WO2011107904A1

WO2011107904A1 - Lighting device with lamp and oled

Info

Publication number: WO2011107904A1
Application number: PCT/IB2011/050766
Authority: WO
Inventors: Georg Henninger; Konrad Sell
Original assignee: Koninklijke Philips Electronics N.V.; Philips Intellectual Property & Standards Gmbh
Priority date: 2010-03-03
Filing date: 2011-02-24
Publication date: 2011-09-09

Abstract

The invention relates to a lighting device (200) comprising a lamp (210), for example a halogen lamp, that emits primary light (L1). Moreover, it comprises a reflector (R) for reflecting said primary light (L1) into a desired direction, wherein said reflector (R) comprises an OLED (230). Controlling the lamp (210) and the OLED independently allows for example to generate a low- level basic illumination with the OLED when the lamp (210) is switched off.

Description

LIGHTING DEVICE WITH LAMP AND OLED

FIELD OF THE INVENTION

The invention relates to a lighting device and to a method for operating such a device, wherein the lighting device comprises a lamp and an OLED (Organic Light Emitting Diode).

BACKGROUND OF THE INVENTION

From the WO 2008/90492 Al, a lighting device is known in which a lamp generates an emission of light that is transmitted through a transparent OLED, wherein light generated by the OLED can additionally be emitted.

SUMMARY OF THE INVENTION

Based on this background it was an object of the present invention to provide an alternative lighting device with an improved functionality.

This object is achieved by a lighting device according to claim 1 and a method according to claim 2. Preferred embodiments are disclosed in the dependent claims.

The lighting device according to the present invention may be adapted for a variety of different applications, for example for interior lighting of rooms or vehicles. It comprises the following components:

At least one lamp for generating an emission of light, wherein said light will in the following be called "primary light" for purposes of reference. The lamp may comprise any known means for generating light, for example at least one filament lamp, fluorescent lamp, luminescent tube, halogen lamp, low-pressure gas discharge lamp, high- pressure gas discharge lamp, LED or OLED.

A reflector for reflecting at least a part of the aforementioned primary light into a predetermined desired direction. The reflector shall further comprise at least one OLED which can generate an emission of light that will be called "secondary light" in the following.

The OLED is most preferably disposed in the space between the lamp and the reflecting surface of the reflector, i.e. on the (interior or exterior) surface where the actual light reflection takes place. Consequently, primary light coming from the lamp must first pass at least partially through the (insofar transparent) OLED before it can reach the reflecting surface. Due to the reflection at the reflecting surface, the emission of secondary light from the OLED will in this case effectively take place in the same direction as the reflection of primary light.

According to a second aspect, the invention relates to a method for operating a lighting device, particularly a lighting device of the kind defined above. The method comprises the following steps:

Generating an emission of primary light with a lamp.

Reflecting at least a part of the primary light into a predetermined direction by a reflector, wherein said reflector comprises at least one OLED.

- Generating an emission of secondary light by the OLED. Preferably, this secondary light is also at least partially reflected by the reflector and thus effectively emitted in the same general direction as the (reflected) primary light.

The described lighting device and the method provide means for generating an overall light emission that is selectively composed of primary light originating from a lamp and secondary light originating from an OLED. As the secondary light of the OLED is generated by a reflector at which the primary light is reflected into a desired direction, several advantages can be achieved: First, the spatial distribution of the secondary light can be made quite similar to that of the primary light. Secondly, the typically large surface area of the reflector can be used for generating secondary light, thus allowing the generation of a comparatively high intensity of OLED light. Thirdly, the lighting device may be realized with small dimensions due to its integrated design of lamp, reflector, and OLED. Moreover, the lighting device allows for an easy realization of mixed light and background illumination.

In the following, various preferred embodiments of the lighting device and the method defined above will be described.

