JPS63995A - Material of thin film light emitting layer - 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 field to which the invention pertains] The present invention provides EL (Electr
(luminescence) A thin film EL element that emits light.

In particular, the thin film light-emitting layer is doped with an optically active transition metal or rare earth element in the matrix. MgS, Ca
The present invention relates to a novel thin film EL device characterized in that it consists of a thin film layer whose base material is a composite of ZnS and at least one selected from S, SrS, and BaS. Furthermore, a thin film is formed by vapor deposition or sputtering using a compound of transition metal or rare earth element that is optically active in the matrix, at least one selected from MgS, CaS, SrS, BaS, and ZnS. The present invention relates to a method for producing a thin film EL string, which comprises preparing a light-emitting layer.

[Technical background of the invention] Dielectric strength voltage of thin film EL elements conventionally driven by alternating current.

In order to improve luminous efficiency and stability of operation, Mn-doped ZnS and Zn! The light emitting layer of 3e etc. is made of Al 203
．． An EL element with a double insulation structure sandwiched between dielectric thin films such as Y2O3 or T103 has been developed, and various light emitting characteristics are being studied. In particular, thin-film EL devices that use Mn-doped ZnS as a light-emitting layer have been well studied, but in recent years, thin-film EL devices that use not only ZnS but also gas, SrS, etc. as base materials have been developed with the aim of making EL panels multicolored. has been attracting attention. For example, a thin film EL device using Eu-doped CaS as a light emitting layer emits red light, and a thin film EL device using Ce doped SrS as a light emitting layer emits green-blue light. However, these systems have a property that the base material has a remarkable hygroscopicity compared to ZnS and is easily hydrolyzed. Such properties increase the defect density of a light emitting layer using these systems as a base material, resulting in a decrease in luminance and durability of the device. or.

Compared to ZnS, in CaS, SrS, etc., Ce, which is a dopant that emits green or blue light, is easily inserted into the base material.
Provides a light-emitting layer that emits high-brightness light. On the other hand, although ZnS has sufficient stability as a base material, it has the disadvantage that some dopants such as Ce are difficult to insert into this base material. Therefore, it is possible to compensate for the weaknesses of these base materials and easily dope them with dopants.

In addition, a base material with excellent moisture resistance and weather resistance is desired.

Among n-vr group compounds, n, - such as Gas and SrS
VI.

The crystal form of group compounds is a salt type structure, and ZnS,
The crystal form of the ■b-■b group compounds such as Zn5s has a wurtzite or zincblende structure. It is known that different compounds of the same crystal type form a solid solution relatively easily and form a mixed crystal. However, when a mixed sintered body of compounds with different crystal types is used as a thin film forming material to form a thin film on a substrate by, for example, vapor deposition or sputtering, there are almost no reports on the crystallinity or crystal structure of the formed thin film.

II-Vl group compounds and n, -Vl, group b compounds both have completely different crystal forms.1 For example, a mixture of SrS and ZnS containing a dopant is used as a material for preparing a thin film, and it can be prepared by vapor deposition or sputtering. The base material of the prepared thin film light-emitting layer has the possibility of exhibiting characteristics that are characteristic of a base material in which both SrS and ZnS exist. Therefore, compounds of transition metals or rare earth elements that are optically active in the matrix and MgS, CaS,
At least one selected from SrS, BaS and Z
As a result of creating thin film EL elements with a double insulation structure using nS as a material for vapor deposition or sputtering, and investigating the light emitting characteristics of the devices, it was discovered that these devices exhibited good EL characteristics, and the present invention was created. completed.

[Object of the invention] The object of the invention is to provide a thin film EL device in which the thin film light emitting layer is
A thin film layer consisting of a composite of a transition metal or rare earth element compound that is optically active in the matrix, at least one selected from MgS, CaS, SrS, BaS, and ZnS as a matrix. The object of the present invention is to provide a novel thin EL device and a method for manufacturing the same.

[Summary of the invention] The present invention provides a thin film EL device in which the thin film light emitting layer is provided.

A thin film layer consisting of a composite of a transition metal or rare earth element compound that is optically active in the matrix, at least one selected from MgS, CaS, SrS, BaS, and ZnS as a matrix. The present invention provides a novel thin film EL device with characteristics and a method for manufacturing the same.

Conventionally, the subject of research has been devices that use thin film emitting layers of thin film EL devices using thin film layers made of ZnS, which is a ■-■ group compound, doped with compounds of transition metals or rare earth elements such as Mn, Tb, Ss, or Ce. It has been said that

ZnS is chemically stable, with less hygroscopicity and less decomposition than other ■-■ group compounds such as CaS, and has a sufficiently large band gap, making it suitable as a base material for thin film light-emitting layers. In other words, by doping ZnS with various dopants, thin films E that emit various colors can be created.
An L element can be manufactured. For example, HoF
, Er F 3,5IIF 3. TbF, ) JdF3.
Alternatively, a thin film E prepared by doping Ttp F3 etc.
L elements emit light in various colors such as red, blue, and green, but the luminance of blue light is a little weaker.

