DE1243269B - Electrolytic cell for generating visible luminescence - Google Patents

Description

Electrolytic cell for the generation of visible luminescence Die Invention relates to electroluminescent phenomena in a solution. It was found that one can emit visible electroluminescence by applying alternating current sufficient voltage to the electrodes, for example those made of platinum or Mercury, an electrolytic cell in an inert solvent, the one fluorescent organic compound and a suitable carrier electrolyte contains, can generate.

Dimethylformamide (DMF) as a solvent, the 2 - 10-3 mol of rubrene as a fluorescent compound and 0.1 mol of tetrabutylammonium perchlorate as the carrier electrolyte contains, for example, represents a system that emits light when it is Located in an electrolytic cell that contains electrodes to which an alternating current is applied with 60 Hertz is applied, without the solution components of the system in any noteworthy Way to be consumed. On each electrode surface or in its immediate vicinity Visible light is emitted as long as an alternating current with sufficient Voltage is applied.

The invention is therefore an electrolytic cell for Generation of visible luminescence upon passage of current, characterized in that that the filling of the electrolytic cell from an inert solvent, a fluorescent organic compound and a carrier electrolyte and that such a high alternating voltage is applied to the cell that the fluorescent organic compound alternating at least during the individual half-waves an electron is added or withdrawn, and this connection when the phase changes in each case back to their original form, but in their excited singlet state is returned.

The organic compound capable of fluorescence is thus either periodic to an oxidized form (i.e., a cation radical) in the anode phase of the applied Potential is oxidized and applied to its excited form in the cathode phase Potential is reduced, or it becomes a reduced form (i.e. an anion radical) reduced in the cathode phase of the applied potential and to its excited Oxidized state in the anode phase of the applied potential. With fluorescent Compounds that emit red light when excited is the least anodic or cathodic voltage amplitude and consequently the smallest voltage change required on an electrode to produce visible light. Against are at fluorescent compounds that emit blue light when excited are larger anodic or cathodic amplitudes and higher voltage differences at the electrode necessary.

The upper and lower limits required to produce light the potential applied to the electrode depend on the fluorescent used organic compound. So either the upper limit of the applied potential have a sufficiently high positive value so that the organic fluorescent properties Compound is converted to an oxidized state or the lower limit of the applied to the electrode potential must be negative enough so that the fluorescent organic compound is converted into a reduced state. Also must the potential difference between the upper and lower values of the applied potential at least sufficient that there is enough energy to transfer the fluorescent organic compound is present in its excited singlet state.

In general, the potential difference between the upper and lower limits of the applied voltage are above about 1.5 volts.

The potentials required for the oxidation or reduction of organic compounds of the type considered here (based on a standard electrode, e.g. the saturated calomel electrode) can easily be determined by standard polarographic methods (see 1. M. K o 1 thoff and JJ L ingane, Polarography, 2nd edition, 1952, Interscience Publishing, New York, NY). The minimum energies required to convert organic compounds of the type under consideration here into their excited singlet states can also be easily determined by methods such as absorption or emission spectroscopy (see SF Mason, Molecular Electronic Absorption Spectra, Quarterly Reviews, 15 , P. 287, 1961).

The device according to the invention can be used in a wide variety of ways, as can be seen from the description elsewhere, e.g. B. in the field lighting or information displays. For example, represents the electrolytic cell of Example 1 is practically an incandescent lamp, the electrolytic cell made of a transparent, closed by a stopper Bottle with two electrodes in it, the ends of which in the system are made of fluorescent Immerse the compound, solvent, and electrolyte. Instead of the pear-shaped Cell can be a tubular or cube-shaped cell or any cell if necessary use a different geometric shape. You can also have several pairs of electrodes in one use the given cell, each pair operating independently if necessary. Further applications are explained in more detail later.

As stated above, both the solution system and by the nature of the electrode the upper limit of the potential difference is evident set. As far as the frequency of the applied alternating voltage is concerned, this can in a range from a few cycles per minute to the radio wave range and above lie.

Numerous organic fluorescent compounds are able to To emit visible light when according to the invention alternating current with sufficient Tension is applied. Examples of such compounds are fluorescent compounds aromatic polycyclic hydrocarbons and polycyclic heterocycles. to these compounds include 1,4-dimethoxyanthracene, 1-methoxy-9,10-diphenylanthracene, 1,4-dimethoxy-9,10-diphenylanthracene, 2,3-benzofluoranthracene, anthracene, rubrene, Pyrene, coronene, decacylene, ß-dinaphthylene oxide, 1,3-diphenylisobenzofuran, 1,7-phenanthroline, Benzo- (1,2,3-g, h: 4,5,6-g ', h') diphenanthridine and N-methylphenothiazine.

