WO2012020009A1 - Lighting means which can in particular be thermoformed - Google Patents

Abstract

The invention relates to a lighting means having a front electrode and a rear electrode comprising an electrode system of at least two electrodes, said system comprising at least one areal first electrode, which can preferably be thermoformed, and at least one areal second electrode, which can preferably be thermoformed, wherein the first electrode has a first main section and the second electrode has a second main section, a plurality of secondary sections originate from the first main section and from the second main section, wherein the main sections and the secondary sections are composed of an electrically conductive material, characterized in that at least some of the secondary sections of the first main section and at least some of the secondary sections of the second main section are each arranged such that they are located between two secondary sections of the respective other main section, wherein a light layer which can be excited electrically is provided between the front electrode and the rear electrode.

Description

 tesa Societas Europaea

 Hamburg

Description In particular deep-drawable illuminant

The invention relates to a luminous means having a front electrode and a back electrode made of an electrode system comprising at least two electrodes, comprising at least one flat and preferably thermoformable first electrode and at least one planar and preferably thermoformable second electrode and the use of such a luminous means in electroluminescent license plates.

So far, electrodes have been used in many technical fields to either allow a current flow in a variety of materials or to build up an electric field in a variety of materials. For this purpose, at least two electrodes are connected to a voltage source. In the simplest case, these electrodes may consist of two simple metal wires.

Particularly demanding is the task of providing electrodes that are transparent and flat at the same time. So far, such flat and transparent electrodes are produced by thin layers of organic conductive polymers such as Polythiophen derivatives or inorganic conductive coatings such as ITO (indium tin oxide). All of these coatings known to those skilled in the art, due to their brittleness, have insufficient flexibility, a high price, a high resistance and are only available and processable together with a carrier material. In particular, the lack of chemical and thermal stability of these coatings represent a particularly severe limitation in their application. The insufficient resistance of conductive coatings such as ITO in combination with other organic materials containing residual monomers and / or residual solvents is well known to those skilled in the art. All these flat and transparent electrodes are not suitable for an application, the one due to their brittleness Embossing process or a deep-drawing process such as in the manufacture of license plates for motor vehicles. For example, DE 10 2006 045 514 A1 discloses a transparent and supported surface electrode made of a curved or wave-shaped lattice grid on a substrate for surface bonding to a rigid pane.

Conventional license plates for motor vehicles are made from a sheet metal blank, which is provided with a reflective layer and is embossed to allow the corresponding individualization by means of a combination of letters and / or numbers. After embossing, the sheet blanks are subjected to a hot roll dyeing process for coloring the embossed character and / or number combinations. Optionally, a transparent protective layer is applied to the finished signs. The disadvantage is that for good visibility of the letter and number combinations in the dark in the immediate vicinity of the license plate on the vehicle, a light source must be arranged, which illuminates the shield so that the incident light rays can be reflected. From DE 198 27 477 A1 a license plate for a motor vehicle is known, which as an active illumination at least in the region of the marking arranged, electrically activatable light-emitting foil arrangement provides that deposits the marking and / or the shield surface. The license plate proposed in DE 200 22 563 U further develops the electroluminescent foil arrangement. However, the electroluminescent film arrangements disclosed therein do not permit embossing of motifs or symbols, in particular letter and / or number combinations.

So-called electroluminescent lamps (EL lamps) consist of a lower electrode, a luminescent layer of matrix and luminous particles, a dielectric and an upper electrode. The individual layers are usually built successively screen-printed on each other. Commercially available pastes are used for printing. The known pastes have the disadvantage that the applied layer after printing and drying is extremely brittle and brittle and loses the bond strength at atmospheric moisture. In a deep-drawing process, as is necessary, for example, for the embossing of license plate numbers, the composite of the layers is therefore destroyed and the conventional electrodes or their conductive coatings break, resulting in non-luminous areas.

A deformable or embossable shield, in particular a license plate for motor vehicles with an electroluminescent structure, is known from DE 102 47 708 B4. There, the base body made of an electrically conductive material, such as aluminum, or has directly or indirectly on a further electrically conductive layer. The electrically conductive base body or its electrically conductive coating thus form a first electrode of a flat capacitor. On the electrically conductive base body or its electrically conductive coating, a layer with an electroluminescent pigmentation is applied. For this purpose, various pigments are suitable, for example based on doped ZnS, ZnSe, ZnS / CdS, which luminesce under the action of an AC electric field. The luminescence occurs only as long as the excitation by the AC field is present. The electroluminescent layer can be applied by various methods, for example, spraying, brushing or special screen printing methods. To build up the electric field, it is necessary that a preferably transparent electrically conductive layer is applied to the electroluminescent layer, which forms the second electrode of the flat capacitor. Information on the nature of the transparent electrically conductive layer are not made.

An embossable license plate comprising an electrically conductive plate having a coating comprising a pressure-sensitive adhesive filled with an electroluminescent filler at least partially covered by an electrically conductive transparent film, the plate and the electrically conductive transparent film being filled to produce electroluminescence Pressure-sensitive adhesive can serve as electrodes is known from WO 2010/037712 A1.

Under deep drawing or deep drawing is below in accordance with DIN 8584 Part 3 (Sep. 2003), Zugdruckumformen a sheet metal blank (also called foil, plate, board or board) in a one-sided open hollow body or a preferred Hollow body in such a smaller cross-section without intentional change in the sheet thickness or - here, for example, electrode thickness - understood.

The elongation at break (elongation at break) is a measure of the mechanical strength and deformability of materials. This material characteristic value indicates the permanent percentage change in length of a specimen (relative to its initial length) that it has at break due to mechanical overloading.

The tensile strength describes the resistance of a body against tensile forces (also tensile strength). The lower the effort, the better the material is suitable for deformability. This term is also used to define the maximum tensile stress as the force per unit of cross-sectional area (measured in Newton per square centimeter or Newton per square millimeter) that a body can withstand until fractured. The tensile strength is the maximum weight load during the tensile test, based on the carrier cross-section. This may be the wire cross-sectional area in the initial state. The tensile strength is related to a body of a material having a cross section of 1 mm ² . The disclosure content of DIN EN 6892-1 is referred to in its entirety and made the content of this document. Tensile strength or maximum force are according to DIN EN ISO 6892-1 according to point 3.9 and point 3.10.1. The measurement is carried out according to DIN EN ISO 6892-1 point 6.2-c (wire rod profiles smaller <4 mm), method A (test speed based on the expansion rate control according to point 10.3). The test methods are carried out at room temperature. DIN EN ISO 6892-1 for metallic materials replaces the previously valid DIN EN 10002-1.

