WO2013124379A1

WO2013124379A1 - Lighting device

Info

Publication number: WO2013124379A1
Application number: PCT/EP2013/053492
Authority: WO
Inventors: Hakim CHOUKRI; Bruno Dussert-Vidalet; Mohamed Khalifa; Hélène CLOAREC
Original assignee: Astron Fiamm Safety
Priority date: 2012-02-23
Filing date: 2013-02-21
Publication date: 2013-08-29
Also published as: FR2987497A1

Abstract

The present invention relates to a lighting device comprising at least one light source configured to generate a light emission (21) by means of a lighting surface (61), characterized in that the light source is an organic light-emitting diode (OLED), the lighting device comprising another lighting surface (62) by means of which the other light emission (22) is generated, each of the lighting surfaces (61, 62) being placed opposite one of the electrodes (2, 8) of the OLED, respectively, so as to enable lighting along the first illuminant by means of the lighting surface (61) and along the second illuminant by means of the other lighting surface (62).

Description

Lighting device

FIELD OF THE INVENTION

The technical field of the invention is that of lighting devices. It may for example be applique lamps, in suspension or on foot.

A particular application is a desk lamp.

BACKGROUND

In the field of lighting, design efforts are often oriented towards design or aesthetic issues.

However, lamps are known for which the light intensity can be varied or the emission frequency band, so as to change the color of the lighting.

There is however the need to offer more features in lighting devices. SUMMARY OF THE INVENTION

A first aspect of the present invention relates to a lighting device comprising at least one light source configured to produce a light emission by an illuminating surface. Advantageously, the monomeric sorbate is an organic electroluminescent diode, DELO, advantageously comprising a stack comprising successively and in order:

a first electrode of a first type of electrode, among anode or cathode, transparent,

a first transport layer of a first type of charge carrier, among electron and hole,

an emission layer,

a second transport layer of a second type of charge carrier among the electron and hole, different from the first type of charged carrier,

a second electrode, of a second type of electrode, different from the first type of electrode,

diode in which said emission layer is configured to emit a white color, such that the light emission is effected through said first electrode and is compliant, in particular with a color rendering index CRI and a correlated color temperature, with a first illuminant which preferably corresponds to daylight, and wherein said second electrode is transparent, and in that the thickness of the second transport layer is adjusted so that another emission is effected at the through said second electrode and is in particular conforming to a color rendering index CRI and correlated color temperature, to a second illuminant, which preferably corresponds to an incandescent bulb, different from the first illuminant. Advantageously, this device is such that it comprises another illuminating face through which the other light emission is produced, the illuminating faces being each disposed respectively with respect to one of the electrodes of the OLED, in order to be able to illuminate according to the first illuminating by the illuminating face and according to the second illuminant by the other illuminating face. Thus, thanks to the invention, it is possible to produce from a single light source of the DELO type two lighting beams each having an illumination specificity. This happens by pooling the source, including a unique OLED, so that benefits are generated, for example for:

- the size of the device;

- the connectors;

- the consumption of electrical energy.

The method according to the invention may additionally optionally have at least any of the following characteristics:

a support having an illuminating part incorporating the OLED and the illuminating faces;

said support is configured to emit the light emission upwards and the other light emission downwards;

the illuminating part of the device according to the invention is orientable;

the device constitutes a table lamp;

it comprises, for at least one of the illuminating faces, a removable occlusion member;

the first illuminant is a D65 illuminant corresponding to daylight;

the second illuminant is an illuminant A corresponding to an incandescent bulb;

the emission layer comprises a hot emission layer configured to emit a hot color and a cold emission layer capable of emitting a cold color, where the cold color is a mixture of blue and green and the hot color is a mixture of red and orange;

the hot emission layer comprises at least two hot emission sub-layers each configured to emit a different partial hot color, said partial hot colors being configured to produce said hot color, and wherein the cold emission layer comprises minus two cold emission sub-layers configured to each emit a different partial cold color, said partial cool colors being configured to produce said cold color;