Numerous carrier electrolytes can be used in the device according to the invention can be applied. However, it is imperative that these electrolytes, for example do not noticeably attenuate the required anodic or cathodic amplitudes and thus a conversion of the organic compound capable of fluorescence into its excited one Prevent condition. It is known to those skilled in the art that an electrolyte which is based on a organic fluorescent compound does not interfere with another compound this type can have a disturbing effect and vice versa. It is therefore within the scope of the invention and, within the skill of the art, use an electrolyte suitable for the organic fluorescent compound used is suitable. The electrolyte should also be in the potential range required for the luminescence reaction be electroinactive, have sufficient conductivity and not quench luminescence works. Suitable electrolytic cations are, for example, tetrasubstituted ones Ammonium ions with lower alkyl radicals or ions of the alkaline earth and alkali metals. Suitable anions are, for example, perchlorate, hexafluoroarsenate, hexafluorophosphate, Chloride or bromide.

Numerous solvents can be used in the device according to the invention be used. For the organic fluorescent compound and the electrolyte is any practically inert organic or inorganic solvent that is in sufficient Dimensions non-protonating and is not reducible, so the desired degree of reversibility is retained (i.e. the lifetime of the radical ion should be at least equal to the reciprocal value of the frequency used), suitable, provided that it is conductive by adding an electrolyte of the type described will.

The following inert solvents are exemplary: Nitriles, e.g. B. acetonitrile; Sulfoxides, e.g. B. dimethyl sulfoxide; Ether, e.g. B. tetrahydrofuran, dioxane, diethyl ether or dimethoxyethane; Alcohols e.g. B. lower alkanols; Amides, for example dimethylformamide; Carbonates, e.g. E.g. propylene carbonate; amines, e.g. B. ethylenediamine; Nitroalkanes, e.g. B. Nitromethane; and dialkyl sulfites, for example dimethyl sulfite.

It is not necessary that these solvents are anhydrous, since it has been found that in some cases up to about 10% water is unaffected visible light emission may be present. It is without any for the professional furthermore it can be seen that there are numerous other practically inert organic and inorganic There are solvents, including those which, although not completely inert, with the inventive Process and the solution system are compatible and practically non-fluorescence-quenching works. Mixtures of solvents can also be used.

In connection with the excited state described above, it should be pointed out that the energy of an excited state is an easily measurable, represents experimental value. For example, the energy difference is between a first excited singlet and its corresponding ground state by the Frequency of the first absorption band in the ultraviolet or visible spectrum of the body is defined in its basic state.

The physical energy released by a reaction is also an experimental size. For example, the energy of a reaction of the type present in the particular embodiment described above, by polarographic Measurements and other known physico-chemical methods can be determined.

The area in which electroluminescence occurs can therefore be made independent measure it and clearly define it with the help of physical data. Consequently one can generate electroluminescence emission with the inventive Device thereby enable that one first the known physical data the fluorescent organic compound and the inert solvent and of the electrolyte to be used.

The temperature at which the device according to the invention operated is not critical; so were excellent results at ambient temperatures obtain. The solvent used is used to achieve the best possible results from Freed air, for example by passing nitrogen through it, thereby improving the conditions and the safety that the solvent is practically inert, is increased.

Example 1 Sufficient tetrabutylammonium perchlorate and rubrene are added to a 50 ml bottle, closed with a rubber stopper, which contains 30 ml of dimethylformamide (DMF) as solvent (which has been made practically air-free by introducing nitrogen) that a 0.1 molar solution of the Electrolytes or a 2-10-3 molar solution of the organic fluorescent compound is present. Through the stopper are two platinum electrodes, each attached to the Case- Organic Electrolyte Molar Solvent game fluorescent compound concentration (a) (b) (a) J (b) (c) 2 rubrons of lithium bromide 2-10-3 0.1 DMF 3 rubrics tetrabutylammonium perchlorate 2-10-3 0.1 950 / () dioxane 5% H20 4 perylene tetrabutylammonium perchlorate 2-10-3 0.1 DMF 5 anthracene tetrabutylammonium perchlorate 2-10-3 0.1 DMF 6 9,10-diphenylanthracene tetrabutylammonium perchlorate 2-10-3 0.1 DMF 7 N-methylphenothiazine tetrabutylammonium perchlorate 2-10-3 0.1 DMF 8 9,10-diphenylanthracene tetrabutylammonium perchlorate 2-10-3 0.1 1,2-dimethoxyethane As in Example 1 above, the grids are lit and visible light is perceived in all examples as long as the power is on.

