Optelectonic Arrangement and Lighting Device

Abstract

An optelectonic arrangement and a lighting device are disclosed. In an embodiment the arrangement includes a semiconductor chip for generating radiation and a radiation conversion element located downstream of the semiconductor chip with respect to a radiation direction, wherein the radiation conversion element includes a plurality of conversion bodies each with a longitudinal extension axis, and wherein a spatial orientation of the longitudinal extension axes has a preferred direction.

Claims

1-18. (canceled)

19. An optoelectronic arrangement comprising: a semiconductor chip for generating radiation; and a radiation conversion element located downstream of the semiconductor chip with respect to a radiation direction, wherein the radiation conversion element comprises a plurality of conversion bodies each with a longitudinal extension axis, and wherein a spatial orientation of the longitudinal extension axes has a preferred direction.

20. The optoelectronic arrangement according to claim 19, wherein the conversion bodies have a maximum transverse extension perpendicular to the longitudinal extension axis, and wherein a ratio of a longitudinal extension along the longitudinal extension axis to the maximum transverse extension is between 2:1 inclusive and 20:1 inclusive.

21. The optoelectronic arrangement according to claim 20, wherein the conversion bodies have a maximum transverse extension of between 1 nm inclusive and 50 nm inclusive.

22. The optoelectronic arrangement according to claim 19, wherein the conversion bodies comprise quantum rods.

23. The optoelectronic arrangement according to claim 22, wherein each quantum rod has a core and a shell that completely surrounds the core.

24. The optoelectronic arrangement according to claim 19, wherein the conversion bodies are based on an inorganic material.

25. The optoelectronic arrangement according to claim 19, wherein the conversion bodies are based on an organic material.

26. The optoelectronic arrangement according to claim 19, wherein the radiation conversion element is completely surrounded by an encapsulation layer.

27. The optoelectronic arrangement according to claim 26, wherein the encapsulation layer contains a layer stack with at least one layer of organic material and/or at least one layer of inorganic material.

28. The optoelectronic arrangement according to claim 22, wherein each quantum rod comprises an organic mantle.

29. The optoelectronic arrangement according to claim 19, wherein the radiation conversion element comprises a matrix material in which the conversion bodies are embedded.

30. The optoelectronic arrangement according to claim 19, wherein the optoelectronic arrangement comprises a plurality of semiconductor chips for generating radiation, and wherein the semiconductor chips are arranged next to one another transversely to the preferred direction of the conversion bodies.

31. A lighting device comprising: an optoelectronic arrangement according to claim 19; and a radiation surface through which the radiation generated during an operation of the optoelectronic arrangement exits.

32. The lighting device according to claim 31, further comprising a light guide with a main surface and a side surface that is oblique or perpendicular to the main surface, wherein the radiation is coupled in through the side surface of the light guide and exits through the main surface.

33. The lighting device according to claim 32, wherein the light guide is designed to be at least partly polarization-maintaining.

34. The lighting device according to claim 31, wherein the radiation direction of the optoelectronic arrangement is perpendicular to the radiation surface.

35. The lighting device according to claim 34, further comprising an optical element with a plurality of prisms arranged downstream of the radiation conversion element in the radiation direction, wherein the prisms extend in a longitudinal direction, and wherein the longitudinal direction is parallel to the preferred direction of the conversion bodies.

36. The lighting device according to claim 31, wherein the lighting device is configured to back-light a liquid crystal display.

37. An optoelectronic arrangement comprising: a semiconductor chip for generating radiation; and a radiation conversion element located downstream of the semiconductor chip with respect to a radiation direction, wherein the radiation conversion element comprises a plurality of conversion bodies each having a longitudinal extension axis, wherein a spatial orientation of the longitudinal extension axes has a preferred direction, and wherein at least one of the following options (i) through (iii) applies: (i) the radiation conversion element is fixed to a radiation exit surface of the semiconductor chip; (ii) the semiconductor chip is arranged in a housing and the radiation conversion element is fixed to the housing; (iii) the optoelectronic arrangement comprises a plurality of semiconductor chips, the semiconductor chips being unhoused semiconductor chips arranged on a connection carrier, wherein the radiation conversion element forms a common radiation conversion element for at least two of the plurality of semiconductor chips and covers at least partly a covering that is arranged between the at least two of the plurality of the semiconductor chips.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further embodiments and developments are described by way of the exemplary embodiments described hereinafter in conjunction with the figures.

