JPH0935869A - Manufacture of electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high intensity and stable green EL element by improving crystalline of a luminous layer thin film without reducing oxide sintered BaTiO3 ceramic which is a substrate concurrently serving as an insulating layer. SOLUTION: An oxide thin film of ZnGa2 O4 system, which is an electron beam exciting fluorescent material formed from at least one kind, is prepared by using an already known method on sintered oxide ceramic having 1000 or more preferably 3000 or more dielectric constant. Next, the film is buried in powder consisting of oxide powder containing at least one kind of this thin film constituting element and of oxide powder containing sulfur. By heat treating at a 600 to 1200 deg.C preferably 900 to 1100 deg.C temperature range in the atmosphere of non-oxidizing gas or non-oxidizing gas partly containing oxidizing gas or non-oxidizing gas partly containing reducing gas or in the atmosphere equivalent to these atmospheres, this thin film is made to function as a luminous layer for an EL element.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing an electroluminescent device.

[0002]

2. Description of the Related Art Electroluminescent devices (hereinafter referred to as E
L element) has been studied for a long time for application to a planar solid state light emitting display device, and there is a strong hope for its practical application. This EL element is structurally characterized in that a crystalline thin film of a phosphor is formed on a glass or plastic film substrate, and the phosphor powder is uniformly dispersed and mixed in an organic dielectric binder. And an inorganic dispersion type characterized in that the phosphor powder is bound with an inorganic binder such as glass.
The inorganic dispersion type EL is often called a ceramics type EL, but it is merely a dispersion of phosphor powder particles in the inorganic binder. Conventionally, E
Regarding the emission color of the L element, Mn-added zinc sulfide (Zn
S: Mn) -based or terbium-added zinc sulfide (ZnS: T)
b) yellow-orange emission and green emission in a double-insulation structure AC drive thin film EL device, and Cu-added zinc sulfide (Zn)
Only S: Cu) -based organic dispersion type AC drive thin film EL devices that emit blue-green light are in practical use.

As an EL element having an emission color other than the above, terbium or terbium fluoride (Tb, F or TbF ₃ ) added ZnS, or a sulfide containing an alkaline earth metal and a group VI element, for example, various emission centers is added. It is known that calcium (CaS), strontium sulfide (SrS) or the like is used for the light emitting layer. Further, it has recently been shown that a strontium thiogallate (SrGa ₂ S ₄ ) material can be used as a light emitting layer for a blue light emitting EL device. Emission colors from red to blue have been realized by these EL devices, although they are still in the research stage.

Recently, research and development of high-brightness EL devices using an oxide-based phosphor in the light-emitting layer have been actively conducted (for example, Japanese Patent Application Nos. 2-254649 and 2-4, which are the inventions of the applicants). -256474). In particular, it is an EL element in which a thin film light emitting layer made of Mn-added zinc silicate (Zn ₂ SiO ₄ : Mn), which is a silicate-based phosphor, is formed on a sintered BaTiO ₃ ceramic as a substrate and an insulating layer, which is the highest when driven at 5 kHz. 5
High-luminance green light emission of 600 cd / m ² is realized.

[0005]

However, in an EL element formed by forming a thin film light emitting layer on an oxide-sintered BaTiO ₃ ceramic which is a substrate and an insulating layer, an EL element using an unheated light emitting layer is sufficient. Therefore, the heat treatment at 750 ° C. or higher is indispensable for improving the crystallinity of the film and realizing high brightness. As a heat treatment atmosphere for the light emitting layer, a non-oxidizing gas such as a weak reducing property has been conventionally effective. However, the heat treatment temperature is 900 ℃
In the above case, the insulating layer is significantly reduced, resulting in EL
There was a problem that the characteristics deteriorate.

The object of the present invention is to improve the crystallinity of the thin film of the light emitting layer without reducing the oxide-sintered BaTiO ₃ ceramic, which also serves as a substrate and an insulating layer, to realize a high-luminance and stable green light-emitting EL device. The present invention provides a manufacturing method for making a thin film made of a ZnGa ₂ O ₄ -based oxide phosphor for electron beam excitation, which has not been conventionally effective, sufficiently function as a light emitting layer for the EL device, and has high brightness, high efficiency and stability. It is an object of the present invention to provide a method for inexpensively and easily manufacturing a green light emitting AC driven thin film EL element.