Improvements are required, especially for thin film E that emits red, blue, and green, the three primary colors of light, for application to color panels.
High brightness and long life of L elements are desired. In order to achieve this objective, it is necessary to improve not only the dopant but also its base material. SrS is inferior to ZnS in terms of chemical stability, but CeP a
The thin film EL device doped with TmFa emits blue light, and has higher luminance than the blue light emitted by a thin film EL device comprising a ZnS light emitting layer doped with TmFa. However, from the viewpoint of extending the life of the thin film EL element, it is desirable that the base material itself be chemically stable. Therefore, in the present invention, the luminance of light emission is high.

In order to improve the base material used in the thin film emitting layer for the purpose of creating a thin film EL element with excellent moisture resistance and weather resistance, Sr'
In order to find a base material that has both properties suitable for blue light emission as shown in No. 3 and chemically stable properties as shown in ZnS, MgS, Ca! 3.9rS, BaS
An attempt was made to combine at least one selected from the following with ZnS.

The thin film emitting layer in the thin film EL device of the present invention contains dopants, MgS, Ca! 3. Sr8. A mixture of at least one selected from BaS and ZnS may be prepared as it is by a vapor deposition method or other suitable method. Alternatively, the thin film light-emitting layer can also be prepared by a method such as a multi-component vapor deposition method without mixing the dopant, at least one selected from MgS, CaS, SrS, and BaS, and ZnS. Considering the workability of creating thin film EL elements,
MgS, CaS, SrS containing dopants.

A method such as a sputtering method or a vapor deposition method using a mixed sintered body of ZnS and at least one selected from BaS as a target is preferably used. Moreover, a suitable transition metal or rare earth element compound can be used as the above-mentioned dopant.

The composite formed in this way is usually a solid solution consisting of one phase as a whole, but there are cases where more than one phase of different crystal types coexists to form a thin film layer.

[Effects of the Invention] According to the present invention, it is possible to create a thin film EL device having a thin film light emitting layer with excellent durability such as moisture resistance and weather resistance. Furthermore, since compounds of various transition metals or rare earth elements can be doped as a new base material for the thin film light emitting layer, thin film EL devices that emit light in various colors can be created by changing the dopant. If a thin film light-emitting layer made of a composite of Sr9 and ZnS is used.

It is possible to create a thin film EL element that emits high-intensity light in a color close to blue.

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited only to these examples.

Example 1 First, a sputtering target for preparing a thin film light emitting layer was prepared. SrS powder (purity 99.9%), ZnS (purity 99.9%) and CeF 3 (purity 99.99%) were mixed for 30 minutes to obtain a mixed powder.

This was used as a sputtering target using a hot press method. Using the light emitting layer target and the Al2O3 dielectric layer target, a thin film layer having a double insulation structure was formed on a transparent electrode by sputtering in an Ar atmosphere to create a thin film EL device.

FIG. 1 shows the structure of the thin film EL device in this example.

A large number of transparent electrodes 2 are arranged in parallel in strips on a glass substrate 1,
On top of that, a first dielectric layer 3 consisting of ^1□03 is placed at 200 mm.
A layer in which CePa was added to a composite film of SrS and ZnS was deformed at about 0 to 3000 A and was used as a 2-light emitting layer 154.
By laminating layers of about 00 to LOOOOA, further superimposing a second dielectric layer 5 made of AI 203 to about 2000 to 3000 A, depositing a back electrode 6 of AI, and forming and arranging it in a band shape in a direction perpendicular to the transparent electrode 2. It is configured.

The thin film EL device constructed as described above was placed in an Ar atmosphere for 50°C.
After heat treatment at 0° C. for 1 hour, the luminescence characteristics of this EL device were investigated by applying an AC sinusoidal voltage with a frequency of 5 kllz. FIG. 2 shows the dependence of luminescence brightness on applied voltage (V). The curve in FIG. 2(A) is a brightness-voltage characteristic curve immediately after applying an AC sinusoidal voltage to the EL element. The value of the threshold voltage is 152v, V rm
Emission brightness at s -182V is 160 cd/m2
Met. FIG. 2(B) shows a luminance-voltage characteristic curve after aging by applying an AC voltage of V rms -182 V to this EL element for 10 hours. Although the threshold voltage and luminance have changed somewhat due to aging, as is clear from Figure 1, the characteristic curve shows the same clear luminescent characteristics as before aging.

The emission spectrum of the color emitted by this EL element is '! J3
As shown in the figure. Further, the chromaticity coordinates of the emitted light color based on this emission spectrum are shown in FIG. As is clear from the figure, this EL
The emitted light color of the element is blue-green.

The color almost matches that of the light emitted by the SrS thin film light emitting layer with CePa as the center of light emission.

