DE10255199A1 - Laminated panel with rigid pane(s) and flat, electrically controllable functional electro luminescent light element - Google Patents

Abstract

In addition to the electroluminescent element (2) there is also at least a conductive film (5), which can be supplied and heated by voltage, independently of electricity supply of the luminescent element. Pref. the film can be automatically supplied with voltage in dependence on temp. control (10) supplied temp. signal of a temp. sensor (11), which is spatially allocated to luminescent element for detecting its temp.

Description

The invention relates to a method for producing a multilayer element with a transparent surface electrode and an electroluminescent lighting element (EL element) with the features of the preamble of claim 1.

A multi-layer element is a unit from a carrier substrate and the in consisting of several layers, applied to the carrier substrate, understood laminated or printed EL element.

To achieve the highest possible luminosity of the EL element, one for the visible light emitted to him requires the most permeable surface electrode possible. The latter is generally included in the layers of the functional element and forms it mostly the interface between the carrier substrate and the functional element.

Highly permeable materials for the emitted visible light are used as the carrier substrate, z. As glass, plastic panes (e.g. polycarbonate) and plastic films (PET polyethylene terephthalate). Are plastic films as the actual carrier substrate used, they can easily stare after assembly of the EL element Substrates are laminated.

The EL element built on its carrier substrate can be used to form an Composite element at least one intermediate adhesive layer and another (rigid) Follow cover layer. It is not absolutely necessary to place the EL element between to embed two rigid panes of a composite pane, but one becomes this Prefer arrangement with regard to the quite high supply voltage for safety reasons. Embedding in a laminate also secures the EL element against mechanical influences as well as against the ingress of moisture and dirt Could cause interference. Is only transparency or light emission to one side on the other hand, non-transparent rigid ones can of course also be used Disks of whatever material are used.

The basic principles of electroluminescence have long been known. A detailed documentation of this technology along with application examples, Material descriptions and light colors that can be generated can be found at the Internet address "http: / / www.dupont.com/mcm/luxprint/about.html" (as of November 2002) for Available so that there is no need to go into details here.

EL elements are therefore mostly produced by screen printing. You can do this first coat the substrate with the transparent electrode (preferably by Sputtering) to which the luminous function layer is applied. This is followed by the dielectric layer, e.g. B. from barium titanate, which has a very high dielectric constant, and then the second electrode, which does not have to be transparent. It consists of one highly electrically conductive metal, such as preferably silver.

The light emission of an EL element starts as soon as the functional layer is in one electrical (alternating) field established between the two electrodes. Where the exact dielectric separation of the electrodes is of secondary importance Importance. However, it must be ensured that no breakthroughs occur anywhere occur because this immediately leads to a local, later spreading destruction of the Functional layer can lead.

The electrical field strength in a printed thick-film EL element can be in the Order of magnitude of some 106 V / m. If the insulation is too weak, it can be too Punctures come in, which show up in the form of black dots or spots. In the Practice is used e.g. B. UV-curing, screen-printable lacquers as additional Isolation or dielectric layer.

EP-A1-0 267 331 describes a composite pane for vehicles with a composite Adhesive layer embedded characters known, which is represented by an EL element or is backlit. The required electrical leads are practically invisible through thin, transparent metallic or oxide conductor tracks or layers represented within the network. After switching on the supply voltage, that seems Illuminated signs without visible leads floating in the window. The said Document discloses two different variants of the EL elements. At the first are both live electrodes are provided on the same substrate bridged by the lighting element, which in turn comprises a bridge electrode. electrical considered, two capacities connected in series are formed. In the second The design is one of the two on both inner surfaces of the composite pane Electrodes applied as a transparent thin layer and is the lighting element between them arranged in addition to the dielectric separating layer.

Here, as in many other cases, the transparent electrodes consist of EL elements very preferably made of indium tin oxide (ITO), the light-emitting (phosphor) Layer to achieve high luminosity directly on this electrode is applied.