[0007]

As a means for solving the above problems, the present invention has a relative dielectric constant of 1000 or more, preferably 3000 or more, and a thickness of 0.04 to 0.7 mm,
For a long time, it is preferable to use at least one kind of phosphor for electron beam excitation on a ferroelectric sintered substrate such as barium titanate (BaTiO ₃ ) which is preferably 0.1 to 0.4 mm as a sintered ceramic substrate and an insulating layer. Known ZnGa ₂ O ₄
-Based oxide thin film, electron beam evaporation method, activated reactive evaporation (ARE) method, sputtering method, cluster ion beam (I
CB) method, ion beam sputtering (IBS) method, chemical vapor deposition (CVD) method, spray method, sol-gel method,
Using known fabrication techniques such as screen printing, atomic layer epitaxial (ALE) growth, molecular beam epitaxial growth (MBE), gas source MBE (or CBE), and electron cyclotron resonance (ECR) thin film fabrication After being formed in vacuum or under various controlled atmospheres, the thin film together with the substrate is embedded in a powder composed of an oxide powder containing at least one of the film-constituting elements and a powder having a reducing action, and a non-oxidizing gas or 600 to 1200 ° C., preferably 900 to 1200 ° C. in an atmosphere of a non-oxidizing gas containing a partially oxidizing gas or a non-oxidizing gas containing a partially reducing gas, or in an atmosphere equivalent to these atmospheres. The thin film was made to sufficiently function as a light emitting layer for an EL device by heat treatment in a temperature range of ˜1100 ° C. It is.

[0008]

In the EL device manufacturing method according to the present invention, a thin film comprising at least one kind of phosphor on the sintered oxide ceramic substrate / insulating layer having a high relative dielectric constant of 3000 or more, preferably 4000 or more. By adopting the combination of forming the above, it became possible to perform high temperature heat treatment at 750 ° C. or higher. By adopting this method,
An AC driven thin film EL element having a high quality light emitting layer having excellent crystallinity can be easily manufactured, and as a result, the EL element having higher light emission luminance and higher light emission efficiency can be realized. . Since the EL element according to the present invention uses the sintered oxide ceramic substrate / insulating layer having a high relative dielectric constant as the insulating layer as described above, it is excellent in the withstand voltage performance, and therefore the catastrophic property. It has an effect that an extremely high electric field can be effectively applied to the light emitting layer without any fear of dielectric breakdown and the emission center can be efficiently excited. The most remarkable effect of the present invention is conventionally
CR which has never been applied as a light emitting layer of EL element
A wide variety of phosphors such as oxygenate-based phosphors and oxide-based phosphors found in phosphors for T or lamps and the like can be fully utilized as a light emitting layer for EL devices. According to the present invention, it is only by applying the heat treatment method to the phosphor thin film formed on the sintered oxide ceramic substrate / insulating layer that the film can effectively function as a light emitting layer for an EL device. This is a great feature. These are considered to result from the following effects. By suppressing the reduction of the insulating layer ceramic, deterioration of the dielectric characteristics of the ceramic can be prevented. The introduction of the sulfurized layer by sulfurizing the surface of the oxide phosphor thin film light emitting layer causes the surface of the light emitting layer to function as a charge supply layer. Further, between the sintered oxide ceramics and the phosphor thin film light emitting layer, 20 nm to 1
Inserting various thin film layers with a thickness of μm, preferably 50 nm to 500 nm is effective as a buffer layer, a charge supply layer, a protective layer, or the like, and as a result, low voltage drive and high efficiency and high emission brightness can be realized. . EL of the present invention
It is significant that many phosphors, which have been rarely used as the light emitting layer for EL devices so far, can be effectively functioned as the light emitting layer by the device manufacturing technology. As a result, it is possible to easily realize not only full-coloring such as multicoloring of red, green, and blue light emission, but also an EL device of white light emission, and thus a wide range of applications can be expected. The present invention will be described below with reference to examples.

