JPS62176095A - Electrolumunescence 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] [Industrial Application Field] The present invention relates to an EL device used as a light emitting display device or a surface light source.
The present invention relates to (electroluminescence) elements, and in particular to electrode structures of EL elements.

[Conventional technology]

Since the discovery in 1936 of so-called electroluminescence, which causes a phosphor material to emit light by applying a voltage, much research and development has been conducted with the aim of applying it to surface light sources and display devices. At present, AC-driven thin-film EL elements, which have a thin film emitting layer consisting of a phosphor layer and an insulating layer and are sandwiched between two electrodes, one of which is transparent, have excellent brightness characteristics and stability, and are being put into practical use as various displays. It is provided.

Figure 4 shows a typical conventional LE element such as Niss.I.D.74.
The double insulation type F noted on page 84 of
A cross-sectional view of an X-film EL element is shown. In FIG. 4, the structure includes a transparent electrode 42, a first insulating layer 43, a phosphor layer 44, a second insulating layer 45, and a back electrode 46, which are laminated on a substrate 41 made of glass.

An AC voltage is applied between the electrodes 42 and 46 by the drive circuit 18, and the phosphor layer 44, such as ZnS:Mn, has an IQ of 6 V/cm or more.
Bright light emission can be obtained by inducing a second high electric field. , :This is because electrons in the light-emitting layer are accelerated at high speed by a high electric field, and the light-emitting centers of Mn, etc. are excited by collision. When ZnS:Mo is used as the phosphor layer 44, the color is yellow-orange, but various colors can be obtained by selecting the luminescent center substance and phosphor material. Furthermore, the insulator layers 43 and 45 prevent excessive direct current from flowing through the element, thereby providing stability against element breakdown. Furthermore, the insulator layers 43 and 45 have a polarization effect and an effect of preventing the diffusion of harmful ions, and contribute to improving device characteristics and reliability.

1. Problems to be Solved by the Invention] As shown in FIG. It has a structure sandwiched between two electrodes. Although such a power station configuration is the simplest, since transparent electrodes such as ITO are also used as wiring electrodes, the resistance value of the transparent electrodes increases power consumption and generates Joule heat. Furthermore, when the driving pulse width is narrow, there is a problem that a sufficiently high voltage is not applied to the light emitting layer.

Means for Solving Problem 1] The Ellen I luminescence device of the present invention is formed on one side of a light emitting layer consisting of an electroluminescent phosphor layer and at least one insulating layer, each of which is connected to a drive circuit. a floating third electrode that is provided on the other surface of the light emitting layer so as to have an overlapping portion with the first and second electrodes and is not connected to an external drive circuit. It consists of:

The electro-luminescence element of the present invention is configured such that a light emitting layer is sandwiched between the second electrode and the third electrode, or only an insulating layer is sandwiched between the first electrode and the second electrode. You can also do it.

1 action] Next, the operation of the present invention will be explained using FIG.

A third electrode made of a transparent electrode is formed on the glass substrate 11, and a first insulating layer 13. Phosphor layer 14, second
A light emitting layer made of an insulator layer 15 is formed, and a first electrode 16 and a second electrode 17 are further formed thereon. The first electrode 16 and the second electrode 17 are directly connected to the drive circuit 18, but the third electrode 12 is a floating electrode that is not connected to the drive circuit 18, as shown in FIG. It is formed so as to have an overlapping portion with the first and second electrodes 16 and 17! First electrode 16 and second electrode 1
7, the applied voltage is applied between the first electrode 16 and the third electrode 12 and between the third electrode 12 and the second electrode 17.
It is applied dividedly in between.

Due to this divided voltage applied, light is emitted at the overlapped portion of the third electrode 12 and the first and second electrodes 16 and 17.

In such a structure of the present invention, the third electrode 12 is formed for each pixel, and there is no adverse effect even if a transparent electrode whose resistance is not so low is used. Further, since the electrodes 16 and 17 to which voltage is directly applied are formed on one side of the light emitting layer, it also has the advantage that connection with an external drive circuit is structurally easy.

〔Example〕

Next, the present invention will be explained in more detail.

A first embodiment of the present invention having the structure shown in FIG. 1 will be specifically described. A third electrode 12 made of a rectangular ITO transparent conductive film is formed on a transparent glass substrate 11, and BaTiO3 is formed as a first insulating layer 13 thereon.
Sputter curtain, ZnS:Mn vapor deposited film as phosphor layer 14,
After sequentially depositing m layers of DaTiO-4 spruce and ivy films as the second insulator layer 15, a first electrode 16 made of an Ae thin film is formed. Second
Electrode 17 was formed. The overlapping areas of the first electrode and the third electrode and the overlapping areas of the second electrode and the third electrode have the same area. The drive circuit 18 that generates the AC voltage pulse is connected to the first electrode 16 of this embodiment,
By connecting the second electrode 17 to the electrode 12 and the electrode 1
6. The overlapping part of 17 emitted bright light.

