Abstract:
An electroluminescence apparatus ( 10, 10′, 10″ ) having a layer sequence ( 12, 13, 14 ), which is arranged on a substrate ( 15 ) and has two electrode layers ( 12, 14 ), and an optically active dielectric intermediate layer ( 13 ) which is located between the electrode layers ( 12, 14 ) and is prepared by detachably applying the layer sequence ( 12, 13, 14 ) to an auxiliary mount ( 11 ) and adhesively applying the layer sequence ( 12, 13, 14 ) to the substrate ( 15 ) with the face which faces away from the auxiliary mount ( 11 ) of the layer sequence ( 12, 13, 14 ) which is located on the auxiliary mount ( 11 ) and detaching the auxiliary mount ( 11 ) from the layer sequence ( 12, 13, 14 ), which adheres to the substrate ( 15 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of electroluminescence lamps and displays, which are designed on the principle of an electrical capacitor. The invention relates to a method for the production of a luminescence apparatus as claimed in the precharacterizing clause of claim  1 , and to a luminescence apparatus produced according to the method. 
         [0003]    2. Prior Art 
         [0004]    Electroluminescence lamps and displays which are designed on the principle of an electrical capacitor and have a dielectric intermediate layer which is arranged between two electrodes and can be excited to illuminate by an AC voltage of, for example, 100 V have been known for a relatively long time and are being increasingly used for everyday purposes because of their simple design and versatile usage options. For example, they can be used for illumination purposes in automobiles (see for example WO-A1-03/037039 or US-A1-2006/0061138) or for illuminated labels (see for example U.S. Pat. No. B1-6,624,569) or as flexible lighting which can be applied to a fabric or the like (see for example WO-A1-98/30069). 
         [0005]    The layer sequence which is actually optically active and comprises a rear electrode, an intermediate layer and a (transparent) front electrode is normally applied to a mechanically robust substrate, for example a flexible film, and is used together with the substrate (see for example U.S. Pat. No. 5,019,748 or US-A1-2002/0190636). If the layer sequence which has been applied to a substrate is shaped three-dimensionally for use using a thermoforming process followed by spraying, as is described in the abovementioned documents WO-A1-03/037039 and US-A1-2006/0061138, limits relating to the bending radii which occur in this case in the apparatus must be complied with in order to prevent damage to the layers and thus deterioration or even partial or complete failure of the lighting function. Since the layer sequence is applied to a substrate, when the overall apparatus comprising the optically active layer sequence and the substrate is bent, the neutral plane is shifted, which is neither stretched nor compressed, towards the substrate as a result of which those layers which are furthest away from the substrate in the layer sequence are loaded more severely during bending. 
         [0006]    Furthermore, the substrate restricts the options for use of the electroluminescence apparatus, because it introduces an additional layer and an additional material into the apparatus, to which attention must be paid during use. 
         [0007]    WO-A1-98/30069, which has already been cited, proposes an elastomeric electroluminescence lamp in which the electroluminescence apparatus, which is in the form of a lamp, is first of all produced on a transfer paper (transfer release paper  102 ) and is then provided with an adhesive layer ( 116 ) on the upper face. The electroluminescence apparatus can then either be transferred directly from the transfer paper to an application and integrated, or an adhesive layer is first of all applied to the upper face, for example containing a hot adhesive and ensuring permanent surface adhesion of the electroluminescence apparatus to substances, pieces of clothing or the like. In this case, however, the electroluminescence apparatus comprises not only the optically active layer sequence of the transparent front electrode (ITO layer  106 ), electroluminescence layer ( 108 ), dielectric layer ( 110 ) and rear electrode ( 112 ), but also a closed sheath, which comprises two comparatively thick sheathing layers ( 104 ,  114 ). The lower sheathing layer ( 104 ) is produced from polyurethane by repeated application (printing), in such a way that it results in a monolithic layer thickness after curing, and therefore acts as a mechanically robust substrate. This also applies to the upper sheathing layer ( 114 ). Overall, this results in a comparatively thick monolithic sheath which makes the electroluminescence apparatus mechanically naturally robust, independently of the transfer paper, but on the other hand restricts the options for use. 