A variety of solutions have also been proposed in which the transparent electrode for various reasons also as a multi-layer system is carried out, in which a dielectric layer adjoins the EL functional layer. At a such distribution of the dielectric layers on both sides of the luminescent layer must the sum of the insulation effects should be sufficiently large.

Especially in the case of thin-film EL elements with an overall low layer thickness it is known (e.g. US-A-6036823, US-A-6358632), layers as thin as possible dielectric constants as high as possible on both sides of the actual EL functional layer provided. This is intended to penetrate the electrical field through the Functional layer can be avoided.

DE-A1-198 25 435 describes an EL arrangement in which thick-film technology is used dielectric layers are arranged on both sides of the EL luminescent layer. There too various measures to influence the color of the emitted light specified.

From various descriptions, highly transparent multiple Layer systems are known, the core of which is electrically conductive metallic or doped Comprise metal oxide thin layers and which are essentially characterized by heat-insulating or -Distinguish reflective properties. With a suitable arrangement of Electrodes, these layer systems can also serve as electrical surface heating, if a current is passed over the extension of the conductive layer, which results as a result of their ohmic resistance warmed. Generally, such include known ones Layer systems also dielectric single or multiple layers, e.g. B. of silicon nitride, etc., the can of course be pierced for electrical contacting of the conductive layers have to. Such layer systems are also already used as antennas.

In the older German patent application 101 64 063.3 is a composite element with a rigid transparent disc, a transparent one attached to it Surface electrode and a flat multilayer EL lighting element described, the transparent surface electrode using additional electrical connections as a heating layer for Setting predetermined temperatures of the EL lighting element can be used. On such composite element can, for. B. can be used as a glass roof in a vehicle illuminates the passenger area as an interior light in the dark.

In an industrial production of flat EL elements, the dielectric must be one EL elements can be printed in two or more passes to achieve the necessary To achieve thickness and insulation. Because the coating after each print must be dried, there are very cumbersome waiting times. Screen printing on curved substrates is complex anyway.

The invention is therefore based on the object of specifying a method by which the Number of printing processes when printing functional layers of an EL element can be reduced on a substrate.

This object is achieved with the features of claim 1. The features of the subclaims give advantageous developments of the method according to the invention.

Accordingly, the EL element is built on a transparent thin-film electrode, which already has at least part of the dielectric separating layer of the EL element includes. Between the actual, electrically conductive electrode layer and the EL Luminous layer is arranged at least one dielectric (partial) layer.

The dielectric layer on top of the transparent surface electrode acts as additional insulator against breakdowns. Using a dielectric Layer system with the insulator described here on the surface, the printing thickness of the dielectric layer to be printed later can be considerably reduced, if necessary a second screen printing operation to apply a layer of lacquer (UV-curing Color). The function of the second dielectric layer may even be possible completely from the dielectric layer on the transparent surface electrode be taken over if their insulation effect is sufficient Light transmission is large enough.

With dielectric interference layer systems, surface resistances of 4-6 Ohm / square and less reached. In contrast, usual thin (transparent) ITO layers surface resistances between 50 and 100 ohms / square. Since the Sheet resistance in the equivalent circuit diagram of an EL element is equal to the series resistance that purely real and for the active power, i.e. the power loss converted into heat, is responsible, the active power and thus the heat development of an EL element by using a surface electrode with a greatly reduced surface resistance in the Comparison with an ITO surface electrode can be reduced many times over.

At the same time, through a targeted selection of materials and layer thicknesses, the layer system forming transparent surface electrode also the visual perception of the (switched off) EL element as well as the perceptible color of the emitted light can be adjusted. Commercial EL luminescent layers correspond in color not necessarily the end customer's ideas.

Should the capacity of the two surface electrodes on both sides of the functional layer formed capacitor can be maintained, so with the use of a very thin dielectric layer at the location of a relatively thick printed dielectric layer also the thickness of the latter can be reduced to the entire Adapt dielectric constant to the reduced gap width of the capacitor. Important is while the insulating layer is isotropic, i. H. the same in all directions possesses dielectric properties and is free of "pinholes".

