EP1993326A1 - Particle with an electro-luminescent element containing nano structures - Google Patents

Abstract

The thick film electroluminescent element (1) is based on zinc sulfide, and has a transparent electrode (3), an electrical luminescent layer (4), a dielectric layer (7) and a back electrode (9). Nano-structures (11) and another dielectric layer (8) are provided. The nanostructures include single-wall carbon nanotubes, multi-wall carbon nanotubes, nanohorns, nanodisks, nanocones and metallic nanowires. Independent claims are also included for the following: (1) a method for manufacturing a thick film electroluminescent element (2) application of thick film electroluminescent element.

Description

The present invention relates to a particle with nanostructures containing electroluminescent element, a method for producing an electroluminescent element according to the invention and the use of an electroluminescent element according to the invention as a decorative element and / or lighting element indoors or for outdoor use, preferably on the outer facades of buildings, in or on home furnishings, in or on land, air or water vehicles or in the advertising industry,

Electroluminescence (hereinafter abbreviated to EL) is the direct luminescence excitation of luminescent pigments or luminophores by an alternating electric field.

Electroluminescent technology has recently become increasingly important. It allows the realization of almost any size, glare-free and shadow-free, homogeneous lighting surfaces. Power consumption and depth (on the order of one millimeter and below) are extremely low. In addition to the backlighting of liquid crystal displays, the typical application involves the backlighting of transparent films which are provided with captions and / or image motifs. Thus, transparent electroluminescent devices, e.g. Electroluminescent phosphor plates based on glass or transparent plastic, e.g. can serve as information carriers, advertising transparencies or for decorative purposes, known from the prior art.

EL elements are often produced by screen printing. For this purpose, a substrate can first be coated with a transparent electrode (preferably by sputtering) onto which a light-emitting layer (EL layer) is applied. is applied. Between the first, transparent electrode and the EL layer, a dielectric layer may be provided. This is followed by a dielectric layer, eg of barium titanate, which has a very high dielectric constant, and then a second electrode, which need not be transparent. It consists of a highly electrically conductive metal, such as silver.

EP-A2-1 434 470 describes a thin film electroluminescent element having a substrate and deposited on the substrate and having in this order an ITO electrode, a first dielectric layer, an electroluminescent layer, a second dielectric layer, and a back electrode. This electroluminescent device, which is formed by chemical vapor deposition, has a fully formed, d, h, closed inorganic electroluminescent layer. In this thin-film electroluminescent element, a separate layer comprising carbon nanotubes (CNT) is formed. contains as the field uses reinforcing layer.

Electroluminescence elements (EL elements for short) based on the so-called thick-film technology with inorganic luminescent pigments or luminophores and AC voltage excitation have also largely become established. Compared to the example in the EP-A2-1 434 470 cited thin-film EL elements are thick-film EL elements less expensive and thus less expensive to manufacture,

The luminescent pigments or luminophores which are used in these EL elements are embedded in a transparent, organic or ceramic binder. Starting materials are usually zinc sulfides which, depending on doping or co-doping and preparation process, produce different, relatively narrow-band emission spectra. The reason for the use of zinc sulfides in the EL layers is, on the one hand, the relatively high emission brightness of the available zinc sulfide EL pigments. The focus of the spectrum determines the respective color of the emitted light, the emission color of an EL element can be adapted by a variety of measures to the desired color impression, these include the doping and co-doping of the luminous pigments, the mixture of two or more EL pigments, the addition of one or more organic and / or inorganic color-converting and / or bif filtering pigments, the coating of the EL pigment with organic and / or inorganic color-converting and / or bif filtering substances, the incorporation of dyes into the polymer matrix in which the luminescent pigments are dispersed, and the incorporation of a color-converting and / or bif filtering layer or film in the structure of the EL element.

The exciting AC voltage field usually has a frequency of a few hundred hertz, wherein the effective value of the operating voltage is often in a range of about 50 to 150 volts. By increasing the voltage can usually achieve a higher luminance, which usually in one area from about 50 to about 200 candelas per square meter. Increasing the frequency usually causes a color shift towards lower wavelengths, but both parameters have to be tuned to achieve a desired illumination effect,

The prior art EL devices based on thick-film technology (also referred to as thick-film electroluminescent elements or thick-film EL element hereinafter) usually use zinc sulfide EL pigments and are prepared according to the prior art by using in the EL light-emitting structures electrodes are applied to the EL layer or corresponding dielectric layers by screen printing or other printing techniques or by PVD method. Due to the different size of zinc sulfide particles with a d ₅₀ value of generally 20 to 30 μm and a corresponding pigment size distribution and thus a relatively thick EL layer in the range of 20 to 50 μm, the EL layers have unevenness z, B, due to different sized EL pigments, agglomerated EL pigments and / or superposition of two or more EL pigments. Due to this relatively uneven EL layer, a good dielectric layer (insulation layer) is required. These insulating layers are generally produced by screen printing processes, wherein the screen printing paste is applied with a doctor blade through a sieve on the surface to be coated, this procedure can lead to an inclusion of air bubbles (so-called "microbubbles"), which then in The insulating effects of the corresponding layers are considerably reduced when screen printing layers are used, these are therefore often duplicated, since these are the smallest air or gas bubbles, especially in the screen printing process. so-called "microbubbles", can not always be avoided and the necessary AC voltage of usually 100 to 200 volts at frequencies from the mains frequency of 50 Hz to 800 Hz and far beyond a high demand on the major impact strength means. Thus, the known from the prior art thick-film EL elements to the disadvantage of not optimally formed dielectric layers. In particular, the layer thickness of the insulating layers is limited to thin layers.

In addition, there is the disadvantage that the known from the prior art electroluminescent elements are poorly three-dimensionally deformable, since the electrode materials tear easily. In individual cases, this can lead to a significant deterioration of the surface conductivity.

Another non-negligible disadvantage of the prior art electroluminescent elements is that generally quite high excitation voltages are required to achieve some emission brightness and that, in general, the Decrease of the initial brightness of EL elements to half the value, the so-called half-life, with a few 100 hours up to about 2,500 hours too fast going on and such EL elements of the prior art for high-quality lighting requirements with over 2,000 hours with a stable Emission brightness and a stable emission color under normal environmental conditions, especially at high humidity and high ambient temperature up to 80 ° C, are not sufficiently stable.