         [0008]    WO-A1-97/26673 also discloses a method for the production of an electroluminescence lamp in which a transparent substrate, which is coated with a transparent conductive layer, and a temporary substrate are produced separately, and a rear electrode, a dielectric layer and a phosphor layer are then successively applied to the temporary substrate using a rolling application technique, and both parts are finally laminated together with the phosphor layer on the conductive layer. On the one hand, splitting the production process between two substrates makes it possible to simplify the application of the layers. On the other hand, however, the choice of final substrates is greatly restricted because they must be suitable for supporting an electrode (in this case the transparent front electrode). 
       SUMMARY OF THE INVENTION 
       [0009]    The object of the invention is therefore to specify a method for the production of an electroluminescence apparatus as well as an electroluminescence apparatus which has been produced according to the method and is designed on the principle of an electrical capacitor, which avoid the disadvantages of known methods and are distinguished in particular by particular simplicity, and cover a considerably broader field of application. 
         [0010]    The object is achieved by the totality of features in claims  1  and  22 . The essence of the invention is to produce a functional layer sequence, which is reduced to what is absolutely necessary, comprising a rear electrode, an optically active dielectric and a front electrode, on an auxiliary mount, using very simple means, which layer sequence is not naturally robust because of its thinness, and can be applied to the final point of use only by direct transfer from the auxiliary mount. In particular, in this case, the assembly formed therein comprising the layer sequence and the substrate can be shaped three-dimensionally at the same time in the second step. 
         [0011]    One refinement of the method according to the invention is characterized in that the first electrode layer, the intermediate layer and the second electrode layer are applied successively to the auxiliary mount within the first step, in that the individual layers of the layer sequence are printed onto the auxiliary mount by means of a printing method, and in that the layers of the layer sequence are printed onto the auxiliary mount by means of screen printing. 
         [0012]    Another refinement is distinguished in that in order to form the optically active dielectric intermediate layer, at least one dielectric layer and one electroluminescence layer are applied to the auxiliary mount in this sequence or the opposite sequence. 
         [0013]    As an alternative to this, in order to form the optically active dielectric intermediate layer, a dielectric material with inclusions which are embedded therein and can be excited for electroluminescence can be applied to the auxiliary mount. 
         [0014]    According to one preferred refinement of the invention, at least one of the two electrode layers is in the form of an optically transparent electrode, with either the first electrode layer or the second electrode layer being in the form of an optically transparent electrode. 
         [0015]    According to a further refinement, an additional layer can be applied first of all, before the layer sequence with the two electrode layers and the intermediate layer located between them is applied to the auxiliary mount, which additional layer can fulfill a very wide range of different objects. In particular, the additional layer may be an insulation and/or adhesion layer. 
         [0016]    An separation layer can also be applied as the additional layer and enables or simplifies the separation of the layer sequence and the auxiliary mount. 
         [0017]    In particular, the separation layer can remain on the auxiliary mount when the auxiliary mount is detached. 
         [0018]    However, it is also feasible for the separation layer to be in the form of an electrically insulating layer and to remain as an insulating cover on the first electrode layer when the auxiliary mount is detached. 
         [0019]    Furthermore, it is feasible that an insulation/adhesion layer is introduced between the layer sequence and the substrate, for insulation and/or better adhesion of the layer sequence on the substrate, with the insulation/adhesion layer preferably being applied to the second electrode layer before the second step. 
         [0020]    According to another refinement of the invention, conductive organic materials, in particular conductive polymers, are used to form at least one of the electrode layers. 
         [0021]    However, it is also feasible that conductive inorganic substances from the range comprising silver, carbon, indium tin oxide (ITO), pigments based on mica with a conductive sheath (Minatec®) are used to form at least one of the electrode layers. 
         [0022]    A material from the range comprising wood, fabric, in particular wool or cotton, metal, plastic, in particular PVC, polyamide, polyester, polystyrene, PP; PUR, PE, polycarbonate, ABS, PMMA, rubber, paper, leather, cork and glass is preferably used as the substrate. 