It is not absolutely necessary to place the electrode layer system on a rigid surface Build up substrate. Rather, the layer system can also be used on a thin plastic Carrier film, e.g. B. deposited from polyethylene terephthalate (PET) and using a suitable adhesive layer can be connected to a rigid substrate. This too is however known per se, so that there is no need to go into this here.

If the EL element is to be printed on a curved glass substrate, then to build up the transparent electrode preferably from a layer system that the withstands high temperatures (approx. 650 ° C) when bending the glass.

Particularly in the latter case, the EL element can be particularly advantageous with such Layers are built up, which in turn are so highly thermally resilient that they after the surface electrode has been deposited, printed onto a flat glass substrate and the temperatures during the subsequent bending treatment are harmless can endure. The possibly printed dielectric layer and the second Surface electrodes are already available with such properties; that is currently being investigated Thermal behavior of suitable EL luminescent layers.

The layer system forming the transparent surface electrode has a further advantage a high thermal insulation effect. This affects z. B. very positive with with EL elements provided glass roof panels for vehicles by the subjective Vehicle occupants' sense of warmth is improved.

In general, a suitable layer system can be used as a heat-resistant solar and / or IR-reflective layer based on silver or other conductive Circumscribe metals.

A layer system that is particularly suitable for the application described here consists of the following layer sequence: substrate-Si ₃ N ₄ -ZnO-Ti / Ag-ZnO-Si ₃ N ₄ - ZnO-Ti-Ag-ZnO-Si ₃ N ₄ . This is resistant to high temperatures, so it can be applied to a glass pane before it is bent and / or tempered, and it has the desired properties in optical (transparency, color) and electrical (sheet resistance, dielectric constant) respects.

The mechanical and chemical resistance of a thin-film system to increase it is also known, in particular the upper anti-reflective layer or a partial layer of the top anti-reflective layer, especially the top one Top layer to form as a mixed oxide layer, that is, as one of several oxides composite layer. This can increase the hardness and chemical resistance of the layer system can be improved.

According to EP-B1-0 304 234, the mixed oxide layer consists of at least two metal oxides, one of which is an oxide of Ti, Zr or Hf, and the other of which is an oxide of Zn, Sn, In or Bi.

EP-A1-0 922 681 describes the formation of the upper anti-reflective layer from two partial layers, of which the upper partial layer consists of a mixed oxide based on zinc and aluminum, in particular with a ZnAl ₂ O ₄ spinel structure.

DE-C1-198 48 751 describes a layer system with a mixed oxide layer that is related on the total metal content 35 to 70 wt% Zn, 29 to 64.5 wt% Sn and 0.5 to 6.5% by weight of one or more of the elements Al, Ga, In, B, Y, La, Ge, Si, As, Sb, Bi, Ce, Contains Ti, Zr, Nb and Ta.

Layer systems with mixed oxide layers of the composition Sn _1-x Zn _x O _{y are} known from US Pat. No. 4,996,105. The mixed oxide layers are sputtered from a stoichiometric zinc-tin alloy in which the ratio Zn: Sn = 1: 1 at%.

The documents EP-A1-0 464 789 and EP-A1-0 751 099 also describe Layer systems with anti-reflective layers made of mixed oxides. In this case, the Mixed oxide layers based on ZnO or SnO an addition of Sn, Al, Cr, Ti, Si, B, Mg or Ga.

Layer systems with a high thermal load are also known in various designs. In a first group of layer systems which can withstand high thermal loads, the anti-reflective layers each consist of Si ₃ N ₄ , which are separated from the functional layer made of silver by thin sacrificial metal layers made of CrNi. The layer system described in EP 0 883 585 B1 also belongs to this group, but in this case the sacrificial metal layer consists of Si. Such layer systems are thermally very stable, but are very expensive to manufacture because of the known problems in sputtering nitrides. In addition, the sputtering of relatively thick Si ₃ N ₄ layers is not without problems because of mechanical stresses in the layers.

