JP2004192987A - Thin film electroluminescent (el) element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film EL element having a luminescent layer formed of a new oxide phosphor thin film capable of emitting light having various colors including blue. <P>SOLUTION: The luminescent layer 4 of this inorganic thin film EL element for a display device contains MSb<SB>2</SB>O<SB>X</SB>(M is any of Mg, Ca, Sr and Ba or a combination thereof; and X=4, 5 or 6) as a matrix, and it is activated with the luminescent center by Mn ions or the like. The thin film EL element is formed by sequentially stacking, on a glass substrate 1, a lower electrode layer 2, a lower insulation layer 3, the luminescent layer 4, an upper insulation layer 5 and an upper electrode layer 6, and EL light emission 7 of the luminescent layer 4 is outputted through the glass substrate 1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin-film electroluminescent device used for an electroluminescent display having features of being thin, having excellent flatness, having a long life, and having high contrast.
[0002]
[Prior art]
It is widely known that an electroluminescent element (hereinafter, referred to as an EL element) applying electroluminescence, which is one of the light emission phenomena, is used for a flat panel display.
[0003]
As a light emitting layer constituting such an EL element, a light emitting layer using a sulfide phosphor thin film such as ZnS: Mn has been conventionally known. On the other hand, it has been attempted to use an oxide phosphor thin film excellent in handling and stability in the air as the light emitting layer. For example, Zn ₂ SiO ₄ : Mn and ZnGa ₂ O ₄ : Mn that emit green light, CaO: Mn that emits red light, and CaO: Pb that emits blue light are known as oxide phosphor thin films (Non-patent Documents). 1).
[0004]
[Non-patent document 1]
"Flat Panel Display Dictionary", supervised by Uchida, Uchiike, Industrial Research Committee [0005]
[Problems to be solved by the invention]
By the way, the above-mentioned oxide phosphor thin film, in particular, a phosphor thin film having Mn ions as a luminescence center, emits various kinds of light such as green, red, and yellow as described above, but does not emit blue light. Not. Therefore, it has been difficult to use the same luminescent center material for each color light in manufacturing a full-color panel that emits each color light of R, G, and B. As a result, when the phosphor thin films for each color light emission are formed, problems such as complicated panel manufacturing process and insufficient emission characteristics due to different film forming conditions such as heat treatment temperature arise. I was
[0006]
Of course, the blue component can be extracted from the emitted blue-green component using a color filter. The emission luminance of the blue component obtained in this way is slightly different depending on the color purity and the characteristics of the color filter. This is about one-tenth of the emission luminance of the original blue-green component.
[0007]
It is also conceivable to manufacture a full-color panel by combining the above-described oxide phosphor thin film with a sulfide-based thin film. For example, when CaGa ₂ S ₄ or SrGa ₂ S ₄ which is a ternary compound thiogallate is used as a base material and Ce ³⁺ ion is activated as a luminescence center, BaAl ₂ S ₄ which is a thioaluminate is used as a base material. When Eu ²⁺ ions are activated, practical blue light emission is obtained.
[0008]
However, the formation of an oxide phosphor thin film requires high-temperature heat treatment in the atmosphere or in an oxygen atmosphere, which oxidizes the sulfide phosphor thin film and exhibits its original light emission performance. It will be difficult to do.
[0009]
Therefore, it is demanded to manufacture a full-color panel capable of emitting light of three primary colors of R, G and B using only the oxide phosphor thin film.
In particular, in consideration of the process of forming an oxide-based phosphor thin film by high-temperature heat treatment, it is demanded that not only the luminescent center element but also a host material be made of the same series of materials as much as possible.
[0010]
The present invention has been made in view of such circumstances, and provides a thin-film EL device in which a light-emitting layer is formed of an oxide phosphor thin film and is formed of a novel base material capable of emitting various colors of light including blue. It is intended for that purpose.
[0011]
Further, the present invention includes a light-emitting layer composed of an oxide phosphor thin film capable of generating three primary colors of R, G, and B using the same light-emitting central element and / or the base material of the light-emitting layer of the same series. It is an object of the present invention to provide a thin film EL device.
[0012]
[Means for Solving the Problems]
In the thin film electroluminescent device (thin film EL device) according to the present invention, a base material of a light emitting layer disposed between two electrode layers is formed by SrSb ₂ O _X (where X = 4, 5, 6). It is characterized by having done.
