GB2496183A - Illumination apparatus - Google Patents

Illumination apparatus Download PDF

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Publication number
GB2496183A
GB2496183A GB1119111.1A GB201119111A GB2496183A GB 2496183 A GB2496183 A GB 2496183A GB 201119111 A GB201119111 A GB 201119111A GB 2496183 A GB2496183 A GB 2496183A
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United Kingdom
Prior art keywords
light emitting
elements
array
emitting elements
inorganic light
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GB1119111.1A
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GB201119111D0 (en
Inventor
Graham John Woodgate
Jonathan Harrold
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OPTOVATE Ltd
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OPTOVATE Ltd
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Priority to GB1119111.1A priority Critical patent/GB2496183A/en
Publication of GB201119111D0 publication Critical patent/GB201119111D0/en
Publication of GB2496183A publication Critical patent/GB2496183A/en
Application status is Withdrawn legal-status Critical

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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21KNON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
    • F21K9/00Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
    • F21K9/20Light sources comprising attachment means
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21KNON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
    • F21K9/00Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
    • F21K9/90Methods of manufacture
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L25/00Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/03Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L51/00, e.g. assemblies of rectifier diodes
    • H01L25/04Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof all the devices being of a type provided for in the same subgroup of groups H01L27/00 - H01L51/00, e.g. assemblies of rectifier diodes the devices not having separate containers
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L25/00Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
    • H01L25/16Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof the devices being of types provided for in two or more different main groups of H01L27/00 - H01L49/00 and H01L51/00, e.g. forming hybrid circuits
    • H01L25/167Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof the devices being of types provided for in two or more different main groups of H01L27/00 - H01L49/00 and H01L51/00, e.g. forming hybrid circuits comprising optoelectronic devices, e.g. LED, photodiodes
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L27/00Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/15Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission
    • H01L27/153Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars
    • H01L27/156Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L27/00Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/28Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including components using organic materials as the active part, or using a combination of organic materials with other materials as the active part
    • H01L27/32Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including components using organic materials as the active part, or using a combination of organic materials with other materials as the active part with components specially adapted for light emission, e.g. flat-panel displays using organic light-emitting diodes [OLED]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L27/00Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/28Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including components using organic materials as the active part, or using a combination of organic materials with other materials as the active part
    • H01L27/32Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including components using organic materials as the active part, or using a combination of organic materials with other materials as the active part with components specially adapted for light emission, e.g. flat-panel displays using organic light-emitting diodes [OLED]
    • H01L27/3225OLED integrated with another component
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V5/00Refractors for light sources
    • F21V5/007Array of lenses or refractors for a cluster of light sources, e.g. for arrangement of multiple light sources in one plane
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21VFUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
    • F21V7/00Reflectors for light sources
    • F21V7/0091Reflectors for light sources using total internal reflection
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21YINDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2105/00Planar light sources
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21YINDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2105/00Planar light sources
    • F21Y2105/10Planar light sources comprising a two-dimensional array of point-like light-generating elements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21YINDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00Light-generating elements of semiconductor light sources
    • F21Y2115/10Light-emitting diodes [LED]
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F21LIGHTING
    • F21YINDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
    • F21Y2115/00Light-generating elements of semiconductor light sources
    • F21Y2115/10Light-emitting diodes [LED]
    • F21Y2115/15Organic light-emitting diodes [OLED]
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L2251/00Indexing scheme relating to organic semiconductor devices covered by group H01L51/00
    • H01L2251/50Organic light emitting devices
    • H01L2251/53Structure
    • H01L2251/5361OLED lamp

Abstract

An illumination apparatus comprises an array of inorganic light emitting elements which is formed by selectively removing inorganic light emitting diodes (LEDs) from an array formed on a monolithic wafer and preserving the relative spatial positions of the diodes then forming an array of the selectively removed inorganic LEDs whilst maintaining the relative spatial positions, so that the inorganic LEDs 6, 8 are interspersed in gaps within an array of organic light emitting diodes (OLEDs) 4, positioned within apertures within OLEDs (see Fig. 6a), or formed on the surface of a continuous layer of OLEDs (see Fig. 7) the inorganic LEDs and OLEDs sharing a common substrate 2. There may be more than one array of inorganic LEDs 6, 8, each with different wavelength characteristics. The inorganic light emitting elements 6, 8 are provided at reduced density compared to the organic light emitting elements, achieving high efficiency, long lifetime and high uniformity for white light illumination over a large area.

Description

ILLUMINATION APPARATUS

The present invention relates to an illumination apparatus and a method for fithrication of the illumination apparatus. Such aa apparatus may be used tbr domestic or professional lighting, and for general illuntination purposcs.

