JPH0362497A - Thin film electroluminescent element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a thin film electroluminescent device (hereinafter referred to as a thin film EL device), particularly a thin film EL device having a dense moisture-proof film.
Regarding elements.

[Prior Art] A thin film EL device is a light emitting device that emits light by applying a high electric field to an EL light emitting layer. The materials used for the EL light-emitting layer are often unstable in the atmosphere, so after the element is formed, a glass plate is attached from the back, and a sealant such as silicone oil is placed between the thin-film EL element and the glass plate. A method has been put into practical use in which the device is isolated from the atmosphere by injecting However, in this case, the manufacturing process of the thin film EL element becomes complicated, and the weight and volume of the element itself become large. Therefore, in order to protect a thin film EL element from the atmosphere, a method has been disclosed in which a moisture-proof film is formed over the entire surface of the element after the element is formed (for example, Japanese Patent Laid-Open No. 81-224290). The moisture-proof membrane must be chemically stable and highly dense. Chemically stable materials include nitrides and carbides, but moisture-proof films made of these materials using conventional techniques have not yet been put into practical use.

[Problems to be Solved by the Invention] The present invention attempts to solve the above-mentioned problems by using a thin film EL cord having a moisture-proof film that is chemically stable and has excellent density.

[Means for Solving the Problems] The structure of the present invention for solving the above problems is an AC thin film electroluminescent material having electrodes perpendicular to each other on both sides of an electroluminescent light emitting layer having an insulating layer on at least one side. This is a thin film electroluminescent element in which the moisture-proof film formed on the outermost part of the nessent element is silicon nitride or aluminum nitride containing a rare earth oxide and having a thickness of 0.5 to 2.0 .mu.m.

With this configuration, an element exhibiting better EL characteristics than the conventional one was obtained.

By adding a rare earth oxide to silicon nitride or aluminum nitride, the density of the produced thin film is improved, and as a result, the sealing effect of the thin film is improved. Therefore, the concentration of the rare earth oxide added needs to be at least 1 wt% or more. Further, no change in density is observed at 5 wt% or more.

Therefore, the concentration range of the rare earth oxide to be added is 1 to 5 vt.
% is desirable.

Further, the moisture-proofing effect cannot be obtained unless the thickness of the moisture-proof film is at least 0.5 μm, and if it exceeds 2.0 μm, peeling occurs after the thin film is formed.

Therefore, the optimum film thickness is preferably in the range of 0.5 to 2.0 μm.

When constructing the present invention, there is no need to particularly limit the method of forming the light emitting layer.

The structure of the thin film EL element is not limited in any way, and therefore conventional structures and materials may be used.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example] Here, SrS having a structure as shown in FIG. 1:
A Ce thin film EL device was fabricated.

A ZnO:Al transparent electrode 2 was formed on a glass substrate 1, and then AIN was formed as an insulating layer 3 using RF magnetron sputtering.

Next, a SrS:Ce thin film, which is the light emitting layer 4, was formed using an electron beam evaporation method at a substrate temperature of 500°C. After forming the light emitting layer, a thin film was formed as the insulating layer 5 in the same manner as before, and finally, as the back electrode 6, an AI thin film was formed.

Finally, a thin film (moisture-proof film 7) was produced by RF magnetron sputtering using a target in which lvt% of Y2O3 was added to AIN. At that time, the film thickness was set to 0.3.0.5.1.
Four types of 0.2.0μa+ were prepared respectively (
Elements with a diameter exceeding 2.0 μm are not considered in this example because the moisture-proof film peels off).

FIG. 2 shows the temporal change in luminance of each of the SrS:Ce thin film EL devices thus obtained. A bipolar pulse wave voltage of 1 kHz and 100 μs was applied to excite the device. For comparison, a similar element that does not form a moisture-proof film and A that does not add Y2O3 and have the same film thickness.
A device using an IN film as a moisture-proof film is also shown.

Table (Explanation of FIG. 2) As can be seen from FIG. 2, the luminance of all devices decreases over time, but the degree of luminance decreases to a lesser extent in the device having a moisture-proof film containing Y2O3. Moreover, among them, it can be seen that the characteristics of the element having the moisture-proof film thickness of 0.5 μm or more are excellent.

As described above, by adding Y2O3 to AIN, EL characteristics superior to those of the prior art were obtained.

In this example, Y2O3 was used as the rare earth oxide, but other rare earth oxides such as La2O3, (: e O
2, P r O2, N d 203, Smz 03, G
Similar effects were obtained using d2O3, DY203, and the like.

Further, even when Si3N4 was used instead of AIN, the same effect of adding the rare earth oxide was obtained.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an element that is easier to manufacture than conventional thin film EL elements and has a longer lifespan.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the specific structure of the thin film EL device of the present invention, and FIG. 2 is a graph showing the relationship between the properties of the moisture-proof film of the thin film EL device and the change in emission intensity of the EL device over time. l...Glass substrate, 2...Transparent electrode, 3.5...
Insulating layer, 4... Light emitting layer, 6... Back electrode, 7...
・Moisture-proof membrane.

Claims (1)

[Claims] The moisture-proof film formed on the outermost side of an AC thin film electroluminescent element having electrodes perpendicular to each other on both sides of an electroluminescent light emitting layer having an insulating layer on at least one side is a film containing a rare earth oxide and having a thickness of 0. .5-2.0
A thin film electroluminescent device characterized in that it is made of μm silicon nitride or aluminum nitride.