JPS58201294A - Electroluminescent element and method of producing same - 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 The present invention relates to an EL (electroluminescence) element used in display devices and the like, and more particularly to an EL element with a new structure that improves luminance and enables low voltage driving.

Conventional EL elements have double insulation, in which an EL light emitting layer is sandwiched between insulator layers on both sides, and then from the outside, transparent electrodes mainly made of indium oxide or tin oxide are sandwiched between metal electrodes such as aluminum. The EL emitter layer is directly formed on the layer type and the transparent electrode mainly made of indium oxide or tin oxide.
There is a single insulating layer type in which an insulating layer and a metal electrode are sequentially provided thereon. When these two types of devices were formed with the same total thickness of the insulating layer and the same thickness of the light emitter layer, the single insulating layer type had the same total thickness as the light emitting layer. It was found that although the emission threshold voltage was lower than that of the insulating layer type, the emission brightness and luminous efficiency were also lower.

The present invention provides a thin film EL element with a reduced emission threshold i-pressure without reducing luminance and luminous efficiency.

Although the device structure of the present invention belongs to a single insulating layer type, at least one of zinc oxide, zinc selenide, and cadmium sulfide is present on one surface of the EL light emitting layer mainly composed of zinc sulfide. It has been discovered that by providing a semiconductor layer consisting of a semiconductor layer and an insulating layer on the other surface, it is possible to form a thin film EL element with high luminance and luminous efficiency and a low driving voltage with good reproducibility. Note that the appropriate thickness of the semiconductor layer is 300 angstroms or more.
If the thickness is thinner than this, the luminous efficiency (2) luminance may be lowered. The reason for this is that the EL
This is considered to be because the light emitting layer and the electrode made of indium oxide or the like on which the semiconductor layer is formed reacted, resulting in a decrease in the luminous efficiency of the EL light emitting layer. Further, after forming at least the semiconductor layer and the EL light emitter layer, at 260°C or higher,
By performing heat treatment at a temperature of 0''C or lower and forming an interdiffusion layer, the drive voltage could be lowered with good reproducibility.

As an EL emitter layer, Mn, Cu, Ag, AI
,Tb.

It has been found that the EL element of the present invention can be constructed using zinc sulfide containing at least one of Dy, Er, Pr, Sm, Ho, Tm, and halides thereof.

The present invention will be explained in detail below. FIG. 2 shows an example of the structure of the element of the present invention.

In the figure, 1 is a glass substrate, Konink 7069
Glass was used. A transparent electrode 2 made of tin-doped indium oxide and having a thickness of 0.1 micron was formed thereon by high-frequency sputtering. A semiconductor layer 3 made of zinc oxide with a thickness of 600 angstroms is formed thereon by high-frequency sputtering.
#l1klf/, 160″c, 1°, and 2×10 Torr of Ar was used as the sputtering gas. Zinc sulfide and manganese as an active material were co-evaporated onto the semiconductor layer 3, and 0.8 atomic % of manganese was deposited. A zinc sulfide EL phosphor layer 4 with a thickness of 0.6 microns was formed containing 0.6 μm in thickness.At this time, the substrate temperature was maintained at 22Q°C, and the deposition was performed at a deposition rate of 1 μm/min. 550'C, 2
Heat treatment was performed for an hour. Next, an insulator layer 6 having a thickness of 0.4 microns was formed by electron beam evaporation of yttrium oxide on the light emitting layer 4 at a substrate temperature of 80''C.Finally, aluminum was vacuum evaporated. In this way, a reflective electrode 6 was formed.

Next, we will discuss the characteristics of the EL device manufactured in this way in the third section.
This will be explained using figures. Line (a) in the figure shows the luminance of the device in this example when a 2KHz sine wave voltage is applied, and line (Φ) in the figure shows the characteristics of the device in which only the semiconductor layer 3 was not formed in this example. (C) o on the transparent electrode,
2 micron thick yttrium oxide, 0.6 micron thick manganese activated zinc sulfide EL phosphor layer, and 0.6 micron thick manganese activated zinc sulfide EL phosphor layer.
．． Sequentially forming yttrium oxide with a thickness of 2 microns,
Finally, the characteristics of a conventional EL element with a double insulating layer structure provided with an aluminum reflective electrode will be shown. As can be seen from FIG. 3, the device of the present invention can achieve
It is possible to reduce only the drive voltage, and it is possible to lower the voltage of the drive circuit.

In this example, a case was explained in which zinc oxide was used as the semiconductor layer, but similar effects could be obtained using zinc selenide or cadmium sulfide.

Furthermore, as a result of research on safety and low voltage, we found that the dielectric constant of strontium titanate, barium titanate, lead titanate, etc., with a thickness of 0.6 to 3 microns as an insulator layer,
It has been found that by using a thin film with high dielectric strength, it is possible to form an EL element with excellent stability that can be driven at low voltage.

As explained above, the device of the present invention can realize an EL device that has high luminance and efficiency and can be driven at a lower voltage than the conventional double insulating layer type EL device. The reason is thought to be that the mechanism for injecting electrons into the EL light emitting layer is different from that of conventional double insulating layer type elements.

The device of the present invention can be applied as a flat display panel by arranging electrodes in a matrix, and has high practical value.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the voltage-luminance characteristics of conventional single insulating layer type and double insulating layer type EL (electroluminescence) elements, and Fig. 2 is an example of the structure of the EL element according to the present invention. The cross-sectional view and FIG. 3 are diagrams showing voltage-luminance characteristics of an EL element according to the present invention and a conventional EL element. 1...Glass substrate, 2...Transparent electrode, 3-
...Semiconductor layer, 4--EL light emitter layer, 6--Insulator layer, 6--Reflecting electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Elevation fJ mouth voltage (Vλ

Claims (1)

[Scope of Claims] (1) An electroluminescent phosphor layer containing zinc sulfide as a main component, comprising zinc oxide, zinc selenide, and cadmium sulfide provided on one surface of the electroluminescent phosphor layer. a semiconductor layer made of at least one type selected from the group consisting of; an insulating layer provided on the other surface of the luminescent layer; and the electroluminescent luminescent material via the semiconductor layer and the insulating layer. An electroluminescent device characterized in that it comprises means for applying an alternating current voltage to the layers. I2) q! characterized in that a semiconductor layer, an electroluminescent layer, an insulator layer, and an electrode are sequentially laminated on a transparent electrode formed on a glass substrate. f71 - Elect IJ Lebanese element according to claim 1. ) The electroluminescent emitter layer is Mn, cu. Ag, Al, Tb, Dy, Er, Pr, Sm, Ho
, Tm, and halides of these.
The electroluminescent device described in Section 1. (4) Claim 1 or 2, characterized in that the thickness of the semiconductor layer is 300 angstroms or more.
The electroluminescent device described in Section 1. (5) Each layer of a semiconductor layer made of at least one member selected from the group consisting of zinc oxide, zinc selenide, and cadmium sulfide, an electroluminescent layer containing zinc sulfide as a main component, and an insulator layer. are formed adjacent to each other in this order, and after the formation of the semiconductor layer and the light emitting layer, heat treatment is performed at a temperature of 260"C or more and 650°C or less to cause interdiffusion between the semiconductor layer and the light emitting layer. A method for manufacturing an electroluminescent device, comprising forming a layer.