Of course, the transparent layer can be used to create the conductive layer system Electrode also other technologies, e.g. As plasma CVD can be used with which in Compared to sputter technology, thicker layers can be achieved.

The second group of thermally highly resilient layer systems includes those which, in addition to nitridic layers such as Si ₃ N ₄ or AIN, also have oxidic layers, particularly in the area of the outer layers. For example, DE 196 40 800 C2 describes a layer system in which an intermediate layer made of a nitride or oxynitride made of the metal of the sacrificial metal layer is arranged between the metallic blocker layer and the oxide or nitride cover layer. Another layer system of this type known from DE 101 05 199 C1 is characterized in that a layer of Si ₃ N ₄ or AlN is arranged between the silver layer and the sacrificial metal layer. In the layer system known from EP 0 834 483 B1 there is an at least 5 nm thick intermediate layer made of TiO ₂ between a sacrificial metal layer made of Ti and the cover layer, and on this intermediate layer a cover layer of an oxide, nitride or oxynitride of Bi, Sn, Zn or a Mixture of these metals arranged.

In a third group of layer systems that can withstand high thermal loads, there are individual layers with the exception of the functional layer and the sacrificial metal layer purely oxidic layers. Oxidic layers are usually simpler and more economical producible as nitridic. However, the sacrificial metal layer has one in these cases relatively large thickness. A layer system of this type is e.g. B. in DE 198 52 358 C1 described. In this case, the sacrificial metal consists of an aluminum alloy one or more of the elements Mg, Mn, Cu, Zn and Si as an alloy component.

This extensive presentation shows that there are a variety of Layer systems that exist as a surface electrode for the present application EL elements can be suitable; the selection or modification of a suitable one Layer systems in the present context only require routine examinations and tests of the professionals concerned.

Further details and advantages of the subject matter of the invention emerge from the Drawing of an embodiment and the following in the following detailed description.

They show in a highly simplified, especially not to scale representation

Fig. 1 is a sectional view, at least a portion of the dielectric surface comprising electrode is constructed of a composite disc having a flat electroluminescent element on a transparent,

Fig. 2 is a detailed view of a contact region for making the external connections of the EL element.

Referring to FIG. 1, a highly transparent for visible light layer system 2 is deposited on a surface of a rigid transparent pane 1, the at least one electrically conductive metallic layer 2.1 - preferably made of silver - includes. This layer 2.1 forms the actual transparent surface electrode of the EL element. Additional layers are provided between layer 2.1 and the pane surface, in particular a dielectric anti-reflective layer, e.g. B. from silicon nitride (Si ₃ N ₄ ) and possibly a growth of the silver layer 2.1 favoring zinc oxide layer (ZnO). In particular in a thermally highly resilient layer system, that is, without damage to the softening temperature of glass, layer system, further intermediate layers, e.g. B. blocker or sacrificial metal layers. Through their combination, sequence and thickness, the desired properties of the layer system (adhesion to the substrate / glass, light refraction, transmission and reflection colors, properties of infrared reflection, electrical conductivity, protection of the silver layer (s) against oxidation etc.) are in wide limits can be influenced. Typical sheet resistances of such layer systems are between 2 and 4 ohms / square. Since layer systems of this type, as already mentioned, are well known, the detailed description of the partial layers is omitted here.

Above the electrode layer 2.1 , at least one dielectric layer 2.2 is likewise deposited, which according to the invention forms part of the dielectric of the capacitor, in the field of which the EL element is made to light up. Even in this area, although not shown, further layers, e.g. B. blockers are added, which ensure the desired properties of the entire layer system in production, during further processing and in the installed state reproducibly and permanently. In particular, the composition and combination of the uppermost (top) layers of such a layer system can also achieve high mechanical wear resistance; In particular, layers of Si ₃ N ₄ are suitable as outer cover layers due to their high hardness.

