DE1251434B - - Google Patents

Description

GERMAN WTVsi ^ PATENT OFFICE German class: 21 f - 89/05

EDITORIAL

Number: 1251434

File number: N 27141 VIII c / 21 f

1 251 434 filing date: August 7, 1965

Open date: October 5, 1967

The invention relates to a method for producing an electroluminescent element with an electroluminescent layer made of a dispersion between two electrodes an electroluminescent substance in a solid, vitreous medium. The invention further relates an element made by such a process.

As is known, electroluminescent elements consist of one arranged between two electrodes electroluminescent substance, which when a voltage is applied, usually an alternating voltage, emits radiation between the electrodes. The most famous electroluminescent substance, the Can also be used in elements according to the invention is copper activated zinc sulfide.

The construction of the elements can be different, but one of the electrodes is always practical for the radiation emitted by the electroluminescent substance is transparent. Most of the time the item has also a solid support, e.g. B. made of glass or metal. The electroluminescent substance is mostly not attached as such between the electrodes, but in the form of a dispersion in a solid Medium. This medium can be glass-like or consist of a synthetic resin. Becomes a transparent one If the carrier is used, it is customary to cover it with a transparent one on the side of the electroluminescent layer To cover electrode, e.g. B. of conductive tin oxide. The other electrode does not need to be transparent and can e.g. consist of a vapor-deposited metal layer or of a by means of a Binder attached metal layer exist. To improve the luminance and to increase it the breakdown voltage of the elements, is often between the electroluminescent layer and the opaque electrode attached an additional layer, which is preferably made of titanium oxide or a titanate of an alkaline earth metal. , .... · · ._, · ■.

It is known that the properties of an electroluminescent element to a great extent by the composition of the electroluminescent layer and by the method of application this layer can be affected. Naturally, it is very important that the actual electroluminescent Substance has high conversion efficiency; but no less important is how that Medium in which the electroluminescent material is dispersed, is composed and like this solid dispersion is produced. In particular, the luminance will decrease after a few hours of use Electroluminescent element

Applicant:

NV Philips' Gloeilampenfabrieken,
Eindhoven (Netherlands)

Representative:

Dipl.-Ing. H. Auer, patent attorney,
Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Henri Hubert Janssens,

Willem Esterveld, Eindhoven (Netherlands)

Claimed. Priority:

Netherlands of August 12, 1964 (6 409 254)

and thus the useful life is greatly influenced by these factors. One therefore finds in the Literature very different regulations for the composition of the medium and for the manufacture

»5 position of the electroluminescent layer. If the medium is glassy, it will often contain an amount, e.g. B. 2 to 10 percent by weight, antimony. In the electroluminescent element according to the invention, the medium is also vitreous and contains antimony.

The purpose of the invention is to use the antimony in. the .. way to introduce into the electroluminescent layer, . that the luminance decreases less during the use of the element.

A method according to the invention for making an electroluminescent element having a applied between two electrodes electro-luminescent layer from a dispersion of a "Electroluminescent substance in a solid, vitreous medium that contains antimony oxide characterized in that grains of the electroluminescent substance are coated with an antimony oxide layer, whereupon the coated grains are mixed with glass-forming ingredients, which mixture is coated on a carrier and then heated so that a continuous electroluminescent layer is formed.

It is not necessary that the total amount of luminescent material be in an element is used according to the invention, previously coated with antimony oxide in the manner described above will.

709 650/169

Claims (3)

It is also not necessary to apply the total amount of antimony in the electroluminescent layer in the form of antimony oxide to the grains of electroluminescent material beforehand. The glass-forming constituents can also contain antimony compounds, for example antimony oxide directly around the grains of the electroluminescent substance greater than the mean concentration in the electroluminescent layer. The ratio between the weight amount of electroluminescent material and the weight amount of antimony oxide with which this material is coated can be selected between 50: 1 and 4: 1. " The elements produced by a method according to the invention have a lower drop in luminance compared to elements in which the antimony is present homogeneously in the medium of the electroluminescent layer. This ao could be explained by the fact that the surrounding antimony oxide layer protects the grains of the electroluminescent material from attack by alkaline components of the medium. The antimony oxide coating can, for. B. be obtained mechanically, chemically or electrochemically. You can z. B. dissolve the desired amount of antimony oxide in hydrochloric acid, which solution is added to an aqueous suspension of the electroluminescent material. By choosing the right pH value, i. H. greater than 10, a large part of the antimony oxide will be on the grains of the electroluminescent material, e.g. B. ZnS1 dejected. The further steps in the production of these elements do not differ from those already known. In order to further explain the invention, some data follow below with regard to the amounts of antimony oxide, the luminance of the elements produced, the decrease in luminance and the composition of the enamel. An electroluminescent, copper-activated ZnS of the usual composition was coated with 2 percent by weight of Sb2O3 in the chemical manner described above. The coated material was then mixed with a glass frit with the following composition: Na2O 9.4 mol percent Li2O. 7.2 mol percent BaO 6.1 mol percent ZnO 25.4 mol percent Al2O3 2.1 mol percent SiO2 17.6 mol percent TiO2 2.7 mol percent As2O3 2.9 mol percent B2O3 26.6 mol percent was coated with a layer of titanium dioxide with a thickness of about 100 μ. The element was then heated to about 700 ° C., whereby an uninterrupted electroluminescent layer was formed. This layer was then covered with a layer of conductive tin oxide which was transparent to light. In the electroluminescent layer, the amount of ZnS was about volume percent. Immediately after manufacture, the luminance of this element was 5.6 candela / m 2 at 220 V and a frequency of 50 Hz. The element was then burned for 100 hours at V and a frequency of 2000 Hz. Measurements were then carried out again at 220 V and 50 Hz. The decrease in luminance was 15% of the initial value. An element was measured for comparison in which the ZnS grains were not previously coated with antimony oxide, but which was otherwise produced in the same way The decrease in luminance was 45% under the same measurement conditions. In another element, a value of 7% was found for the decrease in luminance when the grains were covered with 6 percent by weight of Sb2O3. 1. A method of making an electroluminescent element having one between two Electroluminescent layer made of a dispersion of an electroluminescent layer Substance in a vitreous medium which contains antimony oxide, characterized in that grains of the electroluminescent substance with an antimony oxide layer are coated, the coated grains mixed with vitreous components that The mixture is coated on a carrier and then heated in such a way that an uninterrupted forms electroluminescent layer. 2. The method according to claim 1, characterized in that the weight ratio between the electroluminescent material and the surrounding antimony oxide between 50: 1 and 4: 1. 3. An electroluminescent element produced by a method according to claim 1 or 2 is characterized in that the concentration of antimony oxide immediately around the grains of the electroluminescent substance in the electroluminescent layer is higher than that medium concentration in this layer. Considered publications:
U.S. Patent No. 2,965,784. 709 650/169 9.67 © Bundesdruckerei Berlin