Inorganic light-emitting diodes (iLEDs) fornicd using semiconductor growth onto monolithic wafers can demonstrate significanily higher levels of efficiency compared lo mcandescent sources. In ihis specificatioTi LED refers to an unpackaged LED die (chip) extrncted directly from a monolithic wafer. i.e. a semiconductor element. This is different from packaged LEDs which have been assembled into a package to facilitate subsequent assembly and may fUrther incorporate oplical elements such as a hemispherical structure thai increases light extraction efficiency and size.

To provide white light output, blue iLl D elemenis are commonly combined with a wavelength converting phosphor material. However, such an approach sull'ers froi'a losses including Stokes losses that reduce the achievable ouiptu efficiency and thus increase cost. It would be desirable lo combine highly efficient red, green and blue LEDs in order to overcome losses in the phosphor materials, Such arrangements also advantageously enable colour ttming of the final output to match the lighting user's requirements by adjusting the relative proportion of light in red, green and blue channels of the illuminator. iLED elements can he produced with high quantum efficiency in red and blue output wavelenglhs but material systems can constrain quantum efficiency in the green part of the spectrum. Thus typically it is desirable to use more green chips than red and blue in order to create a white colour output, increasing cost.

Organic light-emitling diodes (OLUD5) formed using coating of organic materials outo substrates are capable ot'production with large areas hut with luminance levels sttbstantially lower than thai achieved by iLEDs.

In this specifieaiion. an illuniinauon apparattts refers to an illuminaiion apparatus whose primary purpose is illtnnination of an environment such as a room or sired scene, or as a display backlighl such as an LCD backlight. An illuminalion apparatus is typically capable of significantly higher luminance Ihan 1000 nits.

This is opposed to fbr exaTnple displays, whose primary purpose is image display by providing light to a viewing observer's eyes so that an image can he seen. Bywayof comparison, if the luminance of a display is very high, for example greater than 1000 nits, then disadvantageously a display can be tmcoinfbrtahly bright to view, Thus the considerations for an illumination apparatus with a primary iliwnination purpose and a display apparatus that provides an incidental illtunination purpose are different. If an illumination apparatus is used as a hacklight in a display apparatus, losses in the spatial light modulator of the display apparatus will reduce Ihe luminance to a level suitable for comfortable viewing. Thus such an arrangement has an incidental illumination function that is not generally suitable for Ihe purpose ot'effieient and bright illumination of an environment.

According to a first aspccl of the present invention there is provided an illumination apparatus whose primary purpose is illtunination as opposed to display, comprising; an array of organic light emitting elements for emitting light at a fust wavelength or spectral band; and an array of inorganic light emitting elements for emitting light at a second wavelength or spectral hand, the second wavelength or spectral band being different from the first wavelengih or spectral band; wherein ihe array of organic lighi emitting elements and the array of inorganic light emilting elements are arrauged on a common substrate with the inorganic light emitting elements interspersed in gaps between the organic light emitting elements; and the array olirlorganie light emitting elements were formed in steps comprising forming a monolithic array of inorganic light emitting elements; selectively removing a plurality of the inorganic light emitting elements from the nionolithic array in a maimer that preserves the relative spatial position of ihe selectively removed inorganic light emitting elements; forming a non-monolithic anay of inorganic light emitting elements with the selectively removed inorganic light emitting elements in a manner that preserves the relative spatial position of the selectively removed inorganic lighi emhting elements; wherein ihe plurality of inorganic lighi emitling elenients that are seleelively removed from the monolithic array are selected such that, in at least one direction, for at least one pair of the selectively removed inorganic light emitting elements in ihe at leasi one direction, for each respective pair there is al least one respective inorganic light emitting element that is not selected that was posilioned in the monolithic array between the pair olselectivelyremoved inorganic light emitting elements in the at least one direction. The illumination apparatus may further comprise at least one furiher array of inorganic lighi emitling elements for emitting light at a third wavelength or spectral hand, the third wavelength or spectral hand being different from the first and second wavelengths or spectral bands, The first wavelength or spectral band maybe a green wavelength or is in the green spectral band. An array of wavelength conversion elements may be arranged in alignment with the array or inorganic light emitting elements, The first, second and third spectral bands may he armnged to provide white light outptit. The illnmination apparatus may thrther comprise a controller arranged to separately control the current in the inorganic light emitting elements and inorganic light enntting elements.