The transmission of the coated pane 1 for visible light is preferably at least 75%. This is a minimum value required for vehicle windshields in Europe.

The glass pane 1 provided with the layer system 2 overall forms the substrate for the EL element. The luminous layer 3 of the EL element is printed on the outer layer of the layer system 2 , preferably using the screen printing method, in such a way that a narrow edge strip of the layer system 2 remains free at least on one side. This edge strip is used to make electrical contact with the electrode layer 2.1 . In a manner known per se, the layer system 2 itself will also be kept a distance of a few millimeters from the edge of the pane in order to avoid corrosion of its metallic layers starting from the edge.

A further dielectric layer 4 was printed over the luminescent layer 3 and finally the second surface electrode 5 of the EL element was printed, likewise preferably using the screen printing method. A conductor track 6 is printed on the exposed edge of the layer system 2 ; this is preferably done in the same operation as printing on the second surface electrode 5 . The conductor track 6 forms the electrical connection for the voltage supply of the transparent electrode layer 2.1 . It is indicated symbolically that the material of the conductor track 6 penetrates the dielectric layer 2.2 . Finally, a pair of cables very simply represents the electrical external connections 7 of the two electrodes 2.1 and 5 . The production of such connections, in particular by soldering, is known per se. For the present application, however, special measures may have to be taken, which will be discussed in more detail in connection with FIG. 2.

The printed layers 3 to 5 and the conductor track 6 are significantly thicker than the individual layers of the layer system and as a whole; the true relationships cannot be shown to scale here. The thicknesses of the printed layers are therefore only partially shown and interrupted by dash-dotted bars. While the total thickness of a layer system of 130 to 180 nm, e.g. B. can vary depending on the desired color, the printed layers 3 , 4 and 5 of the EL element are significantly thicker.

The following table is a comparison of the conventional EL elements as recommended by the manufacturer Dupont and the reduced thicknesses with the transparent electrode modified according to the invention.

It turns out that with a transparent designed according to the invention Surface electrode both the actual luminescent layer and the other layers of the EL elements can be made thinner.

The supply of the EL element with alternating voltage via its two electrodes 2.1 and 5 is symbolically indicated by an arrow denoted by U-, its planar light emission when an alternating electric field is applied by a family of arrows which, starting from the functional layer 3, the layer system 2 and the Pierce disc 1 .

An adhesive layer 8 is provided over the EL element or the second surface electrode 5 , which extends to the outer edge of the pane 1 . It connects a second rigid disk 9 flat to the disk 1 and to the layers applied thereon. The cable pair 7 is also embedded in the adhesive layer 8 . This forms a tight seal of the components of the EL element to the outside. It also protects the layer system 2 because it is bonded directly to the surface of the pane 1 in the uncoated edge area. The adhesive layer can be produced from a meltable thermoplastic film or from a pourable transparent mass, which is filled in a manner known per se into a set space between the two rigid disks 1 and 9 and then cured. It is possible to provide an opaque edge coating, known per se, which is not shown here and which is preferably baked-in screen printing paste and which can also be used for optically laminating the cable connection and, if appropriate, the conductor track 6 in the edge region mentioned. This edge coating would preferably extend so far inwards starting from the outer edge of the pane that its termination runs just below the outer edge of the luminescent layer 3 , it being possible to arrange it above or below the edge of the layer system 2 , ie before or after its deposition is to be brought up. Depending on requirements, the contrast in the transition from the opaque coating to the luminous surface can be resolved in a manner known per se by means of a grid-like gradation.

Of course, structures or subdivisions can also be provided in the visible light field of the EL element, if this is desired. In a particularly simple manner, this would be possible by expanding the edge coating mentioned, by creating a pattern on the surface of the pane 1 (before or after the deposition of the layer system 2 ) in the same operation.

In Fig. 2 in detail, an embodiment is shown of a connection area for the EL element, which is particularly suitable for incorporation in a laminated pane. You can see the coated surface of the pane 1 from above.