In the most simple case, the lamp and the OLED may be controlled commonly, i.e. they may for example electrically be operated in series. According to a preferred embodiment, the lighting device comprises however a control unit for controlling the OLED independently of the lamp. This enables a variety of new applications of the lighting device. As one example, it is possible to switch the lamp off and to generate only secondary light with the OLED. This may be used as a low-level security illumination in a dark room. In case of a motor vehicle, the residual illumination by the secondary OLED light may serve as the low-energy daytime illumination. The control unit may be realized by dedicated electronic hardware, digital data processing hardware with associated software, or a mixture of both as it is known to a person skilled in the art. The reflecting surface of the reflector may simply be planar, which is particularly simple to realize. Alternatively, the reflecting surface may have a three- dimensional shape that is optimally designed to achieve the desired overall light emission of the lighting device from the actual light emission of the lamp. A 3D reflecting surface may be composed of (planar) facets, or it may have a continuously bent shape. In an important example, the reflecting surface will be concave, e.g. cup-shaped. Moreover, the reflecting surface may be rotationally symmetric about some given axis. As the OLED is typically disposed (as a uniform layer) close to the reflecting surface, it will assume the given three- dimensional shape of this surface, too.

The reflecting surface may be produced from any material that has the desired optical reflectivity in the spectral range of the primary light. Most preferably, the reflecting surface may comprise high reflective metals, as e. g. aluminum and/or silver, and/or an interference (IF) filter, as e. g. a so called dichroic.

The part of the OLED in front of the reflecting surface of the reflector must be transparent enough to allow the passage of primary light to said reflecting surface and back again. In a preferred embodiment, the complete OLED is a component that fulfills this prerequisite, having a transparency of typically at least 50 %, preferably at least 70 %, most preferably at least 90 %. Moreover, this transparent OLED is disposed on a reflecting carrier which comprises the reflecting surface. The reflecting carrier may particularly be a reflector or mirroring element as it is known from conventional reflector lamps.

According to an alternative design, the light reflecting surface of the reflector is integrated into the OLED. In this case, the OLED only needs to be transparent up to the reflecting surface. The reflecting surface may in this embodiment for example be constituted by one electrode of the OLED, and the reflector may simply be identical to the (reflecting) OLED.

The OLED is preferably attached to some carrier for mechanical support. This may for instance be the above mentioned reflecting carrier "on" which a transparent OLED is disposed (the term "on" meaning that the OLED is arranged between the lamp and the carrier). In the aforementioned case of an OLED with an integrated reflecting layer, the OLED may also be disposed "on" a carrier. Alternatively, the OLED may be "below" the carrier in the sense that the carrier is arranged between the lamp and the OLED. In the latter case, the carrier must be transparent to allow the passage of primary light to the reflecting surface in the OLED and back. The OLED may be a connected device that is operated as a single unit. In an alternative embodiment of the invention, the OLED comprises a plurality of selectively controllable sub-units. In this case the amount of emitted secondary light and/or its spatial distribution may more readily be controlled.

According to a further development of the aforementioned embodiment, the sub-units of the OLED may have different colors and/or color temperatures. In this case the overall spectral composition of the resulting secondary light emission may selectively be adapted.

In another embodiment of a lighting device with sub-units, said sub-units may be arranged symmetrically with respect to a given point, axis (for example the optical axis of the lamp) and/or plane. The resulting light emission will then be symmetrical, too. The symmetry may preferably be a symmetry with respect to at least one planar mirroring plane and/or a rotational symmetry with respect to a given axis.

The lighting device may optionally comprise an energy storage for supplying the OLED autonomously with energy, for example in cases of emergency and/or a failure of power supply from the public grid. The energy storage may for example be realized by a capacitor or a reloadable battery.

The OLED may in general be composed in any way known to a person skilled in the art. In particular, the OLED may be one in which the active layer is a polymer

(PolyLeds) or one in which the active layer is a Small molecule (SmOLEDs). More information about OLEDs that are applicable in the present invention may be found in the WO 2008/90492 Al.

Besides a reflecting surface and an OLED, the reflector may optionally comprise various other mechanical and/or optical components, for example at least one of the following ones:

A protective transparent layer that may be disposed on at least one reflector surface, particularly on its OLED, to protect it mechanically.

An antireflexion coating that may be disposed on at least one reflector surface, particularly its interface to the ambient air, to prevent losses of primary and/or secondary light due to undesired reflections.

An IR-reflecting layer that may be disposed on at least one reflector surface, particularly in front of the OLED with respect to the light path of the primary light, to prevent damaging of the OLED by infrared light. An UV-reflecting layer and/or an UV-absorbing layer that may be disposed on at least one reflector surface, particularly in front of the OLED with respect to the light path of the primary light, to prevent damaging of the OLED by ultraviolet light.

