DE2411872A1 - METHOD FOR MANUFACTURING A TRANSPARENT ELECTRODE - Google Patents

Description

Munich, 12th Harz 1974

- ₁ - ₅

E.R.A. PATENTS LIMITED

Oleeve Road, Leatherhead, Surrey, England.

Method of making a transparent electrode

Transparent electrodes are used for certain Zv / corners, for example for use in electroluminescent flat objects for exhibition purposes etc /. second hand. Such electrodes have previously been made by a thin layer of a conductive Oxide was deposited on a glass substrate. Suitable oxides are tin oxide and mixtures of tin oxide and indium oxide, of tin oxide and antimony oxide, and of tin oxide and bismuth oxide. The knockdown of the Oxide layer was created by heating the substrate and spraying it with a very fine, e.g. B. atomized spray causes a liquid preparation, e.g. B. a solution of tin (II) chloride in aqueous hydrochloric acid, the decomposes on the hot substrate and leaves the oxide layer behind, or by high-frequency atomization ζ. Β. a collecting electrode made of tin oxide or a! "angling electrode made of tin in an oxygen-containing atmosphere. Both procedures have their downsides. In particular, both require

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Process special and complex gate directions and only give usable results when they are extraordinary be carried out carefully.

For me some purposes, e.g. B. for use in llüssigkristall-Element.en Patterned transparent electrodes are required, but these are known processes, apart from the fundamental process-related disadvantages, are not very suitable, pattern of electrodes to form. Although it could theoretically be possible to create a pattern after the spraying process to achieve that the substrate surface in more suitable Way, masking before spraying and removing the mask after spraying would be the procedure be inconvenient and tend to give poor pattern boundaries. In practice, one Patterning achieved in that the oxide layer once formed was etched. In the lall of the spraying process masking is impracticable and patterning must be effected by etching. The oxide layers are difficult to etch. Require tin oxide layers z. B. a strongly acidic solution, with zinc grains as the etching medium and the procedure is time consuming. In addition, the etching has the technical part that not only one process step, but three such steps in addition to the formation of precipitation are involved, as first the parts of the oxide layer that are retained must be provided with an etch-resistant coating, after which the etching must be carried out by yourself must and finally the etch-resistant coating must be removed.

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The object of the invention is to create an improved Process for the production of transparent electrodes in general and in particular for Manufacture of patterned electrodes.

According to the invention, a transparent electrode is produced in that a liquid substance, the one Organometallic compound contains, is printed on a transparent, heat-resistant substrate and the substrate thereafter up to the conversion of the organometallic compound is heated into a transparent conductive metal oxide layer on the substrate. Both the printing and the heating can be carried out quickly and conveniently, resulting in the desired product in two very satisfactory stages is obtained instead of the technically and economically unsatisfactory Applying a precipitate. ¥ enn a patterned one Electrode is needed, the liquid substance is imprinted in a cough and after heating the oxide layer is obtained in a pattern on the substrate. Accordingly, it becomes difficult and time-consuming etching, which is used in the known methods, avoided.

The substrate used can be made of glass and the printout "Heat-resistant" is used only to mean that the substrate is in the Is able to withstand the thermal conditions that are required to convert the organometallic compound into the metal oxide layer to convict.

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The liquid substance that is printed should have suitable rheological properties for the particular the printing method used. The screen printing process is the preferred method of printing, since a printed layer having a desired large thickness can be easily obtained by this method.

It is usually convenient to use the organometallic compound to apply in Eorm of a liquid preparation, e.g. B. a paste, which is also an organic carrier contains. The carrier must be with the organometallic compound be compatible, d. H. that a solution of the organometallic compound in the carrier physically and chemically stable se in should. The carrier preferably consists of a solvent for the organometal compound and preferably it contains a resin or resin mixture, e.g. B. a cellulosic compound such as a substituted one Cellulose, which is used to give the preparation a suitable consistency for application. The kind A suitable solvent or solvent mixture will depend on the particular organometallic compound used away. In general, the organometallic compound should be readily soluble in the solvent be. In the pail of the screen printing process, the solvent should have a relatively high boiling point prevent undesirable loss of solvent by evaporation during pressing. Preferably the boiling point is at least 100

° n

The most satisfactory proportions for the components in the preparation being applied are determined by the expediency, to have the organometallic compound in solution,

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as well as the need to give the preparation a suitable consistency for the chosen method of application. Usually the preparation should contain up to 90 wt .- ^ solvent, e.g. B. 25 - 80 wt .- ^, depending on the solubility ratios between the organometallic compound and the solvent, and up to 50 wt .- $ of a resin, z. B. 1-20 wt .- ^ o, depending on the type of resin and the consistency desired for the preparation, and 150 wt. -Fo of a metal in the form of the organometal! Compound.