In industrial practice, deviating from the greatly simplified representation of the line feed in FIG. 1, a contact field 10 is placed on the rigid disk 1 , if possible on its edge, in a manner known per se, on which the contact surfaces to be connected to the outside are brought together in close proximity , The advantage of simultaneous, possibly automated soldering to the line sections leading to the outside is thus achieved. A representation of such a multiple connector panel can be found e.g. B. in DE-C2-195 36 131.

In order to achieve the most homogeneous possible introduction of voltage into the transparent surface electrode 2 in the present application, the conductor track 6 is practically guided as a frame around the entire surface of the EL element. This frame is interrupted in the region of a conductor track section 6 ′ as a connection to the second surface electrode 5 . The electrical connection between this conductor 6 'and the surface electrode 5 is of course also in the interest of introducing the electrical potential into this surface as homogeneously as possible, although because of the greater thickness of the surface electrode 5 - compared to the thickness of the transparent surface electrode 2 - and their lower surface resistance no special requirements are to be made.

In the exemplary embodiment, the section 6 'was simply produced simultaneously with the surface electrode 5 and the conductor track 6 by screen printing an electrically conductive paste in the same operation. In order to avoid malfunctions, the contact area 10 , on which the solder contact points for the external connections 7 (indicated here only by dash-dotted lines) are removed from the coating 2 (or not coated at all). When introducing this connection into a pane assembly analogous to FIG. 1, the area between the underside of the ribbon conductor and the pane surface must be carefully sealed, e.g. B. using an adhesive.

Claims (9)

1. A method for producing a multilayer element with a transparent surface electrode ( 2 ), an electroluminescent luminescent layer ( 3 ) and a second surface electrode ( 5 ), the two electrodes being provided with electrical connections ( 6 , 7 ) for applying a voltage (U) are characterized by the following steps: - To form the transparent surface electrode, a thin film system ( 2 ) is applied to a substrate ( 1 ), which comprises at least one electrically conductive partial layer ( 2.1 ) and a subsequent dielectric partial layer ( 2.2 ); - On the thin layer system ( 2 ) an EL light layer ( 3 ) and at least the second surface electrode ( 5 ) are applied in succession by screen printing; - The two surface electrodes ( 2.1 , 5 ) are each connected to an electrical connection element ( 7 ) for connection to the voltage source. 2. The method according to claim 1, wherein a further dielectric layer ( 4 ) is printed between the EL luminescent layer ( 3 ) and the second surface electrode ( 5 ). 3. The method according to claim 1 or 2, characterized in that the transparent surface electrode ( 2 ) is produced by applying a thermally highly resilient, in particular suitable for bending and / or tempering temperatures of glass thin layer system with at least one conductive sub-layer ( 21 ). 4. The method of claim 1 or 2, characterized in that a conductor track (6) is printed to connect the transparent surface electrode (2) to the voltage source on a partial area of the transparent surface electrode (2). 5. The method according to claim 4, characterized in that the conductor track ( 6 ) is printed in the same operation as the second surface electrode ( 5 ). 6. The method according to any one of the preceding claims, characterized in that in the area of a contact field ( 10 ) for making electrical external connections ( 7 ) of the two electrodes ( 2 , 5 ) the thin-film system ( 2 ) locally recessed, that is not applied or after the whole area Application is removed. 7. The method according to any one of the preceding claims, characterized in that a cover layer made of silicon nitride is applied as the dielectric partial layer ( 2.2 ) of the layer system ( 2 ). 8. The method according to any one of the preceding claims 1 to 7, characterized in that the layer system is constructed as follows: substrate-Si ₃ N ₄ - ZnO-Ti / Ag-ZnO-Si ₃ N ₄ -ZnO-Ti-Ag-ZnO -Si ₃ N ₄ . 9. The method according to any one of the preceding claims 1 to 6, characterized characterized in that an oxide or oxynitridische as a dielectric sublayer Layer is applied.