Thus, it is an object of the present invention to provide a thick-film electroluminescent element based on zinc sulfide which preferably does not have the aforementioned disadvantages,

In particular, the thick-film electroluminescent element should be deformable in three dimensions, without causing cracking in the electrodes. In addition, the thick-film electroluminescent element should preferably have an insulation layer with a high dielectric constant, so that the insulation layer can be made relatively thick overall. Furthermore, the EL element should preferably require moderate excitation voltages in order to achieve a certain emission brightness,

This object is achieved by a thick film electroluminescent element based on zinc sulfide, which comprises a first transparent electrode (1), at least one electroluminescent layer, at least one first dielectric layer and at least one second back electrode.

The zinc sulfide based thick film electroluminescent element according to the invention is characterized in that it comprises particles with nanostructures,

In the context of the present invention, the term "particles having nanostructures" is understood to mean nanoscale material structures which are selected from the group consisting of single-wall carbon nanotubes (SWCNTs), multi-wall carbon nanotubes (MWCNTs), Nanohorns, nanodisks, nanocones (d, h, cone-shaped structures), metallic nanowires, and combinations of the aforementioned particles. Corresponding particles with carbon-based nanostructures can be selected, for example, from carbon nanotubes (single-shell and multi-shell), carbon nanofibers (herringbone, leaflet, carbon nanotubes are also internationally referred to as carbon nanotubes, (single-walled and multi-walled), carbon nonionic fibers as carbon nanofibers (herringbone, platelet, screw type),

With regard to metallic nanowires is on the WO 2007/022226 A2 The disclosure of which is incorporated by reference into the present invention with respect to the nanowires disclosed therein WO 2007/022226 A2 described electrically highly conductive and largely transparent silver nanowires are particularly suitable for the present invention,

According to the invention, it is thus provided that the particles with nanostructures are used in the thick-film electroluminescent element according to the invention, whereby the aforementioned objects can be achieved in a surprising manner by the targeted use of the particles with nanostructures in certain layers of the EL element.

In a first embodiment of the present invention, the nanostructured particles are used in a dielectric layer of the thick-film electroluminescent element of the present invention. These insulating layers are generally produced by screen-printing methods, with the screen-printing paste being applied by a squeegee to the surface to be coated. By using correspondingly small amounts of particles with nanostructures in the dielectric layer, it is achieved that the percolation threshold value (= Percolation) of the particles, so the electrical conductivity due to direct electrical contacts of the individual particles added, is not achieved, and it so no ohmic conductivity comes. Thus, the dielectric constant of the dielectric layer is kept high and the insulating effect is pronounced. Moreover, it is possible to make the corresponding dielectric layers thicker than would be possible without the addition of particles with nanostructures. If more than one dielectric layer is used in the EL element according to the invention, the particles with nanostructures may or may only be in one of the dielectric layers be contained in all, for example in two dielectric layers.

In a second embodiment of the present invention, the particles with nanostructures used in accordance with the invention are contained in at least one of the electrode layers, ie in the transparent electrode or the back electrode or in both electrodes. Hereby it is achieved that the resulting EL elements have a significantly improved deformability Due to the pronounced aspect ratio of the particles with nanostructures, the percolation is also increased in the EL layer, which leads to the fact that in a deformation of the EL layers, the conductivity of the individual electrodes is maintained, Overall, there is an improvement in the electrical Surface conductivity of the electrodes,

In a third embodiment of the present invention, the nanostructured particles to be used in the present invention are contained in the EL layer. As a result, a local electrical field increase is achieved in the EL layer and thus locally the excitation field strength of the EL pigments of the EL layer is increased. As a consequence, a reduction of the excitation voltage at the same emission brightness is possible,

In a fourth embodiment of the present invention, the particles are used with nanostructures in at least one separate layer which in particular between the dielectric layer and the EL layer, between two dielectric layers (if two dielectric layers are used) and / or between the transparent front side electrode and the EL layer is arranged. The separate layer provided in this embodiment, comprising particles with nanostructures, is also referred to in the context of the present invention as a "floating electrode layer". Within the scope of this fourth embodiment of the present invention, it is also possible that a plurality of floating electrode layers containing nanostructured particles are present at different positions in the EL element. The floating electrode is a conductive layer or, a layer of high ε, which is ohms connected to no potential, due to the use of corresponding floating electrode layers a more uniform EL emission is effected, ie the overall efficiency of the EL system is increased, this results the possibility of a reduction in the voltage at the same emission brightness or an increase in the emission brightness at the same supply voltage.

1. (1) in einer Elektrodenschicht und einer dielektrischen Schicht;
2. (2) in einer Elektrodenschicht und einer EL-Schicht;
3. (3) in einer Elektrodenschicht und einer floatenden Elektrodenschicht;
4. (4) in einer dielektrischen Schicht und einer EL-Schicht;
5. (5) in einer dielektrischen Schicht und einer floatenden Elektrodenschicht;
6. (6) in einer EL-Schicht und einer floatenden Elektrodenschicht;
7. (7) in einer Elektrodenschicht, einer dielektrischen Schicht und einer EL-Schicht;
8. (8) in einer Elektrodenschicht, einer dielektrischen Schicht und einer floatenden Elektrodenschicht;
9. (9) in einer dielektrischen Schicht, einer EL-Schicht und einer floatenden Elektrodenschicht; und
10. (10) in einer Elektrodenschicht, einer dielektrischen Schicht, einer EL-Schicht und einer floatenden Elektrodenschicht, wobei

In a fifth embodiment of the present invention, the particles may be combined with nanostructures contained in the different layers of the EL element, in particular, particles with nanostructures may simultaneously

1. (1) in an electrode layer and a dielectric layer;
2. (2) in an electrode layer and an EL layer;
3. (3) in an electrode layer and a floating electrode layer;
4. (4) in a dielectric layer and an EL layer;
5. (5) in a dielectric layer and a floating electrode layer;
6. (6) in an EL layer and a floating electrode layer;
7. (7) in an electrode layer, a dielectric layer and an EL layer;
8. (8) in an electrode layer, a dielectric layer and a floating electrode layer;
9. (9) in a dielectric layer, an EL layer and a floating electrode layer; and
10. (10) in an electrode layer, a dielectric layer, an EL layer and a floating electrode layer, wherein

the term in a layer according to the invention is also understood to mean that the particles with nanostructures can also be contained in two or more of these layers, if the EL element according to the invention comprises several of these layers,

In the present invention, the nanostructured particles in the respective layers of the EL element may be homogeneously dispersed or randomly oriented or directed.