- a first partial hot color is red, a second partial hot color is orange, a first partial cold color is blue, and a second partial cold color is green;

the red emission sublayer has a thickness of 13 nm and is doped at 0.5% by weight, the orange emission sublayer has a thickness of 10 nm and is doped at 1.5% by weight the blue emission sublayer has a thickness of 13 nm and is doped at 8% by weight, and the green emission underlayer has a thickness of 6 nm and is doped at 6% by mass;

the thickness of the second transport layer is equal to 162 nm; said first transport layer is doped with a first type of dopant, among P or N, depending on the type of charge carrier transported, P for a hole transport layer and N for an electron transport layer, and wherein said second transport layer is doped with a second type of dopant, different from the first type of dopant;

the device comprises between the first transport layer and the transmission layer, a first blocking layer of a second type of charge carrier, and between the emission layer and the second transport layer, a second layer of blocking a first type of load carrier.

BRIEF INTRODUCTION OF FIGURES

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below as an indication in relation to drawings in which:

FIG. 1 shows in cut view an organic light-emitting diode that can be used according to the invention,

FIG. 2 shows in more detail the emission layer according to the invention,

FIG. 3 presents an energy diagram of such an organic light-emitting diode,

FIG. 4 illustrates the optimization of the thickness of the second transport layer,

FIGS. 5 and 6 respectively represent the emission spectrum of a DELO according to the invention through a first electrode; respectively through a second electrode,

FIG. 7a represents the emission spectra of the two preceding figures, compared with the illuminants D65 and A,

FIG. 7b illustrates the emission spectra of the OLED, in each of its emission directions, for a structure of OLED different from that of FIG. 7a,

- Figure 8 shows a lighting device according to the invention.

DETAILED DESCRIPTION

The lighting device will be described later, for example with reference to the structure of FIG. 8. In general, it takes advantage of the use of at least one organic light-emitting diode hereinafter also abbreviated by DELO (or OLED in English).

In such an organic light-emitting diode, an injection of charge carriers, electrons or positive holes, from the electrodes, electrons from a cathode or positive holes from an anode, is produced under the effect of the application of an electrical voltage between these electrodes. The charge carriers pair in an active layer or emission layer comprising organic photoemitters, to form excitons. Radiative recombination allows the emission of light.

Such an OLED can be used to produce a lighting device according to the invention. Depending on the desired light intensity, one or more such DELOs joined into a plate are used. In order to produce an efficient light, the DELOS should have a bright, preferably white, color.

In order to achieve high quality white lighting, it is necessary to produce the widest possible wavelength spectrum light in the visible. For this, the transmission layer must comprise different types of transmitters.

Depending on the definition parameters, a multitude of different whites can be made, depending on the uses: ambient lighting, work, reading, etc., different blanks can be searched. A white is characterized by various parameters, such as the color rendering index (CRI) or the correlated color temperature (correlated color temperature). CTC). These parameters are grouped into light source models, also called illuminants. There are two illuminants used: the illuminant D65 which corresponds to the daylight, and the illuminant A which corresponds to an incandescent bulb.

A first object of the present invention is a lighting device with at least one organic light-emitting diode, OLED, capable of producing two lights according to two different illuminants.

Such a DELO advantageously comprises a stack comprising successively and in order a first electrode, a first type of electrode, among anode or cathode, transparent, a first transport layer of a first type of charge carrier, among electron and hole, an emission layer, a second transport layer of a second type of charge carrier among electron and hole, different from the first type of charge carrier among electron and hole, different from the first type of charge carrier a second electrode of a second type of electrode, said emission layer being able to emit a white color, such that the emission through said first electrode is substantially in accordance with an illuminant D65, said second electrode being transparent, and the thickness of the second transport layer being adjusted so that the emission through the second second electrode is substantially to an illuminant A.

Another aspect of the invention is a method of adjusting the thicknesses of at least one layer of an OLED.