The tensile strength is not only influenced by the material, but can also be influenced by its pretreatment and its shape. Thus, the greatest tensile strengths are achieved with engineering materials that have been carefully heat treated and are in the form of fine wires. An example of this is steel alloys, especially in the form of fine wires. For such wires, a tensile strength around 370 N / mm ² for steel (St 37) is known, and generally for wires tensile strengths between 100 and 2060 N / mm ² (Newton per square millimeter) are possible, preferably for stainless steels from 1373 to 2060 N. / mm ² . To determine the tensile strengths, in addition to DIN EN 6892-1, as explained above, the old DIN EN 1002, which was partially replaced by DIN EN 6892-1, and in addition to DIN EN ISO 527-1 / -2 / -3 for Plastics, partial replacement for DIN 53455/7, to DIN EN ISO 1924-2, DIN EN ISO 13934-1, DIN EN ISO 13934-2 (maximum tensile strength and maximum tensile yield strength of textile fabrics), DIN EN ISO 7500, DIN 29073-3 ( Maximum tensile strength and elongation of nonwovens) and ISO 5081 (maximum tensile strength and maximum tensile strength of textile fabrics). DIN EN 6892-1 concerns the test method for metal wires. For the determination of the tensile strength of textile fabrics DIN EN ISO 13934-1 is applicable, and in Chapters 8 to 10 and Annex A the experiments are explained in more detail. The disclosure content of the cited DIN EN standards is referred to in its entirety and made the subject of this document.

The tensile elastic modulus (modulus of elasticity, tensile modulus, coefficient of elasticity, Young's modulus) is a material characteristic value by means of which the relationship between stress and strain is described during the deformation of a material with linear elastic behavior. In the case of materials with non-linear-elastic behavior, the tensile elastic modulus in the present case is understood to mean the initial tensile elastic modulus at the onset of the tensile load. The amount of elastic modulus is greater, the more resistance a material opposes to its deformation. The stiffness of a concrete body made of this material also depends on the processing and on the geometry of the body.

Elongation at break and tensile elastic modulus and tensile strength for plastics are determined according to DIN EN ISO 527-3 at room temperature with a defined test specimen (type 5) for a strain rate of 300 mm / min. The disclosure content of DIN EN ISO 527-3 is referred to in its entirety and made part of the content of this document. DIN ISO 527-1 describes methods for determining the tensile properties of plastics and plastic composites. In order to determine the properties of the electrically conductive materials according to the invention, DIN EN ISO 6892-1 is therefore used for metallic materials and DIN EN ISO 527-3 for plastics.

The object of the invention is to provide a transparent, planar light source available, which has a high reliability and can be deep-drawn, in particular, without the risk that the lamp fails completely by the deep drawing process. This object is achieved by a light source, as laid down in the main claim. Advantageous embodiments of the luminous means are the subject of dependent claims. Furthermore, the invention comprises a license plate, which is manufactured using the light bulb.

Accordingly, the invention relates to a luminous means having a front electrode and a back electrode of an electrode system comprising at least two electrodes, comprising at least one flat and preferably thermoformable first electrode and at least one planar and preferably thermoformable second electrode, wherein the first electrode has a first main strand and the second Electrode having a second main strand, depart from the first main strand and the second main strand in each case a plurality of secondary strands, wherein the main strands and the secondary strands consist of an electrically conductive material.

 According to the invention, at least some of the secondary branches of the first main line and at least some of the secondary lines of the second main line are each arranged such that they are located between two secondary lines of the other main line. Between the front electrode and back electrode, an electrically excitable luminescent layer is present.

A specific sequence of layers is provided in the luminous means according to the invention. A layer sequence is in particular a spatial arrangement of individual layers which are arranged perpendicular to their main extension one above the other (stacked). These can each be in direct contact with each other without further layers between them. Alternatively, they can also be separated by further layers, in particular insulating or protective layers. In particular, a sheet-like extension of a system of uniform functionality is referred to as a layer whose dimensions are significantly smaller in one spatial direction than in the other two spatial directions which define the principal extent. Such a layer may be formed compact or perforated and consist of a single material or of different materials, such as the luminescent layer, the latter may in particular be the case if they contribute to the uniform functionality of this layer. A layer can have one over its entire Surface extent constant thickness or different thicknesses. In addition, of course, a layer may also have more than one functionality. According to an advantageous embodiment of the invention, the two main strands of the first and the second electrode are formed jet-shaped and aligned parallel to each other.

 In principle, the main strands can assume any desired shape of any curve, for example a regular shape can be present, such as jet-shaped, semicircular (see FIG. 2), sinusoidal, but any irregular curve can also be adjusted by the main strands. For example, depending on the case of use, the main strands can be present in a very specific shape, in order to achieve the optimum result of a luminaire equipped with them. This can be the case, for example, for the optimal illumination of a license plate.

Further preferably, the secondary strands of the two main strands of the first and the second electrode are formed jet-shaped and are substantially each at right angles from the main strands. The angle at which the secondary strands depart from the main strands may also assume other values, for example 30 °, 45 ° or 60 °, preferably the angle is the same for both main strands.

The secondary strands, like the main strands, can also have any desired curve shape. In order to achieve a uniform luminous intensity of a luminous means equipped with the electrodes according to the invention, it is advantageous that the secondary strands are aligned parallel to one another, ie each secondary strand always has the same distance from the adjacent secondary strands over the entire length of the respective secondary strand.

Furthermore, it is very advantageous if the main strands and secondary strands are arranged in a (mathematical) plane.

When all the advantages mentioned so far are realized, the first and second electrodes are in the form of a comb with parallel tines, the tines of the first electrode engaging in the spaces between the tines of the second electrode and vice versa. In this respect, it represents an advantageous embodiment, when each of the main strand is formed with its side strands in the form of a comb-like electrode and the two comb electrodes are arranged such that the tines of a comb electrode between the tines of the other comb electrode, without the two comb electrodes touch.

This arrangement is shown in FIG.

By means of the product construction of strands according to the invention, it is possible for the first time to generate any other shapes of the double-comb electrode, for example round or oval) (see FIG. 2).

According to a further advantageous embodiment, for example if the illuminant is to be used in a motor vehicle license plate, it is advantageous if the main strands and secondary strands consist of bars with a width of 0.05 to 3.0 mm, preferably 1.5 mm and with a height of 20 nm to 100 μηι, preferably up to 50 μηι exist.

The essential property of the main and secondary strands is to be electrically conductive. In this respect, the specified values for the width and height are preferred guide values. In individual cases, these values can also be exceeded, provided that the remaining conductivity is sufficient for the desired application. The distance between the webs, measured as the distance from web edge to web edge, is preferably 25 to 300 μm, more preferably 50 to 200 μm, particularly preferably 75 to 150 μm.

According to an advantageous embodiment, the first electrode or the second electrode, particularly preferably both electrodes are deep-drawable.

In order to exhibit the inventively preferred deep drawability, it has been found to be advantageous if the electrodes consist of an electrically conductive material, in particular metal-containing material, which at room temperature (20 ° C.) has an elongation at break (or synonymously elongation at break) between 1 and 70%. , especially according to DIN EN ISO 6892-1, point 3.4.2, and a tensile strength of between 5 and 2500 N / mm ² , in particular according to DIN EN 6891-1.

The stated tensile strengths of the electrically conductive materials, for example the metals or alloys mentioned below, in particular as raw materials, are determined according to DIN ISO 6892-1, the tensile strength corresponding to the maximum force according to DIN EN ISO 6892-1 point 3.9 and point 3.10.1 , The measurement is carried out according to the procedure in item 6.2-c (wire rod profiles smaller <4mm), method A (test speed based on the expansion rate control according to item 10.3). The disclosure content of DIN EN ISO 6892-1 as well as all other DINs mentioned is referred to in their entirety and their contents are included in the content of this document.