[0038] In the figures:

[0039] FIG. 1 shows an exemplary embodiment of a radiation conversion element in a perspective, schematic view;

[0040] FIGS. 2A and 2B each show an exemplary embodiment of a lighting device with an optoelectronic arrangement in schematic sectional view;

[0041] FIGS. 3A and 3B show a further exemplary embodiment of an optoelectronic arrangement in schematic plan view (FIG. 3A) and associated side view (FIG. 3B); and

[0042] FIGS. 4A and 4B each show a further exemplary embodiment of a lighting device with an optoelectronic arrangement in schematic view.

[0043] Identical, similar or similarly-acting elements are denoted by the same reference numerals in the Figures. The Figures and the size ratios of the elements shown in the Figures relative to one another are not to scale. Rather individual elements, in particular layer thicknesses, may have been exaggerated for illustrative purposes and/or to provide better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0044] FIG. 1 shows an exemplary embodiment of a radiation conversion element 3, in which the principle of functioning of the optoelectronic arrangement and the mechanism of radiation generation are explained.

[0045] The radiation conversion element 3 comprises a plurality of conversion bodies 40. In the following, by way of example, a configuration is described in which the conversion bodies 40 are quantum rods 4. Alternatively, the conversion bodies can also be based on an organic material and contain, for example, perylene, condensed aromatic compounds, ring systems or planar systems. The quantum rods 4 are embedded in a matrix material 35 of the radiation conversion element. The quantum rods 4 are each designed to be elongated and along a longitudinal extension axis 44 have a longitudinal extension 45 which is greater than a transverse extension 46 perpendicular to the longitudinal extension axis.

[0046] Upon the optical excitation of the quantum rods by primary radiation 20, the quantum rods emit a secondary radiation 30. The intensity of the radiation is proportional to sin.sup.2θ, wherein θ indicates the angle between the longitudinal extension axis 44 and the radiation direction. The quantum rods thus do not emit radiation along their longitudinal extension axis 44. Perpendicular to the longitudinal extension axis 44, i.e., for θ=90° is a main radiation plane 49, which is shown in FIG. 1 schematically as a circle drawn in perspective. The radiation emitted by the quantum rods 4 is polarized respectively. A polarization direction 48 runs parallel to the longitudinal extension axis 44.

[0047] In the radiation conversion element 3 the individual quantum rods 4 are oriented so that the longitudinal extension axes 44 of the quantum rods 4 have a preferred direction 39. The preferred direction in particular runs in the main plane of extension of the radiation conversion element 3. In the shown exemplary embodiment, all of the longitudinal extension axes 44 run parallel to the preferred direction. In this ideal case, the secondary radiation generated by the quantum rods 4 in the radiation conversion element 3 is completely polarized. Individual quantum rods 4 can however also have an orientation of the longitudinal extension axis 44 deviating from the preferred direction 39 so that the secondary radiation 30 is partly polarized. The orientation of the quantum rods can be achieved during the manufacture in that the quantum rods are embedded into the matrix material in the form of a film and the film is anisotropically brought into an expanded state along one direction by the effect of heat. The orientation of the quantum rods is effected in this direction which is retained in the expanded state after the hardening of the matrix material. Alternatively or in addition to heat, the orientation can also be effected mechanically, for example, by traction or electromagnetically.

[0048] In the shown exemplary embodiment, the quantum rods 4 each comprise a core and a shell 42 which completely surrounds the core.

[0049] Furthermore, the quantum rods 4 comprise a mantle which is preferably made from an organic material. The mantle serves to avoid an agglomeration of individual quantum rods 4. The longitudinal extension 45 and the transverse extension 46 of the quantum rods 4 therefore relate to the respective extension of the quantum rods without the mantle 43.