Second [S1 shows the structure LJ of the second embodiment of the present invention,
.

A first electrode 26 made of an A2 thin film is disposed on the substrate 21. After forming the second electrode 27, the first insulator layer 23. ZnS:Mn phosphor layer 24. A second insulator layer 25 was formed. 23.2
As the insulator layers 23 and 25 of No. 5, a BaT:0* sputtered film was used. Finally, the third electrode 22, which is a transparent electrode made of I'O, is formed.

The structure of this embodiment is opposite to that of the first embodiment shown in FIG. Furthermore, in this embodiment, the first electrode 26
The area of the overlapping portion of the second electrode 27 and the third electrode 22 is larger than the area of the overlapping portion of the second electrode 27 and the third electrode 22. When a voltage is applied between the first electrode 26 and the second electrode 27 by the drive circuit 18, the voltage is divided in inverse proportion to the area of the overlapped portion. In this case, light emission first opens as the external voltage increases! , -1 third electrode 22 and second electrode 27
It emits brighter light than the overlapped part. Such light emitting elements can be used, for example, as various indicators.

In the present invention, it is not always necessary to emit light from the overlapping portions of both the third electrode, the first electrobalance electrode, and the second electrode. Furthermore, it is not necessary to have a double insulation structure as a light emitting layer, and a single insulation type may be used. A third embodiment of the present invention with such a side path is shown in FIG. A third electrode 32 made of ITO, a BaTi[)3 insulator layer 33, and a Zn
An S:Mn phosphor layer 34 is formed. Insulator layer 33
is formed on the entire surface, but the phosphor layer 34 is formed on the insulator layer 33.
partially formed on top. As shown in Figure 3, the first
The electrode 36 is formed on the insulator layer 33, and the second electrode 37 is formed on the phosphor layers 3 and 4 so as to overlap with the third electrode 32. By applying a voltage between the first electrode 36 and the second electrode 37, the overlapping portion of the second electrode 37 and the third electrode 32 emits light.

In the first and second embodiments, the external drive voltage had to be higher than that of the conventional EL element, but in the structure of this embodiment, it is not necessary to make the external drive voltage that high. In particular, a material with a high dielectric constant such as BaTiO3 is used as the insulator layer 3.
3 was used to produce this example, and it was possible to emit light with almost the same external driving voltage as a conventional EL element.

1. Effects of the Invention] As described above, the present invention provides a transparent electrode that defines a light-emitting region even though the sheet resistance is relatively high.

This has the effect of not increasing Joule heat and allowing high voltage to be applied even if the drive pulse is slow. Further, it is also possible to easily realize an element having portions with different luminance brightness using a single driving voltage. In addition, since the electrodes that must be connected to an external drive circuit can be formed on only one side of the light-emitting layer, it is structurally easy to connect to an external drive circuit, providing new E-L and freedom in device creation. The degree is added Lp.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the first embodiment of the present invention, FIGS. 2 and 3 are cross-sectional views of the second and third embodiments of the present invention, respectively, and FIGS. Source 11'A ζ゛1
:・,ru. 11.21, 31.41...Substrate, 12, 22°32
...Third electrode, 1B, 23.43...First insulator layer, 33...Insulator layer, 14,24,34.411...
Phosphor layer, 15, 25.45... second insulator layer, 16.
26.36... First electrode, 17, 27.37... Second electrode, 46... Back electrode, 18... Drive circuit, 4
2...Transparent electrode. Figure 1 - Rock 2 Figure Cow 3 Figure Hand -1 Figure

Claims (2)

[Claims] (1) A first electrode and a second electrode formed on one surface of a light emitting layer consisting of an electroluminescent phosphor layer and at least one insulating layer and each connected to a drive circuit, and the other side of the light emitting layer. An electroluminescent element comprising a floating third electrode which is provided on a surface thereof so as to have an overlapping portion with the first electrode and the second electrode, and which is not connected to an external drive circuit. (2) In the electroluminescent device according to claim 1, a light emitting layer is sandwiched between the second electrode and the third electrode, but only an insulating layer is sandwiched between the first electrode and the second electrode. An electroluminescent element characterized by being sandwiched.