Next, the crystal structure of the thin film light emitting layer in the thin 111EL element was investigated by X-ray diffraction. The X-ray diffraction pattern is shown in FIG. 5(A). For comparison, Ce that emits blue-green light
The X-ray diffraction pattern of the SrS thin film light emitting layer doped with F3 is shown in FIG. 5(B). The latter thin film EL device was produced in the same manner as the former. It is well known that the crystal structure of a SrS thin film prepared on a substrate by a vapor deposition method is a salt-type crystal. In the present invention, the X-ray diffraction pattern of the SrS thin film prepared by the sputtering method for comparison (Fig. 5 (B)) almost coincides with the X-ray diffraction pattern of the Sr9 thin film prepared by the vapor deposition method, and its crystal type is recognized to have a salt-type structure. Further 9 C of the present invention
In the X-ray diffraction pattern of the composite thin film light-emitting layer made of SrS and ZnS doped with eF a, no peaks based on wurtzite or zinc blende structure crystals, which are characteristic of ZnS thin films, are observed. The diffraction pattern almost matches that of the SrS thin film shown in FIG. 5(B). moreover,
The composition of this composite thin film was measured using an X-ray microanalyzer (EPM).
A) As a result of the investigation, the atoms constituting the composite thin film Sr
, the atomic % of Zn and S are respectively Sr:Zn:S =
It was 40:3:57. From these results, it is considered that the crystal type of the composite thin film of the present invention has a salt-type structure like the SrS thin film, and has a structure in which Sr in the SrS crystal lattice is partially replaced by Zn.

Example 2 A thin film EL device having a light-emitting layer made of a composite thin film of CaS and ZnS doped with CeF a was prepared according to the method shown in Example 1. This thin film EL device also emitted high-intensity green light similarly to the thin film EL device shown in Example 1, which had a composite thin film of SrS and ZnS doped with CePa as a light emitting layer.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic structure of a thin film EL device according to the present invention. Figure 2 shows CePa-doped SrS in the present invention.
2 shows the luminescent properties of a thin film EL cell having a composite film of Zn9 and Zn9 as a luminescent layer. FIG. 3 shows the emission spectrum of the thin film EL device. FIG. 4 shows chromaticity coordinates based on the emission spectrum of FIG. 3. FIG. 5(A) is an X-ray diffraction pattern of a thin film emissive layer made of a composite film of SrS and ZnS doped with CePa in the present invention, and FIG. 5(B) is an X-ray diffraction pattern of a thin film emissive layer made of SrS doped with CaP3. This is the X-ray diffraction pattern of 1...Glass substrate, 2...Transparent electrode, 3...First
dielectric layer, 4... light emitting layer, 5... second dielectric layer, 6... back electrode, 7... power source. Patent applicant: Toyo Soda Kogyo Co., Ltd. Figure 1 Figure 2 Applied voltage (Vrms) Figure 3 Wavelength λ (nm) Figure 4 Figure 5 Diffraction angle, 2θ (degrees)/Cukα Procedural correction book formula) % formula % 1 Display of the case Patent Application No. 141473 filed in 1985 2 Name of the invention Thin film light emitting layer material 3 Person making the amendment Relationship to the case Patent applicant address 4560 Oaza Tomita, Shinnanyo City, Yamaro Prefecture 746 (Contact information) 107 Akasaka 1-7-7, Minato-ku, Tokyo (transfer building) Toyo Soda Kogyo Co., Ltd. Patent Information Department Phone number (505) 4471 4 Date of amendment order 5 Brief description of drawings in the specification subject to amendment 6 Contents of amendment (1) Lines 14 to 18 of page 13 of the specification are corrected as follows. "Figure 5 shows the X-ray diffraction pattern of the thin film light emitting layer, and (A) in Figure 5 shows the C e Fa in the present invention.
(B) is an X-ray diffraction pattern of a thin film emitting layer made of a composite film of SrS and ZnS doped with CeF a
This is an X-ray diffraction pattern of a thin film light-emitting layer made of SrS doped with . "that's all

Claims (3)

[Claims] (1) In a thin-film EL device, the thin-film light-emitting layer contains at least one selected from MgS, CaS, SrS, and BaS doped with an optically active transition metal or rare earth element in the matrix, and ZnS. A novel thin film EL device characterized by comprising a thin film layer having a composite of as a base material. (2) Forming the thin film emitting layer in the thin film EL element, M
In the base material made of a composite of ZnS and at least one selected from gS, CaS, SrS, and BaS, the mixing ratio of the Zn element contained in the base material is 0.5 mol% to 99%.
．． 5 mol % of the thin film EL device according to claim 1. (3) Compounds of transition metals or rare earth elements that are optically active in the matrix and MgS, CaS, SrS, BaS
A method for producing a thin film EL device, comprising preparing a thin film light emitting layer using at least one selected from the following and ZnS by a vapor deposition method or a sputtering method.