Figure 1 shows an organic light-emitting diode, OLED. Such OLED is characterized by a stack, comprising a transmission layer 5, disposed centrally between two electrodes 2, 8. This emitting layer 5 is still called EML, the English EMission Layer. The application of an electrical voltage between the two electrodes, a cathode 8 also called EK and anode 2 also called EA, performs an injection of charge carriers in the OLED. The charge carriers are of two types: electrons of negative electric charge coming from the cathode 8 and positive holes of positive electrical charge coming from the anode 2. These charge carriers migrate in opposite directions in the OLED, up to meet, ideally in said emission layer 5. They pair two by two, an electron and a hole, to form an exciton. Said exciton, when it is formed in the emission layer 5, because of the particular chemical composition of said emission layer 5, performs a radiative recombination which produces a photon and thus allows light emission.

This light emission in order to be put to use must leave the OLED. For this it is appropriate that at least a first electrode 2, 8 is transparent. This allows a first transmission 21 through this first electrode 2, 8. It should be noted here that if this first electrode 2, 8 is disposed on a substrate 1, said substrate must also be transparent in order to let out said first emission 21 .

Each electrode 2, 8 is able to inject a different type of charge carrier. Anode 2 injects holes. A cathode 8 injects electrons. An anode 2 is typically made of indium tin oxide, ITO, indium zinc oxide, IZO, or alternatively aluminum oxide, indium and zinc oxide, AIZO, in a typical thickness. 120 nm, in order to be transparent.

Within the framework of this description, "transparent" means the property of a component, in particular the electrodes 2, 8 to transmit towards the outside of the OLED a portion and advantageously a majority of the light rays produced at the inside the OLED.

A cathode 8 is typically made of aluminum, Al, silver, Ag, gold, Au, calcium, Ca, magnesium, Mg, or any alloy of these metals. A thickness of less than 50 nm must be respected so that this cathode is transparent.

Said stack can be improved by framing the emission layer 5, by two transport layers 3, 5. Such a stack comprises, on the side of the anode 2, a positive hole transport layer 3, also called HTL of the English Hole Transport Layer, and on the cathode side 8, a transport layer 7 of electrons, also called ETL of the English Electron Transport Layer.

All the layers described herein can be carried out in a known manner by thermal evaporation under a vacuum of less than 10 ^-5 mTorr (or millimeter of mercury). In the context of lighting applications, the desired resultant color is advantageously white. The light emission 21 produces a white quality depending on the composition of the emission layer 5.

As indicated above, depending on the definition parameters, a multitude of different whites can be made. A white is characterized by various parameters, such as the color rendering index (CST) between minus infinity and 100 or the correlated color temperature (CCT). ) between 2700 K (warm light) and 6500 K (cold light). These parameters are grouped into light source models, also called illuminants.

There are two illuminants used: the CRI illuminant D65 of 100 and a CCT of 6500 K which corresponds to daylight, and the illuminant A defined by a CRI of 100 and a CCT of 2800 K which corresponds to light produced by a tungsten filament from an incandescent bulb.

In order to achieve a given white, for example according to the model of illuminant D65, it is necessary to adapt the composition of the emission layer 5.

According to a first characteristic of the invention, the emission layer 5 is able to emit a white color. This white color is determined by varying the composition of the emission layer 5 in such a way that the emission 21 produced through the first transparent electrode 2, 8 is substantially in accordance with an illuminant D65.

According to another characteristic, the second electrode 8, 2 is also transparent. Thus a second emission of light 22, coming out of the OLED by the other electrode and thus by the side opposite to the first emission 21, is advantageously carried out.

The applicant has found that, surprisingly, it was possible to produce different light emissions from both electrodes and, in particular, that light could be emitted having a first illuminant by an electrode and light having another illuminant by the other electrode.

By light having an illuminant is meant that the light emitted is substantially in accordance with the ideal spectrum of the illuminant.

According to another characteristic of the invention, the characteristics the space between the two electrodes 2, 8 is set in such a way as to modify said second emission 22 so that the emission 22 through said second electrode 8, 2 is substantially in accordance with an illuminant A. This dimensional adjustment is advantageously achieved by adjusting the thickness of at least one transport layer such as the second transport layer 7, 3.