The elongation at break or synonymously the elongation at break of the material should be as high as possible in order to enable harmless deformability of the electrodes during the embossing process, ie to exclude a ductile or even brittle fracture.

Therefore, it is preferred if the elongation at break of the material is between 3 to 70%, in particular between 10 to 70%, particularly preferably between 12 to 70%, or even better between 18 to 70% and / or if there is a tensile strength between 5 and 2100 N / mm ² , in particular between 12 to 2100 N / mm ² , more preferably between 50 to 2100 N / mm ² , particularly preferably between 40 to 2000 N / mm ² . Also materials with tensile strengths between 45 to 560 N / mm ² are particularly preferred. Typical preferred materials preferably have values between 40 MPa and 1300 MPa (70 N / mm ² to 2000 N / mm ² ). Thus, preferred materials such as aluminum-containing alloys or steels may have tensile strengths of 16 to 600 N / mm ² at an elongation at break of 16 to 50%. Copper is also preferred and, depending on the processing, may have a tensile strength of 200 to 400 N / mm ² at the mentioned elongations at break. The materials mentioned include a number of metals and their alloys.

Suitable materials include, for example, aluminum or alloys of aluminum containing magnesium. Preferred aluminum-containing alloys have tensile strengths of 60 to 400 N / mm ² at an elongation at break of 20 to 40%, depending on the composition. Other suitable alloys may include alloying additives that affect strength, In addition to magnesium, these include zinc, silicon or manganese. The expert knows that the processing of metals or alloys also influences their material properties. In general, therefore, materials are preferred whose elongation at break in the range between 10 to 70% and / or their tensile strength between 50 to 2100 N / mm ² or in the range between 12 to 1000 N / mm ² , particularly preferably the elongation at break in the range between 15 to 55% and / or the tensile strength between 12 to 1000 N / mm ² .

Further, it is preferable that the elongation at break and the tensile modulus of elasticity of the electrodes at an elongation rate of 300 mm / min and a temperature of 23 ° C have an elongation at break of more than 20%, in particular more than 50% or even more than 100%, and also has a tensile elastic modulus of less than 1000 MPa or even at most 100 MPa. The double comb electrode according to the invention - according to the preferred variant - is highly deformable and is thus also thermoformable or embossable, without reducing their functionality. Due to the tensile strength, the material is sufficiently yielding. At the same time, however, it should also have a high elongation at break in order to be able to be deformed completely non-destructively. In particular, materials in which the two features mentioned are realized at the same time, are sufficiently deformable to deep draw or emboss without restriction of functionality.

The choice of material from which the electrodes of the double comb electrode can be made is large. It is preferred

 · Metal oxide

 • metal alloy

 Metal, preferably silver, copper and / or aluminum and / or

 Electrically conductive polymer (intrinsically conductive polymer and / or extrinsically conductive polymer)

Suitable materials are generally all conductive metals and their alloys, such as aluminum, copper, iron, silver, gold, zinc, tungsten, chromium, lead, titanium, nickel, platinum and gadolinium. A preferred alloy is in addition to iron, copper and / or aluminum-containing alloys and nitinol. Particularly advantageous are electrodes made of metals or alloys which have a high ductility. Steel can deform plastically up to 25% before it breaks. For gold, the ductility is many times greater. The advantage of ductile materials is that they provide good cold ductility, which translates into excellent bending and deep-drawability. Furthermore, many metals have high reflectivity, which has a positive effect on the luminous efficacy of the lamp containing the electrode, since the material absorbs only a small portion of the light.

Materials that do not have high reflectivity are therefore preferably provided with highly regular and / or diffuse (retro) reflective coatings, for example with nanoparticles.

Another advantage of metal electrodes is that they can be produced, stored and processed without a carrier, in particular they can be processed from roll to roll.

Electrically conductive polymers are on the one hand polymers that are in the native solid state, that is, as obtained in the polymerization of suitable monomers, electrical insulators by targeted measures (usually by adding electrically conductive substances such as graphite powder, carbon powder, metal powder) but can be converted into electrical conductors. On the other hand, there are polymers that have electrical conductivity without electrically conductive additives (by structural peculiarities in the molecular structure), they are therefore called intrinsically conductive polymers.

Extrinsically conductive polymers [filled (electrically conductive) polymers] can be described as follows: The classical way of imparting electrical conductivity to polymers is the admixture of conductive fillers, for example metal powders or carbon blacks, which leads to the so-called filled electrically conductive polymers exist as polymer compounds. This method is widely variable in terms of polymers and fillers but provides only electrically conductive polymers of generally relatively low conductivity. These depend strongly on the type and concentration of the fillers used. The charge transport in the filled electrically conductive polymers takes place via a continuous network formed by the fillers in the polymer. Such polymers, for example, prevent electrostatic charging or electromagnetic interference. Examples of this are soot-filled (Polycarbonate) films for thermal printing machines of typewriters or carbon black (polyurethane) foils for the heating of beds and floors.

 In addition to the filled one knows intrinsic electrically conductive polymers with quasi-built electrical conductivity. They are prepared by a modification, by so-called doping, of suitable, in the undoped state, at best semiconducting polymers via oxidation ("p-doping") or reduction reactions ("n-doping"). Suitable polymers for doping are especially those with an extended ττ electron system, for example polyacetylene in the cis and trans form, or those with a sequence of (hetero) aromatic rings in the main chain, such as poly (p-phenylene), polythiophenes or polypyrrole

 For further details, reference is expressly made to the chemistry Lexicon Römpp, keyword "electrically conductive polymers".

The electrically conductive polymer can be produced for example by a conductive coating. Polyaniline, 1,3-diethylene dioxide derivatives of imidazoline or EOlml-2,2, optionally with at least one electrically conductive filler, may be used as the electrically conductive polymer composition, it being possible for the filler to be selected from the group of metal particles comprising silver, gold , Platinum or aluminum and their alloys or graphite, carbon nanoparticles, carbon nanotubes, carbon black, carbon black, fullerenes, fullerene derivatives and acetylene black.

In principle, all suitable electrically conductive fillers which are compatible with the respective polymer composition can be used as electrically conductive fillers. In particular, fillers are used which are selected from the group comprising graphite and carbon black, in particular Leitruß (for example, Printex® XE Degussa), and any combinations thereof. In addition or instead, other carbon-based fillers may also be used, in particular those which are nanoscale, ie have an extension of not more than 500 nm, preferably less than 200 nm or even less than 50 nm, in at least one spatial dimension Examples of carbon nanoparticles such as carbon nanotubes (for example, carbon nanotubes from Ahwahnee or carbon nanotube masterbatches from Hyperion Catalysis), carbon nanofibers, fullerenes and the like. Advantageously, the filler is used in such an amount that the proportion of the filler in the respective polymer mass is large enough to ensure a sufficiently low resistance of the polymer composition, in particular, the percolation limit must be exceeded so that the conductive fillers form a network by mutual contact can form mutual contact. Furthermore, the fillers can be used surface-modified. As a result, the properties of the polymer composition can be specifically influenced, for example in order to improve the dispersibility of carbon nanotubes or carbon black in the polymer composition.

