DE2249867A1 - ELECTROLUMINESCENT ELEMENT OF THE DISPERSION TYPE - Google Patents

Description

Dispersion type electroluminescent element

The invention relates to a light-emitting display element, in which a phosphor capable of electroluminescence (EL) is used, and in particular one which is used for display Dispersion type electroluminescent element.

The EL display elements are generally grouped into the groups of the evaporated film EL cells and the EL cells divided by the dispersion type, the latter group being the electroluminescent phosphor is dispersed in a suitable organic or inorganic binder.

Such organic binders are castor oil, glycerine, acetal synthetic resins, Epoxy resins, methyl methacrylate, polyester, polyethylene, polystyrene, cyanoethyl cellulose, etc., whereas In addition to the inorganic binders, ferroelectric materials such as electroluminescent enamel, barium titanate, Rochelle salt,

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Potassium dihydrogen phosphate and lead titanate include.

The known lilektrolumineszenz cell of the dispersion type has two electrodes between which an electroluminescent layer is enclosed. Between the electroluminescent Layer and the one electrode, an insulating film is arranged to prevent breakdown.

The following must be applied to the organic or inorganic binder Requirements are:

1. It must be suitable with the electroluminescent phosphor Way to be mixable;

2. It must not react chemically with the fluorescent material;

3. It must keep the electroluminescent fluorescent material safe;

4. It must have excellent insulating properties;

5. its aging behavior must be good, i.e. its properties should not change as a function of time;

6. A breakdown voltage must be high compared to the voltage applied have and

7. Its dielectric constant must be large.

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Now, however, the organic binders cannot meet the conditions 3 to 7, while the inorganic binders do not Meet requirement 1. If a breakdown is to be prevented by a special insulating film, the number of Manufacturing step.e and manufacturing costs increased.

It is therefore the object of the present invention to provide an electroluminescent zenzelement of the dispersion type, which is simple in construction and does not have the disadvantages described above.

To solve this problem, the invention is based on an electroluminescent element of the dispersion type with two electrodes and one electroluminescent connected between the two electrodes Layer made of an electroluminescent phosphor is dispersed in a binder.

The object is achieved in that the electroluminescent Layer made from a mixture of 100 parts by weight of electroluminescent cells Phosphor, 30 to 50 parts by weight of liquid crystal and based on the sum of the parts by weight of phosphor and liquid crystal 10 to 40 parts by weight of inorganic binder.

The use of liquid crystal offers the following advantages;

1. The liquid crystal has excellent insulating properties on;

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2 »The liquid crystal can nit in any ratio mixed with the electro-tinescent phosphor -and in this * be dispersed;

3. The liquid crystal can act as an organic binder which is stable over an operating period of several thousand hours without any signs of aging;

4. The liquid crystal is translucent or slightly cloudy so that it can transmit luminescent light extremely efficiently; '. ·, ■ ... ■ .. ■■ '. ■.;. .:> ■:

5. The liquid crystal builds a when a voltage is applied Dipole moment on, so that an electric field is effective can be built up over the phosphor, and

6. The liquid crystal has a relatively large dielectric constant on. On the other hand, the use of an inorganic binder offers the following advantages:

1. The inorganic binder has an extremely high dielectric constant on and

2. It can reflect the electroluminescent light where it is white. _'..... ■■■■ ■ _■:. ■. ■. ■ ... '. ■

The invention will now be described in more detail with reference to the accompanying drawing. From the figures show:

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Fig. 1 shows a cross section through a belonging to the prior art Dispersion type electroluminescent cell and

Fig. 2 shows a corresponding cross section through an inventive Electroluminescent cell. .

The known EL cell shown in FIG. 1 consists of a metal electrode 1, a transparent electrode 2, an electroluminescent layer 3, which consists of a mixture of an electroluminescent phosphor and an organic or an inorganic binder; furthermore belong to the cell made of synthetic resin spacer pieces 4, which are arranged to limit a gap between the electrodes 1 and 3 between these. The gap serves to accommodate the electroluminescent layer 3. Between the electroluminescent layer 3 and the electrode 2 is a insulating film 5 is introduced to prevent insulation breakdown. In addition to the insulating ¹ film 5, the spacers 4 naturally also contribute to the considerable increase in the manufacturing steps and the manufacturing costs.

The electroluminescent cell according to the invention shown in FIG. 2 consists of the two electrodes 11 and 12, of which at least one is translucent and the electroluminescent layer 13, which 'consists of a mixture of an electroluminescent Phosphor, a liquid crystal and an inorganic binding agent, means with the parts by weight given above.

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The liquid crystal is in the liquid at room temperature Condition and then has very good insulation properties. For example, MBBA (methoxy-benzilydene-butyl-aniline), EBBA (ethoxy-benzilydene-buthyl-aniline) or a Mixture of the two can be used.

When operating the element, an operating voltage is applied across the two Electrodes 11 and 12 placed in order to build up an electric field across the electroluminescent layer 13. This will be the luminescence centers of the phosphor are stimulated. If the If the polarity of the applied field is reversed, the excited electrons recombine with the luminescence centers, releasing them of luminescent light which is characteristic of the electroluminescent phosphor used. This light can be viewed through the translucent electrode.

As already described above, the invention uses both the advantages the liquid crystal as well as the advantages of the inorganic binder. It is therefore not necessary that for To prevent an insulation breakdown, an insulating film is installed, so that the brightness of the Klektroluminescent element can be increased and design and manufacture of the element can be simplified. WidthMn shows the electroluminescent element no aging phenomena during operation over a long period of time, but works in a stable manner.

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Claims (2)

. Claims Ty ElectiOluminescence element of the dispersion type with two electrodes and one connected between the two electrodes electroluminescent layer in which an electroluminescent Phosphor is dispersed in a binder, characterized in that the electroluminescent layer consists of a iMixture of 100 parts by weight of electroluminescent phosphor, 30 to 50 parts by weight of liquid crystal and starting from the Sum of the parts by weight of phosphor and liquid crystal TO consists of up to 40 parts by weight of inorganic binder. 2. Element according to claim 1, characterized in that the liquid crystal from the group MBBA (methoxy-benzilydene-butyl-aniline), EBBA (ethoxy-benzilydene-butyl-aniline); and · one of the two · is selected * '"■" »· ^; 9815/0 9AS ..,. 9.4 - I. f. Blank page