[0009]

EXAMPLE 1 FIG. 1 shows a sectional structure of an EL device used as a first example of the present invention. ZnO: Zn powder, G
a ₂ O ₃ and manganese dioxide (MnO ₂ ) powder are uniformly mixed and then fired at 1000 ° C. in an argon atmosphere, and a powder compact is produced as a target. ZnGa with a thickness of 1500 nm on a sintered BaTiO ₃ ceramic substrate / insulating layer with a smooth surface having a rate (εs) of 5000, a thickness (t) of 0.2 mm and a diameter (D) of 20 mm.
_{A 2} O ₄ : Mn thin film was formed. Then, the oxide-based phosphor ZnO: Zn (P
-15 phosphor) powder, gallium oxide powder, and powder having a reducing action in ZnGa ₂ O ₄ : Mn-attached BaTi
Embed O ₃ ceramics and set it in an electric furnace.
Heat treatment was performed in argon at 020 ° C. for 5 hours to give the thin film a function as a light emitting layer for an EL device. afterwards,
On the light emitting layer, aluminum (Al) -doped zinc oxide (Z) with a thickness of 500 nm was formed by magnetron sputtering.
An nO: Al) transparent electrode layer and a metal Al back electrode layer were formed on the opposite surface by a vacuum deposition method to fabricate an EL device. As a result of driving this EL element with a sinusoidal AC voltage of 1 kHz, as shown in FIG. 2, a light emission starting voltage of 100 V, a maximum light emission luminance of 710 cd / m ² (240 V applied), and a light emission efficiency of 0.9 lm / W were transparent. Uniform green light emission was obtained over the entire surface of the electrode. However, the maximum light emission brightness from the EL element not subjected to the heat treatment as described above is 0.
The brightness was as low as 02 cd / m ² . Even when the device is driven at 60 Hz, the maximum emission brightness is 23
It showed a high value of 0 cd / m ² . The effect of improving the brightness by the heat treatment was remarkable. In addition, in the case of an element in which a ZnO-based thin film having a thickness of 50 nm to 500 nm is previously formed as a charge supply layer on BaTiO ₃ ceramics by a sputtering method, and a ZnGa ₂ O ₄ : Mn light emitting layer is formed thereon, The light emission start voltage can be reduced by 10V to 30V,
Moreover, the EL characteristics of the same level or more were realized.

[0010]

Example 2 An oxide-based phosphor Zn in which an ZnGa ₂ O ₄ : Mn light-emitting layer formed on BaTiO ₃ ceramics was charged in an alumina ceramic boat under the same conditions as in Example 1
O: Zn (P-15 phosphor) powder and gallium oxide powder containing sulfur were embedded and set in an electric furnace.
Heat treatment in argon gas at 1020 ° C. for 5 hours,
The thin film was provided with a function as a light emitting layer for EL device. Then, each electrode was attached in the same manner as in Example 1 to fabricate an EL device. As a result of driving this EL element with a sinusoidal AC voltage of 1 kHz, a light emission start voltage of 150 V and a maximum light emission luminance of 600 c
d / m ² (400 V applied), luminous efficiency 0.9 lm / W
Thus, uniform green light emission was obtained over the entire surface of the transparent electrode. It should be noted that, as the atmosphere gas for heat treatment, argon + SO ₂ (5%) or O ₂ + CS ₂ may be used instead of the above to obtain substantially the same E.
The L characteristic was obtained.

