JPH02195684A - Thin film el device - Google Patents

Abstract

PURPOSE:To improve intensity of a thin film EL device with a high withstand voltage thereof kept by laminating plural kinds of high dielectric layers by electron beam deposition for forming an insulation layer. CONSTITUTION:A fluorescent electrode 2 with a thickness of 2000Angstrom is formed on a transparent glass substrate 1 to be a desired pattern. BaTiO3 is laminated thereon with a thickness of 6000Angstrom to be a first insulation layer 3 by sputtering. ZnS:TbF is further laminated thereon with a thickness of 5000Angstrom to be a luminous layer 4 by sputtering. After the laminated body is heated in vacuum at 350 deg.C for an hour, a HfO2 layer 7 of a high dielectric body with film-thickness of 400Angstrom , a SiO2 layer 8 of 600Angstrom and another HfO2 layer 7 of 800Angstrom are laminated on the laminated body in order by electron beam deposition. A second insulation layer 5 in which plural kinds of high dielectric bodies are laminated like a sandwich is thus formed. A back electrode 6 of such as Al with film-thickness of 2000Angstrom is formed on the second insulation layer 5 to form a thin film EL device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an AC-driven thin film EL (electroluminescence) element.

(Prior Art) Generally, this type of thin film EL device is manufactured by, for example,
As disclosed in Japanese Patent No. 170891 and shown in FIG. 4, it has a double insulating layer structure and is made of a transparent insulating plate made of glass or the like. A transparent electrode 2 made of a transparent conductive material is formed, and then SiO2,
AQ201. A first insulating layer 3 made of an oxide insulating material such as YzO+ or Taxes, a light emitting layer 4 made of a fluorescent material in which a luminescent center such as Mn is added to a base material such as ZnS, and a first insulating layer. A second insulating layer 5 made of the same material as the layer 3, and a back electrode 6 made of a conductive material such as A, which faces the transparent electrode 2 and serves as a reflective electrode, are sequentially deposited in this order. It is formed by laminating layers using an appropriate method such as or sputtering.

When an AC voltage is applied between the transparent electrode 2 and the back electrode 6, the electric field generated between the electrodes 2 and 6 causes light emission N4.
emits light and is irradiated to the outside through the substrate l.

(Problem to be Solved by the Invention) In such a thin film EL device, in order to apply a stable electric field to the light emitting layer 4, increase the withstand voltage of the device, and reduce power consumption and heat generation, the insulating layer 3. is usually SiO□ or Si
A high dielectric material having high resistivity and low dielectric loss, such as 3N, was formed singly by a method such as sputtering or vapor deposition. However, since these materials have high resistivity, they have the advantage of increasing the withstand voltage of the insulating layer 3.5; There was a problem in that the brightness of the EL element decreased as a result.

SUMMARY OF THE INVENTION The present invention has been made based on the above problem, and it is an object of the present invention to provide a thin film EL device that can improve brightness while maintaining a high breakdown voltage of the device.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a thin film EL element in which a light emitting layer in which an insulating layer is laminated on the negative side is provided between a transparent electrode and a back electrode that are arranged opposite to each other. The layer is formed by laminating multiple types of high dielectric layers by electron beam evaporation.

(Function) The insulating layer formed by laminating multiple types of high dielectric layers by electron beam evaporation becomes a low resistivity layer, increasing electron injection from the bonding surface with the light emitting layer, while maintaining high breakdown voltage. Emission brightness can be improved.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. In this embodiment, parts having the same functions as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals, and detailed explanation thereof will be omitted. FIG. 1 shows a first embodiment, in which a transparent electrode 2 is formed on a transparent glass substrate 1 (NA-40) to a thickness of 20 mm using a method similar to the conventional example, such as sputtering.
This transparent electrode 2 is patterned into a desired pattern, and BaTi0 is deposited on it by sputtering.
A first insulating layer 3 is formed by stacking + to a thickness of 6000,
Furthermore, 5,000 layers of ZnS:TbF are laminated thereon by a sputtering method to form a light-emitting layer N4. and,
350°C in vacuum.

