DE2249867C3 - Electroluminescent element from dis- - Google Patents

Description

35

The invention relates to a light-emitting display element in which one of the electroluminescent (EL) capable phosphor is used, and in particular an electroluminescent element serving for display from dispersion ^.

The electroluminescent display elements are generally classified into the groups of EL cells with vapor-deposited film and EL cells of the D ₁ dispersion type, the latter group

one electrode is covered with an insulating film | arranged to prevent breakdown.

The following requirements must be placed on the organic or inorganic binder:

1. It must be suitable for mixing with the electroluminescent phosphor;

2. It must not react chemically with the phosphor

gi ^older;

3. It must hold electroluminescent fluorescent material securely;

4. It must have excellent insulating properties;

5. its aging behavior must be good, d. i.e., its properties should vary depending on not change of time;

6. It must have a high breakdown voltage compared to the voltage applied, and

7. Its dielectric constant must be large.

Now, however, the organic binders can not meet the conditions 3 to 7, while the inorganic binders do not meet requirement 1. When a breakthrough by a special insulating film should be prevented, the number of manufacturing steps and the manufacturing cost lifted up.

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

To achieve this object, the invention is based on an electroluminescent element of the dispersion type with two electrodes and one between the two Electroluminescent layer connected to electrodes, in which an elelrtrolumineszenter Phosphor is dispersed in a binder.

The object is achieved in that the electroluminescent layer consists of a mixture 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 10 to 40 parts by weight of inorganic Binder consists.

Using liquid crystal has the following advantages:

1. The liquid crystal has excellent insulating properties;

2. The liquid crystal can be in any proportion with the electroluminescent phosphor mixed and dispersed therein;

is. . . «°

Such organic binders are castor oil,

ST ¹ ? "' _U ^{A <xt} ? - ^K l ^as } ^ha f ^e ' Epmqrd-KuiBthaTO, methyl methacrylate, polyester, polyethylene, polystytoi, cyanoathy ^ cellulose, etc., whereas for the ^ organic ^ binders ferroelectric paints, wi _e zBelektrolummeszente _S email barium titanate Rochelle salt, Kahumdihydrogen phosphate VndBleititanat include,

The well-known electroluminescent cell from Di- »Persion type ΛνβιβΙ two electrodes on, between

55 is stable for several thousand hours without any signs of aging

_{4 the} ρ, ^^^ ' _is translucent or _slightly ^ effective

Lumin can transmit lenz light;

5. _The liquid crystal builds up a dipole moment when a voltage is applied, so that an electric field is effective across the luminous

fabric can be built, and
_{6 the} ηϋ ^^^^ _{indicates a} ' _{e relatively ße Di.}

on

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 based on the drawing

be described in more detail. From the figures shows

F i g. 1 shows a cross section through a prior art

Dispersion type electroluminescent cell belonging to technology, and

F i g. 2 shows a corresponding cross section through an electroluminescent cell according to the invention.

The in the F i g. 1 is a known EL cell shown from a metal electrode 1, a translucent

permeable electrode 2, an electroluminescent layer 3, which consists of a mixture of an electroluminescent Phosphor and an organic or an inorganic binder; Farther belong to the cell made of synthetic resin spacers 4, which limit a gap between the electrodes 1 and 2 are arranged between them. The gap is used to accommodate the electroluminescent layer 3. Between the electroluminescent Layer 3 and the electrode 2, an insulating film 5 is introduced in order to prevent an insulation breakdown. In addition to the insulating Of course, the film S also supports the spacers 4 to considerably increase the manufacturing steps and manufacturing costs.

The electroluminescent cell according to the invention shown in FIG. 2 consists of the two electrodes 11 and 12, at least one of which is transparent is, and the electroluminescent layer 13, which consists of a mixture of sinem electroluminescent ao Phosphor, a liquid crystal and an inorganic binder with the above Parts by weight.

The liquid crystal is in the liquid state at room temperature and then has a very good »5 Insulation properties. For example, MBBA (Methoxy-Benzilyden-Buthy! - Aniline), EBBA (Ethoxy-Benzilyden-Buthyl-Anüin) 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, in order to build up an electric field across the electroluminescent layer 13. This will be the luminescence centers of the phosphor are excited when the polarity of the applied field is reversed the excited electrons recombine with the luminescence centers giving off luminescence light, which is characteristic of the electroluminescent phosphor used. This light can be viewed through the translucent electrode.

As already described above, the invention utilizes both the advantages of the liquid crystal and the advantages of the inorganic binder. It is not necessary, therefore, to incorporate an insulating film to prevent the insulation breakdown, so that the brightness of the electroluminescent element can be increased and the construction and manufacture of the element can be simplified. Furthermore, the electroluminescent element shows no signs of aging over a long period of time during operation, but works stably.

For this. 1 sheet of drawings

Claims (2)

Patent claims: l.Electroluminescent element of the dispersion type with two electrodes and one between the Electroluminescent layer connected to both electrodes, in which an electroluminescent layer Phosphor is dispersed in a binder, characterized in that the electroluminescent layer made from a mixture of 100 parts by weight of electroluminescent Phosphors, 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 consists. 2. Element according to claim 1, characterized in that the liquid crystal from the group MBBA (Methoxy-Benzilyden-Buthyl-Aniline), EBBA (Ethoxy-Benzilyden-Buthyl-Aniline) and a mixture of the two is selected. ao