JPS6040160B2 - electroluminescent device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film electroluminescent device (thin film EL device) that emits light by applying an alternating voltage or an alternating pulse voltage, and relates to a device having a novel laminated structure to obtain particularly excellent characteristics. This is what we are trying to provide.

Conventionally, when an alternating current electric field is applied to a laminated structure in which a thin film emitting layer such as a manganese-activated zinc sulfide thin film is supported by an insulating layer such as silicon oxide (Si02-x), the thin film emitting layer exhibits EL emission. is known.

In such an EL element, an insulating layer with a thickness of approximately 0.2 molar is provided on a glass substrate on which a transparent electrode is formed, a thin film emitting layer of approximately 0.5 molar thickness is provided on top of the insulating layer, and a thin film emitting layer of approximately 0.5 molar thickness is provided on top of the insulating layer. ．．
2. When a skin insulating layer is provided and a metal electrode such as aluminum is provided on the insulating layer, light emission starts with an applied voltage of about 140 V, and the luminance increases as the applied voltage increases. When the applied voltage is further increased, dielectric breakdown occurs at about 200V. When such an EL element is used as a display element, it is desirable that the dielectric breakdown voltage is high and the emission start voltage is low. It is known that increasing the dielectric breakdown voltage can be achieved by increasing the thickness of the insulating layer or the light-emitting layer, but in that case, the emission start voltage also increases, making it impossible to achieve a substantial effect. As a result of various studies to increase the dielectric breakdown voltage and lower the emission starting voltage, the inventors succeeded in achieving the objective by using an oxide for the insulating layer and further arranging the Mn02-x layer in contact with this oxide layer. After seeing the scales of achieving this, we came to complete the present invention.

FIG. 1 is a diagram for explaining one embodiment of the element of the present invention. In the figure, reference numeral 11 denotes the thin film EL element of this embodiment, in which a lower electrode 13 is formed on an insulating substrate 12, and a Mn02-x (OSx<0.5) layer 14 is formed on it. Further, an oxide insulating layer 15, a thin film light emitting layer 16, and an oxide insulating layer 17 are formed in this order on top of the oxide insulating layer 15, and an upper electrode 18 is formed thereon. As the insulating substrate 12, a normal thin film substrate such as glass, alumina, or forsterite can be used.

Either the lower electrode 13 or the upper electrode 18 is made of Sn02
or ln203, and the other is made of N.
, P, Au, or other metals may be used.

The M 2* layer 14 is the most characteristic in this embodiment, and its thickness is suitably between 0.02 and 0.8A.

If it is 0.02mm thinner than the skin, continuous Mn02~
It is difficult to form the layer, and if it is thicker than the 0.8 mound, the effective electric field applied to the thin film light emitting layer 16 will be reduced, and a longer time will be required to form the Mn layer. Therefore, it is not practical. Oxide insulating layers 15, 17
are Be, Mg, Y, Ti, Zr, Hf, Nb, Ta, C
Oxides of r, Mo, W, Zn, AI, Ga, Sj, or lanthanide elements are used, and mixtures or compounds thereof may be used.

The thickness of this insulating layer is suitably 0.02 to 0.8 mm. If it is thinner than 0.02 mounds, it is difficult to form a continuous oxide insulating layer, and if it is thicker than 0.8 mounds, the threshold voltage for light emission will be high; It is not practical because it easily causes dielectric breakdown. The thin film light emitting layer 16 is
For example, zinc sulfide containing active substances can be used. Active substances include Mn, Cu, Ag, TbF3, Sm
F3, ErF3, TmF2, DyF3, PrF3, E-Misaki3, etc. are suitable. The thin film emissive layer 16 may be made of materials other than zinc sulfide, such as SrS or CaS containing active materials.
Any material that shows Ryuba luminescence, such as, may be used. The thickness of this thin film light emitting layer 16 is suitably 0.1 to 2 squares. If it is thinner than 0.1mm, the luminous efficiency will be poor, and if it is thicker than 2mm, the luminous intensity and value voltage will be high, making it impractical. As a result of applying an AC voltage between the lower electrode 13 and the upper electrode 18 and investigating the light emitting characteristics of this device, it was found that M
It has been found that the dielectric breakdown voltage is increased and stable light emission can be obtained compared to the conventional element in which the n02★ layer 14 is not interposed. In addition, even when using a thin insulating layer (for example, a 0.05 mm thick insulating layer), which could not be achieved with almost good reproducibility in conventional EL elements, stable light emission can be obtained, and It emits light automatically, making it possible to lower the value voltage. The effect of the Mn02-X layer, which greatly improves the characteristics of EL devices, is currently not clear, but the Mn02-X layer acts like a solid electrolyte, and the weak parts of the insulating layer, i.e. In order to irreversibly oxidize areas with many oxygen vacancies, or when local dielectric breakdown occurs in the insulating layer, the heat generated causes the 02★ to be reduced and the insulating Mn is reduced.
This is thought to be due to changes in the 2Q. Further, there is a thickness of 0 between the lower electrode 13 and the Mn02-x layer 14.
．． It has been found that by interposing an AI203 layer of 0.02 to 0.5 French, the device can be driven more stably.