According to a second aspect of ihe present invention there is provided a method of manufaciuring an illttmination apparattts whose pri nary purpose is it lumination as opposed to display, the method comprising; providing an array of organic lighi emitting elements for cnntting light at a first wavelengih or spectral hand; and providing an array of inorganic lighi emitting elements for emiiiing light at a second wavelength or spectral band, the second wavelength or spectral band being dilkrent from the first wavelength or spectral hand; wherein the array of organic lighi emitting elements and ihc array of inorganic lighi emilting elementsare provided on a common substrate and arranged such thai the inorganic lighi emitting elements arc positioned ((inierspersed)) in gaps between the organic lighi emitiing elements; and wherein providing the array of inorganic light emitting elements comprises: tbnning a monolithic array of inorganic light emitting elements; selectively removing a plurality of the inorganic light emitting elements from the monolithic array in a manner that presen7es the relative spatial position of the selectivelyreinoved inorganic light emitting elements; forming a non-monolithic array of inorganic light emitting elements with the selectivclyrcmovcd inorganic light emitting elements in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; wherein tIme pluraliiy of inorganic light emitting elements that are selectively removed [loIn the monolithic ar ay are selected such thai, in at least one direction, for ai least one pair of the selectively retnoved inorganic hght emitting elements in the at least one direction. Rn each lespective pair there is at least one respective inorganic lighi emitting element thai is not selecicd that was positioned in the monolithic array between the pair of selectively removed inorganic light emitting elements in the at least one direction.

According to a third aspect of the present invention there is provided an illumination apparatus whose primary pttrpose is illumination as opposed to display, comprising: at least one organic light emitting element for emitting lighi ai a first wavelength or speciral band; and an array of inorganic lighi emitting elements for emitting lighi ai a second wavelength or spectral band, the second wavelengih or spectral hand being differcni from the first wavelength or spectral band; wherein the at least one organic light emitting element and the array of inorganic light emitting elements arc arranged on a conunon substrate with the inorganic light emitting elements interspersed iii apertures within the at least one organic light emitting elements; and the array of inorganic light emitting elements were thrrned in steps comprising toniung a monolithic array of inorganic light emitting elements; selectively removing a plurality of the inorganic light emitting elements from the monolithic array in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; forming a T10T1-monolithie rn-ray of inorganic light emitting elements with the selectively removed inorganic light emitting elements in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; wherein the plurality of inorganic light emitting elements that are selectively removed from the monolithic array are selected such that, in at least one direction, for at least one pair of the selectively removed inorganic light emitting elements in the at least one direction, for each respective pair there is at least one respective inorganic light emitting element that is not selected that was positioned in the monolithic array between the pair olselectivelyremoved inorganic light emitting elements in the at least one direction.

Further aspects ofthe invention are as claimed in the appended claims.

Advantageously the current embodiments provide a large area light source that achieves high efficiency in a first spectral hand, sitch as the hltte part of the speetrttin hyineans of providing microscopic iLliD elements with otttput in the first spectral hand; and high efficiency and lifetime in a second spectral band sttch as the green part of the speetrttm by means of providing macroscopic ()LED elements with otttpttt in the second spectral band. The microscopic iLED elements ale interspersed with the macroscopic regions of OLED elements to achieve a ttniform white appearance to an observer, advantrtgeously improving the appearance of the lamp when viewed directly, and to improve the glare characteristics of the apparattts. Advantageottsly the present embodiments achieve an efficient, white and colotmr tuneable large area lighting apparatus with low cost.

Further, the present embodiments may advantageously comprise common otttpttt coupling optical elements across the array to provide higher output efficiency and low cost of manttfactnrc.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which; Fig. I shows in plan view a combination of iLED elements and (I)LED elements provided on a sttbstmte with a first arrangement; Pig. 2 shows a method to provide a combination of iLET) elements and OLED elemnents over a large urea; Fig.3 shows a further method to provide a combination of iLED elements and OLED elements over a large area; Fig.4 shows a further method to provide a combination of iLED elements and OLED elements over a large rn-ca; Fig.5 shows a method to singnlate a mothersheet comprising a combination of iLED eletnents and OLED elements; Fig.6a shows in plan view a further combination of iLED elements and OLED elemnermts provided on a substrate; Fig6h shows in plan view a further combination of iLED elements and OLE.D elements provided on a stthstrate; Fig.7 shows in plan view a further combination of iLED elements and OLED elements provided on a substrate; Fig8 shows in plan view a thrther combination of iLED elements and OLED elements provided on a substrate; Fig.9 shows in plan view a thither combination of iLED elements and OLED elements provided on a substrate; Fig. 10 shows in plan view an arrangement of coupling optical elements arranged to efficiently extract light from the array of light emitting elements; Fig, 11 shows in cross section all arrangcinent of coupling optical elements arranged to efficiently cxtract light from the array of light emitting elements; Fig. 12 shows in cross section a method to provide tile optical elements of Figs. 10 and 11; Fig. 13 shows a catadioptric optical element array; Fig. 14 shows ill cross scc[ion a further arrallgcmcnt olcoupling optical clcmcitts arranged to efficiently cxI.rac hglll fl-urn the array of lighi ernilling elements nsing the oplical element array of Fig.] 3; Fig. 15 shows in cross section all inteated light diffusing arrangement; and Fig.16 shows in cross section an air spaced lighi diffusing arrangement.