In addition, in combination with the particles having nanostructures in the respective layers of the thick-film electroluminescent element spherical particles, for example, spherical particles with nanostructures such as fullerenes, or ITO (indium tin oxide) particles and / or agglomerates or Aggregates of such spherical nanoparticles with dimensions in the submicron range can be used. The spherical particles in this case have a diameter of generally 1 to 50 nm, preferably 2 to 30 nm, in particular 3 to 15 nm. The spherical particles, irrespective of the diameter, preferably have a length of generally 0.01 to 100 mm, preferably 0.5 to 50 mm, in particular 0.1 to 10 mm. The spherical particles are preferably ITO (indium -Tin-oxides) particles or, generally, electrically conductive metallic or metal oxide or ferroelectric (perovskite) particles,

In a further embodiment of the present invention, so-called single-walled carbon nano-tubes (SWCNTs) or multi-walled carbon nano-tubes (MWCNTs) are used as particles with nanostructures. SWCNTs have the advantage that they are more transparent, for example compared to MWCNTs or other nanostructured particles. However, SWCNTs have a disadvantage in that these particles are relatively expensive. The use of SWCNTs in particular even in isolation, d, h, without the simultaneous use of MWCNTs, is particularly preferred when the corresponding particles are used with nanostructures in the transparent electrode of the front or in floating electrode layers, which adjoin the transparent electrode of the front, since the SWCNT have a higher transparency compared to MWCNT or the other particles with nanostructures, so that the EL emission of the resulting EL element is not reduced.

In the context of the present invention, the term "single-walled carbon nanotubes" (SWCNTs) encompasses various variants of single wall carbon nanotubes, which may also include nanofibers. In the case of single-bulb carbonorbones Nanotubes are essentially cylindrical carbon nanotubes with a diameter of a few nanometers. The preparation of these single-walled carbon nanotubes is known to the person skilled in the art and appropriate prior art methods can be used. These include, for example, the catalytic chemical vapor deposition (CCVD),

These methods often yield fractions that differ in diameter, length, chirality, and electronic properties of SWCNTs. They occur in bundles and are often mixed with one part of amorphous carbon. The SWCNTs are separated from these fractions.

The hitherto known separation methods for SWCNT are based on electron transfer effects on metallic diazonium salts treated SWCNT, on dielectrophoresis, on a particular chemical affinity of semiconducting carbon nonotubes to octadecylamines and on carbon nanotubes, which were coated with single-stranded DNA. The selectivity of these methods can be further improved by intensive centrifugation of pretreated dispersions and application of ion exchange chromatography. In the context of the present invention, it is preferred to use fractionally pure single-walled carbon nanotubes, ie

Fractions of single-walled carbon nanotubes which differ in a parameter selected from the group consisting of diameter, length, chirality, and electronic properties, by at most 50%, more preferably at most 40%, especially at most 30 %, especially not more than 20%, especially not more than 10%.

The SWCNTs used according to the invention are generally known and commercially available. The SWCNTs preferably have an outer diameter between 1 nm and 50 nm, preferably between 3 nm and 25 nm, particularly preferably between 5 nm and 15 nm, and a length between 1 μm and 100 μm, preferably between 1 μm and 50 μm, more preferably between 1 μm and 10 μm, SWCNTs can preferably be homogeneously mixed as pure substance or masterbatch containing in thermoplastics with binders which are used in the respective layer compositions, single-walled carbon nanotubes (SWCNTs) are particularly preferred for the purpose of the present invention because they are thinner and have higher conductivities, whereby the desired effect can be achieved even with less use. At the same time, they are more transparent than other nanostructured particles.

If SWCNTs or MWCNTs or combinations of SWCNTs and MWCNTs are used then the Apsct ratio of the respective particles, d, h, the length to diameter ratio of the respective nanotubes, is generally more than 1: 100, preferably more than 1: 200, more preferably more than 1: 1000. Particles with nanostructures having a longer length are advantageous in that microcracks can be avoided.

Due to the use according to the invention of the particles having nanostructures, in particular in the dielectric layer, it is preferred that the particles having nanostructures have a high dielectric constant or an electrical conductivity. The dielectric constant of the particles with nanostructures should be in the Generally at least 30, preferably at least 50, more preferably at least 100, or infinite,

Moreover, it is preferred to use particles with nanostructures in the insulation or dielectric layers and / or EL layers which have an organic or inorganic insulating layer, which increases the insulation in the individual dielectric layers,

If the nanostructured particles comprise an inorganic insulating layer, then this may generally be formed from an oxide and / or nitridic layer.

When the nanostructured particles in the EL element of the present invention are contained in the EL layer and / or the dielectric layer, their amount in the layer is generally of a magnitude such that the percolation limit is not reached, that is, the electric field Therefore, it is further preferred that the particles having nanostructures in the EL layer or the dielectric layer have a filling percentage of generally less than 2% by weight, preferably less than 1% by weight, more preferably less than 0.5% by weight, in the respective layers, each based on the weight of the layers.

If the particles with nanostructures are present in the electrode layer of the transparent front side and / or the back side, their content is generally 0.1 to 10% by weight, preferably 0.2 to 5% by weight, particularly preferably 0, 3 to 2% by weight in the respective layers, in each case based on the weight of the layers,

When the particles having nanostructures are contained in the floated electrode layer, their content is generally 0.1 to 10% by weight, preferably 0.2 to 5% by weight, in particular from 0.3 to 3% by weight, in each case based on the weight of the layer,

Electroluminescent pigments are contained in the EL layer of the EL element according to the invention. These can be assigned in a preferred manner with the particles with nanostructures in the sense of a non-contiguous hybridization. Hybridization is understood to mean that corresponding nanoparticles are attached to the surface of EL pigments.

Moreover, in the present invention, in the case where the EL element of the present invention comprises a layer comprising nanotube-like nanostructured particles sandwiched between the front transparent electrode and the electroluminescent layer as the floating electrode, the EL Pigments due to the manufacturing process due to this floating layer decrease and the floating layer increases the electric field strength locally and thus increase the EL emission or the supply voltage can be reduced, In this case, preferably SWCNTs are used due to the transparency as particles with nanostructures.