Next, a specific example of the present invention will be described using FIG. 2.

A thin film EL device 21 shown in FIG. 2A was manufactured using the following procedure. Commercially available Nesa Glass 22 is used as a substrate, and its transparent conductive film 2
On the surface coated with Y203, Y203 was deposited to a thickness of 0.1 μm at a substrate temperature of 30,000 ℃ by electron beam evaporation to form an oxide insulating layer 24. Next, set the substrate temperature to 250QO
Zns:Mn (M concentration is 1 mol%) was maintained at 0.
A thin film light emitting layer 25 was formed by electron beam evaporation to a thickness of four peaks. After the deposition, a heat treatment was subsequently performed in a vacuum chamber at a temperature of 55,000 ℃ for 1 hour to improve the characteristics of the thin film light emitting layer 25. Then, on top of this, 0.1
By electron beam evaporating Y203 to the thickness of the skin,
An insulating layer 26 was formed. Note that the substrate temperature at this time is 3
It was set to 50oo. Furthermore, on top of this, a 0.1-thick mountain surface M
The n02M layer 27 was formed by high frequency sputtering. At this time, Mn02 was used as the target, the substrate temperature was 30,000, and the atmosphere was 1:1 of argon and oxygen.
1 mixed gas was used. Furthermore, an AI203 layer 28 having a thickness of 0.05 mm was formed thereon by high frequency sputtering. At this time, an AI203 plate-shaped ceramic was used as the target, the substrate temperature was set to 200 oo, and a 1:1 mixed gas of argon and oxygen was used as the atmosphere. Furthermore, aluminum was vacuum-deposited to a thickness of 0.2 mm to form an upper electrode 29 thereon, thereby completing the thin film EL element 21. FIG. 2B shows voltage-luminance characteristics when a sine wave voltage of 5k ratio is applied between the transparent conductive film 23 and the upper electrode 29 of this thin film EL element 21. In addition, Figure 2B
In , the solid line a shows the voltage-luminance characteristic of this EL element 21, and the broken line b shows the voltage-luminance characteristic of the EL element 21, and the broken line b shows the voltage-luminance characteristic of the EL element 21.
The voltage-luminance characteristics of the device are shown. In addition, an x mark indicates dielectric breakdown. As can be seen from this figure, the EL element according to the present example had an increased dielectric strength compared to the conventional element, and was therefore able to operate more stably than the conventional element, resulting in higher brightness. Next, another specific example of the present invention will be explained using FIG. 3.

