JPS6147097A - Electroluminescent element - 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 Field of Application] The present invention relates to a thin film electroluminescent device (hereinafter abbreviated as EL device) that emits light by applying an alternating electric field to its light emitting layer.

[Conventional technology]

FIG. 3 shows the basic cross-sectional structure of a double-insulated ffEL element, which is a typical thin film EL element. In the figure, a transparent electrode 2 such as ITO, a first insulating layer 3, a light emitting Jf 14, a second insulating JVI 5, and a back electrode 6 are sequentially laminated on a substrate 1 made of glass or the like. Each layer is produced by vacuum evaporation, sputtering, plasma or photonic method, organic gold method, atomic layer epitaxial method, or the like.

The light-emitting layer 4 is made of a thin film of a compound semiconductor such as ZnS or Zn5e, and by adding a suitable luminescent center, electroluminescence peculiar to the luminescent center is generated.

For example, if a hill is doped as a luminescent center, it will be yellow-orange,
Green electroluminescence can be obtained when doped with TbFst, and red electroluminescence can be obtained when doped with Sml.

It is known that electroluminescence occurs when a high electric field of about 1O@V/CR is applied to a light-emitting layer, and electrons accelerated by the field collide and excite a luminescent center.

The light emitting layer 4 made of Zn8 e Zn5e, etc. is used to prevent local excessive current from flowing when a high voltage is applied, leading to insulation and breakdown, as well as to prevent element deterioration due to moisture, etc. -0, A7. It has a sandwiched structure between I18 green bodies 3 and 5 such as O, etc.

[Problem that the invention seeks to solve]

According to a conventional EL element having such a structure, electroluminescence occurs, so that emission #4 has a voltage of 10 V/c! In addition to requiring an electric field comparable to IL, the applied voltage is divided between the light-emitting layer and the insulating layer, so it is necessary to drive at a high voltage. For this reason, it was necessary to form an insulating layer that is free from defects such as pinholes and has a high dielectric breakdown electric field, so that no dielectric breakdown occurs in the EL string. Furthermore, since it is driven at a high voltage, it has the disadvantage that it is difficult to reduce the cost and size of the drive circuit.

On the other hand, in the conventional IL* element having the configuration shown in FIG. 3, metal such as AJ is usually used for the back electrode 6 in order to reduce the resistance. Insulating layers 3, 5 and light emitting rf! 14 is transparent to visible light, it has the disadvantage that externally incident light is reflected by the front panel 1 and the back electrode, making it difficult to see the KL element and worsening the contrast.

Therefore, the present invention was made in consideration of the above circumstances, and it emits light at a lower voltage than conventional EL elements,
The objective is to provide an EL element with high display quality.

[Failure to solve the problem]

The present invention provides a composite film comprising a light-emitting layer sandwiched between a pair of electrodes in a sandwich-like manner, and a thin insulator, a semiconductor, and an insulator successively laminated between at least one electrode and the light-emitting layer. This is an EL element characterized by intervening.

FIG. 1 is a diagram showing the basic cross-sectional configuration of the present invention. In FIG. 1, a transparent electrode 2 is placed on a transparent substrate 21 such as glass.
2. The 149th edge layer 23 is sequentially formed by vacuum evaporation, sputtering, CVD, etc., and then Z n S p
Zn 8 e or Zn 5
A light emitting 71124 is formed using the ivy method. Thereafter, a thin intermediate insulating layer 25, a semiconductor layer, and a third insulating layer d are formed on the light-emitting layer by plasma (2) method, reactive sputtering method, ion blating method, etc., and finally AJ After vacuum-depositing a gold IF4 electrode 28 such as the above, it is covered with a moisture-proof film 29 to complete the EL element. By applying an alternating voltage between this back electrode 28 and the transparent electrode η, electroluminescence is exhibited.

