DE102012016377B4 - Process for the formation of areal structured electrodes - Google Patents

Abstract

A method for forming areal structured electrodes, wherein provided on the surface of a substrate (4) with a first layer (3) consisting of a printable material applied by a thick-film method, wherein a layer thickness of 50 nm to 20 microns is to be maintained; Subsequently, a material removal is carried out with a laser beam, in which in the first layer (3) a trench-shaped recess (5) is formed, which forms a steep flank angle with the side walls of the recess, which is sufficient for an electrical potential separation for at least one in a following step as another on the first layer (3) applied layer (2), which forms an electrode to reach.

Description

The invention relates to a method for forming areal structured electrodes, as they can be used in particular in multi-layered structures. Such electrode structures can be used in particular in organic light emitting diodes (OLEDs) or organic photovoltaic elements (OSC's, OPV's).

In many applications where a planar electrode structure is needed, their patterning / disruption is a challenge if the underlying layers / materials are not allowed to be damaged and shadow masking does not meet the requirements. Important areas of application for solving this problem are OLEDs and organic solar cells / solar modules.

A solution based on lithography processes are so-called cathode separators, which are used in the production of passive matrix (PM) OLED displays for row structuring.

The use of electrode separators may be useful in many variations with different objectives.

That's how it is DE 10 2010 013 755 A1 a method is known in which the production of such separators by means of photolithography on a special, generally applied over the entire surface of the substrate coating layer, which is also referred to as a photoresist, takes place. In the prior art, a protective mask is often applied to an attackable material for structuring in order to prevent the dissolution of the vulnerable material with a solvent. However, this is very complicated and requires a lithography method with many individual steps to be performed.

At the DE 10 2010 013 755 A1 In a known technical solution, the process is simplified by applying two polymers / resists in a structured manner and the first deposited material being more susceptible to an etchant by an etching step than the one above. What remains is a cross-section "mushroom-like" structure, on the flank of which the electrode tears off. As a manufacturing method z. As ink-jet, flexo, screen or gravure printing proposed. But there are some major disadvantages.

Either complicated lithography processes are required, or in conventional printing processes their resolution and reliability is limited. In the latter case, an attackable material is patterned on the substrate and its surface area rendered unassailable by directional irradiation except for the lateral edges for a later etching step. After the etching step, a narrower ridge of the vulnerable material remains under the "unassailable" surface area.

From the not pre-published DE 10 2011 106 390 A1 It is known to form on a substrate at least one electrode forming an electrically conductive layer surface. On this electrically conductive layer is an organic single or multi-layer structure, with which the functionality is determined, and on the single or multi-layer structure, a further electrically conductive layer for forming a plurality of further electrodes is formed.

The electrodes, which are formed with the further electrically conductive layer, are separated from each other by at least one electrically insulating element. In this case, electrically insulating element can be applied directly on the surface of the electrode and / or the surface of the substrate. In the case that an electrically insulating member is formed on the surface of the substrate and the electrically conductive layer is deposited after forming electrically insulating members, separation into a plurality of electrodes formed on the substrate surface can also be achieved. The one or more electrically insulating elements have a height and width which projects beyond the further electrically conductive layer forming the further electrodes to such an extent that, when forming the further electrically conductive layer, it readily breaks off the further electrically conductive layer in the upper one Edge region comes and thereby the further layer is segmented into the individual electrodes.

The application of electrically insulating elements can be effected by printing processes, in particular the Aerosoljet printing. Suitable pasty substances are used in order to be able to form insulating elements with a line width of 20 μm and at the same time a height in the same dimension on a substrate surface. This job is complex and it must be maintained a constant consistency of the printing paste.

In WO 2007/135603 A1 Possibilities for electrically separating conductive layers on OLEDs are described.

US 2011/0248219 A1 concerns the production of fine conductor structures on OLEDs with lift-off technology.

It is therefore an object of the invention possibilities for the production of areal structured Specify electrodes with which they can be formed easier and with less effort.

According to the invention, this object is achieved by a method applying the features of claim 1. Advantageous embodiments can be realized with features described in the subordinate claims.

In the invention, the surface of a substrate is provided with a first layer consisting of a printable material applied with a thick-film method, wherein a layer thickness of 50 nm up to 20 μm is to be maintained. Subsequently, a material removal takes place with a laser beam, in which a grave-shaped depression is formed in the layer. In this case, a steep flank angle is to be formed with the side walls of the depression, which is sufficient to achieve an electrical potential separation for at least one layer applied to the first layer in an ensuing process step as a further layer which forms an electrode.

