Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/80—Constructional details
  • H10K59/875—Arrangements for extracting light from the devices
  • H10K59/879—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/858—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional radiating surfaces
  • H05B33/22—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/35—Non-linear optics
  • G02F1/355—Non-linear optics characterised by the materials used
  • G02F1/361—Organic materials
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F13/00—Illuminated signs; Luminous advertising
  • G09F13/20—Illuminated signs; Luminous advertising with luminescent surfaces or parts
  • G09F13/22—Illuminated signs; Luminous advertising with luminescent surfaces or parts electroluminescent
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
  • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/856—Arrangements for extracting light from the devices comprising reflective means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/80—Constructional details
  • H10K59/875—Arrangements for extracting light from the devices
  • H10K59/878—Arrangements for extracting light from the devices comprising reflective means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
  • H10K59/12—Active-matrix OLED [AMOLED] displays
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
  • H10K59/10—OLED displays
  • H10K59/17—Passive-matrix OLED displays

Definitions

• the invention relates to a lighting or image display panel comprising a one- or two-dimensional matrix of organic electroluminescent cells ("OLED") provided with means to facilitate the extraction of the light emitted by these cells, which significantly improve the light output.
• OLED organic electroluminescent cells
• Such a panel generally comprises a substrate supporting a thin organic light-emitting layer interposed between two networks of electrodes, one of anodes, the other of cathodes, intended to supply the cells; each cell is positioned in an overlap area of an anode and a cathode; in the case of a passive matrix panel, each network is generally formed by electrodes in parallel strips of constant width; the electrodes of the anode network are generally perpendicular to the electrodes of the cathode network; for polychromatic, in particular tri-chromatic, panels the organic electroluminescent thin layer is generally divided into alternating bands of different emission colors.
• the substrate incorporates electronic components for driving the cells; in the case of a passive matrix panel, the substrate is generally made of glass or plastic; the thickness of the substrate is generally between 300 ⁇ m and 1500 ⁇ m, ie 500 to 100 times greater than that of the cells; the side or the diameter of the cells or pixels is generally between 100 ⁇ m and 300 ⁇ m, ie 1 to 15 times less than the thickness of the substrate; the layer of electrodes interposed between the substrate and the light-emitting layer is generally called “lower layer” because, in conventional manufacturing processes, it is applied before the light-emitting layer; the other layer of electrodes, applied after the electroluminescent layer, is called “upper layer”; generally, the strips of the upper layer of electrodes are parallel and centered on those of the electroluminescent layer, which they cover at least partially.
• the light emitted by the panel must pass through the substrate to reach the observer of the images to be viewed (case of emission panels “downwards"), or must not pass through the substrate to reach it (case of "upward” emission panels).
• the light emitted by the panel must pass through one of the electrode layers, either the lower layer (in the case of “down” emission panels) or the upper layer (in the case of "upward” emission panels »), Before exiting through the exit face of the panel where it enters the air towards the observer; the other layer is then generally reflective to recover the light from the cells emitted in the direction opposite to that of the observer and to redirect it towards the outside of the panel via the exit face of the panel.
• One of the electrode layers is therefore generally transparent, for example based on “ITO” to serve as an anode, the other then preferably being metallic, absorbent or even reflective.
• the light extraction systems described in these documents are based on the refraction of the light at the exit of the cells, more precisely on the shape of the exit face of the panel which has a curvature adapted so that the rays which come from the cells reach this face under an incidence lower than the limiting angle of refraction so as to cross it.
• An object of the invention is, in particular, to propose another extraction solution based no longer on the refraction of the rays coming from the cells, but essentially on their reflection.
• the invention relates to a lighting or image display panel comprising a one- or two-dimensional matrix of organic electroluminescent cells deposited on a substrate and grouped at least in lines, characterized in that it comprises, for each cell or group of cells, an optical light extraction element which itself comprises:
• an input interface optically coupled with the emissive surface of said group cell or cells or that of the substrate so as to capture the rays emitted by said cell or cells
• an intermediate reflecting surface which has a curvature adapted so that the rays which strike it from the input interface are returned to the output interface so as to present there an angle of incidence less than the limiting angle of refraction at this output interface so as to cross it.