The conductivity of the polymer masses depends inter alia on the degree of filling of the electrically conductive filler, that is to say its mass fraction in the polymer composition. By increasing the degree of filling, higher conductivities can be achieved. In addition, the electrical conductivity of a polymer composition is also dependent on its base polymer. The degree of filling is advantageously between 1 and 90 wt .-%, in particular between 1 to 60 wt .-% with respect to the total composition. Very preferably between 20 and 50 wt .-% of filler are used.

In order to obtain an electrically conductive polymer composition, the electrically conductive fillers may be admixed with the monomers of the polymer composition prior to the polymerization and / or during the polymerization and / or mixed with the polymers only after the polymerization has ended. Preferably, the electroconductive filler after polymerization is added to a melt of a base polymer of the polymer composition.

As electroconductive polymer compositions, soot-containing semi-crystalline thermoplastics such as polyolefins, polyvinylidene fluoride, polyhexafluoropropylene or polytetrafluoroethylene are commonly used in the prior art. The prior art is described in detail in DE 29 48 350 A1, US Pat. No. 7,592,389 B2, EP 0 673 042 B1 and EP 0 324 842 A1.

The electrically conductive polymer composition preferably also meets the elongation at break and / or tensile strength requirements of the electrically conductive materials according to the invention, that is to say they are preferably in the same range of the values mentioned. Preferably, the electrically conductive polymers also cover at least the Range of elongation at break of said metallic materials, that is, the polymers are at least as elastic as the metallic electrically conductive materials. According to an alternative, the electrodes of the double-comb electrode may be made of an electrically conductive printable ink, lacquer or printing ink, preferably a printing ink or ink containing silver or aluminum. Also preferred is carbon ink or a printing ink containing carbon nanotubes.

Such inks are described in detail in US 2009/039781 A1, US Pat. No. 6,582,628 B2, WO 2003/054981 A1.

Printable electrically conductive silver or aluminum containing pastes may also have a high solids content of this filler of up to 80% by weight of the total composition. These pastes can be binder-containing and dried or baked at elevated temperatures.

In addition to the aforementioned features, the front electrode has a transmission of 5 to 92% in the UV / Vis spectral region, in particular from 20 to 90%, preferably from 40 to 85%, preferably from 50 to 85%, particularly preferably from 50 up to 80% or even from 70 to 75%. Alternative useful ranges may range from 5 to 80% in the UV / Vis spectral region, in particular from 10 to 60%, more preferably from 15 to 55%, preferably from 30 to 55%, preferably from 20 to 55%, most preferably from 25 to 55%. High transmission values increase the luminance of electroluminescent lamps with these electrodes.

Furthermore, it is preferred if the electrodes in the double comb electrode at the same time have a sheet resistance of less than 300 Ω, for example between 0.001 to 300 Ω, better between 0.0005 to 300 Ω, preferably between 0.0001 Ω to 300 Ω. Preferably, the sheet resistance is less than 100 Ω, more preferably less than 50 Ω, more preferably a sheet resistance of less than 1, 0 Ω, especially less than 0.2 Ω, more preferably less than 0.01 Ω, and especially in the range of up to 0.0005 Ω , preferably up to 0.001 Ω. In general, all values of surface resistance between 300 Ω and greater than 0 Ω should be considered as revealed. These sheet resistance values are preferably valid for both electrodes based on metallic and / or on polymeric materials. Alternatively, the resistance of the electrodes is at least one direction below 15 Ω, better below 10 to 15 Ω. The sheet resistance is calculated according to RD = p / d, for example, p (steel) = 1, 5 * 10 ^"7 Ω -m or p (graphite) = 8 * 10 ^_e Q -m are.

The illuminant according to the invention consists of a front electrode and a back electrode, wherein an electrically excitable luminous layer is present between the front electrode and the back electrode.

 The luminescent layer consists of a matrix and luminescent particles which luminesce under the action of an AC electric field, and optionally at least one dielectric layer.

 In the context of the invention, electroluminescent luminous particles are generally chemical substances which are suitable for emitting light with a wavelength of 400 to 800 nm in an alternating electric field. For special applications, it is also possible to use pigments which emit in the UV range (between 10 to 400 nm or in the IR range (between 760 nm to 0.5 mm).

The luminescent particles in the matrix are ZnS, CdS, Zn _x Cdi. _x S, prepared from compounds of the II and VI group of the periodic table, which are usually doped with Cu, Mn, or Ag, or activated, and / or phosphorus-containing luminous particles proven or even those containing a mixture of at least one of these compounds.

It is also known to produce the luminous particles via a micro-encapsulation process. The mass fraction of the luminous means in the matrix can be selected as desired and is in the luminous layer of the invention usually between 1 wt .-% and 90 wt .-%, preferably between 40 wt .-% and 75 wt .-%, in particular between 55 wt .-% and 65 wt .-%. Electric field-excited electroluminescence distinguishes between different forms of application. Thus, there is the thin-film electroluminescence, the equidistant thick-film powder electroluminescence and the alternating-field thick-film powder electroluminescence. Starting materials for the production of the luminescent particles are the abovementioned zinc sulfides or zinc selenides, which are reacted with activators of, for example, copper or manganese and so-called co-activators, such as Chlorine or iodine, can be added to increase the efficiency. For protection against atmospheric moisture, the particles of these compounds or of phosphorus can usually be provided with a protective layer, for example with an inert metal oxide such as aluminum oxide or glass. This protective layer can protect against a rapid drop in luminance in the system as it is caused by moisture.

Particularly preferred polymers for preparing the matrix or as a matrix have a relative permittivity of more than 4.5. It has been found that in the case of a pressure-sensitively adhesive polymer having such a high relative permittivity (permittivity number, relative dielectric constant, formula symbol: ε _Γ ), the luminance of a matrix produced with this polymer with luminous particles as the luminescent layer is very high for the same layer thickness of the luminescent layer. Furthermore, it is particularly advantageous if the matrix as a whole has a relative permittivity of less than 25. In this way, the dielectric losses (imaginary part of the permittivity) can be kept low in the electroluminescence, so that a particularly favorable compromise between the highest possible luminance on the one hand and the lowest possible power loss on the other hand is obtained.

In particular, the polymers disclosed in WO 2007/107591 A1 and DE 10 2008 062 129 A1 are particularly suitable for producing a luminescent layer as a matrix and for producing the matrix. Reference is made in its entirety to the disclosure content of DE 10 2008 062 129 A1 and made the subject matter of the present invention, in particular the disclosure on pages 3, line 8 to page 25, line 18, of the polymers or adhesives mentioned there as the matrix of the luminescent layer use.

The disclosure of WO 2007/107591 A1 is also incorporated by reference, in particular to the disclosure of the PSAs and their preparation on pages 3, line 4 to page 13, line 10, to use them according to the invention as a matrix of the luminescent layer.

DE 10 2006 013 834 A1 also discloses, for example, a pressure-sensitive adhesive which is used as a matrix for the luminous particles (electroluminescent luminous means). In general, the pressure-sensitive adhesives disclosed there can be based on poly (meth) acrylates, silicones, polysiloxanes, synthetic rubbers, polyurethanes and block copolymer-based adhesive systems are used according to the invention as a matrix for the luminescent particles of the luminescent layer. Accordingly, the content of DE 10 2006 013 834 A1 is completely referenced and made the subject of this disclosure.