The first layer should have a layer thickness in the range between 50 nm and 20,000 nm. The layer thickness should be kept as constant as possible over the entire surface. The further layer which forms an electrode may have a layer thickness in the range between 10 nm and 500 nm. This layer thickness depends essentially on the electrical conductivity of the material used for the further layer. It can be smaller with greater electrical conductivity than with lower electrical conductivity. In the case of the respective layer thickness for a further layer, consideration of the optical transparency, which may represent a limitation in the direction of the maximum possible layer thickness, may also play a role. Accordingly, further layers of metal can correspondingly have a smaller layer thickness than layers which are produced with electrically conductive and optically transparent oxides (TCOs).

On a further layer, a conventional multilayer structure, as is usual in OLEDs or organic photovoltaic elements, are applied.

In the production of such organic optoelectronic elements, continuous processes are used, such as roll-to-roll or in-line coating processes. However, it is also possible to work with so-called cluster systems in which the substrate to be coated rotates during the coating in order to obtain the most homogeneous possible coating over the coated surface. In both cases, the electric potential separation in the region of the depression can be further improved by using the shadow cast of a separator in the vapor lobe. This can be exploited especially at the upper edge regions of the trench-shaped depression, if the angle of incidence has been chosen correspondingly with respect to the inclined side walls of a recess, only a small part of the recess in the upper edge region of a recess with electrically conductive material, the further layer forms, be coated. Large deeper surface areas of the side walls of the recess remain so uncoated and form an electrical insulation.

This effect can be achieved in in-line system technology by suitable arrangement of evaporator source to the separator and also to a trained depression with a suitable angle and cluster systems by waiving a movement, preferably a rotational movement of the substrate to be coated.

The flank angle of the side walls of depressions should be at least 75 °, wherein the respective flank angle can be a function of the depth and width of a depression in order to achieve a secure electrical separation. Thus, the flank angle can be smaller for deeper and narrower depressions. However, a minimum width is to be maintained, so that bridging as a result of subsequent layers to be applied can be avoided, which would fill the gap completely, or at least for the most part.

The invention will be explained in more detail by way of example in the following.

Showing:

1 in schematic form an example of an electrode formation obtained by a method according to the invention.

On a substrate 4 , which consists of an electrically conductive material was, by means of a printing process, for. B. screen printing a first layer 3 , which was formed of a dielectric material, applied with a layer thickness of 10 microns. This first layer 3 was then tempered to achieve a sufficient strength.

With printing method layer thicknesses in the range 1 .mu.m to 100 .mu.m, preferably be applied with about 10 microns.

With a laser beam became the first layer 3 structured, in which a grave-shaped depression 5 was formed by material removal. The course of a depression 5 can be formed in a straight line but also arbitrarily along the surface depending on how the structuring has been desired for a desired layout of an optoelectronic or possibly another element.

The depression 5 it had a greater depth than width. The depth can reach the surface of the substrate 4 rich, so be a maximum of 10 microns. The width of the depression 5 is larger here and is in this example at 50 microns. It should have a steep flank on the inner wall of the recess 5 be respected to avoid bridging.

At a minimum thickness of a layer 3 , should have a width for pits 5 be adhered to at least 3 microns in order to avoid "overgrowing" in subsequent coating.

Because of the schematic representation is in 1 a flank angle of the side walls of the recess of 90 ° shown. In the formation of a recess 5 with a laser beam such a flank angle is not or only very difficult to achieve. Depending on the beam quality, a depression tapers 5 starting from the top toward the substrate more or less, so that smaller flank angles are realistic. Steep flank angles up to almost 90 ° can be obtained with so-called "top hat lasers".

After the formation of one or more wells 5 will be at least one more shift 2 applied. Im in 1 As shown, this is an electrode layer of electrically conductive material. So two are electrically through the depression 5 safely separated electrodes 1 and 2 educated.

It can also be a multi-layer construction, with at least one further layer 2 , which forms electrodes, according to the formation of depression (s) 5 be applied.

When applying a multi-layer structure can be considered with conventional shadow masks structuring.

Such a multi-layer structure may also have a cover or top electrode, which has also been deposited as the uppermost layer of an electrically conductive material.

Also for this purpose is an electrical separation of these electrodes by means of one or more recesses 5 possible because the recess forms a sufficiently wide and deep gap, which can not be completely filled with suitable process control for the coating.

As an electrically conductive material, for the formation of electrodes metals such. B. Ag, Al, Ca, Mg, Ba, Li, Au, Cu, Pt, Yb, Pd or alloys thereof, or electrically conductive oxides (TCO's), such as. As ITO, AZO, FTO be used. In their coating, areas of the substrate 4 that with depressions 5 are protected by shadow masks in a conventional manner.