The organometallic compound should be able to form a transparent conductive metal oxide layer after heating to surrender. Transparent conductive layers can be made from a variety of metal oxides and the oxides of two or more metals may be present. For example, the layer consist of tin oxide or of mixtures of tin oxide with indium oxide, with antimony oxide or with bismuth oxide. Thus, for. B. according to the invention an organ ozitmverbindungen or a mixture of an organotin compound with an organoantimony compound or with an organo-bismuth compound be used. Preferably a mixture of an organotin compound is used an organoindium compound is used. Organometallic compounds of all of these metals can easily be incorporated into the corresponding oxides are transferred by heating. A large number of organic residues can be present in the compounds are present, where z. B. aliphatic carboxylate residues are suitable.

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The organometallic compound or compounds should be such that they do not crystallize out of the solution when the solvent evaporates. If such a crystallization occurs, the oxide layer obtained is not conductive and relatively cloudy. In this regard, among the organometallic compounds, there are many organic Groups satisfied. In particular, it has been found that aliphatic ^ Oarboxylatgruppen with a chain of at least 6 carbon atoms are generally very satisfactory in that they are disadvantageous Inhibit crystallization. The octoate group is preferred, expediently a branched one Octoate group or a mixture of such groups.

After application, the applied layer is usually allowed to dry, e.g. B. at room temperature. The heating is conveniently carried out in air using a conveyor belt furnace. The heating conditions in the example given are typical. Peak heating temperatures in the range of 500-700 ^° C. are usually suitable. Any resin in the applied layer must be such that it can be easily removed, e.g. B. by combustion under the heating conditions. It is usually desirable that each resin should be designed in the applied layer so that it quickly burns in air at about 500 G ^0. Many resins that meet this criterion are commercially available.

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The invention is further illustrated by the following example explained:

example

A paste was prepared by mixing 33 parts by weight -6-ft Indium-III-octoate 1.4 wt .- $ of stannous octoate and 65 parts by weight? " an organic vehicle. The indium octoate contained indium octoate in an amount corresponding to an indium content of 7% by weight. The Octoate v / aren 2-Ethylhexanoate. The carrier consisted of 5% ethyl cellulose in terpineol, based on the volume.

The paste was screen printed onto a glass substrate to give a patterned printed layer. The layer was allowed to dry at room temperature. The printed substrate was then heated in air using a conveyor belt oven, the time-temperature profile being bell-shaped and a peak temperature of 600 ^{0 being reached} with a heating time of 20 minutes.

The composition of the fired layer was 25 mol% SnO ₂ and 75 mol _{% In 3} O ₅ . The layer was homogeneous and strongly adhered to the substrate.

The layer was electrically conductive. The specific resistance of the plate was 500 ohms / unit area / 1 / µm. The layer was also optically transparent. The transmission at a wavelength of 800 nm was 97 f> and at a wavelength of 400 nm the transmission was 93 f>.

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The process can be carried out using different mixtures of organometallic compounds or using of a single organometallic compound will. Here, too, transparent conductive layers and the conductivity can be obtained depends on the particular metal or metals present and on the relative amounts of the metals, if 2 or more metals are present, from. Thus, the conductivity of the oxide layer, which according to the invention Process is produced, can be varied, e.g. By increasing the amount of the organotin compound or by using an organotin compound in a mixture with an organoantimonνerbin dung instead of the organoindium compound.

The procedure can also be varied using Firing Conditions "are repeated, again forming a transparent conductive layer the conductivity of which depends, however, on the specific firing conditions.

- patent claims -

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Claims (5)

Claims -Λ
[ .1 * Process for the production of a transparent V_y electrode, characterized in that a liquid Substance that is an organometallic compound contains, is printed on a transparent, heat-resistant substrate and then the substrate until the organometallic compound is converted into a transparent conductive metal oxide layer is heated on the substrate. 2. The method according to claim 1, characterized in that the printing process used the screen printing process is. 3. The method according to claim 1-2, characterized in that the liquid sub- . punch contains organometallic compounds of 2 ' or more metals. 4. The method according to claim 3, characterized in that the liquid substance is a Mixture of an organotin compound with an organoantimony compound, an organosmuth compound or an organoindium compound. 5. The method according to the preceding claims, characterized in that the organic radical of the organometallic compound or compounds an aliphatic carboxylate radical with a chain of at least 6 carbon atoms is. 409838/0848