As described above, when SrSb ₂ O _X is used as the base material of the light-emitting layer, various colors of light including blue can be emitted by appropriately changing the emission center element.
[0013]
The present invention in which SrSb ₂ O _X is used as the base material of the light-emitting layer is based on the fact that in the crystal structure of SrSb ₂ O _X , the distance between the Sr ion that replaces the ion of the emission center element and the oxygen ion is wide, This has been achieved for the first time based on the idea of the present inventor that the influence of oxygen ions on the ion of the luminescent center element will be small and subsequent experiments.
[0014]
In addition, by activating Mn ions as emission centers in SrSb ₂ O _X as the base material, blue EL emission, which has been conventionally required, has become possible.
Further, according to the thin film EL device thus configured, SrSb ₂ O _X : Mn (X = 4, 5, 6) is used as the blue light emitting phosphor thin film, and the green light emitting phosphor thin film is as described above. By using Zn ₂ SiO ₄ : Mn or ZnGa ₂ O ₄ : Mn, at least the emission center element becomes the same, and the process can be simplified.
[0015]
Furthermore, the use as a phosphor thin film for green emitting Mn in this SrSb a base material of ₂ O _X the same series _{CaSb 2 O X (X = 4,5,6} ) and activated as a luminescent center, further A common temperature process can be achieved, and cost reduction can be promoted. In addition, various emission colors can be obtained by a combination of the same series of base material and emission center element, so that a multi-color panel can be easily manufactured.
[0016]
Further, another thin film electroluminescent device according to the present invention is configured as follows.
That is, the base material of the light emitting layer disposed between the two electrode layers is MSb ₂ O _X (where M is an element selected from Mg, Ca, Ba, and Sr, X = 4, 5, 6) It is formed by:
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a thin film electroluminescent (EL) element according to an embodiment of the present invention will be described with reference to the drawings.
[0018]
Hereinafter, the thin film EL device according to the embodiment of the present invention will be specifically described.
The thin-film EL device according to one embodiment of the present invention uses Mn ²⁺ ions as emission centers and uses a ternary compound SrSbO _X (X = 4, 5, 6) for an emission layer.
This thin film EL element is of a double insulating structure type having a cross-sectional structure as shown in FIG.
[0019]
As shown in FIG. 1, in the thin-film EL device according to the present embodiment, a lower electrode layer 2, a lower insulating layer 3, a light emitting layer 4, an upper insulating layer 5, and an upper electrode layer 6 are sequentially stacked on a glass substrate 1. The EL light emission 7 of the light emitting layer 4 is output through the glass substrate 1. Note that a buffer layer may be provided on at least one of the vertically adjacent positions of the light emitting layer 4.
[0020]
The lower electrode layer 2 is a transparent electrode layer made of, for example, ITO (tin-added indium oxide) or ZnO, while the upper (back) electrode layer 6 is an opaque electrode layer made of Al or the like. Each of the electrode layers 2 and 6 has a thickness of, for example, about 200 nm. The upper electrode layer 6 can be a transparent electrode layer.
The upper and lower insulating layers 3 and 5 are made of, for example, Ta ₂ O ₅ and have a thickness of, for example, about 500 nm.
[0021]
Further, the light emitting layer 4 is an oxide phosphor thin film, and is made of SrSb ₂ O _X : Mn (X = 4, 5, 6) as described above. Its layer thickness is, for example, about 0.8 μm.
[0022]
By the way, the Mn ²⁺ ion emits light due to the forbidden transition of the 3d electron, and its emission color is strongly determined by the influence of the ligand. However, so far the oxide phosphor thin film which is known, the influence of oxygen ions is a ligand surrounding the Mn ²⁺ ion is strongly affects Mn ²⁺ ions, from red to green (blue-green) Although light emission in the middle was obtained, light emission in the blue was not obtained.
[0023]
Accordingly, the present inventors by Janin etc., focusing on SrSb ₂ O _X crystals whose crystal structures have been reported (J. Janin and R. Bernard:. . Compt Rend 240 614 (1953)) and M. l. Y. Allusalu (Tr. Inst. Fiz. Astron. Akad. Nauk. Est. SSR. 858 (1958)). That is, according to this report, in the Sr (Ca) Sb ₂ O _X crystal, the distance between Sr ions and oxygen ions is as large as 2.5 °.
[0024]
If the present inventor uses this SrSb ₂ O _X as a base material and uses Mn ions as emission centers, the distance between oxygen ions and Sr ions replaced with Mn ions is as large as 2.5 °, so Mn ions It was thought that the compound could emit blue light without being bound by oxygen ions.