[0011]

Example 3 Zn acetylacetonate (Zn (C ₅ H ₇ O ₂ ) ₂ ) as a Zn raw material, Ca acetylacetonate (Ca (C ₅ H ₇ O ₂ ) ₃ ) as a Ga raw material, and Mn which is an emission center. Tricarbonyl cyclopentadienyl manganese (TCM) was filled in each stainless steel container as a dopant, and the temperature was 93 ° C., 145 ° C. and 25 ° C., respectively.
300cc / min in each stainless steel container kept at
At the same time, the carrier gas at the same flow rate is passed, and at the same time, the mixed gas of Ar + O ₂ (50%), which becomes the oxygen source, is also introduced at the same flow rate to the respective quartz reactors. A gas containing each raw material was supplied onto the glass substrate to form a film under a reduced pressure of 200 Torr. The obtained film was crystallized without subsequent heat treatment, and the EL device manufactured using this film was 250 V
When applied, a maximum emission luminance of 8 cd / m ² green emission was achieved.
Then, the same heat treatment as in Example 1 was performed, and as a result, green light emission with a maximum light emission luminance of 20 cd / m ² was obtained.

The present invention is not limited to the above embodiment, but the thin film light emitting layer may be formed by electron beam vapor deposition or MOCV.
Although it can be formed by the D method, existing crystal growth techniques such as a CVD method using a halide or an MBE growth method can be used. Furthermore, the Zn exemplified in the above-mentioned embodiment
There is no problem in using a transparent conductive film such as a tin oxide (SnO ₂ ) system or an indium tin oxide (ITO) system other than the O: Al transparent electrode layer. The substrate / insulating layer only needs to have a relative dielectric constant of 1000 or more, and is not necessarily BaTiO ₃
Does not have to be. When the light emitting layer is formed by the MOCVD method, Z is formed on the sintered ceramic substrate / insulating layer.
It is particularly effective to form a conductive film having excellent hydrogen resistance such as nO: Al as a protective film for the substrate.

[0013]

According to the present invention, it is possible to use a variety of phosphors, particularly oxide-based phosphors, which could not be used as a light emitting layer material of an EL device or which had insufficient characteristics. You can do it, and the effect is great. That is, as a result of establishing a manufacturing method for causing an oxyacid salt-based phosphor, an oxide-based phosphor, or a sulfide-based phosphor known as an existing electron tube or lamp phosphor to function as a light emitting layer for an EL device, Regardless of the type of the phosphor, it is possible to easily realize white light emission as well as multicolor light emission of red, green and blue and full color light emission. As a result, as an EL element for a light-emitting flat display, or an illumination lamp that takes advantage of the features of a surface light emitter, various pattern displays, or a flat light source, for example, various applied equipment using a liquid crystal display device and commercial power source driven light emission It has the effect of exerting a great deal of power on devices and creating a wide range of applications that have never existed before.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a first embodiment according to the present invention.

FIG. 2 is a typical luminance-applied voltage characteristic diagram of the EL element of Example 1 according to the present invention.

[Explanation of symbols]

1 ... ZnO: Al transparent electrode 2 ... ZnGa2O4: Mn thin film light emitting layer 3 ... Sintered BaTiO ₃ substrate / insulating layer 4 ... Al back electrode 5 ... EL element drive Power supply 6 ... Brightness 7 ... Efficiency

Claims (4)

[Claims] 1. At least one or one layer of an oxide phosphor thin film is formed on a sintered oxide ceramic plate having a relative dielectric constant of 1000 or more, which is also a substrate / insulating layer, and then 600 ° C. in an atmosphere containing sulfur. ~ 1200 ° C, preferably 90
A method for producing an AC-driven thin film electroluminescent element, which comprises giving the thin film a sufficient function as a light emitting layer for an electroluminescent element by performing a heat treatment in a temperature range of 0 ° C to 1100 ° C. 2. The heat treatment is performed under vacuum or in a non-oxidizing gas, or in a partially oxidizing gas, or in a non-oxidizing gas atmosphere containing a partially reducing gas and sulfur, or under these treatment conditions. The method for manufacturing an electroluminescent element according to claim 1, wherein the method is performed in an equivalent atmosphere. 3. The method for manufacturing an electroluminescence device according to claim 1, wherein the thin film made of the phosphor is a phosphor made of at least one kind of zinc gallate (ZnGa ₂ O ₄ ). 4. The method for manufacturing an electroluminescent element according to claim 1, 2 or 3, which is used for manufacturing a surface emitting type illumination lamp, a surface emitting type display panel or a flat type display device having a flat light source.