In order to achieve a quality blank, it is desirable to have a transmission layer 5 capable of emitting in the widest possible wavelength spectrum. For this, as detailed in FIG. 2, the emission layer 5 advantageously comprises a first layer called the hot emission layer 10, made in a composition such that it emits a warm color, and a second layer called a color layer. cold emission 30 carried out according to a composition such that it emits a cold color. Each of these layers is doped with dopant compounds producing photoemitters capable of emitting said cold or hot color together. Said cold color and said hot color are chosen such that they are complementary and that the simultaneous production of the cold color by the cold emission layer 30 and the hot color by the hot emission layer 10 produces the resulting white color desired for the complete emission layer 5 and the OLED.

According to an advantageous embodiment, the cold color is a mixture of blue and green and the hot color is a mixture of red and orange.

A cold or hot emission layer 30, 10 may be produced by a single layer. It is thus possible to produce a cold color, respectively hot, given with a single cold or hot emission layer 10 to include, by doping in a single emission layer 10, 30 photoemitters corresponding to the cold or hot color. desired. If such photoemitters do not exist for such a color, it is still possible to mix light-emitting dopant compounds producing different colors in a monolayer, so that the mixture of these photoemitters produces the color, cold or hot, desired. However it is simpler to dopate a layer with a single compound and thus with a single type of photoemitter and to achieve a layer of a color corresponding to a single dopant. Also, to achieve a color resulting from a mixture of "partial" colors, it is possible and advantageous to produce a cold emission layer 30, respectively hot 10, by means of a superposition of sub-layers of cold emissions 31, 32, respectively hot 1 1, 12, each emission sublayer comprising only a single doping compound.

Thus, to return to the previous example, a cold emission layer 30 producing a mixture of green and blue color can advantageously be produced by superimposing a first cold 31 emission sub-layer and a second emission sublayer cold 32 green. Similarly, a hot emission layer 10 producing a mixture of red and orange color can advantageously be made by superimposing a first hot emission sub-layer 11 1 red and a second hot emission sub-layer 12 orange.

According to this same principle, it is possible to produce a hot or cold emission layer 10, 30 by means of a superposition of three or more sublayers 11, 12, 31, 32.

If the concentration in a transmission sublayer 11, 12 of the hot emission layer 10 is greater, a resultant color / warmer white is obtained inside the OLED. ). On the other hand, if the concentration in an emission sublayer 31, 32 of the cold emission layer 30 is greater, a resulting color / colder white is obtained inside the OLED ( e).

Thanks to a fine adjustment of the pseudo-cavity (by varying the thickness of one of the transport layers 3, 7), an illuminant D65 corresponding to a relatively cooler white than an illuminant A, a first emission 21 In accordance with an illuminant D65 is more preferably obtained by the emission 21 transmitted through the electrode 2, 8 located on the side of the cold emission layer. Thus the cold colors are naturally reinforced in said emission 21.

It will now be given as an illustration a composition of a layer transmission 5 according to one embodiment, comprising two hot sublayers 1 1, 12 and two cold sub-layers 31, 32.

The hot emission layer 10 comprises a first red underlayer 1 1 composed of DNP, either 3,9-di (naphthalen-2-yl) perylene) doped with DCM2, or [2- (2,3,6,7-tetrahydro-1H, 5H-benzo [i, j] quinolizin-9-yl) ethenyl] -4H-pyran-4-ylidene] propane-dinitrile. first emission sub-layer 1 1 Red has a thickness of 13 nm and is doped at 0.5%.

The hot emission layer 10 also comprises a second orange sub-layer 12 composed of α-NPB or (N, N '-diphenyl-N, N' -bis (1-naphthyl) - (1, 1 '- biphenyl) - 4, 4'-diamine) doped with Rubrene or (5, 6, 11, 12-tetraphenylnaphthacene). This second emission sublayer 12 Orange has a thickness of 10 nm and is doped at 1, 5%.

The cold emission layer 30 comprises a first blue sub-layer 31 composed of CBP, either (4, 4'-bis (carbazol-9-yl) biphenyl) doped with DPVBi, or (4, 4 '- bis (2,2 'diphenyl vinyl) -1,1'-biphenyl). This first blue emission sub-layer 31 has a thickness of 13 nm and is doped at 8%.