After heat treatment for 1 hour, first a high dielectric HfO□ (hafnium oxide) layer 7 was formed with a thickness of 400 mm by electron beam evaporation, and then 5T (h (silicon oxide) N8 was formed with a thickness of 600 mm). Finally, Hf (hWi7) is sequentially laminated to a thickness of 800 to form a second insulating layer 5 in which multiple types of high dielectric materials are laminated in a sandwich-like manner. In this case, the oroz layer 7 The film thickness is 200 to 2000 people.

The thickness of layer 8 is within the range of 100 to 2000 layers.

Thereafter, a back electrode 6 having a thickness of 2,000 layers is formed on the second insulating layer 5 by etching or the like to form a thin film EL element.

The thin film EL device of the present invention configured as described above has a second
The insulating layer 5 is formed by an electron beam evaporation method to have a laminated structure of a Hf01 layer 7 and a Si02 layer 8 having different high dielectric constants. In this case, Hf is
When the O,Jii 7 and the SiO□ layer 8 are laminated, the second insulating layer 5 becomes a low resistance layer of about 10"Ω1, and therefore, electrons from the bonding surface between the second insulating layer 5 and the light emitting layer 4 are The injection is increased, and as shown in Figure 2, the luminance and luminous efficiency are approximately doubled compared to the conventional single-layer structure of TatOs, for example. ) is a logarithmic scale.When conventional Taxes are formed by sputtering, the resistivity is 10'6 to 1012Ω0.The second insulating layer 5 is made of 5inz with high breakdown voltage.
Since the layer 8 is included, the withstand voltage of the device is sufficiently high, and if the thickness of the SiO□ layer 8 is within the range of 300 to 1200, particularly good characteristics can be obtained, but if it is thicker than this, the luminance will decrease. decreases, and if the thickness is made thinner than this, dielectric breakdown is likely to occur. In this way, according to the present invention, it is possible to improve luminance while maintaining a high breakdown voltage.

FIG. 3 shows a second embodiment, in which a Tames (tantalum oxide) layer 9 is laminated instead of SiO□N8 in the first embodiment, and is similarly formed by electron beam evaporation. In this case, the film thickness of Tames [9 is 6
00 people, preferably in the range of 100 to 2000 people. Also, as shown in FIG. 2, the voltage and brightness characteristics of the second embodiment are about twice as bright as the conventional one.

Although the embodiments of the present invention have been described in detail above, modifications can be made as appropriate within the scope of the gist of the present invention. For example, in the embodiment described above, the second insulating layer 5 has a three-layer stacked structure, but it may have an at least two-layer structure. Further, the first insulating layer 3 may also have a laminated structure of a plurality of types of high dielectric materials. Furthermore, the type of high dielectric material is not limited to the above embodiments. Further, the present invention can also be applied to a thin film EL element having only one of the insulating layers 3.5.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a thin film EL element in which a light emitting layer having an insulating layer laminated on at least one side is provided between a transparent electrode and a back electrode which are arranged opposite to each other, a plurality of the insulating layers are stacked. By stacking various high dielectric layers by electron beam evaporation, it is possible to provide a thin film EL device that can improve brightness while maintaining a high breakdown voltage of the device.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the first embodiment of the present invention, Fig. 2 is a graph showing the characteristics of applied voltage and brightness, Fig. 3 is a cross-sectional view showing the second embodiment, and Fig. 4 is a conventional example. FIG. 2...-Transparent electrode 4-Light emitting layer 5-Second insulating layer 6-Back electrode 7-HfO2 layer (high dielectric layer) 3---5iOz layer (high dielectric layer)

Claims (1)

[Claims] (1) Thin film E in which a light-emitting layer with an insulating layer laminated on at least one side is provided between a transparent electrode and a back electrode arranged oppositely.
A thin film EL element, wherein the insulating layer is formed by laminating a plurality of types of high dielectric layers by electron beam evaporation.