This thin film EL device 31 shown in FIG. 3A was manufactured by the following procedure. A commercially available aluminum silicate glass was used as a substrate, and after cleaning the glass substrate 32, platinum was sputtered on one surface thereof to form a lower electrode 33 having a thickness of 0.1 Am. A layer 34 of Mn02 to 0.1 mm thick was formed thereon by a pyrolysis method using a manganese nitrate solution. The substrate temperature at this time was about 200 qo. An insulating layer 35 was formed thereon by electron beam evaporation of Si02 to a thickness of 0.05 mound. The substrate temperature at this time was 300°C. Furthermore, on top of this, the substrate temperature is kept at 20,000 and Z
nS: TbF3 (concentration of TbF3 is 5 mol%) at 0.4
Electron beam evaporation was performed to the desired thickness to form a thin film light emitting layer 36. On top of that is a Si02 insulating layer 3 with a thickness of 0.05 mm.
7 was formed in the same manner as described above. By electron beam evaporating 1-03 thereon and forming a transparent electrode 38,
This EL element 31 was completed. And this EL element 3
FIG. 3B shows voltage-luminance characteristics when a 5 kHz sine wave voltage is applied between the transparent electrode 38 and the lower electrode 33 of No. 1. In the figure, the solid line c represents the voltage of this EL element 31 -
The brightness characteristics are shown, and the broken line d shows the voltage-brightness characteristics of a conventional thin film L element that does not include the Mn02* layer. Also, an x mark indicates dielectric breakdown. As can be seen from this figure, by interposing the Mn02-x layer so as to be in contact with the insulating layer, the dielectric breakdown voltage was increased and the luminance could be increased. As described above, the thin film EL element of the present invention uses an oxide for the insulating layer,
Mn02N (OSx<
0.5) Since it has a structure in which layers are arranged, its dielectric strength and stability can be significantly improved, and an extremely thin and stable insulating layer can be formed.
It is possible to substantially lower the threshold voltage for light emission, and is of great practical value.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the lightning field light emitting device according to the present invention, Fig. 2A is a specific block diagram thereof, Fig. 2B is a diagram showing its voltage-luminance characteristics, and Fig. 3 FIG. 3A is a block diagram of another specific example, and FIG. 3B is a diagram showing its voltage-luminance characteristics. 1 1, 21, 31... thin film field L element, 1 4, 2
7, 34...Mn02-x layer, 15, 17, 24,
26, 35, 37... Oxide insulating layer, 16, 2
5, 36... Thin film light emitting layer, 13, 18, 23,
29, 33, 38... Electrode. Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. What is a thin film light emitting layer, an oxide insulating layer provided on both main surfaces of the thin film light emitting layer so as to sandwich the thin film light emitting layer, and the thin film light emitting layer of the oxide insulating layer? MnO_2_-_x (however, 0
≦x<0.5) layer and means for applying an alternating current electric field to the thin film light emitting layer. 2. The electroluminescent device according to claim 1, wherein the thin film luminescent layer is made of zinc sulfide containing an active substance. 3 The active substance is Mn, Cu, Ag, Au, TbF_3,
SmF_3, ErF_3, TmF_3, DyF_3, P
The electroluminescent device according to claim 2, characterized in that it is made of at least one of rF_3 and EuF_3. 4 Oxide insulating layer is Be, Mg, Y, Ti, Zr, Hf
, Nb, Ta, Cr, Mo, W, Zn, Al, Ga, S
2. The electroluminescent device according to claim 1, wherein the electroluminescent device is made of at least one of oxides of i and lanthanide elements. 5. The electroluminescent device according to claim 1 or 4, wherein the oxide insulating layer has a thickness of 0.02 to 0.8 μm. 6. The electroluminescent device according to claim 1, wherein the MnO_2_-_x (0≦x<0.5) layer has a thickness of 0.02 to 0.8 μm. 7 A thin film emitting layer, an oxide insulating layer sandwiching the thin film emitting layer, MnO_2_−_x (where 0≦x< 0.5) layer, Al_2O_ layered on the oxide insulating layer via the MnO_2_-_x layer.
An electroluminescent device comprising: three layers and means for applying an alternating current electric field to the thin film light emitting layer. 8. The electroluminescent device according to claim 7, wherein the thin film luminescent layer is made of zinc sulfide containing an active substance. 9 The active substance is Mn, Cu, Ag, Au, TbF_3,
SmF_3, ErF_3, TmF_3, DyF_3, P
The electroluminescent device according to claim 8, characterized in that it is made of at least one of rF_3 and EuF_3. 10 Oxide insulating layer is Be, Mg, Y, Ti, Zr, H
f, Nb, Ta, Cr, Mo, W, Zn, Al, Ga,
8. The electroluminescent device according to claim 7, wherein the electroluminescent device is made of at least one of Si and an oxide of a lanthanide element. 11. Claim 7 or 10, characterized in that the thickness of the oxide insulating layer is 0.02 to 0.8 μm.
The electroluminescent device described in . 12 MnO_2_-_x (0≦x<0.5)
8. The electroluminescent device according to claim 7, wherein the layer has a thickness of 0.02 to 0.8 μm.