The lighting device may optionally have various further components, for example optical elements for improved light outcoupling from the OLED, protective glasses, an encapsulation and/or sealing etc.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

Fig. 1 schematically shows a section through a first lighting device

according to the present invention in which an OLED is disposed on a reflecting carrier;

Fig. 2 schematically shows a top view onto the lighting device of Figure 1; Fig. 3 schematically shows in a cross-sectional view four possible sequences of layers for the reflector of Figure 1;

Fig. 4 schematically shows a section through a second lighting device

according to the present invention in which an OLED is disposed on the rear side of a transparent carrier;

Fig. 5 schematically shows in a cross-sectional view two possible sequences of layers for the reflector of Figure 4.

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

DESCRIPTION OF PREFERRED EMBODIMENTS

It should be noted that all the Figures are only meant to be schematic, i.e. they are not to scale and the particular design of other lighting devices according to the invention may considerably differ from that shown in the examples.

Figures 1 and 2 show a first embodiment of a lighting device 100 that is designed according to the principles of the present invention. The lighting device 100 is intended to produce an effective light emission in the principal direction of an optical axis A (parallel to the z-axis in Figure 1), and it comprises two main components:

First, it comprises a lamp 110 as a main light emitting element that can selectively emit primary light LI, indicated in Figure 1 by exemplary light rays. The lamp 110 may for example be a filament lamp, fluorescent lamp, luminescent tube, halogen lamp, low-pressure gas discharge lamp, high-pressure gas discharge lamp, or an LED (single or array) or OLED (single or array). Preferably, the lamp 110 is exchangeable.

Secondly, the lighting device 100 comprises a reflector R for reflecting primary light LI of the lamp 110 that was emitted in an undesired direction, thus redirecting it into the desired direction. The side of the reflector R that faces the lamp 110 will in the following be called "front side", while the opposite side is called "rear side". According to the invention, the reflector R comprises two principal components:

The first principal component of the reflector R is a reflecting surface S at which the primary light is actually reflected. In the shown example, the reflecting surface S is the top surface of a reflecting carrier 120. The reflecting material of said carrier may comprise high reflective metals, as e. g. aluminum and/or silver, and/or an IF filter. In an alternative embodiment, the reflecting surface might be at the rear side of the reflecting carrier, with the body material of this carrier being transparent.

The second principal component of the reflector R is an OLED 130. In the shown first embodiment, the OLED 130 is disposed between the lamp 110 and the reflecting surface S on the reflecting carrier 120. The OLED may selectively be controlled to generate an emission of secondary light L2 that is superposed to the emission of primary light LI .

The shape of the reflector R and/or the reflecting surface S may be rotationally symmetric about the optical axis A of the lamp 110, resulting in a cup-shape. In general, the reflector R and/or the reflecting surface S may be arranged symmetrically with respect to a given point, axis and/or plane. Besides this, free shapes without a symmetry are however possible, too, particularly in automotive lighting.

Besides the described main components, the lighting device 100 comprises additional elements that are not or only partly shown in the Figures. Most of all, it further comprises a control unit 140 for selectively and independently controlling the lamp 110 and the OLED 130. It may optionally comprise an energy storage 150, for example a capacitor, for operating the OLED 130 in cases of power failure. Figure 1 further depicts a transparent cover 121 that is disposed as a protection on the opening of the cup-shaped reflector R. The top view onto the lighting device 100 shown in Figure 2 illustrates that the OLED 130 may optionally be composed of a plurality of (in the shown case four)

sub-units 130a, 130b, 130c, 130d. The sub-units are symmetrically arranged about the optical axis A like the petals of a flower, thus yielding a homogenous distribution of the emitted secondary light L2. The sub-units are individually connected to terminals 131a, 132a, ...

13 Id, 132d at their centre and their periphery, respectively (wherein for example the interior terminals 131a-131d could be connected to each other). The connection to individual terminals allows to operate the sub-units independently from each other. In particular, the sub-units 130a, 130b, 130c, 130d may have different colors and/or color temperatures, which allows to adjust the resulting overall output color and/or color temperature of primary light plus secondary light by operating the individual sub-units accordingly. Color temperature tuning is especially important for different shades of white light.

