JPS63128595A - Thin film electroluminescence device - 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 [Technical Field] The present invention relates to a thin film EL that emits light by applying a voltage to the EL light emitting layer.
This invention relates to a technology for chipping devices, and in particular to minimizing sunspots caused by dielectric breakdown.

"Prior art and its problems" A conventional thin film EL element, for example, as shown in FIG. 2, has a transparent electrode 2 made of ITO or the like on a glass substrate 1,
An insulating film 3 made of 2O5, 5j3N4, etc., an EL light emitting layer 4 doped with an activator such as 2nS, an insulating film 5 similar to the above, and a back electrode 6 made of a metal thin film are sequentially laminated to form a thin film. The portion is sealed with a glass cap (not shown) or the like.

This thin film EL element has a transparent electrode 2 and a back electrode 6.
By applying an alternating current voltage of several tens of Hz to several KHz between them, the active species ions in the EL light emitting layer 4 are excited and emit light. This thin film EL element is
In recent years, it has been applied to various displays.

Incidentally, in the case of an AC operation EL, a high voltage of 100 to 400 μ is required to emit light from a thin film EL element, and the higher the applied voltage, the brighter the emitted light becomes. Generally speaking, in order to ensure high voltage, the distance M between the transparent electrode 2 and the back electrode 6 is kept short.
The EL light emitting layer 4 and the insulating layer 5 are formed as thin as possible, and the light emitting layer /j
[I try to make it brighter.]

However, since the above-mentioned high voltage is applied, if there is a defect such as a black spot in the insulating layer 3.5, dielectric breakdown will occur due to a short circuit in that part, and the transparent electrode 2 or the back electrode 6 will have a defective part. Occur. In other words, due to a short circuit, the current flows in a concentrated manner, causing the temperature of that part to become abnormally high, which can lead to the constituent materials melting, etc.
! The defective part caused by the destruction becomes a black dot on the display surface. In this case, the transparent electrode 2 has considerable unevenness,
Since it is difficult to make the thickness of each layer formed thereon uniform, dielectric breakdown due to short circuits is unavoidable to some extent.

If the sunspots caused by dielectric breakdown as described above are small, they are not noticeable to the naked eye, so there is no particular problem.If a partial breakdown causes a short circuit in the surrounding @poles, and the area of breakdown spreads, A black spot is formed that is visible to the naked eye, making it impossible to use the device.

[Object of the Invention] An object of the present invention is to provide a thin film EL element that can be used even if dielectric breakdown occurs by minimizing the traces of dielectric breakdown.

“Structure of the Invention” The thin film EL device according to the present invention includes a transparent binding substrate,
At least a transparent electrode, an EL light emitting layer, an insulating film, and a back electrode are laminated, and a thermally conductive layer with a thermal conductivity of I w/cm or higher than RT is formed at any part of the laminated structure. It is characterized by being

Therefore, when dielectric breakdown occurs in a part due to a short circuit, the heat generated by the short circuit is diffused through the heat conductive layer, so that it is possible to prevent the breakdown from spreading. In this way, if traces due to dielectric breakdown are minimized, the size of the traces is about 1 to 2 um, so they are not visible to the naked eye and are very important for the use of the device! ! It never comes to life.

In the present invention, the location where the heat conductive layer is provided is not particularly limited, and may be provided at any location in the laminated structure. For example, it can be formed: (1) between the substrate and the transparent electrode, (2) outside the back electrode, (2) at any gate of the transparent electrode, EL light emitting layer, insulating layer, and back electrode. Incidentally, when the heat conductive layer is formed closer to the display surface than the transparent light emitting layer, the heat conductive layer must be made of a transparent material. Moreover, in the present invention, the heat conductive layer may be provided in plural layers, and in that case, the number of heat conductive layers can be increased roughly. Roughly speaking, when the thermally conductive layer is formed outside the back electrode, the thermally conductive layer can also serve as a passivation film.

The thermal conductivity of the material of the thermally conductive layer is 1w/cmK, R
A material that is T or more and has electrical insulation properties is used. If the thermal conductivity is less than Iw/cmK, RT, the effects of the present invention cannot be fully expected. Preferred materials for the thermally conductive layer include, for example, helium oxide (BED), silicon oxide (SiC), and aluminum oxide (AIN).
), etc. The thickness of the thermally conductive layer is 500 mm.
Approximately A~2 um is appropriate.