Further, in the present invention, in the case where the EL element of the present invention is provided with a layer comprising particles having nanostructures between the electroluminescence layer and the first insulating layer as a floating electrode, the EL pigments are provided through the EL element Manufacturing process due to this floating layer decrease and the floating layer increases the electric field strength locally and thus increase the EL emission or the supply voltage can be reduced.

The following describes the general structure of suitable EL elements in which particles with nanostructures can be contained according to the manner described above.

electrodes

The EL element according to the invention has a first at least partially transparent electrode and a second return electrode.

For the purposes of the present application, the term "at least partially transparent" means an electrode which is constructed from a material which has a transmission of generally more than 60%, preferably more than 70%, particularly preferably more than 80%, specifically more than 90%.

The return electrode does not necessarily have to be transparent.

Suitable electrical conductive materials for the electrodes are known per se to those skilled in the art. In principle, several types of electrodes are suitable for the production of thick-film EL elements with AC excitation. On the one hand, these are sputtered or vapor deposited indium-tin-oxide electrodes (indium-tin-oxides, ITO) in vacuum on plastic films. They are very thin (some 100 Å) and offer the advantage of high transparency with a relatively low surface resistance (about 60 to 600 Ω).

Furthermore, printing pastes with ITO or ATO (antimony tin oxides, antimony tin oxide) or intrinsically conductive transparent polymer pastes can be used, from which surface electrodes are produced by screen printing, With a thickness of about 5 to 20 microns provide such electrodes only lower transparency with high sheet resistance (up to 50 kΩ), they can be applied in virtually any pattern, even on structured surfaces. Furthermore, they offer a relatively good laminatability, even non-ITO screen printing layers (the term "non-ITO" means all Non-indium-tin-oxide (ITO) screen-printed layers, that is, intrinsically conductive polymeric layers having usually nanoscale electrically conductive pigments, for example DuPont's ATO screen printing pastes designated 7162E or 7164, intrinsically conductive polymer systems such as Orgacon ^® system from Agfa, the Baytron ^® poly (3,4-ethylenedioxythiophene) system from HC Starck GmbH, the system of Ormecon, conductive coating or ink systems from Panipol Oy referred to as organic metal (PEDT-Conductive Polymer polyethylenedioxythiophene) and optionally (with highly flexible binding agents, for example on the basis of PU (polyurethane) is preferably PMMA (Polymethylmethocrylat), PVA (polyvinyl alcohol), modified polyaniline can be used as the material of at least partially transparent electrode of the electroluminescent element Baytron ^® poly 3,4-ethylenedioxythiophene) system from HC Starck GmbH used, examples of electrically conductive polymer films are polyanilines, polythiophenes, polyacetylenes, polypyrroles ( Handbook of Conducting Polymers, 1986 ) with and without metal oxide filling,

In addition, tin oxide (NESA) pastes are also conceivable as corresponding electrode material.

The electrically conductive materials described above may also be applied to a substrate. For example, transparent glasses and thermoplastic films are suitable as carrier material. Corresponding carrier materials are described in more detail below. In the context of the present invention, one or two carrier substrates can be used

These electrode materials can be applied, for example, by means of screen printing, rakein, spraying, brushing onto corresponding carrier materials (substrates), preferably subsequently drying at low temperatures of, for example, 80 to 120 ° C.,

In a preferred embodiment, the application of the electrically conductive coating by means of vacuum or pyrolytic,

Particularly preferably, the electrically conductive coating is a vacuum or pyrolytically produced metallic or metal oxide thin and substantially transparent layer, which preferably has a sheet resistance of 5 mΩ to 3000 Ω / square, more preferably a sheet resistance of 0.1 to 1000 Ω / square, most preferably 5 to 30 Ω / square, and in another preferred embodiment has a daylight transmittance of at least greater than 60% (> 60 to 100%) and in particular greater than 76% (> 76 to 100%),

In addition, electrically conductive glass can be used as an electrode,

A particular preferred type of electrically conductive and highly transparent glass, in particular float glass, are pyrolytically produced layers which have a high surface hardness and whose electrical surface resistance can be adjusted in a very wide range, generally from a few milliohms to 3,000 Ω / square.

Such pyrolytically coated glasses can be well deformed and have a good scratch resistance, in particular scratches do not lead to an electrical interruption of the electrically conductive surface layer, but only to a mostly slight increase in sheet resistance,

Furthermore, pyrolytically produced conductive surface layers are so strongly diffused into the surface by the temperature treatment and anchored in the surface, that in a subsequent application of material an extremely high adhesion to the glass substrate is given, which is also very advantageous for the present invention. In addition, such coatings have a good homogeneity, ie a low scattering of the surface resistance value over large surfaces. This feature also provides an advantage to the present invention.

Electrically conductive and highly transparent thin layers can be produced on a glass substrate, which is preferably used according to the invention, much more efficiently and cost-effectively than on polymeric substrates such as PET or PMMA or PC. The surface electrical resistance is on average 10 times better on glass coatings than on one polymeric film of comparable transparency, eg 3 to 10 ohms / square for glass layers compared to 30 to 100 ohms / square on PET films,

The back electrode is - as in the case of the at least partially transparent electrode - a planar electrode which, however, need not be transparent or at least partially transparent. This electrode is generally constructed of electrically conductive materials based on inorganic or organic substances, for example metals such as Silver, suitable electrodes are furthermore in particular polymeric electrically conductive coatings. The coatings already mentioned above with respect to the at least partially transparent electrode can be used. In addition, those polymeric electrically conductive coatings known to those skilled in the art are not at least partially transparent.