         [0023]    One preferred refinement of the electroluminescence apparatus according to the invention is characterized in that the overall thickness of the layer sequence is about 50 μm. 
         [0024]    A particularly good stretching capability of the electroluminescence apparatus according to the invention, and thus far better flexibility and reliability in use can be achieved if, according to one particularly preferred refinement, the layers of the layer sequence each contain a highly flexible binding agent, in particular based on PU, PMMA, PVA. 
         [0025]    According to one development, an additional layer with insulation and/or adhesion characteristics is arranged on at least one face of the layer sequence. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0026]    The invention will be explained in more detail in the following text with reference to exemplary embodiments and in conjunction with the drawing, in which: 
           [0027]      FIG. 1  uses a number of figure elements  1 ( a ) to  1 ( g ) to show various steps in a production method according to a first exemplary embodiment of the invention; 
           [0028]      FIG. 2  uses a plurality of figure elements  2 ( a ) to  2 ( g ) to show various steps in a production method according to a second exemplary embodiment of the invention, with the figure elements  2 ( f ) and  2 ( g ) relating to alternative refinements; 
           [0029]      FIG. 3  uses a number of figure elements  3 ( a ) to  1 ( f ) to show various steps in a production method according to a third exemplary embodiment of the invention; and 
           [0030]      FIG. 4  uses a plurality of figure elements  4 ( a ) to  4 ( d ) to show various steps in a production method according to a further exemplary embodiment of the invention, in which reinforcement of the transparent electrode layer is provided in order to make better contact. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    A plurality of simplified figure elements  1 ( a ) to  1 ( g ) in  FIG. 1  show various steps in a production method according to a first exemplary embodiment of the invention. The method which is illustrated in  FIG. 1  is based on an auxiliary mount  11  (which in particular is like a film) with anti-adhesion characteristics, for example a conventional baking paper or a lightly siliconized paper, as is used as a mount for self-adhesive labels ( FIG. 1   a ). Other types of auxiliary mounts can, of course, also be used provided that they either themselves have anti-adhesion characteristics or—as explained further below in conjunction with FIG.  2 —can be coated with a suitable separation layer. By way of example, it is feasible for the auxiliary mount  11  to be based on PUR, EP, co-polyamide, TPU, co-polyester, PP, PE or EVA. 
         [0032]    A first electrode layer  12  ( FIG. 1   b ) is applied, in particular by means of screen printing, to the auxiliary mount  11  in a first step. The nature of the first electrode layer  12  is governed by whether the electroluminescence apparatus ( 10  in  FIG. 1   g ) is formed from the front face (illumination face) or from the rear face. If the electroluminescence apparatus  10  is formed from the front face, the first electrode layer  12  must be optically transparent. A multiplicity of different materials and options are available for this purpose. Organic and inorganic systems may be considered as transparent electrode materials:
       organic, water-based: the intrinsically conductive polymer (ICP) which is known by the trade name Baytron®P with binding agents based on PU/polyester/polyether;   organic, solvent-based: the intrinsically conductive polymer (ICP) known by the name Ormecon® based on polyaniline;   inorganic: indium tin oxide (ITO);   inorganic: the lacquer pigment which is known by the trade name Minatec® and based on mica flakes, which are coated with an electrically conductive inorganic layer composed of a mixture of metal oxides.       
 
         [0037]    If the electroluminescence apparatus  10  is formed from the rear face, the first electrode layer  12  may be opaque. In this case, Ag or C may be used as the electrode material and, for example, are dispersed as a filler in the form of powder in a suitable binding agent. 
         [0038]    Once the first electrode layer  12  has dried or set, the optically active, dielectric intermediate layer  13  can be applied, likewise by means of screen printing ( FIG. 1   c ). The intermediate layer  13 , which contains the actual electroluminescence material, for example doped zinc sulfide crystals, may be in the form of a homogeneous layer, as is illustrated in the enlarged illustration on the left-hand side of  FIG. 1   g . The crystal grains are in this case homogeneously embedded in a matrix of dielectric material. However, the intermediate layer  13  may also be a layer sequence comprising at least one separate dielectric layer  13   a  (without electroluminescence material) and an electroluminescence layer  13   b,  as is indicated in the enlarged illustration on the right-hand side of  FIG. 1   g . In this case, the sequence of the two layers may change. 