• each optical element for extracting light from the panel comprises: an input interface optically coupled with the emissive surface of the cells or that of the substrate of the panel, so as to capture the rays emitted by these cells, - a shaped output interface adapted so that the rays emitted by the cells pass through it,
• a reflecting surface modifying the path of these rays so as to decrease the angle of incidence with this output interface.
• the cells are also grouped in columns; one can therefore find one optical extraction element per column.
• the optical coupling with the cells or the substrate is ensured by a layer of adhesive having a refractive index comparable to that of the material of the optical elements.
• the material of the optical extraction elements is transparent; for example, a conventional soda-lime glass of index 1.52, a polymethylmethacrylate of index 1.49 or a polyethylene glycol-terephthalate of index 1.57 is chosen; as this material has a refractive index higher than that of air and closer to that of the light-emitting emitting layer, the rays emitted by a cell of the panel are, after crossing the input interface of an element d extraction, included in a solid angle greater than the solid angle in which they would be after crossing an interface of identical shape, but with air, which means that this optical element captures a proportion of the radiation emitted by cells larger than that which would enter the air directly through these cells in the absence of optical extraction elements; thus, the optical elements very significantly increase the rate of light extraction.
• the optical element is specially designed, according to the invention, so that almost all of the rays which penetrate through the input interface exit through the output interface,
• the output interface if there is no reflecting surface, or, where appropriate, said reflecting surface, do not have a plane surface element; non-planar curved surfaces are in fact the best suited to obtain the best rate of light extraction; in the case where the extraction elements comprise reflective surfaces, the invention therefore extends to cases where the output interfaces are planar, in accordance with most of the examples given below.
• these elements form a network of convex microlenses.
• the convex lens shape of the output interface is particularly well suited so that the rays coming from the input interface form with this interface a lower angle of incidence than if this interface were plane and parallel to the substrate of the panel. ; by reducing the angle of incidence at the interface with air, the rate of light extraction is very significantly increased.
• each microlens is greater than the area of an emitting area or a pixel of the panel.
• each microlens has two planes of symmetry whose intersection is preferably centered on a cell, or a microlens for a row or column of cells, in which case each microlens has a plan of symmetry which is preferably centered on a row or column of cells.
• the subject of the invention is a lighting or image display panel as defined in the claims below, where the elements extraction include a reflective surface; this reflecting surface has a shape adapted so that any ray entering through the input interface of an extraction element comes out of it through the output interface of this element.
• the shape of the output interface of each optical extraction element can be planar or curved; this shape has a curvature adapted so that the rays which come from the input interface, directly or via one or more reflections on the reflecting surface, strike this output interface at an angle of incidence less than the limit angle of refraction at this output interface so as to cross it.
• this surface preferably has a shape adapted so that any ray penetrating through the input interface of an element d extraction comes out through the output interface; this condition is stated in English as the “edge-ray” principle, with reference, in particular, to chapter 4, paragraph 2 of the book entitled “High Collection Nonimaging Optics”, WT Welford & R.
• the reflecting surface has at least one plane of symmetry and each of the two lines of intersection of this surface with a plane perpendicular to this plane of symmetry forms a portion of a parabola, as illustrated in chapter 4, paragraph 3 of this work , in particular in Figure 4.3, where, unlike the invention, such a surface is used as a concentrator; the inlet of the concentrator described in this book becomes the outlet interface of the extraction element according to the invention and the outlet of the concentrator becomes the inlet interface; as illustrated in chapter 4, paragraph 5 of the same work, each of the two lines of intersection forms a succession of portions of parabolas; preferably, the position of the axis and the focal point of the parabola of each line of intersection, as well as the thickness L of the extraction element are chosen so as to satisfy the conditions set out in chapter 4, paragraph 3 of this work, in particular pages 56-57, so as to satisfy the principle of "edge-ray"; by summarizing, preferably, each of the
• optical reflection extraction elements Thanks to the optical reflection extraction elements according to the invention, a very high proportion of the light emitted by the cells can be extracted and panels with high light output are obtained.