Suitable materials of the back electrode are thus preferably selected from the group consisting of metals such as silver, carbon, ITO screen printing layers, ATO screen printing layers, non-ITO screen printing layers, ie intrinsically conductive polymeric systems with usually nanoscale electrically conductive pigments, for example ATO dyes. screen printing pastes with the designation 7162E or 7164 from DuPont, intrinsically conductive polymer systems such as Orgacon ^® system from Agfa, the Baytron ^® poly (3,4-ethylenedioxythiophene) system from H, C Starck GmbH, which (as an organic metal PEDT conductive polymer polyethylenedioxythiophene) system of Ormecon, conductive coating and printing ink systems of Panipol Oy and optionally with highly flexible binders, for example based on PU (polyurethanes), PMMA (polymethylmethocrylot), PVA (polyvinyl alcohol), modified polyaniline, the materials mentioned above to improve the electricity conductivity with Metals such as silver or carbon can be added and / or supplemented with a layer of these materials,

Conductor tracks, connections of the electrodes

For large-area light elements with a light capacitor structure, the surface conductivity for a uniform luminance plays a significant role. Frequently, so-called bus bars are used in large-area lighting elements, in particular in semiconducting LEP or OLED systems, in which relatively large currents flow. In this way, for example, a large area is divided into four small areas, Thus, the voltage drop in the central region of a luminous area is substantially reduced and the uniformity of the luminance or the decrease in brightness in the Reduced center of a light field.

In a zinksulfidischen particulate EL field used in one embodiment of the invention generally greater than 100 volts to over 200 volts AC are applied, and it flow when using a good dielectric or good insulation very low currents. Therefore, in the inventive ZnS thick-film AC-EL element, the problem of current load is much lower than in semiconducting LEP or OLED systems, so that the use of bus bars is not essential, but large-scale lighting elements without the use of bus bars can be provided.

The electrical connections can be made, for example, using electrically conductive and stovable pastes with tin, zinc, silver, palladium, aluminum and other suitable conductive metals or combinations and mixtures or alloys thereof.

In this case, the electrically conductive contact strips are generally applied to the electrically conductive and at least partially transparent thin coatings by means of screen printing, brush application, ink jet, doctor blade, roller, by spraying or by Dispensierauftrag or comparable application methods known in the art and then generally in an oven thermally treated, so that usually attached laterally along a substrate edge strips can be contacted by soldering, terminals or plug electrically conductive.

As long as only low electrical power needs to be applied to electrically conductive coatings, spring contacts or carbon-filled rubber elements or so-called zebra rubber strips are sufficient,

As Leitkleberposten Leitkleberposten based on silver, palladium, copper or gold filled polymer adhesive are preferably used. It is also possible to apply self-adhesive, electrically conductive strips, for example, of tinned copper foil with an adhesive which is electrically conductive in the z-direction, by means of pressing;

The adhesive layer is generally uniformly pressed with a surface pressure of some N / cm ² , and depending on the design, values of 0.013 ohm / cm ^{2 are obtained} (eg Conductive Copper Foil Tape VE 1691 from D & M International, A-8451 Heimschuh). or 0.005 ohms (z, B, Type 1183 from 3M Electrical Products Division, Austin, Texas, USA; according to MIL-STD-200 Method 307 maintained at 5 psi / 3.4 N / cm ² measured over 1 sq.in. surface area) or 0.001 ohms (z, B. Type 1345 from 3M) or 0.003 ohms (z, B, Type 3202 from Holland Shielding Systems BV).

dielectric layer

The EI element according to the invention has at least one dielectric layer, which is provided between the back electrode and the EL layer.

Corresponding dielectric layers are known to the person skilled in the art. Corresponding layers often have high dielectric powders, such as barium titanate, which are preferably dispersed in fluorine-containing plastics or in cyan-based resins. Examples of particularly suitable particles are barium titanate particles in the range of preferably 1.0 to 2.0 μm. These can give a relative dielectric constant of up to 100 at a high degree of filling.

The dielectric layer has a thickness of generally 1 to 50 μm, preferably 2 to 40 μm, particularly preferably 5 to 25 μm, especially 8 to 15 μm / m,

In an embodiment, the EL element according to the invention may also additionally have a further dielectric layer, which are arranged one above the other and together improve the insulation effect or which is interrupted by a floating electrode layer. The use of a second dielectric layer may depend on the quality and pinhole freedom of the depend on the first dielectric layer.

EL layer

The EL element according to the invention comprises an EL layer.

The at least one electroluminescent (EL) layer is generally disposed between the first transparent electrode and a dielectric layer. In this case, the EL layer can be arranged directly after the dielectric layer or it can be If appropriate, one or more further layers are arranged between the dielectric layer and the EL layer. The EL layer is preferably arranged immediately after the dielectric layer.

The at least one electroluminescent EL layer may be arranged on the entire inner surface of the first partially transparent electrode or on one or more partial surfaces of the first at least partially transparent electrode. In the case that the light structure is arranged on a plurality of partial surfaces, the partial surfaces have Generally a distance of 0.5 to 10.0 mm, preferably 1 to 5 mm from each other.

The EL layer is generally composed of a binder matrix with EL pigments homogeneously dispersed therein. The binder matrix is generally chosen such that a good adhesion bond is provided on the electrode layer (or the dielectric layer applied thereon, if applicable) In this case, PVB or PU-based systems are used. In addition to the EL pigments, other additives may also be present in the binder matrix, such as color-converting organic and / or inorganic systems, color additives for a day and night light effect and / or reflective and / or or light-absorbing effect pigments such as aluminum flakes or glass flakes or mica platelets. In general, the proportion of EL pigments in the total mass of the EL layer (degree of filling) is from 20 to 75% by weight, preferably from 50 to 70% by weight,

The EL pigments used in the EL layer generally have a thickness of 1 to 50 μm, preferably 5 to 25 μm,

Preferably, the at least one EL layer is an AC thick film powder electroluminescent (AC-P-EL) light structure,

Thick-film AC-EL systems have been well-known since Destriau 1947 and are usually applied by screen printing on ITO-PET films, since zinc sulfide electroluminophores are used during operation and especially at higher temperatures and have a very severe degradation in a water vapor environment, microencapsulated EL phosphors (pigments) are commonly used today for long lasting thick film AC-EL lamp assemblies. However, it is also possible to use non-microencapsulated pigments in the EL element according to the invention, as further explained below.

For the purposes of the present invention, EL elements are thick-film EL systems which are operated by means of alternating voltage at normative 100 V and 400 Hertz and thus emit a so-called cold light of a few cd / m ² up to a few 100 cd / m ² , In such inorganic thick film AC EL elements, EL screen printing items are generally used.