Fig.1 shows a first embodiment comprising a substrate 2 provided wilh an array of organic light emitting elements 4 comprising regions of green OLED material. An array of inorganic light emitting elements 6 eompnsnlg blue iLNF) elements and arrayof inorganic lighi emitting elements 8 comprising red iLl:D elements are provided in a]ignnlen with the array of OLED elements 4. LEDs are one tbrnl of light emitting elements. The elemenls 6 and 8 comprise inorganic LED elements that are formed in steps comprising forming a monolithic array of light-emitting elements; selectively removing a plurally of light-emitting elements from thc monolithic array in a manner that preserves the relative spatial position of the selectively removed light-emitting elements.;forniing a non-monolithic array of light-emitting elements with the selectively removed light-emitting elements in a maimer tllat preserves the relative spatial position of the selectively removed light emitting elements; wherein the plurality of lighi-emnitting elements that are selectively removed from the monolithic array al-c selected such that, in at least one direction, for at least one pair of the selectively removed lighi-emilting elements in Ihe a] least one direction, for each respective pair there is at least one respective light-emitlmg elemnemit that is nol selected that was positioned in the monohthic array between the pair of selectively removed light-emitling elements in the at least one direction. In this embodiment the inorganic LEDs are formed nsing the method described in (iB2463989 (which is incorporated herein by reference) except where described olherwise below Electrodes and addressing circuitry (not shown) are provided lo achieve electrical eoimeetions to the respective light emitting elements 4, 6 and 8. The addressing circuitry may he arranged lo advantageously achieve connection to the respective elements, and may also he used to control the ontput of at least some of the elements to achieve colour tnning.

It is desirable to combine the advantages of highly efficient blue iLF.l) elements with thc efficiency and lifetime of green OLED elements to provide white light illumination. Advantageonsly such an arrangement can demonstrate high efficiency for all colonm and is colotu' ttmahle. Further, such an apparatus can he made at low cost. However, Ihe luminotms emittance (Ineasured in lumen/rn2) of OLED elements maybe three or more orders of magnitude less than the luininotms einittance of iLED elements; thus OLED elements are munch larger in size than iLED elements. To avoid glare, iLET) lamps typically comprise further directional oplieal elements to increase the effective source size and direct tIme light iimto a limited viewing cone, so that the lamp can only he seen directly from a limited range of angles. However, OLI D elements are much larger and so not well suited to directional optics. In operation, OLED elements nmay thus be easily view-ed directly by all observer. In comparison with iLED only lighting. OLED lighting and tile present hybrid OLED-iLED lighting embodiments consider the glare characteristics for an observer looking directly at the surface of the lighting apparatus during operation. For the glare from such a apparatus to appear unaf onnly while for an observer, it is desirable that the angular size of the group of Light emitting elements comprising respective green regions of array 4, and the blue and red elements of arrays 6 and 8 is smailer than the typical human angular resolvable size, for example 1/2000.

In one example, a ceiling mounted light is arranged at a distance of 2m from an observer, so Ihe angularly resolvable size will be typically less than 1mm. Assuming the luminous erneieney of the elements of Ihe elemenls 6,8 is the same, and if Ihe luminous emittaTice of an iLE.D element is 1000 limes greater than thr an equivalent OLE.D element, then each of the 1LE.D element areas is approximately 30x30micrometres (on a pitch of lxlmm) while the green OLED elements will substantially fill the remaining space. Such an arrangemenl provides a visual colour integration and resulling while appearance of the lamp. By way of comparison, if the iLE.D elements are provided at spacing substantially greater than lxlmrn then glare from the light source will appear to be green, with inlerspersed red and blue emitting regions; the output will nol appear lobe white. Thus it will he appreciated that the while nnitbrmity of the glare from the apparatus tends to he improved by the use of microscopic iLEDs as described interspersed in small gaps between the relalively very much larger macroscopic OLEDs, compared to hypothetical alternative arrangements in which relatively large macroscopic OLI Ds of different colours might he arranged together in an interspersed fashion.

