JPH03184297A - Manufacture of thin film el element - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a non-emission region called a dead-layer on the substrate side insulation film interface of a fluorescent film by interrupting accumulation at least one time when the film thickness of a fluorescent film becomes a given film thickness at the time of fluorescent film accumulation, applying heat treatment, and then again making the accumulation of the fluorescent film. CONSTITUTION:When a fluorescent film is accumulated on a glass substrate 2 where a transparent electrode 1 and a first insulation film 3 are accumulated in order, the accumulation is once interrupted at e.g. a film thickness of 1,000Angstrom or below, a fluorescent film part 4a is formed, and then heat treatment is made for about one hour at a given temperature in vacuum or a S2 atmosphere when the fluorescent film is sulfide. Then a fluorescent film part 4b is accumulated so as to make a desired thickness (thousands Angstrom -1mum extent), the same heat treatment is made, after that a second insulation film 5 and a metal electrode 6 are formed to obtain an EL element. Because this permits the improvement of a defect or distortion, etc., of a dead-layer part having an inferior crystallinity without diffusion to the whole fluorescent film, electron scattering or non-emission transition, etc., due to a crystalline defect can be reduced to improve element efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a method for manufacturing a thin film EL element.

[Summary of the Invention] The present invention makes it possible to eliminate or reduce the phenomenon in which a non-emissive region occurs in a phosphor by simply changing a part of the manufacturing process of an AC-driven thin film EL element.

[Prior Art] In general, as shown in FIG. 2, a conventional method for manufacturing a thin film EL device is to apply a film onto a borosilicate glass substrate 2 coated with ITO, which is a transparent electrode 1, by an EB method, a sputtering method, or the like. Insulating film 3. Fluorescent film 4. A method is used in which the insulating film 5 and the metal electrode 6 are sequentially laminated with a thickness of several thousand angstroms (layers). In this case, the substrate temperature during the formation of the fluorescent film is usually about 200° C., and the heat treatment after formation is usually carried out in a vacuum at about 500° C. for about 1 hour.

[Problems to be Solved by the Invention] However, in the EL device manufactured by the above process, the layered portion 7 of the fluorescent film 4 with a thickness of approximately 1000 mm from the interface of the substrate-side insulating film 3 is a "dead" region that does not emit light.・Layer” (D
It exists as a part called ``ead 1 ayer''.

This layered portion 7 is 111 m in TEM (transmission electron microscope 1).
According to the research, it is known that the crystal grains are small and the crystallinity of this part is inferior to that of other parts.

The light emitting mechanism of an EL element using ZnS:Mn for the fluorescent film is as follows.
Electrons are emitted from the interface level at the insulating film/phosphor film interface to the conduction band of the fluorescent layer due to the tunnel effect, are accelerated by the electric field, and collide with the luminescent center, thereby exciting the luminescent center atom (ion). , it is generally said that it radiates when it relaxes. Therefore, if there is a region with disordered crystallinity as described above, the accelerated electrons will either lose energy due to scattering by grain boundaries or defects, or lose energy through the levels created by the defects even if one emission center is excited. It is thought that light emission does not occur in this part due to causes such as non-radiative transition. This results in a decrease in the efficiency of the entire EL element.

In addition, the crystallinity of the fluorescent film near the insulating film/phosphor film interface on the substrate side is inferior to that of the fluorescent film near the insulating film/g & optical film interface on the metal electrode side (the formation of defect levels near the interface). This difference causes a difference in electron injection efficiency from the interface between the substrate side and the metal electrode side, which manifests as a difference in emission intensity depending on the polarity (positive or negative) of the driving voltage. Such asymmetry in light emission characteristics due to polarity complicates the driving method.

Furthermore, in the conventional method of forming the entire fluorescent film and then heat-treating it, the crystal defects and distortions in one part of the dead layer are reduced to some extent, but the crystallinity of other parts is It is thought that the distortion in the first part of the dead layer and the diffusion of defects will cause the layer to deteriorate even more immediately after it is deposited, and thus is not suitable as a method for improving device performance.

[Object of the Invention] The present invention provides a method for manufacturing a thin film EL device that prevents the formation of a non-emissive region called a “dead layer J” at the substrate-side insulating film interface of a fluorescent film during the manufacturing process of the thin film EL device. The main purpose is to

[Means for Solving Problem Ia] The present invention provides a thin film EL including the steps of forming a transparent electrode on a glass substrate, forming an insulating film on the transparent electrode, and forming a fluorescent film on the insulating film. In the device manufacturing method, during the deposition of the fluorescent film, the deposition is interrupted at least once when the thickness of the fluorescent film reaches a predetermined thickness, and after heat treatment is performed,
The above-mentioned problems are solved by depositing the fluorescent film again.