Thus, it was confirmed that blue light emission was obtained from the light emitting layer 4 formed of SrSb ₂ O _X : Mn (X = 4, 5, 6).
[0025]
Hereinafter, a method of forming the layers 1 to 6 will be described.
[0026]
The lower electrode layer 2 and the upper electrode layer 6 are formed by an electron beam evaporation method, but may be formed by another film formation method, for example, another evaporation method, a sputtering method, an ion plating method, a CVD method, or the like. It is also possible to form.
[0027]
The insulating layers 3 and 5 are formed by a high-frequency magnetron sputtering method, but may be formed by, for example, a vapor deposition method, an ion plating method, or a CVD method.
[0028]
The light emitting layer 4 is formed by an electron beam evaporation method, but is formed by another film formation method, for example, a co-evaporation method, a sputtering method, an ion plating method, a sol-gel method, a CVD method, or the like. It is also possible.
[0029]
Hereinafter, a method for forming the light emitting layer 4 will be described.
The method for forming the light emitting layer 4 includes the following two manufacturing steps.
[0030]
That is, first, the glass substrate 1 is heated to a temperature of about 200 ° C., and materials of SrO, Sb ₂ O ₅ , and MnO are mixed, and the solidified pellet is irradiated with an electron beam to evaporate the material. Then, a thin film of SrSb ₂ O _X : Mn (X = 4, 5, 6) is formed on the insulating layer 3 (first step).
[0031]
Subsequently, crystallization is promoted by performing a heat treatment at about 500 ° C. for about one hour in the atmosphere (second step).
[0032]
【Example】
The light emitting layer 4 was formed by the film forming method described in the above embodiment.
The light emitting layer 4 was formed twice.
[0033]
FIG. 2 shows an X-ray diffraction pattern of the light emitting layer 4 of the present example thus formed. (A) shows the X-ray diffraction pattern of the light emitting layer 4 formed first time, and (B) shows the X-ray diffraction pattern of the light emitting layer 4 formed second time. The film forming conditions such as the heat treatment temperature are slightly different between the first time and the second time.
[0034]
As is clear from FIGS. 2A and 2B, according to the present embodiment, although the composition ratios are slightly different from each other, each of them has a large SrSb ₂ O _X : Mn (X = 4, 5, 6). It was confirmed that a crystalline thin film was formed.
[0035]
FIG. 3 shows an EL emission spectrum when the thin-film EL device provided with the light-emitting layer formed according to the above embodiment is driven. In FIG. 3, the peak located near 450 nm indicates blue light emission due to Mn ²⁺ ions. The peak located near 400 nm near the ultraviolet region indicates light emission by Sb ⁵⁺ , and decreases as light emission by Mn ²⁺ increases.
[0036]
In the above-described embodiment, SrSb ₂ O _X : Mn (X = 4, 5, 6) is used as the phosphor thin film, but ions of Cu, Cr, Pb, Bi, etc. are used instead of Mn ions. It is considered that similar results can be obtained even if is used as the emission center. If ions of rare earth elements are used as emission centers instead of Mn ions, various color lights (for example, R, G, and B color lights) can be emitted according to the type of rare earth elements used as emission centers. Thus, a full-color panel can be manufactured while the base material of the light-emitting layer for each color light is shared, so that the temperature process in the manufacturing process can be shared and the manufacturing cost can be reduced.
[0037]
In the above-described phosphor thin film SrSb ₂ O _X : Mn (X = 4, 5, 6), Sr of the base material is replaced with another element, particularly another 2A group such as Mg, Ca, Ba, and the phosphor. By forming a thin film, it is possible to emit light of various colors. For example, it has been confirmed that a phosphor thin film CaSb ₂ O _x : Mn (X = 4, 5, 6, 6) obtained by replacing Sr with Ca can emit green light having a peak near 510 nm. By adopting such a configuration, it is possible to manufacture a full-color panel using the same series of base material and the same luminescent center element, thereby achieving a further common temperature process and further promoting cost reduction. can do. In addition, various emission colors can be obtained by combining the same series of base material and emission center material, which facilitates production of a multi-color panel.
[0038]
In the case where Sr of the base material of the above-described fluorescent material SrSb ₂ O _X : Mn (X = 4, 5, 6) is replaced with another element, for example, Sr, Mg, Ca, By setting two or more elements selected from the group 2A elements such as Ba and adjusting the mixing ratio of the selected two or more elements, the wavelength of emitted color light can be set to an arbitrary value. is there.