To provide desired output ilitunination, large numbers of iLED elements are preferable. In order to provide a 1 klin whitc light source, such an element may have an area of approximately SOOxSOOmm2 and use 250,000 individual elements in each of the arrays of elements 6, 8. If the individual iLED elements were attached bymeans oI'elcinent-at-a-time pick-and-place operationsthenthe cost of mounting the elements would be prohibitive. Further the electrode attachment steps (for example by means of wire bonding) would provide very high costs and very low oulput efficiency. Advantageously, the present emhodimenls achieve high elhciency operation over large areas by means of seleclive removal of a pluralily of light-emitting elements from a monolilhic iLED array in a manner that preserves the relative spatial posilion of the selectively removed light-emitting elements. Ftjrlher, such elements can he formed over large area to provide Ihe desired output brightness for a single lamp allow cost.

If the iLED elenmenls are formed as shown in Fig.2, then it is possible to conveniently attach many iLl:D elements to the substrate 2 in a single mounting operation, Further the electrodes may he provided by means of photolithography operations and as such may have a small area compared to tIme elemnemmt area, advantageously achieving high output efficiency. A method to form a hybrid iLED-OLED illumination apparatus is shown in Fig.2. In a first step at least one niask 62 mounted on a substrate 63 is used to illuminate a monolithic lighl-emitling element wafer comprising epitaxial layers 60 and subslrale 61. The layer 60 may comprise epitaxial layers that acltieve blue light output in operation. For the purposes of the present specification, the term monolithic refers to consisting ofone piece; solid or unbroken.

In a second processing step, an array 76 of light-emitting elements is fonned in the monolithic wafer 60, 61, Each elenment lmas a position and orientation defined by the mask 62. The nmask is composed of an array of regions, each region defining the structure of at least one Layer of an iLED chip. Regions 65 and 67 represent first and second iLED chips and have separation sI as shown. During exposure through the mask onto the wafer 60. elements 72 and 74 are fonned front regions 65 and 67 of the mask. The separalion sI of the elemnenls 72, 74 is substantially the same as the separation of Ihe mask regions 65, 67 and Ihe orientation of the elenmenls 72, 74 is the same as the orientation of the respective mask regions 65, 67. The integrity of separation si and orientation of elements 72, 74 is preserved through the subsequent processing steps.

Multiple masks may be used to photolithographically fortn the complete iLED structure in the manner described, each with regions with the separalion sI. Such processes preserve a separation and orientations of elements 72 and 74.

In a third step, the array 76 of light-emitting elements may be cut by means of a cutting device 82, which may for exaniple he a scribe, culling wheel, laser or saw. The separation s2 of the eul lines for a respective edge of elements 72. 74 would ideally be the same as the separation sI. however, in practice such a precise separalion is very dillictdt to achieve. Advanlageously the emhodimenl does not require the separalion s2 to he identical lo the separatioa sI.

In a Fourth step, a tool 90 which may For example be an adhesive Film is attached to the array 76, A palterned array of liv lighi is imaged onto the interface of lhe elemenls 72,74 with the subslrale 61 so that separation of the elements From the substrate 61 is achieved, In a 111Th step the tool 90 together with elemenls 72,74 is removed, extracting a sparse array of light emitting elements. The integrity of the separation sI and orientation of the elements 72 and 74 is advantageously preserved in this extraction step, Fig.3 shows a method wherein the sparse array of iLl iD elements, comprising light emitting elements 72,74 are fonned on the substrate 2. Stthstrate 2 may be thrmed with palterned layer of OLED elements 4 and electrode layers (not shown). Open regions 91 may be Formed between Ihe regions 4 of OLED material for example by patterned deposition of the OLED material orby uniform deposition Followed by patterning oF the material, for example by means oFlithography or laser removal. The output colour, for example Ihe white point, may he adjusted by trimnung, e.g. by laser ablation, the emilling area of the OLED elements 4. Advantageously this trimming process could he arranged so that groups of emitting areas have similar white points at the same operating current, In a second step, the sparse array of light emitting elements 72, 74 on tool 90 are aligned wilh Ihe regions 91 and attached lo Ihe substrate 2, for example by means of solder. or eonduclive adhesive, The tool is then removed and eleelrode layers 92, 94 deposited lo provide electrical eonTleetion lo iLED elements 72, 74 and OLED elements 4. Fttrther planarization layers 96 and encapsulation layers 98, such as a glass cover layer may be added. To improve the heatsinking performance of the apparatus, layer 2 may be thinned (hy known techniques such as grinding and polishing) prior to attachment of heatsinks.