DE 10 2006 013 834 A1 describes in particular detail self-adhesive compositions based on poly (meth) acrylate, ie self-adhesive compositions containing as base polymer a polymer of a (meth) acrylate monomer mixture (the term (meth) acrylate is used in the following simplified description and includes both Acrylates as well as methacrylates, ie their acids as well as their derivatives, for example esters). Specifically, this document names mixtures containing from 70% to 100% by weight of the monomer mixture one or more (meth) acrylic esters esterified with alkyl alcohols having from 1 to 30 carbon atoms, and moreover optionally at most 30 wt .-% of one or more olefinically unsaturated monomers having functional groups. In practice, it has been found that electroluminescent devices of good luminosity and long-term stability can be realized when using these self-adhesive composition systems with commercially available illuminants. A particularly preferred embodiment of the invention relates to a luminescent particle matrix, which in turn preferably comprises a polymer of a monomer mixture, relative to the monomer mixture

(A) a predominant proportion, in particular 70 to 99.9 wt .-% of one or more acrylic acid esters and / or methacrylic acid esters having the formula CH ₂ = CH (R3) (COOR ₄ ), wherein the radical R _3, the substituents H and / or CH ₃ and the radical R _{4 is} alkyl chains having 4 to 14 C atoms; and

 (B) 0, 1 to 30 wt .-%, preferably 0.5 to 10 wt .-% of one or more olefinically unsaturated monomers having functional groups, especially with functional groups which can undergo crosslinking, such as acrylic acid, methacrylic acid, hydroxyethyl acrylate , Glycidyl acrylate, glycidyl methacrylate or copolymerizable photoinitiators,

includes. In addition, the matrix may comprise one or more components c) which are copolymerized together with the other components. The comonomers of component (c) may constitute up to 40% by weight of the monomer mixture. Preferably, the proportions of the corresponding components a, b, and c are selected such that the copolymer has a glass transition temperature (T _G ) <15 ° C. The monomers are preferably selected such that the resulting polymers can be used as PSAs at room temperature, in particular such that the resulting polymers have pressure-sensitive adhesive properties according to the Handbook of Pressure Sensitive Adhesive Technology by Donatas Satas (van Nostrand, New York 1989, page The glass transition temperature of the polymers on which the PSAs are based is advantageously below 15 ° C. in terms of a dynamic glass transition temperature for amorphous systems and is understood as the melting temperature for semicrystalline systems which are determined by dynamic mechanical analysis (DMA) at low frequencies (10 rad / s) can be determined.

The control of the desired glass transition temperature can be achieved by applying the equation

J- = y ^ (Gi)

G " ^G >"

in analogy to the Fox equation (see TG Fox, Bull. Am. Phys Soc., 1 (1956) 123) in the composition of the monomer mixture, which is the basis of the polymerization can be achieved. In the equation (G1), n represents the number of runs via the monomers used, w _n the mass fraction of the respective monomer n (% by weight) and T _{G, n} the respective glass transition temperature of the homopolymer from the respective monomers n in K.

The monomers of component (a) are, in particular, plasticizing and / or nonpolar monomers. Their composition in the monomer mixture is chosen so that the resulting polymers can be used at room temperature or higher temperatures as pressure-sensitive adhesives, in other words in such a way that the resulting polymers have tack-adhesive properties. For the monomers (a), preference is given to using acrylic monomers which comprise acrylic and methacrylic acid esters having alkyl groups consisting of 4 to 14 C atoms, preferably 4 to 9 C atoms. Specific examples, without wishing to be limited by this list, are n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl meth acrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate, and their branched isomers such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate. The monomers of component (b) are in particular olefinically unsaturated monomers (b) having functional groups, in particular having functional groups capable of undergoing crosslinking. The crosslinking can be carried out by reaction of the functional groups with themselves, other functional groups or after addition of a suitable crosslinking agent.

For the monomers (b) it is preferred to use monomers having the following functional groups: hydroxyl, carboxy, epoxy, acid amide, isocyanato or amino groups. Especially preferred are monomers with carboxylic acid, sulfonic acid, or phosphonic acid groups.

Particularly preferred examples of the component (b) are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate, 6-hydroxyhexyl methacrylate, N-methylolmethacrylamide, N- (buthoxymethyl) methacrylamide, N-methylolacrylamide, N- (ethoxymethyl) acrylamide, but this list is not exhaustive. Preferred monomers (b) may also contain functional groups which promote subsequent radiant-chemical crosslinking (eg electron beams, UV) or via peroxides. Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers which promote crosslinking by electron irradiation or peroxides are, for example, tetrahydrofurfuryl acrylate, N-tert. Butylacrylamide, allyl acrylate this list is not exhaustive.

In principle, in the sense of component (c), all vinylic-functionalized compounds which are copolymerisable with component (a) and / or component (b) can be used, and can also serve for adjusting the properties of the resulting PSA.

Preferred monomers (c) are, but are not exhaustive, for example, methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, tert-butyl acrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, isobornyl methacrylate, t-butyl phenyl acrylate, t-butyl, Butylaphenyl methacrylate, dodecyl methacrylate, isodecyl acrylate, lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecyl acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate,

2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyladamantyl acrylate, 4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethyl methacrylate, 4-biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofufuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate , Dimethylaminoethyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N- (1-methylundecyl) acrylamide, N- (buthoxymethyl) methacrylamide, N- (ethoxy-methyl) acrylamide, N- (n-octadecyl) acrylamide, furthermore N, N-dialkyl-substituted Amides, such as Ν, Ν-dimethylacrylamide, N, N-dimethylmethylmethacrylamide, N-benzylacrylamides, N-isopropylacrylamide, N-tert-butylacrylamide, N-tert-octylacrylamide, 2-butoxyethyl acrylate, 2-butoxy-ethyl methacrylate, 3 Methyl methoxyacrylate, 3-methoxybutyl acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycol methacrylate, ethylene glycol acrylate .

Ethylene glycol monomethyl acrylate, methoxy polyethylene glycol methacrylate 350, methoxy polyethylene glycol methacrylate 500, propylene glycol mono-methacrylate, butoxy diethylene glycol methacrylate, ethoxy triethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3, 3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2, 3,3,4,4,4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6, 7,7,8,8,8-pentadecafluoro-octyl methacrylate, acrylonitrile, methacrylonitrile, vinyl methyl ether, Ethyl vinyl ether, vinyl isobutyl ether, vinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3 , 4-dimethoxystyrene, N-vinyl lactam, N-vinyl pyrrolidone,

The average molecular weights M _w of the luminescent matrix comprising polyacrylate PSAs are very preferably in the range from 20,000 to 3,000,000 g / mol; or alternatively for a matrix as hot melt pressure sensitive adhesive, preferably in a range of 100,000 to 500,000 g / mol.

