JPS6298595A - Manufacture of thin film el 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] Technical fields> The present invention responds to the application of an electric field (Electr.

Luminescence) Thin film EL that emits light
The present invention relates to a method for manufacturing an element, and particularly to a stabilizing heat treatment after forming a light emitting layer.

<Prior art and its problems> Since the development of a thin film light-emitting device that exhibits high-brightness EL total emission by applying a current electric field to ZnS doped with a luminescent center, numerous studies have been carried out, and in particular, A thin-film light-emitting element with a double insulation structure has a Mn-doped ZnS light-emitting layer sandwiched between insulating layers and sandwiched between electrodes, at least one of which is transparent, to achieve high brightness and long life. Taking advantage of these characteristics, it has been commercialized as a lightweight and thin EL panel.

However, since the above-mentioned thin film light emitting device can only emit yellow-orange light unique to Mn, it is desired to develop a thin film light emitting device that emits light of a different color.

It is known that when a rare earth element or a compound thereof is used as a luminescent center, various luminescent colors can be obtained depending on the type of rare earth element. For example, T b F Sm
When rare earth heptadides such as F 3 lTmFa and P rFa are used, elements that emit green, red, blue, and white light can be obtained, respectively. However, these have problems in terms of brightness, and elements with sufficient practical brightness have not been obtained.

Normally, in a thin film EL layer, heat treatment is performed after forming the light emitting layer with the aim of uniformly diffusing the light emitting centers and improving the crystallinity of the light emitting layer base material. It is desirable to carry out the process at as high a temperature as possible in order to promote the diffusion movement of and eliminate crystal defects. However, in a single thin film EL device that uses rare earth fluoride as the center of luminescence, a phenomenon occurs in which the luminance of the luminescent layer decreases when heat treatment is performed at high temperatures. It usually exists in the range of 400°C to 500°C. Therefore, heat treatment can only be performed at a relatively low temperature, and the crystallinity of the light-emitting layer base material is not sufficiently improved, making it difficult to obtain a thin-film EL element with good light-emitting characteristics.

The reason for the reduction in brightness of thin film EL devices that mainly emit light from rare earth fluorides due to high-temperature heat treatment is that residual gas present in the Pelger during sputtering or vapor deposition of the emissive layer, adsorbed gas in the target or vapor deposition pellet, etc., emit light as impurities. The main factor is considered to be that these impurities are taken into the layer and react with ZnS and rare earth elements during heat treatment, thereby deteriorating the film quality of the light emitting layer.

<Objective of the Invention> The present invention has been made in view of the above-mentioned problems, and is based on a detailed study of vacuum management and material management during sputtering or vapor deposition of a light-emitting layer containing a rare earth element or rare earth compound as the main light-emitting layer. As a result of reducing impurities in the light emitting layer, it was confirmed that the brightness did not decrease even when heat treatment was performed at temperatures higher than 500°C, making it possible to create a thin film EL element that emitted light with higher brightness than before. , we have developed a manufacturing technology that improves the crystallinity of the light-emitting layer base material by setting the heat treatment temperature after forming the light-emitting layer at 500°C or higher, and uniformly dispersing the light-emitting centers to create a thin-film EL device with improved light-emitting characteristics. The purpose is to provide.

<Embodiment> FIG. 1 is a basic configuration diagram of a thin film EL element for explaining one embodiment of the present invention. S no 2 on glass substrate 1
, I To (indium oxide), etc. transparent electrode 2, further laminated thereon with SiN SiO2, Y2O3゜8
4' The lower insulating layer 3 made of At203 or the like is formed to a thickness of +000A to 30% using a thin film production technique such as sputtering or electron beam evaporation.
Approximately 00A is formed. Next, a light emitting layer 4 is formed on the lower insulating layer 3 to a thickness of about 7000 Å by RF sputtering using a ZnS material doped with an appropriate amount of TbF3 as a light emitting center as a sputtering target.

Normally, when forming a thin film by sputtering, grease batter is applied for an appropriate period of time to remove dirt and adsorbed gas from the surface of the sputtering target, which is the material source.
After cleaning the target surface, main sputtering is performed to form a film.However, during this bliss sputtering, the main valve is mostly closed and in a single state, so gases etc. coming out of the target may remain in the bell jar. It is thought that many of these gases are taken in as impurities during film formation during main sputtering and have a negative effect on the light-emitting characteristics.For this reason, when forming the light-emitting layer 4 by RF sputtering, impurities taken into the film. As a means to reduce this, for example, the operation of stopping the bliss sputtering midway and evacuating the inside of the bell jar to a high vacuum and removing the gas extracted from the target from inside the bell jar is performed at least once.The luminescent layer 4 thus obtained is free from impurities. This results in a highly pure ZnS:TbFa layer with suppressed .

After forming the light emitting layer 4, heat treatment is performed at a suitable temperature higher than 500°C. In this example, this temperature was set to 600°C. The heat treatment is carried out in a vacuum or in a gas atmosphere such as an inert gas or a sulfidic gas. An upper insulating layer 5 made of the same material as the lower insulating layer is laminated on the light-emitting layer 4 that has been heat-treated to form a double insulating structure. Furthermore, a back electrode 6 made of A7 or the like is formed on the upper insulating layer 5 by vapor deposition. By connecting the transparent electrode 2 and the back electrode 6 to an AC power source and applying an AC voltage, green EL emission can be obtained from the light emitting layer 4.

FIG. 2 shows the heat treatment conditions after forming the light emitting layer 4 of the thin film EL element described above: no heat treatment, heat treatment at 400°C, heat treatment at 600°C.
FIG. 3 is an explanatory diagram showing emission brightness-applied voltage characteristics in the case of three types of heat treatment at °C. The curve t in the figure is the characteristic curve without heat treatment, t2 is the characteristic curve with heat treatment at 400°C, and t3 is the characteristic curve with heat treatment at 600°C. The curve with the highest luminance efficiency against the applied voltage is t3, and when the luminescent layer 4 is heated to 600°C
Thin-film EL devices subjected to heat treatment under these conditions emit EL light with higher brightness than those under other conditions. This is because there are fewer impurities in the light-emitting layer 4 that react with Tb and F, which can be reacted even with high-temperature heat treatment. This is because things are not formed.

Although the above embodiment describes the case where TbF3 is used as the luminescent center, the present invention is not limited thereto, and can also be applied to the case where other rare earth fluorides are used. In addition to ZnS, the light-emitting layer base material is ZnS.
Sulfides and selenides such as e + Ca S + Cd S are used.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a thin film light emitting device used to explain one embodiment of the present invention. FIG. 2 is a characteristic diagram showing the emission brightness-applied voltage characteristics when the heat treatment conditions after the formation of the light emitting layer are changed. ]...Glass substrate, 2...Transparent electrode, 3...Lower insulating layer, 4...Light emitting layer, 5...Upper insulating layer, 6...
・Rear electrode agent Patent attorney Aihiko Fukushi (and 2 others) No. 1r2J Wholesale Electric 5

Claims (1)

[Claims] 1. Thin film EL having a light-emitting layer in which a light-emitting center is formed by doping a rare earth element or a compound of a rare earth element
In the device manufacturing method, after forming the light emitting layer, 5
1. A method for manufacturing a thin film EL device, characterized in that heat treatment is performed at a temperature higher than 00°C.