• the reflecting surface therefore forms a reflector; one reflector can be found per cell, in which case each reflector preferably has two planes of symmetry, generally perpendicular, the intersection of which passes through the center of a cell; one can find a reflector by rows or columns of cells, in which case each reflector has a single plane of symmetry centered on a row or on a column.
• each extraction element comprises both a lens-shaped output interface and a reflective surface; preferably, this reflecting surface is then of the “CPC” type previously described; examples of such elements are given in chapter 5, paragraph 8 of the work cited above.
• the extraction element also serves to collimate the light; for each extraction element, the exit interface and / or, where appropriate, the reflecting surface then have a shape adapted so that the rays which exit from the exit interface are in a solid angle strictly less than 2 ⁇ steradians; the shape of the output interface and / or that of the reflecting surface are then advantageously adapted so that the rays emitted by the panel are tightened towards a limited area of the space specially intended for observers of the images to be viewed; the performance of the panel is then appreciably improved at no additional cost.
• the optical extraction elements of the panel are in one piece forming an extraction layer.
• This part then brings together all the lenses or parabolic reflectors or other light extraction elements; this arrangement is particularly advantageous, because it is economical both for the manufacture of the extraction elements and for its assembly on the panel, since all the extraction elements are suitably positioned on the various cells of the panel in a single operation; in addition, the extraction layer can then be used to protect the cells of the panel, in particular against the action of ambient water and / or oxygen.
• the cell matrix generally comprises an electroluminescent layer disposed between two layers of electrode networks, a so-called “lower” layer on the side of the substrate and a so-called “upper” layer on the other side, each cell being positioned in an area of covering an electrode of the lower layer and an electrode of the upper layer; such a panel may include other electrode networks, in particular in the case of active matrix panels.
• the extraction elements are then positioned above this upper layer; preferably, the extraction elements, according to the first or second family of embodiments, are in one piece, form an extraction layer, and also form an encapsulation layer which is sealed with the substrate so as to prevent the penetration of gases, such as oxygen or water vapor, into the cells and so as to prevent any risk of degradation of the electroluminescent layer by these gases; the space thus encapsulated can comprise adsorbing or drying agents, capable of adsorbing these gases.
• this desiccant is then placed in cavities which are formed in the thickness of the extraction layer, which are open towards the inside of the panel in the direction of the electroluminescent layer, and which are arranged between the elements of extraction so that the adsorbing agent does not obstruct the passage of light.
• the electrodes of the lower layer are transparent or semi-transparent, there is then a so-called “back-emitting” panel; the extraction elements are then positioned on the face of the substrate opposite to that of this lower layer.
• the extraction layer itself which forms the substrate of the panel; for the manufacture of the panel, it is then on the extraction layer, on the input interface side, that the various layers, in particular of electrodes and electroluminescent material, are deposited, which will constitute the two-dimensional matrix panel cells; the extraction layer is then preferably made of glass.
• the substrate has a fibrous structure whose fibers are adapted and oriented to guide the light from one face to the other of said substrate.
• each extraction element can cover a group of cells, in particular a row of cells, or for example a column of cells if the matrix is two-dimensional; in this case, each extraction element preferably comprises a plane of symmetry centered on this group of cells, row or column.
• each cell of this group emits in the same primary color; in other words, each group of cells then corresponds to cells emitting in the same color.
• each extraction element can cover a single cell; in this case, each extraction element preferably comprises two planes of symmetry whose intersection passes through the center of this cell; in the case of a panel with a two-dimensional matrix of cells, the extraction elements then form a two-dimensional network.
• the surface density of extraction elements can be greater than the surface density of groups of cells or cells of the panel.
• the electrodes of the networks are preferably in the form of parallel conductive strips of constant width; preferably, the electroluminescent layer is then divided into parallel bands emitting different primary colors and arranged alternately; preferably, each electrode strip of the upper layer is then parallel and centered on a strip of the electroluminescent layer.
• the invention is particularly advantageous in the case where the substrate of the panel forms an active matrix; in fact, in order to integrate an active matrix into the electroluminescent panels, it is often necessary to limit the electroluminescent emission surface specific to each cell; this limitation is no longer a disadvantage when using light extraction elements according to the invention.