"Embodiments of the Invention" FIG. 1 shows an embodiment of a thin film EL device according to the present invention. This thin film EL device was manufactured as follows.

That is, on a commercially available glass substrate 11 (ζ), a thermally conductive layer 12 made of silicon carbide (SiC) is formed to a thickness of 2 um by a sputtering method. On this thermally conductive layer 12, a transparent electrode 13 of In2O3-SnO2 type The insulating layer 14 made of Y2O5 is formed on the transparent electrode 13 to a thickness of 300 A using a sputtering method.Subsequently, the insulating layer 14 is An EL light-emitting layer 15 doped with 2nS and Mn! is formed on soil to a thickness of 4000A by sputtering.Roughly, an insulating film 16 made of Y, 205 is formed on the EL light-emitting layer 15 to a thickness of 3000A in the same manner as described above. Then, on this termination layer 16, AI is vacuum deposited to form a back electrode 17 with a thickness of 100 OA.A passivation film (not shown) may be formed on the back electrode 17. .

In this thin film EL element, by applying an alternating current voltage between the transparent electrode 13 and the back electrode 17, the EL light emitting layer 15 emits light, and the pattern of the transparent electrode 13 to which the voltage is applied is displayed on the transparent electrode. It is visible through the glass substrate 11 from the 13 side.

In this thin film EL element, when dielectric breakdown occurs due to whitening, the heat generated by the short circuit is quickly radiated to the outside through the heat conductive layer 1218.
Expansion of the breakdown can be prevented, and the sunspots caused by the dielectric breakdown can be kept as small as possible. The apparent withstand voltage was measured for the thin film El element shown in FIG. 2 without the thermally conductive layer 12 and the thin film El element according to the above example, and the results are shown in the following table.

Note that in the above embodiment, the heat conductive layer 12 is connected to the back electrode 1.
In the thin film EL element formed on the vertical side of 7, the heat conductive layer 12 is placed between the insulating film 14 and the EL light emitting layer 15 and the EL light emitting layer 15
The thin film EL elements formed in the two regions between the insulating film 16 and the insulating film 16 were manufactured respectively, and an effect of improving the apparent withstand voltage similar to that of the above embodiment was observed.

In addition, in the above embodiment, a thin film EL element was manufactured in which the thermally conductive layer 12 was made of beryllium oxide (BED) or aluminum nitride (AIN), but the same effect of improving the apparent withstand voltage as in the above embodiment was obtained. Admitted.

"Effects of the Invention" As explained above, according to the present invention, the thermal conductivity is l
W/cm is provided with a heat conductive layer with a temperature higher than RT, so when dielectric breakdown occurs due to a short, the heat generated by the short quickly diffuses through the heat conductive layer and is dissipated to the outside, reducing the expansion of the breakdown. can be minimized. Therefore, the main sunspots can be made as small as possible through dielectric breakdown, and the apparent withstand voltage can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a thin film EL device according to the present invention, and FIG. 2 is a sectional view showing an example of a conventional thin film EL device. In the figure, 11 is a glass substrate, 12 is a heat conductive layer, 13 is a transparent electrode, 14 is an insulating film, 15 is an E1 light emitting layer, 16 is an insulating film, and 17 is a back electrode.

Claims (5)

[Claims] (1) At least a transparent electrode and an E
In a thin film EL element formed by laminating an L-emitting layer, an insulating film, and a back electrode, a thermal conductivity of 1 W/cmK. A thin film EL device characterized by being formed with a heat conductive layer of RT or higher. (2) The thin film EL element according to claim 1, wherein the thermally conductive layer is made of a transparent material and is formed between the substrate and the transparent electrode. (3) The thin film EL device according to claim 1, wherein the thermally conductive layer is formed outside the back electrode. (4) A thin film EL device according to the first aspect of the present invention, wherein the thermally conductive layer is formed between any one of the transparent electrode, the EL light emitting layer, the insulating film, and the back electrode. (5) A thin film EL device according to any one of claims 1 to 4, wherein the thermally conductive layer is made of a material selected from beryllium oxide, silicon carbide, and aluminum nitride.