The cold emission layer 30 also comprises a second green sub-layer 32 composed of CBP, either (4, 4'-bis (carbazol-9-yl) biphenyl) doped Alq3, or (Tris (8-hydroxyquinolinato) aluminum). This second Green emission sub-layer 32 has a thickness of 6 nm and is doped at 6%.

FIG. 3 illustrates, for a possible embodiment, an OLED comprising a hot emission layer 10 comprising a red emission sublayer 11 and an Orange 12 emission sublayer, and comprising a layer of cold emission 30 comprising a blue emission sublayer 31 and a green emission sub-layer 32, the relative energy diagram of the different layers. Each layer, identified by the same reference sign as in Figures 1 and 2, is represented by a rectangle. The minimum and maximum heights of each rectangle are indicative, on an ordinate axis, of the two energy levels of the corresponding layer.

Such a emission layer composition 5 advantageously produces a first emission 21, through the cold emission layer 30 and the first electrode 2, 8 according to an illuminant D65.

According to an important characteristic of the invention, a second emission 22 can be obtained on the other side of the OLED, emitted through the second electrode 8, 2, provided that this second electrode 8, 2 is transparent. It should be noted here again that if this second electrode 8, 2 is disposed on a substrate, said substrate must also be transparent in order to let out the second emission 22. This second emission 22 is still white, but is no longer a blank according to the illuminant D65.

According to a surprising result, it was found that this second white was close to a reference white defined by another illuminant, namely an illuminant A.

Another embodiment of the structure of the diode according to the invention is given below. Compared with the previous case, the cold and hot emission layers 10 are modified so that:

the cold emission layer 30 is a 25 nm single emitter layer of undoped NPB. This layer emits in the blue and is located on the P side of the OLED PIN because the NPB material is a good hole driver;

the hot emission layer 10 is a single emitter layer of 15 nm composed of Alq 3 doped with 2% DCM 2. This layer emits in the red and is located on the N side of the OLED PIN because the material Alq3 is a good conductor of electrons.

The doping rates indicated in the present description are en masse.

The spectral diagram obtained with this additional structure is given in FIG. 7b.

One of the difficulties overcome by the invention is that the modification of a dimensional parameter of the OLED (the thickness of a layer) causes a modification of the two light emissions.

Therefore, it may seem impossible to adjust the two emissions precisely, especially to coincide with desired illuminants.

An advantageous possibility is to modify at least one of the layers of transport 7, 3, for example by changing their thickness, to reach the illuminants A and D65 simultaneously.

Referring to FIG. 4, a possible method for determining the optimal thickness of said second transport layer 7, 3 is illustrated. FIG. 4 shows the curves x and y in a CIE colorimetric reference frame of the two transmissions 21 and 22. curve 41 has the ordinate x of the color of the first emission 21 as a function of the abscissa of the dimension of the DELO cavity. Curve 42 has on the ordinate the y-coordinate of the color of the first emission 21 as a function of the abscissa dimension of the DELO cavity. The curve 43 has on the ordinate the x-coordinate of the color of the second emission 22 as a function of the abscissa dimension of the DELO cavity. The curve 44 has as ordinate the y-coordinate of the color of the second emission 22 as a function on the abscissa of the dimension of the DELO cavity. The size of the cavity is represented by a vertical bar. It is therefore possible by varying the thickness of the second transport layer 7, 3, to simultaneously vary x and y, in order to obtain a pair of values as close as possible to the color coordinates defining an illuminant A while reaching a D65 illuminant for the first broadcast.

With a transmission layer 5 as defined above, an optimum thickness of the second transport layer 7, 3 of 162 nm makes it possible to obtain a blank of coordinates x = 0.47 and y = 0, 45. Such coordinates are very close to the color of an illuminant A for which x = 0.45 and y = 0.41. For the illuminant D65, we have x = 0.31 and y = 0.33.

The first transport layer 3, 7 has a thickness of 46.2 nm.