Such EL screen-printing pastes are generally based on inorganic substances, suitable substances are, for example, high-purity ZnS, CdS, Zn _x Cd _1-x S compounds of groups II and IV of the Periodic Table of the Elements, with ZnS is particularly preferably used. The aforementioned substances may be doped or activated and optionally further co-activated. For example, copper and / or manganese are used for doping. The co-activation takes place, for example, with chlorine, bromine, iodine and aluminum. The content of alkali and rare earth metals is generally very low in the abovementioned substances, if these are present at all. Very particular preference is given to using ZnS, which is preferably doped or activated with copper and / or manganese and preferably with chlorine , Bromine, iodine and / or aluminum is co-activated.

Common EL emission colors are yellow, green, green-blue, blue-green and white, whereby the emission color white or red can be obtained by mixtures of suitable EL phosphors (pigments) or by Forbkonversion. The color conversion may generally be in the form of a converting layer and / or the addition of appropriate dyes and pigments in the polymeric binder of the screen inks or the polymeric matrix in which the EL pigments are incorporated take place.

In a further embodiment of the present invention, the screen printing matrix used for producing the EL layer are provided with translucent, color-filtering or color-converting dyes and / or pigments. In this way, an emission color white or a day-night light effect can be generated.

In a further embodiment, pigments are used in the EL layer which have an emission in the blue wavelength range from 420 to 480 nm and are provided with a color-converting microencapsulation. In this way, the color white can be emitted.

In one embodiment, as pigments in the EL layer AC-P-EL pigments are used which have an emission in the blue wavelength range of 420 to 480 nm. In addition, the AC-P-EL screen printing matrix preferably has wavelength-controlling inorganic fine particles based on europium (II) activated alkaline earth metal orthosilicate phosphors such as (Ba, Sr, Ca) ₂ SiO ₄ : Eu ²⁺ or YAG phosphors such as Y ₃ Al ₅ O ₁₂ : Ce ³⁺ or Tb ₃ Al ₅ O ₁₂ : Ce ³⁺ or Sr ₂ GaS ₄ : Eu ²⁺ or SrS: EU ²⁺ or (Y, Lu, Gd, Tb) ₃ (Al, Sc, Ga ) ₅ O ₁₂ : Ce ³⁺ or (Zn, Ca, Sr) (S, Se): Eu ²⁺ . In this way, a white emission can be achieved.

According to the prior art, the above-mentioned 'EL phosphor' pigments can be microencapsulated, The inorganic microencapsulation technology good half-lives can be achieved, for example, the EL screen printing system Luxprint ^® for EL the company E, I, du Pont de Nemours and Companies, organic micro-copying technologies and film-wrap laminates based on the various thermoplastic films are also suitable in principle, but have proven to be expensive and not significantly Lebensverlverlggernd.

Suitable zinc sulfide microencapsulated EL phosphors (pigments) are sold by Osram Sylvania, Inc. Towanda € under the trade name GlacierGLO Standard, High Brite and Long Life and the Durel Division of Rogers Corporation, under the trade names 1 PHS001 ^® High-Efficiency Green Encapsulated EL phosphor, 1 PHS002 ^® high-Efficiency Blue-Green EL Encapsulated phosphorus, 1 PHS003 ^® Long-Life Blue Encapsulated EL phosphor, 1 PHS004 ^® Long-Life Orange Encapsulated EL phosphor offered,

The average particle diameters of the microencapsulated pigments suitable in the EL layer are generally 15 to 60 μm, preferably 20 to 35 μm.

Non-microencapsulated fine-grained EL pigments, preferably having a long service life, can also be used in the EL layer of the EL element of the invention. Suitable non-microencapsulated fine-grained zinc sulfide EL phosphors are z, B, in US 6,248,261 and in WO 01/34723 disclosed. These preferably have a cubic crystal structure. The non-microencapsulated pigments preferably have average particle diameters of from 1 to 30 .mu.m, particularly preferably from 3 to 25 .mu.m, very particularly preferably from 5 to 20 .mu.m,

Specially non-microencapsulated EL pigments can be used with smaller pigment dimensions down to less than 10 microns, thereby the transparency of the glass element can be increased.

Thus, non-encapsulated pigments can be added to the screen printing inks suitable according to the present application, preferably taking into account the specific hygroscopic properties of the pigments, preferably the ZnS pigments. In this case, binders are generally used which, on the one hand, have good adhesion to so-called ITO layers (indium). ZinnOxid) or intrinsically conductive polymeric transparent layers, and further have good insulating effect, strengthen the dielectric and thus improve the dielectric strength at high electric field strengths and cause additionally have a good water vapor barrier in the cured state and additionally protect the phosphorus pigments and have a life-prolonging effect.

In one embodiment of the present invention, pigments which are not microencapsulated are used in the AC-P-EL luminescent layer.

The half-lives of the suitable pigments in the EL layer, ie the time in which the initial brightness of the EL element according to the invention has fallen to half, are generally at 100, 80 and 400 hertz 400 to a maximum of 5000 hours, but usually not more than 1000 to 3500 hours.

The brightness values (EL emission) are generally 1 to 200 cd / m ² , preferably 3 to 100 cd / m ² , and are particularly preferably in the range from 1 to 20 cd / m ² for large luminous areas.

However, it is also possible to use pigments with longer or shorter half-lives and higher or lower brightness values in the EL layer of the EL element according to the invention.

In a further embodiment of the present invention, the pigments present in the EL layer have such a small average particle diameter, or such a low degree of filling in the EL layer, or the individual EL layers are made geometrically so small, or the distance of individual EL layers is chosen so large, so that the EL element is designed as non-electrically activated light structure as at least partially transparent or a review is ensured, Suitable pigment particle diameter, filling levels, dimensions of the light elements and distances of the light elements are mentioned above.

substrates

The EL element according to the invention may have on one or both sides of the respective electrodes substrates, such as glasses, plastic films or the like.

In the case of the EL element according to the invention, it is preferred that at least the substrate, which is in contact with the transparent electrode, has a graphically translucent and opaque covering on the inside. An opaque covering design is understood to mean a large-area electroluminescent region which is characterized by a high-resolution graphic display Design is covered opaque and / or translucent, for example, in the sense of red - green - blue translucent designed for signal purposes.

Moreover, it is preferable that the substrate which is in contact with the transparent electrode is a foil which is cold-stretchable below Tg. This gives rise to the possibility of three-dimensionally deforming the resulting EL element,

Moreover, it is preferred that the substrate which is in contact with the back electrode is a foil which is also cold bendably deformable below Tg. This gives rise to the possibility of deforming the resulting EL element three-dimensionally.