Example 9 Example 1 is repeated in every essential point with the exception that carbon is used instead of platinum on the electrode. Visible light is emitted when electricity is applied.

Example 10 Example 1 is repeated with the exception that instead of platinum on the electrode, stainless steel Organic alternating current With- fluorescent electrolyte Polar concentration Solvent Fre- match connection frequency volts ** (a) (b) (a) I (b) (c) Hertz 12 rubrics tetrabutylammonium- 2 - 10-3 0.1 DMF 0.3 2.5 * perchlorate 13 rubrics tetrabutylammonium 2-10-3 0.1 DMF 30 5 perchlorate 14 rubrics tetrabutylammonium 2-10-3 0.1 DMF 100 10 perchlorate 15 2,3-benzofluoranthene sodium perchlorate 2.10-3 0.1 1,2-dimethoxyethane 60 20 16 dinaphthalene oxide tetramethylammonium 2-10-3 0.1 propylene carbonate 60 5 hexafluoroarsenate 17 1,3-diphenylisobenzo-tetrabutylammonium-3 -16-3 0.1 tetrahydrofuran 60 20 furan tetraphenyloborate 18 1,7-phenanthroline Ca (C104) 2 10-3 0.1 dimethyl sulfoxide 60 7 19 1,10-phenanthroline LiC104 4 -10-3 0.1 ethylenediamine 60 15 See footnotes at the end of the table Ends having platinum grids with an area of 6.7 cm2, inserted into the bottle, the grids being naturally immersed in the solution. The vertical electrodes are about 1.27 cm apart. An alternating current (60 Hertz) with a voltage of 3 volts is applied to the electrodes. The grids light up and this visible light is noticeable as long as the power remains on.

Examples 2 to 8 Example 1 is repeated in every essential point except that the following fluorescent compounds, electrolytes and solvents can be used at the indicated concentrations. used will. Visible light is emitted when electricity is applied.

Example 11 Example 1 is repeated with the exception that instead of of platinum is used on the electrode tantalum. When applying electricity emits visible light.

The following examples, which further illustrate the invention, were all carried out practically as in Example 1. The exceptions are indicated in the following table: (Continuation of the table above) Organic Molar Alternating Current In the case of fluorescent electrolyte solvent Fes. game connection concentration across volt ** (a) (b) (a) (b) (c) Hertz 20 Benzo- (1,2,3-g, h: 4,5,6, tetrabutylammonium- 2 -10-2 0,1 1,2-dimethoxyethane 60 10 g'h ') - diphenanthradine perchlorate 21 N-methylphenothiazine tetrapropylammonium 3 -10-3 0.1 propylene carbonate 60 10 hexafluorophosphate 22 9,10-diphenylanthracene tetrabutylammonium 10-2 0.8 1,2-dimethoxyethane 60 15 perchlorate 23 9,10-diphenylanthracene tetrabutylammonium 5-10-2 0.5 1,2-dimethoxyethane 60 12 perchlorate 24 9,10-diphenylanthracene tetrabutylammonium 1-10-2 0.1 1,2-dimethoxyethane 60 10 perchlorate 25 9,10-diphenylanthracene tetrabutylammonium 1-10-3 0.1 tert-butanol 60 20 perchlorate 26 1-methoxy-9,10-diphe-LiA1C14 10-3 1.0 nitromethane 60 10 nylanthracene 27 1,4-dimethoxy-9,10-di-tetrabutylammonium-10-3 0.1 dimethyl sulfite 60 75 phenylanthracene bromide 28 pyrene M9C104 2-10-2 0.1 DMF 20 15 29 coronene tetrabutylammonium 10-3 0.1 1,2-dimethoxyethane 60 20 perchlorate 30 decacyclene tetrabutylammonium 10-3 0.1 1,2-dimethoxyethane 60 20 perchlorate 31 1,4-dimethoxy-NaC104 10-3 0.1 dimethyl sulfoxide 60 10 anthracene * In square waves (from peak to peak). ** Total voltage applied to the cell. Visible electroluminescence is emitted in the examples in the table above. In Examples 1 to 11 and 13 to 31, the voltage changes with time as a sine wave function.

In the table above, frequencies in the order of magnitude of 0.3 to 100 Hertz are listed, but, as already stated, considerably higher frequencies can be used. For example, instead of the frequencies of Example 13, 17, 21 and 26, frequencies of 500, 1000, 10,000 and 15,000, respectively, can be used without the electroluminescence emission changing significantly.