A typical OLED according to the state of the art consists of active organic layers, a cathode, an anode, and a substrate. The active organic layers consist of a hole transport layer (typically about 100 nm thick) and a light emitting polymer (typically about 80 nm thick) for a polymer-based OLED (PolyLeds). The smallmolecule version of an OLED (SmOLEDs) consists of some more layers: hole injecting, emitting, hole blocking and electron transport layer. The OLED active layer is mounted on a substrate which may be sputtered with, for instance, indium tin oxide (ITO), thereby forming an ITO layer of about 150 nm to function as a hole-injecting electrode. The cathode applied on top of the organic layers that may ensure electron injection is of the order of 100 nm. The OLED may optionally be coated by additional transparent protection layers, and it will typically be embedded in an encapsulation.

Based on the aforementioned typical OLED design, Figure 3 shows four possible adapted designs of a reflector R that may be used in a lighting device according to Figure 1. An exemplary light ray indicates in each drawing the layer at which reflection takes place.

The first design shown in Figure 3 a) comprises the following sequence of layers:

- a first electrode layer ELI, which is transparent and may be made from a transparent conductive oxide like ITO;

organic layers OL;

a second electrode layer EL2, which is also transparent and may be made from a transparent conductive oxide like ITO; a reflecting surface S, which may for example be a reflecting interference filter (IF);

a substrate SUB, for example a metal body or plastic body.

The reflective surface S and the substrate SUB may optionally merge into a single layer (constituting a "reflective carrier 120" in Figure 1).

In the second design shown in Figure 3 b), the sequence of the substrate SUB and the reflecting surface S is exchanged with respect to embodiment a), which requires that the substrate SUB must be transparent.

In the third design shown in Figure 3 c), the second electrode is simultaneously the reflecting surface. This integrated layer is denoted as "EL2+S" and may be constituted by a highly reflective metal layer, e.g. Al, Ag and/or alloys thereof.

In the fourth design shown in Figure 3 d), the second electrode is simultaneously the reflecting surface and the substrate. This integrated layer is denoted as "EL2+S+SUB" and may be constituted by a highly reflective metal layer, e.g. Al, Ag and/or alloys thereof.

It should be noted that still other designs of the reflector R in the lighting device 100 of Figure 1 are possible, too.

Figure 4 shows in a schematic side view a lighting device 200 according to a second embodiment of the invention. Components that are similar or identical to that of the first lighting device 100 are indicated with reference signs which are by 100 larger than those of Figures 1 and 2. These components will not be described in detail again.

The essential novelty of the lighting device 200 is that, in its reflector R, the OLED 230 is disposed "below" a transparent carrier 220, i.e. said carrier 220 is located between the lamp 210 and the OLED 230. The transparent carrier 220 has primarily the task to provide mechanical support for the OLED. It is preferably made from a material with a high transparency (e. g. glass, plastics). The OLED 230 can be built directly onto the rear side of the transparent carrier 220, which provides a simple way to realize the lighting device 200 starting from conventional reflector lamps.

Figure 5 shows two possible designs of a reflector R that may be used in a lighting device 200 according to Figure 4. An exemplary light ray indicates in each drawing the layer at which reflection takes place.

The first design shown in Figure 5 a) comprises the following sequence of layers:

a substrate SUB serving as the "transparent carrier 220"; a first electrode layer ELI, which is transparent and may be made from a transparent conductive oxide like ITO;

organic layers OL;

a second electrode layer EL2, which is also transparent and may be made from a transparent conductive oxide like ITO;

a reflecting surface S, which may for example be a reflecting IF. In the second design shown in Figure 5 b), the second electrode is simultaneously the reflecting surface. This integrated layer is denoted as "EL2+S" and may be constituted by a highly reflective metal layer, e.g. Al, Ag and/or alloys thereof.

The reflecting surface S may optionally be coated by additional transparent and/or non-transparent protection layers.

It should be noted that still other designs of the reflector R in the lighting device 200 of Figure 4 are possible, too.

The described lighting devices 100, 200 can be provided with a variety of further components to enhance their performance.