• the invention applies very particularly to image display panels.
• FIGS. 1 and 2 describe electroluminescent panels with “downward” emission , respectively with barriers and without barriers, before application of a light extraction layer according to the invention
• FIGS. 3 and 4 describe electroluminescent panels with “upward” emission, respectively with barriers and without barriers, before application of a light extraction layer according to the invention
• Figures 5 to 9 describe, in side or sectional view and back or front view, emission panels "upwards" without barriers with, according to a first family of embodiments where the light extraction elements are in the form of microlenses: generic case for FIG. 5, case of the use of a gradient index plate as an extraction layer for FIG. 6, case of longitudinal lenses arranged parallel to the rows or to the columns respectively for FIG. 7 and 8, case of an extraction layer formed by a two-dimensional matrix of lenses for FIG. 9.
• FIG. 11 describes, in section, a barrier-free “down” emission electroluminescent panel provided with light extraction elements in the form of reflectors according to a second family of embodiments of light extraction elements;
• Figures 10, 12 to 14 describe, in side or sectional view and back or front view, emission panels "up” without barriers with, according to the second family of embodiments, extraction elements of light in the form of reflectors: generic case for FIG. 10, case of longitudinal reflectors arranged parallel to the rows or columns respectively for FIG. 12 and 13, case of an extraction layer formed by a two-dimensional matrix of reflectors for the Figure 14.
• FIG. 15 and 16 describe sectional views of "down" emission electroluminescent panels, whose substrates are structured in fibers serving as light guides to pass through it and which are provided with reflectors and microlenses respectively .
• - Figure 17 describes a top view of an electroluminescent panel with an active matrix, before application of a light extraction layer.
• the panel according to the invention therefore comprises:
• the advantage of the separation barriers is to provide better electrical insulation between the rows or columns of cells; their disadvantage is an additional cost.
• Tin Oxide "in English) which is then etched to form transparent electrode strips 101; in the case of an active matrix, one would rather engrave rectangles of transparent electrodes; an electrical insulation layer 102 is then deposited, providing recesses or spares, here of rectangular shape, for each electroluminescent cell; there is then produced a network of rectilinear separation barriers 105, parallel, oriented perpendicular to the electrodes 101 of the lower layer, and arranged between the spares or recesses of the insulation layer 102; possible methods of making the barriers are described in document US 5701055 (PIONEER); these barriers are made of insulating material, preferably identical to that of the insulation layer 102; between the barriers 105 and within each savings or recesses in the insulation layer 102, the organic electroluminescent layer is deposited forming strips 103, generally structured itself in several sublayers comprising in particular an organic sublayer of hole injection, an organic electroluminescent sublayer proper, and an electron injection sublayer; for the deposition of these organic sublayers, the
• strips of transparent electrodes 101 are deposited as before; using a mask or set of masks - one for each color - we depositing strips of organic electroluminescent layer 103, of structure and composition identical to those previously described; these strips 103 are parallel, oriented perpendicular to the electrodes 101 of the lower layer, and arranged so as to cover the rectangular areas of the cells; above the light-emitting strips 103, through masks having narrower openings, strips of electrodes 104 are then deposited identical to the previous ones; a “down” emission panel is thus obtained without barriers.
• FIG. 5 describes extraction elements in the form of microlenses 20 deposited on an electroluminescent panel with “upward” emission without barriers as previously described with reference to FIG. 4; each microlens 20 comprises, at the level of each cell, or of each row or column of cells of the panel:
• an outlet interface 23 with a wider opening L s the shape of which has a curvature adapted so that the rays which come from the inlet interface 21, such as that represented by an arrow in solid lines in the figure, strike this output interface 23 at an angle of incidence less than the limiting angle of refraction at this output interface 23, so as to pass through it.
• the extraction of the light emitted by the cells of the panel is considerably improved.
• all of the extraction elements are in one piece and form an extraction layer 200; this extraction layer may be made of transparent polymer material, which makes it possible to form it economically by pressing or injection molding; this extraction layer can also be made of glass; this extraction layer can be assembled on the panel by gluing; the intermediate adhesive layer - not shown - then serves as an optical coupling means with the panel.