In general, the method for designing such a bi-transparent double illuminant DELO comprises the following steps. During a first step, a first emission 21 is determined by choosing the precise composition of the emission layer 5 in order to obtain the characteristics, in particular of color, desired for this first emission 21, for example according to the illuminant D65. Once "set" this first emission 21, it is obtained, thanks to a second electrode This second emission 22 may be adjusted to a certain extent by acting on the dimensional characteristics of the OLED and more particularly by acting on the OLED half located on the side of said second emission 22, for example by modifying the thickness of the second transport layer 7, 3. This adjustment must also take into account the variations that it is likely to induce for the first emission.

With reference to FIGS. 5 to 7b, the results obtained will now be described. FIG. 5 illustrates on a spectral diagram, showing the luminous intensity (given by the relative luminous efficiency value in ordinate as a function of the wavelength (in nm) on the abscissa, the spectrum 55 of the first emission 21. It is recalled for memory the spectra of the different color layers present in the emission layer 5: spectrum 51 of the blue layer, spectrum 52 of the green layer, spectrum 53 of the orange layer and spectrum 54 of the red layer. FIG. 6 illustrates, on a comparable spectral diagram, the spectrum 56 of the second emission 22. It is recalled, as in FIG. 5, the spectra 51 -54 of the color layers present in the emission layer 5.

FIG. 7a shows the spectrum 55 of the first emission 21, the spectrum 56 of the second emission 22, as well as the ideal spectrum 57 of an illuminant D65 and the ideal spectrum 58 of the same spectral diagram, in a comparative manner. an illuminant A. It can be seen that the spectrum 55 of the first emission 21 satisfactorily approaches the ideal spectrum 57 of an illuminant D65 and that the spectrum 56 of the second emission 22 also satisfactorily approaches the ideal spectrum 58 an illuminant A.

As regards the colors obtained with such OLED, the first emission 21 produces a CCT of 6500 K conforming to an illuminant D65 and the second emission 22 produces a CCT of 2900 K conforming to an illuminant A.

With regard to the CRI, for the first issue 21 (D65) a CRI of 84 is obtained and for the second issue 22 (A) a CRI of 80, which advantageously approaches the ideal, defined as equal to 100 for both a D65 illuminant and an illuminant A.

Such an OLED may or may not be of the PIN type. An OLED is of the PIN type when its transport layers 3, 7 are doped. A transport layer 3 Positive holes are typically p-type doped. An electron transport layer 5 is typically N-type doped.

Such an embodiment is called PIN, since an insulating layer, the PIN I, here the light emitting layer EML 5, is flanked by a P-type doped transport layer 3, the PIN P, and by an N-type doped transport layer 7, the N of PIN.

By way of example, a 3-hole transport layer can be produced by means of 2,7-bis [N, N-bis (4-methoxyphenyl) amino] -9,9-spirobifluorene (MeO-Spiro-TPD). ); P hth a locya n i n e (Cu Pc); 4, 4 ', 4 "- tris- (3-methylphenylphenylamino) triphenylamine (m-MTDATA); 2,2', 7,7'-tetra (N, N-di-tolyl) amino-spirobifluorene (spiro TTB); 4,4'-bis- [N- (naphthyl) -N-phenyl-amino] biphenyl (σ-NPD); N, N'-bis (Inaphthyl) N, N'-diphenyl-1 '; biphenyl-4, 4'-diamine (NPB), N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1, biphenyl-4,4'-diamine (TPD), in the case of a P-doped HTL hole transport layer.

For example, an electron transport layer 7 may be carried out using N-arylbenzimidazoles trimer (TPBI); 4,7-Diphenyl-1,10-phenanthroline (Bphen); bis (2-methyl-8-quinolinate) -4-phenylphenolate aluminum (BAIq); tris- (8-hydroxyquinoline) aluminum (Alq3).

The two transport layers 3, 7 each respectively comprise a dopant concentration of 1%.

According to another optional embodiment it is still possible to add to such an OLED at least one blocking layer 4, 6. A blocking layer 4, 6 is a layer capable of blocking / slowing down a type of charge carrier. The type of charge carrier is determined by the type of dopant used. A blocking layer 4, 6 for one type of charge carrier is advantageously disposed, adjacent to the emission layer 5, on the opposite side to the electrode 2, 8 which injects said type of charge carrier.