[The data of the average molecular weight M _w and the polydispersity PD in this document refer to the determination by gel permeation chromatography. The determination is carried out on 100 μΙ clear filtered sample (sample concentration 4 g / l). The eluent used is tetrahydrofuran with 0.1% by volume of trifluoroacetic acid. The measurement takes place at 25 ° C. As precolumn a column type PSS-SDV, 5 μ, 10 ³ A, ID 8.0 mm x 50 mm is used. For separation, the columns of the type PSS-SDV, 5 μ, 10 ³ Ä and 10 ⁵ Ä and 10 ⁶ Ä are used each with ID 8.0 mm x 300 mm (columns from Polymer Standards Service, detection by means of differential refractometer Shodex RI71) , The flow rate is 1, 0 ml per minute. The calibration is performed against PMMA standards (polymethyl methacrylate calibration)]

Also particularly suitable for the further processing according to the invention are polyacrylates which have a narrow molecular weight distribution (polydispersity <4). These compounds become particularly shear-resistant at a relatively low molecular weight after crosslinking. Narrowly distributed polyacrylates can be prepared by anionic polymerization or by controlled radical polymerization, the latter being particularly well suited. Examples are described in US Pat. No. 6,765,078 B2 and DE 100 36 901 A1 or US 2004/092685 A1. Atom Transfer Radical Polymerization (ATRP) can also be used advantageously for the synthesis of narrowly distributed polyacrylates, preference being given to monofunctional or difunctional secondary or tertiary halides as initiator and to abstraction of the halide (s) Cu, Ni, Fe , Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au complexes (EP 0 824 11 1 A1, EP 0 826 698 A1, EP 0 824 110 A1, EP 0 841 346 A1; EP 0 850 957 A1). The different possibilities of ATRP are further described in US Pat. Nos. 5,945,491, 5,854,364 and 5,789,487. In a further very advantageous embodiment of the invention, the matrix is based on a silicone base, in particular a pressure-sensitive adhesive which is chemically or physically crosslinked. In particular, by a radical crosslinking, the time-dependent aging of the silicone PSA, reflected by increasing cohesion and reduced adhesion, can be significantly reduced. Radical crosslinking can advantageously be carried out chemically by the use of peroxy or azo initiators, BPO derivatives (benzoyl peroxide derivatives) and / or by the use of electron beams.

The silicone PSA very advantageously has a high adhesion to nonpolar substrates and silicone rubbers and / or foams as well as to siliconized and / or silicone-containing substrates. Particularly preferably, the crosslinking of the silicone pressure-sensitive adhesive layer is effected by means of electron irradiation (electron beam curing, ESH).

According to the invention, condensation-crosslinking systems comprising silicate resins and polydimethyl or polydiphenylsiloxanes can advantageously be used as silicone PSAs, and also advantageously addition-crosslinking systems comprising silicate resins, polydimethyl- or polydiphenylsiloxanes and crosslinkers (crosslinker substances, in particular functionalized hydrosilanes).

Some commercially available examples of silicone adhesive adhesives which can be employed with excellent effect according to the invention as a matrix are, without wishing to limit the subject matter of the invention by listing:

condensation curing systems: DC 280, DC 282, Q2-7735, DC 7358, Q2-7406 from Dow Corning, PSA 750, PSA 518, PSA 910 from GE Bayer Silikones, KRT 001, KRT 002, KRT 003 from ShinEtsu, PSA 45559 from Wacker Silikones and PSA 400 from Rhodia; addition-curing systems: DC 7657, DC 2013 from Dow Corning, PSA 6574 from GE Bayer Silikones and KR 3700, KR 3701 from ShinEtsu.

In an advantageous embodiment, the matrix comprises a self-sticky polymer or a polymer mixture of a monomer mixture which comprises (meth) acrylic acid derivatives, each of which has at least one functional group the amount comprising cyano groups and nitro groups. By using these monomers, it is possible to obtain polymers which on the one hand are self-tacky and whose relative permittivity on the other hand can be varied over a wide range by changing the mass fraction of these monomers in the resulting polymer. However, it is important in the use of these particular monomers that they be contained in the polymer to a mass fraction of at least 45 wt .-%, in order to obtain a polymer having the particularly preferred relative permittivity of more than 4.5. It has been found to be particularly advantageous if the (meth) acrylic acid derivatives having at least one cyano group and / or nitro group are present in the self-adhesive polymer to a mass fraction of not more than 90% by weight, since the resulting polymers are no longer sufficiently self-adhesive at a higher mass fraction to serve as a base polymer of a self-adhesive. In particular, it is found that the polymers are still outstandingly pressure-sensitively adhesive, up to a content of about 80% by weight, and are still very good hotmelt tacky and have a content of between 80% by weight and a content of such monomers of about 70% by weight. and 90% by weight are just hot melt-sticky. Depending on the specific application, self-adhesive polymers having excellent suitability as a base polymer of a self-adhesive composition which simultaneously has an excellent luminance in the lamp assembly are obtained, in particular, if the mass fraction of the (meth) acrylic acid derivatives having at least one cyano group and / or nitro group is between 50 wt. -% and 60 wt .-% is. The polymers may be of any desired form, for example as block copolymers or random polymers.

Particularly good results are achieved when the polymer used as matrix contains monomers selected from the group comprising unsubstituted or substituted cyanomethyl acrylate, cyanoethyl acrylate, cyanomethyl methacrylate, cyanoethyl methacrylate, (meth) acrylic acid derivatives with 0- (per) cyanoethylated saccharides and / or saccharide acrylates. In this case, self-adhesive polymers are obtained which have a significantly higher long-term stability than conventional self-adhesive polymers. This manifests itself in a relative permittivity of the polymer which remains at least substantially constant over a significantly longer period of time, and moreover in a considerably slower temporal decrease in the luminance when these polymers are used as matrix of the luminescent layer. According to the invention, the relative permittivity of the matrix or the polymer, the PSA or the silicone used to prepare the matrix is greater than 4.5. Furthermore, it is advantageous if the self-sticky polymer is a polymer of a monomer mixture which further comprises substituted and / or unsubstituted (meth) acrylic esters of the general formula CH ₂ = CR ¹ -COOR ² , where R ^{1 is} selected from the group comprising H and CH ₃ and R ^{2 is} selected from the group comprising substituted and unsubstituted alkyl chains having 1 to 20 carbon atoms. In this way, a self-adhesive polymer is obtained whose adhesive properties vary over a wide range and can be adapted to the specific requirements. Even better variation possibilities for the technical adhesive properties arise when the self-adhesive polymer is a polymer of a monomer mixture, which also has olefinically unsaturated monomers with functional groups.

Furthermore, (meth) acrylic acid derivatives having at least one nitro group may in principle be used as all customary and suitable compounds for preparing the matrix. Likewise, (meth) acrylic acid derivatives having at least one cyano group may in principle be selected from all customary and suitable compounds. When using monomers which have cyano groups, a particularly polar polymer is obtained which, however, is neither moisture-sensitive or water-soluble nor hygroscopic and exhibits at most a low water absorption. As monomers with cyano groups such as those of the general formula CH ₂ = C (R ^a ) (COOR ^b ) can be used, wherein R ^{a is} H in acrylic acid or an acrylic acid derivative and in methacrylic acid or a methacrylic acid is CH ₃ , and wherein R ^b a Is the radical derived from the general formula - (CH ₂ ) _c -CH (CN) - (CH ₂ ) _d -H, where c = 0 to 10 and d = 0 to 10, that is, for example - without itself to be limited by this list - cyanomethyl acrylate, cyanoethyl acrylate, cyanomethyl methacrylate and cyanoethyl methacrylate. In addition to or instead of these cyanoalkyl (meth) acrylates, it is also possible to use other cyano-functionalized (meth) acrylic acid derivatives, for example those in which the above R ^{b contains} a 0- (per) cyanoethylated sugar unit (ie a saccharide in which a Hydroxy group, a plurality of hydroxyl groups or all hydroxy groups are present or present as cyanoethanol ethers), for Example O-percyanoethylated 2- (glycosyloxy) ethyl acrylate or corresponding di-, oligo- and polysaccharides. Of course, instead of or in addition to glucose, other saccharides may also be used in these compounds, for example mannose, xylose and the like.