[0050] The quantum rods 4 have a ratio of their longitudinal extension to their maximum transverse extension of between 2:1 inclusive and 20:1 inclusive, for example, between 3:1 inclusive and 10:1 inclusive. The maximum transverse extension is between 1 nm inclusive and 50 nm inclusive, for example, between 2 nm inclusive and 20 nm inclusive. The longitudinal extension is, for example, between 10 nm inclusive and 200 nm inclusive.

[0051] The radiation conversion element 3 comprises in the shown exemplary embodiment by way of example first quantum rods 4A, second quantum rods 4B and third quantum rods 4C. The first, second and third quantum rods are provided to generate secondary radiation portions having different peak wavelengths. For example, the first quantum rods generate radiation in the red spectral range, the second quantum rods generate radiation in the green spectral range and the third quantum rods generate radiation in the blue spectral range. In this case the radiation conversion element 3 can provide radiation portions in the red, green and blue spectral range, which are each polarized or are at least partly polarized. Furthermore, the quantum rods can each comprise spectrally narrow-band radiation so that losses at the color filters of the liquid crystal display can be minimized.

[0052] The first quantum rods 4A, the second quantum rods 4B and the third quantum rods 4C can differ from one another, for example, with regard to the extension and/or material used, in order to achieve peak wavelengths different from one another.

[0053] The radiation conversion element 3 can however also comprise only one type or two types of quantum rods 4 or more than three types of quantum rods.

[0054] The quantum rods 4 preferably contain an inorganic material, in particular a compound semiconductor material. In one arrangement with a core 41 and a shell 42, preferably both the core and the shell contain an inorganic material, in particular a compound semiconductor material. For example, the quantum rods 4 contain cadmium selenide, cadmium sulfide, zinc selenide or indium phosphide.

[0055] An exemplary embodiment of a lighting device 7 with an optoelectronic arrangement 1 is shown in FIG. 2A in a schematic side view. The lighting device 7 comprises the optoelectronic arrangement 1 and a light guide 71.

[0056] The optoelectronic arrangement 1 comprises a semiconductor chip 2 provided for generating radiation. For example, the semiconductor chip includes an active range for generating radiation in the blue or ultraviolet spectral range on the basis of a nitride compound semiconductor material, such as Al.sub.xIn.sub.yGa.sub.1-x-yN with 0≦x≦1, 0≦y≦1 and x+y≦1.

[0057] Furthermore, the optoelectronic arrangement comprises a radiation conversion element 3, which is arranged downstream of the semiconductor chip 2 in a radiation direction 21. The radiation conversion element 3 is thus part of the optoelectronic arrangement. Prior to the exit of the primary radiation generated during the operation of the optoelectronic arrangement in the semiconductor chip from a radiation exit surface 10 of the optoelectronic arrangement the radiation thus has to pass through the radiation conversion element 3. In the configuration shown in FIG. 2A, the radiation conversion element 3 forms the radiation exit surface.

[0058] The radiation conversion element 3 can be designed as described in connection with FIG. 1. The secondary radiation generated by the optoelectronic arrangement 1 in the radiation conversion element 3 and exiting through the radiation exit surface 10 of the optoelectronic arrangement is polarized or at least partly polarized. The preferred direction of the quantum rods is perpendicular to the section plane of FIG. 2A. The optoelectronic arrangement 1 also provides already polarized or at least partly polarized radiation so that during the backlighting of a liquid crystal display losses are reduced at the polarization filter, which is arranged on the radiation inlet side of the liquid crystal display. Furthermore, the secondary radiation determined by the production mechanism by means of oriented quantum rods is generated so that it is at least partly polarized already and the efficiency of the lighting is increased.

[0059] Furthermore, there is no radiation of the quantum rods 4 in the preferred direction, which is parallel to the main plane of extension of the radiation conversion element. This portion of radiation, which could only be coupled in with difficulty into the light guide 71, is thus reduced in favor of increased radiation perpendicular to the radiation exit surface.

[0060] Furthermore, the radiation conversion element 3 comprises an encapsulation layer 32. The encapsulation layer is provided in particular to protect the quantum rods 4 from moisture and/or oxygen. The encapsulation layer covers the radiation conversion element 3 on all sides. The encapsulation layer 32 contains or consists, for example, of a polymer material, such as silicone, epoxy, PET, parylene or polysilazane or is made from an inorganic material, such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide or zirconium oxide. The encapsulation layer can in particular be designed to be multi-layered. Furthermore, the encapsulation layer can also have sequence of layers with at least one organic and one inorganic layer. The encapsulation layer 32 forms the radiation exit surface 10 of the optoelectronic arrangement in the exemplary embodiment shown in FIG. 2A.