Moreover, it is preferred that the EL element is three-dimensionally deformable and in particular is cold bendable deformable below Tg and thus obtains a precisely shaped three-dimensional shape.

The three-dimensionally deformed element can be formed in an injection mold on at least one side with a thermoplastic material,

Production of inventive EL elements

The above-mentioned pastes (screen printing pastes) are usually applied to transparent plastic films or glasses, which in turn have a substantially transparent electrically conductive coating and thereby represent the electrode for the visible side. Subsequently, the dielectric and the backside electrode are produced by printing technology and / or lamination technology.

However, a reverse manufacturing process is also possible, wherein the backside electrode is first prepared or the backside electrode is used in the form of a metallized film and the dielectric is applied to this electrode. Subsequently, the EL layer and subsequently the transparent and electrically conductive top electrode applied. The system obtained can then optionally be laminated with a transparent cover film and thus protected against water vapor or even against mechanical damage.

The EL layer is usually applied by printing by means of screen printing or dispenser application or inkjet application or by a doctor blade process or a roller coating process or a curtain coating process or a transfer process, preferably by screen printing. The EL layer is preferably applied to the surface of the electrode or to the insulation layer applied, if necessary, to the back electrode.

Another object of the present application is the use of an EL element according to the invention as a decorative element and / or lighting element indoors or for outdoor use, preferably on the outer facades of buildings, in or on furnishings, in or on land, air or water vehicles, in building facilities in the automotive industry or in the advertising industry,

The present invention is explained below with reference to figures. The figures represent preferred embodiments and are not intended to be limiting.

The FIGS. 1 to 7 schematically show possible different structures of the EL element according to the invention, each in a sectional design,

In the figures described below, the individual reference symbols have the following meanings:

LIST OF REFERENCE NUMBERS

1

Zinc Sulfide Thick Film AC Electroluminescent Element (EL Element)

2

Substrate / carrier material (top layer or overlay)

3

Transparent electrode (front side)

4

EL-thick film layer

5

EL Pigment:

6

polymer matrix

7

First dielectric layer:

8th

Second dielectric layer:

9

Return electrode:

10

Substrate / substrate (back electrode)

1 1

Particles with nanostructures

12

floating electrode

1 3

further floating electrode

14

SWCNTs in the transparent front side electrode

15

Particles with nanostructures in the first insulation layer

16

Particles with nanostructures in the second insulation layer

1 7

Particles with nanostructures in the back electrode layer

18

Particles with nanostructures in the range of EL pigments

19

SWCNT layer between transparent front electrode and EL layer

20

Particles with nanostructures in the immediate vicinity of the EL pigments

21

EL inverter connection: typically 100 to 200 volts, 1 00 to 2,000 Hz

22

EL emission

FIG. 1 (prior art):

FIG. 1 shows a schematic representation of an exemplary cross section through an EL element (1) with a substrate (2) on which a transparent front side electrode (3) is applied. On the side of the transparent electrode facing away from the substrate, an EL layer (4) with corresponding EL pigments (5) in a polymer matrix (6) is provided. In contact with the EL layer (4) is also located on the side facing away from the transparent electrode (3) side, a dielectric layer (7), to the Dielektrizitötsschicht the back electrode (9) and optionally another substrate (10) adjoins.

FIG. 2 (according to the invention):

FIG. 2 shows a schematic representation of an exemplary cross section through an EL element (1) with a substrate (2) on which a transparent electrode (3) is applied, on the side facing away from the substrate of the transparent electrode is an EL layer (4) provided with corresponding EL pigments (5) in a polymer matrix (6), in contact with the EL layer (4) is also on the side facing away from the transparent electrode (3) side two dielectric layers (7) and (8), The back electrode (9) and optionally a further substrate (10) adjoin the dielectric layer. Particles with nanostructures (11) are contained in the EL layer (4).

FIG. 3 (according to the invention):

FIG. 3 shows a schematic representation of an exemplary cross section through an inventive EL element (1) with a substrate (2) on which a transparent electrode (3) is applied, on the side facing away from the substrate of the transparent electrode an EL layer (4) provided with corresponding EL pigments (5) in a polymer matrix (6). In addition, in contact with the EL layer (4), on the side facing away from the transparent electrode (3) there is a layer (12) which comprises a flooting nanotube-like particle with nanostructures. This layer (12) is followed by two dielectric layers (7) and (8). The back electrode (9) and optionally a further substrate (10) adjoin the dielectric layer.

FIG. 4 (according to the invention):

FIG. 4 shows a schematic representation of an exemplary cross section through an inventive EL element (1) with a substrate (2), on which a transparent electrode (3) is applied. Single wall Corbon nano tubes (14) are contained in the transparent electrode. The side of the transparent electrode facing away from the substrate is provided with an EL layer (4) with corresponding EL pigments (5) in a polymer matrix (6) , Furthermore, particles with nanostructures (11) are still present in this EL layer. In addition, in contact with the EL layer (4) there is a layer (1 2) on the side facing away from the transparent electrode (3) which contains particles Includes nanostructures. Subsequent to the layer (12), two dielectric layers (7) and (8) follow, which are separated from each other by a layer (13) containing particles with nanostructures as the floating electrode. Particles with nanostructures are contained in both dielectric layers (7) and (8) (15, 16). The dielectric layer is followed by the back electrode (9), likewise containing particles with nanostructures (17), and a substrate (10).

FIG. 5 (according to the invention):

FIG. 5 shows a schematic representation of an exemplary cross section through an inventive EL element (1) with a substrate (2) on which a transparent electrode (3) is applied, which is the substrate side facing away from the transparent electrode an EL layer (4) provided with corresponding EL pigments (5) in a polymer matrix (6), in contact with the EL layer (4) is also located on the side facing away from the transparent electrode (2) two dielectric layers ( 7) and (8), the back electrode (9) and optionally another substrate (10) adjoin the dielectric layer. The EL layer (4) comprises ponds with nanostructures in the region of the EL pigments,

FIG. 6 (according to the invention):

FIG. 6 shows a schematic representation of an exemplary cross section through an inventive EL element (1) with a substrate (2) on which a transparent electrode (3) is applied, the side facing away from the substrate of the transparent electrode is first a layer (19), containing particles with nanostructures (here: SWCNT), and then an EL layer (4) provided with corresponding EL pigments (5) in a polymer matrix (6), in contact with the EL layer (4) is also on the dielectric electrode layer (3) facing away from two dielectric layers (7) and (8), to the dielectric layer is followed by the back electrode (9) and optionally another substrate (10), the EL layer (4) comprises nanotubeartige ponds in Range of EL pigments. The element shows an EL emission (22).