Thus, a hole-locking layer 6 is advantageously disposed adjacent to the emitting layer EML 5, on the opposite side, relative to the emitting layer EML 5, to the anode 2 which injects said holes. A hole blocking layer 6 is also called HBL, of the English Hole Blocking Layer. A hole-locking layer 6 is thus advantageously arranged between the ETL electron transport layer 7 and the EML emission layer 5.

Thus, an electron-blocking layer 4 is advantageously disposed adjacent to the emitting layer EML 5, on the opposite side, relative to the emitting layer EML 5, to the cathode 8 which injects said electrons. An electron blocking layer 4 is also called EBL, the English Electron Blocking Layer. An electron blocking layer 4 is thus advantageously arranged between the HTL 3 hole transport layer and the EML 5 emission layer.

Thus arranged, on the side opposite to an electrode 2, 8 which injects a type of charge carrier, a blocking layer 4, 6 able to block this type of charge carrier, prevents said charge carrier from leaving the transmission layer EML 5. The blocking layer (s) 4, 6 thus produce an effect of confinement of the charge carriers, and therefore of the excitons, in the emitting layer EML 5. This has the effect of improving the external light output, in particular producing more photons for the same number of charge carriers injected.

The blocking layer (s) 4, 6 have appropriate energy levels with the neighboring EML 5 emission layer.

By way of example, an electron blocking layer EBL 4 may be produced by means of N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,4-biphenyl-4, 4 '. diamine (TPD), according to a thickness indicative of 10 nm.

By way of example, a hole-locking layer HBL 6 can be produced using benzimidazolylbenzene (TPBi), with a thickness of 10 nm.

Such a DELO, according to any of the embodiments described above, bi-transparent, capable of producing a first emission 21 according to an illuminant D65 on one side of the OLED and a second emission 22 according to an illuminant A on the opposite side of the OLED is advantageously used in a lighting device 60.

With reference to FIG. 8, such a lighting device 60 is illustrated. It comprises conventionally a support 63 and is supplied with electrical energy via a wire 64. Said wire 64 may optionally include a switch 65. Said wire 64 ends with a socket 66 advantageously insertable into a wall outlet 67 to connect the lighting device 60 to the power grid.

The support 63 comprises a useful illuminating part incorporating at least one OLED according to the invention. Said illuminating useful part has a first face 61 and a second opposite face 62. Said at least one OLED is arranged in such a way that one of its electrodes 2, 8 is disposed facing said first face 61 and that other of its electrodes 8, 2 is disposed facing said second face 62. Thus an emission from the first emission 21 and the second emission 22, for example the first emission 21, can illuminate from the first face 61, and the another emission, for example the second emission 22 can illuminate from the second face 62.

The faces 61, 62 may be simple light passage windows or have a glazed surface out any other light passage configuration between a source and a space to be illuminated.

It is thus possible to make a lighting device 60 capable of simultaneously two types of illuminants D65 and A. This is advantageous for several reasons.

If the lighting device 60 is reversible or adjustable it allows the choice to have a daylight-like lighting (D65) effective for example to work, or a more comfortable lighting (A) more pleasant in lighting d inside.

It is thus possible to produce such a selectively occultable lighting device 60 on one or the other of its faces 61, 62, in order to select the light source used from the first emission 21 or the second emission 22.

Alternatively, it is also possible to use both transmissions 21, 22 simultaneously. Thus a lighting device 60 according to the invention is particularly suitable for a table lamp in that it allows a use where the first emission 21, according to D65, is used to illuminate, typically downwards, a work plan requiring effective lighting, while the second emission 22, according to A, is simultaneously used to illuminate, upwards, the user or his environment. Advantageously, such a second emission 22 allows a comfortable lighting in that it can, without inconvenience, to be watched, even directly, by a user.

Upward lighting refers to an average direction of emission directed above a horizontal plane passing through the origin of the average direction beam. Downlighting extends from an average direction opposite to that defined for upward illumination.

A method of using the invention may thus comprise the formation of ambient lighting with a substantially upward illumination and the formation of a working light with illumination of a downlight, for example in the direction of a work plan.