• FIG. 6 shows a variant in which the extraction layer 200 ′ has a homogeneous thickness and contains gradient index zones 20 ′ which play the same role as the extraction optical elements previously described.
• FIGS. 7 to 9 show other variants concerning the shape of the microlenses of the extraction elements:
• each extraction element 20 L has a plane of symmetry, serves for a line of cells of the panel of Figure 7 A, and is centered on a transparent electrode line 101 of this panel;
• each extraction element 20 c has a plane of symmetry, is used for a column of cells of the panel of Figure 8 A, and is centered on an opaque electrode column 104 of this panel;
• FIG. 9 B each extraction element 20 P has an axis of symmetry centered on a cell of the panel at the intersection of a transparent line electrode 101 and an opaque column electrode 104 of the panel of FIG. 9 A, and basically serves for this cell.
• the extraction layer 200 is then optically coupled with the surface of the substrate 100; because of the thickness of the substrate, which is generally between 0.3 to 1.5 mm and which is greater or even much greater than the side or the diameter of the cells or pixels, the amount of light captured by the extraction layer is lower than in the previous cases of “upward” emission; this disadvantage is avoided by using the extraction layer 200 as a substrate, preferably then by using an extraction layer with a gradient of index 200 ′ as shown in FIG. 6.
• the thickness of the extraction elements in the form of microlenses or of the extraction layer is a compromise between the rate of light extraction, the desired level of concentration or collimation (see below), the mechanical rigidity and the level of protection that it is desired that this layer provides to the panel.
• FIG. 10 describes extraction elements in the form of parabolic reflectors 30 of the “CPC” type previously described, deposited on an electroluminescent panel without emission barriers “upwards” as previously described with reference to FIG. 4.
• Each parabolic reflector 30 comprises, at the level of each cell, or of each row or column of cells of the panel:
• extraction elements are in one piece and form an extraction layer 300; preferably, this extraction layer is made of transparent polymer material and is formed by pressing or injection molding.
• the reflective surfaces 32 are formed by aluminizing the areas of the surface of this layer which must be reflective; according to a variant, the reflection is ensured by total reflection.
• the optical coupling at the levels of the input interfaces is carried out using a layer of transparent adhesive of index close to that of the material; but, by coating with glue the input interfaces 33 of the extraction layer, there is a risk of applying glue to the reflective surfaces 32, which would be particularly troublesome if the reflection was ensured by total reflection; aluminizing the reflecting surfaces 32 avoids this drawback. Thanks to such a reflective element 30, the extraction of the light emitted by the cells of the panel is considerably improved.
• FIG. 11 represents a variant where the extraction layer 300 ′ comprising reflectors 30 identical to the previous ones is deposited on an electroluminescent panel without emission barriers “downwards” as previously described with reference to FIG. 2; this variant also differs in that the density of extraction elements is much higher than previously: there are indeed twice as many extraction elements as there are rows of cells or columns of cells or even cells; this variant also differs in that it comprises a network of reflective elements 28 disposed between the substrate 100 and the extraction layer 300 ′, between the input interfaces 31 of adjacent extraction elements; this network of reflective elements 28 makes it possible to further improve the extraction efficiency, as indicated by the path of the light rays shown in the figure.
• Figures 12 to 14 present other variants concerning the shape of the reflectors of the extraction elements:
• each extraction element 30 L has a plane of symmetry, is used for a line of cells of the panel of Figure 12 A, and is centered on a transparent electrode line 101 of this panel;
• each extraction element 30 c has a plane of symmetry, is used for a column of cells of the panel of Figure 13 A, and is centered on an opaque electrode column 104 of this panel;
• FIG. 14 B each extraction element 30 P has an axis of symmetry centered on a cell of the panel at the intersection of a transparent line electrode 101 and an opaque column electrode 104 of the panel of FIG. 14 A, and basically serves for this cell.
• FIGS. 15 and 16 represent two variants of this embodiment, respectively in the case of an extraction layer 300 formed of reflectors 30 and in the case of an extraction layer 200 formed of microlenses 20.