[0061] The semiconductor chip 2 is arranged in a housing body 25. The housing body 25 molds around a first connecting guide 26 and an additional connecting guide 27. The first connecting guide and the additional connecting guide are accessible for the electrical contact of the semiconductor chip 2 from outside the housing body 25 on the side being remote from the radiation exit surface 10. The semiconductor chip 2 is connected via connecting lines 23 to the connecting guide 26 and the additional connecting guide 27. In the shown embodiment, the semiconductor chip 2 has two contacts on the side facing the radiation exit surface 10. Alternatively however, a semiconductor chip can also be used which comprises at least one contact or both contacts on the side facing away from the radiation exit surface 10.

[0062] The semiconductor chip 2 is embedded in a covering 22. The covering 22 contains advantageously a material which is transmissive to the primary radiation, for example, a silicone or an epoxy.

[0063] In the embodiment shown in FIG. 2A, the radiation conversion element 3 is spaced apart from the semiconductor chip 2. The radiation conversion element 3 is fastened to the housing body 25. For example, the radiation conversion element 3 is fastened by means of a securing layer 8. Alternatively, the radiation conversion element can be laminated onto the housing body.

[0064] On the side facing away from the radiation exit surface 10 the connecting guide 26 and the additional connecting guide 27 are connected in an electrically conducting manner to a connection carrier 29, for example, a circuit board.

[0065] The optoelectronic arrangement 1 can of course also comprise more than one semiconductor chip 2 provided for producing radiation, wherein the semiconductor chips can be arranged respectively in a housing or a plurality of semiconductor chips can be arranged in a housing. Furthermore, alternatively a plurality of semiconductor chips can also be arranged without a housing on the connection carrier 29 and electrically contacted. The type of housings for the semiconductor chips 2 can be selected within broad limits. For example, the housing body 25 can also be made from a material which is molded onto the semiconductor chip 2.

[0066] In the embodiment shown in FIG. 2B, the radiation conversion element 3, unlike the one shown in the exemplary embodiment in FIG. 2A, is arranged directly on the semiconductor chip 2. The radiation conversion element 3 is embedded together with the semiconductor chip 2 in the covering 22. The covering can also be used for protecting the radiation conversion element. In this case, it is possible to avoid having an additional encapsulation layer. The covering runs partly between the radiation conversion element and the radiation exit surface 10 of the optoelectronic arrangement.

[0067] FIGS. 3A and 3B show a further exemplary embodiment of an optoelectronic arrangement 1.

[0068] The optoelectronic arrangement comprises a plurality of semiconductor chips 2. The semiconductor chips 2 are arranged without a housing on the connection carrier 29. The radiation conversion element 3 forms a common radiation conversion element for a plurality of semiconductor chips 2, in particular all of the semiconductor chips of the optoelectronic arrangement 1. The radiation conversion element also covers at least partly the covering 22 arranged between the semiconductor chips. In the shown embodiment, the semiconductor chips 2 are arranged in a direction perpendicular to the preferred direction 39 in the form of a strip. Such a configuration of the optoelectronic arrangement 1 is particularly suitable for coupling in laterally into a light guide (See, e.g., FIG. 4A).

[0069] On the side facing the radiation exit surface 10 the semiconductor chips 2 are free of the covering 22. For the covering therefore also a reflective material can be used, for example, a polymer material filled with white pigments, such as a silicone or an epoxy or a hybrid material with a silicone and an epoxy. For example, titanium oxide or zirconium oxide are suitable white pigments.

[0070] Alternatively, the covering 22 can also be designed to be transmissive to radiation. In this case the connection carrier 29 is preferably designed to be reflective, for example, by means of a coating, which is designed to be reflective for the radiation emitted by the optoelectronic arrangement 1, for example, having a reflectivity of at least 60%. Preferably, the coating is metallic. A polarization-maintaining reflection can thus be easily achieved.