         [0039]    Once the intermediate layer  13  has been completed, the second electrode layer  14  can be applied by means of screen printing, as the next layer ( FIG. 1   d ). If the second electrode layer  14  represents the rear electrode, Ag in particular can be used for this purpose. If, in contrast, it is the front electrode, the optically transparent materials mentioned above must be used in an appropriate manner. Apart from this, it is also feasible for both electrode layers  12 ,  14  to be optically transparent, such that, in principle, the electroluminescence apparatus  10  emits light on both faces. 
         [0040]    The finished layer sequence  12 ,  13 ,  14  on the auxiliary mount  11  can now be transferred at its point of use to a (robust) substrate  15  that is provided there ( FIG. 1   e ). In this case, the layer assembly  11 , . . . ,  14  from  FIG. 1   d  is reversed, that is to say it is placed with the second electrode layer  14  on the substrate  15  first and is then connected over an area to the substrate  15 , under the influence of pressure and/or heat (indicated by the arrows in  FIG. 1   e ).  FIG. 1  shows the substrate  15  as a simple flat plate. The substrate  15  may, of course, also be three-dimensionally contoured, as a result of which the layer assembly  11 , . . . ,  14  must be shaped and adapted three-dimensionally. In the same way, however, a three-dimensional shape or contour can also be applied at the same time during connection of the layer assembly  11 , . . . ,  14  and substrate  15  in order in this way to produce a three-dimensionally contoured or shaped electroluminescence apparatus from the initially flat layers  12 , . . . ,  14  and the initially flat substrate  15 . The thinness of the layer sequence  12 , . . . ,  14 , whose thickness is less than 100 μm, preferably about 50 μm, makes a significant contribution to the layer sequence being extraordinarily flexible and adaptable, and it can even be stretched comparatively far without the lighting function deteriorating or being entirely lost. 
         [0041]    The layer sequence  12 , . . . ,  14  can be transferred as an entity or else partially onto substrates  15  composed of different materials. These materials may comprise substances (fabrics), wood, metal, in particular aluminum, paper, leather, cork, glass etc. If it is not possible to form an autonomous assembly between the second electrode layer  14  and the substrate in this case, an additional insulation/adhesion layer  17  must be provided between the two, as shown in  FIG. 3 . Assemblies are possible for substrates  15  composed of PVC, polyamide, polyester, polystyrene, PP, PUR, PE, polyamide, polycarbonate, ABS, PMMA, PS, rubber, neoprene, cellulose acetate, aramid, wool, cotton. 
         [0042]    Once the layer sequence  12 , . . . ,  14  has been permanently adhesively connected to the substrate  15 , the auxiliary mount  11  can be removed ( FIG. 1   f ), as a result of which the substrate  15  remains, with the layer sequence  12 , . . . ,  14  adhering to it ( FIG. 1   g ). Contact can be made with the two electrode layers  12  and  14  in a manner which is known per se and is not described in any more detail here. If the second electrode layer  14  is the (optically transparent) front electrode, the light passes through the substrate  15  provided that it is appropriately transmissive. For example, it is feasible to use as substrate  15  a thin wood veneer which is transparent because of its thickness, and accordingly can be illuminated from the rear. This allows attractive lighting effects to be produced for example in the case of wooden inserts in the interior of an automobile. 
         [0043]    If the aim is for the electroluminescence apparatus  10  to be used as a display, graphics elements (scripts, arrows or the like) can be formed in the layer assembly and provide appropriate information. The graphics elements may be formed by suitable structuring of one or more of the layers  12 , . . . ,  14 . However, it is also feasible to introduce further layers, for example covering layers or the like, which are provided exclusively in order to form the graphics elements. 