• the advantage of using one-piece extraction layers 200, 300 with this type of substrate 100 "and that they provide very good sealing and very good protection of the panel cells which would be insufficiently protected from the water and oxygen by the substrate alone because of its fibrous structure which makes it permeable to water and oxygen; the organic materials of the electroluminescent layer 103 are in fact reputed to degrade rapidly under the action of water or oxygen.
• the extraction layer when it is in one piece, can advantageously serve as an encapsulation layer to significantly improve the protection of the cells against ambient oxygen or water; this advantage is particularly notable in the case of "upward emission" panels, that the extraction elements belong to the first and / or to the second family of embodiments.
• the invention has been described with reference to organic electroluminescent panels without barriers; it also applies to panels with barriers like those of Figures 1 and 3 previously described; in the case of "upward" emission panels, the height of the barriers, generally less than 10 ⁇ m, is not a problem for the application of light extraction elements with reflectors, given the curvature of the reflectors which keeps you away from barriers.
• the light extraction means are adapted to also serve to reduce the opening of the light-emitting conoscope of the panel so as to limit it to the area of the space of the front of the panel which is specially intended for observers of the images to be viewed; the geometry of the output interfaces 23, 33 of extraction elements and / or that of their reflecting surfaces 32 are adapted in a manner known per se to obtain this concentration effect.
• each extraction element provides an outlet opening L s much greater than the emission opening L E of the corresponding cell; the L S / L E ratio is preferably of the order of 4 in the absence of a concentration effect and greater than 4 in the presence of a collimation effect; thanks to the invention, the actual emission surface of the electroluminescent layer can be reduced very significantly at the level of each cell without losing overall light flux at the level of the panel; in fact, the decrease in actual emission surface area at the level of each cell is compensated by the increase in the rate of light extraction.
• the reduction in actual emission area at the level of each cell is particularly advantageous in the case of active matrix panels; in fact, in this type of panel, a certain number of electronic components necessary for driving the cells are etched and inserted into the substrate of the panel, at the level of each cell; however, these components can be bulky and lead to limiting the actual emission surface at the level of each cell; this limitation is no longer a problem when using light extraction means according to the invention.
• FIG. 17 illustrates three adjacent cells 10 R , 10 G , 10 B of an active matrix electroluminescent panel each comprising an electrode of the lower layer connected to a memory component 304, and the single electrode of the upper layer (not shown) formed here of a full transparent or semi-transparent conductive layer; whereas the electrodes of the lower layer must be separated from each other, one can on the contrary be satisfied with a single electrode for the upper layer; the emissive surface of each cell is here defined by the overlap area of the electrode of the lower layer with the single electrode of the upper layer, and not, as in the previously described cases of so-called "passive" matrices, by the crossing between an electrode of the upper layer and an electrode of the lower layer; the surface of the electrode of the lower layer of each cell of the active matrix panel can be advantageously chosen so as to correspond to that of the input interface of the extraction elements according to the invention.
• the invention is particularly advantageous in the case where the two-dimensional matrix of cells is produced by deposition methods with masking or by ink jet printing, in particular the light-emitting layer and the upper layer of electrodes; in fact, as it is possible, thanks to the invention, to decrease the emitting surface of the cells, it is possible to increase the distance separating the electrodes and therefore the width of the patterns of the masks used for the deposition of the different layers or sublayers of the sign ; such masks with larger patterns are much easier to position; therefore, the invention is particularly advantageous in the case of barrier-free panels for the manufacture of which masking methods or inkjet printing methods are generally used.
• the invention also applies to the case of electroluminescent panels whose cells are provided with photoluminescent converter elements, as described for example in the document US51216214; in such panels, the electroluminescent layers of all the cells emit in the same color, for example blue; in red and green cells, there is, above the electroluminescent layer, a photoluminescent element emitting respectively in red and green, under excitation by blue; according to a variant, an optical filtering layer can be added, in particular for blue.

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• Engineering & Computer Science (AREA)
• Theoretical Computer Science (AREA)
• Electroluminescent Light Sources (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

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• 2002
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