[0071] FIG. 4A shows an embodiment of a lighting device 7, wherein the optoelectronic arrangement 1 can in particular be designed as described in connection with FIGS. 3A and 3B.

[0072] The radiation produced during the operation of the optoelectronic arrangement 1 is coupled in by means of a side surface 715 of the light guide 71 of the lighting device. The radiation of the light guide 71 is performed via a main surface 710, which runs along a main plane of extension of the light guide 71. The light guide 71 forms a radiation surface 70 of the lighting device. The preferred direction 39 of the quantum rods 4 is perpendicular to the main surface 710, so that the radiation of the optoelectronic arrangement as described in connection with FIG. 1 is mainly in a narrow-angled radiation pattern 12 parallel to the main plane of extension of the light guide 71. In this way, a particularly efficient coupling in the light guide may be achieved. At the same time the preferred direction in the optoelectronic arrangement as described in connection with FIG. 1 creates a broad-angled radiation in the main plane of extension of the light guide. This results in an efficient mixture of light inside the light guide and thus in a homogenous radiation over the radiation surface 70. In this way, particularly small dead areas at the edge of the lighting device may be obtained.

[0073] The light guide 71 is further preferably designed to be polarization-maintaining, so that the radiation of the lighting device leaving the main surface 710 is at least partly polarized. For this the light guide 71 can have a structure, for example, an additional main surface 711 opposite the main surface, on which the polarization-maintaining deflection takes place (not shown specifically). Alternatively, the light guide can be wedge-shaped, for example. The greater the degree of polarization of the radiation exiting the lighting device, the smaller the losses at a polarization filter of a liquid crystal display arranged downstream.

[0074] Furthermore, in the radiation conversion element 3, there is no radiation in the preferred direction 39. This portion of radiation which would not be supplied to the light guide 71, is thus minimized and the efficiency of the backlighting of a liquid crystal display increased.

[0075] FIG. 4B shows in a schematic perspective representation a lighting device 7, in which the optoelectronic arrangement 1 is used for the direct backlighting a liquid crystal display 8. For this the optoelectronic arrangement 1 comprises a plurality of semiconductor chips 2, which are arranged in the form of a matrix on a connection carrier 29. Of course, also another planar arrangement can be used, for example, in the form of a hexagonal pattern. The main plane of extension of the connection carrier (x-y-plane in FIG. 4B) is parallel to the main plane of extension of the liquid crystal display 8. The radiation directions of the optoelectronic arrangements are respectively perpendicular to the radiation surface 70.

[0076] An optical element 6 is assigned to the optoelectronic arrangement 1. The optical element 6 is shown for more clarity in the form of a detail which is exaggerated in size. The optical element 6 is designed to deflect the radiation from the radiation conversion element 3, which is polarized in the preferred direction 39, to be polarization-maintaining. For this the optical element comprises by way of example a plurality of elongated prisms 61, the longitudinal direction 610 of which is parallel to the preferred direction 39. The optical element 6 can be designed, for example, as a film, which is arranged in the beam path between the semiconductor chips 2 and the liquid crystal display 8.

[0077] The radiation of the quantum rods .sub.4 is performed as described in connection with FIG. 1 with a comparatively narrow angle about the x-axis in FIG. 4B. The semiconductor chips 2 are therefore arranged in the optoelectronic arrangement 1 in the preferred direction 39 (y-direction) preferably at a shorter distance than in direction (x-direction) perpendicular to the preferred direction 39 and in the main plane of extension of the radiation conversion element 3.

[0078] By means of the described optoelectronic arrangement 1 in a particularly efficient manner, it is possible to achieve an even backlighting of a liquid crystal display both with a lateral coupling in a light guide and with direct backlighting. In particular, portions of radiation, which cannot be used for the backlighting, for example, because of an unsuitable radiation direction or unsuitable polarization, can be reduced during the production of radiation in favor of an increase in the usable radiation.

[0079] The invention is not limited to the exemplary embodiments described in the description. Rather the invention includes every new feature and every combination of features which in particular includes every combination of features in the claims, even if this feature or this combination has not been specifically described in the claims or exemplary embodiments.