Thus an iliwnination apparatus whose primary purpose is illumination as opposed to display, comprises an array of organic light emitting elements 4 for emitting light at a first wavelength or spectral band (for examnple a green spectral band); and an array of inorganic light emitting elements 6 for emitting light at a second wavelength or speelral band (for example a bltte spectral hand), the second wavelength or spectral hand being ditierent from the First wavelength or spectral band; wherein the array oF organic light enmitting elenments 4 and the array of inorganic light emilting elements 6 are arranged on a common substrate 2 with Ihe inorganic light emitting elements 6 immterspersed in gaps betweemm the organic light emitting eleiuemmts; and the array of inorganic light emitting elenments 6 were formed in steps conmprising fonning a monolithic array 76 of inorganic light enntting elemmmemmts; selectively removing a plurality of tlme immorgammie light etnitting eletnents 6 from the monolithic array in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements 6; forming a non-monolithic array of inorganic lighl emilting elements 6 with the selectively removed inorganic light emitting elements 6 in a maimer that preserves the relative spatial position of the selectively removed inorganic light emitting elements 6; wherein the plurality of inorganic light emitting elements 6 that are selectively removed from the monolithic array 76 are selected such that, in at least one direction, tin at least one pair of the selectively removed inorganic light emitting elements 6 in the at least one direction, for each respective pair there is at least one respective inorganic light emitting element 6 that is not selected that was positioned in the monolithic array 76 between the pair oI'selcctivcly removed inorganic light cmiiiing elements 6 in the al leasi one direction.

Fig.4 shows in plan viec an arrangement comprising a large substrate 2 on which multiple tools 90, each comprising a sparse array of blue iLED elements are aligned. Further tools 100 comprising red iLED elements may also be aligned with the substrate 2. The subsequent layers 92, 94, 96 and 98 may he added across the whole olthc inothersheet area so that operations on the respective iLFD and OLE]) elements arc pcrfonncd in parallel. In a stibscqucnt processing step the inothcrshcet may he cut to dill reni sizes (e.g for a desired light output andor a speeiflc shape) to suit the application, [hr example along lines 96 as shown in Fig.5.

Advantageously, ihis enables a large area of hybrid iLED-OLED lamp 10 be fabricaled hi parallel, reducing cost.

Fig.6a shows an embodiment wherein the iLLD elements are arranged in holes 10 in a continnotms region, comprising element 4 of OLLD material. Advantageously such an arrangement provides separation of the iLED and OLED addressing and optical output. Wavelength conversion elements 7 may fitrther be provided in aligmnent wiih at least some of the inorganic light emitting elements 6 as shown in Fig.6h. For example, red light emitting elements may he provided by a blue light emitting element 6 and a red conversion phosphor wavelength conversion clctnent 7.

Fig.7 shows a ftnihcr embodiment wherein the iLED elemenis and electrodes (not shown) are fonned onihc sttrface of a continuotts layer of OLED elements. Advantagcottsly snch an arrangement redttees the complexity of the OLE]) layer and uses a single drive circuit, redncing cost Fig.8 shows a further embodiment wherein an OLED layer is fonned over iLED elements for OLE]) maierial strtteturcs that arc iransmissive in the red and blue paris of the spectrum. Advaniageottsly, sttch an arrangement can achieve simplified processing steps, reducing cost. Fttrther, the size of ihe red and blue iLED elements in the present embodiments may he different to compensate for differences in ltuninotms eniittance between blue elements 6 and red elements 8 to advantageously achieve a means to colour balance the illtunination apparatus.

Further, gwding of the tight fiomn the iLED elements 6,8 within the OLE]) laycrs may be ttsed to increase the area over which light from the iLED elements is emitted. Advantageously, this achieves a reduced density of iLED elements to meet visual colour integration requirements. Sttch a redtteed density means that the iLED elemenis can be larger, which nmay improve outpttt efficiency of the devices by achieving a proportionately smaller electrode size compared to iLh[) size.

Fig.9 shows a fi.nihcr embodiment wherein regions 12 of red OLED material arc combined with regions 4 of green OLED material and an array of hltme iLED elements 6. Such an arrangement advantageottsly achieves the advantages of efficiency and large area coating fronm OLED element processing while achieving the high efficiency of blue iLED elements.

TIme arrangements described above achieve substantially Lanmhertian outptit characteristics. however, if a cover substrale is ttsed. light maybe trapped in the layers of OLED material and encapsulation layers.

Fig.l0 shows in plan view output coupling optical elements to inmprove output extraction efficiency, Advantageously, the output optic is substantially the same for cach of the red, green and blue cmitting elements.

