones", i.e. zones of light emission based on organic light emitting diodes (OLEDs), wherein each of these OLED zones comprises at least one corresponding light out-coupling element, and wherein the OLED zones together with said elements generate beams of different characteristics. In this context, the term "beam" shall denote the spatial and spectral emission characteristics of a light source that can for example be described by the intensity I(θ, λ)-dΩ-dλ of light of a wavelength between λ and (λ+dλ) that is emitted into the solid angle dΩ in direction θ. While OLEDs themselves usually have a lambertian emission characteristics, the characteristics of the beams that they generate in combination with the light out-coupling elements can be designed nearly arbitrarily.

b) A controller for selectively supplying power to the OLED zones, i.e. for supplying each OLED zone individually with power independent of the other OLED zone(s). Moreover, the individual amounts of power may be changed during the operation of the lighting device, for instance autonomously by the controller or in response to external inputs from e.g. a user. Preferably, the power supply can be changed continuously or in small steps within a given range. The possibility of an individual power supply will usually require that each OLED zone is connected to the controller via at least one electrode which is electrically separated from other electrodes. The lighting device has the advantage to allow an adjustment of its overall output light beam particularly in shape, size, spectral composition (i.e. color) and/or intensity during its operation simply by changing the power supply to the OLEDs. Moreover, the beam adaptation can be achieved in a continuous manner and without a need for physical changes in the configuration of the device. There are different possibilities to realize the individually controllable

OLED zones. According to a first approach, each OLED zone comprises a separate organic light emitting layer (or short "OLED layer"), wherein the term "organic light emitting layer" shall comprise a multilayer of different organic materials. In this case the spectral composition of the light emitted from the OLED zones can be made different by choosing different organic materials for the zones.

The aforementioned design is particularly realized in the extreme case that the OLED zones of the lighting device comprise two separate OLEDs (i.e. separate organic light emitting layers with associated separate anodes and cathodes). Conventional, stand-alone OLEDs can be used in this case to build the lighting device. Another realization of the design with two separate organic light emitting layers is achieved if these layers are disposed on a common carrier, for example a glass or plastic substrate or a metal electrode, and/or in a common housing. Thus the lighting device can be designed with a unitary structure, provided that the necessary individual control of the OLED zones is guaranteed.

According to a second approach, the OLED zones comprise separate electrodes of the same given polarity (i.e. anode or cathode) contacting one continuous OLED layer. This approach corresponds to the extreme case of a highly integrated design. Thus a simplified manufacture of the lighting device is possible as it suffices to combine a larger, single OLED layer with a structured anode and/or cathode.

The at least two OLED zones of the lighting device preferably generate output light beams that are at least partially non-overlapping. This means that the light beams cannot be made congruent by a simple scaling of their size. Control of the overall beam shape can therefore be achieved by the superposition of two linearly independent emission characteristics.

In another embodiment, the OLED zones generate output light beams of different spectral composition. It will then be possible to adjust the color point or color temperature of the overall emission of the lighting device by setting the power supplies to the OLED zones appropriately.

The light out-coupling elements may be mounted without air gaps to the other components of the OLED zones, e.g. materially bonded to the OLED electrodes and/or to a front cover. Thus a very compact, robust design can be achieved.

Moreover, the light out-coupling elements of the lighting device may particularly comprise a lens, a prism, or a grating.

The light out-coupling elements may be separate optical components. Alternatively, at least one of them may be integrated into a front cover substrate (e.g. glass or plastic) that is disposed at the light emitting side of the lighting device. Such an integration may particularly be achieved by structuring the surface of said front cover, e.g. via a molding or imprinting technology.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. These embodiments will be described by way of example with the help of the accompanying drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically shows a first lighting device according to the present invention with separate OLEDs;

Figure 2 schematically shows a second lighting device according to the present invention with a single OLED layer;

Figure 3 schematically shows a third lighting device according to the present invention with light out-coupling elements integrated into a front cover.

Like reference numbers or numbers differing by integer multiples of 100 refer in the Figures to identical or similar components.

DETAILED DESCRIPTION OF EMBODIMENTS

The lighting device 100 of Figure 1 shows as one extreme case of the realization of the present invention the combination of two separate, stand-alone OLEDs, each of them realizing an individually contro liable "OLED zone" Z and Z', respectively. OLEDs have the advantage that they can be operated at low voltage, have long operational lifetime, and can readily be produced at low costs with large areas and in many colors. For detailed information on OLEDs, reference is made to literature (e.g. Klemens Brunner: "Industrialization of OLEDs for Lighting Applications and Displays", American Physical Society, APS March Meeting, March 121-25, 2005; Joseph Shinar (ed.): "Organic Light Emitting Devices, A survey", Springer, 2004).

The two aforementioned OLEDs are of substantially identical design and comprise the following main components:

An organic light emitting layer 130 ("OLED layer") as primary light emitter. As known to a person skilled in the art, such a layer is usually composed of separate sub-layers, in particular a hole-transport layer, an emitter layer, and an electron transport layer. A transparent electrode 120 of a first polarity, e.g. an indium-tin- oxide (ITO) anode, that is disposed on the light emitting front side of the OLED layer 130 behind a front cover 111, e.g. a glass or plastic plate.

An electrode 140 of a second polarity, e.g. a cathode from a metal like Al, that is disposed on the rear side of the OLED layer 130.

Additional components like a getter 150, a cover 160, and seals for hermetically encapsulating the organic layer 130.