[Function] In the method for manufacturing a thin film EL element described above, since the "dead layer" portion of the layer with inferior crystals is independently heat-treated, defects, distortions, etc. in this portion are alleviated at that point.
After heat treatment, there are defects and distortions.

This prevents it from propagating throughout the membrane.

[Example] Figures 1 (a), (b), (c), and (d) show an example of the manufacturing process of a thin film EL element, and 1 in 0 drawings consists of the following steps, where 1 is a transparent electrode. , 2 is a glass substrate.

3 is a first insulating film, 4 is a fluorescent film, 4a and 4b are fluorescent film parts, 5 is a second insulating film, and 6 is a metal electrode.

[1] First, as shown in FIG. 1(a), on a glass substrate 2 on which a transparent electrode 1 and a first insulating film 3 were sequentially deposited,
When depositing the fluorescent film, the deposition is temporarily interrupted at a film thickness of 1000 Å or less to form the fluorescent film portion 4a.

[2] After that, as shown in FIG. 1(b), in a vacuum or in an s2 atmosphere if the fluorescent film is a granule,
Heat treatment is performed at a temperature of about 400'C to 950'C for about 1 hour.

[3] Next, as shown in Figure 1(c), the desired thickness (
The fluorescent film portion 4b is deposited to a thickness of several thousand nanometers to about 1 μm, and the same heat treatment as in [2] is performed.

[4] After that, a second insulating film 5 and a metal electrode are formed to produce an EL element.

Note that from the above manufacturing steps, steps [11 and [2] may be repeated one or more times.

As described above, by interrupting the deposition of the fluorescent film and performing the heat treatment process, the following effects can be obtained.

(a) Only the layer portion corresponding to the “dead layer”,
Since heat treatment can be performed without being constrained by the fluorescent film deposited on top, rearrangement of atoms is likely to occur, and the effect of heat treatment is significant in improving defects and distortion.

(b) The fluorescent film portion 4b deposited in the above three steps receives the effect of improving the crystallinity of the underlying fluorescent film portion 4b,
Crystallinity such as orientation is improved compared to the case of continuous growth.

(c) Compared to the case where the film is continuously deposited to the desired thickness and then subjected to heat treatment, the "dead layer" part of the layer with poor crystallinity can be heat-treated independently, so that distortion etc. in this part can be reduced. The strain is relaxed at that point, and the strain does not propagate throughout the film after the heat treatment.

Therefore, the EL element manufactured by the above steps is
"Dead layers" can be significantly reduced, and defects and distortions in the entire fluorescent film can also be improved, making it possible to improve luminous efficiency.

Furthermore, the difference in crystallinity in the thickness direction of the fluorescent film can be reduced. That is, since the difference in crystallinity between the second insulating film and the fluorescent film near the first insulating film can be reduced, the asymmetry in the light emission characteristics due to the polarity of the EL drive voltage can be reduced.

[Effects of the Invention] According to the present invention, defects and distortions in "dead layer" portions with poor crystallinity can be improved without being diffused throughout the fluorescent film, so electron scattering and non-radiative transitions due to crystal defects can be improved. can be reduced, and the efficiency of the element can be improved.

Furthermore, since the crystallinity of the fluorescent film near the first insulating film can be improved, the difference in crystallinity between the fluorescent films near the first and second insulating films can be reduced, and the electron injection efficiency from the insulating film/phosphor film interface can be improved. The difference can be reduced. Therefore, it is possible to reduce the complexity of the driving means (circuit) due to the asymmetry of the light emission characteristics due to the difference in the polarity of the driving voltage.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram of a thin film EL device showing an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a conventional thin 11 IEL device. 1......Transparent electrode, 2......
Glass substrate, 3゜5...Insulating film, 4...
......Fluorescent film, 4a, 4b...
Fluorescent film part, 6...Metal electrode.

Claims (1)

[Scope of Claims] A method for manufacturing a thin film EL device comprising the steps of forming a transparent electrode on a glass substrate, forming an insulating film on the transparent electrode, and forming a fluorescent film on the insulating film, comprising: Thin film E characterized in that during film deposition, the deposition is interrupted at least once when the thickness of the fluorescent film reaches a predetermined thickness, and after heat treatment is performed, the fluorescent film is deposited again.
Method for manufacturing L element.