Although it is described herein a preferred embodiment of the invention, it should be understood that the invention is not limited to this mode, and that variations can be made within the scope of the invention. scope of the following claims.

Claims

1. Lighting device comprising at least one light source configured to produce a light emission (21) by an illuminating surface (61),

characterized in that the light source is an organic light-emitting diode, OLED, comprising a stack comprising successively and in order:

a first electrode (2, 8) of a first type of electrode, of transparent anode (2) or cathode (8),

a first transport layer (3, 7) of a first type of charge carrier, among electron and hole,

an emission layer (5),

a second transport layer (7, 3) of a second type of charge carrier among the electron and hole, different from the first type of charge carrier,

a second electrode (8, 2) of a second type of electrode, different from the first type of electrode,

diode in which said emission layer (5) is configured to emit a white color, such that the light emission (21) takes place through said first electrode (2, 8) and is in accordance with a rendering index of CRI color and color temperature correlated to a first illuminant and wherein said second electrode (8, 2) is transparent, and in that the thickness of the second transport layer (7, 3) is adjusted in such a way that another emission (22) is effected through said second electrode (8, 2) and is in accordance with the CRI color rendering index and the correlated color temperature with a second illuminant different from the first illuminant,

the lighting device comprising another illuminating face (62) through which the other light emission (22) is produced, the illuminating faces (61, 62) being each arranged respectively facing one of the electrodes (2, 8). of the OLED, in order to be able to illuminate according to the first illuminant by the illuminating face (61) and according to the second illuminant by the other illuminating face (62).

2. Device according to claim 1 comprising a support having a illuminating part incorporating the OLED and the illuminating faces.

3. Device according to the preceding claim wherein the support is configured to emit the light emission (21) upwards and the other light emission (22) downwards.

4. Device according to claim 2 wherein the illuminating portion is orientable.

5. Device according to one of the preceding claims constituting a table lamp.

6. Device according to one of the preceding claims comprising for at least one of the illuminating faces (61, 62), a removable occlusion member.

7. Device according to one of the preceding claims wherein the first illuminant is an illuminant D65 corresponding to daylight.

8. Device according to one of the preceding claims wherein the second illuminant is an illuminant A corresponding to an incandescent bulb.

Apparatus according to the two preceding claims in combination, wherein the emission layer (5) comprises a hot emission layer (10) configured to emit a warm color and a cold emission layer (30) adapted to emit a cold color, where the cold color is a mixture of blue and green and the warm color is a mixture of red and orange.

10. Device according to the preceding claim, wherein the hot emission layer (10) comprises at least two hot emission sublayers (1 1, 12) configured to each issue a different partial hot color, said partial hot colors being configured to produce said hot color, and wherein the cold emission layer (30) comprises at least two cold emission sub-layers (31, 32) configured to each emit a different partial cold color, said partial cool colors being configured to produce said cold color.

1 1. Device according to the preceding claim, wherein a first partial hot color is red, a second partial hot color is orange, a first partial cold color is blue, and a second Partial cold color is green.

12. Device according to the preceding claim, wherein the red emission underlayer has a thickness of 13 nm and is doped at 0.5% by weight, the orange emission sublayer has a thickness of 10 nm and is doped at 1.5% by weight, the blue emission sublayer has a thickness of 13 nm and is doped at 8% by weight, and the green emission sublayer has a thickness of 6 nm and is doped at 6% by weight.

13. Device according to any one of the preceding claims, wherein the thickness of the second transport layer (7, 3) is equal to 162 nm.

A device according to any one of the preceding claims, wherein said first transport layer (3, 7) is doped with a first type of dopant, among P or N, depending on the type of charge carrier transported, P for a hole transport layer and N for an electron transport layer, and wherein said second transport layer (7, 3) is doped with a second type of dopant, different from the first type of dopant.

15. Device according to the preceding claim, further comprising, between the first transport layer (3, 7) and the emission layer (5), a first blocking layer (4, 6) of a second type of carrier. charging, and between the transmission layer (5) and the second transport layer (7, 3), a second blocking layer (6, 4) of a first type of charge carrier.