However, instead of using monomers having cyano groups and / or nitro groups, it is also possible to produce a pressure-sensitive adhesive polymer based on (meth) acrylates using other monomers which also have a high relative permittivity, for example vinylidene halides in which the above radical For example, R ^{b is} derived from the general formula - (CH ₂ CX ₂ ) n -CH ₃ , where n = 1 to 50 and X is selected from the group comprising F, Cl and Br.

In this way, it is possible to obtain polymers for the matrix of the luminescent layer which are not only self-adhesive and have a corresponding relative permittivity, but also have excellent insulating properties, low (or-for special applications-high) loss factors and high optical transparencies.

In addition to such (meth) acrylate-based polymers, however, it is also possible in principle to use all other polymers for the matrix of the luminescent layer which are customarily used for self-adhesive compositions. In this connection, self-adhesive compositions based on polysiloxane, polyester-based, synthetic rubber-based and / or polyurethane-based are mentioned by way of example, without being unnecessarily limited by this information. Suitable pressure-sensitive adhesive polymers are also those based on block copolymers, for example acrylate block copolymers or styrene block copolymers. Such adhesives are well known in the prior art, wherein also in these the relative permittivity can be selectively increased by the use of functionalized monomers with cyano, halogen or nitro groups.

Acrylate-based polymers which are obtainable, for example, by free-radical polymerization and which contain at least one acrylic monomer of the general formula CH ₂ CC (R ¹ ) (COOR ² ) where R ¹ is H or a CH ₃ radical and R _{3 are} particularly suitable ² is H or is selected from the group of saturated, unbranched or branched, substituted or unsubstituted C ₁ -C ₂ -alkyl radicals. Specific examples, without being limited by this list, are methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, lauryl acrylate , Stearyl acrylate, behenyl acrylate and their branched isomers, for example isobutyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate or isooctyl methacrylate.

Further usable classes of compounds, which are usually used but only in a small amount fraction, are monofunctional acrylates or methacrylates, wherein the radical R ^{2 is selected} from the group of bridged or unbridged cycloalkyl having at least six carbon atoms. The cycloalkyl radicals may also be substituted, for example by C ₁ - to C ₆ -alkyl groups. Specific examples are cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and 3,5-dimethyl adamantyl acrylate.

In a preferred procedure, acrylic monomers and / or comonomers are used which have one or more substituents, in particular polar substituents, for example carboxyl, sulfonic acid, phosphonic acid, hydroxyl, lactam, lactone, N-substituted amide, N, substituted amine, carbamate, epoxy, thiol, alkoxy and ether groups.

It can be used according to an advantageous embodiment further polymers which are prepared from a monomer mixture having in addition to the acrylic monomer olefinically unsaturated monomers having functional groups as comonomers. These may be selected, for example, from the group comprising vinyl compounds having functional groups (for example vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds having aromatic rings and heterocycles in the alpha position), maleic anhydride, styrene, styrene compounds, vinyl acetate, acrylamides and double bond-functionalized Photoinitiators, without limiting themselves by this list.

Basically suitable monomers as functional comonomers are moderately basic comonomers such as single or double N-alkyl-substituted amides, in particular acrylamides. Specific examples are Ν, Ν-dimethylacrylamide, N, N- Dimethylmethacrylamide, N-tert-butylacrylamide, N-vinylpyrrolidone, N-vinyllactam, dimethylaminoethylacrylate, dimethylaminoethylmethacrylate, diethylaminoethylacrylate, diethylaminoethylmethacrylate, N-methylolacrylamide, N-methylolmethacrylamide, N- (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide and N-isopropylacrylamide, although this list is not exhaustive.

Further preferred examples of such comonomers are (in a non-exhaustive list) hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, maleic anhydride, itaconic anhydride, itaconic acid, glyceridyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate,

Glyceryl methacrylate, 6-hydroxyhexyl methacrylate, vinyl acetic acid,

Tetrahydrofurfuryl acrylate, beta-acryloyloxypropionic acid, trichloroacrylic acid, fumaric acid, crotonic acid, aconitic acid and dimethylacrylic acid.

In a further preferred procedure, the comonomers used are vinyl compounds, in particular vinyl esters, vinyl ethers, vinyl halides, vinylidene halides and vinyl compounds with aromatic rings and heterocycles in the alpha position, non-limiting examples being vinyl acetate, vinylformamide, 4-vinylpyridine, ethylvinyl ether, vinyl chloride, vinylidene chloride, styrene , N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid and acrylonitrile.

The at least one comonomer can particularly advantageously be a photoinitiator having a copolymerizable double bond, in particular selected from the group comprising Norrish I photoinitiators, Norrish II photoinitiators, benzoin acrylates or acrylated benzophenones.

EL pastes known from the prior art (for example screen printing pastes as offered by DuPont) can be used as a luminescent layer as an alternative to the pressure-sensitive adhesives. Optionally, the luminescent layer is to be supplemented by a further dielectric layer.

The front electrode is preferably made of a plastic film coated with ITO (Indium Tin Oxide) or Baytron. Baytron® is a polymer composition of the company Bayer. A Baytron FE solution is based on a solution of poly (3,4-ethylenedioxythiophene) -poly (styrene sulfonates) in a mixture of water and ethanol. The person skilled in the art is familiar with the fact that the double-comb electrode according to the invention generally also has electrical connections, that is to say a contact arrangement or contacting electrodes, for electrical connection to an AC voltage source. The illuminant according to the invention can be used particularly advantageously in conjunction with a motor vehicle license plate. In this way, a self-illuminating license plate, which on external lighting means, as they are still common practice, can do without. Preferably, a (retro-) reflective, optically continuous front coating, and / or the rear side of the lighting means are self-adhesive on the front electrode, for example by lamination and / or coating of an adhesive coating.

 The (retro-) reflective front can be realized by laminating a reflection film, better retroreflective film, in particular a transparent reflection film. Such films are (also self-adhesive equipped) available on the company Nippon Carbide as a roll and are currently used as overlay films for bonding to street signs. The (retro) reflective films preferably meet the requirements or standards for motor vehicle license plates.

The film or the coating serve as insulation and / or as a protective layer against dirt, scratches or chemical influences. Self-adhesively treated films are also suitable as films on the upper side in order to bond the license plate to transparent holders on the side of the front electrode. The illuminant is preferably adhered to the license plate, then the laminate can be stamped, packaged and / or embossed.

The license plate can be connected to a voltage source, in particular the electrical system of a vehicle or a self-sufficient power source. By applying an alternating voltage, preferably a voltage in the range of 50 V to 300 V, to the electrode of the lamp, the electroluminescent additives are exposed to an alternating electric field and thus excited to shine.