         [0044]    Within the scope of the invention, it is also feasible, as shown in  FIG. 2 , to first of all provide the auxiliary mount  11  with an additional layer, in particular an separation layer  16  ( FIG. 2   a ) before the same measures are carried out in the further steps ( FIGS. 2   b - 2   e ) as those which have already been explained further above in conjunction with  FIGS. 1   b - 1   e . The separation layer  16  can be removed together with the auxiliary mount  11  on separation of the auxiliary mount  11  ( FIG. 2   f ). This then results in the already known electroluminescence apparatus  10 . 
         [0045]    However, it is also feasible to leave the additional layer or separation layer  16  as (for example an electrically insulating) covering layer on the layer apparatus  12 , . . . ,  14  when the auxiliary mount  11  is separated ( FIG. 2   g ). This then results in the electroluminescence apparatus  10 ′ whose first electrode layer  12  is covered on the outside. However, the additional layer may also have adhesion characteristics which are used when the layer apparatus  12 , . . . ,  14  is also intended to be connected to a substrate on this face. 
         [0046]    Furthermore, as shown in  FIG. 3  and analogously to  FIGS. 1   a - 1   d , it is feasible to apply the layer sequence  12 , . . . ,  14  to the auxiliary mount  11  first of all ( FIGS. 3   a - 3   d ), but then to apply an insulation/adhesion layer  17  to the second electrode layer  14 , which insulation/adhesion layer  17  may have an adhesion-promoting and/or insulating effect between the second electrode layer  14  and the substrate  15  ( FIG. 3   e ). This results in the electroluminescence apparatus  10 ″ ( FIG. 3   f ). 
         [0047]    The optically transparent electrode layer of the layer apparatus  12 , . . . ,  14 , that is to say for example the first electrode layer  12 , is preferably applied very thin, with a thickness of about 5 μm. In order to allow a reliable and permanent contact in this case when contact is subsequently made with the electrode layer, an electrically highly conductive reinforcing layer is arranged in selected areas on the electrode layer, as is illustrated in  FIG. 4  using the example of the first electrode layer  12 . As shown in  FIGS. 4   a  and  4   b,  the reinforcing layer  18  is first of all applied to the auxiliary mount, and its thickness is in the same order of magnitude as the thickness of the first electrode layer. In the example, the reinforcing layer  18  is in the form of an annular busbar which surrounds the entire surface, in order to allow contact to be made uniformly and with low resistance with the entire surface on the first electrode layer  12 . 
         [0048]    The first electrode layer  12  is then ( FIG. 4   c ) printed on and this is then followed by the rest of the procedure according to the steps in  FIGS. 1   c  to  1   f  in order finally to end, in the case of the electroluminescence apparatus  10  shown in  FIG. 4   d,  with the reinforcing layer  18  applied to the transparent front electrode (electrode layer  12 ). 
         [0049]    As has already been indicated further above, the electroluminescence apparatus is distinguished by particularly good flexibility and a good stretching capability without the individual layers becoming detached from one another, or cracking. The capability to stretch the apparatus can be enhanced even further if a specific material is chosen for the individual layers. 
         [0050]    The material of the front electrode (electrode layer  12  or  14 ) may for this purpose in particular be an electrically conductive material on an inorganic or organic basis, for example Baytron® and/or polyaniline and/or polypyrrole, which is modified with highly flexible binding agents, for example based on PU, PMMA, PVA. By way of example, the dielectric intermediate layer  13  may then be composed of a mixture of ZnS, BaTiO3 and the highly flexible binding agents that have been mentioned. The material of the rear electrode (electrode layer  14  or  12 ) may then be an electrically conductive material on an inorganic or organic basis, for example Baytron® and/or polyaniline and/or polypyrrole, once again modified with highly flexible binding agents, for example based on PU, PMMA, PVA. In order to improve the electrical conductivity, the material of this electrode layer  14  or  12  may have silver or carbon added to it, and/or may have a layer composed of these materials added to it. 
         [0051]    The composition of the individual layers  12  to  14  as described above ensures not only immovable adhesion of said layers to one another, but also a stretching capability, which it has not been possible to achieve in the past, of said layers of up to 100%.