A feature of the present invention is that by inserting a thin intermediate insulating layer 25 and a semiconductor layer 26 into the light emitting layer-insulator interface of a conventional EL element, an EL element that emits light at a low voltage with almost no reduction in luminance. can now be produced. The reason for this is that electrons generated and accelerated in the semiconductor layer are injected into the light emitting layer, which causes light emission at low voltage.
It is believed that the inclusion of the intermediate insulating layer forms an energy barrier at the light-emitting layer-semiconductor interface, making it possible to effectively inject only high-energy electrons from the semiconductor layer side to the light-emitting layer side. Therefore, luminous efficiency and brightness comparable to those of conventional elements can be obtained at low voltage.In addition to a-8ixNi-x:H, the insulating layer is made of a-8ix('
A similar effect can be obtained by using l-x:H, a-8iOx:H, or a stacked film. Another feature of the present invention is that the semiconductor layer has a band gap of 1.7.
~1.9eV, so it can sufficiently absorb external incident light,
The reflection from the EL element surface is reduced and the contrast is increased. Examples of the present invention are shown below.

[Example 1] In FIG. 1, about 2000 transparent electrodes 72 such as ITO are deposited on a glass substrate 21 by vacuum evaporation, and then
, 300 OA of BaTi0sJil is deposited by f sputtering method to form a first insulating film Ff123. Substrate temperature 200℃
5,000 layers of ZnS and Mn were deposited by co-evaporation, and heat treated at 550° C. for 2 hours in vacuum. After that, a-8ixNl-x:H was converted to 50 to 50% by plasma CVD method.
150 A to form a thin intermediate insulating layer. This a-
8ixN1-x: H formation is N, NH, and SiH,
Gas gold is used, but for the next a-8i:H semiconductor layer 26, the introduction of Ns-NHs is stopped and only 5IH4 gas is used.
The third insulating layer 27 is again made of N,
, Nu, gas was introduced and a-8ixNl-x:H was 200
Form 0 people. Finally, AJ is vacuum deposited to form the back electrode 4. a-8ixN1-x:H and a-8i
:H film is known to be a very dense film, and is highly effective in preventing deterioration caused by moisture intrusion into the light emitting layer, such as peeling and reduction in brightness. x:H
e a-8i:1(t a-8xxNl-x:H) The composite film made by sequentially laminating the gas composition can easily change the gas composition continuously without interrupting the process.For this reason, dirt, dust, etc. There is very little penetration, making it possible to keep defects that can cause dielectric breakdown to a sufficiently small size.

[Embodiment 2] FIG. 2 is a block diagram showing another embodiment of the present invention. In FIG.
3. Intermediate insulating layer 34, semiconductor layer 35, third insulating WI36
and back metal electrode 37t - were formed in this order by laminating them under the same conditions as in the previous embodiment.

This embodiment has a configuration in which the first insulating layer used in the previous embodiment is removed. By removing the first insulating layer, although the luminance decreased by about 30%, it became possible to significantly lower the luminescence starting voltage.

〔Effect of the invention〕

As mentioned above, the EL hydrogen element of the present invention emits sufficient light at a lower voltage than conventional elements, and further has very little dielectric breakdown, so it is possible to provide an element with a long life. Therefore, it is possible to downsize the drive circuit, provide a compact one-story display, and provide an EL element with excellent display quality and a high contrast ratio compared to conventional EL elements. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an EL hydrogen device showing one embodiment of the present invention, FIG. 2 is a cross-sectional view of an EL hydrogen device showing another embodiment of the present invention, and FIG. 3 is a conventional EL hydrogen device with a double insulation structure. It is a sectional view of a hydrogen element. 21: Glass substrate, 22: Transparent electrode, imperial order...
First insulating layer, stripe...light emitting layer, stripe...intermediate insulating layer, 2
6... Semiconductor layer,... Third insulating layer, O... Back metal electrode, 31... Glass substrate, 32... Transparent electrode, O... Light emitting layer, 34... Intermediate insulating layer, 35...
Semiconductor layer, 36...Third isolation #1 layer, 37... Back metal electrode

Claims (1)

[Claims] (1) A light-emitting layer sandwiched between a pair of electrodes, at least one of which is a transparent electrode, in the shape of a sandwich, and a thin intermediate insulating layer and a semiconductor between the light-emitting layer and at least one of the electrodes. An electroluminescent device characterized by interposing a composite film in which layers and insulating layers are sequentially laminated.