[0039]
The thin-film EL device according to the above-described embodiment is formed by sequentially laminating a lower electrode layer 2, a lower insulating layer 3, a light emitting layer 4, an upper insulating layer 5, and an upper electrode layer 6 on a glass substrate 1. However, a ceramic substrate can be used instead of the glass substrate 1. In particular, by using a ceramic substrate made of a ceramic material having a high dielectric constant, it is possible to have a function as an insulating layer in addition to a function as a substrate. Thereby, the insulating layers 3 and 5 described above can be omitted. As a specific example of the high dielectric constant ceramic substrate, for example, a barium titanate plate (BaTiO ₃ ) having a thickness of 0.2 mm is used. A light emitting layer composed of a thin film of SrSb ₂ O _X : Mn (X = 4, 5, 6, 6) is formed directly on the substrate by using the above-described film forming method. After that, in order to promote crystallization, heat treatment at about 500 ° C. is performed in the air for about 1 hour.
[0040]
In this case, the upper electrode layer is formed directly on the light emitting layer, and the lower electrode layer is formed directly on the surface of the ceramic substrate opposite to the light emitting layer side.
[0041]
The embodiments of the present invention are not limited to those described above, and various other aspects can be changed.
For example, the layer configuration of the thin-film EL element of the present invention is not limited to the above-described embodiment, and may have a layer configuration in which another layer, for example, a buffer layer or the like is interposed between the above-described layers. A layer configuration in which only one insulating layer is present is also possible.
[0042]
Also, the constituent materials, thicknesses, and film forming methods of each layer are not limited to those described above.
[0043]
【The invention's effect】
According to the thin film EL device of the present invention, the base material of the light emitting layer provided between the two electrode layers is formed of SrSb ₂ O _X (where X = 4, 5, 6), whereby The light-emitting layer can emit various colors of light including blue. In particular, when the host material is activated with Mn ions as emission centers, blue light emission that cannot be obtained with a conventional oxide phosphor thin film using Mn ions as emission centers can be obtained.
[0044]
Further, the base material of the light emitting layer disposed between the two electrode layers is MSb ₂ O _X (where M is an element selected from Mg, Ca, Ba, and Sr, and X = 4, 5, 6) By using the same material, it is possible to obtain a thin-film EL element having a light emitting layer capable of generating three primary colors of R, G and B using the same series of base materials, and to use a common temperature process in the manufacturing process. Accordingly, manufacturing costs of a display or the like that performs full-color display can be reduced.
[0045]
In this case, if a light emitting layer capable of generating three primary colors of R, G, and B is formed using the same light emitting center element, for example, Mn, not only the same series of base materials but also the same light emission Since a thin-film EL device having a light-emitting layer capable of generating three primary colors of R, G, and B using the central element can be obtained, the temperature process in the manufacturing process can be further shared, and a full-color EL device can be obtained. The manufacturing cost of a display for displaying can be further reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a layer configuration of a thin film EL device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an X-ray diffraction pattern of a light emitting layer of the thin film EL device according to an example of the present invention. The figure which shows the EL emission spectrum of the thin film EL element which concerns on the Example of this invention.
DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Lower electrode layer 3 Lower insulating layer 4 Light emitting layer 5 Upper insulating layer 6 Upper electrode layer 7 EL light emission

Claims (6)

A thin-film electroluminescent device, wherein a base material of a light emitting layer disposed between two electrode layers is formed of SrSb ₂ O _X (where X = 4, 5, 6). 2. The thin-film electroluminescent device according to claim 1, wherein the base material has a light emitting layer activated by Mn ions as a light emitting center. 2. The thin-film electroluminescent device according to claim 1, wherein the base material has a light-emitting layer in which ions of rare earth elements are activated as light-emission centers. A base material of the light emitting layer disposed between the two electrode layers is formed of MSb ₂ O _X (where M is an element selected from Mg, Ca, Ba, and Sr, X = 4, 5, 6). A thin-film electroluminescent device, comprising: 5. The thin-film electroluminescent device according to claim 4, wherein M constituting said MSb ₂ O _X is a combination of two or more elements selected from Mg, Ca, Ba and Sr. . The thin-film electroluminescent device according to any one of claims 1 to 5, wherein a ceramic plate having the light emitting layer laminated is provided between the two electrode layers.

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