Several parameters can be used in the invention to influence the effect and patterning of electrodes. So, once the layer thickness of the first layer 3 be set. On the other hand, the width and depth of depressions 5 selectable. The depth should be greater than the width, also at the upper edge of the depression.

The formation and dimensioning of the recesses can also be chosen taking into account the materials with which a multilayer structure is formed. The tear-off behavior plays at the upper edges of the recess 5 these substances play a role. Tear off easily, a narrower and not so deep formation of depressions may be sufficient for tough and stretchy fabrics that have a good creep behavior can narrower and deeper depressions 5 be formed.

For many applications, a high electrical conductivity of the structured electrodes 2 desired. Often formed of electrically conductive oxides, such as the TCO's electrodes have a higher electrical resistance sheet than is the case with metals. Therefore, the lines / surfaces, which are later used as carriers for pits 5 should serve, consist of metal or metal-containing pastes that improve the electrical conductivity. They can act as a busbar or as a one-dimensional grid.

In principle, metal thick layers, for example of Ag, can also be used as a separator for electrodes. Such metallic layers can be oxidized by an oxygen treatment and thereby made electrically insulating. This can also be achieved by means of electrochemical treatment. Electrical passivation of metal separators for electrodes is also possible by using ALD and SAMSs.

Flat first layers 3 into the wells 5 can be formed by laser beam, can also act as decoupling or coupling-in, in which the optical refractive index is adjusted and / or electromagnetic radiation scattering particles are used. It is also possible to use multilayer systems with optical refractive index gradients.

First layers 3 can be porous, be formed as thick layers. Their pores improve a decoupling electromagnetic safe radiation. They can also be structured more easily by means of laser radiation. In these porous layers, the surface in the flank region is larger, whereby the separation can be simplified.

There may be two or more electrodes, z. B. an OLED and an OLED layer stack are structured over it. With more than two trained further layers 2 forming electrodes, a plurality of OLEDs or a combination of OLEDs with at least one organic photovoltaic element can be formed one above the other and form a layer stack. It is also an application when contacted on the backsides displays possible. In addition, the reliability can be increased since no edge effects (fences) by anode structuring by means of laser radiation is required.

Claims (11)

Process for the formation of planar structured electrodes, in which the surface of a substrate ( 4 ) with a first layer ( 3 ), which consists of a printable material applied with a thick film method, wherein a layer thickness of 50 nm to 20 microns is to be maintained; Subsequently, a material removal is carried out with a laser beam, in which in the first layer ( 3 ) a trench-shaped depression ( 5 ) is formed, which forms a steep flank angle with the side walls of the depression, which is sufficient for an electrical potential separation for at least one in a subsequent method step as further on the first layer ( 3 ) applied layer ( 2 ), which forms an electrode. Method according to claim 1, characterized in that the first layer ( 3 ) with a layer thickness in the range between 50 nm and 20 μm and the further layer ( 2 ), which forms an electrode, have a layer thickness in the range between 10 nm and 500 nm. Method according to claim 1 or 2, characterized in that with a laser beam in the first layer ( 3 ) a recess ( 5 ) is formed, which has a greater depth than width. Method according to one of the preceding claims, characterized in that with a laser beam in the first layer ( 3 ) a recess ( 5 ) whose side walls have a flank angle between 75 ° and 90 ° with respect to the surface of the substrate ( 4 ) form. Method according to one of the preceding claims, characterized in that with a laser beam in the first layer ( 3 ) a recess ( 5 ) is formed, which extends from the upper edge in the direction of the surface of the substrate ( 4 ) is tapered. Method according to one of the preceding claims, characterized in that lines / surfaces serving as carriers for depressions ( 5 ), are formed of metal or metal-containing pastes. Method according to one of the preceding claims, characterized in that separators for electrodes are formed as metallic thick layers, which are oxidized by an oxygen treatment and thereby made electrically insulating. Method according to one of the preceding claims, characterized in that first layers ( 3 ), into the depressions ( 5 ) are formed by means of a laser beam, adapted to form a decoupling or coupling-in layer in their optical refractive index and / or electromagnetic radiation-scattering particles are used therein. A method according to claim 8, characterized in that multi-layer systems are formed with optical refractive index gradient. Method according to one of the preceding claims, characterized in that the first layer (s) ( 3 ) are formed porous. Method according to one of the preceding claims, characterized in that more than two further layers ( 2 ), which form electrodes, are formed for the formation of an OLED layer stack in a structured form.

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