Thus the front surface of the reflector R (i.e. of the OLED 130 in Figure 1 or of the transparent carrier 220 in Figure 3) may be provided with an antireflexion coating to avoid reflection losses of primary and secondary light at the interface to the air.

Furthermore, the front surface of the reflector R (i.e. of the OLED 130 in Figure 1 or of the transparent carrier 220 in Figure 3) may be provided with an IR reflecting layer, an UV reflecting layer, and/or an UV-b locking layer. In this way negative effects of IR or UV components of the primary light on the OLED can be avoided.

While the Figures suggest a continuously bent shape of the reflector R, the reflector and/or its components might also (at least partially) be composed of a plurality of facets.

The reflector may be composed by several individual planar OLEDs.

In summary, the examples show embodiments of a lighting device in which a three-dimensional OLED is integrated into the reflector of a reflector lamp. The OLED can serve as constant base illumination with low power consumption while the lamp is off. It may add to the light that is reflected from the main light source of the reflector lamp in a way that the amount of light lost by passing twice through the OLED is compensated or at least minimized.

Applications of such lighting devices may be e.g. in automotive lighting. The OLED may for instance provide the daytime running lights, while the primary light serves as headlight unit (or vice versa). Or the OLED may provide a taillight while the primary light serves as a brake light (or vice versa). The OLED may particularly be used to generate a constant light when the lamp is off, e.g. as required for an emergency light during power failure. For this a capacitor and appropriate electronics can be added. In applications of general lighting, the OLED may provide a diffuse background illumination while the primary light (shaped by the reflector) provides a spot-illumination.

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

1. A lighting device (100, 200), comprising

- at least one lamp (110, 210) for generating an emission of primary light (LI);

a reflector (R) for reflecting at least a part of the primary light (LI) into a

predetermined direction, wherein said reflector comprises at least one OLED (130, 230) for generating an emission of secondary light (L2).

2. A method for operating a lighting device (100, 200), comprising:

generating an emission of primary light (LI) with a lamp (110, 210);

reflecting at least a part of the primary light (LI) into a predetermined direction by a reflector (R), wherein said reflector comprises at least one OLED (130, 230);

generating an emission of secondary light (L2) by the OLED.

3. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the lighting device (100, 200) comprises a control unit (140, 240) for controlling the OLED (130, 230) independently of the lamp (110, 210).

4. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the reflecting surface (S) of the reflector (R) has a planar shape or a three-dimensional shape, particularly a cup-shape.

5. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the reflecting surface (S) of the reflector (R) comprises high reflective metals, as e. g. aluminum and/or silver, and/or an interference (IF) filter .

6. The lighting device (100) according to claim 1 or the method according to claim 2,

characterized in that the OLED (130) is transparent and disposed on a reflecting carrier (120).

7. The lighting device (200) according to claim 1 or the method according to claim 2,

characterized in that the reflecting surface (S) of the reflector (R) is integrated into the OLED (230).

8. The lighting device (200) according to claim 1 or the method according to claim 2,

characterized in that the OLED (230) is attached to a transparent carrier (220).

9. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the OLED (130, 230) comprises a plurality of selectively controllable sub-units (130a, 130b, 130c, 130d).

10. The lighting device (100, 200) or the method according to claim 9, characterized in that the sub-units (130a, 130b, 130c, 130d) have different colors and/or color temperatures.

11. The lighting device (100, 200) or the method according to claim 9, characterized in that the arrangement of the sub-units (130a, 130b, 130c, 130d) has a symmetry with respect to a given point, axis (A), and/or plane.

12. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the lighting device (100, 200) comprises an energy storage (150, 250) for supplying the OLED (130, 230) autonomously with energy.

13. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the OLED (130, 230) is selected from the group consisting of PolyLEDs and Small molecule OLEDs.

14. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the refiector (R) comprises a transparent protective coating, an antireflexion coating, an IR-reflecting coating, an UV-reflecting coating, and/or an

UV-absorbing coating.

15. The lighting device (100, 200) according to claim 1 or the method according to claim 2,

characterized in that the lamp (110, 210) comprises a component that is selected from the group consisting of filament lamps, fiuorescent lamps, luminescent tubes, halogen lamps, low-pressure gas discharge lamps, high-pressure gas discharge lamps, LEDs, arrays of LEDs, OLEDs and arrays of OLEDs.