Thus, regions 4 may he provided with the same nonnnal size and spacing, and optical elements 16 provided in alignment with Ihe elements 4, 6.

As shown in cross section in Fig.1 1 the optical elements 16 may be hemispherical optical elements. A further protective transparent substrate 18 and diffuser layer 22 may further he provided and attached 10 the subsirale 2 by means of sealing malerial 20. Such an arrangemenl provides a protected oulpul surface and further optical characteristics that can he used to blur the appearance of the separate red, green and blue elements with high efficiency.

A method to fonn the hemispherical optical elements 16 is shown in Fig. 12. The arrays of elements 4, 6 are provided on substrate 2. A tool 24 is provided in aliginnent with the elements 4, 6 and filled with a material 26 which is cured. On release of the tool 24, oplieal elements 16 are fonned. Advanlageously many optical elements can he thrmed in paralle' over a large area.

To ftrther reduce cost, it would he desirable Ihat the optical elements 16 are formed on a separale substrate that is aligned to a large mothersheet substrate 2 suitable for subsequent dicing. However.

hemispherical optical elements 16 are difficult to fabricate reliably on such a sttbstrate if the input surface of the hemisphere is to he brought into contact with the elements 4, 6, 8. A further embodiment is provided in Fig. 13 comprising a eatadioptrie optical element 38 (eomprisiug reflective and refraclive optical functions) formed on the surface of a substrate 18 and with an inpul apertttre 37.

As shown in Fig. 14, when assembled with the light emitting elements, the elements comprise an outer wall section 28 to provide a total internal reflection t'unelion, a wall section 30 to provide a refractive deflection of light and a central section 32 lo direel light from the source 10 the output. A material 34 with high refractive index can he provided in combination with a malerial 36 with low refractive index so that the light from Ihe emitting elemenls comprising elements 4. 6 may be efficiently coupled from the light emitting elemenls, Advanlageously, the area of Ihe substrate 2 covered by tile OLED elements 4 is preferably maximnised to provide Ihe lowesl cost of the eleTnenis. Thtts, the gaps between emitters are preferably mininused. This can he achieved by arranging the oplieai elements to provide subslantially a ftmll 2 * pi steradian otmtptmt cone angle.

The light enntting elements 4, 6, 8 can be aligned with the input aperture 37 of the optical elements, An optional diffuser 22 may be incorporated to further reduce the directionality of the output. To further increase OLED brightness, OLFI) elements 4 may be incorporated in the gaps between the optical elements providing fl.trther light nnxing between the iLliD and OLE.D elements. Advantageously, the optical elements 38 can he funned over a large. area on substrate 18 so that subslrate 18 can he provided in alignment to stthstrate 2, Individual lamps may be extracted from the array of aligned substrates by dicing the two elements after attachment as shown in FigS. In this manner, low cost with high efficiency may be achieved, It would he desirable to increase the iLl iF) element size preferably to more than 50 mieronmetres, more preferably to ntore than 100 mierometres in order to increase light output by ttsing proportionately smaller electrode sizes. However, tins may achieve loss of visual colour integration as described previously. As shown in Fig.l 5 difli.mser 22 niay he provided for exaniple with a +/-30 degree angular spread, spaced a distance 23 of 3mm from Ihe elements 4, 6. 8 would pmvide an effective light mtegralion area of approximately 3mm width.

This advantageously achieves an ILE.D element size of approximately lOtixiQOnnerometre area. Further Ihe spacing 23 can conveniently be achieved using the thickness of substrate 18 and diffuser 22, thus advantageously providing an integrated structure with good mechanical ruggedness and high transmission efficiency.

By way of colnparisou, an air spaced diffitser could he used to provide higher degree of separalion of the diffuser, for example 25mm, enabling larger chip sizes that may he more suitable for pick-and-place fabrication, However such an arrangement disadvailtageously suffers from increased light losses from surface rdfieclivily of the additional illierthecs of substrate 18 and diffuser 22 with air, thus reducing efficiency compared to the present embodiments. Alternatively by way of comparison, a wide angle diffuser could be used. however, such high angle diffUsers suffer ftom higher losses and degrade efficiency.