FIG. 7 (according to the invention):

FIG. 7 shows a schematic representation of an exemplary cross section through an inventive EL element (1) with a substrate (2), on which a transparent electrode (3) is applied. The side facing away from the substrate of the transparent electrode is first an EL layer (4) provided with corresponding EL pigments (5) in a polymer matrix (6), In contact with this EL layer (4) is also located on the transparent electrode (3) facing away from a floated electrode layer (20) containing particles with nanostructures, as well as two dielectric layers (7) and (8th). The back electrode (9) and optionally a further substrate (10) adjoin the dielectric layer. The element shows an EL emission (22), an EL inverter port (21) is provided.

Claims (28)

A thick-film electroluminescent element based on zinc sulfide, comprising a first transparent electrode, at least one electroluminescent layer, at least one dielectric layer and a second back electrode, characterized in that the thick-film electroluminescent element comprises nanostructured particles, 2. thick-film electroluminescent element according to claim 1, characterized in that the thick-film electroluminescent element additionally has a further dielectric layer. 3. thick-film electroluminescent element according to claim 1 or 2, characterized in that the thick-film electroluminescent element additionally has a first carrier substrate. 4. thick-film electroluminescent element according to claim 1 or 2, characterized in that the thick-film electroluminescent element additionally has a second carrier substrate, 6. thick-film electroluminescent element according to one of claims 1 to 5, characterized in that are selected as particles with nanostructures from the group consisting of single-wall carbon nanotubes (SWCNTs), multi-wall carbon Nano-tubes (MWCNTs), nanohorns, nanodisks, nanocones, metallic nanowires and combinations of the aforementioned particles. 7. thick-film electroluminescent element according to claim 6, characterized in that the particles are homogeneously dispersed with nanostructures or arbitrarily oriented or directed. A thick-film electroluminescent element according to any one of claims 1 to 7, characterized in that spherical particles are used in combination with the nanostructured particles in the thick-film electroluminescent element, 9. thick-film electroluminescent element according to claim 8, characterized in that the spherical particles have dimensions of 1 to 50 nm in diameter and / or 0.01 to 100 mm in length. 10. thick-film electroluminescent element according to one of claims 1 to 9, characterized in that are used as particles with nanostructures SWCNTs or MWCNTs or combinations of both types, each having an aspect ratio of at least 1: 100. 11. Thick film electroluminescent element according to one of claims 1 to 10, characterized in that the particles with nanostructures have a high dielectric constant of at least 30 or electrical conductivity, 12. Thick film electroluminescent element according to one of claims 1 to 1 1, characterized in that the particles are present with nanostructures in at least one of the electrode layers, the EL layers or the dielectric layer. 13. A thick-film electroluminescent element according to claim 12, characterized in that particles with nanostructures are present in the EL layer, The thick-film electroluminescent element according to claim 13, characterized in that the particles having nanostructures in the EL layer are contained at a filling percentage such that the percolation limit is not reached. A thick-film electroluminescent element according to claim 13 or 14, characterized in that the nanostructured particles are present in the EL layer at a fill percentage of less than 2% by weight. 16. Thick film electroluminescent element according to claim 15, characterized in that particles with nanostructures are present in the dielectric layer. A thick-film electroluminescent element according to claim 16, characterized in that the particles having nanostructures are contained in the dielectric layer with a filling percentage not reaching the percolation limit. A thick-film electroluminescent element according to claim 16 or 17, characterized in that the particles with nanostructures are present in the dielectric layer with a filling percentage of less than 2% by weight. 19. Thick film electroluminescent element according to claim 12, characterized in that particles with nanostructures are present in at least one of the electrode layers, The thick-film electroluminescent element according to any one of claims 1 to 19, characterized in that the thick-film electroluminescence element comprises a floating electrode layer containing nanostructured particles between the EL layer and the dielectric layer, 21. A thick-film electroluminescent element according to any one of claims 1 to 20, characterized in that the thick-film electroluminescent element comprises a floating electrode layer containing particles with nanostructures, between a first dielectric layer and a second dielectric layer particles with nanostructures, 22. A thick-film electroluminescent element according to any one of claims 1 to 21, characterized in that the thick-film electroluminescent element in the electroluminescent layer contains electroluminescent pigments, which are coated with the nanostructured particles in the sense of a non-contiguous hybridization, 23. A process for producing a thick-film electroluminescent element according to one of claims 1 to 22 by screen printing, dispensing or ink-jet printing of the individual layers, 24. A method for producing a thick-film electroluminescent element according to claim 23, characterized in that at least the substrate, which is associated with the transparent electrode, the inside is designed graphically translucent translucent and opaque covering. 25. A method for producing a thick-film electroluminescent element according to claim 23 or 24, characterized in that at least the substrate, which is associated with the transparent electrode, below Tg is cold stretchable deformable. 26. A method for producing a thick-film electroluminescent element according to any one of claims 23 to 25, characterized in that at least the substrate, which is associated with the return electrode, is cold bendable deformable below Tg, 27. A method for producing a thick-film electroluminescent element according to one of claims 23 to 26, characterized in that the EL element is three-dimensionally deformable and in particular cold-stretchable below Tg and thus obtains a precisely shaped three-dimensional shape, 28. A method for producing a thick-film electroluminescent element according to any one of claims 23 to 27, characterized in that a three-dimensionally deformed element is formed in an injection mold on at least one side with a thermoplastic plastic, 29. Use of a thick-film electroluminescent element according to any one of claims 1 to 22 or a thick-film electroluminescent element which is obtainable according to the method of claims 23 to 28, as a decorative element and / or lighting element indoors or for outdoor use, preferably at Exterior facades of buildings, in or on furnishings, in or on land, air or water vehicles, in building equipment, in the automotive industry or in the advertising industry.

Images