For other applications besides those already described The invention also includes devices with spaced apart Plates, screens or similar surfaces that act as electrodes; one or more these surfaces can optionally be designed as a sieve or perforated or transparent be. Between these surfaces is the system of fluorescent connection, Solvent and electrolyte brought, preferably in gel form, and through the electrodes and of course alternating current passed through the system in between. Visible light can be seen as a result of the electrodes lighting up.

One or both of these electrodes may contain information which can be produced, for example, with different perforations. If If solid, translucent plates are used as electrodes, these can be replaced by a Information-containing stencil must be covered so that only the light that passes through the stencil becomes visible. You can of course have a number of individual ones Use electrode pairs with electrodes of the type described above, whereby there are more possibilities for using them to present information.

According to a further embodiment of the device according to the invention can have a variety of electrodes of any shape (e.g. straight, curved, or conical rods) can be arranged on a surface, with the electrodes in a system Immerse (gel or solution) of the type described and in pairs or in another suitably connected to the alternating current. By regulating the current Different information can be displayed on each of these pairs on the surface will.

The following examples are intended to illustrate the embodiments in which the system of fluorescent compound, solvent and electrolyte is a gel: Example 32 Example 13 is practically exactly repeated with the exception that 30 percent by weight of polyacrylamide is dissolved in the solvent. One receives a. Gel that can be used as described above, for example sandwiched between two electrode plates. EXAMPLE 33 A solution of 100 %, acrylamide, 100 %, methylenebisacrylamide, 0.5% oa, α-azobisisobutyronitrile, 5 10-3 mol of rubrene and 0.1 mol of tetrabutylammonium perchlorate in dimethylformamide, into which two platinum electrodes are immersed, is used for several hours heated to 60'C until the polymerization has practically ended. A semi-solid gel is obtained. Applying an alternating current of 5 volts and 60 Hertz produces yellow light.

Optionally, the electrolytic cell container can be translucent or transparent, coated with a fluorescent material (e.g. B. outside), and the light emitted at the electrodes can then pass through this substance can be converted into longer-wave light. The following examples illustrate this Embodiment.

Example 34 Example 6 is carried out in a glass container which outside with a 5 mm thick polystyrene film with a content of 1% rhodamine B is covered. When applying alternating current, red light (instead of blue) emitted.

Example 35 Example 34 is repeated, only 10 /, eosin instead of rhodamine B being used. A number of other possibilities result from the prior art in the field of fluorescence phenomena. Thus, instead of an organic fluorescent dye (as in Examples 34 and 35), "crystal phosphors" can be used in the coating. P. P ringsheim, Fluorescence and Phosphorescence, Intersciense Publishers, New York, 1949, Chapter VII.

Claims (10)

Claims: 1. Electrolytic cell for generating visible Luminescence upon passage of current, characterized by the fact that the filling of the electrolytic Cell made from an inert solvent, an organic compound capable of fluorescence and a carrier electrolyte and that such a high alternating voltage is applied to the cell is applied that the fluorescent organic compound during each Half-waves at least one electron is alternately supplied or withdrawn, and however, when the phase changes, this connection returns to its original form is returned to the excited singlet state. 2. Device according to claim 1, characterized in that it is a fluorescent compound as a fluorescent compound aromatic hydrocarbon, a fluorescent polycyclic heterocyclic Compound, rubrene, 9,10-diphenylanthracene, anthracene, perylene or N-methylphenthiazine contains. 3. Apparatus according to claim 1 or 2, characterized in that it contains tetrabutylammonium perchlorate or lithium bromide as electrolyte. 4. Device according to one of claims 1 to 3, characterized in that it is used as a solvent Contains dimethylformamide or 1,2-dimethoxyethane. 5. Device according to one of the Claims 1 to 3, characterized in that they use dioxane as the solvent a water content of up to about 100 / ". 6. Device according to one of the preceding Claims, characterized in that of the spaced apart Electrode surfaces at least one is translucent. 7. Device according to one of claims 1 to 5, characterized in that they have a plurality of electrodes any shape on an electrically insulating support surface as a background for the display of visible information. B. Device according to one of the preceding claims, characterized in that the container of the electrolytic Cell is translucent or translucent. 9. Device according to one of the preceding Claims, characterized in that it contains a gel-like filling. 10. Device according to Claim 8, characterized in that the electrolyte container coated with an organic fluorescent dye or with a crystal phosphor is. References considered: U.S. Patent No. 988104.