In front of the OLED layers 130, corresponding light out-coupling elements are disposed, here represented by two transparent wedge-shaped prisms 110 and 110', respectively. The light out-coupling elements 110, 110' transform the (originally lambertian) emission characteristics of the OLED layers 130 into two different, asymmetric output light beams B and B'. As usual, the output light beams or emission characteristics B, B' are illustrated in the Figure by the loci (dashed lines) of the arrowheads of arrows I(θ) which start at the light emitting point and represent with their length the intensity of light emitted in the arrow-direction θ per unit of solid angle (steradian). If desired, the emission characteristics may additionally differentiate the emission in the spectral range.

The shown two output light beams B, B' are of different shape, in particular mirror-images of each other. Moreover, they can have different colors (i.e. spectral composition) due to e.g. different organic materials in the OLED layers 130 and/or a filtering in the prisms 110 and 110'. By driving the two OLED layers 130 with individual currents i and i', respectively, it will be possible to adjust the overall emission characteristics B+B' of the lighting device 100 with respect to its shape, size, intensity and/or color continuously over a wide range. The aforementioned driving currents i, i' are supplied to the OLED layers 130 via the associated electrodes 120 and 140 by a controller 170. The controller 170 may adapt the supplied powers (or their ratio with a constant total current i + i') for instance autonomously according to a given program, according to some feedback loop with sensors (not shown), or in response to external inputs by a user. In the shown embodiment, the light out-coupling elements 110, 110' are for example made from plastic or glass. They might optionally be combined in a single piece with the front cover 111 to function also as a carrier for the ITO electrode 120, the OLED layer 130, and the metal electrode 140. The latter components may for example be attached to the front cover 111 by vapor deposition.

It should further be noted that the light out-coupling elements could alternatively be realized by (plastic) foils or a (flat) glass substrate embossed with scattering and/or diffractive patterns.

Figure 2 shows as another case of the realization of the present invention a second embodiment of a lighting device 200 with two OLED zones Z, Z' of a highly integrated design. In contrast to the first embodiment, there is now a single, continuous organic light emitting (multi-) layer 130. Two individually controllable OLED zones Z, Z' are established on this layer by two separate electrodes 220 and 220' (e.g. transparent ITO anodes) which are individually connected to the controller 270. A single counter- electrode 240 is disposed on the opposite side of the OLED layer 230. A common getter 250 and a cover 260 accomplish the design. Figure 3 shows as a variant of the aforementioned design a third embodiment of a lighting device 300. In contrast to the first and second embodiments, the light out-coupling elements are realized in this case by a (diffractive) structure 310 in the outer side of the front cover 311 with different diffraction properties for the corresponding light out-coupling elements. A diffraction structure may be as an example a diffraction grating or any other suitable structure. The diffraction properties of each light out-coupling element can be chosen to obtain the desired light beam of each light out-coupling element. Said structure may be imprinted on or embossed in the (glass or plastic) cover 311, e.g. during the molding process of a plastic cover. The structure might alternatively be disposed on the inner side of the cover 311. Though the Figures show lighting devices 100, 200, 300 with just two

OLED zones, it should be noted that in practice a (much) higher number of individually controlled OLED zones may be present to achieve a higher flexibility and to realize more degrees of freedom for the adaptation of the overall output light beam. Moreover, the designs of Figures 1 to 3 can optionally be combined. Finally it is pointed out that in the present application the term

"comprising" does not exclude other elements or steps, that "a" or "an" does not exclude a plurality, and that a single processor or other unit may fulfill the functions of several means. The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Moreover, reference signs in the claims shall not be construed as limiting their scope.

Claims

CLAIMS:

1. A lighting device (100, 200, 300) with adjustable beam characteristics, comprising a) at least two individually controllable OLED zones (Z, Z') with corresponding light out-coupling elements (110, 110', 210, 310) for generating beams (B, B') of different characteristics; b) a controller (170, 270, 370) for selectively supplying power (i, i') to the OLED zones.

2. The lighting device (100) according to claim 1, characterized in that the OLED zones (Z, Z') comprise separate organic light emitting layers (130).

3. The lighting device (100) according to claim 2, characterized in that the OLED zones (Z, Z') comprise two separate OLEDs.

4. The lighting device according to claim 2, characterized in that the organic light emitting layers are disposed on a common carrier and/or in a common housing.

5. The lighting device (200, 300) according to claim 1, characterized in that the OLED zones (Z, Z') comprise separate electrodes (220, 220', 320, 320') of a given polarity contacting a continuous organic light emitting layer (230, 330).

6. The lighting device (100, 200, 300) according to claim 1, characterized in that the OLED (Z, Z') zones generate output light beams (B, B') that are at least partially non-overlapping.

7. The lighting device (100) according to claim 1, characterized in that the OLED zones (Z, Z') generate output light beams (B, B') of different spectral composition.

8. The lighting device (100, 200) according to claim 1, characterized in that the light out-coupling elements (110, 110', 210) are disposed without gap on corresponding OLED components (111, 211).

9. The lighting device (100, 200, 300) according to claim 1, characterized in that the light out-coupling elements comprise a lens, a prism (110, 110', 210), or a grating (310).

10. The lighting device (300) according to claim 1, characterized in that at least one light out-coupling element (310) is integrated in a front cover substrate (311).

11. The lighting device (300) according to claim 10, characterized in that a light out-coupling structure (310) is generated in the front cover substrate (311) by a molding or imprinting technology.