Claims (1)

  1. <claim-text>Claims 1. An illumination apparatus whose primary purpose is illumination as opposed to display, comprising: an array of organic light emitting elements for emitting light at a first wavelength or spectral band; and an array of inorganic light emitting elements for emitting light at a second wavelength or spectral band, the second wavelength or spectral band being di tierent from the first wavelength or spectral band; wherein the array of organic light emittiTig eleTnenis and ihe array of inorganic lighi emitling elements are arranged on a common snhstrate with the inorganic light emitting elements interspersed in gaps between the organic light. emitling elements; and the array of inorganic light emitting elements were formed in steps comprising forming a monoliihic array of inorganic light emitting elements; selectively removing aplurality of the inorganic light emitting elements from the monolithic array in a niamler that preserves the relaiive spatial position of ihc selectively removed inorganic light emitting elements; forming a non-monolithic array of inorganic light eniitting elements with the selectively removed inorganic light emitting elements in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; wherein the plwalily of inorganic light emitting elements that are selectively removed from the monolithic array are selected such that, in at least one direction, for at least one pair of the selectively removed inorganic light emitting elements in the at least one direction, thr each respective pair there is at, leasi one respective inorganic light emitting element that is noi selected thai was positioned in the monoliihie array between the pair of seleciively removed inorganic light emitting elements in the at least one direction.</claim-text> <claim-text>2. Arm illnnmination apparatus according to claim 1 comprising at least one fnrther array of inorganic light emitting elemenis for emiiting light at a third wavelengih or spectral hand, the third wavelength or speciral band being different from the first and second wavelengihs or spectral hands.</claim-text> <claim-text>3. Ar illtnninatioTl apparatus according to claim I or claim 2 wherein the first wavelengih or spectral band is a green wavelength or is in the green spectral hand.</claim-text> <claim-text>4. An illumination apparatus according to any of claims 1 to 3 wherein an array of wavelength conversion elements is arranged in alignment with the array or inorganic tight emitting elements, 5. An illumination apparatus according io any of claims 1 to 4 wherein the fn'st, second and third spectral hands are arranged to provide white light ouipui.6. An illumination apparaius according to any of claims 1 io 5 thither comprising a eonirollcr arranged to separately control the current in the inorganic light etttitting elements and inmorganie light emitting elements.7. A method of nmanufacturing an illumination apparatus whose prinmary purpose is illumination as opposed to display, the method comprising: providing an array of organic light emiiting elements for emitting light at a first wavelength or spectral band; and providing an array of inorganic light emitting elements for emitting light at a second wavelength or spectral hand, the second wavelength or spectral hand being different from the first wavelength or spectral hand; wherein the array of organic light emitting elements and the an-a)' of inorganic light emitting elements are provided on a common substrate and arranged such that the inorganic light emitting elements are positioned ((intersperscd)) in gaps between the organic light emitting elements; and wherein providing ihe array of inorganic lighi emiiiing elements comprises; tbrming a monolithic array of inorganic light emitting elements; selectively removing a pltmralily of the inorganic lighi emiiting elements from the monoliihic array in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements;fonng a non-monolithic array of inorganic light emitting elements with the selectively removed inorganic light emitting elements in a manner that preserves the relative spalial position of the selectively removed inorganic light einitiing elements; wherein the plurality of inorganic light emitting elements that are selectively removed from the monolithic array are selected such that, in at least one direction, for at lea 1 one pair of the selectively removed inorganic lighi emitting elements in the at least one direction, ffir each lespective pair there is at least one respective inorganic light emitting element that is not selected that was positioned in the monolithic array between the pair of selectively remnoved inorganic light emitting elements in the at least one direction.8. An illttmination apparatus whose primary pttrpose is illtmmination as opposed to display, comprising; at least one oiganic light etnitting clement for emitting light at a first wavelength or spectral band; and an array of inorganic light emitling elements for emitting light at a second wavelength or spectral hand, the second wavelength or spectral band being different from the first wavelength or speciral hand; wherein ihe at least one organic light emitting element and the array of inorganic light emitting elements are arranged on a common substrate with the inorganic light emitting elements interspersed in apertures within the at Icasi one organic light emitting clemenis; and the array of inorganic light cmitiing elements were formed in steps comprising fonning a monolithic array of inorganic light emiiiing elements; selectively removing a plurality of the inorganic light emitting elements from the monolithic array in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; forming a non-monolithic array of inorganic light emitting elements with the selectively removed inorganic light emitting elements in a manner that preserves the relative spatial position of the selectively removed inorganic light emitting elements; wherein the plmality of inorganic light emitting elements thai are selectively removed from ihe tnonolithic array are selected such that, in at leasi one direction, for at leasi one pair of the selectively removed inorganic light cmiiiing elements in the at least one direction, for each respective pair there is at least one respective inorganic light emitting elemnent that is not selected that was positioned in the monolithic array between the pair of selectively removed inorganic light emitting elements in the at least one direction.</claim-text>
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