The voltage range specified above can also be undershot or exceeded for certain applications. Thus, for very thin layer thicknesses of the PSA, it may be advantageous, for example, to produce a field strength sufficient for luminescence with lower voltage values than 50 V. For particularly thick PSA layers and three-dimensional bodies formed from the PSA, very high voltage values of over 300 V. Advantage may be to condition a desired illuminance.

The alternating electric field for generating the luminescence advantageously has a frequency of 40 Hz to 3000 Hz, more advantageously between 200 Hz and 2000 Hz, more advantageously between 350 Hz and 1000 Hz. In a further advantageous procedure, an alternating field with 50 Hz is selected. For example, it is possible to work with 230 V / 50 Hz, ie with the voltage and frequency customary in European power grids, in order to be able to dispense with the use of frequency converters. Another advantageous, exemplified alternative is the choice of 110 V / 60 Hz (US power grid).

By means of the present invention, the front electrode, which is preferably coated with ITO or Baytron, is interconnected with the back electrode "contactless" and "flatly" by the principle of the double capacitor, thereby compensating for breaks in the electrically conductive coating.

Any fractures in the coating (preferably made of ITO or Baytron) are compensated by the areal and "non-contact" contacting, which means that the luminous means according to the invention is characterized by a very high degree of reliability.

The area affected by a rupture in this product construction will be at most equal to the simple distance between the comb electrodes. With a correspondingly small selected electrode spacing, this affected area is imperceptible and thus negligible.

By using the comb electrode according to the invention high-cost low-impedance front electrodes (ITO, for example CPFilms OC50) can be dispensed with and resort to cheaper high-resistance variants (for example Baytron or thin ITO coatings) because the relevant surface conduction on the Front electrode takes place only between the strands of the comb electrode. The use of very thin ITO or Baytron coated films increases the light transmission and thus the effective luminance of the lamps.

example

A double comb electrode, as shown in FIG. 1 (ridge width 0.7 mm, ridge spacing 0.3 mm, material: copper) was coated with a pure acrylate composition containing up to 60% by weight with EL pigments (Osram GG43: copper-activated zinc sulfide). filled, laminated by hand and the still open adhesive surface with an ITO film (OC50, CPFilms) also laminated by hand. The pattern was embossed in accordance with DIN for the stamping of license plate numbers (DIN 74069). The double comb electrode was contacted with an AC power source (400 Hz, 200 V) and the luminance was measured. The luminance was 9.7 cd / m ² .

Devices for determining the luminance

The pure acrylate composition was prepared as follows:

For free-radical polymerizations, a conventional 200 L reactor was charged with 4900 g of acrylic acid, 51 kg of 2-ethylhexyl acrylate, 14 kg of methyl acrylate and 53.3 kg of acetone / gasoline / isopropanol (48.5: 48.5: 3). After 45 minutes of passage with nitrogen gas (degassing of the starting mixture) with stirring, the reactor was heated to 58 ° C and 40 g of 2,2'-Azoisobuttersäurenitril (AIBN) was added. Subsequently, the outer heating bath was heated to 75 ° C and the reaction was carried out constantly at this external temperature. After 1 h reaction time again 40 g of AIBN was added. After 5 h and 10 h each was diluted with 15 kg acetone / isopropanol (90:10). After 6 and 8 h 100 g dicyclohexyl peroxydicarbonate (Perkadox ^® 16, Fa. Akzo Nobel) was added dissolved in each 800 g of acetone. The reaction was stopped after 24 h reaction time and cooled to room temperature. To get out of the to produce an adhesive, the reaction product was blended with a 3% solution of aluminum (III) acetylacetonate in acetone (0.3% by weight, based on the weight of the polymer).

FIG. 3 shows that the double-comb electrode according to the invention can be obtained by the meter (continuous electrode in the longitudinal direction, several in number plate heights next to one another) and for use on a license plate in the strip with the electroluminescent PSA. In the case of strip coating, care must be taken to ensure that the continuous edge regions of the electrodes remain free as a contacting possibility

Subsequently, the double comb electrode coated with electroluminescent PSA 3 is cut with the comb electrode 1 and 2, each with a license plate height as width to the roll and covered with a coated with ITO or Baytron film 4 as a front electrode (see Figure 4).

If a phase of the AC voltage source (inverter) is connected to the two combs of the double-comb electrode in this product, the electric field builds up between the electrode and the ITO or Baytron-coated foil, flows via this front electrode to the opposite pole of the comb electrode and builds up here also the electric field on, the EL lamp lights up.

Claims

claims: Illuminant with a front electrode and a back electrode made of an electrode system comprising at least two electrodes, comprising at least one planar and preferably thermoformable first electrode and at least one planar and preferably thermoformable second electrode, wherein the first electrode has a first main strand and the second electrode has a second main strand in each case a plurality of secondary branches depart from the first main branch and from the second main branch, the main branches and the secondary branches consisting of an electrically conductive material, characterized in that at least some of the side strands of the first main strand and at least some of the secondary strands of the second main strand are each arranged so that they are located between two side strands of the other main strand, wherein between front electrode and back electrode, an electrically excitable luminescent layer is present. Illuminant according to claim 1, characterized in that the two main strands of the first and the second electrode are formed in a jet shape and aligned parallel to one another. Illuminant according to Claim 1 or 2, characterized in that the secondary strands of the two main strands of the first and the second electrode are in the form of a jet and substantially project in each case at an angle between 30 ° and 90 ° from the main strands, preferably with one of 30 °, 45 °, 60 ° or 90 °. Illuminant according to at least one of claims 1 to 3, characterized in that the main strands and secondary strands are arranged in one plane. Illuminant according to at least one of the preceding claims, characterized in that the main strands and secondary strands of webs with a width of 0.05 to 3.0 mm, preferably 1, 5 mm and with a height of 20 nm to 100 μηι, preferably up to 50 μηι exist. 6. Lamp according to at least one of the preceding claims,  characterized in that  the distance between the webs, measured as the distance from web edge to web edge, μηι 25 to 300, preferably 50 to 200 μηι, more preferably 75 to 150 μηι. 7. Lamp according to at least one of the preceding claims,  characterized in that  each of the main strand is formed with its side strands in the form of a comb-like electrode and the two comb electrodes are arranged such that the tines of a comb electrode between the tines of the other comb electrode, without touching the two comb electrodes. 8. Lamp according to at least one of the preceding claims,  characterized in that  the first electrode or the second electrode, preferably both electrodes are deep drawable. 9. Illuminant according to at least one of the preceding claims,  characterized in that  the electrodes are made  • metal oxide  • metal alloy  Metal, preferably silver, copper and / or aluminum and / or  Electrically conductive polymer (intrinsically conductive polymer and / or extrinsically conductive polymer) 10. Lamp according to at least one of the preceding claims,  characterized in that the electrodes consist of an electrically conductive material, the at Room temperature (20 ° C) has an elongation at break between 1 and 70% and / or a tensile strength between 5 to 2500 N / mm ² . 1 1. Use of a light source according to at least one of the preceding claims on the top of a motor vehicle license plate. 12. Use of a luminous means according to at least one of the preceding claims on the top of a motor vehicle license plate,  characterized in that  the front electrode has a (retro-) reflective, optically continuous front coating, in particular a film, and / or the rear side of the lighting means is self-adhesive, for example by lamination and / or coating of an adhesive coating. 13. Motor vehicle license plate, containing a lighting means according to at least one of the preceding claims.